1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-1996, 1998-2012 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.
11 @settitle Debugging with @value{GDBN}
12 @setchapternewpage odd
24 @c readline appendices use @vindex, @findex and @ftable,
25 @c annotate.texi and gdbmi use @findex.
29 @c !!set GDB manual's edition---not the same as GDB version!
30 @c This is updated by GNU Press.
33 @c !!set GDB edit command default editor
36 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
38 @c This is a dir.info fragment to support semi-automated addition of
39 @c manuals to an info tree.
40 @dircategory Software development
42 * Gdb: (gdb). The GNU debugger.
46 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
47 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
48 Free Software Foundation, Inc.
50 Permission is granted to copy, distribute and/or modify this document
51 under the terms of the GNU Free Documentation License, Version 1.3 or
52 any later version published by the Free Software Foundation; with the
53 Invariant Sections being ``Free Software'' and ``Free Software Needs
54 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
55 and with the Back-Cover Texts as in (a) below.
57 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
58 this GNU Manual. Buying copies from GNU Press supports the FSF in
59 developing GNU and promoting software freedom.''
63 This file documents the @sc{gnu} debugger @value{GDBN}.
65 This is the @value{EDITION} Edition, of @cite{Debugging with
66 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
67 @ifset VERSION_PACKAGE
68 @value{VERSION_PACKAGE}
70 Version @value{GDBVN}.
76 @title Debugging with @value{GDBN}
77 @subtitle The @sc{gnu} Source-Level Debugger
79 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
80 @ifset VERSION_PACKAGE
82 @subtitle @value{VERSION_PACKAGE}
84 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
88 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
89 \hfill {\it Debugging with @value{GDBN}}\par
90 \hfill \TeX{}info \texinfoversion\par
94 @vskip 0pt plus 1filll
95 Published by the Free Software Foundation @*
96 51 Franklin Street, Fifth Floor,
97 Boston, MA 02110-1301, USA@*
98 ISBN 978-0-9831592-3-0 @*
105 @node Top, Summary, (dir), (dir)
107 @top Debugging with @value{GDBN}
109 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
111 This is the @value{EDITION} Edition, for @value{GDBN}
112 @ifset VERSION_PACKAGE
113 @value{VERSION_PACKAGE}
115 Version @value{GDBVN}.
117 Copyright (C) 1988-2010 Free Software Foundation, Inc.
119 This edition of the GDB manual is dedicated to the memory of Fred
120 Fish. Fred was a long-standing contributor to GDB and to Free
121 software in general. We will miss him.
124 * Summary:: Summary of @value{GDBN}
125 * Sample Session:: A sample @value{GDBN} session
127 * Invocation:: Getting in and out of @value{GDBN}
128 * Commands:: @value{GDBN} commands
129 * Running:: Running programs under @value{GDBN}
130 * Stopping:: Stopping and continuing
131 * Reverse Execution:: Running programs backward
132 * Process Record and Replay:: Recording inferior's execution and replaying it
133 * Stack:: Examining the stack
134 * Source:: Examining source files
135 * Data:: Examining data
136 * Optimized Code:: Debugging optimized code
137 * Macros:: Preprocessor Macros
138 * Tracepoints:: Debugging remote targets non-intrusively
139 * Overlays:: Debugging programs that use overlays
141 * Languages:: Using @value{GDBN} with different languages
143 * Symbols:: Examining the symbol table
144 * Altering:: Altering execution
145 * GDB Files:: @value{GDBN} files
146 * Targets:: Specifying a debugging target
147 * Remote Debugging:: Debugging remote programs
148 * Configurations:: Configuration-specific information
149 * Controlling GDB:: Controlling @value{GDBN}
150 * Extending GDB:: Extending @value{GDBN}
151 * Interpreters:: Command Interpreters
152 * TUI:: @value{GDBN} Text User Interface
153 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
154 * GDB/MI:: @value{GDBN}'s Machine Interface.
155 * Annotations:: @value{GDBN}'s annotation interface.
156 * JIT Interface:: Using the JIT debugging interface.
158 * GDB Bugs:: Reporting bugs in @value{GDBN}
160 @ifset SYSTEM_READLINE
161 * Command Line Editing: (rluserman). Command Line Editing
162 * Using History Interactively: (history). Using History Interactively
164 @ifclear SYSTEM_READLINE
165 * Command Line Editing:: Command Line Editing
166 * Using History Interactively:: Using History Interactively
168 * In Memoriam:: In Memoriam
169 * Formatting Documentation:: How to format and print @value{GDBN} documentation
170 * Installing GDB:: Installing GDB
171 * Maintenance Commands:: Maintenance Commands
172 * Remote Protocol:: GDB Remote Serial Protocol
173 * Agent Expressions:: The GDB Agent Expression Mechanism
174 * Target Descriptions:: How targets can describe themselves to
176 * Operating System Information:: Getting additional information from
178 * Trace File Format:: GDB trace file format
179 * Index Section Format:: .gdb_index section format
180 * Copying:: GNU General Public License says
181 how you can copy and share GDB
182 * GNU Free Documentation License:: The license for this documentation
191 @unnumbered Summary of @value{GDBN}
193 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
194 going on ``inside'' another program while it executes---or what another
195 program was doing at the moment it crashed.
197 @value{GDBN} can do four main kinds of things (plus other things in support of
198 these) to help you catch bugs in the act:
202 Start your program, specifying anything that might affect its behavior.
205 Make your program stop on specified conditions.
208 Examine what has happened, when your program has stopped.
211 Change things in your program, so you can experiment with correcting the
212 effects of one bug and go on to learn about another.
215 You can use @value{GDBN} to debug programs written in C and C@t{++}.
216 For more information, see @ref{Supported Languages,,Supported Languages}.
217 For more information, see @ref{C,,C and C++}.
219 Support for D is partial. For information on D, see
223 Support for Modula-2 is partial. For information on Modula-2, see
224 @ref{Modula-2,,Modula-2}.
226 Support for OpenCL C is partial. For information on OpenCL C, see
227 @ref{OpenCL C,,OpenCL C}.
230 Debugging Pascal programs which use sets, subranges, file variables, or
231 nested functions does not currently work. @value{GDBN} does not support
232 entering expressions, printing values, or similar features using Pascal
236 @value{GDBN} can be used to debug programs written in Fortran, although
237 it may be necessary to refer to some variables with a trailing
240 @value{GDBN} can be used to debug programs written in Objective-C,
241 using either the Apple/NeXT or the GNU Objective-C runtime.
244 * Free Software:: Freely redistributable software
245 * Contributors:: Contributors to GDB
249 @unnumberedsec Free Software
251 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
252 General Public License
253 (GPL). The GPL gives you the freedom to copy or adapt a licensed
254 program---but every person getting a copy also gets with it the
255 freedom to modify that copy (which means that they must get access to
256 the source code), and the freedom to distribute further copies.
257 Typical software companies use copyrights to limit your freedoms; the
258 Free Software Foundation uses the GPL to preserve these freedoms.
260 Fundamentally, the General Public License is a license which says that
261 you have these freedoms and that you cannot take these freedoms away
264 @unnumberedsec Free Software Needs Free Documentation
266 The biggest deficiency in the free software community today is not in
267 the software---it is the lack of good free documentation that we can
268 include with the free software. Many of our most important
269 programs do not come with free reference manuals and free introductory
270 texts. Documentation is an essential part of any software package;
271 when an important free software package does not come with a free
272 manual and a free tutorial, that is a major gap. We have many such
275 Consider Perl, for instance. The tutorial manuals that people
276 normally use are non-free. How did this come about? Because the
277 authors of those manuals published them with restrictive terms---no
278 copying, no modification, source files not available---which exclude
279 them from the free software world.
281 That wasn't the first time this sort of thing happened, and it was far
282 from the last. Many times we have heard a GNU user eagerly describe a
283 manual that he is writing, his intended contribution to the community,
284 only to learn that he had ruined everything by signing a publication
285 contract to make it non-free.
287 Free documentation, like free software, is a matter of freedom, not
288 price. The problem with the non-free manual is not that publishers
289 charge a price for printed copies---that in itself is fine. (The Free
290 Software Foundation sells printed copies of manuals, too.) The
291 problem is the restrictions on the use of the manual. Free manuals
292 are available in source code form, and give you permission to copy and
293 modify. Non-free manuals do not allow this.
295 The criteria of freedom for a free manual are roughly the same as for
296 free software. Redistribution (including the normal kinds of
297 commercial redistribution) must be permitted, so that the manual can
298 accompany every copy of the program, both on-line and on paper.
300 Permission for modification of the technical content is crucial too.
301 When people modify the software, adding or changing features, if they
302 are conscientious they will change the manual too---so they can
303 provide accurate and clear documentation for the modified program. A
304 manual that leaves you no choice but to write a new manual to document
305 a changed version of the program is not really available to our
308 Some kinds of limits on the way modification is handled are
309 acceptable. For example, requirements to preserve the original
310 author's copyright notice, the distribution terms, or the list of
311 authors, are ok. It is also no problem to require modified versions
312 to include notice that they were modified. Even entire sections that
313 may not be deleted or changed are acceptable, as long as they deal
314 with nontechnical topics (like this one). These kinds of restrictions
315 are acceptable because they don't obstruct the community's normal use
318 However, it must be possible to modify all the @emph{technical}
319 content of the manual, and then distribute the result in all the usual
320 media, through all the usual channels. Otherwise, the restrictions
321 obstruct the use of the manual, it is not free, and we need another
322 manual to replace it.
324 Please spread the word about this issue. Our community continues to
325 lose manuals to proprietary publishing. If we spread the word that
326 free software needs free reference manuals and free tutorials, perhaps
327 the next person who wants to contribute by writing documentation will
328 realize, before it is too late, that only free manuals contribute to
329 the free software community.
331 If you are writing documentation, please insist on publishing it under
332 the GNU Free Documentation License or another free documentation
333 license. Remember that this decision requires your approval---you
334 don't have to let the publisher decide. Some commercial publishers
335 will use a free license if you insist, but they will not propose the
336 option; it is up to you to raise the issue and say firmly that this is
337 what you want. If the publisher you are dealing with refuses, please
338 try other publishers. If you're not sure whether a proposed license
339 is free, write to @email{licensing@@gnu.org}.
341 You can encourage commercial publishers to sell more free, copylefted
342 manuals and tutorials by buying them, and particularly by buying
343 copies from the publishers that paid for their writing or for major
344 improvements. Meanwhile, try to avoid buying non-free documentation
345 at all. Check the distribution terms of a manual before you buy it,
346 and insist that whoever seeks your business must respect your freedom.
347 Check the history of the book, and try to reward the publishers that
348 have paid or pay the authors to work on it.
350 The Free Software Foundation maintains a list of free documentation
351 published by other publishers, at
352 @url{http://www.fsf.org/doc/other-free-books.html}.
355 @unnumberedsec Contributors to @value{GDBN}
357 Richard Stallman was the original author of @value{GDBN}, and of many
358 other @sc{gnu} programs. Many others have contributed to its
359 development. This section attempts to credit major contributors. One
360 of the virtues of free software is that everyone is free to contribute
361 to it; with regret, we cannot actually acknowledge everyone here. The
362 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
363 blow-by-blow account.
365 Changes much prior to version 2.0 are lost in the mists of time.
368 @emph{Plea:} Additions to this section are particularly welcome. If you
369 or your friends (or enemies, to be evenhanded) have been unfairly
370 omitted from this list, we would like to add your names!
373 So that they may not regard their many labors as thankless, we
374 particularly thank those who shepherded @value{GDBN} through major
376 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
377 Jim Blandy (release 4.18);
378 Jason Molenda (release 4.17);
379 Stan Shebs (release 4.14);
380 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
381 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
382 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
383 Jim Kingdon (releases 3.5, 3.4, and 3.3);
384 and Randy Smith (releases 3.2, 3.1, and 3.0).
386 Richard Stallman, assisted at various times by Peter TerMaat, Chris
387 Hanson, and Richard Mlynarik, handled releases through 2.8.
389 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
390 in @value{GDBN}, with significant additional contributions from Per
391 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
392 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
393 much general update work leading to release 3.0).
395 @value{GDBN} uses the BFD subroutine library to examine multiple
396 object-file formats; BFD was a joint project of David V.
397 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
399 David Johnson wrote the original COFF support; Pace Willison did
400 the original support for encapsulated COFF.
402 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
404 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
405 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
407 Jean-Daniel Fekete contributed Sun 386i support.
408 Chris Hanson improved the HP9000 support.
409 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
410 David Johnson contributed Encore Umax support.
411 Jyrki Kuoppala contributed Altos 3068 support.
412 Jeff Law contributed HP PA and SOM support.
413 Keith Packard contributed NS32K support.
414 Doug Rabson contributed Acorn Risc Machine support.
415 Bob Rusk contributed Harris Nighthawk CX-UX support.
416 Chris Smith contributed Convex support (and Fortran debugging).
417 Jonathan Stone contributed Pyramid support.
418 Michael Tiemann contributed SPARC support.
419 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
420 Pace Willison contributed Intel 386 support.
421 Jay Vosburgh contributed Symmetry support.
422 Marko Mlinar contributed OpenRISC 1000 support.
424 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
426 Rich Schaefer and Peter Schauer helped with support of SunOS shared
429 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
430 about several machine instruction sets.
432 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
433 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
434 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
435 and RDI targets, respectively.
437 Brian Fox is the author of the readline libraries providing
438 command-line editing and command history.
440 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
441 Modula-2 support, and contributed the Languages chapter of this manual.
443 Fred Fish wrote most of the support for Unix System Vr4.
444 He also enhanced the command-completion support to cover C@t{++} overloaded
447 Hitachi America (now Renesas America), Ltd. sponsored the support for
448 H8/300, H8/500, and Super-H processors.
450 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
452 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
455 Toshiba sponsored the support for the TX39 Mips processor.
457 Matsushita sponsored the support for the MN10200 and MN10300 processors.
459 Fujitsu sponsored the support for SPARClite and FR30 processors.
461 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
464 Michael Snyder added support for tracepoints.
466 Stu Grossman wrote gdbserver.
468 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
469 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
471 The following people at the Hewlett-Packard Company contributed
472 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
473 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
474 compiler, and the Text User Interface (nee Terminal User Interface):
475 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
476 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
477 provided HP-specific information in this manual.
479 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
480 Robert Hoehne made significant contributions to the DJGPP port.
482 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
483 development since 1991. Cygnus engineers who have worked on @value{GDBN}
484 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
485 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
486 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
487 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
488 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
489 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
490 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
491 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
492 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
493 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
494 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
495 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
496 Zuhn have made contributions both large and small.
498 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
499 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
501 Jim Blandy added support for preprocessor macros, while working for Red
504 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
505 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
506 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
507 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
508 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
509 with the migration of old architectures to this new framework.
511 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
512 unwinder framework, this consisting of a fresh new design featuring
513 frame IDs, independent frame sniffers, and the sentinel frame. Mark
514 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
515 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
516 trad unwinders. The architecture-specific changes, each involving a
517 complete rewrite of the architecture's frame code, were carried out by
518 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
519 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
520 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
521 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
524 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
525 Tensilica, Inc.@: contributed support for Xtensa processors. Others
526 who have worked on the Xtensa port of @value{GDBN} in the past include
527 Steve Tjiang, John Newlin, and Scott Foehner.
529 Michael Eager and staff of Xilinx, Inc., contributed support for the
530 Xilinx MicroBlaze architecture.
533 @chapter A Sample @value{GDBN} Session
535 You can use this manual at your leisure to read all about @value{GDBN}.
536 However, a handful of commands are enough to get started using the
537 debugger. This chapter illustrates those commands.
540 In this sample session, we emphasize user input like this: @b{input},
541 to make it easier to pick out from the surrounding output.
544 @c FIXME: this example may not be appropriate for some configs, where
545 @c FIXME...primary interest is in remote use.
547 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
548 processor) exhibits the following bug: sometimes, when we change its
549 quote strings from the default, the commands used to capture one macro
550 definition within another stop working. In the following short @code{m4}
551 session, we define a macro @code{foo} which expands to @code{0000}; we
552 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
553 same thing. However, when we change the open quote string to
554 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
555 procedure fails to define a new synonym @code{baz}:
564 @b{define(bar,defn(`foo'))}
568 @b{changequote(<QUOTE>,<UNQUOTE>)}
570 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
573 m4: End of input: 0: fatal error: EOF in string
577 Let us use @value{GDBN} to try to see what is going on.
580 $ @b{@value{GDBP} m4}
581 @c FIXME: this falsifies the exact text played out, to permit smallbook
582 @c FIXME... format to come out better.
583 @value{GDBN} is free software and you are welcome to distribute copies
584 of it under certain conditions; type "show copying" to see
586 There is absolutely no warranty for @value{GDBN}; type "show warranty"
589 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
594 @value{GDBN} reads only enough symbol data to know where to find the
595 rest when needed; as a result, the first prompt comes up very quickly.
596 We now tell @value{GDBN} to use a narrower display width than usual, so
597 that examples fit in this manual.
600 (@value{GDBP}) @b{set width 70}
604 We need to see how the @code{m4} built-in @code{changequote} works.
605 Having looked at the source, we know the relevant subroutine is
606 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
607 @code{break} command.
610 (@value{GDBP}) @b{break m4_changequote}
611 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
615 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
616 control; as long as control does not reach the @code{m4_changequote}
617 subroutine, the program runs as usual:
620 (@value{GDBP}) @b{run}
621 Starting program: /work/Editorial/gdb/gnu/m4/m4
629 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
630 suspends execution of @code{m4}, displaying information about the
631 context where it stops.
634 @b{changequote(<QUOTE>,<UNQUOTE>)}
636 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
638 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
642 Now we use the command @code{n} (@code{next}) to advance execution to
643 the next line of the current function.
647 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
652 @code{set_quotes} looks like a promising subroutine. We can go into it
653 by using the command @code{s} (@code{step}) instead of @code{next}.
654 @code{step} goes to the next line to be executed in @emph{any}
655 subroutine, so it steps into @code{set_quotes}.
659 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
661 530 if (lquote != def_lquote)
665 The display that shows the subroutine where @code{m4} is now
666 suspended (and its arguments) is called a stack frame display. It
667 shows a summary of the stack. We can use the @code{backtrace}
668 command (which can also be spelled @code{bt}), to see where we are
669 in the stack as a whole: the @code{backtrace} command displays a
670 stack frame for each active subroutine.
673 (@value{GDBP}) @b{bt}
674 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
676 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
678 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
679 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
681 #4 0x79dc in expand_input () at macro.c:40
682 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
686 We step through a few more lines to see what happens. The first two
687 times, we can use @samp{s}; the next two times we use @code{n} to avoid
688 falling into the @code{xstrdup} subroutine.
692 0x3b5c 532 if (rquote != def_rquote)
694 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
695 def_lquote : xstrdup(lq);
697 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
700 538 len_lquote = strlen(rquote);
704 The last line displayed looks a little odd; we can examine the variables
705 @code{lquote} and @code{rquote} to see if they are in fact the new left
706 and right quotes we specified. We use the command @code{p}
707 (@code{print}) to see their values.
710 (@value{GDBP}) @b{p lquote}
711 $1 = 0x35d40 "<QUOTE>"
712 (@value{GDBP}) @b{p rquote}
713 $2 = 0x35d50 "<UNQUOTE>"
717 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
718 To look at some context, we can display ten lines of source
719 surrounding the current line with the @code{l} (@code{list}) command.
725 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
727 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
730 538 len_lquote = strlen(rquote);
731 539 len_rquote = strlen(lquote);
738 Let us step past the two lines that set @code{len_lquote} and
739 @code{len_rquote}, and then examine the values of those variables.
743 539 len_rquote = strlen(lquote);
746 (@value{GDBP}) @b{p len_lquote}
748 (@value{GDBP}) @b{p len_rquote}
753 That certainly looks wrong, assuming @code{len_lquote} and
754 @code{len_rquote} are meant to be the lengths of @code{lquote} and
755 @code{rquote} respectively. We can set them to better values using
756 the @code{p} command, since it can print the value of
757 any expression---and that expression can include subroutine calls and
761 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
763 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
768 Is that enough to fix the problem of using the new quotes with the
769 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
770 executing with the @code{c} (@code{continue}) command, and then try the
771 example that caused trouble initially:
777 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
784 Success! The new quotes now work just as well as the default ones. The
785 problem seems to have been just the two typos defining the wrong
786 lengths. We allow @code{m4} exit by giving it an EOF as input:
790 Program exited normally.
794 The message @samp{Program exited normally.} is from @value{GDBN}; it
795 indicates @code{m4} has finished executing. We can end our @value{GDBN}
796 session with the @value{GDBN} @code{quit} command.
799 (@value{GDBP}) @b{quit}
803 @chapter Getting In and Out of @value{GDBN}
805 This chapter discusses how to start @value{GDBN}, and how to get out of it.
809 type @samp{@value{GDBP}} to start @value{GDBN}.
811 type @kbd{quit} or @kbd{Ctrl-d} to exit.
815 * Invoking GDB:: How to start @value{GDBN}
816 * Quitting GDB:: How to quit @value{GDBN}
817 * Shell Commands:: How to use shell commands inside @value{GDBN}
818 * Logging Output:: How to log @value{GDBN}'s output to a file
822 @section Invoking @value{GDBN}
824 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
825 @value{GDBN} reads commands from the terminal until you tell it to exit.
827 You can also run @code{@value{GDBP}} with a variety of arguments and options,
828 to specify more of your debugging environment at the outset.
830 The command-line options described here are designed
831 to cover a variety of situations; in some environments, some of these
832 options may effectively be unavailable.
834 The most usual way to start @value{GDBN} is with one argument,
835 specifying an executable program:
838 @value{GDBP} @var{program}
842 You can also start with both an executable program and a core file
846 @value{GDBP} @var{program} @var{core}
849 You can, instead, specify a process ID as a second argument, if you want
850 to debug a running process:
853 @value{GDBP} @var{program} 1234
857 would attach @value{GDBN} to process @code{1234} (unless you also have a file
858 named @file{1234}; @value{GDBN} does check for a core file first).
860 Taking advantage of the second command-line argument requires a fairly
861 complete operating system; when you use @value{GDBN} as a remote
862 debugger attached to a bare board, there may not be any notion of
863 ``process'', and there is often no way to get a core dump. @value{GDBN}
864 will warn you if it is unable to attach or to read core dumps.
866 You can optionally have @code{@value{GDBP}} pass any arguments after the
867 executable file to the inferior using @code{--args}. This option stops
870 @value{GDBP} --args gcc -O2 -c foo.c
872 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
873 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
875 You can run @code{@value{GDBP}} without printing the front material, which describes
876 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
883 You can further control how @value{GDBN} starts up by using command-line
884 options. @value{GDBN} itself can remind you of the options available.
894 to display all available options and briefly describe their use
895 (@samp{@value{GDBP} -h} is a shorter equivalent).
897 All options and command line arguments you give are processed
898 in sequential order. The order makes a difference when the
899 @samp{-x} option is used.
903 * File Options:: Choosing files
904 * Mode Options:: Choosing modes
905 * Startup:: What @value{GDBN} does during startup
909 @subsection Choosing Files
911 When @value{GDBN} starts, it reads any arguments other than options as
912 specifying an executable file and core file (or process ID). This is
913 the same as if the arguments were specified by the @samp{-se} and
914 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
915 first argument that does not have an associated option flag as
916 equivalent to the @samp{-se} option followed by that argument; and the
917 second argument that does not have an associated option flag, if any, as
918 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
919 If the second argument begins with a decimal digit, @value{GDBN} will
920 first attempt to attach to it as a process, and if that fails, attempt
921 to open it as a corefile. If you have a corefile whose name begins with
922 a digit, you can prevent @value{GDBN} from treating it as a pid by
923 prefixing it with @file{./}, e.g.@: @file{./12345}.
925 If @value{GDBN} has not been configured to included core file support,
926 such as for most embedded targets, then it will complain about a second
927 argument and ignore it.
929 Many options have both long and short forms; both are shown in the
930 following list. @value{GDBN} also recognizes the long forms if you truncate
931 them, so long as enough of the option is present to be unambiguous.
932 (If you prefer, you can flag option arguments with @samp{--} rather
933 than @samp{-}, though we illustrate the more usual convention.)
935 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
936 @c way, both those who look for -foo and --foo in the index, will find
940 @item -symbols @var{file}
942 @cindex @code{--symbols}
944 Read symbol table from file @var{file}.
946 @item -exec @var{file}
948 @cindex @code{--exec}
950 Use file @var{file} as the executable file to execute when appropriate,
951 and for examining pure data in conjunction with a core dump.
955 Read symbol table from file @var{file} and use it as the executable
958 @item -core @var{file}
960 @cindex @code{--core}
962 Use file @var{file} as a core dump to examine.
964 @item -pid @var{number}
965 @itemx -p @var{number}
968 Connect to process ID @var{number}, as with the @code{attach} command.
970 @item -command @var{file}
972 @cindex @code{--command}
974 Execute commands from file @var{file}. The contents of this file is
975 evaluated exactly as the @code{source} command would.
976 @xref{Command Files,, Command files}.
978 @item -eval-command @var{command}
979 @itemx -ex @var{command}
980 @cindex @code{--eval-command}
982 Execute a single @value{GDBN} command.
984 This option may be used multiple times to call multiple commands. It may
985 also be interleaved with @samp{-command} as required.
988 @value{GDBP} -ex 'target sim' -ex 'load' \
989 -x setbreakpoints -ex 'run' a.out
992 @item -directory @var{directory}
993 @itemx -d @var{directory}
994 @cindex @code{--directory}
996 Add @var{directory} to the path to search for source and script files.
1000 @cindex @code{--readnow}
1002 Read each symbol file's entire symbol table immediately, rather than
1003 the default, which is to read it incrementally as it is needed.
1004 This makes startup slower, but makes future operations faster.
1009 @subsection Choosing Modes
1011 You can run @value{GDBN} in various alternative modes---for example, in
1012 batch mode or quiet mode.
1019 Do not execute commands found in any initialization files. Normally,
1020 @value{GDBN} executes the commands in these files after all the command
1021 options and arguments have been processed. @xref{Command Files,,Command
1027 @cindex @code{--quiet}
1028 @cindex @code{--silent}
1030 ``Quiet''. Do not print the introductory and copyright messages. These
1031 messages are also suppressed in batch mode.
1034 @cindex @code{--batch}
1035 Run in batch mode. Exit with status @code{0} after processing all the
1036 command files specified with @samp{-x} (and all commands from
1037 initialization files, if not inhibited with @samp{-n}). Exit with
1038 nonzero status if an error occurs in executing the @value{GDBN} commands
1039 in the command files. Batch mode also disables pagination, sets unlimited
1040 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1041 off} were in effect (@pxref{Messages/Warnings}).
1043 Batch mode may be useful for running @value{GDBN} as a filter, for
1044 example to download and run a program on another computer; in order to
1045 make this more useful, the message
1048 Program exited normally.
1052 (which is ordinarily issued whenever a program running under
1053 @value{GDBN} control terminates) is not issued when running in batch
1057 @cindex @code{--batch-silent}
1058 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1059 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1060 unaffected). This is much quieter than @samp{-silent} and would be useless
1061 for an interactive session.
1063 This is particularly useful when using targets that give @samp{Loading section}
1064 messages, for example.
1066 Note that targets that give their output via @value{GDBN}, as opposed to
1067 writing directly to @code{stdout}, will also be made silent.
1069 @item -return-child-result
1070 @cindex @code{--return-child-result}
1071 The return code from @value{GDBN} will be the return code from the child
1072 process (the process being debugged), with the following exceptions:
1076 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1077 internal error. In this case the exit code is the same as it would have been
1078 without @samp{-return-child-result}.
1080 The user quits with an explicit value. E.g., @samp{quit 1}.
1082 The child process never runs, or is not allowed to terminate, in which case
1083 the exit code will be -1.
1086 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1087 when @value{GDBN} is being used as a remote program loader or simulator
1092 @cindex @code{--nowindows}
1094 ``No windows''. If @value{GDBN} comes with a graphical user interface
1095 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1096 interface. If no GUI is available, this option has no effect.
1100 @cindex @code{--windows}
1102 If @value{GDBN} includes a GUI, then this option requires it to be
1105 @item -cd @var{directory}
1107 Run @value{GDBN} using @var{directory} as its working directory,
1108 instead of the current directory.
1110 @item -data-directory @var{directory}
1111 @cindex @code{--data-directory}
1112 Run @value{GDBN} using @var{directory} as its data directory.
1113 The data directory is where @value{GDBN} searches for its
1114 auxiliary files. @xref{Data Files}.
1118 @cindex @code{--fullname}
1120 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1121 subprocess. It tells @value{GDBN} to output the full file name and line
1122 number in a standard, recognizable fashion each time a stack frame is
1123 displayed (which includes each time your program stops). This
1124 recognizable format looks like two @samp{\032} characters, followed by
1125 the file name, line number and character position separated by colons,
1126 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1127 @samp{\032} characters as a signal to display the source code for the
1131 @cindex @code{--epoch}
1132 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1133 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1134 routines so as to allow Epoch to display values of expressions in a
1137 @item -annotate @var{level}
1138 @cindex @code{--annotate}
1139 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1140 effect is identical to using @samp{set annotate @var{level}}
1141 (@pxref{Annotations}). The annotation @var{level} controls how much
1142 information @value{GDBN} prints together with its prompt, values of
1143 expressions, source lines, and other types of output. Level 0 is the
1144 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1145 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1146 that control @value{GDBN}, and level 2 has been deprecated.
1148 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1152 @cindex @code{--args}
1153 Change interpretation of command line so that arguments following the
1154 executable file are passed as command line arguments to the inferior.
1155 This option stops option processing.
1157 @item -baud @var{bps}
1159 @cindex @code{--baud}
1161 Set the line speed (baud rate or bits per second) of any serial
1162 interface used by @value{GDBN} for remote debugging.
1164 @item -l @var{timeout}
1166 Set the timeout (in seconds) of any communication used by @value{GDBN}
1167 for remote debugging.
1169 @item -tty @var{device}
1170 @itemx -t @var{device}
1171 @cindex @code{--tty}
1173 Run using @var{device} for your program's standard input and output.
1174 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1176 @c resolve the situation of these eventually
1178 @cindex @code{--tui}
1179 Activate the @dfn{Text User Interface} when starting. The Text User
1180 Interface manages several text windows on the terminal, showing
1181 source, assembly, registers and @value{GDBN} command outputs
1182 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1183 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1184 Using @value{GDBN} under @sc{gnu} Emacs}).
1187 @c @cindex @code{--xdb}
1188 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1189 @c For information, see the file @file{xdb_trans.html}, which is usually
1190 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1193 @item -interpreter @var{interp}
1194 @cindex @code{--interpreter}
1195 Use the interpreter @var{interp} for interface with the controlling
1196 program or device. This option is meant to be set by programs which
1197 communicate with @value{GDBN} using it as a back end.
1198 @xref{Interpreters, , Command Interpreters}.
1200 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1201 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1202 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1203 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1204 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1205 @sc{gdb/mi} interfaces are no longer supported.
1208 @cindex @code{--write}
1209 Open the executable and core files for both reading and writing. This
1210 is equivalent to the @samp{set write on} command inside @value{GDBN}
1214 @cindex @code{--statistics}
1215 This option causes @value{GDBN} to print statistics about time and
1216 memory usage after it completes each command and returns to the prompt.
1219 @cindex @code{--version}
1220 This option causes @value{GDBN} to print its version number and
1221 no-warranty blurb, and exit.
1226 @subsection What @value{GDBN} Does During Startup
1227 @cindex @value{GDBN} startup
1229 Here's the description of what @value{GDBN} does during session startup:
1233 Sets up the command interpreter as specified by the command line
1234 (@pxref{Mode Options, interpreter}).
1238 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1239 used when building @value{GDBN}; @pxref{System-wide configuration,
1240 ,System-wide configuration and settings}) and executes all the commands in
1244 Reads the init file (if any) in your home directory@footnote{On
1245 DOS/Windows systems, the home directory is the one pointed to by the
1246 @code{HOME} environment variable.} and executes all the commands in
1250 Processes command line options and operands.
1253 Reads and executes the commands from init file (if any) in the current
1254 working directory. This is only done if the current directory is
1255 different from your home directory. Thus, you can have more than one
1256 init file, one generic in your home directory, and another, specific
1257 to the program you are debugging, in the directory where you invoke
1261 If the command line specified a program to debug, or a process to
1262 attach to, or a core file, @value{GDBN} loads any auto-loaded
1263 scripts provided for the program or for its loaded shared libraries.
1264 @xref{Auto-loading}.
1266 If you wish to disable the auto-loading during startup,
1267 you must do something like the following:
1270 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1273 The following does not work because the auto-loading is turned off too late:
1276 $ gdb -ex "set auto-load-scripts off" myprogram
1280 Reads command files specified by the @samp{-x} option. @xref{Command
1281 Files}, for more details about @value{GDBN} command files.
1284 Reads the command history recorded in the @dfn{history file}.
1285 @xref{Command History}, for more details about the command history and the
1286 files where @value{GDBN} records it.
1289 Init files use the same syntax as @dfn{command files} (@pxref{Command
1290 Files}) and are processed by @value{GDBN} in the same way. The init
1291 file in your home directory can set options (such as @samp{set
1292 complaints}) that affect subsequent processing of command line options
1293 and operands. Init files are not executed if you use the @samp{-nx}
1294 option (@pxref{Mode Options, ,Choosing Modes}).
1296 To display the list of init files loaded by gdb at startup, you
1297 can use @kbd{gdb --help}.
1299 @cindex init file name
1300 @cindex @file{.gdbinit}
1301 @cindex @file{gdb.ini}
1302 The @value{GDBN} init files are normally called @file{.gdbinit}.
1303 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1304 the limitations of file names imposed by DOS filesystems. The Windows
1305 ports of @value{GDBN} use the standard name, but if they find a
1306 @file{gdb.ini} file, they warn you about that and suggest to rename
1307 the file to the standard name.
1311 @section Quitting @value{GDBN}
1312 @cindex exiting @value{GDBN}
1313 @cindex leaving @value{GDBN}
1316 @kindex quit @r{[}@var{expression}@r{]}
1317 @kindex q @r{(@code{quit})}
1318 @item quit @r{[}@var{expression}@r{]}
1320 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1321 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1322 do not supply @var{expression}, @value{GDBN} will terminate normally;
1323 otherwise it will terminate using the result of @var{expression} as the
1328 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1329 terminates the action of any @value{GDBN} command that is in progress and
1330 returns to @value{GDBN} command level. It is safe to type the interrupt
1331 character at any time because @value{GDBN} does not allow it to take effect
1332 until a time when it is safe.
1334 If you have been using @value{GDBN} to control an attached process or
1335 device, you can release it with the @code{detach} command
1336 (@pxref{Attach, ,Debugging an Already-running Process}).
1338 @node Shell Commands
1339 @section Shell Commands
1341 If you need to execute occasional shell commands during your
1342 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1343 just use the @code{shell} command.
1348 @cindex shell escape
1349 @item shell @var{command-string}
1350 @itemx !@var{command-string}
1351 Invoke a standard shell to execute @var{command-string}.
1352 Note that no space is needed between @code{!} and @var{command-string}.
1353 If it exists, the environment variable @code{SHELL} determines which
1354 shell to run. Otherwise @value{GDBN} uses the default shell
1355 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1358 The utility @code{make} is often needed in development environments.
1359 You do not have to use the @code{shell} command for this purpose in
1364 @cindex calling make
1365 @item make @var{make-args}
1366 Execute the @code{make} program with the specified
1367 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1370 @node Logging Output
1371 @section Logging Output
1372 @cindex logging @value{GDBN} output
1373 @cindex save @value{GDBN} output to a file
1375 You may want to save the output of @value{GDBN} commands to a file.
1376 There are several commands to control @value{GDBN}'s logging.
1380 @item set logging on
1382 @item set logging off
1384 @cindex logging file name
1385 @item set logging file @var{file}
1386 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1387 @item set logging overwrite [on|off]
1388 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1389 you want @code{set logging on} to overwrite the logfile instead.
1390 @item set logging redirect [on|off]
1391 By default, @value{GDBN} output will go to both the terminal and the logfile.
1392 Set @code{redirect} if you want output to go only to the log file.
1393 @kindex show logging
1395 Show the current values of the logging settings.
1399 @chapter @value{GDBN} Commands
1401 You can abbreviate a @value{GDBN} command to the first few letters of the command
1402 name, if that abbreviation is unambiguous; and you can repeat certain
1403 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1404 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1405 show you the alternatives available, if there is more than one possibility).
1408 * Command Syntax:: How to give commands to @value{GDBN}
1409 * Completion:: Command completion
1410 * Help:: How to ask @value{GDBN} for help
1413 @node Command Syntax
1414 @section Command Syntax
1416 A @value{GDBN} command is a single line of input. There is no limit on
1417 how long it can be. It starts with a command name, which is followed by
1418 arguments whose meaning depends on the command name. For example, the
1419 command @code{step} accepts an argument which is the number of times to
1420 step, as in @samp{step 5}. You can also use the @code{step} command
1421 with no arguments. Some commands do not allow any arguments.
1423 @cindex abbreviation
1424 @value{GDBN} command names may always be truncated if that abbreviation is
1425 unambiguous. Other possible command abbreviations are listed in the
1426 documentation for individual commands. In some cases, even ambiguous
1427 abbreviations are allowed; for example, @code{s} is specially defined as
1428 equivalent to @code{step} even though there are other commands whose
1429 names start with @code{s}. You can test abbreviations by using them as
1430 arguments to the @code{help} command.
1432 @cindex repeating commands
1433 @kindex RET @r{(repeat last command)}
1434 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1435 repeat the previous command. Certain commands (for example, @code{run})
1436 will not repeat this way; these are commands whose unintentional
1437 repetition might cause trouble and which you are unlikely to want to
1438 repeat. User-defined commands can disable this feature; see
1439 @ref{Define, dont-repeat}.
1441 The @code{list} and @code{x} commands, when you repeat them with
1442 @key{RET}, construct new arguments rather than repeating
1443 exactly as typed. This permits easy scanning of source or memory.
1445 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1446 output, in a way similar to the common utility @code{more}
1447 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1448 @key{RET} too many in this situation, @value{GDBN} disables command
1449 repetition after any command that generates this sort of display.
1451 @kindex # @r{(a comment)}
1453 Any text from a @kbd{#} to the end of the line is a comment; it does
1454 nothing. This is useful mainly in command files (@pxref{Command
1455 Files,,Command Files}).
1457 @cindex repeating command sequences
1458 @kindex Ctrl-o @r{(operate-and-get-next)}
1459 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1460 commands. This command accepts the current line, like @key{RET}, and
1461 then fetches the next line relative to the current line from the history
1465 @section Command Completion
1468 @cindex word completion
1469 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1470 only one possibility; it can also show you what the valid possibilities
1471 are for the next word in a command, at any time. This works for @value{GDBN}
1472 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1474 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1475 of a word. If there is only one possibility, @value{GDBN} fills in the
1476 word, and waits for you to finish the command (or press @key{RET} to
1477 enter it). For example, if you type
1479 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1480 @c complete accuracy in these examples; space introduced for clarity.
1481 @c If texinfo enhancements make it unnecessary, it would be nice to
1482 @c replace " @key" by "@key" in the following...
1484 (@value{GDBP}) info bre @key{TAB}
1488 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1489 the only @code{info} subcommand beginning with @samp{bre}:
1492 (@value{GDBP}) info breakpoints
1496 You can either press @key{RET} at this point, to run the @code{info
1497 breakpoints} command, or backspace and enter something else, if
1498 @samp{breakpoints} does not look like the command you expected. (If you
1499 were sure you wanted @code{info breakpoints} in the first place, you
1500 might as well just type @key{RET} immediately after @samp{info bre},
1501 to exploit command abbreviations rather than command completion).
1503 If there is more than one possibility for the next word when you press
1504 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1505 characters and try again, or just press @key{TAB} a second time;
1506 @value{GDBN} displays all the possible completions for that word. For
1507 example, you might want to set a breakpoint on a subroutine whose name
1508 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1509 just sounds the bell. Typing @key{TAB} again displays all the
1510 function names in your program that begin with those characters, for
1514 (@value{GDBP}) b make_ @key{TAB}
1515 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1516 make_a_section_from_file make_environ
1517 make_abs_section make_function_type
1518 make_blockvector make_pointer_type
1519 make_cleanup make_reference_type
1520 make_command make_symbol_completion_list
1521 (@value{GDBP}) b make_
1525 After displaying the available possibilities, @value{GDBN} copies your
1526 partial input (@samp{b make_} in the example) so you can finish the
1529 If you just want to see the list of alternatives in the first place, you
1530 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1531 means @kbd{@key{META} ?}. You can type this either by holding down a
1532 key designated as the @key{META} shift on your keyboard (if there is
1533 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1535 @cindex quotes in commands
1536 @cindex completion of quoted strings
1537 Sometimes the string you need, while logically a ``word'', may contain
1538 parentheses or other characters that @value{GDBN} normally excludes from
1539 its notion of a word. To permit word completion to work in this
1540 situation, you may enclose words in @code{'} (single quote marks) in
1541 @value{GDBN} commands.
1543 The most likely situation where you might need this is in typing the
1544 name of a C@t{++} function. This is because C@t{++} allows function
1545 overloading (multiple definitions of the same function, distinguished
1546 by argument type). For example, when you want to set a breakpoint you
1547 may need to distinguish whether you mean the version of @code{name}
1548 that takes an @code{int} parameter, @code{name(int)}, or the version
1549 that takes a @code{float} parameter, @code{name(float)}. To use the
1550 word-completion facilities in this situation, type a single quote
1551 @code{'} at the beginning of the function name. This alerts
1552 @value{GDBN} that it may need to consider more information than usual
1553 when you press @key{TAB} or @kbd{M-?} to request word completion:
1556 (@value{GDBP}) b 'bubble( @kbd{M-?}
1557 bubble(double,double) bubble(int,int)
1558 (@value{GDBP}) b 'bubble(
1561 In some cases, @value{GDBN} can tell that completing a name requires using
1562 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1563 completing as much as it can) if you do not type the quote in the first
1567 (@value{GDBP}) b bub @key{TAB}
1568 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1569 (@value{GDBP}) b 'bubble(
1573 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1574 you have not yet started typing the argument list when you ask for
1575 completion on an overloaded symbol.
1577 For more information about overloaded functions, see @ref{C Plus Plus
1578 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1579 overload-resolution off} to disable overload resolution;
1580 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1582 @cindex completion of structure field names
1583 @cindex structure field name completion
1584 @cindex completion of union field names
1585 @cindex union field name completion
1586 When completing in an expression which looks up a field in a
1587 structure, @value{GDBN} also tries@footnote{The completer can be
1588 confused by certain kinds of invalid expressions. Also, it only
1589 examines the static type of the expression, not the dynamic type.} to
1590 limit completions to the field names available in the type of the
1594 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1595 magic to_fputs to_rewind
1596 to_data to_isatty to_write
1597 to_delete to_put to_write_async_safe
1602 This is because the @code{gdb_stdout} is a variable of the type
1603 @code{struct ui_file} that is defined in @value{GDBN} sources as
1610 ui_file_flush_ftype *to_flush;
1611 ui_file_write_ftype *to_write;
1612 ui_file_write_async_safe_ftype *to_write_async_safe;
1613 ui_file_fputs_ftype *to_fputs;
1614 ui_file_read_ftype *to_read;
1615 ui_file_delete_ftype *to_delete;
1616 ui_file_isatty_ftype *to_isatty;
1617 ui_file_rewind_ftype *to_rewind;
1618 ui_file_put_ftype *to_put;
1625 @section Getting Help
1626 @cindex online documentation
1629 You can always ask @value{GDBN} itself for information on its commands,
1630 using the command @code{help}.
1633 @kindex h @r{(@code{help})}
1636 You can use @code{help} (abbreviated @code{h}) with no arguments to
1637 display a short list of named classes of commands:
1641 List of classes of commands:
1643 aliases -- Aliases of other commands
1644 breakpoints -- Making program stop at certain points
1645 data -- Examining data
1646 files -- Specifying and examining files
1647 internals -- Maintenance commands
1648 obscure -- Obscure features
1649 running -- Running the program
1650 stack -- Examining the stack
1651 status -- Status inquiries
1652 support -- Support facilities
1653 tracepoints -- Tracing of program execution without
1654 stopping the program
1655 user-defined -- User-defined commands
1657 Type "help" followed by a class name for a list of
1658 commands in that class.
1659 Type "help" followed by command name for full
1661 Command name abbreviations are allowed if unambiguous.
1664 @c the above line break eliminates huge line overfull...
1666 @item help @var{class}
1667 Using one of the general help classes as an argument, you can get a
1668 list of the individual commands in that class. For example, here is the
1669 help display for the class @code{status}:
1672 (@value{GDBP}) help status
1677 @c Line break in "show" line falsifies real output, but needed
1678 @c to fit in smallbook page size.
1679 info -- Generic command for showing things
1680 about the program being debugged
1681 show -- Generic command for showing things
1684 Type "help" followed by command name for full
1686 Command name abbreviations are allowed if unambiguous.
1690 @item help @var{command}
1691 With a command name as @code{help} argument, @value{GDBN} displays a
1692 short paragraph on how to use that command.
1695 @item apropos @var{args}
1696 The @code{apropos} command searches through all of the @value{GDBN}
1697 commands, and their documentation, for the regular expression specified in
1698 @var{args}. It prints out all matches found. For example:
1709 set symbol-reloading -- Set dynamic symbol table reloading
1710 multiple times in one run
1711 show symbol-reloading -- Show dynamic symbol table reloading
1712 multiple times in one run
1717 @item complete @var{args}
1718 The @code{complete @var{args}} command lists all the possible completions
1719 for the beginning of a command. Use @var{args} to specify the beginning of the
1720 command you want completed. For example:
1726 @noindent results in:
1737 @noindent This is intended for use by @sc{gnu} Emacs.
1740 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1741 and @code{show} to inquire about the state of your program, or the state
1742 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1743 manual introduces each of them in the appropriate context. The listings
1744 under @code{info} and under @code{show} in the Index point to
1745 all the sub-commands. @xref{Index}.
1750 @kindex i @r{(@code{info})}
1752 This command (abbreviated @code{i}) is for describing the state of your
1753 program. For example, you can show the arguments passed to a function
1754 with @code{info args}, list the registers currently in use with @code{info
1755 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1756 You can get a complete list of the @code{info} sub-commands with
1757 @w{@code{help info}}.
1761 You can assign the result of an expression to an environment variable with
1762 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1763 @code{set prompt $}.
1767 In contrast to @code{info}, @code{show} is for describing the state of
1768 @value{GDBN} itself.
1769 You can change most of the things you can @code{show}, by using the
1770 related command @code{set}; for example, you can control what number
1771 system is used for displays with @code{set radix}, or simply inquire
1772 which is currently in use with @code{show radix}.
1775 To display all the settable parameters and their current
1776 values, you can use @code{show} with no arguments; you may also use
1777 @code{info set}. Both commands produce the same display.
1778 @c FIXME: "info set" violates the rule that "info" is for state of
1779 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1780 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1784 Here are three miscellaneous @code{show} subcommands, all of which are
1785 exceptional in lacking corresponding @code{set} commands:
1788 @kindex show version
1789 @cindex @value{GDBN} version number
1791 Show what version of @value{GDBN} is running. You should include this
1792 information in @value{GDBN} bug-reports. If multiple versions of
1793 @value{GDBN} are in use at your site, you may need to determine which
1794 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1795 commands are introduced, and old ones may wither away. Also, many
1796 system vendors ship variant versions of @value{GDBN}, and there are
1797 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1798 The version number is the same as the one announced when you start
1801 @kindex show copying
1802 @kindex info copying
1803 @cindex display @value{GDBN} copyright
1806 Display information about permission for copying @value{GDBN}.
1808 @kindex show warranty
1809 @kindex info warranty
1811 @itemx info warranty
1812 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1813 if your version of @value{GDBN} comes with one.
1818 @chapter Running Programs Under @value{GDBN}
1820 When you run a program under @value{GDBN}, you must first generate
1821 debugging information when you compile it.
1823 You may start @value{GDBN} with its arguments, if any, in an environment
1824 of your choice. If you are doing native debugging, you may redirect
1825 your program's input and output, debug an already running process, or
1826 kill a child process.
1829 * Compilation:: Compiling for debugging
1830 * Starting:: Starting your program
1831 * Arguments:: Your program's arguments
1832 * Environment:: Your program's environment
1834 * Working Directory:: Your program's working directory
1835 * Input/Output:: Your program's input and output
1836 * Attach:: Debugging an already-running process
1837 * Kill Process:: Killing the child process
1839 * Inferiors and Programs:: Debugging multiple inferiors and programs
1840 * Threads:: Debugging programs with multiple threads
1841 * Forks:: Debugging forks
1842 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1846 @section Compiling for Debugging
1848 In order to debug a program effectively, you need to generate
1849 debugging information when you compile it. This debugging information
1850 is stored in the object file; it describes the data type of each
1851 variable or function and the correspondence between source line numbers
1852 and addresses in the executable code.
1854 To request debugging information, specify the @samp{-g} option when you run
1857 Programs that are to be shipped to your customers are compiled with
1858 optimizations, using the @samp{-O} compiler option. However, some
1859 compilers are unable to handle the @samp{-g} and @samp{-O} options
1860 together. Using those compilers, you cannot generate optimized
1861 executables containing debugging information.
1863 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1864 without @samp{-O}, making it possible to debug optimized code. We
1865 recommend that you @emph{always} use @samp{-g} whenever you compile a
1866 program. You may think your program is correct, but there is no sense
1867 in pushing your luck. For more information, see @ref{Optimized Code}.
1869 Older versions of the @sc{gnu} C compiler permitted a variant option
1870 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1871 format; if your @sc{gnu} C compiler has this option, do not use it.
1873 @value{GDBN} knows about preprocessor macros and can show you their
1874 expansion (@pxref{Macros}). Most compilers do not include information
1875 about preprocessor macros in the debugging information if you specify
1876 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1877 the @sc{gnu} C compiler, provides macro information if you are using
1878 the DWARF debugging format, and specify the option @option{-g3}.
1880 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1881 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1882 information on @value{NGCC} options affecting debug information.
1884 You will have the best debugging experience if you use the latest
1885 version of the DWARF debugging format that your compiler supports.
1886 DWARF is currently the most expressive and best supported debugging
1887 format in @value{GDBN}.
1891 @section Starting your Program
1897 @kindex r @r{(@code{run})}
1900 Use the @code{run} command to start your program under @value{GDBN}.
1901 You must first specify the program name (except on VxWorks) with an
1902 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1903 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1904 (@pxref{Files, ,Commands to Specify Files}).
1908 If you are running your program in an execution environment that
1909 supports processes, @code{run} creates an inferior process and makes
1910 that process run your program. In some environments without processes,
1911 @code{run} jumps to the start of your program. Other targets,
1912 like @samp{remote}, are always running. If you get an error
1913 message like this one:
1916 The "remote" target does not support "run".
1917 Try "help target" or "continue".
1921 then use @code{continue} to run your program. You may need @code{load}
1922 first (@pxref{load}).
1924 The execution of a program is affected by certain information it
1925 receives from its superior. @value{GDBN} provides ways to specify this
1926 information, which you must do @emph{before} starting your program. (You
1927 can change it after starting your program, but such changes only affect
1928 your program the next time you start it.) This information may be
1929 divided into four categories:
1932 @item The @emph{arguments.}
1933 Specify the arguments to give your program as the arguments of the
1934 @code{run} command. If a shell is available on your target, the shell
1935 is used to pass the arguments, so that you may use normal conventions
1936 (such as wildcard expansion or variable substitution) in describing
1938 In Unix systems, you can control which shell is used with the
1939 @code{SHELL} environment variable.
1940 @xref{Arguments, ,Your Program's Arguments}.
1942 @item The @emph{environment.}
1943 Your program normally inherits its environment from @value{GDBN}, but you can
1944 use the @value{GDBN} commands @code{set environment} and @code{unset
1945 environment} to change parts of the environment that affect
1946 your program. @xref{Environment, ,Your Program's Environment}.
1948 @item The @emph{working directory.}
1949 Your program inherits its working directory from @value{GDBN}. You can set
1950 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1951 @xref{Working Directory, ,Your Program's Working Directory}.
1953 @item The @emph{standard input and output.}
1954 Your program normally uses the same device for standard input and
1955 standard output as @value{GDBN} is using. You can redirect input and output
1956 in the @code{run} command line, or you can use the @code{tty} command to
1957 set a different device for your program.
1958 @xref{Input/Output, ,Your Program's Input and Output}.
1961 @emph{Warning:} While input and output redirection work, you cannot use
1962 pipes to pass the output of the program you are debugging to another
1963 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1967 When you issue the @code{run} command, your program begins to execute
1968 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1969 of how to arrange for your program to stop. Once your program has
1970 stopped, you may call functions in your program, using the @code{print}
1971 or @code{call} commands. @xref{Data, ,Examining Data}.
1973 If the modification time of your symbol file has changed since the last
1974 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1975 table, and reads it again. When it does this, @value{GDBN} tries to retain
1976 your current breakpoints.
1981 @cindex run to main procedure
1982 The name of the main procedure can vary from language to language.
1983 With C or C@t{++}, the main procedure name is always @code{main}, but
1984 other languages such as Ada do not require a specific name for their
1985 main procedure. The debugger provides a convenient way to start the
1986 execution of the program and to stop at the beginning of the main
1987 procedure, depending on the language used.
1989 The @samp{start} command does the equivalent of setting a temporary
1990 breakpoint at the beginning of the main procedure and then invoking
1991 the @samp{run} command.
1993 @cindex elaboration phase
1994 Some programs contain an @dfn{elaboration} phase where some startup code is
1995 executed before the main procedure is called. This depends on the
1996 languages used to write your program. In C@t{++}, for instance,
1997 constructors for static and global objects are executed before
1998 @code{main} is called. It is therefore possible that the debugger stops
1999 before reaching the main procedure. However, the temporary breakpoint
2000 will remain to halt execution.
2002 Specify the arguments to give to your program as arguments to the
2003 @samp{start} command. These arguments will be given verbatim to the
2004 underlying @samp{run} command. Note that the same arguments will be
2005 reused if no argument is provided during subsequent calls to
2006 @samp{start} or @samp{run}.
2008 It is sometimes necessary to debug the program during elaboration. In
2009 these cases, using the @code{start} command would stop the execution of
2010 your program too late, as the program would have already completed the
2011 elaboration phase. Under these circumstances, insert breakpoints in your
2012 elaboration code before running your program.
2014 @kindex set exec-wrapper
2015 @item set exec-wrapper @var{wrapper}
2016 @itemx show exec-wrapper
2017 @itemx unset exec-wrapper
2018 When @samp{exec-wrapper} is set, the specified wrapper is used to
2019 launch programs for debugging. @value{GDBN} starts your program
2020 with a shell command of the form @kbd{exec @var{wrapper}
2021 @var{program}}. Quoting is added to @var{program} and its
2022 arguments, but not to @var{wrapper}, so you should add quotes if
2023 appropriate for your shell. The wrapper runs until it executes
2024 your program, and then @value{GDBN} takes control.
2026 You can use any program that eventually calls @code{execve} with
2027 its arguments as a wrapper. Several standard Unix utilities do
2028 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2029 with @code{exec "$@@"} will also work.
2031 For example, you can use @code{env} to pass an environment variable to
2032 the debugged program, without setting the variable in your shell's
2036 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2040 This command is available when debugging locally on most targets, excluding
2041 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2043 @kindex set disable-randomization
2044 @item set disable-randomization
2045 @itemx set disable-randomization on
2046 This option (enabled by default in @value{GDBN}) will turn off the native
2047 randomization of the virtual address space of the started program. This option
2048 is useful for multiple debugging sessions to make the execution better
2049 reproducible and memory addresses reusable across debugging sessions.
2051 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2052 On @sc{gnu}/Linux you can get the same behavior using
2055 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2058 @item set disable-randomization off
2059 Leave the behavior of the started executable unchanged. Some bugs rear their
2060 ugly heads only when the program is loaded at certain addresses. If your bug
2061 disappears when you run the program under @value{GDBN}, that might be because
2062 @value{GDBN} by default disables the address randomization on platforms, such
2063 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2064 disable-randomization off} to try to reproduce such elusive bugs.
2066 On targets where it is available, virtual address space randomization
2067 protects the programs against certain kinds of security attacks. In these
2068 cases the attacker needs to know the exact location of a concrete executable
2069 code. Randomizing its location makes it impossible to inject jumps misusing
2070 a code at its expected addresses.
2072 Prelinking shared libraries provides a startup performance advantage but it
2073 makes addresses in these libraries predictable for privileged processes by
2074 having just unprivileged access at the target system. Reading the shared
2075 library binary gives enough information for assembling the malicious code
2076 misusing it. Still even a prelinked shared library can get loaded at a new
2077 random address just requiring the regular relocation process during the
2078 startup. Shared libraries not already prelinked are always loaded at
2079 a randomly chosen address.
2081 Position independent executables (PIE) contain position independent code
2082 similar to the shared libraries and therefore such executables get loaded at
2083 a randomly chosen address upon startup. PIE executables always load even
2084 already prelinked shared libraries at a random address. You can build such
2085 executable using @command{gcc -fPIE -pie}.
2087 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2088 (as long as the randomization is enabled).
2090 @item show disable-randomization
2091 Show the current setting of the explicit disable of the native randomization of
2092 the virtual address space of the started program.
2097 @section Your Program's Arguments
2099 @cindex arguments (to your program)
2100 The arguments to your program can be specified by the arguments of the
2102 They are passed to a shell, which expands wildcard characters and
2103 performs redirection of I/O, and thence to your program. Your
2104 @code{SHELL} environment variable (if it exists) specifies what shell
2105 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2106 the default shell (@file{/bin/sh} on Unix).
2108 On non-Unix systems, the program is usually invoked directly by
2109 @value{GDBN}, which emulates I/O redirection via the appropriate system
2110 calls, and the wildcard characters are expanded by the startup code of
2111 the program, not by the shell.
2113 @code{run} with no arguments uses the same arguments used by the previous
2114 @code{run}, or those set by the @code{set args} command.
2119 Specify the arguments to be used the next time your program is run. If
2120 @code{set args} has no arguments, @code{run} executes your program
2121 with no arguments. Once you have run your program with arguments,
2122 using @code{set args} before the next @code{run} is the only way to run
2123 it again without arguments.
2127 Show the arguments to give your program when it is started.
2131 @section Your Program's Environment
2133 @cindex environment (of your program)
2134 The @dfn{environment} consists of a set of environment variables and
2135 their values. Environment variables conventionally record such things as
2136 your user name, your home directory, your terminal type, and your search
2137 path for programs to run. Usually you set up environment variables with
2138 the shell and they are inherited by all the other programs you run. When
2139 debugging, it can be useful to try running your program with a modified
2140 environment without having to start @value{GDBN} over again.
2144 @item path @var{directory}
2145 Add @var{directory} to the front of the @code{PATH} environment variable
2146 (the search path for executables) that will be passed to your program.
2147 The value of @code{PATH} used by @value{GDBN} does not change.
2148 You may specify several directory names, separated by whitespace or by a
2149 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2150 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2151 is moved to the front, so it is searched sooner.
2153 You can use the string @samp{$cwd} to refer to whatever is the current
2154 working directory at the time @value{GDBN} searches the path. If you
2155 use @samp{.} instead, it refers to the directory where you executed the
2156 @code{path} command. @value{GDBN} replaces @samp{.} in the
2157 @var{directory} argument (with the current path) before adding
2158 @var{directory} to the search path.
2159 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2160 @c document that, since repeating it would be a no-op.
2164 Display the list of search paths for executables (the @code{PATH}
2165 environment variable).
2167 @kindex show environment
2168 @item show environment @r{[}@var{varname}@r{]}
2169 Print the value of environment variable @var{varname} to be given to
2170 your program when it starts. If you do not supply @var{varname},
2171 print the names and values of all environment variables to be given to
2172 your program. You can abbreviate @code{environment} as @code{env}.
2174 @kindex set environment
2175 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2176 Set environment variable @var{varname} to @var{value}. The value
2177 changes for your program only, not for @value{GDBN} itself. @var{value} may
2178 be any string; the values of environment variables are just strings, and
2179 any interpretation is supplied by your program itself. The @var{value}
2180 parameter is optional; if it is eliminated, the variable is set to a
2182 @c "any string" here does not include leading, trailing
2183 @c blanks. Gnu asks: does anyone care?
2185 For example, this command:
2192 tells the debugged program, when subsequently run, that its user is named
2193 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2194 are not actually required.)
2196 @kindex unset environment
2197 @item unset environment @var{varname}
2198 Remove variable @var{varname} from the environment to be passed to your
2199 program. This is different from @samp{set env @var{varname} =};
2200 @code{unset environment} removes the variable from the environment,
2201 rather than assigning it an empty value.
2204 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2206 by your @code{SHELL} environment variable if it exists (or
2207 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2208 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2209 @file{.bashrc} for BASH---any variables you set in that file affect
2210 your program. You may wish to move setting of environment variables to
2211 files that are only run when you sign on, such as @file{.login} or
2214 @node Working Directory
2215 @section Your Program's Working Directory
2217 @cindex working directory (of your program)
2218 Each time you start your program with @code{run}, it inherits its
2219 working directory from the current working directory of @value{GDBN}.
2220 The @value{GDBN} working directory is initially whatever it inherited
2221 from its parent process (typically the shell), but you can specify a new
2222 working directory in @value{GDBN} with the @code{cd} command.
2224 The @value{GDBN} working directory also serves as a default for the commands
2225 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2230 @cindex change working directory
2231 @item cd @var{directory}
2232 Set the @value{GDBN} working directory to @var{directory}.
2236 Print the @value{GDBN} working directory.
2239 It is generally impossible to find the current working directory of
2240 the process being debugged (since a program can change its directory
2241 during its run). If you work on a system where @value{GDBN} is
2242 configured with the @file{/proc} support, you can use the @code{info
2243 proc} command (@pxref{SVR4 Process Information}) to find out the
2244 current working directory of the debuggee.
2247 @section Your Program's Input and Output
2252 By default, the program you run under @value{GDBN} does input and output to
2253 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2254 to its own terminal modes to interact with you, but it records the terminal
2255 modes your program was using and switches back to them when you continue
2256 running your program.
2259 @kindex info terminal
2261 Displays information recorded by @value{GDBN} about the terminal modes your
2265 You can redirect your program's input and/or output using shell
2266 redirection with the @code{run} command. For example,
2273 starts your program, diverting its output to the file @file{outfile}.
2276 @cindex controlling terminal
2277 Another way to specify where your program should do input and output is
2278 with the @code{tty} command. This command accepts a file name as
2279 argument, and causes this file to be the default for future @code{run}
2280 commands. It also resets the controlling terminal for the child
2281 process, for future @code{run} commands. For example,
2288 directs that processes started with subsequent @code{run} commands
2289 default to do input and output on the terminal @file{/dev/ttyb} and have
2290 that as their controlling terminal.
2292 An explicit redirection in @code{run} overrides the @code{tty} command's
2293 effect on the input/output device, but not its effect on the controlling
2296 When you use the @code{tty} command or redirect input in the @code{run}
2297 command, only the input @emph{for your program} is affected. The input
2298 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2299 for @code{set inferior-tty}.
2301 @cindex inferior tty
2302 @cindex set inferior controlling terminal
2303 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2304 display the name of the terminal that will be used for future runs of your
2308 @item set inferior-tty /dev/ttyb
2309 @kindex set inferior-tty
2310 Set the tty for the program being debugged to /dev/ttyb.
2312 @item show inferior-tty
2313 @kindex show inferior-tty
2314 Show the current tty for the program being debugged.
2318 @section Debugging an Already-running Process
2323 @item attach @var{process-id}
2324 This command attaches to a running process---one that was started
2325 outside @value{GDBN}. (@code{info files} shows your active
2326 targets.) The command takes as argument a process ID. The usual way to
2327 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2328 or with the @samp{jobs -l} shell command.
2330 @code{attach} does not repeat if you press @key{RET} a second time after
2331 executing the command.
2334 To use @code{attach}, your program must be running in an environment
2335 which supports processes; for example, @code{attach} does not work for
2336 programs on bare-board targets that lack an operating system. You must
2337 also have permission to send the process a signal.
2339 When you use @code{attach}, the debugger finds the program running in
2340 the process first by looking in the current working directory, then (if
2341 the program is not found) by using the source file search path
2342 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2343 the @code{file} command to load the program. @xref{Files, ,Commands to
2346 The first thing @value{GDBN} does after arranging to debug the specified
2347 process is to stop it. You can examine and modify an attached process
2348 with all the @value{GDBN} commands that are ordinarily available when
2349 you start processes with @code{run}. You can insert breakpoints; you
2350 can step and continue; you can modify storage. If you would rather the
2351 process continue running, you may use the @code{continue} command after
2352 attaching @value{GDBN} to the process.
2357 When you have finished debugging the attached process, you can use the
2358 @code{detach} command to release it from @value{GDBN} control. Detaching
2359 the process continues its execution. After the @code{detach} command,
2360 that process and @value{GDBN} become completely independent once more, and you
2361 are ready to @code{attach} another process or start one with @code{run}.
2362 @code{detach} does not repeat if you press @key{RET} again after
2363 executing the command.
2366 If you exit @value{GDBN} while you have an attached process, you detach
2367 that process. If you use the @code{run} command, you kill that process.
2368 By default, @value{GDBN} asks for confirmation if you try to do either of these
2369 things; you can control whether or not you need to confirm by using the
2370 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2374 @section Killing the Child Process
2379 Kill the child process in which your program is running under @value{GDBN}.
2382 This command is useful if you wish to debug a core dump instead of a
2383 running process. @value{GDBN} ignores any core dump file while your program
2386 On some operating systems, a program cannot be executed outside @value{GDBN}
2387 while you have breakpoints set on it inside @value{GDBN}. You can use the
2388 @code{kill} command in this situation to permit running your program
2389 outside the debugger.
2391 The @code{kill} command is also useful if you wish to recompile and
2392 relink your program, since on many systems it is impossible to modify an
2393 executable file while it is running in a process. In this case, when you
2394 next type @code{run}, @value{GDBN} notices that the file has changed, and
2395 reads the symbol table again (while trying to preserve your current
2396 breakpoint settings).
2398 @node Inferiors and Programs
2399 @section Debugging Multiple Inferiors and Programs
2401 @value{GDBN} lets you run and debug multiple programs in a single
2402 session. In addition, @value{GDBN} on some systems may let you run
2403 several programs simultaneously (otherwise you have to exit from one
2404 before starting another). In the most general case, you can have
2405 multiple threads of execution in each of multiple processes, launched
2406 from multiple executables.
2409 @value{GDBN} represents the state of each program execution with an
2410 object called an @dfn{inferior}. An inferior typically corresponds to
2411 a process, but is more general and applies also to targets that do not
2412 have processes. Inferiors may be created before a process runs, and
2413 may be retained after a process exits. Inferiors have unique
2414 identifiers that are different from process ids. Usually each
2415 inferior will also have its own distinct address space, although some
2416 embedded targets may have several inferiors running in different parts
2417 of a single address space. Each inferior may in turn have multiple
2418 threads running in it.
2420 To find out what inferiors exist at any moment, use @w{@code{info
2424 @kindex info inferiors
2425 @item info inferiors
2426 Print a list of all inferiors currently being managed by @value{GDBN}.
2428 @value{GDBN} displays for each inferior (in this order):
2432 the inferior number assigned by @value{GDBN}
2435 the target system's inferior identifier
2438 the name of the executable the inferior is running.
2443 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2444 indicates the current inferior.
2448 @c end table here to get a little more width for example
2451 (@value{GDBP}) info inferiors
2452 Num Description Executable
2453 2 process 2307 hello
2454 * 1 process 3401 goodbye
2457 To switch focus between inferiors, use the @code{inferior} command:
2460 @kindex inferior @var{infno}
2461 @item inferior @var{infno}
2462 Make inferior number @var{infno} the current inferior. The argument
2463 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2464 in the first field of the @samp{info inferiors} display.
2468 You can get multiple executables into a debugging session via the
2469 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2470 systems @value{GDBN} can add inferiors to the debug session
2471 automatically by following calls to @code{fork} and @code{exec}. To
2472 remove inferiors from the debugging session use the
2473 @w{@code{remove-inferiors}} command.
2476 @kindex add-inferior
2477 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2478 Adds @var{n} inferiors to be run using @var{executable} as the
2479 executable. @var{n} defaults to 1. If no executable is specified,
2480 the inferiors begins empty, with no program. You can still assign or
2481 change the program assigned to the inferior at any time by using the
2482 @code{file} command with the executable name as its argument.
2484 @kindex clone-inferior
2485 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2486 Adds @var{n} inferiors ready to execute the same program as inferior
2487 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2488 number of the current inferior. This is a convenient command when you
2489 want to run another instance of the inferior you are debugging.
2492 (@value{GDBP}) info inferiors
2493 Num Description Executable
2494 * 1 process 29964 helloworld
2495 (@value{GDBP}) clone-inferior
2498 (@value{GDBP}) info inferiors
2499 Num Description Executable
2501 * 1 process 29964 helloworld
2504 You can now simply switch focus to inferior 2 and run it.
2506 @kindex remove-inferiors
2507 @item remove-inferiors @var{infno}@dots{}
2508 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2509 possible to remove an inferior that is running with this command. For
2510 those, use the @code{kill} or @code{detach} command first.
2514 To quit debugging one of the running inferiors that is not the current
2515 inferior, you can either detach from it by using the @w{@code{detach
2516 inferior}} command (allowing it to run independently), or kill it
2517 using the @w{@code{kill inferiors}} command:
2520 @kindex detach inferiors @var{infno}@dots{}
2521 @item detach inferior @var{infno}@dots{}
2522 Detach from the inferior or inferiors identified by @value{GDBN}
2523 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2524 still stays on the list of inferiors shown by @code{info inferiors},
2525 but its Description will show @samp{<null>}.
2527 @kindex kill inferiors @var{infno}@dots{}
2528 @item kill inferiors @var{infno}@dots{}
2529 Kill the inferior or inferiors identified by @value{GDBN} inferior
2530 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2531 stays on the list of inferiors shown by @code{info inferiors}, but its
2532 Description will show @samp{<null>}.
2535 After the successful completion of a command such as @code{detach},
2536 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2537 a normal process exit, the inferior is still valid and listed with
2538 @code{info inferiors}, ready to be restarted.
2541 To be notified when inferiors are started or exit under @value{GDBN}'s
2542 control use @w{@code{set print inferior-events}}:
2545 @kindex set print inferior-events
2546 @cindex print messages on inferior start and exit
2547 @item set print inferior-events
2548 @itemx set print inferior-events on
2549 @itemx set print inferior-events off
2550 The @code{set print inferior-events} command allows you to enable or
2551 disable printing of messages when @value{GDBN} notices that new
2552 inferiors have started or that inferiors have exited or have been
2553 detached. By default, these messages will not be printed.
2555 @kindex show print inferior-events
2556 @item show print inferior-events
2557 Show whether messages will be printed when @value{GDBN} detects that
2558 inferiors have started, exited or have been detached.
2561 Many commands will work the same with multiple programs as with a
2562 single program: e.g., @code{print myglobal} will simply display the
2563 value of @code{myglobal} in the current inferior.
2566 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2567 get more info about the relationship of inferiors, programs, address
2568 spaces in a debug session. You can do that with the @w{@code{maint
2569 info program-spaces}} command.
2572 @kindex maint info program-spaces
2573 @item maint info program-spaces
2574 Print a list of all program spaces currently being managed by
2577 @value{GDBN} displays for each program space (in this order):
2581 the program space number assigned by @value{GDBN}
2584 the name of the executable loaded into the program space, with e.g.,
2585 the @code{file} command.
2590 An asterisk @samp{*} preceding the @value{GDBN} program space number
2591 indicates the current program space.
2593 In addition, below each program space line, @value{GDBN} prints extra
2594 information that isn't suitable to display in tabular form. For
2595 example, the list of inferiors bound to the program space.
2598 (@value{GDBP}) maint info program-spaces
2601 Bound inferiors: ID 1 (process 21561)
2605 Here we can see that no inferior is running the program @code{hello},
2606 while @code{process 21561} is running the program @code{goodbye}. On
2607 some targets, it is possible that multiple inferiors are bound to the
2608 same program space. The most common example is that of debugging both
2609 the parent and child processes of a @code{vfork} call. For example,
2612 (@value{GDBP}) maint info program-spaces
2615 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2618 Here, both inferior 2 and inferior 1 are running in the same program
2619 space as a result of inferior 1 having executed a @code{vfork} call.
2623 @section Debugging Programs with Multiple Threads
2625 @cindex threads of execution
2626 @cindex multiple threads
2627 @cindex switching threads
2628 In some operating systems, such as HP-UX and Solaris, a single program
2629 may have more than one @dfn{thread} of execution. The precise semantics
2630 of threads differ from one operating system to another, but in general
2631 the threads of a single program are akin to multiple processes---except
2632 that they share one address space (that is, they can all examine and
2633 modify the same variables). On the other hand, each thread has its own
2634 registers and execution stack, and perhaps private memory.
2636 @value{GDBN} provides these facilities for debugging multi-thread
2640 @item automatic notification of new threads
2641 @item @samp{thread @var{threadno}}, a command to switch among threads
2642 @item @samp{info threads}, a command to inquire about existing threads
2643 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2644 a command to apply a command to a list of threads
2645 @item thread-specific breakpoints
2646 @item @samp{set print thread-events}, which controls printing of
2647 messages on thread start and exit.
2648 @item @samp{set libthread-db-search-path @var{path}}, which lets
2649 the user specify which @code{libthread_db} to use if the default choice
2650 isn't compatible with the program.
2654 @emph{Warning:} These facilities are not yet available on every
2655 @value{GDBN} configuration where the operating system supports threads.
2656 If your @value{GDBN} does not support threads, these commands have no
2657 effect. For example, a system without thread support shows no output
2658 from @samp{info threads}, and always rejects the @code{thread} command,
2662 (@value{GDBP}) info threads
2663 (@value{GDBP}) thread 1
2664 Thread ID 1 not known. Use the "info threads" command to
2665 see the IDs of currently known threads.
2667 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2668 @c doesn't support threads"?
2671 @cindex focus of debugging
2672 @cindex current thread
2673 The @value{GDBN} thread debugging facility allows you to observe all
2674 threads while your program runs---but whenever @value{GDBN} takes
2675 control, one thread in particular is always the focus of debugging.
2676 This thread is called the @dfn{current thread}. Debugging commands show
2677 program information from the perspective of the current thread.
2679 @cindex @code{New} @var{systag} message
2680 @cindex thread identifier (system)
2681 @c FIXME-implementors!! It would be more helpful if the [New...] message
2682 @c included GDB's numeric thread handle, so you could just go to that
2683 @c thread without first checking `info threads'.
2684 Whenever @value{GDBN} detects a new thread in your program, it displays
2685 the target system's identification for the thread with a message in the
2686 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2687 whose form varies depending on the particular system. For example, on
2688 @sc{gnu}/Linux, you might see
2691 [New Thread 0x41e02940 (LWP 25582)]
2695 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2696 the @var{systag} is simply something like @samp{process 368}, with no
2699 @c FIXME!! (1) Does the [New...] message appear even for the very first
2700 @c thread of a program, or does it only appear for the
2701 @c second---i.e.@: when it becomes obvious we have a multithread
2703 @c (2) *Is* there necessarily a first thread always? Or do some
2704 @c multithread systems permit starting a program with multiple
2705 @c threads ab initio?
2707 @cindex thread number
2708 @cindex thread identifier (GDB)
2709 For debugging purposes, @value{GDBN} associates its own thread
2710 number---always a single integer---with each thread in your program.
2713 @kindex info threads
2714 @item info threads @r{[}@var{id}@dots{}@r{]}
2715 Display a summary of all threads currently in your program. Optional
2716 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2717 means to print information only about the specified thread or threads.
2718 @value{GDBN} displays for each thread (in this order):
2722 the thread number assigned by @value{GDBN}
2725 the target system's thread identifier (@var{systag})
2728 the thread's name, if one is known. A thread can either be named by
2729 the user (see @code{thread name}, below), or, in some cases, by the
2733 the current stack frame summary for that thread
2737 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2738 indicates the current thread.
2742 @c end table here to get a little more width for example
2745 (@value{GDBP}) info threads
2747 3 process 35 thread 27 0x34e5 in sigpause ()
2748 2 process 35 thread 23 0x34e5 in sigpause ()
2749 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2753 On Solaris, you can display more information about user threads with a
2754 Solaris-specific command:
2757 @item maint info sol-threads
2758 @kindex maint info sol-threads
2759 @cindex thread info (Solaris)
2760 Display info on Solaris user threads.
2764 @kindex thread @var{threadno}
2765 @item thread @var{threadno}
2766 Make thread number @var{threadno} the current thread. The command
2767 argument @var{threadno} is the internal @value{GDBN} thread number, as
2768 shown in the first field of the @samp{info threads} display.
2769 @value{GDBN} responds by displaying the system identifier of the thread
2770 you selected, and its current stack frame summary:
2773 (@value{GDBP}) thread 2
2774 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2775 #0 some_function (ignore=0x0) at example.c:8
2776 8 printf ("hello\n");
2780 As with the @samp{[New @dots{}]} message, the form of the text after
2781 @samp{Switching to} depends on your system's conventions for identifying
2784 @vindex $_thread@r{, convenience variable}
2785 The debugger convenience variable @samp{$_thread} contains the number
2786 of the current thread. You may find this useful in writing breakpoint
2787 conditional expressions, command scripts, and so forth. See
2788 @xref{Convenience Vars,, Convenience Variables}, for general
2789 information on convenience variables.
2791 @kindex thread apply
2792 @cindex apply command to several threads
2793 @item thread apply [@var{threadno} | all] @var{command}
2794 The @code{thread apply} command allows you to apply the named
2795 @var{command} to one or more threads. Specify the numbers of the
2796 threads that you want affected with the command argument
2797 @var{threadno}. It can be a single thread number, one of the numbers
2798 shown in the first field of the @samp{info threads} display; or it
2799 could be a range of thread numbers, as in @code{2-4}. To apply a
2800 command to all threads, type @kbd{thread apply all @var{command}}.
2803 @cindex name a thread
2804 @item thread name [@var{name}]
2805 This command assigns a name to the current thread. If no argument is
2806 given, any existing user-specified name is removed. The thread name
2807 appears in the @samp{info threads} display.
2809 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2810 determine the name of the thread as given by the OS. On these
2811 systems, a name specified with @samp{thread name} will override the
2812 system-give name, and removing the user-specified name will cause
2813 @value{GDBN} to once again display the system-specified name.
2816 @cindex search for a thread
2817 @item thread find [@var{regexp}]
2818 Search for and display thread ids whose name or @var{systag}
2819 matches the supplied regular expression.
2821 As well as being the complement to the @samp{thread name} command,
2822 this command also allows you to identify a thread by its target
2823 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2827 (@value{GDBN}) thread find 26688
2828 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2829 (@value{GDBN}) info thread 4
2831 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2834 @kindex set print thread-events
2835 @cindex print messages on thread start and exit
2836 @item set print thread-events
2837 @itemx set print thread-events on
2838 @itemx set print thread-events off
2839 The @code{set print thread-events} command allows you to enable or
2840 disable printing of messages when @value{GDBN} notices that new threads have
2841 started or that threads have exited. By default, these messages will
2842 be printed if detection of these events is supported by the target.
2843 Note that these messages cannot be disabled on all targets.
2845 @kindex show print thread-events
2846 @item show print thread-events
2847 Show whether messages will be printed when @value{GDBN} detects that threads
2848 have started and exited.
2851 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2852 more information about how @value{GDBN} behaves when you stop and start
2853 programs with multiple threads.
2855 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2856 watchpoints in programs with multiple threads.
2859 @kindex set libthread-db-search-path
2860 @cindex search path for @code{libthread_db}
2861 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2862 If this variable is set, @var{path} is a colon-separated list of
2863 directories @value{GDBN} will use to search for @code{libthread_db}.
2864 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2865 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2866 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2869 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2870 @code{libthread_db} library to obtain information about threads in the
2871 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2872 to find @code{libthread_db}.
2874 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2875 refers to the default system directories that are
2876 normally searched for loading shared libraries.
2878 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2879 refers to the directory from which @code{libpthread}
2880 was loaded in the inferior process.
2882 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2883 @value{GDBN} attempts to initialize it with the current inferior process.
2884 If this initialization fails (which could happen because of a version
2885 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2886 will unload @code{libthread_db}, and continue with the next directory.
2887 If none of @code{libthread_db} libraries initialize successfully,
2888 @value{GDBN} will issue a warning and thread debugging will be disabled.
2890 Setting @code{libthread-db-search-path} is currently implemented
2891 only on some platforms.
2893 @kindex show libthread-db-search-path
2894 @item show libthread-db-search-path
2895 Display current libthread_db search path.
2897 @kindex set debug libthread-db
2898 @kindex show debug libthread-db
2899 @cindex debugging @code{libthread_db}
2900 @item set debug libthread-db
2901 @itemx show debug libthread-db
2902 Turns on or off display of @code{libthread_db}-related events.
2903 Use @code{1} to enable, @code{0} to disable.
2907 @section Debugging Forks
2909 @cindex fork, debugging programs which call
2910 @cindex multiple processes
2911 @cindex processes, multiple
2912 On most systems, @value{GDBN} has no special support for debugging
2913 programs which create additional processes using the @code{fork}
2914 function. When a program forks, @value{GDBN} will continue to debug the
2915 parent process and the child process will run unimpeded. If you have
2916 set a breakpoint in any code which the child then executes, the child
2917 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2918 will cause it to terminate.
2920 However, if you want to debug the child process there is a workaround
2921 which isn't too painful. Put a call to @code{sleep} in the code which
2922 the child process executes after the fork. It may be useful to sleep
2923 only if a certain environment variable is set, or a certain file exists,
2924 so that the delay need not occur when you don't want to run @value{GDBN}
2925 on the child. While the child is sleeping, use the @code{ps} program to
2926 get its process ID. Then tell @value{GDBN} (a new invocation of
2927 @value{GDBN} if you are also debugging the parent process) to attach to
2928 the child process (@pxref{Attach}). From that point on you can debug
2929 the child process just like any other process which you attached to.
2931 On some systems, @value{GDBN} provides support for debugging programs that
2932 create additional processes using the @code{fork} or @code{vfork} functions.
2933 Currently, the only platforms with this feature are HP-UX (11.x and later
2934 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2936 By default, when a program forks, @value{GDBN} will continue to debug
2937 the parent process and the child process will run unimpeded.
2939 If you want to follow the child process instead of the parent process,
2940 use the command @w{@code{set follow-fork-mode}}.
2943 @kindex set follow-fork-mode
2944 @item set follow-fork-mode @var{mode}
2945 Set the debugger response to a program call of @code{fork} or
2946 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2947 process. The @var{mode} argument can be:
2951 The original process is debugged after a fork. The child process runs
2952 unimpeded. This is the default.
2955 The new process is debugged after a fork. The parent process runs
2960 @kindex show follow-fork-mode
2961 @item show follow-fork-mode
2962 Display the current debugger response to a @code{fork} or @code{vfork} call.
2965 @cindex debugging multiple processes
2966 On Linux, if you want to debug both the parent and child processes, use the
2967 command @w{@code{set detach-on-fork}}.
2970 @kindex set detach-on-fork
2971 @item set detach-on-fork @var{mode}
2972 Tells gdb whether to detach one of the processes after a fork, or
2973 retain debugger control over them both.
2977 The child process (or parent process, depending on the value of
2978 @code{follow-fork-mode}) will be detached and allowed to run
2979 independently. This is the default.
2982 Both processes will be held under the control of @value{GDBN}.
2983 One process (child or parent, depending on the value of
2984 @code{follow-fork-mode}) is debugged as usual, while the other
2989 @kindex show detach-on-fork
2990 @item show detach-on-fork
2991 Show whether detach-on-fork mode is on/off.
2994 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2995 will retain control of all forked processes (including nested forks).
2996 You can list the forked processes under the control of @value{GDBN} by
2997 using the @w{@code{info inferiors}} command, and switch from one fork
2998 to another by using the @code{inferior} command (@pxref{Inferiors and
2999 Programs, ,Debugging Multiple Inferiors and Programs}).
3001 To quit debugging one of the forked processes, you can either detach
3002 from it by using the @w{@code{detach inferiors}} command (allowing it
3003 to run independently), or kill it using the @w{@code{kill inferiors}}
3004 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3007 If you ask to debug a child process and a @code{vfork} is followed by an
3008 @code{exec}, @value{GDBN} executes the new target up to the first
3009 breakpoint in the new target. If you have a breakpoint set on
3010 @code{main} in your original program, the breakpoint will also be set on
3011 the child process's @code{main}.
3013 On some systems, when a child process is spawned by @code{vfork}, you
3014 cannot debug the child or parent until an @code{exec} call completes.
3016 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3017 call executes, the new target restarts. To restart the parent
3018 process, use the @code{file} command with the parent executable name
3019 as its argument. By default, after an @code{exec} call executes,
3020 @value{GDBN} discards the symbols of the previous executable image.
3021 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3025 @kindex set follow-exec-mode
3026 @item set follow-exec-mode @var{mode}
3028 Set debugger response to a program call of @code{exec}. An
3029 @code{exec} call replaces the program image of a process.
3031 @code{follow-exec-mode} can be:
3035 @value{GDBN} creates a new inferior and rebinds the process to this
3036 new inferior. The program the process was running before the
3037 @code{exec} call can be restarted afterwards by restarting the
3043 (@value{GDBP}) info inferiors
3045 Id Description Executable
3048 process 12020 is executing new program: prog2
3049 Program exited normally.
3050 (@value{GDBP}) info inferiors
3051 Id Description Executable
3057 @value{GDBN} keeps the process bound to the same inferior. The new
3058 executable image replaces the previous executable loaded in the
3059 inferior. Restarting the inferior after the @code{exec} call, with
3060 e.g., the @code{run} command, restarts the executable the process was
3061 running after the @code{exec} call. This is the default mode.
3066 (@value{GDBP}) info inferiors
3067 Id Description Executable
3070 process 12020 is executing new program: prog2
3071 Program exited normally.
3072 (@value{GDBP}) info inferiors
3073 Id Description Executable
3080 You can use the @code{catch} command to make @value{GDBN} stop whenever
3081 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3082 Catchpoints, ,Setting Catchpoints}.
3084 @node Checkpoint/Restart
3085 @section Setting a @emph{Bookmark} to Return to Later
3090 @cindex snapshot of a process
3091 @cindex rewind program state
3093 On certain operating systems@footnote{Currently, only
3094 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3095 program's state, called a @dfn{checkpoint}, and come back to it
3098 Returning to a checkpoint effectively undoes everything that has
3099 happened in the program since the @code{checkpoint} was saved. This
3100 includes changes in memory, registers, and even (within some limits)
3101 system state. Effectively, it is like going back in time to the
3102 moment when the checkpoint was saved.
3104 Thus, if you're stepping thru a program and you think you're
3105 getting close to the point where things go wrong, you can save
3106 a checkpoint. Then, if you accidentally go too far and miss
3107 the critical statement, instead of having to restart your program
3108 from the beginning, you can just go back to the checkpoint and
3109 start again from there.
3111 This can be especially useful if it takes a lot of time or
3112 steps to reach the point where you think the bug occurs.
3114 To use the @code{checkpoint}/@code{restart} method of debugging:
3119 Save a snapshot of the debugged program's current execution state.
3120 The @code{checkpoint} command takes no arguments, but each checkpoint
3121 is assigned a small integer id, similar to a breakpoint id.
3123 @kindex info checkpoints
3124 @item info checkpoints
3125 List the checkpoints that have been saved in the current debugging
3126 session. For each checkpoint, the following information will be
3133 @item Source line, or label
3136 @kindex restart @var{checkpoint-id}
3137 @item restart @var{checkpoint-id}
3138 Restore the program state that was saved as checkpoint number
3139 @var{checkpoint-id}. All program variables, registers, stack frames
3140 etc.@: will be returned to the values that they had when the checkpoint
3141 was saved. In essence, gdb will ``wind back the clock'' to the point
3142 in time when the checkpoint was saved.
3144 Note that breakpoints, @value{GDBN} variables, command history etc.
3145 are not affected by restoring a checkpoint. In general, a checkpoint
3146 only restores things that reside in the program being debugged, not in
3149 @kindex delete checkpoint @var{checkpoint-id}
3150 @item delete checkpoint @var{checkpoint-id}
3151 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3155 Returning to a previously saved checkpoint will restore the user state
3156 of the program being debugged, plus a significant subset of the system
3157 (OS) state, including file pointers. It won't ``un-write'' data from
3158 a file, but it will rewind the file pointer to the previous location,
3159 so that the previously written data can be overwritten. For files
3160 opened in read mode, the pointer will also be restored so that the
3161 previously read data can be read again.
3163 Of course, characters that have been sent to a printer (or other
3164 external device) cannot be ``snatched back'', and characters received
3165 from eg.@: a serial device can be removed from internal program buffers,
3166 but they cannot be ``pushed back'' into the serial pipeline, ready to
3167 be received again. Similarly, the actual contents of files that have
3168 been changed cannot be restored (at this time).
3170 However, within those constraints, you actually can ``rewind'' your
3171 program to a previously saved point in time, and begin debugging it
3172 again --- and you can change the course of events so as to debug a
3173 different execution path this time.
3175 @cindex checkpoints and process id
3176 Finally, there is one bit of internal program state that will be
3177 different when you return to a checkpoint --- the program's process
3178 id. Each checkpoint will have a unique process id (or @var{pid}),
3179 and each will be different from the program's original @var{pid}.
3180 If your program has saved a local copy of its process id, this could
3181 potentially pose a problem.
3183 @subsection A Non-obvious Benefit of Using Checkpoints
3185 On some systems such as @sc{gnu}/Linux, address space randomization
3186 is performed on new processes for security reasons. This makes it
3187 difficult or impossible to set a breakpoint, or watchpoint, on an
3188 absolute address if you have to restart the program, since the
3189 absolute location of a symbol will change from one execution to the
3192 A checkpoint, however, is an @emph{identical} copy of a process.
3193 Therefore if you create a checkpoint at (eg.@:) the start of main,
3194 and simply return to that checkpoint instead of restarting the
3195 process, you can avoid the effects of address randomization and
3196 your symbols will all stay in the same place.
3199 @chapter Stopping and Continuing
3201 The principal purposes of using a debugger are so that you can stop your
3202 program before it terminates; or so that, if your program runs into
3203 trouble, you can investigate and find out why.
3205 Inside @value{GDBN}, your program may stop for any of several reasons,
3206 such as a signal, a breakpoint, or reaching a new line after a
3207 @value{GDBN} command such as @code{step}. You may then examine and
3208 change variables, set new breakpoints or remove old ones, and then
3209 continue execution. Usually, the messages shown by @value{GDBN} provide
3210 ample explanation of the status of your program---but you can also
3211 explicitly request this information at any time.
3214 @kindex info program
3216 Display information about the status of your program: whether it is
3217 running or not, what process it is, and why it stopped.
3221 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3222 * Continuing and Stepping:: Resuming execution
3223 * Skipping Over Functions and Files::
3224 Skipping over functions and files
3226 * Thread Stops:: Stopping and starting multi-thread programs
3230 @section Breakpoints, Watchpoints, and Catchpoints
3233 A @dfn{breakpoint} makes your program stop whenever a certain point in
3234 the program is reached. For each breakpoint, you can add conditions to
3235 control in finer detail whether your program stops. You can set
3236 breakpoints with the @code{break} command and its variants (@pxref{Set
3237 Breaks, ,Setting Breakpoints}), to specify the place where your program
3238 should stop by line number, function name or exact address in the
3241 On some systems, you can set breakpoints in shared libraries before
3242 the executable is run. There is a minor limitation on HP-UX systems:
3243 you must wait until the executable is run in order to set breakpoints
3244 in shared library routines that are not called directly by the program
3245 (for example, routines that are arguments in a @code{pthread_create}
3249 @cindex data breakpoints
3250 @cindex memory tracing
3251 @cindex breakpoint on memory address
3252 @cindex breakpoint on variable modification
3253 A @dfn{watchpoint} is a special breakpoint that stops your program
3254 when the value of an expression changes. The expression may be a value
3255 of a variable, or it could involve values of one or more variables
3256 combined by operators, such as @samp{a + b}. This is sometimes called
3257 @dfn{data breakpoints}. You must use a different command to set
3258 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3259 from that, you can manage a watchpoint like any other breakpoint: you
3260 enable, disable, and delete both breakpoints and watchpoints using the
3263 You can arrange to have values from your program displayed automatically
3264 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3268 @cindex breakpoint on events
3269 A @dfn{catchpoint} is another special breakpoint that stops your program
3270 when a certain kind of event occurs, such as the throwing of a C@t{++}
3271 exception or the loading of a library. As with watchpoints, you use a
3272 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3273 Catchpoints}), but aside from that, you can manage a catchpoint like any
3274 other breakpoint. (To stop when your program receives a signal, use the
3275 @code{handle} command; see @ref{Signals, ,Signals}.)
3277 @cindex breakpoint numbers
3278 @cindex numbers for breakpoints
3279 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3280 catchpoint when you create it; these numbers are successive integers
3281 starting with one. In many of the commands for controlling various
3282 features of breakpoints you use the breakpoint number to say which
3283 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3284 @dfn{disabled}; if disabled, it has no effect on your program until you
3287 @cindex breakpoint ranges
3288 @cindex ranges of breakpoints
3289 Some @value{GDBN} commands accept a range of breakpoints on which to
3290 operate. A breakpoint range is either a single breakpoint number, like
3291 @samp{5}, or two such numbers, in increasing order, separated by a
3292 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3293 all breakpoints in that range are operated on.
3296 * Set Breaks:: Setting breakpoints
3297 * Set Watchpoints:: Setting watchpoints
3298 * Set Catchpoints:: Setting catchpoints
3299 * Delete Breaks:: Deleting breakpoints
3300 * Disabling:: Disabling breakpoints
3301 * Conditions:: Break conditions
3302 * Break Commands:: Breakpoint command lists
3303 * Save Breakpoints:: How to save breakpoints in a file
3304 * Error in Breakpoints:: ``Cannot insert breakpoints''
3305 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3309 @subsection Setting Breakpoints
3311 @c FIXME LMB what does GDB do if no code on line of breakpt?
3312 @c consider in particular declaration with/without initialization.
3314 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3317 @kindex b @r{(@code{break})}
3318 @vindex $bpnum@r{, convenience variable}
3319 @cindex latest breakpoint
3320 Breakpoints are set with the @code{break} command (abbreviated
3321 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3322 number of the breakpoint you've set most recently; see @ref{Convenience
3323 Vars,, Convenience Variables}, for a discussion of what you can do with
3324 convenience variables.
3327 @item break @var{location}
3328 Set a breakpoint at the given @var{location}, which can specify a
3329 function name, a line number, or an address of an instruction.
3330 (@xref{Specify Location}, for a list of all the possible ways to
3331 specify a @var{location}.) The breakpoint will stop your program just
3332 before it executes any of the code in the specified @var{location}.
3334 When using source languages that permit overloading of symbols, such as
3335 C@t{++}, a function name may refer to more than one possible place to break.
3336 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3339 It is also possible to insert a breakpoint that will stop the program
3340 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3341 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3344 When called without any arguments, @code{break} sets a breakpoint at
3345 the next instruction to be executed in the selected stack frame
3346 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3347 innermost, this makes your program stop as soon as control
3348 returns to that frame. This is similar to the effect of a
3349 @code{finish} command in the frame inside the selected frame---except
3350 that @code{finish} does not leave an active breakpoint. If you use
3351 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3352 the next time it reaches the current location; this may be useful
3355 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3356 least one instruction has been executed. If it did not do this, you
3357 would be unable to proceed past a breakpoint without first disabling the
3358 breakpoint. This rule applies whether or not the breakpoint already
3359 existed when your program stopped.
3361 @item break @dots{} if @var{cond}
3362 Set a breakpoint with condition @var{cond}; evaluate the expression
3363 @var{cond} each time the breakpoint is reached, and stop only if the
3364 value is nonzero---that is, if @var{cond} evaluates as true.
3365 @samp{@dots{}} stands for one of the possible arguments described
3366 above (or no argument) specifying where to break. @xref{Conditions,
3367 ,Break Conditions}, for more information on breakpoint conditions.
3370 @item tbreak @var{args}
3371 Set a breakpoint enabled only for one stop. @var{args} are the
3372 same as for the @code{break} command, and the breakpoint is set in the same
3373 way, but the breakpoint is automatically deleted after the first time your
3374 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3377 @cindex hardware breakpoints
3378 @item hbreak @var{args}
3379 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3380 @code{break} command and the breakpoint is set in the same way, but the
3381 breakpoint requires hardware support and some target hardware may not
3382 have this support. The main purpose of this is EPROM/ROM code
3383 debugging, so you can set a breakpoint at an instruction without
3384 changing the instruction. This can be used with the new trap-generation
3385 provided by SPARClite DSU and most x86-based targets. These targets
3386 will generate traps when a program accesses some data or instruction
3387 address that is assigned to the debug registers. However the hardware
3388 breakpoint registers can take a limited number of breakpoints. For
3389 example, on the DSU, only two data breakpoints can be set at a time, and
3390 @value{GDBN} will reject this command if more than two are used. Delete
3391 or disable unused hardware breakpoints before setting new ones
3392 (@pxref{Disabling, ,Disabling Breakpoints}).
3393 @xref{Conditions, ,Break Conditions}.
3394 For remote targets, you can restrict the number of hardware
3395 breakpoints @value{GDBN} will use, see @ref{set remote
3396 hardware-breakpoint-limit}.
3399 @item thbreak @var{args}
3400 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3401 are the same as for the @code{hbreak} command and the breakpoint is set in
3402 the same way. However, like the @code{tbreak} command,
3403 the breakpoint is automatically deleted after the
3404 first time your program stops there. Also, like the @code{hbreak}
3405 command, the breakpoint requires hardware support and some target hardware
3406 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3407 See also @ref{Conditions, ,Break Conditions}.
3410 @cindex regular expression
3411 @cindex breakpoints at functions matching a regexp
3412 @cindex set breakpoints in many functions
3413 @item rbreak @var{regex}
3414 Set breakpoints on all functions matching the regular expression
3415 @var{regex}. This command sets an unconditional breakpoint on all
3416 matches, printing a list of all breakpoints it set. Once these
3417 breakpoints are set, they are treated just like the breakpoints set with
3418 the @code{break} command. You can delete them, disable them, or make
3419 them conditional the same way as any other breakpoint.
3421 The syntax of the regular expression is the standard one used with tools
3422 like @file{grep}. Note that this is different from the syntax used by
3423 shells, so for instance @code{foo*} matches all functions that include
3424 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3425 @code{.*} leading and trailing the regular expression you supply, so to
3426 match only functions that begin with @code{foo}, use @code{^foo}.
3428 @cindex non-member C@t{++} functions, set breakpoint in
3429 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3430 breakpoints on overloaded functions that are not members of any special
3433 @cindex set breakpoints on all functions
3434 The @code{rbreak} command can be used to set breakpoints in
3435 @strong{all} the functions in a program, like this:
3438 (@value{GDBP}) rbreak .
3441 @item rbreak @var{file}:@var{regex}
3442 If @code{rbreak} is called with a filename qualification, it limits
3443 the search for functions matching the given regular expression to the
3444 specified @var{file}. This can be used, for example, to set breakpoints on
3445 every function in a given file:
3448 (@value{GDBP}) rbreak file.c:.
3451 The colon separating the filename qualifier from the regex may
3452 optionally be surrounded by spaces.
3454 @kindex info breakpoints
3455 @cindex @code{$_} and @code{info breakpoints}
3456 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3457 @itemx info break @r{[}@var{n}@dots{}@r{]}
3458 Print a table of all breakpoints, watchpoints, and catchpoints set and
3459 not deleted. Optional argument @var{n} means print information only
3460 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3461 For each breakpoint, following columns are printed:
3464 @item Breakpoint Numbers
3466 Breakpoint, watchpoint, or catchpoint.
3468 Whether the breakpoint is marked to be disabled or deleted when hit.
3469 @item Enabled or Disabled
3470 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3471 that are not enabled.
3473 Where the breakpoint is in your program, as a memory address. For a
3474 pending breakpoint whose address is not yet known, this field will
3475 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3476 library that has the symbol or line referred by breakpoint is loaded.
3477 See below for details. A breakpoint with several locations will
3478 have @samp{<MULTIPLE>} in this field---see below for details.
3480 Where the breakpoint is in the source for your program, as a file and
3481 line number. For a pending breakpoint, the original string passed to
3482 the breakpoint command will be listed as it cannot be resolved until
3483 the appropriate shared library is loaded in the future.
3487 If a breakpoint is conditional, @code{info break} shows the condition on
3488 the line following the affected breakpoint; breakpoint commands, if any,
3489 are listed after that. A pending breakpoint is allowed to have a condition
3490 specified for it. The condition is not parsed for validity until a shared
3491 library is loaded that allows the pending breakpoint to resolve to a
3495 @code{info break} with a breakpoint
3496 number @var{n} as argument lists only that breakpoint. The
3497 convenience variable @code{$_} and the default examining-address for
3498 the @code{x} command are set to the address of the last breakpoint
3499 listed (@pxref{Memory, ,Examining Memory}).
3502 @code{info break} displays a count of the number of times the breakpoint
3503 has been hit. This is especially useful in conjunction with the
3504 @code{ignore} command. You can ignore a large number of breakpoint
3505 hits, look at the breakpoint info to see how many times the breakpoint
3506 was hit, and then run again, ignoring one less than that number. This
3507 will get you quickly to the last hit of that breakpoint.
3510 @value{GDBN} allows you to set any number of breakpoints at the same place in
3511 your program. There is nothing silly or meaningless about this. When
3512 the breakpoints are conditional, this is even useful
3513 (@pxref{Conditions, ,Break Conditions}).
3515 @cindex multiple locations, breakpoints
3516 @cindex breakpoints, multiple locations
3517 It is possible that a breakpoint corresponds to several locations
3518 in your program. Examples of this situation are:
3522 Multiple functions in the program may have the same name.
3525 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3526 instances of the function body, used in different cases.
3529 For a C@t{++} template function, a given line in the function can
3530 correspond to any number of instantiations.
3533 For an inlined function, a given source line can correspond to
3534 several places where that function is inlined.
3537 In all those cases, @value{GDBN} will insert a breakpoint at all
3538 the relevant locations.
3540 A breakpoint with multiple locations is displayed in the breakpoint
3541 table using several rows---one header row, followed by one row for
3542 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3543 address column. The rows for individual locations contain the actual
3544 addresses for locations, and show the functions to which those
3545 locations belong. The number column for a location is of the form
3546 @var{breakpoint-number}.@var{location-number}.
3551 Num Type Disp Enb Address What
3552 1 breakpoint keep y <MULTIPLE>
3554 breakpoint already hit 1 time
3555 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3556 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3559 Each location can be individually enabled or disabled by passing
3560 @var{breakpoint-number}.@var{location-number} as argument to the
3561 @code{enable} and @code{disable} commands. Note that you cannot
3562 delete the individual locations from the list, you can only delete the
3563 entire list of locations that belong to their parent breakpoint (with
3564 the @kbd{delete @var{num}} command, where @var{num} is the number of
3565 the parent breakpoint, 1 in the above example). Disabling or enabling
3566 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3567 that belong to that breakpoint.
3569 @cindex pending breakpoints
3570 It's quite common to have a breakpoint inside a shared library.
3571 Shared libraries can be loaded and unloaded explicitly,
3572 and possibly repeatedly, as the program is executed. To support
3573 this use case, @value{GDBN} updates breakpoint locations whenever
3574 any shared library is loaded or unloaded. Typically, you would
3575 set a breakpoint in a shared library at the beginning of your
3576 debugging session, when the library is not loaded, and when the
3577 symbols from the library are not available. When you try to set
3578 breakpoint, @value{GDBN} will ask you if you want to set
3579 a so called @dfn{pending breakpoint}---breakpoint whose address
3580 is not yet resolved.
3582 After the program is run, whenever a new shared library is loaded,
3583 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3584 shared library contains the symbol or line referred to by some
3585 pending breakpoint, that breakpoint is resolved and becomes an
3586 ordinary breakpoint. When a library is unloaded, all breakpoints
3587 that refer to its symbols or source lines become pending again.
3589 This logic works for breakpoints with multiple locations, too. For
3590 example, if you have a breakpoint in a C@t{++} template function, and
3591 a newly loaded shared library has an instantiation of that template,
3592 a new location is added to the list of locations for the breakpoint.
3594 Except for having unresolved address, pending breakpoints do not
3595 differ from regular breakpoints. You can set conditions or commands,
3596 enable and disable them and perform other breakpoint operations.
3598 @value{GDBN} provides some additional commands for controlling what
3599 happens when the @samp{break} command cannot resolve breakpoint
3600 address specification to an address:
3602 @kindex set breakpoint pending
3603 @kindex show breakpoint pending
3605 @item set breakpoint pending auto
3606 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3607 location, it queries you whether a pending breakpoint should be created.
3609 @item set breakpoint pending on
3610 This indicates that an unrecognized breakpoint location should automatically
3611 result in a pending breakpoint being created.
3613 @item set breakpoint pending off
3614 This indicates that pending breakpoints are not to be created. Any
3615 unrecognized breakpoint location results in an error. This setting does
3616 not affect any pending breakpoints previously created.
3618 @item show breakpoint pending
3619 Show the current behavior setting for creating pending breakpoints.
3622 The settings above only affect the @code{break} command and its
3623 variants. Once breakpoint is set, it will be automatically updated
3624 as shared libraries are loaded and unloaded.
3626 @cindex automatic hardware breakpoints
3627 For some targets, @value{GDBN} can automatically decide if hardware or
3628 software breakpoints should be used, depending on whether the
3629 breakpoint address is read-only or read-write. This applies to
3630 breakpoints set with the @code{break} command as well as to internal
3631 breakpoints set by commands like @code{next} and @code{finish}. For
3632 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3635 You can control this automatic behaviour with the following commands::
3637 @kindex set breakpoint auto-hw
3638 @kindex show breakpoint auto-hw
3640 @item set breakpoint auto-hw on
3641 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3642 will try to use the target memory map to decide if software or hardware
3643 breakpoint must be used.
3645 @item set breakpoint auto-hw off
3646 This indicates @value{GDBN} should not automatically select breakpoint
3647 type. If the target provides a memory map, @value{GDBN} will warn when
3648 trying to set software breakpoint at a read-only address.
3651 @value{GDBN} normally implements breakpoints by replacing the program code
3652 at the breakpoint address with a special instruction, which, when
3653 executed, given control to the debugger. By default, the program
3654 code is so modified only when the program is resumed. As soon as
3655 the program stops, @value{GDBN} restores the original instructions. This
3656 behaviour guards against leaving breakpoints inserted in the
3657 target should gdb abrubptly disconnect. However, with slow remote
3658 targets, inserting and removing breakpoint can reduce the performance.
3659 This behavior can be controlled with the following commands::
3661 @kindex set breakpoint always-inserted
3662 @kindex show breakpoint always-inserted
3664 @item set breakpoint always-inserted off
3665 All breakpoints, including newly added by the user, are inserted in
3666 the target only when the target is resumed. All breakpoints are
3667 removed from the target when it stops.
3669 @item set breakpoint always-inserted on
3670 Causes all breakpoints to be inserted in the target at all times. If
3671 the user adds a new breakpoint, or changes an existing breakpoint, the
3672 breakpoints in the target are updated immediately. A breakpoint is
3673 removed from the target only when breakpoint itself is removed.
3675 @cindex non-stop mode, and @code{breakpoint always-inserted}
3676 @item set breakpoint always-inserted auto
3677 This is the default mode. If @value{GDBN} is controlling the inferior
3678 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3679 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3680 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3681 @code{breakpoint always-inserted} mode is off.
3684 @cindex negative breakpoint numbers
3685 @cindex internal @value{GDBN} breakpoints
3686 @value{GDBN} itself sometimes sets breakpoints in your program for
3687 special purposes, such as proper handling of @code{longjmp} (in C
3688 programs). These internal breakpoints are assigned negative numbers,
3689 starting with @code{-1}; @samp{info breakpoints} does not display them.
3690 You can see these breakpoints with the @value{GDBN} maintenance command
3691 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3694 @node Set Watchpoints
3695 @subsection Setting Watchpoints
3697 @cindex setting watchpoints
3698 You can use a watchpoint to stop execution whenever the value of an
3699 expression changes, without having to predict a particular place where
3700 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3701 The expression may be as simple as the value of a single variable, or
3702 as complex as many variables combined by operators. Examples include:
3706 A reference to the value of a single variable.
3709 An address cast to an appropriate data type. For example,
3710 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3711 address (assuming an @code{int} occupies 4 bytes).
3714 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3715 expression can use any operators valid in the program's native
3716 language (@pxref{Languages}).
3719 You can set a watchpoint on an expression even if the expression can
3720 not be evaluated yet. For instance, you can set a watchpoint on
3721 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3722 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3723 the expression produces a valid value. If the expression becomes
3724 valid in some other way than changing a variable (e.g.@: if the memory
3725 pointed to by @samp{*global_ptr} becomes readable as the result of a
3726 @code{malloc} call), @value{GDBN} may not stop until the next time
3727 the expression changes.
3729 @cindex software watchpoints
3730 @cindex hardware watchpoints
3731 Depending on your system, watchpoints may be implemented in software or
3732 hardware. @value{GDBN} does software watchpointing by single-stepping your
3733 program and testing the variable's value each time, which is hundreds of
3734 times slower than normal execution. (But this may still be worth it, to
3735 catch errors where you have no clue what part of your program is the
3738 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3739 x86-based targets, @value{GDBN} includes support for hardware
3740 watchpoints, which do not slow down the running of your program.
3744 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3745 Set a watchpoint for an expression. @value{GDBN} will break when the
3746 expression @var{expr} is written into by the program and its value
3747 changes. The simplest (and the most popular) use of this command is
3748 to watch the value of a single variable:
3751 (@value{GDBP}) watch foo
3754 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3755 argument, @value{GDBN} breaks only when the thread identified by
3756 @var{threadnum} changes the value of @var{expr}. If any other threads
3757 change the value of @var{expr}, @value{GDBN} will not break. Note
3758 that watchpoints restricted to a single thread in this way only work
3759 with Hardware Watchpoints.
3761 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3762 (see below). The @code{-location} argument tells @value{GDBN} to
3763 instead watch the memory referred to by @var{expr}. In this case,
3764 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3765 and watch the memory at that address. The type of the result is used
3766 to determine the size of the watched memory. If the expression's
3767 result does not have an address, then @value{GDBN} will print an
3770 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3771 of masked watchpoints, if the current architecture supports this
3772 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3773 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3774 to an address to watch. The mask specifies that some bits of an address
3775 (the bits which are reset in the mask) should be ignored when matching
3776 the address accessed by the inferior against the watchpoint address.
3777 Thus, a masked watchpoint watches many addresses simultaneously---those
3778 addresses whose unmasked bits are identical to the unmasked bits in the
3779 watchpoint address. The @code{mask} argument implies @code{-location}.
3783 (@value{GDBP}) watch foo mask 0xffff00ff
3784 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3788 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3789 Set a watchpoint that will break when the value of @var{expr} is read
3793 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3794 Set a watchpoint that will break when @var{expr} is either read from
3795 or written into by the program.
3797 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3798 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3799 This command prints a list of watchpoints, using the same format as
3800 @code{info break} (@pxref{Set Breaks}).
3803 If you watch for a change in a numerically entered address you need to
3804 dereference it, as the address itself is just a constant number which will
3805 never change. @value{GDBN} refuses to create a watchpoint that watches
3806 a never-changing value:
3809 (@value{GDBP}) watch 0x600850
3810 Cannot watch constant value 0x600850.
3811 (@value{GDBP}) watch *(int *) 0x600850
3812 Watchpoint 1: *(int *) 6293584
3815 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3816 watchpoints execute very quickly, and the debugger reports a change in
3817 value at the exact instruction where the change occurs. If @value{GDBN}
3818 cannot set a hardware watchpoint, it sets a software watchpoint, which
3819 executes more slowly and reports the change in value at the next
3820 @emph{statement}, not the instruction, after the change occurs.
3822 @cindex use only software watchpoints
3823 You can force @value{GDBN} to use only software watchpoints with the
3824 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3825 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3826 the underlying system supports them. (Note that hardware-assisted
3827 watchpoints that were set @emph{before} setting
3828 @code{can-use-hw-watchpoints} to zero will still use the hardware
3829 mechanism of watching expression values.)
3832 @item set can-use-hw-watchpoints
3833 @kindex set can-use-hw-watchpoints
3834 Set whether or not to use hardware watchpoints.
3836 @item show can-use-hw-watchpoints
3837 @kindex show can-use-hw-watchpoints
3838 Show the current mode of using hardware watchpoints.
3841 For remote targets, you can restrict the number of hardware
3842 watchpoints @value{GDBN} will use, see @ref{set remote
3843 hardware-breakpoint-limit}.
3845 When you issue the @code{watch} command, @value{GDBN} reports
3848 Hardware watchpoint @var{num}: @var{expr}
3852 if it was able to set a hardware watchpoint.
3854 Currently, the @code{awatch} and @code{rwatch} commands can only set
3855 hardware watchpoints, because accesses to data that don't change the
3856 value of the watched expression cannot be detected without examining
3857 every instruction as it is being executed, and @value{GDBN} does not do
3858 that currently. If @value{GDBN} finds that it is unable to set a
3859 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3860 will print a message like this:
3863 Expression cannot be implemented with read/access watchpoint.
3866 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3867 data type of the watched expression is wider than what a hardware
3868 watchpoint on the target machine can handle. For example, some systems
3869 can only watch regions that are up to 4 bytes wide; on such systems you
3870 cannot set hardware watchpoints for an expression that yields a
3871 double-precision floating-point number (which is typically 8 bytes
3872 wide). As a work-around, it might be possible to break the large region
3873 into a series of smaller ones and watch them with separate watchpoints.
3875 If you set too many hardware watchpoints, @value{GDBN} might be unable
3876 to insert all of them when you resume the execution of your program.
3877 Since the precise number of active watchpoints is unknown until such
3878 time as the program is about to be resumed, @value{GDBN} might not be
3879 able to warn you about this when you set the watchpoints, and the
3880 warning will be printed only when the program is resumed:
3883 Hardware watchpoint @var{num}: Could not insert watchpoint
3887 If this happens, delete or disable some of the watchpoints.
3889 Watching complex expressions that reference many variables can also
3890 exhaust the resources available for hardware-assisted watchpoints.
3891 That's because @value{GDBN} needs to watch every variable in the
3892 expression with separately allocated resources.
3894 If you call a function interactively using @code{print} or @code{call},
3895 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3896 kind of breakpoint or the call completes.
3898 @value{GDBN} automatically deletes watchpoints that watch local
3899 (automatic) variables, or expressions that involve such variables, when
3900 they go out of scope, that is, when the execution leaves the block in
3901 which these variables were defined. In particular, when the program
3902 being debugged terminates, @emph{all} local variables go out of scope,
3903 and so only watchpoints that watch global variables remain set. If you
3904 rerun the program, you will need to set all such watchpoints again. One
3905 way of doing that would be to set a code breakpoint at the entry to the
3906 @code{main} function and when it breaks, set all the watchpoints.
3908 @cindex watchpoints and threads
3909 @cindex threads and watchpoints
3910 In multi-threaded programs, watchpoints will detect changes to the
3911 watched expression from every thread.
3914 @emph{Warning:} In multi-threaded programs, software watchpoints
3915 have only limited usefulness. If @value{GDBN} creates a software
3916 watchpoint, it can only watch the value of an expression @emph{in a
3917 single thread}. If you are confident that the expression can only
3918 change due to the current thread's activity (and if you are also
3919 confident that no other thread can become current), then you can use
3920 software watchpoints as usual. However, @value{GDBN} may not notice
3921 when a non-current thread's activity changes the expression. (Hardware
3922 watchpoints, in contrast, watch an expression in all threads.)
3925 @xref{set remote hardware-watchpoint-limit}.
3927 @node Set Catchpoints
3928 @subsection Setting Catchpoints
3929 @cindex catchpoints, setting
3930 @cindex exception handlers
3931 @cindex event handling
3933 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3934 kinds of program events, such as C@t{++} exceptions or the loading of a
3935 shared library. Use the @code{catch} command to set a catchpoint.
3939 @item catch @var{event}
3940 Stop when @var{event} occurs. @var{event} can be any of the following:
3943 @cindex stop on C@t{++} exceptions
3944 The throwing of a C@t{++} exception.
3947 The catching of a C@t{++} exception.
3950 @cindex Ada exception catching
3951 @cindex catch Ada exceptions
3952 An Ada exception being raised. If an exception name is specified
3953 at the end of the command (eg @code{catch exception Program_Error}),
3954 the debugger will stop only when this specific exception is raised.
3955 Otherwise, the debugger stops execution when any Ada exception is raised.
3957 When inserting an exception catchpoint on a user-defined exception whose
3958 name is identical to one of the exceptions defined by the language, the
3959 fully qualified name must be used as the exception name. Otherwise,
3960 @value{GDBN} will assume that it should stop on the pre-defined exception
3961 rather than the user-defined one. For instance, assuming an exception
3962 called @code{Constraint_Error} is defined in package @code{Pck}, then
3963 the command to use to catch such exceptions is @kbd{catch exception
3964 Pck.Constraint_Error}.
3966 @item exception unhandled
3967 An exception that was raised but is not handled by the program.
3970 A failed Ada assertion.
3973 @cindex break on fork/exec
3974 A call to @code{exec}. This is currently only available for HP-UX
3978 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3979 @cindex break on a system call.
3980 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3981 syscall is a mechanism for application programs to request a service
3982 from the operating system (OS) or one of the OS system services.
3983 @value{GDBN} can catch some or all of the syscalls issued by the
3984 debuggee, and show the related information for each syscall. If no
3985 argument is specified, calls to and returns from all system calls
3988 @var{name} can be any system call name that is valid for the
3989 underlying OS. Just what syscalls are valid depends on the OS. On
3990 GNU and Unix systems, you can find the full list of valid syscall
3991 names on @file{/usr/include/asm/unistd.h}.
3993 @c For MS-Windows, the syscall names and the corresponding numbers
3994 @c can be found, e.g., on this URL:
3995 @c http://www.metasploit.com/users/opcode/syscalls.html
3996 @c but we don't support Windows syscalls yet.
3998 Normally, @value{GDBN} knows in advance which syscalls are valid for
3999 each OS, so you can use the @value{GDBN} command-line completion
4000 facilities (@pxref{Completion,, command completion}) to list the
4003 You may also specify the system call numerically. A syscall's
4004 number is the value passed to the OS's syscall dispatcher to
4005 identify the requested service. When you specify the syscall by its
4006 name, @value{GDBN} uses its database of syscalls to convert the name
4007 into the corresponding numeric code, but using the number directly
4008 may be useful if @value{GDBN}'s database does not have the complete
4009 list of syscalls on your system (e.g., because @value{GDBN} lags
4010 behind the OS upgrades).
4012 The example below illustrates how this command works if you don't provide
4016 (@value{GDBP}) catch syscall
4017 Catchpoint 1 (syscall)
4019 Starting program: /tmp/catch-syscall
4021 Catchpoint 1 (call to syscall 'close'), \
4022 0xffffe424 in __kernel_vsyscall ()
4026 Catchpoint 1 (returned from syscall 'close'), \
4027 0xffffe424 in __kernel_vsyscall ()
4031 Here is an example of catching a system call by name:
4034 (@value{GDBP}) catch syscall chroot
4035 Catchpoint 1 (syscall 'chroot' [61])
4037 Starting program: /tmp/catch-syscall
4039 Catchpoint 1 (call to syscall 'chroot'), \
4040 0xffffe424 in __kernel_vsyscall ()
4044 Catchpoint 1 (returned from syscall 'chroot'), \
4045 0xffffe424 in __kernel_vsyscall ()
4049 An example of specifying a system call numerically. In the case
4050 below, the syscall number has a corresponding entry in the XML
4051 file, so @value{GDBN} finds its name and prints it:
4054 (@value{GDBP}) catch syscall 252
4055 Catchpoint 1 (syscall(s) 'exit_group')
4057 Starting program: /tmp/catch-syscall
4059 Catchpoint 1 (call to syscall 'exit_group'), \
4060 0xffffe424 in __kernel_vsyscall ()
4064 Program exited normally.
4068 However, there can be situations when there is no corresponding name
4069 in XML file for that syscall number. In this case, @value{GDBN} prints
4070 a warning message saying that it was not able to find the syscall name,
4071 but the catchpoint will be set anyway. See the example below:
4074 (@value{GDBP}) catch syscall 764
4075 warning: The number '764' does not represent a known syscall.
4076 Catchpoint 2 (syscall 764)
4080 If you configure @value{GDBN} using the @samp{--without-expat} option,
4081 it will not be able to display syscall names. Also, if your
4082 architecture does not have an XML file describing its system calls,
4083 you will not be able to see the syscall names. It is important to
4084 notice that these two features are used for accessing the syscall
4085 name database. In either case, you will see a warning like this:
4088 (@value{GDBP}) catch syscall
4089 warning: Could not open "syscalls/i386-linux.xml"
4090 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4091 GDB will not be able to display syscall names.
4092 Catchpoint 1 (syscall)
4096 Of course, the file name will change depending on your architecture and system.
4098 Still using the example above, you can also try to catch a syscall by its
4099 number. In this case, you would see something like:
4102 (@value{GDBP}) catch syscall 252
4103 Catchpoint 1 (syscall(s) 252)
4106 Again, in this case @value{GDBN} would not be able to display syscall's names.
4109 A call to @code{fork}. This is currently only available for HP-UX
4113 A call to @code{vfork}. This is currently only available for HP-UX
4116 @item load @r{[}regexp@r{]}
4117 @itemx unload @r{[}regexp@r{]}
4118 The loading or unloading of a shared library. If @var{regexp} is
4119 given, then the catchpoint will stop only if the regular expression
4120 matches one of the affected libraries.
4124 @item tcatch @var{event}
4125 Set a catchpoint that is enabled only for one stop. The catchpoint is
4126 automatically deleted after the first time the event is caught.
4130 Use the @code{info break} command to list the current catchpoints.
4132 There are currently some limitations to C@t{++} exception handling
4133 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4137 If you call a function interactively, @value{GDBN} normally returns
4138 control to you when the function has finished executing. If the call
4139 raises an exception, however, the call may bypass the mechanism that
4140 returns control to you and cause your program either to abort or to
4141 simply continue running until it hits a breakpoint, catches a signal
4142 that @value{GDBN} is listening for, or exits. This is the case even if
4143 you set a catchpoint for the exception; catchpoints on exceptions are
4144 disabled within interactive calls.
4147 You cannot raise an exception interactively.
4150 You cannot install an exception handler interactively.
4153 @cindex raise exceptions
4154 Sometimes @code{catch} is not the best way to debug exception handling:
4155 if you need to know exactly where an exception is raised, it is better to
4156 stop @emph{before} the exception handler is called, since that way you
4157 can see the stack before any unwinding takes place. If you set a
4158 breakpoint in an exception handler instead, it may not be easy to find
4159 out where the exception was raised.
4161 To stop just before an exception handler is called, you need some
4162 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4163 raised by calling a library function named @code{__raise_exception}
4164 which has the following ANSI C interface:
4167 /* @var{addr} is where the exception identifier is stored.
4168 @var{id} is the exception identifier. */
4169 void __raise_exception (void **addr, void *id);
4173 To make the debugger catch all exceptions before any stack
4174 unwinding takes place, set a breakpoint on @code{__raise_exception}
4175 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4177 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4178 that depends on the value of @var{id}, you can stop your program when
4179 a specific exception is raised. You can use multiple conditional
4180 breakpoints to stop your program when any of a number of exceptions are
4185 @subsection Deleting Breakpoints
4187 @cindex clearing breakpoints, watchpoints, catchpoints
4188 @cindex deleting breakpoints, watchpoints, catchpoints
4189 It is often necessary to eliminate a breakpoint, watchpoint, or
4190 catchpoint once it has done its job and you no longer want your program
4191 to stop there. This is called @dfn{deleting} the breakpoint. A
4192 breakpoint that has been deleted no longer exists; it is forgotten.
4194 With the @code{clear} command you can delete breakpoints according to
4195 where they are in your program. With the @code{delete} command you can
4196 delete individual breakpoints, watchpoints, or catchpoints by specifying
4197 their breakpoint numbers.
4199 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4200 automatically ignores breakpoints on the first instruction to be executed
4201 when you continue execution without changing the execution address.
4206 Delete any breakpoints at the next instruction to be executed in the
4207 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4208 the innermost frame is selected, this is a good way to delete a
4209 breakpoint where your program just stopped.
4211 @item clear @var{location}
4212 Delete any breakpoints set at the specified @var{location}.
4213 @xref{Specify Location}, for the various forms of @var{location}; the
4214 most useful ones are listed below:
4217 @item clear @var{function}
4218 @itemx clear @var{filename}:@var{function}
4219 Delete any breakpoints set at entry to the named @var{function}.
4221 @item clear @var{linenum}
4222 @itemx clear @var{filename}:@var{linenum}
4223 Delete any breakpoints set at or within the code of the specified
4224 @var{linenum} of the specified @var{filename}.
4227 @cindex delete breakpoints
4229 @kindex d @r{(@code{delete})}
4230 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4231 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4232 ranges specified as arguments. If no argument is specified, delete all
4233 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4234 confirm off}). You can abbreviate this command as @code{d}.
4238 @subsection Disabling Breakpoints
4240 @cindex enable/disable a breakpoint
4241 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4242 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4243 it had been deleted, but remembers the information on the breakpoint so
4244 that you can @dfn{enable} it again later.
4246 You disable and enable breakpoints, watchpoints, and catchpoints with
4247 the @code{enable} and @code{disable} commands, optionally specifying
4248 one or more breakpoint numbers as arguments. Use @code{info break} to
4249 print a list of all breakpoints, watchpoints, and catchpoints if you
4250 do not know which numbers to use.
4252 Disabling and enabling a breakpoint that has multiple locations
4253 affects all of its locations.
4255 A breakpoint, watchpoint, or catchpoint can have any of four different
4256 states of enablement:
4260 Enabled. The breakpoint stops your program. A breakpoint set
4261 with the @code{break} command starts out in this state.
4263 Disabled. The breakpoint has no effect on your program.
4265 Enabled once. The breakpoint stops your program, but then becomes
4268 Enabled for deletion. The breakpoint stops your program, but
4269 immediately after it does so it is deleted permanently. A breakpoint
4270 set with the @code{tbreak} command starts out in this state.
4273 You can use the following commands to enable or disable breakpoints,
4274 watchpoints, and catchpoints:
4278 @kindex dis @r{(@code{disable})}
4279 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4280 Disable the specified breakpoints---or all breakpoints, if none are
4281 listed. A disabled breakpoint has no effect but is not forgotten. All
4282 options such as ignore-counts, conditions and commands are remembered in
4283 case the breakpoint is enabled again later. You may abbreviate
4284 @code{disable} as @code{dis}.
4287 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4288 Enable the specified breakpoints (or all defined breakpoints). They
4289 become effective once again in stopping your program.
4291 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4292 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4293 of these breakpoints immediately after stopping your program.
4295 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4296 Enable the specified breakpoints to work once, then die. @value{GDBN}
4297 deletes any of these breakpoints as soon as your program stops there.
4298 Breakpoints set by the @code{tbreak} command start out in this state.
4301 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4302 @c confusing: tbreak is also initially enabled.
4303 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4304 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4305 subsequently, they become disabled or enabled only when you use one of
4306 the commands above. (The command @code{until} can set and delete a
4307 breakpoint of its own, but it does not change the state of your other
4308 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4312 @subsection Break Conditions
4313 @cindex conditional breakpoints
4314 @cindex breakpoint conditions
4316 @c FIXME what is scope of break condition expr? Context where wanted?
4317 @c in particular for a watchpoint?
4318 The simplest sort of breakpoint breaks every time your program reaches a
4319 specified place. You can also specify a @dfn{condition} for a
4320 breakpoint. A condition is just a Boolean expression in your
4321 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4322 a condition evaluates the expression each time your program reaches it,
4323 and your program stops only if the condition is @emph{true}.
4325 This is the converse of using assertions for program validation; in that
4326 situation, you want to stop when the assertion is violated---that is,
4327 when the condition is false. In C, if you want to test an assertion expressed
4328 by the condition @var{assert}, you should set the condition
4329 @samp{! @var{assert}} on the appropriate breakpoint.
4331 Conditions are also accepted for watchpoints; you may not need them,
4332 since a watchpoint is inspecting the value of an expression anyhow---but
4333 it might be simpler, say, to just set a watchpoint on a variable name,
4334 and specify a condition that tests whether the new value is an interesting
4337 Break conditions can have side effects, and may even call functions in
4338 your program. This can be useful, for example, to activate functions
4339 that log program progress, or to use your own print functions to
4340 format special data structures. The effects are completely predictable
4341 unless there is another enabled breakpoint at the same address. (In
4342 that case, @value{GDBN} might see the other breakpoint first and stop your
4343 program without checking the condition of this one.) Note that
4344 breakpoint commands are usually more convenient and flexible than break
4346 purpose of performing side effects when a breakpoint is reached
4347 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4349 Break conditions can be specified when a breakpoint is set, by using
4350 @samp{if} in the arguments to the @code{break} command. @xref{Set
4351 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4352 with the @code{condition} command.
4354 You can also use the @code{if} keyword with the @code{watch} command.
4355 The @code{catch} command does not recognize the @code{if} keyword;
4356 @code{condition} is the only way to impose a further condition on a
4361 @item condition @var{bnum} @var{expression}
4362 Specify @var{expression} as the break condition for breakpoint,
4363 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4364 breakpoint @var{bnum} stops your program only if the value of
4365 @var{expression} is true (nonzero, in C). When you use
4366 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4367 syntactic correctness, and to determine whether symbols in it have
4368 referents in the context of your breakpoint. If @var{expression} uses
4369 symbols not referenced in the context of the breakpoint, @value{GDBN}
4370 prints an error message:
4373 No symbol "foo" in current context.
4378 not actually evaluate @var{expression} at the time the @code{condition}
4379 command (or a command that sets a breakpoint with a condition, like
4380 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4382 @item condition @var{bnum}
4383 Remove the condition from breakpoint number @var{bnum}. It becomes
4384 an ordinary unconditional breakpoint.
4387 @cindex ignore count (of breakpoint)
4388 A special case of a breakpoint condition is to stop only when the
4389 breakpoint has been reached a certain number of times. This is so
4390 useful that there is a special way to do it, using the @dfn{ignore
4391 count} of the breakpoint. Every breakpoint has an ignore count, which
4392 is an integer. Most of the time, the ignore count is zero, and
4393 therefore has no effect. But if your program reaches a breakpoint whose
4394 ignore count is positive, then instead of stopping, it just decrements
4395 the ignore count by one and continues. As a result, if the ignore count
4396 value is @var{n}, the breakpoint does not stop the next @var{n} times
4397 your program reaches it.
4401 @item ignore @var{bnum} @var{count}
4402 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4403 The next @var{count} times the breakpoint is reached, your program's
4404 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4407 To make the breakpoint stop the next time it is reached, specify
4410 When you use @code{continue} to resume execution of your program from a
4411 breakpoint, you can specify an ignore count directly as an argument to
4412 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4413 Stepping,,Continuing and Stepping}.
4415 If a breakpoint has a positive ignore count and a condition, the
4416 condition is not checked. Once the ignore count reaches zero,
4417 @value{GDBN} resumes checking the condition.
4419 You could achieve the effect of the ignore count with a condition such
4420 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4421 is decremented each time. @xref{Convenience Vars, ,Convenience
4425 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4428 @node Break Commands
4429 @subsection Breakpoint Command Lists
4431 @cindex breakpoint commands
4432 You can give any breakpoint (or watchpoint or catchpoint) a series of
4433 commands to execute when your program stops due to that breakpoint. For
4434 example, you might want to print the values of certain expressions, or
4435 enable other breakpoints.
4439 @kindex end@r{ (breakpoint commands)}
4440 @item commands @r{[}@var{range}@dots{}@r{]}
4441 @itemx @dots{} @var{command-list} @dots{}
4443 Specify a list of commands for the given breakpoints. The commands
4444 themselves appear on the following lines. Type a line containing just
4445 @code{end} to terminate the commands.
4447 To remove all commands from a breakpoint, type @code{commands} and
4448 follow it immediately with @code{end}; that is, give no commands.
4450 With no argument, @code{commands} refers to the last breakpoint,
4451 watchpoint, or catchpoint set (not to the breakpoint most recently
4452 encountered). If the most recent breakpoints were set with a single
4453 command, then the @code{commands} will apply to all the breakpoints
4454 set by that command. This applies to breakpoints set by
4455 @code{rbreak}, and also applies when a single @code{break} command
4456 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4460 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4461 disabled within a @var{command-list}.
4463 You can use breakpoint commands to start your program up again. Simply
4464 use the @code{continue} command, or @code{step}, or any other command
4465 that resumes execution.
4467 Any other commands in the command list, after a command that resumes
4468 execution, are ignored. This is because any time you resume execution
4469 (even with a simple @code{next} or @code{step}), you may encounter
4470 another breakpoint---which could have its own command list, leading to
4471 ambiguities about which list to execute.
4474 If the first command you specify in a command list is @code{silent}, the
4475 usual message about stopping at a breakpoint is not printed. This may
4476 be desirable for breakpoints that are to print a specific message and
4477 then continue. If none of the remaining commands print anything, you
4478 see no sign that the breakpoint was reached. @code{silent} is
4479 meaningful only at the beginning of a breakpoint command list.
4481 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4482 print precisely controlled output, and are often useful in silent
4483 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4485 For example, here is how you could use breakpoint commands to print the
4486 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4492 printf "x is %d\n",x
4497 One application for breakpoint commands is to compensate for one bug so
4498 you can test for another. Put a breakpoint just after the erroneous line
4499 of code, give it a condition to detect the case in which something
4500 erroneous has been done, and give it commands to assign correct values
4501 to any variables that need them. End with the @code{continue} command
4502 so that your program does not stop, and start with the @code{silent}
4503 command so that no output is produced. Here is an example:
4514 @node Save Breakpoints
4515 @subsection How to save breakpoints to a file
4517 To save breakpoint definitions to a file use the @w{@code{save
4518 breakpoints}} command.
4521 @kindex save breakpoints
4522 @cindex save breakpoints to a file for future sessions
4523 @item save breakpoints [@var{filename}]
4524 This command saves all current breakpoint definitions together with
4525 their commands and ignore counts, into a file @file{@var{filename}}
4526 suitable for use in a later debugging session. This includes all
4527 types of breakpoints (breakpoints, watchpoints, catchpoints,
4528 tracepoints). To read the saved breakpoint definitions, use the
4529 @code{source} command (@pxref{Command Files}). Note that watchpoints
4530 with expressions involving local variables may fail to be recreated
4531 because it may not be possible to access the context where the
4532 watchpoint is valid anymore. Because the saved breakpoint definitions
4533 are simply a sequence of @value{GDBN} commands that recreate the
4534 breakpoints, you can edit the file in your favorite editing program,
4535 and remove the breakpoint definitions you're not interested in, or
4536 that can no longer be recreated.
4539 @c @ifclear BARETARGET
4540 @node Error in Breakpoints
4541 @subsection ``Cannot insert breakpoints''
4543 If you request too many active hardware-assisted breakpoints and
4544 watchpoints, you will see this error message:
4546 @c FIXME: the precise wording of this message may change; the relevant
4547 @c source change is not committed yet (Sep 3, 1999).
4549 Stopped; cannot insert breakpoints.
4550 You may have requested too many hardware breakpoints and watchpoints.
4554 This message is printed when you attempt to resume the program, since
4555 only then @value{GDBN} knows exactly how many hardware breakpoints and
4556 watchpoints it needs to insert.
4558 When this message is printed, you need to disable or remove some of the
4559 hardware-assisted breakpoints and watchpoints, and then continue.
4561 @node Breakpoint-related Warnings
4562 @subsection ``Breakpoint address adjusted...''
4563 @cindex breakpoint address adjusted
4565 Some processor architectures place constraints on the addresses at
4566 which breakpoints may be placed. For architectures thus constrained,
4567 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4568 with the constraints dictated by the architecture.
4570 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4571 a VLIW architecture in which a number of RISC-like instructions may be
4572 bundled together for parallel execution. The FR-V architecture
4573 constrains the location of a breakpoint instruction within such a
4574 bundle to the instruction with the lowest address. @value{GDBN}
4575 honors this constraint by adjusting a breakpoint's address to the
4576 first in the bundle.
4578 It is not uncommon for optimized code to have bundles which contain
4579 instructions from different source statements, thus it may happen that
4580 a breakpoint's address will be adjusted from one source statement to
4581 another. Since this adjustment may significantly alter @value{GDBN}'s
4582 breakpoint related behavior from what the user expects, a warning is
4583 printed when the breakpoint is first set and also when the breakpoint
4586 A warning like the one below is printed when setting a breakpoint
4587 that's been subject to address adjustment:
4590 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4593 Such warnings are printed both for user settable and @value{GDBN}'s
4594 internal breakpoints. If you see one of these warnings, you should
4595 verify that a breakpoint set at the adjusted address will have the
4596 desired affect. If not, the breakpoint in question may be removed and
4597 other breakpoints may be set which will have the desired behavior.
4598 E.g., it may be sufficient to place the breakpoint at a later
4599 instruction. A conditional breakpoint may also be useful in some
4600 cases to prevent the breakpoint from triggering too often.
4602 @value{GDBN} will also issue a warning when stopping at one of these
4603 adjusted breakpoints:
4606 warning: Breakpoint 1 address previously adjusted from 0x00010414
4610 When this warning is encountered, it may be too late to take remedial
4611 action except in cases where the breakpoint is hit earlier or more
4612 frequently than expected.
4614 @node Continuing and Stepping
4615 @section Continuing and Stepping
4619 @cindex resuming execution
4620 @dfn{Continuing} means resuming program execution until your program
4621 completes normally. In contrast, @dfn{stepping} means executing just
4622 one more ``step'' of your program, where ``step'' may mean either one
4623 line of source code, or one machine instruction (depending on what
4624 particular command you use). Either when continuing or when stepping,
4625 your program may stop even sooner, due to a breakpoint or a signal. (If
4626 it stops due to a signal, you may want to use @code{handle}, or use
4627 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4631 @kindex c @r{(@code{continue})}
4632 @kindex fg @r{(resume foreground execution)}
4633 @item continue @r{[}@var{ignore-count}@r{]}
4634 @itemx c @r{[}@var{ignore-count}@r{]}
4635 @itemx fg @r{[}@var{ignore-count}@r{]}
4636 Resume program execution, at the address where your program last stopped;
4637 any breakpoints set at that address are bypassed. The optional argument
4638 @var{ignore-count} allows you to specify a further number of times to
4639 ignore a breakpoint at this location; its effect is like that of
4640 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4642 The argument @var{ignore-count} is meaningful only when your program
4643 stopped due to a breakpoint. At other times, the argument to
4644 @code{continue} is ignored.
4646 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4647 debugged program is deemed to be the foreground program) are provided
4648 purely for convenience, and have exactly the same behavior as
4652 To resume execution at a different place, you can use @code{return}
4653 (@pxref{Returning, ,Returning from a Function}) to go back to the
4654 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4655 Different Address}) to go to an arbitrary location in your program.
4657 A typical technique for using stepping is to set a breakpoint
4658 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4659 beginning of the function or the section of your program where a problem
4660 is believed to lie, run your program until it stops at that breakpoint,
4661 and then step through the suspect area, examining the variables that are
4662 interesting, until you see the problem happen.
4666 @kindex s @r{(@code{step})}
4668 Continue running your program until control reaches a different source
4669 line, then stop it and return control to @value{GDBN}. This command is
4670 abbreviated @code{s}.
4673 @c "without debugging information" is imprecise; actually "without line
4674 @c numbers in the debugging information". (gcc -g1 has debugging info but
4675 @c not line numbers). But it seems complex to try to make that
4676 @c distinction here.
4677 @emph{Warning:} If you use the @code{step} command while control is
4678 within a function that was compiled without debugging information,
4679 execution proceeds until control reaches a function that does have
4680 debugging information. Likewise, it will not step into a function which
4681 is compiled without debugging information. To step through functions
4682 without debugging information, use the @code{stepi} command, described
4686 The @code{step} command only stops at the first instruction of a source
4687 line. This prevents the multiple stops that could otherwise occur in
4688 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4689 to stop if a function that has debugging information is called within
4690 the line. In other words, @code{step} @emph{steps inside} any functions
4691 called within the line.
4693 Also, the @code{step} command only enters a function if there is line
4694 number information for the function. Otherwise it acts like the
4695 @code{next} command. This avoids problems when using @code{cc -gl}
4696 on MIPS machines. Previously, @code{step} entered subroutines if there
4697 was any debugging information about the routine.
4699 @item step @var{count}
4700 Continue running as in @code{step}, but do so @var{count} times. If a
4701 breakpoint is reached, or a signal not related to stepping occurs before
4702 @var{count} steps, stepping stops right away.
4705 @kindex n @r{(@code{next})}
4706 @item next @r{[}@var{count}@r{]}
4707 Continue to the next source line in the current (innermost) stack frame.
4708 This is similar to @code{step}, but function calls that appear within
4709 the line of code are executed without stopping. Execution stops when
4710 control reaches a different line of code at the original stack level
4711 that was executing when you gave the @code{next} command. This command
4712 is abbreviated @code{n}.
4714 An argument @var{count} is a repeat count, as for @code{step}.
4717 @c FIX ME!! Do we delete this, or is there a way it fits in with
4718 @c the following paragraph? --- Vctoria
4720 @c @code{next} within a function that lacks debugging information acts like
4721 @c @code{step}, but any function calls appearing within the code of the
4722 @c function are executed without stopping.
4724 The @code{next} command only stops at the first instruction of a
4725 source line. This prevents multiple stops that could otherwise occur in
4726 @code{switch} statements, @code{for} loops, etc.
4728 @kindex set step-mode
4730 @cindex functions without line info, and stepping
4731 @cindex stepping into functions with no line info
4732 @itemx set step-mode on
4733 The @code{set step-mode on} command causes the @code{step} command to
4734 stop at the first instruction of a function which contains no debug line
4735 information rather than stepping over it.
4737 This is useful in cases where you may be interested in inspecting the
4738 machine instructions of a function which has no symbolic info and do not
4739 want @value{GDBN} to automatically skip over this function.
4741 @item set step-mode off
4742 Causes the @code{step} command to step over any functions which contains no
4743 debug information. This is the default.
4745 @item show step-mode
4746 Show whether @value{GDBN} will stop in or step over functions without
4747 source line debug information.
4750 @kindex fin @r{(@code{finish})}
4752 Continue running until just after function in the selected stack frame
4753 returns. Print the returned value (if any). This command can be
4754 abbreviated as @code{fin}.
4756 Contrast this with the @code{return} command (@pxref{Returning,
4757 ,Returning from a Function}).
4760 @kindex u @r{(@code{until})}
4761 @cindex run until specified location
4764 Continue running until a source line past the current line, in the
4765 current stack frame, is reached. This command is used to avoid single
4766 stepping through a loop more than once. It is like the @code{next}
4767 command, except that when @code{until} encounters a jump, it
4768 automatically continues execution until the program counter is greater
4769 than the address of the jump.
4771 This means that when you reach the end of a loop after single stepping
4772 though it, @code{until} makes your program continue execution until it
4773 exits the loop. In contrast, a @code{next} command at the end of a loop
4774 simply steps back to the beginning of the loop, which forces you to step
4775 through the next iteration.
4777 @code{until} always stops your program if it attempts to exit the current
4780 @code{until} may produce somewhat counterintuitive results if the order
4781 of machine code does not match the order of the source lines. For
4782 example, in the following excerpt from a debugging session, the @code{f}
4783 (@code{frame}) command shows that execution is stopped at line
4784 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4788 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4790 (@value{GDBP}) until
4791 195 for ( ; argc > 0; NEXTARG) @{
4794 This happened because, for execution efficiency, the compiler had
4795 generated code for the loop closure test at the end, rather than the
4796 start, of the loop---even though the test in a C @code{for}-loop is
4797 written before the body of the loop. The @code{until} command appeared
4798 to step back to the beginning of the loop when it advanced to this
4799 expression; however, it has not really gone to an earlier
4800 statement---not in terms of the actual machine code.
4802 @code{until} with no argument works by means of single
4803 instruction stepping, and hence is slower than @code{until} with an
4806 @item until @var{location}
4807 @itemx u @var{location}
4808 Continue running your program until either the specified location is
4809 reached, or the current stack frame returns. @var{location} is any of
4810 the forms described in @ref{Specify Location}.
4811 This form of the command uses temporary breakpoints, and
4812 hence is quicker than @code{until} without an argument. The specified
4813 location is actually reached only if it is in the current frame. This
4814 implies that @code{until} can be used to skip over recursive function
4815 invocations. For instance in the code below, if the current location is
4816 line @code{96}, issuing @code{until 99} will execute the program up to
4817 line @code{99} in the same invocation of factorial, i.e., after the inner
4818 invocations have returned.
4821 94 int factorial (int value)
4823 96 if (value > 1) @{
4824 97 value *= factorial (value - 1);
4831 @kindex advance @var{location}
4832 @itemx advance @var{location}
4833 Continue running the program up to the given @var{location}. An argument is
4834 required, which should be of one of the forms described in
4835 @ref{Specify Location}.
4836 Execution will also stop upon exit from the current stack
4837 frame. This command is similar to @code{until}, but @code{advance} will
4838 not skip over recursive function calls, and the target location doesn't
4839 have to be in the same frame as the current one.
4843 @kindex si @r{(@code{stepi})}
4845 @itemx stepi @var{arg}
4847 Execute one machine instruction, then stop and return to the debugger.
4849 It is often useful to do @samp{display/i $pc} when stepping by machine
4850 instructions. This makes @value{GDBN} automatically display the next
4851 instruction to be executed, each time your program stops. @xref{Auto
4852 Display,, Automatic Display}.
4854 An argument is a repeat count, as in @code{step}.
4858 @kindex ni @r{(@code{nexti})}
4860 @itemx nexti @var{arg}
4862 Execute one machine instruction, but if it is a function call,
4863 proceed until the function returns.
4865 An argument is a repeat count, as in @code{next}.
4868 @node Skipping Over Functions and Files
4869 @section Skipping Over Functions and Files
4870 @cindex skipping over functions and files
4872 The program you are debugging may contain some functions which are
4873 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4874 skip a function or all functions in a file when stepping.
4876 For example, consider the following C function:
4887 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4888 are not interested in stepping through @code{boring}. If you run @code{step}
4889 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4890 step over both @code{foo} and @code{boring}!
4892 One solution is to @code{step} into @code{boring} and use the @code{finish}
4893 command to immediately exit it. But this can become tedious if @code{boring}
4894 is called from many places.
4896 A more flexible solution is to execute @kbd{skip boring}. This instructs
4897 @value{GDBN} never to step into @code{boring}. Now when you execute
4898 @code{step} at line 103, you'll step over @code{boring} and directly into
4901 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4902 example, @code{skip file boring.c}.
4905 @kindex skip function
4906 @item skip @r{[}@var{linespec}@r{]}
4907 @itemx skip function @r{[}@var{linespec}@r{]}
4908 After running this command, the function named by @var{linespec} or the
4909 function containing the line named by @var{linespec} will be skipped over when
4910 stepping. @xref{Specify Location}.
4912 If you do not specify @var{linespec}, the function you're currently debugging
4915 (If you have a function called @code{file} that you want to skip, use
4916 @kbd{skip function file}.)
4919 @item skip file @r{[}@var{filename}@r{]}
4920 After running this command, any function whose source lives in @var{filename}
4921 will be skipped over when stepping.
4923 If you do not specify @var{filename}, functions whose source lives in the file
4924 you're currently debugging will be skipped.
4927 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4928 These are the commands for managing your list of skips:
4932 @item info skip @r{[}@var{range}@r{]}
4933 Print details about the specified skip(s). If @var{range} is not specified,
4934 print a table with details about all functions and files marked for skipping.
4935 @code{info skip} prints the following information about each skip:
4939 A number identifying this skip.
4941 The type of this skip, either @samp{function} or @samp{file}.
4942 @item Enabled or Disabled
4943 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4945 For function skips, this column indicates the address in memory of the function
4946 being skipped. If you've set a function skip on a function which has not yet
4947 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4948 which has the function is loaded, @code{info skip} will show the function's
4951 For file skips, this field contains the filename being skipped. For functions
4952 skips, this field contains the function name and its line number in the file
4953 where it is defined.
4957 @item skip delete @r{[}@var{range}@r{]}
4958 Delete the specified skip(s). If @var{range} is not specified, delete all
4962 @item skip enable @r{[}@var{range}@r{]}
4963 Enable the specified skip(s). If @var{range} is not specified, enable all
4966 @kindex skip disable
4967 @item skip disable @r{[}@var{range}@r{]}
4968 Disable the specified skip(s). If @var{range} is not specified, disable all
4977 A signal is an asynchronous event that can happen in a program. The
4978 operating system defines the possible kinds of signals, and gives each
4979 kind a name and a number. For example, in Unix @code{SIGINT} is the
4980 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4981 @code{SIGSEGV} is the signal a program gets from referencing a place in
4982 memory far away from all the areas in use; @code{SIGALRM} occurs when
4983 the alarm clock timer goes off (which happens only if your program has
4984 requested an alarm).
4986 @cindex fatal signals
4987 Some signals, including @code{SIGALRM}, are a normal part of the
4988 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4989 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4990 program has not specified in advance some other way to handle the signal.
4991 @code{SIGINT} does not indicate an error in your program, but it is normally
4992 fatal so it can carry out the purpose of the interrupt: to kill the program.
4994 @value{GDBN} has the ability to detect any occurrence of a signal in your
4995 program. You can tell @value{GDBN} in advance what to do for each kind of
4998 @cindex handling signals
4999 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5000 @code{SIGALRM} be silently passed to your program
5001 (so as not to interfere with their role in the program's functioning)
5002 but to stop your program immediately whenever an error signal happens.
5003 You can change these settings with the @code{handle} command.
5006 @kindex info signals
5010 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5011 handle each one. You can use this to see the signal numbers of all
5012 the defined types of signals.
5014 @item info signals @var{sig}
5015 Similar, but print information only about the specified signal number.
5017 @code{info handle} is an alias for @code{info signals}.
5020 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5021 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5022 can be the number of a signal or its name (with or without the
5023 @samp{SIG} at the beginning); a list of signal numbers of the form
5024 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5025 known signals. Optional arguments @var{keywords}, described below,
5026 say what change to make.
5030 The keywords allowed by the @code{handle} command can be abbreviated.
5031 Their full names are:
5035 @value{GDBN} should not stop your program when this signal happens. It may
5036 still print a message telling you that the signal has come in.
5039 @value{GDBN} should stop your program when this signal happens. This implies
5040 the @code{print} keyword as well.
5043 @value{GDBN} should print a message when this signal happens.
5046 @value{GDBN} should not mention the occurrence of the signal at all. This
5047 implies the @code{nostop} keyword as well.
5051 @value{GDBN} should allow your program to see this signal; your program
5052 can handle the signal, or else it may terminate if the signal is fatal
5053 and not handled. @code{pass} and @code{noignore} are synonyms.
5057 @value{GDBN} should not allow your program to see this signal.
5058 @code{nopass} and @code{ignore} are synonyms.
5062 When a signal stops your program, the signal is not visible to the
5064 continue. Your program sees the signal then, if @code{pass} is in
5065 effect for the signal in question @emph{at that time}. In other words,
5066 after @value{GDBN} reports a signal, you can use the @code{handle}
5067 command with @code{pass} or @code{nopass} to control whether your
5068 program sees that signal when you continue.
5070 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5071 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5072 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5075 You can also use the @code{signal} command to prevent your program from
5076 seeing a signal, or cause it to see a signal it normally would not see,
5077 or to give it any signal at any time. For example, if your program stopped
5078 due to some sort of memory reference error, you might store correct
5079 values into the erroneous variables and continue, hoping to see more
5080 execution; but your program would probably terminate immediately as
5081 a result of the fatal signal once it saw the signal. To prevent this,
5082 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5085 @cindex extra signal information
5086 @anchor{extra signal information}
5088 On some targets, @value{GDBN} can inspect extra signal information
5089 associated with the intercepted signal, before it is actually
5090 delivered to the program being debugged. This information is exported
5091 by the convenience variable @code{$_siginfo}, and consists of data
5092 that is passed by the kernel to the signal handler at the time of the
5093 receipt of a signal. The data type of the information itself is
5094 target dependent. You can see the data type using the @code{ptype
5095 $_siginfo} command. On Unix systems, it typically corresponds to the
5096 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5099 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5100 referenced address that raised a segmentation fault.
5104 (@value{GDBP}) continue
5105 Program received signal SIGSEGV, Segmentation fault.
5106 0x0000000000400766 in main ()
5108 (@value{GDBP}) ptype $_siginfo
5115 struct @{...@} _kill;
5116 struct @{...@} _timer;
5118 struct @{...@} _sigchld;
5119 struct @{...@} _sigfault;
5120 struct @{...@} _sigpoll;
5123 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5127 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5128 $1 = (void *) 0x7ffff7ff7000
5132 Depending on target support, @code{$_siginfo} may also be writable.
5135 @section Stopping and Starting Multi-thread Programs
5137 @cindex stopped threads
5138 @cindex threads, stopped
5140 @cindex continuing threads
5141 @cindex threads, continuing
5143 @value{GDBN} supports debugging programs with multiple threads
5144 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5145 are two modes of controlling execution of your program within the
5146 debugger. In the default mode, referred to as @dfn{all-stop mode},
5147 when any thread in your program stops (for example, at a breakpoint
5148 or while being stepped), all other threads in the program are also stopped by
5149 @value{GDBN}. On some targets, @value{GDBN} also supports
5150 @dfn{non-stop mode}, in which other threads can continue to run freely while
5151 you examine the stopped thread in the debugger.
5154 * All-Stop Mode:: All threads stop when GDB takes control
5155 * Non-Stop Mode:: Other threads continue to execute
5156 * Background Execution:: Running your program asynchronously
5157 * Thread-Specific Breakpoints:: Controlling breakpoints
5158 * Interrupted System Calls:: GDB may interfere with system calls
5159 * Observer Mode:: GDB does not alter program behavior
5163 @subsection All-Stop Mode
5165 @cindex all-stop mode
5167 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5168 @emph{all} threads of execution stop, not just the current thread. This
5169 allows you to examine the overall state of the program, including
5170 switching between threads, without worrying that things may change
5173 Conversely, whenever you restart the program, @emph{all} threads start
5174 executing. @emph{This is true even when single-stepping} with commands
5175 like @code{step} or @code{next}.
5177 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5178 Since thread scheduling is up to your debugging target's operating
5179 system (not controlled by @value{GDBN}), other threads may
5180 execute more than one statement while the current thread completes a
5181 single step. Moreover, in general other threads stop in the middle of a
5182 statement, rather than at a clean statement boundary, when the program
5185 You might even find your program stopped in another thread after
5186 continuing or even single-stepping. This happens whenever some other
5187 thread runs into a breakpoint, a signal, or an exception before the
5188 first thread completes whatever you requested.
5190 @cindex automatic thread selection
5191 @cindex switching threads automatically
5192 @cindex threads, automatic switching
5193 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5194 signal, it automatically selects the thread where that breakpoint or
5195 signal happened. @value{GDBN} alerts you to the context switch with a
5196 message such as @samp{[Switching to Thread @var{n}]} to identify the
5199 On some OSes, you can modify @value{GDBN}'s default behavior by
5200 locking the OS scheduler to allow only a single thread to run.
5203 @item set scheduler-locking @var{mode}
5204 @cindex scheduler locking mode
5205 @cindex lock scheduler
5206 Set the scheduler locking mode. If it is @code{off}, then there is no
5207 locking and any thread may run at any time. If @code{on}, then only the
5208 current thread may run when the inferior is resumed. The @code{step}
5209 mode optimizes for single-stepping; it prevents other threads
5210 from preempting the current thread while you are stepping, so that
5211 the focus of debugging does not change unexpectedly.
5212 Other threads only rarely (or never) get a chance to run
5213 when you step. They are more likely to run when you @samp{next} over a
5214 function call, and they are completely free to run when you use commands
5215 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5216 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5217 the current thread away from the thread that you are debugging.
5219 @item show scheduler-locking
5220 Display the current scheduler locking mode.
5223 @cindex resume threads of multiple processes simultaneously
5224 By default, when you issue one of the execution commands such as
5225 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5226 threads of the current inferior to run. For example, if @value{GDBN}
5227 is attached to two inferiors, each with two threads, the
5228 @code{continue} command resumes only the two threads of the current
5229 inferior. This is useful, for example, when you debug a program that
5230 forks and you want to hold the parent stopped (so that, for instance,
5231 it doesn't run to exit), while you debug the child. In other
5232 situations, you may not be interested in inspecting the current state
5233 of any of the processes @value{GDBN} is attached to, and you may want
5234 to resume them all until some breakpoint is hit. In the latter case,
5235 you can instruct @value{GDBN} to allow all threads of all the
5236 inferiors to run with the @w{@code{set schedule-multiple}} command.
5239 @kindex set schedule-multiple
5240 @item set schedule-multiple
5241 Set the mode for allowing threads of multiple processes to be resumed
5242 when an execution command is issued. When @code{on}, all threads of
5243 all processes are allowed to run. When @code{off}, only the threads
5244 of the current process are resumed. The default is @code{off}. The
5245 @code{scheduler-locking} mode takes precedence when set to @code{on},
5246 or while you are stepping and set to @code{step}.
5248 @item show schedule-multiple
5249 Display the current mode for resuming the execution of threads of
5254 @subsection Non-Stop Mode
5256 @cindex non-stop mode
5258 @c This section is really only a place-holder, and needs to be expanded
5259 @c with more details.
5261 For some multi-threaded targets, @value{GDBN} supports an optional
5262 mode of operation in which you can examine stopped program threads in
5263 the debugger while other threads continue to execute freely. This
5264 minimizes intrusion when debugging live systems, such as programs
5265 where some threads have real-time constraints or must continue to
5266 respond to external events. This is referred to as @dfn{non-stop} mode.
5268 In non-stop mode, when a thread stops to report a debugging event,
5269 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5270 threads as well, in contrast to the all-stop mode behavior. Additionally,
5271 execution commands such as @code{continue} and @code{step} apply by default
5272 only to the current thread in non-stop mode, rather than all threads as
5273 in all-stop mode. This allows you to control threads explicitly in
5274 ways that are not possible in all-stop mode --- for example, stepping
5275 one thread while allowing others to run freely, stepping
5276 one thread while holding all others stopped, or stepping several threads
5277 independently and simultaneously.
5279 To enter non-stop mode, use this sequence of commands before you run
5280 or attach to your program:
5283 # Enable the async interface.
5286 # If using the CLI, pagination breaks non-stop.
5289 # Finally, turn it on!
5293 You can use these commands to manipulate the non-stop mode setting:
5296 @kindex set non-stop
5297 @item set non-stop on
5298 Enable selection of non-stop mode.
5299 @item set non-stop off
5300 Disable selection of non-stop mode.
5301 @kindex show non-stop
5303 Show the current non-stop enablement setting.
5306 Note these commands only reflect whether non-stop mode is enabled,
5307 not whether the currently-executing program is being run in non-stop mode.
5308 In particular, the @code{set non-stop} preference is only consulted when
5309 @value{GDBN} starts or connects to the target program, and it is generally
5310 not possible to switch modes once debugging has started. Furthermore,
5311 since not all targets support non-stop mode, even when you have enabled
5312 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5315 In non-stop mode, all execution commands apply only to the current thread
5316 by default. That is, @code{continue} only continues one thread.
5317 To continue all threads, issue @code{continue -a} or @code{c -a}.
5319 You can use @value{GDBN}'s background execution commands
5320 (@pxref{Background Execution}) to run some threads in the background
5321 while you continue to examine or step others from @value{GDBN}.
5322 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5323 always executed asynchronously in non-stop mode.
5325 Suspending execution is done with the @code{interrupt} command when
5326 running in the background, or @kbd{Ctrl-c} during foreground execution.
5327 In all-stop mode, this stops the whole process;
5328 but in non-stop mode the interrupt applies only to the current thread.
5329 To stop the whole program, use @code{interrupt -a}.
5331 Other execution commands do not currently support the @code{-a} option.
5333 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5334 that thread current, as it does in all-stop mode. This is because the
5335 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5336 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5337 changed to a different thread just as you entered a command to operate on the
5338 previously current thread.
5340 @node Background Execution
5341 @subsection Background Execution
5343 @cindex foreground execution
5344 @cindex background execution
5345 @cindex asynchronous execution
5346 @cindex execution, foreground, background and asynchronous
5348 @value{GDBN}'s execution commands have two variants: the normal
5349 foreground (synchronous) behavior, and a background
5350 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5351 the program to report that some thread has stopped before prompting for
5352 another command. In background execution, @value{GDBN} immediately gives
5353 a command prompt so that you can issue other commands while your program runs.
5355 You need to explicitly enable asynchronous mode before you can use
5356 background execution commands. You can use these commands to
5357 manipulate the asynchronous mode setting:
5360 @kindex set target-async
5361 @item set target-async on
5362 Enable asynchronous mode.
5363 @item set target-async off
5364 Disable asynchronous mode.
5365 @kindex show target-async
5366 @item show target-async
5367 Show the current target-async setting.
5370 If the target doesn't support async mode, @value{GDBN} issues an error
5371 message if you attempt to use the background execution commands.
5373 To specify background execution, add a @code{&} to the command. For example,
5374 the background form of the @code{continue} command is @code{continue&}, or
5375 just @code{c&}. The execution commands that accept background execution
5381 @xref{Starting, , Starting your Program}.
5385 @xref{Attach, , Debugging an Already-running Process}.
5389 @xref{Continuing and Stepping, step}.
5393 @xref{Continuing and Stepping, stepi}.
5397 @xref{Continuing and Stepping, next}.
5401 @xref{Continuing and Stepping, nexti}.
5405 @xref{Continuing and Stepping, continue}.
5409 @xref{Continuing and Stepping, finish}.
5413 @xref{Continuing and Stepping, until}.
5417 Background execution is especially useful in conjunction with non-stop
5418 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5419 However, you can also use these commands in the normal all-stop mode with
5420 the restriction that you cannot issue another execution command until the
5421 previous one finishes. Examples of commands that are valid in all-stop
5422 mode while the program is running include @code{help} and @code{info break}.
5424 You can interrupt your program while it is running in the background by
5425 using the @code{interrupt} command.
5432 Suspend execution of the running program. In all-stop mode,
5433 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5434 only the current thread. To stop the whole program in non-stop mode,
5435 use @code{interrupt -a}.
5438 @node Thread-Specific Breakpoints
5439 @subsection Thread-Specific Breakpoints
5441 When your program has multiple threads (@pxref{Threads,, Debugging
5442 Programs with Multiple Threads}), you can choose whether to set
5443 breakpoints on all threads, or on a particular thread.
5446 @cindex breakpoints and threads
5447 @cindex thread breakpoints
5448 @kindex break @dots{} thread @var{threadno}
5449 @item break @var{linespec} thread @var{threadno}
5450 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5451 @var{linespec} specifies source lines; there are several ways of
5452 writing them (@pxref{Specify Location}), but the effect is always to
5453 specify some source line.
5455 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5456 to specify that you only want @value{GDBN} to stop the program when a
5457 particular thread reaches this breakpoint. @var{threadno} is one of the
5458 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5459 column of the @samp{info threads} display.
5461 If you do not specify @samp{thread @var{threadno}} when you set a
5462 breakpoint, the breakpoint applies to @emph{all} threads of your
5465 You can use the @code{thread} qualifier on conditional breakpoints as
5466 well; in this case, place @samp{thread @var{threadno}} before or
5467 after the breakpoint condition, like this:
5470 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5475 @node Interrupted System Calls
5476 @subsection Interrupted System Calls
5478 @cindex thread breakpoints and system calls
5479 @cindex system calls and thread breakpoints
5480 @cindex premature return from system calls
5481 There is an unfortunate side effect when using @value{GDBN} to debug
5482 multi-threaded programs. If one thread stops for a
5483 breakpoint, or for some other reason, and another thread is blocked in a
5484 system call, then the system call may return prematurely. This is a
5485 consequence of the interaction between multiple threads and the signals
5486 that @value{GDBN} uses to implement breakpoints and other events that
5489 To handle this problem, your program should check the return value of
5490 each system call and react appropriately. This is good programming
5493 For example, do not write code like this:
5499 The call to @code{sleep} will return early if a different thread stops
5500 at a breakpoint or for some other reason.
5502 Instead, write this:
5507 unslept = sleep (unslept);
5510 A system call is allowed to return early, so the system is still
5511 conforming to its specification. But @value{GDBN} does cause your
5512 multi-threaded program to behave differently than it would without
5515 Also, @value{GDBN} uses internal breakpoints in the thread library to
5516 monitor certain events such as thread creation and thread destruction.
5517 When such an event happens, a system call in another thread may return
5518 prematurely, even though your program does not appear to stop.
5521 @subsection Observer Mode
5523 If you want to build on non-stop mode and observe program behavior
5524 without any chance of disruption by @value{GDBN}, you can set
5525 variables to disable all of the debugger's attempts to modify state,
5526 whether by writing memory, inserting breakpoints, etc. These operate
5527 at a low level, intercepting operations from all commands.
5529 When all of these are set to @code{off}, then @value{GDBN} is said to
5530 be @dfn{observer mode}. As a convenience, the variable
5531 @code{observer} can be set to disable these, plus enable non-stop
5534 Note that @value{GDBN} will not prevent you from making nonsensical
5535 combinations of these settings. For instance, if you have enabled
5536 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5537 then breakpoints that work by writing trap instructions into the code
5538 stream will still not be able to be placed.
5543 @item set observer on
5544 @itemx set observer off
5545 When set to @code{on}, this disables all the permission variables
5546 below (except for @code{insert-fast-tracepoints}), plus enables
5547 non-stop debugging. Setting this to @code{off} switches back to
5548 normal debugging, though remaining in non-stop mode.
5551 Show whether observer mode is on or off.
5553 @kindex may-write-registers
5554 @item set may-write-registers on
5555 @itemx set may-write-registers off
5556 This controls whether @value{GDBN} will attempt to alter the values of
5557 registers, such as with assignment expressions in @code{print}, or the
5558 @code{jump} command. It defaults to @code{on}.
5560 @item show may-write-registers
5561 Show the current permission to write registers.
5563 @kindex may-write-memory
5564 @item set may-write-memory on
5565 @itemx set may-write-memory off
5566 This controls whether @value{GDBN} will attempt to alter the contents
5567 of memory, such as with assignment expressions in @code{print}. It
5568 defaults to @code{on}.
5570 @item show may-write-memory
5571 Show the current permission to write memory.
5573 @kindex may-insert-breakpoints
5574 @item set may-insert-breakpoints on
5575 @itemx set may-insert-breakpoints off
5576 This controls whether @value{GDBN} will attempt to insert breakpoints.
5577 This affects all breakpoints, including internal breakpoints defined
5578 by @value{GDBN}. It defaults to @code{on}.
5580 @item show may-insert-breakpoints
5581 Show the current permission to insert breakpoints.
5583 @kindex may-insert-tracepoints
5584 @item set may-insert-tracepoints on
5585 @itemx set may-insert-tracepoints off
5586 This controls whether @value{GDBN} will attempt to insert (regular)
5587 tracepoints at the beginning of a tracing experiment. It affects only
5588 non-fast tracepoints, fast tracepoints being under the control of
5589 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5591 @item show may-insert-tracepoints
5592 Show the current permission to insert tracepoints.
5594 @kindex may-insert-fast-tracepoints
5595 @item set may-insert-fast-tracepoints on
5596 @itemx set may-insert-fast-tracepoints off
5597 This controls whether @value{GDBN} will attempt to insert fast
5598 tracepoints at the beginning of a tracing experiment. It affects only
5599 fast tracepoints, regular (non-fast) tracepoints being under the
5600 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5602 @item show may-insert-fast-tracepoints
5603 Show the current permission to insert fast tracepoints.
5605 @kindex may-interrupt
5606 @item set may-interrupt on
5607 @itemx set may-interrupt off
5608 This controls whether @value{GDBN} will attempt to interrupt or stop
5609 program execution. When this variable is @code{off}, the
5610 @code{interrupt} command will have no effect, nor will
5611 @kbd{Ctrl-c}. It defaults to @code{on}.
5613 @item show may-interrupt
5614 Show the current permission to interrupt or stop the program.
5618 @node Reverse Execution
5619 @chapter Running programs backward
5620 @cindex reverse execution
5621 @cindex running programs backward
5623 When you are debugging a program, it is not unusual to realize that
5624 you have gone too far, and some event of interest has already happened.
5625 If the target environment supports it, @value{GDBN} can allow you to
5626 ``rewind'' the program by running it backward.
5628 A target environment that supports reverse execution should be able
5629 to ``undo'' the changes in machine state that have taken place as the
5630 program was executing normally. Variables, registers etc.@: should
5631 revert to their previous values. Obviously this requires a great
5632 deal of sophistication on the part of the target environment; not
5633 all target environments can support reverse execution.
5635 When a program is executed in reverse, the instructions that
5636 have most recently been executed are ``un-executed'', in reverse
5637 order. The program counter runs backward, following the previous
5638 thread of execution in reverse. As each instruction is ``un-executed'',
5639 the values of memory and/or registers that were changed by that
5640 instruction are reverted to their previous states. After executing
5641 a piece of source code in reverse, all side effects of that code
5642 should be ``undone'', and all variables should be returned to their
5643 prior values@footnote{
5644 Note that some side effects are easier to undo than others. For instance,
5645 memory and registers are relatively easy, but device I/O is hard. Some
5646 targets may be able undo things like device I/O, and some may not.
5648 The contract between @value{GDBN} and the reverse executing target
5649 requires only that the target do something reasonable when
5650 @value{GDBN} tells it to execute backwards, and then report the
5651 results back to @value{GDBN}. Whatever the target reports back to
5652 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5653 assumes that the memory and registers that the target reports are in a
5654 consistant state, but @value{GDBN} accepts whatever it is given.
5657 If you are debugging in a target environment that supports
5658 reverse execution, @value{GDBN} provides the following commands.
5661 @kindex reverse-continue
5662 @kindex rc @r{(@code{reverse-continue})}
5663 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5664 @itemx rc @r{[}@var{ignore-count}@r{]}
5665 Beginning at the point where your program last stopped, start executing
5666 in reverse. Reverse execution will stop for breakpoints and synchronous
5667 exceptions (signals), just like normal execution. Behavior of
5668 asynchronous signals depends on the target environment.
5670 @kindex reverse-step
5671 @kindex rs @r{(@code{step})}
5672 @item reverse-step @r{[}@var{count}@r{]}
5673 Run the program backward until control reaches the start of a
5674 different source line; then stop it, and return control to @value{GDBN}.
5676 Like the @code{step} command, @code{reverse-step} will only stop
5677 at the beginning of a source line. It ``un-executes'' the previously
5678 executed source line. If the previous source line included calls to
5679 debuggable functions, @code{reverse-step} will step (backward) into
5680 the called function, stopping at the beginning of the @emph{last}
5681 statement in the called function (typically a return statement).
5683 Also, as with the @code{step} command, if non-debuggable functions are
5684 called, @code{reverse-step} will run thru them backward without stopping.
5686 @kindex reverse-stepi
5687 @kindex rsi @r{(@code{reverse-stepi})}
5688 @item reverse-stepi @r{[}@var{count}@r{]}
5689 Reverse-execute one machine instruction. Note that the instruction
5690 to be reverse-executed is @emph{not} the one pointed to by the program
5691 counter, but the instruction executed prior to that one. For instance,
5692 if the last instruction was a jump, @code{reverse-stepi} will take you
5693 back from the destination of the jump to the jump instruction itself.
5695 @kindex reverse-next
5696 @kindex rn @r{(@code{reverse-next})}
5697 @item reverse-next @r{[}@var{count}@r{]}
5698 Run backward to the beginning of the previous line executed in
5699 the current (innermost) stack frame. If the line contains function
5700 calls, they will be ``un-executed'' without stopping. Starting from
5701 the first line of a function, @code{reverse-next} will take you back
5702 to the caller of that function, @emph{before} the function was called,
5703 just as the normal @code{next} command would take you from the last
5704 line of a function back to its return to its caller
5705 @footnote{Unless the code is too heavily optimized.}.
5707 @kindex reverse-nexti
5708 @kindex rni @r{(@code{reverse-nexti})}
5709 @item reverse-nexti @r{[}@var{count}@r{]}
5710 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5711 in reverse, except that called functions are ``un-executed'' atomically.
5712 That is, if the previously executed instruction was a return from
5713 another function, @code{reverse-nexti} will continue to execute
5714 in reverse until the call to that function (from the current stack
5717 @kindex reverse-finish
5718 @item reverse-finish
5719 Just as the @code{finish} command takes you to the point where the
5720 current function returns, @code{reverse-finish} takes you to the point
5721 where it was called. Instead of ending up at the end of the current
5722 function invocation, you end up at the beginning.
5724 @kindex set exec-direction
5725 @item set exec-direction
5726 Set the direction of target execution.
5727 @itemx set exec-direction reverse
5728 @cindex execute forward or backward in time
5729 @value{GDBN} will perform all execution commands in reverse, until the
5730 exec-direction mode is changed to ``forward''. Affected commands include
5731 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5732 command cannot be used in reverse mode.
5733 @item set exec-direction forward
5734 @value{GDBN} will perform all execution commands in the normal fashion.
5735 This is the default.
5739 @node Process Record and Replay
5740 @chapter Recording Inferior's Execution and Replaying It
5741 @cindex process record and replay
5742 @cindex recording inferior's execution and replaying it
5744 On some platforms, @value{GDBN} provides a special @dfn{process record
5745 and replay} target that can record a log of the process execution, and
5746 replay it later with both forward and reverse execution commands.
5749 When this target is in use, if the execution log includes the record
5750 for the next instruction, @value{GDBN} will debug in @dfn{replay
5751 mode}. In the replay mode, the inferior does not really execute code
5752 instructions. Instead, all the events that normally happen during
5753 code execution are taken from the execution log. While code is not
5754 really executed in replay mode, the values of registers (including the
5755 program counter register) and the memory of the inferior are still
5756 changed as they normally would. Their contents are taken from the
5760 If the record for the next instruction is not in the execution log,
5761 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5762 inferior executes normally, and @value{GDBN} records the execution log
5765 The process record and replay target supports reverse execution
5766 (@pxref{Reverse Execution}), even if the platform on which the
5767 inferior runs does not. However, the reverse execution is limited in
5768 this case by the range of the instructions recorded in the execution
5769 log. In other words, reverse execution on platforms that don't
5770 support it directly can only be done in the replay mode.
5772 When debugging in the reverse direction, @value{GDBN} will work in
5773 replay mode as long as the execution log includes the record for the
5774 previous instruction; otherwise, it will work in record mode, if the
5775 platform supports reverse execution, or stop if not.
5777 For architecture environments that support process record and replay,
5778 @value{GDBN} provides the following commands:
5781 @kindex target record
5785 This command starts the process record and replay target. The process
5786 record and replay target can only debug a process that is already
5787 running. Therefore, you need first to start the process with the
5788 @kbd{run} or @kbd{start} commands, and then start the recording with
5789 the @kbd{target record} command.
5791 Both @code{record} and @code{rec} are aliases of @code{target record}.
5793 @cindex displaced stepping, and process record and replay
5794 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5795 will be automatically disabled when process record and replay target
5796 is started. That's because the process record and replay target
5797 doesn't support displaced stepping.
5799 @cindex non-stop mode, and process record and replay
5800 @cindex asynchronous execution, and process record and replay
5801 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5802 the asynchronous execution mode (@pxref{Background Execution}), the
5803 process record and replay target cannot be started because it doesn't
5804 support these two modes.
5809 Stop the process record and replay target. When process record and
5810 replay target stops, the entire execution log will be deleted and the
5811 inferior will either be terminated, or will remain in its final state.
5813 When you stop the process record and replay target in record mode (at
5814 the end of the execution log), the inferior will be stopped at the
5815 next instruction that would have been recorded. In other words, if
5816 you record for a while and then stop recording, the inferior process
5817 will be left in the same state as if the recording never happened.
5819 On the other hand, if the process record and replay target is stopped
5820 while in replay mode (that is, not at the end of the execution log,
5821 but at some earlier point), the inferior process will become ``live''
5822 at that earlier state, and it will then be possible to continue the
5823 usual ``live'' debugging of the process from that state.
5825 When the inferior process exits, or @value{GDBN} detaches from it,
5826 process record and replay target will automatically stop itself.
5829 @item record save @var{filename}
5830 Save the execution log to a file @file{@var{filename}}.
5831 Default filename is @file{gdb_record.@var{process_id}}, where
5832 @var{process_id} is the process ID of the inferior.
5834 @kindex record restore
5835 @item record restore @var{filename}
5836 Restore the execution log from a file @file{@var{filename}}.
5837 File must have been created with @code{record save}.
5839 @kindex set record insn-number-max
5840 @item set record insn-number-max @var{limit}
5841 Set the limit of instructions to be recorded. Default value is 200000.
5843 If @var{limit} is a positive number, then @value{GDBN} will start
5844 deleting instructions from the log once the number of the record
5845 instructions becomes greater than @var{limit}. For every new recorded
5846 instruction, @value{GDBN} will delete the earliest recorded
5847 instruction to keep the number of recorded instructions at the limit.
5848 (Since deleting recorded instructions loses information, @value{GDBN}
5849 lets you control what happens when the limit is reached, by means of
5850 the @code{stop-at-limit} option, described below.)
5852 If @var{limit} is zero, @value{GDBN} will never delete recorded
5853 instructions from the execution log. The number of recorded
5854 instructions is unlimited in this case.
5856 @kindex show record insn-number-max
5857 @item show record insn-number-max
5858 Show the limit of instructions to be recorded.
5860 @kindex set record stop-at-limit
5861 @item set record stop-at-limit
5862 Control the behavior when the number of recorded instructions reaches
5863 the limit. If ON (the default), @value{GDBN} will stop when the limit
5864 is reached for the first time and ask you whether you want to stop the
5865 inferior or continue running it and recording the execution log. If
5866 you decide to continue recording, each new recorded instruction will
5867 cause the oldest one to be deleted.
5869 If this option is OFF, @value{GDBN} will automatically delete the
5870 oldest record to make room for each new one, without asking.
5872 @kindex show record stop-at-limit
5873 @item show record stop-at-limit
5874 Show the current setting of @code{stop-at-limit}.
5876 @kindex set record memory-query
5877 @item set record memory-query
5878 Control the behavior when @value{GDBN} is unable to record memory
5879 changes caused by an instruction. If ON, @value{GDBN} will query
5880 whether to stop the inferior in that case.
5882 If this option is OFF (the default), @value{GDBN} will automatically
5883 ignore the effect of such instructions on memory. Later, when
5884 @value{GDBN} replays this execution log, it will mark the log of this
5885 instruction as not accessible, and it will not affect the replay
5888 @kindex show record memory-query
5889 @item show record memory-query
5890 Show the current setting of @code{memory-query}.
5894 Show various statistics about the state of process record and its
5895 in-memory execution log buffer, including:
5899 Whether in record mode or replay mode.
5901 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5903 Highest recorded instruction number.
5905 Current instruction about to be replayed (if in replay mode).
5907 Number of instructions contained in the execution log.
5909 Maximum number of instructions that may be contained in the execution log.
5912 @kindex record delete
5915 When record target runs in replay mode (``in the past''), delete the
5916 subsequent execution log and begin to record a new execution log starting
5917 from the current address. This means you will abandon the previously
5918 recorded ``future'' and begin recording a new ``future''.
5923 @chapter Examining the Stack
5925 When your program has stopped, the first thing you need to know is where it
5926 stopped and how it got there.
5929 Each time your program performs a function call, information about the call
5931 That information includes the location of the call in your program,
5932 the arguments of the call,
5933 and the local variables of the function being called.
5934 The information is saved in a block of data called a @dfn{stack frame}.
5935 The stack frames are allocated in a region of memory called the @dfn{call
5938 When your program stops, the @value{GDBN} commands for examining the
5939 stack allow you to see all of this information.
5941 @cindex selected frame
5942 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5943 @value{GDBN} commands refer implicitly to the selected frame. In
5944 particular, whenever you ask @value{GDBN} for the value of a variable in
5945 your program, the value is found in the selected frame. There are
5946 special @value{GDBN} commands to select whichever frame you are
5947 interested in. @xref{Selection, ,Selecting a Frame}.
5949 When your program stops, @value{GDBN} automatically selects the
5950 currently executing frame and describes it briefly, similar to the
5951 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5954 * Frames:: Stack frames
5955 * Backtrace:: Backtraces
5956 * Selection:: Selecting a frame
5957 * Frame Info:: Information on a frame
5962 @section Stack Frames
5964 @cindex frame, definition
5966 The call stack is divided up into contiguous pieces called @dfn{stack
5967 frames}, or @dfn{frames} for short; each frame is the data associated
5968 with one call to one function. The frame contains the arguments given
5969 to the function, the function's local variables, and the address at
5970 which the function is executing.
5972 @cindex initial frame
5973 @cindex outermost frame
5974 @cindex innermost frame
5975 When your program is started, the stack has only one frame, that of the
5976 function @code{main}. This is called the @dfn{initial} frame or the
5977 @dfn{outermost} frame. Each time a function is called, a new frame is
5978 made. Each time a function returns, the frame for that function invocation
5979 is eliminated. If a function is recursive, there can be many frames for
5980 the same function. The frame for the function in which execution is
5981 actually occurring is called the @dfn{innermost} frame. This is the most
5982 recently created of all the stack frames that still exist.
5984 @cindex frame pointer
5985 Inside your program, stack frames are identified by their addresses. A
5986 stack frame consists of many bytes, each of which has its own address; each
5987 kind of computer has a convention for choosing one byte whose
5988 address serves as the address of the frame. Usually this address is kept
5989 in a register called the @dfn{frame pointer register}
5990 (@pxref{Registers, $fp}) while execution is going on in that frame.
5992 @cindex frame number
5993 @value{GDBN} assigns numbers to all existing stack frames, starting with
5994 zero for the innermost frame, one for the frame that called it,
5995 and so on upward. These numbers do not really exist in your program;
5996 they are assigned by @value{GDBN} to give you a way of designating stack
5997 frames in @value{GDBN} commands.
5999 @c The -fomit-frame-pointer below perennially causes hbox overflow
6000 @c underflow problems.
6001 @cindex frameless execution
6002 Some compilers provide a way to compile functions so that they operate
6003 without stack frames. (For example, the @value{NGCC} option
6005 @samp{-fomit-frame-pointer}
6007 generates functions without a frame.)
6008 This is occasionally done with heavily used library functions to save
6009 the frame setup time. @value{GDBN} has limited facilities for dealing
6010 with these function invocations. If the innermost function invocation
6011 has no stack frame, @value{GDBN} nevertheless regards it as though
6012 it had a separate frame, which is numbered zero as usual, allowing
6013 correct tracing of the function call chain. However, @value{GDBN} has
6014 no provision for frameless functions elsewhere in the stack.
6017 @kindex frame@r{, command}
6018 @cindex current stack frame
6019 @item frame @var{args}
6020 The @code{frame} command allows you to move from one stack frame to another,
6021 and to print the stack frame you select. @var{args} may be either the
6022 address of the frame or the stack frame number. Without an argument,
6023 @code{frame} prints the current stack frame.
6025 @kindex select-frame
6026 @cindex selecting frame silently
6028 The @code{select-frame} command allows you to move from one stack frame
6029 to another without printing the frame. This is the silent version of
6037 @cindex call stack traces
6038 A backtrace is a summary of how your program got where it is. It shows one
6039 line per frame, for many frames, starting with the currently executing
6040 frame (frame zero), followed by its caller (frame one), and on up the
6045 @kindex bt @r{(@code{backtrace})}
6048 Print a backtrace of the entire stack: one line per frame for all
6049 frames in the stack.
6051 You can stop the backtrace at any time by typing the system interrupt
6052 character, normally @kbd{Ctrl-c}.
6054 @item backtrace @var{n}
6056 Similar, but print only the innermost @var{n} frames.
6058 @item backtrace -@var{n}
6060 Similar, but print only the outermost @var{n} frames.
6062 @item backtrace full
6064 @itemx bt full @var{n}
6065 @itemx bt full -@var{n}
6066 Print the values of the local variables also. @var{n} specifies the
6067 number of frames to print, as described above.
6072 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6073 are additional aliases for @code{backtrace}.
6075 @cindex multiple threads, backtrace
6076 In a multi-threaded program, @value{GDBN} by default shows the
6077 backtrace only for the current thread. To display the backtrace for
6078 several or all of the threads, use the command @code{thread apply}
6079 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6080 apply all backtrace}, @value{GDBN} will display the backtrace for all
6081 the threads; this is handy when you debug a core dump of a
6082 multi-threaded program.
6084 Each line in the backtrace shows the frame number and the function name.
6085 The program counter value is also shown---unless you use @code{set
6086 print address off}. The backtrace also shows the source file name and
6087 line number, as well as the arguments to the function. The program
6088 counter value is omitted if it is at the beginning of the code for that
6091 Here is an example of a backtrace. It was made with the command
6092 @samp{bt 3}, so it shows the innermost three frames.
6096 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6098 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6099 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6101 (More stack frames follow...)
6106 The display for frame zero does not begin with a program counter
6107 value, indicating that your program has stopped at the beginning of the
6108 code for line @code{993} of @code{builtin.c}.
6111 The value of parameter @code{data} in frame 1 has been replaced by
6112 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6113 only if it is a scalar (integer, pointer, enumeration, etc). See command
6114 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6115 on how to configure the way function parameter values are printed.
6117 @cindex optimized out, in backtrace
6118 @cindex function call arguments, optimized out
6119 If your program was compiled with optimizations, some compilers will
6120 optimize away arguments passed to functions if those arguments are
6121 never used after the call. Such optimizations generate code that
6122 passes arguments through registers, but doesn't store those arguments
6123 in the stack frame. @value{GDBN} has no way of displaying such
6124 arguments in stack frames other than the innermost one. Here's what
6125 such a backtrace might look like:
6129 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6131 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6132 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6134 (More stack frames follow...)
6139 The values of arguments that were not saved in their stack frames are
6140 shown as @samp{<optimized out>}.
6142 If you need to display the values of such optimized-out arguments,
6143 either deduce that from other variables whose values depend on the one
6144 you are interested in, or recompile without optimizations.
6146 @cindex backtrace beyond @code{main} function
6147 @cindex program entry point
6148 @cindex startup code, and backtrace
6149 Most programs have a standard user entry point---a place where system
6150 libraries and startup code transition into user code. For C this is
6151 @code{main}@footnote{
6152 Note that embedded programs (the so-called ``free-standing''
6153 environment) are not required to have a @code{main} function as the
6154 entry point. They could even have multiple entry points.}.
6155 When @value{GDBN} finds the entry function in a backtrace
6156 it will terminate the backtrace, to avoid tracing into highly
6157 system-specific (and generally uninteresting) code.
6159 If you need to examine the startup code, or limit the number of levels
6160 in a backtrace, you can change this behavior:
6163 @item set backtrace past-main
6164 @itemx set backtrace past-main on
6165 @kindex set backtrace
6166 Backtraces will continue past the user entry point.
6168 @item set backtrace past-main off
6169 Backtraces will stop when they encounter the user entry point. This is the
6172 @item show backtrace past-main
6173 @kindex show backtrace
6174 Display the current user entry point backtrace policy.
6176 @item set backtrace past-entry
6177 @itemx set backtrace past-entry on
6178 Backtraces will continue past the internal entry point of an application.
6179 This entry point is encoded by the linker when the application is built,
6180 and is likely before the user entry point @code{main} (or equivalent) is called.
6182 @item set backtrace past-entry off
6183 Backtraces will stop when they encounter the internal entry point of an
6184 application. This is the default.
6186 @item show backtrace past-entry
6187 Display the current internal entry point backtrace policy.
6189 @item set backtrace limit @var{n}
6190 @itemx set backtrace limit 0
6191 @cindex backtrace limit
6192 Limit the backtrace to @var{n} levels. A value of zero means
6195 @item show backtrace limit
6196 Display the current limit on backtrace levels.
6200 @section Selecting a Frame
6202 Most commands for examining the stack and other data in your program work on
6203 whichever stack frame is selected at the moment. Here are the commands for
6204 selecting a stack frame; all of them finish by printing a brief description
6205 of the stack frame just selected.
6208 @kindex frame@r{, selecting}
6209 @kindex f @r{(@code{frame})}
6212 Select frame number @var{n}. Recall that frame zero is the innermost
6213 (currently executing) frame, frame one is the frame that called the
6214 innermost one, and so on. The highest-numbered frame is the one for
6217 @item frame @var{addr}
6219 Select the frame at address @var{addr}. This is useful mainly if the
6220 chaining of stack frames has been damaged by a bug, making it
6221 impossible for @value{GDBN} to assign numbers properly to all frames. In
6222 addition, this can be useful when your program has multiple stacks and
6223 switches between them.
6225 On the SPARC architecture, @code{frame} needs two addresses to
6226 select an arbitrary frame: a frame pointer and a stack pointer.
6228 On the MIPS and Alpha architecture, it needs two addresses: a stack
6229 pointer and a program counter.
6231 On the 29k architecture, it needs three addresses: a register stack
6232 pointer, a program counter, and a memory stack pointer.
6236 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6237 advances toward the outermost frame, to higher frame numbers, to frames
6238 that have existed longer. @var{n} defaults to one.
6241 @kindex do @r{(@code{down})}
6243 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6244 advances toward the innermost frame, to lower frame numbers, to frames
6245 that were created more recently. @var{n} defaults to one. You may
6246 abbreviate @code{down} as @code{do}.
6249 All of these commands end by printing two lines of output describing the
6250 frame. The first line shows the frame number, the function name, the
6251 arguments, and the source file and line number of execution in that
6252 frame. The second line shows the text of that source line.
6260 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6262 10 read_input_file (argv[i]);
6266 After such a printout, the @code{list} command with no arguments
6267 prints ten lines centered on the point of execution in the frame.
6268 You can also edit the program at the point of execution with your favorite
6269 editing program by typing @code{edit}.
6270 @xref{List, ,Printing Source Lines},
6274 @kindex down-silently
6276 @item up-silently @var{n}
6277 @itemx down-silently @var{n}
6278 These two commands are variants of @code{up} and @code{down},
6279 respectively; they differ in that they do their work silently, without
6280 causing display of the new frame. They are intended primarily for use
6281 in @value{GDBN} command scripts, where the output might be unnecessary and
6286 @section Information About a Frame
6288 There are several other commands to print information about the selected
6294 When used without any argument, this command does not change which
6295 frame is selected, but prints a brief description of the currently
6296 selected stack frame. It can be abbreviated @code{f}. With an
6297 argument, this command is used to select a stack frame.
6298 @xref{Selection, ,Selecting a Frame}.
6301 @kindex info f @r{(@code{info frame})}
6304 This command prints a verbose description of the selected stack frame,
6309 the address of the frame
6311 the address of the next frame down (called by this frame)
6313 the address of the next frame up (caller of this frame)
6315 the language in which the source code corresponding to this frame is written
6317 the address of the frame's arguments
6319 the address of the frame's local variables
6321 the program counter saved in it (the address of execution in the caller frame)
6323 which registers were saved in the frame
6326 @noindent The verbose description is useful when
6327 something has gone wrong that has made the stack format fail to fit
6328 the usual conventions.
6330 @item info frame @var{addr}
6331 @itemx info f @var{addr}
6332 Print a verbose description of the frame at address @var{addr}, without
6333 selecting that frame. The selected frame remains unchanged by this
6334 command. This requires the same kind of address (more than one for some
6335 architectures) that you specify in the @code{frame} command.
6336 @xref{Selection, ,Selecting a Frame}.
6340 Print the arguments of the selected frame, each on a separate line.
6344 Print the local variables of the selected frame, each on a separate
6345 line. These are all variables (declared either static or automatic)
6346 accessible at the point of execution of the selected frame.
6352 @chapter Examining Source Files
6354 @value{GDBN} can print parts of your program's source, since the debugging
6355 information recorded in the program tells @value{GDBN} what source files were
6356 used to build it. When your program stops, @value{GDBN} spontaneously prints
6357 the line where it stopped. Likewise, when you select a stack frame
6358 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6359 execution in that frame has stopped. You can print other portions of
6360 source files by explicit command.
6362 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6363 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6364 @value{GDBN} under @sc{gnu} Emacs}.
6367 * List:: Printing source lines
6368 * Specify Location:: How to specify code locations
6369 * Edit:: Editing source files
6370 * Search:: Searching source files
6371 * Source Path:: Specifying source directories
6372 * Machine Code:: Source and machine code
6376 @section Printing Source Lines
6379 @kindex l @r{(@code{list})}
6380 To print lines from a source file, use the @code{list} command
6381 (abbreviated @code{l}). By default, ten lines are printed.
6382 There are several ways to specify what part of the file you want to
6383 print; see @ref{Specify Location}, for the full list.
6385 Here are the forms of the @code{list} command most commonly used:
6388 @item list @var{linenum}
6389 Print lines centered around line number @var{linenum} in the
6390 current source file.
6392 @item list @var{function}
6393 Print lines centered around the beginning of function
6397 Print more lines. If the last lines printed were printed with a
6398 @code{list} command, this prints lines following the last lines
6399 printed; however, if the last line printed was a solitary line printed
6400 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6401 Stack}), this prints lines centered around that line.
6404 Print lines just before the lines last printed.
6407 @cindex @code{list}, how many lines to display
6408 By default, @value{GDBN} prints ten source lines with any of these forms of
6409 the @code{list} command. You can change this using @code{set listsize}:
6412 @kindex set listsize
6413 @item set listsize @var{count}
6414 Make the @code{list} command display @var{count} source lines (unless
6415 the @code{list} argument explicitly specifies some other number).
6417 @kindex show listsize
6419 Display the number of lines that @code{list} prints.
6422 Repeating a @code{list} command with @key{RET} discards the argument,
6423 so it is equivalent to typing just @code{list}. This is more useful
6424 than listing the same lines again. An exception is made for an
6425 argument of @samp{-}; that argument is preserved in repetition so that
6426 each repetition moves up in the source file.
6428 In general, the @code{list} command expects you to supply zero, one or two
6429 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6430 of writing them (@pxref{Specify Location}), but the effect is always
6431 to specify some source line.
6433 Here is a complete description of the possible arguments for @code{list}:
6436 @item list @var{linespec}
6437 Print lines centered around the line specified by @var{linespec}.
6439 @item list @var{first},@var{last}
6440 Print lines from @var{first} to @var{last}. Both arguments are
6441 linespecs. When a @code{list} command has two linespecs, and the
6442 source file of the second linespec is omitted, this refers to
6443 the same source file as the first linespec.
6445 @item list ,@var{last}
6446 Print lines ending with @var{last}.
6448 @item list @var{first},
6449 Print lines starting with @var{first}.
6452 Print lines just after the lines last printed.
6455 Print lines just before the lines last printed.
6458 As described in the preceding table.
6461 @node Specify Location
6462 @section Specifying a Location
6463 @cindex specifying location
6466 Several @value{GDBN} commands accept arguments that specify a location
6467 of your program's code. Since @value{GDBN} is a source-level
6468 debugger, a location usually specifies some line in the source code;
6469 for that reason, locations are also known as @dfn{linespecs}.
6471 Here are all the different ways of specifying a code location that
6472 @value{GDBN} understands:
6476 Specifies the line number @var{linenum} of the current source file.
6479 @itemx +@var{offset}
6480 Specifies the line @var{offset} lines before or after the @dfn{current
6481 line}. For the @code{list} command, the current line is the last one
6482 printed; for the breakpoint commands, this is the line at which
6483 execution stopped in the currently selected @dfn{stack frame}
6484 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6485 used as the second of the two linespecs in a @code{list} command,
6486 this specifies the line @var{offset} lines up or down from the first
6489 @item @var{filename}:@var{linenum}
6490 Specifies the line @var{linenum} in the source file @var{filename}.
6491 If @var{filename} is a relative file name, then it will match any
6492 source file name with the same trailing components. For example, if
6493 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6494 name of @file{/build/trunk/gcc/expr.c}, but not
6495 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6497 @item @var{function}
6498 Specifies the line that begins the body of the function @var{function}.
6499 For example, in C, this is the line with the open brace.
6501 @item @var{function}:@var{label}
6502 Specifies the line where @var{label} appears in @var{function}.
6504 @item @var{filename}:@var{function}
6505 Specifies the line that begins the body of the function @var{function}
6506 in the file @var{filename}. You only need the file name with a
6507 function name to avoid ambiguity when there are identically named
6508 functions in different source files.
6511 Specifies the line at which the label named @var{label} appears.
6512 @value{GDBN} searches for the label in the function corresponding to
6513 the currently selected stack frame. If there is no current selected
6514 stack frame (for instance, if the inferior is not running), then
6515 @value{GDBN} will not search for a label.
6517 @item *@var{address}
6518 Specifies the program address @var{address}. For line-oriented
6519 commands, such as @code{list} and @code{edit}, this specifies a source
6520 line that contains @var{address}. For @code{break} and other
6521 breakpoint oriented commands, this can be used to set breakpoints in
6522 parts of your program which do not have debugging information or
6525 Here @var{address} may be any expression valid in the current working
6526 language (@pxref{Languages, working language}) that specifies a code
6527 address. In addition, as a convenience, @value{GDBN} extends the
6528 semantics of expressions used in locations to cover the situations
6529 that frequently happen during debugging. Here are the various forms
6533 @item @var{expression}
6534 Any expression valid in the current working language.
6536 @item @var{funcaddr}
6537 An address of a function or procedure derived from its name. In C,
6538 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6539 simply the function's name @var{function} (and actually a special case
6540 of a valid expression). In Pascal and Modula-2, this is
6541 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6542 (although the Pascal form also works).
6544 This form specifies the address of the function's first instruction,
6545 before the stack frame and arguments have been set up.
6547 @item '@var{filename}'::@var{funcaddr}
6548 Like @var{funcaddr} above, but also specifies the name of the source
6549 file explicitly. This is useful if the name of the function does not
6550 specify the function unambiguously, e.g., if there are several
6551 functions with identical names in different source files.
6558 @section Editing Source Files
6559 @cindex editing source files
6562 @kindex e @r{(@code{edit})}
6563 To edit the lines in a source file, use the @code{edit} command.
6564 The editing program of your choice
6565 is invoked with the current line set to
6566 the active line in the program.
6567 Alternatively, there are several ways to specify what part of the file you
6568 want to print if you want to see other parts of the program:
6571 @item edit @var{location}
6572 Edit the source file specified by @code{location}. Editing starts at
6573 that @var{location}, e.g., at the specified source line of the
6574 specified file. @xref{Specify Location}, for all the possible forms
6575 of the @var{location} argument; here are the forms of the @code{edit}
6576 command most commonly used:
6579 @item edit @var{number}
6580 Edit the current source file with @var{number} as the active line number.
6582 @item edit @var{function}
6583 Edit the file containing @var{function} at the beginning of its definition.
6588 @subsection Choosing your Editor
6589 You can customize @value{GDBN} to use any editor you want
6591 The only restriction is that your editor (say @code{ex}), recognizes the
6592 following command-line syntax:
6594 ex +@var{number} file
6596 The optional numeric value +@var{number} specifies the number of the line in
6597 the file where to start editing.}.
6598 By default, it is @file{@value{EDITOR}}, but you can change this
6599 by setting the environment variable @code{EDITOR} before using
6600 @value{GDBN}. For example, to configure @value{GDBN} to use the
6601 @code{vi} editor, you could use these commands with the @code{sh} shell:
6607 or in the @code{csh} shell,
6609 setenv EDITOR /usr/bin/vi
6614 @section Searching Source Files
6615 @cindex searching source files
6617 There are two commands for searching through the current source file for a
6622 @kindex forward-search
6623 @item forward-search @var{regexp}
6624 @itemx search @var{regexp}
6625 The command @samp{forward-search @var{regexp}} checks each line,
6626 starting with the one following the last line listed, for a match for
6627 @var{regexp}. It lists the line that is found. You can use the
6628 synonym @samp{search @var{regexp}} or abbreviate the command name as
6631 @kindex reverse-search
6632 @item reverse-search @var{regexp}
6633 The command @samp{reverse-search @var{regexp}} checks each line, starting
6634 with the one before the last line listed and going backward, for a match
6635 for @var{regexp}. It lists the line that is found. You can abbreviate
6636 this command as @code{rev}.
6640 @section Specifying Source Directories
6643 @cindex directories for source files
6644 Executable programs sometimes do not record the directories of the source
6645 files from which they were compiled, just the names. Even when they do,
6646 the directories could be moved between the compilation and your debugging
6647 session. @value{GDBN} has a list of directories to search for source files;
6648 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6649 it tries all the directories in the list, in the order they are present
6650 in the list, until it finds a file with the desired name.
6652 For example, suppose an executable references the file
6653 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6654 @file{/mnt/cross}. The file is first looked up literally; if this
6655 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6656 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6657 message is printed. @value{GDBN} does not look up the parts of the
6658 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6659 Likewise, the subdirectories of the source path are not searched: if
6660 the source path is @file{/mnt/cross}, and the binary refers to
6661 @file{foo.c}, @value{GDBN} would not find it under
6662 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6664 Plain file names, relative file names with leading directories, file
6665 names containing dots, etc.@: are all treated as described above; for
6666 instance, if the source path is @file{/mnt/cross}, and the source file
6667 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6668 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6669 that---@file{/mnt/cross/foo.c}.
6671 Note that the executable search path is @emph{not} used to locate the
6674 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6675 any information it has cached about where source files are found and where
6676 each line is in the file.
6680 When you start @value{GDBN}, its source path includes only @samp{cdir}
6681 and @samp{cwd}, in that order.
6682 To add other directories, use the @code{directory} command.
6684 The search path is used to find both program source files and @value{GDBN}
6685 script files (read using the @samp{-command} option and @samp{source} command).
6687 In addition to the source path, @value{GDBN} provides a set of commands
6688 that manage a list of source path substitution rules. A @dfn{substitution
6689 rule} specifies how to rewrite source directories stored in the program's
6690 debug information in case the sources were moved to a different
6691 directory between compilation and debugging. A rule is made of
6692 two strings, the first specifying what needs to be rewritten in
6693 the path, and the second specifying how it should be rewritten.
6694 In @ref{set substitute-path}, we name these two parts @var{from} and
6695 @var{to} respectively. @value{GDBN} does a simple string replacement
6696 of @var{from} with @var{to} at the start of the directory part of the
6697 source file name, and uses that result instead of the original file
6698 name to look up the sources.
6700 Using the previous example, suppose the @file{foo-1.0} tree has been
6701 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6702 @value{GDBN} to replace @file{/usr/src} in all source path names with
6703 @file{/mnt/cross}. The first lookup will then be
6704 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6705 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6706 substitution rule, use the @code{set substitute-path} command
6707 (@pxref{set substitute-path}).
6709 To avoid unexpected substitution results, a rule is applied only if the
6710 @var{from} part of the directory name ends at a directory separator.
6711 For instance, a rule substituting @file{/usr/source} into
6712 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6713 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6714 is applied only at the beginning of the directory name, this rule will
6715 not be applied to @file{/root/usr/source/baz.c} either.
6717 In many cases, you can achieve the same result using the @code{directory}
6718 command. However, @code{set substitute-path} can be more efficient in
6719 the case where the sources are organized in a complex tree with multiple
6720 subdirectories. With the @code{directory} command, you need to add each
6721 subdirectory of your project. If you moved the entire tree while
6722 preserving its internal organization, then @code{set substitute-path}
6723 allows you to direct the debugger to all the sources with one single
6726 @code{set substitute-path} is also more than just a shortcut command.
6727 The source path is only used if the file at the original location no
6728 longer exists. On the other hand, @code{set substitute-path} modifies
6729 the debugger behavior to look at the rewritten location instead. So, if
6730 for any reason a source file that is not relevant to your executable is
6731 located at the original location, a substitution rule is the only
6732 method available to point @value{GDBN} at the new location.
6734 @cindex @samp{--with-relocated-sources}
6735 @cindex default source path substitution
6736 You can configure a default source path substitution rule by
6737 configuring @value{GDBN} with the
6738 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6739 should be the name of a directory under @value{GDBN}'s configured
6740 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6741 directory names in debug information under @var{dir} will be adjusted
6742 automatically if the installed @value{GDBN} is moved to a new
6743 location. This is useful if @value{GDBN}, libraries or executables
6744 with debug information and corresponding source code are being moved
6748 @item directory @var{dirname} @dots{}
6749 @item dir @var{dirname} @dots{}
6750 Add directory @var{dirname} to the front of the source path. Several
6751 directory names may be given to this command, separated by @samp{:}
6752 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6753 part of absolute file names) or
6754 whitespace. You may specify a directory that is already in the source
6755 path; this moves it forward, so @value{GDBN} searches it sooner.
6759 @vindex $cdir@r{, convenience variable}
6760 @vindex $cwd@r{, convenience variable}
6761 @cindex compilation directory
6762 @cindex current directory
6763 @cindex working directory
6764 @cindex directory, current
6765 @cindex directory, compilation
6766 You can use the string @samp{$cdir} to refer to the compilation
6767 directory (if one is recorded), and @samp{$cwd} to refer to the current
6768 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6769 tracks the current working directory as it changes during your @value{GDBN}
6770 session, while the latter is immediately expanded to the current
6771 directory at the time you add an entry to the source path.
6774 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6776 @c RET-repeat for @code{directory} is explicitly disabled, but since
6777 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6779 @item set directories @var{path-list}
6780 @kindex set directories
6781 Set the source path to @var{path-list}.
6782 @samp{$cdir:$cwd} are added if missing.
6784 @item show directories
6785 @kindex show directories
6786 Print the source path: show which directories it contains.
6788 @anchor{set substitute-path}
6789 @item set substitute-path @var{from} @var{to}
6790 @kindex set substitute-path
6791 Define a source path substitution rule, and add it at the end of the
6792 current list of existing substitution rules. If a rule with the same
6793 @var{from} was already defined, then the old rule is also deleted.
6795 For example, if the file @file{/foo/bar/baz.c} was moved to
6796 @file{/mnt/cross/baz.c}, then the command
6799 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6803 will tell @value{GDBN} to replace @samp{/usr/src} with
6804 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6805 @file{baz.c} even though it was moved.
6807 In the case when more than one substitution rule have been defined,
6808 the rules are evaluated one by one in the order where they have been
6809 defined. The first one matching, if any, is selected to perform
6812 For instance, if we had entered the following commands:
6815 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6816 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6820 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6821 @file{/mnt/include/defs.h} by using the first rule. However, it would
6822 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6823 @file{/mnt/src/lib/foo.c}.
6826 @item unset substitute-path [path]
6827 @kindex unset substitute-path
6828 If a path is specified, search the current list of substitution rules
6829 for a rule that would rewrite that path. Delete that rule if found.
6830 A warning is emitted by the debugger if no rule could be found.
6832 If no path is specified, then all substitution rules are deleted.
6834 @item show substitute-path [path]
6835 @kindex show substitute-path
6836 If a path is specified, then print the source path substitution rule
6837 which would rewrite that path, if any.
6839 If no path is specified, then print all existing source path substitution
6844 If your source path is cluttered with directories that are no longer of
6845 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6846 versions of source. You can correct the situation as follows:
6850 Use @code{directory} with no argument to reset the source path to its default value.
6853 Use @code{directory} with suitable arguments to reinstall the
6854 directories you want in the source path. You can add all the
6855 directories in one command.
6859 @section Source and Machine Code
6860 @cindex source line and its code address
6862 You can use the command @code{info line} to map source lines to program
6863 addresses (and vice versa), and the command @code{disassemble} to display
6864 a range of addresses as machine instructions. You can use the command
6865 @code{set disassemble-next-line} to set whether to disassemble next
6866 source line when execution stops. When run under @sc{gnu} Emacs
6867 mode, the @code{info line} command causes the arrow to point to the
6868 line specified. Also, @code{info line} prints addresses in symbolic form as
6873 @item info line @var{linespec}
6874 Print the starting and ending addresses of the compiled code for
6875 source line @var{linespec}. You can specify source lines in any of
6876 the ways documented in @ref{Specify Location}.
6879 For example, we can use @code{info line} to discover the location of
6880 the object code for the first line of function
6881 @code{m4_changequote}:
6883 @c FIXME: I think this example should also show the addresses in
6884 @c symbolic form, as they usually would be displayed.
6886 (@value{GDBP}) info line m4_changequote
6887 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6891 @cindex code address and its source line
6892 We can also inquire (using @code{*@var{addr}} as the form for
6893 @var{linespec}) what source line covers a particular address:
6895 (@value{GDBP}) info line *0x63ff
6896 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6899 @cindex @code{$_} and @code{info line}
6900 @cindex @code{x} command, default address
6901 @kindex x@r{(examine), and} info line
6902 After @code{info line}, the default address for the @code{x} command
6903 is changed to the starting address of the line, so that @samp{x/i} is
6904 sufficient to begin examining the machine code (@pxref{Memory,
6905 ,Examining Memory}). Also, this address is saved as the value of the
6906 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6911 @cindex assembly instructions
6912 @cindex instructions, assembly
6913 @cindex machine instructions
6914 @cindex listing machine instructions
6916 @itemx disassemble /m
6917 @itemx disassemble /r
6918 This specialized command dumps a range of memory as machine
6919 instructions. It can also print mixed source+disassembly by specifying
6920 the @code{/m} modifier and print the raw instructions in hex as well as
6921 in symbolic form by specifying the @code{/r}.
6922 The default memory range is the function surrounding the
6923 program counter of the selected frame. A single argument to this
6924 command is a program counter value; @value{GDBN} dumps the function
6925 surrounding this value. When two arguments are given, they should
6926 be separated by a comma, possibly surrounded by whitespace. The
6927 arguments specify a range of addresses to dump, in one of two forms:
6930 @item @var{start},@var{end}
6931 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6932 @item @var{start},+@var{length}
6933 the addresses from @var{start} (inclusive) to
6934 @code{@var{start}+@var{length}} (exclusive).
6938 When 2 arguments are specified, the name of the function is also
6939 printed (since there could be several functions in the given range).
6941 The argument(s) can be any expression yielding a numeric value, such as
6942 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6944 If the range of memory being disassembled contains current program counter,
6945 the instruction at that location is shown with a @code{=>} marker.
6948 The following example shows the disassembly of a range of addresses of
6949 HP PA-RISC 2.0 code:
6952 (@value{GDBP}) disas 0x32c4, 0x32e4
6953 Dump of assembler code from 0x32c4 to 0x32e4:
6954 0x32c4 <main+204>: addil 0,dp
6955 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6956 0x32cc <main+212>: ldil 0x3000,r31
6957 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6958 0x32d4 <main+220>: ldo 0(r31),rp
6959 0x32d8 <main+224>: addil -0x800,dp
6960 0x32dc <main+228>: ldo 0x588(r1),r26
6961 0x32e0 <main+232>: ldil 0x3000,r31
6962 End of assembler dump.
6965 Here is an example showing mixed source+assembly for Intel x86, when the
6966 program is stopped just after function prologue:
6969 (@value{GDBP}) disas /m main
6970 Dump of assembler code for function main:
6972 0x08048330 <+0>: push %ebp
6973 0x08048331 <+1>: mov %esp,%ebp
6974 0x08048333 <+3>: sub $0x8,%esp
6975 0x08048336 <+6>: and $0xfffffff0,%esp
6976 0x08048339 <+9>: sub $0x10,%esp
6978 6 printf ("Hello.\n");
6979 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6980 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6984 0x08048348 <+24>: mov $0x0,%eax
6985 0x0804834d <+29>: leave
6986 0x0804834e <+30>: ret
6988 End of assembler dump.
6991 Here is another example showing raw instructions in hex for AMD x86-64,
6994 (gdb) disas /r 0x400281,+10
6995 Dump of assembler code from 0x400281 to 0x40028b:
6996 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6997 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6998 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6999 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7000 End of assembler dump.
7003 Some architectures have more than one commonly-used set of instruction
7004 mnemonics or other syntax.
7006 For programs that were dynamically linked and use shared libraries,
7007 instructions that call functions or branch to locations in the shared
7008 libraries might show a seemingly bogus location---it's actually a
7009 location of the relocation table. On some architectures, @value{GDBN}
7010 might be able to resolve these to actual function names.
7013 @kindex set disassembly-flavor
7014 @cindex Intel disassembly flavor
7015 @cindex AT&T disassembly flavor
7016 @item set disassembly-flavor @var{instruction-set}
7017 Select the instruction set to use when disassembling the
7018 program via the @code{disassemble} or @code{x/i} commands.
7020 Currently this command is only defined for the Intel x86 family. You
7021 can set @var{instruction-set} to either @code{intel} or @code{att}.
7022 The default is @code{att}, the AT&T flavor used by default by Unix
7023 assemblers for x86-based targets.
7025 @kindex show disassembly-flavor
7026 @item show disassembly-flavor
7027 Show the current setting of the disassembly flavor.
7031 @kindex set disassemble-next-line
7032 @kindex show disassemble-next-line
7033 @item set disassemble-next-line
7034 @itemx show disassemble-next-line
7035 Control whether or not @value{GDBN} will disassemble the next source
7036 line or instruction when execution stops. If ON, @value{GDBN} will
7037 display disassembly of the next source line when execution of the
7038 program being debugged stops. This is @emph{in addition} to
7039 displaying the source line itself, which @value{GDBN} always does if
7040 possible. If the next source line cannot be displayed for some reason
7041 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7042 info in the debug info), @value{GDBN} will display disassembly of the
7043 next @emph{instruction} instead of showing the next source line. If
7044 AUTO, @value{GDBN} will display disassembly of next instruction only
7045 if the source line cannot be displayed. This setting causes
7046 @value{GDBN} to display some feedback when you step through a function
7047 with no line info or whose source file is unavailable. The default is
7048 OFF, which means never display the disassembly of the next line or
7054 @chapter Examining Data
7056 @cindex printing data
7057 @cindex examining data
7060 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7061 @c document because it is nonstandard... Under Epoch it displays in a
7062 @c different window or something like that.
7063 The usual way to examine data in your program is with the @code{print}
7064 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7065 evaluates and prints the value of an expression of the language your
7066 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7067 Different Languages}). It may also print the expression using a
7068 Python-based pretty-printer (@pxref{Pretty Printing}).
7071 @item print @var{expr}
7072 @itemx print /@var{f} @var{expr}
7073 @var{expr} is an expression (in the source language). By default the
7074 value of @var{expr} is printed in a format appropriate to its data type;
7075 you can choose a different format by specifying @samp{/@var{f}}, where
7076 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7080 @itemx print /@var{f}
7081 @cindex reprint the last value
7082 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7083 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7084 conveniently inspect the same value in an alternative format.
7087 A more low-level way of examining data is with the @code{x} command.
7088 It examines data in memory at a specified address and prints it in a
7089 specified format. @xref{Memory, ,Examining Memory}.
7091 If you are interested in information about types, or about how the
7092 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7093 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7097 * Expressions:: Expressions
7098 * Ambiguous Expressions:: Ambiguous Expressions
7099 * Variables:: Program variables
7100 * Arrays:: Artificial arrays
7101 * Output Formats:: Output formats
7102 * Memory:: Examining memory
7103 * Auto Display:: Automatic display
7104 * Print Settings:: Print settings
7105 * Pretty Printing:: Python pretty printing
7106 * Value History:: Value history
7107 * Convenience Vars:: Convenience variables
7108 * Registers:: Registers
7109 * Floating Point Hardware:: Floating point hardware
7110 * Vector Unit:: Vector Unit
7111 * OS Information:: Auxiliary data provided by operating system
7112 * Memory Region Attributes:: Memory region attributes
7113 * Dump/Restore Files:: Copy between memory and a file
7114 * Core File Generation:: Cause a program dump its core
7115 * Character Sets:: Debugging programs that use a different
7116 character set than GDB does
7117 * Caching Remote Data:: Data caching for remote targets
7118 * Searching Memory:: Searching memory for a sequence of bytes
7122 @section Expressions
7125 @code{print} and many other @value{GDBN} commands accept an expression and
7126 compute its value. Any kind of constant, variable or operator defined
7127 by the programming language you are using is valid in an expression in
7128 @value{GDBN}. This includes conditional expressions, function calls,
7129 casts, and string constants. It also includes preprocessor macros, if
7130 you compiled your program to include this information; see
7133 @cindex arrays in expressions
7134 @value{GDBN} supports array constants in expressions input by
7135 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7136 you can use the command @code{print @{1, 2, 3@}} to create an array
7137 of three integers. If you pass an array to a function or assign it
7138 to a program variable, @value{GDBN} copies the array to memory that
7139 is @code{malloc}ed in the target program.
7141 Because C is so widespread, most of the expressions shown in examples in
7142 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7143 Languages}, for information on how to use expressions in other
7146 In this section, we discuss operators that you can use in @value{GDBN}
7147 expressions regardless of your programming language.
7149 @cindex casts, in expressions
7150 Casts are supported in all languages, not just in C, because it is so
7151 useful to cast a number into a pointer in order to examine a structure
7152 at that address in memory.
7153 @c FIXME: casts supported---Mod2 true?
7155 @value{GDBN} supports these operators, in addition to those common
7156 to programming languages:
7160 @samp{@@} is a binary operator for treating parts of memory as arrays.
7161 @xref{Arrays, ,Artificial Arrays}, for more information.
7164 @samp{::} allows you to specify a variable in terms of the file or
7165 function where it is defined. @xref{Variables, ,Program Variables}.
7167 @cindex @{@var{type}@}
7168 @cindex type casting memory
7169 @cindex memory, viewing as typed object
7170 @cindex casts, to view memory
7171 @item @{@var{type}@} @var{addr}
7172 Refers to an object of type @var{type} stored at address @var{addr} in
7173 memory. @var{addr} may be any expression whose value is an integer or
7174 pointer (but parentheses are required around binary operators, just as in
7175 a cast). This construct is allowed regardless of what kind of data is
7176 normally supposed to reside at @var{addr}.
7179 @node Ambiguous Expressions
7180 @section Ambiguous Expressions
7181 @cindex ambiguous expressions
7183 Expressions can sometimes contain some ambiguous elements. For instance,
7184 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7185 a single function name to be defined several times, for application in
7186 different contexts. This is called @dfn{overloading}. Another example
7187 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7188 templates and is typically instantiated several times, resulting in
7189 the same function name being defined in different contexts.
7191 In some cases and depending on the language, it is possible to adjust
7192 the expression to remove the ambiguity. For instance in C@t{++}, you
7193 can specify the signature of the function you want to break on, as in
7194 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7195 qualified name of your function often makes the expression unambiguous
7198 When an ambiguity that needs to be resolved is detected, the debugger
7199 has the capability to display a menu of numbered choices for each
7200 possibility, and then waits for the selection with the prompt @samp{>}.
7201 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7202 aborts the current command. If the command in which the expression was
7203 used allows more than one choice to be selected, the next option in the
7204 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7207 For example, the following session excerpt shows an attempt to set a
7208 breakpoint at the overloaded symbol @code{String::after}.
7209 We choose three particular definitions of that function name:
7211 @c FIXME! This is likely to change to show arg type lists, at least
7214 (@value{GDBP}) b String::after
7217 [2] file:String.cc; line number:867
7218 [3] file:String.cc; line number:860
7219 [4] file:String.cc; line number:875
7220 [5] file:String.cc; line number:853
7221 [6] file:String.cc; line number:846
7222 [7] file:String.cc; line number:735
7224 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7225 Breakpoint 2 at 0xb344: file String.cc, line 875.
7226 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7227 Multiple breakpoints were set.
7228 Use the "delete" command to delete unwanted
7235 @kindex set multiple-symbols
7236 @item set multiple-symbols @var{mode}
7237 @cindex multiple-symbols menu
7239 This option allows you to adjust the debugger behavior when an expression
7242 By default, @var{mode} is set to @code{all}. If the command with which
7243 the expression is used allows more than one choice, then @value{GDBN}
7244 automatically selects all possible choices. For instance, inserting
7245 a breakpoint on a function using an ambiguous name results in a breakpoint
7246 inserted on each possible match. However, if a unique choice must be made,
7247 then @value{GDBN} uses the menu to help you disambiguate the expression.
7248 For instance, printing the address of an overloaded function will result
7249 in the use of the menu.
7251 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7252 when an ambiguity is detected.
7254 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7255 an error due to the ambiguity and the command is aborted.
7257 @kindex show multiple-symbols
7258 @item show multiple-symbols
7259 Show the current value of the @code{multiple-symbols} setting.
7263 @section Program Variables
7265 The most common kind of expression to use is the name of a variable
7268 Variables in expressions are understood in the selected stack frame
7269 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7273 global (or file-static)
7280 visible according to the scope rules of the
7281 programming language from the point of execution in that frame
7284 @noindent This means that in the function
7299 you can examine and use the variable @code{a} whenever your program is
7300 executing within the function @code{foo}, but you can only use or
7301 examine the variable @code{b} while your program is executing inside
7302 the block where @code{b} is declared.
7304 @cindex variable name conflict
7305 There is an exception: you can refer to a variable or function whose
7306 scope is a single source file even if the current execution point is not
7307 in this file. But it is possible to have more than one such variable or
7308 function with the same name (in different source files). If that
7309 happens, referring to that name has unpredictable effects. If you wish,
7310 you can specify a static variable in a particular function or file by
7311 using the colon-colon (@code{::}) notation:
7313 @cindex colon-colon, context for variables/functions
7315 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7316 @cindex @code{::}, context for variables/functions
7319 @var{file}::@var{variable}
7320 @var{function}::@var{variable}
7324 Here @var{file} or @var{function} is the name of the context for the
7325 static @var{variable}. In the case of file names, you can use quotes to
7326 make sure @value{GDBN} parses the file name as a single word---for example,
7327 to print a global value of @code{x} defined in @file{f2.c}:
7330 (@value{GDBP}) p 'f2.c'::x
7333 The @code{::} notation is normally used for referring to
7334 static variables, since you typically disambiguate uses of local variables
7335 in functions by selecting the appropriate frame and using the
7336 simple name of the variable. However, you may also use this notation
7337 to refer to local variables in frames enclosing the selected frame:
7346 process (a); /* Stop here */
7357 For example, if there is a breakpoint at the commented line,
7358 here is what you might see
7359 when the program stops after executing the call @code{bar(0)}:
7364 (@value{GDBP}) p bar::a
7367 #2 0x080483d0 in foo (a=5) at foobar.c:12
7370 (@value{GDBP}) p bar::a
7374 @cindex C@t{++} scope resolution
7375 These uses of @samp{::} are very rarely in conflict with the very similar
7376 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7377 scope resolution operator in @value{GDBN} expressions.
7378 @c FIXME: Um, so what happens in one of those rare cases where it's in
7381 @cindex wrong values
7382 @cindex variable values, wrong
7383 @cindex function entry/exit, wrong values of variables
7384 @cindex optimized code, wrong values of variables
7386 @emph{Warning:} Occasionally, a local variable may appear to have the
7387 wrong value at certain points in a function---just after entry to a new
7388 scope, and just before exit.
7390 You may see this problem when you are stepping by machine instructions.
7391 This is because, on most machines, it takes more than one instruction to
7392 set up a stack frame (including local variable definitions); if you are
7393 stepping by machine instructions, variables may appear to have the wrong
7394 values until the stack frame is completely built. On exit, it usually
7395 also takes more than one machine instruction to destroy a stack frame;
7396 after you begin stepping through that group of instructions, local
7397 variable definitions may be gone.
7399 This may also happen when the compiler does significant optimizations.
7400 To be sure of always seeing accurate values, turn off all optimization
7403 @cindex ``No symbol "foo" in current context''
7404 Another possible effect of compiler optimizations is to optimize
7405 unused variables out of existence, or assign variables to registers (as
7406 opposed to memory addresses). Depending on the support for such cases
7407 offered by the debug info format used by the compiler, @value{GDBN}
7408 might not be able to display values for such local variables. If that
7409 happens, @value{GDBN} will print a message like this:
7412 No symbol "foo" in current context.
7415 To solve such problems, either recompile without optimizations, or use a
7416 different debug info format, if the compiler supports several such
7417 formats. @xref{Compilation}, for more information on choosing compiler
7418 options. @xref{C, ,C and C@t{++}}, for more information about debug
7419 info formats that are best suited to C@t{++} programs.
7421 If you ask to print an object whose contents are unknown to
7422 @value{GDBN}, e.g., because its data type is not completely specified
7423 by the debug information, @value{GDBN} will say @samp{<incomplete
7424 type>}. @xref{Symbols, incomplete type}, for more about this.
7426 If you append @kbd{@@entry} string to a function parameter name you get its
7427 value at the time the function got called. If the value is not available an
7428 error message is printed. Entry values are available only with some compilers.
7429 Entry values are normally also printed at the function parameter list according
7430 to @ref{set print entry-values}.
7433 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7439 (gdb) print i@@entry
7443 Strings are identified as arrays of @code{char} values without specified
7444 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7445 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7446 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7447 defines literal string type @code{"char"} as @code{char} without a sign.
7452 signed char var1[] = "A";
7455 You get during debugging
7460 $2 = @{65 'A', 0 '\0'@}
7464 @section Artificial Arrays
7466 @cindex artificial array
7468 @kindex @@@r{, referencing memory as an array}
7469 It is often useful to print out several successive objects of the
7470 same type in memory; a section of an array, or an array of
7471 dynamically determined size for which only a pointer exists in the
7474 You can do this by referring to a contiguous span of memory as an
7475 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7476 operand of @samp{@@} should be the first element of the desired array
7477 and be an individual object. The right operand should be the desired length
7478 of the array. The result is an array value whose elements are all of
7479 the type of the left argument. The first element is actually the left
7480 argument; the second element comes from bytes of memory immediately
7481 following those that hold the first element, and so on. Here is an
7482 example. If a program says
7485 int *array = (int *) malloc (len * sizeof (int));
7489 you can print the contents of @code{array} with
7495 The left operand of @samp{@@} must reside in memory. Array values made
7496 with @samp{@@} in this way behave just like other arrays in terms of
7497 subscripting, and are coerced to pointers when used in expressions.
7498 Artificial arrays most often appear in expressions via the value history
7499 (@pxref{Value History, ,Value History}), after printing one out.
7501 Another way to create an artificial array is to use a cast.
7502 This re-interprets a value as if it were an array.
7503 The value need not be in memory:
7505 (@value{GDBP}) p/x (short[2])0x12345678
7506 $1 = @{0x1234, 0x5678@}
7509 As a convenience, if you leave the array length out (as in
7510 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7511 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7513 (@value{GDBP}) p/x (short[])0x12345678
7514 $2 = @{0x1234, 0x5678@}
7517 Sometimes the artificial array mechanism is not quite enough; in
7518 moderately complex data structures, the elements of interest may not
7519 actually be adjacent---for example, if you are interested in the values
7520 of pointers in an array. One useful work-around in this situation is
7521 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7522 Variables}) as a counter in an expression that prints the first
7523 interesting value, and then repeat that expression via @key{RET}. For
7524 instance, suppose you have an array @code{dtab} of pointers to
7525 structures, and you are interested in the values of a field @code{fv}
7526 in each structure. Here is an example of what you might type:
7536 @node Output Formats
7537 @section Output Formats
7539 @cindex formatted output
7540 @cindex output formats
7541 By default, @value{GDBN} prints a value according to its data type. Sometimes
7542 this is not what you want. For example, you might want to print a number
7543 in hex, or a pointer in decimal. Or you might want to view data in memory
7544 at a certain address as a character string or as an instruction. To do
7545 these things, specify an @dfn{output format} when you print a value.
7547 The simplest use of output formats is to say how to print a value
7548 already computed. This is done by starting the arguments of the
7549 @code{print} command with a slash and a format letter. The format
7550 letters supported are:
7554 Regard the bits of the value as an integer, and print the integer in
7558 Print as integer in signed decimal.
7561 Print as integer in unsigned decimal.
7564 Print as integer in octal.
7567 Print as integer in binary. The letter @samp{t} stands for ``two''.
7568 @footnote{@samp{b} cannot be used because these format letters are also
7569 used with the @code{x} command, where @samp{b} stands for ``byte'';
7570 see @ref{Memory,,Examining Memory}.}
7573 @cindex unknown address, locating
7574 @cindex locate address
7575 Print as an address, both absolute in hexadecimal and as an offset from
7576 the nearest preceding symbol. You can use this format used to discover
7577 where (in what function) an unknown address is located:
7580 (@value{GDBP}) p/a 0x54320
7581 $3 = 0x54320 <_initialize_vx+396>
7585 The command @code{info symbol 0x54320} yields similar results.
7586 @xref{Symbols, info symbol}.
7589 Regard as an integer and print it as a character constant. This
7590 prints both the numerical value and its character representation. The
7591 character representation is replaced with the octal escape @samp{\nnn}
7592 for characters outside the 7-bit @sc{ascii} range.
7594 Without this format, @value{GDBN} displays @code{char},
7595 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7596 constants. Single-byte members of vectors are displayed as integer
7600 Regard the bits of the value as a floating point number and print
7601 using typical floating point syntax.
7604 @cindex printing strings
7605 @cindex printing byte arrays
7606 Regard as a string, if possible. With this format, pointers to single-byte
7607 data are displayed as null-terminated strings and arrays of single-byte data
7608 are displayed as fixed-length strings. Other values are displayed in their
7611 Without this format, @value{GDBN} displays pointers to and arrays of
7612 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7613 strings. Single-byte members of a vector are displayed as an integer
7617 @cindex raw printing
7618 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7619 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7620 Printing}). This typically results in a higher-level display of the
7621 value's contents. The @samp{r} format bypasses any Python
7622 pretty-printer which might exist.
7625 For example, to print the program counter in hex (@pxref{Registers}), type
7632 Note that no space is required before the slash; this is because command
7633 names in @value{GDBN} cannot contain a slash.
7635 To reprint the last value in the value history with a different format,
7636 you can use the @code{print} command with just a format and no
7637 expression. For example, @samp{p/x} reprints the last value in hex.
7640 @section Examining Memory
7642 You can use the command @code{x} (for ``examine'') to examine memory in
7643 any of several formats, independently of your program's data types.
7645 @cindex examining memory
7647 @kindex x @r{(examine memory)}
7648 @item x/@var{nfu} @var{addr}
7651 Use the @code{x} command to examine memory.
7654 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7655 much memory to display and how to format it; @var{addr} is an
7656 expression giving the address where you want to start displaying memory.
7657 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7658 Several commands set convenient defaults for @var{addr}.
7661 @item @var{n}, the repeat count
7662 The repeat count is a decimal integer; the default is 1. It specifies
7663 how much memory (counting by units @var{u}) to display.
7664 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7667 @item @var{f}, the display format
7668 The display format is one of the formats used by @code{print}
7669 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7670 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7671 The default is @samp{x} (hexadecimal) initially. The default changes
7672 each time you use either @code{x} or @code{print}.
7674 @item @var{u}, the unit size
7675 The unit size is any of
7681 Halfwords (two bytes).
7683 Words (four bytes). This is the initial default.
7685 Giant words (eight bytes).
7688 Each time you specify a unit size with @code{x}, that size becomes the
7689 default unit the next time you use @code{x}. For the @samp{i} format,
7690 the unit size is ignored and is normally not written. For the @samp{s} format,
7691 the unit size defaults to @samp{b}, unless it is explicitly given.
7692 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7693 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7694 Note that the results depend on the programming language of the
7695 current compilation unit. If the language is C, the @samp{s}
7696 modifier will use the UTF-16 encoding while @samp{w} will use
7697 UTF-32. The encoding is set by the programming language and cannot
7700 @item @var{addr}, starting display address
7701 @var{addr} is the address where you want @value{GDBN} to begin displaying
7702 memory. The expression need not have a pointer value (though it may);
7703 it is always interpreted as an integer address of a byte of memory.
7704 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7705 @var{addr} is usually just after the last address examined---but several
7706 other commands also set the default address: @code{info breakpoints} (to
7707 the address of the last breakpoint listed), @code{info line} (to the
7708 starting address of a line), and @code{print} (if you use it to display
7709 a value from memory).
7712 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7713 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7714 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7715 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7716 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7718 Since the letters indicating unit sizes are all distinct from the
7719 letters specifying output formats, you do not have to remember whether
7720 unit size or format comes first; either order works. The output
7721 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7722 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7724 Even though the unit size @var{u} is ignored for the formats @samp{s}
7725 and @samp{i}, you might still want to use a count @var{n}; for example,
7726 @samp{3i} specifies that you want to see three machine instructions,
7727 including any operands. For convenience, especially when used with
7728 the @code{display} command, the @samp{i} format also prints branch delay
7729 slot instructions, if any, beyond the count specified, which immediately
7730 follow the last instruction that is within the count. The command
7731 @code{disassemble} gives an alternative way of inspecting machine
7732 instructions; see @ref{Machine Code,,Source and Machine Code}.
7734 All the defaults for the arguments to @code{x} are designed to make it
7735 easy to continue scanning memory with minimal specifications each time
7736 you use @code{x}. For example, after you have inspected three machine
7737 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7738 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7739 the repeat count @var{n} is used again; the other arguments default as
7740 for successive uses of @code{x}.
7742 When examining machine instructions, the instruction at current program
7743 counter is shown with a @code{=>} marker. For example:
7746 (@value{GDBP}) x/5i $pc-6
7747 0x804837f <main+11>: mov %esp,%ebp
7748 0x8048381 <main+13>: push %ecx
7749 0x8048382 <main+14>: sub $0x4,%esp
7750 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7751 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7754 @cindex @code{$_}, @code{$__}, and value history
7755 The addresses and contents printed by the @code{x} command are not saved
7756 in the value history because there is often too much of them and they
7757 would get in the way. Instead, @value{GDBN} makes these values available for
7758 subsequent use in expressions as values of the convenience variables
7759 @code{$_} and @code{$__}. After an @code{x} command, the last address
7760 examined is available for use in expressions in the convenience variable
7761 @code{$_}. The contents of that address, as examined, are available in
7762 the convenience variable @code{$__}.
7764 If the @code{x} command has a repeat count, the address and contents saved
7765 are from the last memory unit printed; this is not the same as the last
7766 address printed if several units were printed on the last line of output.
7768 @cindex remote memory comparison
7769 @cindex verify remote memory image
7770 When you are debugging a program running on a remote target machine
7771 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7772 remote machine's memory against the executable file you downloaded to
7773 the target. The @code{compare-sections} command is provided for such
7777 @kindex compare-sections
7778 @item compare-sections @r{[}@var{section-name}@r{]}
7779 Compare the data of a loadable section @var{section-name} in the
7780 executable file of the program being debugged with the same section in
7781 the remote machine's memory, and report any mismatches. With no
7782 arguments, compares all loadable sections. This command's
7783 availability depends on the target's support for the @code{"qCRC"}
7788 @section Automatic Display
7789 @cindex automatic display
7790 @cindex display of expressions
7792 If you find that you want to print the value of an expression frequently
7793 (to see how it changes), you might want to add it to the @dfn{automatic
7794 display list} so that @value{GDBN} prints its value each time your program stops.
7795 Each expression added to the list is given a number to identify it;
7796 to remove an expression from the list, you specify that number.
7797 The automatic display looks like this:
7801 3: bar[5] = (struct hack *) 0x3804
7805 This display shows item numbers, expressions and their current values. As with
7806 displays you request manually using @code{x} or @code{print}, you can
7807 specify the output format you prefer; in fact, @code{display} decides
7808 whether to use @code{print} or @code{x} depending your format
7809 specification---it uses @code{x} if you specify either the @samp{i}
7810 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7814 @item display @var{expr}
7815 Add the expression @var{expr} to the list of expressions to display
7816 each time your program stops. @xref{Expressions, ,Expressions}.
7818 @code{display} does not repeat if you press @key{RET} again after using it.
7820 @item display/@var{fmt} @var{expr}
7821 For @var{fmt} specifying only a display format and not a size or
7822 count, add the expression @var{expr} to the auto-display list but
7823 arrange to display it each time in the specified format @var{fmt}.
7824 @xref{Output Formats,,Output Formats}.
7826 @item display/@var{fmt} @var{addr}
7827 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7828 number of units, add the expression @var{addr} as a memory address to
7829 be examined each time your program stops. Examining means in effect
7830 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7833 For example, @samp{display/i $pc} can be helpful, to see the machine
7834 instruction about to be executed each time execution stops (@samp{$pc}
7835 is a common name for the program counter; @pxref{Registers, ,Registers}).
7838 @kindex delete display
7840 @item undisplay @var{dnums}@dots{}
7841 @itemx delete display @var{dnums}@dots{}
7842 Remove items from the list of expressions to display. Specify the
7843 numbers of the displays that you want affected with the command
7844 argument @var{dnums}. It can be a single display number, one of the
7845 numbers shown in the first field of the @samp{info display} display;
7846 or it could be a range of display numbers, as in @code{2-4}.
7848 @code{undisplay} does not repeat if you press @key{RET} after using it.
7849 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7851 @kindex disable display
7852 @item disable display @var{dnums}@dots{}
7853 Disable the display of item numbers @var{dnums}. A disabled display
7854 item is not printed automatically, but is not forgotten. It may be
7855 enabled again later. Specify the numbers of the displays that you
7856 want affected with the command argument @var{dnums}. It can be a
7857 single display number, one of the numbers shown in the first field of
7858 the @samp{info display} display; or it could be a range of display
7859 numbers, as in @code{2-4}.
7861 @kindex enable display
7862 @item enable display @var{dnums}@dots{}
7863 Enable display of item numbers @var{dnums}. It becomes effective once
7864 again in auto display of its expression, until you specify otherwise.
7865 Specify the numbers of the displays that you want affected with the
7866 command argument @var{dnums}. It can be a single display number, one
7867 of the numbers shown in the first field of the @samp{info display}
7868 display; or it could be a range of display numbers, as in @code{2-4}.
7871 Display the current values of the expressions on the list, just as is
7872 done when your program stops.
7874 @kindex info display
7876 Print the list of expressions previously set up to display
7877 automatically, each one with its item number, but without showing the
7878 values. This includes disabled expressions, which are marked as such.
7879 It also includes expressions which would not be displayed right now
7880 because they refer to automatic variables not currently available.
7883 @cindex display disabled out of scope
7884 If a display expression refers to local variables, then it does not make
7885 sense outside the lexical context for which it was set up. Such an
7886 expression is disabled when execution enters a context where one of its
7887 variables is not defined. For example, if you give the command
7888 @code{display last_char} while inside a function with an argument
7889 @code{last_char}, @value{GDBN} displays this argument while your program
7890 continues to stop inside that function. When it stops elsewhere---where
7891 there is no variable @code{last_char}---the display is disabled
7892 automatically. The next time your program stops where @code{last_char}
7893 is meaningful, you can enable the display expression once again.
7895 @node Print Settings
7896 @section Print Settings
7898 @cindex format options
7899 @cindex print settings
7900 @value{GDBN} provides the following ways to control how arrays, structures,
7901 and symbols are printed.
7904 These settings are useful for debugging programs in any language:
7908 @item set print address
7909 @itemx set print address on
7910 @cindex print/don't print memory addresses
7911 @value{GDBN} prints memory addresses showing the location of stack
7912 traces, structure values, pointer values, breakpoints, and so forth,
7913 even when it also displays the contents of those addresses. The default
7914 is @code{on}. For example, this is what a stack frame display looks like with
7915 @code{set print address on}:
7920 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7922 530 if (lquote != def_lquote)
7926 @item set print address off
7927 Do not print addresses when displaying their contents. For example,
7928 this is the same stack frame displayed with @code{set print address off}:
7932 (@value{GDBP}) set print addr off
7934 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7935 530 if (lquote != def_lquote)
7939 You can use @samp{set print address off} to eliminate all machine
7940 dependent displays from the @value{GDBN} interface. For example, with
7941 @code{print address off}, you should get the same text for backtraces on
7942 all machines---whether or not they involve pointer arguments.
7945 @item show print address
7946 Show whether or not addresses are to be printed.
7949 When @value{GDBN} prints a symbolic address, it normally prints the
7950 closest earlier symbol plus an offset. If that symbol does not uniquely
7951 identify the address (for example, it is a name whose scope is a single
7952 source file), you may need to clarify. One way to do this is with
7953 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7954 you can set @value{GDBN} to print the source file and line number when
7955 it prints a symbolic address:
7958 @item set print symbol-filename on
7959 @cindex source file and line of a symbol
7960 @cindex symbol, source file and line
7961 Tell @value{GDBN} to print the source file name and line number of a
7962 symbol in the symbolic form of an address.
7964 @item set print symbol-filename off
7965 Do not print source file name and line number of a symbol. This is the
7968 @item show print symbol-filename
7969 Show whether or not @value{GDBN} will print the source file name and
7970 line number of a symbol in the symbolic form of an address.
7973 Another situation where it is helpful to show symbol filenames and line
7974 numbers is when disassembling code; @value{GDBN} shows you the line
7975 number and source file that corresponds to each instruction.
7977 Also, you may wish to see the symbolic form only if the address being
7978 printed is reasonably close to the closest earlier symbol:
7981 @item set print max-symbolic-offset @var{max-offset}
7982 @cindex maximum value for offset of closest symbol
7983 Tell @value{GDBN} to only display the symbolic form of an address if the
7984 offset between the closest earlier symbol and the address is less than
7985 @var{max-offset}. The default is 0, which tells @value{GDBN}
7986 to always print the symbolic form of an address if any symbol precedes it.
7988 @item show print max-symbolic-offset
7989 Ask how large the maximum offset is that @value{GDBN} prints in a
7993 @cindex wild pointer, interpreting
7994 @cindex pointer, finding referent
7995 If you have a pointer and you are not sure where it points, try
7996 @samp{set print symbol-filename on}. Then you can determine the name
7997 and source file location of the variable where it points, using
7998 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7999 For example, here @value{GDBN} shows that a variable @code{ptt} points
8000 at another variable @code{t}, defined in @file{hi2.c}:
8003 (@value{GDBP}) set print symbol-filename on
8004 (@value{GDBP}) p/a ptt
8005 $4 = 0xe008 <t in hi2.c>
8009 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8010 does not show the symbol name and filename of the referent, even with
8011 the appropriate @code{set print} options turned on.
8014 Other settings control how different kinds of objects are printed:
8017 @item set print array
8018 @itemx set print array on
8019 @cindex pretty print arrays
8020 Pretty print arrays. This format is more convenient to read,
8021 but uses more space. The default is off.
8023 @item set print array off
8024 Return to compressed format for arrays.
8026 @item show print array
8027 Show whether compressed or pretty format is selected for displaying
8030 @cindex print array indexes
8031 @item set print array-indexes
8032 @itemx set print array-indexes on
8033 Print the index of each element when displaying arrays. May be more
8034 convenient to locate a given element in the array or quickly find the
8035 index of a given element in that printed array. The default is off.
8037 @item set print array-indexes off
8038 Stop printing element indexes when displaying arrays.
8040 @item show print array-indexes
8041 Show whether the index of each element is printed when displaying
8044 @item set print elements @var{number-of-elements}
8045 @cindex number of array elements to print
8046 @cindex limit on number of printed array elements
8047 Set a limit on how many elements of an array @value{GDBN} will print.
8048 If @value{GDBN} is printing a large array, it stops printing after it has
8049 printed the number of elements set by the @code{set print elements} command.
8050 This limit also applies to the display of strings.
8051 When @value{GDBN} starts, this limit is set to 200.
8052 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8054 @item show print elements
8055 Display the number of elements of a large array that @value{GDBN} will print.
8056 If the number is 0, then the printing is unlimited.
8058 @item set print frame-arguments @var{value}
8059 @kindex set print frame-arguments
8060 @cindex printing frame argument values
8061 @cindex print all frame argument values
8062 @cindex print frame argument values for scalars only
8063 @cindex do not print frame argument values
8064 This command allows to control how the values of arguments are printed
8065 when the debugger prints a frame (@pxref{Frames}). The possible
8070 The values of all arguments are printed.
8073 Print the value of an argument only if it is a scalar. The value of more
8074 complex arguments such as arrays, structures, unions, etc, is replaced
8075 by @code{@dots{}}. This is the default. Here is an example where
8076 only scalar arguments are shown:
8079 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8084 None of the argument values are printed. Instead, the value of each argument
8085 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8088 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8093 By default, only scalar arguments are printed. This command can be used
8094 to configure the debugger to print the value of all arguments, regardless
8095 of their type. However, it is often advantageous to not print the value
8096 of more complex parameters. For instance, it reduces the amount of
8097 information printed in each frame, making the backtrace more readable.
8098 Also, it improves performance when displaying Ada frames, because
8099 the computation of large arguments can sometimes be CPU-intensive,
8100 especially in large applications. Setting @code{print frame-arguments}
8101 to @code{scalars} (the default) or @code{none} avoids this computation,
8102 thus speeding up the display of each Ada frame.
8104 @item show print frame-arguments
8105 Show how the value of arguments should be displayed when printing a frame.
8107 @anchor{set print entry-values}
8108 @item set print entry-values @var{value}
8109 @kindex set print entry-values
8110 Set printing of frame argument values at function entry. In some cases
8111 @value{GDBN} can determine the value of function argument which was passed by
8112 the function caller, even if the value was modified inside the called function
8113 and therefore is different. With optimized code, the current value could be
8114 unavailable, but the entry value may still be known.
8116 The default value is @code{default} (see below for its description). Older
8117 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8118 this feature will behave in the @code{default} setting the same way as with the
8121 This functionality is currently supported only by DWARF 2 debugging format and
8122 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8123 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8126 The @var{value} parameter can be one of the following:
8130 Print only actual parameter values, never print values from function entry
8134 #0 different (val=6)
8135 #0 lost (val=<optimized out>)
8137 #0 invalid (val=<optimized out>)
8141 Print only parameter values from function entry point. The actual parameter
8142 values are never printed.
8144 #0 equal (val@@entry=5)
8145 #0 different (val@@entry=5)
8146 #0 lost (val@@entry=5)
8147 #0 born (val@@entry=<optimized out>)
8148 #0 invalid (val@@entry=<optimized out>)
8152 Print only parameter values from function entry point. If value from function
8153 entry point is not known while the actual value is known, print the actual
8154 value for such parameter.
8156 #0 equal (val@@entry=5)
8157 #0 different (val@@entry=5)
8158 #0 lost (val@@entry=5)
8160 #0 invalid (val@@entry=<optimized out>)
8164 Print actual parameter values. If actual parameter value is not known while
8165 value from function entry point is known, print the entry point value for such
8169 #0 different (val=6)
8170 #0 lost (val@@entry=5)
8172 #0 invalid (val=<optimized out>)
8176 Always print both the actual parameter value and its value from function entry
8177 point, even if values of one or both are not available due to compiler
8180 #0 equal (val=5, val@@entry=5)
8181 #0 different (val=6, val@@entry=5)
8182 #0 lost (val=<optimized out>, val@@entry=5)
8183 #0 born (val=10, val@@entry=<optimized out>)
8184 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8188 Print the actual parameter value if it is known and also its value from
8189 function entry point if it is known. If neither is known, print for the actual
8190 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8191 values are known and identical, print the shortened
8192 @code{param=param@@entry=VALUE} notation.
8194 #0 equal (val=val@@entry=5)
8195 #0 different (val=6, val@@entry=5)
8196 #0 lost (val@@entry=5)
8198 #0 invalid (val=<optimized out>)
8202 Always print the actual parameter value. Print also its value from function
8203 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8204 if both values are known and identical, print the shortened
8205 @code{param=param@@entry=VALUE} notation.
8207 #0 equal (val=val@@entry=5)
8208 #0 different (val=6, val@@entry=5)
8209 #0 lost (val=<optimized out>, val@@entry=5)
8211 #0 invalid (val=<optimized out>)
8215 For analysis messages on possible failures of frame argument values at function
8216 entry resolution see @ref{set debug entry-values}.
8218 @item show print entry-values
8219 Show the method being used for printing of frame argument values at function
8222 @item set print repeats
8223 @cindex repeated array elements
8224 Set the threshold for suppressing display of repeated array
8225 elements. When the number of consecutive identical elements of an
8226 array exceeds the threshold, @value{GDBN} prints the string
8227 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8228 identical repetitions, instead of displaying the identical elements
8229 themselves. Setting the threshold to zero will cause all elements to
8230 be individually printed. The default threshold is 10.
8232 @item show print repeats
8233 Display the current threshold for printing repeated identical
8236 @item set print null-stop
8237 @cindex @sc{null} elements in arrays
8238 Cause @value{GDBN} to stop printing the characters of an array when the first
8239 @sc{null} is encountered. This is useful when large arrays actually
8240 contain only short strings.
8243 @item show print null-stop
8244 Show whether @value{GDBN} stops printing an array on the first
8245 @sc{null} character.
8247 @item set print pretty on
8248 @cindex print structures in indented form
8249 @cindex indentation in structure display
8250 Cause @value{GDBN} to print structures in an indented format with one member
8251 per line, like this:
8266 @item set print pretty off
8267 Cause @value{GDBN} to print structures in a compact format, like this:
8271 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8272 meat = 0x54 "Pork"@}
8277 This is the default format.
8279 @item show print pretty
8280 Show which format @value{GDBN} is using to print structures.
8282 @item set print sevenbit-strings on
8283 @cindex eight-bit characters in strings
8284 @cindex octal escapes in strings
8285 Print using only seven-bit characters; if this option is set,
8286 @value{GDBN} displays any eight-bit characters (in strings or
8287 character values) using the notation @code{\}@var{nnn}. This setting is
8288 best if you are working in English (@sc{ascii}) and you use the
8289 high-order bit of characters as a marker or ``meta'' bit.
8291 @item set print sevenbit-strings off
8292 Print full eight-bit characters. This allows the use of more
8293 international character sets, and is the default.
8295 @item show print sevenbit-strings
8296 Show whether or not @value{GDBN} is printing only seven-bit characters.
8298 @item set print union on
8299 @cindex unions in structures, printing
8300 Tell @value{GDBN} to print unions which are contained in structures
8301 and other unions. This is the default setting.
8303 @item set print union off
8304 Tell @value{GDBN} not to print unions which are contained in
8305 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8308 @item show print union
8309 Ask @value{GDBN} whether or not it will print unions which are contained in
8310 structures and other unions.
8312 For example, given the declarations
8315 typedef enum @{Tree, Bug@} Species;
8316 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8317 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8328 struct thing foo = @{Tree, @{Acorn@}@};
8332 with @code{set print union on} in effect @samp{p foo} would print
8335 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8339 and with @code{set print union off} in effect it would print
8342 $1 = @{it = Tree, form = @{...@}@}
8346 @code{set print union} affects programs written in C-like languages
8352 These settings are of interest when debugging C@t{++} programs:
8355 @cindex demangling C@t{++} names
8356 @item set print demangle
8357 @itemx set print demangle on
8358 Print C@t{++} names in their source form rather than in the encoded
8359 (``mangled'') form passed to the assembler and linker for type-safe
8360 linkage. The default is on.
8362 @item show print demangle
8363 Show whether C@t{++} names are printed in mangled or demangled form.
8365 @item set print asm-demangle
8366 @itemx set print asm-demangle on
8367 Print C@t{++} names in their source form rather than their mangled form, even
8368 in assembler code printouts such as instruction disassemblies.
8371 @item show print asm-demangle
8372 Show whether C@t{++} names in assembly listings are printed in mangled
8375 @cindex C@t{++} symbol decoding style
8376 @cindex symbol decoding style, C@t{++}
8377 @kindex set demangle-style
8378 @item set demangle-style @var{style}
8379 Choose among several encoding schemes used by different compilers to
8380 represent C@t{++} names. The choices for @var{style} are currently:
8384 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8387 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8388 This is the default.
8391 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8394 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8397 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8398 @strong{Warning:} this setting alone is not sufficient to allow
8399 debugging @code{cfront}-generated executables. @value{GDBN} would
8400 require further enhancement to permit that.
8403 If you omit @var{style}, you will see a list of possible formats.
8405 @item show demangle-style
8406 Display the encoding style currently in use for decoding C@t{++} symbols.
8408 @item set print object
8409 @itemx set print object on
8410 @cindex derived type of an object, printing
8411 @cindex display derived types
8412 When displaying a pointer to an object, identify the @emph{actual}
8413 (derived) type of the object rather than the @emph{declared} type, using
8414 the virtual function table. Note that the virtual function table is
8415 required---this feature can only work for objects that have run-time
8416 type identification; a single virtual method in the object's declared
8419 @item set print object off
8420 Display only the declared type of objects, without reference to the
8421 virtual function table. This is the default setting.
8423 @item show print object
8424 Show whether actual, or declared, object types are displayed.
8426 @item set print static-members
8427 @itemx set print static-members on
8428 @cindex static members of C@t{++} objects
8429 Print static members when displaying a C@t{++} object. The default is on.
8431 @item set print static-members off
8432 Do not print static members when displaying a C@t{++} object.
8434 @item show print static-members
8435 Show whether C@t{++} static members are printed or not.
8437 @item set print pascal_static-members
8438 @itemx set print pascal_static-members on
8439 @cindex static members of Pascal objects
8440 @cindex Pascal objects, static members display
8441 Print static members when displaying a Pascal object. The default is on.
8443 @item set print pascal_static-members off
8444 Do not print static members when displaying a Pascal object.
8446 @item show print pascal_static-members
8447 Show whether Pascal static members are printed or not.
8449 @c These don't work with HP ANSI C++ yet.
8450 @item set print vtbl
8451 @itemx set print vtbl on
8452 @cindex pretty print C@t{++} virtual function tables
8453 @cindex virtual functions (C@t{++}) display
8454 @cindex VTBL display
8455 Pretty print C@t{++} virtual function tables. The default is off.
8456 (The @code{vtbl} commands do not work on programs compiled with the HP
8457 ANSI C@t{++} compiler (@code{aCC}).)
8459 @item set print vtbl off
8460 Do not pretty print C@t{++} virtual function tables.
8462 @item show print vtbl
8463 Show whether C@t{++} virtual function tables are pretty printed, or not.
8466 @node Pretty Printing
8467 @section Pretty Printing
8469 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8470 Python code. It greatly simplifies the display of complex objects. This
8471 mechanism works for both MI and the CLI.
8474 * Pretty-Printer Introduction:: Introduction to pretty-printers
8475 * Pretty-Printer Example:: An example pretty-printer
8476 * Pretty-Printer Commands:: Pretty-printer commands
8479 @node Pretty-Printer Introduction
8480 @subsection Pretty-Printer Introduction
8482 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8483 registered for the value. If there is then @value{GDBN} invokes the
8484 pretty-printer to print the value. Otherwise the value is printed normally.
8486 Pretty-printers are normally named. This makes them easy to manage.
8487 The @samp{info pretty-printer} command will list all the installed
8488 pretty-printers with their names.
8489 If a pretty-printer can handle multiple data types, then its
8490 @dfn{subprinters} are the printers for the individual data types.
8491 Each such subprinter has its own name.
8492 The format of the name is @var{printer-name};@var{subprinter-name}.
8494 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8495 Typically they are automatically loaded and registered when the corresponding
8496 debug information is loaded, thus making them available without having to
8497 do anything special.
8499 There are three places where a pretty-printer can be registered.
8503 Pretty-printers registered globally are available when debugging
8507 Pretty-printers registered with a program space are available only
8508 when debugging that program.
8509 @xref{Progspaces In Python}, for more details on program spaces in Python.
8512 Pretty-printers registered with an objfile are loaded and unloaded
8513 with the corresponding objfile (e.g., shared library).
8514 @xref{Objfiles In Python}, for more details on objfiles in Python.
8517 @xref{Selecting Pretty-Printers}, for further information on how
8518 pretty-printers are selected,
8520 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8523 @node Pretty-Printer Example
8524 @subsection Pretty-Printer Example
8526 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8529 (@value{GDBP}) print s
8531 static npos = 4294967295,
8533 <std::allocator<char>> = @{
8534 <__gnu_cxx::new_allocator<char>> = @{
8535 <No data fields>@}, <No data fields>
8537 members of std::basic_string<char, std::char_traits<char>,
8538 std::allocator<char> >::_Alloc_hider:
8539 _M_p = 0x804a014 "abcd"
8544 With a pretty-printer for @code{std::string} only the contents are printed:
8547 (@value{GDBP}) print s
8551 @node Pretty-Printer Commands
8552 @subsection Pretty-Printer Commands
8553 @cindex pretty-printer commands
8556 @kindex info pretty-printer
8557 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8558 Print the list of installed pretty-printers.
8559 This includes disabled pretty-printers, which are marked as such.
8561 @var{object-regexp} is a regular expression matching the objects
8562 whose pretty-printers to list.
8563 Objects can be @code{global}, the program space's file
8564 (@pxref{Progspaces In Python}),
8565 and the object files within that program space (@pxref{Objfiles In Python}).
8566 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8567 looks up a printer from these three objects.
8569 @var{name-regexp} is a regular expression matching the name of the printers
8572 @kindex disable pretty-printer
8573 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8574 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8575 A disabled pretty-printer is not forgotten, it may be enabled again later.
8577 @kindex enable pretty-printer
8578 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8579 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8584 Suppose we have three pretty-printers installed: one from library1.so
8585 named @code{foo} that prints objects of type @code{foo}, and
8586 another from library2.so named @code{bar} that prints two types of objects,
8587 @code{bar1} and @code{bar2}.
8590 (gdb) info pretty-printer
8597 (gdb) info pretty-printer library2
8602 (gdb) disable pretty-printer library1
8604 2 of 3 printers enabled
8605 (gdb) info pretty-printer
8612 (gdb) disable pretty-printer library2 bar:bar1
8614 1 of 3 printers enabled
8615 (gdb) info pretty-printer library2
8622 (gdb) disable pretty-printer library2 bar
8624 0 of 3 printers enabled
8625 (gdb) info pretty-printer library2
8634 Note that for @code{bar} the entire printer can be disabled,
8635 as can each individual subprinter.
8638 @section Value History
8640 @cindex value history
8641 @cindex history of values printed by @value{GDBN}
8642 Values printed by the @code{print} command are saved in the @value{GDBN}
8643 @dfn{value history}. This allows you to refer to them in other expressions.
8644 Values are kept until the symbol table is re-read or discarded
8645 (for example with the @code{file} or @code{symbol-file} commands).
8646 When the symbol table changes, the value history is discarded,
8647 since the values may contain pointers back to the types defined in the
8652 @cindex history number
8653 The values printed are given @dfn{history numbers} by which you can
8654 refer to them. These are successive integers starting with one.
8655 @code{print} shows you the history number assigned to a value by
8656 printing @samp{$@var{num} = } before the value; here @var{num} is the
8659 To refer to any previous value, use @samp{$} followed by the value's
8660 history number. The way @code{print} labels its output is designed to
8661 remind you of this. Just @code{$} refers to the most recent value in
8662 the history, and @code{$$} refers to the value before that.
8663 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8664 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8665 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8667 For example, suppose you have just printed a pointer to a structure and
8668 want to see the contents of the structure. It suffices to type
8674 If you have a chain of structures where the component @code{next} points
8675 to the next one, you can print the contents of the next one with this:
8682 You can print successive links in the chain by repeating this
8683 command---which you can do by just typing @key{RET}.
8685 Note that the history records values, not expressions. If the value of
8686 @code{x} is 4 and you type these commands:
8694 then the value recorded in the value history by the @code{print} command
8695 remains 4 even though the value of @code{x} has changed.
8700 Print the last ten values in the value history, with their item numbers.
8701 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8702 values} does not change the history.
8704 @item show values @var{n}
8705 Print ten history values centered on history item number @var{n}.
8708 Print ten history values just after the values last printed. If no more
8709 values are available, @code{show values +} produces no display.
8712 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8713 same effect as @samp{show values +}.
8715 @node Convenience Vars
8716 @section Convenience Variables
8718 @cindex convenience variables
8719 @cindex user-defined variables
8720 @value{GDBN} provides @dfn{convenience variables} that you can use within
8721 @value{GDBN} to hold on to a value and refer to it later. These variables
8722 exist entirely within @value{GDBN}; they are not part of your program, and
8723 setting a convenience variable has no direct effect on further execution
8724 of your program. That is why you can use them freely.
8726 Convenience variables are prefixed with @samp{$}. Any name preceded by
8727 @samp{$} can be used for a convenience variable, unless it is one of
8728 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8729 (Value history references, in contrast, are @emph{numbers} preceded
8730 by @samp{$}. @xref{Value History, ,Value History}.)
8732 You can save a value in a convenience variable with an assignment
8733 expression, just as you would set a variable in your program.
8737 set $foo = *object_ptr
8741 would save in @code{$foo} the value contained in the object pointed to by
8744 Using a convenience variable for the first time creates it, but its
8745 value is @code{void} until you assign a new value. You can alter the
8746 value with another assignment at any time.
8748 Convenience variables have no fixed types. You can assign a convenience
8749 variable any type of value, including structures and arrays, even if
8750 that variable already has a value of a different type. The convenience
8751 variable, when used as an expression, has the type of its current value.
8754 @kindex show convenience
8755 @cindex show all user variables
8756 @item show convenience
8757 Print a list of convenience variables used so far, and their values.
8758 Abbreviated @code{show conv}.
8760 @kindex init-if-undefined
8761 @cindex convenience variables, initializing
8762 @item init-if-undefined $@var{variable} = @var{expression}
8763 Set a convenience variable if it has not already been set. This is useful
8764 for user-defined commands that keep some state. It is similar, in concept,
8765 to using local static variables with initializers in C (except that
8766 convenience variables are global). It can also be used to allow users to
8767 override default values used in a command script.
8769 If the variable is already defined then the expression is not evaluated so
8770 any side-effects do not occur.
8773 One of the ways to use a convenience variable is as a counter to be
8774 incremented or a pointer to be advanced. For example, to print
8775 a field from successive elements of an array of structures:
8779 print bar[$i++]->contents
8783 Repeat that command by typing @key{RET}.
8785 Some convenience variables are created automatically by @value{GDBN} and given
8786 values likely to be useful.
8789 @vindex $_@r{, convenience variable}
8791 The variable @code{$_} is automatically set by the @code{x} command to
8792 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8793 commands which provide a default address for @code{x} to examine also
8794 set @code{$_} to that address; these commands include @code{info line}
8795 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8796 except when set by the @code{x} command, in which case it is a pointer
8797 to the type of @code{$__}.
8799 @vindex $__@r{, convenience variable}
8801 The variable @code{$__} is automatically set by the @code{x} command
8802 to the value found in the last address examined. Its type is chosen
8803 to match the format in which the data was printed.
8806 @vindex $_exitcode@r{, convenience variable}
8807 The variable @code{$_exitcode} is automatically set to the exit code when
8808 the program being debugged terminates.
8811 @vindex $_sdata@r{, inspect, convenience variable}
8812 The variable @code{$_sdata} contains extra collected static tracepoint
8813 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8814 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8815 if extra static tracepoint data has not been collected.
8818 @vindex $_siginfo@r{, convenience variable}
8819 The variable @code{$_siginfo} contains extra signal information
8820 (@pxref{extra signal information}). Note that @code{$_siginfo}
8821 could be empty, if the application has not yet received any signals.
8822 For example, it will be empty before you execute the @code{run} command.
8825 @vindex $_tlb@r{, convenience variable}
8826 The variable @code{$_tlb} is automatically set when debugging
8827 applications running on MS-Windows in native mode or connected to
8828 gdbserver that supports the @code{qGetTIBAddr} request.
8829 @xref{General Query Packets}.
8830 This variable contains the address of the thread information block.
8834 On HP-UX systems, if you refer to a function or variable name that
8835 begins with a dollar sign, @value{GDBN} searches for a user or system
8836 name first, before it searches for a convenience variable.
8838 @cindex convenience functions
8839 @value{GDBN} also supplies some @dfn{convenience functions}. These
8840 have a syntax similar to convenience variables. A convenience
8841 function can be used in an expression just like an ordinary function;
8842 however, a convenience function is implemented internally to
8847 @kindex help function
8848 @cindex show all convenience functions
8849 Print a list of all convenience functions.
8856 You can refer to machine register contents, in expressions, as variables
8857 with names starting with @samp{$}. The names of registers are different
8858 for each machine; use @code{info registers} to see the names used on
8862 @kindex info registers
8863 @item info registers
8864 Print the names and values of all registers except floating-point
8865 and vector registers (in the selected stack frame).
8867 @kindex info all-registers
8868 @cindex floating point registers
8869 @item info all-registers
8870 Print the names and values of all registers, including floating-point
8871 and vector registers (in the selected stack frame).
8873 @item info registers @var{regname} @dots{}
8874 Print the @dfn{relativized} value of each specified register @var{regname}.
8875 As discussed in detail below, register values are normally relative to
8876 the selected stack frame. @var{regname} may be any register name valid on
8877 the machine you are using, with or without the initial @samp{$}.
8880 @cindex stack pointer register
8881 @cindex program counter register
8882 @cindex process status register
8883 @cindex frame pointer register
8884 @cindex standard registers
8885 @value{GDBN} has four ``standard'' register names that are available (in
8886 expressions) on most machines---whenever they do not conflict with an
8887 architecture's canonical mnemonics for registers. The register names
8888 @code{$pc} and @code{$sp} are used for the program counter register and
8889 the stack pointer. @code{$fp} is used for a register that contains a
8890 pointer to the current stack frame, and @code{$ps} is used for a
8891 register that contains the processor status. For example,
8892 you could print the program counter in hex with
8899 or print the instruction to be executed next with
8906 or add four to the stack pointer@footnote{This is a way of removing
8907 one word from the stack, on machines where stacks grow downward in
8908 memory (most machines, nowadays). This assumes that the innermost
8909 stack frame is selected; setting @code{$sp} is not allowed when other
8910 stack frames are selected. To pop entire frames off the stack,
8911 regardless of machine architecture, use @code{return};
8912 see @ref{Returning, ,Returning from a Function}.} with
8918 Whenever possible, these four standard register names are available on
8919 your machine even though the machine has different canonical mnemonics,
8920 so long as there is no conflict. The @code{info registers} command
8921 shows the canonical names. For example, on the SPARC, @code{info
8922 registers} displays the processor status register as @code{$psr} but you
8923 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8924 is an alias for the @sc{eflags} register.
8926 @value{GDBN} always considers the contents of an ordinary register as an
8927 integer when the register is examined in this way. Some machines have
8928 special registers which can hold nothing but floating point; these
8929 registers are considered to have floating point values. There is no way
8930 to refer to the contents of an ordinary register as floating point value
8931 (although you can @emph{print} it as a floating point value with
8932 @samp{print/f $@var{regname}}).
8934 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8935 means that the data format in which the register contents are saved by
8936 the operating system is not the same one that your program normally
8937 sees. For example, the registers of the 68881 floating point
8938 coprocessor are always saved in ``extended'' (raw) format, but all C
8939 programs expect to work with ``double'' (virtual) format. In such
8940 cases, @value{GDBN} normally works with the virtual format only (the format
8941 that makes sense for your program), but the @code{info registers} command
8942 prints the data in both formats.
8944 @cindex SSE registers (x86)
8945 @cindex MMX registers (x86)
8946 Some machines have special registers whose contents can be interpreted
8947 in several different ways. For example, modern x86-based machines
8948 have SSE and MMX registers that can hold several values packed
8949 together in several different formats. @value{GDBN} refers to such
8950 registers in @code{struct} notation:
8953 (@value{GDBP}) print $xmm1
8955 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8956 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8957 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8958 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8959 v4_int32 = @{0, 20657912, 11, 13@},
8960 v2_int64 = @{88725056443645952, 55834574859@},
8961 uint128 = 0x0000000d0000000b013b36f800000000
8966 To set values of such registers, you need to tell @value{GDBN} which
8967 view of the register you wish to change, as if you were assigning
8968 value to a @code{struct} member:
8971 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8974 Normally, register values are relative to the selected stack frame
8975 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8976 value that the register would contain if all stack frames farther in
8977 were exited and their saved registers restored. In order to see the
8978 true contents of hardware registers, you must select the innermost
8979 frame (with @samp{frame 0}).
8981 However, @value{GDBN} must deduce where registers are saved, from the machine
8982 code generated by your compiler. If some registers are not saved, or if
8983 @value{GDBN} is unable to locate the saved registers, the selected stack
8984 frame makes no difference.
8986 @node Floating Point Hardware
8987 @section Floating Point Hardware
8988 @cindex floating point
8990 Depending on the configuration, @value{GDBN} may be able to give
8991 you more information about the status of the floating point hardware.
8996 Display hardware-dependent information about the floating
8997 point unit. The exact contents and layout vary depending on the
8998 floating point chip. Currently, @samp{info float} is supported on
8999 the ARM and x86 machines.
9003 @section Vector Unit
9006 Depending on the configuration, @value{GDBN} may be able to give you
9007 more information about the status of the vector unit.
9012 Display information about the vector unit. The exact contents and
9013 layout vary depending on the hardware.
9016 @node OS Information
9017 @section Operating System Auxiliary Information
9018 @cindex OS information
9020 @value{GDBN} provides interfaces to useful OS facilities that can help
9021 you debug your program.
9023 @cindex @code{ptrace} system call
9024 @cindex @code{struct user} contents
9025 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9026 machines), it interfaces with the inferior via the @code{ptrace}
9027 system call. The operating system creates a special sata structure,
9028 called @code{struct user}, for this interface. You can use the
9029 command @code{info udot} to display the contents of this data
9035 Display the contents of the @code{struct user} maintained by the OS
9036 kernel for the program being debugged. @value{GDBN} displays the
9037 contents of @code{struct user} as a list of hex numbers, similar to
9038 the @code{examine} command.
9041 @cindex auxiliary vector
9042 @cindex vector, auxiliary
9043 Some operating systems supply an @dfn{auxiliary vector} to programs at
9044 startup. This is akin to the arguments and environment that you
9045 specify for a program, but contains a system-dependent variety of
9046 binary values that tell system libraries important details about the
9047 hardware, operating system, and process. Each value's purpose is
9048 identified by an integer tag; the meanings are well-known but system-specific.
9049 Depending on the configuration and operating system facilities,
9050 @value{GDBN} may be able to show you this information. For remote
9051 targets, this functionality may further depend on the remote stub's
9052 support of the @samp{qXfer:auxv:read} packet, see
9053 @ref{qXfer auxiliary vector read}.
9058 Display the auxiliary vector of the inferior, which can be either a
9059 live process or a core dump file. @value{GDBN} prints each tag value
9060 numerically, and also shows names and text descriptions for recognized
9061 tags. Some values in the vector are numbers, some bit masks, and some
9062 pointers to strings or other data. @value{GDBN} displays each value in the
9063 most appropriate form for a recognized tag, and in hexadecimal for
9064 an unrecognized tag.
9067 On some targets, @value{GDBN} can access operating-system-specific information
9068 and display it to user, without interpretation. For remote targets,
9069 this functionality depends on the remote stub's support of the
9070 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9075 List the types of OS information available for the target. If the
9076 target does not return a list of possible types, this command will
9079 @kindex info os processes
9080 @item info os processes
9081 Display the list of processes on the target. For each process,
9082 @value{GDBN} prints the process identifier, the name of the user, and
9083 the command corresponding to the process.
9086 @node Memory Region Attributes
9087 @section Memory Region Attributes
9088 @cindex memory region attributes
9090 @dfn{Memory region attributes} allow you to describe special handling
9091 required by regions of your target's memory. @value{GDBN} uses
9092 attributes to determine whether to allow certain types of memory
9093 accesses; whether to use specific width accesses; and whether to cache
9094 target memory. By default the description of memory regions is
9095 fetched from the target (if the current target supports this), but the
9096 user can override the fetched regions.
9098 Defined memory regions can be individually enabled and disabled. When a
9099 memory region is disabled, @value{GDBN} uses the default attributes when
9100 accessing memory in that region. Similarly, if no memory regions have
9101 been defined, @value{GDBN} uses the default attributes when accessing
9104 When a memory region is defined, it is given a number to identify it;
9105 to enable, disable, or remove a memory region, you specify that number.
9109 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9110 Define a memory region bounded by @var{lower} and @var{upper} with
9111 attributes @var{attributes}@dots{}, and add it to the list of regions
9112 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9113 case: it is treated as the target's maximum memory address.
9114 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9117 Discard any user changes to the memory regions and use target-supplied
9118 regions, if available, or no regions if the target does not support.
9121 @item delete mem @var{nums}@dots{}
9122 Remove memory regions @var{nums}@dots{} from the list of regions
9123 monitored by @value{GDBN}.
9126 @item disable mem @var{nums}@dots{}
9127 Disable monitoring of memory regions @var{nums}@dots{}.
9128 A disabled memory region is not forgotten.
9129 It may be enabled again later.
9132 @item enable mem @var{nums}@dots{}
9133 Enable monitoring of memory regions @var{nums}@dots{}.
9137 Print a table of all defined memory regions, with the following columns
9141 @item Memory Region Number
9142 @item Enabled or Disabled.
9143 Enabled memory regions are marked with @samp{y}.
9144 Disabled memory regions are marked with @samp{n}.
9147 The address defining the inclusive lower bound of the memory region.
9150 The address defining the exclusive upper bound of the memory region.
9153 The list of attributes set for this memory region.
9158 @subsection Attributes
9160 @subsubsection Memory Access Mode
9161 The access mode attributes set whether @value{GDBN} may make read or
9162 write accesses to a memory region.
9164 While these attributes prevent @value{GDBN} from performing invalid
9165 memory accesses, they do nothing to prevent the target system, I/O DMA,
9166 etc.@: from accessing memory.
9170 Memory is read only.
9172 Memory is write only.
9174 Memory is read/write. This is the default.
9177 @subsubsection Memory Access Size
9178 The access size attribute tells @value{GDBN} to use specific sized
9179 accesses in the memory region. Often memory mapped device registers
9180 require specific sized accesses. If no access size attribute is
9181 specified, @value{GDBN} may use accesses of any size.
9185 Use 8 bit memory accesses.
9187 Use 16 bit memory accesses.
9189 Use 32 bit memory accesses.
9191 Use 64 bit memory accesses.
9194 @c @subsubsection Hardware/Software Breakpoints
9195 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9196 @c will use hardware or software breakpoints for the internal breakpoints
9197 @c used by the step, next, finish, until, etc. commands.
9201 @c Always use hardware breakpoints
9202 @c @item swbreak (default)
9205 @subsubsection Data Cache
9206 The data cache attributes set whether @value{GDBN} will cache target
9207 memory. While this generally improves performance by reducing debug
9208 protocol overhead, it can lead to incorrect results because @value{GDBN}
9209 does not know about volatile variables or memory mapped device
9214 Enable @value{GDBN} to cache target memory.
9216 Disable @value{GDBN} from caching target memory. This is the default.
9219 @subsection Memory Access Checking
9220 @value{GDBN} can be instructed to refuse accesses to memory that is
9221 not explicitly described. This can be useful if accessing such
9222 regions has undesired effects for a specific target, or to provide
9223 better error checking. The following commands control this behaviour.
9226 @kindex set mem inaccessible-by-default
9227 @item set mem inaccessible-by-default [on|off]
9228 If @code{on} is specified, make @value{GDBN} treat memory not
9229 explicitly described by the memory ranges as non-existent and refuse accesses
9230 to such memory. The checks are only performed if there's at least one
9231 memory range defined. If @code{off} is specified, make @value{GDBN}
9232 treat the memory not explicitly described by the memory ranges as RAM.
9233 The default value is @code{on}.
9234 @kindex show mem inaccessible-by-default
9235 @item show mem inaccessible-by-default
9236 Show the current handling of accesses to unknown memory.
9240 @c @subsubsection Memory Write Verification
9241 @c The memory write verification attributes set whether @value{GDBN}
9242 @c will re-reads data after each write to verify the write was successful.
9246 @c @item noverify (default)
9249 @node Dump/Restore Files
9250 @section Copy Between Memory and a File
9251 @cindex dump/restore files
9252 @cindex append data to a file
9253 @cindex dump data to a file
9254 @cindex restore data from a file
9256 You can use the commands @code{dump}, @code{append}, and
9257 @code{restore} to copy data between target memory and a file. The
9258 @code{dump} and @code{append} commands write data to a file, and the
9259 @code{restore} command reads data from a file back into the inferior's
9260 memory. Files may be in binary, Motorola S-record, Intel hex, or
9261 Tektronix Hex format; however, @value{GDBN} can only append to binary
9267 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9268 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9269 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9270 or the value of @var{expr}, to @var{filename} in the given format.
9272 The @var{format} parameter may be any one of:
9279 Motorola S-record format.
9281 Tektronix Hex format.
9284 @value{GDBN} uses the same definitions of these formats as the
9285 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9286 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9290 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9291 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9292 Append the contents of memory from @var{start_addr} to @var{end_addr},
9293 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9294 (@value{GDBN} can only append data to files in raw binary form.)
9297 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9298 Restore the contents of file @var{filename} into memory. The
9299 @code{restore} command can automatically recognize any known @sc{bfd}
9300 file format, except for raw binary. To restore a raw binary file you
9301 must specify the optional keyword @code{binary} after the filename.
9303 If @var{bias} is non-zero, its value will be added to the addresses
9304 contained in the file. Binary files always start at address zero, so
9305 they will be restored at address @var{bias}. Other bfd files have
9306 a built-in location; they will be restored at offset @var{bias}
9309 If @var{start} and/or @var{end} are non-zero, then only data between
9310 file offset @var{start} and file offset @var{end} will be restored.
9311 These offsets are relative to the addresses in the file, before
9312 the @var{bias} argument is applied.
9316 @node Core File Generation
9317 @section How to Produce a Core File from Your Program
9318 @cindex dump core from inferior
9320 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9321 image of a running process and its process status (register values
9322 etc.). Its primary use is post-mortem debugging of a program that
9323 crashed while it ran outside a debugger. A program that crashes
9324 automatically produces a core file, unless this feature is disabled by
9325 the user. @xref{Files}, for information on invoking @value{GDBN} in
9326 the post-mortem debugging mode.
9328 Occasionally, you may wish to produce a core file of the program you
9329 are debugging in order to preserve a snapshot of its state.
9330 @value{GDBN} has a special command for that.
9334 @kindex generate-core-file
9335 @item generate-core-file [@var{file}]
9336 @itemx gcore [@var{file}]
9337 Produce a core dump of the inferior process. The optional argument
9338 @var{file} specifies the file name where to put the core dump. If not
9339 specified, the file name defaults to @file{core.@var{pid}}, where
9340 @var{pid} is the inferior process ID.
9342 Note that this command is implemented only for some systems (as of
9343 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9346 @node Character Sets
9347 @section Character Sets
9348 @cindex character sets
9350 @cindex translating between character sets
9351 @cindex host character set
9352 @cindex target character set
9354 If the program you are debugging uses a different character set to
9355 represent characters and strings than the one @value{GDBN} uses itself,
9356 @value{GDBN} can automatically translate between the character sets for
9357 you. The character set @value{GDBN} uses we call the @dfn{host
9358 character set}; the one the inferior program uses we call the
9359 @dfn{target character set}.
9361 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9362 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9363 remote protocol (@pxref{Remote Debugging}) to debug a program
9364 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9365 then the host character set is Latin-1, and the target character set is
9366 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9367 target-charset EBCDIC-US}, then @value{GDBN} translates between
9368 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9369 character and string literals in expressions.
9371 @value{GDBN} has no way to automatically recognize which character set
9372 the inferior program uses; you must tell it, using the @code{set
9373 target-charset} command, described below.
9375 Here are the commands for controlling @value{GDBN}'s character set
9379 @item set target-charset @var{charset}
9380 @kindex set target-charset
9381 Set the current target character set to @var{charset}. To display the
9382 list of supported target character sets, type
9383 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9385 @item set host-charset @var{charset}
9386 @kindex set host-charset
9387 Set the current host character set to @var{charset}.
9389 By default, @value{GDBN} uses a host character set appropriate to the
9390 system it is running on; you can override that default using the
9391 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9392 automatically determine the appropriate host character set. In this
9393 case, @value{GDBN} uses @samp{UTF-8}.
9395 @value{GDBN} can only use certain character sets as its host character
9396 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9397 @value{GDBN} will list the host character sets it supports.
9399 @item set charset @var{charset}
9401 Set the current host and target character sets to @var{charset}. As
9402 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9403 @value{GDBN} will list the names of the character sets that can be used
9404 for both host and target.
9407 @kindex show charset
9408 Show the names of the current host and target character sets.
9410 @item show host-charset
9411 @kindex show host-charset
9412 Show the name of the current host character set.
9414 @item show target-charset
9415 @kindex show target-charset
9416 Show the name of the current target character set.
9418 @item set target-wide-charset @var{charset}
9419 @kindex set target-wide-charset
9420 Set the current target's wide character set to @var{charset}. This is
9421 the character set used by the target's @code{wchar_t} type. To
9422 display the list of supported wide character sets, type
9423 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9425 @item show target-wide-charset
9426 @kindex show target-wide-charset
9427 Show the name of the current target's wide character set.
9430 Here is an example of @value{GDBN}'s character set support in action.
9431 Assume that the following source code has been placed in the file
9432 @file{charset-test.c}:
9438 = @{72, 101, 108, 108, 111, 44, 32, 119,
9439 111, 114, 108, 100, 33, 10, 0@};
9440 char ibm1047_hello[]
9441 = @{200, 133, 147, 147, 150, 107, 64, 166,
9442 150, 153, 147, 132, 90, 37, 0@};
9446 printf ("Hello, world!\n");
9450 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9451 containing the string @samp{Hello, world!} followed by a newline,
9452 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9454 We compile the program, and invoke the debugger on it:
9457 $ gcc -g charset-test.c -o charset-test
9458 $ gdb -nw charset-test
9459 GNU gdb 2001-12-19-cvs
9460 Copyright 2001 Free Software Foundation, Inc.
9465 We can use the @code{show charset} command to see what character sets
9466 @value{GDBN} is currently using to interpret and display characters and
9470 (@value{GDBP}) show charset
9471 The current host and target character set is `ISO-8859-1'.
9475 For the sake of printing this manual, let's use @sc{ascii} as our
9476 initial character set:
9478 (@value{GDBP}) set charset ASCII
9479 (@value{GDBP}) show charset
9480 The current host and target character set is `ASCII'.
9484 Let's assume that @sc{ascii} is indeed the correct character set for our
9485 host system --- in other words, let's assume that if @value{GDBN} prints
9486 characters using the @sc{ascii} character set, our terminal will display
9487 them properly. Since our current target character set is also
9488 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9491 (@value{GDBP}) print ascii_hello
9492 $1 = 0x401698 "Hello, world!\n"
9493 (@value{GDBP}) print ascii_hello[0]
9498 @value{GDBN} uses the target character set for character and string
9499 literals you use in expressions:
9502 (@value{GDBP}) print '+'
9507 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9510 @value{GDBN} relies on the user to tell it which character set the
9511 target program uses. If we print @code{ibm1047_hello} while our target
9512 character set is still @sc{ascii}, we get jibberish:
9515 (@value{GDBP}) print ibm1047_hello
9516 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9517 (@value{GDBP}) print ibm1047_hello[0]
9522 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9523 @value{GDBN} tells us the character sets it supports:
9526 (@value{GDBP}) set target-charset
9527 ASCII EBCDIC-US IBM1047 ISO-8859-1
9528 (@value{GDBP}) set target-charset
9531 We can select @sc{ibm1047} as our target character set, and examine the
9532 program's strings again. Now the @sc{ascii} string is wrong, but
9533 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9534 target character set, @sc{ibm1047}, to the host character set,
9535 @sc{ascii}, and they display correctly:
9538 (@value{GDBP}) set target-charset IBM1047
9539 (@value{GDBP}) show charset
9540 The current host character set is `ASCII'.
9541 The current target character set is `IBM1047'.
9542 (@value{GDBP}) print ascii_hello
9543 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9544 (@value{GDBP}) print ascii_hello[0]
9546 (@value{GDBP}) print ibm1047_hello
9547 $8 = 0x4016a8 "Hello, world!\n"
9548 (@value{GDBP}) print ibm1047_hello[0]
9553 As above, @value{GDBN} uses the target character set for character and
9554 string literals you use in expressions:
9557 (@value{GDBP}) print '+'
9562 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9565 @node Caching Remote Data
9566 @section Caching Data of Remote Targets
9567 @cindex caching data of remote targets
9569 @value{GDBN} caches data exchanged between the debugger and a
9570 remote target (@pxref{Remote Debugging}). Such caching generally improves
9571 performance, because it reduces the overhead of the remote protocol by
9572 bundling memory reads and writes into large chunks. Unfortunately, simply
9573 caching everything would lead to incorrect results, since @value{GDBN}
9574 does not necessarily know anything about volatile values, memory-mapped I/O
9575 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9576 memory can be changed @emph{while} a gdb command is executing.
9577 Therefore, by default, @value{GDBN} only caches data
9578 known to be on the stack@footnote{In non-stop mode, it is moderately
9579 rare for a running thread to modify the stack of a stopped thread
9580 in a way that would interfere with a backtrace, and caching of
9581 stack reads provides a significant speed up of remote backtraces.}.
9582 Other regions of memory can be explicitly marked as
9583 cacheable; see @pxref{Memory Region Attributes}.
9586 @kindex set remotecache
9587 @item set remotecache on
9588 @itemx set remotecache off
9589 This option no longer does anything; it exists for compatibility
9592 @kindex show remotecache
9593 @item show remotecache
9594 Show the current state of the obsolete remotecache flag.
9596 @kindex set stack-cache
9597 @item set stack-cache on
9598 @itemx set stack-cache off
9599 Enable or disable caching of stack accesses. When @code{ON}, use
9600 caching. By default, this option is @code{ON}.
9602 @kindex show stack-cache
9603 @item show stack-cache
9604 Show the current state of data caching for memory accesses.
9607 @item info dcache @r{[}line@r{]}
9608 Print the information about the data cache performance. The
9609 information displayed includes the dcache width and depth, and for
9610 each cache line, its number, address, and how many times it was
9611 referenced. This command is useful for debugging the data cache
9614 If a line number is specified, the contents of that line will be
9617 @item set dcache size @var{size}
9619 @kindex set dcache size
9620 Set maximum number of entries in dcache (dcache depth above).
9622 @item set dcache line-size @var{line-size}
9623 @cindex dcache line-size
9624 @kindex set dcache line-size
9625 Set number of bytes each dcache entry caches (dcache width above).
9626 Must be a power of 2.
9628 @item show dcache size
9629 @kindex show dcache size
9630 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9632 @item show dcache line-size
9633 @kindex show dcache line-size
9634 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9638 @node Searching Memory
9639 @section Search Memory
9640 @cindex searching memory
9642 Memory can be searched for a particular sequence of bytes with the
9643 @code{find} command.
9647 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9648 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9649 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9650 etc. The search begins at address @var{start_addr} and continues for either
9651 @var{len} bytes or through to @var{end_addr} inclusive.
9654 @var{s} and @var{n} are optional parameters.
9655 They may be specified in either order, apart or together.
9658 @item @var{s}, search query size
9659 The size of each search query value.
9665 halfwords (two bytes)
9669 giant words (eight bytes)
9672 All values are interpreted in the current language.
9673 This means, for example, that if the current source language is C/C@t{++}
9674 then searching for the string ``hello'' includes the trailing '\0'.
9676 If the value size is not specified, it is taken from the
9677 value's type in the current language.
9678 This is useful when one wants to specify the search
9679 pattern as a mixture of types.
9680 Note that this means, for example, that in the case of C-like languages
9681 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9682 which is typically four bytes.
9684 @item @var{n}, maximum number of finds
9685 The maximum number of matches to print. The default is to print all finds.
9688 You can use strings as search values. Quote them with double-quotes
9690 The string value is copied into the search pattern byte by byte,
9691 regardless of the endianness of the target and the size specification.
9693 The address of each match found is printed as well as a count of the
9694 number of matches found.
9696 The address of the last value found is stored in convenience variable
9698 A count of the number of matches is stored in @samp{$numfound}.
9700 For example, if stopped at the @code{printf} in this function:
9706 static char hello[] = "hello-hello";
9707 static struct @{ char c; short s; int i; @}
9708 __attribute__ ((packed)) mixed
9709 = @{ 'c', 0x1234, 0x87654321 @};
9710 printf ("%s\n", hello);
9715 you get during debugging:
9718 (gdb) find &hello[0], +sizeof(hello), "hello"
9719 0x804956d <hello.1620+6>
9721 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9722 0x8049567 <hello.1620>
9723 0x804956d <hello.1620+6>
9725 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9726 0x8049567 <hello.1620>
9728 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9729 0x8049560 <mixed.1625>
9731 (gdb) print $numfound
9734 $2 = (void *) 0x8049560
9737 @node Optimized Code
9738 @chapter Debugging Optimized Code
9739 @cindex optimized code, debugging
9740 @cindex debugging optimized code
9742 Almost all compilers support optimization. With optimization
9743 disabled, the compiler generates assembly code that corresponds
9744 directly to your source code, in a simplistic way. As the compiler
9745 applies more powerful optimizations, the generated assembly code
9746 diverges from your original source code. With help from debugging
9747 information generated by the compiler, @value{GDBN} can map from
9748 the running program back to constructs from your original source.
9750 @value{GDBN} is more accurate with optimization disabled. If you
9751 can recompile without optimization, it is easier to follow the
9752 progress of your program during debugging. But, there are many cases
9753 where you may need to debug an optimized version.
9755 When you debug a program compiled with @samp{-g -O}, remember that the
9756 optimizer has rearranged your code; the debugger shows you what is
9757 really there. Do not be too surprised when the execution path does not
9758 exactly match your source file! An extreme example: if you define a
9759 variable, but never use it, @value{GDBN} never sees that
9760 variable---because the compiler optimizes it out of existence.
9762 Some things do not work as well with @samp{-g -O} as with just
9763 @samp{-g}, particularly on machines with instruction scheduling. If in
9764 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9765 please report it to us as a bug (including a test case!).
9766 @xref{Variables}, for more information about debugging optimized code.
9769 * Inline Functions:: How @value{GDBN} presents inlining
9770 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9773 @node Inline Functions
9774 @section Inline Functions
9775 @cindex inline functions, debugging
9777 @dfn{Inlining} is an optimization that inserts a copy of the function
9778 body directly at each call site, instead of jumping to a shared
9779 routine. @value{GDBN} displays inlined functions just like
9780 non-inlined functions. They appear in backtraces. You can view their
9781 arguments and local variables, step into them with @code{step}, skip
9782 them with @code{next}, and escape from them with @code{finish}.
9783 You can check whether a function was inlined by using the
9784 @code{info frame} command.
9786 For @value{GDBN} to support inlined functions, the compiler must
9787 record information about inlining in the debug information ---
9788 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9789 other compilers do also. @value{GDBN} only supports inlined functions
9790 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9791 do not emit two required attributes (@samp{DW_AT_call_file} and
9792 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9793 function calls with earlier versions of @value{NGCC}. It instead
9794 displays the arguments and local variables of inlined functions as
9795 local variables in the caller.
9797 The body of an inlined function is directly included at its call site;
9798 unlike a non-inlined function, there are no instructions devoted to
9799 the call. @value{GDBN} still pretends that the call site and the
9800 start of the inlined function are different instructions. Stepping to
9801 the call site shows the call site, and then stepping again shows
9802 the first line of the inlined function, even though no additional
9803 instructions are executed.
9805 This makes source-level debugging much clearer; you can see both the
9806 context of the call and then the effect of the call. Only stepping by
9807 a single instruction using @code{stepi} or @code{nexti} does not do
9808 this; single instruction steps always show the inlined body.
9810 There are some ways that @value{GDBN} does not pretend that inlined
9811 function calls are the same as normal calls:
9815 You cannot set breakpoints on inlined functions. @value{GDBN}
9816 either reports that there is no symbol with that name, or else sets the
9817 breakpoint only on non-inlined copies of the function. This limitation
9818 will be removed in a future version of @value{GDBN}; until then,
9819 set a breakpoint by line number on the first line of the inlined
9823 Setting breakpoints at the call site of an inlined function may not
9824 work, because the call site does not contain any code. @value{GDBN}
9825 may incorrectly move the breakpoint to the next line of the enclosing
9826 function, after the call. This limitation will be removed in a future
9827 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9828 or inside the inlined function instead.
9831 @value{GDBN} cannot locate the return value of inlined calls after
9832 using the @code{finish} command. This is a limitation of compiler-generated
9833 debugging information; after @code{finish}, you can step to the next line
9834 and print a variable where your program stored the return value.
9838 @node Tail Call Frames
9839 @section Tail Call Frames
9840 @cindex tail call frames, debugging
9842 Function @code{B} can call function @code{C} in its very last statement. In
9843 unoptimized compilation the call of @code{C} is immediately followed by return
9844 instruction at the end of @code{B} code. Optimizing compiler may replace the
9845 call and return in function @code{B} into one jump to function @code{C}
9846 instead. Such use of a jump instruction is called @dfn{tail call}.
9848 During execution of function @code{C}, there will be no indication in the
9849 function call stack frames that it was tail-called from @code{B}. If function
9850 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9851 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9852 some cases @value{GDBN} can determine that @code{C} was tail-called from
9853 @code{B}, and it will then create fictitious call frame for that, with the
9854 return address set up as if @code{B} called @code{C} normally.
9856 This functionality is currently supported only by DWARF 2 debugging format and
9857 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9858 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9861 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9862 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9866 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9868 Stack level 1, frame at 0x7fffffffda30:
9869 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9870 tail call frame, caller of frame at 0x7fffffffda30
9871 source language c++.
9872 Arglist at unknown address.
9873 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9876 The detection of all the possible code path executions can find them ambiguous.
9877 There is no execution history stored (possible @ref{Reverse Execution} is never
9878 used for this purpose) and the last known caller could have reached the known
9879 callee by multiple different jump sequences. In such case @value{GDBN} still
9880 tries to show at least all the unambiguous top tail callers and all the
9881 unambiguous bottom tail calees, if any.
9884 @anchor{set debug entry-values}
9885 @item set debug entry-values
9886 @kindex set debug entry-values
9887 When set to on, enables printing of analysis messages for both frame argument
9888 values at function entry and tail calls. It will show all the possible valid
9889 tail calls code paths it has considered. It will also print the intersection
9890 of them with the final unambiguous (possibly partial or even empty) code path
9893 @item show debug entry-values
9894 @kindex show debug entry-values
9895 Show the current state of analysis messages printing for both frame argument
9896 values at function entry and tail calls.
9899 The analysis messages for tail calls can for example show why the virtual tail
9900 call frame for function @code{c} has not been recognized (due to the indirect
9901 reference by variable @code{x}):
9904 static void __attribute__((noinline, noclone)) c (void);
9905 void (*x) (void) = c;
9906 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9907 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9908 int main (void) @{ x (); return 0; @}
9910 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9911 DW_TAG_GNU_call_site 0x40039a in main
9913 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9916 #1 0x000000000040039a in main () at t.c:5
9919 Another possibility is an ambiguous virtual tail call frames resolution:
9923 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9924 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9925 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9926 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9927 static void __attribute__((noinline, noclone)) b (void)
9928 @{ if (i) c (); else e (); @}
9929 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9930 int main (void) @{ a (); return 0; @}
9932 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9933 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9934 tailcall: reduced: 0x4004d2(a) |
9937 #1 0x00000000004004d2 in a () at t.c:8
9938 #2 0x0000000000400395 in main () at t.c:9
9941 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9942 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9944 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9945 @ifset HAVE_MAKEINFO_CLICK
9947 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9948 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9950 @ifclear HAVE_MAKEINFO_CLICK
9952 @set CALLSEQ1B @value{CALLSEQ1A}
9953 @set CALLSEQ2B @value{CALLSEQ2A}
9956 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9957 The code can have possible execution paths @value{CALLSEQ1B} or
9958 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9960 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9961 has found. It then finds another possible calling sequcen - that one is
9962 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9963 printed as the @code{reduced:} calling sequence. That one could have many
9964 futher @code{compare:} and @code{reduced:} statements as long as there remain
9965 any non-ambiguous sequence entries.
9967 For the frame of function @code{b} in both cases there are different possible
9968 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9969 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9970 therefore this one is displayed to the user while the ambiguous frames are
9973 There can be also reasons why printing of frame argument values at function
9978 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9979 static void __attribute__((noinline, noclone)) a (int i);
9980 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9981 static void __attribute__((noinline, noclone)) a (int i)
9982 @{ if (i) b (i - 1); else c (0); @}
9983 int main (void) @{ a (5); return 0; @}
9986 #0 c (i=i@@entry=0) at t.c:2
9987 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9988 function "a" at 0x400420 can call itself via tail calls
9989 i=<optimized out>) at t.c:6
9990 #2 0x000000000040036e in main () at t.c:7
9993 @value{GDBN} cannot find out from the inferior state if and how many times did
9994 function @code{a} call itself (via function @code{b}) as these calls would be
9995 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9996 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9997 prints @code{<optimized out>} instead.
10000 @chapter C Preprocessor Macros
10002 Some languages, such as C and C@t{++}, provide a way to define and invoke
10003 ``preprocessor macros'' which expand into strings of tokens.
10004 @value{GDBN} can evaluate expressions containing macro invocations, show
10005 the result of macro expansion, and show a macro's definition, including
10006 where it was defined.
10008 You may need to compile your program specially to provide @value{GDBN}
10009 with information about preprocessor macros. Most compilers do not
10010 include macros in their debugging information, even when you compile
10011 with the @option{-g} flag. @xref{Compilation}.
10013 A program may define a macro at one point, remove that definition later,
10014 and then provide a different definition after that. Thus, at different
10015 points in the program, a macro may have different definitions, or have
10016 no definition at all. If there is a current stack frame, @value{GDBN}
10017 uses the macros in scope at that frame's source code line. Otherwise,
10018 @value{GDBN} uses the macros in scope at the current listing location;
10021 Whenever @value{GDBN} evaluates an expression, it always expands any
10022 macro invocations present in the expression. @value{GDBN} also provides
10023 the following commands for working with macros explicitly.
10027 @kindex macro expand
10028 @cindex macro expansion, showing the results of preprocessor
10029 @cindex preprocessor macro expansion, showing the results of
10030 @cindex expanding preprocessor macros
10031 @item macro expand @var{expression}
10032 @itemx macro exp @var{expression}
10033 Show the results of expanding all preprocessor macro invocations in
10034 @var{expression}. Since @value{GDBN} simply expands macros, but does
10035 not parse the result, @var{expression} need not be a valid expression;
10036 it can be any string of tokens.
10039 @item macro expand-once @var{expression}
10040 @itemx macro exp1 @var{expression}
10041 @cindex expand macro once
10042 @i{(This command is not yet implemented.)} Show the results of
10043 expanding those preprocessor macro invocations that appear explicitly in
10044 @var{expression}. Macro invocations appearing in that expansion are
10045 left unchanged. This command allows you to see the effect of a
10046 particular macro more clearly, without being confused by further
10047 expansions. Since @value{GDBN} simply expands macros, but does not
10048 parse the result, @var{expression} need not be a valid expression; it
10049 can be any string of tokens.
10052 @cindex macro definition, showing
10053 @cindex definition of a macro, showing
10054 @cindex macros, from debug info
10055 @item info macro [-a|-all] [--] @var{macro}
10056 Show the current definition or all definitions of the named @var{macro},
10057 and describe the source location or compiler command-line where that
10058 definition was established. The optional double dash is to signify the end of
10059 argument processing and the beginning of @var{macro} for non C-like macros where
10060 the macro may begin with a hyphen.
10062 @kindex info macros
10063 @item info macros @var{linespec}
10064 Show all macro definitions that are in effect at the location specified
10065 by @var{linespec}, and describe the source location or compiler
10066 command-line where those definitions were established.
10068 @kindex macro define
10069 @cindex user-defined macros
10070 @cindex defining macros interactively
10071 @cindex macros, user-defined
10072 @item macro define @var{macro} @var{replacement-list}
10073 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10074 Introduce a definition for a preprocessor macro named @var{macro},
10075 invocations of which are replaced by the tokens given in
10076 @var{replacement-list}. The first form of this command defines an
10077 ``object-like'' macro, which takes no arguments; the second form
10078 defines a ``function-like'' macro, which takes the arguments given in
10081 A definition introduced by this command is in scope in every
10082 expression evaluated in @value{GDBN}, until it is removed with the
10083 @code{macro undef} command, described below. The definition overrides
10084 all definitions for @var{macro} present in the program being debugged,
10085 as well as any previous user-supplied definition.
10087 @kindex macro undef
10088 @item macro undef @var{macro}
10089 Remove any user-supplied definition for the macro named @var{macro}.
10090 This command only affects definitions provided with the @code{macro
10091 define} command, described above; it cannot remove definitions present
10092 in the program being debugged.
10096 List all the macros defined using the @code{macro define} command.
10099 @cindex macros, example of debugging with
10100 Here is a transcript showing the above commands in action. First, we
10101 show our source files:
10106 #include "sample.h"
10109 #define ADD(x) (M + x)
10114 printf ("Hello, world!\n");
10116 printf ("We're so creative.\n");
10118 printf ("Goodbye, world!\n");
10125 Now, we compile the program using the @sc{gnu} C compiler,
10126 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10127 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10128 and @option{-gdwarf-4}; we recommend always choosing the most recent
10129 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10130 includes information about preprocessor macros in the debugging
10134 $ gcc -gdwarf-2 -g3 sample.c -o sample
10138 Now, we start @value{GDBN} on our sample program:
10142 GNU gdb 2002-05-06-cvs
10143 Copyright 2002 Free Software Foundation, Inc.
10144 GDB is free software, @dots{}
10148 We can expand macros and examine their definitions, even when the
10149 program is not running. @value{GDBN} uses the current listing position
10150 to decide which macro definitions are in scope:
10153 (@value{GDBP}) list main
10156 5 #define ADD(x) (M + x)
10161 10 printf ("Hello, world!\n");
10163 12 printf ("We're so creative.\n");
10164 (@value{GDBP}) info macro ADD
10165 Defined at /home/jimb/gdb/macros/play/sample.c:5
10166 #define ADD(x) (M + x)
10167 (@value{GDBP}) info macro Q
10168 Defined at /home/jimb/gdb/macros/play/sample.h:1
10169 included at /home/jimb/gdb/macros/play/sample.c:2
10171 (@value{GDBP}) macro expand ADD(1)
10172 expands to: (42 + 1)
10173 (@value{GDBP}) macro expand-once ADD(1)
10174 expands to: once (M + 1)
10178 In the example above, note that @code{macro expand-once} expands only
10179 the macro invocation explicit in the original text --- the invocation of
10180 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10181 which was introduced by @code{ADD}.
10183 Once the program is running, @value{GDBN} uses the macro definitions in
10184 force at the source line of the current stack frame:
10187 (@value{GDBP}) break main
10188 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10190 Starting program: /home/jimb/gdb/macros/play/sample
10192 Breakpoint 1, main () at sample.c:10
10193 10 printf ("Hello, world!\n");
10197 At line 10, the definition of the macro @code{N} at line 9 is in force:
10200 (@value{GDBP}) info macro N
10201 Defined at /home/jimb/gdb/macros/play/sample.c:9
10203 (@value{GDBP}) macro expand N Q M
10204 expands to: 28 < 42
10205 (@value{GDBP}) print N Q M
10210 As we step over directives that remove @code{N}'s definition, and then
10211 give it a new definition, @value{GDBN} finds the definition (or lack
10212 thereof) in force at each point:
10215 (@value{GDBP}) next
10217 12 printf ("We're so creative.\n");
10218 (@value{GDBP}) info macro N
10219 The symbol `N' has no definition as a C/C++ preprocessor macro
10220 at /home/jimb/gdb/macros/play/sample.c:12
10221 (@value{GDBP}) next
10223 14 printf ("Goodbye, world!\n");
10224 (@value{GDBP}) info macro N
10225 Defined at /home/jimb/gdb/macros/play/sample.c:13
10227 (@value{GDBP}) macro expand N Q M
10228 expands to: 1729 < 42
10229 (@value{GDBP}) print N Q M
10234 In addition to source files, macros can be defined on the compilation command
10235 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10236 such a way, @value{GDBN} displays the location of their definition as line zero
10237 of the source file submitted to the compiler.
10240 (@value{GDBP}) info macro __STDC__
10241 Defined at /home/jimb/gdb/macros/play/sample.c:0
10248 @chapter Tracepoints
10249 @c This chapter is based on the documentation written by Michael
10250 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10252 @cindex tracepoints
10253 In some applications, it is not feasible for the debugger to interrupt
10254 the program's execution long enough for the developer to learn
10255 anything helpful about its behavior. If the program's correctness
10256 depends on its real-time behavior, delays introduced by a debugger
10257 might cause the program to change its behavior drastically, or perhaps
10258 fail, even when the code itself is correct. It is useful to be able
10259 to observe the program's behavior without interrupting it.
10261 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10262 specify locations in the program, called @dfn{tracepoints}, and
10263 arbitrary expressions to evaluate when those tracepoints are reached.
10264 Later, using the @code{tfind} command, you can examine the values
10265 those expressions had when the program hit the tracepoints. The
10266 expressions may also denote objects in memory---structures or arrays,
10267 for example---whose values @value{GDBN} should record; while visiting
10268 a particular tracepoint, you may inspect those objects as if they were
10269 in memory at that moment. However, because @value{GDBN} records these
10270 values without interacting with you, it can do so quickly and
10271 unobtrusively, hopefully not disturbing the program's behavior.
10273 The tracepoint facility is currently available only for remote
10274 targets. @xref{Targets}. In addition, your remote target must know
10275 how to collect trace data. This functionality is implemented in the
10276 remote stub; however, none of the stubs distributed with @value{GDBN}
10277 support tracepoints as of this writing. The format of the remote
10278 packets used to implement tracepoints are described in @ref{Tracepoint
10281 It is also possible to get trace data from a file, in a manner reminiscent
10282 of corefiles; you specify the filename, and use @code{tfind} to search
10283 through the file. @xref{Trace Files}, for more details.
10285 This chapter describes the tracepoint commands and features.
10288 * Set Tracepoints::
10289 * Analyze Collected Data::
10290 * Tracepoint Variables::
10294 @node Set Tracepoints
10295 @section Commands to Set Tracepoints
10297 Before running such a @dfn{trace experiment}, an arbitrary number of
10298 tracepoints can be set. A tracepoint is actually a special type of
10299 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10300 standard breakpoint commands. For instance, as with breakpoints,
10301 tracepoint numbers are successive integers starting from one, and many
10302 of the commands associated with tracepoints take the tracepoint number
10303 as their argument, to identify which tracepoint to work on.
10305 For each tracepoint, you can specify, in advance, some arbitrary set
10306 of data that you want the target to collect in the trace buffer when
10307 it hits that tracepoint. The collected data can include registers,
10308 local variables, or global data. Later, you can use @value{GDBN}
10309 commands to examine the values these data had at the time the
10310 tracepoint was hit.
10312 Tracepoints do not support every breakpoint feature. Ignore counts on
10313 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10314 commands when they are hit. Tracepoints may not be thread-specific
10317 @cindex fast tracepoints
10318 Some targets may support @dfn{fast tracepoints}, which are inserted in
10319 a different way (such as with a jump instead of a trap), that is
10320 faster but possibly restricted in where they may be installed.
10322 @cindex static tracepoints
10323 @cindex markers, static tracepoints
10324 @cindex probing markers, static tracepoints
10325 Regular and fast tracepoints are dynamic tracing facilities, meaning
10326 that they can be used to insert tracepoints at (almost) any location
10327 in the target. Some targets may also support controlling @dfn{static
10328 tracepoints} from @value{GDBN}. With static tracing, a set of
10329 instrumentation points, also known as @dfn{markers}, are embedded in
10330 the target program, and can be activated or deactivated by name or
10331 address. These are usually placed at locations which facilitate
10332 investigating what the target is actually doing. @value{GDBN}'s
10333 support for static tracing includes being able to list instrumentation
10334 points, and attach them with @value{GDBN} defined high level
10335 tracepoints that expose the whole range of convenience of
10336 @value{GDBN}'s tracepoints support. Namely, support for collecting
10337 registers values and values of global or local (to the instrumentation
10338 point) variables; tracepoint conditions and trace state variables.
10339 The act of installing a @value{GDBN} static tracepoint on an
10340 instrumentation point, or marker, is referred to as @dfn{probing} a
10341 static tracepoint marker.
10343 @code{gdbserver} supports tracepoints on some target systems.
10344 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10346 This section describes commands to set tracepoints and associated
10347 conditions and actions.
10350 * Create and Delete Tracepoints::
10351 * Enable and Disable Tracepoints::
10352 * Tracepoint Passcounts::
10353 * Tracepoint Conditions::
10354 * Trace State Variables::
10355 * Tracepoint Actions::
10356 * Listing Tracepoints::
10357 * Listing Static Tracepoint Markers::
10358 * Starting and Stopping Trace Experiments::
10359 * Tracepoint Restrictions::
10362 @node Create and Delete Tracepoints
10363 @subsection Create and Delete Tracepoints
10366 @cindex set tracepoint
10368 @item trace @var{location}
10369 The @code{trace} command is very similar to the @code{break} command.
10370 Its argument @var{location} can be a source line, a function name, or
10371 an address in the target program. @xref{Specify Location}. The
10372 @code{trace} command defines a tracepoint, which is a point in the
10373 target program where the debugger will briefly stop, collect some
10374 data, and then allow the program to continue. Setting a tracepoint or
10375 changing its actions takes effect immediately if the remote stub
10376 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10378 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10379 these changes don't take effect until the next @code{tstart}
10380 command, and once a trace experiment is running, further changes will
10381 not have any effect until the next trace experiment starts. In addition,
10382 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10383 address is not yet resolved. (This is similar to pending breakpoints.)
10384 Pending tracepoints are not downloaded to the target and not installed
10385 until they are resolved. The resolution of pending tracepoints requires
10386 @value{GDBN} support---when debugging with the remote target, and
10387 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10388 tracing}), pending tracepoints can not be resolved (and downloaded to
10389 the remote stub) while @value{GDBN} is disconnected.
10391 Here are some examples of using the @code{trace} command:
10394 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10396 (@value{GDBP}) @b{trace +2} // 2 lines forward
10398 (@value{GDBP}) @b{trace my_function} // first source line of function
10400 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10402 (@value{GDBP}) @b{trace *0x2117c4} // an address
10406 You can abbreviate @code{trace} as @code{tr}.
10408 @item trace @var{location} if @var{cond}
10409 Set a tracepoint with condition @var{cond}; evaluate the expression
10410 @var{cond} each time the tracepoint is reached, and collect data only
10411 if the value is nonzero---that is, if @var{cond} evaluates as true.
10412 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10413 information on tracepoint conditions.
10415 @item ftrace @var{location} [ if @var{cond} ]
10416 @cindex set fast tracepoint
10417 @cindex fast tracepoints, setting
10419 The @code{ftrace} command sets a fast tracepoint. For targets that
10420 support them, fast tracepoints will use a more efficient but possibly
10421 less general technique to trigger data collection, such as a jump
10422 instruction instead of a trap, or some sort of hardware support. It
10423 may not be possible to create a fast tracepoint at the desired
10424 location, in which case the command will exit with an explanatory
10427 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10430 On 32-bit x86-architecture systems, fast tracepoints normally need to
10431 be placed at an instruction that is 5 bytes or longer, but can be
10432 placed at 4-byte instructions if the low 64K of memory of the target
10433 program is available to install trampolines. Some Unix-type systems,
10434 such as @sc{gnu}/Linux, exclude low addresses from the program's
10435 address space; but for instance with the Linux kernel it is possible
10436 to let @value{GDBN} use this area by doing a @command{sysctl} command
10437 to set the @code{mmap_min_addr} kernel parameter, as in
10440 sudo sysctl -w vm.mmap_min_addr=32768
10444 which sets the low address to 32K, which leaves plenty of room for
10445 trampolines. The minimum address should be set to a page boundary.
10447 @item strace @var{location} [ if @var{cond} ]
10448 @cindex set static tracepoint
10449 @cindex static tracepoints, setting
10450 @cindex probe static tracepoint marker
10452 The @code{strace} command sets a static tracepoint. For targets that
10453 support it, setting a static tracepoint probes a static
10454 instrumentation point, or marker, found at @var{location}. It may not
10455 be possible to set a static tracepoint at the desired location, in
10456 which case the command will exit with an explanatory message.
10458 @value{GDBN} handles arguments to @code{strace} exactly as for
10459 @code{trace}, with the addition that the user can also specify
10460 @code{-m @var{marker}} as @var{location}. This probes the marker
10461 identified by the @var{marker} string identifier. This identifier
10462 depends on the static tracepoint backend library your program is
10463 using. You can find all the marker identifiers in the @samp{ID} field
10464 of the @code{info static-tracepoint-markers} command output.
10465 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10466 Markers}. For example, in the following small program using the UST
10472 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10477 the marker id is composed of joining the first two arguments to the
10478 @code{trace_mark} call with a slash, which translates to:
10481 (@value{GDBP}) info static-tracepoint-markers
10482 Cnt Enb ID Address What
10483 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10489 so you may probe the marker above with:
10492 (@value{GDBP}) strace -m ust/bar33
10495 Static tracepoints accept an extra collect action --- @code{collect
10496 $_sdata}. This collects arbitrary user data passed in the probe point
10497 call to the tracing library. In the UST example above, you'll see
10498 that the third argument to @code{trace_mark} is a printf-like format
10499 string. The user data is then the result of running that formating
10500 string against the following arguments. Note that @code{info
10501 static-tracepoint-markers} command output lists that format string in
10502 the @samp{Data:} field.
10504 You can inspect this data when analyzing the trace buffer, by printing
10505 the $_sdata variable like any other variable available to
10506 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10509 @cindex last tracepoint number
10510 @cindex recent tracepoint number
10511 @cindex tracepoint number
10512 The convenience variable @code{$tpnum} records the tracepoint number
10513 of the most recently set tracepoint.
10515 @kindex delete tracepoint
10516 @cindex tracepoint deletion
10517 @item delete tracepoint @r{[}@var{num}@r{]}
10518 Permanently delete one or more tracepoints. With no argument, the
10519 default is to delete all tracepoints. Note that the regular
10520 @code{delete} command can remove tracepoints also.
10525 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10527 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10531 You can abbreviate this command as @code{del tr}.
10534 @node Enable and Disable Tracepoints
10535 @subsection Enable and Disable Tracepoints
10537 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10540 @kindex disable tracepoint
10541 @item disable tracepoint @r{[}@var{num}@r{]}
10542 Disable tracepoint @var{num}, or all tracepoints if no argument
10543 @var{num} is given. A disabled tracepoint will have no effect during
10544 a trace experiment, but it is not forgotten. You can re-enable
10545 a disabled tracepoint using the @code{enable tracepoint} command.
10546 If the command is issued during a trace experiment and the debug target
10547 has support for disabling tracepoints during a trace experiment, then the
10548 change will be effective immediately. Otherwise, it will be applied to the
10549 next trace experiment.
10551 @kindex enable tracepoint
10552 @item enable tracepoint @r{[}@var{num}@r{]}
10553 Enable tracepoint @var{num}, or all tracepoints. If this command is
10554 issued during a trace experiment and the debug target supports enabling
10555 tracepoints during a trace experiment, then the enabled tracepoints will
10556 become effective immediately. Otherwise, they will become effective the
10557 next time a trace experiment is run.
10560 @node Tracepoint Passcounts
10561 @subsection Tracepoint Passcounts
10565 @cindex tracepoint pass count
10566 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10567 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10568 automatically stop a trace experiment. If a tracepoint's passcount is
10569 @var{n}, then the trace experiment will be automatically stopped on
10570 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10571 @var{num} is not specified, the @code{passcount} command sets the
10572 passcount of the most recently defined tracepoint. If no passcount is
10573 given, the trace experiment will run until stopped explicitly by the
10579 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10580 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10582 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10583 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10584 (@value{GDBP}) @b{trace foo}
10585 (@value{GDBP}) @b{pass 3}
10586 (@value{GDBP}) @b{trace bar}
10587 (@value{GDBP}) @b{pass 2}
10588 (@value{GDBP}) @b{trace baz}
10589 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10590 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10591 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10592 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10596 @node Tracepoint Conditions
10597 @subsection Tracepoint Conditions
10598 @cindex conditional tracepoints
10599 @cindex tracepoint conditions
10601 The simplest sort of tracepoint collects data every time your program
10602 reaches a specified place. You can also specify a @dfn{condition} for
10603 a tracepoint. A condition is just a Boolean expression in your
10604 programming language (@pxref{Expressions, ,Expressions}). A
10605 tracepoint with a condition evaluates the expression each time your
10606 program reaches it, and data collection happens only if the condition
10609 Tracepoint conditions can be specified when a tracepoint is set, by
10610 using @samp{if} in the arguments to the @code{trace} command.
10611 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10612 also be set or changed at any time with the @code{condition} command,
10613 just as with breakpoints.
10615 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10616 the conditional expression itself. Instead, @value{GDBN} encodes the
10617 expression into an agent expression (@pxref{Agent Expressions})
10618 suitable for execution on the target, independently of @value{GDBN}.
10619 Global variables become raw memory locations, locals become stack
10620 accesses, and so forth.
10622 For instance, suppose you have a function that is usually called
10623 frequently, but should not be called after an error has occurred. You
10624 could use the following tracepoint command to collect data about calls
10625 of that function that happen while the error code is propagating
10626 through the program; an unconditional tracepoint could end up
10627 collecting thousands of useless trace frames that you would have to
10631 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10634 @node Trace State Variables
10635 @subsection Trace State Variables
10636 @cindex trace state variables
10638 A @dfn{trace state variable} is a special type of variable that is
10639 created and managed by target-side code. The syntax is the same as
10640 that for GDB's convenience variables (a string prefixed with ``$''),
10641 but they are stored on the target. They must be created explicitly,
10642 using a @code{tvariable} command. They are always 64-bit signed
10645 Trace state variables are remembered by @value{GDBN}, and downloaded
10646 to the target along with tracepoint information when the trace
10647 experiment starts. There are no intrinsic limits on the number of
10648 trace state variables, beyond memory limitations of the target.
10650 @cindex convenience variables, and trace state variables
10651 Although trace state variables are managed by the target, you can use
10652 them in print commands and expressions as if they were convenience
10653 variables; @value{GDBN} will get the current value from the target
10654 while the trace experiment is running. Trace state variables share
10655 the same namespace as other ``$'' variables, which means that you
10656 cannot have trace state variables with names like @code{$23} or
10657 @code{$pc}, nor can you have a trace state variable and a convenience
10658 variable with the same name.
10662 @item tvariable $@var{name} [ = @var{expression} ]
10664 The @code{tvariable} command creates a new trace state variable named
10665 @code{$@var{name}}, and optionally gives it an initial value of
10666 @var{expression}. @var{expression} is evaluated when this command is
10667 entered; the result will be converted to an integer if possible,
10668 otherwise @value{GDBN} will report an error. A subsequent
10669 @code{tvariable} command specifying the same name does not create a
10670 variable, but instead assigns the supplied initial value to the
10671 existing variable of that name, overwriting any previous initial
10672 value. The default initial value is 0.
10674 @item info tvariables
10675 @kindex info tvariables
10676 List all the trace state variables along with their initial values.
10677 Their current values may also be displayed, if the trace experiment is
10680 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10681 @kindex delete tvariable
10682 Delete the given trace state variables, or all of them if no arguments
10687 @node Tracepoint Actions
10688 @subsection Tracepoint Action Lists
10692 @cindex tracepoint actions
10693 @item actions @r{[}@var{num}@r{]}
10694 This command will prompt for a list of actions to be taken when the
10695 tracepoint is hit. If the tracepoint number @var{num} is not
10696 specified, this command sets the actions for the one that was most
10697 recently defined (so that you can define a tracepoint and then say
10698 @code{actions} without bothering about its number). You specify the
10699 actions themselves on the following lines, one action at a time, and
10700 terminate the actions list with a line containing just @code{end}. So
10701 far, the only defined actions are @code{collect}, @code{teval}, and
10702 @code{while-stepping}.
10704 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10705 Commands, ,Breakpoint Command Lists}), except that only the defined
10706 actions are allowed; any other @value{GDBN} command is rejected.
10708 @cindex remove actions from a tracepoint
10709 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10710 and follow it immediately with @samp{end}.
10713 (@value{GDBP}) @b{collect @var{data}} // collect some data
10715 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10717 (@value{GDBP}) @b{end} // signals the end of actions.
10720 In the following example, the action list begins with @code{collect}
10721 commands indicating the things to be collected when the tracepoint is
10722 hit. Then, in order to single-step and collect additional data
10723 following the tracepoint, a @code{while-stepping} command is used,
10724 followed by the list of things to be collected after each step in a
10725 sequence of single steps. The @code{while-stepping} command is
10726 terminated by its own separate @code{end} command. Lastly, the action
10727 list is terminated by an @code{end} command.
10730 (@value{GDBP}) @b{trace foo}
10731 (@value{GDBP}) @b{actions}
10732 Enter actions for tracepoint 1, one per line:
10735 > while-stepping 12
10736 > collect $pc, arr[i]
10741 @kindex collect @r{(tracepoints)}
10742 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10743 Collect values of the given expressions when the tracepoint is hit.
10744 This command accepts a comma-separated list of any valid expressions.
10745 In addition to global, static, or local variables, the following
10746 special arguments are supported:
10750 Collect all registers.
10753 Collect all function arguments.
10756 Collect all local variables.
10759 Collect the return address. This is helpful if you want to see more
10763 @vindex $_sdata@r{, collect}
10764 Collect static tracepoint marker specific data. Only available for
10765 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10766 Lists}. On the UST static tracepoints library backend, an
10767 instrumentation point resembles a @code{printf} function call. The
10768 tracing library is able to collect user specified data formatted to a
10769 character string using the format provided by the programmer that
10770 instrumented the program. Other backends have similar mechanisms.
10771 Here's an example of a UST marker call:
10774 const char master_name[] = "$your_name";
10775 trace_mark(channel1, marker1, "hello %s", master_name)
10778 In this case, collecting @code{$_sdata} collects the string
10779 @samp{hello $yourname}. When analyzing the trace buffer, you can
10780 inspect @samp{$_sdata} like any other variable available to
10784 You can give several consecutive @code{collect} commands, each one
10785 with a single argument, or one @code{collect} command with several
10786 arguments separated by commas; the effect is the same.
10788 The optional @var{mods} changes the usual handling of the arguments.
10789 @code{s} requests that pointers to chars be handled as strings, in
10790 particular collecting the contents of the memory being pointed at, up
10791 to the first zero. The upper bound is by default the value of the
10792 @code{print elements} variable; if @code{s} is followed by a decimal
10793 number, that is the upper bound instead. So for instance
10794 @samp{collect/s25 mystr} collects as many as 25 characters at
10797 The command @code{info scope} (@pxref{Symbols, info scope}) is
10798 particularly useful for figuring out what data to collect.
10800 @kindex teval @r{(tracepoints)}
10801 @item teval @var{expr1}, @var{expr2}, @dots{}
10802 Evaluate the given expressions when the tracepoint is hit. This
10803 command accepts a comma-separated list of expressions. The results
10804 are discarded, so this is mainly useful for assigning values to trace
10805 state variables (@pxref{Trace State Variables}) without adding those
10806 values to the trace buffer, as would be the case if the @code{collect}
10809 @kindex while-stepping @r{(tracepoints)}
10810 @item while-stepping @var{n}
10811 Perform @var{n} single-step instruction traces after the tracepoint,
10812 collecting new data after each step. The @code{while-stepping}
10813 command is followed by the list of what to collect while stepping
10814 (followed by its own @code{end} command):
10817 > while-stepping 12
10818 > collect $regs, myglobal
10824 Note that @code{$pc} is not automatically collected by
10825 @code{while-stepping}; you need to explicitly collect that register if
10826 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10829 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10830 @kindex set default-collect
10831 @cindex default collection action
10832 This variable is a list of expressions to collect at each tracepoint
10833 hit. It is effectively an additional @code{collect} action prepended
10834 to every tracepoint action list. The expressions are parsed
10835 individually for each tracepoint, so for instance a variable named
10836 @code{xyz} may be interpreted as a global for one tracepoint, and a
10837 local for another, as appropriate to the tracepoint's location.
10839 @item show default-collect
10840 @kindex show default-collect
10841 Show the list of expressions that are collected by default at each
10846 @node Listing Tracepoints
10847 @subsection Listing Tracepoints
10850 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10851 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10852 @cindex information about tracepoints
10853 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10854 Display information about the tracepoint @var{num}. If you don't
10855 specify a tracepoint number, displays information about all the
10856 tracepoints defined so far. The format is similar to that used for
10857 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10858 command, simply restricting itself to tracepoints.
10860 A tracepoint's listing may include additional information specific to
10865 its passcount as given by the @code{passcount @var{n}} command
10869 (@value{GDBP}) @b{info trace}
10870 Num Type Disp Enb Address What
10871 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10873 collect globfoo, $regs
10882 This command can be abbreviated @code{info tp}.
10885 @node Listing Static Tracepoint Markers
10886 @subsection Listing Static Tracepoint Markers
10889 @kindex info static-tracepoint-markers
10890 @cindex information about static tracepoint markers
10891 @item info static-tracepoint-markers
10892 Display information about all static tracepoint markers defined in the
10895 For each marker, the following columns are printed:
10899 An incrementing counter, output to help readability. This is not a
10902 The marker ID, as reported by the target.
10903 @item Enabled or Disabled
10904 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10905 that are not enabled.
10907 Where the marker is in your program, as a memory address.
10909 Where the marker is in the source for your program, as a file and line
10910 number. If the debug information included in the program does not
10911 allow @value{GDBN} to locate the source of the marker, this column
10912 will be left blank.
10916 In addition, the following information may be printed for each marker:
10920 User data passed to the tracing library by the marker call. In the
10921 UST backend, this is the format string passed as argument to the
10923 @item Static tracepoints probing the marker
10924 The list of static tracepoints attached to the marker.
10928 (@value{GDBP}) info static-tracepoint-markers
10929 Cnt ID Enb Address What
10930 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10931 Data: number1 %d number2 %d
10932 Probed by static tracepoints: #2
10933 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10939 @node Starting and Stopping Trace Experiments
10940 @subsection Starting and Stopping Trace Experiments
10943 @kindex tstart [ @var{notes} ]
10944 @cindex start a new trace experiment
10945 @cindex collected data discarded
10947 This command starts the trace experiment, and begins collecting data.
10948 It has the side effect of discarding all the data collected in the
10949 trace buffer during the previous trace experiment. If any arguments
10950 are supplied, they are taken as a note and stored with the trace
10951 experiment's state. The notes may be arbitrary text, and are
10952 especially useful with disconnected tracing in a multi-user context;
10953 the notes can explain what the trace is doing, supply user contact
10954 information, and so forth.
10956 @kindex tstop [ @var{notes} ]
10957 @cindex stop a running trace experiment
10959 This command stops the trace experiment. If any arguments are
10960 supplied, they are recorded with the experiment as a note. This is
10961 useful if you are stopping a trace started by someone else, for
10962 instance if the trace is interfering with the system's behavior and
10963 needs to be stopped quickly.
10965 @strong{Note}: a trace experiment and data collection may stop
10966 automatically if any tracepoint's passcount is reached
10967 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10970 @cindex status of trace data collection
10971 @cindex trace experiment, status of
10973 This command displays the status of the current trace data
10977 Here is an example of the commands we described so far:
10980 (@value{GDBP}) @b{trace gdb_c_test}
10981 (@value{GDBP}) @b{actions}
10982 Enter actions for tracepoint #1, one per line.
10983 > collect $regs,$locals,$args
10984 > while-stepping 11
10988 (@value{GDBP}) @b{tstart}
10989 [time passes @dots{}]
10990 (@value{GDBP}) @b{tstop}
10993 @anchor{disconnected tracing}
10994 @cindex disconnected tracing
10995 You can choose to continue running the trace experiment even if
10996 @value{GDBN} disconnects from the target, voluntarily or
10997 involuntarily. For commands such as @code{detach}, the debugger will
10998 ask what you want to do with the trace. But for unexpected
10999 terminations (@value{GDBN} crash, network outage), it would be
11000 unfortunate to lose hard-won trace data, so the variable
11001 @code{disconnected-tracing} lets you decide whether the trace should
11002 continue running without @value{GDBN}.
11005 @item set disconnected-tracing on
11006 @itemx set disconnected-tracing off
11007 @kindex set disconnected-tracing
11008 Choose whether a tracing run should continue to run if @value{GDBN}
11009 has disconnected from the target. Note that @code{detach} or
11010 @code{quit} will ask you directly what to do about a running trace no
11011 matter what this variable's setting, so the variable is mainly useful
11012 for handling unexpected situations, such as loss of the network.
11014 @item show disconnected-tracing
11015 @kindex show disconnected-tracing
11016 Show the current choice for disconnected tracing.
11020 When you reconnect to the target, the trace experiment may or may not
11021 still be running; it might have filled the trace buffer in the
11022 meantime, or stopped for one of the other reasons. If it is running,
11023 it will continue after reconnection.
11025 Upon reconnection, the target will upload information about the
11026 tracepoints in effect. @value{GDBN} will then compare that
11027 information to the set of tracepoints currently defined, and attempt
11028 to match them up, allowing for the possibility that the numbers may
11029 have changed due to creation and deletion in the meantime. If one of
11030 the target's tracepoints does not match any in @value{GDBN}, the
11031 debugger will create a new tracepoint, so that you have a number with
11032 which to specify that tracepoint. This matching-up process is
11033 necessarily heuristic, and it may result in useless tracepoints being
11034 created; you may simply delete them if they are of no use.
11036 @cindex circular trace buffer
11037 If your target agent supports a @dfn{circular trace buffer}, then you
11038 can run a trace experiment indefinitely without filling the trace
11039 buffer; when space runs out, the agent deletes already-collected trace
11040 frames, oldest first, until there is enough room to continue
11041 collecting. This is especially useful if your tracepoints are being
11042 hit too often, and your trace gets terminated prematurely because the
11043 buffer is full. To ask for a circular trace buffer, simply set
11044 @samp{circular-trace-buffer} to on. You can set this at any time,
11045 including during tracing; if the agent can do it, it will change
11046 buffer handling on the fly, otherwise it will not take effect until
11050 @item set circular-trace-buffer on
11051 @itemx set circular-trace-buffer off
11052 @kindex set circular-trace-buffer
11053 Choose whether a tracing run should use a linear or circular buffer
11054 for trace data. A linear buffer will not lose any trace data, but may
11055 fill up prematurely, while a circular buffer will discard old trace
11056 data, but it will have always room for the latest tracepoint hits.
11058 @item show circular-trace-buffer
11059 @kindex show circular-trace-buffer
11060 Show the current choice for the trace buffer. Note that this may not
11061 match the agent's current buffer handling, nor is it guaranteed to
11062 match the setting that might have been in effect during a past run,
11063 for instance if you are looking at frames from a trace file.
11068 @item set trace-user @var{text}
11069 @kindex set trace-user
11071 @item show trace-user
11072 @kindex show trace-user
11074 @item set trace-notes @var{text}
11075 @kindex set trace-notes
11076 Set the trace run's notes.
11078 @item show trace-notes
11079 @kindex show trace-notes
11080 Show the trace run's notes.
11082 @item set trace-stop-notes @var{text}
11083 @kindex set trace-stop-notes
11084 Set the trace run's stop notes. The handling of the note is as for
11085 @code{tstop} arguments; the set command is convenient way to fix a
11086 stop note that is mistaken or incomplete.
11088 @item show trace-stop-notes
11089 @kindex show trace-stop-notes
11090 Show the trace run's stop notes.
11094 @node Tracepoint Restrictions
11095 @subsection Tracepoint Restrictions
11097 @cindex tracepoint restrictions
11098 There are a number of restrictions on the use of tracepoints. As
11099 described above, tracepoint data gathering occurs on the target
11100 without interaction from @value{GDBN}. Thus the full capabilities of
11101 the debugger are not available during data gathering, and then at data
11102 examination time, you will be limited by only having what was
11103 collected. The following items describe some common problems, but it
11104 is not exhaustive, and you may run into additional difficulties not
11110 Tracepoint expressions are intended to gather objects (lvalues). Thus
11111 the full flexibility of GDB's expression evaluator is not available.
11112 You cannot call functions, cast objects to aggregate types, access
11113 convenience variables or modify values (except by assignment to trace
11114 state variables). Some language features may implicitly call
11115 functions (for instance Objective-C fields with accessors), and therefore
11116 cannot be collected either.
11119 Collection of local variables, either individually or in bulk with
11120 @code{$locals} or @code{$args}, during @code{while-stepping} may
11121 behave erratically. The stepping action may enter a new scope (for
11122 instance by stepping into a function), or the location of the variable
11123 may change (for instance it is loaded into a register). The
11124 tracepoint data recorded uses the location information for the
11125 variables that is correct for the tracepoint location. When the
11126 tracepoint is created, it is not possible, in general, to determine
11127 where the steps of a @code{while-stepping} sequence will advance the
11128 program---particularly if a conditional branch is stepped.
11131 Collection of an incompletely-initialized or partially-destroyed object
11132 may result in something that @value{GDBN} cannot display, or displays
11133 in a misleading way.
11136 When @value{GDBN} displays a pointer to character it automatically
11137 dereferences the pointer to also display characters of the string
11138 being pointed to. However, collecting the pointer during tracing does
11139 not automatically collect the string. You need to explicitly
11140 dereference the pointer and provide size information if you want to
11141 collect not only the pointer, but the memory pointed to. For example,
11142 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11146 It is not possible to collect a complete stack backtrace at a
11147 tracepoint. Instead, you may collect the registers and a few hundred
11148 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11149 (adjust to use the name of the actual stack pointer register on your
11150 target architecture, and the amount of stack you wish to capture).
11151 Then the @code{backtrace} command will show a partial backtrace when
11152 using a trace frame. The number of stack frames that can be examined
11153 depends on the sizes of the frames in the collected stack. Note that
11154 if you ask for a block so large that it goes past the bottom of the
11155 stack, the target agent may report an error trying to read from an
11159 If you do not collect registers at a tracepoint, @value{GDBN} can
11160 infer that the value of @code{$pc} must be the same as the address of
11161 the tracepoint and use that when you are looking at a trace frame
11162 for that tracepoint. However, this cannot work if the tracepoint has
11163 multiple locations (for instance if it was set in a function that was
11164 inlined), or if it has a @code{while-stepping} loop. In those cases
11165 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11170 @node Analyze Collected Data
11171 @section Using the Collected Data
11173 After the tracepoint experiment ends, you use @value{GDBN} commands
11174 for examining the trace data. The basic idea is that each tracepoint
11175 collects a trace @dfn{snapshot} every time it is hit and another
11176 snapshot every time it single-steps. All these snapshots are
11177 consecutively numbered from zero and go into a buffer, and you can
11178 examine them later. The way you examine them is to @dfn{focus} on a
11179 specific trace snapshot. When the remote stub is focused on a trace
11180 snapshot, it will respond to all @value{GDBN} requests for memory and
11181 registers by reading from the buffer which belongs to that snapshot,
11182 rather than from @emph{real} memory or registers of the program being
11183 debugged. This means that @strong{all} @value{GDBN} commands
11184 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11185 behave as if we were currently debugging the program state as it was
11186 when the tracepoint occurred. Any requests for data that are not in
11187 the buffer will fail.
11190 * tfind:: How to select a trace snapshot
11191 * tdump:: How to display all data for a snapshot
11192 * save tracepoints:: How to save tracepoints for a future run
11196 @subsection @code{tfind @var{n}}
11199 @cindex select trace snapshot
11200 @cindex find trace snapshot
11201 The basic command for selecting a trace snapshot from the buffer is
11202 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11203 counting from zero. If no argument @var{n} is given, the next
11204 snapshot is selected.
11206 Here are the various forms of using the @code{tfind} command.
11210 Find the first snapshot in the buffer. This is a synonym for
11211 @code{tfind 0} (since 0 is the number of the first snapshot).
11214 Stop debugging trace snapshots, resume @emph{live} debugging.
11217 Same as @samp{tfind none}.
11220 No argument means find the next trace snapshot.
11223 Find the previous trace snapshot before the current one. This permits
11224 retracing earlier steps.
11226 @item tfind tracepoint @var{num}
11227 Find the next snapshot associated with tracepoint @var{num}. Search
11228 proceeds forward from the last examined trace snapshot. If no
11229 argument @var{num} is given, it means find the next snapshot collected
11230 for the same tracepoint as the current snapshot.
11232 @item tfind pc @var{addr}
11233 Find the next snapshot associated with the value @var{addr} of the
11234 program counter. Search proceeds forward from the last examined trace
11235 snapshot. If no argument @var{addr} is given, it means find the next
11236 snapshot with the same value of PC as the current snapshot.
11238 @item tfind outside @var{addr1}, @var{addr2}
11239 Find the next snapshot whose PC is outside the given range of
11240 addresses (exclusive).
11242 @item tfind range @var{addr1}, @var{addr2}
11243 Find the next snapshot whose PC is between @var{addr1} and
11244 @var{addr2} (inclusive).
11246 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11247 Find the next snapshot associated with the source line @var{n}. If
11248 the optional argument @var{file} is given, refer to line @var{n} in
11249 that source file. Search proceeds forward from the last examined
11250 trace snapshot. If no argument @var{n} is given, it means find the
11251 next line other than the one currently being examined; thus saying
11252 @code{tfind line} repeatedly can appear to have the same effect as
11253 stepping from line to line in a @emph{live} debugging session.
11256 The default arguments for the @code{tfind} commands are specifically
11257 designed to make it easy to scan through the trace buffer. For
11258 instance, @code{tfind} with no argument selects the next trace
11259 snapshot, and @code{tfind -} with no argument selects the previous
11260 trace snapshot. So, by giving one @code{tfind} command, and then
11261 simply hitting @key{RET} repeatedly you can examine all the trace
11262 snapshots in order. Or, by saying @code{tfind -} and then hitting
11263 @key{RET} repeatedly you can examine the snapshots in reverse order.
11264 The @code{tfind line} command with no argument selects the snapshot
11265 for the next source line executed. The @code{tfind pc} command with
11266 no argument selects the next snapshot with the same program counter
11267 (PC) as the current frame. The @code{tfind tracepoint} command with
11268 no argument selects the next trace snapshot collected by the same
11269 tracepoint as the current one.
11271 In addition to letting you scan through the trace buffer manually,
11272 these commands make it easy to construct @value{GDBN} scripts that
11273 scan through the trace buffer and print out whatever collected data
11274 you are interested in. Thus, if we want to examine the PC, FP, and SP
11275 registers from each trace frame in the buffer, we can say this:
11278 (@value{GDBP}) @b{tfind start}
11279 (@value{GDBP}) @b{while ($trace_frame != -1)}
11280 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11281 $trace_frame, $pc, $sp, $fp
11285 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11286 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11287 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11288 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11289 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11290 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11291 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11292 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11293 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11294 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11295 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11298 Or, if we want to examine the variable @code{X} at each source line in
11302 (@value{GDBP}) @b{tfind start}
11303 (@value{GDBP}) @b{while ($trace_frame != -1)}
11304 > printf "Frame %d, X == %d\n", $trace_frame, X
11314 @subsection @code{tdump}
11316 @cindex dump all data collected at tracepoint
11317 @cindex tracepoint data, display
11319 This command takes no arguments. It prints all the data collected at
11320 the current trace snapshot.
11323 (@value{GDBP}) @b{trace 444}
11324 (@value{GDBP}) @b{actions}
11325 Enter actions for tracepoint #2, one per line:
11326 > collect $regs, $locals, $args, gdb_long_test
11329 (@value{GDBP}) @b{tstart}
11331 (@value{GDBP}) @b{tfind line 444}
11332 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11334 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11336 (@value{GDBP}) @b{tdump}
11337 Data collected at tracepoint 2, trace frame 1:
11338 d0 0xc4aa0085 -995491707
11342 d4 0x71aea3d 119204413
11345 d7 0x380035 3670069
11346 a0 0x19e24a 1696330
11347 a1 0x3000668 50333288
11349 a3 0x322000 3284992
11350 a4 0x3000698 50333336
11351 a5 0x1ad3cc 1758156
11352 fp 0x30bf3c 0x30bf3c
11353 sp 0x30bf34 0x30bf34
11355 pc 0x20b2c8 0x20b2c8
11359 p = 0x20e5b4 "gdb-test"
11366 gdb_long_test = 17 '\021'
11371 @code{tdump} works by scanning the tracepoint's current collection
11372 actions and printing the value of each expression listed. So
11373 @code{tdump} can fail, if after a run, you change the tracepoint's
11374 actions to mention variables that were not collected during the run.
11376 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11377 uses the collected value of @code{$pc} to distinguish between trace
11378 frames that were collected at the tracepoint hit, and frames that were
11379 collected while stepping. This allows it to correctly choose whether
11380 to display the basic list of collections, or the collections from the
11381 body of the while-stepping loop. However, if @code{$pc} was not collected,
11382 then @code{tdump} will always attempt to dump using the basic collection
11383 list, and may fail if a while-stepping frame does not include all the
11384 same data that is collected at the tracepoint hit.
11385 @c This is getting pretty arcane, example would be good.
11387 @node save tracepoints
11388 @subsection @code{save tracepoints @var{filename}}
11389 @kindex save tracepoints
11390 @kindex save-tracepoints
11391 @cindex save tracepoints for future sessions
11393 This command saves all current tracepoint definitions together with
11394 their actions and passcounts, into a file @file{@var{filename}}
11395 suitable for use in a later debugging session. To read the saved
11396 tracepoint definitions, use the @code{source} command (@pxref{Command
11397 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11398 alias for @w{@code{save tracepoints}}
11400 @node Tracepoint Variables
11401 @section Convenience Variables for Tracepoints
11402 @cindex tracepoint variables
11403 @cindex convenience variables for tracepoints
11406 @vindex $trace_frame
11407 @item (int) $trace_frame
11408 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11409 snapshot is selected.
11411 @vindex $tracepoint
11412 @item (int) $tracepoint
11413 The tracepoint for the current trace snapshot.
11415 @vindex $trace_line
11416 @item (int) $trace_line
11417 The line number for the current trace snapshot.
11419 @vindex $trace_file
11420 @item (char []) $trace_file
11421 The source file for the current trace snapshot.
11423 @vindex $trace_func
11424 @item (char []) $trace_func
11425 The name of the function containing @code{$tracepoint}.
11428 Note: @code{$trace_file} is not suitable for use in @code{printf},
11429 use @code{output} instead.
11431 Here's a simple example of using these convenience variables for
11432 stepping through all the trace snapshots and printing some of their
11433 data. Note that these are not the same as trace state variables,
11434 which are managed by the target.
11437 (@value{GDBP}) @b{tfind start}
11439 (@value{GDBP}) @b{while $trace_frame != -1}
11440 > output $trace_file
11441 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11447 @section Using Trace Files
11448 @cindex trace files
11450 In some situations, the target running a trace experiment may no
11451 longer be available; perhaps it crashed, or the hardware was needed
11452 for a different activity. To handle these cases, you can arrange to
11453 dump the trace data into a file, and later use that file as a source
11454 of trace data, via the @code{target tfile} command.
11459 @item tsave [ -r ] @var{filename}
11460 Save the trace data to @var{filename}. By default, this command
11461 assumes that @var{filename} refers to the host filesystem, so if
11462 necessary @value{GDBN} will copy raw trace data up from the target and
11463 then save it. If the target supports it, you can also supply the
11464 optional argument @code{-r} (``remote'') to direct the target to save
11465 the data directly into @var{filename} in its own filesystem, which may be
11466 more efficient if the trace buffer is very large. (Note, however, that
11467 @code{target tfile} can only read from files accessible to the host.)
11469 @kindex target tfile
11471 @item target tfile @var{filename}
11472 Use the file named @var{filename} as a source of trace data. Commands
11473 that examine data work as they do with a live target, but it is not
11474 possible to run any new trace experiments. @code{tstatus} will report
11475 the state of the trace run at the moment the data was saved, as well
11476 as the current trace frame you are examining. @var{filename} must be
11477 on a filesystem accessible to the host.
11482 @chapter Debugging Programs That Use Overlays
11485 If your program is too large to fit completely in your target system's
11486 memory, you can sometimes use @dfn{overlays} to work around this
11487 problem. @value{GDBN} provides some support for debugging programs that
11491 * How Overlays Work:: A general explanation of overlays.
11492 * Overlay Commands:: Managing overlays in @value{GDBN}.
11493 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11494 mapped by asking the inferior.
11495 * Overlay Sample Program:: A sample program using overlays.
11498 @node How Overlays Work
11499 @section How Overlays Work
11500 @cindex mapped overlays
11501 @cindex unmapped overlays
11502 @cindex load address, overlay's
11503 @cindex mapped address
11504 @cindex overlay area
11506 Suppose you have a computer whose instruction address space is only 64
11507 kilobytes long, but which has much more memory which can be accessed by
11508 other means: special instructions, segment registers, or memory
11509 management hardware, for example. Suppose further that you want to
11510 adapt a program which is larger than 64 kilobytes to run on this system.
11512 One solution is to identify modules of your program which are relatively
11513 independent, and need not call each other directly; call these modules
11514 @dfn{overlays}. Separate the overlays from the main program, and place
11515 their machine code in the larger memory. Place your main program in
11516 instruction memory, but leave at least enough space there to hold the
11517 largest overlay as well.
11519 Now, to call a function located in an overlay, you must first copy that
11520 overlay's machine code from the large memory into the space set aside
11521 for it in the instruction memory, and then jump to its entry point
11524 @c NB: In the below the mapped area's size is greater or equal to the
11525 @c size of all overlays. This is intentional to remind the developer
11526 @c that overlays don't necessarily need to be the same size.
11530 Data Instruction Larger
11531 Address Space Address Space Address Space
11532 +-----------+ +-----------+ +-----------+
11534 +-----------+ +-----------+ +-----------+<-- overlay 1
11535 | program | | main | .----| overlay 1 | load address
11536 | variables | | program | | +-----------+
11537 | and heap | | | | | |
11538 +-----------+ | | | +-----------+<-- overlay 2
11539 | | +-----------+ | | | load address
11540 +-----------+ | | | .-| overlay 2 |
11542 mapped --->+-----------+ | | +-----------+
11543 address | | | | | |
11544 | overlay | <-' | | |
11545 | area | <---' +-----------+<-- overlay 3
11546 | | <---. | | load address
11547 +-----------+ `--| overlay 3 |
11554 @anchor{A code overlay}A code overlay
11558 The diagram (@pxref{A code overlay}) shows a system with separate data
11559 and instruction address spaces. To map an overlay, the program copies
11560 its code from the larger address space to the instruction address space.
11561 Since the overlays shown here all use the same mapped address, only one
11562 may be mapped at a time. For a system with a single address space for
11563 data and instructions, the diagram would be similar, except that the
11564 program variables and heap would share an address space with the main
11565 program and the overlay area.
11567 An overlay loaded into instruction memory and ready for use is called a
11568 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11569 instruction memory. An overlay not present (or only partially present)
11570 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11571 is its address in the larger memory. The mapped address is also called
11572 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11573 called the @dfn{load memory address}, or @dfn{LMA}.
11575 Unfortunately, overlays are not a completely transparent way to adapt a
11576 program to limited instruction memory. They introduce a new set of
11577 global constraints you must keep in mind as you design your program:
11582 Before calling or returning to a function in an overlay, your program
11583 must make sure that overlay is actually mapped. Otherwise, the call or
11584 return will transfer control to the right address, but in the wrong
11585 overlay, and your program will probably crash.
11588 If the process of mapping an overlay is expensive on your system, you
11589 will need to choose your overlays carefully to minimize their effect on
11590 your program's performance.
11593 The executable file you load onto your system must contain each
11594 overlay's instructions, appearing at the overlay's load address, not its
11595 mapped address. However, each overlay's instructions must be relocated
11596 and its symbols defined as if the overlay were at its mapped address.
11597 You can use GNU linker scripts to specify different load and relocation
11598 addresses for pieces of your program; see @ref{Overlay Description,,,
11599 ld.info, Using ld: the GNU linker}.
11602 The procedure for loading executable files onto your system must be able
11603 to load their contents into the larger address space as well as the
11604 instruction and data spaces.
11608 The overlay system described above is rather simple, and could be
11609 improved in many ways:
11614 If your system has suitable bank switch registers or memory management
11615 hardware, you could use those facilities to make an overlay's load area
11616 contents simply appear at their mapped address in instruction space.
11617 This would probably be faster than copying the overlay to its mapped
11618 area in the usual way.
11621 If your overlays are small enough, you could set aside more than one
11622 overlay area, and have more than one overlay mapped at a time.
11625 You can use overlays to manage data, as well as instructions. In
11626 general, data overlays are even less transparent to your design than
11627 code overlays: whereas code overlays only require care when you call or
11628 return to functions, data overlays require care every time you access
11629 the data. Also, if you change the contents of a data overlay, you
11630 must copy its contents back out to its load address before you can copy a
11631 different data overlay into the same mapped area.
11636 @node Overlay Commands
11637 @section Overlay Commands
11639 To use @value{GDBN}'s overlay support, each overlay in your program must
11640 correspond to a separate section of the executable file. The section's
11641 virtual memory address and load memory address must be the overlay's
11642 mapped and load addresses. Identifying overlays with sections allows
11643 @value{GDBN} to determine the appropriate address of a function or
11644 variable, depending on whether the overlay is mapped or not.
11646 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11647 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11652 Disable @value{GDBN}'s overlay support. When overlay support is
11653 disabled, @value{GDBN} assumes that all functions and variables are
11654 always present at their mapped addresses. By default, @value{GDBN}'s
11655 overlay support is disabled.
11657 @item overlay manual
11658 @cindex manual overlay debugging
11659 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11660 relies on you to tell it which overlays are mapped, and which are not,
11661 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11662 commands described below.
11664 @item overlay map-overlay @var{overlay}
11665 @itemx overlay map @var{overlay}
11666 @cindex map an overlay
11667 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11668 be the name of the object file section containing the overlay. When an
11669 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11670 functions and variables at their mapped addresses. @value{GDBN} assumes
11671 that any other overlays whose mapped ranges overlap that of
11672 @var{overlay} are now unmapped.
11674 @item overlay unmap-overlay @var{overlay}
11675 @itemx overlay unmap @var{overlay}
11676 @cindex unmap an overlay
11677 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11678 must be the name of the object file section containing the overlay.
11679 When an overlay is unmapped, @value{GDBN} assumes it can find the
11680 overlay's functions and variables at their load addresses.
11683 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11684 consults a data structure the overlay manager maintains in the inferior
11685 to see which overlays are mapped. For details, see @ref{Automatic
11686 Overlay Debugging}.
11688 @item overlay load-target
11689 @itemx overlay load
11690 @cindex reloading the overlay table
11691 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11692 re-reads the table @value{GDBN} automatically each time the inferior
11693 stops, so this command should only be necessary if you have changed the
11694 overlay mapping yourself using @value{GDBN}. This command is only
11695 useful when using automatic overlay debugging.
11697 @item overlay list-overlays
11698 @itemx overlay list
11699 @cindex listing mapped overlays
11700 Display a list of the overlays currently mapped, along with their mapped
11701 addresses, load addresses, and sizes.
11705 Normally, when @value{GDBN} prints a code address, it includes the name
11706 of the function the address falls in:
11709 (@value{GDBP}) print main
11710 $3 = @{int ()@} 0x11a0 <main>
11713 When overlay debugging is enabled, @value{GDBN} recognizes code in
11714 unmapped overlays, and prints the names of unmapped functions with
11715 asterisks around them. For example, if @code{foo} is a function in an
11716 unmapped overlay, @value{GDBN} prints it this way:
11719 (@value{GDBP}) overlay list
11720 No sections are mapped.
11721 (@value{GDBP}) print foo
11722 $5 = @{int (int)@} 0x100000 <*foo*>
11725 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11729 (@value{GDBP}) overlay list
11730 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11731 mapped at 0x1016 - 0x104a
11732 (@value{GDBP}) print foo
11733 $6 = @{int (int)@} 0x1016 <foo>
11736 When overlay debugging is enabled, @value{GDBN} can find the correct
11737 address for functions and variables in an overlay, whether or not the
11738 overlay is mapped. This allows most @value{GDBN} commands, like
11739 @code{break} and @code{disassemble}, to work normally, even on unmapped
11740 code. However, @value{GDBN}'s breakpoint support has some limitations:
11744 @cindex breakpoints in overlays
11745 @cindex overlays, setting breakpoints in
11746 You can set breakpoints in functions in unmapped overlays, as long as
11747 @value{GDBN} can write to the overlay at its load address.
11749 @value{GDBN} can not set hardware or simulator-based breakpoints in
11750 unmapped overlays. However, if you set a breakpoint at the end of your
11751 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11752 you are using manual overlay management), @value{GDBN} will re-set its
11753 breakpoints properly.
11757 @node Automatic Overlay Debugging
11758 @section Automatic Overlay Debugging
11759 @cindex automatic overlay debugging
11761 @value{GDBN} can automatically track which overlays are mapped and which
11762 are not, given some simple co-operation from the overlay manager in the
11763 inferior. If you enable automatic overlay debugging with the
11764 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11765 looks in the inferior's memory for certain variables describing the
11766 current state of the overlays.
11768 Here are the variables your overlay manager must define to support
11769 @value{GDBN}'s automatic overlay debugging:
11773 @item @code{_ovly_table}:
11774 This variable must be an array of the following structures:
11779 /* The overlay's mapped address. */
11782 /* The size of the overlay, in bytes. */
11783 unsigned long size;
11785 /* The overlay's load address. */
11788 /* Non-zero if the overlay is currently mapped;
11790 unsigned long mapped;
11794 @item @code{_novlys}:
11795 This variable must be a four-byte signed integer, holding the total
11796 number of elements in @code{_ovly_table}.
11800 To decide whether a particular overlay is mapped or not, @value{GDBN}
11801 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11802 @code{lma} members equal the VMA and LMA of the overlay's section in the
11803 executable file. When @value{GDBN} finds a matching entry, it consults
11804 the entry's @code{mapped} member to determine whether the overlay is
11807 In addition, your overlay manager may define a function called
11808 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11809 will silently set a breakpoint there. If the overlay manager then
11810 calls this function whenever it has changed the overlay table, this
11811 will enable @value{GDBN} to accurately keep track of which overlays
11812 are in program memory, and update any breakpoints that may be set
11813 in overlays. This will allow breakpoints to work even if the
11814 overlays are kept in ROM or other non-writable memory while they
11815 are not being executed.
11817 @node Overlay Sample Program
11818 @section Overlay Sample Program
11819 @cindex overlay example program
11821 When linking a program which uses overlays, you must place the overlays
11822 at their load addresses, while relocating them to run at their mapped
11823 addresses. To do this, you must write a linker script (@pxref{Overlay
11824 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11825 since linker scripts are specific to a particular host system, target
11826 architecture, and target memory layout, this manual cannot provide
11827 portable sample code demonstrating @value{GDBN}'s overlay support.
11829 However, the @value{GDBN} source distribution does contain an overlaid
11830 program, with linker scripts for a few systems, as part of its test
11831 suite. The program consists of the following files from
11832 @file{gdb/testsuite/gdb.base}:
11836 The main program file.
11838 A simple overlay manager, used by @file{overlays.c}.
11843 Overlay modules, loaded and used by @file{overlays.c}.
11846 Linker scripts for linking the test program on the @code{d10v-elf}
11847 and @code{m32r-elf} targets.
11850 You can build the test program using the @code{d10v-elf} GCC
11851 cross-compiler like this:
11854 $ d10v-elf-gcc -g -c overlays.c
11855 $ d10v-elf-gcc -g -c ovlymgr.c
11856 $ d10v-elf-gcc -g -c foo.c
11857 $ d10v-elf-gcc -g -c bar.c
11858 $ d10v-elf-gcc -g -c baz.c
11859 $ d10v-elf-gcc -g -c grbx.c
11860 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11861 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11864 The build process is identical for any other architecture, except that
11865 you must substitute the appropriate compiler and linker script for the
11866 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11870 @chapter Using @value{GDBN} with Different Languages
11873 Although programming languages generally have common aspects, they are
11874 rarely expressed in the same manner. For instance, in ANSI C,
11875 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11876 Modula-2, it is accomplished by @code{p^}. Values can also be
11877 represented (and displayed) differently. Hex numbers in C appear as
11878 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11880 @cindex working language
11881 Language-specific information is built into @value{GDBN} for some languages,
11882 allowing you to express operations like the above in your program's
11883 native language, and allowing @value{GDBN} to output values in a manner
11884 consistent with the syntax of your program's native language. The
11885 language you use to build expressions is called the @dfn{working
11889 * Setting:: Switching between source languages
11890 * Show:: Displaying the language
11891 * Checks:: Type and range checks
11892 * Supported Languages:: Supported languages
11893 * Unsupported Languages:: Unsupported languages
11897 @section Switching Between Source Languages
11899 There are two ways to control the working language---either have @value{GDBN}
11900 set it automatically, or select it manually yourself. You can use the
11901 @code{set language} command for either purpose. On startup, @value{GDBN}
11902 defaults to setting the language automatically. The working language is
11903 used to determine how expressions you type are interpreted, how values
11906 In addition to the working language, every source file that
11907 @value{GDBN} knows about has its own working language. For some object
11908 file formats, the compiler might indicate which language a particular
11909 source file is in. However, most of the time @value{GDBN} infers the
11910 language from the name of the file. The language of a source file
11911 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11912 show each frame appropriately for its own language. There is no way to
11913 set the language of a source file from within @value{GDBN}, but you can
11914 set the language associated with a filename extension. @xref{Show, ,
11915 Displaying the Language}.
11917 This is most commonly a problem when you use a program, such
11918 as @code{cfront} or @code{f2c}, that generates C but is written in
11919 another language. In that case, make the
11920 program use @code{#line} directives in its C output; that way
11921 @value{GDBN} will know the correct language of the source code of the original
11922 program, and will display that source code, not the generated C code.
11925 * Filenames:: Filename extensions and languages.
11926 * Manually:: Setting the working language manually
11927 * Automatically:: Having @value{GDBN} infer the source language
11931 @subsection List of Filename Extensions and Languages
11933 If a source file name ends in one of the following extensions, then
11934 @value{GDBN} infers that its language is the one indicated.
11952 C@t{++} source file
11958 Objective-C source file
11962 Fortran source file
11965 Modula-2 source file
11969 Assembler source file. This actually behaves almost like C, but
11970 @value{GDBN} does not skip over function prologues when stepping.
11973 In addition, you may set the language associated with a filename
11974 extension. @xref{Show, , Displaying the Language}.
11977 @subsection Setting the Working Language
11979 If you allow @value{GDBN} to set the language automatically,
11980 expressions are interpreted the same way in your debugging session and
11983 @kindex set language
11984 If you wish, you may set the language manually. To do this, issue the
11985 command @samp{set language @var{lang}}, where @var{lang} is the name of
11986 a language, such as
11987 @code{c} or @code{modula-2}.
11988 For a list of the supported languages, type @samp{set language}.
11990 Setting the language manually prevents @value{GDBN} from updating the working
11991 language automatically. This can lead to confusion if you try
11992 to debug a program when the working language is not the same as the
11993 source language, when an expression is acceptable to both
11994 languages---but means different things. For instance, if the current
11995 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12003 might not have the effect you intended. In C, this means to add
12004 @code{b} and @code{c} and place the result in @code{a}. The result
12005 printed would be the value of @code{a}. In Modula-2, this means to compare
12006 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12008 @node Automatically
12009 @subsection Having @value{GDBN} Infer the Source Language
12011 To have @value{GDBN} set the working language automatically, use
12012 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12013 then infers the working language. That is, when your program stops in a
12014 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12015 working language to the language recorded for the function in that
12016 frame. If the language for a frame is unknown (that is, if the function
12017 or block corresponding to the frame was defined in a source file that
12018 does not have a recognized extension), the current working language is
12019 not changed, and @value{GDBN} issues a warning.
12021 This may not seem necessary for most programs, which are written
12022 entirely in one source language. However, program modules and libraries
12023 written in one source language can be used by a main program written in
12024 a different source language. Using @samp{set language auto} in this
12025 case frees you from having to set the working language manually.
12028 @section Displaying the Language
12030 The following commands help you find out which language is the
12031 working language, and also what language source files were written in.
12034 @item show language
12035 @kindex show language
12036 Display the current working language. This is the
12037 language you can use with commands such as @code{print} to
12038 build and compute expressions that may involve variables in your program.
12041 @kindex info frame@r{, show the source language}
12042 Display the source language for this frame. This language becomes the
12043 working language if you use an identifier from this frame.
12044 @xref{Frame Info, ,Information about a Frame}, to identify the other
12045 information listed here.
12048 @kindex info source@r{, show the source language}
12049 Display the source language of this source file.
12050 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12051 information listed here.
12054 In unusual circumstances, you may have source files with extensions
12055 not in the standard list. You can then set the extension associated
12056 with a language explicitly:
12059 @item set extension-language @var{ext} @var{language}
12060 @kindex set extension-language
12061 Tell @value{GDBN} that source files with extension @var{ext} are to be
12062 assumed as written in the source language @var{language}.
12064 @item info extensions
12065 @kindex info extensions
12066 List all the filename extensions and the associated languages.
12070 @section Type and Range Checking
12073 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12074 checking are included, but they do not yet have any effect. This
12075 section documents the intended facilities.
12077 @c FIXME remove warning when type/range code added
12079 Some languages are designed to guard you against making seemingly common
12080 errors through a series of compile- and run-time checks. These include
12081 checking the type of arguments to functions and operators, and making
12082 sure mathematical overflows are caught at run time. Checks such as
12083 these help to ensure a program's correctness once it has been compiled
12084 by eliminating type mismatches, and providing active checks for range
12085 errors when your program is running.
12087 @value{GDBN} can check for conditions like the above if you wish.
12088 Although @value{GDBN} does not check the statements in your program,
12089 it can check expressions entered directly into @value{GDBN} for
12090 evaluation via the @code{print} command, for example. As with the
12091 working language, @value{GDBN} can also decide whether or not to check
12092 automatically based on your program's source language.
12093 @xref{Supported Languages, ,Supported Languages}, for the default
12094 settings of supported languages.
12097 * Type Checking:: An overview of type checking
12098 * Range Checking:: An overview of range checking
12101 @cindex type checking
12102 @cindex checks, type
12103 @node Type Checking
12104 @subsection An Overview of Type Checking
12106 Some languages, such as Modula-2, are strongly typed, meaning that the
12107 arguments to operators and functions have to be of the correct type,
12108 otherwise an error occurs. These checks prevent type mismatch
12109 errors from ever causing any run-time problems. For example,
12117 The second example fails because the @code{CARDINAL} 1 is not
12118 type-compatible with the @code{REAL} 2.3.
12120 For the expressions you use in @value{GDBN} commands, you can tell the
12121 @value{GDBN} type checker to skip checking;
12122 to treat any mismatches as errors and abandon the expression;
12123 or to only issue warnings when type mismatches occur,
12124 but evaluate the expression anyway. When you choose the last of
12125 these, @value{GDBN} evaluates expressions like the second example above, but
12126 also issues a warning.
12128 Even if you turn type checking off, there may be other reasons
12129 related to type that prevent @value{GDBN} from evaluating an expression.
12130 For instance, @value{GDBN} does not know how to add an @code{int} and
12131 a @code{struct foo}. These particular type errors have nothing to do
12132 with the language in use, and usually arise from expressions, such as
12133 the one described above, which make little sense to evaluate anyway.
12135 Each language defines to what degree it is strict about type. For
12136 instance, both Modula-2 and C require the arguments to arithmetical
12137 operators to be numbers. In C, enumerated types and pointers can be
12138 represented as numbers, so that they are valid arguments to mathematical
12139 operators. @xref{Supported Languages, ,Supported Languages}, for further
12140 details on specific languages.
12142 @value{GDBN} provides some additional commands for controlling the type checker:
12144 @kindex set check type
12145 @kindex show check type
12147 @item set check type auto
12148 Set type checking on or off based on the current working language.
12149 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12152 @item set check type on
12153 @itemx set check type off
12154 Set type checking on or off, overriding the default setting for the
12155 current working language. Issue a warning if the setting does not
12156 match the language default. If any type mismatches occur in
12157 evaluating an expression while type checking is on, @value{GDBN} prints a
12158 message and aborts evaluation of the expression.
12160 @item set check type warn
12161 Cause the type checker to issue warnings, but to always attempt to
12162 evaluate the expression. Evaluating the expression may still
12163 be impossible for other reasons. For example, @value{GDBN} cannot add
12164 numbers and structures.
12167 Show the current setting of the type checker, and whether or not @value{GDBN}
12168 is setting it automatically.
12171 @cindex range checking
12172 @cindex checks, range
12173 @node Range Checking
12174 @subsection An Overview of Range Checking
12176 In some languages (such as Modula-2), it is an error to exceed the
12177 bounds of a type; this is enforced with run-time checks. Such range
12178 checking is meant to ensure program correctness by making sure
12179 computations do not overflow, or indices on an array element access do
12180 not exceed the bounds of the array.
12182 For expressions you use in @value{GDBN} commands, you can tell
12183 @value{GDBN} to treat range errors in one of three ways: ignore them,
12184 always treat them as errors and abandon the expression, or issue
12185 warnings but evaluate the expression anyway.
12187 A range error can result from numerical overflow, from exceeding an
12188 array index bound, or when you type a constant that is not a member
12189 of any type. Some languages, however, do not treat overflows as an
12190 error. In many implementations of C, mathematical overflow causes the
12191 result to ``wrap around'' to lower values---for example, if @var{m} is
12192 the largest integer value, and @var{s} is the smallest, then
12195 @var{m} + 1 @result{} @var{s}
12198 This, too, is specific to individual languages, and in some cases
12199 specific to individual compilers or machines. @xref{Supported Languages, ,
12200 Supported Languages}, for further details on specific languages.
12202 @value{GDBN} provides some additional commands for controlling the range checker:
12204 @kindex set check range
12205 @kindex show check range
12207 @item set check range auto
12208 Set range checking on or off based on the current working language.
12209 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12212 @item set check range on
12213 @itemx set check range off
12214 Set range checking on or off, overriding the default setting for the
12215 current working language. A warning is issued if the setting does not
12216 match the language default. If a range error occurs and range checking is on,
12217 then a message is printed and evaluation of the expression is aborted.
12219 @item set check range warn
12220 Output messages when the @value{GDBN} range checker detects a range error,
12221 but attempt to evaluate the expression anyway. Evaluating the
12222 expression may still be impossible for other reasons, such as accessing
12223 memory that the process does not own (a typical example from many Unix
12227 Show the current setting of the range checker, and whether or not it is
12228 being set automatically by @value{GDBN}.
12231 @node Supported Languages
12232 @section Supported Languages
12234 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12235 assembly, Modula-2, and Ada.
12236 @c This is false ...
12237 Some @value{GDBN} features may be used in expressions regardless of the
12238 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12239 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12240 ,Expressions}) can be used with the constructs of any supported
12243 The following sections detail to what degree each source language is
12244 supported by @value{GDBN}. These sections are not meant to be language
12245 tutorials or references, but serve only as a reference guide to what the
12246 @value{GDBN} expression parser accepts, and what input and output
12247 formats should look like for different languages. There are many good
12248 books written on each of these languages; please look to these for a
12249 language reference or tutorial.
12252 * C:: C and C@t{++}
12254 * Objective-C:: Objective-C
12255 * OpenCL C:: OpenCL C
12256 * Fortran:: Fortran
12258 * Modula-2:: Modula-2
12263 @subsection C and C@t{++}
12265 @cindex C and C@t{++}
12266 @cindex expressions in C or C@t{++}
12268 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12269 to both languages. Whenever this is the case, we discuss those languages
12273 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12274 @cindex @sc{gnu} C@t{++}
12275 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12276 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12277 effectively, you must compile your C@t{++} programs with a supported
12278 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12279 compiler (@code{aCC}).
12282 * C Operators:: C and C@t{++} operators
12283 * C Constants:: C and C@t{++} constants
12284 * C Plus Plus Expressions:: C@t{++} expressions
12285 * C Defaults:: Default settings for C and C@t{++}
12286 * C Checks:: C and C@t{++} type and range checks
12287 * Debugging C:: @value{GDBN} and C
12288 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12289 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12293 @subsubsection C and C@t{++} Operators
12295 @cindex C and C@t{++} operators
12297 Operators must be defined on values of specific types. For instance,
12298 @code{+} is defined on numbers, but not on structures. Operators are
12299 often defined on groups of types.
12301 For the purposes of C and C@t{++}, the following definitions hold:
12306 @emph{Integral types} include @code{int} with any of its storage-class
12307 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12310 @emph{Floating-point types} include @code{float}, @code{double}, and
12311 @code{long double} (if supported by the target platform).
12314 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12317 @emph{Scalar types} include all of the above.
12322 The following operators are supported. They are listed here
12323 in order of increasing precedence:
12327 The comma or sequencing operator. Expressions in a comma-separated list
12328 are evaluated from left to right, with the result of the entire
12329 expression being the last expression evaluated.
12332 Assignment. The value of an assignment expression is the value
12333 assigned. Defined on scalar types.
12336 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12337 and translated to @w{@code{@var{a} = @var{a op b}}}.
12338 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12339 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12340 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12343 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12344 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12348 Logical @sc{or}. Defined on integral types.
12351 Logical @sc{and}. Defined on integral types.
12354 Bitwise @sc{or}. Defined on integral types.
12357 Bitwise exclusive-@sc{or}. Defined on integral types.
12360 Bitwise @sc{and}. Defined on integral types.
12363 Equality and inequality. Defined on scalar types. The value of these
12364 expressions is 0 for false and non-zero for true.
12366 @item <@r{, }>@r{, }<=@r{, }>=
12367 Less than, greater than, less than or equal, greater than or equal.
12368 Defined on scalar types. The value of these expressions is 0 for false
12369 and non-zero for true.
12372 left shift, and right shift. Defined on integral types.
12375 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12378 Addition and subtraction. Defined on integral types, floating-point types and
12381 @item *@r{, }/@r{, }%
12382 Multiplication, division, and modulus. Multiplication and division are
12383 defined on integral and floating-point types. Modulus is defined on
12387 Increment and decrement. When appearing before a variable, the
12388 operation is performed before the variable is used in an expression;
12389 when appearing after it, the variable's value is used before the
12390 operation takes place.
12393 Pointer dereferencing. Defined on pointer types. Same precedence as
12397 Address operator. Defined on variables. Same precedence as @code{++}.
12399 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12400 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12401 to examine the address
12402 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12406 Negative. Defined on integral and floating-point types. Same
12407 precedence as @code{++}.
12410 Logical negation. Defined on integral types. Same precedence as
12414 Bitwise complement operator. Defined on integral types. Same precedence as
12419 Structure member, and pointer-to-structure member. For convenience,
12420 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12421 pointer based on the stored type information.
12422 Defined on @code{struct} and @code{union} data.
12425 Dereferences of pointers to members.
12428 Array indexing. @code{@var{a}[@var{i}]} is defined as
12429 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12432 Function parameter list. Same precedence as @code{->}.
12435 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12436 and @code{class} types.
12439 Doubled colons also represent the @value{GDBN} scope operator
12440 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12444 If an operator is redefined in the user code, @value{GDBN} usually
12445 attempts to invoke the redefined version instead of using the operator's
12446 predefined meaning.
12449 @subsubsection C and C@t{++} Constants
12451 @cindex C and C@t{++} constants
12453 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12458 Integer constants are a sequence of digits. Octal constants are
12459 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12460 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12461 @samp{l}, specifying that the constant should be treated as a
12465 Floating point constants are a sequence of digits, followed by a decimal
12466 point, followed by a sequence of digits, and optionally followed by an
12467 exponent. An exponent is of the form:
12468 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12469 sequence of digits. The @samp{+} is optional for positive exponents.
12470 A floating-point constant may also end with a letter @samp{f} or
12471 @samp{F}, specifying that the constant should be treated as being of
12472 the @code{float} (as opposed to the default @code{double}) type; or with
12473 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12477 Enumerated constants consist of enumerated identifiers, or their
12478 integral equivalents.
12481 Character constants are a single character surrounded by single quotes
12482 (@code{'}), or a number---the ordinal value of the corresponding character
12483 (usually its @sc{ascii} value). Within quotes, the single character may
12484 be represented by a letter or by @dfn{escape sequences}, which are of
12485 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12486 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12487 @samp{@var{x}} is a predefined special character---for example,
12488 @samp{\n} for newline.
12490 Wide character constants can be written by prefixing a character
12491 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12492 form of @samp{x}. The target wide character set is used when
12493 computing the value of this constant (@pxref{Character Sets}).
12496 String constants are a sequence of character constants surrounded by
12497 double quotes (@code{"}). Any valid character constant (as described
12498 above) may appear. Double quotes within the string must be preceded by
12499 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12502 Wide string constants can be written by prefixing a string constant
12503 with @samp{L}, as in C. The target wide character set is used when
12504 computing the value of this constant (@pxref{Character Sets}).
12507 Pointer constants are an integral value. You can also write pointers
12508 to constants using the C operator @samp{&}.
12511 Array constants are comma-separated lists surrounded by braces @samp{@{}
12512 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12513 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12514 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12517 @node C Plus Plus Expressions
12518 @subsubsection C@t{++} Expressions
12520 @cindex expressions in C@t{++}
12521 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12523 @cindex debugging C@t{++} programs
12524 @cindex C@t{++} compilers
12525 @cindex debug formats and C@t{++}
12526 @cindex @value{NGCC} and C@t{++}
12528 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12529 the proper compiler and the proper debug format. Currently,
12530 @value{GDBN} works best when debugging C@t{++} code that is compiled
12531 with the most recent version of @value{NGCC} possible. The DWARF
12532 debugging format is preferred; @value{NGCC} defaults to this on most
12533 popular platforms. Other compilers and/or debug formats are likely to
12534 work badly or not at all when using @value{GDBN} to debug C@t{++}
12535 code. @xref{Compilation}.
12540 @cindex member functions
12542 Member function calls are allowed; you can use expressions like
12545 count = aml->GetOriginal(x, y)
12548 @vindex this@r{, inside C@t{++} member functions}
12549 @cindex namespace in C@t{++}
12551 While a member function is active (in the selected stack frame), your
12552 expressions have the same namespace available as the member function;
12553 that is, @value{GDBN} allows implicit references to the class instance
12554 pointer @code{this} following the same rules as C@t{++}. @code{using}
12555 declarations in the current scope are also respected by @value{GDBN}.
12557 @cindex call overloaded functions
12558 @cindex overloaded functions, calling
12559 @cindex type conversions in C@t{++}
12561 You can call overloaded functions; @value{GDBN} resolves the function
12562 call to the right definition, with some restrictions. @value{GDBN} does not
12563 perform overload resolution involving user-defined type conversions,
12564 calls to constructors, or instantiations of templates that do not exist
12565 in the program. It also cannot handle ellipsis argument lists or
12568 It does perform integral conversions and promotions, floating-point
12569 promotions, arithmetic conversions, pointer conversions, conversions of
12570 class objects to base classes, and standard conversions such as those of
12571 functions or arrays to pointers; it requires an exact match on the
12572 number of function arguments.
12574 Overload resolution is always performed, unless you have specified
12575 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12576 ,@value{GDBN} Features for C@t{++}}.
12578 You must specify @code{set overload-resolution off} in order to use an
12579 explicit function signature to call an overloaded function, as in
12581 p 'foo(char,int)'('x', 13)
12584 The @value{GDBN} command-completion facility can simplify this;
12585 see @ref{Completion, ,Command Completion}.
12587 @cindex reference declarations
12589 @value{GDBN} understands variables declared as C@t{++} references; you can use
12590 them in expressions just as you do in C@t{++} source---they are automatically
12593 In the parameter list shown when @value{GDBN} displays a frame, the values of
12594 reference variables are not displayed (unlike other variables); this
12595 avoids clutter, since references are often used for large structures.
12596 The @emph{address} of a reference variable is always shown, unless
12597 you have specified @samp{set print address off}.
12600 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12601 expressions can use it just as expressions in your program do. Since
12602 one scope may be defined in another, you can use @code{::} repeatedly if
12603 necessary, for example in an expression like
12604 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12605 resolving name scope by reference to source files, in both C and C@t{++}
12606 debugging (@pxref{Variables, ,Program Variables}).
12609 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12614 @subsubsection C and C@t{++} Defaults
12616 @cindex C and C@t{++} defaults
12618 If you allow @value{GDBN} to set type and range checking automatically, they
12619 both default to @code{off} whenever the working language changes to
12620 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12621 selects the working language.
12623 If you allow @value{GDBN} to set the language automatically, it
12624 recognizes source files whose names end with @file{.c}, @file{.C}, or
12625 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12626 these files, it sets the working language to C or C@t{++}.
12627 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12628 for further details.
12630 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12631 @c unimplemented. If (b) changes, it might make sense to let this node
12632 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12635 @subsubsection C and C@t{++} Type and Range Checks
12637 @cindex C and C@t{++} checks
12639 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12640 is not used. However, if you turn type checking on, @value{GDBN}
12641 considers two variables type equivalent if:
12645 The two variables are structured and have the same structure, union, or
12649 The two variables have the same type name, or types that have been
12650 declared equivalent through @code{typedef}.
12653 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12656 The two @code{struct}, @code{union}, or @code{enum} variables are
12657 declared in the same declaration. (Note: this may not be true for all C
12662 Range checking, if turned on, is done on mathematical operations. Array
12663 indices are not checked, since they are often used to index a pointer
12664 that is not itself an array.
12667 @subsubsection @value{GDBN} and C
12669 The @code{set print union} and @code{show print union} commands apply to
12670 the @code{union} type. When set to @samp{on}, any @code{union} that is
12671 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12672 appears as @samp{@{...@}}.
12674 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12675 with pointers and a memory allocation function. @xref{Expressions,
12678 @node Debugging C Plus Plus
12679 @subsubsection @value{GDBN} Features for C@t{++}
12681 @cindex commands for C@t{++}
12683 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12684 designed specifically for use with C@t{++}. Here is a summary:
12687 @cindex break in overloaded functions
12688 @item @r{breakpoint menus}
12689 When you want a breakpoint in a function whose name is overloaded,
12690 @value{GDBN} has the capability to display a menu of possible breakpoint
12691 locations to help you specify which function definition you want.
12692 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12694 @cindex overloading in C@t{++}
12695 @item rbreak @var{regex}
12696 Setting breakpoints using regular expressions is helpful for setting
12697 breakpoints on overloaded functions that are not members of any special
12699 @xref{Set Breaks, ,Setting Breakpoints}.
12701 @cindex C@t{++} exception handling
12704 Debug C@t{++} exception handling using these commands. @xref{Set
12705 Catchpoints, , Setting Catchpoints}.
12707 @cindex inheritance
12708 @item ptype @var{typename}
12709 Print inheritance relationships as well as other information for type
12711 @xref{Symbols, ,Examining the Symbol Table}.
12713 @cindex C@t{++} symbol display
12714 @item set print demangle
12715 @itemx show print demangle
12716 @itemx set print asm-demangle
12717 @itemx show print asm-demangle
12718 Control whether C@t{++} symbols display in their source form, both when
12719 displaying code as C@t{++} source and when displaying disassemblies.
12720 @xref{Print Settings, ,Print Settings}.
12722 @item set print object
12723 @itemx show print object
12724 Choose whether to print derived (actual) or declared types of objects.
12725 @xref{Print Settings, ,Print Settings}.
12727 @item set print vtbl
12728 @itemx show print vtbl
12729 Control the format for printing virtual function tables.
12730 @xref{Print Settings, ,Print Settings}.
12731 (The @code{vtbl} commands do not work on programs compiled with the HP
12732 ANSI C@t{++} compiler (@code{aCC}).)
12734 @kindex set overload-resolution
12735 @cindex overloaded functions, overload resolution
12736 @item set overload-resolution on
12737 Enable overload resolution for C@t{++} expression evaluation. The default
12738 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12739 and searches for a function whose signature matches the argument types,
12740 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12741 Expressions, ,C@t{++} Expressions}, for details).
12742 If it cannot find a match, it emits a message.
12744 @item set overload-resolution off
12745 Disable overload resolution for C@t{++} expression evaluation. For
12746 overloaded functions that are not class member functions, @value{GDBN}
12747 chooses the first function of the specified name that it finds in the
12748 symbol table, whether or not its arguments are of the correct type. For
12749 overloaded functions that are class member functions, @value{GDBN}
12750 searches for a function whose signature @emph{exactly} matches the
12753 @kindex show overload-resolution
12754 @item show overload-resolution
12755 Show the current setting of overload resolution.
12757 @item @r{Overloaded symbol names}
12758 You can specify a particular definition of an overloaded symbol, using
12759 the same notation that is used to declare such symbols in C@t{++}: type
12760 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12761 also use the @value{GDBN} command-line word completion facilities to list the
12762 available choices, or to finish the type list for you.
12763 @xref{Completion,, Command Completion}, for details on how to do this.
12766 @node Decimal Floating Point
12767 @subsubsection Decimal Floating Point format
12768 @cindex decimal floating point format
12770 @value{GDBN} can examine, set and perform computations with numbers in
12771 decimal floating point format, which in the C language correspond to the
12772 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12773 specified by the extension to support decimal floating-point arithmetic.
12775 There are two encodings in use, depending on the architecture: BID (Binary
12776 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12777 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12780 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12781 to manipulate decimal floating point numbers, it is not possible to convert
12782 (using a cast, for example) integers wider than 32-bit to decimal float.
12784 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12785 point computations, error checking in decimal float operations ignores
12786 underflow, overflow and divide by zero exceptions.
12788 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12789 to inspect @code{_Decimal128} values stored in floating point registers.
12790 See @ref{PowerPC,,PowerPC} for more details.
12796 @value{GDBN} can be used to debug programs written in D and compiled with
12797 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12798 specific feature --- dynamic arrays.
12801 @subsection Objective-C
12803 @cindex Objective-C
12804 This section provides information about some commands and command
12805 options that are useful for debugging Objective-C code. See also
12806 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12807 few more commands specific to Objective-C support.
12810 * Method Names in Commands::
12811 * The Print Command with Objective-C::
12814 @node Method Names in Commands
12815 @subsubsection Method Names in Commands
12817 The following commands have been extended to accept Objective-C method
12818 names as line specifications:
12820 @kindex clear@r{, and Objective-C}
12821 @kindex break@r{, and Objective-C}
12822 @kindex info line@r{, and Objective-C}
12823 @kindex jump@r{, and Objective-C}
12824 @kindex list@r{, and Objective-C}
12828 @item @code{info line}
12833 A fully qualified Objective-C method name is specified as
12836 -[@var{Class} @var{methodName}]
12839 where the minus sign is used to indicate an instance method and a
12840 plus sign (not shown) is used to indicate a class method. The class
12841 name @var{Class} and method name @var{methodName} are enclosed in
12842 brackets, similar to the way messages are specified in Objective-C
12843 source code. For example, to set a breakpoint at the @code{create}
12844 instance method of class @code{Fruit} in the program currently being
12848 break -[Fruit create]
12851 To list ten program lines around the @code{initialize} class method,
12855 list +[NSText initialize]
12858 In the current version of @value{GDBN}, the plus or minus sign is
12859 required. In future versions of @value{GDBN}, the plus or minus
12860 sign will be optional, but you can use it to narrow the search. It
12861 is also possible to specify just a method name:
12867 You must specify the complete method name, including any colons. If
12868 your program's source files contain more than one @code{create} method,
12869 you'll be presented with a numbered list of classes that implement that
12870 method. Indicate your choice by number, or type @samp{0} to exit if
12873 As another example, to clear a breakpoint established at the
12874 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12877 clear -[NSWindow makeKeyAndOrderFront:]
12880 @node The Print Command with Objective-C
12881 @subsubsection The Print Command With Objective-C
12882 @cindex Objective-C, print objects
12883 @kindex print-object
12884 @kindex po @r{(@code{print-object})}
12886 The print command has also been extended to accept methods. For example:
12889 print -[@var{object} hash]
12892 @cindex print an Objective-C object description
12893 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12895 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12896 and print the result. Also, an additional command has been added,
12897 @code{print-object} or @code{po} for short, which is meant to print
12898 the description of an object. However, this command may only work
12899 with certain Objective-C libraries that have a particular hook
12900 function, @code{_NSPrintForDebugger}, defined.
12903 @subsection OpenCL C
12906 This section provides information about @value{GDBN}s OpenCL C support.
12909 * OpenCL C Datatypes::
12910 * OpenCL C Expressions::
12911 * OpenCL C Operators::
12914 @node OpenCL C Datatypes
12915 @subsubsection OpenCL C Datatypes
12917 @cindex OpenCL C Datatypes
12918 @value{GDBN} supports the builtin scalar and vector datatypes specified
12919 by OpenCL 1.1. In addition the half- and double-precision floating point
12920 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12921 extensions are also known to @value{GDBN}.
12923 @node OpenCL C Expressions
12924 @subsubsection OpenCL C Expressions
12926 @cindex OpenCL C Expressions
12927 @value{GDBN} supports accesses to vector components including the access as
12928 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12929 supported by @value{GDBN} can be used as well.
12931 @node OpenCL C Operators
12932 @subsubsection OpenCL C Operators
12934 @cindex OpenCL C Operators
12935 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12939 @subsection Fortran
12940 @cindex Fortran-specific support in @value{GDBN}
12942 @value{GDBN} can be used to debug programs written in Fortran, but it
12943 currently supports only the features of Fortran 77 language.
12945 @cindex trailing underscore, in Fortran symbols
12946 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12947 among them) append an underscore to the names of variables and
12948 functions. When you debug programs compiled by those compilers, you
12949 will need to refer to variables and functions with a trailing
12953 * Fortran Operators:: Fortran operators and expressions
12954 * Fortran Defaults:: Default settings for Fortran
12955 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12958 @node Fortran Operators
12959 @subsubsection Fortran Operators and Expressions
12961 @cindex Fortran operators and expressions
12963 Operators must be defined on values of specific types. For instance,
12964 @code{+} is defined on numbers, but not on characters or other non-
12965 arithmetic types. Operators are often defined on groups of types.
12969 The exponentiation operator. It raises the first operand to the power
12973 The range operator. Normally used in the form of array(low:high) to
12974 represent a section of array.
12977 The access component operator. Normally used to access elements in derived
12978 types. Also suitable for unions. As unions aren't part of regular Fortran,
12979 this can only happen when accessing a register that uses a gdbarch-defined
12983 @node Fortran Defaults
12984 @subsubsection Fortran Defaults
12986 @cindex Fortran Defaults
12988 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12989 default uses case-insensitive matches for Fortran symbols. You can
12990 change that with the @samp{set case-insensitive} command, see
12991 @ref{Symbols}, for the details.
12993 @node Special Fortran Commands
12994 @subsubsection Special Fortran Commands
12996 @cindex Special Fortran commands
12998 @value{GDBN} has some commands to support Fortran-specific features,
12999 such as displaying common blocks.
13002 @cindex @code{COMMON} blocks, Fortran
13003 @kindex info common
13004 @item info common @r{[}@var{common-name}@r{]}
13005 This command prints the values contained in the Fortran @code{COMMON}
13006 block whose name is @var{common-name}. With no argument, the names of
13007 all @code{COMMON} blocks visible at the current program location are
13014 @cindex Pascal support in @value{GDBN}, limitations
13015 Debugging Pascal programs which use sets, subranges, file variables, or
13016 nested functions does not currently work. @value{GDBN} does not support
13017 entering expressions, printing values, or similar features using Pascal
13020 The Pascal-specific command @code{set print pascal_static-members}
13021 controls whether static members of Pascal objects are displayed.
13022 @xref{Print Settings, pascal_static-members}.
13025 @subsection Modula-2
13027 @cindex Modula-2, @value{GDBN} support
13029 The extensions made to @value{GDBN} to support Modula-2 only support
13030 output from the @sc{gnu} Modula-2 compiler (which is currently being
13031 developed). Other Modula-2 compilers are not currently supported, and
13032 attempting to debug executables produced by them is most likely
13033 to give an error as @value{GDBN} reads in the executable's symbol
13036 @cindex expressions in Modula-2
13038 * M2 Operators:: Built-in operators
13039 * Built-In Func/Proc:: Built-in functions and procedures
13040 * M2 Constants:: Modula-2 constants
13041 * M2 Types:: Modula-2 types
13042 * M2 Defaults:: Default settings for Modula-2
13043 * Deviations:: Deviations from standard Modula-2
13044 * M2 Checks:: Modula-2 type and range checks
13045 * M2 Scope:: The scope operators @code{::} and @code{.}
13046 * GDB/M2:: @value{GDBN} and Modula-2
13050 @subsubsection Operators
13051 @cindex Modula-2 operators
13053 Operators must be defined on values of specific types. For instance,
13054 @code{+} is defined on numbers, but not on structures. Operators are
13055 often defined on groups of types. For the purposes of Modula-2, the
13056 following definitions hold:
13061 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13065 @emph{Character types} consist of @code{CHAR} and its subranges.
13068 @emph{Floating-point types} consist of @code{REAL}.
13071 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13075 @emph{Scalar types} consist of all of the above.
13078 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13081 @emph{Boolean types} consist of @code{BOOLEAN}.
13085 The following operators are supported, and appear in order of
13086 increasing precedence:
13090 Function argument or array index separator.
13093 Assignment. The value of @var{var} @code{:=} @var{value} is
13097 Less than, greater than on integral, floating-point, or enumerated
13101 Less than or equal to, greater than or equal to
13102 on integral, floating-point and enumerated types, or set inclusion on
13103 set types. Same precedence as @code{<}.
13105 @item =@r{, }<>@r{, }#
13106 Equality and two ways of expressing inequality, valid on scalar types.
13107 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13108 available for inequality, since @code{#} conflicts with the script
13112 Set membership. Defined on set types and the types of their members.
13113 Same precedence as @code{<}.
13116 Boolean disjunction. Defined on boolean types.
13119 Boolean conjunction. Defined on boolean types.
13122 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13125 Addition and subtraction on integral and floating-point types, or union
13126 and difference on set types.
13129 Multiplication on integral and floating-point types, or set intersection
13133 Division on floating-point types, or symmetric set difference on set
13134 types. Same precedence as @code{*}.
13137 Integer division and remainder. Defined on integral types. Same
13138 precedence as @code{*}.
13141 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13144 Pointer dereferencing. Defined on pointer types.
13147 Boolean negation. Defined on boolean types. Same precedence as
13151 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13152 precedence as @code{^}.
13155 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13158 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13162 @value{GDBN} and Modula-2 scope operators.
13166 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13167 treats the use of the operator @code{IN}, or the use of operators
13168 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13169 @code{<=}, and @code{>=} on sets as an error.
13173 @node Built-In Func/Proc
13174 @subsubsection Built-in Functions and Procedures
13175 @cindex Modula-2 built-ins
13177 Modula-2 also makes available several built-in procedures and functions.
13178 In describing these, the following metavariables are used:
13183 represents an @code{ARRAY} variable.
13186 represents a @code{CHAR} constant or variable.
13189 represents a variable or constant of integral type.
13192 represents an identifier that belongs to a set. Generally used in the
13193 same function with the metavariable @var{s}. The type of @var{s} should
13194 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13197 represents a variable or constant of integral or floating-point type.
13200 represents a variable or constant of floating-point type.
13206 represents a variable.
13209 represents a variable or constant of one of many types. See the
13210 explanation of the function for details.
13213 All Modula-2 built-in procedures also return a result, described below.
13217 Returns the absolute value of @var{n}.
13220 If @var{c} is a lower case letter, it returns its upper case
13221 equivalent, otherwise it returns its argument.
13224 Returns the character whose ordinal value is @var{i}.
13227 Decrements the value in the variable @var{v} by one. Returns the new value.
13229 @item DEC(@var{v},@var{i})
13230 Decrements the value in the variable @var{v} by @var{i}. Returns the
13233 @item EXCL(@var{m},@var{s})
13234 Removes the element @var{m} from the set @var{s}. Returns the new
13237 @item FLOAT(@var{i})
13238 Returns the floating point equivalent of the integer @var{i}.
13240 @item HIGH(@var{a})
13241 Returns the index of the last member of @var{a}.
13244 Increments the value in the variable @var{v} by one. Returns the new value.
13246 @item INC(@var{v},@var{i})
13247 Increments the value in the variable @var{v} by @var{i}. Returns the
13250 @item INCL(@var{m},@var{s})
13251 Adds the element @var{m} to the set @var{s} if it is not already
13252 there. Returns the new set.
13255 Returns the maximum value of the type @var{t}.
13258 Returns the minimum value of the type @var{t}.
13261 Returns boolean TRUE if @var{i} is an odd number.
13264 Returns the ordinal value of its argument. For example, the ordinal
13265 value of a character is its @sc{ascii} value (on machines supporting the
13266 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13267 integral, character and enumerated types.
13269 @item SIZE(@var{x})
13270 Returns the size of its argument. @var{x} can be a variable or a type.
13272 @item TRUNC(@var{r})
13273 Returns the integral part of @var{r}.
13275 @item TSIZE(@var{x})
13276 Returns the size of its argument. @var{x} can be a variable or a type.
13278 @item VAL(@var{t},@var{i})
13279 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13283 @emph{Warning:} Sets and their operations are not yet supported, so
13284 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13288 @cindex Modula-2 constants
13290 @subsubsection Constants
13292 @value{GDBN} allows you to express the constants of Modula-2 in the following
13298 Integer constants are simply a sequence of digits. When used in an
13299 expression, a constant is interpreted to be type-compatible with the
13300 rest of the expression. Hexadecimal integers are specified by a
13301 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13304 Floating point constants appear as a sequence of digits, followed by a
13305 decimal point and another sequence of digits. An optional exponent can
13306 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13307 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13308 digits of the floating point constant must be valid decimal (base 10)
13312 Character constants consist of a single character enclosed by a pair of
13313 like quotes, either single (@code{'}) or double (@code{"}). They may
13314 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13315 followed by a @samp{C}.
13318 String constants consist of a sequence of characters enclosed by a
13319 pair of like quotes, either single (@code{'}) or double (@code{"}).
13320 Escape sequences in the style of C are also allowed. @xref{C
13321 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13325 Enumerated constants consist of an enumerated identifier.
13328 Boolean constants consist of the identifiers @code{TRUE} and
13332 Pointer constants consist of integral values only.
13335 Set constants are not yet supported.
13339 @subsubsection Modula-2 Types
13340 @cindex Modula-2 types
13342 Currently @value{GDBN} can print the following data types in Modula-2
13343 syntax: array types, record types, set types, pointer types, procedure
13344 types, enumerated types, subrange types and base types. You can also
13345 print the contents of variables declared using these type.
13346 This section gives a number of simple source code examples together with
13347 sample @value{GDBN} sessions.
13349 The first example contains the following section of code:
13358 and you can request @value{GDBN} to interrogate the type and value of
13359 @code{r} and @code{s}.
13362 (@value{GDBP}) print s
13364 (@value{GDBP}) ptype s
13366 (@value{GDBP}) print r
13368 (@value{GDBP}) ptype r
13373 Likewise if your source code declares @code{s} as:
13377 s: SET ['A'..'Z'] ;
13381 then you may query the type of @code{s} by:
13384 (@value{GDBP}) ptype s
13385 type = SET ['A'..'Z']
13389 Note that at present you cannot interactively manipulate set
13390 expressions using the debugger.
13392 The following example shows how you might declare an array in Modula-2
13393 and how you can interact with @value{GDBN} to print its type and contents:
13397 s: ARRAY [-10..10] OF CHAR ;
13401 (@value{GDBP}) ptype s
13402 ARRAY [-10..10] OF CHAR
13405 Note that the array handling is not yet complete and although the type
13406 is printed correctly, expression handling still assumes that all
13407 arrays have a lower bound of zero and not @code{-10} as in the example
13410 Here are some more type related Modula-2 examples:
13414 colour = (blue, red, yellow, green) ;
13415 t = [blue..yellow] ;
13423 The @value{GDBN} interaction shows how you can query the data type
13424 and value of a variable.
13427 (@value{GDBP}) print s
13429 (@value{GDBP}) ptype t
13430 type = [blue..yellow]
13434 In this example a Modula-2 array is declared and its contents
13435 displayed. Observe that the contents are written in the same way as
13436 their @code{C} counterparts.
13440 s: ARRAY [1..5] OF CARDINAL ;
13446 (@value{GDBP}) print s
13447 $1 = @{1, 0, 0, 0, 0@}
13448 (@value{GDBP}) ptype s
13449 type = ARRAY [1..5] OF CARDINAL
13452 The Modula-2 language interface to @value{GDBN} also understands
13453 pointer types as shown in this example:
13457 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13464 and you can request that @value{GDBN} describes the type of @code{s}.
13467 (@value{GDBP}) ptype s
13468 type = POINTER TO ARRAY [1..5] OF CARDINAL
13471 @value{GDBN} handles compound types as we can see in this example.
13472 Here we combine array types, record types, pointer types and subrange
13483 myarray = ARRAY myrange OF CARDINAL ;
13484 myrange = [-2..2] ;
13486 s: POINTER TO ARRAY myrange OF foo ;
13490 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13494 (@value{GDBP}) ptype s
13495 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13498 f3 : ARRAY [-2..2] OF CARDINAL;
13503 @subsubsection Modula-2 Defaults
13504 @cindex Modula-2 defaults
13506 If type and range checking are set automatically by @value{GDBN}, they
13507 both default to @code{on} whenever the working language changes to
13508 Modula-2. This happens regardless of whether you or @value{GDBN}
13509 selected the working language.
13511 If you allow @value{GDBN} to set the language automatically, then entering
13512 code compiled from a file whose name ends with @file{.mod} sets the
13513 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13514 Infer the Source Language}, for further details.
13517 @subsubsection Deviations from Standard Modula-2
13518 @cindex Modula-2, deviations from
13520 A few changes have been made to make Modula-2 programs easier to debug.
13521 This is done primarily via loosening its type strictness:
13525 Unlike in standard Modula-2, pointer constants can be formed by
13526 integers. This allows you to modify pointer variables during
13527 debugging. (In standard Modula-2, the actual address contained in a
13528 pointer variable is hidden from you; it can only be modified
13529 through direct assignment to another pointer variable or expression that
13530 returned a pointer.)
13533 C escape sequences can be used in strings and characters to represent
13534 non-printable characters. @value{GDBN} prints out strings with these
13535 escape sequences embedded. Single non-printable characters are
13536 printed using the @samp{CHR(@var{nnn})} format.
13539 The assignment operator (@code{:=}) returns the value of its right-hand
13543 All built-in procedures both modify @emph{and} return their argument.
13547 @subsubsection Modula-2 Type and Range Checks
13548 @cindex Modula-2 checks
13551 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13554 @c FIXME remove warning when type/range checks added
13556 @value{GDBN} considers two Modula-2 variables type equivalent if:
13560 They are of types that have been declared equivalent via a @code{TYPE
13561 @var{t1} = @var{t2}} statement
13564 They have been declared on the same line. (Note: This is true of the
13565 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13568 As long as type checking is enabled, any attempt to combine variables
13569 whose types are not equivalent is an error.
13571 Range checking is done on all mathematical operations, assignment, array
13572 index bounds, and all built-in functions and procedures.
13575 @subsubsection The Scope Operators @code{::} and @code{.}
13577 @cindex @code{.}, Modula-2 scope operator
13578 @cindex colon, doubled as scope operator
13580 @vindex colon-colon@r{, in Modula-2}
13581 @c Info cannot handle :: but TeX can.
13584 @vindex ::@r{, in Modula-2}
13587 There are a few subtle differences between the Modula-2 scope operator
13588 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13593 @var{module} . @var{id}
13594 @var{scope} :: @var{id}
13598 where @var{scope} is the name of a module or a procedure,
13599 @var{module} the name of a module, and @var{id} is any declared
13600 identifier within your program, except another module.
13602 Using the @code{::} operator makes @value{GDBN} search the scope
13603 specified by @var{scope} for the identifier @var{id}. If it is not
13604 found in the specified scope, then @value{GDBN} searches all scopes
13605 enclosing the one specified by @var{scope}.
13607 Using the @code{.} operator makes @value{GDBN} search the current scope for
13608 the identifier specified by @var{id} that was imported from the
13609 definition module specified by @var{module}. With this operator, it is
13610 an error if the identifier @var{id} was not imported from definition
13611 module @var{module}, or if @var{id} is not an identifier in
13615 @subsubsection @value{GDBN} and Modula-2
13617 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13618 Five subcommands of @code{set print} and @code{show print} apply
13619 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13620 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13621 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13622 analogue in Modula-2.
13624 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13625 with any language, is not useful with Modula-2. Its
13626 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13627 created in Modula-2 as they can in C or C@t{++}. However, because an
13628 address can be specified by an integral constant, the construct
13629 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13631 @cindex @code{#} in Modula-2
13632 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13633 interpreted as the beginning of a comment. Use @code{<>} instead.
13639 The extensions made to @value{GDBN} for Ada only support
13640 output from the @sc{gnu} Ada (GNAT) compiler.
13641 Other Ada compilers are not currently supported, and
13642 attempting to debug executables produced by them is most likely
13646 @cindex expressions in Ada
13648 * Ada Mode Intro:: General remarks on the Ada syntax
13649 and semantics supported by Ada mode
13651 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13652 * Additions to Ada:: Extensions of the Ada expression syntax.
13653 * Stopping Before Main Program:: Debugging the program during elaboration.
13654 * Ada Tasks:: Listing and setting breakpoints in tasks.
13655 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13656 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13658 * Ada Glitches:: Known peculiarities of Ada mode.
13661 @node Ada Mode Intro
13662 @subsubsection Introduction
13663 @cindex Ada mode, general
13665 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13666 syntax, with some extensions.
13667 The philosophy behind the design of this subset is
13671 That @value{GDBN} should provide basic literals and access to operations for
13672 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13673 leaving more sophisticated computations to subprograms written into the
13674 program (which therefore may be called from @value{GDBN}).
13677 That type safety and strict adherence to Ada language restrictions
13678 are not particularly important to the @value{GDBN} user.
13681 That brevity is important to the @value{GDBN} user.
13684 Thus, for brevity, the debugger acts as if all names declared in
13685 user-written packages are directly visible, even if they are not visible
13686 according to Ada rules, thus making it unnecessary to fully qualify most
13687 names with their packages, regardless of context. Where this causes
13688 ambiguity, @value{GDBN} asks the user's intent.
13690 The debugger will start in Ada mode if it detects an Ada main program.
13691 As for other languages, it will enter Ada mode when stopped in a program that
13692 was translated from an Ada source file.
13694 While in Ada mode, you may use `@t{--}' for comments. This is useful
13695 mostly for documenting command files. The standard @value{GDBN} comment
13696 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13697 middle (to allow based literals).
13699 The debugger supports limited overloading. Given a subprogram call in which
13700 the function symbol has multiple definitions, it will use the number of
13701 actual parameters and some information about their types to attempt to narrow
13702 the set of definitions. It also makes very limited use of context, preferring
13703 procedures to functions in the context of the @code{call} command, and
13704 functions to procedures elsewhere.
13706 @node Omissions from Ada
13707 @subsubsection Omissions from Ada
13708 @cindex Ada, omissions from
13710 Here are the notable omissions from the subset:
13714 Only a subset of the attributes are supported:
13718 @t{'First}, @t{'Last}, and @t{'Length}
13719 on array objects (not on types and subtypes).
13722 @t{'Min} and @t{'Max}.
13725 @t{'Pos} and @t{'Val}.
13731 @t{'Range} on array objects (not subtypes), but only as the right
13732 operand of the membership (@code{in}) operator.
13735 @t{'Access}, @t{'Unchecked_Access}, and
13736 @t{'Unrestricted_Access} (a GNAT extension).
13744 @code{Characters.Latin_1} are not available and
13745 concatenation is not implemented. Thus, escape characters in strings are
13746 not currently available.
13749 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13750 equality of representations. They will generally work correctly
13751 for strings and arrays whose elements have integer or enumeration types.
13752 They may not work correctly for arrays whose element
13753 types have user-defined equality, for arrays of real values
13754 (in particular, IEEE-conformant floating point, because of negative
13755 zeroes and NaNs), and for arrays whose elements contain unused bits with
13756 indeterminate values.
13759 The other component-by-component array operations (@code{and}, @code{or},
13760 @code{xor}, @code{not}, and relational tests other than equality)
13761 are not implemented.
13764 @cindex array aggregates (Ada)
13765 @cindex record aggregates (Ada)
13766 @cindex aggregates (Ada)
13767 There is limited support for array and record aggregates. They are
13768 permitted only on the right sides of assignments, as in these examples:
13771 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13772 (@value{GDBP}) set An_Array := (1, others => 0)
13773 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13774 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13775 (@value{GDBP}) set A_Record := (1, "Peter", True);
13776 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13780 discriminant's value by assigning an aggregate has an
13781 undefined effect if that discriminant is used within the record.
13782 However, you can first modify discriminants by directly assigning to
13783 them (which normally would not be allowed in Ada), and then performing an
13784 aggregate assignment. For example, given a variable @code{A_Rec}
13785 declared to have a type such as:
13788 type Rec (Len : Small_Integer := 0) is record
13790 Vals : IntArray (1 .. Len);
13794 you can assign a value with a different size of @code{Vals} with two
13798 (@value{GDBP}) set A_Rec.Len := 4
13799 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13802 As this example also illustrates, @value{GDBN} is very loose about the usual
13803 rules concerning aggregates. You may leave out some of the
13804 components of an array or record aggregate (such as the @code{Len}
13805 component in the assignment to @code{A_Rec} above); they will retain their
13806 original values upon assignment. You may freely use dynamic values as
13807 indices in component associations. You may even use overlapping or
13808 redundant component associations, although which component values are
13809 assigned in such cases is not defined.
13812 Calls to dispatching subprograms are not implemented.
13815 The overloading algorithm is much more limited (i.e., less selective)
13816 than that of real Ada. It makes only limited use of the context in
13817 which a subexpression appears to resolve its meaning, and it is much
13818 looser in its rules for allowing type matches. As a result, some
13819 function calls will be ambiguous, and the user will be asked to choose
13820 the proper resolution.
13823 The @code{new} operator is not implemented.
13826 Entry calls are not implemented.
13829 Aside from printing, arithmetic operations on the native VAX floating-point
13830 formats are not supported.
13833 It is not possible to slice a packed array.
13836 The names @code{True} and @code{False}, when not part of a qualified name,
13837 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13839 Should your program
13840 redefine these names in a package or procedure (at best a dubious practice),
13841 you will have to use fully qualified names to access their new definitions.
13844 @node Additions to Ada
13845 @subsubsection Additions to Ada
13846 @cindex Ada, deviations from
13848 As it does for other languages, @value{GDBN} makes certain generic
13849 extensions to Ada (@pxref{Expressions}):
13853 If the expression @var{E} is a variable residing in memory (typically
13854 a local variable or array element) and @var{N} is a positive integer,
13855 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13856 @var{N}-1 adjacent variables following it in memory as an array. In
13857 Ada, this operator is generally not necessary, since its prime use is
13858 in displaying parts of an array, and slicing will usually do this in
13859 Ada. However, there are occasional uses when debugging programs in
13860 which certain debugging information has been optimized away.
13863 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13864 appears in function or file @var{B}.'' When @var{B} is a file name,
13865 you must typically surround it in single quotes.
13868 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13869 @var{type} that appears at address @var{addr}.''
13872 A name starting with @samp{$} is a convenience variable
13873 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13876 In addition, @value{GDBN} provides a few other shortcuts and outright
13877 additions specific to Ada:
13881 The assignment statement is allowed as an expression, returning
13882 its right-hand operand as its value. Thus, you may enter
13885 (@value{GDBP}) set x := y + 3
13886 (@value{GDBP}) print A(tmp := y + 1)
13890 The semicolon is allowed as an ``operator,'' returning as its value
13891 the value of its right-hand operand.
13892 This allows, for example,
13893 complex conditional breaks:
13896 (@value{GDBP}) break f
13897 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13901 Rather than use catenation and symbolic character names to introduce special
13902 characters into strings, one may instead use a special bracket notation,
13903 which is also used to print strings. A sequence of characters of the form
13904 @samp{["@var{XX}"]} within a string or character literal denotes the
13905 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13906 sequence of characters @samp{["""]} also denotes a single quotation mark
13907 in strings. For example,
13909 "One line.["0a"]Next line.["0a"]"
13912 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13916 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13917 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13921 (@value{GDBP}) print 'max(x, y)
13925 When printing arrays, @value{GDBN} uses positional notation when the
13926 array has a lower bound of 1, and uses a modified named notation otherwise.
13927 For example, a one-dimensional array of three integers with a lower bound
13928 of 3 might print as
13935 That is, in contrast to valid Ada, only the first component has a @code{=>}
13939 You may abbreviate attributes in expressions with any unique,
13940 multi-character subsequence of
13941 their names (an exact match gets preference).
13942 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13943 in place of @t{a'length}.
13946 @cindex quoting Ada internal identifiers
13947 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13948 to lower case. The GNAT compiler uses upper-case characters for
13949 some of its internal identifiers, which are normally of no interest to users.
13950 For the rare occasions when you actually have to look at them,
13951 enclose them in angle brackets to avoid the lower-case mapping.
13954 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13958 Printing an object of class-wide type or dereferencing an
13959 access-to-class-wide value will display all the components of the object's
13960 specific type (as indicated by its run-time tag). Likewise, component
13961 selection on such a value will operate on the specific type of the
13966 @node Stopping Before Main Program
13967 @subsubsection Stopping at the Very Beginning
13969 @cindex breakpointing Ada elaboration code
13970 It is sometimes necessary to debug the program during elaboration, and
13971 before reaching the main procedure.
13972 As defined in the Ada Reference
13973 Manual, the elaboration code is invoked from a procedure called
13974 @code{adainit}. To run your program up to the beginning of
13975 elaboration, simply use the following two commands:
13976 @code{tbreak adainit} and @code{run}.
13979 @subsubsection Extensions for Ada Tasks
13980 @cindex Ada, tasking
13982 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13983 @value{GDBN} provides the following task-related commands:
13988 This command shows a list of current Ada tasks, as in the following example:
13995 (@value{GDBP}) info tasks
13996 ID TID P-ID Pri State Name
13997 1 8088000 0 15 Child Activation Wait main_task
13998 2 80a4000 1 15 Accept Statement b
13999 3 809a800 1 15 Child Activation Wait a
14000 * 4 80ae800 3 15 Runnable c
14005 In this listing, the asterisk before the last task indicates it to be the
14006 task currently being inspected.
14010 Represents @value{GDBN}'s internal task number.
14016 The parent's task ID (@value{GDBN}'s internal task number).
14019 The base priority of the task.
14022 Current state of the task.
14026 The task has been created but has not been activated. It cannot be
14030 The task is not blocked for any reason known to Ada. (It may be waiting
14031 for a mutex, though.) It is conceptually "executing" in normal mode.
14034 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14035 that were waiting on terminate alternatives have been awakened and have
14036 terminated themselves.
14038 @item Child Activation Wait
14039 The task is waiting for created tasks to complete activation.
14041 @item Accept Statement
14042 The task is waiting on an accept or selective wait statement.
14044 @item Waiting on entry call
14045 The task is waiting on an entry call.
14047 @item Async Select Wait
14048 The task is waiting to start the abortable part of an asynchronous
14052 The task is waiting on a select statement with only a delay
14055 @item Child Termination Wait
14056 The task is sleeping having completed a master within itself, and is
14057 waiting for the tasks dependent on that master to become terminated or
14058 waiting on a terminate Phase.
14060 @item Wait Child in Term Alt
14061 The task is sleeping waiting for tasks on terminate alternatives to
14062 finish terminating.
14064 @item Accepting RV with @var{taskno}
14065 The task is accepting a rendez-vous with the task @var{taskno}.
14069 Name of the task in the program.
14073 @kindex info task @var{taskno}
14074 @item info task @var{taskno}
14075 This command shows detailled informations on the specified task, as in
14076 the following example:
14081 (@value{GDBP}) info tasks
14082 ID TID P-ID Pri State Name
14083 1 8077880 0 15 Child Activation Wait main_task
14084 * 2 807c468 1 15 Runnable task_1
14085 (@value{GDBP}) info task 2
14086 Ada Task: 0x807c468
14089 Parent: 1 (main_task)
14095 @kindex task@r{ (Ada)}
14096 @cindex current Ada task ID
14097 This command prints the ID of the current task.
14103 (@value{GDBP}) info tasks
14104 ID TID P-ID Pri State Name
14105 1 8077870 0 15 Child Activation Wait main_task
14106 * 2 807c458 1 15 Runnable t
14107 (@value{GDBP}) task
14108 [Current task is 2]
14111 @item task @var{taskno}
14112 @cindex Ada task switching
14113 This command is like the @code{thread @var{threadno}}
14114 command (@pxref{Threads}). It switches the context of debugging
14115 from the current task to the given task.
14121 (@value{GDBP}) info tasks
14122 ID TID P-ID Pri State Name
14123 1 8077870 0 15 Child Activation Wait main_task
14124 * 2 807c458 1 15 Runnable t
14125 (@value{GDBP}) task 1
14126 [Switching to task 1]
14127 #0 0x8067726 in pthread_cond_wait ()
14129 #0 0x8067726 in pthread_cond_wait ()
14130 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14131 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14132 #3 0x806153e in system.tasking.stages.activate_tasks ()
14133 #4 0x804aacc in un () at un.adb:5
14136 @item break @var{linespec} task @var{taskno}
14137 @itemx break @var{linespec} task @var{taskno} if @dots{}
14138 @cindex breakpoints and tasks, in Ada
14139 @cindex task breakpoints, in Ada
14140 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14141 These commands are like the @code{break @dots{} thread @dots{}}
14142 command (@pxref{Thread Stops}).
14143 @var{linespec} specifies source lines, as described
14144 in @ref{Specify Location}.
14146 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14147 to specify that you only want @value{GDBN} to stop the program when a
14148 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14149 numeric task identifiers assigned by @value{GDBN}, shown in the first
14150 column of the @samp{info tasks} display.
14152 If you do not specify @samp{task @var{taskno}} when you set a
14153 breakpoint, the breakpoint applies to @emph{all} tasks of your
14156 You can use the @code{task} qualifier on conditional breakpoints as
14157 well; in this case, place @samp{task @var{taskno}} before the
14158 breakpoint condition (before the @code{if}).
14166 (@value{GDBP}) info tasks
14167 ID TID P-ID Pri State Name
14168 1 140022020 0 15 Child Activation Wait main_task
14169 2 140045060 1 15 Accept/Select Wait t2
14170 3 140044840 1 15 Runnable t1
14171 * 4 140056040 1 15 Runnable t3
14172 (@value{GDBP}) b 15 task 2
14173 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14174 (@value{GDBP}) cont
14179 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14181 (@value{GDBP}) info tasks
14182 ID TID P-ID Pri State Name
14183 1 140022020 0 15 Child Activation Wait main_task
14184 * 2 140045060 1 15 Runnable t2
14185 3 140044840 1 15 Runnable t1
14186 4 140056040 1 15 Delay Sleep t3
14190 @node Ada Tasks and Core Files
14191 @subsubsection Tasking Support when Debugging Core Files
14192 @cindex Ada tasking and core file debugging
14194 When inspecting a core file, as opposed to debugging a live program,
14195 tasking support may be limited or even unavailable, depending on
14196 the platform being used.
14197 For instance, on x86-linux, the list of tasks is available, but task
14198 switching is not supported. On Tru64, however, task switching will work
14201 On certain platforms, including Tru64, the debugger needs to perform some
14202 memory writes in order to provide Ada tasking support. When inspecting
14203 a core file, this means that the core file must be opened with read-write
14204 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14205 Under these circumstances, you should make a backup copy of the core
14206 file before inspecting it with @value{GDBN}.
14208 @node Ravenscar Profile
14209 @subsubsection Tasking Support when using the Ravenscar Profile
14210 @cindex Ravenscar Profile
14212 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14213 specifically designed for systems with safety-critical real-time
14217 @kindex set ravenscar task-switching on
14218 @cindex task switching with program using Ravenscar Profile
14219 @item set ravenscar task-switching on
14220 Allows task switching when debugging a program that uses the Ravenscar
14221 Profile. This is the default.
14223 @kindex set ravenscar task-switching off
14224 @item set ravenscar task-switching off
14225 Turn off task switching when debugging a program that uses the Ravenscar
14226 Profile. This is mostly intended to disable the code that adds support
14227 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14228 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14229 To be effective, this command should be run before the program is started.
14231 @kindex show ravenscar task-switching
14232 @item show ravenscar task-switching
14233 Show whether it is possible to switch from task to task in a program
14234 using the Ravenscar Profile.
14239 @subsubsection Known Peculiarities of Ada Mode
14240 @cindex Ada, problems
14242 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14243 we know of several problems with and limitations of Ada mode in
14245 some of which will be fixed with planned future releases of the debugger
14246 and the GNU Ada compiler.
14250 Static constants that the compiler chooses not to materialize as objects in
14251 storage are invisible to the debugger.
14254 Named parameter associations in function argument lists are ignored (the
14255 argument lists are treated as positional).
14258 Many useful library packages are currently invisible to the debugger.
14261 Fixed-point arithmetic, conversions, input, and output is carried out using
14262 floating-point arithmetic, and may give results that only approximate those on
14266 The GNAT compiler never generates the prefix @code{Standard} for any of
14267 the standard symbols defined by the Ada language. @value{GDBN} knows about
14268 this: it will strip the prefix from names when you use it, and will never
14269 look for a name you have so qualified among local symbols, nor match against
14270 symbols in other packages or subprograms. If you have
14271 defined entities anywhere in your program other than parameters and
14272 local variables whose simple names match names in @code{Standard},
14273 GNAT's lack of qualification here can cause confusion. When this happens,
14274 you can usually resolve the confusion
14275 by qualifying the problematic names with package
14276 @code{Standard} explicitly.
14279 Older versions of the compiler sometimes generate erroneous debugging
14280 information, resulting in the debugger incorrectly printing the value
14281 of affected entities. In some cases, the debugger is able to work
14282 around an issue automatically. In other cases, the debugger is able
14283 to work around the issue, but the work-around has to be specifically
14286 @kindex set ada trust-PAD-over-XVS
14287 @kindex show ada trust-PAD-over-XVS
14290 @item set ada trust-PAD-over-XVS on
14291 Configure GDB to strictly follow the GNAT encoding when computing the
14292 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14293 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14294 a complete description of the encoding used by the GNAT compiler).
14295 This is the default.
14297 @item set ada trust-PAD-over-XVS off
14298 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14299 sometimes prints the wrong value for certain entities, changing @code{ada
14300 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14301 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14302 @code{off}, but this incurs a slight performance penalty, so it is
14303 recommended to leave this setting to @code{on} unless necessary.
14307 @node Unsupported Languages
14308 @section Unsupported Languages
14310 @cindex unsupported languages
14311 @cindex minimal language
14312 In addition to the other fully-supported programming languages,
14313 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14314 It does not represent a real programming language, but provides a set
14315 of capabilities close to what the C or assembly languages provide.
14316 This should allow most simple operations to be performed while debugging
14317 an application that uses a language currently not supported by @value{GDBN}.
14319 If the language is set to @code{auto}, @value{GDBN} will automatically
14320 select this language if the current frame corresponds to an unsupported
14324 @chapter Examining the Symbol Table
14326 The commands described in this chapter allow you to inquire about the
14327 symbols (names of variables, functions and types) defined in your
14328 program. This information is inherent in the text of your program and
14329 does not change as your program executes. @value{GDBN} finds it in your
14330 program's symbol table, in the file indicated when you started @value{GDBN}
14331 (@pxref{File Options, ,Choosing Files}), or by one of the
14332 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14334 @cindex symbol names
14335 @cindex names of symbols
14336 @cindex quoting names
14337 Occasionally, you may need to refer to symbols that contain unusual
14338 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14339 most frequent case is in referring to static variables in other
14340 source files (@pxref{Variables,,Program Variables}). File names
14341 are recorded in object files as debugging symbols, but @value{GDBN} would
14342 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14343 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14344 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14351 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14354 @cindex case-insensitive symbol names
14355 @cindex case sensitivity in symbol names
14356 @kindex set case-sensitive
14357 @item set case-sensitive on
14358 @itemx set case-sensitive off
14359 @itemx set case-sensitive auto
14360 Normally, when @value{GDBN} looks up symbols, it matches their names
14361 with case sensitivity determined by the current source language.
14362 Occasionally, you may wish to control that. The command @code{set
14363 case-sensitive} lets you do that by specifying @code{on} for
14364 case-sensitive matches or @code{off} for case-insensitive ones. If
14365 you specify @code{auto}, case sensitivity is reset to the default
14366 suitable for the source language. The default is case-sensitive
14367 matches for all languages except for Fortran, for which the default is
14368 case-insensitive matches.
14370 @kindex show case-sensitive
14371 @item show case-sensitive
14372 This command shows the current setting of case sensitivity for symbols
14375 @kindex info address
14376 @cindex address of a symbol
14377 @item info address @var{symbol}
14378 Describe where the data for @var{symbol} is stored. For a register
14379 variable, this says which register it is kept in. For a non-register
14380 local variable, this prints the stack-frame offset at which the variable
14383 Note the contrast with @samp{print &@var{symbol}}, which does not work
14384 at all for a register variable, and for a stack local variable prints
14385 the exact address of the current instantiation of the variable.
14387 @kindex info symbol
14388 @cindex symbol from address
14389 @cindex closest symbol and offset for an address
14390 @item info symbol @var{addr}
14391 Print the name of a symbol which is stored at the address @var{addr}.
14392 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14393 nearest symbol and an offset from it:
14396 (@value{GDBP}) info symbol 0x54320
14397 _initialize_vx + 396 in section .text
14401 This is the opposite of the @code{info address} command. You can use
14402 it to find out the name of a variable or a function given its address.
14404 For dynamically linked executables, the name of executable or shared
14405 library containing the symbol is also printed:
14408 (@value{GDBP}) info symbol 0x400225
14409 _start + 5 in section .text of /tmp/a.out
14410 (@value{GDBP}) info symbol 0x2aaaac2811cf
14411 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14415 @item whatis [@var{arg}]
14416 Print the data type of @var{arg}, which can be either an expression
14417 or a name of a data type. With no argument, print the data type of
14418 @code{$}, the last value in the value history.
14420 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14421 is not actually evaluated, and any side-effecting operations (such as
14422 assignments or function calls) inside it do not take place.
14424 If @var{arg} is a variable or an expression, @code{whatis} prints its
14425 literal type as it is used in the source code. If the type was
14426 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14427 the data type underlying the @code{typedef}. If the type of the
14428 variable or the expression is a compound data type, such as
14429 @code{struct} or @code{class}, @code{whatis} never prints their
14430 fields or methods. It just prints the @code{struct}/@code{class}
14431 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14432 such a compound data type, use @code{ptype}.
14434 If @var{arg} is a type name that was defined using @code{typedef},
14435 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14436 Unrolling means that @code{whatis} will show the underlying type used
14437 in the @code{typedef} declaration of @var{arg}. However, if that
14438 underlying type is also a @code{typedef}, @code{whatis} will not
14441 For C code, the type names may also have the form @samp{class
14442 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14443 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14446 @item ptype [@var{arg}]
14447 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14448 detailed description of the type, instead of just the name of the type.
14449 @xref{Expressions, ,Expressions}.
14451 Contrary to @code{whatis}, @code{ptype} always unrolls any
14452 @code{typedef}s in its argument declaration, whether the argument is
14453 a variable, expression, or a data type. This means that @code{ptype}
14454 of a variable or an expression will not print literally its type as
14455 present in the source code---use @code{whatis} for that. @code{typedef}s at
14456 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14457 fields, methods and inner @code{class typedef}s of @code{struct}s,
14458 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14460 For example, for this variable declaration:
14463 typedef double real_t;
14464 struct complex @{ real_t real; double imag; @};
14465 typedef struct complex complex_t;
14467 real_t *real_pointer_var;
14471 the two commands give this output:
14475 (@value{GDBP}) whatis var
14477 (@value{GDBP}) ptype var
14478 type = struct complex @{
14482 (@value{GDBP}) whatis complex_t
14483 type = struct complex
14484 (@value{GDBP}) whatis struct complex
14485 type = struct complex
14486 (@value{GDBP}) ptype struct complex
14487 type = struct complex @{
14491 (@value{GDBP}) whatis real_pointer_var
14493 (@value{GDBP}) ptype real_pointer_var
14499 As with @code{whatis}, using @code{ptype} without an argument refers to
14500 the type of @code{$}, the last value in the value history.
14502 @cindex incomplete type
14503 Sometimes, programs use opaque data types or incomplete specifications
14504 of complex data structure. If the debug information included in the
14505 program does not allow @value{GDBN} to display a full declaration of
14506 the data type, it will say @samp{<incomplete type>}. For example,
14507 given these declarations:
14511 struct foo *fooptr;
14515 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14518 (@value{GDBP}) ptype foo
14519 $1 = <incomplete type>
14523 ``Incomplete type'' is C terminology for data types that are not
14524 completely specified.
14527 @item info types @var{regexp}
14529 Print a brief description of all types whose names match the regular
14530 expression @var{regexp} (or all types in your program, if you supply
14531 no argument). Each complete typename is matched as though it were a
14532 complete line; thus, @samp{i type value} gives information on all
14533 types in your program whose names include the string @code{value}, but
14534 @samp{i type ^value$} gives information only on types whose complete
14535 name is @code{value}.
14537 This command differs from @code{ptype} in two ways: first, like
14538 @code{whatis}, it does not print a detailed description; second, it
14539 lists all source files where a type is defined.
14542 @cindex local variables
14543 @item info scope @var{location}
14544 List all the variables local to a particular scope. This command
14545 accepts a @var{location} argument---a function name, a source line, or
14546 an address preceded by a @samp{*}, and prints all the variables local
14547 to the scope defined by that location. (@xref{Specify Location}, for
14548 details about supported forms of @var{location}.) For example:
14551 (@value{GDBP}) @b{info scope command_line_handler}
14552 Scope for command_line_handler:
14553 Symbol rl is an argument at stack/frame offset 8, length 4.
14554 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14555 Symbol linelength is in static storage at address 0x150a1c, length 4.
14556 Symbol p is a local variable in register $esi, length 4.
14557 Symbol p1 is a local variable in register $ebx, length 4.
14558 Symbol nline is a local variable in register $edx, length 4.
14559 Symbol repeat is a local variable at frame offset -8, length 4.
14563 This command is especially useful for determining what data to collect
14564 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14567 @kindex info source
14569 Show information about the current source file---that is, the source file for
14570 the function containing the current point of execution:
14573 the name of the source file, and the directory containing it,
14575 the directory it was compiled in,
14577 its length, in lines,
14579 which programming language it is written in,
14581 whether the executable includes debugging information for that file, and
14582 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14584 whether the debugging information includes information about
14585 preprocessor macros.
14589 @kindex info sources
14591 Print the names of all source files in your program for which there is
14592 debugging information, organized into two lists: files whose symbols
14593 have already been read, and files whose symbols will be read when needed.
14595 @kindex info functions
14596 @item info functions
14597 Print the names and data types of all defined functions.
14599 @item info functions @var{regexp}
14600 Print the names and data types of all defined functions
14601 whose names contain a match for regular expression @var{regexp}.
14602 Thus, @samp{info fun step} finds all functions whose names
14603 include @code{step}; @samp{info fun ^step} finds those whose names
14604 start with @code{step}. If a function name contains characters
14605 that conflict with the regular expression language (e.g.@:
14606 @samp{operator*()}), they may be quoted with a backslash.
14608 @kindex info variables
14609 @item info variables
14610 Print the names and data types of all variables that are defined
14611 outside of functions (i.e.@: excluding local variables).
14613 @item info variables @var{regexp}
14614 Print the names and data types of all variables (except for local
14615 variables) whose names contain a match for regular expression
14618 @kindex info classes
14619 @cindex Objective-C, classes and selectors
14621 @itemx info classes @var{regexp}
14622 Display all Objective-C classes in your program, or
14623 (with the @var{regexp} argument) all those matching a particular regular
14626 @kindex info selectors
14627 @item info selectors
14628 @itemx info selectors @var{regexp}
14629 Display all Objective-C selectors in your program, or
14630 (with the @var{regexp} argument) all those matching a particular regular
14634 This was never implemented.
14635 @kindex info methods
14637 @itemx info methods @var{regexp}
14638 The @code{info methods} command permits the user to examine all defined
14639 methods within C@t{++} program, or (with the @var{regexp} argument) a
14640 specific set of methods found in the various C@t{++} classes. Many
14641 C@t{++} classes provide a large number of methods. Thus, the output
14642 from the @code{ptype} command can be overwhelming and hard to use. The
14643 @code{info-methods} command filters the methods, printing only those
14644 which match the regular-expression @var{regexp}.
14647 @cindex reloading symbols
14648 Some systems allow individual object files that make up your program to
14649 be replaced without stopping and restarting your program. For example,
14650 in VxWorks you can simply recompile a defective object file and keep on
14651 running. If you are running on one of these systems, you can allow
14652 @value{GDBN} to reload the symbols for automatically relinked modules:
14655 @kindex set symbol-reloading
14656 @item set symbol-reloading on
14657 Replace symbol definitions for the corresponding source file when an
14658 object file with a particular name is seen again.
14660 @item set symbol-reloading off
14661 Do not replace symbol definitions when encountering object files of the
14662 same name more than once. This is the default state; if you are not
14663 running on a system that permits automatic relinking of modules, you
14664 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14665 may discard symbols when linking large programs, that may contain
14666 several modules (from different directories or libraries) with the same
14669 @kindex show symbol-reloading
14670 @item show symbol-reloading
14671 Show the current @code{on} or @code{off} setting.
14674 @cindex opaque data types
14675 @kindex set opaque-type-resolution
14676 @item set opaque-type-resolution on
14677 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14678 declared as a pointer to a @code{struct}, @code{class}, or
14679 @code{union}---for example, @code{struct MyType *}---that is used in one
14680 source file although the full declaration of @code{struct MyType} is in
14681 another source file. The default is on.
14683 A change in the setting of this subcommand will not take effect until
14684 the next time symbols for a file are loaded.
14686 @item set opaque-type-resolution off
14687 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14688 is printed as follows:
14690 @{<no data fields>@}
14693 @kindex show opaque-type-resolution
14694 @item show opaque-type-resolution
14695 Show whether opaque types are resolved or not.
14697 @kindex maint print symbols
14698 @cindex symbol dump
14699 @kindex maint print psymbols
14700 @cindex partial symbol dump
14701 @item maint print symbols @var{filename}
14702 @itemx maint print psymbols @var{filename}
14703 @itemx maint print msymbols @var{filename}
14704 Write a dump of debugging symbol data into the file @var{filename}.
14705 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14706 symbols with debugging data are included. If you use @samp{maint print
14707 symbols}, @value{GDBN} includes all the symbols for which it has already
14708 collected full details: that is, @var{filename} reflects symbols for
14709 only those files whose symbols @value{GDBN} has read. You can use the
14710 command @code{info sources} to find out which files these are. If you
14711 use @samp{maint print psymbols} instead, the dump shows information about
14712 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14713 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14714 @samp{maint print msymbols} dumps just the minimal symbol information
14715 required for each object file from which @value{GDBN} has read some symbols.
14716 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14717 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14719 @kindex maint info symtabs
14720 @kindex maint info psymtabs
14721 @cindex listing @value{GDBN}'s internal symbol tables
14722 @cindex symbol tables, listing @value{GDBN}'s internal
14723 @cindex full symbol tables, listing @value{GDBN}'s internal
14724 @cindex partial symbol tables, listing @value{GDBN}'s internal
14725 @item maint info symtabs @r{[} @var{regexp} @r{]}
14726 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14728 List the @code{struct symtab} or @code{struct partial_symtab}
14729 structures whose names match @var{regexp}. If @var{regexp} is not
14730 given, list them all. The output includes expressions which you can
14731 copy into a @value{GDBN} debugging this one to examine a particular
14732 structure in more detail. For example:
14735 (@value{GDBP}) maint info psymtabs dwarf2read
14736 @{ objfile /home/gnu/build/gdb/gdb
14737 ((struct objfile *) 0x82e69d0)
14738 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14739 ((struct partial_symtab *) 0x8474b10)
14742 text addresses 0x814d3c8 -- 0x8158074
14743 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14744 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14745 dependencies (none)
14748 (@value{GDBP}) maint info symtabs
14752 We see that there is one partial symbol table whose filename contains
14753 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14754 and we see that @value{GDBN} has not read in any symtabs yet at all.
14755 If we set a breakpoint on a function, that will cause @value{GDBN} to
14756 read the symtab for the compilation unit containing that function:
14759 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14760 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14762 (@value{GDBP}) maint info symtabs
14763 @{ objfile /home/gnu/build/gdb/gdb
14764 ((struct objfile *) 0x82e69d0)
14765 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14766 ((struct symtab *) 0x86c1f38)
14769 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14770 linetable ((struct linetable *) 0x8370fa0)
14771 debugformat DWARF 2
14780 @chapter Altering Execution
14782 Once you think you have found an error in your program, you might want to
14783 find out for certain whether correcting the apparent error would lead to
14784 correct results in the rest of the run. You can find the answer by
14785 experiment, using the @value{GDBN} features for altering execution of the
14788 For example, you can store new values into variables or memory
14789 locations, give your program a signal, restart it at a different
14790 address, or even return prematurely from a function.
14793 * Assignment:: Assignment to variables
14794 * Jumping:: Continuing at a different address
14795 * Signaling:: Giving your program a signal
14796 * Returning:: Returning from a function
14797 * Calling:: Calling your program's functions
14798 * Patching:: Patching your program
14802 @section Assignment to Variables
14805 @cindex setting variables
14806 To alter the value of a variable, evaluate an assignment expression.
14807 @xref{Expressions, ,Expressions}. For example,
14814 stores the value 4 into the variable @code{x}, and then prints the
14815 value of the assignment expression (which is 4).
14816 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14817 information on operators in supported languages.
14819 @kindex set variable
14820 @cindex variables, setting
14821 If you are not interested in seeing the value of the assignment, use the
14822 @code{set} command instead of the @code{print} command. @code{set} is
14823 really the same as @code{print} except that the expression's value is
14824 not printed and is not put in the value history (@pxref{Value History,
14825 ,Value History}). The expression is evaluated only for its effects.
14827 If the beginning of the argument string of the @code{set} command
14828 appears identical to a @code{set} subcommand, use the @code{set
14829 variable} command instead of just @code{set}. This command is identical
14830 to @code{set} except for its lack of subcommands. For example, if your
14831 program has a variable @code{width}, you get an error if you try to set
14832 a new value with just @samp{set width=13}, because @value{GDBN} has the
14833 command @code{set width}:
14836 (@value{GDBP}) whatis width
14838 (@value{GDBP}) p width
14840 (@value{GDBP}) set width=47
14841 Invalid syntax in expression.
14845 The invalid expression, of course, is @samp{=47}. In
14846 order to actually set the program's variable @code{width}, use
14849 (@value{GDBP}) set var width=47
14852 Because the @code{set} command has many subcommands that can conflict
14853 with the names of program variables, it is a good idea to use the
14854 @code{set variable} command instead of just @code{set}. For example, if
14855 your program has a variable @code{g}, you run into problems if you try
14856 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14857 the command @code{set gnutarget}, abbreviated @code{set g}:
14861 (@value{GDBP}) whatis g
14865 (@value{GDBP}) set g=4
14869 The program being debugged has been started already.
14870 Start it from the beginning? (y or n) y
14871 Starting program: /home/smith/cc_progs/a.out
14872 "/home/smith/cc_progs/a.out": can't open to read symbols:
14873 Invalid bfd target.
14874 (@value{GDBP}) show g
14875 The current BFD target is "=4".
14880 The program variable @code{g} did not change, and you silently set the
14881 @code{gnutarget} to an invalid value. In order to set the variable
14885 (@value{GDBP}) set var g=4
14888 @value{GDBN} allows more implicit conversions in assignments than C; you can
14889 freely store an integer value into a pointer variable or vice versa,
14890 and you can convert any structure to any other structure that is the
14891 same length or shorter.
14892 @comment FIXME: how do structs align/pad in these conversions?
14893 @comment /doc@cygnus.com 18dec1990
14895 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14896 construct to generate a value of specified type at a specified address
14897 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14898 to memory location @code{0x83040} as an integer (which implies a certain size
14899 and representation in memory), and
14902 set @{int@}0x83040 = 4
14906 stores the value 4 into that memory location.
14909 @section Continuing at a Different Address
14911 Ordinarily, when you continue your program, you do so at the place where
14912 it stopped, with the @code{continue} command. You can instead continue at
14913 an address of your own choosing, with the following commands:
14917 @item jump @var{linespec}
14918 @itemx jump @var{location}
14919 Resume execution at line @var{linespec} or at address given by
14920 @var{location}. Execution stops again immediately if there is a
14921 breakpoint there. @xref{Specify Location}, for a description of the
14922 different forms of @var{linespec} and @var{location}. It is common
14923 practice to use the @code{tbreak} command in conjunction with
14924 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14926 The @code{jump} command does not change the current stack frame, or
14927 the stack pointer, or the contents of any memory location or any
14928 register other than the program counter. If line @var{linespec} is in
14929 a different function from the one currently executing, the results may
14930 be bizarre if the two functions expect different patterns of arguments or
14931 of local variables. For this reason, the @code{jump} command requests
14932 confirmation if the specified line is not in the function currently
14933 executing. However, even bizarre results are predictable if you are
14934 well acquainted with the machine-language code of your program.
14937 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14938 On many systems, you can get much the same effect as the @code{jump}
14939 command by storing a new value into the register @code{$pc}. The
14940 difference is that this does not start your program running; it only
14941 changes the address of where it @emph{will} run when you continue. For
14949 makes the next @code{continue} command or stepping command execute at
14950 address @code{0x485}, rather than at the address where your program stopped.
14951 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14953 The most common occasion to use the @code{jump} command is to back
14954 up---perhaps with more breakpoints set---over a portion of a program
14955 that has already executed, in order to examine its execution in more
14960 @section Giving your Program a Signal
14961 @cindex deliver a signal to a program
14965 @item signal @var{signal}
14966 Resume execution where your program stopped, but immediately give it the
14967 signal @var{signal}. @var{signal} can be the name or the number of a
14968 signal. For example, on many systems @code{signal 2} and @code{signal
14969 SIGINT} are both ways of sending an interrupt signal.
14971 Alternatively, if @var{signal} is zero, continue execution without
14972 giving a signal. This is useful when your program stopped on account of
14973 a signal and would ordinary see the signal when resumed with the
14974 @code{continue} command; @samp{signal 0} causes it to resume without a
14977 @code{signal} does not repeat when you press @key{RET} a second time
14978 after executing the command.
14982 Invoking the @code{signal} command is not the same as invoking the
14983 @code{kill} utility from the shell. Sending a signal with @code{kill}
14984 causes @value{GDBN} to decide what to do with the signal depending on
14985 the signal handling tables (@pxref{Signals}). The @code{signal} command
14986 passes the signal directly to your program.
14990 @section Returning from a Function
14993 @cindex returning from a function
14996 @itemx return @var{expression}
14997 You can cancel execution of a function call with the @code{return}
14998 command. If you give an
14999 @var{expression} argument, its value is used as the function's return
15003 When you use @code{return}, @value{GDBN} discards the selected stack frame
15004 (and all frames within it). You can think of this as making the
15005 discarded frame return prematurely. If you wish to specify a value to
15006 be returned, give that value as the argument to @code{return}.
15008 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15009 Frame}), and any other frames inside of it, leaving its caller as the
15010 innermost remaining frame. That frame becomes selected. The
15011 specified value is stored in the registers used for returning values
15014 The @code{return} command does not resume execution; it leaves the
15015 program stopped in the state that would exist if the function had just
15016 returned. In contrast, the @code{finish} command (@pxref{Continuing
15017 and Stepping, ,Continuing and Stepping}) resumes execution until the
15018 selected stack frame returns naturally.
15020 @value{GDBN} needs to know how the @var{expression} argument should be set for
15021 the inferior. The concrete registers assignment depends on the OS ABI and the
15022 type being returned by the selected stack frame. For example it is common for
15023 OS ABI to return floating point values in FPU registers while integer values in
15024 CPU registers. Still some ABIs return even floating point values in CPU
15025 registers. Larger integer widths (such as @code{long long int}) also have
15026 specific placement rules. @value{GDBN} already knows the OS ABI from its
15027 current target so it needs to find out also the type being returned to make the
15028 assignment into the right register(s).
15030 Normally, the selected stack frame has debug info. @value{GDBN} will always
15031 use the debug info instead of the implicit type of @var{expression} when the
15032 debug info is available. For example, if you type @kbd{return -1}, and the
15033 function in the current stack frame is declared to return a @code{long long
15034 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15035 into a @code{long long int}:
15038 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15040 (@value{GDBP}) return -1
15041 Make func return now? (y or n) y
15042 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15043 43 printf ("result=%lld\n", func ());
15047 However, if the selected stack frame does not have a debug info, e.g., if the
15048 function was compiled without debug info, @value{GDBN} has to find out the type
15049 to return from user. Specifying a different type by mistake may set the value
15050 in different inferior registers than the caller code expects. For example,
15051 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15052 of a @code{long long int} result for a debug info less function (on 32-bit
15053 architectures). Therefore the user is required to specify the return type by
15054 an appropriate cast explicitly:
15057 Breakpoint 2, 0x0040050b in func ()
15058 (@value{GDBP}) return -1
15059 Return value type not available for selected stack frame.
15060 Please use an explicit cast of the value to return.
15061 (@value{GDBP}) return (long long int) -1
15062 Make selected stack frame return now? (y or n) y
15063 #0 0x00400526 in main ()
15068 @section Calling Program Functions
15071 @cindex calling functions
15072 @cindex inferior functions, calling
15073 @item print @var{expr}
15074 Evaluate the expression @var{expr} and display the resulting value.
15075 @var{expr} may include calls to functions in the program being
15079 @item call @var{expr}
15080 Evaluate the expression @var{expr} without displaying @code{void}
15083 You can use this variant of the @code{print} command if you want to
15084 execute a function from your program that does not return anything
15085 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15086 with @code{void} returned values that @value{GDBN} will otherwise
15087 print. If the result is not void, it is printed and saved in the
15091 It is possible for the function you call via the @code{print} or
15092 @code{call} command to generate a signal (e.g., if there's a bug in
15093 the function, or if you passed it incorrect arguments). What happens
15094 in that case is controlled by the @code{set unwindonsignal} command.
15096 Similarly, with a C@t{++} program it is possible for the function you
15097 call via the @code{print} or @code{call} command to generate an
15098 exception that is not handled due to the constraints of the dummy
15099 frame. In this case, any exception that is raised in the frame, but has
15100 an out-of-frame exception handler will not be found. GDB builds a
15101 dummy-frame for the inferior function call, and the unwinder cannot
15102 seek for exception handlers outside of this dummy-frame. What happens
15103 in that case is controlled by the
15104 @code{set unwind-on-terminating-exception} command.
15107 @item set unwindonsignal
15108 @kindex set unwindonsignal
15109 @cindex unwind stack in called functions
15110 @cindex call dummy stack unwinding
15111 Set unwinding of the stack if a signal is received while in a function
15112 that @value{GDBN} called in the program being debugged. If set to on,
15113 @value{GDBN} unwinds the stack it created for the call and restores
15114 the context to what it was before the call. If set to off (the
15115 default), @value{GDBN} stops in the frame where the signal was
15118 @item show unwindonsignal
15119 @kindex show unwindonsignal
15120 Show the current setting of stack unwinding in the functions called by
15123 @item set unwind-on-terminating-exception
15124 @kindex set unwind-on-terminating-exception
15125 @cindex unwind stack in called functions with unhandled exceptions
15126 @cindex call dummy stack unwinding on unhandled exception.
15127 Set unwinding of the stack if a C@t{++} exception is raised, but left
15128 unhandled while in a function that @value{GDBN} called in the program being
15129 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15130 it created for the call and restores the context to what it was before
15131 the call. If set to off, @value{GDBN} the exception is delivered to
15132 the default C@t{++} exception handler and the inferior terminated.
15134 @item show unwind-on-terminating-exception
15135 @kindex show unwind-on-terminating-exception
15136 Show the current setting of stack unwinding in the functions called by
15141 @cindex weak alias functions
15142 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15143 for another function. In such case, @value{GDBN} might not pick up
15144 the type information, including the types of the function arguments,
15145 which causes @value{GDBN} to call the inferior function incorrectly.
15146 As a result, the called function will function erroneously and may
15147 even crash. A solution to that is to use the name of the aliased
15151 @section Patching Programs
15153 @cindex patching binaries
15154 @cindex writing into executables
15155 @cindex writing into corefiles
15157 By default, @value{GDBN} opens the file containing your program's
15158 executable code (or the corefile) read-only. This prevents accidental
15159 alterations to machine code; but it also prevents you from intentionally
15160 patching your program's binary.
15162 If you'd like to be able to patch the binary, you can specify that
15163 explicitly with the @code{set write} command. For example, you might
15164 want to turn on internal debugging flags, or even to make emergency
15170 @itemx set write off
15171 If you specify @samp{set write on}, @value{GDBN} opens executable and
15172 core files for both reading and writing; if you specify @kbd{set write
15173 off} (the default), @value{GDBN} opens them read-only.
15175 If you have already loaded a file, you must load it again (using the
15176 @code{exec-file} or @code{core-file} command) after changing @code{set
15177 write}, for your new setting to take effect.
15181 Display whether executable files and core files are opened for writing
15182 as well as reading.
15186 @chapter @value{GDBN} Files
15188 @value{GDBN} needs to know the file name of the program to be debugged,
15189 both in order to read its symbol table and in order to start your
15190 program. To debug a core dump of a previous run, you must also tell
15191 @value{GDBN} the name of the core dump file.
15194 * Files:: Commands to specify files
15195 * Separate Debug Files:: Debugging information in separate files
15196 * Index Files:: Index files speed up GDB
15197 * Symbol Errors:: Errors reading symbol files
15198 * Data Files:: GDB data files
15202 @section Commands to Specify Files
15204 @cindex symbol table
15205 @cindex core dump file
15207 You may want to specify executable and core dump file names. The usual
15208 way to do this is at start-up time, using the arguments to
15209 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15210 Out of @value{GDBN}}).
15212 Occasionally it is necessary to change to a different file during a
15213 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15214 specify a file you want to use. Or you are debugging a remote target
15215 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15216 Program}). In these situations the @value{GDBN} commands to specify
15217 new files are useful.
15220 @cindex executable file
15222 @item file @var{filename}
15223 Use @var{filename} as the program to be debugged. It is read for its
15224 symbols and for the contents of pure memory. It is also the program
15225 executed when you use the @code{run} command. If you do not specify a
15226 directory and the file is not found in the @value{GDBN} working directory,
15227 @value{GDBN} uses the environment variable @code{PATH} as a list of
15228 directories to search, just as the shell does when looking for a program
15229 to run. You can change the value of this variable, for both @value{GDBN}
15230 and your program, using the @code{path} command.
15232 @cindex unlinked object files
15233 @cindex patching object files
15234 You can load unlinked object @file{.o} files into @value{GDBN} using
15235 the @code{file} command. You will not be able to ``run'' an object
15236 file, but you can disassemble functions and inspect variables. Also,
15237 if the underlying BFD functionality supports it, you could use
15238 @kbd{gdb -write} to patch object files using this technique. Note
15239 that @value{GDBN} can neither interpret nor modify relocations in this
15240 case, so branches and some initialized variables will appear to go to
15241 the wrong place. But this feature is still handy from time to time.
15244 @code{file} with no argument makes @value{GDBN} discard any information it
15245 has on both executable file and the symbol table.
15248 @item exec-file @r{[} @var{filename} @r{]}
15249 Specify that the program to be run (but not the symbol table) is found
15250 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15251 if necessary to locate your program. Omitting @var{filename} means to
15252 discard information on the executable file.
15254 @kindex symbol-file
15255 @item symbol-file @r{[} @var{filename} @r{]}
15256 Read symbol table information from file @var{filename}. @code{PATH} is
15257 searched when necessary. Use the @code{file} command to get both symbol
15258 table and program to run from the same file.
15260 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15261 program's symbol table.
15263 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15264 some breakpoints and auto-display expressions. This is because they may
15265 contain pointers to the internal data recording symbols and data types,
15266 which are part of the old symbol table data being discarded inside
15269 @code{symbol-file} does not repeat if you press @key{RET} again after
15272 When @value{GDBN} is configured for a particular environment, it
15273 understands debugging information in whatever format is the standard
15274 generated for that environment; you may use either a @sc{gnu} compiler, or
15275 other compilers that adhere to the local conventions.
15276 Best results are usually obtained from @sc{gnu} compilers; for example,
15277 using @code{@value{NGCC}} you can generate debugging information for
15280 For most kinds of object files, with the exception of old SVR3 systems
15281 using COFF, the @code{symbol-file} command does not normally read the
15282 symbol table in full right away. Instead, it scans the symbol table
15283 quickly to find which source files and which symbols are present. The
15284 details are read later, one source file at a time, as they are needed.
15286 The purpose of this two-stage reading strategy is to make @value{GDBN}
15287 start up faster. For the most part, it is invisible except for
15288 occasional pauses while the symbol table details for a particular source
15289 file are being read. (The @code{set verbose} command can turn these
15290 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15291 Warnings and Messages}.)
15293 We have not implemented the two-stage strategy for COFF yet. When the
15294 symbol table is stored in COFF format, @code{symbol-file} reads the
15295 symbol table data in full right away. Note that ``stabs-in-COFF''
15296 still does the two-stage strategy, since the debug info is actually
15300 @cindex reading symbols immediately
15301 @cindex symbols, reading immediately
15302 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15303 @itemx file @r{[} -readnow @r{]} @var{filename}
15304 You can override the @value{GDBN} two-stage strategy for reading symbol
15305 tables by using the @samp{-readnow} option with any of the commands that
15306 load symbol table information, if you want to be sure @value{GDBN} has the
15307 entire symbol table available.
15309 @c FIXME: for now no mention of directories, since this seems to be in
15310 @c flux. 13mar1992 status is that in theory GDB would look either in
15311 @c current dir or in same dir as myprog; but issues like competing
15312 @c GDB's, or clutter in system dirs, mean that in practice right now
15313 @c only current dir is used. FFish says maybe a special GDB hierarchy
15314 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15318 @item core-file @r{[}@var{filename}@r{]}
15320 Specify the whereabouts of a core dump file to be used as the ``contents
15321 of memory''. Traditionally, core files contain only some parts of the
15322 address space of the process that generated them; @value{GDBN} can access the
15323 executable file itself for other parts.
15325 @code{core-file} with no argument specifies that no core file is
15328 Note that the core file is ignored when your program is actually running
15329 under @value{GDBN}. So, if you have been running your program and you
15330 wish to debug a core file instead, you must kill the subprocess in which
15331 the program is running. To do this, use the @code{kill} command
15332 (@pxref{Kill Process, ,Killing the Child Process}).
15334 @kindex add-symbol-file
15335 @cindex dynamic linking
15336 @item add-symbol-file @var{filename} @var{address}
15337 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15338 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15339 The @code{add-symbol-file} command reads additional symbol table
15340 information from the file @var{filename}. You would use this command
15341 when @var{filename} has been dynamically loaded (by some other means)
15342 into the program that is running. @var{address} should be the memory
15343 address at which the file has been loaded; @value{GDBN} cannot figure
15344 this out for itself. You can additionally specify an arbitrary number
15345 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15346 section name and base address for that section. You can specify any
15347 @var{address} as an expression.
15349 The symbol table of the file @var{filename} is added to the symbol table
15350 originally read with the @code{symbol-file} command. You can use the
15351 @code{add-symbol-file} command any number of times; the new symbol data
15352 thus read keeps adding to the old. To discard all old symbol data
15353 instead, use the @code{symbol-file} command without any arguments.
15355 @cindex relocatable object files, reading symbols from
15356 @cindex object files, relocatable, reading symbols from
15357 @cindex reading symbols from relocatable object files
15358 @cindex symbols, reading from relocatable object files
15359 @cindex @file{.o} files, reading symbols from
15360 Although @var{filename} is typically a shared library file, an
15361 executable file, or some other object file which has been fully
15362 relocated for loading into a process, you can also load symbolic
15363 information from relocatable @file{.o} files, as long as:
15367 the file's symbolic information refers only to linker symbols defined in
15368 that file, not to symbols defined by other object files,
15370 every section the file's symbolic information refers to has actually
15371 been loaded into the inferior, as it appears in the file, and
15373 you can determine the address at which every section was loaded, and
15374 provide these to the @code{add-symbol-file} command.
15378 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15379 relocatable files into an already running program; such systems
15380 typically make the requirements above easy to meet. However, it's
15381 important to recognize that many native systems use complex link
15382 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15383 assembly, for example) that make the requirements difficult to meet. In
15384 general, one cannot assume that using @code{add-symbol-file} to read a
15385 relocatable object file's symbolic information will have the same effect
15386 as linking the relocatable object file into the program in the normal
15389 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15391 @kindex add-symbol-file-from-memory
15392 @cindex @code{syscall DSO}
15393 @cindex load symbols from memory
15394 @item add-symbol-file-from-memory @var{address}
15395 Load symbols from the given @var{address} in a dynamically loaded
15396 object file whose image is mapped directly into the inferior's memory.
15397 For example, the Linux kernel maps a @code{syscall DSO} into each
15398 process's address space; this DSO provides kernel-specific code for
15399 some system calls. The argument can be any expression whose
15400 evaluation yields the address of the file's shared object file header.
15401 For this command to work, you must have used @code{symbol-file} or
15402 @code{exec-file} commands in advance.
15404 @kindex add-shared-symbol-files
15406 @item add-shared-symbol-files @var{library-file}
15407 @itemx assf @var{library-file}
15408 The @code{add-shared-symbol-files} command can currently be used only
15409 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15410 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15411 @value{GDBN} automatically looks for shared libraries, however if
15412 @value{GDBN} does not find yours, you can invoke
15413 @code{add-shared-symbol-files}. It takes one argument: the shared
15414 library's file name. @code{assf} is a shorthand alias for
15415 @code{add-shared-symbol-files}.
15418 @item section @var{section} @var{addr}
15419 The @code{section} command changes the base address of the named
15420 @var{section} of the exec file to @var{addr}. This can be used if the
15421 exec file does not contain section addresses, (such as in the
15422 @code{a.out} format), or when the addresses specified in the file
15423 itself are wrong. Each section must be changed separately. The
15424 @code{info files} command, described below, lists all the sections and
15428 @kindex info target
15431 @code{info files} and @code{info target} are synonymous; both print the
15432 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15433 including the names of the executable and core dump files currently in
15434 use by @value{GDBN}, and the files from which symbols were loaded. The
15435 command @code{help target} lists all possible targets rather than
15438 @kindex maint info sections
15439 @item maint info sections
15440 Another command that can give you extra information about program sections
15441 is @code{maint info sections}. In addition to the section information
15442 displayed by @code{info files}, this command displays the flags and file
15443 offset of each section in the executable and core dump files. In addition,
15444 @code{maint info sections} provides the following command options (which
15445 may be arbitrarily combined):
15449 Display sections for all loaded object files, including shared libraries.
15450 @item @var{sections}
15451 Display info only for named @var{sections}.
15452 @item @var{section-flags}
15453 Display info only for sections for which @var{section-flags} are true.
15454 The section flags that @value{GDBN} currently knows about are:
15457 Section will have space allocated in the process when loaded.
15458 Set for all sections except those containing debug information.
15460 Section will be loaded from the file into the child process memory.
15461 Set for pre-initialized code and data, clear for @code{.bss} sections.
15463 Section needs to be relocated before loading.
15465 Section cannot be modified by the child process.
15467 Section contains executable code only.
15469 Section contains data only (no executable code).
15471 Section will reside in ROM.
15473 Section contains data for constructor/destructor lists.
15475 Section is not empty.
15477 An instruction to the linker to not output the section.
15478 @item COFF_SHARED_LIBRARY
15479 A notification to the linker that the section contains
15480 COFF shared library information.
15482 Section contains common symbols.
15485 @kindex set trust-readonly-sections
15486 @cindex read-only sections
15487 @item set trust-readonly-sections on
15488 Tell @value{GDBN} that readonly sections in your object file
15489 really are read-only (i.e.@: that their contents will not change).
15490 In that case, @value{GDBN} can fetch values from these sections
15491 out of the object file, rather than from the target program.
15492 For some targets (notably embedded ones), this can be a significant
15493 enhancement to debugging performance.
15495 The default is off.
15497 @item set trust-readonly-sections off
15498 Tell @value{GDBN} not to trust readonly sections. This means that
15499 the contents of the section might change while the program is running,
15500 and must therefore be fetched from the target when needed.
15502 @item show trust-readonly-sections
15503 Show the current setting of trusting readonly sections.
15506 All file-specifying commands allow both absolute and relative file names
15507 as arguments. @value{GDBN} always converts the file name to an absolute file
15508 name and remembers it that way.
15510 @cindex shared libraries
15511 @anchor{Shared Libraries}
15512 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15513 and IBM RS/6000 AIX shared libraries.
15515 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15516 shared libraries. @xref{Expat}.
15518 @value{GDBN} automatically loads symbol definitions from shared libraries
15519 when you use the @code{run} command, or when you examine a core file.
15520 (Before you issue the @code{run} command, @value{GDBN} does not understand
15521 references to a function in a shared library, however---unless you are
15522 debugging a core file).
15524 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15525 automatically loads the symbols at the time of the @code{shl_load} call.
15527 @c FIXME: some @value{GDBN} release may permit some refs to undef
15528 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15529 @c FIXME...lib; check this from time to time when updating manual
15531 There are times, however, when you may wish to not automatically load
15532 symbol definitions from shared libraries, such as when they are
15533 particularly large or there are many of them.
15535 To control the automatic loading of shared library symbols, use the
15539 @kindex set auto-solib-add
15540 @item set auto-solib-add @var{mode}
15541 If @var{mode} is @code{on}, symbols from all shared object libraries
15542 will be loaded automatically when the inferior begins execution, you
15543 attach to an independently started inferior, or when the dynamic linker
15544 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15545 is @code{off}, symbols must be loaded manually, using the
15546 @code{sharedlibrary} command. The default value is @code{on}.
15548 @cindex memory used for symbol tables
15549 If your program uses lots of shared libraries with debug info that
15550 takes large amounts of memory, you can decrease the @value{GDBN}
15551 memory footprint by preventing it from automatically loading the
15552 symbols from shared libraries. To that end, type @kbd{set
15553 auto-solib-add off} before running the inferior, then load each
15554 library whose debug symbols you do need with @kbd{sharedlibrary
15555 @var{regexp}}, where @var{regexp} is a regular expression that matches
15556 the libraries whose symbols you want to be loaded.
15558 @kindex show auto-solib-add
15559 @item show auto-solib-add
15560 Display the current autoloading mode.
15563 @cindex load shared library
15564 To explicitly load shared library symbols, use the @code{sharedlibrary}
15568 @kindex info sharedlibrary
15570 @item info share @var{regex}
15571 @itemx info sharedlibrary @var{regex}
15572 Print the names of the shared libraries which are currently loaded
15573 that match @var{regex}. If @var{regex} is omitted then print
15574 all shared libraries that are loaded.
15576 @kindex sharedlibrary
15578 @item sharedlibrary @var{regex}
15579 @itemx share @var{regex}
15580 Load shared object library symbols for files matching a
15581 Unix regular expression.
15582 As with files loaded automatically, it only loads shared libraries
15583 required by your program for a core file or after typing @code{run}. If
15584 @var{regex} is omitted all shared libraries required by your program are
15587 @item nosharedlibrary
15588 @kindex nosharedlibrary
15589 @cindex unload symbols from shared libraries
15590 Unload all shared object library symbols. This discards all symbols
15591 that have been loaded from all shared libraries. Symbols from shared
15592 libraries that were loaded by explicit user requests are not
15596 Sometimes you may wish that @value{GDBN} stops and gives you control
15597 when any of shared library events happen. The best way to do this is
15598 to use @code{catch load} and @code{catch unload} (@pxref{Set
15601 @value{GDBN} also supports the the @code{set stop-on-solib-events}
15602 command for this. This command exists for historical reasons. It is
15603 less useful than setting a catchpoint, because it does not allow for
15604 conditions or commands as a catchpoint does.
15607 @item set stop-on-solib-events
15608 @kindex set stop-on-solib-events
15609 This command controls whether @value{GDBN} should give you control
15610 when the dynamic linker notifies it about some shared library event.
15611 The most common event of interest is loading or unloading of a new
15614 @item show stop-on-solib-events
15615 @kindex show stop-on-solib-events
15616 Show whether @value{GDBN} stops and gives you control when shared
15617 library events happen.
15620 Shared libraries are also supported in many cross or remote debugging
15621 configurations. @value{GDBN} needs to have access to the target's libraries;
15622 this can be accomplished either by providing copies of the libraries
15623 on the host system, or by asking @value{GDBN} to automatically retrieve the
15624 libraries from the target. If copies of the target libraries are
15625 provided, they need to be the same as the target libraries, although the
15626 copies on the target can be stripped as long as the copies on the host are
15629 @cindex where to look for shared libraries
15630 For remote debugging, you need to tell @value{GDBN} where the target
15631 libraries are, so that it can load the correct copies---otherwise, it
15632 may try to load the host's libraries. @value{GDBN} has two variables
15633 to specify the search directories for target libraries.
15636 @cindex prefix for shared library file names
15637 @cindex system root, alternate
15638 @kindex set solib-absolute-prefix
15639 @kindex set sysroot
15640 @item set sysroot @var{path}
15641 Use @var{path} as the system root for the program being debugged. Any
15642 absolute shared library paths will be prefixed with @var{path}; many
15643 runtime loaders store the absolute paths to the shared library in the
15644 target program's memory. If you use @code{set sysroot} to find shared
15645 libraries, they need to be laid out in the same way that they are on
15646 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15649 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15650 retrieve the target libraries from the remote system. This is only
15651 supported when using a remote target that supports the @code{remote get}
15652 command (@pxref{File Transfer,,Sending files to a remote system}).
15653 The part of @var{path} following the initial @file{remote:}
15654 (if present) is used as system root prefix on the remote file system.
15655 @footnote{If you want to specify a local system root using a directory
15656 that happens to be named @file{remote:}, you need to use some equivalent
15657 variant of the name like @file{./remote:}.}
15659 For targets with an MS-DOS based filesystem, such as MS-Windows and
15660 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15661 absolute file name with @var{path}. But first, on Unix hosts,
15662 @value{GDBN} converts all backslash directory separators into forward
15663 slashes, because the backslash is not a directory separator on Unix:
15666 c:\foo\bar.dll @result{} c:/foo/bar.dll
15669 Then, @value{GDBN} attempts prefixing the target file name with
15670 @var{path}, and looks for the resulting file name in the host file
15674 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15677 If that does not find the shared library, @value{GDBN} tries removing
15678 the @samp{:} character from the drive spec, both for convenience, and,
15679 for the case of the host file system not supporting file names with
15683 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15686 This makes it possible to have a system root that mirrors a target
15687 with more than one drive. E.g., you may want to setup your local
15688 copies of the target system shared libraries like so (note @samp{c} vs
15692 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15693 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15694 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15698 and point the system root at @file{/path/to/sysroot}, so that
15699 @value{GDBN} can find the correct copies of both
15700 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15702 If that still does not find the shared library, @value{GDBN} tries
15703 removing the whole drive spec from the target file name:
15706 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15709 This last lookup makes it possible to not care about the drive name,
15710 if you don't want or need to.
15712 The @code{set solib-absolute-prefix} command is an alias for @code{set
15715 @cindex default system root
15716 @cindex @samp{--with-sysroot}
15717 You can set the default system root by using the configure-time
15718 @samp{--with-sysroot} option. If the system root is inside
15719 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15720 @samp{--exec-prefix}), then the default system root will be updated
15721 automatically if the installed @value{GDBN} is moved to a new
15724 @kindex show sysroot
15726 Display the current shared library prefix.
15728 @kindex set solib-search-path
15729 @item set solib-search-path @var{path}
15730 If this variable is set, @var{path} is a colon-separated list of
15731 directories to search for shared libraries. @samp{solib-search-path}
15732 is used after @samp{sysroot} fails to locate the library, or if the
15733 path to the library is relative instead of absolute. If you want to
15734 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15735 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15736 finding your host's libraries. @samp{sysroot} is preferred; setting
15737 it to a nonexistent directory may interfere with automatic loading
15738 of shared library symbols.
15740 @kindex show solib-search-path
15741 @item show solib-search-path
15742 Display the current shared library search path.
15744 @cindex DOS file-name semantics of file names.
15745 @kindex set target-file-system-kind (unix|dos-based|auto)
15746 @kindex show target-file-system-kind
15747 @item set target-file-system-kind @var{kind}
15748 Set assumed file system kind for target reported file names.
15750 Shared library file names as reported by the target system may not
15751 make sense as is on the system @value{GDBN} is running on. For
15752 example, when remote debugging a target that has MS-DOS based file
15753 system semantics, from a Unix host, the target may be reporting to
15754 @value{GDBN} a list of loaded shared libraries with file names such as
15755 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15756 drive letters, so the @samp{c:\} prefix is not normally understood as
15757 indicating an absolute file name, and neither is the backslash
15758 normally considered a directory separator character. In that case,
15759 the native file system would interpret this whole absolute file name
15760 as a relative file name with no directory components. This would make
15761 it impossible to point @value{GDBN} at a copy of the remote target's
15762 shared libraries on the host using @code{set sysroot}, and impractical
15763 with @code{set solib-search-path}. Setting
15764 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15765 to interpret such file names similarly to how the target would, and to
15766 map them to file names valid on @value{GDBN}'s native file system
15767 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15768 to one of the supported file system kinds. In that case, @value{GDBN}
15769 tries to determine the appropriate file system variant based on the
15770 current target's operating system (@pxref{ABI, ,Configuring the
15771 Current ABI}). The supported file system settings are:
15775 Instruct @value{GDBN} to assume the target file system is of Unix
15776 kind. Only file names starting the forward slash (@samp{/}) character
15777 are considered absolute, and the directory separator character is also
15781 Instruct @value{GDBN} to assume the target file system is DOS based.
15782 File names starting with either a forward slash, or a drive letter
15783 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15784 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15785 considered directory separators.
15788 Instruct @value{GDBN} to use the file system kind associated with the
15789 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15790 This is the default.
15794 @cindex file name canonicalization
15795 @cindex base name differences
15796 When processing file names provided by the user, @value{GDBN}
15797 frequently needs to compare them to the file names recorded in the
15798 program's debug info. Normally, @value{GDBN} compares just the
15799 @dfn{base names} of the files as strings, which is reasonably fast
15800 even for very large programs. (The base name of a file is the last
15801 portion of its name, after stripping all the leading directories.)
15802 This shortcut in comparison is based upon the assumption that files
15803 cannot have more than one base name. This is usually true, but
15804 references to files that use symlinks or similar filesystem
15805 facilities violate that assumption. If your program records files
15806 using such facilities, or if you provide file names to @value{GDBN}
15807 using symlinks etc., you can set @code{basenames-may-differ} to
15808 @code{true} to instruct @value{GDBN} to completely canonicalize each
15809 pair of file names it needs to compare. This will make file-name
15810 comparisons accurate, but at a price of a significant slowdown.
15813 @item set basenames-may-differ
15814 @kindex set basenames-may-differ
15815 Set whether a source file may have multiple base names.
15817 @item show basenames-may-differ
15818 @kindex show basenames-may-differ
15819 Show whether a source file may have multiple base names.
15822 @node Separate Debug Files
15823 @section Debugging Information in Separate Files
15824 @cindex separate debugging information files
15825 @cindex debugging information in separate files
15826 @cindex @file{.debug} subdirectories
15827 @cindex debugging information directory, global
15828 @cindex global debugging information directory
15829 @cindex build ID, and separate debugging files
15830 @cindex @file{.build-id} directory
15832 @value{GDBN} allows you to put a program's debugging information in a
15833 file separate from the executable itself, in a way that allows
15834 @value{GDBN} to find and load the debugging information automatically.
15835 Since debugging information can be very large---sometimes larger
15836 than the executable code itself---some systems distribute debugging
15837 information for their executables in separate files, which users can
15838 install only when they need to debug a problem.
15840 @value{GDBN} supports two ways of specifying the separate debug info
15845 The executable contains a @dfn{debug link} that specifies the name of
15846 the separate debug info file. The separate debug file's name is
15847 usually @file{@var{executable}.debug}, where @var{executable} is the
15848 name of the corresponding executable file without leading directories
15849 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15850 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15851 checksum for the debug file, which @value{GDBN} uses to validate that
15852 the executable and the debug file came from the same build.
15855 The executable contains a @dfn{build ID}, a unique bit string that is
15856 also present in the corresponding debug info file. (This is supported
15857 only on some operating systems, notably those which use the ELF format
15858 for binary files and the @sc{gnu} Binutils.) For more details about
15859 this feature, see the description of the @option{--build-id}
15860 command-line option in @ref{Options, , Command Line Options, ld.info,
15861 The GNU Linker}. The debug info file's name is not specified
15862 explicitly by the build ID, but can be computed from the build ID, see
15866 Depending on the way the debug info file is specified, @value{GDBN}
15867 uses two different methods of looking for the debug file:
15871 For the ``debug link'' method, @value{GDBN} looks up the named file in
15872 the directory of the executable file, then in a subdirectory of that
15873 directory named @file{.debug}, and finally under the global debug
15874 directory, in a subdirectory whose name is identical to the leading
15875 directories of the executable's absolute file name.
15878 For the ``build ID'' method, @value{GDBN} looks in the
15879 @file{.build-id} subdirectory of the global debug directory for a file
15880 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15881 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15882 are the rest of the bit string. (Real build ID strings are 32 or more
15883 hex characters, not 10.)
15886 So, for example, suppose you ask @value{GDBN} to debug
15887 @file{/usr/bin/ls}, which has a debug link that specifies the
15888 file @file{ls.debug}, and a build ID whose value in hex is
15889 @code{abcdef1234}. If the global debug directory is
15890 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15891 debug information files, in the indicated order:
15895 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15897 @file{/usr/bin/ls.debug}
15899 @file{/usr/bin/.debug/ls.debug}
15901 @file{/usr/lib/debug/usr/bin/ls.debug}.
15904 You can set the global debugging info directory's name, and view the
15905 name @value{GDBN} is currently using.
15909 @kindex set debug-file-directory
15910 @item set debug-file-directory @var{directories}
15911 Set the directories which @value{GDBN} searches for separate debugging
15912 information files to @var{directory}. Multiple directory components can be set
15913 concatenating them by a directory separator.
15915 @kindex show debug-file-directory
15916 @item show debug-file-directory
15917 Show the directories @value{GDBN} searches for separate debugging
15922 @cindex @code{.gnu_debuglink} sections
15923 @cindex debug link sections
15924 A debug link is a special section of the executable file named
15925 @code{.gnu_debuglink}. The section must contain:
15929 A filename, with any leading directory components removed, followed by
15932 zero to three bytes of padding, as needed to reach the next four-byte
15933 boundary within the section, and
15935 a four-byte CRC checksum, stored in the same endianness used for the
15936 executable file itself. The checksum is computed on the debugging
15937 information file's full contents by the function given below, passing
15938 zero as the @var{crc} argument.
15941 Any executable file format can carry a debug link, as long as it can
15942 contain a section named @code{.gnu_debuglink} with the contents
15945 @cindex @code{.note.gnu.build-id} sections
15946 @cindex build ID sections
15947 The build ID is a special section in the executable file (and in other
15948 ELF binary files that @value{GDBN} may consider). This section is
15949 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15950 It contains unique identification for the built files---the ID remains
15951 the same across multiple builds of the same build tree. The default
15952 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15953 content for the build ID string. The same section with an identical
15954 value is present in the original built binary with symbols, in its
15955 stripped variant, and in the separate debugging information file.
15957 The debugging information file itself should be an ordinary
15958 executable, containing a full set of linker symbols, sections, and
15959 debugging information. The sections of the debugging information file
15960 should have the same names, addresses, and sizes as the original file,
15961 but they need not contain any data---much like a @code{.bss} section
15962 in an ordinary executable.
15964 The @sc{gnu} binary utilities (Binutils) package includes the
15965 @samp{objcopy} utility that can produce
15966 the separated executable / debugging information file pairs using the
15967 following commands:
15970 @kbd{objcopy --only-keep-debug foo foo.debug}
15975 These commands remove the debugging
15976 information from the executable file @file{foo} and place it in the file
15977 @file{foo.debug}. You can use the first, second or both methods to link the
15982 The debug link method needs the following additional command to also leave
15983 behind a debug link in @file{foo}:
15986 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15989 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15990 a version of the @code{strip} command such that the command @kbd{strip foo -f
15991 foo.debug} has the same functionality as the two @code{objcopy} commands and
15992 the @code{ln -s} command above, together.
15995 Build ID gets embedded into the main executable using @code{ld --build-id} or
15996 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15997 compatibility fixes for debug files separation are present in @sc{gnu} binary
15998 utilities (Binutils) package since version 2.18.
16003 @cindex CRC algorithm definition
16004 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16005 IEEE 802.3 using the polynomial:
16007 @c TexInfo requires naked braces for multi-digit exponents for Tex
16008 @c output, but this causes HTML output to barf. HTML has to be set using
16009 @c raw commands. So we end up having to specify this equation in 2
16014 <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>
16015 + <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
16021 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16022 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16026 The function is computed byte at a time, taking the least
16027 significant bit of each byte first. The initial pattern
16028 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16029 the final result is inverted to ensure trailing zeros also affect the
16032 @emph{Note:} This is the same CRC polynomial as used in handling the
16033 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16034 , @value{GDBN} Remote Serial Protocol}). However in the
16035 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16036 significant bit first, and the result is not inverted, so trailing
16037 zeros have no effect on the CRC value.
16039 To complete the description, we show below the code of the function
16040 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16041 initially supplied @code{crc} argument means that an initial call to
16042 this function passing in zero will start computing the CRC using
16045 @kindex gnu_debuglink_crc32
16048 gnu_debuglink_crc32 (unsigned long crc,
16049 unsigned char *buf, size_t len)
16051 static const unsigned long crc32_table[256] =
16053 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16054 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16055 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16056 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16057 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16058 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16059 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16060 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16061 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16062 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16063 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16064 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16065 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16066 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16067 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16068 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16069 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16070 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16071 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16072 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16073 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16074 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16075 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16076 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16077 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16078 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16079 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16080 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16081 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16082 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16083 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16084 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16085 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16086 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16087 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16088 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16089 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16090 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16091 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16092 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16093 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16094 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16095 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16096 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16097 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16098 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16099 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16100 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16101 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16102 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16103 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16106 unsigned char *end;
16108 crc = ~crc & 0xffffffff;
16109 for (end = buf + len; buf < end; ++buf)
16110 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16111 return ~crc & 0xffffffff;
16116 This computation does not apply to the ``build ID'' method.
16120 @section Index Files Speed Up @value{GDBN}
16121 @cindex index files
16122 @cindex @samp{.gdb_index} section
16124 When @value{GDBN} finds a symbol file, it scans the symbols in the
16125 file in order to construct an internal symbol table. This lets most
16126 @value{GDBN} operations work quickly---at the cost of a delay early
16127 on. For large programs, this delay can be quite lengthy, so
16128 @value{GDBN} provides a way to build an index, which speeds up
16131 The index is stored as a section in the symbol file. @value{GDBN} can
16132 write the index to a file, then you can put it into the symbol file
16133 using @command{objcopy}.
16135 To create an index file, use the @code{save gdb-index} command:
16138 @item save gdb-index @var{directory}
16139 @kindex save gdb-index
16140 Create an index file for each symbol file currently known by
16141 @value{GDBN}. Each file is named after its corresponding symbol file,
16142 with @samp{.gdb-index} appended, and is written into the given
16146 Once you have created an index file you can merge it into your symbol
16147 file, here named @file{symfile}, using @command{objcopy}:
16150 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16151 --set-section-flags .gdb_index=readonly symfile symfile
16154 There are currently some limitation on indices. They only work when
16155 for DWARF debugging information, not stabs. And, they do not
16156 currently work for programs using Ada.
16158 @node Symbol Errors
16159 @section Errors Reading Symbol Files
16161 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16162 such as symbol types it does not recognize, or known bugs in compiler
16163 output. By default, @value{GDBN} does not notify you of such problems, since
16164 they are relatively common and primarily of interest to people
16165 debugging compilers. If you are interested in seeing information
16166 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16167 only one message about each such type of problem, no matter how many
16168 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16169 to see how many times the problems occur, with the @code{set
16170 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16173 The messages currently printed, and their meanings, include:
16176 @item inner block not inside outer block in @var{symbol}
16178 The symbol information shows where symbol scopes begin and end
16179 (such as at the start of a function or a block of statements). This
16180 error indicates that an inner scope block is not fully contained
16181 in its outer scope blocks.
16183 @value{GDBN} circumvents the problem by treating the inner block as if it had
16184 the same scope as the outer block. In the error message, @var{symbol}
16185 may be shown as ``@code{(don't know)}'' if the outer block is not a
16188 @item block at @var{address} out of order
16190 The symbol information for symbol scope blocks should occur in
16191 order of increasing addresses. This error indicates that it does not
16194 @value{GDBN} does not circumvent this problem, and has trouble
16195 locating symbols in the source file whose symbols it is reading. (You
16196 can often determine what source file is affected by specifying
16197 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16200 @item bad block start address patched
16202 The symbol information for a symbol scope block has a start address
16203 smaller than the address of the preceding source line. This is known
16204 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16206 @value{GDBN} circumvents the problem by treating the symbol scope block as
16207 starting on the previous source line.
16209 @item bad string table offset in symbol @var{n}
16212 Symbol number @var{n} contains a pointer into the string table which is
16213 larger than the size of the string table.
16215 @value{GDBN} circumvents the problem by considering the symbol to have the
16216 name @code{foo}, which may cause other problems if many symbols end up
16219 @item unknown symbol type @code{0x@var{nn}}
16221 The symbol information contains new data types that @value{GDBN} does
16222 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16223 uncomprehended information, in hexadecimal.
16225 @value{GDBN} circumvents the error by ignoring this symbol information.
16226 This usually allows you to debug your program, though certain symbols
16227 are not accessible. If you encounter such a problem and feel like
16228 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16229 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16230 and examine @code{*bufp} to see the symbol.
16232 @item stub type has NULL name
16234 @value{GDBN} could not find the full definition for a struct or class.
16236 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16237 The symbol information for a C@t{++} member function is missing some
16238 information that recent versions of the compiler should have output for
16241 @item info mismatch between compiler and debugger
16243 @value{GDBN} could not parse a type specification output by the compiler.
16248 @section GDB Data Files
16250 @cindex prefix for data files
16251 @value{GDBN} will sometimes read an auxiliary data file. These files
16252 are kept in a directory known as the @dfn{data directory}.
16254 You can set the data directory's name, and view the name @value{GDBN}
16255 is currently using.
16258 @kindex set data-directory
16259 @item set data-directory @var{directory}
16260 Set the directory which @value{GDBN} searches for auxiliary data files
16261 to @var{directory}.
16263 @kindex show data-directory
16264 @item show data-directory
16265 Show the directory @value{GDBN} searches for auxiliary data files.
16268 @cindex default data directory
16269 @cindex @samp{--with-gdb-datadir}
16270 You can set the default data directory by using the configure-time
16271 @samp{--with-gdb-datadir} option. If the data directory is inside
16272 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16273 @samp{--exec-prefix}), then the default data directory will be updated
16274 automatically if the installed @value{GDBN} is moved to a new
16277 The data directory may also be specified with the
16278 @code{--data-directory} command line option.
16279 @xref{Mode Options}.
16282 @chapter Specifying a Debugging Target
16284 @cindex debugging target
16285 A @dfn{target} is the execution environment occupied by your program.
16287 Often, @value{GDBN} runs in the same host environment as your program;
16288 in that case, the debugging target is specified as a side effect when
16289 you use the @code{file} or @code{core} commands. When you need more
16290 flexibility---for example, running @value{GDBN} on a physically separate
16291 host, or controlling a standalone system over a serial port or a
16292 realtime system over a TCP/IP connection---you can use the @code{target}
16293 command to specify one of the target types configured for @value{GDBN}
16294 (@pxref{Target Commands, ,Commands for Managing Targets}).
16296 @cindex target architecture
16297 It is possible to build @value{GDBN} for several different @dfn{target
16298 architectures}. When @value{GDBN} is built like that, you can choose
16299 one of the available architectures with the @kbd{set architecture}
16303 @kindex set architecture
16304 @kindex show architecture
16305 @item set architecture @var{arch}
16306 This command sets the current target architecture to @var{arch}. The
16307 value of @var{arch} can be @code{"auto"}, in addition to one of the
16308 supported architectures.
16310 @item show architecture
16311 Show the current target architecture.
16313 @item set processor
16315 @kindex set processor
16316 @kindex show processor
16317 These are alias commands for, respectively, @code{set architecture}
16318 and @code{show architecture}.
16322 * Active Targets:: Active targets
16323 * Target Commands:: Commands for managing targets
16324 * Byte Order:: Choosing target byte order
16327 @node Active Targets
16328 @section Active Targets
16330 @cindex stacking targets
16331 @cindex active targets
16332 @cindex multiple targets
16334 There are multiple classes of targets such as: processes, executable files or
16335 recording sessions. Core files belong to the process class, making core file
16336 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16337 on multiple active targets, one in each class. This allows you to (for
16338 example) start a process and inspect its activity, while still having access to
16339 the executable file after the process finishes. Or if you start process
16340 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16341 presented a virtual layer of the recording target, while the process target
16342 remains stopped at the chronologically last point of the process execution.
16344 Use the @code{core-file} and @code{exec-file} commands to select a new core
16345 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16346 specify as a target a process that is already running, use the @code{attach}
16347 command (@pxref{Attach, ,Debugging an Already-running Process}).
16349 @node Target Commands
16350 @section Commands for Managing Targets
16353 @item target @var{type} @var{parameters}
16354 Connects the @value{GDBN} host environment to a target machine or
16355 process. A target is typically a protocol for talking to debugging
16356 facilities. You use the argument @var{type} to specify the type or
16357 protocol of the target machine.
16359 Further @var{parameters} are interpreted by the target protocol, but
16360 typically include things like device names or host names to connect
16361 with, process numbers, and baud rates.
16363 The @code{target} command does not repeat if you press @key{RET} again
16364 after executing the command.
16366 @kindex help target
16368 Displays the names of all targets available. To display targets
16369 currently selected, use either @code{info target} or @code{info files}
16370 (@pxref{Files, ,Commands to Specify Files}).
16372 @item help target @var{name}
16373 Describe a particular target, including any parameters necessary to
16376 @kindex set gnutarget
16377 @item set gnutarget @var{args}
16378 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16379 knows whether it is reading an @dfn{executable},
16380 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16381 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16382 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16385 @emph{Warning:} To specify a file format with @code{set gnutarget},
16386 you must know the actual BFD name.
16390 @xref{Files, , Commands to Specify Files}.
16392 @kindex show gnutarget
16393 @item show gnutarget
16394 Use the @code{show gnutarget} command to display what file format
16395 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16396 @value{GDBN} will determine the file format for each file automatically,
16397 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16400 @cindex common targets
16401 Here are some common targets (available, or not, depending on the GDB
16406 @item target exec @var{program}
16407 @cindex executable file target
16408 An executable file. @samp{target exec @var{program}} is the same as
16409 @samp{exec-file @var{program}}.
16411 @item target core @var{filename}
16412 @cindex core dump file target
16413 A core dump file. @samp{target core @var{filename}} is the same as
16414 @samp{core-file @var{filename}}.
16416 @item target remote @var{medium}
16417 @cindex remote target
16418 A remote system connected to @value{GDBN} via a serial line or network
16419 connection. This command tells @value{GDBN} to use its own remote
16420 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16422 For example, if you have a board connected to @file{/dev/ttya} on the
16423 machine running @value{GDBN}, you could say:
16426 target remote /dev/ttya
16429 @code{target remote} supports the @code{load} command. This is only
16430 useful if you have some other way of getting the stub to the target
16431 system, and you can put it somewhere in memory where it won't get
16432 clobbered by the download.
16434 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16435 @cindex built-in simulator target
16436 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16444 works; however, you cannot assume that a specific memory map, device
16445 drivers, or even basic I/O is available, although some simulators do
16446 provide these. For info about any processor-specific simulator details,
16447 see the appropriate section in @ref{Embedded Processors, ,Embedded
16452 Some configurations may include these targets as well:
16456 @item target nrom @var{dev}
16457 @cindex NetROM ROM emulator target
16458 NetROM ROM emulator. This target only supports downloading.
16462 Different targets are available on different configurations of @value{GDBN};
16463 your configuration may have more or fewer targets.
16465 Many remote targets require you to download the executable's code once
16466 you've successfully established a connection. You may wish to control
16467 various aspects of this process.
16472 @kindex set hash@r{, for remote monitors}
16473 @cindex hash mark while downloading
16474 This command controls whether a hash mark @samp{#} is displayed while
16475 downloading a file to the remote monitor. If on, a hash mark is
16476 displayed after each S-record is successfully downloaded to the
16480 @kindex show hash@r{, for remote monitors}
16481 Show the current status of displaying the hash mark.
16483 @item set debug monitor
16484 @kindex set debug monitor
16485 @cindex display remote monitor communications
16486 Enable or disable display of communications messages between
16487 @value{GDBN} and the remote monitor.
16489 @item show debug monitor
16490 @kindex show debug monitor
16491 Show the current status of displaying communications between
16492 @value{GDBN} and the remote monitor.
16497 @kindex load @var{filename}
16498 @item load @var{filename}
16500 Depending on what remote debugging facilities are configured into
16501 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16502 is meant to make @var{filename} (an executable) available for debugging
16503 on the remote system---by downloading, or dynamic linking, for example.
16504 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16505 the @code{add-symbol-file} command.
16507 If your @value{GDBN} does not have a @code{load} command, attempting to
16508 execute it gets the error message ``@code{You can't do that when your
16509 target is @dots{}}''
16511 The file is loaded at whatever address is specified in the executable.
16512 For some object file formats, you can specify the load address when you
16513 link the program; for other formats, like a.out, the object file format
16514 specifies a fixed address.
16515 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16517 Depending on the remote side capabilities, @value{GDBN} may be able to
16518 load programs into flash memory.
16520 @code{load} does not repeat if you press @key{RET} again after using it.
16524 @section Choosing Target Byte Order
16526 @cindex choosing target byte order
16527 @cindex target byte order
16529 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16530 offer the ability to run either big-endian or little-endian byte
16531 orders. Usually the executable or symbol will include a bit to
16532 designate the endian-ness, and you will not need to worry about
16533 which to use. However, you may still find it useful to adjust
16534 @value{GDBN}'s idea of processor endian-ness manually.
16538 @item set endian big
16539 Instruct @value{GDBN} to assume the target is big-endian.
16541 @item set endian little
16542 Instruct @value{GDBN} to assume the target is little-endian.
16544 @item set endian auto
16545 Instruct @value{GDBN} to use the byte order associated with the
16549 Display @value{GDBN}'s current idea of the target byte order.
16553 Note that these commands merely adjust interpretation of symbolic
16554 data on the host, and that they have absolutely no effect on the
16558 @node Remote Debugging
16559 @chapter Debugging Remote Programs
16560 @cindex remote debugging
16562 If you are trying to debug a program running on a machine that cannot run
16563 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16564 For example, you might use remote debugging on an operating system kernel,
16565 or on a small system which does not have a general purpose operating system
16566 powerful enough to run a full-featured debugger.
16568 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16569 to make this work with particular debugging targets. In addition,
16570 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16571 but not specific to any particular target system) which you can use if you
16572 write the remote stubs---the code that runs on the remote system to
16573 communicate with @value{GDBN}.
16575 Other remote targets may be available in your
16576 configuration of @value{GDBN}; use @code{help target} to list them.
16579 * Connecting:: Connecting to a remote target
16580 * File Transfer:: Sending files to a remote system
16581 * Server:: Using the gdbserver program
16582 * Remote Configuration:: Remote configuration
16583 * Remote Stub:: Implementing a remote stub
16587 @section Connecting to a Remote Target
16589 On the @value{GDBN} host machine, you will need an unstripped copy of
16590 your program, since @value{GDBN} needs symbol and debugging information.
16591 Start up @value{GDBN} as usual, using the name of the local copy of your
16592 program as the first argument.
16594 @cindex @code{target remote}
16595 @value{GDBN} can communicate with the target over a serial line, or
16596 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16597 each case, @value{GDBN} uses the same protocol for debugging your
16598 program; only the medium carrying the debugging packets varies. The
16599 @code{target remote} command establishes a connection to the target.
16600 Its arguments indicate which medium to use:
16604 @item target remote @var{serial-device}
16605 @cindex serial line, @code{target remote}
16606 Use @var{serial-device} to communicate with the target. For example,
16607 to use a serial line connected to the device named @file{/dev/ttyb}:
16610 target remote /dev/ttyb
16613 If you're using a serial line, you may want to give @value{GDBN} the
16614 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16615 (@pxref{Remote Configuration, set remotebaud}) before the
16616 @code{target} command.
16618 @item target remote @code{@var{host}:@var{port}}
16619 @itemx target remote @code{tcp:@var{host}:@var{port}}
16620 @cindex @acronym{TCP} port, @code{target remote}
16621 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16622 The @var{host} may be either a host name or a numeric @acronym{IP}
16623 address; @var{port} must be a decimal number. The @var{host} could be
16624 the target machine itself, if it is directly connected to the net, or
16625 it might be a terminal server which in turn has a serial line to the
16628 For example, to connect to port 2828 on a terminal server named
16632 target remote manyfarms:2828
16635 If your remote target is actually running on the same machine as your
16636 debugger session (e.g.@: a simulator for your target running on the
16637 same host), you can omit the hostname. For example, to connect to
16638 port 1234 on your local machine:
16641 target remote :1234
16645 Note that the colon is still required here.
16647 @item target remote @code{udp:@var{host}:@var{port}}
16648 @cindex @acronym{UDP} port, @code{target remote}
16649 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16650 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16653 target remote udp:manyfarms:2828
16656 When using a @acronym{UDP} connection for remote debugging, you should
16657 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16658 can silently drop packets on busy or unreliable networks, which will
16659 cause havoc with your debugging session.
16661 @item target remote | @var{command}
16662 @cindex pipe, @code{target remote} to
16663 Run @var{command} in the background and communicate with it using a
16664 pipe. The @var{command} is a shell command, to be parsed and expanded
16665 by the system's command shell, @code{/bin/sh}; it should expect remote
16666 protocol packets on its standard input, and send replies on its
16667 standard output. You could use this to run a stand-alone simulator
16668 that speaks the remote debugging protocol, to make net connections
16669 using programs like @code{ssh}, or for other similar tricks.
16671 If @var{command} closes its standard output (perhaps by exiting),
16672 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16673 program has already exited, this will have no effect.)
16677 Once the connection has been established, you can use all the usual
16678 commands to examine and change data. The remote program is already
16679 running; you can use @kbd{step} and @kbd{continue}, and you do not
16680 need to use @kbd{run}.
16682 @cindex interrupting remote programs
16683 @cindex remote programs, interrupting
16684 Whenever @value{GDBN} is waiting for the remote program, if you type the
16685 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16686 program. This may or may not succeed, depending in part on the hardware
16687 and the serial drivers the remote system uses. If you type the
16688 interrupt character once again, @value{GDBN} displays this prompt:
16691 Interrupted while waiting for the program.
16692 Give up (and stop debugging it)? (y or n)
16695 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16696 (If you decide you want to try again later, you can use @samp{target
16697 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16698 goes back to waiting.
16701 @kindex detach (remote)
16703 When you have finished debugging the remote program, you can use the
16704 @code{detach} command to release it from @value{GDBN} control.
16705 Detaching from the target normally resumes its execution, but the results
16706 will depend on your particular remote stub. After the @code{detach}
16707 command, @value{GDBN} is free to connect to another target.
16711 The @code{disconnect} command behaves like @code{detach}, except that
16712 the target is generally not resumed. It will wait for @value{GDBN}
16713 (this instance or another one) to connect and continue debugging. After
16714 the @code{disconnect} command, @value{GDBN} is again free to connect to
16717 @cindex send command to remote monitor
16718 @cindex extend @value{GDBN} for remote targets
16719 @cindex add new commands for external monitor
16721 @item monitor @var{cmd}
16722 This command allows you to send arbitrary commands directly to the
16723 remote monitor. Since @value{GDBN} doesn't care about the commands it
16724 sends like this, this command is the way to extend @value{GDBN}---you
16725 can add new commands that only the external monitor will understand
16729 @node File Transfer
16730 @section Sending files to a remote system
16731 @cindex remote target, file transfer
16732 @cindex file transfer
16733 @cindex sending files to remote systems
16735 Some remote targets offer the ability to transfer files over the same
16736 connection used to communicate with @value{GDBN}. This is convenient
16737 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16738 running @code{gdbserver} over a network interface. For other targets,
16739 e.g.@: embedded devices with only a single serial port, this may be
16740 the only way to upload or download files.
16742 Not all remote targets support these commands.
16746 @item remote put @var{hostfile} @var{targetfile}
16747 Copy file @var{hostfile} from the host system (the machine running
16748 @value{GDBN}) to @var{targetfile} on the target system.
16751 @item remote get @var{targetfile} @var{hostfile}
16752 Copy file @var{targetfile} from the target system to @var{hostfile}
16753 on the host system.
16755 @kindex remote delete
16756 @item remote delete @var{targetfile}
16757 Delete @var{targetfile} from the target system.
16762 @section Using the @code{gdbserver} Program
16765 @cindex remote connection without stubs
16766 @code{gdbserver} is a control program for Unix-like systems, which
16767 allows you to connect your program with a remote @value{GDBN} via
16768 @code{target remote}---but without linking in the usual debugging stub.
16770 @code{gdbserver} is not a complete replacement for the debugging stubs,
16771 because it requires essentially the same operating-system facilities
16772 that @value{GDBN} itself does. In fact, a system that can run
16773 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16774 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16775 because it is a much smaller program than @value{GDBN} itself. It is
16776 also easier to port than all of @value{GDBN}, so you may be able to get
16777 started more quickly on a new system by using @code{gdbserver}.
16778 Finally, if you develop code for real-time systems, you may find that
16779 the tradeoffs involved in real-time operation make it more convenient to
16780 do as much development work as possible on another system, for example
16781 by cross-compiling. You can use @code{gdbserver} to make a similar
16782 choice for debugging.
16784 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16785 or a TCP connection, using the standard @value{GDBN} remote serial
16789 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16790 Do not run @code{gdbserver} connected to any public network; a
16791 @value{GDBN} connection to @code{gdbserver} provides access to the
16792 target system with the same privileges as the user running
16796 @subsection Running @code{gdbserver}
16797 @cindex arguments, to @code{gdbserver}
16798 @cindex @code{gdbserver}, command-line arguments
16800 Run @code{gdbserver} on the target system. You need a copy of the
16801 program you want to debug, including any libraries it requires.
16802 @code{gdbserver} does not need your program's symbol table, so you can
16803 strip the program if necessary to save space. @value{GDBN} on the host
16804 system does all the symbol handling.
16806 To use the server, you must tell it how to communicate with @value{GDBN};
16807 the name of your program; and the arguments for your program. The usual
16811 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16814 @var{comm} is either a device name (to use a serial line), or a TCP
16815 hostname and portnumber, or @code{-} or @code{stdio} to use
16816 stdin/stdout of @code{gdbserver}.
16817 For example, to debug Emacs with the argument
16818 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16822 target> gdbserver /dev/com1 emacs foo.txt
16825 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16828 To use a TCP connection instead of a serial line:
16831 target> gdbserver host:2345 emacs foo.txt
16834 The only difference from the previous example is the first argument,
16835 specifying that you are communicating with the host @value{GDBN} via
16836 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16837 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16838 (Currently, the @samp{host} part is ignored.) You can choose any number
16839 you want for the port number as long as it does not conflict with any
16840 TCP ports already in use on the target system (for example, @code{23} is
16841 reserved for @code{telnet}).@footnote{If you choose a port number that
16842 conflicts with another service, @code{gdbserver} prints an error message
16843 and exits.} You must use the same port number with the host @value{GDBN}
16844 @code{target remote} command.
16846 The @code{stdio} connection is useful when starting @code{gdbserver}
16850 (gdb) target remote | ssh -T hostname gdbserver - hello
16853 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16854 and we don't want escape-character handling. Ssh does this by default when
16855 a command is provided, the flag is provided to make it explicit.
16856 You could elide it if you want to.
16858 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16859 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16860 display through a pipe connected to gdbserver.
16861 Both @code{stdout} and @code{stderr} use the same pipe.
16863 @subsubsection Attaching to a Running Program
16864 @cindex attach to a program, @code{gdbserver}
16865 @cindex @option{--attach}, @code{gdbserver} option
16867 On some targets, @code{gdbserver} can also attach to running programs.
16868 This is accomplished via the @code{--attach} argument. The syntax is:
16871 target> gdbserver --attach @var{comm} @var{pid}
16874 @var{pid} is the process ID of a currently running process. It isn't necessary
16875 to point @code{gdbserver} at a binary for the running process.
16878 You can debug processes by name instead of process ID if your target has the
16879 @code{pidof} utility:
16882 target> gdbserver --attach @var{comm} `pidof @var{program}`
16885 In case more than one copy of @var{program} is running, or @var{program}
16886 has multiple threads, most versions of @code{pidof} support the
16887 @code{-s} option to only return the first process ID.
16889 @subsubsection Multi-Process Mode for @code{gdbserver}
16890 @cindex @code{gdbserver}, multiple processes
16891 @cindex multiple processes with @code{gdbserver}
16893 When you connect to @code{gdbserver} using @code{target remote},
16894 @code{gdbserver} debugs the specified program only once. When the
16895 program exits, or you detach from it, @value{GDBN} closes the connection
16896 and @code{gdbserver} exits.
16898 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16899 enters multi-process mode. When the debugged program exits, or you
16900 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16901 though no program is running. The @code{run} and @code{attach}
16902 commands instruct @code{gdbserver} to run or attach to a new program.
16903 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16904 remote exec-file}) to select the program to run. Command line
16905 arguments are supported, except for wildcard expansion and I/O
16906 redirection (@pxref{Arguments}).
16908 @cindex @option{--multi}, @code{gdbserver} option
16909 To start @code{gdbserver} without supplying an initial command to run
16910 or process ID to attach, use the @option{--multi} command line option.
16911 Then you can connect using @kbd{target extended-remote} and start
16912 the program you want to debug.
16914 In multi-process mode @code{gdbserver} does not automatically exit unless you
16915 use the option @option{--once}. You can terminate it by using
16916 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16917 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16918 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16919 @option{--multi} option to @code{gdbserver} has no influence on that.
16921 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16923 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16925 @code{gdbserver} normally terminates after all of its debugged processes have
16926 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16927 extended-remote}, @code{gdbserver} stays running even with no processes left.
16928 @value{GDBN} normally terminates the spawned debugged process on its exit,
16929 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16930 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16931 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16932 stays running even in the @kbd{target remote} mode.
16934 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16935 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16936 completeness, at most one @value{GDBN} can be connected at a time.
16938 @cindex @option{--once}, @code{gdbserver} option
16939 By default, @code{gdbserver} keeps the listening TCP port open, so that
16940 additional connections are possible. However, if you start @code{gdbserver}
16941 with the @option{--once} option, it will stop listening for any further
16942 connection attempts after connecting to the first @value{GDBN} session. This
16943 means no further connections to @code{gdbserver} will be possible after the
16944 first one. It also means @code{gdbserver} will terminate after the first
16945 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16946 connections and even in the @kbd{target extended-remote} mode. The
16947 @option{--once} option allows reusing the same port number for connecting to
16948 multiple instances of @code{gdbserver} running on the same host, since each
16949 instance closes its port after the first connection.
16951 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16953 @cindex @option{--debug}, @code{gdbserver} option
16954 The @option{--debug} option tells @code{gdbserver} to display extra
16955 status information about the debugging process.
16956 @cindex @option{--remote-debug}, @code{gdbserver} option
16957 The @option{--remote-debug} option tells @code{gdbserver} to display
16958 remote protocol debug output. These options are intended for
16959 @code{gdbserver} development and for bug reports to the developers.
16961 @cindex @option{--wrapper}, @code{gdbserver} option
16962 The @option{--wrapper} option specifies a wrapper to launch programs
16963 for debugging. The option should be followed by the name of the
16964 wrapper, then any command-line arguments to pass to the wrapper, then
16965 @kbd{--} indicating the end of the wrapper arguments.
16967 @code{gdbserver} runs the specified wrapper program with a combined
16968 command line including the wrapper arguments, then the name of the
16969 program to debug, then any arguments to the program. The wrapper
16970 runs until it executes your program, and then @value{GDBN} gains control.
16972 You can use any program that eventually calls @code{execve} with
16973 its arguments as a wrapper. Several standard Unix utilities do
16974 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16975 with @code{exec "$@@"} will also work.
16977 For example, you can use @code{env} to pass an environment variable to
16978 the debugged program, without setting the variable in @code{gdbserver}'s
16982 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16985 @subsection Connecting to @code{gdbserver}
16987 Run @value{GDBN} on the host system.
16989 First make sure you have the necessary symbol files. Load symbols for
16990 your application using the @code{file} command before you connect. Use
16991 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16992 was compiled with the correct sysroot using @code{--with-sysroot}).
16994 The symbol file and target libraries must exactly match the executable
16995 and libraries on the target, with one exception: the files on the host
16996 system should not be stripped, even if the files on the target system
16997 are. Mismatched or missing files will lead to confusing results
16998 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16999 files may also prevent @code{gdbserver} from debugging multi-threaded
17002 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17003 For TCP connections, you must start up @code{gdbserver} prior to using
17004 the @code{target remote} command. Otherwise you may get an error whose
17005 text depends on the host system, but which usually looks something like
17006 @samp{Connection refused}. Don't use the @code{load}
17007 command in @value{GDBN} when using @code{gdbserver}, since the program is
17008 already on the target.
17010 @subsection Monitor Commands for @code{gdbserver}
17011 @cindex monitor commands, for @code{gdbserver}
17012 @anchor{Monitor Commands for gdbserver}
17014 During a @value{GDBN} session using @code{gdbserver}, you can use the
17015 @code{monitor} command to send special requests to @code{gdbserver}.
17016 Here are the available commands.
17020 List the available monitor commands.
17022 @item monitor set debug 0
17023 @itemx monitor set debug 1
17024 Disable or enable general debugging messages.
17026 @item monitor set remote-debug 0
17027 @itemx monitor set remote-debug 1
17028 Disable or enable specific debugging messages associated with the remote
17029 protocol (@pxref{Remote Protocol}).
17031 @item monitor set libthread-db-search-path [PATH]
17032 @cindex gdbserver, search path for @code{libthread_db}
17033 When this command is issued, @var{path} is a colon-separated list of
17034 directories to search for @code{libthread_db} (@pxref{Threads,,set
17035 libthread-db-search-path}). If you omit @var{path},
17036 @samp{libthread-db-search-path} will be reset to its default value.
17038 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17039 not supported in @code{gdbserver}.
17042 Tell gdbserver to exit immediately. This command should be followed by
17043 @code{disconnect} to close the debugging session. @code{gdbserver} will
17044 detach from any attached processes and kill any processes it created.
17045 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17046 of a multi-process mode debug session.
17050 @subsection Tracepoints support in @code{gdbserver}
17051 @cindex tracepoints support in @code{gdbserver}
17053 On some targets, @code{gdbserver} supports tracepoints, fast
17054 tracepoints and static tracepoints.
17056 For fast or static tracepoints to work, a special library called the
17057 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17058 This library is built and distributed as an integral part of
17059 @code{gdbserver}. In addition, support for static tracepoints
17060 requires building the in-process agent library with static tracepoints
17061 support. At present, the UST (LTTng Userspace Tracer,
17062 @url{http://lttng.org/ust}) tracing engine is supported. This support
17063 is automatically available if UST development headers are found in the
17064 standard include path when @code{gdbserver} is built, or if
17065 @code{gdbserver} was explicitly configured using @option{--with-ust}
17066 to point at such headers. You can explicitly disable the support
17067 using @option{--with-ust=no}.
17069 There are several ways to load the in-process agent in your program:
17072 @item Specifying it as dependency at link time
17074 You can link your program dynamically with the in-process agent
17075 library. On most systems, this is accomplished by adding
17076 @code{-linproctrace} to the link command.
17078 @item Using the system's preloading mechanisms
17080 You can force loading the in-process agent at startup time by using
17081 your system's support for preloading shared libraries. Many Unixes
17082 support the concept of preloading user defined libraries. In most
17083 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17084 in the environment. See also the description of @code{gdbserver}'s
17085 @option{--wrapper} command line option.
17087 @item Using @value{GDBN} to force loading the agent at run time
17089 On some systems, you can force the inferior to load a shared library,
17090 by calling a dynamic loader function in the inferior that takes care
17091 of dynamically looking up and loading a shared library. On most Unix
17092 systems, the function is @code{dlopen}. You'll use the @code{call}
17093 command for that. For example:
17096 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17099 Note that on most Unix systems, for the @code{dlopen} function to be
17100 available, the program needs to be linked with @code{-ldl}.
17103 On systems that have a userspace dynamic loader, like most Unix
17104 systems, when you connect to @code{gdbserver} using @code{target
17105 remote}, you'll find that the program is stopped at the dynamic
17106 loader's entry point, and no shared library has been loaded in the
17107 program's address space yet, including the in-process agent. In that
17108 case, before being able to use any of the fast or static tracepoints
17109 features, you need to let the loader run and load the shared
17110 libraries. The simplest way to do that is to run the program to the
17111 main procedure. E.g., if debugging a C or C@t{++} program, start
17112 @code{gdbserver} like so:
17115 $ gdbserver :9999 myprogram
17118 Start GDB and connect to @code{gdbserver} like so, and run to main:
17122 (@value{GDBP}) target remote myhost:9999
17123 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17124 (@value{GDBP}) b main
17125 (@value{GDBP}) continue
17128 The in-process tracing agent library should now be loaded into the
17129 process; you can confirm it with the @code{info sharedlibrary}
17130 command, which will list @file{libinproctrace.so} as loaded in the
17131 process. You are now ready to install fast tracepoints, list static
17132 tracepoint markers, probe static tracepoints markers, and start
17135 @node Remote Configuration
17136 @section Remote Configuration
17139 @kindex show remote
17140 This section documents the configuration options available when
17141 debugging remote programs. For the options related to the File I/O
17142 extensions of the remote protocol, see @ref{system,
17143 system-call-allowed}.
17146 @item set remoteaddresssize @var{bits}
17147 @cindex address size for remote targets
17148 @cindex bits in remote address
17149 Set the maximum size of address in a memory packet to the specified
17150 number of bits. @value{GDBN} will mask off the address bits above
17151 that number, when it passes addresses to the remote target. The
17152 default value is the number of bits in the target's address.
17154 @item show remoteaddresssize
17155 Show the current value of remote address size in bits.
17157 @item set remotebaud @var{n}
17158 @cindex baud rate for remote targets
17159 Set the baud rate for the remote serial I/O to @var{n} baud. The
17160 value is used to set the speed of the serial port used for debugging
17163 @item show remotebaud
17164 Show the current speed of the remote connection.
17166 @item set remotebreak
17167 @cindex interrupt remote programs
17168 @cindex BREAK signal instead of Ctrl-C
17169 @anchor{set remotebreak}
17170 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17171 when you type @kbd{Ctrl-c} to interrupt the program running
17172 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17173 character instead. The default is off, since most remote systems
17174 expect to see @samp{Ctrl-C} as the interrupt signal.
17176 @item show remotebreak
17177 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17178 interrupt the remote program.
17180 @item set remoteflow on
17181 @itemx set remoteflow off
17182 @kindex set remoteflow
17183 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17184 on the serial port used to communicate to the remote target.
17186 @item show remoteflow
17187 @kindex show remoteflow
17188 Show the current setting of hardware flow control.
17190 @item set remotelogbase @var{base}
17191 Set the base (a.k.a.@: radix) of logging serial protocol
17192 communications to @var{base}. Supported values of @var{base} are:
17193 @code{ascii}, @code{octal}, and @code{hex}. The default is
17196 @item show remotelogbase
17197 Show the current setting of the radix for logging remote serial
17200 @item set remotelogfile @var{file}
17201 @cindex record serial communications on file
17202 Record remote serial communications on the named @var{file}. The
17203 default is not to record at all.
17205 @item show remotelogfile.
17206 Show the current setting of the file name on which to record the
17207 serial communications.
17209 @item set remotetimeout @var{num}
17210 @cindex timeout for serial communications
17211 @cindex remote timeout
17212 Set the timeout limit to wait for the remote target to respond to
17213 @var{num} seconds. The default is 2 seconds.
17215 @item show remotetimeout
17216 Show the current number of seconds to wait for the remote target
17219 @cindex limit hardware breakpoints and watchpoints
17220 @cindex remote target, limit break- and watchpoints
17221 @anchor{set remote hardware-watchpoint-limit}
17222 @anchor{set remote hardware-breakpoint-limit}
17223 @item set remote hardware-watchpoint-limit @var{limit}
17224 @itemx set remote hardware-breakpoint-limit @var{limit}
17225 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17226 watchpoints. A limit of -1, the default, is treated as unlimited.
17228 @cindex limit hardware watchpoints length
17229 @cindex remote target, limit watchpoints length
17230 @anchor{set remote hardware-watchpoint-length-limit}
17231 @item set remote hardware-watchpoint-length-limit @var{limit}
17232 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17233 a remote hardware watchpoint. A limit of -1, the default, is treated
17236 @item show remote hardware-watchpoint-length-limit
17237 Show the current limit (in bytes) of the maximum length of
17238 a remote hardware watchpoint.
17240 @item set remote exec-file @var{filename}
17241 @itemx show remote exec-file
17242 @anchor{set remote exec-file}
17243 @cindex executable file, for remote target
17244 Select the file used for @code{run} with @code{target
17245 extended-remote}. This should be set to a filename valid on the
17246 target system. If it is not set, the target will use a default
17247 filename (e.g.@: the last program run).
17249 @item set remote interrupt-sequence
17250 @cindex interrupt remote programs
17251 @cindex select Ctrl-C, BREAK or BREAK-g
17252 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17253 @samp{BREAK-g} as the
17254 sequence to the remote target in order to interrupt the execution.
17255 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17256 is high level of serial line for some certain time.
17257 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17258 It is @code{BREAK} signal followed by character @code{g}.
17260 @item show interrupt-sequence
17261 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17262 is sent by @value{GDBN} to interrupt the remote program.
17263 @code{BREAK-g} is BREAK signal followed by @code{g} and
17264 also known as Magic SysRq g.
17266 @item set remote interrupt-on-connect
17267 @cindex send interrupt-sequence on start
17268 Specify whether interrupt-sequence is sent to remote target when
17269 @value{GDBN} connects to it. This is mostly needed when you debug
17270 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17271 which is known as Magic SysRq g in order to connect @value{GDBN}.
17273 @item show interrupt-on-connect
17274 Show whether interrupt-sequence is sent
17275 to remote target when @value{GDBN} connects to it.
17279 @item set tcp auto-retry on
17280 @cindex auto-retry, for remote TCP target
17281 Enable auto-retry for remote TCP connections. This is useful if the remote
17282 debugging agent is launched in parallel with @value{GDBN}; there is a race
17283 condition because the agent may not become ready to accept the connection
17284 before @value{GDBN} attempts to connect. When auto-retry is
17285 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17286 to establish the connection using the timeout specified by
17287 @code{set tcp connect-timeout}.
17289 @item set tcp auto-retry off
17290 Do not auto-retry failed TCP connections.
17292 @item show tcp auto-retry
17293 Show the current auto-retry setting.
17295 @item set tcp connect-timeout @var{seconds}
17296 @cindex connection timeout, for remote TCP target
17297 @cindex timeout, for remote target connection
17298 Set the timeout for establishing a TCP connection to the remote target to
17299 @var{seconds}. The timeout affects both polling to retry failed connections
17300 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17301 that are merely slow to complete, and represents an approximate cumulative
17304 @item show tcp connect-timeout
17305 Show the current connection timeout setting.
17308 @cindex remote packets, enabling and disabling
17309 The @value{GDBN} remote protocol autodetects the packets supported by
17310 your debugging stub. If you need to override the autodetection, you
17311 can use these commands to enable or disable individual packets. Each
17312 packet can be set to @samp{on} (the remote target supports this
17313 packet), @samp{off} (the remote target does not support this packet),
17314 or @samp{auto} (detect remote target support for this packet). They
17315 all default to @samp{auto}. For more information about each packet,
17316 see @ref{Remote Protocol}.
17318 During normal use, you should not have to use any of these commands.
17319 If you do, that may be a bug in your remote debugging stub, or a bug
17320 in @value{GDBN}. You may want to report the problem to the
17321 @value{GDBN} developers.
17323 For each packet @var{name}, the command to enable or disable the
17324 packet is @code{set remote @var{name}-packet}. The available settings
17327 @multitable @columnfractions 0.28 0.32 0.25
17330 @tab Related Features
17332 @item @code{fetch-register}
17334 @tab @code{info registers}
17336 @item @code{set-register}
17340 @item @code{binary-download}
17342 @tab @code{load}, @code{set}
17344 @item @code{read-aux-vector}
17345 @tab @code{qXfer:auxv:read}
17346 @tab @code{info auxv}
17348 @item @code{symbol-lookup}
17349 @tab @code{qSymbol}
17350 @tab Detecting multiple threads
17352 @item @code{attach}
17353 @tab @code{vAttach}
17356 @item @code{verbose-resume}
17358 @tab Stepping or resuming multiple threads
17364 @item @code{software-breakpoint}
17368 @item @code{hardware-breakpoint}
17372 @item @code{write-watchpoint}
17376 @item @code{read-watchpoint}
17380 @item @code{access-watchpoint}
17384 @item @code{target-features}
17385 @tab @code{qXfer:features:read}
17386 @tab @code{set architecture}
17388 @item @code{library-info}
17389 @tab @code{qXfer:libraries:read}
17390 @tab @code{info sharedlibrary}
17392 @item @code{memory-map}
17393 @tab @code{qXfer:memory-map:read}
17394 @tab @code{info mem}
17396 @item @code{read-sdata-object}
17397 @tab @code{qXfer:sdata:read}
17398 @tab @code{print $_sdata}
17400 @item @code{read-spu-object}
17401 @tab @code{qXfer:spu:read}
17402 @tab @code{info spu}
17404 @item @code{write-spu-object}
17405 @tab @code{qXfer:spu:write}
17406 @tab @code{info spu}
17408 @item @code{read-siginfo-object}
17409 @tab @code{qXfer:siginfo:read}
17410 @tab @code{print $_siginfo}
17412 @item @code{write-siginfo-object}
17413 @tab @code{qXfer:siginfo:write}
17414 @tab @code{set $_siginfo}
17416 @item @code{threads}
17417 @tab @code{qXfer:threads:read}
17418 @tab @code{info threads}
17420 @item @code{get-thread-local-@*storage-address}
17421 @tab @code{qGetTLSAddr}
17422 @tab Displaying @code{__thread} variables
17424 @item @code{get-thread-information-block-address}
17425 @tab @code{qGetTIBAddr}
17426 @tab Display MS-Windows Thread Information Block.
17428 @item @code{search-memory}
17429 @tab @code{qSearch:memory}
17432 @item @code{supported-packets}
17433 @tab @code{qSupported}
17434 @tab Remote communications parameters
17436 @item @code{pass-signals}
17437 @tab @code{QPassSignals}
17438 @tab @code{handle @var{signal}}
17440 @item @code{hostio-close-packet}
17441 @tab @code{vFile:close}
17442 @tab @code{remote get}, @code{remote put}
17444 @item @code{hostio-open-packet}
17445 @tab @code{vFile:open}
17446 @tab @code{remote get}, @code{remote put}
17448 @item @code{hostio-pread-packet}
17449 @tab @code{vFile:pread}
17450 @tab @code{remote get}, @code{remote put}
17452 @item @code{hostio-pwrite-packet}
17453 @tab @code{vFile:pwrite}
17454 @tab @code{remote get}, @code{remote put}
17456 @item @code{hostio-unlink-packet}
17457 @tab @code{vFile:unlink}
17458 @tab @code{remote delete}
17460 @item @code{hostio-readlink-packet}
17461 @tab @code{vFile:readlink}
17464 @item @code{noack-packet}
17465 @tab @code{QStartNoAckMode}
17466 @tab Packet acknowledgment
17468 @item @code{osdata}
17469 @tab @code{qXfer:osdata:read}
17470 @tab @code{info os}
17472 @item @code{query-attached}
17473 @tab @code{qAttached}
17474 @tab Querying remote process attach state.
17476 @item @code{traceframe-info}
17477 @tab @code{qXfer:traceframe-info:read}
17478 @tab Traceframe info
17480 @item @code{install-in-trace}
17481 @tab @code{InstallInTrace}
17482 @tab Install tracepoint in tracing
17484 @item @code{disable-randomization}
17485 @tab @code{QDisableRandomization}
17486 @tab @code{set disable-randomization}
17490 @section Implementing a Remote Stub
17492 @cindex debugging stub, example
17493 @cindex remote stub, example
17494 @cindex stub example, remote debugging
17495 The stub files provided with @value{GDBN} implement the target side of the
17496 communication protocol, and the @value{GDBN} side is implemented in the
17497 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17498 these subroutines to communicate, and ignore the details. (If you're
17499 implementing your own stub file, you can still ignore the details: start
17500 with one of the existing stub files. @file{sparc-stub.c} is the best
17501 organized, and therefore the easiest to read.)
17503 @cindex remote serial debugging, overview
17504 To debug a program running on another machine (the debugging
17505 @dfn{target} machine), you must first arrange for all the usual
17506 prerequisites for the program to run by itself. For example, for a C
17511 A startup routine to set up the C runtime environment; these usually
17512 have a name like @file{crt0}. The startup routine may be supplied by
17513 your hardware supplier, or you may have to write your own.
17516 A C subroutine library to support your program's
17517 subroutine calls, notably managing input and output.
17520 A way of getting your program to the other machine---for example, a
17521 download program. These are often supplied by the hardware
17522 manufacturer, but you may have to write your own from hardware
17526 The next step is to arrange for your program to use a serial port to
17527 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17528 machine). In general terms, the scheme looks like this:
17532 @value{GDBN} already understands how to use this protocol; when everything
17533 else is set up, you can simply use the @samp{target remote} command
17534 (@pxref{Targets,,Specifying a Debugging Target}).
17536 @item On the target,
17537 you must link with your program a few special-purpose subroutines that
17538 implement the @value{GDBN} remote serial protocol. The file containing these
17539 subroutines is called a @dfn{debugging stub}.
17541 On certain remote targets, you can use an auxiliary program
17542 @code{gdbserver} instead of linking a stub into your program.
17543 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17546 The debugging stub is specific to the architecture of the remote
17547 machine; for example, use @file{sparc-stub.c} to debug programs on
17550 @cindex remote serial stub list
17551 These working remote stubs are distributed with @value{GDBN}:
17556 @cindex @file{i386-stub.c}
17559 For Intel 386 and compatible architectures.
17562 @cindex @file{m68k-stub.c}
17563 @cindex Motorola 680x0
17565 For Motorola 680x0 architectures.
17568 @cindex @file{sh-stub.c}
17571 For Renesas SH architectures.
17574 @cindex @file{sparc-stub.c}
17576 For @sc{sparc} architectures.
17578 @item sparcl-stub.c
17579 @cindex @file{sparcl-stub.c}
17582 For Fujitsu @sc{sparclite} architectures.
17586 The @file{README} file in the @value{GDBN} distribution may list other
17587 recently added stubs.
17590 * Stub Contents:: What the stub can do for you
17591 * Bootstrapping:: What you must do for the stub
17592 * Debug Session:: Putting it all together
17595 @node Stub Contents
17596 @subsection What the Stub Can Do for You
17598 @cindex remote serial stub
17599 The debugging stub for your architecture supplies these three
17603 @item set_debug_traps
17604 @findex set_debug_traps
17605 @cindex remote serial stub, initialization
17606 This routine arranges for @code{handle_exception} to run when your
17607 program stops. You must call this subroutine explicitly in your
17608 program's startup code.
17610 @item handle_exception
17611 @findex handle_exception
17612 @cindex remote serial stub, main routine
17613 This is the central workhorse, but your program never calls it
17614 explicitly---the setup code arranges for @code{handle_exception} to
17615 run when a trap is triggered.
17617 @code{handle_exception} takes control when your program stops during
17618 execution (for example, on a breakpoint), and mediates communications
17619 with @value{GDBN} on the host machine. This is where the communications
17620 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17621 representative on the target machine. It begins by sending summary
17622 information on the state of your program, then continues to execute,
17623 retrieving and transmitting any information @value{GDBN} needs, until you
17624 execute a @value{GDBN} command that makes your program resume; at that point,
17625 @code{handle_exception} returns control to your own code on the target
17629 @cindex @code{breakpoint} subroutine, remote
17630 Use this auxiliary subroutine to make your program contain a
17631 breakpoint. Depending on the particular situation, this may be the only
17632 way for @value{GDBN} to get control. For instance, if your target
17633 machine has some sort of interrupt button, you won't need to call this;
17634 pressing the interrupt button transfers control to
17635 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17636 simply receiving characters on the serial port may also trigger a trap;
17637 again, in that situation, you don't need to call @code{breakpoint} from
17638 your own program---simply running @samp{target remote} from the host
17639 @value{GDBN} session gets control.
17641 Call @code{breakpoint} if none of these is true, or if you simply want
17642 to make certain your program stops at a predetermined point for the
17643 start of your debugging session.
17646 @node Bootstrapping
17647 @subsection What You Must Do for the Stub
17649 @cindex remote stub, support routines
17650 The debugging stubs that come with @value{GDBN} are set up for a particular
17651 chip architecture, but they have no information about the rest of your
17652 debugging target machine.
17654 First of all you need to tell the stub how to communicate with the
17658 @item int getDebugChar()
17659 @findex getDebugChar
17660 Write this subroutine to read a single character from the serial port.
17661 It may be identical to @code{getchar} for your target system; a
17662 different name is used to allow you to distinguish the two if you wish.
17664 @item void putDebugChar(int)
17665 @findex putDebugChar
17666 Write this subroutine to write a single character to the serial port.
17667 It may be identical to @code{putchar} for your target system; a
17668 different name is used to allow you to distinguish the two if you wish.
17671 @cindex control C, and remote debugging
17672 @cindex interrupting remote targets
17673 If you want @value{GDBN} to be able to stop your program while it is
17674 running, you need to use an interrupt-driven serial driver, and arrange
17675 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17676 character). That is the character which @value{GDBN} uses to tell the
17677 remote system to stop.
17679 Getting the debugging target to return the proper status to @value{GDBN}
17680 probably requires changes to the standard stub; one quick and dirty way
17681 is to just execute a breakpoint instruction (the ``dirty'' part is that
17682 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17684 Other routines you need to supply are:
17687 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17688 @findex exceptionHandler
17689 Write this function to install @var{exception_address} in the exception
17690 handling tables. You need to do this because the stub does not have any
17691 way of knowing what the exception handling tables on your target system
17692 are like (for example, the processor's table might be in @sc{rom},
17693 containing entries which point to a table in @sc{ram}).
17694 @var{exception_number} is the exception number which should be changed;
17695 its meaning is architecture-dependent (for example, different numbers
17696 might represent divide by zero, misaligned access, etc). When this
17697 exception occurs, control should be transferred directly to
17698 @var{exception_address}, and the processor state (stack, registers,
17699 and so on) should be just as it is when a processor exception occurs. So if
17700 you want to use a jump instruction to reach @var{exception_address}, it
17701 should be a simple jump, not a jump to subroutine.
17703 For the 386, @var{exception_address} should be installed as an interrupt
17704 gate so that interrupts are masked while the handler runs. The gate
17705 should be at privilege level 0 (the most privileged level). The
17706 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17707 help from @code{exceptionHandler}.
17709 @item void flush_i_cache()
17710 @findex flush_i_cache
17711 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17712 instruction cache, if any, on your target machine. If there is no
17713 instruction cache, this subroutine may be a no-op.
17715 On target machines that have instruction caches, @value{GDBN} requires this
17716 function to make certain that the state of your program is stable.
17720 You must also make sure this library routine is available:
17723 @item void *memset(void *, int, int)
17725 This is the standard library function @code{memset} that sets an area of
17726 memory to a known value. If you have one of the free versions of
17727 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17728 either obtain it from your hardware manufacturer, or write your own.
17731 If you do not use the GNU C compiler, you may need other standard
17732 library subroutines as well; this varies from one stub to another,
17733 but in general the stubs are likely to use any of the common library
17734 subroutines which @code{@value{NGCC}} generates as inline code.
17737 @node Debug Session
17738 @subsection Putting it All Together
17740 @cindex remote serial debugging summary
17741 In summary, when your program is ready to debug, you must follow these
17746 Make sure you have defined the supporting low-level routines
17747 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17749 @code{getDebugChar}, @code{putDebugChar},
17750 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17754 Insert these lines in your program's startup code, before the main
17755 procedure is called:
17762 On some machines, when a breakpoint trap is raised, the hardware
17763 automatically makes the PC point to the instruction after the
17764 breakpoint. If your machine doesn't do that, you may need to adjust
17765 @code{handle_exception} to arrange for it to return to the instruction
17766 after the breakpoint on this first invocation, so that your program
17767 doesn't keep hitting the initial breakpoint instead of making
17771 For the 680x0 stub only, you need to provide a variable called
17772 @code{exceptionHook}. Normally you just use:
17775 void (*exceptionHook)() = 0;
17779 but if before calling @code{set_debug_traps}, you set it to point to a
17780 function in your program, that function is called when
17781 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17782 error). The function indicated by @code{exceptionHook} is called with
17783 one parameter: an @code{int} which is the exception number.
17786 Compile and link together: your program, the @value{GDBN} debugging stub for
17787 your target architecture, and the supporting subroutines.
17790 Make sure you have a serial connection between your target machine and
17791 the @value{GDBN} host, and identify the serial port on the host.
17794 @c The "remote" target now provides a `load' command, so we should
17795 @c document that. FIXME.
17796 Download your program to your target machine (or get it there by
17797 whatever means the manufacturer provides), and start it.
17800 Start @value{GDBN} on the host, and connect to the target
17801 (@pxref{Connecting,,Connecting to a Remote Target}).
17805 @node Configurations
17806 @chapter Configuration-Specific Information
17808 While nearly all @value{GDBN} commands are available for all native and
17809 cross versions of the debugger, there are some exceptions. This chapter
17810 describes things that are only available in certain configurations.
17812 There are three major categories of configurations: native
17813 configurations, where the host and target are the same, embedded
17814 operating system configurations, which are usually the same for several
17815 different processor architectures, and bare embedded processors, which
17816 are quite different from each other.
17821 * Embedded Processors::
17828 This section describes details specific to particular native
17833 * BSD libkvm Interface:: Debugging BSD kernel memory images
17834 * SVR4 Process Information:: SVR4 process information
17835 * DJGPP Native:: Features specific to the DJGPP port
17836 * Cygwin Native:: Features specific to the Cygwin port
17837 * Hurd Native:: Features specific to @sc{gnu} Hurd
17838 * Neutrino:: Features specific to QNX Neutrino
17839 * Darwin:: Features specific to Darwin
17845 On HP-UX systems, if you refer to a function or variable name that
17846 begins with a dollar sign, @value{GDBN} searches for a user or system
17847 name first, before it searches for a convenience variable.
17850 @node BSD libkvm Interface
17851 @subsection BSD libkvm Interface
17854 @cindex kernel memory image
17855 @cindex kernel crash dump
17857 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17858 interface that provides a uniform interface for accessing kernel virtual
17859 memory images, including live systems and crash dumps. @value{GDBN}
17860 uses this interface to allow you to debug live kernels and kernel crash
17861 dumps on many native BSD configurations. This is implemented as a
17862 special @code{kvm} debugging target. For debugging a live system, load
17863 the currently running kernel into @value{GDBN} and connect to the
17867 (@value{GDBP}) @b{target kvm}
17870 For debugging crash dumps, provide the file name of the crash dump as an
17874 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17877 Once connected to the @code{kvm} target, the following commands are
17883 Set current context from the @dfn{Process Control Block} (PCB) address.
17886 Set current context from proc address. This command isn't available on
17887 modern FreeBSD systems.
17890 @node SVR4 Process Information
17891 @subsection SVR4 Process Information
17893 @cindex examine process image
17894 @cindex process info via @file{/proc}
17896 Many versions of SVR4 and compatible systems provide a facility called
17897 @samp{/proc} that can be used to examine the image of a running
17898 process using file-system subroutines. If @value{GDBN} is configured
17899 for an operating system with this facility, the command @code{info
17900 proc} is available to report information about the process running
17901 your program, or about any process running on your system. @code{info
17902 proc} works only on SVR4 systems that include the @code{procfs} code.
17903 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17904 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17910 @itemx info proc @var{process-id}
17911 Summarize available information about any running process. If a
17912 process ID is specified by @var{process-id}, display information about
17913 that process; otherwise display information about the program being
17914 debugged. The summary includes the debugged process ID, the command
17915 line used to invoke it, its current working directory, and its
17916 executable file's absolute file name.
17918 On some systems, @var{process-id} can be of the form
17919 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17920 within a process. If the optional @var{pid} part is missing, it means
17921 a thread from the process being debugged (the leading @samp{/} still
17922 needs to be present, or else @value{GDBN} will interpret the number as
17923 a process ID rather than a thread ID).
17925 @item info proc mappings
17926 @cindex memory address space mappings
17927 Report the memory address space ranges accessible in the program, with
17928 information on whether the process has read, write, or execute access
17929 rights to each range. On @sc{gnu}/Linux systems, each memory range
17930 includes the object file which is mapped to that range, instead of the
17931 memory access rights to that range.
17933 @item info proc stat
17934 @itemx info proc status
17935 @cindex process detailed status information
17936 These subcommands are specific to @sc{gnu}/Linux systems. They show
17937 the process-related information, including the user ID and group ID;
17938 how many threads are there in the process; its virtual memory usage;
17939 the signals that are pending, blocked, and ignored; its TTY; its
17940 consumption of system and user time; its stack size; its @samp{nice}
17941 value; etc. For more information, see the @samp{proc} man page
17942 (type @kbd{man 5 proc} from your shell prompt).
17944 @item info proc all
17945 Show all the information about the process described under all of the
17946 above @code{info proc} subcommands.
17949 @comment These sub-options of 'info proc' were not included when
17950 @comment procfs.c was re-written. Keep their descriptions around
17951 @comment against the day when someone finds the time to put them back in.
17952 @kindex info proc times
17953 @item info proc times
17954 Starting time, user CPU time, and system CPU time for your program and
17957 @kindex info proc id
17959 Report on the process IDs related to your program: its own process ID,
17960 the ID of its parent, the process group ID, and the session ID.
17963 @item set procfs-trace
17964 @kindex set procfs-trace
17965 @cindex @code{procfs} API calls
17966 This command enables and disables tracing of @code{procfs} API calls.
17968 @item show procfs-trace
17969 @kindex show procfs-trace
17970 Show the current state of @code{procfs} API call tracing.
17972 @item set procfs-file @var{file}
17973 @kindex set procfs-file
17974 Tell @value{GDBN} to write @code{procfs} API trace to the named
17975 @var{file}. @value{GDBN} appends the trace info to the previous
17976 contents of the file. The default is to display the trace on the
17979 @item show procfs-file
17980 @kindex show procfs-file
17981 Show the file to which @code{procfs} API trace is written.
17983 @item proc-trace-entry
17984 @itemx proc-trace-exit
17985 @itemx proc-untrace-entry
17986 @itemx proc-untrace-exit
17987 @kindex proc-trace-entry
17988 @kindex proc-trace-exit
17989 @kindex proc-untrace-entry
17990 @kindex proc-untrace-exit
17991 These commands enable and disable tracing of entries into and exits
17992 from the @code{syscall} interface.
17995 @kindex info pidlist
17996 @cindex process list, QNX Neutrino
17997 For QNX Neutrino only, this command displays the list of all the
17998 processes and all the threads within each process.
18001 @kindex info meminfo
18002 @cindex mapinfo list, QNX Neutrino
18003 For QNX Neutrino only, this command displays the list of all mapinfos.
18007 @subsection Features for Debugging @sc{djgpp} Programs
18008 @cindex @sc{djgpp} debugging
18009 @cindex native @sc{djgpp} debugging
18010 @cindex MS-DOS-specific commands
18013 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18014 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18015 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18016 top of real-mode DOS systems and their emulations.
18018 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18019 defines a few commands specific to the @sc{djgpp} port. This
18020 subsection describes those commands.
18025 This is a prefix of @sc{djgpp}-specific commands which print
18026 information about the target system and important OS structures.
18029 @cindex MS-DOS system info
18030 @cindex free memory information (MS-DOS)
18031 @item info dos sysinfo
18032 This command displays assorted information about the underlying
18033 platform: the CPU type and features, the OS version and flavor, the
18034 DPMI version, and the available conventional and DPMI memory.
18039 @cindex segment descriptor tables
18040 @cindex descriptor tables display
18042 @itemx info dos ldt
18043 @itemx info dos idt
18044 These 3 commands display entries from, respectively, Global, Local,
18045 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18046 tables are data structures which store a descriptor for each segment
18047 that is currently in use. The segment's selector is an index into a
18048 descriptor table; the table entry for that index holds the
18049 descriptor's base address and limit, and its attributes and access
18052 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18053 segment (used for both data and the stack), and a DOS segment (which
18054 allows access to DOS/BIOS data structures and absolute addresses in
18055 conventional memory). However, the DPMI host will usually define
18056 additional segments in order to support the DPMI environment.
18058 @cindex garbled pointers
18059 These commands allow to display entries from the descriptor tables.
18060 Without an argument, all entries from the specified table are
18061 displayed. An argument, which should be an integer expression, means
18062 display a single entry whose index is given by the argument. For
18063 example, here's a convenient way to display information about the
18064 debugged program's data segment:
18067 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18068 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18072 This comes in handy when you want to see whether a pointer is outside
18073 the data segment's limit (i.e.@: @dfn{garbled}).
18075 @cindex page tables display (MS-DOS)
18077 @itemx info dos pte
18078 These two commands display entries from, respectively, the Page
18079 Directory and the Page Tables. Page Directories and Page Tables are
18080 data structures which control how virtual memory addresses are mapped
18081 into physical addresses. A Page Table includes an entry for every
18082 page of memory that is mapped into the program's address space; there
18083 may be several Page Tables, each one holding up to 4096 entries. A
18084 Page Directory has up to 4096 entries, one each for every Page Table
18085 that is currently in use.
18087 Without an argument, @kbd{info dos pde} displays the entire Page
18088 Directory, and @kbd{info dos pte} displays all the entries in all of
18089 the Page Tables. An argument, an integer expression, given to the
18090 @kbd{info dos pde} command means display only that entry from the Page
18091 Directory table. An argument given to the @kbd{info dos pte} command
18092 means display entries from a single Page Table, the one pointed to by
18093 the specified entry in the Page Directory.
18095 @cindex direct memory access (DMA) on MS-DOS
18096 These commands are useful when your program uses @dfn{DMA} (Direct
18097 Memory Access), which needs physical addresses to program the DMA
18100 These commands are supported only with some DPMI servers.
18102 @cindex physical address from linear address
18103 @item info dos address-pte @var{addr}
18104 This command displays the Page Table entry for a specified linear
18105 address. The argument @var{addr} is a linear address which should
18106 already have the appropriate segment's base address added to it,
18107 because this command accepts addresses which may belong to @emph{any}
18108 segment. For example, here's how to display the Page Table entry for
18109 the page where a variable @code{i} is stored:
18112 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18113 @exdent @code{Page Table entry for address 0x11a00d30:}
18114 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18118 This says that @code{i} is stored at offset @code{0xd30} from the page
18119 whose physical base address is @code{0x02698000}, and shows all the
18120 attributes of that page.
18122 Note that you must cast the addresses of variables to a @code{char *},
18123 since otherwise the value of @code{__djgpp_base_address}, the base
18124 address of all variables and functions in a @sc{djgpp} program, will
18125 be added using the rules of C pointer arithmetics: if @code{i} is
18126 declared an @code{int}, @value{GDBN} will add 4 times the value of
18127 @code{__djgpp_base_address} to the address of @code{i}.
18129 Here's another example, it displays the Page Table entry for the
18133 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18134 @exdent @code{Page Table entry for address 0x29110:}
18135 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18139 (The @code{+ 3} offset is because the transfer buffer's address is the
18140 3rd member of the @code{_go32_info_block} structure.) The output
18141 clearly shows that this DPMI server maps the addresses in conventional
18142 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18143 linear (@code{0x29110}) addresses are identical.
18145 This command is supported only with some DPMI servers.
18148 @cindex DOS serial data link, remote debugging
18149 In addition to native debugging, the DJGPP port supports remote
18150 debugging via a serial data link. The following commands are specific
18151 to remote serial debugging in the DJGPP port of @value{GDBN}.
18154 @kindex set com1base
18155 @kindex set com1irq
18156 @kindex set com2base
18157 @kindex set com2irq
18158 @kindex set com3base
18159 @kindex set com3irq
18160 @kindex set com4base
18161 @kindex set com4irq
18162 @item set com1base @var{addr}
18163 This command sets the base I/O port address of the @file{COM1} serial
18166 @item set com1irq @var{irq}
18167 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18168 for the @file{COM1} serial port.
18170 There are similar commands @samp{set com2base}, @samp{set com3irq},
18171 etc.@: for setting the port address and the @code{IRQ} lines for the
18174 @kindex show com1base
18175 @kindex show com1irq
18176 @kindex show com2base
18177 @kindex show com2irq
18178 @kindex show com3base
18179 @kindex show com3irq
18180 @kindex show com4base
18181 @kindex show com4irq
18182 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18183 display the current settings of the base address and the @code{IRQ}
18184 lines used by the COM ports.
18187 @kindex info serial
18188 @cindex DOS serial port status
18189 This command prints the status of the 4 DOS serial ports. For each
18190 port, it prints whether it's active or not, its I/O base address and
18191 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18192 counts of various errors encountered so far.
18196 @node Cygwin Native
18197 @subsection Features for Debugging MS Windows PE Executables
18198 @cindex MS Windows debugging
18199 @cindex native Cygwin debugging
18200 @cindex Cygwin-specific commands
18202 @value{GDBN} supports native debugging of MS Windows programs, including
18203 DLLs with and without symbolic debugging information.
18205 @cindex Ctrl-BREAK, MS-Windows
18206 @cindex interrupt debuggee on MS-Windows
18207 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18208 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18209 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18210 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18211 sequence, which can be used to interrupt the debuggee even if it
18214 There are various additional Cygwin-specific commands, described in
18215 this section. Working with DLLs that have no debugging symbols is
18216 described in @ref{Non-debug DLL Symbols}.
18221 This is a prefix of MS Windows-specific commands which print
18222 information about the target system and important OS structures.
18224 @item info w32 selector
18225 This command displays information returned by
18226 the Win32 API @code{GetThreadSelectorEntry} function.
18227 It takes an optional argument that is evaluated to
18228 a long value to give the information about this given selector.
18229 Without argument, this command displays information
18230 about the six segment registers.
18232 @item info w32 thread-information-block
18233 This command displays thread specific information stored in the
18234 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18235 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18239 This is a Cygwin-specific alias of @code{info shared}.
18241 @kindex dll-symbols
18243 This command loads symbols from a dll similarly to
18244 add-sym command but without the need to specify a base address.
18246 @kindex set cygwin-exceptions
18247 @cindex debugging the Cygwin DLL
18248 @cindex Cygwin DLL, debugging
18249 @item set cygwin-exceptions @var{mode}
18250 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18251 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18252 @value{GDBN} will delay recognition of exceptions, and may ignore some
18253 exceptions which seem to be caused by internal Cygwin DLL
18254 ``bookkeeping''. This option is meant primarily for debugging the
18255 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18256 @value{GDBN} users with false @code{SIGSEGV} signals.
18258 @kindex show cygwin-exceptions
18259 @item show cygwin-exceptions
18260 Displays whether @value{GDBN} will break on exceptions that happen
18261 inside the Cygwin DLL itself.
18263 @kindex set new-console
18264 @item set new-console @var{mode}
18265 If @var{mode} is @code{on} the debuggee will
18266 be started in a new console on next start.
18267 If @var{mode} is @code{off}, the debuggee will
18268 be started in the same console as the debugger.
18270 @kindex show new-console
18271 @item show new-console
18272 Displays whether a new console is used
18273 when the debuggee is started.
18275 @kindex set new-group
18276 @item set new-group @var{mode}
18277 This boolean value controls whether the debuggee should
18278 start a new group or stay in the same group as the debugger.
18279 This affects the way the Windows OS handles
18282 @kindex show new-group
18283 @item show new-group
18284 Displays current value of new-group boolean.
18286 @kindex set debugevents
18287 @item set debugevents
18288 This boolean value adds debug output concerning kernel events related
18289 to the debuggee seen by the debugger. This includes events that
18290 signal thread and process creation and exit, DLL loading and
18291 unloading, console interrupts, and debugging messages produced by the
18292 Windows @code{OutputDebugString} API call.
18294 @kindex set debugexec
18295 @item set debugexec
18296 This boolean value adds debug output concerning execute events
18297 (such as resume thread) seen by the debugger.
18299 @kindex set debugexceptions
18300 @item set debugexceptions
18301 This boolean value adds debug output concerning exceptions in the
18302 debuggee seen by the debugger.
18304 @kindex set debugmemory
18305 @item set debugmemory
18306 This boolean value adds debug output concerning debuggee memory reads
18307 and writes by the debugger.
18311 This boolean values specifies whether the debuggee is called
18312 via a shell or directly (default value is on).
18316 Displays if the debuggee will be started with a shell.
18321 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18324 @node Non-debug DLL Symbols
18325 @subsubsection Support for DLLs without Debugging Symbols
18326 @cindex DLLs with no debugging symbols
18327 @cindex Minimal symbols and DLLs
18329 Very often on windows, some of the DLLs that your program relies on do
18330 not include symbolic debugging information (for example,
18331 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18332 symbols in a DLL, it relies on the minimal amount of symbolic
18333 information contained in the DLL's export table. This section
18334 describes working with such symbols, known internally to @value{GDBN} as
18335 ``minimal symbols''.
18337 Note that before the debugged program has started execution, no DLLs
18338 will have been loaded. The easiest way around this problem is simply to
18339 start the program --- either by setting a breakpoint or letting the
18340 program run once to completion. It is also possible to force
18341 @value{GDBN} to load a particular DLL before starting the executable ---
18342 see the shared library information in @ref{Files}, or the
18343 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18344 explicitly loading symbols from a DLL with no debugging information will
18345 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18346 which may adversely affect symbol lookup performance.
18348 @subsubsection DLL Name Prefixes
18350 In keeping with the naming conventions used by the Microsoft debugging
18351 tools, DLL export symbols are made available with a prefix based on the
18352 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18353 also entered into the symbol table, so @code{CreateFileA} is often
18354 sufficient. In some cases there will be name clashes within a program
18355 (particularly if the executable itself includes full debugging symbols)
18356 necessitating the use of the fully qualified name when referring to the
18357 contents of the DLL. Use single-quotes around the name to avoid the
18358 exclamation mark (``!'') being interpreted as a language operator.
18360 Note that the internal name of the DLL may be all upper-case, even
18361 though the file name of the DLL is lower-case, or vice-versa. Since
18362 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18363 some confusion. If in doubt, try the @code{info functions} and
18364 @code{info variables} commands or even @code{maint print msymbols}
18365 (@pxref{Symbols}). Here's an example:
18368 (@value{GDBP}) info function CreateFileA
18369 All functions matching regular expression "CreateFileA":
18371 Non-debugging symbols:
18372 0x77e885f4 CreateFileA
18373 0x77e885f4 KERNEL32!CreateFileA
18377 (@value{GDBP}) info function !
18378 All functions matching regular expression "!":
18380 Non-debugging symbols:
18381 0x6100114c cygwin1!__assert
18382 0x61004034 cygwin1!_dll_crt0@@0
18383 0x61004240 cygwin1!dll_crt0(per_process *)
18387 @subsubsection Working with Minimal Symbols
18389 Symbols extracted from a DLL's export table do not contain very much
18390 type information. All that @value{GDBN} can do is guess whether a symbol
18391 refers to a function or variable depending on the linker section that
18392 contains the symbol. Also note that the actual contents of the memory
18393 contained in a DLL are not available unless the program is running. This
18394 means that you cannot examine the contents of a variable or disassemble
18395 a function within a DLL without a running program.
18397 Variables are generally treated as pointers and dereferenced
18398 automatically. For this reason, it is often necessary to prefix a
18399 variable name with the address-of operator (``&'') and provide explicit
18400 type information in the command. Here's an example of the type of
18404 (@value{GDBP}) print 'cygwin1!__argv'
18409 (@value{GDBP}) x 'cygwin1!__argv'
18410 0x10021610: "\230y\""
18413 And two possible solutions:
18416 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18417 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18421 (@value{GDBP}) x/2x &'cygwin1!__argv'
18422 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18423 (@value{GDBP}) x/x 0x10021608
18424 0x10021608: 0x0022fd98
18425 (@value{GDBP}) x/s 0x0022fd98
18426 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18429 Setting a break point within a DLL is possible even before the program
18430 starts execution. However, under these circumstances, @value{GDBN} can't
18431 examine the initial instructions of the function in order to skip the
18432 function's frame set-up code. You can work around this by using ``*&''
18433 to set the breakpoint at a raw memory address:
18436 (@value{GDBP}) break *&'python22!PyOS_Readline'
18437 Breakpoint 1 at 0x1e04eff0
18440 The author of these extensions is not entirely convinced that setting a
18441 break point within a shared DLL like @file{kernel32.dll} is completely
18445 @subsection Commands Specific to @sc{gnu} Hurd Systems
18446 @cindex @sc{gnu} Hurd debugging
18448 This subsection describes @value{GDBN} commands specific to the
18449 @sc{gnu} Hurd native debugging.
18454 @kindex set signals@r{, Hurd command}
18455 @kindex set sigs@r{, Hurd command}
18456 This command toggles the state of inferior signal interception by
18457 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18458 affected by this command. @code{sigs} is a shorthand alias for
18463 @kindex show signals@r{, Hurd command}
18464 @kindex show sigs@r{, Hurd command}
18465 Show the current state of intercepting inferior's signals.
18467 @item set signal-thread
18468 @itemx set sigthread
18469 @kindex set signal-thread
18470 @kindex set sigthread
18471 This command tells @value{GDBN} which thread is the @code{libc} signal
18472 thread. That thread is run when a signal is delivered to a running
18473 process. @code{set sigthread} is the shorthand alias of @code{set
18476 @item show signal-thread
18477 @itemx show sigthread
18478 @kindex show signal-thread
18479 @kindex show sigthread
18480 These two commands show which thread will run when the inferior is
18481 delivered a signal.
18484 @kindex set stopped@r{, Hurd command}
18485 This commands tells @value{GDBN} that the inferior process is stopped,
18486 as with the @code{SIGSTOP} signal. The stopped process can be
18487 continued by delivering a signal to it.
18490 @kindex show stopped@r{, Hurd command}
18491 This command shows whether @value{GDBN} thinks the debuggee is
18494 @item set exceptions
18495 @kindex set exceptions@r{, Hurd command}
18496 Use this command to turn off trapping of exceptions in the inferior.
18497 When exception trapping is off, neither breakpoints nor
18498 single-stepping will work. To restore the default, set exception
18501 @item show exceptions
18502 @kindex show exceptions@r{, Hurd command}
18503 Show the current state of trapping exceptions in the inferior.
18505 @item set task pause
18506 @kindex set task@r{, Hurd commands}
18507 @cindex task attributes (@sc{gnu} Hurd)
18508 @cindex pause current task (@sc{gnu} Hurd)
18509 This command toggles task suspension when @value{GDBN} has control.
18510 Setting it to on takes effect immediately, and the task is suspended
18511 whenever @value{GDBN} gets control. Setting it to off will take
18512 effect the next time the inferior is continued. If this option is set
18513 to off, you can use @code{set thread default pause on} or @code{set
18514 thread pause on} (see below) to pause individual threads.
18516 @item show task pause
18517 @kindex show task@r{, Hurd commands}
18518 Show the current state of task suspension.
18520 @item set task detach-suspend-count
18521 @cindex task suspend count
18522 @cindex detach from task, @sc{gnu} Hurd
18523 This command sets the suspend count the task will be left with when
18524 @value{GDBN} detaches from it.
18526 @item show task detach-suspend-count
18527 Show the suspend count the task will be left with when detaching.
18529 @item set task exception-port
18530 @itemx set task excp
18531 @cindex task exception port, @sc{gnu} Hurd
18532 This command sets the task exception port to which @value{GDBN} will
18533 forward exceptions. The argument should be the value of the @dfn{send
18534 rights} of the task. @code{set task excp} is a shorthand alias.
18536 @item set noninvasive
18537 @cindex noninvasive task options
18538 This command switches @value{GDBN} to a mode that is the least
18539 invasive as far as interfering with the inferior is concerned. This
18540 is the same as using @code{set task pause}, @code{set exceptions}, and
18541 @code{set signals} to values opposite to the defaults.
18543 @item info send-rights
18544 @itemx info receive-rights
18545 @itemx info port-rights
18546 @itemx info port-sets
18547 @itemx info dead-names
18550 @cindex send rights, @sc{gnu} Hurd
18551 @cindex receive rights, @sc{gnu} Hurd
18552 @cindex port rights, @sc{gnu} Hurd
18553 @cindex port sets, @sc{gnu} Hurd
18554 @cindex dead names, @sc{gnu} Hurd
18555 These commands display information about, respectively, send rights,
18556 receive rights, port rights, port sets, and dead names of a task.
18557 There are also shorthand aliases: @code{info ports} for @code{info
18558 port-rights} and @code{info psets} for @code{info port-sets}.
18560 @item set thread pause
18561 @kindex set thread@r{, Hurd command}
18562 @cindex thread properties, @sc{gnu} Hurd
18563 @cindex pause current thread (@sc{gnu} Hurd)
18564 This command toggles current thread suspension when @value{GDBN} has
18565 control. Setting it to on takes effect immediately, and the current
18566 thread is suspended whenever @value{GDBN} gets control. Setting it to
18567 off will take effect the next time the inferior is continued.
18568 Normally, this command has no effect, since when @value{GDBN} has
18569 control, the whole task is suspended. However, if you used @code{set
18570 task pause off} (see above), this command comes in handy to suspend
18571 only the current thread.
18573 @item show thread pause
18574 @kindex show thread@r{, Hurd command}
18575 This command shows the state of current thread suspension.
18577 @item set thread run
18578 This command sets whether the current thread is allowed to run.
18580 @item show thread run
18581 Show whether the current thread is allowed to run.
18583 @item set thread detach-suspend-count
18584 @cindex thread suspend count, @sc{gnu} Hurd
18585 @cindex detach from thread, @sc{gnu} Hurd
18586 This command sets the suspend count @value{GDBN} will leave on a
18587 thread when detaching. This number is relative to the suspend count
18588 found by @value{GDBN} when it notices the thread; use @code{set thread
18589 takeover-suspend-count} to force it to an absolute value.
18591 @item show thread detach-suspend-count
18592 Show the suspend count @value{GDBN} will leave on the thread when
18595 @item set thread exception-port
18596 @itemx set thread excp
18597 Set the thread exception port to which to forward exceptions. This
18598 overrides the port set by @code{set task exception-port} (see above).
18599 @code{set thread excp} is the shorthand alias.
18601 @item set thread takeover-suspend-count
18602 Normally, @value{GDBN}'s thread suspend counts are relative to the
18603 value @value{GDBN} finds when it notices each thread. This command
18604 changes the suspend counts to be absolute instead.
18606 @item set thread default
18607 @itemx show thread default
18608 @cindex thread default settings, @sc{gnu} Hurd
18609 Each of the above @code{set thread} commands has a @code{set thread
18610 default} counterpart (e.g., @code{set thread default pause}, @code{set
18611 thread default exception-port}, etc.). The @code{thread default}
18612 variety of commands sets the default thread properties for all
18613 threads; you can then change the properties of individual threads with
18614 the non-default commands.
18619 @subsection QNX Neutrino
18620 @cindex QNX Neutrino
18622 @value{GDBN} provides the following commands specific to the QNX
18626 @item set debug nto-debug
18627 @kindex set debug nto-debug
18628 When set to on, enables debugging messages specific to the QNX
18631 @item show debug nto-debug
18632 @kindex show debug nto-debug
18633 Show the current state of QNX Neutrino messages.
18640 @value{GDBN} provides the following commands specific to the Darwin target:
18643 @item set debug darwin @var{num}
18644 @kindex set debug darwin
18645 When set to a non zero value, enables debugging messages specific to
18646 the Darwin support. Higher values produce more verbose output.
18648 @item show debug darwin
18649 @kindex show debug darwin
18650 Show the current state of Darwin messages.
18652 @item set debug mach-o @var{num}
18653 @kindex set debug mach-o
18654 When set to a non zero value, enables debugging messages while
18655 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18656 file format used on Darwin for object and executable files.) Higher
18657 values produce more verbose output. This is a command to diagnose
18658 problems internal to @value{GDBN} and should not be needed in normal
18661 @item show debug mach-o
18662 @kindex show debug mach-o
18663 Show the current state of Mach-O file messages.
18665 @item set mach-exceptions on
18666 @itemx set mach-exceptions off
18667 @kindex set mach-exceptions
18668 On Darwin, faults are first reported as a Mach exception and are then
18669 mapped to a Posix signal. Use this command to turn on trapping of
18670 Mach exceptions in the inferior. This might be sometimes useful to
18671 better understand the cause of a fault. The default is off.
18673 @item show mach-exceptions
18674 @kindex show mach-exceptions
18675 Show the current state of exceptions trapping.
18680 @section Embedded Operating Systems
18682 This section describes configurations involving the debugging of
18683 embedded operating systems that are available for several different
18687 * VxWorks:: Using @value{GDBN} with VxWorks
18690 @value{GDBN} includes the ability to debug programs running on
18691 various real-time operating systems.
18694 @subsection Using @value{GDBN} with VxWorks
18700 @kindex target vxworks
18701 @item target vxworks @var{machinename}
18702 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18703 is the target system's machine name or IP address.
18707 On VxWorks, @code{load} links @var{filename} dynamically on the
18708 current target system as well as adding its symbols in @value{GDBN}.
18710 @value{GDBN} enables developers to spawn and debug tasks running on networked
18711 VxWorks targets from a Unix host. Already-running tasks spawned from
18712 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18713 both the Unix host and on the VxWorks target. The program
18714 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18715 installed with the name @code{vxgdb}, to distinguish it from a
18716 @value{GDBN} for debugging programs on the host itself.)
18719 @item VxWorks-timeout @var{args}
18720 @kindex vxworks-timeout
18721 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18722 This option is set by the user, and @var{args} represents the number of
18723 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18724 your VxWorks target is a slow software simulator or is on the far side
18725 of a thin network line.
18728 The following information on connecting to VxWorks was current when
18729 this manual was produced; newer releases of VxWorks may use revised
18732 @findex INCLUDE_RDB
18733 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18734 to include the remote debugging interface routines in the VxWorks
18735 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18736 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18737 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18738 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18739 information on configuring and remaking VxWorks, see the manufacturer's
18741 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18743 Once you have included @file{rdb.a} in your VxWorks system image and set
18744 your Unix execution search path to find @value{GDBN}, you are ready to
18745 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18746 @code{vxgdb}, depending on your installation).
18748 @value{GDBN} comes up showing the prompt:
18755 * VxWorks Connection:: Connecting to VxWorks
18756 * VxWorks Download:: VxWorks download
18757 * VxWorks Attach:: Running tasks
18760 @node VxWorks Connection
18761 @subsubsection Connecting to VxWorks
18763 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18764 network. To connect to a target whose host name is ``@code{tt}'', type:
18767 (vxgdb) target vxworks tt
18771 @value{GDBN} displays messages like these:
18774 Attaching remote machine across net...
18779 @value{GDBN} then attempts to read the symbol tables of any object modules
18780 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18781 these files by searching the directories listed in the command search
18782 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18783 to find an object file, it displays a message such as:
18786 prog.o: No such file or directory.
18789 When this happens, add the appropriate directory to the search path with
18790 the @value{GDBN} command @code{path}, and execute the @code{target}
18793 @node VxWorks Download
18794 @subsubsection VxWorks Download
18796 @cindex download to VxWorks
18797 If you have connected to the VxWorks target and you want to debug an
18798 object that has not yet been loaded, you can use the @value{GDBN}
18799 @code{load} command to download a file from Unix to VxWorks
18800 incrementally. The object file given as an argument to the @code{load}
18801 command is actually opened twice: first by the VxWorks target in order
18802 to download the code, then by @value{GDBN} in order to read the symbol
18803 table. This can lead to problems if the current working directories on
18804 the two systems differ. If both systems have NFS mounted the same
18805 filesystems, you can avoid these problems by using absolute paths.
18806 Otherwise, it is simplest to set the working directory on both systems
18807 to the directory in which the object file resides, and then to reference
18808 the file by its name, without any path. For instance, a program
18809 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18810 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18811 program, type this on VxWorks:
18814 -> cd "@var{vxpath}/vw/demo/rdb"
18818 Then, in @value{GDBN}, type:
18821 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18822 (vxgdb) load prog.o
18825 @value{GDBN} displays a response similar to this:
18828 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18831 You can also use the @code{load} command to reload an object module
18832 after editing and recompiling the corresponding source file. Note that
18833 this makes @value{GDBN} delete all currently-defined breakpoints,
18834 auto-displays, and convenience variables, and to clear the value
18835 history. (This is necessary in order to preserve the integrity of
18836 debugger's data structures that reference the target system's symbol
18839 @node VxWorks Attach
18840 @subsubsection Running Tasks
18842 @cindex running VxWorks tasks
18843 You can also attach to an existing task using the @code{attach} command as
18847 (vxgdb) attach @var{task}
18851 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18852 or suspended when you attach to it. Running tasks are suspended at
18853 the time of attachment.
18855 @node Embedded Processors
18856 @section Embedded Processors
18858 This section goes into details specific to particular embedded
18861 @cindex send command to simulator
18862 Whenever a specific embedded processor has a simulator, @value{GDBN}
18863 allows to send an arbitrary command to the simulator.
18866 @item sim @var{command}
18867 @kindex sim@r{, a command}
18868 Send an arbitrary @var{command} string to the simulator. Consult the
18869 documentation for the specific simulator in use for information about
18870 acceptable commands.
18876 * M32R/D:: Renesas M32R/D
18877 * M68K:: Motorola M68K
18878 * MicroBlaze:: Xilinx MicroBlaze
18879 * MIPS Embedded:: MIPS Embedded
18880 * OpenRISC 1000:: OpenRisc 1000
18881 * PA:: HP PA Embedded
18882 * PowerPC Embedded:: PowerPC Embedded
18883 * Sparclet:: Tsqware Sparclet
18884 * Sparclite:: Fujitsu Sparclite
18885 * Z8000:: Zilog Z8000
18888 * Super-H:: Renesas Super-H
18897 @item target rdi @var{dev}
18898 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18899 use this target to communicate with both boards running the Angel
18900 monitor, or with the EmbeddedICE JTAG debug device.
18903 @item target rdp @var{dev}
18908 @value{GDBN} provides the following ARM-specific commands:
18911 @item set arm disassembler
18913 This commands selects from a list of disassembly styles. The
18914 @code{"std"} style is the standard style.
18916 @item show arm disassembler
18918 Show the current disassembly style.
18920 @item set arm apcs32
18921 @cindex ARM 32-bit mode
18922 This command toggles ARM operation mode between 32-bit and 26-bit.
18924 @item show arm apcs32
18925 Display the current usage of the ARM 32-bit mode.
18927 @item set arm fpu @var{fputype}
18928 This command sets the ARM floating-point unit (FPU) type. The
18929 argument @var{fputype} can be one of these:
18933 Determine the FPU type by querying the OS ABI.
18935 Software FPU, with mixed-endian doubles on little-endian ARM
18938 GCC-compiled FPA co-processor.
18940 Software FPU with pure-endian doubles.
18946 Show the current type of the FPU.
18949 This command forces @value{GDBN} to use the specified ABI.
18952 Show the currently used ABI.
18954 @item set arm fallback-mode (arm|thumb|auto)
18955 @value{GDBN} uses the symbol table, when available, to determine
18956 whether instructions are ARM or Thumb. This command controls
18957 @value{GDBN}'s default behavior when the symbol table is not
18958 available. The default is @samp{auto}, which causes @value{GDBN} to
18959 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18962 @item show arm fallback-mode
18963 Show the current fallback instruction mode.
18965 @item set arm force-mode (arm|thumb|auto)
18966 This command overrides use of the symbol table to determine whether
18967 instructions are ARM or Thumb. The default is @samp{auto}, which
18968 causes @value{GDBN} to use the symbol table and then the setting
18969 of @samp{set arm fallback-mode}.
18971 @item show arm force-mode
18972 Show the current forced instruction mode.
18974 @item set debug arm
18975 Toggle whether to display ARM-specific debugging messages from the ARM
18976 target support subsystem.
18978 @item show debug arm
18979 Show whether ARM-specific debugging messages are enabled.
18982 The following commands are available when an ARM target is debugged
18983 using the RDI interface:
18986 @item rdilogfile @r{[}@var{file}@r{]}
18988 @cindex ADP (Angel Debugger Protocol) logging
18989 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18990 With an argument, sets the log file to the specified @var{file}. With
18991 no argument, show the current log file name. The default log file is
18994 @item rdilogenable @r{[}@var{arg}@r{]}
18995 @kindex rdilogenable
18996 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18997 enables logging, with an argument 0 or @code{"no"} disables it. With
18998 no arguments displays the current setting. When logging is enabled,
18999 ADP packets exchanged between @value{GDBN} and the RDI target device
19000 are logged to a file.
19002 @item set rdiromatzero
19003 @kindex set rdiromatzero
19004 @cindex ROM at zero address, RDI
19005 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19006 vector catching is disabled, so that zero address can be used. If off
19007 (the default), vector catching is enabled. For this command to take
19008 effect, it needs to be invoked prior to the @code{target rdi} command.
19010 @item show rdiromatzero
19011 @kindex show rdiromatzero
19012 Show the current setting of ROM at zero address.
19014 @item set rdiheartbeat
19015 @kindex set rdiheartbeat
19016 @cindex RDI heartbeat
19017 Enable or disable RDI heartbeat packets. It is not recommended to
19018 turn on this option, since it confuses ARM and EPI JTAG interface, as
19019 well as the Angel monitor.
19021 @item show rdiheartbeat
19022 @kindex show rdiheartbeat
19023 Show the setting of RDI heartbeat packets.
19027 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19028 The @value{GDBN} ARM simulator accepts the following optional arguments.
19031 @item --swi-support=@var{type}
19032 Tell the simulator which SWI interfaces to support.
19033 @var{type} may be a comma separated list of the following values.
19034 The default value is @code{all}.
19047 @subsection Renesas M32R/D and M32R/SDI
19050 @kindex target m32r
19051 @item target m32r @var{dev}
19052 Renesas M32R/D ROM monitor.
19054 @kindex target m32rsdi
19055 @item target m32rsdi @var{dev}
19056 Renesas M32R SDI server, connected via parallel port to the board.
19059 The following @value{GDBN} commands are specific to the M32R monitor:
19062 @item set download-path @var{path}
19063 @kindex set download-path
19064 @cindex find downloadable @sc{srec} files (M32R)
19065 Set the default path for finding downloadable @sc{srec} files.
19067 @item show download-path
19068 @kindex show download-path
19069 Show the default path for downloadable @sc{srec} files.
19071 @item set board-address @var{addr}
19072 @kindex set board-address
19073 @cindex M32-EVA target board address
19074 Set the IP address for the M32R-EVA target board.
19076 @item show board-address
19077 @kindex show board-address
19078 Show the current IP address of the target board.
19080 @item set server-address @var{addr}
19081 @kindex set server-address
19082 @cindex download server address (M32R)
19083 Set the IP address for the download server, which is the @value{GDBN}'s
19086 @item show server-address
19087 @kindex show server-address
19088 Display the IP address of the download server.
19090 @item upload @r{[}@var{file}@r{]}
19091 @kindex upload@r{, M32R}
19092 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19093 upload capability. If no @var{file} argument is given, the current
19094 executable file is uploaded.
19096 @item tload @r{[}@var{file}@r{]}
19097 @kindex tload@r{, M32R}
19098 Test the @code{upload} command.
19101 The following commands are available for M32R/SDI:
19106 @cindex reset SDI connection, M32R
19107 This command resets the SDI connection.
19111 This command shows the SDI connection status.
19114 @kindex debug_chaos
19115 @cindex M32R/Chaos debugging
19116 Instructs the remote that M32R/Chaos debugging is to be used.
19118 @item use_debug_dma
19119 @kindex use_debug_dma
19120 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19123 @kindex use_mon_code
19124 Instructs the remote to use the MON_CODE method of accessing memory.
19127 @kindex use_ib_break
19128 Instructs the remote to set breakpoints by IB break.
19130 @item use_dbt_break
19131 @kindex use_dbt_break
19132 Instructs the remote to set breakpoints by DBT.
19138 The Motorola m68k configuration includes ColdFire support, and a
19139 target command for the following ROM monitor.
19143 @kindex target dbug
19144 @item target dbug @var{dev}
19145 dBUG ROM monitor for Motorola ColdFire.
19150 @subsection MicroBlaze
19151 @cindex Xilinx MicroBlaze
19152 @cindex XMD, Xilinx Microprocessor Debugger
19154 The MicroBlaze is a soft-core processor supported on various Xilinx
19155 FPGAs, such as Spartan or Virtex series. Boards with these processors
19156 usually have JTAG ports which connect to a host system running the Xilinx
19157 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19158 This host system is used to download the configuration bitstream to
19159 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19160 communicates with the target board using the JTAG interface and
19161 presents a @code{gdbserver} interface to the board. By default
19162 @code{xmd} uses port @code{1234}. (While it is possible to change
19163 this default port, it requires the use of undocumented @code{xmd}
19164 commands. Contact Xilinx support if you need to do this.)
19166 Use these GDB commands to connect to the MicroBlaze target processor.
19169 @item target remote :1234
19170 Use this command to connect to the target if you are running @value{GDBN}
19171 on the same system as @code{xmd}.
19173 @item target remote @var{xmd-host}:1234
19174 Use this command to connect to the target if it is connected to @code{xmd}
19175 running on a different system named @var{xmd-host}.
19178 Use this command to download a program to the MicroBlaze target.
19180 @item set debug microblaze @var{n}
19181 Enable MicroBlaze-specific debugging messages if non-zero.
19183 @item show debug microblaze @var{n}
19184 Show MicroBlaze-specific debugging level.
19187 @node MIPS Embedded
19188 @subsection MIPS Embedded
19190 @cindex MIPS boards
19191 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19192 MIPS board attached to a serial line. This is available when
19193 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19196 Use these @value{GDBN} commands to specify the connection to your target board:
19199 @item target mips @var{port}
19200 @kindex target mips @var{port}
19201 To run a program on the board, start up @code{@value{GDBP}} with the
19202 name of your program as the argument. To connect to the board, use the
19203 command @samp{target mips @var{port}}, where @var{port} is the name of
19204 the serial port connected to the board. If the program has not already
19205 been downloaded to the board, you may use the @code{load} command to
19206 download it. You can then use all the usual @value{GDBN} commands.
19208 For example, this sequence connects to the target board through a serial
19209 port, and loads and runs a program called @var{prog} through the
19213 host$ @value{GDBP} @var{prog}
19214 @value{GDBN} is free software and @dots{}
19215 (@value{GDBP}) target mips /dev/ttyb
19216 (@value{GDBP}) load @var{prog}
19220 @item target mips @var{hostname}:@var{portnumber}
19221 On some @value{GDBN} host configurations, you can specify a TCP
19222 connection (for instance, to a serial line managed by a terminal
19223 concentrator) instead of a serial port, using the syntax
19224 @samp{@var{hostname}:@var{portnumber}}.
19226 @item target pmon @var{port}
19227 @kindex target pmon @var{port}
19230 @item target ddb @var{port}
19231 @kindex target ddb @var{port}
19232 NEC's DDB variant of PMON for Vr4300.
19234 @item target lsi @var{port}
19235 @kindex target lsi @var{port}
19236 LSI variant of PMON.
19238 @kindex target r3900
19239 @item target r3900 @var{dev}
19240 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19242 @kindex target array
19243 @item target array @var{dev}
19244 Array Tech LSI33K RAID controller board.
19250 @value{GDBN} also supports these special commands for MIPS targets:
19253 @item set mipsfpu double
19254 @itemx set mipsfpu single
19255 @itemx set mipsfpu none
19256 @itemx set mipsfpu auto
19257 @itemx show mipsfpu
19258 @kindex set mipsfpu
19259 @kindex show mipsfpu
19260 @cindex MIPS remote floating point
19261 @cindex floating point, MIPS remote
19262 If your target board does not support the MIPS floating point
19263 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19264 need this, you may wish to put the command in your @value{GDBN} init
19265 file). This tells @value{GDBN} how to find the return value of
19266 functions which return floating point values. It also allows
19267 @value{GDBN} to avoid saving the floating point registers when calling
19268 functions on the board. If you are using a floating point coprocessor
19269 with only single precision floating point support, as on the @sc{r4650}
19270 processor, use the command @samp{set mipsfpu single}. The default
19271 double precision floating point coprocessor may be selected using
19272 @samp{set mipsfpu double}.
19274 In previous versions the only choices were double precision or no
19275 floating point, so @samp{set mipsfpu on} will select double precision
19276 and @samp{set mipsfpu off} will select no floating point.
19278 As usual, you can inquire about the @code{mipsfpu} variable with
19279 @samp{show mipsfpu}.
19281 @item set timeout @var{seconds}
19282 @itemx set retransmit-timeout @var{seconds}
19283 @itemx show timeout
19284 @itemx show retransmit-timeout
19285 @cindex @code{timeout}, MIPS protocol
19286 @cindex @code{retransmit-timeout}, MIPS protocol
19287 @kindex set timeout
19288 @kindex show timeout
19289 @kindex set retransmit-timeout
19290 @kindex show retransmit-timeout
19291 You can control the timeout used while waiting for a packet, in the MIPS
19292 remote protocol, with the @code{set timeout @var{seconds}} command. The
19293 default is 5 seconds. Similarly, you can control the timeout used while
19294 waiting for an acknowledgment of a packet with the @code{set
19295 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19296 You can inspect both values with @code{show timeout} and @code{show
19297 retransmit-timeout}. (These commands are @emph{only} available when
19298 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19300 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19301 is waiting for your program to stop. In that case, @value{GDBN} waits
19302 forever because it has no way of knowing how long the program is going
19303 to run before stopping.
19305 @item set syn-garbage-limit @var{num}
19306 @kindex set syn-garbage-limit@r{, MIPS remote}
19307 @cindex synchronize with remote MIPS target
19308 Limit the maximum number of characters @value{GDBN} should ignore when
19309 it tries to synchronize with the remote target. The default is 10
19310 characters. Setting the limit to -1 means there's no limit.
19312 @item show syn-garbage-limit
19313 @kindex show syn-garbage-limit@r{, MIPS remote}
19314 Show the current limit on the number of characters to ignore when
19315 trying to synchronize with the remote system.
19317 @item set monitor-prompt @var{prompt}
19318 @kindex set monitor-prompt@r{, MIPS remote}
19319 @cindex remote monitor prompt
19320 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19321 remote monitor. The default depends on the target:
19331 @item show monitor-prompt
19332 @kindex show monitor-prompt@r{, MIPS remote}
19333 Show the current strings @value{GDBN} expects as the prompt from the
19336 @item set monitor-warnings
19337 @kindex set monitor-warnings@r{, MIPS remote}
19338 Enable or disable monitor warnings about hardware breakpoints. This
19339 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19340 display warning messages whose codes are returned by the @code{lsi}
19341 PMON monitor for breakpoint commands.
19343 @item show monitor-warnings
19344 @kindex show monitor-warnings@r{, MIPS remote}
19345 Show the current setting of printing monitor warnings.
19347 @item pmon @var{command}
19348 @kindex pmon@r{, MIPS remote}
19349 @cindex send PMON command
19350 This command allows sending an arbitrary @var{command} string to the
19351 monitor. The monitor must be in debug mode for this to work.
19354 @node OpenRISC 1000
19355 @subsection OpenRISC 1000
19356 @cindex OpenRISC 1000
19358 @cindex or1k boards
19359 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19360 about platform and commands.
19364 @kindex target jtag
19365 @item target jtag jtag://@var{host}:@var{port}
19367 Connects to remote JTAG server.
19368 JTAG remote server can be either an or1ksim or JTAG server,
19369 connected via parallel port to the board.
19371 Example: @code{target jtag jtag://localhost:9999}
19374 @item or1ksim @var{command}
19375 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19376 Simulator, proprietary commands can be executed.
19378 @kindex info or1k spr
19379 @item info or1k spr
19380 Displays spr groups.
19382 @item info or1k spr @var{group}
19383 @itemx info or1k spr @var{groupno}
19384 Displays register names in selected group.
19386 @item info or1k spr @var{group} @var{register}
19387 @itemx info or1k spr @var{register}
19388 @itemx info or1k spr @var{groupno} @var{registerno}
19389 @itemx info or1k spr @var{registerno}
19390 Shows information about specified spr register.
19393 @item spr @var{group} @var{register} @var{value}
19394 @itemx spr @var{register @var{value}}
19395 @itemx spr @var{groupno} @var{registerno @var{value}}
19396 @itemx spr @var{registerno @var{value}}
19397 Writes @var{value} to specified spr register.
19400 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19401 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19402 program execution and is thus much faster. Hardware breakpoints/watchpoint
19403 triggers can be set using:
19406 Load effective address/data
19408 Store effective address/data
19410 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19415 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19416 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19418 @code{htrace} commands:
19419 @cindex OpenRISC 1000 htrace
19422 @item hwatch @var{conditional}
19423 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19424 or Data. For example:
19426 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19428 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19432 Display information about current HW trace configuration.
19434 @item htrace trigger @var{conditional}
19435 Set starting criteria for HW trace.
19437 @item htrace qualifier @var{conditional}
19438 Set acquisition qualifier for HW trace.
19440 @item htrace stop @var{conditional}
19441 Set HW trace stopping criteria.
19443 @item htrace record [@var{data}]*
19444 Selects the data to be recorded, when qualifier is met and HW trace was
19447 @item htrace enable
19448 @itemx htrace disable
19449 Enables/disables the HW trace.
19451 @item htrace rewind [@var{filename}]
19452 Clears currently recorded trace data.
19454 If filename is specified, new trace file is made and any newly collected data
19455 will be written there.
19457 @item htrace print [@var{start} [@var{len}]]
19458 Prints trace buffer, using current record configuration.
19460 @item htrace mode continuous
19461 Set continuous trace mode.
19463 @item htrace mode suspend
19464 Set suspend trace mode.
19468 @node PowerPC Embedded
19469 @subsection PowerPC Embedded
19471 @cindex DVC register
19472 @value{GDBN} supports using the DVC (Data Value Compare) register to
19473 implement in hardware simple hardware watchpoint conditions of the form:
19476 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19477 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19480 The DVC register will be automatically used when @value{GDBN} detects
19481 such pattern in a condition expression, and the created watchpoint uses one
19482 debug register (either the @code{exact-watchpoints} option is on and the
19483 variable is scalar, or the variable has a length of one byte). This feature
19484 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19487 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19488 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19489 in which case watchpoints using only one debug register are created when
19490 watching variables of scalar types.
19492 You can create an artificial array to watch an arbitrary memory
19493 region using one of the following commands (@pxref{Expressions}):
19496 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19497 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19500 PowerPC embedded processors support masked watchpoints. See the discussion
19501 about the @code{mask} argument in @ref{Set Watchpoints}.
19503 @cindex ranged breakpoint
19504 PowerPC embedded processors support hardware accelerated
19505 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19506 the inferior whenever it executes an instruction at any address within
19507 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19508 use the @code{break-range} command.
19510 @value{GDBN} provides the following PowerPC-specific commands:
19513 @kindex break-range
19514 @item break-range @var{start-location}, @var{end-location}
19515 Set a breakpoint for an address range.
19516 @var{start-location} and @var{end-location} can specify a function name,
19517 a line number, an offset of lines from the current line or from the start
19518 location, or an address of an instruction (see @ref{Specify Location},
19519 for a list of all the possible ways to specify a @var{location}.)
19520 The breakpoint will stop execution of the inferior whenever it
19521 executes an instruction at any address within the specified range,
19522 (including @var{start-location} and @var{end-location}.)
19524 @kindex set powerpc
19525 @item set powerpc soft-float
19526 @itemx show powerpc soft-float
19527 Force @value{GDBN} to use (or not use) a software floating point calling
19528 convention. By default, @value{GDBN} selects the calling convention based
19529 on the selected architecture and the provided executable file.
19531 @item set powerpc vector-abi
19532 @itemx show powerpc vector-abi
19533 Force @value{GDBN} to use the specified calling convention for vector
19534 arguments and return values. The valid options are @samp{auto};
19535 @samp{generic}, to avoid vector registers even if they are present;
19536 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19537 registers. By default, @value{GDBN} selects the calling convention
19538 based on the selected architecture and the provided executable file.
19540 @item set powerpc exact-watchpoints
19541 @itemx show powerpc exact-watchpoints
19542 Allow @value{GDBN} to use only one debug register when watching a variable
19543 of scalar type, thus assuming that the variable is accessed through the
19544 address of its first byte.
19546 @kindex target dink32
19547 @item target dink32 @var{dev}
19548 DINK32 ROM monitor.
19550 @kindex target ppcbug
19551 @item target ppcbug @var{dev}
19552 @kindex target ppcbug1
19553 @item target ppcbug1 @var{dev}
19554 PPCBUG ROM monitor for PowerPC.
19557 @item target sds @var{dev}
19558 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19561 @cindex SDS protocol
19562 The following commands specific to the SDS protocol are supported
19566 @item set sdstimeout @var{nsec}
19567 @kindex set sdstimeout
19568 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19569 default is 2 seconds.
19571 @item show sdstimeout
19572 @kindex show sdstimeout
19573 Show the current value of the SDS timeout.
19575 @item sds @var{command}
19576 @kindex sds@r{, a command}
19577 Send the specified @var{command} string to the SDS monitor.
19582 @subsection HP PA Embedded
19586 @kindex target op50n
19587 @item target op50n @var{dev}
19588 OP50N monitor, running on an OKI HPPA board.
19590 @kindex target w89k
19591 @item target w89k @var{dev}
19592 W89K monitor, running on a Winbond HPPA board.
19597 @subsection Tsqware Sparclet
19601 @value{GDBN} enables developers to debug tasks running on
19602 Sparclet targets from a Unix host.
19603 @value{GDBN} uses code that runs on
19604 both the Unix host and on the Sparclet target. The program
19605 @code{@value{GDBP}} is installed and executed on the Unix host.
19608 @item remotetimeout @var{args}
19609 @kindex remotetimeout
19610 @value{GDBN} supports the option @code{remotetimeout}.
19611 This option is set by the user, and @var{args} represents the number of
19612 seconds @value{GDBN} waits for responses.
19615 @cindex compiling, on Sparclet
19616 When compiling for debugging, include the options @samp{-g} to get debug
19617 information and @samp{-Ttext} to relocate the program to where you wish to
19618 load it on the target. You may also want to add the options @samp{-n} or
19619 @samp{-N} in order to reduce the size of the sections. Example:
19622 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19625 You can use @code{objdump} to verify that the addresses are what you intended:
19628 sparclet-aout-objdump --headers --syms prog
19631 @cindex running, on Sparclet
19633 your Unix execution search path to find @value{GDBN}, you are ready to
19634 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19635 (or @code{sparclet-aout-gdb}, depending on your installation).
19637 @value{GDBN} comes up showing the prompt:
19644 * Sparclet File:: Setting the file to debug
19645 * Sparclet Connection:: Connecting to Sparclet
19646 * Sparclet Download:: Sparclet download
19647 * Sparclet Execution:: Running and debugging
19650 @node Sparclet File
19651 @subsubsection Setting File to Debug
19653 The @value{GDBN} command @code{file} lets you choose with program to debug.
19656 (gdbslet) file prog
19660 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19661 @value{GDBN} locates
19662 the file by searching the directories listed in the command search
19664 If the file was compiled with debug information (option @samp{-g}), source
19665 files will be searched as well.
19666 @value{GDBN} locates
19667 the source files by searching the directories listed in the directory search
19668 path (@pxref{Environment, ,Your Program's Environment}).
19670 to find a file, it displays a message such as:
19673 prog: No such file or directory.
19676 When this happens, add the appropriate directories to the search paths with
19677 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19678 @code{target} command again.
19680 @node Sparclet Connection
19681 @subsubsection Connecting to Sparclet
19683 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19684 To connect to a target on serial port ``@code{ttya}'', type:
19687 (gdbslet) target sparclet /dev/ttya
19688 Remote target sparclet connected to /dev/ttya
19689 main () at ../prog.c:3
19693 @value{GDBN} displays messages like these:
19699 @node Sparclet Download
19700 @subsubsection Sparclet Download
19702 @cindex download to Sparclet
19703 Once connected to the Sparclet target,
19704 you can use the @value{GDBN}
19705 @code{load} command to download the file from the host to the target.
19706 The file name and load offset should be given as arguments to the @code{load}
19708 Since the file format is aout, the program must be loaded to the starting
19709 address. You can use @code{objdump} to find out what this value is. The load
19710 offset is an offset which is added to the VMA (virtual memory address)
19711 of each of the file's sections.
19712 For instance, if the program
19713 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19714 and bss at 0x12010170, in @value{GDBN}, type:
19717 (gdbslet) load prog 0x12010000
19718 Loading section .text, size 0xdb0 vma 0x12010000
19721 If the code is loaded at a different address then what the program was linked
19722 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19723 to tell @value{GDBN} where to map the symbol table.
19725 @node Sparclet Execution
19726 @subsubsection Running and Debugging
19728 @cindex running and debugging Sparclet programs
19729 You can now begin debugging the task using @value{GDBN}'s execution control
19730 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19731 manual for the list of commands.
19735 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19737 Starting program: prog
19738 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19739 3 char *symarg = 0;
19741 4 char *execarg = "hello!";
19746 @subsection Fujitsu Sparclite
19750 @kindex target sparclite
19751 @item target sparclite @var{dev}
19752 Fujitsu sparclite boards, used only for the purpose of loading.
19753 You must use an additional command to debug the program.
19754 For example: target remote @var{dev} using @value{GDBN} standard
19760 @subsection Zilog Z8000
19763 @cindex simulator, Z8000
19764 @cindex Zilog Z8000 simulator
19766 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19769 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19770 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19771 segmented variant). The simulator recognizes which architecture is
19772 appropriate by inspecting the object code.
19775 @item target sim @var{args}
19777 @kindex target sim@r{, with Z8000}
19778 Debug programs on a simulated CPU. If the simulator supports setup
19779 options, specify them via @var{args}.
19783 After specifying this target, you can debug programs for the simulated
19784 CPU in the same style as programs for your host computer; use the
19785 @code{file} command to load a new program image, the @code{run} command
19786 to run your program, and so on.
19788 As well as making available all the usual machine registers
19789 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19790 additional items of information as specially named registers:
19795 Counts clock-ticks in the simulator.
19798 Counts instructions run in the simulator.
19801 Execution time in 60ths of a second.
19805 You can refer to these values in @value{GDBN} expressions with the usual
19806 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19807 conditional breakpoint that suspends only after at least 5000
19808 simulated clock ticks.
19811 @subsection Atmel AVR
19814 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19815 following AVR-specific commands:
19818 @item info io_registers
19819 @kindex info io_registers@r{, AVR}
19820 @cindex I/O registers (Atmel AVR)
19821 This command displays information about the AVR I/O registers. For
19822 each register, @value{GDBN} prints its number and value.
19829 When configured for debugging CRIS, @value{GDBN} provides the
19830 following CRIS-specific commands:
19833 @item set cris-version @var{ver}
19834 @cindex CRIS version
19835 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19836 The CRIS version affects register names and sizes. This command is useful in
19837 case autodetection of the CRIS version fails.
19839 @item show cris-version
19840 Show the current CRIS version.
19842 @item set cris-dwarf2-cfi
19843 @cindex DWARF-2 CFI and CRIS
19844 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19845 Change to @samp{off} when using @code{gcc-cris} whose version is below
19848 @item show cris-dwarf2-cfi
19849 Show the current state of using DWARF-2 CFI.
19851 @item set cris-mode @var{mode}
19853 Set the current CRIS mode to @var{mode}. It should only be changed when
19854 debugging in guru mode, in which case it should be set to
19855 @samp{guru} (the default is @samp{normal}).
19857 @item show cris-mode
19858 Show the current CRIS mode.
19862 @subsection Renesas Super-H
19865 For the Renesas Super-H processor, @value{GDBN} provides these
19870 @kindex regs@r{, Super-H}
19871 Show the values of all Super-H registers.
19873 @item set sh calling-convention @var{convention}
19874 @kindex set sh calling-convention
19875 Set the calling-convention used when calling functions from @value{GDBN}.
19876 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19877 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19878 convention. If the DWARF-2 information of the called function specifies
19879 that the function follows the Renesas calling convention, the function
19880 is called using the Renesas calling convention. If the calling convention
19881 is set to @samp{renesas}, the Renesas calling convention is always used,
19882 regardless of the DWARF-2 information. This can be used to override the
19883 default of @samp{gcc} if debug information is missing, or the compiler
19884 does not emit the DWARF-2 calling convention entry for a function.
19886 @item show sh calling-convention
19887 @kindex show sh calling-convention
19888 Show the current calling convention setting.
19893 @node Architectures
19894 @section Architectures
19896 This section describes characteristics of architectures that affect
19897 all uses of @value{GDBN} with the architecture, both native and cross.
19904 * HPPA:: HP PA architecture
19905 * SPU:: Cell Broadband Engine SPU architecture
19910 @subsection x86 Architecture-specific Issues
19913 @item set struct-convention @var{mode}
19914 @kindex set struct-convention
19915 @cindex struct return convention
19916 @cindex struct/union returned in registers
19917 Set the convention used by the inferior to return @code{struct}s and
19918 @code{union}s from functions to @var{mode}. Possible values of
19919 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19920 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19921 are returned on the stack, while @code{"reg"} means that a
19922 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19923 be returned in a register.
19925 @item show struct-convention
19926 @kindex show struct-convention
19927 Show the current setting of the convention to return @code{struct}s
19936 @kindex set rstack_high_address
19937 @cindex AMD 29K register stack
19938 @cindex register stack, AMD29K
19939 @item set rstack_high_address @var{address}
19940 On AMD 29000 family processors, registers are saved in a separate
19941 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19942 extent of this stack. Normally, @value{GDBN} just assumes that the
19943 stack is ``large enough''. This may result in @value{GDBN} referencing
19944 memory locations that do not exist. If necessary, you can get around
19945 this problem by specifying the ending address of the register stack with
19946 the @code{set rstack_high_address} command. The argument should be an
19947 address, which you probably want to precede with @samp{0x} to specify in
19950 @kindex show rstack_high_address
19951 @item show rstack_high_address
19952 Display the current limit of the register stack, on AMD 29000 family
19960 See the following section.
19965 @cindex stack on Alpha
19966 @cindex stack on MIPS
19967 @cindex Alpha stack
19969 Alpha- and MIPS-based computers use an unusual stack frame, which
19970 sometimes requires @value{GDBN} to search backward in the object code to
19971 find the beginning of a function.
19973 @cindex response time, MIPS debugging
19974 To improve response time (especially for embedded applications, where
19975 @value{GDBN} may be restricted to a slow serial line for this search)
19976 you may want to limit the size of this search, using one of these
19980 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19981 @item set heuristic-fence-post @var{limit}
19982 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19983 search for the beginning of a function. A value of @var{0} (the
19984 default) means there is no limit. However, except for @var{0}, the
19985 larger the limit the more bytes @code{heuristic-fence-post} must search
19986 and therefore the longer it takes to run. You should only need to use
19987 this command when debugging a stripped executable.
19989 @item show heuristic-fence-post
19990 Display the current limit.
19994 These commands are available @emph{only} when @value{GDBN} is configured
19995 for debugging programs on Alpha or MIPS processors.
19997 Several MIPS-specific commands are available when debugging MIPS
20001 @item set mips abi @var{arg}
20002 @kindex set mips abi
20003 @cindex set ABI for MIPS
20004 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
20005 values of @var{arg} are:
20009 The default ABI associated with the current binary (this is the
20019 @item show mips abi
20020 @kindex show mips abi
20021 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20024 @itemx show mipsfpu
20025 @xref{MIPS Embedded, set mipsfpu}.
20027 @item set mips mask-address @var{arg}
20028 @kindex set mips mask-address
20029 @cindex MIPS addresses, masking
20030 This command determines whether the most-significant 32 bits of 64-bit
20031 MIPS addresses are masked off. The argument @var{arg} can be
20032 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20033 setting, which lets @value{GDBN} determine the correct value.
20035 @item show mips mask-address
20036 @kindex show mips mask-address
20037 Show whether the upper 32 bits of MIPS addresses are masked off or
20040 @item set remote-mips64-transfers-32bit-regs
20041 @kindex set remote-mips64-transfers-32bit-regs
20042 This command controls compatibility with 64-bit MIPS targets that
20043 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20044 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20045 and 64 bits for other registers, set this option to @samp{on}.
20047 @item show remote-mips64-transfers-32bit-regs
20048 @kindex show remote-mips64-transfers-32bit-regs
20049 Show the current setting of compatibility with older MIPS 64 targets.
20051 @item set debug mips
20052 @kindex set debug mips
20053 This command turns on and off debugging messages for the MIPS-specific
20054 target code in @value{GDBN}.
20056 @item show debug mips
20057 @kindex show debug mips
20058 Show the current setting of MIPS debugging messages.
20064 @cindex HPPA support
20066 When @value{GDBN} is debugging the HP PA architecture, it provides the
20067 following special commands:
20070 @item set debug hppa
20071 @kindex set debug hppa
20072 This command determines whether HPPA architecture-specific debugging
20073 messages are to be displayed.
20075 @item show debug hppa
20076 Show whether HPPA debugging messages are displayed.
20078 @item maint print unwind @var{address}
20079 @kindex maint print unwind@r{, HPPA}
20080 This command displays the contents of the unwind table entry at the
20081 given @var{address}.
20087 @subsection Cell Broadband Engine SPU architecture
20088 @cindex Cell Broadband Engine
20091 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20092 it provides the following special commands:
20095 @item info spu event
20097 Display SPU event facility status. Shows current event mask
20098 and pending event status.
20100 @item info spu signal
20101 Display SPU signal notification facility status. Shows pending
20102 signal-control word and signal notification mode of both signal
20103 notification channels.
20105 @item info spu mailbox
20106 Display SPU mailbox facility status. Shows all pending entries,
20107 in order of processing, in each of the SPU Write Outbound,
20108 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20111 Display MFC DMA status. Shows all pending commands in the MFC
20112 DMA queue. For each entry, opcode, tag, class IDs, effective
20113 and local store addresses and transfer size are shown.
20115 @item info spu proxydma
20116 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20117 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20118 and local store addresses and transfer size are shown.
20122 When @value{GDBN} is debugging a combined PowerPC/SPU application
20123 on the Cell Broadband Engine, it provides in addition the following
20127 @item set spu stop-on-load @var{arg}
20129 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20130 will give control to the user when a new SPE thread enters its @code{main}
20131 function. The default is @code{off}.
20133 @item show spu stop-on-load
20135 Show whether to stop for new SPE threads.
20137 @item set spu auto-flush-cache @var{arg}
20138 Set whether to automatically flush the software-managed cache. When set to
20139 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20140 cache to be flushed whenever SPE execution stops. This provides a consistent
20141 view of PowerPC memory that is accessed via the cache. If an application
20142 does not use the software-managed cache, this option has no effect.
20144 @item show spu auto-flush-cache
20145 Show whether to automatically flush the software-managed cache.
20150 @subsection PowerPC
20151 @cindex PowerPC architecture
20153 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20154 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20155 numbers stored in the floating point registers. These values must be stored
20156 in two consecutive registers, always starting at an even register like
20157 @code{f0} or @code{f2}.
20159 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20160 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20161 @code{f2} and @code{f3} for @code{$dl1} and so on.
20163 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20164 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20167 @node Controlling GDB
20168 @chapter Controlling @value{GDBN}
20170 You can alter the way @value{GDBN} interacts with you by using the
20171 @code{set} command. For commands controlling how @value{GDBN} displays
20172 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20177 * Editing:: Command editing
20178 * Command History:: Command history
20179 * Screen Size:: Screen size
20180 * Numbers:: Numbers
20181 * ABI:: Configuring the current ABI
20182 * Messages/Warnings:: Optional warnings and messages
20183 * Debugging Output:: Optional messages about internal happenings
20184 * Other Misc Settings:: Other Miscellaneous Settings
20192 @value{GDBN} indicates its readiness to read a command by printing a string
20193 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20194 can change the prompt string with the @code{set prompt} command. For
20195 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20196 the prompt in one of the @value{GDBN} sessions so that you can always tell
20197 which one you are talking to.
20199 @emph{Note:} @code{set prompt} does not add a space for you after the
20200 prompt you set. This allows you to set a prompt which ends in a space
20201 or a prompt that does not.
20205 @item set prompt @var{newprompt}
20206 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20208 @kindex show prompt
20210 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20213 Versions of @value{GDBN} that ship with Python scripting enabled have
20214 prompt extensions. The commands for interacting with these extensions
20218 @kindex set extended-prompt
20219 @item set extended-prompt @var{prompt}
20220 Set an extended prompt that allows for substitutions.
20221 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20222 substitution. Any escape sequences specified as part of the prompt
20223 string are replaced with the corresponding strings each time the prompt
20229 set extended-prompt Current working directory: \w (gdb)
20232 Note that when an extended-prompt is set, it takes control of the
20233 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20235 @kindex show extended-prompt
20236 @item show extended-prompt
20237 Prints the extended prompt. Any escape sequences specified as part of
20238 the prompt string with @code{set extended-prompt}, are replaced with the
20239 corresponding strings each time the prompt is displayed.
20243 @section Command Editing
20245 @cindex command line editing
20247 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20248 @sc{gnu} library provides consistent behavior for programs which provide a
20249 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20250 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20251 substitution, and a storage and recall of command history across
20252 debugging sessions.
20254 You may control the behavior of command line editing in @value{GDBN} with the
20255 command @code{set}.
20258 @kindex set editing
20261 @itemx set editing on
20262 Enable command line editing (enabled by default).
20264 @item set editing off
20265 Disable command line editing.
20267 @kindex show editing
20269 Show whether command line editing is enabled.
20272 @ifset SYSTEM_READLINE
20273 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20275 @ifclear SYSTEM_READLINE
20276 @xref{Command Line Editing},
20278 for more details about the Readline
20279 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20280 encouraged to read that chapter.
20282 @node Command History
20283 @section Command History
20284 @cindex command history
20286 @value{GDBN} can keep track of the commands you type during your
20287 debugging sessions, so that you can be certain of precisely what
20288 happened. Use these commands to manage the @value{GDBN} command
20291 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20292 package, to provide the history facility.
20293 @ifset SYSTEM_READLINE
20294 @xref{Using History Interactively, , , history, GNU History Library},
20296 @ifclear SYSTEM_READLINE
20297 @xref{Using History Interactively},
20299 for the detailed description of the History library.
20301 To issue a command to @value{GDBN} without affecting certain aspects of
20302 the state which is seen by users, prefix it with @samp{server }
20303 (@pxref{Server Prefix}). This
20304 means that this command will not affect the command history, nor will it
20305 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20306 pressed on a line by itself.
20308 @cindex @code{server}, command prefix
20309 The server prefix does not affect the recording of values into the value
20310 history; to print a value without recording it into the value history,
20311 use the @code{output} command instead of the @code{print} command.
20313 Here is the description of @value{GDBN} commands related to command
20317 @cindex history substitution
20318 @cindex history file
20319 @kindex set history filename
20320 @cindex @env{GDBHISTFILE}, environment variable
20321 @item set history filename @var{fname}
20322 Set the name of the @value{GDBN} command history file to @var{fname}.
20323 This is the file where @value{GDBN} reads an initial command history
20324 list, and where it writes the command history from this session when it
20325 exits. You can access this list through history expansion or through
20326 the history command editing characters listed below. This file defaults
20327 to the value of the environment variable @code{GDBHISTFILE}, or to
20328 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20331 @cindex save command history
20332 @kindex set history save
20333 @item set history save
20334 @itemx set history save on
20335 Record command history in a file, whose name may be specified with the
20336 @code{set history filename} command. By default, this option is disabled.
20338 @item set history save off
20339 Stop recording command history in a file.
20341 @cindex history size
20342 @kindex set history size
20343 @cindex @env{HISTSIZE}, environment variable
20344 @item set history size @var{size}
20345 Set the number of commands which @value{GDBN} keeps in its history list.
20346 This defaults to the value of the environment variable
20347 @code{HISTSIZE}, or to 256 if this variable is not set.
20350 History expansion assigns special meaning to the character @kbd{!}.
20351 @ifset SYSTEM_READLINE
20352 @xref{Event Designators, , , history, GNU History Library},
20354 @ifclear SYSTEM_READLINE
20355 @xref{Event Designators},
20359 @cindex history expansion, turn on/off
20360 Since @kbd{!} is also the logical not operator in C, history expansion
20361 is off by default. If you decide to enable history expansion with the
20362 @code{set history expansion on} command, you may sometimes need to
20363 follow @kbd{!} (when it is used as logical not, in an expression) with
20364 a space or a tab to prevent it from being expanded. The readline
20365 history facilities do not attempt substitution on the strings
20366 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20368 The commands to control history expansion are:
20371 @item set history expansion on
20372 @itemx set history expansion
20373 @kindex set history expansion
20374 Enable history expansion. History expansion is off by default.
20376 @item set history expansion off
20377 Disable history expansion.
20380 @kindex show history
20382 @itemx show history filename
20383 @itemx show history save
20384 @itemx show history size
20385 @itemx show history expansion
20386 These commands display the state of the @value{GDBN} history parameters.
20387 @code{show history} by itself displays all four states.
20392 @kindex show commands
20393 @cindex show last commands
20394 @cindex display command history
20395 @item show commands
20396 Display the last ten commands in the command history.
20398 @item show commands @var{n}
20399 Print ten commands centered on command number @var{n}.
20401 @item show commands +
20402 Print ten commands just after the commands last printed.
20406 @section Screen Size
20407 @cindex size of screen
20408 @cindex pauses in output
20410 Certain commands to @value{GDBN} may produce large amounts of
20411 information output to the screen. To help you read all of it,
20412 @value{GDBN} pauses and asks you for input at the end of each page of
20413 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20414 to discard the remaining output. Also, the screen width setting
20415 determines when to wrap lines of output. Depending on what is being
20416 printed, @value{GDBN} tries to break the line at a readable place,
20417 rather than simply letting it overflow onto the following line.
20419 Normally @value{GDBN} knows the size of the screen from the terminal
20420 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20421 together with the value of the @code{TERM} environment variable and the
20422 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20423 you can override it with the @code{set height} and @code{set
20430 @kindex show height
20431 @item set height @var{lpp}
20433 @itemx set width @var{cpl}
20435 These @code{set} commands specify a screen height of @var{lpp} lines and
20436 a screen width of @var{cpl} characters. The associated @code{show}
20437 commands display the current settings.
20439 If you specify a height of zero lines, @value{GDBN} does not pause during
20440 output no matter how long the output is. This is useful if output is to a
20441 file or to an editor buffer.
20443 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20444 from wrapping its output.
20446 @item set pagination on
20447 @itemx set pagination off
20448 @kindex set pagination
20449 Turn the output pagination on or off; the default is on. Turning
20450 pagination off is the alternative to @code{set height 0}. Note that
20451 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20452 Options, -batch}) also automatically disables pagination.
20454 @item show pagination
20455 @kindex show pagination
20456 Show the current pagination mode.
20461 @cindex number representation
20462 @cindex entering numbers
20464 You can always enter numbers in octal, decimal, or hexadecimal in
20465 @value{GDBN} by the usual conventions: octal numbers begin with
20466 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20467 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20468 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20469 10; likewise, the default display for numbers---when no particular
20470 format is specified---is base 10. You can change the default base for
20471 both input and output with the commands described below.
20474 @kindex set input-radix
20475 @item set input-radix @var{base}
20476 Set the default base for numeric input. Supported choices
20477 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20478 specified either unambiguously or using the current input radix; for
20482 set input-radix 012
20483 set input-radix 10.
20484 set input-radix 0xa
20488 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20489 leaves the input radix unchanged, no matter what it was, since
20490 @samp{10}, being without any leading or trailing signs of its base, is
20491 interpreted in the current radix. Thus, if the current radix is 16,
20492 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20495 @kindex set output-radix
20496 @item set output-radix @var{base}
20497 Set the default base for numeric display. Supported choices
20498 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20499 specified either unambiguously or using the current input radix.
20501 @kindex show input-radix
20502 @item show input-radix
20503 Display the current default base for numeric input.
20505 @kindex show output-radix
20506 @item show output-radix
20507 Display the current default base for numeric display.
20509 @item set radix @r{[}@var{base}@r{]}
20513 These commands set and show the default base for both input and output
20514 of numbers. @code{set radix} sets the radix of input and output to
20515 the same base; without an argument, it resets the radix back to its
20516 default value of 10.
20521 @section Configuring the Current ABI
20523 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20524 application automatically. However, sometimes you need to override its
20525 conclusions. Use these commands to manage @value{GDBN}'s view of the
20532 One @value{GDBN} configuration can debug binaries for multiple operating
20533 system targets, either via remote debugging or native emulation.
20534 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20535 but you can override its conclusion using the @code{set osabi} command.
20536 One example where this is useful is in debugging of binaries which use
20537 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20538 not have the same identifying marks that the standard C library for your
20543 Show the OS ABI currently in use.
20546 With no argument, show the list of registered available OS ABI's.
20548 @item set osabi @var{abi}
20549 Set the current OS ABI to @var{abi}.
20552 @cindex float promotion
20554 Generally, the way that an argument of type @code{float} is passed to a
20555 function depends on whether the function is prototyped. For a prototyped
20556 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20557 according to the architecture's convention for @code{float}. For unprototyped
20558 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20559 @code{double} and then passed.
20561 Unfortunately, some forms of debug information do not reliably indicate whether
20562 a function is prototyped. If @value{GDBN} calls a function that is not marked
20563 as prototyped, it consults @kbd{set coerce-float-to-double}.
20566 @kindex set coerce-float-to-double
20567 @item set coerce-float-to-double
20568 @itemx set coerce-float-to-double on
20569 Arguments of type @code{float} will be promoted to @code{double} when passed
20570 to an unprototyped function. This is the default setting.
20572 @item set coerce-float-to-double off
20573 Arguments of type @code{float} will be passed directly to unprototyped
20576 @kindex show coerce-float-to-double
20577 @item show coerce-float-to-double
20578 Show the current setting of promoting @code{float} to @code{double}.
20582 @kindex show cp-abi
20583 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20584 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20585 used to build your application. @value{GDBN} only fully supports
20586 programs with a single C@t{++} ABI; if your program contains code using
20587 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20588 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20589 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20590 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20591 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20592 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20597 Show the C@t{++} ABI currently in use.
20600 With no argument, show the list of supported C@t{++} ABI's.
20602 @item set cp-abi @var{abi}
20603 @itemx set cp-abi auto
20604 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20607 @node Messages/Warnings
20608 @section Optional Warnings and Messages
20610 @cindex verbose operation
20611 @cindex optional warnings
20612 By default, @value{GDBN} is silent about its inner workings. If you are
20613 running on a slow machine, you may want to use the @code{set verbose}
20614 command. This makes @value{GDBN} tell you when it does a lengthy
20615 internal operation, so you will not think it has crashed.
20617 Currently, the messages controlled by @code{set verbose} are those
20618 which announce that the symbol table for a source file is being read;
20619 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20622 @kindex set verbose
20623 @item set verbose on
20624 Enables @value{GDBN} output of certain informational messages.
20626 @item set verbose off
20627 Disables @value{GDBN} output of certain informational messages.
20629 @kindex show verbose
20631 Displays whether @code{set verbose} is on or off.
20634 By default, if @value{GDBN} encounters bugs in the symbol table of an
20635 object file, it is silent; but if you are debugging a compiler, you may
20636 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20641 @kindex set complaints
20642 @item set complaints @var{limit}
20643 Permits @value{GDBN} to output @var{limit} complaints about each type of
20644 unusual symbols before becoming silent about the problem. Set
20645 @var{limit} to zero to suppress all complaints; set it to a large number
20646 to prevent complaints from being suppressed.
20648 @kindex show complaints
20649 @item show complaints
20650 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20654 @anchor{confirmation requests}
20655 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20656 lot of stupid questions to confirm certain commands. For example, if
20657 you try to run a program which is already running:
20661 The program being debugged has been started already.
20662 Start it from the beginning? (y or n)
20665 If you are willing to unflinchingly face the consequences of your own
20666 commands, you can disable this ``feature'':
20670 @kindex set confirm
20672 @cindex confirmation
20673 @cindex stupid questions
20674 @item set confirm off
20675 Disables confirmation requests. Note that running @value{GDBN} with
20676 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20677 automatically disables confirmation requests.
20679 @item set confirm on
20680 Enables confirmation requests (the default).
20682 @kindex show confirm
20684 Displays state of confirmation requests.
20688 @cindex command tracing
20689 If you need to debug user-defined commands or sourced files you may find it
20690 useful to enable @dfn{command tracing}. In this mode each command will be
20691 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20692 quantity denoting the call depth of each command.
20695 @kindex set trace-commands
20696 @cindex command scripts, debugging
20697 @item set trace-commands on
20698 Enable command tracing.
20699 @item set trace-commands off
20700 Disable command tracing.
20701 @item show trace-commands
20702 Display the current state of command tracing.
20705 @node Debugging Output
20706 @section Optional Messages about Internal Happenings
20707 @cindex optional debugging messages
20709 @value{GDBN} has commands that enable optional debugging messages from
20710 various @value{GDBN} subsystems; normally these commands are of
20711 interest to @value{GDBN} maintainers, or when reporting a bug. This
20712 section documents those commands.
20715 @kindex set exec-done-display
20716 @item set exec-done-display
20717 Turns on or off the notification of asynchronous commands'
20718 completion. When on, @value{GDBN} will print a message when an
20719 asynchronous command finishes its execution. The default is off.
20720 @kindex show exec-done-display
20721 @item show exec-done-display
20722 Displays the current setting of asynchronous command completion
20725 @cindex gdbarch debugging info
20726 @cindex architecture debugging info
20727 @item set debug arch
20728 Turns on or off display of gdbarch debugging info. The default is off
20730 @item show debug arch
20731 Displays the current state of displaying gdbarch debugging info.
20732 @item set debug aix-thread
20733 @cindex AIX threads
20734 Display debugging messages about inner workings of the AIX thread
20736 @item show debug aix-thread
20737 Show the current state of AIX thread debugging info display.
20738 @item set debug check-physname
20740 Check the results of the ``physname'' computation. When reading DWARF
20741 debugging information for C@t{++}, @value{GDBN} attempts to compute
20742 each entity's name. @value{GDBN} can do this computation in two
20743 different ways, depending on exactly what information is present.
20744 When enabled, this setting causes @value{GDBN} to compute the names
20745 both ways and display any discrepancies.
20746 @item show debug check-physname
20747 Show the current state of ``physname'' checking.
20748 @item set debug dwarf2-die
20749 @cindex DWARF2 DIEs
20750 Dump DWARF2 DIEs after they are read in.
20751 The value is the number of nesting levels to print.
20752 A value of zero turns off the display.
20753 @item show debug dwarf2-die
20754 Show the current state of DWARF2 DIE debugging.
20755 @item set debug displaced
20756 @cindex displaced stepping debugging info
20757 Turns on or off display of @value{GDBN} debugging info for the
20758 displaced stepping support. The default is off.
20759 @item show debug displaced
20760 Displays the current state of displaying @value{GDBN} debugging info
20761 related to displaced stepping.
20762 @item set debug event
20763 @cindex event debugging info
20764 Turns on or off display of @value{GDBN} event debugging info. The
20766 @item show debug event
20767 Displays the current state of displaying @value{GDBN} event debugging
20769 @item set debug expression
20770 @cindex expression debugging info
20771 Turns on or off display of debugging info about @value{GDBN}
20772 expression parsing. The default is off.
20773 @item show debug expression
20774 Displays the current state of displaying debugging info about
20775 @value{GDBN} expression parsing.
20776 @item set debug frame
20777 @cindex frame debugging info
20778 Turns on or off display of @value{GDBN} frame debugging info. The
20780 @item show debug frame
20781 Displays the current state of displaying @value{GDBN} frame debugging
20783 @item set debug gnu-nat
20784 @cindex @sc{gnu}/Hurd debug messages
20785 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20786 @item show debug gnu-nat
20787 Show the current state of @sc{gnu}/Hurd debugging messages.
20788 @item set debug infrun
20789 @cindex inferior debugging info
20790 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20791 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20792 for implementing operations such as single-stepping the inferior.
20793 @item show debug infrun
20794 Displays the current state of @value{GDBN} inferior debugging.
20795 @item set debug jit
20796 @cindex just-in-time compilation, debugging messages
20797 Turns on or off debugging messages from JIT debug support.
20798 @item show debug jit
20799 Displays the current state of @value{GDBN} JIT debugging.
20800 @item set debug lin-lwp
20801 @cindex @sc{gnu}/Linux LWP debug messages
20802 @cindex Linux lightweight processes
20803 Turns on or off debugging messages from the Linux LWP debug support.
20804 @item show debug lin-lwp
20805 Show the current state of Linux LWP debugging messages.
20806 @item set debug observer
20807 @cindex observer debugging info
20808 Turns on or off display of @value{GDBN} observer debugging. This
20809 includes info such as the notification of observable events.
20810 @item show debug observer
20811 Displays the current state of observer debugging.
20812 @item set debug overload
20813 @cindex C@t{++} overload debugging info
20814 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20815 info. This includes info such as ranking of functions, etc. The default
20817 @item show debug overload
20818 Displays the current state of displaying @value{GDBN} C@t{++} overload
20820 @cindex expression parser, debugging info
20821 @cindex debug expression parser
20822 @item set debug parser
20823 Turns on or off the display of expression parser debugging output.
20824 Internally, this sets the @code{yydebug} variable in the expression
20825 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20826 details. The default is off.
20827 @item show debug parser
20828 Show the current state of expression parser debugging.
20829 @cindex packets, reporting on stdout
20830 @cindex serial connections, debugging
20831 @cindex debug remote protocol
20832 @cindex remote protocol debugging
20833 @cindex display remote packets
20834 @item set debug remote
20835 Turns on or off display of reports on all packets sent back and forth across
20836 the serial line to the remote machine. The info is printed on the
20837 @value{GDBN} standard output stream. The default is off.
20838 @item show debug remote
20839 Displays the state of display of remote packets.
20840 @item set debug serial
20841 Turns on or off display of @value{GDBN} serial debugging info. The
20843 @item show debug serial
20844 Displays the current state of displaying @value{GDBN} serial debugging
20846 @item set debug solib-frv
20847 @cindex FR-V shared-library debugging
20848 Turns on or off debugging messages for FR-V shared-library code.
20849 @item show debug solib-frv
20850 Display the current state of FR-V shared-library code debugging
20852 @item set debug target
20853 @cindex target debugging info
20854 Turns on or off display of @value{GDBN} target debugging info. This info
20855 includes what is going on at the target level of GDB, as it happens. The
20856 default is 0. Set it to 1 to track events, and to 2 to also track the
20857 value of large memory transfers. Changes to this flag do not take effect
20858 until the next time you connect to a target or use the @code{run} command.
20859 @item show debug target
20860 Displays the current state of displaying @value{GDBN} target debugging
20862 @item set debug timestamp
20863 @cindex timestampping debugging info
20864 Turns on or off display of timestamps with @value{GDBN} debugging info.
20865 When enabled, seconds and microseconds are displayed before each debugging
20867 @item show debug timestamp
20868 Displays the current state of displaying timestamps with @value{GDBN}
20870 @item set debugvarobj
20871 @cindex variable object debugging info
20872 Turns on or off display of @value{GDBN} variable object debugging
20873 info. The default is off.
20874 @item show debugvarobj
20875 Displays the current state of displaying @value{GDBN} variable object
20877 @item set debug xml
20878 @cindex XML parser debugging
20879 Turns on or off debugging messages for built-in XML parsers.
20880 @item show debug xml
20881 Displays the current state of XML debugging messages.
20884 @node Other Misc Settings
20885 @section Other Miscellaneous Settings
20886 @cindex miscellaneous settings
20889 @kindex set interactive-mode
20890 @item set interactive-mode
20891 If @code{on}, forces @value{GDBN} to assume that GDB was started
20892 in a terminal. In practice, this means that @value{GDBN} should wait
20893 for the user to answer queries generated by commands entered at
20894 the command prompt. If @code{off}, forces @value{GDBN} to operate
20895 in the opposite mode, and it uses the default answers to all queries.
20896 If @code{auto} (the default), @value{GDBN} tries to determine whether
20897 its standard input is a terminal, and works in interactive-mode if it
20898 is, non-interactively otherwise.
20900 In the vast majority of cases, the debugger should be able to guess
20901 correctly which mode should be used. But this setting can be useful
20902 in certain specific cases, such as running a MinGW @value{GDBN}
20903 inside a cygwin window.
20905 @kindex show interactive-mode
20906 @item show interactive-mode
20907 Displays whether the debugger is operating in interactive mode or not.
20910 @node Extending GDB
20911 @chapter Extending @value{GDBN}
20912 @cindex extending GDB
20914 @value{GDBN} provides three mechanisms for extension. The first is based
20915 on composition of @value{GDBN} commands, the second is based on the
20916 Python scripting language, and the third is for defining new aliases of
20919 To facilitate the use of the first two extensions, @value{GDBN} is capable
20920 of evaluating the contents of a file. When doing so, @value{GDBN}
20921 can recognize which scripting language is being used by looking at
20922 the filename extension. Files with an unrecognized filename extension
20923 are always treated as a @value{GDBN} Command Files.
20924 @xref{Command Files,, Command files}.
20926 You can control how @value{GDBN} evaluates these files with the following
20930 @kindex set script-extension
20931 @kindex show script-extension
20932 @item set script-extension off
20933 All scripts are always evaluated as @value{GDBN} Command Files.
20935 @item set script-extension soft
20936 The debugger determines the scripting language based on filename
20937 extension. If this scripting language is supported, @value{GDBN}
20938 evaluates the script using that language. Otherwise, it evaluates
20939 the file as a @value{GDBN} Command File.
20941 @item set script-extension strict
20942 The debugger determines the scripting language based on filename
20943 extension, and evaluates the script using that language. If the
20944 language is not supported, then the evaluation fails.
20946 @item show script-extension
20947 Display the current value of the @code{script-extension} option.
20952 * Sequences:: Canned Sequences of Commands
20953 * Python:: Scripting @value{GDBN} using Python
20954 * Aliases:: Creating new spellings of existing commands
20958 @section Canned Sequences of Commands
20960 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20961 Command Lists}), @value{GDBN} provides two ways to store sequences of
20962 commands for execution as a unit: user-defined commands and command
20966 * Define:: How to define your own commands
20967 * Hooks:: Hooks for user-defined commands
20968 * Command Files:: How to write scripts of commands to be stored in a file
20969 * Output:: Commands for controlled output
20973 @subsection User-defined Commands
20975 @cindex user-defined command
20976 @cindex arguments, to user-defined commands
20977 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20978 which you assign a new name as a command. This is done with the
20979 @code{define} command. User commands may accept up to 10 arguments
20980 separated by whitespace. Arguments are accessed within the user command
20981 via @code{$arg0@dots{}$arg9}. A trivial example:
20985 print $arg0 + $arg1 + $arg2
20990 To execute the command use:
20997 This defines the command @code{adder}, which prints the sum of
20998 its three arguments. Note the arguments are text substitutions, so they may
20999 reference variables, use complex expressions, or even perform inferior
21002 @cindex argument count in user-defined commands
21003 @cindex how many arguments (user-defined commands)
21004 In addition, @code{$argc} may be used to find out how many arguments have
21005 been passed. This expands to a number in the range 0@dots{}10.
21010 print $arg0 + $arg1
21013 print $arg0 + $arg1 + $arg2
21021 @item define @var{commandname}
21022 Define a command named @var{commandname}. If there is already a command
21023 by that name, you are asked to confirm that you want to redefine it.
21024 @var{commandname} may be a bare command name consisting of letters,
21025 numbers, dashes, and underscores. It may also start with any predefined
21026 prefix command. For example, @samp{define target my-target} creates
21027 a user-defined @samp{target my-target} command.
21029 The definition of the command is made up of other @value{GDBN} command lines,
21030 which are given following the @code{define} command. The end of these
21031 commands is marked by a line containing @code{end}.
21034 @kindex end@r{ (user-defined commands)}
21035 @item document @var{commandname}
21036 Document the user-defined command @var{commandname}, so that it can be
21037 accessed by @code{help}. The command @var{commandname} must already be
21038 defined. This command reads lines of documentation just as @code{define}
21039 reads the lines of the command definition, ending with @code{end}.
21040 After the @code{document} command is finished, @code{help} on command
21041 @var{commandname} displays the documentation you have written.
21043 You may use the @code{document} command again to change the
21044 documentation of a command. Redefining the command with @code{define}
21045 does not change the documentation.
21047 @kindex dont-repeat
21048 @cindex don't repeat command
21050 Used inside a user-defined command, this tells @value{GDBN} that this
21051 command should not be repeated when the user hits @key{RET}
21052 (@pxref{Command Syntax, repeat last command}).
21054 @kindex help user-defined
21055 @item help user-defined
21056 List all user-defined commands, with the first line of the documentation
21061 @itemx show user @var{commandname}
21062 Display the @value{GDBN} commands used to define @var{commandname} (but
21063 not its documentation). If no @var{commandname} is given, display the
21064 definitions for all user-defined commands.
21066 @cindex infinite recursion in user-defined commands
21067 @kindex show max-user-call-depth
21068 @kindex set max-user-call-depth
21069 @item show max-user-call-depth
21070 @itemx set max-user-call-depth
21071 The value of @code{max-user-call-depth} controls how many recursion
21072 levels are allowed in user-defined commands before @value{GDBN} suspects an
21073 infinite recursion and aborts the command.
21076 In addition to the above commands, user-defined commands frequently
21077 use control flow commands, described in @ref{Command Files}.
21079 When user-defined commands are executed, the
21080 commands of the definition are not printed. An error in any command
21081 stops execution of the user-defined command.
21083 If used interactively, commands that would ask for confirmation proceed
21084 without asking when used inside a user-defined command. Many @value{GDBN}
21085 commands that normally print messages to say what they are doing omit the
21086 messages when used in a user-defined command.
21089 @subsection User-defined Command Hooks
21090 @cindex command hooks
21091 @cindex hooks, for commands
21092 @cindex hooks, pre-command
21095 You may define @dfn{hooks}, which are a special kind of user-defined
21096 command. Whenever you run the command @samp{foo}, if the user-defined
21097 command @samp{hook-foo} exists, it is executed (with no arguments)
21098 before that command.
21100 @cindex hooks, post-command
21102 A hook may also be defined which is run after the command you executed.
21103 Whenever you run the command @samp{foo}, if the user-defined command
21104 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21105 that command. Post-execution hooks may exist simultaneously with
21106 pre-execution hooks, for the same command.
21108 It is valid for a hook to call the command which it hooks. If this
21109 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21111 @c It would be nice if hookpost could be passed a parameter indicating
21112 @c if the command it hooks executed properly or not. FIXME!
21114 @kindex stop@r{, a pseudo-command}
21115 In addition, a pseudo-command, @samp{stop} exists. Defining
21116 (@samp{hook-stop}) makes the associated commands execute every time
21117 execution stops in your program: before breakpoint commands are run,
21118 displays are printed, or the stack frame is printed.
21120 For example, to ignore @code{SIGALRM} signals while
21121 single-stepping, but treat them normally during normal execution,
21126 handle SIGALRM nopass
21130 handle SIGALRM pass
21133 define hook-continue
21134 handle SIGALRM pass
21138 As a further example, to hook at the beginning and end of the @code{echo}
21139 command, and to add extra text to the beginning and end of the message,
21147 define hookpost-echo
21151 (@value{GDBP}) echo Hello World
21152 <<<---Hello World--->>>
21157 You can define a hook for any single-word command in @value{GDBN}, but
21158 not for command aliases; you should define a hook for the basic command
21159 name, e.g.@: @code{backtrace} rather than @code{bt}.
21160 @c FIXME! So how does Joe User discover whether a command is an alias
21162 You can hook a multi-word command by adding @code{hook-} or
21163 @code{hookpost-} to the last word of the command, e.g.@:
21164 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21166 If an error occurs during the execution of your hook, execution of
21167 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21168 (before the command that you actually typed had a chance to run).
21170 If you try to define a hook which does not match any known command, you
21171 get a warning from the @code{define} command.
21173 @node Command Files
21174 @subsection Command Files
21176 @cindex command files
21177 @cindex scripting commands
21178 A command file for @value{GDBN} is a text file made of lines that are
21179 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21180 also be included. An empty line in a command file does nothing; it
21181 does not mean to repeat the last command, as it would from the
21184 You can request the execution of a command file with the @code{source}
21185 command. Note that the @code{source} command is also used to evaluate
21186 scripts that are not Command Files. The exact behavior can be configured
21187 using the @code{script-extension} setting.
21188 @xref{Extending GDB,, Extending GDB}.
21192 @cindex execute commands from a file
21193 @item source [-s] [-v] @var{filename}
21194 Execute the command file @var{filename}.
21197 The lines in a command file are generally executed sequentially,
21198 unless the order of execution is changed by one of the
21199 @emph{flow-control commands} described below. The commands are not
21200 printed as they are executed. An error in any command terminates
21201 execution of the command file and control is returned to the console.
21203 @value{GDBN} first searches for @var{filename} in the current directory.
21204 If the file is not found there, and @var{filename} does not specify a
21205 directory, then @value{GDBN} also looks for the file on the source search path
21206 (specified with the @samp{directory} command);
21207 except that @file{$cdir} is not searched because the compilation directory
21208 is not relevant to scripts.
21210 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21211 on the search path even if @var{filename} specifies a directory.
21212 The search is done by appending @var{filename} to each element of the
21213 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21214 and the search path contains @file{/home/user} then @value{GDBN} will
21215 look for the script @file{/home/user/mylib/myscript}.
21216 The search is also done if @var{filename} is an absolute path.
21217 For example, if @var{filename} is @file{/tmp/myscript} and
21218 the search path contains @file{/home/user} then @value{GDBN} will
21219 look for the script @file{/home/user/tmp/myscript}.
21220 For DOS-like systems, if @var{filename} contains a drive specification,
21221 it is stripped before concatenation. For example, if @var{filename} is
21222 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21223 will look for the script @file{c:/tmp/myscript}.
21225 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21226 each command as it is executed. The option must be given before
21227 @var{filename}, and is interpreted as part of the filename anywhere else.
21229 Commands that would ask for confirmation if used interactively proceed
21230 without asking when used in a command file. Many @value{GDBN} commands that
21231 normally print messages to say what they are doing omit the messages
21232 when called from command files.
21234 @value{GDBN} also accepts command input from standard input. In this
21235 mode, normal output goes to standard output and error output goes to
21236 standard error. Errors in a command file supplied on standard input do
21237 not terminate execution of the command file---execution continues with
21241 gdb < cmds > log 2>&1
21244 (The syntax above will vary depending on the shell used.) This example
21245 will execute commands from the file @file{cmds}. All output and errors
21246 would be directed to @file{log}.
21248 Since commands stored on command files tend to be more general than
21249 commands typed interactively, they frequently need to deal with
21250 complicated situations, such as different or unexpected values of
21251 variables and symbols, changes in how the program being debugged is
21252 built, etc. @value{GDBN} provides a set of flow-control commands to
21253 deal with these complexities. Using these commands, you can write
21254 complex scripts that loop over data structures, execute commands
21255 conditionally, etc.
21262 This command allows to include in your script conditionally executed
21263 commands. The @code{if} command takes a single argument, which is an
21264 expression to evaluate. It is followed by a series of commands that
21265 are executed only if the expression is true (its value is nonzero).
21266 There can then optionally be an @code{else} line, followed by a series
21267 of commands that are only executed if the expression was false. The
21268 end of the list is marked by a line containing @code{end}.
21272 This command allows to write loops. Its syntax is similar to
21273 @code{if}: the command takes a single argument, which is an expression
21274 to evaluate, and must be followed by the commands to execute, one per
21275 line, terminated by an @code{end}. These commands are called the
21276 @dfn{body} of the loop. The commands in the body of @code{while} are
21277 executed repeatedly as long as the expression evaluates to true.
21281 This command exits the @code{while} loop in whose body it is included.
21282 Execution of the script continues after that @code{while}s @code{end}
21285 @kindex loop_continue
21286 @item loop_continue
21287 This command skips the execution of the rest of the body of commands
21288 in the @code{while} loop in whose body it is included. Execution
21289 branches to the beginning of the @code{while} loop, where it evaluates
21290 the controlling expression.
21292 @kindex end@r{ (if/else/while commands)}
21294 Terminate the block of commands that are the body of @code{if},
21295 @code{else}, or @code{while} flow-control commands.
21300 @subsection Commands for Controlled Output
21302 During the execution of a command file or a user-defined command, normal
21303 @value{GDBN} output is suppressed; the only output that appears is what is
21304 explicitly printed by the commands in the definition. This section
21305 describes three commands useful for generating exactly the output you
21310 @item echo @var{text}
21311 @c I do not consider backslash-space a standard C escape sequence
21312 @c because it is not in ANSI.
21313 Print @var{text}. Nonprinting characters can be included in
21314 @var{text} using C escape sequences, such as @samp{\n} to print a
21315 newline. @strong{No newline is printed unless you specify one.}
21316 In addition to the standard C escape sequences, a backslash followed
21317 by a space stands for a space. This is useful for displaying a
21318 string with spaces at the beginning or the end, since leading and
21319 trailing spaces are otherwise trimmed from all arguments.
21320 To print @samp{@w{ }and foo =@w{ }}, use the command
21321 @samp{echo \@w{ }and foo = \@w{ }}.
21323 A backslash at the end of @var{text} can be used, as in C, to continue
21324 the command onto subsequent lines. For example,
21327 echo This is some text\n\
21328 which is continued\n\
21329 onto several lines.\n
21332 produces the same output as
21335 echo This is some text\n
21336 echo which is continued\n
21337 echo onto several lines.\n
21341 @item output @var{expression}
21342 Print the value of @var{expression} and nothing but that value: no
21343 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21344 value history either. @xref{Expressions, ,Expressions}, for more information
21347 @item output/@var{fmt} @var{expression}
21348 Print the value of @var{expression} in format @var{fmt}. You can use
21349 the same formats as for @code{print}. @xref{Output Formats,,Output
21350 Formats}, for more information.
21353 @item printf @var{template}, @var{expressions}@dots{}
21354 Print the values of one or more @var{expressions} under the control of
21355 the string @var{template}. To print several values, make
21356 @var{expressions} be a comma-separated list of individual expressions,
21357 which may be either numbers or pointers. Their values are printed as
21358 specified by @var{template}, exactly as a C program would do by
21359 executing the code below:
21362 printf (@var{template}, @var{expressions}@dots{});
21365 As in @code{C} @code{printf}, ordinary characters in @var{template}
21366 are printed verbatim, while @dfn{conversion specification} introduced
21367 by the @samp{%} character cause subsequent @var{expressions} to be
21368 evaluated, their values converted and formatted according to type and
21369 style information encoded in the conversion specifications, and then
21372 For example, you can print two values in hex like this:
21375 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21378 @code{printf} supports all the standard @code{C} conversion
21379 specifications, including the flags and modifiers between the @samp{%}
21380 character and the conversion letter, with the following exceptions:
21384 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21387 The modifier @samp{*} is not supported for specifying precision or
21391 The @samp{'} flag (for separation of digits into groups according to
21392 @code{LC_NUMERIC'}) is not supported.
21395 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21399 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21402 The conversion letters @samp{a} and @samp{A} are not supported.
21406 Note that the @samp{ll} type modifier is supported only if the
21407 underlying @code{C} implementation used to build @value{GDBN} supports
21408 the @code{long long int} type, and the @samp{L} type modifier is
21409 supported only if @code{long double} type is available.
21411 As in @code{C}, @code{printf} supports simple backslash-escape
21412 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21413 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21414 single character. Octal and hexadecimal escape sequences are not
21417 Additionally, @code{printf} supports conversion specifications for DFP
21418 (@dfn{Decimal Floating Point}) types using the following length modifiers
21419 together with a floating point specifier.
21424 @samp{H} for printing @code{Decimal32} types.
21427 @samp{D} for printing @code{Decimal64} types.
21430 @samp{DD} for printing @code{Decimal128} types.
21433 If the underlying @code{C} implementation used to build @value{GDBN} has
21434 support for the three length modifiers for DFP types, other modifiers
21435 such as width and precision will also be available for @value{GDBN} to use.
21437 In case there is no such @code{C} support, no additional modifiers will be
21438 available and the value will be printed in the standard way.
21440 Here's an example of printing DFP types using the above conversion letters:
21442 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21446 @item eval @var{template}, @var{expressions}@dots{}
21447 Convert the values of one or more @var{expressions} under the control of
21448 the string @var{template} to a command line, and call it.
21453 @section Scripting @value{GDBN} using Python
21454 @cindex python scripting
21455 @cindex scripting with python
21457 You can script @value{GDBN} using the @uref{http://www.python.org/,
21458 Python programming language}. This feature is available only if
21459 @value{GDBN} was configured using @option{--with-python}.
21461 @cindex python directory
21462 Python scripts used by @value{GDBN} should be installed in
21463 @file{@var{data-directory}/python}, where @var{data-directory} is
21464 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21465 This directory, known as the @dfn{python directory},
21466 is automatically added to the Python Search Path in order to allow
21467 the Python interpreter to locate all scripts installed at this location.
21469 Additionally, @value{GDBN} commands and convenience functions which
21470 are written in Python and are located in the
21471 @file{@var{data-directory}/python/gdb/command} or
21472 @file{@var{data-directory}/python/gdb/function} directories are
21473 automatically imported when @value{GDBN} starts.
21476 * Python Commands:: Accessing Python from @value{GDBN}.
21477 * Python API:: Accessing @value{GDBN} from Python.
21478 * Auto-loading:: Automatically loading Python code.
21479 * Python modules:: Python modules provided by @value{GDBN}.
21482 @node Python Commands
21483 @subsection Python Commands
21484 @cindex python commands
21485 @cindex commands to access python
21487 @value{GDBN} provides one command for accessing the Python interpreter,
21488 and one related setting:
21492 @item python @r{[}@var{code}@r{]}
21493 The @code{python} command can be used to evaluate Python code.
21495 If given an argument, the @code{python} command will evaluate the
21496 argument as a Python command. For example:
21499 (@value{GDBP}) python print 23
21503 If you do not provide an argument to @code{python}, it will act as a
21504 multi-line command, like @code{define}. In this case, the Python
21505 script is made up of subsequent command lines, given after the
21506 @code{python} command. This command list is terminated using a line
21507 containing @code{end}. For example:
21510 (@value{GDBP}) python
21512 End with a line saying just "end".
21518 @kindex set python print-stack
21519 @item set python print-stack
21520 By default, @value{GDBN} will print only the message component of a
21521 Python exception when an error occurs in a Python script. This can be
21522 controlled using @code{set python print-stack}: if @code{full}, then
21523 full Python stack printing is enabled; if @code{none}, then Python stack
21524 and message printing is disabled; if @code{message}, the default, only
21525 the message component of the error is printed.
21528 It is also possible to execute a Python script from the @value{GDBN}
21532 @item source @file{script-name}
21533 The script name must end with @samp{.py} and @value{GDBN} must be configured
21534 to recognize the script language based on filename extension using
21535 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21537 @item python execfile ("script-name")
21538 This method is based on the @code{execfile} Python built-in function,
21539 and thus is always available.
21543 @subsection Python API
21545 @cindex programming in python
21547 @cindex python stdout
21548 @cindex python pagination
21549 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21550 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21551 A Python program which outputs to one of these streams may have its
21552 output interrupted by the user (@pxref{Screen Size}). In this
21553 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21556 * Basic Python:: Basic Python Functions.
21557 * Exception Handling:: How Python exceptions are translated.
21558 * Values From Inferior:: Python representation of values.
21559 * Types In Python:: Python representation of types.
21560 * Pretty Printing API:: Pretty-printing values.
21561 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21562 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21563 * Inferiors In Python:: Python representation of inferiors (processes)
21564 * Events In Python:: Listening for events from @value{GDBN}.
21565 * Threads In Python:: Accessing inferior threads from Python.
21566 * Commands In Python:: Implementing new commands in Python.
21567 * Parameters In Python:: Adding new @value{GDBN} parameters.
21568 * Functions In Python:: Writing new convenience functions.
21569 * Progspaces In Python:: Program spaces.
21570 * Objfiles In Python:: Object files.
21571 * Frames In Python:: Accessing inferior stack frames from Python.
21572 * Blocks In Python:: Accessing frame blocks from Python.
21573 * Symbols In Python:: Python representation of symbols.
21574 * Symbol Tables In Python:: Python representation of symbol tables.
21575 * Lazy Strings In Python:: Python representation of lazy strings.
21576 * Breakpoints In Python:: Manipulating breakpoints using Python.
21577 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21582 @subsubsection Basic Python
21584 @cindex python functions
21585 @cindex python module
21587 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21588 methods and classes added by @value{GDBN} are placed in this module.
21589 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21590 use in all scripts evaluated by the @code{python} command.
21592 @findex gdb.PYTHONDIR
21593 @defvar gdb.PYTHONDIR
21594 A string containing the python directory (@pxref{Python}).
21597 @findex gdb.execute
21598 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21599 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21600 If a GDB exception happens while @var{command} runs, it is
21601 translated as described in @ref{Exception Handling,,Exception Handling}.
21603 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21604 command as having originated from the user invoking it interactively.
21605 It must be a boolean value. If omitted, it defaults to @code{False}.
21607 By default, any output produced by @var{command} is sent to
21608 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21609 @code{True}, then output will be collected by @code{gdb.execute} and
21610 returned as a string. The default is @code{False}, in which case the
21611 return value is @code{None}. If @var{to_string} is @code{True}, the
21612 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21613 and height, and its pagination will be disabled; @pxref{Screen Size}.
21616 @findex gdb.breakpoints
21617 @defun gdb.breakpoints ()
21618 Return a sequence holding all of @value{GDBN}'s breakpoints.
21619 @xref{Breakpoints In Python}, for more information.
21622 @findex gdb.parameter
21623 @defun gdb.parameter (parameter)
21624 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21625 string naming the parameter to look up; @var{parameter} may contain
21626 spaces if the parameter has a multi-part name. For example,
21627 @samp{print object} is a valid parameter name.
21629 If the named parameter does not exist, this function throws a
21630 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21631 parameter's value is converted to a Python value of the appropriate
21632 type, and returned.
21635 @findex gdb.history
21636 @defun gdb.history (number)
21637 Return a value from @value{GDBN}'s value history (@pxref{Value
21638 History}). @var{number} indicates which history element to return.
21639 If @var{number} is negative, then @value{GDBN} will take its absolute value
21640 and count backward from the last element (i.e., the most recent element) to
21641 find the value to return. If @var{number} is zero, then @value{GDBN} will
21642 return the most recent element. If the element specified by @var{number}
21643 doesn't exist in the value history, a @code{gdb.error} exception will be
21646 If no exception is raised, the return value is always an instance of
21647 @code{gdb.Value} (@pxref{Values From Inferior}).
21650 @findex gdb.parse_and_eval
21651 @defun gdb.parse_and_eval (expression)
21652 Parse @var{expression} as an expression in the current language,
21653 evaluate it, and return the result as a @code{gdb.Value}.
21654 @var{expression} must be a string.
21656 This function can be useful when implementing a new command
21657 (@pxref{Commands In Python}), as it provides a way to parse the
21658 command's argument as an expression. It is also useful simply to
21659 compute values, for example, it is the only way to get the value of a
21660 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21663 @findex gdb.post_event
21664 @defun gdb.post_event (event)
21665 Put @var{event}, a callable object taking no arguments, into
21666 @value{GDBN}'s internal event queue. This callable will be invoked at
21667 some later point, during @value{GDBN}'s event processing. Events
21668 posted using @code{post_event} will be run in the order in which they
21669 were posted; however, there is no way to know when they will be
21670 processed relative to other events inside @value{GDBN}.
21672 @value{GDBN} is not thread-safe. If your Python program uses multiple
21673 threads, you must be careful to only call @value{GDBN}-specific
21674 functions in the main @value{GDBN} thread. @code{post_event} ensures
21678 (@value{GDBP}) python
21682 > def __init__(self, message):
21683 > self.message = message;
21684 > def __call__(self):
21685 > gdb.write(self.message)
21687 >class MyThread1 (threading.Thread):
21689 > gdb.post_event(Writer("Hello "))
21691 >class MyThread2 (threading.Thread):
21693 > gdb.post_event(Writer("World\n"))
21695 >MyThread1().start()
21696 >MyThread2().start()
21698 (@value{GDBP}) Hello World
21703 @defun gdb.write (string @r{[}, stream{]})
21704 Print a string to @value{GDBN}'s paginated output stream. The
21705 optional @var{stream} determines the stream to print to. The default
21706 stream is @value{GDBN}'s standard output stream. Possible stream
21713 @value{GDBN}'s standard output stream.
21718 @value{GDBN}'s standard error stream.
21723 @value{GDBN}'s log stream (@pxref{Logging Output}).
21726 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21727 call this function and will automatically direct the output to the
21732 @defun gdb.flush ()
21733 Flush the buffer of a @value{GDBN} paginated stream so that the
21734 contents are displayed immediately. @value{GDBN} will flush the
21735 contents of a stream automatically when it encounters a newline in the
21736 buffer. The optional @var{stream} determines the stream to flush. The
21737 default stream is @value{GDBN}'s standard output stream. Possible
21744 @value{GDBN}'s standard output stream.
21749 @value{GDBN}'s standard error stream.
21754 @value{GDBN}'s log stream (@pxref{Logging Output}).
21758 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21759 call this function for the relevant stream.
21762 @findex gdb.target_charset
21763 @defun gdb.target_charset ()
21764 Return the name of the current target character set (@pxref{Character
21765 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21766 that @samp{auto} is never returned.
21769 @findex gdb.target_wide_charset
21770 @defun gdb.target_wide_charset ()
21771 Return the name of the current target wide character set
21772 (@pxref{Character Sets}). This differs from
21773 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21777 @findex gdb.solib_name
21778 @defun gdb.solib_name (address)
21779 Return the name of the shared library holding the given @var{address}
21780 as a string, or @code{None}.
21783 @findex gdb.decode_line
21784 @defun gdb.decode_line @r{[}expression@r{]}
21785 Return locations of the line specified by @var{expression}, or of the
21786 current line if no argument was given. This function returns a Python
21787 tuple containing two elements. The first element contains a string
21788 holding any unparsed section of @var{expression} (or @code{None} if
21789 the expression has been fully parsed). The second element contains
21790 either @code{None} or another tuple that contains all the locations
21791 that match the expression represented as @code{gdb.Symtab_and_line}
21792 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21793 provided, it is decoded the way that @value{GDBN}'s inbuilt
21794 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21797 @defun gdb.prompt_hook (current_prompt)
21798 @anchor{prompt_hook}
21800 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21801 assigned to this operation before a prompt is displayed by
21804 The parameter @code{current_prompt} contains the current @value{GDBN}
21805 prompt. This method must return a Python string, or @code{None}. If
21806 a string is returned, the @value{GDBN} prompt will be set to that
21807 string. If @code{None} is returned, @value{GDBN} will continue to use
21808 the current prompt.
21810 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21811 such as those used by readline for command input, and annotation
21812 related prompts are prohibited from being changed.
21815 @node Exception Handling
21816 @subsubsection Exception Handling
21817 @cindex python exceptions
21818 @cindex exceptions, python
21820 When executing the @code{python} command, Python exceptions
21821 uncaught within the Python code are translated to calls to
21822 @value{GDBN} error-reporting mechanism. If the command that called
21823 @code{python} does not handle the error, @value{GDBN} will
21824 terminate it and print an error message containing the Python
21825 exception name, the associated value, and the Python call stack
21826 backtrace at the point where the exception was raised. Example:
21829 (@value{GDBP}) python print foo
21830 Traceback (most recent call last):
21831 File "<string>", line 1, in <module>
21832 NameError: name 'foo' is not defined
21835 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21836 Python code are converted to Python exceptions. The type of the
21837 Python exception depends on the error.
21841 This is the base class for most exceptions generated by @value{GDBN}.
21842 It is derived from @code{RuntimeError}, for compatibility with earlier
21843 versions of @value{GDBN}.
21845 If an error occurring in @value{GDBN} does not fit into some more
21846 specific category, then the generated exception will have this type.
21848 @item gdb.MemoryError
21849 This is a subclass of @code{gdb.error} which is thrown when an
21850 operation tried to access invalid memory in the inferior.
21852 @item KeyboardInterrupt
21853 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21854 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21857 In all cases, your exception handler will see the @value{GDBN} error
21858 message as its value and the Python call stack backtrace at the Python
21859 statement closest to where the @value{GDBN} error occured as the
21862 @findex gdb.GdbError
21863 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21864 it is useful to be able to throw an exception that doesn't cause a
21865 traceback to be printed. For example, the user may have invoked the
21866 command incorrectly. Use the @code{gdb.GdbError} exception
21867 to handle this case. Example:
21871 >class HelloWorld (gdb.Command):
21872 > """Greet the whole world."""
21873 > def __init__ (self):
21874 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21875 > def invoke (self, args, from_tty):
21876 > argv = gdb.string_to_argv (args)
21877 > if len (argv) != 0:
21878 > raise gdb.GdbError ("hello-world takes no arguments")
21879 > print "Hello, World!"
21882 (gdb) hello-world 42
21883 hello-world takes no arguments
21886 @node Values From Inferior
21887 @subsubsection Values From Inferior
21888 @cindex values from inferior, with Python
21889 @cindex python, working with values from inferior
21891 @cindex @code{gdb.Value}
21892 @value{GDBN} provides values it obtains from the inferior program in
21893 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21894 for its internal bookkeeping of the inferior's values, and for
21895 fetching values when necessary.
21897 Inferior values that are simple scalars can be used directly in
21898 Python expressions that are valid for the value's data type. Here's
21899 an example for an integer or floating-point value @code{some_val}:
21906 As result of this, @code{bar} will also be a @code{gdb.Value} object
21907 whose values are of the same type as those of @code{some_val}.
21909 Inferior values that are structures or instances of some class can
21910 be accessed using the Python @dfn{dictionary syntax}. For example, if
21911 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21912 can access its @code{foo} element with:
21915 bar = some_val['foo']
21918 Again, @code{bar} will also be a @code{gdb.Value} object.
21920 A @code{gdb.Value} that represents a function can be executed via
21921 inferior function call. Any arguments provided to the call must match
21922 the function's prototype, and must be provided in the order specified
21925 For example, @code{some_val} is a @code{gdb.Value} instance
21926 representing a function that takes two integers as arguments. To
21927 execute this function, call it like so:
21930 result = some_val (10,20)
21933 Any values returned from a function call will be stored as a
21936 The following attributes are provided:
21939 @defvar Value.address
21940 If this object is addressable, this read-only attribute holds a
21941 @code{gdb.Value} object representing the address. Otherwise,
21942 this attribute holds @code{None}.
21945 @cindex optimized out value in Python
21946 @defvar Value.is_optimized_out
21947 This read-only boolean attribute is true if the compiler optimized out
21948 this value, thus it is not available for fetching from the inferior.
21952 The type of this @code{gdb.Value}. The value of this attribute is a
21953 @code{gdb.Type} object (@pxref{Types In Python}).
21956 @defvar Value.dynamic_type
21957 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21958 type information (@acronym{RTTI}) to determine the dynamic type of the
21959 value. If this value is of class type, it will return the class in
21960 which the value is embedded, if any. If this value is of pointer or
21961 reference to a class type, it will compute the dynamic type of the
21962 referenced object, and return a pointer or reference to that type,
21963 respectively. In all other cases, it will return the value's static
21966 Note that this feature will only work when debugging a C@t{++} program
21967 that includes @acronym{RTTI} for the object in question. Otherwise,
21968 it will just return the static type of the value as in @kbd{ptype foo}
21969 (@pxref{Symbols, ptype}).
21972 @defvar Value.is_lazy
21973 The value of this read-only boolean attribute is @code{True} if this
21974 @code{gdb.Value} has not yet been fetched from the inferior.
21975 @value{GDBN} does not fetch values until necessary, for efficiency.
21979 myval = gdb.parse_and_eval ('somevar')
21982 The value of @code{somevar} is not fetched at this time. It will be
21983 fetched when the value is needed, or when the @code{fetch_lazy}
21988 The following methods are provided:
21991 @defun Value.__init__ (@var{val})
21992 Many Python values can be converted directly to a @code{gdb.Value} via
21993 this object initializer. Specifically:
21996 @item Python boolean
21997 A Python boolean is converted to the boolean type from the current
22000 @item Python integer
22001 A Python integer is converted to the C @code{long} type for the
22002 current architecture.
22005 A Python long is converted to the C @code{long long} type for the
22006 current architecture.
22009 A Python float is converted to the C @code{double} type for the
22010 current architecture.
22012 @item Python string
22013 A Python string is converted to a target string, using the current
22016 @item @code{gdb.Value}
22017 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22019 @item @code{gdb.LazyString}
22020 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22021 Python}), then the lazy string's @code{value} method is called, and
22022 its result is used.
22026 @defun Value.cast (type)
22027 Return a new instance of @code{gdb.Value} that is the result of
22028 casting this instance to the type described by @var{type}, which must
22029 be a @code{gdb.Type} object. If the cast cannot be performed for some
22030 reason, this method throws an exception.
22033 @defun Value.dereference ()
22034 For pointer data types, this method returns a new @code{gdb.Value} object
22035 whose contents is the object pointed to by the pointer. For example, if
22036 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22043 then you can use the corresponding @code{gdb.Value} to access what
22044 @code{foo} points to like this:
22047 bar = foo.dereference ()
22050 The result @code{bar} will be a @code{gdb.Value} object holding the
22051 value pointed to by @code{foo}.
22054 @defun Value.dynamic_cast (type)
22055 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22056 operator were used. Consult a C@t{++} reference for details.
22059 @defun Value.reinterpret_cast (type)
22060 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22061 operator were used. Consult a C@t{++} reference for details.
22064 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22065 If this @code{gdb.Value} represents a string, then this method
22066 converts the contents to a Python string. Otherwise, this method will
22067 throw an exception.
22069 Strings are recognized in a language-specific way; whether a given
22070 @code{gdb.Value} represents a string is determined by the current
22073 For C-like languages, a value is a string if it is a pointer to or an
22074 array of characters or ints. The string is assumed to be terminated
22075 by a zero of the appropriate width. However if the optional length
22076 argument is given, the string will be converted to that given length,
22077 ignoring any embedded zeros that the string may contain.
22079 If the optional @var{encoding} argument is given, it must be a string
22080 naming the encoding of the string in the @code{gdb.Value}, such as
22081 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22082 the same encodings as the corresponding argument to Python's
22083 @code{string.decode} method, and the Python codec machinery will be used
22084 to convert the string. If @var{encoding} is not given, or if
22085 @var{encoding} is the empty string, then either the @code{target-charset}
22086 (@pxref{Character Sets}) will be used, or a language-specific encoding
22087 will be used, if the current language is able to supply one.
22089 The optional @var{errors} argument is the same as the corresponding
22090 argument to Python's @code{string.decode} method.
22092 If the optional @var{length} argument is given, the string will be
22093 fetched and converted to the given length.
22096 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22097 If this @code{gdb.Value} represents a string, then this method
22098 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22099 In Python}). Otherwise, this method will throw an exception.
22101 If the optional @var{encoding} argument is given, it must be a string
22102 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22103 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22104 @var{encoding} argument is an encoding that @value{GDBN} does
22105 recognize, @value{GDBN} will raise an error.
22107 When a lazy string is printed, the @value{GDBN} encoding machinery is
22108 used to convert the string during printing. If the optional
22109 @var{encoding} argument is not provided, or is an empty string,
22110 @value{GDBN} will automatically select the encoding most suitable for
22111 the string type. For further information on encoding in @value{GDBN}
22112 please see @ref{Character Sets}.
22114 If the optional @var{length} argument is given, the string will be
22115 fetched and encoded to the length of characters specified. If
22116 the @var{length} argument is not provided, the string will be fetched
22117 and encoded until a null of appropriate width is found.
22120 @defun Value.fetch_lazy ()
22121 If the @code{gdb.Value} object is currently a lazy value
22122 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22123 fetched from the inferior. Any errors that occur in the process
22124 will produce a Python exception.
22126 If the @code{gdb.Value} object is not a lazy value, this method
22129 This method does not return a value.
22134 @node Types In Python
22135 @subsubsection Types In Python
22136 @cindex types in Python
22137 @cindex Python, working with types
22140 @value{GDBN} represents types from the inferior using the class
22143 The following type-related functions are available in the @code{gdb}
22146 @findex gdb.lookup_type
22147 @defun gdb.lookup_type (name @r{[}, block@r{]})
22148 This function looks up a type by name. @var{name} is the name of the
22149 type to look up. It must be a string.
22151 If @var{block} is given, then @var{name} is looked up in that scope.
22152 Otherwise, it is searched for globally.
22154 Ordinarily, this function will return an instance of @code{gdb.Type}.
22155 If the named type cannot be found, it will throw an exception.
22158 If the type is a structure or class type, or an enum type, the fields
22159 of that type can be accessed using the Python @dfn{dictionary syntax}.
22160 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22161 a structure type, you can access its @code{foo} field with:
22164 bar = some_type['foo']
22167 @code{bar} will be a @code{gdb.Field} object; see below under the
22168 description of the @code{Type.fields} method for a description of the
22169 @code{gdb.Field} class.
22171 An instance of @code{Type} has the following attributes:
22175 The type code for this type. The type code will be one of the
22176 @code{TYPE_CODE_} constants defined below.
22179 @defvar Type.sizeof
22180 The size of this type, in target @code{char} units. Usually, a
22181 target's @code{char} type will be an 8-bit byte. However, on some
22182 unusual platforms, this type may have a different size.
22186 The tag name for this type. The tag name is the name after
22187 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22188 languages have this concept. If this type has no tag name, then
22189 @code{None} is returned.
22193 The following methods are provided:
22196 @defun Type.fields ()
22197 For structure and union types, this method returns the fields. Range
22198 types have two fields, the minimum and maximum values. Enum types
22199 have one field per enum constant. Function and method types have one
22200 field per parameter. The base types of C@t{++} classes are also
22201 represented as fields. If the type has no fields, or does not fit
22202 into one of these categories, an empty sequence will be returned.
22204 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22207 This attribute is not available for @code{static} fields (as in
22208 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22209 position of the field. For @code{enum} fields, the value is the
22210 enumeration member's integer representation.
22213 The name of the field, or @code{None} for anonymous fields.
22216 This is @code{True} if the field is artificial, usually meaning that
22217 it was provided by the compiler and not the user. This attribute is
22218 always provided, and is @code{False} if the field is not artificial.
22220 @item is_base_class
22221 This is @code{True} if the field represents a base class of a C@t{++}
22222 structure. This attribute is always provided, and is @code{False}
22223 if the field is not a base class of the type that is the argument of
22224 @code{fields}, or if that type was not a C@t{++} class.
22227 If the field is packed, or is a bitfield, then this will have a
22228 non-zero value, which is the size of the field in bits. Otherwise,
22229 this will be zero; in this case the field's size is given by its type.
22232 The type of the field. This is usually an instance of @code{Type},
22233 but it can be @code{None} in some situations.
22237 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22238 Return a new @code{gdb.Type} object which represents an array of this
22239 type. If one argument is given, it is the inclusive upper bound of
22240 the array; in this case the lower bound is zero. If two arguments are
22241 given, the first argument is the lower bound of the array, and the
22242 second argument is the upper bound of the array. An array's length
22243 must not be negative, but the bounds can be.
22246 @defun Type.const ()
22247 Return a new @code{gdb.Type} object which represents a
22248 @code{const}-qualified variant of this type.
22251 @defun Type.volatile ()
22252 Return a new @code{gdb.Type} object which represents a
22253 @code{volatile}-qualified variant of this type.
22256 @defun Type.unqualified ()
22257 Return a new @code{gdb.Type} object which represents an unqualified
22258 variant of this type. That is, the result is neither @code{const} nor
22262 @defun Type.range ()
22263 Return a Python @code{Tuple} object that contains two elements: the
22264 low bound of the argument type and the high bound of that type. If
22265 the type does not have a range, @value{GDBN} will raise a
22266 @code{gdb.error} exception (@pxref{Exception Handling}).
22269 @defun Type.reference ()
22270 Return a new @code{gdb.Type} object which represents a reference to this
22274 @defun Type.pointer ()
22275 Return a new @code{gdb.Type} object which represents a pointer to this
22279 @defun Type.strip_typedefs ()
22280 Return a new @code{gdb.Type} that represents the real type,
22281 after removing all layers of typedefs.
22284 @defun Type.target ()
22285 Return a new @code{gdb.Type} object which represents the target type
22288 For a pointer type, the target type is the type of the pointed-to
22289 object. For an array type (meaning C-like arrays), the target type is
22290 the type of the elements of the array. For a function or method type,
22291 the target type is the type of the return value. For a complex type,
22292 the target type is the type of the elements. For a typedef, the
22293 target type is the aliased type.
22295 If the type does not have a target, this method will throw an
22299 @defun Type.template_argument (n @r{[}, block@r{]})
22300 If this @code{gdb.Type} is an instantiation of a template, this will
22301 return a new @code{gdb.Type} which represents the type of the
22302 @var{n}th template argument.
22304 If this @code{gdb.Type} is not a template type, this will throw an
22305 exception. Ordinarily, only C@t{++} code will have template types.
22307 If @var{block} is given, then @var{name} is looked up in that scope.
22308 Otherwise, it is searched for globally.
22313 Each type has a code, which indicates what category this type falls
22314 into. The available type categories are represented by constants
22315 defined in the @code{gdb} module:
22318 @findex TYPE_CODE_PTR
22319 @findex gdb.TYPE_CODE_PTR
22320 @item gdb.TYPE_CODE_PTR
22321 The type is a pointer.
22323 @findex TYPE_CODE_ARRAY
22324 @findex gdb.TYPE_CODE_ARRAY
22325 @item gdb.TYPE_CODE_ARRAY
22326 The type is an array.
22328 @findex TYPE_CODE_STRUCT
22329 @findex gdb.TYPE_CODE_STRUCT
22330 @item gdb.TYPE_CODE_STRUCT
22331 The type is a structure.
22333 @findex TYPE_CODE_UNION
22334 @findex gdb.TYPE_CODE_UNION
22335 @item gdb.TYPE_CODE_UNION
22336 The type is a union.
22338 @findex TYPE_CODE_ENUM
22339 @findex gdb.TYPE_CODE_ENUM
22340 @item gdb.TYPE_CODE_ENUM
22341 The type is an enum.
22343 @findex TYPE_CODE_FLAGS
22344 @findex gdb.TYPE_CODE_FLAGS
22345 @item gdb.TYPE_CODE_FLAGS
22346 A bit flags type, used for things such as status registers.
22348 @findex TYPE_CODE_FUNC
22349 @findex gdb.TYPE_CODE_FUNC
22350 @item gdb.TYPE_CODE_FUNC
22351 The type is a function.
22353 @findex TYPE_CODE_INT
22354 @findex gdb.TYPE_CODE_INT
22355 @item gdb.TYPE_CODE_INT
22356 The type is an integer type.
22358 @findex TYPE_CODE_FLT
22359 @findex gdb.TYPE_CODE_FLT
22360 @item gdb.TYPE_CODE_FLT
22361 A floating point type.
22363 @findex TYPE_CODE_VOID
22364 @findex gdb.TYPE_CODE_VOID
22365 @item gdb.TYPE_CODE_VOID
22366 The special type @code{void}.
22368 @findex TYPE_CODE_SET
22369 @findex gdb.TYPE_CODE_SET
22370 @item gdb.TYPE_CODE_SET
22373 @findex TYPE_CODE_RANGE
22374 @findex gdb.TYPE_CODE_RANGE
22375 @item gdb.TYPE_CODE_RANGE
22376 A range type, that is, an integer type with bounds.
22378 @findex TYPE_CODE_STRING
22379 @findex gdb.TYPE_CODE_STRING
22380 @item gdb.TYPE_CODE_STRING
22381 A string type. Note that this is only used for certain languages with
22382 language-defined string types; C strings are not represented this way.
22384 @findex TYPE_CODE_BITSTRING
22385 @findex gdb.TYPE_CODE_BITSTRING
22386 @item gdb.TYPE_CODE_BITSTRING
22389 @findex TYPE_CODE_ERROR
22390 @findex gdb.TYPE_CODE_ERROR
22391 @item gdb.TYPE_CODE_ERROR
22392 An unknown or erroneous type.
22394 @findex TYPE_CODE_METHOD
22395 @findex gdb.TYPE_CODE_METHOD
22396 @item gdb.TYPE_CODE_METHOD
22397 A method type, as found in C@t{++} or Java.
22399 @findex TYPE_CODE_METHODPTR
22400 @findex gdb.TYPE_CODE_METHODPTR
22401 @item gdb.TYPE_CODE_METHODPTR
22402 A pointer-to-member-function.
22404 @findex TYPE_CODE_MEMBERPTR
22405 @findex gdb.TYPE_CODE_MEMBERPTR
22406 @item gdb.TYPE_CODE_MEMBERPTR
22407 A pointer-to-member.
22409 @findex TYPE_CODE_REF
22410 @findex gdb.TYPE_CODE_REF
22411 @item gdb.TYPE_CODE_REF
22414 @findex TYPE_CODE_CHAR
22415 @findex gdb.TYPE_CODE_CHAR
22416 @item gdb.TYPE_CODE_CHAR
22419 @findex TYPE_CODE_BOOL
22420 @findex gdb.TYPE_CODE_BOOL
22421 @item gdb.TYPE_CODE_BOOL
22424 @findex TYPE_CODE_COMPLEX
22425 @findex gdb.TYPE_CODE_COMPLEX
22426 @item gdb.TYPE_CODE_COMPLEX
22427 A complex float type.
22429 @findex TYPE_CODE_TYPEDEF
22430 @findex gdb.TYPE_CODE_TYPEDEF
22431 @item gdb.TYPE_CODE_TYPEDEF
22432 A typedef to some other type.
22434 @findex TYPE_CODE_NAMESPACE
22435 @findex gdb.TYPE_CODE_NAMESPACE
22436 @item gdb.TYPE_CODE_NAMESPACE
22437 A C@t{++} namespace.
22439 @findex TYPE_CODE_DECFLOAT
22440 @findex gdb.TYPE_CODE_DECFLOAT
22441 @item gdb.TYPE_CODE_DECFLOAT
22442 A decimal floating point type.
22444 @findex TYPE_CODE_INTERNAL_FUNCTION
22445 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22446 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22447 A function internal to @value{GDBN}. This is the type used to represent
22448 convenience functions.
22451 Further support for types is provided in the @code{gdb.types}
22452 Python module (@pxref{gdb.types}).
22454 @node Pretty Printing API
22455 @subsubsection Pretty Printing API
22457 An example output is provided (@pxref{Pretty Printing}).
22459 A pretty-printer is just an object that holds a value and implements a
22460 specific interface, defined here.
22462 @defun pretty_printer.children (self)
22463 @value{GDBN} will call this method on a pretty-printer to compute the
22464 children of the pretty-printer's value.
22466 This method must return an object conforming to the Python iterator
22467 protocol. Each item returned by the iterator must be a tuple holding
22468 two elements. The first element is the ``name'' of the child; the
22469 second element is the child's value. The value can be any Python
22470 object which is convertible to a @value{GDBN} value.
22472 This method is optional. If it does not exist, @value{GDBN} will act
22473 as though the value has no children.
22476 @defun pretty_printer.display_hint (self)
22477 The CLI may call this method and use its result to change the
22478 formatting of a value. The result will also be supplied to an MI
22479 consumer as a @samp{displayhint} attribute of the variable being
22482 This method is optional. If it does exist, this method must return a
22485 Some display hints are predefined by @value{GDBN}:
22489 Indicate that the object being printed is ``array-like''. The CLI
22490 uses this to respect parameters such as @code{set print elements} and
22491 @code{set print array}.
22494 Indicate that the object being printed is ``map-like'', and that the
22495 children of this value can be assumed to alternate between keys and
22499 Indicate that the object being printed is ``string-like''. If the
22500 printer's @code{to_string} method returns a Python string of some
22501 kind, then @value{GDBN} will call its internal language-specific
22502 string-printing function to format the string. For the CLI this means
22503 adding quotation marks, possibly escaping some characters, respecting
22504 @code{set print elements}, and the like.
22508 @defun pretty_printer.to_string (self)
22509 @value{GDBN} will call this method to display the string
22510 representation of the value passed to the object's constructor.
22512 When printing from the CLI, if the @code{to_string} method exists,
22513 then @value{GDBN} will prepend its result to the values returned by
22514 @code{children}. Exactly how this formatting is done is dependent on
22515 the display hint, and may change as more hints are added. Also,
22516 depending on the print settings (@pxref{Print Settings}), the CLI may
22517 print just the result of @code{to_string} in a stack trace, omitting
22518 the result of @code{children}.
22520 If this method returns a string, it is printed verbatim.
22522 Otherwise, if this method returns an instance of @code{gdb.Value},
22523 then @value{GDBN} prints this value. This may result in a call to
22524 another pretty-printer.
22526 If instead the method returns a Python value which is convertible to a
22527 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22528 the resulting value. Again, this may result in a call to another
22529 pretty-printer. Python scalars (integers, floats, and booleans) and
22530 strings are convertible to @code{gdb.Value}; other types are not.
22532 Finally, if this method returns @code{None} then no further operations
22533 are peformed in this method and nothing is printed.
22535 If the result is not one of these types, an exception is raised.
22538 @value{GDBN} provides a function which can be used to look up the
22539 default pretty-printer for a @code{gdb.Value}:
22541 @findex gdb.default_visualizer
22542 @defun gdb.default_visualizer (value)
22543 This function takes a @code{gdb.Value} object as an argument. If a
22544 pretty-printer for this value exists, then it is returned. If no such
22545 printer exists, then this returns @code{None}.
22548 @node Selecting Pretty-Printers
22549 @subsubsection Selecting Pretty-Printers
22551 The Python list @code{gdb.pretty_printers} contains an array of
22552 functions or callable objects that have been registered via addition
22553 as a pretty-printer. Printers in this list are called @code{global}
22554 printers, they're available when debugging all inferiors.
22555 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22556 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22559 Each function on these lists is passed a single @code{gdb.Value}
22560 argument and should return a pretty-printer object conforming to the
22561 interface definition above (@pxref{Pretty Printing API}). If a function
22562 cannot create a pretty-printer for the value, it should return
22565 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22566 @code{gdb.Objfile} in the current program space and iteratively calls
22567 each enabled lookup routine in the list for that @code{gdb.Objfile}
22568 until it receives a pretty-printer object.
22569 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22570 searches the pretty-printer list of the current program space,
22571 calling each enabled function until an object is returned.
22572 After these lists have been exhausted, it tries the global
22573 @code{gdb.pretty_printers} list, again calling each enabled function until an
22574 object is returned.
22576 The order in which the objfiles are searched is not specified. For a
22577 given list, functions are always invoked from the head of the list,
22578 and iterated over sequentially until the end of the list, or a printer
22579 object is returned.
22581 For various reasons a pretty-printer may not work.
22582 For example, the underlying data structure may have changed and
22583 the pretty-printer is out of date.
22585 The consequences of a broken pretty-printer are severe enough that
22586 @value{GDBN} provides support for enabling and disabling individual
22587 printers. For example, if @code{print frame-arguments} is on,
22588 a backtrace can become highly illegible if any argument is printed
22589 with a broken printer.
22591 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22592 attribute to the registered function or callable object. If this attribute
22593 is present and its value is @code{False}, the printer is disabled, otherwise
22594 the printer is enabled.
22596 @node Writing a Pretty-Printer
22597 @subsubsection Writing a Pretty-Printer
22598 @cindex writing a pretty-printer
22600 A pretty-printer consists of two parts: a lookup function to detect
22601 if the type is supported, and the printer itself.
22603 Here is an example showing how a @code{std::string} printer might be
22604 written. @xref{Pretty Printing API}, for details on the API this class
22608 class StdStringPrinter(object):
22609 "Print a std::string"
22611 def __init__(self, val):
22614 def to_string(self):
22615 return self.val['_M_dataplus']['_M_p']
22617 def display_hint(self):
22621 And here is an example showing how a lookup function for the printer
22622 example above might be written.
22625 def str_lookup_function(val):
22626 lookup_tag = val.type.tag
22627 if lookup_tag == None:
22629 regex = re.compile("^std::basic_string<char,.*>$")
22630 if regex.match(lookup_tag):
22631 return StdStringPrinter(val)
22635 The example lookup function extracts the value's type, and attempts to
22636 match it to a type that it can pretty-print. If it is a type the
22637 printer can pretty-print, it will return a printer object. If not, it
22638 returns @code{None}.
22640 We recommend that you put your core pretty-printers into a Python
22641 package. If your pretty-printers are for use with a library, we
22642 further recommend embedding a version number into the package name.
22643 This practice will enable @value{GDBN} to load multiple versions of
22644 your pretty-printers at the same time, because they will have
22647 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22648 can be evaluated multiple times without changing its meaning. An
22649 ideal auto-load file will consist solely of @code{import}s of your
22650 printer modules, followed by a call to a register pretty-printers with
22651 the current objfile.
22653 Taken as a whole, this approach will scale nicely to multiple
22654 inferiors, each potentially using a different library version.
22655 Embedding a version number in the Python package name will ensure that
22656 @value{GDBN} is able to load both sets of printers simultaneously.
22657 Then, because the search for pretty-printers is done by objfile, and
22658 because your auto-loaded code took care to register your library's
22659 printers with a specific objfile, @value{GDBN} will find the correct
22660 printers for the specific version of the library used by each
22663 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22664 this code might appear in @code{gdb.libstdcxx.v6}:
22667 def register_printers(objfile):
22668 objfile.pretty_printers.append(str_lookup_function)
22672 And then the corresponding contents of the auto-load file would be:
22675 import gdb.libstdcxx.v6
22676 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22679 The previous example illustrates a basic pretty-printer.
22680 There are a few things that can be improved on.
22681 The printer doesn't have a name, making it hard to identify in a
22682 list of installed printers. The lookup function has a name, but
22683 lookup functions can have arbitrary, even identical, names.
22685 Second, the printer only handles one type, whereas a library typically has
22686 several types. One could install a lookup function for each desired type
22687 in the library, but one could also have a single lookup function recognize
22688 several types. The latter is the conventional way this is handled.
22689 If a pretty-printer can handle multiple data types, then its
22690 @dfn{subprinters} are the printers for the individual data types.
22692 The @code{gdb.printing} module provides a formal way of solving these
22693 problems (@pxref{gdb.printing}).
22694 Here is another example that handles multiple types.
22696 These are the types we are going to pretty-print:
22699 struct foo @{ int a, b; @};
22700 struct bar @{ struct foo x, y; @};
22703 Here are the printers:
22707 """Print a foo object."""
22709 def __init__(self, val):
22712 def to_string(self):
22713 return ("a=<" + str(self.val["a"]) +
22714 "> b=<" + str(self.val["b"]) + ">")
22717 """Print a bar object."""
22719 def __init__(self, val):
22722 def to_string(self):
22723 return ("x=<" + str(self.val["x"]) +
22724 "> y=<" + str(self.val["y"]) + ">")
22727 This example doesn't need a lookup function, that is handled by the
22728 @code{gdb.printing} module. Instead a function is provided to build up
22729 the object that handles the lookup.
22732 import gdb.printing
22734 def build_pretty_printer():
22735 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22737 pp.add_printer('foo', '^foo$', fooPrinter)
22738 pp.add_printer('bar', '^bar$', barPrinter)
22742 And here is the autoload support:
22745 import gdb.printing
22747 gdb.printing.register_pretty_printer(
22748 gdb.current_objfile(),
22749 my_library.build_pretty_printer())
22752 Finally, when this printer is loaded into @value{GDBN}, here is the
22753 corresponding output of @samp{info pretty-printer}:
22756 (gdb) info pretty-printer
22763 @node Inferiors In Python
22764 @subsubsection Inferiors In Python
22765 @cindex inferiors in Python
22767 @findex gdb.Inferior
22768 Programs which are being run under @value{GDBN} are called inferiors
22769 (@pxref{Inferiors and Programs}). Python scripts can access
22770 information about and manipulate inferiors controlled by @value{GDBN}
22771 via objects of the @code{gdb.Inferior} class.
22773 The following inferior-related functions are available in the @code{gdb}
22776 @defun gdb.inferiors ()
22777 Return a tuple containing all inferior objects.
22780 @defun gdb.selected_inferior ()
22781 Return an object representing the current inferior.
22784 A @code{gdb.Inferior} object has the following attributes:
22787 @defvar Inferior.num
22788 ID of inferior, as assigned by GDB.
22791 @defvar Inferior.pid
22792 Process ID of the inferior, as assigned by the underlying operating
22796 @defvar Inferior.was_attached
22797 Boolean signaling whether the inferior was created using `attach', or
22798 started by @value{GDBN} itself.
22802 A @code{gdb.Inferior} object has the following methods:
22805 @defun Inferior.is_valid ()
22806 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22807 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22808 if the inferior no longer exists within @value{GDBN}. All other
22809 @code{gdb.Inferior} methods will throw an exception if it is invalid
22810 at the time the method is called.
22813 @defun Inferior.threads ()
22814 This method returns a tuple holding all the threads which are valid
22815 when it is called. If there are no valid threads, the method will
22816 return an empty tuple.
22819 @findex gdb.read_memory
22820 @defun Inferior.read_memory (address, length)
22821 Read @var{length} bytes of memory from the inferior, starting at
22822 @var{address}. Returns a buffer object, which behaves much like an array
22823 or a string. It can be modified and given to the @code{gdb.write_memory}
22827 @findex gdb.write_memory
22828 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22829 Write the contents of @var{buffer} to the inferior, starting at
22830 @var{address}. The @var{buffer} parameter must be a Python object
22831 which supports the buffer protocol, i.e., a string, an array or the
22832 object returned from @code{gdb.read_memory}. If given, @var{length}
22833 determines the number of bytes from @var{buffer} to be written.
22836 @findex gdb.search_memory
22837 @defun Inferior.search_memory (address, length, pattern)
22838 Search a region of the inferior memory starting at @var{address} with
22839 the given @var{length} using the search pattern supplied in
22840 @var{pattern}. The @var{pattern} parameter must be a Python object
22841 which supports the buffer protocol, i.e., a string, an array or the
22842 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22843 containing the address where the pattern was found, or @code{None} if
22844 the pattern could not be found.
22848 @node Events In Python
22849 @subsubsection Events In Python
22850 @cindex inferior events in Python
22852 @value{GDBN} provides a general event facility so that Python code can be
22853 notified of various state changes, particularly changes that occur in
22856 An @dfn{event} is just an object that describes some state change. The
22857 type of the object and its attributes will vary depending on the details
22858 of the change. All the existing events are described below.
22860 In order to be notified of an event, you must register an event handler
22861 with an @dfn{event registry}. An event registry is an object in the
22862 @code{gdb.events} module which dispatches particular events. A registry
22863 provides methods to register and unregister event handlers:
22866 @defun EventRegistry.connect (object)
22867 Add the given callable @var{object} to the registry. This object will be
22868 called when an event corresponding to this registry occurs.
22871 @defun EventRegistry.disconnect (object)
22872 Remove the given @var{object} from the registry. Once removed, the object
22873 will no longer receive notifications of events.
22877 Here is an example:
22880 def exit_handler (event):
22881 print "event type: exit"
22882 print "exit code: %d" % (event.exit_code)
22884 gdb.events.exited.connect (exit_handler)
22887 In the above example we connect our handler @code{exit_handler} to the
22888 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22889 called when the inferior exits. The argument @dfn{event} in this example is
22890 of type @code{gdb.ExitedEvent}. As you can see in the example the
22891 @code{ExitedEvent} object has an attribute which indicates the exit code of
22894 The following is a listing of the event registries that are available and
22895 details of the events they emit:
22900 Emits @code{gdb.ThreadEvent}.
22902 Some events can be thread specific when @value{GDBN} is running in non-stop
22903 mode. When represented in Python, these events all extend
22904 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22905 events which are emitted by this or other modules might extend this event.
22906 Examples of these events are @code{gdb.BreakpointEvent} and
22907 @code{gdb.ContinueEvent}.
22910 @defvar ThreadEvent.inferior_thread
22911 In non-stop mode this attribute will be set to the specific thread which was
22912 involved in the emitted event. Otherwise, it will be set to @code{None}.
22916 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22918 This event indicates that the inferior has been continued after a stop. For
22919 inherited attribute refer to @code{gdb.ThreadEvent} above.
22921 @item events.exited
22922 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22923 @code{events.ExitedEvent} has two attributes:
22925 @defvar ExitedEvent.exit_code
22926 An integer representing the exit code, if available, which the inferior
22927 has returned. (The exit code could be unavailable if, for example,
22928 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22929 the attribute does not exist.
22931 @defvar ExitedEvent inferior
22932 A reference to the inferior which triggered the @code{exited} event.
22937 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22939 Indicates that the inferior has stopped. All events emitted by this registry
22940 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22941 will indicate the stopped thread when @value{GDBN} is running in non-stop
22942 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22944 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22946 This event indicates that the inferior or one of its threads has received as
22947 signal. @code{gdb.SignalEvent} has the following attributes:
22950 @defvar SignalEvent.stop_signal
22951 A string representing the signal received by the inferior. A list of possible
22952 signal values can be obtained by running the command @code{info signals} in
22953 the @value{GDBN} command prompt.
22957 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22959 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22960 been hit, and has the following attributes:
22963 @defvar BreakpointEvent.breakpoints
22964 A sequence containing references to all the breakpoints (type
22965 @code{gdb.Breakpoint}) that were hit.
22966 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22968 @defvar BreakpointEvent.breakpoint
22969 A reference to the first breakpoint that was hit.
22970 This function is maintained for backward compatibility and is now deprecated
22971 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22975 @item events.new_objfile
22976 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22977 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22980 @defvar NewObjFileEvent.new_objfile
22981 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22982 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22988 @node Threads In Python
22989 @subsubsection Threads In Python
22990 @cindex threads in python
22992 @findex gdb.InferiorThread
22993 Python scripts can access information about, and manipulate inferior threads
22994 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22996 The following thread-related functions are available in the @code{gdb}
22999 @findex gdb.selected_thread
23000 @defun gdb.selected_thread ()
23001 This function returns the thread object for the selected thread. If there
23002 is no selected thread, this will return @code{None}.
23005 A @code{gdb.InferiorThread} object has the following attributes:
23008 @defvar InferiorThread.name
23009 The name of the thread. If the user specified a name using
23010 @code{thread name}, then this returns that name. Otherwise, if an
23011 OS-supplied name is available, then it is returned. Otherwise, this
23012 returns @code{None}.
23014 This attribute can be assigned to. The new value must be a string
23015 object, which sets the new name, or @code{None}, which removes any
23016 user-specified thread name.
23019 @defvar InferiorThread.num
23020 ID of the thread, as assigned by GDB.
23023 @defvar InferiorThread.ptid
23024 ID of the thread, as assigned by the operating system. This attribute is a
23025 tuple containing three integers. The first is the Process ID (PID); the second
23026 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23027 Either the LWPID or TID may be 0, which indicates that the operating system
23028 does not use that identifier.
23032 A @code{gdb.InferiorThread} object has the following methods:
23035 @defun InferiorThread.is_valid ()
23036 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23037 @code{False} if not. A @code{gdb.InferiorThread} object will become
23038 invalid if the thread exits, or the inferior that the thread belongs
23039 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23040 exception if it is invalid at the time the method is called.
23043 @defun InferiorThread.switch ()
23044 This changes @value{GDBN}'s currently selected thread to the one represented
23048 @defun InferiorThread.is_stopped ()
23049 Return a Boolean indicating whether the thread is stopped.
23052 @defun InferiorThread.is_running ()
23053 Return a Boolean indicating whether the thread is running.
23056 @defun InferiorThread.is_exited ()
23057 Return a Boolean indicating whether the thread is exited.
23061 @node Commands In Python
23062 @subsubsection Commands In Python
23064 @cindex commands in python
23065 @cindex python commands
23066 You can implement new @value{GDBN} CLI commands in Python. A CLI
23067 command is implemented using an instance of the @code{gdb.Command}
23068 class, most commonly using a subclass.
23070 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23071 The object initializer for @code{Command} registers the new command
23072 with @value{GDBN}. This initializer is normally invoked from the
23073 subclass' own @code{__init__} method.
23075 @var{name} is the name of the command. If @var{name} consists of
23076 multiple words, then the initial words are looked for as prefix
23077 commands. In this case, if one of the prefix commands does not exist,
23078 an exception is raised.
23080 There is no support for multi-line commands.
23082 @var{command_class} should be one of the @samp{COMMAND_} constants
23083 defined below. This argument tells @value{GDBN} how to categorize the
23084 new command in the help system.
23086 @var{completer_class} is an optional argument. If given, it should be
23087 one of the @samp{COMPLETE_} constants defined below. This argument
23088 tells @value{GDBN} how to perform completion for this command. If not
23089 given, @value{GDBN} will attempt to complete using the object's
23090 @code{complete} method (see below); if no such method is found, an
23091 error will occur when completion is attempted.
23093 @var{prefix} is an optional argument. If @code{True}, then the new
23094 command is a prefix command; sub-commands of this command may be
23097 The help text for the new command is taken from the Python
23098 documentation string for the command's class, if there is one. If no
23099 documentation string is provided, the default value ``This command is
23100 not documented.'' is used.
23103 @cindex don't repeat Python command
23104 @defun Command.dont_repeat ()
23105 By default, a @value{GDBN} command is repeated when the user enters a
23106 blank line at the command prompt. A command can suppress this
23107 behavior by invoking the @code{dont_repeat} method. This is similar
23108 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23111 @defun Command.invoke (argument, from_tty)
23112 This method is called by @value{GDBN} when this command is invoked.
23114 @var{argument} is a string. It is the argument to the command, after
23115 leading and trailing whitespace has been stripped.
23117 @var{from_tty} is a boolean argument. When true, this means that the
23118 command was entered by the user at the terminal; when false it means
23119 that the command came from elsewhere.
23121 If this method throws an exception, it is turned into a @value{GDBN}
23122 @code{error} call. Otherwise, the return value is ignored.
23124 @findex gdb.string_to_argv
23125 To break @var{argument} up into an argv-like string use
23126 @code{gdb.string_to_argv}. This function behaves identically to
23127 @value{GDBN}'s internal argument lexer @code{buildargv}.
23128 It is recommended to use this for consistency.
23129 Arguments are separated by spaces and may be quoted.
23133 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23134 ['1', '2 "3', '4 "5', "6 '7"]
23139 @cindex completion of Python commands
23140 @defun Command.complete (text, word)
23141 This method is called by @value{GDBN} when the user attempts
23142 completion on this command. All forms of completion are handled by
23143 this method, that is, the @key{TAB} and @key{M-?} key bindings
23144 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23147 The arguments @var{text} and @var{word} are both strings. @var{text}
23148 holds the complete command line up to the cursor's location.
23149 @var{word} holds the last word of the command line; this is computed
23150 using a word-breaking heuristic.
23152 The @code{complete} method can return several values:
23155 If the return value is a sequence, the contents of the sequence are
23156 used as the completions. It is up to @code{complete} to ensure that the
23157 contents actually do complete the word. A zero-length sequence is
23158 allowed, it means that there were no completions available. Only
23159 string elements of the sequence are used; other elements in the
23160 sequence are ignored.
23163 If the return value is one of the @samp{COMPLETE_} constants defined
23164 below, then the corresponding @value{GDBN}-internal completion
23165 function is invoked, and its result is used.
23168 All other results are treated as though there were no available
23173 When a new command is registered, it must be declared as a member of
23174 some general class of commands. This is used to classify top-level
23175 commands in the on-line help system; note that prefix commands are not
23176 listed under their own category but rather that of their top-level
23177 command. The available classifications are represented by constants
23178 defined in the @code{gdb} module:
23181 @findex COMMAND_NONE
23182 @findex gdb.COMMAND_NONE
23183 @item gdb.COMMAND_NONE
23184 The command does not belong to any particular class. A command in
23185 this category will not be displayed in any of the help categories.
23187 @findex COMMAND_RUNNING
23188 @findex gdb.COMMAND_RUNNING
23189 @item gdb.COMMAND_RUNNING
23190 The command is related to running the inferior. For example,
23191 @code{start}, @code{step}, and @code{continue} are in this category.
23192 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23193 commands in this category.
23195 @findex COMMAND_DATA
23196 @findex gdb.COMMAND_DATA
23197 @item gdb.COMMAND_DATA
23198 The command is related to data or variables. For example,
23199 @code{call}, @code{find}, and @code{print} are in this category. Type
23200 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23203 @findex COMMAND_STACK
23204 @findex gdb.COMMAND_STACK
23205 @item gdb.COMMAND_STACK
23206 The command has to do with manipulation of the stack. For example,
23207 @code{backtrace}, @code{frame}, and @code{return} are in this
23208 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23209 list of commands in this category.
23211 @findex COMMAND_FILES
23212 @findex gdb.COMMAND_FILES
23213 @item gdb.COMMAND_FILES
23214 This class is used for file-related commands. For example,
23215 @code{file}, @code{list} and @code{section} are in this category.
23216 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23217 commands in this category.
23219 @findex COMMAND_SUPPORT
23220 @findex gdb.COMMAND_SUPPORT
23221 @item gdb.COMMAND_SUPPORT
23222 This should be used for ``support facilities'', generally meaning
23223 things that are useful to the user when interacting with @value{GDBN},
23224 but not related to the state of the inferior. For example,
23225 @code{help}, @code{make}, and @code{shell} are in this category. Type
23226 @kbd{help support} at the @value{GDBN} prompt to see a list of
23227 commands in this category.
23229 @findex COMMAND_STATUS
23230 @findex gdb.COMMAND_STATUS
23231 @item gdb.COMMAND_STATUS
23232 The command is an @samp{info}-related command, that is, related to the
23233 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23234 and @code{show} are in this category. Type @kbd{help status} at the
23235 @value{GDBN} prompt to see a list of commands in this category.
23237 @findex COMMAND_BREAKPOINTS
23238 @findex gdb.COMMAND_BREAKPOINTS
23239 @item gdb.COMMAND_BREAKPOINTS
23240 The command has to do with breakpoints. For example, @code{break},
23241 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23242 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23245 @findex COMMAND_TRACEPOINTS
23246 @findex gdb.COMMAND_TRACEPOINTS
23247 @item gdb.COMMAND_TRACEPOINTS
23248 The command has to do with tracepoints. For example, @code{trace},
23249 @code{actions}, and @code{tfind} are in this category. Type
23250 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23251 commands in this category.
23253 @findex COMMAND_OBSCURE
23254 @findex gdb.COMMAND_OBSCURE
23255 @item gdb.COMMAND_OBSCURE
23256 The command is only used in unusual circumstances, or is not of
23257 general interest to users. For example, @code{checkpoint},
23258 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23259 obscure} at the @value{GDBN} prompt to see a list of commands in this
23262 @findex COMMAND_MAINTENANCE
23263 @findex gdb.COMMAND_MAINTENANCE
23264 @item gdb.COMMAND_MAINTENANCE
23265 The command is only useful to @value{GDBN} maintainers. The
23266 @code{maintenance} and @code{flushregs} commands are in this category.
23267 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23268 commands in this category.
23271 A new command can use a predefined completion function, either by
23272 specifying it via an argument at initialization, or by returning it
23273 from the @code{complete} method. These predefined completion
23274 constants are all defined in the @code{gdb} module:
23277 @findex COMPLETE_NONE
23278 @findex gdb.COMPLETE_NONE
23279 @item gdb.COMPLETE_NONE
23280 This constant means that no completion should be done.
23282 @findex COMPLETE_FILENAME
23283 @findex gdb.COMPLETE_FILENAME
23284 @item gdb.COMPLETE_FILENAME
23285 This constant means that filename completion should be performed.
23287 @findex COMPLETE_LOCATION
23288 @findex gdb.COMPLETE_LOCATION
23289 @item gdb.COMPLETE_LOCATION
23290 This constant means that location completion should be done.
23291 @xref{Specify Location}.
23293 @findex COMPLETE_COMMAND
23294 @findex gdb.COMPLETE_COMMAND
23295 @item gdb.COMPLETE_COMMAND
23296 This constant means that completion should examine @value{GDBN}
23299 @findex COMPLETE_SYMBOL
23300 @findex gdb.COMPLETE_SYMBOL
23301 @item gdb.COMPLETE_SYMBOL
23302 This constant means that completion should be done using symbol names
23306 The following code snippet shows how a trivial CLI command can be
23307 implemented in Python:
23310 class HelloWorld (gdb.Command):
23311 """Greet the whole world."""
23313 def __init__ (self):
23314 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23316 def invoke (self, arg, from_tty):
23317 print "Hello, World!"
23322 The last line instantiates the class, and is necessary to trigger the
23323 registration of the command with @value{GDBN}. Depending on how the
23324 Python code is read into @value{GDBN}, you may need to import the
23325 @code{gdb} module explicitly.
23327 @node Parameters In Python
23328 @subsubsection Parameters In Python
23330 @cindex parameters in python
23331 @cindex python parameters
23332 @tindex gdb.Parameter
23334 You can implement new @value{GDBN} parameters using Python. A new
23335 parameter is implemented as an instance of the @code{gdb.Parameter}
23338 Parameters are exposed to the user via the @code{set} and
23339 @code{show} commands. @xref{Help}.
23341 There are many parameters that already exist and can be set in
23342 @value{GDBN}. Two examples are: @code{set follow fork} and
23343 @code{set charset}. Setting these parameters influences certain
23344 behavior in @value{GDBN}. Similarly, you can define parameters that
23345 can be used to influence behavior in custom Python scripts and commands.
23347 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23348 The object initializer for @code{Parameter} registers the new
23349 parameter with @value{GDBN}. This initializer is normally invoked
23350 from the subclass' own @code{__init__} method.
23352 @var{name} is the name of the new parameter. If @var{name} consists
23353 of multiple words, then the initial words are looked for as prefix
23354 parameters. An example of this can be illustrated with the
23355 @code{set print} set of parameters. If @var{name} is
23356 @code{print foo}, then @code{print} will be searched as the prefix
23357 parameter. In this case the parameter can subsequently be accessed in
23358 @value{GDBN} as @code{set print foo}.
23360 If @var{name} consists of multiple words, and no prefix parameter group
23361 can be found, an exception is raised.
23363 @var{command-class} should be one of the @samp{COMMAND_} constants
23364 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23365 categorize the new parameter in the help system.
23367 @var{parameter-class} should be one of the @samp{PARAM_} constants
23368 defined below. This argument tells @value{GDBN} the type of the new
23369 parameter; this information is used for input validation and
23372 If @var{parameter-class} is @code{PARAM_ENUM}, then
23373 @var{enum-sequence} must be a sequence of strings. These strings
23374 represent the possible values for the parameter.
23376 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23377 of a fourth argument will cause an exception to be thrown.
23379 The help text for the new parameter is taken from the Python
23380 documentation string for the parameter's class, if there is one. If
23381 there is no documentation string, a default value is used.
23384 @defvar Parameter.set_doc
23385 If this attribute exists, and is a string, then its value is used as
23386 the help text for this parameter's @code{set} command. The value is
23387 examined when @code{Parameter.__init__} is invoked; subsequent changes
23391 @defvar Parameter.show_doc
23392 If this attribute exists, and is a string, then its value is used as
23393 the help text for this parameter's @code{show} command. The value is
23394 examined when @code{Parameter.__init__} is invoked; subsequent changes
23398 @defvar Parameter.value
23399 The @code{value} attribute holds the underlying value of the
23400 parameter. It can be read and assigned to just as any other
23401 attribute. @value{GDBN} does validation when assignments are made.
23404 There are two methods that should be implemented in any
23405 @code{Parameter} class. These are:
23407 @defun Parameter.get_set_string (self)
23408 @value{GDBN} will call this method when a @var{parameter}'s value has
23409 been changed via the @code{set} API (for example, @kbd{set foo off}).
23410 The @code{value} attribute has already been populated with the new
23411 value and may be used in output. This method must return a string.
23414 @defun Parameter.get_show_string (self, svalue)
23415 @value{GDBN} will call this method when a @var{parameter}'s
23416 @code{show} API has been invoked (for example, @kbd{show foo}). The
23417 argument @code{svalue} receives the string representation of the
23418 current value. This method must return a string.
23421 When a new parameter is defined, its type must be specified. The
23422 available types are represented by constants defined in the @code{gdb}
23426 @findex PARAM_BOOLEAN
23427 @findex gdb.PARAM_BOOLEAN
23428 @item gdb.PARAM_BOOLEAN
23429 The value is a plain boolean. The Python boolean values, @code{True}
23430 and @code{False} are the only valid values.
23432 @findex PARAM_AUTO_BOOLEAN
23433 @findex gdb.PARAM_AUTO_BOOLEAN
23434 @item gdb.PARAM_AUTO_BOOLEAN
23435 The value has three possible states: true, false, and @samp{auto}. In
23436 Python, true and false are represented using boolean constants, and
23437 @samp{auto} is represented using @code{None}.
23439 @findex PARAM_UINTEGER
23440 @findex gdb.PARAM_UINTEGER
23441 @item gdb.PARAM_UINTEGER
23442 The value is an unsigned integer. The value of 0 should be
23443 interpreted to mean ``unlimited''.
23445 @findex PARAM_INTEGER
23446 @findex gdb.PARAM_INTEGER
23447 @item gdb.PARAM_INTEGER
23448 The value is a signed integer. The value of 0 should be interpreted
23449 to mean ``unlimited''.
23451 @findex PARAM_STRING
23452 @findex gdb.PARAM_STRING
23453 @item gdb.PARAM_STRING
23454 The value is a string. When the user modifies the string, any escape
23455 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23456 translated into corresponding characters and encoded into the current
23459 @findex PARAM_STRING_NOESCAPE
23460 @findex gdb.PARAM_STRING_NOESCAPE
23461 @item gdb.PARAM_STRING_NOESCAPE
23462 The value is a string. When the user modifies the string, escapes are
23463 passed through untranslated.
23465 @findex PARAM_OPTIONAL_FILENAME
23466 @findex gdb.PARAM_OPTIONAL_FILENAME
23467 @item gdb.PARAM_OPTIONAL_FILENAME
23468 The value is a either a filename (a string), or @code{None}.
23470 @findex PARAM_FILENAME
23471 @findex gdb.PARAM_FILENAME
23472 @item gdb.PARAM_FILENAME
23473 The value is a filename. This is just like
23474 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23476 @findex PARAM_ZINTEGER
23477 @findex gdb.PARAM_ZINTEGER
23478 @item gdb.PARAM_ZINTEGER
23479 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23480 is interpreted as itself.
23483 @findex gdb.PARAM_ENUM
23484 @item gdb.PARAM_ENUM
23485 The value is a string, which must be one of a collection string
23486 constants provided when the parameter is created.
23489 @node Functions In Python
23490 @subsubsection Writing new convenience functions
23492 @cindex writing convenience functions
23493 @cindex convenience functions in python
23494 @cindex python convenience functions
23495 @tindex gdb.Function
23497 You can implement new convenience functions (@pxref{Convenience Vars})
23498 in Python. A convenience function is an instance of a subclass of the
23499 class @code{gdb.Function}.
23501 @defun Function.__init__ (name)
23502 The initializer for @code{Function} registers the new function with
23503 @value{GDBN}. The argument @var{name} is the name of the function,
23504 a string. The function will be visible to the user as a convenience
23505 variable of type @code{internal function}, whose name is the same as
23506 the given @var{name}.
23508 The documentation for the new function is taken from the documentation
23509 string for the new class.
23512 @defun Function.invoke (@var{*args})
23513 When a convenience function is evaluated, its arguments are converted
23514 to instances of @code{gdb.Value}, and then the function's
23515 @code{invoke} method is called. Note that @value{GDBN} does not
23516 predetermine the arity of convenience functions. Instead, all
23517 available arguments are passed to @code{invoke}, following the
23518 standard Python calling convention. In particular, a convenience
23519 function can have default values for parameters without ill effect.
23521 The return value of this method is used as its value in the enclosing
23522 expression. If an ordinary Python value is returned, it is converted
23523 to a @code{gdb.Value} following the usual rules.
23526 The following code snippet shows how a trivial convenience function can
23527 be implemented in Python:
23530 class Greet (gdb.Function):
23531 """Return string to greet someone.
23532 Takes a name as argument."""
23534 def __init__ (self):
23535 super (Greet, self).__init__ ("greet")
23537 def invoke (self, name):
23538 return "Hello, %s!" % name.string ()
23543 The last line instantiates the class, and is necessary to trigger the
23544 registration of the function with @value{GDBN}. Depending on how the
23545 Python code is read into @value{GDBN}, you may need to import the
23546 @code{gdb} module explicitly.
23548 @node Progspaces In Python
23549 @subsubsection Program Spaces In Python
23551 @cindex progspaces in python
23552 @tindex gdb.Progspace
23554 A program space, or @dfn{progspace}, represents a symbolic view
23555 of an address space.
23556 It consists of all of the objfiles of the program.
23557 @xref{Objfiles In Python}.
23558 @xref{Inferiors and Programs, program spaces}, for more details
23559 about program spaces.
23561 The following progspace-related functions are available in the
23564 @findex gdb.current_progspace
23565 @defun gdb.current_progspace ()
23566 This function returns the program space of the currently selected inferior.
23567 @xref{Inferiors and Programs}.
23570 @findex gdb.progspaces
23571 @defun gdb.progspaces ()
23572 Return a sequence of all the progspaces currently known to @value{GDBN}.
23575 Each progspace is represented by an instance of the @code{gdb.Progspace}
23578 @defvar Progspace.filename
23579 The file name of the progspace as a string.
23582 @defvar Progspace.pretty_printers
23583 The @code{pretty_printers} attribute is a list of functions. It is
23584 used to look up pretty-printers. A @code{Value} is passed to each
23585 function in order; if the function returns @code{None}, then the
23586 search continues. Otherwise, the return value should be an object
23587 which is used to format the value. @xref{Pretty Printing API}, for more
23591 @node Objfiles In Python
23592 @subsubsection Objfiles In Python
23594 @cindex objfiles in python
23595 @tindex gdb.Objfile
23597 @value{GDBN} loads symbols for an inferior from various
23598 symbol-containing files (@pxref{Files}). These include the primary
23599 executable file, any shared libraries used by the inferior, and any
23600 separate debug info files (@pxref{Separate Debug Files}).
23601 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23603 The following objfile-related functions are available in the
23606 @findex gdb.current_objfile
23607 @defun gdb.current_objfile ()
23608 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23609 sets the ``current objfile'' to the corresponding objfile. This
23610 function returns the current objfile. If there is no current objfile,
23611 this function returns @code{None}.
23614 @findex gdb.objfiles
23615 @defun gdb.objfiles ()
23616 Return a sequence of all the objfiles current known to @value{GDBN}.
23617 @xref{Objfiles In Python}.
23620 Each objfile is represented by an instance of the @code{gdb.Objfile}
23623 @defvar Objfile.filename
23624 The file name of the objfile as a string.
23627 @defvar Objfile.pretty_printers
23628 The @code{pretty_printers} attribute is a list of functions. It is
23629 used to look up pretty-printers. A @code{Value} is passed to each
23630 function in order; if the function returns @code{None}, then the
23631 search continues. Otherwise, the return value should be an object
23632 which is used to format the value. @xref{Pretty Printing API}, for more
23636 A @code{gdb.Objfile} object has the following methods:
23638 @defun Objfile.is_valid ()
23639 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23640 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23641 if the object file it refers to is not loaded in @value{GDBN} any
23642 longer. All other @code{gdb.Objfile} methods will throw an exception
23643 if it is invalid at the time the method is called.
23646 @node Frames In Python
23647 @subsubsection Accessing inferior stack frames from Python.
23649 @cindex frames in python
23650 When the debugged program stops, @value{GDBN} is able to analyze its call
23651 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23652 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23653 while its corresponding frame exists in the inferior's stack. If you try
23654 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23655 exception (@pxref{Exception Handling}).
23657 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23661 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23665 The following frame-related functions are available in the @code{gdb} module:
23667 @findex gdb.selected_frame
23668 @defun gdb.selected_frame ()
23669 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23672 @findex gdb.newest_frame
23673 @defun gdb.newest_frame ()
23674 Return the newest frame object for the selected thread.
23677 @defun gdb.frame_stop_reason_string (reason)
23678 Return a string explaining the reason why @value{GDBN} stopped unwinding
23679 frames, as expressed by the given @var{reason} code (an integer, see the
23680 @code{unwind_stop_reason} method further down in this section).
23683 A @code{gdb.Frame} object has the following methods:
23686 @defun Frame.is_valid ()
23687 Returns true if the @code{gdb.Frame} object is valid, false if not.
23688 A frame object can become invalid if the frame it refers to doesn't
23689 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23690 an exception if it is invalid at the time the method is called.
23693 @defun Frame.name ()
23694 Returns the function name of the frame, or @code{None} if it can't be
23698 @defun Frame.type ()
23699 Returns the type of the frame. The value can be one of:
23701 @item gdb.NORMAL_FRAME
23702 An ordinary stack frame.
23704 @item gdb.DUMMY_FRAME
23705 A fake stack frame that was created by @value{GDBN} when performing an
23706 inferior function call.
23708 @item gdb.INLINE_FRAME
23709 A frame representing an inlined function. The function was inlined
23710 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23712 @item gdb.TAILCALL_FRAME
23713 A frame representing a tail call. @xref{Tail Call Frames}.
23715 @item gdb.SIGTRAMP_FRAME
23716 A signal trampoline frame. This is the frame created by the OS when
23717 it calls into a signal handler.
23719 @item gdb.ARCH_FRAME
23720 A fake stack frame representing a cross-architecture call.
23722 @item gdb.SENTINEL_FRAME
23723 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23728 @defun Frame.unwind_stop_reason ()
23729 Return an integer representing the reason why it's not possible to find
23730 more frames toward the outermost frame. Use
23731 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23732 function to a string. The value can be one of:
23735 @item gdb.FRAME_UNWIND_NO_REASON
23736 No particular reason (older frames should be available).
23738 @item gdb.FRAME_UNWIND_NULL_ID
23739 The previous frame's analyzer returns an invalid result.
23741 @item gdb.FRAME_UNWIND_OUTERMOST
23742 This frame is the outermost.
23744 @item gdb.FRAME_UNWIND_UNAVAILABLE
23745 Cannot unwind further, because that would require knowing the
23746 values of registers or memory that have not been collected.
23748 @item gdb.FRAME_UNWIND_INNER_ID
23749 This frame ID looks like it ought to belong to a NEXT frame,
23750 but we got it for a PREV frame. Normally, this is a sign of
23751 unwinder failure. It could also indicate stack corruption.
23753 @item gdb.FRAME_UNWIND_SAME_ID
23754 This frame has the same ID as the previous one. That means
23755 that unwinding further would almost certainly give us another
23756 frame with exactly the same ID, so break the chain. Normally,
23757 this is a sign of unwinder failure. It could also indicate
23760 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23761 The frame unwinder did not find any saved PC, but we needed
23762 one to unwind further.
23764 @item gdb.FRAME_UNWIND_FIRST_ERROR
23765 Any stop reason greater or equal to this value indicates some kind
23766 of error. This special value facilitates writing code that tests
23767 for errors in unwinding in a way that will work correctly even if
23768 the list of the other values is modified in future @value{GDBN}
23769 versions. Using it, you could write:
23771 reason = gdb.selected_frame().unwind_stop_reason ()
23772 reason_str = gdb.frame_stop_reason_string (reason)
23773 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23774 print "An error occured: %s" % reason_str
23781 Returns the frame's resume address.
23784 @defun Frame.block ()
23785 Return the frame's code block. @xref{Blocks In Python}.
23788 @defun Frame.function ()
23789 Return the symbol for the function corresponding to this frame.
23790 @xref{Symbols In Python}.
23793 @defun Frame.older ()
23794 Return the frame that called this frame.
23797 @defun Frame.newer ()
23798 Return the frame called by this frame.
23801 @defun Frame.find_sal ()
23802 Return the frame's symtab and line object.
23803 @xref{Symbol Tables In Python}.
23806 @defun Frame.read_var (variable @r{[}, block@r{]})
23807 Return the value of @var{variable} in this frame. If the optional
23808 argument @var{block} is provided, search for the variable from that
23809 block; otherwise start at the frame's current block (which is
23810 determined by the frame's current program counter). @var{variable}
23811 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23812 @code{gdb.Block} object.
23815 @defun Frame.select ()
23816 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23821 @node Blocks In Python
23822 @subsubsection Accessing frame blocks from Python.
23824 @cindex blocks in python
23827 Within each frame, @value{GDBN} maintains information on each block
23828 stored in that frame. These blocks are organized hierarchically, and
23829 are represented individually in Python as a @code{gdb.Block}.
23830 Please see @ref{Frames In Python}, for a more in-depth discussion on
23831 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23832 detailed technical information on @value{GDBN}'s book-keeping of the
23835 The following block-related functions are available in the @code{gdb}
23838 @findex gdb.block_for_pc
23839 @defun gdb.block_for_pc (pc)
23840 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23841 block cannot be found for the @var{pc} value specified, the function
23842 will return @code{None}.
23845 A @code{gdb.Block} object has the following methods:
23848 @defun Block.is_valid ()
23849 Returns @code{True} if the @code{gdb.Block} object is valid,
23850 @code{False} if not. A block object can become invalid if the block it
23851 refers to doesn't exist anymore in the inferior. All other
23852 @code{gdb.Block} methods will throw an exception if it is invalid at
23853 the time the method is called. This method is also made available to
23854 the Python iterator object that @code{gdb.Block} provides in an iteration
23855 context and via the Python @code{iter} built-in function.
23859 A @code{gdb.Block} object has the following attributes:
23862 @defvar Block.start
23863 The start address of the block. This attribute is not writable.
23867 The end address of the block. This attribute is not writable.
23870 @defvar Block.function
23871 The name of the block represented as a @code{gdb.Symbol}. If the
23872 block is not named, then this attribute holds @code{None}. This
23873 attribute is not writable.
23876 @defvar Block.superblock
23877 The block containing this block. If this parent block does not exist,
23878 this attribute holds @code{None}. This attribute is not writable.
23881 @defvar Block.global_block
23882 The global block associated with this block. This attribute is not
23886 @defvar Block.static_block
23887 The static block associated with this block. This attribute is not
23891 @defvar Block.is_global
23892 @code{True} if the @code{gdb.Block} object is a global block,
23893 @code{False} if not. This attribute is not
23897 @defvar Block.is_static
23898 @code{True} if the @code{gdb.Block} object is a static block,
23899 @code{False} if not. This attribute is not writable.
23903 @node Symbols In Python
23904 @subsubsection Python representation of Symbols.
23906 @cindex symbols in python
23909 @value{GDBN} represents every variable, function and type as an
23910 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23911 Similarly, Python represents these symbols in @value{GDBN} with the
23912 @code{gdb.Symbol} object.
23914 The following symbol-related functions are available in the @code{gdb}
23917 @findex gdb.lookup_symbol
23918 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23919 This function searches for a symbol by name. The search scope can be
23920 restricted to the parameters defined in the optional domain and block
23923 @var{name} is the name of the symbol. It must be a string. The
23924 optional @var{block} argument restricts the search to symbols visible
23925 in that @var{block}. The @var{block} argument must be a
23926 @code{gdb.Block} object. If omitted, the block for the current frame
23927 is used. The optional @var{domain} argument restricts
23928 the search to the domain type. The @var{domain} argument must be a
23929 domain constant defined in the @code{gdb} module and described later
23932 The result is a tuple of two elements.
23933 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23935 If the symbol is found, the second element is @code{True} if the symbol
23936 is a field of a method's object (e.g., @code{this} in C@t{++}),
23937 otherwise it is @code{False}.
23938 If the symbol is not found, the second element is @code{False}.
23941 @findex gdb.lookup_global_symbol
23942 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23943 This function searches for a global symbol by name.
23944 The search scope can be restricted to by the domain argument.
23946 @var{name} is the name of the symbol. It must be a string.
23947 The optional @var{domain} argument restricts the search to the domain type.
23948 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23949 module and described later in this chapter.
23951 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23955 A @code{gdb.Symbol} object has the following attributes:
23958 @defvar Symbol.type
23959 The type of the symbol or @code{None} if no type is recorded.
23960 This attribute is represented as a @code{gdb.Type} object.
23961 @xref{Types In Python}. This attribute is not writable.
23964 @defvar Symbol.symtab
23965 The symbol table in which the symbol appears. This attribute is
23966 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23967 Python}. This attribute is not writable.
23970 @defvar Symbol.name
23971 The name of the symbol as a string. This attribute is not writable.
23974 @defvar Symbol.linkage_name
23975 The name of the symbol, as used by the linker (i.e., may be mangled).
23976 This attribute is not writable.
23979 @defvar Symbol.print_name
23980 The name of the symbol in a form suitable for output. This is either
23981 @code{name} or @code{linkage_name}, depending on whether the user
23982 asked @value{GDBN} to display demangled or mangled names.
23985 @defvar Symbol.addr_class
23986 The address class of the symbol. This classifies how to find the value
23987 of a symbol. Each address class is a constant defined in the
23988 @code{gdb} module and described later in this chapter.
23991 @defvar Symbol.is_argument
23992 @code{True} if the symbol is an argument of a function.
23995 @defvar Symbol.is_constant
23996 @code{True} if the symbol is a constant.
23999 @defvar Symbol.is_function
24000 @code{True} if the symbol is a function or a method.
24003 @defvar Symbol.is_variable
24004 @code{True} if the symbol is a variable.
24008 A @code{gdb.Symbol} object has the following methods:
24011 @defun Symbol.is_valid ()
24012 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24013 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24014 the symbol it refers to does not exist in @value{GDBN} any longer.
24015 All other @code{gdb.Symbol} methods will throw an exception if it is
24016 invalid at the time the method is called.
24020 The available domain categories in @code{gdb.Symbol} are represented
24021 as constants in the @code{gdb} module:
24024 @findex SYMBOL_UNDEF_DOMAIN
24025 @findex gdb.SYMBOL_UNDEF_DOMAIN
24026 @item gdb.SYMBOL_UNDEF_DOMAIN
24027 This is used when a domain has not been discovered or none of the
24028 following domains apply. This usually indicates an error either
24029 in the symbol information or in @value{GDBN}'s handling of symbols.
24030 @findex SYMBOL_VAR_DOMAIN
24031 @findex gdb.SYMBOL_VAR_DOMAIN
24032 @item gdb.SYMBOL_VAR_DOMAIN
24033 This domain contains variables, function names, typedef names and enum
24035 @findex SYMBOL_STRUCT_DOMAIN
24036 @findex gdb.SYMBOL_STRUCT_DOMAIN
24037 @item gdb.SYMBOL_STRUCT_DOMAIN
24038 This domain holds struct, union and enum type names.
24039 @findex SYMBOL_LABEL_DOMAIN
24040 @findex gdb.SYMBOL_LABEL_DOMAIN
24041 @item gdb.SYMBOL_LABEL_DOMAIN
24042 This domain contains names of labels (for gotos).
24043 @findex SYMBOL_VARIABLES_DOMAIN
24044 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24045 @item gdb.SYMBOL_VARIABLES_DOMAIN
24046 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24047 contains everything minus functions and types.
24048 @findex SYMBOL_FUNCTIONS_DOMAIN
24049 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24050 @item gdb.SYMBOL_FUNCTION_DOMAIN
24051 This domain contains all functions.
24052 @findex SYMBOL_TYPES_DOMAIN
24053 @findex gdb.SYMBOL_TYPES_DOMAIN
24054 @item gdb.SYMBOL_TYPES_DOMAIN
24055 This domain contains all types.
24058 The available address class categories in @code{gdb.Symbol} are represented
24059 as constants in the @code{gdb} module:
24062 @findex SYMBOL_LOC_UNDEF
24063 @findex gdb.SYMBOL_LOC_UNDEF
24064 @item gdb.SYMBOL_LOC_UNDEF
24065 If this is returned by address class, it indicates an error either in
24066 the symbol information or in @value{GDBN}'s handling of symbols.
24067 @findex SYMBOL_LOC_CONST
24068 @findex gdb.SYMBOL_LOC_CONST
24069 @item gdb.SYMBOL_LOC_CONST
24070 Value is constant int.
24071 @findex SYMBOL_LOC_STATIC
24072 @findex gdb.SYMBOL_LOC_STATIC
24073 @item gdb.SYMBOL_LOC_STATIC
24074 Value is at a fixed address.
24075 @findex SYMBOL_LOC_REGISTER
24076 @findex gdb.SYMBOL_LOC_REGISTER
24077 @item gdb.SYMBOL_LOC_REGISTER
24078 Value is in a register.
24079 @findex SYMBOL_LOC_ARG
24080 @findex gdb.SYMBOL_LOC_ARG
24081 @item gdb.SYMBOL_LOC_ARG
24082 Value is an argument. This value is at the offset stored within the
24083 symbol inside the frame's argument list.
24084 @findex SYMBOL_LOC_REF_ARG
24085 @findex gdb.SYMBOL_LOC_REF_ARG
24086 @item gdb.SYMBOL_LOC_REF_ARG
24087 Value address is stored in the frame's argument list. Just like
24088 @code{LOC_ARG} except that the value's address is stored at the
24089 offset, not the value itself.
24090 @findex SYMBOL_LOC_REGPARM_ADDR
24091 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24092 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24093 Value is a specified register. Just like @code{LOC_REGISTER} except
24094 the register holds the address of the argument instead of the argument
24096 @findex SYMBOL_LOC_LOCAL
24097 @findex gdb.SYMBOL_LOC_LOCAL
24098 @item gdb.SYMBOL_LOC_LOCAL
24099 Value is a local variable.
24100 @findex SYMBOL_LOC_TYPEDEF
24101 @findex gdb.SYMBOL_LOC_TYPEDEF
24102 @item gdb.SYMBOL_LOC_TYPEDEF
24103 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24105 @findex SYMBOL_LOC_BLOCK
24106 @findex gdb.SYMBOL_LOC_BLOCK
24107 @item gdb.SYMBOL_LOC_BLOCK
24109 @findex SYMBOL_LOC_CONST_BYTES
24110 @findex gdb.SYMBOL_LOC_CONST_BYTES
24111 @item gdb.SYMBOL_LOC_CONST_BYTES
24112 Value is a byte-sequence.
24113 @findex SYMBOL_LOC_UNRESOLVED
24114 @findex gdb.SYMBOL_LOC_UNRESOLVED
24115 @item gdb.SYMBOL_LOC_UNRESOLVED
24116 Value is at a fixed address, but the address of the variable has to be
24117 determined from the minimal symbol table whenever the variable is
24119 @findex SYMBOL_LOC_OPTIMIZED_OUT
24120 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24121 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24122 The value does not actually exist in the program.
24123 @findex SYMBOL_LOC_COMPUTED
24124 @findex gdb.SYMBOL_LOC_COMPUTED
24125 @item gdb.SYMBOL_LOC_COMPUTED
24126 The value's address is a computed location.
24129 @node Symbol Tables In Python
24130 @subsubsection Symbol table representation in Python.
24132 @cindex symbol tables in python
24134 @tindex gdb.Symtab_and_line
24136 Access to symbol table data maintained by @value{GDBN} on the inferior
24137 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24138 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24139 from the @code{find_sal} method in @code{gdb.Frame} object.
24140 @xref{Frames In Python}.
24142 For more information on @value{GDBN}'s symbol table management, see
24143 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24145 A @code{gdb.Symtab_and_line} object has the following attributes:
24148 @defvar Symtab_and_line.symtab
24149 The symbol table object (@code{gdb.Symtab}) for this frame.
24150 This attribute is not writable.
24153 @defvar Symtab_and_line.pc
24154 Indicates the current program counter address. This attribute is not
24158 @defvar Symtab_and_line.line
24159 Indicates the current line number for this object. This
24160 attribute is not writable.
24164 A @code{gdb.Symtab_and_line} object has the following methods:
24167 @defun Symtab_and_line.is_valid ()
24168 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24169 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24170 invalid if the Symbol table and line object it refers to does not
24171 exist in @value{GDBN} any longer. All other
24172 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24173 invalid at the time the method is called.
24177 A @code{gdb.Symtab} object has the following attributes:
24180 @defvar Symtab.filename
24181 The symbol table's source filename. This attribute is not writable.
24184 @defvar Symtab.objfile
24185 The symbol table's backing object file. @xref{Objfiles In Python}.
24186 This attribute is not writable.
24190 A @code{gdb.Symtab} object has the following methods:
24193 @defun Symtab.is_valid ()
24194 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24195 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24196 the symbol table it refers to does not exist in @value{GDBN} any
24197 longer. All other @code{gdb.Symtab} methods will throw an exception
24198 if it is invalid at the time the method is called.
24201 @defun Symtab.fullname ()
24202 Return the symbol table's source absolute file name.
24206 @node Breakpoints In Python
24207 @subsubsection Manipulating breakpoints using Python
24209 @cindex breakpoints in python
24210 @tindex gdb.Breakpoint
24212 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24215 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24216 Create a new breakpoint. @var{spec} is a string naming the
24217 location of the breakpoint, or an expression that defines a
24218 watchpoint. The contents can be any location recognized by the
24219 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24220 command. The optional @var{type} denotes the breakpoint to create
24221 from the types defined later in this chapter. This argument can be
24222 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24223 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24224 allows the breakpoint to become invisible to the user. The breakpoint
24225 will neither be reported when created, nor will it be listed in the
24226 output from @code{info breakpoints} (but will be listed with the
24227 @code{maint info breakpoints} command). The optional @var{wp_class}
24228 argument defines the class of watchpoint to create, if @var{type} is
24229 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24230 assumed to be a @code{gdb.WP_WRITE} class.
24233 @defun Breakpoint.stop (self)
24234 The @code{gdb.Breakpoint} class can be sub-classed and, in
24235 particular, you may choose to implement the @code{stop} method.
24236 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24237 it will be called when the inferior reaches any location of a
24238 breakpoint which instantiates that sub-class. If the method returns
24239 @code{True}, the inferior will be stopped at the location of the
24240 breakpoint, otherwise the inferior will continue.
24242 If there are multiple breakpoints at the same location with a
24243 @code{stop} method, each one will be called regardless of the
24244 return status of the previous. This ensures that all @code{stop}
24245 methods have a chance to execute at that location. In this scenario
24246 if one of the methods returns @code{True} but the others return
24247 @code{False}, the inferior will still be stopped.
24249 You should not alter the execution state of the inferior (i.e.@:, step,
24250 next, etc.), alter the current frame context (i.e.@:, change the current
24251 active frame), or alter, add or delete any breakpoint. As a general
24252 rule, you should not alter any data within @value{GDBN} or the inferior
24255 Example @code{stop} implementation:
24258 class MyBreakpoint (gdb.Breakpoint):
24260 inf_val = gdb.parse_and_eval("foo")
24267 The available watchpoint types represented by constants are defined in the
24272 @findex gdb.WP_READ
24274 Read only watchpoint.
24277 @findex gdb.WP_WRITE
24279 Write only watchpoint.
24282 @findex gdb.WP_ACCESS
24283 @item gdb.WP_ACCESS
24284 Read/Write watchpoint.
24287 @defun Breakpoint.is_valid ()
24288 Return @code{True} if this @code{Breakpoint} object is valid,
24289 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24290 if the user deletes the breakpoint. In this case, the object still
24291 exists, but the underlying breakpoint does not. In the cases of
24292 watchpoint scope, the watchpoint remains valid even if execution of the
24293 inferior leaves the scope of that watchpoint.
24296 @defun Breakpoint.delete
24297 Permanently deletes the @value{GDBN} breakpoint. This also
24298 invalidates the Python @code{Breakpoint} object. Any further access
24299 to this object's attributes or methods will raise an error.
24302 @defvar Breakpoint.enabled
24303 This attribute is @code{True} if the breakpoint is enabled, and
24304 @code{False} otherwise. This attribute is writable.
24307 @defvar Breakpoint.silent
24308 This attribute is @code{True} if the breakpoint is silent, and
24309 @code{False} otherwise. This attribute is writable.
24311 Note that a breakpoint can also be silent if it has commands and the
24312 first command is @code{silent}. This is not reported by the
24313 @code{silent} attribute.
24316 @defvar Breakpoint.thread
24317 If the breakpoint is thread-specific, this attribute holds the thread
24318 id. If the breakpoint is not thread-specific, this attribute is
24319 @code{None}. This attribute is writable.
24322 @defvar Breakpoint.task
24323 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24324 id. If the breakpoint is not task-specific (or the underlying
24325 language is not Ada), this attribute is @code{None}. This attribute
24329 @defvar Breakpoint.ignore_count
24330 This attribute holds the ignore count for the breakpoint, an integer.
24331 This attribute is writable.
24334 @defvar Breakpoint.number
24335 This attribute holds the breakpoint's number --- the identifier used by
24336 the user to manipulate the breakpoint. This attribute is not writable.
24339 @defvar Breakpoint.type
24340 This attribute holds the breakpoint's type --- the identifier used to
24341 determine the actual breakpoint type or use-case. This attribute is not
24345 @defvar Breakpoint.visible
24346 This attribute tells whether the breakpoint is visible to the user
24347 when set, or when the @samp{info breakpoints} command is run. This
24348 attribute is not writable.
24351 The available types are represented by constants defined in the @code{gdb}
24355 @findex BP_BREAKPOINT
24356 @findex gdb.BP_BREAKPOINT
24357 @item gdb.BP_BREAKPOINT
24358 Normal code breakpoint.
24360 @findex BP_WATCHPOINT
24361 @findex gdb.BP_WATCHPOINT
24362 @item gdb.BP_WATCHPOINT
24363 Watchpoint breakpoint.
24365 @findex BP_HARDWARE_WATCHPOINT
24366 @findex gdb.BP_HARDWARE_WATCHPOINT
24367 @item gdb.BP_HARDWARE_WATCHPOINT
24368 Hardware assisted watchpoint.
24370 @findex BP_READ_WATCHPOINT
24371 @findex gdb.BP_READ_WATCHPOINT
24372 @item gdb.BP_READ_WATCHPOINT
24373 Hardware assisted read watchpoint.
24375 @findex BP_ACCESS_WATCHPOINT
24376 @findex gdb.BP_ACCESS_WATCHPOINT
24377 @item gdb.BP_ACCESS_WATCHPOINT
24378 Hardware assisted access watchpoint.
24381 @defvar Breakpoint.hit_count
24382 This attribute holds the hit count for the breakpoint, an integer.
24383 This attribute is writable, but currently it can only be set to zero.
24386 @defvar Breakpoint.location
24387 This attribute holds the location of the breakpoint, as specified by
24388 the user. It is a string. If the breakpoint does not have a location
24389 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24390 attribute is not writable.
24393 @defvar Breakpoint.expression
24394 This attribute holds a breakpoint expression, as specified by
24395 the user. It is a string. If the breakpoint does not have an
24396 expression (the breakpoint is not a watchpoint) the attribute's value
24397 is @code{None}. This attribute is not writable.
24400 @defvar Breakpoint.condition
24401 This attribute holds the condition of the breakpoint, as specified by
24402 the user. It is a string. If there is no condition, this attribute's
24403 value is @code{None}. This attribute is writable.
24406 @defvar Breakpoint.commands
24407 This attribute holds the commands attached to the breakpoint. If
24408 there are commands, this attribute's value is a string holding all the
24409 commands, separated by newlines. If there are no commands, this
24410 attribute is @code{None}. This attribute is not writable.
24413 @node Finish Breakpoints in Python
24414 @subsubsection Finish Breakpoints
24416 @cindex python finish breakpoints
24417 @tindex gdb.FinishBreakpoint
24419 A finish breakpoint is a temporary breakpoint set at the return address of
24420 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24421 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24422 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24423 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24424 Finish breakpoints are thread specific and must be create with the right
24427 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24428 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24429 object @var{frame}. If @var{frame} is not provided, this defaults to the
24430 newest frame. The optional @var{internal} argument allows the breakpoint to
24431 become invisible to the user. @xref{Breakpoints In Python}, for further
24432 details about this argument.
24435 @defun FinishBreakpoint.out_of_scope (self)
24436 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24437 @code{return} command, @dots{}), a function may not properly terminate, and
24438 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24439 situation, the @code{out_of_scope} callback will be triggered.
24441 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24445 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24447 print "normal finish"
24450 def out_of_scope ():
24451 print "abnormal finish"
24455 @defvar FinishBreakpoint.return_value
24456 When @value{GDBN} is stopped at a finish breakpoint and the frame
24457 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24458 attribute will contain a @code{gdb.Value} object corresponding to the return
24459 value of the function. The value will be @code{None} if the function return
24460 type is @code{void} or if the return value was not computable. This attribute
24464 @node Lazy Strings In Python
24465 @subsubsection Python representation of lazy strings.
24467 @cindex lazy strings in python
24468 @tindex gdb.LazyString
24470 A @dfn{lazy string} is a string whose contents is not retrieved or
24471 encoded until it is needed.
24473 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24474 @code{address} that points to a region of memory, an @code{encoding}
24475 that will be used to encode that region of memory, and a @code{length}
24476 to delimit the region of memory that represents the string. The
24477 difference between a @code{gdb.LazyString} and a string wrapped within
24478 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24479 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24480 retrieved and encoded during printing, while a @code{gdb.Value}
24481 wrapping a string is immediately retrieved and encoded on creation.
24483 A @code{gdb.LazyString} object has the following functions:
24485 @defun LazyString.value ()
24486 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24487 will point to the string in memory, but will lose all the delayed
24488 retrieval, encoding and handling that @value{GDBN} applies to a
24489 @code{gdb.LazyString}.
24492 @defvar LazyString.address
24493 This attribute holds the address of the string. This attribute is not
24497 @defvar LazyString.length
24498 This attribute holds the length of the string in characters. If the
24499 length is -1, then the string will be fetched and encoded up to the
24500 first null of appropriate width. This attribute is not writable.
24503 @defvar LazyString.encoding
24504 This attribute holds the encoding that will be applied to the string
24505 when the string is printed by @value{GDBN}. If the encoding is not
24506 set, or contains an empty string, then @value{GDBN} will select the
24507 most appropriate encoding when the string is printed. This attribute
24511 @defvar LazyString.type
24512 This attribute holds the type that is represented by the lazy string's
24513 type. For a lazy string this will always be a pointer type. To
24514 resolve this to the lazy string's character type, use the type's
24515 @code{target} method. @xref{Types In Python}. This attribute is not
24520 @subsection Auto-loading
24521 @cindex auto-loading, Python
24523 When a new object file is read (for example, due to the @code{file}
24524 command, or because the inferior has loaded a shared library),
24525 @value{GDBN} will look for Python support scripts in several ways:
24526 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24529 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24530 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24531 * Which flavor to choose?::
24534 The auto-loading feature is useful for supplying application-specific
24535 debugging commands and scripts.
24537 Auto-loading can be enabled or disabled,
24538 and the list of auto-loaded scripts can be printed.
24541 @kindex set auto-load-scripts
24542 @item set auto-load-scripts [yes|no]
24543 Enable or disable the auto-loading of Python scripts.
24545 @kindex show auto-load-scripts
24546 @item show auto-load-scripts
24547 Show whether auto-loading of Python scripts is enabled or disabled.
24549 @kindex info auto-load-scripts
24550 @cindex print list of auto-loaded scripts
24551 @item info auto-load-scripts [@var{regexp}]
24552 Print the list of all scripts that @value{GDBN} auto-loaded.
24554 Also printed is the list of scripts that were mentioned in
24555 the @code{.debug_gdb_scripts} section and were not found
24556 (@pxref{.debug_gdb_scripts section}).
24557 This is useful because their names are not printed when @value{GDBN}
24558 tries to load them and fails. There may be many of them, and printing
24559 an error message for each one is problematic.
24561 If @var{regexp} is supplied only scripts with matching names are printed.
24566 (gdb) info auto-load-scripts
24568 Yes py-section-script.py
24569 full name: /tmp/py-section-script.py
24570 Missing my-foo-pretty-printers.py
24574 When reading an auto-loaded file, @value{GDBN} sets the
24575 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24576 function (@pxref{Objfiles In Python}). This can be useful for
24577 registering objfile-specific pretty-printers.
24579 @node objfile-gdb.py file
24580 @subsubsection The @file{@var{objfile}-gdb.py} file
24581 @cindex @file{@var{objfile}-gdb.py}
24583 When a new object file is read, @value{GDBN} looks for
24584 a file named @file{@var{objfile}-gdb.py},
24585 where @var{objfile} is the object file's real name, formed by ensuring
24586 that the file name is absolute, following all symlinks, and resolving
24587 @code{.} and @code{..} components. If this file exists and is
24588 readable, @value{GDBN} will evaluate it as a Python script.
24590 If this file does not exist, and if the parameter
24591 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24592 then @value{GDBN} will look for @var{real-name} in all of the
24593 directories mentioned in the value of @code{debug-file-directory}.
24595 Finally, if this file does not exist, then @value{GDBN} will look for
24596 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24597 @var{data-directory} is @value{GDBN}'s data directory (available via
24598 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24599 is the object file's real name, as described above.
24601 @value{GDBN} does not track which files it has already auto-loaded this way.
24602 @value{GDBN} will load the associated script every time the corresponding
24603 @var{objfile} is opened.
24604 So your @file{-gdb.py} file should be careful to avoid errors if it
24605 is evaluated more than once.
24607 @node .debug_gdb_scripts section
24608 @subsubsection The @code{.debug_gdb_scripts} section
24609 @cindex @code{.debug_gdb_scripts} section
24611 For systems using file formats like ELF and COFF,
24612 when @value{GDBN} loads a new object file
24613 it will look for a special section named @samp{.debug_gdb_scripts}.
24614 If this section exists, its contents is a list of names of scripts to load.
24616 @value{GDBN} will look for each specified script file first in the
24617 current directory and then along the source search path
24618 (@pxref{Source Path, ,Specifying Source Directories}),
24619 except that @file{$cdir} is not searched, since the compilation
24620 directory is not relevant to scripts.
24622 Entries can be placed in section @code{.debug_gdb_scripts} with,
24623 for example, this GCC macro:
24626 /* Note: The "MS" section flags are to remove duplicates. */
24627 #define DEFINE_GDB_SCRIPT(script_name) \
24629 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24631 .asciz \"" script_name "\"\n\
24637 Then one can reference the macro in a header or source file like this:
24640 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24643 The script name may include directories if desired.
24645 If the macro is put in a header, any application or library
24646 using this header will get a reference to the specified script.
24648 @node Which flavor to choose?
24649 @subsubsection Which flavor to choose?
24651 Given the multiple ways of auto-loading Python scripts, it might not always
24652 be clear which one to choose. This section provides some guidance.
24654 Benefits of the @file{-gdb.py} way:
24658 Can be used with file formats that don't support multiple sections.
24661 Ease of finding scripts for public libraries.
24663 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24664 in the source search path.
24665 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24666 isn't a source directory in which to find the script.
24669 Doesn't require source code additions.
24672 Benefits of the @code{.debug_gdb_scripts} way:
24676 Works with static linking.
24678 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24679 trigger their loading. When an application is statically linked the only
24680 objfile available is the executable, and it is cumbersome to attach all the
24681 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24684 Works with classes that are entirely inlined.
24686 Some classes can be entirely inlined, and thus there may not be an associated
24687 shared library to attach a @file{-gdb.py} script to.
24690 Scripts needn't be copied out of the source tree.
24692 In some circumstances, apps can be built out of large collections of internal
24693 libraries, and the build infrastructure necessary to install the
24694 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24695 cumbersome. It may be easier to specify the scripts in the
24696 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24697 top of the source tree to the source search path.
24700 @node Python modules
24701 @subsection Python modules
24702 @cindex python modules
24704 @value{GDBN} comes with several modules to assist writing Python code.
24707 * gdb.printing:: Building and registering pretty-printers.
24708 * gdb.types:: Utilities for working with types.
24709 * gdb.prompt:: Utilities for prompt value substitution.
24713 @subsubsection gdb.printing
24714 @cindex gdb.printing
24716 This module provides a collection of utilities for working with
24720 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24721 This class specifies the API that makes @samp{info pretty-printer},
24722 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24723 Pretty-printers should generally inherit from this class.
24725 @item SubPrettyPrinter (@var{name})
24726 For printers that handle multiple types, this class specifies the
24727 corresponding API for the subprinters.
24729 @item RegexpCollectionPrettyPrinter (@var{name})
24730 Utility class for handling multiple printers, all recognized via
24731 regular expressions.
24732 @xref{Writing a Pretty-Printer}, for an example.
24734 @item FlagEnumerationPrinter (@var{name})
24735 A pretty-printer which handles printing of @code{enum} values. Unlike
24736 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
24737 work properly when there is some overlap between the enumeration
24738 constants. @var{name} is the name of the printer and also the name of
24739 the @code{enum} type to look up.
24741 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24742 Register @var{printer} with the pretty-printer list of @var{obj}.
24743 If @var{replace} is @code{True} then any existing copy of the printer
24744 is replaced. Otherwise a @code{RuntimeError} exception is raised
24745 if a printer with the same name already exists.
24749 @subsubsection gdb.types
24752 This module provides a collection of utilities for working with
24753 @code{gdb.Types} objects.
24756 @item get_basic_type (@var{type})
24757 Return @var{type} with const and volatile qualifiers stripped,
24758 and with typedefs and C@t{++} references converted to the underlying type.
24763 typedef const int const_int;
24765 const_int& foo_ref (foo);
24766 int main () @{ return 0; @}
24773 (gdb) python import gdb.types
24774 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24775 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24779 @item has_field (@var{type}, @var{field})
24780 Return @code{True} if @var{type}, assumed to be a type with fields
24781 (e.g., a structure or union), has field @var{field}.
24783 @item make_enum_dict (@var{enum_type})
24784 Return a Python @code{dictionary} type produced from @var{enum_type}.
24786 @item deep_items (@var{type})
24787 Returns a Python iterator similar to the standard
24788 @code{gdb.Type.iteritems} method, except that the iterator returned
24789 by @code{deep_items} will recursively traverse anonymous struct or
24790 union fields. For example:
24804 Then in @value{GDBN}:
24806 (@value{GDBP}) python import gdb.types
24807 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24808 (@value{GDBP}) python print struct_a.keys ()
24810 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24811 @{['a', 'b0', 'b1']@}
24817 @subsubsection gdb.prompt
24820 This module provides a method for prompt value-substitution.
24823 @item substitute_prompt (@var{string})
24824 Return @var{string} with escape sequences substituted by values. Some
24825 escape sequences take arguments. You can specify arguments inside
24826 ``@{@}'' immediately following the escape sequence.
24828 The escape sequences you can pass to this function are:
24832 Substitute a backslash.
24834 Substitute an ESC character.
24836 Substitute the selected frame; an argument names a frame parameter.
24838 Substitute a newline.
24840 Substitute a parameter's value; the argument names the parameter.
24842 Substitute a carriage return.
24844 Substitute the selected thread; an argument names a thread parameter.
24846 Substitute the version of GDB.
24848 Substitute the current working directory.
24850 Begin a sequence of non-printing characters. These sequences are
24851 typically used with the ESC character, and are not counted in the string
24852 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24853 blue-colored ``(gdb)'' prompt where the length is five.
24855 End a sequence of non-printing characters.
24861 substitute_prompt (``frame: \f,
24862 print arguments: \p@{print frame-arguments@}'')
24865 @exdent will return the string:
24868 "frame: main, print arguments: scalars"
24873 @section Creating new spellings of existing commands
24874 @cindex aliases for commands
24876 It is often useful to define alternate spellings of existing commands.
24877 For example, if a new @value{GDBN} command defined in Python has
24878 a long name to type, it is handy to have an abbreviated version of it
24879 that involves less typing.
24881 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24882 of the @samp{step} command even though it is otherwise an ambiguous
24883 abbreviation of other commands like @samp{set} and @samp{show}.
24885 Aliases are also used to provide shortened or more common versions
24886 of multi-word commands. For example, @value{GDBN} provides the
24887 @samp{tty} alias of the @samp{set inferior-tty} command.
24889 You can define a new alias with the @samp{alias} command.
24894 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24898 @var{ALIAS} specifies the name of the new alias.
24899 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24902 @var{COMMAND} specifies the name of an existing command
24903 that is being aliased.
24905 The @samp{-a} option specifies that the new alias is an abbreviation
24906 of the command. Abbreviations are not shown in command
24907 lists displayed by the @samp{help} command.
24909 The @samp{--} option specifies the end of options,
24910 and is useful when @var{ALIAS} begins with a dash.
24912 Here is a simple example showing how to make an abbreviation
24913 of a command so that there is less to type.
24914 Suppose you were tired of typing @samp{disas}, the current
24915 shortest unambiguous abbreviation of the @samp{disassemble} command
24916 and you wanted an even shorter version named @samp{di}.
24917 The following will accomplish this.
24920 (gdb) alias -a di = disas
24923 Note that aliases are different from user-defined commands.
24924 With a user-defined command, you also need to write documentation
24925 for it with the @samp{document} command.
24926 An alias automatically picks up the documentation of the existing command.
24928 Here is an example where we make @samp{elms} an abbreviation of
24929 @samp{elements} in the @samp{set print elements} command.
24930 This is to show that you can make an abbreviation of any part
24934 (gdb) alias -a set print elms = set print elements
24935 (gdb) alias -a show print elms = show print elements
24936 (gdb) set p elms 20
24938 Limit on string chars or array elements to print is 200.
24941 Note that if you are defining an alias of a @samp{set} command,
24942 and you want to have an alias for the corresponding @samp{show}
24943 command, then you need to define the latter separately.
24945 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24946 @var{ALIAS}, just as they are normally.
24949 (gdb) alias -a set pr elms = set p ele
24952 Finally, here is an example showing the creation of a one word
24953 alias for a more complex command.
24954 This creates alias @samp{spe} of the command @samp{set print elements}.
24957 (gdb) alias spe = set print elements
24962 @chapter Command Interpreters
24963 @cindex command interpreters
24965 @value{GDBN} supports multiple command interpreters, and some command
24966 infrastructure to allow users or user interface writers to switch
24967 between interpreters or run commands in other interpreters.
24969 @value{GDBN} currently supports two command interpreters, the console
24970 interpreter (sometimes called the command-line interpreter or @sc{cli})
24971 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24972 describes both of these interfaces in great detail.
24974 By default, @value{GDBN} will start with the console interpreter.
24975 However, the user may choose to start @value{GDBN} with another
24976 interpreter by specifying the @option{-i} or @option{--interpreter}
24977 startup options. Defined interpreters include:
24981 @cindex console interpreter
24982 The traditional console or command-line interpreter. This is the most often
24983 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24984 @value{GDBN} will use this interpreter.
24987 @cindex mi interpreter
24988 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24989 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24990 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24994 @cindex mi2 interpreter
24995 The current @sc{gdb/mi} interface.
24998 @cindex mi1 interpreter
24999 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25003 @cindex invoke another interpreter
25004 The interpreter being used by @value{GDBN} may not be dynamically
25005 switched at runtime. Although possible, this could lead to a very
25006 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
25007 enters the command "interpreter-set console" in a console view,
25008 @value{GDBN} would switch to using the console interpreter, rendering
25009 the IDE inoperable!
25011 @kindex interpreter-exec
25012 Although you may only choose a single interpreter at startup, you may execute
25013 commands in any interpreter from the current interpreter using the appropriate
25014 command. If you are running the console interpreter, simply use the
25015 @code{interpreter-exec} command:
25018 interpreter-exec mi "-data-list-register-names"
25021 @sc{gdb/mi} has a similar command, although it is only available in versions of
25022 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25025 @chapter @value{GDBN} Text User Interface
25027 @cindex Text User Interface
25030 * TUI Overview:: TUI overview
25031 * TUI Keys:: TUI key bindings
25032 * TUI Single Key Mode:: TUI single key mode
25033 * TUI Commands:: TUI-specific commands
25034 * TUI Configuration:: TUI configuration variables
25037 The @value{GDBN} Text User Interface (TUI) is a terminal
25038 interface which uses the @code{curses} library to show the source
25039 file, the assembly output, the program registers and @value{GDBN}
25040 commands in separate text windows. The TUI mode is supported only
25041 on platforms where a suitable version of the @code{curses} library
25044 The TUI mode is enabled by default when you invoke @value{GDBN} as
25045 @samp{@value{GDBP} -tui}.
25046 You can also switch in and out of TUI mode while @value{GDBN} runs by
25047 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25048 @xref{TUI Keys, ,TUI Key Bindings}.
25051 @section TUI Overview
25053 In TUI mode, @value{GDBN} can display several text windows:
25057 This window is the @value{GDBN} command window with the @value{GDBN}
25058 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25059 managed using readline.
25062 The source window shows the source file of the program. The current
25063 line and active breakpoints are displayed in this window.
25066 The assembly window shows the disassembly output of the program.
25069 This window shows the processor registers. Registers are highlighted
25070 when their values change.
25073 The source and assembly windows show the current program position
25074 by highlighting the current line and marking it with a @samp{>} marker.
25075 Breakpoints are indicated with two markers. The first marker
25076 indicates the breakpoint type:
25080 Breakpoint which was hit at least once.
25083 Breakpoint which was never hit.
25086 Hardware breakpoint which was hit at least once.
25089 Hardware breakpoint which was never hit.
25092 The second marker indicates whether the breakpoint is enabled or not:
25096 Breakpoint is enabled.
25099 Breakpoint is disabled.
25102 The source, assembly and register windows are updated when the current
25103 thread changes, when the frame changes, or when the program counter
25106 These windows are not all visible at the same time. The command
25107 window is always visible. The others can be arranged in several
25118 source and assembly,
25121 source and registers, or
25124 assembly and registers.
25127 A status line above the command window shows the following information:
25131 Indicates the current @value{GDBN} target.
25132 (@pxref{Targets, ,Specifying a Debugging Target}).
25135 Gives the current process or thread number.
25136 When no process is being debugged, this field is set to @code{No process}.
25139 Gives the current function name for the selected frame.
25140 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25141 When there is no symbol corresponding to the current program counter,
25142 the string @code{??} is displayed.
25145 Indicates the current line number for the selected frame.
25146 When the current line number is not known, the string @code{??} is displayed.
25149 Indicates the current program counter address.
25153 @section TUI Key Bindings
25154 @cindex TUI key bindings
25156 The TUI installs several key bindings in the readline keymaps
25157 @ifset SYSTEM_READLINE
25158 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25160 @ifclear SYSTEM_READLINE
25161 (@pxref{Command Line Editing}).
25163 The following key bindings are installed for both TUI mode and the
25164 @value{GDBN} standard mode.
25173 Enter or leave the TUI mode. When leaving the TUI mode,
25174 the curses window management stops and @value{GDBN} operates using
25175 its standard mode, writing on the terminal directly. When reentering
25176 the TUI mode, control is given back to the curses windows.
25177 The screen is then refreshed.
25181 Use a TUI layout with only one window. The layout will
25182 either be @samp{source} or @samp{assembly}. When the TUI mode
25183 is not active, it will switch to the TUI mode.
25185 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25189 Use a TUI layout with at least two windows. When the current
25190 layout already has two windows, the next layout with two windows is used.
25191 When a new layout is chosen, one window will always be common to the
25192 previous layout and the new one.
25194 Think of it as the Emacs @kbd{C-x 2} binding.
25198 Change the active window. The TUI associates several key bindings
25199 (like scrolling and arrow keys) with the active window. This command
25200 gives the focus to the next TUI window.
25202 Think of it as the Emacs @kbd{C-x o} binding.
25206 Switch in and out of the TUI SingleKey mode that binds single
25207 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25210 The following key bindings only work in the TUI mode:
25215 Scroll the active window one page up.
25219 Scroll the active window one page down.
25223 Scroll the active window one line up.
25227 Scroll the active window one line down.
25231 Scroll the active window one column left.
25235 Scroll the active window one column right.
25239 Refresh the screen.
25242 Because the arrow keys scroll the active window in the TUI mode, they
25243 are not available for their normal use by readline unless the command
25244 window has the focus. When another window is active, you must use
25245 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25246 and @kbd{C-f} to control the command window.
25248 @node TUI Single Key Mode
25249 @section TUI Single Key Mode
25250 @cindex TUI single key mode
25252 The TUI also provides a @dfn{SingleKey} mode, which binds several
25253 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25254 switch into this mode, where the following key bindings are used:
25257 @kindex c @r{(SingleKey TUI key)}
25261 @kindex d @r{(SingleKey TUI key)}
25265 @kindex f @r{(SingleKey TUI key)}
25269 @kindex n @r{(SingleKey TUI key)}
25273 @kindex q @r{(SingleKey TUI key)}
25275 exit the SingleKey mode.
25277 @kindex r @r{(SingleKey TUI key)}
25281 @kindex s @r{(SingleKey TUI key)}
25285 @kindex u @r{(SingleKey TUI key)}
25289 @kindex v @r{(SingleKey TUI key)}
25293 @kindex w @r{(SingleKey TUI key)}
25298 Other keys temporarily switch to the @value{GDBN} command prompt.
25299 The key that was pressed is inserted in the editing buffer so that
25300 it is possible to type most @value{GDBN} commands without interaction
25301 with the TUI SingleKey mode. Once the command is entered the TUI
25302 SingleKey mode is restored. The only way to permanently leave
25303 this mode is by typing @kbd{q} or @kbd{C-x s}.
25307 @section TUI-specific Commands
25308 @cindex TUI commands
25310 The TUI has specific commands to control the text windows.
25311 These commands are always available, even when @value{GDBN} is not in
25312 the TUI mode. When @value{GDBN} is in the standard mode, most
25313 of these commands will automatically switch to the TUI mode.
25315 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25316 terminal, or @value{GDBN} has been started with the machine interface
25317 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25318 these commands will fail with an error, because it would not be
25319 possible or desirable to enable curses window management.
25324 List and give the size of all displayed windows.
25328 Display the next layout.
25331 Display the previous layout.
25334 Display the source window only.
25337 Display the assembly window only.
25340 Display the source and assembly window.
25343 Display the register window together with the source or assembly window.
25347 Make the next window active for scrolling.
25350 Make the previous window active for scrolling.
25353 Make the source window active for scrolling.
25356 Make the assembly window active for scrolling.
25359 Make the register window active for scrolling.
25362 Make the command window active for scrolling.
25366 Refresh the screen. This is similar to typing @kbd{C-L}.
25368 @item tui reg float
25370 Show the floating point registers in the register window.
25372 @item tui reg general
25373 Show the general registers in the register window.
25376 Show the next register group. The list of register groups as well as
25377 their order is target specific. The predefined register groups are the
25378 following: @code{general}, @code{float}, @code{system}, @code{vector},
25379 @code{all}, @code{save}, @code{restore}.
25381 @item tui reg system
25382 Show the system registers in the register window.
25386 Update the source window and the current execution point.
25388 @item winheight @var{name} +@var{count}
25389 @itemx winheight @var{name} -@var{count}
25391 Change the height of the window @var{name} by @var{count}
25392 lines. Positive counts increase the height, while negative counts
25395 @item tabset @var{nchars}
25397 Set the width of tab stops to be @var{nchars} characters.
25400 @node TUI Configuration
25401 @section TUI Configuration Variables
25402 @cindex TUI configuration variables
25404 Several configuration variables control the appearance of TUI windows.
25407 @item set tui border-kind @var{kind}
25408 @kindex set tui border-kind
25409 Select the border appearance for the source, assembly and register windows.
25410 The possible values are the following:
25413 Use a space character to draw the border.
25416 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25419 Use the Alternate Character Set to draw the border. The border is
25420 drawn using character line graphics if the terminal supports them.
25423 @item set tui border-mode @var{mode}
25424 @kindex set tui border-mode
25425 @itemx set tui active-border-mode @var{mode}
25426 @kindex set tui active-border-mode
25427 Select the display attributes for the borders of the inactive windows
25428 or the active window. The @var{mode} can be one of the following:
25431 Use normal attributes to display the border.
25437 Use reverse video mode.
25440 Use half bright mode.
25442 @item half-standout
25443 Use half bright and standout mode.
25446 Use extra bright or bold mode.
25448 @item bold-standout
25449 Use extra bright or bold and standout mode.
25454 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25457 @cindex @sc{gnu} Emacs
25458 A special interface allows you to use @sc{gnu} Emacs to view (and
25459 edit) the source files for the program you are debugging with
25462 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25463 executable file you want to debug as an argument. This command starts
25464 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25465 created Emacs buffer.
25466 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25468 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25473 All ``terminal'' input and output goes through an Emacs buffer, called
25476 This applies both to @value{GDBN} commands and their output, and to the input
25477 and output done by the program you are debugging.
25479 This is useful because it means that you can copy the text of previous
25480 commands and input them again; you can even use parts of the output
25483 All the facilities of Emacs' Shell mode are available for interacting
25484 with your program. In particular, you can send signals the usual
25485 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25489 @value{GDBN} displays source code through Emacs.
25491 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25492 source file for that frame and puts an arrow (@samp{=>}) at the
25493 left margin of the current line. Emacs uses a separate buffer for
25494 source display, and splits the screen to show both your @value{GDBN} session
25497 Explicit @value{GDBN} @code{list} or search commands still produce output as
25498 usual, but you probably have no reason to use them from Emacs.
25501 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25502 a graphical mode, enabled by default, which provides further buffers
25503 that can control the execution and describe the state of your program.
25504 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25506 If you specify an absolute file name when prompted for the @kbd{M-x
25507 gdb} argument, then Emacs sets your current working directory to where
25508 your program resides. If you only specify the file name, then Emacs
25509 sets your current working directory to the directory associated
25510 with the previous buffer. In this case, @value{GDBN} may find your
25511 program by searching your environment's @code{PATH} variable, but on
25512 some operating systems it might not find the source. So, although the
25513 @value{GDBN} input and output session proceeds normally, the auxiliary
25514 buffer does not display the current source and line of execution.
25516 The initial working directory of @value{GDBN} is printed on the top
25517 line of the GUD buffer and this serves as a default for the commands
25518 that specify files for @value{GDBN} to operate on. @xref{Files,
25519 ,Commands to Specify Files}.
25521 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25522 need to call @value{GDBN} by a different name (for example, if you
25523 keep several configurations around, with different names) you can
25524 customize the Emacs variable @code{gud-gdb-command-name} to run the
25527 In the GUD buffer, you can use these special Emacs commands in
25528 addition to the standard Shell mode commands:
25532 Describe the features of Emacs' GUD Mode.
25535 Execute to another source line, like the @value{GDBN} @code{step} command; also
25536 update the display window to show the current file and location.
25539 Execute to next source line in this function, skipping all function
25540 calls, like the @value{GDBN} @code{next} command. Then update the display window
25541 to show the current file and location.
25544 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25545 display window accordingly.
25548 Execute until exit from the selected stack frame, like the @value{GDBN}
25549 @code{finish} command.
25552 Continue execution of your program, like the @value{GDBN} @code{continue}
25556 Go up the number of frames indicated by the numeric argument
25557 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25558 like the @value{GDBN} @code{up} command.
25561 Go down the number of frames indicated by the numeric argument, like the
25562 @value{GDBN} @code{down} command.
25565 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25566 tells @value{GDBN} to set a breakpoint on the source line point is on.
25568 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25569 separate frame which shows a backtrace when the GUD buffer is current.
25570 Move point to any frame in the stack and type @key{RET} to make it
25571 become the current frame and display the associated source in the
25572 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25573 selected frame become the current one. In graphical mode, the
25574 speedbar displays watch expressions.
25576 If you accidentally delete the source-display buffer, an easy way to get
25577 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25578 request a frame display; when you run under Emacs, this recreates
25579 the source buffer if necessary to show you the context of the current
25582 The source files displayed in Emacs are in ordinary Emacs buffers
25583 which are visiting the source files in the usual way. You can edit
25584 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25585 communicates with Emacs in terms of line numbers. If you add or
25586 delete lines from the text, the line numbers that @value{GDBN} knows cease
25587 to correspond properly with the code.
25589 A more detailed description of Emacs' interaction with @value{GDBN} is
25590 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25593 @c The following dropped because Epoch is nonstandard. Reactivate
25594 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25596 @kindex Emacs Epoch environment
25600 Version 18 of @sc{gnu} Emacs has a built-in window system
25601 called the @code{epoch}
25602 environment. Users of this environment can use a new command,
25603 @code{inspect} which performs identically to @code{print} except that
25604 each value is printed in its own window.
25609 @chapter The @sc{gdb/mi} Interface
25611 @unnumberedsec Function and Purpose
25613 @cindex @sc{gdb/mi}, its purpose
25614 @sc{gdb/mi} is a line based machine oriented text interface to
25615 @value{GDBN} and is activated by specifying using the
25616 @option{--interpreter} command line option (@pxref{Mode Options}). It
25617 is specifically intended to support the development of systems which
25618 use the debugger as just one small component of a larger system.
25620 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25621 in the form of a reference manual.
25623 Note that @sc{gdb/mi} is still under construction, so some of the
25624 features described below are incomplete and subject to change
25625 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25627 @unnumberedsec Notation and Terminology
25629 @cindex notational conventions, for @sc{gdb/mi}
25630 This chapter uses the following notation:
25634 @code{|} separates two alternatives.
25637 @code{[ @var{something} ]} indicates that @var{something} is optional:
25638 it may or may not be given.
25641 @code{( @var{group} )*} means that @var{group} inside the parentheses
25642 may repeat zero or more times.
25645 @code{( @var{group} )+} means that @var{group} inside the parentheses
25646 may repeat one or more times.
25649 @code{"@var{string}"} means a literal @var{string}.
25653 @heading Dependencies
25657 * GDB/MI General Design::
25658 * GDB/MI Command Syntax::
25659 * GDB/MI Compatibility with CLI::
25660 * GDB/MI Development and Front Ends::
25661 * GDB/MI Output Records::
25662 * GDB/MI Simple Examples::
25663 * GDB/MI Command Description Format::
25664 * GDB/MI Breakpoint Commands::
25665 * GDB/MI Program Context::
25666 * GDB/MI Thread Commands::
25667 * GDB/MI Ada Tasking Commands::
25668 * GDB/MI Program Execution::
25669 * GDB/MI Stack Manipulation::
25670 * GDB/MI Variable Objects::
25671 * GDB/MI Data Manipulation::
25672 * GDB/MI Tracepoint Commands::
25673 * GDB/MI Symbol Query::
25674 * GDB/MI File Commands::
25676 * GDB/MI Kod Commands::
25677 * GDB/MI Memory Overlay Commands::
25678 * GDB/MI Signal Handling Commands::
25680 * GDB/MI Target Manipulation::
25681 * GDB/MI File Transfer Commands::
25682 * GDB/MI Miscellaneous Commands::
25685 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25686 @node GDB/MI General Design
25687 @section @sc{gdb/mi} General Design
25688 @cindex GDB/MI General Design
25690 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25691 parts---commands sent to @value{GDBN}, responses to those commands
25692 and notifications. Each command results in exactly one response,
25693 indicating either successful completion of the command, or an error.
25694 For the commands that do not resume the target, the response contains the
25695 requested information. For the commands that resume the target, the
25696 response only indicates whether the target was successfully resumed.
25697 Notifications is the mechanism for reporting changes in the state of the
25698 target, or in @value{GDBN} state, that cannot conveniently be associated with
25699 a command and reported as part of that command response.
25701 The important examples of notifications are:
25705 Exec notifications. These are used to report changes in
25706 target state---when a target is resumed, or stopped. It would not
25707 be feasible to include this information in response of resuming
25708 commands, because one resume commands can result in multiple events in
25709 different threads. Also, quite some time may pass before any event
25710 happens in the target, while a frontend needs to know whether the resuming
25711 command itself was successfully executed.
25714 Console output, and status notifications. Console output
25715 notifications are used to report output of CLI commands, as well as
25716 diagnostics for other commands. Status notifications are used to
25717 report the progress of a long-running operation. Naturally, including
25718 this information in command response would mean no output is produced
25719 until the command is finished, which is undesirable.
25722 General notifications. Commands may have various side effects on
25723 the @value{GDBN} or target state beyond their official purpose. For example,
25724 a command may change the selected thread. Although such changes can
25725 be included in command response, using notification allows for more
25726 orthogonal frontend design.
25730 There's no guarantee that whenever an MI command reports an error,
25731 @value{GDBN} or the target are in any specific state, and especially,
25732 the state is not reverted to the state before the MI command was
25733 processed. Therefore, whenever an MI command results in an error,
25734 we recommend that the frontend refreshes all the information shown in
25735 the user interface.
25739 * Context management::
25740 * Asynchronous and non-stop modes::
25744 @node Context management
25745 @subsection Context management
25747 In most cases when @value{GDBN} accesses the target, this access is
25748 done in context of a specific thread and frame (@pxref{Frames}).
25749 Often, even when accessing global data, the target requires that a thread
25750 be specified. The CLI interface maintains the selected thread and frame,
25751 and supplies them to target on each command. This is convenient,
25752 because a command line user would not want to specify that information
25753 explicitly on each command, and because user interacts with
25754 @value{GDBN} via a single terminal, so no confusion is possible as
25755 to what thread and frame are the current ones.
25757 In the case of MI, the concept of selected thread and frame is less
25758 useful. First, a frontend can easily remember this information
25759 itself. Second, a graphical frontend can have more than one window,
25760 each one used for debugging a different thread, and the frontend might
25761 want to access additional threads for internal purposes. This
25762 increases the risk that by relying on implicitly selected thread, the
25763 frontend may be operating on a wrong one. Therefore, each MI command
25764 should explicitly specify which thread and frame to operate on. To
25765 make it possible, each MI command accepts the @samp{--thread} and
25766 @samp{--frame} options, the value to each is @value{GDBN} identifier
25767 for thread and frame to operate on.
25769 Usually, each top-level window in a frontend allows the user to select
25770 a thread and a frame, and remembers the user selection for further
25771 operations. However, in some cases @value{GDBN} may suggest that the
25772 current thread be changed. For example, when stopping on a breakpoint
25773 it is reasonable to switch to the thread where breakpoint is hit. For
25774 another example, if the user issues the CLI @samp{thread} command via
25775 the frontend, it is desirable to change the frontend's selected thread to the
25776 one specified by user. @value{GDBN} communicates the suggestion to
25777 change current thread using the @samp{=thread-selected} notification.
25778 No such notification is available for the selected frame at the moment.
25780 Note that historically, MI shares the selected thread with CLI, so
25781 frontends used the @code{-thread-select} to execute commands in the
25782 right context. However, getting this to work right is cumbersome. The
25783 simplest way is for frontend to emit @code{-thread-select} command
25784 before every command. This doubles the number of commands that need
25785 to be sent. The alternative approach is to suppress @code{-thread-select}
25786 if the selected thread in @value{GDBN} is supposed to be identical to the
25787 thread the frontend wants to operate on. However, getting this
25788 optimization right can be tricky. In particular, if the frontend
25789 sends several commands to @value{GDBN}, and one of the commands changes the
25790 selected thread, then the behaviour of subsequent commands will
25791 change. So, a frontend should either wait for response from such
25792 problematic commands, or explicitly add @code{-thread-select} for
25793 all subsequent commands. No frontend is known to do this exactly
25794 right, so it is suggested to just always pass the @samp{--thread} and
25795 @samp{--frame} options.
25797 @node Asynchronous and non-stop modes
25798 @subsection Asynchronous command execution and non-stop mode
25800 On some targets, @value{GDBN} is capable of processing MI commands
25801 even while the target is running. This is called @dfn{asynchronous
25802 command execution} (@pxref{Background Execution}). The frontend may
25803 specify a preferrence for asynchronous execution using the
25804 @code{-gdb-set target-async 1} command, which should be emitted before
25805 either running the executable or attaching to the target. After the
25806 frontend has started the executable or attached to the target, it can
25807 find if asynchronous execution is enabled using the
25808 @code{-list-target-features} command.
25810 Even if @value{GDBN} can accept a command while target is running,
25811 many commands that access the target do not work when the target is
25812 running. Therefore, asynchronous command execution is most useful
25813 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25814 it is possible to examine the state of one thread, while other threads
25817 When a given thread is running, MI commands that try to access the
25818 target in the context of that thread may not work, or may work only on
25819 some targets. In particular, commands that try to operate on thread's
25820 stack will not work, on any target. Commands that read memory, or
25821 modify breakpoints, may work or not work, depending on the target. Note
25822 that even commands that operate on global state, such as @code{print},
25823 @code{set}, and breakpoint commands, still access the target in the
25824 context of a specific thread, so frontend should try to find a
25825 stopped thread and perform the operation on that thread (using the
25826 @samp{--thread} option).
25828 Which commands will work in the context of a running thread is
25829 highly target dependent. However, the two commands
25830 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25831 to find the state of a thread, will always work.
25833 @node Thread groups
25834 @subsection Thread groups
25835 @value{GDBN} may be used to debug several processes at the same time.
25836 On some platfroms, @value{GDBN} may support debugging of several
25837 hardware systems, each one having several cores with several different
25838 processes running on each core. This section describes the MI
25839 mechanism to support such debugging scenarios.
25841 The key observation is that regardless of the structure of the
25842 target, MI can have a global list of threads, because most commands that
25843 accept the @samp{--thread} option do not need to know what process that
25844 thread belongs to. Therefore, it is not necessary to introduce
25845 neither additional @samp{--process} option, nor an notion of the
25846 current process in the MI interface. The only strictly new feature
25847 that is required is the ability to find how the threads are grouped
25850 To allow the user to discover such grouping, and to support arbitrary
25851 hierarchy of machines/cores/processes, MI introduces the concept of a
25852 @dfn{thread group}. Thread group is a collection of threads and other
25853 thread groups. A thread group always has a string identifier, a type,
25854 and may have additional attributes specific to the type. A new
25855 command, @code{-list-thread-groups}, returns the list of top-level
25856 thread groups, which correspond to processes that @value{GDBN} is
25857 debugging at the moment. By passing an identifier of a thread group
25858 to the @code{-list-thread-groups} command, it is possible to obtain
25859 the members of specific thread group.
25861 To allow the user to easily discover processes, and other objects, he
25862 wishes to debug, a concept of @dfn{available thread group} is
25863 introduced. Available thread group is an thread group that
25864 @value{GDBN} is not debugging, but that can be attached to, using the
25865 @code{-target-attach} command. The list of available top-level thread
25866 groups can be obtained using @samp{-list-thread-groups --available}.
25867 In general, the content of a thread group may be only retrieved only
25868 after attaching to that thread group.
25870 Thread groups are related to inferiors (@pxref{Inferiors and
25871 Programs}). Each inferior corresponds to a thread group of a special
25872 type @samp{process}, and some additional operations are permitted on
25873 such thread groups.
25875 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25876 @node GDB/MI Command Syntax
25877 @section @sc{gdb/mi} Command Syntax
25880 * GDB/MI Input Syntax::
25881 * GDB/MI Output Syntax::
25884 @node GDB/MI Input Syntax
25885 @subsection @sc{gdb/mi} Input Syntax
25887 @cindex input syntax for @sc{gdb/mi}
25888 @cindex @sc{gdb/mi}, input syntax
25890 @item @var{command} @expansion{}
25891 @code{@var{cli-command} | @var{mi-command}}
25893 @item @var{cli-command} @expansion{}
25894 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25895 @var{cli-command} is any existing @value{GDBN} CLI command.
25897 @item @var{mi-command} @expansion{}
25898 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25899 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25901 @item @var{token} @expansion{}
25902 "any sequence of digits"
25904 @item @var{option} @expansion{}
25905 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25907 @item @var{parameter} @expansion{}
25908 @code{@var{non-blank-sequence} | @var{c-string}}
25910 @item @var{operation} @expansion{}
25911 @emph{any of the operations described in this chapter}
25913 @item @var{non-blank-sequence} @expansion{}
25914 @emph{anything, provided it doesn't contain special characters such as
25915 "-", @var{nl}, """ and of course " "}
25917 @item @var{c-string} @expansion{}
25918 @code{""" @var{seven-bit-iso-c-string-content} """}
25920 @item @var{nl} @expansion{}
25929 The CLI commands are still handled by the @sc{mi} interpreter; their
25930 output is described below.
25933 The @code{@var{token}}, when present, is passed back when the command
25937 Some @sc{mi} commands accept optional arguments as part of the parameter
25938 list. Each option is identified by a leading @samp{-} (dash) and may be
25939 followed by an optional argument parameter. Options occur first in the
25940 parameter list and can be delimited from normal parameters using
25941 @samp{--} (this is useful when some parameters begin with a dash).
25948 We want easy access to the existing CLI syntax (for debugging).
25951 We want it to be easy to spot a @sc{mi} operation.
25954 @node GDB/MI Output Syntax
25955 @subsection @sc{gdb/mi} Output Syntax
25957 @cindex output syntax of @sc{gdb/mi}
25958 @cindex @sc{gdb/mi}, output syntax
25959 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25960 followed, optionally, by a single result record. This result record
25961 is for the most recent command. The sequence of output records is
25962 terminated by @samp{(gdb)}.
25964 If an input command was prefixed with a @code{@var{token}} then the
25965 corresponding output for that command will also be prefixed by that same
25969 @item @var{output} @expansion{}
25970 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25972 @item @var{result-record} @expansion{}
25973 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25975 @item @var{out-of-band-record} @expansion{}
25976 @code{@var{async-record} | @var{stream-record}}
25978 @item @var{async-record} @expansion{}
25979 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25981 @item @var{exec-async-output} @expansion{}
25982 @code{[ @var{token} ] "*" @var{async-output}}
25984 @item @var{status-async-output} @expansion{}
25985 @code{[ @var{token} ] "+" @var{async-output}}
25987 @item @var{notify-async-output} @expansion{}
25988 @code{[ @var{token} ] "=" @var{async-output}}
25990 @item @var{async-output} @expansion{}
25991 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25993 @item @var{result-class} @expansion{}
25994 @code{"done" | "running" | "connected" | "error" | "exit"}
25996 @item @var{async-class} @expansion{}
25997 @code{"stopped" | @var{others}} (where @var{others} will be added
25998 depending on the needs---this is still in development).
26000 @item @var{result} @expansion{}
26001 @code{ @var{variable} "=" @var{value}}
26003 @item @var{variable} @expansion{}
26004 @code{ @var{string} }
26006 @item @var{value} @expansion{}
26007 @code{ @var{const} | @var{tuple} | @var{list} }
26009 @item @var{const} @expansion{}
26010 @code{@var{c-string}}
26012 @item @var{tuple} @expansion{}
26013 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26015 @item @var{list} @expansion{}
26016 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26017 @var{result} ( "," @var{result} )* "]" }
26019 @item @var{stream-record} @expansion{}
26020 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26022 @item @var{console-stream-output} @expansion{}
26023 @code{"~" @var{c-string}}
26025 @item @var{target-stream-output} @expansion{}
26026 @code{"@@" @var{c-string}}
26028 @item @var{log-stream-output} @expansion{}
26029 @code{"&" @var{c-string}}
26031 @item @var{nl} @expansion{}
26034 @item @var{token} @expansion{}
26035 @emph{any sequence of digits}.
26043 All output sequences end in a single line containing a period.
26046 The @code{@var{token}} is from the corresponding request. Note that
26047 for all async output, while the token is allowed by the grammar and
26048 may be output by future versions of @value{GDBN} for select async
26049 output messages, it is generally omitted. Frontends should treat
26050 all async output as reporting general changes in the state of the
26051 target and there should be no need to associate async output to any
26055 @cindex status output in @sc{gdb/mi}
26056 @var{status-async-output} contains on-going status information about the
26057 progress of a slow operation. It can be discarded. All status output is
26058 prefixed by @samp{+}.
26061 @cindex async output in @sc{gdb/mi}
26062 @var{exec-async-output} contains asynchronous state change on the target
26063 (stopped, started, disappeared). All async output is prefixed by
26067 @cindex notify output in @sc{gdb/mi}
26068 @var{notify-async-output} contains supplementary information that the
26069 client should handle (e.g., a new breakpoint information). All notify
26070 output is prefixed by @samp{=}.
26073 @cindex console output in @sc{gdb/mi}
26074 @var{console-stream-output} is output that should be displayed as is in the
26075 console. It is the textual response to a CLI command. All the console
26076 output is prefixed by @samp{~}.
26079 @cindex target output in @sc{gdb/mi}
26080 @var{target-stream-output} is the output produced by the target program.
26081 All the target output is prefixed by @samp{@@}.
26084 @cindex log output in @sc{gdb/mi}
26085 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26086 instance messages that should be displayed as part of an error log. All
26087 the log output is prefixed by @samp{&}.
26090 @cindex list output in @sc{gdb/mi}
26091 New @sc{gdb/mi} commands should only output @var{lists} containing
26097 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26098 details about the various output records.
26100 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26101 @node GDB/MI Compatibility with CLI
26102 @section @sc{gdb/mi} Compatibility with CLI
26104 @cindex compatibility, @sc{gdb/mi} and CLI
26105 @cindex @sc{gdb/mi}, compatibility with CLI
26107 For the developers convenience CLI commands can be entered directly,
26108 but there may be some unexpected behaviour. For example, commands
26109 that query the user will behave as if the user replied yes, breakpoint
26110 command lists are not executed and some CLI commands, such as
26111 @code{if}, @code{when} and @code{define}, prompt for further input with
26112 @samp{>}, which is not valid MI output.
26114 This feature may be removed at some stage in the future and it is
26115 recommended that front ends use the @code{-interpreter-exec} command
26116 (@pxref{-interpreter-exec}).
26118 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26119 @node GDB/MI Development and Front Ends
26120 @section @sc{gdb/mi} Development and Front Ends
26121 @cindex @sc{gdb/mi} development
26123 The application which takes the MI output and presents the state of the
26124 program being debugged to the user is called a @dfn{front end}.
26126 Although @sc{gdb/mi} is still incomplete, it is currently being used
26127 by a variety of front ends to @value{GDBN}. This makes it difficult
26128 to introduce new functionality without breaking existing usage. This
26129 section tries to minimize the problems by describing how the protocol
26132 Some changes in MI need not break a carefully designed front end, and
26133 for these the MI version will remain unchanged. The following is a
26134 list of changes that may occur within one level, so front ends should
26135 parse MI output in a way that can handle them:
26139 New MI commands may be added.
26142 New fields may be added to the output of any MI command.
26145 The range of values for fields with specified values, e.g.,
26146 @code{in_scope} (@pxref{-var-update}) may be extended.
26148 @c The format of field's content e.g type prefix, may change so parse it
26149 @c at your own risk. Yes, in general?
26151 @c The order of fields may change? Shouldn't really matter but it might
26152 @c resolve inconsistencies.
26155 If the changes are likely to break front ends, the MI version level
26156 will be increased by one. This will allow the front end to parse the
26157 output according to the MI version. Apart from mi0, new versions of
26158 @value{GDBN} will not support old versions of MI and it will be the
26159 responsibility of the front end to work with the new one.
26161 @c Starting with mi3, add a new command -mi-version that prints the MI
26164 The best way to avoid unexpected changes in MI that might break your front
26165 end is to make your project known to @value{GDBN} developers and
26166 follow development on @email{gdb@@sourceware.org} and
26167 @email{gdb-patches@@sourceware.org}.
26168 @cindex mailing lists
26170 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26171 @node GDB/MI Output Records
26172 @section @sc{gdb/mi} Output Records
26175 * GDB/MI Result Records::
26176 * GDB/MI Stream Records::
26177 * GDB/MI Async Records::
26178 * GDB/MI Frame Information::
26179 * GDB/MI Thread Information::
26180 * GDB/MI Ada Exception Information::
26183 @node GDB/MI Result Records
26184 @subsection @sc{gdb/mi} Result Records
26186 @cindex result records in @sc{gdb/mi}
26187 @cindex @sc{gdb/mi}, result records
26188 In addition to a number of out-of-band notifications, the response to a
26189 @sc{gdb/mi} command includes one of the following result indications:
26193 @item "^done" [ "," @var{results} ]
26194 The synchronous operation was successful, @code{@var{results}} are the return
26199 This result record is equivalent to @samp{^done}. Historically, it
26200 was output instead of @samp{^done} if the command has resumed the
26201 target. This behaviour is maintained for backward compatibility, but
26202 all frontends should treat @samp{^done} and @samp{^running}
26203 identically and rely on the @samp{*running} output record to determine
26204 which threads are resumed.
26208 @value{GDBN} has connected to a remote target.
26210 @item "^error" "," @var{c-string}
26212 The operation failed. The @code{@var{c-string}} contains the corresponding
26217 @value{GDBN} has terminated.
26221 @node GDB/MI Stream Records
26222 @subsection @sc{gdb/mi} Stream Records
26224 @cindex @sc{gdb/mi}, stream records
26225 @cindex stream records in @sc{gdb/mi}
26226 @value{GDBN} internally maintains a number of output streams: the console, the
26227 target, and the log. The output intended for each of these streams is
26228 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26230 Each stream record begins with a unique @dfn{prefix character} which
26231 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26232 Syntax}). In addition to the prefix, each stream record contains a
26233 @code{@var{string-output}}. This is either raw text (with an implicit new
26234 line) or a quoted C string (which does not contain an implicit newline).
26237 @item "~" @var{string-output}
26238 The console output stream contains text that should be displayed in the
26239 CLI console window. It contains the textual responses to CLI commands.
26241 @item "@@" @var{string-output}
26242 The target output stream contains any textual output from the running
26243 target. This is only present when GDB's event loop is truly
26244 asynchronous, which is currently only the case for remote targets.
26246 @item "&" @var{string-output}
26247 The log stream contains debugging messages being produced by @value{GDBN}'s
26251 @node GDB/MI Async Records
26252 @subsection @sc{gdb/mi} Async Records
26254 @cindex async records in @sc{gdb/mi}
26255 @cindex @sc{gdb/mi}, async records
26256 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26257 additional changes that have occurred. Those changes can either be a
26258 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26259 target activity (e.g., target stopped).
26261 The following is the list of possible async records:
26265 @item *running,thread-id="@var{thread}"
26266 The target is now running. The @var{thread} field tells which
26267 specific thread is now running, and can be @samp{all} if all threads
26268 are running. The frontend should assume that no interaction with a
26269 running thread is possible after this notification is produced.
26270 The frontend should not assume that this notification is output
26271 only once for any command. @value{GDBN} may emit this notification
26272 several times, either for different threads, because it cannot resume
26273 all threads together, or even for a single thread, if the thread must
26274 be stepped though some code before letting it run freely.
26276 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26277 The target has stopped. The @var{reason} field can have one of the
26281 @item breakpoint-hit
26282 A breakpoint was reached.
26283 @item watchpoint-trigger
26284 A watchpoint was triggered.
26285 @item read-watchpoint-trigger
26286 A read watchpoint was triggered.
26287 @item access-watchpoint-trigger
26288 An access watchpoint was triggered.
26289 @item function-finished
26290 An -exec-finish or similar CLI command was accomplished.
26291 @item location-reached
26292 An -exec-until or similar CLI command was accomplished.
26293 @item watchpoint-scope
26294 A watchpoint has gone out of scope.
26295 @item end-stepping-range
26296 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26297 similar CLI command was accomplished.
26298 @item exited-signalled
26299 The inferior exited because of a signal.
26301 The inferior exited.
26302 @item exited-normally
26303 The inferior exited normally.
26304 @item signal-received
26305 A signal was received by the inferior.
26307 The inferior has stopped due to a library being loaded or unloaded.
26308 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26309 set or when a @code{catch load} or @code{catch unload} catchpoint is
26310 in use (@pxref{Set Catchpoints}).
26312 The inferior has forked. This is reported when @code{catch fork}
26313 (@pxref{Set Catchpoints}) has been used.
26315 The inferior has vforked. This is reported in when @code{catch vfork}
26316 (@pxref{Set Catchpoints}) has been used.
26317 @item syscall-entry
26318 The inferior entered a system call. This is reported when @code{catch
26319 syscall} (@pxref{Set Catchpoints}) has been used.
26320 @item syscall-entry
26321 The inferior returned from a system call. This is reported when
26322 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26324 The inferior called @code{exec}. This is reported when @code{catch exec}
26325 (@pxref{Set Catchpoints}) has been used.
26328 The @var{id} field identifies the thread that directly caused the stop
26329 -- for example by hitting a breakpoint. Depending on whether all-stop
26330 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26331 stop all threads, or only the thread that directly triggered the stop.
26332 If all threads are stopped, the @var{stopped} field will have the
26333 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26334 field will be a list of thread identifiers. Presently, this list will
26335 always include a single thread, but frontend should be prepared to see
26336 several threads in the list. The @var{core} field reports the
26337 processor core on which the stop event has happened. This field may be absent
26338 if such information is not available.
26340 @item =thread-group-added,id="@var{id}"
26341 @itemx =thread-group-removed,id="@var{id}"
26342 A thread group was either added or removed. The @var{id} field
26343 contains the @value{GDBN} identifier of the thread group. When a thread
26344 group is added, it generally might not be associated with a running
26345 process. When a thread group is removed, its id becomes invalid and
26346 cannot be used in any way.
26348 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26349 A thread group became associated with a running program,
26350 either because the program was just started or the thread group
26351 was attached to a program. The @var{id} field contains the
26352 @value{GDBN} identifier of the thread group. The @var{pid} field
26353 contains process identifier, specific to the operating system.
26355 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26356 A thread group is no longer associated with a running program,
26357 either because the program has exited, or because it was detached
26358 from. The @var{id} field contains the @value{GDBN} identifier of the
26359 thread group. @var{code} is the exit code of the inferior; it exists
26360 only when the inferior exited with some code.
26362 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26363 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26364 A thread either was created, or has exited. The @var{id} field
26365 contains the @value{GDBN} identifier of the thread. The @var{gid}
26366 field identifies the thread group this thread belongs to.
26368 @item =thread-selected,id="@var{id}"
26369 Informs that the selected thread was changed as result of the last
26370 command. This notification is not emitted as result of @code{-thread-select}
26371 command but is emitted whenever an MI command that is not documented
26372 to change the selected thread actually changes it. In particular,
26373 invoking, directly or indirectly (via user-defined command), the CLI
26374 @code{thread} command, will generate this notification.
26376 We suggest that in response to this notification, front ends
26377 highlight the selected thread and cause subsequent commands to apply to
26380 @item =library-loaded,...
26381 Reports that a new library file was loaded by the program. This
26382 notification has 4 fields---@var{id}, @var{target-name},
26383 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26384 opaque identifier of the library. For remote debugging case,
26385 @var{target-name} and @var{host-name} fields give the name of the
26386 library file on the target, and on the host respectively. For native
26387 debugging, both those fields have the same value. The
26388 @var{symbols-loaded} field is emitted only for backward compatibility
26389 and should not be relied on to convey any useful information. The
26390 @var{thread-group} field, if present, specifies the id of the thread
26391 group in whose context the library was loaded. If the field is
26392 absent, it means the library was loaded in the context of all present
26395 @item =library-unloaded,...
26396 Reports that a library was unloaded by the program. This notification
26397 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26398 the same meaning as for the @code{=library-loaded} notification.
26399 The @var{thread-group} field, if present, specifies the id of the
26400 thread group in whose context the library was unloaded. If the field is
26401 absent, it means the library was unloaded in the context of all present
26404 @item =breakpoint-created,bkpt=@{...@}
26405 @itemx =breakpoint-modified,bkpt=@{...@}
26406 @itemx =breakpoint-deleted,bkpt=@{...@}
26407 Reports that a breakpoint was created, modified, or deleted,
26408 respectively. Only user-visible breakpoints are reported to the MI
26411 The @var{bkpt} argument is of the same form as returned by the various
26412 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26414 Note that if a breakpoint is emitted in the result record of a
26415 command, then it will not also be emitted in an async record.
26419 @node GDB/MI Frame Information
26420 @subsection @sc{gdb/mi} Frame Information
26422 Response from many MI commands includes an information about stack
26423 frame. This information is a tuple that may have the following
26428 The level of the stack frame. The innermost frame has the level of
26429 zero. This field is always present.
26432 The name of the function corresponding to the frame. This field may
26433 be absent if @value{GDBN} is unable to determine the function name.
26436 The code address for the frame. This field is always present.
26439 The name of the source files that correspond to the frame's code
26440 address. This field may be absent.
26443 The source line corresponding to the frames' code address. This field
26447 The name of the binary file (either executable or shared library) the
26448 corresponds to the frame's code address. This field may be absent.
26452 @node GDB/MI Thread Information
26453 @subsection @sc{gdb/mi} Thread Information
26455 Whenever @value{GDBN} has to report an information about a thread, it
26456 uses a tuple with the following fields:
26460 The numeric id assigned to the thread by @value{GDBN}. This field is
26464 Target-specific string identifying the thread. This field is always present.
26467 Additional information about the thread provided by the target.
26468 It is supposed to be human-readable and not interpreted by the
26469 frontend. This field is optional.
26472 Either @samp{stopped} or @samp{running}, depending on whether the
26473 thread is presently running. This field is always present.
26476 The value of this field is an integer number of the processor core the
26477 thread was last seen on. This field is optional.
26480 @node GDB/MI Ada Exception Information
26481 @subsection @sc{gdb/mi} Ada Exception Information
26483 Whenever a @code{*stopped} record is emitted because the program
26484 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26485 @value{GDBN} provides the name of the exception that was raised via
26486 the @code{exception-name} field.
26488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26489 @node GDB/MI Simple Examples
26490 @section Simple Examples of @sc{gdb/mi} Interaction
26491 @cindex @sc{gdb/mi}, simple examples
26493 This subsection presents several simple examples of interaction using
26494 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26495 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26496 the output received from @sc{gdb/mi}.
26498 Note the line breaks shown in the examples are here only for
26499 readability, they don't appear in the real output.
26501 @subheading Setting a Breakpoint
26503 Setting a breakpoint generates synchronous output which contains detailed
26504 information of the breakpoint.
26507 -> -break-insert main
26508 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26509 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26510 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26514 @subheading Program Execution
26516 Program execution generates asynchronous records and MI gives the
26517 reason that execution stopped.
26523 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26524 frame=@{addr="0x08048564",func="main",
26525 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26526 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26531 <- *stopped,reason="exited-normally"
26535 @subheading Quitting @value{GDBN}
26537 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26545 Please note that @samp{^exit} is printed immediately, but it might
26546 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26547 performs necessary cleanups, including killing programs being debugged
26548 or disconnecting from debug hardware, so the frontend should wait till
26549 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26550 fails to exit in reasonable time.
26552 @subheading A Bad Command
26554 Here's what happens if you pass a non-existent command:
26558 <- ^error,msg="Undefined MI command: rubbish"
26563 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26564 @node GDB/MI Command Description Format
26565 @section @sc{gdb/mi} Command Description Format
26567 The remaining sections describe blocks of commands. Each block of
26568 commands is laid out in a fashion similar to this section.
26570 @subheading Motivation
26572 The motivation for this collection of commands.
26574 @subheading Introduction
26576 A brief introduction to this collection of commands as a whole.
26578 @subheading Commands
26580 For each command in the block, the following is described:
26582 @subsubheading Synopsis
26585 -command @var{args}@dots{}
26588 @subsubheading Result
26590 @subsubheading @value{GDBN} Command
26592 The corresponding @value{GDBN} CLI command(s), if any.
26594 @subsubheading Example
26596 Example(s) formatted for readability. Some of the described commands have
26597 not been implemented yet and these are labeled N.A.@: (not available).
26600 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26601 @node GDB/MI Breakpoint Commands
26602 @section @sc{gdb/mi} Breakpoint Commands
26604 @cindex breakpoint commands for @sc{gdb/mi}
26605 @cindex @sc{gdb/mi}, breakpoint commands
26606 This section documents @sc{gdb/mi} commands for manipulating
26609 @subheading The @code{-break-after} Command
26610 @findex -break-after
26612 @subsubheading Synopsis
26615 -break-after @var{number} @var{count}
26618 The breakpoint number @var{number} is not in effect until it has been
26619 hit @var{count} times. To see how this is reflected in the output of
26620 the @samp{-break-list} command, see the description of the
26621 @samp{-break-list} command below.
26623 @subsubheading @value{GDBN} Command
26625 The corresponding @value{GDBN} command is @samp{ignore}.
26627 @subsubheading Example
26632 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26633 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26634 fullname="/home/foo/hello.c",line="5",times="0"@}
26641 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26642 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26643 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26644 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26645 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26646 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26647 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26648 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26649 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26650 line="5",times="0",ignore="3"@}]@}
26655 @subheading The @code{-break-catch} Command
26656 @findex -break-catch
26659 @subheading The @code{-break-commands} Command
26660 @findex -break-commands
26662 @subsubheading Synopsis
26665 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26668 Specifies the CLI commands that should be executed when breakpoint
26669 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26670 are the commands. If no command is specified, any previously-set
26671 commands are cleared. @xref{Break Commands}. Typical use of this
26672 functionality is tracing a program, that is, printing of values of
26673 some variables whenever breakpoint is hit and then continuing.
26675 @subsubheading @value{GDBN} Command
26677 The corresponding @value{GDBN} command is @samp{commands}.
26679 @subsubheading Example
26684 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26685 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26686 fullname="/home/foo/hello.c",line="5",times="0"@}
26688 -break-commands 1 "print v" "continue"
26693 @subheading The @code{-break-condition} Command
26694 @findex -break-condition
26696 @subsubheading Synopsis
26699 -break-condition @var{number} @var{expr}
26702 Breakpoint @var{number} will stop the program only if the condition in
26703 @var{expr} is true. The condition becomes part of the
26704 @samp{-break-list} output (see the description of the @samp{-break-list}
26707 @subsubheading @value{GDBN} Command
26709 The corresponding @value{GDBN} command is @samp{condition}.
26711 @subsubheading Example
26715 -break-condition 1 1
26719 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26720 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26721 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26722 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26723 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26724 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26725 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26726 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26727 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26728 line="5",cond="1",times="0",ignore="3"@}]@}
26732 @subheading The @code{-break-delete} Command
26733 @findex -break-delete
26735 @subsubheading Synopsis
26738 -break-delete ( @var{breakpoint} )+
26741 Delete the breakpoint(s) whose number(s) are specified in the argument
26742 list. This is obviously reflected in the breakpoint list.
26744 @subsubheading @value{GDBN} Command
26746 The corresponding @value{GDBN} command is @samp{delete}.
26748 @subsubheading Example
26756 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26757 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26758 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26759 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26760 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26761 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26762 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26767 @subheading The @code{-break-disable} Command
26768 @findex -break-disable
26770 @subsubheading Synopsis
26773 -break-disable ( @var{breakpoint} )+
26776 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26777 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26779 @subsubheading @value{GDBN} Command
26781 The corresponding @value{GDBN} command is @samp{disable}.
26783 @subsubheading Example
26791 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26792 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26793 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26794 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26795 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26796 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26797 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26798 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26799 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26800 line="5",times="0"@}]@}
26804 @subheading The @code{-break-enable} Command
26805 @findex -break-enable
26807 @subsubheading Synopsis
26810 -break-enable ( @var{breakpoint} )+
26813 Enable (previously disabled) @var{breakpoint}(s).
26815 @subsubheading @value{GDBN} Command
26817 The corresponding @value{GDBN} command is @samp{enable}.
26819 @subsubheading Example
26827 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26828 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26829 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26830 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26831 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26832 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26833 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26834 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26835 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26836 line="5",times="0"@}]@}
26840 @subheading The @code{-break-info} Command
26841 @findex -break-info
26843 @subsubheading Synopsis
26846 -break-info @var{breakpoint}
26850 Get information about a single breakpoint.
26852 @subsubheading @value{GDBN} Command
26854 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26856 @subsubheading Example
26859 @subheading The @code{-break-insert} Command
26860 @findex -break-insert
26862 @subsubheading Synopsis
26865 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26866 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26867 [ -p @var{thread} ] [ @var{location} ]
26871 If specified, @var{location}, can be one of:
26878 @item filename:linenum
26879 @item filename:function
26883 The possible optional parameters of this command are:
26887 Insert a temporary breakpoint.
26889 Insert a hardware breakpoint.
26890 @item -c @var{condition}
26891 Make the breakpoint conditional on @var{condition}.
26892 @item -i @var{ignore-count}
26893 Initialize the @var{ignore-count}.
26895 If @var{location} cannot be parsed (for example if it
26896 refers to unknown files or functions), create a pending
26897 breakpoint. Without this flag, @value{GDBN} will report
26898 an error, and won't create a breakpoint, if @var{location}
26901 Create a disabled breakpoint.
26903 Create a tracepoint. @xref{Tracepoints}. When this parameter
26904 is used together with @samp{-h}, a fast tracepoint is created.
26907 @subsubheading Result
26909 The result is in the form:
26912 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26913 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26914 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26915 times="@var{times}"@}
26919 where @var{number} is the @value{GDBN} number for this breakpoint,
26920 @var{funcname} is the name of the function where the breakpoint was
26921 inserted, @var{filename} is the name of the source file which contains
26922 this function, @var{lineno} is the source line number within that file
26923 and @var{times} the number of times that the breakpoint has been hit
26924 (always 0 for -break-insert but may be greater for -break-info or -break-list
26925 which use the same output).
26927 Note: this format is open to change.
26928 @c An out-of-band breakpoint instead of part of the result?
26930 @subsubheading @value{GDBN} Command
26932 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26933 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26935 @subsubheading Example
26940 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26941 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26943 -break-insert -t foo
26944 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26945 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26948 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26949 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26950 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26951 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26952 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26953 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26954 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26955 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26956 addr="0x0001072c", func="main",file="recursive2.c",
26957 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26958 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26959 addr="0x00010774",func="foo",file="recursive2.c",
26960 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26962 -break-insert -r foo.*
26963 ~int foo(int, int);
26964 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26965 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26969 @subheading The @code{-break-list} Command
26970 @findex -break-list
26972 @subsubheading Synopsis
26978 Displays the list of inserted breakpoints, showing the following fields:
26982 number of the breakpoint
26984 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26986 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26989 is the breakpoint enabled or no: @samp{y} or @samp{n}
26991 memory location at which the breakpoint is set
26993 logical location of the breakpoint, expressed by function name, file
26996 number of times the breakpoint has been hit
26999 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27000 @code{body} field is an empty list.
27002 @subsubheading @value{GDBN} Command
27004 The corresponding @value{GDBN} command is @samp{info break}.
27006 @subsubheading Example
27011 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27012 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27013 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27014 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27015 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27016 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27017 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27018 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27019 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27020 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27021 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27022 line="13",times="0"@}]@}
27026 Here's an example of the result when there are no breakpoints:
27031 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27032 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27033 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27034 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27035 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27036 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27037 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27042 @subheading The @code{-break-passcount} Command
27043 @findex -break-passcount
27045 @subsubheading Synopsis
27048 -break-passcount @var{tracepoint-number} @var{passcount}
27051 Set the passcount for tracepoint @var{tracepoint-number} to
27052 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27053 is not a tracepoint, error is emitted. This corresponds to CLI
27054 command @samp{passcount}.
27056 @subheading The @code{-break-watch} Command
27057 @findex -break-watch
27059 @subsubheading Synopsis
27062 -break-watch [ -a | -r ]
27065 Create a watchpoint. With the @samp{-a} option it will create an
27066 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27067 read from or on a write to the memory location. With the @samp{-r}
27068 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27069 trigger only when the memory location is accessed for reading. Without
27070 either of the options, the watchpoint created is a regular watchpoint,
27071 i.e., it will trigger when the memory location is accessed for writing.
27072 @xref{Set Watchpoints, , Setting Watchpoints}.
27074 Note that @samp{-break-list} will report a single list of watchpoints and
27075 breakpoints inserted.
27077 @subsubheading @value{GDBN} Command
27079 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27082 @subsubheading Example
27084 Setting a watchpoint on a variable in the @code{main} function:
27089 ^done,wpt=@{number="2",exp="x"@}
27094 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27095 value=@{old="-268439212",new="55"@},
27096 frame=@{func="main",args=[],file="recursive2.c",
27097 fullname="/home/foo/bar/recursive2.c",line="5"@}
27101 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27102 the program execution twice: first for the variable changing value, then
27103 for the watchpoint going out of scope.
27108 ^done,wpt=@{number="5",exp="C"@}
27113 *stopped,reason="watchpoint-trigger",
27114 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27115 frame=@{func="callee4",args=[],
27116 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27117 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27122 *stopped,reason="watchpoint-scope",wpnum="5",
27123 frame=@{func="callee3",args=[@{name="strarg",
27124 value="0x11940 \"A string argument.\""@}],
27125 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27126 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27130 Listing breakpoints and watchpoints, at different points in the program
27131 execution. Note that once the watchpoint goes out of scope, it is
27137 ^done,wpt=@{number="2",exp="C"@}
27140 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27141 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27142 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27143 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27144 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27145 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27146 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27147 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27148 addr="0x00010734",func="callee4",
27149 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27150 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27151 bkpt=@{number="2",type="watchpoint",disp="keep",
27152 enabled="y",addr="",what="C",times="0"@}]@}
27157 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27158 value=@{old="-276895068",new="3"@},
27159 frame=@{func="callee4",args=[],
27160 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27161 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27164 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27165 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27166 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27167 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27168 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27169 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27170 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27171 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27172 addr="0x00010734",func="callee4",
27173 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27174 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27175 bkpt=@{number="2",type="watchpoint",disp="keep",
27176 enabled="y",addr="",what="C",times="-5"@}]@}
27180 ^done,reason="watchpoint-scope",wpnum="2",
27181 frame=@{func="callee3",args=[@{name="strarg",
27182 value="0x11940 \"A string argument.\""@}],
27183 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27184 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27187 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27188 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27189 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27190 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27191 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27192 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27193 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27194 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27195 addr="0x00010734",func="callee4",
27196 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27197 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27202 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27203 @node GDB/MI Program Context
27204 @section @sc{gdb/mi} Program Context
27206 @subheading The @code{-exec-arguments} Command
27207 @findex -exec-arguments
27210 @subsubheading Synopsis
27213 -exec-arguments @var{args}
27216 Set the inferior program arguments, to be used in the next
27219 @subsubheading @value{GDBN} Command
27221 The corresponding @value{GDBN} command is @samp{set args}.
27223 @subsubheading Example
27227 -exec-arguments -v word
27234 @subheading The @code{-exec-show-arguments} Command
27235 @findex -exec-show-arguments
27237 @subsubheading Synopsis
27240 -exec-show-arguments
27243 Print the arguments of the program.
27245 @subsubheading @value{GDBN} Command
27247 The corresponding @value{GDBN} command is @samp{show args}.
27249 @subsubheading Example
27254 @subheading The @code{-environment-cd} Command
27255 @findex -environment-cd
27257 @subsubheading Synopsis
27260 -environment-cd @var{pathdir}
27263 Set @value{GDBN}'s working directory.
27265 @subsubheading @value{GDBN} Command
27267 The corresponding @value{GDBN} command is @samp{cd}.
27269 @subsubheading Example
27273 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27279 @subheading The @code{-environment-directory} Command
27280 @findex -environment-directory
27282 @subsubheading Synopsis
27285 -environment-directory [ -r ] [ @var{pathdir} ]+
27288 Add directories @var{pathdir} to beginning of search path for source files.
27289 If the @samp{-r} option is used, the search path is reset to the default
27290 search path. If directories @var{pathdir} are supplied in addition to the
27291 @samp{-r} option, the search path is first reset and then addition
27293 Multiple directories may be specified, separated by blanks. Specifying
27294 multiple directories in a single command
27295 results in the directories added to the beginning of the
27296 search path in the same order they were presented in the command.
27297 If blanks are needed as
27298 part of a directory name, double-quotes should be used around
27299 the name. In the command output, the path will show up separated
27300 by the system directory-separator character. The directory-separator
27301 character must not be used
27302 in any directory name.
27303 If no directories are specified, the current search path is displayed.
27305 @subsubheading @value{GDBN} Command
27307 The corresponding @value{GDBN} command is @samp{dir}.
27309 @subsubheading Example
27313 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27314 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27316 -environment-directory ""
27317 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27319 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27320 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27322 -environment-directory -r
27323 ^done,source-path="$cdir:$cwd"
27328 @subheading The @code{-environment-path} Command
27329 @findex -environment-path
27331 @subsubheading Synopsis
27334 -environment-path [ -r ] [ @var{pathdir} ]+
27337 Add directories @var{pathdir} to beginning of search path for object files.
27338 If the @samp{-r} option is used, the search path is reset to the original
27339 search path that existed at gdb start-up. If directories @var{pathdir} are
27340 supplied in addition to the
27341 @samp{-r} option, the search path is first reset and then addition
27343 Multiple directories may be specified, separated by blanks. Specifying
27344 multiple directories in a single command
27345 results in the directories added to the beginning of the
27346 search path in the same order they were presented in the command.
27347 If blanks are needed as
27348 part of a directory name, double-quotes should be used around
27349 the name. In the command output, the path will show up separated
27350 by the system directory-separator character. The directory-separator
27351 character must not be used
27352 in any directory name.
27353 If no directories are specified, the current path is displayed.
27356 @subsubheading @value{GDBN} Command
27358 The corresponding @value{GDBN} command is @samp{path}.
27360 @subsubheading Example
27365 ^done,path="/usr/bin"
27367 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27368 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27370 -environment-path -r /usr/local/bin
27371 ^done,path="/usr/local/bin:/usr/bin"
27376 @subheading The @code{-environment-pwd} Command
27377 @findex -environment-pwd
27379 @subsubheading Synopsis
27385 Show the current working directory.
27387 @subsubheading @value{GDBN} Command
27389 The corresponding @value{GDBN} command is @samp{pwd}.
27391 @subsubheading Example
27396 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27400 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27401 @node GDB/MI Thread Commands
27402 @section @sc{gdb/mi} Thread Commands
27405 @subheading The @code{-thread-info} Command
27406 @findex -thread-info
27408 @subsubheading Synopsis
27411 -thread-info [ @var{thread-id} ]
27414 Reports information about either a specific thread, if
27415 the @var{thread-id} parameter is present, or about all
27416 threads. When printing information about all threads,
27417 also reports the current thread.
27419 @subsubheading @value{GDBN} Command
27421 The @samp{info thread} command prints the same information
27424 @subsubheading Result
27426 The result is a list of threads. The following attributes are
27427 defined for a given thread:
27431 This field exists only for the current thread. It has the value @samp{*}.
27434 The identifier that @value{GDBN} uses to refer to the thread.
27437 The identifier that the target uses to refer to the thread.
27440 Extra information about the thread, in a target-specific format. This
27444 The name of the thread. If the user specified a name using the
27445 @code{thread name} command, then this name is given. Otherwise, if
27446 @value{GDBN} can extract the thread name from the target, then that
27447 name is given. If @value{GDBN} cannot find the thread name, then this
27451 The stack frame currently executing in the thread.
27454 The thread's state. The @samp{state} field may have the following
27459 The thread is stopped. Frame information is available for stopped
27463 The thread is running. There's no frame information for running
27469 If @value{GDBN} can find the CPU core on which this thread is running,
27470 then this field is the core identifier. This field is optional.
27474 @subsubheading Example
27479 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27480 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27481 args=[]@},state="running"@},
27482 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27483 frame=@{level="0",addr="0x0804891f",func="foo",
27484 args=[@{name="i",value="10"@}],
27485 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27486 state="running"@}],
27487 current-thread-id="1"
27491 @subheading The @code{-thread-list-ids} Command
27492 @findex -thread-list-ids
27494 @subsubheading Synopsis
27500 Produces a list of the currently known @value{GDBN} thread ids. At the
27501 end of the list it also prints the total number of such threads.
27503 This command is retained for historical reasons, the
27504 @code{-thread-info} command should be used instead.
27506 @subsubheading @value{GDBN} Command
27508 Part of @samp{info threads} supplies the same information.
27510 @subsubheading Example
27515 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27516 current-thread-id="1",number-of-threads="3"
27521 @subheading The @code{-thread-select} Command
27522 @findex -thread-select
27524 @subsubheading Synopsis
27527 -thread-select @var{threadnum}
27530 Make @var{threadnum} the current thread. It prints the number of the new
27531 current thread, and the topmost frame for that thread.
27533 This command is deprecated in favor of explicitly using the
27534 @samp{--thread} option to each command.
27536 @subsubheading @value{GDBN} Command
27538 The corresponding @value{GDBN} command is @samp{thread}.
27540 @subsubheading Example
27547 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27548 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27552 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27553 number-of-threads="3"
27556 ^done,new-thread-id="3",
27557 frame=@{level="0",func="vprintf",
27558 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27559 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27563 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27564 @node GDB/MI Ada Tasking Commands
27565 @section @sc{gdb/mi} Ada Tasking Commands
27567 @subheading The @code{-ada-task-info} Command
27568 @findex -ada-task-info
27570 @subsubheading Synopsis
27573 -ada-task-info [ @var{task-id} ]
27576 Reports information about either a specific Ada task, if the
27577 @var{task-id} parameter is present, or about all Ada tasks.
27579 @subsubheading @value{GDBN} Command
27581 The @samp{info tasks} command prints the same information
27582 about all Ada tasks (@pxref{Ada Tasks}).
27584 @subsubheading Result
27586 The result is a table of Ada tasks. The following columns are
27587 defined for each Ada task:
27591 This field exists only for the current thread. It has the value @samp{*}.
27594 The identifier that @value{GDBN} uses to refer to the Ada task.
27597 The identifier that the target uses to refer to the Ada task.
27600 The identifier of the thread corresponding to the Ada task.
27602 This field should always exist, as Ada tasks are always implemented
27603 on top of a thread. But if @value{GDBN} cannot find this corresponding
27604 thread for any reason, the field is omitted.
27607 This field exists only when the task was created by another task.
27608 In this case, it provides the ID of the parent task.
27611 The base priority of the task.
27614 The current state of the task. For a detailed description of the
27615 possible states, see @ref{Ada Tasks}.
27618 The name of the task.
27622 @subsubheading Example
27626 ^done,tasks=@{nr_rows="3",nr_cols="8",
27627 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27628 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27629 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27630 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27631 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27632 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27633 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27634 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27635 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27636 state="Child Termination Wait",name="main_task"@}]@}
27640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27641 @node GDB/MI Program Execution
27642 @section @sc{gdb/mi} Program Execution
27644 These are the asynchronous commands which generate the out-of-band
27645 record @samp{*stopped}. Currently @value{GDBN} only really executes
27646 asynchronously with remote targets and this interaction is mimicked in
27649 @subheading The @code{-exec-continue} Command
27650 @findex -exec-continue
27652 @subsubheading Synopsis
27655 -exec-continue [--reverse] [--all|--thread-group N]
27658 Resumes the execution of the inferior program, which will continue
27659 to execute until it reaches a debugger stop event. If the
27660 @samp{--reverse} option is specified, execution resumes in reverse until
27661 it reaches a stop event. Stop events may include
27664 breakpoints or watchpoints
27666 signals or exceptions
27668 the end of the process (or its beginning under @samp{--reverse})
27670 the end or beginning of a replay log if one is being used.
27672 In all-stop mode (@pxref{All-Stop
27673 Mode}), may resume only one thread, or all threads, depending on the
27674 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27675 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27676 ignored in all-stop mode. If the @samp{--thread-group} options is
27677 specified, then all threads in that thread group are resumed.
27679 @subsubheading @value{GDBN} Command
27681 The corresponding @value{GDBN} corresponding is @samp{continue}.
27683 @subsubheading Example
27690 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27691 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27697 @subheading The @code{-exec-finish} Command
27698 @findex -exec-finish
27700 @subsubheading Synopsis
27703 -exec-finish [--reverse]
27706 Resumes the execution of the inferior program until the current
27707 function is exited. Displays the results returned by the function.
27708 If the @samp{--reverse} option is specified, resumes the reverse
27709 execution of the inferior program until the point where current
27710 function was called.
27712 @subsubheading @value{GDBN} Command
27714 The corresponding @value{GDBN} command is @samp{finish}.
27716 @subsubheading Example
27718 Function returning @code{void}.
27725 *stopped,reason="function-finished",frame=@{func="main",args=[],
27726 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27730 Function returning other than @code{void}. The name of the internal
27731 @value{GDBN} variable storing the result is printed, together with the
27738 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27739 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27740 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27741 gdb-result-var="$1",return-value="0"
27746 @subheading The @code{-exec-interrupt} Command
27747 @findex -exec-interrupt
27749 @subsubheading Synopsis
27752 -exec-interrupt [--all|--thread-group N]
27755 Interrupts the background execution of the target. Note how the token
27756 associated with the stop message is the one for the execution command
27757 that has been interrupted. The token for the interrupt itself only
27758 appears in the @samp{^done} output. If the user is trying to
27759 interrupt a non-running program, an error message will be printed.
27761 Note that when asynchronous execution is enabled, this command is
27762 asynchronous just like other execution commands. That is, first the
27763 @samp{^done} response will be printed, and the target stop will be
27764 reported after that using the @samp{*stopped} notification.
27766 In non-stop mode, only the context thread is interrupted by default.
27767 All threads (in all inferiors) will be interrupted if the
27768 @samp{--all} option is specified. If the @samp{--thread-group}
27769 option is specified, all threads in that group will be interrupted.
27771 @subsubheading @value{GDBN} Command
27773 The corresponding @value{GDBN} command is @samp{interrupt}.
27775 @subsubheading Example
27786 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27787 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27788 fullname="/home/foo/bar/try.c",line="13"@}
27793 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27797 @subheading The @code{-exec-jump} Command
27800 @subsubheading Synopsis
27803 -exec-jump @var{location}
27806 Resumes execution of the inferior program at the location specified by
27807 parameter. @xref{Specify Location}, for a description of the
27808 different forms of @var{location}.
27810 @subsubheading @value{GDBN} Command
27812 The corresponding @value{GDBN} command is @samp{jump}.
27814 @subsubheading Example
27817 -exec-jump foo.c:10
27818 *running,thread-id="all"
27823 @subheading The @code{-exec-next} Command
27826 @subsubheading Synopsis
27829 -exec-next [--reverse]
27832 Resumes execution of the inferior program, stopping when the beginning
27833 of the next source line is reached.
27835 If the @samp{--reverse} option is specified, resumes reverse execution
27836 of the inferior program, stopping at the beginning of the previous
27837 source line. If you issue this command on the first line of a
27838 function, it will take you back to the caller of that function, to the
27839 source line where the function was called.
27842 @subsubheading @value{GDBN} Command
27844 The corresponding @value{GDBN} command is @samp{next}.
27846 @subsubheading Example
27852 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27857 @subheading The @code{-exec-next-instruction} Command
27858 @findex -exec-next-instruction
27860 @subsubheading Synopsis
27863 -exec-next-instruction [--reverse]
27866 Executes one machine instruction. If the instruction is a function
27867 call, continues until the function returns. If the program stops at an
27868 instruction in the middle of a source line, the address will be
27871 If the @samp{--reverse} option is specified, resumes reverse execution
27872 of the inferior program, stopping at the previous instruction. If the
27873 previously executed instruction was a return from another function,
27874 it will continue to execute in reverse until the call to that function
27875 (from the current stack frame) is reached.
27877 @subsubheading @value{GDBN} Command
27879 The corresponding @value{GDBN} command is @samp{nexti}.
27881 @subsubheading Example
27885 -exec-next-instruction
27889 *stopped,reason="end-stepping-range",
27890 addr="0x000100d4",line="5",file="hello.c"
27895 @subheading The @code{-exec-return} Command
27896 @findex -exec-return
27898 @subsubheading Synopsis
27904 Makes current function return immediately. Doesn't execute the inferior.
27905 Displays the new current frame.
27907 @subsubheading @value{GDBN} Command
27909 The corresponding @value{GDBN} command is @samp{return}.
27911 @subsubheading Example
27915 200-break-insert callee4
27916 200^done,bkpt=@{number="1",addr="0x00010734",
27917 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27922 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27923 frame=@{func="callee4",args=[],
27924 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27925 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27931 111^done,frame=@{level="0",func="callee3",
27932 args=[@{name="strarg",
27933 value="0x11940 \"A string argument.\""@}],
27934 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27935 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27940 @subheading The @code{-exec-run} Command
27943 @subsubheading Synopsis
27946 -exec-run [--all | --thread-group N]
27949 Starts execution of the inferior from the beginning. The inferior
27950 executes until either a breakpoint is encountered or the program
27951 exits. In the latter case the output will include an exit code, if
27952 the program has exited exceptionally.
27954 When no option is specified, the current inferior is started. If the
27955 @samp{--thread-group} option is specified, it should refer to a thread
27956 group of type @samp{process}, and that thread group will be started.
27957 If the @samp{--all} option is specified, then all inferiors will be started.
27959 @subsubheading @value{GDBN} Command
27961 The corresponding @value{GDBN} command is @samp{run}.
27963 @subsubheading Examples
27968 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27973 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27974 frame=@{func="main",args=[],file="recursive2.c",
27975 fullname="/home/foo/bar/recursive2.c",line="4"@}
27980 Program exited normally:
27988 *stopped,reason="exited-normally"
27993 Program exited exceptionally:
28001 *stopped,reason="exited",exit-code="01"
28005 Another way the program can terminate is if it receives a signal such as
28006 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28010 *stopped,reason="exited-signalled",signal-name="SIGINT",
28011 signal-meaning="Interrupt"
28015 @c @subheading -exec-signal
28018 @subheading The @code{-exec-step} Command
28021 @subsubheading Synopsis
28024 -exec-step [--reverse]
28027 Resumes execution of the inferior program, stopping when the beginning
28028 of the next source line is reached, if the next source line is not a
28029 function call. If it is, stop at the first instruction of the called
28030 function. If the @samp{--reverse} option is specified, resumes reverse
28031 execution of the inferior program, stopping at the beginning of the
28032 previously executed source line.
28034 @subsubheading @value{GDBN} Command
28036 The corresponding @value{GDBN} command is @samp{step}.
28038 @subsubheading Example
28040 Stepping into a function:
28046 *stopped,reason="end-stepping-range",
28047 frame=@{func="foo",args=[@{name="a",value="10"@},
28048 @{name="b",value="0"@}],file="recursive2.c",
28049 fullname="/home/foo/bar/recursive2.c",line="11"@}
28059 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28064 @subheading The @code{-exec-step-instruction} Command
28065 @findex -exec-step-instruction
28067 @subsubheading Synopsis
28070 -exec-step-instruction [--reverse]
28073 Resumes the inferior which executes one machine instruction. If the
28074 @samp{--reverse} option is specified, resumes reverse execution of the
28075 inferior program, stopping at the previously executed instruction.
28076 The output, once @value{GDBN} has stopped, will vary depending on
28077 whether we have stopped in the middle of a source line or not. In the
28078 former case, the address at which the program stopped will be printed
28081 @subsubheading @value{GDBN} Command
28083 The corresponding @value{GDBN} command is @samp{stepi}.
28085 @subsubheading Example
28089 -exec-step-instruction
28093 *stopped,reason="end-stepping-range",
28094 frame=@{func="foo",args=[],file="try.c",
28095 fullname="/home/foo/bar/try.c",line="10"@}
28097 -exec-step-instruction
28101 *stopped,reason="end-stepping-range",
28102 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28103 fullname="/home/foo/bar/try.c",line="10"@}
28108 @subheading The @code{-exec-until} Command
28109 @findex -exec-until
28111 @subsubheading Synopsis
28114 -exec-until [ @var{location} ]
28117 Executes the inferior until the @var{location} specified in the
28118 argument is reached. If there is no argument, the inferior executes
28119 until a source line greater than the current one is reached. The
28120 reason for stopping in this case will be @samp{location-reached}.
28122 @subsubheading @value{GDBN} Command
28124 The corresponding @value{GDBN} command is @samp{until}.
28126 @subsubheading Example
28130 -exec-until recursive2.c:6
28134 *stopped,reason="location-reached",frame=@{func="main",args=[],
28135 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28140 @subheading -file-clear
28141 Is this going away????
28144 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28145 @node GDB/MI Stack Manipulation
28146 @section @sc{gdb/mi} Stack Manipulation Commands
28149 @subheading The @code{-stack-info-frame} Command
28150 @findex -stack-info-frame
28152 @subsubheading Synopsis
28158 Get info on the selected frame.
28160 @subsubheading @value{GDBN} Command
28162 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28163 (without arguments).
28165 @subsubheading Example
28170 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28171 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28172 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28176 @subheading The @code{-stack-info-depth} Command
28177 @findex -stack-info-depth
28179 @subsubheading Synopsis
28182 -stack-info-depth [ @var{max-depth} ]
28185 Return the depth of the stack. If the integer argument @var{max-depth}
28186 is specified, do not count beyond @var{max-depth} frames.
28188 @subsubheading @value{GDBN} Command
28190 There's no equivalent @value{GDBN} command.
28192 @subsubheading Example
28194 For a stack with frame levels 0 through 11:
28201 -stack-info-depth 4
28204 -stack-info-depth 12
28207 -stack-info-depth 11
28210 -stack-info-depth 13
28215 @subheading The @code{-stack-list-arguments} Command
28216 @findex -stack-list-arguments
28218 @subsubheading Synopsis
28221 -stack-list-arguments @var{print-values}
28222 [ @var{low-frame} @var{high-frame} ]
28225 Display a list of the arguments for the frames between @var{low-frame}
28226 and @var{high-frame} (inclusive). If @var{low-frame} and
28227 @var{high-frame} are not provided, list the arguments for the whole
28228 call stack. If the two arguments are equal, show the single frame
28229 at the corresponding level. It is an error if @var{low-frame} is
28230 larger than the actual number of frames. On the other hand,
28231 @var{high-frame} may be larger than the actual number of frames, in
28232 which case only existing frames will be returned.
28234 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28235 the variables; if it is 1 or @code{--all-values}, print also their
28236 values; and if it is 2 or @code{--simple-values}, print the name,
28237 type and value for simple data types, and the name and type for arrays,
28238 structures and unions.
28240 Use of this command to obtain arguments in a single frame is
28241 deprecated in favor of the @samp{-stack-list-variables} command.
28243 @subsubheading @value{GDBN} Command
28245 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28246 @samp{gdb_get_args} command which partially overlaps with the
28247 functionality of @samp{-stack-list-arguments}.
28249 @subsubheading Example
28256 frame=@{level="0",addr="0x00010734",func="callee4",
28257 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28258 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28259 frame=@{level="1",addr="0x0001076c",func="callee3",
28260 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28261 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28262 frame=@{level="2",addr="0x0001078c",func="callee2",
28263 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28264 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28265 frame=@{level="3",addr="0x000107b4",func="callee1",
28266 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28267 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28268 frame=@{level="4",addr="0x000107e0",func="main",
28269 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28270 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28272 -stack-list-arguments 0
28275 frame=@{level="0",args=[]@},
28276 frame=@{level="1",args=[name="strarg"]@},
28277 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28278 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28279 frame=@{level="4",args=[]@}]
28281 -stack-list-arguments 1
28284 frame=@{level="0",args=[]@},
28286 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28287 frame=@{level="2",args=[
28288 @{name="intarg",value="2"@},
28289 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28290 @{frame=@{level="3",args=[
28291 @{name="intarg",value="2"@},
28292 @{name="strarg",value="0x11940 \"A string argument.\""@},
28293 @{name="fltarg",value="3.5"@}]@},
28294 frame=@{level="4",args=[]@}]
28296 -stack-list-arguments 0 2 2
28297 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28299 -stack-list-arguments 1 2 2
28300 ^done,stack-args=[frame=@{level="2",
28301 args=[@{name="intarg",value="2"@},
28302 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28306 @c @subheading -stack-list-exception-handlers
28309 @subheading The @code{-stack-list-frames} Command
28310 @findex -stack-list-frames
28312 @subsubheading Synopsis
28315 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28318 List the frames currently on the stack. For each frame it displays the
28323 The frame number, 0 being the topmost frame, i.e., the innermost function.
28325 The @code{$pc} value for that frame.
28329 File name of the source file where the function lives.
28330 @item @var{fullname}
28331 The full file name of the source file where the function lives.
28333 Line number corresponding to the @code{$pc}.
28335 The shared library where this function is defined. This is only given
28336 if the frame's function is not known.
28339 If invoked without arguments, this command prints a backtrace for the
28340 whole stack. If given two integer arguments, it shows the frames whose
28341 levels are between the two arguments (inclusive). If the two arguments
28342 are equal, it shows the single frame at the corresponding level. It is
28343 an error if @var{low-frame} is larger than the actual number of
28344 frames. On the other hand, @var{high-frame} may be larger than the
28345 actual number of frames, in which case only existing frames will be returned.
28347 @subsubheading @value{GDBN} Command
28349 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28351 @subsubheading Example
28353 Full stack backtrace:
28359 [frame=@{level="0",addr="0x0001076c",func="foo",
28360 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28361 frame=@{level="1",addr="0x000107a4",func="foo",
28362 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28363 frame=@{level="2",addr="0x000107a4",func="foo",
28364 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28365 frame=@{level="3",addr="0x000107a4",func="foo",
28366 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28367 frame=@{level="4",addr="0x000107a4",func="foo",
28368 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28369 frame=@{level="5",addr="0x000107a4",func="foo",
28370 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28371 frame=@{level="6",addr="0x000107a4",func="foo",
28372 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28373 frame=@{level="7",addr="0x000107a4",func="foo",
28374 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28375 frame=@{level="8",addr="0x000107a4",func="foo",
28376 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28377 frame=@{level="9",addr="0x000107a4",func="foo",
28378 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28379 frame=@{level="10",addr="0x000107a4",func="foo",
28380 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28381 frame=@{level="11",addr="0x00010738",func="main",
28382 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28386 Show frames between @var{low_frame} and @var{high_frame}:
28390 -stack-list-frames 3 5
28392 [frame=@{level="3",addr="0x000107a4",func="foo",
28393 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28394 frame=@{level="4",addr="0x000107a4",func="foo",
28395 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28396 frame=@{level="5",addr="0x000107a4",func="foo",
28397 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28401 Show a single frame:
28405 -stack-list-frames 3 3
28407 [frame=@{level="3",addr="0x000107a4",func="foo",
28408 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28413 @subheading The @code{-stack-list-locals} Command
28414 @findex -stack-list-locals
28416 @subsubheading Synopsis
28419 -stack-list-locals @var{print-values}
28422 Display the local variable names for the selected frame. If
28423 @var{print-values} is 0 or @code{--no-values}, print only the names of
28424 the variables; if it is 1 or @code{--all-values}, print also their
28425 values; and if it is 2 or @code{--simple-values}, print the name,
28426 type and value for simple data types, and the name and type for arrays,
28427 structures and unions. In this last case, a frontend can immediately
28428 display the value of simple data types and create variable objects for
28429 other data types when the user wishes to explore their values in
28432 This command is deprecated in favor of the
28433 @samp{-stack-list-variables} command.
28435 @subsubheading @value{GDBN} Command
28437 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28439 @subsubheading Example
28443 -stack-list-locals 0
28444 ^done,locals=[name="A",name="B",name="C"]
28446 -stack-list-locals --all-values
28447 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28448 @{name="C",value="@{1, 2, 3@}"@}]
28449 -stack-list-locals --simple-values
28450 ^done,locals=[@{name="A",type="int",value="1"@},
28451 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28455 @subheading The @code{-stack-list-variables} Command
28456 @findex -stack-list-variables
28458 @subsubheading Synopsis
28461 -stack-list-variables @var{print-values}
28464 Display the names of local variables and function arguments for the selected frame. If
28465 @var{print-values} is 0 or @code{--no-values}, print only the names of
28466 the variables; if it is 1 or @code{--all-values}, print also their
28467 values; and if it is 2 or @code{--simple-values}, print the name,
28468 type and value for simple data types, and the name and type for arrays,
28469 structures and unions.
28471 @subsubheading Example
28475 -stack-list-variables --thread 1 --frame 0 --all-values
28476 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28481 @subheading The @code{-stack-select-frame} Command
28482 @findex -stack-select-frame
28484 @subsubheading Synopsis
28487 -stack-select-frame @var{framenum}
28490 Change the selected frame. Select a different frame @var{framenum} on
28493 This command in deprecated in favor of passing the @samp{--frame}
28494 option to every command.
28496 @subsubheading @value{GDBN} Command
28498 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28499 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28501 @subsubheading Example
28505 -stack-select-frame 2
28510 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28511 @node GDB/MI Variable Objects
28512 @section @sc{gdb/mi} Variable Objects
28516 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28518 For the implementation of a variable debugger window (locals, watched
28519 expressions, etc.), we are proposing the adaptation of the existing code
28520 used by @code{Insight}.
28522 The two main reasons for that are:
28526 It has been proven in practice (it is already on its second generation).
28529 It will shorten development time (needless to say how important it is
28533 The original interface was designed to be used by Tcl code, so it was
28534 slightly changed so it could be used through @sc{gdb/mi}. This section
28535 describes the @sc{gdb/mi} operations that will be available and gives some
28536 hints about their use.
28538 @emph{Note}: In addition to the set of operations described here, we
28539 expect the @sc{gui} implementation of a variable window to require, at
28540 least, the following operations:
28543 @item @code{-gdb-show} @code{output-radix}
28544 @item @code{-stack-list-arguments}
28545 @item @code{-stack-list-locals}
28546 @item @code{-stack-select-frame}
28551 @subheading Introduction to Variable Objects
28553 @cindex variable objects in @sc{gdb/mi}
28555 Variable objects are "object-oriented" MI interface for examining and
28556 changing values of expressions. Unlike some other MI interfaces that
28557 work with expressions, variable objects are specifically designed for
28558 simple and efficient presentation in the frontend. A variable object
28559 is identified by string name. When a variable object is created, the
28560 frontend specifies the expression for that variable object. The
28561 expression can be a simple variable, or it can be an arbitrary complex
28562 expression, and can even involve CPU registers. After creating a
28563 variable object, the frontend can invoke other variable object
28564 operations---for example to obtain or change the value of a variable
28565 object, or to change display format.
28567 Variable objects have hierarchical tree structure. Any variable object
28568 that corresponds to a composite type, such as structure in C, has
28569 a number of child variable objects, for example corresponding to each
28570 element of a structure. A child variable object can itself have
28571 children, recursively. Recursion ends when we reach
28572 leaf variable objects, which always have built-in types. Child variable
28573 objects are created only by explicit request, so if a frontend
28574 is not interested in the children of a particular variable object, no
28575 child will be created.
28577 For a leaf variable object it is possible to obtain its value as a
28578 string, or set the value from a string. String value can be also
28579 obtained for a non-leaf variable object, but it's generally a string
28580 that only indicates the type of the object, and does not list its
28581 contents. Assignment to a non-leaf variable object is not allowed.
28583 A frontend does not need to read the values of all variable objects each time
28584 the program stops. Instead, MI provides an update command that lists all
28585 variable objects whose values has changed since the last update
28586 operation. This considerably reduces the amount of data that must
28587 be transferred to the frontend. As noted above, children variable
28588 objects are created on demand, and only leaf variable objects have a
28589 real value. As result, gdb will read target memory only for leaf
28590 variables that frontend has created.
28592 The automatic update is not always desirable. For example, a frontend
28593 might want to keep a value of some expression for future reference,
28594 and never update it. For another example, fetching memory is
28595 relatively slow for embedded targets, so a frontend might want
28596 to disable automatic update for the variables that are either not
28597 visible on the screen, or ``closed''. This is possible using so
28598 called ``frozen variable objects''. Such variable objects are never
28599 implicitly updated.
28601 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28602 fixed variable object, the expression is parsed when the variable
28603 object is created, including associating identifiers to specific
28604 variables. The meaning of expression never changes. For a floating
28605 variable object the values of variables whose names appear in the
28606 expressions are re-evaluated every time in the context of the current
28607 frame. Consider this example:
28612 struct work_state state;
28619 If a fixed variable object for the @code{state} variable is created in
28620 this function, and we enter the recursive call, the variable
28621 object will report the value of @code{state} in the top-level
28622 @code{do_work} invocation. On the other hand, a floating variable
28623 object will report the value of @code{state} in the current frame.
28625 If an expression specified when creating a fixed variable object
28626 refers to a local variable, the variable object becomes bound to the
28627 thread and frame in which the variable object is created. When such
28628 variable object is updated, @value{GDBN} makes sure that the
28629 thread/frame combination the variable object is bound to still exists,
28630 and re-evaluates the variable object in context of that thread/frame.
28632 The following is the complete set of @sc{gdb/mi} operations defined to
28633 access this functionality:
28635 @multitable @columnfractions .4 .6
28636 @item @strong{Operation}
28637 @tab @strong{Description}
28639 @item @code{-enable-pretty-printing}
28640 @tab enable Python-based pretty-printing
28641 @item @code{-var-create}
28642 @tab create a variable object
28643 @item @code{-var-delete}
28644 @tab delete the variable object and/or its children
28645 @item @code{-var-set-format}
28646 @tab set the display format of this variable
28647 @item @code{-var-show-format}
28648 @tab show the display format of this variable
28649 @item @code{-var-info-num-children}
28650 @tab tells how many children this object has
28651 @item @code{-var-list-children}
28652 @tab return a list of the object's children
28653 @item @code{-var-info-type}
28654 @tab show the type of this variable object
28655 @item @code{-var-info-expression}
28656 @tab print parent-relative expression that this variable object represents
28657 @item @code{-var-info-path-expression}
28658 @tab print full expression that this variable object represents
28659 @item @code{-var-show-attributes}
28660 @tab is this variable editable? does it exist here?
28661 @item @code{-var-evaluate-expression}
28662 @tab get the value of this variable
28663 @item @code{-var-assign}
28664 @tab set the value of this variable
28665 @item @code{-var-update}
28666 @tab update the variable and its children
28667 @item @code{-var-set-frozen}
28668 @tab set frozeness attribute
28669 @item @code{-var-set-update-range}
28670 @tab set range of children to display on update
28673 In the next subsection we describe each operation in detail and suggest
28674 how it can be used.
28676 @subheading Description And Use of Operations on Variable Objects
28678 @subheading The @code{-enable-pretty-printing} Command
28679 @findex -enable-pretty-printing
28682 -enable-pretty-printing
28685 @value{GDBN} allows Python-based visualizers to affect the output of the
28686 MI variable object commands. However, because there was no way to
28687 implement this in a fully backward-compatible way, a front end must
28688 request that this functionality be enabled.
28690 Once enabled, this feature cannot be disabled.
28692 Note that if Python support has not been compiled into @value{GDBN},
28693 this command will still succeed (and do nothing).
28695 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28696 may work differently in future versions of @value{GDBN}.
28698 @subheading The @code{-var-create} Command
28699 @findex -var-create
28701 @subsubheading Synopsis
28704 -var-create @{@var{name} | "-"@}
28705 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28708 This operation creates a variable object, which allows the monitoring of
28709 a variable, the result of an expression, a memory cell or a CPU
28712 The @var{name} parameter is the string by which the object can be
28713 referenced. It must be unique. If @samp{-} is specified, the varobj
28714 system will generate a string ``varNNNNNN'' automatically. It will be
28715 unique provided that one does not specify @var{name} of that format.
28716 The command fails if a duplicate name is found.
28718 The frame under which the expression should be evaluated can be
28719 specified by @var{frame-addr}. A @samp{*} indicates that the current
28720 frame should be used. A @samp{@@} indicates that a floating variable
28721 object must be created.
28723 @var{expression} is any expression valid on the current language set (must not
28724 begin with a @samp{*}), or one of the following:
28728 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28731 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28734 @samp{$@var{regname}} --- a CPU register name
28737 @cindex dynamic varobj
28738 A varobj's contents may be provided by a Python-based pretty-printer. In this
28739 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28740 have slightly different semantics in some cases. If the
28741 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28742 will never create a dynamic varobj. This ensures backward
28743 compatibility for existing clients.
28745 @subsubheading Result
28747 This operation returns attributes of the newly-created varobj. These
28752 The name of the varobj.
28755 The number of children of the varobj. This number is not necessarily
28756 reliable for a dynamic varobj. Instead, you must examine the
28757 @samp{has_more} attribute.
28760 The varobj's scalar value. For a varobj whose type is some sort of
28761 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28762 will not be interesting.
28765 The varobj's type. This is a string representation of the type, as
28766 would be printed by the @value{GDBN} CLI.
28769 If a variable object is bound to a specific thread, then this is the
28770 thread's identifier.
28773 For a dynamic varobj, this indicates whether there appear to be any
28774 children available. For a non-dynamic varobj, this will be 0.
28777 This attribute will be present and have the value @samp{1} if the
28778 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28779 then this attribute will not be present.
28782 A dynamic varobj can supply a display hint to the front end. The
28783 value comes directly from the Python pretty-printer object's
28784 @code{display_hint} method. @xref{Pretty Printing API}.
28787 Typical output will look like this:
28790 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28791 has_more="@var{has_more}"
28795 @subheading The @code{-var-delete} Command
28796 @findex -var-delete
28798 @subsubheading Synopsis
28801 -var-delete [ -c ] @var{name}
28804 Deletes a previously created variable object and all of its children.
28805 With the @samp{-c} option, just deletes the children.
28807 Returns an error if the object @var{name} is not found.
28810 @subheading The @code{-var-set-format} Command
28811 @findex -var-set-format
28813 @subsubheading Synopsis
28816 -var-set-format @var{name} @var{format-spec}
28819 Sets the output format for the value of the object @var{name} to be
28822 @anchor{-var-set-format}
28823 The syntax for the @var{format-spec} is as follows:
28826 @var{format-spec} @expansion{}
28827 @{binary | decimal | hexadecimal | octal | natural@}
28830 The natural format is the default format choosen automatically
28831 based on the variable type (like decimal for an @code{int}, hex
28832 for pointers, etc.).
28834 For a variable with children, the format is set only on the
28835 variable itself, and the children are not affected.
28837 @subheading The @code{-var-show-format} Command
28838 @findex -var-show-format
28840 @subsubheading Synopsis
28843 -var-show-format @var{name}
28846 Returns the format used to display the value of the object @var{name}.
28849 @var{format} @expansion{}
28854 @subheading The @code{-var-info-num-children} Command
28855 @findex -var-info-num-children
28857 @subsubheading Synopsis
28860 -var-info-num-children @var{name}
28863 Returns the number of children of a variable object @var{name}:
28869 Note that this number is not completely reliable for a dynamic varobj.
28870 It will return the current number of children, but more children may
28874 @subheading The @code{-var-list-children} Command
28875 @findex -var-list-children
28877 @subsubheading Synopsis
28880 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28882 @anchor{-var-list-children}
28884 Return a list of the children of the specified variable object and
28885 create variable objects for them, if they do not already exist. With
28886 a single argument or if @var{print-values} has a value of 0 or
28887 @code{--no-values}, print only the names of the variables; if
28888 @var{print-values} is 1 or @code{--all-values}, also print their
28889 values; and if it is 2 or @code{--simple-values} print the name and
28890 value for simple data types and just the name for arrays, structures
28893 @var{from} and @var{to}, if specified, indicate the range of children
28894 to report. If @var{from} or @var{to} is less than zero, the range is
28895 reset and all children will be reported. Otherwise, children starting
28896 at @var{from} (zero-based) and up to and excluding @var{to} will be
28899 If a child range is requested, it will only affect the current call to
28900 @code{-var-list-children}, but not future calls to @code{-var-update}.
28901 For this, you must instead use @code{-var-set-update-range}. The
28902 intent of this approach is to enable a front end to implement any
28903 update approach it likes; for example, scrolling a view may cause the
28904 front end to request more children with @code{-var-list-children}, and
28905 then the front end could call @code{-var-set-update-range} with a
28906 different range to ensure that future updates are restricted to just
28909 For each child the following results are returned:
28914 Name of the variable object created for this child.
28917 The expression to be shown to the user by the front end to designate this child.
28918 For example this may be the name of a structure member.
28920 For a dynamic varobj, this value cannot be used to form an
28921 expression. There is no way to do this at all with a dynamic varobj.
28923 For C/C@t{++} structures there are several pseudo children returned to
28924 designate access qualifiers. For these pseudo children @var{exp} is
28925 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28926 type and value are not present.
28928 A dynamic varobj will not report the access qualifying
28929 pseudo-children, regardless of the language. This information is not
28930 available at all with a dynamic varobj.
28933 Number of children this child has. For a dynamic varobj, this will be
28937 The type of the child.
28940 If values were requested, this is the value.
28943 If this variable object is associated with a thread, this is the thread id.
28944 Otherwise this result is not present.
28947 If the variable object is frozen, this variable will be present with a value of 1.
28950 The result may have its own attributes:
28954 A dynamic varobj can supply a display hint to the front end. The
28955 value comes directly from the Python pretty-printer object's
28956 @code{display_hint} method. @xref{Pretty Printing API}.
28959 This is an integer attribute which is nonzero if there are children
28960 remaining after the end of the selected range.
28963 @subsubheading Example
28967 -var-list-children n
28968 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28969 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28971 -var-list-children --all-values n
28972 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28973 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28977 @subheading The @code{-var-info-type} Command
28978 @findex -var-info-type
28980 @subsubheading Synopsis
28983 -var-info-type @var{name}
28986 Returns the type of the specified variable @var{name}. The type is
28987 returned as a string in the same format as it is output by the
28991 type=@var{typename}
28995 @subheading The @code{-var-info-expression} Command
28996 @findex -var-info-expression
28998 @subsubheading Synopsis
29001 -var-info-expression @var{name}
29004 Returns a string that is suitable for presenting this
29005 variable object in user interface. The string is generally
29006 not valid expression in the current language, and cannot be evaluated.
29008 For example, if @code{a} is an array, and variable object
29009 @code{A} was created for @code{a}, then we'll get this output:
29012 (gdb) -var-info-expression A.1
29013 ^done,lang="C",exp="1"
29017 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29019 Note that the output of the @code{-var-list-children} command also
29020 includes those expressions, so the @code{-var-info-expression} command
29023 @subheading The @code{-var-info-path-expression} Command
29024 @findex -var-info-path-expression
29026 @subsubheading Synopsis
29029 -var-info-path-expression @var{name}
29032 Returns an expression that can be evaluated in the current
29033 context and will yield the same value that a variable object has.
29034 Compare this with the @code{-var-info-expression} command, which
29035 result can be used only for UI presentation. Typical use of
29036 the @code{-var-info-path-expression} command is creating a
29037 watchpoint from a variable object.
29039 This command is currently not valid for children of a dynamic varobj,
29040 and will give an error when invoked on one.
29042 For example, suppose @code{C} is a C@t{++} class, derived from class
29043 @code{Base}, and that the @code{Base} class has a member called
29044 @code{m_size}. Assume a variable @code{c} is has the type of
29045 @code{C} and a variable object @code{C} was created for variable
29046 @code{c}. Then, we'll get this output:
29048 (gdb) -var-info-path-expression C.Base.public.m_size
29049 ^done,path_expr=((Base)c).m_size)
29052 @subheading The @code{-var-show-attributes} Command
29053 @findex -var-show-attributes
29055 @subsubheading Synopsis
29058 -var-show-attributes @var{name}
29061 List attributes of the specified variable object @var{name}:
29064 status=@var{attr} [ ( ,@var{attr} )* ]
29068 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29070 @subheading The @code{-var-evaluate-expression} Command
29071 @findex -var-evaluate-expression
29073 @subsubheading Synopsis
29076 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29079 Evaluates the expression that is represented by the specified variable
29080 object and returns its value as a string. The format of the string
29081 can be specified with the @samp{-f} option. The possible values of
29082 this option are the same as for @code{-var-set-format}
29083 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29084 the current display format will be used. The current display format
29085 can be changed using the @code{-var-set-format} command.
29091 Note that one must invoke @code{-var-list-children} for a variable
29092 before the value of a child variable can be evaluated.
29094 @subheading The @code{-var-assign} Command
29095 @findex -var-assign
29097 @subsubheading Synopsis
29100 -var-assign @var{name} @var{expression}
29103 Assigns the value of @var{expression} to the variable object specified
29104 by @var{name}. The object must be @samp{editable}. If the variable's
29105 value is altered by the assign, the variable will show up in any
29106 subsequent @code{-var-update} list.
29108 @subsubheading Example
29116 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29120 @subheading The @code{-var-update} Command
29121 @findex -var-update
29123 @subsubheading Synopsis
29126 -var-update [@var{print-values}] @{@var{name} | "*"@}
29129 Reevaluate the expressions corresponding to the variable object
29130 @var{name} and all its direct and indirect children, and return the
29131 list of variable objects whose values have changed; @var{name} must
29132 be a root variable object. Here, ``changed'' means that the result of
29133 @code{-var-evaluate-expression} before and after the
29134 @code{-var-update} is different. If @samp{*} is used as the variable
29135 object names, all existing variable objects are updated, except
29136 for frozen ones (@pxref{-var-set-frozen}). The option
29137 @var{print-values} determines whether both names and values, or just
29138 names are printed. The possible values of this option are the same
29139 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29140 recommended to use the @samp{--all-values} option, to reduce the
29141 number of MI commands needed on each program stop.
29143 With the @samp{*} parameter, if a variable object is bound to a
29144 currently running thread, it will not be updated, without any
29147 If @code{-var-set-update-range} was previously used on a varobj, then
29148 only the selected range of children will be reported.
29150 @code{-var-update} reports all the changed varobjs in a tuple named
29153 Each item in the change list is itself a tuple holding:
29157 The name of the varobj.
29160 If values were requested for this update, then this field will be
29161 present and will hold the value of the varobj.
29164 @anchor{-var-update}
29165 This field is a string which may take one of three values:
29169 The variable object's current value is valid.
29172 The variable object does not currently hold a valid value but it may
29173 hold one in the future if its associated expression comes back into
29177 The variable object no longer holds a valid value.
29178 This can occur when the executable file being debugged has changed,
29179 either through recompilation or by using the @value{GDBN} @code{file}
29180 command. The front end should normally choose to delete these variable
29184 In the future new values may be added to this list so the front should
29185 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29188 This is only present if the varobj is still valid. If the type
29189 changed, then this will be the string @samp{true}; otherwise it will
29193 If the varobj's type changed, then this field will be present and will
29196 @item new_num_children
29197 For a dynamic varobj, if the number of children changed, or if the
29198 type changed, this will be the new number of children.
29200 The @samp{numchild} field in other varobj responses is generally not
29201 valid for a dynamic varobj -- it will show the number of children that
29202 @value{GDBN} knows about, but because dynamic varobjs lazily
29203 instantiate their children, this will not reflect the number of
29204 children which may be available.
29206 The @samp{new_num_children} attribute only reports changes to the
29207 number of children known by @value{GDBN}. This is the only way to
29208 detect whether an update has removed children (which necessarily can
29209 only happen at the end of the update range).
29212 The display hint, if any.
29215 This is an integer value, which will be 1 if there are more children
29216 available outside the varobj's update range.
29219 This attribute will be present and have the value @samp{1} if the
29220 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29221 then this attribute will not be present.
29224 If new children were added to a dynamic varobj within the selected
29225 update range (as set by @code{-var-set-update-range}), then they will
29226 be listed in this attribute.
29229 @subsubheading Example
29236 -var-update --all-values var1
29237 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29238 type_changed="false"@}]
29242 @subheading The @code{-var-set-frozen} Command
29243 @findex -var-set-frozen
29244 @anchor{-var-set-frozen}
29246 @subsubheading Synopsis
29249 -var-set-frozen @var{name} @var{flag}
29252 Set the frozenness flag on the variable object @var{name}. The
29253 @var{flag} parameter should be either @samp{1} to make the variable
29254 frozen or @samp{0} to make it unfrozen. If a variable object is
29255 frozen, then neither itself, nor any of its children, are
29256 implicitly updated by @code{-var-update} of
29257 a parent variable or by @code{-var-update *}. Only
29258 @code{-var-update} of the variable itself will update its value and
29259 values of its children. After a variable object is unfrozen, it is
29260 implicitly updated by all subsequent @code{-var-update} operations.
29261 Unfreezing a variable does not update it, only subsequent
29262 @code{-var-update} does.
29264 @subsubheading Example
29268 -var-set-frozen V 1
29273 @subheading The @code{-var-set-update-range} command
29274 @findex -var-set-update-range
29275 @anchor{-var-set-update-range}
29277 @subsubheading Synopsis
29280 -var-set-update-range @var{name} @var{from} @var{to}
29283 Set the range of children to be returned by future invocations of
29284 @code{-var-update}.
29286 @var{from} and @var{to} indicate the range of children to report. If
29287 @var{from} or @var{to} is less than zero, the range is reset and all
29288 children will be reported. Otherwise, children starting at @var{from}
29289 (zero-based) and up to and excluding @var{to} will be reported.
29291 @subsubheading Example
29295 -var-set-update-range V 1 2
29299 @subheading The @code{-var-set-visualizer} command
29300 @findex -var-set-visualizer
29301 @anchor{-var-set-visualizer}
29303 @subsubheading Synopsis
29306 -var-set-visualizer @var{name} @var{visualizer}
29309 Set a visualizer for the variable object @var{name}.
29311 @var{visualizer} is the visualizer to use. The special value
29312 @samp{None} means to disable any visualizer in use.
29314 If not @samp{None}, @var{visualizer} must be a Python expression.
29315 This expression must evaluate to a callable object which accepts a
29316 single argument. @value{GDBN} will call this object with the value of
29317 the varobj @var{name} as an argument (this is done so that the same
29318 Python pretty-printing code can be used for both the CLI and MI).
29319 When called, this object must return an object which conforms to the
29320 pretty-printing interface (@pxref{Pretty Printing API}).
29322 The pre-defined function @code{gdb.default_visualizer} may be used to
29323 select a visualizer by following the built-in process
29324 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29325 a varobj is created, and so ordinarily is not needed.
29327 This feature is only available if Python support is enabled. The MI
29328 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29329 can be used to check this.
29331 @subsubheading Example
29333 Resetting the visualizer:
29337 -var-set-visualizer V None
29341 Reselecting the default (type-based) visualizer:
29345 -var-set-visualizer V gdb.default_visualizer
29349 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29350 can be used to instantiate this class for a varobj:
29354 -var-set-visualizer V "lambda val: SomeClass()"
29358 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29359 @node GDB/MI Data Manipulation
29360 @section @sc{gdb/mi} Data Manipulation
29362 @cindex data manipulation, in @sc{gdb/mi}
29363 @cindex @sc{gdb/mi}, data manipulation
29364 This section describes the @sc{gdb/mi} commands that manipulate data:
29365 examine memory and registers, evaluate expressions, etc.
29367 @c REMOVED FROM THE INTERFACE.
29368 @c @subheading -data-assign
29369 @c Change the value of a program variable. Plenty of side effects.
29370 @c @subsubheading GDB Command
29372 @c @subsubheading Example
29375 @subheading The @code{-data-disassemble} Command
29376 @findex -data-disassemble
29378 @subsubheading Synopsis
29382 [ -s @var{start-addr} -e @var{end-addr} ]
29383 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29391 @item @var{start-addr}
29392 is the beginning address (or @code{$pc})
29393 @item @var{end-addr}
29395 @item @var{filename}
29396 is the name of the file to disassemble
29397 @item @var{linenum}
29398 is the line number to disassemble around
29400 is the number of disassembly lines to be produced. If it is -1,
29401 the whole function will be disassembled, in case no @var{end-addr} is
29402 specified. If @var{end-addr} is specified as a non-zero value, and
29403 @var{lines} is lower than the number of disassembly lines between
29404 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29405 displayed; if @var{lines} is higher than the number of lines between
29406 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29409 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29410 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29411 mixed source and disassembly with raw opcodes).
29414 @subsubheading Result
29416 The output for each instruction is composed of four fields:
29425 Note that whatever included in the instruction field, is not manipulated
29426 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29428 @subsubheading @value{GDBN} Command
29430 There's no direct mapping from this command to the CLI.
29432 @subsubheading Example
29434 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29438 -data-disassemble -s $pc -e "$pc + 20" -- 0
29441 @{address="0x000107c0",func-name="main",offset="4",
29442 inst="mov 2, %o0"@},
29443 @{address="0x000107c4",func-name="main",offset="8",
29444 inst="sethi %hi(0x11800), %o2"@},
29445 @{address="0x000107c8",func-name="main",offset="12",
29446 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29447 @{address="0x000107cc",func-name="main",offset="16",
29448 inst="sethi %hi(0x11800), %o2"@},
29449 @{address="0x000107d0",func-name="main",offset="20",
29450 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29454 Disassemble the whole @code{main} function. Line 32 is part of
29458 -data-disassemble -f basics.c -l 32 -- 0
29460 @{address="0x000107bc",func-name="main",offset="0",
29461 inst="save %sp, -112, %sp"@},
29462 @{address="0x000107c0",func-name="main",offset="4",
29463 inst="mov 2, %o0"@},
29464 @{address="0x000107c4",func-name="main",offset="8",
29465 inst="sethi %hi(0x11800), %o2"@},
29467 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29468 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29472 Disassemble 3 instructions from the start of @code{main}:
29476 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29478 @{address="0x000107bc",func-name="main",offset="0",
29479 inst="save %sp, -112, %sp"@},
29480 @{address="0x000107c0",func-name="main",offset="4",
29481 inst="mov 2, %o0"@},
29482 @{address="0x000107c4",func-name="main",offset="8",
29483 inst="sethi %hi(0x11800), %o2"@}]
29487 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29491 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29493 src_and_asm_line=@{line="31",
29494 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29495 testsuite/gdb.mi/basics.c",line_asm_insn=[
29496 @{address="0x000107bc",func-name="main",offset="0",
29497 inst="save %sp, -112, %sp"@}]@},
29498 src_and_asm_line=@{line="32",
29499 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29500 testsuite/gdb.mi/basics.c",line_asm_insn=[
29501 @{address="0x000107c0",func-name="main",offset="4",
29502 inst="mov 2, %o0"@},
29503 @{address="0x000107c4",func-name="main",offset="8",
29504 inst="sethi %hi(0x11800), %o2"@}]@}]
29509 @subheading The @code{-data-evaluate-expression} Command
29510 @findex -data-evaluate-expression
29512 @subsubheading Synopsis
29515 -data-evaluate-expression @var{expr}
29518 Evaluate @var{expr} as an expression. The expression could contain an
29519 inferior function call. The function call will execute synchronously.
29520 If the expression contains spaces, it must be enclosed in double quotes.
29522 @subsubheading @value{GDBN} Command
29524 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29525 @samp{call}. In @code{gdbtk} only, there's a corresponding
29526 @samp{gdb_eval} command.
29528 @subsubheading Example
29530 In the following example, the numbers that precede the commands are the
29531 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29532 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29536 211-data-evaluate-expression A
29539 311-data-evaluate-expression &A
29540 311^done,value="0xefffeb7c"
29542 411-data-evaluate-expression A+3
29545 511-data-evaluate-expression "A + 3"
29551 @subheading The @code{-data-list-changed-registers} Command
29552 @findex -data-list-changed-registers
29554 @subsubheading Synopsis
29557 -data-list-changed-registers
29560 Display a list of the registers that have changed.
29562 @subsubheading @value{GDBN} Command
29564 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29565 has the corresponding command @samp{gdb_changed_register_list}.
29567 @subsubheading Example
29569 On a PPC MBX board:
29577 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29578 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29581 -data-list-changed-registers
29582 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29583 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29584 "24","25","26","27","28","30","31","64","65","66","67","69"]
29589 @subheading The @code{-data-list-register-names} Command
29590 @findex -data-list-register-names
29592 @subsubheading Synopsis
29595 -data-list-register-names [ ( @var{regno} )+ ]
29598 Show a list of register names for the current target. If no arguments
29599 are given, it shows a list of the names of all the registers. If
29600 integer numbers are given as arguments, it will print a list of the
29601 names of the registers corresponding to the arguments. To ensure
29602 consistency between a register name and its number, the output list may
29603 include empty register names.
29605 @subsubheading @value{GDBN} Command
29607 @value{GDBN} does not have a command which corresponds to
29608 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29609 corresponding command @samp{gdb_regnames}.
29611 @subsubheading Example
29613 For the PPC MBX board:
29616 -data-list-register-names
29617 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29618 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29619 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29620 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29621 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29622 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29623 "", "pc","ps","cr","lr","ctr","xer"]
29625 -data-list-register-names 1 2 3
29626 ^done,register-names=["r1","r2","r3"]
29630 @subheading The @code{-data-list-register-values} Command
29631 @findex -data-list-register-values
29633 @subsubheading Synopsis
29636 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29639 Display the registers' contents. @var{fmt} is the format according to
29640 which the registers' contents are to be returned, followed by an optional
29641 list of numbers specifying the registers to display. A missing list of
29642 numbers indicates that the contents of all the registers must be returned.
29644 Allowed formats for @var{fmt} are:
29661 @subsubheading @value{GDBN} Command
29663 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29664 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29666 @subsubheading Example
29668 For a PPC MBX board (note: line breaks are for readability only, they
29669 don't appear in the actual output):
29673 -data-list-register-values r 64 65
29674 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29675 @{number="65",value="0x00029002"@}]
29677 -data-list-register-values x
29678 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29679 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29680 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29681 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29682 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29683 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29684 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29685 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29686 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29687 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29688 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29689 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29690 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29691 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29692 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29693 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29694 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29695 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29696 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29697 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29698 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29699 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29700 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29701 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29702 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29703 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29704 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29705 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29706 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29707 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29708 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29709 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29710 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29711 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29712 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29713 @{number="69",value="0x20002b03"@}]
29718 @subheading The @code{-data-read-memory} Command
29719 @findex -data-read-memory
29721 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29723 @subsubheading Synopsis
29726 -data-read-memory [ -o @var{byte-offset} ]
29727 @var{address} @var{word-format} @var{word-size}
29728 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29735 @item @var{address}
29736 An expression specifying the address of the first memory word to be
29737 read. Complex expressions containing embedded white space should be
29738 quoted using the C convention.
29740 @item @var{word-format}
29741 The format to be used to print the memory words. The notation is the
29742 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29745 @item @var{word-size}
29746 The size of each memory word in bytes.
29748 @item @var{nr-rows}
29749 The number of rows in the output table.
29751 @item @var{nr-cols}
29752 The number of columns in the output table.
29755 If present, indicates that each row should include an @sc{ascii} dump. The
29756 value of @var{aschar} is used as a padding character when a byte is not a
29757 member of the printable @sc{ascii} character set (printable @sc{ascii}
29758 characters are those whose code is between 32 and 126, inclusively).
29760 @item @var{byte-offset}
29761 An offset to add to the @var{address} before fetching memory.
29764 This command displays memory contents as a table of @var{nr-rows} by
29765 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29766 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29767 (returned as @samp{total-bytes}). Should less than the requested number
29768 of bytes be returned by the target, the missing words are identified
29769 using @samp{N/A}. The number of bytes read from the target is returned
29770 in @samp{nr-bytes} and the starting address used to read memory in
29773 The address of the next/previous row or page is available in
29774 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29777 @subsubheading @value{GDBN} Command
29779 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29780 @samp{gdb_get_mem} memory read command.
29782 @subsubheading Example
29784 Read six bytes of memory starting at @code{bytes+6} but then offset by
29785 @code{-6} bytes. Format as three rows of two columns. One byte per
29786 word. Display each word in hex.
29790 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29791 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29792 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29793 prev-page="0x0000138a",memory=[
29794 @{addr="0x00001390",data=["0x00","0x01"]@},
29795 @{addr="0x00001392",data=["0x02","0x03"]@},
29796 @{addr="0x00001394",data=["0x04","0x05"]@}]
29800 Read two bytes of memory starting at address @code{shorts + 64} and
29801 display as a single word formatted in decimal.
29805 5-data-read-memory shorts+64 d 2 1 1
29806 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29807 next-row="0x00001512",prev-row="0x0000150e",
29808 next-page="0x00001512",prev-page="0x0000150e",memory=[
29809 @{addr="0x00001510",data=["128"]@}]
29813 Read thirty two bytes of memory starting at @code{bytes+16} and format
29814 as eight rows of four columns. Include a string encoding with @samp{x}
29815 used as the non-printable character.
29819 4-data-read-memory bytes+16 x 1 8 4 x
29820 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29821 next-row="0x000013c0",prev-row="0x0000139c",
29822 next-page="0x000013c0",prev-page="0x00001380",memory=[
29823 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29824 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29825 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29826 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29827 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29828 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29829 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29830 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29834 @subheading The @code{-data-read-memory-bytes} Command
29835 @findex -data-read-memory-bytes
29837 @subsubheading Synopsis
29840 -data-read-memory-bytes [ -o @var{byte-offset} ]
29841 @var{address} @var{count}
29848 @item @var{address}
29849 An expression specifying the address of the first memory word to be
29850 read. Complex expressions containing embedded white space should be
29851 quoted using the C convention.
29854 The number of bytes to read. This should be an integer literal.
29856 @item @var{byte-offset}
29857 The offsets in bytes relative to @var{address} at which to start
29858 reading. This should be an integer literal. This option is provided
29859 so that a frontend is not required to first evaluate address and then
29860 perform address arithmetics itself.
29864 This command attempts to read all accessible memory regions in the
29865 specified range. First, all regions marked as unreadable in the memory
29866 map (if one is defined) will be skipped. @xref{Memory Region
29867 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29868 regions. For each one, if reading full region results in an errors,
29869 @value{GDBN} will try to read a subset of the region.
29871 In general, every single byte in the region may be readable or not,
29872 and the only way to read every readable byte is to try a read at
29873 every address, which is not practical. Therefore, @value{GDBN} will
29874 attempt to read all accessible bytes at either beginning or the end
29875 of the region, using a binary division scheme. This heuristic works
29876 well for reading accross a memory map boundary. Note that if a region
29877 has a readable range that is neither at the beginning or the end,
29878 @value{GDBN} will not read it.
29880 The result record (@pxref{GDB/MI Result Records}) that is output of
29881 the command includes a field named @samp{memory} whose content is a
29882 list of tuples. Each tuple represent a successfully read memory block
29883 and has the following fields:
29887 The start address of the memory block, as hexadecimal literal.
29890 The end address of the memory block, as hexadecimal literal.
29893 The offset of the memory block, as hexadecimal literal, relative to
29894 the start address passed to @code{-data-read-memory-bytes}.
29897 The contents of the memory block, in hex.
29903 @subsubheading @value{GDBN} Command
29905 The corresponding @value{GDBN} command is @samp{x}.
29907 @subsubheading Example
29911 -data-read-memory-bytes &a 10
29912 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29914 contents="01000000020000000300"@}]
29919 @subheading The @code{-data-write-memory-bytes} Command
29920 @findex -data-write-memory-bytes
29922 @subsubheading Synopsis
29925 -data-write-memory-bytes @var{address} @var{contents}
29932 @item @var{address}
29933 An expression specifying the address of the first memory word to be
29934 read. Complex expressions containing embedded white space should be
29935 quoted using the C convention.
29937 @item @var{contents}
29938 The hex-encoded bytes to write.
29942 @subsubheading @value{GDBN} Command
29944 There's no corresponding @value{GDBN} command.
29946 @subsubheading Example
29950 -data-write-memory-bytes &a "aabbccdd"
29956 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29957 @node GDB/MI Tracepoint Commands
29958 @section @sc{gdb/mi} Tracepoint Commands
29960 The commands defined in this section implement MI support for
29961 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29963 @subheading The @code{-trace-find} Command
29964 @findex -trace-find
29966 @subsubheading Synopsis
29969 -trace-find @var{mode} [@var{parameters}@dots{}]
29972 Find a trace frame using criteria defined by @var{mode} and
29973 @var{parameters}. The following table lists permissible
29974 modes and their parameters. For details of operation, see @ref{tfind}.
29979 No parameters are required. Stops examining trace frames.
29982 An integer is required as parameter. Selects tracepoint frame with
29985 @item tracepoint-number
29986 An integer is required as parameter. Finds next
29987 trace frame that corresponds to tracepoint with the specified number.
29990 An address is required as parameter. Finds
29991 next trace frame that corresponds to any tracepoint at the specified
29994 @item pc-inside-range
29995 Two addresses are required as parameters. Finds next trace
29996 frame that corresponds to a tracepoint at an address inside the
29997 specified range. Both bounds are considered to be inside the range.
29999 @item pc-outside-range
30000 Two addresses are required as parameters. Finds
30001 next trace frame that corresponds to a tracepoint at an address outside
30002 the specified range. Both bounds are considered to be inside the range.
30005 Line specification is required as parameter. @xref{Specify Location}.
30006 Finds next trace frame that corresponds to a tracepoint at
30007 the specified location.
30011 If @samp{none} was passed as @var{mode}, the response does not
30012 have fields. Otherwise, the response may have the following fields:
30016 This field has either @samp{0} or @samp{1} as the value, depending
30017 on whether a matching tracepoint was found.
30020 The index of the found traceframe. This field is present iff
30021 the @samp{found} field has value of @samp{1}.
30024 The index of the found tracepoint. This field is present iff
30025 the @samp{found} field has value of @samp{1}.
30028 The information about the frame corresponding to the found trace
30029 frame. This field is present only if a trace frame was found.
30030 @xref{GDB/MI Frame Information}, for description of this field.
30034 @subsubheading @value{GDBN} Command
30036 The corresponding @value{GDBN} command is @samp{tfind}.
30038 @subheading -trace-define-variable
30039 @findex -trace-define-variable
30041 @subsubheading Synopsis
30044 -trace-define-variable @var{name} [ @var{value} ]
30047 Create trace variable @var{name} if it does not exist. If
30048 @var{value} is specified, sets the initial value of the specified
30049 trace variable to that value. Note that the @var{name} should start
30050 with the @samp{$} character.
30052 @subsubheading @value{GDBN} Command
30054 The corresponding @value{GDBN} command is @samp{tvariable}.
30056 @subheading -trace-list-variables
30057 @findex -trace-list-variables
30059 @subsubheading Synopsis
30062 -trace-list-variables
30065 Return a table of all defined trace variables. Each element of the
30066 table has the following fields:
30070 The name of the trace variable. This field is always present.
30073 The initial value. This is a 64-bit signed integer. This
30074 field is always present.
30077 The value the trace variable has at the moment. This is a 64-bit
30078 signed integer. This field is absent iff current value is
30079 not defined, for example if the trace was never run, or is
30084 @subsubheading @value{GDBN} Command
30086 The corresponding @value{GDBN} command is @samp{tvariables}.
30088 @subsubheading Example
30092 -trace-list-variables
30093 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30094 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30095 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30096 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30097 body=[variable=@{name="$trace_timestamp",initial="0"@}
30098 variable=@{name="$foo",initial="10",current="15"@}]@}
30102 @subheading -trace-save
30103 @findex -trace-save
30105 @subsubheading Synopsis
30108 -trace-save [-r ] @var{filename}
30111 Saves the collected trace data to @var{filename}. Without the
30112 @samp{-r} option, the data is downloaded from the target and saved
30113 in a local file. With the @samp{-r} option the target is asked
30114 to perform the save.
30116 @subsubheading @value{GDBN} Command
30118 The corresponding @value{GDBN} command is @samp{tsave}.
30121 @subheading -trace-start
30122 @findex -trace-start
30124 @subsubheading Synopsis
30130 Starts a tracing experiments. The result of this command does not
30133 @subsubheading @value{GDBN} Command
30135 The corresponding @value{GDBN} command is @samp{tstart}.
30137 @subheading -trace-status
30138 @findex -trace-status
30140 @subsubheading Synopsis
30146 Obtains the status of a tracing experiment. The result may include
30147 the following fields:
30152 May have a value of either @samp{0}, when no tracing operations are
30153 supported, @samp{1}, when all tracing operations are supported, or
30154 @samp{file} when examining trace file. In the latter case, examining
30155 of trace frame is possible but new tracing experiement cannot be
30156 started. This field is always present.
30159 May have a value of either @samp{0} or @samp{1} depending on whether
30160 tracing experiement is in progress on target. This field is present
30161 if @samp{supported} field is not @samp{0}.
30164 Report the reason why the tracing was stopped last time. This field
30165 may be absent iff tracing was never stopped on target yet. The
30166 value of @samp{request} means the tracing was stopped as result of
30167 the @code{-trace-stop} command. The value of @samp{overflow} means
30168 the tracing buffer is full. The value of @samp{disconnection} means
30169 tracing was automatically stopped when @value{GDBN} has disconnected.
30170 The value of @samp{passcount} means tracing was stopped when a
30171 tracepoint was passed a maximal number of times for that tracepoint.
30172 This field is present if @samp{supported} field is not @samp{0}.
30174 @item stopping-tracepoint
30175 The number of tracepoint whose passcount as exceeded. This field is
30176 present iff the @samp{stop-reason} field has the value of
30180 @itemx frames-created
30181 The @samp{frames} field is a count of the total number of trace frames
30182 in the trace buffer, while @samp{frames-created} is the total created
30183 during the run, including ones that were discarded, such as when a
30184 circular trace buffer filled up. Both fields are optional.
30188 These fields tell the current size of the tracing buffer and the
30189 remaining space. These fields are optional.
30192 The value of the circular trace buffer flag. @code{1} means that the
30193 trace buffer is circular and old trace frames will be discarded if
30194 necessary to make room, @code{0} means that the trace buffer is linear
30198 The value of the disconnected tracing flag. @code{1} means that
30199 tracing will continue after @value{GDBN} disconnects, @code{0} means
30200 that the trace run will stop.
30204 @subsubheading @value{GDBN} Command
30206 The corresponding @value{GDBN} command is @samp{tstatus}.
30208 @subheading -trace-stop
30209 @findex -trace-stop
30211 @subsubheading Synopsis
30217 Stops a tracing experiment. The result of this command has the same
30218 fields as @code{-trace-status}, except that the @samp{supported} and
30219 @samp{running} fields are not output.
30221 @subsubheading @value{GDBN} Command
30223 The corresponding @value{GDBN} command is @samp{tstop}.
30226 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30227 @node GDB/MI Symbol Query
30228 @section @sc{gdb/mi} Symbol Query Commands
30232 @subheading The @code{-symbol-info-address} Command
30233 @findex -symbol-info-address
30235 @subsubheading Synopsis
30238 -symbol-info-address @var{symbol}
30241 Describe where @var{symbol} is stored.
30243 @subsubheading @value{GDBN} Command
30245 The corresponding @value{GDBN} command is @samp{info address}.
30247 @subsubheading Example
30251 @subheading The @code{-symbol-info-file} Command
30252 @findex -symbol-info-file
30254 @subsubheading Synopsis
30260 Show the file for the symbol.
30262 @subsubheading @value{GDBN} Command
30264 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30265 @samp{gdb_find_file}.
30267 @subsubheading Example
30271 @subheading The @code{-symbol-info-function} Command
30272 @findex -symbol-info-function
30274 @subsubheading Synopsis
30277 -symbol-info-function
30280 Show which function the symbol lives in.
30282 @subsubheading @value{GDBN} Command
30284 @samp{gdb_get_function} in @code{gdbtk}.
30286 @subsubheading Example
30290 @subheading The @code{-symbol-info-line} Command
30291 @findex -symbol-info-line
30293 @subsubheading Synopsis
30299 Show the core addresses of the code for a source line.
30301 @subsubheading @value{GDBN} Command
30303 The corresponding @value{GDBN} command is @samp{info line}.
30304 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30306 @subsubheading Example
30310 @subheading The @code{-symbol-info-symbol} Command
30311 @findex -symbol-info-symbol
30313 @subsubheading Synopsis
30316 -symbol-info-symbol @var{addr}
30319 Describe what symbol is at location @var{addr}.
30321 @subsubheading @value{GDBN} Command
30323 The corresponding @value{GDBN} command is @samp{info symbol}.
30325 @subsubheading Example
30329 @subheading The @code{-symbol-list-functions} Command
30330 @findex -symbol-list-functions
30332 @subsubheading Synopsis
30335 -symbol-list-functions
30338 List the functions in the executable.
30340 @subsubheading @value{GDBN} Command
30342 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30343 @samp{gdb_search} in @code{gdbtk}.
30345 @subsubheading Example
30350 @subheading The @code{-symbol-list-lines} Command
30351 @findex -symbol-list-lines
30353 @subsubheading Synopsis
30356 -symbol-list-lines @var{filename}
30359 Print the list of lines that contain code and their associated program
30360 addresses for the given source filename. The entries are sorted in
30361 ascending PC order.
30363 @subsubheading @value{GDBN} Command
30365 There is no corresponding @value{GDBN} command.
30367 @subsubheading Example
30370 -symbol-list-lines basics.c
30371 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30377 @subheading The @code{-symbol-list-types} Command
30378 @findex -symbol-list-types
30380 @subsubheading Synopsis
30386 List all the type names.
30388 @subsubheading @value{GDBN} Command
30390 The corresponding commands are @samp{info types} in @value{GDBN},
30391 @samp{gdb_search} in @code{gdbtk}.
30393 @subsubheading Example
30397 @subheading The @code{-symbol-list-variables} Command
30398 @findex -symbol-list-variables
30400 @subsubheading Synopsis
30403 -symbol-list-variables
30406 List all the global and static variable names.
30408 @subsubheading @value{GDBN} Command
30410 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30412 @subsubheading Example
30416 @subheading The @code{-symbol-locate} Command
30417 @findex -symbol-locate
30419 @subsubheading Synopsis
30425 @subsubheading @value{GDBN} Command
30427 @samp{gdb_loc} in @code{gdbtk}.
30429 @subsubheading Example
30433 @subheading The @code{-symbol-type} Command
30434 @findex -symbol-type
30436 @subsubheading Synopsis
30439 -symbol-type @var{variable}
30442 Show type of @var{variable}.
30444 @subsubheading @value{GDBN} Command
30446 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30447 @samp{gdb_obj_variable}.
30449 @subsubheading Example
30454 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30455 @node GDB/MI File Commands
30456 @section @sc{gdb/mi} File Commands
30458 This section describes the GDB/MI commands to specify executable file names
30459 and to read in and obtain symbol table information.
30461 @subheading The @code{-file-exec-and-symbols} Command
30462 @findex -file-exec-and-symbols
30464 @subsubheading Synopsis
30467 -file-exec-and-symbols @var{file}
30470 Specify the executable file to be debugged. This file is the one from
30471 which the symbol table is also read. If no file is specified, the
30472 command clears the executable and symbol information. If breakpoints
30473 are set when using this command with no arguments, @value{GDBN} will produce
30474 error messages. Otherwise, no output is produced, except a completion
30477 @subsubheading @value{GDBN} Command
30479 The corresponding @value{GDBN} command is @samp{file}.
30481 @subsubheading Example
30485 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30491 @subheading The @code{-file-exec-file} Command
30492 @findex -file-exec-file
30494 @subsubheading Synopsis
30497 -file-exec-file @var{file}
30500 Specify the executable file to be debugged. Unlike
30501 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30502 from this file. If used without argument, @value{GDBN} clears the information
30503 about the executable file. No output is produced, except a completion
30506 @subsubheading @value{GDBN} Command
30508 The corresponding @value{GDBN} command is @samp{exec-file}.
30510 @subsubheading Example
30514 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30521 @subheading The @code{-file-list-exec-sections} Command
30522 @findex -file-list-exec-sections
30524 @subsubheading Synopsis
30527 -file-list-exec-sections
30530 List the sections of the current executable file.
30532 @subsubheading @value{GDBN} Command
30534 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30535 information as this command. @code{gdbtk} has a corresponding command
30536 @samp{gdb_load_info}.
30538 @subsubheading Example
30543 @subheading The @code{-file-list-exec-source-file} Command
30544 @findex -file-list-exec-source-file
30546 @subsubheading Synopsis
30549 -file-list-exec-source-file
30552 List the line number, the current source file, and the absolute path
30553 to the current source file for the current executable. The macro
30554 information field has a value of @samp{1} or @samp{0} depending on
30555 whether or not the file includes preprocessor macro information.
30557 @subsubheading @value{GDBN} Command
30559 The @value{GDBN} equivalent is @samp{info source}
30561 @subsubheading Example
30565 123-file-list-exec-source-file
30566 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30571 @subheading The @code{-file-list-exec-source-files} Command
30572 @findex -file-list-exec-source-files
30574 @subsubheading Synopsis
30577 -file-list-exec-source-files
30580 List the source files for the current executable.
30582 It will always output the filename, but only when @value{GDBN} can find
30583 the absolute file name of a source file, will it output the fullname.
30585 @subsubheading @value{GDBN} Command
30587 The @value{GDBN} equivalent is @samp{info sources}.
30588 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30590 @subsubheading Example
30593 -file-list-exec-source-files
30595 @{file=foo.c,fullname=/home/foo.c@},
30596 @{file=/home/bar.c,fullname=/home/bar.c@},
30597 @{file=gdb_could_not_find_fullpath.c@}]
30602 @subheading The @code{-file-list-shared-libraries} Command
30603 @findex -file-list-shared-libraries
30605 @subsubheading Synopsis
30608 -file-list-shared-libraries
30611 List the shared libraries in the program.
30613 @subsubheading @value{GDBN} Command
30615 The corresponding @value{GDBN} command is @samp{info shared}.
30617 @subsubheading Example
30621 @subheading The @code{-file-list-symbol-files} Command
30622 @findex -file-list-symbol-files
30624 @subsubheading Synopsis
30627 -file-list-symbol-files
30632 @subsubheading @value{GDBN} Command
30634 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30636 @subsubheading Example
30641 @subheading The @code{-file-symbol-file} Command
30642 @findex -file-symbol-file
30644 @subsubheading Synopsis
30647 -file-symbol-file @var{file}
30650 Read symbol table info from the specified @var{file} argument. When
30651 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30652 produced, except for a completion notification.
30654 @subsubheading @value{GDBN} Command
30656 The corresponding @value{GDBN} command is @samp{symbol-file}.
30658 @subsubheading Example
30662 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30668 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30669 @node GDB/MI Memory Overlay Commands
30670 @section @sc{gdb/mi} Memory Overlay Commands
30672 The memory overlay commands are not implemented.
30674 @c @subheading -overlay-auto
30676 @c @subheading -overlay-list-mapping-state
30678 @c @subheading -overlay-list-overlays
30680 @c @subheading -overlay-map
30682 @c @subheading -overlay-off
30684 @c @subheading -overlay-on
30686 @c @subheading -overlay-unmap
30688 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30689 @node GDB/MI Signal Handling Commands
30690 @section @sc{gdb/mi} Signal Handling Commands
30692 Signal handling commands are not implemented.
30694 @c @subheading -signal-handle
30696 @c @subheading -signal-list-handle-actions
30698 @c @subheading -signal-list-signal-types
30702 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30703 @node GDB/MI Target Manipulation
30704 @section @sc{gdb/mi} Target Manipulation Commands
30707 @subheading The @code{-target-attach} Command
30708 @findex -target-attach
30710 @subsubheading Synopsis
30713 -target-attach @var{pid} | @var{gid} | @var{file}
30716 Attach to a process @var{pid} or a file @var{file} outside of
30717 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30718 group, the id previously returned by
30719 @samp{-list-thread-groups --available} must be used.
30721 @subsubheading @value{GDBN} Command
30723 The corresponding @value{GDBN} command is @samp{attach}.
30725 @subsubheading Example
30729 =thread-created,id="1"
30730 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30736 @subheading The @code{-target-compare-sections} Command
30737 @findex -target-compare-sections
30739 @subsubheading Synopsis
30742 -target-compare-sections [ @var{section} ]
30745 Compare data of section @var{section} on target to the exec file.
30746 Without the argument, all sections are compared.
30748 @subsubheading @value{GDBN} Command
30750 The @value{GDBN} equivalent is @samp{compare-sections}.
30752 @subsubheading Example
30757 @subheading The @code{-target-detach} Command
30758 @findex -target-detach
30760 @subsubheading Synopsis
30763 -target-detach [ @var{pid} | @var{gid} ]
30766 Detach from the remote target which normally resumes its execution.
30767 If either @var{pid} or @var{gid} is specified, detaches from either
30768 the specified process, or specified thread group. There's no output.
30770 @subsubheading @value{GDBN} Command
30772 The corresponding @value{GDBN} command is @samp{detach}.
30774 @subsubheading Example
30784 @subheading The @code{-target-disconnect} Command
30785 @findex -target-disconnect
30787 @subsubheading Synopsis
30793 Disconnect from the remote target. There's no output and the target is
30794 generally not resumed.
30796 @subsubheading @value{GDBN} Command
30798 The corresponding @value{GDBN} command is @samp{disconnect}.
30800 @subsubheading Example
30810 @subheading The @code{-target-download} Command
30811 @findex -target-download
30813 @subsubheading Synopsis
30819 Loads the executable onto the remote target.
30820 It prints out an update message every half second, which includes the fields:
30824 The name of the section.
30826 The size of what has been sent so far for that section.
30828 The size of the section.
30830 The total size of what was sent so far (the current and the previous sections).
30832 The size of the overall executable to download.
30836 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30837 @sc{gdb/mi} Output Syntax}).
30839 In addition, it prints the name and size of the sections, as they are
30840 downloaded. These messages include the following fields:
30844 The name of the section.
30846 The size of the section.
30848 The size of the overall executable to download.
30852 At the end, a summary is printed.
30854 @subsubheading @value{GDBN} Command
30856 The corresponding @value{GDBN} command is @samp{load}.
30858 @subsubheading Example
30860 Note: each status message appears on a single line. Here the messages
30861 have been broken down so that they can fit onto a page.
30866 +download,@{section=".text",section-size="6668",total-size="9880"@}
30867 +download,@{section=".text",section-sent="512",section-size="6668",
30868 total-sent="512",total-size="9880"@}
30869 +download,@{section=".text",section-sent="1024",section-size="6668",
30870 total-sent="1024",total-size="9880"@}
30871 +download,@{section=".text",section-sent="1536",section-size="6668",
30872 total-sent="1536",total-size="9880"@}
30873 +download,@{section=".text",section-sent="2048",section-size="6668",
30874 total-sent="2048",total-size="9880"@}
30875 +download,@{section=".text",section-sent="2560",section-size="6668",
30876 total-sent="2560",total-size="9880"@}
30877 +download,@{section=".text",section-sent="3072",section-size="6668",
30878 total-sent="3072",total-size="9880"@}
30879 +download,@{section=".text",section-sent="3584",section-size="6668",
30880 total-sent="3584",total-size="9880"@}
30881 +download,@{section=".text",section-sent="4096",section-size="6668",
30882 total-sent="4096",total-size="9880"@}
30883 +download,@{section=".text",section-sent="4608",section-size="6668",
30884 total-sent="4608",total-size="9880"@}
30885 +download,@{section=".text",section-sent="5120",section-size="6668",
30886 total-sent="5120",total-size="9880"@}
30887 +download,@{section=".text",section-sent="5632",section-size="6668",
30888 total-sent="5632",total-size="9880"@}
30889 +download,@{section=".text",section-sent="6144",section-size="6668",
30890 total-sent="6144",total-size="9880"@}
30891 +download,@{section=".text",section-sent="6656",section-size="6668",
30892 total-sent="6656",total-size="9880"@}
30893 +download,@{section=".init",section-size="28",total-size="9880"@}
30894 +download,@{section=".fini",section-size="28",total-size="9880"@}
30895 +download,@{section=".data",section-size="3156",total-size="9880"@}
30896 +download,@{section=".data",section-sent="512",section-size="3156",
30897 total-sent="7236",total-size="9880"@}
30898 +download,@{section=".data",section-sent="1024",section-size="3156",
30899 total-sent="7748",total-size="9880"@}
30900 +download,@{section=".data",section-sent="1536",section-size="3156",
30901 total-sent="8260",total-size="9880"@}
30902 +download,@{section=".data",section-sent="2048",section-size="3156",
30903 total-sent="8772",total-size="9880"@}
30904 +download,@{section=".data",section-sent="2560",section-size="3156",
30905 total-sent="9284",total-size="9880"@}
30906 +download,@{section=".data",section-sent="3072",section-size="3156",
30907 total-sent="9796",total-size="9880"@}
30908 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30915 @subheading The @code{-target-exec-status} Command
30916 @findex -target-exec-status
30918 @subsubheading Synopsis
30921 -target-exec-status
30924 Provide information on the state of the target (whether it is running or
30925 not, for instance).
30927 @subsubheading @value{GDBN} Command
30929 There's no equivalent @value{GDBN} command.
30931 @subsubheading Example
30935 @subheading The @code{-target-list-available-targets} Command
30936 @findex -target-list-available-targets
30938 @subsubheading Synopsis
30941 -target-list-available-targets
30944 List the possible targets to connect to.
30946 @subsubheading @value{GDBN} Command
30948 The corresponding @value{GDBN} command is @samp{help target}.
30950 @subsubheading Example
30954 @subheading The @code{-target-list-current-targets} Command
30955 @findex -target-list-current-targets
30957 @subsubheading Synopsis
30960 -target-list-current-targets
30963 Describe the current target.
30965 @subsubheading @value{GDBN} Command
30967 The corresponding information is printed by @samp{info file} (among
30970 @subsubheading Example
30974 @subheading The @code{-target-list-parameters} Command
30975 @findex -target-list-parameters
30977 @subsubheading Synopsis
30980 -target-list-parameters
30986 @subsubheading @value{GDBN} Command
30990 @subsubheading Example
30994 @subheading The @code{-target-select} Command
30995 @findex -target-select
30997 @subsubheading Synopsis
31000 -target-select @var{type} @var{parameters @dots{}}
31003 Connect @value{GDBN} to the remote target. This command takes two args:
31007 The type of target, for instance @samp{remote}, etc.
31008 @item @var{parameters}
31009 Device names, host names and the like. @xref{Target Commands, ,
31010 Commands for Managing Targets}, for more details.
31013 The output is a connection notification, followed by the address at
31014 which the target program is, in the following form:
31017 ^connected,addr="@var{address}",func="@var{function name}",
31018 args=[@var{arg list}]
31021 @subsubheading @value{GDBN} Command
31023 The corresponding @value{GDBN} command is @samp{target}.
31025 @subsubheading Example
31029 -target-select remote /dev/ttya
31030 ^connected,addr="0xfe00a300",func="??",args=[]
31034 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31035 @node GDB/MI File Transfer Commands
31036 @section @sc{gdb/mi} File Transfer Commands
31039 @subheading The @code{-target-file-put} Command
31040 @findex -target-file-put
31042 @subsubheading Synopsis
31045 -target-file-put @var{hostfile} @var{targetfile}
31048 Copy file @var{hostfile} from the host system (the machine running
31049 @value{GDBN}) to @var{targetfile} on the target system.
31051 @subsubheading @value{GDBN} Command
31053 The corresponding @value{GDBN} command is @samp{remote put}.
31055 @subsubheading Example
31059 -target-file-put localfile remotefile
31065 @subheading The @code{-target-file-get} Command
31066 @findex -target-file-get
31068 @subsubheading Synopsis
31071 -target-file-get @var{targetfile} @var{hostfile}
31074 Copy file @var{targetfile} from the target system to @var{hostfile}
31075 on the host system.
31077 @subsubheading @value{GDBN} Command
31079 The corresponding @value{GDBN} command is @samp{remote get}.
31081 @subsubheading Example
31085 -target-file-get remotefile localfile
31091 @subheading The @code{-target-file-delete} Command
31092 @findex -target-file-delete
31094 @subsubheading Synopsis
31097 -target-file-delete @var{targetfile}
31100 Delete @var{targetfile} from the target system.
31102 @subsubheading @value{GDBN} Command
31104 The corresponding @value{GDBN} command is @samp{remote delete}.
31106 @subsubheading Example
31110 -target-file-delete remotefile
31116 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31117 @node GDB/MI Miscellaneous Commands
31118 @section Miscellaneous @sc{gdb/mi} Commands
31120 @c @subheading -gdb-complete
31122 @subheading The @code{-gdb-exit} Command
31125 @subsubheading Synopsis
31131 Exit @value{GDBN} immediately.
31133 @subsubheading @value{GDBN} Command
31135 Approximately corresponds to @samp{quit}.
31137 @subsubheading Example
31147 @subheading The @code{-exec-abort} Command
31148 @findex -exec-abort
31150 @subsubheading Synopsis
31156 Kill the inferior running program.
31158 @subsubheading @value{GDBN} Command
31160 The corresponding @value{GDBN} command is @samp{kill}.
31162 @subsubheading Example
31167 @subheading The @code{-gdb-set} Command
31170 @subsubheading Synopsis
31176 Set an internal @value{GDBN} variable.
31177 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31179 @subsubheading @value{GDBN} Command
31181 The corresponding @value{GDBN} command is @samp{set}.
31183 @subsubheading Example
31193 @subheading The @code{-gdb-show} Command
31196 @subsubheading Synopsis
31202 Show the current value of a @value{GDBN} variable.
31204 @subsubheading @value{GDBN} Command
31206 The corresponding @value{GDBN} command is @samp{show}.
31208 @subsubheading Example
31217 @c @subheading -gdb-source
31220 @subheading The @code{-gdb-version} Command
31221 @findex -gdb-version
31223 @subsubheading Synopsis
31229 Show version information for @value{GDBN}. Used mostly in testing.
31231 @subsubheading @value{GDBN} Command
31233 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31234 default shows this information when you start an interactive session.
31236 @subsubheading Example
31238 @c This example modifies the actual output from GDB to avoid overfull
31244 ~Copyright 2000 Free Software Foundation, Inc.
31245 ~GDB is free software, covered by the GNU General Public License, and
31246 ~you are welcome to change it and/or distribute copies of it under
31247 ~ certain conditions.
31248 ~Type "show copying" to see the conditions.
31249 ~There is absolutely no warranty for GDB. Type "show warranty" for
31251 ~This GDB was configured as
31252 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31257 @subheading The @code{-list-features} Command
31258 @findex -list-features
31260 Returns a list of particular features of the MI protocol that
31261 this version of gdb implements. A feature can be a command,
31262 or a new field in an output of some command, or even an
31263 important bugfix. While a frontend can sometimes detect presence
31264 of a feature at runtime, it is easier to perform detection at debugger
31267 The command returns a list of strings, with each string naming an
31268 available feature. Each returned string is just a name, it does not
31269 have any internal structure. The list of possible feature names
31275 (gdb) -list-features
31276 ^done,result=["feature1","feature2"]
31279 The current list of features is:
31282 @item frozen-varobjs
31283 Indicates support for the @code{-var-set-frozen} command, as well
31284 as possible presense of the @code{frozen} field in the output
31285 of @code{-varobj-create}.
31286 @item pending-breakpoints
31287 Indicates support for the @option{-f} option to the @code{-break-insert}
31290 Indicates Python scripting support, Python-based
31291 pretty-printing commands, and possible presence of the
31292 @samp{display_hint} field in the output of @code{-var-list-children}
31294 Indicates support for the @code{-thread-info} command.
31295 @item data-read-memory-bytes
31296 Indicates support for the @code{-data-read-memory-bytes} and the
31297 @code{-data-write-memory-bytes} commands.
31298 @item breakpoint-notifications
31299 Indicates that changes to breakpoints and breakpoints created via the
31300 CLI will be announced via async records.
31301 @item ada-task-info
31302 Indicates support for the @code{-ada-task-info} command.
31305 @subheading The @code{-list-target-features} Command
31306 @findex -list-target-features
31308 Returns a list of particular features that are supported by the
31309 target. Those features affect the permitted MI commands, but
31310 unlike the features reported by the @code{-list-features} command, the
31311 features depend on which target GDB is using at the moment. Whenever
31312 a target can change, due to commands such as @code{-target-select},
31313 @code{-target-attach} or @code{-exec-run}, the list of target features
31314 may change, and the frontend should obtain it again.
31318 (gdb) -list-features
31319 ^done,result=["async"]
31322 The current list of features is:
31326 Indicates that the target is capable of asynchronous command
31327 execution, which means that @value{GDBN} will accept further commands
31328 while the target is running.
31331 Indicates that the target is capable of reverse execution.
31332 @xref{Reverse Execution}, for more information.
31336 @subheading The @code{-list-thread-groups} Command
31337 @findex -list-thread-groups
31339 @subheading Synopsis
31342 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31345 Lists thread groups (@pxref{Thread groups}). When a single thread
31346 group is passed as the argument, lists the children of that group.
31347 When several thread group are passed, lists information about those
31348 thread groups. Without any parameters, lists information about all
31349 top-level thread groups.
31351 Normally, thread groups that are being debugged are reported.
31352 With the @samp{--available} option, @value{GDBN} reports thread groups
31353 available on the target.
31355 The output of this command may have either a @samp{threads} result or
31356 a @samp{groups} result. The @samp{thread} result has a list of tuples
31357 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31358 Information}). The @samp{groups} result has a list of tuples as value,
31359 each tuple describing a thread group. If top-level groups are
31360 requested (that is, no parameter is passed), or when several groups
31361 are passed, the output always has a @samp{groups} result. The format
31362 of the @samp{group} result is described below.
31364 To reduce the number of roundtrips it's possible to list thread groups
31365 together with their children, by passing the @samp{--recurse} option
31366 and the recursion depth. Presently, only recursion depth of 1 is
31367 permitted. If this option is present, then every reported thread group
31368 will also include its children, either as @samp{group} or
31369 @samp{threads} field.
31371 In general, any combination of option and parameters is permitted, with
31372 the following caveats:
31376 When a single thread group is passed, the output will typically
31377 be the @samp{threads} result. Because threads may not contain
31378 anything, the @samp{recurse} option will be ignored.
31381 When the @samp{--available} option is passed, limited information may
31382 be available. In particular, the list of threads of a process might
31383 be inaccessible. Further, specifying specific thread groups might
31384 not give any performance advantage over listing all thread groups.
31385 The frontend should assume that @samp{-list-thread-groups --available}
31386 is always an expensive operation and cache the results.
31390 The @samp{groups} result is a list of tuples, where each tuple may
31391 have the following fields:
31395 Identifier of the thread group. This field is always present.
31396 The identifier is an opaque string; frontends should not try to
31397 convert it to an integer, even though it might look like one.
31400 The type of the thread group. At present, only @samp{process} is a
31404 The target-specific process identifier. This field is only present
31405 for thread groups of type @samp{process} and only if the process exists.
31408 The number of children this thread group has. This field may be
31409 absent for an available thread group.
31412 This field has a list of tuples as value, each tuple describing a
31413 thread. It may be present if the @samp{--recurse} option is
31414 specified, and it's actually possible to obtain the threads.
31417 This field is a list of integers, each identifying a core that one
31418 thread of the group is running on. This field may be absent if
31419 such information is not available.
31422 The name of the executable file that corresponds to this thread group.
31423 The field is only present for thread groups of type @samp{process},
31424 and only if there is a corresponding executable file.
31428 @subheading Example
31432 -list-thread-groups
31433 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31434 -list-thread-groups 17
31435 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31436 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31437 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31438 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31439 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31440 -list-thread-groups --available
31441 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31442 -list-thread-groups --available --recurse 1
31443 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31444 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31445 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31446 -list-thread-groups --available --recurse 1 17 18
31447 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31448 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31449 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31453 @subheading The @code{-add-inferior} Command
31454 @findex -add-inferior
31456 @subheading Synopsis
31462 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31463 inferior is not associated with any executable. Such association may
31464 be established with the @samp{-file-exec-and-symbols} command
31465 (@pxref{GDB/MI File Commands}). The command response has a single
31466 field, @samp{thread-group}, whose value is the identifier of the
31467 thread group corresponding to the new inferior.
31469 @subheading Example
31474 ^done,thread-group="i3"
31477 @subheading The @code{-interpreter-exec} Command
31478 @findex -interpreter-exec
31480 @subheading Synopsis
31483 -interpreter-exec @var{interpreter} @var{command}
31485 @anchor{-interpreter-exec}
31487 Execute the specified @var{command} in the given @var{interpreter}.
31489 @subheading @value{GDBN} Command
31491 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31493 @subheading Example
31497 -interpreter-exec console "break main"
31498 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31499 &"During symbol reading, bad structure-type format.\n"
31500 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31505 @subheading The @code{-inferior-tty-set} Command
31506 @findex -inferior-tty-set
31508 @subheading Synopsis
31511 -inferior-tty-set /dev/pts/1
31514 Set terminal for future runs of the program being debugged.
31516 @subheading @value{GDBN} Command
31518 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31520 @subheading Example
31524 -inferior-tty-set /dev/pts/1
31529 @subheading The @code{-inferior-tty-show} Command
31530 @findex -inferior-tty-show
31532 @subheading Synopsis
31538 Show terminal for future runs of program being debugged.
31540 @subheading @value{GDBN} Command
31542 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31544 @subheading Example
31548 -inferior-tty-set /dev/pts/1
31552 ^done,inferior_tty_terminal="/dev/pts/1"
31556 @subheading The @code{-enable-timings} Command
31557 @findex -enable-timings
31559 @subheading Synopsis
31562 -enable-timings [yes | no]
31565 Toggle the printing of the wallclock, user and system times for an MI
31566 command as a field in its output. This command is to help frontend
31567 developers optimize the performance of their code. No argument is
31568 equivalent to @samp{yes}.
31570 @subheading @value{GDBN} Command
31574 @subheading Example
31582 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31583 addr="0x080484ed",func="main",file="myprog.c",
31584 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31585 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31593 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31594 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31595 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31596 fullname="/home/nickrob/myprog.c",line="73"@}
31601 @chapter @value{GDBN} Annotations
31603 This chapter describes annotations in @value{GDBN}. Annotations were
31604 designed to interface @value{GDBN} to graphical user interfaces or other
31605 similar programs which want to interact with @value{GDBN} at a
31606 relatively high level.
31608 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31612 This is Edition @value{EDITION}, @value{DATE}.
31616 * Annotations Overview:: What annotations are; the general syntax.
31617 * Server Prefix:: Issuing a command without affecting user state.
31618 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31619 * Errors:: Annotations for error messages.
31620 * Invalidation:: Some annotations describe things now invalid.
31621 * Annotations for Running::
31622 Whether the program is running, how it stopped, etc.
31623 * Source Annotations:: Annotations describing source code.
31626 @node Annotations Overview
31627 @section What is an Annotation?
31628 @cindex annotations
31630 Annotations start with a newline character, two @samp{control-z}
31631 characters, and the name of the annotation. If there is no additional
31632 information associated with this annotation, the name of the annotation
31633 is followed immediately by a newline. If there is additional
31634 information, the name of the annotation is followed by a space, the
31635 additional information, and a newline. The additional information
31636 cannot contain newline characters.
31638 Any output not beginning with a newline and two @samp{control-z}
31639 characters denotes literal output from @value{GDBN}. Currently there is
31640 no need for @value{GDBN} to output a newline followed by two
31641 @samp{control-z} characters, but if there was such a need, the
31642 annotations could be extended with an @samp{escape} annotation which
31643 means those three characters as output.
31645 The annotation @var{level}, which is specified using the
31646 @option{--annotate} command line option (@pxref{Mode Options}), controls
31647 how much information @value{GDBN} prints together with its prompt,
31648 values of expressions, source lines, and other types of output. Level 0
31649 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31650 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31651 for programs that control @value{GDBN}, and level 2 annotations have
31652 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31653 Interface, annotate, GDB's Obsolete Annotations}).
31656 @kindex set annotate
31657 @item set annotate @var{level}
31658 The @value{GDBN} command @code{set annotate} sets the level of
31659 annotations to the specified @var{level}.
31661 @item show annotate
31662 @kindex show annotate
31663 Show the current annotation level.
31666 This chapter describes level 3 annotations.
31668 A simple example of starting up @value{GDBN} with annotations is:
31671 $ @kbd{gdb --annotate=3}
31673 Copyright 2003 Free Software Foundation, Inc.
31674 GDB is free software, covered by the GNU General Public License,
31675 and you are welcome to change it and/or distribute copies of it
31676 under certain conditions.
31677 Type "show copying" to see the conditions.
31678 There is absolutely no warranty for GDB. Type "show warranty"
31680 This GDB was configured as "i386-pc-linux-gnu"
31691 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31692 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31693 denotes a @samp{control-z} character) are annotations; the rest is
31694 output from @value{GDBN}.
31696 @node Server Prefix
31697 @section The Server Prefix
31698 @cindex server prefix
31700 If you prefix a command with @samp{server } then it will not affect
31701 the command history, nor will it affect @value{GDBN}'s notion of which
31702 command to repeat if @key{RET} is pressed on a line by itself. This
31703 means that commands can be run behind a user's back by a front-end in
31704 a transparent manner.
31706 The @code{server } prefix does not affect the recording of values into
31707 the value history; to print a value without recording it into the
31708 value history, use the @code{output} command instead of the
31709 @code{print} command.
31711 Using this prefix also disables confirmation requests
31712 (@pxref{confirmation requests}).
31715 @section Annotation for @value{GDBN} Input
31717 @cindex annotations for prompts
31718 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31719 to know when to send output, when the output from a given command is
31722 Different kinds of input each have a different @dfn{input type}. Each
31723 input type has three annotations: a @code{pre-} annotation, which
31724 denotes the beginning of any prompt which is being output, a plain
31725 annotation, which denotes the end of the prompt, and then a @code{post-}
31726 annotation which denotes the end of any echo which may (or may not) be
31727 associated with the input. For example, the @code{prompt} input type
31728 features the following annotations:
31736 The input types are
31739 @findex pre-prompt annotation
31740 @findex prompt annotation
31741 @findex post-prompt annotation
31743 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31745 @findex pre-commands annotation
31746 @findex commands annotation
31747 @findex post-commands annotation
31749 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31750 command. The annotations are repeated for each command which is input.
31752 @findex pre-overload-choice annotation
31753 @findex overload-choice annotation
31754 @findex post-overload-choice annotation
31755 @item overload-choice
31756 When @value{GDBN} wants the user to select between various overloaded functions.
31758 @findex pre-query annotation
31759 @findex query annotation
31760 @findex post-query annotation
31762 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31764 @findex pre-prompt-for-continue annotation
31765 @findex prompt-for-continue annotation
31766 @findex post-prompt-for-continue annotation
31767 @item prompt-for-continue
31768 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31769 expect this to work well; instead use @code{set height 0} to disable
31770 prompting. This is because the counting of lines is buggy in the
31771 presence of annotations.
31776 @cindex annotations for errors, warnings and interrupts
31778 @findex quit annotation
31783 This annotation occurs right before @value{GDBN} responds to an interrupt.
31785 @findex error annotation
31790 This annotation occurs right before @value{GDBN} responds to an error.
31792 Quit and error annotations indicate that any annotations which @value{GDBN} was
31793 in the middle of may end abruptly. For example, if a
31794 @code{value-history-begin} annotation is followed by a @code{error}, one
31795 cannot expect to receive the matching @code{value-history-end}. One
31796 cannot expect not to receive it either, however; an error annotation
31797 does not necessarily mean that @value{GDBN} is immediately returning all the way
31800 @findex error-begin annotation
31801 A quit or error annotation may be preceded by
31807 Any output between that and the quit or error annotation is the error
31810 Warning messages are not yet annotated.
31811 @c If we want to change that, need to fix warning(), type_error(),
31812 @c range_error(), and possibly other places.
31815 @section Invalidation Notices
31817 @cindex annotations for invalidation messages
31818 The following annotations say that certain pieces of state may have
31822 @findex frames-invalid annotation
31823 @item ^Z^Zframes-invalid
31825 The frames (for example, output from the @code{backtrace} command) may
31828 @findex breakpoints-invalid annotation
31829 @item ^Z^Zbreakpoints-invalid
31831 The breakpoints may have changed. For example, the user just added or
31832 deleted a breakpoint.
31835 @node Annotations for Running
31836 @section Running the Program
31837 @cindex annotations for running programs
31839 @findex starting annotation
31840 @findex stopping annotation
31841 When the program starts executing due to a @value{GDBN} command such as
31842 @code{step} or @code{continue},
31848 is output. When the program stops,
31854 is output. Before the @code{stopped} annotation, a variety of
31855 annotations describe how the program stopped.
31858 @findex exited annotation
31859 @item ^Z^Zexited @var{exit-status}
31860 The program exited, and @var{exit-status} is the exit status (zero for
31861 successful exit, otherwise nonzero).
31863 @findex signalled annotation
31864 @findex signal-name annotation
31865 @findex signal-name-end annotation
31866 @findex signal-string annotation
31867 @findex signal-string-end annotation
31868 @item ^Z^Zsignalled
31869 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31870 annotation continues:
31876 ^Z^Zsignal-name-end
31880 ^Z^Zsignal-string-end
31885 where @var{name} is the name of the signal, such as @code{SIGILL} or
31886 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31887 as @code{Illegal Instruction} or @code{Segmentation fault}.
31888 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31889 user's benefit and have no particular format.
31891 @findex signal annotation
31893 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31894 just saying that the program received the signal, not that it was
31895 terminated with it.
31897 @findex breakpoint annotation
31898 @item ^Z^Zbreakpoint @var{number}
31899 The program hit breakpoint number @var{number}.
31901 @findex watchpoint annotation
31902 @item ^Z^Zwatchpoint @var{number}
31903 The program hit watchpoint number @var{number}.
31906 @node Source Annotations
31907 @section Displaying Source
31908 @cindex annotations for source display
31910 @findex source annotation
31911 The following annotation is used instead of displaying source code:
31914 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31917 where @var{filename} is an absolute file name indicating which source
31918 file, @var{line} is the line number within that file (where 1 is the
31919 first line in the file), @var{character} is the character position
31920 within the file (where 0 is the first character in the file) (for most
31921 debug formats this will necessarily point to the beginning of a line),
31922 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31923 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31924 @var{addr} is the address in the target program associated with the
31925 source which is being displayed. @var{addr} is in the form @samp{0x}
31926 followed by one or more lowercase hex digits (note that this does not
31927 depend on the language).
31929 @node JIT Interface
31930 @chapter JIT Compilation Interface
31931 @cindex just-in-time compilation
31932 @cindex JIT compilation interface
31934 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31935 interface. A JIT compiler is a program or library that generates native
31936 executable code at runtime and executes it, usually in order to achieve good
31937 performance while maintaining platform independence.
31939 Programs that use JIT compilation are normally difficult to debug because
31940 portions of their code are generated at runtime, instead of being loaded from
31941 object files, which is where @value{GDBN} normally finds the program's symbols
31942 and debug information. In order to debug programs that use JIT compilation,
31943 @value{GDBN} has an interface that allows the program to register in-memory
31944 symbol files with @value{GDBN} at runtime.
31946 If you are using @value{GDBN} to debug a program that uses this interface, then
31947 it should work transparently so long as you have not stripped the binary. If
31948 you are developing a JIT compiler, then the interface is documented in the rest
31949 of this chapter. At this time, the only known client of this interface is the
31952 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31953 JIT compiler communicates with @value{GDBN} by writing data into a global
31954 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31955 attaches, it reads a linked list of symbol files from the global variable to
31956 find existing code, and puts a breakpoint in the function so that it can find
31957 out about additional code.
31960 * Declarations:: Relevant C struct declarations
31961 * Registering Code:: Steps to register code
31962 * Unregistering Code:: Steps to unregister code
31963 * Custom Debug Info:: Emit debug information in a custom format
31967 @section JIT Declarations
31969 These are the relevant struct declarations that a C program should include to
31970 implement the interface:
31980 struct jit_code_entry
31982 struct jit_code_entry *next_entry;
31983 struct jit_code_entry *prev_entry;
31984 const char *symfile_addr;
31985 uint64_t symfile_size;
31988 struct jit_descriptor
31991 /* This type should be jit_actions_t, but we use uint32_t
31992 to be explicit about the bitwidth. */
31993 uint32_t action_flag;
31994 struct jit_code_entry *relevant_entry;
31995 struct jit_code_entry *first_entry;
31998 /* GDB puts a breakpoint in this function. */
31999 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32001 /* Make sure to specify the version statically, because the
32002 debugger may check the version before we can set it. */
32003 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32006 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32007 modifications to this global data properly, which can easily be done by putting
32008 a global mutex around modifications to these structures.
32010 @node Registering Code
32011 @section Registering Code
32013 To register code with @value{GDBN}, the JIT should follow this protocol:
32017 Generate an object file in memory with symbols and other desired debug
32018 information. The file must include the virtual addresses of the sections.
32021 Create a code entry for the file, which gives the start and size of the symbol
32025 Add it to the linked list in the JIT descriptor.
32028 Point the relevant_entry field of the descriptor at the entry.
32031 Set @code{action_flag} to @code{JIT_REGISTER} and call
32032 @code{__jit_debug_register_code}.
32035 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32036 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32037 new code. However, the linked list must still be maintained in order to allow
32038 @value{GDBN} to attach to a running process and still find the symbol files.
32040 @node Unregistering Code
32041 @section Unregistering Code
32043 If code is freed, then the JIT should use the following protocol:
32047 Remove the code entry corresponding to the code from the linked list.
32050 Point the @code{relevant_entry} field of the descriptor at the code entry.
32053 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32054 @code{__jit_debug_register_code}.
32057 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32058 and the JIT will leak the memory used for the associated symbol files.
32060 @node Custom Debug Info
32061 @section Custom Debug Info
32062 @cindex custom JIT debug info
32063 @cindex JIT debug info reader
32065 Generating debug information in platform-native file formats (like ELF
32066 or COFF) may be an overkill for JIT compilers; especially if all the
32067 debug info is used for is displaying a meaningful backtrace. The
32068 issue can be resolved by having the JIT writers decide on a debug info
32069 format and also provide a reader that parses the debug info generated
32070 by the JIT compiler. This section gives a brief overview on writing
32071 such a parser. More specific details can be found in the source file
32072 @file{gdb/jit-reader.in}, which is also installed as a header at
32073 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32075 The reader is implemented as a shared object (so this functionality is
32076 not available on platforms which don't allow loading shared objects at
32077 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32078 @code{jit-reader-unload} are provided, to be used to load and unload
32079 the readers from a preconfigured directory. Once loaded, the shared
32080 object is used the parse the debug information emitted by the JIT
32084 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32085 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32088 @node Using JIT Debug Info Readers
32089 @subsection Using JIT Debug Info Readers
32090 @kindex jit-reader-load
32091 @kindex jit-reader-unload
32093 Readers can be loaded and unloaded using the @code{jit-reader-load}
32094 and @code{jit-reader-unload} commands.
32097 @item jit-reader-load @var{reader-name}
32098 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32099 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32100 @var{libdir} is the system library directory, usually
32101 @file{/usr/local/lib}. Only one reader can be active at a time;
32102 trying to load a second reader when one is already loaded will result
32103 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32104 first unloading the current one using @code{jit-reader-load} and then
32105 invoking @code{jit-reader-load}.
32107 @item jit-reader-unload
32108 Unload the currently loaded JIT reader.
32112 @node Writing JIT Debug Info Readers
32113 @subsection Writing JIT Debug Info Readers
32114 @cindex writing JIT debug info readers
32116 As mentioned, a reader is essentially a shared object conforming to a
32117 certain ABI. This ABI is described in @file{jit-reader.h}.
32119 @file{jit-reader.h} defines the structures, macros and functions
32120 required to write a reader. It is installed (along with
32121 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32122 the system include directory.
32124 Readers need to be released under a GPL compatible license. A reader
32125 can be declared as released under such a license by placing the macro
32126 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32128 The entry point for readers is the symbol @code{gdb_init_reader},
32129 which is expected to be a function with the prototype
32131 @findex gdb_init_reader
32133 extern struct gdb_reader_funcs *gdb_init_reader (void);
32136 @cindex @code{struct gdb_reader_funcs}
32138 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32139 functions. These functions are executed to read the debug info
32140 generated by the JIT compiler (@code{read}), to unwind stack frames
32141 (@code{unwind}) and to create canonical frame IDs
32142 (@code{get_Frame_id}). It also has a callback that is called when the
32143 reader is being unloaded (@code{destroy}). The struct looks like this
32146 struct gdb_reader_funcs
32148 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32149 int reader_version;
32151 /* For use by the reader. */
32154 gdb_read_debug_info *read;
32155 gdb_unwind_frame *unwind;
32156 gdb_get_frame_id *get_frame_id;
32157 gdb_destroy_reader *destroy;
32161 @cindex @code{struct gdb_symbol_callbacks}
32162 @cindex @code{struct gdb_unwind_callbacks}
32164 The callbacks are provided with another set of callbacks by
32165 @value{GDBN} to do their job. For @code{read}, these callbacks are
32166 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32167 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32168 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32169 files and new symbol tables inside those object files. @code{struct
32170 gdb_unwind_callbacks} has callbacks to read registers off the current
32171 frame and to write out the values of the registers in the previous
32172 frame. Both have a callback (@code{target_read}) to read bytes off the
32173 target's address space.
32176 @chapter Reporting Bugs in @value{GDBN}
32177 @cindex bugs in @value{GDBN}
32178 @cindex reporting bugs in @value{GDBN}
32180 Your bug reports play an essential role in making @value{GDBN} reliable.
32182 Reporting a bug may help you by bringing a solution to your problem, or it
32183 may not. But in any case the principal function of a bug report is to help
32184 the entire community by making the next version of @value{GDBN} work better. Bug
32185 reports are your contribution to the maintenance of @value{GDBN}.
32187 In order for a bug report to serve its purpose, you must include the
32188 information that enables us to fix the bug.
32191 * Bug Criteria:: Have you found a bug?
32192 * Bug Reporting:: How to report bugs
32196 @section Have You Found a Bug?
32197 @cindex bug criteria
32199 If you are not sure whether you have found a bug, here are some guidelines:
32202 @cindex fatal signal
32203 @cindex debugger crash
32204 @cindex crash of debugger
32206 If the debugger gets a fatal signal, for any input whatever, that is a
32207 @value{GDBN} bug. Reliable debuggers never crash.
32209 @cindex error on valid input
32211 If @value{GDBN} produces an error message for valid input, that is a
32212 bug. (Note that if you're cross debugging, the problem may also be
32213 somewhere in the connection to the target.)
32215 @cindex invalid input
32217 If @value{GDBN} does not produce an error message for invalid input,
32218 that is a bug. However, you should note that your idea of
32219 ``invalid input'' might be our idea of ``an extension'' or ``support
32220 for traditional practice''.
32223 If you are an experienced user of debugging tools, your suggestions
32224 for improvement of @value{GDBN} are welcome in any case.
32227 @node Bug Reporting
32228 @section How to Report Bugs
32229 @cindex bug reports
32230 @cindex @value{GDBN} bugs, reporting
32232 A number of companies and individuals offer support for @sc{gnu} products.
32233 If you obtained @value{GDBN} from a support organization, we recommend you
32234 contact that organization first.
32236 You can find contact information for many support companies and
32237 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32239 @c should add a web page ref...
32242 @ifset BUGURL_DEFAULT
32243 In any event, we also recommend that you submit bug reports for
32244 @value{GDBN}. The preferred method is to submit them directly using
32245 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32246 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32249 @strong{Do not send bug reports to @samp{info-gdb}, or to
32250 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32251 not want to receive bug reports. Those that do have arranged to receive
32254 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32255 serves as a repeater. The mailing list and the newsgroup carry exactly
32256 the same messages. Often people think of posting bug reports to the
32257 newsgroup instead of mailing them. This appears to work, but it has one
32258 problem which can be crucial: a newsgroup posting often lacks a mail
32259 path back to the sender. Thus, if we need to ask for more information,
32260 we may be unable to reach you. For this reason, it is better to send
32261 bug reports to the mailing list.
32263 @ifclear BUGURL_DEFAULT
32264 In any event, we also recommend that you submit bug reports for
32265 @value{GDBN} to @value{BUGURL}.
32269 The fundamental principle of reporting bugs usefully is this:
32270 @strong{report all the facts}. If you are not sure whether to state a
32271 fact or leave it out, state it!
32273 Often people omit facts because they think they know what causes the
32274 problem and assume that some details do not matter. Thus, you might
32275 assume that the name of the variable you use in an example does not matter.
32276 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32277 stray memory reference which happens to fetch from the location where that
32278 name is stored in memory; perhaps, if the name were different, the contents
32279 of that location would fool the debugger into doing the right thing despite
32280 the bug. Play it safe and give a specific, complete example. That is the
32281 easiest thing for you to do, and the most helpful.
32283 Keep in mind that the purpose of a bug report is to enable us to fix the
32284 bug. It may be that the bug has been reported previously, but neither
32285 you nor we can know that unless your bug report is complete and
32288 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32289 bell?'' Those bug reports are useless, and we urge everyone to
32290 @emph{refuse to respond to them} except to chide the sender to report
32293 To enable us to fix the bug, you should include all these things:
32297 The version of @value{GDBN}. @value{GDBN} announces it if you start
32298 with no arguments; you can also print it at any time using @code{show
32301 Without this, we will not know whether there is any point in looking for
32302 the bug in the current version of @value{GDBN}.
32305 The type of machine you are using, and the operating system name and
32309 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32310 ``@value{GCC}--2.8.1''.
32313 What compiler (and its version) was used to compile the program you are
32314 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32315 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32316 to get this information; for other compilers, see the documentation for
32320 The command arguments you gave the compiler to compile your example and
32321 observe the bug. For example, did you use @samp{-O}? To guarantee
32322 you will not omit something important, list them all. A copy of the
32323 Makefile (or the output from make) is sufficient.
32325 If we were to try to guess the arguments, we would probably guess wrong
32326 and then we might not encounter the bug.
32329 A complete input script, and all necessary source files, that will
32333 A description of what behavior you observe that you believe is
32334 incorrect. For example, ``It gets a fatal signal.''
32336 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32337 will certainly notice it. But if the bug is incorrect output, we might
32338 not notice unless it is glaringly wrong. You might as well not give us
32339 a chance to make a mistake.
32341 Even if the problem you experience is a fatal signal, you should still
32342 say so explicitly. Suppose something strange is going on, such as, your
32343 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32344 the C library on your system. (This has happened!) Your copy might
32345 crash and ours would not. If you told us to expect a crash, then when
32346 ours fails to crash, we would know that the bug was not happening for
32347 us. If you had not told us to expect a crash, then we would not be able
32348 to draw any conclusion from our observations.
32351 @cindex recording a session script
32352 To collect all this information, you can use a session recording program
32353 such as @command{script}, which is available on many Unix systems.
32354 Just run your @value{GDBN} session inside @command{script} and then
32355 include the @file{typescript} file with your bug report.
32357 Another way to record a @value{GDBN} session is to run @value{GDBN}
32358 inside Emacs and then save the entire buffer to a file.
32361 If you wish to suggest changes to the @value{GDBN} source, send us context
32362 diffs. If you even discuss something in the @value{GDBN} source, refer to
32363 it by context, not by line number.
32365 The line numbers in our development sources will not match those in your
32366 sources. Your line numbers would convey no useful information to us.
32370 Here are some things that are not necessary:
32374 A description of the envelope of the bug.
32376 Often people who encounter a bug spend a lot of time investigating
32377 which changes to the input file will make the bug go away and which
32378 changes will not affect it.
32380 This is often time consuming and not very useful, because the way we
32381 will find the bug is by running a single example under the debugger
32382 with breakpoints, not by pure deduction from a series of examples.
32383 We recommend that you save your time for something else.
32385 Of course, if you can find a simpler example to report @emph{instead}
32386 of the original one, that is a convenience for us. Errors in the
32387 output will be easier to spot, running under the debugger will take
32388 less time, and so on.
32390 However, simplification is not vital; if you do not want to do this,
32391 report the bug anyway and send us the entire test case you used.
32394 A patch for the bug.
32396 A patch for the bug does help us if it is a good one. But do not omit
32397 the necessary information, such as the test case, on the assumption that
32398 a patch is all we need. We might see problems with your patch and decide
32399 to fix the problem another way, or we might not understand it at all.
32401 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32402 construct an example that will make the program follow a certain path
32403 through the code. If you do not send us the example, we will not be able
32404 to construct one, so we will not be able to verify that the bug is fixed.
32406 And if we cannot understand what bug you are trying to fix, or why your
32407 patch should be an improvement, we will not install it. A test case will
32408 help us to understand.
32411 A guess about what the bug is or what it depends on.
32413 Such guesses are usually wrong. Even we cannot guess right about such
32414 things without first using the debugger to find the facts.
32417 @c The readline documentation is distributed with the readline code
32418 @c and consists of the two following files:
32421 @c Use -I with makeinfo to point to the appropriate directory,
32422 @c environment var TEXINPUTS with TeX.
32423 @ifclear SYSTEM_READLINE
32424 @include rluser.texi
32425 @include hsuser.texi
32429 @appendix In Memoriam
32431 The @value{GDBN} project mourns the loss of the following long-time
32436 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32437 to Free Software in general. Outside of @value{GDBN}, he was known in
32438 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32440 @item Michael Snyder
32441 Michael was one of the Global Maintainers of the @value{GDBN} project,
32442 with contributions recorded as early as 1996, until 2011. In addition
32443 to his day to day participation, he was a large driving force behind
32444 adding Reverse Debugging to @value{GDBN}.
32447 Beyond their technical contributions to the project, they were also
32448 enjoyable members of the Free Software Community. We will miss them.
32450 @node Formatting Documentation
32451 @appendix Formatting Documentation
32453 @cindex @value{GDBN} reference card
32454 @cindex reference card
32455 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32456 for printing with PostScript or Ghostscript, in the @file{gdb}
32457 subdirectory of the main source directory@footnote{In
32458 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32459 release.}. If you can use PostScript or Ghostscript with your printer,
32460 you can print the reference card immediately with @file{refcard.ps}.
32462 The release also includes the source for the reference card. You
32463 can format it, using @TeX{}, by typing:
32469 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32470 mode on US ``letter'' size paper;
32471 that is, on a sheet 11 inches wide by 8.5 inches
32472 high. You will need to specify this form of printing as an option to
32473 your @sc{dvi} output program.
32475 @cindex documentation
32477 All the documentation for @value{GDBN} comes as part of the machine-readable
32478 distribution. The documentation is written in Texinfo format, which is
32479 a documentation system that uses a single source file to produce both
32480 on-line information and a printed manual. You can use one of the Info
32481 formatting commands to create the on-line version of the documentation
32482 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32484 @value{GDBN} includes an already formatted copy of the on-line Info
32485 version of this manual in the @file{gdb} subdirectory. The main Info
32486 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32487 subordinate files matching @samp{gdb.info*} in the same directory. If
32488 necessary, you can print out these files, or read them with any editor;
32489 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32490 Emacs or the standalone @code{info} program, available as part of the
32491 @sc{gnu} Texinfo distribution.
32493 If you want to format these Info files yourself, you need one of the
32494 Info formatting programs, such as @code{texinfo-format-buffer} or
32497 If you have @code{makeinfo} installed, and are in the top level
32498 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32499 version @value{GDBVN}), you can make the Info file by typing:
32506 If you want to typeset and print copies of this manual, you need @TeX{},
32507 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32508 Texinfo definitions file.
32510 @TeX{} is a typesetting program; it does not print files directly, but
32511 produces output files called @sc{dvi} files. To print a typeset
32512 document, you need a program to print @sc{dvi} files. If your system
32513 has @TeX{} installed, chances are it has such a program. The precise
32514 command to use depends on your system; @kbd{lpr -d} is common; another
32515 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32516 require a file name without any extension or a @samp{.dvi} extension.
32518 @TeX{} also requires a macro definitions file called
32519 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32520 written in Texinfo format. On its own, @TeX{} cannot either read or
32521 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32522 and is located in the @file{gdb-@var{version-number}/texinfo}
32525 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32526 typeset and print this manual. First switch to the @file{gdb}
32527 subdirectory of the main source directory (for example, to
32528 @file{gdb-@value{GDBVN}/gdb}) and type:
32534 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32536 @node Installing GDB
32537 @appendix Installing @value{GDBN}
32538 @cindex installation
32541 * Requirements:: Requirements for building @value{GDBN}
32542 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32543 * Separate Objdir:: Compiling @value{GDBN} in another directory
32544 * Config Names:: Specifying names for hosts and targets
32545 * Configure Options:: Summary of options for configure
32546 * System-wide configuration:: Having a system-wide init file
32550 @section Requirements for Building @value{GDBN}
32551 @cindex building @value{GDBN}, requirements for
32553 Building @value{GDBN} requires various tools and packages to be available.
32554 Other packages will be used only if they are found.
32556 @heading Tools/Packages Necessary for Building @value{GDBN}
32558 @item ISO C90 compiler
32559 @value{GDBN} is written in ISO C90. It should be buildable with any
32560 working C90 compiler, e.g.@: GCC.
32564 @heading Tools/Packages Optional for Building @value{GDBN}
32568 @value{GDBN} can use the Expat XML parsing library. This library may be
32569 included with your operating system distribution; if it is not, you
32570 can get the latest version from @url{http://expat.sourceforge.net}.
32571 The @file{configure} script will search for this library in several
32572 standard locations; if it is installed in an unusual path, you can
32573 use the @option{--with-libexpat-prefix} option to specify its location.
32579 Remote protocol memory maps (@pxref{Memory Map Format})
32581 Target descriptions (@pxref{Target Descriptions})
32583 Remote shared library lists (@xref{Library List Format},
32584 or alternatively @pxref{Library List Format for SVR4 Targets})
32586 MS-Windows shared libraries (@pxref{Shared Libraries})
32588 Traceframe info (@pxref{Traceframe Info Format})
32592 @cindex compressed debug sections
32593 @value{GDBN} will use the @samp{zlib} library, if available, to read
32594 compressed debug sections. Some linkers, such as GNU gold, are capable
32595 of producing binaries with compressed debug sections. If @value{GDBN}
32596 is compiled with @samp{zlib}, it will be able to read the debug
32597 information in such binaries.
32599 The @samp{zlib} library is likely included with your operating system
32600 distribution; if it is not, you can get the latest version from
32601 @url{http://zlib.net}.
32604 @value{GDBN}'s features related to character sets (@pxref{Character
32605 Sets}) require a functioning @code{iconv} implementation. If you are
32606 on a GNU system, then this is provided by the GNU C Library. Some
32607 other systems also provide a working @code{iconv}.
32609 If @value{GDBN} is using the @code{iconv} program which is installed
32610 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32611 This is done with @option{--with-iconv-bin} which specifies the
32612 directory that contains the @code{iconv} program.
32614 On systems without @code{iconv}, you can install GNU Libiconv. If you
32615 have previously installed Libiconv, you can use the
32616 @option{--with-libiconv-prefix} option to configure.
32618 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32619 arrange to build Libiconv if a directory named @file{libiconv} appears
32620 in the top-most source directory. If Libiconv is built this way, and
32621 if the operating system does not provide a suitable @code{iconv}
32622 implementation, then the just-built library will automatically be used
32623 by @value{GDBN}. One easy way to set this up is to download GNU
32624 Libiconv, unpack it, and then rename the directory holding the
32625 Libiconv source code to @samp{libiconv}.
32628 @node Running Configure
32629 @section Invoking the @value{GDBN} @file{configure} Script
32630 @cindex configuring @value{GDBN}
32631 @value{GDBN} comes with a @file{configure} script that automates the process
32632 of preparing @value{GDBN} for installation; you can then use @code{make} to
32633 build the @code{gdb} program.
32635 @c irrelevant in info file; it's as current as the code it lives with.
32636 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32637 look at the @file{README} file in the sources; we may have improved the
32638 installation procedures since publishing this manual.}
32641 The @value{GDBN} distribution includes all the source code you need for
32642 @value{GDBN} in a single directory, whose name is usually composed by
32643 appending the version number to @samp{gdb}.
32645 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32646 @file{gdb-@value{GDBVN}} directory. That directory contains:
32649 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32650 script for configuring @value{GDBN} and all its supporting libraries
32652 @item gdb-@value{GDBVN}/gdb
32653 the source specific to @value{GDBN} itself
32655 @item gdb-@value{GDBVN}/bfd
32656 source for the Binary File Descriptor library
32658 @item gdb-@value{GDBVN}/include
32659 @sc{gnu} include files
32661 @item gdb-@value{GDBVN}/libiberty
32662 source for the @samp{-liberty} free software library
32664 @item gdb-@value{GDBVN}/opcodes
32665 source for the library of opcode tables and disassemblers
32667 @item gdb-@value{GDBVN}/readline
32668 source for the @sc{gnu} command-line interface
32670 @item gdb-@value{GDBVN}/glob
32671 source for the @sc{gnu} filename pattern-matching subroutine
32673 @item gdb-@value{GDBVN}/mmalloc
32674 source for the @sc{gnu} memory-mapped malloc package
32677 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32678 from the @file{gdb-@var{version-number}} source directory, which in
32679 this example is the @file{gdb-@value{GDBVN}} directory.
32681 First switch to the @file{gdb-@var{version-number}} source directory
32682 if you are not already in it; then run @file{configure}. Pass the
32683 identifier for the platform on which @value{GDBN} will run as an
32689 cd gdb-@value{GDBVN}
32690 ./configure @var{host}
32695 where @var{host} is an identifier such as @samp{sun4} or
32696 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32697 (You can often leave off @var{host}; @file{configure} tries to guess the
32698 correct value by examining your system.)
32700 Running @samp{configure @var{host}} and then running @code{make} builds the
32701 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32702 libraries, then @code{gdb} itself. The configured source files, and the
32703 binaries, are left in the corresponding source directories.
32706 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32707 system does not recognize this automatically when you run a different
32708 shell, you may need to run @code{sh} on it explicitly:
32711 sh configure @var{host}
32714 If you run @file{configure} from a directory that contains source
32715 directories for multiple libraries or programs, such as the
32716 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32718 creates configuration files for every directory level underneath (unless
32719 you tell it not to, with the @samp{--norecursion} option).
32721 You should run the @file{configure} script from the top directory in the
32722 source tree, the @file{gdb-@var{version-number}} directory. If you run
32723 @file{configure} from one of the subdirectories, you will configure only
32724 that subdirectory. That is usually not what you want. In particular,
32725 if you run the first @file{configure} from the @file{gdb} subdirectory
32726 of the @file{gdb-@var{version-number}} directory, you will omit the
32727 configuration of @file{bfd}, @file{readline}, and other sibling
32728 directories of the @file{gdb} subdirectory. This leads to build errors
32729 about missing include files such as @file{bfd/bfd.h}.
32731 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32732 However, you should make sure that the shell on your path (named by
32733 the @samp{SHELL} environment variable) is publicly readable. Remember
32734 that @value{GDBN} uses the shell to start your program---some systems refuse to
32735 let @value{GDBN} debug child processes whose programs are not readable.
32737 @node Separate Objdir
32738 @section Compiling @value{GDBN} in Another Directory
32740 If you want to run @value{GDBN} versions for several host or target machines,
32741 you need a different @code{gdb} compiled for each combination of
32742 host and target. @file{configure} is designed to make this easy by
32743 allowing you to generate each configuration in a separate subdirectory,
32744 rather than in the source directory. If your @code{make} program
32745 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32746 @code{make} in each of these directories builds the @code{gdb}
32747 program specified there.
32749 To build @code{gdb} in a separate directory, run @file{configure}
32750 with the @samp{--srcdir} option to specify where to find the source.
32751 (You also need to specify a path to find @file{configure}
32752 itself from your working directory. If the path to @file{configure}
32753 would be the same as the argument to @samp{--srcdir}, you can leave out
32754 the @samp{--srcdir} option; it is assumed.)
32756 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32757 separate directory for a Sun 4 like this:
32761 cd gdb-@value{GDBVN}
32764 ../gdb-@value{GDBVN}/configure sun4
32769 When @file{configure} builds a configuration using a remote source
32770 directory, it creates a tree for the binaries with the same structure
32771 (and using the same names) as the tree under the source directory. In
32772 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32773 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32774 @file{gdb-sun4/gdb}.
32776 Make sure that your path to the @file{configure} script has just one
32777 instance of @file{gdb} in it. If your path to @file{configure} looks
32778 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32779 one subdirectory of @value{GDBN}, not the whole package. This leads to
32780 build errors about missing include files such as @file{bfd/bfd.h}.
32782 One popular reason to build several @value{GDBN} configurations in separate
32783 directories is to configure @value{GDBN} for cross-compiling (where
32784 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32785 programs that run on another machine---the @dfn{target}).
32786 You specify a cross-debugging target by
32787 giving the @samp{--target=@var{target}} option to @file{configure}.
32789 When you run @code{make} to build a program or library, you must run
32790 it in a configured directory---whatever directory you were in when you
32791 called @file{configure} (or one of its subdirectories).
32793 The @code{Makefile} that @file{configure} generates in each source
32794 directory also runs recursively. If you type @code{make} in a source
32795 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32796 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32797 will build all the required libraries, and then build GDB.
32799 When you have multiple hosts or targets configured in separate
32800 directories, you can run @code{make} on them in parallel (for example,
32801 if they are NFS-mounted on each of the hosts); they will not interfere
32805 @section Specifying Names for Hosts and Targets
32807 The specifications used for hosts and targets in the @file{configure}
32808 script are based on a three-part naming scheme, but some short predefined
32809 aliases are also supported. The full naming scheme encodes three pieces
32810 of information in the following pattern:
32813 @var{architecture}-@var{vendor}-@var{os}
32816 For example, you can use the alias @code{sun4} as a @var{host} argument,
32817 or as the value for @var{target} in a @code{--target=@var{target}}
32818 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32820 The @file{configure} script accompanying @value{GDBN} does not provide
32821 any query facility to list all supported host and target names or
32822 aliases. @file{configure} calls the Bourne shell script
32823 @code{config.sub} to map abbreviations to full names; you can read the
32824 script, if you wish, or you can use it to test your guesses on
32825 abbreviations---for example:
32828 % sh config.sub i386-linux
32830 % sh config.sub alpha-linux
32831 alpha-unknown-linux-gnu
32832 % sh config.sub hp9k700
32834 % sh config.sub sun4
32835 sparc-sun-sunos4.1.1
32836 % sh config.sub sun3
32837 m68k-sun-sunos4.1.1
32838 % sh config.sub i986v
32839 Invalid configuration `i986v': machine `i986v' not recognized
32843 @code{config.sub} is also distributed in the @value{GDBN} source
32844 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32846 @node Configure Options
32847 @section @file{configure} Options
32849 Here is a summary of the @file{configure} options and arguments that
32850 are most often useful for building @value{GDBN}. @file{configure} also has
32851 several other options not listed here. @inforef{What Configure
32852 Does,,configure.info}, for a full explanation of @file{configure}.
32855 configure @r{[}--help@r{]}
32856 @r{[}--prefix=@var{dir}@r{]}
32857 @r{[}--exec-prefix=@var{dir}@r{]}
32858 @r{[}--srcdir=@var{dirname}@r{]}
32859 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32860 @r{[}--target=@var{target}@r{]}
32865 You may introduce options with a single @samp{-} rather than
32866 @samp{--} if you prefer; but you may abbreviate option names if you use
32871 Display a quick summary of how to invoke @file{configure}.
32873 @item --prefix=@var{dir}
32874 Configure the source to install programs and files under directory
32877 @item --exec-prefix=@var{dir}
32878 Configure the source to install programs under directory
32881 @c avoid splitting the warning from the explanation:
32883 @item --srcdir=@var{dirname}
32884 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32885 @code{make} that implements the @code{VPATH} feature.}@*
32886 Use this option to make configurations in directories separate from the
32887 @value{GDBN} source directories. Among other things, you can use this to
32888 build (or maintain) several configurations simultaneously, in separate
32889 directories. @file{configure} writes configuration-specific files in
32890 the current directory, but arranges for them to use the source in the
32891 directory @var{dirname}. @file{configure} creates directories under
32892 the working directory in parallel to the source directories below
32895 @item --norecursion
32896 Configure only the directory level where @file{configure} is executed; do not
32897 propagate configuration to subdirectories.
32899 @item --target=@var{target}
32900 Configure @value{GDBN} for cross-debugging programs running on the specified
32901 @var{target}. Without this option, @value{GDBN} is configured to debug
32902 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32904 There is no convenient way to generate a list of all available targets.
32906 @item @var{host} @dots{}
32907 Configure @value{GDBN} to run on the specified @var{host}.
32909 There is no convenient way to generate a list of all available hosts.
32912 There are many other options available as well, but they are generally
32913 needed for special purposes only.
32915 @node System-wide configuration
32916 @section System-wide configuration and settings
32917 @cindex system-wide init file
32919 @value{GDBN} can be configured to have a system-wide init file;
32920 this file will be read and executed at startup (@pxref{Startup, , What
32921 @value{GDBN} does during startup}).
32923 Here is the corresponding configure option:
32926 @item --with-system-gdbinit=@var{file}
32927 Specify that the default location of the system-wide init file is
32931 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32932 it may be subject to relocation. Two possible cases:
32936 If the default location of this init file contains @file{$prefix},
32937 it will be subject to relocation. Suppose that the configure options
32938 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32939 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32940 init file is looked for as @file{$install/etc/gdbinit} instead of
32941 @file{$prefix/etc/gdbinit}.
32944 By contrast, if the default location does not contain the prefix,
32945 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32946 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32947 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32948 wherever @value{GDBN} is installed.
32951 @node Maintenance Commands
32952 @appendix Maintenance Commands
32953 @cindex maintenance commands
32954 @cindex internal commands
32956 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32957 includes a number of commands intended for @value{GDBN} developers,
32958 that are not documented elsewhere in this manual. These commands are
32959 provided here for reference. (For commands that turn on debugging
32960 messages, see @ref{Debugging Output}.)
32963 @kindex maint agent
32964 @kindex maint agent-eval
32965 @item maint agent @var{expression}
32966 @itemx maint agent-eval @var{expression}
32967 Translate the given @var{expression} into remote agent bytecodes.
32968 This command is useful for debugging the Agent Expression mechanism
32969 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32970 expression useful for data collection, such as by tracepoints, while
32971 @samp{maint agent-eval} produces an expression that evaluates directly
32972 to a result. For instance, a collection expression for @code{globa +
32973 globb} will include bytecodes to record four bytes of memory at each
32974 of the addresses of @code{globa} and @code{globb}, while discarding
32975 the result of the addition, while an evaluation expression will do the
32976 addition and return the sum.
32978 @kindex maint info breakpoints
32979 @item @anchor{maint info breakpoints}maint info breakpoints
32980 Using the same format as @samp{info breakpoints}, display both the
32981 breakpoints you've set explicitly, and those @value{GDBN} is using for
32982 internal purposes. Internal breakpoints are shown with negative
32983 breakpoint numbers. The type column identifies what kind of breakpoint
32988 Normal, explicitly set breakpoint.
32991 Normal, explicitly set watchpoint.
32994 Internal breakpoint, used to handle correctly stepping through
32995 @code{longjmp} calls.
32997 @item longjmp resume
32998 Internal breakpoint at the target of a @code{longjmp}.
33001 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33004 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33007 Shared library events.
33011 @kindex set displaced-stepping
33012 @kindex show displaced-stepping
33013 @cindex displaced stepping support
33014 @cindex out-of-line single-stepping
33015 @item set displaced-stepping
33016 @itemx show displaced-stepping
33017 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33018 if the target supports it. Displaced stepping is a way to single-step
33019 over breakpoints without removing them from the inferior, by executing
33020 an out-of-line copy of the instruction that was originally at the
33021 breakpoint location. It is also known as out-of-line single-stepping.
33024 @item set displaced-stepping on
33025 If the target architecture supports it, @value{GDBN} will use
33026 displaced stepping to step over breakpoints.
33028 @item set displaced-stepping off
33029 @value{GDBN} will not use displaced stepping to step over breakpoints,
33030 even if such is supported by the target architecture.
33032 @cindex non-stop mode, and @samp{set displaced-stepping}
33033 @item set displaced-stepping auto
33034 This is the default mode. @value{GDBN} will use displaced stepping
33035 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33036 architecture supports displaced stepping.
33039 @kindex maint check-symtabs
33040 @item maint check-symtabs
33041 Check the consistency of psymtabs and symtabs.
33043 @kindex maint cplus first_component
33044 @item maint cplus first_component @var{name}
33045 Print the first C@t{++} class/namespace component of @var{name}.
33047 @kindex maint cplus namespace
33048 @item maint cplus namespace
33049 Print the list of possible C@t{++} namespaces.
33051 @kindex maint demangle
33052 @item maint demangle @var{name}
33053 Demangle a C@t{++} or Objective-C mangled @var{name}.
33055 @kindex maint deprecate
33056 @kindex maint undeprecate
33057 @cindex deprecated commands
33058 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33059 @itemx maint undeprecate @var{command}
33060 Deprecate or undeprecate the named @var{command}. Deprecated commands
33061 cause @value{GDBN} to issue a warning when you use them. The optional
33062 argument @var{replacement} says which newer command should be used in
33063 favor of the deprecated one; if it is given, @value{GDBN} will mention
33064 the replacement as part of the warning.
33066 @kindex maint dump-me
33067 @item maint dump-me
33068 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33069 Cause a fatal signal in the debugger and force it to dump its core.
33070 This is supported only on systems which support aborting a program
33071 with the @code{SIGQUIT} signal.
33073 @kindex maint internal-error
33074 @kindex maint internal-warning
33075 @item maint internal-error @r{[}@var{message-text}@r{]}
33076 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33077 Cause @value{GDBN} to call the internal function @code{internal_error}
33078 or @code{internal_warning} and hence behave as though an internal error
33079 or internal warning has been detected. In addition to reporting the
33080 internal problem, these functions give the user the opportunity to
33081 either quit @value{GDBN} or create a core file of the current
33082 @value{GDBN} session.
33084 These commands take an optional parameter @var{message-text} that is
33085 used as the text of the error or warning message.
33087 Here's an example of using @code{internal-error}:
33090 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33091 @dots{}/maint.c:121: internal-error: testing, 1, 2
33092 A problem internal to GDB has been detected. Further
33093 debugging may prove unreliable.
33094 Quit this debugging session? (y or n) @kbd{n}
33095 Create a core file? (y or n) @kbd{n}
33099 @cindex @value{GDBN} internal error
33100 @cindex internal errors, control of @value{GDBN} behavior
33102 @kindex maint set internal-error
33103 @kindex maint show internal-error
33104 @kindex maint set internal-warning
33105 @kindex maint show internal-warning
33106 @item maint set internal-error @var{action} [ask|yes|no]
33107 @itemx maint show internal-error @var{action}
33108 @itemx maint set internal-warning @var{action} [ask|yes|no]
33109 @itemx maint show internal-warning @var{action}
33110 When @value{GDBN} reports an internal problem (error or warning) it
33111 gives the user the opportunity to both quit @value{GDBN} and create a
33112 core file of the current @value{GDBN} session. These commands let you
33113 override the default behaviour for each particular @var{action},
33114 described in the table below.
33118 You can specify that @value{GDBN} should always (yes) or never (no)
33119 quit. The default is to ask the user what to do.
33122 You can specify that @value{GDBN} should always (yes) or never (no)
33123 create a core file. The default is to ask the user what to do.
33126 @kindex maint packet
33127 @item maint packet @var{text}
33128 If @value{GDBN} is talking to an inferior via the serial protocol,
33129 then this command sends the string @var{text} to the inferior, and
33130 displays the response packet. @value{GDBN} supplies the initial
33131 @samp{$} character, the terminating @samp{#} character, and the
33134 @kindex maint print architecture
33135 @item maint print architecture @r{[}@var{file}@r{]}
33136 Print the entire architecture configuration. The optional argument
33137 @var{file} names the file where the output goes.
33139 @kindex maint print c-tdesc
33140 @item maint print c-tdesc
33141 Print the current target description (@pxref{Target Descriptions}) as
33142 a C source file. The created source file can be used in @value{GDBN}
33143 when an XML parser is not available to parse the description.
33145 @kindex maint print dummy-frames
33146 @item maint print dummy-frames
33147 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33150 (@value{GDBP}) @kbd{b add}
33152 (@value{GDBP}) @kbd{print add(2,3)}
33153 Breakpoint 2, add (a=2, b=3) at @dots{}
33155 The program being debugged stopped while in a function called from GDB.
33157 (@value{GDBP}) @kbd{maint print dummy-frames}
33158 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33159 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33160 call_lo=0x01014000 call_hi=0x01014001
33164 Takes an optional file parameter.
33166 @kindex maint print registers
33167 @kindex maint print raw-registers
33168 @kindex maint print cooked-registers
33169 @kindex maint print register-groups
33170 @kindex maint print remote-registers
33171 @item maint print registers @r{[}@var{file}@r{]}
33172 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33173 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33174 @itemx maint print register-groups @r{[}@var{file}@r{]}
33175 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33176 Print @value{GDBN}'s internal register data structures.
33178 The command @code{maint print raw-registers} includes the contents of
33179 the raw register cache; the command @code{maint print
33180 cooked-registers} includes the (cooked) value of all registers,
33181 including registers which aren't available on the target nor visible
33182 to user; the command @code{maint print register-groups} includes the
33183 groups that each register is a member of; and the command @code{maint
33184 print remote-registers} includes the remote target's register numbers
33185 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33186 @value{GDBN} Internals}.
33188 These commands take an optional parameter, a file name to which to
33189 write the information.
33191 @kindex maint print reggroups
33192 @item maint print reggroups @r{[}@var{file}@r{]}
33193 Print @value{GDBN}'s internal register group data structures. The
33194 optional argument @var{file} tells to what file to write the
33197 The register groups info looks like this:
33200 (@value{GDBP}) @kbd{maint print reggroups}
33213 This command forces @value{GDBN} to flush its internal register cache.
33215 @kindex maint print objfiles
33216 @cindex info for known object files
33217 @item maint print objfiles
33218 Print a dump of all known object files. For each object file, this
33219 command prints its name, address in memory, and all of its psymtabs
33222 @kindex maint print section-scripts
33223 @cindex info for known .debug_gdb_scripts-loaded scripts
33224 @item maint print section-scripts [@var{regexp}]
33225 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33226 If @var{regexp} is specified, only print scripts loaded by object files
33227 matching @var{regexp}.
33228 For each script, this command prints its name as specified in the objfile,
33229 and the full path if known.
33230 @xref{.debug_gdb_scripts section}.
33232 @kindex maint print statistics
33233 @cindex bcache statistics
33234 @item maint print statistics
33235 This command prints, for each object file in the program, various data
33236 about that object file followed by the byte cache (@dfn{bcache})
33237 statistics for the object file. The objfile data includes the number
33238 of minimal, partial, full, and stabs symbols, the number of types
33239 defined by the objfile, the number of as yet unexpanded psym tables,
33240 the number of line tables and string tables, and the amount of memory
33241 used by the various tables. The bcache statistics include the counts,
33242 sizes, and counts of duplicates of all and unique objects, max,
33243 average, and median entry size, total memory used and its overhead and
33244 savings, and various measures of the hash table size and chain
33247 @kindex maint print target-stack
33248 @cindex target stack description
33249 @item maint print target-stack
33250 A @dfn{target} is an interface between the debugger and a particular
33251 kind of file or process. Targets can be stacked in @dfn{strata},
33252 so that more than one target can potentially respond to a request.
33253 In particular, memory accesses will walk down the stack of targets
33254 until they find a target that is interested in handling that particular
33257 This command prints a short description of each layer that was pushed on
33258 the @dfn{target stack}, starting from the top layer down to the bottom one.
33260 @kindex maint print type
33261 @cindex type chain of a data type
33262 @item maint print type @var{expr}
33263 Print the type chain for a type specified by @var{expr}. The argument
33264 can be either a type name or a symbol. If it is a symbol, the type of
33265 that symbol is described. The type chain produced by this command is
33266 a recursive definition of the data type as stored in @value{GDBN}'s
33267 data structures, including its flags and contained types.
33269 @kindex maint set dwarf2 always-disassemble
33270 @kindex maint show dwarf2 always-disassemble
33271 @item maint set dwarf2 always-disassemble
33272 @item maint show dwarf2 always-disassemble
33273 Control the behavior of @code{info address} when using DWARF debugging
33276 The default is @code{off}, which means that @value{GDBN} should try to
33277 describe a variable's location in an easily readable format. When
33278 @code{on}, @value{GDBN} will instead display the DWARF location
33279 expression in an assembly-like format. Note that some locations are
33280 too complex for @value{GDBN} to describe simply; in this case you will
33281 always see the disassembly form.
33283 Here is an example of the resulting disassembly:
33286 (gdb) info addr argc
33287 Symbol "argc" is a complex DWARF expression:
33291 For more information on these expressions, see
33292 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33294 @kindex maint set dwarf2 max-cache-age
33295 @kindex maint show dwarf2 max-cache-age
33296 @item maint set dwarf2 max-cache-age
33297 @itemx maint show dwarf2 max-cache-age
33298 Control the DWARF 2 compilation unit cache.
33300 @cindex DWARF 2 compilation units cache
33301 In object files with inter-compilation-unit references, such as those
33302 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33303 reader needs to frequently refer to previously read compilation units.
33304 This setting controls how long a compilation unit will remain in the
33305 cache if it is not referenced. A higher limit means that cached
33306 compilation units will be stored in memory longer, and more total
33307 memory will be used. Setting it to zero disables caching, which will
33308 slow down @value{GDBN} startup, but reduce memory consumption.
33310 @kindex maint set profile
33311 @kindex maint show profile
33312 @cindex profiling GDB
33313 @item maint set profile
33314 @itemx maint show profile
33315 Control profiling of @value{GDBN}.
33317 Profiling will be disabled until you use the @samp{maint set profile}
33318 command to enable it. When you enable profiling, the system will begin
33319 collecting timing and execution count data; when you disable profiling or
33320 exit @value{GDBN}, the results will be written to a log file. Remember that
33321 if you use profiling, @value{GDBN} will overwrite the profiling log file
33322 (often called @file{gmon.out}). If you have a record of important profiling
33323 data in a @file{gmon.out} file, be sure to move it to a safe location.
33325 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33326 compiled with the @samp{-pg} compiler option.
33328 @kindex maint set show-debug-regs
33329 @kindex maint show show-debug-regs
33330 @cindex hardware debug registers
33331 @item maint set show-debug-regs
33332 @itemx maint show show-debug-regs
33333 Control whether to show variables that mirror the hardware debug
33334 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33335 enabled, the debug registers values are shown when @value{GDBN} inserts or
33336 removes a hardware breakpoint or watchpoint, and when the inferior
33337 triggers a hardware-assisted breakpoint or watchpoint.
33339 @kindex maint set show-all-tib
33340 @kindex maint show show-all-tib
33341 @item maint set show-all-tib
33342 @itemx maint show show-all-tib
33343 Control whether to show all non zero areas within a 1k block starting
33344 at thread local base, when using the @samp{info w32 thread-information-block}
33347 @kindex maint space
33348 @cindex memory used by commands
33350 Control whether to display memory usage for each command. If set to a
33351 nonzero value, @value{GDBN} will display how much memory each command
33352 took, following the command's own output. This can also be requested
33353 by invoking @value{GDBN} with the @option{--statistics} command-line
33354 switch (@pxref{Mode Options}).
33357 @cindex time of command execution
33359 Control whether to display the execution time of @value{GDBN} for each command.
33360 If set to a nonzero value, @value{GDBN} will display how much time it
33361 took to execute each command, following the command's own output.
33362 Both CPU time and wallclock time are printed.
33363 Printing both is useful when trying to determine whether the cost is
33364 CPU or, e.g., disk/network, latency.
33365 Note that the CPU time printed is for @value{GDBN} only, it does not include
33366 the execution time of the inferior because there's no mechanism currently
33367 to compute how much time was spent by @value{GDBN} and how much time was
33368 spent by the program been debugged.
33369 This can also be requested by invoking @value{GDBN} with the
33370 @option{--statistics} command-line switch (@pxref{Mode Options}).
33372 @kindex maint translate-address
33373 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33374 Find the symbol stored at the location specified by the address
33375 @var{addr} and an optional section name @var{section}. If found,
33376 @value{GDBN} prints the name of the closest symbol and an offset from
33377 the symbol's location to the specified address. This is similar to
33378 the @code{info address} command (@pxref{Symbols}), except that this
33379 command also allows to find symbols in other sections.
33381 If section was not specified, the section in which the symbol was found
33382 is also printed. For dynamically linked executables, the name of
33383 executable or shared library containing the symbol is printed as well.
33387 The following command is useful for non-interactive invocations of
33388 @value{GDBN}, such as in the test suite.
33391 @item set watchdog @var{nsec}
33392 @kindex set watchdog
33393 @cindex watchdog timer
33394 @cindex timeout for commands
33395 Set the maximum number of seconds @value{GDBN} will wait for the
33396 target operation to finish. If this time expires, @value{GDBN}
33397 reports and error and the command is aborted.
33399 @item show watchdog
33400 Show the current setting of the target wait timeout.
33403 @node Remote Protocol
33404 @appendix @value{GDBN} Remote Serial Protocol
33409 * Stop Reply Packets::
33410 * General Query Packets::
33411 * Architecture-Specific Protocol Details::
33412 * Tracepoint Packets::
33413 * Host I/O Packets::
33415 * Notification Packets::
33416 * Remote Non-Stop::
33417 * Packet Acknowledgment::
33419 * File-I/O Remote Protocol Extension::
33420 * Library List Format::
33421 * Library List Format for SVR4 Targets::
33422 * Memory Map Format::
33423 * Thread List Format::
33424 * Traceframe Info Format::
33430 There may be occasions when you need to know something about the
33431 protocol---for example, if there is only one serial port to your target
33432 machine, you might want your program to do something special if it
33433 recognizes a packet meant for @value{GDBN}.
33435 In the examples below, @samp{->} and @samp{<-} are used to indicate
33436 transmitted and received data, respectively.
33438 @cindex protocol, @value{GDBN} remote serial
33439 @cindex serial protocol, @value{GDBN} remote
33440 @cindex remote serial protocol
33441 All @value{GDBN} commands and responses (other than acknowledgments
33442 and notifications, see @ref{Notification Packets}) are sent as a
33443 @var{packet}. A @var{packet} is introduced with the character
33444 @samp{$}, the actual @var{packet-data}, and the terminating character
33445 @samp{#} followed by a two-digit @var{checksum}:
33448 @code{$}@var{packet-data}@code{#}@var{checksum}
33452 @cindex checksum, for @value{GDBN} remote
33454 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33455 characters between the leading @samp{$} and the trailing @samp{#} (an
33456 eight bit unsigned checksum).
33458 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33459 specification also included an optional two-digit @var{sequence-id}:
33462 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33465 @cindex sequence-id, for @value{GDBN} remote
33467 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33468 has never output @var{sequence-id}s. Stubs that handle packets added
33469 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33471 When either the host or the target machine receives a packet, the first
33472 response expected is an acknowledgment: either @samp{+} (to indicate
33473 the package was received correctly) or @samp{-} (to request
33477 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33482 The @samp{+}/@samp{-} acknowledgments can be disabled
33483 once a connection is established.
33484 @xref{Packet Acknowledgment}, for details.
33486 The host (@value{GDBN}) sends @var{command}s, and the target (the
33487 debugging stub incorporated in your program) sends a @var{response}. In
33488 the case of step and continue @var{command}s, the response is only sent
33489 when the operation has completed, and the target has again stopped all
33490 threads in all attached processes. This is the default all-stop mode
33491 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33492 execution mode; see @ref{Remote Non-Stop}, for details.
33494 @var{packet-data} consists of a sequence of characters with the
33495 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33498 @cindex remote protocol, field separator
33499 Fields within the packet should be separated using @samp{,} @samp{;} or
33500 @samp{:}. Except where otherwise noted all numbers are represented in
33501 @sc{hex} with leading zeros suppressed.
33503 Implementors should note that prior to @value{GDBN} 5.0, the character
33504 @samp{:} could not appear as the third character in a packet (as it
33505 would potentially conflict with the @var{sequence-id}).
33507 @cindex remote protocol, binary data
33508 @anchor{Binary Data}
33509 Binary data in most packets is encoded either as two hexadecimal
33510 digits per byte of binary data. This allowed the traditional remote
33511 protocol to work over connections which were only seven-bit clean.
33512 Some packets designed more recently assume an eight-bit clean
33513 connection, and use a more efficient encoding to send and receive
33516 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33517 as an escape character. Any escaped byte is transmitted as the escape
33518 character followed by the original character XORed with @code{0x20}.
33519 For example, the byte @code{0x7d} would be transmitted as the two
33520 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33521 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33522 @samp{@}}) must always be escaped. Responses sent by the stub
33523 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33524 is not interpreted as the start of a run-length encoded sequence
33527 Response @var{data} can be run-length encoded to save space.
33528 Run-length encoding replaces runs of identical characters with one
33529 instance of the repeated character, followed by a @samp{*} and a
33530 repeat count. The repeat count is itself sent encoded, to avoid
33531 binary characters in @var{data}: a value of @var{n} is sent as
33532 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33533 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33534 code 32) for a repeat count of 3. (This is because run-length
33535 encoding starts to win for counts 3 or more.) Thus, for example,
33536 @samp{0* } is a run-length encoding of ``0000'': the space character
33537 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33540 The printable characters @samp{#} and @samp{$} or with a numeric value
33541 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33542 seven repeats (@samp{$}) can be expanded using a repeat count of only
33543 five (@samp{"}). For example, @samp{00000000} can be encoded as
33546 The error response returned for some packets includes a two character
33547 error number. That number is not well defined.
33549 @cindex empty response, for unsupported packets
33550 For any @var{command} not supported by the stub, an empty response
33551 (@samp{$#00}) should be returned. That way it is possible to extend the
33552 protocol. A newer @value{GDBN} can tell if a packet is supported based
33555 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33556 commands for register access, and the @samp{m} and @samp{M} commands
33557 for memory access. Stubs that only control single-threaded targets
33558 can implement run control with the @samp{c} (continue), and @samp{s}
33559 (step) commands. Stubs that support multi-threading targets should
33560 support the @samp{vCont} command. All other commands are optional.
33565 The following table provides a complete list of all currently defined
33566 @var{command}s and their corresponding response @var{data}.
33567 @xref{File-I/O Remote Protocol Extension}, for details about the File
33568 I/O extension of the remote protocol.
33570 Each packet's description has a template showing the packet's overall
33571 syntax, followed by an explanation of the packet's meaning. We
33572 include spaces in some of the templates for clarity; these are not
33573 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33574 separate its components. For example, a template like @samp{foo
33575 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33576 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33577 @var{baz}. @value{GDBN} does not transmit a space character between the
33578 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33581 @cindex @var{thread-id}, in remote protocol
33582 @anchor{thread-id syntax}
33583 Several packets and replies include a @var{thread-id} field to identify
33584 a thread. Normally these are positive numbers with a target-specific
33585 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33586 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33589 In addition, the remote protocol supports a multiprocess feature in
33590 which the @var{thread-id} syntax is extended to optionally include both
33591 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33592 The @var{pid} (process) and @var{tid} (thread) components each have the
33593 format described above: a positive number with target-specific
33594 interpretation formatted as a big-endian hex string, literal @samp{-1}
33595 to indicate all processes or threads (respectively), or @samp{0} to
33596 indicate an arbitrary process or thread. Specifying just a process, as
33597 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33598 error to specify all processes but a specific thread, such as
33599 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33600 for those packets and replies explicitly documented to include a process
33601 ID, rather than a @var{thread-id}.
33603 The multiprocess @var{thread-id} syntax extensions are only used if both
33604 @value{GDBN} and the stub report support for the @samp{multiprocess}
33605 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33608 Note that all packet forms beginning with an upper- or lower-case
33609 letter, other than those described here, are reserved for future use.
33611 Here are the packet descriptions.
33616 @cindex @samp{!} packet
33617 @anchor{extended mode}
33618 Enable extended mode. In extended mode, the remote server is made
33619 persistent. The @samp{R} packet is used to restart the program being
33625 The remote target both supports and has enabled extended mode.
33629 @cindex @samp{?} packet
33630 Indicate the reason the target halted. The reply is the same as for
33631 step and continue. This packet has a special interpretation when the
33632 target is in non-stop mode; see @ref{Remote Non-Stop}.
33635 @xref{Stop Reply Packets}, for the reply specifications.
33637 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33638 @cindex @samp{A} packet
33639 Initialized @code{argv[]} array passed into program. @var{arglen}
33640 specifies the number of bytes in the hex encoded byte stream
33641 @var{arg}. See @code{gdbserver} for more details.
33646 The arguments were set.
33652 @cindex @samp{b} packet
33653 (Don't use this packet; its behavior is not well-defined.)
33654 Change the serial line speed to @var{baud}.
33656 JTC: @emph{When does the transport layer state change? When it's
33657 received, or after the ACK is transmitted. In either case, there are
33658 problems if the command or the acknowledgment packet is dropped.}
33660 Stan: @emph{If people really wanted to add something like this, and get
33661 it working for the first time, they ought to modify ser-unix.c to send
33662 some kind of out-of-band message to a specially-setup stub and have the
33663 switch happen "in between" packets, so that from remote protocol's point
33664 of view, nothing actually happened.}
33666 @item B @var{addr},@var{mode}
33667 @cindex @samp{B} packet
33668 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33669 breakpoint at @var{addr}.
33671 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33672 (@pxref{insert breakpoint or watchpoint packet}).
33674 @cindex @samp{bc} packet
33677 Backward continue. Execute the target system in reverse. No parameter.
33678 @xref{Reverse Execution}, for more information.
33681 @xref{Stop Reply Packets}, for the reply specifications.
33683 @cindex @samp{bs} packet
33686 Backward single step. Execute one instruction in reverse. No parameter.
33687 @xref{Reverse Execution}, for more information.
33690 @xref{Stop Reply Packets}, for the reply specifications.
33692 @item c @r{[}@var{addr}@r{]}
33693 @cindex @samp{c} packet
33694 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33695 resume at current address.
33697 This packet is deprecated for multi-threading support. @xref{vCont
33701 @xref{Stop Reply Packets}, for the reply specifications.
33703 @item C @var{sig}@r{[};@var{addr}@r{]}
33704 @cindex @samp{C} packet
33705 Continue with signal @var{sig} (hex signal number). If
33706 @samp{;@var{addr}} is omitted, resume at same address.
33708 This packet is deprecated for multi-threading support. @xref{vCont
33712 @xref{Stop Reply Packets}, for the reply specifications.
33715 @cindex @samp{d} packet
33718 Don't use this packet; instead, define a general set packet
33719 (@pxref{General Query Packets}).
33723 @cindex @samp{D} packet
33724 The first form of the packet is used to detach @value{GDBN} from the
33725 remote system. It is sent to the remote target
33726 before @value{GDBN} disconnects via the @code{detach} command.
33728 The second form, including a process ID, is used when multiprocess
33729 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33730 detach only a specific process. The @var{pid} is specified as a
33731 big-endian hex string.
33741 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33742 @cindex @samp{F} packet
33743 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33744 This is part of the File-I/O protocol extension. @xref{File-I/O
33745 Remote Protocol Extension}, for the specification.
33748 @anchor{read registers packet}
33749 @cindex @samp{g} packet
33750 Read general registers.
33754 @item @var{XX@dots{}}
33755 Each byte of register data is described by two hex digits. The bytes
33756 with the register are transmitted in target byte order. The size of
33757 each register and their position within the @samp{g} packet are
33758 determined by the @value{GDBN} internal gdbarch functions
33759 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33760 specification of several standard @samp{g} packets is specified below.
33762 When reading registers from a trace frame (@pxref{Analyze Collected
33763 Data,,Using the Collected Data}), the stub may also return a string of
33764 literal @samp{x}'s in place of the register data digits, to indicate
33765 that the corresponding register has not been collected, thus its value
33766 is unavailable. For example, for an architecture with 4 registers of
33767 4 bytes each, the following reply indicates to @value{GDBN} that
33768 registers 0 and 2 have not been collected, while registers 1 and 3
33769 have been collected, and both have zero value:
33773 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33780 @item G @var{XX@dots{}}
33781 @cindex @samp{G} packet
33782 Write general registers. @xref{read registers packet}, for a
33783 description of the @var{XX@dots{}} data.
33793 @item H @var{op} @var{thread-id}
33794 @cindex @samp{H} packet
33795 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33796 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33797 it should be @samp{c} for step and continue operations (note that this
33798 is deprecated, supporting the @samp{vCont} command is a better
33799 option), @samp{g} for other operations. The thread designator
33800 @var{thread-id} has the format and interpretation described in
33801 @ref{thread-id syntax}.
33812 @c 'H': How restrictive (or permissive) is the thread model. If a
33813 @c thread is selected and stopped, are other threads allowed
33814 @c to continue to execute? As I mentioned above, I think the
33815 @c semantics of each command when a thread is selected must be
33816 @c described. For example:
33818 @c 'g': If the stub supports threads and a specific thread is
33819 @c selected, returns the register block from that thread;
33820 @c otherwise returns current registers.
33822 @c 'G' If the stub supports threads and a specific thread is
33823 @c selected, sets the registers of the register block of
33824 @c that thread; otherwise sets current registers.
33826 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33827 @anchor{cycle step packet}
33828 @cindex @samp{i} packet
33829 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33830 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33831 step starting at that address.
33834 @cindex @samp{I} packet
33835 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33839 @cindex @samp{k} packet
33842 FIXME: @emph{There is no description of how to operate when a specific
33843 thread context has been selected (i.e.@: does 'k' kill only that
33846 @item m @var{addr},@var{length}
33847 @cindex @samp{m} packet
33848 Read @var{length} bytes of memory starting at address @var{addr}.
33849 Note that @var{addr} may not be aligned to any particular boundary.
33851 The stub need not use any particular size or alignment when gathering
33852 data from memory for the response; even if @var{addr} is word-aligned
33853 and @var{length} is a multiple of the word size, the stub is free to
33854 use byte accesses, or not. For this reason, this packet may not be
33855 suitable for accessing memory-mapped I/O devices.
33856 @cindex alignment of remote memory accesses
33857 @cindex size of remote memory accesses
33858 @cindex memory, alignment and size of remote accesses
33862 @item @var{XX@dots{}}
33863 Memory contents; each byte is transmitted as a two-digit hexadecimal
33864 number. The reply may contain fewer bytes than requested if the
33865 server was able to read only part of the region of memory.
33870 @item M @var{addr},@var{length}:@var{XX@dots{}}
33871 @cindex @samp{M} packet
33872 Write @var{length} bytes of memory starting at address @var{addr}.
33873 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33874 hexadecimal number.
33881 for an error (this includes the case where only part of the data was
33886 @cindex @samp{p} packet
33887 Read the value of register @var{n}; @var{n} is in hex.
33888 @xref{read registers packet}, for a description of how the returned
33889 register value is encoded.
33893 @item @var{XX@dots{}}
33894 the register's value
33898 Indicating an unrecognized @var{query}.
33901 @item P @var{n@dots{}}=@var{r@dots{}}
33902 @anchor{write register packet}
33903 @cindex @samp{P} packet
33904 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33905 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33906 digits for each byte in the register (target byte order).
33916 @item q @var{name} @var{params}@dots{}
33917 @itemx Q @var{name} @var{params}@dots{}
33918 @cindex @samp{q} packet
33919 @cindex @samp{Q} packet
33920 General query (@samp{q}) and set (@samp{Q}). These packets are
33921 described fully in @ref{General Query Packets}.
33924 @cindex @samp{r} packet
33925 Reset the entire system.
33927 Don't use this packet; use the @samp{R} packet instead.
33930 @cindex @samp{R} packet
33931 Restart the program being debugged. @var{XX}, while needed, is ignored.
33932 This packet is only available in extended mode (@pxref{extended mode}).
33934 The @samp{R} packet has no reply.
33936 @item s @r{[}@var{addr}@r{]}
33937 @cindex @samp{s} packet
33938 Single step. @var{addr} is the address at which to resume. If
33939 @var{addr} is omitted, resume at same address.
33941 This packet is deprecated for multi-threading support. @xref{vCont
33945 @xref{Stop Reply Packets}, for the reply specifications.
33947 @item S @var{sig}@r{[};@var{addr}@r{]}
33948 @anchor{step with signal packet}
33949 @cindex @samp{S} packet
33950 Step with signal. This is analogous to the @samp{C} packet, but
33951 requests a single-step, rather than a normal resumption of execution.
33953 This packet is deprecated for multi-threading support. @xref{vCont
33957 @xref{Stop Reply Packets}, for the reply specifications.
33959 @item t @var{addr}:@var{PP},@var{MM}
33960 @cindex @samp{t} packet
33961 Search backwards starting at address @var{addr} for a match with pattern
33962 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33963 @var{addr} must be at least 3 digits.
33965 @item T @var{thread-id}
33966 @cindex @samp{T} packet
33967 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33972 thread is still alive
33978 Packets starting with @samp{v} are identified by a multi-letter name,
33979 up to the first @samp{;} or @samp{?} (or the end of the packet).
33981 @item vAttach;@var{pid}
33982 @cindex @samp{vAttach} packet
33983 Attach to a new process with the specified process ID @var{pid}.
33984 The process ID is a
33985 hexadecimal integer identifying the process. In all-stop mode, all
33986 threads in the attached process are stopped; in non-stop mode, it may be
33987 attached without being stopped if that is supported by the target.
33989 @c In non-stop mode, on a successful vAttach, the stub should set the
33990 @c current thread to a thread of the newly-attached process. After
33991 @c attaching, GDB queries for the attached process's thread ID with qC.
33992 @c Also note that, from a user perspective, whether or not the
33993 @c target is stopped on attach in non-stop mode depends on whether you
33994 @c use the foreground or background version of the attach command, not
33995 @c on what vAttach does; GDB does the right thing with respect to either
33996 @c stopping or restarting threads.
33998 This packet is only available in extended mode (@pxref{extended mode}).
34004 @item @r{Any stop packet}
34005 for success in all-stop mode (@pxref{Stop Reply Packets})
34007 for success in non-stop mode (@pxref{Remote Non-Stop})
34010 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34011 @cindex @samp{vCont} packet
34012 @anchor{vCont packet}
34013 Resume the inferior, specifying different actions for each thread.
34014 If an action is specified with no @var{thread-id}, then it is applied to any
34015 threads that don't have a specific action specified; if no default action is
34016 specified then other threads should remain stopped in all-stop mode and
34017 in their current state in non-stop mode.
34018 Specifying multiple
34019 default actions is an error; specifying no actions is also an error.
34020 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34022 Currently supported actions are:
34028 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34032 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34037 The optional argument @var{addr} normally associated with the
34038 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34039 not supported in @samp{vCont}.
34041 The @samp{t} action is only relevant in non-stop mode
34042 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34043 A stop reply should be generated for any affected thread not already stopped.
34044 When a thread is stopped by means of a @samp{t} action,
34045 the corresponding stop reply should indicate that the thread has stopped with
34046 signal @samp{0}, regardless of whether the target uses some other signal
34047 as an implementation detail.
34049 The stub must support @samp{vCont} if it reports support for
34050 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34051 this case @samp{vCont} actions can be specified to apply to all threads
34052 in a process by using the @samp{p@var{pid}.-1} form of the
34056 @xref{Stop Reply Packets}, for the reply specifications.
34059 @cindex @samp{vCont?} packet
34060 Request a list of actions supported by the @samp{vCont} packet.
34064 @item vCont@r{[};@var{action}@dots{}@r{]}
34065 The @samp{vCont} packet is supported. Each @var{action} is a supported
34066 command in the @samp{vCont} packet.
34068 The @samp{vCont} packet is not supported.
34071 @item vFile:@var{operation}:@var{parameter}@dots{}
34072 @cindex @samp{vFile} packet
34073 Perform a file operation on the target system. For details,
34074 see @ref{Host I/O Packets}.
34076 @item vFlashErase:@var{addr},@var{length}
34077 @cindex @samp{vFlashErase} packet
34078 Direct the stub to erase @var{length} bytes of flash starting at
34079 @var{addr}. The region may enclose any number of flash blocks, but
34080 its start and end must fall on block boundaries, as indicated by the
34081 flash block size appearing in the memory map (@pxref{Memory Map
34082 Format}). @value{GDBN} groups flash memory programming operations
34083 together, and sends a @samp{vFlashDone} request after each group; the
34084 stub is allowed to delay erase operation until the @samp{vFlashDone}
34085 packet is received.
34095 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34096 @cindex @samp{vFlashWrite} packet
34097 Direct the stub to write data to flash address @var{addr}. The data
34098 is passed in binary form using the same encoding as for the @samp{X}
34099 packet (@pxref{Binary Data}). The memory ranges specified by
34100 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34101 not overlap, and must appear in order of increasing addresses
34102 (although @samp{vFlashErase} packets for higher addresses may already
34103 have been received; the ordering is guaranteed only between
34104 @samp{vFlashWrite} packets). If a packet writes to an address that was
34105 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34106 target-specific method, the results are unpredictable.
34114 for vFlashWrite addressing non-flash memory
34120 @cindex @samp{vFlashDone} packet
34121 Indicate to the stub that flash programming operation is finished.
34122 The stub is permitted to delay or batch the effects of a group of
34123 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34124 @samp{vFlashDone} packet is received. The contents of the affected
34125 regions of flash memory are unpredictable until the @samp{vFlashDone}
34126 request is completed.
34128 @item vKill;@var{pid}
34129 @cindex @samp{vKill} packet
34130 Kill the process with the specified process ID. @var{pid} is a
34131 hexadecimal integer identifying the process. This packet is used in
34132 preference to @samp{k} when multiprocess protocol extensions are
34133 supported; see @ref{multiprocess extensions}.
34143 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34144 @cindex @samp{vRun} packet
34145 Run the program @var{filename}, passing it each @var{argument} on its
34146 command line. The file and arguments are hex-encoded strings. If
34147 @var{filename} is an empty string, the stub may use a default program
34148 (e.g.@: the last program run). The program is created in the stopped
34151 @c FIXME: What about non-stop mode?
34153 This packet is only available in extended mode (@pxref{extended mode}).
34159 @item @r{Any stop packet}
34160 for success (@pxref{Stop Reply Packets})
34164 @anchor{vStopped packet}
34165 @cindex @samp{vStopped} packet
34167 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34168 reply and prompt for the stub to report another one.
34172 @item @r{Any stop packet}
34173 if there is another unreported stop event (@pxref{Stop Reply Packets})
34175 if there are no unreported stop events
34178 @item X @var{addr},@var{length}:@var{XX@dots{}}
34180 @cindex @samp{X} packet
34181 Write data to memory, where the data is transmitted in binary.
34182 @var{addr} is address, @var{length} is number of bytes,
34183 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34193 @item z @var{type},@var{addr},@var{kind}
34194 @itemx Z @var{type},@var{addr},@var{kind}
34195 @anchor{insert breakpoint or watchpoint packet}
34196 @cindex @samp{z} packet
34197 @cindex @samp{Z} packets
34198 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34199 watchpoint starting at address @var{address} of kind @var{kind}.
34201 Each breakpoint and watchpoint packet @var{type} is documented
34204 @emph{Implementation notes: A remote target shall return an empty string
34205 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34206 remote target shall support either both or neither of a given
34207 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34208 avoid potential problems with duplicate packets, the operations should
34209 be implemented in an idempotent way.}
34211 @item z0,@var{addr},@var{kind}
34212 @itemx Z0,@var{addr},@var{kind}
34213 @cindex @samp{z0} packet
34214 @cindex @samp{Z0} packet
34215 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34216 @var{addr} of type @var{kind}.
34218 A memory breakpoint is implemented by replacing the instruction at
34219 @var{addr} with a software breakpoint or trap instruction. The
34220 @var{kind} is target-specific and typically indicates the size of
34221 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34222 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34223 architectures have additional meanings for @var{kind};
34224 see @ref{Architecture-Specific Protocol Details}.
34226 @emph{Implementation note: It is possible for a target to copy or move
34227 code that contains memory breakpoints (e.g., when implementing
34228 overlays). The behavior of this packet, in the presence of such a
34229 target, is not defined.}
34241 @item z1,@var{addr},@var{kind}
34242 @itemx Z1,@var{addr},@var{kind}
34243 @cindex @samp{z1} packet
34244 @cindex @samp{Z1} packet
34245 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34246 address @var{addr}.
34248 A hardware breakpoint is implemented using a mechanism that is not
34249 dependant on being able to modify the target's memory. @var{kind}
34250 has the same meaning as in @samp{Z0} packets.
34252 @emph{Implementation note: A hardware breakpoint is not affected by code
34265 @item z2,@var{addr},@var{kind}
34266 @itemx Z2,@var{addr},@var{kind}
34267 @cindex @samp{z2} packet
34268 @cindex @samp{Z2} packet
34269 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34270 @var{kind} is interpreted as the number of bytes to watch.
34282 @item z3,@var{addr},@var{kind}
34283 @itemx Z3,@var{addr},@var{kind}
34284 @cindex @samp{z3} packet
34285 @cindex @samp{Z3} packet
34286 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34287 @var{kind} is interpreted as the number of bytes to watch.
34299 @item z4,@var{addr},@var{kind}
34300 @itemx Z4,@var{addr},@var{kind}
34301 @cindex @samp{z4} packet
34302 @cindex @samp{Z4} packet
34303 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34304 @var{kind} is interpreted as the number of bytes to watch.
34318 @node Stop Reply Packets
34319 @section Stop Reply Packets
34320 @cindex stop reply packets
34322 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34323 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34324 receive any of the below as a reply. Except for @samp{?}
34325 and @samp{vStopped}, that reply is only returned
34326 when the target halts. In the below the exact meaning of @dfn{signal
34327 number} is defined by the header @file{include/gdb/signals.h} in the
34328 @value{GDBN} source code.
34330 As in the description of request packets, we include spaces in the
34331 reply templates for clarity; these are not part of the reply packet's
34332 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34338 The program received signal number @var{AA} (a two-digit hexadecimal
34339 number). This is equivalent to a @samp{T} response with no
34340 @var{n}:@var{r} pairs.
34342 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34343 @cindex @samp{T} packet reply
34344 The program received signal number @var{AA} (a two-digit hexadecimal
34345 number). This is equivalent to an @samp{S} response, except that the
34346 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34347 and other information directly in the stop reply packet, reducing
34348 round-trip latency. Single-step and breakpoint traps are reported
34349 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34353 If @var{n} is a hexadecimal number, it is a register number, and the
34354 corresponding @var{r} gives that register's value. @var{r} is a
34355 series of bytes in target byte order, with each byte given by a
34356 two-digit hex number.
34359 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34360 the stopped thread, as specified in @ref{thread-id syntax}.
34363 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34364 the core on which the stop event was detected.
34367 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34368 specific event that stopped the target. The currently defined stop
34369 reasons are listed below. @var{aa} should be @samp{05}, the trap
34370 signal. At most one stop reason should be present.
34373 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34374 and go on to the next; this allows us to extend the protocol in the
34378 The currently defined stop reasons are:
34384 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34387 @cindex shared library events, remote reply
34389 The packet indicates that the loaded libraries have changed.
34390 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34391 list of loaded libraries. @var{r} is ignored.
34393 @cindex replay log events, remote reply
34395 The packet indicates that the target cannot continue replaying
34396 logged execution events, because it has reached the end (or the
34397 beginning when executing backward) of the log. The value of @var{r}
34398 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34399 for more information.
34403 @itemx W @var{AA} ; process:@var{pid}
34404 The process exited, and @var{AA} is the exit status. This is only
34405 applicable to certain targets.
34407 The second form of the response, including the process ID of the exited
34408 process, can be used only when @value{GDBN} has reported support for
34409 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34410 The @var{pid} is formatted as a big-endian hex string.
34413 @itemx X @var{AA} ; process:@var{pid}
34414 The process terminated with signal @var{AA}.
34416 The second form of the response, including the process ID of the
34417 terminated process, can be used only when @value{GDBN} has reported
34418 support for multiprocess protocol extensions; see @ref{multiprocess
34419 extensions}. The @var{pid} is formatted as a big-endian hex string.
34421 @item O @var{XX}@dots{}
34422 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34423 written as the program's console output. This can happen at any time
34424 while the program is running and the debugger should continue to wait
34425 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34427 @item F @var{call-id},@var{parameter}@dots{}
34428 @var{call-id} is the identifier which says which host system call should
34429 be called. This is just the name of the function. Translation into the
34430 correct system call is only applicable as it's defined in @value{GDBN}.
34431 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34434 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34435 this very system call.
34437 The target replies with this packet when it expects @value{GDBN} to
34438 call a host system call on behalf of the target. @value{GDBN} replies
34439 with an appropriate @samp{F} packet and keeps up waiting for the next
34440 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34441 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34442 Protocol Extension}, for more details.
34446 @node General Query Packets
34447 @section General Query Packets
34448 @cindex remote query requests
34450 Packets starting with @samp{q} are @dfn{general query packets};
34451 packets starting with @samp{Q} are @dfn{general set packets}. General
34452 query and set packets are a semi-unified form for retrieving and
34453 sending information to and from the stub.
34455 The initial letter of a query or set packet is followed by a name
34456 indicating what sort of thing the packet applies to. For example,
34457 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34458 definitions with the stub. These packet names follow some
34463 The name must not contain commas, colons or semicolons.
34465 Most @value{GDBN} query and set packets have a leading upper case
34468 The names of custom vendor packets should use a company prefix, in
34469 lower case, followed by a period. For example, packets designed at
34470 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34471 foos) or @samp{Qacme.bar} (for setting bars).
34474 The name of a query or set packet should be separated from any
34475 parameters by a @samp{:}; the parameters themselves should be
34476 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34477 full packet name, and check for a separator or the end of the packet,
34478 in case two packet names share a common prefix. New packets should not begin
34479 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34480 packets predate these conventions, and have arguments without any terminator
34481 for the packet name; we suspect they are in widespread use in places that
34482 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34483 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34486 Like the descriptions of the other packets, each description here
34487 has a template showing the packet's overall syntax, followed by an
34488 explanation of the packet's meaning. We include spaces in some of the
34489 templates for clarity; these are not part of the packet's syntax. No
34490 @value{GDBN} packet uses spaces to separate its components.
34492 Here are the currently defined query and set packets:
34496 @item QAllow:@var{op}:@var{val}@dots{}
34497 @cindex @samp{QAllow} packet
34498 Specify which operations @value{GDBN} expects to request of the
34499 target, as a semicolon-separated list of operation name and value
34500 pairs. Possible values for @var{op} include @samp{WriteReg},
34501 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34502 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34503 indicating that @value{GDBN} will not request the operation, or 1,
34504 indicating that it may. (The target can then use this to set up its
34505 own internals optimally, for instance if the debugger never expects to
34506 insert breakpoints, it may not need to install its own trap handler.)
34509 @cindex current thread, remote request
34510 @cindex @samp{qC} packet
34511 Return the current thread ID.
34515 @item QC @var{thread-id}
34516 Where @var{thread-id} is a thread ID as documented in
34517 @ref{thread-id syntax}.
34518 @item @r{(anything else)}
34519 Any other reply implies the old thread ID.
34522 @item qCRC:@var{addr},@var{length}
34523 @cindex CRC of memory block, remote request
34524 @cindex @samp{qCRC} packet
34525 Compute the CRC checksum of a block of memory using CRC-32 defined in
34526 IEEE 802.3. The CRC is computed byte at a time, taking the most
34527 significant bit of each byte first. The initial pattern code
34528 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34530 @emph{Note:} This is the same CRC used in validating separate debug
34531 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34532 Files}). However the algorithm is slightly different. When validating
34533 separate debug files, the CRC is computed taking the @emph{least}
34534 significant bit of each byte first, and the final result is inverted to
34535 detect trailing zeros.
34540 An error (such as memory fault)
34541 @item C @var{crc32}
34542 The specified memory region's checksum is @var{crc32}.
34545 @item QDisableRandomization:@var{value}
34546 @cindex disable address space randomization, remote request
34547 @cindex @samp{QDisableRandomization} packet
34548 Some target operating systems will randomize the virtual address space
34549 of the inferior process as a security feature, but provide a feature
34550 to disable such randomization, e.g.@: to allow for a more deterministic
34551 debugging experience. On such systems, this packet with a @var{value}
34552 of 1 directs the target to disable address space randomization for
34553 processes subsequently started via @samp{vRun} packets, while a packet
34554 with a @var{value} of 0 tells the target to enable address space
34557 This packet is only available in extended mode (@pxref{extended mode}).
34562 The request succeeded.
34565 An error occurred. @var{nn} are hex digits.
34568 An empty reply indicates that @samp{QDisableRandomization} is not supported
34572 This packet is not probed by default; the remote stub must request it,
34573 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34574 This should only be done on targets that actually support disabling
34575 address space randomization.
34578 @itemx qsThreadInfo
34579 @cindex list active threads, remote request
34580 @cindex @samp{qfThreadInfo} packet
34581 @cindex @samp{qsThreadInfo} packet
34582 Obtain a list of all active thread IDs from the target (OS). Since there
34583 may be too many active threads to fit into one reply packet, this query
34584 works iteratively: it may require more than one query/reply sequence to
34585 obtain the entire list of threads. The first query of the sequence will
34586 be the @samp{qfThreadInfo} query; subsequent queries in the
34587 sequence will be the @samp{qsThreadInfo} query.
34589 NOTE: This packet replaces the @samp{qL} query (see below).
34593 @item m @var{thread-id}
34595 @item m @var{thread-id},@var{thread-id}@dots{}
34596 a comma-separated list of thread IDs
34598 (lower case letter @samp{L}) denotes end of list.
34601 In response to each query, the target will reply with a list of one or
34602 more thread IDs, separated by commas.
34603 @value{GDBN} will respond to each reply with a request for more thread
34604 ids (using the @samp{qs} form of the query), until the target responds
34605 with @samp{l} (lower-case ell, for @dfn{last}).
34606 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34609 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34610 @cindex get thread-local storage address, remote request
34611 @cindex @samp{qGetTLSAddr} packet
34612 Fetch the address associated with thread local storage specified
34613 by @var{thread-id}, @var{offset}, and @var{lm}.
34615 @var{thread-id} is the thread ID associated with the
34616 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34618 @var{offset} is the (big endian, hex encoded) offset associated with the
34619 thread local variable. (This offset is obtained from the debug
34620 information associated with the variable.)
34622 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34623 load module associated with the thread local storage. For example,
34624 a @sc{gnu}/Linux system will pass the link map address of the shared
34625 object associated with the thread local storage under consideration.
34626 Other operating environments may choose to represent the load module
34627 differently, so the precise meaning of this parameter will vary.
34631 @item @var{XX}@dots{}
34632 Hex encoded (big endian) bytes representing the address of the thread
34633 local storage requested.
34636 An error occurred. @var{nn} are hex digits.
34639 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34642 @item qGetTIBAddr:@var{thread-id}
34643 @cindex get thread information block address
34644 @cindex @samp{qGetTIBAddr} packet
34645 Fetch address of the Windows OS specific Thread Information Block.
34647 @var{thread-id} is the thread ID associated with the thread.
34651 @item @var{XX}@dots{}
34652 Hex encoded (big endian) bytes representing the linear address of the
34653 thread information block.
34656 An error occured. This means that either the thread was not found, or the
34657 address could not be retrieved.
34660 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34663 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34664 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34665 digit) is one to indicate the first query and zero to indicate a
34666 subsequent query; @var{threadcount} (two hex digits) is the maximum
34667 number of threads the response packet can contain; and @var{nextthread}
34668 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34669 returned in the response as @var{argthread}.
34671 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34675 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34676 Where: @var{count} (two hex digits) is the number of threads being
34677 returned; @var{done} (one hex digit) is zero to indicate more threads
34678 and one indicates no further threads; @var{argthreadid} (eight hex
34679 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34680 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34681 digits). See @code{remote.c:parse_threadlist_response()}.
34685 @cindex section offsets, remote request
34686 @cindex @samp{qOffsets} packet
34687 Get section offsets that the target used when relocating the downloaded
34692 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34693 Relocate the @code{Text} section by @var{xxx} from its original address.
34694 Relocate the @code{Data} section by @var{yyy} from its original address.
34695 If the object file format provides segment information (e.g.@: @sc{elf}
34696 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34697 segments by the supplied offsets.
34699 @emph{Note: while a @code{Bss} offset may be included in the response,
34700 @value{GDBN} ignores this and instead applies the @code{Data} offset
34701 to the @code{Bss} section.}
34703 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34704 Relocate the first segment of the object file, which conventionally
34705 contains program code, to a starting address of @var{xxx}. If
34706 @samp{DataSeg} is specified, relocate the second segment, which
34707 conventionally contains modifiable data, to a starting address of
34708 @var{yyy}. @value{GDBN} will report an error if the object file
34709 does not contain segment information, or does not contain at least
34710 as many segments as mentioned in the reply. Extra segments are
34711 kept at fixed offsets relative to the last relocated segment.
34714 @item qP @var{mode} @var{thread-id}
34715 @cindex thread information, remote request
34716 @cindex @samp{qP} packet
34717 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34718 encoded 32 bit mode; @var{thread-id} is a thread ID
34719 (@pxref{thread-id syntax}).
34721 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34724 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34728 @cindex non-stop mode, remote request
34729 @cindex @samp{QNonStop} packet
34731 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34732 @xref{Remote Non-Stop}, for more information.
34737 The request succeeded.
34740 An error occurred. @var{nn} are hex digits.
34743 An empty reply indicates that @samp{QNonStop} is not supported by
34747 This packet is not probed by default; the remote stub must request it,
34748 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34749 Use of this packet is controlled by the @code{set non-stop} command;
34750 @pxref{Non-Stop Mode}.
34752 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34753 @cindex pass signals to inferior, remote request
34754 @cindex @samp{QPassSignals} packet
34755 @anchor{QPassSignals}
34756 Each listed @var{signal} should be passed directly to the inferior process.
34757 Signals are numbered identically to continue packets and stop replies
34758 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34759 strictly greater than the previous item. These signals do not need to stop
34760 the inferior, or be reported to @value{GDBN}. All other signals should be
34761 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34762 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34763 new list. This packet improves performance when using @samp{handle
34764 @var{signal} nostop noprint pass}.
34769 The request succeeded.
34772 An error occurred. @var{nn} are hex digits.
34775 An empty reply indicates that @samp{QPassSignals} is not supported by
34779 Use of this packet is controlled by the @code{set remote pass-signals}
34780 command (@pxref{Remote Configuration, set remote pass-signals}).
34781 This packet is not probed by default; the remote stub must request it,
34782 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34784 @item qRcmd,@var{command}
34785 @cindex execute remote command, remote request
34786 @cindex @samp{qRcmd} packet
34787 @var{command} (hex encoded) is passed to the local interpreter for
34788 execution. Invalid commands should be reported using the output
34789 string. Before the final result packet, the target may also respond
34790 with a number of intermediate @samp{O@var{output}} console output
34791 packets. @emph{Implementors should note that providing access to a
34792 stubs's interpreter may have security implications}.
34797 A command response with no output.
34799 A command response with the hex encoded output string @var{OUTPUT}.
34801 Indicate a badly formed request.
34803 An empty reply indicates that @samp{qRcmd} is not recognized.
34806 (Note that the @code{qRcmd} packet's name is separated from the
34807 command by a @samp{,}, not a @samp{:}, contrary to the naming
34808 conventions above. Please don't use this packet as a model for new
34811 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34812 @cindex searching memory, in remote debugging
34813 @cindex @samp{qSearch:memory} packet
34814 @anchor{qSearch memory}
34815 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34816 @var{address} and @var{length} are encoded in hex.
34817 @var{search-pattern} is a sequence of bytes, hex encoded.
34822 The pattern was not found.
34824 The pattern was found at @var{address}.
34826 A badly formed request or an error was encountered while searching memory.
34828 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34831 @item QStartNoAckMode
34832 @cindex @samp{QStartNoAckMode} packet
34833 @anchor{QStartNoAckMode}
34834 Request that the remote stub disable the normal @samp{+}/@samp{-}
34835 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34840 The stub has switched to no-acknowledgment mode.
34841 @value{GDBN} acknowledges this reponse,
34842 but neither the stub nor @value{GDBN} shall send or expect further
34843 @samp{+}/@samp{-} acknowledgments in the current connection.
34845 An empty reply indicates that the stub does not support no-acknowledgment mode.
34848 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34849 @cindex supported packets, remote query
34850 @cindex features of the remote protocol
34851 @cindex @samp{qSupported} packet
34852 @anchor{qSupported}
34853 Tell the remote stub about features supported by @value{GDBN}, and
34854 query the stub for features it supports. This packet allows
34855 @value{GDBN} and the remote stub to take advantage of each others'
34856 features. @samp{qSupported} also consolidates multiple feature probes
34857 at startup, to improve @value{GDBN} performance---a single larger
34858 packet performs better than multiple smaller probe packets on
34859 high-latency links. Some features may enable behavior which must not
34860 be on by default, e.g.@: because it would confuse older clients or
34861 stubs. Other features may describe packets which could be
34862 automatically probed for, but are not. These features must be
34863 reported before @value{GDBN} will use them. This ``default
34864 unsupported'' behavior is not appropriate for all packets, but it
34865 helps to keep the initial connection time under control with new
34866 versions of @value{GDBN} which support increasing numbers of packets.
34870 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34871 The stub supports or does not support each returned @var{stubfeature},
34872 depending on the form of each @var{stubfeature} (see below for the
34875 An empty reply indicates that @samp{qSupported} is not recognized,
34876 or that no features needed to be reported to @value{GDBN}.
34879 The allowed forms for each feature (either a @var{gdbfeature} in the
34880 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34884 @item @var{name}=@var{value}
34885 The remote protocol feature @var{name} is supported, and associated
34886 with the specified @var{value}. The format of @var{value} depends
34887 on the feature, but it must not include a semicolon.
34889 The remote protocol feature @var{name} is supported, and does not
34890 need an associated value.
34892 The remote protocol feature @var{name} is not supported.
34894 The remote protocol feature @var{name} may be supported, and
34895 @value{GDBN} should auto-detect support in some other way when it is
34896 needed. This form will not be used for @var{gdbfeature} notifications,
34897 but may be used for @var{stubfeature} responses.
34900 Whenever the stub receives a @samp{qSupported} request, the
34901 supplied set of @value{GDBN} features should override any previous
34902 request. This allows @value{GDBN} to put the stub in a known
34903 state, even if the stub had previously been communicating with
34904 a different version of @value{GDBN}.
34906 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34911 This feature indicates whether @value{GDBN} supports multiprocess
34912 extensions to the remote protocol. @value{GDBN} does not use such
34913 extensions unless the stub also reports that it supports them by
34914 including @samp{multiprocess+} in its @samp{qSupported} reply.
34915 @xref{multiprocess extensions}, for details.
34918 This feature indicates that @value{GDBN} supports the XML target
34919 description. If the stub sees @samp{xmlRegisters=} with target
34920 specific strings separated by a comma, it will report register
34924 This feature indicates whether @value{GDBN} supports the
34925 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34926 instruction reply packet}).
34929 Stubs should ignore any unknown values for
34930 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34931 packet supports receiving packets of unlimited length (earlier
34932 versions of @value{GDBN} may reject overly long responses). Additional values
34933 for @var{gdbfeature} may be defined in the future to let the stub take
34934 advantage of new features in @value{GDBN}, e.g.@: incompatible
34935 improvements in the remote protocol---the @samp{multiprocess} feature is
34936 an example of such a feature. The stub's reply should be independent
34937 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34938 describes all the features it supports, and then the stub replies with
34939 all the features it supports.
34941 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34942 responses, as long as each response uses one of the standard forms.
34944 Some features are flags. A stub which supports a flag feature
34945 should respond with a @samp{+} form response. Other features
34946 require values, and the stub should respond with an @samp{=}
34949 Each feature has a default value, which @value{GDBN} will use if
34950 @samp{qSupported} is not available or if the feature is not mentioned
34951 in the @samp{qSupported} response. The default values are fixed; a
34952 stub is free to omit any feature responses that match the defaults.
34954 Not all features can be probed, but for those which can, the probing
34955 mechanism is useful: in some cases, a stub's internal
34956 architecture may not allow the protocol layer to know some information
34957 about the underlying target in advance. This is especially common in
34958 stubs which may be configured for multiple targets.
34960 These are the currently defined stub features and their properties:
34962 @multitable @columnfractions 0.35 0.2 0.12 0.2
34963 @c NOTE: The first row should be @headitem, but we do not yet require
34964 @c a new enough version of Texinfo (4.7) to use @headitem.
34966 @tab Value Required
34970 @item @samp{PacketSize}
34975 @item @samp{qXfer:auxv:read}
34980 @item @samp{qXfer:features:read}
34985 @item @samp{qXfer:libraries:read}
34990 @item @samp{qXfer:memory-map:read}
34995 @item @samp{qXfer:sdata:read}
35000 @item @samp{qXfer:spu:read}
35005 @item @samp{qXfer:spu:write}
35010 @item @samp{qXfer:siginfo:read}
35015 @item @samp{qXfer:siginfo:write}
35020 @item @samp{qXfer:threads:read}
35025 @item @samp{qXfer:traceframe-info:read}
35030 @item @samp{qXfer:fdpic:read}
35035 @item @samp{QNonStop}
35040 @item @samp{QPassSignals}
35045 @item @samp{QStartNoAckMode}
35050 @item @samp{multiprocess}
35055 @item @samp{ConditionalTracepoints}
35060 @item @samp{ReverseContinue}
35065 @item @samp{ReverseStep}
35070 @item @samp{TracepointSource}
35075 @item @samp{QAllow}
35080 @item @samp{QDisableRandomization}
35085 @item @samp{EnableDisableTracepoints}
35090 @item @samp{tracenz}
35097 These are the currently defined stub features, in more detail:
35100 @cindex packet size, remote protocol
35101 @item PacketSize=@var{bytes}
35102 The remote stub can accept packets up to at least @var{bytes} in
35103 length. @value{GDBN} will send packets up to this size for bulk
35104 transfers, and will never send larger packets. This is a limit on the
35105 data characters in the packet, including the frame and checksum.
35106 There is no trailing NUL byte in a remote protocol packet; if the stub
35107 stores packets in a NUL-terminated format, it should allow an extra
35108 byte in its buffer for the NUL. If this stub feature is not supported,
35109 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35111 @item qXfer:auxv:read
35112 The remote stub understands the @samp{qXfer:auxv:read} packet
35113 (@pxref{qXfer auxiliary vector read}).
35115 @item qXfer:features:read
35116 The remote stub understands the @samp{qXfer:features:read} packet
35117 (@pxref{qXfer target description read}).
35119 @item qXfer:libraries:read
35120 The remote stub understands the @samp{qXfer:libraries:read} packet
35121 (@pxref{qXfer library list read}).
35123 @item qXfer:libraries-svr4:read
35124 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35125 (@pxref{qXfer svr4 library list read}).
35127 @item qXfer:memory-map:read
35128 The remote stub understands the @samp{qXfer:memory-map:read} packet
35129 (@pxref{qXfer memory map read}).
35131 @item qXfer:sdata:read
35132 The remote stub understands the @samp{qXfer:sdata:read} packet
35133 (@pxref{qXfer sdata read}).
35135 @item qXfer:spu:read
35136 The remote stub understands the @samp{qXfer:spu:read} packet
35137 (@pxref{qXfer spu read}).
35139 @item qXfer:spu:write
35140 The remote stub understands the @samp{qXfer:spu:write} packet
35141 (@pxref{qXfer spu write}).
35143 @item qXfer:siginfo:read
35144 The remote stub understands the @samp{qXfer:siginfo:read} packet
35145 (@pxref{qXfer siginfo read}).
35147 @item qXfer:siginfo:write
35148 The remote stub understands the @samp{qXfer:siginfo:write} packet
35149 (@pxref{qXfer siginfo write}).
35151 @item qXfer:threads:read
35152 The remote stub understands the @samp{qXfer:threads:read} packet
35153 (@pxref{qXfer threads read}).
35155 @item qXfer:traceframe-info:read
35156 The remote stub understands the @samp{qXfer:traceframe-info:read}
35157 packet (@pxref{qXfer traceframe info read}).
35159 @item qXfer:fdpic:read
35160 The remote stub understands the @samp{qXfer:fdpic:read}
35161 packet (@pxref{qXfer fdpic loadmap read}).
35164 The remote stub understands the @samp{QNonStop} packet
35165 (@pxref{QNonStop}).
35168 The remote stub understands the @samp{QPassSignals} packet
35169 (@pxref{QPassSignals}).
35171 @item QStartNoAckMode
35172 The remote stub understands the @samp{QStartNoAckMode} packet and
35173 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35176 @anchor{multiprocess extensions}
35177 @cindex multiprocess extensions, in remote protocol
35178 The remote stub understands the multiprocess extensions to the remote
35179 protocol syntax. The multiprocess extensions affect the syntax of
35180 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35181 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35182 replies. Note that reporting this feature indicates support for the
35183 syntactic extensions only, not that the stub necessarily supports
35184 debugging of more than one process at a time. The stub must not use
35185 multiprocess extensions in packet replies unless @value{GDBN} has also
35186 indicated it supports them in its @samp{qSupported} request.
35188 @item qXfer:osdata:read
35189 The remote stub understands the @samp{qXfer:osdata:read} packet
35190 ((@pxref{qXfer osdata read}).
35192 @item ConditionalTracepoints
35193 The remote stub accepts and implements conditional expressions defined
35194 for tracepoints (@pxref{Tracepoint Conditions}).
35196 @item ReverseContinue
35197 The remote stub accepts and implements the reverse continue packet
35201 The remote stub accepts and implements the reverse step packet
35204 @item TracepointSource
35205 The remote stub understands the @samp{QTDPsrc} packet that supplies
35206 the source form of tracepoint definitions.
35209 The remote stub understands the @samp{QAllow} packet.
35211 @item QDisableRandomization
35212 The remote stub understands the @samp{QDisableRandomization} packet.
35214 @item StaticTracepoint
35215 @cindex static tracepoints, in remote protocol
35216 The remote stub supports static tracepoints.
35218 @item InstallInTrace
35219 @anchor{install tracepoint in tracing}
35220 The remote stub supports installing tracepoint in tracing.
35222 @item EnableDisableTracepoints
35223 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35224 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35225 to be enabled and disabled while a trace experiment is running.
35228 @cindex string tracing, in remote protocol
35229 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35230 See @ref{Bytecode Descriptions} for details about the bytecode.
35235 @cindex symbol lookup, remote request
35236 @cindex @samp{qSymbol} packet
35237 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35238 requests. Accept requests from the target for the values of symbols.
35243 The target does not need to look up any (more) symbols.
35244 @item qSymbol:@var{sym_name}
35245 The target requests the value of symbol @var{sym_name} (hex encoded).
35246 @value{GDBN} may provide the value by using the
35247 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35251 @item qSymbol:@var{sym_value}:@var{sym_name}
35252 Set the value of @var{sym_name} to @var{sym_value}.
35254 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35255 target has previously requested.
35257 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35258 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35264 The target does not need to look up any (more) symbols.
35265 @item qSymbol:@var{sym_name}
35266 The target requests the value of a new symbol @var{sym_name} (hex
35267 encoded). @value{GDBN} will continue to supply the values of symbols
35268 (if available), until the target ceases to request them.
35273 @item QTDisconnected
35280 @itemx qTMinFTPILen
35282 @xref{Tracepoint Packets}.
35284 @item qThreadExtraInfo,@var{thread-id}
35285 @cindex thread attributes info, remote request
35286 @cindex @samp{qThreadExtraInfo} packet
35287 Obtain a printable string description of a thread's attributes from
35288 the target OS. @var{thread-id} is a thread ID;
35289 see @ref{thread-id syntax}. This
35290 string may contain anything that the target OS thinks is interesting
35291 for @value{GDBN} to tell the user about the thread. The string is
35292 displayed in @value{GDBN}'s @code{info threads} display. Some
35293 examples of possible thread extra info strings are @samp{Runnable}, or
35294 @samp{Blocked on Mutex}.
35298 @item @var{XX}@dots{}
35299 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35300 comprising the printable string containing the extra information about
35301 the thread's attributes.
35304 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35305 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35306 conventions above. Please don't use this packet as a model for new
35325 @xref{Tracepoint Packets}.
35327 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35328 @cindex read special object, remote request
35329 @cindex @samp{qXfer} packet
35330 @anchor{qXfer read}
35331 Read uninterpreted bytes from the target's special data area
35332 identified by the keyword @var{object}. Request @var{length} bytes
35333 starting at @var{offset} bytes into the data. The content and
35334 encoding of @var{annex} is specific to @var{object}; it can supply
35335 additional details about what data to access.
35337 Here are the specific requests of this form defined so far. All
35338 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35339 formats, listed below.
35342 @item qXfer:auxv:read::@var{offset},@var{length}
35343 @anchor{qXfer auxiliary vector read}
35344 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35345 auxiliary vector}. Note @var{annex} must be empty.
35347 This packet is not probed by default; the remote stub must request it,
35348 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35350 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35351 @anchor{qXfer target description read}
35352 Access the @dfn{target description}. @xref{Target Descriptions}. The
35353 annex specifies which XML document to access. The main description is
35354 always loaded from the @samp{target.xml} annex.
35356 This packet is not probed by default; the remote stub must request it,
35357 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35359 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35360 @anchor{qXfer library list read}
35361 Access the target's list of loaded libraries. @xref{Library List Format}.
35362 The annex part of the generic @samp{qXfer} packet must be empty
35363 (@pxref{qXfer read}).
35365 Targets which maintain a list of libraries in the program's memory do
35366 not need to implement this packet; it is designed for platforms where
35367 the operating system manages the list of loaded libraries.
35369 This packet is not probed by default; the remote stub must request it,
35370 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35372 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35373 @anchor{qXfer svr4 library list read}
35374 Access the target's list of loaded libraries when the target is an SVR4
35375 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35376 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35378 This packet is optional for better performance on SVR4 targets.
35379 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35381 This packet is not probed by default; the remote stub must request it,
35382 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35384 @item qXfer:memory-map:read::@var{offset},@var{length}
35385 @anchor{qXfer memory map read}
35386 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35387 annex part of the generic @samp{qXfer} packet must be empty
35388 (@pxref{qXfer read}).
35390 This packet is not probed by default; the remote stub must request it,
35391 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35393 @item qXfer:sdata:read::@var{offset},@var{length}
35394 @anchor{qXfer sdata read}
35396 Read contents of the extra collected static tracepoint marker
35397 information. The annex part of the generic @samp{qXfer} packet must
35398 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35401 This packet is not probed by default; the remote stub must request it,
35402 by supplying an appropriate @samp{qSupported} response
35403 (@pxref{qSupported}).
35405 @item qXfer:siginfo:read::@var{offset},@var{length}
35406 @anchor{qXfer siginfo read}
35407 Read contents of the extra signal information on the target
35408 system. The annex part of the generic @samp{qXfer} packet must be
35409 empty (@pxref{qXfer read}).
35411 This packet is not probed by default; the remote stub must request it,
35412 by supplying an appropriate @samp{qSupported} response
35413 (@pxref{qSupported}).
35415 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35416 @anchor{qXfer spu read}
35417 Read contents of an @code{spufs} file on the target system. The
35418 annex specifies which file to read; it must be of the form
35419 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35420 in the target process, and @var{name} identifes the @code{spufs} file
35421 in that context to be accessed.
35423 This packet is not probed by default; the remote stub must request it,
35424 by supplying an appropriate @samp{qSupported} response
35425 (@pxref{qSupported}).
35427 @item qXfer:threads:read::@var{offset},@var{length}
35428 @anchor{qXfer threads read}
35429 Access the list of threads on target. @xref{Thread List Format}. The
35430 annex part of the generic @samp{qXfer} packet must be empty
35431 (@pxref{qXfer read}).
35433 This packet is not probed by default; the remote stub must request it,
35434 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35436 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35437 @anchor{qXfer traceframe info read}
35439 Return a description of the current traceframe's contents.
35440 @xref{Traceframe Info Format}. The annex part of the generic
35441 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35443 This packet is not probed by default; the remote stub must request it,
35444 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35446 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35447 @anchor{qXfer fdpic loadmap read}
35448 Read contents of @code{loadmap}s on the target system. The
35449 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35450 executable @code{loadmap} or interpreter @code{loadmap} to read.
35452 This packet is not probed by default; the remote stub must request it,
35453 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35455 @item qXfer:osdata:read::@var{offset},@var{length}
35456 @anchor{qXfer osdata read}
35457 Access the target's @dfn{operating system information}.
35458 @xref{Operating System Information}.
35465 Data @var{data} (@pxref{Binary Data}) has been read from the
35466 target. There may be more data at a higher address (although
35467 it is permitted to return @samp{m} even for the last valid
35468 block of data, as long as at least one byte of data was read).
35469 @var{data} may have fewer bytes than the @var{length} in the
35473 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35474 There is no more data to be read. @var{data} may have fewer bytes
35475 than the @var{length} in the request.
35478 The @var{offset} in the request is at the end of the data.
35479 There is no more data to be read.
35482 The request was malformed, or @var{annex} was invalid.
35485 The offset was invalid, or there was an error encountered reading the data.
35486 @var{nn} is a hex-encoded @code{errno} value.
35489 An empty reply indicates the @var{object} string was not recognized by
35490 the stub, or that the object does not support reading.
35493 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35494 @cindex write data into object, remote request
35495 @anchor{qXfer write}
35496 Write uninterpreted bytes into the target's special data area
35497 identified by the keyword @var{object}, starting at @var{offset} bytes
35498 into the data. @var{data}@dots{} is the binary-encoded data
35499 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35500 is specific to @var{object}; it can supply additional details about what data
35503 Here are the specific requests of this form defined so far. All
35504 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35505 formats, listed below.
35508 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35509 @anchor{qXfer siginfo write}
35510 Write @var{data} to the extra signal information on the target system.
35511 The annex part of the generic @samp{qXfer} packet must be
35512 empty (@pxref{qXfer write}).
35514 This packet is not probed by default; the remote stub must request it,
35515 by supplying an appropriate @samp{qSupported} response
35516 (@pxref{qSupported}).
35518 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35519 @anchor{qXfer spu write}
35520 Write @var{data} to an @code{spufs} file on the target system. The
35521 annex specifies which file to write; it must be of the form
35522 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35523 in the target process, and @var{name} identifes the @code{spufs} file
35524 in that context to be accessed.
35526 This packet is not probed by default; the remote stub must request it,
35527 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35533 @var{nn} (hex encoded) is the number of bytes written.
35534 This may be fewer bytes than supplied in the request.
35537 The request was malformed, or @var{annex} was invalid.
35540 The offset was invalid, or there was an error encountered writing the data.
35541 @var{nn} is a hex-encoded @code{errno} value.
35544 An empty reply indicates the @var{object} string was not
35545 recognized by the stub, or that the object does not support writing.
35548 @item qXfer:@var{object}:@var{operation}:@dots{}
35549 Requests of this form may be added in the future. When a stub does
35550 not recognize the @var{object} keyword, or its support for
35551 @var{object} does not recognize the @var{operation} keyword, the stub
35552 must respond with an empty packet.
35554 @item qAttached:@var{pid}
35555 @cindex query attached, remote request
35556 @cindex @samp{qAttached} packet
35557 Return an indication of whether the remote server attached to an
35558 existing process or created a new process. When the multiprocess
35559 protocol extensions are supported (@pxref{multiprocess extensions}),
35560 @var{pid} is an integer in hexadecimal format identifying the target
35561 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35562 the query packet will be simplified as @samp{qAttached}.
35564 This query is used, for example, to know whether the remote process
35565 should be detached or killed when a @value{GDBN} session is ended with
35566 the @code{quit} command.
35571 The remote server attached to an existing process.
35573 The remote server created a new process.
35575 A badly formed request or an error was encountered.
35580 @node Architecture-Specific Protocol Details
35581 @section Architecture-Specific Protocol Details
35583 This section describes how the remote protocol is applied to specific
35584 target architectures. Also see @ref{Standard Target Features}, for
35585 details of XML target descriptions for each architecture.
35589 @subsubsection Breakpoint Kinds
35591 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35596 16-bit Thumb mode breakpoint.
35599 32-bit Thumb mode (Thumb-2) breakpoint.
35602 32-bit ARM mode breakpoint.
35608 @subsubsection Register Packet Format
35610 The following @code{g}/@code{G} packets have previously been defined.
35611 In the below, some thirty-two bit registers are transferred as
35612 sixty-four bits. Those registers should be zero/sign extended (which?)
35613 to fill the space allocated. Register bytes are transferred in target
35614 byte order. The two nibbles within a register byte are transferred
35615 most-significant - least-significant.
35621 All registers are transferred as thirty-two bit quantities in the order:
35622 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35623 registers; fsr; fir; fp.
35627 All registers are transferred as sixty-four bit quantities (including
35628 thirty-two bit registers such as @code{sr}). The ordering is the same
35633 @node Tracepoint Packets
35634 @section Tracepoint Packets
35635 @cindex tracepoint packets
35636 @cindex packets, tracepoint
35638 Here we describe the packets @value{GDBN} uses to implement
35639 tracepoints (@pxref{Tracepoints}).
35643 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35644 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35645 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35646 the tracepoint is disabled. @var{step} is the tracepoint's step
35647 count, and @var{pass} is its pass count. If an @samp{F} is present,
35648 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35649 the number of bytes that the target should copy elsewhere to make room
35650 for the tracepoint. If an @samp{X} is present, it introduces a
35651 tracepoint condition, which consists of a hexadecimal length, followed
35652 by a comma and hex-encoded bytes, in a manner similar to action
35653 encodings as described below. If the trailing @samp{-} is present,
35654 further @samp{QTDP} packets will follow to specify this tracepoint's
35660 The packet was understood and carried out.
35662 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35664 The packet was not recognized.
35667 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35668 Define actions to be taken when a tracepoint is hit. @var{n} and
35669 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35670 this tracepoint. This packet may only be sent immediately after
35671 another @samp{QTDP} packet that ended with a @samp{-}. If the
35672 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35673 specifying more actions for this tracepoint.
35675 In the series of action packets for a given tracepoint, at most one
35676 can have an @samp{S} before its first @var{action}. If such a packet
35677 is sent, it and the following packets define ``while-stepping''
35678 actions. Any prior packets define ordinary actions --- that is, those
35679 taken when the tracepoint is first hit. If no action packet has an
35680 @samp{S}, then all the packets in the series specify ordinary
35681 tracepoint actions.
35683 The @samp{@var{action}@dots{}} portion of the packet is a series of
35684 actions, concatenated without separators. Each action has one of the
35690 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35691 a hexadecimal number whose @var{i}'th bit is set if register number
35692 @var{i} should be collected. (The least significant bit is numbered
35693 zero.) Note that @var{mask} may be any number of digits long; it may
35694 not fit in a 32-bit word.
35696 @item M @var{basereg},@var{offset},@var{len}
35697 Collect @var{len} bytes of memory starting at the address in register
35698 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35699 @samp{-1}, then the range has a fixed address: @var{offset} is the
35700 address of the lowest byte to collect. The @var{basereg},
35701 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35702 values (the @samp{-1} value for @var{basereg} is a special case).
35704 @item X @var{len},@var{expr}
35705 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35706 it directs. @var{expr} is an agent expression, as described in
35707 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35708 two-digit hex number in the packet; @var{len} is the number of bytes
35709 in the expression (and thus one-half the number of hex digits in the
35714 Any number of actions may be packed together in a single @samp{QTDP}
35715 packet, as long as the packet does not exceed the maximum packet
35716 length (400 bytes, for many stubs). There may be only one @samp{R}
35717 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35718 actions. Any registers referred to by @samp{M} and @samp{X} actions
35719 must be collected by a preceding @samp{R} action. (The
35720 ``while-stepping'' actions are treated as if they were attached to a
35721 separate tracepoint, as far as these restrictions are concerned.)
35726 The packet was understood and carried out.
35728 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35730 The packet was not recognized.
35733 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35734 @cindex @samp{QTDPsrc} packet
35735 Specify a source string of tracepoint @var{n} at address @var{addr}.
35736 This is useful to get accurate reproduction of the tracepoints
35737 originally downloaded at the beginning of the trace run. @var{type}
35738 is the name of the tracepoint part, such as @samp{cond} for the
35739 tracepoint's conditional expression (see below for a list of types), while
35740 @var{bytes} is the string, encoded in hexadecimal.
35742 @var{start} is the offset of the @var{bytes} within the overall source
35743 string, while @var{slen} is the total length of the source string.
35744 This is intended for handling source strings that are longer than will
35745 fit in a single packet.
35746 @c Add detailed example when this info is moved into a dedicated
35747 @c tracepoint descriptions section.
35749 The available string types are @samp{at} for the location,
35750 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35751 @value{GDBN} sends a separate packet for each command in the action
35752 list, in the same order in which the commands are stored in the list.
35754 The target does not need to do anything with source strings except
35755 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35758 Although this packet is optional, and @value{GDBN} will only send it
35759 if the target replies with @samp{TracepointSource} @xref{General
35760 Query Packets}, it makes both disconnected tracing and trace files
35761 much easier to use. Otherwise the user must be careful that the
35762 tracepoints in effect while looking at trace frames are identical to
35763 the ones in effect during the trace run; even a small discrepancy
35764 could cause @samp{tdump} not to work, or a particular trace frame not
35767 @item QTDV:@var{n}:@var{value}
35768 @cindex define trace state variable, remote request
35769 @cindex @samp{QTDV} packet
35770 Create a new trace state variable, number @var{n}, with an initial
35771 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35772 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35773 the option of not using this packet for initial values of zero; the
35774 target should simply create the trace state variables as they are
35775 mentioned in expressions.
35777 @item QTFrame:@var{n}
35778 Select the @var{n}'th tracepoint frame from the buffer, and use the
35779 register and memory contents recorded there to answer subsequent
35780 request packets from @value{GDBN}.
35782 A successful reply from the stub indicates that the stub has found the
35783 requested frame. The response is a series of parts, concatenated
35784 without separators, describing the frame we selected. Each part has
35785 one of the following forms:
35789 The selected frame is number @var{n} in the trace frame buffer;
35790 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35791 was no frame matching the criteria in the request packet.
35794 The selected trace frame records a hit of tracepoint number @var{t};
35795 @var{t} is a hexadecimal number.
35799 @item QTFrame:pc:@var{addr}
35800 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35801 currently selected frame whose PC is @var{addr};
35802 @var{addr} is a hexadecimal number.
35804 @item QTFrame:tdp:@var{t}
35805 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35806 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35807 is a hexadecimal number.
35809 @item QTFrame:range:@var{start}:@var{end}
35810 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35811 currently selected frame whose PC is between @var{start} (inclusive)
35812 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35815 @item QTFrame:outside:@var{start}:@var{end}
35816 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35817 frame @emph{outside} the given range of addresses (exclusive).
35820 This packet requests the minimum length of instruction at which a fast
35821 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
35822 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
35823 it depends on the target system being able to create trampolines in
35824 the first 64K of memory, which might or might not be possible for that
35825 system. So the reply to this packet will be 4 if it is able to
35832 The minimum instruction length is currently unknown.
35834 The minimum instruction length is @var{length}, where @var{length} is greater
35835 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
35836 that a fast tracepoint may be placed on any instruction regardless of size.
35838 An error has occurred.
35840 An empty reply indicates that the request is not supported by the stub.
35844 Begin the tracepoint experiment. Begin collecting data from
35845 tracepoint hits in the trace frame buffer. This packet supports the
35846 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35847 instruction reply packet}).
35850 End the tracepoint experiment. Stop collecting trace frames.
35852 @item QTEnable:@var{n}:@var{addr}
35854 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35855 experiment. If the tracepoint was previously disabled, then collection
35856 of data from it will resume.
35858 @item QTDisable:@var{n}:@var{addr}
35860 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35861 experiment. No more data will be collected from the tracepoint unless
35862 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35865 Clear the table of tracepoints, and empty the trace frame buffer.
35867 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35868 Establish the given ranges of memory as ``transparent''. The stub
35869 will answer requests for these ranges from memory's current contents,
35870 if they were not collected as part of the tracepoint hit.
35872 @value{GDBN} uses this to mark read-only regions of memory, like those
35873 containing program code. Since these areas never change, they should
35874 still have the same contents they did when the tracepoint was hit, so
35875 there's no reason for the stub to refuse to provide their contents.
35877 @item QTDisconnected:@var{value}
35878 Set the choice to what to do with the tracing run when @value{GDBN}
35879 disconnects from the target. A @var{value} of 1 directs the target to
35880 continue the tracing run, while 0 tells the target to stop tracing if
35881 @value{GDBN} is no longer in the picture.
35884 Ask the stub if there is a trace experiment running right now.
35886 The reply has the form:
35890 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35891 @var{running} is a single digit @code{1} if the trace is presently
35892 running, or @code{0} if not. It is followed by semicolon-separated
35893 optional fields that an agent may use to report additional status.
35897 If the trace is not running, the agent may report any of several
35898 explanations as one of the optional fields:
35903 No trace has been run yet.
35905 @item tstop[:@var{text}]:0
35906 The trace was stopped by a user-originated stop command. The optional
35907 @var{text} field is a user-supplied string supplied as part of the
35908 stop command (for instance, an explanation of why the trace was
35909 stopped manually). It is hex-encoded.
35912 The trace stopped because the trace buffer filled up.
35914 @item tdisconnected:0
35915 The trace stopped because @value{GDBN} disconnected from the target.
35917 @item tpasscount:@var{tpnum}
35918 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35920 @item terror:@var{text}:@var{tpnum}
35921 The trace stopped because tracepoint @var{tpnum} had an error. The
35922 string @var{text} is available to describe the nature of the error
35923 (for instance, a divide by zero in the condition expression).
35924 @var{text} is hex encoded.
35927 The trace stopped for some other reason.
35931 Additional optional fields supply statistical and other information.
35932 Although not required, they are extremely useful for users monitoring
35933 the progress of a trace run. If a trace has stopped, and these
35934 numbers are reported, they must reflect the state of the just-stopped
35939 @item tframes:@var{n}
35940 The number of trace frames in the buffer.
35942 @item tcreated:@var{n}
35943 The total number of trace frames created during the run. This may
35944 be larger than the trace frame count, if the buffer is circular.
35946 @item tsize:@var{n}
35947 The total size of the trace buffer, in bytes.
35949 @item tfree:@var{n}
35950 The number of bytes still unused in the buffer.
35952 @item circular:@var{n}
35953 The value of the circular trace buffer flag. @code{1} means that the
35954 trace buffer is circular and old trace frames will be discarded if
35955 necessary to make room, @code{0} means that the trace buffer is linear
35958 @item disconn:@var{n}
35959 The value of the disconnected tracing flag. @code{1} means that
35960 tracing will continue after @value{GDBN} disconnects, @code{0} means
35961 that the trace run will stop.
35965 @item qTP:@var{tp}:@var{addr}
35966 @cindex tracepoint status, remote request
35967 @cindex @samp{qTP} packet
35968 Ask the stub for the current state of tracepoint number @var{tp} at
35969 address @var{addr}.
35973 @item V@var{hits}:@var{usage}
35974 The tracepoint has been hit @var{hits} times so far during the trace
35975 run, and accounts for @var{usage} in the trace buffer. Note that
35976 @code{while-stepping} steps are not counted as separate hits, but the
35977 steps' space consumption is added into the usage number.
35981 @item qTV:@var{var}
35982 @cindex trace state variable value, remote request
35983 @cindex @samp{qTV} packet
35984 Ask the stub for the value of the trace state variable number @var{var}.
35989 The value of the variable is @var{value}. This will be the current
35990 value of the variable if the user is examining a running target, or a
35991 saved value if the variable was collected in the trace frame that the
35992 user is looking at. Note that multiple requests may result in
35993 different reply values, such as when requesting values while the
35994 program is running.
35997 The value of the variable is unknown. This would occur, for example,
35998 if the user is examining a trace frame in which the requested variable
36004 These packets request data about tracepoints that are being used by
36005 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36006 of data, and multiple @code{qTsP} to get additional pieces. Replies
36007 to these packets generally take the form of the @code{QTDP} packets
36008 that define tracepoints. (FIXME add detailed syntax)
36012 These packets request data about trace state variables that are on the
36013 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36014 and multiple @code{qTsV} to get additional variables. Replies to
36015 these packets follow the syntax of the @code{QTDV} packets that define
36016 trace state variables.
36020 These packets request data about static tracepoint markers that exist
36021 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36022 first piece of data, and multiple @code{qTsSTM} to get additional
36023 pieces. Replies to these packets take the following form:
36027 @item m @var{address}:@var{id}:@var{extra}
36029 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36030 a comma-separated list of markers
36032 (lower case letter @samp{L}) denotes end of list.
36034 An error occurred. @var{nn} are hex digits.
36036 An empty reply indicates that the request is not supported by the
36040 @var{address} is encoded in hex.
36041 @var{id} and @var{extra} are strings encoded in hex.
36043 In response to each query, the target will reply with a list of one or
36044 more markers, separated by commas. @value{GDBN} will respond to each
36045 reply with a request for more markers (using the @samp{qs} form of the
36046 query), until the target responds with @samp{l} (lower-case ell, for
36049 @item qTSTMat:@var{address}
36050 This packets requests data about static tracepoint markers in the
36051 target program at @var{address}. Replies to this packet follow the
36052 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36053 tracepoint markers.
36055 @item QTSave:@var{filename}
36056 This packet directs the target to save trace data to the file name
36057 @var{filename} in the target's filesystem. @var{filename} is encoded
36058 as a hex string; the interpretation of the file name (relative vs
36059 absolute, wild cards, etc) is up to the target.
36061 @item qTBuffer:@var{offset},@var{len}
36062 Return up to @var{len} bytes of the current contents of trace buffer,
36063 starting at @var{offset}. The trace buffer is treated as if it were
36064 a contiguous collection of traceframes, as per the trace file format.
36065 The reply consists as many hex-encoded bytes as the target can deliver
36066 in a packet; it is not an error to return fewer than were asked for.
36067 A reply consisting of just @code{l} indicates that no bytes are
36070 @item QTBuffer:circular:@var{value}
36071 This packet directs the target to use a circular trace buffer if
36072 @var{value} is 1, or a linear buffer if the value is 0.
36074 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36075 This packet adds optional textual notes to the trace run. Allowable
36076 types include @code{user}, @code{notes}, and @code{tstop}, the
36077 @var{text} fields are arbitrary strings, hex-encoded.
36081 @subsection Relocate instruction reply packet
36082 When installing fast tracepoints in memory, the target may need to
36083 relocate the instruction currently at the tracepoint address to a
36084 different address in memory. For most instructions, a simple copy is
36085 enough, but, for example, call instructions that implicitly push the
36086 return address on the stack, and relative branches or other
36087 PC-relative instructions require offset adjustment, so that the effect
36088 of executing the instruction at a different address is the same as if
36089 it had executed in the original location.
36091 In response to several of the tracepoint packets, the target may also
36092 respond with a number of intermediate @samp{qRelocInsn} request
36093 packets before the final result packet, to have @value{GDBN} handle
36094 this relocation operation. If a packet supports this mechanism, its
36095 documentation will explicitly say so. See for example the above
36096 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36097 format of the request is:
36100 @item qRelocInsn:@var{from};@var{to}
36102 This requests @value{GDBN} to copy instruction at address @var{from}
36103 to address @var{to}, possibly adjusted so that executing the
36104 instruction at @var{to} has the same effect as executing it at
36105 @var{from}. @value{GDBN} writes the adjusted instruction to target
36106 memory starting at @var{to}.
36111 @item qRelocInsn:@var{adjusted_size}
36112 Informs the stub the relocation is complete. @var{adjusted_size} is
36113 the length in bytes of resulting relocated instruction sequence.
36115 A badly formed request was detected, or an error was encountered while
36116 relocating the instruction.
36119 @node Host I/O Packets
36120 @section Host I/O Packets
36121 @cindex Host I/O, remote protocol
36122 @cindex file transfer, remote protocol
36124 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36125 operations on the far side of a remote link. For example, Host I/O is
36126 used to upload and download files to a remote target with its own
36127 filesystem. Host I/O uses the same constant values and data structure
36128 layout as the target-initiated File-I/O protocol. However, the
36129 Host I/O packets are structured differently. The target-initiated
36130 protocol relies on target memory to store parameters and buffers.
36131 Host I/O requests are initiated by @value{GDBN}, and the
36132 target's memory is not involved. @xref{File-I/O Remote Protocol
36133 Extension}, for more details on the target-initiated protocol.
36135 The Host I/O request packets all encode a single operation along with
36136 its arguments. They have this format:
36140 @item vFile:@var{operation}: @var{parameter}@dots{}
36141 @var{operation} is the name of the particular request; the target
36142 should compare the entire packet name up to the second colon when checking
36143 for a supported operation. The format of @var{parameter} depends on
36144 the operation. Numbers are always passed in hexadecimal. Negative
36145 numbers have an explicit minus sign (i.e.@: two's complement is not
36146 used). Strings (e.g.@: filenames) are encoded as a series of
36147 hexadecimal bytes. The last argument to a system call may be a
36148 buffer of escaped binary data (@pxref{Binary Data}).
36152 The valid responses to Host I/O packets are:
36156 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36157 @var{result} is the integer value returned by this operation, usually
36158 non-negative for success and -1 for errors. If an error has occured,
36159 @var{errno} will be included in the result. @var{errno} will have a
36160 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36161 operations which return data, @var{attachment} supplies the data as a
36162 binary buffer. Binary buffers in response packets are escaped in the
36163 normal way (@pxref{Binary Data}). See the individual packet
36164 documentation for the interpretation of @var{result} and
36168 An empty response indicates that this operation is not recognized.
36172 These are the supported Host I/O operations:
36175 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36176 Open a file at @var{pathname} and return a file descriptor for it, or
36177 return -1 if an error occurs. @var{pathname} is a string,
36178 @var{flags} is an integer indicating a mask of open flags
36179 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36180 of mode bits to use if the file is created (@pxref{mode_t Values}).
36181 @xref{open}, for details of the open flags and mode values.
36183 @item vFile:close: @var{fd}
36184 Close the open file corresponding to @var{fd} and return 0, or
36185 -1 if an error occurs.
36187 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36188 Read data from the open file corresponding to @var{fd}. Up to
36189 @var{count} bytes will be read from the file, starting at @var{offset}
36190 relative to the start of the file. The target may read fewer bytes;
36191 common reasons include packet size limits and an end-of-file
36192 condition. The number of bytes read is returned. Zero should only be
36193 returned for a successful read at the end of the file, or if
36194 @var{count} was zero.
36196 The data read should be returned as a binary attachment on success.
36197 If zero bytes were read, the response should include an empty binary
36198 attachment (i.e.@: a trailing semicolon). The return value is the
36199 number of target bytes read; the binary attachment may be longer if
36200 some characters were escaped.
36202 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36203 Write @var{data} (a binary buffer) to the open file corresponding
36204 to @var{fd}. Start the write at @var{offset} from the start of the
36205 file. Unlike many @code{write} system calls, there is no
36206 separate @var{count} argument; the length of @var{data} in the
36207 packet is used. @samp{vFile:write} returns the number of bytes written,
36208 which may be shorter than the length of @var{data}, or -1 if an
36211 @item vFile:unlink: @var{pathname}
36212 Delete the file at @var{pathname} on the target. Return 0,
36213 or -1 if an error occurs. @var{pathname} is a string.
36215 @item vFile:readlink: @var{filename}
36216 Read value of symbolic link @var{filename} on the target. Return
36217 the number of bytes read, or -1 if an error occurs.
36219 The data read should be returned as a binary attachment on success.
36220 If zero bytes were read, the response should include an empty binary
36221 attachment (i.e.@: a trailing semicolon). The return value is the
36222 number of target bytes read; the binary attachment may be longer if
36223 some characters were escaped.
36228 @section Interrupts
36229 @cindex interrupts (remote protocol)
36231 When a program on the remote target is running, @value{GDBN} may
36232 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36233 a @code{BREAK} followed by @code{g},
36234 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36236 The precise meaning of @code{BREAK} is defined by the transport
36237 mechanism and may, in fact, be undefined. @value{GDBN} does not
36238 currently define a @code{BREAK} mechanism for any of the network
36239 interfaces except for TCP, in which case @value{GDBN} sends the
36240 @code{telnet} BREAK sequence.
36242 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36243 transport mechanisms. It is represented by sending the single byte
36244 @code{0x03} without any of the usual packet overhead described in
36245 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36246 transmitted as part of a packet, it is considered to be packet data
36247 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36248 (@pxref{X packet}), used for binary downloads, may include an unescaped
36249 @code{0x03} as part of its packet.
36251 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36252 When Linux kernel receives this sequence from serial port,
36253 it stops execution and connects to gdb.
36255 Stubs are not required to recognize these interrupt mechanisms and the
36256 precise meaning associated with receipt of the interrupt is
36257 implementation defined. If the target supports debugging of multiple
36258 threads and/or processes, it should attempt to interrupt all
36259 currently-executing threads and processes.
36260 If the stub is successful at interrupting the
36261 running program, it should send one of the stop
36262 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36263 of successfully stopping the program in all-stop mode, and a stop reply
36264 for each stopped thread in non-stop mode.
36265 Interrupts received while the
36266 program is stopped are discarded.
36268 @node Notification Packets
36269 @section Notification Packets
36270 @cindex notification packets
36271 @cindex packets, notification
36273 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36274 packets that require no acknowledgment. Both the GDB and the stub
36275 may send notifications (although the only notifications defined at
36276 present are sent by the stub). Notifications carry information
36277 without incurring the round-trip latency of an acknowledgment, and so
36278 are useful for low-impact communications where occasional packet loss
36281 A notification packet has the form @samp{% @var{data} #
36282 @var{checksum}}, where @var{data} is the content of the notification,
36283 and @var{checksum} is a checksum of @var{data}, computed and formatted
36284 as for ordinary @value{GDBN} packets. A notification's @var{data}
36285 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36286 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36287 to acknowledge the notification's receipt or to report its corruption.
36289 Every notification's @var{data} begins with a name, which contains no
36290 colon characters, followed by a colon character.
36292 Recipients should silently ignore corrupted notifications and
36293 notifications they do not understand. Recipients should restart
36294 timeout periods on receipt of a well-formed notification, whether or
36295 not they understand it.
36297 Senders should only send the notifications described here when this
36298 protocol description specifies that they are permitted. In the
36299 future, we may extend the protocol to permit existing notifications in
36300 new contexts; this rule helps older senders avoid confusing newer
36303 (Older versions of @value{GDBN} ignore bytes received until they see
36304 the @samp{$} byte that begins an ordinary packet, so new stubs may
36305 transmit notifications without fear of confusing older clients. There
36306 are no notifications defined for @value{GDBN} to send at the moment, but we
36307 assume that most older stubs would ignore them, as well.)
36309 The following notification packets from the stub to @value{GDBN} are
36313 @item Stop: @var{reply}
36314 Report an asynchronous stop event in non-stop mode.
36315 The @var{reply} has the form of a stop reply, as
36316 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36317 for information on how these notifications are acknowledged by
36321 @node Remote Non-Stop
36322 @section Remote Protocol Support for Non-Stop Mode
36324 @value{GDBN}'s remote protocol supports non-stop debugging of
36325 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36326 supports non-stop mode, it should report that to @value{GDBN} by including
36327 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36329 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36330 establishing a new connection with the stub. Entering non-stop mode
36331 does not alter the state of any currently-running threads, but targets
36332 must stop all threads in any already-attached processes when entering
36333 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36334 probe the target state after a mode change.
36336 In non-stop mode, when an attached process encounters an event that
36337 would otherwise be reported with a stop reply, it uses the
36338 asynchronous notification mechanism (@pxref{Notification Packets}) to
36339 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36340 in all processes are stopped when a stop reply is sent, in non-stop
36341 mode only the thread reporting the stop event is stopped. That is,
36342 when reporting a @samp{S} or @samp{T} response to indicate completion
36343 of a step operation, hitting a breakpoint, or a fault, only the
36344 affected thread is stopped; any other still-running threads continue
36345 to run. When reporting a @samp{W} or @samp{X} response, all running
36346 threads belonging to other attached processes continue to run.
36348 Only one stop reply notification at a time may be pending; if
36349 additional stop events occur before @value{GDBN} has acknowledged the
36350 previous notification, they must be queued by the stub for later
36351 synchronous transmission in response to @samp{vStopped} packets from
36352 @value{GDBN}. Because the notification mechanism is unreliable,
36353 the stub is permitted to resend a stop reply notification
36354 if it believes @value{GDBN} may not have received it. @value{GDBN}
36355 ignores additional stop reply notifications received before it has
36356 finished processing a previous notification and the stub has completed
36357 sending any queued stop events.
36359 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36360 notification at any time. Specifically, they may appear when
36361 @value{GDBN} is not otherwise reading input from the stub, or when
36362 @value{GDBN} is expecting to read a normal synchronous response or a
36363 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36364 Notification packets are distinct from any other communication from
36365 the stub so there is no ambiguity.
36367 After receiving a stop reply notification, @value{GDBN} shall
36368 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36369 as a regular, synchronous request to the stub. Such acknowledgment
36370 is not required to happen immediately, as @value{GDBN} is permitted to
36371 send other, unrelated packets to the stub first, which the stub should
36374 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36375 stop events to report to @value{GDBN}, it shall respond by sending a
36376 normal stop reply response. @value{GDBN} shall then send another
36377 @samp{vStopped} packet to solicit further responses; again, it is
36378 permitted to send other, unrelated packets as well which the stub
36379 should process normally.
36381 If the stub receives a @samp{vStopped} packet and there are no
36382 additional stop events to report, the stub shall return an @samp{OK}
36383 response. At this point, if further stop events occur, the stub shall
36384 send a new stop reply notification, @value{GDBN} shall accept the
36385 notification, and the process shall be repeated.
36387 In non-stop mode, the target shall respond to the @samp{?} packet as
36388 follows. First, any incomplete stop reply notification/@samp{vStopped}
36389 sequence in progress is abandoned. The target must begin a new
36390 sequence reporting stop events for all stopped threads, whether or not
36391 it has previously reported those events to @value{GDBN}. The first
36392 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36393 subsequent stop replies are sent as responses to @samp{vStopped} packets
36394 using the mechanism described above. The target must not send
36395 asynchronous stop reply notifications until the sequence is complete.
36396 If all threads are running when the target receives the @samp{?} packet,
36397 or if the target is not attached to any process, it shall respond
36400 @node Packet Acknowledgment
36401 @section Packet Acknowledgment
36403 @cindex acknowledgment, for @value{GDBN} remote
36404 @cindex packet acknowledgment, for @value{GDBN} remote
36405 By default, when either the host or the target machine receives a packet,
36406 the first response expected is an acknowledgment: either @samp{+} (to indicate
36407 the package was received correctly) or @samp{-} (to request retransmission).
36408 This mechanism allows the @value{GDBN} remote protocol to operate over
36409 unreliable transport mechanisms, such as a serial line.
36411 In cases where the transport mechanism is itself reliable (such as a pipe or
36412 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36413 It may be desirable to disable them in that case to reduce communication
36414 overhead, or for other reasons. This can be accomplished by means of the
36415 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36417 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36418 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36419 and response format still includes the normal checksum, as described in
36420 @ref{Overview}, but the checksum may be ignored by the receiver.
36422 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36423 no-acknowledgment mode, it should report that to @value{GDBN}
36424 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36425 @pxref{qSupported}.
36426 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36427 disabled via the @code{set remote noack-packet off} command
36428 (@pxref{Remote Configuration}),
36429 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36430 Only then may the stub actually turn off packet acknowledgments.
36431 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36432 response, which can be safely ignored by the stub.
36434 Note that @code{set remote noack-packet} command only affects negotiation
36435 between @value{GDBN} and the stub when subsequent connections are made;
36436 it does not affect the protocol acknowledgment state for any current
36438 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36439 new connection is established,
36440 there is also no protocol request to re-enable the acknowledgments
36441 for the current connection, once disabled.
36446 Example sequence of a target being re-started. Notice how the restart
36447 does not get any direct output:
36452 @emph{target restarts}
36455 <- @code{T001:1234123412341234}
36459 Example sequence of a target being stepped by a single instruction:
36462 -> @code{G1445@dots{}}
36467 <- @code{T001:1234123412341234}
36471 <- @code{1455@dots{}}
36475 @node File-I/O Remote Protocol Extension
36476 @section File-I/O Remote Protocol Extension
36477 @cindex File-I/O remote protocol extension
36480 * File-I/O Overview::
36481 * Protocol Basics::
36482 * The F Request Packet::
36483 * The F Reply Packet::
36484 * The Ctrl-C Message::
36486 * List of Supported Calls::
36487 * Protocol-specific Representation of Datatypes::
36489 * File-I/O Examples::
36492 @node File-I/O Overview
36493 @subsection File-I/O Overview
36494 @cindex file-i/o overview
36496 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36497 target to use the host's file system and console I/O to perform various
36498 system calls. System calls on the target system are translated into a
36499 remote protocol packet to the host system, which then performs the needed
36500 actions and returns a response packet to the target system.
36501 This simulates file system operations even on targets that lack file systems.
36503 The protocol is defined to be independent of both the host and target systems.
36504 It uses its own internal representation of datatypes and values. Both
36505 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36506 translating the system-dependent value representations into the internal
36507 protocol representations when data is transmitted.
36509 The communication is synchronous. A system call is possible only when
36510 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36511 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36512 the target is stopped to allow deterministic access to the target's
36513 memory. Therefore File-I/O is not interruptible by target signals. On
36514 the other hand, it is possible to interrupt File-I/O by a user interrupt
36515 (@samp{Ctrl-C}) within @value{GDBN}.
36517 The target's request to perform a host system call does not finish
36518 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36519 after finishing the system call, the target returns to continuing the
36520 previous activity (continue, step). No additional continue or step
36521 request from @value{GDBN} is required.
36524 (@value{GDBP}) continue
36525 <- target requests 'system call X'
36526 target is stopped, @value{GDBN} executes system call
36527 -> @value{GDBN} returns result
36528 ... target continues, @value{GDBN} returns to wait for the target
36529 <- target hits breakpoint and sends a Txx packet
36532 The protocol only supports I/O on the console and to regular files on
36533 the host file system. Character or block special devices, pipes,
36534 named pipes, sockets or any other communication method on the host
36535 system are not supported by this protocol.
36537 File I/O is not supported in non-stop mode.
36539 @node Protocol Basics
36540 @subsection Protocol Basics
36541 @cindex protocol basics, file-i/o
36543 The File-I/O protocol uses the @code{F} packet as the request as well
36544 as reply packet. Since a File-I/O system call can only occur when
36545 @value{GDBN} is waiting for a response from the continuing or stepping target,
36546 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36547 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36548 This @code{F} packet contains all information needed to allow @value{GDBN}
36549 to call the appropriate host system call:
36553 A unique identifier for the requested system call.
36556 All parameters to the system call. Pointers are given as addresses
36557 in the target memory address space. Pointers to strings are given as
36558 pointer/length pair. Numerical values are given as they are.
36559 Numerical control flags are given in a protocol-specific representation.
36563 At this point, @value{GDBN} has to perform the following actions.
36567 If the parameters include pointer values to data needed as input to a
36568 system call, @value{GDBN} requests this data from the target with a
36569 standard @code{m} packet request. This additional communication has to be
36570 expected by the target implementation and is handled as any other @code{m}
36574 @value{GDBN} translates all value from protocol representation to host
36575 representation as needed. Datatypes are coerced into the host types.
36578 @value{GDBN} calls the system call.
36581 It then coerces datatypes back to protocol representation.
36584 If the system call is expected to return data in buffer space specified
36585 by pointer parameters to the call, the data is transmitted to the
36586 target using a @code{M} or @code{X} packet. This packet has to be expected
36587 by the target implementation and is handled as any other @code{M} or @code{X}
36592 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36593 necessary information for the target to continue. This at least contains
36600 @code{errno}, if has been changed by the system call.
36607 After having done the needed type and value coercion, the target continues
36608 the latest continue or step action.
36610 @node The F Request Packet
36611 @subsection The @code{F} Request Packet
36612 @cindex file-i/o request packet
36613 @cindex @code{F} request packet
36615 The @code{F} request packet has the following format:
36618 @item F@var{call-id},@var{parameter@dots{}}
36620 @var{call-id} is the identifier to indicate the host system call to be called.
36621 This is just the name of the function.
36623 @var{parameter@dots{}} are the parameters to the system call.
36624 Parameters are hexadecimal integer values, either the actual values in case
36625 of scalar datatypes, pointers to target buffer space in case of compound
36626 datatypes and unspecified memory areas, or pointer/length pairs in case
36627 of string parameters. These are appended to the @var{call-id} as a
36628 comma-delimited list. All values are transmitted in ASCII
36629 string representation, pointer/length pairs separated by a slash.
36635 @node The F Reply Packet
36636 @subsection The @code{F} Reply Packet
36637 @cindex file-i/o reply packet
36638 @cindex @code{F} reply packet
36640 The @code{F} reply packet has the following format:
36644 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36646 @var{retcode} is the return code of the system call as hexadecimal value.
36648 @var{errno} is the @code{errno} set by the call, in protocol-specific
36650 This parameter can be omitted if the call was successful.
36652 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36653 case, @var{errno} must be sent as well, even if the call was successful.
36654 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36661 or, if the call was interrupted before the host call has been performed:
36668 assuming 4 is the protocol-specific representation of @code{EINTR}.
36673 @node The Ctrl-C Message
36674 @subsection The @samp{Ctrl-C} Message
36675 @cindex ctrl-c message, in file-i/o protocol
36677 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36678 reply packet (@pxref{The F Reply Packet}),
36679 the target should behave as if it had
36680 gotten a break message. The meaning for the target is ``system call
36681 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36682 (as with a break message) and return to @value{GDBN} with a @code{T02}
36685 It's important for the target to know in which
36686 state the system call was interrupted. There are two possible cases:
36690 The system call hasn't been performed on the host yet.
36693 The system call on the host has been finished.
36697 These two states can be distinguished by the target by the value of the
36698 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36699 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36700 on POSIX systems. In any other case, the target may presume that the
36701 system call has been finished --- successfully or not --- and should behave
36702 as if the break message arrived right after the system call.
36704 @value{GDBN} must behave reliably. If the system call has not been called
36705 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36706 @code{errno} in the packet. If the system call on the host has been finished
36707 before the user requests a break, the full action must be finished by
36708 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36709 The @code{F} packet may only be sent when either nothing has happened
36710 or the full action has been completed.
36713 @subsection Console I/O
36714 @cindex console i/o as part of file-i/o
36716 By default and if not explicitly closed by the target system, the file
36717 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36718 on the @value{GDBN} console is handled as any other file output operation
36719 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36720 by @value{GDBN} so that after the target read request from file descriptor
36721 0 all following typing is buffered until either one of the following
36726 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36728 system call is treated as finished.
36731 The user presses @key{RET}. This is treated as end of input with a trailing
36735 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36736 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36740 If the user has typed more characters than fit in the buffer given to
36741 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36742 either another @code{read(0, @dots{})} is requested by the target, or debugging
36743 is stopped at the user's request.
36746 @node List of Supported Calls
36747 @subsection List of Supported Calls
36748 @cindex list of supported file-i/o calls
36765 @unnumberedsubsubsec open
36766 @cindex open, file-i/o system call
36771 int open(const char *pathname, int flags);
36772 int open(const char *pathname, int flags, mode_t mode);
36776 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36779 @var{flags} is the bitwise @code{OR} of the following values:
36783 If the file does not exist it will be created. The host
36784 rules apply as far as file ownership and time stamps
36788 When used with @code{O_CREAT}, if the file already exists it is
36789 an error and open() fails.
36792 If the file already exists and the open mode allows
36793 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36794 truncated to zero length.
36797 The file is opened in append mode.
36800 The file is opened for reading only.
36803 The file is opened for writing only.
36806 The file is opened for reading and writing.
36810 Other bits are silently ignored.
36814 @var{mode} is the bitwise @code{OR} of the following values:
36818 User has read permission.
36821 User has write permission.
36824 Group has read permission.
36827 Group has write permission.
36830 Others have read permission.
36833 Others have write permission.
36837 Other bits are silently ignored.
36840 @item Return value:
36841 @code{open} returns the new file descriptor or -1 if an error
36848 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36851 @var{pathname} refers to a directory.
36854 The requested access is not allowed.
36857 @var{pathname} was too long.
36860 A directory component in @var{pathname} does not exist.
36863 @var{pathname} refers to a device, pipe, named pipe or socket.
36866 @var{pathname} refers to a file on a read-only filesystem and
36867 write access was requested.
36870 @var{pathname} is an invalid pointer value.
36873 No space on device to create the file.
36876 The process already has the maximum number of files open.
36879 The limit on the total number of files open on the system
36883 The call was interrupted by the user.
36889 @unnumberedsubsubsec close
36890 @cindex close, file-i/o system call
36899 @samp{Fclose,@var{fd}}
36901 @item Return value:
36902 @code{close} returns zero on success, or -1 if an error occurred.
36908 @var{fd} isn't a valid open file descriptor.
36911 The call was interrupted by the user.
36917 @unnumberedsubsubsec read
36918 @cindex read, file-i/o system call
36923 int read(int fd, void *buf, unsigned int count);
36927 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36929 @item Return value:
36930 On success, the number of bytes read is returned.
36931 Zero indicates end of file. If count is zero, read
36932 returns zero as well. On error, -1 is returned.
36938 @var{fd} is not a valid file descriptor or is not open for
36942 @var{bufptr} is an invalid pointer value.
36945 The call was interrupted by the user.
36951 @unnumberedsubsubsec write
36952 @cindex write, file-i/o system call
36957 int write(int fd, const void *buf, unsigned int count);
36961 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36963 @item Return value:
36964 On success, the number of bytes written are returned.
36965 Zero indicates nothing was written. On error, -1
36972 @var{fd} is not a valid file descriptor or is not open for
36976 @var{bufptr} is an invalid pointer value.
36979 An attempt was made to write a file that exceeds the
36980 host-specific maximum file size allowed.
36983 No space on device to write the data.
36986 The call was interrupted by the user.
36992 @unnumberedsubsubsec lseek
36993 @cindex lseek, file-i/o system call
36998 long lseek (int fd, long offset, int flag);
37002 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37004 @var{flag} is one of:
37008 The offset is set to @var{offset} bytes.
37011 The offset is set to its current location plus @var{offset}
37015 The offset is set to the size of the file plus @var{offset}
37019 @item Return value:
37020 On success, the resulting unsigned offset in bytes from
37021 the beginning of the file is returned. Otherwise, a
37022 value of -1 is returned.
37028 @var{fd} is not a valid open file descriptor.
37031 @var{fd} is associated with the @value{GDBN} console.
37034 @var{flag} is not a proper value.
37037 The call was interrupted by the user.
37043 @unnumberedsubsubsec rename
37044 @cindex rename, file-i/o system call
37049 int rename(const char *oldpath, const char *newpath);
37053 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37055 @item Return value:
37056 On success, zero is returned. On error, -1 is returned.
37062 @var{newpath} is an existing directory, but @var{oldpath} is not a
37066 @var{newpath} is a non-empty directory.
37069 @var{oldpath} or @var{newpath} is a directory that is in use by some
37073 An attempt was made to make a directory a subdirectory
37077 A component used as a directory in @var{oldpath} or new
37078 path is not a directory. Or @var{oldpath} is a directory
37079 and @var{newpath} exists but is not a directory.
37082 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37085 No access to the file or the path of the file.
37089 @var{oldpath} or @var{newpath} was too long.
37092 A directory component in @var{oldpath} or @var{newpath} does not exist.
37095 The file is on a read-only filesystem.
37098 The device containing the file has no room for the new
37102 The call was interrupted by the user.
37108 @unnumberedsubsubsec unlink
37109 @cindex unlink, file-i/o system call
37114 int unlink(const char *pathname);
37118 @samp{Funlink,@var{pathnameptr}/@var{len}}
37120 @item Return value:
37121 On success, zero is returned. On error, -1 is returned.
37127 No access to the file or the path of the file.
37130 The system does not allow unlinking of directories.
37133 The file @var{pathname} cannot be unlinked because it's
37134 being used by another process.
37137 @var{pathnameptr} is an invalid pointer value.
37140 @var{pathname} was too long.
37143 A directory component in @var{pathname} does not exist.
37146 A component of the path is not a directory.
37149 The file is on a read-only filesystem.
37152 The call was interrupted by the user.
37158 @unnumberedsubsubsec stat/fstat
37159 @cindex fstat, file-i/o system call
37160 @cindex stat, file-i/o system call
37165 int stat(const char *pathname, struct stat *buf);
37166 int fstat(int fd, struct stat *buf);
37170 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37171 @samp{Ffstat,@var{fd},@var{bufptr}}
37173 @item Return value:
37174 On success, zero is returned. On error, -1 is returned.
37180 @var{fd} is not a valid open file.
37183 A directory component in @var{pathname} does not exist or the
37184 path is an empty string.
37187 A component of the path is not a directory.
37190 @var{pathnameptr} is an invalid pointer value.
37193 No access to the file or the path of the file.
37196 @var{pathname} was too long.
37199 The call was interrupted by the user.
37205 @unnumberedsubsubsec gettimeofday
37206 @cindex gettimeofday, file-i/o system call
37211 int gettimeofday(struct timeval *tv, void *tz);
37215 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37217 @item Return value:
37218 On success, 0 is returned, -1 otherwise.
37224 @var{tz} is a non-NULL pointer.
37227 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37233 @unnumberedsubsubsec isatty
37234 @cindex isatty, file-i/o system call
37239 int isatty(int fd);
37243 @samp{Fisatty,@var{fd}}
37245 @item Return value:
37246 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37252 The call was interrupted by the user.
37257 Note that the @code{isatty} call is treated as a special case: it returns
37258 1 to the target if the file descriptor is attached
37259 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37260 would require implementing @code{ioctl} and would be more complex than
37265 @unnumberedsubsubsec system
37266 @cindex system, file-i/o system call
37271 int system(const char *command);
37275 @samp{Fsystem,@var{commandptr}/@var{len}}
37277 @item Return value:
37278 If @var{len} is zero, the return value indicates whether a shell is
37279 available. A zero return value indicates a shell is not available.
37280 For non-zero @var{len}, the value returned is -1 on error and the
37281 return status of the command otherwise. Only the exit status of the
37282 command is returned, which is extracted from the host's @code{system}
37283 return value by calling @code{WEXITSTATUS(retval)}. In case
37284 @file{/bin/sh} could not be executed, 127 is returned.
37290 The call was interrupted by the user.
37295 @value{GDBN} takes over the full task of calling the necessary host calls
37296 to perform the @code{system} call. The return value of @code{system} on
37297 the host is simplified before it's returned
37298 to the target. Any termination signal information from the child process
37299 is discarded, and the return value consists
37300 entirely of the exit status of the called command.
37302 Due to security concerns, the @code{system} call is by default refused
37303 by @value{GDBN}. The user has to allow this call explicitly with the
37304 @code{set remote system-call-allowed 1} command.
37307 @item set remote system-call-allowed
37308 @kindex set remote system-call-allowed
37309 Control whether to allow the @code{system} calls in the File I/O
37310 protocol for the remote target. The default is zero (disabled).
37312 @item show remote system-call-allowed
37313 @kindex show remote system-call-allowed
37314 Show whether the @code{system} calls are allowed in the File I/O
37318 @node Protocol-specific Representation of Datatypes
37319 @subsection Protocol-specific Representation of Datatypes
37320 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37323 * Integral Datatypes::
37325 * Memory Transfer::
37330 @node Integral Datatypes
37331 @unnumberedsubsubsec Integral Datatypes
37332 @cindex integral datatypes, in file-i/o protocol
37334 The integral datatypes used in the system calls are @code{int},
37335 @code{unsigned int}, @code{long}, @code{unsigned long},
37336 @code{mode_t}, and @code{time_t}.
37338 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37339 implemented as 32 bit values in this protocol.
37341 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37343 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37344 in @file{limits.h}) to allow range checking on host and target.
37346 @code{time_t} datatypes are defined as seconds since the Epoch.
37348 All integral datatypes transferred as part of a memory read or write of a
37349 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37352 @node Pointer Values
37353 @unnumberedsubsubsec Pointer Values
37354 @cindex pointer values, in file-i/o protocol
37356 Pointers to target data are transmitted as they are. An exception
37357 is made for pointers to buffers for which the length isn't
37358 transmitted as part of the function call, namely strings. Strings
37359 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37366 which is a pointer to data of length 18 bytes at position 0x1aaf.
37367 The length is defined as the full string length in bytes, including
37368 the trailing null byte. For example, the string @code{"hello world"}
37369 at address 0x123456 is transmitted as
37375 @node Memory Transfer
37376 @unnumberedsubsubsec Memory Transfer
37377 @cindex memory transfer, in file-i/o protocol
37379 Structured data which is transferred using a memory read or write (for
37380 example, a @code{struct stat}) is expected to be in a protocol-specific format
37381 with all scalar multibyte datatypes being big endian. Translation to
37382 this representation needs to be done both by the target before the @code{F}
37383 packet is sent, and by @value{GDBN} before
37384 it transfers memory to the target. Transferred pointers to structured
37385 data should point to the already-coerced data at any time.
37389 @unnumberedsubsubsec struct stat
37390 @cindex struct stat, in file-i/o protocol
37392 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37393 is defined as follows:
37397 unsigned int st_dev; /* device */
37398 unsigned int st_ino; /* inode */
37399 mode_t st_mode; /* protection */
37400 unsigned int st_nlink; /* number of hard links */
37401 unsigned int st_uid; /* user ID of owner */
37402 unsigned int st_gid; /* group ID of owner */
37403 unsigned int st_rdev; /* device type (if inode device) */
37404 unsigned long st_size; /* total size, in bytes */
37405 unsigned long st_blksize; /* blocksize for filesystem I/O */
37406 unsigned long st_blocks; /* number of blocks allocated */
37407 time_t st_atime; /* time of last access */
37408 time_t st_mtime; /* time of last modification */
37409 time_t st_ctime; /* time of last change */
37413 The integral datatypes conform to the definitions given in the
37414 appropriate section (see @ref{Integral Datatypes}, for details) so this
37415 structure is of size 64 bytes.
37417 The values of several fields have a restricted meaning and/or
37423 A value of 0 represents a file, 1 the console.
37426 No valid meaning for the target. Transmitted unchanged.
37429 Valid mode bits are described in @ref{Constants}. Any other
37430 bits have currently no meaning for the target.
37435 No valid meaning for the target. Transmitted unchanged.
37440 These values have a host and file system dependent
37441 accuracy. Especially on Windows hosts, the file system may not
37442 support exact timing values.
37445 The target gets a @code{struct stat} of the above representation and is
37446 responsible for coercing it to the target representation before
37449 Note that due to size differences between the host, target, and protocol
37450 representations of @code{struct stat} members, these members could eventually
37451 get truncated on the target.
37453 @node struct timeval
37454 @unnumberedsubsubsec struct timeval
37455 @cindex struct timeval, in file-i/o protocol
37457 The buffer of type @code{struct timeval} used by the File-I/O protocol
37458 is defined as follows:
37462 time_t tv_sec; /* second */
37463 long tv_usec; /* microsecond */
37467 The integral datatypes conform to the definitions given in the
37468 appropriate section (see @ref{Integral Datatypes}, for details) so this
37469 structure is of size 8 bytes.
37472 @subsection Constants
37473 @cindex constants, in file-i/o protocol
37475 The following values are used for the constants inside of the
37476 protocol. @value{GDBN} and target are responsible for translating these
37477 values before and after the call as needed.
37488 @unnumberedsubsubsec Open Flags
37489 @cindex open flags, in file-i/o protocol
37491 All values are given in hexadecimal representation.
37503 @node mode_t Values
37504 @unnumberedsubsubsec mode_t Values
37505 @cindex mode_t values, in file-i/o protocol
37507 All values are given in octal representation.
37524 @unnumberedsubsubsec Errno Values
37525 @cindex errno values, in file-i/o protocol
37527 All values are given in decimal representation.
37552 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37553 any error value not in the list of supported error numbers.
37556 @unnumberedsubsubsec Lseek Flags
37557 @cindex lseek flags, in file-i/o protocol
37566 @unnumberedsubsubsec Limits
37567 @cindex limits, in file-i/o protocol
37569 All values are given in decimal representation.
37572 INT_MIN -2147483648
37574 UINT_MAX 4294967295
37575 LONG_MIN -9223372036854775808
37576 LONG_MAX 9223372036854775807
37577 ULONG_MAX 18446744073709551615
37580 @node File-I/O Examples
37581 @subsection File-I/O Examples
37582 @cindex file-i/o examples
37584 Example sequence of a write call, file descriptor 3, buffer is at target
37585 address 0x1234, 6 bytes should be written:
37588 <- @code{Fwrite,3,1234,6}
37589 @emph{request memory read from target}
37592 @emph{return "6 bytes written"}
37596 Example sequence of a read call, file descriptor 3, buffer is at target
37597 address 0x1234, 6 bytes should be read:
37600 <- @code{Fread,3,1234,6}
37601 @emph{request memory write to target}
37602 -> @code{X1234,6:XXXXXX}
37603 @emph{return "6 bytes read"}
37607 Example sequence of a read call, call fails on the host due to invalid
37608 file descriptor (@code{EBADF}):
37611 <- @code{Fread,3,1234,6}
37615 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37619 <- @code{Fread,3,1234,6}
37624 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37628 <- @code{Fread,3,1234,6}
37629 -> @code{X1234,6:XXXXXX}
37633 @node Library List Format
37634 @section Library List Format
37635 @cindex library list format, remote protocol
37637 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37638 same process as your application to manage libraries. In this case,
37639 @value{GDBN} can use the loader's symbol table and normal memory
37640 operations to maintain a list of shared libraries. On other
37641 platforms, the operating system manages loaded libraries.
37642 @value{GDBN} can not retrieve the list of currently loaded libraries
37643 through memory operations, so it uses the @samp{qXfer:libraries:read}
37644 packet (@pxref{qXfer library list read}) instead. The remote stub
37645 queries the target's operating system and reports which libraries
37648 The @samp{qXfer:libraries:read} packet returns an XML document which
37649 lists loaded libraries and their offsets. Each library has an
37650 associated name and one or more segment or section base addresses,
37651 which report where the library was loaded in memory.
37653 For the common case of libraries that are fully linked binaries, the
37654 library should have a list of segments. If the target supports
37655 dynamic linking of a relocatable object file, its library XML element
37656 should instead include a list of allocated sections. The segment or
37657 section bases are start addresses, not relocation offsets; they do not
37658 depend on the library's link-time base addresses.
37660 @value{GDBN} must be linked with the Expat library to support XML
37661 library lists. @xref{Expat}.
37663 A simple memory map, with one loaded library relocated by a single
37664 offset, looks like this:
37668 <library name="/lib/libc.so.6">
37669 <segment address="0x10000000"/>
37674 Another simple memory map, with one loaded library with three
37675 allocated sections (.text, .data, .bss), looks like this:
37679 <library name="sharedlib.o">
37680 <section address="0x10000000"/>
37681 <section address="0x20000000"/>
37682 <section address="0x30000000"/>
37687 The format of a library list is described by this DTD:
37690 <!-- library-list: Root element with versioning -->
37691 <!ELEMENT library-list (library)*>
37692 <!ATTLIST library-list version CDATA #FIXED "1.0">
37693 <!ELEMENT library (segment*, section*)>
37694 <!ATTLIST library name CDATA #REQUIRED>
37695 <!ELEMENT segment EMPTY>
37696 <!ATTLIST segment address CDATA #REQUIRED>
37697 <!ELEMENT section EMPTY>
37698 <!ATTLIST section address CDATA #REQUIRED>
37701 In addition, segments and section descriptors cannot be mixed within a
37702 single library element, and you must supply at least one segment or
37703 section for each library.
37705 @node Library List Format for SVR4 Targets
37706 @section Library List Format for SVR4 Targets
37707 @cindex library list format, remote protocol
37709 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37710 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37711 shared libraries. Still a special library list provided by this packet is
37712 more efficient for the @value{GDBN} remote protocol.
37714 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37715 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37716 target, the following parameters are reported:
37720 @code{name}, the absolute file name from the @code{l_name} field of
37721 @code{struct link_map}.
37723 @code{lm} with address of @code{struct link_map} used for TLS
37724 (Thread Local Storage) access.
37726 @code{l_addr}, the displacement as read from the field @code{l_addr} of
37727 @code{struct link_map}. For prelinked libraries this is not an absolute
37728 memory address. It is a displacement of absolute memory address against
37729 address the file was prelinked to during the library load.
37731 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
37734 Additionally the single @code{main-lm} attribute specifies address of
37735 @code{struct link_map} used for the main executable. This parameter is used
37736 for TLS access and its presence is optional.
37738 @value{GDBN} must be linked with the Expat library to support XML
37739 SVR4 library lists. @xref{Expat}.
37741 A simple memory map, with two loaded libraries (which do not use prelink),
37745 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
37746 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
37748 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
37750 </library-list-svr>
37753 The format of an SVR4 library list is described by this DTD:
37756 <!-- library-list-svr4: Root element with versioning -->
37757 <!ELEMENT library-list-svr4 (library)*>
37758 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
37759 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
37760 <!ELEMENT library EMPTY>
37761 <!ATTLIST library name CDATA #REQUIRED>
37762 <!ATTLIST library lm CDATA #REQUIRED>
37763 <!ATTLIST library l_addr CDATA #REQUIRED>
37764 <!ATTLIST library l_ld CDATA #REQUIRED>
37767 @node Memory Map Format
37768 @section Memory Map Format
37769 @cindex memory map format
37771 To be able to write into flash memory, @value{GDBN} needs to obtain a
37772 memory map from the target. This section describes the format of the
37775 The memory map is obtained using the @samp{qXfer:memory-map:read}
37776 (@pxref{qXfer memory map read}) packet and is an XML document that
37777 lists memory regions.
37779 @value{GDBN} must be linked with the Expat library to support XML
37780 memory maps. @xref{Expat}.
37782 The top-level structure of the document is shown below:
37785 <?xml version="1.0"?>
37786 <!DOCTYPE memory-map
37787 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37788 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37794 Each region can be either:
37799 A region of RAM starting at @var{addr} and extending for @var{length}
37803 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37808 A region of read-only memory:
37811 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37816 A region of flash memory, with erasure blocks @var{blocksize}
37820 <memory type="flash" start="@var{addr}" length="@var{length}">
37821 <property name="blocksize">@var{blocksize}</property>
37827 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37828 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37829 packets to write to addresses in such ranges.
37831 The formal DTD for memory map format is given below:
37834 <!-- ................................................... -->
37835 <!-- Memory Map XML DTD ................................ -->
37836 <!-- File: memory-map.dtd .............................. -->
37837 <!-- .................................... .............. -->
37838 <!-- memory-map.dtd -->
37839 <!-- memory-map: Root element with versioning -->
37840 <!ELEMENT memory-map (memory | property)>
37841 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37842 <!ELEMENT memory (property)>
37843 <!-- memory: Specifies a memory region,
37844 and its type, or device. -->
37845 <!ATTLIST memory type CDATA #REQUIRED
37846 start CDATA #REQUIRED
37847 length CDATA #REQUIRED
37848 device CDATA #IMPLIED>
37849 <!-- property: Generic attribute tag -->
37850 <!ELEMENT property (#PCDATA | property)*>
37851 <!ATTLIST property name CDATA #REQUIRED>
37854 @node Thread List Format
37855 @section Thread List Format
37856 @cindex thread list format
37858 To efficiently update the list of threads and their attributes,
37859 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37860 (@pxref{qXfer threads read}) and obtains the XML document with
37861 the following structure:
37864 <?xml version="1.0"?>
37866 <thread id="id" core="0">
37867 ... description ...
37872 Each @samp{thread} element must have the @samp{id} attribute that
37873 identifies the thread (@pxref{thread-id syntax}). The
37874 @samp{core} attribute, if present, specifies which processor core
37875 the thread was last executing on. The content of the of @samp{thread}
37876 element is interpreted as human-readable auxilliary information.
37878 @node Traceframe Info Format
37879 @section Traceframe Info Format
37880 @cindex traceframe info format
37882 To be able to know which objects in the inferior can be examined when
37883 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37884 memory ranges, registers and trace state variables that have been
37885 collected in a traceframe.
37887 This list is obtained using the @samp{qXfer:traceframe-info:read}
37888 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37890 @value{GDBN} must be linked with the Expat library to support XML
37891 traceframe info discovery. @xref{Expat}.
37893 The top-level structure of the document is shown below:
37896 <?xml version="1.0"?>
37897 <!DOCTYPE traceframe-info
37898 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37899 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37905 Each traceframe block can be either:
37910 A region of collected memory starting at @var{addr} and extending for
37911 @var{length} bytes from there:
37914 <memory start="@var{addr}" length="@var{length}"/>
37919 The formal DTD for the traceframe info format is given below:
37922 <!ELEMENT traceframe-info (memory)* >
37923 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37925 <!ELEMENT memory EMPTY>
37926 <!ATTLIST memory start CDATA #REQUIRED
37927 length CDATA #REQUIRED>
37930 @include agentexpr.texi
37932 @node Target Descriptions
37933 @appendix Target Descriptions
37934 @cindex target descriptions
37936 One of the challenges of using @value{GDBN} to debug embedded systems
37937 is that there are so many minor variants of each processor
37938 architecture in use. It is common practice for vendors to start with
37939 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37940 and then make changes to adapt it to a particular market niche. Some
37941 architectures have hundreds of variants, available from dozens of
37942 vendors. This leads to a number of problems:
37946 With so many different customized processors, it is difficult for
37947 the @value{GDBN} maintainers to keep up with the changes.
37949 Since individual variants may have short lifetimes or limited
37950 audiences, it may not be worthwhile to carry information about every
37951 variant in the @value{GDBN} source tree.
37953 When @value{GDBN} does support the architecture of the embedded system
37954 at hand, the task of finding the correct architecture name to give the
37955 @command{set architecture} command can be error-prone.
37958 To address these problems, the @value{GDBN} remote protocol allows a
37959 target system to not only identify itself to @value{GDBN}, but to
37960 actually describe its own features. This lets @value{GDBN} support
37961 processor variants it has never seen before --- to the extent that the
37962 descriptions are accurate, and that @value{GDBN} understands them.
37964 @value{GDBN} must be linked with the Expat library to support XML
37965 target descriptions. @xref{Expat}.
37968 * Retrieving Descriptions:: How descriptions are fetched from a target.
37969 * Target Description Format:: The contents of a target description.
37970 * Predefined Target Types:: Standard types available for target
37972 * Standard Target Features:: Features @value{GDBN} knows about.
37975 @node Retrieving Descriptions
37976 @section Retrieving Descriptions
37978 Target descriptions can be read from the target automatically, or
37979 specified by the user manually. The default behavior is to read the
37980 description from the target. @value{GDBN} retrieves it via the remote
37981 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37982 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37983 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37984 XML document, of the form described in @ref{Target Description
37987 Alternatively, you can specify a file to read for the target description.
37988 If a file is set, the target will not be queried. The commands to
37989 specify a file are:
37992 @cindex set tdesc filename
37993 @item set tdesc filename @var{path}
37994 Read the target description from @var{path}.
37996 @cindex unset tdesc filename
37997 @item unset tdesc filename
37998 Do not read the XML target description from a file. @value{GDBN}
37999 will use the description supplied by the current target.
38001 @cindex show tdesc filename
38002 @item show tdesc filename
38003 Show the filename to read for a target description, if any.
38007 @node Target Description Format
38008 @section Target Description Format
38009 @cindex target descriptions, XML format
38011 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38012 document which complies with the Document Type Definition provided in
38013 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38014 means you can use generally available tools like @command{xmllint} to
38015 check that your feature descriptions are well-formed and valid.
38016 However, to help people unfamiliar with XML write descriptions for
38017 their targets, we also describe the grammar here.
38019 Target descriptions can identify the architecture of the remote target
38020 and (for some architectures) provide information about custom register
38021 sets. They can also identify the OS ABI of the remote target.
38022 @value{GDBN} can use this information to autoconfigure for your
38023 target, or to warn you if you connect to an unsupported target.
38025 Here is a simple target description:
38028 <target version="1.0">
38029 <architecture>i386:x86-64</architecture>
38034 This minimal description only says that the target uses
38035 the x86-64 architecture.
38037 A target description has the following overall form, with [ ] marking
38038 optional elements and @dots{} marking repeatable elements. The elements
38039 are explained further below.
38042 <?xml version="1.0"?>
38043 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38044 <target version="1.0">
38045 @r{[}@var{architecture}@r{]}
38046 @r{[}@var{osabi}@r{]}
38047 @r{[}@var{compatible}@r{]}
38048 @r{[}@var{feature}@dots{}@r{]}
38053 The description is generally insensitive to whitespace and line
38054 breaks, under the usual common-sense rules. The XML version
38055 declaration and document type declaration can generally be omitted
38056 (@value{GDBN} does not require them), but specifying them may be
38057 useful for XML validation tools. The @samp{version} attribute for
38058 @samp{<target>} may also be omitted, but we recommend
38059 including it; if future versions of @value{GDBN} use an incompatible
38060 revision of @file{gdb-target.dtd}, they will detect and report
38061 the version mismatch.
38063 @subsection Inclusion
38064 @cindex target descriptions, inclusion
38067 @cindex <xi:include>
38070 It can sometimes be valuable to split a target description up into
38071 several different annexes, either for organizational purposes, or to
38072 share files between different possible target descriptions. You can
38073 divide a description into multiple files by replacing any element of
38074 the target description with an inclusion directive of the form:
38077 <xi:include href="@var{document}"/>
38081 When @value{GDBN} encounters an element of this form, it will retrieve
38082 the named XML @var{document}, and replace the inclusion directive with
38083 the contents of that document. If the current description was read
38084 using @samp{qXfer}, then so will be the included document;
38085 @var{document} will be interpreted as the name of an annex. If the
38086 current description was read from a file, @value{GDBN} will look for
38087 @var{document} as a file in the same directory where it found the
38088 original description.
38090 @subsection Architecture
38091 @cindex <architecture>
38093 An @samp{<architecture>} element has this form:
38096 <architecture>@var{arch}</architecture>
38099 @var{arch} is one of the architectures from the set accepted by
38100 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38103 @cindex @code{<osabi>}
38105 This optional field was introduced in @value{GDBN} version 7.0.
38106 Previous versions of @value{GDBN} ignore it.
38108 An @samp{<osabi>} element has this form:
38111 <osabi>@var{abi-name}</osabi>
38114 @var{abi-name} is an OS ABI name from the same selection accepted by
38115 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38117 @subsection Compatible Architecture
38118 @cindex @code{<compatible>}
38120 This optional field was introduced in @value{GDBN} version 7.0.
38121 Previous versions of @value{GDBN} ignore it.
38123 A @samp{<compatible>} element has this form:
38126 <compatible>@var{arch}</compatible>
38129 @var{arch} is one of the architectures from the set accepted by
38130 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38132 A @samp{<compatible>} element is used to specify that the target
38133 is able to run binaries in some other than the main target architecture
38134 given by the @samp{<architecture>} element. For example, on the
38135 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38136 or @code{powerpc:common64}, but the system is able to run binaries
38137 in the @code{spu} architecture as well. The way to describe this
38138 capability with @samp{<compatible>} is as follows:
38141 <architecture>powerpc:common</architecture>
38142 <compatible>spu</compatible>
38145 @subsection Features
38148 Each @samp{<feature>} describes some logical portion of the target
38149 system. Features are currently used to describe available CPU
38150 registers and the types of their contents. A @samp{<feature>} element
38154 <feature name="@var{name}">
38155 @r{[}@var{type}@dots{}@r{]}
38161 Each feature's name should be unique within the description. The name
38162 of a feature does not matter unless @value{GDBN} has some special
38163 knowledge of the contents of that feature; if it does, the feature
38164 should have its standard name. @xref{Standard Target Features}.
38168 Any register's value is a collection of bits which @value{GDBN} must
38169 interpret. The default interpretation is a two's complement integer,
38170 but other types can be requested by name in the register description.
38171 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38172 Target Types}), and the description can define additional composite types.
38174 Each type element must have an @samp{id} attribute, which gives
38175 a unique (within the containing @samp{<feature>}) name to the type.
38176 Types must be defined before they are used.
38179 Some targets offer vector registers, which can be treated as arrays
38180 of scalar elements. These types are written as @samp{<vector>} elements,
38181 specifying the array element type, @var{type}, and the number of elements,
38185 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38189 If a register's value is usefully viewed in multiple ways, define it
38190 with a union type containing the useful representations. The
38191 @samp{<union>} element contains one or more @samp{<field>} elements,
38192 each of which has a @var{name} and a @var{type}:
38195 <union id="@var{id}">
38196 <field name="@var{name}" type="@var{type}"/>
38202 If a register's value is composed from several separate values, define
38203 it with a structure type. There are two forms of the @samp{<struct>}
38204 element; a @samp{<struct>} element must either contain only bitfields
38205 or contain no bitfields. If the structure contains only bitfields,
38206 its total size in bytes must be specified, each bitfield must have an
38207 explicit start and end, and bitfields are automatically assigned an
38208 integer type. The field's @var{start} should be less than or
38209 equal to its @var{end}, and zero represents the least significant bit.
38212 <struct id="@var{id}" size="@var{size}">
38213 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38218 If the structure contains no bitfields, then each field has an
38219 explicit type, and no implicit padding is added.
38222 <struct id="@var{id}">
38223 <field name="@var{name}" type="@var{type}"/>
38229 If a register's value is a series of single-bit flags, define it with
38230 a flags type. The @samp{<flags>} element has an explicit @var{size}
38231 and contains one or more @samp{<field>} elements. Each field has a
38232 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38236 <flags id="@var{id}" size="@var{size}">
38237 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38242 @subsection Registers
38245 Each register is represented as an element with this form:
38248 <reg name="@var{name}"
38249 bitsize="@var{size}"
38250 @r{[}regnum="@var{num}"@r{]}
38251 @r{[}save-restore="@var{save-restore}"@r{]}
38252 @r{[}type="@var{type}"@r{]}
38253 @r{[}group="@var{group}"@r{]}/>
38257 The components are as follows:
38262 The register's name; it must be unique within the target description.
38265 The register's size, in bits.
38268 The register's number. If omitted, a register's number is one greater
38269 than that of the previous register (either in the current feature or in
38270 a preceding feature); the first register in the target description
38271 defaults to zero. This register number is used to read or write
38272 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38273 packets, and registers appear in the @code{g} and @code{G} packets
38274 in order of increasing register number.
38277 Whether the register should be preserved across inferior function
38278 calls; this must be either @code{yes} or @code{no}. The default is
38279 @code{yes}, which is appropriate for most registers except for
38280 some system control registers; this is not related to the target's
38284 The type of the register. @var{type} may be a predefined type, a type
38285 defined in the current feature, or one of the special types @code{int}
38286 and @code{float}. @code{int} is an integer type of the correct size
38287 for @var{bitsize}, and @code{float} is a floating point type (in the
38288 architecture's normal floating point format) of the correct size for
38289 @var{bitsize}. The default is @code{int}.
38292 The register group to which this register belongs. @var{group} must
38293 be either @code{general}, @code{float}, or @code{vector}. If no
38294 @var{group} is specified, @value{GDBN} will not display the register
38295 in @code{info registers}.
38299 @node Predefined Target Types
38300 @section Predefined Target Types
38301 @cindex target descriptions, predefined types
38303 Type definitions in the self-description can build up composite types
38304 from basic building blocks, but can not define fundamental types. Instead,
38305 standard identifiers are provided by @value{GDBN} for the fundamental
38306 types. The currently supported types are:
38315 Signed integer types holding the specified number of bits.
38322 Unsigned integer types holding the specified number of bits.
38326 Pointers to unspecified code and data. The program counter and
38327 any dedicated return address register may be marked as code
38328 pointers; printing a code pointer converts it into a symbolic
38329 address. The stack pointer and any dedicated address registers
38330 may be marked as data pointers.
38333 Single precision IEEE floating point.
38336 Double precision IEEE floating point.
38339 The 12-byte extended precision format used by ARM FPA registers.
38342 The 10-byte extended precision format used by x87 registers.
38345 32bit @sc{eflags} register used by x86.
38348 32bit @sc{mxcsr} register used by x86.
38352 @node Standard Target Features
38353 @section Standard Target Features
38354 @cindex target descriptions, standard features
38356 A target description must contain either no registers or all the
38357 target's registers. If the description contains no registers, then
38358 @value{GDBN} will assume a default register layout, selected based on
38359 the architecture. If the description contains any registers, the
38360 default layout will not be used; the standard registers must be
38361 described in the target description, in such a way that @value{GDBN}
38362 can recognize them.
38364 This is accomplished by giving specific names to feature elements
38365 which contain standard registers. @value{GDBN} will look for features
38366 with those names and verify that they contain the expected registers;
38367 if any known feature is missing required registers, or if any required
38368 feature is missing, @value{GDBN} will reject the target
38369 description. You can add additional registers to any of the
38370 standard features --- @value{GDBN} will display them just as if
38371 they were added to an unrecognized feature.
38373 This section lists the known features and their expected contents.
38374 Sample XML documents for these features are included in the
38375 @value{GDBN} source tree, in the directory @file{gdb/features}.
38377 Names recognized by @value{GDBN} should include the name of the
38378 company or organization which selected the name, and the overall
38379 architecture to which the feature applies; so e.g.@: the feature
38380 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38382 The names of registers are not case sensitive for the purpose
38383 of recognizing standard features, but @value{GDBN} will only display
38384 registers using the capitalization used in the description.
38391 * PowerPC Features::
38397 @subsection ARM Features
38398 @cindex target descriptions, ARM features
38400 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38402 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38403 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38405 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38406 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38407 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38410 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38411 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38413 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38414 it should contain at least registers @samp{wR0} through @samp{wR15} and
38415 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38416 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38418 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38419 should contain at least registers @samp{d0} through @samp{d15}. If
38420 they are present, @samp{d16} through @samp{d31} should also be included.
38421 @value{GDBN} will synthesize the single-precision registers from
38422 halves of the double-precision registers.
38424 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38425 need to contain registers; it instructs @value{GDBN} to display the
38426 VFP double-precision registers as vectors and to synthesize the
38427 quad-precision registers from pairs of double-precision registers.
38428 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38429 be present and include 32 double-precision registers.
38431 @node i386 Features
38432 @subsection i386 Features
38433 @cindex target descriptions, i386 features
38435 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38436 targets. It should describe the following registers:
38440 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38442 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38444 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38445 @samp{fs}, @samp{gs}
38447 @samp{st0} through @samp{st7}
38449 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38450 @samp{foseg}, @samp{fooff} and @samp{fop}
38453 The register sets may be different, depending on the target.
38455 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38456 describe registers:
38460 @samp{xmm0} through @samp{xmm7} for i386
38462 @samp{xmm0} through @samp{xmm15} for amd64
38467 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38468 @samp{org.gnu.gdb.i386.sse} feature. It should
38469 describe the upper 128 bits of @sc{ymm} registers:
38473 @samp{ymm0h} through @samp{ymm7h} for i386
38475 @samp{ymm0h} through @samp{ymm15h} for amd64
38478 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38479 describe a single register, @samp{orig_eax}.
38481 @node MIPS Features
38482 @subsection MIPS Features
38483 @cindex target descriptions, MIPS features
38485 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38486 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38487 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38490 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38491 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38492 registers. They may be 32-bit or 64-bit depending on the target.
38494 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38495 it may be optional in a future version of @value{GDBN}. It should
38496 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38497 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38499 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38500 contain a single register, @samp{restart}, which is used by the
38501 Linux kernel to control restartable syscalls.
38503 @node M68K Features
38504 @subsection M68K Features
38505 @cindex target descriptions, M68K features
38508 @item @samp{org.gnu.gdb.m68k.core}
38509 @itemx @samp{org.gnu.gdb.coldfire.core}
38510 @itemx @samp{org.gnu.gdb.fido.core}
38511 One of those features must be always present.
38512 The feature that is present determines which flavor of m68k is
38513 used. The feature that is present should contain registers
38514 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38515 @samp{sp}, @samp{ps} and @samp{pc}.
38517 @item @samp{org.gnu.gdb.coldfire.fp}
38518 This feature is optional. If present, it should contain registers
38519 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38523 @node PowerPC Features
38524 @subsection PowerPC Features
38525 @cindex target descriptions, PowerPC features
38527 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38528 targets. It should contain registers @samp{r0} through @samp{r31},
38529 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38530 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38532 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38533 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38535 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38536 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38539 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38540 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38541 will combine these registers with the floating point registers
38542 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38543 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38544 through @samp{vs63}, the set of vector registers for POWER7.
38546 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38547 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38548 @samp{spefscr}. SPE targets should provide 32-bit registers in
38549 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38550 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38551 these to present registers @samp{ev0} through @samp{ev31} to the
38554 @node TIC6x Features
38555 @subsection TMS320C6x Features
38556 @cindex target descriptions, TIC6x features
38557 @cindex target descriptions, TMS320C6x features
38558 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38559 targets. It should contain registers @samp{A0} through @samp{A15},
38560 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38562 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38563 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38564 through @samp{B31}.
38566 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38567 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38569 @node Operating System Information
38570 @appendix Operating System Information
38571 @cindex operating system information
38577 Users of @value{GDBN} often wish to obtain information about the state of
38578 the operating system running on the target---for example the list of
38579 processes, or the list of open files. This section describes the
38580 mechanism that makes it possible. This mechanism is similar to the
38581 target features mechanism (@pxref{Target Descriptions}), but focuses
38582 on a different aspect of target.
38584 Operating system information is retrived from the target via the
38585 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38586 read}). The object name in the request should be @samp{osdata}, and
38587 the @var{annex} identifies the data to be fetched.
38590 @appendixsection Process list
38591 @cindex operating system information, process list
38593 When requesting the process list, the @var{annex} field in the
38594 @samp{qXfer} request should be @samp{processes}. The returned data is
38595 an XML document. The formal syntax of this document is defined in
38596 @file{gdb/features/osdata.dtd}.
38598 An example document is:
38601 <?xml version="1.0"?>
38602 <!DOCTYPE target SYSTEM "osdata.dtd">
38603 <osdata type="processes">
38605 <column name="pid">1</column>
38606 <column name="user">root</column>
38607 <column name="command">/sbin/init</column>
38608 <column name="cores">1,2,3</column>
38613 Each item should include a column whose name is @samp{pid}. The value
38614 of that column should identify the process on the target. The
38615 @samp{user} and @samp{command} columns are optional, and will be
38616 displayed by @value{GDBN}. The @samp{cores} column, if present,
38617 should contain a comma-separated list of cores that this process
38618 is running on. Target may provide additional columns,
38619 which @value{GDBN} currently ignores.
38621 @node Trace File Format
38622 @appendix Trace File Format
38623 @cindex trace file format
38625 The trace file comes in three parts: a header, a textual description
38626 section, and a trace frame section with binary data.
38628 The header has the form @code{\x7fTRACE0\n}. The first byte is
38629 @code{0x7f} so as to indicate that the file contains binary data,
38630 while the @code{0} is a version number that may have different values
38633 The description section consists of multiple lines of @sc{ascii} text
38634 separated by newline characters (@code{0xa}). The lines may include a
38635 variety of optional descriptive or context-setting information, such
38636 as tracepoint definitions or register set size. @value{GDBN} will
38637 ignore any line that it does not recognize. An empty line marks the end
38640 @c FIXME add some specific types of data
38642 The trace frame section consists of a number of consecutive frames.
38643 Each frame begins with a two-byte tracepoint number, followed by a
38644 four-byte size giving the amount of data in the frame. The data in
38645 the frame consists of a number of blocks, each introduced by a
38646 character indicating its type (at least register, memory, and trace
38647 state variable). The data in this section is raw binary, not a
38648 hexadecimal or other encoding; its endianness matches the target's
38651 @c FIXME bi-arch may require endianness/arch info in description section
38654 @item R @var{bytes}
38655 Register block. The number and ordering of bytes matches that of a
38656 @code{g} packet in the remote protocol. Note that these are the
38657 actual bytes, in target order and @value{GDBN} register order, not a
38658 hexadecimal encoding.
38660 @item M @var{address} @var{length} @var{bytes}...
38661 Memory block. This is a contiguous block of memory, at the 8-byte
38662 address @var{address}, with a 2-byte length @var{length}, followed by
38663 @var{length} bytes.
38665 @item V @var{number} @var{value}
38666 Trace state variable block. This records the 8-byte signed value
38667 @var{value} of trace state variable numbered @var{number}.
38671 Future enhancements of the trace file format may include additional types
38674 @node Index Section Format
38675 @appendix @code{.gdb_index} section format
38676 @cindex .gdb_index section format
38677 @cindex index section format
38679 This section documents the index section that is created by @code{save
38680 gdb-index} (@pxref{Index Files}). The index section is
38681 DWARF-specific; some knowledge of DWARF is assumed in this
38684 The mapped index file format is designed to be directly
38685 @code{mmap}able on any architecture. In most cases, a datum is
38686 represented using a little-endian 32-bit integer value, called an
38687 @code{offset_type}. Big endian machines must byte-swap the values
38688 before using them. Exceptions to this rule are noted. The data is
38689 laid out such that alignment is always respected.
38691 A mapped index consists of several areas, laid out in order.
38695 The file header. This is a sequence of values, of @code{offset_type}
38696 unless otherwise noted:
38700 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38701 Version 4 differs by its hashing function.
38704 The offset, from the start of the file, of the CU list.
38707 The offset, from the start of the file, of the types CU list. Note
38708 that this area can be empty, in which case this offset will be equal
38709 to the next offset.
38712 The offset, from the start of the file, of the address area.
38715 The offset, from the start of the file, of the symbol table.
38718 The offset, from the start of the file, of the constant pool.
38722 The CU list. This is a sequence of pairs of 64-bit little-endian
38723 values, sorted by the CU offset. The first element in each pair is
38724 the offset of a CU in the @code{.debug_info} section. The second
38725 element in each pair is the length of that CU. References to a CU
38726 elsewhere in the map are done using a CU index, which is just the
38727 0-based index into this table. Note that if there are type CUs, then
38728 conceptually CUs and type CUs form a single list for the purposes of
38732 The types CU list. This is a sequence of triplets of 64-bit
38733 little-endian values. In a triplet, the first value is the CU offset,
38734 the second value is the type offset in the CU, and the third value is
38735 the type signature. The types CU list is not sorted.
38738 The address area. The address area consists of a sequence of address
38739 entries. Each address entry has three elements:
38743 The low address. This is a 64-bit little-endian value.
38746 The high address. This is a 64-bit little-endian value. Like
38747 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38750 The CU index. This is an @code{offset_type} value.
38754 The symbol table. This is an open-addressed hash table. The size of
38755 the hash table is always a power of 2.
38757 Each slot in the hash table consists of a pair of @code{offset_type}
38758 values. The first value is the offset of the symbol's name in the
38759 constant pool. The second value is the offset of the CU vector in the
38762 If both values are 0, then this slot in the hash table is empty. This
38763 is ok because while 0 is a valid constant pool index, it cannot be a
38764 valid index for both a string and a CU vector.
38766 The hash value for a table entry is computed by applying an
38767 iterative hash function to the symbol's name. Starting with an
38768 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38769 the string is incorporated into the hash using the formula depending on the
38774 The formula is @code{r = r * 67 + c - 113}.
38777 The formula is @code{r = r * 67 + tolower (c) - 113}.
38780 The terminating @samp{\0} is not incorporated into the hash.
38782 The step size used in the hash table is computed via
38783 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38784 value, and @samp{size} is the size of the hash table. The step size
38785 is used to find the next candidate slot when handling a hash
38788 The names of C@t{++} symbols in the hash table are canonicalized. We
38789 don't currently have a simple description of the canonicalization
38790 algorithm; if you intend to create new index sections, you must read
38794 The constant pool. This is simply a bunch of bytes. It is organized
38795 so that alignment is correct: CU vectors are stored first, followed by
38798 A CU vector in the constant pool is a sequence of @code{offset_type}
38799 values. The first value is the number of CU indices in the vector.
38800 Each subsequent value is the index of a CU in the CU list. This
38801 element in the hash table is used to indicate which CUs define the
38804 A string in the constant pool is zero-terminated.
38809 @node GNU Free Documentation License
38810 @appendix GNU Free Documentation License
38819 % I think something like @colophon should be in texinfo. In the
38821 \long\def\colophon{\hbox to0pt{}\vfill
38822 \centerline{The body of this manual is set in}
38823 \centerline{\fontname\tenrm,}
38824 \centerline{with headings in {\bf\fontname\tenbf}}
38825 \centerline{and examples in {\tt\fontname\tentt}.}
38826 \centerline{{\it\fontname\tenit\/},}
38827 \centerline{{\bf\fontname\tenbf}, and}
38828 \centerline{{\sl\fontname\tensl\/}}
38829 \centerline{are used for emphasis.}\vfill}
38831 % Blame: doc@cygnus.com, 1991.