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
4118 @item tcatch @var{event}
4119 Set a catchpoint that is enabled only for one stop. The catchpoint is
4120 automatically deleted after the first time the event is caught.
4124 Use the @code{info break} command to list the current catchpoints.
4126 There are currently some limitations to C@t{++} exception handling
4127 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4131 If you call a function interactively, @value{GDBN} normally returns
4132 control to you when the function has finished executing. If the call
4133 raises an exception, however, the call may bypass the mechanism that
4134 returns control to you and cause your program either to abort or to
4135 simply continue running until it hits a breakpoint, catches a signal
4136 that @value{GDBN} is listening for, or exits. This is the case even if
4137 you set a catchpoint for the exception; catchpoints on exceptions are
4138 disabled within interactive calls.
4141 You cannot raise an exception interactively.
4144 You cannot install an exception handler interactively.
4147 @cindex raise exceptions
4148 Sometimes @code{catch} is not the best way to debug exception handling:
4149 if you need to know exactly where an exception is raised, it is better to
4150 stop @emph{before} the exception handler is called, since that way you
4151 can see the stack before any unwinding takes place. If you set a
4152 breakpoint in an exception handler instead, it may not be easy to find
4153 out where the exception was raised.
4155 To stop just before an exception handler is called, you need some
4156 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4157 raised by calling a library function named @code{__raise_exception}
4158 which has the following ANSI C interface:
4161 /* @var{addr} is where the exception identifier is stored.
4162 @var{id} is the exception identifier. */
4163 void __raise_exception (void **addr, void *id);
4167 To make the debugger catch all exceptions before any stack
4168 unwinding takes place, set a breakpoint on @code{__raise_exception}
4169 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4171 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4172 that depends on the value of @var{id}, you can stop your program when
4173 a specific exception is raised. You can use multiple conditional
4174 breakpoints to stop your program when any of a number of exceptions are
4179 @subsection Deleting Breakpoints
4181 @cindex clearing breakpoints, watchpoints, catchpoints
4182 @cindex deleting breakpoints, watchpoints, catchpoints
4183 It is often necessary to eliminate a breakpoint, watchpoint, or
4184 catchpoint once it has done its job and you no longer want your program
4185 to stop there. This is called @dfn{deleting} the breakpoint. A
4186 breakpoint that has been deleted no longer exists; it is forgotten.
4188 With the @code{clear} command you can delete breakpoints according to
4189 where they are in your program. With the @code{delete} command you can
4190 delete individual breakpoints, watchpoints, or catchpoints by specifying
4191 their breakpoint numbers.
4193 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4194 automatically ignores breakpoints on the first instruction to be executed
4195 when you continue execution without changing the execution address.
4200 Delete any breakpoints at the next instruction to be executed in the
4201 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4202 the innermost frame is selected, this is a good way to delete a
4203 breakpoint where your program just stopped.
4205 @item clear @var{location}
4206 Delete any breakpoints set at the specified @var{location}.
4207 @xref{Specify Location}, for the various forms of @var{location}; the
4208 most useful ones are listed below:
4211 @item clear @var{function}
4212 @itemx clear @var{filename}:@var{function}
4213 Delete any breakpoints set at entry to the named @var{function}.
4215 @item clear @var{linenum}
4216 @itemx clear @var{filename}:@var{linenum}
4217 Delete any breakpoints set at or within the code of the specified
4218 @var{linenum} of the specified @var{filename}.
4221 @cindex delete breakpoints
4223 @kindex d @r{(@code{delete})}
4224 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4225 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4226 ranges specified as arguments. If no argument is specified, delete all
4227 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4228 confirm off}). You can abbreviate this command as @code{d}.
4232 @subsection Disabling Breakpoints
4234 @cindex enable/disable a breakpoint
4235 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4236 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4237 it had been deleted, but remembers the information on the breakpoint so
4238 that you can @dfn{enable} it again later.
4240 You disable and enable breakpoints, watchpoints, and catchpoints with
4241 the @code{enable} and @code{disable} commands, optionally specifying
4242 one or more breakpoint numbers as arguments. Use @code{info break} to
4243 print a list of all breakpoints, watchpoints, and catchpoints if you
4244 do not know which numbers to use.
4246 Disabling and enabling a breakpoint that has multiple locations
4247 affects all of its locations.
4249 A breakpoint, watchpoint, or catchpoint can have any of four different
4250 states of enablement:
4254 Enabled. The breakpoint stops your program. A breakpoint set
4255 with the @code{break} command starts out in this state.
4257 Disabled. The breakpoint has no effect on your program.
4259 Enabled once. The breakpoint stops your program, but then becomes
4262 Enabled for deletion. The breakpoint stops your program, but
4263 immediately after it does so it is deleted permanently. A breakpoint
4264 set with the @code{tbreak} command starts out in this state.
4267 You can use the following commands to enable or disable breakpoints,
4268 watchpoints, and catchpoints:
4272 @kindex dis @r{(@code{disable})}
4273 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4274 Disable the specified breakpoints---or all breakpoints, if none are
4275 listed. A disabled breakpoint has no effect but is not forgotten. All
4276 options such as ignore-counts, conditions and commands are remembered in
4277 case the breakpoint is enabled again later. You may abbreviate
4278 @code{disable} as @code{dis}.
4281 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4282 Enable the specified breakpoints (or all defined breakpoints). They
4283 become effective once again in stopping your program.
4285 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4286 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4287 of these breakpoints immediately after stopping your program.
4289 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4290 Enable the specified breakpoints to work once, then die. @value{GDBN}
4291 deletes any of these breakpoints as soon as your program stops there.
4292 Breakpoints set by the @code{tbreak} command start out in this state.
4295 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4296 @c confusing: tbreak is also initially enabled.
4297 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4298 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4299 subsequently, they become disabled or enabled only when you use one of
4300 the commands above. (The command @code{until} can set and delete a
4301 breakpoint of its own, but it does not change the state of your other
4302 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4306 @subsection Break Conditions
4307 @cindex conditional breakpoints
4308 @cindex breakpoint conditions
4310 @c FIXME what is scope of break condition expr? Context where wanted?
4311 @c in particular for a watchpoint?
4312 The simplest sort of breakpoint breaks every time your program reaches a
4313 specified place. You can also specify a @dfn{condition} for a
4314 breakpoint. A condition is just a Boolean expression in your
4315 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4316 a condition evaluates the expression each time your program reaches it,
4317 and your program stops only if the condition is @emph{true}.
4319 This is the converse of using assertions for program validation; in that
4320 situation, you want to stop when the assertion is violated---that is,
4321 when the condition is false. In C, if you want to test an assertion expressed
4322 by the condition @var{assert}, you should set the condition
4323 @samp{! @var{assert}} on the appropriate breakpoint.
4325 Conditions are also accepted for watchpoints; you may not need them,
4326 since a watchpoint is inspecting the value of an expression anyhow---but
4327 it might be simpler, say, to just set a watchpoint on a variable name,
4328 and specify a condition that tests whether the new value is an interesting
4331 Break conditions can have side effects, and may even call functions in
4332 your program. This can be useful, for example, to activate functions
4333 that log program progress, or to use your own print functions to
4334 format special data structures. The effects are completely predictable
4335 unless there is another enabled breakpoint at the same address. (In
4336 that case, @value{GDBN} might see the other breakpoint first and stop your
4337 program without checking the condition of this one.) Note that
4338 breakpoint commands are usually more convenient and flexible than break
4340 purpose of performing side effects when a breakpoint is reached
4341 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4343 Break conditions can be specified when a breakpoint is set, by using
4344 @samp{if} in the arguments to the @code{break} command. @xref{Set
4345 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4346 with the @code{condition} command.
4348 You can also use the @code{if} keyword with the @code{watch} command.
4349 The @code{catch} command does not recognize the @code{if} keyword;
4350 @code{condition} is the only way to impose a further condition on a
4355 @item condition @var{bnum} @var{expression}
4356 Specify @var{expression} as the break condition for breakpoint,
4357 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4358 breakpoint @var{bnum} stops your program only if the value of
4359 @var{expression} is true (nonzero, in C). When you use
4360 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4361 syntactic correctness, and to determine whether symbols in it have
4362 referents in the context of your breakpoint. If @var{expression} uses
4363 symbols not referenced in the context of the breakpoint, @value{GDBN}
4364 prints an error message:
4367 No symbol "foo" in current context.
4372 not actually evaluate @var{expression} at the time the @code{condition}
4373 command (or a command that sets a breakpoint with a condition, like
4374 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4376 @item condition @var{bnum}
4377 Remove the condition from breakpoint number @var{bnum}. It becomes
4378 an ordinary unconditional breakpoint.
4381 @cindex ignore count (of breakpoint)
4382 A special case of a breakpoint condition is to stop only when the
4383 breakpoint has been reached a certain number of times. This is so
4384 useful that there is a special way to do it, using the @dfn{ignore
4385 count} of the breakpoint. Every breakpoint has an ignore count, which
4386 is an integer. Most of the time, the ignore count is zero, and
4387 therefore has no effect. But if your program reaches a breakpoint whose
4388 ignore count is positive, then instead of stopping, it just decrements
4389 the ignore count by one and continues. As a result, if the ignore count
4390 value is @var{n}, the breakpoint does not stop the next @var{n} times
4391 your program reaches it.
4395 @item ignore @var{bnum} @var{count}
4396 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4397 The next @var{count} times the breakpoint is reached, your program's
4398 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4401 To make the breakpoint stop the next time it is reached, specify
4404 When you use @code{continue} to resume execution of your program from a
4405 breakpoint, you can specify an ignore count directly as an argument to
4406 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4407 Stepping,,Continuing and Stepping}.
4409 If a breakpoint has a positive ignore count and a condition, the
4410 condition is not checked. Once the ignore count reaches zero,
4411 @value{GDBN} resumes checking the condition.
4413 You could achieve the effect of the ignore count with a condition such
4414 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4415 is decremented each time. @xref{Convenience Vars, ,Convenience
4419 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4422 @node Break Commands
4423 @subsection Breakpoint Command Lists
4425 @cindex breakpoint commands
4426 You can give any breakpoint (or watchpoint or catchpoint) a series of
4427 commands to execute when your program stops due to that breakpoint. For
4428 example, you might want to print the values of certain expressions, or
4429 enable other breakpoints.
4433 @kindex end@r{ (breakpoint commands)}
4434 @item commands @r{[}@var{range}@dots{}@r{]}
4435 @itemx @dots{} @var{command-list} @dots{}
4437 Specify a list of commands for the given breakpoints. The commands
4438 themselves appear on the following lines. Type a line containing just
4439 @code{end} to terminate the commands.
4441 To remove all commands from a breakpoint, type @code{commands} and
4442 follow it immediately with @code{end}; that is, give no commands.
4444 With no argument, @code{commands} refers to the last breakpoint,
4445 watchpoint, or catchpoint set (not to the breakpoint most recently
4446 encountered). If the most recent breakpoints were set with a single
4447 command, then the @code{commands} will apply to all the breakpoints
4448 set by that command. This applies to breakpoints set by
4449 @code{rbreak}, and also applies when a single @code{break} command
4450 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4454 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4455 disabled within a @var{command-list}.
4457 You can use breakpoint commands to start your program up again. Simply
4458 use the @code{continue} command, or @code{step}, or any other command
4459 that resumes execution.
4461 Any other commands in the command list, after a command that resumes
4462 execution, are ignored. This is because any time you resume execution
4463 (even with a simple @code{next} or @code{step}), you may encounter
4464 another breakpoint---which could have its own command list, leading to
4465 ambiguities about which list to execute.
4468 If the first command you specify in a command list is @code{silent}, the
4469 usual message about stopping at a breakpoint is not printed. This may
4470 be desirable for breakpoints that are to print a specific message and
4471 then continue. If none of the remaining commands print anything, you
4472 see no sign that the breakpoint was reached. @code{silent} is
4473 meaningful only at the beginning of a breakpoint command list.
4475 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4476 print precisely controlled output, and are often useful in silent
4477 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4479 For example, here is how you could use breakpoint commands to print the
4480 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4486 printf "x is %d\n",x
4491 One application for breakpoint commands is to compensate for one bug so
4492 you can test for another. Put a breakpoint just after the erroneous line
4493 of code, give it a condition to detect the case in which something
4494 erroneous has been done, and give it commands to assign correct values
4495 to any variables that need them. End with the @code{continue} command
4496 so that your program does not stop, and start with the @code{silent}
4497 command so that no output is produced. Here is an example:
4508 @node Save Breakpoints
4509 @subsection How to save breakpoints to a file
4511 To save breakpoint definitions to a file use the @w{@code{save
4512 breakpoints}} command.
4515 @kindex save breakpoints
4516 @cindex save breakpoints to a file for future sessions
4517 @item save breakpoints [@var{filename}]
4518 This command saves all current breakpoint definitions together with
4519 their commands and ignore counts, into a file @file{@var{filename}}
4520 suitable for use in a later debugging session. This includes all
4521 types of breakpoints (breakpoints, watchpoints, catchpoints,
4522 tracepoints). To read the saved breakpoint definitions, use the
4523 @code{source} command (@pxref{Command Files}). Note that watchpoints
4524 with expressions involving local variables may fail to be recreated
4525 because it may not be possible to access the context where the
4526 watchpoint is valid anymore. Because the saved breakpoint definitions
4527 are simply a sequence of @value{GDBN} commands that recreate the
4528 breakpoints, you can edit the file in your favorite editing program,
4529 and remove the breakpoint definitions you're not interested in, or
4530 that can no longer be recreated.
4533 @c @ifclear BARETARGET
4534 @node Error in Breakpoints
4535 @subsection ``Cannot insert breakpoints''
4537 If you request too many active hardware-assisted breakpoints and
4538 watchpoints, you will see this error message:
4540 @c FIXME: the precise wording of this message may change; the relevant
4541 @c source change is not committed yet (Sep 3, 1999).
4543 Stopped; cannot insert breakpoints.
4544 You may have requested too many hardware breakpoints and watchpoints.
4548 This message is printed when you attempt to resume the program, since
4549 only then @value{GDBN} knows exactly how many hardware breakpoints and
4550 watchpoints it needs to insert.
4552 When this message is printed, you need to disable or remove some of the
4553 hardware-assisted breakpoints and watchpoints, and then continue.
4555 @node Breakpoint-related Warnings
4556 @subsection ``Breakpoint address adjusted...''
4557 @cindex breakpoint address adjusted
4559 Some processor architectures place constraints on the addresses at
4560 which breakpoints may be placed. For architectures thus constrained,
4561 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4562 with the constraints dictated by the architecture.
4564 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4565 a VLIW architecture in which a number of RISC-like instructions may be
4566 bundled together for parallel execution. The FR-V architecture
4567 constrains the location of a breakpoint instruction within such a
4568 bundle to the instruction with the lowest address. @value{GDBN}
4569 honors this constraint by adjusting a breakpoint's address to the
4570 first in the bundle.
4572 It is not uncommon for optimized code to have bundles which contain
4573 instructions from different source statements, thus it may happen that
4574 a breakpoint's address will be adjusted from one source statement to
4575 another. Since this adjustment may significantly alter @value{GDBN}'s
4576 breakpoint related behavior from what the user expects, a warning is
4577 printed when the breakpoint is first set and also when the breakpoint
4580 A warning like the one below is printed when setting a breakpoint
4581 that's been subject to address adjustment:
4584 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4587 Such warnings are printed both for user settable and @value{GDBN}'s
4588 internal breakpoints. If you see one of these warnings, you should
4589 verify that a breakpoint set at the adjusted address will have the
4590 desired affect. If not, the breakpoint in question may be removed and
4591 other breakpoints may be set which will have the desired behavior.
4592 E.g., it may be sufficient to place the breakpoint at a later
4593 instruction. A conditional breakpoint may also be useful in some
4594 cases to prevent the breakpoint from triggering too often.
4596 @value{GDBN} will also issue a warning when stopping at one of these
4597 adjusted breakpoints:
4600 warning: Breakpoint 1 address previously adjusted from 0x00010414
4604 When this warning is encountered, it may be too late to take remedial
4605 action except in cases where the breakpoint is hit earlier or more
4606 frequently than expected.
4608 @node Continuing and Stepping
4609 @section Continuing and Stepping
4613 @cindex resuming execution
4614 @dfn{Continuing} means resuming program execution until your program
4615 completes normally. In contrast, @dfn{stepping} means executing just
4616 one more ``step'' of your program, where ``step'' may mean either one
4617 line of source code, or one machine instruction (depending on what
4618 particular command you use). Either when continuing or when stepping,
4619 your program may stop even sooner, due to a breakpoint or a signal. (If
4620 it stops due to a signal, you may want to use @code{handle}, or use
4621 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4625 @kindex c @r{(@code{continue})}
4626 @kindex fg @r{(resume foreground execution)}
4627 @item continue @r{[}@var{ignore-count}@r{]}
4628 @itemx c @r{[}@var{ignore-count}@r{]}
4629 @itemx fg @r{[}@var{ignore-count}@r{]}
4630 Resume program execution, at the address where your program last stopped;
4631 any breakpoints set at that address are bypassed. The optional argument
4632 @var{ignore-count} allows you to specify a further number of times to
4633 ignore a breakpoint at this location; its effect is like that of
4634 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4636 The argument @var{ignore-count} is meaningful only when your program
4637 stopped due to a breakpoint. At other times, the argument to
4638 @code{continue} is ignored.
4640 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4641 debugged program is deemed to be the foreground program) are provided
4642 purely for convenience, and have exactly the same behavior as
4646 To resume execution at a different place, you can use @code{return}
4647 (@pxref{Returning, ,Returning from a Function}) to go back to the
4648 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4649 Different Address}) to go to an arbitrary location in your program.
4651 A typical technique for using stepping is to set a breakpoint
4652 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4653 beginning of the function or the section of your program where a problem
4654 is believed to lie, run your program until it stops at that breakpoint,
4655 and then step through the suspect area, examining the variables that are
4656 interesting, until you see the problem happen.
4660 @kindex s @r{(@code{step})}
4662 Continue running your program until control reaches a different source
4663 line, then stop it and return control to @value{GDBN}. This command is
4664 abbreviated @code{s}.
4667 @c "without debugging information" is imprecise; actually "without line
4668 @c numbers in the debugging information". (gcc -g1 has debugging info but
4669 @c not line numbers). But it seems complex to try to make that
4670 @c distinction here.
4671 @emph{Warning:} If you use the @code{step} command while control is
4672 within a function that was compiled without debugging information,
4673 execution proceeds until control reaches a function that does have
4674 debugging information. Likewise, it will not step into a function which
4675 is compiled without debugging information. To step through functions
4676 without debugging information, use the @code{stepi} command, described
4680 The @code{step} command only stops at the first instruction of a source
4681 line. This prevents the multiple stops that could otherwise occur in
4682 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4683 to stop if a function that has debugging information is called within
4684 the line. In other words, @code{step} @emph{steps inside} any functions
4685 called within the line.
4687 Also, the @code{step} command only enters a function if there is line
4688 number information for the function. Otherwise it acts like the
4689 @code{next} command. This avoids problems when using @code{cc -gl}
4690 on MIPS machines. Previously, @code{step} entered subroutines if there
4691 was any debugging information about the routine.
4693 @item step @var{count}
4694 Continue running as in @code{step}, but do so @var{count} times. If a
4695 breakpoint is reached, or a signal not related to stepping occurs before
4696 @var{count} steps, stepping stops right away.
4699 @kindex n @r{(@code{next})}
4700 @item next @r{[}@var{count}@r{]}
4701 Continue to the next source line in the current (innermost) stack frame.
4702 This is similar to @code{step}, but function calls that appear within
4703 the line of code are executed without stopping. Execution stops when
4704 control reaches a different line of code at the original stack level
4705 that was executing when you gave the @code{next} command. This command
4706 is abbreviated @code{n}.
4708 An argument @var{count} is a repeat count, as for @code{step}.
4711 @c FIX ME!! Do we delete this, or is there a way it fits in with
4712 @c the following paragraph? --- Vctoria
4714 @c @code{next} within a function that lacks debugging information acts like
4715 @c @code{step}, but any function calls appearing within the code of the
4716 @c function are executed without stopping.
4718 The @code{next} command only stops at the first instruction of a
4719 source line. This prevents multiple stops that could otherwise occur in
4720 @code{switch} statements, @code{for} loops, etc.
4722 @kindex set step-mode
4724 @cindex functions without line info, and stepping
4725 @cindex stepping into functions with no line info
4726 @itemx set step-mode on
4727 The @code{set step-mode on} command causes the @code{step} command to
4728 stop at the first instruction of a function which contains no debug line
4729 information rather than stepping over it.
4731 This is useful in cases where you may be interested in inspecting the
4732 machine instructions of a function which has no symbolic info and do not
4733 want @value{GDBN} to automatically skip over this function.
4735 @item set step-mode off
4736 Causes the @code{step} command to step over any functions which contains no
4737 debug information. This is the default.
4739 @item show step-mode
4740 Show whether @value{GDBN} will stop in or step over functions without
4741 source line debug information.
4744 @kindex fin @r{(@code{finish})}
4746 Continue running until just after function in the selected stack frame
4747 returns. Print the returned value (if any). This command can be
4748 abbreviated as @code{fin}.
4750 Contrast this with the @code{return} command (@pxref{Returning,
4751 ,Returning from a Function}).
4754 @kindex u @r{(@code{until})}
4755 @cindex run until specified location
4758 Continue running until a source line past the current line, in the
4759 current stack frame, is reached. This command is used to avoid single
4760 stepping through a loop more than once. It is like the @code{next}
4761 command, except that when @code{until} encounters a jump, it
4762 automatically continues execution until the program counter is greater
4763 than the address of the jump.
4765 This means that when you reach the end of a loop after single stepping
4766 though it, @code{until} makes your program continue execution until it
4767 exits the loop. In contrast, a @code{next} command at the end of a loop
4768 simply steps back to the beginning of the loop, which forces you to step
4769 through the next iteration.
4771 @code{until} always stops your program if it attempts to exit the current
4774 @code{until} may produce somewhat counterintuitive results if the order
4775 of machine code does not match the order of the source lines. For
4776 example, in the following excerpt from a debugging session, the @code{f}
4777 (@code{frame}) command shows that execution is stopped at line
4778 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4782 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4784 (@value{GDBP}) until
4785 195 for ( ; argc > 0; NEXTARG) @{
4788 This happened because, for execution efficiency, the compiler had
4789 generated code for the loop closure test at the end, rather than the
4790 start, of the loop---even though the test in a C @code{for}-loop is
4791 written before the body of the loop. The @code{until} command appeared
4792 to step back to the beginning of the loop when it advanced to this
4793 expression; however, it has not really gone to an earlier
4794 statement---not in terms of the actual machine code.
4796 @code{until} with no argument works by means of single
4797 instruction stepping, and hence is slower than @code{until} with an
4800 @item until @var{location}
4801 @itemx u @var{location}
4802 Continue running your program until either the specified location is
4803 reached, or the current stack frame returns. @var{location} is any of
4804 the forms described in @ref{Specify Location}.
4805 This form of the command uses temporary breakpoints, and
4806 hence is quicker than @code{until} without an argument. The specified
4807 location is actually reached only if it is in the current frame. This
4808 implies that @code{until} can be used to skip over recursive function
4809 invocations. For instance in the code below, if the current location is
4810 line @code{96}, issuing @code{until 99} will execute the program up to
4811 line @code{99} in the same invocation of factorial, i.e., after the inner
4812 invocations have returned.
4815 94 int factorial (int value)
4817 96 if (value > 1) @{
4818 97 value *= factorial (value - 1);
4825 @kindex advance @var{location}
4826 @itemx advance @var{location}
4827 Continue running the program up to the given @var{location}. An argument is
4828 required, which should be of one of the forms described in
4829 @ref{Specify Location}.
4830 Execution will also stop upon exit from the current stack
4831 frame. This command is similar to @code{until}, but @code{advance} will
4832 not skip over recursive function calls, and the target location doesn't
4833 have to be in the same frame as the current one.
4837 @kindex si @r{(@code{stepi})}
4839 @itemx stepi @var{arg}
4841 Execute one machine instruction, then stop and return to the debugger.
4843 It is often useful to do @samp{display/i $pc} when stepping by machine
4844 instructions. This makes @value{GDBN} automatically display the next
4845 instruction to be executed, each time your program stops. @xref{Auto
4846 Display,, Automatic Display}.
4848 An argument is a repeat count, as in @code{step}.
4852 @kindex ni @r{(@code{nexti})}
4854 @itemx nexti @var{arg}
4856 Execute one machine instruction, but if it is a function call,
4857 proceed until the function returns.
4859 An argument is a repeat count, as in @code{next}.
4862 @node Skipping Over Functions and Files
4863 @section Skipping Over Functions and Files
4864 @cindex skipping over functions and files
4866 The program you are debugging may contain some functions which are
4867 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4868 skip a function or all functions in a file when stepping.
4870 For example, consider the following C function:
4881 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4882 are not interested in stepping through @code{boring}. If you run @code{step}
4883 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4884 step over both @code{foo} and @code{boring}!
4886 One solution is to @code{step} into @code{boring} and use the @code{finish}
4887 command to immediately exit it. But this can become tedious if @code{boring}
4888 is called from many places.
4890 A more flexible solution is to execute @kbd{skip boring}. This instructs
4891 @value{GDBN} never to step into @code{boring}. Now when you execute
4892 @code{step} at line 103, you'll step over @code{boring} and directly into
4895 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4896 example, @code{skip file boring.c}.
4899 @kindex skip function
4900 @item skip @r{[}@var{linespec}@r{]}
4901 @itemx skip function @r{[}@var{linespec}@r{]}
4902 After running this command, the function named by @var{linespec} or the
4903 function containing the line named by @var{linespec} will be skipped over when
4904 stepping. @xref{Specify Location}.
4906 If you do not specify @var{linespec}, the function you're currently debugging
4909 (If you have a function called @code{file} that you want to skip, use
4910 @kbd{skip function file}.)
4913 @item skip file @r{[}@var{filename}@r{]}
4914 After running this command, any function whose source lives in @var{filename}
4915 will be skipped over when stepping.
4917 If you do not specify @var{filename}, functions whose source lives in the file
4918 you're currently debugging will be skipped.
4921 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4922 These are the commands for managing your list of skips:
4926 @item info skip @r{[}@var{range}@r{]}
4927 Print details about the specified skip(s). If @var{range} is not specified,
4928 print a table with details about all functions and files marked for skipping.
4929 @code{info skip} prints the following information about each skip:
4933 A number identifying this skip.
4935 The type of this skip, either @samp{function} or @samp{file}.
4936 @item Enabled or Disabled
4937 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4939 For function skips, this column indicates the address in memory of the function
4940 being skipped. If you've set a function skip on a function which has not yet
4941 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4942 which has the function is loaded, @code{info skip} will show the function's
4945 For file skips, this field contains the filename being skipped. For functions
4946 skips, this field contains the function name and its line number in the file
4947 where it is defined.
4951 @item skip delete @r{[}@var{range}@r{]}
4952 Delete the specified skip(s). If @var{range} is not specified, delete all
4956 @item skip enable @r{[}@var{range}@r{]}
4957 Enable the specified skip(s). If @var{range} is not specified, enable all
4960 @kindex skip disable
4961 @item skip disable @r{[}@var{range}@r{]}
4962 Disable the specified skip(s). If @var{range} is not specified, disable all
4971 A signal is an asynchronous event that can happen in a program. The
4972 operating system defines the possible kinds of signals, and gives each
4973 kind a name and a number. For example, in Unix @code{SIGINT} is the
4974 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4975 @code{SIGSEGV} is the signal a program gets from referencing a place in
4976 memory far away from all the areas in use; @code{SIGALRM} occurs when
4977 the alarm clock timer goes off (which happens only if your program has
4978 requested an alarm).
4980 @cindex fatal signals
4981 Some signals, including @code{SIGALRM}, are a normal part of the
4982 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4983 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4984 program has not specified in advance some other way to handle the signal.
4985 @code{SIGINT} does not indicate an error in your program, but it is normally
4986 fatal so it can carry out the purpose of the interrupt: to kill the program.
4988 @value{GDBN} has the ability to detect any occurrence of a signal in your
4989 program. You can tell @value{GDBN} in advance what to do for each kind of
4992 @cindex handling signals
4993 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4994 @code{SIGALRM} be silently passed to your program
4995 (so as not to interfere with their role in the program's functioning)
4996 but to stop your program immediately whenever an error signal happens.
4997 You can change these settings with the @code{handle} command.
5000 @kindex info signals
5004 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5005 handle each one. You can use this to see the signal numbers of all
5006 the defined types of signals.
5008 @item info signals @var{sig}
5009 Similar, but print information only about the specified signal number.
5011 @code{info handle} is an alias for @code{info signals}.
5014 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5015 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5016 can be the number of a signal or its name (with or without the
5017 @samp{SIG} at the beginning); a list of signal numbers of the form
5018 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5019 known signals. Optional arguments @var{keywords}, described below,
5020 say what change to make.
5024 The keywords allowed by the @code{handle} command can be abbreviated.
5025 Their full names are:
5029 @value{GDBN} should not stop your program when this signal happens. It may
5030 still print a message telling you that the signal has come in.
5033 @value{GDBN} should stop your program when this signal happens. This implies
5034 the @code{print} keyword as well.
5037 @value{GDBN} should print a message when this signal happens.
5040 @value{GDBN} should not mention the occurrence of the signal at all. This
5041 implies the @code{nostop} keyword as well.
5045 @value{GDBN} should allow your program to see this signal; your program
5046 can handle the signal, or else it may terminate if the signal is fatal
5047 and not handled. @code{pass} and @code{noignore} are synonyms.
5051 @value{GDBN} should not allow your program to see this signal.
5052 @code{nopass} and @code{ignore} are synonyms.
5056 When a signal stops your program, the signal is not visible to the
5058 continue. Your program sees the signal then, if @code{pass} is in
5059 effect for the signal in question @emph{at that time}. In other words,
5060 after @value{GDBN} reports a signal, you can use the @code{handle}
5061 command with @code{pass} or @code{nopass} to control whether your
5062 program sees that signal when you continue.
5064 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5065 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5066 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5069 You can also use the @code{signal} command to prevent your program from
5070 seeing a signal, or cause it to see a signal it normally would not see,
5071 or to give it any signal at any time. For example, if your program stopped
5072 due to some sort of memory reference error, you might store correct
5073 values into the erroneous variables and continue, hoping to see more
5074 execution; but your program would probably terminate immediately as
5075 a result of the fatal signal once it saw the signal. To prevent this,
5076 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5079 @cindex extra signal information
5080 @anchor{extra signal information}
5082 On some targets, @value{GDBN} can inspect extra signal information
5083 associated with the intercepted signal, before it is actually
5084 delivered to the program being debugged. This information is exported
5085 by the convenience variable @code{$_siginfo}, and consists of data
5086 that is passed by the kernel to the signal handler at the time of the
5087 receipt of a signal. The data type of the information itself is
5088 target dependent. You can see the data type using the @code{ptype
5089 $_siginfo} command. On Unix systems, it typically corresponds to the
5090 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5093 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5094 referenced address that raised a segmentation fault.
5098 (@value{GDBP}) continue
5099 Program received signal SIGSEGV, Segmentation fault.
5100 0x0000000000400766 in main ()
5102 (@value{GDBP}) ptype $_siginfo
5109 struct @{...@} _kill;
5110 struct @{...@} _timer;
5112 struct @{...@} _sigchld;
5113 struct @{...@} _sigfault;
5114 struct @{...@} _sigpoll;
5117 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5121 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5122 $1 = (void *) 0x7ffff7ff7000
5126 Depending on target support, @code{$_siginfo} may also be writable.
5129 @section Stopping and Starting Multi-thread Programs
5131 @cindex stopped threads
5132 @cindex threads, stopped
5134 @cindex continuing threads
5135 @cindex threads, continuing
5137 @value{GDBN} supports debugging programs with multiple threads
5138 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5139 are two modes of controlling execution of your program within the
5140 debugger. In the default mode, referred to as @dfn{all-stop mode},
5141 when any thread in your program stops (for example, at a breakpoint
5142 or while being stepped), all other threads in the program are also stopped by
5143 @value{GDBN}. On some targets, @value{GDBN} also supports
5144 @dfn{non-stop mode}, in which other threads can continue to run freely while
5145 you examine the stopped thread in the debugger.
5148 * All-Stop Mode:: All threads stop when GDB takes control
5149 * Non-Stop Mode:: Other threads continue to execute
5150 * Background Execution:: Running your program asynchronously
5151 * Thread-Specific Breakpoints:: Controlling breakpoints
5152 * Interrupted System Calls:: GDB may interfere with system calls
5153 * Observer Mode:: GDB does not alter program behavior
5157 @subsection All-Stop Mode
5159 @cindex all-stop mode
5161 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5162 @emph{all} threads of execution stop, not just the current thread. This
5163 allows you to examine the overall state of the program, including
5164 switching between threads, without worrying that things may change
5167 Conversely, whenever you restart the program, @emph{all} threads start
5168 executing. @emph{This is true even when single-stepping} with commands
5169 like @code{step} or @code{next}.
5171 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5172 Since thread scheduling is up to your debugging target's operating
5173 system (not controlled by @value{GDBN}), other threads may
5174 execute more than one statement while the current thread completes a
5175 single step. Moreover, in general other threads stop in the middle of a
5176 statement, rather than at a clean statement boundary, when the program
5179 You might even find your program stopped in another thread after
5180 continuing or even single-stepping. This happens whenever some other
5181 thread runs into a breakpoint, a signal, or an exception before the
5182 first thread completes whatever you requested.
5184 @cindex automatic thread selection
5185 @cindex switching threads automatically
5186 @cindex threads, automatic switching
5187 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5188 signal, it automatically selects the thread where that breakpoint or
5189 signal happened. @value{GDBN} alerts you to the context switch with a
5190 message such as @samp{[Switching to Thread @var{n}]} to identify the
5193 On some OSes, you can modify @value{GDBN}'s default behavior by
5194 locking the OS scheduler to allow only a single thread to run.
5197 @item set scheduler-locking @var{mode}
5198 @cindex scheduler locking mode
5199 @cindex lock scheduler
5200 Set the scheduler locking mode. If it is @code{off}, then there is no
5201 locking and any thread may run at any time. If @code{on}, then only the
5202 current thread may run when the inferior is resumed. The @code{step}
5203 mode optimizes for single-stepping; it prevents other threads
5204 from preempting the current thread while you are stepping, so that
5205 the focus of debugging does not change unexpectedly.
5206 Other threads only rarely (or never) get a chance to run
5207 when you step. They are more likely to run when you @samp{next} over a
5208 function call, and they are completely free to run when you use commands
5209 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5210 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5211 the current thread away from the thread that you are debugging.
5213 @item show scheduler-locking
5214 Display the current scheduler locking mode.
5217 @cindex resume threads of multiple processes simultaneously
5218 By default, when you issue one of the execution commands such as
5219 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5220 threads of the current inferior to run. For example, if @value{GDBN}
5221 is attached to two inferiors, each with two threads, the
5222 @code{continue} command resumes only the two threads of the current
5223 inferior. This is useful, for example, when you debug a program that
5224 forks and you want to hold the parent stopped (so that, for instance,
5225 it doesn't run to exit), while you debug the child. In other
5226 situations, you may not be interested in inspecting the current state
5227 of any of the processes @value{GDBN} is attached to, and you may want
5228 to resume them all until some breakpoint is hit. In the latter case,
5229 you can instruct @value{GDBN} to allow all threads of all the
5230 inferiors to run with the @w{@code{set schedule-multiple}} command.
5233 @kindex set schedule-multiple
5234 @item set schedule-multiple
5235 Set the mode for allowing threads of multiple processes to be resumed
5236 when an execution command is issued. When @code{on}, all threads of
5237 all processes are allowed to run. When @code{off}, only the threads
5238 of the current process are resumed. The default is @code{off}. The
5239 @code{scheduler-locking} mode takes precedence when set to @code{on},
5240 or while you are stepping and set to @code{step}.
5242 @item show schedule-multiple
5243 Display the current mode for resuming the execution of threads of
5248 @subsection Non-Stop Mode
5250 @cindex non-stop mode
5252 @c This section is really only a place-holder, and needs to be expanded
5253 @c with more details.
5255 For some multi-threaded targets, @value{GDBN} supports an optional
5256 mode of operation in which you can examine stopped program threads in
5257 the debugger while other threads continue to execute freely. This
5258 minimizes intrusion when debugging live systems, such as programs
5259 where some threads have real-time constraints or must continue to
5260 respond to external events. This is referred to as @dfn{non-stop} mode.
5262 In non-stop mode, when a thread stops to report a debugging event,
5263 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5264 threads as well, in contrast to the all-stop mode behavior. Additionally,
5265 execution commands such as @code{continue} and @code{step} apply by default
5266 only to the current thread in non-stop mode, rather than all threads as
5267 in all-stop mode. This allows you to control threads explicitly in
5268 ways that are not possible in all-stop mode --- for example, stepping
5269 one thread while allowing others to run freely, stepping
5270 one thread while holding all others stopped, or stepping several threads
5271 independently and simultaneously.
5273 To enter non-stop mode, use this sequence of commands before you run
5274 or attach to your program:
5277 # Enable the async interface.
5280 # If using the CLI, pagination breaks non-stop.
5283 # Finally, turn it on!
5287 You can use these commands to manipulate the non-stop mode setting:
5290 @kindex set non-stop
5291 @item set non-stop on
5292 Enable selection of non-stop mode.
5293 @item set non-stop off
5294 Disable selection of non-stop mode.
5295 @kindex show non-stop
5297 Show the current non-stop enablement setting.
5300 Note these commands only reflect whether non-stop mode is enabled,
5301 not whether the currently-executing program is being run in non-stop mode.
5302 In particular, the @code{set non-stop} preference is only consulted when
5303 @value{GDBN} starts or connects to the target program, and it is generally
5304 not possible to switch modes once debugging has started. Furthermore,
5305 since not all targets support non-stop mode, even when you have enabled
5306 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5309 In non-stop mode, all execution commands apply only to the current thread
5310 by default. That is, @code{continue} only continues one thread.
5311 To continue all threads, issue @code{continue -a} or @code{c -a}.
5313 You can use @value{GDBN}'s background execution commands
5314 (@pxref{Background Execution}) to run some threads in the background
5315 while you continue to examine or step others from @value{GDBN}.
5316 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5317 always executed asynchronously in non-stop mode.
5319 Suspending execution is done with the @code{interrupt} command when
5320 running in the background, or @kbd{Ctrl-c} during foreground execution.
5321 In all-stop mode, this stops the whole process;
5322 but in non-stop mode the interrupt applies only to the current thread.
5323 To stop the whole program, use @code{interrupt -a}.
5325 Other execution commands do not currently support the @code{-a} option.
5327 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5328 that thread current, as it does in all-stop mode. This is because the
5329 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5330 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5331 changed to a different thread just as you entered a command to operate on the
5332 previously current thread.
5334 @node Background Execution
5335 @subsection Background Execution
5337 @cindex foreground execution
5338 @cindex background execution
5339 @cindex asynchronous execution
5340 @cindex execution, foreground, background and asynchronous
5342 @value{GDBN}'s execution commands have two variants: the normal
5343 foreground (synchronous) behavior, and a background
5344 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5345 the program to report that some thread has stopped before prompting for
5346 another command. In background execution, @value{GDBN} immediately gives
5347 a command prompt so that you can issue other commands while your program runs.
5349 You need to explicitly enable asynchronous mode before you can use
5350 background execution commands. You can use these commands to
5351 manipulate the asynchronous mode setting:
5354 @kindex set target-async
5355 @item set target-async on
5356 Enable asynchronous mode.
5357 @item set target-async off
5358 Disable asynchronous mode.
5359 @kindex show target-async
5360 @item show target-async
5361 Show the current target-async setting.
5364 If the target doesn't support async mode, @value{GDBN} issues an error
5365 message if you attempt to use the background execution commands.
5367 To specify background execution, add a @code{&} to the command. For example,
5368 the background form of the @code{continue} command is @code{continue&}, or
5369 just @code{c&}. The execution commands that accept background execution
5375 @xref{Starting, , Starting your Program}.
5379 @xref{Attach, , Debugging an Already-running Process}.
5383 @xref{Continuing and Stepping, step}.
5387 @xref{Continuing and Stepping, stepi}.
5391 @xref{Continuing and Stepping, next}.
5395 @xref{Continuing and Stepping, nexti}.
5399 @xref{Continuing and Stepping, continue}.
5403 @xref{Continuing and Stepping, finish}.
5407 @xref{Continuing and Stepping, until}.
5411 Background execution is especially useful in conjunction with non-stop
5412 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5413 However, you can also use these commands in the normal all-stop mode with
5414 the restriction that you cannot issue another execution command until the
5415 previous one finishes. Examples of commands that are valid in all-stop
5416 mode while the program is running include @code{help} and @code{info break}.
5418 You can interrupt your program while it is running in the background by
5419 using the @code{interrupt} command.
5426 Suspend execution of the running program. In all-stop mode,
5427 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5428 only the current thread. To stop the whole program in non-stop mode,
5429 use @code{interrupt -a}.
5432 @node Thread-Specific Breakpoints
5433 @subsection Thread-Specific Breakpoints
5435 When your program has multiple threads (@pxref{Threads,, Debugging
5436 Programs with Multiple Threads}), you can choose whether to set
5437 breakpoints on all threads, or on a particular thread.
5440 @cindex breakpoints and threads
5441 @cindex thread breakpoints
5442 @kindex break @dots{} thread @var{threadno}
5443 @item break @var{linespec} thread @var{threadno}
5444 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5445 @var{linespec} specifies source lines; there are several ways of
5446 writing them (@pxref{Specify Location}), but the effect is always to
5447 specify some source line.
5449 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5450 to specify that you only want @value{GDBN} to stop the program when a
5451 particular thread reaches this breakpoint. @var{threadno} is one of the
5452 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5453 column of the @samp{info threads} display.
5455 If you do not specify @samp{thread @var{threadno}} when you set a
5456 breakpoint, the breakpoint applies to @emph{all} threads of your
5459 You can use the @code{thread} qualifier on conditional breakpoints as
5460 well; in this case, place @samp{thread @var{threadno}} before or
5461 after the breakpoint condition, like this:
5464 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5469 @node Interrupted System Calls
5470 @subsection Interrupted System Calls
5472 @cindex thread breakpoints and system calls
5473 @cindex system calls and thread breakpoints
5474 @cindex premature return from system calls
5475 There is an unfortunate side effect when using @value{GDBN} to debug
5476 multi-threaded programs. If one thread stops for a
5477 breakpoint, or for some other reason, and another thread is blocked in a
5478 system call, then the system call may return prematurely. This is a
5479 consequence of the interaction between multiple threads and the signals
5480 that @value{GDBN} uses to implement breakpoints and other events that
5483 To handle this problem, your program should check the return value of
5484 each system call and react appropriately. This is good programming
5487 For example, do not write code like this:
5493 The call to @code{sleep} will return early if a different thread stops
5494 at a breakpoint or for some other reason.
5496 Instead, write this:
5501 unslept = sleep (unslept);
5504 A system call is allowed to return early, so the system is still
5505 conforming to its specification. But @value{GDBN} does cause your
5506 multi-threaded program to behave differently than it would without
5509 Also, @value{GDBN} uses internal breakpoints in the thread library to
5510 monitor certain events such as thread creation and thread destruction.
5511 When such an event happens, a system call in another thread may return
5512 prematurely, even though your program does not appear to stop.
5515 @subsection Observer Mode
5517 If you want to build on non-stop mode and observe program behavior
5518 without any chance of disruption by @value{GDBN}, you can set
5519 variables to disable all of the debugger's attempts to modify state,
5520 whether by writing memory, inserting breakpoints, etc. These operate
5521 at a low level, intercepting operations from all commands.
5523 When all of these are set to @code{off}, then @value{GDBN} is said to
5524 be @dfn{observer mode}. As a convenience, the variable
5525 @code{observer} can be set to disable these, plus enable non-stop
5528 Note that @value{GDBN} will not prevent you from making nonsensical
5529 combinations of these settings. For instance, if you have enabled
5530 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5531 then breakpoints that work by writing trap instructions into the code
5532 stream will still not be able to be placed.
5537 @item set observer on
5538 @itemx set observer off
5539 When set to @code{on}, this disables all the permission variables
5540 below (except for @code{insert-fast-tracepoints}), plus enables
5541 non-stop debugging. Setting this to @code{off} switches back to
5542 normal debugging, though remaining in non-stop mode.
5545 Show whether observer mode is on or off.
5547 @kindex may-write-registers
5548 @item set may-write-registers on
5549 @itemx set may-write-registers off
5550 This controls whether @value{GDBN} will attempt to alter the values of
5551 registers, such as with assignment expressions in @code{print}, or the
5552 @code{jump} command. It defaults to @code{on}.
5554 @item show may-write-registers
5555 Show the current permission to write registers.
5557 @kindex may-write-memory
5558 @item set may-write-memory on
5559 @itemx set may-write-memory off
5560 This controls whether @value{GDBN} will attempt to alter the contents
5561 of memory, such as with assignment expressions in @code{print}. It
5562 defaults to @code{on}.
5564 @item show may-write-memory
5565 Show the current permission to write memory.
5567 @kindex may-insert-breakpoints
5568 @item set may-insert-breakpoints on
5569 @itemx set may-insert-breakpoints off
5570 This controls whether @value{GDBN} will attempt to insert breakpoints.
5571 This affects all breakpoints, including internal breakpoints defined
5572 by @value{GDBN}. It defaults to @code{on}.
5574 @item show may-insert-breakpoints
5575 Show the current permission to insert breakpoints.
5577 @kindex may-insert-tracepoints
5578 @item set may-insert-tracepoints on
5579 @itemx set may-insert-tracepoints off
5580 This controls whether @value{GDBN} will attempt to insert (regular)
5581 tracepoints at the beginning of a tracing experiment. It affects only
5582 non-fast tracepoints, fast tracepoints being under the control of
5583 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5585 @item show may-insert-tracepoints
5586 Show the current permission to insert tracepoints.
5588 @kindex may-insert-fast-tracepoints
5589 @item set may-insert-fast-tracepoints on
5590 @itemx set may-insert-fast-tracepoints off
5591 This controls whether @value{GDBN} will attempt to insert fast
5592 tracepoints at the beginning of a tracing experiment. It affects only
5593 fast tracepoints, regular (non-fast) tracepoints being under the
5594 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5596 @item show may-insert-fast-tracepoints
5597 Show the current permission to insert fast tracepoints.
5599 @kindex may-interrupt
5600 @item set may-interrupt on
5601 @itemx set may-interrupt off
5602 This controls whether @value{GDBN} will attempt to interrupt or stop
5603 program execution. When this variable is @code{off}, the
5604 @code{interrupt} command will have no effect, nor will
5605 @kbd{Ctrl-c}. It defaults to @code{on}.
5607 @item show may-interrupt
5608 Show the current permission to interrupt or stop the program.
5612 @node Reverse Execution
5613 @chapter Running programs backward
5614 @cindex reverse execution
5615 @cindex running programs backward
5617 When you are debugging a program, it is not unusual to realize that
5618 you have gone too far, and some event of interest has already happened.
5619 If the target environment supports it, @value{GDBN} can allow you to
5620 ``rewind'' the program by running it backward.
5622 A target environment that supports reverse execution should be able
5623 to ``undo'' the changes in machine state that have taken place as the
5624 program was executing normally. Variables, registers etc.@: should
5625 revert to their previous values. Obviously this requires a great
5626 deal of sophistication on the part of the target environment; not
5627 all target environments can support reverse execution.
5629 When a program is executed in reverse, the instructions that
5630 have most recently been executed are ``un-executed'', in reverse
5631 order. The program counter runs backward, following the previous
5632 thread of execution in reverse. As each instruction is ``un-executed'',
5633 the values of memory and/or registers that were changed by that
5634 instruction are reverted to their previous states. After executing
5635 a piece of source code in reverse, all side effects of that code
5636 should be ``undone'', and all variables should be returned to their
5637 prior values@footnote{
5638 Note that some side effects are easier to undo than others. For instance,
5639 memory and registers are relatively easy, but device I/O is hard. Some
5640 targets may be able undo things like device I/O, and some may not.
5642 The contract between @value{GDBN} and the reverse executing target
5643 requires only that the target do something reasonable when
5644 @value{GDBN} tells it to execute backwards, and then report the
5645 results back to @value{GDBN}. Whatever the target reports back to
5646 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5647 assumes that the memory and registers that the target reports are in a
5648 consistant state, but @value{GDBN} accepts whatever it is given.
5651 If you are debugging in a target environment that supports
5652 reverse execution, @value{GDBN} provides the following commands.
5655 @kindex reverse-continue
5656 @kindex rc @r{(@code{reverse-continue})}
5657 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5658 @itemx rc @r{[}@var{ignore-count}@r{]}
5659 Beginning at the point where your program last stopped, start executing
5660 in reverse. Reverse execution will stop for breakpoints and synchronous
5661 exceptions (signals), just like normal execution. Behavior of
5662 asynchronous signals depends on the target environment.
5664 @kindex reverse-step
5665 @kindex rs @r{(@code{step})}
5666 @item reverse-step @r{[}@var{count}@r{]}
5667 Run the program backward until control reaches the start of a
5668 different source line; then stop it, and return control to @value{GDBN}.
5670 Like the @code{step} command, @code{reverse-step} will only stop
5671 at the beginning of a source line. It ``un-executes'' the previously
5672 executed source line. If the previous source line included calls to
5673 debuggable functions, @code{reverse-step} will step (backward) into
5674 the called function, stopping at the beginning of the @emph{last}
5675 statement in the called function (typically a return statement).
5677 Also, as with the @code{step} command, if non-debuggable functions are
5678 called, @code{reverse-step} will run thru them backward without stopping.
5680 @kindex reverse-stepi
5681 @kindex rsi @r{(@code{reverse-stepi})}
5682 @item reverse-stepi @r{[}@var{count}@r{]}
5683 Reverse-execute one machine instruction. Note that the instruction
5684 to be reverse-executed is @emph{not} the one pointed to by the program
5685 counter, but the instruction executed prior to that one. For instance,
5686 if the last instruction was a jump, @code{reverse-stepi} will take you
5687 back from the destination of the jump to the jump instruction itself.
5689 @kindex reverse-next
5690 @kindex rn @r{(@code{reverse-next})}
5691 @item reverse-next @r{[}@var{count}@r{]}
5692 Run backward to the beginning of the previous line executed in
5693 the current (innermost) stack frame. If the line contains function
5694 calls, they will be ``un-executed'' without stopping. Starting from
5695 the first line of a function, @code{reverse-next} will take you back
5696 to the caller of that function, @emph{before} the function was called,
5697 just as the normal @code{next} command would take you from the last
5698 line of a function back to its return to its caller
5699 @footnote{Unless the code is too heavily optimized.}.
5701 @kindex reverse-nexti
5702 @kindex rni @r{(@code{reverse-nexti})}
5703 @item reverse-nexti @r{[}@var{count}@r{]}
5704 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5705 in reverse, except that called functions are ``un-executed'' atomically.
5706 That is, if the previously executed instruction was a return from
5707 another function, @code{reverse-nexti} will continue to execute
5708 in reverse until the call to that function (from the current stack
5711 @kindex reverse-finish
5712 @item reverse-finish
5713 Just as the @code{finish} command takes you to the point where the
5714 current function returns, @code{reverse-finish} takes you to the point
5715 where it was called. Instead of ending up at the end of the current
5716 function invocation, you end up at the beginning.
5718 @kindex set exec-direction
5719 @item set exec-direction
5720 Set the direction of target execution.
5721 @itemx set exec-direction reverse
5722 @cindex execute forward or backward in time
5723 @value{GDBN} will perform all execution commands in reverse, until the
5724 exec-direction mode is changed to ``forward''. Affected commands include
5725 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5726 command cannot be used in reverse mode.
5727 @item set exec-direction forward
5728 @value{GDBN} will perform all execution commands in the normal fashion.
5729 This is the default.
5733 @node Process Record and Replay
5734 @chapter Recording Inferior's Execution and Replaying It
5735 @cindex process record and replay
5736 @cindex recording inferior's execution and replaying it
5738 On some platforms, @value{GDBN} provides a special @dfn{process record
5739 and replay} target that can record a log of the process execution, and
5740 replay it later with both forward and reverse execution commands.
5743 When this target is in use, if the execution log includes the record
5744 for the next instruction, @value{GDBN} will debug in @dfn{replay
5745 mode}. In the replay mode, the inferior does not really execute code
5746 instructions. Instead, all the events that normally happen during
5747 code execution are taken from the execution log. While code is not
5748 really executed in replay mode, the values of registers (including the
5749 program counter register) and the memory of the inferior are still
5750 changed as they normally would. Their contents are taken from the
5754 If the record for the next instruction is not in the execution log,
5755 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5756 inferior executes normally, and @value{GDBN} records the execution log
5759 The process record and replay target supports reverse execution
5760 (@pxref{Reverse Execution}), even if the platform on which the
5761 inferior runs does not. However, the reverse execution is limited in
5762 this case by the range of the instructions recorded in the execution
5763 log. In other words, reverse execution on platforms that don't
5764 support it directly can only be done in the replay mode.
5766 When debugging in the reverse direction, @value{GDBN} will work in
5767 replay mode as long as the execution log includes the record for the
5768 previous instruction; otherwise, it will work in record mode, if the
5769 platform supports reverse execution, or stop if not.
5771 For architecture environments that support process record and replay,
5772 @value{GDBN} provides the following commands:
5775 @kindex target record
5779 This command starts the process record and replay target. The process
5780 record and replay target can only debug a process that is already
5781 running. Therefore, you need first to start the process with the
5782 @kbd{run} or @kbd{start} commands, and then start the recording with
5783 the @kbd{target record} command.
5785 Both @code{record} and @code{rec} are aliases of @code{target record}.
5787 @cindex displaced stepping, and process record and replay
5788 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5789 will be automatically disabled when process record and replay target
5790 is started. That's because the process record and replay target
5791 doesn't support displaced stepping.
5793 @cindex non-stop mode, and process record and replay
5794 @cindex asynchronous execution, and process record and replay
5795 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5796 the asynchronous execution mode (@pxref{Background Execution}), the
5797 process record and replay target cannot be started because it doesn't
5798 support these two modes.
5803 Stop the process record and replay target. When process record and
5804 replay target stops, the entire execution log will be deleted and the
5805 inferior will either be terminated, or will remain in its final state.
5807 When you stop the process record and replay target in record mode (at
5808 the end of the execution log), the inferior will be stopped at the
5809 next instruction that would have been recorded. In other words, if
5810 you record for a while and then stop recording, the inferior process
5811 will be left in the same state as if the recording never happened.
5813 On the other hand, if the process record and replay target is stopped
5814 while in replay mode (that is, not at the end of the execution log,
5815 but at some earlier point), the inferior process will become ``live''
5816 at that earlier state, and it will then be possible to continue the
5817 usual ``live'' debugging of the process from that state.
5819 When the inferior process exits, or @value{GDBN} detaches from it,
5820 process record and replay target will automatically stop itself.
5823 @item record save @var{filename}
5824 Save the execution log to a file @file{@var{filename}}.
5825 Default filename is @file{gdb_record.@var{process_id}}, where
5826 @var{process_id} is the process ID of the inferior.
5828 @kindex record restore
5829 @item record restore @var{filename}
5830 Restore the execution log from a file @file{@var{filename}}.
5831 File must have been created with @code{record save}.
5833 @kindex set record insn-number-max
5834 @item set record insn-number-max @var{limit}
5835 Set the limit of instructions to be recorded. Default value is 200000.
5837 If @var{limit} is a positive number, then @value{GDBN} will start
5838 deleting instructions from the log once the number of the record
5839 instructions becomes greater than @var{limit}. For every new recorded
5840 instruction, @value{GDBN} will delete the earliest recorded
5841 instruction to keep the number of recorded instructions at the limit.
5842 (Since deleting recorded instructions loses information, @value{GDBN}
5843 lets you control what happens when the limit is reached, by means of
5844 the @code{stop-at-limit} option, described below.)
5846 If @var{limit} is zero, @value{GDBN} will never delete recorded
5847 instructions from the execution log. The number of recorded
5848 instructions is unlimited in this case.
5850 @kindex show record insn-number-max
5851 @item show record insn-number-max
5852 Show the limit of instructions to be recorded.
5854 @kindex set record stop-at-limit
5855 @item set record stop-at-limit
5856 Control the behavior when the number of recorded instructions reaches
5857 the limit. If ON (the default), @value{GDBN} will stop when the limit
5858 is reached for the first time and ask you whether you want to stop the
5859 inferior or continue running it and recording the execution log. If
5860 you decide to continue recording, each new recorded instruction will
5861 cause the oldest one to be deleted.
5863 If this option is OFF, @value{GDBN} will automatically delete the
5864 oldest record to make room for each new one, without asking.
5866 @kindex show record stop-at-limit
5867 @item show record stop-at-limit
5868 Show the current setting of @code{stop-at-limit}.
5870 @kindex set record memory-query
5871 @item set record memory-query
5872 Control the behavior when @value{GDBN} is unable to record memory
5873 changes caused by an instruction. If ON, @value{GDBN} will query
5874 whether to stop the inferior in that case.
5876 If this option is OFF (the default), @value{GDBN} will automatically
5877 ignore the effect of such instructions on memory. Later, when
5878 @value{GDBN} replays this execution log, it will mark the log of this
5879 instruction as not accessible, and it will not affect the replay
5882 @kindex show record memory-query
5883 @item show record memory-query
5884 Show the current setting of @code{memory-query}.
5888 Show various statistics about the state of process record and its
5889 in-memory execution log buffer, including:
5893 Whether in record mode or replay mode.
5895 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5897 Highest recorded instruction number.
5899 Current instruction about to be replayed (if in replay mode).
5901 Number of instructions contained in the execution log.
5903 Maximum number of instructions that may be contained in the execution log.
5906 @kindex record delete
5909 When record target runs in replay mode (``in the past''), delete the
5910 subsequent execution log and begin to record a new execution log starting
5911 from the current address. This means you will abandon the previously
5912 recorded ``future'' and begin recording a new ``future''.
5917 @chapter Examining the Stack
5919 When your program has stopped, the first thing you need to know is where it
5920 stopped and how it got there.
5923 Each time your program performs a function call, information about the call
5925 That information includes the location of the call in your program,
5926 the arguments of the call,
5927 and the local variables of the function being called.
5928 The information is saved in a block of data called a @dfn{stack frame}.
5929 The stack frames are allocated in a region of memory called the @dfn{call
5932 When your program stops, the @value{GDBN} commands for examining the
5933 stack allow you to see all of this information.
5935 @cindex selected frame
5936 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5937 @value{GDBN} commands refer implicitly to the selected frame. In
5938 particular, whenever you ask @value{GDBN} for the value of a variable in
5939 your program, the value is found in the selected frame. There are
5940 special @value{GDBN} commands to select whichever frame you are
5941 interested in. @xref{Selection, ,Selecting a Frame}.
5943 When your program stops, @value{GDBN} automatically selects the
5944 currently executing frame and describes it briefly, similar to the
5945 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5948 * Frames:: Stack frames
5949 * Backtrace:: Backtraces
5950 * Selection:: Selecting a frame
5951 * Frame Info:: Information on a frame
5956 @section Stack Frames
5958 @cindex frame, definition
5960 The call stack is divided up into contiguous pieces called @dfn{stack
5961 frames}, or @dfn{frames} for short; each frame is the data associated
5962 with one call to one function. The frame contains the arguments given
5963 to the function, the function's local variables, and the address at
5964 which the function is executing.
5966 @cindex initial frame
5967 @cindex outermost frame
5968 @cindex innermost frame
5969 When your program is started, the stack has only one frame, that of the
5970 function @code{main}. This is called the @dfn{initial} frame or the
5971 @dfn{outermost} frame. Each time a function is called, a new frame is
5972 made. Each time a function returns, the frame for that function invocation
5973 is eliminated. If a function is recursive, there can be many frames for
5974 the same function. The frame for the function in which execution is
5975 actually occurring is called the @dfn{innermost} frame. This is the most
5976 recently created of all the stack frames that still exist.
5978 @cindex frame pointer
5979 Inside your program, stack frames are identified by their addresses. A
5980 stack frame consists of many bytes, each of which has its own address; each
5981 kind of computer has a convention for choosing one byte whose
5982 address serves as the address of the frame. Usually this address is kept
5983 in a register called the @dfn{frame pointer register}
5984 (@pxref{Registers, $fp}) while execution is going on in that frame.
5986 @cindex frame number
5987 @value{GDBN} assigns numbers to all existing stack frames, starting with
5988 zero for the innermost frame, one for the frame that called it,
5989 and so on upward. These numbers do not really exist in your program;
5990 they are assigned by @value{GDBN} to give you a way of designating stack
5991 frames in @value{GDBN} commands.
5993 @c The -fomit-frame-pointer below perennially causes hbox overflow
5994 @c underflow problems.
5995 @cindex frameless execution
5996 Some compilers provide a way to compile functions so that they operate
5997 without stack frames. (For example, the @value{NGCC} option
5999 @samp{-fomit-frame-pointer}
6001 generates functions without a frame.)
6002 This is occasionally done with heavily used library functions to save
6003 the frame setup time. @value{GDBN} has limited facilities for dealing
6004 with these function invocations. If the innermost function invocation
6005 has no stack frame, @value{GDBN} nevertheless regards it as though
6006 it had a separate frame, which is numbered zero as usual, allowing
6007 correct tracing of the function call chain. However, @value{GDBN} has
6008 no provision for frameless functions elsewhere in the stack.
6011 @kindex frame@r{, command}
6012 @cindex current stack frame
6013 @item frame @var{args}
6014 The @code{frame} command allows you to move from one stack frame to another,
6015 and to print the stack frame you select. @var{args} may be either the
6016 address of the frame or the stack frame number. Without an argument,
6017 @code{frame} prints the current stack frame.
6019 @kindex select-frame
6020 @cindex selecting frame silently
6022 The @code{select-frame} command allows you to move from one stack frame
6023 to another without printing the frame. This is the silent version of
6031 @cindex call stack traces
6032 A backtrace is a summary of how your program got where it is. It shows one
6033 line per frame, for many frames, starting with the currently executing
6034 frame (frame zero), followed by its caller (frame one), and on up the
6039 @kindex bt @r{(@code{backtrace})}
6042 Print a backtrace of the entire stack: one line per frame for all
6043 frames in the stack.
6045 You can stop the backtrace at any time by typing the system interrupt
6046 character, normally @kbd{Ctrl-c}.
6048 @item backtrace @var{n}
6050 Similar, but print only the innermost @var{n} frames.
6052 @item backtrace -@var{n}
6054 Similar, but print only the outermost @var{n} frames.
6056 @item backtrace full
6058 @itemx bt full @var{n}
6059 @itemx bt full -@var{n}
6060 Print the values of the local variables also. @var{n} specifies the
6061 number of frames to print, as described above.
6066 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6067 are additional aliases for @code{backtrace}.
6069 @cindex multiple threads, backtrace
6070 In a multi-threaded program, @value{GDBN} by default shows the
6071 backtrace only for the current thread. To display the backtrace for
6072 several or all of the threads, use the command @code{thread apply}
6073 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6074 apply all backtrace}, @value{GDBN} will display the backtrace for all
6075 the threads; this is handy when you debug a core dump of a
6076 multi-threaded program.
6078 Each line in the backtrace shows the frame number and the function name.
6079 The program counter value is also shown---unless you use @code{set
6080 print address off}. The backtrace also shows the source file name and
6081 line number, as well as the arguments to the function. The program
6082 counter value is omitted if it is at the beginning of the code for that
6085 Here is an example of a backtrace. It was made with the command
6086 @samp{bt 3}, so it shows the innermost three frames.
6090 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6092 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6093 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6095 (More stack frames follow...)
6100 The display for frame zero does not begin with a program counter
6101 value, indicating that your program has stopped at the beginning of the
6102 code for line @code{993} of @code{builtin.c}.
6105 The value of parameter @code{data} in frame 1 has been replaced by
6106 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6107 only if it is a scalar (integer, pointer, enumeration, etc). See command
6108 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6109 on how to configure the way function parameter values are printed.
6111 @cindex optimized out, in backtrace
6112 @cindex function call arguments, optimized out
6113 If your program was compiled with optimizations, some compilers will
6114 optimize away arguments passed to functions if those arguments are
6115 never used after the call. Such optimizations generate code that
6116 passes arguments through registers, but doesn't store those arguments
6117 in the stack frame. @value{GDBN} has no way of displaying such
6118 arguments in stack frames other than the innermost one. Here's what
6119 such a backtrace might look like:
6123 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6125 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6126 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6128 (More stack frames follow...)
6133 The values of arguments that were not saved in their stack frames are
6134 shown as @samp{<optimized out>}.
6136 If you need to display the values of such optimized-out arguments,
6137 either deduce that from other variables whose values depend on the one
6138 you are interested in, or recompile without optimizations.
6140 @cindex backtrace beyond @code{main} function
6141 @cindex program entry point
6142 @cindex startup code, and backtrace
6143 Most programs have a standard user entry point---a place where system
6144 libraries and startup code transition into user code. For C this is
6145 @code{main}@footnote{
6146 Note that embedded programs (the so-called ``free-standing''
6147 environment) are not required to have a @code{main} function as the
6148 entry point. They could even have multiple entry points.}.
6149 When @value{GDBN} finds the entry function in a backtrace
6150 it will terminate the backtrace, to avoid tracing into highly
6151 system-specific (and generally uninteresting) code.
6153 If you need to examine the startup code, or limit the number of levels
6154 in a backtrace, you can change this behavior:
6157 @item set backtrace past-main
6158 @itemx set backtrace past-main on
6159 @kindex set backtrace
6160 Backtraces will continue past the user entry point.
6162 @item set backtrace past-main off
6163 Backtraces will stop when they encounter the user entry point. This is the
6166 @item show backtrace past-main
6167 @kindex show backtrace
6168 Display the current user entry point backtrace policy.
6170 @item set backtrace past-entry
6171 @itemx set backtrace past-entry on
6172 Backtraces will continue past the internal entry point of an application.
6173 This entry point is encoded by the linker when the application is built,
6174 and is likely before the user entry point @code{main} (or equivalent) is called.
6176 @item set backtrace past-entry off
6177 Backtraces will stop when they encounter the internal entry point of an
6178 application. This is the default.
6180 @item show backtrace past-entry
6181 Display the current internal entry point backtrace policy.
6183 @item set backtrace limit @var{n}
6184 @itemx set backtrace limit 0
6185 @cindex backtrace limit
6186 Limit the backtrace to @var{n} levels. A value of zero means
6189 @item show backtrace limit
6190 Display the current limit on backtrace levels.
6194 @section Selecting a Frame
6196 Most commands for examining the stack and other data in your program work on
6197 whichever stack frame is selected at the moment. Here are the commands for
6198 selecting a stack frame; all of them finish by printing a brief description
6199 of the stack frame just selected.
6202 @kindex frame@r{, selecting}
6203 @kindex f @r{(@code{frame})}
6206 Select frame number @var{n}. Recall that frame zero is the innermost
6207 (currently executing) frame, frame one is the frame that called the
6208 innermost one, and so on. The highest-numbered frame is the one for
6211 @item frame @var{addr}
6213 Select the frame at address @var{addr}. This is useful mainly if the
6214 chaining of stack frames has been damaged by a bug, making it
6215 impossible for @value{GDBN} to assign numbers properly to all frames. In
6216 addition, this can be useful when your program has multiple stacks and
6217 switches between them.
6219 On the SPARC architecture, @code{frame} needs two addresses to
6220 select an arbitrary frame: a frame pointer and a stack pointer.
6222 On the MIPS and Alpha architecture, it needs two addresses: a stack
6223 pointer and a program counter.
6225 On the 29k architecture, it needs three addresses: a register stack
6226 pointer, a program counter, and a memory stack pointer.
6230 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6231 advances toward the outermost frame, to higher frame numbers, to frames
6232 that have existed longer. @var{n} defaults to one.
6235 @kindex do @r{(@code{down})}
6237 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6238 advances toward the innermost frame, to lower frame numbers, to frames
6239 that were created more recently. @var{n} defaults to one. You may
6240 abbreviate @code{down} as @code{do}.
6243 All of these commands end by printing two lines of output describing the
6244 frame. The first line shows the frame number, the function name, the
6245 arguments, and the source file and line number of execution in that
6246 frame. The second line shows the text of that source line.
6254 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6256 10 read_input_file (argv[i]);
6260 After such a printout, the @code{list} command with no arguments
6261 prints ten lines centered on the point of execution in the frame.
6262 You can also edit the program at the point of execution with your favorite
6263 editing program by typing @code{edit}.
6264 @xref{List, ,Printing Source Lines},
6268 @kindex down-silently
6270 @item up-silently @var{n}
6271 @itemx down-silently @var{n}
6272 These two commands are variants of @code{up} and @code{down},
6273 respectively; they differ in that they do their work silently, without
6274 causing display of the new frame. They are intended primarily for use
6275 in @value{GDBN} command scripts, where the output might be unnecessary and
6280 @section Information About a Frame
6282 There are several other commands to print information about the selected
6288 When used without any argument, this command does not change which
6289 frame is selected, but prints a brief description of the currently
6290 selected stack frame. It can be abbreviated @code{f}. With an
6291 argument, this command is used to select a stack frame.
6292 @xref{Selection, ,Selecting a Frame}.
6295 @kindex info f @r{(@code{info frame})}
6298 This command prints a verbose description of the selected stack frame,
6303 the address of the frame
6305 the address of the next frame down (called by this frame)
6307 the address of the next frame up (caller of this frame)
6309 the language in which the source code corresponding to this frame is written
6311 the address of the frame's arguments
6313 the address of the frame's local variables
6315 the program counter saved in it (the address of execution in the caller frame)
6317 which registers were saved in the frame
6320 @noindent The verbose description is useful when
6321 something has gone wrong that has made the stack format fail to fit
6322 the usual conventions.
6324 @item info frame @var{addr}
6325 @itemx info f @var{addr}
6326 Print a verbose description of the frame at address @var{addr}, without
6327 selecting that frame. The selected frame remains unchanged by this
6328 command. This requires the same kind of address (more than one for some
6329 architectures) that you specify in the @code{frame} command.
6330 @xref{Selection, ,Selecting a Frame}.
6334 Print the arguments of the selected frame, each on a separate line.
6338 Print the local variables of the selected frame, each on a separate
6339 line. These are all variables (declared either static or automatic)
6340 accessible at the point of execution of the selected frame.
6343 @cindex catch exceptions, list active handlers
6344 @cindex exception handlers, how to list
6346 Print a list of all the exception handlers that are active in the
6347 current stack frame at the current point of execution. To see other
6348 exception handlers, visit the associated frame (using the @code{up},
6349 @code{down}, or @code{frame} commands); then type @code{info catch}.
6350 @xref{Set Catchpoints, , Setting Catchpoints}.
6356 @chapter Examining Source Files
6358 @value{GDBN} can print parts of your program's source, since the debugging
6359 information recorded in the program tells @value{GDBN} what source files were
6360 used to build it. When your program stops, @value{GDBN} spontaneously prints
6361 the line where it stopped. Likewise, when you select a stack frame
6362 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6363 execution in that frame has stopped. You can print other portions of
6364 source files by explicit command.
6366 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6367 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6368 @value{GDBN} under @sc{gnu} Emacs}.
6371 * List:: Printing source lines
6372 * Specify Location:: How to specify code locations
6373 * Edit:: Editing source files
6374 * Search:: Searching source files
6375 * Source Path:: Specifying source directories
6376 * Machine Code:: Source and machine code
6380 @section Printing Source Lines
6383 @kindex l @r{(@code{list})}
6384 To print lines from a source file, use the @code{list} command
6385 (abbreviated @code{l}). By default, ten lines are printed.
6386 There are several ways to specify what part of the file you want to
6387 print; see @ref{Specify Location}, for the full list.
6389 Here are the forms of the @code{list} command most commonly used:
6392 @item list @var{linenum}
6393 Print lines centered around line number @var{linenum} in the
6394 current source file.
6396 @item list @var{function}
6397 Print lines centered around the beginning of function
6401 Print more lines. If the last lines printed were printed with a
6402 @code{list} command, this prints lines following the last lines
6403 printed; however, if the last line printed was a solitary line printed
6404 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6405 Stack}), this prints lines centered around that line.
6408 Print lines just before the lines last printed.
6411 @cindex @code{list}, how many lines to display
6412 By default, @value{GDBN} prints ten source lines with any of these forms of
6413 the @code{list} command. You can change this using @code{set listsize}:
6416 @kindex set listsize
6417 @item set listsize @var{count}
6418 Make the @code{list} command display @var{count} source lines (unless
6419 the @code{list} argument explicitly specifies some other number).
6421 @kindex show listsize
6423 Display the number of lines that @code{list} prints.
6426 Repeating a @code{list} command with @key{RET} discards the argument,
6427 so it is equivalent to typing just @code{list}. This is more useful
6428 than listing the same lines again. An exception is made for an
6429 argument of @samp{-}; that argument is preserved in repetition so that
6430 each repetition moves up in the source file.
6432 In general, the @code{list} command expects you to supply zero, one or two
6433 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6434 of writing them (@pxref{Specify Location}), but the effect is always
6435 to specify some source line.
6437 Here is a complete description of the possible arguments for @code{list}:
6440 @item list @var{linespec}
6441 Print lines centered around the line specified by @var{linespec}.
6443 @item list @var{first},@var{last}
6444 Print lines from @var{first} to @var{last}. Both arguments are
6445 linespecs. When a @code{list} command has two linespecs, and the
6446 source file of the second linespec is omitted, this refers to
6447 the same source file as the first linespec.
6449 @item list ,@var{last}
6450 Print lines ending with @var{last}.
6452 @item list @var{first},
6453 Print lines starting with @var{first}.
6456 Print lines just after the lines last printed.
6459 Print lines just before the lines last printed.
6462 As described in the preceding table.
6465 @node Specify Location
6466 @section Specifying a Location
6467 @cindex specifying location
6470 Several @value{GDBN} commands accept arguments that specify a location
6471 of your program's code. Since @value{GDBN} is a source-level
6472 debugger, a location usually specifies some line in the source code;
6473 for that reason, locations are also known as @dfn{linespecs}.
6475 Here are all the different ways of specifying a code location that
6476 @value{GDBN} understands:
6480 Specifies the line number @var{linenum} of the current source file.
6483 @itemx +@var{offset}
6484 Specifies the line @var{offset} lines before or after the @dfn{current
6485 line}. For the @code{list} command, the current line is the last one
6486 printed; for the breakpoint commands, this is the line at which
6487 execution stopped in the currently selected @dfn{stack frame}
6488 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6489 used as the second of the two linespecs in a @code{list} command,
6490 this specifies the line @var{offset} lines up or down from the first
6493 @item @var{filename}:@var{linenum}
6494 Specifies the line @var{linenum} in the source file @var{filename}.
6495 If @var{filename} is a relative file name, then it will match any
6496 source file name with the same trailing components. For example, if
6497 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6498 name of @file{/build/trunk/gcc/expr.c}, but not
6499 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6501 @item @var{function}
6502 Specifies the line that begins the body of the function @var{function}.
6503 For example, in C, this is the line with the open brace.
6505 @item @var{function}:@var{label}
6506 Specifies the line where @var{label} appears in @var{function}.
6508 @item @var{filename}:@var{function}
6509 Specifies the line that begins the body of the function @var{function}
6510 in the file @var{filename}. You only need the file name with a
6511 function name to avoid ambiguity when there are identically named
6512 functions in different source files.
6515 Specifies the line at which the label named @var{label} appears.
6516 @value{GDBN} searches for the label in the function corresponding to
6517 the currently selected stack frame. If there is no current selected
6518 stack frame (for instance, if the inferior is not running), then
6519 @value{GDBN} will not search for a label.
6521 @item *@var{address}
6522 Specifies the program address @var{address}. For line-oriented
6523 commands, such as @code{list} and @code{edit}, this specifies a source
6524 line that contains @var{address}. For @code{break} and other
6525 breakpoint oriented commands, this can be used to set breakpoints in
6526 parts of your program which do not have debugging information or
6529 Here @var{address} may be any expression valid in the current working
6530 language (@pxref{Languages, working language}) that specifies a code
6531 address. In addition, as a convenience, @value{GDBN} extends the
6532 semantics of expressions used in locations to cover the situations
6533 that frequently happen during debugging. Here are the various forms
6537 @item @var{expression}
6538 Any expression valid in the current working language.
6540 @item @var{funcaddr}
6541 An address of a function or procedure derived from its name. In C,
6542 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6543 simply the function's name @var{function} (and actually a special case
6544 of a valid expression). In Pascal and Modula-2, this is
6545 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6546 (although the Pascal form also works).
6548 This form specifies the address of the function's first instruction,
6549 before the stack frame and arguments have been set up.
6551 @item '@var{filename}'::@var{funcaddr}
6552 Like @var{funcaddr} above, but also specifies the name of the source
6553 file explicitly. This is useful if the name of the function does not
6554 specify the function unambiguously, e.g., if there are several
6555 functions with identical names in different source files.
6562 @section Editing Source Files
6563 @cindex editing source files
6566 @kindex e @r{(@code{edit})}
6567 To edit the lines in a source file, use the @code{edit} command.
6568 The editing program of your choice
6569 is invoked with the current line set to
6570 the active line in the program.
6571 Alternatively, there are several ways to specify what part of the file you
6572 want to print if you want to see other parts of the program:
6575 @item edit @var{location}
6576 Edit the source file specified by @code{location}. Editing starts at
6577 that @var{location}, e.g., at the specified source line of the
6578 specified file. @xref{Specify Location}, for all the possible forms
6579 of the @var{location} argument; here are the forms of the @code{edit}
6580 command most commonly used:
6583 @item edit @var{number}
6584 Edit the current source file with @var{number} as the active line number.
6586 @item edit @var{function}
6587 Edit the file containing @var{function} at the beginning of its definition.
6592 @subsection Choosing your Editor
6593 You can customize @value{GDBN} to use any editor you want
6595 The only restriction is that your editor (say @code{ex}), recognizes the
6596 following command-line syntax:
6598 ex +@var{number} file
6600 The optional numeric value +@var{number} specifies the number of the line in
6601 the file where to start editing.}.
6602 By default, it is @file{@value{EDITOR}}, but you can change this
6603 by setting the environment variable @code{EDITOR} before using
6604 @value{GDBN}. For example, to configure @value{GDBN} to use the
6605 @code{vi} editor, you could use these commands with the @code{sh} shell:
6611 or in the @code{csh} shell,
6613 setenv EDITOR /usr/bin/vi
6618 @section Searching Source Files
6619 @cindex searching source files
6621 There are two commands for searching through the current source file for a
6626 @kindex forward-search
6627 @item forward-search @var{regexp}
6628 @itemx search @var{regexp}
6629 The command @samp{forward-search @var{regexp}} checks each line,
6630 starting with the one following the last line listed, for a match for
6631 @var{regexp}. It lists the line that is found. You can use the
6632 synonym @samp{search @var{regexp}} or abbreviate the command name as
6635 @kindex reverse-search
6636 @item reverse-search @var{regexp}
6637 The command @samp{reverse-search @var{regexp}} checks each line, starting
6638 with the one before the last line listed and going backward, for a match
6639 for @var{regexp}. It lists the line that is found. You can abbreviate
6640 this command as @code{rev}.
6644 @section Specifying Source Directories
6647 @cindex directories for source files
6648 Executable programs sometimes do not record the directories of the source
6649 files from which they were compiled, just the names. Even when they do,
6650 the directories could be moved between the compilation and your debugging
6651 session. @value{GDBN} has a list of directories to search for source files;
6652 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6653 it tries all the directories in the list, in the order they are present
6654 in the list, until it finds a file with the desired name.
6656 For example, suppose an executable references the file
6657 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6658 @file{/mnt/cross}. The file is first looked up literally; if this
6659 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6660 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6661 message is printed. @value{GDBN} does not look up the parts of the
6662 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6663 Likewise, the subdirectories of the source path are not searched: if
6664 the source path is @file{/mnt/cross}, and the binary refers to
6665 @file{foo.c}, @value{GDBN} would not find it under
6666 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6668 Plain file names, relative file names with leading directories, file
6669 names containing dots, etc.@: are all treated as described above; for
6670 instance, if the source path is @file{/mnt/cross}, and the source file
6671 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6672 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6673 that---@file{/mnt/cross/foo.c}.
6675 Note that the executable search path is @emph{not} used to locate the
6678 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6679 any information it has cached about where source files are found and where
6680 each line is in the file.
6684 When you start @value{GDBN}, its source path includes only @samp{cdir}
6685 and @samp{cwd}, in that order.
6686 To add other directories, use the @code{directory} command.
6688 The search path is used to find both program source files and @value{GDBN}
6689 script files (read using the @samp{-command} option and @samp{source} command).
6691 In addition to the source path, @value{GDBN} provides a set of commands
6692 that manage a list of source path substitution rules. A @dfn{substitution
6693 rule} specifies how to rewrite source directories stored in the program's
6694 debug information in case the sources were moved to a different
6695 directory between compilation and debugging. A rule is made of
6696 two strings, the first specifying what needs to be rewritten in
6697 the path, and the second specifying how it should be rewritten.
6698 In @ref{set substitute-path}, we name these two parts @var{from} and
6699 @var{to} respectively. @value{GDBN} does a simple string replacement
6700 of @var{from} with @var{to} at the start of the directory part of the
6701 source file name, and uses that result instead of the original file
6702 name to look up the sources.
6704 Using the previous example, suppose the @file{foo-1.0} tree has been
6705 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6706 @value{GDBN} to replace @file{/usr/src} in all source path names with
6707 @file{/mnt/cross}. The first lookup will then be
6708 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6709 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6710 substitution rule, use the @code{set substitute-path} command
6711 (@pxref{set substitute-path}).
6713 To avoid unexpected substitution results, a rule is applied only if the
6714 @var{from} part of the directory name ends at a directory separator.
6715 For instance, a rule substituting @file{/usr/source} into
6716 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6717 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6718 is applied only at the beginning of the directory name, this rule will
6719 not be applied to @file{/root/usr/source/baz.c} either.
6721 In many cases, you can achieve the same result using the @code{directory}
6722 command. However, @code{set substitute-path} can be more efficient in
6723 the case where the sources are organized in a complex tree with multiple
6724 subdirectories. With the @code{directory} command, you need to add each
6725 subdirectory of your project. If you moved the entire tree while
6726 preserving its internal organization, then @code{set substitute-path}
6727 allows you to direct the debugger to all the sources with one single
6730 @code{set substitute-path} is also more than just a shortcut command.
6731 The source path is only used if the file at the original location no
6732 longer exists. On the other hand, @code{set substitute-path} modifies
6733 the debugger behavior to look at the rewritten location instead. So, if
6734 for any reason a source file that is not relevant to your executable is
6735 located at the original location, a substitution rule is the only
6736 method available to point @value{GDBN} at the new location.
6738 @cindex @samp{--with-relocated-sources}
6739 @cindex default source path substitution
6740 You can configure a default source path substitution rule by
6741 configuring @value{GDBN} with the
6742 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6743 should be the name of a directory under @value{GDBN}'s configured
6744 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6745 directory names in debug information under @var{dir} will be adjusted
6746 automatically if the installed @value{GDBN} is moved to a new
6747 location. This is useful if @value{GDBN}, libraries or executables
6748 with debug information and corresponding source code are being moved
6752 @item directory @var{dirname} @dots{}
6753 @item dir @var{dirname} @dots{}
6754 Add directory @var{dirname} to the front of the source path. Several
6755 directory names may be given to this command, separated by @samp{:}
6756 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6757 part of absolute file names) or
6758 whitespace. You may specify a directory that is already in the source
6759 path; this moves it forward, so @value{GDBN} searches it sooner.
6763 @vindex $cdir@r{, convenience variable}
6764 @vindex $cwd@r{, convenience variable}
6765 @cindex compilation directory
6766 @cindex current directory
6767 @cindex working directory
6768 @cindex directory, current
6769 @cindex directory, compilation
6770 You can use the string @samp{$cdir} to refer to the compilation
6771 directory (if one is recorded), and @samp{$cwd} to refer to the current
6772 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6773 tracks the current working directory as it changes during your @value{GDBN}
6774 session, while the latter is immediately expanded to the current
6775 directory at the time you add an entry to the source path.
6778 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6780 @c RET-repeat for @code{directory} is explicitly disabled, but since
6781 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6783 @item set directories @var{path-list}
6784 @kindex set directories
6785 Set the source path to @var{path-list}.
6786 @samp{$cdir:$cwd} are added if missing.
6788 @item show directories
6789 @kindex show directories
6790 Print the source path: show which directories it contains.
6792 @anchor{set substitute-path}
6793 @item set substitute-path @var{from} @var{to}
6794 @kindex set substitute-path
6795 Define a source path substitution rule, and add it at the end of the
6796 current list of existing substitution rules. If a rule with the same
6797 @var{from} was already defined, then the old rule is also deleted.
6799 For example, if the file @file{/foo/bar/baz.c} was moved to
6800 @file{/mnt/cross/baz.c}, then the command
6803 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6807 will tell @value{GDBN} to replace @samp{/usr/src} with
6808 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6809 @file{baz.c} even though it was moved.
6811 In the case when more than one substitution rule have been defined,
6812 the rules are evaluated one by one in the order where they have been
6813 defined. The first one matching, if any, is selected to perform
6816 For instance, if we had entered the following commands:
6819 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6820 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6824 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6825 @file{/mnt/include/defs.h} by using the first rule. However, it would
6826 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6827 @file{/mnt/src/lib/foo.c}.
6830 @item unset substitute-path [path]
6831 @kindex unset substitute-path
6832 If a path is specified, search the current list of substitution rules
6833 for a rule that would rewrite that path. Delete that rule if found.
6834 A warning is emitted by the debugger if no rule could be found.
6836 If no path is specified, then all substitution rules are deleted.
6838 @item show substitute-path [path]
6839 @kindex show substitute-path
6840 If a path is specified, then print the source path substitution rule
6841 which would rewrite that path, if any.
6843 If no path is specified, then print all existing source path substitution
6848 If your source path is cluttered with directories that are no longer of
6849 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6850 versions of source. You can correct the situation as follows:
6854 Use @code{directory} with no argument to reset the source path to its default value.
6857 Use @code{directory} with suitable arguments to reinstall the
6858 directories you want in the source path. You can add all the
6859 directories in one command.
6863 @section Source and Machine Code
6864 @cindex source line and its code address
6866 You can use the command @code{info line} to map source lines to program
6867 addresses (and vice versa), and the command @code{disassemble} to display
6868 a range of addresses as machine instructions. You can use the command
6869 @code{set disassemble-next-line} to set whether to disassemble next
6870 source line when execution stops. When run under @sc{gnu} Emacs
6871 mode, the @code{info line} command causes the arrow to point to the
6872 line specified. Also, @code{info line} prints addresses in symbolic form as
6877 @item info line @var{linespec}
6878 Print the starting and ending addresses of the compiled code for
6879 source line @var{linespec}. You can specify source lines in any of
6880 the ways documented in @ref{Specify Location}.
6883 For example, we can use @code{info line} to discover the location of
6884 the object code for the first line of function
6885 @code{m4_changequote}:
6887 @c FIXME: I think this example should also show the addresses in
6888 @c symbolic form, as they usually would be displayed.
6890 (@value{GDBP}) info line m4_changequote
6891 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6895 @cindex code address and its source line
6896 We can also inquire (using @code{*@var{addr}} as the form for
6897 @var{linespec}) what source line covers a particular address:
6899 (@value{GDBP}) info line *0x63ff
6900 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6903 @cindex @code{$_} and @code{info line}
6904 @cindex @code{x} command, default address
6905 @kindex x@r{(examine), and} info line
6906 After @code{info line}, the default address for the @code{x} command
6907 is changed to the starting address of the line, so that @samp{x/i} is
6908 sufficient to begin examining the machine code (@pxref{Memory,
6909 ,Examining Memory}). Also, this address is saved as the value of the
6910 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6915 @cindex assembly instructions
6916 @cindex instructions, assembly
6917 @cindex machine instructions
6918 @cindex listing machine instructions
6920 @itemx disassemble /m
6921 @itemx disassemble /r
6922 This specialized command dumps a range of memory as machine
6923 instructions. It can also print mixed source+disassembly by specifying
6924 the @code{/m} modifier and print the raw instructions in hex as well as
6925 in symbolic form by specifying the @code{/r}.
6926 The default memory range is the function surrounding the
6927 program counter of the selected frame. A single argument to this
6928 command is a program counter value; @value{GDBN} dumps the function
6929 surrounding this value. When two arguments are given, they should
6930 be separated by a comma, possibly surrounded by whitespace. The
6931 arguments specify a range of addresses to dump, in one of two forms:
6934 @item @var{start},@var{end}
6935 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6936 @item @var{start},+@var{length}
6937 the addresses from @var{start} (inclusive) to
6938 @code{@var{start}+@var{length}} (exclusive).
6942 When 2 arguments are specified, the name of the function is also
6943 printed (since there could be several functions in the given range).
6945 The argument(s) can be any expression yielding a numeric value, such as
6946 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6948 If the range of memory being disassembled contains current program counter,
6949 the instruction at that location is shown with a @code{=>} marker.
6952 The following example shows the disassembly of a range of addresses of
6953 HP PA-RISC 2.0 code:
6956 (@value{GDBP}) disas 0x32c4, 0x32e4
6957 Dump of assembler code from 0x32c4 to 0x32e4:
6958 0x32c4 <main+204>: addil 0,dp
6959 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6960 0x32cc <main+212>: ldil 0x3000,r31
6961 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6962 0x32d4 <main+220>: ldo 0(r31),rp
6963 0x32d8 <main+224>: addil -0x800,dp
6964 0x32dc <main+228>: ldo 0x588(r1),r26
6965 0x32e0 <main+232>: ldil 0x3000,r31
6966 End of assembler dump.
6969 Here is an example showing mixed source+assembly for Intel x86, when the
6970 program is stopped just after function prologue:
6973 (@value{GDBP}) disas /m main
6974 Dump of assembler code for function main:
6976 0x08048330 <+0>: push %ebp
6977 0x08048331 <+1>: mov %esp,%ebp
6978 0x08048333 <+3>: sub $0x8,%esp
6979 0x08048336 <+6>: and $0xfffffff0,%esp
6980 0x08048339 <+9>: sub $0x10,%esp
6982 6 printf ("Hello.\n");
6983 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6984 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6988 0x08048348 <+24>: mov $0x0,%eax
6989 0x0804834d <+29>: leave
6990 0x0804834e <+30>: ret
6992 End of assembler dump.
6995 Here is another example showing raw instructions in hex for AMD x86-64,
6998 (gdb) disas /r 0x400281,+10
6999 Dump of assembler code from 0x400281 to 0x40028b:
7000 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7001 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7002 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7003 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7004 End of assembler dump.
7007 Some architectures have more than one commonly-used set of instruction
7008 mnemonics or other syntax.
7010 For programs that were dynamically linked and use shared libraries,
7011 instructions that call functions or branch to locations in the shared
7012 libraries might show a seemingly bogus location---it's actually a
7013 location of the relocation table. On some architectures, @value{GDBN}
7014 might be able to resolve these to actual function names.
7017 @kindex set disassembly-flavor
7018 @cindex Intel disassembly flavor
7019 @cindex AT&T disassembly flavor
7020 @item set disassembly-flavor @var{instruction-set}
7021 Select the instruction set to use when disassembling the
7022 program via the @code{disassemble} or @code{x/i} commands.
7024 Currently this command is only defined for the Intel x86 family. You
7025 can set @var{instruction-set} to either @code{intel} or @code{att}.
7026 The default is @code{att}, the AT&T flavor used by default by Unix
7027 assemblers for x86-based targets.
7029 @kindex show disassembly-flavor
7030 @item show disassembly-flavor
7031 Show the current setting of the disassembly flavor.
7035 @kindex set disassemble-next-line
7036 @kindex show disassemble-next-line
7037 @item set disassemble-next-line
7038 @itemx show disassemble-next-line
7039 Control whether or not @value{GDBN} will disassemble the next source
7040 line or instruction when execution stops. If ON, @value{GDBN} will
7041 display disassembly of the next source line when execution of the
7042 program being debugged stops. This is @emph{in addition} to
7043 displaying the source line itself, which @value{GDBN} always does if
7044 possible. If the next source line cannot be displayed for some reason
7045 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7046 info in the debug info), @value{GDBN} will display disassembly of the
7047 next @emph{instruction} instead of showing the next source line. If
7048 AUTO, @value{GDBN} will display disassembly of next instruction only
7049 if the source line cannot be displayed. This setting causes
7050 @value{GDBN} to display some feedback when you step through a function
7051 with no line info or whose source file is unavailable. The default is
7052 OFF, which means never display the disassembly of the next line or
7058 @chapter Examining Data
7060 @cindex printing data
7061 @cindex examining data
7064 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7065 @c document because it is nonstandard... Under Epoch it displays in a
7066 @c different window or something like that.
7067 The usual way to examine data in your program is with the @code{print}
7068 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7069 evaluates and prints the value of an expression of the language your
7070 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7071 Different Languages}). It may also print the expression using a
7072 Python-based pretty-printer (@pxref{Pretty Printing}).
7075 @item print @var{expr}
7076 @itemx print /@var{f} @var{expr}
7077 @var{expr} is an expression (in the source language). By default the
7078 value of @var{expr} is printed in a format appropriate to its data type;
7079 you can choose a different format by specifying @samp{/@var{f}}, where
7080 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7084 @itemx print /@var{f}
7085 @cindex reprint the last value
7086 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7087 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7088 conveniently inspect the same value in an alternative format.
7091 A more low-level way of examining data is with the @code{x} command.
7092 It examines data in memory at a specified address and prints it in a
7093 specified format. @xref{Memory, ,Examining Memory}.
7095 If you are interested in information about types, or about how the
7096 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7097 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7101 * Expressions:: Expressions
7102 * Ambiguous Expressions:: Ambiguous Expressions
7103 * Variables:: Program variables
7104 * Arrays:: Artificial arrays
7105 * Output Formats:: Output formats
7106 * Memory:: Examining memory
7107 * Auto Display:: Automatic display
7108 * Print Settings:: Print settings
7109 * Pretty Printing:: Python pretty printing
7110 * Value History:: Value history
7111 * Convenience Vars:: Convenience variables
7112 * Registers:: Registers
7113 * Floating Point Hardware:: Floating point hardware
7114 * Vector Unit:: Vector Unit
7115 * OS Information:: Auxiliary data provided by operating system
7116 * Memory Region Attributes:: Memory region attributes
7117 * Dump/Restore Files:: Copy between memory and a file
7118 * Core File Generation:: Cause a program dump its core
7119 * Character Sets:: Debugging programs that use a different
7120 character set than GDB does
7121 * Caching Remote Data:: Data caching for remote targets
7122 * Searching Memory:: Searching memory for a sequence of bytes
7126 @section Expressions
7129 @code{print} and many other @value{GDBN} commands accept an expression and
7130 compute its value. Any kind of constant, variable or operator defined
7131 by the programming language you are using is valid in an expression in
7132 @value{GDBN}. This includes conditional expressions, function calls,
7133 casts, and string constants. It also includes preprocessor macros, if
7134 you compiled your program to include this information; see
7137 @cindex arrays in expressions
7138 @value{GDBN} supports array constants in expressions input by
7139 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7140 you can use the command @code{print @{1, 2, 3@}} to create an array
7141 of three integers. If you pass an array to a function or assign it
7142 to a program variable, @value{GDBN} copies the array to memory that
7143 is @code{malloc}ed in the target program.
7145 Because C is so widespread, most of the expressions shown in examples in
7146 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7147 Languages}, for information on how to use expressions in other
7150 In this section, we discuss operators that you can use in @value{GDBN}
7151 expressions regardless of your programming language.
7153 @cindex casts, in expressions
7154 Casts are supported in all languages, not just in C, because it is so
7155 useful to cast a number into a pointer in order to examine a structure
7156 at that address in memory.
7157 @c FIXME: casts supported---Mod2 true?
7159 @value{GDBN} supports these operators, in addition to those common
7160 to programming languages:
7164 @samp{@@} is a binary operator for treating parts of memory as arrays.
7165 @xref{Arrays, ,Artificial Arrays}, for more information.
7168 @samp{::} allows you to specify a variable in terms of the file or
7169 function where it is defined. @xref{Variables, ,Program Variables}.
7171 @cindex @{@var{type}@}
7172 @cindex type casting memory
7173 @cindex memory, viewing as typed object
7174 @cindex casts, to view memory
7175 @item @{@var{type}@} @var{addr}
7176 Refers to an object of type @var{type} stored at address @var{addr} in
7177 memory. @var{addr} may be any expression whose value is an integer or
7178 pointer (but parentheses are required around binary operators, just as in
7179 a cast). This construct is allowed regardless of what kind of data is
7180 normally supposed to reside at @var{addr}.
7183 @node Ambiguous Expressions
7184 @section Ambiguous Expressions
7185 @cindex ambiguous expressions
7187 Expressions can sometimes contain some ambiguous elements. For instance,
7188 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7189 a single function name to be defined several times, for application in
7190 different contexts. This is called @dfn{overloading}. Another example
7191 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7192 templates and is typically instantiated several times, resulting in
7193 the same function name being defined in different contexts.
7195 In some cases and depending on the language, it is possible to adjust
7196 the expression to remove the ambiguity. For instance in C@t{++}, you
7197 can specify the signature of the function you want to break on, as in
7198 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7199 qualified name of your function often makes the expression unambiguous
7202 When an ambiguity that needs to be resolved is detected, the debugger
7203 has the capability to display a menu of numbered choices for each
7204 possibility, and then waits for the selection with the prompt @samp{>}.
7205 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7206 aborts the current command. If the command in which the expression was
7207 used allows more than one choice to be selected, the next option in the
7208 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7211 For example, the following session excerpt shows an attempt to set a
7212 breakpoint at the overloaded symbol @code{String::after}.
7213 We choose three particular definitions of that function name:
7215 @c FIXME! This is likely to change to show arg type lists, at least
7218 (@value{GDBP}) b String::after
7221 [2] file:String.cc; line number:867
7222 [3] file:String.cc; line number:860
7223 [4] file:String.cc; line number:875
7224 [5] file:String.cc; line number:853
7225 [6] file:String.cc; line number:846
7226 [7] file:String.cc; line number:735
7228 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7229 Breakpoint 2 at 0xb344: file String.cc, line 875.
7230 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7231 Multiple breakpoints were set.
7232 Use the "delete" command to delete unwanted
7239 @kindex set multiple-symbols
7240 @item set multiple-symbols @var{mode}
7241 @cindex multiple-symbols menu
7243 This option allows you to adjust the debugger behavior when an expression
7246 By default, @var{mode} is set to @code{all}. If the command with which
7247 the expression is used allows more than one choice, then @value{GDBN}
7248 automatically selects all possible choices. For instance, inserting
7249 a breakpoint on a function using an ambiguous name results in a breakpoint
7250 inserted on each possible match. However, if a unique choice must be made,
7251 then @value{GDBN} uses the menu to help you disambiguate the expression.
7252 For instance, printing the address of an overloaded function will result
7253 in the use of the menu.
7255 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7256 when an ambiguity is detected.
7258 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7259 an error due to the ambiguity and the command is aborted.
7261 @kindex show multiple-symbols
7262 @item show multiple-symbols
7263 Show the current value of the @code{multiple-symbols} setting.
7267 @section Program Variables
7269 The most common kind of expression to use is the name of a variable
7272 Variables in expressions are understood in the selected stack frame
7273 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7277 global (or file-static)
7284 visible according to the scope rules of the
7285 programming language from the point of execution in that frame
7288 @noindent This means that in the function
7303 you can examine and use the variable @code{a} whenever your program is
7304 executing within the function @code{foo}, but you can only use or
7305 examine the variable @code{b} while your program is executing inside
7306 the block where @code{b} is declared.
7308 @cindex variable name conflict
7309 There is an exception: you can refer to a variable or function whose
7310 scope is a single source file even if the current execution point is not
7311 in this file. But it is possible to have more than one such variable or
7312 function with the same name (in different source files). If that
7313 happens, referring to that name has unpredictable effects. If you wish,
7314 you can specify a static variable in a particular function or file by
7315 using the colon-colon (@code{::}) notation:
7317 @cindex colon-colon, context for variables/functions
7319 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7320 @cindex @code{::}, context for variables/functions
7323 @var{file}::@var{variable}
7324 @var{function}::@var{variable}
7328 Here @var{file} or @var{function} is the name of the context for the
7329 static @var{variable}. In the case of file names, you can use quotes to
7330 make sure @value{GDBN} parses the file name as a single word---for example,
7331 to print a global value of @code{x} defined in @file{f2.c}:
7334 (@value{GDBP}) p 'f2.c'::x
7337 The @code{::} notation is normally used for referring to
7338 static variables, since you typically disambiguate uses of local variables
7339 in functions by selecting the appropriate frame and using the
7340 simple name of the variable. However, you may also use this notation
7341 to refer to local variables in frames enclosing the selected frame:
7350 process (a); /* Stop here */
7361 For example, if there is a breakpoint at the commented line,
7362 here is what you might see
7363 when the program stops after executing the call @code{bar(0)}:
7368 (@value{GDBP}) p bar::a
7371 #2 0x080483d0 in foo (a=5) at foobar.c:12
7374 (@value{GDBP}) p bar::a
7378 @cindex C@t{++} scope resolution
7379 These uses of @samp{::} are very rarely in conflict with the very similar
7380 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7381 scope resolution operator in @value{GDBN} expressions.
7382 @c FIXME: Um, so what happens in one of those rare cases where it's in
7385 @cindex wrong values
7386 @cindex variable values, wrong
7387 @cindex function entry/exit, wrong values of variables
7388 @cindex optimized code, wrong values of variables
7390 @emph{Warning:} Occasionally, a local variable may appear to have the
7391 wrong value at certain points in a function---just after entry to a new
7392 scope, and just before exit.
7394 You may see this problem when you are stepping by machine instructions.
7395 This is because, on most machines, it takes more than one instruction to
7396 set up a stack frame (including local variable definitions); if you are
7397 stepping by machine instructions, variables may appear to have the wrong
7398 values until the stack frame is completely built. On exit, it usually
7399 also takes more than one machine instruction to destroy a stack frame;
7400 after you begin stepping through that group of instructions, local
7401 variable definitions may be gone.
7403 This may also happen when the compiler does significant optimizations.
7404 To be sure of always seeing accurate values, turn off all optimization
7407 @cindex ``No symbol "foo" in current context''
7408 Another possible effect of compiler optimizations is to optimize
7409 unused variables out of existence, or assign variables to registers (as
7410 opposed to memory addresses). Depending on the support for such cases
7411 offered by the debug info format used by the compiler, @value{GDBN}
7412 might not be able to display values for such local variables. If that
7413 happens, @value{GDBN} will print a message like this:
7416 No symbol "foo" in current context.
7419 To solve such problems, either recompile without optimizations, or use a
7420 different debug info format, if the compiler supports several such
7421 formats. @xref{Compilation}, for more information on choosing compiler
7422 options. @xref{C, ,C and C@t{++}}, for more information about debug
7423 info formats that are best suited to C@t{++} programs.
7425 If you ask to print an object whose contents are unknown to
7426 @value{GDBN}, e.g., because its data type is not completely specified
7427 by the debug information, @value{GDBN} will say @samp{<incomplete
7428 type>}. @xref{Symbols, incomplete type}, for more about this.
7430 If you append @kbd{@@entry} string to a function parameter name you get its
7431 value at the time the function got called. If the value is not available an
7432 error message is printed. Entry values are available only with some compilers.
7433 Entry values are normally also printed at the function parameter list according
7434 to @ref{set print entry-values}.
7437 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7443 (gdb) print i@@entry
7447 Strings are identified as arrays of @code{char} values without specified
7448 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7449 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7450 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7451 defines literal string type @code{"char"} as @code{char} without a sign.
7456 signed char var1[] = "A";
7459 You get during debugging
7464 $2 = @{65 'A', 0 '\0'@}
7468 @section Artificial Arrays
7470 @cindex artificial array
7472 @kindex @@@r{, referencing memory as an array}
7473 It is often useful to print out several successive objects of the
7474 same type in memory; a section of an array, or an array of
7475 dynamically determined size for which only a pointer exists in the
7478 You can do this by referring to a contiguous span of memory as an
7479 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7480 operand of @samp{@@} should be the first element of the desired array
7481 and be an individual object. The right operand should be the desired length
7482 of the array. The result is an array value whose elements are all of
7483 the type of the left argument. The first element is actually the left
7484 argument; the second element comes from bytes of memory immediately
7485 following those that hold the first element, and so on. Here is an
7486 example. If a program says
7489 int *array = (int *) malloc (len * sizeof (int));
7493 you can print the contents of @code{array} with
7499 The left operand of @samp{@@} must reside in memory. Array values made
7500 with @samp{@@} in this way behave just like other arrays in terms of
7501 subscripting, and are coerced to pointers when used in expressions.
7502 Artificial arrays most often appear in expressions via the value history
7503 (@pxref{Value History, ,Value History}), after printing one out.
7505 Another way to create an artificial array is to use a cast.
7506 This re-interprets a value as if it were an array.
7507 The value need not be in memory:
7509 (@value{GDBP}) p/x (short[2])0x12345678
7510 $1 = @{0x1234, 0x5678@}
7513 As a convenience, if you leave the array length out (as in
7514 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7515 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7517 (@value{GDBP}) p/x (short[])0x12345678
7518 $2 = @{0x1234, 0x5678@}
7521 Sometimes the artificial array mechanism is not quite enough; in
7522 moderately complex data structures, the elements of interest may not
7523 actually be adjacent---for example, if you are interested in the values
7524 of pointers in an array. One useful work-around in this situation is
7525 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7526 Variables}) as a counter in an expression that prints the first
7527 interesting value, and then repeat that expression via @key{RET}. For
7528 instance, suppose you have an array @code{dtab} of pointers to
7529 structures, and you are interested in the values of a field @code{fv}
7530 in each structure. Here is an example of what you might type:
7540 @node Output Formats
7541 @section Output Formats
7543 @cindex formatted output
7544 @cindex output formats
7545 By default, @value{GDBN} prints a value according to its data type. Sometimes
7546 this is not what you want. For example, you might want to print a number
7547 in hex, or a pointer in decimal. Or you might want to view data in memory
7548 at a certain address as a character string or as an instruction. To do
7549 these things, specify an @dfn{output format} when you print a value.
7551 The simplest use of output formats is to say how to print a value
7552 already computed. This is done by starting the arguments of the
7553 @code{print} command with a slash and a format letter. The format
7554 letters supported are:
7558 Regard the bits of the value as an integer, and print the integer in
7562 Print as integer in signed decimal.
7565 Print as integer in unsigned decimal.
7568 Print as integer in octal.
7571 Print as integer in binary. The letter @samp{t} stands for ``two''.
7572 @footnote{@samp{b} cannot be used because these format letters are also
7573 used with the @code{x} command, where @samp{b} stands for ``byte'';
7574 see @ref{Memory,,Examining Memory}.}
7577 @cindex unknown address, locating
7578 @cindex locate address
7579 Print as an address, both absolute in hexadecimal and as an offset from
7580 the nearest preceding symbol. You can use this format used to discover
7581 where (in what function) an unknown address is located:
7584 (@value{GDBP}) p/a 0x54320
7585 $3 = 0x54320 <_initialize_vx+396>
7589 The command @code{info symbol 0x54320} yields similar results.
7590 @xref{Symbols, info symbol}.
7593 Regard as an integer and print it as a character constant. This
7594 prints both the numerical value and its character representation. The
7595 character representation is replaced with the octal escape @samp{\nnn}
7596 for characters outside the 7-bit @sc{ascii} range.
7598 Without this format, @value{GDBN} displays @code{char},
7599 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7600 constants. Single-byte members of vectors are displayed as integer
7604 Regard the bits of the value as a floating point number and print
7605 using typical floating point syntax.
7608 @cindex printing strings
7609 @cindex printing byte arrays
7610 Regard as a string, if possible. With this format, pointers to single-byte
7611 data are displayed as null-terminated strings and arrays of single-byte data
7612 are displayed as fixed-length strings. Other values are displayed in their
7615 Without this format, @value{GDBN} displays pointers to and arrays of
7616 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7617 strings. Single-byte members of a vector are displayed as an integer
7621 @cindex raw printing
7622 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7623 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7624 Printing}). This typically results in a higher-level display of the
7625 value's contents. The @samp{r} format bypasses any Python
7626 pretty-printer which might exist.
7629 For example, to print the program counter in hex (@pxref{Registers}), type
7636 Note that no space is required before the slash; this is because command
7637 names in @value{GDBN} cannot contain a slash.
7639 To reprint the last value in the value history with a different format,
7640 you can use the @code{print} command with just a format and no
7641 expression. For example, @samp{p/x} reprints the last value in hex.
7644 @section Examining Memory
7646 You can use the command @code{x} (for ``examine'') to examine memory in
7647 any of several formats, independently of your program's data types.
7649 @cindex examining memory
7651 @kindex x @r{(examine memory)}
7652 @item x/@var{nfu} @var{addr}
7655 Use the @code{x} command to examine memory.
7658 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7659 much memory to display and how to format it; @var{addr} is an
7660 expression giving the address where you want to start displaying memory.
7661 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7662 Several commands set convenient defaults for @var{addr}.
7665 @item @var{n}, the repeat count
7666 The repeat count is a decimal integer; the default is 1. It specifies
7667 how much memory (counting by units @var{u}) to display.
7668 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7671 @item @var{f}, the display format
7672 The display format is one of the formats used by @code{print}
7673 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7674 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7675 The default is @samp{x} (hexadecimal) initially. The default changes
7676 each time you use either @code{x} or @code{print}.
7678 @item @var{u}, the unit size
7679 The unit size is any of
7685 Halfwords (two bytes).
7687 Words (four bytes). This is the initial default.
7689 Giant words (eight bytes).
7692 Each time you specify a unit size with @code{x}, that size becomes the
7693 default unit the next time you use @code{x}. For the @samp{i} format,
7694 the unit size is ignored and is normally not written. For the @samp{s} format,
7695 the unit size defaults to @samp{b}, unless it is explicitly given.
7696 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7697 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7698 Note that the results depend on the programming language of the
7699 current compilation unit. If the language is C, the @samp{s}
7700 modifier will use the UTF-16 encoding while @samp{w} will use
7701 UTF-32. The encoding is set by the programming language and cannot
7704 @item @var{addr}, starting display address
7705 @var{addr} is the address where you want @value{GDBN} to begin displaying
7706 memory. The expression need not have a pointer value (though it may);
7707 it is always interpreted as an integer address of a byte of memory.
7708 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7709 @var{addr} is usually just after the last address examined---but several
7710 other commands also set the default address: @code{info breakpoints} (to
7711 the address of the last breakpoint listed), @code{info line} (to the
7712 starting address of a line), and @code{print} (if you use it to display
7713 a value from memory).
7716 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7717 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7718 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7719 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7720 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7722 Since the letters indicating unit sizes are all distinct from the
7723 letters specifying output formats, you do not have to remember whether
7724 unit size or format comes first; either order works. The output
7725 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7726 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7728 Even though the unit size @var{u} is ignored for the formats @samp{s}
7729 and @samp{i}, you might still want to use a count @var{n}; for example,
7730 @samp{3i} specifies that you want to see three machine instructions,
7731 including any operands. For convenience, especially when used with
7732 the @code{display} command, the @samp{i} format also prints branch delay
7733 slot instructions, if any, beyond the count specified, which immediately
7734 follow the last instruction that is within the count. The command
7735 @code{disassemble} gives an alternative way of inspecting machine
7736 instructions; see @ref{Machine Code,,Source and Machine Code}.
7738 All the defaults for the arguments to @code{x} are designed to make it
7739 easy to continue scanning memory with minimal specifications each time
7740 you use @code{x}. For example, after you have inspected three machine
7741 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7742 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7743 the repeat count @var{n} is used again; the other arguments default as
7744 for successive uses of @code{x}.
7746 When examining machine instructions, the instruction at current program
7747 counter is shown with a @code{=>} marker. For example:
7750 (@value{GDBP}) x/5i $pc-6
7751 0x804837f <main+11>: mov %esp,%ebp
7752 0x8048381 <main+13>: push %ecx
7753 0x8048382 <main+14>: sub $0x4,%esp
7754 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7755 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7758 @cindex @code{$_}, @code{$__}, and value history
7759 The addresses and contents printed by the @code{x} command are not saved
7760 in the value history because there is often too much of them and they
7761 would get in the way. Instead, @value{GDBN} makes these values available for
7762 subsequent use in expressions as values of the convenience variables
7763 @code{$_} and @code{$__}. After an @code{x} command, the last address
7764 examined is available for use in expressions in the convenience variable
7765 @code{$_}. The contents of that address, as examined, are available in
7766 the convenience variable @code{$__}.
7768 If the @code{x} command has a repeat count, the address and contents saved
7769 are from the last memory unit printed; this is not the same as the last
7770 address printed if several units were printed on the last line of output.
7772 @cindex remote memory comparison
7773 @cindex verify remote memory image
7774 When you are debugging a program running on a remote target machine
7775 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7776 remote machine's memory against the executable file you downloaded to
7777 the target. The @code{compare-sections} command is provided for such
7781 @kindex compare-sections
7782 @item compare-sections @r{[}@var{section-name}@r{]}
7783 Compare the data of a loadable section @var{section-name} in the
7784 executable file of the program being debugged with the same section in
7785 the remote machine's memory, and report any mismatches. With no
7786 arguments, compares all loadable sections. This command's
7787 availability depends on the target's support for the @code{"qCRC"}
7792 @section Automatic Display
7793 @cindex automatic display
7794 @cindex display of expressions
7796 If you find that you want to print the value of an expression frequently
7797 (to see how it changes), you might want to add it to the @dfn{automatic
7798 display list} so that @value{GDBN} prints its value each time your program stops.
7799 Each expression added to the list is given a number to identify it;
7800 to remove an expression from the list, you specify that number.
7801 The automatic display looks like this:
7805 3: bar[5] = (struct hack *) 0x3804
7809 This display shows item numbers, expressions and their current values. As with
7810 displays you request manually using @code{x} or @code{print}, you can
7811 specify the output format you prefer; in fact, @code{display} decides
7812 whether to use @code{print} or @code{x} depending your format
7813 specification---it uses @code{x} if you specify either the @samp{i}
7814 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7818 @item display @var{expr}
7819 Add the expression @var{expr} to the list of expressions to display
7820 each time your program stops. @xref{Expressions, ,Expressions}.
7822 @code{display} does not repeat if you press @key{RET} again after using it.
7824 @item display/@var{fmt} @var{expr}
7825 For @var{fmt} specifying only a display format and not a size or
7826 count, add the expression @var{expr} to the auto-display list but
7827 arrange to display it each time in the specified format @var{fmt}.
7828 @xref{Output Formats,,Output Formats}.
7830 @item display/@var{fmt} @var{addr}
7831 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7832 number of units, add the expression @var{addr} as a memory address to
7833 be examined each time your program stops. Examining means in effect
7834 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7837 For example, @samp{display/i $pc} can be helpful, to see the machine
7838 instruction about to be executed each time execution stops (@samp{$pc}
7839 is a common name for the program counter; @pxref{Registers, ,Registers}).
7842 @kindex delete display
7844 @item undisplay @var{dnums}@dots{}
7845 @itemx delete display @var{dnums}@dots{}
7846 Remove items from the list of expressions to display. Specify the
7847 numbers of the displays that you want affected with the command
7848 argument @var{dnums}. It can be a single display number, one of the
7849 numbers shown in the first field of the @samp{info display} display;
7850 or it could be a range of display numbers, as in @code{2-4}.
7852 @code{undisplay} does not repeat if you press @key{RET} after using it.
7853 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7855 @kindex disable display
7856 @item disable display @var{dnums}@dots{}
7857 Disable the display of item numbers @var{dnums}. A disabled display
7858 item is not printed automatically, but is not forgotten. It may be
7859 enabled again later. Specify the numbers of the displays that you
7860 want affected with the command argument @var{dnums}. It can be a
7861 single display number, one of the numbers shown in the first field of
7862 the @samp{info display} display; or it could be a range of display
7863 numbers, as in @code{2-4}.
7865 @kindex enable display
7866 @item enable display @var{dnums}@dots{}
7867 Enable display of item numbers @var{dnums}. It becomes effective once
7868 again in auto display of its expression, until you specify otherwise.
7869 Specify the numbers of the displays that you want affected with the
7870 command argument @var{dnums}. It can be a single display number, one
7871 of the numbers shown in the first field of the @samp{info display}
7872 display; or it could be a range of display numbers, as in @code{2-4}.
7875 Display the current values of the expressions on the list, just as is
7876 done when your program stops.
7878 @kindex info display
7880 Print the list of expressions previously set up to display
7881 automatically, each one with its item number, but without showing the
7882 values. This includes disabled expressions, which are marked as such.
7883 It also includes expressions which would not be displayed right now
7884 because they refer to automatic variables not currently available.
7887 @cindex display disabled out of scope
7888 If a display expression refers to local variables, then it does not make
7889 sense outside the lexical context for which it was set up. Such an
7890 expression is disabled when execution enters a context where one of its
7891 variables is not defined. For example, if you give the command
7892 @code{display last_char} while inside a function with an argument
7893 @code{last_char}, @value{GDBN} displays this argument while your program
7894 continues to stop inside that function. When it stops elsewhere---where
7895 there is no variable @code{last_char}---the display is disabled
7896 automatically. The next time your program stops where @code{last_char}
7897 is meaningful, you can enable the display expression once again.
7899 @node Print Settings
7900 @section Print Settings
7902 @cindex format options
7903 @cindex print settings
7904 @value{GDBN} provides the following ways to control how arrays, structures,
7905 and symbols are printed.
7908 These settings are useful for debugging programs in any language:
7912 @item set print address
7913 @itemx set print address on
7914 @cindex print/don't print memory addresses
7915 @value{GDBN} prints memory addresses showing the location of stack
7916 traces, structure values, pointer values, breakpoints, and so forth,
7917 even when it also displays the contents of those addresses. The default
7918 is @code{on}. For example, this is what a stack frame display looks like with
7919 @code{set print address on}:
7924 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7926 530 if (lquote != def_lquote)
7930 @item set print address off
7931 Do not print addresses when displaying their contents. For example,
7932 this is the same stack frame displayed with @code{set print address off}:
7936 (@value{GDBP}) set print addr off
7938 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7939 530 if (lquote != def_lquote)
7943 You can use @samp{set print address off} to eliminate all machine
7944 dependent displays from the @value{GDBN} interface. For example, with
7945 @code{print address off}, you should get the same text for backtraces on
7946 all machines---whether or not they involve pointer arguments.
7949 @item show print address
7950 Show whether or not addresses are to be printed.
7953 When @value{GDBN} prints a symbolic address, it normally prints the
7954 closest earlier symbol plus an offset. If that symbol does not uniquely
7955 identify the address (for example, it is a name whose scope is a single
7956 source file), you may need to clarify. One way to do this is with
7957 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7958 you can set @value{GDBN} to print the source file and line number when
7959 it prints a symbolic address:
7962 @item set print symbol-filename on
7963 @cindex source file and line of a symbol
7964 @cindex symbol, source file and line
7965 Tell @value{GDBN} to print the source file name and line number of a
7966 symbol in the symbolic form of an address.
7968 @item set print symbol-filename off
7969 Do not print source file name and line number of a symbol. This is the
7972 @item show print symbol-filename
7973 Show whether or not @value{GDBN} will print the source file name and
7974 line number of a symbol in the symbolic form of an address.
7977 Another situation where it is helpful to show symbol filenames and line
7978 numbers is when disassembling code; @value{GDBN} shows you the line
7979 number and source file that corresponds to each instruction.
7981 Also, you may wish to see the symbolic form only if the address being
7982 printed is reasonably close to the closest earlier symbol:
7985 @item set print max-symbolic-offset @var{max-offset}
7986 @cindex maximum value for offset of closest symbol
7987 Tell @value{GDBN} to only display the symbolic form of an address if the
7988 offset between the closest earlier symbol and the address is less than
7989 @var{max-offset}. The default is 0, which tells @value{GDBN}
7990 to always print the symbolic form of an address if any symbol precedes it.
7992 @item show print max-symbolic-offset
7993 Ask how large the maximum offset is that @value{GDBN} prints in a
7997 @cindex wild pointer, interpreting
7998 @cindex pointer, finding referent
7999 If you have a pointer and you are not sure where it points, try
8000 @samp{set print symbol-filename on}. Then you can determine the name
8001 and source file location of the variable where it points, using
8002 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8003 For example, here @value{GDBN} shows that a variable @code{ptt} points
8004 at another variable @code{t}, defined in @file{hi2.c}:
8007 (@value{GDBP}) set print symbol-filename on
8008 (@value{GDBP}) p/a ptt
8009 $4 = 0xe008 <t in hi2.c>
8013 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8014 does not show the symbol name and filename of the referent, even with
8015 the appropriate @code{set print} options turned on.
8018 Other settings control how different kinds of objects are printed:
8021 @item set print array
8022 @itemx set print array on
8023 @cindex pretty print arrays
8024 Pretty print arrays. This format is more convenient to read,
8025 but uses more space. The default is off.
8027 @item set print array off
8028 Return to compressed format for arrays.
8030 @item show print array
8031 Show whether compressed or pretty format is selected for displaying
8034 @cindex print array indexes
8035 @item set print array-indexes
8036 @itemx set print array-indexes on
8037 Print the index of each element when displaying arrays. May be more
8038 convenient to locate a given element in the array or quickly find the
8039 index of a given element in that printed array. The default is off.
8041 @item set print array-indexes off
8042 Stop printing element indexes when displaying arrays.
8044 @item show print array-indexes
8045 Show whether the index of each element is printed when displaying
8048 @item set print elements @var{number-of-elements}
8049 @cindex number of array elements to print
8050 @cindex limit on number of printed array elements
8051 Set a limit on how many elements of an array @value{GDBN} will print.
8052 If @value{GDBN} is printing a large array, it stops printing after it has
8053 printed the number of elements set by the @code{set print elements} command.
8054 This limit also applies to the display of strings.
8055 When @value{GDBN} starts, this limit is set to 200.
8056 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8058 @item show print elements
8059 Display the number of elements of a large array that @value{GDBN} will print.
8060 If the number is 0, then the printing is unlimited.
8062 @item set print frame-arguments @var{value}
8063 @kindex set print frame-arguments
8064 @cindex printing frame argument values
8065 @cindex print all frame argument values
8066 @cindex print frame argument values for scalars only
8067 @cindex do not print frame argument values
8068 This command allows to control how the values of arguments are printed
8069 when the debugger prints a frame (@pxref{Frames}). The possible
8074 The values of all arguments are printed.
8077 Print the value of an argument only if it is a scalar. The value of more
8078 complex arguments such as arrays, structures, unions, etc, is replaced
8079 by @code{@dots{}}. This is the default. Here is an example where
8080 only scalar arguments are shown:
8083 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8088 None of the argument values are printed. Instead, the value of each argument
8089 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8092 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8097 By default, only scalar arguments are printed. This command can be used
8098 to configure the debugger to print the value of all arguments, regardless
8099 of their type. However, it is often advantageous to not print the value
8100 of more complex parameters. For instance, it reduces the amount of
8101 information printed in each frame, making the backtrace more readable.
8102 Also, it improves performance when displaying Ada frames, because
8103 the computation of large arguments can sometimes be CPU-intensive,
8104 especially in large applications. Setting @code{print frame-arguments}
8105 to @code{scalars} (the default) or @code{none} avoids this computation,
8106 thus speeding up the display of each Ada frame.
8108 @item show print frame-arguments
8109 Show how the value of arguments should be displayed when printing a frame.
8111 @anchor{set print entry-values}
8112 @item set print entry-values @var{value}
8113 @kindex set print entry-values
8114 Set printing of frame argument values at function entry. In some cases
8115 @value{GDBN} can determine the value of function argument which was passed by
8116 the function caller, even if the value was modified inside the called function
8117 and therefore is different. With optimized code, the current value could be
8118 unavailable, but the entry value may still be known.
8120 The default value is @code{default} (see below for its description). Older
8121 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8122 this feature will behave in the @code{default} setting the same way as with the
8125 This functionality is currently supported only by DWARF 2 debugging format and
8126 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8127 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8130 The @var{value} parameter can be one of the following:
8134 Print only actual parameter values, never print values from function entry
8138 #0 different (val=6)
8139 #0 lost (val=<optimized out>)
8141 #0 invalid (val=<optimized out>)
8145 Print only parameter values from function entry point. The actual parameter
8146 values are never printed.
8148 #0 equal (val@@entry=5)
8149 #0 different (val@@entry=5)
8150 #0 lost (val@@entry=5)
8151 #0 born (val@@entry=<optimized out>)
8152 #0 invalid (val@@entry=<optimized out>)
8156 Print only parameter values from function entry point. If value from function
8157 entry point is not known while the actual value is known, print the actual
8158 value for such parameter.
8160 #0 equal (val@@entry=5)
8161 #0 different (val@@entry=5)
8162 #0 lost (val@@entry=5)
8164 #0 invalid (val@@entry=<optimized out>)
8168 Print actual parameter values. If actual parameter value is not known while
8169 value from function entry point is known, print the entry point value for such
8173 #0 different (val=6)
8174 #0 lost (val@@entry=5)
8176 #0 invalid (val=<optimized out>)
8180 Always print both the actual parameter value and its value from function entry
8181 point, even if values of one or both are not available due to compiler
8184 #0 equal (val=5, val@@entry=5)
8185 #0 different (val=6, val@@entry=5)
8186 #0 lost (val=<optimized out>, val@@entry=5)
8187 #0 born (val=10, val@@entry=<optimized out>)
8188 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8192 Print the actual parameter value if it is known and also its value from
8193 function entry point if it is known. If neither is known, print for the actual
8194 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8195 values are known and identical, print the shortened
8196 @code{param=param@@entry=VALUE} notation.
8198 #0 equal (val=val@@entry=5)
8199 #0 different (val=6, val@@entry=5)
8200 #0 lost (val@@entry=5)
8202 #0 invalid (val=<optimized out>)
8206 Always print the actual parameter value. Print also its value from function
8207 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8208 if both values are known and identical, print the shortened
8209 @code{param=param@@entry=VALUE} notation.
8211 #0 equal (val=val@@entry=5)
8212 #0 different (val=6, val@@entry=5)
8213 #0 lost (val=<optimized out>, val@@entry=5)
8215 #0 invalid (val=<optimized out>)
8219 For analysis messages on possible failures of frame argument values at function
8220 entry resolution see @ref{set debug entry-values}.
8222 @item show print entry-values
8223 Show the method being used for printing of frame argument values at function
8226 @item set print repeats
8227 @cindex repeated array elements
8228 Set the threshold for suppressing display of repeated array
8229 elements. When the number of consecutive identical elements of an
8230 array exceeds the threshold, @value{GDBN} prints the string
8231 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8232 identical repetitions, instead of displaying the identical elements
8233 themselves. Setting the threshold to zero will cause all elements to
8234 be individually printed. The default threshold is 10.
8236 @item show print repeats
8237 Display the current threshold for printing repeated identical
8240 @item set print null-stop
8241 @cindex @sc{null} elements in arrays
8242 Cause @value{GDBN} to stop printing the characters of an array when the first
8243 @sc{null} is encountered. This is useful when large arrays actually
8244 contain only short strings.
8247 @item show print null-stop
8248 Show whether @value{GDBN} stops printing an array on the first
8249 @sc{null} character.
8251 @item set print pretty on
8252 @cindex print structures in indented form
8253 @cindex indentation in structure display
8254 Cause @value{GDBN} to print structures in an indented format with one member
8255 per line, like this:
8270 @item set print pretty off
8271 Cause @value{GDBN} to print structures in a compact format, like this:
8275 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8276 meat = 0x54 "Pork"@}
8281 This is the default format.
8283 @item show print pretty
8284 Show which format @value{GDBN} is using to print structures.
8286 @item set print sevenbit-strings on
8287 @cindex eight-bit characters in strings
8288 @cindex octal escapes in strings
8289 Print using only seven-bit characters; if this option is set,
8290 @value{GDBN} displays any eight-bit characters (in strings or
8291 character values) using the notation @code{\}@var{nnn}. This setting is
8292 best if you are working in English (@sc{ascii}) and you use the
8293 high-order bit of characters as a marker or ``meta'' bit.
8295 @item set print sevenbit-strings off
8296 Print full eight-bit characters. This allows the use of more
8297 international character sets, and is the default.
8299 @item show print sevenbit-strings
8300 Show whether or not @value{GDBN} is printing only seven-bit characters.
8302 @item set print union on
8303 @cindex unions in structures, printing
8304 Tell @value{GDBN} to print unions which are contained in structures
8305 and other unions. This is the default setting.
8307 @item set print union off
8308 Tell @value{GDBN} not to print unions which are contained in
8309 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8312 @item show print union
8313 Ask @value{GDBN} whether or not it will print unions which are contained in
8314 structures and other unions.
8316 For example, given the declarations
8319 typedef enum @{Tree, Bug@} Species;
8320 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8321 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8332 struct thing foo = @{Tree, @{Acorn@}@};
8336 with @code{set print union on} in effect @samp{p foo} would print
8339 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8343 and with @code{set print union off} in effect it would print
8346 $1 = @{it = Tree, form = @{...@}@}
8350 @code{set print union} affects programs written in C-like languages
8356 These settings are of interest when debugging C@t{++} programs:
8359 @cindex demangling C@t{++} names
8360 @item set print demangle
8361 @itemx set print demangle on
8362 Print C@t{++} names in their source form rather than in the encoded
8363 (``mangled'') form passed to the assembler and linker for type-safe
8364 linkage. The default is on.
8366 @item show print demangle
8367 Show whether C@t{++} names are printed in mangled or demangled form.
8369 @item set print asm-demangle
8370 @itemx set print asm-demangle on
8371 Print C@t{++} names in their source form rather than their mangled form, even
8372 in assembler code printouts such as instruction disassemblies.
8375 @item show print asm-demangle
8376 Show whether C@t{++} names in assembly listings are printed in mangled
8379 @cindex C@t{++} symbol decoding style
8380 @cindex symbol decoding style, C@t{++}
8381 @kindex set demangle-style
8382 @item set demangle-style @var{style}
8383 Choose among several encoding schemes used by different compilers to
8384 represent C@t{++} names. The choices for @var{style} are currently:
8388 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8391 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8392 This is the default.
8395 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8398 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8401 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8402 @strong{Warning:} this setting alone is not sufficient to allow
8403 debugging @code{cfront}-generated executables. @value{GDBN} would
8404 require further enhancement to permit that.
8407 If you omit @var{style}, you will see a list of possible formats.
8409 @item show demangle-style
8410 Display the encoding style currently in use for decoding C@t{++} symbols.
8412 @item set print object
8413 @itemx set print object on
8414 @cindex derived type of an object, printing
8415 @cindex display derived types
8416 When displaying a pointer to an object, identify the @emph{actual}
8417 (derived) type of the object rather than the @emph{declared} type, using
8418 the virtual function table. Note that the virtual function table is
8419 required---this feature can only work for objects that have run-time
8420 type identification; a single virtual method in the object's declared
8423 @item set print object off
8424 Display only the declared type of objects, without reference to the
8425 virtual function table. This is the default setting.
8427 @item show print object
8428 Show whether actual, or declared, object types are displayed.
8430 @item set print static-members
8431 @itemx set print static-members on
8432 @cindex static members of C@t{++} objects
8433 Print static members when displaying a C@t{++} object. The default is on.
8435 @item set print static-members off
8436 Do not print static members when displaying a C@t{++} object.
8438 @item show print static-members
8439 Show whether C@t{++} static members are printed or not.
8441 @item set print pascal_static-members
8442 @itemx set print pascal_static-members on
8443 @cindex static members of Pascal objects
8444 @cindex Pascal objects, static members display
8445 Print static members when displaying a Pascal object. The default is on.
8447 @item set print pascal_static-members off
8448 Do not print static members when displaying a Pascal object.
8450 @item show print pascal_static-members
8451 Show whether Pascal static members are printed or not.
8453 @c These don't work with HP ANSI C++ yet.
8454 @item set print vtbl
8455 @itemx set print vtbl on
8456 @cindex pretty print C@t{++} virtual function tables
8457 @cindex virtual functions (C@t{++}) display
8458 @cindex VTBL display
8459 Pretty print C@t{++} virtual function tables. The default is off.
8460 (The @code{vtbl} commands do not work on programs compiled with the HP
8461 ANSI C@t{++} compiler (@code{aCC}).)
8463 @item set print vtbl off
8464 Do not pretty print C@t{++} virtual function tables.
8466 @item show print vtbl
8467 Show whether C@t{++} virtual function tables are pretty printed, or not.
8470 @node Pretty Printing
8471 @section Pretty Printing
8473 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8474 Python code. It greatly simplifies the display of complex objects. This
8475 mechanism works for both MI and the CLI.
8478 * Pretty-Printer Introduction:: Introduction to pretty-printers
8479 * Pretty-Printer Example:: An example pretty-printer
8480 * Pretty-Printer Commands:: Pretty-printer commands
8483 @node Pretty-Printer Introduction
8484 @subsection Pretty-Printer Introduction
8486 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8487 registered for the value. If there is then @value{GDBN} invokes the
8488 pretty-printer to print the value. Otherwise the value is printed normally.
8490 Pretty-printers are normally named. This makes them easy to manage.
8491 The @samp{info pretty-printer} command will list all the installed
8492 pretty-printers with their names.
8493 If a pretty-printer can handle multiple data types, then its
8494 @dfn{subprinters} are the printers for the individual data types.
8495 Each such subprinter has its own name.
8496 The format of the name is @var{printer-name};@var{subprinter-name}.
8498 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8499 Typically they are automatically loaded and registered when the corresponding
8500 debug information is loaded, thus making them available without having to
8501 do anything special.
8503 There are three places where a pretty-printer can be registered.
8507 Pretty-printers registered globally are available when debugging
8511 Pretty-printers registered with a program space are available only
8512 when debugging that program.
8513 @xref{Progspaces In Python}, for more details on program spaces in Python.
8516 Pretty-printers registered with an objfile are loaded and unloaded
8517 with the corresponding objfile (e.g., shared library).
8518 @xref{Objfiles In Python}, for more details on objfiles in Python.
8521 @xref{Selecting Pretty-Printers}, for further information on how
8522 pretty-printers are selected,
8524 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8527 @node Pretty-Printer Example
8528 @subsection Pretty-Printer Example
8530 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8533 (@value{GDBP}) print s
8535 static npos = 4294967295,
8537 <std::allocator<char>> = @{
8538 <__gnu_cxx::new_allocator<char>> = @{
8539 <No data fields>@}, <No data fields>
8541 members of std::basic_string<char, std::char_traits<char>,
8542 std::allocator<char> >::_Alloc_hider:
8543 _M_p = 0x804a014 "abcd"
8548 With a pretty-printer for @code{std::string} only the contents are printed:
8551 (@value{GDBP}) print s
8555 @node Pretty-Printer Commands
8556 @subsection Pretty-Printer Commands
8557 @cindex pretty-printer commands
8560 @kindex info pretty-printer
8561 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8562 Print the list of installed pretty-printers.
8563 This includes disabled pretty-printers, which are marked as such.
8565 @var{object-regexp} is a regular expression matching the objects
8566 whose pretty-printers to list.
8567 Objects can be @code{global}, the program space's file
8568 (@pxref{Progspaces In Python}),
8569 and the object files within that program space (@pxref{Objfiles In Python}).
8570 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8571 looks up a printer from these three objects.
8573 @var{name-regexp} is a regular expression matching the name of the printers
8576 @kindex disable pretty-printer
8577 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8578 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8579 A disabled pretty-printer is not forgotten, it may be enabled again later.
8581 @kindex enable pretty-printer
8582 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8583 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8588 Suppose we have three pretty-printers installed: one from library1.so
8589 named @code{foo} that prints objects of type @code{foo}, and
8590 another from library2.so named @code{bar} that prints two types of objects,
8591 @code{bar1} and @code{bar2}.
8594 (gdb) info pretty-printer
8601 (gdb) info pretty-printer library2
8606 (gdb) disable pretty-printer library1
8608 2 of 3 printers enabled
8609 (gdb) info pretty-printer
8616 (gdb) disable pretty-printer library2 bar:bar1
8618 1 of 3 printers enabled
8619 (gdb) info pretty-printer library2
8626 (gdb) disable pretty-printer library2 bar
8628 0 of 3 printers enabled
8629 (gdb) info pretty-printer library2
8638 Note that for @code{bar} the entire printer can be disabled,
8639 as can each individual subprinter.
8642 @section Value History
8644 @cindex value history
8645 @cindex history of values printed by @value{GDBN}
8646 Values printed by the @code{print} command are saved in the @value{GDBN}
8647 @dfn{value history}. This allows you to refer to them in other expressions.
8648 Values are kept until the symbol table is re-read or discarded
8649 (for example with the @code{file} or @code{symbol-file} commands).
8650 When the symbol table changes, the value history is discarded,
8651 since the values may contain pointers back to the types defined in the
8656 @cindex history number
8657 The values printed are given @dfn{history numbers} by which you can
8658 refer to them. These are successive integers starting with one.
8659 @code{print} shows you the history number assigned to a value by
8660 printing @samp{$@var{num} = } before the value; here @var{num} is the
8663 To refer to any previous value, use @samp{$} followed by the value's
8664 history number. The way @code{print} labels its output is designed to
8665 remind you of this. Just @code{$} refers to the most recent value in
8666 the history, and @code{$$} refers to the value before that.
8667 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8668 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8669 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8671 For example, suppose you have just printed a pointer to a structure and
8672 want to see the contents of the structure. It suffices to type
8678 If you have a chain of structures where the component @code{next} points
8679 to the next one, you can print the contents of the next one with this:
8686 You can print successive links in the chain by repeating this
8687 command---which you can do by just typing @key{RET}.
8689 Note that the history records values, not expressions. If the value of
8690 @code{x} is 4 and you type these commands:
8698 then the value recorded in the value history by the @code{print} command
8699 remains 4 even though the value of @code{x} has changed.
8704 Print the last ten values in the value history, with their item numbers.
8705 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8706 values} does not change the history.
8708 @item show values @var{n}
8709 Print ten history values centered on history item number @var{n}.
8712 Print ten history values just after the values last printed. If no more
8713 values are available, @code{show values +} produces no display.
8716 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8717 same effect as @samp{show values +}.
8719 @node Convenience Vars
8720 @section Convenience Variables
8722 @cindex convenience variables
8723 @cindex user-defined variables
8724 @value{GDBN} provides @dfn{convenience variables} that you can use within
8725 @value{GDBN} to hold on to a value and refer to it later. These variables
8726 exist entirely within @value{GDBN}; they are not part of your program, and
8727 setting a convenience variable has no direct effect on further execution
8728 of your program. That is why you can use them freely.
8730 Convenience variables are prefixed with @samp{$}. Any name preceded by
8731 @samp{$} can be used for a convenience variable, unless it is one of
8732 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8733 (Value history references, in contrast, are @emph{numbers} preceded
8734 by @samp{$}. @xref{Value History, ,Value History}.)
8736 You can save a value in a convenience variable with an assignment
8737 expression, just as you would set a variable in your program.
8741 set $foo = *object_ptr
8745 would save in @code{$foo} the value contained in the object pointed to by
8748 Using a convenience variable for the first time creates it, but its
8749 value is @code{void} until you assign a new value. You can alter the
8750 value with another assignment at any time.
8752 Convenience variables have no fixed types. You can assign a convenience
8753 variable any type of value, including structures and arrays, even if
8754 that variable already has a value of a different type. The convenience
8755 variable, when used as an expression, has the type of its current value.
8758 @kindex show convenience
8759 @cindex show all user variables
8760 @item show convenience
8761 Print a list of convenience variables used so far, and their values.
8762 Abbreviated @code{show conv}.
8764 @kindex init-if-undefined
8765 @cindex convenience variables, initializing
8766 @item init-if-undefined $@var{variable} = @var{expression}
8767 Set a convenience variable if it has not already been set. This is useful
8768 for user-defined commands that keep some state. It is similar, in concept,
8769 to using local static variables with initializers in C (except that
8770 convenience variables are global). It can also be used to allow users to
8771 override default values used in a command script.
8773 If the variable is already defined then the expression is not evaluated so
8774 any side-effects do not occur.
8777 One of the ways to use a convenience variable is as a counter to be
8778 incremented or a pointer to be advanced. For example, to print
8779 a field from successive elements of an array of structures:
8783 print bar[$i++]->contents
8787 Repeat that command by typing @key{RET}.
8789 Some convenience variables are created automatically by @value{GDBN} and given
8790 values likely to be useful.
8793 @vindex $_@r{, convenience variable}
8795 The variable @code{$_} is automatically set by the @code{x} command to
8796 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8797 commands which provide a default address for @code{x} to examine also
8798 set @code{$_} to that address; these commands include @code{info line}
8799 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8800 except when set by the @code{x} command, in which case it is a pointer
8801 to the type of @code{$__}.
8803 @vindex $__@r{, convenience variable}
8805 The variable @code{$__} is automatically set by the @code{x} command
8806 to the value found in the last address examined. Its type is chosen
8807 to match the format in which the data was printed.
8810 @vindex $_exitcode@r{, convenience variable}
8811 The variable @code{$_exitcode} is automatically set to the exit code when
8812 the program being debugged terminates.
8815 @vindex $_sdata@r{, inspect, convenience variable}
8816 The variable @code{$_sdata} contains extra collected static tracepoint
8817 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8818 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8819 if extra static tracepoint data has not been collected.
8822 @vindex $_siginfo@r{, convenience variable}
8823 The variable @code{$_siginfo} contains extra signal information
8824 (@pxref{extra signal information}). Note that @code{$_siginfo}
8825 could be empty, if the application has not yet received any signals.
8826 For example, it will be empty before you execute the @code{run} command.
8829 @vindex $_tlb@r{, convenience variable}
8830 The variable @code{$_tlb} is automatically set when debugging
8831 applications running on MS-Windows in native mode or connected to
8832 gdbserver that supports the @code{qGetTIBAddr} request.
8833 @xref{General Query Packets}.
8834 This variable contains the address of the thread information block.
8838 On HP-UX systems, if you refer to a function or variable name that
8839 begins with a dollar sign, @value{GDBN} searches for a user or system
8840 name first, before it searches for a convenience variable.
8842 @cindex convenience functions
8843 @value{GDBN} also supplies some @dfn{convenience functions}. These
8844 have a syntax similar to convenience variables. A convenience
8845 function can be used in an expression just like an ordinary function;
8846 however, a convenience function is implemented internally to
8851 @kindex help function
8852 @cindex show all convenience functions
8853 Print a list of all convenience functions.
8860 You can refer to machine register contents, in expressions, as variables
8861 with names starting with @samp{$}. The names of registers are different
8862 for each machine; use @code{info registers} to see the names used on
8866 @kindex info registers
8867 @item info registers
8868 Print the names and values of all registers except floating-point
8869 and vector registers (in the selected stack frame).
8871 @kindex info all-registers
8872 @cindex floating point registers
8873 @item info all-registers
8874 Print the names and values of all registers, including floating-point
8875 and vector registers (in the selected stack frame).
8877 @item info registers @var{regname} @dots{}
8878 Print the @dfn{relativized} value of each specified register @var{regname}.
8879 As discussed in detail below, register values are normally relative to
8880 the selected stack frame. @var{regname} may be any register name valid on
8881 the machine you are using, with or without the initial @samp{$}.
8884 @cindex stack pointer register
8885 @cindex program counter register
8886 @cindex process status register
8887 @cindex frame pointer register
8888 @cindex standard registers
8889 @value{GDBN} has four ``standard'' register names that are available (in
8890 expressions) on most machines---whenever they do not conflict with an
8891 architecture's canonical mnemonics for registers. The register names
8892 @code{$pc} and @code{$sp} are used for the program counter register and
8893 the stack pointer. @code{$fp} is used for a register that contains a
8894 pointer to the current stack frame, and @code{$ps} is used for a
8895 register that contains the processor status. For example,
8896 you could print the program counter in hex with
8903 or print the instruction to be executed next with
8910 or add four to the stack pointer@footnote{This is a way of removing
8911 one word from the stack, on machines where stacks grow downward in
8912 memory (most machines, nowadays). This assumes that the innermost
8913 stack frame is selected; setting @code{$sp} is not allowed when other
8914 stack frames are selected. To pop entire frames off the stack,
8915 regardless of machine architecture, use @code{return};
8916 see @ref{Returning, ,Returning from a Function}.} with
8922 Whenever possible, these four standard register names are available on
8923 your machine even though the machine has different canonical mnemonics,
8924 so long as there is no conflict. The @code{info registers} command
8925 shows the canonical names. For example, on the SPARC, @code{info
8926 registers} displays the processor status register as @code{$psr} but you
8927 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8928 is an alias for the @sc{eflags} register.
8930 @value{GDBN} always considers the contents of an ordinary register as an
8931 integer when the register is examined in this way. Some machines have
8932 special registers which can hold nothing but floating point; these
8933 registers are considered to have floating point values. There is no way
8934 to refer to the contents of an ordinary register as floating point value
8935 (although you can @emph{print} it as a floating point value with
8936 @samp{print/f $@var{regname}}).
8938 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8939 means that the data format in which the register contents are saved by
8940 the operating system is not the same one that your program normally
8941 sees. For example, the registers of the 68881 floating point
8942 coprocessor are always saved in ``extended'' (raw) format, but all C
8943 programs expect to work with ``double'' (virtual) format. In such
8944 cases, @value{GDBN} normally works with the virtual format only (the format
8945 that makes sense for your program), but the @code{info registers} command
8946 prints the data in both formats.
8948 @cindex SSE registers (x86)
8949 @cindex MMX registers (x86)
8950 Some machines have special registers whose contents can be interpreted
8951 in several different ways. For example, modern x86-based machines
8952 have SSE and MMX registers that can hold several values packed
8953 together in several different formats. @value{GDBN} refers to such
8954 registers in @code{struct} notation:
8957 (@value{GDBP}) print $xmm1
8959 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8960 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8961 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8962 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8963 v4_int32 = @{0, 20657912, 11, 13@},
8964 v2_int64 = @{88725056443645952, 55834574859@},
8965 uint128 = 0x0000000d0000000b013b36f800000000
8970 To set values of such registers, you need to tell @value{GDBN} which
8971 view of the register you wish to change, as if you were assigning
8972 value to a @code{struct} member:
8975 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8978 Normally, register values are relative to the selected stack frame
8979 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8980 value that the register would contain if all stack frames farther in
8981 were exited and their saved registers restored. In order to see the
8982 true contents of hardware registers, you must select the innermost
8983 frame (with @samp{frame 0}).
8985 However, @value{GDBN} must deduce where registers are saved, from the machine
8986 code generated by your compiler. If some registers are not saved, or if
8987 @value{GDBN} is unable to locate the saved registers, the selected stack
8988 frame makes no difference.
8990 @node Floating Point Hardware
8991 @section Floating Point Hardware
8992 @cindex floating point
8994 Depending on the configuration, @value{GDBN} may be able to give
8995 you more information about the status of the floating point hardware.
9000 Display hardware-dependent information about the floating
9001 point unit. The exact contents and layout vary depending on the
9002 floating point chip. Currently, @samp{info float} is supported on
9003 the ARM and x86 machines.
9007 @section Vector Unit
9010 Depending on the configuration, @value{GDBN} may be able to give you
9011 more information about the status of the vector unit.
9016 Display information about the vector unit. The exact contents and
9017 layout vary depending on the hardware.
9020 @node OS Information
9021 @section Operating System Auxiliary Information
9022 @cindex OS information
9024 @value{GDBN} provides interfaces to useful OS facilities that can help
9025 you debug your program.
9027 @cindex @code{ptrace} system call
9028 @cindex @code{struct user} contents
9029 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9030 machines), it interfaces with the inferior via the @code{ptrace}
9031 system call. The operating system creates a special sata structure,
9032 called @code{struct user}, for this interface. You can use the
9033 command @code{info udot} to display the contents of this data
9039 Display the contents of the @code{struct user} maintained by the OS
9040 kernel for the program being debugged. @value{GDBN} displays the
9041 contents of @code{struct user} as a list of hex numbers, similar to
9042 the @code{examine} command.
9045 @cindex auxiliary vector
9046 @cindex vector, auxiliary
9047 Some operating systems supply an @dfn{auxiliary vector} to programs at
9048 startup. This is akin to the arguments and environment that you
9049 specify for a program, but contains a system-dependent variety of
9050 binary values that tell system libraries important details about the
9051 hardware, operating system, and process. Each value's purpose is
9052 identified by an integer tag; the meanings are well-known but system-specific.
9053 Depending on the configuration and operating system facilities,
9054 @value{GDBN} may be able to show you this information. For remote
9055 targets, this functionality may further depend on the remote stub's
9056 support of the @samp{qXfer:auxv:read} packet, see
9057 @ref{qXfer auxiliary vector read}.
9062 Display the auxiliary vector of the inferior, which can be either a
9063 live process or a core dump file. @value{GDBN} prints each tag value
9064 numerically, and also shows names and text descriptions for recognized
9065 tags. Some values in the vector are numbers, some bit masks, and some
9066 pointers to strings or other data. @value{GDBN} displays each value in the
9067 most appropriate form for a recognized tag, and in hexadecimal for
9068 an unrecognized tag.
9071 On some targets, @value{GDBN} can access operating-system-specific information
9072 and display it to user, without interpretation. For remote targets,
9073 this functionality depends on the remote stub's support of the
9074 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9079 List the types of OS information available for the target. If the
9080 target does not return a list of possible types, this command will
9083 @kindex info os processes
9084 @item info os processes
9085 Display the list of processes on the target. For each process,
9086 @value{GDBN} prints the process identifier, the name of the user, and
9087 the command corresponding to the process.
9090 @node Memory Region Attributes
9091 @section Memory Region Attributes
9092 @cindex memory region attributes
9094 @dfn{Memory region attributes} allow you to describe special handling
9095 required by regions of your target's memory. @value{GDBN} uses
9096 attributes to determine whether to allow certain types of memory
9097 accesses; whether to use specific width accesses; and whether to cache
9098 target memory. By default the description of memory regions is
9099 fetched from the target (if the current target supports this), but the
9100 user can override the fetched regions.
9102 Defined memory regions can be individually enabled and disabled. When a
9103 memory region is disabled, @value{GDBN} uses the default attributes when
9104 accessing memory in that region. Similarly, if no memory regions have
9105 been defined, @value{GDBN} uses the default attributes when accessing
9108 When a memory region is defined, it is given a number to identify it;
9109 to enable, disable, or remove a memory region, you specify that number.
9113 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9114 Define a memory region bounded by @var{lower} and @var{upper} with
9115 attributes @var{attributes}@dots{}, and add it to the list of regions
9116 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9117 case: it is treated as the target's maximum memory address.
9118 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9121 Discard any user changes to the memory regions and use target-supplied
9122 regions, if available, or no regions if the target does not support.
9125 @item delete mem @var{nums}@dots{}
9126 Remove memory regions @var{nums}@dots{} from the list of regions
9127 monitored by @value{GDBN}.
9130 @item disable mem @var{nums}@dots{}
9131 Disable monitoring of memory regions @var{nums}@dots{}.
9132 A disabled memory region is not forgotten.
9133 It may be enabled again later.
9136 @item enable mem @var{nums}@dots{}
9137 Enable monitoring of memory regions @var{nums}@dots{}.
9141 Print a table of all defined memory regions, with the following columns
9145 @item Memory Region Number
9146 @item Enabled or Disabled.
9147 Enabled memory regions are marked with @samp{y}.
9148 Disabled memory regions are marked with @samp{n}.
9151 The address defining the inclusive lower bound of the memory region.
9154 The address defining the exclusive upper bound of the memory region.
9157 The list of attributes set for this memory region.
9162 @subsection Attributes
9164 @subsubsection Memory Access Mode
9165 The access mode attributes set whether @value{GDBN} may make read or
9166 write accesses to a memory region.
9168 While these attributes prevent @value{GDBN} from performing invalid
9169 memory accesses, they do nothing to prevent the target system, I/O DMA,
9170 etc.@: from accessing memory.
9174 Memory is read only.
9176 Memory is write only.
9178 Memory is read/write. This is the default.
9181 @subsubsection Memory Access Size
9182 The access size attribute tells @value{GDBN} to use specific sized
9183 accesses in the memory region. Often memory mapped device registers
9184 require specific sized accesses. If no access size attribute is
9185 specified, @value{GDBN} may use accesses of any size.
9189 Use 8 bit memory accesses.
9191 Use 16 bit memory accesses.
9193 Use 32 bit memory accesses.
9195 Use 64 bit memory accesses.
9198 @c @subsubsection Hardware/Software Breakpoints
9199 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9200 @c will use hardware or software breakpoints for the internal breakpoints
9201 @c used by the step, next, finish, until, etc. commands.
9205 @c Always use hardware breakpoints
9206 @c @item swbreak (default)
9209 @subsubsection Data Cache
9210 The data cache attributes set whether @value{GDBN} will cache target
9211 memory. While this generally improves performance by reducing debug
9212 protocol overhead, it can lead to incorrect results because @value{GDBN}
9213 does not know about volatile variables or memory mapped device
9218 Enable @value{GDBN} to cache target memory.
9220 Disable @value{GDBN} from caching target memory. This is the default.
9223 @subsection Memory Access Checking
9224 @value{GDBN} can be instructed to refuse accesses to memory that is
9225 not explicitly described. This can be useful if accessing such
9226 regions has undesired effects for a specific target, or to provide
9227 better error checking. The following commands control this behaviour.
9230 @kindex set mem inaccessible-by-default
9231 @item set mem inaccessible-by-default [on|off]
9232 If @code{on} is specified, make @value{GDBN} treat memory not
9233 explicitly described by the memory ranges as non-existent and refuse accesses
9234 to such memory. The checks are only performed if there's at least one
9235 memory range defined. If @code{off} is specified, make @value{GDBN}
9236 treat the memory not explicitly described by the memory ranges as RAM.
9237 The default value is @code{on}.
9238 @kindex show mem inaccessible-by-default
9239 @item show mem inaccessible-by-default
9240 Show the current handling of accesses to unknown memory.
9244 @c @subsubsection Memory Write Verification
9245 @c The memory write verification attributes set whether @value{GDBN}
9246 @c will re-reads data after each write to verify the write was successful.
9250 @c @item noverify (default)
9253 @node Dump/Restore Files
9254 @section Copy Between Memory and a File
9255 @cindex dump/restore files
9256 @cindex append data to a file
9257 @cindex dump data to a file
9258 @cindex restore data from a file
9260 You can use the commands @code{dump}, @code{append}, and
9261 @code{restore} to copy data between target memory and a file. The
9262 @code{dump} and @code{append} commands write data to a file, and the
9263 @code{restore} command reads data from a file back into the inferior's
9264 memory. Files may be in binary, Motorola S-record, Intel hex, or
9265 Tektronix Hex format; however, @value{GDBN} can only append to binary
9271 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9272 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9273 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9274 or the value of @var{expr}, to @var{filename} in the given format.
9276 The @var{format} parameter may be any one of:
9283 Motorola S-record format.
9285 Tektronix Hex format.
9288 @value{GDBN} uses the same definitions of these formats as the
9289 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9290 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9294 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9295 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9296 Append the contents of memory from @var{start_addr} to @var{end_addr},
9297 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9298 (@value{GDBN} can only append data to files in raw binary form.)
9301 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9302 Restore the contents of file @var{filename} into memory. The
9303 @code{restore} command can automatically recognize any known @sc{bfd}
9304 file format, except for raw binary. To restore a raw binary file you
9305 must specify the optional keyword @code{binary} after the filename.
9307 If @var{bias} is non-zero, its value will be added to the addresses
9308 contained in the file. Binary files always start at address zero, so
9309 they will be restored at address @var{bias}. Other bfd files have
9310 a built-in location; they will be restored at offset @var{bias}
9313 If @var{start} and/or @var{end} are non-zero, then only data between
9314 file offset @var{start} and file offset @var{end} will be restored.
9315 These offsets are relative to the addresses in the file, before
9316 the @var{bias} argument is applied.
9320 @node Core File Generation
9321 @section How to Produce a Core File from Your Program
9322 @cindex dump core from inferior
9324 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9325 image of a running process and its process status (register values
9326 etc.). Its primary use is post-mortem debugging of a program that
9327 crashed while it ran outside a debugger. A program that crashes
9328 automatically produces a core file, unless this feature is disabled by
9329 the user. @xref{Files}, for information on invoking @value{GDBN} in
9330 the post-mortem debugging mode.
9332 Occasionally, you may wish to produce a core file of the program you
9333 are debugging in order to preserve a snapshot of its state.
9334 @value{GDBN} has a special command for that.
9338 @kindex generate-core-file
9339 @item generate-core-file [@var{file}]
9340 @itemx gcore [@var{file}]
9341 Produce a core dump of the inferior process. The optional argument
9342 @var{file} specifies the file name where to put the core dump. If not
9343 specified, the file name defaults to @file{core.@var{pid}}, where
9344 @var{pid} is the inferior process ID.
9346 Note that this command is implemented only for some systems (as of
9347 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9350 @node Character Sets
9351 @section Character Sets
9352 @cindex character sets
9354 @cindex translating between character sets
9355 @cindex host character set
9356 @cindex target character set
9358 If the program you are debugging uses a different character set to
9359 represent characters and strings than the one @value{GDBN} uses itself,
9360 @value{GDBN} can automatically translate between the character sets for
9361 you. The character set @value{GDBN} uses we call the @dfn{host
9362 character set}; the one the inferior program uses we call the
9363 @dfn{target character set}.
9365 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9366 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9367 remote protocol (@pxref{Remote Debugging}) to debug a program
9368 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9369 then the host character set is Latin-1, and the target character set is
9370 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9371 target-charset EBCDIC-US}, then @value{GDBN} translates between
9372 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9373 character and string literals in expressions.
9375 @value{GDBN} has no way to automatically recognize which character set
9376 the inferior program uses; you must tell it, using the @code{set
9377 target-charset} command, described below.
9379 Here are the commands for controlling @value{GDBN}'s character set
9383 @item set target-charset @var{charset}
9384 @kindex set target-charset
9385 Set the current target character set to @var{charset}. To display the
9386 list of supported target character sets, type
9387 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9389 @item set host-charset @var{charset}
9390 @kindex set host-charset
9391 Set the current host character set to @var{charset}.
9393 By default, @value{GDBN} uses a host character set appropriate to the
9394 system it is running on; you can override that default using the
9395 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9396 automatically determine the appropriate host character set. In this
9397 case, @value{GDBN} uses @samp{UTF-8}.
9399 @value{GDBN} can only use certain character sets as its host character
9400 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9401 @value{GDBN} will list the host character sets it supports.
9403 @item set charset @var{charset}
9405 Set the current host and target character sets to @var{charset}. As
9406 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9407 @value{GDBN} will list the names of the character sets that can be used
9408 for both host and target.
9411 @kindex show charset
9412 Show the names of the current host and target character sets.
9414 @item show host-charset
9415 @kindex show host-charset
9416 Show the name of the current host character set.
9418 @item show target-charset
9419 @kindex show target-charset
9420 Show the name of the current target character set.
9422 @item set target-wide-charset @var{charset}
9423 @kindex set target-wide-charset
9424 Set the current target's wide character set to @var{charset}. This is
9425 the character set used by the target's @code{wchar_t} type. To
9426 display the list of supported wide character sets, type
9427 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9429 @item show target-wide-charset
9430 @kindex show target-wide-charset
9431 Show the name of the current target's wide character set.
9434 Here is an example of @value{GDBN}'s character set support in action.
9435 Assume that the following source code has been placed in the file
9436 @file{charset-test.c}:
9442 = @{72, 101, 108, 108, 111, 44, 32, 119,
9443 111, 114, 108, 100, 33, 10, 0@};
9444 char ibm1047_hello[]
9445 = @{200, 133, 147, 147, 150, 107, 64, 166,
9446 150, 153, 147, 132, 90, 37, 0@};
9450 printf ("Hello, world!\n");
9454 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9455 containing the string @samp{Hello, world!} followed by a newline,
9456 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9458 We compile the program, and invoke the debugger on it:
9461 $ gcc -g charset-test.c -o charset-test
9462 $ gdb -nw charset-test
9463 GNU gdb 2001-12-19-cvs
9464 Copyright 2001 Free Software Foundation, Inc.
9469 We can use the @code{show charset} command to see what character sets
9470 @value{GDBN} is currently using to interpret and display characters and
9474 (@value{GDBP}) show charset
9475 The current host and target character set is `ISO-8859-1'.
9479 For the sake of printing this manual, let's use @sc{ascii} as our
9480 initial character set:
9482 (@value{GDBP}) set charset ASCII
9483 (@value{GDBP}) show charset
9484 The current host and target character set is `ASCII'.
9488 Let's assume that @sc{ascii} is indeed the correct character set for our
9489 host system --- in other words, let's assume that if @value{GDBN} prints
9490 characters using the @sc{ascii} character set, our terminal will display
9491 them properly. Since our current target character set is also
9492 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9495 (@value{GDBP}) print ascii_hello
9496 $1 = 0x401698 "Hello, world!\n"
9497 (@value{GDBP}) print ascii_hello[0]
9502 @value{GDBN} uses the target character set for character and string
9503 literals you use in expressions:
9506 (@value{GDBP}) print '+'
9511 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9514 @value{GDBN} relies on the user to tell it which character set the
9515 target program uses. If we print @code{ibm1047_hello} while our target
9516 character set is still @sc{ascii}, we get jibberish:
9519 (@value{GDBP}) print ibm1047_hello
9520 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9521 (@value{GDBP}) print ibm1047_hello[0]
9526 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9527 @value{GDBN} tells us the character sets it supports:
9530 (@value{GDBP}) set target-charset
9531 ASCII EBCDIC-US IBM1047 ISO-8859-1
9532 (@value{GDBP}) set target-charset
9535 We can select @sc{ibm1047} as our target character set, and examine the
9536 program's strings again. Now the @sc{ascii} string is wrong, but
9537 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9538 target character set, @sc{ibm1047}, to the host character set,
9539 @sc{ascii}, and they display correctly:
9542 (@value{GDBP}) set target-charset IBM1047
9543 (@value{GDBP}) show charset
9544 The current host character set is `ASCII'.
9545 The current target character set is `IBM1047'.
9546 (@value{GDBP}) print ascii_hello
9547 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9548 (@value{GDBP}) print ascii_hello[0]
9550 (@value{GDBP}) print ibm1047_hello
9551 $8 = 0x4016a8 "Hello, world!\n"
9552 (@value{GDBP}) print ibm1047_hello[0]
9557 As above, @value{GDBN} uses the target character set for character and
9558 string literals you use in expressions:
9561 (@value{GDBP}) print '+'
9566 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9569 @node Caching Remote Data
9570 @section Caching Data of Remote Targets
9571 @cindex caching data of remote targets
9573 @value{GDBN} caches data exchanged between the debugger and a
9574 remote target (@pxref{Remote Debugging}). Such caching generally improves
9575 performance, because it reduces the overhead of the remote protocol by
9576 bundling memory reads and writes into large chunks. Unfortunately, simply
9577 caching everything would lead to incorrect results, since @value{GDBN}
9578 does not necessarily know anything about volatile values, memory-mapped I/O
9579 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9580 memory can be changed @emph{while} a gdb command is executing.
9581 Therefore, by default, @value{GDBN} only caches data
9582 known to be on the stack@footnote{In non-stop mode, it is moderately
9583 rare for a running thread to modify the stack of a stopped thread
9584 in a way that would interfere with a backtrace, and caching of
9585 stack reads provides a significant speed up of remote backtraces.}.
9586 Other regions of memory can be explicitly marked as
9587 cacheable; see @pxref{Memory Region Attributes}.
9590 @kindex set remotecache
9591 @item set remotecache on
9592 @itemx set remotecache off
9593 This option no longer does anything; it exists for compatibility
9596 @kindex show remotecache
9597 @item show remotecache
9598 Show the current state of the obsolete remotecache flag.
9600 @kindex set stack-cache
9601 @item set stack-cache on
9602 @itemx set stack-cache off
9603 Enable or disable caching of stack accesses. When @code{ON}, use
9604 caching. By default, this option is @code{ON}.
9606 @kindex show stack-cache
9607 @item show stack-cache
9608 Show the current state of data caching for memory accesses.
9611 @item info dcache @r{[}line@r{]}
9612 Print the information about the data cache performance. The
9613 information displayed includes the dcache width and depth, and for
9614 each cache line, its number, address, and how many times it was
9615 referenced. This command is useful for debugging the data cache
9618 If a line number is specified, the contents of that line will be
9621 @item set dcache size @var{size}
9623 @kindex set dcache size
9624 Set maximum number of entries in dcache (dcache depth above).
9626 @item set dcache line-size @var{line-size}
9627 @cindex dcache line-size
9628 @kindex set dcache line-size
9629 Set number of bytes each dcache entry caches (dcache width above).
9630 Must be a power of 2.
9632 @item show dcache size
9633 @kindex show dcache size
9634 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9636 @item show dcache line-size
9637 @kindex show dcache line-size
9638 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9642 @node Searching Memory
9643 @section Search Memory
9644 @cindex searching memory
9646 Memory can be searched for a particular sequence of bytes with the
9647 @code{find} command.
9651 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9652 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9653 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9654 etc. The search begins at address @var{start_addr} and continues for either
9655 @var{len} bytes or through to @var{end_addr} inclusive.
9658 @var{s} and @var{n} are optional parameters.
9659 They may be specified in either order, apart or together.
9662 @item @var{s}, search query size
9663 The size of each search query value.
9669 halfwords (two bytes)
9673 giant words (eight bytes)
9676 All values are interpreted in the current language.
9677 This means, for example, that if the current source language is C/C@t{++}
9678 then searching for the string ``hello'' includes the trailing '\0'.
9680 If the value size is not specified, it is taken from the
9681 value's type in the current language.
9682 This is useful when one wants to specify the search
9683 pattern as a mixture of types.
9684 Note that this means, for example, that in the case of C-like languages
9685 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9686 which is typically four bytes.
9688 @item @var{n}, maximum number of finds
9689 The maximum number of matches to print. The default is to print all finds.
9692 You can use strings as search values. Quote them with double-quotes
9694 The string value is copied into the search pattern byte by byte,
9695 regardless of the endianness of the target and the size specification.
9697 The address of each match found is printed as well as a count of the
9698 number of matches found.
9700 The address of the last value found is stored in convenience variable
9702 A count of the number of matches is stored in @samp{$numfound}.
9704 For example, if stopped at the @code{printf} in this function:
9710 static char hello[] = "hello-hello";
9711 static struct @{ char c; short s; int i; @}
9712 __attribute__ ((packed)) mixed
9713 = @{ 'c', 0x1234, 0x87654321 @};
9714 printf ("%s\n", hello);
9719 you get during debugging:
9722 (gdb) find &hello[0], +sizeof(hello), "hello"
9723 0x804956d <hello.1620+6>
9725 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9726 0x8049567 <hello.1620>
9727 0x804956d <hello.1620+6>
9729 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9730 0x8049567 <hello.1620>
9732 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9733 0x8049560 <mixed.1625>
9735 (gdb) print $numfound
9738 $2 = (void *) 0x8049560
9741 @node Optimized Code
9742 @chapter Debugging Optimized Code
9743 @cindex optimized code, debugging
9744 @cindex debugging optimized code
9746 Almost all compilers support optimization. With optimization
9747 disabled, the compiler generates assembly code that corresponds
9748 directly to your source code, in a simplistic way. As the compiler
9749 applies more powerful optimizations, the generated assembly code
9750 diverges from your original source code. With help from debugging
9751 information generated by the compiler, @value{GDBN} can map from
9752 the running program back to constructs from your original source.
9754 @value{GDBN} is more accurate with optimization disabled. If you
9755 can recompile without optimization, it is easier to follow the
9756 progress of your program during debugging. But, there are many cases
9757 where you may need to debug an optimized version.
9759 When you debug a program compiled with @samp{-g -O}, remember that the
9760 optimizer has rearranged your code; the debugger shows you what is
9761 really there. Do not be too surprised when the execution path does not
9762 exactly match your source file! An extreme example: if you define a
9763 variable, but never use it, @value{GDBN} never sees that
9764 variable---because the compiler optimizes it out of existence.
9766 Some things do not work as well with @samp{-g -O} as with just
9767 @samp{-g}, particularly on machines with instruction scheduling. If in
9768 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9769 please report it to us as a bug (including a test case!).
9770 @xref{Variables}, for more information about debugging optimized code.
9773 * Inline Functions:: How @value{GDBN} presents inlining
9774 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9777 @node Inline Functions
9778 @section Inline Functions
9779 @cindex inline functions, debugging
9781 @dfn{Inlining} is an optimization that inserts a copy of the function
9782 body directly at each call site, instead of jumping to a shared
9783 routine. @value{GDBN} displays inlined functions just like
9784 non-inlined functions. They appear in backtraces. You can view their
9785 arguments and local variables, step into them with @code{step}, skip
9786 them with @code{next}, and escape from them with @code{finish}.
9787 You can check whether a function was inlined by using the
9788 @code{info frame} command.
9790 For @value{GDBN} to support inlined functions, the compiler must
9791 record information about inlining in the debug information ---
9792 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9793 other compilers do also. @value{GDBN} only supports inlined functions
9794 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9795 do not emit two required attributes (@samp{DW_AT_call_file} and
9796 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9797 function calls with earlier versions of @value{NGCC}. It instead
9798 displays the arguments and local variables of inlined functions as
9799 local variables in the caller.
9801 The body of an inlined function is directly included at its call site;
9802 unlike a non-inlined function, there are no instructions devoted to
9803 the call. @value{GDBN} still pretends that the call site and the
9804 start of the inlined function are different instructions. Stepping to
9805 the call site shows the call site, and then stepping again shows
9806 the first line of the inlined function, even though no additional
9807 instructions are executed.
9809 This makes source-level debugging much clearer; you can see both the
9810 context of the call and then the effect of the call. Only stepping by
9811 a single instruction using @code{stepi} or @code{nexti} does not do
9812 this; single instruction steps always show the inlined body.
9814 There are some ways that @value{GDBN} does not pretend that inlined
9815 function calls are the same as normal calls:
9819 You cannot set breakpoints on inlined functions. @value{GDBN}
9820 either reports that there is no symbol with that name, or else sets the
9821 breakpoint only on non-inlined copies of the function. This limitation
9822 will be removed in a future version of @value{GDBN}; until then,
9823 set a breakpoint by line number on the first line of the inlined
9827 Setting breakpoints at the call site of an inlined function may not
9828 work, because the call site does not contain any code. @value{GDBN}
9829 may incorrectly move the breakpoint to the next line of the enclosing
9830 function, after the call. This limitation will be removed in a future
9831 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9832 or inside the inlined function instead.
9835 @value{GDBN} cannot locate the return value of inlined calls after
9836 using the @code{finish} command. This is a limitation of compiler-generated
9837 debugging information; after @code{finish}, you can step to the next line
9838 and print a variable where your program stored the return value.
9842 @node Tail Call Frames
9843 @section Tail Call Frames
9844 @cindex tail call frames, debugging
9846 Function @code{B} can call function @code{C} in its very last statement. In
9847 unoptimized compilation the call of @code{C} is immediately followed by return
9848 instruction at the end of @code{B} code. Optimizing compiler may replace the
9849 call and return in function @code{B} into one jump to function @code{C}
9850 instead. Such use of a jump instruction is called @dfn{tail call}.
9852 During execution of function @code{C}, there will be no indication in the
9853 function call stack frames that it was tail-called from @code{B}. If function
9854 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9855 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9856 some cases @value{GDBN} can determine that @code{C} was tail-called from
9857 @code{B}, and it will then create fictitious call frame for that, with the
9858 return address set up as if @code{B} called @code{C} normally.
9860 This functionality is currently supported only by DWARF 2 debugging format and
9861 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9862 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9865 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9866 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9870 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9872 Stack level 1, frame at 0x7fffffffda30:
9873 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9874 tail call frame, caller of frame at 0x7fffffffda30
9875 source language c++.
9876 Arglist at unknown address.
9877 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9880 The detection of all the possible code path executions can find them ambiguous.
9881 There is no execution history stored (possible @ref{Reverse Execution} is never
9882 used for this purpose) and the last known caller could have reached the known
9883 callee by multiple different jump sequences. In such case @value{GDBN} still
9884 tries to show at least all the unambiguous top tail callers and all the
9885 unambiguous bottom tail calees, if any.
9888 @anchor{set debug entry-values}
9889 @item set debug entry-values
9890 @kindex set debug entry-values
9891 When set to on, enables printing of analysis messages for both frame argument
9892 values at function entry and tail calls. It will show all the possible valid
9893 tail calls code paths it has considered. It will also print the intersection
9894 of them with the final unambiguous (possibly partial or even empty) code path
9897 @item show debug entry-values
9898 @kindex show debug entry-values
9899 Show the current state of analysis messages printing for both frame argument
9900 values at function entry and tail calls.
9903 The analysis messages for tail calls can for example show why the virtual tail
9904 call frame for function @code{c} has not been recognized (due to the indirect
9905 reference by variable @code{x}):
9908 static void __attribute__((noinline, noclone)) c (void);
9909 void (*x) (void) = c;
9910 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9911 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9912 int main (void) @{ x (); return 0; @}
9914 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9915 DW_TAG_GNU_call_site 0x40039a in main
9917 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9920 #1 0x000000000040039a in main () at t.c:5
9923 Another possibility is an ambiguous virtual tail call frames resolution:
9927 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9928 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9929 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9930 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9931 static void __attribute__((noinline, noclone)) b (void)
9932 @{ if (i) c (); else e (); @}
9933 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9934 int main (void) @{ a (); return 0; @}
9936 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9937 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9938 tailcall: reduced: 0x4004d2(a) |
9941 #1 0x00000000004004d2 in a () at t.c:8
9942 #2 0x0000000000400395 in main () at t.c:9
9945 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9946 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9948 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9949 @ifset HAVE_MAKEINFO_CLICK
9951 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9952 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9954 @ifclear HAVE_MAKEINFO_CLICK
9956 @set CALLSEQ1B @value{CALLSEQ1A}
9957 @set CALLSEQ2B @value{CALLSEQ2A}
9960 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9961 The code can have possible execution paths @value{CALLSEQ1B} or
9962 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9964 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9965 has found. It then finds another possible calling sequcen - that one is
9966 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9967 printed as the @code{reduced:} calling sequence. That one could have many
9968 futher @code{compare:} and @code{reduced:} statements as long as there remain
9969 any non-ambiguous sequence entries.
9971 For the frame of function @code{b} in both cases there are different possible
9972 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9973 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9974 therefore this one is displayed to the user while the ambiguous frames are
9977 There can be also reasons why printing of frame argument values at function
9982 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9983 static void __attribute__((noinline, noclone)) a (int i);
9984 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9985 static void __attribute__((noinline, noclone)) a (int i)
9986 @{ if (i) b (i - 1); else c (0); @}
9987 int main (void) @{ a (5); return 0; @}
9990 #0 c (i=i@@entry=0) at t.c:2
9991 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9992 function "a" at 0x400420 can call itself via tail calls
9993 i=<optimized out>) at t.c:6
9994 #2 0x000000000040036e in main () at t.c:7
9997 @value{GDBN} cannot find out from the inferior state if and how many times did
9998 function @code{a} call itself (via function @code{b}) as these calls would be
9999 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10000 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10001 prints @code{<optimized out>} instead.
10004 @chapter C Preprocessor Macros
10006 Some languages, such as C and C@t{++}, provide a way to define and invoke
10007 ``preprocessor macros'' which expand into strings of tokens.
10008 @value{GDBN} can evaluate expressions containing macro invocations, show
10009 the result of macro expansion, and show a macro's definition, including
10010 where it was defined.
10012 You may need to compile your program specially to provide @value{GDBN}
10013 with information about preprocessor macros. Most compilers do not
10014 include macros in their debugging information, even when you compile
10015 with the @option{-g} flag. @xref{Compilation}.
10017 A program may define a macro at one point, remove that definition later,
10018 and then provide a different definition after that. Thus, at different
10019 points in the program, a macro may have different definitions, or have
10020 no definition at all. If there is a current stack frame, @value{GDBN}
10021 uses the macros in scope at that frame's source code line. Otherwise,
10022 @value{GDBN} uses the macros in scope at the current listing location;
10025 Whenever @value{GDBN} evaluates an expression, it always expands any
10026 macro invocations present in the expression. @value{GDBN} also provides
10027 the following commands for working with macros explicitly.
10031 @kindex macro expand
10032 @cindex macro expansion, showing the results of preprocessor
10033 @cindex preprocessor macro expansion, showing the results of
10034 @cindex expanding preprocessor macros
10035 @item macro expand @var{expression}
10036 @itemx macro exp @var{expression}
10037 Show the results of expanding all preprocessor macro invocations in
10038 @var{expression}. Since @value{GDBN} simply expands macros, but does
10039 not parse the result, @var{expression} need not be a valid expression;
10040 it can be any string of tokens.
10043 @item macro expand-once @var{expression}
10044 @itemx macro exp1 @var{expression}
10045 @cindex expand macro once
10046 @i{(This command is not yet implemented.)} Show the results of
10047 expanding those preprocessor macro invocations that appear explicitly in
10048 @var{expression}. Macro invocations appearing in that expansion are
10049 left unchanged. This command allows you to see the effect of a
10050 particular macro more clearly, without being confused by further
10051 expansions. Since @value{GDBN} simply expands macros, but does not
10052 parse the result, @var{expression} need not be a valid expression; it
10053 can be any string of tokens.
10056 @cindex macro definition, showing
10057 @cindex definition of a macro, showing
10058 @cindex macros, from debug info
10059 @item info macro [-a|-all] [--] @var{macro}
10060 Show the current definition or all definitions of the named @var{macro},
10061 and describe the source location or compiler command-line where that
10062 definition was established. The optional double dash is to signify the end of
10063 argument processing and the beginning of @var{macro} for non C-like macros where
10064 the macro may begin with a hyphen.
10066 @kindex info macros
10067 @item info macros @var{linespec}
10068 Show all macro definitions that are in effect at the location specified
10069 by @var{linespec}, and describe the source location or compiler
10070 command-line where those definitions were established.
10072 @kindex macro define
10073 @cindex user-defined macros
10074 @cindex defining macros interactively
10075 @cindex macros, user-defined
10076 @item macro define @var{macro} @var{replacement-list}
10077 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10078 Introduce a definition for a preprocessor macro named @var{macro},
10079 invocations of which are replaced by the tokens given in
10080 @var{replacement-list}. The first form of this command defines an
10081 ``object-like'' macro, which takes no arguments; the second form
10082 defines a ``function-like'' macro, which takes the arguments given in
10085 A definition introduced by this command is in scope in every
10086 expression evaluated in @value{GDBN}, until it is removed with the
10087 @code{macro undef} command, described below. The definition overrides
10088 all definitions for @var{macro} present in the program being debugged,
10089 as well as any previous user-supplied definition.
10091 @kindex macro undef
10092 @item macro undef @var{macro}
10093 Remove any user-supplied definition for the macro named @var{macro}.
10094 This command only affects definitions provided with the @code{macro
10095 define} command, described above; it cannot remove definitions present
10096 in the program being debugged.
10100 List all the macros defined using the @code{macro define} command.
10103 @cindex macros, example of debugging with
10104 Here is a transcript showing the above commands in action. First, we
10105 show our source files:
10110 #include "sample.h"
10113 #define ADD(x) (M + x)
10118 printf ("Hello, world!\n");
10120 printf ("We're so creative.\n");
10122 printf ("Goodbye, world!\n");
10129 Now, we compile the program using the @sc{gnu} C compiler,
10130 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10131 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10132 and @option{-gdwarf-4}; we recommend always choosing the most recent
10133 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10134 includes information about preprocessor macros in the debugging
10138 $ gcc -gdwarf-2 -g3 sample.c -o sample
10142 Now, we start @value{GDBN} on our sample program:
10146 GNU gdb 2002-05-06-cvs
10147 Copyright 2002 Free Software Foundation, Inc.
10148 GDB is free software, @dots{}
10152 We can expand macros and examine their definitions, even when the
10153 program is not running. @value{GDBN} uses the current listing position
10154 to decide which macro definitions are in scope:
10157 (@value{GDBP}) list main
10160 5 #define ADD(x) (M + x)
10165 10 printf ("Hello, world!\n");
10167 12 printf ("We're so creative.\n");
10168 (@value{GDBP}) info macro ADD
10169 Defined at /home/jimb/gdb/macros/play/sample.c:5
10170 #define ADD(x) (M + x)
10171 (@value{GDBP}) info macro Q
10172 Defined at /home/jimb/gdb/macros/play/sample.h:1
10173 included at /home/jimb/gdb/macros/play/sample.c:2
10175 (@value{GDBP}) macro expand ADD(1)
10176 expands to: (42 + 1)
10177 (@value{GDBP}) macro expand-once ADD(1)
10178 expands to: once (M + 1)
10182 In the example above, note that @code{macro expand-once} expands only
10183 the macro invocation explicit in the original text --- the invocation of
10184 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10185 which was introduced by @code{ADD}.
10187 Once the program is running, @value{GDBN} uses the macro definitions in
10188 force at the source line of the current stack frame:
10191 (@value{GDBP}) break main
10192 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10194 Starting program: /home/jimb/gdb/macros/play/sample
10196 Breakpoint 1, main () at sample.c:10
10197 10 printf ("Hello, world!\n");
10201 At line 10, the definition of the macro @code{N} at line 9 is in force:
10204 (@value{GDBP}) info macro N
10205 Defined at /home/jimb/gdb/macros/play/sample.c:9
10207 (@value{GDBP}) macro expand N Q M
10208 expands to: 28 < 42
10209 (@value{GDBP}) print N Q M
10214 As we step over directives that remove @code{N}'s definition, and then
10215 give it a new definition, @value{GDBN} finds the definition (or lack
10216 thereof) in force at each point:
10219 (@value{GDBP}) next
10221 12 printf ("We're so creative.\n");
10222 (@value{GDBP}) info macro N
10223 The symbol `N' has no definition as a C/C++ preprocessor macro
10224 at /home/jimb/gdb/macros/play/sample.c:12
10225 (@value{GDBP}) next
10227 14 printf ("Goodbye, world!\n");
10228 (@value{GDBP}) info macro N
10229 Defined at /home/jimb/gdb/macros/play/sample.c:13
10231 (@value{GDBP}) macro expand N Q M
10232 expands to: 1729 < 42
10233 (@value{GDBP}) print N Q M
10238 In addition to source files, macros can be defined on the compilation command
10239 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10240 such a way, @value{GDBN} displays the location of their definition as line zero
10241 of the source file submitted to the compiler.
10244 (@value{GDBP}) info macro __STDC__
10245 Defined at /home/jimb/gdb/macros/play/sample.c:0
10252 @chapter Tracepoints
10253 @c This chapter is based on the documentation written by Michael
10254 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10256 @cindex tracepoints
10257 In some applications, it is not feasible for the debugger to interrupt
10258 the program's execution long enough for the developer to learn
10259 anything helpful about its behavior. If the program's correctness
10260 depends on its real-time behavior, delays introduced by a debugger
10261 might cause the program to change its behavior drastically, or perhaps
10262 fail, even when the code itself is correct. It is useful to be able
10263 to observe the program's behavior without interrupting it.
10265 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10266 specify locations in the program, called @dfn{tracepoints}, and
10267 arbitrary expressions to evaluate when those tracepoints are reached.
10268 Later, using the @code{tfind} command, you can examine the values
10269 those expressions had when the program hit the tracepoints. The
10270 expressions may also denote objects in memory---structures or arrays,
10271 for example---whose values @value{GDBN} should record; while visiting
10272 a particular tracepoint, you may inspect those objects as if they were
10273 in memory at that moment. However, because @value{GDBN} records these
10274 values without interacting with you, it can do so quickly and
10275 unobtrusively, hopefully not disturbing the program's behavior.
10277 The tracepoint facility is currently available only for remote
10278 targets. @xref{Targets}. In addition, your remote target must know
10279 how to collect trace data. This functionality is implemented in the
10280 remote stub; however, none of the stubs distributed with @value{GDBN}
10281 support tracepoints as of this writing. The format of the remote
10282 packets used to implement tracepoints are described in @ref{Tracepoint
10285 It is also possible to get trace data from a file, in a manner reminiscent
10286 of corefiles; you specify the filename, and use @code{tfind} to search
10287 through the file. @xref{Trace Files}, for more details.
10289 This chapter describes the tracepoint commands and features.
10292 * Set Tracepoints::
10293 * Analyze Collected Data::
10294 * Tracepoint Variables::
10298 @node Set Tracepoints
10299 @section Commands to Set Tracepoints
10301 Before running such a @dfn{trace experiment}, an arbitrary number of
10302 tracepoints can be set. A tracepoint is actually a special type of
10303 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10304 standard breakpoint commands. For instance, as with breakpoints,
10305 tracepoint numbers are successive integers starting from one, and many
10306 of the commands associated with tracepoints take the tracepoint number
10307 as their argument, to identify which tracepoint to work on.
10309 For each tracepoint, you can specify, in advance, some arbitrary set
10310 of data that you want the target to collect in the trace buffer when
10311 it hits that tracepoint. The collected data can include registers,
10312 local variables, or global data. Later, you can use @value{GDBN}
10313 commands to examine the values these data had at the time the
10314 tracepoint was hit.
10316 Tracepoints do not support every breakpoint feature. Ignore counts on
10317 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10318 commands when they are hit. Tracepoints may not be thread-specific
10321 @cindex fast tracepoints
10322 Some targets may support @dfn{fast tracepoints}, which are inserted in
10323 a different way (such as with a jump instead of a trap), that is
10324 faster but possibly restricted in where they may be installed.
10326 @cindex static tracepoints
10327 @cindex markers, static tracepoints
10328 @cindex probing markers, static tracepoints
10329 Regular and fast tracepoints are dynamic tracing facilities, meaning
10330 that they can be used to insert tracepoints at (almost) any location
10331 in the target. Some targets may also support controlling @dfn{static
10332 tracepoints} from @value{GDBN}. With static tracing, a set of
10333 instrumentation points, also known as @dfn{markers}, are embedded in
10334 the target program, and can be activated or deactivated by name or
10335 address. These are usually placed at locations which facilitate
10336 investigating what the target is actually doing. @value{GDBN}'s
10337 support for static tracing includes being able to list instrumentation
10338 points, and attach them with @value{GDBN} defined high level
10339 tracepoints that expose the whole range of convenience of
10340 @value{GDBN}'s tracepoints support. Namely, support for collecting
10341 registers values and values of global or local (to the instrumentation
10342 point) variables; tracepoint conditions and trace state variables.
10343 The act of installing a @value{GDBN} static tracepoint on an
10344 instrumentation point, or marker, is referred to as @dfn{probing} a
10345 static tracepoint marker.
10347 @code{gdbserver} supports tracepoints on some target systems.
10348 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10350 This section describes commands to set tracepoints and associated
10351 conditions and actions.
10354 * Create and Delete Tracepoints::
10355 * Enable and Disable Tracepoints::
10356 * Tracepoint Passcounts::
10357 * Tracepoint Conditions::
10358 * Trace State Variables::
10359 * Tracepoint Actions::
10360 * Listing Tracepoints::
10361 * Listing Static Tracepoint Markers::
10362 * Starting and Stopping Trace Experiments::
10363 * Tracepoint Restrictions::
10366 @node Create and Delete Tracepoints
10367 @subsection Create and Delete Tracepoints
10370 @cindex set tracepoint
10372 @item trace @var{location}
10373 The @code{trace} command is very similar to the @code{break} command.
10374 Its argument @var{location} can be a source line, a function name, or
10375 an address in the target program. @xref{Specify Location}. The
10376 @code{trace} command defines a tracepoint, which is a point in the
10377 target program where the debugger will briefly stop, collect some
10378 data, and then allow the program to continue. Setting a tracepoint or
10379 changing its actions takes effect immediately if the remote stub
10380 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10382 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10383 these changes don't take effect until the next @code{tstart}
10384 command, and once a trace experiment is running, further changes will
10385 not have any effect until the next trace experiment starts. In addition,
10386 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10387 address is not yet resolved. (This is similar to pending breakpoints.)
10388 Pending tracepoints are not downloaded to the target and not installed
10389 until they are resolved. The resolution of pending tracepoints requires
10390 @value{GDBN} support---when debugging with the remote target, and
10391 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10392 tracing}), pending tracepoints can not be resolved (and downloaded to
10393 the remote stub) while @value{GDBN} is disconnected.
10395 Here are some examples of using the @code{trace} command:
10398 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10400 (@value{GDBP}) @b{trace +2} // 2 lines forward
10402 (@value{GDBP}) @b{trace my_function} // first source line of function
10404 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10406 (@value{GDBP}) @b{trace *0x2117c4} // an address
10410 You can abbreviate @code{trace} as @code{tr}.
10412 @item trace @var{location} if @var{cond}
10413 Set a tracepoint with condition @var{cond}; evaluate the expression
10414 @var{cond} each time the tracepoint is reached, and collect data only
10415 if the value is nonzero---that is, if @var{cond} evaluates as true.
10416 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10417 information on tracepoint conditions.
10419 @item ftrace @var{location} [ if @var{cond} ]
10420 @cindex set fast tracepoint
10421 @cindex fast tracepoints, setting
10423 The @code{ftrace} command sets a fast tracepoint. For targets that
10424 support them, fast tracepoints will use a more efficient but possibly
10425 less general technique to trigger data collection, such as a jump
10426 instruction instead of a trap, or some sort of hardware support. It
10427 may not be possible to create a fast tracepoint at the desired
10428 location, in which case the command will exit with an explanatory
10431 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10434 On 32-bit x86-architecture systems, fast tracepoints normally need to
10435 be placed at an instruction that is 5 bytes or longer, but can be
10436 placed at 4-byte instructions if the low 64K of memory of the target
10437 program is available to install trampolines. Some Unix-type systems,
10438 such as @sc{gnu}/Linux, exclude low addresses from the program's
10439 address space; but for instance with the Linux kernel it is possible
10440 to let @value{GDBN} use this area by doing a @command{sysctl} command
10441 to set the @code{mmap_min_addr} kernel parameter, as in
10444 sudo sysctl -w vm.mmap_min_addr=32768
10448 which sets the low address to 32K, which leaves plenty of room for
10449 trampolines. The minimum address should be set to a page boundary.
10451 @item strace @var{location} [ if @var{cond} ]
10452 @cindex set static tracepoint
10453 @cindex static tracepoints, setting
10454 @cindex probe static tracepoint marker
10456 The @code{strace} command sets a static tracepoint. For targets that
10457 support it, setting a static tracepoint probes a static
10458 instrumentation point, or marker, found at @var{location}. It may not
10459 be possible to set a static tracepoint at the desired location, in
10460 which case the command will exit with an explanatory message.
10462 @value{GDBN} handles arguments to @code{strace} exactly as for
10463 @code{trace}, with the addition that the user can also specify
10464 @code{-m @var{marker}} as @var{location}. This probes the marker
10465 identified by the @var{marker} string identifier. This identifier
10466 depends on the static tracepoint backend library your program is
10467 using. You can find all the marker identifiers in the @samp{ID} field
10468 of the @code{info static-tracepoint-markers} command output.
10469 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10470 Markers}. For example, in the following small program using the UST
10476 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10481 the marker id is composed of joining the first two arguments to the
10482 @code{trace_mark} call with a slash, which translates to:
10485 (@value{GDBP}) info static-tracepoint-markers
10486 Cnt Enb ID Address What
10487 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10493 so you may probe the marker above with:
10496 (@value{GDBP}) strace -m ust/bar33
10499 Static tracepoints accept an extra collect action --- @code{collect
10500 $_sdata}. This collects arbitrary user data passed in the probe point
10501 call to the tracing library. In the UST example above, you'll see
10502 that the third argument to @code{trace_mark} is a printf-like format
10503 string. The user data is then the result of running that formating
10504 string against the following arguments. Note that @code{info
10505 static-tracepoint-markers} command output lists that format string in
10506 the @samp{Data:} field.
10508 You can inspect this data when analyzing the trace buffer, by printing
10509 the $_sdata variable like any other variable available to
10510 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10513 @cindex last tracepoint number
10514 @cindex recent tracepoint number
10515 @cindex tracepoint number
10516 The convenience variable @code{$tpnum} records the tracepoint number
10517 of the most recently set tracepoint.
10519 @kindex delete tracepoint
10520 @cindex tracepoint deletion
10521 @item delete tracepoint @r{[}@var{num}@r{]}
10522 Permanently delete one or more tracepoints. With no argument, the
10523 default is to delete all tracepoints. Note that the regular
10524 @code{delete} command can remove tracepoints also.
10529 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10531 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10535 You can abbreviate this command as @code{del tr}.
10538 @node Enable and Disable Tracepoints
10539 @subsection Enable and Disable Tracepoints
10541 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10544 @kindex disable tracepoint
10545 @item disable tracepoint @r{[}@var{num}@r{]}
10546 Disable tracepoint @var{num}, or all tracepoints if no argument
10547 @var{num} is given. A disabled tracepoint will have no effect during
10548 a trace experiment, but it is not forgotten. You can re-enable
10549 a disabled tracepoint using the @code{enable tracepoint} command.
10550 If the command is issued during a trace experiment and the debug target
10551 has support for disabling tracepoints during a trace experiment, then the
10552 change will be effective immediately. Otherwise, it will be applied to the
10553 next trace experiment.
10555 @kindex enable tracepoint
10556 @item enable tracepoint @r{[}@var{num}@r{]}
10557 Enable tracepoint @var{num}, or all tracepoints. If this command is
10558 issued during a trace experiment and the debug target supports enabling
10559 tracepoints during a trace experiment, then the enabled tracepoints will
10560 become effective immediately. Otherwise, they will become effective the
10561 next time a trace experiment is run.
10564 @node Tracepoint Passcounts
10565 @subsection Tracepoint Passcounts
10569 @cindex tracepoint pass count
10570 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10571 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10572 automatically stop a trace experiment. If a tracepoint's passcount is
10573 @var{n}, then the trace experiment will be automatically stopped on
10574 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10575 @var{num} is not specified, the @code{passcount} command sets the
10576 passcount of the most recently defined tracepoint. If no passcount is
10577 given, the trace experiment will run until stopped explicitly by the
10583 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10584 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10586 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10587 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10588 (@value{GDBP}) @b{trace foo}
10589 (@value{GDBP}) @b{pass 3}
10590 (@value{GDBP}) @b{trace bar}
10591 (@value{GDBP}) @b{pass 2}
10592 (@value{GDBP}) @b{trace baz}
10593 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10594 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10595 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10596 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10600 @node Tracepoint Conditions
10601 @subsection Tracepoint Conditions
10602 @cindex conditional tracepoints
10603 @cindex tracepoint conditions
10605 The simplest sort of tracepoint collects data every time your program
10606 reaches a specified place. You can also specify a @dfn{condition} for
10607 a tracepoint. A condition is just a Boolean expression in your
10608 programming language (@pxref{Expressions, ,Expressions}). A
10609 tracepoint with a condition evaluates the expression each time your
10610 program reaches it, and data collection happens only if the condition
10613 Tracepoint conditions can be specified when a tracepoint is set, by
10614 using @samp{if} in the arguments to the @code{trace} command.
10615 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10616 also be set or changed at any time with the @code{condition} command,
10617 just as with breakpoints.
10619 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10620 the conditional expression itself. Instead, @value{GDBN} encodes the
10621 expression into an agent expression (@pxref{Agent Expressions})
10622 suitable for execution on the target, independently of @value{GDBN}.
10623 Global variables become raw memory locations, locals become stack
10624 accesses, and so forth.
10626 For instance, suppose you have a function that is usually called
10627 frequently, but should not be called after an error has occurred. You
10628 could use the following tracepoint command to collect data about calls
10629 of that function that happen while the error code is propagating
10630 through the program; an unconditional tracepoint could end up
10631 collecting thousands of useless trace frames that you would have to
10635 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10638 @node Trace State Variables
10639 @subsection Trace State Variables
10640 @cindex trace state variables
10642 A @dfn{trace state variable} is a special type of variable that is
10643 created and managed by target-side code. The syntax is the same as
10644 that for GDB's convenience variables (a string prefixed with ``$''),
10645 but they are stored on the target. They must be created explicitly,
10646 using a @code{tvariable} command. They are always 64-bit signed
10649 Trace state variables are remembered by @value{GDBN}, and downloaded
10650 to the target along with tracepoint information when the trace
10651 experiment starts. There are no intrinsic limits on the number of
10652 trace state variables, beyond memory limitations of the target.
10654 @cindex convenience variables, and trace state variables
10655 Although trace state variables are managed by the target, you can use
10656 them in print commands and expressions as if they were convenience
10657 variables; @value{GDBN} will get the current value from the target
10658 while the trace experiment is running. Trace state variables share
10659 the same namespace as other ``$'' variables, which means that you
10660 cannot have trace state variables with names like @code{$23} or
10661 @code{$pc}, nor can you have a trace state variable and a convenience
10662 variable with the same name.
10666 @item tvariable $@var{name} [ = @var{expression} ]
10668 The @code{tvariable} command creates a new trace state variable named
10669 @code{$@var{name}}, and optionally gives it an initial value of
10670 @var{expression}. @var{expression} is evaluated when this command is
10671 entered; the result will be converted to an integer if possible,
10672 otherwise @value{GDBN} will report an error. A subsequent
10673 @code{tvariable} command specifying the same name does not create a
10674 variable, but instead assigns the supplied initial value to the
10675 existing variable of that name, overwriting any previous initial
10676 value. The default initial value is 0.
10678 @item info tvariables
10679 @kindex info tvariables
10680 List all the trace state variables along with their initial values.
10681 Their current values may also be displayed, if the trace experiment is
10684 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10685 @kindex delete tvariable
10686 Delete the given trace state variables, or all of them if no arguments
10691 @node Tracepoint Actions
10692 @subsection Tracepoint Action Lists
10696 @cindex tracepoint actions
10697 @item actions @r{[}@var{num}@r{]}
10698 This command will prompt for a list of actions to be taken when the
10699 tracepoint is hit. If the tracepoint number @var{num} is not
10700 specified, this command sets the actions for the one that was most
10701 recently defined (so that you can define a tracepoint and then say
10702 @code{actions} without bothering about its number). You specify the
10703 actions themselves on the following lines, one action at a time, and
10704 terminate the actions list with a line containing just @code{end}. So
10705 far, the only defined actions are @code{collect}, @code{teval}, and
10706 @code{while-stepping}.
10708 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10709 Commands, ,Breakpoint Command Lists}), except that only the defined
10710 actions are allowed; any other @value{GDBN} command is rejected.
10712 @cindex remove actions from a tracepoint
10713 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10714 and follow it immediately with @samp{end}.
10717 (@value{GDBP}) @b{collect @var{data}} // collect some data
10719 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10721 (@value{GDBP}) @b{end} // signals the end of actions.
10724 In the following example, the action list begins with @code{collect}
10725 commands indicating the things to be collected when the tracepoint is
10726 hit. Then, in order to single-step and collect additional data
10727 following the tracepoint, a @code{while-stepping} command is used,
10728 followed by the list of things to be collected after each step in a
10729 sequence of single steps. The @code{while-stepping} command is
10730 terminated by its own separate @code{end} command. Lastly, the action
10731 list is terminated by an @code{end} command.
10734 (@value{GDBP}) @b{trace foo}
10735 (@value{GDBP}) @b{actions}
10736 Enter actions for tracepoint 1, one per line:
10739 > while-stepping 12
10740 > collect $pc, arr[i]
10745 @kindex collect @r{(tracepoints)}
10746 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10747 Collect values of the given expressions when the tracepoint is hit.
10748 This command accepts a comma-separated list of any valid expressions.
10749 In addition to global, static, or local variables, the following
10750 special arguments are supported:
10754 Collect all registers.
10757 Collect all function arguments.
10760 Collect all local variables.
10763 Collect the return address. This is helpful if you want to see more
10767 @vindex $_sdata@r{, collect}
10768 Collect static tracepoint marker specific data. Only available for
10769 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10770 Lists}. On the UST static tracepoints library backend, an
10771 instrumentation point resembles a @code{printf} function call. The
10772 tracing library is able to collect user specified data formatted to a
10773 character string using the format provided by the programmer that
10774 instrumented the program. Other backends have similar mechanisms.
10775 Here's an example of a UST marker call:
10778 const char master_name[] = "$your_name";
10779 trace_mark(channel1, marker1, "hello %s", master_name)
10782 In this case, collecting @code{$_sdata} collects the string
10783 @samp{hello $yourname}. When analyzing the trace buffer, you can
10784 inspect @samp{$_sdata} like any other variable available to
10788 You can give several consecutive @code{collect} commands, each one
10789 with a single argument, or one @code{collect} command with several
10790 arguments separated by commas; the effect is the same.
10792 The optional @var{mods} changes the usual handling of the arguments.
10793 @code{s} requests that pointers to chars be handled as strings, in
10794 particular collecting the contents of the memory being pointed at, up
10795 to the first zero. The upper bound is by default the value of the
10796 @code{print elements} variable; if @code{s} is followed by a decimal
10797 number, that is the upper bound instead. So for instance
10798 @samp{collect/s25 mystr} collects as many as 25 characters at
10801 The command @code{info scope} (@pxref{Symbols, info scope}) is
10802 particularly useful for figuring out what data to collect.
10804 @kindex teval @r{(tracepoints)}
10805 @item teval @var{expr1}, @var{expr2}, @dots{}
10806 Evaluate the given expressions when the tracepoint is hit. This
10807 command accepts a comma-separated list of expressions. The results
10808 are discarded, so this is mainly useful for assigning values to trace
10809 state variables (@pxref{Trace State Variables}) without adding those
10810 values to the trace buffer, as would be the case if the @code{collect}
10813 @kindex while-stepping @r{(tracepoints)}
10814 @item while-stepping @var{n}
10815 Perform @var{n} single-step instruction traces after the tracepoint,
10816 collecting new data after each step. The @code{while-stepping}
10817 command is followed by the list of what to collect while stepping
10818 (followed by its own @code{end} command):
10821 > while-stepping 12
10822 > collect $regs, myglobal
10828 Note that @code{$pc} is not automatically collected by
10829 @code{while-stepping}; you need to explicitly collect that register if
10830 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10833 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10834 @kindex set default-collect
10835 @cindex default collection action
10836 This variable is a list of expressions to collect at each tracepoint
10837 hit. It is effectively an additional @code{collect} action prepended
10838 to every tracepoint action list. The expressions are parsed
10839 individually for each tracepoint, so for instance a variable named
10840 @code{xyz} may be interpreted as a global for one tracepoint, and a
10841 local for another, as appropriate to the tracepoint's location.
10843 @item show default-collect
10844 @kindex show default-collect
10845 Show the list of expressions that are collected by default at each
10850 @node Listing Tracepoints
10851 @subsection Listing Tracepoints
10854 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10855 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10856 @cindex information about tracepoints
10857 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10858 Display information about the tracepoint @var{num}. If you don't
10859 specify a tracepoint number, displays information about all the
10860 tracepoints defined so far. The format is similar to that used for
10861 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10862 command, simply restricting itself to tracepoints.
10864 A tracepoint's listing may include additional information specific to
10869 its passcount as given by the @code{passcount @var{n}} command
10873 (@value{GDBP}) @b{info trace}
10874 Num Type Disp Enb Address What
10875 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10877 collect globfoo, $regs
10886 This command can be abbreviated @code{info tp}.
10889 @node Listing Static Tracepoint Markers
10890 @subsection Listing Static Tracepoint Markers
10893 @kindex info static-tracepoint-markers
10894 @cindex information about static tracepoint markers
10895 @item info static-tracepoint-markers
10896 Display information about all static tracepoint markers defined in the
10899 For each marker, the following columns are printed:
10903 An incrementing counter, output to help readability. This is not a
10906 The marker ID, as reported by the target.
10907 @item Enabled or Disabled
10908 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10909 that are not enabled.
10911 Where the marker is in your program, as a memory address.
10913 Where the marker is in the source for your program, as a file and line
10914 number. If the debug information included in the program does not
10915 allow @value{GDBN} to locate the source of the marker, this column
10916 will be left blank.
10920 In addition, the following information may be printed for each marker:
10924 User data passed to the tracing library by the marker call. In the
10925 UST backend, this is the format string passed as argument to the
10927 @item Static tracepoints probing the marker
10928 The list of static tracepoints attached to the marker.
10932 (@value{GDBP}) info static-tracepoint-markers
10933 Cnt ID Enb Address What
10934 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10935 Data: number1 %d number2 %d
10936 Probed by static tracepoints: #2
10937 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10943 @node Starting and Stopping Trace Experiments
10944 @subsection Starting and Stopping Trace Experiments
10947 @kindex tstart [ @var{notes} ]
10948 @cindex start a new trace experiment
10949 @cindex collected data discarded
10951 This command starts the trace experiment, and begins collecting data.
10952 It has the side effect of discarding all the data collected in the
10953 trace buffer during the previous trace experiment. If any arguments
10954 are supplied, they are taken as a note and stored with the trace
10955 experiment's state. The notes may be arbitrary text, and are
10956 especially useful with disconnected tracing in a multi-user context;
10957 the notes can explain what the trace is doing, supply user contact
10958 information, and so forth.
10960 @kindex tstop [ @var{notes} ]
10961 @cindex stop a running trace experiment
10963 This command stops the trace experiment. If any arguments are
10964 supplied, they are recorded with the experiment as a note. This is
10965 useful if you are stopping a trace started by someone else, for
10966 instance if the trace is interfering with the system's behavior and
10967 needs to be stopped quickly.
10969 @strong{Note}: a trace experiment and data collection may stop
10970 automatically if any tracepoint's passcount is reached
10971 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10974 @cindex status of trace data collection
10975 @cindex trace experiment, status of
10977 This command displays the status of the current trace data
10981 Here is an example of the commands we described so far:
10984 (@value{GDBP}) @b{trace gdb_c_test}
10985 (@value{GDBP}) @b{actions}
10986 Enter actions for tracepoint #1, one per line.
10987 > collect $regs,$locals,$args
10988 > while-stepping 11
10992 (@value{GDBP}) @b{tstart}
10993 [time passes @dots{}]
10994 (@value{GDBP}) @b{tstop}
10997 @anchor{disconnected tracing}
10998 @cindex disconnected tracing
10999 You can choose to continue running the trace experiment even if
11000 @value{GDBN} disconnects from the target, voluntarily or
11001 involuntarily. For commands such as @code{detach}, the debugger will
11002 ask what you want to do with the trace. But for unexpected
11003 terminations (@value{GDBN} crash, network outage), it would be
11004 unfortunate to lose hard-won trace data, so the variable
11005 @code{disconnected-tracing} lets you decide whether the trace should
11006 continue running without @value{GDBN}.
11009 @item set disconnected-tracing on
11010 @itemx set disconnected-tracing off
11011 @kindex set disconnected-tracing
11012 Choose whether a tracing run should continue to run if @value{GDBN}
11013 has disconnected from the target. Note that @code{detach} or
11014 @code{quit} will ask you directly what to do about a running trace no
11015 matter what this variable's setting, so the variable is mainly useful
11016 for handling unexpected situations, such as loss of the network.
11018 @item show disconnected-tracing
11019 @kindex show disconnected-tracing
11020 Show the current choice for disconnected tracing.
11024 When you reconnect to the target, the trace experiment may or may not
11025 still be running; it might have filled the trace buffer in the
11026 meantime, or stopped for one of the other reasons. If it is running,
11027 it will continue after reconnection.
11029 Upon reconnection, the target will upload information about the
11030 tracepoints in effect. @value{GDBN} will then compare that
11031 information to the set of tracepoints currently defined, and attempt
11032 to match them up, allowing for the possibility that the numbers may
11033 have changed due to creation and deletion in the meantime. If one of
11034 the target's tracepoints does not match any in @value{GDBN}, the
11035 debugger will create a new tracepoint, so that you have a number with
11036 which to specify that tracepoint. This matching-up process is
11037 necessarily heuristic, and it may result in useless tracepoints being
11038 created; you may simply delete them if they are of no use.
11040 @cindex circular trace buffer
11041 If your target agent supports a @dfn{circular trace buffer}, then you
11042 can run a trace experiment indefinitely without filling the trace
11043 buffer; when space runs out, the agent deletes already-collected trace
11044 frames, oldest first, until there is enough room to continue
11045 collecting. This is especially useful if your tracepoints are being
11046 hit too often, and your trace gets terminated prematurely because the
11047 buffer is full. To ask for a circular trace buffer, simply set
11048 @samp{circular-trace-buffer} to on. You can set this at any time,
11049 including during tracing; if the agent can do it, it will change
11050 buffer handling on the fly, otherwise it will not take effect until
11054 @item set circular-trace-buffer on
11055 @itemx set circular-trace-buffer off
11056 @kindex set circular-trace-buffer
11057 Choose whether a tracing run should use a linear or circular buffer
11058 for trace data. A linear buffer will not lose any trace data, but may
11059 fill up prematurely, while a circular buffer will discard old trace
11060 data, but it will have always room for the latest tracepoint hits.
11062 @item show circular-trace-buffer
11063 @kindex show circular-trace-buffer
11064 Show the current choice for the trace buffer. Note that this may not
11065 match the agent's current buffer handling, nor is it guaranteed to
11066 match the setting that might have been in effect during a past run,
11067 for instance if you are looking at frames from a trace file.
11072 @item set trace-user @var{text}
11073 @kindex set trace-user
11075 @item show trace-user
11076 @kindex show trace-user
11078 @item set trace-notes @var{text}
11079 @kindex set trace-notes
11080 Set the trace run's notes.
11082 @item show trace-notes
11083 @kindex show trace-notes
11084 Show the trace run's notes.
11086 @item set trace-stop-notes @var{text}
11087 @kindex set trace-stop-notes
11088 Set the trace run's stop notes. The handling of the note is as for
11089 @code{tstop} arguments; the set command is convenient way to fix a
11090 stop note that is mistaken or incomplete.
11092 @item show trace-stop-notes
11093 @kindex show trace-stop-notes
11094 Show the trace run's stop notes.
11098 @node Tracepoint Restrictions
11099 @subsection Tracepoint Restrictions
11101 @cindex tracepoint restrictions
11102 There are a number of restrictions on the use of tracepoints. As
11103 described above, tracepoint data gathering occurs on the target
11104 without interaction from @value{GDBN}. Thus the full capabilities of
11105 the debugger are not available during data gathering, and then at data
11106 examination time, you will be limited by only having what was
11107 collected. The following items describe some common problems, but it
11108 is not exhaustive, and you may run into additional difficulties not
11114 Tracepoint expressions are intended to gather objects (lvalues). Thus
11115 the full flexibility of GDB's expression evaluator is not available.
11116 You cannot call functions, cast objects to aggregate types, access
11117 convenience variables or modify values (except by assignment to trace
11118 state variables). Some language features may implicitly call
11119 functions (for instance Objective-C fields with accessors), and therefore
11120 cannot be collected either.
11123 Collection of local variables, either individually or in bulk with
11124 @code{$locals} or @code{$args}, during @code{while-stepping} may
11125 behave erratically. The stepping action may enter a new scope (for
11126 instance by stepping into a function), or the location of the variable
11127 may change (for instance it is loaded into a register). The
11128 tracepoint data recorded uses the location information for the
11129 variables that is correct for the tracepoint location. When the
11130 tracepoint is created, it is not possible, in general, to determine
11131 where the steps of a @code{while-stepping} sequence will advance the
11132 program---particularly if a conditional branch is stepped.
11135 Collection of an incompletely-initialized or partially-destroyed object
11136 may result in something that @value{GDBN} cannot display, or displays
11137 in a misleading way.
11140 When @value{GDBN} displays a pointer to character it automatically
11141 dereferences the pointer to also display characters of the string
11142 being pointed to. However, collecting the pointer during tracing does
11143 not automatically collect the string. You need to explicitly
11144 dereference the pointer and provide size information if you want to
11145 collect not only the pointer, but the memory pointed to. For example,
11146 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11150 It is not possible to collect a complete stack backtrace at a
11151 tracepoint. Instead, you may collect the registers and a few hundred
11152 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11153 (adjust to use the name of the actual stack pointer register on your
11154 target architecture, and the amount of stack you wish to capture).
11155 Then the @code{backtrace} command will show a partial backtrace when
11156 using a trace frame. The number of stack frames that can be examined
11157 depends on the sizes of the frames in the collected stack. Note that
11158 if you ask for a block so large that it goes past the bottom of the
11159 stack, the target agent may report an error trying to read from an
11163 If you do not collect registers at a tracepoint, @value{GDBN} can
11164 infer that the value of @code{$pc} must be the same as the address of
11165 the tracepoint and use that when you are looking at a trace frame
11166 for that tracepoint. However, this cannot work if the tracepoint has
11167 multiple locations (for instance if it was set in a function that was
11168 inlined), or if it has a @code{while-stepping} loop. In those cases
11169 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11174 @node Analyze Collected Data
11175 @section Using the Collected Data
11177 After the tracepoint experiment ends, you use @value{GDBN} commands
11178 for examining the trace data. The basic idea is that each tracepoint
11179 collects a trace @dfn{snapshot} every time it is hit and another
11180 snapshot every time it single-steps. All these snapshots are
11181 consecutively numbered from zero and go into a buffer, and you can
11182 examine them later. The way you examine them is to @dfn{focus} on a
11183 specific trace snapshot. When the remote stub is focused on a trace
11184 snapshot, it will respond to all @value{GDBN} requests for memory and
11185 registers by reading from the buffer which belongs to that snapshot,
11186 rather than from @emph{real} memory or registers of the program being
11187 debugged. This means that @strong{all} @value{GDBN} commands
11188 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11189 behave as if we were currently debugging the program state as it was
11190 when the tracepoint occurred. Any requests for data that are not in
11191 the buffer will fail.
11194 * tfind:: How to select a trace snapshot
11195 * tdump:: How to display all data for a snapshot
11196 * save tracepoints:: How to save tracepoints for a future run
11200 @subsection @code{tfind @var{n}}
11203 @cindex select trace snapshot
11204 @cindex find trace snapshot
11205 The basic command for selecting a trace snapshot from the buffer is
11206 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11207 counting from zero. If no argument @var{n} is given, the next
11208 snapshot is selected.
11210 Here are the various forms of using the @code{tfind} command.
11214 Find the first snapshot in the buffer. This is a synonym for
11215 @code{tfind 0} (since 0 is the number of the first snapshot).
11218 Stop debugging trace snapshots, resume @emph{live} debugging.
11221 Same as @samp{tfind none}.
11224 No argument means find the next trace snapshot.
11227 Find the previous trace snapshot before the current one. This permits
11228 retracing earlier steps.
11230 @item tfind tracepoint @var{num}
11231 Find the next snapshot associated with tracepoint @var{num}. Search
11232 proceeds forward from the last examined trace snapshot. If no
11233 argument @var{num} is given, it means find the next snapshot collected
11234 for the same tracepoint as the current snapshot.
11236 @item tfind pc @var{addr}
11237 Find the next snapshot associated with the value @var{addr} of the
11238 program counter. Search proceeds forward from the last examined trace
11239 snapshot. If no argument @var{addr} is given, it means find the next
11240 snapshot with the same value of PC as the current snapshot.
11242 @item tfind outside @var{addr1}, @var{addr2}
11243 Find the next snapshot whose PC is outside the given range of
11244 addresses (exclusive).
11246 @item tfind range @var{addr1}, @var{addr2}
11247 Find the next snapshot whose PC is between @var{addr1} and
11248 @var{addr2} (inclusive).
11250 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11251 Find the next snapshot associated with the source line @var{n}. If
11252 the optional argument @var{file} is given, refer to line @var{n} in
11253 that source file. Search proceeds forward from the last examined
11254 trace snapshot. If no argument @var{n} is given, it means find the
11255 next line other than the one currently being examined; thus saying
11256 @code{tfind line} repeatedly can appear to have the same effect as
11257 stepping from line to line in a @emph{live} debugging session.
11260 The default arguments for the @code{tfind} commands are specifically
11261 designed to make it easy to scan through the trace buffer. For
11262 instance, @code{tfind} with no argument selects the next trace
11263 snapshot, and @code{tfind -} with no argument selects the previous
11264 trace snapshot. So, by giving one @code{tfind} command, and then
11265 simply hitting @key{RET} repeatedly you can examine all the trace
11266 snapshots in order. Or, by saying @code{tfind -} and then hitting
11267 @key{RET} repeatedly you can examine the snapshots in reverse order.
11268 The @code{tfind line} command with no argument selects the snapshot
11269 for the next source line executed. The @code{tfind pc} command with
11270 no argument selects the next snapshot with the same program counter
11271 (PC) as the current frame. The @code{tfind tracepoint} command with
11272 no argument selects the next trace snapshot collected by the same
11273 tracepoint as the current one.
11275 In addition to letting you scan through the trace buffer manually,
11276 these commands make it easy to construct @value{GDBN} scripts that
11277 scan through the trace buffer and print out whatever collected data
11278 you are interested in. Thus, if we want to examine the PC, FP, and SP
11279 registers from each trace frame in the buffer, we can say this:
11282 (@value{GDBP}) @b{tfind start}
11283 (@value{GDBP}) @b{while ($trace_frame != -1)}
11284 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11285 $trace_frame, $pc, $sp, $fp
11289 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11290 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11291 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11292 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11293 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11294 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11295 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11296 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11297 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11298 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11299 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11302 Or, if we want to examine the variable @code{X} at each source line in
11306 (@value{GDBP}) @b{tfind start}
11307 (@value{GDBP}) @b{while ($trace_frame != -1)}
11308 > printf "Frame %d, X == %d\n", $trace_frame, X
11318 @subsection @code{tdump}
11320 @cindex dump all data collected at tracepoint
11321 @cindex tracepoint data, display
11323 This command takes no arguments. It prints all the data collected at
11324 the current trace snapshot.
11327 (@value{GDBP}) @b{trace 444}
11328 (@value{GDBP}) @b{actions}
11329 Enter actions for tracepoint #2, one per line:
11330 > collect $regs, $locals, $args, gdb_long_test
11333 (@value{GDBP}) @b{tstart}
11335 (@value{GDBP}) @b{tfind line 444}
11336 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11338 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11340 (@value{GDBP}) @b{tdump}
11341 Data collected at tracepoint 2, trace frame 1:
11342 d0 0xc4aa0085 -995491707
11346 d4 0x71aea3d 119204413
11349 d7 0x380035 3670069
11350 a0 0x19e24a 1696330
11351 a1 0x3000668 50333288
11353 a3 0x322000 3284992
11354 a4 0x3000698 50333336
11355 a5 0x1ad3cc 1758156
11356 fp 0x30bf3c 0x30bf3c
11357 sp 0x30bf34 0x30bf34
11359 pc 0x20b2c8 0x20b2c8
11363 p = 0x20e5b4 "gdb-test"
11370 gdb_long_test = 17 '\021'
11375 @code{tdump} works by scanning the tracepoint's current collection
11376 actions and printing the value of each expression listed. So
11377 @code{tdump} can fail, if after a run, you change the tracepoint's
11378 actions to mention variables that were not collected during the run.
11380 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11381 uses the collected value of @code{$pc} to distinguish between trace
11382 frames that were collected at the tracepoint hit, and frames that were
11383 collected while stepping. This allows it to correctly choose whether
11384 to display the basic list of collections, or the collections from the
11385 body of the while-stepping loop. However, if @code{$pc} was not collected,
11386 then @code{tdump} will always attempt to dump using the basic collection
11387 list, and may fail if a while-stepping frame does not include all the
11388 same data that is collected at the tracepoint hit.
11389 @c This is getting pretty arcane, example would be good.
11391 @node save tracepoints
11392 @subsection @code{save tracepoints @var{filename}}
11393 @kindex save tracepoints
11394 @kindex save-tracepoints
11395 @cindex save tracepoints for future sessions
11397 This command saves all current tracepoint definitions together with
11398 their actions and passcounts, into a file @file{@var{filename}}
11399 suitable for use in a later debugging session. To read the saved
11400 tracepoint definitions, use the @code{source} command (@pxref{Command
11401 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11402 alias for @w{@code{save tracepoints}}
11404 @node Tracepoint Variables
11405 @section Convenience Variables for Tracepoints
11406 @cindex tracepoint variables
11407 @cindex convenience variables for tracepoints
11410 @vindex $trace_frame
11411 @item (int) $trace_frame
11412 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11413 snapshot is selected.
11415 @vindex $tracepoint
11416 @item (int) $tracepoint
11417 The tracepoint for the current trace snapshot.
11419 @vindex $trace_line
11420 @item (int) $trace_line
11421 The line number for the current trace snapshot.
11423 @vindex $trace_file
11424 @item (char []) $trace_file
11425 The source file for the current trace snapshot.
11427 @vindex $trace_func
11428 @item (char []) $trace_func
11429 The name of the function containing @code{$tracepoint}.
11432 Note: @code{$trace_file} is not suitable for use in @code{printf},
11433 use @code{output} instead.
11435 Here's a simple example of using these convenience variables for
11436 stepping through all the trace snapshots and printing some of their
11437 data. Note that these are not the same as trace state variables,
11438 which are managed by the target.
11441 (@value{GDBP}) @b{tfind start}
11443 (@value{GDBP}) @b{while $trace_frame != -1}
11444 > output $trace_file
11445 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11451 @section Using Trace Files
11452 @cindex trace files
11454 In some situations, the target running a trace experiment may no
11455 longer be available; perhaps it crashed, or the hardware was needed
11456 for a different activity. To handle these cases, you can arrange to
11457 dump the trace data into a file, and later use that file as a source
11458 of trace data, via the @code{target tfile} command.
11463 @item tsave [ -r ] @var{filename}
11464 Save the trace data to @var{filename}. By default, this command
11465 assumes that @var{filename} refers to the host filesystem, so if
11466 necessary @value{GDBN} will copy raw trace data up from the target and
11467 then save it. If the target supports it, you can also supply the
11468 optional argument @code{-r} (``remote'') to direct the target to save
11469 the data directly into @var{filename} in its own filesystem, which may be
11470 more efficient if the trace buffer is very large. (Note, however, that
11471 @code{target tfile} can only read from files accessible to the host.)
11473 @kindex target tfile
11475 @item target tfile @var{filename}
11476 Use the file named @var{filename} as a source of trace data. Commands
11477 that examine data work as they do with a live target, but it is not
11478 possible to run any new trace experiments. @code{tstatus} will report
11479 the state of the trace run at the moment the data was saved, as well
11480 as the current trace frame you are examining. @var{filename} must be
11481 on a filesystem accessible to the host.
11486 @chapter Debugging Programs That Use Overlays
11489 If your program is too large to fit completely in your target system's
11490 memory, you can sometimes use @dfn{overlays} to work around this
11491 problem. @value{GDBN} provides some support for debugging programs that
11495 * How Overlays Work:: A general explanation of overlays.
11496 * Overlay Commands:: Managing overlays in @value{GDBN}.
11497 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11498 mapped by asking the inferior.
11499 * Overlay Sample Program:: A sample program using overlays.
11502 @node How Overlays Work
11503 @section How Overlays Work
11504 @cindex mapped overlays
11505 @cindex unmapped overlays
11506 @cindex load address, overlay's
11507 @cindex mapped address
11508 @cindex overlay area
11510 Suppose you have a computer whose instruction address space is only 64
11511 kilobytes long, but which has much more memory which can be accessed by
11512 other means: special instructions, segment registers, or memory
11513 management hardware, for example. Suppose further that you want to
11514 adapt a program which is larger than 64 kilobytes to run on this system.
11516 One solution is to identify modules of your program which are relatively
11517 independent, and need not call each other directly; call these modules
11518 @dfn{overlays}. Separate the overlays from the main program, and place
11519 their machine code in the larger memory. Place your main program in
11520 instruction memory, but leave at least enough space there to hold the
11521 largest overlay as well.
11523 Now, to call a function located in an overlay, you must first copy that
11524 overlay's machine code from the large memory into the space set aside
11525 for it in the instruction memory, and then jump to its entry point
11528 @c NB: In the below the mapped area's size is greater or equal to the
11529 @c size of all overlays. This is intentional to remind the developer
11530 @c that overlays don't necessarily need to be the same size.
11534 Data Instruction Larger
11535 Address Space Address Space Address Space
11536 +-----------+ +-----------+ +-----------+
11538 +-----------+ +-----------+ +-----------+<-- overlay 1
11539 | program | | main | .----| overlay 1 | load address
11540 | variables | | program | | +-----------+
11541 | and heap | | | | | |
11542 +-----------+ | | | +-----------+<-- overlay 2
11543 | | +-----------+ | | | load address
11544 +-----------+ | | | .-| overlay 2 |
11546 mapped --->+-----------+ | | +-----------+
11547 address | | | | | |
11548 | overlay | <-' | | |
11549 | area | <---' +-----------+<-- overlay 3
11550 | | <---. | | load address
11551 +-----------+ `--| overlay 3 |
11558 @anchor{A code overlay}A code overlay
11562 The diagram (@pxref{A code overlay}) shows a system with separate data
11563 and instruction address spaces. To map an overlay, the program copies
11564 its code from the larger address space to the instruction address space.
11565 Since the overlays shown here all use the same mapped address, only one
11566 may be mapped at a time. For a system with a single address space for
11567 data and instructions, the diagram would be similar, except that the
11568 program variables and heap would share an address space with the main
11569 program and the overlay area.
11571 An overlay loaded into instruction memory and ready for use is called a
11572 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11573 instruction memory. An overlay not present (or only partially present)
11574 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11575 is its address in the larger memory. The mapped address is also called
11576 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11577 called the @dfn{load memory address}, or @dfn{LMA}.
11579 Unfortunately, overlays are not a completely transparent way to adapt a
11580 program to limited instruction memory. They introduce a new set of
11581 global constraints you must keep in mind as you design your program:
11586 Before calling or returning to a function in an overlay, your program
11587 must make sure that overlay is actually mapped. Otherwise, the call or
11588 return will transfer control to the right address, but in the wrong
11589 overlay, and your program will probably crash.
11592 If the process of mapping an overlay is expensive on your system, you
11593 will need to choose your overlays carefully to minimize their effect on
11594 your program's performance.
11597 The executable file you load onto your system must contain each
11598 overlay's instructions, appearing at the overlay's load address, not its
11599 mapped address. However, each overlay's instructions must be relocated
11600 and its symbols defined as if the overlay were at its mapped address.
11601 You can use GNU linker scripts to specify different load and relocation
11602 addresses for pieces of your program; see @ref{Overlay Description,,,
11603 ld.info, Using ld: the GNU linker}.
11606 The procedure for loading executable files onto your system must be able
11607 to load their contents into the larger address space as well as the
11608 instruction and data spaces.
11612 The overlay system described above is rather simple, and could be
11613 improved in many ways:
11618 If your system has suitable bank switch registers or memory management
11619 hardware, you could use those facilities to make an overlay's load area
11620 contents simply appear at their mapped address in instruction space.
11621 This would probably be faster than copying the overlay to its mapped
11622 area in the usual way.
11625 If your overlays are small enough, you could set aside more than one
11626 overlay area, and have more than one overlay mapped at a time.
11629 You can use overlays to manage data, as well as instructions. In
11630 general, data overlays are even less transparent to your design than
11631 code overlays: whereas code overlays only require care when you call or
11632 return to functions, data overlays require care every time you access
11633 the data. Also, if you change the contents of a data overlay, you
11634 must copy its contents back out to its load address before you can copy a
11635 different data overlay into the same mapped area.
11640 @node Overlay Commands
11641 @section Overlay Commands
11643 To use @value{GDBN}'s overlay support, each overlay in your program must
11644 correspond to a separate section of the executable file. The section's
11645 virtual memory address and load memory address must be the overlay's
11646 mapped and load addresses. Identifying overlays with sections allows
11647 @value{GDBN} to determine the appropriate address of a function or
11648 variable, depending on whether the overlay is mapped or not.
11650 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11651 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11656 Disable @value{GDBN}'s overlay support. When overlay support is
11657 disabled, @value{GDBN} assumes that all functions and variables are
11658 always present at their mapped addresses. By default, @value{GDBN}'s
11659 overlay support is disabled.
11661 @item overlay manual
11662 @cindex manual overlay debugging
11663 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11664 relies on you to tell it which overlays are mapped, and which are not,
11665 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11666 commands described below.
11668 @item overlay map-overlay @var{overlay}
11669 @itemx overlay map @var{overlay}
11670 @cindex map an overlay
11671 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11672 be the name of the object file section containing the overlay. When an
11673 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11674 functions and variables at their mapped addresses. @value{GDBN} assumes
11675 that any other overlays whose mapped ranges overlap that of
11676 @var{overlay} are now unmapped.
11678 @item overlay unmap-overlay @var{overlay}
11679 @itemx overlay unmap @var{overlay}
11680 @cindex unmap an overlay
11681 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11682 must be the name of the object file section containing the overlay.
11683 When an overlay is unmapped, @value{GDBN} assumes it can find the
11684 overlay's functions and variables at their load addresses.
11687 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11688 consults a data structure the overlay manager maintains in the inferior
11689 to see which overlays are mapped. For details, see @ref{Automatic
11690 Overlay Debugging}.
11692 @item overlay load-target
11693 @itemx overlay load
11694 @cindex reloading the overlay table
11695 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11696 re-reads the table @value{GDBN} automatically each time the inferior
11697 stops, so this command should only be necessary if you have changed the
11698 overlay mapping yourself using @value{GDBN}. This command is only
11699 useful when using automatic overlay debugging.
11701 @item overlay list-overlays
11702 @itemx overlay list
11703 @cindex listing mapped overlays
11704 Display a list of the overlays currently mapped, along with their mapped
11705 addresses, load addresses, and sizes.
11709 Normally, when @value{GDBN} prints a code address, it includes the name
11710 of the function the address falls in:
11713 (@value{GDBP}) print main
11714 $3 = @{int ()@} 0x11a0 <main>
11717 When overlay debugging is enabled, @value{GDBN} recognizes code in
11718 unmapped overlays, and prints the names of unmapped functions with
11719 asterisks around them. For example, if @code{foo} is a function in an
11720 unmapped overlay, @value{GDBN} prints it this way:
11723 (@value{GDBP}) overlay list
11724 No sections are mapped.
11725 (@value{GDBP}) print foo
11726 $5 = @{int (int)@} 0x100000 <*foo*>
11729 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11733 (@value{GDBP}) overlay list
11734 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11735 mapped at 0x1016 - 0x104a
11736 (@value{GDBP}) print foo
11737 $6 = @{int (int)@} 0x1016 <foo>
11740 When overlay debugging is enabled, @value{GDBN} can find the correct
11741 address for functions and variables in an overlay, whether or not the
11742 overlay is mapped. This allows most @value{GDBN} commands, like
11743 @code{break} and @code{disassemble}, to work normally, even on unmapped
11744 code. However, @value{GDBN}'s breakpoint support has some limitations:
11748 @cindex breakpoints in overlays
11749 @cindex overlays, setting breakpoints in
11750 You can set breakpoints in functions in unmapped overlays, as long as
11751 @value{GDBN} can write to the overlay at its load address.
11753 @value{GDBN} can not set hardware or simulator-based breakpoints in
11754 unmapped overlays. However, if you set a breakpoint at the end of your
11755 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11756 you are using manual overlay management), @value{GDBN} will re-set its
11757 breakpoints properly.
11761 @node Automatic Overlay Debugging
11762 @section Automatic Overlay Debugging
11763 @cindex automatic overlay debugging
11765 @value{GDBN} can automatically track which overlays are mapped and which
11766 are not, given some simple co-operation from the overlay manager in the
11767 inferior. If you enable automatic overlay debugging with the
11768 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11769 looks in the inferior's memory for certain variables describing the
11770 current state of the overlays.
11772 Here are the variables your overlay manager must define to support
11773 @value{GDBN}'s automatic overlay debugging:
11777 @item @code{_ovly_table}:
11778 This variable must be an array of the following structures:
11783 /* The overlay's mapped address. */
11786 /* The size of the overlay, in bytes. */
11787 unsigned long size;
11789 /* The overlay's load address. */
11792 /* Non-zero if the overlay is currently mapped;
11794 unsigned long mapped;
11798 @item @code{_novlys}:
11799 This variable must be a four-byte signed integer, holding the total
11800 number of elements in @code{_ovly_table}.
11804 To decide whether a particular overlay is mapped or not, @value{GDBN}
11805 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11806 @code{lma} members equal the VMA and LMA of the overlay's section in the
11807 executable file. When @value{GDBN} finds a matching entry, it consults
11808 the entry's @code{mapped} member to determine whether the overlay is
11811 In addition, your overlay manager may define a function called
11812 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11813 will silently set a breakpoint there. If the overlay manager then
11814 calls this function whenever it has changed the overlay table, this
11815 will enable @value{GDBN} to accurately keep track of which overlays
11816 are in program memory, and update any breakpoints that may be set
11817 in overlays. This will allow breakpoints to work even if the
11818 overlays are kept in ROM or other non-writable memory while they
11819 are not being executed.
11821 @node Overlay Sample Program
11822 @section Overlay Sample Program
11823 @cindex overlay example program
11825 When linking a program which uses overlays, you must place the overlays
11826 at their load addresses, while relocating them to run at their mapped
11827 addresses. To do this, you must write a linker script (@pxref{Overlay
11828 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11829 since linker scripts are specific to a particular host system, target
11830 architecture, and target memory layout, this manual cannot provide
11831 portable sample code demonstrating @value{GDBN}'s overlay support.
11833 However, the @value{GDBN} source distribution does contain an overlaid
11834 program, with linker scripts for a few systems, as part of its test
11835 suite. The program consists of the following files from
11836 @file{gdb/testsuite/gdb.base}:
11840 The main program file.
11842 A simple overlay manager, used by @file{overlays.c}.
11847 Overlay modules, loaded and used by @file{overlays.c}.
11850 Linker scripts for linking the test program on the @code{d10v-elf}
11851 and @code{m32r-elf} targets.
11854 You can build the test program using the @code{d10v-elf} GCC
11855 cross-compiler like this:
11858 $ d10v-elf-gcc -g -c overlays.c
11859 $ d10v-elf-gcc -g -c ovlymgr.c
11860 $ d10v-elf-gcc -g -c foo.c
11861 $ d10v-elf-gcc -g -c bar.c
11862 $ d10v-elf-gcc -g -c baz.c
11863 $ d10v-elf-gcc -g -c grbx.c
11864 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11865 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11868 The build process is identical for any other architecture, except that
11869 you must substitute the appropriate compiler and linker script for the
11870 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11874 @chapter Using @value{GDBN} with Different Languages
11877 Although programming languages generally have common aspects, they are
11878 rarely expressed in the same manner. For instance, in ANSI C,
11879 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11880 Modula-2, it is accomplished by @code{p^}. Values can also be
11881 represented (and displayed) differently. Hex numbers in C appear as
11882 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11884 @cindex working language
11885 Language-specific information is built into @value{GDBN} for some languages,
11886 allowing you to express operations like the above in your program's
11887 native language, and allowing @value{GDBN} to output values in a manner
11888 consistent with the syntax of your program's native language. The
11889 language you use to build expressions is called the @dfn{working
11893 * Setting:: Switching between source languages
11894 * Show:: Displaying the language
11895 * Checks:: Type and range checks
11896 * Supported Languages:: Supported languages
11897 * Unsupported Languages:: Unsupported languages
11901 @section Switching Between Source Languages
11903 There are two ways to control the working language---either have @value{GDBN}
11904 set it automatically, or select it manually yourself. You can use the
11905 @code{set language} command for either purpose. On startup, @value{GDBN}
11906 defaults to setting the language automatically. The working language is
11907 used to determine how expressions you type are interpreted, how values
11910 In addition to the working language, every source file that
11911 @value{GDBN} knows about has its own working language. For some object
11912 file formats, the compiler might indicate which language a particular
11913 source file is in. However, most of the time @value{GDBN} infers the
11914 language from the name of the file. The language of a source file
11915 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11916 show each frame appropriately for its own language. There is no way to
11917 set the language of a source file from within @value{GDBN}, but you can
11918 set the language associated with a filename extension. @xref{Show, ,
11919 Displaying the Language}.
11921 This is most commonly a problem when you use a program, such
11922 as @code{cfront} or @code{f2c}, that generates C but is written in
11923 another language. In that case, make the
11924 program use @code{#line} directives in its C output; that way
11925 @value{GDBN} will know the correct language of the source code of the original
11926 program, and will display that source code, not the generated C code.
11929 * Filenames:: Filename extensions and languages.
11930 * Manually:: Setting the working language manually
11931 * Automatically:: Having @value{GDBN} infer the source language
11935 @subsection List of Filename Extensions and Languages
11937 If a source file name ends in one of the following extensions, then
11938 @value{GDBN} infers that its language is the one indicated.
11956 C@t{++} source file
11962 Objective-C source file
11966 Fortran source file
11969 Modula-2 source file
11973 Assembler source file. This actually behaves almost like C, but
11974 @value{GDBN} does not skip over function prologues when stepping.
11977 In addition, you may set the language associated with a filename
11978 extension. @xref{Show, , Displaying the Language}.
11981 @subsection Setting the Working Language
11983 If you allow @value{GDBN} to set the language automatically,
11984 expressions are interpreted the same way in your debugging session and
11987 @kindex set language
11988 If you wish, you may set the language manually. To do this, issue the
11989 command @samp{set language @var{lang}}, where @var{lang} is the name of
11990 a language, such as
11991 @code{c} or @code{modula-2}.
11992 For a list of the supported languages, type @samp{set language}.
11994 Setting the language manually prevents @value{GDBN} from updating the working
11995 language automatically. This can lead to confusion if you try
11996 to debug a program when the working language is not the same as the
11997 source language, when an expression is acceptable to both
11998 languages---but means different things. For instance, if the current
11999 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12007 might not have the effect you intended. In C, this means to add
12008 @code{b} and @code{c} and place the result in @code{a}. The result
12009 printed would be the value of @code{a}. In Modula-2, this means to compare
12010 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12012 @node Automatically
12013 @subsection Having @value{GDBN} Infer the Source Language
12015 To have @value{GDBN} set the working language automatically, use
12016 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12017 then infers the working language. That is, when your program stops in a
12018 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12019 working language to the language recorded for the function in that
12020 frame. If the language for a frame is unknown (that is, if the function
12021 or block corresponding to the frame was defined in a source file that
12022 does not have a recognized extension), the current working language is
12023 not changed, and @value{GDBN} issues a warning.
12025 This may not seem necessary for most programs, which are written
12026 entirely in one source language. However, program modules and libraries
12027 written in one source language can be used by a main program written in
12028 a different source language. Using @samp{set language auto} in this
12029 case frees you from having to set the working language manually.
12032 @section Displaying the Language
12034 The following commands help you find out which language is the
12035 working language, and also what language source files were written in.
12038 @item show language
12039 @kindex show language
12040 Display the current working language. This is the
12041 language you can use with commands such as @code{print} to
12042 build and compute expressions that may involve variables in your program.
12045 @kindex info frame@r{, show the source language}
12046 Display the source language for this frame. This language becomes the
12047 working language if you use an identifier from this frame.
12048 @xref{Frame Info, ,Information about a Frame}, to identify the other
12049 information listed here.
12052 @kindex info source@r{, show the source language}
12053 Display the source language of this source file.
12054 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12055 information listed here.
12058 In unusual circumstances, you may have source files with extensions
12059 not in the standard list. You can then set the extension associated
12060 with a language explicitly:
12063 @item set extension-language @var{ext} @var{language}
12064 @kindex set extension-language
12065 Tell @value{GDBN} that source files with extension @var{ext} are to be
12066 assumed as written in the source language @var{language}.
12068 @item info extensions
12069 @kindex info extensions
12070 List all the filename extensions and the associated languages.
12074 @section Type and Range Checking
12077 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12078 checking are included, but they do not yet have any effect. This
12079 section documents the intended facilities.
12081 @c FIXME remove warning when type/range code added
12083 Some languages are designed to guard you against making seemingly common
12084 errors through a series of compile- and run-time checks. These include
12085 checking the type of arguments to functions and operators, and making
12086 sure mathematical overflows are caught at run time. Checks such as
12087 these help to ensure a program's correctness once it has been compiled
12088 by eliminating type mismatches, and providing active checks for range
12089 errors when your program is running.
12091 @value{GDBN} can check for conditions like the above if you wish.
12092 Although @value{GDBN} does not check the statements in your program,
12093 it can check expressions entered directly into @value{GDBN} for
12094 evaluation via the @code{print} command, for example. As with the
12095 working language, @value{GDBN} can also decide whether or not to check
12096 automatically based on your program's source language.
12097 @xref{Supported Languages, ,Supported Languages}, for the default
12098 settings of supported languages.
12101 * Type Checking:: An overview of type checking
12102 * Range Checking:: An overview of range checking
12105 @cindex type checking
12106 @cindex checks, type
12107 @node Type Checking
12108 @subsection An Overview of Type Checking
12110 Some languages, such as Modula-2, are strongly typed, meaning that the
12111 arguments to operators and functions have to be of the correct type,
12112 otherwise an error occurs. These checks prevent type mismatch
12113 errors from ever causing any run-time problems. For example,
12121 The second example fails because the @code{CARDINAL} 1 is not
12122 type-compatible with the @code{REAL} 2.3.
12124 For the expressions you use in @value{GDBN} commands, you can tell the
12125 @value{GDBN} type checker to skip checking;
12126 to treat any mismatches as errors and abandon the expression;
12127 or to only issue warnings when type mismatches occur,
12128 but evaluate the expression anyway. When you choose the last of
12129 these, @value{GDBN} evaluates expressions like the second example above, but
12130 also issues a warning.
12132 Even if you turn type checking off, there may be other reasons
12133 related to type that prevent @value{GDBN} from evaluating an expression.
12134 For instance, @value{GDBN} does not know how to add an @code{int} and
12135 a @code{struct foo}. These particular type errors have nothing to do
12136 with the language in use, and usually arise from expressions, such as
12137 the one described above, which make little sense to evaluate anyway.
12139 Each language defines to what degree it is strict about type. For
12140 instance, both Modula-2 and C require the arguments to arithmetical
12141 operators to be numbers. In C, enumerated types and pointers can be
12142 represented as numbers, so that they are valid arguments to mathematical
12143 operators. @xref{Supported Languages, ,Supported Languages}, for further
12144 details on specific languages.
12146 @value{GDBN} provides some additional commands for controlling the type checker:
12148 @kindex set check type
12149 @kindex show check type
12151 @item set check type auto
12152 Set type checking on or off based on the current working language.
12153 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12156 @item set check type on
12157 @itemx set check type off
12158 Set type checking on or off, overriding the default setting for the
12159 current working language. Issue a warning if the setting does not
12160 match the language default. If any type mismatches occur in
12161 evaluating an expression while type checking is on, @value{GDBN} prints a
12162 message and aborts evaluation of the expression.
12164 @item set check type warn
12165 Cause the type checker to issue warnings, but to always attempt to
12166 evaluate the expression. Evaluating the expression may still
12167 be impossible for other reasons. For example, @value{GDBN} cannot add
12168 numbers and structures.
12171 Show the current setting of the type checker, and whether or not @value{GDBN}
12172 is setting it automatically.
12175 @cindex range checking
12176 @cindex checks, range
12177 @node Range Checking
12178 @subsection An Overview of Range Checking
12180 In some languages (such as Modula-2), it is an error to exceed the
12181 bounds of a type; this is enforced with run-time checks. Such range
12182 checking is meant to ensure program correctness by making sure
12183 computations do not overflow, or indices on an array element access do
12184 not exceed the bounds of the array.
12186 For expressions you use in @value{GDBN} commands, you can tell
12187 @value{GDBN} to treat range errors in one of three ways: ignore them,
12188 always treat them as errors and abandon the expression, or issue
12189 warnings but evaluate the expression anyway.
12191 A range error can result from numerical overflow, from exceeding an
12192 array index bound, or when you type a constant that is not a member
12193 of any type. Some languages, however, do not treat overflows as an
12194 error. In many implementations of C, mathematical overflow causes the
12195 result to ``wrap around'' to lower values---for example, if @var{m} is
12196 the largest integer value, and @var{s} is the smallest, then
12199 @var{m} + 1 @result{} @var{s}
12202 This, too, is specific to individual languages, and in some cases
12203 specific to individual compilers or machines. @xref{Supported Languages, ,
12204 Supported Languages}, for further details on specific languages.
12206 @value{GDBN} provides some additional commands for controlling the range checker:
12208 @kindex set check range
12209 @kindex show check range
12211 @item set check range auto
12212 Set range checking on or off based on the current working language.
12213 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12216 @item set check range on
12217 @itemx set check range off
12218 Set range checking on or off, overriding the default setting for the
12219 current working language. A warning is issued if the setting does not
12220 match the language default. If a range error occurs and range checking is on,
12221 then a message is printed and evaluation of the expression is aborted.
12223 @item set check range warn
12224 Output messages when the @value{GDBN} range checker detects a range error,
12225 but attempt to evaluate the expression anyway. Evaluating the
12226 expression may still be impossible for other reasons, such as accessing
12227 memory that the process does not own (a typical example from many Unix
12231 Show the current setting of the range checker, and whether or not it is
12232 being set automatically by @value{GDBN}.
12235 @node Supported Languages
12236 @section Supported Languages
12238 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12239 assembly, Modula-2, and Ada.
12240 @c This is false ...
12241 Some @value{GDBN} features may be used in expressions regardless of the
12242 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12243 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12244 ,Expressions}) can be used with the constructs of any supported
12247 The following sections detail to what degree each source language is
12248 supported by @value{GDBN}. These sections are not meant to be language
12249 tutorials or references, but serve only as a reference guide to what the
12250 @value{GDBN} expression parser accepts, and what input and output
12251 formats should look like for different languages. There are many good
12252 books written on each of these languages; please look to these for a
12253 language reference or tutorial.
12256 * C:: C and C@t{++}
12258 * Objective-C:: Objective-C
12259 * OpenCL C:: OpenCL C
12260 * Fortran:: Fortran
12262 * Modula-2:: Modula-2
12267 @subsection C and C@t{++}
12269 @cindex C and C@t{++}
12270 @cindex expressions in C or C@t{++}
12272 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12273 to both languages. Whenever this is the case, we discuss those languages
12277 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12278 @cindex @sc{gnu} C@t{++}
12279 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12280 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12281 effectively, you must compile your C@t{++} programs with a supported
12282 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12283 compiler (@code{aCC}).
12286 * C Operators:: C and C@t{++} operators
12287 * C Constants:: C and C@t{++} constants
12288 * C Plus Plus Expressions:: C@t{++} expressions
12289 * C Defaults:: Default settings for C and C@t{++}
12290 * C Checks:: C and C@t{++} type and range checks
12291 * Debugging C:: @value{GDBN} and C
12292 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12293 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12297 @subsubsection C and C@t{++} Operators
12299 @cindex C and C@t{++} operators
12301 Operators must be defined on values of specific types. For instance,
12302 @code{+} is defined on numbers, but not on structures. Operators are
12303 often defined on groups of types.
12305 For the purposes of C and C@t{++}, the following definitions hold:
12310 @emph{Integral types} include @code{int} with any of its storage-class
12311 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12314 @emph{Floating-point types} include @code{float}, @code{double}, and
12315 @code{long double} (if supported by the target platform).
12318 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12321 @emph{Scalar types} include all of the above.
12326 The following operators are supported. They are listed here
12327 in order of increasing precedence:
12331 The comma or sequencing operator. Expressions in a comma-separated list
12332 are evaluated from left to right, with the result of the entire
12333 expression being the last expression evaluated.
12336 Assignment. The value of an assignment expression is the value
12337 assigned. Defined on scalar types.
12340 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12341 and translated to @w{@code{@var{a} = @var{a op b}}}.
12342 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12343 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12344 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12347 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12348 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12352 Logical @sc{or}. Defined on integral types.
12355 Logical @sc{and}. Defined on integral types.
12358 Bitwise @sc{or}. Defined on integral types.
12361 Bitwise exclusive-@sc{or}. Defined on integral types.
12364 Bitwise @sc{and}. Defined on integral types.
12367 Equality and inequality. Defined on scalar types. The value of these
12368 expressions is 0 for false and non-zero for true.
12370 @item <@r{, }>@r{, }<=@r{, }>=
12371 Less than, greater than, less than or equal, greater than or equal.
12372 Defined on scalar types. The value of these expressions is 0 for false
12373 and non-zero for true.
12376 left shift, and right shift. Defined on integral types.
12379 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12382 Addition and subtraction. Defined on integral types, floating-point types and
12385 @item *@r{, }/@r{, }%
12386 Multiplication, division, and modulus. Multiplication and division are
12387 defined on integral and floating-point types. Modulus is defined on
12391 Increment and decrement. When appearing before a variable, the
12392 operation is performed before the variable is used in an expression;
12393 when appearing after it, the variable's value is used before the
12394 operation takes place.
12397 Pointer dereferencing. Defined on pointer types. Same precedence as
12401 Address operator. Defined on variables. Same precedence as @code{++}.
12403 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12404 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12405 to examine the address
12406 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12410 Negative. Defined on integral and floating-point types. Same
12411 precedence as @code{++}.
12414 Logical negation. Defined on integral types. Same precedence as
12418 Bitwise complement operator. Defined on integral types. Same precedence as
12423 Structure member, and pointer-to-structure member. For convenience,
12424 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12425 pointer based on the stored type information.
12426 Defined on @code{struct} and @code{union} data.
12429 Dereferences of pointers to members.
12432 Array indexing. @code{@var{a}[@var{i}]} is defined as
12433 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12436 Function parameter list. Same precedence as @code{->}.
12439 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12440 and @code{class} types.
12443 Doubled colons also represent the @value{GDBN} scope operator
12444 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12448 If an operator is redefined in the user code, @value{GDBN} usually
12449 attempts to invoke the redefined version instead of using the operator's
12450 predefined meaning.
12453 @subsubsection C and C@t{++} Constants
12455 @cindex C and C@t{++} constants
12457 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12462 Integer constants are a sequence of digits. Octal constants are
12463 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12464 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12465 @samp{l}, specifying that the constant should be treated as a
12469 Floating point constants are a sequence of digits, followed by a decimal
12470 point, followed by a sequence of digits, and optionally followed by an
12471 exponent. An exponent is of the form:
12472 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12473 sequence of digits. The @samp{+} is optional for positive exponents.
12474 A floating-point constant may also end with a letter @samp{f} or
12475 @samp{F}, specifying that the constant should be treated as being of
12476 the @code{float} (as opposed to the default @code{double}) type; or with
12477 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12481 Enumerated constants consist of enumerated identifiers, or their
12482 integral equivalents.
12485 Character constants are a single character surrounded by single quotes
12486 (@code{'}), or a number---the ordinal value of the corresponding character
12487 (usually its @sc{ascii} value). Within quotes, the single character may
12488 be represented by a letter or by @dfn{escape sequences}, which are of
12489 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12490 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12491 @samp{@var{x}} is a predefined special character---for example,
12492 @samp{\n} for newline.
12494 Wide character constants can be written by prefixing a character
12495 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12496 form of @samp{x}. The target wide character set is used when
12497 computing the value of this constant (@pxref{Character Sets}).
12500 String constants are a sequence of character constants surrounded by
12501 double quotes (@code{"}). Any valid character constant (as described
12502 above) may appear. Double quotes within the string must be preceded by
12503 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12506 Wide string constants can be written by prefixing a string constant
12507 with @samp{L}, as in C. The target wide character set is used when
12508 computing the value of this constant (@pxref{Character Sets}).
12511 Pointer constants are an integral value. You can also write pointers
12512 to constants using the C operator @samp{&}.
12515 Array constants are comma-separated lists surrounded by braces @samp{@{}
12516 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12517 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12518 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12521 @node C Plus Plus Expressions
12522 @subsubsection C@t{++} Expressions
12524 @cindex expressions in C@t{++}
12525 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12527 @cindex debugging C@t{++} programs
12528 @cindex C@t{++} compilers
12529 @cindex debug formats and C@t{++}
12530 @cindex @value{NGCC} and C@t{++}
12532 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12533 the proper compiler and the proper debug format. Currently,
12534 @value{GDBN} works best when debugging C@t{++} code that is compiled
12535 with the most recent version of @value{NGCC} possible. The DWARF
12536 debugging format is preferred; @value{NGCC} defaults to this on most
12537 popular platforms. Other compilers and/or debug formats are likely to
12538 work badly or not at all when using @value{GDBN} to debug C@t{++}
12539 code. @xref{Compilation}.
12544 @cindex member functions
12546 Member function calls are allowed; you can use expressions like
12549 count = aml->GetOriginal(x, y)
12552 @vindex this@r{, inside C@t{++} member functions}
12553 @cindex namespace in C@t{++}
12555 While a member function is active (in the selected stack frame), your
12556 expressions have the same namespace available as the member function;
12557 that is, @value{GDBN} allows implicit references to the class instance
12558 pointer @code{this} following the same rules as C@t{++}. @code{using}
12559 declarations in the current scope are also respected by @value{GDBN}.
12561 @cindex call overloaded functions
12562 @cindex overloaded functions, calling
12563 @cindex type conversions in C@t{++}
12565 You can call overloaded functions; @value{GDBN} resolves the function
12566 call to the right definition, with some restrictions. @value{GDBN} does not
12567 perform overload resolution involving user-defined type conversions,
12568 calls to constructors, or instantiations of templates that do not exist
12569 in the program. It also cannot handle ellipsis argument lists or
12572 It does perform integral conversions and promotions, floating-point
12573 promotions, arithmetic conversions, pointer conversions, conversions of
12574 class objects to base classes, and standard conversions such as those of
12575 functions or arrays to pointers; it requires an exact match on the
12576 number of function arguments.
12578 Overload resolution is always performed, unless you have specified
12579 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12580 ,@value{GDBN} Features for C@t{++}}.
12582 You must specify @code{set overload-resolution off} in order to use an
12583 explicit function signature to call an overloaded function, as in
12585 p 'foo(char,int)'('x', 13)
12588 The @value{GDBN} command-completion facility can simplify this;
12589 see @ref{Completion, ,Command Completion}.
12591 @cindex reference declarations
12593 @value{GDBN} understands variables declared as C@t{++} references; you can use
12594 them in expressions just as you do in C@t{++} source---they are automatically
12597 In the parameter list shown when @value{GDBN} displays a frame, the values of
12598 reference variables are not displayed (unlike other variables); this
12599 avoids clutter, since references are often used for large structures.
12600 The @emph{address} of a reference variable is always shown, unless
12601 you have specified @samp{set print address off}.
12604 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12605 expressions can use it just as expressions in your program do. Since
12606 one scope may be defined in another, you can use @code{::} repeatedly if
12607 necessary, for example in an expression like
12608 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12609 resolving name scope by reference to source files, in both C and C@t{++}
12610 debugging (@pxref{Variables, ,Program Variables}).
12613 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12618 @subsubsection C and C@t{++} Defaults
12620 @cindex C and C@t{++} defaults
12622 If you allow @value{GDBN} to set type and range checking automatically, they
12623 both default to @code{off} whenever the working language changes to
12624 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12625 selects the working language.
12627 If you allow @value{GDBN} to set the language automatically, it
12628 recognizes source files whose names end with @file{.c}, @file{.C}, or
12629 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12630 these files, it sets the working language to C or C@t{++}.
12631 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12632 for further details.
12634 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12635 @c unimplemented. If (b) changes, it might make sense to let this node
12636 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12639 @subsubsection C and C@t{++} Type and Range Checks
12641 @cindex C and C@t{++} checks
12643 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12644 is not used. However, if you turn type checking on, @value{GDBN}
12645 considers two variables type equivalent if:
12649 The two variables are structured and have the same structure, union, or
12653 The two variables have the same type name, or types that have been
12654 declared equivalent through @code{typedef}.
12657 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12660 The two @code{struct}, @code{union}, or @code{enum} variables are
12661 declared in the same declaration. (Note: this may not be true for all C
12666 Range checking, if turned on, is done on mathematical operations. Array
12667 indices are not checked, since they are often used to index a pointer
12668 that is not itself an array.
12671 @subsubsection @value{GDBN} and C
12673 The @code{set print union} and @code{show print union} commands apply to
12674 the @code{union} type. When set to @samp{on}, any @code{union} that is
12675 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12676 appears as @samp{@{...@}}.
12678 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12679 with pointers and a memory allocation function. @xref{Expressions,
12682 @node Debugging C Plus Plus
12683 @subsubsection @value{GDBN} Features for C@t{++}
12685 @cindex commands for C@t{++}
12687 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12688 designed specifically for use with C@t{++}. Here is a summary:
12691 @cindex break in overloaded functions
12692 @item @r{breakpoint menus}
12693 When you want a breakpoint in a function whose name is overloaded,
12694 @value{GDBN} has the capability to display a menu of possible breakpoint
12695 locations to help you specify which function definition you want.
12696 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12698 @cindex overloading in C@t{++}
12699 @item rbreak @var{regex}
12700 Setting breakpoints using regular expressions is helpful for setting
12701 breakpoints on overloaded functions that are not members of any special
12703 @xref{Set Breaks, ,Setting Breakpoints}.
12705 @cindex C@t{++} exception handling
12708 Debug C@t{++} exception handling using these commands. @xref{Set
12709 Catchpoints, , Setting Catchpoints}.
12711 @cindex inheritance
12712 @item ptype @var{typename}
12713 Print inheritance relationships as well as other information for type
12715 @xref{Symbols, ,Examining the Symbol Table}.
12717 @cindex C@t{++} symbol display
12718 @item set print demangle
12719 @itemx show print demangle
12720 @itemx set print asm-demangle
12721 @itemx show print asm-demangle
12722 Control whether C@t{++} symbols display in their source form, both when
12723 displaying code as C@t{++} source and when displaying disassemblies.
12724 @xref{Print Settings, ,Print Settings}.
12726 @item set print object
12727 @itemx show print object
12728 Choose whether to print derived (actual) or declared types of objects.
12729 @xref{Print Settings, ,Print Settings}.
12731 @item set print vtbl
12732 @itemx show print vtbl
12733 Control the format for printing virtual function tables.
12734 @xref{Print Settings, ,Print Settings}.
12735 (The @code{vtbl} commands do not work on programs compiled with the HP
12736 ANSI C@t{++} compiler (@code{aCC}).)
12738 @kindex set overload-resolution
12739 @cindex overloaded functions, overload resolution
12740 @item set overload-resolution on
12741 Enable overload resolution for C@t{++} expression evaluation. The default
12742 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12743 and searches for a function whose signature matches the argument types,
12744 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12745 Expressions, ,C@t{++} Expressions}, for details).
12746 If it cannot find a match, it emits a message.
12748 @item set overload-resolution off
12749 Disable overload resolution for C@t{++} expression evaluation. For
12750 overloaded functions that are not class member functions, @value{GDBN}
12751 chooses the first function of the specified name that it finds in the
12752 symbol table, whether or not its arguments are of the correct type. For
12753 overloaded functions that are class member functions, @value{GDBN}
12754 searches for a function whose signature @emph{exactly} matches the
12757 @kindex show overload-resolution
12758 @item show overload-resolution
12759 Show the current setting of overload resolution.
12761 @item @r{Overloaded symbol names}
12762 You can specify a particular definition of an overloaded symbol, using
12763 the same notation that is used to declare such symbols in C@t{++}: type
12764 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12765 also use the @value{GDBN} command-line word completion facilities to list the
12766 available choices, or to finish the type list for you.
12767 @xref{Completion,, Command Completion}, for details on how to do this.
12770 @node Decimal Floating Point
12771 @subsubsection Decimal Floating Point format
12772 @cindex decimal floating point format
12774 @value{GDBN} can examine, set and perform computations with numbers in
12775 decimal floating point format, which in the C language correspond to the
12776 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12777 specified by the extension to support decimal floating-point arithmetic.
12779 There are two encodings in use, depending on the architecture: BID (Binary
12780 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12781 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12784 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12785 to manipulate decimal floating point numbers, it is not possible to convert
12786 (using a cast, for example) integers wider than 32-bit to decimal float.
12788 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12789 point computations, error checking in decimal float operations ignores
12790 underflow, overflow and divide by zero exceptions.
12792 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12793 to inspect @code{_Decimal128} values stored in floating point registers.
12794 See @ref{PowerPC,,PowerPC} for more details.
12800 @value{GDBN} can be used to debug programs written in D and compiled with
12801 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12802 specific feature --- dynamic arrays.
12805 @subsection Objective-C
12807 @cindex Objective-C
12808 This section provides information about some commands and command
12809 options that are useful for debugging Objective-C code. See also
12810 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12811 few more commands specific to Objective-C support.
12814 * Method Names in Commands::
12815 * The Print Command with Objective-C::
12818 @node Method Names in Commands
12819 @subsubsection Method Names in Commands
12821 The following commands have been extended to accept Objective-C method
12822 names as line specifications:
12824 @kindex clear@r{, and Objective-C}
12825 @kindex break@r{, and Objective-C}
12826 @kindex info line@r{, and Objective-C}
12827 @kindex jump@r{, and Objective-C}
12828 @kindex list@r{, and Objective-C}
12832 @item @code{info line}
12837 A fully qualified Objective-C method name is specified as
12840 -[@var{Class} @var{methodName}]
12843 where the minus sign is used to indicate an instance method and a
12844 plus sign (not shown) is used to indicate a class method. The class
12845 name @var{Class} and method name @var{methodName} are enclosed in
12846 brackets, similar to the way messages are specified in Objective-C
12847 source code. For example, to set a breakpoint at the @code{create}
12848 instance method of class @code{Fruit} in the program currently being
12852 break -[Fruit create]
12855 To list ten program lines around the @code{initialize} class method,
12859 list +[NSText initialize]
12862 In the current version of @value{GDBN}, the plus or minus sign is
12863 required. In future versions of @value{GDBN}, the plus or minus
12864 sign will be optional, but you can use it to narrow the search. It
12865 is also possible to specify just a method name:
12871 You must specify the complete method name, including any colons. If
12872 your program's source files contain more than one @code{create} method,
12873 you'll be presented with a numbered list of classes that implement that
12874 method. Indicate your choice by number, or type @samp{0} to exit if
12877 As another example, to clear a breakpoint established at the
12878 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12881 clear -[NSWindow makeKeyAndOrderFront:]
12884 @node The Print Command with Objective-C
12885 @subsubsection The Print Command With Objective-C
12886 @cindex Objective-C, print objects
12887 @kindex print-object
12888 @kindex po @r{(@code{print-object})}
12890 The print command has also been extended to accept methods. For example:
12893 print -[@var{object} hash]
12896 @cindex print an Objective-C object description
12897 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12899 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12900 and print the result. Also, an additional command has been added,
12901 @code{print-object} or @code{po} for short, which is meant to print
12902 the description of an object. However, this command may only work
12903 with certain Objective-C libraries that have a particular hook
12904 function, @code{_NSPrintForDebugger}, defined.
12907 @subsection OpenCL C
12910 This section provides information about @value{GDBN}s OpenCL C support.
12913 * OpenCL C Datatypes::
12914 * OpenCL C Expressions::
12915 * OpenCL C Operators::
12918 @node OpenCL C Datatypes
12919 @subsubsection OpenCL C Datatypes
12921 @cindex OpenCL C Datatypes
12922 @value{GDBN} supports the builtin scalar and vector datatypes specified
12923 by OpenCL 1.1. In addition the half- and double-precision floating point
12924 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12925 extensions are also known to @value{GDBN}.
12927 @node OpenCL C Expressions
12928 @subsubsection OpenCL C Expressions
12930 @cindex OpenCL C Expressions
12931 @value{GDBN} supports accesses to vector components including the access as
12932 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12933 supported by @value{GDBN} can be used as well.
12935 @node OpenCL C Operators
12936 @subsubsection OpenCL C Operators
12938 @cindex OpenCL C Operators
12939 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12943 @subsection Fortran
12944 @cindex Fortran-specific support in @value{GDBN}
12946 @value{GDBN} can be used to debug programs written in Fortran, but it
12947 currently supports only the features of Fortran 77 language.
12949 @cindex trailing underscore, in Fortran symbols
12950 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12951 among them) append an underscore to the names of variables and
12952 functions. When you debug programs compiled by those compilers, you
12953 will need to refer to variables and functions with a trailing
12957 * Fortran Operators:: Fortran operators and expressions
12958 * Fortran Defaults:: Default settings for Fortran
12959 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12962 @node Fortran Operators
12963 @subsubsection Fortran Operators and Expressions
12965 @cindex Fortran operators and expressions
12967 Operators must be defined on values of specific types. For instance,
12968 @code{+} is defined on numbers, but not on characters or other non-
12969 arithmetic types. Operators are often defined on groups of types.
12973 The exponentiation operator. It raises the first operand to the power
12977 The range operator. Normally used in the form of array(low:high) to
12978 represent a section of array.
12981 The access component operator. Normally used to access elements in derived
12982 types. Also suitable for unions. As unions aren't part of regular Fortran,
12983 this can only happen when accessing a register that uses a gdbarch-defined
12987 @node Fortran Defaults
12988 @subsubsection Fortran Defaults
12990 @cindex Fortran Defaults
12992 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12993 default uses case-insensitive matches for Fortran symbols. You can
12994 change that with the @samp{set case-insensitive} command, see
12995 @ref{Symbols}, for the details.
12997 @node Special Fortran Commands
12998 @subsubsection Special Fortran Commands
13000 @cindex Special Fortran commands
13002 @value{GDBN} has some commands to support Fortran-specific features,
13003 such as displaying common blocks.
13006 @cindex @code{COMMON} blocks, Fortran
13007 @kindex info common
13008 @item info common @r{[}@var{common-name}@r{]}
13009 This command prints the values contained in the Fortran @code{COMMON}
13010 block whose name is @var{common-name}. With no argument, the names of
13011 all @code{COMMON} blocks visible at the current program location are
13018 @cindex Pascal support in @value{GDBN}, limitations
13019 Debugging Pascal programs which use sets, subranges, file variables, or
13020 nested functions does not currently work. @value{GDBN} does not support
13021 entering expressions, printing values, or similar features using Pascal
13024 The Pascal-specific command @code{set print pascal_static-members}
13025 controls whether static members of Pascal objects are displayed.
13026 @xref{Print Settings, pascal_static-members}.
13029 @subsection Modula-2
13031 @cindex Modula-2, @value{GDBN} support
13033 The extensions made to @value{GDBN} to support Modula-2 only support
13034 output from the @sc{gnu} Modula-2 compiler (which is currently being
13035 developed). Other Modula-2 compilers are not currently supported, and
13036 attempting to debug executables produced by them is most likely
13037 to give an error as @value{GDBN} reads in the executable's symbol
13040 @cindex expressions in Modula-2
13042 * M2 Operators:: Built-in operators
13043 * Built-In Func/Proc:: Built-in functions and procedures
13044 * M2 Constants:: Modula-2 constants
13045 * M2 Types:: Modula-2 types
13046 * M2 Defaults:: Default settings for Modula-2
13047 * Deviations:: Deviations from standard Modula-2
13048 * M2 Checks:: Modula-2 type and range checks
13049 * M2 Scope:: The scope operators @code{::} and @code{.}
13050 * GDB/M2:: @value{GDBN} and Modula-2
13054 @subsubsection Operators
13055 @cindex Modula-2 operators
13057 Operators must be defined on values of specific types. For instance,
13058 @code{+} is defined on numbers, but not on structures. Operators are
13059 often defined on groups of types. For the purposes of Modula-2, the
13060 following definitions hold:
13065 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13069 @emph{Character types} consist of @code{CHAR} and its subranges.
13072 @emph{Floating-point types} consist of @code{REAL}.
13075 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13079 @emph{Scalar types} consist of all of the above.
13082 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13085 @emph{Boolean types} consist of @code{BOOLEAN}.
13089 The following operators are supported, and appear in order of
13090 increasing precedence:
13094 Function argument or array index separator.
13097 Assignment. The value of @var{var} @code{:=} @var{value} is
13101 Less than, greater than on integral, floating-point, or enumerated
13105 Less than or equal to, greater than or equal to
13106 on integral, floating-point and enumerated types, or set inclusion on
13107 set types. Same precedence as @code{<}.
13109 @item =@r{, }<>@r{, }#
13110 Equality and two ways of expressing inequality, valid on scalar types.
13111 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13112 available for inequality, since @code{#} conflicts with the script
13116 Set membership. Defined on set types and the types of their members.
13117 Same precedence as @code{<}.
13120 Boolean disjunction. Defined on boolean types.
13123 Boolean conjunction. Defined on boolean types.
13126 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13129 Addition and subtraction on integral and floating-point types, or union
13130 and difference on set types.
13133 Multiplication on integral and floating-point types, or set intersection
13137 Division on floating-point types, or symmetric set difference on set
13138 types. Same precedence as @code{*}.
13141 Integer division and remainder. Defined on integral types. Same
13142 precedence as @code{*}.
13145 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13148 Pointer dereferencing. Defined on pointer types.
13151 Boolean negation. Defined on boolean types. Same precedence as
13155 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13156 precedence as @code{^}.
13159 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13162 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13166 @value{GDBN} and Modula-2 scope operators.
13170 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13171 treats the use of the operator @code{IN}, or the use of operators
13172 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13173 @code{<=}, and @code{>=} on sets as an error.
13177 @node Built-In Func/Proc
13178 @subsubsection Built-in Functions and Procedures
13179 @cindex Modula-2 built-ins
13181 Modula-2 also makes available several built-in procedures and functions.
13182 In describing these, the following metavariables are used:
13187 represents an @code{ARRAY} variable.
13190 represents a @code{CHAR} constant or variable.
13193 represents a variable or constant of integral type.
13196 represents an identifier that belongs to a set. Generally used in the
13197 same function with the metavariable @var{s}. The type of @var{s} should
13198 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13201 represents a variable or constant of integral or floating-point type.
13204 represents a variable or constant of floating-point type.
13210 represents a variable.
13213 represents a variable or constant of one of many types. See the
13214 explanation of the function for details.
13217 All Modula-2 built-in procedures also return a result, described below.
13221 Returns the absolute value of @var{n}.
13224 If @var{c} is a lower case letter, it returns its upper case
13225 equivalent, otherwise it returns its argument.
13228 Returns the character whose ordinal value is @var{i}.
13231 Decrements the value in the variable @var{v} by one. Returns the new value.
13233 @item DEC(@var{v},@var{i})
13234 Decrements the value in the variable @var{v} by @var{i}. Returns the
13237 @item EXCL(@var{m},@var{s})
13238 Removes the element @var{m} from the set @var{s}. Returns the new
13241 @item FLOAT(@var{i})
13242 Returns the floating point equivalent of the integer @var{i}.
13244 @item HIGH(@var{a})
13245 Returns the index of the last member of @var{a}.
13248 Increments the value in the variable @var{v} by one. Returns the new value.
13250 @item INC(@var{v},@var{i})
13251 Increments the value in the variable @var{v} by @var{i}. Returns the
13254 @item INCL(@var{m},@var{s})
13255 Adds the element @var{m} to the set @var{s} if it is not already
13256 there. Returns the new set.
13259 Returns the maximum value of the type @var{t}.
13262 Returns the minimum value of the type @var{t}.
13265 Returns boolean TRUE if @var{i} is an odd number.
13268 Returns the ordinal value of its argument. For example, the ordinal
13269 value of a character is its @sc{ascii} value (on machines supporting the
13270 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13271 integral, character and enumerated types.
13273 @item SIZE(@var{x})
13274 Returns the size of its argument. @var{x} can be a variable or a type.
13276 @item TRUNC(@var{r})
13277 Returns the integral part of @var{r}.
13279 @item TSIZE(@var{x})
13280 Returns the size of its argument. @var{x} can be a variable or a type.
13282 @item VAL(@var{t},@var{i})
13283 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13287 @emph{Warning:} Sets and their operations are not yet supported, so
13288 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13292 @cindex Modula-2 constants
13294 @subsubsection Constants
13296 @value{GDBN} allows you to express the constants of Modula-2 in the following
13302 Integer constants are simply a sequence of digits. When used in an
13303 expression, a constant is interpreted to be type-compatible with the
13304 rest of the expression. Hexadecimal integers are specified by a
13305 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13308 Floating point constants appear as a sequence of digits, followed by a
13309 decimal point and another sequence of digits. An optional exponent can
13310 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13311 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13312 digits of the floating point constant must be valid decimal (base 10)
13316 Character constants consist of a single character enclosed by a pair of
13317 like quotes, either single (@code{'}) or double (@code{"}). They may
13318 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13319 followed by a @samp{C}.
13322 String constants consist of a sequence of characters enclosed by a
13323 pair of like quotes, either single (@code{'}) or double (@code{"}).
13324 Escape sequences in the style of C are also allowed. @xref{C
13325 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13329 Enumerated constants consist of an enumerated identifier.
13332 Boolean constants consist of the identifiers @code{TRUE} and
13336 Pointer constants consist of integral values only.
13339 Set constants are not yet supported.
13343 @subsubsection Modula-2 Types
13344 @cindex Modula-2 types
13346 Currently @value{GDBN} can print the following data types in Modula-2
13347 syntax: array types, record types, set types, pointer types, procedure
13348 types, enumerated types, subrange types and base types. You can also
13349 print the contents of variables declared using these type.
13350 This section gives a number of simple source code examples together with
13351 sample @value{GDBN} sessions.
13353 The first example contains the following section of code:
13362 and you can request @value{GDBN} to interrogate the type and value of
13363 @code{r} and @code{s}.
13366 (@value{GDBP}) print s
13368 (@value{GDBP}) ptype s
13370 (@value{GDBP}) print r
13372 (@value{GDBP}) ptype r
13377 Likewise if your source code declares @code{s} as:
13381 s: SET ['A'..'Z'] ;
13385 then you may query the type of @code{s} by:
13388 (@value{GDBP}) ptype s
13389 type = SET ['A'..'Z']
13393 Note that at present you cannot interactively manipulate set
13394 expressions using the debugger.
13396 The following example shows how you might declare an array in Modula-2
13397 and how you can interact with @value{GDBN} to print its type and contents:
13401 s: ARRAY [-10..10] OF CHAR ;
13405 (@value{GDBP}) ptype s
13406 ARRAY [-10..10] OF CHAR
13409 Note that the array handling is not yet complete and although the type
13410 is printed correctly, expression handling still assumes that all
13411 arrays have a lower bound of zero and not @code{-10} as in the example
13414 Here are some more type related Modula-2 examples:
13418 colour = (blue, red, yellow, green) ;
13419 t = [blue..yellow] ;
13427 The @value{GDBN} interaction shows how you can query the data type
13428 and value of a variable.
13431 (@value{GDBP}) print s
13433 (@value{GDBP}) ptype t
13434 type = [blue..yellow]
13438 In this example a Modula-2 array is declared and its contents
13439 displayed. Observe that the contents are written in the same way as
13440 their @code{C} counterparts.
13444 s: ARRAY [1..5] OF CARDINAL ;
13450 (@value{GDBP}) print s
13451 $1 = @{1, 0, 0, 0, 0@}
13452 (@value{GDBP}) ptype s
13453 type = ARRAY [1..5] OF CARDINAL
13456 The Modula-2 language interface to @value{GDBN} also understands
13457 pointer types as shown in this example:
13461 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13468 and you can request that @value{GDBN} describes the type of @code{s}.
13471 (@value{GDBP}) ptype s
13472 type = POINTER TO ARRAY [1..5] OF CARDINAL
13475 @value{GDBN} handles compound types as we can see in this example.
13476 Here we combine array types, record types, pointer types and subrange
13487 myarray = ARRAY myrange OF CARDINAL ;
13488 myrange = [-2..2] ;
13490 s: POINTER TO ARRAY myrange OF foo ;
13494 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13498 (@value{GDBP}) ptype s
13499 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13502 f3 : ARRAY [-2..2] OF CARDINAL;
13507 @subsubsection Modula-2 Defaults
13508 @cindex Modula-2 defaults
13510 If type and range checking are set automatically by @value{GDBN}, they
13511 both default to @code{on} whenever the working language changes to
13512 Modula-2. This happens regardless of whether you or @value{GDBN}
13513 selected the working language.
13515 If you allow @value{GDBN} to set the language automatically, then entering
13516 code compiled from a file whose name ends with @file{.mod} sets the
13517 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13518 Infer the Source Language}, for further details.
13521 @subsubsection Deviations from Standard Modula-2
13522 @cindex Modula-2, deviations from
13524 A few changes have been made to make Modula-2 programs easier to debug.
13525 This is done primarily via loosening its type strictness:
13529 Unlike in standard Modula-2, pointer constants can be formed by
13530 integers. This allows you to modify pointer variables during
13531 debugging. (In standard Modula-2, the actual address contained in a
13532 pointer variable is hidden from you; it can only be modified
13533 through direct assignment to another pointer variable or expression that
13534 returned a pointer.)
13537 C escape sequences can be used in strings and characters to represent
13538 non-printable characters. @value{GDBN} prints out strings with these
13539 escape sequences embedded. Single non-printable characters are
13540 printed using the @samp{CHR(@var{nnn})} format.
13543 The assignment operator (@code{:=}) returns the value of its right-hand
13547 All built-in procedures both modify @emph{and} return their argument.
13551 @subsubsection Modula-2 Type and Range Checks
13552 @cindex Modula-2 checks
13555 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13558 @c FIXME remove warning when type/range checks added
13560 @value{GDBN} considers two Modula-2 variables type equivalent if:
13564 They are of types that have been declared equivalent via a @code{TYPE
13565 @var{t1} = @var{t2}} statement
13568 They have been declared on the same line. (Note: This is true of the
13569 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13572 As long as type checking is enabled, any attempt to combine variables
13573 whose types are not equivalent is an error.
13575 Range checking is done on all mathematical operations, assignment, array
13576 index bounds, and all built-in functions and procedures.
13579 @subsubsection The Scope Operators @code{::} and @code{.}
13581 @cindex @code{.}, Modula-2 scope operator
13582 @cindex colon, doubled as scope operator
13584 @vindex colon-colon@r{, in Modula-2}
13585 @c Info cannot handle :: but TeX can.
13588 @vindex ::@r{, in Modula-2}
13591 There are a few subtle differences between the Modula-2 scope operator
13592 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13597 @var{module} . @var{id}
13598 @var{scope} :: @var{id}
13602 where @var{scope} is the name of a module or a procedure,
13603 @var{module} the name of a module, and @var{id} is any declared
13604 identifier within your program, except another module.
13606 Using the @code{::} operator makes @value{GDBN} search the scope
13607 specified by @var{scope} for the identifier @var{id}. If it is not
13608 found in the specified scope, then @value{GDBN} searches all scopes
13609 enclosing the one specified by @var{scope}.
13611 Using the @code{.} operator makes @value{GDBN} search the current scope for
13612 the identifier specified by @var{id} that was imported from the
13613 definition module specified by @var{module}. With this operator, it is
13614 an error if the identifier @var{id} was not imported from definition
13615 module @var{module}, or if @var{id} is not an identifier in
13619 @subsubsection @value{GDBN} and Modula-2
13621 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13622 Five subcommands of @code{set print} and @code{show print} apply
13623 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13624 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13625 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13626 analogue in Modula-2.
13628 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13629 with any language, is not useful with Modula-2. Its
13630 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13631 created in Modula-2 as they can in C or C@t{++}. However, because an
13632 address can be specified by an integral constant, the construct
13633 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13635 @cindex @code{#} in Modula-2
13636 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13637 interpreted as the beginning of a comment. Use @code{<>} instead.
13643 The extensions made to @value{GDBN} for Ada only support
13644 output from the @sc{gnu} Ada (GNAT) compiler.
13645 Other Ada compilers are not currently supported, and
13646 attempting to debug executables produced by them is most likely
13650 @cindex expressions in Ada
13652 * Ada Mode Intro:: General remarks on the Ada syntax
13653 and semantics supported by Ada mode
13655 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13656 * Additions to Ada:: Extensions of the Ada expression syntax.
13657 * Stopping Before Main Program:: Debugging the program during elaboration.
13658 * Ada Tasks:: Listing and setting breakpoints in tasks.
13659 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13660 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13662 * Ada Glitches:: Known peculiarities of Ada mode.
13665 @node Ada Mode Intro
13666 @subsubsection Introduction
13667 @cindex Ada mode, general
13669 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13670 syntax, with some extensions.
13671 The philosophy behind the design of this subset is
13675 That @value{GDBN} should provide basic literals and access to operations for
13676 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13677 leaving more sophisticated computations to subprograms written into the
13678 program (which therefore may be called from @value{GDBN}).
13681 That type safety and strict adherence to Ada language restrictions
13682 are not particularly important to the @value{GDBN} user.
13685 That brevity is important to the @value{GDBN} user.
13688 Thus, for brevity, the debugger acts as if all names declared in
13689 user-written packages are directly visible, even if they are not visible
13690 according to Ada rules, thus making it unnecessary to fully qualify most
13691 names with their packages, regardless of context. Where this causes
13692 ambiguity, @value{GDBN} asks the user's intent.
13694 The debugger will start in Ada mode if it detects an Ada main program.
13695 As for other languages, it will enter Ada mode when stopped in a program that
13696 was translated from an Ada source file.
13698 While in Ada mode, you may use `@t{--}' for comments. This is useful
13699 mostly for documenting command files. The standard @value{GDBN} comment
13700 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13701 middle (to allow based literals).
13703 The debugger supports limited overloading. Given a subprogram call in which
13704 the function symbol has multiple definitions, it will use the number of
13705 actual parameters and some information about their types to attempt to narrow
13706 the set of definitions. It also makes very limited use of context, preferring
13707 procedures to functions in the context of the @code{call} command, and
13708 functions to procedures elsewhere.
13710 @node Omissions from Ada
13711 @subsubsection Omissions from Ada
13712 @cindex Ada, omissions from
13714 Here are the notable omissions from the subset:
13718 Only a subset of the attributes are supported:
13722 @t{'First}, @t{'Last}, and @t{'Length}
13723 on array objects (not on types and subtypes).
13726 @t{'Min} and @t{'Max}.
13729 @t{'Pos} and @t{'Val}.
13735 @t{'Range} on array objects (not subtypes), but only as the right
13736 operand of the membership (@code{in}) operator.
13739 @t{'Access}, @t{'Unchecked_Access}, and
13740 @t{'Unrestricted_Access} (a GNAT extension).
13748 @code{Characters.Latin_1} are not available and
13749 concatenation is not implemented. Thus, escape characters in strings are
13750 not currently available.
13753 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13754 equality of representations. They will generally work correctly
13755 for strings and arrays whose elements have integer or enumeration types.
13756 They may not work correctly for arrays whose element
13757 types have user-defined equality, for arrays of real values
13758 (in particular, IEEE-conformant floating point, because of negative
13759 zeroes and NaNs), and for arrays whose elements contain unused bits with
13760 indeterminate values.
13763 The other component-by-component array operations (@code{and}, @code{or},
13764 @code{xor}, @code{not}, and relational tests other than equality)
13765 are not implemented.
13768 @cindex array aggregates (Ada)
13769 @cindex record aggregates (Ada)
13770 @cindex aggregates (Ada)
13771 There is limited support for array and record aggregates. They are
13772 permitted only on the right sides of assignments, as in these examples:
13775 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13776 (@value{GDBP}) set An_Array := (1, others => 0)
13777 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13778 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13779 (@value{GDBP}) set A_Record := (1, "Peter", True);
13780 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13784 discriminant's value by assigning an aggregate has an
13785 undefined effect if that discriminant is used within the record.
13786 However, you can first modify discriminants by directly assigning to
13787 them (which normally would not be allowed in Ada), and then performing an
13788 aggregate assignment. For example, given a variable @code{A_Rec}
13789 declared to have a type such as:
13792 type Rec (Len : Small_Integer := 0) is record
13794 Vals : IntArray (1 .. Len);
13798 you can assign a value with a different size of @code{Vals} with two
13802 (@value{GDBP}) set A_Rec.Len := 4
13803 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13806 As this example also illustrates, @value{GDBN} is very loose about the usual
13807 rules concerning aggregates. You may leave out some of the
13808 components of an array or record aggregate (such as the @code{Len}
13809 component in the assignment to @code{A_Rec} above); they will retain their
13810 original values upon assignment. You may freely use dynamic values as
13811 indices in component associations. You may even use overlapping or
13812 redundant component associations, although which component values are
13813 assigned in such cases is not defined.
13816 Calls to dispatching subprograms are not implemented.
13819 The overloading algorithm is much more limited (i.e., less selective)
13820 than that of real Ada. It makes only limited use of the context in
13821 which a subexpression appears to resolve its meaning, and it is much
13822 looser in its rules for allowing type matches. As a result, some
13823 function calls will be ambiguous, and the user will be asked to choose
13824 the proper resolution.
13827 The @code{new} operator is not implemented.
13830 Entry calls are not implemented.
13833 Aside from printing, arithmetic operations on the native VAX floating-point
13834 formats are not supported.
13837 It is not possible to slice a packed array.
13840 The names @code{True} and @code{False}, when not part of a qualified name,
13841 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13843 Should your program
13844 redefine these names in a package or procedure (at best a dubious practice),
13845 you will have to use fully qualified names to access their new definitions.
13848 @node Additions to Ada
13849 @subsubsection Additions to Ada
13850 @cindex Ada, deviations from
13852 As it does for other languages, @value{GDBN} makes certain generic
13853 extensions to Ada (@pxref{Expressions}):
13857 If the expression @var{E} is a variable residing in memory (typically
13858 a local variable or array element) and @var{N} is a positive integer,
13859 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13860 @var{N}-1 adjacent variables following it in memory as an array. In
13861 Ada, this operator is generally not necessary, since its prime use is
13862 in displaying parts of an array, and slicing will usually do this in
13863 Ada. However, there are occasional uses when debugging programs in
13864 which certain debugging information has been optimized away.
13867 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13868 appears in function or file @var{B}.'' When @var{B} is a file name,
13869 you must typically surround it in single quotes.
13872 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13873 @var{type} that appears at address @var{addr}.''
13876 A name starting with @samp{$} is a convenience variable
13877 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13880 In addition, @value{GDBN} provides a few other shortcuts and outright
13881 additions specific to Ada:
13885 The assignment statement is allowed as an expression, returning
13886 its right-hand operand as its value. Thus, you may enter
13889 (@value{GDBP}) set x := y + 3
13890 (@value{GDBP}) print A(tmp := y + 1)
13894 The semicolon is allowed as an ``operator,'' returning as its value
13895 the value of its right-hand operand.
13896 This allows, for example,
13897 complex conditional breaks:
13900 (@value{GDBP}) break f
13901 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13905 Rather than use catenation and symbolic character names to introduce special
13906 characters into strings, one may instead use a special bracket notation,
13907 which is also used to print strings. A sequence of characters of the form
13908 @samp{["@var{XX}"]} within a string or character literal denotes the
13909 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13910 sequence of characters @samp{["""]} also denotes a single quotation mark
13911 in strings. For example,
13913 "One line.["0a"]Next line.["0a"]"
13916 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13920 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13921 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13925 (@value{GDBP}) print 'max(x, y)
13929 When printing arrays, @value{GDBN} uses positional notation when the
13930 array has a lower bound of 1, and uses a modified named notation otherwise.
13931 For example, a one-dimensional array of three integers with a lower bound
13932 of 3 might print as
13939 That is, in contrast to valid Ada, only the first component has a @code{=>}
13943 You may abbreviate attributes in expressions with any unique,
13944 multi-character subsequence of
13945 their names (an exact match gets preference).
13946 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13947 in place of @t{a'length}.
13950 @cindex quoting Ada internal identifiers
13951 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13952 to lower case. The GNAT compiler uses upper-case characters for
13953 some of its internal identifiers, which are normally of no interest to users.
13954 For the rare occasions when you actually have to look at them,
13955 enclose them in angle brackets to avoid the lower-case mapping.
13958 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13962 Printing an object of class-wide type or dereferencing an
13963 access-to-class-wide value will display all the components of the object's
13964 specific type (as indicated by its run-time tag). Likewise, component
13965 selection on such a value will operate on the specific type of the
13970 @node Stopping Before Main Program
13971 @subsubsection Stopping at the Very Beginning
13973 @cindex breakpointing Ada elaboration code
13974 It is sometimes necessary to debug the program during elaboration, and
13975 before reaching the main procedure.
13976 As defined in the Ada Reference
13977 Manual, the elaboration code is invoked from a procedure called
13978 @code{adainit}. To run your program up to the beginning of
13979 elaboration, simply use the following two commands:
13980 @code{tbreak adainit} and @code{run}.
13983 @subsubsection Extensions for Ada Tasks
13984 @cindex Ada, tasking
13986 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13987 @value{GDBN} provides the following task-related commands:
13992 This command shows a list of current Ada tasks, as in the following example:
13999 (@value{GDBP}) info tasks
14000 ID TID P-ID Pri State Name
14001 1 8088000 0 15 Child Activation Wait main_task
14002 2 80a4000 1 15 Accept Statement b
14003 3 809a800 1 15 Child Activation Wait a
14004 * 4 80ae800 3 15 Runnable c
14009 In this listing, the asterisk before the last task indicates it to be the
14010 task currently being inspected.
14014 Represents @value{GDBN}'s internal task number.
14020 The parent's task ID (@value{GDBN}'s internal task number).
14023 The base priority of the task.
14026 Current state of the task.
14030 The task has been created but has not been activated. It cannot be
14034 The task is not blocked for any reason known to Ada. (It may be waiting
14035 for a mutex, though.) It is conceptually "executing" in normal mode.
14038 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14039 that were waiting on terminate alternatives have been awakened and have
14040 terminated themselves.
14042 @item Child Activation Wait
14043 The task is waiting for created tasks to complete activation.
14045 @item Accept Statement
14046 The task is waiting on an accept or selective wait statement.
14048 @item Waiting on entry call
14049 The task is waiting on an entry call.
14051 @item Async Select Wait
14052 The task is waiting to start the abortable part of an asynchronous
14056 The task is waiting on a select statement with only a delay
14059 @item Child Termination Wait
14060 The task is sleeping having completed a master within itself, and is
14061 waiting for the tasks dependent on that master to become terminated or
14062 waiting on a terminate Phase.
14064 @item Wait Child in Term Alt
14065 The task is sleeping waiting for tasks on terminate alternatives to
14066 finish terminating.
14068 @item Accepting RV with @var{taskno}
14069 The task is accepting a rendez-vous with the task @var{taskno}.
14073 Name of the task in the program.
14077 @kindex info task @var{taskno}
14078 @item info task @var{taskno}
14079 This command shows detailled informations on the specified task, as in
14080 the following example:
14085 (@value{GDBP}) info tasks
14086 ID TID P-ID Pri State Name
14087 1 8077880 0 15 Child Activation Wait main_task
14088 * 2 807c468 1 15 Runnable task_1
14089 (@value{GDBP}) info task 2
14090 Ada Task: 0x807c468
14093 Parent: 1 (main_task)
14099 @kindex task@r{ (Ada)}
14100 @cindex current Ada task ID
14101 This command prints the ID of the current task.
14107 (@value{GDBP}) info tasks
14108 ID TID P-ID Pri State Name
14109 1 8077870 0 15 Child Activation Wait main_task
14110 * 2 807c458 1 15 Runnable t
14111 (@value{GDBP}) task
14112 [Current task is 2]
14115 @item task @var{taskno}
14116 @cindex Ada task switching
14117 This command is like the @code{thread @var{threadno}}
14118 command (@pxref{Threads}). It switches the context of debugging
14119 from the current task to the given task.
14125 (@value{GDBP}) info tasks
14126 ID TID P-ID Pri State Name
14127 1 8077870 0 15 Child Activation Wait main_task
14128 * 2 807c458 1 15 Runnable t
14129 (@value{GDBP}) task 1
14130 [Switching to task 1]
14131 #0 0x8067726 in pthread_cond_wait ()
14133 #0 0x8067726 in pthread_cond_wait ()
14134 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14135 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14136 #3 0x806153e in system.tasking.stages.activate_tasks ()
14137 #4 0x804aacc in un () at un.adb:5
14140 @item break @var{linespec} task @var{taskno}
14141 @itemx break @var{linespec} task @var{taskno} if @dots{}
14142 @cindex breakpoints and tasks, in Ada
14143 @cindex task breakpoints, in Ada
14144 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14145 These commands are like the @code{break @dots{} thread @dots{}}
14146 command (@pxref{Thread Stops}).
14147 @var{linespec} specifies source lines, as described
14148 in @ref{Specify Location}.
14150 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14151 to specify that you only want @value{GDBN} to stop the program when a
14152 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14153 numeric task identifiers assigned by @value{GDBN}, shown in the first
14154 column of the @samp{info tasks} display.
14156 If you do not specify @samp{task @var{taskno}} when you set a
14157 breakpoint, the breakpoint applies to @emph{all} tasks of your
14160 You can use the @code{task} qualifier on conditional breakpoints as
14161 well; in this case, place @samp{task @var{taskno}} before the
14162 breakpoint condition (before the @code{if}).
14170 (@value{GDBP}) info tasks
14171 ID TID P-ID Pri State Name
14172 1 140022020 0 15 Child Activation Wait main_task
14173 2 140045060 1 15 Accept/Select Wait t2
14174 3 140044840 1 15 Runnable t1
14175 * 4 140056040 1 15 Runnable t3
14176 (@value{GDBP}) b 15 task 2
14177 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14178 (@value{GDBP}) cont
14183 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14185 (@value{GDBP}) info tasks
14186 ID TID P-ID Pri State Name
14187 1 140022020 0 15 Child Activation Wait main_task
14188 * 2 140045060 1 15 Runnable t2
14189 3 140044840 1 15 Runnable t1
14190 4 140056040 1 15 Delay Sleep t3
14194 @node Ada Tasks and Core Files
14195 @subsubsection Tasking Support when Debugging Core Files
14196 @cindex Ada tasking and core file debugging
14198 When inspecting a core file, as opposed to debugging a live program,
14199 tasking support may be limited or even unavailable, depending on
14200 the platform being used.
14201 For instance, on x86-linux, the list of tasks is available, but task
14202 switching is not supported. On Tru64, however, task switching will work
14205 On certain platforms, including Tru64, the debugger needs to perform some
14206 memory writes in order to provide Ada tasking support. When inspecting
14207 a core file, this means that the core file must be opened with read-write
14208 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14209 Under these circumstances, you should make a backup copy of the core
14210 file before inspecting it with @value{GDBN}.
14212 @node Ravenscar Profile
14213 @subsubsection Tasking Support when using the Ravenscar Profile
14214 @cindex Ravenscar Profile
14216 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14217 specifically designed for systems with safety-critical real-time
14221 @kindex set ravenscar task-switching on
14222 @cindex task switching with program using Ravenscar Profile
14223 @item set ravenscar task-switching on
14224 Allows task switching when debugging a program that uses the Ravenscar
14225 Profile. This is the default.
14227 @kindex set ravenscar task-switching off
14228 @item set ravenscar task-switching off
14229 Turn off task switching when debugging a program that uses the Ravenscar
14230 Profile. This is mostly intended to disable the code that adds support
14231 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14232 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14233 To be effective, this command should be run before the program is started.
14235 @kindex show ravenscar task-switching
14236 @item show ravenscar task-switching
14237 Show whether it is possible to switch from task to task in a program
14238 using the Ravenscar Profile.
14243 @subsubsection Known Peculiarities of Ada Mode
14244 @cindex Ada, problems
14246 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14247 we know of several problems with and limitations of Ada mode in
14249 some of which will be fixed with planned future releases of the debugger
14250 and the GNU Ada compiler.
14254 Static constants that the compiler chooses not to materialize as objects in
14255 storage are invisible to the debugger.
14258 Named parameter associations in function argument lists are ignored (the
14259 argument lists are treated as positional).
14262 Many useful library packages are currently invisible to the debugger.
14265 Fixed-point arithmetic, conversions, input, and output is carried out using
14266 floating-point arithmetic, and may give results that only approximate those on
14270 The GNAT compiler never generates the prefix @code{Standard} for any of
14271 the standard symbols defined by the Ada language. @value{GDBN} knows about
14272 this: it will strip the prefix from names when you use it, and will never
14273 look for a name you have so qualified among local symbols, nor match against
14274 symbols in other packages or subprograms. If you have
14275 defined entities anywhere in your program other than parameters and
14276 local variables whose simple names match names in @code{Standard},
14277 GNAT's lack of qualification here can cause confusion. When this happens,
14278 you can usually resolve the confusion
14279 by qualifying the problematic names with package
14280 @code{Standard} explicitly.
14283 Older versions of the compiler sometimes generate erroneous debugging
14284 information, resulting in the debugger incorrectly printing the value
14285 of affected entities. In some cases, the debugger is able to work
14286 around an issue automatically. In other cases, the debugger is able
14287 to work around the issue, but the work-around has to be specifically
14290 @kindex set ada trust-PAD-over-XVS
14291 @kindex show ada trust-PAD-over-XVS
14294 @item set ada trust-PAD-over-XVS on
14295 Configure GDB to strictly follow the GNAT encoding when computing the
14296 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14297 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14298 a complete description of the encoding used by the GNAT compiler).
14299 This is the default.
14301 @item set ada trust-PAD-over-XVS off
14302 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14303 sometimes prints the wrong value for certain entities, changing @code{ada
14304 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14305 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14306 @code{off}, but this incurs a slight performance penalty, so it is
14307 recommended to leave this setting to @code{on} unless necessary.
14311 @node Unsupported Languages
14312 @section Unsupported Languages
14314 @cindex unsupported languages
14315 @cindex minimal language
14316 In addition to the other fully-supported programming languages,
14317 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14318 It does not represent a real programming language, but provides a set
14319 of capabilities close to what the C or assembly languages provide.
14320 This should allow most simple operations to be performed while debugging
14321 an application that uses a language currently not supported by @value{GDBN}.
14323 If the language is set to @code{auto}, @value{GDBN} will automatically
14324 select this language if the current frame corresponds to an unsupported
14328 @chapter Examining the Symbol Table
14330 The commands described in this chapter allow you to inquire about the
14331 symbols (names of variables, functions and types) defined in your
14332 program. This information is inherent in the text of your program and
14333 does not change as your program executes. @value{GDBN} finds it in your
14334 program's symbol table, in the file indicated when you started @value{GDBN}
14335 (@pxref{File Options, ,Choosing Files}), or by one of the
14336 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14338 @cindex symbol names
14339 @cindex names of symbols
14340 @cindex quoting names
14341 Occasionally, you may need to refer to symbols that contain unusual
14342 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14343 most frequent case is in referring to static variables in other
14344 source files (@pxref{Variables,,Program Variables}). File names
14345 are recorded in object files as debugging symbols, but @value{GDBN} would
14346 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14347 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14348 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14355 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14358 @cindex case-insensitive symbol names
14359 @cindex case sensitivity in symbol names
14360 @kindex set case-sensitive
14361 @item set case-sensitive on
14362 @itemx set case-sensitive off
14363 @itemx set case-sensitive auto
14364 Normally, when @value{GDBN} looks up symbols, it matches their names
14365 with case sensitivity determined by the current source language.
14366 Occasionally, you may wish to control that. The command @code{set
14367 case-sensitive} lets you do that by specifying @code{on} for
14368 case-sensitive matches or @code{off} for case-insensitive ones. If
14369 you specify @code{auto}, case sensitivity is reset to the default
14370 suitable for the source language. The default is case-sensitive
14371 matches for all languages except for Fortran, for which the default is
14372 case-insensitive matches.
14374 @kindex show case-sensitive
14375 @item show case-sensitive
14376 This command shows the current setting of case sensitivity for symbols
14379 @kindex info address
14380 @cindex address of a symbol
14381 @item info address @var{symbol}
14382 Describe where the data for @var{symbol} is stored. For a register
14383 variable, this says which register it is kept in. For a non-register
14384 local variable, this prints the stack-frame offset at which the variable
14387 Note the contrast with @samp{print &@var{symbol}}, which does not work
14388 at all for a register variable, and for a stack local variable prints
14389 the exact address of the current instantiation of the variable.
14391 @kindex info symbol
14392 @cindex symbol from address
14393 @cindex closest symbol and offset for an address
14394 @item info symbol @var{addr}
14395 Print the name of a symbol which is stored at the address @var{addr}.
14396 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14397 nearest symbol and an offset from it:
14400 (@value{GDBP}) info symbol 0x54320
14401 _initialize_vx + 396 in section .text
14405 This is the opposite of the @code{info address} command. You can use
14406 it to find out the name of a variable or a function given its address.
14408 For dynamically linked executables, the name of executable or shared
14409 library containing the symbol is also printed:
14412 (@value{GDBP}) info symbol 0x400225
14413 _start + 5 in section .text of /tmp/a.out
14414 (@value{GDBP}) info symbol 0x2aaaac2811cf
14415 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14419 @item whatis [@var{arg}]
14420 Print the data type of @var{arg}, which can be either an expression
14421 or a name of a data type. With no argument, print the data type of
14422 @code{$}, the last value in the value history.
14424 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14425 is not actually evaluated, and any side-effecting operations (such as
14426 assignments or function calls) inside it do not take place.
14428 If @var{arg} is a variable or an expression, @code{whatis} prints its
14429 literal type as it is used in the source code. If the type was
14430 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14431 the data type underlying the @code{typedef}. If the type of the
14432 variable or the expression is a compound data type, such as
14433 @code{struct} or @code{class}, @code{whatis} never prints their
14434 fields or methods. It just prints the @code{struct}/@code{class}
14435 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14436 such a compound data type, use @code{ptype}.
14438 If @var{arg} is a type name that was defined using @code{typedef},
14439 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14440 Unrolling means that @code{whatis} will show the underlying type used
14441 in the @code{typedef} declaration of @var{arg}. However, if that
14442 underlying type is also a @code{typedef}, @code{whatis} will not
14445 For C code, the type names may also have the form @samp{class
14446 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14447 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14450 @item ptype [@var{arg}]
14451 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14452 detailed description of the type, instead of just the name of the type.
14453 @xref{Expressions, ,Expressions}.
14455 Contrary to @code{whatis}, @code{ptype} always unrolls any
14456 @code{typedef}s in its argument declaration, whether the argument is
14457 a variable, expression, or a data type. This means that @code{ptype}
14458 of a variable or an expression will not print literally its type as
14459 present in the source code---use @code{whatis} for that. @code{typedef}s at
14460 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14461 fields, methods and inner @code{class typedef}s of @code{struct}s,
14462 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14464 For example, for this variable declaration:
14467 typedef double real_t;
14468 struct complex @{ real_t real; double imag; @};
14469 typedef struct complex complex_t;
14471 real_t *real_pointer_var;
14475 the two commands give this output:
14479 (@value{GDBP}) whatis var
14481 (@value{GDBP}) ptype var
14482 type = struct complex @{
14486 (@value{GDBP}) whatis complex_t
14487 type = struct complex
14488 (@value{GDBP}) whatis struct complex
14489 type = struct complex
14490 (@value{GDBP}) ptype struct complex
14491 type = struct complex @{
14495 (@value{GDBP}) whatis real_pointer_var
14497 (@value{GDBP}) ptype real_pointer_var
14503 As with @code{whatis}, using @code{ptype} without an argument refers to
14504 the type of @code{$}, the last value in the value history.
14506 @cindex incomplete type
14507 Sometimes, programs use opaque data types or incomplete specifications
14508 of complex data structure. If the debug information included in the
14509 program does not allow @value{GDBN} to display a full declaration of
14510 the data type, it will say @samp{<incomplete type>}. For example,
14511 given these declarations:
14515 struct foo *fooptr;
14519 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14522 (@value{GDBP}) ptype foo
14523 $1 = <incomplete type>
14527 ``Incomplete type'' is C terminology for data types that are not
14528 completely specified.
14531 @item info types @var{regexp}
14533 Print a brief description of all types whose names match the regular
14534 expression @var{regexp} (or all types in your program, if you supply
14535 no argument). Each complete typename is matched as though it were a
14536 complete line; thus, @samp{i type value} gives information on all
14537 types in your program whose names include the string @code{value}, but
14538 @samp{i type ^value$} gives information only on types whose complete
14539 name is @code{value}.
14541 This command differs from @code{ptype} in two ways: first, like
14542 @code{whatis}, it does not print a detailed description; second, it
14543 lists all source files where a type is defined.
14546 @cindex local variables
14547 @item info scope @var{location}
14548 List all the variables local to a particular scope. This command
14549 accepts a @var{location} argument---a function name, a source line, or
14550 an address preceded by a @samp{*}, and prints all the variables local
14551 to the scope defined by that location. (@xref{Specify Location}, for
14552 details about supported forms of @var{location}.) For example:
14555 (@value{GDBP}) @b{info scope command_line_handler}
14556 Scope for command_line_handler:
14557 Symbol rl is an argument at stack/frame offset 8, length 4.
14558 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14559 Symbol linelength is in static storage at address 0x150a1c, length 4.
14560 Symbol p is a local variable in register $esi, length 4.
14561 Symbol p1 is a local variable in register $ebx, length 4.
14562 Symbol nline is a local variable in register $edx, length 4.
14563 Symbol repeat is a local variable at frame offset -8, length 4.
14567 This command is especially useful for determining what data to collect
14568 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14571 @kindex info source
14573 Show information about the current source file---that is, the source file for
14574 the function containing the current point of execution:
14577 the name of the source file, and the directory containing it,
14579 the directory it was compiled in,
14581 its length, in lines,
14583 which programming language it is written in,
14585 whether the executable includes debugging information for that file, and
14586 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14588 whether the debugging information includes information about
14589 preprocessor macros.
14593 @kindex info sources
14595 Print the names of all source files in your program for which there is
14596 debugging information, organized into two lists: files whose symbols
14597 have already been read, and files whose symbols will be read when needed.
14599 @kindex info functions
14600 @item info functions
14601 Print the names and data types of all defined functions.
14603 @item info functions @var{regexp}
14604 Print the names and data types of all defined functions
14605 whose names contain a match for regular expression @var{regexp}.
14606 Thus, @samp{info fun step} finds all functions whose names
14607 include @code{step}; @samp{info fun ^step} finds those whose names
14608 start with @code{step}. If a function name contains characters
14609 that conflict with the regular expression language (e.g.@:
14610 @samp{operator*()}), they may be quoted with a backslash.
14612 @kindex info variables
14613 @item info variables
14614 Print the names and data types of all variables that are defined
14615 outside of functions (i.e.@: excluding local variables).
14617 @item info variables @var{regexp}
14618 Print the names and data types of all variables (except for local
14619 variables) whose names contain a match for regular expression
14622 @kindex info classes
14623 @cindex Objective-C, classes and selectors
14625 @itemx info classes @var{regexp}
14626 Display all Objective-C classes in your program, or
14627 (with the @var{regexp} argument) all those matching a particular regular
14630 @kindex info selectors
14631 @item info selectors
14632 @itemx info selectors @var{regexp}
14633 Display all Objective-C selectors in your program, or
14634 (with the @var{regexp} argument) all those matching a particular regular
14638 This was never implemented.
14639 @kindex info methods
14641 @itemx info methods @var{regexp}
14642 The @code{info methods} command permits the user to examine all defined
14643 methods within C@t{++} program, or (with the @var{regexp} argument) a
14644 specific set of methods found in the various C@t{++} classes. Many
14645 C@t{++} classes provide a large number of methods. Thus, the output
14646 from the @code{ptype} command can be overwhelming and hard to use. The
14647 @code{info-methods} command filters the methods, printing only those
14648 which match the regular-expression @var{regexp}.
14651 @cindex reloading symbols
14652 Some systems allow individual object files that make up your program to
14653 be replaced without stopping and restarting your program. For example,
14654 in VxWorks you can simply recompile a defective object file and keep on
14655 running. If you are running on one of these systems, you can allow
14656 @value{GDBN} to reload the symbols for automatically relinked modules:
14659 @kindex set symbol-reloading
14660 @item set symbol-reloading on
14661 Replace symbol definitions for the corresponding source file when an
14662 object file with a particular name is seen again.
14664 @item set symbol-reloading off
14665 Do not replace symbol definitions when encountering object files of the
14666 same name more than once. This is the default state; if you are not
14667 running on a system that permits automatic relinking of modules, you
14668 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14669 may discard symbols when linking large programs, that may contain
14670 several modules (from different directories or libraries) with the same
14673 @kindex show symbol-reloading
14674 @item show symbol-reloading
14675 Show the current @code{on} or @code{off} setting.
14678 @cindex opaque data types
14679 @kindex set opaque-type-resolution
14680 @item set opaque-type-resolution on
14681 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14682 declared as a pointer to a @code{struct}, @code{class}, or
14683 @code{union}---for example, @code{struct MyType *}---that is used in one
14684 source file although the full declaration of @code{struct MyType} is in
14685 another source file. The default is on.
14687 A change in the setting of this subcommand will not take effect until
14688 the next time symbols for a file are loaded.
14690 @item set opaque-type-resolution off
14691 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14692 is printed as follows:
14694 @{<no data fields>@}
14697 @kindex show opaque-type-resolution
14698 @item show opaque-type-resolution
14699 Show whether opaque types are resolved or not.
14701 @kindex maint print symbols
14702 @cindex symbol dump
14703 @kindex maint print psymbols
14704 @cindex partial symbol dump
14705 @item maint print symbols @var{filename}
14706 @itemx maint print psymbols @var{filename}
14707 @itemx maint print msymbols @var{filename}
14708 Write a dump of debugging symbol data into the file @var{filename}.
14709 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14710 symbols with debugging data are included. If you use @samp{maint print
14711 symbols}, @value{GDBN} includes all the symbols for which it has already
14712 collected full details: that is, @var{filename} reflects symbols for
14713 only those files whose symbols @value{GDBN} has read. You can use the
14714 command @code{info sources} to find out which files these are. If you
14715 use @samp{maint print psymbols} instead, the dump shows information about
14716 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14717 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14718 @samp{maint print msymbols} dumps just the minimal symbol information
14719 required for each object file from which @value{GDBN} has read some symbols.
14720 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14721 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14723 @kindex maint info symtabs
14724 @kindex maint info psymtabs
14725 @cindex listing @value{GDBN}'s internal symbol tables
14726 @cindex symbol tables, listing @value{GDBN}'s internal
14727 @cindex full symbol tables, listing @value{GDBN}'s internal
14728 @cindex partial symbol tables, listing @value{GDBN}'s internal
14729 @item maint info symtabs @r{[} @var{regexp} @r{]}
14730 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14732 List the @code{struct symtab} or @code{struct partial_symtab}
14733 structures whose names match @var{regexp}. If @var{regexp} is not
14734 given, list them all. The output includes expressions which you can
14735 copy into a @value{GDBN} debugging this one to examine a particular
14736 structure in more detail. For example:
14739 (@value{GDBP}) maint info psymtabs dwarf2read
14740 @{ objfile /home/gnu/build/gdb/gdb
14741 ((struct objfile *) 0x82e69d0)
14742 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14743 ((struct partial_symtab *) 0x8474b10)
14746 text addresses 0x814d3c8 -- 0x8158074
14747 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14748 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14749 dependencies (none)
14752 (@value{GDBP}) maint info symtabs
14756 We see that there is one partial symbol table whose filename contains
14757 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14758 and we see that @value{GDBN} has not read in any symtabs yet at all.
14759 If we set a breakpoint on a function, that will cause @value{GDBN} to
14760 read the symtab for the compilation unit containing that function:
14763 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14764 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14766 (@value{GDBP}) maint info symtabs
14767 @{ objfile /home/gnu/build/gdb/gdb
14768 ((struct objfile *) 0x82e69d0)
14769 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14770 ((struct symtab *) 0x86c1f38)
14773 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14774 linetable ((struct linetable *) 0x8370fa0)
14775 debugformat DWARF 2
14784 @chapter Altering Execution
14786 Once you think you have found an error in your program, you might want to
14787 find out for certain whether correcting the apparent error would lead to
14788 correct results in the rest of the run. You can find the answer by
14789 experiment, using the @value{GDBN} features for altering execution of the
14792 For example, you can store new values into variables or memory
14793 locations, give your program a signal, restart it at a different
14794 address, or even return prematurely from a function.
14797 * Assignment:: Assignment to variables
14798 * Jumping:: Continuing at a different address
14799 * Signaling:: Giving your program a signal
14800 * Returning:: Returning from a function
14801 * Calling:: Calling your program's functions
14802 * Patching:: Patching your program
14806 @section Assignment to Variables
14809 @cindex setting variables
14810 To alter the value of a variable, evaluate an assignment expression.
14811 @xref{Expressions, ,Expressions}. For example,
14818 stores the value 4 into the variable @code{x}, and then prints the
14819 value of the assignment expression (which is 4).
14820 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14821 information on operators in supported languages.
14823 @kindex set variable
14824 @cindex variables, setting
14825 If you are not interested in seeing the value of the assignment, use the
14826 @code{set} command instead of the @code{print} command. @code{set} is
14827 really the same as @code{print} except that the expression's value is
14828 not printed and is not put in the value history (@pxref{Value History,
14829 ,Value History}). The expression is evaluated only for its effects.
14831 If the beginning of the argument string of the @code{set} command
14832 appears identical to a @code{set} subcommand, use the @code{set
14833 variable} command instead of just @code{set}. This command is identical
14834 to @code{set} except for its lack of subcommands. For example, if your
14835 program has a variable @code{width}, you get an error if you try to set
14836 a new value with just @samp{set width=13}, because @value{GDBN} has the
14837 command @code{set width}:
14840 (@value{GDBP}) whatis width
14842 (@value{GDBP}) p width
14844 (@value{GDBP}) set width=47
14845 Invalid syntax in expression.
14849 The invalid expression, of course, is @samp{=47}. In
14850 order to actually set the program's variable @code{width}, use
14853 (@value{GDBP}) set var width=47
14856 Because the @code{set} command has many subcommands that can conflict
14857 with the names of program variables, it is a good idea to use the
14858 @code{set variable} command instead of just @code{set}. For example, if
14859 your program has a variable @code{g}, you run into problems if you try
14860 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14861 the command @code{set gnutarget}, abbreviated @code{set g}:
14865 (@value{GDBP}) whatis g
14869 (@value{GDBP}) set g=4
14873 The program being debugged has been started already.
14874 Start it from the beginning? (y or n) y
14875 Starting program: /home/smith/cc_progs/a.out
14876 "/home/smith/cc_progs/a.out": can't open to read symbols:
14877 Invalid bfd target.
14878 (@value{GDBP}) show g
14879 The current BFD target is "=4".
14884 The program variable @code{g} did not change, and you silently set the
14885 @code{gnutarget} to an invalid value. In order to set the variable
14889 (@value{GDBP}) set var g=4
14892 @value{GDBN} allows more implicit conversions in assignments than C; you can
14893 freely store an integer value into a pointer variable or vice versa,
14894 and you can convert any structure to any other structure that is the
14895 same length or shorter.
14896 @comment FIXME: how do structs align/pad in these conversions?
14897 @comment /doc@cygnus.com 18dec1990
14899 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14900 construct to generate a value of specified type at a specified address
14901 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14902 to memory location @code{0x83040} as an integer (which implies a certain size
14903 and representation in memory), and
14906 set @{int@}0x83040 = 4
14910 stores the value 4 into that memory location.
14913 @section Continuing at a Different Address
14915 Ordinarily, when you continue your program, you do so at the place where
14916 it stopped, with the @code{continue} command. You can instead continue at
14917 an address of your own choosing, with the following commands:
14921 @item jump @var{linespec}
14922 @itemx jump @var{location}
14923 Resume execution at line @var{linespec} or at address given by
14924 @var{location}. Execution stops again immediately if there is a
14925 breakpoint there. @xref{Specify Location}, for a description of the
14926 different forms of @var{linespec} and @var{location}. It is common
14927 practice to use the @code{tbreak} command in conjunction with
14928 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14930 The @code{jump} command does not change the current stack frame, or
14931 the stack pointer, or the contents of any memory location or any
14932 register other than the program counter. If line @var{linespec} is in
14933 a different function from the one currently executing, the results may
14934 be bizarre if the two functions expect different patterns of arguments or
14935 of local variables. For this reason, the @code{jump} command requests
14936 confirmation if the specified line is not in the function currently
14937 executing. However, even bizarre results are predictable if you are
14938 well acquainted with the machine-language code of your program.
14941 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14942 On many systems, you can get much the same effect as the @code{jump}
14943 command by storing a new value into the register @code{$pc}. The
14944 difference is that this does not start your program running; it only
14945 changes the address of where it @emph{will} run when you continue. For
14953 makes the next @code{continue} command or stepping command execute at
14954 address @code{0x485}, rather than at the address where your program stopped.
14955 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14957 The most common occasion to use the @code{jump} command is to back
14958 up---perhaps with more breakpoints set---over a portion of a program
14959 that has already executed, in order to examine its execution in more
14964 @section Giving your Program a Signal
14965 @cindex deliver a signal to a program
14969 @item signal @var{signal}
14970 Resume execution where your program stopped, but immediately give it the
14971 signal @var{signal}. @var{signal} can be the name or the number of a
14972 signal. For example, on many systems @code{signal 2} and @code{signal
14973 SIGINT} are both ways of sending an interrupt signal.
14975 Alternatively, if @var{signal} is zero, continue execution without
14976 giving a signal. This is useful when your program stopped on account of
14977 a signal and would ordinary see the signal when resumed with the
14978 @code{continue} command; @samp{signal 0} causes it to resume without a
14981 @code{signal} does not repeat when you press @key{RET} a second time
14982 after executing the command.
14986 Invoking the @code{signal} command is not the same as invoking the
14987 @code{kill} utility from the shell. Sending a signal with @code{kill}
14988 causes @value{GDBN} to decide what to do with the signal depending on
14989 the signal handling tables (@pxref{Signals}). The @code{signal} command
14990 passes the signal directly to your program.
14994 @section Returning from a Function
14997 @cindex returning from a function
15000 @itemx return @var{expression}
15001 You can cancel execution of a function call with the @code{return}
15002 command. If you give an
15003 @var{expression} argument, its value is used as the function's return
15007 When you use @code{return}, @value{GDBN} discards the selected stack frame
15008 (and all frames within it). You can think of this as making the
15009 discarded frame return prematurely. If you wish to specify a value to
15010 be returned, give that value as the argument to @code{return}.
15012 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15013 Frame}), and any other frames inside of it, leaving its caller as the
15014 innermost remaining frame. That frame becomes selected. The
15015 specified value is stored in the registers used for returning values
15018 The @code{return} command does not resume execution; it leaves the
15019 program stopped in the state that would exist if the function had just
15020 returned. In contrast, the @code{finish} command (@pxref{Continuing
15021 and Stepping, ,Continuing and Stepping}) resumes execution until the
15022 selected stack frame returns naturally.
15024 @value{GDBN} needs to know how the @var{expression} argument should be set for
15025 the inferior. The concrete registers assignment depends on the OS ABI and the
15026 type being returned by the selected stack frame. For example it is common for
15027 OS ABI to return floating point values in FPU registers while integer values in
15028 CPU registers. Still some ABIs return even floating point values in CPU
15029 registers. Larger integer widths (such as @code{long long int}) also have
15030 specific placement rules. @value{GDBN} already knows the OS ABI from its
15031 current target so it needs to find out also the type being returned to make the
15032 assignment into the right register(s).
15034 Normally, the selected stack frame has debug info. @value{GDBN} will always
15035 use the debug info instead of the implicit type of @var{expression} when the
15036 debug info is available. For example, if you type @kbd{return -1}, and the
15037 function in the current stack frame is declared to return a @code{long long
15038 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15039 into a @code{long long int}:
15042 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15044 (@value{GDBP}) return -1
15045 Make func return now? (y or n) y
15046 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15047 43 printf ("result=%lld\n", func ());
15051 However, if the selected stack frame does not have a debug info, e.g., if the
15052 function was compiled without debug info, @value{GDBN} has to find out the type
15053 to return from user. Specifying a different type by mistake may set the value
15054 in different inferior registers than the caller code expects. For example,
15055 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15056 of a @code{long long int} result for a debug info less function (on 32-bit
15057 architectures). Therefore the user is required to specify the return type by
15058 an appropriate cast explicitly:
15061 Breakpoint 2, 0x0040050b in func ()
15062 (@value{GDBP}) return -1
15063 Return value type not available for selected stack frame.
15064 Please use an explicit cast of the value to return.
15065 (@value{GDBP}) return (long long int) -1
15066 Make selected stack frame return now? (y or n) y
15067 #0 0x00400526 in main ()
15072 @section Calling Program Functions
15075 @cindex calling functions
15076 @cindex inferior functions, calling
15077 @item print @var{expr}
15078 Evaluate the expression @var{expr} and display the resulting value.
15079 @var{expr} may include calls to functions in the program being
15083 @item call @var{expr}
15084 Evaluate the expression @var{expr} without displaying @code{void}
15087 You can use this variant of the @code{print} command if you want to
15088 execute a function from your program that does not return anything
15089 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15090 with @code{void} returned values that @value{GDBN} will otherwise
15091 print. If the result is not void, it is printed and saved in the
15095 It is possible for the function you call via the @code{print} or
15096 @code{call} command to generate a signal (e.g., if there's a bug in
15097 the function, or if you passed it incorrect arguments). What happens
15098 in that case is controlled by the @code{set unwindonsignal} command.
15100 Similarly, with a C@t{++} program it is possible for the function you
15101 call via the @code{print} or @code{call} command to generate an
15102 exception that is not handled due to the constraints of the dummy
15103 frame. In this case, any exception that is raised in the frame, but has
15104 an out-of-frame exception handler will not be found. GDB builds a
15105 dummy-frame for the inferior function call, and the unwinder cannot
15106 seek for exception handlers outside of this dummy-frame. What happens
15107 in that case is controlled by the
15108 @code{set unwind-on-terminating-exception} command.
15111 @item set unwindonsignal
15112 @kindex set unwindonsignal
15113 @cindex unwind stack in called functions
15114 @cindex call dummy stack unwinding
15115 Set unwinding of the stack if a signal is received while in a function
15116 that @value{GDBN} called in the program being debugged. If set to on,
15117 @value{GDBN} unwinds the stack it created for the call and restores
15118 the context to what it was before the call. If set to off (the
15119 default), @value{GDBN} stops in the frame where the signal was
15122 @item show unwindonsignal
15123 @kindex show unwindonsignal
15124 Show the current setting of stack unwinding in the functions called by
15127 @item set unwind-on-terminating-exception
15128 @kindex set unwind-on-terminating-exception
15129 @cindex unwind stack in called functions with unhandled exceptions
15130 @cindex call dummy stack unwinding on unhandled exception.
15131 Set unwinding of the stack if a C@t{++} exception is raised, but left
15132 unhandled while in a function that @value{GDBN} called in the program being
15133 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15134 it created for the call and restores the context to what it was before
15135 the call. If set to off, @value{GDBN} the exception is delivered to
15136 the default C@t{++} exception handler and the inferior terminated.
15138 @item show unwind-on-terminating-exception
15139 @kindex show unwind-on-terminating-exception
15140 Show the current setting of stack unwinding in the functions called by
15145 @cindex weak alias functions
15146 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15147 for another function. In such case, @value{GDBN} might not pick up
15148 the type information, including the types of the function arguments,
15149 which causes @value{GDBN} to call the inferior function incorrectly.
15150 As a result, the called function will function erroneously and may
15151 even crash. A solution to that is to use the name of the aliased
15155 @section Patching Programs
15157 @cindex patching binaries
15158 @cindex writing into executables
15159 @cindex writing into corefiles
15161 By default, @value{GDBN} opens the file containing your program's
15162 executable code (or the corefile) read-only. This prevents accidental
15163 alterations to machine code; but it also prevents you from intentionally
15164 patching your program's binary.
15166 If you'd like to be able to patch the binary, you can specify that
15167 explicitly with the @code{set write} command. For example, you might
15168 want to turn on internal debugging flags, or even to make emergency
15174 @itemx set write off
15175 If you specify @samp{set write on}, @value{GDBN} opens executable and
15176 core files for both reading and writing; if you specify @kbd{set write
15177 off} (the default), @value{GDBN} opens them read-only.
15179 If you have already loaded a file, you must load it again (using the
15180 @code{exec-file} or @code{core-file} command) after changing @code{set
15181 write}, for your new setting to take effect.
15185 Display whether executable files and core files are opened for writing
15186 as well as reading.
15190 @chapter @value{GDBN} Files
15192 @value{GDBN} needs to know the file name of the program to be debugged,
15193 both in order to read its symbol table and in order to start your
15194 program. To debug a core dump of a previous run, you must also tell
15195 @value{GDBN} the name of the core dump file.
15198 * Files:: Commands to specify files
15199 * Separate Debug Files:: Debugging information in separate files
15200 * Index Files:: Index files speed up GDB
15201 * Symbol Errors:: Errors reading symbol files
15202 * Data Files:: GDB data files
15206 @section Commands to Specify Files
15208 @cindex symbol table
15209 @cindex core dump file
15211 You may want to specify executable and core dump file names. The usual
15212 way to do this is at start-up time, using the arguments to
15213 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15214 Out of @value{GDBN}}).
15216 Occasionally it is necessary to change to a different file during a
15217 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15218 specify a file you want to use. Or you are debugging a remote target
15219 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15220 Program}). In these situations the @value{GDBN} commands to specify
15221 new files are useful.
15224 @cindex executable file
15226 @item file @var{filename}
15227 Use @var{filename} as the program to be debugged. It is read for its
15228 symbols and for the contents of pure memory. It is also the program
15229 executed when you use the @code{run} command. If you do not specify a
15230 directory and the file is not found in the @value{GDBN} working directory,
15231 @value{GDBN} uses the environment variable @code{PATH} as a list of
15232 directories to search, just as the shell does when looking for a program
15233 to run. You can change the value of this variable, for both @value{GDBN}
15234 and your program, using the @code{path} command.
15236 @cindex unlinked object files
15237 @cindex patching object files
15238 You can load unlinked object @file{.o} files into @value{GDBN} using
15239 the @code{file} command. You will not be able to ``run'' an object
15240 file, but you can disassemble functions and inspect variables. Also,
15241 if the underlying BFD functionality supports it, you could use
15242 @kbd{gdb -write} to patch object files using this technique. Note
15243 that @value{GDBN} can neither interpret nor modify relocations in this
15244 case, so branches and some initialized variables will appear to go to
15245 the wrong place. But this feature is still handy from time to time.
15248 @code{file} with no argument makes @value{GDBN} discard any information it
15249 has on both executable file and the symbol table.
15252 @item exec-file @r{[} @var{filename} @r{]}
15253 Specify that the program to be run (but not the symbol table) is found
15254 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15255 if necessary to locate your program. Omitting @var{filename} means to
15256 discard information on the executable file.
15258 @kindex symbol-file
15259 @item symbol-file @r{[} @var{filename} @r{]}
15260 Read symbol table information from file @var{filename}. @code{PATH} is
15261 searched when necessary. Use the @code{file} command to get both symbol
15262 table and program to run from the same file.
15264 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15265 program's symbol table.
15267 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15268 some breakpoints and auto-display expressions. This is because they may
15269 contain pointers to the internal data recording symbols and data types,
15270 which are part of the old symbol table data being discarded inside
15273 @code{symbol-file} does not repeat if you press @key{RET} again after
15276 When @value{GDBN} is configured for a particular environment, it
15277 understands debugging information in whatever format is the standard
15278 generated for that environment; you may use either a @sc{gnu} compiler, or
15279 other compilers that adhere to the local conventions.
15280 Best results are usually obtained from @sc{gnu} compilers; for example,
15281 using @code{@value{NGCC}} you can generate debugging information for
15284 For most kinds of object files, with the exception of old SVR3 systems
15285 using COFF, the @code{symbol-file} command does not normally read the
15286 symbol table in full right away. Instead, it scans the symbol table
15287 quickly to find which source files and which symbols are present. The
15288 details are read later, one source file at a time, as they are needed.
15290 The purpose of this two-stage reading strategy is to make @value{GDBN}
15291 start up faster. For the most part, it is invisible except for
15292 occasional pauses while the symbol table details for a particular source
15293 file are being read. (The @code{set verbose} command can turn these
15294 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15295 Warnings and Messages}.)
15297 We have not implemented the two-stage strategy for COFF yet. When the
15298 symbol table is stored in COFF format, @code{symbol-file} reads the
15299 symbol table data in full right away. Note that ``stabs-in-COFF''
15300 still does the two-stage strategy, since the debug info is actually
15304 @cindex reading symbols immediately
15305 @cindex symbols, reading immediately
15306 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15307 @itemx file @r{[} -readnow @r{]} @var{filename}
15308 You can override the @value{GDBN} two-stage strategy for reading symbol
15309 tables by using the @samp{-readnow} option with any of the commands that
15310 load symbol table information, if you want to be sure @value{GDBN} has the
15311 entire symbol table available.
15313 @c FIXME: for now no mention of directories, since this seems to be in
15314 @c flux. 13mar1992 status is that in theory GDB would look either in
15315 @c current dir or in same dir as myprog; but issues like competing
15316 @c GDB's, or clutter in system dirs, mean that in practice right now
15317 @c only current dir is used. FFish says maybe a special GDB hierarchy
15318 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15322 @item core-file @r{[}@var{filename}@r{]}
15324 Specify the whereabouts of a core dump file to be used as the ``contents
15325 of memory''. Traditionally, core files contain only some parts of the
15326 address space of the process that generated them; @value{GDBN} can access the
15327 executable file itself for other parts.
15329 @code{core-file} with no argument specifies that no core file is
15332 Note that the core file is ignored when your program is actually running
15333 under @value{GDBN}. So, if you have been running your program and you
15334 wish to debug a core file instead, you must kill the subprocess in which
15335 the program is running. To do this, use the @code{kill} command
15336 (@pxref{Kill Process, ,Killing the Child Process}).
15338 @kindex add-symbol-file
15339 @cindex dynamic linking
15340 @item add-symbol-file @var{filename} @var{address}
15341 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15342 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15343 The @code{add-symbol-file} command reads additional symbol table
15344 information from the file @var{filename}. You would use this command
15345 when @var{filename} has been dynamically loaded (by some other means)
15346 into the program that is running. @var{address} should be the memory
15347 address at which the file has been loaded; @value{GDBN} cannot figure
15348 this out for itself. You can additionally specify an arbitrary number
15349 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15350 section name and base address for that section. You can specify any
15351 @var{address} as an expression.
15353 The symbol table of the file @var{filename} is added to the symbol table
15354 originally read with the @code{symbol-file} command. You can use the
15355 @code{add-symbol-file} command any number of times; the new symbol data
15356 thus read keeps adding to the old. To discard all old symbol data
15357 instead, use the @code{symbol-file} command without any arguments.
15359 @cindex relocatable object files, reading symbols from
15360 @cindex object files, relocatable, reading symbols from
15361 @cindex reading symbols from relocatable object files
15362 @cindex symbols, reading from relocatable object files
15363 @cindex @file{.o} files, reading symbols from
15364 Although @var{filename} is typically a shared library file, an
15365 executable file, or some other object file which has been fully
15366 relocated for loading into a process, you can also load symbolic
15367 information from relocatable @file{.o} files, as long as:
15371 the file's symbolic information refers only to linker symbols defined in
15372 that file, not to symbols defined by other object files,
15374 every section the file's symbolic information refers to has actually
15375 been loaded into the inferior, as it appears in the file, and
15377 you can determine the address at which every section was loaded, and
15378 provide these to the @code{add-symbol-file} command.
15382 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15383 relocatable files into an already running program; such systems
15384 typically make the requirements above easy to meet. However, it's
15385 important to recognize that many native systems use complex link
15386 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15387 assembly, for example) that make the requirements difficult to meet. In
15388 general, one cannot assume that using @code{add-symbol-file} to read a
15389 relocatable object file's symbolic information will have the same effect
15390 as linking the relocatable object file into the program in the normal
15393 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15395 @kindex add-symbol-file-from-memory
15396 @cindex @code{syscall DSO}
15397 @cindex load symbols from memory
15398 @item add-symbol-file-from-memory @var{address}
15399 Load symbols from the given @var{address} in a dynamically loaded
15400 object file whose image is mapped directly into the inferior's memory.
15401 For example, the Linux kernel maps a @code{syscall DSO} into each
15402 process's address space; this DSO provides kernel-specific code for
15403 some system calls. The argument can be any expression whose
15404 evaluation yields the address of the file's shared object file header.
15405 For this command to work, you must have used @code{symbol-file} or
15406 @code{exec-file} commands in advance.
15408 @kindex add-shared-symbol-files
15410 @item add-shared-symbol-files @var{library-file}
15411 @itemx assf @var{library-file}
15412 The @code{add-shared-symbol-files} command can currently be used only
15413 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15414 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15415 @value{GDBN} automatically looks for shared libraries, however if
15416 @value{GDBN} does not find yours, you can invoke
15417 @code{add-shared-symbol-files}. It takes one argument: the shared
15418 library's file name. @code{assf} is a shorthand alias for
15419 @code{add-shared-symbol-files}.
15422 @item section @var{section} @var{addr}
15423 The @code{section} command changes the base address of the named
15424 @var{section} of the exec file to @var{addr}. This can be used if the
15425 exec file does not contain section addresses, (such as in the
15426 @code{a.out} format), or when the addresses specified in the file
15427 itself are wrong. Each section must be changed separately. The
15428 @code{info files} command, described below, lists all the sections and
15432 @kindex info target
15435 @code{info files} and @code{info target} are synonymous; both print the
15436 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15437 including the names of the executable and core dump files currently in
15438 use by @value{GDBN}, and the files from which symbols were loaded. The
15439 command @code{help target} lists all possible targets rather than
15442 @kindex maint info sections
15443 @item maint info sections
15444 Another command that can give you extra information about program sections
15445 is @code{maint info sections}. In addition to the section information
15446 displayed by @code{info files}, this command displays the flags and file
15447 offset of each section in the executable and core dump files. In addition,
15448 @code{maint info sections} provides the following command options (which
15449 may be arbitrarily combined):
15453 Display sections for all loaded object files, including shared libraries.
15454 @item @var{sections}
15455 Display info only for named @var{sections}.
15456 @item @var{section-flags}
15457 Display info only for sections for which @var{section-flags} are true.
15458 The section flags that @value{GDBN} currently knows about are:
15461 Section will have space allocated in the process when loaded.
15462 Set for all sections except those containing debug information.
15464 Section will be loaded from the file into the child process memory.
15465 Set for pre-initialized code and data, clear for @code{.bss} sections.
15467 Section needs to be relocated before loading.
15469 Section cannot be modified by the child process.
15471 Section contains executable code only.
15473 Section contains data only (no executable code).
15475 Section will reside in ROM.
15477 Section contains data for constructor/destructor lists.
15479 Section is not empty.
15481 An instruction to the linker to not output the section.
15482 @item COFF_SHARED_LIBRARY
15483 A notification to the linker that the section contains
15484 COFF shared library information.
15486 Section contains common symbols.
15489 @kindex set trust-readonly-sections
15490 @cindex read-only sections
15491 @item set trust-readonly-sections on
15492 Tell @value{GDBN} that readonly sections in your object file
15493 really are read-only (i.e.@: that their contents will not change).
15494 In that case, @value{GDBN} can fetch values from these sections
15495 out of the object file, rather than from the target program.
15496 For some targets (notably embedded ones), this can be a significant
15497 enhancement to debugging performance.
15499 The default is off.
15501 @item set trust-readonly-sections off
15502 Tell @value{GDBN} not to trust readonly sections. This means that
15503 the contents of the section might change while the program is running,
15504 and must therefore be fetched from the target when needed.
15506 @item show trust-readonly-sections
15507 Show the current setting of trusting readonly sections.
15510 All file-specifying commands allow both absolute and relative file names
15511 as arguments. @value{GDBN} always converts the file name to an absolute file
15512 name and remembers it that way.
15514 @cindex shared libraries
15515 @anchor{Shared Libraries}
15516 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15517 and IBM RS/6000 AIX shared libraries.
15519 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15520 shared libraries. @xref{Expat}.
15522 @value{GDBN} automatically loads symbol definitions from shared libraries
15523 when you use the @code{run} command, or when you examine a core file.
15524 (Before you issue the @code{run} command, @value{GDBN} does not understand
15525 references to a function in a shared library, however---unless you are
15526 debugging a core file).
15528 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15529 automatically loads the symbols at the time of the @code{shl_load} call.
15531 @c FIXME: some @value{GDBN} release may permit some refs to undef
15532 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15533 @c FIXME...lib; check this from time to time when updating manual
15535 There are times, however, when you may wish to not automatically load
15536 symbol definitions from shared libraries, such as when they are
15537 particularly large or there are many of them.
15539 To control the automatic loading of shared library symbols, use the
15543 @kindex set auto-solib-add
15544 @item set auto-solib-add @var{mode}
15545 If @var{mode} is @code{on}, symbols from all shared object libraries
15546 will be loaded automatically when the inferior begins execution, you
15547 attach to an independently started inferior, or when the dynamic linker
15548 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15549 is @code{off}, symbols must be loaded manually, using the
15550 @code{sharedlibrary} command. The default value is @code{on}.
15552 @cindex memory used for symbol tables
15553 If your program uses lots of shared libraries with debug info that
15554 takes large amounts of memory, you can decrease the @value{GDBN}
15555 memory footprint by preventing it from automatically loading the
15556 symbols from shared libraries. To that end, type @kbd{set
15557 auto-solib-add off} before running the inferior, then load each
15558 library whose debug symbols you do need with @kbd{sharedlibrary
15559 @var{regexp}}, where @var{regexp} is a regular expression that matches
15560 the libraries whose symbols you want to be loaded.
15562 @kindex show auto-solib-add
15563 @item show auto-solib-add
15564 Display the current autoloading mode.
15567 @cindex load shared library
15568 To explicitly load shared library symbols, use the @code{sharedlibrary}
15572 @kindex info sharedlibrary
15574 @item info share @var{regex}
15575 @itemx info sharedlibrary @var{regex}
15576 Print the names of the shared libraries which are currently loaded
15577 that match @var{regex}. If @var{regex} is omitted then print
15578 all shared libraries that are loaded.
15580 @kindex sharedlibrary
15582 @item sharedlibrary @var{regex}
15583 @itemx share @var{regex}
15584 Load shared object library symbols for files matching a
15585 Unix regular expression.
15586 As with files loaded automatically, it only loads shared libraries
15587 required by your program for a core file or after typing @code{run}. If
15588 @var{regex} is omitted all shared libraries required by your program are
15591 @item nosharedlibrary
15592 @kindex nosharedlibrary
15593 @cindex unload symbols from shared libraries
15594 Unload all shared object library symbols. This discards all symbols
15595 that have been loaded from all shared libraries. Symbols from shared
15596 libraries that were loaded by explicit user requests are not
15600 Sometimes you may wish that @value{GDBN} stops and gives you control
15601 when any of shared library events happen. Use the @code{set
15602 stop-on-solib-events} command for this:
15605 @item set stop-on-solib-events
15606 @kindex set stop-on-solib-events
15607 This command controls whether @value{GDBN} should give you control
15608 when the dynamic linker notifies it about some shared library event.
15609 The most common event of interest is loading or unloading of a new
15612 @item show stop-on-solib-events
15613 @kindex show stop-on-solib-events
15614 Show whether @value{GDBN} stops and gives you control when shared
15615 library events happen.
15618 Shared libraries are also supported in many cross or remote debugging
15619 configurations. @value{GDBN} needs to have access to the target's libraries;
15620 this can be accomplished either by providing copies of the libraries
15621 on the host system, or by asking @value{GDBN} to automatically retrieve the
15622 libraries from the target. If copies of the target libraries are
15623 provided, they need to be the same as the target libraries, although the
15624 copies on the target can be stripped as long as the copies on the host are
15627 @cindex where to look for shared libraries
15628 For remote debugging, you need to tell @value{GDBN} where the target
15629 libraries are, so that it can load the correct copies---otherwise, it
15630 may try to load the host's libraries. @value{GDBN} has two variables
15631 to specify the search directories for target libraries.
15634 @cindex prefix for shared library file names
15635 @cindex system root, alternate
15636 @kindex set solib-absolute-prefix
15637 @kindex set sysroot
15638 @item set sysroot @var{path}
15639 Use @var{path} as the system root for the program being debugged. Any
15640 absolute shared library paths will be prefixed with @var{path}; many
15641 runtime loaders store the absolute paths to the shared library in the
15642 target program's memory. If you use @code{set sysroot} to find shared
15643 libraries, they need to be laid out in the same way that they are on
15644 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15647 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15648 retrieve the target libraries from the remote system. This is only
15649 supported when using a remote target that supports the @code{remote get}
15650 command (@pxref{File Transfer,,Sending files to a remote system}).
15651 The part of @var{path} following the initial @file{remote:}
15652 (if present) is used as system root prefix on the remote file system.
15653 @footnote{If you want to specify a local system root using a directory
15654 that happens to be named @file{remote:}, you need to use some equivalent
15655 variant of the name like @file{./remote:}.}
15657 For targets with an MS-DOS based filesystem, such as MS-Windows and
15658 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15659 absolute file name with @var{path}. But first, on Unix hosts,
15660 @value{GDBN} converts all backslash directory separators into forward
15661 slashes, because the backslash is not a directory separator on Unix:
15664 c:\foo\bar.dll @result{} c:/foo/bar.dll
15667 Then, @value{GDBN} attempts prefixing the target file name with
15668 @var{path}, and looks for the resulting file name in the host file
15672 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15675 If that does not find the shared library, @value{GDBN} tries removing
15676 the @samp{:} character from the drive spec, both for convenience, and,
15677 for the case of the host file system not supporting file names with
15681 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15684 This makes it possible to have a system root that mirrors a target
15685 with more than one drive. E.g., you may want to setup your local
15686 copies of the target system shared libraries like so (note @samp{c} vs
15690 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15691 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15692 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15696 and point the system root at @file{/path/to/sysroot}, so that
15697 @value{GDBN} can find the correct copies of both
15698 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15700 If that still does not find the shared library, @value{GDBN} tries
15701 removing the whole drive spec from the target file name:
15704 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15707 This last lookup makes it possible to not care about the drive name,
15708 if you don't want or need to.
15710 The @code{set solib-absolute-prefix} command is an alias for @code{set
15713 @cindex default system root
15714 @cindex @samp{--with-sysroot}
15715 You can set the default system root by using the configure-time
15716 @samp{--with-sysroot} option. If the system root is inside
15717 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15718 @samp{--exec-prefix}), then the default system root will be updated
15719 automatically if the installed @value{GDBN} is moved to a new
15722 @kindex show sysroot
15724 Display the current shared library prefix.
15726 @kindex set solib-search-path
15727 @item set solib-search-path @var{path}
15728 If this variable is set, @var{path} is a colon-separated list of
15729 directories to search for shared libraries. @samp{solib-search-path}
15730 is used after @samp{sysroot} fails to locate the library, or if the
15731 path to the library is relative instead of absolute. If you want to
15732 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15733 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15734 finding your host's libraries. @samp{sysroot} is preferred; setting
15735 it to a nonexistent directory may interfere with automatic loading
15736 of shared library symbols.
15738 @kindex show solib-search-path
15739 @item show solib-search-path
15740 Display the current shared library search path.
15742 @cindex DOS file-name semantics of file names.
15743 @kindex set target-file-system-kind (unix|dos-based|auto)
15744 @kindex show target-file-system-kind
15745 @item set target-file-system-kind @var{kind}
15746 Set assumed file system kind for target reported file names.
15748 Shared library file names as reported by the target system may not
15749 make sense as is on the system @value{GDBN} is running on. For
15750 example, when remote debugging a target that has MS-DOS based file
15751 system semantics, from a Unix host, the target may be reporting to
15752 @value{GDBN} a list of loaded shared libraries with file names such as
15753 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15754 drive letters, so the @samp{c:\} prefix is not normally understood as
15755 indicating an absolute file name, and neither is the backslash
15756 normally considered a directory separator character. In that case,
15757 the native file system would interpret this whole absolute file name
15758 as a relative file name with no directory components. This would make
15759 it impossible to point @value{GDBN} at a copy of the remote target's
15760 shared libraries on the host using @code{set sysroot}, and impractical
15761 with @code{set solib-search-path}. Setting
15762 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15763 to interpret such file names similarly to how the target would, and to
15764 map them to file names valid on @value{GDBN}'s native file system
15765 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15766 to one of the supported file system kinds. In that case, @value{GDBN}
15767 tries to determine the appropriate file system variant based on the
15768 current target's operating system (@pxref{ABI, ,Configuring the
15769 Current ABI}). The supported file system settings are:
15773 Instruct @value{GDBN} to assume the target file system is of Unix
15774 kind. Only file names starting the forward slash (@samp{/}) character
15775 are considered absolute, and the directory separator character is also
15779 Instruct @value{GDBN} to assume the target file system is DOS based.
15780 File names starting with either a forward slash, or a drive letter
15781 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15782 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15783 considered directory separators.
15786 Instruct @value{GDBN} to use the file system kind associated with the
15787 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15788 This is the default.
15792 @cindex file name canonicalization
15793 @cindex base name differences
15794 When processing file names provided by the user, @value{GDBN}
15795 frequently needs to compare them to the file names recorded in the
15796 program's debug info. Normally, @value{GDBN} compares just the
15797 @dfn{base names} of the files as strings, which is reasonably fast
15798 even for very large programs. (The base name of a file is the last
15799 portion of its name, after stripping all the leading directories.)
15800 This shortcut in comparison is based upon the assumption that files
15801 cannot have more than one base name. This is usually true, but
15802 references to files that use symlinks or similar filesystem
15803 facilities violate that assumption. If your program records files
15804 using such facilities, or if you provide file names to @value{GDBN}
15805 using symlinks etc., you can set @code{basenames-may-differ} to
15806 @code{true} to instruct @value{GDBN} to completely canonicalize each
15807 pair of file names it needs to compare. This will make file-name
15808 comparisons accurate, but at a price of a significant slowdown.
15811 @item set basenames-may-differ
15812 @kindex set basenames-may-differ
15813 Set whether a source file may have multiple base names.
15815 @item show basenames-may-differ
15816 @kindex show basenames-may-differ
15817 Show whether a source file may have multiple base names.
15820 @node Separate Debug Files
15821 @section Debugging Information in Separate Files
15822 @cindex separate debugging information files
15823 @cindex debugging information in separate files
15824 @cindex @file{.debug} subdirectories
15825 @cindex debugging information directory, global
15826 @cindex global debugging information directory
15827 @cindex build ID, and separate debugging files
15828 @cindex @file{.build-id} directory
15830 @value{GDBN} allows you to put a program's debugging information in a
15831 file separate from the executable itself, in a way that allows
15832 @value{GDBN} to find and load the debugging information automatically.
15833 Since debugging information can be very large---sometimes larger
15834 than the executable code itself---some systems distribute debugging
15835 information for their executables in separate files, which users can
15836 install only when they need to debug a problem.
15838 @value{GDBN} supports two ways of specifying the separate debug info
15843 The executable contains a @dfn{debug link} that specifies the name of
15844 the separate debug info file. The separate debug file's name is
15845 usually @file{@var{executable}.debug}, where @var{executable} is the
15846 name of the corresponding executable file without leading directories
15847 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15848 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15849 checksum for the debug file, which @value{GDBN} uses to validate that
15850 the executable and the debug file came from the same build.
15853 The executable contains a @dfn{build ID}, a unique bit string that is
15854 also present in the corresponding debug info file. (This is supported
15855 only on some operating systems, notably those which use the ELF format
15856 for binary files and the @sc{gnu} Binutils.) For more details about
15857 this feature, see the description of the @option{--build-id}
15858 command-line option in @ref{Options, , Command Line Options, ld.info,
15859 The GNU Linker}. The debug info file's name is not specified
15860 explicitly by the build ID, but can be computed from the build ID, see
15864 Depending on the way the debug info file is specified, @value{GDBN}
15865 uses two different methods of looking for the debug file:
15869 For the ``debug link'' method, @value{GDBN} looks up the named file in
15870 the directory of the executable file, then in a subdirectory of that
15871 directory named @file{.debug}, and finally under the global debug
15872 directory, in a subdirectory whose name is identical to the leading
15873 directories of the executable's absolute file name.
15876 For the ``build ID'' method, @value{GDBN} looks in the
15877 @file{.build-id} subdirectory of the global debug directory for a file
15878 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15879 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15880 are the rest of the bit string. (Real build ID strings are 32 or more
15881 hex characters, not 10.)
15884 So, for example, suppose you ask @value{GDBN} to debug
15885 @file{/usr/bin/ls}, which has a debug link that specifies the
15886 file @file{ls.debug}, and a build ID whose value in hex is
15887 @code{abcdef1234}. If the global debug directory is
15888 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15889 debug information files, in the indicated order:
15893 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15895 @file{/usr/bin/ls.debug}
15897 @file{/usr/bin/.debug/ls.debug}
15899 @file{/usr/lib/debug/usr/bin/ls.debug}.
15902 You can set the global debugging info directory's name, and view the
15903 name @value{GDBN} is currently using.
15907 @kindex set debug-file-directory
15908 @item set debug-file-directory @var{directories}
15909 Set the directories which @value{GDBN} searches for separate debugging
15910 information files to @var{directory}. Multiple directory components can be set
15911 concatenating them by a directory separator.
15913 @kindex show debug-file-directory
15914 @item show debug-file-directory
15915 Show the directories @value{GDBN} searches for separate debugging
15920 @cindex @code{.gnu_debuglink} sections
15921 @cindex debug link sections
15922 A debug link is a special section of the executable file named
15923 @code{.gnu_debuglink}. The section must contain:
15927 A filename, with any leading directory components removed, followed by
15930 zero to three bytes of padding, as needed to reach the next four-byte
15931 boundary within the section, and
15933 a four-byte CRC checksum, stored in the same endianness used for the
15934 executable file itself. The checksum is computed on the debugging
15935 information file's full contents by the function given below, passing
15936 zero as the @var{crc} argument.
15939 Any executable file format can carry a debug link, as long as it can
15940 contain a section named @code{.gnu_debuglink} with the contents
15943 @cindex @code{.note.gnu.build-id} sections
15944 @cindex build ID sections
15945 The build ID is a special section in the executable file (and in other
15946 ELF binary files that @value{GDBN} may consider). This section is
15947 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15948 It contains unique identification for the built files---the ID remains
15949 the same across multiple builds of the same build tree. The default
15950 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15951 content for the build ID string. The same section with an identical
15952 value is present in the original built binary with symbols, in its
15953 stripped variant, and in the separate debugging information file.
15955 The debugging information file itself should be an ordinary
15956 executable, containing a full set of linker symbols, sections, and
15957 debugging information. The sections of the debugging information file
15958 should have the same names, addresses, and sizes as the original file,
15959 but they need not contain any data---much like a @code{.bss} section
15960 in an ordinary executable.
15962 The @sc{gnu} binary utilities (Binutils) package includes the
15963 @samp{objcopy} utility that can produce
15964 the separated executable / debugging information file pairs using the
15965 following commands:
15968 @kbd{objcopy --only-keep-debug foo foo.debug}
15973 These commands remove the debugging
15974 information from the executable file @file{foo} and place it in the file
15975 @file{foo.debug}. You can use the first, second or both methods to link the
15980 The debug link method needs the following additional command to also leave
15981 behind a debug link in @file{foo}:
15984 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15987 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15988 a version of the @code{strip} command such that the command @kbd{strip foo -f
15989 foo.debug} has the same functionality as the two @code{objcopy} commands and
15990 the @code{ln -s} command above, together.
15993 Build ID gets embedded into the main executable using @code{ld --build-id} or
15994 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15995 compatibility fixes for debug files separation are present in @sc{gnu} binary
15996 utilities (Binutils) package since version 2.18.
16001 @cindex CRC algorithm definition
16002 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16003 IEEE 802.3 using the polynomial:
16005 @c TexInfo requires naked braces for multi-digit exponents for Tex
16006 @c output, but this causes HTML output to barf. HTML has to be set using
16007 @c raw commands. So we end up having to specify this equation in 2
16012 <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>
16013 + <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
16019 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16020 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16024 The function is computed byte at a time, taking the least
16025 significant bit of each byte first. The initial pattern
16026 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16027 the final result is inverted to ensure trailing zeros also affect the
16030 @emph{Note:} This is the same CRC polynomial as used in handling the
16031 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16032 , @value{GDBN} Remote Serial Protocol}). However in the
16033 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16034 significant bit first, and the result is not inverted, so trailing
16035 zeros have no effect on the CRC value.
16037 To complete the description, we show below the code of the function
16038 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16039 initially supplied @code{crc} argument means that an initial call to
16040 this function passing in zero will start computing the CRC using
16043 @kindex gnu_debuglink_crc32
16046 gnu_debuglink_crc32 (unsigned long crc,
16047 unsigned char *buf, size_t len)
16049 static const unsigned long crc32_table[256] =
16051 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16052 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16053 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16054 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16055 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16056 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16057 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16058 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16059 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16060 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16061 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16062 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16063 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16064 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16065 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16066 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16067 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16068 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16069 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16070 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16071 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16072 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16073 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16074 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16075 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16076 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16077 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16078 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16079 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16080 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16081 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16082 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16083 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16084 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16085 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16086 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16087 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16088 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16089 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16090 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16091 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16092 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16093 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16094 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16095 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16096 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16097 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16098 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16099 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16100 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16101 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16104 unsigned char *end;
16106 crc = ~crc & 0xffffffff;
16107 for (end = buf + len; buf < end; ++buf)
16108 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16109 return ~crc & 0xffffffff;
16114 This computation does not apply to the ``build ID'' method.
16118 @section Index Files Speed Up @value{GDBN}
16119 @cindex index files
16120 @cindex @samp{.gdb_index} section
16122 When @value{GDBN} finds a symbol file, it scans the symbols in the
16123 file in order to construct an internal symbol table. This lets most
16124 @value{GDBN} operations work quickly---at the cost of a delay early
16125 on. For large programs, this delay can be quite lengthy, so
16126 @value{GDBN} provides a way to build an index, which speeds up
16129 The index is stored as a section in the symbol file. @value{GDBN} can
16130 write the index to a file, then you can put it into the symbol file
16131 using @command{objcopy}.
16133 To create an index file, use the @code{save gdb-index} command:
16136 @item save gdb-index @var{directory}
16137 @kindex save gdb-index
16138 Create an index file for each symbol file currently known by
16139 @value{GDBN}. Each file is named after its corresponding symbol file,
16140 with @samp{.gdb-index} appended, and is written into the given
16144 Once you have created an index file you can merge it into your symbol
16145 file, here named @file{symfile}, using @command{objcopy}:
16148 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16149 --set-section-flags .gdb_index=readonly symfile symfile
16152 There are currently some limitation on indices. They only work when
16153 for DWARF debugging information, not stabs. And, they do not
16154 currently work for programs using Ada.
16156 @node Symbol Errors
16157 @section Errors Reading Symbol Files
16159 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16160 such as symbol types it does not recognize, or known bugs in compiler
16161 output. By default, @value{GDBN} does not notify you of such problems, since
16162 they are relatively common and primarily of interest to people
16163 debugging compilers. If you are interested in seeing information
16164 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16165 only one message about each such type of problem, no matter how many
16166 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16167 to see how many times the problems occur, with the @code{set
16168 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16171 The messages currently printed, and their meanings, include:
16174 @item inner block not inside outer block in @var{symbol}
16176 The symbol information shows where symbol scopes begin and end
16177 (such as at the start of a function or a block of statements). This
16178 error indicates that an inner scope block is not fully contained
16179 in its outer scope blocks.
16181 @value{GDBN} circumvents the problem by treating the inner block as if it had
16182 the same scope as the outer block. In the error message, @var{symbol}
16183 may be shown as ``@code{(don't know)}'' if the outer block is not a
16186 @item block at @var{address} out of order
16188 The symbol information for symbol scope blocks should occur in
16189 order of increasing addresses. This error indicates that it does not
16192 @value{GDBN} does not circumvent this problem, and has trouble
16193 locating symbols in the source file whose symbols it is reading. (You
16194 can often determine what source file is affected by specifying
16195 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16198 @item bad block start address patched
16200 The symbol information for a symbol scope block has a start address
16201 smaller than the address of the preceding source line. This is known
16202 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16204 @value{GDBN} circumvents the problem by treating the symbol scope block as
16205 starting on the previous source line.
16207 @item bad string table offset in symbol @var{n}
16210 Symbol number @var{n} contains a pointer into the string table which is
16211 larger than the size of the string table.
16213 @value{GDBN} circumvents the problem by considering the symbol to have the
16214 name @code{foo}, which may cause other problems if many symbols end up
16217 @item unknown symbol type @code{0x@var{nn}}
16219 The symbol information contains new data types that @value{GDBN} does
16220 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16221 uncomprehended information, in hexadecimal.
16223 @value{GDBN} circumvents the error by ignoring this symbol information.
16224 This usually allows you to debug your program, though certain symbols
16225 are not accessible. If you encounter such a problem and feel like
16226 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16227 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16228 and examine @code{*bufp} to see the symbol.
16230 @item stub type has NULL name
16232 @value{GDBN} could not find the full definition for a struct or class.
16234 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16235 The symbol information for a C@t{++} member function is missing some
16236 information that recent versions of the compiler should have output for
16239 @item info mismatch between compiler and debugger
16241 @value{GDBN} could not parse a type specification output by the compiler.
16246 @section GDB Data Files
16248 @cindex prefix for data files
16249 @value{GDBN} will sometimes read an auxiliary data file. These files
16250 are kept in a directory known as the @dfn{data directory}.
16252 You can set the data directory's name, and view the name @value{GDBN}
16253 is currently using.
16256 @kindex set data-directory
16257 @item set data-directory @var{directory}
16258 Set the directory which @value{GDBN} searches for auxiliary data files
16259 to @var{directory}.
16261 @kindex show data-directory
16262 @item show data-directory
16263 Show the directory @value{GDBN} searches for auxiliary data files.
16266 @cindex default data directory
16267 @cindex @samp{--with-gdb-datadir}
16268 You can set the default data directory by using the configure-time
16269 @samp{--with-gdb-datadir} option. If the data directory is inside
16270 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16271 @samp{--exec-prefix}), then the default data directory will be updated
16272 automatically if the installed @value{GDBN} is moved to a new
16275 The data directory may also be specified with the
16276 @code{--data-directory} command line option.
16277 @xref{Mode Options}.
16280 @chapter Specifying a Debugging Target
16282 @cindex debugging target
16283 A @dfn{target} is the execution environment occupied by your program.
16285 Often, @value{GDBN} runs in the same host environment as your program;
16286 in that case, the debugging target is specified as a side effect when
16287 you use the @code{file} or @code{core} commands. When you need more
16288 flexibility---for example, running @value{GDBN} on a physically separate
16289 host, or controlling a standalone system over a serial port or a
16290 realtime system over a TCP/IP connection---you can use the @code{target}
16291 command to specify one of the target types configured for @value{GDBN}
16292 (@pxref{Target Commands, ,Commands for Managing Targets}).
16294 @cindex target architecture
16295 It is possible to build @value{GDBN} for several different @dfn{target
16296 architectures}. When @value{GDBN} is built like that, you can choose
16297 one of the available architectures with the @kbd{set architecture}
16301 @kindex set architecture
16302 @kindex show architecture
16303 @item set architecture @var{arch}
16304 This command sets the current target architecture to @var{arch}. The
16305 value of @var{arch} can be @code{"auto"}, in addition to one of the
16306 supported architectures.
16308 @item show architecture
16309 Show the current target architecture.
16311 @item set processor
16313 @kindex set processor
16314 @kindex show processor
16315 These are alias commands for, respectively, @code{set architecture}
16316 and @code{show architecture}.
16320 * Active Targets:: Active targets
16321 * Target Commands:: Commands for managing targets
16322 * Byte Order:: Choosing target byte order
16325 @node Active Targets
16326 @section Active Targets
16328 @cindex stacking targets
16329 @cindex active targets
16330 @cindex multiple targets
16332 There are multiple classes of targets such as: processes, executable files or
16333 recording sessions. Core files belong to the process class, making core file
16334 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16335 on multiple active targets, one in each class. This allows you to (for
16336 example) start a process and inspect its activity, while still having access to
16337 the executable file after the process finishes. Or if you start process
16338 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16339 presented a virtual layer of the recording target, while the process target
16340 remains stopped at the chronologically last point of the process execution.
16342 Use the @code{core-file} and @code{exec-file} commands to select a new core
16343 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16344 specify as a target a process that is already running, use the @code{attach}
16345 command (@pxref{Attach, ,Debugging an Already-running Process}).
16347 @node Target Commands
16348 @section Commands for Managing Targets
16351 @item target @var{type} @var{parameters}
16352 Connects the @value{GDBN} host environment to a target machine or
16353 process. A target is typically a protocol for talking to debugging
16354 facilities. You use the argument @var{type} to specify the type or
16355 protocol of the target machine.
16357 Further @var{parameters} are interpreted by the target protocol, but
16358 typically include things like device names or host names to connect
16359 with, process numbers, and baud rates.
16361 The @code{target} command does not repeat if you press @key{RET} again
16362 after executing the command.
16364 @kindex help target
16366 Displays the names of all targets available. To display targets
16367 currently selected, use either @code{info target} or @code{info files}
16368 (@pxref{Files, ,Commands to Specify Files}).
16370 @item help target @var{name}
16371 Describe a particular target, including any parameters necessary to
16374 @kindex set gnutarget
16375 @item set gnutarget @var{args}
16376 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16377 knows whether it is reading an @dfn{executable},
16378 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16379 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16380 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16383 @emph{Warning:} To specify a file format with @code{set gnutarget},
16384 you must know the actual BFD name.
16388 @xref{Files, , Commands to Specify Files}.
16390 @kindex show gnutarget
16391 @item show gnutarget
16392 Use the @code{show gnutarget} command to display what file format
16393 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16394 @value{GDBN} will determine the file format for each file automatically,
16395 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16398 @cindex common targets
16399 Here are some common targets (available, or not, depending on the GDB
16404 @item target exec @var{program}
16405 @cindex executable file target
16406 An executable file. @samp{target exec @var{program}} is the same as
16407 @samp{exec-file @var{program}}.
16409 @item target core @var{filename}
16410 @cindex core dump file target
16411 A core dump file. @samp{target core @var{filename}} is the same as
16412 @samp{core-file @var{filename}}.
16414 @item target remote @var{medium}
16415 @cindex remote target
16416 A remote system connected to @value{GDBN} via a serial line or network
16417 connection. This command tells @value{GDBN} to use its own remote
16418 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16420 For example, if you have a board connected to @file{/dev/ttya} on the
16421 machine running @value{GDBN}, you could say:
16424 target remote /dev/ttya
16427 @code{target remote} supports the @code{load} command. This is only
16428 useful if you have some other way of getting the stub to the target
16429 system, and you can put it somewhere in memory where it won't get
16430 clobbered by the download.
16432 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16433 @cindex built-in simulator target
16434 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16442 works; however, you cannot assume that a specific memory map, device
16443 drivers, or even basic I/O is available, although some simulators do
16444 provide these. For info about any processor-specific simulator details,
16445 see the appropriate section in @ref{Embedded Processors, ,Embedded
16450 Some configurations may include these targets as well:
16454 @item target nrom @var{dev}
16455 @cindex NetROM ROM emulator target
16456 NetROM ROM emulator. This target only supports downloading.
16460 Different targets are available on different configurations of @value{GDBN};
16461 your configuration may have more or fewer targets.
16463 Many remote targets require you to download the executable's code once
16464 you've successfully established a connection. You may wish to control
16465 various aspects of this process.
16470 @kindex set hash@r{, for remote monitors}
16471 @cindex hash mark while downloading
16472 This command controls whether a hash mark @samp{#} is displayed while
16473 downloading a file to the remote monitor. If on, a hash mark is
16474 displayed after each S-record is successfully downloaded to the
16478 @kindex show hash@r{, for remote monitors}
16479 Show the current status of displaying the hash mark.
16481 @item set debug monitor
16482 @kindex set debug monitor
16483 @cindex display remote monitor communications
16484 Enable or disable display of communications messages between
16485 @value{GDBN} and the remote monitor.
16487 @item show debug monitor
16488 @kindex show debug monitor
16489 Show the current status of displaying communications between
16490 @value{GDBN} and the remote monitor.
16495 @kindex load @var{filename}
16496 @item load @var{filename}
16498 Depending on what remote debugging facilities are configured into
16499 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16500 is meant to make @var{filename} (an executable) available for debugging
16501 on the remote system---by downloading, or dynamic linking, for example.
16502 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16503 the @code{add-symbol-file} command.
16505 If your @value{GDBN} does not have a @code{load} command, attempting to
16506 execute it gets the error message ``@code{You can't do that when your
16507 target is @dots{}}''
16509 The file is loaded at whatever address is specified in the executable.
16510 For some object file formats, you can specify the load address when you
16511 link the program; for other formats, like a.out, the object file format
16512 specifies a fixed address.
16513 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16515 Depending on the remote side capabilities, @value{GDBN} may be able to
16516 load programs into flash memory.
16518 @code{load} does not repeat if you press @key{RET} again after using it.
16522 @section Choosing Target Byte Order
16524 @cindex choosing target byte order
16525 @cindex target byte order
16527 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16528 offer the ability to run either big-endian or little-endian byte
16529 orders. Usually the executable or symbol will include a bit to
16530 designate the endian-ness, and you will not need to worry about
16531 which to use. However, you may still find it useful to adjust
16532 @value{GDBN}'s idea of processor endian-ness manually.
16536 @item set endian big
16537 Instruct @value{GDBN} to assume the target is big-endian.
16539 @item set endian little
16540 Instruct @value{GDBN} to assume the target is little-endian.
16542 @item set endian auto
16543 Instruct @value{GDBN} to use the byte order associated with the
16547 Display @value{GDBN}'s current idea of the target byte order.
16551 Note that these commands merely adjust interpretation of symbolic
16552 data on the host, and that they have absolutely no effect on the
16556 @node Remote Debugging
16557 @chapter Debugging Remote Programs
16558 @cindex remote debugging
16560 If you are trying to debug a program running on a machine that cannot run
16561 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16562 For example, you might use remote debugging on an operating system kernel,
16563 or on a small system which does not have a general purpose operating system
16564 powerful enough to run a full-featured debugger.
16566 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16567 to make this work with particular debugging targets. In addition,
16568 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16569 but not specific to any particular target system) which you can use if you
16570 write the remote stubs---the code that runs on the remote system to
16571 communicate with @value{GDBN}.
16573 Other remote targets may be available in your
16574 configuration of @value{GDBN}; use @code{help target} to list them.
16577 * Connecting:: Connecting to a remote target
16578 * File Transfer:: Sending files to a remote system
16579 * Server:: Using the gdbserver program
16580 * Remote Configuration:: Remote configuration
16581 * Remote Stub:: Implementing a remote stub
16585 @section Connecting to a Remote Target
16587 On the @value{GDBN} host machine, you will need an unstripped copy of
16588 your program, since @value{GDBN} needs symbol and debugging information.
16589 Start up @value{GDBN} as usual, using the name of the local copy of your
16590 program as the first argument.
16592 @cindex @code{target remote}
16593 @value{GDBN} can communicate with the target over a serial line, or
16594 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16595 each case, @value{GDBN} uses the same protocol for debugging your
16596 program; only the medium carrying the debugging packets varies. The
16597 @code{target remote} command establishes a connection to the target.
16598 Its arguments indicate which medium to use:
16602 @item target remote @var{serial-device}
16603 @cindex serial line, @code{target remote}
16604 Use @var{serial-device} to communicate with the target. For example,
16605 to use a serial line connected to the device named @file{/dev/ttyb}:
16608 target remote /dev/ttyb
16611 If you're using a serial line, you may want to give @value{GDBN} the
16612 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16613 (@pxref{Remote Configuration, set remotebaud}) before the
16614 @code{target} command.
16616 @item target remote @code{@var{host}:@var{port}}
16617 @itemx target remote @code{tcp:@var{host}:@var{port}}
16618 @cindex @acronym{TCP} port, @code{target remote}
16619 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16620 The @var{host} may be either a host name or a numeric @acronym{IP}
16621 address; @var{port} must be a decimal number. The @var{host} could be
16622 the target machine itself, if it is directly connected to the net, or
16623 it might be a terminal server which in turn has a serial line to the
16626 For example, to connect to port 2828 on a terminal server named
16630 target remote manyfarms:2828
16633 If your remote target is actually running on the same machine as your
16634 debugger session (e.g.@: a simulator for your target running on the
16635 same host), you can omit the hostname. For example, to connect to
16636 port 1234 on your local machine:
16639 target remote :1234
16643 Note that the colon is still required here.
16645 @item target remote @code{udp:@var{host}:@var{port}}
16646 @cindex @acronym{UDP} port, @code{target remote}
16647 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16648 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16651 target remote udp:manyfarms:2828
16654 When using a @acronym{UDP} connection for remote debugging, you should
16655 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16656 can silently drop packets on busy or unreliable networks, which will
16657 cause havoc with your debugging session.
16659 @item target remote | @var{command}
16660 @cindex pipe, @code{target remote} to
16661 Run @var{command} in the background and communicate with it using a
16662 pipe. The @var{command} is a shell command, to be parsed and expanded
16663 by the system's command shell, @code{/bin/sh}; it should expect remote
16664 protocol packets on its standard input, and send replies on its
16665 standard output. You could use this to run a stand-alone simulator
16666 that speaks the remote debugging protocol, to make net connections
16667 using programs like @code{ssh}, or for other similar tricks.
16669 If @var{command} closes its standard output (perhaps by exiting),
16670 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16671 program has already exited, this will have no effect.)
16675 Once the connection has been established, you can use all the usual
16676 commands to examine and change data. The remote program is already
16677 running; you can use @kbd{step} and @kbd{continue}, and you do not
16678 need to use @kbd{run}.
16680 @cindex interrupting remote programs
16681 @cindex remote programs, interrupting
16682 Whenever @value{GDBN} is waiting for the remote program, if you type the
16683 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16684 program. This may or may not succeed, depending in part on the hardware
16685 and the serial drivers the remote system uses. If you type the
16686 interrupt character once again, @value{GDBN} displays this prompt:
16689 Interrupted while waiting for the program.
16690 Give up (and stop debugging it)? (y or n)
16693 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16694 (If you decide you want to try again later, you can use @samp{target
16695 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16696 goes back to waiting.
16699 @kindex detach (remote)
16701 When you have finished debugging the remote program, you can use the
16702 @code{detach} command to release it from @value{GDBN} control.
16703 Detaching from the target normally resumes its execution, but the results
16704 will depend on your particular remote stub. After the @code{detach}
16705 command, @value{GDBN} is free to connect to another target.
16709 The @code{disconnect} command behaves like @code{detach}, except that
16710 the target is generally not resumed. It will wait for @value{GDBN}
16711 (this instance or another one) to connect and continue debugging. After
16712 the @code{disconnect} command, @value{GDBN} is again free to connect to
16715 @cindex send command to remote monitor
16716 @cindex extend @value{GDBN} for remote targets
16717 @cindex add new commands for external monitor
16719 @item monitor @var{cmd}
16720 This command allows you to send arbitrary commands directly to the
16721 remote monitor. Since @value{GDBN} doesn't care about the commands it
16722 sends like this, this command is the way to extend @value{GDBN}---you
16723 can add new commands that only the external monitor will understand
16727 @node File Transfer
16728 @section Sending files to a remote system
16729 @cindex remote target, file transfer
16730 @cindex file transfer
16731 @cindex sending files to remote systems
16733 Some remote targets offer the ability to transfer files over the same
16734 connection used to communicate with @value{GDBN}. This is convenient
16735 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16736 running @code{gdbserver} over a network interface. For other targets,
16737 e.g.@: embedded devices with only a single serial port, this may be
16738 the only way to upload or download files.
16740 Not all remote targets support these commands.
16744 @item remote put @var{hostfile} @var{targetfile}
16745 Copy file @var{hostfile} from the host system (the machine running
16746 @value{GDBN}) to @var{targetfile} on the target system.
16749 @item remote get @var{targetfile} @var{hostfile}
16750 Copy file @var{targetfile} from the target system to @var{hostfile}
16751 on the host system.
16753 @kindex remote delete
16754 @item remote delete @var{targetfile}
16755 Delete @var{targetfile} from the target system.
16760 @section Using the @code{gdbserver} Program
16763 @cindex remote connection without stubs
16764 @code{gdbserver} is a control program for Unix-like systems, which
16765 allows you to connect your program with a remote @value{GDBN} via
16766 @code{target remote}---but without linking in the usual debugging stub.
16768 @code{gdbserver} is not a complete replacement for the debugging stubs,
16769 because it requires essentially the same operating-system facilities
16770 that @value{GDBN} itself does. In fact, a system that can run
16771 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16772 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16773 because it is a much smaller program than @value{GDBN} itself. It is
16774 also easier to port than all of @value{GDBN}, so you may be able to get
16775 started more quickly on a new system by using @code{gdbserver}.
16776 Finally, if you develop code for real-time systems, you may find that
16777 the tradeoffs involved in real-time operation make it more convenient to
16778 do as much development work as possible on another system, for example
16779 by cross-compiling. You can use @code{gdbserver} to make a similar
16780 choice for debugging.
16782 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16783 or a TCP connection, using the standard @value{GDBN} remote serial
16787 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16788 Do not run @code{gdbserver} connected to any public network; a
16789 @value{GDBN} connection to @code{gdbserver} provides access to the
16790 target system with the same privileges as the user running
16794 @subsection Running @code{gdbserver}
16795 @cindex arguments, to @code{gdbserver}
16796 @cindex @code{gdbserver}, command-line arguments
16798 Run @code{gdbserver} on the target system. You need a copy of the
16799 program you want to debug, including any libraries it requires.
16800 @code{gdbserver} does not need your program's symbol table, so you can
16801 strip the program if necessary to save space. @value{GDBN} on the host
16802 system does all the symbol handling.
16804 To use the server, you must tell it how to communicate with @value{GDBN};
16805 the name of your program; and the arguments for your program. The usual
16809 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16812 @var{comm} is either a device name (to use a serial line), or a TCP
16813 hostname and portnumber, or @code{-} or @code{stdio} to use
16814 stdin/stdout of @code{gdbserver}.
16815 For example, to debug Emacs with the argument
16816 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16820 target> gdbserver /dev/com1 emacs foo.txt
16823 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16826 To use a TCP connection instead of a serial line:
16829 target> gdbserver host:2345 emacs foo.txt
16832 The only difference from the previous example is the first argument,
16833 specifying that you are communicating with the host @value{GDBN} via
16834 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16835 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16836 (Currently, the @samp{host} part is ignored.) You can choose any number
16837 you want for the port number as long as it does not conflict with any
16838 TCP ports already in use on the target system (for example, @code{23} is
16839 reserved for @code{telnet}).@footnote{If you choose a port number that
16840 conflicts with another service, @code{gdbserver} prints an error message
16841 and exits.} You must use the same port number with the host @value{GDBN}
16842 @code{target remote} command.
16844 The @code{stdio} connection is useful when starting @code{gdbserver}
16848 (gdb) target remote | ssh -T hostname gdbserver - hello
16851 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16852 and we don't want escape-character handling. Ssh does this by default when
16853 a command is provided, the flag is provided to make it explicit.
16854 You could elide it if you want to.
16856 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16857 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16858 display through a pipe connected to gdbserver.
16859 Both @code{stdout} and @code{stderr} use the same pipe.
16861 @subsubsection Attaching to a Running Program
16862 @cindex attach to a program, @code{gdbserver}
16863 @cindex @option{--attach}, @code{gdbserver} option
16865 On some targets, @code{gdbserver} can also attach to running programs.
16866 This is accomplished via the @code{--attach} argument. The syntax is:
16869 target> gdbserver --attach @var{comm} @var{pid}
16872 @var{pid} is the process ID of a currently running process. It isn't necessary
16873 to point @code{gdbserver} at a binary for the running process.
16876 You can debug processes by name instead of process ID if your target has the
16877 @code{pidof} utility:
16880 target> gdbserver --attach @var{comm} `pidof @var{program}`
16883 In case more than one copy of @var{program} is running, or @var{program}
16884 has multiple threads, most versions of @code{pidof} support the
16885 @code{-s} option to only return the first process ID.
16887 @subsubsection Multi-Process Mode for @code{gdbserver}
16888 @cindex @code{gdbserver}, multiple processes
16889 @cindex multiple processes with @code{gdbserver}
16891 When you connect to @code{gdbserver} using @code{target remote},
16892 @code{gdbserver} debugs the specified program only once. When the
16893 program exits, or you detach from it, @value{GDBN} closes the connection
16894 and @code{gdbserver} exits.
16896 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16897 enters multi-process mode. When the debugged program exits, or you
16898 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16899 though no program is running. The @code{run} and @code{attach}
16900 commands instruct @code{gdbserver} to run or attach to a new program.
16901 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16902 remote exec-file}) to select the program to run. Command line
16903 arguments are supported, except for wildcard expansion and I/O
16904 redirection (@pxref{Arguments}).
16906 @cindex @option{--multi}, @code{gdbserver} option
16907 To start @code{gdbserver} without supplying an initial command to run
16908 or process ID to attach, use the @option{--multi} command line option.
16909 Then you can connect using @kbd{target extended-remote} and start
16910 the program you want to debug.
16912 In multi-process mode @code{gdbserver} does not automatically exit unless you
16913 use the option @option{--once}. You can terminate it by using
16914 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16915 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16916 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16917 @option{--multi} option to @code{gdbserver} has no influence on that.
16919 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16921 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16923 @code{gdbserver} normally terminates after all of its debugged processes have
16924 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16925 extended-remote}, @code{gdbserver} stays running even with no processes left.
16926 @value{GDBN} normally terminates the spawned debugged process on its exit,
16927 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16928 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16929 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16930 stays running even in the @kbd{target remote} mode.
16932 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16933 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16934 completeness, at most one @value{GDBN} can be connected at a time.
16936 @cindex @option{--once}, @code{gdbserver} option
16937 By default, @code{gdbserver} keeps the listening TCP port open, so that
16938 additional connections are possible. However, if you start @code{gdbserver}
16939 with the @option{--once} option, it will stop listening for any further
16940 connection attempts after connecting to the first @value{GDBN} session. This
16941 means no further connections to @code{gdbserver} will be possible after the
16942 first one. It also means @code{gdbserver} will terminate after the first
16943 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16944 connections and even in the @kbd{target extended-remote} mode. The
16945 @option{--once} option allows reusing the same port number for connecting to
16946 multiple instances of @code{gdbserver} running on the same host, since each
16947 instance closes its port after the first connection.
16949 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16951 @cindex @option{--debug}, @code{gdbserver} option
16952 The @option{--debug} option tells @code{gdbserver} to display extra
16953 status information about the debugging process.
16954 @cindex @option{--remote-debug}, @code{gdbserver} option
16955 The @option{--remote-debug} option tells @code{gdbserver} to display
16956 remote protocol debug output. These options are intended for
16957 @code{gdbserver} development and for bug reports to the developers.
16959 @cindex @option{--wrapper}, @code{gdbserver} option
16960 The @option{--wrapper} option specifies a wrapper to launch programs
16961 for debugging. The option should be followed by the name of the
16962 wrapper, then any command-line arguments to pass to the wrapper, then
16963 @kbd{--} indicating the end of the wrapper arguments.
16965 @code{gdbserver} runs the specified wrapper program with a combined
16966 command line including the wrapper arguments, then the name of the
16967 program to debug, then any arguments to the program. The wrapper
16968 runs until it executes your program, and then @value{GDBN} gains control.
16970 You can use any program that eventually calls @code{execve} with
16971 its arguments as a wrapper. Several standard Unix utilities do
16972 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16973 with @code{exec "$@@"} will also work.
16975 For example, you can use @code{env} to pass an environment variable to
16976 the debugged program, without setting the variable in @code{gdbserver}'s
16980 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16983 @subsection Connecting to @code{gdbserver}
16985 Run @value{GDBN} on the host system.
16987 First make sure you have the necessary symbol files. Load symbols for
16988 your application using the @code{file} command before you connect. Use
16989 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16990 was compiled with the correct sysroot using @code{--with-sysroot}).
16992 The symbol file and target libraries must exactly match the executable
16993 and libraries on the target, with one exception: the files on the host
16994 system should not be stripped, even if the files on the target system
16995 are. Mismatched or missing files will lead to confusing results
16996 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16997 files may also prevent @code{gdbserver} from debugging multi-threaded
17000 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17001 For TCP connections, you must start up @code{gdbserver} prior to using
17002 the @code{target remote} command. Otherwise you may get an error whose
17003 text depends on the host system, but which usually looks something like
17004 @samp{Connection refused}. Don't use the @code{load}
17005 command in @value{GDBN} when using @code{gdbserver}, since the program is
17006 already on the target.
17008 @subsection Monitor Commands for @code{gdbserver}
17009 @cindex monitor commands, for @code{gdbserver}
17010 @anchor{Monitor Commands for gdbserver}
17012 During a @value{GDBN} session using @code{gdbserver}, you can use the
17013 @code{monitor} command to send special requests to @code{gdbserver}.
17014 Here are the available commands.
17018 List the available monitor commands.
17020 @item monitor set debug 0
17021 @itemx monitor set debug 1
17022 Disable or enable general debugging messages.
17024 @item monitor set remote-debug 0
17025 @itemx monitor set remote-debug 1
17026 Disable or enable specific debugging messages associated with the remote
17027 protocol (@pxref{Remote Protocol}).
17029 @item monitor set libthread-db-search-path [PATH]
17030 @cindex gdbserver, search path for @code{libthread_db}
17031 When this command is issued, @var{path} is a colon-separated list of
17032 directories to search for @code{libthread_db} (@pxref{Threads,,set
17033 libthread-db-search-path}). If you omit @var{path},
17034 @samp{libthread-db-search-path} will be reset to its default value.
17036 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17037 not supported in @code{gdbserver}.
17040 Tell gdbserver to exit immediately. This command should be followed by
17041 @code{disconnect} to close the debugging session. @code{gdbserver} will
17042 detach from any attached processes and kill any processes it created.
17043 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17044 of a multi-process mode debug session.
17048 @subsection Tracepoints support in @code{gdbserver}
17049 @cindex tracepoints support in @code{gdbserver}
17051 On some targets, @code{gdbserver} supports tracepoints, fast
17052 tracepoints and static tracepoints.
17054 For fast or static tracepoints to work, a special library called the
17055 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17056 This library is built and distributed as an integral part of
17057 @code{gdbserver}. In addition, support for static tracepoints
17058 requires building the in-process agent library with static tracepoints
17059 support. At present, the UST (LTTng Userspace Tracer,
17060 @url{http://lttng.org/ust}) tracing engine is supported. This support
17061 is automatically available if UST development headers are found in the
17062 standard include path when @code{gdbserver} is built, or if
17063 @code{gdbserver} was explicitly configured using @option{--with-ust}
17064 to point at such headers. You can explicitly disable the support
17065 using @option{--with-ust=no}.
17067 There are several ways to load the in-process agent in your program:
17070 @item Specifying it as dependency at link time
17072 You can link your program dynamically with the in-process agent
17073 library. On most systems, this is accomplished by adding
17074 @code{-linproctrace} to the link command.
17076 @item Using the system's preloading mechanisms
17078 You can force loading the in-process agent at startup time by using
17079 your system's support for preloading shared libraries. Many Unixes
17080 support the concept of preloading user defined libraries. In most
17081 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17082 in the environment. See also the description of @code{gdbserver}'s
17083 @option{--wrapper} command line option.
17085 @item Using @value{GDBN} to force loading the agent at run time
17087 On some systems, you can force the inferior to load a shared library,
17088 by calling a dynamic loader function in the inferior that takes care
17089 of dynamically looking up and loading a shared library. On most Unix
17090 systems, the function is @code{dlopen}. You'll use the @code{call}
17091 command for that. For example:
17094 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17097 Note that on most Unix systems, for the @code{dlopen} function to be
17098 available, the program needs to be linked with @code{-ldl}.
17101 On systems that have a userspace dynamic loader, like most Unix
17102 systems, when you connect to @code{gdbserver} using @code{target
17103 remote}, you'll find that the program is stopped at the dynamic
17104 loader's entry point, and no shared library has been loaded in the
17105 program's address space yet, including the in-process agent. In that
17106 case, before being able to use any of the fast or static tracepoints
17107 features, you need to let the loader run and load the shared
17108 libraries. The simplest way to do that is to run the program to the
17109 main procedure. E.g., if debugging a C or C@t{++} program, start
17110 @code{gdbserver} like so:
17113 $ gdbserver :9999 myprogram
17116 Start GDB and connect to @code{gdbserver} like so, and run to main:
17120 (@value{GDBP}) target remote myhost:9999
17121 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17122 (@value{GDBP}) b main
17123 (@value{GDBP}) continue
17126 The in-process tracing agent library should now be loaded into the
17127 process; you can confirm it with the @code{info sharedlibrary}
17128 command, which will list @file{libinproctrace.so} as loaded in the
17129 process. You are now ready to install fast tracepoints, list static
17130 tracepoint markers, probe static tracepoints markers, and start
17133 @node Remote Configuration
17134 @section Remote Configuration
17137 @kindex show remote
17138 This section documents the configuration options available when
17139 debugging remote programs. For the options related to the File I/O
17140 extensions of the remote protocol, see @ref{system,
17141 system-call-allowed}.
17144 @item set remoteaddresssize @var{bits}
17145 @cindex address size for remote targets
17146 @cindex bits in remote address
17147 Set the maximum size of address in a memory packet to the specified
17148 number of bits. @value{GDBN} will mask off the address bits above
17149 that number, when it passes addresses to the remote target. The
17150 default value is the number of bits in the target's address.
17152 @item show remoteaddresssize
17153 Show the current value of remote address size in bits.
17155 @item set remotebaud @var{n}
17156 @cindex baud rate for remote targets
17157 Set the baud rate for the remote serial I/O to @var{n} baud. The
17158 value is used to set the speed of the serial port used for debugging
17161 @item show remotebaud
17162 Show the current speed of the remote connection.
17164 @item set remotebreak
17165 @cindex interrupt remote programs
17166 @cindex BREAK signal instead of Ctrl-C
17167 @anchor{set remotebreak}
17168 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17169 when you type @kbd{Ctrl-c} to interrupt the program running
17170 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17171 character instead. The default is off, since most remote systems
17172 expect to see @samp{Ctrl-C} as the interrupt signal.
17174 @item show remotebreak
17175 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17176 interrupt the remote program.
17178 @item set remoteflow on
17179 @itemx set remoteflow off
17180 @kindex set remoteflow
17181 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17182 on the serial port used to communicate to the remote target.
17184 @item show remoteflow
17185 @kindex show remoteflow
17186 Show the current setting of hardware flow control.
17188 @item set remotelogbase @var{base}
17189 Set the base (a.k.a.@: radix) of logging serial protocol
17190 communications to @var{base}. Supported values of @var{base} are:
17191 @code{ascii}, @code{octal}, and @code{hex}. The default is
17194 @item show remotelogbase
17195 Show the current setting of the radix for logging remote serial
17198 @item set remotelogfile @var{file}
17199 @cindex record serial communications on file
17200 Record remote serial communications on the named @var{file}. The
17201 default is not to record at all.
17203 @item show remotelogfile.
17204 Show the current setting of the file name on which to record the
17205 serial communications.
17207 @item set remotetimeout @var{num}
17208 @cindex timeout for serial communications
17209 @cindex remote timeout
17210 Set the timeout limit to wait for the remote target to respond to
17211 @var{num} seconds. The default is 2 seconds.
17213 @item show remotetimeout
17214 Show the current number of seconds to wait for the remote target
17217 @cindex limit hardware breakpoints and watchpoints
17218 @cindex remote target, limit break- and watchpoints
17219 @anchor{set remote hardware-watchpoint-limit}
17220 @anchor{set remote hardware-breakpoint-limit}
17221 @item set remote hardware-watchpoint-limit @var{limit}
17222 @itemx set remote hardware-breakpoint-limit @var{limit}
17223 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17224 watchpoints. A limit of -1, the default, is treated as unlimited.
17226 @cindex limit hardware watchpoints length
17227 @cindex remote target, limit watchpoints length
17228 @anchor{set remote hardware-watchpoint-length-limit}
17229 @item set remote hardware-watchpoint-length-limit @var{limit}
17230 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17231 a remote hardware watchpoint. A limit of -1, the default, is treated
17234 @item show remote hardware-watchpoint-length-limit
17235 Show the current limit (in bytes) of the maximum length of
17236 a remote hardware watchpoint.
17238 @item set remote exec-file @var{filename}
17239 @itemx show remote exec-file
17240 @anchor{set remote exec-file}
17241 @cindex executable file, for remote target
17242 Select the file used for @code{run} with @code{target
17243 extended-remote}. This should be set to a filename valid on the
17244 target system. If it is not set, the target will use a default
17245 filename (e.g.@: the last program run).
17247 @item set remote interrupt-sequence
17248 @cindex interrupt remote programs
17249 @cindex select Ctrl-C, BREAK or BREAK-g
17250 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17251 @samp{BREAK-g} as the
17252 sequence to the remote target in order to interrupt the execution.
17253 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17254 is high level of serial line for some certain time.
17255 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17256 It is @code{BREAK} signal followed by character @code{g}.
17258 @item show interrupt-sequence
17259 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17260 is sent by @value{GDBN} to interrupt the remote program.
17261 @code{BREAK-g} is BREAK signal followed by @code{g} and
17262 also known as Magic SysRq g.
17264 @item set remote interrupt-on-connect
17265 @cindex send interrupt-sequence on start
17266 Specify whether interrupt-sequence is sent to remote target when
17267 @value{GDBN} connects to it. This is mostly needed when you debug
17268 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17269 which is known as Magic SysRq g in order to connect @value{GDBN}.
17271 @item show interrupt-on-connect
17272 Show whether interrupt-sequence is sent
17273 to remote target when @value{GDBN} connects to it.
17277 @item set tcp auto-retry on
17278 @cindex auto-retry, for remote TCP target
17279 Enable auto-retry for remote TCP connections. This is useful if the remote
17280 debugging agent is launched in parallel with @value{GDBN}; there is a race
17281 condition because the agent may not become ready to accept the connection
17282 before @value{GDBN} attempts to connect. When auto-retry is
17283 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17284 to establish the connection using the timeout specified by
17285 @code{set tcp connect-timeout}.
17287 @item set tcp auto-retry off
17288 Do not auto-retry failed TCP connections.
17290 @item show tcp auto-retry
17291 Show the current auto-retry setting.
17293 @item set tcp connect-timeout @var{seconds}
17294 @cindex connection timeout, for remote TCP target
17295 @cindex timeout, for remote target connection
17296 Set the timeout for establishing a TCP connection to the remote target to
17297 @var{seconds}. The timeout affects both polling to retry failed connections
17298 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17299 that are merely slow to complete, and represents an approximate cumulative
17302 @item show tcp connect-timeout
17303 Show the current connection timeout setting.
17306 @cindex remote packets, enabling and disabling
17307 The @value{GDBN} remote protocol autodetects the packets supported by
17308 your debugging stub. If you need to override the autodetection, you
17309 can use these commands to enable or disable individual packets. Each
17310 packet can be set to @samp{on} (the remote target supports this
17311 packet), @samp{off} (the remote target does not support this packet),
17312 or @samp{auto} (detect remote target support for this packet). They
17313 all default to @samp{auto}. For more information about each packet,
17314 see @ref{Remote Protocol}.
17316 During normal use, you should not have to use any of these commands.
17317 If you do, that may be a bug in your remote debugging stub, or a bug
17318 in @value{GDBN}. You may want to report the problem to the
17319 @value{GDBN} developers.
17321 For each packet @var{name}, the command to enable or disable the
17322 packet is @code{set remote @var{name}-packet}. The available settings
17325 @multitable @columnfractions 0.28 0.32 0.25
17328 @tab Related Features
17330 @item @code{fetch-register}
17332 @tab @code{info registers}
17334 @item @code{set-register}
17338 @item @code{binary-download}
17340 @tab @code{load}, @code{set}
17342 @item @code{read-aux-vector}
17343 @tab @code{qXfer:auxv:read}
17344 @tab @code{info auxv}
17346 @item @code{symbol-lookup}
17347 @tab @code{qSymbol}
17348 @tab Detecting multiple threads
17350 @item @code{attach}
17351 @tab @code{vAttach}
17354 @item @code{verbose-resume}
17356 @tab Stepping or resuming multiple threads
17362 @item @code{software-breakpoint}
17366 @item @code{hardware-breakpoint}
17370 @item @code{write-watchpoint}
17374 @item @code{read-watchpoint}
17378 @item @code{access-watchpoint}
17382 @item @code{target-features}
17383 @tab @code{qXfer:features:read}
17384 @tab @code{set architecture}
17386 @item @code{library-info}
17387 @tab @code{qXfer:libraries:read}
17388 @tab @code{info sharedlibrary}
17390 @item @code{memory-map}
17391 @tab @code{qXfer:memory-map:read}
17392 @tab @code{info mem}
17394 @item @code{read-sdata-object}
17395 @tab @code{qXfer:sdata:read}
17396 @tab @code{print $_sdata}
17398 @item @code{read-spu-object}
17399 @tab @code{qXfer:spu:read}
17400 @tab @code{info spu}
17402 @item @code{write-spu-object}
17403 @tab @code{qXfer:spu:write}
17404 @tab @code{info spu}
17406 @item @code{read-siginfo-object}
17407 @tab @code{qXfer:siginfo:read}
17408 @tab @code{print $_siginfo}
17410 @item @code{write-siginfo-object}
17411 @tab @code{qXfer:siginfo:write}
17412 @tab @code{set $_siginfo}
17414 @item @code{threads}
17415 @tab @code{qXfer:threads:read}
17416 @tab @code{info threads}
17418 @item @code{get-thread-local-@*storage-address}
17419 @tab @code{qGetTLSAddr}
17420 @tab Displaying @code{__thread} variables
17422 @item @code{get-thread-information-block-address}
17423 @tab @code{qGetTIBAddr}
17424 @tab Display MS-Windows Thread Information Block.
17426 @item @code{search-memory}
17427 @tab @code{qSearch:memory}
17430 @item @code{supported-packets}
17431 @tab @code{qSupported}
17432 @tab Remote communications parameters
17434 @item @code{pass-signals}
17435 @tab @code{QPassSignals}
17436 @tab @code{handle @var{signal}}
17438 @item @code{hostio-close-packet}
17439 @tab @code{vFile:close}
17440 @tab @code{remote get}, @code{remote put}
17442 @item @code{hostio-open-packet}
17443 @tab @code{vFile:open}
17444 @tab @code{remote get}, @code{remote put}
17446 @item @code{hostio-pread-packet}
17447 @tab @code{vFile:pread}
17448 @tab @code{remote get}, @code{remote put}
17450 @item @code{hostio-pwrite-packet}
17451 @tab @code{vFile:pwrite}
17452 @tab @code{remote get}, @code{remote put}
17454 @item @code{hostio-unlink-packet}
17455 @tab @code{vFile:unlink}
17456 @tab @code{remote delete}
17458 @item @code{hostio-readlink-packet}
17459 @tab @code{vFile:readlink}
17462 @item @code{noack-packet}
17463 @tab @code{QStartNoAckMode}
17464 @tab Packet acknowledgment
17466 @item @code{osdata}
17467 @tab @code{qXfer:osdata:read}
17468 @tab @code{info os}
17470 @item @code{query-attached}
17471 @tab @code{qAttached}
17472 @tab Querying remote process attach state.
17474 @item @code{traceframe-info}
17475 @tab @code{qXfer:traceframe-info:read}
17476 @tab Traceframe info
17478 @item @code{install-in-trace}
17479 @tab @code{InstallInTrace}
17480 @tab Install tracepoint in tracing
17482 @item @code{disable-randomization}
17483 @tab @code{QDisableRandomization}
17484 @tab @code{set disable-randomization}
17488 @section Implementing a Remote Stub
17490 @cindex debugging stub, example
17491 @cindex remote stub, example
17492 @cindex stub example, remote debugging
17493 The stub files provided with @value{GDBN} implement the target side of the
17494 communication protocol, and the @value{GDBN} side is implemented in the
17495 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17496 these subroutines to communicate, and ignore the details. (If you're
17497 implementing your own stub file, you can still ignore the details: start
17498 with one of the existing stub files. @file{sparc-stub.c} is the best
17499 organized, and therefore the easiest to read.)
17501 @cindex remote serial debugging, overview
17502 To debug a program running on another machine (the debugging
17503 @dfn{target} machine), you must first arrange for all the usual
17504 prerequisites for the program to run by itself. For example, for a C
17509 A startup routine to set up the C runtime environment; these usually
17510 have a name like @file{crt0}. The startup routine may be supplied by
17511 your hardware supplier, or you may have to write your own.
17514 A C subroutine library to support your program's
17515 subroutine calls, notably managing input and output.
17518 A way of getting your program to the other machine---for example, a
17519 download program. These are often supplied by the hardware
17520 manufacturer, but you may have to write your own from hardware
17524 The next step is to arrange for your program to use a serial port to
17525 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17526 machine). In general terms, the scheme looks like this:
17530 @value{GDBN} already understands how to use this protocol; when everything
17531 else is set up, you can simply use the @samp{target remote} command
17532 (@pxref{Targets,,Specifying a Debugging Target}).
17534 @item On the target,
17535 you must link with your program a few special-purpose subroutines that
17536 implement the @value{GDBN} remote serial protocol. The file containing these
17537 subroutines is called a @dfn{debugging stub}.
17539 On certain remote targets, you can use an auxiliary program
17540 @code{gdbserver} instead of linking a stub into your program.
17541 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17544 The debugging stub is specific to the architecture of the remote
17545 machine; for example, use @file{sparc-stub.c} to debug programs on
17548 @cindex remote serial stub list
17549 These working remote stubs are distributed with @value{GDBN}:
17554 @cindex @file{i386-stub.c}
17557 For Intel 386 and compatible architectures.
17560 @cindex @file{m68k-stub.c}
17561 @cindex Motorola 680x0
17563 For Motorola 680x0 architectures.
17566 @cindex @file{sh-stub.c}
17569 For Renesas SH architectures.
17572 @cindex @file{sparc-stub.c}
17574 For @sc{sparc} architectures.
17576 @item sparcl-stub.c
17577 @cindex @file{sparcl-stub.c}
17580 For Fujitsu @sc{sparclite} architectures.
17584 The @file{README} file in the @value{GDBN} distribution may list other
17585 recently added stubs.
17588 * Stub Contents:: What the stub can do for you
17589 * Bootstrapping:: What you must do for the stub
17590 * Debug Session:: Putting it all together
17593 @node Stub Contents
17594 @subsection What the Stub Can Do for You
17596 @cindex remote serial stub
17597 The debugging stub for your architecture supplies these three
17601 @item set_debug_traps
17602 @findex set_debug_traps
17603 @cindex remote serial stub, initialization
17604 This routine arranges for @code{handle_exception} to run when your
17605 program stops. You must call this subroutine explicitly in your
17606 program's startup code.
17608 @item handle_exception
17609 @findex handle_exception
17610 @cindex remote serial stub, main routine
17611 This is the central workhorse, but your program never calls it
17612 explicitly---the setup code arranges for @code{handle_exception} to
17613 run when a trap is triggered.
17615 @code{handle_exception} takes control when your program stops during
17616 execution (for example, on a breakpoint), and mediates communications
17617 with @value{GDBN} on the host machine. This is where the communications
17618 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17619 representative on the target machine. It begins by sending summary
17620 information on the state of your program, then continues to execute,
17621 retrieving and transmitting any information @value{GDBN} needs, until you
17622 execute a @value{GDBN} command that makes your program resume; at that point,
17623 @code{handle_exception} returns control to your own code on the target
17627 @cindex @code{breakpoint} subroutine, remote
17628 Use this auxiliary subroutine to make your program contain a
17629 breakpoint. Depending on the particular situation, this may be the only
17630 way for @value{GDBN} to get control. For instance, if your target
17631 machine has some sort of interrupt button, you won't need to call this;
17632 pressing the interrupt button transfers control to
17633 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17634 simply receiving characters on the serial port may also trigger a trap;
17635 again, in that situation, you don't need to call @code{breakpoint} from
17636 your own program---simply running @samp{target remote} from the host
17637 @value{GDBN} session gets control.
17639 Call @code{breakpoint} if none of these is true, or if you simply want
17640 to make certain your program stops at a predetermined point for the
17641 start of your debugging session.
17644 @node Bootstrapping
17645 @subsection What You Must Do for the Stub
17647 @cindex remote stub, support routines
17648 The debugging stubs that come with @value{GDBN} are set up for a particular
17649 chip architecture, but they have no information about the rest of your
17650 debugging target machine.
17652 First of all you need to tell the stub how to communicate with the
17656 @item int getDebugChar()
17657 @findex getDebugChar
17658 Write this subroutine to read a single character from the serial port.
17659 It may be identical to @code{getchar} for your target system; a
17660 different name is used to allow you to distinguish the two if you wish.
17662 @item void putDebugChar(int)
17663 @findex putDebugChar
17664 Write this subroutine to write a single character to the serial port.
17665 It may be identical to @code{putchar} for your target system; a
17666 different name is used to allow you to distinguish the two if you wish.
17669 @cindex control C, and remote debugging
17670 @cindex interrupting remote targets
17671 If you want @value{GDBN} to be able to stop your program while it is
17672 running, you need to use an interrupt-driven serial driver, and arrange
17673 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17674 character). That is the character which @value{GDBN} uses to tell the
17675 remote system to stop.
17677 Getting the debugging target to return the proper status to @value{GDBN}
17678 probably requires changes to the standard stub; one quick and dirty way
17679 is to just execute a breakpoint instruction (the ``dirty'' part is that
17680 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17682 Other routines you need to supply are:
17685 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17686 @findex exceptionHandler
17687 Write this function to install @var{exception_address} in the exception
17688 handling tables. You need to do this because the stub does not have any
17689 way of knowing what the exception handling tables on your target system
17690 are like (for example, the processor's table might be in @sc{rom},
17691 containing entries which point to a table in @sc{ram}).
17692 @var{exception_number} is the exception number which should be changed;
17693 its meaning is architecture-dependent (for example, different numbers
17694 might represent divide by zero, misaligned access, etc). When this
17695 exception occurs, control should be transferred directly to
17696 @var{exception_address}, and the processor state (stack, registers,
17697 and so on) should be just as it is when a processor exception occurs. So if
17698 you want to use a jump instruction to reach @var{exception_address}, it
17699 should be a simple jump, not a jump to subroutine.
17701 For the 386, @var{exception_address} should be installed as an interrupt
17702 gate so that interrupts are masked while the handler runs. The gate
17703 should be at privilege level 0 (the most privileged level). The
17704 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17705 help from @code{exceptionHandler}.
17707 @item void flush_i_cache()
17708 @findex flush_i_cache
17709 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17710 instruction cache, if any, on your target machine. If there is no
17711 instruction cache, this subroutine may be a no-op.
17713 On target machines that have instruction caches, @value{GDBN} requires this
17714 function to make certain that the state of your program is stable.
17718 You must also make sure this library routine is available:
17721 @item void *memset(void *, int, int)
17723 This is the standard library function @code{memset} that sets an area of
17724 memory to a known value. If you have one of the free versions of
17725 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17726 either obtain it from your hardware manufacturer, or write your own.
17729 If you do not use the GNU C compiler, you may need other standard
17730 library subroutines as well; this varies from one stub to another,
17731 but in general the stubs are likely to use any of the common library
17732 subroutines which @code{@value{NGCC}} generates as inline code.
17735 @node Debug Session
17736 @subsection Putting it All Together
17738 @cindex remote serial debugging summary
17739 In summary, when your program is ready to debug, you must follow these
17744 Make sure you have defined the supporting low-level routines
17745 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17747 @code{getDebugChar}, @code{putDebugChar},
17748 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17752 Insert these lines in your program's startup code, before the main
17753 procedure is called:
17760 On some machines, when a breakpoint trap is raised, the hardware
17761 automatically makes the PC point to the instruction after the
17762 breakpoint. If your machine doesn't do that, you may need to adjust
17763 @code{handle_exception} to arrange for it to return to the instruction
17764 after the breakpoint on this first invocation, so that your program
17765 doesn't keep hitting the initial breakpoint instead of making
17769 For the 680x0 stub only, you need to provide a variable called
17770 @code{exceptionHook}. Normally you just use:
17773 void (*exceptionHook)() = 0;
17777 but if before calling @code{set_debug_traps}, you set it to point to a
17778 function in your program, that function is called when
17779 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17780 error). The function indicated by @code{exceptionHook} is called with
17781 one parameter: an @code{int} which is the exception number.
17784 Compile and link together: your program, the @value{GDBN} debugging stub for
17785 your target architecture, and the supporting subroutines.
17788 Make sure you have a serial connection between your target machine and
17789 the @value{GDBN} host, and identify the serial port on the host.
17792 @c The "remote" target now provides a `load' command, so we should
17793 @c document that. FIXME.
17794 Download your program to your target machine (or get it there by
17795 whatever means the manufacturer provides), and start it.
17798 Start @value{GDBN} on the host, and connect to the target
17799 (@pxref{Connecting,,Connecting to a Remote Target}).
17803 @node Configurations
17804 @chapter Configuration-Specific Information
17806 While nearly all @value{GDBN} commands are available for all native and
17807 cross versions of the debugger, there are some exceptions. This chapter
17808 describes things that are only available in certain configurations.
17810 There are three major categories of configurations: native
17811 configurations, where the host and target are the same, embedded
17812 operating system configurations, which are usually the same for several
17813 different processor architectures, and bare embedded processors, which
17814 are quite different from each other.
17819 * Embedded Processors::
17826 This section describes details specific to particular native
17831 * BSD libkvm Interface:: Debugging BSD kernel memory images
17832 * SVR4 Process Information:: SVR4 process information
17833 * DJGPP Native:: Features specific to the DJGPP port
17834 * Cygwin Native:: Features specific to the Cygwin port
17835 * Hurd Native:: Features specific to @sc{gnu} Hurd
17836 * Neutrino:: Features specific to QNX Neutrino
17837 * Darwin:: Features specific to Darwin
17843 On HP-UX systems, if you refer to a function or variable name that
17844 begins with a dollar sign, @value{GDBN} searches for a user or system
17845 name first, before it searches for a convenience variable.
17848 @node BSD libkvm Interface
17849 @subsection BSD libkvm Interface
17852 @cindex kernel memory image
17853 @cindex kernel crash dump
17855 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17856 interface that provides a uniform interface for accessing kernel virtual
17857 memory images, including live systems and crash dumps. @value{GDBN}
17858 uses this interface to allow you to debug live kernels and kernel crash
17859 dumps on many native BSD configurations. This is implemented as a
17860 special @code{kvm} debugging target. For debugging a live system, load
17861 the currently running kernel into @value{GDBN} and connect to the
17865 (@value{GDBP}) @b{target kvm}
17868 For debugging crash dumps, provide the file name of the crash dump as an
17872 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17875 Once connected to the @code{kvm} target, the following commands are
17881 Set current context from the @dfn{Process Control Block} (PCB) address.
17884 Set current context from proc address. This command isn't available on
17885 modern FreeBSD systems.
17888 @node SVR4 Process Information
17889 @subsection SVR4 Process Information
17891 @cindex examine process image
17892 @cindex process info via @file{/proc}
17894 Many versions of SVR4 and compatible systems provide a facility called
17895 @samp{/proc} that can be used to examine the image of a running
17896 process using file-system subroutines. If @value{GDBN} is configured
17897 for an operating system with this facility, the command @code{info
17898 proc} is available to report information about the process running
17899 your program, or about any process running on your system. @code{info
17900 proc} works only on SVR4 systems that include the @code{procfs} code.
17901 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17902 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17908 @itemx info proc @var{process-id}
17909 Summarize available information about any running process. If a
17910 process ID is specified by @var{process-id}, display information about
17911 that process; otherwise display information about the program being
17912 debugged. The summary includes the debugged process ID, the command
17913 line used to invoke it, its current working directory, and its
17914 executable file's absolute file name.
17916 On some systems, @var{process-id} can be of the form
17917 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17918 within a process. If the optional @var{pid} part is missing, it means
17919 a thread from the process being debugged (the leading @samp{/} still
17920 needs to be present, or else @value{GDBN} will interpret the number as
17921 a process ID rather than a thread ID).
17923 @item info proc mappings
17924 @cindex memory address space mappings
17925 Report the memory address space ranges accessible in the program, with
17926 information on whether the process has read, write, or execute access
17927 rights to each range. On @sc{gnu}/Linux systems, each memory range
17928 includes the object file which is mapped to that range, instead of the
17929 memory access rights to that range.
17931 @item info proc stat
17932 @itemx info proc status
17933 @cindex process detailed status information
17934 These subcommands are specific to @sc{gnu}/Linux systems. They show
17935 the process-related information, including the user ID and group ID;
17936 how many threads are there in the process; its virtual memory usage;
17937 the signals that are pending, blocked, and ignored; its TTY; its
17938 consumption of system and user time; its stack size; its @samp{nice}
17939 value; etc. For more information, see the @samp{proc} man page
17940 (type @kbd{man 5 proc} from your shell prompt).
17942 @item info proc all
17943 Show all the information about the process described under all of the
17944 above @code{info proc} subcommands.
17947 @comment These sub-options of 'info proc' were not included when
17948 @comment procfs.c was re-written. Keep their descriptions around
17949 @comment against the day when someone finds the time to put them back in.
17950 @kindex info proc times
17951 @item info proc times
17952 Starting time, user CPU time, and system CPU time for your program and
17955 @kindex info proc id
17957 Report on the process IDs related to your program: its own process ID,
17958 the ID of its parent, the process group ID, and the session ID.
17961 @item set procfs-trace
17962 @kindex set procfs-trace
17963 @cindex @code{procfs} API calls
17964 This command enables and disables tracing of @code{procfs} API calls.
17966 @item show procfs-trace
17967 @kindex show procfs-trace
17968 Show the current state of @code{procfs} API call tracing.
17970 @item set procfs-file @var{file}
17971 @kindex set procfs-file
17972 Tell @value{GDBN} to write @code{procfs} API trace to the named
17973 @var{file}. @value{GDBN} appends the trace info to the previous
17974 contents of the file. The default is to display the trace on the
17977 @item show procfs-file
17978 @kindex show procfs-file
17979 Show the file to which @code{procfs} API trace is written.
17981 @item proc-trace-entry
17982 @itemx proc-trace-exit
17983 @itemx proc-untrace-entry
17984 @itemx proc-untrace-exit
17985 @kindex proc-trace-entry
17986 @kindex proc-trace-exit
17987 @kindex proc-untrace-entry
17988 @kindex proc-untrace-exit
17989 These commands enable and disable tracing of entries into and exits
17990 from the @code{syscall} interface.
17993 @kindex info pidlist
17994 @cindex process list, QNX Neutrino
17995 For QNX Neutrino only, this command displays the list of all the
17996 processes and all the threads within each process.
17999 @kindex info meminfo
18000 @cindex mapinfo list, QNX Neutrino
18001 For QNX Neutrino only, this command displays the list of all mapinfos.
18005 @subsection Features for Debugging @sc{djgpp} Programs
18006 @cindex @sc{djgpp} debugging
18007 @cindex native @sc{djgpp} debugging
18008 @cindex MS-DOS-specific commands
18011 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18012 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18013 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18014 top of real-mode DOS systems and their emulations.
18016 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18017 defines a few commands specific to the @sc{djgpp} port. This
18018 subsection describes those commands.
18023 This is a prefix of @sc{djgpp}-specific commands which print
18024 information about the target system and important OS structures.
18027 @cindex MS-DOS system info
18028 @cindex free memory information (MS-DOS)
18029 @item info dos sysinfo
18030 This command displays assorted information about the underlying
18031 platform: the CPU type and features, the OS version and flavor, the
18032 DPMI version, and the available conventional and DPMI memory.
18037 @cindex segment descriptor tables
18038 @cindex descriptor tables display
18040 @itemx info dos ldt
18041 @itemx info dos idt
18042 These 3 commands display entries from, respectively, Global, Local,
18043 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18044 tables are data structures which store a descriptor for each segment
18045 that is currently in use. The segment's selector is an index into a
18046 descriptor table; the table entry for that index holds the
18047 descriptor's base address and limit, and its attributes and access
18050 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18051 segment (used for both data and the stack), and a DOS segment (which
18052 allows access to DOS/BIOS data structures and absolute addresses in
18053 conventional memory). However, the DPMI host will usually define
18054 additional segments in order to support the DPMI environment.
18056 @cindex garbled pointers
18057 These commands allow to display entries from the descriptor tables.
18058 Without an argument, all entries from the specified table are
18059 displayed. An argument, which should be an integer expression, means
18060 display a single entry whose index is given by the argument. For
18061 example, here's a convenient way to display information about the
18062 debugged program's data segment:
18065 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18066 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18070 This comes in handy when you want to see whether a pointer is outside
18071 the data segment's limit (i.e.@: @dfn{garbled}).
18073 @cindex page tables display (MS-DOS)
18075 @itemx info dos pte
18076 These two commands display entries from, respectively, the Page
18077 Directory and the Page Tables. Page Directories and Page Tables are
18078 data structures which control how virtual memory addresses are mapped
18079 into physical addresses. A Page Table includes an entry for every
18080 page of memory that is mapped into the program's address space; there
18081 may be several Page Tables, each one holding up to 4096 entries. A
18082 Page Directory has up to 4096 entries, one each for every Page Table
18083 that is currently in use.
18085 Without an argument, @kbd{info dos pde} displays the entire Page
18086 Directory, and @kbd{info dos pte} displays all the entries in all of
18087 the Page Tables. An argument, an integer expression, given to the
18088 @kbd{info dos pde} command means display only that entry from the Page
18089 Directory table. An argument given to the @kbd{info dos pte} command
18090 means display entries from a single Page Table, the one pointed to by
18091 the specified entry in the Page Directory.
18093 @cindex direct memory access (DMA) on MS-DOS
18094 These commands are useful when your program uses @dfn{DMA} (Direct
18095 Memory Access), which needs physical addresses to program the DMA
18098 These commands are supported only with some DPMI servers.
18100 @cindex physical address from linear address
18101 @item info dos address-pte @var{addr}
18102 This command displays the Page Table entry for a specified linear
18103 address. The argument @var{addr} is a linear address which should
18104 already have the appropriate segment's base address added to it,
18105 because this command accepts addresses which may belong to @emph{any}
18106 segment. For example, here's how to display the Page Table entry for
18107 the page where a variable @code{i} is stored:
18110 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18111 @exdent @code{Page Table entry for address 0x11a00d30:}
18112 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18116 This says that @code{i} is stored at offset @code{0xd30} from the page
18117 whose physical base address is @code{0x02698000}, and shows all the
18118 attributes of that page.
18120 Note that you must cast the addresses of variables to a @code{char *},
18121 since otherwise the value of @code{__djgpp_base_address}, the base
18122 address of all variables and functions in a @sc{djgpp} program, will
18123 be added using the rules of C pointer arithmetics: if @code{i} is
18124 declared an @code{int}, @value{GDBN} will add 4 times the value of
18125 @code{__djgpp_base_address} to the address of @code{i}.
18127 Here's another example, it displays the Page Table entry for the
18131 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18132 @exdent @code{Page Table entry for address 0x29110:}
18133 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18137 (The @code{+ 3} offset is because the transfer buffer's address is the
18138 3rd member of the @code{_go32_info_block} structure.) The output
18139 clearly shows that this DPMI server maps the addresses in conventional
18140 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18141 linear (@code{0x29110}) addresses are identical.
18143 This command is supported only with some DPMI servers.
18146 @cindex DOS serial data link, remote debugging
18147 In addition to native debugging, the DJGPP port supports remote
18148 debugging via a serial data link. The following commands are specific
18149 to remote serial debugging in the DJGPP port of @value{GDBN}.
18152 @kindex set com1base
18153 @kindex set com1irq
18154 @kindex set com2base
18155 @kindex set com2irq
18156 @kindex set com3base
18157 @kindex set com3irq
18158 @kindex set com4base
18159 @kindex set com4irq
18160 @item set com1base @var{addr}
18161 This command sets the base I/O port address of the @file{COM1} serial
18164 @item set com1irq @var{irq}
18165 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18166 for the @file{COM1} serial port.
18168 There are similar commands @samp{set com2base}, @samp{set com3irq},
18169 etc.@: for setting the port address and the @code{IRQ} lines for the
18172 @kindex show com1base
18173 @kindex show com1irq
18174 @kindex show com2base
18175 @kindex show com2irq
18176 @kindex show com3base
18177 @kindex show com3irq
18178 @kindex show com4base
18179 @kindex show com4irq
18180 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18181 display the current settings of the base address and the @code{IRQ}
18182 lines used by the COM ports.
18185 @kindex info serial
18186 @cindex DOS serial port status
18187 This command prints the status of the 4 DOS serial ports. For each
18188 port, it prints whether it's active or not, its I/O base address and
18189 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18190 counts of various errors encountered so far.
18194 @node Cygwin Native
18195 @subsection Features for Debugging MS Windows PE Executables
18196 @cindex MS Windows debugging
18197 @cindex native Cygwin debugging
18198 @cindex Cygwin-specific commands
18200 @value{GDBN} supports native debugging of MS Windows programs, including
18201 DLLs with and without symbolic debugging information.
18203 @cindex Ctrl-BREAK, MS-Windows
18204 @cindex interrupt debuggee on MS-Windows
18205 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18206 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18207 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18208 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18209 sequence, which can be used to interrupt the debuggee even if it
18212 There are various additional Cygwin-specific commands, described in
18213 this section. Working with DLLs that have no debugging symbols is
18214 described in @ref{Non-debug DLL Symbols}.
18219 This is a prefix of MS Windows-specific commands which print
18220 information about the target system and important OS structures.
18222 @item info w32 selector
18223 This command displays information returned by
18224 the Win32 API @code{GetThreadSelectorEntry} function.
18225 It takes an optional argument that is evaluated to
18226 a long value to give the information about this given selector.
18227 Without argument, this command displays information
18228 about the six segment registers.
18230 @item info w32 thread-information-block
18231 This command displays thread specific information stored in the
18232 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18233 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18237 This is a Cygwin-specific alias of @code{info shared}.
18239 @kindex dll-symbols
18241 This command loads symbols from a dll similarly to
18242 add-sym command but without the need to specify a base address.
18244 @kindex set cygwin-exceptions
18245 @cindex debugging the Cygwin DLL
18246 @cindex Cygwin DLL, debugging
18247 @item set cygwin-exceptions @var{mode}
18248 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18249 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18250 @value{GDBN} will delay recognition of exceptions, and may ignore some
18251 exceptions which seem to be caused by internal Cygwin DLL
18252 ``bookkeeping''. This option is meant primarily for debugging the
18253 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18254 @value{GDBN} users with false @code{SIGSEGV} signals.
18256 @kindex show cygwin-exceptions
18257 @item show cygwin-exceptions
18258 Displays whether @value{GDBN} will break on exceptions that happen
18259 inside the Cygwin DLL itself.
18261 @kindex set new-console
18262 @item set new-console @var{mode}
18263 If @var{mode} is @code{on} the debuggee will
18264 be started in a new console on next start.
18265 If @var{mode} is @code{off}, the debuggee will
18266 be started in the same console as the debugger.
18268 @kindex show new-console
18269 @item show new-console
18270 Displays whether a new console is used
18271 when the debuggee is started.
18273 @kindex set new-group
18274 @item set new-group @var{mode}
18275 This boolean value controls whether the debuggee should
18276 start a new group or stay in the same group as the debugger.
18277 This affects the way the Windows OS handles
18280 @kindex show new-group
18281 @item show new-group
18282 Displays current value of new-group boolean.
18284 @kindex set debugevents
18285 @item set debugevents
18286 This boolean value adds debug output concerning kernel events related
18287 to the debuggee seen by the debugger. This includes events that
18288 signal thread and process creation and exit, DLL loading and
18289 unloading, console interrupts, and debugging messages produced by the
18290 Windows @code{OutputDebugString} API call.
18292 @kindex set debugexec
18293 @item set debugexec
18294 This boolean value adds debug output concerning execute events
18295 (such as resume thread) seen by the debugger.
18297 @kindex set debugexceptions
18298 @item set debugexceptions
18299 This boolean value adds debug output concerning exceptions in the
18300 debuggee seen by the debugger.
18302 @kindex set debugmemory
18303 @item set debugmemory
18304 This boolean value adds debug output concerning debuggee memory reads
18305 and writes by the debugger.
18309 This boolean values specifies whether the debuggee is called
18310 via a shell or directly (default value is on).
18314 Displays if the debuggee will be started with a shell.
18319 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18322 @node Non-debug DLL Symbols
18323 @subsubsection Support for DLLs without Debugging Symbols
18324 @cindex DLLs with no debugging symbols
18325 @cindex Minimal symbols and DLLs
18327 Very often on windows, some of the DLLs that your program relies on do
18328 not include symbolic debugging information (for example,
18329 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18330 symbols in a DLL, it relies on the minimal amount of symbolic
18331 information contained in the DLL's export table. This section
18332 describes working with such symbols, known internally to @value{GDBN} as
18333 ``minimal symbols''.
18335 Note that before the debugged program has started execution, no DLLs
18336 will have been loaded. The easiest way around this problem is simply to
18337 start the program --- either by setting a breakpoint or letting the
18338 program run once to completion. It is also possible to force
18339 @value{GDBN} to load a particular DLL before starting the executable ---
18340 see the shared library information in @ref{Files}, or the
18341 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18342 explicitly loading symbols from a DLL with no debugging information will
18343 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18344 which may adversely affect symbol lookup performance.
18346 @subsubsection DLL Name Prefixes
18348 In keeping with the naming conventions used by the Microsoft debugging
18349 tools, DLL export symbols are made available with a prefix based on the
18350 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18351 also entered into the symbol table, so @code{CreateFileA} is often
18352 sufficient. In some cases there will be name clashes within a program
18353 (particularly if the executable itself includes full debugging symbols)
18354 necessitating the use of the fully qualified name when referring to the
18355 contents of the DLL. Use single-quotes around the name to avoid the
18356 exclamation mark (``!'') being interpreted as a language operator.
18358 Note that the internal name of the DLL may be all upper-case, even
18359 though the file name of the DLL is lower-case, or vice-versa. Since
18360 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18361 some confusion. If in doubt, try the @code{info functions} and
18362 @code{info variables} commands or even @code{maint print msymbols}
18363 (@pxref{Symbols}). Here's an example:
18366 (@value{GDBP}) info function CreateFileA
18367 All functions matching regular expression "CreateFileA":
18369 Non-debugging symbols:
18370 0x77e885f4 CreateFileA
18371 0x77e885f4 KERNEL32!CreateFileA
18375 (@value{GDBP}) info function !
18376 All functions matching regular expression "!":
18378 Non-debugging symbols:
18379 0x6100114c cygwin1!__assert
18380 0x61004034 cygwin1!_dll_crt0@@0
18381 0x61004240 cygwin1!dll_crt0(per_process *)
18385 @subsubsection Working with Minimal Symbols
18387 Symbols extracted from a DLL's export table do not contain very much
18388 type information. All that @value{GDBN} can do is guess whether a symbol
18389 refers to a function or variable depending on the linker section that
18390 contains the symbol. Also note that the actual contents of the memory
18391 contained in a DLL are not available unless the program is running. This
18392 means that you cannot examine the contents of a variable or disassemble
18393 a function within a DLL without a running program.
18395 Variables are generally treated as pointers and dereferenced
18396 automatically. For this reason, it is often necessary to prefix a
18397 variable name with the address-of operator (``&'') and provide explicit
18398 type information in the command. Here's an example of the type of
18402 (@value{GDBP}) print 'cygwin1!__argv'
18407 (@value{GDBP}) x 'cygwin1!__argv'
18408 0x10021610: "\230y\""
18411 And two possible solutions:
18414 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18415 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18419 (@value{GDBP}) x/2x &'cygwin1!__argv'
18420 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18421 (@value{GDBP}) x/x 0x10021608
18422 0x10021608: 0x0022fd98
18423 (@value{GDBP}) x/s 0x0022fd98
18424 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18427 Setting a break point within a DLL is possible even before the program
18428 starts execution. However, under these circumstances, @value{GDBN} can't
18429 examine the initial instructions of the function in order to skip the
18430 function's frame set-up code. You can work around this by using ``*&''
18431 to set the breakpoint at a raw memory address:
18434 (@value{GDBP}) break *&'python22!PyOS_Readline'
18435 Breakpoint 1 at 0x1e04eff0
18438 The author of these extensions is not entirely convinced that setting a
18439 break point within a shared DLL like @file{kernel32.dll} is completely
18443 @subsection Commands Specific to @sc{gnu} Hurd Systems
18444 @cindex @sc{gnu} Hurd debugging
18446 This subsection describes @value{GDBN} commands specific to the
18447 @sc{gnu} Hurd native debugging.
18452 @kindex set signals@r{, Hurd command}
18453 @kindex set sigs@r{, Hurd command}
18454 This command toggles the state of inferior signal interception by
18455 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18456 affected by this command. @code{sigs} is a shorthand alias for
18461 @kindex show signals@r{, Hurd command}
18462 @kindex show sigs@r{, Hurd command}
18463 Show the current state of intercepting inferior's signals.
18465 @item set signal-thread
18466 @itemx set sigthread
18467 @kindex set signal-thread
18468 @kindex set sigthread
18469 This command tells @value{GDBN} which thread is the @code{libc} signal
18470 thread. That thread is run when a signal is delivered to a running
18471 process. @code{set sigthread} is the shorthand alias of @code{set
18474 @item show signal-thread
18475 @itemx show sigthread
18476 @kindex show signal-thread
18477 @kindex show sigthread
18478 These two commands show which thread will run when the inferior is
18479 delivered a signal.
18482 @kindex set stopped@r{, Hurd command}
18483 This commands tells @value{GDBN} that the inferior process is stopped,
18484 as with the @code{SIGSTOP} signal. The stopped process can be
18485 continued by delivering a signal to it.
18488 @kindex show stopped@r{, Hurd command}
18489 This command shows whether @value{GDBN} thinks the debuggee is
18492 @item set exceptions
18493 @kindex set exceptions@r{, Hurd command}
18494 Use this command to turn off trapping of exceptions in the inferior.
18495 When exception trapping is off, neither breakpoints nor
18496 single-stepping will work. To restore the default, set exception
18499 @item show exceptions
18500 @kindex show exceptions@r{, Hurd command}
18501 Show the current state of trapping exceptions in the inferior.
18503 @item set task pause
18504 @kindex set task@r{, Hurd commands}
18505 @cindex task attributes (@sc{gnu} Hurd)
18506 @cindex pause current task (@sc{gnu} Hurd)
18507 This command toggles task suspension when @value{GDBN} has control.
18508 Setting it to on takes effect immediately, and the task is suspended
18509 whenever @value{GDBN} gets control. Setting it to off will take
18510 effect the next time the inferior is continued. If this option is set
18511 to off, you can use @code{set thread default pause on} or @code{set
18512 thread pause on} (see below) to pause individual threads.
18514 @item show task pause
18515 @kindex show task@r{, Hurd commands}
18516 Show the current state of task suspension.
18518 @item set task detach-suspend-count
18519 @cindex task suspend count
18520 @cindex detach from task, @sc{gnu} Hurd
18521 This command sets the suspend count the task will be left with when
18522 @value{GDBN} detaches from it.
18524 @item show task detach-suspend-count
18525 Show the suspend count the task will be left with when detaching.
18527 @item set task exception-port
18528 @itemx set task excp
18529 @cindex task exception port, @sc{gnu} Hurd
18530 This command sets the task exception port to which @value{GDBN} will
18531 forward exceptions. The argument should be the value of the @dfn{send
18532 rights} of the task. @code{set task excp} is a shorthand alias.
18534 @item set noninvasive
18535 @cindex noninvasive task options
18536 This command switches @value{GDBN} to a mode that is the least
18537 invasive as far as interfering with the inferior is concerned. This
18538 is the same as using @code{set task pause}, @code{set exceptions}, and
18539 @code{set signals} to values opposite to the defaults.
18541 @item info send-rights
18542 @itemx info receive-rights
18543 @itemx info port-rights
18544 @itemx info port-sets
18545 @itemx info dead-names
18548 @cindex send rights, @sc{gnu} Hurd
18549 @cindex receive rights, @sc{gnu} Hurd
18550 @cindex port rights, @sc{gnu} Hurd
18551 @cindex port sets, @sc{gnu} Hurd
18552 @cindex dead names, @sc{gnu} Hurd
18553 These commands display information about, respectively, send rights,
18554 receive rights, port rights, port sets, and dead names of a task.
18555 There are also shorthand aliases: @code{info ports} for @code{info
18556 port-rights} and @code{info psets} for @code{info port-sets}.
18558 @item set thread pause
18559 @kindex set thread@r{, Hurd command}
18560 @cindex thread properties, @sc{gnu} Hurd
18561 @cindex pause current thread (@sc{gnu} Hurd)
18562 This command toggles current thread suspension when @value{GDBN} has
18563 control. Setting it to on takes effect immediately, and the current
18564 thread is suspended whenever @value{GDBN} gets control. Setting it to
18565 off will take effect the next time the inferior is continued.
18566 Normally, this command has no effect, since when @value{GDBN} has
18567 control, the whole task is suspended. However, if you used @code{set
18568 task pause off} (see above), this command comes in handy to suspend
18569 only the current thread.
18571 @item show thread pause
18572 @kindex show thread@r{, Hurd command}
18573 This command shows the state of current thread suspension.
18575 @item set thread run
18576 This command sets whether the current thread is allowed to run.
18578 @item show thread run
18579 Show whether the current thread is allowed to run.
18581 @item set thread detach-suspend-count
18582 @cindex thread suspend count, @sc{gnu} Hurd
18583 @cindex detach from thread, @sc{gnu} Hurd
18584 This command sets the suspend count @value{GDBN} will leave on a
18585 thread when detaching. This number is relative to the suspend count
18586 found by @value{GDBN} when it notices the thread; use @code{set thread
18587 takeover-suspend-count} to force it to an absolute value.
18589 @item show thread detach-suspend-count
18590 Show the suspend count @value{GDBN} will leave on the thread when
18593 @item set thread exception-port
18594 @itemx set thread excp
18595 Set the thread exception port to which to forward exceptions. This
18596 overrides the port set by @code{set task exception-port} (see above).
18597 @code{set thread excp} is the shorthand alias.
18599 @item set thread takeover-suspend-count
18600 Normally, @value{GDBN}'s thread suspend counts are relative to the
18601 value @value{GDBN} finds when it notices each thread. This command
18602 changes the suspend counts to be absolute instead.
18604 @item set thread default
18605 @itemx show thread default
18606 @cindex thread default settings, @sc{gnu} Hurd
18607 Each of the above @code{set thread} commands has a @code{set thread
18608 default} counterpart (e.g., @code{set thread default pause}, @code{set
18609 thread default exception-port}, etc.). The @code{thread default}
18610 variety of commands sets the default thread properties for all
18611 threads; you can then change the properties of individual threads with
18612 the non-default commands.
18617 @subsection QNX Neutrino
18618 @cindex QNX Neutrino
18620 @value{GDBN} provides the following commands specific to the QNX
18624 @item set debug nto-debug
18625 @kindex set debug nto-debug
18626 When set to on, enables debugging messages specific to the QNX
18629 @item show debug nto-debug
18630 @kindex show debug nto-debug
18631 Show the current state of QNX Neutrino messages.
18638 @value{GDBN} provides the following commands specific to the Darwin target:
18641 @item set debug darwin @var{num}
18642 @kindex set debug darwin
18643 When set to a non zero value, enables debugging messages specific to
18644 the Darwin support. Higher values produce more verbose output.
18646 @item show debug darwin
18647 @kindex show debug darwin
18648 Show the current state of Darwin messages.
18650 @item set debug mach-o @var{num}
18651 @kindex set debug mach-o
18652 When set to a non zero value, enables debugging messages while
18653 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18654 file format used on Darwin for object and executable files.) Higher
18655 values produce more verbose output. This is a command to diagnose
18656 problems internal to @value{GDBN} and should not be needed in normal
18659 @item show debug mach-o
18660 @kindex show debug mach-o
18661 Show the current state of Mach-O file messages.
18663 @item set mach-exceptions on
18664 @itemx set mach-exceptions off
18665 @kindex set mach-exceptions
18666 On Darwin, faults are first reported as a Mach exception and are then
18667 mapped to a Posix signal. Use this command to turn on trapping of
18668 Mach exceptions in the inferior. This might be sometimes useful to
18669 better understand the cause of a fault. The default is off.
18671 @item show mach-exceptions
18672 @kindex show mach-exceptions
18673 Show the current state of exceptions trapping.
18678 @section Embedded Operating Systems
18680 This section describes configurations involving the debugging of
18681 embedded operating systems that are available for several different
18685 * VxWorks:: Using @value{GDBN} with VxWorks
18688 @value{GDBN} includes the ability to debug programs running on
18689 various real-time operating systems.
18692 @subsection Using @value{GDBN} with VxWorks
18698 @kindex target vxworks
18699 @item target vxworks @var{machinename}
18700 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18701 is the target system's machine name or IP address.
18705 On VxWorks, @code{load} links @var{filename} dynamically on the
18706 current target system as well as adding its symbols in @value{GDBN}.
18708 @value{GDBN} enables developers to spawn and debug tasks running on networked
18709 VxWorks targets from a Unix host. Already-running tasks spawned from
18710 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18711 both the Unix host and on the VxWorks target. The program
18712 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18713 installed with the name @code{vxgdb}, to distinguish it from a
18714 @value{GDBN} for debugging programs on the host itself.)
18717 @item VxWorks-timeout @var{args}
18718 @kindex vxworks-timeout
18719 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18720 This option is set by the user, and @var{args} represents the number of
18721 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18722 your VxWorks target is a slow software simulator or is on the far side
18723 of a thin network line.
18726 The following information on connecting to VxWorks was current when
18727 this manual was produced; newer releases of VxWorks may use revised
18730 @findex INCLUDE_RDB
18731 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18732 to include the remote debugging interface routines in the VxWorks
18733 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18734 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18735 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18736 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18737 information on configuring and remaking VxWorks, see the manufacturer's
18739 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18741 Once you have included @file{rdb.a} in your VxWorks system image and set
18742 your Unix execution search path to find @value{GDBN}, you are ready to
18743 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18744 @code{vxgdb}, depending on your installation).
18746 @value{GDBN} comes up showing the prompt:
18753 * VxWorks Connection:: Connecting to VxWorks
18754 * VxWorks Download:: VxWorks download
18755 * VxWorks Attach:: Running tasks
18758 @node VxWorks Connection
18759 @subsubsection Connecting to VxWorks
18761 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18762 network. To connect to a target whose host name is ``@code{tt}'', type:
18765 (vxgdb) target vxworks tt
18769 @value{GDBN} displays messages like these:
18772 Attaching remote machine across net...
18777 @value{GDBN} then attempts to read the symbol tables of any object modules
18778 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18779 these files by searching the directories listed in the command search
18780 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18781 to find an object file, it displays a message such as:
18784 prog.o: No such file or directory.
18787 When this happens, add the appropriate directory to the search path with
18788 the @value{GDBN} command @code{path}, and execute the @code{target}
18791 @node VxWorks Download
18792 @subsubsection VxWorks Download
18794 @cindex download to VxWorks
18795 If you have connected to the VxWorks target and you want to debug an
18796 object that has not yet been loaded, you can use the @value{GDBN}
18797 @code{load} command to download a file from Unix to VxWorks
18798 incrementally. The object file given as an argument to the @code{load}
18799 command is actually opened twice: first by the VxWorks target in order
18800 to download the code, then by @value{GDBN} in order to read the symbol
18801 table. This can lead to problems if the current working directories on
18802 the two systems differ. If both systems have NFS mounted the same
18803 filesystems, you can avoid these problems by using absolute paths.
18804 Otherwise, it is simplest to set the working directory on both systems
18805 to the directory in which the object file resides, and then to reference
18806 the file by its name, without any path. For instance, a program
18807 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18808 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18809 program, type this on VxWorks:
18812 -> cd "@var{vxpath}/vw/demo/rdb"
18816 Then, in @value{GDBN}, type:
18819 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18820 (vxgdb) load prog.o
18823 @value{GDBN} displays a response similar to this:
18826 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18829 You can also use the @code{load} command to reload an object module
18830 after editing and recompiling the corresponding source file. Note that
18831 this makes @value{GDBN} delete all currently-defined breakpoints,
18832 auto-displays, and convenience variables, and to clear the value
18833 history. (This is necessary in order to preserve the integrity of
18834 debugger's data structures that reference the target system's symbol
18837 @node VxWorks Attach
18838 @subsubsection Running Tasks
18840 @cindex running VxWorks tasks
18841 You can also attach to an existing task using the @code{attach} command as
18845 (vxgdb) attach @var{task}
18849 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18850 or suspended when you attach to it. Running tasks are suspended at
18851 the time of attachment.
18853 @node Embedded Processors
18854 @section Embedded Processors
18856 This section goes into details specific to particular embedded
18859 @cindex send command to simulator
18860 Whenever a specific embedded processor has a simulator, @value{GDBN}
18861 allows to send an arbitrary command to the simulator.
18864 @item sim @var{command}
18865 @kindex sim@r{, a command}
18866 Send an arbitrary @var{command} string to the simulator. Consult the
18867 documentation for the specific simulator in use for information about
18868 acceptable commands.
18874 * M32R/D:: Renesas M32R/D
18875 * M68K:: Motorola M68K
18876 * MicroBlaze:: Xilinx MicroBlaze
18877 * MIPS Embedded:: MIPS Embedded
18878 * OpenRISC 1000:: OpenRisc 1000
18879 * PA:: HP PA Embedded
18880 * PowerPC Embedded:: PowerPC Embedded
18881 * Sparclet:: Tsqware Sparclet
18882 * Sparclite:: Fujitsu Sparclite
18883 * Z8000:: Zilog Z8000
18886 * Super-H:: Renesas Super-H
18895 @item target rdi @var{dev}
18896 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18897 use this target to communicate with both boards running the Angel
18898 monitor, or with the EmbeddedICE JTAG debug device.
18901 @item target rdp @var{dev}
18906 @value{GDBN} provides the following ARM-specific commands:
18909 @item set arm disassembler
18911 This commands selects from a list of disassembly styles. The
18912 @code{"std"} style is the standard style.
18914 @item show arm disassembler
18916 Show the current disassembly style.
18918 @item set arm apcs32
18919 @cindex ARM 32-bit mode
18920 This command toggles ARM operation mode between 32-bit and 26-bit.
18922 @item show arm apcs32
18923 Display the current usage of the ARM 32-bit mode.
18925 @item set arm fpu @var{fputype}
18926 This command sets the ARM floating-point unit (FPU) type. The
18927 argument @var{fputype} can be one of these:
18931 Determine the FPU type by querying the OS ABI.
18933 Software FPU, with mixed-endian doubles on little-endian ARM
18936 GCC-compiled FPA co-processor.
18938 Software FPU with pure-endian doubles.
18944 Show the current type of the FPU.
18947 This command forces @value{GDBN} to use the specified ABI.
18950 Show the currently used ABI.
18952 @item set arm fallback-mode (arm|thumb|auto)
18953 @value{GDBN} uses the symbol table, when available, to determine
18954 whether instructions are ARM or Thumb. This command controls
18955 @value{GDBN}'s default behavior when the symbol table is not
18956 available. The default is @samp{auto}, which causes @value{GDBN} to
18957 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18960 @item show arm fallback-mode
18961 Show the current fallback instruction mode.
18963 @item set arm force-mode (arm|thumb|auto)
18964 This command overrides use of the symbol table to determine whether
18965 instructions are ARM or Thumb. The default is @samp{auto}, which
18966 causes @value{GDBN} to use the symbol table and then the setting
18967 of @samp{set arm fallback-mode}.
18969 @item show arm force-mode
18970 Show the current forced instruction mode.
18972 @item set debug arm
18973 Toggle whether to display ARM-specific debugging messages from the ARM
18974 target support subsystem.
18976 @item show debug arm
18977 Show whether ARM-specific debugging messages are enabled.
18980 The following commands are available when an ARM target is debugged
18981 using the RDI interface:
18984 @item rdilogfile @r{[}@var{file}@r{]}
18986 @cindex ADP (Angel Debugger Protocol) logging
18987 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18988 With an argument, sets the log file to the specified @var{file}. With
18989 no argument, show the current log file name. The default log file is
18992 @item rdilogenable @r{[}@var{arg}@r{]}
18993 @kindex rdilogenable
18994 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18995 enables logging, with an argument 0 or @code{"no"} disables it. With
18996 no arguments displays the current setting. When logging is enabled,
18997 ADP packets exchanged between @value{GDBN} and the RDI target device
18998 are logged to a file.
19000 @item set rdiromatzero
19001 @kindex set rdiromatzero
19002 @cindex ROM at zero address, RDI
19003 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19004 vector catching is disabled, so that zero address can be used. If off
19005 (the default), vector catching is enabled. For this command to take
19006 effect, it needs to be invoked prior to the @code{target rdi} command.
19008 @item show rdiromatzero
19009 @kindex show rdiromatzero
19010 Show the current setting of ROM at zero address.
19012 @item set rdiheartbeat
19013 @kindex set rdiheartbeat
19014 @cindex RDI heartbeat
19015 Enable or disable RDI heartbeat packets. It is not recommended to
19016 turn on this option, since it confuses ARM and EPI JTAG interface, as
19017 well as the Angel monitor.
19019 @item show rdiheartbeat
19020 @kindex show rdiheartbeat
19021 Show the setting of RDI heartbeat packets.
19025 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19026 The @value{GDBN} ARM simulator accepts the following optional arguments.
19029 @item --swi-support=@var{type}
19030 Tell the simulator which SWI interfaces to support.
19031 @var{type} may be a comma separated list of the following values.
19032 The default value is @code{all}.
19045 @subsection Renesas M32R/D and M32R/SDI
19048 @kindex target m32r
19049 @item target m32r @var{dev}
19050 Renesas M32R/D ROM monitor.
19052 @kindex target m32rsdi
19053 @item target m32rsdi @var{dev}
19054 Renesas M32R SDI server, connected via parallel port to the board.
19057 The following @value{GDBN} commands are specific to the M32R monitor:
19060 @item set download-path @var{path}
19061 @kindex set download-path
19062 @cindex find downloadable @sc{srec} files (M32R)
19063 Set the default path for finding downloadable @sc{srec} files.
19065 @item show download-path
19066 @kindex show download-path
19067 Show the default path for downloadable @sc{srec} files.
19069 @item set board-address @var{addr}
19070 @kindex set board-address
19071 @cindex M32-EVA target board address
19072 Set the IP address for the M32R-EVA target board.
19074 @item show board-address
19075 @kindex show board-address
19076 Show the current IP address of the target board.
19078 @item set server-address @var{addr}
19079 @kindex set server-address
19080 @cindex download server address (M32R)
19081 Set the IP address for the download server, which is the @value{GDBN}'s
19084 @item show server-address
19085 @kindex show server-address
19086 Display the IP address of the download server.
19088 @item upload @r{[}@var{file}@r{]}
19089 @kindex upload@r{, M32R}
19090 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19091 upload capability. If no @var{file} argument is given, the current
19092 executable file is uploaded.
19094 @item tload @r{[}@var{file}@r{]}
19095 @kindex tload@r{, M32R}
19096 Test the @code{upload} command.
19099 The following commands are available for M32R/SDI:
19104 @cindex reset SDI connection, M32R
19105 This command resets the SDI connection.
19109 This command shows the SDI connection status.
19112 @kindex debug_chaos
19113 @cindex M32R/Chaos debugging
19114 Instructs the remote that M32R/Chaos debugging is to be used.
19116 @item use_debug_dma
19117 @kindex use_debug_dma
19118 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19121 @kindex use_mon_code
19122 Instructs the remote to use the MON_CODE method of accessing memory.
19125 @kindex use_ib_break
19126 Instructs the remote to set breakpoints by IB break.
19128 @item use_dbt_break
19129 @kindex use_dbt_break
19130 Instructs the remote to set breakpoints by DBT.
19136 The Motorola m68k configuration includes ColdFire support, and a
19137 target command for the following ROM monitor.
19141 @kindex target dbug
19142 @item target dbug @var{dev}
19143 dBUG ROM monitor for Motorola ColdFire.
19148 @subsection MicroBlaze
19149 @cindex Xilinx MicroBlaze
19150 @cindex XMD, Xilinx Microprocessor Debugger
19152 The MicroBlaze is a soft-core processor supported on various Xilinx
19153 FPGAs, such as Spartan or Virtex series. Boards with these processors
19154 usually have JTAG ports which connect to a host system running the Xilinx
19155 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19156 This host system is used to download the configuration bitstream to
19157 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19158 communicates with the target board using the JTAG interface and
19159 presents a @code{gdbserver} interface to the board. By default
19160 @code{xmd} uses port @code{1234}. (While it is possible to change
19161 this default port, it requires the use of undocumented @code{xmd}
19162 commands. Contact Xilinx support if you need to do this.)
19164 Use these GDB commands to connect to the MicroBlaze target processor.
19167 @item target remote :1234
19168 Use this command to connect to the target if you are running @value{GDBN}
19169 on the same system as @code{xmd}.
19171 @item target remote @var{xmd-host}:1234
19172 Use this command to connect to the target if it is connected to @code{xmd}
19173 running on a different system named @var{xmd-host}.
19176 Use this command to download a program to the MicroBlaze target.
19178 @item set debug microblaze @var{n}
19179 Enable MicroBlaze-specific debugging messages if non-zero.
19181 @item show debug microblaze @var{n}
19182 Show MicroBlaze-specific debugging level.
19185 @node MIPS Embedded
19186 @subsection MIPS Embedded
19188 @cindex MIPS boards
19189 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19190 MIPS board attached to a serial line. This is available when
19191 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19194 Use these @value{GDBN} commands to specify the connection to your target board:
19197 @item target mips @var{port}
19198 @kindex target mips @var{port}
19199 To run a program on the board, start up @code{@value{GDBP}} with the
19200 name of your program as the argument. To connect to the board, use the
19201 command @samp{target mips @var{port}}, where @var{port} is the name of
19202 the serial port connected to the board. If the program has not already
19203 been downloaded to the board, you may use the @code{load} command to
19204 download it. You can then use all the usual @value{GDBN} commands.
19206 For example, this sequence connects to the target board through a serial
19207 port, and loads and runs a program called @var{prog} through the
19211 host$ @value{GDBP} @var{prog}
19212 @value{GDBN} is free software and @dots{}
19213 (@value{GDBP}) target mips /dev/ttyb
19214 (@value{GDBP}) load @var{prog}
19218 @item target mips @var{hostname}:@var{portnumber}
19219 On some @value{GDBN} host configurations, you can specify a TCP
19220 connection (for instance, to a serial line managed by a terminal
19221 concentrator) instead of a serial port, using the syntax
19222 @samp{@var{hostname}:@var{portnumber}}.
19224 @item target pmon @var{port}
19225 @kindex target pmon @var{port}
19228 @item target ddb @var{port}
19229 @kindex target ddb @var{port}
19230 NEC's DDB variant of PMON for Vr4300.
19232 @item target lsi @var{port}
19233 @kindex target lsi @var{port}
19234 LSI variant of PMON.
19236 @kindex target r3900
19237 @item target r3900 @var{dev}
19238 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19240 @kindex target array
19241 @item target array @var{dev}
19242 Array Tech LSI33K RAID controller board.
19248 @value{GDBN} also supports these special commands for MIPS targets:
19251 @item set mipsfpu double
19252 @itemx set mipsfpu single
19253 @itemx set mipsfpu none
19254 @itemx set mipsfpu auto
19255 @itemx show mipsfpu
19256 @kindex set mipsfpu
19257 @kindex show mipsfpu
19258 @cindex MIPS remote floating point
19259 @cindex floating point, MIPS remote
19260 If your target board does not support the MIPS floating point
19261 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19262 need this, you may wish to put the command in your @value{GDBN} init
19263 file). This tells @value{GDBN} how to find the return value of
19264 functions which return floating point values. It also allows
19265 @value{GDBN} to avoid saving the floating point registers when calling
19266 functions on the board. If you are using a floating point coprocessor
19267 with only single precision floating point support, as on the @sc{r4650}
19268 processor, use the command @samp{set mipsfpu single}. The default
19269 double precision floating point coprocessor may be selected using
19270 @samp{set mipsfpu double}.
19272 In previous versions the only choices were double precision or no
19273 floating point, so @samp{set mipsfpu on} will select double precision
19274 and @samp{set mipsfpu off} will select no floating point.
19276 As usual, you can inquire about the @code{mipsfpu} variable with
19277 @samp{show mipsfpu}.
19279 @item set timeout @var{seconds}
19280 @itemx set retransmit-timeout @var{seconds}
19281 @itemx show timeout
19282 @itemx show retransmit-timeout
19283 @cindex @code{timeout}, MIPS protocol
19284 @cindex @code{retransmit-timeout}, MIPS protocol
19285 @kindex set timeout
19286 @kindex show timeout
19287 @kindex set retransmit-timeout
19288 @kindex show retransmit-timeout
19289 You can control the timeout used while waiting for a packet, in the MIPS
19290 remote protocol, with the @code{set timeout @var{seconds}} command. The
19291 default is 5 seconds. Similarly, you can control the timeout used while
19292 waiting for an acknowledgment of a packet with the @code{set
19293 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19294 You can inspect both values with @code{show timeout} and @code{show
19295 retransmit-timeout}. (These commands are @emph{only} available when
19296 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19298 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19299 is waiting for your program to stop. In that case, @value{GDBN} waits
19300 forever because it has no way of knowing how long the program is going
19301 to run before stopping.
19303 @item set syn-garbage-limit @var{num}
19304 @kindex set syn-garbage-limit@r{, MIPS remote}
19305 @cindex synchronize with remote MIPS target
19306 Limit the maximum number of characters @value{GDBN} should ignore when
19307 it tries to synchronize with the remote target. The default is 10
19308 characters. Setting the limit to -1 means there's no limit.
19310 @item show syn-garbage-limit
19311 @kindex show syn-garbage-limit@r{, MIPS remote}
19312 Show the current limit on the number of characters to ignore when
19313 trying to synchronize with the remote system.
19315 @item set monitor-prompt @var{prompt}
19316 @kindex set monitor-prompt@r{, MIPS remote}
19317 @cindex remote monitor prompt
19318 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19319 remote monitor. The default depends on the target:
19329 @item show monitor-prompt
19330 @kindex show monitor-prompt@r{, MIPS remote}
19331 Show the current strings @value{GDBN} expects as the prompt from the
19334 @item set monitor-warnings
19335 @kindex set monitor-warnings@r{, MIPS remote}
19336 Enable or disable monitor warnings about hardware breakpoints. This
19337 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19338 display warning messages whose codes are returned by the @code{lsi}
19339 PMON monitor for breakpoint commands.
19341 @item show monitor-warnings
19342 @kindex show monitor-warnings@r{, MIPS remote}
19343 Show the current setting of printing monitor warnings.
19345 @item pmon @var{command}
19346 @kindex pmon@r{, MIPS remote}
19347 @cindex send PMON command
19348 This command allows sending an arbitrary @var{command} string to the
19349 monitor. The monitor must be in debug mode for this to work.
19352 @node OpenRISC 1000
19353 @subsection OpenRISC 1000
19354 @cindex OpenRISC 1000
19356 @cindex or1k boards
19357 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19358 about platform and commands.
19362 @kindex target jtag
19363 @item target jtag jtag://@var{host}:@var{port}
19365 Connects to remote JTAG server.
19366 JTAG remote server can be either an or1ksim or JTAG server,
19367 connected via parallel port to the board.
19369 Example: @code{target jtag jtag://localhost:9999}
19372 @item or1ksim @var{command}
19373 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19374 Simulator, proprietary commands can be executed.
19376 @kindex info or1k spr
19377 @item info or1k spr
19378 Displays spr groups.
19380 @item info or1k spr @var{group}
19381 @itemx info or1k spr @var{groupno}
19382 Displays register names in selected group.
19384 @item info or1k spr @var{group} @var{register}
19385 @itemx info or1k spr @var{register}
19386 @itemx info or1k spr @var{groupno} @var{registerno}
19387 @itemx info or1k spr @var{registerno}
19388 Shows information about specified spr register.
19391 @item spr @var{group} @var{register} @var{value}
19392 @itemx spr @var{register @var{value}}
19393 @itemx spr @var{groupno} @var{registerno @var{value}}
19394 @itemx spr @var{registerno @var{value}}
19395 Writes @var{value} to specified spr register.
19398 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19399 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19400 program execution and is thus much faster. Hardware breakpoints/watchpoint
19401 triggers can be set using:
19404 Load effective address/data
19406 Store effective address/data
19408 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19413 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19414 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19416 @code{htrace} commands:
19417 @cindex OpenRISC 1000 htrace
19420 @item hwatch @var{conditional}
19421 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19422 or Data. For example:
19424 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19426 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19430 Display information about current HW trace configuration.
19432 @item htrace trigger @var{conditional}
19433 Set starting criteria for HW trace.
19435 @item htrace qualifier @var{conditional}
19436 Set acquisition qualifier for HW trace.
19438 @item htrace stop @var{conditional}
19439 Set HW trace stopping criteria.
19441 @item htrace record [@var{data}]*
19442 Selects the data to be recorded, when qualifier is met and HW trace was
19445 @item htrace enable
19446 @itemx htrace disable
19447 Enables/disables the HW trace.
19449 @item htrace rewind [@var{filename}]
19450 Clears currently recorded trace data.
19452 If filename is specified, new trace file is made and any newly collected data
19453 will be written there.
19455 @item htrace print [@var{start} [@var{len}]]
19456 Prints trace buffer, using current record configuration.
19458 @item htrace mode continuous
19459 Set continuous trace mode.
19461 @item htrace mode suspend
19462 Set suspend trace mode.
19466 @node PowerPC Embedded
19467 @subsection PowerPC Embedded
19469 @cindex DVC register
19470 @value{GDBN} supports using the DVC (Data Value Compare) register to
19471 implement in hardware simple hardware watchpoint conditions of the form:
19474 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19475 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19478 The DVC register will be automatically used when @value{GDBN} detects
19479 such pattern in a condition expression, and the created watchpoint uses one
19480 debug register (either the @code{exact-watchpoints} option is on and the
19481 variable is scalar, or the variable has a length of one byte). This feature
19482 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19485 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19486 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19487 in which case watchpoints using only one debug register are created when
19488 watching variables of scalar types.
19490 You can create an artificial array to watch an arbitrary memory
19491 region using one of the following commands (@pxref{Expressions}):
19494 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19495 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19498 PowerPC embedded processors support masked watchpoints. See the discussion
19499 about the @code{mask} argument in @ref{Set Watchpoints}.
19501 @cindex ranged breakpoint
19502 PowerPC embedded processors support hardware accelerated
19503 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19504 the inferior whenever it executes an instruction at any address within
19505 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19506 use the @code{break-range} command.
19508 @value{GDBN} provides the following PowerPC-specific commands:
19511 @kindex break-range
19512 @item break-range @var{start-location}, @var{end-location}
19513 Set a breakpoint for an address range.
19514 @var{start-location} and @var{end-location} can specify a function name,
19515 a line number, an offset of lines from the current line or from the start
19516 location, or an address of an instruction (see @ref{Specify Location},
19517 for a list of all the possible ways to specify a @var{location}.)
19518 The breakpoint will stop execution of the inferior whenever it
19519 executes an instruction at any address within the specified range,
19520 (including @var{start-location} and @var{end-location}.)
19522 @kindex set powerpc
19523 @item set powerpc soft-float
19524 @itemx show powerpc soft-float
19525 Force @value{GDBN} to use (or not use) a software floating point calling
19526 convention. By default, @value{GDBN} selects the calling convention based
19527 on the selected architecture and the provided executable file.
19529 @item set powerpc vector-abi
19530 @itemx show powerpc vector-abi
19531 Force @value{GDBN} to use the specified calling convention for vector
19532 arguments and return values. The valid options are @samp{auto};
19533 @samp{generic}, to avoid vector registers even if they are present;
19534 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19535 registers. By default, @value{GDBN} selects the calling convention
19536 based on the selected architecture and the provided executable file.
19538 @item set powerpc exact-watchpoints
19539 @itemx show powerpc exact-watchpoints
19540 Allow @value{GDBN} to use only one debug register when watching a variable
19541 of scalar type, thus assuming that the variable is accessed through the
19542 address of its first byte.
19544 @kindex target dink32
19545 @item target dink32 @var{dev}
19546 DINK32 ROM monitor.
19548 @kindex target ppcbug
19549 @item target ppcbug @var{dev}
19550 @kindex target ppcbug1
19551 @item target ppcbug1 @var{dev}
19552 PPCBUG ROM monitor for PowerPC.
19555 @item target sds @var{dev}
19556 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19559 @cindex SDS protocol
19560 The following commands specific to the SDS protocol are supported
19564 @item set sdstimeout @var{nsec}
19565 @kindex set sdstimeout
19566 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19567 default is 2 seconds.
19569 @item show sdstimeout
19570 @kindex show sdstimeout
19571 Show the current value of the SDS timeout.
19573 @item sds @var{command}
19574 @kindex sds@r{, a command}
19575 Send the specified @var{command} string to the SDS monitor.
19580 @subsection HP PA Embedded
19584 @kindex target op50n
19585 @item target op50n @var{dev}
19586 OP50N monitor, running on an OKI HPPA board.
19588 @kindex target w89k
19589 @item target w89k @var{dev}
19590 W89K monitor, running on a Winbond HPPA board.
19595 @subsection Tsqware Sparclet
19599 @value{GDBN} enables developers to debug tasks running on
19600 Sparclet targets from a Unix host.
19601 @value{GDBN} uses code that runs on
19602 both the Unix host and on the Sparclet target. The program
19603 @code{@value{GDBP}} is installed and executed on the Unix host.
19606 @item remotetimeout @var{args}
19607 @kindex remotetimeout
19608 @value{GDBN} supports the option @code{remotetimeout}.
19609 This option is set by the user, and @var{args} represents the number of
19610 seconds @value{GDBN} waits for responses.
19613 @cindex compiling, on Sparclet
19614 When compiling for debugging, include the options @samp{-g} to get debug
19615 information and @samp{-Ttext} to relocate the program to where you wish to
19616 load it on the target. You may also want to add the options @samp{-n} or
19617 @samp{-N} in order to reduce the size of the sections. Example:
19620 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19623 You can use @code{objdump} to verify that the addresses are what you intended:
19626 sparclet-aout-objdump --headers --syms prog
19629 @cindex running, on Sparclet
19631 your Unix execution search path to find @value{GDBN}, you are ready to
19632 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19633 (or @code{sparclet-aout-gdb}, depending on your installation).
19635 @value{GDBN} comes up showing the prompt:
19642 * Sparclet File:: Setting the file to debug
19643 * Sparclet Connection:: Connecting to Sparclet
19644 * Sparclet Download:: Sparclet download
19645 * Sparclet Execution:: Running and debugging
19648 @node Sparclet File
19649 @subsubsection Setting File to Debug
19651 The @value{GDBN} command @code{file} lets you choose with program to debug.
19654 (gdbslet) file prog
19658 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19659 @value{GDBN} locates
19660 the file by searching the directories listed in the command search
19662 If the file was compiled with debug information (option @samp{-g}), source
19663 files will be searched as well.
19664 @value{GDBN} locates
19665 the source files by searching the directories listed in the directory search
19666 path (@pxref{Environment, ,Your Program's Environment}).
19668 to find a file, it displays a message such as:
19671 prog: No such file or directory.
19674 When this happens, add the appropriate directories to the search paths with
19675 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19676 @code{target} command again.
19678 @node Sparclet Connection
19679 @subsubsection Connecting to Sparclet
19681 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19682 To connect to a target on serial port ``@code{ttya}'', type:
19685 (gdbslet) target sparclet /dev/ttya
19686 Remote target sparclet connected to /dev/ttya
19687 main () at ../prog.c:3
19691 @value{GDBN} displays messages like these:
19697 @node Sparclet Download
19698 @subsubsection Sparclet Download
19700 @cindex download to Sparclet
19701 Once connected to the Sparclet target,
19702 you can use the @value{GDBN}
19703 @code{load} command to download the file from the host to the target.
19704 The file name and load offset should be given as arguments to the @code{load}
19706 Since the file format is aout, the program must be loaded to the starting
19707 address. You can use @code{objdump} to find out what this value is. The load
19708 offset is an offset which is added to the VMA (virtual memory address)
19709 of each of the file's sections.
19710 For instance, if the program
19711 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19712 and bss at 0x12010170, in @value{GDBN}, type:
19715 (gdbslet) load prog 0x12010000
19716 Loading section .text, size 0xdb0 vma 0x12010000
19719 If the code is loaded at a different address then what the program was linked
19720 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19721 to tell @value{GDBN} where to map the symbol table.
19723 @node Sparclet Execution
19724 @subsubsection Running and Debugging
19726 @cindex running and debugging Sparclet programs
19727 You can now begin debugging the task using @value{GDBN}'s execution control
19728 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19729 manual for the list of commands.
19733 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19735 Starting program: prog
19736 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19737 3 char *symarg = 0;
19739 4 char *execarg = "hello!";
19744 @subsection Fujitsu Sparclite
19748 @kindex target sparclite
19749 @item target sparclite @var{dev}
19750 Fujitsu sparclite boards, used only for the purpose of loading.
19751 You must use an additional command to debug the program.
19752 For example: target remote @var{dev} using @value{GDBN} standard
19758 @subsection Zilog Z8000
19761 @cindex simulator, Z8000
19762 @cindex Zilog Z8000 simulator
19764 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19767 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19768 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19769 segmented variant). The simulator recognizes which architecture is
19770 appropriate by inspecting the object code.
19773 @item target sim @var{args}
19775 @kindex target sim@r{, with Z8000}
19776 Debug programs on a simulated CPU. If the simulator supports setup
19777 options, specify them via @var{args}.
19781 After specifying this target, you can debug programs for the simulated
19782 CPU in the same style as programs for your host computer; use the
19783 @code{file} command to load a new program image, the @code{run} command
19784 to run your program, and so on.
19786 As well as making available all the usual machine registers
19787 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19788 additional items of information as specially named registers:
19793 Counts clock-ticks in the simulator.
19796 Counts instructions run in the simulator.
19799 Execution time in 60ths of a second.
19803 You can refer to these values in @value{GDBN} expressions with the usual
19804 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19805 conditional breakpoint that suspends only after at least 5000
19806 simulated clock ticks.
19809 @subsection Atmel AVR
19812 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19813 following AVR-specific commands:
19816 @item info io_registers
19817 @kindex info io_registers@r{, AVR}
19818 @cindex I/O registers (Atmel AVR)
19819 This command displays information about the AVR I/O registers. For
19820 each register, @value{GDBN} prints its number and value.
19827 When configured for debugging CRIS, @value{GDBN} provides the
19828 following CRIS-specific commands:
19831 @item set cris-version @var{ver}
19832 @cindex CRIS version
19833 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19834 The CRIS version affects register names and sizes. This command is useful in
19835 case autodetection of the CRIS version fails.
19837 @item show cris-version
19838 Show the current CRIS version.
19840 @item set cris-dwarf2-cfi
19841 @cindex DWARF-2 CFI and CRIS
19842 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19843 Change to @samp{off} when using @code{gcc-cris} whose version is below
19846 @item show cris-dwarf2-cfi
19847 Show the current state of using DWARF-2 CFI.
19849 @item set cris-mode @var{mode}
19851 Set the current CRIS mode to @var{mode}. It should only be changed when
19852 debugging in guru mode, in which case it should be set to
19853 @samp{guru} (the default is @samp{normal}).
19855 @item show cris-mode
19856 Show the current CRIS mode.
19860 @subsection Renesas Super-H
19863 For the Renesas Super-H processor, @value{GDBN} provides these
19868 @kindex regs@r{, Super-H}
19869 Show the values of all Super-H registers.
19871 @item set sh calling-convention @var{convention}
19872 @kindex set sh calling-convention
19873 Set the calling-convention used when calling functions from @value{GDBN}.
19874 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19875 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19876 convention. If the DWARF-2 information of the called function specifies
19877 that the function follows the Renesas calling convention, the function
19878 is called using the Renesas calling convention. If the calling convention
19879 is set to @samp{renesas}, the Renesas calling convention is always used,
19880 regardless of the DWARF-2 information. This can be used to override the
19881 default of @samp{gcc} if debug information is missing, or the compiler
19882 does not emit the DWARF-2 calling convention entry for a function.
19884 @item show sh calling-convention
19885 @kindex show sh calling-convention
19886 Show the current calling convention setting.
19891 @node Architectures
19892 @section Architectures
19894 This section describes characteristics of architectures that affect
19895 all uses of @value{GDBN} with the architecture, both native and cross.
19902 * HPPA:: HP PA architecture
19903 * SPU:: Cell Broadband Engine SPU architecture
19908 @subsection x86 Architecture-specific Issues
19911 @item set struct-convention @var{mode}
19912 @kindex set struct-convention
19913 @cindex struct return convention
19914 @cindex struct/union returned in registers
19915 Set the convention used by the inferior to return @code{struct}s and
19916 @code{union}s from functions to @var{mode}. Possible values of
19917 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19918 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19919 are returned on the stack, while @code{"reg"} means that a
19920 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19921 be returned in a register.
19923 @item show struct-convention
19924 @kindex show struct-convention
19925 Show the current setting of the convention to return @code{struct}s
19934 @kindex set rstack_high_address
19935 @cindex AMD 29K register stack
19936 @cindex register stack, AMD29K
19937 @item set rstack_high_address @var{address}
19938 On AMD 29000 family processors, registers are saved in a separate
19939 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19940 extent of this stack. Normally, @value{GDBN} just assumes that the
19941 stack is ``large enough''. This may result in @value{GDBN} referencing
19942 memory locations that do not exist. If necessary, you can get around
19943 this problem by specifying the ending address of the register stack with
19944 the @code{set rstack_high_address} command. The argument should be an
19945 address, which you probably want to precede with @samp{0x} to specify in
19948 @kindex show rstack_high_address
19949 @item show rstack_high_address
19950 Display the current limit of the register stack, on AMD 29000 family
19958 See the following section.
19963 @cindex stack on Alpha
19964 @cindex stack on MIPS
19965 @cindex Alpha stack
19967 Alpha- and MIPS-based computers use an unusual stack frame, which
19968 sometimes requires @value{GDBN} to search backward in the object code to
19969 find the beginning of a function.
19971 @cindex response time, MIPS debugging
19972 To improve response time (especially for embedded applications, where
19973 @value{GDBN} may be restricted to a slow serial line for this search)
19974 you may want to limit the size of this search, using one of these
19978 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19979 @item set heuristic-fence-post @var{limit}
19980 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19981 search for the beginning of a function. A value of @var{0} (the
19982 default) means there is no limit. However, except for @var{0}, the
19983 larger the limit the more bytes @code{heuristic-fence-post} must search
19984 and therefore the longer it takes to run. You should only need to use
19985 this command when debugging a stripped executable.
19987 @item show heuristic-fence-post
19988 Display the current limit.
19992 These commands are available @emph{only} when @value{GDBN} is configured
19993 for debugging programs on Alpha or MIPS processors.
19995 Several MIPS-specific commands are available when debugging MIPS
19999 @item set mips abi @var{arg}
20000 @kindex set mips abi
20001 @cindex set ABI for MIPS
20002 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
20003 values of @var{arg} are:
20007 The default ABI associated with the current binary (this is the
20017 @item show mips abi
20018 @kindex show mips abi
20019 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20022 @itemx show mipsfpu
20023 @xref{MIPS Embedded, set mipsfpu}.
20025 @item set mips mask-address @var{arg}
20026 @kindex set mips mask-address
20027 @cindex MIPS addresses, masking
20028 This command determines whether the most-significant 32 bits of 64-bit
20029 MIPS addresses are masked off. The argument @var{arg} can be
20030 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20031 setting, which lets @value{GDBN} determine the correct value.
20033 @item show mips mask-address
20034 @kindex show mips mask-address
20035 Show whether the upper 32 bits of MIPS addresses are masked off or
20038 @item set remote-mips64-transfers-32bit-regs
20039 @kindex set remote-mips64-transfers-32bit-regs
20040 This command controls compatibility with 64-bit MIPS targets that
20041 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20042 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20043 and 64 bits for other registers, set this option to @samp{on}.
20045 @item show remote-mips64-transfers-32bit-regs
20046 @kindex show remote-mips64-transfers-32bit-regs
20047 Show the current setting of compatibility with older MIPS 64 targets.
20049 @item set debug mips
20050 @kindex set debug mips
20051 This command turns on and off debugging messages for the MIPS-specific
20052 target code in @value{GDBN}.
20054 @item show debug mips
20055 @kindex show debug mips
20056 Show the current setting of MIPS debugging messages.
20062 @cindex HPPA support
20064 When @value{GDBN} is debugging the HP PA architecture, it provides the
20065 following special commands:
20068 @item set debug hppa
20069 @kindex set debug hppa
20070 This command determines whether HPPA architecture-specific debugging
20071 messages are to be displayed.
20073 @item show debug hppa
20074 Show whether HPPA debugging messages are displayed.
20076 @item maint print unwind @var{address}
20077 @kindex maint print unwind@r{, HPPA}
20078 This command displays the contents of the unwind table entry at the
20079 given @var{address}.
20085 @subsection Cell Broadband Engine SPU architecture
20086 @cindex Cell Broadband Engine
20089 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20090 it provides the following special commands:
20093 @item info spu event
20095 Display SPU event facility status. Shows current event mask
20096 and pending event status.
20098 @item info spu signal
20099 Display SPU signal notification facility status. Shows pending
20100 signal-control word and signal notification mode of both signal
20101 notification channels.
20103 @item info spu mailbox
20104 Display SPU mailbox facility status. Shows all pending entries,
20105 in order of processing, in each of the SPU Write Outbound,
20106 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20109 Display MFC DMA status. Shows all pending commands in the MFC
20110 DMA queue. For each entry, opcode, tag, class IDs, effective
20111 and local store addresses and transfer size are shown.
20113 @item info spu proxydma
20114 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20115 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20116 and local store addresses and transfer size are shown.
20120 When @value{GDBN} is debugging a combined PowerPC/SPU application
20121 on the Cell Broadband Engine, it provides in addition the following
20125 @item set spu stop-on-load @var{arg}
20127 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20128 will give control to the user when a new SPE thread enters its @code{main}
20129 function. The default is @code{off}.
20131 @item show spu stop-on-load
20133 Show whether to stop for new SPE threads.
20135 @item set spu auto-flush-cache @var{arg}
20136 Set whether to automatically flush the software-managed cache. When set to
20137 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20138 cache to be flushed whenever SPE execution stops. This provides a consistent
20139 view of PowerPC memory that is accessed via the cache. If an application
20140 does not use the software-managed cache, this option has no effect.
20142 @item show spu auto-flush-cache
20143 Show whether to automatically flush the software-managed cache.
20148 @subsection PowerPC
20149 @cindex PowerPC architecture
20151 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20152 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20153 numbers stored in the floating point registers. These values must be stored
20154 in two consecutive registers, always starting at an even register like
20155 @code{f0} or @code{f2}.
20157 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20158 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20159 @code{f2} and @code{f3} for @code{$dl1} and so on.
20161 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20162 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20165 @node Controlling GDB
20166 @chapter Controlling @value{GDBN}
20168 You can alter the way @value{GDBN} interacts with you by using the
20169 @code{set} command. For commands controlling how @value{GDBN} displays
20170 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20175 * Editing:: Command editing
20176 * Command History:: Command history
20177 * Screen Size:: Screen size
20178 * Numbers:: Numbers
20179 * ABI:: Configuring the current ABI
20180 * Messages/Warnings:: Optional warnings and messages
20181 * Debugging Output:: Optional messages about internal happenings
20182 * Other Misc Settings:: Other Miscellaneous Settings
20190 @value{GDBN} indicates its readiness to read a command by printing a string
20191 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20192 can change the prompt string with the @code{set prompt} command. For
20193 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20194 the prompt in one of the @value{GDBN} sessions so that you can always tell
20195 which one you are talking to.
20197 @emph{Note:} @code{set prompt} does not add a space for you after the
20198 prompt you set. This allows you to set a prompt which ends in a space
20199 or a prompt that does not.
20203 @item set prompt @var{newprompt}
20204 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20206 @kindex show prompt
20208 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20211 Versions of @value{GDBN} that ship with Python scripting enabled have
20212 prompt extensions. The commands for interacting with these extensions
20216 @kindex set extended-prompt
20217 @item set extended-prompt @var{prompt}
20218 Set an extended prompt that allows for substitutions.
20219 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20220 substitution. Any escape sequences specified as part of the prompt
20221 string are replaced with the corresponding strings each time the prompt
20227 set extended-prompt Current working directory: \w (gdb)
20230 Note that when an extended-prompt is set, it takes control of the
20231 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20233 @kindex show extended-prompt
20234 @item show extended-prompt
20235 Prints the extended prompt. Any escape sequences specified as part of
20236 the prompt string with @code{set extended-prompt}, are replaced with the
20237 corresponding strings each time the prompt is displayed.
20241 @section Command Editing
20243 @cindex command line editing
20245 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20246 @sc{gnu} library provides consistent behavior for programs which provide a
20247 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20248 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20249 substitution, and a storage and recall of command history across
20250 debugging sessions.
20252 You may control the behavior of command line editing in @value{GDBN} with the
20253 command @code{set}.
20256 @kindex set editing
20259 @itemx set editing on
20260 Enable command line editing (enabled by default).
20262 @item set editing off
20263 Disable command line editing.
20265 @kindex show editing
20267 Show whether command line editing is enabled.
20270 @ifset SYSTEM_READLINE
20271 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20273 @ifclear SYSTEM_READLINE
20274 @xref{Command Line Editing},
20276 for more details about the Readline
20277 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20278 encouraged to read that chapter.
20280 @node Command History
20281 @section Command History
20282 @cindex command history
20284 @value{GDBN} can keep track of the commands you type during your
20285 debugging sessions, so that you can be certain of precisely what
20286 happened. Use these commands to manage the @value{GDBN} command
20289 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20290 package, to provide the history facility.
20291 @ifset SYSTEM_READLINE
20292 @xref{Using History Interactively, , , history, GNU History Library},
20294 @ifclear SYSTEM_READLINE
20295 @xref{Using History Interactively},
20297 for the detailed description of the History library.
20299 To issue a command to @value{GDBN} without affecting certain aspects of
20300 the state which is seen by users, prefix it with @samp{server }
20301 (@pxref{Server Prefix}). This
20302 means that this command will not affect the command history, nor will it
20303 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20304 pressed on a line by itself.
20306 @cindex @code{server}, command prefix
20307 The server prefix does not affect the recording of values into the value
20308 history; to print a value without recording it into the value history,
20309 use the @code{output} command instead of the @code{print} command.
20311 Here is the description of @value{GDBN} commands related to command
20315 @cindex history substitution
20316 @cindex history file
20317 @kindex set history filename
20318 @cindex @env{GDBHISTFILE}, environment variable
20319 @item set history filename @var{fname}
20320 Set the name of the @value{GDBN} command history file to @var{fname}.
20321 This is the file where @value{GDBN} reads an initial command history
20322 list, and where it writes the command history from this session when it
20323 exits. You can access this list through history expansion or through
20324 the history command editing characters listed below. This file defaults
20325 to the value of the environment variable @code{GDBHISTFILE}, or to
20326 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20329 @cindex save command history
20330 @kindex set history save
20331 @item set history save
20332 @itemx set history save on
20333 Record command history in a file, whose name may be specified with the
20334 @code{set history filename} command. By default, this option is disabled.
20336 @item set history save off
20337 Stop recording command history in a file.
20339 @cindex history size
20340 @kindex set history size
20341 @cindex @env{HISTSIZE}, environment variable
20342 @item set history size @var{size}
20343 Set the number of commands which @value{GDBN} keeps in its history list.
20344 This defaults to the value of the environment variable
20345 @code{HISTSIZE}, or to 256 if this variable is not set.
20348 History expansion assigns special meaning to the character @kbd{!}.
20349 @ifset SYSTEM_READLINE
20350 @xref{Event Designators, , , history, GNU History Library},
20352 @ifclear SYSTEM_READLINE
20353 @xref{Event Designators},
20357 @cindex history expansion, turn on/off
20358 Since @kbd{!} is also the logical not operator in C, history expansion
20359 is off by default. If you decide to enable history expansion with the
20360 @code{set history expansion on} command, you may sometimes need to
20361 follow @kbd{!} (when it is used as logical not, in an expression) with
20362 a space or a tab to prevent it from being expanded. The readline
20363 history facilities do not attempt substitution on the strings
20364 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20366 The commands to control history expansion are:
20369 @item set history expansion on
20370 @itemx set history expansion
20371 @kindex set history expansion
20372 Enable history expansion. History expansion is off by default.
20374 @item set history expansion off
20375 Disable history expansion.
20378 @kindex show history
20380 @itemx show history filename
20381 @itemx show history save
20382 @itemx show history size
20383 @itemx show history expansion
20384 These commands display the state of the @value{GDBN} history parameters.
20385 @code{show history} by itself displays all four states.
20390 @kindex show commands
20391 @cindex show last commands
20392 @cindex display command history
20393 @item show commands
20394 Display the last ten commands in the command history.
20396 @item show commands @var{n}
20397 Print ten commands centered on command number @var{n}.
20399 @item show commands +
20400 Print ten commands just after the commands last printed.
20404 @section Screen Size
20405 @cindex size of screen
20406 @cindex pauses in output
20408 Certain commands to @value{GDBN} may produce large amounts of
20409 information output to the screen. To help you read all of it,
20410 @value{GDBN} pauses and asks you for input at the end of each page of
20411 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20412 to discard the remaining output. Also, the screen width setting
20413 determines when to wrap lines of output. Depending on what is being
20414 printed, @value{GDBN} tries to break the line at a readable place,
20415 rather than simply letting it overflow onto the following line.
20417 Normally @value{GDBN} knows the size of the screen from the terminal
20418 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20419 together with the value of the @code{TERM} environment variable and the
20420 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20421 you can override it with the @code{set height} and @code{set
20428 @kindex show height
20429 @item set height @var{lpp}
20431 @itemx set width @var{cpl}
20433 These @code{set} commands specify a screen height of @var{lpp} lines and
20434 a screen width of @var{cpl} characters. The associated @code{show}
20435 commands display the current settings.
20437 If you specify a height of zero lines, @value{GDBN} does not pause during
20438 output no matter how long the output is. This is useful if output is to a
20439 file or to an editor buffer.
20441 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20442 from wrapping its output.
20444 @item set pagination on
20445 @itemx set pagination off
20446 @kindex set pagination
20447 Turn the output pagination on or off; the default is on. Turning
20448 pagination off is the alternative to @code{set height 0}. Note that
20449 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20450 Options, -batch}) also automatically disables pagination.
20452 @item show pagination
20453 @kindex show pagination
20454 Show the current pagination mode.
20459 @cindex number representation
20460 @cindex entering numbers
20462 You can always enter numbers in octal, decimal, or hexadecimal in
20463 @value{GDBN} by the usual conventions: octal numbers begin with
20464 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20465 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20466 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20467 10; likewise, the default display for numbers---when no particular
20468 format is specified---is base 10. You can change the default base for
20469 both input and output with the commands described below.
20472 @kindex set input-radix
20473 @item set input-radix @var{base}
20474 Set the default base for numeric input. Supported choices
20475 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20476 specified either unambiguously or using the current input radix; for
20480 set input-radix 012
20481 set input-radix 10.
20482 set input-radix 0xa
20486 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20487 leaves the input radix unchanged, no matter what it was, since
20488 @samp{10}, being without any leading or trailing signs of its base, is
20489 interpreted in the current radix. Thus, if the current radix is 16,
20490 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20493 @kindex set output-radix
20494 @item set output-radix @var{base}
20495 Set the default base for numeric display. Supported choices
20496 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20497 specified either unambiguously or using the current input radix.
20499 @kindex show input-radix
20500 @item show input-radix
20501 Display the current default base for numeric input.
20503 @kindex show output-radix
20504 @item show output-radix
20505 Display the current default base for numeric display.
20507 @item set radix @r{[}@var{base}@r{]}
20511 These commands set and show the default base for both input and output
20512 of numbers. @code{set radix} sets the radix of input and output to
20513 the same base; without an argument, it resets the radix back to its
20514 default value of 10.
20519 @section Configuring the Current ABI
20521 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20522 application automatically. However, sometimes you need to override its
20523 conclusions. Use these commands to manage @value{GDBN}'s view of the
20530 One @value{GDBN} configuration can debug binaries for multiple operating
20531 system targets, either via remote debugging or native emulation.
20532 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20533 but you can override its conclusion using the @code{set osabi} command.
20534 One example where this is useful is in debugging of binaries which use
20535 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20536 not have the same identifying marks that the standard C library for your
20541 Show the OS ABI currently in use.
20544 With no argument, show the list of registered available OS ABI's.
20546 @item set osabi @var{abi}
20547 Set the current OS ABI to @var{abi}.
20550 @cindex float promotion
20552 Generally, the way that an argument of type @code{float} is passed to a
20553 function depends on whether the function is prototyped. For a prototyped
20554 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20555 according to the architecture's convention for @code{float}. For unprototyped
20556 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20557 @code{double} and then passed.
20559 Unfortunately, some forms of debug information do not reliably indicate whether
20560 a function is prototyped. If @value{GDBN} calls a function that is not marked
20561 as prototyped, it consults @kbd{set coerce-float-to-double}.
20564 @kindex set coerce-float-to-double
20565 @item set coerce-float-to-double
20566 @itemx set coerce-float-to-double on
20567 Arguments of type @code{float} will be promoted to @code{double} when passed
20568 to an unprototyped function. This is the default setting.
20570 @item set coerce-float-to-double off
20571 Arguments of type @code{float} will be passed directly to unprototyped
20574 @kindex show coerce-float-to-double
20575 @item show coerce-float-to-double
20576 Show the current setting of promoting @code{float} to @code{double}.
20580 @kindex show cp-abi
20581 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20582 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20583 used to build your application. @value{GDBN} only fully supports
20584 programs with a single C@t{++} ABI; if your program contains code using
20585 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20586 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20587 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20588 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20589 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20590 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20595 Show the C@t{++} ABI currently in use.
20598 With no argument, show the list of supported C@t{++} ABI's.
20600 @item set cp-abi @var{abi}
20601 @itemx set cp-abi auto
20602 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20605 @node Messages/Warnings
20606 @section Optional Warnings and Messages
20608 @cindex verbose operation
20609 @cindex optional warnings
20610 By default, @value{GDBN} is silent about its inner workings. If you are
20611 running on a slow machine, you may want to use the @code{set verbose}
20612 command. This makes @value{GDBN} tell you when it does a lengthy
20613 internal operation, so you will not think it has crashed.
20615 Currently, the messages controlled by @code{set verbose} are those
20616 which announce that the symbol table for a source file is being read;
20617 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20620 @kindex set verbose
20621 @item set verbose on
20622 Enables @value{GDBN} output of certain informational messages.
20624 @item set verbose off
20625 Disables @value{GDBN} output of certain informational messages.
20627 @kindex show verbose
20629 Displays whether @code{set verbose} is on or off.
20632 By default, if @value{GDBN} encounters bugs in the symbol table of an
20633 object file, it is silent; but if you are debugging a compiler, you may
20634 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20639 @kindex set complaints
20640 @item set complaints @var{limit}
20641 Permits @value{GDBN} to output @var{limit} complaints about each type of
20642 unusual symbols before becoming silent about the problem. Set
20643 @var{limit} to zero to suppress all complaints; set it to a large number
20644 to prevent complaints from being suppressed.
20646 @kindex show complaints
20647 @item show complaints
20648 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20652 @anchor{confirmation requests}
20653 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20654 lot of stupid questions to confirm certain commands. For example, if
20655 you try to run a program which is already running:
20659 The program being debugged has been started already.
20660 Start it from the beginning? (y or n)
20663 If you are willing to unflinchingly face the consequences of your own
20664 commands, you can disable this ``feature'':
20668 @kindex set confirm
20670 @cindex confirmation
20671 @cindex stupid questions
20672 @item set confirm off
20673 Disables confirmation requests. Note that running @value{GDBN} with
20674 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20675 automatically disables confirmation requests.
20677 @item set confirm on
20678 Enables confirmation requests (the default).
20680 @kindex show confirm
20682 Displays state of confirmation requests.
20686 @cindex command tracing
20687 If you need to debug user-defined commands or sourced files you may find it
20688 useful to enable @dfn{command tracing}. In this mode each command will be
20689 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20690 quantity denoting the call depth of each command.
20693 @kindex set trace-commands
20694 @cindex command scripts, debugging
20695 @item set trace-commands on
20696 Enable command tracing.
20697 @item set trace-commands off
20698 Disable command tracing.
20699 @item show trace-commands
20700 Display the current state of command tracing.
20703 @node Debugging Output
20704 @section Optional Messages about Internal Happenings
20705 @cindex optional debugging messages
20707 @value{GDBN} has commands that enable optional debugging messages from
20708 various @value{GDBN} subsystems; normally these commands are of
20709 interest to @value{GDBN} maintainers, or when reporting a bug. This
20710 section documents those commands.
20713 @kindex set exec-done-display
20714 @item set exec-done-display
20715 Turns on or off the notification of asynchronous commands'
20716 completion. When on, @value{GDBN} will print a message when an
20717 asynchronous command finishes its execution. The default is off.
20718 @kindex show exec-done-display
20719 @item show exec-done-display
20720 Displays the current setting of asynchronous command completion
20723 @cindex gdbarch debugging info
20724 @cindex architecture debugging info
20725 @item set debug arch
20726 Turns on or off display of gdbarch debugging info. The default is off
20728 @item show debug arch
20729 Displays the current state of displaying gdbarch debugging info.
20730 @item set debug aix-thread
20731 @cindex AIX threads
20732 Display debugging messages about inner workings of the AIX thread
20734 @item show debug aix-thread
20735 Show the current state of AIX thread debugging info display.
20736 @item set debug check-physname
20738 Check the results of the ``physname'' computation. When reading DWARF
20739 debugging information for C@t{++}, @value{GDBN} attempts to compute
20740 each entity's name. @value{GDBN} can do this computation in two
20741 different ways, depending on exactly what information is present.
20742 When enabled, this setting causes @value{GDBN} to compute the names
20743 both ways and display any discrepancies.
20744 @item show debug check-physname
20745 Show the current state of ``physname'' checking.
20746 @item set debug dwarf2-die
20747 @cindex DWARF2 DIEs
20748 Dump DWARF2 DIEs after they are read in.
20749 The value is the number of nesting levels to print.
20750 A value of zero turns off the display.
20751 @item show debug dwarf2-die
20752 Show the current state of DWARF2 DIE debugging.
20753 @item set debug displaced
20754 @cindex displaced stepping debugging info
20755 Turns on or off display of @value{GDBN} debugging info for the
20756 displaced stepping support. The default is off.
20757 @item show debug displaced
20758 Displays the current state of displaying @value{GDBN} debugging info
20759 related to displaced stepping.
20760 @item set debug event
20761 @cindex event debugging info
20762 Turns on or off display of @value{GDBN} event debugging info. The
20764 @item show debug event
20765 Displays the current state of displaying @value{GDBN} event debugging
20767 @item set debug expression
20768 @cindex expression debugging info
20769 Turns on or off display of debugging info about @value{GDBN}
20770 expression parsing. The default is off.
20771 @item show debug expression
20772 Displays the current state of displaying debugging info about
20773 @value{GDBN} expression parsing.
20774 @item set debug frame
20775 @cindex frame debugging info
20776 Turns on or off display of @value{GDBN} frame debugging info. The
20778 @item show debug frame
20779 Displays the current state of displaying @value{GDBN} frame debugging
20781 @item set debug gnu-nat
20782 @cindex @sc{gnu}/Hurd debug messages
20783 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20784 @item show debug gnu-nat
20785 Show the current state of @sc{gnu}/Hurd debugging messages.
20786 @item set debug infrun
20787 @cindex inferior debugging info
20788 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20789 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20790 for implementing operations such as single-stepping the inferior.
20791 @item show debug infrun
20792 Displays the current state of @value{GDBN} inferior debugging.
20793 @item set debug jit
20794 @cindex just-in-time compilation, debugging messages
20795 Turns on or off debugging messages from JIT debug support.
20796 @item show debug jit
20797 Displays the current state of @value{GDBN} JIT debugging.
20798 @item set debug lin-lwp
20799 @cindex @sc{gnu}/Linux LWP debug messages
20800 @cindex Linux lightweight processes
20801 Turns on or off debugging messages from the Linux LWP debug support.
20802 @item show debug lin-lwp
20803 Show the current state of Linux LWP debugging messages.
20804 @item set debug observer
20805 @cindex observer debugging info
20806 Turns on or off display of @value{GDBN} observer debugging. This
20807 includes info such as the notification of observable events.
20808 @item show debug observer
20809 Displays the current state of observer debugging.
20810 @item set debug overload
20811 @cindex C@t{++} overload debugging info
20812 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20813 info. This includes info such as ranking of functions, etc. The default
20815 @item show debug overload
20816 Displays the current state of displaying @value{GDBN} C@t{++} overload
20818 @cindex expression parser, debugging info
20819 @cindex debug expression parser
20820 @item set debug parser
20821 Turns on or off the display of expression parser debugging output.
20822 Internally, this sets the @code{yydebug} variable in the expression
20823 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20824 details. The default is off.
20825 @item show debug parser
20826 Show the current state of expression parser debugging.
20827 @cindex packets, reporting on stdout
20828 @cindex serial connections, debugging
20829 @cindex debug remote protocol
20830 @cindex remote protocol debugging
20831 @cindex display remote packets
20832 @item set debug remote
20833 Turns on or off display of reports on all packets sent back and forth across
20834 the serial line to the remote machine. The info is printed on the
20835 @value{GDBN} standard output stream. The default is off.
20836 @item show debug remote
20837 Displays the state of display of remote packets.
20838 @item set debug serial
20839 Turns on or off display of @value{GDBN} serial debugging info. The
20841 @item show debug serial
20842 Displays the current state of displaying @value{GDBN} serial debugging
20844 @item set debug solib-frv
20845 @cindex FR-V shared-library debugging
20846 Turns on or off debugging messages for FR-V shared-library code.
20847 @item show debug solib-frv
20848 Display the current state of FR-V shared-library code debugging
20850 @item set debug target
20851 @cindex target debugging info
20852 Turns on or off display of @value{GDBN} target debugging info. This info
20853 includes what is going on at the target level of GDB, as it happens. The
20854 default is 0. Set it to 1 to track events, and to 2 to also track the
20855 value of large memory transfers. Changes to this flag do not take effect
20856 until the next time you connect to a target or use the @code{run} command.
20857 @item show debug target
20858 Displays the current state of displaying @value{GDBN} target debugging
20860 @item set debug timestamp
20861 @cindex timestampping debugging info
20862 Turns on or off display of timestamps with @value{GDBN} debugging info.
20863 When enabled, seconds and microseconds are displayed before each debugging
20865 @item show debug timestamp
20866 Displays the current state of displaying timestamps with @value{GDBN}
20868 @item set debugvarobj
20869 @cindex variable object debugging info
20870 Turns on or off display of @value{GDBN} variable object debugging
20871 info. The default is off.
20872 @item show debugvarobj
20873 Displays the current state of displaying @value{GDBN} variable object
20875 @item set debug xml
20876 @cindex XML parser debugging
20877 Turns on or off debugging messages for built-in XML parsers.
20878 @item show debug xml
20879 Displays the current state of XML debugging messages.
20882 @node Other Misc Settings
20883 @section Other Miscellaneous Settings
20884 @cindex miscellaneous settings
20887 @kindex set interactive-mode
20888 @item set interactive-mode
20889 If @code{on}, forces @value{GDBN} to assume that GDB was started
20890 in a terminal. In practice, this means that @value{GDBN} should wait
20891 for the user to answer queries generated by commands entered at
20892 the command prompt. If @code{off}, forces @value{GDBN} to operate
20893 in the opposite mode, and it uses the default answers to all queries.
20894 If @code{auto} (the default), @value{GDBN} tries to determine whether
20895 its standard input is a terminal, and works in interactive-mode if it
20896 is, non-interactively otherwise.
20898 In the vast majority of cases, the debugger should be able to guess
20899 correctly which mode should be used. But this setting can be useful
20900 in certain specific cases, such as running a MinGW @value{GDBN}
20901 inside a cygwin window.
20903 @kindex show interactive-mode
20904 @item show interactive-mode
20905 Displays whether the debugger is operating in interactive mode or not.
20908 @node Extending GDB
20909 @chapter Extending @value{GDBN}
20910 @cindex extending GDB
20912 @value{GDBN} provides three mechanisms for extension. The first is based
20913 on composition of @value{GDBN} commands, the second is based on the
20914 Python scripting language, and the third is for defining new aliases of
20917 To facilitate the use of the first two extensions, @value{GDBN} is capable
20918 of evaluating the contents of a file. When doing so, @value{GDBN}
20919 can recognize which scripting language is being used by looking at
20920 the filename extension. Files with an unrecognized filename extension
20921 are always treated as a @value{GDBN} Command Files.
20922 @xref{Command Files,, Command files}.
20924 You can control how @value{GDBN} evaluates these files with the following
20928 @kindex set script-extension
20929 @kindex show script-extension
20930 @item set script-extension off
20931 All scripts are always evaluated as @value{GDBN} Command Files.
20933 @item set script-extension soft
20934 The debugger determines the scripting language based on filename
20935 extension. If this scripting language is supported, @value{GDBN}
20936 evaluates the script using that language. Otherwise, it evaluates
20937 the file as a @value{GDBN} Command File.
20939 @item set script-extension strict
20940 The debugger determines the scripting language based on filename
20941 extension, and evaluates the script using that language. If the
20942 language is not supported, then the evaluation fails.
20944 @item show script-extension
20945 Display the current value of the @code{script-extension} option.
20950 * Sequences:: Canned Sequences of Commands
20951 * Python:: Scripting @value{GDBN} using Python
20952 * Aliases:: Creating new spellings of existing commands
20956 @section Canned Sequences of Commands
20958 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20959 Command Lists}), @value{GDBN} provides two ways to store sequences of
20960 commands for execution as a unit: user-defined commands and command
20964 * Define:: How to define your own commands
20965 * Hooks:: Hooks for user-defined commands
20966 * Command Files:: How to write scripts of commands to be stored in a file
20967 * Output:: Commands for controlled output
20971 @subsection User-defined Commands
20973 @cindex user-defined command
20974 @cindex arguments, to user-defined commands
20975 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20976 which you assign a new name as a command. This is done with the
20977 @code{define} command. User commands may accept up to 10 arguments
20978 separated by whitespace. Arguments are accessed within the user command
20979 via @code{$arg0@dots{}$arg9}. A trivial example:
20983 print $arg0 + $arg1 + $arg2
20988 To execute the command use:
20995 This defines the command @code{adder}, which prints the sum of
20996 its three arguments. Note the arguments are text substitutions, so they may
20997 reference variables, use complex expressions, or even perform inferior
21000 @cindex argument count in user-defined commands
21001 @cindex how many arguments (user-defined commands)
21002 In addition, @code{$argc} may be used to find out how many arguments have
21003 been passed. This expands to a number in the range 0@dots{}10.
21008 print $arg0 + $arg1
21011 print $arg0 + $arg1 + $arg2
21019 @item define @var{commandname}
21020 Define a command named @var{commandname}. If there is already a command
21021 by that name, you are asked to confirm that you want to redefine it.
21022 @var{commandname} may be a bare command name consisting of letters,
21023 numbers, dashes, and underscores. It may also start with any predefined
21024 prefix command. For example, @samp{define target my-target} creates
21025 a user-defined @samp{target my-target} command.
21027 The definition of the command is made up of other @value{GDBN} command lines,
21028 which are given following the @code{define} command. The end of these
21029 commands is marked by a line containing @code{end}.
21032 @kindex end@r{ (user-defined commands)}
21033 @item document @var{commandname}
21034 Document the user-defined command @var{commandname}, so that it can be
21035 accessed by @code{help}. The command @var{commandname} must already be
21036 defined. This command reads lines of documentation just as @code{define}
21037 reads the lines of the command definition, ending with @code{end}.
21038 After the @code{document} command is finished, @code{help} on command
21039 @var{commandname} displays the documentation you have written.
21041 You may use the @code{document} command again to change the
21042 documentation of a command. Redefining the command with @code{define}
21043 does not change the documentation.
21045 @kindex dont-repeat
21046 @cindex don't repeat command
21048 Used inside a user-defined command, this tells @value{GDBN} that this
21049 command should not be repeated when the user hits @key{RET}
21050 (@pxref{Command Syntax, repeat last command}).
21052 @kindex help user-defined
21053 @item help user-defined
21054 List all user-defined commands, with the first line of the documentation
21059 @itemx show user @var{commandname}
21060 Display the @value{GDBN} commands used to define @var{commandname} (but
21061 not its documentation). If no @var{commandname} is given, display the
21062 definitions for all user-defined commands.
21064 @cindex infinite recursion in user-defined commands
21065 @kindex show max-user-call-depth
21066 @kindex set max-user-call-depth
21067 @item show max-user-call-depth
21068 @itemx set max-user-call-depth
21069 The value of @code{max-user-call-depth} controls how many recursion
21070 levels are allowed in user-defined commands before @value{GDBN} suspects an
21071 infinite recursion and aborts the command.
21074 In addition to the above commands, user-defined commands frequently
21075 use control flow commands, described in @ref{Command Files}.
21077 When user-defined commands are executed, the
21078 commands of the definition are not printed. An error in any command
21079 stops execution of the user-defined command.
21081 If used interactively, commands that would ask for confirmation proceed
21082 without asking when used inside a user-defined command. Many @value{GDBN}
21083 commands that normally print messages to say what they are doing omit the
21084 messages when used in a user-defined command.
21087 @subsection User-defined Command Hooks
21088 @cindex command hooks
21089 @cindex hooks, for commands
21090 @cindex hooks, pre-command
21093 You may define @dfn{hooks}, which are a special kind of user-defined
21094 command. Whenever you run the command @samp{foo}, if the user-defined
21095 command @samp{hook-foo} exists, it is executed (with no arguments)
21096 before that command.
21098 @cindex hooks, post-command
21100 A hook may also be defined which is run after the command you executed.
21101 Whenever you run the command @samp{foo}, if the user-defined command
21102 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21103 that command. Post-execution hooks may exist simultaneously with
21104 pre-execution hooks, for the same command.
21106 It is valid for a hook to call the command which it hooks. If this
21107 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21109 @c It would be nice if hookpost could be passed a parameter indicating
21110 @c if the command it hooks executed properly or not. FIXME!
21112 @kindex stop@r{, a pseudo-command}
21113 In addition, a pseudo-command, @samp{stop} exists. Defining
21114 (@samp{hook-stop}) makes the associated commands execute every time
21115 execution stops in your program: before breakpoint commands are run,
21116 displays are printed, or the stack frame is printed.
21118 For example, to ignore @code{SIGALRM} signals while
21119 single-stepping, but treat them normally during normal execution,
21124 handle SIGALRM nopass
21128 handle SIGALRM pass
21131 define hook-continue
21132 handle SIGALRM pass
21136 As a further example, to hook at the beginning and end of the @code{echo}
21137 command, and to add extra text to the beginning and end of the message,
21145 define hookpost-echo
21149 (@value{GDBP}) echo Hello World
21150 <<<---Hello World--->>>
21155 You can define a hook for any single-word command in @value{GDBN}, but
21156 not for command aliases; you should define a hook for the basic command
21157 name, e.g.@: @code{backtrace} rather than @code{bt}.
21158 @c FIXME! So how does Joe User discover whether a command is an alias
21160 You can hook a multi-word command by adding @code{hook-} or
21161 @code{hookpost-} to the last word of the command, e.g.@:
21162 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21164 If an error occurs during the execution of your hook, execution of
21165 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21166 (before the command that you actually typed had a chance to run).
21168 If you try to define a hook which does not match any known command, you
21169 get a warning from the @code{define} command.
21171 @node Command Files
21172 @subsection Command Files
21174 @cindex command files
21175 @cindex scripting commands
21176 A command file for @value{GDBN} is a text file made of lines that are
21177 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21178 also be included. An empty line in a command file does nothing; it
21179 does not mean to repeat the last command, as it would from the
21182 You can request the execution of a command file with the @code{source}
21183 command. Note that the @code{source} command is also used to evaluate
21184 scripts that are not Command Files. The exact behavior can be configured
21185 using the @code{script-extension} setting.
21186 @xref{Extending GDB,, Extending GDB}.
21190 @cindex execute commands from a file
21191 @item source [-s] [-v] @var{filename}
21192 Execute the command file @var{filename}.
21195 The lines in a command file are generally executed sequentially,
21196 unless the order of execution is changed by one of the
21197 @emph{flow-control commands} described below. The commands are not
21198 printed as they are executed. An error in any command terminates
21199 execution of the command file and control is returned to the console.
21201 @value{GDBN} first searches for @var{filename} in the current directory.
21202 If the file is not found there, and @var{filename} does not specify a
21203 directory, then @value{GDBN} also looks for the file on the source search path
21204 (specified with the @samp{directory} command);
21205 except that @file{$cdir} is not searched because the compilation directory
21206 is not relevant to scripts.
21208 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21209 on the search path even if @var{filename} specifies a directory.
21210 The search is done by appending @var{filename} to each element of the
21211 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21212 and the search path contains @file{/home/user} then @value{GDBN} will
21213 look for the script @file{/home/user/mylib/myscript}.
21214 The search is also done if @var{filename} is an absolute path.
21215 For example, if @var{filename} is @file{/tmp/myscript} and
21216 the search path contains @file{/home/user} then @value{GDBN} will
21217 look for the script @file{/home/user/tmp/myscript}.
21218 For DOS-like systems, if @var{filename} contains a drive specification,
21219 it is stripped before concatenation. For example, if @var{filename} is
21220 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21221 will look for the script @file{c:/tmp/myscript}.
21223 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21224 each command as it is executed. The option must be given before
21225 @var{filename}, and is interpreted as part of the filename anywhere else.
21227 Commands that would ask for confirmation if used interactively proceed
21228 without asking when used in a command file. Many @value{GDBN} commands that
21229 normally print messages to say what they are doing omit the messages
21230 when called from command files.
21232 @value{GDBN} also accepts command input from standard input. In this
21233 mode, normal output goes to standard output and error output goes to
21234 standard error. Errors in a command file supplied on standard input do
21235 not terminate execution of the command file---execution continues with
21239 gdb < cmds > log 2>&1
21242 (The syntax above will vary depending on the shell used.) This example
21243 will execute commands from the file @file{cmds}. All output and errors
21244 would be directed to @file{log}.
21246 Since commands stored on command files tend to be more general than
21247 commands typed interactively, they frequently need to deal with
21248 complicated situations, such as different or unexpected values of
21249 variables and symbols, changes in how the program being debugged is
21250 built, etc. @value{GDBN} provides a set of flow-control commands to
21251 deal with these complexities. Using these commands, you can write
21252 complex scripts that loop over data structures, execute commands
21253 conditionally, etc.
21260 This command allows to include in your script conditionally executed
21261 commands. The @code{if} command takes a single argument, which is an
21262 expression to evaluate. It is followed by a series of commands that
21263 are executed only if the expression is true (its value is nonzero).
21264 There can then optionally be an @code{else} line, followed by a series
21265 of commands that are only executed if the expression was false. The
21266 end of the list is marked by a line containing @code{end}.
21270 This command allows to write loops. Its syntax is similar to
21271 @code{if}: the command takes a single argument, which is an expression
21272 to evaluate, and must be followed by the commands to execute, one per
21273 line, terminated by an @code{end}. These commands are called the
21274 @dfn{body} of the loop. The commands in the body of @code{while} are
21275 executed repeatedly as long as the expression evaluates to true.
21279 This command exits the @code{while} loop in whose body it is included.
21280 Execution of the script continues after that @code{while}s @code{end}
21283 @kindex loop_continue
21284 @item loop_continue
21285 This command skips the execution of the rest of the body of commands
21286 in the @code{while} loop in whose body it is included. Execution
21287 branches to the beginning of the @code{while} loop, where it evaluates
21288 the controlling expression.
21290 @kindex end@r{ (if/else/while commands)}
21292 Terminate the block of commands that are the body of @code{if},
21293 @code{else}, or @code{while} flow-control commands.
21298 @subsection Commands for Controlled Output
21300 During the execution of a command file or a user-defined command, normal
21301 @value{GDBN} output is suppressed; the only output that appears is what is
21302 explicitly printed by the commands in the definition. This section
21303 describes three commands useful for generating exactly the output you
21308 @item echo @var{text}
21309 @c I do not consider backslash-space a standard C escape sequence
21310 @c because it is not in ANSI.
21311 Print @var{text}. Nonprinting characters can be included in
21312 @var{text} using C escape sequences, such as @samp{\n} to print a
21313 newline. @strong{No newline is printed unless you specify one.}
21314 In addition to the standard C escape sequences, a backslash followed
21315 by a space stands for a space. This is useful for displaying a
21316 string with spaces at the beginning or the end, since leading and
21317 trailing spaces are otherwise trimmed from all arguments.
21318 To print @samp{@w{ }and foo =@w{ }}, use the command
21319 @samp{echo \@w{ }and foo = \@w{ }}.
21321 A backslash at the end of @var{text} can be used, as in C, to continue
21322 the command onto subsequent lines. For example,
21325 echo This is some text\n\
21326 which is continued\n\
21327 onto several lines.\n
21330 produces the same output as
21333 echo This is some text\n
21334 echo which is continued\n
21335 echo onto several lines.\n
21339 @item output @var{expression}
21340 Print the value of @var{expression} and nothing but that value: no
21341 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21342 value history either. @xref{Expressions, ,Expressions}, for more information
21345 @item output/@var{fmt} @var{expression}
21346 Print the value of @var{expression} in format @var{fmt}. You can use
21347 the same formats as for @code{print}. @xref{Output Formats,,Output
21348 Formats}, for more information.
21351 @item printf @var{template}, @var{expressions}@dots{}
21352 Print the values of one or more @var{expressions} under the control of
21353 the string @var{template}. To print several values, make
21354 @var{expressions} be a comma-separated list of individual expressions,
21355 which may be either numbers or pointers. Their values are printed as
21356 specified by @var{template}, exactly as a C program would do by
21357 executing the code below:
21360 printf (@var{template}, @var{expressions}@dots{});
21363 As in @code{C} @code{printf}, ordinary characters in @var{template}
21364 are printed verbatim, while @dfn{conversion specification} introduced
21365 by the @samp{%} character cause subsequent @var{expressions} to be
21366 evaluated, their values converted and formatted according to type and
21367 style information encoded in the conversion specifications, and then
21370 For example, you can print two values in hex like this:
21373 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21376 @code{printf} supports all the standard @code{C} conversion
21377 specifications, including the flags and modifiers between the @samp{%}
21378 character and the conversion letter, with the following exceptions:
21382 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21385 The modifier @samp{*} is not supported for specifying precision or
21389 The @samp{'} flag (for separation of digits into groups according to
21390 @code{LC_NUMERIC'}) is not supported.
21393 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21397 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21400 The conversion letters @samp{a} and @samp{A} are not supported.
21404 Note that the @samp{ll} type modifier is supported only if the
21405 underlying @code{C} implementation used to build @value{GDBN} supports
21406 the @code{long long int} type, and the @samp{L} type modifier is
21407 supported only if @code{long double} type is available.
21409 As in @code{C}, @code{printf} supports simple backslash-escape
21410 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21411 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21412 single character. Octal and hexadecimal escape sequences are not
21415 Additionally, @code{printf} supports conversion specifications for DFP
21416 (@dfn{Decimal Floating Point}) types using the following length modifiers
21417 together with a floating point specifier.
21422 @samp{H} for printing @code{Decimal32} types.
21425 @samp{D} for printing @code{Decimal64} types.
21428 @samp{DD} for printing @code{Decimal128} types.
21431 If the underlying @code{C} implementation used to build @value{GDBN} has
21432 support for the three length modifiers for DFP types, other modifiers
21433 such as width and precision will also be available for @value{GDBN} to use.
21435 In case there is no such @code{C} support, no additional modifiers will be
21436 available and the value will be printed in the standard way.
21438 Here's an example of printing DFP types using the above conversion letters:
21440 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21444 @item eval @var{template}, @var{expressions}@dots{}
21445 Convert the values of one or more @var{expressions} under the control of
21446 the string @var{template} to a command line, and call it.
21451 @section Scripting @value{GDBN} using Python
21452 @cindex python scripting
21453 @cindex scripting with python
21455 You can script @value{GDBN} using the @uref{http://www.python.org/,
21456 Python programming language}. This feature is available only if
21457 @value{GDBN} was configured using @option{--with-python}.
21459 @cindex python directory
21460 Python scripts used by @value{GDBN} should be installed in
21461 @file{@var{data-directory}/python}, where @var{data-directory} is
21462 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21463 This directory, known as the @dfn{python directory},
21464 is automatically added to the Python Search Path in order to allow
21465 the Python interpreter to locate all scripts installed at this location.
21467 Additionally, @value{GDBN} commands and convenience functions which
21468 are written in Python and are located in the
21469 @file{@var{data-directory}/python/gdb/command} or
21470 @file{@var{data-directory}/python/gdb/function} directories are
21471 automatically imported when @value{GDBN} starts.
21474 * Python Commands:: Accessing Python from @value{GDBN}.
21475 * Python API:: Accessing @value{GDBN} from Python.
21476 * Auto-loading:: Automatically loading Python code.
21477 * Python modules:: Python modules provided by @value{GDBN}.
21480 @node Python Commands
21481 @subsection Python Commands
21482 @cindex python commands
21483 @cindex commands to access python
21485 @value{GDBN} provides one command for accessing the Python interpreter,
21486 and one related setting:
21490 @item python @r{[}@var{code}@r{]}
21491 The @code{python} command can be used to evaluate Python code.
21493 If given an argument, the @code{python} command will evaluate the
21494 argument as a Python command. For example:
21497 (@value{GDBP}) python print 23
21501 If you do not provide an argument to @code{python}, it will act as a
21502 multi-line command, like @code{define}. In this case, the Python
21503 script is made up of subsequent command lines, given after the
21504 @code{python} command. This command list is terminated using a line
21505 containing @code{end}. For example:
21508 (@value{GDBP}) python
21510 End with a line saying just "end".
21516 @kindex set python print-stack
21517 @item set python print-stack
21518 By default, @value{GDBN} will print only the message component of a
21519 Python exception when an error occurs in a Python script. This can be
21520 controlled using @code{set python print-stack}: if @code{full}, then
21521 full Python stack printing is enabled; if @code{none}, then Python stack
21522 and message printing is disabled; if @code{message}, the default, only
21523 the message component of the error is printed.
21526 It is also possible to execute a Python script from the @value{GDBN}
21530 @item source @file{script-name}
21531 The script name must end with @samp{.py} and @value{GDBN} must be configured
21532 to recognize the script language based on filename extension using
21533 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21535 @item python execfile ("script-name")
21536 This method is based on the @code{execfile} Python built-in function,
21537 and thus is always available.
21541 @subsection Python API
21543 @cindex programming in python
21545 @cindex python stdout
21546 @cindex python pagination
21547 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21548 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21549 A Python program which outputs to one of these streams may have its
21550 output interrupted by the user (@pxref{Screen Size}). In this
21551 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21554 * Basic Python:: Basic Python Functions.
21555 * Exception Handling:: How Python exceptions are translated.
21556 * Values From Inferior:: Python representation of values.
21557 * Types In Python:: Python representation of types.
21558 * Pretty Printing API:: Pretty-printing values.
21559 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21560 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21561 * Inferiors In Python:: Python representation of inferiors (processes)
21562 * Events In Python:: Listening for events from @value{GDBN}.
21563 * Threads In Python:: Accessing inferior threads from Python.
21564 * Commands In Python:: Implementing new commands in Python.
21565 * Parameters In Python:: Adding new @value{GDBN} parameters.
21566 * Functions In Python:: Writing new convenience functions.
21567 * Progspaces In Python:: Program spaces.
21568 * Objfiles In Python:: Object files.
21569 * Frames In Python:: Accessing inferior stack frames from Python.
21570 * Blocks In Python:: Accessing frame blocks from Python.
21571 * Symbols In Python:: Python representation of symbols.
21572 * Symbol Tables In Python:: Python representation of symbol tables.
21573 * Lazy Strings In Python:: Python representation of lazy strings.
21574 * Breakpoints In Python:: Manipulating breakpoints using Python.
21575 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21580 @subsubsection Basic Python
21582 @cindex python functions
21583 @cindex python module
21585 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21586 methods and classes added by @value{GDBN} are placed in this module.
21587 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21588 use in all scripts evaluated by the @code{python} command.
21590 @findex gdb.PYTHONDIR
21591 @defvar gdb.PYTHONDIR
21592 A string containing the python directory (@pxref{Python}).
21595 @findex gdb.execute
21596 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21597 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21598 If a GDB exception happens while @var{command} runs, it is
21599 translated as described in @ref{Exception Handling,,Exception Handling}.
21601 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21602 command as having originated from the user invoking it interactively.
21603 It must be a boolean value. If omitted, it defaults to @code{False}.
21605 By default, any output produced by @var{command} is sent to
21606 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21607 @code{True}, then output will be collected by @code{gdb.execute} and
21608 returned as a string. The default is @code{False}, in which case the
21609 return value is @code{None}. If @var{to_string} is @code{True}, the
21610 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21611 and height, and its pagination will be disabled; @pxref{Screen Size}.
21614 @findex gdb.breakpoints
21615 @defun gdb.breakpoints ()
21616 Return a sequence holding all of @value{GDBN}'s breakpoints.
21617 @xref{Breakpoints In Python}, for more information.
21620 @findex gdb.parameter
21621 @defun gdb.parameter (parameter)
21622 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21623 string naming the parameter to look up; @var{parameter} may contain
21624 spaces if the parameter has a multi-part name. For example,
21625 @samp{print object} is a valid parameter name.
21627 If the named parameter does not exist, this function throws a
21628 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21629 parameter's value is converted to a Python value of the appropriate
21630 type, and returned.
21633 @findex gdb.history
21634 @defun gdb.history (number)
21635 Return a value from @value{GDBN}'s value history (@pxref{Value
21636 History}). @var{number} indicates which history element to return.
21637 If @var{number} is negative, then @value{GDBN} will take its absolute value
21638 and count backward from the last element (i.e., the most recent element) to
21639 find the value to return. If @var{number} is zero, then @value{GDBN} will
21640 return the most recent element. If the element specified by @var{number}
21641 doesn't exist in the value history, a @code{gdb.error} exception will be
21644 If no exception is raised, the return value is always an instance of
21645 @code{gdb.Value} (@pxref{Values From Inferior}).
21648 @findex gdb.parse_and_eval
21649 @defun gdb.parse_and_eval (expression)
21650 Parse @var{expression} as an expression in the current language,
21651 evaluate it, and return the result as a @code{gdb.Value}.
21652 @var{expression} must be a string.
21654 This function can be useful when implementing a new command
21655 (@pxref{Commands In Python}), as it provides a way to parse the
21656 command's argument as an expression. It is also useful simply to
21657 compute values, for example, it is the only way to get the value of a
21658 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21661 @findex gdb.post_event
21662 @defun gdb.post_event (event)
21663 Put @var{event}, a callable object taking no arguments, into
21664 @value{GDBN}'s internal event queue. This callable will be invoked at
21665 some later point, during @value{GDBN}'s event processing. Events
21666 posted using @code{post_event} will be run in the order in which they
21667 were posted; however, there is no way to know when they will be
21668 processed relative to other events inside @value{GDBN}.
21670 @value{GDBN} is not thread-safe. If your Python program uses multiple
21671 threads, you must be careful to only call @value{GDBN}-specific
21672 functions in the main @value{GDBN} thread. @code{post_event} ensures
21676 (@value{GDBP}) python
21680 > def __init__(self, message):
21681 > self.message = message;
21682 > def __call__(self):
21683 > gdb.write(self.message)
21685 >class MyThread1 (threading.Thread):
21687 > gdb.post_event(Writer("Hello "))
21689 >class MyThread2 (threading.Thread):
21691 > gdb.post_event(Writer("World\n"))
21693 >MyThread1().start()
21694 >MyThread2().start()
21696 (@value{GDBP}) Hello World
21701 @defun gdb.write (string @r{[}, stream{]})
21702 Print a string to @value{GDBN}'s paginated output stream. The
21703 optional @var{stream} determines the stream to print to. The default
21704 stream is @value{GDBN}'s standard output stream. Possible stream
21711 @value{GDBN}'s standard output stream.
21716 @value{GDBN}'s standard error stream.
21721 @value{GDBN}'s log stream (@pxref{Logging Output}).
21724 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21725 call this function and will automatically direct the output to the
21730 @defun gdb.flush ()
21731 Flush the buffer of a @value{GDBN} paginated stream so that the
21732 contents are displayed immediately. @value{GDBN} will flush the
21733 contents of a stream automatically when it encounters a newline in the
21734 buffer. The optional @var{stream} determines the stream to flush. The
21735 default stream is @value{GDBN}'s standard output stream. Possible
21742 @value{GDBN}'s standard output stream.
21747 @value{GDBN}'s standard error stream.
21752 @value{GDBN}'s log stream (@pxref{Logging Output}).
21756 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21757 call this function for the relevant stream.
21760 @findex gdb.target_charset
21761 @defun gdb.target_charset ()
21762 Return the name of the current target character set (@pxref{Character
21763 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21764 that @samp{auto} is never returned.
21767 @findex gdb.target_wide_charset
21768 @defun gdb.target_wide_charset ()
21769 Return the name of the current target wide character set
21770 (@pxref{Character Sets}). This differs from
21771 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21775 @findex gdb.solib_name
21776 @defun gdb.solib_name (address)
21777 Return the name of the shared library holding the given @var{address}
21778 as a string, or @code{None}.
21781 @findex gdb.decode_line
21782 @defun gdb.decode_line @r{[}expression@r{]}
21783 Return locations of the line specified by @var{expression}, or of the
21784 current line if no argument was given. This function returns a Python
21785 tuple containing two elements. The first element contains a string
21786 holding any unparsed section of @var{expression} (or @code{None} if
21787 the expression has been fully parsed). The second element contains
21788 either @code{None} or another tuple that contains all the locations
21789 that match the expression represented as @code{gdb.Symtab_and_line}
21790 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21791 provided, it is decoded the way that @value{GDBN}'s inbuilt
21792 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21795 @defun gdb.prompt_hook (current_prompt)
21796 @anchor{prompt_hook}
21798 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21799 assigned to this operation before a prompt is displayed by
21802 The parameter @code{current_prompt} contains the current @value{GDBN}
21803 prompt. This method must return a Python string, or @code{None}. If
21804 a string is returned, the @value{GDBN} prompt will be set to that
21805 string. If @code{None} is returned, @value{GDBN} will continue to use
21806 the current prompt.
21808 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21809 such as those used by readline for command input, and annotation
21810 related prompts are prohibited from being changed.
21813 @node Exception Handling
21814 @subsubsection Exception Handling
21815 @cindex python exceptions
21816 @cindex exceptions, python
21818 When executing the @code{python} command, Python exceptions
21819 uncaught within the Python code are translated to calls to
21820 @value{GDBN} error-reporting mechanism. If the command that called
21821 @code{python} does not handle the error, @value{GDBN} will
21822 terminate it and print an error message containing the Python
21823 exception name, the associated value, and the Python call stack
21824 backtrace at the point where the exception was raised. Example:
21827 (@value{GDBP}) python print foo
21828 Traceback (most recent call last):
21829 File "<string>", line 1, in <module>
21830 NameError: name 'foo' is not defined
21833 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21834 Python code are converted to Python exceptions. The type of the
21835 Python exception depends on the error.
21839 This is the base class for most exceptions generated by @value{GDBN}.
21840 It is derived from @code{RuntimeError}, for compatibility with earlier
21841 versions of @value{GDBN}.
21843 If an error occurring in @value{GDBN} does not fit into some more
21844 specific category, then the generated exception will have this type.
21846 @item gdb.MemoryError
21847 This is a subclass of @code{gdb.error} which is thrown when an
21848 operation tried to access invalid memory in the inferior.
21850 @item KeyboardInterrupt
21851 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21852 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21855 In all cases, your exception handler will see the @value{GDBN} error
21856 message as its value and the Python call stack backtrace at the Python
21857 statement closest to where the @value{GDBN} error occured as the
21860 @findex gdb.GdbError
21861 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21862 it is useful to be able to throw an exception that doesn't cause a
21863 traceback to be printed. For example, the user may have invoked the
21864 command incorrectly. Use the @code{gdb.GdbError} exception
21865 to handle this case. Example:
21869 >class HelloWorld (gdb.Command):
21870 > """Greet the whole world."""
21871 > def __init__ (self):
21872 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21873 > def invoke (self, args, from_tty):
21874 > argv = gdb.string_to_argv (args)
21875 > if len (argv) != 0:
21876 > raise gdb.GdbError ("hello-world takes no arguments")
21877 > print "Hello, World!"
21880 (gdb) hello-world 42
21881 hello-world takes no arguments
21884 @node Values From Inferior
21885 @subsubsection Values From Inferior
21886 @cindex values from inferior, with Python
21887 @cindex python, working with values from inferior
21889 @cindex @code{gdb.Value}
21890 @value{GDBN} provides values it obtains from the inferior program in
21891 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21892 for its internal bookkeeping of the inferior's values, and for
21893 fetching values when necessary.
21895 Inferior values that are simple scalars can be used directly in
21896 Python expressions that are valid for the value's data type. Here's
21897 an example for an integer or floating-point value @code{some_val}:
21904 As result of this, @code{bar} will also be a @code{gdb.Value} object
21905 whose values are of the same type as those of @code{some_val}.
21907 Inferior values that are structures or instances of some class can
21908 be accessed using the Python @dfn{dictionary syntax}. For example, if
21909 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21910 can access its @code{foo} element with:
21913 bar = some_val['foo']
21916 Again, @code{bar} will also be a @code{gdb.Value} object.
21918 A @code{gdb.Value} that represents a function can be executed via
21919 inferior function call. Any arguments provided to the call must match
21920 the function's prototype, and must be provided in the order specified
21923 For example, @code{some_val} is a @code{gdb.Value} instance
21924 representing a function that takes two integers as arguments. To
21925 execute this function, call it like so:
21928 result = some_val (10,20)
21931 Any values returned from a function call will be stored as a
21934 The following attributes are provided:
21937 @defvar Value.address
21938 If this object is addressable, this read-only attribute holds a
21939 @code{gdb.Value} object representing the address. Otherwise,
21940 this attribute holds @code{None}.
21943 @cindex optimized out value in Python
21944 @defvar Value.is_optimized_out
21945 This read-only boolean attribute is true if the compiler optimized out
21946 this value, thus it is not available for fetching from the inferior.
21950 The type of this @code{gdb.Value}. The value of this attribute is a
21951 @code{gdb.Type} object (@pxref{Types In Python}).
21954 @defvar Value.dynamic_type
21955 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21956 type information (@acronym{RTTI}) to determine the dynamic type of the
21957 value. If this value is of class type, it will return the class in
21958 which the value is embedded, if any. If this value is of pointer or
21959 reference to a class type, it will compute the dynamic type of the
21960 referenced object, and return a pointer or reference to that type,
21961 respectively. In all other cases, it will return the value's static
21964 Note that this feature will only work when debugging a C@t{++} program
21965 that includes @acronym{RTTI} for the object in question. Otherwise,
21966 it will just return the static type of the value as in @kbd{ptype foo}
21967 (@pxref{Symbols, ptype}).
21970 @defvar Value.is_lazy
21971 The value of this read-only boolean attribute is @code{True} if this
21972 @code{gdb.Value} has not yet been fetched from the inferior.
21973 @value{GDBN} does not fetch values until necessary, for efficiency.
21977 myval = gdb.parse_and_eval ('somevar')
21980 The value of @code{somevar} is not fetched at this time. It will be
21981 fetched when the value is needed, or when the @code{fetch_lazy}
21986 The following methods are provided:
21989 @defun Value.__init__ (@var{val})
21990 Many Python values can be converted directly to a @code{gdb.Value} via
21991 this object initializer. Specifically:
21994 @item Python boolean
21995 A Python boolean is converted to the boolean type from the current
21998 @item Python integer
21999 A Python integer is converted to the C @code{long} type for the
22000 current architecture.
22003 A Python long is converted to the C @code{long long} type for the
22004 current architecture.
22007 A Python float is converted to the C @code{double} type for the
22008 current architecture.
22010 @item Python string
22011 A Python string is converted to a target string, using the current
22014 @item @code{gdb.Value}
22015 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22017 @item @code{gdb.LazyString}
22018 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22019 Python}), then the lazy string's @code{value} method is called, and
22020 its result is used.
22024 @defun Value.cast (type)
22025 Return a new instance of @code{gdb.Value} that is the result of
22026 casting this instance to the type described by @var{type}, which must
22027 be a @code{gdb.Type} object. If the cast cannot be performed for some
22028 reason, this method throws an exception.
22031 @defun Value.dereference ()
22032 For pointer data types, this method returns a new @code{gdb.Value} object
22033 whose contents is the object pointed to by the pointer. For example, if
22034 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22041 then you can use the corresponding @code{gdb.Value} to access what
22042 @code{foo} points to like this:
22045 bar = foo.dereference ()
22048 The result @code{bar} will be a @code{gdb.Value} object holding the
22049 value pointed to by @code{foo}.
22052 @defun Value.dynamic_cast (type)
22053 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22054 operator were used. Consult a C@t{++} reference for details.
22057 @defun Value.reinterpret_cast (type)
22058 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22059 operator were used. Consult a C@t{++} reference for details.
22062 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22063 If this @code{gdb.Value} represents a string, then this method
22064 converts the contents to a Python string. Otherwise, this method will
22065 throw an exception.
22067 Strings are recognized in a language-specific way; whether a given
22068 @code{gdb.Value} represents a string is determined by the current
22071 For C-like languages, a value is a string if it is a pointer to or an
22072 array of characters or ints. The string is assumed to be terminated
22073 by a zero of the appropriate width. However if the optional length
22074 argument is given, the string will be converted to that given length,
22075 ignoring any embedded zeros that the string may contain.
22077 If the optional @var{encoding} argument is given, it must be a string
22078 naming the encoding of the string in the @code{gdb.Value}, such as
22079 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22080 the same encodings as the corresponding argument to Python's
22081 @code{string.decode} method, and the Python codec machinery will be used
22082 to convert the string. If @var{encoding} is not given, or if
22083 @var{encoding} is the empty string, then either the @code{target-charset}
22084 (@pxref{Character Sets}) will be used, or a language-specific encoding
22085 will be used, if the current language is able to supply one.
22087 The optional @var{errors} argument is the same as the corresponding
22088 argument to Python's @code{string.decode} method.
22090 If the optional @var{length} argument is given, the string will be
22091 fetched and converted to the given length.
22094 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22095 If this @code{gdb.Value} represents a string, then this method
22096 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22097 In Python}). Otherwise, this method will throw an exception.
22099 If the optional @var{encoding} argument is given, it must be a string
22100 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22101 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22102 @var{encoding} argument is an encoding that @value{GDBN} does
22103 recognize, @value{GDBN} will raise an error.
22105 When a lazy string is printed, the @value{GDBN} encoding machinery is
22106 used to convert the string during printing. If the optional
22107 @var{encoding} argument is not provided, or is an empty string,
22108 @value{GDBN} will automatically select the encoding most suitable for
22109 the string type. For further information on encoding in @value{GDBN}
22110 please see @ref{Character Sets}.
22112 If the optional @var{length} argument is given, the string will be
22113 fetched and encoded to the length of characters specified. If
22114 the @var{length} argument is not provided, the string will be fetched
22115 and encoded until a null of appropriate width is found.
22118 @defun Value.fetch_lazy ()
22119 If the @code{gdb.Value} object is currently a lazy value
22120 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22121 fetched from the inferior. Any errors that occur in the process
22122 will produce a Python exception.
22124 If the @code{gdb.Value} object is not a lazy value, this method
22127 This method does not return a value.
22132 @node Types In Python
22133 @subsubsection Types In Python
22134 @cindex types in Python
22135 @cindex Python, working with types
22138 @value{GDBN} represents types from the inferior using the class
22141 The following type-related functions are available in the @code{gdb}
22144 @findex gdb.lookup_type
22145 @defun gdb.lookup_type (name @r{[}, block@r{]})
22146 This function looks up a type by name. @var{name} is the name of the
22147 type to look up. It must be a string.
22149 If @var{block} is given, then @var{name} is looked up in that scope.
22150 Otherwise, it is searched for globally.
22152 Ordinarily, this function will return an instance of @code{gdb.Type}.
22153 If the named type cannot be found, it will throw an exception.
22156 If the type is a structure or class type, or an enum type, the fields
22157 of that type can be accessed using the Python @dfn{dictionary syntax}.
22158 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22159 a structure type, you can access its @code{foo} field with:
22162 bar = some_type['foo']
22165 @code{bar} will be a @code{gdb.Field} object; see below under the
22166 description of the @code{Type.fields} method for a description of the
22167 @code{gdb.Field} class.
22169 An instance of @code{Type} has the following attributes:
22173 The type code for this type. The type code will be one of the
22174 @code{TYPE_CODE_} constants defined below.
22177 @defvar Type.sizeof
22178 The size of this type, in target @code{char} units. Usually, a
22179 target's @code{char} type will be an 8-bit byte. However, on some
22180 unusual platforms, this type may have a different size.
22184 The tag name for this type. The tag name is the name after
22185 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22186 languages have this concept. If this type has no tag name, then
22187 @code{None} is returned.
22191 The following methods are provided:
22194 @defun Type.fields ()
22195 For structure and union types, this method returns the fields. Range
22196 types have two fields, the minimum and maximum values. Enum types
22197 have one field per enum constant. Function and method types have one
22198 field per parameter. The base types of C@t{++} classes are also
22199 represented as fields. If the type has no fields, or does not fit
22200 into one of these categories, an empty sequence will be returned.
22202 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22205 This attribute is not available for @code{static} fields (as in
22206 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22207 position of the field. For @code{enum} fields, the value is the
22208 enumeration member's integer representation.
22211 The name of the field, or @code{None} for anonymous fields.
22214 This is @code{True} if the field is artificial, usually meaning that
22215 it was provided by the compiler and not the user. This attribute is
22216 always provided, and is @code{False} if the field is not artificial.
22218 @item is_base_class
22219 This is @code{True} if the field represents a base class of a C@t{++}
22220 structure. This attribute is always provided, and is @code{False}
22221 if the field is not a base class of the type that is the argument of
22222 @code{fields}, or if that type was not a C@t{++} class.
22225 If the field is packed, or is a bitfield, then this will have a
22226 non-zero value, which is the size of the field in bits. Otherwise,
22227 this will be zero; in this case the field's size is given by its type.
22230 The type of the field. This is usually an instance of @code{Type},
22231 but it can be @code{None} in some situations.
22235 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22236 Return a new @code{gdb.Type} object which represents an array of this
22237 type. If one argument is given, it is the inclusive upper bound of
22238 the array; in this case the lower bound is zero. If two arguments are
22239 given, the first argument is the lower bound of the array, and the
22240 second argument is the upper bound of the array. An array's length
22241 must not be negative, but the bounds can be.
22244 @defun Type.const ()
22245 Return a new @code{gdb.Type} object which represents a
22246 @code{const}-qualified variant of this type.
22249 @defun Type.volatile ()
22250 Return a new @code{gdb.Type} object which represents a
22251 @code{volatile}-qualified variant of this type.
22254 @defun Type.unqualified ()
22255 Return a new @code{gdb.Type} object which represents an unqualified
22256 variant of this type. That is, the result is neither @code{const} nor
22260 @defun Type.range ()
22261 Return a Python @code{Tuple} object that contains two elements: the
22262 low bound of the argument type and the high bound of that type. If
22263 the type does not have a range, @value{GDBN} will raise a
22264 @code{gdb.error} exception (@pxref{Exception Handling}).
22267 @defun Type.reference ()
22268 Return a new @code{gdb.Type} object which represents a reference to this
22272 @defun Type.pointer ()
22273 Return a new @code{gdb.Type} object which represents a pointer to this
22277 @defun Type.strip_typedefs ()
22278 Return a new @code{gdb.Type} that represents the real type,
22279 after removing all layers of typedefs.
22282 @defun Type.target ()
22283 Return a new @code{gdb.Type} object which represents the target type
22286 For a pointer type, the target type is the type of the pointed-to
22287 object. For an array type (meaning C-like arrays), the target type is
22288 the type of the elements of the array. For a function or method type,
22289 the target type is the type of the return value. For a complex type,
22290 the target type is the type of the elements. For a typedef, the
22291 target type is the aliased type.
22293 If the type does not have a target, this method will throw an
22297 @defun Type.template_argument (n @r{[}, block@r{]})
22298 If this @code{gdb.Type} is an instantiation of a template, this will
22299 return a new @code{gdb.Type} which represents the type of the
22300 @var{n}th template argument.
22302 If this @code{gdb.Type} is not a template type, this will throw an
22303 exception. Ordinarily, only C@t{++} code will have template types.
22305 If @var{block} is given, then @var{name} is looked up in that scope.
22306 Otherwise, it is searched for globally.
22311 Each type has a code, which indicates what category this type falls
22312 into. The available type categories are represented by constants
22313 defined in the @code{gdb} module:
22316 @findex TYPE_CODE_PTR
22317 @findex gdb.TYPE_CODE_PTR
22318 @item gdb.TYPE_CODE_PTR
22319 The type is a pointer.
22321 @findex TYPE_CODE_ARRAY
22322 @findex gdb.TYPE_CODE_ARRAY
22323 @item gdb.TYPE_CODE_ARRAY
22324 The type is an array.
22326 @findex TYPE_CODE_STRUCT
22327 @findex gdb.TYPE_CODE_STRUCT
22328 @item gdb.TYPE_CODE_STRUCT
22329 The type is a structure.
22331 @findex TYPE_CODE_UNION
22332 @findex gdb.TYPE_CODE_UNION
22333 @item gdb.TYPE_CODE_UNION
22334 The type is a union.
22336 @findex TYPE_CODE_ENUM
22337 @findex gdb.TYPE_CODE_ENUM
22338 @item gdb.TYPE_CODE_ENUM
22339 The type is an enum.
22341 @findex TYPE_CODE_FLAGS
22342 @findex gdb.TYPE_CODE_FLAGS
22343 @item gdb.TYPE_CODE_FLAGS
22344 A bit flags type, used for things such as status registers.
22346 @findex TYPE_CODE_FUNC
22347 @findex gdb.TYPE_CODE_FUNC
22348 @item gdb.TYPE_CODE_FUNC
22349 The type is a function.
22351 @findex TYPE_CODE_INT
22352 @findex gdb.TYPE_CODE_INT
22353 @item gdb.TYPE_CODE_INT
22354 The type is an integer type.
22356 @findex TYPE_CODE_FLT
22357 @findex gdb.TYPE_CODE_FLT
22358 @item gdb.TYPE_CODE_FLT
22359 A floating point type.
22361 @findex TYPE_CODE_VOID
22362 @findex gdb.TYPE_CODE_VOID
22363 @item gdb.TYPE_CODE_VOID
22364 The special type @code{void}.
22366 @findex TYPE_CODE_SET
22367 @findex gdb.TYPE_CODE_SET
22368 @item gdb.TYPE_CODE_SET
22371 @findex TYPE_CODE_RANGE
22372 @findex gdb.TYPE_CODE_RANGE
22373 @item gdb.TYPE_CODE_RANGE
22374 A range type, that is, an integer type with bounds.
22376 @findex TYPE_CODE_STRING
22377 @findex gdb.TYPE_CODE_STRING
22378 @item gdb.TYPE_CODE_STRING
22379 A string type. Note that this is only used for certain languages with
22380 language-defined string types; C strings are not represented this way.
22382 @findex TYPE_CODE_BITSTRING
22383 @findex gdb.TYPE_CODE_BITSTRING
22384 @item gdb.TYPE_CODE_BITSTRING
22387 @findex TYPE_CODE_ERROR
22388 @findex gdb.TYPE_CODE_ERROR
22389 @item gdb.TYPE_CODE_ERROR
22390 An unknown or erroneous type.
22392 @findex TYPE_CODE_METHOD
22393 @findex gdb.TYPE_CODE_METHOD
22394 @item gdb.TYPE_CODE_METHOD
22395 A method type, as found in C@t{++} or Java.
22397 @findex TYPE_CODE_METHODPTR
22398 @findex gdb.TYPE_CODE_METHODPTR
22399 @item gdb.TYPE_CODE_METHODPTR
22400 A pointer-to-member-function.
22402 @findex TYPE_CODE_MEMBERPTR
22403 @findex gdb.TYPE_CODE_MEMBERPTR
22404 @item gdb.TYPE_CODE_MEMBERPTR
22405 A pointer-to-member.
22407 @findex TYPE_CODE_REF
22408 @findex gdb.TYPE_CODE_REF
22409 @item gdb.TYPE_CODE_REF
22412 @findex TYPE_CODE_CHAR
22413 @findex gdb.TYPE_CODE_CHAR
22414 @item gdb.TYPE_CODE_CHAR
22417 @findex TYPE_CODE_BOOL
22418 @findex gdb.TYPE_CODE_BOOL
22419 @item gdb.TYPE_CODE_BOOL
22422 @findex TYPE_CODE_COMPLEX
22423 @findex gdb.TYPE_CODE_COMPLEX
22424 @item gdb.TYPE_CODE_COMPLEX
22425 A complex float type.
22427 @findex TYPE_CODE_TYPEDEF
22428 @findex gdb.TYPE_CODE_TYPEDEF
22429 @item gdb.TYPE_CODE_TYPEDEF
22430 A typedef to some other type.
22432 @findex TYPE_CODE_NAMESPACE
22433 @findex gdb.TYPE_CODE_NAMESPACE
22434 @item gdb.TYPE_CODE_NAMESPACE
22435 A C@t{++} namespace.
22437 @findex TYPE_CODE_DECFLOAT
22438 @findex gdb.TYPE_CODE_DECFLOAT
22439 @item gdb.TYPE_CODE_DECFLOAT
22440 A decimal floating point type.
22442 @findex TYPE_CODE_INTERNAL_FUNCTION
22443 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22444 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22445 A function internal to @value{GDBN}. This is the type used to represent
22446 convenience functions.
22449 Further support for types is provided in the @code{gdb.types}
22450 Python module (@pxref{gdb.types}).
22452 @node Pretty Printing API
22453 @subsubsection Pretty Printing API
22455 An example output is provided (@pxref{Pretty Printing}).
22457 A pretty-printer is just an object that holds a value and implements a
22458 specific interface, defined here.
22460 @defun pretty_printer.children (self)
22461 @value{GDBN} will call this method on a pretty-printer to compute the
22462 children of the pretty-printer's value.
22464 This method must return an object conforming to the Python iterator
22465 protocol. Each item returned by the iterator must be a tuple holding
22466 two elements. The first element is the ``name'' of the child; the
22467 second element is the child's value. The value can be any Python
22468 object which is convertible to a @value{GDBN} value.
22470 This method is optional. If it does not exist, @value{GDBN} will act
22471 as though the value has no children.
22474 @defun pretty_printer.display_hint (self)
22475 The CLI may call this method and use its result to change the
22476 formatting of a value. The result will also be supplied to an MI
22477 consumer as a @samp{displayhint} attribute of the variable being
22480 This method is optional. If it does exist, this method must return a
22483 Some display hints are predefined by @value{GDBN}:
22487 Indicate that the object being printed is ``array-like''. The CLI
22488 uses this to respect parameters such as @code{set print elements} and
22489 @code{set print array}.
22492 Indicate that the object being printed is ``map-like'', and that the
22493 children of this value can be assumed to alternate between keys and
22497 Indicate that the object being printed is ``string-like''. If the
22498 printer's @code{to_string} method returns a Python string of some
22499 kind, then @value{GDBN} will call its internal language-specific
22500 string-printing function to format the string. For the CLI this means
22501 adding quotation marks, possibly escaping some characters, respecting
22502 @code{set print elements}, and the like.
22506 @defun pretty_printer.to_string (self)
22507 @value{GDBN} will call this method to display the string
22508 representation of the value passed to the object's constructor.
22510 When printing from the CLI, if the @code{to_string} method exists,
22511 then @value{GDBN} will prepend its result to the values returned by
22512 @code{children}. Exactly how this formatting is done is dependent on
22513 the display hint, and may change as more hints are added. Also,
22514 depending on the print settings (@pxref{Print Settings}), the CLI may
22515 print just the result of @code{to_string} in a stack trace, omitting
22516 the result of @code{children}.
22518 If this method returns a string, it is printed verbatim.
22520 Otherwise, if this method returns an instance of @code{gdb.Value},
22521 then @value{GDBN} prints this value. This may result in a call to
22522 another pretty-printer.
22524 If instead the method returns a Python value which is convertible to a
22525 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22526 the resulting value. Again, this may result in a call to another
22527 pretty-printer. Python scalars (integers, floats, and booleans) and
22528 strings are convertible to @code{gdb.Value}; other types are not.
22530 Finally, if this method returns @code{None} then no further operations
22531 are peformed in this method and nothing is printed.
22533 If the result is not one of these types, an exception is raised.
22536 @value{GDBN} provides a function which can be used to look up the
22537 default pretty-printer for a @code{gdb.Value}:
22539 @findex gdb.default_visualizer
22540 @defun gdb.default_visualizer (value)
22541 This function takes a @code{gdb.Value} object as an argument. If a
22542 pretty-printer for this value exists, then it is returned. If no such
22543 printer exists, then this returns @code{None}.
22546 @node Selecting Pretty-Printers
22547 @subsubsection Selecting Pretty-Printers
22549 The Python list @code{gdb.pretty_printers} contains an array of
22550 functions or callable objects that have been registered via addition
22551 as a pretty-printer. Printers in this list are called @code{global}
22552 printers, they're available when debugging all inferiors.
22553 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22554 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22557 Each function on these lists is passed a single @code{gdb.Value}
22558 argument and should return a pretty-printer object conforming to the
22559 interface definition above (@pxref{Pretty Printing API}). If a function
22560 cannot create a pretty-printer for the value, it should return
22563 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22564 @code{gdb.Objfile} in the current program space and iteratively calls
22565 each enabled lookup routine in the list for that @code{gdb.Objfile}
22566 until it receives a pretty-printer object.
22567 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22568 searches the pretty-printer list of the current program space,
22569 calling each enabled function until an object is returned.
22570 After these lists have been exhausted, it tries the global
22571 @code{gdb.pretty_printers} list, again calling each enabled function until an
22572 object is returned.
22574 The order in which the objfiles are searched is not specified. For a
22575 given list, functions are always invoked from the head of the list,
22576 and iterated over sequentially until the end of the list, or a printer
22577 object is returned.
22579 For various reasons a pretty-printer may not work.
22580 For example, the underlying data structure may have changed and
22581 the pretty-printer is out of date.
22583 The consequences of a broken pretty-printer are severe enough that
22584 @value{GDBN} provides support for enabling and disabling individual
22585 printers. For example, if @code{print frame-arguments} is on,
22586 a backtrace can become highly illegible if any argument is printed
22587 with a broken printer.
22589 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22590 attribute to the registered function or callable object. If this attribute
22591 is present and its value is @code{False}, the printer is disabled, otherwise
22592 the printer is enabled.
22594 @node Writing a Pretty-Printer
22595 @subsubsection Writing a Pretty-Printer
22596 @cindex writing a pretty-printer
22598 A pretty-printer consists of two parts: a lookup function to detect
22599 if the type is supported, and the printer itself.
22601 Here is an example showing how a @code{std::string} printer might be
22602 written. @xref{Pretty Printing API}, for details on the API this class
22606 class StdStringPrinter(object):
22607 "Print a std::string"
22609 def __init__(self, val):
22612 def to_string(self):
22613 return self.val['_M_dataplus']['_M_p']
22615 def display_hint(self):
22619 And here is an example showing how a lookup function for the printer
22620 example above might be written.
22623 def str_lookup_function(val):
22624 lookup_tag = val.type.tag
22625 if lookup_tag == None:
22627 regex = re.compile("^std::basic_string<char,.*>$")
22628 if regex.match(lookup_tag):
22629 return StdStringPrinter(val)
22633 The example lookup function extracts the value's type, and attempts to
22634 match it to a type that it can pretty-print. If it is a type the
22635 printer can pretty-print, it will return a printer object. If not, it
22636 returns @code{None}.
22638 We recommend that you put your core pretty-printers into a Python
22639 package. If your pretty-printers are for use with a library, we
22640 further recommend embedding a version number into the package name.
22641 This practice will enable @value{GDBN} to load multiple versions of
22642 your pretty-printers at the same time, because they will have
22645 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22646 can be evaluated multiple times without changing its meaning. An
22647 ideal auto-load file will consist solely of @code{import}s of your
22648 printer modules, followed by a call to a register pretty-printers with
22649 the current objfile.
22651 Taken as a whole, this approach will scale nicely to multiple
22652 inferiors, each potentially using a different library version.
22653 Embedding a version number in the Python package name will ensure that
22654 @value{GDBN} is able to load both sets of printers simultaneously.
22655 Then, because the search for pretty-printers is done by objfile, and
22656 because your auto-loaded code took care to register your library's
22657 printers with a specific objfile, @value{GDBN} will find the correct
22658 printers for the specific version of the library used by each
22661 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22662 this code might appear in @code{gdb.libstdcxx.v6}:
22665 def register_printers(objfile):
22666 objfile.pretty_printers.append(str_lookup_function)
22670 And then the corresponding contents of the auto-load file would be:
22673 import gdb.libstdcxx.v6
22674 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22677 The previous example illustrates a basic pretty-printer.
22678 There are a few things that can be improved on.
22679 The printer doesn't have a name, making it hard to identify in a
22680 list of installed printers. The lookup function has a name, but
22681 lookup functions can have arbitrary, even identical, names.
22683 Second, the printer only handles one type, whereas a library typically has
22684 several types. One could install a lookup function for each desired type
22685 in the library, but one could also have a single lookup function recognize
22686 several types. The latter is the conventional way this is handled.
22687 If a pretty-printer can handle multiple data types, then its
22688 @dfn{subprinters} are the printers for the individual data types.
22690 The @code{gdb.printing} module provides a formal way of solving these
22691 problems (@pxref{gdb.printing}).
22692 Here is another example that handles multiple types.
22694 These are the types we are going to pretty-print:
22697 struct foo @{ int a, b; @};
22698 struct bar @{ struct foo x, y; @};
22701 Here are the printers:
22705 """Print a foo object."""
22707 def __init__(self, val):
22710 def to_string(self):
22711 return ("a=<" + str(self.val["a"]) +
22712 "> b=<" + str(self.val["b"]) + ">")
22715 """Print a bar object."""
22717 def __init__(self, val):
22720 def to_string(self):
22721 return ("x=<" + str(self.val["x"]) +
22722 "> y=<" + str(self.val["y"]) + ">")
22725 This example doesn't need a lookup function, that is handled by the
22726 @code{gdb.printing} module. Instead a function is provided to build up
22727 the object that handles the lookup.
22730 import gdb.printing
22732 def build_pretty_printer():
22733 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22735 pp.add_printer('foo', '^foo$', fooPrinter)
22736 pp.add_printer('bar', '^bar$', barPrinter)
22740 And here is the autoload support:
22743 import gdb.printing
22745 gdb.printing.register_pretty_printer(
22746 gdb.current_objfile(),
22747 my_library.build_pretty_printer())
22750 Finally, when this printer is loaded into @value{GDBN}, here is the
22751 corresponding output of @samp{info pretty-printer}:
22754 (gdb) info pretty-printer
22761 @node Inferiors In Python
22762 @subsubsection Inferiors In Python
22763 @cindex inferiors in Python
22765 @findex gdb.Inferior
22766 Programs which are being run under @value{GDBN} are called inferiors
22767 (@pxref{Inferiors and Programs}). Python scripts can access
22768 information about and manipulate inferiors controlled by @value{GDBN}
22769 via objects of the @code{gdb.Inferior} class.
22771 The following inferior-related functions are available in the @code{gdb}
22774 @defun gdb.inferiors ()
22775 Return a tuple containing all inferior objects.
22778 @defun gdb.selected_inferior ()
22779 Return an object representing the current inferior.
22782 A @code{gdb.Inferior} object has the following attributes:
22785 @defvar Inferior.num
22786 ID of inferior, as assigned by GDB.
22789 @defvar Inferior.pid
22790 Process ID of the inferior, as assigned by the underlying operating
22794 @defvar Inferior.was_attached
22795 Boolean signaling whether the inferior was created using `attach', or
22796 started by @value{GDBN} itself.
22800 A @code{gdb.Inferior} object has the following methods:
22803 @defun Inferior.is_valid ()
22804 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22805 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22806 if the inferior no longer exists within @value{GDBN}. All other
22807 @code{gdb.Inferior} methods will throw an exception if it is invalid
22808 at the time the method is called.
22811 @defun Inferior.threads ()
22812 This method returns a tuple holding all the threads which are valid
22813 when it is called. If there are no valid threads, the method will
22814 return an empty tuple.
22817 @findex gdb.read_memory
22818 @defun Inferior.read_memory (address, length)
22819 Read @var{length} bytes of memory from the inferior, starting at
22820 @var{address}. Returns a buffer object, which behaves much like an array
22821 or a string. It can be modified and given to the @code{gdb.write_memory}
22825 @findex gdb.write_memory
22826 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22827 Write the contents of @var{buffer} to the inferior, starting at
22828 @var{address}. The @var{buffer} parameter must be a Python object
22829 which supports the buffer protocol, i.e., a string, an array or the
22830 object returned from @code{gdb.read_memory}. If given, @var{length}
22831 determines the number of bytes from @var{buffer} to be written.
22834 @findex gdb.search_memory
22835 @defun Inferior.search_memory (address, length, pattern)
22836 Search a region of the inferior memory starting at @var{address} with
22837 the given @var{length} using the search pattern supplied in
22838 @var{pattern}. The @var{pattern} parameter must be a Python object
22839 which supports the buffer protocol, i.e., a string, an array or the
22840 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22841 containing the address where the pattern was found, or @code{None} if
22842 the pattern could not be found.
22846 @node Events In Python
22847 @subsubsection Events In Python
22848 @cindex inferior events in Python
22850 @value{GDBN} provides a general event facility so that Python code can be
22851 notified of various state changes, particularly changes that occur in
22854 An @dfn{event} is just an object that describes some state change. The
22855 type of the object and its attributes will vary depending on the details
22856 of the change. All the existing events are described below.
22858 In order to be notified of an event, you must register an event handler
22859 with an @dfn{event registry}. An event registry is an object in the
22860 @code{gdb.events} module which dispatches particular events. A registry
22861 provides methods to register and unregister event handlers:
22864 @defun EventRegistry.connect (object)
22865 Add the given callable @var{object} to the registry. This object will be
22866 called when an event corresponding to this registry occurs.
22869 @defun EventRegistry.disconnect (object)
22870 Remove the given @var{object} from the registry. Once removed, the object
22871 will no longer receive notifications of events.
22875 Here is an example:
22878 def exit_handler (event):
22879 print "event type: exit"
22880 print "exit code: %d" % (event.exit_code)
22882 gdb.events.exited.connect (exit_handler)
22885 In the above example we connect our handler @code{exit_handler} to the
22886 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22887 called when the inferior exits. The argument @dfn{event} in this example is
22888 of type @code{gdb.ExitedEvent}. As you can see in the example the
22889 @code{ExitedEvent} object has an attribute which indicates the exit code of
22892 The following is a listing of the event registries that are available and
22893 details of the events they emit:
22898 Emits @code{gdb.ThreadEvent}.
22900 Some events can be thread specific when @value{GDBN} is running in non-stop
22901 mode. When represented in Python, these events all extend
22902 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22903 events which are emitted by this or other modules might extend this event.
22904 Examples of these events are @code{gdb.BreakpointEvent} and
22905 @code{gdb.ContinueEvent}.
22908 @defvar ThreadEvent.inferior_thread
22909 In non-stop mode this attribute will be set to the specific thread which was
22910 involved in the emitted event. Otherwise, it will be set to @code{None}.
22914 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22916 This event indicates that the inferior has been continued after a stop. For
22917 inherited attribute refer to @code{gdb.ThreadEvent} above.
22919 @item events.exited
22920 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22921 @code{events.ExitedEvent} has two attributes:
22923 @defvar ExitedEvent.exit_code
22924 An integer representing the exit code, if available, which the inferior
22925 has returned. (The exit code could be unavailable if, for example,
22926 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22927 the attribute does not exist.
22929 @defvar ExitedEvent inferior
22930 A reference to the inferior which triggered the @code{exited} event.
22935 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22937 Indicates that the inferior has stopped. All events emitted by this registry
22938 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22939 will indicate the stopped thread when @value{GDBN} is running in non-stop
22940 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22942 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22944 This event indicates that the inferior or one of its threads has received as
22945 signal. @code{gdb.SignalEvent} has the following attributes:
22948 @defvar SignalEvent.stop_signal
22949 A string representing the signal received by the inferior. A list of possible
22950 signal values can be obtained by running the command @code{info signals} in
22951 the @value{GDBN} command prompt.
22955 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22957 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22958 been hit, and has the following attributes:
22961 @defvar BreakpointEvent.breakpoints
22962 A sequence containing references to all the breakpoints (type
22963 @code{gdb.Breakpoint}) that were hit.
22964 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22966 @defvar BreakpointEvent.breakpoint
22967 A reference to the first breakpoint that was hit.
22968 This function is maintained for backward compatibility and is now deprecated
22969 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22973 @item events.new_objfile
22974 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22975 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22978 @defvar NewObjFileEvent.new_objfile
22979 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22980 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22986 @node Threads In Python
22987 @subsubsection Threads In Python
22988 @cindex threads in python
22990 @findex gdb.InferiorThread
22991 Python scripts can access information about, and manipulate inferior threads
22992 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22994 The following thread-related functions are available in the @code{gdb}
22997 @findex gdb.selected_thread
22998 @defun gdb.selected_thread ()
22999 This function returns the thread object for the selected thread. If there
23000 is no selected thread, this will return @code{None}.
23003 A @code{gdb.InferiorThread} object has the following attributes:
23006 @defvar InferiorThread.name
23007 The name of the thread. If the user specified a name using
23008 @code{thread name}, then this returns that name. Otherwise, if an
23009 OS-supplied name is available, then it is returned. Otherwise, this
23010 returns @code{None}.
23012 This attribute can be assigned to. The new value must be a string
23013 object, which sets the new name, or @code{None}, which removes any
23014 user-specified thread name.
23017 @defvar InferiorThread.num
23018 ID of the thread, as assigned by GDB.
23021 @defvar InferiorThread.ptid
23022 ID of the thread, as assigned by the operating system. This attribute is a
23023 tuple containing three integers. The first is the Process ID (PID); the second
23024 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23025 Either the LWPID or TID may be 0, which indicates that the operating system
23026 does not use that identifier.
23030 A @code{gdb.InferiorThread} object has the following methods:
23033 @defun InferiorThread.is_valid ()
23034 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23035 @code{False} if not. A @code{gdb.InferiorThread} object will become
23036 invalid if the thread exits, or the inferior that the thread belongs
23037 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23038 exception if it is invalid at the time the method is called.
23041 @defun InferiorThread.switch ()
23042 This changes @value{GDBN}'s currently selected thread to the one represented
23046 @defun InferiorThread.is_stopped ()
23047 Return a Boolean indicating whether the thread is stopped.
23050 @defun InferiorThread.is_running ()
23051 Return a Boolean indicating whether the thread is running.
23054 @defun InferiorThread.is_exited ()
23055 Return a Boolean indicating whether the thread is exited.
23059 @node Commands In Python
23060 @subsubsection Commands In Python
23062 @cindex commands in python
23063 @cindex python commands
23064 You can implement new @value{GDBN} CLI commands in Python. A CLI
23065 command is implemented using an instance of the @code{gdb.Command}
23066 class, most commonly using a subclass.
23068 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23069 The object initializer for @code{Command} registers the new command
23070 with @value{GDBN}. This initializer is normally invoked from the
23071 subclass' own @code{__init__} method.
23073 @var{name} is the name of the command. If @var{name} consists of
23074 multiple words, then the initial words are looked for as prefix
23075 commands. In this case, if one of the prefix commands does not exist,
23076 an exception is raised.
23078 There is no support for multi-line commands.
23080 @var{command_class} should be one of the @samp{COMMAND_} constants
23081 defined below. This argument tells @value{GDBN} how to categorize the
23082 new command in the help system.
23084 @var{completer_class} is an optional argument. If given, it should be
23085 one of the @samp{COMPLETE_} constants defined below. This argument
23086 tells @value{GDBN} how to perform completion for this command. If not
23087 given, @value{GDBN} will attempt to complete using the object's
23088 @code{complete} method (see below); if no such method is found, an
23089 error will occur when completion is attempted.
23091 @var{prefix} is an optional argument. If @code{True}, then the new
23092 command is a prefix command; sub-commands of this command may be
23095 The help text for the new command is taken from the Python
23096 documentation string for the command's class, if there is one. If no
23097 documentation string is provided, the default value ``This command is
23098 not documented.'' is used.
23101 @cindex don't repeat Python command
23102 @defun Command.dont_repeat ()
23103 By default, a @value{GDBN} command is repeated when the user enters a
23104 blank line at the command prompt. A command can suppress this
23105 behavior by invoking the @code{dont_repeat} method. This is similar
23106 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23109 @defun Command.invoke (argument, from_tty)
23110 This method is called by @value{GDBN} when this command is invoked.
23112 @var{argument} is a string. It is the argument to the command, after
23113 leading and trailing whitespace has been stripped.
23115 @var{from_tty} is a boolean argument. When true, this means that the
23116 command was entered by the user at the terminal; when false it means
23117 that the command came from elsewhere.
23119 If this method throws an exception, it is turned into a @value{GDBN}
23120 @code{error} call. Otherwise, the return value is ignored.
23122 @findex gdb.string_to_argv
23123 To break @var{argument} up into an argv-like string use
23124 @code{gdb.string_to_argv}. This function behaves identically to
23125 @value{GDBN}'s internal argument lexer @code{buildargv}.
23126 It is recommended to use this for consistency.
23127 Arguments are separated by spaces and may be quoted.
23131 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23132 ['1', '2 "3', '4 "5', "6 '7"]
23137 @cindex completion of Python commands
23138 @defun Command.complete (text, word)
23139 This method is called by @value{GDBN} when the user attempts
23140 completion on this command. All forms of completion are handled by
23141 this method, that is, the @key{TAB} and @key{M-?} key bindings
23142 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23145 The arguments @var{text} and @var{word} are both strings. @var{text}
23146 holds the complete command line up to the cursor's location.
23147 @var{word} holds the last word of the command line; this is computed
23148 using a word-breaking heuristic.
23150 The @code{complete} method can return several values:
23153 If the return value is a sequence, the contents of the sequence are
23154 used as the completions. It is up to @code{complete} to ensure that the
23155 contents actually do complete the word. A zero-length sequence is
23156 allowed, it means that there were no completions available. Only
23157 string elements of the sequence are used; other elements in the
23158 sequence are ignored.
23161 If the return value is one of the @samp{COMPLETE_} constants defined
23162 below, then the corresponding @value{GDBN}-internal completion
23163 function is invoked, and its result is used.
23166 All other results are treated as though there were no available
23171 When a new command is registered, it must be declared as a member of
23172 some general class of commands. This is used to classify top-level
23173 commands in the on-line help system; note that prefix commands are not
23174 listed under their own category but rather that of their top-level
23175 command. The available classifications are represented by constants
23176 defined in the @code{gdb} module:
23179 @findex COMMAND_NONE
23180 @findex gdb.COMMAND_NONE
23181 @item gdb.COMMAND_NONE
23182 The command does not belong to any particular class. A command in
23183 this category will not be displayed in any of the help categories.
23185 @findex COMMAND_RUNNING
23186 @findex gdb.COMMAND_RUNNING
23187 @item gdb.COMMAND_RUNNING
23188 The command is related to running the inferior. For example,
23189 @code{start}, @code{step}, and @code{continue} are in this category.
23190 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23191 commands in this category.
23193 @findex COMMAND_DATA
23194 @findex gdb.COMMAND_DATA
23195 @item gdb.COMMAND_DATA
23196 The command is related to data or variables. For example,
23197 @code{call}, @code{find}, and @code{print} are in this category. Type
23198 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23201 @findex COMMAND_STACK
23202 @findex gdb.COMMAND_STACK
23203 @item gdb.COMMAND_STACK
23204 The command has to do with manipulation of the stack. For example,
23205 @code{backtrace}, @code{frame}, and @code{return} are in this
23206 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23207 list of commands in this category.
23209 @findex COMMAND_FILES
23210 @findex gdb.COMMAND_FILES
23211 @item gdb.COMMAND_FILES
23212 This class is used for file-related commands. For example,
23213 @code{file}, @code{list} and @code{section} are in this category.
23214 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23215 commands in this category.
23217 @findex COMMAND_SUPPORT
23218 @findex gdb.COMMAND_SUPPORT
23219 @item gdb.COMMAND_SUPPORT
23220 This should be used for ``support facilities'', generally meaning
23221 things that are useful to the user when interacting with @value{GDBN},
23222 but not related to the state of the inferior. For example,
23223 @code{help}, @code{make}, and @code{shell} are in this category. Type
23224 @kbd{help support} at the @value{GDBN} prompt to see a list of
23225 commands in this category.
23227 @findex COMMAND_STATUS
23228 @findex gdb.COMMAND_STATUS
23229 @item gdb.COMMAND_STATUS
23230 The command is an @samp{info}-related command, that is, related to the
23231 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23232 and @code{show} are in this category. Type @kbd{help status} at the
23233 @value{GDBN} prompt to see a list of commands in this category.
23235 @findex COMMAND_BREAKPOINTS
23236 @findex gdb.COMMAND_BREAKPOINTS
23237 @item gdb.COMMAND_BREAKPOINTS
23238 The command has to do with breakpoints. For example, @code{break},
23239 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23240 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23243 @findex COMMAND_TRACEPOINTS
23244 @findex gdb.COMMAND_TRACEPOINTS
23245 @item gdb.COMMAND_TRACEPOINTS
23246 The command has to do with tracepoints. For example, @code{trace},
23247 @code{actions}, and @code{tfind} are in this category. Type
23248 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23249 commands in this category.
23251 @findex COMMAND_OBSCURE
23252 @findex gdb.COMMAND_OBSCURE
23253 @item gdb.COMMAND_OBSCURE
23254 The command is only used in unusual circumstances, or is not of
23255 general interest to users. For example, @code{checkpoint},
23256 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23257 obscure} at the @value{GDBN} prompt to see a list of commands in this
23260 @findex COMMAND_MAINTENANCE
23261 @findex gdb.COMMAND_MAINTENANCE
23262 @item gdb.COMMAND_MAINTENANCE
23263 The command is only useful to @value{GDBN} maintainers. The
23264 @code{maintenance} and @code{flushregs} commands are in this category.
23265 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23266 commands in this category.
23269 A new command can use a predefined completion function, either by
23270 specifying it via an argument at initialization, or by returning it
23271 from the @code{complete} method. These predefined completion
23272 constants are all defined in the @code{gdb} module:
23275 @findex COMPLETE_NONE
23276 @findex gdb.COMPLETE_NONE
23277 @item gdb.COMPLETE_NONE
23278 This constant means that no completion should be done.
23280 @findex COMPLETE_FILENAME
23281 @findex gdb.COMPLETE_FILENAME
23282 @item gdb.COMPLETE_FILENAME
23283 This constant means that filename completion should be performed.
23285 @findex COMPLETE_LOCATION
23286 @findex gdb.COMPLETE_LOCATION
23287 @item gdb.COMPLETE_LOCATION
23288 This constant means that location completion should be done.
23289 @xref{Specify Location}.
23291 @findex COMPLETE_COMMAND
23292 @findex gdb.COMPLETE_COMMAND
23293 @item gdb.COMPLETE_COMMAND
23294 This constant means that completion should examine @value{GDBN}
23297 @findex COMPLETE_SYMBOL
23298 @findex gdb.COMPLETE_SYMBOL
23299 @item gdb.COMPLETE_SYMBOL
23300 This constant means that completion should be done using symbol names
23304 The following code snippet shows how a trivial CLI command can be
23305 implemented in Python:
23308 class HelloWorld (gdb.Command):
23309 """Greet the whole world."""
23311 def __init__ (self):
23312 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23314 def invoke (self, arg, from_tty):
23315 print "Hello, World!"
23320 The last line instantiates the class, and is necessary to trigger the
23321 registration of the command with @value{GDBN}. Depending on how the
23322 Python code is read into @value{GDBN}, you may need to import the
23323 @code{gdb} module explicitly.
23325 @node Parameters In Python
23326 @subsubsection Parameters In Python
23328 @cindex parameters in python
23329 @cindex python parameters
23330 @tindex gdb.Parameter
23332 You can implement new @value{GDBN} parameters using Python. A new
23333 parameter is implemented as an instance of the @code{gdb.Parameter}
23336 Parameters are exposed to the user via the @code{set} and
23337 @code{show} commands. @xref{Help}.
23339 There are many parameters that already exist and can be set in
23340 @value{GDBN}. Two examples are: @code{set follow fork} and
23341 @code{set charset}. Setting these parameters influences certain
23342 behavior in @value{GDBN}. Similarly, you can define parameters that
23343 can be used to influence behavior in custom Python scripts and commands.
23345 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23346 The object initializer for @code{Parameter} registers the new
23347 parameter with @value{GDBN}. This initializer is normally invoked
23348 from the subclass' own @code{__init__} method.
23350 @var{name} is the name of the new parameter. If @var{name} consists
23351 of multiple words, then the initial words are looked for as prefix
23352 parameters. An example of this can be illustrated with the
23353 @code{set print} set of parameters. If @var{name} is
23354 @code{print foo}, then @code{print} will be searched as the prefix
23355 parameter. In this case the parameter can subsequently be accessed in
23356 @value{GDBN} as @code{set print foo}.
23358 If @var{name} consists of multiple words, and no prefix parameter group
23359 can be found, an exception is raised.
23361 @var{command-class} should be one of the @samp{COMMAND_} constants
23362 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23363 categorize the new parameter in the help system.
23365 @var{parameter-class} should be one of the @samp{PARAM_} constants
23366 defined below. This argument tells @value{GDBN} the type of the new
23367 parameter; this information is used for input validation and
23370 If @var{parameter-class} is @code{PARAM_ENUM}, then
23371 @var{enum-sequence} must be a sequence of strings. These strings
23372 represent the possible values for the parameter.
23374 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23375 of a fourth argument will cause an exception to be thrown.
23377 The help text for the new parameter is taken from the Python
23378 documentation string for the parameter's class, if there is one. If
23379 there is no documentation string, a default value is used.
23382 @defvar Parameter.set_doc
23383 If this attribute exists, and is a string, then its value is used as
23384 the help text for this parameter's @code{set} command. The value is
23385 examined when @code{Parameter.__init__} is invoked; subsequent changes
23389 @defvar Parameter.show_doc
23390 If this attribute exists, and is a string, then its value is used as
23391 the help text for this parameter's @code{show} command. The value is
23392 examined when @code{Parameter.__init__} is invoked; subsequent changes
23396 @defvar Parameter.value
23397 The @code{value} attribute holds the underlying value of the
23398 parameter. It can be read and assigned to just as any other
23399 attribute. @value{GDBN} does validation when assignments are made.
23402 There are two methods that should be implemented in any
23403 @code{Parameter} class. These are:
23405 @defun Parameter.get_set_string (self)
23406 @value{GDBN} will call this method when a @var{parameter}'s value has
23407 been changed via the @code{set} API (for example, @kbd{set foo off}).
23408 The @code{value} attribute has already been populated with the new
23409 value and may be used in output. This method must return a string.
23412 @defun Parameter.get_show_string (self, svalue)
23413 @value{GDBN} will call this method when a @var{parameter}'s
23414 @code{show} API has been invoked (for example, @kbd{show foo}). The
23415 argument @code{svalue} receives the string representation of the
23416 current value. This method must return a string.
23419 When a new parameter is defined, its type must be specified. The
23420 available types are represented by constants defined in the @code{gdb}
23424 @findex PARAM_BOOLEAN
23425 @findex gdb.PARAM_BOOLEAN
23426 @item gdb.PARAM_BOOLEAN
23427 The value is a plain boolean. The Python boolean values, @code{True}
23428 and @code{False} are the only valid values.
23430 @findex PARAM_AUTO_BOOLEAN
23431 @findex gdb.PARAM_AUTO_BOOLEAN
23432 @item gdb.PARAM_AUTO_BOOLEAN
23433 The value has three possible states: true, false, and @samp{auto}. In
23434 Python, true and false are represented using boolean constants, and
23435 @samp{auto} is represented using @code{None}.
23437 @findex PARAM_UINTEGER
23438 @findex gdb.PARAM_UINTEGER
23439 @item gdb.PARAM_UINTEGER
23440 The value is an unsigned integer. The value of 0 should be
23441 interpreted to mean ``unlimited''.
23443 @findex PARAM_INTEGER
23444 @findex gdb.PARAM_INTEGER
23445 @item gdb.PARAM_INTEGER
23446 The value is a signed integer. The value of 0 should be interpreted
23447 to mean ``unlimited''.
23449 @findex PARAM_STRING
23450 @findex gdb.PARAM_STRING
23451 @item gdb.PARAM_STRING
23452 The value is a string. When the user modifies the string, any escape
23453 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23454 translated into corresponding characters and encoded into the current
23457 @findex PARAM_STRING_NOESCAPE
23458 @findex gdb.PARAM_STRING_NOESCAPE
23459 @item gdb.PARAM_STRING_NOESCAPE
23460 The value is a string. When the user modifies the string, escapes are
23461 passed through untranslated.
23463 @findex PARAM_OPTIONAL_FILENAME
23464 @findex gdb.PARAM_OPTIONAL_FILENAME
23465 @item gdb.PARAM_OPTIONAL_FILENAME
23466 The value is a either a filename (a string), or @code{None}.
23468 @findex PARAM_FILENAME
23469 @findex gdb.PARAM_FILENAME
23470 @item gdb.PARAM_FILENAME
23471 The value is a filename. This is just like
23472 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23474 @findex PARAM_ZINTEGER
23475 @findex gdb.PARAM_ZINTEGER
23476 @item gdb.PARAM_ZINTEGER
23477 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23478 is interpreted as itself.
23481 @findex gdb.PARAM_ENUM
23482 @item gdb.PARAM_ENUM
23483 The value is a string, which must be one of a collection string
23484 constants provided when the parameter is created.
23487 @node Functions In Python
23488 @subsubsection Writing new convenience functions
23490 @cindex writing convenience functions
23491 @cindex convenience functions in python
23492 @cindex python convenience functions
23493 @tindex gdb.Function
23495 You can implement new convenience functions (@pxref{Convenience Vars})
23496 in Python. A convenience function is an instance of a subclass of the
23497 class @code{gdb.Function}.
23499 @defun Function.__init__ (name)
23500 The initializer for @code{Function} registers the new function with
23501 @value{GDBN}. The argument @var{name} is the name of the function,
23502 a string. The function will be visible to the user as a convenience
23503 variable of type @code{internal function}, whose name is the same as
23504 the given @var{name}.
23506 The documentation for the new function is taken from the documentation
23507 string for the new class.
23510 @defun Function.invoke (@var{*args})
23511 When a convenience function is evaluated, its arguments are converted
23512 to instances of @code{gdb.Value}, and then the function's
23513 @code{invoke} method is called. Note that @value{GDBN} does not
23514 predetermine the arity of convenience functions. Instead, all
23515 available arguments are passed to @code{invoke}, following the
23516 standard Python calling convention. In particular, a convenience
23517 function can have default values for parameters without ill effect.
23519 The return value of this method is used as its value in the enclosing
23520 expression. If an ordinary Python value is returned, it is converted
23521 to a @code{gdb.Value} following the usual rules.
23524 The following code snippet shows how a trivial convenience function can
23525 be implemented in Python:
23528 class Greet (gdb.Function):
23529 """Return string to greet someone.
23530 Takes a name as argument."""
23532 def __init__ (self):
23533 super (Greet, self).__init__ ("greet")
23535 def invoke (self, name):
23536 return "Hello, %s!" % name.string ()
23541 The last line instantiates the class, and is necessary to trigger the
23542 registration of the function with @value{GDBN}. Depending on how the
23543 Python code is read into @value{GDBN}, you may need to import the
23544 @code{gdb} module explicitly.
23546 @node Progspaces In Python
23547 @subsubsection Program Spaces In Python
23549 @cindex progspaces in python
23550 @tindex gdb.Progspace
23552 A program space, or @dfn{progspace}, represents a symbolic view
23553 of an address space.
23554 It consists of all of the objfiles of the program.
23555 @xref{Objfiles In Python}.
23556 @xref{Inferiors and Programs, program spaces}, for more details
23557 about program spaces.
23559 The following progspace-related functions are available in the
23562 @findex gdb.current_progspace
23563 @defun gdb.current_progspace ()
23564 This function returns the program space of the currently selected inferior.
23565 @xref{Inferiors and Programs}.
23568 @findex gdb.progspaces
23569 @defun gdb.progspaces ()
23570 Return a sequence of all the progspaces currently known to @value{GDBN}.
23573 Each progspace is represented by an instance of the @code{gdb.Progspace}
23576 @defvar Progspace.filename
23577 The file name of the progspace as a string.
23580 @defvar Progspace.pretty_printers
23581 The @code{pretty_printers} attribute is a list of functions. It is
23582 used to look up pretty-printers. A @code{Value} is passed to each
23583 function in order; if the function returns @code{None}, then the
23584 search continues. Otherwise, the return value should be an object
23585 which is used to format the value. @xref{Pretty Printing API}, for more
23589 @node Objfiles In Python
23590 @subsubsection Objfiles In Python
23592 @cindex objfiles in python
23593 @tindex gdb.Objfile
23595 @value{GDBN} loads symbols for an inferior from various
23596 symbol-containing files (@pxref{Files}). These include the primary
23597 executable file, any shared libraries used by the inferior, and any
23598 separate debug info files (@pxref{Separate Debug Files}).
23599 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23601 The following objfile-related functions are available in the
23604 @findex gdb.current_objfile
23605 @defun gdb.current_objfile ()
23606 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23607 sets the ``current objfile'' to the corresponding objfile. This
23608 function returns the current objfile. If there is no current objfile,
23609 this function returns @code{None}.
23612 @findex gdb.objfiles
23613 @defun gdb.objfiles ()
23614 Return a sequence of all the objfiles current known to @value{GDBN}.
23615 @xref{Objfiles In Python}.
23618 Each objfile is represented by an instance of the @code{gdb.Objfile}
23621 @defvar Objfile.filename
23622 The file name of the objfile as a string.
23625 @defvar Objfile.pretty_printers
23626 The @code{pretty_printers} attribute is a list of functions. It is
23627 used to look up pretty-printers. A @code{Value} is passed to each
23628 function in order; if the function returns @code{None}, then the
23629 search continues. Otherwise, the return value should be an object
23630 which is used to format the value. @xref{Pretty Printing API}, for more
23634 A @code{gdb.Objfile} object has the following methods:
23636 @defun Objfile.is_valid ()
23637 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23638 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23639 if the object file it refers to is not loaded in @value{GDBN} any
23640 longer. All other @code{gdb.Objfile} methods will throw an exception
23641 if it is invalid at the time the method is called.
23644 @node Frames In Python
23645 @subsubsection Accessing inferior stack frames from Python.
23647 @cindex frames in python
23648 When the debugged program stops, @value{GDBN} is able to analyze its call
23649 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23650 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23651 while its corresponding frame exists in the inferior's stack. If you try
23652 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23653 exception (@pxref{Exception Handling}).
23655 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23659 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23663 The following frame-related functions are available in the @code{gdb} module:
23665 @findex gdb.selected_frame
23666 @defun gdb.selected_frame ()
23667 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23670 @findex gdb.newest_frame
23671 @defun gdb.newest_frame ()
23672 Return the newest frame object for the selected thread.
23675 @defun gdb.frame_stop_reason_string (reason)
23676 Return a string explaining the reason why @value{GDBN} stopped unwinding
23677 frames, as expressed by the given @var{reason} code (an integer, see the
23678 @code{unwind_stop_reason} method further down in this section).
23681 A @code{gdb.Frame} object has the following methods:
23684 @defun Frame.is_valid ()
23685 Returns true if the @code{gdb.Frame} object is valid, false if not.
23686 A frame object can become invalid if the frame it refers to doesn't
23687 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23688 an exception if it is invalid at the time the method is called.
23691 @defun Frame.name ()
23692 Returns the function name of the frame, or @code{None} if it can't be
23696 @defun Frame.type ()
23697 Returns the type of the frame. The value can be one of:
23699 @item gdb.NORMAL_FRAME
23700 An ordinary stack frame.
23702 @item gdb.DUMMY_FRAME
23703 A fake stack frame that was created by @value{GDBN} when performing an
23704 inferior function call.
23706 @item gdb.INLINE_FRAME
23707 A frame representing an inlined function. The function was inlined
23708 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23710 @item gdb.TAILCALL_FRAME
23711 A frame representing a tail call. @xref{Tail Call Frames}.
23713 @item gdb.SIGTRAMP_FRAME
23714 A signal trampoline frame. This is the frame created by the OS when
23715 it calls into a signal handler.
23717 @item gdb.ARCH_FRAME
23718 A fake stack frame representing a cross-architecture call.
23720 @item gdb.SENTINEL_FRAME
23721 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23726 @defun Frame.unwind_stop_reason ()
23727 Return an integer representing the reason why it's not possible to find
23728 more frames toward the outermost frame. Use
23729 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23730 function to a string. The value can be one of:
23733 @item gdb.FRAME_UNWIND_NO_REASON
23734 No particular reason (older frames should be available).
23736 @item gdb.FRAME_UNWIND_NULL_ID
23737 The previous frame's analyzer returns an invalid result.
23739 @item gdb.FRAME_UNWIND_OUTERMOST
23740 This frame is the outermost.
23742 @item gdb.FRAME_UNWIND_UNAVAILABLE
23743 Cannot unwind further, because that would require knowing the
23744 values of registers or memory that have not been collected.
23746 @item gdb.FRAME_UNWIND_INNER_ID
23747 This frame ID looks like it ought to belong to a NEXT frame,
23748 but we got it for a PREV frame. Normally, this is a sign of
23749 unwinder failure. It could also indicate stack corruption.
23751 @item gdb.FRAME_UNWIND_SAME_ID
23752 This frame has the same ID as the previous one. That means
23753 that unwinding further would almost certainly give us another
23754 frame with exactly the same ID, so break the chain. Normally,
23755 this is a sign of unwinder failure. It could also indicate
23758 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23759 The frame unwinder did not find any saved PC, but we needed
23760 one to unwind further.
23762 @item gdb.FRAME_UNWIND_FIRST_ERROR
23763 Any stop reason greater or equal to this value indicates some kind
23764 of error. This special value facilitates writing code that tests
23765 for errors in unwinding in a way that will work correctly even if
23766 the list of the other values is modified in future @value{GDBN}
23767 versions. Using it, you could write:
23769 reason = gdb.selected_frame().unwind_stop_reason ()
23770 reason_str = gdb.frame_stop_reason_string (reason)
23771 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23772 print "An error occured: %s" % reason_str
23779 Returns the frame's resume address.
23782 @defun Frame.block ()
23783 Return the frame's code block. @xref{Blocks In Python}.
23786 @defun Frame.function ()
23787 Return the symbol for the function corresponding to this frame.
23788 @xref{Symbols In Python}.
23791 @defun Frame.older ()
23792 Return the frame that called this frame.
23795 @defun Frame.newer ()
23796 Return the frame called by this frame.
23799 @defun Frame.find_sal ()
23800 Return the frame's symtab and line object.
23801 @xref{Symbol Tables In Python}.
23804 @defun Frame.read_var (variable @r{[}, block@r{]})
23805 Return the value of @var{variable} in this frame. If the optional
23806 argument @var{block} is provided, search for the variable from that
23807 block; otherwise start at the frame's current block (which is
23808 determined by the frame's current program counter). @var{variable}
23809 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23810 @code{gdb.Block} object.
23813 @defun Frame.select ()
23814 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23819 @node Blocks In Python
23820 @subsubsection Accessing frame blocks from Python.
23822 @cindex blocks in python
23825 Within each frame, @value{GDBN} maintains information on each block
23826 stored in that frame. These blocks are organized hierarchically, and
23827 are represented individually in Python as a @code{gdb.Block}.
23828 Please see @ref{Frames In Python}, for a more in-depth discussion on
23829 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23830 detailed technical information on @value{GDBN}'s book-keeping of the
23833 The following block-related functions are available in the @code{gdb}
23836 @findex gdb.block_for_pc
23837 @defun gdb.block_for_pc (pc)
23838 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23839 block cannot be found for the @var{pc} value specified, the function
23840 will return @code{None}.
23843 A @code{gdb.Block} object has the following methods:
23846 @defun Block.is_valid ()
23847 Returns @code{True} if the @code{gdb.Block} object is valid,
23848 @code{False} if not. A block object can become invalid if the block it
23849 refers to doesn't exist anymore in the inferior. All other
23850 @code{gdb.Block} methods will throw an exception if it is invalid at
23851 the time the method is called. This method is also made available to
23852 the Python iterator object that @code{gdb.Block} provides in an iteration
23853 context and via the Python @code{iter} built-in function.
23857 A @code{gdb.Block} object has the following attributes:
23860 @defvar Block.start
23861 The start address of the block. This attribute is not writable.
23865 The end address of the block. This attribute is not writable.
23868 @defvar Block.function
23869 The name of the block represented as a @code{gdb.Symbol}. If the
23870 block is not named, then this attribute holds @code{None}. This
23871 attribute is not writable.
23874 @defvar Block.superblock
23875 The block containing this block. If this parent block does not exist,
23876 this attribute holds @code{None}. This attribute is not writable.
23879 @defvar Block.global_block
23880 The global block associated with this block. This attribute is not
23884 @defvar Block.static_block
23885 The static block associated with this block. This attribute is not
23889 @defvar Block.is_global
23890 @code{True} if the @code{gdb.Block} object is a global block,
23891 @code{False} if not. This attribute is not
23895 @defvar Block.is_static
23896 @code{True} if the @code{gdb.Block} object is a static block,
23897 @code{False} if not. This attribute is not writable.
23901 @node Symbols In Python
23902 @subsubsection Python representation of Symbols.
23904 @cindex symbols in python
23907 @value{GDBN} represents every variable, function and type as an
23908 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23909 Similarly, Python represents these symbols in @value{GDBN} with the
23910 @code{gdb.Symbol} object.
23912 The following symbol-related functions are available in the @code{gdb}
23915 @findex gdb.lookup_symbol
23916 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23917 This function searches for a symbol by name. The search scope can be
23918 restricted to the parameters defined in the optional domain and block
23921 @var{name} is the name of the symbol. It must be a string. The
23922 optional @var{block} argument restricts the search to symbols visible
23923 in that @var{block}. The @var{block} argument must be a
23924 @code{gdb.Block} object. If omitted, the block for the current frame
23925 is used. The optional @var{domain} argument restricts
23926 the search to the domain type. The @var{domain} argument must be a
23927 domain constant defined in the @code{gdb} module and described later
23930 The result is a tuple of two elements.
23931 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23933 If the symbol is found, the second element is @code{True} if the symbol
23934 is a field of a method's object (e.g., @code{this} in C@t{++}),
23935 otherwise it is @code{False}.
23936 If the symbol is not found, the second element is @code{False}.
23939 @findex gdb.lookup_global_symbol
23940 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23941 This function searches for a global symbol by name.
23942 The search scope can be restricted to by the domain argument.
23944 @var{name} is the name of the symbol. It must be a string.
23945 The optional @var{domain} argument restricts the search to the domain type.
23946 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23947 module and described later in this chapter.
23949 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23953 A @code{gdb.Symbol} object has the following attributes:
23956 @defvar Symbol.type
23957 The type of the symbol or @code{None} if no type is recorded.
23958 This attribute is represented as a @code{gdb.Type} object.
23959 @xref{Types In Python}. This attribute is not writable.
23962 @defvar Symbol.symtab
23963 The symbol table in which the symbol appears. This attribute is
23964 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23965 Python}. This attribute is not writable.
23968 @defvar Symbol.name
23969 The name of the symbol as a string. This attribute is not writable.
23972 @defvar Symbol.linkage_name
23973 The name of the symbol, as used by the linker (i.e., may be mangled).
23974 This attribute is not writable.
23977 @defvar Symbol.print_name
23978 The name of the symbol in a form suitable for output. This is either
23979 @code{name} or @code{linkage_name}, depending on whether the user
23980 asked @value{GDBN} to display demangled or mangled names.
23983 @defvar Symbol.addr_class
23984 The address class of the symbol. This classifies how to find the value
23985 of a symbol. Each address class is a constant defined in the
23986 @code{gdb} module and described later in this chapter.
23989 @defvar Symbol.is_argument
23990 @code{True} if the symbol is an argument of a function.
23993 @defvar Symbol.is_constant
23994 @code{True} if the symbol is a constant.
23997 @defvar Symbol.is_function
23998 @code{True} if the symbol is a function or a method.
24001 @defvar Symbol.is_variable
24002 @code{True} if the symbol is a variable.
24006 A @code{gdb.Symbol} object has the following methods:
24009 @defun Symbol.is_valid ()
24010 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24011 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24012 the symbol it refers to does not exist in @value{GDBN} any longer.
24013 All other @code{gdb.Symbol} methods will throw an exception if it is
24014 invalid at the time the method is called.
24018 The available domain categories in @code{gdb.Symbol} are represented
24019 as constants in the @code{gdb} module:
24022 @findex SYMBOL_UNDEF_DOMAIN
24023 @findex gdb.SYMBOL_UNDEF_DOMAIN
24024 @item gdb.SYMBOL_UNDEF_DOMAIN
24025 This is used when a domain has not been discovered or none of the
24026 following domains apply. This usually indicates an error either
24027 in the symbol information or in @value{GDBN}'s handling of symbols.
24028 @findex SYMBOL_VAR_DOMAIN
24029 @findex gdb.SYMBOL_VAR_DOMAIN
24030 @item gdb.SYMBOL_VAR_DOMAIN
24031 This domain contains variables, function names, typedef names and enum
24033 @findex SYMBOL_STRUCT_DOMAIN
24034 @findex gdb.SYMBOL_STRUCT_DOMAIN
24035 @item gdb.SYMBOL_STRUCT_DOMAIN
24036 This domain holds struct, union and enum type names.
24037 @findex SYMBOL_LABEL_DOMAIN
24038 @findex gdb.SYMBOL_LABEL_DOMAIN
24039 @item gdb.SYMBOL_LABEL_DOMAIN
24040 This domain contains names of labels (for gotos).
24041 @findex SYMBOL_VARIABLES_DOMAIN
24042 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24043 @item gdb.SYMBOL_VARIABLES_DOMAIN
24044 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24045 contains everything minus functions and types.
24046 @findex SYMBOL_FUNCTIONS_DOMAIN
24047 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24048 @item gdb.SYMBOL_FUNCTION_DOMAIN
24049 This domain contains all functions.
24050 @findex SYMBOL_TYPES_DOMAIN
24051 @findex gdb.SYMBOL_TYPES_DOMAIN
24052 @item gdb.SYMBOL_TYPES_DOMAIN
24053 This domain contains all types.
24056 The available address class categories in @code{gdb.Symbol} are represented
24057 as constants in the @code{gdb} module:
24060 @findex SYMBOL_LOC_UNDEF
24061 @findex gdb.SYMBOL_LOC_UNDEF
24062 @item gdb.SYMBOL_LOC_UNDEF
24063 If this is returned by address class, it indicates an error either in
24064 the symbol information or in @value{GDBN}'s handling of symbols.
24065 @findex SYMBOL_LOC_CONST
24066 @findex gdb.SYMBOL_LOC_CONST
24067 @item gdb.SYMBOL_LOC_CONST
24068 Value is constant int.
24069 @findex SYMBOL_LOC_STATIC
24070 @findex gdb.SYMBOL_LOC_STATIC
24071 @item gdb.SYMBOL_LOC_STATIC
24072 Value is at a fixed address.
24073 @findex SYMBOL_LOC_REGISTER
24074 @findex gdb.SYMBOL_LOC_REGISTER
24075 @item gdb.SYMBOL_LOC_REGISTER
24076 Value is in a register.
24077 @findex SYMBOL_LOC_ARG
24078 @findex gdb.SYMBOL_LOC_ARG
24079 @item gdb.SYMBOL_LOC_ARG
24080 Value is an argument. This value is at the offset stored within the
24081 symbol inside the frame's argument list.
24082 @findex SYMBOL_LOC_REF_ARG
24083 @findex gdb.SYMBOL_LOC_REF_ARG
24084 @item gdb.SYMBOL_LOC_REF_ARG
24085 Value address is stored in the frame's argument list. Just like
24086 @code{LOC_ARG} except that the value's address is stored at the
24087 offset, not the value itself.
24088 @findex SYMBOL_LOC_REGPARM_ADDR
24089 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24090 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24091 Value is a specified register. Just like @code{LOC_REGISTER} except
24092 the register holds the address of the argument instead of the argument
24094 @findex SYMBOL_LOC_LOCAL
24095 @findex gdb.SYMBOL_LOC_LOCAL
24096 @item gdb.SYMBOL_LOC_LOCAL
24097 Value is a local variable.
24098 @findex SYMBOL_LOC_TYPEDEF
24099 @findex gdb.SYMBOL_LOC_TYPEDEF
24100 @item gdb.SYMBOL_LOC_TYPEDEF
24101 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24103 @findex SYMBOL_LOC_BLOCK
24104 @findex gdb.SYMBOL_LOC_BLOCK
24105 @item gdb.SYMBOL_LOC_BLOCK
24107 @findex SYMBOL_LOC_CONST_BYTES
24108 @findex gdb.SYMBOL_LOC_CONST_BYTES
24109 @item gdb.SYMBOL_LOC_CONST_BYTES
24110 Value is a byte-sequence.
24111 @findex SYMBOL_LOC_UNRESOLVED
24112 @findex gdb.SYMBOL_LOC_UNRESOLVED
24113 @item gdb.SYMBOL_LOC_UNRESOLVED
24114 Value is at a fixed address, but the address of the variable has to be
24115 determined from the minimal symbol table whenever the variable is
24117 @findex SYMBOL_LOC_OPTIMIZED_OUT
24118 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24119 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24120 The value does not actually exist in the program.
24121 @findex SYMBOL_LOC_COMPUTED
24122 @findex gdb.SYMBOL_LOC_COMPUTED
24123 @item gdb.SYMBOL_LOC_COMPUTED
24124 The value's address is a computed location.
24127 @node Symbol Tables In Python
24128 @subsubsection Symbol table representation in Python.
24130 @cindex symbol tables in python
24132 @tindex gdb.Symtab_and_line
24134 Access to symbol table data maintained by @value{GDBN} on the inferior
24135 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24136 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24137 from the @code{find_sal} method in @code{gdb.Frame} object.
24138 @xref{Frames In Python}.
24140 For more information on @value{GDBN}'s symbol table management, see
24141 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24143 A @code{gdb.Symtab_and_line} object has the following attributes:
24146 @defvar Symtab_and_line.symtab
24147 The symbol table object (@code{gdb.Symtab}) for this frame.
24148 This attribute is not writable.
24151 @defvar Symtab_and_line.pc
24152 Indicates the current program counter address. This attribute is not
24156 @defvar Symtab_and_line.line
24157 Indicates the current line number for this object. This
24158 attribute is not writable.
24162 A @code{gdb.Symtab_and_line} object has the following methods:
24165 @defun Symtab_and_line.is_valid ()
24166 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24167 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24168 invalid if the Symbol table and line object it refers to does not
24169 exist in @value{GDBN} any longer. All other
24170 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24171 invalid at the time the method is called.
24175 A @code{gdb.Symtab} object has the following attributes:
24178 @defvar Symtab.filename
24179 The symbol table's source filename. This attribute is not writable.
24182 @defvar Symtab.objfile
24183 The symbol table's backing object file. @xref{Objfiles In Python}.
24184 This attribute is not writable.
24188 A @code{gdb.Symtab} object has the following methods:
24191 @defun Symtab.is_valid ()
24192 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24193 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24194 the symbol table it refers to does not exist in @value{GDBN} any
24195 longer. All other @code{gdb.Symtab} methods will throw an exception
24196 if it is invalid at the time the method is called.
24199 @defun Symtab.fullname ()
24200 Return the symbol table's source absolute file name.
24204 @node Breakpoints In Python
24205 @subsubsection Manipulating breakpoints using Python
24207 @cindex breakpoints in python
24208 @tindex gdb.Breakpoint
24210 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24213 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24214 Create a new breakpoint. @var{spec} is a string naming the
24215 location of the breakpoint, or an expression that defines a
24216 watchpoint. The contents can be any location recognized by the
24217 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24218 command. The optional @var{type} denotes the breakpoint to create
24219 from the types defined later in this chapter. This argument can be
24220 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24221 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24222 allows the breakpoint to become invisible to the user. The breakpoint
24223 will neither be reported when created, nor will it be listed in the
24224 output from @code{info breakpoints} (but will be listed with the
24225 @code{maint info breakpoints} command). The optional @var{wp_class}
24226 argument defines the class of watchpoint to create, if @var{type} is
24227 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24228 assumed to be a @code{gdb.WP_WRITE} class.
24231 @defun Breakpoint.stop (self)
24232 The @code{gdb.Breakpoint} class can be sub-classed and, in
24233 particular, you may choose to implement the @code{stop} method.
24234 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24235 it will be called when the inferior reaches any location of a
24236 breakpoint which instantiates that sub-class. If the method returns
24237 @code{True}, the inferior will be stopped at the location of the
24238 breakpoint, otherwise the inferior will continue.
24240 If there are multiple breakpoints at the same location with a
24241 @code{stop} method, each one will be called regardless of the
24242 return status of the previous. This ensures that all @code{stop}
24243 methods have a chance to execute at that location. In this scenario
24244 if one of the methods returns @code{True} but the others return
24245 @code{False}, the inferior will still be stopped.
24247 You should not alter the execution state of the inferior (i.e.@:, step,
24248 next, etc.), alter the current frame context (i.e.@:, change the current
24249 active frame), or alter, add or delete any breakpoint. As a general
24250 rule, you should not alter any data within @value{GDBN} or the inferior
24253 Example @code{stop} implementation:
24256 class MyBreakpoint (gdb.Breakpoint):
24258 inf_val = gdb.parse_and_eval("foo")
24265 The available watchpoint types represented by constants are defined in the
24270 @findex gdb.WP_READ
24272 Read only watchpoint.
24275 @findex gdb.WP_WRITE
24277 Write only watchpoint.
24280 @findex gdb.WP_ACCESS
24281 @item gdb.WP_ACCESS
24282 Read/Write watchpoint.
24285 @defun Breakpoint.is_valid ()
24286 Return @code{True} if this @code{Breakpoint} object is valid,
24287 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24288 if the user deletes the breakpoint. In this case, the object still
24289 exists, but the underlying breakpoint does not. In the cases of
24290 watchpoint scope, the watchpoint remains valid even if execution of the
24291 inferior leaves the scope of that watchpoint.
24294 @defun Breakpoint.delete
24295 Permanently deletes the @value{GDBN} breakpoint. This also
24296 invalidates the Python @code{Breakpoint} object. Any further access
24297 to this object's attributes or methods will raise an error.
24300 @defvar Breakpoint.enabled
24301 This attribute is @code{True} if the breakpoint is enabled, and
24302 @code{False} otherwise. This attribute is writable.
24305 @defvar Breakpoint.silent
24306 This attribute is @code{True} if the breakpoint is silent, and
24307 @code{False} otherwise. This attribute is writable.
24309 Note that a breakpoint can also be silent if it has commands and the
24310 first command is @code{silent}. This is not reported by the
24311 @code{silent} attribute.
24314 @defvar Breakpoint.thread
24315 If the breakpoint is thread-specific, this attribute holds the thread
24316 id. If the breakpoint is not thread-specific, this attribute is
24317 @code{None}. This attribute is writable.
24320 @defvar Breakpoint.task
24321 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24322 id. If the breakpoint is not task-specific (or the underlying
24323 language is not Ada), this attribute is @code{None}. This attribute
24327 @defvar Breakpoint.ignore_count
24328 This attribute holds the ignore count for the breakpoint, an integer.
24329 This attribute is writable.
24332 @defvar Breakpoint.number
24333 This attribute holds the breakpoint's number --- the identifier used by
24334 the user to manipulate the breakpoint. This attribute is not writable.
24337 @defvar Breakpoint.type
24338 This attribute holds the breakpoint's type --- the identifier used to
24339 determine the actual breakpoint type or use-case. This attribute is not
24343 @defvar Breakpoint.visible
24344 This attribute tells whether the breakpoint is visible to the user
24345 when set, or when the @samp{info breakpoints} command is run. This
24346 attribute is not writable.
24349 The available types are represented by constants defined in the @code{gdb}
24353 @findex BP_BREAKPOINT
24354 @findex gdb.BP_BREAKPOINT
24355 @item gdb.BP_BREAKPOINT
24356 Normal code breakpoint.
24358 @findex BP_WATCHPOINT
24359 @findex gdb.BP_WATCHPOINT
24360 @item gdb.BP_WATCHPOINT
24361 Watchpoint breakpoint.
24363 @findex BP_HARDWARE_WATCHPOINT
24364 @findex gdb.BP_HARDWARE_WATCHPOINT
24365 @item gdb.BP_HARDWARE_WATCHPOINT
24366 Hardware assisted watchpoint.
24368 @findex BP_READ_WATCHPOINT
24369 @findex gdb.BP_READ_WATCHPOINT
24370 @item gdb.BP_READ_WATCHPOINT
24371 Hardware assisted read watchpoint.
24373 @findex BP_ACCESS_WATCHPOINT
24374 @findex gdb.BP_ACCESS_WATCHPOINT
24375 @item gdb.BP_ACCESS_WATCHPOINT
24376 Hardware assisted access watchpoint.
24379 @defvar Breakpoint.hit_count
24380 This attribute holds the hit count for the breakpoint, an integer.
24381 This attribute is writable, but currently it can only be set to zero.
24384 @defvar Breakpoint.location
24385 This attribute holds the location of the breakpoint, as specified by
24386 the user. It is a string. If the breakpoint does not have a location
24387 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24388 attribute is not writable.
24391 @defvar Breakpoint.expression
24392 This attribute holds a breakpoint expression, as specified by
24393 the user. It is a string. If the breakpoint does not have an
24394 expression (the breakpoint is not a watchpoint) the attribute's value
24395 is @code{None}. This attribute is not writable.
24398 @defvar Breakpoint.condition
24399 This attribute holds the condition of the breakpoint, as specified by
24400 the user. It is a string. If there is no condition, this attribute's
24401 value is @code{None}. This attribute is writable.
24404 @defvar Breakpoint.commands
24405 This attribute holds the commands attached to the breakpoint. If
24406 there are commands, this attribute's value is a string holding all the
24407 commands, separated by newlines. If there are no commands, this
24408 attribute is @code{None}. This attribute is not writable.
24411 @node Finish Breakpoints in Python
24412 @subsubsection Finish Breakpoints
24414 @cindex python finish breakpoints
24415 @tindex gdb.FinishBreakpoint
24417 A finish breakpoint is a temporary breakpoint set at the return address of
24418 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24419 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24420 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24421 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24422 Finish breakpoints are thread specific and must be create with the right
24425 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24426 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24427 object @var{frame}. If @var{frame} is not provided, this defaults to the
24428 newest frame. The optional @var{internal} argument allows the breakpoint to
24429 become invisible to the user. @xref{Breakpoints In Python}, for further
24430 details about this argument.
24433 @defun FinishBreakpoint.out_of_scope (self)
24434 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24435 @code{return} command, @dots{}), a function may not properly terminate, and
24436 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24437 situation, the @code{out_of_scope} callback will be triggered.
24439 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24443 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24445 print "normal finish"
24448 def out_of_scope ():
24449 print "abnormal finish"
24453 @defvar FinishBreakpoint.return_value
24454 When @value{GDBN} is stopped at a finish breakpoint and the frame
24455 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24456 attribute will contain a @code{gdb.Value} object corresponding to the return
24457 value of the function. The value will be @code{None} if the function return
24458 type is @code{void} or if the return value was not computable. This attribute
24462 @node Lazy Strings In Python
24463 @subsubsection Python representation of lazy strings.
24465 @cindex lazy strings in python
24466 @tindex gdb.LazyString
24468 A @dfn{lazy string} is a string whose contents is not retrieved or
24469 encoded until it is needed.
24471 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24472 @code{address} that points to a region of memory, an @code{encoding}
24473 that will be used to encode that region of memory, and a @code{length}
24474 to delimit the region of memory that represents the string. The
24475 difference between a @code{gdb.LazyString} and a string wrapped within
24476 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24477 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24478 retrieved and encoded during printing, while a @code{gdb.Value}
24479 wrapping a string is immediately retrieved and encoded on creation.
24481 A @code{gdb.LazyString} object has the following functions:
24483 @defun LazyString.value ()
24484 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24485 will point to the string in memory, but will lose all the delayed
24486 retrieval, encoding and handling that @value{GDBN} applies to a
24487 @code{gdb.LazyString}.
24490 @defvar LazyString.address
24491 This attribute holds the address of the string. This attribute is not
24495 @defvar LazyString.length
24496 This attribute holds the length of the string in characters. If the
24497 length is -1, then the string will be fetched and encoded up to the
24498 first null of appropriate width. This attribute is not writable.
24501 @defvar LazyString.encoding
24502 This attribute holds the encoding that will be applied to the string
24503 when the string is printed by @value{GDBN}. If the encoding is not
24504 set, or contains an empty string, then @value{GDBN} will select the
24505 most appropriate encoding when the string is printed. This attribute
24509 @defvar LazyString.type
24510 This attribute holds the type that is represented by the lazy string's
24511 type. For a lazy string this will always be a pointer type. To
24512 resolve this to the lazy string's character type, use the type's
24513 @code{target} method. @xref{Types In Python}. This attribute is not
24518 @subsection Auto-loading
24519 @cindex auto-loading, Python
24521 When a new object file is read (for example, due to the @code{file}
24522 command, or because the inferior has loaded a shared library),
24523 @value{GDBN} will look for Python support scripts in several ways:
24524 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24527 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24528 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24529 * Which flavor to choose?::
24532 The auto-loading feature is useful for supplying application-specific
24533 debugging commands and scripts.
24535 Auto-loading can be enabled or disabled,
24536 and the list of auto-loaded scripts can be printed.
24539 @kindex set auto-load-scripts
24540 @item set auto-load-scripts [yes|no]
24541 Enable or disable the auto-loading of Python scripts.
24543 @kindex show auto-load-scripts
24544 @item show auto-load-scripts
24545 Show whether auto-loading of Python scripts is enabled or disabled.
24547 @kindex info auto-load-scripts
24548 @cindex print list of auto-loaded scripts
24549 @item info auto-load-scripts [@var{regexp}]
24550 Print the list of all scripts that @value{GDBN} auto-loaded.
24552 Also printed is the list of scripts that were mentioned in
24553 the @code{.debug_gdb_scripts} section and were not found
24554 (@pxref{.debug_gdb_scripts section}).
24555 This is useful because their names are not printed when @value{GDBN}
24556 tries to load them and fails. There may be many of them, and printing
24557 an error message for each one is problematic.
24559 If @var{regexp} is supplied only scripts with matching names are printed.
24564 (gdb) info auto-load-scripts
24566 Yes py-section-script.py
24567 full name: /tmp/py-section-script.py
24568 Missing my-foo-pretty-printers.py
24572 When reading an auto-loaded file, @value{GDBN} sets the
24573 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24574 function (@pxref{Objfiles In Python}). This can be useful for
24575 registering objfile-specific pretty-printers.
24577 @node objfile-gdb.py file
24578 @subsubsection The @file{@var{objfile}-gdb.py} file
24579 @cindex @file{@var{objfile}-gdb.py}
24581 When a new object file is read, @value{GDBN} looks for
24582 a file named @file{@var{objfile}-gdb.py},
24583 where @var{objfile} is the object file's real name, formed by ensuring
24584 that the file name is absolute, following all symlinks, and resolving
24585 @code{.} and @code{..} components. If this file exists and is
24586 readable, @value{GDBN} will evaluate it as a Python script.
24588 If this file does not exist, and if the parameter
24589 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24590 then @value{GDBN} will look for @var{real-name} in all of the
24591 directories mentioned in the value of @code{debug-file-directory}.
24593 Finally, if this file does not exist, then @value{GDBN} will look for
24594 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24595 @var{data-directory} is @value{GDBN}'s data directory (available via
24596 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24597 is the object file's real name, as described above.
24599 @value{GDBN} does not track which files it has already auto-loaded this way.
24600 @value{GDBN} will load the associated script every time the corresponding
24601 @var{objfile} is opened.
24602 So your @file{-gdb.py} file should be careful to avoid errors if it
24603 is evaluated more than once.
24605 @node .debug_gdb_scripts section
24606 @subsubsection The @code{.debug_gdb_scripts} section
24607 @cindex @code{.debug_gdb_scripts} section
24609 For systems using file formats like ELF and COFF,
24610 when @value{GDBN} loads a new object file
24611 it will look for a special section named @samp{.debug_gdb_scripts}.
24612 If this section exists, its contents is a list of names of scripts to load.
24614 @value{GDBN} will look for each specified script file first in the
24615 current directory and then along the source search path
24616 (@pxref{Source Path, ,Specifying Source Directories}),
24617 except that @file{$cdir} is not searched, since the compilation
24618 directory is not relevant to scripts.
24620 Entries can be placed in section @code{.debug_gdb_scripts} with,
24621 for example, this GCC macro:
24624 /* Note: The "MS" section flags are to remove duplicates. */
24625 #define DEFINE_GDB_SCRIPT(script_name) \
24627 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24629 .asciz \"" script_name "\"\n\
24635 Then one can reference the macro in a header or source file like this:
24638 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24641 The script name may include directories if desired.
24643 If the macro is put in a header, any application or library
24644 using this header will get a reference to the specified script.
24646 @node Which flavor to choose?
24647 @subsubsection Which flavor to choose?
24649 Given the multiple ways of auto-loading Python scripts, it might not always
24650 be clear which one to choose. This section provides some guidance.
24652 Benefits of the @file{-gdb.py} way:
24656 Can be used with file formats that don't support multiple sections.
24659 Ease of finding scripts for public libraries.
24661 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24662 in the source search path.
24663 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24664 isn't a source directory in which to find the script.
24667 Doesn't require source code additions.
24670 Benefits of the @code{.debug_gdb_scripts} way:
24674 Works with static linking.
24676 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24677 trigger their loading. When an application is statically linked the only
24678 objfile available is the executable, and it is cumbersome to attach all the
24679 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24682 Works with classes that are entirely inlined.
24684 Some classes can be entirely inlined, and thus there may not be an associated
24685 shared library to attach a @file{-gdb.py} script to.
24688 Scripts needn't be copied out of the source tree.
24690 In some circumstances, apps can be built out of large collections of internal
24691 libraries, and the build infrastructure necessary to install the
24692 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24693 cumbersome. It may be easier to specify the scripts in the
24694 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24695 top of the source tree to the source search path.
24698 @node Python modules
24699 @subsection Python modules
24700 @cindex python modules
24702 @value{GDBN} comes with several modules to assist writing Python code.
24705 * gdb.printing:: Building and registering pretty-printers.
24706 * gdb.types:: Utilities for working with types.
24707 * gdb.prompt:: Utilities for prompt value substitution.
24711 @subsubsection gdb.printing
24712 @cindex gdb.printing
24714 This module provides a collection of utilities for working with
24718 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24719 This class specifies the API that makes @samp{info pretty-printer},
24720 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24721 Pretty-printers should generally inherit from this class.
24723 @item SubPrettyPrinter (@var{name})
24724 For printers that handle multiple types, this class specifies the
24725 corresponding API for the subprinters.
24727 @item RegexpCollectionPrettyPrinter (@var{name})
24728 Utility class for handling multiple printers, all recognized via
24729 regular expressions.
24730 @xref{Writing a Pretty-Printer}, for an example.
24732 @item FlagEnumerationPrinter (@var{name})
24733 A pretty-printer which handles printing of @code{enum} values. Unlike
24734 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
24735 work properly when there is some overlap between the enumeration
24736 constants. @var{name} is the name of the printer and also the name of
24737 the @code{enum} type to look up.
24739 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24740 Register @var{printer} with the pretty-printer list of @var{obj}.
24741 If @var{replace} is @code{True} then any existing copy of the printer
24742 is replaced. Otherwise a @code{RuntimeError} exception is raised
24743 if a printer with the same name already exists.
24747 @subsubsection gdb.types
24750 This module provides a collection of utilities for working with
24751 @code{gdb.Types} objects.
24754 @item get_basic_type (@var{type})
24755 Return @var{type} with const and volatile qualifiers stripped,
24756 and with typedefs and C@t{++} references converted to the underlying type.
24761 typedef const int const_int;
24763 const_int& foo_ref (foo);
24764 int main () @{ return 0; @}
24771 (gdb) python import gdb.types
24772 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24773 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24777 @item has_field (@var{type}, @var{field})
24778 Return @code{True} if @var{type}, assumed to be a type with fields
24779 (e.g., a structure or union), has field @var{field}.
24781 @item make_enum_dict (@var{enum_type})
24782 Return a Python @code{dictionary} type produced from @var{enum_type}.
24784 @item deep_items (@var{type})
24785 Returns a Python iterator similar to the standard
24786 @code{gdb.Type.iteritems} method, except that the iterator returned
24787 by @code{deep_items} will recursively traverse anonymous struct or
24788 union fields. For example:
24802 Then in @value{GDBN}:
24804 (@value{GDBP}) python import gdb.types
24805 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24806 (@value{GDBP}) python print struct_a.keys ()
24808 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24809 @{['a', 'b0', 'b1']@}
24815 @subsubsection gdb.prompt
24818 This module provides a method for prompt value-substitution.
24821 @item substitute_prompt (@var{string})
24822 Return @var{string} with escape sequences substituted by values. Some
24823 escape sequences take arguments. You can specify arguments inside
24824 ``@{@}'' immediately following the escape sequence.
24826 The escape sequences you can pass to this function are:
24830 Substitute a backslash.
24832 Substitute an ESC character.
24834 Substitute the selected frame; an argument names a frame parameter.
24836 Substitute a newline.
24838 Substitute a parameter's value; the argument names the parameter.
24840 Substitute a carriage return.
24842 Substitute the selected thread; an argument names a thread parameter.
24844 Substitute the version of GDB.
24846 Substitute the current working directory.
24848 Begin a sequence of non-printing characters. These sequences are
24849 typically used with the ESC character, and are not counted in the string
24850 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24851 blue-colored ``(gdb)'' prompt where the length is five.
24853 End a sequence of non-printing characters.
24859 substitute_prompt (``frame: \f,
24860 print arguments: \p@{print frame-arguments@}'')
24863 @exdent will return the string:
24866 "frame: main, print arguments: scalars"
24871 @section Creating new spellings of existing commands
24872 @cindex aliases for commands
24874 It is often useful to define alternate spellings of existing commands.
24875 For example, if a new @value{GDBN} command defined in Python has
24876 a long name to type, it is handy to have an abbreviated version of it
24877 that involves less typing.
24879 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24880 of the @samp{step} command even though it is otherwise an ambiguous
24881 abbreviation of other commands like @samp{set} and @samp{show}.
24883 Aliases are also used to provide shortened or more common versions
24884 of multi-word commands. For example, @value{GDBN} provides the
24885 @samp{tty} alias of the @samp{set inferior-tty} command.
24887 You can define a new alias with the @samp{alias} command.
24892 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24896 @var{ALIAS} specifies the name of the new alias.
24897 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24900 @var{COMMAND} specifies the name of an existing command
24901 that is being aliased.
24903 The @samp{-a} option specifies that the new alias is an abbreviation
24904 of the command. Abbreviations are not shown in command
24905 lists displayed by the @samp{help} command.
24907 The @samp{--} option specifies the end of options,
24908 and is useful when @var{ALIAS} begins with a dash.
24910 Here is a simple example showing how to make an abbreviation
24911 of a command so that there is less to type.
24912 Suppose you were tired of typing @samp{disas}, the current
24913 shortest unambiguous abbreviation of the @samp{disassemble} command
24914 and you wanted an even shorter version named @samp{di}.
24915 The following will accomplish this.
24918 (gdb) alias -a di = disas
24921 Note that aliases are different from user-defined commands.
24922 With a user-defined command, you also need to write documentation
24923 for it with the @samp{document} command.
24924 An alias automatically picks up the documentation of the existing command.
24926 Here is an example where we make @samp{elms} an abbreviation of
24927 @samp{elements} in the @samp{set print elements} command.
24928 This is to show that you can make an abbreviation of any part
24932 (gdb) alias -a set print elms = set print elements
24933 (gdb) alias -a show print elms = show print elements
24934 (gdb) set p elms 20
24936 Limit on string chars or array elements to print is 200.
24939 Note that if you are defining an alias of a @samp{set} command,
24940 and you want to have an alias for the corresponding @samp{show}
24941 command, then you need to define the latter separately.
24943 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24944 @var{ALIAS}, just as they are normally.
24947 (gdb) alias -a set pr elms = set p ele
24950 Finally, here is an example showing the creation of a one word
24951 alias for a more complex command.
24952 This creates alias @samp{spe} of the command @samp{set print elements}.
24955 (gdb) alias spe = set print elements
24960 @chapter Command Interpreters
24961 @cindex command interpreters
24963 @value{GDBN} supports multiple command interpreters, and some command
24964 infrastructure to allow users or user interface writers to switch
24965 between interpreters or run commands in other interpreters.
24967 @value{GDBN} currently supports two command interpreters, the console
24968 interpreter (sometimes called the command-line interpreter or @sc{cli})
24969 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24970 describes both of these interfaces in great detail.
24972 By default, @value{GDBN} will start with the console interpreter.
24973 However, the user may choose to start @value{GDBN} with another
24974 interpreter by specifying the @option{-i} or @option{--interpreter}
24975 startup options. Defined interpreters include:
24979 @cindex console interpreter
24980 The traditional console or command-line interpreter. This is the most often
24981 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24982 @value{GDBN} will use this interpreter.
24985 @cindex mi interpreter
24986 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24987 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24988 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24992 @cindex mi2 interpreter
24993 The current @sc{gdb/mi} interface.
24996 @cindex mi1 interpreter
24997 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25001 @cindex invoke another interpreter
25002 The interpreter being used by @value{GDBN} may not be dynamically
25003 switched at runtime. Although possible, this could lead to a very
25004 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
25005 enters the command "interpreter-set console" in a console view,
25006 @value{GDBN} would switch to using the console interpreter, rendering
25007 the IDE inoperable!
25009 @kindex interpreter-exec
25010 Although you may only choose a single interpreter at startup, you may execute
25011 commands in any interpreter from the current interpreter using the appropriate
25012 command. If you are running the console interpreter, simply use the
25013 @code{interpreter-exec} command:
25016 interpreter-exec mi "-data-list-register-names"
25019 @sc{gdb/mi} has a similar command, although it is only available in versions of
25020 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25023 @chapter @value{GDBN} Text User Interface
25025 @cindex Text User Interface
25028 * TUI Overview:: TUI overview
25029 * TUI Keys:: TUI key bindings
25030 * TUI Single Key Mode:: TUI single key mode
25031 * TUI Commands:: TUI-specific commands
25032 * TUI Configuration:: TUI configuration variables
25035 The @value{GDBN} Text User Interface (TUI) is a terminal
25036 interface which uses the @code{curses} library to show the source
25037 file, the assembly output, the program registers and @value{GDBN}
25038 commands in separate text windows. The TUI mode is supported only
25039 on platforms where a suitable version of the @code{curses} library
25042 The TUI mode is enabled by default when you invoke @value{GDBN} as
25043 @samp{@value{GDBP} -tui}.
25044 You can also switch in and out of TUI mode while @value{GDBN} runs by
25045 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25046 @xref{TUI Keys, ,TUI Key Bindings}.
25049 @section TUI Overview
25051 In TUI mode, @value{GDBN} can display several text windows:
25055 This window is the @value{GDBN} command window with the @value{GDBN}
25056 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25057 managed using readline.
25060 The source window shows the source file of the program. The current
25061 line and active breakpoints are displayed in this window.
25064 The assembly window shows the disassembly output of the program.
25067 This window shows the processor registers. Registers are highlighted
25068 when their values change.
25071 The source and assembly windows show the current program position
25072 by highlighting the current line and marking it with a @samp{>} marker.
25073 Breakpoints are indicated with two markers. The first marker
25074 indicates the breakpoint type:
25078 Breakpoint which was hit at least once.
25081 Breakpoint which was never hit.
25084 Hardware breakpoint which was hit at least once.
25087 Hardware breakpoint which was never hit.
25090 The second marker indicates whether the breakpoint is enabled or not:
25094 Breakpoint is enabled.
25097 Breakpoint is disabled.
25100 The source, assembly and register windows are updated when the current
25101 thread changes, when the frame changes, or when the program counter
25104 These windows are not all visible at the same time. The command
25105 window is always visible. The others can be arranged in several
25116 source and assembly,
25119 source and registers, or
25122 assembly and registers.
25125 A status line above the command window shows the following information:
25129 Indicates the current @value{GDBN} target.
25130 (@pxref{Targets, ,Specifying a Debugging Target}).
25133 Gives the current process or thread number.
25134 When no process is being debugged, this field is set to @code{No process}.
25137 Gives the current function name for the selected frame.
25138 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25139 When there is no symbol corresponding to the current program counter,
25140 the string @code{??} is displayed.
25143 Indicates the current line number for the selected frame.
25144 When the current line number is not known, the string @code{??} is displayed.
25147 Indicates the current program counter address.
25151 @section TUI Key Bindings
25152 @cindex TUI key bindings
25154 The TUI installs several key bindings in the readline keymaps
25155 @ifset SYSTEM_READLINE
25156 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25158 @ifclear SYSTEM_READLINE
25159 (@pxref{Command Line Editing}).
25161 The following key bindings are installed for both TUI mode and the
25162 @value{GDBN} standard mode.
25171 Enter or leave the TUI mode. When leaving the TUI mode,
25172 the curses window management stops and @value{GDBN} operates using
25173 its standard mode, writing on the terminal directly. When reentering
25174 the TUI mode, control is given back to the curses windows.
25175 The screen is then refreshed.
25179 Use a TUI layout with only one window. The layout will
25180 either be @samp{source} or @samp{assembly}. When the TUI mode
25181 is not active, it will switch to the TUI mode.
25183 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25187 Use a TUI layout with at least two windows. When the current
25188 layout already has two windows, the next layout with two windows is used.
25189 When a new layout is chosen, one window will always be common to the
25190 previous layout and the new one.
25192 Think of it as the Emacs @kbd{C-x 2} binding.
25196 Change the active window. The TUI associates several key bindings
25197 (like scrolling and arrow keys) with the active window. This command
25198 gives the focus to the next TUI window.
25200 Think of it as the Emacs @kbd{C-x o} binding.
25204 Switch in and out of the TUI SingleKey mode that binds single
25205 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25208 The following key bindings only work in the TUI mode:
25213 Scroll the active window one page up.
25217 Scroll the active window one page down.
25221 Scroll the active window one line up.
25225 Scroll the active window one line down.
25229 Scroll the active window one column left.
25233 Scroll the active window one column right.
25237 Refresh the screen.
25240 Because the arrow keys scroll the active window in the TUI mode, they
25241 are not available for their normal use by readline unless the command
25242 window has the focus. When another window is active, you must use
25243 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25244 and @kbd{C-f} to control the command window.
25246 @node TUI Single Key Mode
25247 @section TUI Single Key Mode
25248 @cindex TUI single key mode
25250 The TUI also provides a @dfn{SingleKey} mode, which binds several
25251 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25252 switch into this mode, where the following key bindings are used:
25255 @kindex c @r{(SingleKey TUI key)}
25259 @kindex d @r{(SingleKey TUI key)}
25263 @kindex f @r{(SingleKey TUI key)}
25267 @kindex n @r{(SingleKey TUI key)}
25271 @kindex q @r{(SingleKey TUI key)}
25273 exit the SingleKey mode.
25275 @kindex r @r{(SingleKey TUI key)}
25279 @kindex s @r{(SingleKey TUI key)}
25283 @kindex u @r{(SingleKey TUI key)}
25287 @kindex v @r{(SingleKey TUI key)}
25291 @kindex w @r{(SingleKey TUI key)}
25296 Other keys temporarily switch to the @value{GDBN} command prompt.
25297 The key that was pressed is inserted in the editing buffer so that
25298 it is possible to type most @value{GDBN} commands without interaction
25299 with the TUI SingleKey mode. Once the command is entered the TUI
25300 SingleKey mode is restored. The only way to permanently leave
25301 this mode is by typing @kbd{q} or @kbd{C-x s}.
25305 @section TUI-specific Commands
25306 @cindex TUI commands
25308 The TUI has specific commands to control the text windows.
25309 These commands are always available, even when @value{GDBN} is not in
25310 the TUI mode. When @value{GDBN} is in the standard mode, most
25311 of these commands will automatically switch to the TUI mode.
25313 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25314 terminal, or @value{GDBN} has been started with the machine interface
25315 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25316 these commands will fail with an error, because it would not be
25317 possible or desirable to enable curses window management.
25322 List and give the size of all displayed windows.
25326 Display the next layout.
25329 Display the previous layout.
25332 Display the source window only.
25335 Display the assembly window only.
25338 Display the source and assembly window.
25341 Display the register window together with the source or assembly window.
25345 Make the next window active for scrolling.
25348 Make the previous window active for scrolling.
25351 Make the source window active for scrolling.
25354 Make the assembly window active for scrolling.
25357 Make the register window active for scrolling.
25360 Make the command window active for scrolling.
25364 Refresh the screen. This is similar to typing @kbd{C-L}.
25366 @item tui reg float
25368 Show the floating point registers in the register window.
25370 @item tui reg general
25371 Show the general registers in the register window.
25374 Show the next register group. The list of register groups as well as
25375 their order is target specific. The predefined register groups are the
25376 following: @code{general}, @code{float}, @code{system}, @code{vector},
25377 @code{all}, @code{save}, @code{restore}.
25379 @item tui reg system
25380 Show the system registers in the register window.
25384 Update the source window and the current execution point.
25386 @item winheight @var{name} +@var{count}
25387 @itemx winheight @var{name} -@var{count}
25389 Change the height of the window @var{name} by @var{count}
25390 lines. Positive counts increase the height, while negative counts
25393 @item tabset @var{nchars}
25395 Set the width of tab stops to be @var{nchars} characters.
25398 @node TUI Configuration
25399 @section TUI Configuration Variables
25400 @cindex TUI configuration variables
25402 Several configuration variables control the appearance of TUI windows.
25405 @item set tui border-kind @var{kind}
25406 @kindex set tui border-kind
25407 Select the border appearance for the source, assembly and register windows.
25408 The possible values are the following:
25411 Use a space character to draw the border.
25414 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25417 Use the Alternate Character Set to draw the border. The border is
25418 drawn using character line graphics if the terminal supports them.
25421 @item set tui border-mode @var{mode}
25422 @kindex set tui border-mode
25423 @itemx set tui active-border-mode @var{mode}
25424 @kindex set tui active-border-mode
25425 Select the display attributes for the borders of the inactive windows
25426 or the active window. The @var{mode} can be one of the following:
25429 Use normal attributes to display the border.
25435 Use reverse video mode.
25438 Use half bright mode.
25440 @item half-standout
25441 Use half bright and standout mode.
25444 Use extra bright or bold mode.
25446 @item bold-standout
25447 Use extra bright or bold and standout mode.
25452 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25455 @cindex @sc{gnu} Emacs
25456 A special interface allows you to use @sc{gnu} Emacs to view (and
25457 edit) the source files for the program you are debugging with
25460 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25461 executable file you want to debug as an argument. This command starts
25462 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25463 created Emacs buffer.
25464 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25466 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25471 All ``terminal'' input and output goes through an Emacs buffer, called
25474 This applies both to @value{GDBN} commands and their output, and to the input
25475 and output done by the program you are debugging.
25477 This is useful because it means that you can copy the text of previous
25478 commands and input them again; you can even use parts of the output
25481 All the facilities of Emacs' Shell mode are available for interacting
25482 with your program. In particular, you can send signals the usual
25483 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25487 @value{GDBN} displays source code through Emacs.
25489 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25490 source file for that frame and puts an arrow (@samp{=>}) at the
25491 left margin of the current line. Emacs uses a separate buffer for
25492 source display, and splits the screen to show both your @value{GDBN} session
25495 Explicit @value{GDBN} @code{list} or search commands still produce output as
25496 usual, but you probably have no reason to use them from Emacs.
25499 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25500 a graphical mode, enabled by default, which provides further buffers
25501 that can control the execution and describe the state of your program.
25502 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25504 If you specify an absolute file name when prompted for the @kbd{M-x
25505 gdb} argument, then Emacs sets your current working directory to where
25506 your program resides. If you only specify the file name, then Emacs
25507 sets your current working directory to the directory associated
25508 with the previous buffer. In this case, @value{GDBN} may find your
25509 program by searching your environment's @code{PATH} variable, but on
25510 some operating systems it might not find the source. So, although the
25511 @value{GDBN} input and output session proceeds normally, the auxiliary
25512 buffer does not display the current source and line of execution.
25514 The initial working directory of @value{GDBN} is printed on the top
25515 line of the GUD buffer and this serves as a default for the commands
25516 that specify files for @value{GDBN} to operate on. @xref{Files,
25517 ,Commands to Specify Files}.
25519 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25520 need to call @value{GDBN} by a different name (for example, if you
25521 keep several configurations around, with different names) you can
25522 customize the Emacs variable @code{gud-gdb-command-name} to run the
25525 In the GUD buffer, you can use these special Emacs commands in
25526 addition to the standard Shell mode commands:
25530 Describe the features of Emacs' GUD Mode.
25533 Execute to another source line, like the @value{GDBN} @code{step} command; also
25534 update the display window to show the current file and location.
25537 Execute to next source line in this function, skipping all function
25538 calls, like the @value{GDBN} @code{next} command. Then update the display window
25539 to show the current file and location.
25542 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25543 display window accordingly.
25546 Execute until exit from the selected stack frame, like the @value{GDBN}
25547 @code{finish} command.
25550 Continue execution of your program, like the @value{GDBN} @code{continue}
25554 Go up the number of frames indicated by the numeric argument
25555 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25556 like the @value{GDBN} @code{up} command.
25559 Go down the number of frames indicated by the numeric argument, like the
25560 @value{GDBN} @code{down} command.
25563 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25564 tells @value{GDBN} to set a breakpoint on the source line point is on.
25566 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25567 separate frame which shows a backtrace when the GUD buffer is current.
25568 Move point to any frame in the stack and type @key{RET} to make it
25569 become the current frame and display the associated source in the
25570 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25571 selected frame become the current one. In graphical mode, the
25572 speedbar displays watch expressions.
25574 If you accidentally delete the source-display buffer, an easy way to get
25575 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25576 request a frame display; when you run under Emacs, this recreates
25577 the source buffer if necessary to show you the context of the current
25580 The source files displayed in Emacs are in ordinary Emacs buffers
25581 which are visiting the source files in the usual way. You can edit
25582 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25583 communicates with Emacs in terms of line numbers. If you add or
25584 delete lines from the text, the line numbers that @value{GDBN} knows cease
25585 to correspond properly with the code.
25587 A more detailed description of Emacs' interaction with @value{GDBN} is
25588 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25591 @c The following dropped because Epoch is nonstandard. Reactivate
25592 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25594 @kindex Emacs Epoch environment
25598 Version 18 of @sc{gnu} Emacs has a built-in window system
25599 called the @code{epoch}
25600 environment. Users of this environment can use a new command,
25601 @code{inspect} which performs identically to @code{print} except that
25602 each value is printed in its own window.
25607 @chapter The @sc{gdb/mi} Interface
25609 @unnumberedsec Function and Purpose
25611 @cindex @sc{gdb/mi}, its purpose
25612 @sc{gdb/mi} is a line based machine oriented text interface to
25613 @value{GDBN} and is activated by specifying using the
25614 @option{--interpreter} command line option (@pxref{Mode Options}). It
25615 is specifically intended to support the development of systems which
25616 use the debugger as just one small component of a larger system.
25618 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25619 in the form of a reference manual.
25621 Note that @sc{gdb/mi} is still under construction, so some of the
25622 features described below are incomplete and subject to change
25623 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25625 @unnumberedsec Notation and Terminology
25627 @cindex notational conventions, for @sc{gdb/mi}
25628 This chapter uses the following notation:
25632 @code{|} separates two alternatives.
25635 @code{[ @var{something} ]} indicates that @var{something} is optional:
25636 it may or may not be given.
25639 @code{( @var{group} )*} means that @var{group} inside the parentheses
25640 may repeat zero or more times.
25643 @code{( @var{group} )+} means that @var{group} inside the parentheses
25644 may repeat one or more times.
25647 @code{"@var{string}"} means a literal @var{string}.
25651 @heading Dependencies
25655 * GDB/MI General Design::
25656 * GDB/MI Command Syntax::
25657 * GDB/MI Compatibility with CLI::
25658 * GDB/MI Development and Front Ends::
25659 * GDB/MI Output Records::
25660 * GDB/MI Simple Examples::
25661 * GDB/MI Command Description Format::
25662 * GDB/MI Breakpoint Commands::
25663 * GDB/MI Program Context::
25664 * GDB/MI Thread Commands::
25665 * GDB/MI Ada Tasking Commands::
25666 * GDB/MI Program Execution::
25667 * GDB/MI Stack Manipulation::
25668 * GDB/MI Variable Objects::
25669 * GDB/MI Data Manipulation::
25670 * GDB/MI Tracepoint Commands::
25671 * GDB/MI Symbol Query::
25672 * GDB/MI File Commands::
25674 * GDB/MI Kod Commands::
25675 * GDB/MI Memory Overlay Commands::
25676 * GDB/MI Signal Handling Commands::
25678 * GDB/MI Target Manipulation::
25679 * GDB/MI File Transfer Commands::
25680 * GDB/MI Miscellaneous Commands::
25683 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25684 @node GDB/MI General Design
25685 @section @sc{gdb/mi} General Design
25686 @cindex GDB/MI General Design
25688 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25689 parts---commands sent to @value{GDBN}, responses to those commands
25690 and notifications. Each command results in exactly one response,
25691 indicating either successful completion of the command, or an error.
25692 For the commands that do not resume the target, the response contains the
25693 requested information. For the commands that resume the target, the
25694 response only indicates whether the target was successfully resumed.
25695 Notifications is the mechanism for reporting changes in the state of the
25696 target, or in @value{GDBN} state, that cannot conveniently be associated with
25697 a command and reported as part of that command response.
25699 The important examples of notifications are:
25703 Exec notifications. These are used to report changes in
25704 target state---when a target is resumed, or stopped. It would not
25705 be feasible to include this information in response of resuming
25706 commands, because one resume commands can result in multiple events in
25707 different threads. Also, quite some time may pass before any event
25708 happens in the target, while a frontend needs to know whether the resuming
25709 command itself was successfully executed.
25712 Console output, and status notifications. Console output
25713 notifications are used to report output of CLI commands, as well as
25714 diagnostics for other commands. Status notifications are used to
25715 report the progress of a long-running operation. Naturally, including
25716 this information in command response would mean no output is produced
25717 until the command is finished, which is undesirable.
25720 General notifications. Commands may have various side effects on
25721 the @value{GDBN} or target state beyond their official purpose. For example,
25722 a command may change the selected thread. Although such changes can
25723 be included in command response, using notification allows for more
25724 orthogonal frontend design.
25728 There's no guarantee that whenever an MI command reports an error,
25729 @value{GDBN} or the target are in any specific state, and especially,
25730 the state is not reverted to the state before the MI command was
25731 processed. Therefore, whenever an MI command results in an error,
25732 we recommend that the frontend refreshes all the information shown in
25733 the user interface.
25737 * Context management::
25738 * Asynchronous and non-stop modes::
25742 @node Context management
25743 @subsection Context management
25745 In most cases when @value{GDBN} accesses the target, this access is
25746 done in context of a specific thread and frame (@pxref{Frames}).
25747 Often, even when accessing global data, the target requires that a thread
25748 be specified. The CLI interface maintains the selected thread and frame,
25749 and supplies them to target on each command. This is convenient,
25750 because a command line user would not want to specify that information
25751 explicitly on each command, and because user interacts with
25752 @value{GDBN} via a single terminal, so no confusion is possible as
25753 to what thread and frame are the current ones.
25755 In the case of MI, the concept of selected thread and frame is less
25756 useful. First, a frontend can easily remember this information
25757 itself. Second, a graphical frontend can have more than one window,
25758 each one used for debugging a different thread, and the frontend might
25759 want to access additional threads for internal purposes. This
25760 increases the risk that by relying on implicitly selected thread, the
25761 frontend may be operating on a wrong one. Therefore, each MI command
25762 should explicitly specify which thread and frame to operate on. To
25763 make it possible, each MI command accepts the @samp{--thread} and
25764 @samp{--frame} options, the value to each is @value{GDBN} identifier
25765 for thread and frame to operate on.
25767 Usually, each top-level window in a frontend allows the user to select
25768 a thread and a frame, and remembers the user selection for further
25769 operations. However, in some cases @value{GDBN} may suggest that the
25770 current thread be changed. For example, when stopping on a breakpoint
25771 it is reasonable to switch to the thread where breakpoint is hit. For
25772 another example, if the user issues the CLI @samp{thread} command via
25773 the frontend, it is desirable to change the frontend's selected thread to the
25774 one specified by user. @value{GDBN} communicates the suggestion to
25775 change current thread using the @samp{=thread-selected} notification.
25776 No such notification is available for the selected frame at the moment.
25778 Note that historically, MI shares the selected thread with CLI, so
25779 frontends used the @code{-thread-select} to execute commands in the
25780 right context. However, getting this to work right is cumbersome. The
25781 simplest way is for frontend to emit @code{-thread-select} command
25782 before every command. This doubles the number of commands that need
25783 to be sent. The alternative approach is to suppress @code{-thread-select}
25784 if the selected thread in @value{GDBN} is supposed to be identical to the
25785 thread the frontend wants to operate on. However, getting this
25786 optimization right can be tricky. In particular, if the frontend
25787 sends several commands to @value{GDBN}, and one of the commands changes the
25788 selected thread, then the behaviour of subsequent commands will
25789 change. So, a frontend should either wait for response from such
25790 problematic commands, or explicitly add @code{-thread-select} for
25791 all subsequent commands. No frontend is known to do this exactly
25792 right, so it is suggested to just always pass the @samp{--thread} and
25793 @samp{--frame} options.
25795 @node Asynchronous and non-stop modes
25796 @subsection Asynchronous command execution and non-stop mode
25798 On some targets, @value{GDBN} is capable of processing MI commands
25799 even while the target is running. This is called @dfn{asynchronous
25800 command execution} (@pxref{Background Execution}). The frontend may
25801 specify a preferrence for asynchronous execution using the
25802 @code{-gdb-set target-async 1} command, which should be emitted before
25803 either running the executable or attaching to the target. After the
25804 frontend has started the executable or attached to the target, it can
25805 find if asynchronous execution is enabled using the
25806 @code{-list-target-features} command.
25808 Even if @value{GDBN} can accept a command while target is running,
25809 many commands that access the target do not work when the target is
25810 running. Therefore, asynchronous command execution is most useful
25811 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25812 it is possible to examine the state of one thread, while other threads
25815 When a given thread is running, MI commands that try to access the
25816 target in the context of that thread may not work, or may work only on
25817 some targets. In particular, commands that try to operate on thread's
25818 stack will not work, on any target. Commands that read memory, or
25819 modify breakpoints, may work or not work, depending on the target. Note
25820 that even commands that operate on global state, such as @code{print},
25821 @code{set}, and breakpoint commands, still access the target in the
25822 context of a specific thread, so frontend should try to find a
25823 stopped thread and perform the operation on that thread (using the
25824 @samp{--thread} option).
25826 Which commands will work in the context of a running thread is
25827 highly target dependent. However, the two commands
25828 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25829 to find the state of a thread, will always work.
25831 @node Thread groups
25832 @subsection Thread groups
25833 @value{GDBN} may be used to debug several processes at the same time.
25834 On some platfroms, @value{GDBN} may support debugging of several
25835 hardware systems, each one having several cores with several different
25836 processes running on each core. This section describes the MI
25837 mechanism to support such debugging scenarios.
25839 The key observation is that regardless of the structure of the
25840 target, MI can have a global list of threads, because most commands that
25841 accept the @samp{--thread} option do not need to know what process that
25842 thread belongs to. Therefore, it is not necessary to introduce
25843 neither additional @samp{--process} option, nor an notion of the
25844 current process in the MI interface. The only strictly new feature
25845 that is required is the ability to find how the threads are grouped
25848 To allow the user to discover such grouping, and to support arbitrary
25849 hierarchy of machines/cores/processes, MI introduces the concept of a
25850 @dfn{thread group}. Thread group is a collection of threads and other
25851 thread groups. A thread group always has a string identifier, a type,
25852 and may have additional attributes specific to the type. A new
25853 command, @code{-list-thread-groups}, returns the list of top-level
25854 thread groups, which correspond to processes that @value{GDBN} is
25855 debugging at the moment. By passing an identifier of a thread group
25856 to the @code{-list-thread-groups} command, it is possible to obtain
25857 the members of specific thread group.
25859 To allow the user to easily discover processes, and other objects, he
25860 wishes to debug, a concept of @dfn{available thread group} is
25861 introduced. Available thread group is an thread group that
25862 @value{GDBN} is not debugging, but that can be attached to, using the
25863 @code{-target-attach} command. The list of available top-level thread
25864 groups can be obtained using @samp{-list-thread-groups --available}.
25865 In general, the content of a thread group may be only retrieved only
25866 after attaching to that thread group.
25868 Thread groups are related to inferiors (@pxref{Inferiors and
25869 Programs}). Each inferior corresponds to a thread group of a special
25870 type @samp{process}, and some additional operations are permitted on
25871 such thread groups.
25873 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25874 @node GDB/MI Command Syntax
25875 @section @sc{gdb/mi} Command Syntax
25878 * GDB/MI Input Syntax::
25879 * GDB/MI Output Syntax::
25882 @node GDB/MI Input Syntax
25883 @subsection @sc{gdb/mi} Input Syntax
25885 @cindex input syntax for @sc{gdb/mi}
25886 @cindex @sc{gdb/mi}, input syntax
25888 @item @var{command} @expansion{}
25889 @code{@var{cli-command} | @var{mi-command}}
25891 @item @var{cli-command} @expansion{}
25892 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25893 @var{cli-command} is any existing @value{GDBN} CLI command.
25895 @item @var{mi-command} @expansion{}
25896 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25897 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25899 @item @var{token} @expansion{}
25900 "any sequence of digits"
25902 @item @var{option} @expansion{}
25903 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25905 @item @var{parameter} @expansion{}
25906 @code{@var{non-blank-sequence} | @var{c-string}}
25908 @item @var{operation} @expansion{}
25909 @emph{any of the operations described in this chapter}
25911 @item @var{non-blank-sequence} @expansion{}
25912 @emph{anything, provided it doesn't contain special characters such as
25913 "-", @var{nl}, """ and of course " "}
25915 @item @var{c-string} @expansion{}
25916 @code{""" @var{seven-bit-iso-c-string-content} """}
25918 @item @var{nl} @expansion{}
25927 The CLI commands are still handled by the @sc{mi} interpreter; their
25928 output is described below.
25931 The @code{@var{token}}, when present, is passed back when the command
25935 Some @sc{mi} commands accept optional arguments as part of the parameter
25936 list. Each option is identified by a leading @samp{-} (dash) and may be
25937 followed by an optional argument parameter. Options occur first in the
25938 parameter list and can be delimited from normal parameters using
25939 @samp{--} (this is useful when some parameters begin with a dash).
25946 We want easy access to the existing CLI syntax (for debugging).
25949 We want it to be easy to spot a @sc{mi} operation.
25952 @node GDB/MI Output Syntax
25953 @subsection @sc{gdb/mi} Output Syntax
25955 @cindex output syntax of @sc{gdb/mi}
25956 @cindex @sc{gdb/mi}, output syntax
25957 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25958 followed, optionally, by a single result record. This result record
25959 is for the most recent command. The sequence of output records is
25960 terminated by @samp{(gdb)}.
25962 If an input command was prefixed with a @code{@var{token}} then the
25963 corresponding output for that command will also be prefixed by that same
25967 @item @var{output} @expansion{}
25968 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25970 @item @var{result-record} @expansion{}
25971 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25973 @item @var{out-of-band-record} @expansion{}
25974 @code{@var{async-record} | @var{stream-record}}
25976 @item @var{async-record} @expansion{}
25977 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25979 @item @var{exec-async-output} @expansion{}
25980 @code{[ @var{token} ] "*" @var{async-output}}
25982 @item @var{status-async-output} @expansion{}
25983 @code{[ @var{token} ] "+" @var{async-output}}
25985 @item @var{notify-async-output} @expansion{}
25986 @code{[ @var{token} ] "=" @var{async-output}}
25988 @item @var{async-output} @expansion{}
25989 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25991 @item @var{result-class} @expansion{}
25992 @code{"done" | "running" | "connected" | "error" | "exit"}
25994 @item @var{async-class} @expansion{}
25995 @code{"stopped" | @var{others}} (where @var{others} will be added
25996 depending on the needs---this is still in development).
25998 @item @var{result} @expansion{}
25999 @code{ @var{variable} "=" @var{value}}
26001 @item @var{variable} @expansion{}
26002 @code{ @var{string} }
26004 @item @var{value} @expansion{}
26005 @code{ @var{const} | @var{tuple} | @var{list} }
26007 @item @var{const} @expansion{}
26008 @code{@var{c-string}}
26010 @item @var{tuple} @expansion{}
26011 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26013 @item @var{list} @expansion{}
26014 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26015 @var{result} ( "," @var{result} )* "]" }
26017 @item @var{stream-record} @expansion{}
26018 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26020 @item @var{console-stream-output} @expansion{}
26021 @code{"~" @var{c-string}}
26023 @item @var{target-stream-output} @expansion{}
26024 @code{"@@" @var{c-string}}
26026 @item @var{log-stream-output} @expansion{}
26027 @code{"&" @var{c-string}}
26029 @item @var{nl} @expansion{}
26032 @item @var{token} @expansion{}
26033 @emph{any sequence of digits}.
26041 All output sequences end in a single line containing a period.
26044 The @code{@var{token}} is from the corresponding request. Note that
26045 for all async output, while the token is allowed by the grammar and
26046 may be output by future versions of @value{GDBN} for select async
26047 output messages, it is generally omitted. Frontends should treat
26048 all async output as reporting general changes in the state of the
26049 target and there should be no need to associate async output to any
26053 @cindex status output in @sc{gdb/mi}
26054 @var{status-async-output} contains on-going status information about the
26055 progress of a slow operation. It can be discarded. All status output is
26056 prefixed by @samp{+}.
26059 @cindex async output in @sc{gdb/mi}
26060 @var{exec-async-output} contains asynchronous state change on the target
26061 (stopped, started, disappeared). All async output is prefixed by
26065 @cindex notify output in @sc{gdb/mi}
26066 @var{notify-async-output} contains supplementary information that the
26067 client should handle (e.g., a new breakpoint information). All notify
26068 output is prefixed by @samp{=}.
26071 @cindex console output in @sc{gdb/mi}
26072 @var{console-stream-output} is output that should be displayed as is in the
26073 console. It is the textual response to a CLI command. All the console
26074 output is prefixed by @samp{~}.
26077 @cindex target output in @sc{gdb/mi}
26078 @var{target-stream-output} is the output produced by the target program.
26079 All the target output is prefixed by @samp{@@}.
26082 @cindex log output in @sc{gdb/mi}
26083 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26084 instance messages that should be displayed as part of an error log. All
26085 the log output is prefixed by @samp{&}.
26088 @cindex list output in @sc{gdb/mi}
26089 New @sc{gdb/mi} commands should only output @var{lists} containing
26095 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26096 details about the various output records.
26098 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26099 @node GDB/MI Compatibility with CLI
26100 @section @sc{gdb/mi} Compatibility with CLI
26102 @cindex compatibility, @sc{gdb/mi} and CLI
26103 @cindex @sc{gdb/mi}, compatibility with CLI
26105 For the developers convenience CLI commands can be entered directly,
26106 but there may be some unexpected behaviour. For example, commands
26107 that query the user will behave as if the user replied yes, breakpoint
26108 command lists are not executed and some CLI commands, such as
26109 @code{if}, @code{when} and @code{define}, prompt for further input with
26110 @samp{>}, which is not valid MI output.
26112 This feature may be removed at some stage in the future and it is
26113 recommended that front ends use the @code{-interpreter-exec} command
26114 (@pxref{-interpreter-exec}).
26116 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26117 @node GDB/MI Development and Front Ends
26118 @section @sc{gdb/mi} Development and Front Ends
26119 @cindex @sc{gdb/mi} development
26121 The application which takes the MI output and presents the state of the
26122 program being debugged to the user is called a @dfn{front end}.
26124 Although @sc{gdb/mi} is still incomplete, it is currently being used
26125 by a variety of front ends to @value{GDBN}. This makes it difficult
26126 to introduce new functionality without breaking existing usage. This
26127 section tries to minimize the problems by describing how the protocol
26130 Some changes in MI need not break a carefully designed front end, and
26131 for these the MI version will remain unchanged. The following is a
26132 list of changes that may occur within one level, so front ends should
26133 parse MI output in a way that can handle them:
26137 New MI commands may be added.
26140 New fields may be added to the output of any MI command.
26143 The range of values for fields with specified values, e.g.,
26144 @code{in_scope} (@pxref{-var-update}) may be extended.
26146 @c The format of field's content e.g type prefix, may change so parse it
26147 @c at your own risk. Yes, in general?
26149 @c The order of fields may change? Shouldn't really matter but it might
26150 @c resolve inconsistencies.
26153 If the changes are likely to break front ends, the MI version level
26154 will be increased by one. This will allow the front end to parse the
26155 output according to the MI version. Apart from mi0, new versions of
26156 @value{GDBN} will not support old versions of MI and it will be the
26157 responsibility of the front end to work with the new one.
26159 @c Starting with mi3, add a new command -mi-version that prints the MI
26162 The best way to avoid unexpected changes in MI that might break your front
26163 end is to make your project known to @value{GDBN} developers and
26164 follow development on @email{gdb@@sourceware.org} and
26165 @email{gdb-patches@@sourceware.org}.
26166 @cindex mailing lists
26168 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26169 @node GDB/MI Output Records
26170 @section @sc{gdb/mi} Output Records
26173 * GDB/MI Result Records::
26174 * GDB/MI Stream Records::
26175 * GDB/MI Async Records::
26176 * GDB/MI Frame Information::
26177 * GDB/MI Thread Information::
26178 * GDB/MI Ada Exception Information::
26181 @node GDB/MI Result Records
26182 @subsection @sc{gdb/mi} Result Records
26184 @cindex result records in @sc{gdb/mi}
26185 @cindex @sc{gdb/mi}, result records
26186 In addition to a number of out-of-band notifications, the response to a
26187 @sc{gdb/mi} command includes one of the following result indications:
26191 @item "^done" [ "," @var{results} ]
26192 The synchronous operation was successful, @code{@var{results}} are the return
26197 This result record is equivalent to @samp{^done}. Historically, it
26198 was output instead of @samp{^done} if the command has resumed the
26199 target. This behaviour is maintained for backward compatibility, but
26200 all frontends should treat @samp{^done} and @samp{^running}
26201 identically and rely on the @samp{*running} output record to determine
26202 which threads are resumed.
26206 @value{GDBN} has connected to a remote target.
26208 @item "^error" "," @var{c-string}
26210 The operation failed. The @code{@var{c-string}} contains the corresponding
26215 @value{GDBN} has terminated.
26219 @node GDB/MI Stream Records
26220 @subsection @sc{gdb/mi} Stream Records
26222 @cindex @sc{gdb/mi}, stream records
26223 @cindex stream records in @sc{gdb/mi}
26224 @value{GDBN} internally maintains a number of output streams: the console, the
26225 target, and the log. The output intended for each of these streams is
26226 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26228 Each stream record begins with a unique @dfn{prefix character} which
26229 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26230 Syntax}). In addition to the prefix, each stream record contains a
26231 @code{@var{string-output}}. This is either raw text (with an implicit new
26232 line) or a quoted C string (which does not contain an implicit newline).
26235 @item "~" @var{string-output}
26236 The console output stream contains text that should be displayed in the
26237 CLI console window. It contains the textual responses to CLI commands.
26239 @item "@@" @var{string-output}
26240 The target output stream contains any textual output from the running
26241 target. This is only present when GDB's event loop is truly
26242 asynchronous, which is currently only the case for remote targets.
26244 @item "&" @var{string-output}
26245 The log stream contains debugging messages being produced by @value{GDBN}'s
26249 @node GDB/MI Async Records
26250 @subsection @sc{gdb/mi} Async Records
26252 @cindex async records in @sc{gdb/mi}
26253 @cindex @sc{gdb/mi}, async records
26254 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26255 additional changes that have occurred. Those changes can either be a
26256 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26257 target activity (e.g., target stopped).
26259 The following is the list of possible async records:
26263 @item *running,thread-id="@var{thread}"
26264 The target is now running. The @var{thread} field tells which
26265 specific thread is now running, and can be @samp{all} if all threads
26266 are running. The frontend should assume that no interaction with a
26267 running thread is possible after this notification is produced.
26268 The frontend should not assume that this notification is output
26269 only once for any command. @value{GDBN} may emit this notification
26270 several times, either for different threads, because it cannot resume
26271 all threads together, or even for a single thread, if the thread must
26272 be stepped though some code before letting it run freely.
26274 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26275 The target has stopped. The @var{reason} field can have one of the
26279 @item breakpoint-hit
26280 A breakpoint was reached.
26281 @item watchpoint-trigger
26282 A watchpoint was triggered.
26283 @item read-watchpoint-trigger
26284 A read watchpoint was triggered.
26285 @item access-watchpoint-trigger
26286 An access watchpoint was triggered.
26287 @item function-finished
26288 An -exec-finish or similar CLI command was accomplished.
26289 @item location-reached
26290 An -exec-until or similar CLI command was accomplished.
26291 @item watchpoint-scope
26292 A watchpoint has gone out of scope.
26293 @item end-stepping-range
26294 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26295 similar CLI command was accomplished.
26296 @item exited-signalled
26297 The inferior exited because of a signal.
26299 The inferior exited.
26300 @item exited-normally
26301 The inferior exited normally.
26302 @item signal-received
26303 A signal was received by the inferior.
26305 The inferior has stopped due to a library being loaded or unloaded.
26306 This can only happen when @code{stop-on-solib-events} (@pxref{Files})
26309 The inferior has forked. This is reported when @code{catch fork}
26310 (@pxref{Set Catchpoints}) has been used.
26312 The inferior has vforked. This is reported in when @code{catch vfork}
26313 (@pxref{Set Catchpoints}) has been used.
26314 @item syscall-entry
26315 The inferior entered a system call. This is reported when @code{catch
26316 syscall} (@pxref{Set Catchpoints}) has been used.
26317 @item syscall-entry
26318 The inferior returned from a system call. This is reported when
26319 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26321 The inferior called @code{exec}. This is reported when @code{catch exec}
26322 (@pxref{Set Catchpoints}) has been used.
26325 The @var{id} field identifies the thread that directly caused the stop
26326 -- for example by hitting a breakpoint. Depending on whether all-stop
26327 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26328 stop all threads, or only the thread that directly triggered the stop.
26329 If all threads are stopped, the @var{stopped} field will have the
26330 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26331 field will be a list of thread identifiers. Presently, this list will
26332 always include a single thread, but frontend should be prepared to see
26333 several threads in the list. The @var{core} field reports the
26334 processor core on which the stop event has happened. This field may be absent
26335 if such information is not available.
26337 @item =thread-group-added,id="@var{id}"
26338 @itemx =thread-group-removed,id="@var{id}"
26339 A thread group was either added or removed. The @var{id} field
26340 contains the @value{GDBN} identifier of the thread group. When a thread
26341 group is added, it generally might not be associated with a running
26342 process. When a thread group is removed, its id becomes invalid and
26343 cannot be used in any way.
26345 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26346 A thread group became associated with a running program,
26347 either because the program was just started or the thread group
26348 was attached to a program. The @var{id} field contains the
26349 @value{GDBN} identifier of the thread group. The @var{pid} field
26350 contains process identifier, specific to the operating system.
26352 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26353 A thread group is no longer associated with a running program,
26354 either because the program has exited, or because it was detached
26355 from. The @var{id} field contains the @value{GDBN} identifier of the
26356 thread group. @var{code} is the exit code of the inferior; it exists
26357 only when the inferior exited with some code.
26359 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26360 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26361 A thread either was created, or has exited. The @var{id} field
26362 contains the @value{GDBN} identifier of the thread. The @var{gid}
26363 field identifies the thread group this thread belongs to.
26365 @item =thread-selected,id="@var{id}"
26366 Informs that the selected thread was changed as result of the last
26367 command. This notification is not emitted as result of @code{-thread-select}
26368 command but is emitted whenever an MI command that is not documented
26369 to change the selected thread actually changes it. In particular,
26370 invoking, directly or indirectly (via user-defined command), the CLI
26371 @code{thread} command, will generate this notification.
26373 We suggest that in response to this notification, front ends
26374 highlight the selected thread and cause subsequent commands to apply to
26377 @item =library-loaded,...
26378 Reports that a new library file was loaded by the program. This
26379 notification has 4 fields---@var{id}, @var{target-name},
26380 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26381 opaque identifier of the library. For remote debugging case,
26382 @var{target-name} and @var{host-name} fields give the name of the
26383 library file on the target, and on the host respectively. For native
26384 debugging, both those fields have the same value. The
26385 @var{symbols-loaded} field is emitted only for backward compatibility
26386 and should not be relied on to convey any useful information. The
26387 @var{thread-group} field, if present, specifies the id of the thread
26388 group in whose context the library was loaded. If the field is
26389 absent, it means the library was loaded in the context of all present
26392 @item =library-unloaded,...
26393 Reports that a library was unloaded by the program. This notification
26394 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26395 the same meaning as for the @code{=library-loaded} notification.
26396 The @var{thread-group} field, if present, specifies the id of the
26397 thread group in whose context the library was unloaded. If the field is
26398 absent, it means the library was unloaded in the context of all present
26401 @item =breakpoint-created,bkpt=@{...@}
26402 @itemx =breakpoint-modified,bkpt=@{...@}
26403 @itemx =breakpoint-deleted,bkpt=@{...@}
26404 Reports that a breakpoint was created, modified, or deleted,
26405 respectively. Only user-visible breakpoints are reported to the MI
26408 The @var{bkpt} argument is of the same form as returned by the various
26409 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26411 Note that if a breakpoint is emitted in the result record of a
26412 command, then it will not also be emitted in an async record.
26416 @node GDB/MI Frame Information
26417 @subsection @sc{gdb/mi} Frame Information
26419 Response from many MI commands includes an information about stack
26420 frame. This information is a tuple that may have the following
26425 The level of the stack frame. The innermost frame has the level of
26426 zero. This field is always present.
26429 The name of the function corresponding to the frame. This field may
26430 be absent if @value{GDBN} is unable to determine the function name.
26433 The code address for the frame. This field is always present.
26436 The name of the source files that correspond to the frame's code
26437 address. This field may be absent.
26440 The source line corresponding to the frames' code address. This field
26444 The name of the binary file (either executable or shared library) the
26445 corresponds to the frame's code address. This field may be absent.
26449 @node GDB/MI Thread Information
26450 @subsection @sc{gdb/mi} Thread Information
26452 Whenever @value{GDBN} has to report an information about a thread, it
26453 uses a tuple with the following fields:
26457 The numeric id assigned to the thread by @value{GDBN}. This field is
26461 Target-specific string identifying the thread. This field is always present.
26464 Additional information about the thread provided by the target.
26465 It is supposed to be human-readable and not interpreted by the
26466 frontend. This field is optional.
26469 Either @samp{stopped} or @samp{running}, depending on whether the
26470 thread is presently running. This field is always present.
26473 The value of this field is an integer number of the processor core the
26474 thread was last seen on. This field is optional.
26477 @node GDB/MI Ada Exception Information
26478 @subsection @sc{gdb/mi} Ada Exception Information
26480 Whenever a @code{*stopped} record is emitted because the program
26481 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26482 @value{GDBN} provides the name of the exception that was raised via
26483 the @code{exception-name} field.
26485 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26486 @node GDB/MI Simple Examples
26487 @section Simple Examples of @sc{gdb/mi} Interaction
26488 @cindex @sc{gdb/mi}, simple examples
26490 This subsection presents several simple examples of interaction using
26491 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26492 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26493 the output received from @sc{gdb/mi}.
26495 Note the line breaks shown in the examples are here only for
26496 readability, they don't appear in the real output.
26498 @subheading Setting a Breakpoint
26500 Setting a breakpoint generates synchronous output which contains detailed
26501 information of the breakpoint.
26504 -> -break-insert main
26505 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26506 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26507 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26511 @subheading Program Execution
26513 Program execution generates asynchronous records and MI gives the
26514 reason that execution stopped.
26520 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26521 frame=@{addr="0x08048564",func="main",
26522 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26523 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26528 <- *stopped,reason="exited-normally"
26532 @subheading Quitting @value{GDBN}
26534 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26542 Please note that @samp{^exit} is printed immediately, but it might
26543 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26544 performs necessary cleanups, including killing programs being debugged
26545 or disconnecting from debug hardware, so the frontend should wait till
26546 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26547 fails to exit in reasonable time.
26549 @subheading A Bad Command
26551 Here's what happens if you pass a non-existent command:
26555 <- ^error,msg="Undefined MI command: rubbish"
26560 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26561 @node GDB/MI Command Description Format
26562 @section @sc{gdb/mi} Command Description Format
26564 The remaining sections describe blocks of commands. Each block of
26565 commands is laid out in a fashion similar to this section.
26567 @subheading Motivation
26569 The motivation for this collection of commands.
26571 @subheading Introduction
26573 A brief introduction to this collection of commands as a whole.
26575 @subheading Commands
26577 For each command in the block, the following is described:
26579 @subsubheading Synopsis
26582 -command @var{args}@dots{}
26585 @subsubheading Result
26587 @subsubheading @value{GDBN} Command
26589 The corresponding @value{GDBN} CLI command(s), if any.
26591 @subsubheading Example
26593 Example(s) formatted for readability. Some of the described commands have
26594 not been implemented yet and these are labeled N.A.@: (not available).
26597 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26598 @node GDB/MI Breakpoint Commands
26599 @section @sc{gdb/mi} Breakpoint Commands
26601 @cindex breakpoint commands for @sc{gdb/mi}
26602 @cindex @sc{gdb/mi}, breakpoint commands
26603 This section documents @sc{gdb/mi} commands for manipulating
26606 @subheading The @code{-break-after} Command
26607 @findex -break-after
26609 @subsubheading Synopsis
26612 -break-after @var{number} @var{count}
26615 The breakpoint number @var{number} is not in effect until it has been
26616 hit @var{count} times. To see how this is reflected in the output of
26617 the @samp{-break-list} command, see the description of the
26618 @samp{-break-list} command below.
26620 @subsubheading @value{GDBN} Command
26622 The corresponding @value{GDBN} command is @samp{ignore}.
26624 @subsubheading Example
26629 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26630 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26631 fullname="/home/foo/hello.c",line="5",times="0"@}
26638 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26639 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26640 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26641 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26642 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26643 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26644 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26645 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26646 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26647 line="5",times="0",ignore="3"@}]@}
26652 @subheading The @code{-break-catch} Command
26653 @findex -break-catch
26656 @subheading The @code{-break-commands} Command
26657 @findex -break-commands
26659 @subsubheading Synopsis
26662 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26665 Specifies the CLI commands that should be executed when breakpoint
26666 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26667 are the commands. If no command is specified, any previously-set
26668 commands are cleared. @xref{Break Commands}. Typical use of this
26669 functionality is tracing a program, that is, printing of values of
26670 some variables whenever breakpoint is hit and then continuing.
26672 @subsubheading @value{GDBN} Command
26674 The corresponding @value{GDBN} command is @samp{commands}.
26676 @subsubheading Example
26681 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26682 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26683 fullname="/home/foo/hello.c",line="5",times="0"@}
26685 -break-commands 1 "print v" "continue"
26690 @subheading The @code{-break-condition} Command
26691 @findex -break-condition
26693 @subsubheading Synopsis
26696 -break-condition @var{number} @var{expr}
26699 Breakpoint @var{number} will stop the program only if the condition in
26700 @var{expr} is true. The condition becomes part of the
26701 @samp{-break-list} output (see the description of the @samp{-break-list}
26704 @subsubheading @value{GDBN} Command
26706 The corresponding @value{GDBN} command is @samp{condition}.
26708 @subsubheading Example
26712 -break-condition 1 1
26716 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26717 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26718 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26719 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26720 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26721 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26722 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26723 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26724 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26725 line="5",cond="1",times="0",ignore="3"@}]@}
26729 @subheading The @code{-break-delete} Command
26730 @findex -break-delete
26732 @subsubheading Synopsis
26735 -break-delete ( @var{breakpoint} )+
26738 Delete the breakpoint(s) whose number(s) are specified in the argument
26739 list. This is obviously reflected in the breakpoint list.
26741 @subsubheading @value{GDBN} Command
26743 The corresponding @value{GDBN} command is @samp{delete}.
26745 @subsubheading Example
26753 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26754 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26755 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26756 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26757 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26758 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26759 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26764 @subheading The @code{-break-disable} Command
26765 @findex -break-disable
26767 @subsubheading Synopsis
26770 -break-disable ( @var{breakpoint} )+
26773 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26774 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26776 @subsubheading @value{GDBN} Command
26778 The corresponding @value{GDBN} command is @samp{disable}.
26780 @subsubheading Example
26788 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26789 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26790 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26791 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26792 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26793 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26794 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26795 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26796 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26797 line="5",times="0"@}]@}
26801 @subheading The @code{-break-enable} Command
26802 @findex -break-enable
26804 @subsubheading Synopsis
26807 -break-enable ( @var{breakpoint} )+
26810 Enable (previously disabled) @var{breakpoint}(s).
26812 @subsubheading @value{GDBN} Command
26814 The corresponding @value{GDBN} command is @samp{enable}.
26816 @subsubheading Example
26824 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26825 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26826 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26827 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26828 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26829 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26830 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26831 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26832 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26833 line="5",times="0"@}]@}
26837 @subheading The @code{-break-info} Command
26838 @findex -break-info
26840 @subsubheading Synopsis
26843 -break-info @var{breakpoint}
26847 Get information about a single breakpoint.
26849 @subsubheading @value{GDBN} Command
26851 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26853 @subsubheading Example
26856 @subheading The @code{-break-insert} Command
26857 @findex -break-insert
26859 @subsubheading Synopsis
26862 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26863 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26864 [ -p @var{thread} ] [ @var{location} ]
26868 If specified, @var{location}, can be one of:
26875 @item filename:linenum
26876 @item filename:function
26880 The possible optional parameters of this command are:
26884 Insert a temporary breakpoint.
26886 Insert a hardware breakpoint.
26887 @item -c @var{condition}
26888 Make the breakpoint conditional on @var{condition}.
26889 @item -i @var{ignore-count}
26890 Initialize the @var{ignore-count}.
26892 If @var{location} cannot be parsed (for example if it
26893 refers to unknown files or functions), create a pending
26894 breakpoint. Without this flag, @value{GDBN} will report
26895 an error, and won't create a breakpoint, if @var{location}
26898 Create a disabled breakpoint.
26900 Create a tracepoint. @xref{Tracepoints}. When this parameter
26901 is used together with @samp{-h}, a fast tracepoint is created.
26904 @subsubheading Result
26906 The result is in the form:
26909 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26910 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26911 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26912 times="@var{times}"@}
26916 where @var{number} is the @value{GDBN} number for this breakpoint,
26917 @var{funcname} is the name of the function where the breakpoint was
26918 inserted, @var{filename} is the name of the source file which contains
26919 this function, @var{lineno} is the source line number within that file
26920 and @var{times} the number of times that the breakpoint has been hit
26921 (always 0 for -break-insert but may be greater for -break-info or -break-list
26922 which use the same output).
26924 Note: this format is open to change.
26925 @c An out-of-band breakpoint instead of part of the result?
26927 @subsubheading @value{GDBN} Command
26929 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26930 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26932 @subsubheading Example
26937 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26938 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26940 -break-insert -t foo
26941 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26942 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26945 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26946 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26947 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26948 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26949 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26950 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26951 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26952 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26953 addr="0x0001072c", func="main",file="recursive2.c",
26954 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26955 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26956 addr="0x00010774",func="foo",file="recursive2.c",
26957 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26959 -break-insert -r foo.*
26960 ~int foo(int, int);
26961 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26962 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26966 @subheading The @code{-break-list} Command
26967 @findex -break-list
26969 @subsubheading Synopsis
26975 Displays the list of inserted breakpoints, showing the following fields:
26979 number of the breakpoint
26981 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26983 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26986 is the breakpoint enabled or no: @samp{y} or @samp{n}
26988 memory location at which the breakpoint is set
26990 logical location of the breakpoint, expressed by function name, file
26993 number of times the breakpoint has been hit
26996 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26997 @code{body} field is an empty list.
26999 @subsubheading @value{GDBN} Command
27001 The corresponding @value{GDBN} command is @samp{info break}.
27003 @subsubheading Example
27008 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27009 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27010 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27011 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27012 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27013 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27014 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27015 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27016 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27017 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27018 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27019 line="13",times="0"@}]@}
27023 Here's an example of the result when there are no breakpoints:
27028 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27029 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27030 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27031 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27032 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27033 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27034 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27039 @subheading The @code{-break-passcount} Command
27040 @findex -break-passcount
27042 @subsubheading Synopsis
27045 -break-passcount @var{tracepoint-number} @var{passcount}
27048 Set the passcount for tracepoint @var{tracepoint-number} to
27049 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27050 is not a tracepoint, error is emitted. This corresponds to CLI
27051 command @samp{passcount}.
27053 @subheading The @code{-break-watch} Command
27054 @findex -break-watch
27056 @subsubheading Synopsis
27059 -break-watch [ -a | -r ]
27062 Create a watchpoint. With the @samp{-a} option it will create an
27063 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27064 read from or on a write to the memory location. With the @samp{-r}
27065 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27066 trigger only when the memory location is accessed for reading. Without
27067 either of the options, the watchpoint created is a regular watchpoint,
27068 i.e., it will trigger when the memory location is accessed for writing.
27069 @xref{Set Watchpoints, , Setting Watchpoints}.
27071 Note that @samp{-break-list} will report a single list of watchpoints and
27072 breakpoints inserted.
27074 @subsubheading @value{GDBN} Command
27076 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27079 @subsubheading Example
27081 Setting a watchpoint on a variable in the @code{main} function:
27086 ^done,wpt=@{number="2",exp="x"@}
27091 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27092 value=@{old="-268439212",new="55"@},
27093 frame=@{func="main",args=[],file="recursive2.c",
27094 fullname="/home/foo/bar/recursive2.c",line="5"@}
27098 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27099 the program execution twice: first for the variable changing value, then
27100 for the watchpoint going out of scope.
27105 ^done,wpt=@{number="5",exp="C"@}
27110 *stopped,reason="watchpoint-trigger",
27111 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27112 frame=@{func="callee4",args=[],
27113 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27114 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27119 *stopped,reason="watchpoint-scope",wpnum="5",
27120 frame=@{func="callee3",args=[@{name="strarg",
27121 value="0x11940 \"A string argument.\""@}],
27122 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27123 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27127 Listing breakpoints and watchpoints, at different points in the program
27128 execution. Note that once the watchpoint goes out of scope, it is
27134 ^done,wpt=@{number="2",exp="C"@}
27137 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27138 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27139 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27140 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27141 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27142 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27143 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27144 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27145 addr="0x00010734",func="callee4",
27146 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27147 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27148 bkpt=@{number="2",type="watchpoint",disp="keep",
27149 enabled="y",addr="",what="C",times="0"@}]@}
27154 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27155 value=@{old="-276895068",new="3"@},
27156 frame=@{func="callee4",args=[],
27157 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27158 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27161 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27162 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27163 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27164 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27165 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27166 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27167 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27168 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27169 addr="0x00010734",func="callee4",
27170 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27171 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27172 bkpt=@{number="2",type="watchpoint",disp="keep",
27173 enabled="y",addr="",what="C",times="-5"@}]@}
27177 ^done,reason="watchpoint-scope",wpnum="2",
27178 frame=@{func="callee3",args=[@{name="strarg",
27179 value="0x11940 \"A string argument.\""@}],
27180 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27181 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27184 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27185 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27186 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27187 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27188 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27189 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27190 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27191 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27192 addr="0x00010734",func="callee4",
27193 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27194 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27199 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27200 @node GDB/MI Program Context
27201 @section @sc{gdb/mi} Program Context
27203 @subheading The @code{-exec-arguments} Command
27204 @findex -exec-arguments
27207 @subsubheading Synopsis
27210 -exec-arguments @var{args}
27213 Set the inferior program arguments, to be used in the next
27216 @subsubheading @value{GDBN} Command
27218 The corresponding @value{GDBN} command is @samp{set args}.
27220 @subsubheading Example
27224 -exec-arguments -v word
27231 @subheading The @code{-exec-show-arguments} Command
27232 @findex -exec-show-arguments
27234 @subsubheading Synopsis
27237 -exec-show-arguments
27240 Print the arguments of the program.
27242 @subsubheading @value{GDBN} Command
27244 The corresponding @value{GDBN} command is @samp{show args}.
27246 @subsubheading Example
27251 @subheading The @code{-environment-cd} Command
27252 @findex -environment-cd
27254 @subsubheading Synopsis
27257 -environment-cd @var{pathdir}
27260 Set @value{GDBN}'s working directory.
27262 @subsubheading @value{GDBN} Command
27264 The corresponding @value{GDBN} command is @samp{cd}.
27266 @subsubheading Example
27270 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27276 @subheading The @code{-environment-directory} Command
27277 @findex -environment-directory
27279 @subsubheading Synopsis
27282 -environment-directory [ -r ] [ @var{pathdir} ]+
27285 Add directories @var{pathdir} to beginning of search path for source files.
27286 If the @samp{-r} option is used, the search path is reset to the default
27287 search path. If directories @var{pathdir} are supplied in addition to the
27288 @samp{-r} option, the search path is first reset and then addition
27290 Multiple directories may be specified, separated by blanks. Specifying
27291 multiple directories in a single command
27292 results in the directories added to the beginning of the
27293 search path in the same order they were presented in the command.
27294 If blanks are needed as
27295 part of a directory name, double-quotes should be used around
27296 the name. In the command output, the path will show up separated
27297 by the system directory-separator character. The directory-separator
27298 character must not be used
27299 in any directory name.
27300 If no directories are specified, the current search path is displayed.
27302 @subsubheading @value{GDBN} Command
27304 The corresponding @value{GDBN} command is @samp{dir}.
27306 @subsubheading Example
27310 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27311 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27313 -environment-directory ""
27314 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27316 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27317 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27319 -environment-directory -r
27320 ^done,source-path="$cdir:$cwd"
27325 @subheading The @code{-environment-path} Command
27326 @findex -environment-path
27328 @subsubheading Synopsis
27331 -environment-path [ -r ] [ @var{pathdir} ]+
27334 Add directories @var{pathdir} to beginning of search path for object files.
27335 If the @samp{-r} option is used, the search path is reset to the original
27336 search path that existed at gdb start-up. If directories @var{pathdir} are
27337 supplied in addition to the
27338 @samp{-r} option, the search path is first reset and then addition
27340 Multiple directories may be specified, separated by blanks. Specifying
27341 multiple directories in a single command
27342 results in the directories added to the beginning of the
27343 search path in the same order they were presented in the command.
27344 If blanks are needed as
27345 part of a directory name, double-quotes should be used around
27346 the name. In the command output, the path will show up separated
27347 by the system directory-separator character. The directory-separator
27348 character must not be used
27349 in any directory name.
27350 If no directories are specified, the current path is displayed.
27353 @subsubheading @value{GDBN} Command
27355 The corresponding @value{GDBN} command is @samp{path}.
27357 @subsubheading Example
27362 ^done,path="/usr/bin"
27364 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27365 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27367 -environment-path -r /usr/local/bin
27368 ^done,path="/usr/local/bin:/usr/bin"
27373 @subheading The @code{-environment-pwd} Command
27374 @findex -environment-pwd
27376 @subsubheading Synopsis
27382 Show the current working directory.
27384 @subsubheading @value{GDBN} Command
27386 The corresponding @value{GDBN} command is @samp{pwd}.
27388 @subsubheading Example
27393 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27397 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27398 @node GDB/MI Thread Commands
27399 @section @sc{gdb/mi} Thread Commands
27402 @subheading The @code{-thread-info} Command
27403 @findex -thread-info
27405 @subsubheading Synopsis
27408 -thread-info [ @var{thread-id} ]
27411 Reports information about either a specific thread, if
27412 the @var{thread-id} parameter is present, or about all
27413 threads. When printing information about all threads,
27414 also reports the current thread.
27416 @subsubheading @value{GDBN} Command
27418 The @samp{info thread} command prints the same information
27421 @subsubheading Result
27423 The result is a list of threads. The following attributes are
27424 defined for a given thread:
27428 This field exists only for the current thread. It has the value @samp{*}.
27431 The identifier that @value{GDBN} uses to refer to the thread.
27434 The identifier that the target uses to refer to the thread.
27437 Extra information about the thread, in a target-specific format. This
27441 The name of the thread. If the user specified a name using the
27442 @code{thread name} command, then this name is given. Otherwise, if
27443 @value{GDBN} can extract the thread name from the target, then that
27444 name is given. If @value{GDBN} cannot find the thread name, then this
27448 The stack frame currently executing in the thread.
27451 The thread's state. The @samp{state} field may have the following
27456 The thread is stopped. Frame information is available for stopped
27460 The thread is running. There's no frame information for running
27466 If @value{GDBN} can find the CPU core on which this thread is running,
27467 then this field is the core identifier. This field is optional.
27471 @subsubheading Example
27476 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27477 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27478 args=[]@},state="running"@},
27479 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27480 frame=@{level="0",addr="0x0804891f",func="foo",
27481 args=[@{name="i",value="10"@}],
27482 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27483 state="running"@}],
27484 current-thread-id="1"
27488 @subheading The @code{-thread-list-ids} Command
27489 @findex -thread-list-ids
27491 @subsubheading Synopsis
27497 Produces a list of the currently known @value{GDBN} thread ids. At the
27498 end of the list it also prints the total number of such threads.
27500 This command is retained for historical reasons, the
27501 @code{-thread-info} command should be used instead.
27503 @subsubheading @value{GDBN} Command
27505 Part of @samp{info threads} supplies the same information.
27507 @subsubheading Example
27512 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27513 current-thread-id="1",number-of-threads="3"
27518 @subheading The @code{-thread-select} Command
27519 @findex -thread-select
27521 @subsubheading Synopsis
27524 -thread-select @var{threadnum}
27527 Make @var{threadnum} the current thread. It prints the number of the new
27528 current thread, and the topmost frame for that thread.
27530 This command is deprecated in favor of explicitly using the
27531 @samp{--thread} option to each command.
27533 @subsubheading @value{GDBN} Command
27535 The corresponding @value{GDBN} command is @samp{thread}.
27537 @subsubheading Example
27544 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27545 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27549 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27550 number-of-threads="3"
27553 ^done,new-thread-id="3",
27554 frame=@{level="0",func="vprintf",
27555 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27556 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27560 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27561 @node GDB/MI Ada Tasking Commands
27562 @section @sc{gdb/mi} Ada Tasking Commands
27564 @subheading The @code{-ada-task-info} Command
27565 @findex -ada-task-info
27567 @subsubheading Synopsis
27570 -ada-task-info [ @var{task-id} ]
27573 Reports information about either a specific Ada task, if the
27574 @var{task-id} parameter is present, or about all Ada tasks.
27576 @subsubheading @value{GDBN} Command
27578 The @samp{info tasks} command prints the same information
27579 about all Ada tasks (@pxref{Ada Tasks}).
27581 @subsubheading Result
27583 The result is a table of Ada tasks. The following columns are
27584 defined for each Ada task:
27588 This field exists only for the current thread. It has the value @samp{*}.
27591 The identifier that @value{GDBN} uses to refer to the Ada task.
27594 The identifier that the target uses to refer to the Ada task.
27597 The identifier of the thread corresponding to the Ada task.
27599 This field should always exist, as Ada tasks are always implemented
27600 on top of a thread. But if @value{GDBN} cannot find this corresponding
27601 thread for any reason, the field is omitted.
27604 This field exists only when the task was created by another task.
27605 In this case, it provides the ID of the parent task.
27608 The base priority of the task.
27611 The current state of the task. For a detailed description of the
27612 possible states, see @ref{Ada Tasks}.
27615 The name of the task.
27619 @subsubheading Example
27623 ^done,tasks=@{nr_rows="3",nr_cols="8",
27624 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27625 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27626 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27627 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27628 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27629 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27630 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27631 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27632 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27633 state="Child Termination Wait",name="main_task"@}]@}
27637 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27638 @node GDB/MI Program Execution
27639 @section @sc{gdb/mi} Program Execution
27641 These are the asynchronous commands which generate the out-of-band
27642 record @samp{*stopped}. Currently @value{GDBN} only really executes
27643 asynchronously with remote targets and this interaction is mimicked in
27646 @subheading The @code{-exec-continue} Command
27647 @findex -exec-continue
27649 @subsubheading Synopsis
27652 -exec-continue [--reverse] [--all|--thread-group N]
27655 Resumes the execution of the inferior program, which will continue
27656 to execute until it reaches a debugger stop event. If the
27657 @samp{--reverse} option is specified, execution resumes in reverse until
27658 it reaches a stop event. Stop events may include
27661 breakpoints or watchpoints
27663 signals or exceptions
27665 the end of the process (or its beginning under @samp{--reverse})
27667 the end or beginning of a replay log if one is being used.
27669 In all-stop mode (@pxref{All-Stop
27670 Mode}), may resume only one thread, or all threads, depending on the
27671 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27672 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27673 ignored in all-stop mode. If the @samp{--thread-group} options is
27674 specified, then all threads in that thread group are resumed.
27676 @subsubheading @value{GDBN} Command
27678 The corresponding @value{GDBN} corresponding is @samp{continue}.
27680 @subsubheading Example
27687 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27688 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27694 @subheading The @code{-exec-finish} Command
27695 @findex -exec-finish
27697 @subsubheading Synopsis
27700 -exec-finish [--reverse]
27703 Resumes the execution of the inferior program until the current
27704 function is exited. Displays the results returned by the function.
27705 If the @samp{--reverse} option is specified, resumes the reverse
27706 execution of the inferior program until the point where current
27707 function was called.
27709 @subsubheading @value{GDBN} Command
27711 The corresponding @value{GDBN} command is @samp{finish}.
27713 @subsubheading Example
27715 Function returning @code{void}.
27722 *stopped,reason="function-finished",frame=@{func="main",args=[],
27723 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27727 Function returning other than @code{void}. The name of the internal
27728 @value{GDBN} variable storing the result is printed, together with the
27735 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27736 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27737 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27738 gdb-result-var="$1",return-value="0"
27743 @subheading The @code{-exec-interrupt} Command
27744 @findex -exec-interrupt
27746 @subsubheading Synopsis
27749 -exec-interrupt [--all|--thread-group N]
27752 Interrupts the background execution of the target. Note how the token
27753 associated with the stop message is the one for the execution command
27754 that has been interrupted. The token for the interrupt itself only
27755 appears in the @samp{^done} output. If the user is trying to
27756 interrupt a non-running program, an error message will be printed.
27758 Note that when asynchronous execution is enabled, this command is
27759 asynchronous just like other execution commands. That is, first the
27760 @samp{^done} response will be printed, and the target stop will be
27761 reported after that using the @samp{*stopped} notification.
27763 In non-stop mode, only the context thread is interrupted by default.
27764 All threads (in all inferiors) will be interrupted if the
27765 @samp{--all} option is specified. If the @samp{--thread-group}
27766 option is specified, all threads in that group will be interrupted.
27768 @subsubheading @value{GDBN} Command
27770 The corresponding @value{GDBN} command is @samp{interrupt}.
27772 @subsubheading Example
27783 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27784 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27785 fullname="/home/foo/bar/try.c",line="13"@}
27790 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27794 @subheading The @code{-exec-jump} Command
27797 @subsubheading Synopsis
27800 -exec-jump @var{location}
27803 Resumes execution of the inferior program at the location specified by
27804 parameter. @xref{Specify Location}, for a description of the
27805 different forms of @var{location}.
27807 @subsubheading @value{GDBN} Command
27809 The corresponding @value{GDBN} command is @samp{jump}.
27811 @subsubheading Example
27814 -exec-jump foo.c:10
27815 *running,thread-id="all"
27820 @subheading The @code{-exec-next} Command
27823 @subsubheading Synopsis
27826 -exec-next [--reverse]
27829 Resumes execution of the inferior program, stopping when the beginning
27830 of the next source line is reached.
27832 If the @samp{--reverse} option is specified, resumes reverse execution
27833 of the inferior program, stopping at the beginning of the previous
27834 source line. If you issue this command on the first line of a
27835 function, it will take you back to the caller of that function, to the
27836 source line where the function was called.
27839 @subsubheading @value{GDBN} Command
27841 The corresponding @value{GDBN} command is @samp{next}.
27843 @subsubheading Example
27849 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27854 @subheading The @code{-exec-next-instruction} Command
27855 @findex -exec-next-instruction
27857 @subsubheading Synopsis
27860 -exec-next-instruction [--reverse]
27863 Executes one machine instruction. If the instruction is a function
27864 call, continues until the function returns. If the program stops at an
27865 instruction in the middle of a source line, the address will be
27868 If the @samp{--reverse} option is specified, resumes reverse execution
27869 of the inferior program, stopping at the previous instruction. If the
27870 previously executed instruction was a return from another function,
27871 it will continue to execute in reverse until the call to that function
27872 (from the current stack frame) is reached.
27874 @subsubheading @value{GDBN} Command
27876 The corresponding @value{GDBN} command is @samp{nexti}.
27878 @subsubheading Example
27882 -exec-next-instruction
27886 *stopped,reason="end-stepping-range",
27887 addr="0x000100d4",line="5",file="hello.c"
27892 @subheading The @code{-exec-return} Command
27893 @findex -exec-return
27895 @subsubheading Synopsis
27901 Makes current function return immediately. Doesn't execute the inferior.
27902 Displays the new current frame.
27904 @subsubheading @value{GDBN} Command
27906 The corresponding @value{GDBN} command is @samp{return}.
27908 @subsubheading Example
27912 200-break-insert callee4
27913 200^done,bkpt=@{number="1",addr="0x00010734",
27914 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27919 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27920 frame=@{func="callee4",args=[],
27921 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27922 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27928 111^done,frame=@{level="0",func="callee3",
27929 args=[@{name="strarg",
27930 value="0x11940 \"A string argument.\""@}],
27931 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27932 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27937 @subheading The @code{-exec-run} Command
27940 @subsubheading Synopsis
27943 -exec-run [--all | --thread-group N]
27946 Starts execution of the inferior from the beginning. The inferior
27947 executes until either a breakpoint is encountered or the program
27948 exits. In the latter case the output will include an exit code, if
27949 the program has exited exceptionally.
27951 When no option is specified, the current inferior is started. If the
27952 @samp{--thread-group} option is specified, it should refer to a thread
27953 group of type @samp{process}, and that thread group will be started.
27954 If the @samp{--all} option is specified, then all inferiors will be started.
27956 @subsubheading @value{GDBN} Command
27958 The corresponding @value{GDBN} command is @samp{run}.
27960 @subsubheading Examples
27965 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27970 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27971 frame=@{func="main",args=[],file="recursive2.c",
27972 fullname="/home/foo/bar/recursive2.c",line="4"@}
27977 Program exited normally:
27985 *stopped,reason="exited-normally"
27990 Program exited exceptionally:
27998 *stopped,reason="exited",exit-code="01"
28002 Another way the program can terminate is if it receives a signal such as
28003 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28007 *stopped,reason="exited-signalled",signal-name="SIGINT",
28008 signal-meaning="Interrupt"
28012 @c @subheading -exec-signal
28015 @subheading The @code{-exec-step} Command
28018 @subsubheading Synopsis
28021 -exec-step [--reverse]
28024 Resumes execution of the inferior program, stopping when the beginning
28025 of the next source line is reached, if the next source line is not a
28026 function call. If it is, stop at the first instruction of the called
28027 function. If the @samp{--reverse} option is specified, resumes reverse
28028 execution of the inferior program, stopping at the beginning of the
28029 previously executed source line.
28031 @subsubheading @value{GDBN} Command
28033 The corresponding @value{GDBN} command is @samp{step}.
28035 @subsubheading Example
28037 Stepping into a function:
28043 *stopped,reason="end-stepping-range",
28044 frame=@{func="foo",args=[@{name="a",value="10"@},
28045 @{name="b",value="0"@}],file="recursive2.c",
28046 fullname="/home/foo/bar/recursive2.c",line="11"@}
28056 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28061 @subheading The @code{-exec-step-instruction} Command
28062 @findex -exec-step-instruction
28064 @subsubheading Synopsis
28067 -exec-step-instruction [--reverse]
28070 Resumes the inferior which executes one machine instruction. If the
28071 @samp{--reverse} option is specified, resumes reverse execution of the
28072 inferior program, stopping at the previously executed instruction.
28073 The output, once @value{GDBN} has stopped, will vary depending on
28074 whether we have stopped in the middle of a source line or not. In the
28075 former case, the address at which the program stopped will be printed
28078 @subsubheading @value{GDBN} Command
28080 The corresponding @value{GDBN} command is @samp{stepi}.
28082 @subsubheading Example
28086 -exec-step-instruction
28090 *stopped,reason="end-stepping-range",
28091 frame=@{func="foo",args=[],file="try.c",
28092 fullname="/home/foo/bar/try.c",line="10"@}
28094 -exec-step-instruction
28098 *stopped,reason="end-stepping-range",
28099 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28100 fullname="/home/foo/bar/try.c",line="10"@}
28105 @subheading The @code{-exec-until} Command
28106 @findex -exec-until
28108 @subsubheading Synopsis
28111 -exec-until [ @var{location} ]
28114 Executes the inferior until the @var{location} specified in the
28115 argument is reached. If there is no argument, the inferior executes
28116 until a source line greater than the current one is reached. The
28117 reason for stopping in this case will be @samp{location-reached}.
28119 @subsubheading @value{GDBN} Command
28121 The corresponding @value{GDBN} command is @samp{until}.
28123 @subsubheading Example
28127 -exec-until recursive2.c:6
28131 *stopped,reason="location-reached",frame=@{func="main",args=[],
28132 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28137 @subheading -file-clear
28138 Is this going away????
28141 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28142 @node GDB/MI Stack Manipulation
28143 @section @sc{gdb/mi} Stack Manipulation Commands
28146 @subheading The @code{-stack-info-frame} Command
28147 @findex -stack-info-frame
28149 @subsubheading Synopsis
28155 Get info on the selected frame.
28157 @subsubheading @value{GDBN} Command
28159 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28160 (without arguments).
28162 @subsubheading Example
28167 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28168 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28169 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28173 @subheading The @code{-stack-info-depth} Command
28174 @findex -stack-info-depth
28176 @subsubheading Synopsis
28179 -stack-info-depth [ @var{max-depth} ]
28182 Return the depth of the stack. If the integer argument @var{max-depth}
28183 is specified, do not count beyond @var{max-depth} frames.
28185 @subsubheading @value{GDBN} Command
28187 There's no equivalent @value{GDBN} command.
28189 @subsubheading Example
28191 For a stack with frame levels 0 through 11:
28198 -stack-info-depth 4
28201 -stack-info-depth 12
28204 -stack-info-depth 11
28207 -stack-info-depth 13
28212 @subheading The @code{-stack-list-arguments} Command
28213 @findex -stack-list-arguments
28215 @subsubheading Synopsis
28218 -stack-list-arguments @var{print-values}
28219 [ @var{low-frame} @var{high-frame} ]
28222 Display a list of the arguments for the frames between @var{low-frame}
28223 and @var{high-frame} (inclusive). If @var{low-frame} and
28224 @var{high-frame} are not provided, list the arguments for the whole
28225 call stack. If the two arguments are equal, show the single frame
28226 at the corresponding level. It is an error if @var{low-frame} is
28227 larger than the actual number of frames. On the other hand,
28228 @var{high-frame} may be larger than the actual number of frames, in
28229 which case only existing frames will be returned.
28231 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28232 the variables; if it is 1 or @code{--all-values}, print also their
28233 values; and if it is 2 or @code{--simple-values}, print the name,
28234 type and value for simple data types, and the name and type for arrays,
28235 structures and unions.
28237 Use of this command to obtain arguments in a single frame is
28238 deprecated in favor of the @samp{-stack-list-variables} command.
28240 @subsubheading @value{GDBN} Command
28242 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28243 @samp{gdb_get_args} command which partially overlaps with the
28244 functionality of @samp{-stack-list-arguments}.
28246 @subsubheading Example
28253 frame=@{level="0",addr="0x00010734",func="callee4",
28254 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28255 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28256 frame=@{level="1",addr="0x0001076c",func="callee3",
28257 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28258 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28259 frame=@{level="2",addr="0x0001078c",func="callee2",
28260 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28261 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28262 frame=@{level="3",addr="0x000107b4",func="callee1",
28263 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28264 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28265 frame=@{level="4",addr="0x000107e0",func="main",
28266 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28267 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28269 -stack-list-arguments 0
28272 frame=@{level="0",args=[]@},
28273 frame=@{level="1",args=[name="strarg"]@},
28274 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28275 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28276 frame=@{level="4",args=[]@}]
28278 -stack-list-arguments 1
28281 frame=@{level="0",args=[]@},
28283 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28284 frame=@{level="2",args=[
28285 @{name="intarg",value="2"@},
28286 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28287 @{frame=@{level="3",args=[
28288 @{name="intarg",value="2"@},
28289 @{name="strarg",value="0x11940 \"A string argument.\""@},
28290 @{name="fltarg",value="3.5"@}]@},
28291 frame=@{level="4",args=[]@}]
28293 -stack-list-arguments 0 2 2
28294 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28296 -stack-list-arguments 1 2 2
28297 ^done,stack-args=[frame=@{level="2",
28298 args=[@{name="intarg",value="2"@},
28299 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28303 @c @subheading -stack-list-exception-handlers
28306 @subheading The @code{-stack-list-frames} Command
28307 @findex -stack-list-frames
28309 @subsubheading Synopsis
28312 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28315 List the frames currently on the stack. For each frame it displays the
28320 The frame number, 0 being the topmost frame, i.e., the innermost function.
28322 The @code{$pc} value for that frame.
28326 File name of the source file where the function lives.
28327 @item @var{fullname}
28328 The full file name of the source file where the function lives.
28330 Line number corresponding to the @code{$pc}.
28332 The shared library where this function is defined. This is only given
28333 if the frame's function is not known.
28336 If invoked without arguments, this command prints a backtrace for the
28337 whole stack. If given two integer arguments, it shows the frames whose
28338 levels are between the two arguments (inclusive). If the two arguments
28339 are equal, it shows the single frame at the corresponding level. It is
28340 an error if @var{low-frame} is larger than the actual number of
28341 frames. On the other hand, @var{high-frame} may be larger than the
28342 actual number of frames, in which case only existing frames will be returned.
28344 @subsubheading @value{GDBN} Command
28346 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28348 @subsubheading Example
28350 Full stack backtrace:
28356 [frame=@{level="0",addr="0x0001076c",func="foo",
28357 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28358 frame=@{level="1",addr="0x000107a4",func="foo",
28359 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28360 frame=@{level="2",addr="0x000107a4",func="foo",
28361 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28362 frame=@{level="3",addr="0x000107a4",func="foo",
28363 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28364 frame=@{level="4",addr="0x000107a4",func="foo",
28365 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28366 frame=@{level="5",addr="0x000107a4",func="foo",
28367 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28368 frame=@{level="6",addr="0x000107a4",func="foo",
28369 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28370 frame=@{level="7",addr="0x000107a4",func="foo",
28371 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28372 frame=@{level="8",addr="0x000107a4",func="foo",
28373 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28374 frame=@{level="9",addr="0x000107a4",func="foo",
28375 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28376 frame=@{level="10",addr="0x000107a4",func="foo",
28377 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28378 frame=@{level="11",addr="0x00010738",func="main",
28379 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28383 Show frames between @var{low_frame} and @var{high_frame}:
28387 -stack-list-frames 3 5
28389 [frame=@{level="3",addr="0x000107a4",func="foo",
28390 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28391 frame=@{level="4",addr="0x000107a4",func="foo",
28392 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28393 frame=@{level="5",addr="0x000107a4",func="foo",
28394 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28398 Show a single frame:
28402 -stack-list-frames 3 3
28404 [frame=@{level="3",addr="0x000107a4",func="foo",
28405 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28410 @subheading The @code{-stack-list-locals} Command
28411 @findex -stack-list-locals
28413 @subsubheading Synopsis
28416 -stack-list-locals @var{print-values}
28419 Display the local variable names for the selected frame. If
28420 @var{print-values} is 0 or @code{--no-values}, print only the names of
28421 the variables; if it is 1 or @code{--all-values}, print also their
28422 values; and if it is 2 or @code{--simple-values}, print the name,
28423 type and value for simple data types, and the name and type for arrays,
28424 structures and unions. In this last case, a frontend can immediately
28425 display the value of simple data types and create variable objects for
28426 other data types when the user wishes to explore their values in
28429 This command is deprecated in favor of the
28430 @samp{-stack-list-variables} command.
28432 @subsubheading @value{GDBN} Command
28434 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28436 @subsubheading Example
28440 -stack-list-locals 0
28441 ^done,locals=[name="A",name="B",name="C"]
28443 -stack-list-locals --all-values
28444 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28445 @{name="C",value="@{1, 2, 3@}"@}]
28446 -stack-list-locals --simple-values
28447 ^done,locals=[@{name="A",type="int",value="1"@},
28448 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28452 @subheading The @code{-stack-list-variables} Command
28453 @findex -stack-list-variables
28455 @subsubheading Synopsis
28458 -stack-list-variables @var{print-values}
28461 Display the names of local variables and function arguments for the selected frame. If
28462 @var{print-values} is 0 or @code{--no-values}, print only the names of
28463 the variables; if it is 1 or @code{--all-values}, print also their
28464 values; and if it is 2 or @code{--simple-values}, print the name,
28465 type and value for simple data types, and the name and type for arrays,
28466 structures and unions.
28468 @subsubheading Example
28472 -stack-list-variables --thread 1 --frame 0 --all-values
28473 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28478 @subheading The @code{-stack-select-frame} Command
28479 @findex -stack-select-frame
28481 @subsubheading Synopsis
28484 -stack-select-frame @var{framenum}
28487 Change the selected frame. Select a different frame @var{framenum} on
28490 This command in deprecated in favor of passing the @samp{--frame}
28491 option to every command.
28493 @subsubheading @value{GDBN} Command
28495 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28496 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28498 @subsubheading Example
28502 -stack-select-frame 2
28507 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28508 @node GDB/MI Variable Objects
28509 @section @sc{gdb/mi} Variable Objects
28513 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28515 For the implementation of a variable debugger window (locals, watched
28516 expressions, etc.), we are proposing the adaptation of the existing code
28517 used by @code{Insight}.
28519 The two main reasons for that are:
28523 It has been proven in practice (it is already on its second generation).
28526 It will shorten development time (needless to say how important it is
28530 The original interface was designed to be used by Tcl code, so it was
28531 slightly changed so it could be used through @sc{gdb/mi}. This section
28532 describes the @sc{gdb/mi} operations that will be available and gives some
28533 hints about their use.
28535 @emph{Note}: In addition to the set of operations described here, we
28536 expect the @sc{gui} implementation of a variable window to require, at
28537 least, the following operations:
28540 @item @code{-gdb-show} @code{output-radix}
28541 @item @code{-stack-list-arguments}
28542 @item @code{-stack-list-locals}
28543 @item @code{-stack-select-frame}
28548 @subheading Introduction to Variable Objects
28550 @cindex variable objects in @sc{gdb/mi}
28552 Variable objects are "object-oriented" MI interface for examining and
28553 changing values of expressions. Unlike some other MI interfaces that
28554 work with expressions, variable objects are specifically designed for
28555 simple and efficient presentation in the frontend. A variable object
28556 is identified by string name. When a variable object is created, the
28557 frontend specifies the expression for that variable object. The
28558 expression can be a simple variable, or it can be an arbitrary complex
28559 expression, and can even involve CPU registers. After creating a
28560 variable object, the frontend can invoke other variable object
28561 operations---for example to obtain or change the value of a variable
28562 object, or to change display format.
28564 Variable objects have hierarchical tree structure. Any variable object
28565 that corresponds to a composite type, such as structure in C, has
28566 a number of child variable objects, for example corresponding to each
28567 element of a structure. A child variable object can itself have
28568 children, recursively. Recursion ends when we reach
28569 leaf variable objects, which always have built-in types. Child variable
28570 objects are created only by explicit request, so if a frontend
28571 is not interested in the children of a particular variable object, no
28572 child will be created.
28574 For a leaf variable object it is possible to obtain its value as a
28575 string, or set the value from a string. String value can be also
28576 obtained for a non-leaf variable object, but it's generally a string
28577 that only indicates the type of the object, and does not list its
28578 contents. Assignment to a non-leaf variable object is not allowed.
28580 A frontend does not need to read the values of all variable objects each time
28581 the program stops. Instead, MI provides an update command that lists all
28582 variable objects whose values has changed since the last update
28583 operation. This considerably reduces the amount of data that must
28584 be transferred to the frontend. As noted above, children variable
28585 objects are created on demand, and only leaf variable objects have a
28586 real value. As result, gdb will read target memory only for leaf
28587 variables that frontend has created.
28589 The automatic update is not always desirable. For example, a frontend
28590 might want to keep a value of some expression for future reference,
28591 and never update it. For another example, fetching memory is
28592 relatively slow for embedded targets, so a frontend might want
28593 to disable automatic update for the variables that are either not
28594 visible on the screen, or ``closed''. This is possible using so
28595 called ``frozen variable objects''. Such variable objects are never
28596 implicitly updated.
28598 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28599 fixed variable object, the expression is parsed when the variable
28600 object is created, including associating identifiers to specific
28601 variables. The meaning of expression never changes. For a floating
28602 variable object the values of variables whose names appear in the
28603 expressions are re-evaluated every time in the context of the current
28604 frame. Consider this example:
28609 struct work_state state;
28616 If a fixed variable object for the @code{state} variable is created in
28617 this function, and we enter the recursive call, the variable
28618 object will report the value of @code{state} in the top-level
28619 @code{do_work} invocation. On the other hand, a floating variable
28620 object will report the value of @code{state} in the current frame.
28622 If an expression specified when creating a fixed variable object
28623 refers to a local variable, the variable object becomes bound to the
28624 thread and frame in which the variable object is created. When such
28625 variable object is updated, @value{GDBN} makes sure that the
28626 thread/frame combination the variable object is bound to still exists,
28627 and re-evaluates the variable object in context of that thread/frame.
28629 The following is the complete set of @sc{gdb/mi} operations defined to
28630 access this functionality:
28632 @multitable @columnfractions .4 .6
28633 @item @strong{Operation}
28634 @tab @strong{Description}
28636 @item @code{-enable-pretty-printing}
28637 @tab enable Python-based pretty-printing
28638 @item @code{-var-create}
28639 @tab create a variable object
28640 @item @code{-var-delete}
28641 @tab delete the variable object and/or its children
28642 @item @code{-var-set-format}
28643 @tab set the display format of this variable
28644 @item @code{-var-show-format}
28645 @tab show the display format of this variable
28646 @item @code{-var-info-num-children}
28647 @tab tells how many children this object has
28648 @item @code{-var-list-children}
28649 @tab return a list of the object's children
28650 @item @code{-var-info-type}
28651 @tab show the type of this variable object
28652 @item @code{-var-info-expression}
28653 @tab print parent-relative expression that this variable object represents
28654 @item @code{-var-info-path-expression}
28655 @tab print full expression that this variable object represents
28656 @item @code{-var-show-attributes}
28657 @tab is this variable editable? does it exist here?
28658 @item @code{-var-evaluate-expression}
28659 @tab get the value of this variable
28660 @item @code{-var-assign}
28661 @tab set the value of this variable
28662 @item @code{-var-update}
28663 @tab update the variable and its children
28664 @item @code{-var-set-frozen}
28665 @tab set frozeness attribute
28666 @item @code{-var-set-update-range}
28667 @tab set range of children to display on update
28670 In the next subsection we describe each operation in detail and suggest
28671 how it can be used.
28673 @subheading Description And Use of Operations on Variable Objects
28675 @subheading The @code{-enable-pretty-printing} Command
28676 @findex -enable-pretty-printing
28679 -enable-pretty-printing
28682 @value{GDBN} allows Python-based visualizers to affect the output of the
28683 MI variable object commands. However, because there was no way to
28684 implement this in a fully backward-compatible way, a front end must
28685 request that this functionality be enabled.
28687 Once enabled, this feature cannot be disabled.
28689 Note that if Python support has not been compiled into @value{GDBN},
28690 this command will still succeed (and do nothing).
28692 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28693 may work differently in future versions of @value{GDBN}.
28695 @subheading The @code{-var-create} Command
28696 @findex -var-create
28698 @subsubheading Synopsis
28701 -var-create @{@var{name} | "-"@}
28702 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28705 This operation creates a variable object, which allows the monitoring of
28706 a variable, the result of an expression, a memory cell or a CPU
28709 The @var{name} parameter is the string by which the object can be
28710 referenced. It must be unique. If @samp{-} is specified, the varobj
28711 system will generate a string ``varNNNNNN'' automatically. It will be
28712 unique provided that one does not specify @var{name} of that format.
28713 The command fails if a duplicate name is found.
28715 The frame under which the expression should be evaluated can be
28716 specified by @var{frame-addr}. A @samp{*} indicates that the current
28717 frame should be used. A @samp{@@} indicates that a floating variable
28718 object must be created.
28720 @var{expression} is any expression valid on the current language set (must not
28721 begin with a @samp{*}), or one of the following:
28725 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28728 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28731 @samp{$@var{regname}} --- a CPU register name
28734 @cindex dynamic varobj
28735 A varobj's contents may be provided by a Python-based pretty-printer. In this
28736 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28737 have slightly different semantics in some cases. If the
28738 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28739 will never create a dynamic varobj. This ensures backward
28740 compatibility for existing clients.
28742 @subsubheading Result
28744 This operation returns attributes of the newly-created varobj. These
28749 The name of the varobj.
28752 The number of children of the varobj. This number is not necessarily
28753 reliable for a dynamic varobj. Instead, you must examine the
28754 @samp{has_more} attribute.
28757 The varobj's scalar value. For a varobj whose type is some sort of
28758 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28759 will not be interesting.
28762 The varobj's type. This is a string representation of the type, as
28763 would be printed by the @value{GDBN} CLI.
28766 If a variable object is bound to a specific thread, then this is the
28767 thread's identifier.
28770 For a dynamic varobj, this indicates whether there appear to be any
28771 children available. For a non-dynamic varobj, this will be 0.
28774 This attribute will be present and have the value @samp{1} if the
28775 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28776 then this attribute will not be present.
28779 A dynamic varobj can supply a display hint to the front end. The
28780 value comes directly from the Python pretty-printer object's
28781 @code{display_hint} method. @xref{Pretty Printing API}.
28784 Typical output will look like this:
28787 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28788 has_more="@var{has_more}"
28792 @subheading The @code{-var-delete} Command
28793 @findex -var-delete
28795 @subsubheading Synopsis
28798 -var-delete [ -c ] @var{name}
28801 Deletes a previously created variable object and all of its children.
28802 With the @samp{-c} option, just deletes the children.
28804 Returns an error if the object @var{name} is not found.
28807 @subheading The @code{-var-set-format} Command
28808 @findex -var-set-format
28810 @subsubheading Synopsis
28813 -var-set-format @var{name} @var{format-spec}
28816 Sets the output format for the value of the object @var{name} to be
28819 @anchor{-var-set-format}
28820 The syntax for the @var{format-spec} is as follows:
28823 @var{format-spec} @expansion{}
28824 @{binary | decimal | hexadecimal | octal | natural@}
28827 The natural format is the default format choosen automatically
28828 based on the variable type (like decimal for an @code{int}, hex
28829 for pointers, etc.).
28831 For a variable with children, the format is set only on the
28832 variable itself, and the children are not affected.
28834 @subheading The @code{-var-show-format} Command
28835 @findex -var-show-format
28837 @subsubheading Synopsis
28840 -var-show-format @var{name}
28843 Returns the format used to display the value of the object @var{name}.
28846 @var{format} @expansion{}
28851 @subheading The @code{-var-info-num-children} Command
28852 @findex -var-info-num-children
28854 @subsubheading Synopsis
28857 -var-info-num-children @var{name}
28860 Returns the number of children of a variable object @var{name}:
28866 Note that this number is not completely reliable for a dynamic varobj.
28867 It will return the current number of children, but more children may
28871 @subheading The @code{-var-list-children} Command
28872 @findex -var-list-children
28874 @subsubheading Synopsis
28877 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28879 @anchor{-var-list-children}
28881 Return a list of the children of the specified variable object and
28882 create variable objects for them, if they do not already exist. With
28883 a single argument or if @var{print-values} has a value of 0 or
28884 @code{--no-values}, print only the names of the variables; if
28885 @var{print-values} is 1 or @code{--all-values}, also print their
28886 values; and if it is 2 or @code{--simple-values} print the name and
28887 value for simple data types and just the name for arrays, structures
28890 @var{from} and @var{to}, if specified, indicate the range of children
28891 to report. If @var{from} or @var{to} is less than zero, the range is
28892 reset and all children will be reported. Otherwise, children starting
28893 at @var{from} (zero-based) and up to and excluding @var{to} will be
28896 If a child range is requested, it will only affect the current call to
28897 @code{-var-list-children}, but not future calls to @code{-var-update}.
28898 For this, you must instead use @code{-var-set-update-range}. The
28899 intent of this approach is to enable a front end to implement any
28900 update approach it likes; for example, scrolling a view may cause the
28901 front end to request more children with @code{-var-list-children}, and
28902 then the front end could call @code{-var-set-update-range} with a
28903 different range to ensure that future updates are restricted to just
28906 For each child the following results are returned:
28911 Name of the variable object created for this child.
28914 The expression to be shown to the user by the front end to designate this child.
28915 For example this may be the name of a structure member.
28917 For a dynamic varobj, this value cannot be used to form an
28918 expression. There is no way to do this at all with a dynamic varobj.
28920 For C/C@t{++} structures there are several pseudo children returned to
28921 designate access qualifiers. For these pseudo children @var{exp} is
28922 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28923 type and value are not present.
28925 A dynamic varobj will not report the access qualifying
28926 pseudo-children, regardless of the language. This information is not
28927 available at all with a dynamic varobj.
28930 Number of children this child has. For a dynamic varobj, this will be
28934 The type of the child.
28937 If values were requested, this is the value.
28940 If this variable object is associated with a thread, this is the thread id.
28941 Otherwise this result is not present.
28944 If the variable object is frozen, this variable will be present with a value of 1.
28947 The result may have its own attributes:
28951 A dynamic varobj can supply a display hint to the front end. The
28952 value comes directly from the Python pretty-printer object's
28953 @code{display_hint} method. @xref{Pretty Printing API}.
28956 This is an integer attribute which is nonzero if there are children
28957 remaining after the end of the selected range.
28960 @subsubheading Example
28964 -var-list-children n
28965 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28966 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28968 -var-list-children --all-values n
28969 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28970 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28974 @subheading The @code{-var-info-type} Command
28975 @findex -var-info-type
28977 @subsubheading Synopsis
28980 -var-info-type @var{name}
28983 Returns the type of the specified variable @var{name}. The type is
28984 returned as a string in the same format as it is output by the
28988 type=@var{typename}
28992 @subheading The @code{-var-info-expression} Command
28993 @findex -var-info-expression
28995 @subsubheading Synopsis
28998 -var-info-expression @var{name}
29001 Returns a string that is suitable for presenting this
29002 variable object in user interface. The string is generally
29003 not valid expression in the current language, and cannot be evaluated.
29005 For example, if @code{a} is an array, and variable object
29006 @code{A} was created for @code{a}, then we'll get this output:
29009 (gdb) -var-info-expression A.1
29010 ^done,lang="C",exp="1"
29014 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29016 Note that the output of the @code{-var-list-children} command also
29017 includes those expressions, so the @code{-var-info-expression} command
29020 @subheading The @code{-var-info-path-expression} Command
29021 @findex -var-info-path-expression
29023 @subsubheading Synopsis
29026 -var-info-path-expression @var{name}
29029 Returns an expression that can be evaluated in the current
29030 context and will yield the same value that a variable object has.
29031 Compare this with the @code{-var-info-expression} command, which
29032 result can be used only for UI presentation. Typical use of
29033 the @code{-var-info-path-expression} command is creating a
29034 watchpoint from a variable object.
29036 This command is currently not valid for children of a dynamic varobj,
29037 and will give an error when invoked on one.
29039 For example, suppose @code{C} is a C@t{++} class, derived from class
29040 @code{Base}, and that the @code{Base} class has a member called
29041 @code{m_size}. Assume a variable @code{c} is has the type of
29042 @code{C} and a variable object @code{C} was created for variable
29043 @code{c}. Then, we'll get this output:
29045 (gdb) -var-info-path-expression C.Base.public.m_size
29046 ^done,path_expr=((Base)c).m_size)
29049 @subheading The @code{-var-show-attributes} Command
29050 @findex -var-show-attributes
29052 @subsubheading Synopsis
29055 -var-show-attributes @var{name}
29058 List attributes of the specified variable object @var{name}:
29061 status=@var{attr} [ ( ,@var{attr} )* ]
29065 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29067 @subheading The @code{-var-evaluate-expression} Command
29068 @findex -var-evaluate-expression
29070 @subsubheading Synopsis
29073 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29076 Evaluates the expression that is represented by the specified variable
29077 object and returns its value as a string. The format of the string
29078 can be specified with the @samp{-f} option. The possible values of
29079 this option are the same as for @code{-var-set-format}
29080 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29081 the current display format will be used. The current display format
29082 can be changed using the @code{-var-set-format} command.
29088 Note that one must invoke @code{-var-list-children} for a variable
29089 before the value of a child variable can be evaluated.
29091 @subheading The @code{-var-assign} Command
29092 @findex -var-assign
29094 @subsubheading Synopsis
29097 -var-assign @var{name} @var{expression}
29100 Assigns the value of @var{expression} to the variable object specified
29101 by @var{name}. The object must be @samp{editable}. If the variable's
29102 value is altered by the assign, the variable will show up in any
29103 subsequent @code{-var-update} list.
29105 @subsubheading Example
29113 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29117 @subheading The @code{-var-update} Command
29118 @findex -var-update
29120 @subsubheading Synopsis
29123 -var-update [@var{print-values}] @{@var{name} | "*"@}
29126 Reevaluate the expressions corresponding to the variable object
29127 @var{name} and all its direct and indirect children, and return the
29128 list of variable objects whose values have changed; @var{name} must
29129 be a root variable object. Here, ``changed'' means that the result of
29130 @code{-var-evaluate-expression} before and after the
29131 @code{-var-update} is different. If @samp{*} is used as the variable
29132 object names, all existing variable objects are updated, except
29133 for frozen ones (@pxref{-var-set-frozen}). The option
29134 @var{print-values} determines whether both names and values, or just
29135 names are printed. The possible values of this option are the same
29136 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29137 recommended to use the @samp{--all-values} option, to reduce the
29138 number of MI commands needed on each program stop.
29140 With the @samp{*} parameter, if a variable object is bound to a
29141 currently running thread, it will not be updated, without any
29144 If @code{-var-set-update-range} was previously used on a varobj, then
29145 only the selected range of children will be reported.
29147 @code{-var-update} reports all the changed varobjs in a tuple named
29150 Each item in the change list is itself a tuple holding:
29154 The name of the varobj.
29157 If values were requested for this update, then this field will be
29158 present and will hold the value of the varobj.
29161 @anchor{-var-update}
29162 This field is a string which may take one of three values:
29166 The variable object's current value is valid.
29169 The variable object does not currently hold a valid value but it may
29170 hold one in the future if its associated expression comes back into
29174 The variable object no longer holds a valid value.
29175 This can occur when the executable file being debugged has changed,
29176 either through recompilation or by using the @value{GDBN} @code{file}
29177 command. The front end should normally choose to delete these variable
29181 In the future new values may be added to this list so the front should
29182 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29185 This is only present if the varobj is still valid. If the type
29186 changed, then this will be the string @samp{true}; otherwise it will
29190 If the varobj's type changed, then this field will be present and will
29193 @item new_num_children
29194 For a dynamic varobj, if the number of children changed, or if the
29195 type changed, this will be the new number of children.
29197 The @samp{numchild} field in other varobj responses is generally not
29198 valid for a dynamic varobj -- it will show the number of children that
29199 @value{GDBN} knows about, but because dynamic varobjs lazily
29200 instantiate their children, this will not reflect the number of
29201 children which may be available.
29203 The @samp{new_num_children} attribute only reports changes to the
29204 number of children known by @value{GDBN}. This is the only way to
29205 detect whether an update has removed children (which necessarily can
29206 only happen at the end of the update range).
29209 The display hint, if any.
29212 This is an integer value, which will be 1 if there are more children
29213 available outside the varobj's update range.
29216 This attribute will be present and have the value @samp{1} if the
29217 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29218 then this attribute will not be present.
29221 If new children were added to a dynamic varobj within the selected
29222 update range (as set by @code{-var-set-update-range}), then they will
29223 be listed in this attribute.
29226 @subsubheading Example
29233 -var-update --all-values var1
29234 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29235 type_changed="false"@}]
29239 @subheading The @code{-var-set-frozen} Command
29240 @findex -var-set-frozen
29241 @anchor{-var-set-frozen}
29243 @subsubheading Synopsis
29246 -var-set-frozen @var{name} @var{flag}
29249 Set the frozenness flag on the variable object @var{name}. The
29250 @var{flag} parameter should be either @samp{1} to make the variable
29251 frozen or @samp{0} to make it unfrozen. If a variable object is
29252 frozen, then neither itself, nor any of its children, are
29253 implicitly updated by @code{-var-update} of
29254 a parent variable or by @code{-var-update *}. Only
29255 @code{-var-update} of the variable itself will update its value and
29256 values of its children. After a variable object is unfrozen, it is
29257 implicitly updated by all subsequent @code{-var-update} operations.
29258 Unfreezing a variable does not update it, only subsequent
29259 @code{-var-update} does.
29261 @subsubheading Example
29265 -var-set-frozen V 1
29270 @subheading The @code{-var-set-update-range} command
29271 @findex -var-set-update-range
29272 @anchor{-var-set-update-range}
29274 @subsubheading Synopsis
29277 -var-set-update-range @var{name} @var{from} @var{to}
29280 Set the range of children to be returned by future invocations of
29281 @code{-var-update}.
29283 @var{from} and @var{to} indicate the range of children to report. If
29284 @var{from} or @var{to} is less than zero, the range is reset and all
29285 children will be reported. Otherwise, children starting at @var{from}
29286 (zero-based) and up to and excluding @var{to} will be reported.
29288 @subsubheading Example
29292 -var-set-update-range V 1 2
29296 @subheading The @code{-var-set-visualizer} command
29297 @findex -var-set-visualizer
29298 @anchor{-var-set-visualizer}
29300 @subsubheading Synopsis
29303 -var-set-visualizer @var{name} @var{visualizer}
29306 Set a visualizer for the variable object @var{name}.
29308 @var{visualizer} is the visualizer to use. The special value
29309 @samp{None} means to disable any visualizer in use.
29311 If not @samp{None}, @var{visualizer} must be a Python expression.
29312 This expression must evaluate to a callable object which accepts a
29313 single argument. @value{GDBN} will call this object with the value of
29314 the varobj @var{name} as an argument (this is done so that the same
29315 Python pretty-printing code can be used for both the CLI and MI).
29316 When called, this object must return an object which conforms to the
29317 pretty-printing interface (@pxref{Pretty Printing API}).
29319 The pre-defined function @code{gdb.default_visualizer} may be used to
29320 select a visualizer by following the built-in process
29321 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29322 a varobj is created, and so ordinarily is not needed.
29324 This feature is only available if Python support is enabled. The MI
29325 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29326 can be used to check this.
29328 @subsubheading Example
29330 Resetting the visualizer:
29334 -var-set-visualizer V None
29338 Reselecting the default (type-based) visualizer:
29342 -var-set-visualizer V gdb.default_visualizer
29346 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29347 can be used to instantiate this class for a varobj:
29351 -var-set-visualizer V "lambda val: SomeClass()"
29355 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29356 @node GDB/MI Data Manipulation
29357 @section @sc{gdb/mi} Data Manipulation
29359 @cindex data manipulation, in @sc{gdb/mi}
29360 @cindex @sc{gdb/mi}, data manipulation
29361 This section describes the @sc{gdb/mi} commands that manipulate data:
29362 examine memory and registers, evaluate expressions, etc.
29364 @c REMOVED FROM THE INTERFACE.
29365 @c @subheading -data-assign
29366 @c Change the value of a program variable. Plenty of side effects.
29367 @c @subsubheading GDB Command
29369 @c @subsubheading Example
29372 @subheading The @code{-data-disassemble} Command
29373 @findex -data-disassemble
29375 @subsubheading Synopsis
29379 [ -s @var{start-addr} -e @var{end-addr} ]
29380 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29388 @item @var{start-addr}
29389 is the beginning address (or @code{$pc})
29390 @item @var{end-addr}
29392 @item @var{filename}
29393 is the name of the file to disassemble
29394 @item @var{linenum}
29395 is the line number to disassemble around
29397 is the number of disassembly lines to be produced. If it is -1,
29398 the whole function will be disassembled, in case no @var{end-addr} is
29399 specified. If @var{end-addr} is specified as a non-zero value, and
29400 @var{lines} is lower than the number of disassembly lines between
29401 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29402 displayed; if @var{lines} is higher than the number of lines between
29403 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29406 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29407 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29408 mixed source and disassembly with raw opcodes).
29411 @subsubheading Result
29413 The output for each instruction is composed of four fields:
29422 Note that whatever included in the instruction field, is not manipulated
29423 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29425 @subsubheading @value{GDBN} Command
29427 There's no direct mapping from this command to the CLI.
29429 @subsubheading Example
29431 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29435 -data-disassemble -s $pc -e "$pc + 20" -- 0
29438 @{address="0x000107c0",func-name="main",offset="4",
29439 inst="mov 2, %o0"@},
29440 @{address="0x000107c4",func-name="main",offset="8",
29441 inst="sethi %hi(0x11800), %o2"@},
29442 @{address="0x000107c8",func-name="main",offset="12",
29443 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29444 @{address="0x000107cc",func-name="main",offset="16",
29445 inst="sethi %hi(0x11800), %o2"@},
29446 @{address="0x000107d0",func-name="main",offset="20",
29447 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29451 Disassemble the whole @code{main} function. Line 32 is part of
29455 -data-disassemble -f basics.c -l 32 -- 0
29457 @{address="0x000107bc",func-name="main",offset="0",
29458 inst="save %sp, -112, %sp"@},
29459 @{address="0x000107c0",func-name="main",offset="4",
29460 inst="mov 2, %o0"@},
29461 @{address="0x000107c4",func-name="main",offset="8",
29462 inst="sethi %hi(0x11800), %o2"@},
29464 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29465 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29469 Disassemble 3 instructions from the start of @code{main}:
29473 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29475 @{address="0x000107bc",func-name="main",offset="0",
29476 inst="save %sp, -112, %sp"@},
29477 @{address="0x000107c0",func-name="main",offset="4",
29478 inst="mov 2, %o0"@},
29479 @{address="0x000107c4",func-name="main",offset="8",
29480 inst="sethi %hi(0x11800), %o2"@}]
29484 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29488 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29490 src_and_asm_line=@{line="31",
29491 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29492 testsuite/gdb.mi/basics.c",line_asm_insn=[
29493 @{address="0x000107bc",func-name="main",offset="0",
29494 inst="save %sp, -112, %sp"@}]@},
29495 src_and_asm_line=@{line="32",
29496 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29497 testsuite/gdb.mi/basics.c",line_asm_insn=[
29498 @{address="0x000107c0",func-name="main",offset="4",
29499 inst="mov 2, %o0"@},
29500 @{address="0x000107c4",func-name="main",offset="8",
29501 inst="sethi %hi(0x11800), %o2"@}]@}]
29506 @subheading The @code{-data-evaluate-expression} Command
29507 @findex -data-evaluate-expression
29509 @subsubheading Synopsis
29512 -data-evaluate-expression @var{expr}
29515 Evaluate @var{expr} as an expression. The expression could contain an
29516 inferior function call. The function call will execute synchronously.
29517 If the expression contains spaces, it must be enclosed in double quotes.
29519 @subsubheading @value{GDBN} Command
29521 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29522 @samp{call}. In @code{gdbtk} only, there's a corresponding
29523 @samp{gdb_eval} command.
29525 @subsubheading Example
29527 In the following example, the numbers that precede the commands are the
29528 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29529 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29533 211-data-evaluate-expression A
29536 311-data-evaluate-expression &A
29537 311^done,value="0xefffeb7c"
29539 411-data-evaluate-expression A+3
29542 511-data-evaluate-expression "A + 3"
29548 @subheading The @code{-data-list-changed-registers} Command
29549 @findex -data-list-changed-registers
29551 @subsubheading Synopsis
29554 -data-list-changed-registers
29557 Display a list of the registers that have changed.
29559 @subsubheading @value{GDBN} Command
29561 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29562 has the corresponding command @samp{gdb_changed_register_list}.
29564 @subsubheading Example
29566 On a PPC MBX board:
29574 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29575 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29578 -data-list-changed-registers
29579 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29580 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29581 "24","25","26","27","28","30","31","64","65","66","67","69"]
29586 @subheading The @code{-data-list-register-names} Command
29587 @findex -data-list-register-names
29589 @subsubheading Synopsis
29592 -data-list-register-names [ ( @var{regno} )+ ]
29595 Show a list of register names for the current target. If no arguments
29596 are given, it shows a list of the names of all the registers. If
29597 integer numbers are given as arguments, it will print a list of the
29598 names of the registers corresponding to the arguments. To ensure
29599 consistency between a register name and its number, the output list may
29600 include empty register names.
29602 @subsubheading @value{GDBN} Command
29604 @value{GDBN} does not have a command which corresponds to
29605 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29606 corresponding command @samp{gdb_regnames}.
29608 @subsubheading Example
29610 For the PPC MBX board:
29613 -data-list-register-names
29614 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29615 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29616 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29617 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29618 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29619 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29620 "", "pc","ps","cr","lr","ctr","xer"]
29622 -data-list-register-names 1 2 3
29623 ^done,register-names=["r1","r2","r3"]
29627 @subheading The @code{-data-list-register-values} Command
29628 @findex -data-list-register-values
29630 @subsubheading Synopsis
29633 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29636 Display the registers' contents. @var{fmt} is the format according to
29637 which the registers' contents are to be returned, followed by an optional
29638 list of numbers specifying the registers to display. A missing list of
29639 numbers indicates that the contents of all the registers must be returned.
29641 Allowed formats for @var{fmt} are:
29658 @subsubheading @value{GDBN} Command
29660 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29661 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29663 @subsubheading Example
29665 For a PPC MBX board (note: line breaks are for readability only, they
29666 don't appear in the actual output):
29670 -data-list-register-values r 64 65
29671 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29672 @{number="65",value="0x00029002"@}]
29674 -data-list-register-values x
29675 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29676 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29677 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29678 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29679 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29680 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29681 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29682 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29683 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29684 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29685 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29686 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29687 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29688 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29689 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29690 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29691 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29692 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29693 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29694 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29695 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29696 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29697 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29698 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29699 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29700 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29701 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29702 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29703 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29704 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29705 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29706 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29707 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29708 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29709 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29710 @{number="69",value="0x20002b03"@}]
29715 @subheading The @code{-data-read-memory} Command
29716 @findex -data-read-memory
29718 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29720 @subsubheading Synopsis
29723 -data-read-memory [ -o @var{byte-offset} ]
29724 @var{address} @var{word-format} @var{word-size}
29725 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29732 @item @var{address}
29733 An expression specifying the address of the first memory word to be
29734 read. Complex expressions containing embedded white space should be
29735 quoted using the C convention.
29737 @item @var{word-format}
29738 The format to be used to print the memory words. The notation is the
29739 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29742 @item @var{word-size}
29743 The size of each memory word in bytes.
29745 @item @var{nr-rows}
29746 The number of rows in the output table.
29748 @item @var{nr-cols}
29749 The number of columns in the output table.
29752 If present, indicates that each row should include an @sc{ascii} dump. The
29753 value of @var{aschar} is used as a padding character when a byte is not a
29754 member of the printable @sc{ascii} character set (printable @sc{ascii}
29755 characters are those whose code is between 32 and 126, inclusively).
29757 @item @var{byte-offset}
29758 An offset to add to the @var{address} before fetching memory.
29761 This command displays memory contents as a table of @var{nr-rows} by
29762 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29763 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29764 (returned as @samp{total-bytes}). Should less than the requested number
29765 of bytes be returned by the target, the missing words are identified
29766 using @samp{N/A}. The number of bytes read from the target is returned
29767 in @samp{nr-bytes} and the starting address used to read memory in
29770 The address of the next/previous row or page is available in
29771 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29774 @subsubheading @value{GDBN} Command
29776 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29777 @samp{gdb_get_mem} memory read command.
29779 @subsubheading Example
29781 Read six bytes of memory starting at @code{bytes+6} but then offset by
29782 @code{-6} bytes. Format as three rows of two columns. One byte per
29783 word. Display each word in hex.
29787 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29788 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29789 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29790 prev-page="0x0000138a",memory=[
29791 @{addr="0x00001390",data=["0x00","0x01"]@},
29792 @{addr="0x00001392",data=["0x02","0x03"]@},
29793 @{addr="0x00001394",data=["0x04","0x05"]@}]
29797 Read two bytes of memory starting at address @code{shorts + 64} and
29798 display as a single word formatted in decimal.
29802 5-data-read-memory shorts+64 d 2 1 1
29803 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29804 next-row="0x00001512",prev-row="0x0000150e",
29805 next-page="0x00001512",prev-page="0x0000150e",memory=[
29806 @{addr="0x00001510",data=["128"]@}]
29810 Read thirty two bytes of memory starting at @code{bytes+16} and format
29811 as eight rows of four columns. Include a string encoding with @samp{x}
29812 used as the non-printable character.
29816 4-data-read-memory bytes+16 x 1 8 4 x
29817 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29818 next-row="0x000013c0",prev-row="0x0000139c",
29819 next-page="0x000013c0",prev-page="0x00001380",memory=[
29820 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29821 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29822 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29823 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29824 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29825 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29826 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29827 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29831 @subheading The @code{-data-read-memory-bytes} Command
29832 @findex -data-read-memory-bytes
29834 @subsubheading Synopsis
29837 -data-read-memory-bytes [ -o @var{byte-offset} ]
29838 @var{address} @var{count}
29845 @item @var{address}
29846 An expression specifying the address of the first memory word to be
29847 read. Complex expressions containing embedded white space should be
29848 quoted using the C convention.
29851 The number of bytes to read. This should be an integer literal.
29853 @item @var{byte-offset}
29854 The offsets in bytes relative to @var{address} at which to start
29855 reading. This should be an integer literal. This option is provided
29856 so that a frontend is not required to first evaluate address and then
29857 perform address arithmetics itself.
29861 This command attempts to read all accessible memory regions in the
29862 specified range. First, all regions marked as unreadable in the memory
29863 map (if one is defined) will be skipped. @xref{Memory Region
29864 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29865 regions. For each one, if reading full region results in an errors,
29866 @value{GDBN} will try to read a subset of the region.
29868 In general, every single byte in the region may be readable or not,
29869 and the only way to read every readable byte is to try a read at
29870 every address, which is not practical. Therefore, @value{GDBN} will
29871 attempt to read all accessible bytes at either beginning or the end
29872 of the region, using a binary division scheme. This heuristic works
29873 well for reading accross a memory map boundary. Note that if a region
29874 has a readable range that is neither at the beginning or the end,
29875 @value{GDBN} will not read it.
29877 The result record (@pxref{GDB/MI Result Records}) that is output of
29878 the command includes a field named @samp{memory} whose content is a
29879 list of tuples. Each tuple represent a successfully read memory block
29880 and has the following fields:
29884 The start address of the memory block, as hexadecimal literal.
29887 The end address of the memory block, as hexadecimal literal.
29890 The offset of the memory block, as hexadecimal literal, relative to
29891 the start address passed to @code{-data-read-memory-bytes}.
29894 The contents of the memory block, in hex.
29900 @subsubheading @value{GDBN} Command
29902 The corresponding @value{GDBN} command is @samp{x}.
29904 @subsubheading Example
29908 -data-read-memory-bytes &a 10
29909 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29911 contents="01000000020000000300"@}]
29916 @subheading The @code{-data-write-memory-bytes} Command
29917 @findex -data-write-memory-bytes
29919 @subsubheading Synopsis
29922 -data-write-memory-bytes @var{address} @var{contents}
29929 @item @var{address}
29930 An expression specifying the address of the first memory word to be
29931 read. Complex expressions containing embedded white space should be
29932 quoted using the C convention.
29934 @item @var{contents}
29935 The hex-encoded bytes to write.
29939 @subsubheading @value{GDBN} Command
29941 There's no corresponding @value{GDBN} command.
29943 @subsubheading Example
29947 -data-write-memory-bytes &a "aabbccdd"
29953 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29954 @node GDB/MI Tracepoint Commands
29955 @section @sc{gdb/mi} Tracepoint Commands
29957 The commands defined in this section implement MI support for
29958 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29960 @subheading The @code{-trace-find} Command
29961 @findex -trace-find
29963 @subsubheading Synopsis
29966 -trace-find @var{mode} [@var{parameters}@dots{}]
29969 Find a trace frame using criteria defined by @var{mode} and
29970 @var{parameters}. The following table lists permissible
29971 modes and their parameters. For details of operation, see @ref{tfind}.
29976 No parameters are required. Stops examining trace frames.
29979 An integer is required as parameter. Selects tracepoint frame with
29982 @item tracepoint-number
29983 An integer is required as parameter. Finds next
29984 trace frame that corresponds to tracepoint with the specified number.
29987 An address is required as parameter. Finds
29988 next trace frame that corresponds to any tracepoint at the specified
29991 @item pc-inside-range
29992 Two addresses are required as parameters. Finds next trace
29993 frame that corresponds to a tracepoint at an address inside the
29994 specified range. Both bounds are considered to be inside the range.
29996 @item pc-outside-range
29997 Two addresses are required as parameters. Finds
29998 next trace frame that corresponds to a tracepoint at an address outside
29999 the specified range. Both bounds are considered to be inside the range.
30002 Line specification is required as parameter. @xref{Specify Location}.
30003 Finds next trace frame that corresponds to a tracepoint at
30004 the specified location.
30008 If @samp{none} was passed as @var{mode}, the response does not
30009 have fields. Otherwise, the response may have the following fields:
30013 This field has either @samp{0} or @samp{1} as the value, depending
30014 on whether a matching tracepoint was found.
30017 The index of the found traceframe. This field is present iff
30018 the @samp{found} field has value of @samp{1}.
30021 The index of the found tracepoint. This field is present iff
30022 the @samp{found} field has value of @samp{1}.
30025 The information about the frame corresponding to the found trace
30026 frame. This field is present only if a trace frame was found.
30027 @xref{GDB/MI Frame Information}, for description of this field.
30031 @subsubheading @value{GDBN} Command
30033 The corresponding @value{GDBN} command is @samp{tfind}.
30035 @subheading -trace-define-variable
30036 @findex -trace-define-variable
30038 @subsubheading Synopsis
30041 -trace-define-variable @var{name} [ @var{value} ]
30044 Create trace variable @var{name} if it does not exist. If
30045 @var{value} is specified, sets the initial value of the specified
30046 trace variable to that value. Note that the @var{name} should start
30047 with the @samp{$} character.
30049 @subsubheading @value{GDBN} Command
30051 The corresponding @value{GDBN} command is @samp{tvariable}.
30053 @subheading -trace-list-variables
30054 @findex -trace-list-variables
30056 @subsubheading Synopsis
30059 -trace-list-variables
30062 Return a table of all defined trace variables. Each element of the
30063 table has the following fields:
30067 The name of the trace variable. This field is always present.
30070 The initial value. This is a 64-bit signed integer. This
30071 field is always present.
30074 The value the trace variable has at the moment. This is a 64-bit
30075 signed integer. This field is absent iff current value is
30076 not defined, for example if the trace was never run, or is
30081 @subsubheading @value{GDBN} Command
30083 The corresponding @value{GDBN} command is @samp{tvariables}.
30085 @subsubheading Example
30089 -trace-list-variables
30090 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30091 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30092 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30093 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30094 body=[variable=@{name="$trace_timestamp",initial="0"@}
30095 variable=@{name="$foo",initial="10",current="15"@}]@}
30099 @subheading -trace-save
30100 @findex -trace-save
30102 @subsubheading Synopsis
30105 -trace-save [-r ] @var{filename}
30108 Saves the collected trace data to @var{filename}. Without the
30109 @samp{-r} option, the data is downloaded from the target and saved
30110 in a local file. With the @samp{-r} option the target is asked
30111 to perform the save.
30113 @subsubheading @value{GDBN} Command
30115 The corresponding @value{GDBN} command is @samp{tsave}.
30118 @subheading -trace-start
30119 @findex -trace-start
30121 @subsubheading Synopsis
30127 Starts a tracing experiments. The result of this command does not
30130 @subsubheading @value{GDBN} Command
30132 The corresponding @value{GDBN} command is @samp{tstart}.
30134 @subheading -trace-status
30135 @findex -trace-status
30137 @subsubheading Synopsis
30143 Obtains the status of a tracing experiment. The result may include
30144 the following fields:
30149 May have a value of either @samp{0}, when no tracing operations are
30150 supported, @samp{1}, when all tracing operations are supported, or
30151 @samp{file} when examining trace file. In the latter case, examining
30152 of trace frame is possible but new tracing experiement cannot be
30153 started. This field is always present.
30156 May have a value of either @samp{0} or @samp{1} depending on whether
30157 tracing experiement is in progress on target. This field is present
30158 if @samp{supported} field is not @samp{0}.
30161 Report the reason why the tracing was stopped last time. This field
30162 may be absent iff tracing was never stopped on target yet. The
30163 value of @samp{request} means the tracing was stopped as result of
30164 the @code{-trace-stop} command. The value of @samp{overflow} means
30165 the tracing buffer is full. The value of @samp{disconnection} means
30166 tracing was automatically stopped when @value{GDBN} has disconnected.
30167 The value of @samp{passcount} means tracing was stopped when a
30168 tracepoint was passed a maximal number of times for that tracepoint.
30169 This field is present if @samp{supported} field is not @samp{0}.
30171 @item stopping-tracepoint
30172 The number of tracepoint whose passcount as exceeded. This field is
30173 present iff the @samp{stop-reason} field has the value of
30177 @itemx frames-created
30178 The @samp{frames} field is a count of the total number of trace frames
30179 in the trace buffer, while @samp{frames-created} is the total created
30180 during the run, including ones that were discarded, such as when a
30181 circular trace buffer filled up. Both fields are optional.
30185 These fields tell the current size of the tracing buffer and the
30186 remaining space. These fields are optional.
30189 The value of the circular trace buffer flag. @code{1} means that the
30190 trace buffer is circular and old trace frames will be discarded if
30191 necessary to make room, @code{0} means that the trace buffer is linear
30195 The value of the disconnected tracing flag. @code{1} means that
30196 tracing will continue after @value{GDBN} disconnects, @code{0} means
30197 that the trace run will stop.
30201 @subsubheading @value{GDBN} Command
30203 The corresponding @value{GDBN} command is @samp{tstatus}.
30205 @subheading -trace-stop
30206 @findex -trace-stop
30208 @subsubheading Synopsis
30214 Stops a tracing experiment. The result of this command has the same
30215 fields as @code{-trace-status}, except that the @samp{supported} and
30216 @samp{running} fields are not output.
30218 @subsubheading @value{GDBN} Command
30220 The corresponding @value{GDBN} command is @samp{tstop}.
30223 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30224 @node GDB/MI Symbol Query
30225 @section @sc{gdb/mi} Symbol Query Commands
30229 @subheading The @code{-symbol-info-address} Command
30230 @findex -symbol-info-address
30232 @subsubheading Synopsis
30235 -symbol-info-address @var{symbol}
30238 Describe where @var{symbol} is stored.
30240 @subsubheading @value{GDBN} Command
30242 The corresponding @value{GDBN} command is @samp{info address}.
30244 @subsubheading Example
30248 @subheading The @code{-symbol-info-file} Command
30249 @findex -symbol-info-file
30251 @subsubheading Synopsis
30257 Show the file for the symbol.
30259 @subsubheading @value{GDBN} Command
30261 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30262 @samp{gdb_find_file}.
30264 @subsubheading Example
30268 @subheading The @code{-symbol-info-function} Command
30269 @findex -symbol-info-function
30271 @subsubheading Synopsis
30274 -symbol-info-function
30277 Show which function the symbol lives in.
30279 @subsubheading @value{GDBN} Command
30281 @samp{gdb_get_function} in @code{gdbtk}.
30283 @subsubheading Example
30287 @subheading The @code{-symbol-info-line} Command
30288 @findex -symbol-info-line
30290 @subsubheading Synopsis
30296 Show the core addresses of the code for a source line.
30298 @subsubheading @value{GDBN} Command
30300 The corresponding @value{GDBN} command is @samp{info line}.
30301 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30303 @subsubheading Example
30307 @subheading The @code{-symbol-info-symbol} Command
30308 @findex -symbol-info-symbol
30310 @subsubheading Synopsis
30313 -symbol-info-symbol @var{addr}
30316 Describe what symbol is at location @var{addr}.
30318 @subsubheading @value{GDBN} Command
30320 The corresponding @value{GDBN} command is @samp{info symbol}.
30322 @subsubheading Example
30326 @subheading The @code{-symbol-list-functions} Command
30327 @findex -symbol-list-functions
30329 @subsubheading Synopsis
30332 -symbol-list-functions
30335 List the functions in the executable.
30337 @subsubheading @value{GDBN} Command
30339 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30340 @samp{gdb_search} in @code{gdbtk}.
30342 @subsubheading Example
30347 @subheading The @code{-symbol-list-lines} Command
30348 @findex -symbol-list-lines
30350 @subsubheading Synopsis
30353 -symbol-list-lines @var{filename}
30356 Print the list of lines that contain code and their associated program
30357 addresses for the given source filename. The entries are sorted in
30358 ascending PC order.
30360 @subsubheading @value{GDBN} Command
30362 There is no corresponding @value{GDBN} command.
30364 @subsubheading Example
30367 -symbol-list-lines basics.c
30368 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30374 @subheading The @code{-symbol-list-types} Command
30375 @findex -symbol-list-types
30377 @subsubheading Synopsis
30383 List all the type names.
30385 @subsubheading @value{GDBN} Command
30387 The corresponding commands are @samp{info types} in @value{GDBN},
30388 @samp{gdb_search} in @code{gdbtk}.
30390 @subsubheading Example
30394 @subheading The @code{-symbol-list-variables} Command
30395 @findex -symbol-list-variables
30397 @subsubheading Synopsis
30400 -symbol-list-variables
30403 List all the global and static variable names.
30405 @subsubheading @value{GDBN} Command
30407 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30409 @subsubheading Example
30413 @subheading The @code{-symbol-locate} Command
30414 @findex -symbol-locate
30416 @subsubheading Synopsis
30422 @subsubheading @value{GDBN} Command
30424 @samp{gdb_loc} in @code{gdbtk}.
30426 @subsubheading Example
30430 @subheading The @code{-symbol-type} Command
30431 @findex -symbol-type
30433 @subsubheading Synopsis
30436 -symbol-type @var{variable}
30439 Show type of @var{variable}.
30441 @subsubheading @value{GDBN} Command
30443 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30444 @samp{gdb_obj_variable}.
30446 @subsubheading Example
30451 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30452 @node GDB/MI File Commands
30453 @section @sc{gdb/mi} File Commands
30455 This section describes the GDB/MI commands to specify executable file names
30456 and to read in and obtain symbol table information.
30458 @subheading The @code{-file-exec-and-symbols} Command
30459 @findex -file-exec-and-symbols
30461 @subsubheading Synopsis
30464 -file-exec-and-symbols @var{file}
30467 Specify the executable file to be debugged. This file is the one from
30468 which the symbol table is also read. If no file is specified, the
30469 command clears the executable and symbol information. If breakpoints
30470 are set when using this command with no arguments, @value{GDBN} will produce
30471 error messages. Otherwise, no output is produced, except a completion
30474 @subsubheading @value{GDBN} Command
30476 The corresponding @value{GDBN} command is @samp{file}.
30478 @subsubheading Example
30482 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30488 @subheading The @code{-file-exec-file} Command
30489 @findex -file-exec-file
30491 @subsubheading Synopsis
30494 -file-exec-file @var{file}
30497 Specify the executable file to be debugged. Unlike
30498 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30499 from this file. If used without argument, @value{GDBN} clears the information
30500 about the executable file. No output is produced, except a completion
30503 @subsubheading @value{GDBN} Command
30505 The corresponding @value{GDBN} command is @samp{exec-file}.
30507 @subsubheading Example
30511 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30518 @subheading The @code{-file-list-exec-sections} Command
30519 @findex -file-list-exec-sections
30521 @subsubheading Synopsis
30524 -file-list-exec-sections
30527 List the sections of the current executable file.
30529 @subsubheading @value{GDBN} Command
30531 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30532 information as this command. @code{gdbtk} has a corresponding command
30533 @samp{gdb_load_info}.
30535 @subsubheading Example
30540 @subheading The @code{-file-list-exec-source-file} Command
30541 @findex -file-list-exec-source-file
30543 @subsubheading Synopsis
30546 -file-list-exec-source-file
30549 List the line number, the current source file, and the absolute path
30550 to the current source file for the current executable. The macro
30551 information field has a value of @samp{1} or @samp{0} depending on
30552 whether or not the file includes preprocessor macro information.
30554 @subsubheading @value{GDBN} Command
30556 The @value{GDBN} equivalent is @samp{info source}
30558 @subsubheading Example
30562 123-file-list-exec-source-file
30563 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30568 @subheading The @code{-file-list-exec-source-files} Command
30569 @findex -file-list-exec-source-files
30571 @subsubheading Synopsis
30574 -file-list-exec-source-files
30577 List the source files for the current executable.
30579 It will always output the filename, but only when @value{GDBN} can find
30580 the absolute file name of a source file, will it output the fullname.
30582 @subsubheading @value{GDBN} Command
30584 The @value{GDBN} equivalent is @samp{info sources}.
30585 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30587 @subsubheading Example
30590 -file-list-exec-source-files
30592 @{file=foo.c,fullname=/home/foo.c@},
30593 @{file=/home/bar.c,fullname=/home/bar.c@},
30594 @{file=gdb_could_not_find_fullpath.c@}]
30599 @subheading The @code{-file-list-shared-libraries} Command
30600 @findex -file-list-shared-libraries
30602 @subsubheading Synopsis
30605 -file-list-shared-libraries
30608 List the shared libraries in the program.
30610 @subsubheading @value{GDBN} Command
30612 The corresponding @value{GDBN} command is @samp{info shared}.
30614 @subsubheading Example
30618 @subheading The @code{-file-list-symbol-files} Command
30619 @findex -file-list-symbol-files
30621 @subsubheading Synopsis
30624 -file-list-symbol-files
30629 @subsubheading @value{GDBN} Command
30631 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30633 @subsubheading Example
30638 @subheading The @code{-file-symbol-file} Command
30639 @findex -file-symbol-file
30641 @subsubheading Synopsis
30644 -file-symbol-file @var{file}
30647 Read symbol table info from the specified @var{file} argument. When
30648 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30649 produced, except for a completion notification.
30651 @subsubheading @value{GDBN} Command
30653 The corresponding @value{GDBN} command is @samp{symbol-file}.
30655 @subsubheading Example
30659 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30665 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30666 @node GDB/MI Memory Overlay Commands
30667 @section @sc{gdb/mi} Memory Overlay Commands
30669 The memory overlay commands are not implemented.
30671 @c @subheading -overlay-auto
30673 @c @subheading -overlay-list-mapping-state
30675 @c @subheading -overlay-list-overlays
30677 @c @subheading -overlay-map
30679 @c @subheading -overlay-off
30681 @c @subheading -overlay-on
30683 @c @subheading -overlay-unmap
30685 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30686 @node GDB/MI Signal Handling Commands
30687 @section @sc{gdb/mi} Signal Handling Commands
30689 Signal handling commands are not implemented.
30691 @c @subheading -signal-handle
30693 @c @subheading -signal-list-handle-actions
30695 @c @subheading -signal-list-signal-types
30699 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30700 @node GDB/MI Target Manipulation
30701 @section @sc{gdb/mi} Target Manipulation Commands
30704 @subheading The @code{-target-attach} Command
30705 @findex -target-attach
30707 @subsubheading Synopsis
30710 -target-attach @var{pid} | @var{gid} | @var{file}
30713 Attach to a process @var{pid} or a file @var{file} outside of
30714 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30715 group, the id previously returned by
30716 @samp{-list-thread-groups --available} must be used.
30718 @subsubheading @value{GDBN} Command
30720 The corresponding @value{GDBN} command is @samp{attach}.
30722 @subsubheading Example
30726 =thread-created,id="1"
30727 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30733 @subheading The @code{-target-compare-sections} Command
30734 @findex -target-compare-sections
30736 @subsubheading Synopsis
30739 -target-compare-sections [ @var{section} ]
30742 Compare data of section @var{section} on target to the exec file.
30743 Without the argument, all sections are compared.
30745 @subsubheading @value{GDBN} Command
30747 The @value{GDBN} equivalent is @samp{compare-sections}.
30749 @subsubheading Example
30754 @subheading The @code{-target-detach} Command
30755 @findex -target-detach
30757 @subsubheading Synopsis
30760 -target-detach [ @var{pid} | @var{gid} ]
30763 Detach from the remote target which normally resumes its execution.
30764 If either @var{pid} or @var{gid} is specified, detaches from either
30765 the specified process, or specified thread group. There's no output.
30767 @subsubheading @value{GDBN} Command
30769 The corresponding @value{GDBN} command is @samp{detach}.
30771 @subsubheading Example
30781 @subheading The @code{-target-disconnect} Command
30782 @findex -target-disconnect
30784 @subsubheading Synopsis
30790 Disconnect from the remote target. There's no output and the target is
30791 generally not resumed.
30793 @subsubheading @value{GDBN} Command
30795 The corresponding @value{GDBN} command is @samp{disconnect}.
30797 @subsubheading Example
30807 @subheading The @code{-target-download} Command
30808 @findex -target-download
30810 @subsubheading Synopsis
30816 Loads the executable onto the remote target.
30817 It prints out an update message every half second, which includes the fields:
30821 The name of the section.
30823 The size of what has been sent so far for that section.
30825 The size of the section.
30827 The total size of what was sent so far (the current and the previous sections).
30829 The size of the overall executable to download.
30833 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30834 @sc{gdb/mi} Output Syntax}).
30836 In addition, it prints the name and size of the sections, as they are
30837 downloaded. These messages include the following fields:
30841 The name of the section.
30843 The size of the section.
30845 The size of the overall executable to download.
30849 At the end, a summary is printed.
30851 @subsubheading @value{GDBN} Command
30853 The corresponding @value{GDBN} command is @samp{load}.
30855 @subsubheading Example
30857 Note: each status message appears on a single line. Here the messages
30858 have been broken down so that they can fit onto a page.
30863 +download,@{section=".text",section-size="6668",total-size="9880"@}
30864 +download,@{section=".text",section-sent="512",section-size="6668",
30865 total-sent="512",total-size="9880"@}
30866 +download,@{section=".text",section-sent="1024",section-size="6668",
30867 total-sent="1024",total-size="9880"@}
30868 +download,@{section=".text",section-sent="1536",section-size="6668",
30869 total-sent="1536",total-size="9880"@}
30870 +download,@{section=".text",section-sent="2048",section-size="6668",
30871 total-sent="2048",total-size="9880"@}
30872 +download,@{section=".text",section-sent="2560",section-size="6668",
30873 total-sent="2560",total-size="9880"@}
30874 +download,@{section=".text",section-sent="3072",section-size="6668",
30875 total-sent="3072",total-size="9880"@}
30876 +download,@{section=".text",section-sent="3584",section-size="6668",
30877 total-sent="3584",total-size="9880"@}
30878 +download,@{section=".text",section-sent="4096",section-size="6668",
30879 total-sent="4096",total-size="9880"@}
30880 +download,@{section=".text",section-sent="4608",section-size="6668",
30881 total-sent="4608",total-size="9880"@}
30882 +download,@{section=".text",section-sent="5120",section-size="6668",
30883 total-sent="5120",total-size="9880"@}
30884 +download,@{section=".text",section-sent="5632",section-size="6668",
30885 total-sent="5632",total-size="9880"@}
30886 +download,@{section=".text",section-sent="6144",section-size="6668",
30887 total-sent="6144",total-size="9880"@}
30888 +download,@{section=".text",section-sent="6656",section-size="6668",
30889 total-sent="6656",total-size="9880"@}
30890 +download,@{section=".init",section-size="28",total-size="9880"@}
30891 +download,@{section=".fini",section-size="28",total-size="9880"@}
30892 +download,@{section=".data",section-size="3156",total-size="9880"@}
30893 +download,@{section=".data",section-sent="512",section-size="3156",
30894 total-sent="7236",total-size="9880"@}
30895 +download,@{section=".data",section-sent="1024",section-size="3156",
30896 total-sent="7748",total-size="9880"@}
30897 +download,@{section=".data",section-sent="1536",section-size="3156",
30898 total-sent="8260",total-size="9880"@}
30899 +download,@{section=".data",section-sent="2048",section-size="3156",
30900 total-sent="8772",total-size="9880"@}
30901 +download,@{section=".data",section-sent="2560",section-size="3156",
30902 total-sent="9284",total-size="9880"@}
30903 +download,@{section=".data",section-sent="3072",section-size="3156",
30904 total-sent="9796",total-size="9880"@}
30905 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30912 @subheading The @code{-target-exec-status} Command
30913 @findex -target-exec-status
30915 @subsubheading Synopsis
30918 -target-exec-status
30921 Provide information on the state of the target (whether it is running or
30922 not, for instance).
30924 @subsubheading @value{GDBN} Command
30926 There's no equivalent @value{GDBN} command.
30928 @subsubheading Example
30932 @subheading The @code{-target-list-available-targets} Command
30933 @findex -target-list-available-targets
30935 @subsubheading Synopsis
30938 -target-list-available-targets
30941 List the possible targets to connect to.
30943 @subsubheading @value{GDBN} Command
30945 The corresponding @value{GDBN} command is @samp{help target}.
30947 @subsubheading Example
30951 @subheading The @code{-target-list-current-targets} Command
30952 @findex -target-list-current-targets
30954 @subsubheading Synopsis
30957 -target-list-current-targets
30960 Describe the current target.
30962 @subsubheading @value{GDBN} Command
30964 The corresponding information is printed by @samp{info file} (among
30967 @subsubheading Example
30971 @subheading The @code{-target-list-parameters} Command
30972 @findex -target-list-parameters
30974 @subsubheading Synopsis
30977 -target-list-parameters
30983 @subsubheading @value{GDBN} Command
30987 @subsubheading Example
30991 @subheading The @code{-target-select} Command
30992 @findex -target-select
30994 @subsubheading Synopsis
30997 -target-select @var{type} @var{parameters @dots{}}
31000 Connect @value{GDBN} to the remote target. This command takes two args:
31004 The type of target, for instance @samp{remote}, etc.
31005 @item @var{parameters}
31006 Device names, host names and the like. @xref{Target Commands, ,
31007 Commands for Managing Targets}, for more details.
31010 The output is a connection notification, followed by the address at
31011 which the target program is, in the following form:
31014 ^connected,addr="@var{address}",func="@var{function name}",
31015 args=[@var{arg list}]
31018 @subsubheading @value{GDBN} Command
31020 The corresponding @value{GDBN} command is @samp{target}.
31022 @subsubheading Example
31026 -target-select remote /dev/ttya
31027 ^connected,addr="0xfe00a300",func="??",args=[]
31031 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31032 @node GDB/MI File Transfer Commands
31033 @section @sc{gdb/mi} File Transfer Commands
31036 @subheading The @code{-target-file-put} Command
31037 @findex -target-file-put
31039 @subsubheading Synopsis
31042 -target-file-put @var{hostfile} @var{targetfile}
31045 Copy file @var{hostfile} from the host system (the machine running
31046 @value{GDBN}) to @var{targetfile} on the target system.
31048 @subsubheading @value{GDBN} Command
31050 The corresponding @value{GDBN} command is @samp{remote put}.
31052 @subsubheading Example
31056 -target-file-put localfile remotefile
31062 @subheading The @code{-target-file-get} Command
31063 @findex -target-file-get
31065 @subsubheading Synopsis
31068 -target-file-get @var{targetfile} @var{hostfile}
31071 Copy file @var{targetfile} from the target system to @var{hostfile}
31072 on the host system.
31074 @subsubheading @value{GDBN} Command
31076 The corresponding @value{GDBN} command is @samp{remote get}.
31078 @subsubheading Example
31082 -target-file-get remotefile localfile
31088 @subheading The @code{-target-file-delete} Command
31089 @findex -target-file-delete
31091 @subsubheading Synopsis
31094 -target-file-delete @var{targetfile}
31097 Delete @var{targetfile} from the target system.
31099 @subsubheading @value{GDBN} Command
31101 The corresponding @value{GDBN} command is @samp{remote delete}.
31103 @subsubheading Example
31107 -target-file-delete remotefile
31113 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31114 @node GDB/MI Miscellaneous Commands
31115 @section Miscellaneous @sc{gdb/mi} Commands
31117 @c @subheading -gdb-complete
31119 @subheading The @code{-gdb-exit} Command
31122 @subsubheading Synopsis
31128 Exit @value{GDBN} immediately.
31130 @subsubheading @value{GDBN} Command
31132 Approximately corresponds to @samp{quit}.
31134 @subsubheading Example
31144 @subheading The @code{-exec-abort} Command
31145 @findex -exec-abort
31147 @subsubheading Synopsis
31153 Kill the inferior running program.
31155 @subsubheading @value{GDBN} Command
31157 The corresponding @value{GDBN} command is @samp{kill}.
31159 @subsubheading Example
31164 @subheading The @code{-gdb-set} Command
31167 @subsubheading Synopsis
31173 Set an internal @value{GDBN} variable.
31174 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31176 @subsubheading @value{GDBN} Command
31178 The corresponding @value{GDBN} command is @samp{set}.
31180 @subsubheading Example
31190 @subheading The @code{-gdb-show} Command
31193 @subsubheading Synopsis
31199 Show the current value of a @value{GDBN} variable.
31201 @subsubheading @value{GDBN} Command
31203 The corresponding @value{GDBN} command is @samp{show}.
31205 @subsubheading Example
31214 @c @subheading -gdb-source
31217 @subheading The @code{-gdb-version} Command
31218 @findex -gdb-version
31220 @subsubheading Synopsis
31226 Show version information for @value{GDBN}. Used mostly in testing.
31228 @subsubheading @value{GDBN} Command
31230 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31231 default shows this information when you start an interactive session.
31233 @subsubheading Example
31235 @c This example modifies the actual output from GDB to avoid overfull
31241 ~Copyright 2000 Free Software Foundation, Inc.
31242 ~GDB is free software, covered by the GNU General Public License, and
31243 ~you are welcome to change it and/or distribute copies of it under
31244 ~ certain conditions.
31245 ~Type "show copying" to see the conditions.
31246 ~There is absolutely no warranty for GDB. Type "show warranty" for
31248 ~This GDB was configured as
31249 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31254 @subheading The @code{-list-features} Command
31255 @findex -list-features
31257 Returns a list of particular features of the MI protocol that
31258 this version of gdb implements. A feature can be a command,
31259 or a new field in an output of some command, or even an
31260 important bugfix. While a frontend can sometimes detect presence
31261 of a feature at runtime, it is easier to perform detection at debugger
31264 The command returns a list of strings, with each string naming an
31265 available feature. Each returned string is just a name, it does not
31266 have any internal structure. The list of possible feature names
31272 (gdb) -list-features
31273 ^done,result=["feature1","feature2"]
31276 The current list of features is:
31279 @item frozen-varobjs
31280 Indicates support for the @code{-var-set-frozen} command, as well
31281 as possible presense of the @code{frozen} field in the output
31282 of @code{-varobj-create}.
31283 @item pending-breakpoints
31284 Indicates support for the @option{-f} option to the @code{-break-insert}
31287 Indicates Python scripting support, Python-based
31288 pretty-printing commands, and possible presence of the
31289 @samp{display_hint} field in the output of @code{-var-list-children}
31291 Indicates support for the @code{-thread-info} command.
31292 @item data-read-memory-bytes
31293 Indicates support for the @code{-data-read-memory-bytes} and the
31294 @code{-data-write-memory-bytes} commands.
31295 @item breakpoint-notifications
31296 Indicates that changes to breakpoints and breakpoints created via the
31297 CLI will be announced via async records.
31298 @item ada-task-info
31299 Indicates support for the @code{-ada-task-info} command.
31302 @subheading The @code{-list-target-features} Command
31303 @findex -list-target-features
31305 Returns a list of particular features that are supported by the
31306 target. Those features affect the permitted MI commands, but
31307 unlike the features reported by the @code{-list-features} command, the
31308 features depend on which target GDB is using at the moment. Whenever
31309 a target can change, due to commands such as @code{-target-select},
31310 @code{-target-attach} or @code{-exec-run}, the list of target features
31311 may change, and the frontend should obtain it again.
31315 (gdb) -list-features
31316 ^done,result=["async"]
31319 The current list of features is:
31323 Indicates that the target is capable of asynchronous command
31324 execution, which means that @value{GDBN} will accept further commands
31325 while the target is running.
31328 Indicates that the target is capable of reverse execution.
31329 @xref{Reverse Execution}, for more information.
31333 @subheading The @code{-list-thread-groups} Command
31334 @findex -list-thread-groups
31336 @subheading Synopsis
31339 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31342 Lists thread groups (@pxref{Thread groups}). When a single thread
31343 group is passed as the argument, lists the children of that group.
31344 When several thread group are passed, lists information about those
31345 thread groups. Without any parameters, lists information about all
31346 top-level thread groups.
31348 Normally, thread groups that are being debugged are reported.
31349 With the @samp{--available} option, @value{GDBN} reports thread groups
31350 available on the target.
31352 The output of this command may have either a @samp{threads} result or
31353 a @samp{groups} result. The @samp{thread} result has a list of tuples
31354 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31355 Information}). The @samp{groups} result has a list of tuples as value,
31356 each tuple describing a thread group. If top-level groups are
31357 requested (that is, no parameter is passed), or when several groups
31358 are passed, the output always has a @samp{groups} result. The format
31359 of the @samp{group} result is described below.
31361 To reduce the number of roundtrips it's possible to list thread groups
31362 together with their children, by passing the @samp{--recurse} option
31363 and the recursion depth. Presently, only recursion depth of 1 is
31364 permitted. If this option is present, then every reported thread group
31365 will also include its children, either as @samp{group} or
31366 @samp{threads} field.
31368 In general, any combination of option and parameters is permitted, with
31369 the following caveats:
31373 When a single thread group is passed, the output will typically
31374 be the @samp{threads} result. Because threads may not contain
31375 anything, the @samp{recurse} option will be ignored.
31378 When the @samp{--available} option is passed, limited information may
31379 be available. In particular, the list of threads of a process might
31380 be inaccessible. Further, specifying specific thread groups might
31381 not give any performance advantage over listing all thread groups.
31382 The frontend should assume that @samp{-list-thread-groups --available}
31383 is always an expensive operation and cache the results.
31387 The @samp{groups} result is a list of tuples, where each tuple may
31388 have the following fields:
31392 Identifier of the thread group. This field is always present.
31393 The identifier is an opaque string; frontends should not try to
31394 convert it to an integer, even though it might look like one.
31397 The type of the thread group. At present, only @samp{process} is a
31401 The target-specific process identifier. This field is only present
31402 for thread groups of type @samp{process} and only if the process exists.
31405 The number of children this thread group has. This field may be
31406 absent for an available thread group.
31409 This field has a list of tuples as value, each tuple describing a
31410 thread. It may be present if the @samp{--recurse} option is
31411 specified, and it's actually possible to obtain the threads.
31414 This field is a list of integers, each identifying a core that one
31415 thread of the group is running on. This field may be absent if
31416 such information is not available.
31419 The name of the executable file that corresponds to this thread group.
31420 The field is only present for thread groups of type @samp{process},
31421 and only if there is a corresponding executable file.
31425 @subheading Example
31429 -list-thread-groups
31430 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31431 -list-thread-groups 17
31432 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31433 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31434 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31435 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31436 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31437 -list-thread-groups --available
31438 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31439 -list-thread-groups --available --recurse 1
31440 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31441 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31442 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31443 -list-thread-groups --available --recurse 1 17 18
31444 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31445 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31446 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31450 @subheading The @code{-add-inferior} Command
31451 @findex -add-inferior
31453 @subheading Synopsis
31459 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31460 inferior is not associated with any executable. Such association may
31461 be established with the @samp{-file-exec-and-symbols} command
31462 (@pxref{GDB/MI File Commands}). The command response has a single
31463 field, @samp{thread-group}, whose value is the identifier of the
31464 thread group corresponding to the new inferior.
31466 @subheading Example
31471 ^done,thread-group="i3"
31474 @subheading The @code{-interpreter-exec} Command
31475 @findex -interpreter-exec
31477 @subheading Synopsis
31480 -interpreter-exec @var{interpreter} @var{command}
31482 @anchor{-interpreter-exec}
31484 Execute the specified @var{command} in the given @var{interpreter}.
31486 @subheading @value{GDBN} Command
31488 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31490 @subheading Example
31494 -interpreter-exec console "break main"
31495 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31496 &"During symbol reading, bad structure-type format.\n"
31497 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31502 @subheading The @code{-inferior-tty-set} Command
31503 @findex -inferior-tty-set
31505 @subheading Synopsis
31508 -inferior-tty-set /dev/pts/1
31511 Set terminal for future runs of the program being debugged.
31513 @subheading @value{GDBN} Command
31515 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31517 @subheading Example
31521 -inferior-tty-set /dev/pts/1
31526 @subheading The @code{-inferior-tty-show} Command
31527 @findex -inferior-tty-show
31529 @subheading Synopsis
31535 Show terminal for future runs of program being debugged.
31537 @subheading @value{GDBN} Command
31539 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31541 @subheading Example
31545 -inferior-tty-set /dev/pts/1
31549 ^done,inferior_tty_terminal="/dev/pts/1"
31553 @subheading The @code{-enable-timings} Command
31554 @findex -enable-timings
31556 @subheading Synopsis
31559 -enable-timings [yes | no]
31562 Toggle the printing of the wallclock, user and system times for an MI
31563 command as a field in its output. This command is to help frontend
31564 developers optimize the performance of their code. No argument is
31565 equivalent to @samp{yes}.
31567 @subheading @value{GDBN} Command
31571 @subheading Example
31579 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31580 addr="0x080484ed",func="main",file="myprog.c",
31581 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31582 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31590 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31591 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31592 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31593 fullname="/home/nickrob/myprog.c",line="73"@}
31598 @chapter @value{GDBN} Annotations
31600 This chapter describes annotations in @value{GDBN}. Annotations were
31601 designed to interface @value{GDBN} to graphical user interfaces or other
31602 similar programs which want to interact with @value{GDBN} at a
31603 relatively high level.
31605 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31609 This is Edition @value{EDITION}, @value{DATE}.
31613 * Annotations Overview:: What annotations are; the general syntax.
31614 * Server Prefix:: Issuing a command without affecting user state.
31615 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31616 * Errors:: Annotations for error messages.
31617 * Invalidation:: Some annotations describe things now invalid.
31618 * Annotations for Running::
31619 Whether the program is running, how it stopped, etc.
31620 * Source Annotations:: Annotations describing source code.
31623 @node Annotations Overview
31624 @section What is an Annotation?
31625 @cindex annotations
31627 Annotations start with a newline character, two @samp{control-z}
31628 characters, and the name of the annotation. If there is no additional
31629 information associated with this annotation, the name of the annotation
31630 is followed immediately by a newline. If there is additional
31631 information, the name of the annotation is followed by a space, the
31632 additional information, and a newline. The additional information
31633 cannot contain newline characters.
31635 Any output not beginning with a newline and two @samp{control-z}
31636 characters denotes literal output from @value{GDBN}. Currently there is
31637 no need for @value{GDBN} to output a newline followed by two
31638 @samp{control-z} characters, but if there was such a need, the
31639 annotations could be extended with an @samp{escape} annotation which
31640 means those three characters as output.
31642 The annotation @var{level}, which is specified using the
31643 @option{--annotate} command line option (@pxref{Mode Options}), controls
31644 how much information @value{GDBN} prints together with its prompt,
31645 values of expressions, source lines, and other types of output. Level 0
31646 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31647 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31648 for programs that control @value{GDBN}, and level 2 annotations have
31649 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31650 Interface, annotate, GDB's Obsolete Annotations}).
31653 @kindex set annotate
31654 @item set annotate @var{level}
31655 The @value{GDBN} command @code{set annotate} sets the level of
31656 annotations to the specified @var{level}.
31658 @item show annotate
31659 @kindex show annotate
31660 Show the current annotation level.
31663 This chapter describes level 3 annotations.
31665 A simple example of starting up @value{GDBN} with annotations is:
31668 $ @kbd{gdb --annotate=3}
31670 Copyright 2003 Free Software Foundation, Inc.
31671 GDB is free software, covered by the GNU General Public License,
31672 and you are welcome to change it and/or distribute copies of it
31673 under certain conditions.
31674 Type "show copying" to see the conditions.
31675 There is absolutely no warranty for GDB. Type "show warranty"
31677 This GDB was configured as "i386-pc-linux-gnu"
31688 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31689 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31690 denotes a @samp{control-z} character) are annotations; the rest is
31691 output from @value{GDBN}.
31693 @node Server Prefix
31694 @section The Server Prefix
31695 @cindex server prefix
31697 If you prefix a command with @samp{server } then it will not affect
31698 the command history, nor will it affect @value{GDBN}'s notion of which
31699 command to repeat if @key{RET} is pressed on a line by itself. This
31700 means that commands can be run behind a user's back by a front-end in
31701 a transparent manner.
31703 The @code{server } prefix does not affect the recording of values into
31704 the value history; to print a value without recording it into the
31705 value history, use the @code{output} command instead of the
31706 @code{print} command.
31708 Using this prefix also disables confirmation requests
31709 (@pxref{confirmation requests}).
31712 @section Annotation for @value{GDBN} Input
31714 @cindex annotations for prompts
31715 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31716 to know when to send output, when the output from a given command is
31719 Different kinds of input each have a different @dfn{input type}. Each
31720 input type has three annotations: a @code{pre-} annotation, which
31721 denotes the beginning of any prompt which is being output, a plain
31722 annotation, which denotes the end of the prompt, and then a @code{post-}
31723 annotation which denotes the end of any echo which may (or may not) be
31724 associated with the input. For example, the @code{prompt} input type
31725 features the following annotations:
31733 The input types are
31736 @findex pre-prompt annotation
31737 @findex prompt annotation
31738 @findex post-prompt annotation
31740 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31742 @findex pre-commands annotation
31743 @findex commands annotation
31744 @findex post-commands annotation
31746 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31747 command. The annotations are repeated for each command which is input.
31749 @findex pre-overload-choice annotation
31750 @findex overload-choice annotation
31751 @findex post-overload-choice annotation
31752 @item overload-choice
31753 When @value{GDBN} wants the user to select between various overloaded functions.
31755 @findex pre-query annotation
31756 @findex query annotation
31757 @findex post-query annotation
31759 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31761 @findex pre-prompt-for-continue annotation
31762 @findex prompt-for-continue annotation
31763 @findex post-prompt-for-continue annotation
31764 @item prompt-for-continue
31765 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31766 expect this to work well; instead use @code{set height 0} to disable
31767 prompting. This is because the counting of lines is buggy in the
31768 presence of annotations.
31773 @cindex annotations for errors, warnings and interrupts
31775 @findex quit annotation
31780 This annotation occurs right before @value{GDBN} responds to an interrupt.
31782 @findex error annotation
31787 This annotation occurs right before @value{GDBN} responds to an error.
31789 Quit and error annotations indicate that any annotations which @value{GDBN} was
31790 in the middle of may end abruptly. For example, if a
31791 @code{value-history-begin} annotation is followed by a @code{error}, one
31792 cannot expect to receive the matching @code{value-history-end}. One
31793 cannot expect not to receive it either, however; an error annotation
31794 does not necessarily mean that @value{GDBN} is immediately returning all the way
31797 @findex error-begin annotation
31798 A quit or error annotation may be preceded by
31804 Any output between that and the quit or error annotation is the error
31807 Warning messages are not yet annotated.
31808 @c If we want to change that, need to fix warning(), type_error(),
31809 @c range_error(), and possibly other places.
31812 @section Invalidation Notices
31814 @cindex annotations for invalidation messages
31815 The following annotations say that certain pieces of state may have
31819 @findex frames-invalid annotation
31820 @item ^Z^Zframes-invalid
31822 The frames (for example, output from the @code{backtrace} command) may
31825 @findex breakpoints-invalid annotation
31826 @item ^Z^Zbreakpoints-invalid
31828 The breakpoints may have changed. For example, the user just added or
31829 deleted a breakpoint.
31832 @node Annotations for Running
31833 @section Running the Program
31834 @cindex annotations for running programs
31836 @findex starting annotation
31837 @findex stopping annotation
31838 When the program starts executing due to a @value{GDBN} command such as
31839 @code{step} or @code{continue},
31845 is output. When the program stops,
31851 is output. Before the @code{stopped} annotation, a variety of
31852 annotations describe how the program stopped.
31855 @findex exited annotation
31856 @item ^Z^Zexited @var{exit-status}
31857 The program exited, and @var{exit-status} is the exit status (zero for
31858 successful exit, otherwise nonzero).
31860 @findex signalled annotation
31861 @findex signal-name annotation
31862 @findex signal-name-end annotation
31863 @findex signal-string annotation
31864 @findex signal-string-end annotation
31865 @item ^Z^Zsignalled
31866 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31867 annotation continues:
31873 ^Z^Zsignal-name-end
31877 ^Z^Zsignal-string-end
31882 where @var{name} is the name of the signal, such as @code{SIGILL} or
31883 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31884 as @code{Illegal Instruction} or @code{Segmentation fault}.
31885 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31886 user's benefit and have no particular format.
31888 @findex signal annotation
31890 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31891 just saying that the program received the signal, not that it was
31892 terminated with it.
31894 @findex breakpoint annotation
31895 @item ^Z^Zbreakpoint @var{number}
31896 The program hit breakpoint number @var{number}.
31898 @findex watchpoint annotation
31899 @item ^Z^Zwatchpoint @var{number}
31900 The program hit watchpoint number @var{number}.
31903 @node Source Annotations
31904 @section Displaying Source
31905 @cindex annotations for source display
31907 @findex source annotation
31908 The following annotation is used instead of displaying source code:
31911 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31914 where @var{filename} is an absolute file name indicating which source
31915 file, @var{line} is the line number within that file (where 1 is the
31916 first line in the file), @var{character} is the character position
31917 within the file (where 0 is the first character in the file) (for most
31918 debug formats this will necessarily point to the beginning of a line),
31919 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31920 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31921 @var{addr} is the address in the target program associated with the
31922 source which is being displayed. @var{addr} is in the form @samp{0x}
31923 followed by one or more lowercase hex digits (note that this does not
31924 depend on the language).
31926 @node JIT Interface
31927 @chapter JIT Compilation Interface
31928 @cindex just-in-time compilation
31929 @cindex JIT compilation interface
31931 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31932 interface. A JIT compiler is a program or library that generates native
31933 executable code at runtime and executes it, usually in order to achieve good
31934 performance while maintaining platform independence.
31936 Programs that use JIT compilation are normally difficult to debug because
31937 portions of their code are generated at runtime, instead of being loaded from
31938 object files, which is where @value{GDBN} normally finds the program's symbols
31939 and debug information. In order to debug programs that use JIT compilation,
31940 @value{GDBN} has an interface that allows the program to register in-memory
31941 symbol files with @value{GDBN} at runtime.
31943 If you are using @value{GDBN} to debug a program that uses this interface, then
31944 it should work transparently so long as you have not stripped the binary. If
31945 you are developing a JIT compiler, then the interface is documented in the rest
31946 of this chapter. At this time, the only known client of this interface is the
31949 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31950 JIT compiler communicates with @value{GDBN} by writing data into a global
31951 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31952 attaches, it reads a linked list of symbol files from the global variable to
31953 find existing code, and puts a breakpoint in the function so that it can find
31954 out about additional code.
31957 * Declarations:: Relevant C struct declarations
31958 * Registering Code:: Steps to register code
31959 * Unregistering Code:: Steps to unregister code
31960 * Custom Debug Info:: Emit debug information in a custom format
31964 @section JIT Declarations
31966 These are the relevant struct declarations that a C program should include to
31967 implement the interface:
31977 struct jit_code_entry
31979 struct jit_code_entry *next_entry;
31980 struct jit_code_entry *prev_entry;
31981 const char *symfile_addr;
31982 uint64_t symfile_size;
31985 struct jit_descriptor
31988 /* This type should be jit_actions_t, but we use uint32_t
31989 to be explicit about the bitwidth. */
31990 uint32_t action_flag;
31991 struct jit_code_entry *relevant_entry;
31992 struct jit_code_entry *first_entry;
31995 /* GDB puts a breakpoint in this function. */
31996 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31998 /* Make sure to specify the version statically, because the
31999 debugger may check the version before we can set it. */
32000 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32003 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32004 modifications to this global data properly, which can easily be done by putting
32005 a global mutex around modifications to these structures.
32007 @node Registering Code
32008 @section Registering Code
32010 To register code with @value{GDBN}, the JIT should follow this protocol:
32014 Generate an object file in memory with symbols and other desired debug
32015 information. The file must include the virtual addresses of the sections.
32018 Create a code entry for the file, which gives the start and size of the symbol
32022 Add it to the linked list in the JIT descriptor.
32025 Point the relevant_entry field of the descriptor at the entry.
32028 Set @code{action_flag} to @code{JIT_REGISTER} and call
32029 @code{__jit_debug_register_code}.
32032 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32033 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32034 new code. However, the linked list must still be maintained in order to allow
32035 @value{GDBN} to attach to a running process and still find the symbol files.
32037 @node Unregistering Code
32038 @section Unregistering Code
32040 If code is freed, then the JIT should use the following protocol:
32044 Remove the code entry corresponding to the code from the linked list.
32047 Point the @code{relevant_entry} field of the descriptor at the code entry.
32050 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32051 @code{__jit_debug_register_code}.
32054 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32055 and the JIT will leak the memory used for the associated symbol files.
32057 @node Custom Debug Info
32058 @section Custom Debug Info
32059 @cindex custom JIT debug info
32060 @cindex JIT debug info reader
32062 Generating debug information in platform-native file formats (like ELF
32063 or COFF) may be an overkill for JIT compilers; especially if all the
32064 debug info is used for is displaying a meaningful backtrace. The
32065 issue can be resolved by having the JIT writers decide on a debug info
32066 format and also provide a reader that parses the debug info generated
32067 by the JIT compiler. This section gives a brief overview on writing
32068 such a parser. More specific details can be found in the source file
32069 @file{gdb/jit-reader.in}, which is also installed as a header at
32070 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32072 The reader is implemented as a shared object (so this functionality is
32073 not available on platforms which don't allow loading shared objects at
32074 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32075 @code{jit-reader-unload} are provided, to be used to load and unload
32076 the readers from a preconfigured directory. Once loaded, the shared
32077 object is used the parse the debug information emitted by the JIT
32081 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32082 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32085 @node Using JIT Debug Info Readers
32086 @subsection Using JIT Debug Info Readers
32087 @kindex jit-reader-load
32088 @kindex jit-reader-unload
32090 Readers can be loaded and unloaded using the @code{jit-reader-load}
32091 and @code{jit-reader-unload} commands.
32094 @item jit-reader-load @var{reader-name}
32095 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32096 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32097 @var{libdir} is the system library directory, usually
32098 @file{/usr/local/lib}. Only one reader can be active at a time;
32099 trying to load a second reader when one is already loaded will result
32100 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32101 first unloading the current one using @code{jit-reader-load} and then
32102 invoking @code{jit-reader-load}.
32104 @item jit-reader-unload
32105 Unload the currently loaded JIT reader.
32109 @node Writing JIT Debug Info Readers
32110 @subsection Writing JIT Debug Info Readers
32111 @cindex writing JIT debug info readers
32113 As mentioned, a reader is essentially a shared object conforming to a
32114 certain ABI. This ABI is described in @file{jit-reader.h}.
32116 @file{jit-reader.h} defines the structures, macros and functions
32117 required to write a reader. It is installed (along with
32118 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32119 the system include directory.
32121 Readers need to be released under a GPL compatible license. A reader
32122 can be declared as released under such a license by placing the macro
32123 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32125 The entry point for readers is the symbol @code{gdb_init_reader},
32126 which is expected to be a function with the prototype
32128 @findex gdb_init_reader
32130 extern struct gdb_reader_funcs *gdb_init_reader (void);
32133 @cindex @code{struct gdb_reader_funcs}
32135 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32136 functions. These functions are executed to read the debug info
32137 generated by the JIT compiler (@code{read}), to unwind stack frames
32138 (@code{unwind}) and to create canonical frame IDs
32139 (@code{get_Frame_id}). It also has a callback that is called when the
32140 reader is being unloaded (@code{destroy}). The struct looks like this
32143 struct gdb_reader_funcs
32145 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32146 int reader_version;
32148 /* For use by the reader. */
32151 gdb_read_debug_info *read;
32152 gdb_unwind_frame *unwind;
32153 gdb_get_frame_id *get_frame_id;
32154 gdb_destroy_reader *destroy;
32158 @cindex @code{struct gdb_symbol_callbacks}
32159 @cindex @code{struct gdb_unwind_callbacks}
32161 The callbacks are provided with another set of callbacks by
32162 @value{GDBN} to do their job. For @code{read}, these callbacks are
32163 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32164 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32165 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32166 files and new symbol tables inside those object files. @code{struct
32167 gdb_unwind_callbacks} has callbacks to read registers off the current
32168 frame and to write out the values of the registers in the previous
32169 frame. Both have a callback (@code{target_read}) to read bytes off the
32170 target's address space.
32173 @chapter Reporting Bugs in @value{GDBN}
32174 @cindex bugs in @value{GDBN}
32175 @cindex reporting bugs in @value{GDBN}
32177 Your bug reports play an essential role in making @value{GDBN} reliable.
32179 Reporting a bug may help you by bringing a solution to your problem, or it
32180 may not. But in any case the principal function of a bug report is to help
32181 the entire community by making the next version of @value{GDBN} work better. Bug
32182 reports are your contribution to the maintenance of @value{GDBN}.
32184 In order for a bug report to serve its purpose, you must include the
32185 information that enables us to fix the bug.
32188 * Bug Criteria:: Have you found a bug?
32189 * Bug Reporting:: How to report bugs
32193 @section Have You Found a Bug?
32194 @cindex bug criteria
32196 If you are not sure whether you have found a bug, here are some guidelines:
32199 @cindex fatal signal
32200 @cindex debugger crash
32201 @cindex crash of debugger
32203 If the debugger gets a fatal signal, for any input whatever, that is a
32204 @value{GDBN} bug. Reliable debuggers never crash.
32206 @cindex error on valid input
32208 If @value{GDBN} produces an error message for valid input, that is a
32209 bug. (Note that if you're cross debugging, the problem may also be
32210 somewhere in the connection to the target.)
32212 @cindex invalid input
32214 If @value{GDBN} does not produce an error message for invalid input,
32215 that is a bug. However, you should note that your idea of
32216 ``invalid input'' might be our idea of ``an extension'' or ``support
32217 for traditional practice''.
32220 If you are an experienced user of debugging tools, your suggestions
32221 for improvement of @value{GDBN} are welcome in any case.
32224 @node Bug Reporting
32225 @section How to Report Bugs
32226 @cindex bug reports
32227 @cindex @value{GDBN} bugs, reporting
32229 A number of companies and individuals offer support for @sc{gnu} products.
32230 If you obtained @value{GDBN} from a support organization, we recommend you
32231 contact that organization first.
32233 You can find contact information for many support companies and
32234 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32236 @c should add a web page ref...
32239 @ifset BUGURL_DEFAULT
32240 In any event, we also recommend that you submit bug reports for
32241 @value{GDBN}. The preferred method is to submit them directly using
32242 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32243 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32246 @strong{Do not send bug reports to @samp{info-gdb}, or to
32247 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32248 not want to receive bug reports. Those that do have arranged to receive
32251 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32252 serves as a repeater. The mailing list and the newsgroup carry exactly
32253 the same messages. Often people think of posting bug reports to the
32254 newsgroup instead of mailing them. This appears to work, but it has one
32255 problem which can be crucial: a newsgroup posting often lacks a mail
32256 path back to the sender. Thus, if we need to ask for more information,
32257 we may be unable to reach you. For this reason, it is better to send
32258 bug reports to the mailing list.
32260 @ifclear BUGURL_DEFAULT
32261 In any event, we also recommend that you submit bug reports for
32262 @value{GDBN} to @value{BUGURL}.
32266 The fundamental principle of reporting bugs usefully is this:
32267 @strong{report all the facts}. If you are not sure whether to state a
32268 fact or leave it out, state it!
32270 Often people omit facts because they think they know what causes the
32271 problem and assume that some details do not matter. Thus, you might
32272 assume that the name of the variable you use in an example does not matter.
32273 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32274 stray memory reference which happens to fetch from the location where that
32275 name is stored in memory; perhaps, if the name were different, the contents
32276 of that location would fool the debugger into doing the right thing despite
32277 the bug. Play it safe and give a specific, complete example. That is the
32278 easiest thing for you to do, and the most helpful.
32280 Keep in mind that the purpose of a bug report is to enable us to fix the
32281 bug. It may be that the bug has been reported previously, but neither
32282 you nor we can know that unless your bug report is complete and
32285 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32286 bell?'' Those bug reports are useless, and we urge everyone to
32287 @emph{refuse to respond to them} except to chide the sender to report
32290 To enable us to fix the bug, you should include all these things:
32294 The version of @value{GDBN}. @value{GDBN} announces it if you start
32295 with no arguments; you can also print it at any time using @code{show
32298 Without this, we will not know whether there is any point in looking for
32299 the bug in the current version of @value{GDBN}.
32302 The type of machine you are using, and the operating system name and
32306 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32307 ``@value{GCC}--2.8.1''.
32310 What compiler (and its version) was used to compile the program you are
32311 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32312 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32313 to get this information; for other compilers, see the documentation for
32317 The command arguments you gave the compiler to compile your example and
32318 observe the bug. For example, did you use @samp{-O}? To guarantee
32319 you will not omit something important, list them all. A copy of the
32320 Makefile (or the output from make) is sufficient.
32322 If we were to try to guess the arguments, we would probably guess wrong
32323 and then we might not encounter the bug.
32326 A complete input script, and all necessary source files, that will
32330 A description of what behavior you observe that you believe is
32331 incorrect. For example, ``It gets a fatal signal.''
32333 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32334 will certainly notice it. But if the bug is incorrect output, we might
32335 not notice unless it is glaringly wrong. You might as well not give us
32336 a chance to make a mistake.
32338 Even if the problem you experience is a fatal signal, you should still
32339 say so explicitly. Suppose something strange is going on, such as, your
32340 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32341 the C library on your system. (This has happened!) Your copy might
32342 crash and ours would not. If you told us to expect a crash, then when
32343 ours fails to crash, we would know that the bug was not happening for
32344 us. If you had not told us to expect a crash, then we would not be able
32345 to draw any conclusion from our observations.
32348 @cindex recording a session script
32349 To collect all this information, you can use a session recording program
32350 such as @command{script}, which is available on many Unix systems.
32351 Just run your @value{GDBN} session inside @command{script} and then
32352 include the @file{typescript} file with your bug report.
32354 Another way to record a @value{GDBN} session is to run @value{GDBN}
32355 inside Emacs and then save the entire buffer to a file.
32358 If you wish to suggest changes to the @value{GDBN} source, send us context
32359 diffs. If you even discuss something in the @value{GDBN} source, refer to
32360 it by context, not by line number.
32362 The line numbers in our development sources will not match those in your
32363 sources. Your line numbers would convey no useful information to us.
32367 Here are some things that are not necessary:
32371 A description of the envelope of the bug.
32373 Often people who encounter a bug spend a lot of time investigating
32374 which changes to the input file will make the bug go away and which
32375 changes will not affect it.
32377 This is often time consuming and not very useful, because the way we
32378 will find the bug is by running a single example under the debugger
32379 with breakpoints, not by pure deduction from a series of examples.
32380 We recommend that you save your time for something else.
32382 Of course, if you can find a simpler example to report @emph{instead}
32383 of the original one, that is a convenience for us. Errors in the
32384 output will be easier to spot, running under the debugger will take
32385 less time, and so on.
32387 However, simplification is not vital; if you do not want to do this,
32388 report the bug anyway and send us the entire test case you used.
32391 A patch for the bug.
32393 A patch for the bug does help us if it is a good one. But do not omit
32394 the necessary information, such as the test case, on the assumption that
32395 a patch is all we need. We might see problems with your patch and decide
32396 to fix the problem another way, or we might not understand it at all.
32398 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32399 construct an example that will make the program follow a certain path
32400 through the code. If you do not send us the example, we will not be able
32401 to construct one, so we will not be able to verify that the bug is fixed.
32403 And if we cannot understand what bug you are trying to fix, or why your
32404 patch should be an improvement, we will not install it. A test case will
32405 help us to understand.
32408 A guess about what the bug is or what it depends on.
32410 Such guesses are usually wrong. Even we cannot guess right about such
32411 things without first using the debugger to find the facts.
32414 @c The readline documentation is distributed with the readline code
32415 @c and consists of the two following files:
32418 @c Use -I with makeinfo to point to the appropriate directory,
32419 @c environment var TEXINPUTS with TeX.
32420 @ifclear SYSTEM_READLINE
32421 @include rluser.texi
32422 @include hsuser.texi
32426 @appendix In Memoriam
32428 The @value{GDBN} project mourns the loss of the following long-time
32433 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32434 to Free Software in general. Outside of @value{GDBN}, he was known in
32435 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32437 @item Michael Snyder
32438 Michael was one of the Global Maintainers of the @value{GDBN} project,
32439 with contributions recorded as early as 1996, until 2011. In addition
32440 to his day to day participation, he was a large driving force behind
32441 adding Reverse Debugging to @value{GDBN}.
32444 Beyond their technical contributions to the project, they were also
32445 enjoyable members of the Free Software Community. We will miss them.
32447 @node Formatting Documentation
32448 @appendix Formatting Documentation
32450 @cindex @value{GDBN} reference card
32451 @cindex reference card
32452 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32453 for printing with PostScript or Ghostscript, in the @file{gdb}
32454 subdirectory of the main source directory@footnote{In
32455 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32456 release.}. If you can use PostScript or Ghostscript with your printer,
32457 you can print the reference card immediately with @file{refcard.ps}.
32459 The release also includes the source for the reference card. You
32460 can format it, using @TeX{}, by typing:
32466 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32467 mode on US ``letter'' size paper;
32468 that is, on a sheet 11 inches wide by 8.5 inches
32469 high. You will need to specify this form of printing as an option to
32470 your @sc{dvi} output program.
32472 @cindex documentation
32474 All the documentation for @value{GDBN} comes as part of the machine-readable
32475 distribution. The documentation is written in Texinfo format, which is
32476 a documentation system that uses a single source file to produce both
32477 on-line information and a printed manual. You can use one of the Info
32478 formatting commands to create the on-line version of the documentation
32479 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32481 @value{GDBN} includes an already formatted copy of the on-line Info
32482 version of this manual in the @file{gdb} subdirectory. The main Info
32483 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32484 subordinate files matching @samp{gdb.info*} in the same directory. If
32485 necessary, you can print out these files, or read them with any editor;
32486 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32487 Emacs or the standalone @code{info} program, available as part of the
32488 @sc{gnu} Texinfo distribution.
32490 If you want to format these Info files yourself, you need one of the
32491 Info formatting programs, such as @code{texinfo-format-buffer} or
32494 If you have @code{makeinfo} installed, and are in the top level
32495 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32496 version @value{GDBVN}), you can make the Info file by typing:
32503 If you want to typeset and print copies of this manual, you need @TeX{},
32504 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32505 Texinfo definitions file.
32507 @TeX{} is a typesetting program; it does not print files directly, but
32508 produces output files called @sc{dvi} files. To print a typeset
32509 document, you need a program to print @sc{dvi} files. If your system
32510 has @TeX{} installed, chances are it has such a program. The precise
32511 command to use depends on your system; @kbd{lpr -d} is common; another
32512 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32513 require a file name without any extension or a @samp{.dvi} extension.
32515 @TeX{} also requires a macro definitions file called
32516 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32517 written in Texinfo format. On its own, @TeX{} cannot either read or
32518 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32519 and is located in the @file{gdb-@var{version-number}/texinfo}
32522 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32523 typeset and print this manual. First switch to the @file{gdb}
32524 subdirectory of the main source directory (for example, to
32525 @file{gdb-@value{GDBVN}/gdb}) and type:
32531 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32533 @node Installing GDB
32534 @appendix Installing @value{GDBN}
32535 @cindex installation
32538 * Requirements:: Requirements for building @value{GDBN}
32539 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32540 * Separate Objdir:: Compiling @value{GDBN} in another directory
32541 * Config Names:: Specifying names for hosts and targets
32542 * Configure Options:: Summary of options for configure
32543 * System-wide configuration:: Having a system-wide init file
32547 @section Requirements for Building @value{GDBN}
32548 @cindex building @value{GDBN}, requirements for
32550 Building @value{GDBN} requires various tools and packages to be available.
32551 Other packages will be used only if they are found.
32553 @heading Tools/Packages Necessary for Building @value{GDBN}
32555 @item ISO C90 compiler
32556 @value{GDBN} is written in ISO C90. It should be buildable with any
32557 working C90 compiler, e.g.@: GCC.
32561 @heading Tools/Packages Optional for Building @value{GDBN}
32565 @value{GDBN} can use the Expat XML parsing library. This library may be
32566 included with your operating system distribution; if it is not, you
32567 can get the latest version from @url{http://expat.sourceforge.net}.
32568 The @file{configure} script will search for this library in several
32569 standard locations; if it is installed in an unusual path, you can
32570 use the @option{--with-libexpat-prefix} option to specify its location.
32576 Remote protocol memory maps (@pxref{Memory Map Format})
32578 Target descriptions (@pxref{Target Descriptions})
32580 Remote shared library lists (@xref{Library List Format},
32581 or alternatively @pxref{Library List Format for SVR4 Targets})
32583 MS-Windows shared libraries (@pxref{Shared Libraries})
32585 Traceframe info (@pxref{Traceframe Info Format})
32589 @cindex compressed debug sections
32590 @value{GDBN} will use the @samp{zlib} library, if available, to read
32591 compressed debug sections. Some linkers, such as GNU gold, are capable
32592 of producing binaries with compressed debug sections. If @value{GDBN}
32593 is compiled with @samp{zlib}, it will be able to read the debug
32594 information in such binaries.
32596 The @samp{zlib} library is likely included with your operating system
32597 distribution; if it is not, you can get the latest version from
32598 @url{http://zlib.net}.
32601 @value{GDBN}'s features related to character sets (@pxref{Character
32602 Sets}) require a functioning @code{iconv} implementation. If you are
32603 on a GNU system, then this is provided by the GNU C Library. Some
32604 other systems also provide a working @code{iconv}.
32606 If @value{GDBN} is using the @code{iconv} program which is installed
32607 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32608 This is done with @option{--with-iconv-bin} which specifies the
32609 directory that contains the @code{iconv} program.
32611 On systems without @code{iconv}, you can install GNU Libiconv. If you
32612 have previously installed Libiconv, you can use the
32613 @option{--with-libiconv-prefix} option to configure.
32615 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32616 arrange to build Libiconv if a directory named @file{libiconv} appears
32617 in the top-most source directory. If Libiconv is built this way, and
32618 if the operating system does not provide a suitable @code{iconv}
32619 implementation, then the just-built library will automatically be used
32620 by @value{GDBN}. One easy way to set this up is to download GNU
32621 Libiconv, unpack it, and then rename the directory holding the
32622 Libiconv source code to @samp{libiconv}.
32625 @node Running Configure
32626 @section Invoking the @value{GDBN} @file{configure} Script
32627 @cindex configuring @value{GDBN}
32628 @value{GDBN} comes with a @file{configure} script that automates the process
32629 of preparing @value{GDBN} for installation; you can then use @code{make} to
32630 build the @code{gdb} program.
32632 @c irrelevant in info file; it's as current as the code it lives with.
32633 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32634 look at the @file{README} file in the sources; we may have improved the
32635 installation procedures since publishing this manual.}
32638 The @value{GDBN} distribution includes all the source code you need for
32639 @value{GDBN} in a single directory, whose name is usually composed by
32640 appending the version number to @samp{gdb}.
32642 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32643 @file{gdb-@value{GDBVN}} directory. That directory contains:
32646 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32647 script for configuring @value{GDBN} and all its supporting libraries
32649 @item gdb-@value{GDBVN}/gdb
32650 the source specific to @value{GDBN} itself
32652 @item gdb-@value{GDBVN}/bfd
32653 source for the Binary File Descriptor library
32655 @item gdb-@value{GDBVN}/include
32656 @sc{gnu} include files
32658 @item gdb-@value{GDBVN}/libiberty
32659 source for the @samp{-liberty} free software library
32661 @item gdb-@value{GDBVN}/opcodes
32662 source for the library of opcode tables and disassemblers
32664 @item gdb-@value{GDBVN}/readline
32665 source for the @sc{gnu} command-line interface
32667 @item gdb-@value{GDBVN}/glob
32668 source for the @sc{gnu} filename pattern-matching subroutine
32670 @item gdb-@value{GDBVN}/mmalloc
32671 source for the @sc{gnu} memory-mapped malloc package
32674 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32675 from the @file{gdb-@var{version-number}} source directory, which in
32676 this example is the @file{gdb-@value{GDBVN}} directory.
32678 First switch to the @file{gdb-@var{version-number}} source directory
32679 if you are not already in it; then run @file{configure}. Pass the
32680 identifier for the platform on which @value{GDBN} will run as an
32686 cd gdb-@value{GDBVN}
32687 ./configure @var{host}
32692 where @var{host} is an identifier such as @samp{sun4} or
32693 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32694 (You can often leave off @var{host}; @file{configure} tries to guess the
32695 correct value by examining your system.)
32697 Running @samp{configure @var{host}} and then running @code{make} builds the
32698 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32699 libraries, then @code{gdb} itself. The configured source files, and the
32700 binaries, are left in the corresponding source directories.
32703 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32704 system does not recognize this automatically when you run a different
32705 shell, you may need to run @code{sh} on it explicitly:
32708 sh configure @var{host}
32711 If you run @file{configure} from a directory that contains source
32712 directories for multiple libraries or programs, such as the
32713 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32715 creates configuration files for every directory level underneath (unless
32716 you tell it not to, with the @samp{--norecursion} option).
32718 You should run the @file{configure} script from the top directory in the
32719 source tree, the @file{gdb-@var{version-number}} directory. If you run
32720 @file{configure} from one of the subdirectories, you will configure only
32721 that subdirectory. That is usually not what you want. In particular,
32722 if you run the first @file{configure} from the @file{gdb} subdirectory
32723 of the @file{gdb-@var{version-number}} directory, you will omit the
32724 configuration of @file{bfd}, @file{readline}, and other sibling
32725 directories of the @file{gdb} subdirectory. This leads to build errors
32726 about missing include files such as @file{bfd/bfd.h}.
32728 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32729 However, you should make sure that the shell on your path (named by
32730 the @samp{SHELL} environment variable) is publicly readable. Remember
32731 that @value{GDBN} uses the shell to start your program---some systems refuse to
32732 let @value{GDBN} debug child processes whose programs are not readable.
32734 @node Separate Objdir
32735 @section Compiling @value{GDBN} in Another Directory
32737 If you want to run @value{GDBN} versions for several host or target machines,
32738 you need a different @code{gdb} compiled for each combination of
32739 host and target. @file{configure} is designed to make this easy by
32740 allowing you to generate each configuration in a separate subdirectory,
32741 rather than in the source directory. If your @code{make} program
32742 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32743 @code{make} in each of these directories builds the @code{gdb}
32744 program specified there.
32746 To build @code{gdb} in a separate directory, run @file{configure}
32747 with the @samp{--srcdir} option to specify where to find the source.
32748 (You also need to specify a path to find @file{configure}
32749 itself from your working directory. If the path to @file{configure}
32750 would be the same as the argument to @samp{--srcdir}, you can leave out
32751 the @samp{--srcdir} option; it is assumed.)
32753 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32754 separate directory for a Sun 4 like this:
32758 cd gdb-@value{GDBVN}
32761 ../gdb-@value{GDBVN}/configure sun4
32766 When @file{configure} builds a configuration using a remote source
32767 directory, it creates a tree for the binaries with the same structure
32768 (and using the same names) as the tree under the source directory. In
32769 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32770 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32771 @file{gdb-sun4/gdb}.
32773 Make sure that your path to the @file{configure} script has just one
32774 instance of @file{gdb} in it. If your path to @file{configure} looks
32775 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32776 one subdirectory of @value{GDBN}, not the whole package. This leads to
32777 build errors about missing include files such as @file{bfd/bfd.h}.
32779 One popular reason to build several @value{GDBN} configurations in separate
32780 directories is to configure @value{GDBN} for cross-compiling (where
32781 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32782 programs that run on another machine---the @dfn{target}).
32783 You specify a cross-debugging target by
32784 giving the @samp{--target=@var{target}} option to @file{configure}.
32786 When you run @code{make} to build a program or library, you must run
32787 it in a configured directory---whatever directory you were in when you
32788 called @file{configure} (or one of its subdirectories).
32790 The @code{Makefile} that @file{configure} generates in each source
32791 directory also runs recursively. If you type @code{make} in a source
32792 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32793 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32794 will build all the required libraries, and then build GDB.
32796 When you have multiple hosts or targets configured in separate
32797 directories, you can run @code{make} on them in parallel (for example,
32798 if they are NFS-mounted on each of the hosts); they will not interfere
32802 @section Specifying Names for Hosts and Targets
32804 The specifications used for hosts and targets in the @file{configure}
32805 script are based on a three-part naming scheme, but some short predefined
32806 aliases are also supported. The full naming scheme encodes three pieces
32807 of information in the following pattern:
32810 @var{architecture}-@var{vendor}-@var{os}
32813 For example, you can use the alias @code{sun4} as a @var{host} argument,
32814 or as the value for @var{target} in a @code{--target=@var{target}}
32815 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32817 The @file{configure} script accompanying @value{GDBN} does not provide
32818 any query facility to list all supported host and target names or
32819 aliases. @file{configure} calls the Bourne shell script
32820 @code{config.sub} to map abbreviations to full names; you can read the
32821 script, if you wish, or you can use it to test your guesses on
32822 abbreviations---for example:
32825 % sh config.sub i386-linux
32827 % sh config.sub alpha-linux
32828 alpha-unknown-linux-gnu
32829 % sh config.sub hp9k700
32831 % sh config.sub sun4
32832 sparc-sun-sunos4.1.1
32833 % sh config.sub sun3
32834 m68k-sun-sunos4.1.1
32835 % sh config.sub i986v
32836 Invalid configuration `i986v': machine `i986v' not recognized
32840 @code{config.sub} is also distributed in the @value{GDBN} source
32841 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32843 @node Configure Options
32844 @section @file{configure} Options
32846 Here is a summary of the @file{configure} options and arguments that
32847 are most often useful for building @value{GDBN}. @file{configure} also has
32848 several other options not listed here. @inforef{What Configure
32849 Does,,configure.info}, for a full explanation of @file{configure}.
32852 configure @r{[}--help@r{]}
32853 @r{[}--prefix=@var{dir}@r{]}
32854 @r{[}--exec-prefix=@var{dir}@r{]}
32855 @r{[}--srcdir=@var{dirname}@r{]}
32856 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32857 @r{[}--target=@var{target}@r{]}
32862 You may introduce options with a single @samp{-} rather than
32863 @samp{--} if you prefer; but you may abbreviate option names if you use
32868 Display a quick summary of how to invoke @file{configure}.
32870 @item --prefix=@var{dir}
32871 Configure the source to install programs and files under directory
32874 @item --exec-prefix=@var{dir}
32875 Configure the source to install programs under directory
32878 @c avoid splitting the warning from the explanation:
32880 @item --srcdir=@var{dirname}
32881 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32882 @code{make} that implements the @code{VPATH} feature.}@*
32883 Use this option to make configurations in directories separate from the
32884 @value{GDBN} source directories. Among other things, you can use this to
32885 build (or maintain) several configurations simultaneously, in separate
32886 directories. @file{configure} writes configuration-specific files in
32887 the current directory, but arranges for them to use the source in the
32888 directory @var{dirname}. @file{configure} creates directories under
32889 the working directory in parallel to the source directories below
32892 @item --norecursion
32893 Configure only the directory level where @file{configure} is executed; do not
32894 propagate configuration to subdirectories.
32896 @item --target=@var{target}
32897 Configure @value{GDBN} for cross-debugging programs running on the specified
32898 @var{target}. Without this option, @value{GDBN} is configured to debug
32899 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32901 There is no convenient way to generate a list of all available targets.
32903 @item @var{host} @dots{}
32904 Configure @value{GDBN} to run on the specified @var{host}.
32906 There is no convenient way to generate a list of all available hosts.
32909 There are many other options available as well, but they are generally
32910 needed for special purposes only.
32912 @node System-wide configuration
32913 @section System-wide configuration and settings
32914 @cindex system-wide init file
32916 @value{GDBN} can be configured to have a system-wide init file;
32917 this file will be read and executed at startup (@pxref{Startup, , What
32918 @value{GDBN} does during startup}).
32920 Here is the corresponding configure option:
32923 @item --with-system-gdbinit=@var{file}
32924 Specify that the default location of the system-wide init file is
32928 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32929 it may be subject to relocation. Two possible cases:
32933 If the default location of this init file contains @file{$prefix},
32934 it will be subject to relocation. Suppose that the configure options
32935 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32936 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32937 init file is looked for as @file{$install/etc/gdbinit} instead of
32938 @file{$prefix/etc/gdbinit}.
32941 By contrast, if the default location does not contain the prefix,
32942 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32943 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32944 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32945 wherever @value{GDBN} is installed.
32948 @node Maintenance Commands
32949 @appendix Maintenance Commands
32950 @cindex maintenance commands
32951 @cindex internal commands
32953 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32954 includes a number of commands intended for @value{GDBN} developers,
32955 that are not documented elsewhere in this manual. These commands are
32956 provided here for reference. (For commands that turn on debugging
32957 messages, see @ref{Debugging Output}.)
32960 @kindex maint agent
32961 @kindex maint agent-eval
32962 @item maint agent @var{expression}
32963 @itemx maint agent-eval @var{expression}
32964 Translate the given @var{expression} into remote agent bytecodes.
32965 This command is useful for debugging the Agent Expression mechanism
32966 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32967 expression useful for data collection, such as by tracepoints, while
32968 @samp{maint agent-eval} produces an expression that evaluates directly
32969 to a result. For instance, a collection expression for @code{globa +
32970 globb} will include bytecodes to record four bytes of memory at each
32971 of the addresses of @code{globa} and @code{globb}, while discarding
32972 the result of the addition, while an evaluation expression will do the
32973 addition and return the sum.
32975 @kindex maint info breakpoints
32976 @item @anchor{maint info breakpoints}maint info breakpoints
32977 Using the same format as @samp{info breakpoints}, display both the
32978 breakpoints you've set explicitly, and those @value{GDBN} is using for
32979 internal purposes. Internal breakpoints are shown with negative
32980 breakpoint numbers. The type column identifies what kind of breakpoint
32985 Normal, explicitly set breakpoint.
32988 Normal, explicitly set watchpoint.
32991 Internal breakpoint, used to handle correctly stepping through
32992 @code{longjmp} calls.
32994 @item longjmp resume
32995 Internal breakpoint at the target of a @code{longjmp}.
32998 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33001 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33004 Shared library events.
33008 @kindex set displaced-stepping
33009 @kindex show displaced-stepping
33010 @cindex displaced stepping support
33011 @cindex out-of-line single-stepping
33012 @item set displaced-stepping
33013 @itemx show displaced-stepping
33014 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33015 if the target supports it. Displaced stepping is a way to single-step
33016 over breakpoints without removing them from the inferior, by executing
33017 an out-of-line copy of the instruction that was originally at the
33018 breakpoint location. It is also known as out-of-line single-stepping.
33021 @item set displaced-stepping on
33022 If the target architecture supports it, @value{GDBN} will use
33023 displaced stepping to step over breakpoints.
33025 @item set displaced-stepping off
33026 @value{GDBN} will not use displaced stepping to step over breakpoints,
33027 even if such is supported by the target architecture.
33029 @cindex non-stop mode, and @samp{set displaced-stepping}
33030 @item set displaced-stepping auto
33031 This is the default mode. @value{GDBN} will use displaced stepping
33032 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33033 architecture supports displaced stepping.
33036 @kindex maint check-symtabs
33037 @item maint check-symtabs
33038 Check the consistency of psymtabs and symtabs.
33040 @kindex maint cplus first_component
33041 @item maint cplus first_component @var{name}
33042 Print the first C@t{++} class/namespace component of @var{name}.
33044 @kindex maint cplus namespace
33045 @item maint cplus namespace
33046 Print the list of possible C@t{++} namespaces.
33048 @kindex maint demangle
33049 @item maint demangle @var{name}
33050 Demangle a C@t{++} or Objective-C mangled @var{name}.
33052 @kindex maint deprecate
33053 @kindex maint undeprecate
33054 @cindex deprecated commands
33055 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33056 @itemx maint undeprecate @var{command}
33057 Deprecate or undeprecate the named @var{command}. Deprecated commands
33058 cause @value{GDBN} to issue a warning when you use them. The optional
33059 argument @var{replacement} says which newer command should be used in
33060 favor of the deprecated one; if it is given, @value{GDBN} will mention
33061 the replacement as part of the warning.
33063 @kindex maint dump-me
33064 @item maint dump-me
33065 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33066 Cause a fatal signal in the debugger and force it to dump its core.
33067 This is supported only on systems which support aborting a program
33068 with the @code{SIGQUIT} signal.
33070 @kindex maint internal-error
33071 @kindex maint internal-warning
33072 @item maint internal-error @r{[}@var{message-text}@r{]}
33073 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33074 Cause @value{GDBN} to call the internal function @code{internal_error}
33075 or @code{internal_warning} and hence behave as though an internal error
33076 or internal warning has been detected. In addition to reporting the
33077 internal problem, these functions give the user the opportunity to
33078 either quit @value{GDBN} or create a core file of the current
33079 @value{GDBN} session.
33081 These commands take an optional parameter @var{message-text} that is
33082 used as the text of the error or warning message.
33084 Here's an example of using @code{internal-error}:
33087 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33088 @dots{}/maint.c:121: internal-error: testing, 1, 2
33089 A problem internal to GDB has been detected. Further
33090 debugging may prove unreliable.
33091 Quit this debugging session? (y or n) @kbd{n}
33092 Create a core file? (y or n) @kbd{n}
33096 @cindex @value{GDBN} internal error
33097 @cindex internal errors, control of @value{GDBN} behavior
33099 @kindex maint set internal-error
33100 @kindex maint show internal-error
33101 @kindex maint set internal-warning
33102 @kindex maint show internal-warning
33103 @item maint set internal-error @var{action} [ask|yes|no]
33104 @itemx maint show internal-error @var{action}
33105 @itemx maint set internal-warning @var{action} [ask|yes|no]
33106 @itemx maint show internal-warning @var{action}
33107 When @value{GDBN} reports an internal problem (error or warning) it
33108 gives the user the opportunity to both quit @value{GDBN} and create a
33109 core file of the current @value{GDBN} session. These commands let you
33110 override the default behaviour for each particular @var{action},
33111 described in the table below.
33115 You can specify that @value{GDBN} should always (yes) or never (no)
33116 quit. The default is to ask the user what to do.
33119 You can specify that @value{GDBN} should always (yes) or never (no)
33120 create a core file. The default is to ask the user what to do.
33123 @kindex maint packet
33124 @item maint packet @var{text}
33125 If @value{GDBN} is talking to an inferior via the serial protocol,
33126 then this command sends the string @var{text} to the inferior, and
33127 displays the response packet. @value{GDBN} supplies the initial
33128 @samp{$} character, the terminating @samp{#} character, and the
33131 @kindex maint print architecture
33132 @item maint print architecture @r{[}@var{file}@r{]}
33133 Print the entire architecture configuration. The optional argument
33134 @var{file} names the file where the output goes.
33136 @kindex maint print c-tdesc
33137 @item maint print c-tdesc
33138 Print the current target description (@pxref{Target Descriptions}) as
33139 a C source file. The created source file can be used in @value{GDBN}
33140 when an XML parser is not available to parse the description.
33142 @kindex maint print dummy-frames
33143 @item maint print dummy-frames
33144 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33147 (@value{GDBP}) @kbd{b add}
33149 (@value{GDBP}) @kbd{print add(2,3)}
33150 Breakpoint 2, add (a=2, b=3) at @dots{}
33152 The program being debugged stopped while in a function called from GDB.
33154 (@value{GDBP}) @kbd{maint print dummy-frames}
33155 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33156 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33157 call_lo=0x01014000 call_hi=0x01014001
33161 Takes an optional file parameter.
33163 @kindex maint print registers
33164 @kindex maint print raw-registers
33165 @kindex maint print cooked-registers
33166 @kindex maint print register-groups
33167 @kindex maint print remote-registers
33168 @item maint print registers @r{[}@var{file}@r{]}
33169 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33170 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33171 @itemx maint print register-groups @r{[}@var{file}@r{]}
33172 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33173 Print @value{GDBN}'s internal register data structures.
33175 The command @code{maint print raw-registers} includes the contents of
33176 the raw register cache; the command @code{maint print
33177 cooked-registers} includes the (cooked) value of all registers,
33178 including registers which aren't available on the target nor visible
33179 to user; the command @code{maint print register-groups} includes the
33180 groups that each register is a member of; and the command @code{maint
33181 print remote-registers} includes the remote target's register numbers
33182 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33183 @value{GDBN} Internals}.
33185 These commands take an optional parameter, a file name to which to
33186 write the information.
33188 @kindex maint print reggroups
33189 @item maint print reggroups @r{[}@var{file}@r{]}
33190 Print @value{GDBN}'s internal register group data structures. The
33191 optional argument @var{file} tells to what file to write the
33194 The register groups info looks like this:
33197 (@value{GDBP}) @kbd{maint print reggroups}
33210 This command forces @value{GDBN} to flush its internal register cache.
33212 @kindex maint print objfiles
33213 @cindex info for known object files
33214 @item maint print objfiles
33215 Print a dump of all known object files. For each object file, this
33216 command prints its name, address in memory, and all of its psymtabs
33219 @kindex maint print section-scripts
33220 @cindex info for known .debug_gdb_scripts-loaded scripts
33221 @item maint print section-scripts [@var{regexp}]
33222 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33223 If @var{regexp} is specified, only print scripts loaded by object files
33224 matching @var{regexp}.
33225 For each script, this command prints its name as specified in the objfile,
33226 and the full path if known.
33227 @xref{.debug_gdb_scripts section}.
33229 @kindex maint print statistics
33230 @cindex bcache statistics
33231 @item maint print statistics
33232 This command prints, for each object file in the program, various data
33233 about that object file followed by the byte cache (@dfn{bcache})
33234 statistics for the object file. The objfile data includes the number
33235 of minimal, partial, full, and stabs symbols, the number of types
33236 defined by the objfile, the number of as yet unexpanded psym tables,
33237 the number of line tables and string tables, and the amount of memory
33238 used by the various tables. The bcache statistics include the counts,
33239 sizes, and counts of duplicates of all and unique objects, max,
33240 average, and median entry size, total memory used and its overhead and
33241 savings, and various measures of the hash table size and chain
33244 @kindex maint print target-stack
33245 @cindex target stack description
33246 @item maint print target-stack
33247 A @dfn{target} is an interface between the debugger and a particular
33248 kind of file or process. Targets can be stacked in @dfn{strata},
33249 so that more than one target can potentially respond to a request.
33250 In particular, memory accesses will walk down the stack of targets
33251 until they find a target that is interested in handling that particular
33254 This command prints a short description of each layer that was pushed on
33255 the @dfn{target stack}, starting from the top layer down to the bottom one.
33257 @kindex maint print type
33258 @cindex type chain of a data type
33259 @item maint print type @var{expr}
33260 Print the type chain for a type specified by @var{expr}. The argument
33261 can be either a type name or a symbol. If it is a symbol, the type of
33262 that symbol is described. The type chain produced by this command is
33263 a recursive definition of the data type as stored in @value{GDBN}'s
33264 data structures, including its flags and contained types.
33266 @kindex maint set dwarf2 always-disassemble
33267 @kindex maint show dwarf2 always-disassemble
33268 @item maint set dwarf2 always-disassemble
33269 @item maint show dwarf2 always-disassemble
33270 Control the behavior of @code{info address} when using DWARF debugging
33273 The default is @code{off}, which means that @value{GDBN} should try to
33274 describe a variable's location in an easily readable format. When
33275 @code{on}, @value{GDBN} will instead display the DWARF location
33276 expression in an assembly-like format. Note that some locations are
33277 too complex for @value{GDBN} to describe simply; in this case you will
33278 always see the disassembly form.
33280 Here is an example of the resulting disassembly:
33283 (gdb) info addr argc
33284 Symbol "argc" is a complex DWARF expression:
33288 For more information on these expressions, see
33289 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33291 @kindex maint set dwarf2 max-cache-age
33292 @kindex maint show dwarf2 max-cache-age
33293 @item maint set dwarf2 max-cache-age
33294 @itemx maint show dwarf2 max-cache-age
33295 Control the DWARF 2 compilation unit cache.
33297 @cindex DWARF 2 compilation units cache
33298 In object files with inter-compilation-unit references, such as those
33299 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33300 reader needs to frequently refer to previously read compilation units.
33301 This setting controls how long a compilation unit will remain in the
33302 cache if it is not referenced. A higher limit means that cached
33303 compilation units will be stored in memory longer, and more total
33304 memory will be used. Setting it to zero disables caching, which will
33305 slow down @value{GDBN} startup, but reduce memory consumption.
33307 @kindex maint set profile
33308 @kindex maint show profile
33309 @cindex profiling GDB
33310 @item maint set profile
33311 @itemx maint show profile
33312 Control profiling of @value{GDBN}.
33314 Profiling will be disabled until you use the @samp{maint set profile}
33315 command to enable it. When you enable profiling, the system will begin
33316 collecting timing and execution count data; when you disable profiling or
33317 exit @value{GDBN}, the results will be written to a log file. Remember that
33318 if you use profiling, @value{GDBN} will overwrite the profiling log file
33319 (often called @file{gmon.out}). If you have a record of important profiling
33320 data in a @file{gmon.out} file, be sure to move it to a safe location.
33322 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33323 compiled with the @samp{-pg} compiler option.
33325 @kindex maint set show-debug-regs
33326 @kindex maint show show-debug-regs
33327 @cindex hardware debug registers
33328 @item maint set show-debug-regs
33329 @itemx maint show show-debug-regs
33330 Control whether to show variables that mirror the hardware debug
33331 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33332 enabled, the debug registers values are shown when @value{GDBN} inserts or
33333 removes a hardware breakpoint or watchpoint, and when the inferior
33334 triggers a hardware-assisted breakpoint or watchpoint.
33336 @kindex maint set show-all-tib
33337 @kindex maint show show-all-tib
33338 @item maint set show-all-tib
33339 @itemx maint show show-all-tib
33340 Control whether to show all non zero areas within a 1k block starting
33341 at thread local base, when using the @samp{info w32 thread-information-block}
33344 @kindex maint space
33345 @cindex memory used by commands
33347 Control whether to display memory usage for each command. If set to a
33348 nonzero value, @value{GDBN} will display how much memory each command
33349 took, following the command's own output. This can also be requested
33350 by invoking @value{GDBN} with the @option{--statistics} command-line
33351 switch (@pxref{Mode Options}).
33354 @cindex time of command execution
33356 Control whether to display the execution time of @value{GDBN} for each command.
33357 If set to a nonzero value, @value{GDBN} will display how much time it
33358 took to execute each command, following the command's own output.
33359 Both CPU time and wallclock time are printed.
33360 Printing both is useful when trying to determine whether the cost is
33361 CPU or, e.g., disk/network, latency.
33362 Note that the CPU time printed is for @value{GDBN} only, it does not include
33363 the execution time of the inferior because there's no mechanism currently
33364 to compute how much time was spent by @value{GDBN} and how much time was
33365 spent by the program been debugged.
33366 This can also be requested by invoking @value{GDBN} with the
33367 @option{--statistics} command-line switch (@pxref{Mode Options}).
33369 @kindex maint translate-address
33370 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33371 Find the symbol stored at the location specified by the address
33372 @var{addr} and an optional section name @var{section}. If found,
33373 @value{GDBN} prints the name of the closest symbol and an offset from
33374 the symbol's location to the specified address. This is similar to
33375 the @code{info address} command (@pxref{Symbols}), except that this
33376 command also allows to find symbols in other sections.
33378 If section was not specified, the section in which the symbol was found
33379 is also printed. For dynamically linked executables, the name of
33380 executable or shared library containing the symbol is printed as well.
33384 The following command is useful for non-interactive invocations of
33385 @value{GDBN}, such as in the test suite.
33388 @item set watchdog @var{nsec}
33389 @kindex set watchdog
33390 @cindex watchdog timer
33391 @cindex timeout for commands
33392 Set the maximum number of seconds @value{GDBN} will wait for the
33393 target operation to finish. If this time expires, @value{GDBN}
33394 reports and error and the command is aborted.
33396 @item show watchdog
33397 Show the current setting of the target wait timeout.
33400 @node Remote Protocol
33401 @appendix @value{GDBN} Remote Serial Protocol
33406 * Stop Reply Packets::
33407 * General Query Packets::
33408 * Architecture-Specific Protocol Details::
33409 * Tracepoint Packets::
33410 * Host I/O Packets::
33412 * Notification Packets::
33413 * Remote Non-Stop::
33414 * Packet Acknowledgment::
33416 * File-I/O Remote Protocol Extension::
33417 * Library List Format::
33418 * Library List Format for SVR4 Targets::
33419 * Memory Map Format::
33420 * Thread List Format::
33421 * Traceframe Info Format::
33427 There may be occasions when you need to know something about the
33428 protocol---for example, if there is only one serial port to your target
33429 machine, you might want your program to do something special if it
33430 recognizes a packet meant for @value{GDBN}.
33432 In the examples below, @samp{->} and @samp{<-} are used to indicate
33433 transmitted and received data, respectively.
33435 @cindex protocol, @value{GDBN} remote serial
33436 @cindex serial protocol, @value{GDBN} remote
33437 @cindex remote serial protocol
33438 All @value{GDBN} commands and responses (other than acknowledgments
33439 and notifications, see @ref{Notification Packets}) are sent as a
33440 @var{packet}. A @var{packet} is introduced with the character
33441 @samp{$}, the actual @var{packet-data}, and the terminating character
33442 @samp{#} followed by a two-digit @var{checksum}:
33445 @code{$}@var{packet-data}@code{#}@var{checksum}
33449 @cindex checksum, for @value{GDBN} remote
33451 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33452 characters between the leading @samp{$} and the trailing @samp{#} (an
33453 eight bit unsigned checksum).
33455 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33456 specification also included an optional two-digit @var{sequence-id}:
33459 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33462 @cindex sequence-id, for @value{GDBN} remote
33464 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33465 has never output @var{sequence-id}s. Stubs that handle packets added
33466 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33468 When either the host or the target machine receives a packet, the first
33469 response expected is an acknowledgment: either @samp{+} (to indicate
33470 the package was received correctly) or @samp{-} (to request
33474 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33479 The @samp{+}/@samp{-} acknowledgments can be disabled
33480 once a connection is established.
33481 @xref{Packet Acknowledgment}, for details.
33483 The host (@value{GDBN}) sends @var{command}s, and the target (the
33484 debugging stub incorporated in your program) sends a @var{response}. In
33485 the case of step and continue @var{command}s, the response is only sent
33486 when the operation has completed, and the target has again stopped all
33487 threads in all attached processes. This is the default all-stop mode
33488 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33489 execution mode; see @ref{Remote Non-Stop}, for details.
33491 @var{packet-data} consists of a sequence of characters with the
33492 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33495 @cindex remote protocol, field separator
33496 Fields within the packet should be separated using @samp{,} @samp{;} or
33497 @samp{:}. Except where otherwise noted all numbers are represented in
33498 @sc{hex} with leading zeros suppressed.
33500 Implementors should note that prior to @value{GDBN} 5.0, the character
33501 @samp{:} could not appear as the third character in a packet (as it
33502 would potentially conflict with the @var{sequence-id}).
33504 @cindex remote protocol, binary data
33505 @anchor{Binary Data}
33506 Binary data in most packets is encoded either as two hexadecimal
33507 digits per byte of binary data. This allowed the traditional remote
33508 protocol to work over connections which were only seven-bit clean.
33509 Some packets designed more recently assume an eight-bit clean
33510 connection, and use a more efficient encoding to send and receive
33513 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33514 as an escape character. Any escaped byte is transmitted as the escape
33515 character followed by the original character XORed with @code{0x20}.
33516 For example, the byte @code{0x7d} would be transmitted as the two
33517 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33518 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33519 @samp{@}}) must always be escaped. Responses sent by the stub
33520 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33521 is not interpreted as the start of a run-length encoded sequence
33524 Response @var{data} can be run-length encoded to save space.
33525 Run-length encoding replaces runs of identical characters with one
33526 instance of the repeated character, followed by a @samp{*} and a
33527 repeat count. The repeat count is itself sent encoded, to avoid
33528 binary characters in @var{data}: a value of @var{n} is sent as
33529 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33530 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33531 code 32) for a repeat count of 3. (This is because run-length
33532 encoding starts to win for counts 3 or more.) Thus, for example,
33533 @samp{0* } is a run-length encoding of ``0000'': the space character
33534 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33537 The printable characters @samp{#} and @samp{$} or with a numeric value
33538 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33539 seven repeats (@samp{$}) can be expanded using a repeat count of only
33540 five (@samp{"}). For example, @samp{00000000} can be encoded as
33543 The error response returned for some packets includes a two character
33544 error number. That number is not well defined.
33546 @cindex empty response, for unsupported packets
33547 For any @var{command} not supported by the stub, an empty response
33548 (@samp{$#00}) should be returned. That way it is possible to extend the
33549 protocol. A newer @value{GDBN} can tell if a packet is supported based
33552 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33553 commands for register access, and the @samp{m} and @samp{M} commands
33554 for memory access. Stubs that only control single-threaded targets
33555 can implement run control with the @samp{c} (continue), and @samp{s}
33556 (step) commands. Stubs that support multi-threading targets should
33557 support the @samp{vCont} command. All other commands are optional.
33562 The following table provides a complete list of all currently defined
33563 @var{command}s and their corresponding response @var{data}.
33564 @xref{File-I/O Remote Protocol Extension}, for details about the File
33565 I/O extension of the remote protocol.
33567 Each packet's description has a template showing the packet's overall
33568 syntax, followed by an explanation of the packet's meaning. We
33569 include spaces in some of the templates for clarity; these are not
33570 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33571 separate its components. For example, a template like @samp{foo
33572 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33573 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33574 @var{baz}. @value{GDBN} does not transmit a space character between the
33575 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33578 @cindex @var{thread-id}, in remote protocol
33579 @anchor{thread-id syntax}
33580 Several packets and replies include a @var{thread-id} field to identify
33581 a thread. Normally these are positive numbers with a target-specific
33582 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33583 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33586 In addition, the remote protocol supports a multiprocess feature in
33587 which the @var{thread-id} syntax is extended to optionally include both
33588 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33589 The @var{pid} (process) and @var{tid} (thread) components each have the
33590 format described above: a positive number with target-specific
33591 interpretation formatted as a big-endian hex string, literal @samp{-1}
33592 to indicate all processes or threads (respectively), or @samp{0} to
33593 indicate an arbitrary process or thread. Specifying just a process, as
33594 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33595 error to specify all processes but a specific thread, such as
33596 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33597 for those packets and replies explicitly documented to include a process
33598 ID, rather than a @var{thread-id}.
33600 The multiprocess @var{thread-id} syntax extensions are only used if both
33601 @value{GDBN} and the stub report support for the @samp{multiprocess}
33602 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33605 Note that all packet forms beginning with an upper- or lower-case
33606 letter, other than those described here, are reserved for future use.
33608 Here are the packet descriptions.
33613 @cindex @samp{!} packet
33614 @anchor{extended mode}
33615 Enable extended mode. In extended mode, the remote server is made
33616 persistent. The @samp{R} packet is used to restart the program being
33622 The remote target both supports and has enabled extended mode.
33626 @cindex @samp{?} packet
33627 Indicate the reason the target halted. The reply is the same as for
33628 step and continue. This packet has a special interpretation when the
33629 target is in non-stop mode; see @ref{Remote Non-Stop}.
33632 @xref{Stop Reply Packets}, for the reply specifications.
33634 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33635 @cindex @samp{A} packet
33636 Initialized @code{argv[]} array passed into program. @var{arglen}
33637 specifies the number of bytes in the hex encoded byte stream
33638 @var{arg}. See @code{gdbserver} for more details.
33643 The arguments were set.
33649 @cindex @samp{b} packet
33650 (Don't use this packet; its behavior is not well-defined.)
33651 Change the serial line speed to @var{baud}.
33653 JTC: @emph{When does the transport layer state change? When it's
33654 received, or after the ACK is transmitted. In either case, there are
33655 problems if the command or the acknowledgment packet is dropped.}
33657 Stan: @emph{If people really wanted to add something like this, and get
33658 it working for the first time, they ought to modify ser-unix.c to send
33659 some kind of out-of-band message to a specially-setup stub and have the
33660 switch happen "in between" packets, so that from remote protocol's point
33661 of view, nothing actually happened.}
33663 @item B @var{addr},@var{mode}
33664 @cindex @samp{B} packet
33665 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33666 breakpoint at @var{addr}.
33668 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33669 (@pxref{insert breakpoint or watchpoint packet}).
33671 @cindex @samp{bc} packet
33674 Backward continue. Execute the target system in reverse. No parameter.
33675 @xref{Reverse Execution}, for more information.
33678 @xref{Stop Reply Packets}, for the reply specifications.
33680 @cindex @samp{bs} packet
33683 Backward single step. Execute one instruction in reverse. No parameter.
33684 @xref{Reverse Execution}, for more information.
33687 @xref{Stop Reply Packets}, for the reply specifications.
33689 @item c @r{[}@var{addr}@r{]}
33690 @cindex @samp{c} packet
33691 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33692 resume at current address.
33694 This packet is deprecated for multi-threading support. @xref{vCont
33698 @xref{Stop Reply Packets}, for the reply specifications.
33700 @item C @var{sig}@r{[};@var{addr}@r{]}
33701 @cindex @samp{C} packet
33702 Continue with signal @var{sig} (hex signal number). If
33703 @samp{;@var{addr}} is omitted, resume at same address.
33705 This packet is deprecated for multi-threading support. @xref{vCont
33709 @xref{Stop Reply Packets}, for the reply specifications.
33712 @cindex @samp{d} packet
33715 Don't use this packet; instead, define a general set packet
33716 (@pxref{General Query Packets}).
33720 @cindex @samp{D} packet
33721 The first form of the packet is used to detach @value{GDBN} from the
33722 remote system. It is sent to the remote target
33723 before @value{GDBN} disconnects via the @code{detach} command.
33725 The second form, including a process ID, is used when multiprocess
33726 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33727 detach only a specific process. The @var{pid} is specified as a
33728 big-endian hex string.
33738 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33739 @cindex @samp{F} packet
33740 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33741 This is part of the File-I/O protocol extension. @xref{File-I/O
33742 Remote Protocol Extension}, for the specification.
33745 @anchor{read registers packet}
33746 @cindex @samp{g} packet
33747 Read general registers.
33751 @item @var{XX@dots{}}
33752 Each byte of register data is described by two hex digits. The bytes
33753 with the register are transmitted in target byte order. The size of
33754 each register and their position within the @samp{g} packet are
33755 determined by the @value{GDBN} internal gdbarch functions
33756 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33757 specification of several standard @samp{g} packets is specified below.
33759 When reading registers from a trace frame (@pxref{Analyze Collected
33760 Data,,Using the Collected Data}), the stub may also return a string of
33761 literal @samp{x}'s in place of the register data digits, to indicate
33762 that the corresponding register has not been collected, thus its value
33763 is unavailable. For example, for an architecture with 4 registers of
33764 4 bytes each, the following reply indicates to @value{GDBN} that
33765 registers 0 and 2 have not been collected, while registers 1 and 3
33766 have been collected, and both have zero value:
33770 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33777 @item G @var{XX@dots{}}
33778 @cindex @samp{G} packet
33779 Write general registers. @xref{read registers packet}, for a
33780 description of the @var{XX@dots{}} data.
33790 @item H @var{op} @var{thread-id}
33791 @cindex @samp{H} packet
33792 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33793 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33794 it should be @samp{c} for step and continue operations (note that this
33795 is deprecated, supporting the @samp{vCont} command is a better
33796 option), @samp{g} for other operations. The thread designator
33797 @var{thread-id} has the format and interpretation described in
33798 @ref{thread-id syntax}.
33809 @c 'H': How restrictive (or permissive) is the thread model. If a
33810 @c thread is selected and stopped, are other threads allowed
33811 @c to continue to execute? As I mentioned above, I think the
33812 @c semantics of each command when a thread is selected must be
33813 @c described. For example:
33815 @c 'g': If the stub supports threads and a specific thread is
33816 @c selected, returns the register block from that thread;
33817 @c otherwise returns current registers.
33819 @c 'G' If the stub supports threads and a specific thread is
33820 @c selected, sets the registers of the register block of
33821 @c that thread; otherwise sets current registers.
33823 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33824 @anchor{cycle step packet}
33825 @cindex @samp{i} packet
33826 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33827 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33828 step starting at that address.
33831 @cindex @samp{I} packet
33832 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33836 @cindex @samp{k} packet
33839 FIXME: @emph{There is no description of how to operate when a specific
33840 thread context has been selected (i.e.@: does 'k' kill only that
33843 @item m @var{addr},@var{length}
33844 @cindex @samp{m} packet
33845 Read @var{length} bytes of memory starting at address @var{addr}.
33846 Note that @var{addr} may not be aligned to any particular boundary.
33848 The stub need not use any particular size or alignment when gathering
33849 data from memory for the response; even if @var{addr} is word-aligned
33850 and @var{length} is a multiple of the word size, the stub is free to
33851 use byte accesses, or not. For this reason, this packet may not be
33852 suitable for accessing memory-mapped I/O devices.
33853 @cindex alignment of remote memory accesses
33854 @cindex size of remote memory accesses
33855 @cindex memory, alignment and size of remote accesses
33859 @item @var{XX@dots{}}
33860 Memory contents; each byte is transmitted as a two-digit hexadecimal
33861 number. The reply may contain fewer bytes than requested if the
33862 server was able to read only part of the region of memory.
33867 @item M @var{addr},@var{length}:@var{XX@dots{}}
33868 @cindex @samp{M} packet
33869 Write @var{length} bytes of memory starting at address @var{addr}.
33870 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33871 hexadecimal number.
33878 for an error (this includes the case where only part of the data was
33883 @cindex @samp{p} packet
33884 Read the value of register @var{n}; @var{n} is in hex.
33885 @xref{read registers packet}, for a description of how the returned
33886 register value is encoded.
33890 @item @var{XX@dots{}}
33891 the register's value
33895 Indicating an unrecognized @var{query}.
33898 @item P @var{n@dots{}}=@var{r@dots{}}
33899 @anchor{write register packet}
33900 @cindex @samp{P} packet
33901 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33902 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33903 digits for each byte in the register (target byte order).
33913 @item q @var{name} @var{params}@dots{}
33914 @itemx Q @var{name} @var{params}@dots{}
33915 @cindex @samp{q} packet
33916 @cindex @samp{Q} packet
33917 General query (@samp{q}) and set (@samp{Q}). These packets are
33918 described fully in @ref{General Query Packets}.
33921 @cindex @samp{r} packet
33922 Reset the entire system.
33924 Don't use this packet; use the @samp{R} packet instead.
33927 @cindex @samp{R} packet
33928 Restart the program being debugged. @var{XX}, while needed, is ignored.
33929 This packet is only available in extended mode (@pxref{extended mode}).
33931 The @samp{R} packet has no reply.
33933 @item s @r{[}@var{addr}@r{]}
33934 @cindex @samp{s} packet
33935 Single step. @var{addr} is the address at which to resume. If
33936 @var{addr} is omitted, resume at same address.
33938 This packet is deprecated for multi-threading support. @xref{vCont
33942 @xref{Stop Reply Packets}, for the reply specifications.
33944 @item S @var{sig}@r{[};@var{addr}@r{]}
33945 @anchor{step with signal packet}
33946 @cindex @samp{S} packet
33947 Step with signal. This is analogous to the @samp{C} packet, but
33948 requests a single-step, rather than a normal resumption of execution.
33950 This packet is deprecated for multi-threading support. @xref{vCont
33954 @xref{Stop Reply Packets}, for the reply specifications.
33956 @item t @var{addr}:@var{PP},@var{MM}
33957 @cindex @samp{t} packet
33958 Search backwards starting at address @var{addr} for a match with pattern
33959 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33960 @var{addr} must be at least 3 digits.
33962 @item T @var{thread-id}
33963 @cindex @samp{T} packet
33964 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33969 thread is still alive
33975 Packets starting with @samp{v} are identified by a multi-letter name,
33976 up to the first @samp{;} or @samp{?} (or the end of the packet).
33978 @item vAttach;@var{pid}
33979 @cindex @samp{vAttach} packet
33980 Attach to a new process with the specified process ID @var{pid}.
33981 The process ID is a
33982 hexadecimal integer identifying the process. In all-stop mode, all
33983 threads in the attached process are stopped; in non-stop mode, it may be
33984 attached without being stopped if that is supported by the target.
33986 @c In non-stop mode, on a successful vAttach, the stub should set the
33987 @c current thread to a thread of the newly-attached process. After
33988 @c attaching, GDB queries for the attached process's thread ID with qC.
33989 @c Also note that, from a user perspective, whether or not the
33990 @c target is stopped on attach in non-stop mode depends on whether you
33991 @c use the foreground or background version of the attach command, not
33992 @c on what vAttach does; GDB does the right thing with respect to either
33993 @c stopping or restarting threads.
33995 This packet is only available in extended mode (@pxref{extended mode}).
34001 @item @r{Any stop packet}
34002 for success in all-stop mode (@pxref{Stop Reply Packets})
34004 for success in non-stop mode (@pxref{Remote Non-Stop})
34007 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34008 @cindex @samp{vCont} packet
34009 @anchor{vCont packet}
34010 Resume the inferior, specifying different actions for each thread.
34011 If an action is specified with no @var{thread-id}, then it is applied to any
34012 threads that don't have a specific action specified; if no default action is
34013 specified then other threads should remain stopped in all-stop mode and
34014 in their current state in non-stop mode.
34015 Specifying multiple
34016 default actions is an error; specifying no actions is also an error.
34017 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34019 Currently supported actions are:
34025 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34029 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34034 The optional argument @var{addr} normally associated with the
34035 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34036 not supported in @samp{vCont}.
34038 The @samp{t} action is only relevant in non-stop mode
34039 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34040 A stop reply should be generated for any affected thread not already stopped.
34041 When a thread is stopped by means of a @samp{t} action,
34042 the corresponding stop reply should indicate that the thread has stopped with
34043 signal @samp{0}, regardless of whether the target uses some other signal
34044 as an implementation detail.
34047 @xref{Stop Reply Packets}, for the reply specifications.
34050 @cindex @samp{vCont?} packet
34051 Request a list of actions supported by the @samp{vCont} packet.
34055 @item vCont@r{[};@var{action}@dots{}@r{]}
34056 The @samp{vCont} packet is supported. Each @var{action} is a supported
34057 command in the @samp{vCont} packet.
34059 The @samp{vCont} packet is not supported.
34062 @item vFile:@var{operation}:@var{parameter}@dots{}
34063 @cindex @samp{vFile} packet
34064 Perform a file operation on the target system. For details,
34065 see @ref{Host I/O Packets}.
34067 @item vFlashErase:@var{addr},@var{length}
34068 @cindex @samp{vFlashErase} packet
34069 Direct the stub to erase @var{length} bytes of flash starting at
34070 @var{addr}. The region may enclose any number of flash blocks, but
34071 its start and end must fall on block boundaries, as indicated by the
34072 flash block size appearing in the memory map (@pxref{Memory Map
34073 Format}). @value{GDBN} groups flash memory programming operations
34074 together, and sends a @samp{vFlashDone} request after each group; the
34075 stub is allowed to delay erase operation until the @samp{vFlashDone}
34076 packet is received.
34078 The stub must support @samp{vCont} if it reports support for
34079 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34080 this case @samp{vCont} actions can be specified to apply to all threads
34081 in a process by using the @samp{p@var{pid}.-1} form of the
34092 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34093 @cindex @samp{vFlashWrite} packet
34094 Direct the stub to write data to flash address @var{addr}. The data
34095 is passed in binary form using the same encoding as for the @samp{X}
34096 packet (@pxref{Binary Data}). The memory ranges specified by
34097 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34098 not overlap, and must appear in order of increasing addresses
34099 (although @samp{vFlashErase} packets for higher addresses may already
34100 have been received; the ordering is guaranteed only between
34101 @samp{vFlashWrite} packets). If a packet writes to an address that was
34102 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34103 target-specific method, the results are unpredictable.
34111 for vFlashWrite addressing non-flash memory
34117 @cindex @samp{vFlashDone} packet
34118 Indicate to the stub that flash programming operation is finished.
34119 The stub is permitted to delay or batch the effects of a group of
34120 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34121 @samp{vFlashDone} packet is received. The contents of the affected
34122 regions of flash memory are unpredictable until the @samp{vFlashDone}
34123 request is completed.
34125 @item vKill;@var{pid}
34126 @cindex @samp{vKill} packet
34127 Kill the process with the specified process ID. @var{pid} is a
34128 hexadecimal integer identifying the process. This packet is used in
34129 preference to @samp{k} when multiprocess protocol extensions are
34130 supported; see @ref{multiprocess extensions}.
34140 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34141 @cindex @samp{vRun} packet
34142 Run the program @var{filename}, passing it each @var{argument} on its
34143 command line. The file and arguments are hex-encoded strings. If
34144 @var{filename} is an empty string, the stub may use a default program
34145 (e.g.@: the last program run). The program is created in the stopped
34148 @c FIXME: What about non-stop mode?
34150 This packet is only available in extended mode (@pxref{extended mode}).
34156 @item @r{Any stop packet}
34157 for success (@pxref{Stop Reply Packets})
34161 @anchor{vStopped packet}
34162 @cindex @samp{vStopped} packet
34164 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34165 reply and prompt for the stub to report another one.
34169 @item @r{Any stop packet}
34170 if there is another unreported stop event (@pxref{Stop Reply Packets})
34172 if there are no unreported stop events
34175 @item X @var{addr},@var{length}:@var{XX@dots{}}
34177 @cindex @samp{X} packet
34178 Write data to memory, where the data is transmitted in binary.
34179 @var{addr} is address, @var{length} is number of bytes,
34180 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34190 @item z @var{type},@var{addr},@var{kind}
34191 @itemx Z @var{type},@var{addr},@var{kind}
34192 @anchor{insert breakpoint or watchpoint packet}
34193 @cindex @samp{z} packet
34194 @cindex @samp{Z} packets
34195 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34196 watchpoint starting at address @var{address} of kind @var{kind}.
34198 Each breakpoint and watchpoint packet @var{type} is documented
34201 @emph{Implementation notes: A remote target shall return an empty string
34202 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34203 remote target shall support either both or neither of a given
34204 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34205 avoid potential problems with duplicate packets, the operations should
34206 be implemented in an idempotent way.}
34208 @item z0,@var{addr},@var{kind}
34209 @itemx Z0,@var{addr},@var{kind}
34210 @cindex @samp{z0} packet
34211 @cindex @samp{Z0} packet
34212 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34213 @var{addr} of type @var{kind}.
34215 A memory breakpoint is implemented by replacing the instruction at
34216 @var{addr} with a software breakpoint or trap instruction. The
34217 @var{kind} is target-specific and typically indicates the size of
34218 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34219 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34220 architectures have additional meanings for @var{kind};
34221 see @ref{Architecture-Specific Protocol Details}.
34223 @emph{Implementation note: It is possible for a target to copy or move
34224 code that contains memory breakpoints (e.g., when implementing
34225 overlays). The behavior of this packet, in the presence of such a
34226 target, is not defined.}
34238 @item z1,@var{addr},@var{kind}
34239 @itemx Z1,@var{addr},@var{kind}
34240 @cindex @samp{z1} packet
34241 @cindex @samp{Z1} packet
34242 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34243 address @var{addr}.
34245 A hardware breakpoint is implemented using a mechanism that is not
34246 dependant on being able to modify the target's memory. @var{kind}
34247 has the same meaning as in @samp{Z0} packets.
34249 @emph{Implementation note: A hardware breakpoint is not affected by code
34262 @item z2,@var{addr},@var{kind}
34263 @itemx Z2,@var{addr},@var{kind}
34264 @cindex @samp{z2} packet
34265 @cindex @samp{Z2} packet
34266 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34267 @var{kind} is interpreted as the number of bytes to watch.
34279 @item z3,@var{addr},@var{kind}
34280 @itemx Z3,@var{addr},@var{kind}
34281 @cindex @samp{z3} packet
34282 @cindex @samp{Z3} packet
34283 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34284 @var{kind} is interpreted as the number of bytes to watch.
34296 @item z4,@var{addr},@var{kind}
34297 @itemx Z4,@var{addr},@var{kind}
34298 @cindex @samp{z4} packet
34299 @cindex @samp{Z4} packet
34300 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34301 @var{kind} is interpreted as the number of bytes to watch.
34315 @node Stop Reply Packets
34316 @section Stop Reply Packets
34317 @cindex stop reply packets
34319 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34320 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34321 receive any of the below as a reply. Except for @samp{?}
34322 and @samp{vStopped}, that reply is only returned
34323 when the target halts. In the below the exact meaning of @dfn{signal
34324 number} is defined by the header @file{include/gdb/signals.h} in the
34325 @value{GDBN} source code.
34327 As in the description of request packets, we include spaces in the
34328 reply templates for clarity; these are not part of the reply packet's
34329 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34335 The program received signal number @var{AA} (a two-digit hexadecimal
34336 number). This is equivalent to a @samp{T} response with no
34337 @var{n}:@var{r} pairs.
34339 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34340 @cindex @samp{T} packet reply
34341 The program received signal number @var{AA} (a two-digit hexadecimal
34342 number). This is equivalent to an @samp{S} response, except that the
34343 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34344 and other information directly in the stop reply packet, reducing
34345 round-trip latency. Single-step and breakpoint traps are reported
34346 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34350 If @var{n} is a hexadecimal number, it is a register number, and the
34351 corresponding @var{r} gives that register's value. @var{r} is a
34352 series of bytes in target byte order, with each byte given by a
34353 two-digit hex number.
34356 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34357 the stopped thread, as specified in @ref{thread-id syntax}.
34360 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34361 the core on which the stop event was detected.
34364 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34365 specific event that stopped the target. The currently defined stop
34366 reasons are listed below. @var{aa} should be @samp{05}, the trap
34367 signal. At most one stop reason should be present.
34370 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34371 and go on to the next; this allows us to extend the protocol in the
34375 The currently defined stop reasons are:
34381 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34384 @cindex shared library events, remote reply
34386 The packet indicates that the loaded libraries have changed.
34387 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34388 list of loaded libraries. @var{r} is ignored.
34390 @cindex replay log events, remote reply
34392 The packet indicates that the target cannot continue replaying
34393 logged execution events, because it has reached the end (or the
34394 beginning when executing backward) of the log. The value of @var{r}
34395 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34396 for more information.
34400 @itemx W @var{AA} ; process:@var{pid}
34401 The process exited, and @var{AA} is the exit status. This is only
34402 applicable to certain targets.
34404 The second form of the response, including the process ID of the exited
34405 process, can be used only when @value{GDBN} has reported support for
34406 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34407 The @var{pid} is formatted as a big-endian hex string.
34410 @itemx X @var{AA} ; process:@var{pid}
34411 The process terminated with signal @var{AA}.
34413 The second form of the response, including the process ID of the
34414 terminated process, can be used only when @value{GDBN} has reported
34415 support for multiprocess protocol extensions; see @ref{multiprocess
34416 extensions}. The @var{pid} is formatted as a big-endian hex string.
34418 @item O @var{XX}@dots{}
34419 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34420 written as the program's console output. This can happen at any time
34421 while the program is running and the debugger should continue to wait
34422 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34424 @item F @var{call-id},@var{parameter}@dots{}
34425 @var{call-id} is the identifier which says which host system call should
34426 be called. This is just the name of the function. Translation into the
34427 correct system call is only applicable as it's defined in @value{GDBN}.
34428 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34431 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34432 this very system call.
34434 The target replies with this packet when it expects @value{GDBN} to
34435 call a host system call on behalf of the target. @value{GDBN} replies
34436 with an appropriate @samp{F} packet and keeps up waiting for the next
34437 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34438 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34439 Protocol Extension}, for more details.
34443 @node General Query Packets
34444 @section General Query Packets
34445 @cindex remote query requests
34447 Packets starting with @samp{q} are @dfn{general query packets};
34448 packets starting with @samp{Q} are @dfn{general set packets}. General
34449 query and set packets are a semi-unified form for retrieving and
34450 sending information to and from the stub.
34452 The initial letter of a query or set packet is followed by a name
34453 indicating what sort of thing the packet applies to. For example,
34454 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34455 definitions with the stub. These packet names follow some
34460 The name must not contain commas, colons or semicolons.
34462 Most @value{GDBN} query and set packets have a leading upper case
34465 The names of custom vendor packets should use a company prefix, in
34466 lower case, followed by a period. For example, packets designed at
34467 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34468 foos) or @samp{Qacme.bar} (for setting bars).
34471 The name of a query or set packet should be separated from any
34472 parameters by a @samp{:}; the parameters themselves should be
34473 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34474 full packet name, and check for a separator or the end of the packet,
34475 in case two packet names share a common prefix. New packets should not begin
34476 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34477 packets predate these conventions, and have arguments without any terminator
34478 for the packet name; we suspect they are in widespread use in places that
34479 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34480 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34483 Like the descriptions of the other packets, each description here
34484 has a template showing the packet's overall syntax, followed by an
34485 explanation of the packet's meaning. We include spaces in some of the
34486 templates for clarity; these are not part of the packet's syntax. No
34487 @value{GDBN} packet uses spaces to separate its components.
34489 Here are the currently defined query and set packets:
34493 @item QAllow:@var{op}:@var{val}@dots{}
34494 @cindex @samp{QAllow} packet
34495 Specify which operations @value{GDBN} expects to request of the
34496 target, as a semicolon-separated list of operation name and value
34497 pairs. Possible values for @var{op} include @samp{WriteReg},
34498 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34499 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34500 indicating that @value{GDBN} will not request the operation, or 1,
34501 indicating that it may. (The target can then use this to set up its
34502 own internals optimally, for instance if the debugger never expects to
34503 insert breakpoints, it may not need to install its own trap handler.)
34506 @cindex current thread, remote request
34507 @cindex @samp{qC} packet
34508 Return the current thread ID.
34512 @item QC @var{thread-id}
34513 Where @var{thread-id} is a thread ID as documented in
34514 @ref{thread-id syntax}.
34515 @item @r{(anything else)}
34516 Any other reply implies the old thread ID.
34519 @item qCRC:@var{addr},@var{length}
34520 @cindex CRC of memory block, remote request
34521 @cindex @samp{qCRC} packet
34522 Compute the CRC checksum of a block of memory using CRC-32 defined in
34523 IEEE 802.3. The CRC is computed byte at a time, taking the most
34524 significant bit of each byte first. The initial pattern code
34525 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34527 @emph{Note:} This is the same CRC used in validating separate debug
34528 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34529 Files}). However the algorithm is slightly different. When validating
34530 separate debug files, the CRC is computed taking the @emph{least}
34531 significant bit of each byte first, and the final result is inverted to
34532 detect trailing zeros.
34537 An error (such as memory fault)
34538 @item C @var{crc32}
34539 The specified memory region's checksum is @var{crc32}.
34542 @item QDisableRandomization:@var{value}
34543 @cindex disable address space randomization, remote request
34544 @cindex @samp{QDisableRandomization} packet
34545 Some target operating systems will randomize the virtual address space
34546 of the inferior process as a security feature, but provide a feature
34547 to disable such randomization, e.g.@: to allow for a more deterministic
34548 debugging experience. On such systems, this packet with a @var{value}
34549 of 1 directs the target to disable address space randomization for
34550 processes subsequently started via @samp{vRun} packets, while a packet
34551 with a @var{value} of 0 tells the target to enable address space
34554 This packet is only available in extended mode (@pxref{extended mode}).
34559 The request succeeded.
34562 An error occurred. @var{nn} are hex digits.
34565 An empty reply indicates that @samp{QDisableRandomization} is not supported
34569 This packet is not probed by default; the remote stub must request it,
34570 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34571 This should only be done on targets that actually support disabling
34572 address space randomization.
34575 @itemx qsThreadInfo
34576 @cindex list active threads, remote request
34577 @cindex @samp{qfThreadInfo} packet
34578 @cindex @samp{qsThreadInfo} packet
34579 Obtain a list of all active thread IDs from the target (OS). Since there
34580 may be too many active threads to fit into one reply packet, this query
34581 works iteratively: it may require more than one query/reply sequence to
34582 obtain the entire list of threads. The first query of the sequence will
34583 be the @samp{qfThreadInfo} query; subsequent queries in the
34584 sequence will be the @samp{qsThreadInfo} query.
34586 NOTE: This packet replaces the @samp{qL} query (see below).
34590 @item m @var{thread-id}
34592 @item m @var{thread-id},@var{thread-id}@dots{}
34593 a comma-separated list of thread IDs
34595 (lower case letter @samp{L}) denotes end of list.
34598 In response to each query, the target will reply with a list of one or
34599 more thread IDs, separated by commas.
34600 @value{GDBN} will respond to each reply with a request for more thread
34601 ids (using the @samp{qs} form of the query), until the target responds
34602 with @samp{l} (lower-case ell, for @dfn{last}).
34603 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34606 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34607 @cindex get thread-local storage address, remote request
34608 @cindex @samp{qGetTLSAddr} packet
34609 Fetch the address associated with thread local storage specified
34610 by @var{thread-id}, @var{offset}, and @var{lm}.
34612 @var{thread-id} is the thread ID associated with the
34613 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34615 @var{offset} is the (big endian, hex encoded) offset associated with the
34616 thread local variable. (This offset is obtained from the debug
34617 information associated with the variable.)
34619 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34620 load module associated with the thread local storage. For example,
34621 a @sc{gnu}/Linux system will pass the link map address of the shared
34622 object associated with the thread local storage under consideration.
34623 Other operating environments may choose to represent the load module
34624 differently, so the precise meaning of this parameter will vary.
34628 @item @var{XX}@dots{}
34629 Hex encoded (big endian) bytes representing the address of the thread
34630 local storage requested.
34633 An error occurred. @var{nn} are hex digits.
34636 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34639 @item qGetTIBAddr:@var{thread-id}
34640 @cindex get thread information block address
34641 @cindex @samp{qGetTIBAddr} packet
34642 Fetch address of the Windows OS specific Thread Information Block.
34644 @var{thread-id} is the thread ID associated with the thread.
34648 @item @var{XX}@dots{}
34649 Hex encoded (big endian) bytes representing the linear address of the
34650 thread information block.
34653 An error occured. This means that either the thread was not found, or the
34654 address could not be retrieved.
34657 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34660 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34661 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34662 digit) is one to indicate the first query and zero to indicate a
34663 subsequent query; @var{threadcount} (two hex digits) is the maximum
34664 number of threads the response packet can contain; and @var{nextthread}
34665 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34666 returned in the response as @var{argthread}.
34668 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34672 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34673 Where: @var{count} (two hex digits) is the number of threads being
34674 returned; @var{done} (one hex digit) is zero to indicate more threads
34675 and one indicates no further threads; @var{argthreadid} (eight hex
34676 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34677 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34678 digits). See @code{remote.c:parse_threadlist_response()}.
34682 @cindex section offsets, remote request
34683 @cindex @samp{qOffsets} packet
34684 Get section offsets that the target used when relocating the downloaded
34689 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34690 Relocate the @code{Text} section by @var{xxx} from its original address.
34691 Relocate the @code{Data} section by @var{yyy} from its original address.
34692 If the object file format provides segment information (e.g.@: @sc{elf}
34693 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34694 segments by the supplied offsets.
34696 @emph{Note: while a @code{Bss} offset may be included in the response,
34697 @value{GDBN} ignores this and instead applies the @code{Data} offset
34698 to the @code{Bss} section.}
34700 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34701 Relocate the first segment of the object file, which conventionally
34702 contains program code, to a starting address of @var{xxx}. If
34703 @samp{DataSeg} is specified, relocate the second segment, which
34704 conventionally contains modifiable data, to a starting address of
34705 @var{yyy}. @value{GDBN} will report an error if the object file
34706 does not contain segment information, or does not contain at least
34707 as many segments as mentioned in the reply. Extra segments are
34708 kept at fixed offsets relative to the last relocated segment.
34711 @item qP @var{mode} @var{thread-id}
34712 @cindex thread information, remote request
34713 @cindex @samp{qP} packet
34714 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34715 encoded 32 bit mode; @var{thread-id} is a thread ID
34716 (@pxref{thread-id syntax}).
34718 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34721 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34725 @cindex non-stop mode, remote request
34726 @cindex @samp{QNonStop} packet
34728 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34729 @xref{Remote Non-Stop}, for more information.
34734 The request succeeded.
34737 An error occurred. @var{nn} are hex digits.
34740 An empty reply indicates that @samp{QNonStop} is not supported by
34744 This packet is not probed by default; the remote stub must request it,
34745 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34746 Use of this packet is controlled by the @code{set non-stop} command;
34747 @pxref{Non-Stop Mode}.
34749 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34750 @cindex pass signals to inferior, remote request
34751 @cindex @samp{QPassSignals} packet
34752 @anchor{QPassSignals}
34753 Each listed @var{signal} should be passed directly to the inferior process.
34754 Signals are numbered identically to continue packets and stop replies
34755 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34756 strictly greater than the previous item. These signals do not need to stop
34757 the inferior, or be reported to @value{GDBN}. All other signals should be
34758 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34759 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34760 new list. This packet improves performance when using @samp{handle
34761 @var{signal} nostop noprint pass}.
34766 The request succeeded.
34769 An error occurred. @var{nn} are hex digits.
34772 An empty reply indicates that @samp{QPassSignals} is not supported by
34776 Use of this packet is controlled by the @code{set remote pass-signals}
34777 command (@pxref{Remote Configuration, set remote pass-signals}).
34778 This packet is not probed by default; the remote stub must request it,
34779 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34781 @item qRcmd,@var{command}
34782 @cindex execute remote command, remote request
34783 @cindex @samp{qRcmd} packet
34784 @var{command} (hex encoded) is passed to the local interpreter for
34785 execution. Invalid commands should be reported using the output
34786 string. Before the final result packet, the target may also respond
34787 with a number of intermediate @samp{O@var{output}} console output
34788 packets. @emph{Implementors should note that providing access to a
34789 stubs's interpreter may have security implications}.
34794 A command response with no output.
34796 A command response with the hex encoded output string @var{OUTPUT}.
34798 Indicate a badly formed request.
34800 An empty reply indicates that @samp{qRcmd} is not recognized.
34803 (Note that the @code{qRcmd} packet's name is separated from the
34804 command by a @samp{,}, not a @samp{:}, contrary to the naming
34805 conventions above. Please don't use this packet as a model for new
34808 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34809 @cindex searching memory, in remote debugging
34810 @cindex @samp{qSearch:memory} packet
34811 @anchor{qSearch memory}
34812 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34813 @var{address} and @var{length} are encoded in hex.
34814 @var{search-pattern} is a sequence of bytes, hex encoded.
34819 The pattern was not found.
34821 The pattern was found at @var{address}.
34823 A badly formed request or an error was encountered while searching memory.
34825 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34828 @item QStartNoAckMode
34829 @cindex @samp{QStartNoAckMode} packet
34830 @anchor{QStartNoAckMode}
34831 Request that the remote stub disable the normal @samp{+}/@samp{-}
34832 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34837 The stub has switched to no-acknowledgment mode.
34838 @value{GDBN} acknowledges this reponse,
34839 but neither the stub nor @value{GDBN} shall send or expect further
34840 @samp{+}/@samp{-} acknowledgments in the current connection.
34842 An empty reply indicates that the stub does not support no-acknowledgment mode.
34845 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34846 @cindex supported packets, remote query
34847 @cindex features of the remote protocol
34848 @cindex @samp{qSupported} packet
34849 @anchor{qSupported}
34850 Tell the remote stub about features supported by @value{GDBN}, and
34851 query the stub for features it supports. This packet allows
34852 @value{GDBN} and the remote stub to take advantage of each others'
34853 features. @samp{qSupported} also consolidates multiple feature probes
34854 at startup, to improve @value{GDBN} performance---a single larger
34855 packet performs better than multiple smaller probe packets on
34856 high-latency links. Some features may enable behavior which must not
34857 be on by default, e.g.@: because it would confuse older clients or
34858 stubs. Other features may describe packets which could be
34859 automatically probed for, but are not. These features must be
34860 reported before @value{GDBN} will use them. This ``default
34861 unsupported'' behavior is not appropriate for all packets, but it
34862 helps to keep the initial connection time under control with new
34863 versions of @value{GDBN} which support increasing numbers of packets.
34867 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34868 The stub supports or does not support each returned @var{stubfeature},
34869 depending on the form of each @var{stubfeature} (see below for the
34872 An empty reply indicates that @samp{qSupported} is not recognized,
34873 or that no features needed to be reported to @value{GDBN}.
34876 The allowed forms for each feature (either a @var{gdbfeature} in the
34877 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34881 @item @var{name}=@var{value}
34882 The remote protocol feature @var{name} is supported, and associated
34883 with the specified @var{value}. The format of @var{value} depends
34884 on the feature, but it must not include a semicolon.
34886 The remote protocol feature @var{name} is supported, and does not
34887 need an associated value.
34889 The remote protocol feature @var{name} is not supported.
34891 The remote protocol feature @var{name} may be supported, and
34892 @value{GDBN} should auto-detect support in some other way when it is
34893 needed. This form will not be used for @var{gdbfeature} notifications,
34894 but may be used for @var{stubfeature} responses.
34897 Whenever the stub receives a @samp{qSupported} request, the
34898 supplied set of @value{GDBN} features should override any previous
34899 request. This allows @value{GDBN} to put the stub in a known
34900 state, even if the stub had previously been communicating with
34901 a different version of @value{GDBN}.
34903 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34908 This feature indicates whether @value{GDBN} supports multiprocess
34909 extensions to the remote protocol. @value{GDBN} does not use such
34910 extensions unless the stub also reports that it supports them by
34911 including @samp{multiprocess+} in its @samp{qSupported} reply.
34912 @xref{multiprocess extensions}, for details.
34915 This feature indicates that @value{GDBN} supports the XML target
34916 description. If the stub sees @samp{xmlRegisters=} with target
34917 specific strings separated by a comma, it will report register
34921 This feature indicates whether @value{GDBN} supports the
34922 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34923 instruction reply packet}).
34926 Stubs should ignore any unknown values for
34927 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34928 packet supports receiving packets of unlimited length (earlier
34929 versions of @value{GDBN} may reject overly long responses). Additional values
34930 for @var{gdbfeature} may be defined in the future to let the stub take
34931 advantage of new features in @value{GDBN}, e.g.@: incompatible
34932 improvements in the remote protocol---the @samp{multiprocess} feature is
34933 an example of such a feature. The stub's reply should be independent
34934 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34935 describes all the features it supports, and then the stub replies with
34936 all the features it supports.
34938 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34939 responses, as long as each response uses one of the standard forms.
34941 Some features are flags. A stub which supports a flag feature
34942 should respond with a @samp{+} form response. Other features
34943 require values, and the stub should respond with an @samp{=}
34946 Each feature has a default value, which @value{GDBN} will use if
34947 @samp{qSupported} is not available or if the feature is not mentioned
34948 in the @samp{qSupported} response. The default values are fixed; a
34949 stub is free to omit any feature responses that match the defaults.
34951 Not all features can be probed, but for those which can, the probing
34952 mechanism is useful: in some cases, a stub's internal
34953 architecture may not allow the protocol layer to know some information
34954 about the underlying target in advance. This is especially common in
34955 stubs which may be configured for multiple targets.
34957 These are the currently defined stub features and their properties:
34959 @multitable @columnfractions 0.35 0.2 0.12 0.2
34960 @c NOTE: The first row should be @headitem, but we do not yet require
34961 @c a new enough version of Texinfo (4.7) to use @headitem.
34963 @tab Value Required
34967 @item @samp{PacketSize}
34972 @item @samp{qXfer:auxv:read}
34977 @item @samp{qXfer:features:read}
34982 @item @samp{qXfer:libraries:read}
34987 @item @samp{qXfer:memory-map:read}
34992 @item @samp{qXfer:sdata:read}
34997 @item @samp{qXfer:spu:read}
35002 @item @samp{qXfer:spu:write}
35007 @item @samp{qXfer:siginfo:read}
35012 @item @samp{qXfer:siginfo:write}
35017 @item @samp{qXfer:threads:read}
35022 @item @samp{qXfer:traceframe-info:read}
35027 @item @samp{qXfer:fdpic:read}
35032 @item @samp{QNonStop}
35037 @item @samp{QPassSignals}
35042 @item @samp{QStartNoAckMode}
35047 @item @samp{multiprocess}
35052 @item @samp{ConditionalTracepoints}
35057 @item @samp{ReverseContinue}
35062 @item @samp{ReverseStep}
35067 @item @samp{TracepointSource}
35072 @item @samp{QAllow}
35077 @item @samp{QDisableRandomization}
35082 @item @samp{EnableDisableTracepoints}
35087 @item @samp{tracenz}
35094 These are the currently defined stub features, in more detail:
35097 @cindex packet size, remote protocol
35098 @item PacketSize=@var{bytes}
35099 The remote stub can accept packets up to at least @var{bytes} in
35100 length. @value{GDBN} will send packets up to this size for bulk
35101 transfers, and will never send larger packets. This is a limit on the
35102 data characters in the packet, including the frame and checksum.
35103 There is no trailing NUL byte in a remote protocol packet; if the stub
35104 stores packets in a NUL-terminated format, it should allow an extra
35105 byte in its buffer for the NUL. If this stub feature is not supported,
35106 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35108 @item qXfer:auxv:read
35109 The remote stub understands the @samp{qXfer:auxv:read} packet
35110 (@pxref{qXfer auxiliary vector read}).
35112 @item qXfer:features:read
35113 The remote stub understands the @samp{qXfer:features:read} packet
35114 (@pxref{qXfer target description read}).
35116 @item qXfer:libraries:read
35117 The remote stub understands the @samp{qXfer:libraries:read} packet
35118 (@pxref{qXfer library list read}).
35120 @item qXfer:libraries-svr4:read
35121 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35122 (@pxref{qXfer svr4 library list read}).
35124 @item qXfer:memory-map:read
35125 The remote stub understands the @samp{qXfer:memory-map:read} packet
35126 (@pxref{qXfer memory map read}).
35128 @item qXfer:sdata:read
35129 The remote stub understands the @samp{qXfer:sdata:read} packet
35130 (@pxref{qXfer sdata read}).
35132 @item qXfer:spu:read
35133 The remote stub understands the @samp{qXfer:spu:read} packet
35134 (@pxref{qXfer spu read}).
35136 @item qXfer:spu:write
35137 The remote stub understands the @samp{qXfer:spu:write} packet
35138 (@pxref{qXfer spu write}).
35140 @item qXfer:siginfo:read
35141 The remote stub understands the @samp{qXfer:siginfo:read} packet
35142 (@pxref{qXfer siginfo read}).
35144 @item qXfer:siginfo:write
35145 The remote stub understands the @samp{qXfer:siginfo:write} packet
35146 (@pxref{qXfer siginfo write}).
35148 @item qXfer:threads:read
35149 The remote stub understands the @samp{qXfer:threads:read} packet
35150 (@pxref{qXfer threads read}).
35152 @item qXfer:traceframe-info:read
35153 The remote stub understands the @samp{qXfer:traceframe-info:read}
35154 packet (@pxref{qXfer traceframe info read}).
35156 @item qXfer:fdpic:read
35157 The remote stub understands the @samp{qXfer:fdpic:read}
35158 packet (@pxref{qXfer fdpic loadmap read}).
35161 The remote stub understands the @samp{QNonStop} packet
35162 (@pxref{QNonStop}).
35165 The remote stub understands the @samp{QPassSignals} packet
35166 (@pxref{QPassSignals}).
35168 @item QStartNoAckMode
35169 The remote stub understands the @samp{QStartNoAckMode} packet and
35170 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35173 @anchor{multiprocess extensions}
35174 @cindex multiprocess extensions, in remote protocol
35175 The remote stub understands the multiprocess extensions to the remote
35176 protocol syntax. The multiprocess extensions affect the syntax of
35177 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35178 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35179 replies. Note that reporting this feature indicates support for the
35180 syntactic extensions only, not that the stub necessarily supports
35181 debugging of more than one process at a time. The stub must not use
35182 multiprocess extensions in packet replies unless @value{GDBN} has also
35183 indicated it supports them in its @samp{qSupported} request.
35185 @item qXfer:osdata:read
35186 The remote stub understands the @samp{qXfer:osdata:read} packet
35187 ((@pxref{qXfer osdata read}).
35189 @item ConditionalTracepoints
35190 The remote stub accepts and implements conditional expressions defined
35191 for tracepoints (@pxref{Tracepoint Conditions}).
35193 @item ReverseContinue
35194 The remote stub accepts and implements the reverse continue packet
35198 The remote stub accepts and implements the reverse step packet
35201 @item TracepointSource
35202 The remote stub understands the @samp{QTDPsrc} packet that supplies
35203 the source form of tracepoint definitions.
35206 The remote stub understands the @samp{QAllow} packet.
35208 @item QDisableRandomization
35209 The remote stub understands the @samp{QDisableRandomization} packet.
35211 @item StaticTracepoint
35212 @cindex static tracepoints, in remote protocol
35213 The remote stub supports static tracepoints.
35215 @item InstallInTrace
35216 @anchor{install tracepoint in tracing}
35217 The remote stub supports installing tracepoint in tracing.
35219 @item EnableDisableTracepoints
35220 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35221 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35222 to be enabled and disabled while a trace experiment is running.
35225 @cindex string tracing, in remote protocol
35226 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35227 See @ref{Bytecode Descriptions} for details about the bytecode.
35232 @cindex symbol lookup, remote request
35233 @cindex @samp{qSymbol} packet
35234 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35235 requests. Accept requests from the target for the values of symbols.
35240 The target does not need to look up any (more) symbols.
35241 @item qSymbol:@var{sym_name}
35242 The target requests the value of symbol @var{sym_name} (hex encoded).
35243 @value{GDBN} may provide the value by using the
35244 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35248 @item qSymbol:@var{sym_value}:@var{sym_name}
35249 Set the value of @var{sym_name} to @var{sym_value}.
35251 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35252 target has previously requested.
35254 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35255 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35261 The target does not need to look up any (more) symbols.
35262 @item qSymbol:@var{sym_name}
35263 The target requests the value of a new symbol @var{sym_name} (hex
35264 encoded). @value{GDBN} will continue to supply the values of symbols
35265 (if available), until the target ceases to request them.
35270 @item QTDisconnected
35277 @itemx qTMinFTPILen
35279 @xref{Tracepoint Packets}.
35281 @item qThreadExtraInfo,@var{thread-id}
35282 @cindex thread attributes info, remote request
35283 @cindex @samp{qThreadExtraInfo} packet
35284 Obtain a printable string description of a thread's attributes from
35285 the target OS. @var{thread-id} is a thread ID;
35286 see @ref{thread-id syntax}. This
35287 string may contain anything that the target OS thinks is interesting
35288 for @value{GDBN} to tell the user about the thread. The string is
35289 displayed in @value{GDBN}'s @code{info threads} display. Some
35290 examples of possible thread extra info strings are @samp{Runnable}, or
35291 @samp{Blocked on Mutex}.
35295 @item @var{XX}@dots{}
35296 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35297 comprising the printable string containing the extra information about
35298 the thread's attributes.
35301 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35302 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35303 conventions above. Please don't use this packet as a model for new
35322 @xref{Tracepoint Packets}.
35324 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35325 @cindex read special object, remote request
35326 @cindex @samp{qXfer} packet
35327 @anchor{qXfer read}
35328 Read uninterpreted bytes from the target's special data area
35329 identified by the keyword @var{object}. Request @var{length} bytes
35330 starting at @var{offset} bytes into the data. The content and
35331 encoding of @var{annex} is specific to @var{object}; it can supply
35332 additional details about what data to access.
35334 Here are the specific requests of this form defined so far. All
35335 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35336 formats, listed below.
35339 @item qXfer:auxv:read::@var{offset},@var{length}
35340 @anchor{qXfer auxiliary vector read}
35341 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35342 auxiliary vector}. Note @var{annex} must be empty.
35344 This packet is not probed by default; the remote stub must request it,
35345 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35347 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35348 @anchor{qXfer target description read}
35349 Access the @dfn{target description}. @xref{Target Descriptions}. The
35350 annex specifies which XML document to access. The main description is
35351 always loaded from the @samp{target.xml} annex.
35353 This packet is not probed by default; the remote stub must request it,
35354 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35356 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35357 @anchor{qXfer library list read}
35358 Access the target's list of loaded libraries. @xref{Library List Format}.
35359 The annex part of the generic @samp{qXfer} packet must be empty
35360 (@pxref{qXfer read}).
35362 Targets which maintain a list of libraries in the program's memory do
35363 not need to implement this packet; it is designed for platforms where
35364 the operating system manages the list of loaded libraries.
35366 This packet is not probed by default; the remote stub must request it,
35367 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35369 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35370 @anchor{qXfer svr4 library list read}
35371 Access the target's list of loaded libraries when the target is an SVR4
35372 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35373 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35375 This packet is optional for better performance on SVR4 targets.
35376 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35378 This packet is not probed by default; the remote stub must request it,
35379 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35381 @item qXfer:memory-map:read::@var{offset},@var{length}
35382 @anchor{qXfer memory map read}
35383 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35384 annex part of the generic @samp{qXfer} packet must be empty
35385 (@pxref{qXfer read}).
35387 This packet is not probed by default; the remote stub must request it,
35388 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35390 @item qXfer:sdata:read::@var{offset},@var{length}
35391 @anchor{qXfer sdata read}
35393 Read contents of the extra collected static tracepoint marker
35394 information. The annex part of the generic @samp{qXfer} packet must
35395 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35398 This packet is not probed by default; the remote stub must request it,
35399 by supplying an appropriate @samp{qSupported} response
35400 (@pxref{qSupported}).
35402 @item qXfer:siginfo:read::@var{offset},@var{length}
35403 @anchor{qXfer siginfo read}
35404 Read contents of the extra signal information on the target
35405 system. The annex part of the generic @samp{qXfer} packet must be
35406 empty (@pxref{qXfer read}).
35408 This packet is not probed by default; the remote stub must request it,
35409 by supplying an appropriate @samp{qSupported} response
35410 (@pxref{qSupported}).
35412 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35413 @anchor{qXfer spu read}
35414 Read contents of an @code{spufs} file on the target system. The
35415 annex specifies which file to read; it must be of the form
35416 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35417 in the target process, and @var{name} identifes the @code{spufs} file
35418 in that context to be accessed.
35420 This packet is not probed by default; the remote stub must request it,
35421 by supplying an appropriate @samp{qSupported} response
35422 (@pxref{qSupported}).
35424 @item qXfer:threads:read::@var{offset},@var{length}
35425 @anchor{qXfer threads read}
35426 Access the list of threads on target. @xref{Thread List Format}. The
35427 annex part of the generic @samp{qXfer} packet must be empty
35428 (@pxref{qXfer read}).
35430 This packet is not probed by default; the remote stub must request it,
35431 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35433 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35434 @anchor{qXfer traceframe info read}
35436 Return a description of the current traceframe's contents.
35437 @xref{Traceframe Info Format}. The annex part of the generic
35438 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35440 This packet is not probed by default; the remote stub must request it,
35441 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35443 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35444 @anchor{qXfer fdpic loadmap read}
35445 Read contents of @code{loadmap}s on the target system. The
35446 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35447 executable @code{loadmap} or interpreter @code{loadmap} to read.
35449 This packet is not probed by default; the remote stub must request it,
35450 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35452 @item qXfer:osdata:read::@var{offset},@var{length}
35453 @anchor{qXfer osdata read}
35454 Access the target's @dfn{operating system information}.
35455 @xref{Operating System Information}.
35462 Data @var{data} (@pxref{Binary Data}) has been read from the
35463 target. There may be more data at a higher address (although
35464 it is permitted to return @samp{m} even for the last valid
35465 block of data, as long as at least one byte of data was read).
35466 @var{data} may have fewer bytes than the @var{length} in the
35470 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35471 There is no more data to be read. @var{data} may have fewer bytes
35472 than the @var{length} in the request.
35475 The @var{offset} in the request is at the end of the data.
35476 There is no more data to be read.
35479 The request was malformed, or @var{annex} was invalid.
35482 The offset was invalid, or there was an error encountered reading the data.
35483 @var{nn} is a hex-encoded @code{errno} value.
35486 An empty reply indicates the @var{object} string was not recognized by
35487 the stub, or that the object does not support reading.
35490 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35491 @cindex write data into object, remote request
35492 @anchor{qXfer write}
35493 Write uninterpreted bytes into the target's special data area
35494 identified by the keyword @var{object}, starting at @var{offset} bytes
35495 into the data. @var{data}@dots{} is the binary-encoded data
35496 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35497 is specific to @var{object}; it can supply additional details about what data
35500 Here are the specific requests of this form defined so far. All
35501 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35502 formats, listed below.
35505 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35506 @anchor{qXfer siginfo write}
35507 Write @var{data} to the extra signal information on the target system.
35508 The annex part of the generic @samp{qXfer} packet must be
35509 empty (@pxref{qXfer write}).
35511 This packet is not probed by default; the remote stub must request it,
35512 by supplying an appropriate @samp{qSupported} response
35513 (@pxref{qSupported}).
35515 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35516 @anchor{qXfer spu write}
35517 Write @var{data} to an @code{spufs} file on the target system. The
35518 annex specifies which file to write; it must be of the form
35519 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35520 in the target process, and @var{name} identifes the @code{spufs} file
35521 in that context to be accessed.
35523 This packet is not probed by default; the remote stub must request it,
35524 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35530 @var{nn} (hex encoded) is the number of bytes written.
35531 This may be fewer bytes than supplied in the request.
35534 The request was malformed, or @var{annex} was invalid.
35537 The offset was invalid, or there was an error encountered writing the data.
35538 @var{nn} is a hex-encoded @code{errno} value.
35541 An empty reply indicates the @var{object} string was not
35542 recognized by the stub, or that the object does not support writing.
35545 @item qXfer:@var{object}:@var{operation}:@dots{}
35546 Requests of this form may be added in the future. When a stub does
35547 not recognize the @var{object} keyword, or its support for
35548 @var{object} does not recognize the @var{operation} keyword, the stub
35549 must respond with an empty packet.
35551 @item qAttached:@var{pid}
35552 @cindex query attached, remote request
35553 @cindex @samp{qAttached} packet
35554 Return an indication of whether the remote server attached to an
35555 existing process or created a new process. When the multiprocess
35556 protocol extensions are supported (@pxref{multiprocess extensions}),
35557 @var{pid} is an integer in hexadecimal format identifying the target
35558 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35559 the query packet will be simplified as @samp{qAttached}.
35561 This query is used, for example, to know whether the remote process
35562 should be detached or killed when a @value{GDBN} session is ended with
35563 the @code{quit} command.
35568 The remote server attached to an existing process.
35570 The remote server created a new process.
35572 A badly formed request or an error was encountered.
35577 @node Architecture-Specific Protocol Details
35578 @section Architecture-Specific Protocol Details
35580 This section describes how the remote protocol is applied to specific
35581 target architectures. Also see @ref{Standard Target Features}, for
35582 details of XML target descriptions for each architecture.
35586 @subsubsection Breakpoint Kinds
35588 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35593 16-bit Thumb mode breakpoint.
35596 32-bit Thumb mode (Thumb-2) breakpoint.
35599 32-bit ARM mode breakpoint.
35605 @subsubsection Register Packet Format
35607 The following @code{g}/@code{G} packets have previously been defined.
35608 In the below, some thirty-two bit registers are transferred as
35609 sixty-four bits. Those registers should be zero/sign extended (which?)
35610 to fill the space allocated. Register bytes are transferred in target
35611 byte order. The two nibbles within a register byte are transferred
35612 most-significant - least-significant.
35618 All registers are transferred as thirty-two bit quantities in the order:
35619 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35620 registers; fsr; fir; fp.
35624 All registers are transferred as sixty-four bit quantities (including
35625 thirty-two bit registers such as @code{sr}). The ordering is the same
35630 @node Tracepoint Packets
35631 @section Tracepoint Packets
35632 @cindex tracepoint packets
35633 @cindex packets, tracepoint
35635 Here we describe the packets @value{GDBN} uses to implement
35636 tracepoints (@pxref{Tracepoints}).
35640 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35641 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35642 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35643 the tracepoint is disabled. @var{step} is the tracepoint's step
35644 count, and @var{pass} is its pass count. If an @samp{F} is present,
35645 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35646 the number of bytes that the target should copy elsewhere to make room
35647 for the tracepoint. If an @samp{X} is present, it introduces a
35648 tracepoint condition, which consists of a hexadecimal length, followed
35649 by a comma and hex-encoded bytes, in a manner similar to action
35650 encodings as described below. If the trailing @samp{-} is present,
35651 further @samp{QTDP} packets will follow to specify this tracepoint's
35657 The packet was understood and carried out.
35659 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35661 The packet was not recognized.
35664 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35665 Define actions to be taken when a tracepoint is hit. @var{n} and
35666 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35667 this tracepoint. This packet may only be sent immediately after
35668 another @samp{QTDP} packet that ended with a @samp{-}. If the
35669 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35670 specifying more actions for this tracepoint.
35672 In the series of action packets for a given tracepoint, at most one
35673 can have an @samp{S} before its first @var{action}. If such a packet
35674 is sent, it and the following packets define ``while-stepping''
35675 actions. Any prior packets define ordinary actions --- that is, those
35676 taken when the tracepoint is first hit. If no action packet has an
35677 @samp{S}, then all the packets in the series specify ordinary
35678 tracepoint actions.
35680 The @samp{@var{action}@dots{}} portion of the packet is a series of
35681 actions, concatenated without separators. Each action has one of the
35687 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35688 a hexadecimal number whose @var{i}'th bit is set if register number
35689 @var{i} should be collected. (The least significant bit is numbered
35690 zero.) Note that @var{mask} may be any number of digits long; it may
35691 not fit in a 32-bit word.
35693 @item M @var{basereg},@var{offset},@var{len}
35694 Collect @var{len} bytes of memory starting at the address in register
35695 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35696 @samp{-1}, then the range has a fixed address: @var{offset} is the
35697 address of the lowest byte to collect. The @var{basereg},
35698 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35699 values (the @samp{-1} value for @var{basereg} is a special case).
35701 @item X @var{len},@var{expr}
35702 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35703 it directs. @var{expr} is an agent expression, as described in
35704 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35705 two-digit hex number in the packet; @var{len} is the number of bytes
35706 in the expression (and thus one-half the number of hex digits in the
35711 Any number of actions may be packed together in a single @samp{QTDP}
35712 packet, as long as the packet does not exceed the maximum packet
35713 length (400 bytes, for many stubs). There may be only one @samp{R}
35714 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35715 actions. Any registers referred to by @samp{M} and @samp{X} actions
35716 must be collected by a preceding @samp{R} action. (The
35717 ``while-stepping'' actions are treated as if they were attached to a
35718 separate tracepoint, as far as these restrictions are concerned.)
35723 The packet was understood and carried out.
35725 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35727 The packet was not recognized.
35730 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35731 @cindex @samp{QTDPsrc} packet
35732 Specify a source string of tracepoint @var{n} at address @var{addr}.
35733 This is useful to get accurate reproduction of the tracepoints
35734 originally downloaded at the beginning of the trace run. @var{type}
35735 is the name of the tracepoint part, such as @samp{cond} for the
35736 tracepoint's conditional expression (see below for a list of types), while
35737 @var{bytes} is the string, encoded in hexadecimal.
35739 @var{start} is the offset of the @var{bytes} within the overall source
35740 string, while @var{slen} is the total length of the source string.
35741 This is intended for handling source strings that are longer than will
35742 fit in a single packet.
35743 @c Add detailed example when this info is moved into a dedicated
35744 @c tracepoint descriptions section.
35746 The available string types are @samp{at} for the location,
35747 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35748 @value{GDBN} sends a separate packet for each command in the action
35749 list, in the same order in which the commands are stored in the list.
35751 The target does not need to do anything with source strings except
35752 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35755 Although this packet is optional, and @value{GDBN} will only send it
35756 if the target replies with @samp{TracepointSource} @xref{General
35757 Query Packets}, it makes both disconnected tracing and trace files
35758 much easier to use. Otherwise the user must be careful that the
35759 tracepoints in effect while looking at trace frames are identical to
35760 the ones in effect during the trace run; even a small discrepancy
35761 could cause @samp{tdump} not to work, or a particular trace frame not
35764 @item QTDV:@var{n}:@var{value}
35765 @cindex define trace state variable, remote request
35766 @cindex @samp{QTDV} packet
35767 Create a new trace state variable, number @var{n}, with an initial
35768 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35769 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35770 the option of not using this packet for initial values of zero; the
35771 target should simply create the trace state variables as they are
35772 mentioned in expressions.
35774 @item QTFrame:@var{n}
35775 Select the @var{n}'th tracepoint frame from the buffer, and use the
35776 register and memory contents recorded there to answer subsequent
35777 request packets from @value{GDBN}.
35779 A successful reply from the stub indicates that the stub has found the
35780 requested frame. The response is a series of parts, concatenated
35781 without separators, describing the frame we selected. Each part has
35782 one of the following forms:
35786 The selected frame is number @var{n} in the trace frame buffer;
35787 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35788 was no frame matching the criteria in the request packet.
35791 The selected trace frame records a hit of tracepoint number @var{t};
35792 @var{t} is a hexadecimal number.
35796 @item QTFrame:pc:@var{addr}
35797 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35798 currently selected frame whose PC is @var{addr};
35799 @var{addr} is a hexadecimal number.
35801 @item QTFrame:tdp:@var{t}
35802 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35803 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35804 is a hexadecimal number.
35806 @item QTFrame:range:@var{start}:@var{end}
35807 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35808 currently selected frame whose PC is between @var{start} (inclusive)
35809 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35812 @item QTFrame:outside:@var{start}:@var{end}
35813 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35814 frame @emph{outside} the given range of addresses (exclusive).
35817 This packet requests the minimum length of instruction at which a fast
35818 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
35819 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
35820 it depends on the target system being able to create trampolines in
35821 the first 64K of memory, which might or might not be possible for that
35822 system. So the reply to this packet will be 4 if it is able to
35829 The minimum instruction length is currently unknown.
35831 The minimum instruction length is @var{length}, where @var{length} is greater
35832 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
35833 that a fast tracepoint may be placed on any instruction regardless of size.
35835 An error has occurred.
35837 An empty reply indicates that the request is not supported by the stub.
35841 Begin the tracepoint experiment. Begin collecting data from
35842 tracepoint hits in the trace frame buffer. This packet supports the
35843 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35844 instruction reply packet}).
35847 End the tracepoint experiment. Stop collecting trace frames.
35849 @item QTEnable:@var{n}:@var{addr}
35851 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35852 experiment. If the tracepoint was previously disabled, then collection
35853 of data from it will resume.
35855 @item QTDisable:@var{n}:@var{addr}
35857 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35858 experiment. No more data will be collected from the tracepoint unless
35859 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35862 Clear the table of tracepoints, and empty the trace frame buffer.
35864 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35865 Establish the given ranges of memory as ``transparent''. The stub
35866 will answer requests for these ranges from memory's current contents,
35867 if they were not collected as part of the tracepoint hit.
35869 @value{GDBN} uses this to mark read-only regions of memory, like those
35870 containing program code. Since these areas never change, they should
35871 still have the same contents they did when the tracepoint was hit, so
35872 there's no reason for the stub to refuse to provide their contents.
35874 @item QTDisconnected:@var{value}
35875 Set the choice to what to do with the tracing run when @value{GDBN}
35876 disconnects from the target. A @var{value} of 1 directs the target to
35877 continue the tracing run, while 0 tells the target to stop tracing if
35878 @value{GDBN} is no longer in the picture.
35881 Ask the stub if there is a trace experiment running right now.
35883 The reply has the form:
35887 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35888 @var{running} is a single digit @code{1} if the trace is presently
35889 running, or @code{0} if not. It is followed by semicolon-separated
35890 optional fields that an agent may use to report additional status.
35894 If the trace is not running, the agent may report any of several
35895 explanations as one of the optional fields:
35900 No trace has been run yet.
35902 @item tstop[:@var{text}]:0
35903 The trace was stopped by a user-originated stop command. The optional
35904 @var{text} field is a user-supplied string supplied as part of the
35905 stop command (for instance, an explanation of why the trace was
35906 stopped manually). It is hex-encoded.
35909 The trace stopped because the trace buffer filled up.
35911 @item tdisconnected:0
35912 The trace stopped because @value{GDBN} disconnected from the target.
35914 @item tpasscount:@var{tpnum}
35915 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35917 @item terror:@var{text}:@var{tpnum}
35918 The trace stopped because tracepoint @var{tpnum} had an error. The
35919 string @var{text} is available to describe the nature of the error
35920 (for instance, a divide by zero in the condition expression).
35921 @var{text} is hex encoded.
35924 The trace stopped for some other reason.
35928 Additional optional fields supply statistical and other information.
35929 Although not required, they are extremely useful for users monitoring
35930 the progress of a trace run. If a trace has stopped, and these
35931 numbers are reported, they must reflect the state of the just-stopped
35936 @item tframes:@var{n}
35937 The number of trace frames in the buffer.
35939 @item tcreated:@var{n}
35940 The total number of trace frames created during the run. This may
35941 be larger than the trace frame count, if the buffer is circular.
35943 @item tsize:@var{n}
35944 The total size of the trace buffer, in bytes.
35946 @item tfree:@var{n}
35947 The number of bytes still unused in the buffer.
35949 @item circular:@var{n}
35950 The value of the circular trace buffer flag. @code{1} means that the
35951 trace buffer is circular and old trace frames will be discarded if
35952 necessary to make room, @code{0} means that the trace buffer is linear
35955 @item disconn:@var{n}
35956 The value of the disconnected tracing flag. @code{1} means that
35957 tracing will continue after @value{GDBN} disconnects, @code{0} means
35958 that the trace run will stop.
35962 @item qTP:@var{tp}:@var{addr}
35963 @cindex tracepoint status, remote request
35964 @cindex @samp{qTP} packet
35965 Ask the stub for the current state of tracepoint number @var{tp} at
35966 address @var{addr}.
35970 @item V@var{hits}:@var{usage}
35971 The tracepoint has been hit @var{hits} times so far during the trace
35972 run, and accounts for @var{usage} in the trace buffer. Note that
35973 @code{while-stepping} steps are not counted as separate hits, but the
35974 steps' space consumption is added into the usage number.
35978 @item qTV:@var{var}
35979 @cindex trace state variable value, remote request
35980 @cindex @samp{qTV} packet
35981 Ask the stub for the value of the trace state variable number @var{var}.
35986 The value of the variable is @var{value}. This will be the current
35987 value of the variable if the user is examining a running target, or a
35988 saved value if the variable was collected in the trace frame that the
35989 user is looking at. Note that multiple requests may result in
35990 different reply values, such as when requesting values while the
35991 program is running.
35994 The value of the variable is unknown. This would occur, for example,
35995 if the user is examining a trace frame in which the requested variable
36001 These packets request data about tracepoints that are being used by
36002 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36003 of data, and multiple @code{qTsP} to get additional pieces. Replies
36004 to these packets generally take the form of the @code{QTDP} packets
36005 that define tracepoints. (FIXME add detailed syntax)
36009 These packets request data about trace state variables that are on the
36010 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36011 and multiple @code{qTsV} to get additional variables. Replies to
36012 these packets follow the syntax of the @code{QTDV} packets that define
36013 trace state variables.
36017 These packets request data about static tracepoint markers that exist
36018 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36019 first piece of data, and multiple @code{qTsSTM} to get additional
36020 pieces. Replies to these packets take the following form:
36024 @item m @var{address}:@var{id}:@var{extra}
36026 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36027 a comma-separated list of markers
36029 (lower case letter @samp{L}) denotes end of list.
36031 An error occurred. @var{nn} are hex digits.
36033 An empty reply indicates that the request is not supported by the
36037 @var{address} is encoded in hex.
36038 @var{id} and @var{extra} are strings encoded in hex.
36040 In response to each query, the target will reply with a list of one or
36041 more markers, separated by commas. @value{GDBN} will respond to each
36042 reply with a request for more markers (using the @samp{qs} form of the
36043 query), until the target responds with @samp{l} (lower-case ell, for
36046 @item qTSTMat:@var{address}
36047 This packets requests data about static tracepoint markers in the
36048 target program at @var{address}. Replies to this packet follow the
36049 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36050 tracepoint markers.
36052 @item QTSave:@var{filename}
36053 This packet directs the target to save trace data to the file name
36054 @var{filename} in the target's filesystem. @var{filename} is encoded
36055 as a hex string; the interpretation of the file name (relative vs
36056 absolute, wild cards, etc) is up to the target.
36058 @item qTBuffer:@var{offset},@var{len}
36059 Return up to @var{len} bytes of the current contents of trace buffer,
36060 starting at @var{offset}. The trace buffer is treated as if it were
36061 a contiguous collection of traceframes, as per the trace file format.
36062 The reply consists as many hex-encoded bytes as the target can deliver
36063 in a packet; it is not an error to return fewer than were asked for.
36064 A reply consisting of just @code{l} indicates that no bytes are
36067 @item QTBuffer:circular:@var{value}
36068 This packet directs the target to use a circular trace buffer if
36069 @var{value} is 1, or a linear buffer if the value is 0.
36071 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36072 This packet adds optional textual notes to the trace run. Allowable
36073 types include @code{user}, @code{notes}, and @code{tstop}, the
36074 @var{text} fields are arbitrary strings, hex-encoded.
36078 @subsection Relocate instruction reply packet
36079 When installing fast tracepoints in memory, the target may need to
36080 relocate the instruction currently at the tracepoint address to a
36081 different address in memory. For most instructions, a simple copy is
36082 enough, but, for example, call instructions that implicitly push the
36083 return address on the stack, and relative branches or other
36084 PC-relative instructions require offset adjustment, so that the effect
36085 of executing the instruction at a different address is the same as if
36086 it had executed in the original location.
36088 In response to several of the tracepoint packets, the target may also
36089 respond with a number of intermediate @samp{qRelocInsn} request
36090 packets before the final result packet, to have @value{GDBN} handle
36091 this relocation operation. If a packet supports this mechanism, its
36092 documentation will explicitly say so. See for example the above
36093 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36094 format of the request is:
36097 @item qRelocInsn:@var{from};@var{to}
36099 This requests @value{GDBN} to copy instruction at address @var{from}
36100 to address @var{to}, possibly adjusted so that executing the
36101 instruction at @var{to} has the same effect as executing it at
36102 @var{from}. @value{GDBN} writes the adjusted instruction to target
36103 memory starting at @var{to}.
36108 @item qRelocInsn:@var{adjusted_size}
36109 Informs the stub the relocation is complete. @var{adjusted_size} is
36110 the length in bytes of resulting relocated instruction sequence.
36112 A badly formed request was detected, or an error was encountered while
36113 relocating the instruction.
36116 @node Host I/O Packets
36117 @section Host I/O Packets
36118 @cindex Host I/O, remote protocol
36119 @cindex file transfer, remote protocol
36121 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36122 operations on the far side of a remote link. For example, Host I/O is
36123 used to upload and download files to a remote target with its own
36124 filesystem. Host I/O uses the same constant values and data structure
36125 layout as the target-initiated File-I/O protocol. However, the
36126 Host I/O packets are structured differently. The target-initiated
36127 protocol relies on target memory to store parameters and buffers.
36128 Host I/O requests are initiated by @value{GDBN}, and the
36129 target's memory is not involved. @xref{File-I/O Remote Protocol
36130 Extension}, for more details on the target-initiated protocol.
36132 The Host I/O request packets all encode a single operation along with
36133 its arguments. They have this format:
36137 @item vFile:@var{operation}: @var{parameter}@dots{}
36138 @var{operation} is the name of the particular request; the target
36139 should compare the entire packet name up to the second colon when checking
36140 for a supported operation. The format of @var{parameter} depends on
36141 the operation. Numbers are always passed in hexadecimal. Negative
36142 numbers have an explicit minus sign (i.e.@: two's complement is not
36143 used). Strings (e.g.@: filenames) are encoded as a series of
36144 hexadecimal bytes. The last argument to a system call may be a
36145 buffer of escaped binary data (@pxref{Binary Data}).
36149 The valid responses to Host I/O packets are:
36153 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36154 @var{result} is the integer value returned by this operation, usually
36155 non-negative for success and -1 for errors. If an error has occured,
36156 @var{errno} will be included in the result. @var{errno} will have a
36157 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36158 operations which return data, @var{attachment} supplies the data as a
36159 binary buffer. Binary buffers in response packets are escaped in the
36160 normal way (@pxref{Binary Data}). See the individual packet
36161 documentation for the interpretation of @var{result} and
36165 An empty response indicates that this operation is not recognized.
36169 These are the supported Host I/O operations:
36172 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36173 Open a file at @var{pathname} and return a file descriptor for it, or
36174 return -1 if an error occurs. @var{pathname} is a string,
36175 @var{flags} is an integer indicating a mask of open flags
36176 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36177 of mode bits to use if the file is created (@pxref{mode_t Values}).
36178 @xref{open}, for details of the open flags and mode values.
36180 @item vFile:close: @var{fd}
36181 Close the open file corresponding to @var{fd} and return 0, or
36182 -1 if an error occurs.
36184 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36185 Read data from the open file corresponding to @var{fd}. Up to
36186 @var{count} bytes will be read from the file, starting at @var{offset}
36187 relative to the start of the file. The target may read fewer bytes;
36188 common reasons include packet size limits and an end-of-file
36189 condition. The number of bytes read is returned. Zero should only be
36190 returned for a successful read at the end of the file, or if
36191 @var{count} was zero.
36193 The data read should be returned as a binary attachment on success.
36194 If zero bytes were read, the response should include an empty binary
36195 attachment (i.e.@: a trailing semicolon). The return value is the
36196 number of target bytes read; the binary attachment may be longer if
36197 some characters were escaped.
36199 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36200 Write @var{data} (a binary buffer) to the open file corresponding
36201 to @var{fd}. Start the write at @var{offset} from the start of the
36202 file. Unlike many @code{write} system calls, there is no
36203 separate @var{count} argument; the length of @var{data} in the
36204 packet is used. @samp{vFile:write} returns the number of bytes written,
36205 which may be shorter than the length of @var{data}, or -1 if an
36208 @item vFile:unlink: @var{pathname}
36209 Delete the file at @var{pathname} on the target. Return 0,
36210 or -1 if an error occurs. @var{pathname} is a string.
36212 @item vFile:readlink: @var{filename}
36213 Read value of symbolic link @var{filename} on the target. Return
36214 the number of bytes read, or -1 if an error occurs.
36216 The data read should be returned as a binary attachment on success.
36217 If zero bytes were read, the response should include an empty binary
36218 attachment (i.e.@: a trailing semicolon). The return value is the
36219 number of target bytes read; the binary attachment may be longer if
36220 some characters were escaped.
36225 @section Interrupts
36226 @cindex interrupts (remote protocol)
36228 When a program on the remote target is running, @value{GDBN} may
36229 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36230 a @code{BREAK} followed by @code{g},
36231 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36233 The precise meaning of @code{BREAK} is defined by the transport
36234 mechanism and may, in fact, be undefined. @value{GDBN} does not
36235 currently define a @code{BREAK} mechanism for any of the network
36236 interfaces except for TCP, in which case @value{GDBN} sends the
36237 @code{telnet} BREAK sequence.
36239 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36240 transport mechanisms. It is represented by sending the single byte
36241 @code{0x03} without any of the usual packet overhead described in
36242 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36243 transmitted as part of a packet, it is considered to be packet data
36244 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36245 (@pxref{X packet}), used for binary downloads, may include an unescaped
36246 @code{0x03} as part of its packet.
36248 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36249 When Linux kernel receives this sequence from serial port,
36250 it stops execution and connects to gdb.
36252 Stubs are not required to recognize these interrupt mechanisms and the
36253 precise meaning associated with receipt of the interrupt is
36254 implementation defined. If the target supports debugging of multiple
36255 threads and/or processes, it should attempt to interrupt all
36256 currently-executing threads and processes.
36257 If the stub is successful at interrupting the
36258 running program, it should send one of the stop
36259 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36260 of successfully stopping the program in all-stop mode, and a stop reply
36261 for each stopped thread in non-stop mode.
36262 Interrupts received while the
36263 program is stopped are discarded.
36265 @node Notification Packets
36266 @section Notification Packets
36267 @cindex notification packets
36268 @cindex packets, notification
36270 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36271 packets that require no acknowledgment. Both the GDB and the stub
36272 may send notifications (although the only notifications defined at
36273 present are sent by the stub). Notifications carry information
36274 without incurring the round-trip latency of an acknowledgment, and so
36275 are useful for low-impact communications where occasional packet loss
36278 A notification packet has the form @samp{% @var{data} #
36279 @var{checksum}}, where @var{data} is the content of the notification,
36280 and @var{checksum} is a checksum of @var{data}, computed and formatted
36281 as for ordinary @value{GDBN} packets. A notification's @var{data}
36282 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36283 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36284 to acknowledge the notification's receipt or to report its corruption.
36286 Every notification's @var{data} begins with a name, which contains no
36287 colon characters, followed by a colon character.
36289 Recipients should silently ignore corrupted notifications and
36290 notifications they do not understand. Recipients should restart
36291 timeout periods on receipt of a well-formed notification, whether or
36292 not they understand it.
36294 Senders should only send the notifications described here when this
36295 protocol description specifies that they are permitted. In the
36296 future, we may extend the protocol to permit existing notifications in
36297 new contexts; this rule helps older senders avoid confusing newer
36300 (Older versions of @value{GDBN} ignore bytes received until they see
36301 the @samp{$} byte that begins an ordinary packet, so new stubs may
36302 transmit notifications without fear of confusing older clients. There
36303 are no notifications defined for @value{GDBN} to send at the moment, but we
36304 assume that most older stubs would ignore them, as well.)
36306 The following notification packets from the stub to @value{GDBN} are
36310 @item Stop: @var{reply}
36311 Report an asynchronous stop event in non-stop mode.
36312 The @var{reply} has the form of a stop reply, as
36313 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36314 for information on how these notifications are acknowledged by
36318 @node Remote Non-Stop
36319 @section Remote Protocol Support for Non-Stop Mode
36321 @value{GDBN}'s remote protocol supports non-stop debugging of
36322 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36323 supports non-stop mode, it should report that to @value{GDBN} by including
36324 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36326 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36327 establishing a new connection with the stub. Entering non-stop mode
36328 does not alter the state of any currently-running threads, but targets
36329 must stop all threads in any already-attached processes when entering
36330 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36331 probe the target state after a mode change.
36333 In non-stop mode, when an attached process encounters an event that
36334 would otherwise be reported with a stop reply, it uses the
36335 asynchronous notification mechanism (@pxref{Notification Packets}) to
36336 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36337 in all processes are stopped when a stop reply is sent, in non-stop
36338 mode only the thread reporting the stop event is stopped. That is,
36339 when reporting a @samp{S} or @samp{T} response to indicate completion
36340 of a step operation, hitting a breakpoint, or a fault, only the
36341 affected thread is stopped; any other still-running threads continue
36342 to run. When reporting a @samp{W} or @samp{X} response, all running
36343 threads belonging to other attached processes continue to run.
36345 Only one stop reply notification at a time may be pending; if
36346 additional stop events occur before @value{GDBN} has acknowledged the
36347 previous notification, they must be queued by the stub for later
36348 synchronous transmission in response to @samp{vStopped} packets from
36349 @value{GDBN}. Because the notification mechanism is unreliable,
36350 the stub is permitted to resend a stop reply notification
36351 if it believes @value{GDBN} may not have received it. @value{GDBN}
36352 ignores additional stop reply notifications received before it has
36353 finished processing a previous notification and the stub has completed
36354 sending any queued stop events.
36356 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36357 notification at any time. Specifically, they may appear when
36358 @value{GDBN} is not otherwise reading input from the stub, or when
36359 @value{GDBN} is expecting to read a normal synchronous response or a
36360 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36361 Notification packets are distinct from any other communication from
36362 the stub so there is no ambiguity.
36364 After receiving a stop reply notification, @value{GDBN} shall
36365 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36366 as a regular, synchronous request to the stub. Such acknowledgment
36367 is not required to happen immediately, as @value{GDBN} is permitted to
36368 send other, unrelated packets to the stub first, which the stub should
36371 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36372 stop events to report to @value{GDBN}, it shall respond by sending a
36373 normal stop reply response. @value{GDBN} shall then send another
36374 @samp{vStopped} packet to solicit further responses; again, it is
36375 permitted to send other, unrelated packets as well which the stub
36376 should process normally.
36378 If the stub receives a @samp{vStopped} packet and there are no
36379 additional stop events to report, the stub shall return an @samp{OK}
36380 response. At this point, if further stop events occur, the stub shall
36381 send a new stop reply notification, @value{GDBN} shall accept the
36382 notification, and the process shall be repeated.
36384 In non-stop mode, the target shall respond to the @samp{?} packet as
36385 follows. First, any incomplete stop reply notification/@samp{vStopped}
36386 sequence in progress is abandoned. The target must begin a new
36387 sequence reporting stop events for all stopped threads, whether or not
36388 it has previously reported those events to @value{GDBN}. The first
36389 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36390 subsequent stop replies are sent as responses to @samp{vStopped} packets
36391 using the mechanism described above. The target must not send
36392 asynchronous stop reply notifications until the sequence is complete.
36393 If all threads are running when the target receives the @samp{?} packet,
36394 or if the target is not attached to any process, it shall respond
36397 @node Packet Acknowledgment
36398 @section Packet Acknowledgment
36400 @cindex acknowledgment, for @value{GDBN} remote
36401 @cindex packet acknowledgment, for @value{GDBN} remote
36402 By default, when either the host or the target machine receives a packet,
36403 the first response expected is an acknowledgment: either @samp{+} (to indicate
36404 the package was received correctly) or @samp{-} (to request retransmission).
36405 This mechanism allows the @value{GDBN} remote protocol to operate over
36406 unreliable transport mechanisms, such as a serial line.
36408 In cases where the transport mechanism is itself reliable (such as a pipe or
36409 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36410 It may be desirable to disable them in that case to reduce communication
36411 overhead, or for other reasons. This can be accomplished by means of the
36412 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36414 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36415 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36416 and response format still includes the normal checksum, as described in
36417 @ref{Overview}, but the checksum may be ignored by the receiver.
36419 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36420 no-acknowledgment mode, it should report that to @value{GDBN}
36421 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36422 @pxref{qSupported}.
36423 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36424 disabled via the @code{set remote noack-packet off} command
36425 (@pxref{Remote Configuration}),
36426 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36427 Only then may the stub actually turn off packet acknowledgments.
36428 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36429 response, which can be safely ignored by the stub.
36431 Note that @code{set remote noack-packet} command only affects negotiation
36432 between @value{GDBN} and the stub when subsequent connections are made;
36433 it does not affect the protocol acknowledgment state for any current
36435 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36436 new connection is established,
36437 there is also no protocol request to re-enable the acknowledgments
36438 for the current connection, once disabled.
36443 Example sequence of a target being re-started. Notice how the restart
36444 does not get any direct output:
36449 @emph{target restarts}
36452 <- @code{T001:1234123412341234}
36456 Example sequence of a target being stepped by a single instruction:
36459 -> @code{G1445@dots{}}
36464 <- @code{T001:1234123412341234}
36468 <- @code{1455@dots{}}
36472 @node File-I/O Remote Protocol Extension
36473 @section File-I/O Remote Protocol Extension
36474 @cindex File-I/O remote protocol extension
36477 * File-I/O Overview::
36478 * Protocol Basics::
36479 * The F Request Packet::
36480 * The F Reply Packet::
36481 * The Ctrl-C Message::
36483 * List of Supported Calls::
36484 * Protocol-specific Representation of Datatypes::
36486 * File-I/O Examples::
36489 @node File-I/O Overview
36490 @subsection File-I/O Overview
36491 @cindex file-i/o overview
36493 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36494 target to use the host's file system and console I/O to perform various
36495 system calls. System calls on the target system are translated into a
36496 remote protocol packet to the host system, which then performs the needed
36497 actions and returns a response packet to the target system.
36498 This simulates file system operations even on targets that lack file systems.
36500 The protocol is defined to be independent of both the host and target systems.
36501 It uses its own internal representation of datatypes and values. Both
36502 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36503 translating the system-dependent value representations into the internal
36504 protocol representations when data is transmitted.
36506 The communication is synchronous. A system call is possible only when
36507 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36508 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36509 the target is stopped to allow deterministic access to the target's
36510 memory. Therefore File-I/O is not interruptible by target signals. On
36511 the other hand, it is possible to interrupt File-I/O by a user interrupt
36512 (@samp{Ctrl-C}) within @value{GDBN}.
36514 The target's request to perform a host system call does not finish
36515 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36516 after finishing the system call, the target returns to continuing the
36517 previous activity (continue, step). No additional continue or step
36518 request from @value{GDBN} is required.
36521 (@value{GDBP}) continue
36522 <- target requests 'system call X'
36523 target is stopped, @value{GDBN} executes system call
36524 -> @value{GDBN} returns result
36525 ... target continues, @value{GDBN} returns to wait for the target
36526 <- target hits breakpoint and sends a Txx packet
36529 The protocol only supports I/O on the console and to regular files on
36530 the host file system. Character or block special devices, pipes,
36531 named pipes, sockets or any other communication method on the host
36532 system are not supported by this protocol.
36534 File I/O is not supported in non-stop mode.
36536 @node Protocol Basics
36537 @subsection Protocol Basics
36538 @cindex protocol basics, file-i/o
36540 The File-I/O protocol uses the @code{F} packet as the request as well
36541 as reply packet. Since a File-I/O system call can only occur when
36542 @value{GDBN} is waiting for a response from the continuing or stepping target,
36543 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36544 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36545 This @code{F} packet contains all information needed to allow @value{GDBN}
36546 to call the appropriate host system call:
36550 A unique identifier for the requested system call.
36553 All parameters to the system call. Pointers are given as addresses
36554 in the target memory address space. Pointers to strings are given as
36555 pointer/length pair. Numerical values are given as they are.
36556 Numerical control flags are given in a protocol-specific representation.
36560 At this point, @value{GDBN} has to perform the following actions.
36564 If the parameters include pointer values to data needed as input to a
36565 system call, @value{GDBN} requests this data from the target with a
36566 standard @code{m} packet request. This additional communication has to be
36567 expected by the target implementation and is handled as any other @code{m}
36571 @value{GDBN} translates all value from protocol representation to host
36572 representation as needed. Datatypes are coerced into the host types.
36575 @value{GDBN} calls the system call.
36578 It then coerces datatypes back to protocol representation.
36581 If the system call is expected to return data in buffer space specified
36582 by pointer parameters to the call, the data is transmitted to the
36583 target using a @code{M} or @code{X} packet. This packet has to be expected
36584 by the target implementation and is handled as any other @code{M} or @code{X}
36589 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36590 necessary information for the target to continue. This at least contains
36597 @code{errno}, if has been changed by the system call.
36604 After having done the needed type and value coercion, the target continues
36605 the latest continue or step action.
36607 @node The F Request Packet
36608 @subsection The @code{F} Request Packet
36609 @cindex file-i/o request packet
36610 @cindex @code{F} request packet
36612 The @code{F} request packet has the following format:
36615 @item F@var{call-id},@var{parameter@dots{}}
36617 @var{call-id} is the identifier to indicate the host system call to be called.
36618 This is just the name of the function.
36620 @var{parameter@dots{}} are the parameters to the system call.
36621 Parameters are hexadecimal integer values, either the actual values in case
36622 of scalar datatypes, pointers to target buffer space in case of compound
36623 datatypes and unspecified memory areas, or pointer/length pairs in case
36624 of string parameters. These are appended to the @var{call-id} as a
36625 comma-delimited list. All values are transmitted in ASCII
36626 string representation, pointer/length pairs separated by a slash.
36632 @node The F Reply Packet
36633 @subsection The @code{F} Reply Packet
36634 @cindex file-i/o reply packet
36635 @cindex @code{F} reply packet
36637 The @code{F} reply packet has the following format:
36641 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36643 @var{retcode} is the return code of the system call as hexadecimal value.
36645 @var{errno} is the @code{errno} set by the call, in protocol-specific
36647 This parameter can be omitted if the call was successful.
36649 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36650 case, @var{errno} must be sent as well, even if the call was successful.
36651 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36658 or, if the call was interrupted before the host call has been performed:
36665 assuming 4 is the protocol-specific representation of @code{EINTR}.
36670 @node The Ctrl-C Message
36671 @subsection The @samp{Ctrl-C} Message
36672 @cindex ctrl-c message, in file-i/o protocol
36674 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36675 reply packet (@pxref{The F Reply Packet}),
36676 the target should behave as if it had
36677 gotten a break message. The meaning for the target is ``system call
36678 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36679 (as with a break message) and return to @value{GDBN} with a @code{T02}
36682 It's important for the target to know in which
36683 state the system call was interrupted. There are two possible cases:
36687 The system call hasn't been performed on the host yet.
36690 The system call on the host has been finished.
36694 These two states can be distinguished by the target by the value of the
36695 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36696 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36697 on POSIX systems. In any other case, the target may presume that the
36698 system call has been finished --- successfully or not --- and should behave
36699 as if the break message arrived right after the system call.
36701 @value{GDBN} must behave reliably. If the system call has not been called
36702 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36703 @code{errno} in the packet. If the system call on the host has been finished
36704 before the user requests a break, the full action must be finished by
36705 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36706 The @code{F} packet may only be sent when either nothing has happened
36707 or the full action has been completed.
36710 @subsection Console I/O
36711 @cindex console i/o as part of file-i/o
36713 By default and if not explicitly closed by the target system, the file
36714 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36715 on the @value{GDBN} console is handled as any other file output operation
36716 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36717 by @value{GDBN} so that after the target read request from file descriptor
36718 0 all following typing is buffered until either one of the following
36723 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36725 system call is treated as finished.
36728 The user presses @key{RET}. This is treated as end of input with a trailing
36732 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36733 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36737 If the user has typed more characters than fit in the buffer given to
36738 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36739 either another @code{read(0, @dots{})} is requested by the target, or debugging
36740 is stopped at the user's request.
36743 @node List of Supported Calls
36744 @subsection List of Supported Calls
36745 @cindex list of supported file-i/o calls
36762 @unnumberedsubsubsec open
36763 @cindex open, file-i/o system call
36768 int open(const char *pathname, int flags);
36769 int open(const char *pathname, int flags, mode_t mode);
36773 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36776 @var{flags} is the bitwise @code{OR} of the following values:
36780 If the file does not exist it will be created. The host
36781 rules apply as far as file ownership and time stamps
36785 When used with @code{O_CREAT}, if the file already exists it is
36786 an error and open() fails.
36789 If the file already exists and the open mode allows
36790 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36791 truncated to zero length.
36794 The file is opened in append mode.
36797 The file is opened for reading only.
36800 The file is opened for writing only.
36803 The file is opened for reading and writing.
36807 Other bits are silently ignored.
36811 @var{mode} is the bitwise @code{OR} of the following values:
36815 User has read permission.
36818 User has write permission.
36821 Group has read permission.
36824 Group has write permission.
36827 Others have read permission.
36830 Others have write permission.
36834 Other bits are silently ignored.
36837 @item Return value:
36838 @code{open} returns the new file descriptor or -1 if an error
36845 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36848 @var{pathname} refers to a directory.
36851 The requested access is not allowed.
36854 @var{pathname} was too long.
36857 A directory component in @var{pathname} does not exist.
36860 @var{pathname} refers to a device, pipe, named pipe or socket.
36863 @var{pathname} refers to a file on a read-only filesystem and
36864 write access was requested.
36867 @var{pathname} is an invalid pointer value.
36870 No space on device to create the file.
36873 The process already has the maximum number of files open.
36876 The limit on the total number of files open on the system
36880 The call was interrupted by the user.
36886 @unnumberedsubsubsec close
36887 @cindex close, file-i/o system call
36896 @samp{Fclose,@var{fd}}
36898 @item Return value:
36899 @code{close} returns zero on success, or -1 if an error occurred.
36905 @var{fd} isn't a valid open file descriptor.
36908 The call was interrupted by the user.
36914 @unnumberedsubsubsec read
36915 @cindex read, file-i/o system call
36920 int read(int fd, void *buf, unsigned int count);
36924 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36926 @item Return value:
36927 On success, the number of bytes read is returned.
36928 Zero indicates end of file. If count is zero, read
36929 returns zero as well. On error, -1 is returned.
36935 @var{fd} is not a valid file descriptor or is not open for
36939 @var{bufptr} is an invalid pointer value.
36942 The call was interrupted by the user.
36948 @unnumberedsubsubsec write
36949 @cindex write, file-i/o system call
36954 int write(int fd, const void *buf, unsigned int count);
36958 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36960 @item Return value:
36961 On success, the number of bytes written are returned.
36962 Zero indicates nothing was written. On error, -1
36969 @var{fd} is not a valid file descriptor or is not open for
36973 @var{bufptr} is an invalid pointer value.
36976 An attempt was made to write a file that exceeds the
36977 host-specific maximum file size allowed.
36980 No space on device to write the data.
36983 The call was interrupted by the user.
36989 @unnumberedsubsubsec lseek
36990 @cindex lseek, file-i/o system call
36995 long lseek (int fd, long offset, int flag);
36999 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37001 @var{flag} is one of:
37005 The offset is set to @var{offset} bytes.
37008 The offset is set to its current location plus @var{offset}
37012 The offset is set to the size of the file plus @var{offset}
37016 @item Return value:
37017 On success, the resulting unsigned offset in bytes from
37018 the beginning of the file is returned. Otherwise, a
37019 value of -1 is returned.
37025 @var{fd} is not a valid open file descriptor.
37028 @var{fd} is associated with the @value{GDBN} console.
37031 @var{flag} is not a proper value.
37034 The call was interrupted by the user.
37040 @unnumberedsubsubsec rename
37041 @cindex rename, file-i/o system call
37046 int rename(const char *oldpath, const char *newpath);
37050 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37052 @item Return value:
37053 On success, zero is returned. On error, -1 is returned.
37059 @var{newpath} is an existing directory, but @var{oldpath} is not a
37063 @var{newpath} is a non-empty directory.
37066 @var{oldpath} or @var{newpath} is a directory that is in use by some
37070 An attempt was made to make a directory a subdirectory
37074 A component used as a directory in @var{oldpath} or new
37075 path is not a directory. Or @var{oldpath} is a directory
37076 and @var{newpath} exists but is not a directory.
37079 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37082 No access to the file or the path of the file.
37086 @var{oldpath} or @var{newpath} was too long.
37089 A directory component in @var{oldpath} or @var{newpath} does not exist.
37092 The file is on a read-only filesystem.
37095 The device containing the file has no room for the new
37099 The call was interrupted by the user.
37105 @unnumberedsubsubsec unlink
37106 @cindex unlink, file-i/o system call
37111 int unlink(const char *pathname);
37115 @samp{Funlink,@var{pathnameptr}/@var{len}}
37117 @item Return value:
37118 On success, zero is returned. On error, -1 is returned.
37124 No access to the file or the path of the file.
37127 The system does not allow unlinking of directories.
37130 The file @var{pathname} cannot be unlinked because it's
37131 being used by another process.
37134 @var{pathnameptr} is an invalid pointer value.
37137 @var{pathname} was too long.
37140 A directory component in @var{pathname} does not exist.
37143 A component of the path is not a directory.
37146 The file is on a read-only filesystem.
37149 The call was interrupted by the user.
37155 @unnumberedsubsubsec stat/fstat
37156 @cindex fstat, file-i/o system call
37157 @cindex stat, file-i/o system call
37162 int stat(const char *pathname, struct stat *buf);
37163 int fstat(int fd, struct stat *buf);
37167 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37168 @samp{Ffstat,@var{fd},@var{bufptr}}
37170 @item Return value:
37171 On success, zero is returned. On error, -1 is returned.
37177 @var{fd} is not a valid open file.
37180 A directory component in @var{pathname} does not exist or the
37181 path is an empty string.
37184 A component of the path is not a directory.
37187 @var{pathnameptr} is an invalid pointer value.
37190 No access to the file or the path of the file.
37193 @var{pathname} was too long.
37196 The call was interrupted by the user.
37202 @unnumberedsubsubsec gettimeofday
37203 @cindex gettimeofday, file-i/o system call
37208 int gettimeofday(struct timeval *tv, void *tz);
37212 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37214 @item Return value:
37215 On success, 0 is returned, -1 otherwise.
37221 @var{tz} is a non-NULL pointer.
37224 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37230 @unnumberedsubsubsec isatty
37231 @cindex isatty, file-i/o system call
37236 int isatty(int fd);
37240 @samp{Fisatty,@var{fd}}
37242 @item Return value:
37243 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37249 The call was interrupted by the user.
37254 Note that the @code{isatty} call is treated as a special case: it returns
37255 1 to the target if the file descriptor is attached
37256 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37257 would require implementing @code{ioctl} and would be more complex than
37262 @unnumberedsubsubsec system
37263 @cindex system, file-i/o system call
37268 int system(const char *command);
37272 @samp{Fsystem,@var{commandptr}/@var{len}}
37274 @item Return value:
37275 If @var{len} is zero, the return value indicates whether a shell is
37276 available. A zero return value indicates a shell is not available.
37277 For non-zero @var{len}, the value returned is -1 on error and the
37278 return status of the command otherwise. Only the exit status of the
37279 command is returned, which is extracted from the host's @code{system}
37280 return value by calling @code{WEXITSTATUS(retval)}. In case
37281 @file{/bin/sh} could not be executed, 127 is returned.
37287 The call was interrupted by the user.
37292 @value{GDBN} takes over the full task of calling the necessary host calls
37293 to perform the @code{system} call. The return value of @code{system} on
37294 the host is simplified before it's returned
37295 to the target. Any termination signal information from the child process
37296 is discarded, and the return value consists
37297 entirely of the exit status of the called command.
37299 Due to security concerns, the @code{system} call is by default refused
37300 by @value{GDBN}. The user has to allow this call explicitly with the
37301 @code{set remote system-call-allowed 1} command.
37304 @item set remote system-call-allowed
37305 @kindex set remote system-call-allowed
37306 Control whether to allow the @code{system} calls in the File I/O
37307 protocol for the remote target. The default is zero (disabled).
37309 @item show remote system-call-allowed
37310 @kindex show remote system-call-allowed
37311 Show whether the @code{system} calls are allowed in the File I/O
37315 @node Protocol-specific Representation of Datatypes
37316 @subsection Protocol-specific Representation of Datatypes
37317 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37320 * Integral Datatypes::
37322 * Memory Transfer::
37327 @node Integral Datatypes
37328 @unnumberedsubsubsec Integral Datatypes
37329 @cindex integral datatypes, in file-i/o protocol
37331 The integral datatypes used in the system calls are @code{int},
37332 @code{unsigned int}, @code{long}, @code{unsigned long},
37333 @code{mode_t}, and @code{time_t}.
37335 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37336 implemented as 32 bit values in this protocol.
37338 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37340 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37341 in @file{limits.h}) to allow range checking on host and target.
37343 @code{time_t} datatypes are defined as seconds since the Epoch.
37345 All integral datatypes transferred as part of a memory read or write of a
37346 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37349 @node Pointer Values
37350 @unnumberedsubsubsec Pointer Values
37351 @cindex pointer values, in file-i/o protocol
37353 Pointers to target data are transmitted as they are. An exception
37354 is made for pointers to buffers for which the length isn't
37355 transmitted as part of the function call, namely strings. Strings
37356 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37363 which is a pointer to data of length 18 bytes at position 0x1aaf.
37364 The length is defined as the full string length in bytes, including
37365 the trailing null byte. For example, the string @code{"hello world"}
37366 at address 0x123456 is transmitted as
37372 @node Memory Transfer
37373 @unnumberedsubsubsec Memory Transfer
37374 @cindex memory transfer, in file-i/o protocol
37376 Structured data which is transferred using a memory read or write (for
37377 example, a @code{struct stat}) is expected to be in a protocol-specific format
37378 with all scalar multibyte datatypes being big endian. Translation to
37379 this representation needs to be done both by the target before the @code{F}
37380 packet is sent, and by @value{GDBN} before
37381 it transfers memory to the target. Transferred pointers to structured
37382 data should point to the already-coerced data at any time.
37386 @unnumberedsubsubsec struct stat
37387 @cindex struct stat, in file-i/o protocol
37389 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37390 is defined as follows:
37394 unsigned int st_dev; /* device */
37395 unsigned int st_ino; /* inode */
37396 mode_t st_mode; /* protection */
37397 unsigned int st_nlink; /* number of hard links */
37398 unsigned int st_uid; /* user ID of owner */
37399 unsigned int st_gid; /* group ID of owner */
37400 unsigned int st_rdev; /* device type (if inode device) */
37401 unsigned long st_size; /* total size, in bytes */
37402 unsigned long st_blksize; /* blocksize for filesystem I/O */
37403 unsigned long st_blocks; /* number of blocks allocated */
37404 time_t st_atime; /* time of last access */
37405 time_t st_mtime; /* time of last modification */
37406 time_t st_ctime; /* time of last change */
37410 The integral datatypes conform to the definitions given in the
37411 appropriate section (see @ref{Integral Datatypes}, for details) so this
37412 structure is of size 64 bytes.
37414 The values of several fields have a restricted meaning and/or
37420 A value of 0 represents a file, 1 the console.
37423 No valid meaning for the target. Transmitted unchanged.
37426 Valid mode bits are described in @ref{Constants}. Any other
37427 bits have currently no meaning for the target.
37432 No valid meaning for the target. Transmitted unchanged.
37437 These values have a host and file system dependent
37438 accuracy. Especially on Windows hosts, the file system may not
37439 support exact timing values.
37442 The target gets a @code{struct stat} of the above representation and is
37443 responsible for coercing it to the target representation before
37446 Note that due to size differences between the host, target, and protocol
37447 representations of @code{struct stat} members, these members could eventually
37448 get truncated on the target.
37450 @node struct timeval
37451 @unnumberedsubsubsec struct timeval
37452 @cindex struct timeval, in file-i/o protocol
37454 The buffer of type @code{struct timeval} used by the File-I/O protocol
37455 is defined as follows:
37459 time_t tv_sec; /* second */
37460 long tv_usec; /* microsecond */
37464 The integral datatypes conform to the definitions given in the
37465 appropriate section (see @ref{Integral Datatypes}, for details) so this
37466 structure is of size 8 bytes.
37469 @subsection Constants
37470 @cindex constants, in file-i/o protocol
37472 The following values are used for the constants inside of the
37473 protocol. @value{GDBN} and target are responsible for translating these
37474 values before and after the call as needed.
37485 @unnumberedsubsubsec Open Flags
37486 @cindex open flags, in file-i/o protocol
37488 All values are given in hexadecimal representation.
37500 @node mode_t Values
37501 @unnumberedsubsubsec mode_t Values
37502 @cindex mode_t values, in file-i/o protocol
37504 All values are given in octal representation.
37521 @unnumberedsubsubsec Errno Values
37522 @cindex errno values, in file-i/o protocol
37524 All values are given in decimal representation.
37549 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37550 any error value not in the list of supported error numbers.
37553 @unnumberedsubsubsec Lseek Flags
37554 @cindex lseek flags, in file-i/o protocol
37563 @unnumberedsubsubsec Limits
37564 @cindex limits, in file-i/o protocol
37566 All values are given in decimal representation.
37569 INT_MIN -2147483648
37571 UINT_MAX 4294967295
37572 LONG_MIN -9223372036854775808
37573 LONG_MAX 9223372036854775807
37574 ULONG_MAX 18446744073709551615
37577 @node File-I/O Examples
37578 @subsection File-I/O Examples
37579 @cindex file-i/o examples
37581 Example sequence of a write call, file descriptor 3, buffer is at target
37582 address 0x1234, 6 bytes should be written:
37585 <- @code{Fwrite,3,1234,6}
37586 @emph{request memory read from target}
37589 @emph{return "6 bytes written"}
37593 Example sequence of a read call, file descriptor 3, buffer is at target
37594 address 0x1234, 6 bytes should be read:
37597 <- @code{Fread,3,1234,6}
37598 @emph{request memory write to target}
37599 -> @code{X1234,6:XXXXXX}
37600 @emph{return "6 bytes read"}
37604 Example sequence of a read call, call fails on the host due to invalid
37605 file descriptor (@code{EBADF}):
37608 <- @code{Fread,3,1234,6}
37612 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37616 <- @code{Fread,3,1234,6}
37621 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37625 <- @code{Fread,3,1234,6}
37626 -> @code{X1234,6:XXXXXX}
37630 @node Library List Format
37631 @section Library List Format
37632 @cindex library list format, remote protocol
37634 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37635 same process as your application to manage libraries. In this case,
37636 @value{GDBN} can use the loader's symbol table and normal memory
37637 operations to maintain a list of shared libraries. On other
37638 platforms, the operating system manages loaded libraries.
37639 @value{GDBN} can not retrieve the list of currently loaded libraries
37640 through memory operations, so it uses the @samp{qXfer:libraries:read}
37641 packet (@pxref{qXfer library list read}) instead. The remote stub
37642 queries the target's operating system and reports which libraries
37645 The @samp{qXfer:libraries:read} packet returns an XML document which
37646 lists loaded libraries and their offsets. Each library has an
37647 associated name and one or more segment or section base addresses,
37648 which report where the library was loaded in memory.
37650 For the common case of libraries that are fully linked binaries, the
37651 library should have a list of segments. If the target supports
37652 dynamic linking of a relocatable object file, its library XML element
37653 should instead include a list of allocated sections. The segment or
37654 section bases are start addresses, not relocation offsets; they do not
37655 depend on the library's link-time base addresses.
37657 @value{GDBN} must be linked with the Expat library to support XML
37658 library lists. @xref{Expat}.
37660 A simple memory map, with one loaded library relocated by a single
37661 offset, looks like this:
37665 <library name="/lib/libc.so.6">
37666 <segment address="0x10000000"/>
37671 Another simple memory map, with one loaded library with three
37672 allocated sections (.text, .data, .bss), looks like this:
37676 <library name="sharedlib.o">
37677 <section address="0x10000000"/>
37678 <section address="0x20000000"/>
37679 <section address="0x30000000"/>
37684 The format of a library list is described by this DTD:
37687 <!-- library-list: Root element with versioning -->
37688 <!ELEMENT library-list (library)*>
37689 <!ATTLIST library-list version CDATA #FIXED "1.0">
37690 <!ELEMENT library (segment*, section*)>
37691 <!ATTLIST library name CDATA #REQUIRED>
37692 <!ELEMENT segment EMPTY>
37693 <!ATTLIST segment address CDATA #REQUIRED>
37694 <!ELEMENT section EMPTY>
37695 <!ATTLIST section address CDATA #REQUIRED>
37698 In addition, segments and section descriptors cannot be mixed within a
37699 single library element, and you must supply at least one segment or
37700 section for each library.
37702 @node Library List Format for SVR4 Targets
37703 @section Library List Format for SVR4 Targets
37704 @cindex library list format, remote protocol
37706 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37707 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37708 shared libraries. Still a special library list provided by this packet is
37709 more efficient for the @value{GDBN} remote protocol.
37711 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37712 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37713 target, the following parameters are reported:
37717 @code{name}, the absolute file name from the @code{l_name} field of
37718 @code{struct link_map}.
37720 @code{lm} with address of @code{struct link_map} used for TLS
37721 (Thread Local Storage) access.
37723 @code{l_addr}, the displacement as read from the field @code{l_addr} of
37724 @code{struct link_map}. For prelinked libraries this is not an absolute
37725 memory address. It is a displacement of absolute memory address against
37726 address the file was prelinked to during the library load.
37728 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
37731 Additionally the single @code{main-lm} attribute specifies address of
37732 @code{struct link_map} used for the main executable. This parameter is used
37733 for TLS access and its presence is optional.
37735 @value{GDBN} must be linked with the Expat library to support XML
37736 SVR4 library lists. @xref{Expat}.
37738 A simple memory map, with two loaded libraries (which do not use prelink),
37742 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
37743 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
37745 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
37747 </library-list-svr>
37750 The format of an SVR4 library list is described by this DTD:
37753 <!-- library-list-svr4: Root element with versioning -->
37754 <!ELEMENT library-list-svr4 (library)*>
37755 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
37756 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
37757 <!ELEMENT library EMPTY>
37758 <!ATTLIST library name CDATA #REQUIRED>
37759 <!ATTLIST library lm CDATA #REQUIRED>
37760 <!ATTLIST library l_addr CDATA #REQUIRED>
37761 <!ATTLIST library l_ld CDATA #REQUIRED>
37764 @node Memory Map Format
37765 @section Memory Map Format
37766 @cindex memory map format
37768 To be able to write into flash memory, @value{GDBN} needs to obtain a
37769 memory map from the target. This section describes the format of the
37772 The memory map is obtained using the @samp{qXfer:memory-map:read}
37773 (@pxref{qXfer memory map read}) packet and is an XML document that
37774 lists memory regions.
37776 @value{GDBN} must be linked with the Expat library to support XML
37777 memory maps. @xref{Expat}.
37779 The top-level structure of the document is shown below:
37782 <?xml version="1.0"?>
37783 <!DOCTYPE memory-map
37784 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37785 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37791 Each region can be either:
37796 A region of RAM starting at @var{addr} and extending for @var{length}
37800 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37805 A region of read-only memory:
37808 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37813 A region of flash memory, with erasure blocks @var{blocksize}
37817 <memory type="flash" start="@var{addr}" length="@var{length}">
37818 <property name="blocksize">@var{blocksize}</property>
37824 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37825 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37826 packets to write to addresses in such ranges.
37828 The formal DTD for memory map format is given below:
37831 <!-- ................................................... -->
37832 <!-- Memory Map XML DTD ................................ -->
37833 <!-- File: memory-map.dtd .............................. -->
37834 <!-- .................................... .............. -->
37835 <!-- memory-map.dtd -->
37836 <!-- memory-map: Root element with versioning -->
37837 <!ELEMENT memory-map (memory | property)>
37838 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37839 <!ELEMENT memory (property)>
37840 <!-- memory: Specifies a memory region,
37841 and its type, or device. -->
37842 <!ATTLIST memory type CDATA #REQUIRED
37843 start CDATA #REQUIRED
37844 length CDATA #REQUIRED
37845 device CDATA #IMPLIED>
37846 <!-- property: Generic attribute tag -->
37847 <!ELEMENT property (#PCDATA | property)*>
37848 <!ATTLIST property name CDATA #REQUIRED>
37851 @node Thread List Format
37852 @section Thread List Format
37853 @cindex thread list format
37855 To efficiently update the list of threads and their attributes,
37856 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37857 (@pxref{qXfer threads read}) and obtains the XML document with
37858 the following structure:
37861 <?xml version="1.0"?>
37863 <thread id="id" core="0">
37864 ... description ...
37869 Each @samp{thread} element must have the @samp{id} attribute that
37870 identifies the thread (@pxref{thread-id syntax}). The
37871 @samp{core} attribute, if present, specifies which processor core
37872 the thread was last executing on. The content of the of @samp{thread}
37873 element is interpreted as human-readable auxilliary information.
37875 @node Traceframe Info Format
37876 @section Traceframe Info Format
37877 @cindex traceframe info format
37879 To be able to know which objects in the inferior can be examined when
37880 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37881 memory ranges, registers and trace state variables that have been
37882 collected in a traceframe.
37884 This list is obtained using the @samp{qXfer:traceframe-info:read}
37885 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37887 @value{GDBN} must be linked with the Expat library to support XML
37888 traceframe info discovery. @xref{Expat}.
37890 The top-level structure of the document is shown below:
37893 <?xml version="1.0"?>
37894 <!DOCTYPE traceframe-info
37895 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37896 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37902 Each traceframe block can be either:
37907 A region of collected memory starting at @var{addr} and extending for
37908 @var{length} bytes from there:
37911 <memory start="@var{addr}" length="@var{length}"/>
37916 The formal DTD for the traceframe info format is given below:
37919 <!ELEMENT traceframe-info (memory)* >
37920 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37922 <!ELEMENT memory EMPTY>
37923 <!ATTLIST memory start CDATA #REQUIRED
37924 length CDATA #REQUIRED>
37927 @include agentexpr.texi
37929 @node Target Descriptions
37930 @appendix Target Descriptions
37931 @cindex target descriptions
37933 One of the challenges of using @value{GDBN} to debug embedded systems
37934 is that there are so many minor variants of each processor
37935 architecture in use. It is common practice for vendors to start with
37936 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37937 and then make changes to adapt it to a particular market niche. Some
37938 architectures have hundreds of variants, available from dozens of
37939 vendors. This leads to a number of problems:
37943 With so many different customized processors, it is difficult for
37944 the @value{GDBN} maintainers to keep up with the changes.
37946 Since individual variants may have short lifetimes or limited
37947 audiences, it may not be worthwhile to carry information about every
37948 variant in the @value{GDBN} source tree.
37950 When @value{GDBN} does support the architecture of the embedded system
37951 at hand, the task of finding the correct architecture name to give the
37952 @command{set architecture} command can be error-prone.
37955 To address these problems, the @value{GDBN} remote protocol allows a
37956 target system to not only identify itself to @value{GDBN}, but to
37957 actually describe its own features. This lets @value{GDBN} support
37958 processor variants it has never seen before --- to the extent that the
37959 descriptions are accurate, and that @value{GDBN} understands them.
37961 @value{GDBN} must be linked with the Expat library to support XML
37962 target descriptions. @xref{Expat}.
37965 * Retrieving Descriptions:: How descriptions are fetched from a target.
37966 * Target Description Format:: The contents of a target description.
37967 * Predefined Target Types:: Standard types available for target
37969 * Standard Target Features:: Features @value{GDBN} knows about.
37972 @node Retrieving Descriptions
37973 @section Retrieving Descriptions
37975 Target descriptions can be read from the target automatically, or
37976 specified by the user manually. The default behavior is to read the
37977 description from the target. @value{GDBN} retrieves it via the remote
37978 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37979 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37980 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37981 XML document, of the form described in @ref{Target Description
37984 Alternatively, you can specify a file to read for the target description.
37985 If a file is set, the target will not be queried. The commands to
37986 specify a file are:
37989 @cindex set tdesc filename
37990 @item set tdesc filename @var{path}
37991 Read the target description from @var{path}.
37993 @cindex unset tdesc filename
37994 @item unset tdesc filename
37995 Do not read the XML target description from a file. @value{GDBN}
37996 will use the description supplied by the current target.
37998 @cindex show tdesc filename
37999 @item show tdesc filename
38000 Show the filename to read for a target description, if any.
38004 @node Target Description Format
38005 @section Target Description Format
38006 @cindex target descriptions, XML format
38008 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38009 document which complies with the Document Type Definition provided in
38010 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38011 means you can use generally available tools like @command{xmllint} to
38012 check that your feature descriptions are well-formed and valid.
38013 However, to help people unfamiliar with XML write descriptions for
38014 their targets, we also describe the grammar here.
38016 Target descriptions can identify the architecture of the remote target
38017 and (for some architectures) provide information about custom register
38018 sets. They can also identify the OS ABI of the remote target.
38019 @value{GDBN} can use this information to autoconfigure for your
38020 target, or to warn you if you connect to an unsupported target.
38022 Here is a simple target description:
38025 <target version="1.0">
38026 <architecture>i386:x86-64</architecture>
38031 This minimal description only says that the target uses
38032 the x86-64 architecture.
38034 A target description has the following overall form, with [ ] marking
38035 optional elements and @dots{} marking repeatable elements. The elements
38036 are explained further below.
38039 <?xml version="1.0"?>
38040 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38041 <target version="1.0">
38042 @r{[}@var{architecture}@r{]}
38043 @r{[}@var{osabi}@r{]}
38044 @r{[}@var{compatible}@r{]}
38045 @r{[}@var{feature}@dots{}@r{]}
38050 The description is generally insensitive to whitespace and line
38051 breaks, under the usual common-sense rules. The XML version
38052 declaration and document type declaration can generally be omitted
38053 (@value{GDBN} does not require them), but specifying them may be
38054 useful for XML validation tools. The @samp{version} attribute for
38055 @samp{<target>} may also be omitted, but we recommend
38056 including it; if future versions of @value{GDBN} use an incompatible
38057 revision of @file{gdb-target.dtd}, they will detect and report
38058 the version mismatch.
38060 @subsection Inclusion
38061 @cindex target descriptions, inclusion
38064 @cindex <xi:include>
38067 It can sometimes be valuable to split a target description up into
38068 several different annexes, either for organizational purposes, or to
38069 share files between different possible target descriptions. You can
38070 divide a description into multiple files by replacing any element of
38071 the target description with an inclusion directive of the form:
38074 <xi:include href="@var{document}"/>
38078 When @value{GDBN} encounters an element of this form, it will retrieve
38079 the named XML @var{document}, and replace the inclusion directive with
38080 the contents of that document. If the current description was read
38081 using @samp{qXfer}, then so will be the included document;
38082 @var{document} will be interpreted as the name of an annex. If the
38083 current description was read from a file, @value{GDBN} will look for
38084 @var{document} as a file in the same directory where it found the
38085 original description.
38087 @subsection Architecture
38088 @cindex <architecture>
38090 An @samp{<architecture>} element has this form:
38093 <architecture>@var{arch}</architecture>
38096 @var{arch} is one of the architectures from the set accepted by
38097 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38100 @cindex @code{<osabi>}
38102 This optional field was introduced in @value{GDBN} version 7.0.
38103 Previous versions of @value{GDBN} ignore it.
38105 An @samp{<osabi>} element has this form:
38108 <osabi>@var{abi-name}</osabi>
38111 @var{abi-name} is an OS ABI name from the same selection accepted by
38112 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38114 @subsection Compatible Architecture
38115 @cindex @code{<compatible>}
38117 This optional field was introduced in @value{GDBN} version 7.0.
38118 Previous versions of @value{GDBN} ignore it.
38120 A @samp{<compatible>} element has this form:
38123 <compatible>@var{arch}</compatible>
38126 @var{arch} is one of the architectures from the set accepted by
38127 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38129 A @samp{<compatible>} element is used to specify that the target
38130 is able to run binaries in some other than the main target architecture
38131 given by the @samp{<architecture>} element. For example, on the
38132 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38133 or @code{powerpc:common64}, but the system is able to run binaries
38134 in the @code{spu} architecture as well. The way to describe this
38135 capability with @samp{<compatible>} is as follows:
38138 <architecture>powerpc:common</architecture>
38139 <compatible>spu</compatible>
38142 @subsection Features
38145 Each @samp{<feature>} describes some logical portion of the target
38146 system. Features are currently used to describe available CPU
38147 registers and the types of their contents. A @samp{<feature>} element
38151 <feature name="@var{name}">
38152 @r{[}@var{type}@dots{}@r{]}
38158 Each feature's name should be unique within the description. The name
38159 of a feature does not matter unless @value{GDBN} has some special
38160 knowledge of the contents of that feature; if it does, the feature
38161 should have its standard name. @xref{Standard Target Features}.
38165 Any register's value is a collection of bits which @value{GDBN} must
38166 interpret. The default interpretation is a two's complement integer,
38167 but other types can be requested by name in the register description.
38168 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38169 Target Types}), and the description can define additional composite types.
38171 Each type element must have an @samp{id} attribute, which gives
38172 a unique (within the containing @samp{<feature>}) name to the type.
38173 Types must be defined before they are used.
38176 Some targets offer vector registers, which can be treated as arrays
38177 of scalar elements. These types are written as @samp{<vector>} elements,
38178 specifying the array element type, @var{type}, and the number of elements,
38182 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38186 If a register's value is usefully viewed in multiple ways, define it
38187 with a union type containing the useful representations. The
38188 @samp{<union>} element contains one or more @samp{<field>} elements,
38189 each of which has a @var{name} and a @var{type}:
38192 <union id="@var{id}">
38193 <field name="@var{name}" type="@var{type}"/>
38199 If a register's value is composed from several separate values, define
38200 it with a structure type. There are two forms of the @samp{<struct>}
38201 element; a @samp{<struct>} element must either contain only bitfields
38202 or contain no bitfields. If the structure contains only bitfields,
38203 its total size in bytes must be specified, each bitfield must have an
38204 explicit start and end, and bitfields are automatically assigned an
38205 integer type. The field's @var{start} should be less than or
38206 equal to its @var{end}, and zero represents the least significant bit.
38209 <struct id="@var{id}" size="@var{size}">
38210 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38215 If the structure contains no bitfields, then each field has an
38216 explicit type, and no implicit padding is added.
38219 <struct id="@var{id}">
38220 <field name="@var{name}" type="@var{type}"/>
38226 If a register's value is a series of single-bit flags, define it with
38227 a flags type. The @samp{<flags>} element has an explicit @var{size}
38228 and contains one or more @samp{<field>} elements. Each field has a
38229 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38233 <flags id="@var{id}" size="@var{size}">
38234 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38239 @subsection Registers
38242 Each register is represented as an element with this form:
38245 <reg name="@var{name}"
38246 bitsize="@var{size}"
38247 @r{[}regnum="@var{num}"@r{]}
38248 @r{[}save-restore="@var{save-restore}"@r{]}
38249 @r{[}type="@var{type}"@r{]}
38250 @r{[}group="@var{group}"@r{]}/>
38254 The components are as follows:
38259 The register's name; it must be unique within the target description.
38262 The register's size, in bits.
38265 The register's number. If omitted, a register's number is one greater
38266 than that of the previous register (either in the current feature or in
38267 a preceding feature); the first register in the target description
38268 defaults to zero. This register number is used to read or write
38269 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38270 packets, and registers appear in the @code{g} and @code{G} packets
38271 in order of increasing register number.
38274 Whether the register should be preserved across inferior function
38275 calls; this must be either @code{yes} or @code{no}. The default is
38276 @code{yes}, which is appropriate for most registers except for
38277 some system control registers; this is not related to the target's
38281 The type of the register. @var{type} may be a predefined type, a type
38282 defined in the current feature, or one of the special types @code{int}
38283 and @code{float}. @code{int} is an integer type of the correct size
38284 for @var{bitsize}, and @code{float} is a floating point type (in the
38285 architecture's normal floating point format) of the correct size for
38286 @var{bitsize}. The default is @code{int}.
38289 The register group to which this register belongs. @var{group} must
38290 be either @code{general}, @code{float}, or @code{vector}. If no
38291 @var{group} is specified, @value{GDBN} will not display the register
38292 in @code{info registers}.
38296 @node Predefined Target Types
38297 @section Predefined Target Types
38298 @cindex target descriptions, predefined types
38300 Type definitions in the self-description can build up composite types
38301 from basic building blocks, but can not define fundamental types. Instead,
38302 standard identifiers are provided by @value{GDBN} for the fundamental
38303 types. The currently supported types are:
38312 Signed integer types holding the specified number of bits.
38319 Unsigned integer types holding the specified number of bits.
38323 Pointers to unspecified code and data. The program counter and
38324 any dedicated return address register may be marked as code
38325 pointers; printing a code pointer converts it into a symbolic
38326 address. The stack pointer and any dedicated address registers
38327 may be marked as data pointers.
38330 Single precision IEEE floating point.
38333 Double precision IEEE floating point.
38336 The 12-byte extended precision format used by ARM FPA registers.
38339 The 10-byte extended precision format used by x87 registers.
38342 32bit @sc{eflags} register used by x86.
38345 32bit @sc{mxcsr} register used by x86.
38349 @node Standard Target Features
38350 @section Standard Target Features
38351 @cindex target descriptions, standard features
38353 A target description must contain either no registers or all the
38354 target's registers. If the description contains no registers, then
38355 @value{GDBN} will assume a default register layout, selected based on
38356 the architecture. If the description contains any registers, the
38357 default layout will not be used; the standard registers must be
38358 described in the target description, in such a way that @value{GDBN}
38359 can recognize them.
38361 This is accomplished by giving specific names to feature elements
38362 which contain standard registers. @value{GDBN} will look for features
38363 with those names and verify that they contain the expected registers;
38364 if any known feature is missing required registers, or if any required
38365 feature is missing, @value{GDBN} will reject the target
38366 description. You can add additional registers to any of the
38367 standard features --- @value{GDBN} will display them just as if
38368 they were added to an unrecognized feature.
38370 This section lists the known features and their expected contents.
38371 Sample XML documents for these features are included in the
38372 @value{GDBN} source tree, in the directory @file{gdb/features}.
38374 Names recognized by @value{GDBN} should include the name of the
38375 company or organization which selected the name, and the overall
38376 architecture to which the feature applies; so e.g.@: the feature
38377 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38379 The names of registers are not case sensitive for the purpose
38380 of recognizing standard features, but @value{GDBN} will only display
38381 registers using the capitalization used in the description.
38388 * PowerPC Features::
38394 @subsection ARM Features
38395 @cindex target descriptions, ARM features
38397 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38399 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38400 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38402 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38403 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38404 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38407 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38408 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38410 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38411 it should contain at least registers @samp{wR0} through @samp{wR15} and
38412 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38413 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38415 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38416 should contain at least registers @samp{d0} through @samp{d15}. If
38417 they are present, @samp{d16} through @samp{d31} should also be included.
38418 @value{GDBN} will synthesize the single-precision registers from
38419 halves of the double-precision registers.
38421 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38422 need to contain registers; it instructs @value{GDBN} to display the
38423 VFP double-precision registers as vectors and to synthesize the
38424 quad-precision registers from pairs of double-precision registers.
38425 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38426 be present and include 32 double-precision registers.
38428 @node i386 Features
38429 @subsection i386 Features
38430 @cindex target descriptions, i386 features
38432 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38433 targets. It should describe the following registers:
38437 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38439 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38441 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38442 @samp{fs}, @samp{gs}
38444 @samp{st0} through @samp{st7}
38446 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38447 @samp{foseg}, @samp{fooff} and @samp{fop}
38450 The register sets may be different, depending on the target.
38452 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38453 describe registers:
38457 @samp{xmm0} through @samp{xmm7} for i386
38459 @samp{xmm0} through @samp{xmm15} for amd64
38464 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38465 @samp{org.gnu.gdb.i386.sse} feature. It should
38466 describe the upper 128 bits of @sc{ymm} registers:
38470 @samp{ymm0h} through @samp{ymm7h} for i386
38472 @samp{ymm0h} through @samp{ymm15h} for amd64
38475 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38476 describe a single register, @samp{orig_eax}.
38478 @node MIPS Features
38479 @subsection MIPS Features
38480 @cindex target descriptions, MIPS features
38482 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38483 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38484 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38487 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38488 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38489 registers. They may be 32-bit or 64-bit depending on the target.
38491 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38492 it may be optional in a future version of @value{GDBN}. It should
38493 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38494 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38496 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38497 contain a single register, @samp{restart}, which is used by the
38498 Linux kernel to control restartable syscalls.
38500 @node M68K Features
38501 @subsection M68K Features
38502 @cindex target descriptions, M68K features
38505 @item @samp{org.gnu.gdb.m68k.core}
38506 @itemx @samp{org.gnu.gdb.coldfire.core}
38507 @itemx @samp{org.gnu.gdb.fido.core}
38508 One of those features must be always present.
38509 The feature that is present determines which flavor of m68k is
38510 used. The feature that is present should contain registers
38511 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38512 @samp{sp}, @samp{ps} and @samp{pc}.
38514 @item @samp{org.gnu.gdb.coldfire.fp}
38515 This feature is optional. If present, it should contain registers
38516 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38520 @node PowerPC Features
38521 @subsection PowerPC Features
38522 @cindex target descriptions, PowerPC features
38524 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38525 targets. It should contain registers @samp{r0} through @samp{r31},
38526 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38527 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38529 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38530 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38532 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38533 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38536 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38537 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38538 will combine these registers with the floating point registers
38539 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38540 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38541 through @samp{vs63}, the set of vector registers for POWER7.
38543 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38544 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38545 @samp{spefscr}. SPE targets should provide 32-bit registers in
38546 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38547 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38548 these to present registers @samp{ev0} through @samp{ev31} to the
38551 @node TIC6x Features
38552 @subsection TMS320C6x Features
38553 @cindex target descriptions, TIC6x features
38554 @cindex target descriptions, TMS320C6x features
38555 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38556 targets. It should contain registers @samp{A0} through @samp{A15},
38557 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38559 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38560 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38561 through @samp{B31}.
38563 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38564 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38566 @node Operating System Information
38567 @appendix Operating System Information
38568 @cindex operating system information
38574 Users of @value{GDBN} often wish to obtain information about the state of
38575 the operating system running on the target---for example the list of
38576 processes, or the list of open files. This section describes the
38577 mechanism that makes it possible. This mechanism is similar to the
38578 target features mechanism (@pxref{Target Descriptions}), but focuses
38579 on a different aspect of target.
38581 Operating system information is retrived from the target via the
38582 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38583 read}). The object name in the request should be @samp{osdata}, and
38584 the @var{annex} identifies the data to be fetched.
38587 @appendixsection Process list
38588 @cindex operating system information, process list
38590 When requesting the process list, the @var{annex} field in the
38591 @samp{qXfer} request should be @samp{processes}. The returned data is
38592 an XML document. The formal syntax of this document is defined in
38593 @file{gdb/features/osdata.dtd}.
38595 An example document is:
38598 <?xml version="1.0"?>
38599 <!DOCTYPE target SYSTEM "osdata.dtd">
38600 <osdata type="processes">
38602 <column name="pid">1</column>
38603 <column name="user">root</column>
38604 <column name="command">/sbin/init</column>
38605 <column name="cores">1,2,3</column>
38610 Each item should include a column whose name is @samp{pid}. The value
38611 of that column should identify the process on the target. The
38612 @samp{user} and @samp{command} columns are optional, and will be
38613 displayed by @value{GDBN}. The @samp{cores} column, if present,
38614 should contain a comma-separated list of cores that this process
38615 is running on. Target may provide additional columns,
38616 which @value{GDBN} currently ignores.
38618 @node Trace File Format
38619 @appendix Trace File Format
38620 @cindex trace file format
38622 The trace file comes in three parts: a header, a textual description
38623 section, and a trace frame section with binary data.
38625 The header has the form @code{\x7fTRACE0\n}. The first byte is
38626 @code{0x7f} so as to indicate that the file contains binary data,
38627 while the @code{0} is a version number that may have different values
38630 The description section consists of multiple lines of @sc{ascii} text
38631 separated by newline characters (@code{0xa}). The lines may include a
38632 variety of optional descriptive or context-setting information, such
38633 as tracepoint definitions or register set size. @value{GDBN} will
38634 ignore any line that it does not recognize. An empty line marks the end
38637 @c FIXME add some specific types of data
38639 The trace frame section consists of a number of consecutive frames.
38640 Each frame begins with a two-byte tracepoint number, followed by a
38641 four-byte size giving the amount of data in the frame. The data in
38642 the frame consists of a number of blocks, each introduced by a
38643 character indicating its type (at least register, memory, and trace
38644 state variable). The data in this section is raw binary, not a
38645 hexadecimal or other encoding; its endianness matches the target's
38648 @c FIXME bi-arch may require endianness/arch info in description section
38651 @item R @var{bytes}
38652 Register block. The number and ordering of bytes matches that of a
38653 @code{g} packet in the remote protocol. Note that these are the
38654 actual bytes, in target order and @value{GDBN} register order, not a
38655 hexadecimal encoding.
38657 @item M @var{address} @var{length} @var{bytes}...
38658 Memory block. This is a contiguous block of memory, at the 8-byte
38659 address @var{address}, with a 2-byte length @var{length}, followed by
38660 @var{length} bytes.
38662 @item V @var{number} @var{value}
38663 Trace state variable block. This records the 8-byte signed value
38664 @var{value} of trace state variable numbered @var{number}.
38668 Future enhancements of the trace file format may include additional types
38671 @node Index Section Format
38672 @appendix @code{.gdb_index} section format
38673 @cindex .gdb_index section format
38674 @cindex index section format
38676 This section documents the index section that is created by @code{save
38677 gdb-index} (@pxref{Index Files}). The index section is
38678 DWARF-specific; some knowledge of DWARF is assumed in this
38681 The mapped index file format is designed to be directly
38682 @code{mmap}able on any architecture. In most cases, a datum is
38683 represented using a little-endian 32-bit integer value, called an
38684 @code{offset_type}. Big endian machines must byte-swap the values
38685 before using them. Exceptions to this rule are noted. The data is
38686 laid out such that alignment is always respected.
38688 A mapped index consists of several areas, laid out in order.
38692 The file header. This is a sequence of values, of @code{offset_type}
38693 unless otherwise noted:
38697 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38698 Version 4 differs by its hashing function.
38701 The offset, from the start of the file, of the CU list.
38704 The offset, from the start of the file, of the types CU list. Note
38705 that this area can be empty, in which case this offset will be equal
38706 to the next offset.
38709 The offset, from the start of the file, of the address area.
38712 The offset, from the start of the file, of the symbol table.
38715 The offset, from the start of the file, of the constant pool.
38719 The CU list. This is a sequence of pairs of 64-bit little-endian
38720 values, sorted by the CU offset. The first element in each pair is
38721 the offset of a CU in the @code{.debug_info} section. The second
38722 element in each pair is the length of that CU. References to a CU
38723 elsewhere in the map are done using a CU index, which is just the
38724 0-based index into this table. Note that if there are type CUs, then
38725 conceptually CUs and type CUs form a single list for the purposes of
38729 The types CU list. This is a sequence of triplets of 64-bit
38730 little-endian values. In a triplet, the first value is the CU offset,
38731 the second value is the type offset in the CU, and the third value is
38732 the type signature. The types CU list is not sorted.
38735 The address area. The address area consists of a sequence of address
38736 entries. Each address entry has three elements:
38740 The low address. This is a 64-bit little-endian value.
38743 The high address. This is a 64-bit little-endian value. Like
38744 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38747 The CU index. This is an @code{offset_type} value.
38751 The symbol table. This is an open-addressed hash table. The size of
38752 the hash table is always a power of 2.
38754 Each slot in the hash table consists of a pair of @code{offset_type}
38755 values. The first value is the offset of the symbol's name in the
38756 constant pool. The second value is the offset of the CU vector in the
38759 If both values are 0, then this slot in the hash table is empty. This
38760 is ok because while 0 is a valid constant pool index, it cannot be a
38761 valid index for both a string and a CU vector.
38763 The hash value for a table entry is computed by applying an
38764 iterative hash function to the symbol's name. Starting with an
38765 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38766 the string is incorporated into the hash using the formula depending on the
38771 The formula is @code{r = r * 67 + c - 113}.
38774 The formula is @code{r = r * 67 + tolower (c) - 113}.
38777 The terminating @samp{\0} is not incorporated into the hash.
38779 The step size used in the hash table is computed via
38780 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38781 value, and @samp{size} is the size of the hash table. The step size
38782 is used to find the next candidate slot when handling a hash
38785 The names of C@t{++} symbols in the hash table are canonicalized. We
38786 don't currently have a simple description of the canonicalization
38787 algorithm; if you intend to create new index sections, you must read
38791 The constant pool. This is simply a bunch of bytes. It is organized
38792 so that alignment is correct: CU vectors are stored first, followed by
38795 A CU vector in the constant pool is a sequence of @code{offset_type}
38796 values. The first value is the number of CU indices in the vector.
38797 Each subsequent value is the index of a CU in the CU list. This
38798 element in the hash table is used to indicate which CUs define the
38801 A string in the constant pool is zero-terminated.
38806 @node GNU Free Documentation License
38807 @appendix GNU Free Documentation License
38816 % I think something like @colophon should be in texinfo. In the
38818 \long\def\colophon{\hbox to0pt{}\vfill
38819 \centerline{The body of this manual is set in}
38820 \centerline{\fontname\tenrm,}
38821 \centerline{with headings in {\bf\fontname\tenbf}}
38822 \centerline{and examples in {\tt\fontname\tentt}.}
38823 \centerline{{\it\fontname\tenit\/},}
38824 \centerline{{\bf\fontname\tenbf}, and}
38825 \centerline{{\sl\fontname\tensl\/}}
38826 \centerline{are used for emphasis.}\vfill}
38828 % Blame: doc@cygnus.com, 1991.