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 Target Data:: Data caching for 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 Target Data
10827 @section Caching Data of Targets
10828 @cindex caching data of targets
10830 @value{GDBN} caches data exchanged between the debugger and a target.
10831 Such caching generally improves performance in remote debugging
10832 (@pxref{Remote Debugging}), because it reduces the overhead of the
10833 remote protocol by bundling memory reads and writes into large chunks.
10834 Unfortunately, simply caching everything would lead to incorrect results,
10835 since @value{GDBN} does not necessarily know anything about volatile
10836 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10837 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10839 Therefore, by default, @value{GDBN} only caches data
10840 known to be on the stack@footnote{In non-stop mode, it is moderately
10841 rare for a running thread to modify the stack of a stopped thread
10842 in a way that would interfere with a backtrace, and caching of
10843 stack reads provides a significant speed up of remote backtraces.}.
10844 Other regions of memory can be explicitly marked as
10845 cacheable; see @pxref{Memory Region Attributes}.
10848 @kindex set remotecache
10849 @item set remotecache on
10850 @itemx set remotecache off
10851 This option no longer does anything; it exists for compatibility
10854 @kindex show remotecache
10855 @item show remotecache
10856 Show the current state of the obsolete remotecache flag.
10858 @kindex set stack-cache
10859 @item set stack-cache on
10860 @itemx set stack-cache off
10861 Enable or disable caching of stack accesses. When @code{ON}, use
10862 caching. By default, this option is @code{ON}.
10864 @kindex show stack-cache
10865 @item show stack-cache
10866 Show the current state of data caching for memory accesses.
10868 @kindex info dcache
10869 @item info dcache @r{[}line@r{]}
10870 Print the information about the data cache performance. The
10871 information displayed includes the dcache width and depth, and for
10872 each cache line, its number, address, and how many times it was
10873 referenced. This command is useful for debugging the data cache
10876 If a line number is specified, the contents of that line will be
10879 @item set dcache size @var{size}
10880 @cindex dcache size
10881 @kindex set dcache size
10882 Set maximum number of entries in dcache (dcache depth above).
10884 @item set dcache line-size @var{line-size}
10885 @cindex dcache line-size
10886 @kindex set dcache line-size
10887 Set number of bytes each dcache entry caches (dcache width above).
10888 Must be a power of 2.
10890 @item show dcache size
10891 @kindex show dcache size
10892 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10894 @item show dcache line-size
10895 @kindex show dcache line-size
10896 Show default size of dcache lines.
10900 @node Searching Memory
10901 @section Search Memory
10902 @cindex searching memory
10904 Memory can be searched for a particular sequence of bytes with the
10905 @code{find} command.
10909 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10910 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10911 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10912 etc. The search begins at address @var{start_addr} and continues for either
10913 @var{len} bytes or through to @var{end_addr} inclusive.
10916 @var{s} and @var{n} are optional parameters.
10917 They may be specified in either order, apart or together.
10920 @item @var{s}, search query size
10921 The size of each search query value.
10927 halfwords (two bytes)
10931 giant words (eight bytes)
10934 All values are interpreted in the current language.
10935 This means, for example, that if the current source language is C/C@t{++}
10936 then searching for the string ``hello'' includes the trailing '\0'.
10938 If the value size is not specified, it is taken from the
10939 value's type in the current language.
10940 This is useful when one wants to specify the search
10941 pattern as a mixture of types.
10942 Note that this means, for example, that in the case of C-like languages
10943 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10944 which is typically four bytes.
10946 @item @var{n}, maximum number of finds
10947 The maximum number of matches to print. The default is to print all finds.
10950 You can use strings as search values. Quote them with double-quotes
10952 The string value is copied into the search pattern byte by byte,
10953 regardless of the endianness of the target and the size specification.
10955 The address of each match found is printed as well as a count of the
10956 number of matches found.
10958 The address of the last value found is stored in convenience variable
10960 A count of the number of matches is stored in @samp{$numfound}.
10962 For example, if stopped at the @code{printf} in this function:
10968 static char hello[] = "hello-hello";
10969 static struct @{ char c; short s; int i; @}
10970 __attribute__ ((packed)) mixed
10971 = @{ 'c', 0x1234, 0x87654321 @};
10972 printf ("%s\n", hello);
10977 you get during debugging:
10980 (gdb) find &hello[0], +sizeof(hello), "hello"
10981 0x804956d <hello.1620+6>
10983 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10984 0x8049567 <hello.1620>
10985 0x804956d <hello.1620+6>
10987 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10988 0x8049567 <hello.1620>
10990 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10991 0x8049560 <mixed.1625>
10993 (gdb) print $numfound
10996 $2 = (void *) 0x8049560
10999 @node Optimized Code
11000 @chapter Debugging Optimized Code
11001 @cindex optimized code, debugging
11002 @cindex debugging optimized code
11004 Almost all compilers support optimization. With optimization
11005 disabled, the compiler generates assembly code that corresponds
11006 directly to your source code, in a simplistic way. As the compiler
11007 applies more powerful optimizations, the generated assembly code
11008 diverges from your original source code. With help from debugging
11009 information generated by the compiler, @value{GDBN} can map from
11010 the running program back to constructs from your original source.
11012 @value{GDBN} is more accurate with optimization disabled. If you
11013 can recompile without optimization, it is easier to follow the
11014 progress of your program during debugging. But, there are many cases
11015 where you may need to debug an optimized version.
11017 When you debug a program compiled with @samp{-g -O}, remember that the
11018 optimizer has rearranged your code; the debugger shows you what is
11019 really there. Do not be too surprised when the execution path does not
11020 exactly match your source file! An extreme example: if you define a
11021 variable, but never use it, @value{GDBN} never sees that
11022 variable---because the compiler optimizes it out of existence.
11024 Some things do not work as well with @samp{-g -O} as with just
11025 @samp{-g}, particularly on machines with instruction scheduling. If in
11026 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11027 please report it to us as a bug (including a test case!).
11028 @xref{Variables}, for more information about debugging optimized code.
11031 * Inline Functions:: How @value{GDBN} presents inlining
11032 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11035 @node Inline Functions
11036 @section Inline Functions
11037 @cindex inline functions, debugging
11039 @dfn{Inlining} is an optimization that inserts a copy of the function
11040 body directly at each call site, instead of jumping to a shared
11041 routine. @value{GDBN} displays inlined functions just like
11042 non-inlined functions. They appear in backtraces. You can view their
11043 arguments and local variables, step into them with @code{step}, skip
11044 them with @code{next}, and escape from them with @code{finish}.
11045 You can check whether a function was inlined by using the
11046 @code{info frame} command.
11048 For @value{GDBN} to support inlined functions, the compiler must
11049 record information about inlining in the debug information ---
11050 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11051 other compilers do also. @value{GDBN} only supports inlined functions
11052 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11053 do not emit two required attributes (@samp{DW_AT_call_file} and
11054 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11055 function calls with earlier versions of @value{NGCC}. It instead
11056 displays the arguments and local variables of inlined functions as
11057 local variables in the caller.
11059 The body of an inlined function is directly included at its call site;
11060 unlike a non-inlined function, there are no instructions devoted to
11061 the call. @value{GDBN} still pretends that the call site and the
11062 start of the inlined function are different instructions. Stepping to
11063 the call site shows the call site, and then stepping again shows
11064 the first line of the inlined function, even though no additional
11065 instructions are executed.
11067 This makes source-level debugging much clearer; you can see both the
11068 context of the call and then the effect of the call. Only stepping by
11069 a single instruction using @code{stepi} or @code{nexti} does not do
11070 this; single instruction steps always show the inlined body.
11072 There are some ways that @value{GDBN} does not pretend that inlined
11073 function calls are the same as normal calls:
11077 Setting breakpoints at the call site of an inlined function may not
11078 work, because the call site does not contain any code. @value{GDBN}
11079 may incorrectly move the breakpoint to the next line of the enclosing
11080 function, after the call. This limitation will be removed in a future
11081 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11082 or inside the inlined function instead.
11085 @value{GDBN} cannot locate the return value of inlined calls after
11086 using the @code{finish} command. This is a limitation of compiler-generated
11087 debugging information; after @code{finish}, you can step to the next line
11088 and print a variable where your program stored the return value.
11092 @node Tail Call Frames
11093 @section Tail Call Frames
11094 @cindex tail call frames, debugging
11096 Function @code{B} can call function @code{C} in its very last statement. In
11097 unoptimized compilation the call of @code{C} is immediately followed by return
11098 instruction at the end of @code{B} code. Optimizing compiler may replace the
11099 call and return in function @code{B} into one jump to function @code{C}
11100 instead. Such use of a jump instruction is called @dfn{tail call}.
11102 During execution of function @code{C}, there will be no indication in the
11103 function call stack frames that it was tail-called from @code{B}. If function
11104 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11105 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11106 some cases @value{GDBN} can determine that @code{C} was tail-called from
11107 @code{B}, and it will then create fictitious call frame for that, with the
11108 return address set up as if @code{B} called @code{C} normally.
11110 This functionality is currently supported only by DWARF 2 debugging format and
11111 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11112 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11115 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11116 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11120 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11122 Stack level 1, frame at 0x7fffffffda30:
11123 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11124 tail call frame, caller of frame at 0x7fffffffda30
11125 source language c++.
11126 Arglist at unknown address.
11127 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11130 The detection of all the possible code path executions can find them ambiguous.
11131 There is no execution history stored (possible @ref{Reverse Execution} is never
11132 used for this purpose) and the last known caller could have reached the known
11133 callee by multiple different jump sequences. In such case @value{GDBN} still
11134 tries to show at least all the unambiguous top tail callers and all the
11135 unambiguous bottom tail calees, if any.
11138 @anchor{set debug entry-values}
11139 @item set debug entry-values
11140 @kindex set debug entry-values
11141 When set to on, enables printing of analysis messages for both frame argument
11142 values at function entry and tail calls. It will show all the possible valid
11143 tail calls code paths it has considered. It will also print the intersection
11144 of them with the final unambiguous (possibly partial or even empty) code path
11147 @item show debug entry-values
11148 @kindex show debug entry-values
11149 Show the current state of analysis messages printing for both frame argument
11150 values at function entry and tail calls.
11153 The analysis messages for tail calls can for example show why the virtual tail
11154 call frame for function @code{c} has not been recognized (due to the indirect
11155 reference by variable @code{x}):
11158 static void __attribute__((noinline, noclone)) c (void);
11159 void (*x) (void) = c;
11160 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11161 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11162 int main (void) @{ x (); return 0; @}
11164 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11165 DW_TAG_GNU_call_site 0x40039a in main
11167 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11170 #1 0x000000000040039a in main () at t.c:5
11173 Another possibility is an ambiguous virtual tail call frames resolution:
11177 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11178 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11179 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11180 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11181 static void __attribute__((noinline, noclone)) b (void)
11182 @{ if (i) c (); else e (); @}
11183 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11184 int main (void) @{ a (); return 0; @}
11186 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11187 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11188 tailcall: reduced: 0x4004d2(a) |
11191 #1 0x00000000004004d2 in a () at t.c:8
11192 #2 0x0000000000400395 in main () at t.c:9
11195 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11196 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11198 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11199 @ifset HAVE_MAKEINFO_CLICK
11200 @set ARROW @click{}
11201 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11202 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11204 @ifclear HAVE_MAKEINFO_CLICK
11206 @set CALLSEQ1B @value{CALLSEQ1A}
11207 @set CALLSEQ2B @value{CALLSEQ2A}
11210 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11211 The code can have possible execution paths @value{CALLSEQ1B} or
11212 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11214 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11215 has found. It then finds another possible calling sequcen - that one is
11216 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11217 printed as the @code{reduced:} calling sequence. That one could have many
11218 futher @code{compare:} and @code{reduced:} statements as long as there remain
11219 any non-ambiguous sequence entries.
11221 For the frame of function @code{b} in both cases there are different possible
11222 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11223 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11224 therefore this one is displayed to the user while the ambiguous frames are
11227 There can be also reasons why printing of frame argument values at function
11232 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11233 static void __attribute__((noinline, noclone)) a (int i);
11234 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11235 static void __attribute__((noinline, noclone)) a (int i)
11236 @{ if (i) b (i - 1); else c (0); @}
11237 int main (void) @{ a (5); return 0; @}
11240 #0 c (i=i@@entry=0) at t.c:2
11241 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11242 function "a" at 0x400420 can call itself via tail calls
11243 i=<optimized out>) at t.c:6
11244 #2 0x000000000040036e in main () at t.c:7
11247 @value{GDBN} cannot find out from the inferior state if and how many times did
11248 function @code{a} call itself (via function @code{b}) as these calls would be
11249 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11250 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11251 prints @code{<optimized out>} instead.
11254 @chapter C Preprocessor Macros
11256 Some languages, such as C and C@t{++}, provide a way to define and invoke
11257 ``preprocessor macros'' which expand into strings of tokens.
11258 @value{GDBN} can evaluate expressions containing macro invocations, show
11259 the result of macro expansion, and show a macro's definition, including
11260 where it was defined.
11262 You may need to compile your program specially to provide @value{GDBN}
11263 with information about preprocessor macros. Most compilers do not
11264 include macros in their debugging information, even when you compile
11265 with the @option{-g} flag. @xref{Compilation}.
11267 A program may define a macro at one point, remove that definition later,
11268 and then provide a different definition after that. Thus, at different
11269 points in the program, a macro may have different definitions, or have
11270 no definition at all. If there is a current stack frame, @value{GDBN}
11271 uses the macros in scope at that frame's source code line. Otherwise,
11272 @value{GDBN} uses the macros in scope at the current listing location;
11275 Whenever @value{GDBN} evaluates an expression, it always expands any
11276 macro invocations present in the expression. @value{GDBN} also provides
11277 the following commands for working with macros explicitly.
11281 @kindex macro expand
11282 @cindex macro expansion, showing the results of preprocessor
11283 @cindex preprocessor macro expansion, showing the results of
11284 @cindex expanding preprocessor macros
11285 @item macro expand @var{expression}
11286 @itemx macro exp @var{expression}
11287 Show the results of expanding all preprocessor macro invocations in
11288 @var{expression}. Since @value{GDBN} simply expands macros, but does
11289 not parse the result, @var{expression} need not be a valid expression;
11290 it can be any string of tokens.
11293 @item macro expand-once @var{expression}
11294 @itemx macro exp1 @var{expression}
11295 @cindex expand macro once
11296 @i{(This command is not yet implemented.)} Show the results of
11297 expanding those preprocessor macro invocations that appear explicitly in
11298 @var{expression}. Macro invocations appearing in that expansion are
11299 left unchanged. This command allows you to see the effect of a
11300 particular macro more clearly, without being confused by further
11301 expansions. Since @value{GDBN} simply expands macros, but does not
11302 parse the result, @var{expression} need not be a valid expression; it
11303 can be any string of tokens.
11306 @cindex macro definition, showing
11307 @cindex definition of a macro, showing
11308 @cindex macros, from debug info
11309 @item info macro [-a|-all] [--] @var{macro}
11310 Show the current definition or all definitions of the named @var{macro},
11311 and describe the source location or compiler command-line where that
11312 definition was established. The optional double dash is to signify the end of
11313 argument processing and the beginning of @var{macro} for non C-like macros where
11314 the macro may begin with a hyphen.
11316 @kindex info macros
11317 @item info macros @var{linespec}
11318 Show all macro definitions that are in effect at the location specified
11319 by @var{linespec}, and describe the source location or compiler
11320 command-line where those definitions were established.
11322 @kindex macro define
11323 @cindex user-defined macros
11324 @cindex defining macros interactively
11325 @cindex macros, user-defined
11326 @item macro define @var{macro} @var{replacement-list}
11327 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11328 Introduce a definition for a preprocessor macro named @var{macro},
11329 invocations of which are replaced by the tokens given in
11330 @var{replacement-list}. The first form of this command defines an
11331 ``object-like'' macro, which takes no arguments; the second form
11332 defines a ``function-like'' macro, which takes the arguments given in
11335 A definition introduced by this command is in scope in every
11336 expression evaluated in @value{GDBN}, until it is removed with the
11337 @code{macro undef} command, described below. The definition overrides
11338 all definitions for @var{macro} present in the program being debugged,
11339 as well as any previous user-supplied definition.
11341 @kindex macro undef
11342 @item macro undef @var{macro}
11343 Remove any user-supplied definition for the macro named @var{macro}.
11344 This command only affects definitions provided with the @code{macro
11345 define} command, described above; it cannot remove definitions present
11346 in the program being debugged.
11350 List all the macros defined using the @code{macro define} command.
11353 @cindex macros, example of debugging with
11354 Here is a transcript showing the above commands in action. First, we
11355 show our source files:
11360 #include "sample.h"
11363 #define ADD(x) (M + x)
11368 printf ("Hello, world!\n");
11370 printf ("We're so creative.\n");
11372 printf ("Goodbye, world!\n");
11379 Now, we compile the program using the @sc{gnu} C compiler,
11380 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11381 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11382 and @option{-gdwarf-4}; we recommend always choosing the most recent
11383 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11384 includes information about preprocessor macros in the debugging
11388 $ gcc -gdwarf-2 -g3 sample.c -o sample
11392 Now, we start @value{GDBN} on our sample program:
11396 GNU gdb 2002-05-06-cvs
11397 Copyright 2002 Free Software Foundation, Inc.
11398 GDB is free software, @dots{}
11402 We can expand macros and examine their definitions, even when the
11403 program is not running. @value{GDBN} uses the current listing position
11404 to decide which macro definitions are in scope:
11407 (@value{GDBP}) list main
11410 5 #define ADD(x) (M + x)
11415 10 printf ("Hello, world!\n");
11417 12 printf ("We're so creative.\n");
11418 (@value{GDBP}) info macro ADD
11419 Defined at /home/jimb/gdb/macros/play/sample.c:5
11420 #define ADD(x) (M + x)
11421 (@value{GDBP}) info macro Q
11422 Defined at /home/jimb/gdb/macros/play/sample.h:1
11423 included at /home/jimb/gdb/macros/play/sample.c:2
11425 (@value{GDBP}) macro expand ADD(1)
11426 expands to: (42 + 1)
11427 (@value{GDBP}) macro expand-once ADD(1)
11428 expands to: once (M + 1)
11432 In the example above, note that @code{macro expand-once} expands only
11433 the macro invocation explicit in the original text --- the invocation of
11434 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11435 which was introduced by @code{ADD}.
11437 Once the program is running, @value{GDBN} uses the macro definitions in
11438 force at the source line of the current stack frame:
11441 (@value{GDBP}) break main
11442 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11444 Starting program: /home/jimb/gdb/macros/play/sample
11446 Breakpoint 1, main () at sample.c:10
11447 10 printf ("Hello, world!\n");
11451 At line 10, the definition of the macro @code{N} at line 9 is in force:
11454 (@value{GDBP}) info macro N
11455 Defined at /home/jimb/gdb/macros/play/sample.c:9
11457 (@value{GDBP}) macro expand N Q M
11458 expands to: 28 < 42
11459 (@value{GDBP}) print N Q M
11464 As we step over directives that remove @code{N}'s definition, and then
11465 give it a new definition, @value{GDBN} finds the definition (or lack
11466 thereof) in force at each point:
11469 (@value{GDBP}) next
11471 12 printf ("We're so creative.\n");
11472 (@value{GDBP}) info macro N
11473 The symbol `N' has no definition as a C/C++ preprocessor macro
11474 at /home/jimb/gdb/macros/play/sample.c:12
11475 (@value{GDBP}) next
11477 14 printf ("Goodbye, world!\n");
11478 (@value{GDBP}) info macro N
11479 Defined at /home/jimb/gdb/macros/play/sample.c:13
11481 (@value{GDBP}) macro expand N Q M
11482 expands to: 1729 < 42
11483 (@value{GDBP}) print N Q M
11488 In addition to source files, macros can be defined on the compilation command
11489 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11490 such a way, @value{GDBN} displays the location of their definition as line zero
11491 of the source file submitted to the compiler.
11494 (@value{GDBP}) info macro __STDC__
11495 Defined at /home/jimb/gdb/macros/play/sample.c:0
11502 @chapter Tracepoints
11503 @c This chapter is based on the documentation written by Michael
11504 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11506 @cindex tracepoints
11507 In some applications, it is not feasible for the debugger to interrupt
11508 the program's execution long enough for the developer to learn
11509 anything helpful about its behavior. If the program's correctness
11510 depends on its real-time behavior, delays introduced by a debugger
11511 might cause the program to change its behavior drastically, or perhaps
11512 fail, even when the code itself is correct. It is useful to be able
11513 to observe the program's behavior without interrupting it.
11515 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11516 specify locations in the program, called @dfn{tracepoints}, and
11517 arbitrary expressions to evaluate when those tracepoints are reached.
11518 Later, using the @code{tfind} command, you can examine the values
11519 those expressions had when the program hit the tracepoints. The
11520 expressions may also denote objects in memory---structures or arrays,
11521 for example---whose values @value{GDBN} should record; while visiting
11522 a particular tracepoint, you may inspect those objects as if they were
11523 in memory at that moment. However, because @value{GDBN} records these
11524 values without interacting with you, it can do so quickly and
11525 unobtrusively, hopefully not disturbing the program's behavior.
11527 The tracepoint facility is currently available only for remote
11528 targets. @xref{Targets}. In addition, your remote target must know
11529 how to collect trace data. This functionality is implemented in the
11530 remote stub; however, none of the stubs distributed with @value{GDBN}
11531 support tracepoints as of this writing. The format of the remote
11532 packets used to implement tracepoints are described in @ref{Tracepoint
11535 It is also possible to get trace data from a file, in a manner reminiscent
11536 of corefiles; you specify the filename, and use @code{tfind} to search
11537 through the file. @xref{Trace Files}, for more details.
11539 This chapter describes the tracepoint commands and features.
11542 * Set Tracepoints::
11543 * Analyze Collected Data::
11544 * Tracepoint Variables::
11548 @node Set Tracepoints
11549 @section Commands to Set Tracepoints
11551 Before running such a @dfn{trace experiment}, an arbitrary number of
11552 tracepoints can be set. A tracepoint is actually a special type of
11553 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11554 standard breakpoint commands. For instance, as with breakpoints,
11555 tracepoint numbers are successive integers starting from one, and many
11556 of the commands associated with tracepoints take the tracepoint number
11557 as their argument, to identify which tracepoint to work on.
11559 For each tracepoint, you can specify, in advance, some arbitrary set
11560 of data that you want the target to collect in the trace buffer when
11561 it hits that tracepoint. The collected data can include registers,
11562 local variables, or global data. Later, you can use @value{GDBN}
11563 commands to examine the values these data had at the time the
11564 tracepoint was hit.
11566 Tracepoints do not support every breakpoint feature. Ignore counts on
11567 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11568 commands when they are hit. Tracepoints may not be thread-specific
11571 @cindex fast tracepoints
11572 Some targets may support @dfn{fast tracepoints}, which are inserted in
11573 a different way (such as with a jump instead of a trap), that is
11574 faster but possibly restricted in where they may be installed.
11576 @cindex static tracepoints
11577 @cindex markers, static tracepoints
11578 @cindex probing markers, static tracepoints
11579 Regular and fast tracepoints are dynamic tracing facilities, meaning
11580 that they can be used to insert tracepoints at (almost) any location
11581 in the target. Some targets may also support controlling @dfn{static
11582 tracepoints} from @value{GDBN}. With static tracing, a set of
11583 instrumentation points, also known as @dfn{markers}, are embedded in
11584 the target program, and can be activated or deactivated by name or
11585 address. These are usually placed at locations which facilitate
11586 investigating what the target is actually doing. @value{GDBN}'s
11587 support for static tracing includes being able to list instrumentation
11588 points, and attach them with @value{GDBN} defined high level
11589 tracepoints that expose the whole range of convenience of
11590 @value{GDBN}'s tracepoints support. Namely, support for collecting
11591 registers values and values of global or local (to the instrumentation
11592 point) variables; tracepoint conditions and trace state variables.
11593 The act of installing a @value{GDBN} static tracepoint on an
11594 instrumentation point, or marker, is referred to as @dfn{probing} a
11595 static tracepoint marker.
11597 @code{gdbserver} supports tracepoints on some target systems.
11598 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11600 This section describes commands to set tracepoints and associated
11601 conditions and actions.
11604 * Create and Delete Tracepoints::
11605 * Enable and Disable Tracepoints::
11606 * Tracepoint Passcounts::
11607 * Tracepoint Conditions::
11608 * Trace State Variables::
11609 * Tracepoint Actions::
11610 * Listing Tracepoints::
11611 * Listing Static Tracepoint Markers::
11612 * Starting and Stopping Trace Experiments::
11613 * Tracepoint Restrictions::
11616 @node Create and Delete Tracepoints
11617 @subsection Create and Delete Tracepoints
11620 @cindex set tracepoint
11622 @item trace @var{location}
11623 The @code{trace} command is very similar to the @code{break} command.
11624 Its argument @var{location} can be a source line, a function name, or
11625 an address in the target program. @xref{Specify Location}. The
11626 @code{trace} command defines a tracepoint, which is a point in the
11627 target program where the debugger will briefly stop, collect some
11628 data, and then allow the program to continue. Setting a tracepoint or
11629 changing its actions takes effect immediately if the remote stub
11630 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11632 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11633 these changes don't take effect until the next @code{tstart}
11634 command, and once a trace experiment is running, further changes will
11635 not have any effect until the next trace experiment starts. In addition,
11636 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11637 address is not yet resolved. (This is similar to pending breakpoints.)
11638 Pending tracepoints are not downloaded to the target and not installed
11639 until they are resolved. The resolution of pending tracepoints requires
11640 @value{GDBN} support---when debugging with the remote target, and
11641 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11642 tracing}), pending tracepoints can not be resolved (and downloaded to
11643 the remote stub) while @value{GDBN} is disconnected.
11645 Here are some examples of using the @code{trace} command:
11648 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11650 (@value{GDBP}) @b{trace +2} // 2 lines forward
11652 (@value{GDBP}) @b{trace my_function} // first source line of function
11654 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11656 (@value{GDBP}) @b{trace *0x2117c4} // an address
11660 You can abbreviate @code{trace} as @code{tr}.
11662 @item trace @var{location} if @var{cond}
11663 Set a tracepoint with condition @var{cond}; evaluate the expression
11664 @var{cond} each time the tracepoint is reached, and collect data only
11665 if the value is nonzero---that is, if @var{cond} evaluates as true.
11666 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11667 information on tracepoint conditions.
11669 @item ftrace @var{location} [ if @var{cond} ]
11670 @cindex set fast tracepoint
11671 @cindex fast tracepoints, setting
11673 The @code{ftrace} command sets a fast tracepoint. For targets that
11674 support them, fast tracepoints will use a more efficient but possibly
11675 less general technique to trigger data collection, such as a jump
11676 instruction instead of a trap, or some sort of hardware support. It
11677 may not be possible to create a fast tracepoint at the desired
11678 location, in which case the command will exit with an explanatory
11681 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11684 On 32-bit x86-architecture systems, fast tracepoints normally need to
11685 be placed at an instruction that is 5 bytes or longer, but can be
11686 placed at 4-byte instructions if the low 64K of memory of the target
11687 program is available to install trampolines. Some Unix-type systems,
11688 such as @sc{gnu}/Linux, exclude low addresses from the program's
11689 address space; but for instance with the Linux kernel it is possible
11690 to let @value{GDBN} use this area by doing a @command{sysctl} command
11691 to set the @code{mmap_min_addr} kernel parameter, as in
11694 sudo sysctl -w vm.mmap_min_addr=32768
11698 which sets the low address to 32K, which leaves plenty of room for
11699 trampolines. The minimum address should be set to a page boundary.
11701 @item strace @var{location} [ if @var{cond} ]
11702 @cindex set static tracepoint
11703 @cindex static tracepoints, setting
11704 @cindex probe static tracepoint marker
11706 The @code{strace} command sets a static tracepoint. For targets that
11707 support it, setting a static tracepoint probes a static
11708 instrumentation point, or marker, found at @var{location}. It may not
11709 be possible to set a static tracepoint at the desired location, in
11710 which case the command will exit with an explanatory message.
11712 @value{GDBN} handles arguments to @code{strace} exactly as for
11713 @code{trace}, with the addition that the user can also specify
11714 @code{-m @var{marker}} as @var{location}. This probes the marker
11715 identified by the @var{marker} string identifier. This identifier
11716 depends on the static tracepoint backend library your program is
11717 using. You can find all the marker identifiers in the @samp{ID} field
11718 of the @code{info static-tracepoint-markers} command output.
11719 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11720 Markers}. For example, in the following small program using the UST
11726 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11731 the marker id is composed of joining the first two arguments to the
11732 @code{trace_mark} call with a slash, which translates to:
11735 (@value{GDBP}) info static-tracepoint-markers
11736 Cnt Enb ID Address What
11737 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11743 so you may probe the marker above with:
11746 (@value{GDBP}) strace -m ust/bar33
11749 Static tracepoints accept an extra collect action --- @code{collect
11750 $_sdata}. This collects arbitrary user data passed in the probe point
11751 call to the tracing library. In the UST example above, you'll see
11752 that the third argument to @code{trace_mark} is a printf-like format
11753 string. The user data is then the result of running that formating
11754 string against the following arguments. Note that @code{info
11755 static-tracepoint-markers} command output lists that format string in
11756 the @samp{Data:} field.
11758 You can inspect this data when analyzing the trace buffer, by printing
11759 the $_sdata variable like any other variable available to
11760 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11763 @cindex last tracepoint number
11764 @cindex recent tracepoint number
11765 @cindex tracepoint number
11766 The convenience variable @code{$tpnum} records the tracepoint number
11767 of the most recently set tracepoint.
11769 @kindex delete tracepoint
11770 @cindex tracepoint deletion
11771 @item delete tracepoint @r{[}@var{num}@r{]}
11772 Permanently delete one or more tracepoints. With no argument, the
11773 default is to delete all tracepoints. Note that the regular
11774 @code{delete} command can remove tracepoints also.
11779 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11781 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11785 You can abbreviate this command as @code{del tr}.
11788 @node Enable and Disable Tracepoints
11789 @subsection Enable and Disable Tracepoints
11791 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11794 @kindex disable tracepoint
11795 @item disable tracepoint @r{[}@var{num}@r{]}
11796 Disable tracepoint @var{num}, or all tracepoints if no argument
11797 @var{num} is given. A disabled tracepoint will have no effect during
11798 a trace experiment, but it is not forgotten. You can re-enable
11799 a disabled tracepoint using the @code{enable tracepoint} command.
11800 If the command is issued during a trace experiment and the debug target
11801 has support for disabling tracepoints during a trace experiment, then the
11802 change will be effective immediately. Otherwise, it will be applied to the
11803 next trace experiment.
11805 @kindex enable tracepoint
11806 @item enable tracepoint @r{[}@var{num}@r{]}
11807 Enable tracepoint @var{num}, or all tracepoints. If this command is
11808 issued during a trace experiment and the debug target supports enabling
11809 tracepoints during a trace experiment, then the enabled tracepoints will
11810 become effective immediately. Otherwise, they will become effective the
11811 next time a trace experiment is run.
11814 @node Tracepoint Passcounts
11815 @subsection Tracepoint Passcounts
11819 @cindex tracepoint pass count
11820 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11821 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11822 automatically stop a trace experiment. If a tracepoint's passcount is
11823 @var{n}, then the trace experiment will be automatically stopped on
11824 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11825 @var{num} is not specified, the @code{passcount} command sets the
11826 passcount of the most recently defined tracepoint. If no passcount is
11827 given, the trace experiment will run until stopped explicitly by the
11833 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11834 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11836 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11837 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11838 (@value{GDBP}) @b{trace foo}
11839 (@value{GDBP}) @b{pass 3}
11840 (@value{GDBP}) @b{trace bar}
11841 (@value{GDBP}) @b{pass 2}
11842 (@value{GDBP}) @b{trace baz}
11843 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11844 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11845 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11846 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11850 @node Tracepoint Conditions
11851 @subsection Tracepoint Conditions
11852 @cindex conditional tracepoints
11853 @cindex tracepoint conditions
11855 The simplest sort of tracepoint collects data every time your program
11856 reaches a specified place. You can also specify a @dfn{condition} for
11857 a tracepoint. A condition is just a Boolean expression in your
11858 programming language (@pxref{Expressions, ,Expressions}). A
11859 tracepoint with a condition evaluates the expression each time your
11860 program reaches it, and data collection happens only if the condition
11863 Tracepoint conditions can be specified when a tracepoint is set, by
11864 using @samp{if} in the arguments to the @code{trace} command.
11865 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11866 also be set or changed at any time with the @code{condition} command,
11867 just as with breakpoints.
11869 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11870 the conditional expression itself. Instead, @value{GDBN} encodes the
11871 expression into an agent expression (@pxref{Agent Expressions})
11872 suitable for execution on the target, independently of @value{GDBN}.
11873 Global variables become raw memory locations, locals become stack
11874 accesses, and so forth.
11876 For instance, suppose you have a function that is usually called
11877 frequently, but should not be called after an error has occurred. You
11878 could use the following tracepoint command to collect data about calls
11879 of that function that happen while the error code is propagating
11880 through the program; an unconditional tracepoint could end up
11881 collecting thousands of useless trace frames that you would have to
11885 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11888 @node Trace State Variables
11889 @subsection Trace State Variables
11890 @cindex trace state variables
11892 A @dfn{trace state variable} is a special type of variable that is
11893 created and managed by target-side code. The syntax is the same as
11894 that for GDB's convenience variables (a string prefixed with ``$''),
11895 but they are stored on the target. They must be created explicitly,
11896 using a @code{tvariable} command. They are always 64-bit signed
11899 Trace state variables are remembered by @value{GDBN}, and downloaded
11900 to the target along with tracepoint information when the trace
11901 experiment starts. There are no intrinsic limits on the number of
11902 trace state variables, beyond memory limitations of the target.
11904 @cindex convenience variables, and trace state variables
11905 Although trace state variables are managed by the target, you can use
11906 them in print commands and expressions as if they were convenience
11907 variables; @value{GDBN} will get the current value from the target
11908 while the trace experiment is running. Trace state variables share
11909 the same namespace as other ``$'' variables, which means that you
11910 cannot have trace state variables with names like @code{$23} or
11911 @code{$pc}, nor can you have a trace state variable and a convenience
11912 variable with the same name.
11916 @item tvariable $@var{name} [ = @var{expression} ]
11918 The @code{tvariable} command creates a new trace state variable named
11919 @code{$@var{name}}, and optionally gives it an initial value of
11920 @var{expression}. @var{expression} is evaluated when this command is
11921 entered; the result will be converted to an integer if possible,
11922 otherwise @value{GDBN} will report an error. A subsequent
11923 @code{tvariable} command specifying the same name does not create a
11924 variable, but instead assigns the supplied initial value to the
11925 existing variable of that name, overwriting any previous initial
11926 value. The default initial value is 0.
11928 @item info tvariables
11929 @kindex info tvariables
11930 List all the trace state variables along with their initial values.
11931 Their current values may also be displayed, if the trace experiment is
11934 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11935 @kindex delete tvariable
11936 Delete the given trace state variables, or all of them if no arguments
11941 @node Tracepoint Actions
11942 @subsection Tracepoint Action Lists
11946 @cindex tracepoint actions
11947 @item actions @r{[}@var{num}@r{]}
11948 This command will prompt for a list of actions to be taken when the
11949 tracepoint is hit. If the tracepoint number @var{num} is not
11950 specified, this command sets the actions for the one that was most
11951 recently defined (so that you can define a tracepoint and then say
11952 @code{actions} without bothering about its number). You specify the
11953 actions themselves on the following lines, one action at a time, and
11954 terminate the actions list with a line containing just @code{end}. So
11955 far, the only defined actions are @code{collect}, @code{teval}, and
11956 @code{while-stepping}.
11958 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11959 Commands, ,Breakpoint Command Lists}), except that only the defined
11960 actions are allowed; any other @value{GDBN} command is rejected.
11962 @cindex remove actions from a tracepoint
11963 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11964 and follow it immediately with @samp{end}.
11967 (@value{GDBP}) @b{collect @var{data}} // collect some data
11969 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11971 (@value{GDBP}) @b{end} // signals the end of actions.
11974 In the following example, the action list begins with @code{collect}
11975 commands indicating the things to be collected when the tracepoint is
11976 hit. Then, in order to single-step and collect additional data
11977 following the tracepoint, a @code{while-stepping} command is used,
11978 followed by the list of things to be collected after each step in a
11979 sequence of single steps. The @code{while-stepping} command is
11980 terminated by its own separate @code{end} command. Lastly, the action
11981 list is terminated by an @code{end} command.
11984 (@value{GDBP}) @b{trace foo}
11985 (@value{GDBP}) @b{actions}
11986 Enter actions for tracepoint 1, one per line:
11989 > while-stepping 12
11990 > collect $pc, arr[i]
11995 @kindex collect @r{(tracepoints)}
11996 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11997 Collect values of the given expressions when the tracepoint is hit.
11998 This command accepts a comma-separated list of any valid expressions.
11999 In addition to global, static, or local variables, the following
12000 special arguments are supported:
12004 Collect all registers.
12007 Collect all function arguments.
12010 Collect all local variables.
12013 Collect the return address. This is helpful if you want to see more
12017 Collects the number of arguments from the static probe at which the
12018 tracepoint is located.
12019 @xref{Static Probe Points}.
12021 @item $_probe_arg@var{n}
12022 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12023 from the static probe at which the tracepoint is located.
12024 @xref{Static Probe Points}.
12027 @vindex $_sdata@r{, collect}
12028 Collect static tracepoint marker specific data. Only available for
12029 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12030 Lists}. On the UST static tracepoints library backend, an
12031 instrumentation point resembles a @code{printf} function call. The
12032 tracing library is able to collect user specified data formatted to a
12033 character string using the format provided by the programmer that
12034 instrumented the program. Other backends have similar mechanisms.
12035 Here's an example of a UST marker call:
12038 const char master_name[] = "$your_name";
12039 trace_mark(channel1, marker1, "hello %s", master_name)
12042 In this case, collecting @code{$_sdata} collects the string
12043 @samp{hello $yourname}. When analyzing the trace buffer, you can
12044 inspect @samp{$_sdata} like any other variable available to
12048 You can give several consecutive @code{collect} commands, each one
12049 with a single argument, or one @code{collect} command with several
12050 arguments separated by commas; the effect is the same.
12052 The optional @var{mods} changes the usual handling of the arguments.
12053 @code{s} requests that pointers to chars be handled as strings, in
12054 particular collecting the contents of the memory being pointed at, up
12055 to the first zero. The upper bound is by default the value of the
12056 @code{print elements} variable; if @code{s} is followed by a decimal
12057 number, that is the upper bound instead. So for instance
12058 @samp{collect/s25 mystr} collects as many as 25 characters at
12061 The command @code{info scope} (@pxref{Symbols, info scope}) is
12062 particularly useful for figuring out what data to collect.
12064 @kindex teval @r{(tracepoints)}
12065 @item teval @var{expr1}, @var{expr2}, @dots{}
12066 Evaluate the given expressions when the tracepoint is hit. This
12067 command accepts a comma-separated list of expressions. The results
12068 are discarded, so this is mainly useful for assigning values to trace
12069 state variables (@pxref{Trace State Variables}) without adding those
12070 values to the trace buffer, as would be the case if the @code{collect}
12073 @kindex while-stepping @r{(tracepoints)}
12074 @item while-stepping @var{n}
12075 Perform @var{n} single-step instruction traces after the tracepoint,
12076 collecting new data after each step. The @code{while-stepping}
12077 command is followed by the list of what to collect while stepping
12078 (followed by its own @code{end} command):
12081 > while-stepping 12
12082 > collect $regs, myglobal
12088 Note that @code{$pc} is not automatically collected by
12089 @code{while-stepping}; you need to explicitly collect that register if
12090 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12093 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12094 @kindex set default-collect
12095 @cindex default collection action
12096 This variable is a list of expressions to collect at each tracepoint
12097 hit. It is effectively an additional @code{collect} action prepended
12098 to every tracepoint action list. The expressions are parsed
12099 individually for each tracepoint, so for instance a variable named
12100 @code{xyz} may be interpreted as a global for one tracepoint, and a
12101 local for another, as appropriate to the tracepoint's location.
12103 @item show default-collect
12104 @kindex show default-collect
12105 Show the list of expressions that are collected by default at each
12110 @node Listing Tracepoints
12111 @subsection Listing Tracepoints
12114 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12115 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12116 @cindex information about tracepoints
12117 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12118 Display information about the tracepoint @var{num}. If you don't
12119 specify a tracepoint number, displays information about all the
12120 tracepoints defined so far. The format is similar to that used for
12121 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12122 command, simply restricting itself to tracepoints.
12124 A tracepoint's listing may include additional information specific to
12129 its passcount as given by the @code{passcount @var{n}} command
12132 the state about installed on target of each location
12136 (@value{GDBP}) @b{info trace}
12137 Num Type Disp Enb Address What
12138 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12140 collect globfoo, $regs
12145 2 tracepoint keep y <MULTIPLE>
12147 2.1 y 0x0804859c in func4 at change-loc.h:35
12148 installed on target
12149 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12150 installed on target
12151 2.3 y <PENDING> set_tracepoint
12152 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12153 not installed on target
12158 This command can be abbreviated @code{info tp}.
12161 @node Listing Static Tracepoint Markers
12162 @subsection Listing Static Tracepoint Markers
12165 @kindex info static-tracepoint-markers
12166 @cindex information about static tracepoint markers
12167 @item info static-tracepoint-markers
12168 Display information about all static tracepoint markers defined in the
12171 For each marker, the following columns are printed:
12175 An incrementing counter, output to help readability. This is not a
12178 The marker ID, as reported by the target.
12179 @item Enabled or Disabled
12180 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12181 that are not enabled.
12183 Where the marker is in your program, as a memory address.
12185 Where the marker is in the source for your program, as a file and line
12186 number. If the debug information included in the program does not
12187 allow @value{GDBN} to locate the source of the marker, this column
12188 will be left blank.
12192 In addition, the following information may be printed for each marker:
12196 User data passed to the tracing library by the marker call. In the
12197 UST backend, this is the format string passed as argument to the
12199 @item Static tracepoints probing the marker
12200 The list of static tracepoints attached to the marker.
12204 (@value{GDBP}) info static-tracepoint-markers
12205 Cnt ID Enb Address What
12206 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12207 Data: number1 %d number2 %d
12208 Probed by static tracepoints: #2
12209 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12215 @node Starting and Stopping Trace Experiments
12216 @subsection Starting and Stopping Trace Experiments
12219 @kindex tstart [ @var{notes} ]
12220 @cindex start a new trace experiment
12221 @cindex collected data discarded
12223 This command starts the trace experiment, and begins collecting data.
12224 It has the side effect of discarding all the data collected in the
12225 trace buffer during the previous trace experiment. If any arguments
12226 are supplied, they are taken as a note and stored with the trace
12227 experiment's state. The notes may be arbitrary text, and are
12228 especially useful with disconnected tracing in a multi-user context;
12229 the notes can explain what the trace is doing, supply user contact
12230 information, and so forth.
12232 @kindex tstop [ @var{notes} ]
12233 @cindex stop a running trace experiment
12235 This command stops the trace experiment. If any arguments are
12236 supplied, they are recorded with the experiment as a note. This is
12237 useful if you are stopping a trace started by someone else, for
12238 instance if the trace is interfering with the system's behavior and
12239 needs to be stopped quickly.
12241 @strong{Note}: a trace experiment and data collection may stop
12242 automatically if any tracepoint's passcount is reached
12243 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12246 @cindex status of trace data collection
12247 @cindex trace experiment, status of
12249 This command displays the status of the current trace data
12253 Here is an example of the commands we described so far:
12256 (@value{GDBP}) @b{trace gdb_c_test}
12257 (@value{GDBP}) @b{actions}
12258 Enter actions for tracepoint #1, one per line.
12259 > collect $regs,$locals,$args
12260 > while-stepping 11
12264 (@value{GDBP}) @b{tstart}
12265 [time passes @dots{}]
12266 (@value{GDBP}) @b{tstop}
12269 @anchor{disconnected tracing}
12270 @cindex disconnected tracing
12271 You can choose to continue running the trace experiment even if
12272 @value{GDBN} disconnects from the target, voluntarily or
12273 involuntarily. For commands such as @code{detach}, the debugger will
12274 ask what you want to do with the trace. But for unexpected
12275 terminations (@value{GDBN} crash, network outage), it would be
12276 unfortunate to lose hard-won trace data, so the variable
12277 @code{disconnected-tracing} lets you decide whether the trace should
12278 continue running without @value{GDBN}.
12281 @item set disconnected-tracing on
12282 @itemx set disconnected-tracing off
12283 @kindex set disconnected-tracing
12284 Choose whether a tracing run should continue to run if @value{GDBN}
12285 has disconnected from the target. Note that @code{detach} or
12286 @code{quit} will ask you directly what to do about a running trace no
12287 matter what this variable's setting, so the variable is mainly useful
12288 for handling unexpected situations, such as loss of the network.
12290 @item show disconnected-tracing
12291 @kindex show disconnected-tracing
12292 Show the current choice for disconnected tracing.
12296 When you reconnect to the target, the trace experiment may or may not
12297 still be running; it might have filled the trace buffer in the
12298 meantime, or stopped for one of the other reasons. If it is running,
12299 it will continue after reconnection.
12301 Upon reconnection, the target will upload information about the
12302 tracepoints in effect. @value{GDBN} will then compare that
12303 information to the set of tracepoints currently defined, and attempt
12304 to match them up, allowing for the possibility that the numbers may
12305 have changed due to creation and deletion in the meantime. If one of
12306 the target's tracepoints does not match any in @value{GDBN}, the
12307 debugger will create a new tracepoint, so that you have a number with
12308 which to specify that tracepoint. This matching-up process is
12309 necessarily heuristic, and it may result in useless tracepoints being
12310 created; you may simply delete them if they are of no use.
12312 @cindex circular trace buffer
12313 If your target agent supports a @dfn{circular trace buffer}, then you
12314 can run a trace experiment indefinitely without filling the trace
12315 buffer; when space runs out, the agent deletes already-collected trace
12316 frames, oldest first, until there is enough room to continue
12317 collecting. This is especially useful if your tracepoints are being
12318 hit too often, and your trace gets terminated prematurely because the
12319 buffer is full. To ask for a circular trace buffer, simply set
12320 @samp{circular-trace-buffer} to on. You can set this at any time,
12321 including during tracing; if the agent can do it, it will change
12322 buffer handling on the fly, otherwise it will not take effect until
12326 @item set circular-trace-buffer on
12327 @itemx set circular-trace-buffer off
12328 @kindex set circular-trace-buffer
12329 Choose whether a tracing run should use a linear or circular buffer
12330 for trace data. A linear buffer will not lose any trace data, but may
12331 fill up prematurely, while a circular buffer will discard old trace
12332 data, but it will have always room for the latest tracepoint hits.
12334 @item show circular-trace-buffer
12335 @kindex show circular-trace-buffer
12336 Show the current choice for the trace buffer. Note that this may not
12337 match the agent's current buffer handling, nor is it guaranteed to
12338 match the setting that might have been in effect during a past run,
12339 for instance if you are looking at frames from a trace file.
12344 @item set trace-buffer-size @var{n}
12345 @itemx set trace-buffer-size unlimited
12346 @kindex set trace-buffer-size
12347 Request that the target use a trace buffer of @var{n} bytes. Not all
12348 targets will honor the request; they may have a compiled-in size for
12349 the trace buffer, or some other limitation. Set to a value of
12350 @code{unlimited} or @code{-1} to let the target use whatever size it
12351 likes. This is also the default.
12353 @item show trace-buffer-size
12354 @kindex show trace-buffer-size
12355 Show the current requested size for the trace buffer. Note that this
12356 will only match the actual size if the target supports size-setting,
12357 and was able to handle the requested size. For instance, if the
12358 target can only change buffer size between runs, this variable will
12359 not reflect the change until the next run starts. Use @code{tstatus}
12360 to get a report of the actual buffer size.
12364 @item set trace-user @var{text}
12365 @kindex set trace-user
12367 @item show trace-user
12368 @kindex show trace-user
12370 @item set trace-notes @var{text}
12371 @kindex set trace-notes
12372 Set the trace run's notes.
12374 @item show trace-notes
12375 @kindex show trace-notes
12376 Show the trace run's notes.
12378 @item set trace-stop-notes @var{text}
12379 @kindex set trace-stop-notes
12380 Set the trace run's stop notes. The handling of the note is as for
12381 @code{tstop} arguments; the set command is convenient way to fix a
12382 stop note that is mistaken or incomplete.
12384 @item show trace-stop-notes
12385 @kindex show trace-stop-notes
12386 Show the trace run's stop notes.
12390 @node Tracepoint Restrictions
12391 @subsection Tracepoint Restrictions
12393 @cindex tracepoint restrictions
12394 There are a number of restrictions on the use of tracepoints. As
12395 described above, tracepoint data gathering occurs on the target
12396 without interaction from @value{GDBN}. Thus the full capabilities of
12397 the debugger are not available during data gathering, and then at data
12398 examination time, you will be limited by only having what was
12399 collected. The following items describe some common problems, but it
12400 is not exhaustive, and you may run into additional difficulties not
12406 Tracepoint expressions are intended to gather objects (lvalues). Thus
12407 the full flexibility of GDB's expression evaluator is not available.
12408 You cannot call functions, cast objects to aggregate types, access
12409 convenience variables or modify values (except by assignment to trace
12410 state variables). Some language features may implicitly call
12411 functions (for instance Objective-C fields with accessors), and therefore
12412 cannot be collected either.
12415 Collection of local variables, either individually or in bulk with
12416 @code{$locals} or @code{$args}, during @code{while-stepping} may
12417 behave erratically. The stepping action may enter a new scope (for
12418 instance by stepping into a function), or the location of the variable
12419 may change (for instance it is loaded into a register). The
12420 tracepoint data recorded uses the location information for the
12421 variables that is correct for the tracepoint location. When the
12422 tracepoint is created, it is not possible, in general, to determine
12423 where the steps of a @code{while-stepping} sequence will advance the
12424 program---particularly if a conditional branch is stepped.
12427 Collection of an incompletely-initialized or partially-destroyed object
12428 may result in something that @value{GDBN} cannot display, or displays
12429 in a misleading way.
12432 When @value{GDBN} displays a pointer to character it automatically
12433 dereferences the pointer to also display characters of the string
12434 being pointed to. However, collecting the pointer during tracing does
12435 not automatically collect the string. You need to explicitly
12436 dereference the pointer and provide size information if you want to
12437 collect not only the pointer, but the memory pointed to. For example,
12438 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12442 It is not possible to collect a complete stack backtrace at a
12443 tracepoint. Instead, you may collect the registers and a few hundred
12444 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12445 (adjust to use the name of the actual stack pointer register on your
12446 target architecture, and the amount of stack you wish to capture).
12447 Then the @code{backtrace} command will show a partial backtrace when
12448 using a trace frame. The number of stack frames that can be examined
12449 depends on the sizes of the frames in the collected stack. Note that
12450 if you ask for a block so large that it goes past the bottom of the
12451 stack, the target agent may report an error trying to read from an
12455 If you do not collect registers at a tracepoint, @value{GDBN} can
12456 infer that the value of @code{$pc} must be the same as the address of
12457 the tracepoint and use that when you are looking at a trace frame
12458 for that tracepoint. However, this cannot work if the tracepoint has
12459 multiple locations (for instance if it was set in a function that was
12460 inlined), or if it has a @code{while-stepping} loop. In those cases
12461 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12466 @node Analyze Collected Data
12467 @section Using the Collected Data
12469 After the tracepoint experiment ends, you use @value{GDBN} commands
12470 for examining the trace data. The basic idea is that each tracepoint
12471 collects a trace @dfn{snapshot} every time it is hit and another
12472 snapshot every time it single-steps. All these snapshots are
12473 consecutively numbered from zero and go into a buffer, and you can
12474 examine them later. The way you examine them is to @dfn{focus} on a
12475 specific trace snapshot. When the remote stub is focused on a trace
12476 snapshot, it will respond to all @value{GDBN} requests for memory and
12477 registers by reading from the buffer which belongs to that snapshot,
12478 rather than from @emph{real} memory or registers of the program being
12479 debugged. This means that @strong{all} @value{GDBN} commands
12480 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12481 behave as if we were currently debugging the program state as it was
12482 when the tracepoint occurred. Any requests for data that are not in
12483 the buffer will fail.
12486 * tfind:: How to select a trace snapshot
12487 * tdump:: How to display all data for a snapshot
12488 * save tracepoints:: How to save tracepoints for a future run
12492 @subsection @code{tfind @var{n}}
12495 @cindex select trace snapshot
12496 @cindex find trace snapshot
12497 The basic command for selecting a trace snapshot from the buffer is
12498 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12499 counting from zero. If no argument @var{n} is given, the next
12500 snapshot is selected.
12502 Here are the various forms of using the @code{tfind} command.
12506 Find the first snapshot in the buffer. This is a synonym for
12507 @code{tfind 0} (since 0 is the number of the first snapshot).
12510 Stop debugging trace snapshots, resume @emph{live} debugging.
12513 Same as @samp{tfind none}.
12516 No argument means find the next trace snapshot.
12519 Find the previous trace snapshot before the current one. This permits
12520 retracing earlier steps.
12522 @item tfind tracepoint @var{num}
12523 Find the next snapshot associated with tracepoint @var{num}. Search
12524 proceeds forward from the last examined trace snapshot. If no
12525 argument @var{num} is given, it means find the next snapshot collected
12526 for the same tracepoint as the current snapshot.
12528 @item tfind pc @var{addr}
12529 Find the next snapshot associated with the value @var{addr} of the
12530 program counter. Search proceeds forward from the last examined trace
12531 snapshot. If no argument @var{addr} is given, it means find the next
12532 snapshot with the same value of PC as the current snapshot.
12534 @item tfind outside @var{addr1}, @var{addr2}
12535 Find the next snapshot whose PC is outside the given range of
12536 addresses (exclusive).
12538 @item tfind range @var{addr1}, @var{addr2}
12539 Find the next snapshot whose PC is between @var{addr1} and
12540 @var{addr2} (inclusive).
12542 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12543 Find the next snapshot associated with the source line @var{n}. If
12544 the optional argument @var{file} is given, refer to line @var{n} in
12545 that source file. Search proceeds forward from the last examined
12546 trace snapshot. If no argument @var{n} is given, it means find the
12547 next line other than the one currently being examined; thus saying
12548 @code{tfind line} repeatedly can appear to have the same effect as
12549 stepping from line to line in a @emph{live} debugging session.
12552 The default arguments for the @code{tfind} commands are specifically
12553 designed to make it easy to scan through the trace buffer. For
12554 instance, @code{tfind} with no argument selects the next trace
12555 snapshot, and @code{tfind -} with no argument selects the previous
12556 trace snapshot. So, by giving one @code{tfind} command, and then
12557 simply hitting @key{RET} repeatedly you can examine all the trace
12558 snapshots in order. Or, by saying @code{tfind -} and then hitting
12559 @key{RET} repeatedly you can examine the snapshots in reverse order.
12560 The @code{tfind line} command with no argument selects the snapshot
12561 for the next source line executed. The @code{tfind pc} command with
12562 no argument selects the next snapshot with the same program counter
12563 (PC) as the current frame. The @code{tfind tracepoint} command with
12564 no argument selects the next trace snapshot collected by the same
12565 tracepoint as the current one.
12567 In addition to letting you scan through the trace buffer manually,
12568 these commands make it easy to construct @value{GDBN} scripts that
12569 scan through the trace buffer and print out whatever collected data
12570 you are interested in. Thus, if we want to examine the PC, FP, and SP
12571 registers from each trace frame in the buffer, we can say this:
12574 (@value{GDBP}) @b{tfind start}
12575 (@value{GDBP}) @b{while ($trace_frame != -1)}
12576 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12577 $trace_frame, $pc, $sp, $fp
12581 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12582 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12583 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12584 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12585 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12586 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12587 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12588 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12589 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12590 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12591 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12594 Or, if we want to examine the variable @code{X} at each source line in
12598 (@value{GDBP}) @b{tfind start}
12599 (@value{GDBP}) @b{while ($trace_frame != -1)}
12600 > printf "Frame %d, X == %d\n", $trace_frame, X
12610 @subsection @code{tdump}
12612 @cindex dump all data collected at tracepoint
12613 @cindex tracepoint data, display
12615 This command takes no arguments. It prints all the data collected at
12616 the current trace snapshot.
12619 (@value{GDBP}) @b{trace 444}
12620 (@value{GDBP}) @b{actions}
12621 Enter actions for tracepoint #2, one per line:
12622 > collect $regs, $locals, $args, gdb_long_test
12625 (@value{GDBP}) @b{tstart}
12627 (@value{GDBP}) @b{tfind line 444}
12628 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12630 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12632 (@value{GDBP}) @b{tdump}
12633 Data collected at tracepoint 2, trace frame 1:
12634 d0 0xc4aa0085 -995491707
12638 d4 0x71aea3d 119204413
12641 d7 0x380035 3670069
12642 a0 0x19e24a 1696330
12643 a1 0x3000668 50333288
12645 a3 0x322000 3284992
12646 a4 0x3000698 50333336
12647 a5 0x1ad3cc 1758156
12648 fp 0x30bf3c 0x30bf3c
12649 sp 0x30bf34 0x30bf34
12651 pc 0x20b2c8 0x20b2c8
12655 p = 0x20e5b4 "gdb-test"
12662 gdb_long_test = 17 '\021'
12667 @code{tdump} works by scanning the tracepoint's current collection
12668 actions and printing the value of each expression listed. So
12669 @code{tdump} can fail, if after a run, you change the tracepoint's
12670 actions to mention variables that were not collected during the run.
12672 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12673 uses the collected value of @code{$pc} to distinguish between trace
12674 frames that were collected at the tracepoint hit, and frames that were
12675 collected while stepping. This allows it to correctly choose whether
12676 to display the basic list of collections, or the collections from the
12677 body of the while-stepping loop. However, if @code{$pc} was not collected,
12678 then @code{tdump} will always attempt to dump using the basic collection
12679 list, and may fail if a while-stepping frame does not include all the
12680 same data that is collected at the tracepoint hit.
12681 @c This is getting pretty arcane, example would be good.
12683 @node save tracepoints
12684 @subsection @code{save tracepoints @var{filename}}
12685 @kindex save tracepoints
12686 @kindex save-tracepoints
12687 @cindex save tracepoints for future sessions
12689 This command saves all current tracepoint definitions together with
12690 their actions and passcounts, into a file @file{@var{filename}}
12691 suitable for use in a later debugging session. To read the saved
12692 tracepoint definitions, use the @code{source} command (@pxref{Command
12693 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12694 alias for @w{@code{save tracepoints}}
12696 @node Tracepoint Variables
12697 @section Convenience Variables for Tracepoints
12698 @cindex tracepoint variables
12699 @cindex convenience variables for tracepoints
12702 @vindex $trace_frame
12703 @item (int) $trace_frame
12704 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12705 snapshot is selected.
12707 @vindex $tracepoint
12708 @item (int) $tracepoint
12709 The tracepoint for the current trace snapshot.
12711 @vindex $trace_line
12712 @item (int) $trace_line
12713 The line number for the current trace snapshot.
12715 @vindex $trace_file
12716 @item (char []) $trace_file
12717 The source file for the current trace snapshot.
12719 @vindex $trace_func
12720 @item (char []) $trace_func
12721 The name of the function containing @code{$tracepoint}.
12724 Note: @code{$trace_file} is not suitable for use in @code{printf},
12725 use @code{output} instead.
12727 Here's a simple example of using these convenience variables for
12728 stepping through all the trace snapshots and printing some of their
12729 data. Note that these are not the same as trace state variables,
12730 which are managed by the target.
12733 (@value{GDBP}) @b{tfind start}
12735 (@value{GDBP}) @b{while $trace_frame != -1}
12736 > output $trace_file
12737 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12743 @section Using Trace Files
12744 @cindex trace files
12746 In some situations, the target running a trace experiment may no
12747 longer be available; perhaps it crashed, or the hardware was needed
12748 for a different activity. To handle these cases, you can arrange to
12749 dump the trace data into a file, and later use that file as a source
12750 of trace data, via the @code{target tfile} command.
12755 @item tsave [ -r ] @var{filename}
12756 @itemx tsave [-ctf] @var{dirname}
12757 Save the trace data to @var{filename}. By default, this command
12758 assumes that @var{filename} refers to the host filesystem, so if
12759 necessary @value{GDBN} will copy raw trace data up from the target and
12760 then save it. If the target supports it, you can also supply the
12761 optional argument @code{-r} (``remote'') to direct the target to save
12762 the data directly into @var{filename} in its own filesystem, which may be
12763 more efficient if the trace buffer is very large. (Note, however, that
12764 @code{target tfile} can only read from files accessible to the host.)
12765 By default, this command will save trace frame in tfile format.
12766 You can supply the optional argument @code{-ctf} to save date in CTF
12767 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12768 that can be shared by multiple debugging and tracing tools. Please go to
12769 @indicateurl{http://www.efficios.com/ctf} to get more information.
12771 @kindex target tfile
12775 @item target tfile @var{filename}
12776 @itemx target ctf @var{dirname}
12777 Use the file named @var{filename} or directory named @var{dirname} as
12778 a source of trace data. Commands that examine data work as they do with
12779 a live target, but it is not possible to run any new trace experiments.
12780 @code{tstatus} will report the state of the trace run at the moment
12781 the data was saved, as well as the current trace frame you are examining.
12782 @var{filename} or @var{dirname} must be on a filesystem accessible to
12786 (@value{GDBP}) target ctf ctf.ctf
12787 (@value{GDBP}) tfind
12788 Found trace frame 0, tracepoint 2
12789 39 ++a; /* set tracepoint 1 here */
12790 (@value{GDBP}) tdump
12791 Data collected at tracepoint 2, trace frame 0:
12795 c = @{"123", "456", "789", "123", "456", "789"@}
12796 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12804 @chapter Debugging Programs That Use Overlays
12807 If your program is too large to fit completely in your target system's
12808 memory, you can sometimes use @dfn{overlays} to work around this
12809 problem. @value{GDBN} provides some support for debugging programs that
12813 * How Overlays Work:: A general explanation of overlays.
12814 * Overlay Commands:: Managing overlays in @value{GDBN}.
12815 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12816 mapped by asking the inferior.
12817 * Overlay Sample Program:: A sample program using overlays.
12820 @node How Overlays Work
12821 @section How Overlays Work
12822 @cindex mapped overlays
12823 @cindex unmapped overlays
12824 @cindex load address, overlay's
12825 @cindex mapped address
12826 @cindex overlay area
12828 Suppose you have a computer whose instruction address space is only 64
12829 kilobytes long, but which has much more memory which can be accessed by
12830 other means: special instructions, segment registers, or memory
12831 management hardware, for example. Suppose further that you want to
12832 adapt a program which is larger than 64 kilobytes to run on this system.
12834 One solution is to identify modules of your program which are relatively
12835 independent, and need not call each other directly; call these modules
12836 @dfn{overlays}. Separate the overlays from the main program, and place
12837 their machine code in the larger memory. Place your main program in
12838 instruction memory, but leave at least enough space there to hold the
12839 largest overlay as well.
12841 Now, to call a function located in an overlay, you must first copy that
12842 overlay's machine code from the large memory into the space set aside
12843 for it in the instruction memory, and then jump to its entry point
12846 @c NB: In the below the mapped area's size is greater or equal to the
12847 @c size of all overlays. This is intentional to remind the developer
12848 @c that overlays don't necessarily need to be the same size.
12852 Data Instruction Larger
12853 Address Space Address Space Address Space
12854 +-----------+ +-----------+ +-----------+
12856 +-----------+ +-----------+ +-----------+<-- overlay 1
12857 | program | | main | .----| overlay 1 | load address
12858 | variables | | program | | +-----------+
12859 | and heap | | | | | |
12860 +-----------+ | | | +-----------+<-- overlay 2
12861 | | +-----------+ | | | load address
12862 +-----------+ | | | .-| overlay 2 |
12864 mapped --->+-----------+ | | +-----------+
12865 address | | | | | |
12866 | overlay | <-' | | |
12867 | area | <---' +-----------+<-- overlay 3
12868 | | <---. | | load address
12869 +-----------+ `--| overlay 3 |
12876 @anchor{A code overlay}A code overlay
12880 The diagram (@pxref{A code overlay}) shows a system with separate data
12881 and instruction address spaces. To map an overlay, the program copies
12882 its code from the larger address space to the instruction address space.
12883 Since the overlays shown here all use the same mapped address, only one
12884 may be mapped at a time. For a system with a single address space for
12885 data and instructions, the diagram would be similar, except that the
12886 program variables and heap would share an address space with the main
12887 program and the overlay area.
12889 An overlay loaded into instruction memory and ready for use is called a
12890 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12891 instruction memory. An overlay not present (or only partially present)
12892 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12893 is its address in the larger memory. The mapped address is also called
12894 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12895 called the @dfn{load memory address}, or @dfn{LMA}.
12897 Unfortunately, overlays are not a completely transparent way to adapt a
12898 program to limited instruction memory. They introduce a new set of
12899 global constraints you must keep in mind as you design your program:
12904 Before calling or returning to a function in an overlay, your program
12905 must make sure that overlay is actually mapped. Otherwise, the call or
12906 return will transfer control to the right address, but in the wrong
12907 overlay, and your program will probably crash.
12910 If the process of mapping an overlay is expensive on your system, you
12911 will need to choose your overlays carefully to minimize their effect on
12912 your program's performance.
12915 The executable file you load onto your system must contain each
12916 overlay's instructions, appearing at the overlay's load address, not its
12917 mapped address. However, each overlay's instructions must be relocated
12918 and its symbols defined as if the overlay were at its mapped address.
12919 You can use GNU linker scripts to specify different load and relocation
12920 addresses for pieces of your program; see @ref{Overlay Description,,,
12921 ld.info, Using ld: the GNU linker}.
12924 The procedure for loading executable files onto your system must be able
12925 to load their contents into the larger address space as well as the
12926 instruction and data spaces.
12930 The overlay system described above is rather simple, and could be
12931 improved in many ways:
12936 If your system has suitable bank switch registers or memory management
12937 hardware, you could use those facilities to make an overlay's load area
12938 contents simply appear at their mapped address in instruction space.
12939 This would probably be faster than copying the overlay to its mapped
12940 area in the usual way.
12943 If your overlays are small enough, you could set aside more than one
12944 overlay area, and have more than one overlay mapped at a time.
12947 You can use overlays to manage data, as well as instructions. In
12948 general, data overlays are even less transparent to your design than
12949 code overlays: whereas code overlays only require care when you call or
12950 return to functions, data overlays require care every time you access
12951 the data. Also, if you change the contents of a data overlay, you
12952 must copy its contents back out to its load address before you can copy a
12953 different data overlay into the same mapped area.
12958 @node Overlay Commands
12959 @section Overlay Commands
12961 To use @value{GDBN}'s overlay support, each overlay in your program must
12962 correspond to a separate section of the executable file. The section's
12963 virtual memory address and load memory address must be the overlay's
12964 mapped and load addresses. Identifying overlays with sections allows
12965 @value{GDBN} to determine the appropriate address of a function or
12966 variable, depending on whether the overlay is mapped or not.
12968 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12969 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12974 Disable @value{GDBN}'s overlay support. When overlay support is
12975 disabled, @value{GDBN} assumes that all functions and variables are
12976 always present at their mapped addresses. By default, @value{GDBN}'s
12977 overlay support is disabled.
12979 @item overlay manual
12980 @cindex manual overlay debugging
12981 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12982 relies on you to tell it which overlays are mapped, and which are not,
12983 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12984 commands described below.
12986 @item overlay map-overlay @var{overlay}
12987 @itemx overlay map @var{overlay}
12988 @cindex map an overlay
12989 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12990 be the name of the object file section containing the overlay. When an
12991 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12992 functions and variables at their mapped addresses. @value{GDBN} assumes
12993 that any other overlays whose mapped ranges overlap that of
12994 @var{overlay} are now unmapped.
12996 @item overlay unmap-overlay @var{overlay}
12997 @itemx overlay unmap @var{overlay}
12998 @cindex unmap an overlay
12999 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13000 must be the name of the object file section containing the overlay.
13001 When an overlay is unmapped, @value{GDBN} assumes it can find the
13002 overlay's functions and variables at their load addresses.
13005 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13006 consults a data structure the overlay manager maintains in the inferior
13007 to see which overlays are mapped. For details, see @ref{Automatic
13008 Overlay Debugging}.
13010 @item overlay load-target
13011 @itemx overlay load
13012 @cindex reloading the overlay table
13013 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13014 re-reads the table @value{GDBN} automatically each time the inferior
13015 stops, so this command should only be necessary if you have changed the
13016 overlay mapping yourself using @value{GDBN}. This command is only
13017 useful when using automatic overlay debugging.
13019 @item overlay list-overlays
13020 @itemx overlay list
13021 @cindex listing mapped overlays
13022 Display a list of the overlays currently mapped, along with their mapped
13023 addresses, load addresses, and sizes.
13027 Normally, when @value{GDBN} prints a code address, it includes the name
13028 of the function the address falls in:
13031 (@value{GDBP}) print main
13032 $3 = @{int ()@} 0x11a0 <main>
13035 When overlay debugging is enabled, @value{GDBN} recognizes code in
13036 unmapped overlays, and prints the names of unmapped functions with
13037 asterisks around them. For example, if @code{foo} is a function in an
13038 unmapped overlay, @value{GDBN} prints it this way:
13041 (@value{GDBP}) overlay list
13042 No sections are mapped.
13043 (@value{GDBP}) print foo
13044 $5 = @{int (int)@} 0x100000 <*foo*>
13047 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13051 (@value{GDBP}) overlay list
13052 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13053 mapped at 0x1016 - 0x104a
13054 (@value{GDBP}) print foo
13055 $6 = @{int (int)@} 0x1016 <foo>
13058 When overlay debugging is enabled, @value{GDBN} can find the correct
13059 address for functions and variables in an overlay, whether or not the
13060 overlay is mapped. This allows most @value{GDBN} commands, like
13061 @code{break} and @code{disassemble}, to work normally, even on unmapped
13062 code. However, @value{GDBN}'s breakpoint support has some limitations:
13066 @cindex breakpoints in overlays
13067 @cindex overlays, setting breakpoints in
13068 You can set breakpoints in functions in unmapped overlays, as long as
13069 @value{GDBN} can write to the overlay at its load address.
13071 @value{GDBN} can not set hardware or simulator-based breakpoints in
13072 unmapped overlays. However, if you set a breakpoint at the end of your
13073 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13074 you are using manual overlay management), @value{GDBN} will re-set its
13075 breakpoints properly.
13079 @node Automatic Overlay Debugging
13080 @section Automatic Overlay Debugging
13081 @cindex automatic overlay debugging
13083 @value{GDBN} can automatically track which overlays are mapped and which
13084 are not, given some simple co-operation from the overlay manager in the
13085 inferior. If you enable automatic overlay debugging with the
13086 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13087 looks in the inferior's memory for certain variables describing the
13088 current state of the overlays.
13090 Here are the variables your overlay manager must define to support
13091 @value{GDBN}'s automatic overlay debugging:
13095 @item @code{_ovly_table}:
13096 This variable must be an array of the following structures:
13101 /* The overlay's mapped address. */
13104 /* The size of the overlay, in bytes. */
13105 unsigned long size;
13107 /* The overlay's load address. */
13110 /* Non-zero if the overlay is currently mapped;
13112 unsigned long mapped;
13116 @item @code{_novlys}:
13117 This variable must be a four-byte signed integer, holding the total
13118 number of elements in @code{_ovly_table}.
13122 To decide whether a particular overlay is mapped or not, @value{GDBN}
13123 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13124 @code{lma} members equal the VMA and LMA of the overlay's section in the
13125 executable file. When @value{GDBN} finds a matching entry, it consults
13126 the entry's @code{mapped} member to determine whether the overlay is
13129 In addition, your overlay manager may define a function called
13130 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13131 will silently set a breakpoint there. If the overlay manager then
13132 calls this function whenever it has changed the overlay table, this
13133 will enable @value{GDBN} to accurately keep track of which overlays
13134 are in program memory, and update any breakpoints that may be set
13135 in overlays. This will allow breakpoints to work even if the
13136 overlays are kept in ROM or other non-writable memory while they
13137 are not being executed.
13139 @node Overlay Sample Program
13140 @section Overlay Sample Program
13141 @cindex overlay example program
13143 When linking a program which uses overlays, you must place the overlays
13144 at their load addresses, while relocating them to run at their mapped
13145 addresses. To do this, you must write a linker script (@pxref{Overlay
13146 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13147 since linker scripts are specific to a particular host system, target
13148 architecture, and target memory layout, this manual cannot provide
13149 portable sample code demonstrating @value{GDBN}'s overlay support.
13151 However, the @value{GDBN} source distribution does contain an overlaid
13152 program, with linker scripts for a few systems, as part of its test
13153 suite. The program consists of the following files from
13154 @file{gdb/testsuite/gdb.base}:
13158 The main program file.
13160 A simple overlay manager, used by @file{overlays.c}.
13165 Overlay modules, loaded and used by @file{overlays.c}.
13168 Linker scripts for linking the test program on the @code{d10v-elf}
13169 and @code{m32r-elf} targets.
13172 You can build the test program using the @code{d10v-elf} GCC
13173 cross-compiler like this:
13176 $ d10v-elf-gcc -g -c overlays.c
13177 $ d10v-elf-gcc -g -c ovlymgr.c
13178 $ d10v-elf-gcc -g -c foo.c
13179 $ d10v-elf-gcc -g -c bar.c
13180 $ d10v-elf-gcc -g -c baz.c
13181 $ d10v-elf-gcc -g -c grbx.c
13182 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13183 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13186 The build process is identical for any other architecture, except that
13187 you must substitute the appropriate compiler and linker script for the
13188 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13192 @chapter Using @value{GDBN} with Different Languages
13195 Although programming languages generally have common aspects, they are
13196 rarely expressed in the same manner. For instance, in ANSI C,
13197 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13198 Modula-2, it is accomplished by @code{p^}. Values can also be
13199 represented (and displayed) differently. Hex numbers in C appear as
13200 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13202 @cindex working language
13203 Language-specific information is built into @value{GDBN} for some languages,
13204 allowing you to express operations like the above in your program's
13205 native language, and allowing @value{GDBN} to output values in a manner
13206 consistent with the syntax of your program's native language. The
13207 language you use to build expressions is called the @dfn{working
13211 * Setting:: Switching between source languages
13212 * Show:: Displaying the language
13213 * Checks:: Type and range checks
13214 * Supported Languages:: Supported languages
13215 * Unsupported Languages:: Unsupported languages
13219 @section Switching Between Source Languages
13221 There are two ways to control the working language---either have @value{GDBN}
13222 set it automatically, or select it manually yourself. You can use the
13223 @code{set language} command for either purpose. On startup, @value{GDBN}
13224 defaults to setting the language automatically. The working language is
13225 used to determine how expressions you type are interpreted, how values
13228 In addition to the working language, every source file that
13229 @value{GDBN} knows about has its own working language. For some object
13230 file formats, the compiler might indicate which language a particular
13231 source file is in. However, most of the time @value{GDBN} infers the
13232 language from the name of the file. The language of a source file
13233 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13234 show each frame appropriately for its own language. There is no way to
13235 set the language of a source file from within @value{GDBN}, but you can
13236 set the language associated with a filename extension. @xref{Show, ,
13237 Displaying the Language}.
13239 This is most commonly a problem when you use a program, such
13240 as @code{cfront} or @code{f2c}, that generates C but is written in
13241 another language. In that case, make the
13242 program use @code{#line} directives in its C output; that way
13243 @value{GDBN} will know the correct language of the source code of the original
13244 program, and will display that source code, not the generated C code.
13247 * Filenames:: Filename extensions and languages.
13248 * Manually:: Setting the working language manually
13249 * Automatically:: Having @value{GDBN} infer the source language
13253 @subsection List of Filename Extensions and Languages
13255 If a source file name ends in one of the following extensions, then
13256 @value{GDBN} infers that its language is the one indicated.
13274 C@t{++} source file
13280 Objective-C source file
13284 Fortran source file
13287 Modula-2 source file
13291 Assembler source file. This actually behaves almost like C, but
13292 @value{GDBN} does not skip over function prologues when stepping.
13295 In addition, you may set the language associated with a filename
13296 extension. @xref{Show, , Displaying the Language}.
13299 @subsection Setting the Working Language
13301 If you allow @value{GDBN} to set the language automatically,
13302 expressions are interpreted the same way in your debugging session and
13305 @kindex set language
13306 If you wish, you may set the language manually. To do this, issue the
13307 command @samp{set language @var{lang}}, where @var{lang} is the name of
13308 a language, such as
13309 @code{c} or @code{modula-2}.
13310 For a list of the supported languages, type @samp{set language}.
13312 Setting the language manually prevents @value{GDBN} from updating the working
13313 language automatically. This can lead to confusion if you try
13314 to debug a program when the working language is not the same as the
13315 source language, when an expression is acceptable to both
13316 languages---but means different things. For instance, if the current
13317 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13325 might not have the effect you intended. In C, this means to add
13326 @code{b} and @code{c} and place the result in @code{a}. The result
13327 printed would be the value of @code{a}. In Modula-2, this means to compare
13328 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13330 @node Automatically
13331 @subsection Having @value{GDBN} Infer the Source Language
13333 To have @value{GDBN} set the working language automatically, use
13334 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13335 then infers the working language. That is, when your program stops in a
13336 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13337 working language to the language recorded for the function in that
13338 frame. If the language for a frame is unknown (that is, if the function
13339 or block corresponding to the frame was defined in a source file that
13340 does not have a recognized extension), the current working language is
13341 not changed, and @value{GDBN} issues a warning.
13343 This may not seem necessary for most programs, which are written
13344 entirely in one source language. However, program modules and libraries
13345 written in one source language can be used by a main program written in
13346 a different source language. Using @samp{set language auto} in this
13347 case frees you from having to set the working language manually.
13350 @section Displaying the Language
13352 The following commands help you find out which language is the
13353 working language, and also what language source files were written in.
13356 @item show language
13357 @anchor{show language}
13358 @kindex show language
13359 Display the current working language. This is the
13360 language you can use with commands such as @code{print} to
13361 build and compute expressions that may involve variables in your program.
13364 @kindex info frame@r{, show the source language}
13365 Display the source language for this frame. This language becomes the
13366 working language if you use an identifier from this frame.
13367 @xref{Frame Info, ,Information about a Frame}, to identify the other
13368 information listed here.
13371 @kindex info source@r{, show the source language}
13372 Display the source language of this source file.
13373 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13374 information listed here.
13377 In unusual circumstances, you may have source files with extensions
13378 not in the standard list. You can then set the extension associated
13379 with a language explicitly:
13382 @item set extension-language @var{ext} @var{language}
13383 @kindex set extension-language
13384 Tell @value{GDBN} that source files with extension @var{ext} are to be
13385 assumed as written in the source language @var{language}.
13387 @item info extensions
13388 @kindex info extensions
13389 List all the filename extensions and the associated languages.
13393 @section Type and Range Checking
13395 Some languages are designed to guard you against making seemingly common
13396 errors through a series of compile- and run-time checks. These include
13397 checking the type of arguments to functions and operators and making
13398 sure mathematical overflows are caught at run time. Checks such as
13399 these help to ensure a program's correctness once it has been compiled
13400 by eliminating type mismatches and providing active checks for range
13401 errors when your program is running.
13403 By default @value{GDBN} checks for these errors according to the
13404 rules of the current source language. Although @value{GDBN} does not check
13405 the statements in your program, it can check expressions entered directly
13406 into @value{GDBN} for evaluation via the @code{print} command, for example.
13409 * Type Checking:: An overview of type checking
13410 * Range Checking:: An overview of range checking
13413 @cindex type checking
13414 @cindex checks, type
13415 @node Type Checking
13416 @subsection An Overview of Type Checking
13418 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13419 arguments to operators and functions have to be of the correct type,
13420 otherwise an error occurs. These checks prevent type mismatch
13421 errors from ever causing any run-time problems. For example,
13424 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13426 (@value{GDBP}) print obj.my_method (0)
13429 (@value{GDBP}) print obj.my_method (0x1234)
13430 Cannot resolve method klass::my_method to any overloaded instance
13433 The second example fails because in C@t{++} the integer constant
13434 @samp{0x1234} is not type-compatible with the pointer parameter type.
13436 For the expressions you use in @value{GDBN} commands, you can tell
13437 @value{GDBN} to not enforce strict type checking or
13438 to treat any mismatches as errors and abandon the expression;
13439 When type checking is disabled, @value{GDBN} successfully evaluates
13440 expressions like the second example above.
13442 Even if type checking is off, there may be other reasons
13443 related to type that prevent @value{GDBN} from evaluating an expression.
13444 For instance, @value{GDBN} does not know how to add an @code{int} and
13445 a @code{struct foo}. These particular type errors have nothing to do
13446 with the language in use and usually arise from expressions which make
13447 little sense to evaluate anyway.
13449 @value{GDBN} provides some additional commands for controlling type checking:
13451 @kindex set check type
13452 @kindex show check type
13454 @item set check type on
13455 @itemx set check type off
13456 Set strict type checking on or off. If any type mismatches occur in
13457 evaluating an expression while type checking is on, @value{GDBN} prints a
13458 message and aborts evaluation of the expression.
13460 @item show check type
13461 Show the current setting of type checking and whether @value{GDBN}
13462 is enforcing strict type checking rules.
13465 @cindex range checking
13466 @cindex checks, range
13467 @node Range Checking
13468 @subsection An Overview of Range Checking
13470 In some languages (such as Modula-2), it is an error to exceed the
13471 bounds of a type; this is enforced with run-time checks. Such range
13472 checking is meant to ensure program correctness by making sure
13473 computations do not overflow, or indices on an array element access do
13474 not exceed the bounds of the array.
13476 For expressions you use in @value{GDBN} commands, you can tell
13477 @value{GDBN} to treat range errors in one of three ways: ignore them,
13478 always treat them as errors and abandon the expression, or issue
13479 warnings but evaluate the expression anyway.
13481 A range error can result from numerical overflow, from exceeding an
13482 array index bound, or when you type a constant that is not a member
13483 of any type. Some languages, however, do not treat overflows as an
13484 error. In many implementations of C, mathematical overflow causes the
13485 result to ``wrap around'' to lower values---for example, if @var{m} is
13486 the largest integer value, and @var{s} is the smallest, then
13489 @var{m} + 1 @result{} @var{s}
13492 This, too, is specific to individual languages, and in some cases
13493 specific to individual compilers or machines. @xref{Supported Languages, ,
13494 Supported Languages}, for further details on specific languages.
13496 @value{GDBN} provides some additional commands for controlling the range checker:
13498 @kindex set check range
13499 @kindex show check range
13501 @item set check range auto
13502 Set range checking on or off based on the current working language.
13503 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13506 @item set check range on
13507 @itemx set check range off
13508 Set range checking on or off, overriding the default setting for the
13509 current working language. A warning is issued if the setting does not
13510 match the language default. If a range error occurs and range checking is on,
13511 then a message is printed and evaluation of the expression is aborted.
13513 @item set check range warn
13514 Output messages when the @value{GDBN} range checker detects a range error,
13515 but attempt to evaluate the expression anyway. Evaluating the
13516 expression may still be impossible for other reasons, such as accessing
13517 memory that the process does not own (a typical example from many Unix
13521 Show the current setting of the range checker, and whether or not it is
13522 being set automatically by @value{GDBN}.
13525 @node Supported Languages
13526 @section Supported Languages
13528 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13529 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13530 @c This is false ...
13531 Some @value{GDBN} features may be used in expressions regardless of the
13532 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13533 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13534 ,Expressions}) can be used with the constructs of any supported
13537 The following sections detail to what degree each source language is
13538 supported by @value{GDBN}. These sections are not meant to be language
13539 tutorials or references, but serve only as a reference guide to what the
13540 @value{GDBN} expression parser accepts, and what input and output
13541 formats should look like for different languages. There are many good
13542 books written on each of these languages; please look to these for a
13543 language reference or tutorial.
13546 * C:: C and C@t{++}
13549 * Objective-C:: Objective-C
13550 * OpenCL C:: OpenCL C
13551 * Fortran:: Fortran
13553 * Modula-2:: Modula-2
13558 @subsection C and C@t{++}
13560 @cindex C and C@t{++}
13561 @cindex expressions in C or C@t{++}
13563 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13564 to both languages. Whenever this is the case, we discuss those languages
13568 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13569 @cindex @sc{gnu} C@t{++}
13570 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13571 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13572 effectively, you must compile your C@t{++} programs with a supported
13573 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13574 compiler (@code{aCC}).
13577 * C Operators:: C and C@t{++} operators
13578 * C Constants:: C and C@t{++} constants
13579 * C Plus Plus Expressions:: C@t{++} expressions
13580 * C Defaults:: Default settings for C and C@t{++}
13581 * C Checks:: C and C@t{++} type and range checks
13582 * Debugging C:: @value{GDBN} and C
13583 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13584 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13588 @subsubsection C and C@t{++} Operators
13590 @cindex C and C@t{++} operators
13592 Operators must be defined on values of specific types. For instance,
13593 @code{+} is defined on numbers, but not on structures. Operators are
13594 often defined on groups of types.
13596 For the purposes of C and C@t{++}, the following definitions hold:
13601 @emph{Integral types} include @code{int} with any of its storage-class
13602 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13605 @emph{Floating-point types} include @code{float}, @code{double}, and
13606 @code{long double} (if supported by the target platform).
13609 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13612 @emph{Scalar types} include all of the above.
13617 The following operators are supported. They are listed here
13618 in order of increasing precedence:
13622 The comma or sequencing operator. Expressions in a comma-separated list
13623 are evaluated from left to right, with the result of the entire
13624 expression being the last expression evaluated.
13627 Assignment. The value of an assignment expression is the value
13628 assigned. Defined on scalar types.
13631 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13632 and translated to @w{@code{@var{a} = @var{a op b}}}.
13633 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13634 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13635 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13638 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13639 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13643 Logical @sc{or}. Defined on integral types.
13646 Logical @sc{and}. Defined on integral types.
13649 Bitwise @sc{or}. Defined on integral types.
13652 Bitwise exclusive-@sc{or}. Defined on integral types.
13655 Bitwise @sc{and}. Defined on integral types.
13658 Equality and inequality. Defined on scalar types. The value of these
13659 expressions is 0 for false and non-zero for true.
13661 @item <@r{, }>@r{, }<=@r{, }>=
13662 Less than, greater than, less than or equal, greater than or equal.
13663 Defined on scalar types. The value of these expressions is 0 for false
13664 and non-zero for true.
13667 left shift, and right shift. Defined on integral types.
13670 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13673 Addition and subtraction. Defined on integral types, floating-point types and
13676 @item *@r{, }/@r{, }%
13677 Multiplication, division, and modulus. Multiplication and division are
13678 defined on integral and floating-point types. Modulus is defined on
13682 Increment and decrement. When appearing before a variable, the
13683 operation is performed before the variable is used in an expression;
13684 when appearing after it, the variable's value is used before the
13685 operation takes place.
13688 Pointer dereferencing. Defined on pointer types. Same precedence as
13692 Address operator. Defined on variables. Same precedence as @code{++}.
13694 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13695 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13696 to examine the address
13697 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13701 Negative. Defined on integral and floating-point types. Same
13702 precedence as @code{++}.
13705 Logical negation. Defined on integral types. Same precedence as
13709 Bitwise complement operator. Defined on integral types. Same precedence as
13714 Structure member, and pointer-to-structure member. For convenience,
13715 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13716 pointer based on the stored type information.
13717 Defined on @code{struct} and @code{union} data.
13720 Dereferences of pointers to members.
13723 Array indexing. @code{@var{a}[@var{i}]} is defined as
13724 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13727 Function parameter list. Same precedence as @code{->}.
13730 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13731 and @code{class} types.
13734 Doubled colons also represent the @value{GDBN} scope operator
13735 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13739 If an operator is redefined in the user code, @value{GDBN} usually
13740 attempts to invoke the redefined version instead of using the operator's
13741 predefined meaning.
13744 @subsubsection C and C@t{++} Constants
13746 @cindex C and C@t{++} constants
13748 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13753 Integer constants are a sequence of digits. Octal constants are
13754 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13755 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13756 @samp{l}, specifying that the constant should be treated as a
13760 Floating point constants are a sequence of digits, followed by a decimal
13761 point, followed by a sequence of digits, and optionally followed by an
13762 exponent. An exponent is of the form:
13763 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13764 sequence of digits. The @samp{+} is optional for positive exponents.
13765 A floating-point constant may also end with a letter @samp{f} or
13766 @samp{F}, specifying that the constant should be treated as being of
13767 the @code{float} (as opposed to the default @code{double}) type; or with
13768 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13772 Enumerated constants consist of enumerated identifiers, or their
13773 integral equivalents.
13776 Character constants are a single character surrounded by single quotes
13777 (@code{'}), or a number---the ordinal value of the corresponding character
13778 (usually its @sc{ascii} value). Within quotes, the single character may
13779 be represented by a letter or by @dfn{escape sequences}, which are of
13780 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13781 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13782 @samp{@var{x}} is a predefined special character---for example,
13783 @samp{\n} for newline.
13785 Wide character constants can be written by prefixing a character
13786 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13787 form of @samp{x}. The target wide character set is used when
13788 computing the value of this constant (@pxref{Character Sets}).
13791 String constants are a sequence of character constants surrounded by
13792 double quotes (@code{"}). Any valid character constant (as described
13793 above) may appear. Double quotes within the string must be preceded by
13794 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13797 Wide string constants can be written by prefixing a string constant
13798 with @samp{L}, as in C. The target wide character set is used when
13799 computing the value of this constant (@pxref{Character Sets}).
13802 Pointer constants are an integral value. You can also write pointers
13803 to constants using the C operator @samp{&}.
13806 Array constants are comma-separated lists surrounded by braces @samp{@{}
13807 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13808 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13809 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13812 @node C Plus Plus Expressions
13813 @subsubsection C@t{++} Expressions
13815 @cindex expressions in C@t{++}
13816 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13818 @cindex debugging C@t{++} programs
13819 @cindex C@t{++} compilers
13820 @cindex debug formats and C@t{++}
13821 @cindex @value{NGCC} and C@t{++}
13823 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13824 the proper compiler and the proper debug format. Currently,
13825 @value{GDBN} works best when debugging C@t{++} code that is compiled
13826 with the most recent version of @value{NGCC} possible. The DWARF
13827 debugging format is preferred; @value{NGCC} defaults to this on most
13828 popular platforms. Other compilers and/or debug formats are likely to
13829 work badly or not at all when using @value{GDBN} to debug C@t{++}
13830 code. @xref{Compilation}.
13835 @cindex member functions
13837 Member function calls are allowed; you can use expressions like
13840 count = aml->GetOriginal(x, y)
13843 @vindex this@r{, inside C@t{++} member functions}
13844 @cindex namespace in C@t{++}
13846 While a member function is active (in the selected stack frame), your
13847 expressions have the same namespace available as the member function;
13848 that is, @value{GDBN} allows implicit references to the class instance
13849 pointer @code{this} following the same rules as C@t{++}. @code{using}
13850 declarations in the current scope are also respected by @value{GDBN}.
13852 @cindex call overloaded functions
13853 @cindex overloaded functions, calling
13854 @cindex type conversions in C@t{++}
13856 You can call overloaded functions; @value{GDBN} resolves the function
13857 call to the right definition, with some restrictions. @value{GDBN} does not
13858 perform overload resolution involving user-defined type conversions,
13859 calls to constructors, or instantiations of templates that do not exist
13860 in the program. It also cannot handle ellipsis argument lists or
13863 It does perform integral conversions and promotions, floating-point
13864 promotions, arithmetic conversions, pointer conversions, conversions of
13865 class objects to base classes, and standard conversions such as those of
13866 functions or arrays to pointers; it requires an exact match on the
13867 number of function arguments.
13869 Overload resolution is always performed, unless you have specified
13870 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13871 ,@value{GDBN} Features for C@t{++}}.
13873 You must specify @code{set overload-resolution off} in order to use an
13874 explicit function signature to call an overloaded function, as in
13876 p 'foo(char,int)'('x', 13)
13879 The @value{GDBN} command-completion facility can simplify this;
13880 see @ref{Completion, ,Command Completion}.
13882 @cindex reference declarations
13884 @value{GDBN} understands variables declared as C@t{++} references; you can use
13885 them in expressions just as you do in C@t{++} source---they are automatically
13888 In the parameter list shown when @value{GDBN} displays a frame, the values of
13889 reference variables are not displayed (unlike other variables); this
13890 avoids clutter, since references are often used for large structures.
13891 The @emph{address} of a reference variable is always shown, unless
13892 you have specified @samp{set print address off}.
13895 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13896 expressions can use it just as expressions in your program do. Since
13897 one scope may be defined in another, you can use @code{::} repeatedly if
13898 necessary, for example in an expression like
13899 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13900 resolving name scope by reference to source files, in both C and C@t{++}
13901 debugging (@pxref{Variables, ,Program Variables}).
13904 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13909 @subsubsection C and C@t{++} Defaults
13911 @cindex C and C@t{++} defaults
13913 If you allow @value{GDBN} to set range checking automatically, it
13914 defaults to @code{off} whenever the working language changes to
13915 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13916 selects the working language.
13918 If you allow @value{GDBN} to set the language automatically, it
13919 recognizes source files whose names end with @file{.c}, @file{.C}, or
13920 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13921 these files, it sets the working language to C or C@t{++}.
13922 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13923 for further details.
13926 @subsubsection C and C@t{++} Type and Range Checks
13928 @cindex C and C@t{++} checks
13930 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13931 checking is used. However, if you turn type checking off, @value{GDBN}
13932 will allow certain non-standard conversions, such as promoting integer
13933 constants to pointers.
13935 Range checking, if turned on, is done on mathematical operations. Array
13936 indices are not checked, since they are often used to index a pointer
13937 that is not itself an array.
13940 @subsubsection @value{GDBN} and C
13942 The @code{set print union} and @code{show print union} commands apply to
13943 the @code{union} type. When set to @samp{on}, any @code{union} that is
13944 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13945 appears as @samp{@{...@}}.
13947 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13948 with pointers and a memory allocation function. @xref{Expressions,
13951 @node Debugging C Plus Plus
13952 @subsubsection @value{GDBN} Features for C@t{++}
13954 @cindex commands for C@t{++}
13956 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13957 designed specifically for use with C@t{++}. Here is a summary:
13960 @cindex break in overloaded functions
13961 @item @r{breakpoint menus}
13962 When you want a breakpoint in a function whose name is overloaded,
13963 @value{GDBN} has the capability to display a menu of possible breakpoint
13964 locations to help you specify which function definition you want.
13965 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13967 @cindex overloading in C@t{++}
13968 @item rbreak @var{regex}
13969 Setting breakpoints using regular expressions is helpful for setting
13970 breakpoints on overloaded functions that are not members of any special
13972 @xref{Set Breaks, ,Setting Breakpoints}.
13974 @cindex C@t{++} exception handling
13976 @itemx catch rethrow
13978 Debug C@t{++} exception handling using these commands. @xref{Set
13979 Catchpoints, , Setting Catchpoints}.
13981 @cindex inheritance
13982 @item ptype @var{typename}
13983 Print inheritance relationships as well as other information for type
13985 @xref{Symbols, ,Examining the Symbol Table}.
13987 @item info vtbl @var{expression}.
13988 The @code{info vtbl} command can be used to display the virtual
13989 method tables of the object computed by @var{expression}. This shows
13990 one entry per virtual table; there may be multiple virtual tables when
13991 multiple inheritance is in use.
13993 @cindex C@t{++} symbol display
13994 @item set print demangle
13995 @itemx show print demangle
13996 @itemx set print asm-demangle
13997 @itemx show print asm-demangle
13998 Control whether C@t{++} symbols display in their source form, both when
13999 displaying code as C@t{++} source and when displaying disassemblies.
14000 @xref{Print Settings, ,Print Settings}.
14002 @item set print object
14003 @itemx show print object
14004 Choose whether to print derived (actual) or declared types of objects.
14005 @xref{Print Settings, ,Print Settings}.
14007 @item set print vtbl
14008 @itemx show print vtbl
14009 Control the format for printing virtual function tables.
14010 @xref{Print Settings, ,Print Settings}.
14011 (The @code{vtbl} commands do not work on programs compiled with the HP
14012 ANSI C@t{++} compiler (@code{aCC}).)
14014 @kindex set overload-resolution
14015 @cindex overloaded functions, overload resolution
14016 @item set overload-resolution on
14017 Enable overload resolution for C@t{++} expression evaluation. The default
14018 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14019 and searches for a function whose signature matches the argument types,
14020 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14021 Expressions, ,C@t{++} Expressions}, for details).
14022 If it cannot find a match, it emits a message.
14024 @item set overload-resolution off
14025 Disable overload resolution for C@t{++} expression evaluation. For
14026 overloaded functions that are not class member functions, @value{GDBN}
14027 chooses the first function of the specified name that it finds in the
14028 symbol table, whether or not its arguments are of the correct type. For
14029 overloaded functions that are class member functions, @value{GDBN}
14030 searches for a function whose signature @emph{exactly} matches the
14033 @kindex show overload-resolution
14034 @item show overload-resolution
14035 Show the current setting of overload resolution.
14037 @item @r{Overloaded symbol names}
14038 You can specify a particular definition of an overloaded symbol, using
14039 the same notation that is used to declare such symbols in C@t{++}: type
14040 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14041 also use the @value{GDBN} command-line word completion facilities to list the
14042 available choices, or to finish the type list for you.
14043 @xref{Completion,, Command Completion}, for details on how to do this.
14046 @node Decimal Floating Point
14047 @subsubsection Decimal Floating Point format
14048 @cindex decimal floating point format
14050 @value{GDBN} can examine, set and perform computations with numbers in
14051 decimal floating point format, which in the C language correspond to the
14052 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14053 specified by the extension to support decimal floating-point arithmetic.
14055 There are two encodings in use, depending on the architecture: BID (Binary
14056 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14057 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14060 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14061 to manipulate decimal floating point numbers, it is not possible to convert
14062 (using a cast, for example) integers wider than 32-bit to decimal float.
14064 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14065 point computations, error checking in decimal float operations ignores
14066 underflow, overflow and divide by zero exceptions.
14068 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14069 to inspect @code{_Decimal128} values stored in floating point registers.
14070 See @ref{PowerPC,,PowerPC} for more details.
14076 @value{GDBN} can be used to debug programs written in D and compiled with
14077 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14078 specific feature --- dynamic arrays.
14083 @cindex Go (programming language)
14084 @value{GDBN} can be used to debug programs written in Go and compiled with
14085 @file{gccgo} or @file{6g} compilers.
14087 Here is a summary of the Go-specific features and restrictions:
14090 @cindex current Go package
14091 @item The current Go package
14092 The name of the current package does not need to be specified when
14093 specifying global variables and functions.
14095 For example, given the program:
14099 var myglob = "Shall we?"
14105 When stopped inside @code{main} either of these work:
14109 (gdb) p main.myglob
14112 @cindex builtin Go types
14113 @item Builtin Go types
14114 The @code{string} type is recognized by @value{GDBN} and is printed
14117 @cindex builtin Go functions
14118 @item Builtin Go functions
14119 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14120 function and handles it internally.
14122 @cindex restrictions on Go expressions
14123 @item Restrictions on Go expressions
14124 All Go operators are supported except @code{&^}.
14125 The Go @code{_} ``blank identifier'' is not supported.
14126 Automatic dereferencing of pointers is not supported.
14130 @subsection Objective-C
14132 @cindex Objective-C
14133 This section provides information about some commands and command
14134 options that are useful for debugging Objective-C code. See also
14135 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14136 few more commands specific to Objective-C support.
14139 * Method Names in Commands::
14140 * The Print Command with Objective-C::
14143 @node Method Names in Commands
14144 @subsubsection Method Names in Commands
14146 The following commands have been extended to accept Objective-C method
14147 names as line specifications:
14149 @kindex clear@r{, and Objective-C}
14150 @kindex break@r{, and Objective-C}
14151 @kindex info line@r{, and Objective-C}
14152 @kindex jump@r{, and Objective-C}
14153 @kindex list@r{, and Objective-C}
14157 @item @code{info line}
14162 A fully qualified Objective-C method name is specified as
14165 -[@var{Class} @var{methodName}]
14168 where the minus sign is used to indicate an instance method and a
14169 plus sign (not shown) is used to indicate a class method. The class
14170 name @var{Class} and method name @var{methodName} are enclosed in
14171 brackets, similar to the way messages are specified in Objective-C
14172 source code. For example, to set a breakpoint at the @code{create}
14173 instance method of class @code{Fruit} in the program currently being
14177 break -[Fruit create]
14180 To list ten program lines around the @code{initialize} class method,
14184 list +[NSText initialize]
14187 In the current version of @value{GDBN}, the plus or minus sign is
14188 required. In future versions of @value{GDBN}, the plus or minus
14189 sign will be optional, but you can use it to narrow the search. It
14190 is also possible to specify just a method name:
14196 You must specify the complete method name, including any colons. If
14197 your program's source files contain more than one @code{create} method,
14198 you'll be presented with a numbered list of classes that implement that
14199 method. Indicate your choice by number, or type @samp{0} to exit if
14202 As another example, to clear a breakpoint established at the
14203 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14206 clear -[NSWindow makeKeyAndOrderFront:]
14209 @node The Print Command with Objective-C
14210 @subsubsection The Print Command With Objective-C
14211 @cindex Objective-C, print objects
14212 @kindex print-object
14213 @kindex po @r{(@code{print-object})}
14215 The print command has also been extended to accept methods. For example:
14218 print -[@var{object} hash]
14221 @cindex print an Objective-C object description
14222 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14224 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14225 and print the result. Also, an additional command has been added,
14226 @code{print-object} or @code{po} for short, which is meant to print
14227 the description of an object. However, this command may only work
14228 with certain Objective-C libraries that have a particular hook
14229 function, @code{_NSPrintForDebugger}, defined.
14232 @subsection OpenCL C
14235 This section provides information about @value{GDBN}s OpenCL C support.
14238 * OpenCL C Datatypes::
14239 * OpenCL C Expressions::
14240 * OpenCL C Operators::
14243 @node OpenCL C Datatypes
14244 @subsubsection OpenCL C Datatypes
14246 @cindex OpenCL C Datatypes
14247 @value{GDBN} supports the builtin scalar and vector datatypes specified
14248 by OpenCL 1.1. In addition the half- and double-precision floating point
14249 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14250 extensions are also known to @value{GDBN}.
14252 @node OpenCL C Expressions
14253 @subsubsection OpenCL C Expressions
14255 @cindex OpenCL C Expressions
14256 @value{GDBN} supports accesses to vector components including the access as
14257 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14258 supported by @value{GDBN} can be used as well.
14260 @node OpenCL C Operators
14261 @subsubsection OpenCL C Operators
14263 @cindex OpenCL C Operators
14264 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14268 @subsection Fortran
14269 @cindex Fortran-specific support in @value{GDBN}
14271 @value{GDBN} can be used to debug programs written in Fortran, but it
14272 currently supports only the features of Fortran 77 language.
14274 @cindex trailing underscore, in Fortran symbols
14275 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14276 among them) append an underscore to the names of variables and
14277 functions. When you debug programs compiled by those compilers, you
14278 will need to refer to variables and functions with a trailing
14282 * Fortran Operators:: Fortran operators and expressions
14283 * Fortran Defaults:: Default settings for Fortran
14284 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14287 @node Fortran Operators
14288 @subsubsection Fortran Operators and Expressions
14290 @cindex Fortran operators and expressions
14292 Operators must be defined on values of specific types. For instance,
14293 @code{+} is defined on numbers, but not on characters or other non-
14294 arithmetic types. Operators are often defined on groups of types.
14298 The exponentiation operator. It raises the first operand to the power
14302 The range operator. Normally used in the form of array(low:high) to
14303 represent a section of array.
14306 The access component operator. Normally used to access elements in derived
14307 types. Also suitable for unions. As unions aren't part of regular Fortran,
14308 this can only happen when accessing a register that uses a gdbarch-defined
14312 @node Fortran Defaults
14313 @subsubsection Fortran Defaults
14315 @cindex Fortran Defaults
14317 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14318 default uses case-insensitive matches for Fortran symbols. You can
14319 change that with the @samp{set case-insensitive} command, see
14320 @ref{Symbols}, for the details.
14322 @node Special Fortran Commands
14323 @subsubsection Special Fortran Commands
14325 @cindex Special Fortran commands
14327 @value{GDBN} has some commands to support Fortran-specific features,
14328 such as displaying common blocks.
14331 @cindex @code{COMMON} blocks, Fortran
14332 @kindex info common
14333 @item info common @r{[}@var{common-name}@r{]}
14334 This command prints the values contained in the Fortran @code{COMMON}
14335 block whose name is @var{common-name}. With no argument, the names of
14336 all @code{COMMON} blocks visible at the current program location are
14343 @cindex Pascal support in @value{GDBN}, limitations
14344 Debugging Pascal programs which use sets, subranges, file variables, or
14345 nested functions does not currently work. @value{GDBN} does not support
14346 entering expressions, printing values, or similar features using Pascal
14349 The Pascal-specific command @code{set print pascal_static-members}
14350 controls whether static members of Pascal objects are displayed.
14351 @xref{Print Settings, pascal_static-members}.
14354 @subsection Modula-2
14356 @cindex Modula-2, @value{GDBN} support
14358 The extensions made to @value{GDBN} to support Modula-2 only support
14359 output from the @sc{gnu} Modula-2 compiler (which is currently being
14360 developed). Other Modula-2 compilers are not currently supported, and
14361 attempting to debug executables produced by them is most likely
14362 to give an error as @value{GDBN} reads in the executable's symbol
14365 @cindex expressions in Modula-2
14367 * M2 Operators:: Built-in operators
14368 * Built-In Func/Proc:: Built-in functions and procedures
14369 * M2 Constants:: Modula-2 constants
14370 * M2 Types:: Modula-2 types
14371 * M2 Defaults:: Default settings for Modula-2
14372 * Deviations:: Deviations from standard Modula-2
14373 * M2 Checks:: Modula-2 type and range checks
14374 * M2 Scope:: The scope operators @code{::} and @code{.}
14375 * GDB/M2:: @value{GDBN} and Modula-2
14379 @subsubsection Operators
14380 @cindex Modula-2 operators
14382 Operators must be defined on values of specific types. For instance,
14383 @code{+} is defined on numbers, but not on structures. Operators are
14384 often defined on groups of types. For the purposes of Modula-2, the
14385 following definitions hold:
14390 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14394 @emph{Character types} consist of @code{CHAR} and its subranges.
14397 @emph{Floating-point types} consist of @code{REAL}.
14400 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14404 @emph{Scalar types} consist of all of the above.
14407 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14410 @emph{Boolean types} consist of @code{BOOLEAN}.
14414 The following operators are supported, and appear in order of
14415 increasing precedence:
14419 Function argument or array index separator.
14422 Assignment. The value of @var{var} @code{:=} @var{value} is
14426 Less than, greater than on integral, floating-point, or enumerated
14430 Less than or equal to, greater than or equal to
14431 on integral, floating-point and enumerated types, or set inclusion on
14432 set types. Same precedence as @code{<}.
14434 @item =@r{, }<>@r{, }#
14435 Equality and two ways of expressing inequality, valid on scalar types.
14436 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14437 available for inequality, since @code{#} conflicts with the script
14441 Set membership. Defined on set types and the types of their members.
14442 Same precedence as @code{<}.
14445 Boolean disjunction. Defined on boolean types.
14448 Boolean conjunction. Defined on boolean types.
14451 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14454 Addition and subtraction on integral and floating-point types, or union
14455 and difference on set types.
14458 Multiplication on integral and floating-point types, or set intersection
14462 Division on floating-point types, or symmetric set difference on set
14463 types. Same precedence as @code{*}.
14466 Integer division and remainder. Defined on integral types. Same
14467 precedence as @code{*}.
14470 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14473 Pointer dereferencing. Defined on pointer types.
14476 Boolean negation. Defined on boolean types. Same precedence as
14480 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14481 precedence as @code{^}.
14484 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14487 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14491 @value{GDBN} and Modula-2 scope operators.
14495 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14496 treats the use of the operator @code{IN}, or the use of operators
14497 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14498 @code{<=}, and @code{>=} on sets as an error.
14502 @node Built-In Func/Proc
14503 @subsubsection Built-in Functions and Procedures
14504 @cindex Modula-2 built-ins
14506 Modula-2 also makes available several built-in procedures and functions.
14507 In describing these, the following metavariables are used:
14512 represents an @code{ARRAY} variable.
14515 represents a @code{CHAR} constant or variable.
14518 represents a variable or constant of integral type.
14521 represents an identifier that belongs to a set. Generally used in the
14522 same function with the metavariable @var{s}. The type of @var{s} should
14523 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14526 represents a variable or constant of integral or floating-point type.
14529 represents a variable or constant of floating-point type.
14535 represents a variable.
14538 represents a variable or constant of one of many types. See the
14539 explanation of the function for details.
14542 All Modula-2 built-in procedures also return a result, described below.
14546 Returns the absolute value of @var{n}.
14549 If @var{c} is a lower case letter, it returns its upper case
14550 equivalent, otherwise it returns its argument.
14553 Returns the character whose ordinal value is @var{i}.
14556 Decrements the value in the variable @var{v} by one. Returns the new value.
14558 @item DEC(@var{v},@var{i})
14559 Decrements the value in the variable @var{v} by @var{i}. Returns the
14562 @item EXCL(@var{m},@var{s})
14563 Removes the element @var{m} from the set @var{s}. Returns the new
14566 @item FLOAT(@var{i})
14567 Returns the floating point equivalent of the integer @var{i}.
14569 @item HIGH(@var{a})
14570 Returns the index of the last member of @var{a}.
14573 Increments the value in the variable @var{v} by one. Returns the new value.
14575 @item INC(@var{v},@var{i})
14576 Increments the value in the variable @var{v} by @var{i}. Returns the
14579 @item INCL(@var{m},@var{s})
14580 Adds the element @var{m} to the set @var{s} if it is not already
14581 there. Returns the new set.
14584 Returns the maximum value of the type @var{t}.
14587 Returns the minimum value of the type @var{t}.
14590 Returns boolean TRUE if @var{i} is an odd number.
14593 Returns the ordinal value of its argument. For example, the ordinal
14594 value of a character is its @sc{ascii} value (on machines supporting the
14595 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14596 integral, character and enumerated types.
14598 @item SIZE(@var{x})
14599 Returns the size of its argument. @var{x} can be a variable or a type.
14601 @item TRUNC(@var{r})
14602 Returns the integral part of @var{r}.
14604 @item TSIZE(@var{x})
14605 Returns the size of its argument. @var{x} can be a variable or a type.
14607 @item VAL(@var{t},@var{i})
14608 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14612 @emph{Warning:} Sets and their operations are not yet supported, so
14613 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14617 @cindex Modula-2 constants
14619 @subsubsection Constants
14621 @value{GDBN} allows you to express the constants of Modula-2 in the following
14627 Integer constants are simply a sequence of digits. When used in an
14628 expression, a constant is interpreted to be type-compatible with the
14629 rest of the expression. Hexadecimal integers are specified by a
14630 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14633 Floating point constants appear as a sequence of digits, followed by a
14634 decimal point and another sequence of digits. An optional exponent can
14635 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14636 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14637 digits of the floating point constant must be valid decimal (base 10)
14641 Character constants consist of a single character enclosed by a pair of
14642 like quotes, either single (@code{'}) or double (@code{"}). They may
14643 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14644 followed by a @samp{C}.
14647 String constants consist of a sequence of characters enclosed by a
14648 pair of like quotes, either single (@code{'}) or double (@code{"}).
14649 Escape sequences in the style of C are also allowed. @xref{C
14650 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14654 Enumerated constants consist of an enumerated identifier.
14657 Boolean constants consist of the identifiers @code{TRUE} and
14661 Pointer constants consist of integral values only.
14664 Set constants are not yet supported.
14668 @subsubsection Modula-2 Types
14669 @cindex Modula-2 types
14671 Currently @value{GDBN} can print the following data types in Modula-2
14672 syntax: array types, record types, set types, pointer types, procedure
14673 types, enumerated types, subrange types and base types. You can also
14674 print the contents of variables declared using these type.
14675 This section gives a number of simple source code examples together with
14676 sample @value{GDBN} sessions.
14678 The first example contains the following section of code:
14687 and you can request @value{GDBN} to interrogate the type and value of
14688 @code{r} and @code{s}.
14691 (@value{GDBP}) print s
14693 (@value{GDBP}) ptype s
14695 (@value{GDBP}) print r
14697 (@value{GDBP}) ptype r
14702 Likewise if your source code declares @code{s} as:
14706 s: SET ['A'..'Z'] ;
14710 then you may query the type of @code{s} by:
14713 (@value{GDBP}) ptype s
14714 type = SET ['A'..'Z']
14718 Note that at present you cannot interactively manipulate set
14719 expressions using the debugger.
14721 The following example shows how you might declare an array in Modula-2
14722 and how you can interact with @value{GDBN} to print its type and contents:
14726 s: ARRAY [-10..10] OF CHAR ;
14730 (@value{GDBP}) ptype s
14731 ARRAY [-10..10] OF CHAR
14734 Note that the array handling is not yet complete and although the type
14735 is printed correctly, expression handling still assumes that all
14736 arrays have a lower bound of zero and not @code{-10} as in the example
14739 Here are some more type related Modula-2 examples:
14743 colour = (blue, red, yellow, green) ;
14744 t = [blue..yellow] ;
14752 The @value{GDBN} interaction shows how you can query the data type
14753 and value of a variable.
14756 (@value{GDBP}) print s
14758 (@value{GDBP}) ptype t
14759 type = [blue..yellow]
14763 In this example a Modula-2 array is declared and its contents
14764 displayed. Observe that the contents are written in the same way as
14765 their @code{C} counterparts.
14769 s: ARRAY [1..5] OF CARDINAL ;
14775 (@value{GDBP}) print s
14776 $1 = @{1, 0, 0, 0, 0@}
14777 (@value{GDBP}) ptype s
14778 type = ARRAY [1..5] OF CARDINAL
14781 The Modula-2 language interface to @value{GDBN} also understands
14782 pointer types as shown in this example:
14786 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14793 and you can request that @value{GDBN} describes the type of @code{s}.
14796 (@value{GDBP}) ptype s
14797 type = POINTER TO ARRAY [1..5] OF CARDINAL
14800 @value{GDBN} handles compound types as we can see in this example.
14801 Here we combine array types, record types, pointer types and subrange
14812 myarray = ARRAY myrange OF CARDINAL ;
14813 myrange = [-2..2] ;
14815 s: POINTER TO ARRAY myrange OF foo ;
14819 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14823 (@value{GDBP}) ptype s
14824 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14827 f3 : ARRAY [-2..2] OF CARDINAL;
14832 @subsubsection Modula-2 Defaults
14833 @cindex Modula-2 defaults
14835 If type and range checking are set automatically by @value{GDBN}, they
14836 both default to @code{on} whenever the working language changes to
14837 Modula-2. This happens regardless of whether you or @value{GDBN}
14838 selected the working language.
14840 If you allow @value{GDBN} to set the language automatically, then entering
14841 code compiled from a file whose name ends with @file{.mod} sets the
14842 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14843 Infer the Source Language}, for further details.
14846 @subsubsection Deviations from Standard Modula-2
14847 @cindex Modula-2, deviations from
14849 A few changes have been made to make Modula-2 programs easier to debug.
14850 This is done primarily via loosening its type strictness:
14854 Unlike in standard Modula-2, pointer constants can be formed by
14855 integers. This allows you to modify pointer variables during
14856 debugging. (In standard Modula-2, the actual address contained in a
14857 pointer variable is hidden from you; it can only be modified
14858 through direct assignment to another pointer variable or expression that
14859 returned a pointer.)
14862 C escape sequences can be used in strings and characters to represent
14863 non-printable characters. @value{GDBN} prints out strings with these
14864 escape sequences embedded. Single non-printable characters are
14865 printed using the @samp{CHR(@var{nnn})} format.
14868 The assignment operator (@code{:=}) returns the value of its right-hand
14872 All built-in procedures both modify @emph{and} return their argument.
14876 @subsubsection Modula-2 Type and Range Checks
14877 @cindex Modula-2 checks
14880 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14883 @c FIXME remove warning when type/range checks added
14885 @value{GDBN} considers two Modula-2 variables type equivalent if:
14889 They are of types that have been declared equivalent via a @code{TYPE
14890 @var{t1} = @var{t2}} statement
14893 They have been declared on the same line. (Note: This is true of the
14894 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14897 As long as type checking is enabled, any attempt to combine variables
14898 whose types are not equivalent is an error.
14900 Range checking is done on all mathematical operations, assignment, array
14901 index bounds, and all built-in functions and procedures.
14904 @subsubsection The Scope Operators @code{::} and @code{.}
14906 @cindex @code{.}, Modula-2 scope operator
14907 @cindex colon, doubled as scope operator
14909 @vindex colon-colon@r{, in Modula-2}
14910 @c Info cannot handle :: but TeX can.
14913 @vindex ::@r{, in Modula-2}
14916 There are a few subtle differences between the Modula-2 scope operator
14917 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14922 @var{module} . @var{id}
14923 @var{scope} :: @var{id}
14927 where @var{scope} is the name of a module or a procedure,
14928 @var{module} the name of a module, and @var{id} is any declared
14929 identifier within your program, except another module.
14931 Using the @code{::} operator makes @value{GDBN} search the scope
14932 specified by @var{scope} for the identifier @var{id}. If it is not
14933 found in the specified scope, then @value{GDBN} searches all scopes
14934 enclosing the one specified by @var{scope}.
14936 Using the @code{.} operator makes @value{GDBN} search the current scope for
14937 the identifier specified by @var{id} that was imported from the
14938 definition module specified by @var{module}. With this operator, it is
14939 an error if the identifier @var{id} was not imported from definition
14940 module @var{module}, or if @var{id} is not an identifier in
14944 @subsubsection @value{GDBN} and Modula-2
14946 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14947 Five subcommands of @code{set print} and @code{show print} apply
14948 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14949 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14950 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14951 analogue in Modula-2.
14953 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14954 with any language, is not useful with Modula-2. Its
14955 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14956 created in Modula-2 as they can in C or C@t{++}. However, because an
14957 address can be specified by an integral constant, the construct
14958 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14960 @cindex @code{#} in Modula-2
14961 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14962 interpreted as the beginning of a comment. Use @code{<>} instead.
14968 The extensions made to @value{GDBN} for Ada only support
14969 output from the @sc{gnu} Ada (GNAT) compiler.
14970 Other Ada compilers are not currently supported, and
14971 attempting to debug executables produced by them is most likely
14975 @cindex expressions in Ada
14977 * Ada Mode Intro:: General remarks on the Ada syntax
14978 and semantics supported by Ada mode
14980 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14981 * Additions to Ada:: Extensions of the Ada expression syntax.
14982 * Stopping Before Main Program:: Debugging the program during elaboration.
14983 * Ada Exceptions:: Ada Exceptions
14984 * Ada Tasks:: Listing and setting breakpoints in tasks.
14985 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14986 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14988 * Ada Glitches:: Known peculiarities of Ada mode.
14991 @node Ada Mode Intro
14992 @subsubsection Introduction
14993 @cindex Ada mode, general
14995 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14996 syntax, with some extensions.
14997 The philosophy behind the design of this subset is
15001 That @value{GDBN} should provide basic literals and access to operations for
15002 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15003 leaving more sophisticated computations to subprograms written into the
15004 program (which therefore may be called from @value{GDBN}).
15007 That type safety and strict adherence to Ada language restrictions
15008 are not particularly important to the @value{GDBN} user.
15011 That brevity is important to the @value{GDBN} user.
15014 Thus, for brevity, the debugger acts as if all names declared in
15015 user-written packages are directly visible, even if they are not visible
15016 according to Ada rules, thus making it unnecessary to fully qualify most
15017 names with their packages, regardless of context. Where this causes
15018 ambiguity, @value{GDBN} asks the user's intent.
15020 The debugger will start in Ada mode if it detects an Ada main program.
15021 As for other languages, it will enter Ada mode when stopped in a program that
15022 was translated from an Ada source file.
15024 While in Ada mode, you may use `@t{--}' for comments. This is useful
15025 mostly for documenting command files. The standard @value{GDBN} comment
15026 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15027 middle (to allow based literals).
15029 The debugger supports limited overloading. Given a subprogram call in which
15030 the function symbol has multiple definitions, it will use the number of
15031 actual parameters and some information about their types to attempt to narrow
15032 the set of definitions. It also makes very limited use of context, preferring
15033 procedures to functions in the context of the @code{call} command, and
15034 functions to procedures elsewhere.
15036 @node Omissions from Ada
15037 @subsubsection Omissions from Ada
15038 @cindex Ada, omissions from
15040 Here are the notable omissions from the subset:
15044 Only a subset of the attributes are supported:
15048 @t{'First}, @t{'Last}, and @t{'Length}
15049 on array objects (not on types and subtypes).
15052 @t{'Min} and @t{'Max}.
15055 @t{'Pos} and @t{'Val}.
15061 @t{'Range} on array objects (not subtypes), but only as the right
15062 operand of the membership (@code{in}) operator.
15065 @t{'Access}, @t{'Unchecked_Access}, and
15066 @t{'Unrestricted_Access} (a GNAT extension).
15074 @code{Characters.Latin_1} are not available and
15075 concatenation is not implemented. Thus, escape characters in strings are
15076 not currently available.
15079 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15080 equality of representations. They will generally work correctly
15081 for strings and arrays whose elements have integer or enumeration types.
15082 They may not work correctly for arrays whose element
15083 types have user-defined equality, for arrays of real values
15084 (in particular, IEEE-conformant floating point, because of negative
15085 zeroes and NaNs), and for arrays whose elements contain unused bits with
15086 indeterminate values.
15089 The other component-by-component array operations (@code{and}, @code{or},
15090 @code{xor}, @code{not}, and relational tests other than equality)
15091 are not implemented.
15094 @cindex array aggregates (Ada)
15095 @cindex record aggregates (Ada)
15096 @cindex aggregates (Ada)
15097 There is limited support for array and record aggregates. They are
15098 permitted only on the right sides of assignments, as in these examples:
15101 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15102 (@value{GDBP}) set An_Array := (1, others => 0)
15103 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15104 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15105 (@value{GDBP}) set A_Record := (1, "Peter", True);
15106 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15110 discriminant's value by assigning an aggregate has an
15111 undefined effect if that discriminant is used within the record.
15112 However, you can first modify discriminants by directly assigning to
15113 them (which normally would not be allowed in Ada), and then performing an
15114 aggregate assignment. For example, given a variable @code{A_Rec}
15115 declared to have a type such as:
15118 type Rec (Len : Small_Integer := 0) is record
15120 Vals : IntArray (1 .. Len);
15124 you can assign a value with a different size of @code{Vals} with two
15128 (@value{GDBP}) set A_Rec.Len := 4
15129 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15132 As this example also illustrates, @value{GDBN} is very loose about the usual
15133 rules concerning aggregates. You may leave out some of the
15134 components of an array or record aggregate (such as the @code{Len}
15135 component in the assignment to @code{A_Rec} above); they will retain their
15136 original values upon assignment. You may freely use dynamic values as
15137 indices in component associations. You may even use overlapping or
15138 redundant component associations, although which component values are
15139 assigned in such cases is not defined.
15142 Calls to dispatching subprograms are not implemented.
15145 The overloading algorithm is much more limited (i.e., less selective)
15146 than that of real Ada. It makes only limited use of the context in
15147 which a subexpression appears to resolve its meaning, and it is much
15148 looser in its rules for allowing type matches. As a result, some
15149 function calls will be ambiguous, and the user will be asked to choose
15150 the proper resolution.
15153 The @code{new} operator is not implemented.
15156 Entry calls are not implemented.
15159 Aside from printing, arithmetic operations on the native VAX floating-point
15160 formats are not supported.
15163 It is not possible to slice a packed array.
15166 The names @code{True} and @code{False}, when not part of a qualified name,
15167 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15169 Should your program
15170 redefine these names in a package or procedure (at best a dubious practice),
15171 you will have to use fully qualified names to access their new definitions.
15174 @node Additions to Ada
15175 @subsubsection Additions to Ada
15176 @cindex Ada, deviations from
15178 As it does for other languages, @value{GDBN} makes certain generic
15179 extensions to Ada (@pxref{Expressions}):
15183 If the expression @var{E} is a variable residing in memory (typically
15184 a local variable or array element) and @var{N} is a positive integer,
15185 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15186 @var{N}-1 adjacent variables following it in memory as an array. In
15187 Ada, this operator is generally not necessary, since its prime use is
15188 in displaying parts of an array, and slicing will usually do this in
15189 Ada. However, there are occasional uses when debugging programs in
15190 which certain debugging information has been optimized away.
15193 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15194 appears in function or file @var{B}.'' When @var{B} is a file name,
15195 you must typically surround it in single quotes.
15198 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15199 @var{type} that appears at address @var{addr}.''
15202 A name starting with @samp{$} is a convenience variable
15203 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15206 In addition, @value{GDBN} provides a few other shortcuts and outright
15207 additions specific to Ada:
15211 The assignment statement is allowed as an expression, returning
15212 its right-hand operand as its value. Thus, you may enter
15215 (@value{GDBP}) set x := y + 3
15216 (@value{GDBP}) print A(tmp := y + 1)
15220 The semicolon is allowed as an ``operator,'' returning as its value
15221 the value of its right-hand operand.
15222 This allows, for example,
15223 complex conditional breaks:
15226 (@value{GDBP}) break f
15227 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15231 Rather than use catenation and symbolic character names to introduce special
15232 characters into strings, one may instead use a special bracket notation,
15233 which is also used to print strings. A sequence of characters of the form
15234 @samp{["@var{XX}"]} within a string or character literal denotes the
15235 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15236 sequence of characters @samp{["""]} also denotes a single quotation mark
15237 in strings. For example,
15239 "One line.["0a"]Next line.["0a"]"
15242 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15246 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15247 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15251 (@value{GDBP}) print 'max(x, y)
15255 When printing arrays, @value{GDBN} uses positional notation when the
15256 array has a lower bound of 1, and uses a modified named notation otherwise.
15257 For example, a one-dimensional array of three integers with a lower bound
15258 of 3 might print as
15265 That is, in contrast to valid Ada, only the first component has a @code{=>}
15269 You may abbreviate attributes in expressions with any unique,
15270 multi-character subsequence of
15271 their names (an exact match gets preference).
15272 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15273 in place of @t{a'length}.
15276 @cindex quoting Ada internal identifiers
15277 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15278 to lower case. The GNAT compiler uses upper-case characters for
15279 some of its internal identifiers, which are normally of no interest to users.
15280 For the rare occasions when you actually have to look at them,
15281 enclose them in angle brackets to avoid the lower-case mapping.
15284 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15288 Printing an object of class-wide type or dereferencing an
15289 access-to-class-wide value will display all the components of the object's
15290 specific type (as indicated by its run-time tag). Likewise, component
15291 selection on such a value will operate on the specific type of the
15296 @node Stopping Before Main Program
15297 @subsubsection Stopping at the Very Beginning
15299 @cindex breakpointing Ada elaboration code
15300 It is sometimes necessary to debug the program during elaboration, and
15301 before reaching the main procedure.
15302 As defined in the Ada Reference
15303 Manual, the elaboration code is invoked from a procedure called
15304 @code{adainit}. To run your program up to the beginning of
15305 elaboration, simply use the following two commands:
15306 @code{tbreak adainit} and @code{run}.
15308 @node Ada Exceptions
15309 @subsubsection Ada Exceptions
15311 A command is provided to list all Ada exceptions:
15314 @kindex info exceptions
15315 @item info exceptions
15316 @itemx info exceptions @var{regexp}
15317 The @code{info exceptions} command allows you to list all Ada exceptions
15318 defined within the program being debugged, as well as their addresses.
15319 With a regular expression, @var{regexp}, as argument, only those exceptions
15320 whose names match @var{regexp} are listed.
15323 Below is a small example, showing how the command can be used, first
15324 without argument, and next with a regular expression passed as an
15328 (@value{GDBP}) info exceptions
15329 All defined Ada exceptions:
15330 constraint_error: 0x613da0
15331 program_error: 0x613d20
15332 storage_error: 0x613ce0
15333 tasking_error: 0x613ca0
15334 const.aint_global_e: 0x613b00
15335 (@value{GDBP}) info exceptions const.aint
15336 All Ada exceptions matching regular expression "const.aint":
15337 constraint_error: 0x613da0
15338 const.aint_global_e: 0x613b00
15341 It is also possible to ask @value{GDBN} to stop your program's execution
15342 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15345 @subsubsection Extensions for Ada Tasks
15346 @cindex Ada, tasking
15348 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15349 @value{GDBN} provides the following task-related commands:
15354 This command shows a list of current Ada tasks, as in the following example:
15361 (@value{GDBP}) info tasks
15362 ID TID P-ID Pri State Name
15363 1 8088000 0 15 Child Activation Wait main_task
15364 2 80a4000 1 15 Accept Statement b
15365 3 809a800 1 15 Child Activation Wait a
15366 * 4 80ae800 3 15 Runnable c
15371 In this listing, the asterisk before the last task indicates it to be the
15372 task currently being inspected.
15376 Represents @value{GDBN}'s internal task number.
15382 The parent's task ID (@value{GDBN}'s internal task number).
15385 The base priority of the task.
15388 Current state of the task.
15392 The task has been created but has not been activated. It cannot be
15396 The task is not blocked for any reason known to Ada. (It may be waiting
15397 for a mutex, though.) It is conceptually "executing" in normal mode.
15400 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15401 that were waiting on terminate alternatives have been awakened and have
15402 terminated themselves.
15404 @item Child Activation Wait
15405 The task is waiting for created tasks to complete activation.
15407 @item Accept Statement
15408 The task is waiting on an accept or selective wait statement.
15410 @item Waiting on entry call
15411 The task is waiting on an entry call.
15413 @item Async Select Wait
15414 The task is waiting to start the abortable part of an asynchronous
15418 The task is waiting on a select statement with only a delay
15421 @item Child Termination Wait
15422 The task is sleeping having completed a master within itself, and is
15423 waiting for the tasks dependent on that master to become terminated or
15424 waiting on a terminate Phase.
15426 @item Wait Child in Term Alt
15427 The task is sleeping waiting for tasks on terminate alternatives to
15428 finish terminating.
15430 @item Accepting RV with @var{taskno}
15431 The task is accepting a rendez-vous with the task @var{taskno}.
15435 Name of the task in the program.
15439 @kindex info task @var{taskno}
15440 @item info task @var{taskno}
15441 This command shows detailled informations on the specified task, as in
15442 the following example:
15447 (@value{GDBP}) info tasks
15448 ID TID P-ID Pri State Name
15449 1 8077880 0 15 Child Activation Wait main_task
15450 * 2 807c468 1 15 Runnable task_1
15451 (@value{GDBP}) info task 2
15452 Ada Task: 0x807c468
15455 Parent: 1 (main_task)
15461 @kindex task@r{ (Ada)}
15462 @cindex current Ada task ID
15463 This command prints the ID of the current task.
15469 (@value{GDBP}) info tasks
15470 ID TID P-ID Pri State Name
15471 1 8077870 0 15 Child Activation Wait main_task
15472 * 2 807c458 1 15 Runnable t
15473 (@value{GDBP}) task
15474 [Current task is 2]
15477 @item task @var{taskno}
15478 @cindex Ada task switching
15479 This command is like the @code{thread @var{threadno}}
15480 command (@pxref{Threads}). It switches the context of debugging
15481 from the current task to the given task.
15487 (@value{GDBP}) info tasks
15488 ID TID P-ID Pri State Name
15489 1 8077870 0 15 Child Activation Wait main_task
15490 * 2 807c458 1 15 Runnable t
15491 (@value{GDBP}) task 1
15492 [Switching to task 1]
15493 #0 0x8067726 in pthread_cond_wait ()
15495 #0 0x8067726 in pthread_cond_wait ()
15496 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15497 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15498 #3 0x806153e in system.tasking.stages.activate_tasks ()
15499 #4 0x804aacc in un () at un.adb:5
15502 @item break @var{linespec} task @var{taskno}
15503 @itemx break @var{linespec} task @var{taskno} if @dots{}
15504 @cindex breakpoints and tasks, in Ada
15505 @cindex task breakpoints, in Ada
15506 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15507 These commands are like the @code{break @dots{} thread @dots{}}
15508 command (@pxref{Thread Stops}).
15509 @var{linespec} specifies source lines, as described
15510 in @ref{Specify Location}.
15512 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15513 to specify that you only want @value{GDBN} to stop the program when a
15514 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15515 numeric task identifiers assigned by @value{GDBN}, shown in the first
15516 column of the @samp{info tasks} display.
15518 If you do not specify @samp{task @var{taskno}} when you set a
15519 breakpoint, the breakpoint applies to @emph{all} tasks of your
15522 You can use the @code{task} qualifier on conditional breakpoints as
15523 well; in this case, place @samp{task @var{taskno}} before the
15524 breakpoint condition (before the @code{if}).
15532 (@value{GDBP}) info tasks
15533 ID TID P-ID Pri State Name
15534 1 140022020 0 15 Child Activation Wait main_task
15535 2 140045060 1 15 Accept/Select Wait t2
15536 3 140044840 1 15 Runnable t1
15537 * 4 140056040 1 15 Runnable t3
15538 (@value{GDBP}) b 15 task 2
15539 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15540 (@value{GDBP}) cont
15545 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15547 (@value{GDBP}) info tasks
15548 ID TID P-ID Pri State Name
15549 1 140022020 0 15 Child Activation Wait main_task
15550 * 2 140045060 1 15 Runnable t2
15551 3 140044840 1 15 Runnable t1
15552 4 140056040 1 15 Delay Sleep t3
15556 @node Ada Tasks and Core Files
15557 @subsubsection Tasking Support when Debugging Core Files
15558 @cindex Ada tasking and core file debugging
15560 When inspecting a core file, as opposed to debugging a live program,
15561 tasking support may be limited or even unavailable, depending on
15562 the platform being used.
15563 For instance, on x86-linux, the list of tasks is available, but task
15564 switching is not supported. On Tru64, however, task switching will work
15567 On certain platforms, including Tru64, the debugger needs to perform some
15568 memory writes in order to provide Ada tasking support. When inspecting
15569 a core file, this means that the core file must be opened with read-write
15570 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15571 Under these circumstances, you should make a backup copy of the core
15572 file before inspecting it with @value{GDBN}.
15574 @node Ravenscar Profile
15575 @subsubsection Tasking Support when using the Ravenscar Profile
15576 @cindex Ravenscar Profile
15578 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15579 specifically designed for systems with safety-critical real-time
15583 @kindex set ravenscar task-switching on
15584 @cindex task switching with program using Ravenscar Profile
15585 @item set ravenscar task-switching on
15586 Allows task switching when debugging a program that uses the Ravenscar
15587 Profile. This is the default.
15589 @kindex set ravenscar task-switching off
15590 @item set ravenscar task-switching off
15591 Turn off task switching when debugging a program that uses the Ravenscar
15592 Profile. This is mostly intended to disable the code that adds support
15593 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15594 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15595 To be effective, this command should be run before the program is started.
15597 @kindex show ravenscar task-switching
15598 @item show ravenscar task-switching
15599 Show whether it is possible to switch from task to task in a program
15600 using the Ravenscar Profile.
15605 @subsubsection Known Peculiarities of Ada Mode
15606 @cindex Ada, problems
15608 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15609 we know of several problems with and limitations of Ada mode in
15611 some of which will be fixed with planned future releases of the debugger
15612 and the GNU Ada compiler.
15616 Static constants that the compiler chooses not to materialize as objects in
15617 storage are invisible to the debugger.
15620 Named parameter associations in function argument lists are ignored (the
15621 argument lists are treated as positional).
15624 Many useful library packages are currently invisible to the debugger.
15627 Fixed-point arithmetic, conversions, input, and output is carried out using
15628 floating-point arithmetic, and may give results that only approximate those on
15632 The GNAT compiler never generates the prefix @code{Standard} for any of
15633 the standard symbols defined by the Ada language. @value{GDBN} knows about
15634 this: it will strip the prefix from names when you use it, and will never
15635 look for a name you have so qualified among local symbols, nor match against
15636 symbols in other packages or subprograms. If you have
15637 defined entities anywhere in your program other than parameters and
15638 local variables whose simple names match names in @code{Standard},
15639 GNAT's lack of qualification here can cause confusion. When this happens,
15640 you can usually resolve the confusion
15641 by qualifying the problematic names with package
15642 @code{Standard} explicitly.
15645 Older versions of the compiler sometimes generate erroneous debugging
15646 information, resulting in the debugger incorrectly printing the value
15647 of affected entities. In some cases, the debugger is able to work
15648 around an issue automatically. In other cases, the debugger is able
15649 to work around the issue, but the work-around has to be specifically
15652 @kindex set ada trust-PAD-over-XVS
15653 @kindex show ada trust-PAD-over-XVS
15656 @item set ada trust-PAD-over-XVS on
15657 Configure GDB to strictly follow the GNAT encoding when computing the
15658 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15659 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15660 a complete description of the encoding used by the GNAT compiler).
15661 This is the default.
15663 @item set ada trust-PAD-over-XVS off
15664 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15665 sometimes prints the wrong value for certain entities, changing @code{ada
15666 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15667 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15668 @code{off}, but this incurs a slight performance penalty, so it is
15669 recommended to leave this setting to @code{on} unless necessary.
15673 @node Unsupported Languages
15674 @section Unsupported Languages
15676 @cindex unsupported languages
15677 @cindex minimal language
15678 In addition to the other fully-supported programming languages,
15679 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15680 It does not represent a real programming language, but provides a set
15681 of capabilities close to what the C or assembly languages provide.
15682 This should allow most simple operations to be performed while debugging
15683 an application that uses a language currently not supported by @value{GDBN}.
15685 If the language is set to @code{auto}, @value{GDBN} will automatically
15686 select this language if the current frame corresponds to an unsupported
15690 @chapter Examining the Symbol Table
15692 The commands described in this chapter allow you to inquire about the
15693 symbols (names of variables, functions and types) defined in your
15694 program. This information is inherent in the text of your program and
15695 does not change as your program executes. @value{GDBN} finds it in your
15696 program's symbol table, in the file indicated when you started @value{GDBN}
15697 (@pxref{File Options, ,Choosing Files}), or by one of the
15698 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15700 @cindex symbol names
15701 @cindex names of symbols
15702 @cindex quoting names
15703 Occasionally, you may need to refer to symbols that contain unusual
15704 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15705 most frequent case is in referring to static variables in other
15706 source files (@pxref{Variables,,Program Variables}). File names
15707 are recorded in object files as debugging symbols, but @value{GDBN} would
15708 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15709 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15710 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15717 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15720 @cindex case-insensitive symbol names
15721 @cindex case sensitivity in symbol names
15722 @kindex set case-sensitive
15723 @item set case-sensitive on
15724 @itemx set case-sensitive off
15725 @itemx set case-sensitive auto
15726 Normally, when @value{GDBN} looks up symbols, it matches their names
15727 with case sensitivity determined by the current source language.
15728 Occasionally, you may wish to control that. The command @code{set
15729 case-sensitive} lets you do that by specifying @code{on} for
15730 case-sensitive matches or @code{off} for case-insensitive ones. If
15731 you specify @code{auto}, case sensitivity is reset to the default
15732 suitable for the source language. The default is case-sensitive
15733 matches for all languages except for Fortran, for which the default is
15734 case-insensitive matches.
15736 @kindex show case-sensitive
15737 @item show case-sensitive
15738 This command shows the current setting of case sensitivity for symbols
15741 @kindex set print type methods
15742 @item set print type methods
15743 @itemx set print type methods on
15744 @itemx set print type methods off
15745 Normally, when @value{GDBN} prints a class, it displays any methods
15746 declared in that class. You can control this behavior either by
15747 passing the appropriate flag to @code{ptype}, or using @command{set
15748 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15749 display the methods; this is the default. Specifying @code{off} will
15750 cause @value{GDBN} to omit the methods.
15752 @kindex show print type methods
15753 @item show print type methods
15754 This command shows the current setting of method display when printing
15757 @kindex set print type typedefs
15758 @item set print type typedefs
15759 @itemx set print type typedefs on
15760 @itemx set print type typedefs off
15762 Normally, when @value{GDBN} prints a class, it displays any typedefs
15763 defined in that class. You can control this behavior either by
15764 passing the appropriate flag to @code{ptype}, or using @command{set
15765 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15766 display the typedef definitions; this is the default. Specifying
15767 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15768 Note that this controls whether the typedef definition itself is
15769 printed, not whether typedef names are substituted when printing other
15772 @kindex show print type typedefs
15773 @item show print type typedefs
15774 This command shows the current setting of typedef display when
15777 @kindex info address
15778 @cindex address of a symbol
15779 @item info address @var{symbol}
15780 Describe where the data for @var{symbol} is stored. For a register
15781 variable, this says which register it is kept in. For a non-register
15782 local variable, this prints the stack-frame offset at which the variable
15785 Note the contrast with @samp{print &@var{symbol}}, which does not work
15786 at all for a register variable, and for a stack local variable prints
15787 the exact address of the current instantiation of the variable.
15789 @kindex info symbol
15790 @cindex symbol from address
15791 @cindex closest symbol and offset for an address
15792 @item info symbol @var{addr}
15793 Print the name of a symbol which is stored at the address @var{addr}.
15794 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15795 nearest symbol and an offset from it:
15798 (@value{GDBP}) info symbol 0x54320
15799 _initialize_vx + 396 in section .text
15803 This is the opposite of the @code{info address} command. You can use
15804 it to find out the name of a variable or a function given its address.
15806 For dynamically linked executables, the name of executable or shared
15807 library containing the symbol is also printed:
15810 (@value{GDBP}) info symbol 0x400225
15811 _start + 5 in section .text of /tmp/a.out
15812 (@value{GDBP}) info symbol 0x2aaaac2811cf
15813 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15817 @item whatis[/@var{flags}] [@var{arg}]
15818 Print the data type of @var{arg}, which can be either an expression
15819 or a name of a data type. With no argument, print the data type of
15820 @code{$}, the last value in the value history.
15822 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15823 is not actually evaluated, and any side-effecting operations (such as
15824 assignments or function calls) inside it do not take place.
15826 If @var{arg} is a variable or an expression, @code{whatis} prints its
15827 literal type as it is used in the source code. If the type was
15828 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15829 the data type underlying the @code{typedef}. If the type of the
15830 variable or the expression is a compound data type, such as
15831 @code{struct} or @code{class}, @code{whatis} never prints their
15832 fields or methods. It just prints the @code{struct}/@code{class}
15833 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15834 such a compound data type, use @code{ptype}.
15836 If @var{arg} is a type name that was defined using @code{typedef},
15837 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15838 Unrolling means that @code{whatis} will show the underlying type used
15839 in the @code{typedef} declaration of @var{arg}. However, if that
15840 underlying type is also a @code{typedef}, @code{whatis} will not
15843 For C code, the type names may also have the form @samp{class
15844 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15845 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15847 @var{flags} can be used to modify how the type is displayed.
15848 Available flags are:
15852 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15853 parameters and typedefs defined in a class when printing the class'
15854 members. The @code{/r} flag disables this.
15857 Do not print methods defined in the class.
15860 Print methods defined in the class. This is the default, but the flag
15861 exists in case you change the default with @command{set print type methods}.
15864 Do not print typedefs defined in the class. Note that this controls
15865 whether the typedef definition itself is printed, not whether typedef
15866 names are substituted when printing other types.
15869 Print typedefs defined in the class. This is the default, but the flag
15870 exists in case you change the default with @command{set print type typedefs}.
15874 @item ptype[/@var{flags}] [@var{arg}]
15875 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15876 detailed description of the type, instead of just the name of the type.
15877 @xref{Expressions, ,Expressions}.
15879 Contrary to @code{whatis}, @code{ptype} always unrolls any
15880 @code{typedef}s in its argument declaration, whether the argument is
15881 a variable, expression, or a data type. This means that @code{ptype}
15882 of a variable or an expression will not print literally its type as
15883 present in the source code---use @code{whatis} for that. @code{typedef}s at
15884 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15885 fields, methods and inner @code{class typedef}s of @code{struct}s,
15886 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15888 For example, for this variable declaration:
15891 typedef double real_t;
15892 struct complex @{ real_t real; double imag; @};
15893 typedef struct complex complex_t;
15895 real_t *real_pointer_var;
15899 the two commands give this output:
15903 (@value{GDBP}) whatis var
15905 (@value{GDBP}) ptype var
15906 type = struct complex @{
15910 (@value{GDBP}) whatis complex_t
15911 type = struct complex
15912 (@value{GDBP}) whatis struct complex
15913 type = struct complex
15914 (@value{GDBP}) ptype struct complex
15915 type = struct complex @{
15919 (@value{GDBP}) whatis real_pointer_var
15921 (@value{GDBP}) ptype real_pointer_var
15927 As with @code{whatis}, using @code{ptype} without an argument refers to
15928 the type of @code{$}, the last value in the value history.
15930 @cindex incomplete type
15931 Sometimes, programs use opaque data types or incomplete specifications
15932 of complex data structure. If the debug information included in the
15933 program does not allow @value{GDBN} to display a full declaration of
15934 the data type, it will say @samp{<incomplete type>}. For example,
15935 given these declarations:
15939 struct foo *fooptr;
15943 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15946 (@value{GDBP}) ptype foo
15947 $1 = <incomplete type>
15951 ``Incomplete type'' is C terminology for data types that are not
15952 completely specified.
15955 @item info types @var{regexp}
15957 Print a brief description of all types whose names match the regular
15958 expression @var{regexp} (or all types in your program, if you supply
15959 no argument). Each complete typename is matched as though it were a
15960 complete line; thus, @samp{i type value} gives information on all
15961 types in your program whose names include the string @code{value}, but
15962 @samp{i type ^value$} gives information only on types whose complete
15963 name is @code{value}.
15965 This command differs from @code{ptype} in two ways: first, like
15966 @code{whatis}, it does not print a detailed description; second, it
15967 lists all source files where a type is defined.
15969 @kindex info type-printers
15970 @item info type-printers
15971 Versions of @value{GDBN} that ship with Python scripting enabled may
15972 have ``type printers'' available. When using @command{ptype} or
15973 @command{whatis}, these printers are consulted when the name of a type
15974 is needed. @xref{Type Printing API}, for more information on writing
15977 @code{info type-printers} displays all the available type printers.
15979 @kindex enable type-printer
15980 @kindex disable type-printer
15981 @item enable type-printer @var{name}@dots{}
15982 @item disable type-printer @var{name}@dots{}
15983 These commands can be used to enable or disable type printers.
15986 @cindex local variables
15987 @item info scope @var{location}
15988 List all the variables local to a particular scope. This command
15989 accepts a @var{location} argument---a function name, a source line, or
15990 an address preceded by a @samp{*}, and prints all the variables local
15991 to the scope defined by that location. (@xref{Specify Location}, for
15992 details about supported forms of @var{location}.) For example:
15995 (@value{GDBP}) @b{info scope command_line_handler}
15996 Scope for command_line_handler:
15997 Symbol rl is an argument at stack/frame offset 8, length 4.
15998 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15999 Symbol linelength is in static storage at address 0x150a1c, length 4.
16000 Symbol p is a local variable in register $esi, length 4.
16001 Symbol p1 is a local variable in register $ebx, length 4.
16002 Symbol nline is a local variable in register $edx, length 4.
16003 Symbol repeat is a local variable at frame offset -8, length 4.
16007 This command is especially useful for determining what data to collect
16008 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16011 @kindex info source
16013 Show information about the current source file---that is, the source file for
16014 the function containing the current point of execution:
16017 the name of the source file, and the directory containing it,
16019 the directory it was compiled in,
16021 its length, in lines,
16023 which programming language it is written in,
16025 whether the executable includes debugging information for that file, and
16026 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16028 whether the debugging information includes information about
16029 preprocessor macros.
16033 @kindex info sources
16035 Print the names of all source files in your program for which there is
16036 debugging information, organized into two lists: files whose symbols
16037 have already been read, and files whose symbols will be read when needed.
16039 @kindex info functions
16040 @item info functions
16041 Print the names and data types of all defined functions.
16043 @item info functions @var{regexp}
16044 Print the names and data types of all defined functions
16045 whose names contain a match for regular expression @var{regexp}.
16046 Thus, @samp{info fun step} finds all functions whose names
16047 include @code{step}; @samp{info fun ^step} finds those whose names
16048 start with @code{step}. If a function name contains characters
16049 that conflict with the regular expression language (e.g.@:
16050 @samp{operator*()}), they may be quoted with a backslash.
16052 @kindex info variables
16053 @item info variables
16054 Print the names and data types of all variables that are defined
16055 outside of functions (i.e.@: excluding local variables).
16057 @item info variables @var{regexp}
16058 Print the names and data types of all variables (except for local
16059 variables) whose names contain a match for regular expression
16062 @kindex info classes
16063 @cindex Objective-C, classes and selectors
16065 @itemx info classes @var{regexp}
16066 Display all Objective-C classes in your program, or
16067 (with the @var{regexp} argument) all those matching a particular regular
16070 @kindex info selectors
16071 @item info selectors
16072 @itemx info selectors @var{regexp}
16073 Display all Objective-C selectors in your program, or
16074 (with the @var{regexp} argument) all those matching a particular regular
16078 This was never implemented.
16079 @kindex info methods
16081 @itemx info methods @var{regexp}
16082 The @code{info methods} command permits the user to examine all defined
16083 methods within C@t{++} program, or (with the @var{regexp} argument) a
16084 specific set of methods found in the various C@t{++} classes. Many
16085 C@t{++} classes provide a large number of methods. Thus, the output
16086 from the @code{ptype} command can be overwhelming and hard to use. The
16087 @code{info-methods} command filters the methods, printing only those
16088 which match the regular-expression @var{regexp}.
16091 @cindex opaque data types
16092 @kindex set opaque-type-resolution
16093 @item set opaque-type-resolution on
16094 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16095 declared as a pointer to a @code{struct}, @code{class}, or
16096 @code{union}---for example, @code{struct MyType *}---that is used in one
16097 source file although the full declaration of @code{struct MyType} is in
16098 another source file. The default is on.
16100 A change in the setting of this subcommand will not take effect until
16101 the next time symbols for a file are loaded.
16103 @item set opaque-type-resolution off
16104 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16105 is printed as follows:
16107 @{<no data fields>@}
16110 @kindex show opaque-type-resolution
16111 @item show opaque-type-resolution
16112 Show whether opaque types are resolved or not.
16114 @kindex maint print symbols
16115 @cindex symbol dump
16116 @kindex maint print psymbols
16117 @cindex partial symbol dump
16118 @kindex maint print msymbols
16119 @cindex minimal symbol dump
16120 @item maint print symbols @var{filename}
16121 @itemx maint print psymbols @var{filename}
16122 @itemx maint print msymbols @var{filename}
16123 Write a dump of debugging symbol data into the file @var{filename}.
16124 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16125 symbols with debugging data are included. If you use @samp{maint print
16126 symbols}, @value{GDBN} includes all the symbols for which it has already
16127 collected full details: that is, @var{filename} reflects symbols for
16128 only those files whose symbols @value{GDBN} has read. You can use the
16129 command @code{info sources} to find out which files these are. If you
16130 use @samp{maint print psymbols} instead, the dump shows information about
16131 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16132 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16133 @samp{maint print msymbols} dumps just the minimal symbol information
16134 required for each object file from which @value{GDBN} has read some symbols.
16135 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16136 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16138 @kindex maint info symtabs
16139 @kindex maint info psymtabs
16140 @cindex listing @value{GDBN}'s internal symbol tables
16141 @cindex symbol tables, listing @value{GDBN}'s internal
16142 @cindex full symbol tables, listing @value{GDBN}'s internal
16143 @cindex partial symbol tables, listing @value{GDBN}'s internal
16144 @item maint info symtabs @r{[} @var{regexp} @r{]}
16145 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16147 List the @code{struct symtab} or @code{struct partial_symtab}
16148 structures whose names match @var{regexp}. If @var{regexp} is not
16149 given, list them all. The output includes expressions which you can
16150 copy into a @value{GDBN} debugging this one to examine a particular
16151 structure in more detail. For example:
16154 (@value{GDBP}) maint info psymtabs dwarf2read
16155 @{ objfile /home/gnu/build/gdb/gdb
16156 ((struct objfile *) 0x82e69d0)
16157 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16158 ((struct partial_symtab *) 0x8474b10)
16161 text addresses 0x814d3c8 -- 0x8158074
16162 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16163 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16164 dependencies (none)
16167 (@value{GDBP}) maint info symtabs
16171 We see that there is one partial symbol table whose filename contains
16172 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16173 and we see that @value{GDBN} has not read in any symtabs yet at all.
16174 If we set a breakpoint on a function, that will cause @value{GDBN} to
16175 read the symtab for the compilation unit containing that function:
16178 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16179 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16181 (@value{GDBP}) maint info symtabs
16182 @{ objfile /home/gnu/build/gdb/gdb
16183 ((struct objfile *) 0x82e69d0)
16184 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16185 ((struct symtab *) 0x86c1f38)
16188 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16189 linetable ((struct linetable *) 0x8370fa0)
16190 debugformat DWARF 2
16199 @chapter Altering Execution
16201 Once you think you have found an error in your program, you might want to
16202 find out for certain whether correcting the apparent error would lead to
16203 correct results in the rest of the run. You can find the answer by
16204 experiment, using the @value{GDBN} features for altering execution of the
16207 For example, you can store new values into variables or memory
16208 locations, give your program a signal, restart it at a different
16209 address, or even return prematurely from a function.
16212 * Assignment:: Assignment to variables
16213 * Jumping:: Continuing at a different address
16214 * Signaling:: Giving your program a signal
16215 * Returning:: Returning from a function
16216 * Calling:: Calling your program's functions
16217 * Patching:: Patching your program
16221 @section Assignment to Variables
16224 @cindex setting variables
16225 To alter the value of a variable, evaluate an assignment expression.
16226 @xref{Expressions, ,Expressions}. For example,
16233 stores the value 4 into the variable @code{x}, and then prints the
16234 value of the assignment expression (which is 4).
16235 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16236 information on operators in supported languages.
16238 @kindex set variable
16239 @cindex variables, setting
16240 If you are not interested in seeing the value of the assignment, use the
16241 @code{set} command instead of the @code{print} command. @code{set} is
16242 really the same as @code{print} except that the expression's value is
16243 not printed and is not put in the value history (@pxref{Value History,
16244 ,Value History}). The expression is evaluated only for its effects.
16246 If the beginning of the argument string of the @code{set} command
16247 appears identical to a @code{set} subcommand, use the @code{set
16248 variable} command instead of just @code{set}. This command is identical
16249 to @code{set} except for its lack of subcommands. For example, if your
16250 program has a variable @code{width}, you get an error if you try to set
16251 a new value with just @samp{set width=13}, because @value{GDBN} has the
16252 command @code{set width}:
16255 (@value{GDBP}) whatis width
16257 (@value{GDBP}) p width
16259 (@value{GDBP}) set width=47
16260 Invalid syntax in expression.
16264 The invalid expression, of course, is @samp{=47}. In
16265 order to actually set the program's variable @code{width}, use
16268 (@value{GDBP}) set var width=47
16271 Because the @code{set} command has many subcommands that can conflict
16272 with the names of program variables, it is a good idea to use the
16273 @code{set variable} command instead of just @code{set}. For example, if
16274 your program has a variable @code{g}, you run into problems if you try
16275 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16276 the command @code{set gnutarget}, abbreviated @code{set g}:
16280 (@value{GDBP}) whatis g
16284 (@value{GDBP}) set g=4
16288 The program being debugged has been started already.
16289 Start it from the beginning? (y or n) y
16290 Starting program: /home/smith/cc_progs/a.out
16291 "/home/smith/cc_progs/a.out": can't open to read symbols:
16292 Invalid bfd target.
16293 (@value{GDBP}) show g
16294 The current BFD target is "=4".
16299 The program variable @code{g} did not change, and you silently set the
16300 @code{gnutarget} to an invalid value. In order to set the variable
16304 (@value{GDBP}) set var g=4
16307 @value{GDBN} allows more implicit conversions in assignments than C; you can
16308 freely store an integer value into a pointer variable or vice versa,
16309 and you can convert any structure to any other structure that is the
16310 same length or shorter.
16311 @comment FIXME: how do structs align/pad in these conversions?
16312 @comment /doc@cygnus.com 18dec1990
16314 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16315 construct to generate a value of specified type at a specified address
16316 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16317 to memory location @code{0x83040} as an integer (which implies a certain size
16318 and representation in memory), and
16321 set @{int@}0x83040 = 4
16325 stores the value 4 into that memory location.
16328 @section Continuing at a Different Address
16330 Ordinarily, when you continue your program, you do so at the place where
16331 it stopped, with the @code{continue} command. You can instead continue at
16332 an address of your own choosing, with the following commands:
16336 @kindex j @r{(@code{jump})}
16337 @item jump @var{linespec}
16338 @itemx j @var{linespec}
16339 @itemx jump @var{location}
16340 @itemx j @var{location}
16341 Resume execution at line @var{linespec} or at address given by
16342 @var{location}. Execution stops again immediately if there is a
16343 breakpoint there. @xref{Specify Location}, for a description of the
16344 different forms of @var{linespec} and @var{location}. It is common
16345 practice to use the @code{tbreak} command in conjunction with
16346 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16348 The @code{jump} command does not change the current stack frame, or
16349 the stack pointer, or the contents of any memory location or any
16350 register other than the program counter. If line @var{linespec} is in
16351 a different function from the one currently executing, the results may
16352 be bizarre if the two functions expect different patterns of arguments or
16353 of local variables. For this reason, the @code{jump} command requests
16354 confirmation if the specified line is not in the function currently
16355 executing. However, even bizarre results are predictable if you are
16356 well acquainted with the machine-language code of your program.
16359 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16360 On many systems, you can get much the same effect as the @code{jump}
16361 command by storing a new value into the register @code{$pc}. The
16362 difference is that this does not start your program running; it only
16363 changes the address of where it @emph{will} run when you continue. For
16371 makes the next @code{continue} command or stepping command execute at
16372 address @code{0x485}, rather than at the address where your program stopped.
16373 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16375 The most common occasion to use the @code{jump} command is to back
16376 up---perhaps with more breakpoints set---over a portion of a program
16377 that has already executed, in order to examine its execution in more
16382 @section Giving your Program a Signal
16383 @cindex deliver a signal to a program
16387 @item signal @var{signal}
16388 Resume execution where your program stopped, but immediately give it the
16389 signal @var{signal}. @var{signal} can be the name or the number of a
16390 signal. For example, on many systems @code{signal 2} and @code{signal
16391 SIGINT} are both ways of sending an interrupt signal.
16393 Alternatively, if @var{signal} is zero, continue execution without
16394 giving a signal. This is useful when your program stopped on account of
16395 a signal and would ordinarily see the signal when resumed with the
16396 @code{continue} command; @samp{signal 0} causes it to resume without a
16399 @code{signal} does not repeat when you press @key{RET} a second time
16400 after executing the command.
16404 Invoking the @code{signal} command is not the same as invoking the
16405 @code{kill} utility from the shell. Sending a signal with @code{kill}
16406 causes @value{GDBN} to decide what to do with the signal depending on
16407 the signal handling tables (@pxref{Signals}). The @code{signal} command
16408 passes the signal directly to your program.
16412 @section Returning from a Function
16415 @cindex returning from a function
16418 @itemx return @var{expression}
16419 You can cancel execution of a function call with the @code{return}
16420 command. If you give an
16421 @var{expression} argument, its value is used as the function's return
16425 When you use @code{return}, @value{GDBN} discards the selected stack frame
16426 (and all frames within it). You can think of this as making the
16427 discarded frame return prematurely. If you wish to specify a value to
16428 be returned, give that value as the argument to @code{return}.
16430 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16431 Frame}), and any other frames inside of it, leaving its caller as the
16432 innermost remaining frame. That frame becomes selected. The
16433 specified value is stored in the registers used for returning values
16436 The @code{return} command does not resume execution; it leaves the
16437 program stopped in the state that would exist if the function had just
16438 returned. In contrast, the @code{finish} command (@pxref{Continuing
16439 and Stepping, ,Continuing and Stepping}) resumes execution until the
16440 selected stack frame returns naturally.
16442 @value{GDBN} needs to know how the @var{expression} argument should be set for
16443 the inferior. The concrete registers assignment depends on the OS ABI and the
16444 type being returned by the selected stack frame. For example it is common for
16445 OS ABI to return floating point values in FPU registers while integer values in
16446 CPU registers. Still some ABIs return even floating point values in CPU
16447 registers. Larger integer widths (such as @code{long long int}) also have
16448 specific placement rules. @value{GDBN} already knows the OS ABI from its
16449 current target so it needs to find out also the type being returned to make the
16450 assignment into the right register(s).
16452 Normally, the selected stack frame has debug info. @value{GDBN} will always
16453 use the debug info instead of the implicit type of @var{expression} when the
16454 debug info is available. For example, if you type @kbd{return -1}, and the
16455 function in the current stack frame is declared to return a @code{long long
16456 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16457 into a @code{long long int}:
16460 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16462 (@value{GDBP}) return -1
16463 Make func return now? (y or n) y
16464 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16465 43 printf ("result=%lld\n", func ());
16469 However, if the selected stack frame does not have a debug info, e.g., if the
16470 function was compiled without debug info, @value{GDBN} has to find out the type
16471 to return from user. Specifying a different type by mistake may set the value
16472 in different inferior registers than the caller code expects. For example,
16473 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16474 of a @code{long long int} result for a debug info less function (on 32-bit
16475 architectures). Therefore the user is required to specify the return type by
16476 an appropriate cast explicitly:
16479 Breakpoint 2, 0x0040050b in func ()
16480 (@value{GDBP}) return -1
16481 Return value type not available for selected stack frame.
16482 Please use an explicit cast of the value to return.
16483 (@value{GDBP}) return (long long int) -1
16484 Make selected stack frame return now? (y or n) y
16485 #0 0x00400526 in main ()
16490 @section Calling Program Functions
16493 @cindex calling functions
16494 @cindex inferior functions, calling
16495 @item print @var{expr}
16496 Evaluate the expression @var{expr} and display the resulting value.
16497 @var{expr} may include calls to functions in the program being
16501 @item call @var{expr}
16502 Evaluate the expression @var{expr} without displaying @code{void}
16505 You can use this variant of the @code{print} command if you want to
16506 execute a function from your program that does not return anything
16507 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16508 with @code{void} returned values that @value{GDBN} will otherwise
16509 print. If the result is not void, it is printed and saved in the
16513 It is possible for the function you call via the @code{print} or
16514 @code{call} command to generate a signal (e.g., if there's a bug in
16515 the function, or if you passed it incorrect arguments). What happens
16516 in that case is controlled by the @code{set unwindonsignal} command.
16518 Similarly, with a C@t{++} program it is possible for the function you
16519 call via the @code{print} or @code{call} command to generate an
16520 exception that is not handled due to the constraints of the dummy
16521 frame. In this case, any exception that is raised in the frame, but has
16522 an out-of-frame exception handler will not be found. GDB builds a
16523 dummy-frame for the inferior function call, and the unwinder cannot
16524 seek for exception handlers outside of this dummy-frame. What happens
16525 in that case is controlled by the
16526 @code{set unwind-on-terminating-exception} command.
16529 @item set unwindonsignal
16530 @kindex set unwindonsignal
16531 @cindex unwind stack in called functions
16532 @cindex call dummy stack unwinding
16533 Set unwinding of the stack if a signal is received while in a function
16534 that @value{GDBN} called in the program being debugged. If set to on,
16535 @value{GDBN} unwinds the stack it created for the call and restores
16536 the context to what it was before the call. If set to off (the
16537 default), @value{GDBN} stops in the frame where the signal was
16540 @item show unwindonsignal
16541 @kindex show unwindonsignal
16542 Show the current setting of stack unwinding in the functions called by
16545 @item set unwind-on-terminating-exception
16546 @kindex set unwind-on-terminating-exception
16547 @cindex unwind stack in called functions with unhandled exceptions
16548 @cindex call dummy stack unwinding on unhandled exception.
16549 Set unwinding of the stack if a C@t{++} exception is raised, but left
16550 unhandled while in a function that @value{GDBN} called in the program being
16551 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16552 it created for the call and restores the context to what it was before
16553 the call. If set to off, @value{GDBN} the exception is delivered to
16554 the default C@t{++} exception handler and the inferior terminated.
16556 @item show unwind-on-terminating-exception
16557 @kindex show unwind-on-terminating-exception
16558 Show the current setting of stack unwinding in the functions called by
16563 @cindex weak alias functions
16564 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16565 for another function. In such case, @value{GDBN} might not pick up
16566 the type information, including the types of the function arguments,
16567 which causes @value{GDBN} to call the inferior function incorrectly.
16568 As a result, the called function will function erroneously and may
16569 even crash. A solution to that is to use the name of the aliased
16573 @section Patching Programs
16575 @cindex patching binaries
16576 @cindex writing into executables
16577 @cindex writing into corefiles
16579 By default, @value{GDBN} opens the file containing your program's
16580 executable code (or the corefile) read-only. This prevents accidental
16581 alterations to machine code; but it also prevents you from intentionally
16582 patching your program's binary.
16584 If you'd like to be able to patch the binary, you can specify that
16585 explicitly with the @code{set write} command. For example, you might
16586 want to turn on internal debugging flags, or even to make emergency
16592 @itemx set write off
16593 If you specify @samp{set write on}, @value{GDBN} opens executable and
16594 core files for both reading and writing; if you specify @kbd{set write
16595 off} (the default), @value{GDBN} opens them read-only.
16597 If you have already loaded a file, you must load it again (using the
16598 @code{exec-file} or @code{core-file} command) after changing @code{set
16599 write}, for your new setting to take effect.
16603 Display whether executable files and core files are opened for writing
16604 as well as reading.
16608 @chapter @value{GDBN} Files
16610 @value{GDBN} needs to know the file name of the program to be debugged,
16611 both in order to read its symbol table and in order to start your
16612 program. To debug a core dump of a previous run, you must also tell
16613 @value{GDBN} the name of the core dump file.
16616 * Files:: Commands to specify files
16617 * Separate Debug Files:: Debugging information in separate files
16618 * MiniDebugInfo:: Debugging information in a special section
16619 * Index Files:: Index files speed up GDB
16620 * Symbol Errors:: Errors reading symbol files
16621 * Data Files:: GDB data files
16625 @section Commands to Specify Files
16627 @cindex symbol table
16628 @cindex core dump file
16630 You may want to specify executable and core dump file names. The usual
16631 way to do this is at start-up time, using the arguments to
16632 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16633 Out of @value{GDBN}}).
16635 Occasionally it is necessary to change to a different file during a
16636 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16637 specify a file you want to use. Or you are debugging a remote target
16638 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16639 Program}). In these situations the @value{GDBN} commands to specify
16640 new files are useful.
16643 @cindex executable file
16645 @item file @var{filename}
16646 Use @var{filename} as the program to be debugged. It is read for its
16647 symbols and for the contents of pure memory. It is also the program
16648 executed when you use the @code{run} command. If you do not specify a
16649 directory and the file is not found in the @value{GDBN} working directory,
16650 @value{GDBN} uses the environment variable @code{PATH} as a list of
16651 directories to search, just as the shell does when looking for a program
16652 to run. You can change the value of this variable, for both @value{GDBN}
16653 and your program, using the @code{path} command.
16655 @cindex unlinked object files
16656 @cindex patching object files
16657 You can load unlinked object @file{.o} files into @value{GDBN} using
16658 the @code{file} command. You will not be able to ``run'' an object
16659 file, but you can disassemble functions and inspect variables. Also,
16660 if the underlying BFD functionality supports it, you could use
16661 @kbd{gdb -write} to patch object files using this technique. Note
16662 that @value{GDBN} can neither interpret nor modify relocations in this
16663 case, so branches and some initialized variables will appear to go to
16664 the wrong place. But this feature is still handy from time to time.
16667 @code{file} with no argument makes @value{GDBN} discard any information it
16668 has on both executable file and the symbol table.
16671 @item exec-file @r{[} @var{filename} @r{]}
16672 Specify that the program to be run (but not the symbol table) is found
16673 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16674 if necessary to locate your program. Omitting @var{filename} means to
16675 discard information on the executable file.
16677 @kindex symbol-file
16678 @item symbol-file @r{[} @var{filename} @r{]}
16679 Read symbol table information from file @var{filename}. @code{PATH} is
16680 searched when necessary. Use the @code{file} command to get both symbol
16681 table and program to run from the same file.
16683 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16684 program's symbol table.
16686 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16687 some breakpoints and auto-display expressions. This is because they may
16688 contain pointers to the internal data recording symbols and data types,
16689 which are part of the old symbol table data being discarded inside
16692 @code{symbol-file} does not repeat if you press @key{RET} again after
16695 When @value{GDBN} is configured for a particular environment, it
16696 understands debugging information in whatever format is the standard
16697 generated for that environment; you may use either a @sc{gnu} compiler, or
16698 other compilers that adhere to the local conventions.
16699 Best results are usually obtained from @sc{gnu} compilers; for example,
16700 using @code{@value{NGCC}} you can generate debugging information for
16703 For most kinds of object files, with the exception of old SVR3 systems
16704 using COFF, the @code{symbol-file} command does not normally read the
16705 symbol table in full right away. Instead, it scans the symbol table
16706 quickly to find which source files and which symbols are present. The
16707 details are read later, one source file at a time, as they are needed.
16709 The purpose of this two-stage reading strategy is to make @value{GDBN}
16710 start up faster. For the most part, it is invisible except for
16711 occasional pauses while the symbol table details for a particular source
16712 file are being read. (The @code{set verbose} command can turn these
16713 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16714 Warnings and Messages}.)
16716 We have not implemented the two-stage strategy for COFF yet. When the
16717 symbol table is stored in COFF format, @code{symbol-file} reads the
16718 symbol table data in full right away. Note that ``stabs-in-COFF''
16719 still does the two-stage strategy, since the debug info is actually
16723 @cindex reading symbols immediately
16724 @cindex symbols, reading immediately
16725 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16726 @itemx file @r{[} -readnow @r{]} @var{filename}
16727 You can override the @value{GDBN} two-stage strategy for reading symbol
16728 tables by using the @samp{-readnow} option with any of the commands that
16729 load symbol table information, if you want to be sure @value{GDBN} has the
16730 entire symbol table available.
16732 @c FIXME: for now no mention of directories, since this seems to be in
16733 @c flux. 13mar1992 status is that in theory GDB would look either in
16734 @c current dir or in same dir as myprog; but issues like competing
16735 @c GDB's, or clutter in system dirs, mean that in practice right now
16736 @c only current dir is used. FFish says maybe a special GDB hierarchy
16737 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16741 @item core-file @r{[}@var{filename}@r{]}
16743 Specify the whereabouts of a core dump file to be used as the ``contents
16744 of memory''. Traditionally, core files contain only some parts of the
16745 address space of the process that generated them; @value{GDBN} can access the
16746 executable file itself for other parts.
16748 @code{core-file} with no argument specifies that no core file is
16751 Note that the core file is ignored when your program is actually running
16752 under @value{GDBN}. So, if you have been running your program and you
16753 wish to debug a core file instead, you must kill the subprocess in which
16754 the program is running. To do this, use the @code{kill} command
16755 (@pxref{Kill Process, ,Killing the Child Process}).
16757 @kindex add-symbol-file
16758 @cindex dynamic linking
16759 @item add-symbol-file @var{filename} @var{address}
16760 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16761 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16762 The @code{add-symbol-file} command reads additional symbol table
16763 information from the file @var{filename}. You would use this command
16764 when @var{filename} has been dynamically loaded (by some other means)
16765 into the program that is running. @var{address} should be the memory
16766 address at which the file has been loaded; @value{GDBN} cannot figure
16767 this out for itself. You can additionally specify an arbitrary number
16768 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16769 section name and base address for that section. You can specify any
16770 @var{address} as an expression.
16772 The symbol table of the file @var{filename} is added to the symbol table
16773 originally read with the @code{symbol-file} command. You can use the
16774 @code{add-symbol-file} command any number of times; the new symbol data
16775 thus read is kept in addition to the old.
16777 Changes can be reverted using the command @code{remove-symbol-file}.
16779 @cindex relocatable object files, reading symbols from
16780 @cindex object files, relocatable, reading symbols from
16781 @cindex reading symbols from relocatable object files
16782 @cindex symbols, reading from relocatable object files
16783 @cindex @file{.o} files, reading symbols from
16784 Although @var{filename} is typically a shared library file, an
16785 executable file, or some other object file which has been fully
16786 relocated for loading into a process, you can also load symbolic
16787 information from relocatable @file{.o} files, as long as:
16791 the file's symbolic information refers only to linker symbols defined in
16792 that file, not to symbols defined by other object files,
16794 every section the file's symbolic information refers to has actually
16795 been loaded into the inferior, as it appears in the file, and
16797 you can determine the address at which every section was loaded, and
16798 provide these to the @code{add-symbol-file} command.
16802 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16803 relocatable files into an already running program; such systems
16804 typically make the requirements above easy to meet. However, it's
16805 important to recognize that many native systems use complex link
16806 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16807 assembly, for example) that make the requirements difficult to meet. In
16808 general, one cannot assume that using @code{add-symbol-file} to read a
16809 relocatable object file's symbolic information will have the same effect
16810 as linking the relocatable object file into the program in the normal
16813 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16815 @kindex remove-symbol-file
16816 @item remove-symbol-file @var{filename}
16817 @item remove-symbol-file -a @var{address}
16818 Remove a symbol file added via the @code{add-symbol-file} command. The
16819 file to remove can be identified by its @var{filename} or by an @var{address}
16820 that lies within the boundaries of this symbol file in memory. Example:
16823 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16824 add symbol table from file "/home/user/gdb/mylib.so" at
16825 .text_addr = 0x7ffff7ff9480
16827 Reading symbols from /home/user/gdb/mylib.so...done.
16828 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16829 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16834 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16836 @kindex add-symbol-file-from-memory
16837 @cindex @code{syscall DSO}
16838 @cindex load symbols from memory
16839 @item add-symbol-file-from-memory @var{address}
16840 Load symbols from the given @var{address} in a dynamically loaded
16841 object file whose image is mapped directly into the inferior's memory.
16842 For example, the Linux kernel maps a @code{syscall DSO} into each
16843 process's address space; this DSO provides kernel-specific code for
16844 some system calls. The argument can be any expression whose
16845 evaluation yields the address of the file's shared object file header.
16846 For this command to work, you must have used @code{symbol-file} or
16847 @code{exec-file} commands in advance.
16849 @kindex add-shared-symbol-files
16851 @item add-shared-symbol-files @var{library-file}
16852 @itemx assf @var{library-file}
16853 The @code{add-shared-symbol-files} command can currently be used only
16854 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16855 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16856 @value{GDBN} automatically looks for shared libraries, however if
16857 @value{GDBN} does not find yours, you can invoke
16858 @code{add-shared-symbol-files}. It takes one argument: the shared
16859 library's file name. @code{assf} is a shorthand alias for
16860 @code{add-shared-symbol-files}.
16863 @item section @var{section} @var{addr}
16864 The @code{section} command changes the base address of the named
16865 @var{section} of the exec file to @var{addr}. This can be used if the
16866 exec file does not contain section addresses, (such as in the
16867 @code{a.out} format), or when the addresses specified in the file
16868 itself are wrong. Each section must be changed separately. The
16869 @code{info files} command, described below, lists all the sections and
16873 @kindex info target
16876 @code{info files} and @code{info target} are synonymous; both print the
16877 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16878 including the names of the executable and core dump files currently in
16879 use by @value{GDBN}, and the files from which symbols were loaded. The
16880 command @code{help target} lists all possible targets rather than
16883 @kindex maint info sections
16884 @item maint info sections
16885 Another command that can give you extra information about program sections
16886 is @code{maint info sections}. In addition to the section information
16887 displayed by @code{info files}, this command displays the flags and file
16888 offset of each section in the executable and core dump files. In addition,
16889 @code{maint info sections} provides the following command options (which
16890 may be arbitrarily combined):
16894 Display sections for all loaded object files, including shared libraries.
16895 @item @var{sections}
16896 Display info only for named @var{sections}.
16897 @item @var{section-flags}
16898 Display info only for sections for which @var{section-flags} are true.
16899 The section flags that @value{GDBN} currently knows about are:
16902 Section will have space allocated in the process when loaded.
16903 Set for all sections except those containing debug information.
16905 Section will be loaded from the file into the child process memory.
16906 Set for pre-initialized code and data, clear for @code{.bss} sections.
16908 Section needs to be relocated before loading.
16910 Section cannot be modified by the child process.
16912 Section contains executable code only.
16914 Section contains data only (no executable code).
16916 Section will reside in ROM.
16918 Section contains data for constructor/destructor lists.
16920 Section is not empty.
16922 An instruction to the linker to not output the section.
16923 @item COFF_SHARED_LIBRARY
16924 A notification to the linker that the section contains
16925 COFF shared library information.
16927 Section contains common symbols.
16930 @kindex set trust-readonly-sections
16931 @cindex read-only sections
16932 @item set trust-readonly-sections on
16933 Tell @value{GDBN} that readonly sections in your object file
16934 really are read-only (i.e.@: that their contents will not change).
16935 In that case, @value{GDBN} can fetch values from these sections
16936 out of the object file, rather than from the target program.
16937 For some targets (notably embedded ones), this can be a significant
16938 enhancement to debugging performance.
16940 The default is off.
16942 @item set trust-readonly-sections off
16943 Tell @value{GDBN} not to trust readonly sections. This means that
16944 the contents of the section might change while the program is running,
16945 and must therefore be fetched from the target when needed.
16947 @item show trust-readonly-sections
16948 Show the current setting of trusting readonly sections.
16951 All file-specifying commands allow both absolute and relative file names
16952 as arguments. @value{GDBN} always converts the file name to an absolute file
16953 name and remembers it that way.
16955 @cindex shared libraries
16956 @anchor{Shared Libraries}
16957 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16958 and IBM RS/6000 AIX shared libraries.
16960 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16961 shared libraries. @xref{Expat}.
16963 @value{GDBN} automatically loads symbol definitions from shared libraries
16964 when you use the @code{run} command, or when you examine a core file.
16965 (Before you issue the @code{run} command, @value{GDBN} does not understand
16966 references to a function in a shared library, however---unless you are
16967 debugging a core file).
16969 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16970 automatically loads the symbols at the time of the @code{shl_load} call.
16972 @c FIXME: some @value{GDBN} release may permit some refs to undef
16973 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16974 @c FIXME...lib; check this from time to time when updating manual
16976 There are times, however, when you may wish to not automatically load
16977 symbol definitions from shared libraries, such as when they are
16978 particularly large or there are many of them.
16980 To control the automatic loading of shared library symbols, use the
16984 @kindex set auto-solib-add
16985 @item set auto-solib-add @var{mode}
16986 If @var{mode} is @code{on}, symbols from all shared object libraries
16987 will be loaded automatically when the inferior begins execution, you
16988 attach to an independently started inferior, or when the dynamic linker
16989 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16990 is @code{off}, symbols must be loaded manually, using the
16991 @code{sharedlibrary} command. The default value is @code{on}.
16993 @cindex memory used for symbol tables
16994 If your program uses lots of shared libraries with debug info that
16995 takes large amounts of memory, you can decrease the @value{GDBN}
16996 memory footprint by preventing it from automatically loading the
16997 symbols from shared libraries. To that end, type @kbd{set
16998 auto-solib-add off} before running the inferior, then load each
16999 library whose debug symbols you do need with @kbd{sharedlibrary
17000 @var{regexp}}, where @var{regexp} is a regular expression that matches
17001 the libraries whose symbols you want to be loaded.
17003 @kindex show auto-solib-add
17004 @item show auto-solib-add
17005 Display the current autoloading mode.
17008 @cindex load shared library
17009 To explicitly load shared library symbols, use the @code{sharedlibrary}
17013 @kindex info sharedlibrary
17015 @item info share @var{regex}
17016 @itemx info sharedlibrary @var{regex}
17017 Print the names of the shared libraries which are currently loaded
17018 that match @var{regex}. If @var{regex} is omitted then print
17019 all shared libraries that are loaded.
17021 @kindex sharedlibrary
17023 @item sharedlibrary @var{regex}
17024 @itemx share @var{regex}
17025 Load shared object library symbols for files matching a
17026 Unix regular expression.
17027 As with files loaded automatically, it only loads shared libraries
17028 required by your program for a core file or after typing @code{run}. If
17029 @var{regex} is omitted all shared libraries required by your program are
17032 @item nosharedlibrary
17033 @kindex nosharedlibrary
17034 @cindex unload symbols from shared libraries
17035 Unload all shared object library symbols. This discards all symbols
17036 that have been loaded from all shared libraries. Symbols from shared
17037 libraries that were loaded by explicit user requests are not
17041 Sometimes you may wish that @value{GDBN} stops and gives you control
17042 when any of shared library events happen. The best way to do this is
17043 to use @code{catch load} and @code{catch unload} (@pxref{Set
17046 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17047 command for this. This command exists for historical reasons. It is
17048 less useful than setting a catchpoint, because it does not allow for
17049 conditions or commands as a catchpoint does.
17052 @item set stop-on-solib-events
17053 @kindex set stop-on-solib-events
17054 This command controls whether @value{GDBN} should give you control
17055 when the dynamic linker notifies it about some shared library event.
17056 The most common event of interest is loading or unloading of a new
17059 @item show stop-on-solib-events
17060 @kindex show stop-on-solib-events
17061 Show whether @value{GDBN} stops and gives you control when shared
17062 library events happen.
17065 Shared libraries are also supported in many cross or remote debugging
17066 configurations. @value{GDBN} needs to have access to the target's libraries;
17067 this can be accomplished either by providing copies of the libraries
17068 on the host system, or by asking @value{GDBN} to automatically retrieve the
17069 libraries from the target. If copies of the target libraries are
17070 provided, they need to be the same as the target libraries, although the
17071 copies on the target can be stripped as long as the copies on the host are
17074 @cindex where to look for shared libraries
17075 For remote debugging, you need to tell @value{GDBN} where the target
17076 libraries are, so that it can load the correct copies---otherwise, it
17077 may try to load the host's libraries. @value{GDBN} has two variables
17078 to specify the search directories for target libraries.
17081 @cindex prefix for shared library file names
17082 @cindex system root, alternate
17083 @kindex set solib-absolute-prefix
17084 @kindex set sysroot
17085 @item set sysroot @var{path}
17086 Use @var{path} as the system root for the program being debugged. Any
17087 absolute shared library paths will be prefixed with @var{path}; many
17088 runtime loaders store the absolute paths to the shared library in the
17089 target program's memory. If you use @code{set sysroot} to find shared
17090 libraries, they need to be laid out in the same way that they are on
17091 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17094 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17095 retrieve the target libraries from the remote system. This is only
17096 supported when using a remote target that supports the @code{remote get}
17097 command (@pxref{File Transfer,,Sending files to a remote system}).
17098 The part of @var{path} following the initial @file{remote:}
17099 (if present) is used as system root prefix on the remote file system.
17100 @footnote{If you want to specify a local system root using a directory
17101 that happens to be named @file{remote:}, you need to use some equivalent
17102 variant of the name like @file{./remote:}.}
17104 For targets with an MS-DOS based filesystem, such as MS-Windows and
17105 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17106 absolute file name with @var{path}. But first, on Unix hosts,
17107 @value{GDBN} converts all backslash directory separators into forward
17108 slashes, because the backslash is not a directory separator on Unix:
17111 c:\foo\bar.dll @result{} c:/foo/bar.dll
17114 Then, @value{GDBN} attempts prefixing the target file name with
17115 @var{path}, and looks for the resulting file name in the host file
17119 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17122 If that does not find the shared library, @value{GDBN} tries removing
17123 the @samp{:} character from the drive spec, both for convenience, and,
17124 for the case of the host file system not supporting file names with
17128 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17131 This makes it possible to have a system root that mirrors a target
17132 with more than one drive. E.g., you may want to setup your local
17133 copies of the target system shared libraries like so (note @samp{c} vs
17137 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17138 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17139 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17143 and point the system root at @file{/path/to/sysroot}, so that
17144 @value{GDBN} can find the correct copies of both
17145 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17147 If that still does not find the shared library, @value{GDBN} tries
17148 removing the whole drive spec from the target file name:
17151 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17154 This last lookup makes it possible to not care about the drive name,
17155 if you don't want or need to.
17157 The @code{set solib-absolute-prefix} command is an alias for @code{set
17160 @cindex default system root
17161 @cindex @samp{--with-sysroot}
17162 You can set the default system root by using the configure-time
17163 @samp{--with-sysroot} option. If the system root is inside
17164 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17165 @samp{--exec-prefix}), then the default system root will be updated
17166 automatically if the installed @value{GDBN} is moved to a new
17169 @kindex show sysroot
17171 Display the current shared library prefix.
17173 @kindex set solib-search-path
17174 @item set solib-search-path @var{path}
17175 If this variable is set, @var{path} is a colon-separated list of
17176 directories to search for shared libraries. @samp{solib-search-path}
17177 is used after @samp{sysroot} fails to locate the library, or if the
17178 path to the library is relative instead of absolute. If you want to
17179 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17180 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17181 finding your host's libraries. @samp{sysroot} is preferred; setting
17182 it to a nonexistent directory may interfere with automatic loading
17183 of shared library symbols.
17185 @kindex show solib-search-path
17186 @item show solib-search-path
17187 Display the current shared library search path.
17189 @cindex DOS file-name semantics of file names.
17190 @kindex set target-file-system-kind (unix|dos-based|auto)
17191 @kindex show target-file-system-kind
17192 @item set target-file-system-kind @var{kind}
17193 Set assumed file system kind for target reported file names.
17195 Shared library file names as reported by the target system may not
17196 make sense as is on the system @value{GDBN} is running on. For
17197 example, when remote debugging a target that has MS-DOS based file
17198 system semantics, from a Unix host, the target may be reporting to
17199 @value{GDBN} a list of loaded shared libraries with file names such as
17200 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17201 drive letters, so the @samp{c:\} prefix is not normally understood as
17202 indicating an absolute file name, and neither is the backslash
17203 normally considered a directory separator character. In that case,
17204 the native file system would interpret this whole absolute file name
17205 as a relative file name with no directory components. This would make
17206 it impossible to point @value{GDBN} at a copy of the remote target's
17207 shared libraries on the host using @code{set sysroot}, and impractical
17208 with @code{set solib-search-path}. Setting
17209 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17210 to interpret such file names similarly to how the target would, and to
17211 map them to file names valid on @value{GDBN}'s native file system
17212 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17213 to one of the supported file system kinds. In that case, @value{GDBN}
17214 tries to determine the appropriate file system variant based on the
17215 current target's operating system (@pxref{ABI, ,Configuring the
17216 Current ABI}). The supported file system settings are:
17220 Instruct @value{GDBN} to assume the target file system is of Unix
17221 kind. Only file names starting the forward slash (@samp{/}) character
17222 are considered absolute, and the directory separator character is also
17226 Instruct @value{GDBN} to assume the target file system is DOS based.
17227 File names starting with either a forward slash, or a drive letter
17228 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17229 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17230 considered directory separators.
17233 Instruct @value{GDBN} to use the file system kind associated with the
17234 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17235 This is the default.
17239 @cindex file name canonicalization
17240 @cindex base name differences
17241 When processing file names provided by the user, @value{GDBN}
17242 frequently needs to compare them to the file names recorded in the
17243 program's debug info. Normally, @value{GDBN} compares just the
17244 @dfn{base names} of the files as strings, which is reasonably fast
17245 even for very large programs. (The base name of a file is the last
17246 portion of its name, after stripping all the leading directories.)
17247 This shortcut in comparison is based upon the assumption that files
17248 cannot have more than one base name. This is usually true, but
17249 references to files that use symlinks or similar filesystem
17250 facilities violate that assumption. If your program records files
17251 using such facilities, or if you provide file names to @value{GDBN}
17252 using symlinks etc., you can set @code{basenames-may-differ} to
17253 @code{true} to instruct @value{GDBN} to completely canonicalize each
17254 pair of file names it needs to compare. This will make file-name
17255 comparisons accurate, but at a price of a significant slowdown.
17258 @item set basenames-may-differ
17259 @kindex set basenames-may-differ
17260 Set whether a source file may have multiple base names.
17262 @item show basenames-may-differ
17263 @kindex show basenames-may-differ
17264 Show whether a source file may have multiple base names.
17267 @node Separate Debug Files
17268 @section Debugging Information in Separate Files
17269 @cindex separate debugging information files
17270 @cindex debugging information in separate files
17271 @cindex @file{.debug} subdirectories
17272 @cindex debugging information directory, global
17273 @cindex global debugging information directories
17274 @cindex build ID, and separate debugging files
17275 @cindex @file{.build-id} directory
17277 @value{GDBN} allows you to put a program's debugging information in a
17278 file separate from the executable itself, in a way that allows
17279 @value{GDBN} to find and load the debugging information automatically.
17280 Since debugging information can be very large---sometimes larger
17281 than the executable code itself---some systems distribute debugging
17282 information for their executables in separate files, which users can
17283 install only when they need to debug a problem.
17285 @value{GDBN} supports two ways of specifying the separate debug info
17290 The executable contains a @dfn{debug link} that specifies the name of
17291 the separate debug info file. The separate debug file's name is
17292 usually @file{@var{executable}.debug}, where @var{executable} is the
17293 name of the corresponding executable file without leading directories
17294 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17295 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17296 checksum for the debug file, which @value{GDBN} uses to validate that
17297 the executable and the debug file came from the same build.
17300 The executable contains a @dfn{build ID}, a unique bit string that is
17301 also present in the corresponding debug info file. (This is supported
17302 only on some operating systems, notably those which use the ELF format
17303 for binary files and the @sc{gnu} Binutils.) For more details about
17304 this feature, see the description of the @option{--build-id}
17305 command-line option in @ref{Options, , Command Line Options, ld.info,
17306 The GNU Linker}. The debug info file's name is not specified
17307 explicitly by the build ID, but can be computed from the build ID, see
17311 Depending on the way the debug info file is specified, @value{GDBN}
17312 uses two different methods of looking for the debug file:
17316 For the ``debug link'' method, @value{GDBN} looks up the named file in
17317 the directory of the executable file, then in a subdirectory of that
17318 directory named @file{.debug}, and finally under each one of the global debug
17319 directories, in a subdirectory whose name is identical to the leading
17320 directories of the executable's absolute file name.
17323 For the ``build ID'' method, @value{GDBN} looks in the
17324 @file{.build-id} subdirectory of each one of the global debug directories for
17325 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17326 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17327 are the rest of the bit string. (Real build ID strings are 32 or more
17328 hex characters, not 10.)
17331 So, for example, suppose you ask @value{GDBN} to debug
17332 @file{/usr/bin/ls}, which has a debug link that specifies the
17333 file @file{ls.debug}, and a build ID whose value in hex is
17334 @code{abcdef1234}. If the list of the global debug directories includes
17335 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17336 debug information files, in the indicated order:
17340 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17342 @file{/usr/bin/ls.debug}
17344 @file{/usr/bin/.debug/ls.debug}
17346 @file{/usr/lib/debug/usr/bin/ls.debug}.
17349 @anchor{debug-file-directory}
17350 Global debugging info directories default to what is set by @value{GDBN}
17351 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17352 you can also set the global debugging info directories, and view the list
17353 @value{GDBN} is currently using.
17357 @kindex set debug-file-directory
17358 @item set debug-file-directory @var{directories}
17359 Set the directories which @value{GDBN} searches for separate debugging
17360 information files to @var{directory}. Multiple path components can be set
17361 concatenating them by a path separator.
17363 @kindex show debug-file-directory
17364 @item show debug-file-directory
17365 Show the directories @value{GDBN} searches for separate debugging
17370 @cindex @code{.gnu_debuglink} sections
17371 @cindex debug link sections
17372 A debug link is a special section of the executable file named
17373 @code{.gnu_debuglink}. The section must contain:
17377 A filename, with any leading directory components removed, followed by
17380 zero to three bytes of padding, as needed to reach the next four-byte
17381 boundary within the section, and
17383 a four-byte CRC checksum, stored in the same endianness used for the
17384 executable file itself. The checksum is computed on the debugging
17385 information file's full contents by the function given below, passing
17386 zero as the @var{crc} argument.
17389 Any executable file format can carry a debug link, as long as it can
17390 contain a section named @code{.gnu_debuglink} with the contents
17393 @cindex @code{.note.gnu.build-id} sections
17394 @cindex build ID sections
17395 The build ID is a special section in the executable file (and in other
17396 ELF binary files that @value{GDBN} may consider). This section is
17397 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17398 It contains unique identification for the built files---the ID remains
17399 the same across multiple builds of the same build tree. The default
17400 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17401 content for the build ID string. The same section with an identical
17402 value is present in the original built binary with symbols, in its
17403 stripped variant, and in the separate debugging information file.
17405 The debugging information file itself should be an ordinary
17406 executable, containing a full set of linker symbols, sections, and
17407 debugging information. The sections of the debugging information file
17408 should have the same names, addresses, and sizes as the original file,
17409 but they need not contain any data---much like a @code{.bss} section
17410 in an ordinary executable.
17412 The @sc{gnu} binary utilities (Binutils) package includes the
17413 @samp{objcopy} utility that can produce
17414 the separated executable / debugging information file pairs using the
17415 following commands:
17418 @kbd{objcopy --only-keep-debug foo foo.debug}
17423 These commands remove the debugging
17424 information from the executable file @file{foo} and place it in the file
17425 @file{foo.debug}. You can use the first, second or both methods to link the
17430 The debug link method needs the following additional command to also leave
17431 behind a debug link in @file{foo}:
17434 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17437 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17438 a version of the @code{strip} command such that the command @kbd{strip foo -f
17439 foo.debug} has the same functionality as the two @code{objcopy} commands and
17440 the @code{ln -s} command above, together.
17443 Build ID gets embedded into the main executable using @code{ld --build-id} or
17444 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17445 compatibility fixes for debug files separation are present in @sc{gnu} binary
17446 utilities (Binutils) package since version 2.18.
17451 @cindex CRC algorithm definition
17452 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17453 IEEE 802.3 using the polynomial:
17455 @c TexInfo requires naked braces for multi-digit exponents for Tex
17456 @c output, but this causes HTML output to barf. HTML has to be set using
17457 @c raw commands. So we end up having to specify this equation in 2
17462 <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>
17463 + <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
17469 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17470 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17474 The function is computed byte at a time, taking the least
17475 significant bit of each byte first. The initial pattern
17476 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17477 the final result is inverted to ensure trailing zeros also affect the
17480 @emph{Note:} This is the same CRC polynomial as used in handling the
17481 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17482 , @value{GDBN} Remote Serial Protocol}). However in the
17483 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17484 significant bit first, and the result is not inverted, so trailing
17485 zeros have no effect on the CRC value.
17487 To complete the description, we show below the code of the function
17488 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17489 initially supplied @code{crc} argument means that an initial call to
17490 this function passing in zero will start computing the CRC using
17493 @kindex gnu_debuglink_crc32
17496 gnu_debuglink_crc32 (unsigned long crc,
17497 unsigned char *buf, size_t len)
17499 static const unsigned long crc32_table[256] =
17501 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17502 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17503 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17504 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17505 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17506 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17507 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17508 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17509 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17510 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17511 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17512 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17513 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17514 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17515 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17516 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17517 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17518 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17519 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17520 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17521 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17522 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17523 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17524 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17525 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17526 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17527 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17528 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17529 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17530 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17531 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17532 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17533 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17534 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17535 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17536 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17537 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17538 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17539 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17540 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17541 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17542 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17543 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17544 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17545 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17546 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17547 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17548 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17549 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17550 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17551 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17554 unsigned char *end;
17556 crc = ~crc & 0xffffffff;
17557 for (end = buf + len; buf < end; ++buf)
17558 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17559 return ~crc & 0xffffffff;
17564 This computation does not apply to the ``build ID'' method.
17566 @node MiniDebugInfo
17567 @section Debugging information in a special section
17568 @cindex separate debug sections
17569 @cindex @samp{.gnu_debugdata} section
17571 Some systems ship pre-built executables and libraries that have a
17572 special @samp{.gnu_debugdata} section. This feature is called
17573 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17574 is used to supply extra symbols for backtraces.
17576 The intent of this section is to provide extra minimal debugging
17577 information for use in simple backtraces. It is not intended to be a
17578 replacement for full separate debugging information (@pxref{Separate
17579 Debug Files}). The example below shows the intended use; however,
17580 @value{GDBN} does not currently put restrictions on what sort of
17581 debugging information might be included in the section.
17583 @value{GDBN} has support for this extension. If the section exists,
17584 then it is used provided that no other source of debugging information
17585 can be found, and that @value{GDBN} was configured with LZMA support.
17587 This section can be easily created using @command{objcopy} and other
17588 standard utilities:
17591 # Extract the dynamic symbols from the main binary, there is no need
17592 # to also have these in the normal symbol table.
17593 nm -D @var{binary} --format=posix --defined-only \
17594 | awk '@{ print $1 @}' | sort > dynsyms
17596 # Extract all the text (i.e. function) symbols from the debuginfo.
17597 # (Note that we actually also accept "D" symbols, for the benefit
17598 # of platforms like PowerPC64 that use function descriptors.)
17599 nm @var{binary} --format=posix --defined-only \
17600 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17603 # Keep all the function symbols not already in the dynamic symbol
17605 comm -13 dynsyms funcsyms > keep_symbols
17607 # Separate full debug info into debug binary.
17608 objcopy --only-keep-debug @var{binary} debug
17610 # Copy the full debuginfo, keeping only a minimal set of symbols and
17611 # removing some unnecessary sections.
17612 objcopy -S --remove-section .gdb_index --remove-section .comment \
17613 --keep-symbols=keep_symbols debug mini_debuginfo
17615 # Drop the full debug info from the original binary.
17616 strip --strip-all -R .comment @var{binary}
17618 # Inject the compressed data into the .gnu_debugdata section of the
17621 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17625 @section Index Files Speed Up @value{GDBN}
17626 @cindex index files
17627 @cindex @samp{.gdb_index} section
17629 When @value{GDBN} finds a symbol file, it scans the symbols in the
17630 file in order to construct an internal symbol table. This lets most
17631 @value{GDBN} operations work quickly---at the cost of a delay early
17632 on. For large programs, this delay can be quite lengthy, so
17633 @value{GDBN} provides a way to build an index, which speeds up
17636 The index is stored as a section in the symbol file. @value{GDBN} can
17637 write the index to a file, then you can put it into the symbol file
17638 using @command{objcopy}.
17640 To create an index file, use the @code{save gdb-index} command:
17643 @item save gdb-index @var{directory}
17644 @kindex save gdb-index
17645 Create an index file for each symbol file currently known by
17646 @value{GDBN}. Each file is named after its corresponding symbol file,
17647 with @samp{.gdb-index} appended, and is written into the given
17651 Once you have created an index file you can merge it into your symbol
17652 file, here named @file{symfile}, using @command{objcopy}:
17655 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17656 --set-section-flags .gdb_index=readonly symfile symfile
17659 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17660 sections that have been deprecated. Usually they are deprecated because
17661 they are missing a new feature or have performance issues.
17662 To tell @value{GDBN} to use a deprecated index section anyway
17663 specify @code{set use-deprecated-index-sections on}.
17664 The default is @code{off}.
17665 This can speed up startup, but may result in some functionality being lost.
17666 @xref{Index Section Format}.
17668 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17669 must be done before gdb reads the file. The following will not work:
17672 $ gdb -ex "set use-deprecated-index-sections on" <program>
17675 Instead you must do, for example,
17678 $ gdb -iex "set use-deprecated-index-sections on" <program>
17681 There are currently some limitation on indices. They only work when
17682 for DWARF debugging information, not stabs. And, they do not
17683 currently work for programs using Ada.
17685 @node Symbol Errors
17686 @section Errors Reading Symbol Files
17688 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17689 such as symbol types it does not recognize, or known bugs in compiler
17690 output. By default, @value{GDBN} does not notify you of such problems, since
17691 they are relatively common and primarily of interest to people
17692 debugging compilers. If you are interested in seeing information
17693 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17694 only one message about each such type of problem, no matter how many
17695 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17696 to see how many times the problems occur, with the @code{set
17697 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17700 The messages currently printed, and their meanings, include:
17703 @item inner block not inside outer block in @var{symbol}
17705 The symbol information shows where symbol scopes begin and end
17706 (such as at the start of a function or a block of statements). This
17707 error indicates that an inner scope block is not fully contained
17708 in its outer scope blocks.
17710 @value{GDBN} circumvents the problem by treating the inner block as if it had
17711 the same scope as the outer block. In the error message, @var{symbol}
17712 may be shown as ``@code{(don't know)}'' if the outer block is not a
17715 @item block at @var{address} out of order
17717 The symbol information for symbol scope blocks should occur in
17718 order of increasing addresses. This error indicates that it does not
17721 @value{GDBN} does not circumvent this problem, and has trouble
17722 locating symbols in the source file whose symbols it is reading. (You
17723 can often determine what source file is affected by specifying
17724 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17727 @item bad block start address patched
17729 The symbol information for a symbol scope block has a start address
17730 smaller than the address of the preceding source line. This is known
17731 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17733 @value{GDBN} circumvents the problem by treating the symbol scope block as
17734 starting on the previous source line.
17736 @item bad string table offset in symbol @var{n}
17739 Symbol number @var{n} contains a pointer into the string table which is
17740 larger than the size of the string table.
17742 @value{GDBN} circumvents the problem by considering the symbol to have the
17743 name @code{foo}, which may cause other problems if many symbols end up
17746 @item unknown symbol type @code{0x@var{nn}}
17748 The symbol information contains new data types that @value{GDBN} does
17749 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17750 uncomprehended information, in hexadecimal.
17752 @value{GDBN} circumvents the error by ignoring this symbol information.
17753 This usually allows you to debug your program, though certain symbols
17754 are not accessible. If you encounter such a problem and feel like
17755 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17756 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17757 and examine @code{*bufp} to see the symbol.
17759 @item stub type has NULL name
17761 @value{GDBN} could not find the full definition for a struct or class.
17763 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17764 The symbol information for a C@t{++} member function is missing some
17765 information that recent versions of the compiler should have output for
17768 @item info mismatch between compiler and debugger
17770 @value{GDBN} could not parse a type specification output by the compiler.
17775 @section GDB Data Files
17777 @cindex prefix for data files
17778 @value{GDBN} will sometimes read an auxiliary data file. These files
17779 are kept in a directory known as the @dfn{data directory}.
17781 You can set the data directory's name, and view the name @value{GDBN}
17782 is currently using.
17785 @kindex set data-directory
17786 @item set data-directory @var{directory}
17787 Set the directory which @value{GDBN} searches for auxiliary data files
17788 to @var{directory}.
17790 @kindex show data-directory
17791 @item show data-directory
17792 Show the directory @value{GDBN} searches for auxiliary data files.
17795 @cindex default data directory
17796 @cindex @samp{--with-gdb-datadir}
17797 You can set the default data directory by using the configure-time
17798 @samp{--with-gdb-datadir} option. If the data directory is inside
17799 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17800 @samp{--exec-prefix}), then the default data directory will be updated
17801 automatically if the installed @value{GDBN} is moved to a new
17804 The data directory may also be specified with the
17805 @code{--data-directory} command line option.
17806 @xref{Mode Options}.
17809 @chapter Specifying a Debugging Target
17811 @cindex debugging target
17812 A @dfn{target} is the execution environment occupied by your program.
17814 Often, @value{GDBN} runs in the same host environment as your program;
17815 in that case, the debugging target is specified as a side effect when
17816 you use the @code{file} or @code{core} commands. When you need more
17817 flexibility---for example, running @value{GDBN} on a physically separate
17818 host, or controlling a standalone system over a serial port or a
17819 realtime system over a TCP/IP connection---you can use the @code{target}
17820 command to specify one of the target types configured for @value{GDBN}
17821 (@pxref{Target Commands, ,Commands for Managing Targets}).
17823 @cindex target architecture
17824 It is possible to build @value{GDBN} for several different @dfn{target
17825 architectures}. When @value{GDBN} is built like that, you can choose
17826 one of the available architectures with the @kbd{set architecture}
17830 @kindex set architecture
17831 @kindex show architecture
17832 @item set architecture @var{arch}
17833 This command sets the current target architecture to @var{arch}. The
17834 value of @var{arch} can be @code{"auto"}, in addition to one of the
17835 supported architectures.
17837 @item show architecture
17838 Show the current target architecture.
17840 @item set processor
17842 @kindex set processor
17843 @kindex show processor
17844 These are alias commands for, respectively, @code{set architecture}
17845 and @code{show architecture}.
17849 * Active Targets:: Active targets
17850 * Target Commands:: Commands for managing targets
17851 * Byte Order:: Choosing target byte order
17854 @node Active Targets
17855 @section Active Targets
17857 @cindex stacking targets
17858 @cindex active targets
17859 @cindex multiple targets
17861 There are multiple classes of targets such as: processes, executable files or
17862 recording sessions. Core files belong to the process class, making core file
17863 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17864 on multiple active targets, one in each class. This allows you to (for
17865 example) start a process and inspect its activity, while still having access to
17866 the executable file after the process finishes. Or if you start process
17867 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17868 presented a virtual layer of the recording target, while the process target
17869 remains stopped at the chronologically last point of the process execution.
17871 Use the @code{core-file} and @code{exec-file} commands to select a new core
17872 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17873 specify as a target a process that is already running, use the @code{attach}
17874 command (@pxref{Attach, ,Debugging an Already-running Process}).
17876 @node Target Commands
17877 @section Commands for Managing Targets
17880 @item target @var{type} @var{parameters}
17881 Connects the @value{GDBN} host environment to a target machine or
17882 process. A target is typically a protocol for talking to debugging
17883 facilities. You use the argument @var{type} to specify the type or
17884 protocol of the target machine.
17886 Further @var{parameters} are interpreted by the target protocol, but
17887 typically include things like device names or host names to connect
17888 with, process numbers, and baud rates.
17890 The @code{target} command does not repeat if you press @key{RET} again
17891 after executing the command.
17893 @kindex help target
17895 Displays the names of all targets available. To display targets
17896 currently selected, use either @code{info target} or @code{info files}
17897 (@pxref{Files, ,Commands to Specify Files}).
17899 @item help target @var{name}
17900 Describe a particular target, including any parameters necessary to
17903 @kindex set gnutarget
17904 @item set gnutarget @var{args}
17905 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17906 knows whether it is reading an @dfn{executable},
17907 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17908 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17909 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17912 @emph{Warning:} To specify a file format with @code{set gnutarget},
17913 you must know the actual BFD name.
17917 @xref{Files, , Commands to Specify Files}.
17919 @kindex show gnutarget
17920 @item show gnutarget
17921 Use the @code{show gnutarget} command to display what file format
17922 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17923 @value{GDBN} will determine the file format for each file automatically,
17924 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17927 @cindex common targets
17928 Here are some common targets (available, or not, depending on the GDB
17933 @item target exec @var{program}
17934 @cindex executable file target
17935 An executable file. @samp{target exec @var{program}} is the same as
17936 @samp{exec-file @var{program}}.
17938 @item target core @var{filename}
17939 @cindex core dump file target
17940 A core dump file. @samp{target core @var{filename}} is the same as
17941 @samp{core-file @var{filename}}.
17943 @item target remote @var{medium}
17944 @cindex remote target
17945 A remote system connected to @value{GDBN} via a serial line or network
17946 connection. This command tells @value{GDBN} to use its own remote
17947 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17949 For example, if you have a board connected to @file{/dev/ttya} on the
17950 machine running @value{GDBN}, you could say:
17953 target remote /dev/ttya
17956 @code{target remote} supports the @code{load} command. This is only
17957 useful if you have some other way of getting the stub to the target
17958 system, and you can put it somewhere in memory where it won't get
17959 clobbered by the download.
17961 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17962 @cindex built-in simulator target
17963 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17971 works; however, you cannot assume that a specific memory map, device
17972 drivers, or even basic I/O is available, although some simulators do
17973 provide these. For info about any processor-specific simulator details,
17974 see the appropriate section in @ref{Embedded Processors, ,Embedded
17979 Different targets are available on different configurations of @value{GDBN};
17980 your configuration may have more or fewer targets.
17982 Many remote targets require you to download the executable's code once
17983 you've successfully established a connection. You may wish to control
17984 various aspects of this process.
17989 @kindex set hash@r{, for remote monitors}
17990 @cindex hash mark while downloading
17991 This command controls whether a hash mark @samp{#} is displayed while
17992 downloading a file to the remote monitor. If on, a hash mark is
17993 displayed after each S-record is successfully downloaded to the
17997 @kindex show hash@r{, for remote monitors}
17998 Show the current status of displaying the hash mark.
18000 @item set debug monitor
18001 @kindex set debug monitor
18002 @cindex display remote monitor communications
18003 Enable or disable display of communications messages between
18004 @value{GDBN} and the remote monitor.
18006 @item show debug monitor
18007 @kindex show debug monitor
18008 Show the current status of displaying communications between
18009 @value{GDBN} and the remote monitor.
18014 @kindex load @var{filename}
18015 @item load @var{filename}
18017 Depending on what remote debugging facilities are configured into
18018 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18019 is meant to make @var{filename} (an executable) available for debugging
18020 on the remote system---by downloading, or dynamic linking, for example.
18021 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18022 the @code{add-symbol-file} command.
18024 If your @value{GDBN} does not have a @code{load} command, attempting to
18025 execute it gets the error message ``@code{You can't do that when your
18026 target is @dots{}}''
18028 The file is loaded at whatever address is specified in the executable.
18029 For some object file formats, you can specify the load address when you
18030 link the program; for other formats, like a.out, the object file format
18031 specifies a fixed address.
18032 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18034 Depending on the remote side capabilities, @value{GDBN} may be able to
18035 load programs into flash memory.
18037 @code{load} does not repeat if you press @key{RET} again after using it.
18041 @section Choosing Target Byte Order
18043 @cindex choosing target byte order
18044 @cindex target byte order
18046 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18047 offer the ability to run either big-endian or little-endian byte
18048 orders. Usually the executable or symbol will include a bit to
18049 designate the endian-ness, and you will not need to worry about
18050 which to use. However, you may still find it useful to adjust
18051 @value{GDBN}'s idea of processor endian-ness manually.
18055 @item set endian big
18056 Instruct @value{GDBN} to assume the target is big-endian.
18058 @item set endian little
18059 Instruct @value{GDBN} to assume the target is little-endian.
18061 @item set endian auto
18062 Instruct @value{GDBN} to use the byte order associated with the
18066 Display @value{GDBN}'s current idea of the target byte order.
18070 Note that these commands merely adjust interpretation of symbolic
18071 data on the host, and that they have absolutely no effect on the
18075 @node Remote Debugging
18076 @chapter Debugging Remote Programs
18077 @cindex remote debugging
18079 If you are trying to debug a program running on a machine that cannot run
18080 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18081 For example, you might use remote debugging on an operating system kernel,
18082 or on a small system which does not have a general purpose operating system
18083 powerful enough to run a full-featured debugger.
18085 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18086 to make this work with particular debugging targets. In addition,
18087 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18088 but not specific to any particular target system) which you can use if you
18089 write the remote stubs---the code that runs on the remote system to
18090 communicate with @value{GDBN}.
18092 Other remote targets may be available in your
18093 configuration of @value{GDBN}; use @code{help target} to list them.
18096 * Connecting:: Connecting to a remote target
18097 * File Transfer:: Sending files to a remote system
18098 * Server:: Using the gdbserver program
18099 * Remote Configuration:: Remote configuration
18100 * Remote Stub:: Implementing a remote stub
18104 @section Connecting to a Remote Target
18106 On the @value{GDBN} host machine, you will need an unstripped copy of
18107 your program, since @value{GDBN} needs symbol and debugging information.
18108 Start up @value{GDBN} as usual, using the name of the local copy of your
18109 program as the first argument.
18111 @cindex @code{target remote}
18112 @value{GDBN} can communicate with the target over a serial line, or
18113 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18114 each case, @value{GDBN} uses the same protocol for debugging your
18115 program; only the medium carrying the debugging packets varies. The
18116 @code{target remote} command establishes a connection to the target.
18117 Its arguments indicate which medium to use:
18121 @item target remote @var{serial-device}
18122 @cindex serial line, @code{target remote}
18123 Use @var{serial-device} to communicate with the target. For example,
18124 to use a serial line connected to the device named @file{/dev/ttyb}:
18127 target remote /dev/ttyb
18130 If you're using a serial line, you may want to give @value{GDBN} the
18131 @samp{--baud} option, or use the @code{set serial baud} command
18132 (@pxref{Remote Configuration, set serial baud}) before the
18133 @code{target} command.
18135 @item target remote @code{@var{host}:@var{port}}
18136 @itemx target remote @code{tcp:@var{host}:@var{port}}
18137 @cindex @acronym{TCP} port, @code{target remote}
18138 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18139 The @var{host} may be either a host name or a numeric @acronym{IP}
18140 address; @var{port} must be a decimal number. The @var{host} could be
18141 the target machine itself, if it is directly connected to the net, or
18142 it might be a terminal server which in turn has a serial line to the
18145 For example, to connect to port 2828 on a terminal server named
18149 target remote manyfarms:2828
18152 If your remote target is actually running on the same machine as your
18153 debugger session (e.g.@: a simulator for your target running on the
18154 same host), you can omit the hostname. For example, to connect to
18155 port 1234 on your local machine:
18158 target remote :1234
18162 Note that the colon is still required here.
18164 @item target remote @code{udp:@var{host}:@var{port}}
18165 @cindex @acronym{UDP} port, @code{target remote}
18166 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18167 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18170 target remote udp:manyfarms:2828
18173 When using a @acronym{UDP} connection for remote debugging, you should
18174 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18175 can silently drop packets on busy or unreliable networks, which will
18176 cause havoc with your debugging session.
18178 @item target remote | @var{command}
18179 @cindex pipe, @code{target remote} to
18180 Run @var{command} in the background and communicate with it using a
18181 pipe. The @var{command} is a shell command, to be parsed and expanded
18182 by the system's command shell, @code{/bin/sh}; it should expect remote
18183 protocol packets on its standard input, and send replies on its
18184 standard output. You could use this to run a stand-alone simulator
18185 that speaks the remote debugging protocol, to make net connections
18186 using programs like @code{ssh}, or for other similar tricks.
18188 If @var{command} closes its standard output (perhaps by exiting),
18189 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18190 program has already exited, this will have no effect.)
18194 Once the connection has been established, you can use all the usual
18195 commands to examine and change data. The remote program is already
18196 running; you can use @kbd{step} and @kbd{continue}, and you do not
18197 need to use @kbd{run}.
18199 @cindex interrupting remote programs
18200 @cindex remote programs, interrupting
18201 Whenever @value{GDBN} is waiting for the remote program, if you type the
18202 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18203 program. This may or may not succeed, depending in part on the hardware
18204 and the serial drivers the remote system uses. If you type the
18205 interrupt character once again, @value{GDBN} displays this prompt:
18208 Interrupted while waiting for the program.
18209 Give up (and stop debugging it)? (y or n)
18212 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18213 (If you decide you want to try again later, you can use @samp{target
18214 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18215 goes back to waiting.
18218 @kindex detach (remote)
18220 When you have finished debugging the remote program, you can use the
18221 @code{detach} command to release it from @value{GDBN} control.
18222 Detaching from the target normally resumes its execution, but the results
18223 will depend on your particular remote stub. After the @code{detach}
18224 command, @value{GDBN} is free to connect to another target.
18228 The @code{disconnect} command behaves like @code{detach}, except that
18229 the target is generally not resumed. It will wait for @value{GDBN}
18230 (this instance or another one) to connect and continue debugging. After
18231 the @code{disconnect} command, @value{GDBN} is again free to connect to
18234 @cindex send command to remote monitor
18235 @cindex extend @value{GDBN} for remote targets
18236 @cindex add new commands for external monitor
18238 @item monitor @var{cmd}
18239 This command allows you to send arbitrary commands directly to the
18240 remote monitor. Since @value{GDBN} doesn't care about the commands it
18241 sends like this, this command is the way to extend @value{GDBN}---you
18242 can add new commands that only the external monitor will understand
18246 @node File Transfer
18247 @section Sending files to a remote system
18248 @cindex remote target, file transfer
18249 @cindex file transfer
18250 @cindex sending files to remote systems
18252 Some remote targets offer the ability to transfer files over the same
18253 connection used to communicate with @value{GDBN}. This is convenient
18254 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18255 running @code{gdbserver} over a network interface. For other targets,
18256 e.g.@: embedded devices with only a single serial port, this may be
18257 the only way to upload or download files.
18259 Not all remote targets support these commands.
18263 @item remote put @var{hostfile} @var{targetfile}
18264 Copy file @var{hostfile} from the host system (the machine running
18265 @value{GDBN}) to @var{targetfile} on the target system.
18268 @item remote get @var{targetfile} @var{hostfile}
18269 Copy file @var{targetfile} from the target system to @var{hostfile}
18270 on the host system.
18272 @kindex remote delete
18273 @item remote delete @var{targetfile}
18274 Delete @var{targetfile} from the target system.
18279 @section Using the @code{gdbserver} Program
18282 @cindex remote connection without stubs
18283 @code{gdbserver} is a control program for Unix-like systems, which
18284 allows you to connect your program with a remote @value{GDBN} via
18285 @code{target remote}---but without linking in the usual debugging stub.
18287 @code{gdbserver} is not a complete replacement for the debugging stubs,
18288 because it requires essentially the same operating-system facilities
18289 that @value{GDBN} itself does. In fact, a system that can run
18290 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18291 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18292 because it is a much smaller program than @value{GDBN} itself. It is
18293 also easier to port than all of @value{GDBN}, so you may be able to get
18294 started more quickly on a new system by using @code{gdbserver}.
18295 Finally, if you develop code for real-time systems, you may find that
18296 the tradeoffs involved in real-time operation make it more convenient to
18297 do as much development work as possible on another system, for example
18298 by cross-compiling. You can use @code{gdbserver} to make a similar
18299 choice for debugging.
18301 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18302 or a TCP connection, using the standard @value{GDBN} remote serial
18306 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18307 Do not run @code{gdbserver} connected to any public network; a
18308 @value{GDBN} connection to @code{gdbserver} provides access to the
18309 target system with the same privileges as the user running
18313 @subsection Running @code{gdbserver}
18314 @cindex arguments, to @code{gdbserver}
18315 @cindex @code{gdbserver}, command-line arguments
18317 Run @code{gdbserver} on the target system. You need a copy of the
18318 program you want to debug, including any libraries it requires.
18319 @code{gdbserver} does not need your program's symbol table, so you can
18320 strip the program if necessary to save space. @value{GDBN} on the host
18321 system does all the symbol handling.
18323 To use the server, you must tell it how to communicate with @value{GDBN};
18324 the name of your program; and the arguments for your program. The usual
18328 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18331 @var{comm} is either a device name (to use a serial line), or a TCP
18332 hostname and portnumber, or @code{-} or @code{stdio} to use
18333 stdin/stdout of @code{gdbserver}.
18334 For example, to debug Emacs with the argument
18335 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18339 target> gdbserver /dev/com1 emacs foo.txt
18342 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18345 To use a TCP connection instead of a serial line:
18348 target> gdbserver host:2345 emacs foo.txt
18351 The only difference from the previous example is the first argument,
18352 specifying that you are communicating with the host @value{GDBN} via
18353 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18354 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18355 (Currently, the @samp{host} part is ignored.) You can choose any number
18356 you want for the port number as long as it does not conflict with any
18357 TCP ports already in use on the target system (for example, @code{23} is
18358 reserved for @code{telnet}).@footnote{If you choose a port number that
18359 conflicts with another service, @code{gdbserver} prints an error message
18360 and exits.} You must use the same port number with the host @value{GDBN}
18361 @code{target remote} command.
18363 The @code{stdio} connection is useful when starting @code{gdbserver}
18367 (gdb) target remote | ssh -T hostname gdbserver - hello
18370 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18371 and we don't want escape-character handling. Ssh does this by default when
18372 a command is provided, the flag is provided to make it explicit.
18373 You could elide it if you want to.
18375 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18376 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18377 display through a pipe connected to gdbserver.
18378 Both @code{stdout} and @code{stderr} use the same pipe.
18380 @subsubsection Attaching to a Running Program
18381 @cindex attach to a program, @code{gdbserver}
18382 @cindex @option{--attach}, @code{gdbserver} option
18384 On some targets, @code{gdbserver} can also attach to running programs.
18385 This is accomplished via the @code{--attach} argument. The syntax is:
18388 target> gdbserver --attach @var{comm} @var{pid}
18391 @var{pid} is the process ID of a currently running process. It isn't necessary
18392 to point @code{gdbserver} at a binary for the running process.
18395 You can debug processes by name instead of process ID if your target has the
18396 @code{pidof} utility:
18399 target> gdbserver --attach @var{comm} `pidof @var{program}`
18402 In case more than one copy of @var{program} is running, or @var{program}
18403 has multiple threads, most versions of @code{pidof} support the
18404 @code{-s} option to only return the first process ID.
18406 @subsubsection Multi-Process Mode for @code{gdbserver}
18407 @cindex @code{gdbserver}, multiple processes
18408 @cindex multiple processes with @code{gdbserver}
18410 When you connect to @code{gdbserver} using @code{target remote},
18411 @code{gdbserver} debugs the specified program only once. When the
18412 program exits, or you detach from it, @value{GDBN} closes the connection
18413 and @code{gdbserver} exits.
18415 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18416 enters multi-process mode. When the debugged program exits, or you
18417 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18418 though no program is running. The @code{run} and @code{attach}
18419 commands instruct @code{gdbserver} to run or attach to a new program.
18420 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18421 remote exec-file}) to select the program to run. Command line
18422 arguments are supported, except for wildcard expansion and I/O
18423 redirection (@pxref{Arguments}).
18425 @cindex @option{--multi}, @code{gdbserver} option
18426 To start @code{gdbserver} without supplying an initial command to run
18427 or process ID to attach, use the @option{--multi} command line option.
18428 Then you can connect using @kbd{target extended-remote} and start
18429 the program you want to debug.
18431 In multi-process mode @code{gdbserver} does not automatically exit unless you
18432 use the option @option{--once}. You can terminate it by using
18433 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18434 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18435 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18436 @option{--multi} option to @code{gdbserver} has no influence on that.
18438 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18440 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18442 @code{gdbserver} normally terminates after all of its debugged processes have
18443 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18444 extended-remote}, @code{gdbserver} stays running even with no processes left.
18445 @value{GDBN} normally terminates the spawned debugged process on its exit,
18446 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18447 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18448 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18449 stays running even in the @kbd{target remote} mode.
18451 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18452 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18453 completeness, at most one @value{GDBN} can be connected at a time.
18455 @cindex @option{--once}, @code{gdbserver} option
18456 By default, @code{gdbserver} keeps the listening TCP port open, so that
18457 subsequent connections are possible. However, if you start @code{gdbserver}
18458 with the @option{--once} option, it will stop listening for any further
18459 connection attempts after connecting to the first @value{GDBN} session. This
18460 means no further connections to @code{gdbserver} will be possible after the
18461 first one. It also means @code{gdbserver} will terminate after the first
18462 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18463 connections and even in the @kbd{target extended-remote} mode. The
18464 @option{--once} option allows reusing the same port number for connecting to
18465 multiple instances of @code{gdbserver} running on the same host, since each
18466 instance closes its port after the first connection.
18468 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18470 @cindex @option{--debug}, @code{gdbserver} option
18471 The @option{--debug} option tells @code{gdbserver} to display extra
18472 status information about the debugging process.
18473 @cindex @option{--remote-debug}, @code{gdbserver} option
18474 The @option{--remote-debug} option tells @code{gdbserver} to display
18475 remote protocol debug output. These options are intended for
18476 @code{gdbserver} development and for bug reports to the developers.
18478 @cindex @option{--wrapper}, @code{gdbserver} option
18479 The @option{--wrapper} option specifies a wrapper to launch programs
18480 for debugging. The option should be followed by the name of the
18481 wrapper, then any command-line arguments to pass to the wrapper, then
18482 @kbd{--} indicating the end of the wrapper arguments.
18484 @code{gdbserver} runs the specified wrapper program with a combined
18485 command line including the wrapper arguments, then the name of the
18486 program to debug, then any arguments to the program. The wrapper
18487 runs until it executes your program, and then @value{GDBN} gains control.
18489 You can use any program that eventually calls @code{execve} with
18490 its arguments as a wrapper. Several standard Unix utilities do
18491 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18492 with @code{exec "$@@"} will also work.
18494 For example, you can use @code{env} to pass an environment variable to
18495 the debugged program, without setting the variable in @code{gdbserver}'s
18499 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18502 @subsection Connecting to @code{gdbserver}
18504 Run @value{GDBN} on the host system.
18506 First make sure you have the necessary symbol files. Load symbols for
18507 your application using the @code{file} command before you connect. Use
18508 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18509 was compiled with the correct sysroot using @code{--with-sysroot}).
18511 The symbol file and target libraries must exactly match the executable
18512 and libraries on the target, with one exception: the files on the host
18513 system should not be stripped, even if the files on the target system
18514 are. Mismatched or missing files will lead to confusing results
18515 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18516 files may also prevent @code{gdbserver} from debugging multi-threaded
18519 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18520 For TCP connections, you must start up @code{gdbserver} prior to using
18521 the @code{target remote} command. Otherwise you may get an error whose
18522 text depends on the host system, but which usually looks something like
18523 @samp{Connection refused}. Don't use the @code{load}
18524 command in @value{GDBN} when using @code{gdbserver}, since the program is
18525 already on the target.
18527 @subsection Monitor Commands for @code{gdbserver}
18528 @cindex monitor commands, for @code{gdbserver}
18529 @anchor{Monitor Commands for gdbserver}
18531 During a @value{GDBN} session using @code{gdbserver}, you can use the
18532 @code{monitor} command to send special requests to @code{gdbserver}.
18533 Here are the available commands.
18537 List the available monitor commands.
18539 @item monitor set debug 0
18540 @itemx monitor set debug 1
18541 Disable or enable general debugging messages.
18543 @item monitor set remote-debug 0
18544 @itemx monitor set remote-debug 1
18545 Disable or enable specific debugging messages associated with the remote
18546 protocol (@pxref{Remote Protocol}).
18548 @item monitor set libthread-db-search-path [PATH]
18549 @cindex gdbserver, search path for @code{libthread_db}
18550 When this command is issued, @var{path} is a colon-separated list of
18551 directories to search for @code{libthread_db} (@pxref{Threads,,set
18552 libthread-db-search-path}). If you omit @var{path},
18553 @samp{libthread-db-search-path} will be reset to its default value.
18555 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18556 not supported in @code{gdbserver}.
18559 Tell gdbserver to exit immediately. This command should be followed by
18560 @code{disconnect} to close the debugging session. @code{gdbserver} will
18561 detach from any attached processes and kill any processes it created.
18562 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18563 of a multi-process mode debug session.
18567 @subsection Tracepoints support in @code{gdbserver}
18568 @cindex tracepoints support in @code{gdbserver}
18570 On some targets, @code{gdbserver} supports tracepoints, fast
18571 tracepoints and static tracepoints.
18573 For fast or static tracepoints to work, a special library called the
18574 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18575 This library is built and distributed as an integral part of
18576 @code{gdbserver}. In addition, support for static tracepoints
18577 requires building the in-process agent library with static tracepoints
18578 support. At present, the UST (LTTng Userspace Tracer,
18579 @url{http://lttng.org/ust}) tracing engine is supported. This support
18580 is automatically available if UST development headers are found in the
18581 standard include path when @code{gdbserver} is built, or if
18582 @code{gdbserver} was explicitly configured using @option{--with-ust}
18583 to point at such headers. You can explicitly disable the support
18584 using @option{--with-ust=no}.
18586 There are several ways to load the in-process agent in your program:
18589 @item Specifying it as dependency at link time
18591 You can link your program dynamically with the in-process agent
18592 library. On most systems, this is accomplished by adding
18593 @code{-linproctrace} to the link command.
18595 @item Using the system's preloading mechanisms
18597 You can force loading the in-process agent at startup time by using
18598 your system's support for preloading shared libraries. Many Unixes
18599 support the concept of preloading user defined libraries. In most
18600 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18601 in the environment. See also the description of @code{gdbserver}'s
18602 @option{--wrapper} command line option.
18604 @item Using @value{GDBN} to force loading the agent at run time
18606 On some systems, you can force the inferior to load a shared library,
18607 by calling a dynamic loader function in the inferior that takes care
18608 of dynamically looking up and loading a shared library. On most Unix
18609 systems, the function is @code{dlopen}. You'll use the @code{call}
18610 command for that. For example:
18613 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18616 Note that on most Unix systems, for the @code{dlopen} function to be
18617 available, the program needs to be linked with @code{-ldl}.
18620 On systems that have a userspace dynamic loader, like most Unix
18621 systems, when you connect to @code{gdbserver} using @code{target
18622 remote}, you'll find that the program is stopped at the dynamic
18623 loader's entry point, and no shared library has been loaded in the
18624 program's address space yet, including the in-process agent. In that
18625 case, before being able to use any of the fast or static tracepoints
18626 features, you need to let the loader run and load the shared
18627 libraries. The simplest way to do that is to run the program to the
18628 main procedure. E.g., if debugging a C or C@t{++} program, start
18629 @code{gdbserver} like so:
18632 $ gdbserver :9999 myprogram
18635 Start GDB and connect to @code{gdbserver} like so, and run to main:
18639 (@value{GDBP}) target remote myhost:9999
18640 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18641 (@value{GDBP}) b main
18642 (@value{GDBP}) continue
18645 The in-process tracing agent library should now be loaded into the
18646 process; you can confirm it with the @code{info sharedlibrary}
18647 command, which will list @file{libinproctrace.so} as loaded in the
18648 process. You are now ready to install fast tracepoints, list static
18649 tracepoint markers, probe static tracepoints markers, and start
18652 @node Remote Configuration
18653 @section Remote Configuration
18656 @kindex show remote
18657 This section documents the configuration options available when
18658 debugging remote programs. For the options related to the File I/O
18659 extensions of the remote protocol, see @ref{system,
18660 system-call-allowed}.
18663 @item set remoteaddresssize @var{bits}
18664 @cindex address size for remote targets
18665 @cindex bits in remote address
18666 Set the maximum size of address in a memory packet to the specified
18667 number of bits. @value{GDBN} will mask off the address bits above
18668 that number, when it passes addresses to the remote target. The
18669 default value is the number of bits in the target's address.
18671 @item show remoteaddresssize
18672 Show the current value of remote address size in bits.
18674 @item set serial baud @var{n}
18675 @cindex baud rate for remote targets
18676 Set the baud rate for the remote serial I/O to @var{n} baud. The
18677 value is used to set the speed of the serial port used for debugging
18680 @item show serial baud
18681 Show the current speed of the remote connection.
18683 @item set remotebreak
18684 @cindex interrupt remote programs
18685 @cindex BREAK signal instead of Ctrl-C
18686 @anchor{set remotebreak}
18687 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18688 when you type @kbd{Ctrl-c} to interrupt the program running
18689 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18690 character instead. The default is off, since most remote systems
18691 expect to see @samp{Ctrl-C} as the interrupt signal.
18693 @item show remotebreak
18694 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18695 interrupt the remote program.
18697 @item set remoteflow on
18698 @itemx set remoteflow off
18699 @kindex set remoteflow
18700 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18701 on the serial port used to communicate to the remote target.
18703 @item show remoteflow
18704 @kindex show remoteflow
18705 Show the current setting of hardware flow control.
18707 @item set remotelogbase @var{base}
18708 Set the base (a.k.a.@: radix) of logging serial protocol
18709 communications to @var{base}. Supported values of @var{base} are:
18710 @code{ascii}, @code{octal}, and @code{hex}. The default is
18713 @item show remotelogbase
18714 Show the current setting of the radix for logging remote serial
18717 @item set remotelogfile @var{file}
18718 @cindex record serial communications on file
18719 Record remote serial communications on the named @var{file}. The
18720 default is not to record at all.
18722 @item show remotelogfile.
18723 Show the current setting of the file name on which to record the
18724 serial communications.
18726 @item set remotetimeout @var{num}
18727 @cindex timeout for serial communications
18728 @cindex remote timeout
18729 Set the timeout limit to wait for the remote target to respond to
18730 @var{num} seconds. The default is 2 seconds.
18732 @item show remotetimeout
18733 Show the current number of seconds to wait for the remote target
18736 @cindex limit hardware breakpoints and watchpoints
18737 @cindex remote target, limit break- and watchpoints
18738 @anchor{set remote hardware-watchpoint-limit}
18739 @anchor{set remote hardware-breakpoint-limit}
18740 @item set remote hardware-watchpoint-limit @var{limit}
18741 @itemx set remote hardware-breakpoint-limit @var{limit}
18742 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18743 watchpoints. A limit of -1, the default, is treated as unlimited.
18745 @cindex limit hardware watchpoints length
18746 @cindex remote target, limit watchpoints length
18747 @anchor{set remote hardware-watchpoint-length-limit}
18748 @item set remote hardware-watchpoint-length-limit @var{limit}
18749 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18750 a remote hardware watchpoint. A limit of -1, the default, is treated
18753 @item show remote hardware-watchpoint-length-limit
18754 Show the current limit (in bytes) of the maximum length of
18755 a remote hardware watchpoint.
18757 @item set remote exec-file @var{filename}
18758 @itemx show remote exec-file
18759 @anchor{set remote exec-file}
18760 @cindex executable file, for remote target
18761 Select the file used for @code{run} with @code{target
18762 extended-remote}. This should be set to a filename valid on the
18763 target system. If it is not set, the target will use a default
18764 filename (e.g.@: the last program run).
18766 @item set remote interrupt-sequence
18767 @cindex interrupt remote programs
18768 @cindex select Ctrl-C, BREAK or BREAK-g
18769 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18770 @samp{BREAK-g} as the
18771 sequence to the remote target in order to interrupt the execution.
18772 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18773 is high level of serial line for some certain time.
18774 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18775 It is @code{BREAK} signal followed by character @code{g}.
18777 @item show interrupt-sequence
18778 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18779 is sent by @value{GDBN} to interrupt the remote program.
18780 @code{BREAK-g} is BREAK signal followed by @code{g} and
18781 also known as Magic SysRq g.
18783 @item set remote interrupt-on-connect
18784 @cindex send interrupt-sequence on start
18785 Specify whether interrupt-sequence is sent to remote target when
18786 @value{GDBN} connects to it. This is mostly needed when you debug
18787 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18788 which is known as Magic SysRq g in order to connect @value{GDBN}.
18790 @item show interrupt-on-connect
18791 Show whether interrupt-sequence is sent
18792 to remote target when @value{GDBN} connects to it.
18796 @item set tcp auto-retry on
18797 @cindex auto-retry, for remote TCP target
18798 Enable auto-retry for remote TCP connections. This is useful if the remote
18799 debugging agent is launched in parallel with @value{GDBN}; there is a race
18800 condition because the agent may not become ready to accept the connection
18801 before @value{GDBN} attempts to connect. When auto-retry is
18802 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18803 to establish the connection using the timeout specified by
18804 @code{set tcp connect-timeout}.
18806 @item set tcp auto-retry off
18807 Do not auto-retry failed TCP connections.
18809 @item show tcp auto-retry
18810 Show the current auto-retry setting.
18812 @item set tcp connect-timeout @var{seconds}
18813 @itemx set tcp connect-timeout unlimited
18814 @cindex connection timeout, for remote TCP target
18815 @cindex timeout, for remote target connection
18816 Set the timeout for establishing a TCP connection to the remote target to
18817 @var{seconds}. The timeout affects both polling to retry failed connections
18818 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18819 that are merely slow to complete, and represents an approximate cumulative
18820 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18821 @value{GDBN} will keep attempting to establish a connection forever,
18822 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18824 @item show tcp connect-timeout
18825 Show the current connection timeout setting.
18828 @cindex remote packets, enabling and disabling
18829 The @value{GDBN} remote protocol autodetects the packets supported by
18830 your debugging stub. If you need to override the autodetection, you
18831 can use these commands to enable or disable individual packets. Each
18832 packet can be set to @samp{on} (the remote target supports this
18833 packet), @samp{off} (the remote target does not support this packet),
18834 or @samp{auto} (detect remote target support for this packet). They
18835 all default to @samp{auto}. For more information about each packet,
18836 see @ref{Remote Protocol}.
18838 During normal use, you should not have to use any of these commands.
18839 If you do, that may be a bug in your remote debugging stub, or a bug
18840 in @value{GDBN}. You may want to report the problem to the
18841 @value{GDBN} developers.
18843 For each packet @var{name}, the command to enable or disable the
18844 packet is @code{set remote @var{name}-packet}. The available settings
18847 @multitable @columnfractions 0.28 0.32 0.25
18850 @tab Related Features
18852 @item @code{fetch-register}
18854 @tab @code{info registers}
18856 @item @code{set-register}
18860 @item @code{binary-download}
18862 @tab @code{load}, @code{set}
18864 @item @code{read-aux-vector}
18865 @tab @code{qXfer:auxv:read}
18866 @tab @code{info auxv}
18868 @item @code{symbol-lookup}
18869 @tab @code{qSymbol}
18870 @tab Detecting multiple threads
18872 @item @code{attach}
18873 @tab @code{vAttach}
18876 @item @code{verbose-resume}
18878 @tab Stepping or resuming multiple threads
18884 @item @code{software-breakpoint}
18888 @item @code{hardware-breakpoint}
18892 @item @code{write-watchpoint}
18896 @item @code{read-watchpoint}
18900 @item @code{access-watchpoint}
18904 @item @code{target-features}
18905 @tab @code{qXfer:features:read}
18906 @tab @code{set architecture}
18908 @item @code{library-info}
18909 @tab @code{qXfer:libraries:read}
18910 @tab @code{info sharedlibrary}
18912 @item @code{memory-map}
18913 @tab @code{qXfer:memory-map:read}
18914 @tab @code{info mem}
18916 @item @code{read-sdata-object}
18917 @tab @code{qXfer:sdata:read}
18918 @tab @code{print $_sdata}
18920 @item @code{read-spu-object}
18921 @tab @code{qXfer:spu:read}
18922 @tab @code{info spu}
18924 @item @code{write-spu-object}
18925 @tab @code{qXfer:spu:write}
18926 @tab @code{info spu}
18928 @item @code{read-siginfo-object}
18929 @tab @code{qXfer:siginfo:read}
18930 @tab @code{print $_siginfo}
18932 @item @code{write-siginfo-object}
18933 @tab @code{qXfer:siginfo:write}
18934 @tab @code{set $_siginfo}
18936 @item @code{threads}
18937 @tab @code{qXfer:threads:read}
18938 @tab @code{info threads}
18940 @item @code{get-thread-local-@*storage-address}
18941 @tab @code{qGetTLSAddr}
18942 @tab Displaying @code{__thread} variables
18944 @item @code{get-thread-information-block-address}
18945 @tab @code{qGetTIBAddr}
18946 @tab Display MS-Windows Thread Information Block.
18948 @item @code{search-memory}
18949 @tab @code{qSearch:memory}
18952 @item @code{supported-packets}
18953 @tab @code{qSupported}
18954 @tab Remote communications parameters
18956 @item @code{pass-signals}
18957 @tab @code{QPassSignals}
18958 @tab @code{handle @var{signal}}
18960 @item @code{program-signals}
18961 @tab @code{QProgramSignals}
18962 @tab @code{handle @var{signal}}
18964 @item @code{hostio-close-packet}
18965 @tab @code{vFile:close}
18966 @tab @code{remote get}, @code{remote put}
18968 @item @code{hostio-open-packet}
18969 @tab @code{vFile:open}
18970 @tab @code{remote get}, @code{remote put}
18972 @item @code{hostio-pread-packet}
18973 @tab @code{vFile:pread}
18974 @tab @code{remote get}, @code{remote put}
18976 @item @code{hostio-pwrite-packet}
18977 @tab @code{vFile:pwrite}
18978 @tab @code{remote get}, @code{remote put}
18980 @item @code{hostio-unlink-packet}
18981 @tab @code{vFile:unlink}
18982 @tab @code{remote delete}
18984 @item @code{hostio-readlink-packet}
18985 @tab @code{vFile:readlink}
18988 @item @code{noack-packet}
18989 @tab @code{QStartNoAckMode}
18990 @tab Packet acknowledgment
18992 @item @code{osdata}
18993 @tab @code{qXfer:osdata:read}
18994 @tab @code{info os}
18996 @item @code{query-attached}
18997 @tab @code{qAttached}
18998 @tab Querying remote process attach state.
19000 @item @code{trace-buffer-size}
19001 @tab @code{QTBuffer:size}
19002 @tab @code{set trace-buffer-size}
19004 @item @code{trace-status}
19005 @tab @code{qTStatus}
19006 @tab @code{tstatus}
19008 @item @code{traceframe-info}
19009 @tab @code{qXfer:traceframe-info:read}
19010 @tab Traceframe info
19012 @item @code{install-in-trace}
19013 @tab @code{InstallInTrace}
19014 @tab Install tracepoint in tracing
19016 @item @code{disable-randomization}
19017 @tab @code{QDisableRandomization}
19018 @tab @code{set disable-randomization}
19020 @item @code{conditional-breakpoints-packet}
19021 @tab @code{Z0 and Z1}
19022 @tab @code{Support for target-side breakpoint condition evaluation}
19026 @section Implementing a Remote Stub
19028 @cindex debugging stub, example
19029 @cindex remote stub, example
19030 @cindex stub example, remote debugging
19031 The stub files provided with @value{GDBN} implement the target side of the
19032 communication protocol, and the @value{GDBN} side is implemented in the
19033 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19034 these subroutines to communicate, and ignore the details. (If you're
19035 implementing your own stub file, you can still ignore the details: start
19036 with one of the existing stub files. @file{sparc-stub.c} is the best
19037 organized, and therefore the easiest to read.)
19039 @cindex remote serial debugging, overview
19040 To debug a program running on another machine (the debugging
19041 @dfn{target} machine), you must first arrange for all the usual
19042 prerequisites for the program to run by itself. For example, for a C
19047 A startup routine to set up the C runtime environment; these usually
19048 have a name like @file{crt0}. The startup routine may be supplied by
19049 your hardware supplier, or you may have to write your own.
19052 A C subroutine library to support your program's
19053 subroutine calls, notably managing input and output.
19056 A way of getting your program to the other machine---for example, a
19057 download program. These are often supplied by the hardware
19058 manufacturer, but you may have to write your own from hardware
19062 The next step is to arrange for your program to use a serial port to
19063 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19064 machine). In general terms, the scheme looks like this:
19068 @value{GDBN} already understands how to use this protocol; when everything
19069 else is set up, you can simply use the @samp{target remote} command
19070 (@pxref{Targets,,Specifying a Debugging Target}).
19072 @item On the target,
19073 you must link with your program a few special-purpose subroutines that
19074 implement the @value{GDBN} remote serial protocol. The file containing these
19075 subroutines is called a @dfn{debugging stub}.
19077 On certain remote targets, you can use an auxiliary program
19078 @code{gdbserver} instead of linking a stub into your program.
19079 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19082 The debugging stub is specific to the architecture of the remote
19083 machine; for example, use @file{sparc-stub.c} to debug programs on
19086 @cindex remote serial stub list
19087 These working remote stubs are distributed with @value{GDBN}:
19092 @cindex @file{i386-stub.c}
19095 For Intel 386 and compatible architectures.
19098 @cindex @file{m68k-stub.c}
19099 @cindex Motorola 680x0
19101 For Motorola 680x0 architectures.
19104 @cindex @file{sh-stub.c}
19107 For Renesas SH architectures.
19110 @cindex @file{sparc-stub.c}
19112 For @sc{sparc} architectures.
19114 @item sparcl-stub.c
19115 @cindex @file{sparcl-stub.c}
19118 For Fujitsu @sc{sparclite} architectures.
19122 The @file{README} file in the @value{GDBN} distribution may list other
19123 recently added stubs.
19126 * Stub Contents:: What the stub can do for you
19127 * Bootstrapping:: What you must do for the stub
19128 * Debug Session:: Putting it all together
19131 @node Stub Contents
19132 @subsection What the Stub Can Do for You
19134 @cindex remote serial stub
19135 The debugging stub for your architecture supplies these three
19139 @item set_debug_traps
19140 @findex set_debug_traps
19141 @cindex remote serial stub, initialization
19142 This routine arranges for @code{handle_exception} to run when your
19143 program stops. You must call this subroutine explicitly in your
19144 program's startup code.
19146 @item handle_exception
19147 @findex handle_exception
19148 @cindex remote serial stub, main routine
19149 This is the central workhorse, but your program never calls it
19150 explicitly---the setup code arranges for @code{handle_exception} to
19151 run when a trap is triggered.
19153 @code{handle_exception} takes control when your program stops during
19154 execution (for example, on a breakpoint), and mediates communications
19155 with @value{GDBN} on the host machine. This is where the communications
19156 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19157 representative on the target machine. It begins by sending summary
19158 information on the state of your program, then continues to execute,
19159 retrieving and transmitting any information @value{GDBN} needs, until you
19160 execute a @value{GDBN} command that makes your program resume; at that point,
19161 @code{handle_exception} returns control to your own code on the target
19165 @cindex @code{breakpoint} subroutine, remote
19166 Use this auxiliary subroutine to make your program contain a
19167 breakpoint. Depending on the particular situation, this may be the only
19168 way for @value{GDBN} to get control. For instance, if your target
19169 machine has some sort of interrupt button, you won't need to call this;
19170 pressing the interrupt button transfers control to
19171 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19172 simply receiving characters on the serial port may also trigger a trap;
19173 again, in that situation, you don't need to call @code{breakpoint} from
19174 your own program---simply running @samp{target remote} from the host
19175 @value{GDBN} session gets control.
19177 Call @code{breakpoint} if none of these is true, or if you simply want
19178 to make certain your program stops at a predetermined point for the
19179 start of your debugging session.
19182 @node Bootstrapping
19183 @subsection What You Must Do for the Stub
19185 @cindex remote stub, support routines
19186 The debugging stubs that come with @value{GDBN} are set up for a particular
19187 chip architecture, but they have no information about the rest of your
19188 debugging target machine.
19190 First of all you need to tell the stub how to communicate with the
19194 @item int getDebugChar()
19195 @findex getDebugChar
19196 Write this subroutine to read a single character from the serial port.
19197 It may be identical to @code{getchar} for your target system; a
19198 different name is used to allow you to distinguish the two if you wish.
19200 @item void putDebugChar(int)
19201 @findex putDebugChar
19202 Write this subroutine to write a single character to the serial port.
19203 It may be identical to @code{putchar} for your target system; a
19204 different name is used to allow you to distinguish the two if you wish.
19207 @cindex control C, and remote debugging
19208 @cindex interrupting remote targets
19209 If you want @value{GDBN} to be able to stop your program while it is
19210 running, you need to use an interrupt-driven serial driver, and arrange
19211 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19212 character). That is the character which @value{GDBN} uses to tell the
19213 remote system to stop.
19215 Getting the debugging target to return the proper status to @value{GDBN}
19216 probably requires changes to the standard stub; one quick and dirty way
19217 is to just execute a breakpoint instruction (the ``dirty'' part is that
19218 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19220 Other routines you need to supply are:
19223 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19224 @findex exceptionHandler
19225 Write this function to install @var{exception_address} in the exception
19226 handling tables. You need to do this because the stub does not have any
19227 way of knowing what the exception handling tables on your target system
19228 are like (for example, the processor's table might be in @sc{rom},
19229 containing entries which point to a table in @sc{ram}).
19230 @var{exception_number} is the exception number which should be changed;
19231 its meaning is architecture-dependent (for example, different numbers
19232 might represent divide by zero, misaligned access, etc). When this
19233 exception occurs, control should be transferred directly to
19234 @var{exception_address}, and the processor state (stack, registers,
19235 and so on) should be just as it is when a processor exception occurs. So if
19236 you want to use a jump instruction to reach @var{exception_address}, it
19237 should be a simple jump, not a jump to subroutine.
19239 For the 386, @var{exception_address} should be installed as an interrupt
19240 gate so that interrupts are masked while the handler runs. The gate
19241 should be at privilege level 0 (the most privileged level). The
19242 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19243 help from @code{exceptionHandler}.
19245 @item void flush_i_cache()
19246 @findex flush_i_cache
19247 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19248 instruction cache, if any, on your target machine. If there is no
19249 instruction cache, this subroutine may be a no-op.
19251 On target machines that have instruction caches, @value{GDBN} requires this
19252 function to make certain that the state of your program is stable.
19256 You must also make sure this library routine is available:
19259 @item void *memset(void *, int, int)
19261 This is the standard library function @code{memset} that sets an area of
19262 memory to a known value. If you have one of the free versions of
19263 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19264 either obtain it from your hardware manufacturer, or write your own.
19267 If you do not use the GNU C compiler, you may need other standard
19268 library subroutines as well; this varies from one stub to another,
19269 but in general the stubs are likely to use any of the common library
19270 subroutines which @code{@value{NGCC}} generates as inline code.
19273 @node Debug Session
19274 @subsection Putting it All Together
19276 @cindex remote serial debugging summary
19277 In summary, when your program is ready to debug, you must follow these
19282 Make sure you have defined the supporting low-level routines
19283 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19285 @code{getDebugChar}, @code{putDebugChar},
19286 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19290 Insert these lines in your program's startup code, before the main
19291 procedure is called:
19298 On some machines, when a breakpoint trap is raised, the hardware
19299 automatically makes the PC point to the instruction after the
19300 breakpoint. If your machine doesn't do that, you may need to adjust
19301 @code{handle_exception} to arrange for it to return to the instruction
19302 after the breakpoint on this first invocation, so that your program
19303 doesn't keep hitting the initial breakpoint instead of making
19307 For the 680x0 stub only, you need to provide a variable called
19308 @code{exceptionHook}. Normally you just use:
19311 void (*exceptionHook)() = 0;
19315 but if before calling @code{set_debug_traps}, you set it to point to a
19316 function in your program, that function is called when
19317 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19318 error). The function indicated by @code{exceptionHook} is called with
19319 one parameter: an @code{int} which is the exception number.
19322 Compile and link together: your program, the @value{GDBN} debugging stub for
19323 your target architecture, and the supporting subroutines.
19326 Make sure you have a serial connection between your target machine and
19327 the @value{GDBN} host, and identify the serial port on the host.
19330 @c The "remote" target now provides a `load' command, so we should
19331 @c document that. FIXME.
19332 Download your program to your target machine (or get it there by
19333 whatever means the manufacturer provides), and start it.
19336 Start @value{GDBN} on the host, and connect to the target
19337 (@pxref{Connecting,,Connecting to a Remote Target}).
19341 @node Configurations
19342 @chapter Configuration-Specific Information
19344 While nearly all @value{GDBN} commands are available for all native and
19345 cross versions of the debugger, there are some exceptions. This chapter
19346 describes things that are only available in certain configurations.
19348 There are three major categories of configurations: native
19349 configurations, where the host and target are the same, embedded
19350 operating system configurations, which are usually the same for several
19351 different processor architectures, and bare embedded processors, which
19352 are quite different from each other.
19357 * Embedded Processors::
19364 This section describes details specific to particular native
19369 * BSD libkvm Interface:: Debugging BSD kernel memory images
19370 * SVR4 Process Information:: SVR4 process information
19371 * DJGPP Native:: Features specific to the DJGPP port
19372 * Cygwin Native:: Features specific to the Cygwin port
19373 * Hurd Native:: Features specific to @sc{gnu} Hurd
19374 * Darwin:: Features specific to Darwin
19380 On HP-UX systems, if you refer to a function or variable name that
19381 begins with a dollar sign, @value{GDBN} searches for a user or system
19382 name first, before it searches for a convenience variable.
19385 @node BSD libkvm Interface
19386 @subsection BSD libkvm Interface
19389 @cindex kernel memory image
19390 @cindex kernel crash dump
19392 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19393 interface that provides a uniform interface for accessing kernel virtual
19394 memory images, including live systems and crash dumps. @value{GDBN}
19395 uses this interface to allow you to debug live kernels and kernel crash
19396 dumps on many native BSD configurations. This is implemented as a
19397 special @code{kvm} debugging target. For debugging a live system, load
19398 the currently running kernel into @value{GDBN} and connect to the
19402 (@value{GDBP}) @b{target kvm}
19405 For debugging crash dumps, provide the file name of the crash dump as an
19409 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19412 Once connected to the @code{kvm} target, the following commands are
19418 Set current context from the @dfn{Process Control Block} (PCB) address.
19421 Set current context from proc address. This command isn't available on
19422 modern FreeBSD systems.
19425 @node SVR4 Process Information
19426 @subsection SVR4 Process Information
19428 @cindex examine process image
19429 @cindex process info via @file{/proc}
19431 Many versions of SVR4 and compatible systems provide a facility called
19432 @samp{/proc} that can be used to examine the image of a running
19433 process using file-system subroutines.
19435 If @value{GDBN} is configured for an operating system with this
19436 facility, the command @code{info proc} is available to report
19437 information about the process running your program, or about any
19438 process running on your system. This includes, as of this writing,
19439 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19440 not HP-UX, for example.
19442 This command may also work on core files that were created on a system
19443 that has the @samp{/proc} facility.
19449 @itemx info proc @var{process-id}
19450 Summarize available information about any running process. If a
19451 process ID is specified by @var{process-id}, display information about
19452 that process; otherwise display information about the program being
19453 debugged. The summary includes the debugged process ID, the command
19454 line used to invoke it, its current working directory, and its
19455 executable file's absolute file name.
19457 On some systems, @var{process-id} can be of the form
19458 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19459 within a process. If the optional @var{pid} part is missing, it means
19460 a thread from the process being debugged (the leading @samp{/} still
19461 needs to be present, or else @value{GDBN} will interpret the number as
19462 a process ID rather than a thread ID).
19464 @item info proc cmdline
19465 @cindex info proc cmdline
19466 Show the original command line of the process. This command is
19467 specific to @sc{gnu}/Linux.
19469 @item info proc cwd
19470 @cindex info proc cwd
19471 Show the current working directory of the process. This command is
19472 specific to @sc{gnu}/Linux.
19474 @item info proc exe
19475 @cindex info proc exe
19476 Show the name of executable of the process. This command is specific
19479 @item info proc mappings
19480 @cindex memory address space mappings
19481 Report the memory address space ranges accessible in the program, with
19482 information on whether the process has read, write, or execute access
19483 rights to each range. On @sc{gnu}/Linux systems, each memory range
19484 includes the object file which is mapped to that range, instead of the
19485 memory access rights to that range.
19487 @item info proc stat
19488 @itemx info proc status
19489 @cindex process detailed status information
19490 These subcommands are specific to @sc{gnu}/Linux systems. They show
19491 the process-related information, including the user ID and group ID;
19492 how many threads are there in the process; its virtual memory usage;
19493 the signals that are pending, blocked, and ignored; its TTY; its
19494 consumption of system and user time; its stack size; its @samp{nice}
19495 value; etc. For more information, see the @samp{proc} man page
19496 (type @kbd{man 5 proc} from your shell prompt).
19498 @item info proc all
19499 Show all the information about the process described under all of the
19500 above @code{info proc} subcommands.
19503 @comment These sub-options of 'info proc' were not included when
19504 @comment procfs.c was re-written. Keep their descriptions around
19505 @comment against the day when someone finds the time to put them back in.
19506 @kindex info proc times
19507 @item info proc times
19508 Starting time, user CPU time, and system CPU time for your program and
19511 @kindex info proc id
19513 Report on the process IDs related to your program: its own process ID,
19514 the ID of its parent, the process group ID, and the session ID.
19517 @item set procfs-trace
19518 @kindex set procfs-trace
19519 @cindex @code{procfs} API calls
19520 This command enables and disables tracing of @code{procfs} API calls.
19522 @item show procfs-trace
19523 @kindex show procfs-trace
19524 Show the current state of @code{procfs} API call tracing.
19526 @item set procfs-file @var{file}
19527 @kindex set procfs-file
19528 Tell @value{GDBN} to write @code{procfs} API trace to the named
19529 @var{file}. @value{GDBN} appends the trace info to the previous
19530 contents of the file. The default is to display the trace on the
19533 @item show procfs-file
19534 @kindex show procfs-file
19535 Show the file to which @code{procfs} API trace is written.
19537 @item proc-trace-entry
19538 @itemx proc-trace-exit
19539 @itemx proc-untrace-entry
19540 @itemx proc-untrace-exit
19541 @kindex proc-trace-entry
19542 @kindex proc-trace-exit
19543 @kindex proc-untrace-entry
19544 @kindex proc-untrace-exit
19545 These commands enable and disable tracing of entries into and exits
19546 from the @code{syscall} interface.
19549 @kindex info pidlist
19550 @cindex process list, QNX Neutrino
19551 For QNX Neutrino only, this command displays the list of all the
19552 processes and all the threads within each process.
19555 @kindex info meminfo
19556 @cindex mapinfo list, QNX Neutrino
19557 For QNX Neutrino only, this command displays the list of all mapinfos.
19561 @subsection Features for Debugging @sc{djgpp} Programs
19562 @cindex @sc{djgpp} debugging
19563 @cindex native @sc{djgpp} debugging
19564 @cindex MS-DOS-specific commands
19567 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19568 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19569 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19570 top of real-mode DOS systems and their emulations.
19572 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19573 defines a few commands specific to the @sc{djgpp} port. This
19574 subsection describes those commands.
19579 This is a prefix of @sc{djgpp}-specific commands which print
19580 information about the target system and important OS structures.
19583 @cindex MS-DOS system info
19584 @cindex free memory information (MS-DOS)
19585 @item info dos sysinfo
19586 This command displays assorted information about the underlying
19587 platform: the CPU type and features, the OS version and flavor, the
19588 DPMI version, and the available conventional and DPMI memory.
19593 @cindex segment descriptor tables
19594 @cindex descriptor tables display
19596 @itemx info dos ldt
19597 @itemx info dos idt
19598 These 3 commands display entries from, respectively, Global, Local,
19599 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19600 tables are data structures which store a descriptor for each segment
19601 that is currently in use. The segment's selector is an index into a
19602 descriptor table; the table entry for that index holds the
19603 descriptor's base address and limit, and its attributes and access
19606 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19607 segment (used for both data and the stack), and a DOS segment (which
19608 allows access to DOS/BIOS data structures and absolute addresses in
19609 conventional memory). However, the DPMI host will usually define
19610 additional segments in order to support the DPMI environment.
19612 @cindex garbled pointers
19613 These commands allow to display entries from the descriptor tables.
19614 Without an argument, all entries from the specified table are
19615 displayed. An argument, which should be an integer expression, means
19616 display a single entry whose index is given by the argument. For
19617 example, here's a convenient way to display information about the
19618 debugged program's data segment:
19621 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19622 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19626 This comes in handy when you want to see whether a pointer is outside
19627 the data segment's limit (i.e.@: @dfn{garbled}).
19629 @cindex page tables display (MS-DOS)
19631 @itemx info dos pte
19632 These two commands display entries from, respectively, the Page
19633 Directory and the Page Tables. Page Directories and Page Tables are
19634 data structures which control how virtual memory addresses are mapped
19635 into physical addresses. A Page Table includes an entry for every
19636 page of memory that is mapped into the program's address space; there
19637 may be several Page Tables, each one holding up to 4096 entries. A
19638 Page Directory has up to 4096 entries, one each for every Page Table
19639 that is currently in use.
19641 Without an argument, @kbd{info dos pde} displays the entire Page
19642 Directory, and @kbd{info dos pte} displays all the entries in all of
19643 the Page Tables. An argument, an integer expression, given to the
19644 @kbd{info dos pde} command means display only that entry from the Page
19645 Directory table. An argument given to the @kbd{info dos pte} command
19646 means display entries from a single Page Table, the one pointed to by
19647 the specified entry in the Page Directory.
19649 @cindex direct memory access (DMA) on MS-DOS
19650 These commands are useful when your program uses @dfn{DMA} (Direct
19651 Memory Access), which needs physical addresses to program the DMA
19654 These commands are supported only with some DPMI servers.
19656 @cindex physical address from linear address
19657 @item info dos address-pte @var{addr}
19658 This command displays the Page Table entry for a specified linear
19659 address. The argument @var{addr} is a linear address which should
19660 already have the appropriate segment's base address added to it,
19661 because this command accepts addresses which may belong to @emph{any}
19662 segment. For example, here's how to display the Page Table entry for
19663 the page where a variable @code{i} is stored:
19666 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19667 @exdent @code{Page Table entry for address 0x11a00d30:}
19668 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19672 This says that @code{i} is stored at offset @code{0xd30} from the page
19673 whose physical base address is @code{0x02698000}, and shows all the
19674 attributes of that page.
19676 Note that you must cast the addresses of variables to a @code{char *},
19677 since otherwise the value of @code{__djgpp_base_address}, the base
19678 address of all variables and functions in a @sc{djgpp} program, will
19679 be added using the rules of C pointer arithmetics: if @code{i} is
19680 declared an @code{int}, @value{GDBN} will add 4 times the value of
19681 @code{__djgpp_base_address} to the address of @code{i}.
19683 Here's another example, it displays the Page Table entry for the
19687 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19688 @exdent @code{Page Table entry for address 0x29110:}
19689 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19693 (The @code{+ 3} offset is because the transfer buffer's address is the
19694 3rd member of the @code{_go32_info_block} structure.) The output
19695 clearly shows that this DPMI server maps the addresses in conventional
19696 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19697 linear (@code{0x29110}) addresses are identical.
19699 This command is supported only with some DPMI servers.
19702 @cindex DOS serial data link, remote debugging
19703 In addition to native debugging, the DJGPP port supports remote
19704 debugging via a serial data link. The following commands are specific
19705 to remote serial debugging in the DJGPP port of @value{GDBN}.
19708 @kindex set com1base
19709 @kindex set com1irq
19710 @kindex set com2base
19711 @kindex set com2irq
19712 @kindex set com3base
19713 @kindex set com3irq
19714 @kindex set com4base
19715 @kindex set com4irq
19716 @item set com1base @var{addr}
19717 This command sets the base I/O port address of the @file{COM1} serial
19720 @item set com1irq @var{irq}
19721 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19722 for the @file{COM1} serial port.
19724 There are similar commands @samp{set com2base}, @samp{set com3irq},
19725 etc.@: for setting the port address and the @code{IRQ} lines for the
19728 @kindex show com1base
19729 @kindex show com1irq
19730 @kindex show com2base
19731 @kindex show com2irq
19732 @kindex show com3base
19733 @kindex show com3irq
19734 @kindex show com4base
19735 @kindex show com4irq
19736 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19737 display the current settings of the base address and the @code{IRQ}
19738 lines used by the COM ports.
19741 @kindex info serial
19742 @cindex DOS serial port status
19743 This command prints the status of the 4 DOS serial ports. For each
19744 port, it prints whether it's active or not, its I/O base address and
19745 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19746 counts of various errors encountered so far.
19750 @node Cygwin Native
19751 @subsection Features for Debugging MS Windows PE Executables
19752 @cindex MS Windows debugging
19753 @cindex native Cygwin debugging
19754 @cindex Cygwin-specific commands
19756 @value{GDBN} supports native debugging of MS Windows programs, including
19757 DLLs with and without symbolic debugging information.
19759 @cindex Ctrl-BREAK, MS-Windows
19760 @cindex interrupt debuggee on MS-Windows
19761 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19762 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19763 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19764 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19765 sequence, which can be used to interrupt the debuggee even if it
19768 There are various additional Cygwin-specific commands, described in
19769 this section. Working with DLLs that have no debugging symbols is
19770 described in @ref{Non-debug DLL Symbols}.
19775 This is a prefix of MS Windows-specific commands which print
19776 information about the target system and important OS structures.
19778 @item info w32 selector
19779 This command displays information returned by
19780 the Win32 API @code{GetThreadSelectorEntry} function.
19781 It takes an optional argument that is evaluated to
19782 a long value to give the information about this given selector.
19783 Without argument, this command displays information
19784 about the six segment registers.
19786 @item info w32 thread-information-block
19787 This command displays thread specific information stored in the
19788 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19789 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19793 This is a Cygwin-specific alias of @code{info shared}.
19795 @kindex dll-symbols
19797 This command loads symbols from a dll similarly to
19798 add-sym command but without the need to specify a base address.
19800 @kindex set cygwin-exceptions
19801 @cindex debugging the Cygwin DLL
19802 @cindex Cygwin DLL, debugging
19803 @item set cygwin-exceptions @var{mode}
19804 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19805 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19806 @value{GDBN} will delay recognition of exceptions, and may ignore some
19807 exceptions which seem to be caused by internal Cygwin DLL
19808 ``bookkeeping''. This option is meant primarily for debugging the
19809 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19810 @value{GDBN} users with false @code{SIGSEGV} signals.
19812 @kindex show cygwin-exceptions
19813 @item show cygwin-exceptions
19814 Displays whether @value{GDBN} will break on exceptions that happen
19815 inside the Cygwin DLL itself.
19817 @kindex set new-console
19818 @item set new-console @var{mode}
19819 If @var{mode} is @code{on} the debuggee will
19820 be started in a new console on next start.
19821 If @var{mode} is @code{off}, the debuggee will
19822 be started in the same console as the debugger.
19824 @kindex show new-console
19825 @item show new-console
19826 Displays whether a new console is used
19827 when the debuggee is started.
19829 @kindex set new-group
19830 @item set new-group @var{mode}
19831 This boolean value controls whether the debuggee should
19832 start a new group or stay in the same group as the debugger.
19833 This affects the way the Windows OS handles
19836 @kindex show new-group
19837 @item show new-group
19838 Displays current value of new-group boolean.
19840 @kindex set debugevents
19841 @item set debugevents
19842 This boolean value adds debug output concerning kernel events related
19843 to the debuggee seen by the debugger. This includes events that
19844 signal thread and process creation and exit, DLL loading and
19845 unloading, console interrupts, and debugging messages produced by the
19846 Windows @code{OutputDebugString} API call.
19848 @kindex set debugexec
19849 @item set debugexec
19850 This boolean value adds debug output concerning execute events
19851 (such as resume thread) seen by the debugger.
19853 @kindex set debugexceptions
19854 @item set debugexceptions
19855 This boolean value adds debug output concerning exceptions in the
19856 debuggee seen by the debugger.
19858 @kindex set debugmemory
19859 @item set debugmemory
19860 This boolean value adds debug output concerning debuggee memory reads
19861 and writes by the debugger.
19865 This boolean values specifies whether the debuggee is called
19866 via a shell or directly (default value is on).
19870 Displays if the debuggee will be started with a shell.
19875 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19878 @node Non-debug DLL Symbols
19879 @subsubsection Support for DLLs without Debugging Symbols
19880 @cindex DLLs with no debugging symbols
19881 @cindex Minimal symbols and DLLs
19883 Very often on windows, some of the DLLs that your program relies on do
19884 not include symbolic debugging information (for example,
19885 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19886 symbols in a DLL, it relies on the minimal amount of symbolic
19887 information contained in the DLL's export table. This section
19888 describes working with such symbols, known internally to @value{GDBN} as
19889 ``minimal symbols''.
19891 Note that before the debugged program has started execution, no DLLs
19892 will have been loaded. The easiest way around this problem is simply to
19893 start the program --- either by setting a breakpoint or letting the
19894 program run once to completion. It is also possible to force
19895 @value{GDBN} to load a particular DLL before starting the executable ---
19896 see the shared library information in @ref{Files}, or the
19897 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19898 explicitly loading symbols from a DLL with no debugging information will
19899 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19900 which may adversely affect symbol lookup performance.
19902 @subsubsection DLL Name Prefixes
19904 In keeping with the naming conventions used by the Microsoft debugging
19905 tools, DLL export symbols are made available with a prefix based on the
19906 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19907 also entered into the symbol table, so @code{CreateFileA} is often
19908 sufficient. In some cases there will be name clashes within a program
19909 (particularly if the executable itself includes full debugging symbols)
19910 necessitating the use of the fully qualified name when referring to the
19911 contents of the DLL. Use single-quotes around the name to avoid the
19912 exclamation mark (``!'') being interpreted as a language operator.
19914 Note that the internal name of the DLL may be all upper-case, even
19915 though the file name of the DLL is lower-case, or vice-versa. Since
19916 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19917 some confusion. If in doubt, try the @code{info functions} and
19918 @code{info variables} commands or even @code{maint print msymbols}
19919 (@pxref{Symbols}). Here's an example:
19922 (@value{GDBP}) info function CreateFileA
19923 All functions matching regular expression "CreateFileA":
19925 Non-debugging symbols:
19926 0x77e885f4 CreateFileA
19927 0x77e885f4 KERNEL32!CreateFileA
19931 (@value{GDBP}) info function !
19932 All functions matching regular expression "!":
19934 Non-debugging symbols:
19935 0x6100114c cygwin1!__assert
19936 0x61004034 cygwin1!_dll_crt0@@0
19937 0x61004240 cygwin1!dll_crt0(per_process *)
19941 @subsubsection Working with Minimal Symbols
19943 Symbols extracted from a DLL's export table do not contain very much
19944 type information. All that @value{GDBN} can do is guess whether a symbol
19945 refers to a function or variable depending on the linker section that
19946 contains the symbol. Also note that the actual contents of the memory
19947 contained in a DLL are not available unless the program is running. This
19948 means that you cannot examine the contents of a variable or disassemble
19949 a function within a DLL without a running program.
19951 Variables are generally treated as pointers and dereferenced
19952 automatically. For this reason, it is often necessary to prefix a
19953 variable name with the address-of operator (``&'') and provide explicit
19954 type information in the command. Here's an example of the type of
19958 (@value{GDBP}) print 'cygwin1!__argv'
19963 (@value{GDBP}) x 'cygwin1!__argv'
19964 0x10021610: "\230y\""
19967 And two possible solutions:
19970 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19971 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19975 (@value{GDBP}) x/2x &'cygwin1!__argv'
19976 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19977 (@value{GDBP}) x/x 0x10021608
19978 0x10021608: 0x0022fd98
19979 (@value{GDBP}) x/s 0x0022fd98
19980 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19983 Setting a break point within a DLL is possible even before the program
19984 starts execution. However, under these circumstances, @value{GDBN} can't
19985 examine the initial instructions of the function in order to skip the
19986 function's frame set-up code. You can work around this by using ``*&''
19987 to set the breakpoint at a raw memory address:
19990 (@value{GDBP}) break *&'python22!PyOS_Readline'
19991 Breakpoint 1 at 0x1e04eff0
19994 The author of these extensions is not entirely convinced that setting a
19995 break point within a shared DLL like @file{kernel32.dll} is completely
19999 @subsection Commands Specific to @sc{gnu} Hurd Systems
20000 @cindex @sc{gnu} Hurd debugging
20002 This subsection describes @value{GDBN} commands specific to the
20003 @sc{gnu} Hurd native debugging.
20008 @kindex set signals@r{, Hurd command}
20009 @kindex set sigs@r{, Hurd command}
20010 This command toggles the state of inferior signal interception by
20011 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20012 affected by this command. @code{sigs} is a shorthand alias for
20017 @kindex show signals@r{, Hurd command}
20018 @kindex show sigs@r{, Hurd command}
20019 Show the current state of intercepting inferior's signals.
20021 @item set signal-thread
20022 @itemx set sigthread
20023 @kindex set signal-thread
20024 @kindex set sigthread
20025 This command tells @value{GDBN} which thread is the @code{libc} signal
20026 thread. That thread is run when a signal is delivered to a running
20027 process. @code{set sigthread} is the shorthand alias of @code{set
20030 @item show signal-thread
20031 @itemx show sigthread
20032 @kindex show signal-thread
20033 @kindex show sigthread
20034 These two commands show which thread will run when the inferior is
20035 delivered a signal.
20038 @kindex set stopped@r{, Hurd command}
20039 This commands tells @value{GDBN} that the inferior process is stopped,
20040 as with the @code{SIGSTOP} signal. The stopped process can be
20041 continued by delivering a signal to it.
20044 @kindex show stopped@r{, Hurd command}
20045 This command shows whether @value{GDBN} thinks the debuggee is
20048 @item set exceptions
20049 @kindex set exceptions@r{, Hurd command}
20050 Use this command to turn off trapping of exceptions in the inferior.
20051 When exception trapping is off, neither breakpoints nor
20052 single-stepping will work. To restore the default, set exception
20055 @item show exceptions
20056 @kindex show exceptions@r{, Hurd command}
20057 Show the current state of trapping exceptions in the inferior.
20059 @item set task pause
20060 @kindex set task@r{, Hurd commands}
20061 @cindex task attributes (@sc{gnu} Hurd)
20062 @cindex pause current task (@sc{gnu} Hurd)
20063 This command toggles task suspension when @value{GDBN} has control.
20064 Setting it to on takes effect immediately, and the task is suspended
20065 whenever @value{GDBN} gets control. Setting it to off will take
20066 effect the next time the inferior is continued. If this option is set
20067 to off, you can use @code{set thread default pause on} or @code{set
20068 thread pause on} (see below) to pause individual threads.
20070 @item show task pause
20071 @kindex show task@r{, Hurd commands}
20072 Show the current state of task suspension.
20074 @item set task detach-suspend-count
20075 @cindex task suspend count
20076 @cindex detach from task, @sc{gnu} Hurd
20077 This command sets the suspend count the task will be left with when
20078 @value{GDBN} detaches from it.
20080 @item show task detach-suspend-count
20081 Show the suspend count the task will be left with when detaching.
20083 @item set task exception-port
20084 @itemx set task excp
20085 @cindex task exception port, @sc{gnu} Hurd
20086 This command sets the task exception port to which @value{GDBN} will
20087 forward exceptions. The argument should be the value of the @dfn{send
20088 rights} of the task. @code{set task excp} is a shorthand alias.
20090 @item set noninvasive
20091 @cindex noninvasive task options
20092 This command switches @value{GDBN} to a mode that is the least
20093 invasive as far as interfering with the inferior is concerned. This
20094 is the same as using @code{set task pause}, @code{set exceptions}, and
20095 @code{set signals} to values opposite to the defaults.
20097 @item info send-rights
20098 @itemx info receive-rights
20099 @itemx info port-rights
20100 @itemx info port-sets
20101 @itemx info dead-names
20104 @cindex send rights, @sc{gnu} Hurd
20105 @cindex receive rights, @sc{gnu} Hurd
20106 @cindex port rights, @sc{gnu} Hurd
20107 @cindex port sets, @sc{gnu} Hurd
20108 @cindex dead names, @sc{gnu} Hurd
20109 These commands display information about, respectively, send rights,
20110 receive rights, port rights, port sets, and dead names of a task.
20111 There are also shorthand aliases: @code{info ports} for @code{info
20112 port-rights} and @code{info psets} for @code{info port-sets}.
20114 @item set thread pause
20115 @kindex set thread@r{, Hurd command}
20116 @cindex thread properties, @sc{gnu} Hurd
20117 @cindex pause current thread (@sc{gnu} Hurd)
20118 This command toggles current thread suspension when @value{GDBN} has
20119 control. Setting it to on takes effect immediately, and the current
20120 thread is suspended whenever @value{GDBN} gets control. Setting it to
20121 off will take effect the next time the inferior is continued.
20122 Normally, this command has no effect, since when @value{GDBN} has
20123 control, the whole task is suspended. However, if you used @code{set
20124 task pause off} (see above), this command comes in handy to suspend
20125 only the current thread.
20127 @item show thread pause
20128 @kindex show thread@r{, Hurd command}
20129 This command shows the state of current thread suspension.
20131 @item set thread run
20132 This command sets whether the current thread is allowed to run.
20134 @item show thread run
20135 Show whether the current thread is allowed to run.
20137 @item set thread detach-suspend-count
20138 @cindex thread suspend count, @sc{gnu} Hurd
20139 @cindex detach from thread, @sc{gnu} Hurd
20140 This command sets the suspend count @value{GDBN} will leave on a
20141 thread when detaching. This number is relative to the suspend count
20142 found by @value{GDBN} when it notices the thread; use @code{set thread
20143 takeover-suspend-count} to force it to an absolute value.
20145 @item show thread detach-suspend-count
20146 Show the suspend count @value{GDBN} will leave on the thread when
20149 @item set thread exception-port
20150 @itemx set thread excp
20151 Set the thread exception port to which to forward exceptions. This
20152 overrides the port set by @code{set task exception-port} (see above).
20153 @code{set thread excp} is the shorthand alias.
20155 @item set thread takeover-suspend-count
20156 Normally, @value{GDBN}'s thread suspend counts are relative to the
20157 value @value{GDBN} finds when it notices each thread. This command
20158 changes the suspend counts to be absolute instead.
20160 @item set thread default
20161 @itemx show thread default
20162 @cindex thread default settings, @sc{gnu} Hurd
20163 Each of the above @code{set thread} commands has a @code{set thread
20164 default} counterpart (e.g., @code{set thread default pause}, @code{set
20165 thread default exception-port}, etc.). The @code{thread default}
20166 variety of commands sets the default thread properties for all
20167 threads; you can then change the properties of individual threads with
20168 the non-default commands.
20175 @value{GDBN} provides the following commands specific to the Darwin target:
20178 @item set debug darwin @var{num}
20179 @kindex set debug darwin
20180 When set to a non zero value, enables debugging messages specific to
20181 the Darwin support. Higher values produce more verbose output.
20183 @item show debug darwin
20184 @kindex show debug darwin
20185 Show the current state of Darwin messages.
20187 @item set debug mach-o @var{num}
20188 @kindex set debug mach-o
20189 When set to a non zero value, enables debugging messages while
20190 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20191 file format used on Darwin for object and executable files.) Higher
20192 values produce more verbose output. This is a command to diagnose
20193 problems internal to @value{GDBN} and should not be needed in normal
20196 @item show debug mach-o
20197 @kindex show debug mach-o
20198 Show the current state of Mach-O file messages.
20200 @item set mach-exceptions on
20201 @itemx set mach-exceptions off
20202 @kindex set mach-exceptions
20203 On Darwin, faults are first reported as a Mach exception and are then
20204 mapped to a Posix signal. Use this command to turn on trapping of
20205 Mach exceptions in the inferior. This might be sometimes useful to
20206 better understand the cause of a fault. The default is off.
20208 @item show mach-exceptions
20209 @kindex show mach-exceptions
20210 Show the current state of exceptions trapping.
20215 @section Embedded Operating Systems
20217 This section describes configurations involving the debugging of
20218 embedded operating systems that are available for several different
20222 * VxWorks:: Using @value{GDBN} with VxWorks
20225 @value{GDBN} includes the ability to debug programs running on
20226 various real-time operating systems.
20229 @subsection Using @value{GDBN} with VxWorks
20235 @kindex target vxworks
20236 @item target vxworks @var{machinename}
20237 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20238 is the target system's machine name or IP address.
20242 On VxWorks, @code{load} links @var{filename} dynamically on the
20243 current target system as well as adding its symbols in @value{GDBN}.
20245 @value{GDBN} enables developers to spawn and debug tasks running on networked
20246 VxWorks targets from a Unix host. Already-running tasks spawned from
20247 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20248 both the Unix host and on the VxWorks target. The program
20249 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20250 installed with the name @code{vxgdb}, to distinguish it from a
20251 @value{GDBN} for debugging programs on the host itself.)
20254 @item VxWorks-timeout @var{args}
20255 @kindex vxworks-timeout
20256 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20257 This option is set by the user, and @var{args} represents the number of
20258 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20259 your VxWorks target is a slow software simulator or is on the far side
20260 of a thin network line.
20263 The following information on connecting to VxWorks was current when
20264 this manual was produced; newer releases of VxWorks may use revised
20267 @findex INCLUDE_RDB
20268 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20269 to include the remote debugging interface routines in the VxWorks
20270 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20271 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20272 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20273 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20274 information on configuring and remaking VxWorks, see the manufacturer's
20276 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20278 Once you have included @file{rdb.a} in your VxWorks system image and set
20279 your Unix execution search path to find @value{GDBN}, you are ready to
20280 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20281 @code{vxgdb}, depending on your installation).
20283 @value{GDBN} comes up showing the prompt:
20290 * VxWorks Connection:: Connecting to VxWorks
20291 * VxWorks Download:: VxWorks download
20292 * VxWorks Attach:: Running tasks
20295 @node VxWorks Connection
20296 @subsubsection Connecting to VxWorks
20298 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20299 network. To connect to a target whose host name is ``@code{tt}'', type:
20302 (vxgdb) target vxworks tt
20306 @value{GDBN} displays messages like these:
20309 Attaching remote machine across net...
20314 @value{GDBN} then attempts to read the symbol tables of any object modules
20315 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20316 these files by searching the directories listed in the command search
20317 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20318 to find an object file, it displays a message such as:
20321 prog.o: No such file or directory.
20324 When this happens, add the appropriate directory to the search path with
20325 the @value{GDBN} command @code{path}, and execute the @code{target}
20328 @node VxWorks Download
20329 @subsubsection VxWorks Download
20331 @cindex download to VxWorks
20332 If you have connected to the VxWorks target and you want to debug an
20333 object that has not yet been loaded, you can use the @value{GDBN}
20334 @code{load} command to download a file from Unix to VxWorks
20335 incrementally. The object file given as an argument to the @code{load}
20336 command is actually opened twice: first by the VxWorks target in order
20337 to download the code, then by @value{GDBN} in order to read the symbol
20338 table. This can lead to problems if the current working directories on
20339 the two systems differ. If both systems have NFS mounted the same
20340 filesystems, you can avoid these problems by using absolute paths.
20341 Otherwise, it is simplest to set the working directory on both systems
20342 to the directory in which the object file resides, and then to reference
20343 the file by its name, without any path. For instance, a program
20344 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20345 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20346 program, type this on VxWorks:
20349 -> cd "@var{vxpath}/vw/demo/rdb"
20353 Then, in @value{GDBN}, type:
20356 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20357 (vxgdb) load prog.o
20360 @value{GDBN} displays a response similar to this:
20363 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20366 You can also use the @code{load} command to reload an object module
20367 after editing and recompiling the corresponding source file. Note that
20368 this makes @value{GDBN} delete all currently-defined breakpoints,
20369 auto-displays, and convenience variables, and to clear the value
20370 history. (This is necessary in order to preserve the integrity of
20371 debugger's data structures that reference the target system's symbol
20374 @node VxWorks Attach
20375 @subsubsection Running Tasks
20377 @cindex running VxWorks tasks
20378 You can also attach to an existing task using the @code{attach} command as
20382 (vxgdb) attach @var{task}
20386 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20387 or suspended when you attach to it. Running tasks are suspended at
20388 the time of attachment.
20390 @node Embedded Processors
20391 @section Embedded Processors
20393 This section goes into details specific to particular embedded
20396 @cindex send command to simulator
20397 Whenever a specific embedded processor has a simulator, @value{GDBN}
20398 allows to send an arbitrary command to the simulator.
20401 @item sim @var{command}
20402 @kindex sim@r{, a command}
20403 Send an arbitrary @var{command} string to the simulator. Consult the
20404 documentation for the specific simulator in use for information about
20405 acceptable commands.
20411 * M32R/D:: Renesas M32R/D
20412 * M68K:: Motorola M68K
20413 * MicroBlaze:: Xilinx MicroBlaze
20414 * MIPS Embedded:: MIPS Embedded
20415 * PowerPC Embedded:: PowerPC Embedded
20416 * PA:: HP PA Embedded
20417 * Sparclet:: Tsqware Sparclet
20418 * Sparclite:: Fujitsu Sparclite
20419 * Z8000:: Zilog Z8000
20422 * Super-H:: Renesas Super-H
20431 @item target rdi @var{dev}
20432 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20433 use this target to communicate with both boards running the Angel
20434 monitor, or with the EmbeddedICE JTAG debug device.
20437 @item target rdp @var{dev}
20442 @value{GDBN} provides the following ARM-specific commands:
20445 @item set arm disassembler
20447 This commands selects from a list of disassembly styles. The
20448 @code{"std"} style is the standard style.
20450 @item show arm disassembler
20452 Show the current disassembly style.
20454 @item set arm apcs32
20455 @cindex ARM 32-bit mode
20456 This command toggles ARM operation mode between 32-bit and 26-bit.
20458 @item show arm apcs32
20459 Display the current usage of the ARM 32-bit mode.
20461 @item set arm fpu @var{fputype}
20462 This command sets the ARM floating-point unit (FPU) type. The
20463 argument @var{fputype} can be one of these:
20467 Determine the FPU type by querying the OS ABI.
20469 Software FPU, with mixed-endian doubles on little-endian ARM
20472 GCC-compiled FPA co-processor.
20474 Software FPU with pure-endian doubles.
20480 Show the current type of the FPU.
20483 This command forces @value{GDBN} to use the specified ABI.
20486 Show the currently used ABI.
20488 @item set arm fallback-mode (arm|thumb|auto)
20489 @value{GDBN} uses the symbol table, when available, to determine
20490 whether instructions are ARM or Thumb. This command controls
20491 @value{GDBN}'s default behavior when the symbol table is not
20492 available. The default is @samp{auto}, which causes @value{GDBN} to
20493 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20496 @item show arm fallback-mode
20497 Show the current fallback instruction mode.
20499 @item set arm force-mode (arm|thumb|auto)
20500 This command overrides use of the symbol table to determine whether
20501 instructions are ARM or Thumb. The default is @samp{auto}, which
20502 causes @value{GDBN} to use the symbol table and then the setting
20503 of @samp{set arm fallback-mode}.
20505 @item show arm force-mode
20506 Show the current forced instruction mode.
20508 @item set debug arm
20509 Toggle whether to display ARM-specific debugging messages from the ARM
20510 target support subsystem.
20512 @item show debug arm
20513 Show whether ARM-specific debugging messages are enabled.
20516 The following commands are available when an ARM target is debugged
20517 using the RDI interface:
20520 @item rdilogfile @r{[}@var{file}@r{]}
20522 @cindex ADP (Angel Debugger Protocol) logging
20523 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20524 With an argument, sets the log file to the specified @var{file}. With
20525 no argument, show the current log file name. The default log file is
20528 @item rdilogenable @r{[}@var{arg}@r{]}
20529 @kindex rdilogenable
20530 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20531 enables logging, with an argument 0 or @code{"no"} disables it. With
20532 no arguments displays the current setting. When logging is enabled,
20533 ADP packets exchanged between @value{GDBN} and the RDI target device
20534 are logged to a file.
20536 @item set rdiromatzero
20537 @kindex set rdiromatzero
20538 @cindex ROM at zero address, RDI
20539 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20540 vector catching is disabled, so that zero address can be used. If off
20541 (the default), vector catching is enabled. For this command to take
20542 effect, it needs to be invoked prior to the @code{target rdi} command.
20544 @item show rdiromatzero
20545 @kindex show rdiromatzero
20546 Show the current setting of ROM at zero address.
20548 @item set rdiheartbeat
20549 @kindex set rdiheartbeat
20550 @cindex RDI heartbeat
20551 Enable or disable RDI heartbeat packets. It is not recommended to
20552 turn on this option, since it confuses ARM and EPI JTAG interface, as
20553 well as the Angel monitor.
20555 @item show rdiheartbeat
20556 @kindex show rdiheartbeat
20557 Show the setting of RDI heartbeat packets.
20561 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20562 The @value{GDBN} ARM simulator accepts the following optional arguments.
20565 @item --swi-support=@var{type}
20566 Tell the simulator which SWI interfaces to support.
20567 @var{type} may be a comma separated list of the following values.
20568 The default value is @code{all}.
20581 @subsection Renesas M32R/D and M32R/SDI
20584 @kindex target m32r
20585 @item target m32r @var{dev}
20586 Renesas M32R/D ROM monitor.
20588 @kindex target m32rsdi
20589 @item target m32rsdi @var{dev}
20590 Renesas M32R SDI server, connected via parallel port to the board.
20593 The following @value{GDBN} commands are specific to the M32R monitor:
20596 @item set download-path @var{path}
20597 @kindex set download-path
20598 @cindex find downloadable @sc{srec} files (M32R)
20599 Set the default path for finding downloadable @sc{srec} files.
20601 @item show download-path
20602 @kindex show download-path
20603 Show the default path for downloadable @sc{srec} files.
20605 @item set board-address @var{addr}
20606 @kindex set board-address
20607 @cindex M32-EVA target board address
20608 Set the IP address for the M32R-EVA target board.
20610 @item show board-address
20611 @kindex show board-address
20612 Show the current IP address of the target board.
20614 @item set server-address @var{addr}
20615 @kindex set server-address
20616 @cindex download server address (M32R)
20617 Set the IP address for the download server, which is the @value{GDBN}'s
20620 @item show server-address
20621 @kindex show server-address
20622 Display the IP address of the download server.
20624 @item upload @r{[}@var{file}@r{]}
20625 @kindex upload@r{, M32R}
20626 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20627 upload capability. If no @var{file} argument is given, the current
20628 executable file is uploaded.
20630 @item tload @r{[}@var{file}@r{]}
20631 @kindex tload@r{, M32R}
20632 Test the @code{upload} command.
20635 The following commands are available for M32R/SDI:
20640 @cindex reset SDI connection, M32R
20641 This command resets the SDI connection.
20645 This command shows the SDI connection status.
20648 @kindex debug_chaos
20649 @cindex M32R/Chaos debugging
20650 Instructs the remote that M32R/Chaos debugging is to be used.
20652 @item use_debug_dma
20653 @kindex use_debug_dma
20654 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20657 @kindex use_mon_code
20658 Instructs the remote to use the MON_CODE method of accessing memory.
20661 @kindex use_ib_break
20662 Instructs the remote to set breakpoints by IB break.
20664 @item use_dbt_break
20665 @kindex use_dbt_break
20666 Instructs the remote to set breakpoints by DBT.
20672 The Motorola m68k configuration includes ColdFire support, and a
20673 target command for the following ROM monitor.
20677 @kindex target dbug
20678 @item target dbug @var{dev}
20679 dBUG ROM monitor for Motorola ColdFire.
20684 @subsection MicroBlaze
20685 @cindex Xilinx MicroBlaze
20686 @cindex XMD, Xilinx Microprocessor Debugger
20688 The MicroBlaze is a soft-core processor supported on various Xilinx
20689 FPGAs, such as Spartan or Virtex series. Boards with these processors
20690 usually have JTAG ports which connect to a host system running the Xilinx
20691 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20692 This host system is used to download the configuration bitstream to
20693 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20694 communicates with the target board using the JTAG interface and
20695 presents a @code{gdbserver} interface to the board. By default
20696 @code{xmd} uses port @code{1234}. (While it is possible to change
20697 this default port, it requires the use of undocumented @code{xmd}
20698 commands. Contact Xilinx support if you need to do this.)
20700 Use these GDB commands to connect to the MicroBlaze target processor.
20703 @item target remote :1234
20704 Use this command to connect to the target if you are running @value{GDBN}
20705 on the same system as @code{xmd}.
20707 @item target remote @var{xmd-host}:1234
20708 Use this command to connect to the target if it is connected to @code{xmd}
20709 running on a different system named @var{xmd-host}.
20712 Use this command to download a program to the MicroBlaze target.
20714 @item set debug microblaze @var{n}
20715 Enable MicroBlaze-specific debugging messages if non-zero.
20717 @item show debug microblaze @var{n}
20718 Show MicroBlaze-specific debugging level.
20721 @node MIPS Embedded
20722 @subsection @acronym{MIPS} Embedded
20724 @cindex @acronym{MIPS} boards
20725 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20726 @acronym{MIPS} board attached to a serial line. This is available when
20727 you configure @value{GDBN} with @samp{--target=mips-elf}.
20730 Use these @value{GDBN} commands to specify the connection to your target board:
20733 @item target mips @var{port}
20734 @kindex target mips @var{port}
20735 To run a program on the board, start up @code{@value{GDBP}} with the
20736 name of your program as the argument. To connect to the board, use the
20737 command @samp{target mips @var{port}}, where @var{port} is the name of
20738 the serial port connected to the board. If the program has not already
20739 been downloaded to the board, you may use the @code{load} command to
20740 download it. You can then use all the usual @value{GDBN} commands.
20742 For example, this sequence connects to the target board through a serial
20743 port, and loads and runs a program called @var{prog} through the
20747 host$ @value{GDBP} @var{prog}
20748 @value{GDBN} is free software and @dots{}
20749 (@value{GDBP}) target mips /dev/ttyb
20750 (@value{GDBP}) load @var{prog}
20754 @item target mips @var{hostname}:@var{portnumber}
20755 On some @value{GDBN} host configurations, you can specify a TCP
20756 connection (for instance, to a serial line managed by a terminal
20757 concentrator) instead of a serial port, using the syntax
20758 @samp{@var{hostname}:@var{portnumber}}.
20760 @item target pmon @var{port}
20761 @kindex target pmon @var{port}
20764 @item target ddb @var{port}
20765 @kindex target ddb @var{port}
20766 NEC's DDB variant of PMON for Vr4300.
20768 @item target lsi @var{port}
20769 @kindex target lsi @var{port}
20770 LSI variant of PMON.
20772 @kindex target r3900
20773 @item target r3900 @var{dev}
20774 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20776 @kindex target array
20777 @item target array @var{dev}
20778 Array Tech LSI33K RAID controller board.
20784 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20787 @item set mipsfpu double
20788 @itemx set mipsfpu single
20789 @itemx set mipsfpu none
20790 @itemx set mipsfpu auto
20791 @itemx show mipsfpu
20792 @kindex set mipsfpu
20793 @kindex show mipsfpu
20794 @cindex @acronym{MIPS} remote floating point
20795 @cindex floating point, @acronym{MIPS} remote
20796 If your target board does not support the @acronym{MIPS} floating point
20797 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20798 need this, you may wish to put the command in your @value{GDBN} init
20799 file). This tells @value{GDBN} how to find the return value of
20800 functions which return floating point values. It also allows
20801 @value{GDBN} to avoid saving the floating point registers when calling
20802 functions on the board. If you are using a floating point coprocessor
20803 with only single precision floating point support, as on the @sc{r4650}
20804 processor, use the command @samp{set mipsfpu single}. The default
20805 double precision floating point coprocessor may be selected using
20806 @samp{set mipsfpu double}.
20808 In previous versions the only choices were double precision or no
20809 floating point, so @samp{set mipsfpu on} will select double precision
20810 and @samp{set mipsfpu off} will select no floating point.
20812 As usual, you can inquire about the @code{mipsfpu} variable with
20813 @samp{show mipsfpu}.
20815 @item set timeout @var{seconds}
20816 @itemx set retransmit-timeout @var{seconds}
20817 @itemx show timeout
20818 @itemx show retransmit-timeout
20819 @cindex @code{timeout}, @acronym{MIPS} protocol
20820 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20821 @kindex set timeout
20822 @kindex show timeout
20823 @kindex set retransmit-timeout
20824 @kindex show retransmit-timeout
20825 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20826 remote protocol, with the @code{set timeout @var{seconds}} command. The
20827 default is 5 seconds. Similarly, you can control the timeout used while
20828 waiting for an acknowledgment of a packet with the @code{set
20829 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20830 You can inspect both values with @code{show timeout} and @code{show
20831 retransmit-timeout}. (These commands are @emph{only} available when
20832 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20834 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20835 is waiting for your program to stop. In that case, @value{GDBN} waits
20836 forever because it has no way of knowing how long the program is going
20837 to run before stopping.
20839 @item set syn-garbage-limit @var{num}
20840 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20841 @cindex synchronize with remote @acronym{MIPS} target
20842 Limit the maximum number of characters @value{GDBN} should ignore when
20843 it tries to synchronize with the remote target. The default is 10
20844 characters. Setting the limit to -1 means there's no limit.
20846 @item show syn-garbage-limit
20847 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20848 Show the current limit on the number of characters to ignore when
20849 trying to synchronize with the remote system.
20851 @item set monitor-prompt @var{prompt}
20852 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20853 @cindex remote monitor prompt
20854 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20855 remote monitor. The default depends on the target:
20865 @item show monitor-prompt
20866 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20867 Show the current strings @value{GDBN} expects as the prompt from the
20870 @item set monitor-warnings
20871 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20872 Enable or disable monitor warnings about hardware breakpoints. This
20873 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20874 display warning messages whose codes are returned by the @code{lsi}
20875 PMON monitor for breakpoint commands.
20877 @item show monitor-warnings
20878 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20879 Show the current setting of printing monitor warnings.
20881 @item pmon @var{command}
20882 @kindex pmon@r{, @acronym{MIPS} remote}
20883 @cindex send PMON command
20884 This command allows sending an arbitrary @var{command} string to the
20885 monitor. The monitor must be in debug mode for this to work.
20888 @node PowerPC Embedded
20889 @subsection PowerPC Embedded
20891 @cindex DVC register
20892 @value{GDBN} supports using the DVC (Data Value Compare) register to
20893 implement in hardware simple hardware watchpoint conditions of the form:
20896 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20897 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20900 The DVC register will be automatically used when @value{GDBN} detects
20901 such pattern in a condition expression, and the created watchpoint uses one
20902 debug register (either the @code{exact-watchpoints} option is on and the
20903 variable is scalar, or the variable has a length of one byte). This feature
20904 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20907 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20908 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20909 in which case watchpoints using only one debug register are created when
20910 watching variables of scalar types.
20912 You can create an artificial array to watch an arbitrary memory
20913 region using one of the following commands (@pxref{Expressions}):
20916 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20917 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20920 PowerPC embedded processors support masked watchpoints. See the discussion
20921 about the @code{mask} argument in @ref{Set Watchpoints}.
20923 @cindex ranged breakpoint
20924 PowerPC embedded processors support hardware accelerated
20925 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20926 the inferior whenever it executes an instruction at any address within
20927 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20928 use the @code{break-range} command.
20930 @value{GDBN} provides the following PowerPC-specific commands:
20933 @kindex break-range
20934 @item break-range @var{start-location}, @var{end-location}
20935 Set a breakpoint for an address range.
20936 @var{start-location} and @var{end-location} can specify a function name,
20937 a line number, an offset of lines from the current line or from the start
20938 location, or an address of an instruction (see @ref{Specify Location},
20939 for a list of all the possible ways to specify a @var{location}.)
20940 The breakpoint will stop execution of the inferior whenever it
20941 executes an instruction at any address within the specified range,
20942 (including @var{start-location} and @var{end-location}.)
20944 @kindex set powerpc
20945 @item set powerpc soft-float
20946 @itemx show powerpc soft-float
20947 Force @value{GDBN} to use (or not use) a software floating point calling
20948 convention. By default, @value{GDBN} selects the calling convention based
20949 on the selected architecture and the provided executable file.
20951 @item set powerpc vector-abi
20952 @itemx show powerpc vector-abi
20953 Force @value{GDBN} to use the specified calling convention for vector
20954 arguments and return values. The valid options are @samp{auto};
20955 @samp{generic}, to avoid vector registers even if they are present;
20956 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20957 registers. By default, @value{GDBN} selects the calling convention
20958 based on the selected architecture and the provided executable file.
20960 @item set powerpc exact-watchpoints
20961 @itemx show powerpc exact-watchpoints
20962 Allow @value{GDBN} to use only one debug register when watching a variable
20963 of scalar type, thus assuming that the variable is accessed through the
20964 address of its first byte.
20966 @kindex target dink32
20967 @item target dink32 @var{dev}
20968 DINK32 ROM monitor.
20970 @kindex target ppcbug
20971 @item target ppcbug @var{dev}
20972 @kindex target ppcbug1
20973 @item target ppcbug1 @var{dev}
20974 PPCBUG ROM monitor for PowerPC.
20977 @item target sds @var{dev}
20978 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20981 @cindex SDS protocol
20982 The following commands specific to the SDS protocol are supported
20986 @item set sdstimeout @var{nsec}
20987 @kindex set sdstimeout
20988 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20989 default is 2 seconds.
20991 @item show sdstimeout
20992 @kindex show sdstimeout
20993 Show the current value of the SDS timeout.
20995 @item sds @var{command}
20996 @kindex sds@r{, a command}
20997 Send the specified @var{command} string to the SDS monitor.
21002 @subsection HP PA Embedded
21006 @kindex target op50n
21007 @item target op50n @var{dev}
21008 OP50N monitor, running on an OKI HPPA board.
21010 @kindex target w89k
21011 @item target w89k @var{dev}
21012 W89K monitor, running on a Winbond HPPA board.
21017 @subsection Tsqware Sparclet
21021 @value{GDBN} enables developers to debug tasks running on
21022 Sparclet targets from a Unix host.
21023 @value{GDBN} uses code that runs on
21024 both the Unix host and on the Sparclet target. The program
21025 @code{@value{GDBP}} is installed and executed on the Unix host.
21028 @item remotetimeout @var{args}
21029 @kindex remotetimeout
21030 @value{GDBN} supports the option @code{remotetimeout}.
21031 This option is set by the user, and @var{args} represents the number of
21032 seconds @value{GDBN} waits for responses.
21035 @cindex compiling, on Sparclet
21036 When compiling for debugging, include the options @samp{-g} to get debug
21037 information and @samp{-Ttext} to relocate the program to where you wish to
21038 load it on the target. You may also want to add the options @samp{-n} or
21039 @samp{-N} in order to reduce the size of the sections. Example:
21042 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21045 You can use @code{objdump} to verify that the addresses are what you intended:
21048 sparclet-aout-objdump --headers --syms prog
21051 @cindex running, on Sparclet
21053 your Unix execution search path to find @value{GDBN}, you are ready to
21054 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21055 (or @code{sparclet-aout-gdb}, depending on your installation).
21057 @value{GDBN} comes up showing the prompt:
21064 * Sparclet File:: Setting the file to debug
21065 * Sparclet Connection:: Connecting to Sparclet
21066 * Sparclet Download:: Sparclet download
21067 * Sparclet Execution:: Running and debugging
21070 @node Sparclet File
21071 @subsubsection Setting File to Debug
21073 The @value{GDBN} command @code{file} lets you choose with program to debug.
21076 (gdbslet) file prog
21080 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21081 @value{GDBN} locates
21082 the file by searching the directories listed in the command search
21084 If the file was compiled with debug information (option @samp{-g}), source
21085 files will be searched as well.
21086 @value{GDBN} locates
21087 the source files by searching the directories listed in the directory search
21088 path (@pxref{Environment, ,Your Program's Environment}).
21090 to find a file, it displays a message such as:
21093 prog: No such file or directory.
21096 When this happens, add the appropriate directories to the search paths with
21097 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21098 @code{target} command again.
21100 @node Sparclet Connection
21101 @subsubsection Connecting to Sparclet
21103 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21104 To connect to a target on serial port ``@code{ttya}'', type:
21107 (gdbslet) target sparclet /dev/ttya
21108 Remote target sparclet connected to /dev/ttya
21109 main () at ../prog.c:3
21113 @value{GDBN} displays messages like these:
21119 @node Sparclet Download
21120 @subsubsection Sparclet Download
21122 @cindex download to Sparclet
21123 Once connected to the Sparclet target,
21124 you can use the @value{GDBN}
21125 @code{load} command to download the file from the host to the target.
21126 The file name and load offset should be given as arguments to the @code{load}
21128 Since the file format is aout, the program must be loaded to the starting
21129 address. You can use @code{objdump} to find out what this value is. The load
21130 offset is an offset which is added to the VMA (virtual memory address)
21131 of each of the file's sections.
21132 For instance, if the program
21133 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21134 and bss at 0x12010170, in @value{GDBN}, type:
21137 (gdbslet) load prog 0x12010000
21138 Loading section .text, size 0xdb0 vma 0x12010000
21141 If the code is loaded at a different address then what the program was linked
21142 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21143 to tell @value{GDBN} where to map the symbol table.
21145 @node Sparclet Execution
21146 @subsubsection Running and Debugging
21148 @cindex running and debugging Sparclet programs
21149 You can now begin debugging the task using @value{GDBN}'s execution control
21150 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21151 manual for the list of commands.
21155 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21157 Starting program: prog
21158 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21159 3 char *symarg = 0;
21161 4 char *execarg = "hello!";
21166 @subsection Fujitsu Sparclite
21170 @kindex target sparclite
21171 @item target sparclite @var{dev}
21172 Fujitsu sparclite boards, used only for the purpose of loading.
21173 You must use an additional command to debug the program.
21174 For example: target remote @var{dev} using @value{GDBN} standard
21180 @subsection Zilog Z8000
21183 @cindex simulator, Z8000
21184 @cindex Zilog Z8000 simulator
21186 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21189 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21190 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21191 segmented variant). The simulator recognizes which architecture is
21192 appropriate by inspecting the object code.
21195 @item target sim @var{args}
21197 @kindex target sim@r{, with Z8000}
21198 Debug programs on a simulated CPU. If the simulator supports setup
21199 options, specify them via @var{args}.
21203 After specifying this target, you can debug programs for the simulated
21204 CPU in the same style as programs for your host computer; use the
21205 @code{file} command to load a new program image, the @code{run} command
21206 to run your program, and so on.
21208 As well as making available all the usual machine registers
21209 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21210 additional items of information as specially named registers:
21215 Counts clock-ticks in the simulator.
21218 Counts instructions run in the simulator.
21221 Execution time in 60ths of a second.
21225 You can refer to these values in @value{GDBN} expressions with the usual
21226 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21227 conditional breakpoint that suspends only after at least 5000
21228 simulated clock ticks.
21231 @subsection Atmel AVR
21234 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21235 following AVR-specific commands:
21238 @item info io_registers
21239 @kindex info io_registers@r{, AVR}
21240 @cindex I/O registers (Atmel AVR)
21241 This command displays information about the AVR I/O registers. For
21242 each register, @value{GDBN} prints its number and value.
21249 When configured for debugging CRIS, @value{GDBN} provides the
21250 following CRIS-specific commands:
21253 @item set cris-version @var{ver}
21254 @cindex CRIS version
21255 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21256 The CRIS version affects register names and sizes. This command is useful in
21257 case autodetection of the CRIS version fails.
21259 @item show cris-version
21260 Show the current CRIS version.
21262 @item set cris-dwarf2-cfi
21263 @cindex DWARF-2 CFI and CRIS
21264 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21265 Change to @samp{off} when using @code{gcc-cris} whose version is below
21268 @item show cris-dwarf2-cfi
21269 Show the current state of using DWARF-2 CFI.
21271 @item set cris-mode @var{mode}
21273 Set the current CRIS mode to @var{mode}. It should only be changed when
21274 debugging in guru mode, in which case it should be set to
21275 @samp{guru} (the default is @samp{normal}).
21277 @item show cris-mode
21278 Show the current CRIS mode.
21282 @subsection Renesas Super-H
21285 For the Renesas Super-H processor, @value{GDBN} provides these
21289 @item set sh calling-convention @var{convention}
21290 @kindex set sh calling-convention
21291 Set the calling-convention used when calling functions from @value{GDBN}.
21292 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21293 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21294 convention. If the DWARF-2 information of the called function specifies
21295 that the function follows the Renesas calling convention, the function
21296 is called using the Renesas calling convention. If the calling convention
21297 is set to @samp{renesas}, the Renesas calling convention is always used,
21298 regardless of the DWARF-2 information. This can be used to override the
21299 default of @samp{gcc} if debug information is missing, or the compiler
21300 does not emit the DWARF-2 calling convention entry for a function.
21302 @item show sh calling-convention
21303 @kindex show sh calling-convention
21304 Show the current calling convention setting.
21309 @node Architectures
21310 @section Architectures
21312 This section describes characteristics of architectures that affect
21313 all uses of @value{GDBN} with the architecture, both native and cross.
21320 * HPPA:: HP PA architecture
21321 * SPU:: Cell Broadband Engine SPU architecture
21327 @subsection AArch64
21328 @cindex AArch64 support
21330 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21331 following special commands:
21334 @item set debug aarch64
21335 @kindex set debug aarch64
21336 This command determines whether AArch64 architecture-specific debugging
21337 messages are to be displayed.
21339 @item show debug aarch64
21340 Show whether AArch64 debugging messages are displayed.
21345 @subsection x86 Architecture-specific Issues
21348 @item set struct-convention @var{mode}
21349 @kindex set struct-convention
21350 @cindex struct return convention
21351 @cindex struct/union returned in registers
21352 Set the convention used by the inferior to return @code{struct}s and
21353 @code{union}s from functions to @var{mode}. Possible values of
21354 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21355 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21356 are returned on the stack, while @code{"reg"} means that a
21357 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21358 be returned in a register.
21360 @item show struct-convention
21361 @kindex show struct-convention
21362 Show the current setting of the convention to return @code{struct}s
21369 See the following section.
21372 @subsection @acronym{MIPS}
21374 @cindex stack on Alpha
21375 @cindex stack on @acronym{MIPS}
21376 @cindex Alpha stack
21377 @cindex @acronym{MIPS} stack
21378 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21379 sometimes requires @value{GDBN} to search backward in the object code to
21380 find the beginning of a function.
21382 @cindex response time, @acronym{MIPS} debugging
21383 To improve response time (especially for embedded applications, where
21384 @value{GDBN} may be restricted to a slow serial line for this search)
21385 you may want to limit the size of this search, using one of these
21389 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21390 @item set heuristic-fence-post @var{limit}
21391 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21392 search for the beginning of a function. A value of @var{0} (the
21393 default) means there is no limit. However, except for @var{0}, the
21394 larger the limit the more bytes @code{heuristic-fence-post} must search
21395 and therefore the longer it takes to run. You should only need to use
21396 this command when debugging a stripped executable.
21398 @item show heuristic-fence-post
21399 Display the current limit.
21403 These commands are available @emph{only} when @value{GDBN} is configured
21404 for debugging programs on Alpha or @acronym{MIPS} processors.
21406 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21410 @item set mips abi @var{arg}
21411 @kindex set mips abi
21412 @cindex set ABI for @acronym{MIPS}
21413 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21414 values of @var{arg} are:
21418 The default ABI associated with the current binary (this is the
21428 @item show mips abi
21429 @kindex show mips abi
21430 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21432 @item set mips compression @var{arg}
21433 @kindex set mips compression
21434 @cindex code compression, @acronym{MIPS}
21435 Tell @value{GDBN} which @acronym{MIPS} compressed
21436 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21437 inferior. @value{GDBN} uses this for code disassembly and other
21438 internal interpretation purposes. This setting is only referred to
21439 when no executable has been associated with the debugging session or
21440 the executable does not provide information about the encoding it uses.
21441 Otherwise this setting is automatically updated from information
21442 provided by the executable.
21444 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21445 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21446 executables containing @acronym{MIPS16} code frequently are not
21447 identified as such.
21449 This setting is ``sticky''; that is, it retains its value across
21450 debugging sessions until reset either explicitly with this command or
21451 implicitly from an executable.
21453 The compiler and/or assembler typically add symbol table annotations to
21454 identify functions compiled for the @acronym{MIPS16} or
21455 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21456 are present, @value{GDBN} uses them in preference to the global
21457 compressed @acronym{ISA} encoding setting.
21459 @item show mips compression
21460 @kindex show mips compression
21461 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21462 @value{GDBN} to debug the inferior.
21465 @itemx show mipsfpu
21466 @xref{MIPS Embedded, set mipsfpu}.
21468 @item set mips mask-address @var{arg}
21469 @kindex set mips mask-address
21470 @cindex @acronym{MIPS} addresses, masking
21471 This command determines whether the most-significant 32 bits of 64-bit
21472 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21473 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21474 setting, which lets @value{GDBN} determine the correct value.
21476 @item show mips mask-address
21477 @kindex show mips mask-address
21478 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21481 @item set remote-mips64-transfers-32bit-regs
21482 @kindex set remote-mips64-transfers-32bit-regs
21483 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21484 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21485 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21486 and 64 bits for other registers, set this option to @samp{on}.
21488 @item show remote-mips64-transfers-32bit-regs
21489 @kindex show remote-mips64-transfers-32bit-regs
21490 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21492 @item set debug mips
21493 @kindex set debug mips
21494 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21495 target code in @value{GDBN}.
21497 @item show debug mips
21498 @kindex show debug mips
21499 Show the current setting of @acronym{MIPS} debugging messages.
21505 @cindex HPPA support
21507 When @value{GDBN} is debugging the HP PA architecture, it provides the
21508 following special commands:
21511 @item set debug hppa
21512 @kindex set debug hppa
21513 This command determines whether HPPA architecture-specific debugging
21514 messages are to be displayed.
21516 @item show debug hppa
21517 Show whether HPPA debugging messages are displayed.
21519 @item maint print unwind @var{address}
21520 @kindex maint print unwind@r{, HPPA}
21521 This command displays the contents of the unwind table entry at the
21522 given @var{address}.
21528 @subsection Cell Broadband Engine SPU architecture
21529 @cindex Cell Broadband Engine
21532 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21533 it provides the following special commands:
21536 @item info spu event
21538 Display SPU event facility status. Shows current event mask
21539 and pending event status.
21541 @item info spu signal
21542 Display SPU signal notification facility status. Shows pending
21543 signal-control word and signal notification mode of both signal
21544 notification channels.
21546 @item info spu mailbox
21547 Display SPU mailbox facility status. Shows all pending entries,
21548 in order of processing, in each of the SPU Write Outbound,
21549 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21552 Display MFC DMA status. Shows all pending commands in the MFC
21553 DMA queue. For each entry, opcode, tag, class IDs, effective
21554 and local store addresses and transfer size are shown.
21556 @item info spu proxydma
21557 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21558 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21559 and local store addresses and transfer size are shown.
21563 When @value{GDBN} is debugging a combined PowerPC/SPU application
21564 on the Cell Broadband Engine, it provides in addition the following
21568 @item set spu stop-on-load @var{arg}
21570 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21571 will give control to the user when a new SPE thread enters its @code{main}
21572 function. The default is @code{off}.
21574 @item show spu stop-on-load
21576 Show whether to stop for new SPE threads.
21578 @item set spu auto-flush-cache @var{arg}
21579 Set whether to automatically flush the software-managed cache. When set to
21580 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21581 cache to be flushed whenever SPE execution stops. This provides a consistent
21582 view of PowerPC memory that is accessed via the cache. If an application
21583 does not use the software-managed cache, this option has no effect.
21585 @item show spu auto-flush-cache
21586 Show whether to automatically flush the software-managed cache.
21591 @subsection PowerPC
21592 @cindex PowerPC architecture
21594 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21595 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21596 numbers stored in the floating point registers. These values must be stored
21597 in two consecutive registers, always starting at an even register like
21598 @code{f0} or @code{f2}.
21600 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21601 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21602 @code{f2} and @code{f3} for @code{$dl1} and so on.
21604 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21605 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21608 @subsection Nios II
21609 @cindex Nios II architecture
21611 When @value{GDBN} is debugging the Nios II architecture,
21612 it provides the following special commands:
21616 @item set debug nios2
21617 @kindex set debug nios2
21618 This command turns on and off debugging messages for the Nios II
21619 target code in @value{GDBN}.
21621 @item show debug nios2
21622 @kindex show debug nios2
21623 Show the current setting of Nios II debugging messages.
21626 @node Controlling GDB
21627 @chapter Controlling @value{GDBN}
21629 You can alter the way @value{GDBN} interacts with you by using the
21630 @code{set} command. For commands controlling how @value{GDBN} displays
21631 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21636 * Editing:: Command editing
21637 * Command History:: Command history
21638 * Screen Size:: Screen size
21639 * Numbers:: Numbers
21640 * ABI:: Configuring the current ABI
21641 * Auto-loading:: Automatically loading associated files
21642 * Messages/Warnings:: Optional warnings and messages
21643 * Debugging Output:: Optional messages about internal happenings
21644 * Other Misc Settings:: Other Miscellaneous Settings
21652 @value{GDBN} indicates its readiness to read a command by printing a string
21653 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21654 can change the prompt string with the @code{set prompt} command. For
21655 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21656 the prompt in one of the @value{GDBN} sessions so that you can always tell
21657 which one you are talking to.
21659 @emph{Note:} @code{set prompt} does not add a space for you after the
21660 prompt you set. This allows you to set a prompt which ends in a space
21661 or a prompt that does not.
21665 @item set prompt @var{newprompt}
21666 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21668 @kindex show prompt
21670 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21673 Versions of @value{GDBN} that ship with Python scripting enabled have
21674 prompt extensions. The commands for interacting with these extensions
21678 @kindex set extended-prompt
21679 @item set extended-prompt @var{prompt}
21680 Set an extended prompt that allows for substitutions.
21681 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21682 substitution. Any escape sequences specified as part of the prompt
21683 string are replaced with the corresponding strings each time the prompt
21689 set extended-prompt Current working directory: \w (gdb)
21692 Note that when an extended-prompt is set, it takes control of the
21693 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21695 @kindex show extended-prompt
21696 @item show extended-prompt
21697 Prints the extended prompt. Any escape sequences specified as part of
21698 the prompt string with @code{set extended-prompt}, are replaced with the
21699 corresponding strings each time the prompt is displayed.
21703 @section Command Editing
21705 @cindex command line editing
21707 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21708 @sc{gnu} library provides consistent behavior for programs which provide a
21709 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21710 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21711 substitution, and a storage and recall of command history across
21712 debugging sessions.
21714 You may control the behavior of command line editing in @value{GDBN} with the
21715 command @code{set}.
21718 @kindex set editing
21721 @itemx set editing on
21722 Enable command line editing (enabled by default).
21724 @item set editing off
21725 Disable command line editing.
21727 @kindex show editing
21729 Show whether command line editing is enabled.
21732 @ifset SYSTEM_READLINE
21733 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21735 @ifclear SYSTEM_READLINE
21736 @xref{Command Line Editing},
21738 for more details about the Readline
21739 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21740 encouraged to read that chapter.
21742 @node Command History
21743 @section Command History
21744 @cindex command history
21746 @value{GDBN} can keep track of the commands you type during your
21747 debugging sessions, so that you can be certain of precisely what
21748 happened. Use these commands to manage the @value{GDBN} command
21751 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21752 package, to provide the history facility.
21753 @ifset SYSTEM_READLINE
21754 @xref{Using History Interactively, , , history, GNU History Library},
21756 @ifclear SYSTEM_READLINE
21757 @xref{Using History Interactively},
21759 for the detailed description of the History library.
21761 To issue a command to @value{GDBN} without affecting certain aspects of
21762 the state which is seen by users, prefix it with @samp{server }
21763 (@pxref{Server Prefix}). This
21764 means that this command will not affect the command history, nor will it
21765 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21766 pressed on a line by itself.
21768 @cindex @code{server}, command prefix
21769 The server prefix does not affect the recording of values into the value
21770 history; to print a value without recording it into the value history,
21771 use the @code{output} command instead of the @code{print} command.
21773 Here is the description of @value{GDBN} commands related to command
21777 @cindex history substitution
21778 @cindex history file
21779 @kindex set history filename
21780 @cindex @env{GDBHISTFILE}, environment variable
21781 @item set history filename @var{fname}
21782 Set the name of the @value{GDBN} command history file to @var{fname}.
21783 This is the file where @value{GDBN} reads an initial command history
21784 list, and where it writes the command history from this session when it
21785 exits. You can access this list through history expansion or through
21786 the history command editing characters listed below. This file defaults
21787 to the value of the environment variable @code{GDBHISTFILE}, or to
21788 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21791 @cindex save command history
21792 @kindex set history save
21793 @item set history save
21794 @itemx set history save on
21795 Record command history in a file, whose name may be specified with the
21796 @code{set history filename} command. By default, this option is disabled.
21798 @item set history save off
21799 Stop recording command history in a file.
21801 @cindex history size
21802 @kindex set history size
21803 @cindex @env{HISTSIZE}, environment variable
21804 @item set history size @var{size}
21805 @itemx set history size unlimited
21806 Set the number of commands which @value{GDBN} keeps in its history list.
21807 This defaults to the value of the environment variable
21808 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21809 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21810 history list is unlimited.
21813 History expansion assigns special meaning to the character @kbd{!}.
21814 @ifset SYSTEM_READLINE
21815 @xref{Event Designators, , , history, GNU History Library},
21817 @ifclear SYSTEM_READLINE
21818 @xref{Event Designators},
21822 @cindex history expansion, turn on/off
21823 Since @kbd{!} is also the logical not operator in C, history expansion
21824 is off by default. If you decide to enable history expansion with the
21825 @code{set history expansion on} command, you may sometimes need to
21826 follow @kbd{!} (when it is used as logical not, in an expression) with
21827 a space or a tab to prevent it from being expanded. The readline
21828 history facilities do not attempt substitution on the strings
21829 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21831 The commands to control history expansion are:
21834 @item set history expansion on
21835 @itemx set history expansion
21836 @kindex set history expansion
21837 Enable history expansion. History expansion is off by default.
21839 @item set history expansion off
21840 Disable history expansion.
21843 @kindex show history
21845 @itemx show history filename
21846 @itemx show history save
21847 @itemx show history size
21848 @itemx show history expansion
21849 These commands display the state of the @value{GDBN} history parameters.
21850 @code{show history} by itself displays all four states.
21855 @kindex show commands
21856 @cindex show last commands
21857 @cindex display command history
21858 @item show commands
21859 Display the last ten commands in the command history.
21861 @item show commands @var{n}
21862 Print ten commands centered on command number @var{n}.
21864 @item show commands +
21865 Print ten commands just after the commands last printed.
21869 @section Screen Size
21870 @cindex size of screen
21871 @cindex pauses in output
21873 Certain commands to @value{GDBN} may produce large amounts of
21874 information output to the screen. To help you read all of it,
21875 @value{GDBN} pauses and asks you for input at the end of each page of
21876 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21877 to discard the remaining output. Also, the screen width setting
21878 determines when to wrap lines of output. Depending on what is being
21879 printed, @value{GDBN} tries to break the line at a readable place,
21880 rather than simply letting it overflow onto the following line.
21882 Normally @value{GDBN} knows the size of the screen from the terminal
21883 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21884 together with the value of the @code{TERM} environment variable and the
21885 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21886 you can override it with the @code{set height} and @code{set
21893 @kindex show height
21894 @item set height @var{lpp}
21895 @itemx set height unlimited
21897 @itemx set width @var{cpl}
21898 @itemx set width unlimited
21900 These @code{set} commands specify a screen height of @var{lpp} lines and
21901 a screen width of @var{cpl} characters. The associated @code{show}
21902 commands display the current settings.
21904 If you specify a height of either @code{unlimited} or zero lines,
21905 @value{GDBN} does not pause during output no matter how long the
21906 output is. This is useful if output is to a file or to an editor
21909 Likewise, you can specify @samp{set width unlimited} or @samp{set
21910 width 0} to prevent @value{GDBN} from wrapping its output.
21912 @item set pagination on
21913 @itemx set pagination off
21914 @kindex set pagination
21915 Turn the output pagination on or off; the default is on. Turning
21916 pagination off is the alternative to @code{set height unlimited}. Note that
21917 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21918 Options, -batch}) also automatically disables pagination.
21920 @item show pagination
21921 @kindex show pagination
21922 Show the current pagination mode.
21927 @cindex number representation
21928 @cindex entering numbers
21930 You can always enter numbers in octal, decimal, or hexadecimal in
21931 @value{GDBN} by the usual conventions: octal numbers begin with
21932 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21933 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21934 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21935 10; likewise, the default display for numbers---when no particular
21936 format is specified---is base 10. You can change the default base for
21937 both input and output with the commands described below.
21940 @kindex set input-radix
21941 @item set input-radix @var{base}
21942 Set the default base for numeric input. Supported choices
21943 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21944 specified either unambiguously or using the current input radix; for
21948 set input-radix 012
21949 set input-radix 10.
21950 set input-radix 0xa
21954 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21955 leaves the input radix unchanged, no matter what it was, since
21956 @samp{10}, being without any leading or trailing signs of its base, is
21957 interpreted in the current radix. Thus, if the current radix is 16,
21958 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21961 @kindex set output-radix
21962 @item set output-radix @var{base}
21963 Set the default base for numeric display. Supported choices
21964 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21965 specified either unambiguously or using the current input radix.
21967 @kindex show input-radix
21968 @item show input-radix
21969 Display the current default base for numeric input.
21971 @kindex show output-radix
21972 @item show output-radix
21973 Display the current default base for numeric display.
21975 @item set radix @r{[}@var{base}@r{]}
21979 These commands set and show the default base for both input and output
21980 of numbers. @code{set radix} sets the radix of input and output to
21981 the same base; without an argument, it resets the radix back to its
21982 default value of 10.
21987 @section Configuring the Current ABI
21989 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21990 application automatically. However, sometimes you need to override its
21991 conclusions. Use these commands to manage @value{GDBN}'s view of the
21997 @cindex Newlib OS ABI and its influence on the longjmp handling
21999 One @value{GDBN} configuration can debug binaries for multiple operating
22000 system targets, either via remote debugging or native emulation.
22001 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22002 but you can override its conclusion using the @code{set osabi} command.
22003 One example where this is useful is in debugging of binaries which use
22004 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22005 not have the same identifying marks that the standard C library for your
22008 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22009 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22010 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22011 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22015 Show the OS ABI currently in use.
22018 With no argument, show the list of registered available OS ABI's.
22020 @item set osabi @var{abi}
22021 Set the current OS ABI to @var{abi}.
22024 @cindex float promotion
22026 Generally, the way that an argument of type @code{float} is passed to a
22027 function depends on whether the function is prototyped. For a prototyped
22028 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22029 according to the architecture's convention for @code{float}. For unprototyped
22030 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22031 @code{double} and then passed.
22033 Unfortunately, some forms of debug information do not reliably indicate whether
22034 a function is prototyped. If @value{GDBN} calls a function that is not marked
22035 as prototyped, it consults @kbd{set coerce-float-to-double}.
22038 @kindex set coerce-float-to-double
22039 @item set coerce-float-to-double
22040 @itemx set coerce-float-to-double on
22041 Arguments of type @code{float} will be promoted to @code{double} when passed
22042 to an unprototyped function. This is the default setting.
22044 @item set coerce-float-to-double off
22045 Arguments of type @code{float} will be passed directly to unprototyped
22048 @kindex show coerce-float-to-double
22049 @item show coerce-float-to-double
22050 Show the current setting of promoting @code{float} to @code{double}.
22054 @kindex show cp-abi
22055 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22056 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22057 used to build your application. @value{GDBN} only fully supports
22058 programs with a single C@t{++} ABI; if your program contains code using
22059 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22060 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22061 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22062 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22063 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22064 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22069 Show the C@t{++} ABI currently in use.
22072 With no argument, show the list of supported C@t{++} ABI's.
22074 @item set cp-abi @var{abi}
22075 @itemx set cp-abi auto
22076 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22080 @section Automatically loading associated files
22081 @cindex auto-loading
22083 @value{GDBN} sometimes reads files with commands and settings automatically,
22084 without being explicitly told so by the user. We call this feature
22085 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22086 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22087 results or introduce security risks (e.g., if the file comes from untrusted
22090 Note that loading of these associated files (including the local @file{.gdbinit}
22091 file) requires accordingly configured @code{auto-load safe-path}
22092 (@pxref{Auto-loading safe path}).
22094 For these reasons, @value{GDBN} includes commands and options to let you
22095 control when to auto-load files and which files should be auto-loaded.
22098 @anchor{set auto-load off}
22099 @kindex set auto-load off
22100 @item set auto-load off
22101 Globally disable loading of all auto-loaded files.
22102 You may want to use this command with the @samp{-iex} option
22103 (@pxref{Option -init-eval-command}) such as:
22105 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22108 Be aware that system init file (@pxref{System-wide configuration})
22109 and init files from your home directory (@pxref{Home Directory Init File})
22110 still get read (as they come from generally trusted directories).
22111 To prevent @value{GDBN} from auto-loading even those init files, use the
22112 @option{-nx} option (@pxref{Mode Options}), in addition to
22113 @code{set auto-load no}.
22115 @anchor{show auto-load}
22116 @kindex show auto-load
22117 @item show auto-load
22118 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22122 (gdb) show auto-load
22123 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22124 libthread-db: Auto-loading of inferior specific libthread_db is on.
22125 local-gdbinit: Auto-loading of .gdbinit script from current directory
22127 python-scripts: Auto-loading of Python scripts is on.
22128 safe-path: List of directories from which it is safe to auto-load files
22129 is $debugdir:$datadir/auto-load.
22130 scripts-directory: List of directories from which to load auto-loaded scripts
22131 is $debugdir:$datadir/auto-load.
22134 @anchor{info auto-load}
22135 @kindex info auto-load
22136 @item info auto-load
22137 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22141 (gdb) info auto-load
22144 Yes /home/user/gdb/gdb-gdb.gdb
22145 libthread-db: No auto-loaded libthread-db.
22146 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22150 Yes /home/user/gdb/gdb-gdb.py
22154 These are various kinds of files @value{GDBN} can automatically load:
22158 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
22160 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
22162 @xref{dotdebug_gdb_scripts section},
22163 controlled by @ref{set auto-load python-scripts}.
22165 @xref{Init File in the Current Directory},
22166 controlled by @ref{set auto-load local-gdbinit}.
22168 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
22171 These are @value{GDBN} control commands for the auto-loading:
22173 @multitable @columnfractions .5 .5
22174 @item @xref{set auto-load off}.
22175 @tab Disable auto-loading globally.
22176 @item @xref{show auto-load}.
22177 @tab Show setting of all kinds of files.
22178 @item @xref{info auto-load}.
22179 @tab Show state of all kinds of files.
22180 @item @xref{set auto-load gdb-scripts}.
22181 @tab Control for @value{GDBN} command scripts.
22182 @item @xref{show auto-load gdb-scripts}.
22183 @tab Show setting of @value{GDBN} command scripts.
22184 @item @xref{info auto-load gdb-scripts}.
22185 @tab Show state of @value{GDBN} command scripts.
22186 @item @xref{set auto-load python-scripts}.
22187 @tab Control for @value{GDBN} Python scripts.
22188 @item @xref{show auto-load python-scripts}.
22189 @tab Show setting of @value{GDBN} Python scripts.
22190 @item @xref{info auto-load python-scripts}.
22191 @tab Show state of @value{GDBN} Python scripts.
22192 @item @xref{set auto-load scripts-directory}.
22193 @tab Control for @value{GDBN} auto-loaded scripts location.
22194 @item @xref{show auto-load scripts-directory}.
22195 @tab Show @value{GDBN} auto-loaded scripts location.
22196 @item @xref{set auto-load local-gdbinit}.
22197 @tab Control for init file in the current directory.
22198 @item @xref{show auto-load local-gdbinit}.
22199 @tab Show setting of init file in the current directory.
22200 @item @xref{info auto-load local-gdbinit}.
22201 @tab Show state of init file in the current directory.
22202 @item @xref{set auto-load libthread-db}.
22203 @tab Control for thread debugging library.
22204 @item @xref{show auto-load libthread-db}.
22205 @tab Show setting of thread debugging library.
22206 @item @xref{info auto-load libthread-db}.
22207 @tab Show state of thread debugging library.
22208 @item @xref{set auto-load safe-path}.
22209 @tab Control directories trusted for automatic loading.
22210 @item @xref{show auto-load safe-path}.
22211 @tab Show directories trusted for automatic loading.
22212 @item @xref{add-auto-load-safe-path}.
22213 @tab Add directory trusted for automatic loading.
22217 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22218 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22219 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
22220 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22221 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22222 @xref{Python Auto-loading}.
22225 @node Init File in the Current Directory
22226 @subsection Automatically loading init file in the current directory
22227 @cindex auto-loading init file in the current directory
22229 By default, @value{GDBN} reads and executes the canned sequences of commands
22230 from init file (if any) in the current working directory,
22231 see @ref{Init File in the Current Directory during Startup}.
22233 Note that loading of this local @file{.gdbinit} file also requires accordingly
22234 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22237 @anchor{set auto-load local-gdbinit}
22238 @kindex set auto-load local-gdbinit
22239 @item set auto-load local-gdbinit [on|off]
22240 Enable or disable the auto-loading of canned sequences of commands
22241 (@pxref{Sequences}) found in init file in the current directory.
22243 @anchor{show auto-load local-gdbinit}
22244 @kindex show auto-load local-gdbinit
22245 @item show auto-load local-gdbinit
22246 Show whether auto-loading of canned sequences of commands from init file in the
22247 current directory is enabled or disabled.
22249 @anchor{info auto-load local-gdbinit}
22250 @kindex info auto-load local-gdbinit
22251 @item info auto-load local-gdbinit
22252 Print whether canned sequences of commands from init file in the
22253 current directory have been auto-loaded.
22256 @node libthread_db.so.1 file
22257 @subsection Automatically loading thread debugging library
22258 @cindex auto-loading libthread_db.so.1
22260 This feature is currently present only on @sc{gnu}/Linux native hosts.
22262 @value{GDBN} reads in some cases thread debugging library from places specific
22263 to the inferior (@pxref{set libthread-db-search-path}).
22265 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22266 without checking this @samp{set auto-load libthread-db} switch as system
22267 libraries have to be trusted in general. In all other cases of
22268 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22269 auto-load libthread-db} is enabled before trying to open such thread debugging
22272 Note that loading of this debugging library also requires accordingly configured
22273 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22276 @anchor{set auto-load libthread-db}
22277 @kindex set auto-load libthread-db
22278 @item set auto-load libthread-db [on|off]
22279 Enable or disable the auto-loading of inferior specific thread debugging library.
22281 @anchor{show auto-load libthread-db}
22282 @kindex show auto-load libthread-db
22283 @item show auto-load libthread-db
22284 Show whether auto-loading of inferior specific thread debugging library is
22285 enabled or disabled.
22287 @anchor{info auto-load libthread-db}
22288 @kindex info auto-load libthread-db
22289 @item info auto-load libthread-db
22290 Print the list of all loaded inferior specific thread debugging libraries and
22291 for each such library print list of inferior @var{pid}s using it.
22294 @node objfile-gdb.gdb file
22295 @subsection The @file{@var{objfile}-gdb.gdb} file
22296 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
22298 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
22299 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
22300 auto-load gdb-scripts} is set to @samp{on}.
22302 Note that loading of this script file also requires accordingly configured
22303 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22305 For more background refer to the similar Python scripts auto-loading
22306 description (@pxref{objfile-gdb.py file}).
22309 @anchor{set auto-load gdb-scripts}
22310 @kindex set auto-load gdb-scripts
22311 @item set auto-load gdb-scripts [on|off]
22312 Enable or disable the auto-loading of canned sequences of commands scripts.
22314 @anchor{show auto-load gdb-scripts}
22315 @kindex show auto-load gdb-scripts
22316 @item show auto-load gdb-scripts
22317 Show whether auto-loading of canned sequences of commands scripts is enabled or
22320 @anchor{info auto-load gdb-scripts}
22321 @kindex info auto-load gdb-scripts
22322 @cindex print list of auto-loaded canned sequences of commands scripts
22323 @item info auto-load gdb-scripts [@var{regexp}]
22324 Print the list of all canned sequences of commands scripts that @value{GDBN}
22328 If @var{regexp} is supplied only canned sequences of commands scripts with
22329 matching names are printed.
22331 @node Auto-loading safe path
22332 @subsection Security restriction for auto-loading
22333 @cindex auto-loading safe-path
22335 As the files of inferior can come from untrusted source (such as submitted by
22336 an application user) @value{GDBN} does not always load any files automatically.
22337 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22338 directories trusted for loading files not explicitly requested by user.
22339 Each directory can also be a shell wildcard pattern.
22341 If the path is not set properly you will see a warning and the file will not
22346 Reading symbols from /home/user/gdb/gdb...done.
22347 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22348 declined by your `auto-load safe-path' set
22349 to "$debugdir:$datadir/auto-load".
22350 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22351 declined by your `auto-load safe-path' set
22352 to "$debugdir:$datadir/auto-load".
22356 To instruct @value{GDBN} to go ahead and use the init files anyway,
22357 invoke @value{GDBN} like this:
22360 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22363 The list of trusted directories is controlled by the following commands:
22366 @anchor{set auto-load safe-path}
22367 @kindex set auto-load safe-path
22368 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22369 Set the list of directories (and their subdirectories) trusted for automatic
22370 loading and execution of scripts. You can also enter a specific trusted file.
22371 Each directory can also be a shell wildcard pattern; wildcards do not match
22372 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22373 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22374 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22375 its default value as specified during @value{GDBN} compilation.
22377 The list of directories uses path separator (@samp{:} on GNU and Unix
22378 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22379 to the @env{PATH} environment variable.
22381 @anchor{show auto-load safe-path}
22382 @kindex show auto-load safe-path
22383 @item show auto-load safe-path
22384 Show the list of directories trusted for automatic loading and execution of
22387 @anchor{add-auto-load-safe-path}
22388 @kindex add-auto-load-safe-path
22389 @item add-auto-load-safe-path
22390 Add an entry (or list of entries) the list of directories trusted for automatic
22391 loading and execution of scripts. Multiple entries may be delimited by the
22392 host platform path separator in use.
22395 This variable defaults to what @code{--with-auto-load-dir} has been configured
22396 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22397 substitution applies the same as for @ref{set auto-load scripts-directory}.
22398 The default @code{set auto-load safe-path} value can be also overriden by
22399 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22401 Setting this variable to @file{/} disables this security protection,
22402 corresponding @value{GDBN} configuration option is
22403 @option{--without-auto-load-safe-path}.
22404 This variable is supposed to be set to the system directories writable by the
22405 system superuser only. Users can add their source directories in init files in
22406 their home directories (@pxref{Home Directory Init File}). See also deprecated
22407 init file in the current directory
22408 (@pxref{Init File in the Current Directory during Startup}).
22410 To force @value{GDBN} to load the files it declined to load in the previous
22411 example, you could use one of the following ways:
22414 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22415 Specify this trusted directory (or a file) as additional component of the list.
22416 You have to specify also any existing directories displayed by
22417 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22419 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22420 Specify this directory as in the previous case but just for a single
22421 @value{GDBN} session.
22423 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22424 Disable auto-loading safety for a single @value{GDBN} session.
22425 This assumes all the files you debug during this @value{GDBN} session will come
22426 from trusted sources.
22428 @item @kbd{./configure --without-auto-load-safe-path}
22429 During compilation of @value{GDBN} you may disable any auto-loading safety.
22430 This assumes all the files you will ever debug with this @value{GDBN} come from
22434 On the other hand you can also explicitly forbid automatic files loading which
22435 also suppresses any such warning messages:
22438 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22439 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22441 @item @file{~/.gdbinit}: @samp{set auto-load no}
22442 Disable auto-loading globally for the user
22443 (@pxref{Home Directory Init File}). While it is improbable, you could also
22444 use system init file instead (@pxref{System-wide configuration}).
22447 This setting applies to the file names as entered by user. If no entry matches
22448 @value{GDBN} tries as a last resort to also resolve all the file names into
22449 their canonical form (typically resolving symbolic links) and compare the
22450 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22451 own before starting the comparison so a canonical form of directories is
22452 recommended to be entered.
22454 @node Auto-loading verbose mode
22455 @subsection Displaying files tried for auto-load
22456 @cindex auto-loading verbose mode
22458 For better visibility of all the file locations where you can place scripts to
22459 be auto-loaded with inferior --- or to protect yourself against accidental
22460 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22461 all the files attempted to be loaded. Both existing and non-existing files may
22464 For example the list of directories from which it is safe to auto-load files
22465 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22466 may not be too obvious while setting it up.
22469 (gdb) set debug auto-load on
22470 (gdb) file ~/src/t/true
22471 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22472 for objfile "/tmp/true".
22473 auto-load: Updating directories of "/usr:/opt".
22474 auto-load: Using directory "/usr".
22475 auto-load: Using directory "/opt".
22476 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22477 by your `auto-load safe-path' set to "/usr:/opt".
22481 @anchor{set debug auto-load}
22482 @kindex set debug auto-load
22483 @item set debug auto-load [on|off]
22484 Set whether to print the filenames attempted to be auto-loaded.
22486 @anchor{show debug auto-load}
22487 @kindex show debug auto-load
22488 @item show debug auto-load
22489 Show whether printing of the filenames attempted to be auto-loaded is turned
22493 @node Messages/Warnings
22494 @section Optional Warnings and Messages
22496 @cindex verbose operation
22497 @cindex optional warnings
22498 By default, @value{GDBN} is silent about its inner workings. If you are
22499 running on a slow machine, you may want to use the @code{set verbose}
22500 command. This makes @value{GDBN} tell you when it does a lengthy
22501 internal operation, so you will not think it has crashed.
22503 Currently, the messages controlled by @code{set verbose} are those
22504 which announce that the symbol table for a source file is being read;
22505 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22508 @kindex set verbose
22509 @item set verbose on
22510 Enables @value{GDBN} output of certain informational messages.
22512 @item set verbose off
22513 Disables @value{GDBN} output of certain informational messages.
22515 @kindex show verbose
22517 Displays whether @code{set verbose} is on or off.
22520 By default, if @value{GDBN} encounters bugs in the symbol table of an
22521 object file, it is silent; but if you are debugging a compiler, you may
22522 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22527 @kindex set complaints
22528 @item set complaints @var{limit}
22529 Permits @value{GDBN} to output @var{limit} complaints about each type of
22530 unusual symbols before becoming silent about the problem. Set
22531 @var{limit} to zero to suppress all complaints; set it to a large number
22532 to prevent complaints from being suppressed.
22534 @kindex show complaints
22535 @item show complaints
22536 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22540 @anchor{confirmation requests}
22541 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22542 lot of stupid questions to confirm certain commands. For example, if
22543 you try to run a program which is already running:
22547 The program being debugged has been started already.
22548 Start it from the beginning? (y or n)
22551 If you are willing to unflinchingly face the consequences of your own
22552 commands, you can disable this ``feature'':
22556 @kindex set confirm
22558 @cindex confirmation
22559 @cindex stupid questions
22560 @item set confirm off
22561 Disables confirmation requests. Note that running @value{GDBN} with
22562 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22563 automatically disables confirmation requests.
22565 @item set confirm on
22566 Enables confirmation requests (the default).
22568 @kindex show confirm
22570 Displays state of confirmation requests.
22574 @cindex command tracing
22575 If you need to debug user-defined commands or sourced files you may find it
22576 useful to enable @dfn{command tracing}. In this mode each command will be
22577 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22578 quantity denoting the call depth of each command.
22581 @kindex set trace-commands
22582 @cindex command scripts, debugging
22583 @item set trace-commands on
22584 Enable command tracing.
22585 @item set trace-commands off
22586 Disable command tracing.
22587 @item show trace-commands
22588 Display the current state of command tracing.
22591 @node Debugging Output
22592 @section Optional Messages about Internal Happenings
22593 @cindex optional debugging messages
22595 @value{GDBN} has commands that enable optional debugging messages from
22596 various @value{GDBN} subsystems; normally these commands are of
22597 interest to @value{GDBN} maintainers, or when reporting a bug. This
22598 section documents those commands.
22601 @kindex set exec-done-display
22602 @item set exec-done-display
22603 Turns on or off the notification of asynchronous commands'
22604 completion. When on, @value{GDBN} will print a message when an
22605 asynchronous command finishes its execution. The default is off.
22606 @kindex show exec-done-display
22607 @item show exec-done-display
22608 Displays the current setting of asynchronous command completion
22611 @cindex ARM AArch64
22612 @item set debug aarch64
22613 Turns on or off display of debugging messages related to ARM AArch64.
22614 The default is off.
22616 @item show debug aarch64
22617 Displays the current state of displaying debugging messages related to
22619 @cindex gdbarch debugging info
22620 @cindex architecture debugging info
22621 @item set debug arch
22622 Turns on or off display of gdbarch debugging info. The default is off
22623 @item show debug arch
22624 Displays the current state of displaying gdbarch debugging info.
22625 @item set debug aix-solib
22626 @cindex AIX shared library debugging
22627 Control display of debugging messages from the AIX shared library
22628 support module. The default is off.
22629 @item show debug aix-thread
22630 Show the current state of displaying AIX shared library debugging messages.
22631 @item set debug aix-thread
22632 @cindex AIX threads
22633 Display debugging messages about inner workings of the AIX thread
22635 @item show debug aix-thread
22636 Show the current state of AIX thread debugging info display.
22637 @item set debug check-physname
22639 Check the results of the ``physname'' computation. When reading DWARF
22640 debugging information for C@t{++}, @value{GDBN} attempts to compute
22641 each entity's name. @value{GDBN} can do this computation in two
22642 different ways, depending on exactly what information is present.
22643 When enabled, this setting causes @value{GDBN} to compute the names
22644 both ways and display any discrepancies.
22645 @item show debug check-physname
22646 Show the current state of ``physname'' checking.
22647 @item set debug coff-pe-read
22648 @cindex COFF/PE exported symbols
22649 Control display of debugging messages related to reading of COFF/PE
22650 exported symbols. The default is off.
22651 @item show debug coff-pe-read
22652 Displays the current state of displaying debugging messages related to
22653 reading of COFF/PE exported symbols.
22654 @item set debug dwarf2-die
22655 @cindex DWARF2 DIEs
22656 Dump DWARF2 DIEs after they are read in.
22657 The value is the number of nesting levels to print.
22658 A value of zero turns off the display.
22659 @item show debug dwarf2-die
22660 Show the current state of DWARF2 DIE debugging.
22661 @item set debug dwarf2-read
22662 @cindex DWARF2 Reading
22663 Turns on or off display of debugging messages related to reading
22664 DWARF debug info. The default is 0 (off).
22665 A value of 1 provides basic information.
22666 A value greater than 1 provides more verbose information.
22667 @item show debug dwarf2-read
22668 Show the current state of DWARF2 reader debugging.
22669 @item set debug displaced
22670 @cindex displaced stepping debugging info
22671 Turns on or off display of @value{GDBN} debugging info for the
22672 displaced stepping support. The default is off.
22673 @item show debug displaced
22674 Displays the current state of displaying @value{GDBN} debugging info
22675 related to displaced stepping.
22676 @item set debug event
22677 @cindex event debugging info
22678 Turns on or off display of @value{GDBN} event debugging info. The
22680 @item show debug event
22681 Displays the current state of displaying @value{GDBN} event debugging
22683 @item set debug expression
22684 @cindex expression debugging info
22685 Turns on or off display of debugging info about @value{GDBN}
22686 expression parsing. The default is off.
22687 @item show debug expression
22688 Displays the current state of displaying debugging info about
22689 @value{GDBN} expression parsing.
22690 @item set debug frame
22691 @cindex frame debugging info
22692 Turns on or off display of @value{GDBN} frame debugging info. The
22694 @item show debug frame
22695 Displays the current state of displaying @value{GDBN} frame debugging
22697 @item set debug gnu-nat
22698 @cindex @sc{gnu}/Hurd debug messages
22699 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22700 @item show debug gnu-nat
22701 Show the current state of @sc{gnu}/Hurd debugging messages.
22702 @item set debug infrun
22703 @cindex inferior debugging info
22704 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22705 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22706 for implementing operations such as single-stepping the inferior.
22707 @item show debug infrun
22708 Displays the current state of @value{GDBN} inferior debugging.
22709 @item set debug jit
22710 @cindex just-in-time compilation, debugging messages
22711 Turns on or off debugging messages from JIT debug support.
22712 @item show debug jit
22713 Displays the current state of @value{GDBN} JIT debugging.
22714 @item set debug lin-lwp
22715 @cindex @sc{gnu}/Linux LWP debug messages
22716 @cindex Linux lightweight processes
22717 Turns on or off debugging messages from the Linux LWP debug support.
22718 @item show debug lin-lwp
22719 Show the current state of Linux LWP debugging messages.
22720 @item set debug mach-o
22721 @cindex Mach-O symbols processing
22722 Control display of debugging messages related to Mach-O symbols
22723 processing. The default is off.
22724 @item show debug mach-o
22725 Displays the current state of displaying debugging messages related to
22726 reading of COFF/PE exported symbols.
22727 @item set debug notification
22728 @cindex remote async notification debugging info
22729 Turns on or off debugging messages about remote async notification.
22730 The default is off.
22731 @item show debug notification
22732 Displays the current state of remote async notification debugging messages.
22733 @item set debug observer
22734 @cindex observer debugging info
22735 Turns on or off display of @value{GDBN} observer debugging. This
22736 includes info such as the notification of observable events.
22737 @item show debug observer
22738 Displays the current state of observer debugging.
22739 @item set debug overload
22740 @cindex C@t{++} overload debugging info
22741 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22742 info. This includes info such as ranking of functions, etc. The default
22744 @item show debug overload
22745 Displays the current state of displaying @value{GDBN} C@t{++} overload
22747 @cindex expression parser, debugging info
22748 @cindex debug expression parser
22749 @item set debug parser
22750 Turns on or off the display of expression parser debugging output.
22751 Internally, this sets the @code{yydebug} variable in the expression
22752 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22753 details. The default is off.
22754 @item show debug parser
22755 Show the current state of expression parser debugging.
22756 @cindex packets, reporting on stdout
22757 @cindex serial connections, debugging
22758 @cindex debug remote protocol
22759 @cindex remote protocol debugging
22760 @cindex display remote packets
22761 @item set debug remote
22762 Turns on or off display of reports on all packets sent back and forth across
22763 the serial line to the remote machine. The info is printed on the
22764 @value{GDBN} standard output stream. The default is off.
22765 @item show debug remote
22766 Displays the state of display of remote packets.
22767 @item set debug serial
22768 Turns on or off display of @value{GDBN} serial debugging info. The
22770 @item show debug serial
22771 Displays the current state of displaying @value{GDBN} serial debugging
22773 @item set debug solib-frv
22774 @cindex FR-V shared-library debugging
22775 Turns on or off debugging messages for FR-V shared-library code.
22776 @item show debug solib-frv
22777 Display the current state of FR-V shared-library code debugging
22779 @item set debug symfile
22780 @cindex symbol file functions
22781 Turns on or off display of debugging messages related to symbol file functions.
22782 The default is off. @xref{Files}.
22783 @item show debug symfile
22784 Show the current state of symbol file debugging messages.
22785 @item set debug symtab-create
22786 @cindex symbol table creation
22787 Turns on or off display of debugging messages related to symbol table creation.
22788 The default is 0 (off).
22789 A value of 1 provides basic information.
22790 A value greater than 1 provides more verbose information.
22791 @item show debug symtab-create
22792 Show the current state of symbol table creation debugging.
22793 @item set debug target
22794 @cindex target debugging info
22795 Turns on or off display of @value{GDBN} target debugging info. This info
22796 includes what is going on at the target level of GDB, as it happens. The
22797 default is 0. Set it to 1 to track events, and to 2 to also track the
22798 value of large memory transfers. Changes to this flag do not take effect
22799 until the next time you connect to a target or use the @code{run} command.
22800 @item show debug target
22801 Displays the current state of displaying @value{GDBN} target debugging
22803 @item set debug timestamp
22804 @cindex timestampping debugging info
22805 Turns on or off display of timestamps with @value{GDBN} debugging info.
22806 When enabled, seconds and microseconds are displayed before each debugging
22808 @item show debug timestamp
22809 Displays the current state of displaying timestamps with @value{GDBN}
22811 @item set debugvarobj
22812 @cindex variable object debugging info
22813 Turns on or off display of @value{GDBN} variable object debugging
22814 info. The default is off.
22815 @item show debugvarobj
22816 Displays the current state of displaying @value{GDBN} variable object
22818 @item set debug xml
22819 @cindex XML parser debugging
22820 Turns on or off debugging messages for built-in XML parsers.
22821 @item show debug xml
22822 Displays the current state of XML debugging messages.
22825 @node Other Misc Settings
22826 @section Other Miscellaneous Settings
22827 @cindex miscellaneous settings
22830 @kindex set interactive-mode
22831 @item set interactive-mode
22832 If @code{on}, forces @value{GDBN} to assume that GDB was started
22833 in a terminal. In practice, this means that @value{GDBN} should wait
22834 for the user to answer queries generated by commands entered at
22835 the command prompt. If @code{off}, forces @value{GDBN} to operate
22836 in the opposite mode, and it uses the default answers to all queries.
22837 If @code{auto} (the default), @value{GDBN} tries to determine whether
22838 its standard input is a terminal, and works in interactive-mode if it
22839 is, non-interactively otherwise.
22841 In the vast majority of cases, the debugger should be able to guess
22842 correctly which mode should be used. But this setting can be useful
22843 in certain specific cases, such as running a MinGW @value{GDBN}
22844 inside a cygwin window.
22846 @kindex show interactive-mode
22847 @item show interactive-mode
22848 Displays whether the debugger is operating in interactive mode or not.
22851 @node Extending GDB
22852 @chapter Extending @value{GDBN}
22853 @cindex extending GDB
22855 @value{GDBN} provides three mechanisms for extension. The first is based
22856 on composition of @value{GDBN} commands, the second is based on the
22857 Python scripting language, and the third is for defining new aliases of
22860 To facilitate the use of the first two extensions, @value{GDBN} is capable
22861 of evaluating the contents of a file. When doing so, @value{GDBN}
22862 can recognize which scripting language is being used by looking at
22863 the filename extension. Files with an unrecognized filename extension
22864 are always treated as a @value{GDBN} Command Files.
22865 @xref{Command Files,, Command files}.
22867 You can control how @value{GDBN} evaluates these files with the following
22871 @kindex set script-extension
22872 @kindex show script-extension
22873 @item set script-extension off
22874 All scripts are always evaluated as @value{GDBN} Command Files.
22876 @item set script-extension soft
22877 The debugger determines the scripting language based on filename
22878 extension. If this scripting language is supported, @value{GDBN}
22879 evaluates the script using that language. Otherwise, it evaluates
22880 the file as a @value{GDBN} Command File.
22882 @item set script-extension strict
22883 The debugger determines the scripting language based on filename
22884 extension, and evaluates the script using that language. If the
22885 language is not supported, then the evaluation fails.
22887 @item show script-extension
22888 Display the current value of the @code{script-extension} option.
22893 * Sequences:: Canned Sequences of Commands
22894 * Python:: Scripting @value{GDBN} using Python
22895 * Aliases:: Creating new spellings of existing commands
22899 @section Canned Sequences of Commands
22901 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22902 Command Lists}), @value{GDBN} provides two ways to store sequences of
22903 commands for execution as a unit: user-defined commands and command
22907 * Define:: How to define your own commands
22908 * Hooks:: Hooks for user-defined commands
22909 * Command Files:: How to write scripts of commands to be stored in a file
22910 * Output:: Commands for controlled output
22914 @subsection User-defined Commands
22916 @cindex user-defined command
22917 @cindex arguments, to user-defined commands
22918 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22919 which you assign a new name as a command. This is done with the
22920 @code{define} command. User commands may accept up to 10 arguments
22921 separated by whitespace. Arguments are accessed within the user command
22922 via @code{$arg0@dots{}$arg9}. A trivial example:
22926 print $arg0 + $arg1 + $arg2
22931 To execute the command use:
22938 This defines the command @code{adder}, which prints the sum of
22939 its three arguments. Note the arguments are text substitutions, so they may
22940 reference variables, use complex expressions, or even perform inferior
22943 @cindex argument count in user-defined commands
22944 @cindex how many arguments (user-defined commands)
22945 In addition, @code{$argc} may be used to find out how many arguments have
22946 been passed. This expands to a number in the range 0@dots{}10.
22951 print $arg0 + $arg1
22954 print $arg0 + $arg1 + $arg2
22962 @item define @var{commandname}
22963 Define a command named @var{commandname}. If there is already a command
22964 by that name, you are asked to confirm that you want to redefine it.
22965 @var{commandname} may be a bare command name consisting of letters,
22966 numbers, dashes, and underscores. It may also start with any predefined
22967 prefix command. For example, @samp{define target my-target} creates
22968 a user-defined @samp{target my-target} command.
22970 The definition of the command is made up of other @value{GDBN} command lines,
22971 which are given following the @code{define} command. The end of these
22972 commands is marked by a line containing @code{end}.
22975 @kindex end@r{ (user-defined commands)}
22976 @item document @var{commandname}
22977 Document the user-defined command @var{commandname}, so that it can be
22978 accessed by @code{help}. The command @var{commandname} must already be
22979 defined. This command reads lines of documentation just as @code{define}
22980 reads the lines of the command definition, ending with @code{end}.
22981 After the @code{document} command is finished, @code{help} on command
22982 @var{commandname} displays the documentation you have written.
22984 You may use the @code{document} command again to change the
22985 documentation of a command. Redefining the command with @code{define}
22986 does not change the documentation.
22988 @kindex dont-repeat
22989 @cindex don't repeat command
22991 Used inside a user-defined command, this tells @value{GDBN} that this
22992 command should not be repeated when the user hits @key{RET}
22993 (@pxref{Command Syntax, repeat last command}).
22995 @kindex help user-defined
22996 @item help user-defined
22997 List all user-defined commands and all python commands defined in class
22998 COMAND_USER. The first line of the documentation or docstring is
23003 @itemx show user @var{commandname}
23004 Display the @value{GDBN} commands used to define @var{commandname} (but
23005 not its documentation). If no @var{commandname} is given, display the
23006 definitions for all user-defined commands.
23007 This does not work for user-defined python commands.
23009 @cindex infinite recursion in user-defined commands
23010 @kindex show max-user-call-depth
23011 @kindex set max-user-call-depth
23012 @item show max-user-call-depth
23013 @itemx set max-user-call-depth
23014 The value of @code{max-user-call-depth} controls how many recursion
23015 levels are allowed in user-defined commands before @value{GDBN} suspects an
23016 infinite recursion and aborts the command.
23017 This does not apply to user-defined python commands.
23020 In addition to the above commands, user-defined commands frequently
23021 use control flow commands, described in @ref{Command Files}.
23023 When user-defined commands are executed, the
23024 commands of the definition are not printed. An error in any command
23025 stops execution of the user-defined command.
23027 If used interactively, commands that would ask for confirmation proceed
23028 without asking when used inside a user-defined command. Many @value{GDBN}
23029 commands that normally print messages to say what they are doing omit the
23030 messages when used in a user-defined command.
23033 @subsection User-defined Command Hooks
23034 @cindex command hooks
23035 @cindex hooks, for commands
23036 @cindex hooks, pre-command
23039 You may define @dfn{hooks}, which are a special kind of user-defined
23040 command. Whenever you run the command @samp{foo}, if the user-defined
23041 command @samp{hook-foo} exists, it is executed (with no arguments)
23042 before that command.
23044 @cindex hooks, post-command
23046 A hook may also be defined which is run after the command you executed.
23047 Whenever you run the command @samp{foo}, if the user-defined command
23048 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23049 that command. Post-execution hooks may exist simultaneously with
23050 pre-execution hooks, for the same command.
23052 It is valid for a hook to call the command which it hooks. If this
23053 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23055 @c It would be nice if hookpost could be passed a parameter indicating
23056 @c if the command it hooks executed properly or not. FIXME!
23058 @kindex stop@r{, a pseudo-command}
23059 In addition, a pseudo-command, @samp{stop} exists. Defining
23060 (@samp{hook-stop}) makes the associated commands execute every time
23061 execution stops in your program: before breakpoint commands are run,
23062 displays are printed, or the stack frame is printed.
23064 For example, to ignore @code{SIGALRM} signals while
23065 single-stepping, but treat them normally during normal execution,
23070 handle SIGALRM nopass
23074 handle SIGALRM pass
23077 define hook-continue
23078 handle SIGALRM pass
23082 As a further example, to hook at the beginning and end of the @code{echo}
23083 command, and to add extra text to the beginning and end of the message,
23091 define hookpost-echo
23095 (@value{GDBP}) echo Hello World
23096 <<<---Hello World--->>>
23101 You can define a hook for any single-word command in @value{GDBN}, but
23102 not for command aliases; you should define a hook for the basic command
23103 name, e.g.@: @code{backtrace} rather than @code{bt}.
23104 @c FIXME! So how does Joe User discover whether a command is an alias
23106 You can hook a multi-word command by adding @code{hook-} or
23107 @code{hookpost-} to the last word of the command, e.g.@:
23108 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23110 If an error occurs during the execution of your hook, execution of
23111 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23112 (before the command that you actually typed had a chance to run).
23114 If you try to define a hook which does not match any known command, you
23115 get a warning from the @code{define} command.
23117 @node Command Files
23118 @subsection Command Files
23120 @cindex command files
23121 @cindex scripting commands
23122 A command file for @value{GDBN} is a text file made of lines that are
23123 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23124 also be included. An empty line in a command file does nothing; it
23125 does not mean to repeat the last command, as it would from the
23128 You can request the execution of a command file with the @code{source}
23129 command. Note that the @code{source} command is also used to evaluate
23130 scripts that are not Command Files. The exact behavior can be configured
23131 using the @code{script-extension} setting.
23132 @xref{Extending GDB,, Extending GDB}.
23136 @cindex execute commands from a file
23137 @item source [-s] [-v] @var{filename}
23138 Execute the command file @var{filename}.
23141 The lines in a command file are generally executed sequentially,
23142 unless the order of execution is changed by one of the
23143 @emph{flow-control commands} described below. The commands are not
23144 printed as they are executed. An error in any command terminates
23145 execution of the command file and control is returned to the console.
23147 @value{GDBN} first searches for @var{filename} in the current directory.
23148 If the file is not found there, and @var{filename} does not specify a
23149 directory, then @value{GDBN} also looks for the file on the source search path
23150 (specified with the @samp{directory} command);
23151 except that @file{$cdir} is not searched because the compilation directory
23152 is not relevant to scripts.
23154 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23155 on the search path even if @var{filename} specifies a directory.
23156 The search is done by appending @var{filename} to each element of the
23157 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23158 and the search path contains @file{/home/user} then @value{GDBN} will
23159 look for the script @file{/home/user/mylib/myscript}.
23160 The search is also done if @var{filename} is an absolute path.
23161 For example, if @var{filename} is @file{/tmp/myscript} and
23162 the search path contains @file{/home/user} then @value{GDBN} will
23163 look for the script @file{/home/user/tmp/myscript}.
23164 For DOS-like systems, if @var{filename} contains a drive specification,
23165 it is stripped before concatenation. For example, if @var{filename} is
23166 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23167 will look for the script @file{c:/tmp/myscript}.
23169 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23170 each command as it is executed. The option must be given before
23171 @var{filename}, and is interpreted as part of the filename anywhere else.
23173 Commands that would ask for confirmation if used interactively proceed
23174 without asking when used in a command file. Many @value{GDBN} commands that
23175 normally print messages to say what they are doing omit the messages
23176 when called from command files.
23178 @value{GDBN} also accepts command input from standard input. In this
23179 mode, normal output goes to standard output and error output goes to
23180 standard error. Errors in a command file supplied on standard input do
23181 not terminate execution of the command file---execution continues with
23185 gdb < cmds > log 2>&1
23188 (The syntax above will vary depending on the shell used.) This example
23189 will execute commands from the file @file{cmds}. All output and errors
23190 would be directed to @file{log}.
23192 Since commands stored on command files tend to be more general than
23193 commands typed interactively, they frequently need to deal with
23194 complicated situations, such as different or unexpected values of
23195 variables and symbols, changes in how the program being debugged is
23196 built, etc. @value{GDBN} provides a set of flow-control commands to
23197 deal with these complexities. Using these commands, you can write
23198 complex scripts that loop over data structures, execute commands
23199 conditionally, etc.
23206 This command allows to include in your script conditionally executed
23207 commands. The @code{if} command takes a single argument, which is an
23208 expression to evaluate. It is followed by a series of commands that
23209 are executed only if the expression is true (its value is nonzero).
23210 There can then optionally be an @code{else} line, followed by a series
23211 of commands that are only executed if the expression was false. The
23212 end of the list is marked by a line containing @code{end}.
23216 This command allows to write loops. Its syntax is similar to
23217 @code{if}: the command takes a single argument, which is an expression
23218 to evaluate, and must be followed by the commands to execute, one per
23219 line, terminated by an @code{end}. These commands are called the
23220 @dfn{body} of the loop. The commands in the body of @code{while} are
23221 executed repeatedly as long as the expression evaluates to true.
23225 This command exits the @code{while} loop in whose body it is included.
23226 Execution of the script continues after that @code{while}s @code{end}
23229 @kindex loop_continue
23230 @item loop_continue
23231 This command skips the execution of the rest of the body of commands
23232 in the @code{while} loop in whose body it is included. Execution
23233 branches to the beginning of the @code{while} loop, where it evaluates
23234 the controlling expression.
23236 @kindex end@r{ (if/else/while commands)}
23238 Terminate the block of commands that are the body of @code{if},
23239 @code{else}, or @code{while} flow-control commands.
23244 @subsection Commands for Controlled Output
23246 During the execution of a command file or a user-defined command, normal
23247 @value{GDBN} output is suppressed; the only output that appears is what is
23248 explicitly printed by the commands in the definition. This section
23249 describes three commands useful for generating exactly the output you
23254 @item echo @var{text}
23255 @c I do not consider backslash-space a standard C escape sequence
23256 @c because it is not in ANSI.
23257 Print @var{text}. Nonprinting characters can be included in
23258 @var{text} using C escape sequences, such as @samp{\n} to print a
23259 newline. @strong{No newline is printed unless you specify one.}
23260 In addition to the standard C escape sequences, a backslash followed
23261 by a space stands for a space. This is useful for displaying a
23262 string with spaces at the beginning or the end, since leading and
23263 trailing spaces are otherwise trimmed from all arguments.
23264 To print @samp{@w{ }and foo =@w{ }}, use the command
23265 @samp{echo \@w{ }and foo = \@w{ }}.
23267 A backslash at the end of @var{text} can be used, as in C, to continue
23268 the command onto subsequent lines. For example,
23271 echo This is some text\n\
23272 which is continued\n\
23273 onto several lines.\n
23276 produces the same output as
23279 echo This is some text\n
23280 echo which is continued\n
23281 echo onto several lines.\n
23285 @item output @var{expression}
23286 Print the value of @var{expression} and nothing but that value: no
23287 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23288 value history either. @xref{Expressions, ,Expressions}, for more information
23291 @item output/@var{fmt} @var{expression}
23292 Print the value of @var{expression} in format @var{fmt}. You can use
23293 the same formats as for @code{print}. @xref{Output Formats,,Output
23294 Formats}, for more information.
23297 @item printf @var{template}, @var{expressions}@dots{}
23298 Print the values of one or more @var{expressions} under the control of
23299 the string @var{template}. To print several values, make
23300 @var{expressions} be a comma-separated list of individual expressions,
23301 which may be either numbers or pointers. Their values are printed as
23302 specified by @var{template}, exactly as a C program would do by
23303 executing the code below:
23306 printf (@var{template}, @var{expressions}@dots{});
23309 As in @code{C} @code{printf}, ordinary characters in @var{template}
23310 are printed verbatim, while @dfn{conversion specification} introduced
23311 by the @samp{%} character cause subsequent @var{expressions} to be
23312 evaluated, their values converted and formatted according to type and
23313 style information encoded in the conversion specifications, and then
23316 For example, you can print two values in hex like this:
23319 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23322 @code{printf} supports all the standard @code{C} conversion
23323 specifications, including the flags and modifiers between the @samp{%}
23324 character and the conversion letter, with the following exceptions:
23328 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23331 The modifier @samp{*} is not supported for specifying precision or
23335 The @samp{'} flag (for separation of digits into groups according to
23336 @code{LC_NUMERIC'}) is not supported.
23339 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23343 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23346 The conversion letters @samp{a} and @samp{A} are not supported.
23350 Note that the @samp{ll} type modifier is supported only if the
23351 underlying @code{C} implementation used to build @value{GDBN} supports
23352 the @code{long long int} type, and the @samp{L} type modifier is
23353 supported only if @code{long double} type is available.
23355 As in @code{C}, @code{printf} supports simple backslash-escape
23356 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23357 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23358 single character. Octal and hexadecimal escape sequences are not
23361 Additionally, @code{printf} supports conversion specifications for DFP
23362 (@dfn{Decimal Floating Point}) types using the following length modifiers
23363 together with a floating point specifier.
23368 @samp{H} for printing @code{Decimal32} types.
23371 @samp{D} for printing @code{Decimal64} types.
23374 @samp{DD} for printing @code{Decimal128} types.
23377 If the underlying @code{C} implementation used to build @value{GDBN} has
23378 support for the three length modifiers for DFP types, other modifiers
23379 such as width and precision will also be available for @value{GDBN} to use.
23381 In case there is no such @code{C} support, no additional modifiers will be
23382 available and the value will be printed in the standard way.
23384 Here's an example of printing DFP types using the above conversion letters:
23386 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23390 @item eval @var{template}, @var{expressions}@dots{}
23391 Convert the values of one or more @var{expressions} under the control of
23392 the string @var{template} to a command line, and call it.
23397 @section Scripting @value{GDBN} using Python
23398 @cindex python scripting
23399 @cindex scripting with python
23401 You can script @value{GDBN} using the @uref{http://www.python.org/,
23402 Python programming language}. This feature is available only if
23403 @value{GDBN} was configured using @option{--with-python}.
23405 @cindex python directory
23406 Python scripts used by @value{GDBN} should be installed in
23407 @file{@var{data-directory}/python}, where @var{data-directory} is
23408 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23409 This directory, known as the @dfn{python directory},
23410 is automatically added to the Python Search Path in order to allow
23411 the Python interpreter to locate all scripts installed at this location.
23413 Additionally, @value{GDBN} commands and convenience functions which
23414 are written in Python and are located in the
23415 @file{@var{data-directory}/python/gdb/command} or
23416 @file{@var{data-directory}/python/gdb/function} directories are
23417 automatically imported when @value{GDBN} starts.
23420 * Python Commands:: Accessing Python from @value{GDBN}.
23421 * Python API:: Accessing @value{GDBN} from Python.
23422 * Python Auto-loading:: Automatically loading Python code.
23423 * Python modules:: Python modules provided by @value{GDBN}.
23426 @node Python Commands
23427 @subsection Python Commands
23428 @cindex python commands
23429 @cindex commands to access python
23431 @value{GDBN} provides two commands for accessing the Python interpreter,
23432 and one related setting:
23435 @kindex python-interactive
23437 @item python-interactive @r{[}@var{command}@r{]}
23438 @itemx pi @r{[}@var{command}@r{]}
23439 Without an argument, the @code{python-interactive} command can be used
23440 to start an interactive Python prompt. To return to @value{GDBN},
23441 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23443 Alternatively, a single-line Python command can be given as an
23444 argument and evaluated. If the command is an expression, the result
23445 will be printed; otherwise, nothing will be printed. For example:
23448 (@value{GDBP}) python-interactive 2 + 3
23454 @item python @r{[}@var{command}@r{]}
23455 @itemx py @r{[}@var{command}@r{]}
23456 The @code{python} command can be used to evaluate Python code.
23458 If given an argument, the @code{python} command will evaluate the
23459 argument as a Python command. For example:
23462 (@value{GDBP}) python print 23
23466 If you do not provide an argument to @code{python}, it will act as a
23467 multi-line command, like @code{define}. In this case, the Python
23468 script is made up of subsequent command lines, given after the
23469 @code{python} command. This command list is terminated using a line
23470 containing @code{end}. For example:
23473 (@value{GDBP}) python
23475 End with a line saying just "end".
23481 @kindex set python print-stack
23482 @item set python print-stack
23483 By default, @value{GDBN} will print only the message component of a
23484 Python exception when an error occurs in a Python script. This can be
23485 controlled using @code{set python print-stack}: if @code{full}, then
23486 full Python stack printing is enabled; if @code{none}, then Python stack
23487 and message printing is disabled; if @code{message}, the default, only
23488 the message component of the error is printed.
23491 It is also possible to execute a Python script from the @value{GDBN}
23495 @item source @file{script-name}
23496 The script name must end with @samp{.py} and @value{GDBN} must be configured
23497 to recognize the script language based on filename extension using
23498 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23500 @item python execfile ("script-name")
23501 This method is based on the @code{execfile} Python built-in function,
23502 and thus is always available.
23506 @subsection Python API
23508 @cindex programming in python
23510 You can get quick online help for @value{GDBN}'s Python API by issuing
23511 the command @w{@kbd{python help (gdb)}}.
23513 Functions and methods which have two or more optional arguments allow
23514 them to be specified using keyword syntax. This allows passing some
23515 optional arguments while skipping others. Example:
23516 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23519 * Basic Python:: Basic Python Functions.
23520 * Exception Handling:: How Python exceptions are translated.
23521 * Values From Inferior:: Python representation of values.
23522 * Types In Python:: Python representation of types.
23523 * Pretty Printing API:: Pretty-printing values.
23524 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23525 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23526 * Type Printing API:: Pretty-printing types.
23527 * Frame Filter API:: Filtering Frames.
23528 * Frame Decorator API:: Decorating Frames.
23529 * Writing a Frame Filter:: Writing a Frame Filter.
23530 * Inferiors In Python:: Python representation of inferiors (processes)
23531 * Events In Python:: Listening for events from @value{GDBN}.
23532 * Threads In Python:: Accessing inferior threads from Python.
23533 * Commands In Python:: Implementing new commands in Python.
23534 * Parameters In Python:: Adding new @value{GDBN} parameters.
23535 * Functions In Python:: Writing new convenience functions.
23536 * Progspaces In Python:: Program spaces.
23537 * Objfiles In Python:: Object files.
23538 * Frames In Python:: Accessing inferior stack frames from Python.
23539 * Blocks In Python:: Accessing blocks from Python.
23540 * Symbols In Python:: Python representation of symbols.
23541 * Symbol Tables In Python:: Python representation of symbol tables.
23542 * Line Tables In Python:: Python representation of line tables.
23543 * Breakpoints In Python:: Manipulating breakpoints using Python.
23544 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23546 * Lazy Strings In Python:: Python representation of lazy strings.
23547 * Architectures In Python:: Python representation of architectures.
23551 @subsubsection Basic Python
23553 @cindex python stdout
23554 @cindex python pagination
23555 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23556 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23557 A Python program which outputs to one of these streams may have its
23558 output interrupted by the user (@pxref{Screen Size}). In this
23559 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23561 Some care must be taken when writing Python code to run in
23562 @value{GDBN}. Two things worth noting in particular:
23566 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23567 Python code must not override these, or even change the options using
23568 @code{sigaction}. If your program changes the handling of these
23569 signals, @value{GDBN} will most likely stop working correctly. Note
23570 that it is unfortunately common for GUI toolkits to install a
23571 @code{SIGCHLD} handler.
23574 @value{GDBN} takes care to mark its internal file descriptors as
23575 close-on-exec. However, this cannot be done in a thread-safe way on
23576 all platforms. Your Python programs should be aware of this and
23577 should both create new file descriptors with the close-on-exec flag
23578 set and arrange to close unneeded file descriptors before starting a
23582 @cindex python functions
23583 @cindex python module
23585 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23586 methods and classes added by @value{GDBN} are placed in this module.
23587 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23588 use in all scripts evaluated by the @code{python} command.
23590 @findex gdb.PYTHONDIR
23591 @defvar gdb.PYTHONDIR
23592 A string containing the python directory (@pxref{Python}).
23595 @findex gdb.execute
23596 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23597 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23598 If a GDB exception happens while @var{command} runs, it is
23599 translated as described in @ref{Exception Handling,,Exception Handling}.
23601 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23602 command as having originated from the user invoking it interactively.
23603 It must be a boolean value. If omitted, it defaults to @code{False}.
23605 By default, any output produced by @var{command} is sent to
23606 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23607 @code{True}, then output will be collected by @code{gdb.execute} and
23608 returned as a string. The default is @code{False}, in which case the
23609 return value is @code{None}. If @var{to_string} is @code{True}, the
23610 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23611 and height, and its pagination will be disabled; @pxref{Screen Size}.
23614 @findex gdb.breakpoints
23615 @defun gdb.breakpoints ()
23616 Return a sequence holding all of @value{GDBN}'s breakpoints.
23617 @xref{Breakpoints In Python}, for more information.
23620 @findex gdb.parameter
23621 @defun gdb.parameter (parameter)
23622 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23623 string naming the parameter to look up; @var{parameter} may contain
23624 spaces if the parameter has a multi-part name. For example,
23625 @samp{print object} is a valid parameter name.
23627 If the named parameter does not exist, this function throws a
23628 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23629 parameter's value is converted to a Python value of the appropriate
23630 type, and returned.
23633 @findex gdb.history
23634 @defun gdb.history (number)
23635 Return a value from @value{GDBN}'s value history (@pxref{Value
23636 History}). @var{number} indicates which history element to return.
23637 If @var{number} is negative, then @value{GDBN} will take its absolute value
23638 and count backward from the last element (i.e., the most recent element) to
23639 find the value to return. If @var{number} is zero, then @value{GDBN} will
23640 return the most recent element. If the element specified by @var{number}
23641 doesn't exist in the value history, a @code{gdb.error} exception will be
23644 If no exception is raised, the return value is always an instance of
23645 @code{gdb.Value} (@pxref{Values From Inferior}).
23648 @findex gdb.parse_and_eval
23649 @defun gdb.parse_and_eval (expression)
23650 Parse @var{expression} as an expression in the current language,
23651 evaluate it, and return the result as a @code{gdb.Value}.
23652 @var{expression} must be a string.
23654 This function can be useful when implementing a new command
23655 (@pxref{Commands In Python}), as it provides a way to parse the
23656 command's argument as an expression. It is also useful simply to
23657 compute values, for example, it is the only way to get the value of a
23658 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23661 @findex gdb.find_pc_line
23662 @defun gdb.find_pc_line (pc)
23663 Return the @code{gdb.Symtab_and_line} object corresponding to the
23664 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23665 value of @var{pc} is passed as an argument, then the @code{symtab} and
23666 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23667 will be @code{None} and 0 respectively.
23670 @findex gdb.post_event
23671 @defun gdb.post_event (event)
23672 Put @var{event}, a callable object taking no arguments, into
23673 @value{GDBN}'s internal event queue. This callable will be invoked at
23674 some later point, during @value{GDBN}'s event processing. Events
23675 posted using @code{post_event} will be run in the order in which they
23676 were posted; however, there is no way to know when they will be
23677 processed relative to other events inside @value{GDBN}.
23679 @value{GDBN} is not thread-safe. If your Python program uses multiple
23680 threads, you must be careful to only call @value{GDBN}-specific
23681 functions in the main @value{GDBN} thread. @code{post_event} ensures
23685 (@value{GDBP}) python
23689 > def __init__(self, message):
23690 > self.message = message;
23691 > def __call__(self):
23692 > gdb.write(self.message)
23694 >class MyThread1 (threading.Thread):
23696 > gdb.post_event(Writer("Hello "))
23698 >class MyThread2 (threading.Thread):
23700 > gdb.post_event(Writer("World\n"))
23702 >MyThread1().start()
23703 >MyThread2().start()
23705 (@value{GDBP}) Hello World
23710 @defun gdb.write (string @r{[}, stream{]})
23711 Print a string to @value{GDBN}'s paginated output stream. The
23712 optional @var{stream} determines the stream to print to. The default
23713 stream is @value{GDBN}'s standard output stream. Possible stream
23720 @value{GDBN}'s standard output stream.
23725 @value{GDBN}'s standard error stream.
23730 @value{GDBN}'s log stream (@pxref{Logging Output}).
23733 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23734 call this function and will automatically direct the output to the
23739 @defun gdb.flush ()
23740 Flush the buffer of a @value{GDBN} paginated stream so that the
23741 contents are displayed immediately. @value{GDBN} will flush the
23742 contents of a stream automatically when it encounters a newline in the
23743 buffer. The optional @var{stream} determines the stream to flush. The
23744 default stream is @value{GDBN}'s standard output stream. Possible
23751 @value{GDBN}'s standard output stream.
23756 @value{GDBN}'s standard error stream.
23761 @value{GDBN}'s log stream (@pxref{Logging Output}).
23765 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23766 call this function for the relevant stream.
23769 @findex gdb.target_charset
23770 @defun gdb.target_charset ()
23771 Return the name of the current target character set (@pxref{Character
23772 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23773 that @samp{auto} is never returned.
23776 @findex gdb.target_wide_charset
23777 @defun gdb.target_wide_charset ()
23778 Return the name of the current target wide character set
23779 (@pxref{Character Sets}). This differs from
23780 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23784 @findex gdb.solib_name
23785 @defun gdb.solib_name (address)
23786 Return the name of the shared library holding the given @var{address}
23787 as a string, or @code{None}.
23790 @findex gdb.decode_line
23791 @defun gdb.decode_line @r{[}expression@r{]}
23792 Return locations of the line specified by @var{expression}, or of the
23793 current line if no argument was given. This function returns a Python
23794 tuple containing two elements. The first element contains a string
23795 holding any unparsed section of @var{expression} (or @code{None} if
23796 the expression has been fully parsed). The second element contains
23797 either @code{None} or another tuple that contains all the locations
23798 that match the expression represented as @code{gdb.Symtab_and_line}
23799 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23800 provided, it is decoded the way that @value{GDBN}'s inbuilt
23801 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23804 @defun gdb.prompt_hook (current_prompt)
23805 @anchor{prompt_hook}
23807 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23808 assigned to this operation before a prompt is displayed by
23811 The parameter @code{current_prompt} contains the current @value{GDBN}
23812 prompt. This method must return a Python string, or @code{None}. If
23813 a string is returned, the @value{GDBN} prompt will be set to that
23814 string. If @code{None} is returned, @value{GDBN} will continue to use
23815 the current prompt.
23817 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23818 such as those used by readline for command input, and annotation
23819 related prompts are prohibited from being changed.
23822 @node Exception Handling
23823 @subsubsection Exception Handling
23824 @cindex python exceptions
23825 @cindex exceptions, python
23827 When executing the @code{python} command, Python exceptions
23828 uncaught within the Python code are translated to calls to
23829 @value{GDBN} error-reporting mechanism. If the command that called
23830 @code{python} does not handle the error, @value{GDBN} will
23831 terminate it and print an error message containing the Python
23832 exception name, the associated value, and the Python call stack
23833 backtrace at the point where the exception was raised. Example:
23836 (@value{GDBP}) python print foo
23837 Traceback (most recent call last):
23838 File "<string>", line 1, in <module>
23839 NameError: name 'foo' is not defined
23842 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23843 Python code are converted to Python exceptions. The type of the
23844 Python exception depends on the error.
23848 This is the base class for most exceptions generated by @value{GDBN}.
23849 It is derived from @code{RuntimeError}, for compatibility with earlier
23850 versions of @value{GDBN}.
23852 If an error occurring in @value{GDBN} does not fit into some more
23853 specific category, then the generated exception will have this type.
23855 @item gdb.MemoryError
23856 This is a subclass of @code{gdb.error} which is thrown when an
23857 operation tried to access invalid memory in the inferior.
23859 @item KeyboardInterrupt
23860 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23861 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23864 In all cases, your exception handler will see the @value{GDBN} error
23865 message as its value and the Python call stack backtrace at the Python
23866 statement closest to where the @value{GDBN} error occured as the
23869 @findex gdb.GdbError
23870 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23871 it is useful to be able to throw an exception that doesn't cause a
23872 traceback to be printed. For example, the user may have invoked the
23873 command incorrectly. Use the @code{gdb.GdbError} exception
23874 to handle this case. Example:
23878 >class HelloWorld (gdb.Command):
23879 > """Greet the whole world."""
23880 > def __init__ (self):
23881 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23882 > def invoke (self, args, from_tty):
23883 > argv = gdb.string_to_argv (args)
23884 > if len (argv) != 0:
23885 > raise gdb.GdbError ("hello-world takes no arguments")
23886 > print "Hello, World!"
23889 (gdb) hello-world 42
23890 hello-world takes no arguments
23893 @node Values From Inferior
23894 @subsubsection Values From Inferior
23895 @cindex values from inferior, with Python
23896 @cindex python, working with values from inferior
23898 @cindex @code{gdb.Value}
23899 @value{GDBN} provides values it obtains from the inferior program in
23900 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23901 for its internal bookkeeping of the inferior's values, and for
23902 fetching values when necessary.
23904 Inferior values that are simple scalars can be used directly in
23905 Python expressions that are valid for the value's data type. Here's
23906 an example for an integer or floating-point value @code{some_val}:
23913 As result of this, @code{bar} will also be a @code{gdb.Value} object
23914 whose values are of the same type as those of @code{some_val}.
23916 Inferior values that are structures or instances of some class can
23917 be accessed using the Python @dfn{dictionary syntax}. For example, if
23918 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23919 can access its @code{foo} element with:
23922 bar = some_val['foo']
23925 Again, @code{bar} will also be a @code{gdb.Value} object.
23927 A @code{gdb.Value} that represents a function can be executed via
23928 inferior function call. Any arguments provided to the call must match
23929 the function's prototype, and must be provided in the order specified
23932 For example, @code{some_val} is a @code{gdb.Value} instance
23933 representing a function that takes two integers as arguments. To
23934 execute this function, call it like so:
23937 result = some_val (10,20)
23940 Any values returned from a function call will be stored as a
23943 The following attributes are provided:
23945 @defvar Value.address
23946 If this object is addressable, this read-only attribute holds a
23947 @code{gdb.Value} object representing the address. Otherwise,
23948 this attribute holds @code{None}.
23951 @cindex optimized out value in Python
23952 @defvar Value.is_optimized_out
23953 This read-only boolean attribute is true if the compiler optimized out
23954 this value, thus it is not available for fetching from the inferior.
23958 The type of this @code{gdb.Value}. The value of this attribute is a
23959 @code{gdb.Type} object (@pxref{Types In Python}).
23962 @defvar Value.dynamic_type
23963 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23964 type information (@acronym{RTTI}) to determine the dynamic type of the
23965 value. If this value is of class type, it will return the class in
23966 which the value is embedded, if any. If this value is of pointer or
23967 reference to a class type, it will compute the dynamic type of the
23968 referenced object, and return a pointer or reference to that type,
23969 respectively. In all other cases, it will return the value's static
23972 Note that this feature will only work when debugging a C@t{++} program
23973 that includes @acronym{RTTI} for the object in question. Otherwise,
23974 it will just return the static type of the value as in @kbd{ptype foo}
23975 (@pxref{Symbols, ptype}).
23978 @defvar Value.is_lazy
23979 The value of this read-only boolean attribute is @code{True} if this
23980 @code{gdb.Value} has not yet been fetched from the inferior.
23981 @value{GDBN} does not fetch values until necessary, for efficiency.
23985 myval = gdb.parse_and_eval ('somevar')
23988 The value of @code{somevar} is not fetched at this time. It will be
23989 fetched when the value is needed, or when the @code{fetch_lazy}
23993 The following methods are provided:
23995 @defun Value.__init__ (@var{val})
23996 Many Python values can be converted directly to a @code{gdb.Value} via
23997 this object initializer. Specifically:
24000 @item Python boolean
24001 A Python boolean is converted to the boolean type from the current
24004 @item Python integer
24005 A Python integer is converted to the C @code{long} type for the
24006 current architecture.
24009 A Python long is converted to the C @code{long long} type for the
24010 current architecture.
24013 A Python float is converted to the C @code{double} type for the
24014 current architecture.
24016 @item Python string
24017 A Python string is converted to a target string, using the current
24020 @item @code{gdb.Value}
24021 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
24023 @item @code{gdb.LazyString}
24024 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
24025 Python}), then the lazy string's @code{value} method is called, and
24026 its result is used.
24030 @defun Value.cast (type)
24031 Return a new instance of @code{gdb.Value} that is the result of
24032 casting this instance to the type described by @var{type}, which must
24033 be a @code{gdb.Type} object. If the cast cannot be performed for some
24034 reason, this method throws an exception.
24037 @defun Value.dereference ()
24038 For pointer data types, this method returns a new @code{gdb.Value} object
24039 whose contents is the object pointed to by the pointer. For example, if
24040 @code{foo} is a C pointer to an @code{int}, declared in your C program as
24047 then you can use the corresponding @code{gdb.Value} to access what
24048 @code{foo} points to like this:
24051 bar = foo.dereference ()
24054 The result @code{bar} will be a @code{gdb.Value} object holding the
24055 value pointed to by @code{foo}.
24057 A similar function @code{Value.referenced_value} exists which also
24058 returns @code{gdb.Value} objects corresonding to the values pointed to
24059 by pointer values (and additionally, values referenced by reference
24060 values). However, the behavior of @code{Value.dereference}
24061 differs from @code{Value.referenced_value} by the fact that the
24062 behavior of @code{Value.dereference} is identical to applying the C
24063 unary operator @code{*} on a given value. For example, consider a
24064 reference to a pointer @code{ptrref}, declared in your C@t{++} program
24068 typedef int *intptr;
24072 intptr &ptrref = ptr;
24075 Though @code{ptrref} is a reference value, one can apply the method
24076 @code{Value.dereference} to the @code{gdb.Value} object corresponding
24077 to it and obtain a @code{gdb.Value} which is identical to that
24078 corresponding to @code{val}. However, if you apply the method
24079 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
24080 object identical to that corresponding to @code{ptr}.
24083 py_ptrref = gdb.parse_and_eval ("ptrref")
24084 py_val = py_ptrref.dereference ()
24085 py_ptr = py_ptrref.referenced_value ()
24088 The @code{gdb.Value} object @code{py_val} is identical to that
24089 corresponding to @code{val}, and @code{py_ptr} is identical to that
24090 corresponding to @code{ptr}. In general, @code{Value.dereference} can
24091 be applied whenever the C unary operator @code{*} can be applied
24092 to the corresponding C value. For those cases where applying both
24093 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
24094 the results obtained need not be identical (as we have seen in the above
24095 example). The results are however identical when applied on
24096 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
24097 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
24100 @defun Value.referenced_value ()
24101 For pointer or reference data types, this method returns a new
24102 @code{gdb.Value} object corresponding to the value referenced by the
24103 pointer/reference value. For pointer data types,
24104 @code{Value.dereference} and @code{Value.referenced_value} produce
24105 identical results. The difference between these methods is that
24106 @code{Value.dereference} cannot get the values referenced by reference
24107 values. For example, consider a reference to an @code{int}, declared
24108 in your C@t{++} program as
24116 then applying @code{Value.dereference} to the @code{gdb.Value} object
24117 corresponding to @code{ref} will result in an error, while applying
24118 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24119 identical to that corresponding to @code{val}.
24122 py_ref = gdb.parse_and_eval ("ref")
24123 er_ref = py_ref.dereference () # Results in error
24124 py_val = py_ref.referenced_value () # Returns the referenced value
24127 The @code{gdb.Value} object @code{py_val} is identical to that
24128 corresponding to @code{val}.
24131 @defun Value.dynamic_cast (type)
24132 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24133 operator were used. Consult a C@t{++} reference for details.
24136 @defun Value.reinterpret_cast (type)
24137 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24138 operator were used. Consult a C@t{++} reference for details.
24141 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24142 If this @code{gdb.Value} represents a string, then this method
24143 converts the contents to a Python string. Otherwise, this method will
24144 throw an exception.
24146 Strings are recognized in a language-specific way; whether a given
24147 @code{gdb.Value} represents a string is determined by the current
24150 For C-like languages, a value is a string if it is a pointer to or an
24151 array of characters or ints. The string is assumed to be terminated
24152 by a zero of the appropriate width. However if the optional length
24153 argument is given, the string will be converted to that given length,
24154 ignoring any embedded zeros that the string may contain.
24156 If the optional @var{encoding} argument is given, it must be a string
24157 naming the encoding of the string in the @code{gdb.Value}, such as
24158 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24159 the same encodings as the corresponding argument to Python's
24160 @code{string.decode} method, and the Python codec machinery will be used
24161 to convert the string. If @var{encoding} is not given, or if
24162 @var{encoding} is the empty string, then either the @code{target-charset}
24163 (@pxref{Character Sets}) will be used, or a language-specific encoding
24164 will be used, if the current language is able to supply one.
24166 The optional @var{errors} argument is the same as the corresponding
24167 argument to Python's @code{string.decode} method.
24169 If the optional @var{length} argument is given, the string will be
24170 fetched and converted to the given length.
24173 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24174 If this @code{gdb.Value} represents a string, then this method
24175 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24176 In Python}). Otherwise, this method will throw an exception.
24178 If the optional @var{encoding} argument is given, it must be a string
24179 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24180 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24181 @var{encoding} argument is an encoding that @value{GDBN} does
24182 recognize, @value{GDBN} will raise an error.
24184 When a lazy string is printed, the @value{GDBN} encoding machinery is
24185 used to convert the string during printing. If the optional
24186 @var{encoding} argument is not provided, or is an empty string,
24187 @value{GDBN} will automatically select the encoding most suitable for
24188 the string type. For further information on encoding in @value{GDBN}
24189 please see @ref{Character Sets}.
24191 If the optional @var{length} argument is given, the string will be
24192 fetched and encoded to the length of characters specified. If
24193 the @var{length} argument is not provided, the string will be fetched
24194 and encoded until a null of appropriate width is found.
24197 @defun Value.fetch_lazy ()
24198 If the @code{gdb.Value} object is currently a lazy value
24199 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24200 fetched from the inferior. Any errors that occur in the process
24201 will produce a Python exception.
24203 If the @code{gdb.Value} object is not a lazy value, this method
24206 This method does not return a value.
24210 @node Types In Python
24211 @subsubsection Types In Python
24212 @cindex types in Python
24213 @cindex Python, working with types
24216 @value{GDBN} represents types from the inferior using the class
24219 The following type-related functions are available in the @code{gdb}
24222 @findex gdb.lookup_type
24223 @defun gdb.lookup_type (name @r{[}, block@r{]})
24224 This function looks up a type by name. @var{name} is the name of the
24225 type to look up. It must be a string.
24227 If @var{block} is given, then @var{name} is looked up in that scope.
24228 Otherwise, it is searched for globally.
24230 Ordinarily, this function will return an instance of @code{gdb.Type}.
24231 If the named type cannot be found, it will throw an exception.
24234 If the type is a structure or class type, or an enum type, the fields
24235 of that type can be accessed using the Python @dfn{dictionary syntax}.
24236 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24237 a structure type, you can access its @code{foo} field with:
24240 bar = some_type['foo']
24243 @code{bar} will be a @code{gdb.Field} object; see below under the
24244 description of the @code{Type.fields} method for a description of the
24245 @code{gdb.Field} class.
24247 An instance of @code{Type} has the following attributes:
24250 The type code for this type. The type code will be one of the
24251 @code{TYPE_CODE_} constants defined below.
24254 @defvar Type.sizeof
24255 The size of this type, in target @code{char} units. Usually, a
24256 target's @code{char} type will be an 8-bit byte. However, on some
24257 unusual platforms, this type may have a different size.
24261 The tag name for this type. The tag name is the name after
24262 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24263 languages have this concept. If this type has no tag name, then
24264 @code{None} is returned.
24267 The following methods are provided:
24269 @defun Type.fields ()
24270 For structure and union types, this method returns the fields. Range
24271 types have two fields, the minimum and maximum values. Enum types
24272 have one field per enum constant. Function and method types have one
24273 field per parameter. The base types of C@t{++} classes are also
24274 represented as fields. If the type has no fields, or does not fit
24275 into one of these categories, an empty sequence will be returned.
24277 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24280 This attribute is not available for @code{static} fields (as in
24281 C@t{++} or Java). For non-@code{static} fields, the value is the bit
24282 position of the field. For @code{enum} fields, the value is the
24283 enumeration member's integer representation.
24286 The name of the field, or @code{None} for anonymous fields.
24289 This is @code{True} if the field is artificial, usually meaning that
24290 it was provided by the compiler and not the user. This attribute is
24291 always provided, and is @code{False} if the field is not artificial.
24293 @item is_base_class
24294 This is @code{True} if the field represents a base class of a C@t{++}
24295 structure. This attribute is always provided, and is @code{False}
24296 if the field is not a base class of the type that is the argument of
24297 @code{fields}, or if that type was not a C@t{++} class.
24300 If the field is packed, or is a bitfield, then this will have a
24301 non-zero value, which is the size of the field in bits. Otherwise,
24302 this will be zero; in this case the field's size is given by its type.
24305 The type of the field. This is usually an instance of @code{Type},
24306 but it can be @code{None} in some situations.
24310 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24311 Return a new @code{gdb.Type} object which represents an array of this
24312 type. If one argument is given, it is the inclusive upper bound of
24313 the array; in this case the lower bound is zero. If two arguments are
24314 given, the first argument is the lower bound of the array, and the
24315 second argument is the upper bound of the array. An array's length
24316 must not be negative, but the bounds can be.
24319 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24320 Return a new @code{gdb.Type} object which represents a vector of this
24321 type. If one argument is given, it is the inclusive upper bound of
24322 the vector; in this case the lower bound is zero. If two arguments are
24323 given, the first argument is the lower bound of the vector, and the
24324 second argument is the upper bound of the vector. A vector's length
24325 must not be negative, but the bounds can be.
24327 The difference between an @code{array} and a @code{vector} is that
24328 arrays behave like in C: when used in expressions they decay to a pointer
24329 to the first element whereas vectors are treated as first class values.
24332 @defun Type.const ()
24333 Return a new @code{gdb.Type} object which represents a
24334 @code{const}-qualified variant of this type.
24337 @defun Type.volatile ()
24338 Return a new @code{gdb.Type} object which represents a
24339 @code{volatile}-qualified variant of this type.
24342 @defun Type.unqualified ()
24343 Return a new @code{gdb.Type} object which represents an unqualified
24344 variant of this type. That is, the result is neither @code{const} nor
24348 @defun Type.range ()
24349 Return a Python @code{Tuple} object that contains two elements: the
24350 low bound of the argument type and the high bound of that type. If
24351 the type does not have a range, @value{GDBN} will raise a
24352 @code{gdb.error} exception (@pxref{Exception Handling}).
24355 @defun Type.reference ()
24356 Return a new @code{gdb.Type} object which represents a reference to this
24360 @defun Type.pointer ()
24361 Return a new @code{gdb.Type} object which represents a pointer to this
24365 @defun Type.strip_typedefs ()
24366 Return a new @code{gdb.Type} that represents the real type,
24367 after removing all layers of typedefs.
24370 @defun Type.target ()
24371 Return a new @code{gdb.Type} object which represents the target type
24374 For a pointer type, the target type is the type of the pointed-to
24375 object. For an array type (meaning C-like arrays), the target type is
24376 the type of the elements of the array. For a function or method type,
24377 the target type is the type of the return value. For a complex type,
24378 the target type is the type of the elements. For a typedef, the
24379 target type is the aliased type.
24381 If the type does not have a target, this method will throw an
24385 @defun Type.template_argument (n @r{[}, block@r{]})
24386 If this @code{gdb.Type} is an instantiation of a template, this will
24387 return a new @code{gdb.Type} which represents the type of the
24388 @var{n}th template argument.
24390 If this @code{gdb.Type} is not a template type, this will throw an
24391 exception. Ordinarily, only C@t{++} code will have template types.
24393 If @var{block} is given, then @var{name} is looked up in that scope.
24394 Otherwise, it is searched for globally.
24398 Each type has a code, which indicates what category this type falls
24399 into. The available type categories are represented by constants
24400 defined in the @code{gdb} module:
24403 @findex TYPE_CODE_PTR
24404 @findex gdb.TYPE_CODE_PTR
24405 @item gdb.TYPE_CODE_PTR
24406 The type is a pointer.
24408 @findex TYPE_CODE_ARRAY
24409 @findex gdb.TYPE_CODE_ARRAY
24410 @item gdb.TYPE_CODE_ARRAY
24411 The type is an array.
24413 @findex TYPE_CODE_STRUCT
24414 @findex gdb.TYPE_CODE_STRUCT
24415 @item gdb.TYPE_CODE_STRUCT
24416 The type is a structure.
24418 @findex TYPE_CODE_UNION
24419 @findex gdb.TYPE_CODE_UNION
24420 @item gdb.TYPE_CODE_UNION
24421 The type is a union.
24423 @findex TYPE_CODE_ENUM
24424 @findex gdb.TYPE_CODE_ENUM
24425 @item gdb.TYPE_CODE_ENUM
24426 The type is an enum.
24428 @findex TYPE_CODE_FLAGS
24429 @findex gdb.TYPE_CODE_FLAGS
24430 @item gdb.TYPE_CODE_FLAGS
24431 A bit flags type, used for things such as status registers.
24433 @findex TYPE_CODE_FUNC
24434 @findex gdb.TYPE_CODE_FUNC
24435 @item gdb.TYPE_CODE_FUNC
24436 The type is a function.
24438 @findex TYPE_CODE_INT
24439 @findex gdb.TYPE_CODE_INT
24440 @item gdb.TYPE_CODE_INT
24441 The type is an integer type.
24443 @findex TYPE_CODE_FLT
24444 @findex gdb.TYPE_CODE_FLT
24445 @item gdb.TYPE_CODE_FLT
24446 A floating point type.
24448 @findex TYPE_CODE_VOID
24449 @findex gdb.TYPE_CODE_VOID
24450 @item gdb.TYPE_CODE_VOID
24451 The special type @code{void}.
24453 @findex TYPE_CODE_SET
24454 @findex gdb.TYPE_CODE_SET
24455 @item gdb.TYPE_CODE_SET
24458 @findex TYPE_CODE_RANGE
24459 @findex gdb.TYPE_CODE_RANGE
24460 @item gdb.TYPE_CODE_RANGE
24461 A range type, that is, an integer type with bounds.
24463 @findex TYPE_CODE_STRING
24464 @findex gdb.TYPE_CODE_STRING
24465 @item gdb.TYPE_CODE_STRING
24466 A string type. Note that this is only used for certain languages with
24467 language-defined string types; C strings are not represented this way.
24469 @findex TYPE_CODE_BITSTRING
24470 @findex gdb.TYPE_CODE_BITSTRING
24471 @item gdb.TYPE_CODE_BITSTRING
24472 A string of bits. It is deprecated.
24474 @findex TYPE_CODE_ERROR
24475 @findex gdb.TYPE_CODE_ERROR
24476 @item gdb.TYPE_CODE_ERROR
24477 An unknown or erroneous type.
24479 @findex TYPE_CODE_METHOD
24480 @findex gdb.TYPE_CODE_METHOD
24481 @item gdb.TYPE_CODE_METHOD
24482 A method type, as found in C@t{++} or Java.
24484 @findex TYPE_CODE_METHODPTR
24485 @findex gdb.TYPE_CODE_METHODPTR
24486 @item gdb.TYPE_CODE_METHODPTR
24487 A pointer-to-member-function.
24489 @findex TYPE_CODE_MEMBERPTR
24490 @findex gdb.TYPE_CODE_MEMBERPTR
24491 @item gdb.TYPE_CODE_MEMBERPTR
24492 A pointer-to-member.
24494 @findex TYPE_CODE_REF
24495 @findex gdb.TYPE_CODE_REF
24496 @item gdb.TYPE_CODE_REF
24499 @findex TYPE_CODE_CHAR
24500 @findex gdb.TYPE_CODE_CHAR
24501 @item gdb.TYPE_CODE_CHAR
24504 @findex TYPE_CODE_BOOL
24505 @findex gdb.TYPE_CODE_BOOL
24506 @item gdb.TYPE_CODE_BOOL
24509 @findex TYPE_CODE_COMPLEX
24510 @findex gdb.TYPE_CODE_COMPLEX
24511 @item gdb.TYPE_CODE_COMPLEX
24512 A complex float type.
24514 @findex TYPE_CODE_TYPEDEF
24515 @findex gdb.TYPE_CODE_TYPEDEF
24516 @item gdb.TYPE_CODE_TYPEDEF
24517 A typedef to some other type.
24519 @findex TYPE_CODE_NAMESPACE
24520 @findex gdb.TYPE_CODE_NAMESPACE
24521 @item gdb.TYPE_CODE_NAMESPACE
24522 A C@t{++} namespace.
24524 @findex TYPE_CODE_DECFLOAT
24525 @findex gdb.TYPE_CODE_DECFLOAT
24526 @item gdb.TYPE_CODE_DECFLOAT
24527 A decimal floating point type.
24529 @findex TYPE_CODE_INTERNAL_FUNCTION
24530 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24531 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24532 A function internal to @value{GDBN}. This is the type used to represent
24533 convenience functions.
24536 Further support for types is provided in the @code{gdb.types}
24537 Python module (@pxref{gdb.types}).
24539 @node Pretty Printing API
24540 @subsubsection Pretty Printing API
24542 An example output is provided (@pxref{Pretty Printing}).
24544 A pretty-printer is just an object that holds a value and implements a
24545 specific interface, defined here.
24547 @defun pretty_printer.children (self)
24548 @value{GDBN} will call this method on a pretty-printer to compute the
24549 children of the pretty-printer's value.
24551 This method must return an object conforming to the Python iterator
24552 protocol. Each item returned by the iterator must be a tuple holding
24553 two elements. The first element is the ``name'' of the child; the
24554 second element is the child's value. The value can be any Python
24555 object which is convertible to a @value{GDBN} value.
24557 This method is optional. If it does not exist, @value{GDBN} will act
24558 as though the value has no children.
24561 @defun pretty_printer.display_hint (self)
24562 The CLI may call this method and use its result to change the
24563 formatting of a value. The result will also be supplied to an MI
24564 consumer as a @samp{displayhint} attribute of the variable being
24567 This method is optional. If it does exist, this method must return a
24570 Some display hints are predefined by @value{GDBN}:
24574 Indicate that the object being printed is ``array-like''. The CLI
24575 uses this to respect parameters such as @code{set print elements} and
24576 @code{set print array}.
24579 Indicate that the object being printed is ``map-like'', and that the
24580 children of this value can be assumed to alternate between keys and
24584 Indicate that the object being printed is ``string-like''. If the
24585 printer's @code{to_string} method returns a Python string of some
24586 kind, then @value{GDBN} will call its internal language-specific
24587 string-printing function to format the string. For the CLI this means
24588 adding quotation marks, possibly escaping some characters, respecting
24589 @code{set print elements}, and the like.
24593 @defun pretty_printer.to_string (self)
24594 @value{GDBN} will call this method to display the string
24595 representation of the value passed to the object's constructor.
24597 When printing from the CLI, if the @code{to_string} method exists,
24598 then @value{GDBN} will prepend its result to the values returned by
24599 @code{children}. Exactly how this formatting is done is dependent on
24600 the display hint, and may change as more hints are added. Also,
24601 depending on the print settings (@pxref{Print Settings}), the CLI may
24602 print just the result of @code{to_string} in a stack trace, omitting
24603 the result of @code{children}.
24605 If this method returns a string, it is printed verbatim.
24607 Otherwise, if this method returns an instance of @code{gdb.Value},
24608 then @value{GDBN} prints this value. This may result in a call to
24609 another pretty-printer.
24611 If instead the method returns a Python value which is convertible to a
24612 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24613 the resulting value. Again, this may result in a call to another
24614 pretty-printer. Python scalars (integers, floats, and booleans) and
24615 strings are convertible to @code{gdb.Value}; other types are not.
24617 Finally, if this method returns @code{None} then no further operations
24618 are peformed in this method and nothing is printed.
24620 If the result is not one of these types, an exception is raised.
24623 @value{GDBN} provides a function which can be used to look up the
24624 default pretty-printer for a @code{gdb.Value}:
24626 @findex gdb.default_visualizer
24627 @defun gdb.default_visualizer (value)
24628 This function takes a @code{gdb.Value} object as an argument. If a
24629 pretty-printer for this value exists, then it is returned. If no such
24630 printer exists, then this returns @code{None}.
24633 @node Selecting Pretty-Printers
24634 @subsubsection Selecting Pretty-Printers
24636 The Python list @code{gdb.pretty_printers} contains an array of
24637 functions or callable objects that have been registered via addition
24638 as a pretty-printer. Printers in this list are called @code{global}
24639 printers, they're available when debugging all inferiors.
24640 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24641 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24644 Each function on these lists is passed a single @code{gdb.Value}
24645 argument and should return a pretty-printer object conforming to the
24646 interface definition above (@pxref{Pretty Printing API}). If a function
24647 cannot create a pretty-printer for the value, it should return
24650 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24651 @code{gdb.Objfile} in the current program space and iteratively calls
24652 each enabled lookup routine in the list for that @code{gdb.Objfile}
24653 until it receives a pretty-printer object.
24654 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24655 searches the pretty-printer list of the current program space,
24656 calling each enabled function until an object is returned.
24657 After these lists have been exhausted, it tries the global
24658 @code{gdb.pretty_printers} list, again calling each enabled function until an
24659 object is returned.
24661 The order in which the objfiles are searched is not specified. For a
24662 given list, functions are always invoked from the head of the list,
24663 and iterated over sequentially until the end of the list, or a printer
24664 object is returned.
24666 For various reasons a pretty-printer may not work.
24667 For example, the underlying data structure may have changed and
24668 the pretty-printer is out of date.
24670 The consequences of a broken pretty-printer are severe enough that
24671 @value{GDBN} provides support for enabling and disabling individual
24672 printers. For example, if @code{print frame-arguments} is on,
24673 a backtrace can become highly illegible if any argument is printed
24674 with a broken printer.
24676 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24677 attribute to the registered function or callable object. If this attribute
24678 is present and its value is @code{False}, the printer is disabled, otherwise
24679 the printer is enabled.
24681 @node Writing a Pretty-Printer
24682 @subsubsection Writing a Pretty-Printer
24683 @cindex writing a pretty-printer
24685 A pretty-printer consists of two parts: a lookup function to detect
24686 if the type is supported, and the printer itself.
24688 Here is an example showing how a @code{std::string} printer might be
24689 written. @xref{Pretty Printing API}, for details on the API this class
24693 class StdStringPrinter(object):
24694 "Print a std::string"
24696 def __init__(self, val):
24699 def to_string(self):
24700 return self.val['_M_dataplus']['_M_p']
24702 def display_hint(self):
24706 And here is an example showing how a lookup function for the printer
24707 example above might be written.
24710 def str_lookup_function(val):
24711 lookup_tag = val.type.tag
24712 if lookup_tag == None:
24714 regex = re.compile("^std::basic_string<char,.*>$")
24715 if regex.match(lookup_tag):
24716 return StdStringPrinter(val)
24720 The example lookup function extracts the value's type, and attempts to
24721 match it to a type that it can pretty-print. If it is a type the
24722 printer can pretty-print, it will return a printer object. If not, it
24723 returns @code{None}.
24725 We recommend that you put your core pretty-printers into a Python
24726 package. If your pretty-printers are for use with a library, we
24727 further recommend embedding a version number into the package name.
24728 This practice will enable @value{GDBN} to load multiple versions of
24729 your pretty-printers at the same time, because they will have
24732 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24733 can be evaluated multiple times without changing its meaning. An
24734 ideal auto-load file will consist solely of @code{import}s of your
24735 printer modules, followed by a call to a register pretty-printers with
24736 the current objfile.
24738 Taken as a whole, this approach will scale nicely to multiple
24739 inferiors, each potentially using a different library version.
24740 Embedding a version number in the Python package name will ensure that
24741 @value{GDBN} is able to load both sets of printers simultaneously.
24742 Then, because the search for pretty-printers is done by objfile, and
24743 because your auto-loaded code took care to register your library's
24744 printers with a specific objfile, @value{GDBN} will find the correct
24745 printers for the specific version of the library used by each
24748 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24749 this code might appear in @code{gdb.libstdcxx.v6}:
24752 def register_printers(objfile):
24753 objfile.pretty_printers.append(str_lookup_function)
24757 And then the corresponding contents of the auto-load file would be:
24760 import gdb.libstdcxx.v6
24761 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24764 The previous example illustrates a basic pretty-printer.
24765 There are a few things that can be improved on.
24766 The printer doesn't have a name, making it hard to identify in a
24767 list of installed printers. The lookup function has a name, but
24768 lookup functions can have arbitrary, even identical, names.
24770 Second, the printer only handles one type, whereas a library typically has
24771 several types. One could install a lookup function for each desired type
24772 in the library, but one could also have a single lookup function recognize
24773 several types. The latter is the conventional way this is handled.
24774 If a pretty-printer can handle multiple data types, then its
24775 @dfn{subprinters} are the printers for the individual data types.
24777 The @code{gdb.printing} module provides a formal way of solving these
24778 problems (@pxref{gdb.printing}).
24779 Here is another example that handles multiple types.
24781 These are the types we are going to pretty-print:
24784 struct foo @{ int a, b; @};
24785 struct bar @{ struct foo x, y; @};
24788 Here are the printers:
24792 """Print a foo object."""
24794 def __init__(self, val):
24797 def to_string(self):
24798 return ("a=<" + str(self.val["a"]) +
24799 "> b=<" + str(self.val["b"]) + ">")
24802 """Print a bar object."""
24804 def __init__(self, val):
24807 def to_string(self):
24808 return ("x=<" + str(self.val["x"]) +
24809 "> y=<" + str(self.val["y"]) + ">")
24812 This example doesn't need a lookup function, that is handled by the
24813 @code{gdb.printing} module. Instead a function is provided to build up
24814 the object that handles the lookup.
24817 import gdb.printing
24819 def build_pretty_printer():
24820 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24822 pp.add_printer('foo', '^foo$', fooPrinter)
24823 pp.add_printer('bar', '^bar$', barPrinter)
24827 And here is the autoload support:
24830 import gdb.printing
24832 gdb.printing.register_pretty_printer(
24833 gdb.current_objfile(),
24834 my_library.build_pretty_printer())
24837 Finally, when this printer is loaded into @value{GDBN}, here is the
24838 corresponding output of @samp{info pretty-printer}:
24841 (gdb) info pretty-printer
24848 @node Type Printing API
24849 @subsubsection Type Printing API
24850 @cindex type printing API for Python
24852 @value{GDBN} provides a way for Python code to customize type display.
24853 This is mainly useful for substituting canonical typedef names for
24856 @cindex type printer
24857 A @dfn{type printer} is just a Python object conforming to a certain
24858 protocol. A simple base class implementing the protocol is provided;
24859 see @ref{gdb.types}. A type printer must supply at least:
24861 @defivar type_printer enabled
24862 A boolean which is True if the printer is enabled, and False
24863 otherwise. This is manipulated by the @code{enable type-printer}
24864 and @code{disable type-printer} commands.
24867 @defivar type_printer name
24868 The name of the type printer. This must be a string. This is used by
24869 the @code{enable type-printer} and @code{disable type-printer}
24873 @defmethod type_printer instantiate (self)
24874 This is called by @value{GDBN} at the start of type-printing. It is
24875 only called if the type printer is enabled. This method must return a
24876 new object that supplies a @code{recognize} method, as described below.
24880 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24881 will compute a list of type recognizers. This is done by iterating
24882 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24883 followed by the per-progspace type printers (@pxref{Progspaces In
24884 Python}), and finally the global type printers.
24886 @value{GDBN} will call the @code{instantiate} method of each enabled
24887 type printer. If this method returns @code{None}, then the result is
24888 ignored; otherwise, it is appended to the list of recognizers.
24890 Then, when @value{GDBN} is going to display a type name, it iterates
24891 over the list of recognizers. For each one, it calls the recognition
24892 function, stopping if the function returns a non-@code{None} value.
24893 The recognition function is defined as:
24895 @defmethod type_recognizer recognize (self, type)
24896 If @var{type} is not recognized, return @code{None}. Otherwise,
24897 return a string which is to be printed as the name of @var{type}.
24898 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24902 @value{GDBN} uses this two-pass approach so that type printers can
24903 efficiently cache information without holding on to it too long. For
24904 example, it can be convenient to look up type information in a type
24905 printer and hold it for a recognizer's lifetime; if a single pass were
24906 done then type printers would have to make use of the event system in
24907 order to avoid holding information that could become stale as the
24910 @node Frame Filter API
24911 @subsubsection Filtering Frames.
24912 @cindex frame filters api
24914 Frame filters are Python objects that manipulate the visibility of a
24915 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24918 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24919 commands (@pxref{GDB/MI}), those that return a collection of frames
24920 are affected. The commands that work with frame filters are:
24922 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24923 @code{-stack-list-frames}
24924 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24925 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24926 -stack-list-variables command}), @code{-stack-list-arguments}
24927 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
24928 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
24929 -stack-list-locals command}).
24931 A frame filter works by taking an iterator as an argument, applying
24932 actions to the contents of that iterator, and returning another
24933 iterator (or, possibly, the same iterator it was provided in the case
24934 where the filter does not perform any operations). Typically, frame
24935 filters utilize tools such as the Python's @code{itertools} module to
24936 work with and create new iterators from the source iterator.
24937 Regardless of how a filter chooses to apply actions, it must not alter
24938 the underlying @value{GDBN} frame or frames, or attempt to alter the
24939 call-stack within @value{GDBN}. This preserves data integrity within
24940 @value{GDBN}. Frame filters are executed on a priority basis and care
24941 should be taken that some frame filters may have been executed before,
24942 and that some frame filters will be executed after.
24944 An important consideration when designing frame filters, and well
24945 worth reflecting upon, is that frame filters should avoid unwinding
24946 the call stack if possible. Some stacks can run very deep, into the
24947 tens of thousands in some cases. To search every frame when a frame
24948 filter executes may be too expensive at that step. The frame filter
24949 cannot know how many frames it has to iterate over, and it may have to
24950 iterate through them all. This ends up duplicating effort as
24951 @value{GDBN} performs this iteration when it prints the frames. If
24952 the filter can defer unwinding frames until frame decorators are
24953 executed, after the last filter has executed, it should. @xref{Frame
24954 Decorator API}, for more information on decorators. Also, there are
24955 examples for both frame decorators and filters in later chapters.
24956 @xref{Writing a Frame Filter}, for more information.
24958 The Python dictionary @code{gdb.frame_filters} contains key/object
24959 pairings that comprise a frame filter. Frame filters in this
24960 dictionary are called @code{global} frame filters, and they are
24961 available when debugging all inferiors. These frame filters must
24962 register with the dictionary directly. In addition to the
24963 @code{global} dictionary, there are other dictionaries that are loaded
24964 with different inferiors via auto-loading (@pxref{Python
24965 Auto-loading}). The two other areas where frame filter dictionaries
24966 can be found are: @code{gdb.Progspace} which contains a
24967 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
24968 object which also contains a @code{frame_filters} dictionary
24971 When a command is executed from @value{GDBN} that is compatible with
24972 frame filters, @value{GDBN} combines the @code{global},
24973 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
24974 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
24975 several frames, and thus several object files, might be in use.
24976 @value{GDBN} then prunes any frame filter whose @code{enabled}
24977 attribute is @code{False}. This pruned list is then sorted according
24978 to the @code{priority} attribute in each filter.
24980 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
24981 creates an iterator which wraps each frame in the call stack in a
24982 @code{FrameDecorator} object, and calls each filter in order. The
24983 output from the previous filter will always be the input to the next
24986 Frame filters have a mandatory interface which each frame filter must
24987 implement, defined here:
24989 @defun FrameFilter.filter (iterator)
24990 @value{GDBN} will call this method on a frame filter when it has
24991 reached the order in the priority list for that filter.
24993 For example, if there are four frame filters:
25004 The order that the frame filters will be called is:
25007 Filter3 -> Filter2 -> Filter1 -> Filter4
25010 Note that the output from @code{Filter3} is passed to the input of
25011 @code{Filter2}, and so on.
25013 This @code{filter} method is passed a Python iterator. This iterator
25014 contains a sequence of frame decorators that wrap each
25015 @code{gdb.Frame}, or a frame decorator that wraps another frame
25016 decorator. The first filter that is executed in the sequence of frame
25017 filters will receive an iterator entirely comprised of default
25018 @code{FrameDecorator} objects. However, after each frame filter is
25019 executed, the previous frame filter may have wrapped some or all of
25020 the frame decorators with their own frame decorator. As frame
25021 decorators must also conform to a mandatory interface, these
25022 decorators can be assumed to act in a uniform manner (@pxref{Frame
25025 This method must return an object conforming to the Python iterator
25026 protocol. Each item in the iterator must be an object conforming to
25027 the frame decorator interface. If a frame filter does not wish to
25028 perform any operations on this iterator, it should return that
25029 iterator untouched.
25031 This method is not optional. If it does not exist, @value{GDBN} will
25032 raise and print an error.
25035 @defvar FrameFilter.name
25036 The @code{name} attribute must be Python string which contains the
25037 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
25038 Management}). This attribute may contain any combination of letters
25039 or numbers. Care should be taken to ensure that it is unique. This
25040 attribute is mandatory.
25043 @defvar FrameFilter.enabled
25044 The @code{enabled} attribute must be Python boolean. This attribute
25045 indicates to @value{GDBN} whether the frame filter is enabled, and
25046 should be considered when frame filters are executed. If
25047 @code{enabled} is @code{True}, then the frame filter will be executed
25048 when any of the backtrace commands detailed earlier in this chapter
25049 are executed. If @code{enabled} is @code{False}, then the frame
25050 filter will not be executed. This attribute is mandatory.
25053 @defvar FrameFilter.priority
25054 The @code{priority} attribute must be Python integer. This attribute
25055 controls the order of execution in relation to other frame filters.
25056 There are no imposed limits on the range of @code{priority} other than
25057 it must be a valid integer. The higher the @code{priority} attribute,
25058 the sooner the frame filter will be executed in relation to other
25059 frame filters. Although @code{priority} can be negative, it is
25060 recommended practice to assume zero is the lowest priority that a
25061 frame filter can be assigned. Frame filters that have the same
25062 priority are executed in unsorted order in that priority slot. This
25063 attribute is mandatory.
25066 @node Frame Decorator API
25067 @subsubsection Decorating Frames.
25068 @cindex frame decorator api
25070 Frame decorators are sister objects to frame filters (@pxref{Frame
25071 Filter API}). Frame decorators are applied by a frame filter and can
25072 only be used in conjunction with frame filters.
25074 The purpose of a frame decorator is to customize the printed content
25075 of each @code{gdb.Frame} in commands where frame filters are executed.
25076 This concept is called decorating a frame. Frame decorators decorate
25077 a @code{gdb.Frame} with Python code contained within each API call.
25078 This separates the actual data contained in a @code{gdb.Frame} from
25079 the decorated data produced by a frame decorator. This abstraction is
25080 necessary to maintain integrity of the data contained in each
25083 Frame decorators have a mandatory interface, defined below.
25085 @value{GDBN} already contains a frame decorator called
25086 @code{FrameDecorator}. This contains substantial amounts of
25087 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
25088 recommended that other frame decorators inherit and extend this
25089 object, and only to override the methods needed.
25091 @defun FrameDecorator.elided (self)
25093 The @code{elided} method groups frames together in a hierarchical
25094 system. An example would be an interpreter, where multiple low-level
25095 frames make up a single call in the interpreted language. In this
25096 example, the frame filter would elide the low-level frames and present
25097 a single high-level frame, representing the call in the interpreted
25098 language, to the user.
25100 The @code{elided} function must return an iterable and this iterable
25101 must contain the frames that are being elided wrapped in a suitable
25102 frame decorator. If no frames are being elided this function may
25103 return an empty iterable, or @code{None}. Elided frames are indented
25104 from normal frames in a @code{CLI} backtrace, or in the case of
25105 @code{GDB/MI}, are placed in the @code{children} field of the eliding
25108 It is the frame filter's task to also filter out the elided frames from
25109 the source iterator. This will avoid printing the frame twice.
25112 @defun FrameDecorator.function (self)
25114 This method returns the name of the function in the frame that is to
25117 This method must return a Python string describing the function, or
25120 If this function returns @code{None}, @value{GDBN} will not print any
25121 data for this field.
25124 @defun FrameDecorator.address (self)
25126 This method returns the address of the frame that is to be printed.
25128 This method must return a Python numeric integer type of sufficient
25129 size to describe the address of the frame, or @code{None}.
25131 If this function returns a @code{None}, @value{GDBN} will not print
25132 any data for this field.
25135 @defun FrameDecorator.filename (self)
25137 This method returns the filename and path associated with this frame.
25139 This method must return a Python string containing the filename and
25140 the path to the object file backing the frame, or @code{None}.
25142 If this function returns a @code{None}, @value{GDBN} will not print
25143 any data for this field.
25146 @defun FrameDecorator.line (self):
25148 This method returns the line number associated with the current
25149 position within the function addressed by this frame.
25151 This method must return a Python integer type, or @code{None}.
25153 If this function returns a @code{None}, @value{GDBN} will not print
25154 any data for this field.
25157 @defun FrameDecorator.frame_args (self)
25158 @anchor{frame_args}
25160 This method must return an iterable, or @code{None}. Returning an
25161 empty iterable, or @code{None} means frame arguments will not be
25162 printed for this frame. This iterable must contain objects that
25163 implement two methods, described here.
25165 This object must implement a @code{argument} method which takes a
25166 single @code{self} parameter and must return a @code{gdb.Symbol}
25167 (@pxref{Symbols In Python}), or a Python string. The object must also
25168 implement a @code{value} method which takes a single @code{self}
25169 parameter and must return a @code{gdb.Value} (@pxref{Values From
25170 Inferior}), a Python value, or @code{None}. If the @code{value}
25171 method returns @code{None}, and the @code{argument} method returns a
25172 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25173 the @code{gdb.Symbol} automatically.
25178 class SymValueWrapper():
25180 def __init__(self, symbol, value):
25190 class SomeFrameDecorator()
25193 def frame_args(self):
25196 block = self.inferior_frame.block()
25200 # Iterate over all symbols in a block. Only add
25201 # symbols that are arguments.
25203 if not sym.is_argument:
25205 args.append(SymValueWrapper(sym,None))
25207 # Add example synthetic argument.
25208 args.append(SymValueWrapper(``foo'', 42))
25214 @defun FrameDecorator.frame_locals (self)
25216 This method must return an iterable or @code{None}. Returning an
25217 empty iterable, or @code{None} means frame local arguments will not be
25218 printed for this frame.
25220 The object interface, the description of the various strategies for
25221 reading frame locals, and the example are largely similar to those
25222 described in the @code{frame_args} function, (@pxref{frame_args,,The
25223 frame filter frame_args function}). Below is a modified example:
25226 class SomeFrameDecorator()
25229 def frame_locals(self):
25232 block = self.inferior_frame.block()
25236 # Iterate over all symbols in a block. Add all
25237 # symbols, except arguments.
25239 if sym.is_argument:
25241 vars.append(SymValueWrapper(sym,None))
25243 # Add an example of a synthetic local variable.
25244 vars.append(SymValueWrapper(``bar'', 99))
25250 @defun FrameDecorator.inferior_frame (self):
25252 This method must return the underlying @code{gdb.Frame} that this
25253 frame decorator is decorating. @value{GDBN} requires the underlying
25254 frame for internal frame information to determine how to print certain
25255 values when printing a frame.
25258 @node Writing a Frame Filter
25259 @subsubsection Writing a Frame Filter
25260 @cindex writing a frame filter
25262 There are three basic elements that a frame filter must implement: it
25263 must correctly implement the documented interface (@pxref{Frame Filter
25264 API}), it must register itself with @value{GDBN}, and finally, it must
25265 decide if it is to work on the data provided by @value{GDBN}. In all
25266 cases, whether it works on the iterator or not, each frame filter must
25267 return an iterator. A bare-bones frame filter follows the pattern in
25268 the following example.
25273 class FrameFilter():
25275 def __init__(self):
25276 # Frame filter attribute creation.
25278 # 'name' is the name of the filter that GDB will display.
25280 # 'priority' is the priority of the filter relative to other
25283 # 'enabled' is a boolean that indicates whether this filter is
25284 # enabled and should be executed.
25287 self.priority = 100
25288 self.enabled = True
25290 # Register this frame filter with the global frame_filters
25292 gdb.frame_filters[self.name] = self
25294 def filter(self, frame_iter):
25295 # Just return the iterator.
25299 The frame filter in the example above implements the three
25300 requirements for all frame filters. It implements the API, self
25301 registers, and makes a decision on the iterator (in this case, it just
25302 returns the iterator untouched).
25304 The first step is attribute creation and assignment, and as shown in
25305 the comments the filter assigns the following attributes: @code{name},
25306 @code{priority} and whether the filter should be enabled with the
25307 @code{enabled} attribute.
25309 The second step is registering the frame filter with the dictionary or
25310 dictionaries that the frame filter has interest in. As shown in the
25311 comments, this filter just registers itself with the global dictionary
25312 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25313 is a dictionary that is initialized in the @code{gdb} module when
25314 @value{GDBN} starts. What dictionary a filter registers with is an
25315 important consideration. Generally, if a filter is specific to a set
25316 of code, it should be registered either in the @code{objfile} or
25317 @code{progspace} dictionaries as they are specific to the program
25318 currently loaded in @value{GDBN}. The global dictionary is always
25319 present in @value{GDBN} and is never unloaded. Any filters registered
25320 with the global dictionary will exist until @value{GDBN} exits. To
25321 avoid filters that may conflict, it is generally better to register
25322 frame filters against the dictionaries that more closely align with
25323 the usage of the filter currently in question. @xref{Python
25324 Auto-loading}, for further information on auto-loading Python scripts.
25326 @value{GDBN} takes a hands-off approach to frame filter registration,
25327 therefore it is the frame filter's responsibility to ensure
25328 registration has occurred, and that any exceptions are handled
25329 appropriately. In particular, you may wish to handle exceptions
25330 relating to Python dictionary key uniqueness. It is mandatory that
25331 the dictionary key is the same as frame filter's @code{name}
25332 attribute. When a user manages frame filters (@pxref{Frame Filter
25333 Management}), the names @value{GDBN} will display are those contained
25334 in the @code{name} attribute.
25336 The final step of this example is the implementation of the
25337 @code{filter} method. As shown in the example comments, we define the
25338 @code{filter} method and note that the method must take an iterator,
25339 and also must return an iterator. In this bare-bones example, the
25340 frame filter is not very useful as it just returns the iterator
25341 untouched. However this is a valid operation for frame filters that
25342 have the @code{enabled} attribute set, but decide not to operate on
25345 In the next example, the frame filter operates on all frames and
25346 utilizes a frame decorator to perform some work on the frames.
25347 @xref{Frame Decorator API}, for further information on the frame
25348 decorator interface.
25350 This example works on inlined frames. It highlights frames which are
25351 inlined by tagging them with an ``[inlined]'' tag. By applying a
25352 frame decorator to all frames with the Python @code{itertools imap}
25353 method, the example defers actions to the frame decorator. Frame
25354 decorators are only processed when @value{GDBN} prints the backtrace.
25356 This introduces a new decision making topic: whether to perform
25357 decision making operations at the filtering step, or at the printing
25358 step. In this example's approach, it does not perform any filtering
25359 decisions at the filtering step beyond mapping a frame decorator to
25360 each frame. This allows the actual decision making to be performed
25361 when each frame is printed. This is an important consideration, and
25362 well worth reflecting upon when designing a frame filter. An issue
25363 that frame filters should avoid is unwinding the stack if possible.
25364 Some stacks can run very deep, into the tens of thousands in some
25365 cases. To search every frame to determine if it is inlined ahead of
25366 time may be too expensive at the filtering step. The frame filter
25367 cannot know how many frames it has to iterate over, and it would have
25368 to iterate through them all. This ends up duplicating effort as
25369 @value{GDBN} performs this iteration when it prints the frames.
25371 In this example decision making can be deferred to the printing step.
25372 As each frame is printed, the frame decorator can examine each frame
25373 in turn when @value{GDBN} iterates. From a performance viewpoint,
25374 this is the most appropriate decision to make as it avoids duplicating
25375 the effort that the printing step would undertake anyway. Also, if
25376 there are many frame filters unwinding the stack during filtering, it
25377 can substantially delay the printing of the backtrace which will
25378 result in large memory usage, and a poor user experience.
25381 class InlineFilter():
25383 def __init__(self):
25384 self.name = "InlinedFrameFilter"
25385 self.priority = 100
25386 self.enabled = True
25387 gdb.frame_filters[self.name] = self
25389 def filter(self, frame_iter):
25390 frame_iter = itertools.imap(InlinedFrameDecorator,
25395 This frame filter is somewhat similar to the earlier example, except
25396 that the @code{filter} method applies a frame decorator object called
25397 @code{InlinedFrameDecorator} to each element in the iterator. The
25398 @code{imap} Python method is light-weight. It does not proactively
25399 iterate over the iterator, but rather creates a new iterator which
25400 wraps the existing one.
25402 Below is the frame decorator for this example.
25405 class InlinedFrameDecorator(FrameDecorator):
25407 def __init__(self, fobj):
25408 super(InlinedFrameDecorator, self).__init__(fobj)
25410 def function(self):
25411 frame = fobj.inferior_frame()
25412 name = str(frame.name())
25414 if frame.type() == gdb.INLINE_FRAME:
25415 name = name + " [inlined]"
25420 This frame decorator only defines and overrides the @code{function}
25421 method. It lets the supplied @code{FrameDecorator}, which is shipped
25422 with @value{GDBN}, perform the other work associated with printing
25425 The combination of these two objects create this output from a
25429 #0 0x004004e0 in bar () at inline.c:11
25430 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25431 #2 0x00400566 in main () at inline.c:31
25434 So in the case of this example, a frame decorator is applied to all
25435 frames, regardless of whether they may be inlined or not. As
25436 @value{GDBN} iterates over the iterator produced by the frame filters,
25437 @value{GDBN} executes each frame decorator which then makes a decision
25438 on what to print in the @code{function} callback. Using a strategy
25439 like this is a way to defer decisions on the frame content to printing
25442 @subheading Eliding Frames
25444 It might be that the above example is not desirable for representing
25445 inlined frames, and a hierarchical approach may be preferred. If we
25446 want to hierarchically represent frames, the @code{elided} frame
25447 decorator interface might be preferable.
25449 This example approaches the issue with the @code{elided} method. This
25450 example is quite long, but very simplistic. It is out-of-scope for
25451 this section to write a complete example that comprehensively covers
25452 all approaches of finding and printing inlined frames. However, this
25453 example illustrates the approach an author might use.
25455 This example comprises of three sections.
25458 class InlineFrameFilter():
25460 def __init__(self):
25461 self.name = "InlinedFrameFilter"
25462 self.priority = 100
25463 self.enabled = True
25464 gdb.frame_filters[self.name] = self
25466 def filter(self, frame_iter):
25467 return ElidingInlineIterator(frame_iter)
25470 This frame filter is very similar to the other examples. The only
25471 difference is this frame filter is wrapping the iterator provided to
25472 it (@code{frame_iter}) with a custom iterator called
25473 @code{ElidingInlineIterator}. This again defers actions to when
25474 @value{GDBN} prints the backtrace, as the iterator is not traversed
25477 The iterator for this example is as follows. It is in this section of
25478 the example where decisions are made on the content of the backtrace.
25481 class ElidingInlineIterator:
25482 def __init__(self, ii):
25483 self.input_iterator = ii
25485 def __iter__(self):
25489 frame = next(self.input_iterator)
25491 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25495 eliding_frame = next(self.input_iterator)
25496 except StopIteration:
25498 return ElidingFrameDecorator(eliding_frame, [frame])
25501 This iterator implements the Python iterator protocol. When the
25502 @code{next} function is called (when @value{GDBN} prints each frame),
25503 the iterator checks if this frame decorator, @code{frame}, is wrapping
25504 an inlined frame. If it is not, it returns the existing frame decorator
25505 untouched. If it is wrapping an inlined frame, it assumes that the
25506 inlined frame was contained within the next oldest frame,
25507 @code{eliding_frame}, which it fetches. It then creates and returns a
25508 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25509 elided frame, and the eliding frame.
25512 class ElidingInlineDecorator(FrameDecorator):
25514 def __init__(self, frame, elided_frames):
25515 super(ElidingInlineDecorator, self).__init__(frame)
25517 self.elided_frames = elided_frames
25520 return iter(self.elided_frames)
25523 This frame decorator overrides one function and returns the inlined
25524 frame in the @code{elided} method. As before it lets
25525 @code{FrameDecorator} do the rest of the work involved in printing
25526 this frame. This produces the following output.
25529 #0 0x004004e0 in bar () at inline.c:11
25530 #2 0x00400529 in main () at inline.c:25
25531 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25534 In that output, @code{max} which has been inlined into @code{main} is
25535 printed hierarchically. Another approach would be to combine the
25536 @code{function} method, and the @code{elided} method to both print a
25537 marker in the inlined frame, and also show the hierarchical
25540 @node Inferiors In Python
25541 @subsubsection Inferiors In Python
25542 @cindex inferiors in Python
25544 @findex gdb.Inferior
25545 Programs which are being run under @value{GDBN} are called inferiors
25546 (@pxref{Inferiors and Programs}). Python scripts can access
25547 information about and manipulate inferiors controlled by @value{GDBN}
25548 via objects of the @code{gdb.Inferior} class.
25550 The following inferior-related functions are available in the @code{gdb}
25553 @defun gdb.inferiors ()
25554 Return a tuple containing all inferior objects.
25557 @defun gdb.selected_inferior ()
25558 Return an object representing the current inferior.
25561 A @code{gdb.Inferior} object has the following attributes:
25563 @defvar Inferior.num
25564 ID of inferior, as assigned by GDB.
25567 @defvar Inferior.pid
25568 Process ID of the inferior, as assigned by the underlying operating
25572 @defvar Inferior.was_attached
25573 Boolean signaling whether the inferior was created using `attach', or
25574 started by @value{GDBN} itself.
25577 A @code{gdb.Inferior} object has the following methods:
25579 @defun Inferior.is_valid ()
25580 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25581 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25582 if the inferior no longer exists within @value{GDBN}. All other
25583 @code{gdb.Inferior} methods will throw an exception if it is invalid
25584 at the time the method is called.
25587 @defun Inferior.threads ()
25588 This method returns a tuple holding all the threads which are valid
25589 when it is called. If there are no valid threads, the method will
25590 return an empty tuple.
25593 @findex Inferior.read_memory
25594 @defun Inferior.read_memory (address, length)
25595 Read @var{length} bytes of memory from the inferior, starting at
25596 @var{address}. Returns a buffer object, which behaves much like an array
25597 or a string. It can be modified and given to the
25598 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25599 value is a @code{memoryview} object.
25602 @findex Inferior.write_memory
25603 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25604 Write the contents of @var{buffer} to the inferior, starting at
25605 @var{address}. The @var{buffer} parameter must be a Python object
25606 which supports the buffer protocol, i.e., a string, an array or the
25607 object returned from @code{Inferior.read_memory}. If given, @var{length}
25608 determines the number of bytes from @var{buffer} to be written.
25611 @findex gdb.search_memory
25612 @defun Inferior.search_memory (address, length, pattern)
25613 Search a region of the inferior memory starting at @var{address} with
25614 the given @var{length} using the search pattern supplied in
25615 @var{pattern}. The @var{pattern} parameter must be a Python object
25616 which supports the buffer protocol, i.e., a string, an array or the
25617 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25618 containing the address where the pattern was found, or @code{None} if
25619 the pattern could not be found.
25622 @node Events In Python
25623 @subsubsection Events In Python
25624 @cindex inferior events in Python
25626 @value{GDBN} provides a general event facility so that Python code can be
25627 notified of various state changes, particularly changes that occur in
25630 An @dfn{event} is just an object that describes some state change. The
25631 type of the object and its attributes will vary depending on the details
25632 of the change. All the existing events are described below.
25634 In order to be notified of an event, you must register an event handler
25635 with an @dfn{event registry}. An event registry is an object in the
25636 @code{gdb.events} module which dispatches particular events. A registry
25637 provides methods to register and unregister event handlers:
25639 @defun EventRegistry.connect (object)
25640 Add the given callable @var{object} to the registry. This object will be
25641 called when an event corresponding to this registry occurs.
25644 @defun EventRegistry.disconnect (object)
25645 Remove the given @var{object} from the registry. Once removed, the object
25646 will no longer receive notifications of events.
25649 Here is an example:
25652 def exit_handler (event):
25653 print "event type: exit"
25654 print "exit code: %d" % (event.exit_code)
25656 gdb.events.exited.connect (exit_handler)
25659 In the above example we connect our handler @code{exit_handler} to the
25660 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25661 called when the inferior exits. The argument @dfn{event} in this example is
25662 of type @code{gdb.ExitedEvent}. As you can see in the example the
25663 @code{ExitedEvent} object has an attribute which indicates the exit code of
25666 The following is a listing of the event registries that are available and
25667 details of the events they emit:
25672 Emits @code{gdb.ThreadEvent}.
25674 Some events can be thread specific when @value{GDBN} is running in non-stop
25675 mode. When represented in Python, these events all extend
25676 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25677 events which are emitted by this or other modules might extend this event.
25678 Examples of these events are @code{gdb.BreakpointEvent} and
25679 @code{gdb.ContinueEvent}.
25681 @defvar ThreadEvent.inferior_thread
25682 In non-stop mode this attribute will be set to the specific thread which was
25683 involved in the emitted event. Otherwise, it will be set to @code{None}.
25686 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25688 This event indicates that the inferior has been continued after a stop. For
25689 inherited attribute refer to @code{gdb.ThreadEvent} above.
25691 @item events.exited
25692 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25693 @code{events.ExitedEvent} has two attributes:
25694 @defvar ExitedEvent.exit_code
25695 An integer representing the exit code, if available, which the inferior
25696 has returned. (The exit code could be unavailable if, for example,
25697 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25698 the attribute does not exist.
25700 @defvar ExitedEvent inferior
25701 A reference to the inferior which triggered the @code{exited} event.
25705 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25707 Indicates that the inferior has stopped. All events emitted by this registry
25708 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25709 will indicate the stopped thread when @value{GDBN} is running in non-stop
25710 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25712 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25714 This event indicates that the inferior or one of its threads has received as
25715 signal. @code{gdb.SignalEvent} has the following attributes:
25717 @defvar SignalEvent.stop_signal
25718 A string representing the signal received by the inferior. A list of possible
25719 signal values can be obtained by running the command @code{info signals} in
25720 the @value{GDBN} command prompt.
25723 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25725 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25726 been hit, and has the following attributes:
25728 @defvar BreakpointEvent.breakpoints
25729 A sequence containing references to all the breakpoints (type
25730 @code{gdb.Breakpoint}) that were hit.
25731 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25733 @defvar BreakpointEvent.breakpoint
25734 A reference to the first breakpoint that was hit.
25735 This function is maintained for backward compatibility and is now deprecated
25736 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25739 @item events.new_objfile
25740 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25741 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25743 @defvar NewObjFileEvent.new_objfile
25744 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25745 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25750 @node Threads In Python
25751 @subsubsection Threads In Python
25752 @cindex threads in python
25754 @findex gdb.InferiorThread
25755 Python scripts can access information about, and manipulate inferior threads
25756 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25758 The following thread-related functions are available in the @code{gdb}
25761 @findex gdb.selected_thread
25762 @defun gdb.selected_thread ()
25763 This function returns the thread object for the selected thread. If there
25764 is no selected thread, this will return @code{None}.
25767 A @code{gdb.InferiorThread} object has the following attributes:
25769 @defvar InferiorThread.name
25770 The name of the thread. If the user specified a name using
25771 @code{thread name}, then this returns that name. Otherwise, if an
25772 OS-supplied name is available, then it is returned. Otherwise, this
25773 returns @code{None}.
25775 This attribute can be assigned to. The new value must be a string
25776 object, which sets the new name, or @code{None}, which removes any
25777 user-specified thread name.
25780 @defvar InferiorThread.num
25781 ID of the thread, as assigned by GDB.
25784 @defvar InferiorThread.ptid
25785 ID of the thread, as assigned by the operating system. This attribute is a
25786 tuple containing three integers. The first is the Process ID (PID); the second
25787 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25788 Either the LWPID or TID may be 0, which indicates that the operating system
25789 does not use that identifier.
25792 A @code{gdb.InferiorThread} object has the following methods:
25794 @defun InferiorThread.is_valid ()
25795 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25796 @code{False} if not. A @code{gdb.InferiorThread} object will become
25797 invalid if the thread exits, or the inferior that the thread belongs
25798 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25799 exception if it is invalid at the time the method is called.
25802 @defun InferiorThread.switch ()
25803 This changes @value{GDBN}'s currently selected thread to the one represented
25807 @defun InferiorThread.is_stopped ()
25808 Return a Boolean indicating whether the thread is stopped.
25811 @defun InferiorThread.is_running ()
25812 Return a Boolean indicating whether the thread is running.
25815 @defun InferiorThread.is_exited ()
25816 Return a Boolean indicating whether the thread is exited.
25819 @node Commands In Python
25820 @subsubsection Commands In Python
25822 @cindex commands in python
25823 @cindex python commands
25824 You can implement new @value{GDBN} CLI commands in Python. A CLI
25825 command is implemented using an instance of the @code{gdb.Command}
25826 class, most commonly using a subclass.
25828 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25829 The object initializer for @code{Command} registers the new command
25830 with @value{GDBN}. This initializer is normally invoked from the
25831 subclass' own @code{__init__} method.
25833 @var{name} is the name of the command. If @var{name} consists of
25834 multiple words, then the initial words are looked for as prefix
25835 commands. In this case, if one of the prefix commands does not exist,
25836 an exception is raised.
25838 There is no support for multi-line commands.
25840 @var{command_class} should be one of the @samp{COMMAND_} constants
25841 defined below. This argument tells @value{GDBN} how to categorize the
25842 new command in the help system.
25844 @var{completer_class} is an optional argument. If given, it should be
25845 one of the @samp{COMPLETE_} constants defined below. This argument
25846 tells @value{GDBN} how to perform completion for this command. If not
25847 given, @value{GDBN} will attempt to complete using the object's
25848 @code{complete} method (see below); if no such method is found, an
25849 error will occur when completion is attempted.
25851 @var{prefix} is an optional argument. If @code{True}, then the new
25852 command is a prefix command; sub-commands of this command may be
25855 The help text for the new command is taken from the Python
25856 documentation string for the command's class, if there is one. If no
25857 documentation string is provided, the default value ``This command is
25858 not documented.'' is used.
25861 @cindex don't repeat Python command
25862 @defun Command.dont_repeat ()
25863 By default, a @value{GDBN} command is repeated when the user enters a
25864 blank line at the command prompt. A command can suppress this
25865 behavior by invoking the @code{dont_repeat} method. This is similar
25866 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25869 @defun Command.invoke (argument, from_tty)
25870 This method is called by @value{GDBN} when this command is invoked.
25872 @var{argument} is a string. It is the argument to the command, after
25873 leading and trailing whitespace has been stripped.
25875 @var{from_tty} is a boolean argument. When true, this means that the
25876 command was entered by the user at the terminal; when false it means
25877 that the command came from elsewhere.
25879 If this method throws an exception, it is turned into a @value{GDBN}
25880 @code{error} call. Otherwise, the return value is ignored.
25882 @findex gdb.string_to_argv
25883 To break @var{argument} up into an argv-like string use
25884 @code{gdb.string_to_argv}. This function behaves identically to
25885 @value{GDBN}'s internal argument lexer @code{buildargv}.
25886 It is recommended to use this for consistency.
25887 Arguments are separated by spaces and may be quoted.
25891 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25892 ['1', '2 "3', '4 "5', "6 '7"]
25897 @cindex completion of Python commands
25898 @defun Command.complete (text, word)
25899 This method is called by @value{GDBN} when the user attempts
25900 completion on this command. All forms of completion are handled by
25901 this method, that is, the @key{TAB} and @key{M-?} key bindings
25902 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25905 The arguments @var{text} and @var{word} are both strings. @var{text}
25906 holds the complete command line up to the cursor's location.
25907 @var{word} holds the last word of the command line; this is computed
25908 using a word-breaking heuristic.
25910 The @code{complete} method can return several values:
25913 If the return value is a sequence, the contents of the sequence are
25914 used as the completions. It is up to @code{complete} to ensure that the
25915 contents actually do complete the word. A zero-length sequence is
25916 allowed, it means that there were no completions available. Only
25917 string elements of the sequence are used; other elements in the
25918 sequence are ignored.
25921 If the return value is one of the @samp{COMPLETE_} constants defined
25922 below, then the corresponding @value{GDBN}-internal completion
25923 function is invoked, and its result is used.
25926 All other results are treated as though there were no available
25931 When a new command is registered, it must be declared as a member of
25932 some general class of commands. This is used to classify top-level
25933 commands in the on-line help system; note that prefix commands are not
25934 listed under their own category but rather that of their top-level
25935 command. The available classifications are represented by constants
25936 defined in the @code{gdb} module:
25939 @findex COMMAND_NONE
25940 @findex gdb.COMMAND_NONE
25941 @item gdb.COMMAND_NONE
25942 The command does not belong to any particular class. A command in
25943 this category will not be displayed in any of the help categories.
25945 @findex COMMAND_RUNNING
25946 @findex gdb.COMMAND_RUNNING
25947 @item gdb.COMMAND_RUNNING
25948 The command is related to running the inferior. For example,
25949 @code{start}, @code{step}, and @code{continue} are in this category.
25950 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
25951 commands in this category.
25953 @findex COMMAND_DATA
25954 @findex gdb.COMMAND_DATA
25955 @item gdb.COMMAND_DATA
25956 The command is related to data or variables. For example,
25957 @code{call}, @code{find}, and @code{print} are in this category. Type
25958 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
25961 @findex COMMAND_STACK
25962 @findex gdb.COMMAND_STACK
25963 @item gdb.COMMAND_STACK
25964 The command has to do with manipulation of the stack. For example,
25965 @code{backtrace}, @code{frame}, and @code{return} are in this
25966 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
25967 list of commands in this category.
25969 @findex COMMAND_FILES
25970 @findex gdb.COMMAND_FILES
25971 @item gdb.COMMAND_FILES
25972 This class is used for file-related commands. For example,
25973 @code{file}, @code{list} and @code{section} are in this category.
25974 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
25975 commands in this category.
25977 @findex COMMAND_SUPPORT
25978 @findex gdb.COMMAND_SUPPORT
25979 @item gdb.COMMAND_SUPPORT
25980 This should be used for ``support facilities'', generally meaning
25981 things that are useful to the user when interacting with @value{GDBN},
25982 but not related to the state of the inferior. For example,
25983 @code{help}, @code{make}, and @code{shell} are in this category. Type
25984 @kbd{help support} at the @value{GDBN} prompt to see a list of
25985 commands in this category.
25987 @findex COMMAND_STATUS
25988 @findex gdb.COMMAND_STATUS
25989 @item gdb.COMMAND_STATUS
25990 The command is an @samp{info}-related command, that is, related to the
25991 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
25992 and @code{show} are in this category. Type @kbd{help status} at the
25993 @value{GDBN} prompt to see a list of commands in this category.
25995 @findex COMMAND_BREAKPOINTS
25996 @findex gdb.COMMAND_BREAKPOINTS
25997 @item gdb.COMMAND_BREAKPOINTS
25998 The command has to do with breakpoints. For example, @code{break},
25999 @code{clear}, and @code{delete} are in this category. Type @kbd{help
26000 breakpoints} at the @value{GDBN} prompt to see a list of commands in
26003 @findex COMMAND_TRACEPOINTS
26004 @findex gdb.COMMAND_TRACEPOINTS
26005 @item gdb.COMMAND_TRACEPOINTS
26006 The command has to do with tracepoints. For example, @code{trace},
26007 @code{actions}, and @code{tfind} are in this category. Type
26008 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
26009 commands in this category.
26011 @findex COMMAND_USER
26012 @findex gdb.COMMAND_USER
26013 @item gdb.COMMAND_USER
26014 The command is a general purpose command for the user, and typically
26015 does not fit in one of the other categories.
26016 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
26017 a list of commands in this category, as well as the list of gdb macros
26018 (@pxref{Sequences}).
26020 @findex COMMAND_OBSCURE
26021 @findex gdb.COMMAND_OBSCURE
26022 @item gdb.COMMAND_OBSCURE
26023 The command is only used in unusual circumstances, or is not of
26024 general interest to users. For example, @code{checkpoint},
26025 @code{fork}, and @code{stop} are in this category. Type @kbd{help
26026 obscure} at the @value{GDBN} prompt to see a list of commands in this
26029 @findex COMMAND_MAINTENANCE
26030 @findex gdb.COMMAND_MAINTENANCE
26031 @item gdb.COMMAND_MAINTENANCE
26032 The command is only useful to @value{GDBN} maintainers. The
26033 @code{maintenance} and @code{flushregs} commands are in this category.
26034 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
26035 commands in this category.
26038 A new command can use a predefined completion function, either by
26039 specifying it via an argument at initialization, or by returning it
26040 from the @code{complete} method. These predefined completion
26041 constants are all defined in the @code{gdb} module:
26044 @findex COMPLETE_NONE
26045 @findex gdb.COMPLETE_NONE
26046 @item gdb.COMPLETE_NONE
26047 This constant means that no completion should be done.
26049 @findex COMPLETE_FILENAME
26050 @findex gdb.COMPLETE_FILENAME
26051 @item gdb.COMPLETE_FILENAME
26052 This constant means that filename completion should be performed.
26054 @findex COMPLETE_LOCATION
26055 @findex gdb.COMPLETE_LOCATION
26056 @item gdb.COMPLETE_LOCATION
26057 This constant means that location completion should be done.
26058 @xref{Specify Location}.
26060 @findex COMPLETE_COMMAND
26061 @findex gdb.COMPLETE_COMMAND
26062 @item gdb.COMPLETE_COMMAND
26063 This constant means that completion should examine @value{GDBN}
26066 @findex COMPLETE_SYMBOL
26067 @findex gdb.COMPLETE_SYMBOL
26068 @item gdb.COMPLETE_SYMBOL
26069 This constant means that completion should be done using symbol names
26072 @findex COMPLETE_EXPRESSION
26073 @findex gdb.COMPLETE_EXPRESSION
26074 @item gdb.COMPLETE_EXPRESSION
26075 This constant means that completion should be done on expressions.
26076 Often this means completing on symbol names, but some language
26077 parsers also have support for completing on field names.
26080 The following code snippet shows how a trivial CLI command can be
26081 implemented in Python:
26084 class HelloWorld (gdb.Command):
26085 """Greet the whole world."""
26087 def __init__ (self):
26088 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
26090 def invoke (self, arg, from_tty):
26091 print "Hello, World!"
26096 The last line instantiates the class, and is necessary to trigger the
26097 registration of the command with @value{GDBN}. Depending on how the
26098 Python code is read into @value{GDBN}, you may need to import the
26099 @code{gdb} module explicitly.
26101 @node Parameters In Python
26102 @subsubsection Parameters In Python
26104 @cindex parameters in python
26105 @cindex python parameters
26106 @tindex gdb.Parameter
26108 You can implement new @value{GDBN} parameters using Python. A new
26109 parameter is implemented as an instance of the @code{gdb.Parameter}
26112 Parameters are exposed to the user via the @code{set} and
26113 @code{show} commands. @xref{Help}.
26115 There are many parameters that already exist and can be set in
26116 @value{GDBN}. Two examples are: @code{set follow fork} and
26117 @code{set charset}. Setting these parameters influences certain
26118 behavior in @value{GDBN}. Similarly, you can define parameters that
26119 can be used to influence behavior in custom Python scripts and commands.
26121 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26122 The object initializer for @code{Parameter} registers the new
26123 parameter with @value{GDBN}. This initializer is normally invoked
26124 from the subclass' own @code{__init__} method.
26126 @var{name} is the name of the new parameter. If @var{name} consists
26127 of multiple words, then the initial words are looked for as prefix
26128 parameters. An example of this can be illustrated with the
26129 @code{set print} set of parameters. If @var{name} is
26130 @code{print foo}, then @code{print} will be searched as the prefix
26131 parameter. In this case the parameter can subsequently be accessed in
26132 @value{GDBN} as @code{set print foo}.
26134 If @var{name} consists of multiple words, and no prefix parameter group
26135 can be found, an exception is raised.
26137 @var{command-class} should be one of the @samp{COMMAND_} constants
26138 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26139 categorize the new parameter in the help system.
26141 @var{parameter-class} should be one of the @samp{PARAM_} constants
26142 defined below. This argument tells @value{GDBN} the type of the new
26143 parameter; this information is used for input validation and
26146 If @var{parameter-class} is @code{PARAM_ENUM}, then
26147 @var{enum-sequence} must be a sequence of strings. These strings
26148 represent the possible values for the parameter.
26150 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26151 of a fourth argument will cause an exception to be thrown.
26153 The help text for the new parameter is taken from the Python
26154 documentation string for the parameter's class, if there is one. If
26155 there is no documentation string, a default value is used.
26158 @defvar Parameter.set_doc
26159 If this attribute exists, and is a string, then its value is used as
26160 the help text for this parameter's @code{set} command. The value is
26161 examined when @code{Parameter.__init__} is invoked; subsequent changes
26165 @defvar Parameter.show_doc
26166 If this attribute exists, and is a string, then its value is used as
26167 the help text for this parameter's @code{show} command. The value is
26168 examined when @code{Parameter.__init__} is invoked; subsequent changes
26172 @defvar Parameter.value
26173 The @code{value} attribute holds the underlying value of the
26174 parameter. It can be read and assigned to just as any other
26175 attribute. @value{GDBN} does validation when assignments are made.
26178 There are two methods that should be implemented in any
26179 @code{Parameter} class. These are:
26181 @defun Parameter.get_set_string (self)
26182 @value{GDBN} will call this method when a @var{parameter}'s value has
26183 been changed via the @code{set} API (for example, @kbd{set foo off}).
26184 The @code{value} attribute has already been populated with the new
26185 value and may be used in output. This method must return a string.
26188 @defun Parameter.get_show_string (self, svalue)
26189 @value{GDBN} will call this method when a @var{parameter}'s
26190 @code{show} API has been invoked (for example, @kbd{show foo}). The
26191 argument @code{svalue} receives the string representation of the
26192 current value. This method must return a string.
26195 When a new parameter is defined, its type must be specified. The
26196 available types are represented by constants defined in the @code{gdb}
26200 @findex PARAM_BOOLEAN
26201 @findex gdb.PARAM_BOOLEAN
26202 @item gdb.PARAM_BOOLEAN
26203 The value is a plain boolean. The Python boolean values, @code{True}
26204 and @code{False} are the only valid values.
26206 @findex PARAM_AUTO_BOOLEAN
26207 @findex gdb.PARAM_AUTO_BOOLEAN
26208 @item gdb.PARAM_AUTO_BOOLEAN
26209 The value has three possible states: true, false, and @samp{auto}. In
26210 Python, true and false are represented using boolean constants, and
26211 @samp{auto} is represented using @code{None}.
26213 @findex PARAM_UINTEGER
26214 @findex gdb.PARAM_UINTEGER
26215 @item gdb.PARAM_UINTEGER
26216 The value is an unsigned integer. The value of 0 should be
26217 interpreted to mean ``unlimited''.
26219 @findex PARAM_INTEGER
26220 @findex gdb.PARAM_INTEGER
26221 @item gdb.PARAM_INTEGER
26222 The value is a signed integer. The value of 0 should be interpreted
26223 to mean ``unlimited''.
26225 @findex PARAM_STRING
26226 @findex gdb.PARAM_STRING
26227 @item gdb.PARAM_STRING
26228 The value is a string. When the user modifies the string, any escape
26229 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26230 translated into corresponding characters and encoded into the current
26233 @findex PARAM_STRING_NOESCAPE
26234 @findex gdb.PARAM_STRING_NOESCAPE
26235 @item gdb.PARAM_STRING_NOESCAPE
26236 The value is a string. When the user modifies the string, escapes are
26237 passed through untranslated.
26239 @findex PARAM_OPTIONAL_FILENAME
26240 @findex gdb.PARAM_OPTIONAL_FILENAME
26241 @item gdb.PARAM_OPTIONAL_FILENAME
26242 The value is a either a filename (a string), or @code{None}.
26244 @findex PARAM_FILENAME
26245 @findex gdb.PARAM_FILENAME
26246 @item gdb.PARAM_FILENAME
26247 The value is a filename. This is just like
26248 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26250 @findex PARAM_ZINTEGER
26251 @findex gdb.PARAM_ZINTEGER
26252 @item gdb.PARAM_ZINTEGER
26253 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26254 is interpreted as itself.
26257 @findex gdb.PARAM_ENUM
26258 @item gdb.PARAM_ENUM
26259 The value is a string, which must be one of a collection string
26260 constants provided when the parameter is created.
26263 @node Functions In Python
26264 @subsubsection Writing new convenience functions
26266 @cindex writing convenience functions
26267 @cindex convenience functions in python
26268 @cindex python convenience functions
26269 @tindex gdb.Function
26271 You can implement new convenience functions (@pxref{Convenience Vars})
26272 in Python. A convenience function is an instance of a subclass of the
26273 class @code{gdb.Function}.
26275 @defun Function.__init__ (name)
26276 The initializer for @code{Function} registers the new function with
26277 @value{GDBN}. The argument @var{name} is the name of the function,
26278 a string. The function will be visible to the user as a convenience
26279 variable of type @code{internal function}, whose name is the same as
26280 the given @var{name}.
26282 The documentation for the new function is taken from the documentation
26283 string for the new class.
26286 @defun Function.invoke (@var{*args})
26287 When a convenience function is evaluated, its arguments are converted
26288 to instances of @code{gdb.Value}, and then the function's
26289 @code{invoke} method is called. Note that @value{GDBN} does not
26290 predetermine the arity of convenience functions. Instead, all
26291 available arguments are passed to @code{invoke}, following the
26292 standard Python calling convention. In particular, a convenience
26293 function can have default values for parameters without ill effect.
26295 The return value of this method is used as its value in the enclosing
26296 expression. If an ordinary Python value is returned, it is converted
26297 to a @code{gdb.Value} following the usual rules.
26300 The following code snippet shows how a trivial convenience function can
26301 be implemented in Python:
26304 class Greet (gdb.Function):
26305 """Return string to greet someone.
26306 Takes a name as argument."""
26308 def __init__ (self):
26309 super (Greet, self).__init__ ("greet")
26311 def invoke (self, name):
26312 return "Hello, %s!" % name.string ()
26317 The last line instantiates the class, and is necessary to trigger the
26318 registration of the function with @value{GDBN}. Depending on how the
26319 Python code is read into @value{GDBN}, you may need to import the
26320 @code{gdb} module explicitly.
26322 Now you can use the function in an expression:
26325 (gdb) print $greet("Bob")
26329 @node Progspaces In Python
26330 @subsubsection Program Spaces In Python
26332 @cindex progspaces in python
26333 @tindex gdb.Progspace
26335 A program space, or @dfn{progspace}, represents a symbolic view
26336 of an address space.
26337 It consists of all of the objfiles of the program.
26338 @xref{Objfiles In Python}.
26339 @xref{Inferiors and Programs, program spaces}, for more details
26340 about program spaces.
26342 The following progspace-related functions are available in the
26345 @findex gdb.current_progspace
26346 @defun gdb.current_progspace ()
26347 This function returns the program space of the currently selected inferior.
26348 @xref{Inferiors and Programs}.
26351 @findex gdb.progspaces
26352 @defun gdb.progspaces ()
26353 Return a sequence of all the progspaces currently known to @value{GDBN}.
26356 Each progspace is represented by an instance of the @code{gdb.Progspace}
26359 @defvar Progspace.filename
26360 The file name of the progspace as a string.
26363 @defvar Progspace.pretty_printers
26364 The @code{pretty_printers} attribute is a list of functions. It is
26365 used to look up pretty-printers. A @code{Value} is passed to each
26366 function in order; if the function returns @code{None}, then the
26367 search continues. Otherwise, the return value should be an object
26368 which is used to format the value. @xref{Pretty Printing API}, for more
26372 @defvar Progspace.type_printers
26373 The @code{type_printers} attribute is a list of type printer objects.
26374 @xref{Type Printing API}, for more information.
26377 @defvar Progspace.frame_filters
26378 The @code{frame_filters} attribute is a dictionary of frame filter
26379 objects. @xref{Frame Filter API}, for more information.
26382 @node Objfiles In Python
26383 @subsubsection Objfiles In Python
26385 @cindex objfiles in python
26386 @tindex gdb.Objfile
26388 @value{GDBN} loads symbols for an inferior from various
26389 symbol-containing files (@pxref{Files}). These include the primary
26390 executable file, any shared libraries used by the inferior, and any
26391 separate debug info files (@pxref{Separate Debug Files}).
26392 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26394 The following objfile-related functions are available in the
26397 @findex gdb.current_objfile
26398 @defun gdb.current_objfile ()
26399 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26400 sets the ``current objfile'' to the corresponding objfile. This
26401 function returns the current objfile. If there is no current objfile,
26402 this function returns @code{None}.
26405 @findex gdb.objfiles
26406 @defun gdb.objfiles ()
26407 Return a sequence of all the objfiles current known to @value{GDBN}.
26408 @xref{Objfiles In Python}.
26411 Each objfile is represented by an instance of the @code{gdb.Objfile}
26414 @defvar Objfile.filename
26415 The file name of the objfile as a string.
26418 @defvar Objfile.pretty_printers
26419 The @code{pretty_printers} attribute is a list of functions. It is
26420 used to look up pretty-printers. A @code{Value} is passed to each
26421 function in order; if the function returns @code{None}, then the
26422 search continues. Otherwise, the return value should be an object
26423 which is used to format the value. @xref{Pretty Printing API}, for more
26427 @defvar Objfile.type_printers
26428 The @code{type_printers} attribute is a list of type printer objects.
26429 @xref{Type Printing API}, for more information.
26432 @defvar Objfile.frame_filters
26433 The @code{frame_filters} attribute is a dictionary of frame filter
26434 objects. @xref{Frame Filter API}, for more information.
26437 A @code{gdb.Objfile} object has the following methods:
26439 @defun Objfile.is_valid ()
26440 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26441 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26442 if the object file it refers to is not loaded in @value{GDBN} any
26443 longer. All other @code{gdb.Objfile} methods will throw an exception
26444 if it is invalid at the time the method is called.
26447 @node Frames In Python
26448 @subsubsection Accessing inferior stack frames from Python.
26450 @cindex frames in python
26451 When the debugged program stops, @value{GDBN} is able to analyze its call
26452 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26453 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26454 while its corresponding frame exists in the inferior's stack. If you try
26455 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26456 exception (@pxref{Exception Handling}).
26458 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26462 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26466 The following frame-related functions are available in the @code{gdb} module:
26468 @findex gdb.selected_frame
26469 @defun gdb.selected_frame ()
26470 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26473 @findex gdb.newest_frame
26474 @defun gdb.newest_frame ()
26475 Return the newest frame object for the selected thread.
26478 @defun gdb.frame_stop_reason_string (reason)
26479 Return a string explaining the reason why @value{GDBN} stopped unwinding
26480 frames, as expressed by the given @var{reason} code (an integer, see the
26481 @code{unwind_stop_reason} method further down in this section).
26484 A @code{gdb.Frame} object has the following methods:
26486 @defun Frame.is_valid ()
26487 Returns true if the @code{gdb.Frame} object is valid, false if not.
26488 A frame object can become invalid if the frame it refers to doesn't
26489 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26490 an exception if it is invalid at the time the method is called.
26493 @defun Frame.name ()
26494 Returns the function name of the frame, or @code{None} if it can't be
26498 @defun Frame.architecture ()
26499 Returns the @code{gdb.Architecture} object corresponding to the frame's
26500 architecture. @xref{Architectures In Python}.
26503 @defun Frame.type ()
26504 Returns the type of the frame. The value can be one of:
26506 @item gdb.NORMAL_FRAME
26507 An ordinary stack frame.
26509 @item gdb.DUMMY_FRAME
26510 A fake stack frame that was created by @value{GDBN} when performing an
26511 inferior function call.
26513 @item gdb.INLINE_FRAME
26514 A frame representing an inlined function. The function was inlined
26515 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26517 @item gdb.TAILCALL_FRAME
26518 A frame representing a tail call. @xref{Tail Call Frames}.
26520 @item gdb.SIGTRAMP_FRAME
26521 A signal trampoline frame. This is the frame created by the OS when
26522 it calls into a signal handler.
26524 @item gdb.ARCH_FRAME
26525 A fake stack frame representing a cross-architecture call.
26527 @item gdb.SENTINEL_FRAME
26528 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26533 @defun Frame.unwind_stop_reason ()
26534 Return an integer representing the reason why it's not possible to find
26535 more frames toward the outermost frame. Use
26536 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26537 function to a string. The value can be one of:
26540 @item gdb.FRAME_UNWIND_NO_REASON
26541 No particular reason (older frames should be available).
26543 @item gdb.FRAME_UNWIND_NULL_ID
26544 The previous frame's analyzer returns an invalid result.
26546 @item gdb.FRAME_UNWIND_OUTERMOST
26547 This frame is the outermost.
26549 @item gdb.FRAME_UNWIND_UNAVAILABLE
26550 Cannot unwind further, because that would require knowing the
26551 values of registers or memory that have not been collected.
26553 @item gdb.FRAME_UNWIND_INNER_ID
26554 This frame ID looks like it ought to belong to a NEXT frame,
26555 but we got it for a PREV frame. Normally, this is a sign of
26556 unwinder failure. It could also indicate stack corruption.
26558 @item gdb.FRAME_UNWIND_SAME_ID
26559 This frame has the same ID as the previous one. That means
26560 that unwinding further would almost certainly give us another
26561 frame with exactly the same ID, so break the chain. Normally,
26562 this is a sign of unwinder failure. It could also indicate
26565 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26566 The frame unwinder did not find any saved PC, but we needed
26567 one to unwind further.
26569 @item gdb.FRAME_UNWIND_FIRST_ERROR
26570 Any stop reason greater or equal to this value indicates some kind
26571 of error. This special value facilitates writing code that tests
26572 for errors in unwinding in a way that will work correctly even if
26573 the list of the other values is modified in future @value{GDBN}
26574 versions. Using it, you could write:
26576 reason = gdb.selected_frame().unwind_stop_reason ()
26577 reason_str = gdb.frame_stop_reason_string (reason)
26578 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26579 print "An error occured: %s" % reason_str
26586 Returns the frame's resume address.
26589 @defun Frame.block ()
26590 Return the frame's code block. @xref{Blocks In Python}.
26593 @defun Frame.function ()
26594 Return the symbol for the function corresponding to this frame.
26595 @xref{Symbols In Python}.
26598 @defun Frame.older ()
26599 Return the frame that called this frame.
26602 @defun Frame.newer ()
26603 Return the frame called by this frame.
26606 @defun Frame.find_sal ()
26607 Return the frame's symtab and line object.
26608 @xref{Symbol Tables In Python}.
26611 @defun Frame.read_var (variable @r{[}, block@r{]})
26612 Return the value of @var{variable} in this frame. If the optional
26613 argument @var{block} is provided, search for the variable from that
26614 block; otherwise start at the frame's current block (which is
26615 determined by the frame's current program counter). @var{variable}
26616 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26617 @code{gdb.Block} object.
26620 @defun Frame.select ()
26621 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26625 @node Blocks In Python
26626 @subsubsection Accessing blocks from Python.
26628 @cindex blocks in python
26631 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26632 roughly to a scope in the source code. Blocks are organized
26633 hierarchically, and are represented individually in Python as a
26634 @code{gdb.Block}. Blocks rely on debugging information being
26637 A frame has a block. Please see @ref{Frames In Python}, for a more
26638 in-depth discussion of frames.
26640 The outermost block is known as the @dfn{global block}. The global
26641 block typically holds public global variables and functions.
26643 The block nested just inside the global block is the @dfn{static
26644 block}. The static block typically holds file-scoped variables and
26647 @value{GDBN} provides a method to get a block's superblock, but there
26648 is currently no way to examine the sub-blocks of a block, or to
26649 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26652 Here is a short example that should help explain blocks:
26655 /* This is in the global block. */
26658 /* This is in the static block. */
26659 static int file_scope;
26661 /* 'function' is in the global block, and 'argument' is
26662 in a block nested inside of 'function'. */
26663 int function (int argument)
26665 /* 'local' is in a block inside 'function'. It may or may
26666 not be in the same block as 'argument'. */
26670 /* 'inner' is in a block whose superblock is the one holding
26674 /* If this call is expanded by the compiler, you may see
26675 a nested block here whose function is 'inline_function'
26676 and whose superblock is the one holding 'inner'. */
26677 inline_function ();
26682 A @code{gdb.Block} is iterable. The iterator returns the symbols
26683 (@pxref{Symbols In Python}) local to the block. Python programs
26684 should not assume that a specific block object will always contain a
26685 given symbol, since changes in @value{GDBN} features and
26686 infrastructure may cause symbols move across blocks in a symbol
26689 The following block-related functions are available in the @code{gdb}
26692 @findex gdb.block_for_pc
26693 @defun gdb.block_for_pc (pc)
26694 Return the innermost @code{gdb.Block} containing the given @var{pc}
26695 value. If the block cannot be found for the @var{pc} value specified,
26696 the function will return @code{None}.
26699 A @code{gdb.Block} object has the following methods:
26701 @defun Block.is_valid ()
26702 Returns @code{True} if the @code{gdb.Block} object is valid,
26703 @code{False} if not. A block object can become invalid if the block it
26704 refers to doesn't exist anymore in the inferior. All other
26705 @code{gdb.Block} methods will throw an exception if it is invalid at
26706 the time the method is called. The block's validity is also checked
26707 during iteration over symbols of the block.
26710 A @code{gdb.Block} object has the following attributes:
26712 @defvar Block.start
26713 The start address of the block. This attribute is not writable.
26717 The end address of the block. This attribute is not writable.
26720 @defvar Block.function
26721 The name of the block represented as a @code{gdb.Symbol}. If the
26722 block is not named, then this attribute holds @code{None}. This
26723 attribute is not writable.
26725 For ordinary function blocks, the superblock is the static block.
26726 However, you should note that it is possible for a function block to
26727 have a superblock that is not the static block -- for instance this
26728 happens for an inlined function.
26731 @defvar Block.superblock
26732 The block containing this block. If this parent block does not exist,
26733 this attribute holds @code{None}. This attribute is not writable.
26736 @defvar Block.global_block
26737 The global block associated with this block. This attribute is not
26741 @defvar Block.static_block
26742 The static block associated with this block. This attribute is not
26746 @defvar Block.is_global
26747 @code{True} if the @code{gdb.Block} object is a global block,
26748 @code{False} if not. This attribute is not
26752 @defvar Block.is_static
26753 @code{True} if the @code{gdb.Block} object is a static block,
26754 @code{False} if not. This attribute is not writable.
26757 @node Symbols In Python
26758 @subsubsection Python representation of Symbols.
26760 @cindex symbols in python
26763 @value{GDBN} represents every variable, function and type as an
26764 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26765 Similarly, Python represents these symbols in @value{GDBN} with the
26766 @code{gdb.Symbol} object.
26768 The following symbol-related functions are available in the @code{gdb}
26771 @findex gdb.lookup_symbol
26772 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26773 This function searches for a symbol by name. The search scope can be
26774 restricted to the parameters defined in the optional domain and block
26777 @var{name} is the name of the symbol. It must be a string. The
26778 optional @var{block} argument restricts the search to symbols visible
26779 in that @var{block}. The @var{block} argument must be a
26780 @code{gdb.Block} object. If omitted, the block for the current frame
26781 is used. The optional @var{domain} argument restricts
26782 the search to the domain type. The @var{domain} argument must be a
26783 domain constant defined in the @code{gdb} module and described later
26786 The result is a tuple of two elements.
26787 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26789 If the symbol is found, the second element is @code{True} if the symbol
26790 is a field of a method's object (e.g., @code{this} in C@t{++}),
26791 otherwise it is @code{False}.
26792 If the symbol is not found, the second element is @code{False}.
26795 @findex gdb.lookup_global_symbol
26796 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26797 This function searches for a global symbol by name.
26798 The search scope can be restricted to by the domain argument.
26800 @var{name} is the name of the symbol. It must be a string.
26801 The optional @var{domain} argument restricts the search to the domain type.
26802 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26803 module and described later in this chapter.
26805 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26809 A @code{gdb.Symbol} object has the following attributes:
26811 @defvar Symbol.type
26812 The type of the symbol or @code{None} if no type is recorded.
26813 This attribute is represented as a @code{gdb.Type} object.
26814 @xref{Types In Python}. This attribute is not writable.
26817 @defvar Symbol.symtab
26818 The symbol table in which the symbol appears. This attribute is
26819 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26820 Python}. This attribute is not writable.
26823 @defvar Symbol.line
26824 The line number in the source code at which the symbol was defined.
26825 This is an integer.
26828 @defvar Symbol.name
26829 The name of the symbol as a string. This attribute is not writable.
26832 @defvar Symbol.linkage_name
26833 The name of the symbol, as used by the linker (i.e., may be mangled).
26834 This attribute is not writable.
26837 @defvar Symbol.print_name
26838 The name of the symbol in a form suitable for output. This is either
26839 @code{name} or @code{linkage_name}, depending on whether the user
26840 asked @value{GDBN} to display demangled or mangled names.
26843 @defvar Symbol.addr_class
26844 The address class of the symbol. This classifies how to find the value
26845 of a symbol. Each address class is a constant defined in the
26846 @code{gdb} module and described later in this chapter.
26849 @defvar Symbol.needs_frame
26850 This is @code{True} if evaluating this symbol's value requires a frame
26851 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26852 local variables will require a frame, but other symbols will not.
26855 @defvar Symbol.is_argument
26856 @code{True} if the symbol is an argument of a function.
26859 @defvar Symbol.is_constant
26860 @code{True} if the symbol is a constant.
26863 @defvar Symbol.is_function
26864 @code{True} if the symbol is a function or a method.
26867 @defvar Symbol.is_variable
26868 @code{True} if the symbol is a variable.
26871 A @code{gdb.Symbol} object has the following methods:
26873 @defun Symbol.is_valid ()
26874 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26875 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26876 the symbol it refers to does not exist in @value{GDBN} any longer.
26877 All other @code{gdb.Symbol} methods will throw an exception if it is
26878 invalid at the time the method is called.
26881 @defun Symbol.value (@r{[}frame@r{]})
26882 Compute the value of the symbol, as a @code{gdb.Value}. For
26883 functions, this computes the address of the function, cast to the
26884 appropriate type. If the symbol requires a frame in order to compute
26885 its value, then @var{frame} must be given. If @var{frame} is not
26886 given, or if @var{frame} is invalid, then this method will throw an
26890 The available domain categories in @code{gdb.Symbol} are represented
26891 as constants in the @code{gdb} module:
26894 @findex SYMBOL_UNDEF_DOMAIN
26895 @findex gdb.SYMBOL_UNDEF_DOMAIN
26896 @item gdb.SYMBOL_UNDEF_DOMAIN
26897 This is used when a domain has not been discovered or none of the
26898 following domains apply. This usually indicates an error either
26899 in the symbol information or in @value{GDBN}'s handling of symbols.
26900 @findex SYMBOL_VAR_DOMAIN
26901 @findex gdb.SYMBOL_VAR_DOMAIN
26902 @item gdb.SYMBOL_VAR_DOMAIN
26903 This domain contains variables, function names, typedef names and enum
26905 @findex SYMBOL_STRUCT_DOMAIN
26906 @findex gdb.SYMBOL_STRUCT_DOMAIN
26907 @item gdb.SYMBOL_STRUCT_DOMAIN
26908 This domain holds struct, union and enum type names.
26909 @findex SYMBOL_LABEL_DOMAIN
26910 @findex gdb.SYMBOL_LABEL_DOMAIN
26911 @item gdb.SYMBOL_LABEL_DOMAIN
26912 This domain contains names of labels (for gotos).
26913 @findex SYMBOL_VARIABLES_DOMAIN
26914 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26915 @item gdb.SYMBOL_VARIABLES_DOMAIN
26916 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26917 contains everything minus functions and types.
26918 @findex SYMBOL_FUNCTIONS_DOMAIN
26919 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26920 @item gdb.SYMBOL_FUNCTION_DOMAIN
26921 This domain contains all functions.
26922 @findex SYMBOL_TYPES_DOMAIN
26923 @findex gdb.SYMBOL_TYPES_DOMAIN
26924 @item gdb.SYMBOL_TYPES_DOMAIN
26925 This domain contains all types.
26928 The available address class categories in @code{gdb.Symbol} are represented
26929 as constants in the @code{gdb} module:
26932 @findex SYMBOL_LOC_UNDEF
26933 @findex gdb.SYMBOL_LOC_UNDEF
26934 @item gdb.SYMBOL_LOC_UNDEF
26935 If this is returned by address class, it indicates an error either in
26936 the symbol information or in @value{GDBN}'s handling of symbols.
26937 @findex SYMBOL_LOC_CONST
26938 @findex gdb.SYMBOL_LOC_CONST
26939 @item gdb.SYMBOL_LOC_CONST
26940 Value is constant int.
26941 @findex SYMBOL_LOC_STATIC
26942 @findex gdb.SYMBOL_LOC_STATIC
26943 @item gdb.SYMBOL_LOC_STATIC
26944 Value is at a fixed address.
26945 @findex SYMBOL_LOC_REGISTER
26946 @findex gdb.SYMBOL_LOC_REGISTER
26947 @item gdb.SYMBOL_LOC_REGISTER
26948 Value is in a register.
26949 @findex SYMBOL_LOC_ARG
26950 @findex gdb.SYMBOL_LOC_ARG
26951 @item gdb.SYMBOL_LOC_ARG
26952 Value is an argument. This value is at the offset stored within the
26953 symbol inside the frame's argument list.
26954 @findex SYMBOL_LOC_REF_ARG
26955 @findex gdb.SYMBOL_LOC_REF_ARG
26956 @item gdb.SYMBOL_LOC_REF_ARG
26957 Value address is stored in the frame's argument list. Just like
26958 @code{LOC_ARG} except that the value's address is stored at the
26959 offset, not the value itself.
26960 @findex SYMBOL_LOC_REGPARM_ADDR
26961 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
26962 @item gdb.SYMBOL_LOC_REGPARM_ADDR
26963 Value is a specified register. Just like @code{LOC_REGISTER} except
26964 the register holds the address of the argument instead of the argument
26966 @findex SYMBOL_LOC_LOCAL
26967 @findex gdb.SYMBOL_LOC_LOCAL
26968 @item gdb.SYMBOL_LOC_LOCAL
26969 Value is a local variable.
26970 @findex SYMBOL_LOC_TYPEDEF
26971 @findex gdb.SYMBOL_LOC_TYPEDEF
26972 @item gdb.SYMBOL_LOC_TYPEDEF
26973 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
26975 @findex SYMBOL_LOC_BLOCK
26976 @findex gdb.SYMBOL_LOC_BLOCK
26977 @item gdb.SYMBOL_LOC_BLOCK
26979 @findex SYMBOL_LOC_CONST_BYTES
26980 @findex gdb.SYMBOL_LOC_CONST_BYTES
26981 @item gdb.SYMBOL_LOC_CONST_BYTES
26982 Value is a byte-sequence.
26983 @findex SYMBOL_LOC_UNRESOLVED
26984 @findex gdb.SYMBOL_LOC_UNRESOLVED
26985 @item gdb.SYMBOL_LOC_UNRESOLVED
26986 Value is at a fixed address, but the address of the variable has to be
26987 determined from the minimal symbol table whenever the variable is
26989 @findex SYMBOL_LOC_OPTIMIZED_OUT
26990 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
26991 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
26992 The value does not actually exist in the program.
26993 @findex SYMBOL_LOC_COMPUTED
26994 @findex gdb.SYMBOL_LOC_COMPUTED
26995 @item gdb.SYMBOL_LOC_COMPUTED
26996 The value's address is a computed location.
26999 @node Symbol Tables In Python
27000 @subsubsection Symbol table representation in Python.
27002 @cindex symbol tables in python
27004 @tindex gdb.Symtab_and_line
27006 Access to symbol table data maintained by @value{GDBN} on the inferior
27007 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
27008 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
27009 from the @code{find_sal} method in @code{gdb.Frame} object.
27010 @xref{Frames In Python}.
27012 For more information on @value{GDBN}'s symbol table management, see
27013 @ref{Symbols, ,Examining the Symbol Table}, for more information.
27015 A @code{gdb.Symtab_and_line} object has the following attributes:
27017 @defvar Symtab_and_line.symtab
27018 The symbol table object (@code{gdb.Symtab}) for this frame.
27019 This attribute is not writable.
27022 @defvar Symtab_and_line.pc
27023 Indicates the start of the address range occupied by code for the
27024 current source line. This attribute is not writable.
27027 @defvar Symtab_and_line.last
27028 Indicates the end of the address range occupied by code for the current
27029 source line. This attribute is not writable.
27032 @defvar Symtab_and_line.line
27033 Indicates the current line number for this object. This
27034 attribute is not writable.
27037 A @code{gdb.Symtab_and_line} object has the following methods:
27039 @defun Symtab_and_line.is_valid ()
27040 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
27041 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
27042 invalid if the Symbol table and line object it refers to does not
27043 exist in @value{GDBN} any longer. All other
27044 @code{gdb.Symtab_and_line} methods will throw an exception if it is
27045 invalid at the time the method is called.
27048 A @code{gdb.Symtab} object has the following attributes:
27050 @defvar Symtab.filename
27051 The symbol table's source filename. This attribute is not writable.
27054 @defvar Symtab.objfile
27055 The symbol table's backing object file. @xref{Objfiles In Python}.
27056 This attribute is not writable.
27059 A @code{gdb.Symtab} object has the following methods:
27061 @defun Symtab.is_valid ()
27062 Returns @code{True} if the @code{gdb.Symtab} object is valid,
27063 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
27064 the symbol table it refers to does not exist in @value{GDBN} any
27065 longer. All other @code{gdb.Symtab} methods will throw an exception
27066 if it is invalid at the time the method is called.
27069 @defun Symtab.fullname ()
27070 Return the symbol table's source absolute file name.
27073 @defun Symtab.global_block ()
27074 Return the global block of the underlying symbol table.
27075 @xref{Blocks In Python}.
27078 @defun Symtab.static_block ()
27079 Return the static block of the underlying symbol table.
27080 @xref{Blocks In Python}.
27083 @defun Symtab.linetable ()
27084 Return the line table associated with the symbol table.
27085 @xref{Line Tables In Python}.
27088 @node Line Tables In Python
27089 @subsubsection Manipulating line tables using Python
27091 @cindex line tables in python
27092 @tindex gdb.LineTable
27094 Python code can request and inspect line table information from a
27095 symbol table that is loaded in @value{GDBN}. A line table is a
27096 mapping of source lines to their executable locations in memory. To
27097 acquire the line table information for a particular symbol table, use
27098 the @code{linetable} function (@pxref{Symbol Tables In Python}).
27100 A @code{gdb.LineTable} is iterable. The iterator returns
27101 @code{LineTableEntry} objects that correspond to the source line and
27102 address for each line table entry. @code{LineTableEntry} objects have
27103 the following attributes:
27105 @defvar LineTableEntry.line
27106 The source line number for this line table entry. This number
27107 corresponds to the actual line of source. This attribute is not
27111 @defvar LineTableEntry.pc
27112 The address that is associated with the line table entry where the
27113 executable code for that source line resides in memory. This
27114 attribute is not writable.
27117 As there can be multiple addresses for a single source line, you may
27118 receive multiple @code{LineTableEntry} objects with matching
27119 @code{line} attributes, but with different @code{pc} attributes. The
27120 iterator is sorted in ascending @code{pc} order. Here is a small
27121 example illustrating iterating over a line table.
27124 symtab = gdb.selected_frame().find_sal().symtab
27125 linetable = symtab.linetable()
27126 for line in linetable:
27127 print "Line: "+str(line.line)+" Address: "+hex(line.pc)
27130 This will have the following output:
27133 Line: 33 Address: 0x4005c8L
27134 Line: 37 Address: 0x4005caL
27135 Line: 39 Address: 0x4005d2L
27136 Line: 40 Address: 0x4005f8L
27137 Line: 42 Address: 0x4005ffL
27138 Line: 44 Address: 0x400608L
27139 Line: 42 Address: 0x40060cL
27140 Line: 45 Address: 0x400615L
27143 In addition to being able to iterate over a @code{LineTable}, it also
27144 has the following direct access methods:
27146 @defun LineTable.line (line)
27147 Return a Python @code{Tuple} of @code{LineTableEntry} objects for any
27148 entries in the line table for the given @var{line}. @var{line} refers
27149 to the source code line. If there are no entries for that source code
27150 @var{line}, the Python @code{None} is returned.
27153 @defun LineTable.has_line (line)
27154 Return a Python @code{Boolean} indicating whether there is an entry in
27155 the line table for this source line. Return @code{True} if an entry
27156 is found, or @code{False} if not.
27159 @defun LineTable.source_lines ()
27160 Return a Python @code{List} of the source line numbers in the symbol
27161 table. Only lines with executable code locations are returned. The
27162 contents of the @code{List} will just be the source line entries
27163 represented as Python @code{Long} values.
27166 @node Breakpoints In Python
27167 @subsubsection Manipulating breakpoints using Python
27169 @cindex breakpoints in python
27170 @tindex gdb.Breakpoint
27172 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
27175 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
27176 Create a new breakpoint. @var{spec} is a string naming the location
27177 of the breakpoint, or an expression that defines a watchpoint. The
27178 contents can be any location recognized by the @code{break} command,
27179 or in the case of a watchpoint, by the @code{watch} command. The
27180 optional @var{type} denotes the breakpoint to create from the types
27181 defined later in this chapter. This argument can be either:
27182 @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
27183 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal}
27184 argument allows the breakpoint to become invisible to the user. The
27185 breakpoint will neither be reported when created, nor will it be
27186 listed in the output from @code{info breakpoints} (but will be listed
27187 with the @code{maint info breakpoints} command). The optional
27188 @var{temporary} argument makes the breakpoint a temporary breakpoint.
27189 Temporary breakpoints are deleted after they have been hit. Any
27190 further access to the Python breakpoint after it has been hit will
27191 result in a runtime error (as that breakpoint has now been
27192 automatically deleted). The optional @var{wp_class} argument defines
27193 the class of watchpoint to create, if @var{type} is
27194 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it
27195 is assumed to be a @code{gdb.WP_WRITE} class.
27198 @defun Breakpoint.stop (self)
27199 The @code{gdb.Breakpoint} class can be sub-classed and, in
27200 particular, you may choose to implement the @code{stop} method.
27201 If this method is defined in a sub-class of @code{gdb.Breakpoint},
27202 it will be called when the inferior reaches any location of a
27203 breakpoint which instantiates that sub-class. If the method returns
27204 @code{True}, the inferior will be stopped at the location of the
27205 breakpoint, otherwise the inferior will continue.
27207 If there are multiple breakpoints at the same location with a
27208 @code{stop} method, each one will be called regardless of the
27209 return status of the previous. This ensures that all @code{stop}
27210 methods have a chance to execute at that location. In this scenario
27211 if one of the methods returns @code{True} but the others return
27212 @code{False}, the inferior will still be stopped.
27214 You should not alter the execution state of the inferior (i.e.@:, step,
27215 next, etc.), alter the current frame context (i.e.@:, change the current
27216 active frame), or alter, add or delete any breakpoint. As a general
27217 rule, you should not alter any data within @value{GDBN} or the inferior
27220 Example @code{stop} implementation:
27223 class MyBreakpoint (gdb.Breakpoint):
27225 inf_val = gdb.parse_and_eval("foo")
27232 The available watchpoint types represented by constants are defined in the
27237 @findex gdb.WP_READ
27239 Read only watchpoint.
27242 @findex gdb.WP_WRITE
27244 Write only watchpoint.
27247 @findex gdb.WP_ACCESS
27248 @item gdb.WP_ACCESS
27249 Read/Write watchpoint.
27252 @defun Breakpoint.is_valid ()
27253 Return @code{True} if this @code{Breakpoint} object is valid,
27254 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27255 if the user deletes the breakpoint. In this case, the object still
27256 exists, but the underlying breakpoint does not. In the cases of
27257 watchpoint scope, the watchpoint remains valid even if execution of the
27258 inferior leaves the scope of that watchpoint.
27261 @defun Breakpoint.delete
27262 Permanently deletes the @value{GDBN} breakpoint. This also
27263 invalidates the Python @code{Breakpoint} object. Any further access
27264 to this object's attributes or methods will raise an error.
27267 @defvar Breakpoint.enabled
27268 This attribute is @code{True} if the breakpoint is enabled, and
27269 @code{False} otherwise. This attribute is writable.
27272 @defvar Breakpoint.silent
27273 This attribute is @code{True} if the breakpoint is silent, and
27274 @code{False} otherwise. This attribute is writable.
27276 Note that a breakpoint can also be silent if it has commands and the
27277 first command is @code{silent}. This is not reported by the
27278 @code{silent} attribute.
27281 @defvar Breakpoint.thread
27282 If the breakpoint is thread-specific, this attribute holds the thread
27283 id. If the breakpoint is not thread-specific, this attribute is
27284 @code{None}. This attribute is writable.
27287 @defvar Breakpoint.task
27288 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27289 id. If the breakpoint is not task-specific (or the underlying
27290 language is not Ada), this attribute is @code{None}. This attribute
27294 @defvar Breakpoint.ignore_count
27295 This attribute holds the ignore count for the breakpoint, an integer.
27296 This attribute is writable.
27299 @defvar Breakpoint.number
27300 This attribute holds the breakpoint's number --- the identifier used by
27301 the user to manipulate the breakpoint. This attribute is not writable.
27304 @defvar Breakpoint.type
27305 This attribute holds the breakpoint's type --- the identifier used to
27306 determine the actual breakpoint type or use-case. This attribute is not
27310 @defvar Breakpoint.visible
27311 This attribute tells whether the breakpoint is visible to the user
27312 when set, or when the @samp{info breakpoints} command is run. This
27313 attribute is not writable.
27316 @defvar Breakpoint.temporary
27317 This attribute indicates whether the breakpoint was created as a
27318 temporary breakpoint. Temporary breakpoints are automatically deleted
27319 after that breakpoint has been hit. Access to this attribute, and all
27320 other attributes and functions other than the @code{is_valid}
27321 function, will result in an error after the breakpoint has been hit
27322 (as it has been automatically deleted). This attribute is not
27326 The available types are represented by constants defined in the @code{gdb}
27330 @findex BP_BREAKPOINT
27331 @findex gdb.BP_BREAKPOINT
27332 @item gdb.BP_BREAKPOINT
27333 Normal code breakpoint.
27335 @findex BP_WATCHPOINT
27336 @findex gdb.BP_WATCHPOINT
27337 @item gdb.BP_WATCHPOINT
27338 Watchpoint breakpoint.
27340 @findex BP_HARDWARE_WATCHPOINT
27341 @findex gdb.BP_HARDWARE_WATCHPOINT
27342 @item gdb.BP_HARDWARE_WATCHPOINT
27343 Hardware assisted watchpoint.
27345 @findex BP_READ_WATCHPOINT
27346 @findex gdb.BP_READ_WATCHPOINT
27347 @item gdb.BP_READ_WATCHPOINT
27348 Hardware assisted read watchpoint.
27350 @findex BP_ACCESS_WATCHPOINT
27351 @findex gdb.BP_ACCESS_WATCHPOINT
27352 @item gdb.BP_ACCESS_WATCHPOINT
27353 Hardware assisted access watchpoint.
27356 @defvar Breakpoint.hit_count
27357 This attribute holds the hit count for the breakpoint, an integer.
27358 This attribute is writable, but currently it can only be set to zero.
27361 @defvar Breakpoint.location
27362 This attribute holds the location of the breakpoint, as specified by
27363 the user. It is a string. If the breakpoint does not have a location
27364 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27365 attribute is not writable.
27368 @defvar Breakpoint.expression
27369 This attribute holds a breakpoint expression, as specified by
27370 the user. It is a string. If the breakpoint does not have an
27371 expression (the breakpoint is not a watchpoint) the attribute's value
27372 is @code{None}. This attribute is not writable.
27375 @defvar Breakpoint.condition
27376 This attribute holds the condition of the breakpoint, as specified by
27377 the user. It is a string. If there is no condition, this attribute's
27378 value is @code{None}. This attribute is writable.
27381 @defvar Breakpoint.commands
27382 This attribute holds the commands attached to the breakpoint. If
27383 there are commands, this attribute's value is a string holding all the
27384 commands, separated by newlines. If there are no commands, this
27385 attribute is @code{None}. This attribute is not writable.
27388 @node Finish Breakpoints in Python
27389 @subsubsection Finish Breakpoints
27391 @cindex python finish breakpoints
27392 @tindex gdb.FinishBreakpoint
27394 A finish breakpoint is a temporary breakpoint set at the return address of
27395 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27396 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27397 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27398 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27399 Finish breakpoints are thread specific and must be create with the right
27402 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27403 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27404 object @var{frame}. If @var{frame} is not provided, this defaults to the
27405 newest frame. The optional @var{internal} argument allows the breakpoint to
27406 become invisible to the user. @xref{Breakpoints In Python}, for further
27407 details about this argument.
27410 @defun FinishBreakpoint.out_of_scope (self)
27411 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27412 @code{return} command, @dots{}), a function may not properly terminate, and
27413 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27414 situation, the @code{out_of_scope} callback will be triggered.
27416 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27420 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27422 print "normal finish"
27425 def out_of_scope ():
27426 print "abnormal finish"
27430 @defvar FinishBreakpoint.return_value
27431 When @value{GDBN} is stopped at a finish breakpoint and the frame
27432 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27433 attribute will contain a @code{gdb.Value} object corresponding to the return
27434 value of the function. The value will be @code{None} if the function return
27435 type is @code{void} or if the return value was not computable. This attribute
27439 @node Lazy Strings In Python
27440 @subsubsection Python representation of lazy strings.
27442 @cindex lazy strings in python
27443 @tindex gdb.LazyString
27445 A @dfn{lazy string} is a string whose contents is not retrieved or
27446 encoded until it is needed.
27448 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27449 @code{address} that points to a region of memory, an @code{encoding}
27450 that will be used to encode that region of memory, and a @code{length}
27451 to delimit the region of memory that represents the string. The
27452 difference between a @code{gdb.LazyString} and a string wrapped within
27453 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27454 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27455 retrieved and encoded during printing, while a @code{gdb.Value}
27456 wrapping a string is immediately retrieved and encoded on creation.
27458 A @code{gdb.LazyString} object has the following functions:
27460 @defun LazyString.value ()
27461 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27462 will point to the string in memory, but will lose all the delayed
27463 retrieval, encoding and handling that @value{GDBN} applies to a
27464 @code{gdb.LazyString}.
27467 @defvar LazyString.address
27468 This attribute holds the address of the string. This attribute is not
27472 @defvar LazyString.length
27473 This attribute holds the length of the string in characters. If the
27474 length is -1, then the string will be fetched and encoded up to the
27475 first null of appropriate width. This attribute is not writable.
27478 @defvar LazyString.encoding
27479 This attribute holds the encoding that will be applied to the string
27480 when the string is printed by @value{GDBN}. If the encoding is not
27481 set, or contains an empty string, then @value{GDBN} will select the
27482 most appropriate encoding when the string is printed. This attribute
27486 @defvar LazyString.type
27487 This attribute holds the type that is represented by the lazy string's
27488 type. For a lazy string this will always be a pointer type. To
27489 resolve this to the lazy string's character type, use the type's
27490 @code{target} method. @xref{Types In Python}. This attribute is not
27494 @node Architectures In Python
27495 @subsubsection Python representation of architectures
27496 @cindex Python architectures
27498 @value{GDBN} uses architecture specific parameters and artifacts in a
27499 number of its various computations. An architecture is represented
27500 by an instance of the @code{gdb.Architecture} class.
27502 A @code{gdb.Architecture} class has the following methods:
27504 @defun Architecture.name ()
27505 Return the name (string value) of the architecture.
27508 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27509 Return a list of disassembled instructions starting from the memory
27510 address @var{start_pc}. The optional arguments @var{end_pc} and
27511 @var{count} determine the number of instructions in the returned list.
27512 If both the optional arguments @var{end_pc} and @var{count} are
27513 specified, then a list of at most @var{count} disassembled instructions
27514 whose start address falls in the closed memory address interval from
27515 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27516 specified, but @var{count} is specified, then @var{count} number of
27517 instructions starting from the address @var{start_pc} are returned. If
27518 @var{count} is not specified but @var{end_pc} is specified, then all
27519 instructions whose start address falls in the closed memory address
27520 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27521 @var{end_pc} nor @var{count} are specified, then a single instruction at
27522 @var{start_pc} is returned. For all of these cases, each element of the
27523 returned list is a Python @code{dict} with the following string keys:
27528 The value corresponding to this key is a Python long integer capturing
27529 the memory address of the instruction.
27532 The value corresponding to this key is a string value which represents
27533 the instruction with assembly language mnemonics. The assembly
27534 language flavor used is the same as that specified by the current CLI
27535 variable @code{disassembly-flavor}. @xref{Machine Code}.
27538 The value corresponding to this key is the length (integer value) of the
27539 instruction in bytes.
27544 @node Python Auto-loading
27545 @subsection Python Auto-loading
27546 @cindex Python auto-loading
27548 When a new object file is read (for example, due to the @code{file}
27549 command, or because the inferior has loaded a shared library),
27550 @value{GDBN} will look for Python support scripts in several ways:
27551 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
27552 and @code{.debug_gdb_scripts} section
27553 (@pxref{dotdebug_gdb_scripts section}).
27555 The auto-loading feature is useful for supplying application-specific
27556 debugging commands and scripts.
27558 Auto-loading can be enabled or disabled,
27559 and the list of auto-loaded scripts can be printed.
27562 @anchor{set auto-load python-scripts}
27563 @kindex set auto-load python-scripts
27564 @item set auto-load python-scripts [on|off]
27565 Enable or disable the auto-loading of Python scripts.
27567 @anchor{show auto-load python-scripts}
27568 @kindex show auto-load python-scripts
27569 @item show auto-load python-scripts
27570 Show whether auto-loading of Python scripts is enabled or disabled.
27572 @anchor{info auto-load python-scripts}
27573 @kindex info auto-load python-scripts
27574 @cindex print list of auto-loaded Python scripts
27575 @item info auto-load python-scripts [@var{regexp}]
27576 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27578 Also printed is the list of Python scripts that were mentioned in
27579 the @code{.debug_gdb_scripts} section and were not found
27580 (@pxref{dotdebug_gdb_scripts section}).
27581 This is useful because their names are not printed when @value{GDBN}
27582 tries to load them and fails. There may be many of them, and printing
27583 an error message for each one is problematic.
27585 If @var{regexp} is supplied only Python scripts with matching names are printed.
27590 (gdb) info auto-load python-scripts
27592 Yes py-section-script.py
27593 full name: /tmp/py-section-script.py
27594 No my-foo-pretty-printers.py
27598 When reading an auto-loaded file, @value{GDBN} sets the
27599 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27600 function (@pxref{Objfiles In Python}). This can be useful for
27601 registering objfile-specific pretty-printers and frame-filters.
27604 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
27605 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27606 * Which flavor to choose?::
27609 @node objfile-gdb.py file
27610 @subsubsection The @file{@var{objfile}-gdb.py} file
27611 @cindex @file{@var{objfile}-gdb.py}
27613 When a new object file is read, @value{GDBN} looks for
27614 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
27615 where @var{objfile} is the object file's real name, formed by ensuring
27616 that the file name is absolute, following all symlinks, and resolving
27617 @code{.} and @code{..} components. If this file exists and is
27618 readable, @value{GDBN} will evaluate it as a Python script.
27620 If this file does not exist, then @value{GDBN} will look for
27621 @var{script-name} file in all of the directories as specified below.
27623 Note that loading of this script file also requires accordingly configured
27624 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27626 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27627 scripts normally according to its @file{.exe} filename. But if no scripts are
27628 found @value{GDBN} also tries script filenames matching the object file without
27629 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27630 is attempted on any platform. This makes the script filenames compatible
27631 between Unix and MS-Windows hosts.
27634 @anchor{set auto-load scripts-directory}
27635 @kindex set auto-load scripts-directory
27636 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27637 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27638 may be delimited by the host platform path separator in use
27639 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27641 Each entry here needs to be covered also by the security setting
27642 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27644 @anchor{with-auto-load-dir}
27645 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27646 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27647 configuration option @option{--with-auto-load-dir}.
27649 Any reference to @file{$debugdir} will get replaced by
27650 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27651 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27652 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27653 @file{$datadir} must be placed as a directory component --- either alone or
27654 delimited by @file{/} or @file{\} directory separators, depending on the host
27657 The list of directories uses path separator (@samp{:} on GNU and Unix
27658 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27659 to the @env{PATH} environment variable.
27661 @anchor{show auto-load scripts-directory}
27662 @kindex show auto-load scripts-directory
27663 @item show auto-load scripts-directory
27664 Show @value{GDBN} auto-loaded scripts location.
27667 @value{GDBN} does not track which files it has already auto-loaded this way.
27668 @value{GDBN} will load the associated script every time the corresponding
27669 @var{objfile} is opened.
27670 So your @file{-gdb.py} file should be careful to avoid errors if it
27671 is evaluated more than once.
27673 @node dotdebug_gdb_scripts section
27674 @subsubsection The @code{.debug_gdb_scripts} section
27675 @cindex @code{.debug_gdb_scripts} section
27677 For systems using file formats like ELF and COFF,
27678 when @value{GDBN} loads a new object file
27679 it will look for a special section named @samp{.debug_gdb_scripts}.
27680 If this section exists, its contents is a list of names of scripts to load.
27682 @value{GDBN} will look for each specified script file first in the
27683 current directory and then along the source search path
27684 (@pxref{Source Path, ,Specifying Source Directories}),
27685 except that @file{$cdir} is not searched, since the compilation
27686 directory is not relevant to scripts.
27688 Entries can be placed in section @code{.debug_gdb_scripts} with,
27689 for example, this GCC macro:
27692 /* Note: The "MS" section flags are to remove duplicates. */
27693 #define DEFINE_GDB_SCRIPT(script_name) \
27695 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27697 .asciz \"" script_name "\"\n\
27703 Then one can reference the macro in a header or source file like this:
27706 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
27709 The script name may include directories if desired.
27711 Note that loading of this script file also requires accordingly configured
27712 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27714 If the macro is put in a header, any application or library
27715 using this header will get a reference to the specified script.
27717 @node Which flavor to choose?
27718 @subsubsection Which flavor to choose?
27720 Given the multiple ways of auto-loading Python scripts, it might not always
27721 be clear which one to choose. This section provides some guidance.
27723 Benefits of the @file{-gdb.py} way:
27727 Can be used with file formats that don't support multiple sections.
27730 Ease of finding scripts for public libraries.
27732 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27733 in the source search path.
27734 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27735 isn't a source directory in which to find the script.
27738 Doesn't require source code additions.
27741 Benefits of the @code{.debug_gdb_scripts} way:
27745 Works with static linking.
27747 Scripts for libraries done the @file{-gdb.py} way require an objfile to
27748 trigger their loading. When an application is statically linked the only
27749 objfile available is the executable, and it is cumbersome to attach all the
27750 scripts from all the input libraries to the executable's @file{-gdb.py} script.
27753 Works with classes that are entirely inlined.
27755 Some classes can be entirely inlined, and thus there may not be an associated
27756 shared library to attach a @file{-gdb.py} script to.
27759 Scripts needn't be copied out of the source tree.
27761 In some circumstances, apps can be built out of large collections of internal
27762 libraries, and the build infrastructure necessary to install the
27763 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
27764 cumbersome. It may be easier to specify the scripts in the
27765 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27766 top of the source tree to the source search path.
27769 @node Python modules
27770 @subsection Python modules
27771 @cindex python modules
27773 @value{GDBN} comes with several modules to assist writing Python code.
27776 * gdb.printing:: Building and registering pretty-printers.
27777 * gdb.types:: Utilities for working with types.
27778 * gdb.prompt:: Utilities for prompt value substitution.
27782 @subsubsection gdb.printing
27783 @cindex gdb.printing
27785 This module provides a collection of utilities for working with
27789 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27790 This class specifies the API that makes @samp{info pretty-printer},
27791 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27792 Pretty-printers should generally inherit from this class.
27794 @item SubPrettyPrinter (@var{name})
27795 For printers that handle multiple types, this class specifies the
27796 corresponding API for the subprinters.
27798 @item RegexpCollectionPrettyPrinter (@var{name})
27799 Utility class for handling multiple printers, all recognized via
27800 regular expressions.
27801 @xref{Writing a Pretty-Printer}, for an example.
27803 @item FlagEnumerationPrinter (@var{name})
27804 A pretty-printer which handles printing of @code{enum} values. Unlike
27805 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27806 work properly when there is some overlap between the enumeration
27807 constants. @var{name} is the name of the printer and also the name of
27808 the @code{enum} type to look up.
27810 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27811 Register @var{printer} with the pretty-printer list of @var{obj}.
27812 If @var{replace} is @code{True} then any existing copy of the printer
27813 is replaced. Otherwise a @code{RuntimeError} exception is raised
27814 if a printer with the same name already exists.
27818 @subsubsection gdb.types
27821 This module provides a collection of utilities for working with
27822 @code{gdb.Type} objects.
27825 @item get_basic_type (@var{type})
27826 Return @var{type} with const and volatile qualifiers stripped,
27827 and with typedefs and C@t{++} references converted to the underlying type.
27832 typedef const int const_int;
27834 const_int& foo_ref (foo);
27835 int main () @{ return 0; @}
27842 (gdb) python import gdb.types
27843 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27844 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27848 @item has_field (@var{type}, @var{field})
27849 Return @code{True} if @var{type}, assumed to be a type with fields
27850 (e.g., a structure or union), has field @var{field}.
27852 @item make_enum_dict (@var{enum_type})
27853 Return a Python @code{dictionary} type produced from @var{enum_type}.
27855 @item deep_items (@var{type})
27856 Returns a Python iterator similar to the standard
27857 @code{gdb.Type.iteritems} method, except that the iterator returned
27858 by @code{deep_items} will recursively traverse anonymous struct or
27859 union fields. For example:
27873 Then in @value{GDBN}:
27875 (@value{GDBP}) python import gdb.types
27876 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27877 (@value{GDBP}) python print struct_a.keys ()
27879 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27880 @{['a', 'b0', 'b1']@}
27883 @item get_type_recognizers ()
27884 Return a list of the enabled type recognizers for the current context.
27885 This is called by @value{GDBN} during the type-printing process
27886 (@pxref{Type Printing API}).
27888 @item apply_type_recognizers (recognizers, type_obj)
27889 Apply the type recognizers, @var{recognizers}, to the type object
27890 @var{type_obj}. If any recognizer returns a string, return that
27891 string. Otherwise, return @code{None}. This is called by
27892 @value{GDBN} during the type-printing process (@pxref{Type Printing
27895 @item register_type_printer (locus, printer)
27896 This is a convenience function to register a type printer.
27897 @var{printer} is the type printer to register. It must implement the
27898 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27899 which case the printer is registered with that objfile; a
27900 @code{gdb.Progspace}, in which case the printer is registered with
27901 that progspace; or @code{None}, in which case the printer is
27902 registered globally.
27905 This is a base class that implements the type printer protocol. Type
27906 printers are encouraged, but not required, to derive from this class.
27907 It defines a constructor:
27909 @defmethod TypePrinter __init__ (self, name)
27910 Initialize the type printer with the given name. The new printer
27911 starts in the enabled state.
27917 @subsubsection gdb.prompt
27920 This module provides a method for prompt value-substitution.
27923 @item substitute_prompt (@var{string})
27924 Return @var{string} with escape sequences substituted by values. Some
27925 escape sequences take arguments. You can specify arguments inside
27926 ``@{@}'' immediately following the escape sequence.
27928 The escape sequences you can pass to this function are:
27932 Substitute a backslash.
27934 Substitute an ESC character.
27936 Substitute the selected frame; an argument names a frame parameter.
27938 Substitute a newline.
27940 Substitute a parameter's value; the argument names the parameter.
27942 Substitute a carriage return.
27944 Substitute the selected thread; an argument names a thread parameter.
27946 Substitute the version of GDB.
27948 Substitute the current working directory.
27950 Begin a sequence of non-printing characters. These sequences are
27951 typically used with the ESC character, and are not counted in the string
27952 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27953 blue-colored ``(gdb)'' prompt where the length is five.
27955 End a sequence of non-printing characters.
27961 substitute_prompt (``frame: \f,
27962 print arguments: \p@{print frame-arguments@}'')
27965 @exdent will return the string:
27968 "frame: main, print arguments: scalars"
27973 @section Creating new spellings of existing commands
27974 @cindex aliases for commands
27976 It is often useful to define alternate spellings of existing commands.
27977 For example, if a new @value{GDBN} command defined in Python has
27978 a long name to type, it is handy to have an abbreviated version of it
27979 that involves less typing.
27981 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27982 of the @samp{step} command even though it is otherwise an ambiguous
27983 abbreviation of other commands like @samp{set} and @samp{show}.
27985 Aliases are also used to provide shortened or more common versions
27986 of multi-word commands. For example, @value{GDBN} provides the
27987 @samp{tty} alias of the @samp{set inferior-tty} command.
27989 You can define a new alias with the @samp{alias} command.
27994 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27998 @var{ALIAS} specifies the name of the new alias.
27999 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
28002 @var{COMMAND} specifies the name of an existing command
28003 that is being aliased.
28005 The @samp{-a} option specifies that the new alias is an abbreviation
28006 of the command. Abbreviations are not shown in command
28007 lists displayed by the @samp{help} command.
28009 The @samp{--} option specifies the end of options,
28010 and is useful when @var{ALIAS} begins with a dash.
28012 Here is a simple example showing how to make an abbreviation
28013 of a command so that there is less to type.
28014 Suppose you were tired of typing @samp{disas}, the current
28015 shortest unambiguous abbreviation of the @samp{disassemble} command
28016 and you wanted an even shorter version named @samp{di}.
28017 The following will accomplish this.
28020 (gdb) alias -a di = disas
28023 Note that aliases are different from user-defined commands.
28024 With a user-defined command, you also need to write documentation
28025 for it with the @samp{document} command.
28026 An alias automatically picks up the documentation of the existing command.
28028 Here is an example where we make @samp{elms} an abbreviation of
28029 @samp{elements} in the @samp{set print elements} command.
28030 This is to show that you can make an abbreviation of any part
28034 (gdb) alias -a set print elms = set print elements
28035 (gdb) alias -a show print elms = show print elements
28036 (gdb) set p elms 20
28038 Limit on string chars or array elements to print is 200.
28041 Note that if you are defining an alias of a @samp{set} command,
28042 and you want to have an alias for the corresponding @samp{show}
28043 command, then you need to define the latter separately.
28045 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
28046 @var{ALIAS}, just as they are normally.
28049 (gdb) alias -a set pr elms = set p ele
28052 Finally, here is an example showing the creation of a one word
28053 alias for a more complex command.
28054 This creates alias @samp{spe} of the command @samp{set print elements}.
28057 (gdb) alias spe = set print elements
28062 @chapter Command Interpreters
28063 @cindex command interpreters
28065 @value{GDBN} supports multiple command interpreters, and some command
28066 infrastructure to allow users or user interface writers to switch
28067 between interpreters or run commands in other interpreters.
28069 @value{GDBN} currently supports two command interpreters, the console
28070 interpreter (sometimes called the command-line interpreter or @sc{cli})
28071 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28072 describes both of these interfaces in great detail.
28074 By default, @value{GDBN} will start with the console interpreter.
28075 However, the user may choose to start @value{GDBN} with another
28076 interpreter by specifying the @option{-i} or @option{--interpreter}
28077 startup options. Defined interpreters include:
28081 @cindex console interpreter
28082 The traditional console or command-line interpreter. This is the most often
28083 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28084 @value{GDBN} will use this interpreter.
28087 @cindex mi interpreter
28088 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
28089 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28090 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28094 @cindex mi2 interpreter
28095 The current @sc{gdb/mi} interface.
28098 @cindex mi1 interpreter
28099 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
28103 @cindex invoke another interpreter
28104 The interpreter being used by @value{GDBN} may not be dynamically
28105 switched at runtime. Although possible, this could lead to a very
28106 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
28107 enters the command "interpreter-set console" in a console view,
28108 @value{GDBN} would switch to using the console interpreter, rendering
28109 the IDE inoperable!
28111 @kindex interpreter-exec
28112 Although you may only choose a single interpreter at startup, you may execute
28113 commands in any interpreter from the current interpreter using the appropriate
28114 command. If you are running the console interpreter, simply use the
28115 @code{interpreter-exec} command:
28118 interpreter-exec mi "-data-list-register-names"
28121 @sc{gdb/mi} has a similar command, although it is only available in versions of
28122 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28125 @chapter @value{GDBN} Text User Interface
28127 @cindex Text User Interface
28130 * TUI Overview:: TUI overview
28131 * TUI Keys:: TUI key bindings
28132 * TUI Single Key Mode:: TUI single key mode
28133 * TUI Commands:: TUI-specific commands
28134 * TUI Configuration:: TUI configuration variables
28137 The @value{GDBN} Text User Interface (TUI) is a terminal
28138 interface which uses the @code{curses} library to show the source
28139 file, the assembly output, the program registers and @value{GDBN}
28140 commands in separate text windows. The TUI mode is supported only
28141 on platforms where a suitable version of the @code{curses} library
28144 The TUI mode is enabled by default when you invoke @value{GDBN} as
28145 @samp{@value{GDBP} -tui}.
28146 You can also switch in and out of TUI mode while @value{GDBN} runs by
28147 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
28148 @xref{TUI Keys, ,TUI Key Bindings}.
28151 @section TUI Overview
28153 In TUI mode, @value{GDBN} can display several text windows:
28157 This window is the @value{GDBN} command window with the @value{GDBN}
28158 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28159 managed using readline.
28162 The source window shows the source file of the program. The current
28163 line and active breakpoints are displayed in this window.
28166 The assembly window shows the disassembly output of the program.
28169 This window shows the processor registers. Registers are highlighted
28170 when their values change.
28173 The source and assembly windows show the current program position
28174 by highlighting the current line and marking it with a @samp{>} marker.
28175 Breakpoints are indicated with two markers. The first marker
28176 indicates the breakpoint type:
28180 Breakpoint which was hit at least once.
28183 Breakpoint which was never hit.
28186 Hardware breakpoint which was hit at least once.
28189 Hardware breakpoint which was never hit.
28192 The second marker indicates whether the breakpoint is enabled or not:
28196 Breakpoint is enabled.
28199 Breakpoint is disabled.
28202 The source, assembly and register windows are updated when the current
28203 thread changes, when the frame changes, or when the program counter
28206 These windows are not all visible at the same time. The command
28207 window is always visible. The others can be arranged in several
28218 source and assembly,
28221 source and registers, or
28224 assembly and registers.
28227 A status line above the command window shows the following information:
28231 Indicates the current @value{GDBN} target.
28232 (@pxref{Targets, ,Specifying a Debugging Target}).
28235 Gives the current process or thread number.
28236 When no process is being debugged, this field is set to @code{No process}.
28239 Gives the current function name for the selected frame.
28240 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28241 When there is no symbol corresponding to the current program counter,
28242 the string @code{??} is displayed.
28245 Indicates the current line number for the selected frame.
28246 When the current line number is not known, the string @code{??} is displayed.
28249 Indicates the current program counter address.
28253 @section TUI Key Bindings
28254 @cindex TUI key bindings
28256 The TUI installs several key bindings in the readline keymaps
28257 @ifset SYSTEM_READLINE
28258 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28260 @ifclear SYSTEM_READLINE
28261 (@pxref{Command Line Editing}).
28263 The following key bindings are installed for both TUI mode and the
28264 @value{GDBN} standard mode.
28273 Enter or leave the TUI mode. When leaving the TUI mode,
28274 the curses window management stops and @value{GDBN} operates using
28275 its standard mode, writing on the terminal directly. When reentering
28276 the TUI mode, control is given back to the curses windows.
28277 The screen is then refreshed.
28281 Use a TUI layout with only one window. The layout will
28282 either be @samp{source} or @samp{assembly}. When the TUI mode
28283 is not active, it will switch to the TUI mode.
28285 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28289 Use a TUI layout with at least two windows. When the current
28290 layout already has two windows, the next layout with two windows is used.
28291 When a new layout is chosen, one window will always be common to the
28292 previous layout and the new one.
28294 Think of it as the Emacs @kbd{C-x 2} binding.
28298 Change the active window. The TUI associates several key bindings
28299 (like scrolling and arrow keys) with the active window. This command
28300 gives the focus to the next TUI window.
28302 Think of it as the Emacs @kbd{C-x o} binding.
28306 Switch in and out of the TUI SingleKey mode that binds single
28307 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28310 The following key bindings only work in the TUI mode:
28315 Scroll the active window one page up.
28319 Scroll the active window one page down.
28323 Scroll the active window one line up.
28327 Scroll the active window one line down.
28331 Scroll the active window one column left.
28335 Scroll the active window one column right.
28339 Refresh the screen.
28342 Because the arrow keys scroll the active window in the TUI mode, they
28343 are not available for their normal use by readline unless the command
28344 window has the focus. When another window is active, you must use
28345 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28346 and @kbd{C-f} to control the command window.
28348 @node TUI Single Key Mode
28349 @section TUI Single Key Mode
28350 @cindex TUI single key mode
28352 The TUI also provides a @dfn{SingleKey} mode, which binds several
28353 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28354 switch into this mode, where the following key bindings are used:
28357 @kindex c @r{(SingleKey TUI key)}
28361 @kindex d @r{(SingleKey TUI key)}
28365 @kindex f @r{(SingleKey TUI key)}
28369 @kindex n @r{(SingleKey TUI key)}
28373 @kindex q @r{(SingleKey TUI key)}
28375 exit the SingleKey mode.
28377 @kindex r @r{(SingleKey TUI key)}
28381 @kindex s @r{(SingleKey TUI key)}
28385 @kindex u @r{(SingleKey TUI key)}
28389 @kindex v @r{(SingleKey TUI key)}
28393 @kindex w @r{(SingleKey TUI key)}
28398 Other keys temporarily switch to the @value{GDBN} command prompt.
28399 The key that was pressed is inserted in the editing buffer so that
28400 it is possible to type most @value{GDBN} commands without interaction
28401 with the TUI SingleKey mode. Once the command is entered the TUI
28402 SingleKey mode is restored. The only way to permanently leave
28403 this mode is by typing @kbd{q} or @kbd{C-x s}.
28407 @section TUI-specific Commands
28408 @cindex TUI commands
28410 The TUI has specific commands to control the text windows.
28411 These commands are always available, even when @value{GDBN} is not in
28412 the TUI mode. When @value{GDBN} is in the standard mode, most
28413 of these commands will automatically switch to the TUI mode.
28415 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28416 terminal, or @value{GDBN} has been started with the machine interface
28417 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28418 these commands will fail with an error, because it would not be
28419 possible or desirable to enable curses window management.
28424 List and give the size of all displayed windows.
28428 Display the next layout.
28431 Display the previous layout.
28434 Display the source window only.
28437 Display the assembly window only.
28440 Display the source and assembly window.
28443 Display the register window together with the source or assembly window.
28447 Make the next window active for scrolling.
28450 Make the previous window active for scrolling.
28453 Make the source window active for scrolling.
28456 Make the assembly window active for scrolling.
28459 Make the register window active for scrolling.
28462 Make the command window active for scrolling.
28466 Refresh the screen. This is similar to typing @kbd{C-L}.
28468 @item tui reg float
28470 Show the floating point registers in the register window.
28472 @item tui reg general
28473 Show the general registers in the register window.
28476 Show the next register group. The list of register groups as well as
28477 their order is target specific. The predefined register groups are the
28478 following: @code{general}, @code{float}, @code{system}, @code{vector},
28479 @code{all}, @code{save}, @code{restore}.
28481 @item tui reg system
28482 Show the system registers in the register window.
28486 Update the source window and the current execution point.
28488 @item winheight @var{name} +@var{count}
28489 @itemx winheight @var{name} -@var{count}
28491 Change the height of the window @var{name} by @var{count}
28492 lines. Positive counts increase the height, while negative counts
28495 @item tabset @var{nchars}
28497 Set the width of tab stops to be @var{nchars} characters.
28500 @node TUI Configuration
28501 @section TUI Configuration Variables
28502 @cindex TUI configuration variables
28504 Several configuration variables control the appearance of TUI windows.
28507 @item set tui border-kind @var{kind}
28508 @kindex set tui border-kind
28509 Select the border appearance for the source, assembly and register windows.
28510 The possible values are the following:
28513 Use a space character to draw the border.
28516 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28519 Use the Alternate Character Set to draw the border. The border is
28520 drawn using character line graphics if the terminal supports them.
28523 @item set tui border-mode @var{mode}
28524 @kindex set tui border-mode
28525 @itemx set tui active-border-mode @var{mode}
28526 @kindex set tui active-border-mode
28527 Select the display attributes for the borders of the inactive windows
28528 or the active window. The @var{mode} can be one of the following:
28531 Use normal attributes to display the border.
28537 Use reverse video mode.
28540 Use half bright mode.
28542 @item half-standout
28543 Use half bright and standout mode.
28546 Use extra bright or bold mode.
28548 @item bold-standout
28549 Use extra bright or bold and standout mode.
28554 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28557 @cindex @sc{gnu} Emacs
28558 A special interface allows you to use @sc{gnu} Emacs to view (and
28559 edit) the source files for the program you are debugging with
28562 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28563 executable file you want to debug as an argument. This command starts
28564 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28565 created Emacs buffer.
28566 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28568 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28573 All ``terminal'' input and output goes through an Emacs buffer, called
28576 This applies both to @value{GDBN} commands and their output, and to the input
28577 and output done by the program you are debugging.
28579 This is useful because it means that you can copy the text of previous
28580 commands and input them again; you can even use parts of the output
28583 All the facilities of Emacs' Shell mode are available for interacting
28584 with your program. In particular, you can send signals the usual
28585 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28589 @value{GDBN} displays source code through Emacs.
28591 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28592 source file for that frame and puts an arrow (@samp{=>}) at the
28593 left margin of the current line. Emacs uses a separate buffer for
28594 source display, and splits the screen to show both your @value{GDBN} session
28597 Explicit @value{GDBN} @code{list} or search commands still produce output as
28598 usual, but you probably have no reason to use them from Emacs.
28601 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28602 a graphical mode, enabled by default, which provides further buffers
28603 that can control the execution and describe the state of your program.
28604 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28606 If you specify an absolute file name when prompted for the @kbd{M-x
28607 gdb} argument, then Emacs sets your current working directory to where
28608 your program resides. If you only specify the file name, then Emacs
28609 sets your current working directory to the directory associated
28610 with the previous buffer. In this case, @value{GDBN} may find your
28611 program by searching your environment's @code{PATH} variable, but on
28612 some operating systems it might not find the source. So, although the
28613 @value{GDBN} input and output session proceeds normally, the auxiliary
28614 buffer does not display the current source and line of execution.
28616 The initial working directory of @value{GDBN} is printed on the top
28617 line of the GUD buffer and this serves as a default for the commands
28618 that specify files for @value{GDBN} to operate on. @xref{Files,
28619 ,Commands to Specify Files}.
28621 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28622 need to call @value{GDBN} by a different name (for example, if you
28623 keep several configurations around, with different names) you can
28624 customize the Emacs variable @code{gud-gdb-command-name} to run the
28627 In the GUD buffer, you can use these special Emacs commands in
28628 addition to the standard Shell mode commands:
28632 Describe the features of Emacs' GUD Mode.
28635 Execute to another source line, like the @value{GDBN} @code{step} command; also
28636 update the display window to show the current file and location.
28639 Execute to next source line in this function, skipping all function
28640 calls, like the @value{GDBN} @code{next} command. Then update the display window
28641 to show the current file and location.
28644 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28645 display window accordingly.
28648 Execute until exit from the selected stack frame, like the @value{GDBN}
28649 @code{finish} command.
28652 Continue execution of your program, like the @value{GDBN} @code{continue}
28656 Go up the number of frames indicated by the numeric argument
28657 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28658 like the @value{GDBN} @code{up} command.
28661 Go down the number of frames indicated by the numeric argument, like the
28662 @value{GDBN} @code{down} command.
28665 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28666 tells @value{GDBN} to set a breakpoint on the source line point is on.
28668 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28669 separate frame which shows a backtrace when the GUD buffer is current.
28670 Move point to any frame in the stack and type @key{RET} to make it
28671 become the current frame and display the associated source in the
28672 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28673 selected frame become the current one. In graphical mode, the
28674 speedbar displays watch expressions.
28676 If you accidentally delete the source-display buffer, an easy way to get
28677 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28678 request a frame display; when you run under Emacs, this recreates
28679 the source buffer if necessary to show you the context of the current
28682 The source files displayed in Emacs are in ordinary Emacs buffers
28683 which are visiting the source files in the usual way. You can edit
28684 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28685 communicates with Emacs in terms of line numbers. If you add or
28686 delete lines from the text, the line numbers that @value{GDBN} knows cease
28687 to correspond properly with the code.
28689 A more detailed description of Emacs' interaction with @value{GDBN} is
28690 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28694 @chapter The @sc{gdb/mi} Interface
28696 @unnumberedsec Function and Purpose
28698 @cindex @sc{gdb/mi}, its purpose
28699 @sc{gdb/mi} is a line based machine oriented text interface to
28700 @value{GDBN} and is activated by specifying using the
28701 @option{--interpreter} command line option (@pxref{Mode Options}). It
28702 is specifically intended to support the development of systems which
28703 use the debugger as just one small component of a larger system.
28705 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28706 in the form of a reference manual.
28708 Note that @sc{gdb/mi} is still under construction, so some of the
28709 features described below are incomplete and subject to change
28710 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28712 @unnumberedsec Notation and Terminology
28714 @cindex notational conventions, for @sc{gdb/mi}
28715 This chapter uses the following notation:
28719 @code{|} separates two alternatives.
28722 @code{[ @var{something} ]} indicates that @var{something} is optional:
28723 it may or may not be given.
28726 @code{( @var{group} )*} means that @var{group} inside the parentheses
28727 may repeat zero or more times.
28730 @code{( @var{group} )+} means that @var{group} inside the parentheses
28731 may repeat one or more times.
28734 @code{"@var{string}"} means a literal @var{string}.
28738 @heading Dependencies
28742 * GDB/MI General Design::
28743 * GDB/MI Command Syntax::
28744 * GDB/MI Compatibility with CLI::
28745 * GDB/MI Development and Front Ends::
28746 * GDB/MI Output Records::
28747 * GDB/MI Simple Examples::
28748 * GDB/MI Command Description Format::
28749 * GDB/MI Breakpoint Commands::
28750 * GDB/MI Catchpoint Commands::
28751 * GDB/MI Program Context::
28752 * GDB/MI Thread Commands::
28753 * GDB/MI Ada Tasking Commands::
28754 * GDB/MI Program Execution::
28755 * GDB/MI Stack Manipulation::
28756 * GDB/MI Variable Objects::
28757 * GDB/MI Data Manipulation::
28758 * GDB/MI Tracepoint Commands::
28759 * GDB/MI Symbol Query::
28760 * GDB/MI File Commands::
28762 * GDB/MI Kod Commands::
28763 * GDB/MI Memory Overlay Commands::
28764 * GDB/MI Signal Handling Commands::
28766 * GDB/MI Target Manipulation::
28767 * GDB/MI File Transfer Commands::
28768 * GDB/MI Ada Exceptions Commands::
28769 * GDB/MI Miscellaneous Commands::
28772 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28773 @node GDB/MI General Design
28774 @section @sc{gdb/mi} General Design
28775 @cindex GDB/MI General Design
28777 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28778 parts---commands sent to @value{GDBN}, responses to those commands
28779 and notifications. Each command results in exactly one response,
28780 indicating either successful completion of the command, or an error.
28781 For the commands that do not resume the target, the response contains the
28782 requested information. For the commands that resume the target, the
28783 response only indicates whether the target was successfully resumed.
28784 Notifications is the mechanism for reporting changes in the state of the
28785 target, or in @value{GDBN} state, that cannot conveniently be associated with
28786 a command and reported as part of that command response.
28788 The important examples of notifications are:
28792 Exec notifications. These are used to report changes in
28793 target state---when a target is resumed, or stopped. It would not
28794 be feasible to include this information in response of resuming
28795 commands, because one resume commands can result in multiple events in
28796 different threads. Also, quite some time may pass before any event
28797 happens in the target, while a frontend needs to know whether the resuming
28798 command itself was successfully executed.
28801 Console output, and status notifications. Console output
28802 notifications are used to report output of CLI commands, as well as
28803 diagnostics for other commands. Status notifications are used to
28804 report the progress of a long-running operation. Naturally, including
28805 this information in command response would mean no output is produced
28806 until the command is finished, which is undesirable.
28809 General notifications. Commands may have various side effects on
28810 the @value{GDBN} or target state beyond their official purpose. For example,
28811 a command may change the selected thread. Although such changes can
28812 be included in command response, using notification allows for more
28813 orthogonal frontend design.
28817 There's no guarantee that whenever an MI command reports an error,
28818 @value{GDBN} or the target are in any specific state, and especially,
28819 the state is not reverted to the state before the MI command was
28820 processed. Therefore, whenever an MI command results in an error,
28821 we recommend that the frontend refreshes all the information shown in
28822 the user interface.
28826 * Context management::
28827 * Asynchronous and non-stop modes::
28831 @node Context management
28832 @subsection Context management
28834 @subsubsection Threads and Frames
28836 In most cases when @value{GDBN} accesses the target, this access is
28837 done in context of a specific thread and frame (@pxref{Frames}).
28838 Often, even when accessing global data, the target requires that a thread
28839 be specified. The CLI interface maintains the selected thread and frame,
28840 and supplies them to target on each command. This is convenient,
28841 because a command line user would not want to specify that information
28842 explicitly on each command, and because user interacts with
28843 @value{GDBN} via a single terminal, so no confusion is possible as
28844 to what thread and frame are the current ones.
28846 In the case of MI, the concept of selected thread and frame is less
28847 useful. First, a frontend can easily remember this information
28848 itself. Second, a graphical frontend can have more than one window,
28849 each one used for debugging a different thread, and the frontend might
28850 want to access additional threads for internal purposes. This
28851 increases the risk that by relying on implicitly selected thread, the
28852 frontend may be operating on a wrong one. Therefore, each MI command
28853 should explicitly specify which thread and frame to operate on. To
28854 make it possible, each MI command accepts the @samp{--thread} and
28855 @samp{--frame} options, the value to each is @value{GDBN} identifier
28856 for thread and frame to operate on.
28858 Usually, each top-level window in a frontend allows the user to select
28859 a thread and a frame, and remembers the user selection for further
28860 operations. However, in some cases @value{GDBN} may suggest that the
28861 current thread be changed. For example, when stopping on a breakpoint
28862 it is reasonable to switch to the thread where breakpoint is hit. For
28863 another example, if the user issues the CLI @samp{thread} command via
28864 the frontend, it is desirable to change the frontend's selected thread to the
28865 one specified by user. @value{GDBN} communicates the suggestion to
28866 change current thread using the @samp{=thread-selected} notification.
28867 No such notification is available for the selected frame at the moment.
28869 Note that historically, MI shares the selected thread with CLI, so
28870 frontends used the @code{-thread-select} to execute commands in the
28871 right context. However, getting this to work right is cumbersome. The
28872 simplest way is for frontend to emit @code{-thread-select} command
28873 before every command. This doubles the number of commands that need
28874 to be sent. The alternative approach is to suppress @code{-thread-select}
28875 if the selected thread in @value{GDBN} is supposed to be identical to the
28876 thread the frontend wants to operate on. However, getting this
28877 optimization right can be tricky. In particular, if the frontend
28878 sends several commands to @value{GDBN}, and one of the commands changes the
28879 selected thread, then the behaviour of subsequent commands will
28880 change. So, a frontend should either wait for response from such
28881 problematic commands, or explicitly add @code{-thread-select} for
28882 all subsequent commands. No frontend is known to do this exactly
28883 right, so it is suggested to just always pass the @samp{--thread} and
28884 @samp{--frame} options.
28886 @subsubsection Language
28888 The execution of several commands depends on which language is selected.
28889 By default, the current language (@pxref{show language}) is used.
28890 But for commands known to be language-sensitive, it is recommended
28891 to use the @samp{--language} option. This option takes one argument,
28892 which is the name of the language to use while executing the command.
28896 -data-evaluate-expression --language c "sizeof (void*)"
28901 The valid language names are the same names accepted by the
28902 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28903 @samp{local} or @samp{unknown}.
28905 @node Asynchronous and non-stop modes
28906 @subsection Asynchronous command execution and non-stop mode
28908 On some targets, @value{GDBN} is capable of processing MI commands
28909 even while the target is running. This is called @dfn{asynchronous
28910 command execution} (@pxref{Background Execution}). The frontend may
28911 specify a preferrence for asynchronous execution using the
28912 @code{-gdb-set target-async 1} command, which should be emitted before
28913 either running the executable or attaching to the target. After the
28914 frontend has started the executable or attached to the target, it can
28915 find if asynchronous execution is enabled using the
28916 @code{-list-target-features} command.
28918 Even if @value{GDBN} can accept a command while target is running,
28919 many commands that access the target do not work when the target is
28920 running. Therefore, asynchronous command execution is most useful
28921 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28922 it is possible to examine the state of one thread, while other threads
28925 When a given thread is running, MI commands that try to access the
28926 target in the context of that thread may not work, or may work only on
28927 some targets. In particular, commands that try to operate on thread's
28928 stack will not work, on any target. Commands that read memory, or
28929 modify breakpoints, may work or not work, depending on the target. Note
28930 that even commands that operate on global state, such as @code{print},
28931 @code{set}, and breakpoint commands, still access the target in the
28932 context of a specific thread, so frontend should try to find a
28933 stopped thread and perform the operation on that thread (using the
28934 @samp{--thread} option).
28936 Which commands will work in the context of a running thread is
28937 highly target dependent. However, the two commands
28938 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28939 to find the state of a thread, will always work.
28941 @node Thread groups
28942 @subsection Thread groups
28943 @value{GDBN} may be used to debug several processes at the same time.
28944 On some platfroms, @value{GDBN} may support debugging of several
28945 hardware systems, each one having several cores with several different
28946 processes running on each core. This section describes the MI
28947 mechanism to support such debugging scenarios.
28949 The key observation is that regardless of the structure of the
28950 target, MI can have a global list of threads, because most commands that
28951 accept the @samp{--thread} option do not need to know what process that
28952 thread belongs to. Therefore, it is not necessary to introduce
28953 neither additional @samp{--process} option, nor an notion of the
28954 current process in the MI interface. The only strictly new feature
28955 that is required is the ability to find how the threads are grouped
28958 To allow the user to discover such grouping, and to support arbitrary
28959 hierarchy of machines/cores/processes, MI introduces the concept of a
28960 @dfn{thread group}. Thread group is a collection of threads and other
28961 thread groups. A thread group always has a string identifier, a type,
28962 and may have additional attributes specific to the type. A new
28963 command, @code{-list-thread-groups}, returns the list of top-level
28964 thread groups, which correspond to processes that @value{GDBN} is
28965 debugging at the moment. By passing an identifier of a thread group
28966 to the @code{-list-thread-groups} command, it is possible to obtain
28967 the members of specific thread group.
28969 To allow the user to easily discover processes, and other objects, he
28970 wishes to debug, a concept of @dfn{available thread group} is
28971 introduced. Available thread group is an thread group that
28972 @value{GDBN} is not debugging, but that can be attached to, using the
28973 @code{-target-attach} command. The list of available top-level thread
28974 groups can be obtained using @samp{-list-thread-groups --available}.
28975 In general, the content of a thread group may be only retrieved only
28976 after attaching to that thread group.
28978 Thread groups are related to inferiors (@pxref{Inferiors and
28979 Programs}). Each inferior corresponds to a thread group of a special
28980 type @samp{process}, and some additional operations are permitted on
28981 such thread groups.
28983 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28984 @node GDB/MI Command Syntax
28985 @section @sc{gdb/mi} Command Syntax
28988 * GDB/MI Input Syntax::
28989 * GDB/MI Output Syntax::
28992 @node GDB/MI Input Syntax
28993 @subsection @sc{gdb/mi} Input Syntax
28995 @cindex input syntax for @sc{gdb/mi}
28996 @cindex @sc{gdb/mi}, input syntax
28998 @item @var{command} @expansion{}
28999 @code{@var{cli-command} | @var{mi-command}}
29001 @item @var{cli-command} @expansion{}
29002 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29003 @var{cli-command} is any existing @value{GDBN} CLI command.
29005 @item @var{mi-command} @expansion{}
29006 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29007 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29009 @item @var{token} @expansion{}
29010 "any sequence of digits"
29012 @item @var{option} @expansion{}
29013 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29015 @item @var{parameter} @expansion{}
29016 @code{@var{non-blank-sequence} | @var{c-string}}
29018 @item @var{operation} @expansion{}
29019 @emph{any of the operations described in this chapter}
29021 @item @var{non-blank-sequence} @expansion{}
29022 @emph{anything, provided it doesn't contain special characters such as
29023 "-", @var{nl}, """ and of course " "}
29025 @item @var{c-string} @expansion{}
29026 @code{""" @var{seven-bit-iso-c-string-content} """}
29028 @item @var{nl} @expansion{}
29037 The CLI commands are still handled by the @sc{mi} interpreter; their
29038 output is described below.
29041 The @code{@var{token}}, when present, is passed back when the command
29045 Some @sc{mi} commands accept optional arguments as part of the parameter
29046 list. Each option is identified by a leading @samp{-} (dash) and may be
29047 followed by an optional argument parameter. Options occur first in the
29048 parameter list and can be delimited from normal parameters using
29049 @samp{--} (this is useful when some parameters begin with a dash).
29056 We want easy access to the existing CLI syntax (for debugging).
29059 We want it to be easy to spot a @sc{mi} operation.
29062 @node GDB/MI Output Syntax
29063 @subsection @sc{gdb/mi} Output Syntax
29065 @cindex output syntax of @sc{gdb/mi}
29066 @cindex @sc{gdb/mi}, output syntax
29067 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29068 followed, optionally, by a single result record. This result record
29069 is for the most recent command. The sequence of output records is
29070 terminated by @samp{(gdb)}.
29072 If an input command was prefixed with a @code{@var{token}} then the
29073 corresponding output for that command will also be prefixed by that same
29077 @item @var{output} @expansion{}
29078 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29080 @item @var{result-record} @expansion{}
29081 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29083 @item @var{out-of-band-record} @expansion{}
29084 @code{@var{async-record} | @var{stream-record}}
29086 @item @var{async-record} @expansion{}
29087 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29089 @item @var{exec-async-output} @expansion{}
29090 @code{[ @var{token} ] "*" @var{async-output}}
29092 @item @var{status-async-output} @expansion{}
29093 @code{[ @var{token} ] "+" @var{async-output}}
29095 @item @var{notify-async-output} @expansion{}
29096 @code{[ @var{token} ] "=" @var{async-output}}
29098 @item @var{async-output} @expansion{}
29099 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
29101 @item @var{result-class} @expansion{}
29102 @code{"done" | "running" | "connected" | "error" | "exit"}
29104 @item @var{async-class} @expansion{}
29105 @code{"stopped" | @var{others}} (where @var{others} will be added
29106 depending on the needs---this is still in development).
29108 @item @var{result} @expansion{}
29109 @code{ @var{variable} "=" @var{value}}
29111 @item @var{variable} @expansion{}
29112 @code{ @var{string} }
29114 @item @var{value} @expansion{}
29115 @code{ @var{const} | @var{tuple} | @var{list} }
29117 @item @var{const} @expansion{}
29118 @code{@var{c-string}}
29120 @item @var{tuple} @expansion{}
29121 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29123 @item @var{list} @expansion{}
29124 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29125 @var{result} ( "," @var{result} )* "]" }
29127 @item @var{stream-record} @expansion{}
29128 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29130 @item @var{console-stream-output} @expansion{}
29131 @code{"~" @var{c-string}}
29133 @item @var{target-stream-output} @expansion{}
29134 @code{"@@" @var{c-string}}
29136 @item @var{log-stream-output} @expansion{}
29137 @code{"&" @var{c-string}}
29139 @item @var{nl} @expansion{}
29142 @item @var{token} @expansion{}
29143 @emph{any sequence of digits}.
29151 All output sequences end in a single line containing a period.
29154 The @code{@var{token}} is from the corresponding request. Note that
29155 for all async output, while the token is allowed by the grammar and
29156 may be output by future versions of @value{GDBN} for select async
29157 output messages, it is generally omitted. Frontends should treat
29158 all async output as reporting general changes in the state of the
29159 target and there should be no need to associate async output to any
29163 @cindex status output in @sc{gdb/mi}
29164 @var{status-async-output} contains on-going status information about the
29165 progress of a slow operation. It can be discarded. All status output is
29166 prefixed by @samp{+}.
29169 @cindex async output in @sc{gdb/mi}
29170 @var{exec-async-output} contains asynchronous state change on the target
29171 (stopped, started, disappeared). All async output is prefixed by
29175 @cindex notify output in @sc{gdb/mi}
29176 @var{notify-async-output} contains supplementary information that the
29177 client should handle (e.g., a new breakpoint information). All notify
29178 output is prefixed by @samp{=}.
29181 @cindex console output in @sc{gdb/mi}
29182 @var{console-stream-output} is output that should be displayed as is in the
29183 console. It is the textual response to a CLI command. All the console
29184 output is prefixed by @samp{~}.
29187 @cindex target output in @sc{gdb/mi}
29188 @var{target-stream-output} is the output produced by the target program.
29189 All the target output is prefixed by @samp{@@}.
29192 @cindex log output in @sc{gdb/mi}
29193 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29194 instance messages that should be displayed as part of an error log. All
29195 the log output is prefixed by @samp{&}.
29198 @cindex list output in @sc{gdb/mi}
29199 New @sc{gdb/mi} commands should only output @var{lists} containing
29205 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29206 details about the various output records.
29208 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29209 @node GDB/MI Compatibility with CLI
29210 @section @sc{gdb/mi} Compatibility with CLI
29212 @cindex compatibility, @sc{gdb/mi} and CLI
29213 @cindex @sc{gdb/mi}, compatibility with CLI
29215 For the developers convenience CLI commands can be entered directly,
29216 but there may be some unexpected behaviour. For example, commands
29217 that query the user will behave as if the user replied yes, breakpoint
29218 command lists are not executed and some CLI commands, such as
29219 @code{if}, @code{when} and @code{define}, prompt for further input with
29220 @samp{>}, which is not valid MI output.
29222 This feature may be removed at some stage in the future and it is
29223 recommended that front ends use the @code{-interpreter-exec} command
29224 (@pxref{-interpreter-exec}).
29226 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29227 @node GDB/MI Development and Front Ends
29228 @section @sc{gdb/mi} Development and Front Ends
29229 @cindex @sc{gdb/mi} development
29231 The application which takes the MI output and presents the state of the
29232 program being debugged to the user is called a @dfn{front end}.
29234 Although @sc{gdb/mi} is still incomplete, it is currently being used
29235 by a variety of front ends to @value{GDBN}. This makes it difficult
29236 to introduce new functionality without breaking existing usage. This
29237 section tries to minimize the problems by describing how the protocol
29240 Some changes in MI need not break a carefully designed front end, and
29241 for these the MI version will remain unchanged. The following is a
29242 list of changes that may occur within one level, so front ends should
29243 parse MI output in a way that can handle them:
29247 New MI commands may be added.
29250 New fields may be added to the output of any MI command.
29253 The range of values for fields with specified values, e.g.,
29254 @code{in_scope} (@pxref{-var-update}) may be extended.
29256 @c The format of field's content e.g type prefix, may change so parse it
29257 @c at your own risk. Yes, in general?
29259 @c The order of fields may change? Shouldn't really matter but it might
29260 @c resolve inconsistencies.
29263 If the changes are likely to break front ends, the MI version level
29264 will be increased by one. This will allow the front end to parse the
29265 output according to the MI version. Apart from mi0, new versions of
29266 @value{GDBN} will not support old versions of MI and it will be the
29267 responsibility of the front end to work with the new one.
29269 @c Starting with mi3, add a new command -mi-version that prints the MI
29272 The best way to avoid unexpected changes in MI that might break your front
29273 end is to make your project known to @value{GDBN} developers and
29274 follow development on @email{gdb@@sourceware.org} and
29275 @email{gdb-patches@@sourceware.org}.
29276 @cindex mailing lists
29278 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29279 @node GDB/MI Output Records
29280 @section @sc{gdb/mi} Output Records
29283 * GDB/MI Result Records::
29284 * GDB/MI Stream Records::
29285 * GDB/MI Async Records::
29286 * GDB/MI Breakpoint Information::
29287 * GDB/MI Frame Information::
29288 * GDB/MI Thread Information::
29289 * GDB/MI Ada Exception Information::
29292 @node GDB/MI Result Records
29293 @subsection @sc{gdb/mi} Result Records
29295 @cindex result records in @sc{gdb/mi}
29296 @cindex @sc{gdb/mi}, result records
29297 In addition to a number of out-of-band notifications, the response to a
29298 @sc{gdb/mi} command includes one of the following result indications:
29302 @item "^done" [ "," @var{results} ]
29303 The synchronous operation was successful, @code{@var{results}} are the return
29308 This result record is equivalent to @samp{^done}. Historically, it
29309 was output instead of @samp{^done} if the command has resumed the
29310 target. This behaviour is maintained for backward compatibility, but
29311 all frontends should treat @samp{^done} and @samp{^running}
29312 identically and rely on the @samp{*running} output record to determine
29313 which threads are resumed.
29317 @value{GDBN} has connected to a remote target.
29319 @item "^error" "," @var{c-string}
29321 The operation failed. The @code{@var{c-string}} contains the corresponding
29326 @value{GDBN} has terminated.
29330 @node GDB/MI Stream Records
29331 @subsection @sc{gdb/mi} Stream Records
29333 @cindex @sc{gdb/mi}, stream records
29334 @cindex stream records in @sc{gdb/mi}
29335 @value{GDBN} internally maintains a number of output streams: the console, the
29336 target, and the log. The output intended for each of these streams is
29337 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29339 Each stream record begins with a unique @dfn{prefix character} which
29340 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29341 Syntax}). In addition to the prefix, each stream record contains a
29342 @code{@var{string-output}}. This is either raw text (with an implicit new
29343 line) or a quoted C string (which does not contain an implicit newline).
29346 @item "~" @var{string-output}
29347 The console output stream contains text that should be displayed in the
29348 CLI console window. It contains the textual responses to CLI commands.
29350 @item "@@" @var{string-output}
29351 The target output stream contains any textual output from the running
29352 target. This is only present when GDB's event loop is truly
29353 asynchronous, which is currently only the case for remote targets.
29355 @item "&" @var{string-output}
29356 The log stream contains debugging messages being produced by @value{GDBN}'s
29360 @node GDB/MI Async Records
29361 @subsection @sc{gdb/mi} Async Records
29363 @cindex async records in @sc{gdb/mi}
29364 @cindex @sc{gdb/mi}, async records
29365 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29366 additional changes that have occurred. Those changes can either be a
29367 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29368 target activity (e.g., target stopped).
29370 The following is the list of possible async records:
29374 @item *running,thread-id="@var{thread}"
29375 The target is now running. The @var{thread} field tells which
29376 specific thread is now running, and can be @samp{all} if all threads
29377 are running. The frontend should assume that no interaction with a
29378 running thread is possible after this notification is produced.
29379 The frontend should not assume that this notification is output
29380 only once for any command. @value{GDBN} may emit this notification
29381 several times, either for different threads, because it cannot resume
29382 all threads together, or even for a single thread, if the thread must
29383 be stepped though some code before letting it run freely.
29385 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29386 The target has stopped. The @var{reason} field can have one of the
29390 @item breakpoint-hit
29391 A breakpoint was reached.
29392 @item watchpoint-trigger
29393 A watchpoint was triggered.
29394 @item read-watchpoint-trigger
29395 A read watchpoint was triggered.
29396 @item access-watchpoint-trigger
29397 An access watchpoint was triggered.
29398 @item function-finished
29399 An -exec-finish or similar CLI command was accomplished.
29400 @item location-reached
29401 An -exec-until or similar CLI command was accomplished.
29402 @item watchpoint-scope
29403 A watchpoint has gone out of scope.
29404 @item end-stepping-range
29405 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29406 similar CLI command was accomplished.
29407 @item exited-signalled
29408 The inferior exited because of a signal.
29410 The inferior exited.
29411 @item exited-normally
29412 The inferior exited normally.
29413 @item signal-received
29414 A signal was received by the inferior.
29416 The inferior has stopped due to a library being loaded or unloaded.
29417 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29418 set or when a @code{catch load} or @code{catch unload} catchpoint is
29419 in use (@pxref{Set Catchpoints}).
29421 The inferior has forked. This is reported when @code{catch fork}
29422 (@pxref{Set Catchpoints}) has been used.
29424 The inferior has vforked. This is reported in when @code{catch vfork}
29425 (@pxref{Set Catchpoints}) has been used.
29426 @item syscall-entry
29427 The inferior entered a system call. This is reported when @code{catch
29428 syscall} (@pxref{Set Catchpoints}) has been used.
29429 @item syscall-entry
29430 The inferior returned from a system call. This is reported when
29431 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29433 The inferior called @code{exec}. This is reported when @code{catch exec}
29434 (@pxref{Set Catchpoints}) has been used.
29437 The @var{id} field identifies the thread that directly caused the stop
29438 -- for example by hitting a breakpoint. Depending on whether all-stop
29439 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29440 stop all threads, or only the thread that directly triggered the stop.
29441 If all threads are stopped, the @var{stopped} field will have the
29442 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29443 field will be a list of thread identifiers. Presently, this list will
29444 always include a single thread, but frontend should be prepared to see
29445 several threads in the list. The @var{core} field reports the
29446 processor core on which the stop event has happened. This field may be absent
29447 if such information is not available.
29449 @item =thread-group-added,id="@var{id}"
29450 @itemx =thread-group-removed,id="@var{id}"
29451 A thread group was either added or removed. The @var{id} field
29452 contains the @value{GDBN} identifier of the thread group. When a thread
29453 group is added, it generally might not be associated with a running
29454 process. When a thread group is removed, its id becomes invalid and
29455 cannot be used in any way.
29457 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29458 A thread group became associated with a running program,
29459 either because the program was just started or the thread group
29460 was attached to a program. The @var{id} field contains the
29461 @value{GDBN} identifier of the thread group. The @var{pid} field
29462 contains process identifier, specific to the operating system.
29464 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29465 A thread group is no longer associated with a running program,
29466 either because the program has exited, or because it was detached
29467 from. The @var{id} field contains the @value{GDBN} identifier of the
29468 thread group. @var{code} is the exit code of the inferior; it exists
29469 only when the inferior exited with some code.
29471 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29472 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29473 A thread either was created, or has exited. The @var{id} field
29474 contains the @value{GDBN} identifier of the thread. The @var{gid}
29475 field identifies the thread group this thread belongs to.
29477 @item =thread-selected,id="@var{id}"
29478 Informs that the selected thread was changed as result of the last
29479 command. This notification is not emitted as result of @code{-thread-select}
29480 command but is emitted whenever an MI command that is not documented
29481 to change the selected thread actually changes it. In particular,
29482 invoking, directly or indirectly (via user-defined command), the CLI
29483 @code{thread} command, will generate this notification.
29485 We suggest that in response to this notification, front ends
29486 highlight the selected thread and cause subsequent commands to apply to
29489 @item =library-loaded,...
29490 Reports that a new library file was loaded by the program. This
29491 notification has 4 fields---@var{id}, @var{target-name},
29492 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29493 opaque identifier of the library. For remote debugging case,
29494 @var{target-name} and @var{host-name} fields give the name of the
29495 library file on the target, and on the host respectively. For native
29496 debugging, both those fields have the same value. The
29497 @var{symbols-loaded} field is emitted only for backward compatibility
29498 and should not be relied on to convey any useful information. The
29499 @var{thread-group} field, if present, specifies the id of the thread
29500 group in whose context the library was loaded. If the field is
29501 absent, it means the library was loaded in the context of all present
29504 @item =library-unloaded,...
29505 Reports that a library was unloaded by the program. This notification
29506 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29507 the same meaning as for the @code{=library-loaded} notification.
29508 The @var{thread-group} field, if present, specifies the id of the
29509 thread group in whose context the library was unloaded. If the field is
29510 absent, it means the library was unloaded in the context of all present
29513 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29514 @itemx =traceframe-changed,end
29515 Reports that the trace frame was changed and its new number is
29516 @var{tfnum}. The number of the tracepoint associated with this trace
29517 frame is @var{tpnum}.
29519 @item =tsv-created,name=@var{name},initial=@var{initial}
29520 Reports that the new trace state variable @var{name} is created with
29521 initial value @var{initial}.
29523 @item =tsv-deleted,name=@var{name}
29524 @itemx =tsv-deleted
29525 Reports that the trace state variable @var{name} is deleted or all
29526 trace state variables are deleted.
29528 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29529 Reports that the trace state variable @var{name} is modified with
29530 the initial value @var{initial}. The current value @var{current} of
29531 trace state variable is optional and is reported if the current
29532 value of trace state variable is known.
29534 @item =breakpoint-created,bkpt=@{...@}
29535 @itemx =breakpoint-modified,bkpt=@{...@}
29536 @itemx =breakpoint-deleted,id=@var{number}
29537 Reports that a breakpoint was created, modified, or deleted,
29538 respectively. Only user-visible breakpoints are reported to the MI
29541 The @var{bkpt} argument is of the same form as returned by the various
29542 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29543 @var{number} is the ordinal number of the breakpoint.
29545 Note that if a breakpoint is emitted in the result record of a
29546 command, then it will not also be emitted in an async record.
29548 @item =record-started,thread-group="@var{id}"
29549 @itemx =record-stopped,thread-group="@var{id}"
29550 Execution log recording was either started or stopped on an
29551 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29552 group corresponding to the affected inferior.
29554 @item =cmd-param-changed,param=@var{param},value=@var{value}
29555 Reports that a parameter of the command @code{set @var{param}} is
29556 changed to @var{value}. In the multi-word @code{set} command,
29557 the @var{param} is the whole parameter list to @code{set} command.
29558 For example, In command @code{set check type on}, @var{param}
29559 is @code{check type} and @var{value} is @code{on}.
29561 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29562 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29563 written in an inferior. The @var{id} is the identifier of the
29564 thread group corresponding to the affected inferior. The optional
29565 @code{type="code"} part is reported if the memory written to holds
29569 @node GDB/MI Breakpoint Information
29570 @subsection @sc{gdb/mi} Breakpoint Information
29572 When @value{GDBN} reports information about a breakpoint, a
29573 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29578 The breakpoint number. For a breakpoint that represents one location
29579 of a multi-location breakpoint, this will be a dotted pair, like
29583 The type of the breakpoint. For ordinary breakpoints this will be
29584 @samp{breakpoint}, but many values are possible.
29587 If the type of the breakpoint is @samp{catchpoint}, then this
29588 indicates the exact type of catchpoint.
29591 This is the breakpoint disposition---either @samp{del}, meaning that
29592 the breakpoint will be deleted at the next stop, or @samp{keep},
29593 meaning that the breakpoint will not be deleted.
29596 This indicates whether the breakpoint is enabled, in which case the
29597 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29598 Note that this is not the same as the field @code{enable}.
29601 The address of the breakpoint. This may be a hexidecimal number,
29602 giving the address; or the string @samp{<PENDING>}, for a pending
29603 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29604 multiple locations. This field will not be present if no address can
29605 be determined. For example, a watchpoint does not have an address.
29608 If known, the function in which the breakpoint appears.
29609 If not known, this field is not present.
29612 The name of the source file which contains this function, if known.
29613 If not known, this field is not present.
29616 The full file name of the source file which contains this function, if
29617 known. If not known, this field is not present.
29620 The line number at which this breakpoint appears, if known.
29621 If not known, this field is not present.
29624 If the source file is not known, this field may be provided. If
29625 provided, this holds the address of the breakpoint, possibly followed
29629 If this breakpoint is pending, this field is present and holds the
29630 text used to set the breakpoint, as entered by the user.
29633 Where this breakpoint's condition is evaluated, either @samp{host} or
29637 If this is a thread-specific breakpoint, then this identifies the
29638 thread in which the breakpoint can trigger.
29641 If this breakpoint is restricted to a particular Ada task, then this
29642 field will hold the task identifier.
29645 If the breakpoint is conditional, this is the condition expression.
29648 The ignore count of the breakpoint.
29651 The enable count of the breakpoint.
29653 @item traceframe-usage
29656 @item static-tracepoint-marker-string-id
29657 For a static tracepoint, the name of the static tracepoint marker.
29660 For a masked watchpoint, this is the mask.
29663 A tracepoint's pass count.
29665 @item original-location
29666 The location of the breakpoint as originally specified by the user.
29667 This field is optional.
29670 The number of times the breakpoint has been hit.
29673 This field is only given for tracepoints. This is either @samp{y},
29674 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29678 Some extra data, the exact contents of which are type-dependent.
29682 For example, here is what the output of @code{-break-insert}
29683 (@pxref{GDB/MI Breakpoint Commands}) might be:
29686 -> -break-insert main
29687 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29688 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29689 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29694 @node GDB/MI Frame Information
29695 @subsection @sc{gdb/mi} Frame Information
29697 Response from many MI commands includes an information about stack
29698 frame. This information is a tuple that may have the following
29703 The level of the stack frame. The innermost frame has the level of
29704 zero. This field is always present.
29707 The name of the function corresponding to the frame. This field may
29708 be absent if @value{GDBN} is unable to determine the function name.
29711 The code address for the frame. This field is always present.
29714 The name of the source files that correspond to the frame's code
29715 address. This field may be absent.
29718 The source line corresponding to the frames' code address. This field
29722 The name of the binary file (either executable or shared library) the
29723 corresponds to the frame's code address. This field may be absent.
29727 @node GDB/MI Thread Information
29728 @subsection @sc{gdb/mi} Thread Information
29730 Whenever @value{GDBN} has to report an information about a thread, it
29731 uses a tuple with the following fields:
29735 The numeric id assigned to the thread by @value{GDBN}. This field is
29739 Target-specific string identifying the thread. This field is always present.
29742 Additional information about the thread provided by the target.
29743 It is supposed to be human-readable and not interpreted by the
29744 frontend. This field is optional.
29747 Either @samp{stopped} or @samp{running}, depending on whether the
29748 thread is presently running. This field is always present.
29751 The value of this field is an integer number of the processor core the
29752 thread was last seen on. This field is optional.
29755 @node GDB/MI Ada Exception Information
29756 @subsection @sc{gdb/mi} Ada Exception Information
29758 Whenever a @code{*stopped} record is emitted because the program
29759 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29760 @value{GDBN} provides the name of the exception that was raised via
29761 the @code{exception-name} field.
29763 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29764 @node GDB/MI Simple Examples
29765 @section Simple Examples of @sc{gdb/mi} Interaction
29766 @cindex @sc{gdb/mi}, simple examples
29768 This subsection presents several simple examples of interaction using
29769 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29770 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29771 the output received from @sc{gdb/mi}.
29773 Note the line breaks shown in the examples are here only for
29774 readability, they don't appear in the real output.
29776 @subheading Setting a Breakpoint
29778 Setting a breakpoint generates synchronous output which contains detailed
29779 information of the breakpoint.
29782 -> -break-insert main
29783 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29784 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29785 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29790 @subheading Program Execution
29792 Program execution generates asynchronous records and MI gives the
29793 reason that execution stopped.
29799 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29800 frame=@{addr="0x08048564",func="main",
29801 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29802 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29807 <- *stopped,reason="exited-normally"
29811 @subheading Quitting @value{GDBN}
29813 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29821 Please note that @samp{^exit} is printed immediately, but it might
29822 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29823 performs necessary cleanups, including killing programs being debugged
29824 or disconnecting from debug hardware, so the frontend should wait till
29825 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29826 fails to exit in reasonable time.
29828 @subheading A Bad Command
29830 Here's what happens if you pass a non-existent command:
29834 <- ^error,msg="Undefined MI command: rubbish"
29839 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29840 @node GDB/MI Command Description Format
29841 @section @sc{gdb/mi} Command Description Format
29843 The remaining sections describe blocks of commands. Each block of
29844 commands is laid out in a fashion similar to this section.
29846 @subheading Motivation
29848 The motivation for this collection of commands.
29850 @subheading Introduction
29852 A brief introduction to this collection of commands as a whole.
29854 @subheading Commands
29856 For each command in the block, the following is described:
29858 @subsubheading Synopsis
29861 -command @var{args}@dots{}
29864 @subsubheading Result
29866 @subsubheading @value{GDBN} Command
29868 The corresponding @value{GDBN} CLI command(s), if any.
29870 @subsubheading Example
29872 Example(s) formatted for readability. Some of the described commands have
29873 not been implemented yet and these are labeled N.A.@: (not available).
29876 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29877 @node GDB/MI Breakpoint Commands
29878 @section @sc{gdb/mi} Breakpoint Commands
29880 @cindex breakpoint commands for @sc{gdb/mi}
29881 @cindex @sc{gdb/mi}, breakpoint commands
29882 This section documents @sc{gdb/mi} commands for manipulating
29885 @subheading The @code{-break-after} Command
29886 @findex -break-after
29888 @subsubheading Synopsis
29891 -break-after @var{number} @var{count}
29894 The breakpoint number @var{number} is not in effect until it has been
29895 hit @var{count} times. To see how this is reflected in the output of
29896 the @samp{-break-list} command, see the description of the
29897 @samp{-break-list} command below.
29899 @subsubheading @value{GDBN} Command
29901 The corresponding @value{GDBN} command is @samp{ignore}.
29903 @subsubheading Example
29908 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29909 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29910 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29918 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29919 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29920 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29921 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29922 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29923 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29924 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29925 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29926 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29927 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29932 @subheading The @code{-break-catch} Command
29933 @findex -break-catch
29936 @subheading The @code{-break-commands} Command
29937 @findex -break-commands
29939 @subsubheading Synopsis
29942 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29945 Specifies the CLI commands that should be executed when breakpoint
29946 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29947 are the commands. If no command is specified, any previously-set
29948 commands are cleared. @xref{Break Commands}. Typical use of this
29949 functionality is tracing a program, that is, printing of values of
29950 some variables whenever breakpoint is hit and then continuing.
29952 @subsubheading @value{GDBN} Command
29954 The corresponding @value{GDBN} command is @samp{commands}.
29956 @subsubheading Example
29961 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29962 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29963 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29966 -break-commands 1 "print v" "continue"
29971 @subheading The @code{-break-condition} Command
29972 @findex -break-condition
29974 @subsubheading Synopsis
29977 -break-condition @var{number} @var{expr}
29980 Breakpoint @var{number} will stop the program only if the condition in
29981 @var{expr} is true. The condition becomes part of the
29982 @samp{-break-list} output (see the description of the @samp{-break-list}
29985 @subsubheading @value{GDBN} Command
29987 The corresponding @value{GDBN} command is @samp{condition}.
29989 @subsubheading Example
29993 -break-condition 1 1
29997 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29998 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29999 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30000 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30001 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30002 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30003 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30004 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30005 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30006 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30010 @subheading The @code{-break-delete} Command
30011 @findex -break-delete
30013 @subsubheading Synopsis
30016 -break-delete ( @var{breakpoint} )+
30019 Delete the breakpoint(s) whose number(s) are specified in the argument
30020 list. This is obviously reflected in the breakpoint list.
30022 @subsubheading @value{GDBN} Command
30024 The corresponding @value{GDBN} command is @samp{delete}.
30026 @subsubheading Example
30034 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30035 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30036 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30037 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30038 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30039 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30040 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30045 @subheading The @code{-break-disable} Command
30046 @findex -break-disable
30048 @subsubheading Synopsis
30051 -break-disable ( @var{breakpoint} )+
30054 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30055 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30057 @subsubheading @value{GDBN} Command
30059 The corresponding @value{GDBN} command is @samp{disable}.
30061 @subsubheading Example
30069 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30070 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30071 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30072 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30073 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30074 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30075 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30076 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30077 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30078 line="5",thread-groups=["i1"],times="0"@}]@}
30082 @subheading The @code{-break-enable} Command
30083 @findex -break-enable
30085 @subsubheading Synopsis
30088 -break-enable ( @var{breakpoint} )+
30091 Enable (previously disabled) @var{breakpoint}(s).
30093 @subsubheading @value{GDBN} Command
30095 The corresponding @value{GDBN} command is @samp{enable}.
30097 @subsubheading Example
30105 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30106 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30107 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30108 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30109 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30110 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30111 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30112 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30113 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30114 line="5",thread-groups=["i1"],times="0"@}]@}
30118 @subheading The @code{-break-info} Command
30119 @findex -break-info
30121 @subsubheading Synopsis
30124 -break-info @var{breakpoint}
30128 Get information about a single breakpoint.
30130 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30131 Information}, for details on the format of each breakpoint in the
30134 @subsubheading @value{GDBN} Command
30136 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30138 @subsubheading Example
30141 @subheading The @code{-break-insert} Command
30142 @findex -break-insert
30144 @subsubheading Synopsis
30147 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30148 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30149 [ -p @var{thread-id} ] [ @var{location} ]
30153 If specified, @var{location}, can be one of:
30160 @item filename:linenum
30161 @item filename:function
30165 The possible optional parameters of this command are:
30169 Insert a temporary breakpoint.
30171 Insert a hardware breakpoint.
30173 If @var{location} cannot be parsed (for example if it
30174 refers to unknown files or functions), create a pending
30175 breakpoint. Without this flag, @value{GDBN} will report
30176 an error, and won't create a breakpoint, if @var{location}
30179 Create a disabled breakpoint.
30181 Create a tracepoint. @xref{Tracepoints}. When this parameter
30182 is used together with @samp{-h}, a fast tracepoint is created.
30183 @item -c @var{condition}
30184 Make the breakpoint conditional on @var{condition}.
30185 @item -i @var{ignore-count}
30186 Initialize the @var{ignore-count}.
30187 @item -p @var{thread-id}
30188 Restrict the breakpoint to the specified @var{thread-id}.
30191 @subsubheading Result
30193 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30194 resulting breakpoint.
30196 Note: this format is open to change.
30197 @c An out-of-band breakpoint instead of part of the result?
30199 @subsubheading @value{GDBN} Command
30201 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30202 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30204 @subsubheading Example
30209 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30210 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30213 -break-insert -t foo
30214 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30215 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30219 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30220 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30221 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30222 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30223 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30224 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30225 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30226 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30227 addr="0x0001072c", func="main",file="recursive2.c",
30228 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30230 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30231 addr="0x00010774",func="foo",file="recursive2.c",
30232 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30235 @c -break-insert -r foo.*
30236 @c ~int foo(int, int);
30237 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30238 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30243 @subheading The @code{-dprintf-insert} Command
30244 @findex -dprintf-insert
30246 @subsubheading Synopsis
30249 -dprintf-insert [ -t ] [ -f ] [ -d ]
30250 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30251 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30256 If specified, @var{location}, can be one of:
30259 @item @var{function}
30262 @c @item @var{linenum}
30263 @item @var{filename}:@var{linenum}
30264 @item @var{filename}:function
30265 @item *@var{address}
30268 The possible optional parameters of this command are:
30272 Insert a temporary breakpoint.
30274 If @var{location} cannot be parsed (for example, if it
30275 refers to unknown files or functions), create a pending
30276 breakpoint. Without this flag, @value{GDBN} will report
30277 an error, and won't create a breakpoint, if @var{location}
30280 Create a disabled breakpoint.
30281 @item -c @var{condition}
30282 Make the breakpoint conditional on @var{condition}.
30283 @item -i @var{ignore-count}
30284 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30285 to @var{ignore-count}.
30286 @item -p @var{thread-id}
30287 Restrict the breakpoint to the specified @var{thread-id}.
30290 @subsubheading Result
30292 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30293 resulting breakpoint.
30295 @c An out-of-band breakpoint instead of part of the result?
30297 @subsubheading @value{GDBN} Command
30299 The corresponding @value{GDBN} command is @samp{dprintf}.
30301 @subsubheading Example
30305 4-dprintf-insert foo "At foo entry\n"
30306 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30307 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30308 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30309 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30310 original-location="foo"@}
30312 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30313 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30314 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30315 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30316 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30317 original-location="mi-dprintf.c:26"@}
30321 @subheading The @code{-break-list} Command
30322 @findex -break-list
30324 @subsubheading Synopsis
30330 Displays the list of inserted breakpoints, showing the following fields:
30334 number of the breakpoint
30336 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30338 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30341 is the breakpoint enabled or no: @samp{y} or @samp{n}
30343 memory location at which the breakpoint is set
30345 logical location of the breakpoint, expressed by function name, file
30347 @item Thread-groups
30348 list of thread groups to which this breakpoint applies
30350 number of times the breakpoint has been hit
30353 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30354 @code{body} field is an empty list.
30356 @subsubheading @value{GDBN} Command
30358 The corresponding @value{GDBN} command is @samp{info break}.
30360 @subsubheading Example
30365 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30366 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30367 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30368 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30369 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30370 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30371 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30372 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30373 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30375 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30376 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30377 line="13",thread-groups=["i1"],times="0"@}]@}
30381 Here's an example of the result when there are no breakpoints:
30386 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30387 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30388 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30389 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30390 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30391 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30392 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30397 @subheading The @code{-break-passcount} Command
30398 @findex -break-passcount
30400 @subsubheading Synopsis
30403 -break-passcount @var{tracepoint-number} @var{passcount}
30406 Set the passcount for tracepoint @var{tracepoint-number} to
30407 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30408 is not a tracepoint, error is emitted. This corresponds to CLI
30409 command @samp{passcount}.
30411 @subheading The @code{-break-watch} Command
30412 @findex -break-watch
30414 @subsubheading Synopsis
30417 -break-watch [ -a | -r ]
30420 Create a watchpoint. With the @samp{-a} option it will create an
30421 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30422 read from or on a write to the memory location. With the @samp{-r}
30423 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30424 trigger only when the memory location is accessed for reading. Without
30425 either of the options, the watchpoint created is a regular watchpoint,
30426 i.e., it will trigger when the memory location is accessed for writing.
30427 @xref{Set Watchpoints, , Setting Watchpoints}.
30429 Note that @samp{-break-list} will report a single list of watchpoints and
30430 breakpoints inserted.
30432 @subsubheading @value{GDBN} Command
30434 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30437 @subsubheading Example
30439 Setting a watchpoint on a variable in the @code{main} function:
30444 ^done,wpt=@{number="2",exp="x"@}
30449 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30450 value=@{old="-268439212",new="55"@},
30451 frame=@{func="main",args=[],file="recursive2.c",
30452 fullname="/home/foo/bar/recursive2.c",line="5"@}
30456 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30457 the program execution twice: first for the variable changing value, then
30458 for the watchpoint going out of scope.
30463 ^done,wpt=@{number="5",exp="C"@}
30468 *stopped,reason="watchpoint-trigger",
30469 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30470 frame=@{func="callee4",args=[],
30471 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30472 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30477 *stopped,reason="watchpoint-scope",wpnum="5",
30478 frame=@{func="callee3",args=[@{name="strarg",
30479 value="0x11940 \"A string argument.\""@}],
30480 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30481 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30485 Listing breakpoints and watchpoints, at different points in the program
30486 execution. Note that once the watchpoint goes out of scope, it is
30492 ^done,wpt=@{number="2",exp="C"@}
30495 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30496 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30497 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30498 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30499 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30500 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30501 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30502 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30503 addr="0x00010734",func="callee4",
30504 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30505 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30507 bkpt=@{number="2",type="watchpoint",disp="keep",
30508 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30513 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30514 value=@{old="-276895068",new="3"@},
30515 frame=@{func="callee4",args=[],
30516 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30517 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30520 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30521 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30522 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30523 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30524 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30525 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30526 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30527 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30528 addr="0x00010734",func="callee4",
30529 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30530 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30532 bkpt=@{number="2",type="watchpoint",disp="keep",
30533 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30537 ^done,reason="watchpoint-scope",wpnum="2",
30538 frame=@{func="callee3",args=[@{name="strarg",
30539 value="0x11940 \"A string argument.\""@}],
30540 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30541 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30544 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30545 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30546 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30547 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30548 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30549 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30550 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30551 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30552 addr="0x00010734",func="callee4",
30553 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30554 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30555 thread-groups=["i1"],times="1"@}]@}
30560 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30561 @node GDB/MI Catchpoint Commands
30562 @section @sc{gdb/mi} Catchpoint Commands
30564 This section documents @sc{gdb/mi} commands for manipulating
30568 * Shared Library GDB/MI Catchpoint Commands::
30569 * Ada Exception GDB/MI Catchpoint Commands::
30572 @node Shared Library GDB/MI Catchpoint Commands
30573 @subsection Shared Library @sc{gdb/mi} Catchpoints
30575 @subheading The @code{-catch-load} Command
30576 @findex -catch-load
30578 @subsubheading Synopsis
30581 -catch-load [ -t ] [ -d ] @var{regexp}
30584 Add a catchpoint for library load events. If the @samp{-t} option is used,
30585 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30586 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30587 in a disabled state. The @samp{regexp} argument is a regular
30588 expression used to match the name of the loaded library.
30591 @subsubheading @value{GDBN} Command
30593 The corresponding @value{GDBN} command is @samp{catch load}.
30595 @subsubheading Example
30598 -catch-load -t foo.so
30599 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30600 what="load of library matching foo.so",catch-type="load",times="0"@}
30605 @subheading The @code{-catch-unload} Command
30606 @findex -catch-unload
30608 @subsubheading Synopsis
30611 -catch-unload [ -t ] [ -d ] @var{regexp}
30614 Add a catchpoint for library unload events. If the @samp{-t} option is
30615 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30616 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30617 created in a disabled state. The @samp{regexp} argument is a regular
30618 expression used to match the name of the unloaded library.
30620 @subsubheading @value{GDBN} Command
30622 The corresponding @value{GDBN} command is @samp{catch unload}.
30624 @subsubheading Example
30627 -catch-unload -d bar.so
30628 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30629 what="load of library matching bar.so",catch-type="unload",times="0"@}
30633 @node Ada Exception GDB/MI Catchpoint Commands
30634 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30636 The following @sc{gdb/mi} commands can be used to create catchpoints
30637 that stop the execution when Ada exceptions are being raised.
30639 @subheading The @code{-catch-assert} Command
30640 @findex -catch-assert
30642 @subsubheading Synopsis
30645 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30648 Add a catchpoint for failed Ada assertions.
30650 The possible optional parameters for this command are:
30653 @item -c @var{condition}
30654 Make the catchpoint conditional on @var{condition}.
30656 Create a disabled catchpoint.
30658 Create a temporary catchpoint.
30661 @subsubheading @value{GDBN} Command
30663 The corresponding @value{GDBN} command is @samp{catch assert}.
30665 @subsubheading Example
30669 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30670 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30671 thread-groups=["i1"],times="0",
30672 original-location="__gnat_debug_raise_assert_failure"@}
30676 @subheading The @code{-catch-exception} Command
30677 @findex -catch-exception
30679 @subsubheading Synopsis
30682 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30686 Add a catchpoint stopping when Ada exceptions are raised.
30687 By default, the command stops the program when any Ada exception
30688 gets raised. But it is also possible, by using some of the
30689 optional parameters described below, to create more selective
30692 The possible optional parameters for this command are:
30695 @item -c @var{condition}
30696 Make the catchpoint conditional on @var{condition}.
30698 Create a disabled catchpoint.
30699 @item -e @var{exception-name}
30700 Only stop when @var{exception-name} is raised. This option cannot
30701 be used combined with @samp{-u}.
30703 Create a temporary catchpoint.
30705 Stop only when an unhandled exception gets raised. This option
30706 cannot be used combined with @samp{-e}.
30709 @subsubheading @value{GDBN} Command
30711 The corresponding @value{GDBN} commands are @samp{catch exception}
30712 and @samp{catch exception unhandled}.
30714 @subsubheading Example
30717 -catch-exception -e Program_Error
30718 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30719 enabled="y",addr="0x0000000000404874",
30720 what="`Program_Error' Ada exception", thread-groups=["i1"],
30721 times="0",original-location="__gnat_debug_raise_exception"@}
30725 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30726 @node GDB/MI Program Context
30727 @section @sc{gdb/mi} Program Context
30729 @subheading The @code{-exec-arguments} Command
30730 @findex -exec-arguments
30733 @subsubheading Synopsis
30736 -exec-arguments @var{args}
30739 Set the inferior program arguments, to be used in the next
30742 @subsubheading @value{GDBN} Command
30744 The corresponding @value{GDBN} command is @samp{set args}.
30746 @subsubheading Example
30750 -exec-arguments -v word
30757 @subheading The @code{-exec-show-arguments} Command
30758 @findex -exec-show-arguments
30760 @subsubheading Synopsis
30763 -exec-show-arguments
30766 Print the arguments of the program.
30768 @subsubheading @value{GDBN} Command
30770 The corresponding @value{GDBN} command is @samp{show args}.
30772 @subsubheading Example
30777 @subheading The @code{-environment-cd} Command
30778 @findex -environment-cd
30780 @subsubheading Synopsis
30783 -environment-cd @var{pathdir}
30786 Set @value{GDBN}'s working directory.
30788 @subsubheading @value{GDBN} Command
30790 The corresponding @value{GDBN} command is @samp{cd}.
30792 @subsubheading Example
30796 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30802 @subheading The @code{-environment-directory} Command
30803 @findex -environment-directory
30805 @subsubheading Synopsis
30808 -environment-directory [ -r ] [ @var{pathdir} ]+
30811 Add directories @var{pathdir} to beginning of search path for source files.
30812 If the @samp{-r} option is used, the search path is reset to the default
30813 search path. If directories @var{pathdir} are supplied in addition to the
30814 @samp{-r} option, the search path is first reset and then addition
30816 Multiple directories may be specified, separated by blanks. Specifying
30817 multiple directories in a single command
30818 results in the directories added to the beginning of the
30819 search path in the same order they were presented in the command.
30820 If blanks are needed as
30821 part of a directory name, double-quotes should be used around
30822 the name. In the command output, the path will show up separated
30823 by the system directory-separator character. The directory-separator
30824 character must not be used
30825 in any directory name.
30826 If no directories are specified, the current search path is displayed.
30828 @subsubheading @value{GDBN} Command
30830 The corresponding @value{GDBN} command is @samp{dir}.
30832 @subsubheading Example
30836 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30837 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30839 -environment-directory ""
30840 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30842 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30843 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30845 -environment-directory -r
30846 ^done,source-path="$cdir:$cwd"
30851 @subheading The @code{-environment-path} Command
30852 @findex -environment-path
30854 @subsubheading Synopsis
30857 -environment-path [ -r ] [ @var{pathdir} ]+
30860 Add directories @var{pathdir} to beginning of search path for object files.
30861 If the @samp{-r} option is used, the search path is reset to the original
30862 search path that existed at gdb start-up. If directories @var{pathdir} are
30863 supplied in addition to the
30864 @samp{-r} option, the search path is first reset and then addition
30866 Multiple directories may be specified, separated by blanks. Specifying
30867 multiple directories in a single command
30868 results in the directories added to the beginning of the
30869 search path in the same order they were presented in the command.
30870 If blanks are needed as
30871 part of a directory name, double-quotes should be used around
30872 the name. In the command output, the path will show up separated
30873 by the system directory-separator character. The directory-separator
30874 character must not be used
30875 in any directory name.
30876 If no directories are specified, the current path is displayed.
30879 @subsubheading @value{GDBN} Command
30881 The corresponding @value{GDBN} command is @samp{path}.
30883 @subsubheading Example
30888 ^done,path="/usr/bin"
30890 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30891 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30893 -environment-path -r /usr/local/bin
30894 ^done,path="/usr/local/bin:/usr/bin"
30899 @subheading The @code{-environment-pwd} Command
30900 @findex -environment-pwd
30902 @subsubheading Synopsis
30908 Show the current working directory.
30910 @subsubheading @value{GDBN} Command
30912 The corresponding @value{GDBN} command is @samp{pwd}.
30914 @subsubheading Example
30919 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30924 @node GDB/MI Thread Commands
30925 @section @sc{gdb/mi} Thread Commands
30928 @subheading The @code{-thread-info} Command
30929 @findex -thread-info
30931 @subsubheading Synopsis
30934 -thread-info [ @var{thread-id} ]
30937 Reports information about either a specific thread, if
30938 the @var{thread-id} parameter is present, or about all
30939 threads. When printing information about all threads,
30940 also reports the current thread.
30942 @subsubheading @value{GDBN} Command
30944 The @samp{info thread} command prints the same information
30947 @subsubheading Result
30949 The result is a list of threads. The following attributes are
30950 defined for a given thread:
30954 This field exists only for the current thread. It has the value @samp{*}.
30957 The identifier that @value{GDBN} uses to refer to the thread.
30960 The identifier that the target uses to refer to the thread.
30963 Extra information about the thread, in a target-specific format. This
30967 The name of the thread. If the user specified a name using the
30968 @code{thread name} command, then this name is given. Otherwise, if
30969 @value{GDBN} can extract the thread name from the target, then that
30970 name is given. If @value{GDBN} cannot find the thread name, then this
30974 The stack frame currently executing in the thread.
30977 The thread's state. The @samp{state} field may have the following
30982 The thread is stopped. Frame information is available for stopped
30986 The thread is running. There's no frame information for running
30992 If @value{GDBN} can find the CPU core on which this thread is running,
30993 then this field is the core identifier. This field is optional.
30997 @subsubheading Example
31002 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31003 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31004 args=[]@},state="running"@},
31005 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31006 frame=@{level="0",addr="0x0804891f",func="foo",
31007 args=[@{name="i",value="10"@}],
31008 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
31009 state="running"@}],
31010 current-thread-id="1"
31014 @subheading The @code{-thread-list-ids} Command
31015 @findex -thread-list-ids
31017 @subsubheading Synopsis
31023 Produces a list of the currently known @value{GDBN} thread ids. At the
31024 end of the list it also prints the total number of such threads.
31026 This command is retained for historical reasons, the
31027 @code{-thread-info} command should be used instead.
31029 @subsubheading @value{GDBN} Command
31031 Part of @samp{info threads} supplies the same information.
31033 @subsubheading Example
31038 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31039 current-thread-id="1",number-of-threads="3"
31044 @subheading The @code{-thread-select} Command
31045 @findex -thread-select
31047 @subsubheading Synopsis
31050 -thread-select @var{threadnum}
31053 Make @var{threadnum} the current thread. It prints the number of the new
31054 current thread, and the topmost frame for that thread.
31056 This command is deprecated in favor of explicitly using the
31057 @samp{--thread} option to each command.
31059 @subsubheading @value{GDBN} Command
31061 The corresponding @value{GDBN} command is @samp{thread}.
31063 @subsubheading Example
31070 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31071 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31075 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31076 number-of-threads="3"
31079 ^done,new-thread-id="3",
31080 frame=@{level="0",func="vprintf",
31081 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31082 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
31086 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31087 @node GDB/MI Ada Tasking Commands
31088 @section @sc{gdb/mi} Ada Tasking Commands
31090 @subheading The @code{-ada-task-info} Command
31091 @findex -ada-task-info
31093 @subsubheading Synopsis
31096 -ada-task-info [ @var{task-id} ]
31099 Reports information about either a specific Ada task, if the
31100 @var{task-id} parameter is present, or about all Ada tasks.
31102 @subsubheading @value{GDBN} Command
31104 The @samp{info tasks} command prints the same information
31105 about all Ada tasks (@pxref{Ada Tasks}).
31107 @subsubheading Result
31109 The result is a table of Ada tasks. The following columns are
31110 defined for each Ada task:
31114 This field exists only for the current thread. It has the value @samp{*}.
31117 The identifier that @value{GDBN} uses to refer to the Ada task.
31120 The identifier that the target uses to refer to the Ada task.
31123 The identifier of the thread corresponding to the Ada task.
31125 This field should always exist, as Ada tasks are always implemented
31126 on top of a thread. But if @value{GDBN} cannot find this corresponding
31127 thread for any reason, the field is omitted.
31130 This field exists only when the task was created by another task.
31131 In this case, it provides the ID of the parent task.
31134 The base priority of the task.
31137 The current state of the task. For a detailed description of the
31138 possible states, see @ref{Ada Tasks}.
31141 The name of the task.
31145 @subsubheading Example
31149 ^done,tasks=@{nr_rows="3",nr_cols="8",
31150 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31151 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31152 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31153 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31154 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31155 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31156 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31157 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31158 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31159 state="Child Termination Wait",name="main_task"@}]@}
31163 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31164 @node GDB/MI Program Execution
31165 @section @sc{gdb/mi} Program Execution
31167 These are the asynchronous commands which generate the out-of-band
31168 record @samp{*stopped}. Currently @value{GDBN} only really executes
31169 asynchronously with remote targets and this interaction is mimicked in
31172 @subheading The @code{-exec-continue} Command
31173 @findex -exec-continue
31175 @subsubheading Synopsis
31178 -exec-continue [--reverse] [--all|--thread-group N]
31181 Resumes the execution of the inferior program, which will continue
31182 to execute until it reaches a debugger stop event. If the
31183 @samp{--reverse} option is specified, execution resumes in reverse until
31184 it reaches a stop event. Stop events may include
31187 breakpoints or watchpoints
31189 signals or exceptions
31191 the end of the process (or its beginning under @samp{--reverse})
31193 the end or beginning of a replay log if one is being used.
31195 In all-stop mode (@pxref{All-Stop
31196 Mode}), may resume only one thread, or all threads, depending on the
31197 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31198 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31199 ignored in all-stop mode. If the @samp{--thread-group} options is
31200 specified, then all threads in that thread group are resumed.
31202 @subsubheading @value{GDBN} Command
31204 The corresponding @value{GDBN} corresponding is @samp{continue}.
31206 @subsubheading Example
31213 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31214 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31220 @subheading The @code{-exec-finish} Command
31221 @findex -exec-finish
31223 @subsubheading Synopsis
31226 -exec-finish [--reverse]
31229 Resumes the execution of the inferior program until the current
31230 function is exited. Displays the results returned by the function.
31231 If the @samp{--reverse} option is specified, resumes the reverse
31232 execution of the inferior program until the point where current
31233 function was called.
31235 @subsubheading @value{GDBN} Command
31237 The corresponding @value{GDBN} command is @samp{finish}.
31239 @subsubheading Example
31241 Function returning @code{void}.
31248 *stopped,reason="function-finished",frame=@{func="main",args=[],
31249 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31253 Function returning other than @code{void}. The name of the internal
31254 @value{GDBN} variable storing the result is printed, together with the
31261 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31262 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31263 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31264 gdb-result-var="$1",return-value="0"
31269 @subheading The @code{-exec-interrupt} Command
31270 @findex -exec-interrupt
31272 @subsubheading Synopsis
31275 -exec-interrupt [--all|--thread-group N]
31278 Interrupts the background execution of the target. Note how the token
31279 associated with the stop message is the one for the execution command
31280 that has been interrupted. The token for the interrupt itself only
31281 appears in the @samp{^done} output. If the user is trying to
31282 interrupt a non-running program, an error message will be printed.
31284 Note that when asynchronous execution is enabled, this command is
31285 asynchronous just like other execution commands. That is, first the
31286 @samp{^done} response will be printed, and the target stop will be
31287 reported after that using the @samp{*stopped} notification.
31289 In non-stop mode, only the context thread is interrupted by default.
31290 All threads (in all inferiors) will be interrupted if the
31291 @samp{--all} option is specified. If the @samp{--thread-group}
31292 option is specified, all threads in that group will be interrupted.
31294 @subsubheading @value{GDBN} Command
31296 The corresponding @value{GDBN} command is @samp{interrupt}.
31298 @subsubheading Example
31309 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31310 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31311 fullname="/home/foo/bar/try.c",line="13"@}
31316 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31320 @subheading The @code{-exec-jump} Command
31323 @subsubheading Synopsis
31326 -exec-jump @var{location}
31329 Resumes execution of the inferior program at the location specified by
31330 parameter. @xref{Specify Location}, for a description of the
31331 different forms of @var{location}.
31333 @subsubheading @value{GDBN} Command
31335 The corresponding @value{GDBN} command is @samp{jump}.
31337 @subsubheading Example
31340 -exec-jump foo.c:10
31341 *running,thread-id="all"
31346 @subheading The @code{-exec-next} Command
31349 @subsubheading Synopsis
31352 -exec-next [--reverse]
31355 Resumes execution of the inferior program, stopping when the beginning
31356 of the next source line is reached.
31358 If the @samp{--reverse} option is specified, resumes reverse execution
31359 of the inferior program, stopping at the beginning of the previous
31360 source line. If you issue this command on the first line of a
31361 function, it will take you back to the caller of that function, to the
31362 source line where the function was called.
31365 @subsubheading @value{GDBN} Command
31367 The corresponding @value{GDBN} command is @samp{next}.
31369 @subsubheading Example
31375 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31380 @subheading The @code{-exec-next-instruction} Command
31381 @findex -exec-next-instruction
31383 @subsubheading Synopsis
31386 -exec-next-instruction [--reverse]
31389 Executes one machine instruction. If the instruction is a function
31390 call, continues until the function returns. If the program stops at an
31391 instruction in the middle of a source line, the address will be
31394 If the @samp{--reverse} option is specified, resumes reverse execution
31395 of the inferior program, stopping at the previous instruction. If the
31396 previously executed instruction was a return from another function,
31397 it will continue to execute in reverse until the call to that function
31398 (from the current stack frame) is reached.
31400 @subsubheading @value{GDBN} Command
31402 The corresponding @value{GDBN} command is @samp{nexti}.
31404 @subsubheading Example
31408 -exec-next-instruction
31412 *stopped,reason="end-stepping-range",
31413 addr="0x000100d4",line="5",file="hello.c"
31418 @subheading The @code{-exec-return} Command
31419 @findex -exec-return
31421 @subsubheading Synopsis
31427 Makes current function return immediately. Doesn't execute the inferior.
31428 Displays the new current frame.
31430 @subsubheading @value{GDBN} Command
31432 The corresponding @value{GDBN} command is @samp{return}.
31434 @subsubheading Example
31438 200-break-insert callee4
31439 200^done,bkpt=@{number="1",addr="0x00010734",
31440 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31445 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31446 frame=@{func="callee4",args=[],
31447 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31448 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31454 111^done,frame=@{level="0",func="callee3",
31455 args=[@{name="strarg",
31456 value="0x11940 \"A string argument.\""@}],
31457 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31458 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31463 @subheading The @code{-exec-run} Command
31466 @subsubheading Synopsis
31469 -exec-run [ --all | --thread-group N ] [ --start ]
31472 Starts execution of the inferior from the beginning. The inferior
31473 executes until either a breakpoint is encountered or the program
31474 exits. In the latter case the output will include an exit code, if
31475 the program has exited exceptionally.
31477 When neither the @samp{--all} nor the @samp{--thread-group} option
31478 is specified, the current inferior is started. If the
31479 @samp{--thread-group} option is specified, it should refer to a thread
31480 group of type @samp{process}, and that thread group will be started.
31481 If the @samp{--all} option is specified, then all inferiors will be started.
31483 Using the @samp{--start} option instructs the debugger to stop
31484 the execution at the start of the inferior's main subprogram,
31485 following the same behavior as the @code{start} command
31486 (@pxref{Starting}).
31488 @subsubheading @value{GDBN} Command
31490 The corresponding @value{GDBN} command is @samp{run}.
31492 @subsubheading Examples
31497 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31502 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31503 frame=@{func="main",args=[],file="recursive2.c",
31504 fullname="/home/foo/bar/recursive2.c",line="4"@}
31509 Program exited normally:
31517 *stopped,reason="exited-normally"
31522 Program exited exceptionally:
31530 *stopped,reason="exited",exit-code="01"
31534 Another way the program can terminate is if it receives a signal such as
31535 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31539 *stopped,reason="exited-signalled",signal-name="SIGINT",
31540 signal-meaning="Interrupt"
31544 @c @subheading -exec-signal
31547 @subheading The @code{-exec-step} Command
31550 @subsubheading Synopsis
31553 -exec-step [--reverse]
31556 Resumes execution of the inferior program, stopping when the beginning
31557 of the next source line is reached, if the next source line is not a
31558 function call. If it is, stop at the first instruction of the called
31559 function. If the @samp{--reverse} option is specified, resumes reverse
31560 execution of the inferior program, stopping at the beginning of the
31561 previously executed source line.
31563 @subsubheading @value{GDBN} Command
31565 The corresponding @value{GDBN} command is @samp{step}.
31567 @subsubheading Example
31569 Stepping into a function:
31575 *stopped,reason="end-stepping-range",
31576 frame=@{func="foo",args=[@{name="a",value="10"@},
31577 @{name="b",value="0"@}],file="recursive2.c",
31578 fullname="/home/foo/bar/recursive2.c",line="11"@}
31588 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31593 @subheading The @code{-exec-step-instruction} Command
31594 @findex -exec-step-instruction
31596 @subsubheading Synopsis
31599 -exec-step-instruction [--reverse]
31602 Resumes the inferior which executes one machine instruction. If the
31603 @samp{--reverse} option is specified, resumes reverse execution of the
31604 inferior program, stopping at the previously executed instruction.
31605 The output, once @value{GDBN} has stopped, will vary depending on
31606 whether we have stopped in the middle of a source line or not. In the
31607 former case, the address at which the program stopped will be printed
31610 @subsubheading @value{GDBN} Command
31612 The corresponding @value{GDBN} command is @samp{stepi}.
31614 @subsubheading Example
31618 -exec-step-instruction
31622 *stopped,reason="end-stepping-range",
31623 frame=@{func="foo",args=[],file="try.c",
31624 fullname="/home/foo/bar/try.c",line="10"@}
31626 -exec-step-instruction
31630 *stopped,reason="end-stepping-range",
31631 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31632 fullname="/home/foo/bar/try.c",line="10"@}
31637 @subheading The @code{-exec-until} Command
31638 @findex -exec-until
31640 @subsubheading Synopsis
31643 -exec-until [ @var{location} ]
31646 Executes the inferior until the @var{location} specified in the
31647 argument is reached. If there is no argument, the inferior executes
31648 until a source line greater than the current one is reached. The
31649 reason for stopping in this case will be @samp{location-reached}.
31651 @subsubheading @value{GDBN} Command
31653 The corresponding @value{GDBN} command is @samp{until}.
31655 @subsubheading Example
31659 -exec-until recursive2.c:6
31663 *stopped,reason="location-reached",frame=@{func="main",args=[],
31664 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31669 @subheading -file-clear
31670 Is this going away????
31673 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31674 @node GDB/MI Stack Manipulation
31675 @section @sc{gdb/mi} Stack Manipulation Commands
31677 @subheading The @code{-enable-frame-filters} Command
31678 @findex -enable-frame-filters
31681 -enable-frame-filters
31684 @value{GDBN} allows Python-based frame filters to affect the output of
31685 the MI commands relating to stack traces. As there is no way to
31686 implement this in a fully backward-compatible way, a front end must
31687 request that this functionality be enabled.
31689 Once enabled, this feature cannot be disabled.
31691 Note that if Python support has not been compiled into @value{GDBN},
31692 this command will still succeed (and do nothing).
31694 @subheading The @code{-stack-info-frame} Command
31695 @findex -stack-info-frame
31697 @subsubheading Synopsis
31703 Get info on the selected frame.
31705 @subsubheading @value{GDBN} Command
31707 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31708 (without arguments).
31710 @subsubheading Example
31715 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31716 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31717 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31721 @subheading The @code{-stack-info-depth} Command
31722 @findex -stack-info-depth
31724 @subsubheading Synopsis
31727 -stack-info-depth [ @var{max-depth} ]
31730 Return the depth of the stack. If the integer argument @var{max-depth}
31731 is specified, do not count beyond @var{max-depth} frames.
31733 @subsubheading @value{GDBN} Command
31735 There's no equivalent @value{GDBN} command.
31737 @subsubheading Example
31739 For a stack with frame levels 0 through 11:
31746 -stack-info-depth 4
31749 -stack-info-depth 12
31752 -stack-info-depth 11
31755 -stack-info-depth 13
31760 @anchor{-stack-list-arguments}
31761 @subheading The @code{-stack-list-arguments} Command
31762 @findex -stack-list-arguments
31764 @subsubheading Synopsis
31767 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31768 [ @var{low-frame} @var{high-frame} ]
31771 Display a list of the arguments for the frames between @var{low-frame}
31772 and @var{high-frame} (inclusive). If @var{low-frame} and
31773 @var{high-frame} are not provided, list the arguments for the whole
31774 call stack. If the two arguments are equal, show the single frame
31775 at the corresponding level. It is an error if @var{low-frame} is
31776 larger than the actual number of frames. On the other hand,
31777 @var{high-frame} may be larger than the actual number of frames, in
31778 which case only existing frames will be returned.
31780 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31781 the variables; if it is 1 or @code{--all-values}, print also their
31782 values; and if it is 2 or @code{--simple-values}, print the name,
31783 type and value for simple data types, and the name and type for arrays,
31784 structures and unions. If the option @code{--no-frame-filters} is
31785 supplied, then Python frame filters will not be executed.
31787 If the @code{--skip-unavailable} option is specified, arguments that
31788 are not available are not listed. Partially available arguments
31789 are still displayed, however.
31791 Use of this command to obtain arguments in a single frame is
31792 deprecated in favor of the @samp{-stack-list-variables} command.
31794 @subsubheading @value{GDBN} Command
31796 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31797 @samp{gdb_get_args} command which partially overlaps with the
31798 functionality of @samp{-stack-list-arguments}.
31800 @subsubheading Example
31807 frame=@{level="0",addr="0x00010734",func="callee4",
31808 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31809 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31810 frame=@{level="1",addr="0x0001076c",func="callee3",
31811 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31812 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31813 frame=@{level="2",addr="0x0001078c",func="callee2",
31814 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31815 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31816 frame=@{level="3",addr="0x000107b4",func="callee1",
31817 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31818 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31819 frame=@{level="4",addr="0x000107e0",func="main",
31820 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31821 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31823 -stack-list-arguments 0
31826 frame=@{level="0",args=[]@},
31827 frame=@{level="1",args=[name="strarg"]@},
31828 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31829 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31830 frame=@{level="4",args=[]@}]
31832 -stack-list-arguments 1
31835 frame=@{level="0",args=[]@},
31837 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31838 frame=@{level="2",args=[
31839 @{name="intarg",value="2"@},
31840 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31841 @{frame=@{level="3",args=[
31842 @{name="intarg",value="2"@},
31843 @{name="strarg",value="0x11940 \"A string argument.\""@},
31844 @{name="fltarg",value="3.5"@}]@},
31845 frame=@{level="4",args=[]@}]
31847 -stack-list-arguments 0 2 2
31848 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31850 -stack-list-arguments 1 2 2
31851 ^done,stack-args=[frame=@{level="2",
31852 args=[@{name="intarg",value="2"@},
31853 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31857 @c @subheading -stack-list-exception-handlers
31860 @anchor{-stack-list-frames}
31861 @subheading The @code{-stack-list-frames} Command
31862 @findex -stack-list-frames
31864 @subsubheading Synopsis
31867 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31870 List the frames currently on the stack. For each frame it displays the
31875 The frame number, 0 being the topmost frame, i.e., the innermost function.
31877 The @code{$pc} value for that frame.
31881 File name of the source file where the function lives.
31882 @item @var{fullname}
31883 The full file name of the source file where the function lives.
31885 Line number corresponding to the @code{$pc}.
31887 The shared library where this function is defined. This is only given
31888 if the frame's function is not known.
31891 If invoked without arguments, this command prints a backtrace for the
31892 whole stack. If given two integer arguments, it shows the frames whose
31893 levels are between the two arguments (inclusive). If the two arguments
31894 are equal, it shows the single frame at the corresponding level. It is
31895 an error if @var{low-frame} is larger than the actual number of
31896 frames. On the other hand, @var{high-frame} may be larger than the
31897 actual number of frames, in which case only existing frames will be
31898 returned. If the option @code{--no-frame-filters} is supplied, then
31899 Python frame filters will not be executed.
31901 @subsubheading @value{GDBN} Command
31903 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31905 @subsubheading Example
31907 Full stack backtrace:
31913 [frame=@{level="0",addr="0x0001076c",func="foo",
31914 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
31915 frame=@{level="1",addr="0x000107a4",func="foo",
31916 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31917 frame=@{level="2",addr="0x000107a4",func="foo",
31918 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31919 frame=@{level="3",addr="0x000107a4",func="foo",
31920 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31921 frame=@{level="4",addr="0x000107a4",func="foo",
31922 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31923 frame=@{level="5",addr="0x000107a4",func="foo",
31924 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31925 frame=@{level="6",addr="0x000107a4",func="foo",
31926 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31927 frame=@{level="7",addr="0x000107a4",func="foo",
31928 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31929 frame=@{level="8",addr="0x000107a4",func="foo",
31930 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31931 frame=@{level="9",addr="0x000107a4",func="foo",
31932 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31933 frame=@{level="10",addr="0x000107a4",func="foo",
31934 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31935 frame=@{level="11",addr="0x00010738",func="main",
31936 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
31940 Show frames between @var{low_frame} and @var{high_frame}:
31944 -stack-list-frames 3 5
31946 [frame=@{level="3",addr="0x000107a4",func="foo",
31947 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31948 frame=@{level="4",addr="0x000107a4",func="foo",
31949 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31950 frame=@{level="5",addr="0x000107a4",func="foo",
31951 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31955 Show a single frame:
31959 -stack-list-frames 3 3
31961 [frame=@{level="3",addr="0x000107a4",func="foo",
31962 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31967 @subheading The @code{-stack-list-locals} Command
31968 @findex -stack-list-locals
31969 @anchor{-stack-list-locals}
31971 @subsubheading Synopsis
31974 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31977 Display the local variable names for the selected frame. If
31978 @var{print-values} is 0 or @code{--no-values}, print only the names of
31979 the variables; if it is 1 or @code{--all-values}, print also their
31980 values; and if it is 2 or @code{--simple-values}, print the name,
31981 type and value for simple data types, and the name and type for arrays,
31982 structures and unions. In this last case, a frontend can immediately
31983 display the value of simple data types and create variable objects for
31984 other data types when the user wishes to explore their values in
31985 more detail. If the option @code{--no-frame-filters} is supplied, then
31986 Python frame filters will not be executed.
31988 If the @code{--skip-unavailable} option is specified, local variables
31989 that are not available are not listed. Partially available local
31990 variables are still displayed, however.
31992 This command is deprecated in favor of the
31993 @samp{-stack-list-variables} command.
31995 @subsubheading @value{GDBN} Command
31997 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
31999 @subsubheading Example
32003 -stack-list-locals 0
32004 ^done,locals=[name="A",name="B",name="C"]
32006 -stack-list-locals --all-values
32007 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32008 @{name="C",value="@{1, 2, 3@}"@}]
32009 -stack-list-locals --simple-values
32010 ^done,locals=[@{name="A",type="int",value="1"@},
32011 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32015 @anchor{-stack-list-variables}
32016 @subheading The @code{-stack-list-variables} Command
32017 @findex -stack-list-variables
32019 @subsubheading Synopsis
32022 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32025 Display the names of local variables and function arguments for the selected frame. If
32026 @var{print-values} is 0 or @code{--no-values}, print only the names of
32027 the variables; if it is 1 or @code{--all-values}, print also their
32028 values; and if it is 2 or @code{--simple-values}, print the name,
32029 type and value for simple data types, and the name and type for arrays,
32030 structures and unions. If the option @code{--no-frame-filters} is
32031 supplied, then Python frame filters will not be executed.
32033 If the @code{--skip-unavailable} option is specified, local variables
32034 and arguments that are not available are not listed. Partially
32035 available arguments and local variables are still displayed, however.
32037 @subsubheading Example
32041 -stack-list-variables --thread 1 --frame 0 --all-values
32042 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32047 @subheading The @code{-stack-select-frame} Command
32048 @findex -stack-select-frame
32050 @subsubheading Synopsis
32053 -stack-select-frame @var{framenum}
32056 Change the selected frame. Select a different frame @var{framenum} on
32059 This command in deprecated in favor of passing the @samp{--frame}
32060 option to every command.
32062 @subsubheading @value{GDBN} Command
32064 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32065 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32067 @subsubheading Example
32071 -stack-select-frame 2
32076 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32077 @node GDB/MI Variable Objects
32078 @section @sc{gdb/mi} Variable Objects
32082 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32084 For the implementation of a variable debugger window (locals, watched
32085 expressions, etc.), we are proposing the adaptation of the existing code
32086 used by @code{Insight}.
32088 The two main reasons for that are:
32092 It has been proven in practice (it is already on its second generation).
32095 It will shorten development time (needless to say how important it is
32099 The original interface was designed to be used by Tcl code, so it was
32100 slightly changed so it could be used through @sc{gdb/mi}. This section
32101 describes the @sc{gdb/mi} operations that will be available and gives some
32102 hints about their use.
32104 @emph{Note}: In addition to the set of operations described here, we
32105 expect the @sc{gui} implementation of a variable window to require, at
32106 least, the following operations:
32109 @item @code{-gdb-show} @code{output-radix}
32110 @item @code{-stack-list-arguments}
32111 @item @code{-stack-list-locals}
32112 @item @code{-stack-select-frame}
32117 @subheading Introduction to Variable Objects
32119 @cindex variable objects in @sc{gdb/mi}
32121 Variable objects are "object-oriented" MI interface for examining and
32122 changing values of expressions. Unlike some other MI interfaces that
32123 work with expressions, variable objects are specifically designed for
32124 simple and efficient presentation in the frontend. A variable object
32125 is identified by string name. When a variable object is created, the
32126 frontend specifies the expression for that variable object. The
32127 expression can be a simple variable, or it can be an arbitrary complex
32128 expression, and can even involve CPU registers. After creating a
32129 variable object, the frontend can invoke other variable object
32130 operations---for example to obtain or change the value of a variable
32131 object, or to change display format.
32133 Variable objects have hierarchical tree structure. Any variable object
32134 that corresponds to a composite type, such as structure in C, has
32135 a number of child variable objects, for example corresponding to each
32136 element of a structure. A child variable object can itself have
32137 children, recursively. Recursion ends when we reach
32138 leaf variable objects, which always have built-in types. Child variable
32139 objects are created only by explicit request, so if a frontend
32140 is not interested in the children of a particular variable object, no
32141 child will be created.
32143 For a leaf variable object it is possible to obtain its value as a
32144 string, or set the value from a string. String value can be also
32145 obtained for a non-leaf variable object, but it's generally a string
32146 that only indicates the type of the object, and does not list its
32147 contents. Assignment to a non-leaf variable object is not allowed.
32149 A frontend does not need to read the values of all variable objects each time
32150 the program stops. Instead, MI provides an update command that lists all
32151 variable objects whose values has changed since the last update
32152 operation. This considerably reduces the amount of data that must
32153 be transferred to the frontend. As noted above, children variable
32154 objects are created on demand, and only leaf variable objects have a
32155 real value. As result, gdb will read target memory only for leaf
32156 variables that frontend has created.
32158 The automatic update is not always desirable. For example, a frontend
32159 might want to keep a value of some expression for future reference,
32160 and never update it. For another example, fetching memory is
32161 relatively slow for embedded targets, so a frontend might want
32162 to disable automatic update for the variables that are either not
32163 visible on the screen, or ``closed''. This is possible using so
32164 called ``frozen variable objects''. Such variable objects are never
32165 implicitly updated.
32167 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32168 fixed variable object, the expression is parsed when the variable
32169 object is created, including associating identifiers to specific
32170 variables. The meaning of expression never changes. For a floating
32171 variable object the values of variables whose names appear in the
32172 expressions are re-evaluated every time in the context of the current
32173 frame. Consider this example:
32178 struct work_state state;
32185 If a fixed variable object for the @code{state} variable is created in
32186 this function, and we enter the recursive call, the variable
32187 object will report the value of @code{state} in the top-level
32188 @code{do_work} invocation. On the other hand, a floating variable
32189 object will report the value of @code{state} in the current frame.
32191 If an expression specified when creating a fixed variable object
32192 refers to a local variable, the variable object becomes bound to the
32193 thread and frame in which the variable object is created. When such
32194 variable object is updated, @value{GDBN} makes sure that the
32195 thread/frame combination the variable object is bound to still exists,
32196 and re-evaluates the variable object in context of that thread/frame.
32198 The following is the complete set of @sc{gdb/mi} operations defined to
32199 access this functionality:
32201 @multitable @columnfractions .4 .6
32202 @item @strong{Operation}
32203 @tab @strong{Description}
32205 @item @code{-enable-pretty-printing}
32206 @tab enable Python-based pretty-printing
32207 @item @code{-var-create}
32208 @tab create a variable object
32209 @item @code{-var-delete}
32210 @tab delete the variable object and/or its children
32211 @item @code{-var-set-format}
32212 @tab set the display format of this variable
32213 @item @code{-var-show-format}
32214 @tab show the display format of this variable
32215 @item @code{-var-info-num-children}
32216 @tab tells how many children this object has
32217 @item @code{-var-list-children}
32218 @tab return a list of the object's children
32219 @item @code{-var-info-type}
32220 @tab show the type of this variable object
32221 @item @code{-var-info-expression}
32222 @tab print parent-relative expression that this variable object represents
32223 @item @code{-var-info-path-expression}
32224 @tab print full expression that this variable object represents
32225 @item @code{-var-show-attributes}
32226 @tab is this variable editable? does it exist here?
32227 @item @code{-var-evaluate-expression}
32228 @tab get the value of this variable
32229 @item @code{-var-assign}
32230 @tab set the value of this variable
32231 @item @code{-var-update}
32232 @tab update the variable and its children
32233 @item @code{-var-set-frozen}
32234 @tab set frozeness attribute
32235 @item @code{-var-set-update-range}
32236 @tab set range of children to display on update
32239 In the next subsection we describe each operation in detail and suggest
32240 how it can be used.
32242 @subheading Description And Use of Operations on Variable Objects
32244 @subheading The @code{-enable-pretty-printing} Command
32245 @findex -enable-pretty-printing
32248 -enable-pretty-printing
32251 @value{GDBN} allows Python-based visualizers to affect the output of the
32252 MI variable object commands. However, because there was no way to
32253 implement this in a fully backward-compatible way, a front end must
32254 request that this functionality be enabled.
32256 Once enabled, this feature cannot be disabled.
32258 Note that if Python support has not been compiled into @value{GDBN},
32259 this command will still succeed (and do nothing).
32261 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32262 may work differently in future versions of @value{GDBN}.
32264 @subheading The @code{-var-create} Command
32265 @findex -var-create
32267 @subsubheading Synopsis
32270 -var-create @{@var{name} | "-"@}
32271 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32274 This operation creates a variable object, which allows the monitoring of
32275 a variable, the result of an expression, a memory cell or a CPU
32278 The @var{name} parameter is the string by which the object can be
32279 referenced. It must be unique. If @samp{-} is specified, the varobj
32280 system will generate a string ``varNNNNNN'' automatically. It will be
32281 unique provided that one does not specify @var{name} of that format.
32282 The command fails if a duplicate name is found.
32284 The frame under which the expression should be evaluated can be
32285 specified by @var{frame-addr}. A @samp{*} indicates that the current
32286 frame should be used. A @samp{@@} indicates that a floating variable
32287 object must be created.
32289 @var{expression} is any expression valid on the current language set (must not
32290 begin with a @samp{*}), or one of the following:
32294 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32297 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32300 @samp{$@var{regname}} --- a CPU register name
32303 @cindex dynamic varobj
32304 A varobj's contents may be provided by a Python-based pretty-printer. In this
32305 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32306 have slightly different semantics in some cases. If the
32307 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32308 will never create a dynamic varobj. This ensures backward
32309 compatibility for existing clients.
32311 @subsubheading Result
32313 This operation returns attributes of the newly-created varobj. These
32318 The name of the varobj.
32321 The number of children of the varobj. This number is not necessarily
32322 reliable for a dynamic varobj. Instead, you must examine the
32323 @samp{has_more} attribute.
32326 The varobj's scalar value. For a varobj whose type is some sort of
32327 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32328 will not be interesting.
32331 The varobj's type. This is a string representation of the type, as
32332 would be printed by the @value{GDBN} CLI. If @samp{print object}
32333 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32334 @emph{actual} (derived) type of the object is shown rather than the
32335 @emph{declared} one.
32338 If a variable object is bound to a specific thread, then this is the
32339 thread's identifier.
32342 For a dynamic varobj, this indicates whether there appear to be any
32343 children available. For a non-dynamic varobj, this will be 0.
32346 This attribute will be present and have the value @samp{1} if the
32347 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32348 then this attribute will not be present.
32351 A dynamic varobj can supply a display hint to the front end. The
32352 value comes directly from the Python pretty-printer object's
32353 @code{display_hint} method. @xref{Pretty Printing API}.
32356 Typical output will look like this:
32359 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32360 has_more="@var{has_more}"
32364 @subheading The @code{-var-delete} Command
32365 @findex -var-delete
32367 @subsubheading Synopsis
32370 -var-delete [ -c ] @var{name}
32373 Deletes a previously created variable object and all of its children.
32374 With the @samp{-c} option, just deletes the children.
32376 Returns an error if the object @var{name} is not found.
32379 @subheading The @code{-var-set-format} Command
32380 @findex -var-set-format
32382 @subsubheading Synopsis
32385 -var-set-format @var{name} @var{format-spec}
32388 Sets the output format for the value of the object @var{name} to be
32391 @anchor{-var-set-format}
32392 The syntax for the @var{format-spec} is as follows:
32395 @var{format-spec} @expansion{}
32396 @{binary | decimal | hexadecimal | octal | natural@}
32399 The natural format is the default format choosen automatically
32400 based on the variable type (like decimal for an @code{int}, hex
32401 for pointers, etc.).
32403 For a variable with children, the format is set only on the
32404 variable itself, and the children are not affected.
32406 @subheading The @code{-var-show-format} Command
32407 @findex -var-show-format
32409 @subsubheading Synopsis
32412 -var-show-format @var{name}
32415 Returns the format used to display the value of the object @var{name}.
32418 @var{format} @expansion{}
32423 @subheading The @code{-var-info-num-children} Command
32424 @findex -var-info-num-children
32426 @subsubheading Synopsis
32429 -var-info-num-children @var{name}
32432 Returns the number of children of a variable object @var{name}:
32438 Note that this number is not completely reliable for a dynamic varobj.
32439 It will return the current number of children, but more children may
32443 @subheading The @code{-var-list-children} Command
32444 @findex -var-list-children
32446 @subsubheading Synopsis
32449 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32451 @anchor{-var-list-children}
32453 Return a list of the children of the specified variable object and
32454 create variable objects for them, if they do not already exist. With
32455 a single argument or if @var{print-values} has a value of 0 or
32456 @code{--no-values}, print only the names of the variables; if
32457 @var{print-values} is 1 or @code{--all-values}, also print their
32458 values; and if it is 2 or @code{--simple-values} print the name and
32459 value for simple data types and just the name for arrays, structures
32462 @var{from} and @var{to}, if specified, indicate the range of children
32463 to report. If @var{from} or @var{to} is less than zero, the range is
32464 reset and all children will be reported. Otherwise, children starting
32465 at @var{from} (zero-based) and up to and excluding @var{to} will be
32468 If a child range is requested, it will only affect the current call to
32469 @code{-var-list-children}, but not future calls to @code{-var-update}.
32470 For this, you must instead use @code{-var-set-update-range}. The
32471 intent of this approach is to enable a front end to implement any
32472 update approach it likes; for example, scrolling a view may cause the
32473 front end to request more children with @code{-var-list-children}, and
32474 then the front end could call @code{-var-set-update-range} with a
32475 different range to ensure that future updates are restricted to just
32478 For each child the following results are returned:
32483 Name of the variable object created for this child.
32486 The expression to be shown to the user by the front end to designate this child.
32487 For example this may be the name of a structure member.
32489 For a dynamic varobj, this value cannot be used to form an
32490 expression. There is no way to do this at all with a dynamic varobj.
32492 For C/C@t{++} structures there are several pseudo children returned to
32493 designate access qualifiers. For these pseudo children @var{exp} is
32494 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32495 type and value are not present.
32497 A dynamic varobj will not report the access qualifying
32498 pseudo-children, regardless of the language. This information is not
32499 available at all with a dynamic varobj.
32502 Number of children this child has. For a dynamic varobj, this will be
32506 The type of the child. If @samp{print object}
32507 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32508 @emph{actual} (derived) type of the object is shown rather than the
32509 @emph{declared} one.
32512 If values were requested, this is the value.
32515 If this variable object is associated with a thread, this is the thread id.
32516 Otherwise this result is not present.
32519 If the variable object is frozen, this variable will be present with a value of 1.
32522 The result may have its own attributes:
32526 A dynamic varobj can supply a display hint to the front end. The
32527 value comes directly from the Python pretty-printer object's
32528 @code{display_hint} method. @xref{Pretty Printing API}.
32531 This is an integer attribute which is nonzero if there are children
32532 remaining after the end of the selected range.
32535 @subsubheading Example
32539 -var-list-children n
32540 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32541 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32543 -var-list-children --all-values n
32544 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32545 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32549 @subheading The @code{-var-info-type} Command
32550 @findex -var-info-type
32552 @subsubheading Synopsis
32555 -var-info-type @var{name}
32558 Returns the type of the specified variable @var{name}. The type is
32559 returned as a string in the same format as it is output by the
32563 type=@var{typename}
32567 @subheading The @code{-var-info-expression} Command
32568 @findex -var-info-expression
32570 @subsubheading Synopsis
32573 -var-info-expression @var{name}
32576 Returns a string that is suitable for presenting this
32577 variable object in user interface. The string is generally
32578 not valid expression in the current language, and cannot be evaluated.
32580 For example, if @code{a} is an array, and variable object
32581 @code{A} was created for @code{a}, then we'll get this output:
32584 (gdb) -var-info-expression A.1
32585 ^done,lang="C",exp="1"
32589 Here, the value of @code{lang} is the language name, which can be
32590 found in @ref{Supported Languages}.
32592 Note that the output of the @code{-var-list-children} command also
32593 includes those expressions, so the @code{-var-info-expression} command
32596 @subheading The @code{-var-info-path-expression} Command
32597 @findex -var-info-path-expression
32599 @subsubheading Synopsis
32602 -var-info-path-expression @var{name}
32605 Returns an expression that can be evaluated in the current
32606 context and will yield the same value that a variable object has.
32607 Compare this with the @code{-var-info-expression} command, which
32608 result can be used only for UI presentation. Typical use of
32609 the @code{-var-info-path-expression} command is creating a
32610 watchpoint from a variable object.
32612 This command is currently not valid for children of a dynamic varobj,
32613 and will give an error when invoked on one.
32615 For example, suppose @code{C} is a C@t{++} class, derived from class
32616 @code{Base}, and that the @code{Base} class has a member called
32617 @code{m_size}. Assume a variable @code{c} is has the type of
32618 @code{C} and a variable object @code{C} was created for variable
32619 @code{c}. Then, we'll get this output:
32621 (gdb) -var-info-path-expression C.Base.public.m_size
32622 ^done,path_expr=((Base)c).m_size)
32625 @subheading The @code{-var-show-attributes} Command
32626 @findex -var-show-attributes
32628 @subsubheading Synopsis
32631 -var-show-attributes @var{name}
32634 List attributes of the specified variable object @var{name}:
32637 status=@var{attr} [ ( ,@var{attr} )* ]
32641 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32643 @subheading The @code{-var-evaluate-expression} Command
32644 @findex -var-evaluate-expression
32646 @subsubheading Synopsis
32649 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32652 Evaluates the expression that is represented by the specified variable
32653 object and returns its value as a string. The format of the string
32654 can be specified with the @samp{-f} option. The possible values of
32655 this option are the same as for @code{-var-set-format}
32656 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32657 the current display format will be used. The current display format
32658 can be changed using the @code{-var-set-format} command.
32664 Note that one must invoke @code{-var-list-children} for a variable
32665 before the value of a child variable can be evaluated.
32667 @subheading The @code{-var-assign} Command
32668 @findex -var-assign
32670 @subsubheading Synopsis
32673 -var-assign @var{name} @var{expression}
32676 Assigns the value of @var{expression} to the variable object specified
32677 by @var{name}. The object must be @samp{editable}. If the variable's
32678 value is altered by the assign, the variable will show up in any
32679 subsequent @code{-var-update} list.
32681 @subsubheading Example
32689 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32693 @subheading The @code{-var-update} Command
32694 @findex -var-update
32696 @subsubheading Synopsis
32699 -var-update [@var{print-values}] @{@var{name} | "*"@}
32702 Reevaluate the expressions corresponding to the variable object
32703 @var{name} and all its direct and indirect children, and return the
32704 list of variable objects whose values have changed; @var{name} must
32705 be a root variable object. Here, ``changed'' means that the result of
32706 @code{-var-evaluate-expression} before and after the
32707 @code{-var-update} is different. If @samp{*} is used as the variable
32708 object names, all existing variable objects are updated, except
32709 for frozen ones (@pxref{-var-set-frozen}). The option
32710 @var{print-values} determines whether both names and values, or just
32711 names are printed. The possible values of this option are the same
32712 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32713 recommended to use the @samp{--all-values} option, to reduce the
32714 number of MI commands needed on each program stop.
32716 With the @samp{*} parameter, if a variable object is bound to a
32717 currently running thread, it will not be updated, without any
32720 If @code{-var-set-update-range} was previously used on a varobj, then
32721 only the selected range of children will be reported.
32723 @code{-var-update} reports all the changed varobjs in a tuple named
32726 Each item in the change list is itself a tuple holding:
32730 The name of the varobj.
32733 If values were requested for this update, then this field will be
32734 present and will hold the value of the varobj.
32737 @anchor{-var-update}
32738 This field is a string which may take one of three values:
32742 The variable object's current value is valid.
32745 The variable object does not currently hold a valid value but it may
32746 hold one in the future if its associated expression comes back into
32750 The variable object no longer holds a valid value.
32751 This can occur when the executable file being debugged has changed,
32752 either through recompilation or by using the @value{GDBN} @code{file}
32753 command. The front end should normally choose to delete these variable
32757 In the future new values may be added to this list so the front should
32758 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32761 This is only present if the varobj is still valid. If the type
32762 changed, then this will be the string @samp{true}; otherwise it will
32765 When a varobj's type changes, its children are also likely to have
32766 become incorrect. Therefore, the varobj's children are automatically
32767 deleted when this attribute is @samp{true}. Also, the varobj's update
32768 range, when set using the @code{-var-set-update-range} command, is
32772 If the varobj's type changed, then this field will be present and will
32775 @item new_num_children
32776 For a dynamic varobj, if the number of children changed, or if the
32777 type changed, this will be the new number of children.
32779 The @samp{numchild} field in other varobj responses is generally not
32780 valid for a dynamic varobj -- it will show the number of children that
32781 @value{GDBN} knows about, but because dynamic varobjs lazily
32782 instantiate their children, this will not reflect the number of
32783 children which may be available.
32785 The @samp{new_num_children} attribute only reports changes to the
32786 number of children known by @value{GDBN}. This is the only way to
32787 detect whether an update has removed children (which necessarily can
32788 only happen at the end of the update range).
32791 The display hint, if any.
32794 This is an integer value, which will be 1 if there are more children
32795 available outside the varobj's update range.
32798 This attribute will be present and have the value @samp{1} if the
32799 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32800 then this attribute will not be present.
32803 If new children were added to a dynamic varobj within the selected
32804 update range (as set by @code{-var-set-update-range}), then they will
32805 be listed in this attribute.
32808 @subsubheading Example
32815 -var-update --all-values var1
32816 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32817 type_changed="false"@}]
32821 @subheading The @code{-var-set-frozen} Command
32822 @findex -var-set-frozen
32823 @anchor{-var-set-frozen}
32825 @subsubheading Synopsis
32828 -var-set-frozen @var{name} @var{flag}
32831 Set the frozenness flag on the variable object @var{name}. The
32832 @var{flag} parameter should be either @samp{1} to make the variable
32833 frozen or @samp{0} to make it unfrozen. If a variable object is
32834 frozen, then neither itself, nor any of its children, are
32835 implicitly updated by @code{-var-update} of
32836 a parent variable or by @code{-var-update *}. Only
32837 @code{-var-update} of the variable itself will update its value and
32838 values of its children. After a variable object is unfrozen, it is
32839 implicitly updated by all subsequent @code{-var-update} operations.
32840 Unfreezing a variable does not update it, only subsequent
32841 @code{-var-update} does.
32843 @subsubheading Example
32847 -var-set-frozen V 1
32852 @subheading The @code{-var-set-update-range} command
32853 @findex -var-set-update-range
32854 @anchor{-var-set-update-range}
32856 @subsubheading Synopsis
32859 -var-set-update-range @var{name} @var{from} @var{to}
32862 Set the range of children to be returned by future invocations of
32863 @code{-var-update}.
32865 @var{from} and @var{to} indicate the range of children to report. If
32866 @var{from} or @var{to} is less than zero, the range is reset and all
32867 children will be reported. Otherwise, children starting at @var{from}
32868 (zero-based) and up to and excluding @var{to} will be reported.
32870 @subsubheading Example
32874 -var-set-update-range V 1 2
32878 @subheading The @code{-var-set-visualizer} command
32879 @findex -var-set-visualizer
32880 @anchor{-var-set-visualizer}
32882 @subsubheading Synopsis
32885 -var-set-visualizer @var{name} @var{visualizer}
32888 Set a visualizer for the variable object @var{name}.
32890 @var{visualizer} is the visualizer to use. The special value
32891 @samp{None} means to disable any visualizer in use.
32893 If not @samp{None}, @var{visualizer} must be a Python expression.
32894 This expression must evaluate to a callable object which accepts a
32895 single argument. @value{GDBN} will call this object with the value of
32896 the varobj @var{name} as an argument (this is done so that the same
32897 Python pretty-printing code can be used for both the CLI and MI).
32898 When called, this object must return an object which conforms to the
32899 pretty-printing interface (@pxref{Pretty Printing API}).
32901 The pre-defined function @code{gdb.default_visualizer} may be used to
32902 select a visualizer by following the built-in process
32903 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32904 a varobj is created, and so ordinarily is not needed.
32906 This feature is only available if Python support is enabled. The MI
32907 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
32908 can be used to check this.
32910 @subsubheading Example
32912 Resetting the visualizer:
32916 -var-set-visualizer V None
32920 Reselecting the default (type-based) visualizer:
32924 -var-set-visualizer V gdb.default_visualizer
32928 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32929 can be used to instantiate this class for a varobj:
32933 -var-set-visualizer V "lambda val: SomeClass()"
32937 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32938 @node GDB/MI Data Manipulation
32939 @section @sc{gdb/mi} Data Manipulation
32941 @cindex data manipulation, in @sc{gdb/mi}
32942 @cindex @sc{gdb/mi}, data manipulation
32943 This section describes the @sc{gdb/mi} commands that manipulate data:
32944 examine memory and registers, evaluate expressions, etc.
32946 @c REMOVED FROM THE INTERFACE.
32947 @c @subheading -data-assign
32948 @c Change the value of a program variable. Plenty of side effects.
32949 @c @subsubheading GDB Command
32951 @c @subsubheading Example
32954 @subheading The @code{-data-disassemble} Command
32955 @findex -data-disassemble
32957 @subsubheading Synopsis
32961 [ -s @var{start-addr} -e @var{end-addr} ]
32962 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32970 @item @var{start-addr}
32971 is the beginning address (or @code{$pc})
32972 @item @var{end-addr}
32974 @item @var{filename}
32975 is the name of the file to disassemble
32976 @item @var{linenum}
32977 is the line number to disassemble around
32979 is the number of disassembly lines to be produced. If it is -1,
32980 the whole function will be disassembled, in case no @var{end-addr} is
32981 specified. If @var{end-addr} is specified as a non-zero value, and
32982 @var{lines} is lower than the number of disassembly lines between
32983 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
32984 displayed; if @var{lines} is higher than the number of lines between
32985 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
32988 is either 0 (meaning only disassembly), 1 (meaning mixed source and
32989 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
32990 mixed source and disassembly with raw opcodes).
32993 @subsubheading Result
32995 The result of the @code{-data-disassemble} command will be a list named
32996 @samp{asm_insns}, the contents of this list depend on the @var{mode}
32997 used with the @code{-data-disassemble} command.
32999 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33004 The address at which this instruction was disassembled.
33007 The name of the function this instruction is within.
33010 The decimal offset in bytes from the start of @samp{func-name}.
33013 The text disassembly for this @samp{address}.
33016 This field is only present for mode 2. This contains the raw opcode
33017 bytes for the @samp{inst} field.
33021 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
33022 @samp{src_and_asm_line}, each of which has the following fields:
33026 The line number within @samp{file}.
33029 The file name from the compilation unit. This might be an absolute
33030 file name or a relative file name depending on the compile command
33034 Absolute file name of @samp{file}. It is converted to a canonical form
33035 using the source file search path
33036 (@pxref{Source Path, ,Specifying Source Directories})
33037 and after resolving all the symbolic links.
33039 If the source file is not found this field will contain the path as
33040 present in the debug information.
33042 @item line_asm_insn
33043 This is a list of tuples containing the disassembly for @samp{line} in
33044 @samp{file}. The fields of each tuple are the same as for
33045 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33046 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33051 Note that whatever included in the @samp{inst} field, is not
33052 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33055 @subsubheading @value{GDBN} Command
33057 The corresponding @value{GDBN} command is @samp{disassemble}.
33059 @subsubheading Example
33061 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33065 -data-disassemble -s $pc -e "$pc + 20" -- 0
33068 @{address="0x000107c0",func-name="main",offset="4",
33069 inst="mov 2, %o0"@},
33070 @{address="0x000107c4",func-name="main",offset="8",
33071 inst="sethi %hi(0x11800), %o2"@},
33072 @{address="0x000107c8",func-name="main",offset="12",
33073 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33074 @{address="0x000107cc",func-name="main",offset="16",
33075 inst="sethi %hi(0x11800), %o2"@},
33076 @{address="0x000107d0",func-name="main",offset="20",
33077 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33081 Disassemble the whole @code{main} function. Line 32 is part of
33085 -data-disassemble -f basics.c -l 32 -- 0
33087 @{address="0x000107bc",func-name="main",offset="0",
33088 inst="save %sp, -112, %sp"@},
33089 @{address="0x000107c0",func-name="main",offset="4",
33090 inst="mov 2, %o0"@},
33091 @{address="0x000107c4",func-name="main",offset="8",
33092 inst="sethi %hi(0x11800), %o2"@},
33094 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33095 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33099 Disassemble 3 instructions from the start of @code{main}:
33103 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33105 @{address="0x000107bc",func-name="main",offset="0",
33106 inst="save %sp, -112, %sp"@},
33107 @{address="0x000107c0",func-name="main",offset="4",
33108 inst="mov 2, %o0"@},
33109 @{address="0x000107c4",func-name="main",offset="8",
33110 inst="sethi %hi(0x11800), %o2"@}]
33114 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33118 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33120 src_and_asm_line=@{line="31",
33121 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33122 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33123 line_asm_insn=[@{address="0x000107bc",
33124 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33125 src_and_asm_line=@{line="32",
33126 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33127 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33128 line_asm_insn=[@{address="0x000107c0",
33129 func-name="main",offset="4",inst="mov 2, %o0"@},
33130 @{address="0x000107c4",func-name="main",offset="8",
33131 inst="sethi %hi(0x11800), %o2"@}]@}]
33136 @subheading The @code{-data-evaluate-expression} Command
33137 @findex -data-evaluate-expression
33139 @subsubheading Synopsis
33142 -data-evaluate-expression @var{expr}
33145 Evaluate @var{expr} as an expression. The expression could contain an
33146 inferior function call. The function call will execute synchronously.
33147 If the expression contains spaces, it must be enclosed in double quotes.
33149 @subsubheading @value{GDBN} Command
33151 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33152 @samp{call}. In @code{gdbtk} only, there's a corresponding
33153 @samp{gdb_eval} command.
33155 @subsubheading Example
33157 In the following example, the numbers that precede the commands are the
33158 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33159 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33163 211-data-evaluate-expression A
33166 311-data-evaluate-expression &A
33167 311^done,value="0xefffeb7c"
33169 411-data-evaluate-expression A+3
33172 511-data-evaluate-expression "A + 3"
33178 @subheading The @code{-data-list-changed-registers} Command
33179 @findex -data-list-changed-registers
33181 @subsubheading Synopsis
33184 -data-list-changed-registers
33187 Display a list of the registers that have changed.
33189 @subsubheading @value{GDBN} Command
33191 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33192 has the corresponding command @samp{gdb_changed_register_list}.
33194 @subsubheading Example
33196 On a PPC MBX board:
33204 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33205 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33208 -data-list-changed-registers
33209 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33210 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33211 "24","25","26","27","28","30","31","64","65","66","67","69"]
33216 @subheading The @code{-data-list-register-names} Command
33217 @findex -data-list-register-names
33219 @subsubheading Synopsis
33222 -data-list-register-names [ ( @var{regno} )+ ]
33225 Show a list of register names for the current target. If no arguments
33226 are given, it shows a list of the names of all the registers. If
33227 integer numbers are given as arguments, it will print a list of the
33228 names of the registers corresponding to the arguments. To ensure
33229 consistency between a register name and its number, the output list may
33230 include empty register names.
33232 @subsubheading @value{GDBN} Command
33234 @value{GDBN} does not have a command which corresponds to
33235 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33236 corresponding command @samp{gdb_regnames}.
33238 @subsubheading Example
33240 For the PPC MBX board:
33243 -data-list-register-names
33244 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33245 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33246 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33247 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33248 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33249 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33250 "", "pc","ps","cr","lr","ctr","xer"]
33252 -data-list-register-names 1 2 3
33253 ^done,register-names=["r1","r2","r3"]
33257 @subheading The @code{-data-list-register-values} Command
33258 @findex -data-list-register-values
33260 @subsubheading Synopsis
33263 -data-list-register-values
33264 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33267 Display the registers' contents. @var{fmt} is the format according to
33268 which the registers' contents are to be returned, followed by an optional
33269 list of numbers specifying the registers to display. A missing list of
33270 numbers indicates that the contents of all the registers must be
33271 returned. The @code{--skip-unavailable} option indicates that only
33272 the available registers are to be returned.
33274 Allowed formats for @var{fmt} are:
33291 @subsubheading @value{GDBN} Command
33293 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33294 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33296 @subsubheading Example
33298 For a PPC MBX board (note: line breaks are for readability only, they
33299 don't appear in the actual output):
33303 -data-list-register-values r 64 65
33304 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33305 @{number="65",value="0x00029002"@}]
33307 -data-list-register-values x
33308 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33309 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33310 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33311 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33312 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33313 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33314 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33315 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33316 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33317 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33318 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33319 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33320 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33321 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33322 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33323 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33324 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33325 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33326 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33327 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33328 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33329 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33330 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33331 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33332 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33333 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33334 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33335 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33336 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33337 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33338 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33339 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33340 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33341 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33342 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33343 @{number="69",value="0x20002b03"@}]
33348 @subheading The @code{-data-read-memory} Command
33349 @findex -data-read-memory
33351 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33353 @subsubheading Synopsis
33356 -data-read-memory [ -o @var{byte-offset} ]
33357 @var{address} @var{word-format} @var{word-size}
33358 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33365 @item @var{address}
33366 An expression specifying the address of the first memory word to be
33367 read. Complex expressions containing embedded white space should be
33368 quoted using the C convention.
33370 @item @var{word-format}
33371 The format to be used to print the memory words. The notation is the
33372 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33375 @item @var{word-size}
33376 The size of each memory word in bytes.
33378 @item @var{nr-rows}
33379 The number of rows in the output table.
33381 @item @var{nr-cols}
33382 The number of columns in the output table.
33385 If present, indicates that each row should include an @sc{ascii} dump. The
33386 value of @var{aschar} is used as a padding character when a byte is not a
33387 member of the printable @sc{ascii} character set (printable @sc{ascii}
33388 characters are those whose code is between 32 and 126, inclusively).
33390 @item @var{byte-offset}
33391 An offset to add to the @var{address} before fetching memory.
33394 This command displays memory contents as a table of @var{nr-rows} by
33395 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33396 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33397 (returned as @samp{total-bytes}). Should less than the requested number
33398 of bytes be returned by the target, the missing words are identified
33399 using @samp{N/A}. The number of bytes read from the target is returned
33400 in @samp{nr-bytes} and the starting address used to read memory in
33403 The address of the next/previous row or page is available in
33404 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33407 @subsubheading @value{GDBN} Command
33409 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33410 @samp{gdb_get_mem} memory read command.
33412 @subsubheading Example
33414 Read six bytes of memory starting at @code{bytes+6} but then offset by
33415 @code{-6} bytes. Format as three rows of two columns. One byte per
33416 word. Display each word in hex.
33420 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33421 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33422 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33423 prev-page="0x0000138a",memory=[
33424 @{addr="0x00001390",data=["0x00","0x01"]@},
33425 @{addr="0x00001392",data=["0x02","0x03"]@},
33426 @{addr="0x00001394",data=["0x04","0x05"]@}]
33430 Read two bytes of memory starting at address @code{shorts + 64} and
33431 display as a single word formatted in decimal.
33435 5-data-read-memory shorts+64 d 2 1 1
33436 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33437 next-row="0x00001512",prev-row="0x0000150e",
33438 next-page="0x00001512",prev-page="0x0000150e",memory=[
33439 @{addr="0x00001510",data=["128"]@}]
33443 Read thirty two bytes of memory starting at @code{bytes+16} and format
33444 as eight rows of four columns. Include a string encoding with @samp{x}
33445 used as the non-printable character.
33449 4-data-read-memory bytes+16 x 1 8 4 x
33450 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33451 next-row="0x000013c0",prev-row="0x0000139c",
33452 next-page="0x000013c0",prev-page="0x00001380",memory=[
33453 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33454 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33455 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33456 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33457 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33458 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33459 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33460 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33464 @subheading The @code{-data-read-memory-bytes} Command
33465 @findex -data-read-memory-bytes
33467 @subsubheading Synopsis
33470 -data-read-memory-bytes [ -o @var{byte-offset} ]
33471 @var{address} @var{count}
33478 @item @var{address}
33479 An expression specifying the address of the first memory word to be
33480 read. Complex expressions containing embedded white space should be
33481 quoted using the C convention.
33484 The number of bytes to read. This should be an integer literal.
33486 @item @var{byte-offset}
33487 The offsets in bytes relative to @var{address} at which to start
33488 reading. This should be an integer literal. This option is provided
33489 so that a frontend is not required to first evaluate address and then
33490 perform address arithmetics itself.
33494 This command attempts to read all accessible memory regions in the
33495 specified range. First, all regions marked as unreadable in the memory
33496 map (if one is defined) will be skipped. @xref{Memory Region
33497 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33498 regions. For each one, if reading full region results in an errors,
33499 @value{GDBN} will try to read a subset of the region.
33501 In general, every single byte in the region may be readable or not,
33502 and the only way to read every readable byte is to try a read at
33503 every address, which is not practical. Therefore, @value{GDBN} will
33504 attempt to read all accessible bytes at either beginning or the end
33505 of the region, using a binary division scheme. This heuristic works
33506 well for reading accross a memory map boundary. Note that if a region
33507 has a readable range that is neither at the beginning or the end,
33508 @value{GDBN} will not read it.
33510 The result record (@pxref{GDB/MI Result Records}) that is output of
33511 the command includes a field named @samp{memory} whose content is a
33512 list of tuples. Each tuple represent a successfully read memory block
33513 and has the following fields:
33517 The start address of the memory block, as hexadecimal literal.
33520 The end address of the memory block, as hexadecimal literal.
33523 The offset of the memory block, as hexadecimal literal, relative to
33524 the start address passed to @code{-data-read-memory-bytes}.
33527 The contents of the memory block, in hex.
33533 @subsubheading @value{GDBN} Command
33535 The corresponding @value{GDBN} command is @samp{x}.
33537 @subsubheading Example
33541 -data-read-memory-bytes &a 10
33542 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33544 contents="01000000020000000300"@}]
33549 @subheading The @code{-data-write-memory-bytes} Command
33550 @findex -data-write-memory-bytes
33552 @subsubheading Synopsis
33555 -data-write-memory-bytes @var{address} @var{contents}
33556 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33563 @item @var{address}
33564 An expression specifying the address of the first memory word to be
33565 read. Complex expressions containing embedded white space should be
33566 quoted using the C convention.
33568 @item @var{contents}
33569 The hex-encoded bytes to write.
33572 Optional argument indicating the number of bytes to be written. If @var{count}
33573 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33574 write @var{contents} until it fills @var{count} bytes.
33578 @subsubheading @value{GDBN} Command
33580 There's no corresponding @value{GDBN} command.
33582 @subsubheading Example
33586 -data-write-memory-bytes &a "aabbccdd"
33593 -data-write-memory-bytes &a "aabbccdd" 16e
33598 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33599 @node GDB/MI Tracepoint Commands
33600 @section @sc{gdb/mi} Tracepoint Commands
33602 The commands defined in this section implement MI support for
33603 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33605 @subheading The @code{-trace-find} Command
33606 @findex -trace-find
33608 @subsubheading Synopsis
33611 -trace-find @var{mode} [@var{parameters}@dots{}]
33614 Find a trace frame using criteria defined by @var{mode} and
33615 @var{parameters}. The following table lists permissible
33616 modes and their parameters. For details of operation, see @ref{tfind}.
33621 No parameters are required. Stops examining trace frames.
33624 An integer is required as parameter. Selects tracepoint frame with
33627 @item tracepoint-number
33628 An integer is required as parameter. Finds next
33629 trace frame that corresponds to tracepoint with the specified number.
33632 An address is required as parameter. Finds
33633 next trace frame that corresponds to any tracepoint at the specified
33636 @item pc-inside-range
33637 Two addresses are required as parameters. Finds next trace
33638 frame that corresponds to a tracepoint at an address inside the
33639 specified range. Both bounds are considered to be inside the range.
33641 @item pc-outside-range
33642 Two addresses are required as parameters. Finds
33643 next trace frame that corresponds to a tracepoint at an address outside
33644 the specified range. Both bounds are considered to be inside the range.
33647 Line specification is required as parameter. @xref{Specify Location}.
33648 Finds next trace frame that corresponds to a tracepoint at
33649 the specified location.
33653 If @samp{none} was passed as @var{mode}, the response does not
33654 have fields. Otherwise, the response may have the following fields:
33658 This field has either @samp{0} or @samp{1} as the value, depending
33659 on whether a matching tracepoint was found.
33662 The index of the found traceframe. This field is present iff
33663 the @samp{found} field has value of @samp{1}.
33666 The index of the found tracepoint. This field is present iff
33667 the @samp{found} field has value of @samp{1}.
33670 The information about the frame corresponding to the found trace
33671 frame. This field is present only if a trace frame was found.
33672 @xref{GDB/MI Frame Information}, for description of this field.
33676 @subsubheading @value{GDBN} Command
33678 The corresponding @value{GDBN} command is @samp{tfind}.
33680 @subheading -trace-define-variable
33681 @findex -trace-define-variable
33683 @subsubheading Synopsis
33686 -trace-define-variable @var{name} [ @var{value} ]
33689 Create trace variable @var{name} if it does not exist. If
33690 @var{value} is specified, sets the initial value of the specified
33691 trace variable to that value. Note that the @var{name} should start
33692 with the @samp{$} character.
33694 @subsubheading @value{GDBN} Command
33696 The corresponding @value{GDBN} command is @samp{tvariable}.
33698 @subheading The @code{-trace-frame-collected} Command
33699 @findex -trace-frame-collected
33701 @subsubheading Synopsis
33704 -trace-frame-collected
33705 [--var-print-values @var{var_pval}]
33706 [--comp-print-values @var{comp_pval}]
33707 [--registers-format @var{regformat}]
33708 [--memory-contents]
33711 This command returns the set of collected objects, register names,
33712 trace state variable names, memory ranges and computed expressions
33713 that have been collected at a particular trace frame. The optional
33714 parameters to the command affect the output format in different ways.
33715 See the output description table below for more details.
33717 The reported names can be used in the normal manner to create
33718 varobjs and inspect the objects themselves. The items returned by
33719 this command are categorized so that it is clear which is a variable,
33720 which is a register, which is a trace state variable, which is a
33721 memory range and which is a computed expression.
33723 For instance, if the actions were
33725 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33726 collect *(int*)0xaf02bef0@@40
33730 the object collected in its entirety would be @code{myVar}. The
33731 object @code{myArray} would be partially collected, because only the
33732 element at index @code{myIndex} would be collected. The remaining
33733 objects would be computed expressions.
33735 An example output would be:
33739 -trace-frame-collected
33741 explicit-variables=[@{name="myVar",value="1"@}],
33742 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33743 @{name="myObj.field",value="0"@},
33744 @{name="myPtr->field",value="1"@},
33745 @{name="myCount + 2",value="3"@},
33746 @{name="$tvar1 + 1",value="43970027"@}],
33747 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33748 @{number="1",value="0x0"@},
33749 @{number="2",value="0x4"@},
33751 @{number="125",value="0x0"@}],
33752 tvars=[@{name="$tvar1",current="43970026"@}],
33753 memory=[@{address="0x0000000000602264",length="4"@},
33754 @{address="0x0000000000615bc0",length="4"@}]
33761 @item explicit-variables
33762 The set of objects that have been collected in their entirety (as
33763 opposed to collecting just a few elements of an array or a few struct
33764 members). For each object, its name and value are printed.
33765 The @code{--var-print-values} option affects how or whether the value
33766 field is output. If @var{var_pval} is 0, then print only the names;
33767 if it is 1, print also their values; and if it is 2, print the name,
33768 type and value for simple data types, and the name and type for
33769 arrays, structures and unions.
33771 @item computed-expressions
33772 The set of computed expressions that have been collected at the
33773 current trace frame. The @code{--comp-print-values} option affects
33774 this set like the @code{--var-print-values} option affects the
33775 @code{explicit-variables} set. See above.
33778 The registers that have been collected at the current trace frame.
33779 For each register collected, the name and current value are returned.
33780 The value is formatted according to the @code{--registers-format}
33781 option. See the @command{-data-list-register-values} command for a
33782 list of the allowed formats. The default is @samp{x}.
33785 The trace state variables that have been collected at the current
33786 trace frame. For each trace state variable collected, the name and
33787 current value are returned.
33790 The set of memory ranges that have been collected at the current trace
33791 frame. Its content is a list of tuples. Each tuple represents a
33792 collected memory range and has the following fields:
33796 The start address of the memory range, as hexadecimal literal.
33799 The length of the memory range, as decimal literal.
33802 The contents of the memory block, in hex. This field is only present
33803 if the @code{--memory-contents} option is specified.
33809 @subsubheading @value{GDBN} Command
33811 There is no corresponding @value{GDBN} command.
33813 @subsubheading Example
33815 @subheading -trace-list-variables
33816 @findex -trace-list-variables
33818 @subsubheading Synopsis
33821 -trace-list-variables
33824 Return a table of all defined trace variables. Each element of the
33825 table has the following fields:
33829 The name of the trace variable. This field is always present.
33832 The initial value. This is a 64-bit signed integer. This
33833 field is always present.
33836 The value the trace variable has at the moment. This is a 64-bit
33837 signed integer. This field is absent iff current value is
33838 not defined, for example if the trace was never run, or is
33843 @subsubheading @value{GDBN} Command
33845 The corresponding @value{GDBN} command is @samp{tvariables}.
33847 @subsubheading Example
33851 -trace-list-variables
33852 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33853 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33854 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33855 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33856 body=[variable=@{name="$trace_timestamp",initial="0"@}
33857 variable=@{name="$foo",initial="10",current="15"@}]@}
33861 @subheading -trace-save
33862 @findex -trace-save
33864 @subsubheading Synopsis
33867 -trace-save [-r ] @var{filename}
33870 Saves the collected trace data to @var{filename}. Without the
33871 @samp{-r} option, the data is downloaded from the target and saved
33872 in a local file. With the @samp{-r} option the target is asked
33873 to perform the save.
33875 @subsubheading @value{GDBN} Command
33877 The corresponding @value{GDBN} command is @samp{tsave}.
33880 @subheading -trace-start
33881 @findex -trace-start
33883 @subsubheading Synopsis
33889 Starts a tracing experiments. The result of this command does not
33892 @subsubheading @value{GDBN} Command
33894 The corresponding @value{GDBN} command is @samp{tstart}.
33896 @subheading -trace-status
33897 @findex -trace-status
33899 @subsubheading Synopsis
33905 Obtains the status of a tracing experiment. The result may include
33906 the following fields:
33911 May have a value of either @samp{0}, when no tracing operations are
33912 supported, @samp{1}, when all tracing operations are supported, or
33913 @samp{file} when examining trace file. In the latter case, examining
33914 of trace frame is possible but new tracing experiement cannot be
33915 started. This field is always present.
33918 May have a value of either @samp{0} or @samp{1} depending on whether
33919 tracing experiement is in progress on target. This field is present
33920 if @samp{supported} field is not @samp{0}.
33923 Report the reason why the tracing was stopped last time. This field
33924 may be absent iff tracing was never stopped on target yet. The
33925 value of @samp{request} means the tracing was stopped as result of
33926 the @code{-trace-stop} command. The value of @samp{overflow} means
33927 the tracing buffer is full. The value of @samp{disconnection} means
33928 tracing was automatically stopped when @value{GDBN} has disconnected.
33929 The value of @samp{passcount} means tracing was stopped when a
33930 tracepoint was passed a maximal number of times for that tracepoint.
33931 This field is present if @samp{supported} field is not @samp{0}.
33933 @item stopping-tracepoint
33934 The number of tracepoint whose passcount as exceeded. This field is
33935 present iff the @samp{stop-reason} field has the value of
33939 @itemx frames-created
33940 The @samp{frames} field is a count of the total number of trace frames
33941 in the trace buffer, while @samp{frames-created} is the total created
33942 during the run, including ones that were discarded, such as when a
33943 circular trace buffer filled up. Both fields are optional.
33947 These fields tell the current size of the tracing buffer and the
33948 remaining space. These fields are optional.
33951 The value of the circular trace buffer flag. @code{1} means that the
33952 trace buffer is circular and old trace frames will be discarded if
33953 necessary to make room, @code{0} means that the trace buffer is linear
33957 The value of the disconnected tracing flag. @code{1} means that
33958 tracing will continue after @value{GDBN} disconnects, @code{0} means
33959 that the trace run will stop.
33962 The filename of the trace file being examined. This field is
33963 optional, and only present when examining a trace file.
33967 @subsubheading @value{GDBN} Command
33969 The corresponding @value{GDBN} command is @samp{tstatus}.
33971 @subheading -trace-stop
33972 @findex -trace-stop
33974 @subsubheading Synopsis
33980 Stops a tracing experiment. The result of this command has the same
33981 fields as @code{-trace-status}, except that the @samp{supported} and
33982 @samp{running} fields are not output.
33984 @subsubheading @value{GDBN} Command
33986 The corresponding @value{GDBN} command is @samp{tstop}.
33989 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33990 @node GDB/MI Symbol Query
33991 @section @sc{gdb/mi} Symbol Query Commands
33995 @subheading The @code{-symbol-info-address} Command
33996 @findex -symbol-info-address
33998 @subsubheading Synopsis
34001 -symbol-info-address @var{symbol}
34004 Describe where @var{symbol} is stored.
34006 @subsubheading @value{GDBN} Command
34008 The corresponding @value{GDBN} command is @samp{info address}.
34010 @subsubheading Example
34014 @subheading The @code{-symbol-info-file} Command
34015 @findex -symbol-info-file
34017 @subsubheading Synopsis
34023 Show the file for the symbol.
34025 @subsubheading @value{GDBN} Command
34027 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34028 @samp{gdb_find_file}.
34030 @subsubheading Example
34034 @subheading The @code{-symbol-info-function} Command
34035 @findex -symbol-info-function
34037 @subsubheading Synopsis
34040 -symbol-info-function
34043 Show which function the symbol lives in.
34045 @subsubheading @value{GDBN} Command
34047 @samp{gdb_get_function} in @code{gdbtk}.
34049 @subsubheading Example
34053 @subheading The @code{-symbol-info-line} Command
34054 @findex -symbol-info-line
34056 @subsubheading Synopsis
34062 Show the core addresses of the code for a source line.
34064 @subsubheading @value{GDBN} Command
34066 The corresponding @value{GDBN} command is @samp{info line}.
34067 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34069 @subsubheading Example
34073 @subheading The @code{-symbol-info-symbol} Command
34074 @findex -symbol-info-symbol
34076 @subsubheading Synopsis
34079 -symbol-info-symbol @var{addr}
34082 Describe what symbol is at location @var{addr}.
34084 @subsubheading @value{GDBN} Command
34086 The corresponding @value{GDBN} command is @samp{info symbol}.
34088 @subsubheading Example
34092 @subheading The @code{-symbol-list-functions} Command
34093 @findex -symbol-list-functions
34095 @subsubheading Synopsis
34098 -symbol-list-functions
34101 List the functions in the executable.
34103 @subsubheading @value{GDBN} Command
34105 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34106 @samp{gdb_search} in @code{gdbtk}.
34108 @subsubheading Example
34113 @subheading The @code{-symbol-list-lines} Command
34114 @findex -symbol-list-lines
34116 @subsubheading Synopsis
34119 -symbol-list-lines @var{filename}
34122 Print the list of lines that contain code and their associated program
34123 addresses for the given source filename. The entries are sorted in
34124 ascending PC order.
34126 @subsubheading @value{GDBN} Command
34128 There is no corresponding @value{GDBN} command.
34130 @subsubheading Example
34133 -symbol-list-lines basics.c
34134 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34140 @subheading The @code{-symbol-list-types} Command
34141 @findex -symbol-list-types
34143 @subsubheading Synopsis
34149 List all the type names.
34151 @subsubheading @value{GDBN} Command
34153 The corresponding commands are @samp{info types} in @value{GDBN},
34154 @samp{gdb_search} in @code{gdbtk}.
34156 @subsubheading Example
34160 @subheading The @code{-symbol-list-variables} Command
34161 @findex -symbol-list-variables
34163 @subsubheading Synopsis
34166 -symbol-list-variables
34169 List all the global and static variable names.
34171 @subsubheading @value{GDBN} Command
34173 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34175 @subsubheading Example
34179 @subheading The @code{-symbol-locate} Command
34180 @findex -symbol-locate
34182 @subsubheading Synopsis
34188 @subsubheading @value{GDBN} Command
34190 @samp{gdb_loc} in @code{gdbtk}.
34192 @subsubheading Example
34196 @subheading The @code{-symbol-type} Command
34197 @findex -symbol-type
34199 @subsubheading Synopsis
34202 -symbol-type @var{variable}
34205 Show type of @var{variable}.
34207 @subsubheading @value{GDBN} Command
34209 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34210 @samp{gdb_obj_variable}.
34212 @subsubheading Example
34217 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34218 @node GDB/MI File Commands
34219 @section @sc{gdb/mi} File Commands
34221 This section describes the GDB/MI commands to specify executable file names
34222 and to read in and obtain symbol table information.
34224 @subheading The @code{-file-exec-and-symbols} Command
34225 @findex -file-exec-and-symbols
34227 @subsubheading Synopsis
34230 -file-exec-and-symbols @var{file}
34233 Specify the executable file to be debugged. This file is the one from
34234 which the symbol table is also read. If no file is specified, the
34235 command clears the executable and symbol information. If breakpoints
34236 are set when using this command with no arguments, @value{GDBN} will produce
34237 error messages. Otherwise, no output is produced, except a completion
34240 @subsubheading @value{GDBN} Command
34242 The corresponding @value{GDBN} command is @samp{file}.
34244 @subsubheading Example
34248 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34254 @subheading The @code{-file-exec-file} Command
34255 @findex -file-exec-file
34257 @subsubheading Synopsis
34260 -file-exec-file @var{file}
34263 Specify the executable file to be debugged. Unlike
34264 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34265 from this file. If used without argument, @value{GDBN} clears the information
34266 about the executable file. No output is produced, except a completion
34269 @subsubheading @value{GDBN} Command
34271 The corresponding @value{GDBN} command is @samp{exec-file}.
34273 @subsubheading Example
34277 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34284 @subheading The @code{-file-list-exec-sections} Command
34285 @findex -file-list-exec-sections
34287 @subsubheading Synopsis
34290 -file-list-exec-sections
34293 List the sections of the current executable file.
34295 @subsubheading @value{GDBN} Command
34297 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34298 information as this command. @code{gdbtk} has a corresponding command
34299 @samp{gdb_load_info}.
34301 @subsubheading Example
34306 @subheading The @code{-file-list-exec-source-file} Command
34307 @findex -file-list-exec-source-file
34309 @subsubheading Synopsis
34312 -file-list-exec-source-file
34315 List the line number, the current source file, and the absolute path
34316 to the current source file for the current executable. The macro
34317 information field has a value of @samp{1} or @samp{0} depending on
34318 whether or not the file includes preprocessor macro information.
34320 @subsubheading @value{GDBN} Command
34322 The @value{GDBN} equivalent is @samp{info source}
34324 @subsubheading Example
34328 123-file-list-exec-source-file
34329 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34334 @subheading The @code{-file-list-exec-source-files} Command
34335 @findex -file-list-exec-source-files
34337 @subsubheading Synopsis
34340 -file-list-exec-source-files
34343 List the source files for the current executable.
34345 It will always output both the filename and fullname (absolute file
34346 name) of a source file.
34348 @subsubheading @value{GDBN} Command
34350 The @value{GDBN} equivalent is @samp{info sources}.
34351 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34353 @subsubheading Example
34356 -file-list-exec-source-files
34358 @{file=foo.c,fullname=/home/foo.c@},
34359 @{file=/home/bar.c,fullname=/home/bar.c@},
34360 @{file=gdb_could_not_find_fullpath.c@}]
34365 @subheading The @code{-file-list-shared-libraries} Command
34366 @findex -file-list-shared-libraries
34368 @subsubheading Synopsis
34371 -file-list-shared-libraries
34374 List the shared libraries in the program.
34376 @subsubheading @value{GDBN} Command
34378 The corresponding @value{GDBN} command is @samp{info shared}.
34380 @subsubheading Example
34384 @subheading The @code{-file-list-symbol-files} Command
34385 @findex -file-list-symbol-files
34387 @subsubheading Synopsis
34390 -file-list-symbol-files
34395 @subsubheading @value{GDBN} Command
34397 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34399 @subsubheading Example
34404 @subheading The @code{-file-symbol-file} Command
34405 @findex -file-symbol-file
34407 @subsubheading Synopsis
34410 -file-symbol-file @var{file}
34413 Read symbol table info from the specified @var{file} argument. When
34414 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34415 produced, except for a completion notification.
34417 @subsubheading @value{GDBN} Command
34419 The corresponding @value{GDBN} command is @samp{symbol-file}.
34421 @subsubheading Example
34425 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34431 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34432 @node GDB/MI Memory Overlay Commands
34433 @section @sc{gdb/mi} Memory Overlay Commands
34435 The memory overlay commands are not implemented.
34437 @c @subheading -overlay-auto
34439 @c @subheading -overlay-list-mapping-state
34441 @c @subheading -overlay-list-overlays
34443 @c @subheading -overlay-map
34445 @c @subheading -overlay-off
34447 @c @subheading -overlay-on
34449 @c @subheading -overlay-unmap
34451 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34452 @node GDB/MI Signal Handling Commands
34453 @section @sc{gdb/mi} Signal Handling Commands
34455 Signal handling commands are not implemented.
34457 @c @subheading -signal-handle
34459 @c @subheading -signal-list-handle-actions
34461 @c @subheading -signal-list-signal-types
34465 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34466 @node GDB/MI Target Manipulation
34467 @section @sc{gdb/mi} Target Manipulation Commands
34470 @subheading The @code{-target-attach} Command
34471 @findex -target-attach
34473 @subsubheading Synopsis
34476 -target-attach @var{pid} | @var{gid} | @var{file}
34479 Attach to a process @var{pid} or a file @var{file} outside of
34480 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34481 group, the id previously returned by
34482 @samp{-list-thread-groups --available} must be used.
34484 @subsubheading @value{GDBN} Command
34486 The corresponding @value{GDBN} command is @samp{attach}.
34488 @subsubheading Example
34492 =thread-created,id="1"
34493 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34499 @subheading The @code{-target-compare-sections} Command
34500 @findex -target-compare-sections
34502 @subsubheading Synopsis
34505 -target-compare-sections [ @var{section} ]
34508 Compare data of section @var{section} on target to the exec file.
34509 Without the argument, all sections are compared.
34511 @subsubheading @value{GDBN} Command
34513 The @value{GDBN} equivalent is @samp{compare-sections}.
34515 @subsubheading Example
34520 @subheading The @code{-target-detach} Command
34521 @findex -target-detach
34523 @subsubheading Synopsis
34526 -target-detach [ @var{pid} | @var{gid} ]
34529 Detach from the remote target which normally resumes its execution.
34530 If either @var{pid} or @var{gid} is specified, detaches from either
34531 the specified process, or specified thread group. There's no output.
34533 @subsubheading @value{GDBN} Command
34535 The corresponding @value{GDBN} command is @samp{detach}.
34537 @subsubheading Example
34547 @subheading The @code{-target-disconnect} Command
34548 @findex -target-disconnect
34550 @subsubheading Synopsis
34556 Disconnect from the remote target. There's no output and the target is
34557 generally not resumed.
34559 @subsubheading @value{GDBN} Command
34561 The corresponding @value{GDBN} command is @samp{disconnect}.
34563 @subsubheading Example
34573 @subheading The @code{-target-download} Command
34574 @findex -target-download
34576 @subsubheading Synopsis
34582 Loads the executable onto the remote target.
34583 It prints out an update message every half second, which includes the fields:
34587 The name of the section.
34589 The size of what has been sent so far for that section.
34591 The size of the section.
34593 The total size of what was sent so far (the current and the previous sections).
34595 The size of the overall executable to download.
34599 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34600 @sc{gdb/mi} Output Syntax}).
34602 In addition, it prints the name and size of the sections, as they are
34603 downloaded. These messages include the following fields:
34607 The name of the section.
34609 The size of the section.
34611 The size of the overall executable to download.
34615 At the end, a summary is printed.
34617 @subsubheading @value{GDBN} Command
34619 The corresponding @value{GDBN} command is @samp{load}.
34621 @subsubheading Example
34623 Note: each status message appears on a single line. Here the messages
34624 have been broken down so that they can fit onto a page.
34629 +download,@{section=".text",section-size="6668",total-size="9880"@}
34630 +download,@{section=".text",section-sent="512",section-size="6668",
34631 total-sent="512",total-size="9880"@}
34632 +download,@{section=".text",section-sent="1024",section-size="6668",
34633 total-sent="1024",total-size="9880"@}
34634 +download,@{section=".text",section-sent="1536",section-size="6668",
34635 total-sent="1536",total-size="9880"@}
34636 +download,@{section=".text",section-sent="2048",section-size="6668",
34637 total-sent="2048",total-size="9880"@}
34638 +download,@{section=".text",section-sent="2560",section-size="6668",
34639 total-sent="2560",total-size="9880"@}
34640 +download,@{section=".text",section-sent="3072",section-size="6668",
34641 total-sent="3072",total-size="9880"@}
34642 +download,@{section=".text",section-sent="3584",section-size="6668",
34643 total-sent="3584",total-size="9880"@}
34644 +download,@{section=".text",section-sent="4096",section-size="6668",
34645 total-sent="4096",total-size="9880"@}
34646 +download,@{section=".text",section-sent="4608",section-size="6668",
34647 total-sent="4608",total-size="9880"@}
34648 +download,@{section=".text",section-sent="5120",section-size="6668",
34649 total-sent="5120",total-size="9880"@}
34650 +download,@{section=".text",section-sent="5632",section-size="6668",
34651 total-sent="5632",total-size="9880"@}
34652 +download,@{section=".text",section-sent="6144",section-size="6668",
34653 total-sent="6144",total-size="9880"@}
34654 +download,@{section=".text",section-sent="6656",section-size="6668",
34655 total-sent="6656",total-size="9880"@}
34656 +download,@{section=".init",section-size="28",total-size="9880"@}
34657 +download,@{section=".fini",section-size="28",total-size="9880"@}
34658 +download,@{section=".data",section-size="3156",total-size="9880"@}
34659 +download,@{section=".data",section-sent="512",section-size="3156",
34660 total-sent="7236",total-size="9880"@}
34661 +download,@{section=".data",section-sent="1024",section-size="3156",
34662 total-sent="7748",total-size="9880"@}
34663 +download,@{section=".data",section-sent="1536",section-size="3156",
34664 total-sent="8260",total-size="9880"@}
34665 +download,@{section=".data",section-sent="2048",section-size="3156",
34666 total-sent="8772",total-size="9880"@}
34667 +download,@{section=".data",section-sent="2560",section-size="3156",
34668 total-sent="9284",total-size="9880"@}
34669 +download,@{section=".data",section-sent="3072",section-size="3156",
34670 total-sent="9796",total-size="9880"@}
34671 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34678 @subheading The @code{-target-exec-status} Command
34679 @findex -target-exec-status
34681 @subsubheading Synopsis
34684 -target-exec-status
34687 Provide information on the state of the target (whether it is running or
34688 not, for instance).
34690 @subsubheading @value{GDBN} Command
34692 There's no equivalent @value{GDBN} command.
34694 @subsubheading Example
34698 @subheading The @code{-target-list-available-targets} Command
34699 @findex -target-list-available-targets
34701 @subsubheading Synopsis
34704 -target-list-available-targets
34707 List the possible targets to connect to.
34709 @subsubheading @value{GDBN} Command
34711 The corresponding @value{GDBN} command is @samp{help target}.
34713 @subsubheading Example
34717 @subheading The @code{-target-list-current-targets} Command
34718 @findex -target-list-current-targets
34720 @subsubheading Synopsis
34723 -target-list-current-targets
34726 Describe the current target.
34728 @subsubheading @value{GDBN} Command
34730 The corresponding information is printed by @samp{info file} (among
34733 @subsubheading Example
34737 @subheading The @code{-target-list-parameters} Command
34738 @findex -target-list-parameters
34740 @subsubheading Synopsis
34743 -target-list-parameters
34749 @subsubheading @value{GDBN} Command
34753 @subsubheading Example
34757 @subheading The @code{-target-select} Command
34758 @findex -target-select
34760 @subsubheading Synopsis
34763 -target-select @var{type} @var{parameters @dots{}}
34766 Connect @value{GDBN} to the remote target. This command takes two args:
34770 The type of target, for instance @samp{remote}, etc.
34771 @item @var{parameters}
34772 Device names, host names and the like. @xref{Target Commands, ,
34773 Commands for Managing Targets}, for more details.
34776 The output is a connection notification, followed by the address at
34777 which the target program is, in the following form:
34780 ^connected,addr="@var{address}",func="@var{function name}",
34781 args=[@var{arg list}]
34784 @subsubheading @value{GDBN} Command
34786 The corresponding @value{GDBN} command is @samp{target}.
34788 @subsubheading Example
34792 -target-select remote /dev/ttya
34793 ^connected,addr="0xfe00a300",func="??",args=[]
34797 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34798 @node GDB/MI File Transfer Commands
34799 @section @sc{gdb/mi} File Transfer Commands
34802 @subheading The @code{-target-file-put} Command
34803 @findex -target-file-put
34805 @subsubheading Synopsis
34808 -target-file-put @var{hostfile} @var{targetfile}
34811 Copy file @var{hostfile} from the host system (the machine running
34812 @value{GDBN}) to @var{targetfile} on the target system.
34814 @subsubheading @value{GDBN} Command
34816 The corresponding @value{GDBN} command is @samp{remote put}.
34818 @subsubheading Example
34822 -target-file-put localfile remotefile
34828 @subheading The @code{-target-file-get} Command
34829 @findex -target-file-get
34831 @subsubheading Synopsis
34834 -target-file-get @var{targetfile} @var{hostfile}
34837 Copy file @var{targetfile} from the target system to @var{hostfile}
34838 on the host system.
34840 @subsubheading @value{GDBN} Command
34842 The corresponding @value{GDBN} command is @samp{remote get}.
34844 @subsubheading Example
34848 -target-file-get remotefile localfile
34854 @subheading The @code{-target-file-delete} Command
34855 @findex -target-file-delete
34857 @subsubheading Synopsis
34860 -target-file-delete @var{targetfile}
34863 Delete @var{targetfile} from the target system.
34865 @subsubheading @value{GDBN} Command
34867 The corresponding @value{GDBN} command is @samp{remote delete}.
34869 @subsubheading Example
34873 -target-file-delete remotefile
34879 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34880 @node GDB/MI Ada Exceptions Commands
34881 @section Ada Exceptions @sc{gdb/mi} Commands
34883 @subheading The @code{-info-ada-exceptions} Command
34884 @findex -info-ada-exceptions
34886 @subsubheading Synopsis
34889 -info-ada-exceptions [ @var{regexp}]
34892 List all Ada exceptions defined within the program being debugged.
34893 With a regular expression @var{regexp}, only those exceptions whose
34894 names match @var{regexp} are listed.
34896 @subsubheading @value{GDBN} Command
34898 The corresponding @value{GDBN} command is @samp{info exceptions}.
34900 @subsubheading Result
34902 The result is a table of Ada exceptions. The following columns are
34903 defined for each exception:
34907 The name of the exception.
34910 The address of the exception.
34914 @subsubheading Example
34917 -info-ada-exceptions aint
34918 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
34919 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
34920 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
34921 body=[@{name="constraint_error",address="0x0000000000613da0"@},
34922 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
34925 @subheading Catching Ada Exceptions
34927 The commands describing how to ask @value{GDBN} to stop when a program
34928 raises an exception are described at @ref{Ada Exception GDB/MI
34929 Catchpoint Commands}.
34932 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34933 @node GDB/MI Miscellaneous Commands
34934 @section Miscellaneous @sc{gdb/mi} Commands
34936 @c @subheading -gdb-complete
34938 @subheading The @code{-gdb-exit} Command
34941 @subsubheading Synopsis
34947 Exit @value{GDBN} immediately.
34949 @subsubheading @value{GDBN} Command
34951 Approximately corresponds to @samp{quit}.
34953 @subsubheading Example
34963 @subheading The @code{-exec-abort} Command
34964 @findex -exec-abort
34966 @subsubheading Synopsis
34972 Kill the inferior running program.
34974 @subsubheading @value{GDBN} Command
34976 The corresponding @value{GDBN} command is @samp{kill}.
34978 @subsubheading Example
34983 @subheading The @code{-gdb-set} Command
34986 @subsubheading Synopsis
34992 Set an internal @value{GDBN} variable.
34993 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34995 @subsubheading @value{GDBN} Command
34997 The corresponding @value{GDBN} command is @samp{set}.
34999 @subsubheading Example
35009 @subheading The @code{-gdb-show} Command
35012 @subsubheading Synopsis
35018 Show the current value of a @value{GDBN} variable.
35020 @subsubheading @value{GDBN} Command
35022 The corresponding @value{GDBN} command is @samp{show}.
35024 @subsubheading Example
35033 @c @subheading -gdb-source
35036 @subheading The @code{-gdb-version} Command
35037 @findex -gdb-version
35039 @subsubheading Synopsis
35045 Show version information for @value{GDBN}. Used mostly in testing.
35047 @subsubheading @value{GDBN} Command
35049 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35050 default shows this information when you start an interactive session.
35052 @subsubheading Example
35054 @c This example modifies the actual output from GDB to avoid overfull
35060 ~Copyright 2000 Free Software Foundation, Inc.
35061 ~GDB is free software, covered by the GNU General Public License, and
35062 ~you are welcome to change it and/or distribute copies of it under
35063 ~ certain conditions.
35064 ~Type "show copying" to see the conditions.
35065 ~There is absolutely no warranty for GDB. Type "show warranty" for
35067 ~This GDB was configured as
35068 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35073 @subheading The @code{-list-features} Command
35074 @findex -list-features
35076 Returns a list of particular features of the MI protocol that
35077 this version of gdb implements. A feature can be a command,
35078 or a new field in an output of some command, or even an
35079 important bugfix. While a frontend can sometimes detect presence
35080 of a feature at runtime, it is easier to perform detection at debugger
35083 The command returns a list of strings, with each string naming an
35084 available feature. Each returned string is just a name, it does not
35085 have any internal structure. The list of possible feature names
35091 (gdb) -list-features
35092 ^done,result=["feature1","feature2"]
35095 The current list of features is:
35098 @item frozen-varobjs
35099 Indicates support for the @code{-var-set-frozen} command, as well
35100 as possible presense of the @code{frozen} field in the output
35101 of @code{-varobj-create}.
35102 @item pending-breakpoints
35103 Indicates support for the @option{-f} option to the @code{-break-insert}
35106 Indicates Python scripting support, Python-based
35107 pretty-printing commands, and possible presence of the
35108 @samp{display_hint} field in the output of @code{-var-list-children}
35110 Indicates support for the @code{-thread-info} command.
35111 @item data-read-memory-bytes
35112 Indicates support for the @code{-data-read-memory-bytes} and the
35113 @code{-data-write-memory-bytes} commands.
35114 @item breakpoint-notifications
35115 Indicates that changes to breakpoints and breakpoints created via the
35116 CLI will be announced via async records.
35117 @item ada-task-info
35118 Indicates support for the @code{-ada-task-info} command.
35119 @item ada-exceptions
35120 Indicates support for the following commands, all of them related to Ada
35121 exceptions: @code{-info-ada-exceptions}, @code{-catch-assert} and
35122 @code{-catch-exception}.
35123 @item language-option
35124 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35125 option (@pxref{Context management}).
35128 @subheading The @code{-list-target-features} Command
35129 @findex -list-target-features
35131 Returns a list of particular features that are supported by the
35132 target. Those features affect the permitted MI commands, but
35133 unlike the features reported by the @code{-list-features} command, the
35134 features depend on which target GDB is using at the moment. Whenever
35135 a target can change, due to commands such as @code{-target-select},
35136 @code{-target-attach} or @code{-exec-run}, the list of target features
35137 may change, and the frontend should obtain it again.
35141 (gdb) -list-target-features
35142 ^done,result=["async"]
35145 The current list of features is:
35149 Indicates that the target is capable of asynchronous command
35150 execution, which means that @value{GDBN} will accept further commands
35151 while the target is running.
35154 Indicates that the target is capable of reverse execution.
35155 @xref{Reverse Execution}, for more information.
35159 @subheading The @code{-list-thread-groups} Command
35160 @findex -list-thread-groups
35162 @subheading Synopsis
35165 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35168 Lists thread groups (@pxref{Thread groups}). When a single thread
35169 group is passed as the argument, lists the children of that group.
35170 When several thread group are passed, lists information about those
35171 thread groups. Without any parameters, lists information about all
35172 top-level thread groups.
35174 Normally, thread groups that are being debugged are reported.
35175 With the @samp{--available} option, @value{GDBN} reports thread groups
35176 available on the target.
35178 The output of this command may have either a @samp{threads} result or
35179 a @samp{groups} result. The @samp{thread} result has a list of tuples
35180 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35181 Information}). The @samp{groups} result has a list of tuples as value,
35182 each tuple describing a thread group. If top-level groups are
35183 requested (that is, no parameter is passed), or when several groups
35184 are passed, the output always has a @samp{groups} result. The format
35185 of the @samp{group} result is described below.
35187 To reduce the number of roundtrips it's possible to list thread groups
35188 together with their children, by passing the @samp{--recurse} option
35189 and the recursion depth. Presently, only recursion depth of 1 is
35190 permitted. If this option is present, then every reported thread group
35191 will also include its children, either as @samp{group} or
35192 @samp{threads} field.
35194 In general, any combination of option and parameters is permitted, with
35195 the following caveats:
35199 When a single thread group is passed, the output will typically
35200 be the @samp{threads} result. Because threads may not contain
35201 anything, the @samp{recurse} option will be ignored.
35204 When the @samp{--available} option is passed, limited information may
35205 be available. In particular, the list of threads of a process might
35206 be inaccessible. Further, specifying specific thread groups might
35207 not give any performance advantage over listing all thread groups.
35208 The frontend should assume that @samp{-list-thread-groups --available}
35209 is always an expensive operation and cache the results.
35213 The @samp{groups} result is a list of tuples, where each tuple may
35214 have the following fields:
35218 Identifier of the thread group. This field is always present.
35219 The identifier is an opaque string; frontends should not try to
35220 convert it to an integer, even though it might look like one.
35223 The type of the thread group. At present, only @samp{process} is a
35227 The target-specific process identifier. This field is only present
35228 for thread groups of type @samp{process} and only if the process exists.
35231 The number of children this thread group has. This field may be
35232 absent for an available thread group.
35235 This field has a list of tuples as value, each tuple describing a
35236 thread. It may be present if the @samp{--recurse} option is
35237 specified, and it's actually possible to obtain the threads.
35240 This field is a list of integers, each identifying a core that one
35241 thread of the group is running on. This field may be absent if
35242 such information is not available.
35245 The name of the executable file that corresponds to this thread group.
35246 The field is only present for thread groups of type @samp{process},
35247 and only if there is a corresponding executable file.
35251 @subheading Example
35255 -list-thread-groups
35256 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35257 -list-thread-groups 17
35258 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35259 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35260 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35261 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35262 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
35263 -list-thread-groups --available
35264 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35265 -list-thread-groups --available --recurse 1
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]@}]@},..]
35269 -list-thread-groups --available --recurse 1 17 18
35270 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35271 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35272 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35275 @subheading The @code{-info-os} Command
35278 @subsubheading Synopsis
35281 -info-os [ @var{type} ]
35284 If no argument is supplied, the command returns a table of available
35285 operating-system-specific information types. If one of these types is
35286 supplied as an argument @var{type}, then the command returns a table
35287 of data of that type.
35289 The types of information available depend on the target operating
35292 @subsubheading @value{GDBN} Command
35294 The corresponding @value{GDBN} command is @samp{info os}.
35296 @subsubheading Example
35298 When run on a @sc{gnu}/Linux system, the output will look something
35304 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35305 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35306 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35307 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35308 body=[item=@{col0="processes",col1="Listing of all processes",
35309 col2="Processes"@},
35310 item=@{col0="procgroups",col1="Listing of all process groups",
35311 col2="Process groups"@},
35312 item=@{col0="threads",col1="Listing of all threads",
35314 item=@{col0="files",col1="Listing of all file descriptors",
35315 col2="File descriptors"@},
35316 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35318 item=@{col0="shm",col1="Listing of all shared-memory regions",
35319 col2="Shared-memory regions"@},
35320 item=@{col0="semaphores",col1="Listing of all semaphores",
35321 col2="Semaphores"@},
35322 item=@{col0="msg",col1="Listing of all message queues",
35323 col2="Message queues"@},
35324 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35325 col2="Kernel modules"@}]@}
35328 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35329 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35330 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35331 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35332 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35333 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35334 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35335 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35337 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35338 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35342 (Note that the MI output here includes a @code{"Title"} column that
35343 does not appear in command-line @code{info os}; this column is useful
35344 for MI clients that want to enumerate the types of data, such as in a
35345 popup menu, but is needless clutter on the command line, and
35346 @code{info os} omits it.)
35348 @subheading The @code{-add-inferior} Command
35349 @findex -add-inferior
35351 @subheading Synopsis
35357 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35358 inferior is not associated with any executable. Such association may
35359 be established with the @samp{-file-exec-and-symbols} command
35360 (@pxref{GDB/MI File Commands}). The command response has a single
35361 field, @samp{inferior}, whose value is the identifier of the
35362 thread group corresponding to the new inferior.
35364 @subheading Example
35369 ^done,inferior="i3"
35372 @subheading The @code{-interpreter-exec} Command
35373 @findex -interpreter-exec
35375 @subheading Synopsis
35378 -interpreter-exec @var{interpreter} @var{command}
35380 @anchor{-interpreter-exec}
35382 Execute the specified @var{command} in the given @var{interpreter}.
35384 @subheading @value{GDBN} Command
35386 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35388 @subheading Example
35392 -interpreter-exec console "break main"
35393 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35394 &"During symbol reading, bad structure-type format.\n"
35395 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35400 @subheading The @code{-inferior-tty-set} Command
35401 @findex -inferior-tty-set
35403 @subheading Synopsis
35406 -inferior-tty-set /dev/pts/1
35409 Set terminal for future runs of the program being debugged.
35411 @subheading @value{GDBN} Command
35413 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35415 @subheading Example
35419 -inferior-tty-set /dev/pts/1
35424 @subheading The @code{-inferior-tty-show} Command
35425 @findex -inferior-tty-show
35427 @subheading Synopsis
35433 Show terminal for future runs of program being debugged.
35435 @subheading @value{GDBN} Command
35437 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35439 @subheading Example
35443 -inferior-tty-set /dev/pts/1
35447 ^done,inferior_tty_terminal="/dev/pts/1"
35451 @subheading The @code{-enable-timings} Command
35452 @findex -enable-timings
35454 @subheading Synopsis
35457 -enable-timings [yes | no]
35460 Toggle the printing of the wallclock, user and system times for an MI
35461 command as a field in its output. This command is to help frontend
35462 developers optimize the performance of their code. No argument is
35463 equivalent to @samp{yes}.
35465 @subheading @value{GDBN} Command
35469 @subheading Example
35477 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35478 addr="0x080484ed",func="main",file="myprog.c",
35479 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35481 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35489 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35490 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35491 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35492 fullname="/home/nickrob/myprog.c",line="73"@}
35497 @chapter @value{GDBN} Annotations
35499 This chapter describes annotations in @value{GDBN}. Annotations were
35500 designed to interface @value{GDBN} to graphical user interfaces or other
35501 similar programs which want to interact with @value{GDBN} at a
35502 relatively high level.
35504 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35508 This is Edition @value{EDITION}, @value{DATE}.
35512 * Annotations Overview:: What annotations are; the general syntax.
35513 * Server Prefix:: Issuing a command without affecting user state.
35514 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35515 * Errors:: Annotations for error messages.
35516 * Invalidation:: Some annotations describe things now invalid.
35517 * Annotations for Running::
35518 Whether the program is running, how it stopped, etc.
35519 * Source Annotations:: Annotations describing source code.
35522 @node Annotations Overview
35523 @section What is an Annotation?
35524 @cindex annotations
35526 Annotations start with a newline character, two @samp{control-z}
35527 characters, and the name of the annotation. If there is no additional
35528 information associated with this annotation, the name of the annotation
35529 is followed immediately by a newline. If there is additional
35530 information, the name of the annotation is followed by a space, the
35531 additional information, and a newline. The additional information
35532 cannot contain newline characters.
35534 Any output not beginning with a newline and two @samp{control-z}
35535 characters denotes literal output from @value{GDBN}. Currently there is
35536 no need for @value{GDBN} to output a newline followed by two
35537 @samp{control-z} characters, but if there was such a need, the
35538 annotations could be extended with an @samp{escape} annotation which
35539 means those three characters as output.
35541 The annotation @var{level}, which is specified using the
35542 @option{--annotate} command line option (@pxref{Mode Options}), controls
35543 how much information @value{GDBN} prints together with its prompt,
35544 values of expressions, source lines, and other types of output. Level 0
35545 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35546 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35547 for programs that control @value{GDBN}, and level 2 annotations have
35548 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35549 Interface, annotate, GDB's Obsolete Annotations}).
35552 @kindex set annotate
35553 @item set annotate @var{level}
35554 The @value{GDBN} command @code{set annotate} sets the level of
35555 annotations to the specified @var{level}.
35557 @item show annotate
35558 @kindex show annotate
35559 Show the current annotation level.
35562 This chapter describes level 3 annotations.
35564 A simple example of starting up @value{GDBN} with annotations is:
35567 $ @kbd{gdb --annotate=3}
35569 Copyright 2003 Free Software Foundation, Inc.
35570 GDB is free software, covered by the GNU General Public License,
35571 and you are welcome to change it and/or distribute copies of it
35572 under certain conditions.
35573 Type "show copying" to see the conditions.
35574 There is absolutely no warranty for GDB. Type "show warranty"
35576 This GDB was configured as "i386-pc-linux-gnu"
35587 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35588 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35589 denotes a @samp{control-z} character) are annotations; the rest is
35590 output from @value{GDBN}.
35592 @node Server Prefix
35593 @section The Server Prefix
35594 @cindex server prefix
35596 If you prefix a command with @samp{server } then it will not affect
35597 the command history, nor will it affect @value{GDBN}'s notion of which
35598 command to repeat if @key{RET} is pressed on a line by itself. This
35599 means that commands can be run behind a user's back by a front-end in
35600 a transparent manner.
35602 The @code{server } prefix does not affect the recording of values into
35603 the value history; to print a value without recording it into the
35604 value history, use the @code{output} command instead of the
35605 @code{print} command.
35607 Using this prefix also disables confirmation requests
35608 (@pxref{confirmation requests}).
35611 @section Annotation for @value{GDBN} Input
35613 @cindex annotations for prompts
35614 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35615 to know when to send output, when the output from a given command is
35618 Different kinds of input each have a different @dfn{input type}. Each
35619 input type has three annotations: a @code{pre-} annotation, which
35620 denotes the beginning of any prompt which is being output, a plain
35621 annotation, which denotes the end of the prompt, and then a @code{post-}
35622 annotation which denotes the end of any echo which may (or may not) be
35623 associated with the input. For example, the @code{prompt} input type
35624 features the following annotations:
35632 The input types are
35635 @findex pre-prompt annotation
35636 @findex prompt annotation
35637 @findex post-prompt annotation
35639 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35641 @findex pre-commands annotation
35642 @findex commands annotation
35643 @findex post-commands annotation
35645 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35646 command. The annotations are repeated for each command which is input.
35648 @findex pre-overload-choice annotation
35649 @findex overload-choice annotation
35650 @findex post-overload-choice annotation
35651 @item overload-choice
35652 When @value{GDBN} wants the user to select between various overloaded functions.
35654 @findex pre-query annotation
35655 @findex query annotation
35656 @findex post-query annotation
35658 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35660 @findex pre-prompt-for-continue annotation
35661 @findex prompt-for-continue annotation
35662 @findex post-prompt-for-continue annotation
35663 @item prompt-for-continue
35664 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35665 expect this to work well; instead use @code{set height 0} to disable
35666 prompting. This is because the counting of lines is buggy in the
35667 presence of annotations.
35672 @cindex annotations for errors, warnings and interrupts
35674 @findex quit annotation
35679 This annotation occurs right before @value{GDBN} responds to an interrupt.
35681 @findex error annotation
35686 This annotation occurs right before @value{GDBN} responds to an error.
35688 Quit and error annotations indicate that any annotations which @value{GDBN} was
35689 in the middle of may end abruptly. For example, if a
35690 @code{value-history-begin} annotation is followed by a @code{error}, one
35691 cannot expect to receive the matching @code{value-history-end}. One
35692 cannot expect not to receive it either, however; an error annotation
35693 does not necessarily mean that @value{GDBN} is immediately returning all the way
35696 @findex error-begin annotation
35697 A quit or error annotation may be preceded by
35703 Any output between that and the quit or error annotation is the error
35706 Warning messages are not yet annotated.
35707 @c If we want to change that, need to fix warning(), type_error(),
35708 @c range_error(), and possibly other places.
35711 @section Invalidation Notices
35713 @cindex annotations for invalidation messages
35714 The following annotations say that certain pieces of state may have
35718 @findex frames-invalid annotation
35719 @item ^Z^Zframes-invalid
35721 The frames (for example, output from the @code{backtrace} command) may
35724 @findex breakpoints-invalid annotation
35725 @item ^Z^Zbreakpoints-invalid
35727 The breakpoints may have changed. For example, the user just added or
35728 deleted a breakpoint.
35731 @node Annotations for Running
35732 @section Running the Program
35733 @cindex annotations for running programs
35735 @findex starting annotation
35736 @findex stopping annotation
35737 When the program starts executing due to a @value{GDBN} command such as
35738 @code{step} or @code{continue},
35744 is output. When the program stops,
35750 is output. Before the @code{stopped} annotation, a variety of
35751 annotations describe how the program stopped.
35754 @findex exited annotation
35755 @item ^Z^Zexited @var{exit-status}
35756 The program exited, and @var{exit-status} is the exit status (zero for
35757 successful exit, otherwise nonzero).
35759 @findex signalled annotation
35760 @findex signal-name annotation
35761 @findex signal-name-end annotation
35762 @findex signal-string annotation
35763 @findex signal-string-end annotation
35764 @item ^Z^Zsignalled
35765 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35766 annotation continues:
35772 ^Z^Zsignal-name-end
35776 ^Z^Zsignal-string-end
35781 where @var{name} is the name of the signal, such as @code{SIGILL} or
35782 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35783 as @code{Illegal Instruction} or @code{Segmentation fault}.
35784 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35785 user's benefit and have no particular format.
35787 @findex signal annotation
35789 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35790 just saying that the program received the signal, not that it was
35791 terminated with it.
35793 @findex breakpoint annotation
35794 @item ^Z^Zbreakpoint @var{number}
35795 The program hit breakpoint number @var{number}.
35797 @findex watchpoint annotation
35798 @item ^Z^Zwatchpoint @var{number}
35799 The program hit watchpoint number @var{number}.
35802 @node Source Annotations
35803 @section Displaying Source
35804 @cindex annotations for source display
35806 @findex source annotation
35807 The following annotation is used instead of displaying source code:
35810 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35813 where @var{filename} is an absolute file name indicating which source
35814 file, @var{line} is the line number within that file (where 1 is the
35815 first line in the file), @var{character} is the character position
35816 within the file (where 0 is the first character in the file) (for most
35817 debug formats this will necessarily point to the beginning of a line),
35818 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35819 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35820 @var{addr} is the address in the target program associated with the
35821 source which is being displayed. @var{addr} is in the form @samp{0x}
35822 followed by one or more lowercase hex digits (note that this does not
35823 depend on the language).
35825 @node JIT Interface
35826 @chapter JIT Compilation Interface
35827 @cindex just-in-time compilation
35828 @cindex JIT compilation interface
35830 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35831 interface. A JIT compiler is a program or library that generates native
35832 executable code at runtime and executes it, usually in order to achieve good
35833 performance while maintaining platform independence.
35835 Programs that use JIT compilation are normally difficult to debug because
35836 portions of their code are generated at runtime, instead of being loaded from
35837 object files, which is where @value{GDBN} normally finds the program's symbols
35838 and debug information. In order to debug programs that use JIT compilation,
35839 @value{GDBN} has an interface that allows the program to register in-memory
35840 symbol files with @value{GDBN} at runtime.
35842 If you are using @value{GDBN} to debug a program that uses this interface, then
35843 it should work transparently so long as you have not stripped the binary. If
35844 you are developing a JIT compiler, then the interface is documented in the rest
35845 of this chapter. At this time, the only known client of this interface is the
35848 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35849 JIT compiler communicates with @value{GDBN} by writing data into a global
35850 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35851 attaches, it reads a linked list of symbol files from the global variable to
35852 find existing code, and puts a breakpoint in the function so that it can find
35853 out about additional code.
35856 * Declarations:: Relevant C struct declarations
35857 * Registering Code:: Steps to register code
35858 * Unregistering Code:: Steps to unregister code
35859 * Custom Debug Info:: Emit debug information in a custom format
35863 @section JIT Declarations
35865 These are the relevant struct declarations that a C program should include to
35866 implement the interface:
35876 struct jit_code_entry
35878 struct jit_code_entry *next_entry;
35879 struct jit_code_entry *prev_entry;
35880 const char *symfile_addr;
35881 uint64_t symfile_size;
35884 struct jit_descriptor
35887 /* This type should be jit_actions_t, but we use uint32_t
35888 to be explicit about the bitwidth. */
35889 uint32_t action_flag;
35890 struct jit_code_entry *relevant_entry;
35891 struct jit_code_entry *first_entry;
35894 /* GDB puts a breakpoint in this function. */
35895 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35897 /* Make sure to specify the version statically, because the
35898 debugger may check the version before we can set it. */
35899 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35902 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35903 modifications to this global data properly, which can easily be done by putting
35904 a global mutex around modifications to these structures.
35906 @node Registering Code
35907 @section Registering Code
35909 To register code with @value{GDBN}, the JIT should follow this protocol:
35913 Generate an object file in memory with symbols and other desired debug
35914 information. The file must include the virtual addresses of the sections.
35917 Create a code entry for the file, which gives the start and size of the symbol
35921 Add it to the linked list in the JIT descriptor.
35924 Point the relevant_entry field of the descriptor at the entry.
35927 Set @code{action_flag} to @code{JIT_REGISTER} and call
35928 @code{__jit_debug_register_code}.
35931 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35932 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35933 new code. However, the linked list must still be maintained in order to allow
35934 @value{GDBN} to attach to a running process and still find the symbol files.
35936 @node Unregistering Code
35937 @section Unregistering Code
35939 If code is freed, then the JIT should use the following protocol:
35943 Remove the code entry corresponding to the code from the linked list.
35946 Point the @code{relevant_entry} field of the descriptor at the code entry.
35949 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35950 @code{__jit_debug_register_code}.
35953 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35954 and the JIT will leak the memory used for the associated symbol files.
35956 @node Custom Debug Info
35957 @section Custom Debug Info
35958 @cindex custom JIT debug info
35959 @cindex JIT debug info reader
35961 Generating debug information in platform-native file formats (like ELF
35962 or COFF) may be an overkill for JIT compilers; especially if all the
35963 debug info is used for is displaying a meaningful backtrace. The
35964 issue can be resolved by having the JIT writers decide on a debug info
35965 format and also provide a reader that parses the debug info generated
35966 by the JIT compiler. This section gives a brief overview on writing
35967 such a parser. More specific details can be found in the source file
35968 @file{gdb/jit-reader.in}, which is also installed as a header at
35969 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35971 The reader is implemented as a shared object (so this functionality is
35972 not available on platforms which don't allow loading shared objects at
35973 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35974 @code{jit-reader-unload} are provided, to be used to load and unload
35975 the readers from a preconfigured directory. Once loaded, the shared
35976 object is used the parse the debug information emitted by the JIT
35980 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35981 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35984 @node Using JIT Debug Info Readers
35985 @subsection Using JIT Debug Info Readers
35986 @kindex jit-reader-load
35987 @kindex jit-reader-unload
35989 Readers can be loaded and unloaded using the @code{jit-reader-load}
35990 and @code{jit-reader-unload} commands.
35993 @item jit-reader-load @var{reader}
35994 Load the JIT reader named @var{reader}. @var{reader} is a shared
35995 object specified as either an absolute or a relative file name. In
35996 the latter case, @value{GDBN} will try to load the reader from a
35997 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35998 system (here @var{libdir} is the system library directory, often
35999 @file{/usr/local/lib}).
36001 Only one reader can be active at a time; trying to load a second
36002 reader when one is already loaded will result in @value{GDBN}
36003 reporting an error. A new JIT reader can be loaded by first unloading
36004 the current one using @code{jit-reader-unload} and then invoking
36005 @code{jit-reader-load}.
36007 @item jit-reader-unload
36008 Unload the currently loaded JIT reader.
36012 @node Writing JIT Debug Info Readers
36013 @subsection Writing JIT Debug Info Readers
36014 @cindex writing JIT debug info readers
36016 As mentioned, a reader is essentially a shared object conforming to a
36017 certain ABI. This ABI is described in @file{jit-reader.h}.
36019 @file{jit-reader.h} defines the structures, macros and functions
36020 required to write a reader. It is installed (along with
36021 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36022 the system include directory.
36024 Readers need to be released under a GPL compatible license. A reader
36025 can be declared as released under such a license by placing the macro
36026 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36028 The entry point for readers is the symbol @code{gdb_init_reader},
36029 which is expected to be a function with the prototype
36031 @findex gdb_init_reader
36033 extern struct gdb_reader_funcs *gdb_init_reader (void);
36036 @cindex @code{struct gdb_reader_funcs}
36038 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36039 functions. These functions are executed to read the debug info
36040 generated by the JIT compiler (@code{read}), to unwind stack frames
36041 (@code{unwind}) and to create canonical frame IDs
36042 (@code{get_Frame_id}). It also has a callback that is called when the
36043 reader is being unloaded (@code{destroy}). The struct looks like this
36046 struct gdb_reader_funcs
36048 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36049 int reader_version;
36051 /* For use by the reader. */
36054 gdb_read_debug_info *read;
36055 gdb_unwind_frame *unwind;
36056 gdb_get_frame_id *get_frame_id;
36057 gdb_destroy_reader *destroy;
36061 @cindex @code{struct gdb_symbol_callbacks}
36062 @cindex @code{struct gdb_unwind_callbacks}
36064 The callbacks are provided with another set of callbacks by
36065 @value{GDBN} to do their job. For @code{read}, these callbacks are
36066 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36067 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36068 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36069 files and new symbol tables inside those object files. @code{struct
36070 gdb_unwind_callbacks} has callbacks to read registers off the current
36071 frame and to write out the values of the registers in the previous
36072 frame. Both have a callback (@code{target_read}) to read bytes off the
36073 target's address space.
36075 @node In-Process Agent
36076 @chapter In-Process Agent
36077 @cindex debugging agent
36078 The traditional debugging model is conceptually low-speed, but works fine,
36079 because most bugs can be reproduced in debugging-mode execution. However,
36080 as multi-core or many-core processors are becoming mainstream, and
36081 multi-threaded programs become more and more popular, there should be more
36082 and more bugs that only manifest themselves at normal-mode execution, for
36083 example, thread races, because debugger's interference with the program's
36084 timing may conceal the bugs. On the other hand, in some applications,
36085 it is not feasible for the debugger to interrupt the program's execution
36086 long enough for the developer to learn anything helpful about its behavior.
36087 If the program's correctness depends on its real-time behavior, delays
36088 introduced by a debugger might cause the program to fail, even when the
36089 code itself is correct. It is useful to be able to observe the program's
36090 behavior without interrupting it.
36092 Therefore, traditional debugging model is too intrusive to reproduce
36093 some bugs. In order to reduce the interference with the program, we can
36094 reduce the number of operations performed by debugger. The
36095 @dfn{In-Process Agent}, a shared library, is running within the same
36096 process with inferior, and is able to perform some debugging operations
36097 itself. As a result, debugger is only involved when necessary, and
36098 performance of debugging can be improved accordingly. Note that
36099 interference with program can be reduced but can't be removed completely,
36100 because the in-process agent will still stop or slow down the program.
36102 The in-process agent can interpret and execute Agent Expressions
36103 (@pxref{Agent Expressions}) during performing debugging operations. The
36104 agent expressions can be used for different purposes, such as collecting
36105 data in tracepoints, and condition evaluation in breakpoints.
36107 @anchor{Control Agent}
36108 You can control whether the in-process agent is used as an aid for
36109 debugging with the following commands:
36112 @kindex set agent on
36114 Causes the in-process agent to perform some operations on behalf of the
36115 debugger. Just which operations requested by the user will be done
36116 by the in-process agent depends on the its capabilities. For example,
36117 if you request to evaluate breakpoint conditions in the in-process agent,
36118 and the in-process agent has such capability as well, then breakpoint
36119 conditions will be evaluated in the in-process agent.
36121 @kindex set agent off
36122 @item set agent off
36123 Disables execution of debugging operations by the in-process agent. All
36124 of the operations will be performed by @value{GDBN}.
36128 Display the current setting of execution of debugging operations by
36129 the in-process agent.
36133 * In-Process Agent Protocol::
36136 @node In-Process Agent Protocol
36137 @section In-Process Agent Protocol
36138 @cindex in-process agent protocol
36140 The in-process agent is able to communicate with both @value{GDBN} and
36141 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36142 used for communications between @value{GDBN} or GDBserver and the IPA.
36143 In general, @value{GDBN} or GDBserver sends commands
36144 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36145 in-process agent replies back with the return result of the command, or
36146 some other information. The data sent to in-process agent is composed
36147 of primitive data types, such as 4-byte or 8-byte type, and composite
36148 types, which are called objects (@pxref{IPA Protocol Objects}).
36151 * IPA Protocol Objects::
36152 * IPA Protocol Commands::
36155 @node IPA Protocol Objects
36156 @subsection IPA Protocol Objects
36157 @cindex ipa protocol objects
36159 The commands sent to and results received from agent may contain some
36160 complex data types called @dfn{objects}.
36162 The in-process agent is running on the same machine with @value{GDBN}
36163 or GDBserver, so it doesn't have to handle as much differences between
36164 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36165 However, there are still some differences of two ends in two processes:
36169 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36170 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36172 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36173 GDBserver is compiled with one, and in-process agent is compiled with
36177 Here are the IPA Protocol Objects:
36181 agent expression object. It represents an agent expression
36182 (@pxref{Agent Expressions}).
36183 @anchor{agent expression object}
36185 tracepoint action object. It represents a tracepoint action
36186 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36187 memory, static trace data and to evaluate expression.
36188 @anchor{tracepoint action object}
36190 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36191 @anchor{tracepoint object}
36195 The following table describes important attributes of each IPA protocol
36198 @multitable @columnfractions .30 .20 .50
36199 @headitem Name @tab Size @tab Description
36200 @item @emph{agent expression object} @tab @tab
36201 @item length @tab 4 @tab length of bytes code
36202 @item byte code @tab @var{length} @tab contents of byte code
36203 @item @emph{tracepoint action for collecting memory} @tab @tab
36204 @item 'M' @tab 1 @tab type of tracepoint action
36205 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36206 address of the lowest byte to collect, otherwise @var{addr} is the offset
36207 of @var{basereg} for memory collecting.
36208 @item len @tab 8 @tab length of memory for collecting
36209 @item basereg @tab 4 @tab the register number containing the starting
36210 memory address for collecting.
36211 @item @emph{tracepoint action for collecting registers} @tab @tab
36212 @item 'R' @tab 1 @tab type of tracepoint action
36213 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36214 @item 'L' @tab 1 @tab type of tracepoint action
36215 @item @emph{tracepoint action for expression evaluation} @tab @tab
36216 @item 'X' @tab 1 @tab type of tracepoint action
36217 @item agent expression @tab length of @tab @ref{agent expression object}
36218 @item @emph{tracepoint object} @tab @tab
36219 @item number @tab 4 @tab number of tracepoint
36220 @item address @tab 8 @tab address of tracepoint inserted on
36221 @item type @tab 4 @tab type of tracepoint
36222 @item enabled @tab 1 @tab enable or disable of tracepoint
36223 @item step_count @tab 8 @tab step
36224 @item pass_count @tab 8 @tab pass
36225 @item numactions @tab 4 @tab number of tracepoint actions
36226 @item hit count @tab 8 @tab hit count
36227 @item trace frame usage @tab 8 @tab trace frame usage
36228 @item compiled_cond @tab 8 @tab compiled condition
36229 @item orig_size @tab 8 @tab orig size
36230 @item condition @tab 4 if condition is NULL otherwise length of
36231 @ref{agent expression object}
36232 @tab zero if condition is NULL, otherwise is
36233 @ref{agent expression object}
36234 @item actions @tab variable
36235 @tab numactions number of @ref{tracepoint action object}
36238 @node IPA Protocol Commands
36239 @subsection IPA Protocol Commands
36240 @cindex ipa protocol commands
36242 The spaces in each command are delimiters to ease reading this commands
36243 specification. They don't exist in real commands.
36247 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36248 Installs a new fast tracepoint described by @var{tracepoint_object}
36249 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
36250 head of @dfn{jumppad}, which is used to jump to data collection routine
36255 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36256 @var{target_address} is address of tracepoint in the inferior.
36257 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36258 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36259 @var{fjump} contains a sequence of instructions jump to jumppad entry.
36260 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36267 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36268 is about to kill inferiors.
36276 @item probe_marker_at:@var{address}
36277 Asks in-process agent to probe the marker at @var{address}.
36284 @item unprobe_marker_at:@var{address}
36285 Asks in-process agent to unprobe the marker at @var{address}.
36289 @chapter Reporting Bugs in @value{GDBN}
36290 @cindex bugs in @value{GDBN}
36291 @cindex reporting bugs in @value{GDBN}
36293 Your bug reports play an essential role in making @value{GDBN} reliable.
36295 Reporting a bug may help you by bringing a solution to your problem, or it
36296 may not. But in any case the principal function of a bug report is to help
36297 the entire community by making the next version of @value{GDBN} work better. Bug
36298 reports are your contribution to the maintenance of @value{GDBN}.
36300 In order for a bug report to serve its purpose, you must include the
36301 information that enables us to fix the bug.
36304 * Bug Criteria:: Have you found a bug?
36305 * Bug Reporting:: How to report bugs
36309 @section Have You Found a Bug?
36310 @cindex bug criteria
36312 If you are not sure whether you have found a bug, here are some guidelines:
36315 @cindex fatal signal
36316 @cindex debugger crash
36317 @cindex crash of debugger
36319 If the debugger gets a fatal signal, for any input whatever, that is a
36320 @value{GDBN} bug. Reliable debuggers never crash.
36322 @cindex error on valid input
36324 If @value{GDBN} produces an error message for valid input, that is a
36325 bug. (Note that if you're cross debugging, the problem may also be
36326 somewhere in the connection to the target.)
36328 @cindex invalid input
36330 If @value{GDBN} does not produce an error message for invalid input,
36331 that is a bug. However, you should note that your idea of
36332 ``invalid input'' might be our idea of ``an extension'' or ``support
36333 for traditional practice''.
36336 If you are an experienced user of debugging tools, your suggestions
36337 for improvement of @value{GDBN} are welcome in any case.
36340 @node Bug Reporting
36341 @section How to Report Bugs
36342 @cindex bug reports
36343 @cindex @value{GDBN} bugs, reporting
36345 A number of companies and individuals offer support for @sc{gnu} products.
36346 If you obtained @value{GDBN} from a support organization, we recommend you
36347 contact that organization first.
36349 You can find contact information for many support companies and
36350 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36352 @c should add a web page ref...
36355 @ifset BUGURL_DEFAULT
36356 In any event, we also recommend that you submit bug reports for
36357 @value{GDBN}. The preferred method is to submit them directly using
36358 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36359 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36362 @strong{Do not send bug reports to @samp{info-gdb}, or to
36363 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36364 not want to receive bug reports. Those that do have arranged to receive
36367 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36368 serves as a repeater. The mailing list and the newsgroup carry exactly
36369 the same messages. Often people think of posting bug reports to the
36370 newsgroup instead of mailing them. This appears to work, but it has one
36371 problem which can be crucial: a newsgroup posting often lacks a mail
36372 path back to the sender. Thus, if we need to ask for more information,
36373 we may be unable to reach you. For this reason, it is better to send
36374 bug reports to the mailing list.
36376 @ifclear BUGURL_DEFAULT
36377 In any event, we also recommend that you submit bug reports for
36378 @value{GDBN} to @value{BUGURL}.
36382 The fundamental principle of reporting bugs usefully is this:
36383 @strong{report all the facts}. If you are not sure whether to state a
36384 fact or leave it out, state it!
36386 Often people omit facts because they think they know what causes the
36387 problem and assume that some details do not matter. Thus, you might
36388 assume that the name of the variable you use in an example does not matter.
36389 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36390 stray memory reference which happens to fetch from the location where that
36391 name is stored in memory; perhaps, if the name were different, the contents
36392 of that location would fool the debugger into doing the right thing despite
36393 the bug. Play it safe and give a specific, complete example. That is the
36394 easiest thing for you to do, and the most helpful.
36396 Keep in mind that the purpose of a bug report is to enable us to fix the
36397 bug. It may be that the bug has been reported previously, but neither
36398 you nor we can know that unless your bug report is complete and
36401 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36402 bell?'' Those bug reports are useless, and we urge everyone to
36403 @emph{refuse to respond to them} except to chide the sender to report
36406 To enable us to fix the bug, you should include all these things:
36410 The version of @value{GDBN}. @value{GDBN} announces it if you start
36411 with no arguments; you can also print it at any time using @code{show
36414 Without this, we will not know whether there is any point in looking for
36415 the bug in the current version of @value{GDBN}.
36418 The type of machine you are using, and the operating system name and
36422 The details of the @value{GDBN} build-time configuration.
36423 @value{GDBN} shows these details if you invoke it with the
36424 @option{--configuration} command-line option, or if you type
36425 @code{show configuration} at @value{GDBN}'s prompt.
36428 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36429 ``@value{GCC}--2.8.1''.
36432 What compiler (and its version) was used to compile the program you are
36433 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36434 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36435 to get this information; for other compilers, see the documentation for
36439 The command arguments you gave the compiler to compile your example and
36440 observe the bug. For example, did you use @samp{-O}? To guarantee
36441 you will not omit something important, list them all. A copy of the
36442 Makefile (or the output from make) is sufficient.
36444 If we were to try to guess the arguments, we would probably guess wrong
36445 and then we might not encounter the bug.
36448 A complete input script, and all necessary source files, that will
36452 A description of what behavior you observe that you believe is
36453 incorrect. For example, ``It gets a fatal signal.''
36455 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36456 will certainly notice it. But if the bug is incorrect output, we might
36457 not notice unless it is glaringly wrong. You might as well not give us
36458 a chance to make a mistake.
36460 Even if the problem you experience is a fatal signal, you should still
36461 say so explicitly. Suppose something strange is going on, such as, your
36462 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36463 the C library on your system. (This has happened!) Your copy might
36464 crash and ours would not. If you told us to expect a crash, then when
36465 ours fails to crash, we would know that the bug was not happening for
36466 us. If you had not told us to expect a crash, then we would not be able
36467 to draw any conclusion from our observations.
36470 @cindex recording a session script
36471 To collect all this information, you can use a session recording program
36472 such as @command{script}, which is available on many Unix systems.
36473 Just run your @value{GDBN} session inside @command{script} and then
36474 include the @file{typescript} file with your bug report.
36476 Another way to record a @value{GDBN} session is to run @value{GDBN}
36477 inside Emacs and then save the entire buffer to a file.
36480 If you wish to suggest changes to the @value{GDBN} source, send us context
36481 diffs. If you even discuss something in the @value{GDBN} source, refer to
36482 it by context, not by line number.
36484 The line numbers in our development sources will not match those in your
36485 sources. Your line numbers would convey no useful information to us.
36489 Here are some things that are not necessary:
36493 A description of the envelope of the bug.
36495 Often people who encounter a bug spend a lot of time investigating
36496 which changes to the input file will make the bug go away and which
36497 changes will not affect it.
36499 This is often time consuming and not very useful, because the way we
36500 will find the bug is by running a single example under the debugger
36501 with breakpoints, not by pure deduction from a series of examples.
36502 We recommend that you save your time for something else.
36504 Of course, if you can find a simpler example to report @emph{instead}
36505 of the original one, that is a convenience for us. Errors in the
36506 output will be easier to spot, running under the debugger will take
36507 less time, and so on.
36509 However, simplification is not vital; if you do not want to do this,
36510 report the bug anyway and send us the entire test case you used.
36513 A patch for the bug.
36515 A patch for the bug does help us if it is a good one. But do not omit
36516 the necessary information, such as the test case, on the assumption that
36517 a patch is all we need. We might see problems with your patch and decide
36518 to fix the problem another way, or we might not understand it at all.
36520 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36521 construct an example that will make the program follow a certain path
36522 through the code. If you do not send us the example, we will not be able
36523 to construct one, so we will not be able to verify that the bug is fixed.
36525 And if we cannot understand what bug you are trying to fix, or why your
36526 patch should be an improvement, we will not install it. A test case will
36527 help us to understand.
36530 A guess about what the bug is or what it depends on.
36532 Such guesses are usually wrong. Even we cannot guess right about such
36533 things without first using the debugger to find the facts.
36536 @c The readline documentation is distributed with the readline code
36537 @c and consists of the two following files:
36540 @c Use -I with makeinfo to point to the appropriate directory,
36541 @c environment var TEXINPUTS with TeX.
36542 @ifclear SYSTEM_READLINE
36543 @include rluser.texi
36544 @include hsuser.texi
36548 @appendix In Memoriam
36550 The @value{GDBN} project mourns the loss of the following long-time
36555 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36556 to Free Software in general. Outside of @value{GDBN}, he was known in
36557 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36559 @item Michael Snyder
36560 Michael was one of the Global Maintainers of the @value{GDBN} project,
36561 with contributions recorded as early as 1996, until 2011. In addition
36562 to his day to day participation, he was a large driving force behind
36563 adding Reverse Debugging to @value{GDBN}.
36566 Beyond their technical contributions to the project, they were also
36567 enjoyable members of the Free Software Community. We will miss them.
36569 @node Formatting Documentation
36570 @appendix Formatting Documentation
36572 @cindex @value{GDBN} reference card
36573 @cindex reference card
36574 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36575 for printing with PostScript or Ghostscript, in the @file{gdb}
36576 subdirectory of the main source directory@footnote{In
36577 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36578 release.}. If you can use PostScript or Ghostscript with your printer,
36579 you can print the reference card immediately with @file{refcard.ps}.
36581 The release also includes the source for the reference card. You
36582 can format it, using @TeX{}, by typing:
36588 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36589 mode on US ``letter'' size paper;
36590 that is, on a sheet 11 inches wide by 8.5 inches
36591 high. You will need to specify this form of printing as an option to
36592 your @sc{dvi} output program.
36594 @cindex documentation
36596 All the documentation for @value{GDBN} comes as part of the machine-readable
36597 distribution. The documentation is written in Texinfo format, which is
36598 a documentation system that uses a single source file to produce both
36599 on-line information and a printed manual. You can use one of the Info
36600 formatting commands to create the on-line version of the documentation
36601 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36603 @value{GDBN} includes an already formatted copy of the on-line Info
36604 version of this manual in the @file{gdb} subdirectory. The main Info
36605 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36606 subordinate files matching @samp{gdb.info*} in the same directory. If
36607 necessary, you can print out these files, or read them with any editor;
36608 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36609 Emacs or the standalone @code{info} program, available as part of the
36610 @sc{gnu} Texinfo distribution.
36612 If you want to format these Info files yourself, you need one of the
36613 Info formatting programs, such as @code{texinfo-format-buffer} or
36616 If you have @code{makeinfo} installed, and are in the top level
36617 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36618 version @value{GDBVN}), you can make the Info file by typing:
36625 If you want to typeset and print copies of this manual, you need @TeX{},
36626 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36627 Texinfo definitions file.
36629 @TeX{} is a typesetting program; it does not print files directly, but
36630 produces output files called @sc{dvi} files. To print a typeset
36631 document, you need a program to print @sc{dvi} files. If your system
36632 has @TeX{} installed, chances are it has such a program. The precise
36633 command to use depends on your system; @kbd{lpr -d} is common; another
36634 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36635 require a file name without any extension or a @samp{.dvi} extension.
36637 @TeX{} also requires a macro definitions file called
36638 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36639 written in Texinfo format. On its own, @TeX{} cannot either read or
36640 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36641 and is located in the @file{gdb-@var{version-number}/texinfo}
36644 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36645 typeset and print this manual. First switch to the @file{gdb}
36646 subdirectory of the main source directory (for example, to
36647 @file{gdb-@value{GDBVN}/gdb}) and type:
36653 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36655 @node Installing GDB
36656 @appendix Installing @value{GDBN}
36657 @cindex installation
36660 * Requirements:: Requirements for building @value{GDBN}
36661 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36662 * Separate Objdir:: Compiling @value{GDBN} in another directory
36663 * Config Names:: Specifying names for hosts and targets
36664 * Configure Options:: Summary of options for configure
36665 * System-wide configuration:: Having a system-wide init file
36669 @section Requirements for Building @value{GDBN}
36670 @cindex building @value{GDBN}, requirements for
36672 Building @value{GDBN} requires various tools and packages to be available.
36673 Other packages will be used only if they are found.
36675 @heading Tools/Packages Necessary for Building @value{GDBN}
36677 @item ISO C90 compiler
36678 @value{GDBN} is written in ISO C90. It should be buildable with any
36679 working C90 compiler, e.g.@: GCC.
36683 @heading Tools/Packages Optional for Building @value{GDBN}
36687 @value{GDBN} can use the Expat XML parsing library. This library may be
36688 included with your operating system distribution; if it is not, you
36689 can get the latest version from @url{http://expat.sourceforge.net}.
36690 The @file{configure} script will search for this library in several
36691 standard locations; if it is installed in an unusual path, you can
36692 use the @option{--with-libexpat-prefix} option to specify its location.
36698 Remote protocol memory maps (@pxref{Memory Map Format})
36700 Target descriptions (@pxref{Target Descriptions})
36702 Remote shared library lists (@xref{Library List Format},
36703 or alternatively @pxref{Library List Format for SVR4 Targets})
36705 MS-Windows shared libraries (@pxref{Shared Libraries})
36707 Traceframe info (@pxref{Traceframe Info Format})
36709 Branch trace (@pxref{Branch Trace Format})
36713 @cindex compressed debug sections
36714 @value{GDBN} will use the @samp{zlib} library, if available, to read
36715 compressed debug sections. Some linkers, such as GNU gold, are capable
36716 of producing binaries with compressed debug sections. If @value{GDBN}
36717 is compiled with @samp{zlib}, it will be able to read the debug
36718 information in such binaries.
36720 The @samp{zlib} library is likely included with your operating system
36721 distribution; if it is not, you can get the latest version from
36722 @url{http://zlib.net}.
36725 @value{GDBN}'s features related to character sets (@pxref{Character
36726 Sets}) require a functioning @code{iconv} implementation. If you are
36727 on a GNU system, then this is provided by the GNU C Library. Some
36728 other systems also provide a working @code{iconv}.
36730 If @value{GDBN} is using the @code{iconv} program which is installed
36731 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36732 This is done with @option{--with-iconv-bin} which specifies the
36733 directory that contains the @code{iconv} program.
36735 On systems without @code{iconv}, you can install GNU Libiconv. If you
36736 have previously installed Libiconv, you can use the
36737 @option{--with-libiconv-prefix} option to configure.
36739 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36740 arrange to build Libiconv if a directory named @file{libiconv} appears
36741 in the top-most source directory. If Libiconv is built this way, and
36742 if the operating system does not provide a suitable @code{iconv}
36743 implementation, then the just-built library will automatically be used
36744 by @value{GDBN}. One easy way to set this up is to download GNU
36745 Libiconv, unpack it, and then rename the directory holding the
36746 Libiconv source code to @samp{libiconv}.
36749 @node Running Configure
36750 @section Invoking the @value{GDBN} @file{configure} Script
36751 @cindex configuring @value{GDBN}
36752 @value{GDBN} comes with a @file{configure} script that automates the process
36753 of preparing @value{GDBN} for installation; you can then use @code{make} to
36754 build the @code{gdb} program.
36756 @c irrelevant in info file; it's as current as the code it lives with.
36757 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36758 look at the @file{README} file in the sources; we may have improved the
36759 installation procedures since publishing this manual.}
36762 The @value{GDBN} distribution includes all the source code you need for
36763 @value{GDBN} in a single directory, whose name is usually composed by
36764 appending the version number to @samp{gdb}.
36766 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36767 @file{gdb-@value{GDBVN}} directory. That directory contains:
36770 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36771 script for configuring @value{GDBN} and all its supporting libraries
36773 @item gdb-@value{GDBVN}/gdb
36774 the source specific to @value{GDBN} itself
36776 @item gdb-@value{GDBVN}/bfd
36777 source for the Binary File Descriptor library
36779 @item gdb-@value{GDBVN}/include
36780 @sc{gnu} include files
36782 @item gdb-@value{GDBVN}/libiberty
36783 source for the @samp{-liberty} free software library
36785 @item gdb-@value{GDBVN}/opcodes
36786 source for the library of opcode tables and disassemblers
36788 @item gdb-@value{GDBVN}/readline
36789 source for the @sc{gnu} command-line interface
36791 @item gdb-@value{GDBVN}/glob
36792 source for the @sc{gnu} filename pattern-matching subroutine
36794 @item gdb-@value{GDBVN}/mmalloc
36795 source for the @sc{gnu} memory-mapped malloc package
36798 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36799 from the @file{gdb-@var{version-number}} source directory, which in
36800 this example is the @file{gdb-@value{GDBVN}} directory.
36802 First switch to the @file{gdb-@var{version-number}} source directory
36803 if you are not already in it; then run @file{configure}. Pass the
36804 identifier for the platform on which @value{GDBN} will run as an
36810 cd gdb-@value{GDBVN}
36811 ./configure @var{host}
36816 where @var{host} is an identifier such as @samp{sun4} or
36817 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
36818 (You can often leave off @var{host}; @file{configure} tries to guess the
36819 correct value by examining your system.)
36821 Running @samp{configure @var{host}} and then running @code{make} builds the
36822 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
36823 libraries, then @code{gdb} itself. The configured source files, and the
36824 binaries, are left in the corresponding source directories.
36827 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36828 system does not recognize this automatically when you run a different
36829 shell, you may need to run @code{sh} on it explicitly:
36832 sh configure @var{host}
36835 If you run @file{configure} from a directory that contains source
36836 directories for multiple libraries or programs, such as the
36837 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
36839 creates configuration files for every directory level underneath (unless
36840 you tell it not to, with the @samp{--norecursion} option).
36842 You should run the @file{configure} script from the top directory in the
36843 source tree, the @file{gdb-@var{version-number}} directory. If you run
36844 @file{configure} from one of the subdirectories, you will configure only
36845 that subdirectory. That is usually not what you want. In particular,
36846 if you run the first @file{configure} from the @file{gdb} subdirectory
36847 of the @file{gdb-@var{version-number}} directory, you will omit the
36848 configuration of @file{bfd}, @file{readline}, and other sibling
36849 directories of the @file{gdb} subdirectory. This leads to build errors
36850 about missing include files such as @file{bfd/bfd.h}.
36852 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
36853 However, you should make sure that the shell on your path (named by
36854 the @samp{SHELL} environment variable) is publicly readable. Remember
36855 that @value{GDBN} uses the shell to start your program---some systems refuse to
36856 let @value{GDBN} debug child processes whose programs are not readable.
36858 @node Separate Objdir
36859 @section Compiling @value{GDBN} in Another Directory
36861 If you want to run @value{GDBN} versions for several host or target machines,
36862 you need a different @code{gdb} compiled for each combination of
36863 host and target. @file{configure} is designed to make this easy by
36864 allowing you to generate each configuration in a separate subdirectory,
36865 rather than in the source directory. If your @code{make} program
36866 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36867 @code{make} in each of these directories builds the @code{gdb}
36868 program specified there.
36870 To build @code{gdb} in a separate directory, run @file{configure}
36871 with the @samp{--srcdir} option to specify where to find the source.
36872 (You also need to specify a path to find @file{configure}
36873 itself from your working directory. If the path to @file{configure}
36874 would be the same as the argument to @samp{--srcdir}, you can leave out
36875 the @samp{--srcdir} option; it is assumed.)
36877 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36878 separate directory for a Sun 4 like this:
36882 cd gdb-@value{GDBVN}
36885 ../gdb-@value{GDBVN}/configure sun4
36890 When @file{configure} builds a configuration using a remote source
36891 directory, it creates a tree for the binaries with the same structure
36892 (and using the same names) as the tree under the source directory. In
36893 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36894 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36895 @file{gdb-sun4/gdb}.
36897 Make sure that your path to the @file{configure} script has just one
36898 instance of @file{gdb} in it. If your path to @file{configure} looks
36899 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36900 one subdirectory of @value{GDBN}, not the whole package. This leads to
36901 build errors about missing include files such as @file{bfd/bfd.h}.
36903 One popular reason to build several @value{GDBN} configurations in separate
36904 directories is to configure @value{GDBN} for cross-compiling (where
36905 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36906 programs that run on another machine---the @dfn{target}).
36907 You specify a cross-debugging target by
36908 giving the @samp{--target=@var{target}} option to @file{configure}.
36910 When you run @code{make} to build a program or library, you must run
36911 it in a configured directory---whatever directory you were in when you
36912 called @file{configure} (or one of its subdirectories).
36914 The @code{Makefile} that @file{configure} generates in each source
36915 directory also runs recursively. If you type @code{make} in a source
36916 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36917 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36918 will build all the required libraries, and then build GDB.
36920 When you have multiple hosts or targets configured in separate
36921 directories, you can run @code{make} on them in parallel (for example,
36922 if they are NFS-mounted on each of the hosts); they will not interfere
36926 @section Specifying Names for Hosts and Targets
36928 The specifications used for hosts and targets in the @file{configure}
36929 script are based on a three-part naming scheme, but some short predefined
36930 aliases are also supported. The full naming scheme encodes three pieces
36931 of information in the following pattern:
36934 @var{architecture}-@var{vendor}-@var{os}
36937 For example, you can use the alias @code{sun4} as a @var{host} argument,
36938 or as the value for @var{target} in a @code{--target=@var{target}}
36939 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36941 The @file{configure} script accompanying @value{GDBN} does not provide
36942 any query facility to list all supported host and target names or
36943 aliases. @file{configure} calls the Bourne shell script
36944 @code{config.sub} to map abbreviations to full names; you can read the
36945 script, if you wish, or you can use it to test your guesses on
36946 abbreviations---for example:
36949 % sh config.sub i386-linux
36951 % sh config.sub alpha-linux
36952 alpha-unknown-linux-gnu
36953 % sh config.sub hp9k700
36955 % sh config.sub sun4
36956 sparc-sun-sunos4.1.1
36957 % sh config.sub sun3
36958 m68k-sun-sunos4.1.1
36959 % sh config.sub i986v
36960 Invalid configuration `i986v': machine `i986v' not recognized
36964 @code{config.sub} is also distributed in the @value{GDBN} source
36965 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36967 @node Configure Options
36968 @section @file{configure} Options
36970 Here is a summary of the @file{configure} options and arguments that
36971 are most often useful for building @value{GDBN}. @file{configure} also has
36972 several other options not listed here. @inforef{What Configure
36973 Does,,configure.info}, for a full explanation of @file{configure}.
36976 configure @r{[}--help@r{]}
36977 @r{[}--prefix=@var{dir}@r{]}
36978 @r{[}--exec-prefix=@var{dir}@r{]}
36979 @r{[}--srcdir=@var{dirname}@r{]}
36980 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
36981 @r{[}--target=@var{target}@r{]}
36986 You may introduce options with a single @samp{-} rather than
36987 @samp{--} if you prefer; but you may abbreviate option names if you use
36992 Display a quick summary of how to invoke @file{configure}.
36994 @item --prefix=@var{dir}
36995 Configure the source to install programs and files under directory
36998 @item --exec-prefix=@var{dir}
36999 Configure the source to install programs under directory
37002 @c avoid splitting the warning from the explanation:
37004 @item --srcdir=@var{dirname}
37005 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
37006 @code{make} that implements the @code{VPATH} feature.}@*
37007 Use this option to make configurations in directories separate from the
37008 @value{GDBN} source directories. Among other things, you can use this to
37009 build (or maintain) several configurations simultaneously, in separate
37010 directories. @file{configure} writes configuration-specific files in
37011 the current directory, but arranges for them to use the source in the
37012 directory @var{dirname}. @file{configure} creates directories under
37013 the working directory in parallel to the source directories below
37016 @item --norecursion
37017 Configure only the directory level where @file{configure} is executed; do not
37018 propagate configuration to subdirectories.
37020 @item --target=@var{target}
37021 Configure @value{GDBN} for cross-debugging programs running on the specified
37022 @var{target}. Without this option, @value{GDBN} is configured to debug
37023 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37025 There is no convenient way to generate a list of all available targets.
37027 @item @var{host} @dots{}
37028 Configure @value{GDBN} to run on the specified @var{host}.
37030 There is no convenient way to generate a list of all available hosts.
37033 There are many other options available as well, but they are generally
37034 needed for special purposes only.
37036 @node System-wide configuration
37037 @section System-wide configuration and settings
37038 @cindex system-wide init file
37040 @value{GDBN} can be configured to have a system-wide init file;
37041 this file will be read and executed at startup (@pxref{Startup, , What
37042 @value{GDBN} does during startup}).
37044 Here is the corresponding configure option:
37047 @item --with-system-gdbinit=@var{file}
37048 Specify that the default location of the system-wide init file is
37052 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37053 it may be subject to relocation. Two possible cases:
37057 If the default location of this init file contains @file{$prefix},
37058 it will be subject to relocation. Suppose that the configure options
37059 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37060 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37061 init file is looked for as @file{$install/etc/gdbinit} instead of
37062 @file{$prefix/etc/gdbinit}.
37065 By contrast, if the default location does not contain the prefix,
37066 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37067 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37068 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37069 wherever @value{GDBN} is installed.
37072 If the configured location of the system-wide init file (as given by the
37073 @option{--with-system-gdbinit} option at configure time) is in the
37074 data-directory (as specified by @option{--with-gdb-datadir} at configure
37075 time) or in one of its subdirectories, then @value{GDBN} will look for the
37076 system-wide init file in the directory specified by the
37077 @option{--data-directory} command-line option.
37078 Note that the system-wide init file is only read once, during @value{GDBN}
37079 initialization. If the data-directory is changed after @value{GDBN} has
37080 started with the @code{set data-directory} command, the file will not be
37084 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37087 @node System-wide Configuration Scripts
37088 @subsection Installed System-wide Configuration Scripts
37089 @cindex system-wide configuration scripts
37091 The @file{system-gdbinit} directory, located inside the data-directory
37092 (as specified by @option{--with-gdb-datadir} at configure time) contains
37093 a number of scripts which can be used as system-wide init files. To
37094 automatically source those scripts at startup, @value{GDBN} should be
37095 configured with @option{--with-system-gdbinit}. Otherwise, any user
37096 should be able to source them by hand as needed.
37098 The following scripts are currently available:
37101 @item @file{elinos.py}
37103 @cindex ELinOS system-wide configuration script
37104 This script is useful when debugging a program on an ELinOS target.
37105 It takes advantage of the environment variables defined in a standard
37106 ELinOS environment in order to determine the location of the system
37107 shared libraries, and then sets the @samp{solib-absolute-prefix}
37108 and @samp{solib-search-path} variables appropriately.
37110 @item @file{wrs-linux.py}
37111 @pindex wrs-linux.py
37112 @cindex Wind River Linux system-wide configuration script
37113 This script is useful when debugging a program on a target running
37114 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37115 the host-side sysroot used by the target system.
37119 @node Maintenance Commands
37120 @appendix Maintenance Commands
37121 @cindex maintenance commands
37122 @cindex internal commands
37124 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37125 includes a number of commands intended for @value{GDBN} developers,
37126 that are not documented elsewhere in this manual. These commands are
37127 provided here for reference. (For commands that turn on debugging
37128 messages, see @ref{Debugging Output}.)
37131 @kindex maint agent
37132 @kindex maint agent-eval
37133 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37134 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37135 Translate the given @var{expression} into remote agent bytecodes.
37136 This command is useful for debugging the Agent Expression mechanism
37137 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37138 expression useful for data collection, such as by tracepoints, while
37139 @samp{maint agent-eval} produces an expression that evaluates directly
37140 to a result. For instance, a collection expression for @code{globa +
37141 globb} will include bytecodes to record four bytes of memory at each
37142 of the addresses of @code{globa} and @code{globb}, while discarding
37143 the result of the addition, while an evaluation expression will do the
37144 addition and return the sum.
37145 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37146 If not, generate remote agent bytecode for current frame PC address.
37148 @kindex maint agent-printf
37149 @item maint agent-printf @var{format},@var{expr},...
37150 Translate the given format string and list of argument expressions
37151 into remote agent bytecodes and display them as a disassembled list.
37152 This command is useful for debugging the agent version of dynamic
37153 printf (@pxref{Dynamic Printf}).
37155 @kindex maint info breakpoints
37156 @item @anchor{maint info breakpoints}maint info breakpoints
37157 Using the same format as @samp{info breakpoints}, display both the
37158 breakpoints you've set explicitly, and those @value{GDBN} is using for
37159 internal purposes. Internal breakpoints are shown with negative
37160 breakpoint numbers. The type column identifies what kind of breakpoint
37165 Normal, explicitly set breakpoint.
37168 Normal, explicitly set watchpoint.
37171 Internal breakpoint, used to handle correctly stepping through
37172 @code{longjmp} calls.
37174 @item longjmp resume
37175 Internal breakpoint at the target of a @code{longjmp}.
37178 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37181 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37184 Shared library events.
37188 @kindex maint info bfds
37189 @item maint info bfds
37190 This prints information about each @code{bfd} object that is known to
37191 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
37193 @kindex set displaced-stepping
37194 @kindex show displaced-stepping
37195 @cindex displaced stepping support
37196 @cindex out-of-line single-stepping
37197 @item set displaced-stepping
37198 @itemx show displaced-stepping
37199 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37200 if the target supports it. Displaced stepping is a way to single-step
37201 over breakpoints without removing them from the inferior, by executing
37202 an out-of-line copy of the instruction that was originally at the
37203 breakpoint location. It is also known as out-of-line single-stepping.
37206 @item set displaced-stepping on
37207 If the target architecture supports it, @value{GDBN} will use
37208 displaced stepping to step over breakpoints.
37210 @item set displaced-stepping off
37211 @value{GDBN} will not use displaced stepping to step over breakpoints,
37212 even if such is supported by the target architecture.
37214 @cindex non-stop mode, and @samp{set displaced-stepping}
37215 @item set displaced-stepping auto
37216 This is the default mode. @value{GDBN} will use displaced stepping
37217 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37218 architecture supports displaced stepping.
37221 @kindex maint check-psymtabs
37222 @item maint check-psymtabs
37223 Check the consistency of currently expanded psymtabs versus symtabs.
37224 Use this to check, for example, whether a symbol is in one but not the other.
37226 @kindex maint check-symtabs
37227 @item maint check-symtabs
37228 Check the consistency of currently expanded symtabs.
37230 @kindex maint expand-symtabs
37231 @item maint expand-symtabs [@var{regexp}]
37232 Expand symbol tables.
37233 If @var{regexp} is specified, only expand symbol tables for file
37234 names matching @var{regexp}.
37236 @kindex maint cplus first_component
37237 @item maint cplus first_component @var{name}
37238 Print the first C@t{++} class/namespace component of @var{name}.
37240 @kindex maint cplus namespace
37241 @item maint cplus namespace
37242 Print the list of possible C@t{++} namespaces.
37244 @kindex maint demangle
37245 @item maint demangle @var{name}
37246 Demangle a C@t{++} or Objective-C mangled @var{name}.
37248 @kindex maint deprecate
37249 @kindex maint undeprecate
37250 @cindex deprecated commands
37251 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37252 @itemx maint undeprecate @var{command}
37253 Deprecate or undeprecate the named @var{command}. Deprecated commands
37254 cause @value{GDBN} to issue a warning when you use them. The optional
37255 argument @var{replacement} says which newer command should be used in
37256 favor of the deprecated one; if it is given, @value{GDBN} will mention
37257 the replacement as part of the warning.
37259 @kindex maint dump-me
37260 @item maint dump-me
37261 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37262 Cause a fatal signal in the debugger and force it to dump its core.
37263 This is supported only on systems which support aborting a program
37264 with the @code{SIGQUIT} signal.
37266 @kindex maint internal-error
37267 @kindex maint internal-warning
37268 @item maint internal-error @r{[}@var{message-text}@r{]}
37269 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37270 Cause @value{GDBN} to call the internal function @code{internal_error}
37271 or @code{internal_warning} and hence behave as though an internal error
37272 or internal warning has been detected. In addition to reporting the
37273 internal problem, these functions give the user the opportunity to
37274 either quit @value{GDBN} or create a core file of the current
37275 @value{GDBN} session.
37277 These commands take an optional parameter @var{message-text} that is
37278 used as the text of the error or warning message.
37280 Here's an example of using @code{internal-error}:
37283 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37284 @dots{}/maint.c:121: internal-error: testing, 1, 2
37285 A problem internal to GDB has been detected. Further
37286 debugging may prove unreliable.
37287 Quit this debugging session? (y or n) @kbd{n}
37288 Create a core file? (y or n) @kbd{n}
37292 @cindex @value{GDBN} internal error
37293 @cindex internal errors, control of @value{GDBN} behavior
37295 @kindex maint set internal-error
37296 @kindex maint show internal-error
37297 @kindex maint set internal-warning
37298 @kindex maint show internal-warning
37299 @item maint set internal-error @var{action} [ask|yes|no]
37300 @itemx maint show internal-error @var{action}
37301 @itemx maint set internal-warning @var{action} [ask|yes|no]
37302 @itemx maint show internal-warning @var{action}
37303 When @value{GDBN} reports an internal problem (error or warning) it
37304 gives the user the opportunity to both quit @value{GDBN} and create a
37305 core file of the current @value{GDBN} session. These commands let you
37306 override the default behaviour for each particular @var{action},
37307 described in the table below.
37311 You can specify that @value{GDBN} should always (yes) or never (no)
37312 quit. The default is to ask the user what to do.
37315 You can specify that @value{GDBN} should always (yes) or never (no)
37316 create a core file. The default is to ask the user what to do.
37319 @kindex maint packet
37320 @item maint packet @var{text}
37321 If @value{GDBN} is talking to an inferior via the serial protocol,
37322 then this command sends the string @var{text} to the inferior, and
37323 displays the response packet. @value{GDBN} supplies the initial
37324 @samp{$} character, the terminating @samp{#} character, and the
37327 @kindex maint print architecture
37328 @item maint print architecture @r{[}@var{file}@r{]}
37329 Print the entire architecture configuration. The optional argument
37330 @var{file} names the file where the output goes.
37332 @kindex maint print c-tdesc
37333 @item maint print c-tdesc
37334 Print the current target description (@pxref{Target Descriptions}) as
37335 a C source file. The created source file can be used in @value{GDBN}
37336 when an XML parser is not available to parse the description.
37338 @kindex maint print dummy-frames
37339 @item maint print dummy-frames
37340 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37343 (@value{GDBP}) @kbd{b add}
37345 (@value{GDBP}) @kbd{print add(2,3)}
37346 Breakpoint 2, add (a=2, b=3) at @dots{}
37348 The program being debugged stopped while in a function called from GDB.
37350 (@value{GDBP}) @kbd{maint print dummy-frames}
37351 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37352 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37353 call_lo=0x01014000 call_hi=0x01014001
37357 Takes an optional file parameter.
37359 @kindex maint print registers
37360 @kindex maint print raw-registers
37361 @kindex maint print cooked-registers
37362 @kindex maint print register-groups
37363 @kindex maint print remote-registers
37364 @item maint print registers @r{[}@var{file}@r{]}
37365 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37366 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37367 @itemx maint print register-groups @r{[}@var{file}@r{]}
37368 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37369 Print @value{GDBN}'s internal register data structures.
37371 The command @code{maint print raw-registers} includes the contents of
37372 the raw register cache; the command @code{maint print
37373 cooked-registers} includes the (cooked) value of all registers,
37374 including registers which aren't available on the target nor visible
37375 to user; the command @code{maint print register-groups} includes the
37376 groups that each register is a member of; and the command @code{maint
37377 print remote-registers} includes the remote target's register numbers
37378 and offsets in the `G' packets.
37380 These commands take an optional parameter, a file name to which to
37381 write the information.
37383 @kindex maint print reggroups
37384 @item maint print reggroups @r{[}@var{file}@r{]}
37385 Print @value{GDBN}'s internal register group data structures. The
37386 optional argument @var{file} tells to what file to write the
37389 The register groups info looks like this:
37392 (@value{GDBP}) @kbd{maint print reggroups}
37405 This command forces @value{GDBN} to flush its internal register cache.
37407 @kindex maint print objfiles
37408 @cindex info for known object files
37409 @item maint print objfiles @r{[}@var{regexp}@r{]}
37410 Print a dump of all known object files.
37411 If @var{regexp} is specified, only print object files whose names
37412 match @var{regexp}. For each object file, this command prints its name,
37413 address in memory, and all of its psymtabs and symtabs.
37415 @kindex maint print section-scripts
37416 @cindex info for known .debug_gdb_scripts-loaded scripts
37417 @item maint print section-scripts [@var{regexp}]
37418 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37419 If @var{regexp} is specified, only print scripts loaded by object files
37420 matching @var{regexp}.
37421 For each script, this command prints its name as specified in the objfile,
37422 and the full path if known.
37423 @xref{dotdebug_gdb_scripts section}.
37425 @kindex maint print statistics
37426 @cindex bcache statistics
37427 @item maint print statistics
37428 This command prints, for each object file in the program, various data
37429 about that object file followed by the byte cache (@dfn{bcache})
37430 statistics for the object file. The objfile data includes the number
37431 of minimal, partial, full, and stabs symbols, the number of types
37432 defined by the objfile, the number of as yet unexpanded psym tables,
37433 the number of line tables and string tables, and the amount of memory
37434 used by the various tables. The bcache statistics include the counts,
37435 sizes, and counts of duplicates of all and unique objects, max,
37436 average, and median entry size, total memory used and its overhead and
37437 savings, and various measures of the hash table size and chain
37440 @kindex maint print target-stack
37441 @cindex target stack description
37442 @item maint print target-stack
37443 A @dfn{target} is an interface between the debugger and a particular
37444 kind of file or process. Targets can be stacked in @dfn{strata},
37445 so that more than one target can potentially respond to a request.
37446 In particular, memory accesses will walk down the stack of targets
37447 until they find a target that is interested in handling that particular
37450 This command prints a short description of each layer that was pushed on
37451 the @dfn{target stack}, starting from the top layer down to the bottom one.
37453 @kindex maint print type
37454 @cindex type chain of a data type
37455 @item maint print type @var{expr}
37456 Print the type chain for a type specified by @var{expr}. The argument
37457 can be either a type name or a symbol. If it is a symbol, the type of
37458 that symbol is described. The type chain produced by this command is
37459 a recursive definition of the data type as stored in @value{GDBN}'s
37460 data structures, including its flags and contained types.
37462 @kindex maint set dwarf2 always-disassemble
37463 @kindex maint show dwarf2 always-disassemble
37464 @item maint set dwarf2 always-disassemble
37465 @item maint show dwarf2 always-disassemble
37466 Control the behavior of @code{info address} when using DWARF debugging
37469 The default is @code{off}, which means that @value{GDBN} should try to
37470 describe a variable's location in an easily readable format. When
37471 @code{on}, @value{GDBN} will instead display the DWARF location
37472 expression in an assembly-like format. Note that some locations are
37473 too complex for @value{GDBN} to describe simply; in this case you will
37474 always see the disassembly form.
37476 Here is an example of the resulting disassembly:
37479 (gdb) info addr argc
37480 Symbol "argc" is a complex DWARF expression:
37484 For more information on these expressions, see
37485 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37487 @kindex maint set dwarf2 max-cache-age
37488 @kindex maint show dwarf2 max-cache-age
37489 @item maint set dwarf2 max-cache-age
37490 @itemx maint show dwarf2 max-cache-age
37491 Control the DWARF 2 compilation unit cache.
37493 @cindex DWARF 2 compilation units cache
37494 In object files with inter-compilation-unit references, such as those
37495 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37496 reader needs to frequently refer to previously read compilation units.
37497 This setting controls how long a compilation unit will remain in the
37498 cache if it is not referenced. A higher limit means that cached
37499 compilation units will be stored in memory longer, and more total
37500 memory will be used. Setting it to zero disables caching, which will
37501 slow down @value{GDBN} startup, but reduce memory consumption.
37503 @kindex maint set profile
37504 @kindex maint show profile
37505 @cindex profiling GDB
37506 @item maint set profile
37507 @itemx maint show profile
37508 Control profiling of @value{GDBN}.
37510 Profiling will be disabled until you use the @samp{maint set profile}
37511 command to enable it. When you enable profiling, the system will begin
37512 collecting timing and execution count data; when you disable profiling or
37513 exit @value{GDBN}, the results will be written to a log file. Remember that
37514 if you use profiling, @value{GDBN} will overwrite the profiling log file
37515 (often called @file{gmon.out}). If you have a record of important profiling
37516 data in a @file{gmon.out} file, be sure to move it to a safe location.
37518 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37519 compiled with the @samp{-pg} compiler option.
37521 @kindex maint set show-debug-regs
37522 @kindex maint show show-debug-regs
37523 @cindex hardware debug registers
37524 @item maint set show-debug-regs
37525 @itemx maint show show-debug-regs
37526 Control whether to show variables that mirror the hardware debug
37527 registers. Use @code{ON} to enable, @code{OFF} to disable. If
37528 enabled, the debug registers values are shown when @value{GDBN} inserts or
37529 removes a hardware breakpoint or watchpoint, and when the inferior
37530 triggers a hardware-assisted breakpoint or watchpoint.
37532 @kindex maint set show-all-tib
37533 @kindex maint show show-all-tib
37534 @item maint set show-all-tib
37535 @itemx maint show show-all-tib
37536 Control whether to show all non zero areas within a 1k block starting
37537 at thread local base, when using the @samp{info w32 thread-information-block}
37540 @kindex maint set per-command
37541 @kindex maint show per-command
37542 @item maint set per-command
37543 @itemx maint show per-command
37544 @cindex resources used by commands
37546 @value{GDBN} can display the resources used by each command.
37547 This is useful in debugging performance problems.
37550 @item maint set per-command space [on|off]
37551 @itemx maint show per-command space
37552 Enable or disable the printing of the memory used by GDB for each command.
37553 If enabled, @value{GDBN} will display how much memory each command
37554 took, following the command's own output.
37555 This can also be requested by invoking @value{GDBN} with the
37556 @option{--statistics} command-line switch (@pxref{Mode Options}).
37558 @item maint set per-command time [on|off]
37559 @itemx maint show per-command time
37560 Enable or disable the printing of the execution time of @value{GDBN}
37562 If enabled, @value{GDBN} will display how much time it
37563 took to execute each command, following the command's own output.
37564 Both CPU time and wallclock time are printed.
37565 Printing both is useful when trying to determine whether the cost is
37566 CPU or, e.g., disk/network latency.
37567 Note that the CPU time printed is for @value{GDBN} only, it does not include
37568 the execution time of the inferior because there's no mechanism currently
37569 to compute how much time was spent by @value{GDBN} and how much time was
37570 spent by the program been debugged.
37571 This can also be requested by invoking @value{GDBN} with the
37572 @option{--statistics} command-line switch (@pxref{Mode Options}).
37574 @item maint set per-command symtab [on|off]
37575 @itemx maint show per-command symtab
37576 Enable or disable the printing of basic symbol table statistics
37578 If enabled, @value{GDBN} will display the following information:
37582 number of symbol tables
37584 number of primary symbol tables
37586 number of blocks in the blockvector
37590 @kindex maint space
37591 @cindex memory used by commands
37592 @item maint space @var{value}
37593 An alias for @code{maint set per-command space}.
37594 A non-zero value enables it, zero disables it.
37597 @cindex time of command execution
37598 @item maint time @var{value}
37599 An alias for @code{maint set per-command time}.
37600 A non-zero value enables it, zero disables it.
37602 @kindex maint translate-address
37603 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37604 Find the symbol stored at the location specified by the address
37605 @var{addr} and an optional section name @var{section}. If found,
37606 @value{GDBN} prints the name of the closest symbol and an offset from
37607 the symbol's location to the specified address. This is similar to
37608 the @code{info address} command (@pxref{Symbols}), except that this
37609 command also allows to find symbols in other sections.
37611 If section was not specified, the section in which the symbol was found
37612 is also printed. For dynamically linked executables, the name of
37613 executable or shared library containing the symbol is printed as well.
37617 The following command is useful for non-interactive invocations of
37618 @value{GDBN}, such as in the test suite.
37621 @item set watchdog @var{nsec}
37622 @kindex set watchdog
37623 @cindex watchdog timer
37624 @cindex timeout for commands
37625 Set the maximum number of seconds @value{GDBN} will wait for the
37626 target operation to finish. If this time expires, @value{GDBN}
37627 reports and error and the command is aborted.
37629 @item show watchdog
37630 Show the current setting of the target wait timeout.
37633 @node Remote Protocol
37634 @appendix @value{GDBN} Remote Serial Protocol
37639 * Stop Reply Packets::
37640 * General Query Packets::
37641 * Architecture-Specific Protocol Details::
37642 * Tracepoint Packets::
37643 * Host I/O Packets::
37645 * Notification Packets::
37646 * Remote Non-Stop::
37647 * Packet Acknowledgment::
37649 * File-I/O Remote Protocol Extension::
37650 * Library List Format::
37651 * Library List Format for SVR4 Targets::
37652 * Memory Map Format::
37653 * Thread List Format::
37654 * Traceframe Info Format::
37655 * Branch Trace Format::
37661 There may be occasions when you need to know something about the
37662 protocol---for example, if there is only one serial port to your target
37663 machine, you might want your program to do something special if it
37664 recognizes a packet meant for @value{GDBN}.
37666 In the examples below, @samp{->} and @samp{<-} are used to indicate
37667 transmitted and received data, respectively.
37669 @cindex protocol, @value{GDBN} remote serial
37670 @cindex serial protocol, @value{GDBN} remote
37671 @cindex remote serial protocol
37672 All @value{GDBN} commands and responses (other than acknowledgments
37673 and notifications, see @ref{Notification Packets}) are sent as a
37674 @var{packet}. A @var{packet} is introduced with the character
37675 @samp{$}, the actual @var{packet-data}, and the terminating character
37676 @samp{#} followed by a two-digit @var{checksum}:
37679 @code{$}@var{packet-data}@code{#}@var{checksum}
37683 @cindex checksum, for @value{GDBN} remote
37685 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37686 characters between the leading @samp{$} and the trailing @samp{#} (an
37687 eight bit unsigned checksum).
37689 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37690 specification also included an optional two-digit @var{sequence-id}:
37693 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37696 @cindex sequence-id, for @value{GDBN} remote
37698 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37699 has never output @var{sequence-id}s. Stubs that handle packets added
37700 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37702 When either the host or the target machine receives a packet, the first
37703 response expected is an acknowledgment: either @samp{+} (to indicate
37704 the package was received correctly) or @samp{-} (to request
37708 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37713 The @samp{+}/@samp{-} acknowledgments can be disabled
37714 once a connection is established.
37715 @xref{Packet Acknowledgment}, for details.
37717 The host (@value{GDBN}) sends @var{command}s, and the target (the
37718 debugging stub incorporated in your program) sends a @var{response}. In
37719 the case of step and continue @var{command}s, the response is only sent
37720 when the operation has completed, and the target has again stopped all
37721 threads in all attached processes. This is the default all-stop mode
37722 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37723 execution mode; see @ref{Remote Non-Stop}, for details.
37725 @var{packet-data} consists of a sequence of characters with the
37726 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37729 @cindex remote protocol, field separator
37730 Fields within the packet should be separated using @samp{,} @samp{;} or
37731 @samp{:}. Except where otherwise noted all numbers are represented in
37732 @sc{hex} with leading zeros suppressed.
37734 Implementors should note that prior to @value{GDBN} 5.0, the character
37735 @samp{:} could not appear as the third character in a packet (as it
37736 would potentially conflict with the @var{sequence-id}).
37738 @cindex remote protocol, binary data
37739 @anchor{Binary Data}
37740 Binary data in most packets is encoded either as two hexadecimal
37741 digits per byte of binary data. This allowed the traditional remote
37742 protocol to work over connections which were only seven-bit clean.
37743 Some packets designed more recently assume an eight-bit clean
37744 connection, and use a more efficient encoding to send and receive
37747 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37748 as an escape character. Any escaped byte is transmitted as the escape
37749 character followed by the original character XORed with @code{0x20}.
37750 For example, the byte @code{0x7d} would be transmitted as the two
37751 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37752 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37753 @samp{@}}) must always be escaped. Responses sent by the stub
37754 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37755 is not interpreted as the start of a run-length encoded sequence
37758 Response @var{data} can be run-length encoded to save space.
37759 Run-length encoding replaces runs of identical characters with one
37760 instance of the repeated character, followed by a @samp{*} and a
37761 repeat count. The repeat count is itself sent encoded, to avoid
37762 binary characters in @var{data}: a value of @var{n} is sent as
37763 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37764 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37765 code 32) for a repeat count of 3. (This is because run-length
37766 encoding starts to win for counts 3 or more.) Thus, for example,
37767 @samp{0* } is a run-length encoding of ``0000'': the space character
37768 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37771 The printable characters @samp{#} and @samp{$} or with a numeric value
37772 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37773 seven repeats (@samp{$}) can be expanded using a repeat count of only
37774 five (@samp{"}). For example, @samp{00000000} can be encoded as
37777 The error response returned for some packets includes a two character
37778 error number. That number is not well defined.
37780 @cindex empty response, for unsupported packets
37781 For any @var{command} not supported by the stub, an empty response
37782 (@samp{$#00}) should be returned. That way it is possible to extend the
37783 protocol. A newer @value{GDBN} can tell if a packet is supported based
37786 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37787 commands for register access, and the @samp{m} and @samp{M} commands
37788 for memory access. Stubs that only control single-threaded targets
37789 can implement run control with the @samp{c} (continue), and @samp{s}
37790 (step) commands. Stubs that support multi-threading targets should
37791 support the @samp{vCont} command. All other commands are optional.
37796 The following table provides a complete list of all currently defined
37797 @var{command}s and their corresponding response @var{data}.
37798 @xref{File-I/O Remote Protocol Extension}, for details about the File
37799 I/O extension of the remote protocol.
37801 Each packet's description has a template showing the packet's overall
37802 syntax, followed by an explanation of the packet's meaning. We
37803 include spaces in some of the templates for clarity; these are not
37804 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37805 separate its components. For example, a template like @samp{foo
37806 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37807 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37808 @var{baz}. @value{GDBN} does not transmit a space character between the
37809 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37812 @cindex @var{thread-id}, in remote protocol
37813 @anchor{thread-id syntax}
37814 Several packets and replies include a @var{thread-id} field to identify
37815 a thread. Normally these are positive numbers with a target-specific
37816 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37817 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37820 In addition, the remote protocol supports a multiprocess feature in
37821 which the @var{thread-id} syntax is extended to optionally include both
37822 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37823 The @var{pid} (process) and @var{tid} (thread) components each have the
37824 format described above: a positive number with target-specific
37825 interpretation formatted as a big-endian hex string, literal @samp{-1}
37826 to indicate all processes or threads (respectively), or @samp{0} to
37827 indicate an arbitrary process or thread. Specifying just a process, as
37828 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37829 error to specify all processes but a specific thread, such as
37830 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37831 for those packets and replies explicitly documented to include a process
37832 ID, rather than a @var{thread-id}.
37834 The multiprocess @var{thread-id} syntax extensions are only used if both
37835 @value{GDBN} and the stub report support for the @samp{multiprocess}
37836 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37839 Note that all packet forms beginning with an upper- or lower-case
37840 letter, other than those described here, are reserved for future use.
37842 Here are the packet descriptions.
37847 @cindex @samp{!} packet
37848 @anchor{extended mode}
37849 Enable extended mode. In extended mode, the remote server is made
37850 persistent. The @samp{R} packet is used to restart the program being
37856 The remote target both supports and has enabled extended mode.
37860 @cindex @samp{?} packet
37861 Indicate the reason the target halted. The reply is the same as for
37862 step and continue. This packet has a special interpretation when the
37863 target is in non-stop mode; see @ref{Remote Non-Stop}.
37866 @xref{Stop Reply Packets}, for the reply specifications.
37868 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37869 @cindex @samp{A} packet
37870 Initialized @code{argv[]} array passed into program. @var{arglen}
37871 specifies the number of bytes in the hex encoded byte stream
37872 @var{arg}. See @code{gdbserver} for more details.
37877 The arguments were set.
37883 @cindex @samp{b} packet
37884 (Don't use this packet; its behavior is not well-defined.)
37885 Change the serial line speed to @var{baud}.
37887 JTC: @emph{When does the transport layer state change? When it's
37888 received, or after the ACK is transmitted. In either case, there are
37889 problems if the command or the acknowledgment packet is dropped.}
37891 Stan: @emph{If people really wanted to add something like this, and get
37892 it working for the first time, they ought to modify ser-unix.c to send
37893 some kind of out-of-band message to a specially-setup stub and have the
37894 switch happen "in between" packets, so that from remote protocol's point
37895 of view, nothing actually happened.}
37897 @item B @var{addr},@var{mode}
37898 @cindex @samp{B} packet
37899 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37900 breakpoint at @var{addr}.
37902 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37903 (@pxref{insert breakpoint or watchpoint packet}).
37905 @cindex @samp{bc} packet
37908 Backward continue. Execute the target system in reverse. No parameter.
37909 @xref{Reverse Execution}, for more information.
37912 @xref{Stop Reply Packets}, for the reply specifications.
37914 @cindex @samp{bs} packet
37917 Backward single step. Execute one instruction in reverse. No parameter.
37918 @xref{Reverse Execution}, for more information.
37921 @xref{Stop Reply Packets}, for the reply specifications.
37923 @item c @r{[}@var{addr}@r{]}
37924 @cindex @samp{c} packet
37925 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
37926 resume at current address.
37928 This packet is deprecated for multi-threading support. @xref{vCont
37932 @xref{Stop Reply Packets}, for the reply specifications.
37934 @item C @var{sig}@r{[};@var{addr}@r{]}
37935 @cindex @samp{C} packet
37936 Continue with signal @var{sig} (hex signal number). If
37937 @samp{;@var{addr}} is omitted, resume at same address.
37939 This packet is deprecated for multi-threading support. @xref{vCont
37943 @xref{Stop Reply Packets}, for the reply specifications.
37946 @cindex @samp{d} packet
37949 Don't use this packet; instead, define a general set packet
37950 (@pxref{General Query Packets}).
37954 @cindex @samp{D} packet
37955 The first form of the packet is used to detach @value{GDBN} from the
37956 remote system. It is sent to the remote target
37957 before @value{GDBN} disconnects via the @code{detach} command.
37959 The second form, including a process ID, is used when multiprocess
37960 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37961 detach only a specific process. The @var{pid} is specified as a
37962 big-endian hex string.
37972 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37973 @cindex @samp{F} packet
37974 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37975 This is part of the File-I/O protocol extension. @xref{File-I/O
37976 Remote Protocol Extension}, for the specification.
37979 @anchor{read registers packet}
37980 @cindex @samp{g} packet
37981 Read general registers.
37985 @item @var{XX@dots{}}
37986 Each byte of register data is described by two hex digits. The bytes
37987 with the register are transmitted in target byte order. The size of
37988 each register and their position within the @samp{g} packet are
37989 determined by the @value{GDBN} internal gdbarch functions
37990 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
37991 specification of several standard @samp{g} packets is specified below.
37993 When reading registers from a trace frame (@pxref{Analyze Collected
37994 Data,,Using the Collected Data}), the stub may also return a string of
37995 literal @samp{x}'s in place of the register data digits, to indicate
37996 that the corresponding register has not been collected, thus its value
37997 is unavailable. For example, for an architecture with 4 registers of
37998 4 bytes each, the following reply indicates to @value{GDBN} that
37999 registers 0 and 2 have not been collected, while registers 1 and 3
38000 have been collected, and both have zero value:
38004 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38011 @item G @var{XX@dots{}}
38012 @cindex @samp{G} packet
38013 Write general registers. @xref{read registers packet}, for a
38014 description of the @var{XX@dots{}} data.
38024 @item H @var{op} @var{thread-id}
38025 @cindex @samp{H} packet
38026 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38027 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
38028 it should be @samp{c} for step and continue operations (note that this
38029 is deprecated, supporting the @samp{vCont} command is a better
38030 option), @samp{g} for other operations. The thread designator
38031 @var{thread-id} has the format and interpretation described in
38032 @ref{thread-id syntax}.
38043 @c 'H': How restrictive (or permissive) is the thread model. If a
38044 @c thread is selected and stopped, are other threads allowed
38045 @c to continue to execute? As I mentioned above, I think the
38046 @c semantics of each command when a thread is selected must be
38047 @c described. For example:
38049 @c 'g': If the stub supports threads and a specific thread is
38050 @c selected, returns the register block from that thread;
38051 @c otherwise returns current registers.
38053 @c 'G' If the stub supports threads and a specific thread is
38054 @c selected, sets the registers of the register block of
38055 @c that thread; otherwise sets current registers.
38057 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38058 @anchor{cycle step packet}
38059 @cindex @samp{i} packet
38060 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38061 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38062 step starting at that address.
38065 @cindex @samp{I} packet
38066 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38070 @cindex @samp{k} packet
38073 FIXME: @emph{There is no description of how to operate when a specific
38074 thread context has been selected (i.e.@: does 'k' kill only that
38077 @item m @var{addr},@var{length}
38078 @cindex @samp{m} packet
38079 Read @var{length} bytes of memory starting at address @var{addr}.
38080 Note that @var{addr} may not be aligned to any particular boundary.
38082 The stub need not use any particular size or alignment when gathering
38083 data from memory for the response; even if @var{addr} is word-aligned
38084 and @var{length} is a multiple of the word size, the stub is free to
38085 use byte accesses, or not. For this reason, this packet may not be
38086 suitable for accessing memory-mapped I/O devices.
38087 @cindex alignment of remote memory accesses
38088 @cindex size of remote memory accesses
38089 @cindex memory, alignment and size of remote accesses
38093 @item @var{XX@dots{}}
38094 Memory contents; each byte is transmitted as a two-digit hexadecimal
38095 number. The reply may contain fewer bytes than requested if the
38096 server was able to read only part of the region of memory.
38101 @item M @var{addr},@var{length}:@var{XX@dots{}}
38102 @cindex @samp{M} packet
38103 Write @var{length} bytes of memory starting at address @var{addr}.
38104 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
38105 hexadecimal number.
38112 for an error (this includes the case where only part of the data was
38117 @cindex @samp{p} packet
38118 Read the value of register @var{n}; @var{n} is in hex.
38119 @xref{read registers packet}, for a description of how the returned
38120 register value is encoded.
38124 @item @var{XX@dots{}}
38125 the register's value
38129 Indicating an unrecognized @var{query}.
38132 @item P @var{n@dots{}}=@var{r@dots{}}
38133 @anchor{write register packet}
38134 @cindex @samp{P} packet
38135 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38136 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38137 digits for each byte in the register (target byte order).
38147 @item q @var{name} @var{params}@dots{}
38148 @itemx Q @var{name} @var{params}@dots{}
38149 @cindex @samp{q} packet
38150 @cindex @samp{Q} packet
38151 General query (@samp{q}) and set (@samp{Q}). These packets are
38152 described fully in @ref{General Query Packets}.
38155 @cindex @samp{r} packet
38156 Reset the entire system.
38158 Don't use this packet; use the @samp{R} packet instead.
38161 @cindex @samp{R} packet
38162 Restart the program being debugged. @var{XX}, while needed, is ignored.
38163 This packet is only available in extended mode (@pxref{extended mode}).
38165 The @samp{R} packet has no reply.
38167 @item s @r{[}@var{addr}@r{]}
38168 @cindex @samp{s} packet
38169 Single step. @var{addr} is the address at which to resume. If
38170 @var{addr} is omitted, resume at same address.
38172 This packet is deprecated for multi-threading support. @xref{vCont
38176 @xref{Stop Reply Packets}, for the reply specifications.
38178 @item S @var{sig}@r{[};@var{addr}@r{]}
38179 @anchor{step with signal packet}
38180 @cindex @samp{S} packet
38181 Step with signal. This is analogous to the @samp{C} packet, but
38182 requests a single-step, rather than a normal resumption of execution.
38184 This packet is deprecated for multi-threading support. @xref{vCont
38188 @xref{Stop Reply Packets}, for the reply specifications.
38190 @item t @var{addr}:@var{PP},@var{MM}
38191 @cindex @samp{t} packet
38192 Search backwards starting at address @var{addr} for a match with pattern
38193 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
38194 @var{addr} must be at least 3 digits.
38196 @item T @var{thread-id}
38197 @cindex @samp{T} packet
38198 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38203 thread is still alive
38209 Packets starting with @samp{v} are identified by a multi-letter name,
38210 up to the first @samp{;} or @samp{?} (or the end of the packet).
38212 @item vAttach;@var{pid}
38213 @cindex @samp{vAttach} packet
38214 Attach to a new process with the specified process ID @var{pid}.
38215 The process ID is a
38216 hexadecimal integer identifying the process. In all-stop mode, all
38217 threads in the attached process are stopped; in non-stop mode, it may be
38218 attached without being stopped if that is supported by the target.
38220 @c In non-stop mode, on a successful vAttach, the stub should set the
38221 @c current thread to a thread of the newly-attached process. After
38222 @c attaching, GDB queries for the attached process's thread ID with qC.
38223 @c Also note that, from a user perspective, whether or not the
38224 @c target is stopped on attach in non-stop mode depends on whether you
38225 @c use the foreground or background version of the attach command, not
38226 @c on what vAttach does; GDB does the right thing with respect to either
38227 @c stopping or restarting threads.
38229 This packet is only available in extended mode (@pxref{extended mode}).
38235 @item @r{Any stop packet}
38236 for success in all-stop mode (@pxref{Stop Reply Packets})
38238 for success in non-stop mode (@pxref{Remote Non-Stop})
38241 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38242 @cindex @samp{vCont} packet
38243 @anchor{vCont packet}
38244 Resume the inferior, specifying different actions for each thread.
38245 If an action is specified with no @var{thread-id}, then it is applied to any
38246 threads that don't have a specific action specified; if no default action is
38247 specified then other threads should remain stopped in all-stop mode and
38248 in their current state in non-stop mode.
38249 Specifying multiple
38250 default actions is an error; specifying no actions is also an error.
38251 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
38253 Currently supported actions are:
38259 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38263 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38266 @item r @var{start},@var{end}
38267 Step once, and then keep stepping as long as the thread stops at
38268 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38269 The remote stub reports a stop reply when either the thread goes out
38270 of the range or is stopped due to an unrelated reason, such as hitting
38271 a breakpoint. @xref{range stepping}.
38273 If the range is empty (@var{start} == @var{end}), then the action
38274 becomes equivalent to the @samp{s} action. In other words,
38275 single-step once, and report the stop (even if the stepped instruction
38276 jumps to @var{start}).
38278 (A stop reply may be sent at any point even if the PC is still within
38279 the stepping range; for example, it is valid to implement this packet
38280 in a degenerate way as a single instruction step operation.)
38284 The optional argument @var{addr} normally associated with the
38285 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38286 not supported in @samp{vCont}.
38288 The @samp{t} action is only relevant in non-stop mode
38289 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38290 A stop reply should be generated for any affected thread not already stopped.
38291 When a thread is stopped by means of a @samp{t} action,
38292 the corresponding stop reply should indicate that the thread has stopped with
38293 signal @samp{0}, regardless of whether the target uses some other signal
38294 as an implementation detail.
38296 The stub must support @samp{vCont} if it reports support for
38297 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38298 this case @samp{vCont} actions can be specified to apply to all threads
38299 in a process by using the @samp{p@var{pid}.-1} form of the
38303 @xref{Stop Reply Packets}, for the reply specifications.
38306 @cindex @samp{vCont?} packet
38307 Request a list of actions supported by the @samp{vCont} packet.
38311 @item vCont@r{[};@var{action}@dots{}@r{]}
38312 The @samp{vCont} packet is supported. Each @var{action} is a supported
38313 command in the @samp{vCont} packet.
38315 The @samp{vCont} packet is not supported.
38318 @item vFile:@var{operation}:@var{parameter}@dots{}
38319 @cindex @samp{vFile} packet
38320 Perform a file operation on the target system. For details,
38321 see @ref{Host I/O Packets}.
38323 @item vFlashErase:@var{addr},@var{length}
38324 @cindex @samp{vFlashErase} packet
38325 Direct the stub to erase @var{length} bytes of flash starting at
38326 @var{addr}. The region may enclose any number of flash blocks, but
38327 its start and end must fall on block boundaries, as indicated by the
38328 flash block size appearing in the memory map (@pxref{Memory Map
38329 Format}). @value{GDBN} groups flash memory programming operations
38330 together, and sends a @samp{vFlashDone} request after each group; the
38331 stub is allowed to delay erase operation until the @samp{vFlashDone}
38332 packet is received.
38342 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38343 @cindex @samp{vFlashWrite} packet
38344 Direct the stub to write data to flash address @var{addr}. The data
38345 is passed in binary form using the same encoding as for the @samp{X}
38346 packet (@pxref{Binary Data}). The memory ranges specified by
38347 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38348 not overlap, and must appear in order of increasing addresses
38349 (although @samp{vFlashErase} packets for higher addresses may already
38350 have been received; the ordering is guaranteed only between
38351 @samp{vFlashWrite} packets). If a packet writes to an address that was
38352 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38353 target-specific method, the results are unpredictable.
38361 for vFlashWrite addressing non-flash memory
38367 @cindex @samp{vFlashDone} packet
38368 Indicate to the stub that flash programming operation is finished.
38369 The stub is permitted to delay or batch the effects of a group of
38370 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38371 @samp{vFlashDone} packet is received. The contents of the affected
38372 regions of flash memory are unpredictable until the @samp{vFlashDone}
38373 request is completed.
38375 @item vKill;@var{pid}
38376 @cindex @samp{vKill} packet
38377 Kill the process with the specified process ID. @var{pid} is a
38378 hexadecimal integer identifying the process. This packet is used in
38379 preference to @samp{k} when multiprocess protocol extensions are
38380 supported; see @ref{multiprocess extensions}.
38390 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38391 @cindex @samp{vRun} packet
38392 Run the program @var{filename}, passing it each @var{argument} on its
38393 command line. The file and arguments are hex-encoded strings. If
38394 @var{filename} is an empty string, the stub may use a default program
38395 (e.g.@: the last program run). The program is created in the stopped
38398 @c FIXME: What about non-stop mode?
38400 This packet is only available in extended mode (@pxref{extended mode}).
38406 @item @r{Any stop packet}
38407 for success (@pxref{Stop Reply Packets})
38411 @cindex @samp{vStopped} packet
38412 @xref{Notification Packets}.
38414 @item X @var{addr},@var{length}:@var{XX@dots{}}
38416 @cindex @samp{X} packet
38417 Write data to memory, where the data is transmitted in binary.
38418 @var{addr} is address, @var{length} is number of bytes,
38419 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38429 @item z @var{type},@var{addr},@var{kind}
38430 @itemx Z @var{type},@var{addr},@var{kind}
38431 @anchor{insert breakpoint or watchpoint packet}
38432 @cindex @samp{z} packet
38433 @cindex @samp{Z} packets
38434 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38435 watchpoint starting at address @var{address} of kind @var{kind}.
38437 Each breakpoint and watchpoint packet @var{type} is documented
38440 @emph{Implementation notes: A remote target shall return an empty string
38441 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38442 remote target shall support either both or neither of a given
38443 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38444 avoid potential problems with duplicate packets, the operations should
38445 be implemented in an idempotent way.}
38447 @item z0,@var{addr},@var{kind}
38448 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38449 @cindex @samp{z0} packet
38450 @cindex @samp{Z0} packet
38451 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38452 @var{addr} of type @var{kind}.
38454 A memory breakpoint is implemented by replacing the instruction at
38455 @var{addr} with a software breakpoint or trap instruction. The
38456 @var{kind} is target-specific and typically indicates the size of
38457 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38458 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38459 architectures have additional meanings for @var{kind};
38460 @var{cond_list} is an optional list of conditional expressions in bytecode
38461 form that should be evaluated on the target's side. These are the
38462 conditions that should be taken into consideration when deciding if
38463 the breakpoint trigger should be reported back to @var{GDBN}.
38465 The @var{cond_list} parameter is comprised of a series of expressions,
38466 concatenated without separators. Each expression has the following form:
38470 @item X @var{len},@var{expr}
38471 @var{len} is the length of the bytecode expression and @var{expr} is the
38472 actual conditional expression in bytecode form.
38476 The optional @var{cmd_list} parameter introduces commands that may be
38477 run on the target, rather than being reported back to @value{GDBN}.
38478 The parameter starts with a numeric flag @var{persist}; if the flag is
38479 nonzero, then the breakpoint may remain active and the commands
38480 continue to be run even when @value{GDBN} disconnects from the target.
38481 Following this flag is a series of expressions concatenated with no
38482 separators. Each expression has the following form:
38486 @item X @var{len},@var{expr}
38487 @var{len} is the length of the bytecode expression and @var{expr} is the
38488 actual conditional expression in bytecode form.
38492 see @ref{Architecture-Specific Protocol Details}.
38494 @emph{Implementation note: It is possible for a target to copy or move
38495 code that contains memory breakpoints (e.g., when implementing
38496 overlays). The behavior of this packet, in the presence of such a
38497 target, is not defined.}
38509 @item z1,@var{addr},@var{kind}
38510 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38511 @cindex @samp{z1} packet
38512 @cindex @samp{Z1} packet
38513 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38514 address @var{addr}.
38516 A hardware breakpoint is implemented using a mechanism that is not
38517 dependant on being able to modify the target's memory. @var{kind}
38518 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38520 @emph{Implementation note: A hardware breakpoint is not affected by code
38533 @item z2,@var{addr},@var{kind}
38534 @itemx Z2,@var{addr},@var{kind}
38535 @cindex @samp{z2} packet
38536 @cindex @samp{Z2} packet
38537 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38538 @var{kind} is interpreted as the number of bytes to watch.
38550 @item z3,@var{addr},@var{kind}
38551 @itemx Z3,@var{addr},@var{kind}
38552 @cindex @samp{z3} packet
38553 @cindex @samp{Z3} packet
38554 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38555 @var{kind} is interpreted as the number of bytes to watch.
38567 @item z4,@var{addr},@var{kind}
38568 @itemx Z4,@var{addr},@var{kind}
38569 @cindex @samp{z4} packet
38570 @cindex @samp{Z4} packet
38571 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38572 @var{kind} is interpreted as the number of bytes to watch.
38586 @node Stop Reply Packets
38587 @section Stop Reply Packets
38588 @cindex stop reply packets
38590 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38591 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38592 receive any of the below as a reply. Except for @samp{?}
38593 and @samp{vStopped}, that reply is only returned
38594 when the target halts. In the below the exact meaning of @dfn{signal
38595 number} is defined by the header @file{include/gdb/signals.h} in the
38596 @value{GDBN} source code.
38598 As in the description of request packets, we include spaces in the
38599 reply templates for clarity; these are not part of the reply packet's
38600 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38606 The program received signal number @var{AA} (a two-digit hexadecimal
38607 number). This is equivalent to a @samp{T} response with no
38608 @var{n}:@var{r} pairs.
38610 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38611 @cindex @samp{T} packet reply
38612 The program received signal number @var{AA} (a two-digit hexadecimal
38613 number). This is equivalent to an @samp{S} response, except that the
38614 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38615 and other information directly in the stop reply packet, reducing
38616 round-trip latency. Single-step and breakpoint traps are reported
38617 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38621 If @var{n} is a hexadecimal number, it is a register number, and the
38622 corresponding @var{r} gives that register's value. @var{r} is a
38623 series of bytes in target byte order, with each byte given by a
38624 two-digit hex number.
38627 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38628 the stopped thread, as specified in @ref{thread-id syntax}.
38631 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38632 the core on which the stop event was detected.
38635 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38636 specific event that stopped the target. The currently defined stop
38637 reasons are listed below. @var{aa} should be @samp{05}, the trap
38638 signal. At most one stop reason should be present.
38641 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38642 and go on to the next; this allows us to extend the protocol in the
38646 The currently defined stop reasons are:
38652 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38655 @cindex shared library events, remote reply
38657 The packet indicates that the loaded libraries have changed.
38658 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38659 list of loaded libraries. @var{r} is ignored.
38661 @cindex replay log events, remote reply
38663 The packet indicates that the target cannot continue replaying
38664 logged execution events, because it has reached the end (or the
38665 beginning when executing backward) of the log. The value of @var{r}
38666 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38667 for more information.
38671 @itemx W @var{AA} ; process:@var{pid}
38672 The process exited, and @var{AA} is the exit status. This is only
38673 applicable to certain targets.
38675 The second form of the response, including the process ID of the exited
38676 process, can be used only when @value{GDBN} has reported support for
38677 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38678 The @var{pid} is formatted as a big-endian hex string.
38681 @itemx X @var{AA} ; process:@var{pid}
38682 The process terminated with signal @var{AA}.
38684 The second form of the response, including the process ID of the
38685 terminated process, can be used only when @value{GDBN} has reported
38686 support for multiprocess protocol extensions; see @ref{multiprocess
38687 extensions}. The @var{pid} is formatted as a big-endian hex string.
38689 @item O @var{XX}@dots{}
38690 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38691 written as the program's console output. This can happen at any time
38692 while the program is running and the debugger should continue to wait
38693 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38695 @item F @var{call-id},@var{parameter}@dots{}
38696 @var{call-id} is the identifier which says which host system call should
38697 be called. This is just the name of the function. Translation into the
38698 correct system call is only applicable as it's defined in @value{GDBN}.
38699 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38702 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38703 this very system call.
38705 The target replies with this packet when it expects @value{GDBN} to
38706 call a host system call on behalf of the target. @value{GDBN} replies
38707 with an appropriate @samp{F} packet and keeps up waiting for the next
38708 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38709 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38710 Protocol Extension}, for more details.
38714 @node General Query Packets
38715 @section General Query Packets
38716 @cindex remote query requests
38718 Packets starting with @samp{q} are @dfn{general query packets};
38719 packets starting with @samp{Q} are @dfn{general set packets}. General
38720 query and set packets are a semi-unified form for retrieving and
38721 sending information to and from the stub.
38723 The initial letter of a query or set packet is followed by a name
38724 indicating what sort of thing the packet applies to. For example,
38725 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38726 definitions with the stub. These packet names follow some
38731 The name must not contain commas, colons or semicolons.
38733 Most @value{GDBN} query and set packets have a leading upper case
38736 The names of custom vendor packets should use a company prefix, in
38737 lower case, followed by a period. For example, packets designed at
38738 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38739 foos) or @samp{Qacme.bar} (for setting bars).
38742 The name of a query or set packet should be separated from any
38743 parameters by a @samp{:}; the parameters themselves should be
38744 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38745 full packet name, and check for a separator or the end of the packet,
38746 in case two packet names share a common prefix. New packets should not begin
38747 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38748 packets predate these conventions, and have arguments without any terminator
38749 for the packet name; we suspect they are in widespread use in places that
38750 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38751 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38754 Like the descriptions of the other packets, each description here
38755 has a template showing the packet's overall syntax, followed by an
38756 explanation of the packet's meaning. We include spaces in some of the
38757 templates for clarity; these are not part of the packet's syntax. No
38758 @value{GDBN} packet uses spaces to separate its components.
38760 Here are the currently defined query and set packets:
38766 Turn on or off the agent as a helper to perform some debugging operations
38767 delegated from @value{GDBN} (@pxref{Control Agent}).
38769 @item QAllow:@var{op}:@var{val}@dots{}
38770 @cindex @samp{QAllow} packet
38771 Specify which operations @value{GDBN} expects to request of the
38772 target, as a semicolon-separated list of operation name and value
38773 pairs. Possible values for @var{op} include @samp{WriteReg},
38774 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38775 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38776 indicating that @value{GDBN} will not request the operation, or 1,
38777 indicating that it may. (The target can then use this to set up its
38778 own internals optimally, for instance if the debugger never expects to
38779 insert breakpoints, it may not need to install its own trap handler.)
38782 @cindex current thread, remote request
38783 @cindex @samp{qC} packet
38784 Return the current thread ID.
38788 @item QC @var{thread-id}
38789 Where @var{thread-id} is a thread ID as documented in
38790 @ref{thread-id syntax}.
38791 @item @r{(anything else)}
38792 Any other reply implies the old thread ID.
38795 @item qCRC:@var{addr},@var{length}
38796 @cindex CRC of memory block, remote request
38797 @cindex @samp{qCRC} packet
38798 Compute the CRC checksum of a block of memory using CRC-32 defined in
38799 IEEE 802.3. The CRC is computed byte at a time, taking the most
38800 significant bit of each byte first. The initial pattern code
38801 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38803 @emph{Note:} This is the same CRC used in validating separate debug
38804 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38805 Files}). However the algorithm is slightly different. When validating
38806 separate debug files, the CRC is computed taking the @emph{least}
38807 significant bit of each byte first, and the final result is inverted to
38808 detect trailing zeros.
38813 An error (such as memory fault)
38814 @item C @var{crc32}
38815 The specified memory region's checksum is @var{crc32}.
38818 @item QDisableRandomization:@var{value}
38819 @cindex disable address space randomization, remote request
38820 @cindex @samp{QDisableRandomization} packet
38821 Some target operating systems will randomize the virtual address space
38822 of the inferior process as a security feature, but provide a feature
38823 to disable such randomization, e.g.@: to allow for a more deterministic
38824 debugging experience. On such systems, this packet with a @var{value}
38825 of 1 directs the target to disable address space randomization for
38826 processes subsequently started via @samp{vRun} packets, while a packet
38827 with a @var{value} of 0 tells the target to enable address space
38830 This packet is only available in extended mode (@pxref{extended mode}).
38835 The request succeeded.
38838 An error occurred. @var{nn} are hex digits.
38841 An empty reply indicates that @samp{QDisableRandomization} is not supported
38845 This packet is not probed by default; the remote stub must request it,
38846 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38847 This should only be done on targets that actually support disabling
38848 address space randomization.
38851 @itemx qsThreadInfo
38852 @cindex list active threads, remote request
38853 @cindex @samp{qfThreadInfo} packet
38854 @cindex @samp{qsThreadInfo} packet
38855 Obtain a list of all active thread IDs from the target (OS). Since there
38856 may be too many active threads to fit into one reply packet, this query
38857 works iteratively: it may require more than one query/reply sequence to
38858 obtain the entire list of threads. The first query of the sequence will
38859 be the @samp{qfThreadInfo} query; subsequent queries in the
38860 sequence will be the @samp{qsThreadInfo} query.
38862 NOTE: This packet replaces the @samp{qL} query (see below).
38866 @item m @var{thread-id}
38868 @item m @var{thread-id},@var{thread-id}@dots{}
38869 a comma-separated list of thread IDs
38871 (lower case letter @samp{L}) denotes end of list.
38874 In response to each query, the target will reply with a list of one or
38875 more thread IDs, separated by commas.
38876 @value{GDBN} will respond to each reply with a request for more thread
38877 ids (using the @samp{qs} form of the query), until the target responds
38878 with @samp{l} (lower-case ell, for @dfn{last}).
38879 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38882 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38883 @cindex get thread-local storage address, remote request
38884 @cindex @samp{qGetTLSAddr} packet
38885 Fetch the address associated with thread local storage specified
38886 by @var{thread-id}, @var{offset}, and @var{lm}.
38888 @var{thread-id} is the thread ID associated with the
38889 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38891 @var{offset} is the (big endian, hex encoded) offset associated with the
38892 thread local variable. (This offset is obtained from the debug
38893 information associated with the variable.)
38895 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38896 load module associated with the thread local storage. For example,
38897 a @sc{gnu}/Linux system will pass the link map address of the shared
38898 object associated with the thread local storage under consideration.
38899 Other operating environments may choose to represent the load module
38900 differently, so the precise meaning of this parameter will vary.
38904 @item @var{XX}@dots{}
38905 Hex encoded (big endian) bytes representing the address of the thread
38906 local storage requested.
38909 An error occurred. @var{nn} are hex digits.
38912 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38915 @item qGetTIBAddr:@var{thread-id}
38916 @cindex get thread information block address
38917 @cindex @samp{qGetTIBAddr} packet
38918 Fetch address of the Windows OS specific Thread Information Block.
38920 @var{thread-id} is the thread ID associated with the thread.
38924 @item @var{XX}@dots{}
38925 Hex encoded (big endian) bytes representing the linear address of the
38926 thread information block.
38929 An error occured. This means that either the thread was not found, or the
38930 address could not be retrieved.
38933 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38936 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38937 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38938 digit) is one to indicate the first query and zero to indicate a
38939 subsequent query; @var{threadcount} (two hex digits) is the maximum
38940 number of threads the response packet can contain; and @var{nextthread}
38941 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38942 returned in the response as @var{argthread}.
38944 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38948 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38949 Where: @var{count} (two hex digits) is the number of threads being
38950 returned; @var{done} (one hex digit) is zero to indicate more threads
38951 and one indicates no further threads; @var{argthreadid} (eight hex
38952 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38953 is a sequence of thread IDs from the target. @var{threadid} (eight hex
38954 digits). See @code{remote.c:parse_threadlist_response()}.
38958 @cindex section offsets, remote request
38959 @cindex @samp{qOffsets} packet
38960 Get section offsets that the target used when relocating the downloaded
38965 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38966 Relocate the @code{Text} section by @var{xxx} from its original address.
38967 Relocate the @code{Data} section by @var{yyy} from its original address.
38968 If the object file format provides segment information (e.g.@: @sc{elf}
38969 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38970 segments by the supplied offsets.
38972 @emph{Note: while a @code{Bss} offset may be included in the response,
38973 @value{GDBN} ignores this and instead applies the @code{Data} offset
38974 to the @code{Bss} section.}
38976 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38977 Relocate the first segment of the object file, which conventionally
38978 contains program code, to a starting address of @var{xxx}. If
38979 @samp{DataSeg} is specified, relocate the second segment, which
38980 conventionally contains modifiable data, to a starting address of
38981 @var{yyy}. @value{GDBN} will report an error if the object file
38982 does not contain segment information, or does not contain at least
38983 as many segments as mentioned in the reply. Extra segments are
38984 kept at fixed offsets relative to the last relocated segment.
38987 @item qP @var{mode} @var{thread-id}
38988 @cindex thread information, remote request
38989 @cindex @samp{qP} packet
38990 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38991 encoded 32 bit mode; @var{thread-id} is a thread ID
38992 (@pxref{thread-id syntax}).
38994 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38997 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
39001 @cindex non-stop mode, remote request
39002 @cindex @samp{QNonStop} packet
39004 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39005 @xref{Remote Non-Stop}, for more information.
39010 The request succeeded.
39013 An error occurred. @var{nn} are hex digits.
39016 An empty reply indicates that @samp{QNonStop} is not supported by
39020 This packet is not probed by default; the remote stub must request it,
39021 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39022 Use of this packet is controlled by the @code{set non-stop} command;
39023 @pxref{Non-Stop Mode}.
39025 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39026 @cindex pass signals to inferior, remote request
39027 @cindex @samp{QPassSignals} packet
39028 @anchor{QPassSignals}
39029 Each listed @var{signal} should be passed directly to the inferior process.
39030 Signals are numbered identically to continue packets and stop replies
39031 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39032 strictly greater than the previous item. These signals do not need to stop
39033 the inferior, or be reported to @value{GDBN}. All other signals should be
39034 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39035 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39036 new list. This packet improves performance when using @samp{handle
39037 @var{signal} nostop noprint pass}.
39042 The request succeeded.
39045 An error occurred. @var{nn} are hex digits.
39048 An empty reply indicates that @samp{QPassSignals} is not supported by
39052 Use of this packet is controlled by the @code{set remote pass-signals}
39053 command (@pxref{Remote Configuration, set remote pass-signals}).
39054 This packet is not probed by default; the remote stub must request it,
39055 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39057 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39058 @cindex signals the inferior may see, remote request
39059 @cindex @samp{QProgramSignals} packet
39060 @anchor{QProgramSignals}
39061 Each listed @var{signal} may be delivered to the inferior process.
39062 Others should be silently discarded.
39064 In some cases, the remote stub may need to decide whether to deliver a
39065 signal to the program or not without @value{GDBN} involvement. One
39066 example of that is while detaching --- the program's threads may have
39067 stopped for signals that haven't yet had a chance of being reported to
39068 @value{GDBN}, and so the remote stub can use the signal list specified
39069 by this packet to know whether to deliver or ignore those pending
39072 This does not influence whether to deliver a signal as requested by a
39073 resumption packet (@pxref{vCont packet}).
39075 Signals are numbered identically to continue packets and stop replies
39076 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39077 strictly greater than the previous item. Multiple
39078 @samp{QProgramSignals} packets do not combine; any earlier
39079 @samp{QProgramSignals} list is completely replaced by the new list.
39084 The request succeeded.
39087 An error occurred. @var{nn} are hex digits.
39090 An empty reply indicates that @samp{QProgramSignals} is not supported
39094 Use of this packet is controlled by the @code{set remote program-signals}
39095 command (@pxref{Remote Configuration, set remote program-signals}).
39096 This packet is not probed by default; the remote stub must request it,
39097 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39099 @item qRcmd,@var{command}
39100 @cindex execute remote command, remote request
39101 @cindex @samp{qRcmd} packet
39102 @var{command} (hex encoded) is passed to the local interpreter for
39103 execution. Invalid commands should be reported using the output
39104 string. Before the final result packet, the target may also respond
39105 with a number of intermediate @samp{O@var{output}} console output
39106 packets. @emph{Implementors should note that providing access to a
39107 stubs's interpreter may have security implications}.
39112 A command response with no output.
39114 A command response with the hex encoded output string @var{OUTPUT}.
39116 Indicate a badly formed request.
39118 An empty reply indicates that @samp{qRcmd} is not recognized.
39121 (Note that the @code{qRcmd} packet's name is separated from the
39122 command by a @samp{,}, not a @samp{:}, contrary to the naming
39123 conventions above. Please don't use this packet as a model for new
39126 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39127 @cindex searching memory, in remote debugging
39129 @cindex @samp{qSearch:memory} packet
39131 @cindex @samp{qSearch memory} packet
39132 @anchor{qSearch memory}
39133 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39134 @var{address} and @var{length} are encoded in hex.
39135 @var{search-pattern} is a sequence of bytes, hex encoded.
39140 The pattern was not found.
39142 The pattern was found at @var{address}.
39144 A badly formed request or an error was encountered while searching memory.
39146 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39149 @item QStartNoAckMode
39150 @cindex @samp{QStartNoAckMode} packet
39151 @anchor{QStartNoAckMode}
39152 Request that the remote stub disable the normal @samp{+}/@samp{-}
39153 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39158 The stub has switched to no-acknowledgment mode.
39159 @value{GDBN} acknowledges this reponse,
39160 but neither the stub nor @value{GDBN} shall send or expect further
39161 @samp{+}/@samp{-} acknowledgments in the current connection.
39163 An empty reply indicates that the stub does not support no-acknowledgment mode.
39166 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39167 @cindex supported packets, remote query
39168 @cindex features of the remote protocol
39169 @cindex @samp{qSupported} packet
39170 @anchor{qSupported}
39171 Tell the remote stub about features supported by @value{GDBN}, and
39172 query the stub for features it supports. This packet allows
39173 @value{GDBN} and the remote stub to take advantage of each others'
39174 features. @samp{qSupported} also consolidates multiple feature probes
39175 at startup, to improve @value{GDBN} performance---a single larger
39176 packet performs better than multiple smaller probe packets on
39177 high-latency links. Some features may enable behavior which must not
39178 be on by default, e.g.@: because it would confuse older clients or
39179 stubs. Other features may describe packets which could be
39180 automatically probed for, but are not. These features must be
39181 reported before @value{GDBN} will use them. This ``default
39182 unsupported'' behavior is not appropriate for all packets, but it
39183 helps to keep the initial connection time under control with new
39184 versions of @value{GDBN} which support increasing numbers of packets.
39188 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39189 The stub supports or does not support each returned @var{stubfeature},
39190 depending on the form of each @var{stubfeature} (see below for the
39193 An empty reply indicates that @samp{qSupported} is not recognized,
39194 or that no features needed to be reported to @value{GDBN}.
39197 The allowed forms for each feature (either a @var{gdbfeature} in the
39198 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39202 @item @var{name}=@var{value}
39203 The remote protocol feature @var{name} is supported, and associated
39204 with the specified @var{value}. The format of @var{value} depends
39205 on the feature, but it must not include a semicolon.
39207 The remote protocol feature @var{name} is supported, and does not
39208 need an associated value.
39210 The remote protocol feature @var{name} is not supported.
39212 The remote protocol feature @var{name} may be supported, and
39213 @value{GDBN} should auto-detect support in some other way when it is
39214 needed. This form will not be used for @var{gdbfeature} notifications,
39215 but may be used for @var{stubfeature} responses.
39218 Whenever the stub receives a @samp{qSupported} request, the
39219 supplied set of @value{GDBN} features should override any previous
39220 request. This allows @value{GDBN} to put the stub in a known
39221 state, even if the stub had previously been communicating with
39222 a different version of @value{GDBN}.
39224 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39229 This feature indicates whether @value{GDBN} supports multiprocess
39230 extensions to the remote protocol. @value{GDBN} does not use such
39231 extensions unless the stub also reports that it supports them by
39232 including @samp{multiprocess+} in its @samp{qSupported} reply.
39233 @xref{multiprocess extensions}, for details.
39236 This feature indicates that @value{GDBN} supports the XML target
39237 description. If the stub sees @samp{xmlRegisters=} with target
39238 specific strings separated by a comma, it will report register
39242 This feature indicates whether @value{GDBN} supports the
39243 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39244 instruction reply packet}).
39247 Stubs should ignore any unknown values for
39248 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39249 packet supports receiving packets of unlimited length (earlier
39250 versions of @value{GDBN} may reject overly long responses). Additional values
39251 for @var{gdbfeature} may be defined in the future to let the stub take
39252 advantage of new features in @value{GDBN}, e.g.@: incompatible
39253 improvements in the remote protocol---the @samp{multiprocess} feature is
39254 an example of such a feature. The stub's reply should be independent
39255 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39256 describes all the features it supports, and then the stub replies with
39257 all the features it supports.
39259 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39260 responses, as long as each response uses one of the standard forms.
39262 Some features are flags. A stub which supports a flag feature
39263 should respond with a @samp{+} form response. Other features
39264 require values, and the stub should respond with an @samp{=}
39267 Each feature has a default value, which @value{GDBN} will use if
39268 @samp{qSupported} is not available or if the feature is not mentioned
39269 in the @samp{qSupported} response. The default values are fixed; a
39270 stub is free to omit any feature responses that match the defaults.
39272 Not all features can be probed, but for those which can, the probing
39273 mechanism is useful: in some cases, a stub's internal
39274 architecture may not allow the protocol layer to know some information
39275 about the underlying target in advance. This is especially common in
39276 stubs which may be configured for multiple targets.
39278 These are the currently defined stub features and their properties:
39280 @multitable @columnfractions 0.35 0.2 0.12 0.2
39281 @c NOTE: The first row should be @headitem, but we do not yet require
39282 @c a new enough version of Texinfo (4.7) to use @headitem.
39284 @tab Value Required
39288 @item @samp{PacketSize}
39293 @item @samp{qXfer:auxv:read}
39298 @item @samp{qXfer:btrace:read}
39303 @item @samp{qXfer:features:read}
39308 @item @samp{qXfer:libraries:read}
39313 @item @samp{qXfer:libraries-svr4:read}
39318 @item @samp{augmented-libraries-svr4-read}
39323 @item @samp{qXfer:memory-map:read}
39328 @item @samp{qXfer:sdata:read}
39333 @item @samp{qXfer:spu:read}
39338 @item @samp{qXfer:spu:write}
39343 @item @samp{qXfer:siginfo:read}
39348 @item @samp{qXfer:siginfo:write}
39353 @item @samp{qXfer:threads:read}
39358 @item @samp{qXfer:traceframe-info:read}
39363 @item @samp{qXfer:uib:read}
39368 @item @samp{qXfer:fdpic:read}
39373 @item @samp{Qbtrace:off}
39378 @item @samp{Qbtrace:bts}
39383 @item @samp{QNonStop}
39388 @item @samp{QPassSignals}
39393 @item @samp{QStartNoAckMode}
39398 @item @samp{multiprocess}
39403 @item @samp{ConditionalBreakpoints}
39408 @item @samp{ConditionalTracepoints}
39413 @item @samp{ReverseContinue}
39418 @item @samp{ReverseStep}
39423 @item @samp{TracepointSource}
39428 @item @samp{QAgent}
39433 @item @samp{QAllow}
39438 @item @samp{QDisableRandomization}
39443 @item @samp{EnableDisableTracepoints}
39448 @item @samp{QTBuffer:size}
39453 @item @samp{tracenz}
39458 @item @samp{BreakpointCommands}
39465 These are the currently defined stub features, in more detail:
39468 @cindex packet size, remote protocol
39469 @item PacketSize=@var{bytes}
39470 The remote stub can accept packets up to at least @var{bytes} in
39471 length. @value{GDBN} will send packets up to this size for bulk
39472 transfers, and will never send larger packets. This is a limit on the
39473 data characters in the packet, including the frame and checksum.
39474 There is no trailing NUL byte in a remote protocol packet; if the stub
39475 stores packets in a NUL-terminated format, it should allow an extra
39476 byte in its buffer for the NUL. If this stub feature is not supported,
39477 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39479 @item qXfer:auxv:read
39480 The remote stub understands the @samp{qXfer:auxv:read} packet
39481 (@pxref{qXfer auxiliary vector read}).
39483 @item qXfer:btrace:read
39484 The remote stub understands the @samp{qXfer:btrace:read}
39485 packet (@pxref{qXfer btrace read}).
39487 @item qXfer:features:read
39488 The remote stub understands the @samp{qXfer:features:read} packet
39489 (@pxref{qXfer target description read}).
39491 @item qXfer:libraries:read
39492 The remote stub understands the @samp{qXfer:libraries:read} packet
39493 (@pxref{qXfer library list read}).
39495 @item qXfer:libraries-svr4:read
39496 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39497 (@pxref{qXfer svr4 library list read}).
39499 @item augmented-libraries-svr4-read
39500 The remote stub understands the augmented form of the
39501 @samp{qXfer:libraries-svr4:read} packet
39502 (@pxref{qXfer svr4 library list read}).
39504 @item qXfer:memory-map:read
39505 The remote stub understands the @samp{qXfer:memory-map:read} packet
39506 (@pxref{qXfer memory map read}).
39508 @item qXfer:sdata:read
39509 The remote stub understands the @samp{qXfer:sdata:read} packet
39510 (@pxref{qXfer sdata read}).
39512 @item qXfer:spu:read
39513 The remote stub understands the @samp{qXfer:spu:read} packet
39514 (@pxref{qXfer spu read}).
39516 @item qXfer:spu:write
39517 The remote stub understands the @samp{qXfer:spu:write} packet
39518 (@pxref{qXfer spu write}).
39520 @item qXfer:siginfo:read
39521 The remote stub understands the @samp{qXfer:siginfo:read} packet
39522 (@pxref{qXfer siginfo read}).
39524 @item qXfer:siginfo:write
39525 The remote stub understands the @samp{qXfer:siginfo:write} packet
39526 (@pxref{qXfer siginfo write}).
39528 @item qXfer:threads:read
39529 The remote stub understands the @samp{qXfer:threads:read} packet
39530 (@pxref{qXfer threads read}).
39532 @item qXfer:traceframe-info:read
39533 The remote stub understands the @samp{qXfer:traceframe-info:read}
39534 packet (@pxref{qXfer traceframe info read}).
39536 @item qXfer:uib:read
39537 The remote stub understands the @samp{qXfer:uib:read}
39538 packet (@pxref{qXfer unwind info block}).
39540 @item qXfer:fdpic:read
39541 The remote stub understands the @samp{qXfer:fdpic:read}
39542 packet (@pxref{qXfer fdpic loadmap read}).
39545 The remote stub understands the @samp{QNonStop} packet
39546 (@pxref{QNonStop}).
39549 The remote stub understands the @samp{QPassSignals} packet
39550 (@pxref{QPassSignals}).
39552 @item QStartNoAckMode
39553 The remote stub understands the @samp{QStartNoAckMode} packet and
39554 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39557 @anchor{multiprocess extensions}
39558 @cindex multiprocess extensions, in remote protocol
39559 The remote stub understands the multiprocess extensions to the remote
39560 protocol syntax. The multiprocess extensions affect the syntax of
39561 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39562 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39563 replies. Note that reporting this feature indicates support for the
39564 syntactic extensions only, not that the stub necessarily supports
39565 debugging of more than one process at a time. The stub must not use
39566 multiprocess extensions in packet replies unless @value{GDBN} has also
39567 indicated it supports them in its @samp{qSupported} request.
39569 @item qXfer:osdata:read
39570 The remote stub understands the @samp{qXfer:osdata:read} packet
39571 ((@pxref{qXfer osdata read}).
39573 @item ConditionalBreakpoints
39574 The target accepts and implements evaluation of conditional expressions
39575 defined for breakpoints. The target will only report breakpoint triggers
39576 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39578 @item ConditionalTracepoints
39579 The remote stub accepts and implements conditional expressions defined
39580 for tracepoints (@pxref{Tracepoint Conditions}).
39582 @item ReverseContinue
39583 The remote stub accepts and implements the reverse continue packet
39587 The remote stub accepts and implements the reverse step packet
39590 @item TracepointSource
39591 The remote stub understands the @samp{QTDPsrc} packet that supplies
39592 the source form of tracepoint definitions.
39595 The remote stub understands the @samp{QAgent} packet.
39598 The remote stub understands the @samp{QAllow} packet.
39600 @item QDisableRandomization
39601 The remote stub understands the @samp{QDisableRandomization} packet.
39603 @item StaticTracepoint
39604 @cindex static tracepoints, in remote protocol
39605 The remote stub supports static tracepoints.
39607 @item InstallInTrace
39608 @anchor{install tracepoint in tracing}
39609 The remote stub supports installing tracepoint in tracing.
39611 @item EnableDisableTracepoints
39612 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39613 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39614 to be enabled and disabled while a trace experiment is running.
39616 @item QTBuffer:size
39617 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39618 packet that allows to change the size of the trace buffer.
39621 @cindex string tracing, in remote protocol
39622 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39623 See @ref{Bytecode Descriptions} for details about the bytecode.
39625 @item BreakpointCommands
39626 @cindex breakpoint commands, in remote protocol
39627 The remote stub supports running a breakpoint's command list itself,
39628 rather than reporting the hit to @value{GDBN}.
39631 The remote stub understands the @samp{Qbtrace:off} packet.
39634 The remote stub understands the @samp{Qbtrace:bts} packet.
39639 @cindex symbol lookup, remote request
39640 @cindex @samp{qSymbol} packet
39641 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39642 requests. Accept requests from the target for the values of symbols.
39647 The target does not need to look up any (more) symbols.
39648 @item qSymbol:@var{sym_name}
39649 The target requests the value of symbol @var{sym_name} (hex encoded).
39650 @value{GDBN} may provide the value by using the
39651 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39655 @item qSymbol:@var{sym_value}:@var{sym_name}
39656 Set the value of @var{sym_name} to @var{sym_value}.
39658 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39659 target has previously requested.
39661 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39662 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39668 The target does not need to look up any (more) symbols.
39669 @item qSymbol:@var{sym_name}
39670 The target requests the value of a new symbol @var{sym_name} (hex
39671 encoded). @value{GDBN} will continue to supply the values of symbols
39672 (if available), until the target ceases to request them.
39677 @itemx QTDisconnected
39684 @itemx qTMinFTPILen
39686 @xref{Tracepoint Packets}.
39688 @item qThreadExtraInfo,@var{thread-id}
39689 @cindex thread attributes info, remote request
39690 @cindex @samp{qThreadExtraInfo} packet
39691 Obtain a printable string description of a thread's attributes from
39692 the target OS. @var{thread-id} is a thread ID;
39693 see @ref{thread-id syntax}. This
39694 string may contain anything that the target OS thinks is interesting
39695 for @value{GDBN} to tell the user about the thread. The string is
39696 displayed in @value{GDBN}'s @code{info threads} display. Some
39697 examples of possible thread extra info strings are @samp{Runnable}, or
39698 @samp{Blocked on Mutex}.
39702 @item @var{XX}@dots{}
39703 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39704 comprising the printable string containing the extra information about
39705 the thread's attributes.
39708 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39709 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39710 conventions above. Please don't use this packet as a model for new
39729 @xref{Tracepoint Packets}.
39731 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39732 @cindex read special object, remote request
39733 @cindex @samp{qXfer} packet
39734 @anchor{qXfer read}
39735 Read uninterpreted bytes from the target's special data area
39736 identified by the keyword @var{object}. Request @var{length} bytes
39737 starting at @var{offset} bytes into the data. The content and
39738 encoding of @var{annex} is specific to @var{object}; it can supply
39739 additional details about what data to access.
39741 Here are the specific requests of this form defined so far. All
39742 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39743 formats, listed below.
39746 @item qXfer:auxv:read::@var{offset},@var{length}
39747 @anchor{qXfer auxiliary vector read}
39748 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39749 auxiliary vector}. Note @var{annex} must be empty.
39751 This packet is not probed by default; the remote stub must request it,
39752 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39754 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39755 @anchor{qXfer btrace read}
39757 Return a description of the current branch trace.
39758 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39759 packet may have one of the following values:
39763 Returns all available branch trace.
39766 Returns all available branch trace if the branch trace changed since
39767 the last read request.
39770 This packet is not probed by default; the remote stub must request it
39771 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39773 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39774 @anchor{qXfer target description read}
39775 Access the @dfn{target description}. @xref{Target Descriptions}. The
39776 annex specifies which XML document to access. The main description is
39777 always loaded from the @samp{target.xml} annex.
39779 This packet is not probed by default; the remote stub must request it,
39780 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39782 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39783 @anchor{qXfer library list read}
39784 Access the target's list of loaded libraries. @xref{Library List Format}.
39785 The annex part of the generic @samp{qXfer} packet must be empty
39786 (@pxref{qXfer read}).
39788 Targets which maintain a list of libraries in the program's memory do
39789 not need to implement this packet; it is designed for platforms where
39790 the operating system manages the list of loaded libraries.
39792 This packet is not probed by default; the remote stub must request it,
39793 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39795 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39796 @anchor{qXfer svr4 library list read}
39797 Access the target's list of loaded libraries when the target is an SVR4
39798 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39799 of the generic @samp{qXfer} packet must be empty unless the remote
39800 stub indicated it supports the augmented form of this packet
39801 by supplying an appropriate @samp{qSupported} response
39802 (@pxref{qXfer read}, @ref{qSupported}).
39804 This packet is optional for better performance on SVR4 targets.
39805 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39807 This packet is not probed by default; the remote stub must request it,
39808 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39810 If the remote stub indicates it supports the augmented form of this
39811 packet then the annex part of the generic @samp{qXfer} packet may
39812 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39813 arguments. The currently supported arguments are:
39816 @item start=@var{address}
39817 A hexadecimal number specifying the address of the @samp{struct
39818 link_map} to start reading the library list from. If unset or zero
39819 then the first @samp{struct link_map} in the library list will be
39820 chosen as the starting point.
39822 @item prev=@var{address}
39823 A hexadecimal number specifying the address of the @samp{struct
39824 link_map} immediately preceding the @samp{struct link_map}
39825 specified by the @samp{start} argument. If unset or zero then
39826 the remote stub will expect that no @samp{struct link_map}
39827 exists prior to the starting point.
39831 Arguments that are not understood by the remote stub will be silently
39834 @item qXfer:memory-map:read::@var{offset},@var{length}
39835 @anchor{qXfer memory map read}
39836 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39837 annex part of the generic @samp{qXfer} packet must be empty
39838 (@pxref{qXfer read}).
39840 This packet is not probed by default; the remote stub must request it,
39841 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39843 @item qXfer:sdata:read::@var{offset},@var{length}
39844 @anchor{qXfer sdata read}
39846 Read contents of the extra collected static tracepoint marker
39847 information. The annex part of the generic @samp{qXfer} packet must
39848 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39851 This packet is not probed by default; the remote stub must request it,
39852 by supplying an appropriate @samp{qSupported} response
39853 (@pxref{qSupported}).
39855 @item qXfer:siginfo:read::@var{offset},@var{length}
39856 @anchor{qXfer siginfo read}
39857 Read contents of the extra signal information on the target
39858 system. The annex part of the generic @samp{qXfer} packet must be
39859 empty (@pxref{qXfer read}).
39861 This packet is not probed by default; the remote stub must request it,
39862 by supplying an appropriate @samp{qSupported} response
39863 (@pxref{qSupported}).
39865 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39866 @anchor{qXfer spu read}
39867 Read contents of an @code{spufs} file on the target system. The
39868 annex specifies which file to read; it must be of the form
39869 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39870 in the target process, and @var{name} identifes the @code{spufs} file
39871 in that context to be accessed.
39873 This packet is not probed by default; the remote stub must request it,
39874 by supplying an appropriate @samp{qSupported} response
39875 (@pxref{qSupported}).
39877 @item qXfer:threads:read::@var{offset},@var{length}
39878 @anchor{qXfer threads read}
39879 Access the list of threads on target. @xref{Thread List Format}. The
39880 annex part of the generic @samp{qXfer} packet must be empty
39881 (@pxref{qXfer read}).
39883 This packet is not probed by default; the remote stub must request it,
39884 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39886 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39887 @anchor{qXfer traceframe info read}
39889 Return a description of the current traceframe's contents.
39890 @xref{Traceframe Info Format}. The annex part of the generic
39891 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39893 This packet is not probed by default; the remote stub must request it,
39894 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39896 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39897 @anchor{qXfer unwind info block}
39899 Return the unwind information block for @var{pc}. This packet is used
39900 on OpenVMS/ia64 to ask the kernel unwind information.
39902 This packet is not probed by default.
39904 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39905 @anchor{qXfer fdpic loadmap read}
39906 Read contents of @code{loadmap}s on the target system. The
39907 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39908 executable @code{loadmap} or interpreter @code{loadmap} to read.
39910 This packet is not probed by default; the remote stub must request it,
39911 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39913 @item qXfer:osdata:read::@var{offset},@var{length}
39914 @anchor{qXfer osdata read}
39915 Access the target's @dfn{operating system information}.
39916 @xref{Operating System Information}.
39923 Data @var{data} (@pxref{Binary Data}) has been read from the
39924 target. There may be more data at a higher address (although
39925 it is permitted to return @samp{m} even for the last valid
39926 block of data, as long as at least one byte of data was read).
39927 @var{data} may have fewer bytes than the @var{length} in the
39931 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39932 There is no more data to be read. @var{data} may have fewer bytes
39933 than the @var{length} in the request.
39936 The @var{offset} in the request is at the end of the data.
39937 There is no more data to be read.
39940 The request was malformed, or @var{annex} was invalid.
39943 The offset was invalid, or there was an error encountered reading the data.
39944 @var{nn} is a hex-encoded @code{errno} value.
39947 An empty reply indicates the @var{object} string was not recognized by
39948 the stub, or that the object does not support reading.
39951 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39952 @cindex write data into object, remote request
39953 @anchor{qXfer write}
39954 Write uninterpreted bytes into the target's special data area
39955 identified by the keyword @var{object}, starting at @var{offset} bytes
39956 into the data. @var{data}@dots{} is the binary-encoded data
39957 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
39958 is specific to @var{object}; it can supply additional details about what data
39961 Here are the specific requests of this form defined so far. All
39962 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39963 formats, listed below.
39966 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39967 @anchor{qXfer siginfo write}
39968 Write @var{data} to the extra signal information on the target system.
39969 The annex part of the generic @samp{qXfer} packet must be
39970 empty (@pxref{qXfer write}).
39972 This packet is not probed by default; the remote stub must request it,
39973 by supplying an appropriate @samp{qSupported} response
39974 (@pxref{qSupported}).
39976 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39977 @anchor{qXfer spu write}
39978 Write @var{data} to an @code{spufs} file on the target system. The
39979 annex specifies which file to write; it must be of the form
39980 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39981 in the target process, and @var{name} identifes the @code{spufs} file
39982 in that context to be accessed.
39984 This packet is not probed by default; the remote stub must request it,
39985 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39991 @var{nn} (hex encoded) is the number of bytes written.
39992 This may be fewer bytes than supplied in the request.
39995 The request was malformed, or @var{annex} was invalid.
39998 The offset was invalid, or there was an error encountered writing the data.
39999 @var{nn} is a hex-encoded @code{errno} value.
40002 An empty reply indicates the @var{object} string was not
40003 recognized by the stub, or that the object does not support writing.
40006 @item qXfer:@var{object}:@var{operation}:@dots{}
40007 Requests of this form may be added in the future. When a stub does
40008 not recognize the @var{object} keyword, or its support for
40009 @var{object} does not recognize the @var{operation} keyword, the stub
40010 must respond with an empty packet.
40012 @item qAttached:@var{pid}
40013 @cindex query attached, remote request
40014 @cindex @samp{qAttached} packet
40015 Return an indication of whether the remote server attached to an
40016 existing process or created a new process. When the multiprocess
40017 protocol extensions are supported (@pxref{multiprocess extensions}),
40018 @var{pid} is an integer in hexadecimal format identifying the target
40019 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40020 the query packet will be simplified as @samp{qAttached}.
40022 This query is used, for example, to know whether the remote process
40023 should be detached or killed when a @value{GDBN} session is ended with
40024 the @code{quit} command.
40029 The remote server attached to an existing process.
40031 The remote server created a new process.
40033 A badly formed request or an error was encountered.
40037 Enable branch tracing for the current thread using bts tracing.
40042 Branch tracing has been enabled.
40044 A badly formed request or an error was encountered.
40048 Disable branch tracing for the current thread.
40053 Branch tracing has been disabled.
40055 A badly formed request or an error was encountered.
40060 @node Architecture-Specific Protocol Details
40061 @section Architecture-Specific Protocol Details
40063 This section describes how the remote protocol is applied to specific
40064 target architectures. Also see @ref{Standard Target Features}, for
40065 details of XML target descriptions for each architecture.
40068 * ARM-Specific Protocol Details::
40069 * MIPS-Specific Protocol Details::
40072 @node ARM-Specific Protocol Details
40073 @subsection @acronym{ARM}-specific Protocol Details
40076 * ARM Breakpoint Kinds::
40079 @node ARM Breakpoint Kinds
40080 @subsubsection @acronym{ARM} Breakpoint Kinds
40081 @cindex breakpoint kinds, @acronym{ARM}
40083 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40088 16-bit Thumb mode breakpoint.
40091 32-bit Thumb mode (Thumb-2) breakpoint.
40094 32-bit @acronym{ARM} mode breakpoint.
40098 @node MIPS-Specific Protocol Details
40099 @subsection @acronym{MIPS}-specific Protocol Details
40102 * MIPS Register packet Format::
40103 * MIPS Breakpoint Kinds::
40106 @node MIPS Register packet Format
40107 @subsubsection @acronym{MIPS} Register Packet Format
40108 @cindex register packet format, @acronym{MIPS}
40110 The following @code{g}/@code{G} packets have previously been defined.
40111 In the below, some thirty-two bit registers are transferred as
40112 sixty-four bits. Those registers should be zero/sign extended (which?)
40113 to fill the space allocated. Register bytes are transferred in target
40114 byte order. The two nibbles within a register byte are transferred
40115 most-significant -- least-significant.
40120 All registers are transferred as thirty-two bit quantities in the order:
40121 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40122 registers; fsr; fir; fp.
40125 All registers are transferred as sixty-four bit quantities (including
40126 thirty-two bit registers such as @code{sr}). The ordering is the same
40131 @node MIPS Breakpoint Kinds
40132 @subsubsection @acronym{MIPS} Breakpoint Kinds
40133 @cindex breakpoint kinds, @acronym{MIPS}
40135 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40140 16-bit @acronym{MIPS16} mode breakpoint.
40143 16-bit @acronym{microMIPS} mode breakpoint.
40146 32-bit standard @acronym{MIPS} mode breakpoint.
40149 32-bit @acronym{microMIPS} mode breakpoint.
40153 @node Tracepoint Packets
40154 @section Tracepoint Packets
40155 @cindex tracepoint packets
40156 @cindex packets, tracepoint
40158 Here we describe the packets @value{GDBN} uses to implement
40159 tracepoints (@pxref{Tracepoints}).
40163 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40164 @cindex @samp{QTDP} packet
40165 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40166 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40167 the tracepoint is disabled. @var{step} is the tracepoint's step
40168 count, and @var{pass} is its pass count. If an @samp{F} is present,
40169 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40170 the number of bytes that the target should copy elsewhere to make room
40171 for the tracepoint. If an @samp{X} is present, it introduces a
40172 tracepoint condition, which consists of a hexadecimal length, followed
40173 by a comma and hex-encoded bytes, in a manner similar to action
40174 encodings as described below. If the trailing @samp{-} is present,
40175 further @samp{QTDP} packets will follow to specify this tracepoint's
40181 The packet was understood and carried out.
40183 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40185 The packet was not recognized.
40188 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40189 Define actions to be taken when a tracepoint is hit. @var{n} and
40190 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40191 this tracepoint. This packet may only be sent immediately after
40192 another @samp{QTDP} packet that ended with a @samp{-}. If the
40193 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40194 specifying more actions for this tracepoint.
40196 In the series of action packets for a given tracepoint, at most one
40197 can have an @samp{S} before its first @var{action}. If such a packet
40198 is sent, it and the following packets define ``while-stepping''
40199 actions. Any prior packets define ordinary actions --- that is, those
40200 taken when the tracepoint is first hit. If no action packet has an
40201 @samp{S}, then all the packets in the series specify ordinary
40202 tracepoint actions.
40204 The @samp{@var{action}@dots{}} portion of the packet is a series of
40205 actions, concatenated without separators. Each action has one of the
40211 Collect the registers whose bits are set in @var{mask}. @var{mask} is
40212 a hexadecimal number whose @var{i}'th bit is set if register number
40213 @var{i} should be collected. (The least significant bit is numbered
40214 zero.) Note that @var{mask} may be any number of digits long; it may
40215 not fit in a 32-bit word.
40217 @item M @var{basereg},@var{offset},@var{len}
40218 Collect @var{len} bytes of memory starting at the address in register
40219 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40220 @samp{-1}, then the range has a fixed address: @var{offset} is the
40221 address of the lowest byte to collect. The @var{basereg},
40222 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40223 values (the @samp{-1} value for @var{basereg} is a special case).
40225 @item X @var{len},@var{expr}
40226 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40227 it directs. @var{expr} is an agent expression, as described in
40228 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40229 two-digit hex number in the packet; @var{len} is the number of bytes
40230 in the expression (and thus one-half the number of hex digits in the
40235 Any number of actions may be packed together in a single @samp{QTDP}
40236 packet, as long as the packet does not exceed the maximum packet
40237 length (400 bytes, for many stubs). There may be only one @samp{R}
40238 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40239 actions. Any registers referred to by @samp{M} and @samp{X} actions
40240 must be collected by a preceding @samp{R} action. (The
40241 ``while-stepping'' actions are treated as if they were attached to a
40242 separate tracepoint, as far as these restrictions are concerned.)
40247 The packet was understood and carried out.
40249 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40251 The packet was not recognized.
40254 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40255 @cindex @samp{QTDPsrc} packet
40256 Specify a source string of tracepoint @var{n} at address @var{addr}.
40257 This is useful to get accurate reproduction of the tracepoints
40258 originally downloaded at the beginning of the trace run. @var{type}
40259 is the name of the tracepoint part, such as @samp{cond} for the
40260 tracepoint's conditional expression (see below for a list of types), while
40261 @var{bytes} is the string, encoded in hexadecimal.
40263 @var{start} is the offset of the @var{bytes} within the overall source
40264 string, while @var{slen} is the total length of the source string.
40265 This is intended for handling source strings that are longer than will
40266 fit in a single packet.
40267 @c Add detailed example when this info is moved into a dedicated
40268 @c tracepoint descriptions section.
40270 The available string types are @samp{at} for the location,
40271 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40272 @value{GDBN} sends a separate packet for each command in the action
40273 list, in the same order in which the commands are stored in the list.
40275 The target does not need to do anything with source strings except
40276 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40279 Although this packet is optional, and @value{GDBN} will only send it
40280 if the target replies with @samp{TracepointSource} @xref{General
40281 Query Packets}, it makes both disconnected tracing and trace files
40282 much easier to use. Otherwise the user must be careful that the
40283 tracepoints in effect while looking at trace frames are identical to
40284 the ones in effect during the trace run; even a small discrepancy
40285 could cause @samp{tdump} not to work, or a particular trace frame not
40288 @item QTDV:@var{n}:@var{value}
40289 @cindex define trace state variable, remote request
40290 @cindex @samp{QTDV} packet
40291 Create a new trace state variable, number @var{n}, with an initial
40292 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40293 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40294 the option of not using this packet for initial values of zero; the
40295 target should simply create the trace state variables as they are
40296 mentioned in expressions.
40298 @item QTFrame:@var{n}
40299 @cindex @samp{QTFrame} packet
40300 Select the @var{n}'th tracepoint frame from the buffer, and use the
40301 register and memory contents recorded there to answer subsequent
40302 request packets from @value{GDBN}.
40304 A successful reply from the stub indicates that the stub has found the
40305 requested frame. The response is a series of parts, concatenated
40306 without separators, describing the frame we selected. Each part has
40307 one of the following forms:
40311 The selected frame is number @var{n} in the trace frame buffer;
40312 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40313 was no frame matching the criteria in the request packet.
40316 The selected trace frame records a hit of tracepoint number @var{t};
40317 @var{t} is a hexadecimal number.
40321 @item QTFrame:pc:@var{addr}
40322 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40323 currently selected frame whose PC is @var{addr};
40324 @var{addr} is a hexadecimal number.
40326 @item QTFrame:tdp:@var{t}
40327 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40328 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40329 is a hexadecimal number.
40331 @item QTFrame:range:@var{start}:@var{end}
40332 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40333 currently selected frame whose PC is between @var{start} (inclusive)
40334 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40337 @item QTFrame:outside:@var{start}:@var{end}
40338 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40339 frame @emph{outside} the given range of addresses (exclusive).
40342 @cindex @samp{qTMinFTPILen} packet
40343 This packet requests the minimum length of instruction at which a fast
40344 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40345 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40346 it depends on the target system being able to create trampolines in
40347 the first 64K of memory, which might or might not be possible for that
40348 system. So the reply to this packet will be 4 if it is able to
40355 The minimum instruction length is currently unknown.
40357 The minimum instruction length is @var{length}, where @var{length} is greater
40358 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40359 that a fast tracepoint may be placed on any instruction regardless of size.
40361 An error has occurred.
40363 An empty reply indicates that the request is not supported by the stub.
40367 @cindex @samp{QTStart} packet
40368 Begin the tracepoint experiment. Begin collecting data from
40369 tracepoint hits in the trace frame buffer. This packet supports the
40370 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40371 instruction reply packet}).
40374 @cindex @samp{QTStop} packet
40375 End the tracepoint experiment. Stop collecting trace frames.
40377 @item QTEnable:@var{n}:@var{addr}
40379 @cindex @samp{QTEnable} packet
40380 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40381 experiment. If the tracepoint was previously disabled, then collection
40382 of data from it will resume.
40384 @item QTDisable:@var{n}:@var{addr}
40386 @cindex @samp{QTDisable} packet
40387 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40388 experiment. No more data will be collected from the tracepoint unless
40389 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40392 @cindex @samp{QTinit} packet
40393 Clear the table of tracepoints, and empty the trace frame buffer.
40395 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40396 @cindex @samp{QTro} packet
40397 Establish the given ranges of memory as ``transparent''. The stub
40398 will answer requests for these ranges from memory's current contents,
40399 if they were not collected as part of the tracepoint hit.
40401 @value{GDBN} uses this to mark read-only regions of memory, like those
40402 containing program code. Since these areas never change, they should
40403 still have the same contents they did when the tracepoint was hit, so
40404 there's no reason for the stub to refuse to provide their contents.
40406 @item QTDisconnected:@var{value}
40407 @cindex @samp{QTDisconnected} packet
40408 Set the choice to what to do with the tracing run when @value{GDBN}
40409 disconnects from the target. A @var{value} of 1 directs the target to
40410 continue the tracing run, while 0 tells the target to stop tracing if
40411 @value{GDBN} is no longer in the picture.
40414 @cindex @samp{qTStatus} packet
40415 Ask the stub if there is a trace experiment running right now.
40417 The reply has the form:
40421 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40422 @var{running} is a single digit @code{1} if the trace is presently
40423 running, or @code{0} if not. It is followed by semicolon-separated
40424 optional fields that an agent may use to report additional status.
40428 If the trace is not running, the agent may report any of several
40429 explanations as one of the optional fields:
40434 No trace has been run yet.
40436 @item tstop[:@var{text}]:0
40437 The trace was stopped by a user-originated stop command. The optional
40438 @var{text} field is a user-supplied string supplied as part of the
40439 stop command (for instance, an explanation of why the trace was
40440 stopped manually). It is hex-encoded.
40443 The trace stopped because the trace buffer filled up.
40445 @item tdisconnected:0
40446 The trace stopped because @value{GDBN} disconnected from the target.
40448 @item tpasscount:@var{tpnum}
40449 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40451 @item terror:@var{text}:@var{tpnum}
40452 The trace stopped because tracepoint @var{tpnum} had an error. The
40453 string @var{text} is available to describe the nature of the error
40454 (for instance, a divide by zero in the condition expression).
40455 @var{text} is hex encoded.
40458 The trace stopped for some other reason.
40462 Additional optional fields supply statistical and other information.
40463 Although not required, they are extremely useful for users monitoring
40464 the progress of a trace run. If a trace has stopped, and these
40465 numbers are reported, they must reflect the state of the just-stopped
40470 @item tframes:@var{n}
40471 The number of trace frames in the buffer.
40473 @item tcreated:@var{n}
40474 The total number of trace frames created during the run. This may
40475 be larger than the trace frame count, if the buffer is circular.
40477 @item tsize:@var{n}
40478 The total size of the trace buffer, in bytes.
40480 @item tfree:@var{n}
40481 The number of bytes still unused in the buffer.
40483 @item circular:@var{n}
40484 The value of the circular trace buffer flag. @code{1} means that the
40485 trace buffer is circular and old trace frames will be discarded if
40486 necessary to make room, @code{0} means that the trace buffer is linear
40489 @item disconn:@var{n}
40490 The value of the disconnected tracing flag. @code{1} means that
40491 tracing will continue after @value{GDBN} disconnects, @code{0} means
40492 that the trace run will stop.
40496 @item qTP:@var{tp}:@var{addr}
40497 @cindex tracepoint status, remote request
40498 @cindex @samp{qTP} packet
40499 Ask the stub for the current state of tracepoint number @var{tp} at
40500 address @var{addr}.
40504 @item V@var{hits}:@var{usage}
40505 The tracepoint has been hit @var{hits} times so far during the trace
40506 run, and accounts for @var{usage} in the trace buffer. Note that
40507 @code{while-stepping} steps are not counted as separate hits, but the
40508 steps' space consumption is added into the usage number.
40512 @item qTV:@var{var}
40513 @cindex trace state variable value, remote request
40514 @cindex @samp{qTV} packet
40515 Ask the stub for the value of the trace state variable number @var{var}.
40520 The value of the variable is @var{value}. This will be the current
40521 value of the variable if the user is examining a running target, or a
40522 saved value if the variable was collected in the trace frame that the
40523 user is looking at. Note that multiple requests may result in
40524 different reply values, such as when requesting values while the
40525 program is running.
40528 The value of the variable is unknown. This would occur, for example,
40529 if the user is examining a trace frame in which the requested variable
40534 @cindex @samp{qTfP} packet
40536 @cindex @samp{qTsP} packet
40537 These packets request data about tracepoints that are being used by
40538 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40539 of data, and multiple @code{qTsP} to get additional pieces. Replies
40540 to these packets generally take the form of the @code{QTDP} packets
40541 that define tracepoints. (FIXME add detailed syntax)
40544 @cindex @samp{qTfV} packet
40546 @cindex @samp{qTsV} packet
40547 These packets request data about trace state variables that are on the
40548 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40549 and multiple @code{qTsV} to get additional variables. Replies to
40550 these packets follow the syntax of the @code{QTDV} packets that define
40551 trace state variables.
40557 @cindex @samp{qTfSTM} packet
40558 @cindex @samp{qTsSTM} packet
40559 These packets request data about static tracepoint markers that exist
40560 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40561 first piece of data, and multiple @code{qTsSTM} to get additional
40562 pieces. Replies to these packets take the following form:
40566 @item m @var{address}:@var{id}:@var{extra}
40568 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40569 a comma-separated list of markers
40571 (lower case letter @samp{L}) denotes end of list.
40573 An error occurred. @var{nn} are hex digits.
40575 An empty reply indicates that the request is not supported by the
40579 @var{address} is encoded in hex.
40580 @var{id} and @var{extra} are strings encoded in hex.
40582 In response to each query, the target will reply with a list of one or
40583 more markers, separated by commas. @value{GDBN} will respond to each
40584 reply with a request for more markers (using the @samp{qs} form of the
40585 query), until the target responds with @samp{l} (lower-case ell, for
40588 @item qTSTMat:@var{address}
40590 @cindex @samp{qTSTMat} packet
40591 This packets requests data about static tracepoint markers in the
40592 target program at @var{address}. Replies to this packet follow the
40593 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40594 tracepoint markers.
40596 @item QTSave:@var{filename}
40597 @cindex @samp{QTSave} packet
40598 This packet directs the target to save trace data to the file name
40599 @var{filename} in the target's filesystem. @var{filename} is encoded
40600 as a hex string; the interpretation of the file name (relative vs
40601 absolute, wild cards, etc) is up to the target.
40603 @item qTBuffer:@var{offset},@var{len}
40604 @cindex @samp{qTBuffer} packet
40605 Return up to @var{len} bytes of the current contents of trace buffer,
40606 starting at @var{offset}. The trace buffer is treated as if it were
40607 a contiguous collection of traceframes, as per the trace file format.
40608 The reply consists as many hex-encoded bytes as the target can deliver
40609 in a packet; it is not an error to return fewer than were asked for.
40610 A reply consisting of just @code{l} indicates that no bytes are
40613 @item QTBuffer:circular:@var{value}
40614 This packet directs the target to use a circular trace buffer if
40615 @var{value} is 1, or a linear buffer if the value is 0.
40617 @item QTBuffer:size:@var{size}
40618 @anchor{QTBuffer-size}
40619 @cindex @samp{QTBuffer size} packet
40620 This packet directs the target to make the trace buffer be of size
40621 @var{size} if possible. A value of @code{-1} tells the target to
40622 use whatever size it prefers.
40624 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40625 @cindex @samp{QTNotes} packet
40626 This packet adds optional textual notes to the trace run. Allowable
40627 types include @code{user}, @code{notes}, and @code{tstop}, the
40628 @var{text} fields are arbitrary strings, hex-encoded.
40632 @subsection Relocate instruction reply packet
40633 When installing fast tracepoints in memory, the target may need to
40634 relocate the instruction currently at the tracepoint address to a
40635 different address in memory. For most instructions, a simple copy is
40636 enough, but, for example, call instructions that implicitly push the
40637 return address on the stack, and relative branches or other
40638 PC-relative instructions require offset adjustment, so that the effect
40639 of executing the instruction at a different address is the same as if
40640 it had executed in the original location.
40642 In response to several of the tracepoint packets, the target may also
40643 respond with a number of intermediate @samp{qRelocInsn} request
40644 packets before the final result packet, to have @value{GDBN} handle
40645 this relocation operation. If a packet supports this mechanism, its
40646 documentation will explicitly say so. See for example the above
40647 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40648 format of the request is:
40651 @item qRelocInsn:@var{from};@var{to}
40653 This requests @value{GDBN} to copy instruction at address @var{from}
40654 to address @var{to}, possibly adjusted so that executing the
40655 instruction at @var{to} has the same effect as executing it at
40656 @var{from}. @value{GDBN} writes the adjusted instruction to target
40657 memory starting at @var{to}.
40662 @item qRelocInsn:@var{adjusted_size}
40663 Informs the stub the relocation is complete. @var{adjusted_size} is
40664 the length in bytes of resulting relocated instruction sequence.
40666 A badly formed request was detected, or an error was encountered while
40667 relocating the instruction.
40670 @node Host I/O Packets
40671 @section Host I/O Packets
40672 @cindex Host I/O, remote protocol
40673 @cindex file transfer, remote protocol
40675 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40676 operations on the far side of a remote link. For example, Host I/O is
40677 used to upload and download files to a remote target with its own
40678 filesystem. Host I/O uses the same constant values and data structure
40679 layout as the target-initiated File-I/O protocol. However, the
40680 Host I/O packets are structured differently. The target-initiated
40681 protocol relies on target memory to store parameters and buffers.
40682 Host I/O requests are initiated by @value{GDBN}, and the
40683 target's memory is not involved. @xref{File-I/O Remote Protocol
40684 Extension}, for more details on the target-initiated protocol.
40686 The Host I/O request packets all encode a single operation along with
40687 its arguments. They have this format:
40691 @item vFile:@var{operation}: @var{parameter}@dots{}
40692 @var{operation} is the name of the particular request; the target
40693 should compare the entire packet name up to the second colon when checking
40694 for a supported operation. The format of @var{parameter} depends on
40695 the operation. Numbers are always passed in hexadecimal. Negative
40696 numbers have an explicit minus sign (i.e.@: two's complement is not
40697 used). Strings (e.g.@: filenames) are encoded as a series of
40698 hexadecimal bytes. The last argument to a system call may be a
40699 buffer of escaped binary data (@pxref{Binary Data}).
40703 The valid responses to Host I/O packets are:
40707 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40708 @var{result} is the integer value returned by this operation, usually
40709 non-negative for success and -1 for errors. If an error has occured,
40710 @var{errno} will be included in the result. @var{errno} will have a
40711 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40712 operations which return data, @var{attachment} supplies the data as a
40713 binary buffer. Binary buffers in response packets are escaped in the
40714 normal way (@pxref{Binary Data}). See the individual packet
40715 documentation for the interpretation of @var{result} and
40719 An empty response indicates that this operation is not recognized.
40723 These are the supported Host I/O operations:
40726 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40727 Open a file at @var{pathname} and return a file descriptor for it, or
40728 return -1 if an error occurs. @var{pathname} is a string,
40729 @var{flags} is an integer indicating a mask of open flags
40730 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40731 of mode bits to use if the file is created (@pxref{mode_t Values}).
40732 @xref{open}, for details of the open flags and mode values.
40734 @item vFile:close: @var{fd}
40735 Close the open file corresponding to @var{fd} and return 0, or
40736 -1 if an error occurs.
40738 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40739 Read data from the open file corresponding to @var{fd}. Up to
40740 @var{count} bytes will be read from the file, starting at @var{offset}
40741 relative to the start of the file. The target may read fewer bytes;
40742 common reasons include packet size limits and an end-of-file
40743 condition. The number of bytes read is returned. Zero should only be
40744 returned for a successful read at the end of the file, or if
40745 @var{count} was zero.
40747 The data read should be returned as a binary attachment on success.
40748 If zero bytes were read, the response should include an empty binary
40749 attachment (i.e.@: a trailing semicolon). The return value is the
40750 number of target bytes read; the binary attachment may be longer if
40751 some characters were escaped.
40753 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40754 Write @var{data} (a binary buffer) to the open file corresponding
40755 to @var{fd}. Start the write at @var{offset} from the start of the
40756 file. Unlike many @code{write} system calls, there is no
40757 separate @var{count} argument; the length of @var{data} in the
40758 packet is used. @samp{vFile:write} returns the number of bytes written,
40759 which may be shorter than the length of @var{data}, or -1 if an
40762 @item vFile:unlink: @var{pathname}
40763 Delete the file at @var{pathname} on the target. Return 0,
40764 or -1 if an error occurs. @var{pathname} is a string.
40766 @item vFile:readlink: @var{filename}
40767 Read value of symbolic link @var{filename} on the target. Return
40768 the number of bytes read, or -1 if an error occurs.
40770 The data read should be returned as a binary attachment on success.
40771 If zero bytes were read, the response should include an empty binary
40772 attachment (i.e.@: a trailing semicolon). The return value is the
40773 number of target bytes read; the binary attachment may be longer if
40774 some characters were escaped.
40779 @section Interrupts
40780 @cindex interrupts (remote protocol)
40782 When a program on the remote target is running, @value{GDBN} may
40783 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40784 a @code{BREAK} followed by @code{g},
40785 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40787 The precise meaning of @code{BREAK} is defined by the transport
40788 mechanism and may, in fact, be undefined. @value{GDBN} does not
40789 currently define a @code{BREAK} mechanism for any of the network
40790 interfaces except for TCP, in which case @value{GDBN} sends the
40791 @code{telnet} BREAK sequence.
40793 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40794 transport mechanisms. It is represented by sending the single byte
40795 @code{0x03} without any of the usual packet overhead described in
40796 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40797 transmitted as part of a packet, it is considered to be packet data
40798 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40799 (@pxref{X packet}), used for binary downloads, may include an unescaped
40800 @code{0x03} as part of its packet.
40802 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40803 When Linux kernel receives this sequence from serial port,
40804 it stops execution and connects to gdb.
40806 Stubs are not required to recognize these interrupt mechanisms and the
40807 precise meaning associated with receipt of the interrupt is
40808 implementation defined. If the target supports debugging of multiple
40809 threads and/or processes, it should attempt to interrupt all
40810 currently-executing threads and processes.
40811 If the stub is successful at interrupting the
40812 running program, it should send one of the stop
40813 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40814 of successfully stopping the program in all-stop mode, and a stop reply
40815 for each stopped thread in non-stop mode.
40816 Interrupts received while the
40817 program is stopped are discarded.
40819 @node Notification Packets
40820 @section Notification Packets
40821 @cindex notification packets
40822 @cindex packets, notification
40824 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40825 packets that require no acknowledgment. Both the GDB and the stub
40826 may send notifications (although the only notifications defined at
40827 present are sent by the stub). Notifications carry information
40828 without incurring the round-trip latency of an acknowledgment, and so
40829 are useful for low-impact communications where occasional packet loss
40832 A notification packet has the form @samp{% @var{data} #
40833 @var{checksum}}, where @var{data} is the content of the notification,
40834 and @var{checksum} is a checksum of @var{data}, computed and formatted
40835 as for ordinary @value{GDBN} packets. A notification's @var{data}
40836 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40837 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40838 to acknowledge the notification's receipt or to report its corruption.
40840 Every notification's @var{data} begins with a name, which contains no
40841 colon characters, followed by a colon character.
40843 Recipients should silently ignore corrupted notifications and
40844 notifications they do not understand. Recipients should restart
40845 timeout periods on receipt of a well-formed notification, whether or
40846 not they understand it.
40848 Senders should only send the notifications described here when this
40849 protocol description specifies that they are permitted. In the
40850 future, we may extend the protocol to permit existing notifications in
40851 new contexts; this rule helps older senders avoid confusing newer
40854 (Older versions of @value{GDBN} ignore bytes received until they see
40855 the @samp{$} byte that begins an ordinary packet, so new stubs may
40856 transmit notifications without fear of confusing older clients. There
40857 are no notifications defined for @value{GDBN} to send at the moment, but we
40858 assume that most older stubs would ignore them, as well.)
40860 Each notification is comprised of three parts:
40862 @item @var{name}:@var{event}
40863 The notification packet is sent by the side that initiates the
40864 exchange (currently, only the stub does that), with @var{event}
40865 carrying the specific information about the notification.
40866 @var{name} is the name of the notification.
40868 The acknowledge sent by the other side, usually @value{GDBN}, to
40869 acknowledge the exchange and request the event.
40872 The purpose of an asynchronous notification mechanism is to report to
40873 @value{GDBN} that something interesting happened in the remote stub.
40875 The remote stub may send notification @var{name}:@var{event}
40876 at any time, but @value{GDBN} acknowledges the notification when
40877 appropriate. The notification event is pending before @value{GDBN}
40878 acknowledges. Only one notification at a time may be pending; if
40879 additional events occur before @value{GDBN} has acknowledged the
40880 previous notification, they must be queued by the stub for later
40881 synchronous transmission in response to @var{ack} packets from
40882 @value{GDBN}. Because the notification mechanism is unreliable,
40883 the stub is permitted to resend a notification if it believes
40884 @value{GDBN} may not have received it.
40886 Specifically, notifications may appear when @value{GDBN} is not
40887 otherwise reading input from the stub, or when @value{GDBN} is
40888 expecting to read a normal synchronous response or a
40889 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40890 Notification packets are distinct from any other communication from
40891 the stub so there is no ambiguity.
40893 After receiving a notification, @value{GDBN} shall acknowledge it by
40894 sending a @var{ack} packet as a regular, synchronous request to the
40895 stub. Such acknowledgment is not required to happen immediately, as
40896 @value{GDBN} is permitted to send other, unrelated packets to the
40897 stub first, which the stub should process normally.
40899 Upon receiving a @var{ack} packet, if the stub has other queued
40900 events to report to @value{GDBN}, it shall respond by sending a
40901 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40902 packet to solicit further responses; again, it is permitted to send
40903 other, unrelated packets as well which the stub should process
40906 If the stub receives a @var{ack} packet and there are no additional
40907 @var{event} to report, the stub shall return an @samp{OK} response.
40908 At this point, @value{GDBN} has finished processing a notification
40909 and the stub has completed sending any queued events. @value{GDBN}
40910 won't accept any new notifications until the final @samp{OK} is
40911 received . If further notification events occur, the stub shall send
40912 a new notification, @value{GDBN} shall accept the notification, and
40913 the process shall be repeated.
40915 The process of asynchronous notification can be illustrated by the
40918 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40921 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40923 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40928 The following notifications are defined:
40929 @multitable @columnfractions 0.12 0.12 0.38 0.38
40938 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40939 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40940 for information on how these notifications are acknowledged by
40942 @tab Report an asynchronous stop event in non-stop mode.
40946 @node Remote Non-Stop
40947 @section Remote Protocol Support for Non-Stop Mode
40949 @value{GDBN}'s remote protocol supports non-stop debugging of
40950 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40951 supports non-stop mode, it should report that to @value{GDBN} by including
40952 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40954 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40955 establishing a new connection with the stub. Entering non-stop mode
40956 does not alter the state of any currently-running threads, but targets
40957 must stop all threads in any already-attached processes when entering
40958 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40959 probe the target state after a mode change.
40961 In non-stop mode, when an attached process encounters an event that
40962 would otherwise be reported with a stop reply, it uses the
40963 asynchronous notification mechanism (@pxref{Notification Packets}) to
40964 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40965 in all processes are stopped when a stop reply is sent, in non-stop
40966 mode only the thread reporting the stop event is stopped. That is,
40967 when reporting a @samp{S} or @samp{T} response to indicate completion
40968 of a step operation, hitting a breakpoint, or a fault, only the
40969 affected thread is stopped; any other still-running threads continue
40970 to run. When reporting a @samp{W} or @samp{X} response, all running
40971 threads belonging to other attached processes continue to run.
40973 In non-stop mode, the target shall respond to the @samp{?} packet as
40974 follows. First, any incomplete stop reply notification/@samp{vStopped}
40975 sequence in progress is abandoned. The target must begin a new
40976 sequence reporting stop events for all stopped threads, whether or not
40977 it has previously reported those events to @value{GDBN}. The first
40978 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40979 subsequent stop replies are sent as responses to @samp{vStopped} packets
40980 using the mechanism described above. The target must not send
40981 asynchronous stop reply notifications until the sequence is complete.
40982 If all threads are running when the target receives the @samp{?} packet,
40983 or if the target is not attached to any process, it shall respond
40986 @node Packet Acknowledgment
40987 @section Packet Acknowledgment
40989 @cindex acknowledgment, for @value{GDBN} remote
40990 @cindex packet acknowledgment, for @value{GDBN} remote
40991 By default, when either the host or the target machine receives a packet,
40992 the first response expected is an acknowledgment: either @samp{+} (to indicate
40993 the package was received correctly) or @samp{-} (to request retransmission).
40994 This mechanism allows the @value{GDBN} remote protocol to operate over
40995 unreliable transport mechanisms, such as a serial line.
40997 In cases where the transport mechanism is itself reliable (such as a pipe or
40998 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40999 It may be desirable to disable them in that case to reduce communication
41000 overhead, or for other reasons. This can be accomplished by means of the
41001 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41003 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41004 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41005 and response format still includes the normal checksum, as described in
41006 @ref{Overview}, but the checksum may be ignored by the receiver.
41008 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41009 no-acknowledgment mode, it should report that to @value{GDBN}
41010 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41011 @pxref{qSupported}.
41012 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41013 disabled via the @code{set remote noack-packet off} command
41014 (@pxref{Remote Configuration}),
41015 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41016 Only then may the stub actually turn off packet acknowledgments.
41017 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41018 response, which can be safely ignored by the stub.
41020 Note that @code{set remote noack-packet} command only affects negotiation
41021 between @value{GDBN} and the stub when subsequent connections are made;
41022 it does not affect the protocol acknowledgment state for any current
41024 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41025 new connection is established,
41026 there is also no protocol request to re-enable the acknowledgments
41027 for the current connection, once disabled.
41032 Example sequence of a target being re-started. Notice how the restart
41033 does not get any direct output:
41038 @emph{target restarts}
41041 <- @code{T001:1234123412341234}
41045 Example sequence of a target being stepped by a single instruction:
41048 -> @code{G1445@dots{}}
41053 <- @code{T001:1234123412341234}
41057 <- @code{1455@dots{}}
41061 @node File-I/O Remote Protocol Extension
41062 @section File-I/O Remote Protocol Extension
41063 @cindex File-I/O remote protocol extension
41066 * File-I/O Overview::
41067 * Protocol Basics::
41068 * The F Request Packet::
41069 * The F Reply Packet::
41070 * The Ctrl-C Message::
41072 * List of Supported Calls::
41073 * Protocol-specific Representation of Datatypes::
41075 * File-I/O Examples::
41078 @node File-I/O Overview
41079 @subsection File-I/O Overview
41080 @cindex file-i/o overview
41082 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41083 target to use the host's file system and console I/O to perform various
41084 system calls. System calls on the target system are translated into a
41085 remote protocol packet to the host system, which then performs the needed
41086 actions and returns a response packet to the target system.
41087 This simulates file system operations even on targets that lack file systems.
41089 The protocol is defined to be independent of both the host and target systems.
41090 It uses its own internal representation of datatypes and values. Both
41091 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41092 translating the system-dependent value representations into the internal
41093 protocol representations when data is transmitted.
41095 The communication is synchronous. A system call is possible only when
41096 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41097 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41098 the target is stopped to allow deterministic access to the target's
41099 memory. Therefore File-I/O is not interruptible by target signals. On
41100 the other hand, it is possible to interrupt File-I/O by a user interrupt
41101 (@samp{Ctrl-C}) within @value{GDBN}.
41103 The target's request to perform a host system call does not finish
41104 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41105 after finishing the system call, the target returns to continuing the
41106 previous activity (continue, step). No additional continue or step
41107 request from @value{GDBN} is required.
41110 (@value{GDBP}) continue
41111 <- target requests 'system call X'
41112 target is stopped, @value{GDBN} executes system call
41113 -> @value{GDBN} returns result
41114 ... target continues, @value{GDBN} returns to wait for the target
41115 <- target hits breakpoint and sends a Txx packet
41118 The protocol only supports I/O on the console and to regular files on
41119 the host file system. Character or block special devices, pipes,
41120 named pipes, sockets or any other communication method on the host
41121 system are not supported by this protocol.
41123 File I/O is not supported in non-stop mode.
41125 @node Protocol Basics
41126 @subsection Protocol Basics
41127 @cindex protocol basics, file-i/o
41129 The File-I/O protocol uses the @code{F} packet as the request as well
41130 as reply packet. Since a File-I/O system call can only occur when
41131 @value{GDBN} is waiting for a response from the continuing or stepping target,
41132 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41133 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41134 This @code{F} packet contains all information needed to allow @value{GDBN}
41135 to call the appropriate host system call:
41139 A unique identifier for the requested system call.
41142 All parameters to the system call. Pointers are given as addresses
41143 in the target memory address space. Pointers to strings are given as
41144 pointer/length pair. Numerical values are given as they are.
41145 Numerical control flags are given in a protocol-specific representation.
41149 At this point, @value{GDBN} has to perform the following actions.
41153 If the parameters include pointer values to data needed as input to a
41154 system call, @value{GDBN} requests this data from the target with a
41155 standard @code{m} packet request. This additional communication has to be
41156 expected by the target implementation and is handled as any other @code{m}
41160 @value{GDBN} translates all value from protocol representation to host
41161 representation as needed. Datatypes are coerced into the host types.
41164 @value{GDBN} calls the system call.
41167 It then coerces datatypes back to protocol representation.
41170 If the system call is expected to return data in buffer space specified
41171 by pointer parameters to the call, the data is transmitted to the
41172 target using a @code{M} or @code{X} packet. This packet has to be expected
41173 by the target implementation and is handled as any other @code{M} or @code{X}
41178 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41179 necessary information for the target to continue. This at least contains
41186 @code{errno}, if has been changed by the system call.
41193 After having done the needed type and value coercion, the target continues
41194 the latest continue or step action.
41196 @node The F Request Packet
41197 @subsection The @code{F} Request Packet
41198 @cindex file-i/o request packet
41199 @cindex @code{F} request packet
41201 The @code{F} request packet has the following format:
41204 @item F@var{call-id},@var{parameter@dots{}}
41206 @var{call-id} is the identifier to indicate the host system call to be called.
41207 This is just the name of the function.
41209 @var{parameter@dots{}} are the parameters to the system call.
41210 Parameters are hexadecimal integer values, either the actual values in case
41211 of scalar datatypes, pointers to target buffer space in case of compound
41212 datatypes and unspecified memory areas, or pointer/length pairs in case
41213 of string parameters. These are appended to the @var{call-id} as a
41214 comma-delimited list. All values are transmitted in ASCII
41215 string representation, pointer/length pairs separated by a slash.
41221 @node The F Reply Packet
41222 @subsection The @code{F} Reply Packet
41223 @cindex file-i/o reply packet
41224 @cindex @code{F} reply packet
41226 The @code{F} reply packet has the following format:
41230 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41232 @var{retcode} is the return code of the system call as hexadecimal value.
41234 @var{errno} is the @code{errno} set by the call, in protocol-specific
41236 This parameter can be omitted if the call was successful.
41238 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41239 case, @var{errno} must be sent as well, even if the call was successful.
41240 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41247 or, if the call was interrupted before the host call has been performed:
41254 assuming 4 is the protocol-specific representation of @code{EINTR}.
41259 @node The Ctrl-C Message
41260 @subsection The @samp{Ctrl-C} Message
41261 @cindex ctrl-c message, in file-i/o protocol
41263 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41264 reply packet (@pxref{The F Reply Packet}),
41265 the target should behave as if it had
41266 gotten a break message. The meaning for the target is ``system call
41267 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41268 (as with a break message) and return to @value{GDBN} with a @code{T02}
41271 It's important for the target to know in which
41272 state the system call was interrupted. There are two possible cases:
41276 The system call hasn't been performed on the host yet.
41279 The system call on the host has been finished.
41283 These two states can be distinguished by the target by the value of the
41284 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41285 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41286 on POSIX systems. In any other case, the target may presume that the
41287 system call has been finished --- successfully or not --- and should behave
41288 as if the break message arrived right after the system call.
41290 @value{GDBN} must behave reliably. If the system call has not been called
41291 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41292 @code{errno} in the packet. If the system call on the host has been finished
41293 before the user requests a break, the full action must be finished by
41294 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41295 The @code{F} packet may only be sent when either nothing has happened
41296 or the full action has been completed.
41299 @subsection Console I/O
41300 @cindex console i/o as part of file-i/o
41302 By default and if not explicitly closed by the target system, the file
41303 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41304 on the @value{GDBN} console is handled as any other file output operation
41305 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41306 by @value{GDBN} so that after the target read request from file descriptor
41307 0 all following typing is buffered until either one of the following
41312 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41314 system call is treated as finished.
41317 The user presses @key{RET}. This is treated as end of input with a trailing
41321 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41322 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41326 If the user has typed more characters than fit in the buffer given to
41327 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41328 either another @code{read(0, @dots{})} is requested by the target, or debugging
41329 is stopped at the user's request.
41332 @node List of Supported Calls
41333 @subsection List of Supported Calls
41334 @cindex list of supported file-i/o calls
41351 @unnumberedsubsubsec open
41352 @cindex open, file-i/o system call
41357 int open(const char *pathname, int flags);
41358 int open(const char *pathname, int flags, mode_t mode);
41362 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41365 @var{flags} is the bitwise @code{OR} of the following values:
41369 If the file does not exist it will be created. The host
41370 rules apply as far as file ownership and time stamps
41374 When used with @code{O_CREAT}, if the file already exists it is
41375 an error and open() fails.
41378 If the file already exists and the open mode allows
41379 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41380 truncated to zero length.
41383 The file is opened in append mode.
41386 The file is opened for reading only.
41389 The file is opened for writing only.
41392 The file is opened for reading and writing.
41396 Other bits are silently ignored.
41400 @var{mode} is the bitwise @code{OR} of the following values:
41404 User has read permission.
41407 User has write permission.
41410 Group has read permission.
41413 Group has write permission.
41416 Others have read permission.
41419 Others have write permission.
41423 Other bits are silently ignored.
41426 @item Return value:
41427 @code{open} returns the new file descriptor or -1 if an error
41434 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41437 @var{pathname} refers to a directory.
41440 The requested access is not allowed.
41443 @var{pathname} was too long.
41446 A directory component in @var{pathname} does not exist.
41449 @var{pathname} refers to a device, pipe, named pipe or socket.
41452 @var{pathname} refers to a file on a read-only filesystem and
41453 write access was requested.
41456 @var{pathname} is an invalid pointer value.
41459 No space on device to create the file.
41462 The process already has the maximum number of files open.
41465 The limit on the total number of files open on the system
41469 The call was interrupted by the user.
41475 @unnumberedsubsubsec close
41476 @cindex close, file-i/o system call
41485 @samp{Fclose,@var{fd}}
41487 @item Return value:
41488 @code{close} returns zero on success, or -1 if an error occurred.
41494 @var{fd} isn't a valid open file descriptor.
41497 The call was interrupted by the user.
41503 @unnumberedsubsubsec read
41504 @cindex read, file-i/o system call
41509 int read(int fd, void *buf, unsigned int count);
41513 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41515 @item Return value:
41516 On success, the number of bytes read is returned.
41517 Zero indicates end of file. If count is zero, read
41518 returns zero as well. On error, -1 is returned.
41524 @var{fd} is not a valid file descriptor or is not open for
41528 @var{bufptr} is an invalid pointer value.
41531 The call was interrupted by the user.
41537 @unnumberedsubsubsec write
41538 @cindex write, file-i/o system call
41543 int write(int fd, const void *buf, unsigned int count);
41547 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41549 @item Return value:
41550 On success, the number of bytes written are returned.
41551 Zero indicates nothing was written. On error, -1
41558 @var{fd} is not a valid file descriptor or is not open for
41562 @var{bufptr} is an invalid pointer value.
41565 An attempt was made to write a file that exceeds the
41566 host-specific maximum file size allowed.
41569 No space on device to write the data.
41572 The call was interrupted by the user.
41578 @unnumberedsubsubsec lseek
41579 @cindex lseek, file-i/o system call
41584 long lseek (int fd, long offset, int flag);
41588 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41590 @var{flag} is one of:
41594 The offset is set to @var{offset} bytes.
41597 The offset is set to its current location plus @var{offset}
41601 The offset is set to the size of the file plus @var{offset}
41605 @item Return value:
41606 On success, the resulting unsigned offset in bytes from
41607 the beginning of the file is returned. Otherwise, a
41608 value of -1 is returned.
41614 @var{fd} is not a valid open file descriptor.
41617 @var{fd} is associated with the @value{GDBN} console.
41620 @var{flag} is not a proper value.
41623 The call was interrupted by the user.
41629 @unnumberedsubsubsec rename
41630 @cindex rename, file-i/o system call
41635 int rename(const char *oldpath, const char *newpath);
41639 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41641 @item Return value:
41642 On success, zero is returned. On error, -1 is returned.
41648 @var{newpath} is an existing directory, but @var{oldpath} is not a
41652 @var{newpath} is a non-empty directory.
41655 @var{oldpath} or @var{newpath} is a directory that is in use by some
41659 An attempt was made to make a directory a subdirectory
41663 A component used as a directory in @var{oldpath} or new
41664 path is not a directory. Or @var{oldpath} is a directory
41665 and @var{newpath} exists but is not a directory.
41668 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41671 No access to the file or the path of the file.
41675 @var{oldpath} or @var{newpath} was too long.
41678 A directory component in @var{oldpath} or @var{newpath} does not exist.
41681 The file is on a read-only filesystem.
41684 The device containing the file has no room for the new
41688 The call was interrupted by the user.
41694 @unnumberedsubsubsec unlink
41695 @cindex unlink, file-i/o system call
41700 int unlink(const char *pathname);
41704 @samp{Funlink,@var{pathnameptr}/@var{len}}
41706 @item Return value:
41707 On success, zero is returned. On error, -1 is returned.
41713 No access to the file or the path of the file.
41716 The system does not allow unlinking of directories.
41719 The file @var{pathname} cannot be unlinked because it's
41720 being used by another process.
41723 @var{pathnameptr} is an invalid pointer value.
41726 @var{pathname} was too long.
41729 A directory component in @var{pathname} does not exist.
41732 A component of the path is not a directory.
41735 The file is on a read-only filesystem.
41738 The call was interrupted by the user.
41744 @unnumberedsubsubsec stat/fstat
41745 @cindex fstat, file-i/o system call
41746 @cindex stat, file-i/o system call
41751 int stat(const char *pathname, struct stat *buf);
41752 int fstat(int fd, struct stat *buf);
41756 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41757 @samp{Ffstat,@var{fd},@var{bufptr}}
41759 @item Return value:
41760 On success, zero is returned. On error, -1 is returned.
41766 @var{fd} is not a valid open file.
41769 A directory component in @var{pathname} does not exist or the
41770 path is an empty string.
41773 A component of the path is not a directory.
41776 @var{pathnameptr} is an invalid pointer value.
41779 No access to the file or the path of the file.
41782 @var{pathname} was too long.
41785 The call was interrupted by the user.
41791 @unnumberedsubsubsec gettimeofday
41792 @cindex gettimeofday, file-i/o system call
41797 int gettimeofday(struct timeval *tv, void *tz);
41801 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41803 @item Return value:
41804 On success, 0 is returned, -1 otherwise.
41810 @var{tz} is a non-NULL pointer.
41813 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41819 @unnumberedsubsubsec isatty
41820 @cindex isatty, file-i/o system call
41825 int isatty(int fd);
41829 @samp{Fisatty,@var{fd}}
41831 @item Return value:
41832 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41838 The call was interrupted by the user.
41843 Note that the @code{isatty} call is treated as a special case: it returns
41844 1 to the target if the file descriptor is attached
41845 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41846 would require implementing @code{ioctl} and would be more complex than
41851 @unnumberedsubsubsec system
41852 @cindex system, file-i/o system call
41857 int system(const char *command);
41861 @samp{Fsystem,@var{commandptr}/@var{len}}
41863 @item Return value:
41864 If @var{len} is zero, the return value indicates whether a shell is
41865 available. A zero return value indicates a shell is not available.
41866 For non-zero @var{len}, the value returned is -1 on error and the
41867 return status of the command otherwise. Only the exit status of the
41868 command is returned, which is extracted from the host's @code{system}
41869 return value by calling @code{WEXITSTATUS(retval)}. In case
41870 @file{/bin/sh} could not be executed, 127 is returned.
41876 The call was interrupted by the user.
41881 @value{GDBN} takes over the full task of calling the necessary host calls
41882 to perform the @code{system} call. The return value of @code{system} on
41883 the host is simplified before it's returned
41884 to the target. Any termination signal information from the child process
41885 is discarded, and the return value consists
41886 entirely of the exit status of the called command.
41888 Due to security concerns, the @code{system} call is by default refused
41889 by @value{GDBN}. The user has to allow this call explicitly with the
41890 @code{set remote system-call-allowed 1} command.
41893 @item set remote system-call-allowed
41894 @kindex set remote system-call-allowed
41895 Control whether to allow the @code{system} calls in the File I/O
41896 protocol for the remote target. The default is zero (disabled).
41898 @item show remote system-call-allowed
41899 @kindex show remote system-call-allowed
41900 Show whether the @code{system} calls are allowed in the File I/O
41904 @node Protocol-specific Representation of Datatypes
41905 @subsection Protocol-specific Representation of Datatypes
41906 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41909 * Integral Datatypes::
41911 * Memory Transfer::
41916 @node Integral Datatypes
41917 @unnumberedsubsubsec Integral Datatypes
41918 @cindex integral datatypes, in file-i/o protocol
41920 The integral datatypes used in the system calls are @code{int},
41921 @code{unsigned int}, @code{long}, @code{unsigned long},
41922 @code{mode_t}, and @code{time_t}.
41924 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41925 implemented as 32 bit values in this protocol.
41927 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41929 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41930 in @file{limits.h}) to allow range checking on host and target.
41932 @code{time_t} datatypes are defined as seconds since the Epoch.
41934 All integral datatypes transferred as part of a memory read or write of a
41935 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41938 @node Pointer Values
41939 @unnumberedsubsubsec Pointer Values
41940 @cindex pointer values, in file-i/o protocol
41942 Pointers to target data are transmitted as they are. An exception
41943 is made for pointers to buffers for which the length isn't
41944 transmitted as part of the function call, namely strings. Strings
41945 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41952 which is a pointer to data of length 18 bytes at position 0x1aaf.
41953 The length is defined as the full string length in bytes, including
41954 the trailing null byte. For example, the string @code{"hello world"}
41955 at address 0x123456 is transmitted as
41961 @node Memory Transfer
41962 @unnumberedsubsubsec Memory Transfer
41963 @cindex memory transfer, in file-i/o protocol
41965 Structured data which is transferred using a memory read or write (for
41966 example, a @code{struct stat}) is expected to be in a protocol-specific format
41967 with all scalar multibyte datatypes being big endian. Translation to
41968 this representation needs to be done both by the target before the @code{F}
41969 packet is sent, and by @value{GDBN} before
41970 it transfers memory to the target. Transferred pointers to structured
41971 data should point to the already-coerced data at any time.
41975 @unnumberedsubsubsec struct stat
41976 @cindex struct stat, in file-i/o protocol
41978 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41979 is defined as follows:
41983 unsigned int st_dev; /* device */
41984 unsigned int st_ino; /* inode */
41985 mode_t st_mode; /* protection */
41986 unsigned int st_nlink; /* number of hard links */
41987 unsigned int st_uid; /* user ID of owner */
41988 unsigned int st_gid; /* group ID of owner */
41989 unsigned int st_rdev; /* device type (if inode device) */
41990 unsigned long st_size; /* total size, in bytes */
41991 unsigned long st_blksize; /* blocksize for filesystem I/O */
41992 unsigned long st_blocks; /* number of blocks allocated */
41993 time_t st_atime; /* time of last access */
41994 time_t st_mtime; /* time of last modification */
41995 time_t st_ctime; /* time of last change */
41999 The integral datatypes conform to the definitions given in the
42000 appropriate section (see @ref{Integral Datatypes}, for details) so this
42001 structure is of size 64 bytes.
42003 The values of several fields have a restricted meaning and/or
42009 A value of 0 represents a file, 1 the console.
42012 No valid meaning for the target. Transmitted unchanged.
42015 Valid mode bits are described in @ref{Constants}. Any other
42016 bits have currently no meaning for the target.
42021 No valid meaning for the target. Transmitted unchanged.
42026 These values have a host and file system dependent
42027 accuracy. Especially on Windows hosts, the file system may not
42028 support exact timing values.
42031 The target gets a @code{struct stat} of the above representation and is
42032 responsible for coercing it to the target representation before
42035 Note that due to size differences between the host, target, and protocol
42036 representations of @code{struct stat} members, these members could eventually
42037 get truncated on the target.
42039 @node struct timeval
42040 @unnumberedsubsubsec struct timeval
42041 @cindex struct timeval, in file-i/o protocol
42043 The buffer of type @code{struct timeval} used by the File-I/O protocol
42044 is defined as follows:
42048 time_t tv_sec; /* second */
42049 long tv_usec; /* microsecond */
42053 The integral datatypes conform to the definitions given in the
42054 appropriate section (see @ref{Integral Datatypes}, for details) so this
42055 structure is of size 8 bytes.
42058 @subsection Constants
42059 @cindex constants, in file-i/o protocol
42061 The following values are used for the constants inside of the
42062 protocol. @value{GDBN} and target are responsible for translating these
42063 values before and after the call as needed.
42074 @unnumberedsubsubsec Open Flags
42075 @cindex open flags, in file-i/o protocol
42077 All values are given in hexadecimal representation.
42089 @node mode_t Values
42090 @unnumberedsubsubsec mode_t Values
42091 @cindex mode_t values, in file-i/o protocol
42093 All values are given in octal representation.
42110 @unnumberedsubsubsec Errno Values
42111 @cindex errno values, in file-i/o protocol
42113 All values are given in decimal representation.
42138 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42139 any error value not in the list of supported error numbers.
42142 @unnumberedsubsubsec Lseek Flags
42143 @cindex lseek flags, in file-i/o protocol
42152 @unnumberedsubsubsec Limits
42153 @cindex limits, in file-i/o protocol
42155 All values are given in decimal representation.
42158 INT_MIN -2147483648
42160 UINT_MAX 4294967295
42161 LONG_MIN -9223372036854775808
42162 LONG_MAX 9223372036854775807
42163 ULONG_MAX 18446744073709551615
42166 @node File-I/O Examples
42167 @subsection File-I/O Examples
42168 @cindex file-i/o examples
42170 Example sequence of a write call, file descriptor 3, buffer is at target
42171 address 0x1234, 6 bytes should be written:
42174 <- @code{Fwrite,3,1234,6}
42175 @emph{request memory read from target}
42178 @emph{return "6 bytes written"}
42182 Example sequence of a read call, file descriptor 3, buffer is at target
42183 address 0x1234, 6 bytes should be read:
42186 <- @code{Fread,3,1234,6}
42187 @emph{request memory write to target}
42188 -> @code{X1234,6:XXXXXX}
42189 @emph{return "6 bytes read"}
42193 Example sequence of a read call, call fails on the host due to invalid
42194 file descriptor (@code{EBADF}):
42197 <- @code{Fread,3,1234,6}
42201 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42205 <- @code{Fread,3,1234,6}
42210 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42214 <- @code{Fread,3,1234,6}
42215 -> @code{X1234,6:XXXXXX}
42219 @node Library List Format
42220 @section Library List Format
42221 @cindex library list format, remote protocol
42223 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42224 same process as your application to manage libraries. In this case,
42225 @value{GDBN} can use the loader's symbol table and normal memory
42226 operations to maintain a list of shared libraries. On other
42227 platforms, the operating system manages loaded libraries.
42228 @value{GDBN} can not retrieve the list of currently loaded libraries
42229 through memory operations, so it uses the @samp{qXfer:libraries:read}
42230 packet (@pxref{qXfer library list read}) instead. The remote stub
42231 queries the target's operating system and reports which libraries
42234 The @samp{qXfer:libraries:read} packet returns an XML document which
42235 lists loaded libraries and their offsets. Each library has an
42236 associated name and one or more segment or section base addresses,
42237 which report where the library was loaded in memory.
42239 For the common case of libraries that are fully linked binaries, the
42240 library should have a list of segments. If the target supports
42241 dynamic linking of a relocatable object file, its library XML element
42242 should instead include a list of allocated sections. The segment or
42243 section bases are start addresses, not relocation offsets; they do not
42244 depend on the library's link-time base addresses.
42246 @value{GDBN} must be linked with the Expat library to support XML
42247 library lists. @xref{Expat}.
42249 A simple memory map, with one loaded library relocated by a single
42250 offset, looks like this:
42254 <library name="/lib/libc.so.6">
42255 <segment address="0x10000000"/>
42260 Another simple memory map, with one loaded library with three
42261 allocated sections (.text, .data, .bss), looks like this:
42265 <library name="sharedlib.o">
42266 <section address="0x10000000"/>
42267 <section address="0x20000000"/>
42268 <section address="0x30000000"/>
42273 The format of a library list is described by this DTD:
42276 <!-- library-list: Root element with versioning -->
42277 <!ELEMENT library-list (library)*>
42278 <!ATTLIST library-list version CDATA #FIXED "1.0">
42279 <!ELEMENT library (segment*, section*)>
42280 <!ATTLIST library name CDATA #REQUIRED>
42281 <!ELEMENT segment EMPTY>
42282 <!ATTLIST segment address CDATA #REQUIRED>
42283 <!ELEMENT section EMPTY>
42284 <!ATTLIST section address CDATA #REQUIRED>
42287 In addition, segments and section descriptors cannot be mixed within a
42288 single library element, and you must supply at least one segment or
42289 section for each library.
42291 @node Library List Format for SVR4 Targets
42292 @section Library List Format for SVR4 Targets
42293 @cindex library list format, remote protocol
42295 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42296 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42297 shared libraries. Still a special library list provided by this packet is
42298 more efficient for the @value{GDBN} remote protocol.
42300 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42301 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42302 target, the following parameters are reported:
42306 @code{name}, the absolute file name from the @code{l_name} field of
42307 @code{struct link_map}.
42309 @code{lm} with address of @code{struct link_map} used for TLS
42310 (Thread Local Storage) access.
42312 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42313 @code{struct link_map}. For prelinked libraries this is not an absolute
42314 memory address. It is a displacement of absolute memory address against
42315 address the file was prelinked to during the library load.
42317 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42320 Additionally the single @code{main-lm} attribute specifies address of
42321 @code{struct link_map} used for the main executable. This parameter is used
42322 for TLS access and its presence is optional.
42324 @value{GDBN} must be linked with the Expat library to support XML
42325 SVR4 library lists. @xref{Expat}.
42327 A simple memory map, with two loaded libraries (which do not use prelink),
42331 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42332 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42334 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42336 </library-list-svr>
42339 The format of an SVR4 library list is described by this DTD:
42342 <!-- library-list-svr4: Root element with versioning -->
42343 <!ELEMENT library-list-svr4 (library)*>
42344 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42345 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42346 <!ELEMENT library EMPTY>
42347 <!ATTLIST library name CDATA #REQUIRED>
42348 <!ATTLIST library lm CDATA #REQUIRED>
42349 <!ATTLIST library l_addr CDATA #REQUIRED>
42350 <!ATTLIST library l_ld CDATA #REQUIRED>
42353 @node Memory Map Format
42354 @section Memory Map Format
42355 @cindex memory map format
42357 To be able to write into flash memory, @value{GDBN} needs to obtain a
42358 memory map from the target. This section describes the format of the
42361 The memory map is obtained using the @samp{qXfer:memory-map:read}
42362 (@pxref{qXfer memory map read}) packet and is an XML document that
42363 lists memory regions.
42365 @value{GDBN} must be linked with the Expat library to support XML
42366 memory maps. @xref{Expat}.
42368 The top-level structure of the document is shown below:
42371 <?xml version="1.0"?>
42372 <!DOCTYPE memory-map
42373 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42374 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42380 Each region can be either:
42385 A region of RAM starting at @var{addr} and extending for @var{length}
42389 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42394 A region of read-only memory:
42397 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42402 A region of flash memory, with erasure blocks @var{blocksize}
42406 <memory type="flash" start="@var{addr}" length="@var{length}">
42407 <property name="blocksize">@var{blocksize}</property>
42413 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42414 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42415 packets to write to addresses in such ranges.
42417 The formal DTD for memory map format is given below:
42420 <!-- ................................................... -->
42421 <!-- Memory Map XML DTD ................................ -->
42422 <!-- File: memory-map.dtd .............................. -->
42423 <!-- .................................... .............. -->
42424 <!-- memory-map.dtd -->
42425 <!-- memory-map: Root element with versioning -->
42426 <!ELEMENT memory-map (memory | property)>
42427 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42428 <!ELEMENT memory (property)>
42429 <!-- memory: Specifies a memory region,
42430 and its type, or device. -->
42431 <!ATTLIST memory type CDATA #REQUIRED
42432 start CDATA #REQUIRED
42433 length CDATA #REQUIRED
42434 device CDATA #IMPLIED>
42435 <!-- property: Generic attribute tag -->
42436 <!ELEMENT property (#PCDATA | property)*>
42437 <!ATTLIST property name CDATA #REQUIRED>
42440 @node Thread List Format
42441 @section Thread List Format
42442 @cindex thread list format
42444 To efficiently update the list of threads and their attributes,
42445 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42446 (@pxref{qXfer threads read}) and obtains the XML document with
42447 the following structure:
42450 <?xml version="1.0"?>
42452 <thread id="id" core="0">
42453 ... description ...
42458 Each @samp{thread} element must have the @samp{id} attribute that
42459 identifies the thread (@pxref{thread-id syntax}). The
42460 @samp{core} attribute, if present, specifies which processor core
42461 the thread was last executing on. The content of the of @samp{thread}
42462 element is interpreted as human-readable auxilliary information.
42464 @node Traceframe Info Format
42465 @section Traceframe Info Format
42466 @cindex traceframe info format
42468 To be able to know which objects in the inferior can be examined when
42469 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42470 memory ranges, registers and trace state variables that have been
42471 collected in a traceframe.
42473 This list is obtained using the @samp{qXfer:traceframe-info:read}
42474 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42476 @value{GDBN} must be linked with the Expat library to support XML
42477 traceframe info discovery. @xref{Expat}.
42479 The top-level structure of the document is shown below:
42482 <?xml version="1.0"?>
42483 <!DOCTYPE traceframe-info
42484 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42485 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42491 Each traceframe block can be either:
42496 A region of collected memory starting at @var{addr} and extending for
42497 @var{length} bytes from there:
42500 <memory start="@var{addr}" length="@var{length}"/>
42504 A block indicating trace state variable numbered @var{number} has been
42508 <tvar id="@var{number}"/>
42513 The formal DTD for the traceframe info format is given below:
42516 <!ELEMENT traceframe-info (memory | tvar)* >
42517 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42519 <!ELEMENT memory EMPTY>
42520 <!ATTLIST memory start CDATA #REQUIRED
42521 length CDATA #REQUIRED>
42523 <!ATTLIST tvar id CDATA #REQUIRED>
42526 @node Branch Trace Format
42527 @section Branch Trace Format
42528 @cindex branch trace format
42530 In order to display the branch trace of an inferior thread,
42531 @value{GDBN} needs to obtain the list of branches. This list is
42532 represented as list of sequential code blocks that are connected via
42533 branches. The code in each block has been executed sequentially.
42535 This list is obtained using the @samp{qXfer:btrace:read}
42536 (@pxref{qXfer btrace read}) packet and is an XML document.
42538 @value{GDBN} must be linked with the Expat library to support XML
42539 traceframe info discovery. @xref{Expat}.
42541 The top-level structure of the document is shown below:
42544 <?xml version="1.0"?>
42546 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42547 "http://sourceware.org/gdb/gdb-btrace.dtd">
42556 A block of sequentially executed instructions starting at @var{begin}
42557 and ending at @var{end}:
42560 <block begin="@var{begin}" end="@var{end}"/>
42565 The formal DTD for the branch trace format is given below:
42568 <!ELEMENT btrace (block)* >
42569 <!ATTLIST btrace version CDATA #FIXED "1.0">
42571 <!ELEMENT block EMPTY>
42572 <!ATTLIST block begin CDATA #REQUIRED
42573 end CDATA #REQUIRED>
42576 @include agentexpr.texi
42578 @node Target Descriptions
42579 @appendix Target Descriptions
42580 @cindex target descriptions
42582 One of the challenges of using @value{GDBN} to debug embedded systems
42583 is that there are so many minor variants of each processor
42584 architecture in use. It is common practice for vendors to start with
42585 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42586 and then make changes to adapt it to a particular market niche. Some
42587 architectures have hundreds of variants, available from dozens of
42588 vendors. This leads to a number of problems:
42592 With so many different customized processors, it is difficult for
42593 the @value{GDBN} maintainers to keep up with the changes.
42595 Since individual variants may have short lifetimes or limited
42596 audiences, it may not be worthwhile to carry information about every
42597 variant in the @value{GDBN} source tree.
42599 When @value{GDBN} does support the architecture of the embedded system
42600 at hand, the task of finding the correct architecture name to give the
42601 @command{set architecture} command can be error-prone.
42604 To address these problems, the @value{GDBN} remote protocol allows a
42605 target system to not only identify itself to @value{GDBN}, but to
42606 actually describe its own features. This lets @value{GDBN} support
42607 processor variants it has never seen before --- to the extent that the
42608 descriptions are accurate, and that @value{GDBN} understands them.
42610 @value{GDBN} must be linked with the Expat library to support XML
42611 target descriptions. @xref{Expat}.
42614 * Retrieving Descriptions:: How descriptions are fetched from a target.
42615 * Target Description Format:: The contents of a target description.
42616 * Predefined Target Types:: Standard types available for target
42618 * Standard Target Features:: Features @value{GDBN} knows about.
42621 @node Retrieving Descriptions
42622 @section Retrieving Descriptions
42624 Target descriptions can be read from the target automatically, or
42625 specified by the user manually. The default behavior is to read the
42626 description from the target. @value{GDBN} retrieves it via the remote
42627 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42628 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42629 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42630 XML document, of the form described in @ref{Target Description
42633 Alternatively, you can specify a file to read for the target description.
42634 If a file is set, the target will not be queried. The commands to
42635 specify a file are:
42638 @cindex set tdesc filename
42639 @item set tdesc filename @var{path}
42640 Read the target description from @var{path}.
42642 @cindex unset tdesc filename
42643 @item unset tdesc filename
42644 Do not read the XML target description from a file. @value{GDBN}
42645 will use the description supplied by the current target.
42647 @cindex show tdesc filename
42648 @item show tdesc filename
42649 Show the filename to read for a target description, if any.
42653 @node Target Description Format
42654 @section Target Description Format
42655 @cindex target descriptions, XML format
42657 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42658 document which complies with the Document Type Definition provided in
42659 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42660 means you can use generally available tools like @command{xmllint} to
42661 check that your feature descriptions are well-formed and valid.
42662 However, to help people unfamiliar with XML write descriptions for
42663 their targets, we also describe the grammar here.
42665 Target descriptions can identify the architecture of the remote target
42666 and (for some architectures) provide information about custom register
42667 sets. They can also identify the OS ABI of the remote target.
42668 @value{GDBN} can use this information to autoconfigure for your
42669 target, or to warn you if you connect to an unsupported target.
42671 Here is a simple target description:
42674 <target version="1.0">
42675 <architecture>i386:x86-64</architecture>
42680 This minimal description only says that the target uses
42681 the x86-64 architecture.
42683 A target description has the following overall form, with [ ] marking
42684 optional elements and @dots{} marking repeatable elements. The elements
42685 are explained further below.
42688 <?xml version="1.0"?>
42689 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42690 <target version="1.0">
42691 @r{[}@var{architecture}@r{]}
42692 @r{[}@var{osabi}@r{]}
42693 @r{[}@var{compatible}@r{]}
42694 @r{[}@var{feature}@dots{}@r{]}
42699 The description is generally insensitive to whitespace and line
42700 breaks, under the usual common-sense rules. The XML version
42701 declaration and document type declaration can generally be omitted
42702 (@value{GDBN} does not require them), but specifying them may be
42703 useful for XML validation tools. The @samp{version} attribute for
42704 @samp{<target>} may also be omitted, but we recommend
42705 including it; if future versions of @value{GDBN} use an incompatible
42706 revision of @file{gdb-target.dtd}, they will detect and report
42707 the version mismatch.
42709 @subsection Inclusion
42710 @cindex target descriptions, inclusion
42713 @cindex <xi:include>
42716 It can sometimes be valuable to split a target description up into
42717 several different annexes, either for organizational purposes, or to
42718 share files between different possible target descriptions. You can
42719 divide a description into multiple files by replacing any element of
42720 the target description with an inclusion directive of the form:
42723 <xi:include href="@var{document}"/>
42727 When @value{GDBN} encounters an element of this form, it will retrieve
42728 the named XML @var{document}, and replace the inclusion directive with
42729 the contents of that document. If the current description was read
42730 using @samp{qXfer}, then so will be the included document;
42731 @var{document} will be interpreted as the name of an annex. If the
42732 current description was read from a file, @value{GDBN} will look for
42733 @var{document} as a file in the same directory where it found the
42734 original description.
42736 @subsection Architecture
42737 @cindex <architecture>
42739 An @samp{<architecture>} element has this form:
42742 <architecture>@var{arch}</architecture>
42745 @var{arch} is one of the architectures from the set accepted by
42746 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42749 @cindex @code{<osabi>}
42751 This optional field was introduced in @value{GDBN} version 7.0.
42752 Previous versions of @value{GDBN} ignore it.
42754 An @samp{<osabi>} element has this form:
42757 <osabi>@var{abi-name}</osabi>
42760 @var{abi-name} is an OS ABI name from the same selection accepted by
42761 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42763 @subsection Compatible Architecture
42764 @cindex @code{<compatible>}
42766 This optional field was introduced in @value{GDBN} version 7.0.
42767 Previous versions of @value{GDBN} ignore it.
42769 A @samp{<compatible>} element has this form:
42772 <compatible>@var{arch}</compatible>
42775 @var{arch} is one of the architectures from the set accepted by
42776 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42778 A @samp{<compatible>} element is used to specify that the target
42779 is able to run binaries in some other than the main target architecture
42780 given by the @samp{<architecture>} element. For example, on the
42781 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42782 or @code{powerpc:common64}, but the system is able to run binaries
42783 in the @code{spu} architecture as well. The way to describe this
42784 capability with @samp{<compatible>} is as follows:
42787 <architecture>powerpc:common</architecture>
42788 <compatible>spu</compatible>
42791 @subsection Features
42794 Each @samp{<feature>} describes some logical portion of the target
42795 system. Features are currently used to describe available CPU
42796 registers and the types of their contents. A @samp{<feature>} element
42800 <feature name="@var{name}">
42801 @r{[}@var{type}@dots{}@r{]}
42807 Each feature's name should be unique within the description. The name
42808 of a feature does not matter unless @value{GDBN} has some special
42809 knowledge of the contents of that feature; if it does, the feature
42810 should have its standard name. @xref{Standard Target Features}.
42814 Any register's value is a collection of bits which @value{GDBN} must
42815 interpret. The default interpretation is a two's complement integer,
42816 but other types can be requested by name in the register description.
42817 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42818 Target Types}), and the description can define additional composite types.
42820 Each type element must have an @samp{id} attribute, which gives
42821 a unique (within the containing @samp{<feature>}) name to the type.
42822 Types must be defined before they are used.
42825 Some targets offer vector registers, which can be treated as arrays
42826 of scalar elements. These types are written as @samp{<vector>} elements,
42827 specifying the array element type, @var{type}, and the number of elements,
42831 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42835 If a register's value is usefully viewed in multiple ways, define it
42836 with a union type containing the useful representations. The
42837 @samp{<union>} element contains one or more @samp{<field>} elements,
42838 each of which has a @var{name} and a @var{type}:
42841 <union id="@var{id}">
42842 <field name="@var{name}" type="@var{type}"/>
42848 If a register's value is composed from several separate values, define
42849 it with a structure type. There are two forms of the @samp{<struct>}
42850 element; a @samp{<struct>} element must either contain only bitfields
42851 or contain no bitfields. If the structure contains only bitfields,
42852 its total size in bytes must be specified, each bitfield must have an
42853 explicit start and end, and bitfields are automatically assigned an
42854 integer type. The field's @var{start} should be less than or
42855 equal to its @var{end}, and zero represents the least significant bit.
42858 <struct id="@var{id}" size="@var{size}">
42859 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42864 If the structure contains no bitfields, then each field has an
42865 explicit type, and no implicit padding is added.
42868 <struct id="@var{id}">
42869 <field name="@var{name}" type="@var{type}"/>
42875 If a register's value is a series of single-bit flags, define it with
42876 a flags type. The @samp{<flags>} element has an explicit @var{size}
42877 and contains one or more @samp{<field>} elements. Each field has a
42878 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
42882 <flags id="@var{id}" size="@var{size}">
42883 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42888 @subsection Registers
42891 Each register is represented as an element with this form:
42894 <reg name="@var{name}"
42895 bitsize="@var{size}"
42896 @r{[}regnum="@var{num}"@r{]}
42897 @r{[}save-restore="@var{save-restore}"@r{]}
42898 @r{[}type="@var{type}"@r{]}
42899 @r{[}group="@var{group}"@r{]}/>
42903 The components are as follows:
42908 The register's name; it must be unique within the target description.
42911 The register's size, in bits.
42914 The register's number. If omitted, a register's number is one greater
42915 than that of the previous register (either in the current feature or in
42916 a preceding feature); the first register in the target description
42917 defaults to zero. This register number is used to read or write
42918 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42919 packets, and registers appear in the @code{g} and @code{G} packets
42920 in order of increasing register number.
42923 Whether the register should be preserved across inferior function
42924 calls; this must be either @code{yes} or @code{no}. The default is
42925 @code{yes}, which is appropriate for most registers except for
42926 some system control registers; this is not related to the target's
42930 The type of the register. @var{type} may be a predefined type, a type
42931 defined in the current feature, or one of the special types @code{int}
42932 and @code{float}. @code{int} is an integer type of the correct size
42933 for @var{bitsize}, and @code{float} is a floating point type (in the
42934 architecture's normal floating point format) of the correct size for
42935 @var{bitsize}. The default is @code{int}.
42938 The register group to which this register belongs. @var{group} must
42939 be either @code{general}, @code{float}, or @code{vector}. If no
42940 @var{group} is specified, @value{GDBN} will not display the register
42941 in @code{info registers}.
42945 @node Predefined Target Types
42946 @section Predefined Target Types
42947 @cindex target descriptions, predefined types
42949 Type definitions in the self-description can build up composite types
42950 from basic building blocks, but can not define fundamental types. Instead,
42951 standard identifiers are provided by @value{GDBN} for the fundamental
42952 types. The currently supported types are:
42961 Signed integer types holding the specified number of bits.
42968 Unsigned integer types holding the specified number of bits.
42972 Pointers to unspecified code and data. The program counter and
42973 any dedicated return address register may be marked as code
42974 pointers; printing a code pointer converts it into a symbolic
42975 address. The stack pointer and any dedicated address registers
42976 may be marked as data pointers.
42979 Single precision IEEE floating point.
42982 Double precision IEEE floating point.
42985 The 12-byte extended precision format used by ARM FPA registers.
42988 The 10-byte extended precision format used by x87 registers.
42991 32bit @sc{eflags} register used by x86.
42994 32bit @sc{mxcsr} register used by x86.
42998 @node Standard Target Features
42999 @section Standard Target Features
43000 @cindex target descriptions, standard features
43002 A target description must contain either no registers or all the
43003 target's registers. If the description contains no registers, then
43004 @value{GDBN} will assume a default register layout, selected based on
43005 the architecture. If the description contains any registers, the
43006 default layout will not be used; the standard registers must be
43007 described in the target description, in such a way that @value{GDBN}
43008 can recognize them.
43010 This is accomplished by giving specific names to feature elements
43011 which contain standard registers. @value{GDBN} will look for features
43012 with those names and verify that they contain the expected registers;
43013 if any known feature is missing required registers, or if any required
43014 feature is missing, @value{GDBN} will reject the target
43015 description. You can add additional registers to any of the
43016 standard features --- @value{GDBN} will display them just as if
43017 they were added to an unrecognized feature.
43019 This section lists the known features and their expected contents.
43020 Sample XML documents for these features are included in the
43021 @value{GDBN} source tree, in the directory @file{gdb/features}.
43023 Names recognized by @value{GDBN} should include the name of the
43024 company or organization which selected the name, and the overall
43025 architecture to which the feature applies; so e.g.@: the feature
43026 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43028 The names of registers are not case sensitive for the purpose
43029 of recognizing standard features, but @value{GDBN} will only display
43030 registers using the capitalization used in the description.
43033 * AArch64 Features::
43038 * Nios II Features::
43039 * PowerPC Features::
43040 * S/390 and System z Features::
43045 @node AArch64 Features
43046 @subsection AArch64 Features
43047 @cindex target descriptions, AArch64 features
43049 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43050 targets. It should contain registers @samp{x0} through @samp{x30},
43051 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43053 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43054 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43058 @subsection ARM Features
43059 @cindex target descriptions, ARM features
43061 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43063 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43064 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43066 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43067 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43068 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43071 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43072 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43074 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43075 it should contain at least registers @samp{wR0} through @samp{wR15} and
43076 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43077 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43079 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43080 should contain at least registers @samp{d0} through @samp{d15}. If
43081 they are present, @samp{d16} through @samp{d31} should also be included.
43082 @value{GDBN} will synthesize the single-precision registers from
43083 halves of the double-precision registers.
43085 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43086 need to contain registers; it instructs @value{GDBN} to display the
43087 VFP double-precision registers as vectors and to synthesize the
43088 quad-precision registers from pairs of double-precision registers.
43089 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43090 be present and include 32 double-precision registers.
43092 @node i386 Features
43093 @subsection i386 Features
43094 @cindex target descriptions, i386 features
43096 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43097 targets. It should describe the following registers:
43101 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43103 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43105 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43106 @samp{fs}, @samp{gs}
43108 @samp{st0} through @samp{st7}
43110 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43111 @samp{foseg}, @samp{fooff} and @samp{fop}
43114 The register sets may be different, depending on the target.
43116 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43117 describe registers:
43121 @samp{xmm0} through @samp{xmm7} for i386
43123 @samp{xmm0} through @samp{xmm15} for amd64
43128 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43129 @samp{org.gnu.gdb.i386.sse} feature. It should
43130 describe the upper 128 bits of @sc{ymm} registers:
43134 @samp{ymm0h} through @samp{ymm7h} for i386
43136 @samp{ymm0h} through @samp{ymm15h} for amd64
43139 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43140 describe a single register, @samp{orig_eax}.
43142 @node MIPS Features
43143 @subsection @acronym{MIPS} Features
43144 @cindex target descriptions, @acronym{MIPS} features
43146 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43147 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43148 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43151 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43152 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43153 registers. They may be 32-bit or 64-bit depending on the target.
43155 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43156 it may be optional in a future version of @value{GDBN}. It should
43157 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43158 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43160 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43161 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43162 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43163 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43165 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43166 contain a single register, @samp{restart}, which is used by the
43167 Linux kernel to control restartable syscalls.
43169 @node M68K Features
43170 @subsection M68K Features
43171 @cindex target descriptions, M68K features
43174 @item @samp{org.gnu.gdb.m68k.core}
43175 @itemx @samp{org.gnu.gdb.coldfire.core}
43176 @itemx @samp{org.gnu.gdb.fido.core}
43177 One of those features must be always present.
43178 The feature that is present determines which flavor of m68k is
43179 used. The feature that is present should contain registers
43180 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43181 @samp{sp}, @samp{ps} and @samp{pc}.
43183 @item @samp{org.gnu.gdb.coldfire.fp}
43184 This feature is optional. If present, it should contain registers
43185 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43189 @node Nios II Features
43190 @subsection Nios II Features
43191 @cindex target descriptions, Nios II features
43193 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43194 targets. It should contain the 32 core registers (@samp{zero},
43195 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43196 @samp{pc}, and the 16 control registers (@samp{status} through
43199 @node PowerPC Features
43200 @subsection PowerPC Features
43201 @cindex target descriptions, PowerPC features
43203 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43204 targets. It should contain registers @samp{r0} through @samp{r31},
43205 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43206 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43208 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43209 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43211 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43212 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43215 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43216 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43217 will combine these registers with the floating point registers
43218 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43219 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43220 through @samp{vs63}, the set of vector registers for POWER7.
43222 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43223 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43224 @samp{spefscr}. SPE targets should provide 32-bit registers in
43225 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43226 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43227 these to present registers @samp{ev0} through @samp{ev31} to the
43230 @node S/390 and System z Features
43231 @subsection S/390 and System z Features
43232 @cindex target descriptions, S/390 features
43233 @cindex target descriptions, System z features
43235 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43236 System z targets. It should contain the PSW and the 16 general
43237 registers. In particular, System z targets should provide the 64-bit
43238 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43239 S/390 targets should provide the 32-bit versions of these registers.
43240 A System z target that runs in 31-bit addressing mode should provide
43241 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43242 register's upper halves @samp{r0h} through @samp{r15h}, and their
43243 lower halves @samp{r0l} through @samp{r15l}.
43245 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43246 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43249 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43250 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43252 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43253 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43254 targets and 32-bit otherwise. In addition, the feature may contain
43255 the @samp{last_break} register, whose width depends on the addressing
43256 mode, as well as the @samp{system_call} register, which is always
43259 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43260 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43261 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43263 @node TIC6x Features
43264 @subsection TMS320C6x Features
43265 @cindex target descriptions, TIC6x features
43266 @cindex target descriptions, TMS320C6x features
43267 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43268 targets. It should contain registers @samp{A0} through @samp{A15},
43269 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43271 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43272 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43273 through @samp{B31}.
43275 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43276 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43278 @node Operating System Information
43279 @appendix Operating System Information
43280 @cindex operating system information
43286 Users of @value{GDBN} often wish to obtain information about the state of
43287 the operating system running on the target---for example the list of
43288 processes, or the list of open files. This section describes the
43289 mechanism that makes it possible. This mechanism is similar to the
43290 target features mechanism (@pxref{Target Descriptions}), but focuses
43291 on a different aspect of target.
43293 Operating system information is retrived from the target via the
43294 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43295 read}). The object name in the request should be @samp{osdata}, and
43296 the @var{annex} identifies the data to be fetched.
43299 @appendixsection Process list
43300 @cindex operating system information, process list
43302 When requesting the process list, the @var{annex} field in the
43303 @samp{qXfer} request should be @samp{processes}. The returned data is
43304 an XML document. The formal syntax of this document is defined in
43305 @file{gdb/features/osdata.dtd}.
43307 An example document is:
43310 <?xml version="1.0"?>
43311 <!DOCTYPE target SYSTEM "osdata.dtd">
43312 <osdata type="processes">
43314 <column name="pid">1</column>
43315 <column name="user">root</column>
43316 <column name="command">/sbin/init</column>
43317 <column name="cores">1,2,3</column>
43322 Each item should include a column whose name is @samp{pid}. The value
43323 of that column should identify the process on the target. The
43324 @samp{user} and @samp{command} columns are optional, and will be
43325 displayed by @value{GDBN}. The @samp{cores} column, if present,
43326 should contain a comma-separated list of cores that this process
43327 is running on. Target may provide additional columns,
43328 which @value{GDBN} currently ignores.
43330 @node Trace File Format
43331 @appendix Trace File Format
43332 @cindex trace file format
43334 The trace file comes in three parts: a header, a textual description
43335 section, and a trace frame section with binary data.
43337 The header has the form @code{\x7fTRACE0\n}. The first byte is
43338 @code{0x7f} so as to indicate that the file contains binary data,
43339 while the @code{0} is a version number that may have different values
43342 The description section consists of multiple lines of @sc{ascii} text
43343 separated by newline characters (@code{0xa}). The lines may include a
43344 variety of optional descriptive or context-setting information, such
43345 as tracepoint definitions or register set size. @value{GDBN} will
43346 ignore any line that it does not recognize. An empty line marks the end
43349 @c FIXME add some specific types of data
43351 The trace frame section consists of a number of consecutive frames.
43352 Each frame begins with a two-byte tracepoint number, followed by a
43353 four-byte size giving the amount of data in the frame. The data in
43354 the frame consists of a number of blocks, each introduced by a
43355 character indicating its type (at least register, memory, and trace
43356 state variable). The data in this section is raw binary, not a
43357 hexadecimal or other encoding; its endianness matches the target's
43360 @c FIXME bi-arch may require endianness/arch info in description section
43363 @item R @var{bytes}
43364 Register block. The number and ordering of bytes matches that of a
43365 @code{g} packet in the remote protocol. Note that these are the
43366 actual bytes, in target order and @value{GDBN} register order, not a
43367 hexadecimal encoding.
43369 @item M @var{address} @var{length} @var{bytes}...
43370 Memory block. This is a contiguous block of memory, at the 8-byte
43371 address @var{address}, with a 2-byte length @var{length}, followed by
43372 @var{length} bytes.
43374 @item V @var{number} @var{value}
43375 Trace state variable block. This records the 8-byte signed value
43376 @var{value} of trace state variable numbered @var{number}.
43380 Future enhancements of the trace file format may include additional types
43383 @node Index Section Format
43384 @appendix @code{.gdb_index} section format
43385 @cindex .gdb_index section format
43386 @cindex index section format
43388 This section documents the index section that is created by @code{save
43389 gdb-index} (@pxref{Index Files}). The index section is
43390 DWARF-specific; some knowledge of DWARF is assumed in this
43393 The mapped index file format is designed to be directly
43394 @code{mmap}able on any architecture. In most cases, a datum is
43395 represented using a little-endian 32-bit integer value, called an
43396 @code{offset_type}. Big endian machines must byte-swap the values
43397 before using them. Exceptions to this rule are noted. The data is
43398 laid out such that alignment is always respected.
43400 A mapped index consists of several areas, laid out in order.
43404 The file header. This is a sequence of values, of @code{offset_type}
43405 unless otherwise noted:
43409 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43410 Version 4 uses a different hashing function from versions 5 and 6.
43411 Version 6 includes symbols for inlined functions, whereas versions 4
43412 and 5 do not. Version 7 adds attributes to the CU indices in the
43413 symbol table. Version 8 specifies that symbols from DWARF type units
43414 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43415 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43417 @value{GDBN} will only read version 4, 5, or 6 indices
43418 by specifying @code{set use-deprecated-index-sections on}.
43419 GDB has a workaround for potentially broken version 7 indices so it is
43420 currently not flagged as deprecated.
43423 The offset, from the start of the file, of the CU list.
43426 The offset, from the start of the file, of the types CU list. Note
43427 that this area can be empty, in which case this offset will be equal
43428 to the next offset.
43431 The offset, from the start of the file, of the address area.
43434 The offset, from the start of the file, of the symbol table.
43437 The offset, from the start of the file, of the constant pool.
43441 The CU list. This is a sequence of pairs of 64-bit little-endian
43442 values, sorted by the CU offset. The first element in each pair is
43443 the offset of a CU in the @code{.debug_info} section. The second
43444 element in each pair is the length of that CU. References to a CU
43445 elsewhere in the map are done using a CU index, which is just the
43446 0-based index into this table. Note that if there are type CUs, then
43447 conceptually CUs and type CUs form a single list for the purposes of
43451 The types CU list. This is a sequence of triplets of 64-bit
43452 little-endian values. In a triplet, the first value is the CU offset,
43453 the second value is the type offset in the CU, and the third value is
43454 the type signature. The types CU list is not sorted.
43457 The address area. The address area consists of a sequence of address
43458 entries. Each address entry has three elements:
43462 The low address. This is a 64-bit little-endian value.
43465 The high address. This is a 64-bit little-endian value. Like
43466 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43469 The CU index. This is an @code{offset_type} value.
43473 The symbol table. This is an open-addressed hash table. The size of
43474 the hash table is always a power of 2.
43476 Each slot in the hash table consists of a pair of @code{offset_type}
43477 values. The first value is the offset of the symbol's name in the
43478 constant pool. The second value is the offset of the CU vector in the
43481 If both values are 0, then this slot in the hash table is empty. This
43482 is ok because while 0 is a valid constant pool index, it cannot be a
43483 valid index for both a string and a CU vector.
43485 The hash value for a table entry is computed by applying an
43486 iterative hash function to the symbol's name. Starting with an
43487 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43488 the string is incorporated into the hash using the formula depending on the
43493 The formula is @code{r = r * 67 + c - 113}.
43495 @item Versions 5 to 7
43496 The formula is @code{r = r * 67 + tolower (c) - 113}.
43499 The terminating @samp{\0} is not incorporated into the hash.
43501 The step size used in the hash table is computed via
43502 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43503 value, and @samp{size} is the size of the hash table. The step size
43504 is used to find the next candidate slot when handling a hash
43507 The names of C@t{++} symbols in the hash table are canonicalized. We
43508 don't currently have a simple description of the canonicalization
43509 algorithm; if you intend to create new index sections, you must read
43513 The constant pool. This is simply a bunch of bytes. It is organized
43514 so that alignment is correct: CU vectors are stored first, followed by
43517 A CU vector in the constant pool is a sequence of @code{offset_type}
43518 values. The first value is the number of CU indices in the vector.
43519 Each subsequent value is the index and symbol attributes of a CU in
43520 the CU list. This element in the hash table is used to indicate which
43521 CUs define the symbol and how the symbol is used.
43522 See below for the format of each CU index+attributes entry.
43524 A string in the constant pool is zero-terminated.
43527 Attributes were added to CU index values in @code{.gdb_index} version 7.
43528 If a symbol has multiple uses within a CU then there is one
43529 CU index+attributes value for each use.
43531 The format of each CU index+attributes entry is as follows
43537 This is the index of the CU in the CU list.
43539 These bits are reserved for future purposes and must be zero.
43541 The kind of the symbol in the CU.
43545 This value is reserved and should not be used.
43546 By reserving zero the full @code{offset_type} value is backwards compatible
43547 with previous versions of the index.
43549 The symbol is a type.
43551 The symbol is a variable or an enum value.
43553 The symbol is a function.
43555 Any other kind of symbol.
43557 These values are reserved.
43561 This bit is zero if the value is global and one if it is static.
43563 The determination of whether a symbol is global or static is complicated.
43564 The authorative reference is the file @file{dwarf2read.c} in
43565 @value{GDBN} sources.
43569 This pseudo-code describes the computation of a symbol's kind and
43570 global/static attributes in the index.
43573 is_external = get_attribute (die, DW_AT_external);
43574 language = get_attribute (cu_die, DW_AT_language);
43577 case DW_TAG_typedef:
43578 case DW_TAG_base_type:
43579 case DW_TAG_subrange_type:
43583 case DW_TAG_enumerator:
43585 is_static = (language != CPLUS && language != JAVA);
43587 case DW_TAG_subprogram:
43589 is_static = ! (is_external || language == ADA);
43591 case DW_TAG_constant:
43593 is_static = ! is_external;
43595 case DW_TAG_variable:
43597 is_static = ! is_external;
43599 case DW_TAG_namespace:
43603 case DW_TAG_class_type:
43604 case DW_TAG_interface_type:
43605 case DW_TAG_structure_type:
43606 case DW_TAG_union_type:
43607 case DW_TAG_enumeration_type:
43609 is_static = (language != CPLUS && language != JAVA);
43617 @appendix Manual pages
43621 * gdb man:: The GNU Debugger man page
43622 * gdbserver man:: Remote Server for the GNU Debugger man page
43623 * gcore man:: Generate a core file of a running program
43624 * gdbinit man:: gdbinit scripts
43630 @c man title gdb The GNU Debugger
43632 @c man begin SYNOPSIS gdb
43633 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43634 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43635 [@option{-b}@w{ }@var{bps}]
43636 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43637 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43638 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43639 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43640 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43643 @c man begin DESCRIPTION gdb
43644 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43645 going on ``inside'' another program while it executes -- or what another
43646 program was doing at the moment it crashed.
43648 @value{GDBN} can do four main kinds of things (plus other things in support of
43649 these) to help you catch bugs in the act:
43653 Start your program, specifying anything that might affect its behavior.
43656 Make your program stop on specified conditions.
43659 Examine what has happened, when your program has stopped.
43662 Change things in your program, so you can experiment with correcting the
43663 effects of one bug and go on to learn about another.
43666 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43669 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43670 commands from the terminal until you tell it to exit with the @value{GDBN}
43671 command @code{quit}. You can get online help from @value{GDBN} itself
43672 by using the command @code{help}.
43674 You can run @code{gdb} with no arguments or options; but the most
43675 usual way to start @value{GDBN} is with one argument or two, specifying an
43676 executable program as the argument:
43682 You can also start with both an executable program and a core file specified:
43688 You can, instead, specify a process ID as a second argument, if you want
43689 to debug a running process:
43697 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43698 named @file{1234}; @value{GDBN} does check for a core file first).
43699 With option @option{-p} you can omit the @var{program} filename.
43701 Here are some of the most frequently needed @value{GDBN} commands:
43703 @c pod2man highlights the right hand side of the @item lines.
43705 @item break [@var{file}:]@var{functiop}
43706 Set a breakpoint at @var{function} (in @var{file}).
43708 @item run [@var{arglist}]
43709 Start your program (with @var{arglist}, if specified).
43712 Backtrace: display the program stack.
43714 @item print @var{expr}
43715 Display the value of an expression.
43718 Continue running your program (after stopping, e.g. at a breakpoint).
43721 Execute next program line (after stopping); step @emph{over} any
43722 function calls in the line.
43724 @item edit [@var{file}:]@var{function}
43725 look at the program line where it is presently stopped.
43727 @item list [@var{file}:]@var{function}
43728 type the text of the program in the vicinity of where it is presently stopped.
43731 Execute next program line (after stopping); step @emph{into} any
43732 function calls in the line.
43734 @item help [@var{name}]
43735 Show information about @value{GDBN} command @var{name}, or general information
43736 about using @value{GDBN}.
43739 Exit from @value{GDBN}.
43743 For full details on @value{GDBN},
43744 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43745 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43746 as the @code{gdb} entry in the @code{info} program.
43750 @c man begin OPTIONS gdb
43751 Any arguments other than options specify an executable
43752 file and core file (or process ID); that is, the first argument
43753 encountered with no
43754 associated option flag is equivalent to a @option{-se} option, and the second,
43755 if any, is equivalent to a @option{-c} option if it's the name of a file.
43757 both long and short forms; both are shown here. The long forms are also
43758 recognized if you truncate them, so long as enough of the option is
43759 present to be unambiguous. (If you prefer, you can flag option
43760 arguments with @option{+} rather than @option{-}, though we illustrate the
43761 more usual convention.)
43763 All the options and command line arguments you give are processed
43764 in sequential order. The order makes a difference when the @option{-x}
43770 List all options, with brief explanations.
43772 @item -symbols=@var{file}
43773 @itemx -s @var{file}
43774 Read symbol table from file @var{file}.
43777 Enable writing into executable and core files.
43779 @item -exec=@var{file}
43780 @itemx -e @var{file}
43781 Use file @var{file} as the executable file to execute when
43782 appropriate, and for examining pure data in conjunction with a core
43785 @item -se=@var{file}
43786 Read symbol table from file @var{file} and use it as the executable
43789 @item -core=@var{file}
43790 @itemx -c @var{file}
43791 Use file @var{file} as a core dump to examine.
43793 @item -command=@var{file}
43794 @itemx -x @var{file}
43795 Execute @value{GDBN} commands from file @var{file}.
43797 @item -ex @var{command}
43798 Execute given @value{GDBN} @var{command}.
43800 @item -directory=@var{directory}
43801 @itemx -d @var{directory}
43802 Add @var{directory} to the path to search for source files.
43805 Do not execute commands from @file{~/.gdbinit}.
43809 Do not execute commands from any @file{.gdbinit} initialization files.
43813 ``Quiet''. Do not print the introductory and copyright messages. These
43814 messages are also suppressed in batch mode.
43817 Run in batch mode. Exit with status @code{0} after processing all the command
43818 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43819 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43820 commands in the command files.
43822 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43823 download and run a program on another computer; in order to make this
43824 more useful, the message
43827 Program exited normally.
43831 (which is ordinarily issued whenever a program running under @value{GDBN} control
43832 terminates) is not issued when running in batch mode.
43834 @item -cd=@var{directory}
43835 Run @value{GDBN} using @var{directory} as its working directory,
43836 instead of the current directory.
43840 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43841 @value{GDBN} to output the full file name and line number in a standard,
43842 recognizable fashion each time a stack frame is displayed (which
43843 includes each time the program stops). This recognizable format looks
43844 like two @samp{\032} characters, followed by the file name, line number
43845 and character position separated by colons, and a newline. The
43846 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43847 characters as a signal to display the source code for the frame.
43850 Set the line speed (baud rate or bits per second) of any serial
43851 interface used by @value{GDBN} for remote debugging.
43853 @item -tty=@var{device}
43854 Run using @var{device} for your program's standard input and output.
43858 @c man begin SEEALSO gdb
43860 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43861 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43862 documentation are properly installed at your site, the command
43869 should give you access to the complete manual.
43871 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43872 Richard M. Stallman and Roland H. Pesch, July 1991.
43876 @node gdbserver man
43877 @heading gdbserver man
43879 @c man title gdbserver Remote Server for the GNU Debugger
43881 @c man begin SYNOPSIS gdbserver
43882 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43884 gdbserver --attach @var{comm} @var{pid}
43886 gdbserver --multi @var{comm}
43890 @c man begin DESCRIPTION gdbserver
43891 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43892 than the one which is running the program being debugged.
43895 @subheading Usage (server (target) side)
43898 Usage (server (target) side):
43901 First, you need to have a copy of the program you want to debug put onto
43902 the target system. The program can be stripped to save space if needed, as
43903 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43904 the @value{GDBN} running on the host system.
43906 To use the server, you log on to the target system, and run the @command{gdbserver}
43907 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43908 your program, and (c) its arguments. The general syntax is:
43911 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43914 For example, using a serial port, you might say:
43918 @c @file would wrap it as F</dev/com1>.
43919 target> gdbserver /dev/com1 emacs foo.txt
43922 target> gdbserver @file{/dev/com1} emacs foo.txt
43926 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43927 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43928 waits patiently for the host @value{GDBN} to communicate with it.
43930 To use a TCP connection, you could say:
43933 target> gdbserver host:2345 emacs foo.txt
43936 This says pretty much the same thing as the last example, except that we are
43937 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43938 that we are expecting to see a TCP connection from @code{host} to local TCP port
43939 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43940 want for the port number as long as it does not conflict with any existing TCP
43941 ports on the target system. This same port number must be used in the host
43942 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43943 you chose a port number that conflicts with another service, @command{gdbserver} will
43944 print an error message and exit.
43946 @command{gdbserver} can also attach to running programs.
43947 This is accomplished via the @option{--attach} argument. The syntax is:
43950 target> gdbserver --attach @var{comm} @var{pid}
43953 @var{pid} is the process ID of a currently running process. It isn't
43954 necessary to point @command{gdbserver} at a binary for the running process.
43956 To start @code{gdbserver} without supplying an initial command to run
43957 or process ID to attach, use the @option{--multi} command line option.
43958 In such case you should connect using @kbd{target extended-remote} to start
43959 the program you want to debug.
43962 target> gdbserver --multi @var{comm}
43966 @subheading Usage (host side)
43972 You need an unstripped copy of the target program on your host system, since
43973 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43974 would, with the target program as the first argument. (You may need to use the
43975 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43976 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43977 new command you need to know about is @code{target remote}
43978 (or @code{target extended-remote}). Its argument is either
43979 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43980 descriptor. For example:
43984 @c @file would wrap it as F</dev/ttyb>.
43985 (gdb) target remote /dev/ttyb
43988 (gdb) target remote @file{/dev/ttyb}
43993 communicates with the server via serial line @file{/dev/ttyb}, and:
43996 (gdb) target remote the-target:2345
44000 communicates via a TCP connection to port 2345 on host `the-target', where
44001 you previously started up @command{gdbserver} with the same port number. Note that for
44002 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44003 command, otherwise you may get an error that looks something like
44004 `Connection refused'.
44006 @command{gdbserver} can also debug multiple inferiors at once,
44009 the @value{GDBN} manual in node @code{Inferiors and Programs}
44010 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44013 @ref{Inferiors and Programs}.
44015 In such case use the @code{extended-remote} @value{GDBN} command variant:
44018 (gdb) target extended-remote the-target:2345
44021 The @command{gdbserver} option @option{--multi} may or may not be used in such
44025 @c man begin OPTIONS gdbserver
44026 There are three different modes for invoking @command{gdbserver}:
44031 Debug a specific program specified by its program name:
44034 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44037 The @var{comm} parameter specifies how should the server communicate
44038 with @value{GDBN}; it is either a device name (to use a serial line),
44039 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44040 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44041 debug in @var{prog}. Any remaining arguments will be passed to the
44042 program verbatim. When the program exits, @value{GDBN} will close the
44043 connection, and @code{gdbserver} will exit.
44046 Debug a specific program by specifying the process ID of a running
44050 gdbserver --attach @var{comm} @var{pid}
44053 The @var{comm} parameter is as described above. Supply the process ID
44054 of a running program in @var{pid}; @value{GDBN} will do everything
44055 else. Like with the previous mode, when the process @var{pid} exits,
44056 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44059 Multi-process mode -- debug more than one program/process:
44062 gdbserver --multi @var{comm}
44065 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44066 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44067 close the connection when a process being debugged exits, so you can
44068 debug several processes in the same session.
44071 In each of the modes you may specify these options:
44076 List all options, with brief explanations.
44079 This option causes @command{gdbserver} to print its version number and exit.
44082 @command{gdbserver} will attach to a running program. The syntax is:
44085 target> gdbserver --attach @var{comm} @var{pid}
44088 @var{pid} is the process ID of a currently running process. It isn't
44089 necessary to point @command{gdbserver} at a binary for the running process.
44092 To start @code{gdbserver} without supplying an initial command to run
44093 or process ID to attach, use this command line option.
44094 Then you can connect using @kbd{target extended-remote} and start
44095 the program you want to debug. The syntax is:
44098 target> gdbserver --multi @var{comm}
44102 Instruct @code{gdbserver} to display extra status information about the debugging
44104 This option is intended for @code{gdbserver} development and for bug reports to
44107 @item --remote-debug
44108 Instruct @code{gdbserver} to display remote protocol debug output.
44109 This option is intended for @code{gdbserver} development and for bug reports to
44113 Specify a wrapper to launch programs
44114 for debugging. The option should be followed by the name of the
44115 wrapper, then any command-line arguments to pass to the wrapper, then
44116 @kbd{--} indicating the end of the wrapper arguments.
44119 By default, @command{gdbserver} keeps the listening TCP port open, so that
44120 additional connections are possible. However, if you start @code{gdbserver}
44121 with the @option{--once} option, it will stop listening for any further
44122 connection attempts after connecting to the first @value{GDBN} session.
44124 @c --disable-packet is not documented for users.
44126 @c --disable-randomization and --no-disable-randomization are superseded by
44127 @c QDisableRandomization.
44132 @c man begin SEEALSO gdbserver
44134 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44135 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44136 documentation are properly installed at your site, the command
44142 should give you access to the complete manual.
44144 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44145 Richard M. Stallman and Roland H. Pesch, July 1991.
44152 @c man title gcore Generate a core file of a running program
44155 @c man begin SYNOPSIS gcore
44156 gcore [-o @var{filename}] @var{pid}
44160 @c man begin DESCRIPTION gcore
44161 Generate a core dump of a running program with process ID @var{pid}.
44162 Produced file is equivalent to a kernel produced core file as if the process
44163 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
44164 limit). Unlike after a crash, after @command{gcore} the program remains
44165 running without any change.
44168 @c man begin OPTIONS gcore
44170 @item -o @var{filename}
44171 The optional argument
44172 @var{filename} specifies the file name where to put the core dump.
44173 If not specified, the file name defaults to @file{core.@var{pid}},
44174 where @var{pid} is the running program process ID.
44178 @c man begin SEEALSO gcore
44180 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44181 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44182 documentation are properly installed at your site, the command
44189 should give you access to the complete manual.
44191 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44192 Richard M. Stallman and Roland H. Pesch, July 1991.
44199 @c man title gdbinit GDB initialization scripts
44202 @c man begin SYNOPSIS gdbinit
44203 @ifset SYSTEM_GDBINIT
44204 @value{SYSTEM_GDBINIT}
44213 @c man begin DESCRIPTION gdbinit
44214 These files contain @value{GDBN} commands to automatically execute during
44215 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44218 the @value{GDBN} manual in node @code{Sequences}
44219 -- shell command @code{info -f gdb -n Sequences}.
44225 Please read more in
44227 the @value{GDBN} manual in node @code{Startup}
44228 -- shell command @code{info -f gdb -n Startup}.
44235 @ifset SYSTEM_GDBINIT
44236 @item @value{SYSTEM_GDBINIT}
44238 @ifclear SYSTEM_GDBINIT
44239 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44241 System-wide initialization file. It is executed unless user specified
44242 @value{GDBN} option @code{-nx} or @code{-n}.
44245 the @value{GDBN} manual in node @code{System-wide configuration}
44246 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44249 @ref{System-wide configuration}.
44253 User initialization file. It is executed unless user specified
44254 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44257 Initialization file for current directory. It may need to be enabled with
44258 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44261 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44262 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44265 @ref{Init File in the Current Directory}.
44270 @c man begin SEEALSO gdbinit
44272 gdb(1), @code{info -f gdb -n Startup}
44274 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44275 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44276 documentation are properly installed at your site, the command
44282 should give you access to the complete manual.
44284 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44285 Richard M. Stallman and Roland H. Pesch, July 1991.
44291 @node GNU Free Documentation License
44292 @appendix GNU Free Documentation License
44295 @node Concept Index
44296 @unnumbered Concept Index
44300 @node Command and Variable Index
44301 @unnumbered Command, Variable, and Function Index
44306 % I think something like @@colophon should be in texinfo. In the
44308 \long\def\colophon{\hbox to0pt{}\vfill
44309 \centerline{The body of this manual is set in}
44310 \centerline{\fontname\tenrm,}
44311 \centerline{with headings in {\bf\fontname\tenbf}}
44312 \centerline{and examples in {\tt\fontname\tentt}.}
44313 \centerline{{\it\fontname\tenit\/},}
44314 \centerline{{\bf\fontname\tenbf}, and}
44315 \centerline{{\sl\fontname\tensl\/}}
44316 \centerline{are used for emphasis.}\vfill}
44318 % Blame: doc@@cygnus.com, 1991.