1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
3 @c 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 @c 2010, 2011 Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
107 @node Top, Summary, (dir), (dir)
109 @top Debugging with @value{GDBN}
111 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
113 This is the @value{EDITION} Edition, for @value{GDBN}
114 @ifset VERSION_PACKAGE
115 @value{VERSION_PACKAGE}
117 Version @value{GDBVN}.
119 Copyright (C) 1988-2010 Free Software Foundation, Inc.
121 This edition of the GDB manual is dedicated to the memory of Fred
122 Fish. Fred was a long-standing contributor to GDB and to Free
123 software in general. We will miss him.
126 * Summary:: Summary of @value{GDBN}
127 * Sample Session:: A sample @value{GDBN} session
129 * Invocation:: Getting in and out of @value{GDBN}
130 * Commands:: @value{GDBN} commands
131 * Running:: Running programs under @value{GDBN}
132 * Stopping:: Stopping and continuing
133 * Reverse Execution:: Running programs backward
134 * Process Record and Replay:: Recording inferior's execution and replaying it
135 * Stack:: Examining the stack
136 * Source:: Examining source files
137 * Data:: Examining data
138 * Optimized Code:: Debugging optimized code
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Extending GDB:: Extending @value{GDBN}
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
158 * JIT Interface:: Using the JIT debugging interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 @ifset SYSTEM_READLINE
163 * Command Line Editing: (rluserman). Command Line Editing
164 * Using History Interactively: (history). Using History Interactively
166 @ifclear SYSTEM_READLINE
167 * Command Line Editing:: Command Line Editing
168 * Using History Interactively:: Using History Interactively
170 * In Memoriam:: In Memoriam
171 * Formatting Documentation:: How to format and print @value{GDBN} documentation
172 * Installing GDB:: Installing GDB
173 * Maintenance Commands:: Maintenance Commands
174 * Remote Protocol:: GDB Remote Serial Protocol
175 * Agent Expressions:: The GDB Agent Expression Mechanism
176 * Target Descriptions:: How targets can describe themselves to
178 * Operating System Information:: Getting additional information from
180 * Trace File Format:: GDB trace file format
181 * Index Section Format:: .gdb_index section format
182 * Copying:: GNU General Public License says
183 how you can copy and share GDB
184 * GNU Free Documentation License:: The license for this documentation
193 @unnumbered Summary of @value{GDBN}
195 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
196 going on ``inside'' another program while it executes---or what another
197 program was doing at the moment it crashed.
199 @value{GDBN} can do four main kinds of things (plus other things in support of
200 these) to help you catch bugs in the act:
204 Start your program, specifying anything that might affect its behavior.
207 Make your program stop on specified conditions.
210 Examine what has happened, when your program has stopped.
213 Change things in your program, so you can experiment with correcting the
214 effects of one bug and go on to learn about another.
217 You can use @value{GDBN} to debug programs written in C and C@t{++}.
218 For more information, see @ref{Supported Languages,,Supported Languages}.
219 For more information, see @ref{C,,C and C++}.
221 Support for D is partial. For information on D, see
225 Support for Modula-2 is partial. For information on Modula-2, see
226 @ref{Modula-2,,Modula-2}.
228 Support for OpenCL C is partial. For information on OpenCL C, see
229 @ref{OpenCL C,,OpenCL C}.
232 Debugging Pascal programs which use sets, subranges, file variables, or
233 nested functions does not currently work. @value{GDBN} does not support
234 entering expressions, printing values, or similar features using Pascal
238 @value{GDBN} can be used to debug programs written in Fortran, although
239 it may be necessary to refer to some variables with a trailing
242 @value{GDBN} can be used to debug programs written in Objective-C,
243 using either the Apple/NeXT or the GNU Objective-C runtime.
246 * Free Software:: Freely redistributable software
247 * Contributors:: Contributors to GDB
251 @unnumberedsec Free Software
253 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
254 General Public License
255 (GPL). The GPL gives you the freedom to copy or adapt a licensed
256 program---but every person getting a copy also gets with it the
257 freedom to modify that copy (which means that they must get access to
258 the source code), and the freedom to distribute further copies.
259 Typical software companies use copyrights to limit your freedoms; the
260 Free Software Foundation uses the GPL to preserve these freedoms.
262 Fundamentally, the General Public License is a license which says that
263 you have these freedoms and that you cannot take these freedoms away
266 @unnumberedsec Free Software Needs Free Documentation
268 The biggest deficiency in the free software community today is not in
269 the software---it is the lack of good free documentation that we can
270 include with the free software. Many of our most important
271 programs do not come with free reference manuals and free introductory
272 texts. Documentation is an essential part of any software package;
273 when an important free software package does not come with a free
274 manual and a free tutorial, that is a major gap. We have many such
277 Consider Perl, for instance. The tutorial manuals that people
278 normally use are non-free. How did this come about? Because the
279 authors of those manuals published them with restrictive terms---no
280 copying, no modification, source files not available---which exclude
281 them from the free software world.
283 That wasn't the first time this sort of thing happened, and it was far
284 from the last. Many times we have heard a GNU user eagerly describe a
285 manual that he is writing, his intended contribution to the community,
286 only to learn that he had ruined everything by signing a publication
287 contract to make it non-free.
289 Free documentation, like free software, is a matter of freedom, not
290 price. The problem with the non-free manual is not that publishers
291 charge a price for printed copies---that in itself is fine. (The Free
292 Software Foundation sells printed copies of manuals, too.) The
293 problem is the restrictions on the use of the manual. Free manuals
294 are available in source code form, and give you permission to copy and
295 modify. Non-free manuals do not allow this.
297 The criteria of freedom for a free manual are roughly the same as for
298 free software. Redistribution (including the normal kinds of
299 commercial redistribution) must be permitted, so that the manual can
300 accompany every copy of the program, both on-line and on paper.
302 Permission for modification of the technical content is crucial too.
303 When people modify the software, adding or changing features, if they
304 are conscientious they will change the manual too---so they can
305 provide accurate and clear documentation for the modified program. A
306 manual that leaves you no choice but to write a new manual to document
307 a changed version of the program is not really available to our
310 Some kinds of limits on the way modification is handled are
311 acceptable. For example, requirements to preserve the original
312 author's copyright notice, the distribution terms, or the list of
313 authors, are ok. It is also no problem to require modified versions
314 to include notice that they were modified. Even entire sections that
315 may not be deleted or changed are acceptable, as long as they deal
316 with nontechnical topics (like this one). These kinds of restrictions
317 are acceptable because they don't obstruct the community's normal use
320 However, it must be possible to modify all the @emph{technical}
321 content of the manual, and then distribute the result in all the usual
322 media, through all the usual channels. Otherwise, the restrictions
323 obstruct the use of the manual, it is not free, and we need another
324 manual to replace it.
326 Please spread the word about this issue. Our community continues to
327 lose manuals to proprietary publishing. If we spread the word that
328 free software needs free reference manuals and free tutorials, perhaps
329 the next person who wants to contribute by writing documentation will
330 realize, before it is too late, that only free manuals contribute to
331 the free software community.
333 If you are writing documentation, please insist on publishing it under
334 the GNU Free Documentation License or another free documentation
335 license. Remember that this decision requires your approval---you
336 don't have to let the publisher decide. Some commercial publishers
337 will use a free license if you insist, but they will not propose the
338 option; it is up to you to raise the issue and say firmly that this is
339 what you want. If the publisher you are dealing with refuses, please
340 try other publishers. If you're not sure whether a proposed license
341 is free, write to @email{licensing@@gnu.org}.
343 You can encourage commercial publishers to sell more free, copylefted
344 manuals and tutorials by buying them, and particularly by buying
345 copies from the publishers that paid for their writing or for major
346 improvements. Meanwhile, try to avoid buying non-free documentation
347 at all. Check the distribution terms of a manual before you buy it,
348 and insist that whoever seeks your business must respect your freedom.
349 Check the history of the book, and try to reward the publishers that
350 have paid or pay the authors to work on it.
352 The Free Software Foundation maintains a list of free documentation
353 published by other publishers, at
354 @url{http://www.fsf.org/doc/other-free-books.html}.
357 @unnumberedsec Contributors to @value{GDBN}
359 Richard Stallman was the original author of @value{GDBN}, and of many
360 other @sc{gnu} programs. Many others have contributed to its
361 development. This section attempts to credit major contributors. One
362 of the virtues of free software is that everyone is free to contribute
363 to it; with regret, we cannot actually acknowledge everyone here. The
364 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
365 blow-by-blow account.
367 Changes much prior to version 2.0 are lost in the mists of time.
370 @emph{Plea:} Additions to this section are particularly welcome. If you
371 or your friends (or enemies, to be evenhanded) have been unfairly
372 omitted from this list, we would like to add your names!
375 So that they may not regard their many labors as thankless, we
376 particularly thank those who shepherded @value{GDBN} through major
378 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
379 Jim Blandy (release 4.18);
380 Jason Molenda (release 4.17);
381 Stan Shebs (release 4.14);
382 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
383 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
384 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
385 Jim Kingdon (releases 3.5, 3.4, and 3.3);
386 and Randy Smith (releases 3.2, 3.1, and 3.0).
388 Richard Stallman, assisted at various times by Peter TerMaat, Chris
389 Hanson, and Richard Mlynarik, handled releases through 2.8.
391 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
392 in @value{GDBN}, with significant additional contributions from Per
393 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
394 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
395 much general update work leading to release 3.0).
397 @value{GDBN} uses the BFD subroutine library to examine multiple
398 object-file formats; BFD was a joint project of David V.
399 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
401 David Johnson wrote the original COFF support; Pace Willison did
402 the original support for encapsulated COFF.
404 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
406 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
407 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
409 Jean-Daniel Fekete contributed Sun 386i support.
410 Chris Hanson improved the HP9000 support.
411 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
412 David Johnson contributed Encore Umax support.
413 Jyrki Kuoppala contributed Altos 3068 support.
414 Jeff Law contributed HP PA and SOM support.
415 Keith Packard contributed NS32K support.
416 Doug Rabson contributed Acorn Risc Machine support.
417 Bob Rusk contributed Harris Nighthawk CX-UX support.
418 Chris Smith contributed Convex support (and Fortran debugging).
419 Jonathan Stone contributed Pyramid support.
420 Michael Tiemann contributed SPARC support.
421 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
422 Pace Willison contributed Intel 386 support.
423 Jay Vosburgh contributed Symmetry support.
424 Marko Mlinar contributed OpenRISC 1000 support.
426 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
428 Rich Schaefer and Peter Schauer helped with support of SunOS shared
431 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
432 about several machine instruction sets.
434 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
435 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
436 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
437 and RDI targets, respectively.
439 Brian Fox is the author of the readline libraries providing
440 command-line editing and command history.
442 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
443 Modula-2 support, and contributed the Languages chapter of this manual.
445 Fred Fish wrote most of the support for Unix System Vr4.
446 He also enhanced the command-completion support to cover C@t{++} overloaded
449 Hitachi America (now Renesas America), Ltd. sponsored the support for
450 H8/300, H8/500, and Super-H processors.
452 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
454 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
457 Toshiba sponsored the support for the TX39 Mips processor.
459 Matsushita sponsored the support for the MN10200 and MN10300 processors.
461 Fujitsu sponsored the support for SPARClite and FR30 processors.
463 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
466 Michael Snyder added support for tracepoints.
468 Stu Grossman wrote gdbserver.
470 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
471 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
473 The following people at the Hewlett-Packard Company contributed
474 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
475 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
476 compiler, and the Text User Interface (nee Terminal User Interface):
477 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
478 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
479 provided HP-specific information in this manual.
481 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
482 Robert Hoehne made significant contributions to the DJGPP port.
484 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
485 development since 1991. Cygnus engineers who have worked on @value{GDBN}
486 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
487 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
488 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
489 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
490 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
491 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
492 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
493 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
494 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
495 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
496 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
497 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
498 Zuhn have made contributions both large and small.
500 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
501 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
503 Jim Blandy added support for preprocessor macros, while working for Red
506 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
507 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
508 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
509 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
510 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
511 with the migration of old architectures to this new framework.
513 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
514 unwinder framework, this consisting of a fresh new design featuring
515 frame IDs, independent frame sniffers, and the sentinel frame. Mark
516 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
517 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
518 trad unwinders. The architecture-specific changes, each involving a
519 complete rewrite of the architecture's frame code, were carried out by
520 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
521 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
522 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
523 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
526 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
527 Tensilica, Inc.@: contributed support for Xtensa processors. Others
528 who have worked on the Xtensa port of @value{GDBN} in the past include
529 Steve Tjiang, John Newlin, and Scott Foehner.
531 Michael Eager and staff of Xilinx, Inc., contributed support for the
532 Xilinx MicroBlaze architecture.
535 @chapter A Sample @value{GDBN} Session
537 You can use this manual at your leisure to read all about @value{GDBN}.
538 However, a handful of commands are enough to get started using the
539 debugger. This chapter illustrates those commands.
542 In this sample session, we emphasize user input like this: @b{input},
543 to make it easier to pick out from the surrounding output.
546 @c FIXME: this example may not be appropriate for some configs, where
547 @c FIXME...primary interest is in remote use.
549 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
550 processor) exhibits the following bug: sometimes, when we change its
551 quote strings from the default, the commands used to capture one macro
552 definition within another stop working. In the following short @code{m4}
553 session, we define a macro @code{foo} which expands to @code{0000}; we
554 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
555 same thing. However, when we change the open quote string to
556 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
557 procedure fails to define a new synonym @code{baz}:
566 @b{define(bar,defn(`foo'))}
570 @b{changequote(<QUOTE>,<UNQUOTE>)}
572 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
575 m4: End of input: 0: fatal error: EOF in string
579 Let us use @value{GDBN} to try to see what is going on.
582 $ @b{@value{GDBP} m4}
583 @c FIXME: this falsifies the exact text played out, to permit smallbook
584 @c FIXME... format to come out better.
585 @value{GDBN} is free software and you are welcome to distribute copies
586 of it under certain conditions; type "show copying" to see
588 There is absolutely no warranty for @value{GDBN}; type "show warranty"
591 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
596 @value{GDBN} reads only enough symbol data to know where to find the
597 rest when needed; as a result, the first prompt comes up very quickly.
598 We now tell @value{GDBN} to use a narrower display width than usual, so
599 that examples fit in this manual.
602 (@value{GDBP}) @b{set width 70}
606 We need to see how the @code{m4} built-in @code{changequote} works.
607 Having looked at the source, we know the relevant subroutine is
608 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
609 @code{break} command.
612 (@value{GDBP}) @b{break m4_changequote}
613 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
617 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
618 control; as long as control does not reach the @code{m4_changequote}
619 subroutine, the program runs as usual:
622 (@value{GDBP}) @b{run}
623 Starting program: /work/Editorial/gdb/gnu/m4/m4
631 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
632 suspends execution of @code{m4}, displaying information about the
633 context where it stops.
636 @b{changequote(<QUOTE>,<UNQUOTE>)}
638 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
640 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
644 Now we use the command @code{n} (@code{next}) to advance execution to
645 the next line of the current function.
649 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
654 @code{set_quotes} looks like a promising subroutine. We can go into it
655 by using the command @code{s} (@code{step}) instead of @code{next}.
656 @code{step} goes to the next line to be executed in @emph{any}
657 subroutine, so it steps into @code{set_quotes}.
661 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
663 530 if (lquote != def_lquote)
667 The display that shows the subroutine where @code{m4} is now
668 suspended (and its arguments) is called a stack frame display. It
669 shows a summary of the stack. We can use the @code{backtrace}
670 command (which can also be spelled @code{bt}), to see where we are
671 in the stack as a whole: the @code{backtrace} command displays a
672 stack frame for each active subroutine.
675 (@value{GDBP}) @b{bt}
676 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
680 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
681 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
683 #4 0x79dc in expand_input () at macro.c:40
684 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
688 We step through a few more lines to see what happens. The first two
689 times, we can use @samp{s}; the next two times we use @code{n} to avoid
690 falling into the @code{xstrdup} subroutine.
694 0x3b5c 532 if (rquote != def_rquote)
696 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
697 def_lquote : xstrdup(lq);
699 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
702 538 len_lquote = strlen(rquote);
706 The last line displayed looks a little odd; we can examine the variables
707 @code{lquote} and @code{rquote} to see if they are in fact the new left
708 and right quotes we specified. We use the command @code{p}
709 (@code{print}) to see their values.
712 (@value{GDBP}) @b{p lquote}
713 $1 = 0x35d40 "<QUOTE>"
714 (@value{GDBP}) @b{p rquote}
715 $2 = 0x35d50 "<UNQUOTE>"
719 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
720 To look at some context, we can display ten lines of source
721 surrounding the current line with the @code{l} (@code{list}) command.
727 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
733 539 len_rquote = strlen(lquote);
740 Let us step past the two lines that set @code{len_lquote} and
741 @code{len_rquote}, and then examine the values of those variables.
745 539 len_rquote = strlen(lquote);
748 (@value{GDBP}) @b{p len_lquote}
750 (@value{GDBP}) @b{p len_rquote}
755 That certainly looks wrong, assuming @code{len_lquote} and
756 @code{len_rquote} are meant to be the lengths of @code{lquote} and
757 @code{rquote} respectively. We can set them to better values using
758 the @code{p} command, since it can print the value of
759 any expression---and that expression can include subroutine calls and
763 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
765 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
770 Is that enough to fix the problem of using the new quotes with the
771 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
772 executing with the @code{c} (@code{continue}) command, and then try the
773 example that caused trouble initially:
779 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
786 Success! The new quotes now work just as well as the default ones. The
787 problem seems to have been just the two typos defining the wrong
788 lengths. We allow @code{m4} exit by giving it an EOF as input:
792 Program exited normally.
796 The message @samp{Program exited normally.} is from @value{GDBN}; it
797 indicates @code{m4} has finished executing. We can end our @value{GDBN}
798 session with the @value{GDBN} @code{quit} command.
801 (@value{GDBP}) @b{quit}
805 @chapter Getting In and Out of @value{GDBN}
807 This chapter discusses how to start @value{GDBN}, and how to get out of it.
811 type @samp{@value{GDBP}} to start @value{GDBN}.
813 type @kbd{quit} or @kbd{Ctrl-d} to exit.
817 * Invoking GDB:: How to start @value{GDBN}
818 * Quitting GDB:: How to quit @value{GDBN}
819 * Shell Commands:: How to use shell commands inside @value{GDBN}
820 * Logging Output:: How to log @value{GDBN}'s output to a file
824 @section Invoking @value{GDBN}
826 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
827 @value{GDBN} reads commands from the terminal until you tell it to exit.
829 You can also run @code{@value{GDBP}} with a variety of arguments and options,
830 to specify more of your debugging environment at the outset.
832 The command-line options described here are designed
833 to cover a variety of situations; in some environments, some of these
834 options may effectively be unavailable.
836 The most usual way to start @value{GDBN} is with one argument,
837 specifying an executable program:
840 @value{GDBP} @var{program}
844 You can also start with both an executable program and a core file
848 @value{GDBP} @var{program} @var{core}
851 You can, instead, specify a process ID as a second argument, if you want
852 to debug a running process:
855 @value{GDBP} @var{program} 1234
859 would attach @value{GDBN} to process @code{1234} (unless you also have a file
860 named @file{1234}; @value{GDBN} does check for a core file first).
862 Taking advantage of the second command-line argument requires a fairly
863 complete operating system; when you use @value{GDBN} as a remote
864 debugger attached to a bare board, there may not be any notion of
865 ``process'', and there is often no way to get a core dump. @value{GDBN}
866 will warn you if it is unable to attach or to read core dumps.
868 You can optionally have @code{@value{GDBP}} pass any arguments after the
869 executable file to the inferior using @code{--args}. This option stops
872 @value{GDBP} --args gcc -O2 -c foo.c
874 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
875 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
877 You can run @code{@value{GDBP}} without printing the front material, which describes
878 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
885 You can further control how @value{GDBN} starts up by using command-line
886 options. @value{GDBN} itself can remind you of the options available.
896 to display all available options and briefly describe their use
897 (@samp{@value{GDBP} -h} is a shorter equivalent).
899 All options and command line arguments you give are processed
900 in sequential order. The order makes a difference when the
901 @samp{-x} option is used.
905 * File Options:: Choosing files
906 * Mode Options:: Choosing modes
907 * Startup:: What @value{GDBN} does during startup
911 @subsection Choosing Files
913 When @value{GDBN} starts, it reads any arguments other than options as
914 specifying an executable file and core file (or process ID). This is
915 the same as if the arguments were specified by the @samp{-se} and
916 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
917 first argument that does not have an associated option flag as
918 equivalent to the @samp{-se} option followed by that argument; and the
919 second argument that does not have an associated option flag, if any, as
920 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
921 If the second argument begins with a decimal digit, @value{GDBN} will
922 first attempt to attach to it as a process, and if that fails, attempt
923 to open it as a corefile. If you have a corefile whose name begins with
924 a digit, you can prevent @value{GDBN} from treating it as a pid by
925 prefixing it with @file{./}, e.g.@: @file{./12345}.
927 If @value{GDBN} has not been configured to included core file support,
928 such as for most embedded targets, then it will complain about a second
929 argument and ignore it.
931 Many options have both long and short forms; both are shown in the
932 following list. @value{GDBN} also recognizes the long forms if you truncate
933 them, so long as enough of the option is present to be unambiguous.
934 (If you prefer, you can flag option arguments with @samp{--} rather
935 than @samp{-}, though we illustrate the more usual convention.)
937 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
938 @c way, both those who look for -foo and --foo in the index, will find
942 @item -symbols @var{file}
944 @cindex @code{--symbols}
946 Read symbol table from file @var{file}.
948 @item -exec @var{file}
950 @cindex @code{--exec}
952 Use file @var{file} as the executable file to execute when appropriate,
953 and for examining pure data in conjunction with a core dump.
957 Read symbol table from file @var{file} and use it as the executable
960 @item -core @var{file}
962 @cindex @code{--core}
964 Use file @var{file} as a core dump to examine.
966 @item -pid @var{number}
967 @itemx -p @var{number}
970 Connect to process ID @var{number}, as with the @code{attach} command.
972 @item -command @var{file}
974 @cindex @code{--command}
976 Execute commands from file @var{file}. The contents of this file is
977 evaluated exactly as the @code{source} command would.
978 @xref{Command Files,, Command files}.
980 @item -eval-command @var{command}
981 @itemx -ex @var{command}
982 @cindex @code{--eval-command}
984 Execute a single @value{GDBN} command.
986 This option may be used multiple times to call multiple commands. It may
987 also be interleaved with @samp{-command} as required.
990 @value{GDBP} -ex 'target sim' -ex 'load' \
991 -x setbreakpoints -ex 'run' a.out
994 @item -directory @var{directory}
995 @itemx -d @var{directory}
996 @cindex @code{--directory}
998 Add @var{directory} to the path to search for source and script files.
1002 @cindex @code{--readnow}
1004 Read each symbol file's entire symbol table immediately, rather than
1005 the default, which is to read it incrementally as it is needed.
1006 This makes startup slower, but makes future operations faster.
1011 @subsection Choosing Modes
1013 You can run @value{GDBN} in various alternative modes---for example, in
1014 batch mode or quiet mode.
1021 Do not execute commands found in any initialization files. Normally,
1022 @value{GDBN} executes the commands in these files after all the command
1023 options and arguments have been processed. @xref{Command Files,,Command
1029 @cindex @code{--quiet}
1030 @cindex @code{--silent}
1032 ``Quiet''. Do not print the introductory and copyright messages. These
1033 messages are also suppressed in batch mode.
1036 @cindex @code{--batch}
1037 Run in batch mode. Exit with status @code{0} after processing all the
1038 command files specified with @samp{-x} (and all commands from
1039 initialization files, if not inhibited with @samp{-n}). Exit with
1040 nonzero status if an error occurs in executing the @value{GDBN} commands
1041 in the command files. Batch mode also disables pagination, sets unlimited
1042 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1043 off} were in effect (@pxref{Messages/Warnings}).
1045 Batch mode may be useful for running @value{GDBN} as a filter, for
1046 example to download and run a program on another computer; in order to
1047 make this more useful, the message
1050 Program exited normally.
1054 (which is ordinarily issued whenever a program running under
1055 @value{GDBN} control terminates) is not issued when running in batch
1059 @cindex @code{--batch-silent}
1060 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1061 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1062 unaffected). This is much quieter than @samp{-silent} and would be useless
1063 for an interactive session.
1065 This is particularly useful when using targets that give @samp{Loading section}
1066 messages, for example.
1068 Note that targets that give their output via @value{GDBN}, as opposed to
1069 writing directly to @code{stdout}, will also be made silent.
1071 @item -return-child-result
1072 @cindex @code{--return-child-result}
1073 The return code from @value{GDBN} will be the return code from the child
1074 process (the process being debugged), with the following exceptions:
1078 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1079 internal error. In this case the exit code is the same as it would have been
1080 without @samp{-return-child-result}.
1082 The user quits with an explicit value. E.g., @samp{quit 1}.
1084 The child process never runs, or is not allowed to terminate, in which case
1085 the exit code will be -1.
1088 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1089 when @value{GDBN} is being used as a remote program loader or simulator
1094 @cindex @code{--nowindows}
1096 ``No windows''. If @value{GDBN} comes with a graphical user interface
1097 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1098 interface. If no GUI is available, this option has no effect.
1102 @cindex @code{--windows}
1104 If @value{GDBN} includes a GUI, then this option requires it to be
1107 @item -cd @var{directory}
1109 Run @value{GDBN} using @var{directory} as its working directory,
1110 instead of the current directory.
1112 @item -data-directory @var{directory}
1113 @cindex @code{--data-directory}
1114 Run @value{GDBN} using @var{directory} as its data directory.
1115 The data directory is where @value{GDBN} searches for its
1116 auxiliary files. @xref{Data Files}.
1120 @cindex @code{--fullname}
1122 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1123 subprocess. It tells @value{GDBN} to output the full file name and line
1124 number in a standard, recognizable fashion each time a stack frame is
1125 displayed (which includes each time your program stops). This
1126 recognizable format looks like two @samp{\032} characters, followed by
1127 the file name, line number and character position separated by colons,
1128 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1129 @samp{\032} characters as a signal to display the source code for the
1133 @cindex @code{--epoch}
1134 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1135 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1136 routines so as to allow Epoch to display values of expressions in a
1139 @item -annotate @var{level}
1140 @cindex @code{--annotate}
1141 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1142 effect is identical to using @samp{set annotate @var{level}}
1143 (@pxref{Annotations}). The annotation @var{level} controls how much
1144 information @value{GDBN} prints together with its prompt, values of
1145 expressions, source lines, and other types of output. Level 0 is the
1146 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1147 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1148 that control @value{GDBN}, and level 2 has been deprecated.
1150 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1154 @cindex @code{--args}
1155 Change interpretation of command line so that arguments following the
1156 executable file are passed as command line arguments to the inferior.
1157 This option stops option processing.
1159 @item -baud @var{bps}
1161 @cindex @code{--baud}
1163 Set the line speed (baud rate or bits per second) of any serial
1164 interface used by @value{GDBN} for remote debugging.
1166 @item -l @var{timeout}
1168 Set the timeout (in seconds) of any communication used by @value{GDBN}
1169 for remote debugging.
1171 @item -tty @var{device}
1172 @itemx -t @var{device}
1173 @cindex @code{--tty}
1175 Run using @var{device} for your program's standard input and output.
1176 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1178 @c resolve the situation of these eventually
1180 @cindex @code{--tui}
1181 Activate the @dfn{Text User Interface} when starting. The Text User
1182 Interface manages several text windows on the terminal, showing
1183 source, assembly, registers and @value{GDBN} command outputs
1184 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1185 Text User Interface can be enabled by invoking the program
1186 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1187 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1190 @c @cindex @code{--xdb}
1191 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1192 @c For information, see the file @file{xdb_trans.html}, which is usually
1193 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1196 @item -interpreter @var{interp}
1197 @cindex @code{--interpreter}
1198 Use the interpreter @var{interp} for interface with the controlling
1199 program or device. This option is meant to be set by programs which
1200 communicate with @value{GDBN} using it as a back end.
1201 @xref{Interpreters, , Command Interpreters}.
1203 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1204 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1205 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1206 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1207 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1208 @sc{gdb/mi} interfaces are no longer supported.
1211 @cindex @code{--write}
1212 Open the executable and core files for both reading and writing. This
1213 is equivalent to the @samp{set write on} command inside @value{GDBN}
1217 @cindex @code{--statistics}
1218 This option causes @value{GDBN} to print statistics about time and
1219 memory usage after it completes each command and returns to the prompt.
1222 @cindex @code{--version}
1223 This option causes @value{GDBN} to print its version number and
1224 no-warranty blurb, and exit.
1229 @subsection What @value{GDBN} Does During Startup
1230 @cindex @value{GDBN} startup
1232 Here's the description of what @value{GDBN} does during session startup:
1236 Sets up the command interpreter as specified by the command line
1237 (@pxref{Mode Options, interpreter}).
1241 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1242 used when building @value{GDBN}; @pxref{System-wide configuration,
1243 ,System-wide configuration and settings}) and executes all the commands in
1247 Reads the init file (if any) in your home directory@footnote{On
1248 DOS/Windows systems, the home directory is the one pointed to by the
1249 @code{HOME} environment variable.} and executes all the commands in
1253 Processes command line options and operands.
1256 Reads and executes the commands from init file (if any) in the current
1257 working directory. This is only done if the current directory is
1258 different from your home directory. Thus, you can have more than one
1259 init file, one generic in your home directory, and another, specific
1260 to the program you are debugging, in the directory where you invoke
1264 If the command line specified a program to debug, or a process to
1265 attach to, or a core file, @value{GDBN} loads any auto-loaded
1266 scripts provided for the program or for its loaded shared libraries.
1267 @xref{Auto-loading}.
1269 If you wish to disable the auto-loading during startup,
1270 you must do something like the following:
1273 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1276 The following does not work because the auto-loading is turned off too late:
1279 $ gdb -ex "set auto-load-scripts off" myprogram
1283 Reads command files specified by the @samp{-x} option. @xref{Command
1284 Files}, for more details about @value{GDBN} command files.
1287 Reads the command history recorded in the @dfn{history file}.
1288 @xref{Command History}, for more details about the command history and the
1289 files where @value{GDBN} records it.
1292 Init files use the same syntax as @dfn{command files} (@pxref{Command
1293 Files}) and are processed by @value{GDBN} in the same way. The init
1294 file in your home directory can set options (such as @samp{set
1295 complaints}) that affect subsequent processing of command line options
1296 and operands. Init files are not executed if you use the @samp{-nx}
1297 option (@pxref{Mode Options, ,Choosing Modes}).
1299 To display the list of init files loaded by gdb at startup, you
1300 can use @kbd{gdb --help}.
1302 @cindex init file name
1303 @cindex @file{.gdbinit}
1304 @cindex @file{gdb.ini}
1305 The @value{GDBN} init files are normally called @file{.gdbinit}.
1306 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1307 the limitations of file names imposed by DOS filesystems. The Windows
1308 ports of @value{GDBN} use the standard name, but if they find a
1309 @file{gdb.ini} file, they warn you about that and suggest to rename
1310 the file to the standard name.
1314 @section Quitting @value{GDBN}
1315 @cindex exiting @value{GDBN}
1316 @cindex leaving @value{GDBN}
1319 @kindex quit @r{[}@var{expression}@r{]}
1320 @kindex q @r{(@code{quit})}
1321 @item quit @r{[}@var{expression}@r{]}
1323 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1324 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1325 do not supply @var{expression}, @value{GDBN} will terminate normally;
1326 otherwise it will terminate using the result of @var{expression} as the
1331 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1332 terminates the action of any @value{GDBN} command that is in progress and
1333 returns to @value{GDBN} command level. It is safe to type the interrupt
1334 character at any time because @value{GDBN} does not allow it to take effect
1335 until a time when it is safe.
1337 If you have been using @value{GDBN} to control an attached process or
1338 device, you can release it with the @code{detach} command
1339 (@pxref{Attach, ,Debugging an Already-running Process}).
1341 @node Shell Commands
1342 @section Shell Commands
1344 If you need to execute occasional shell commands during your
1345 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1346 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command string}
1352 Invoke a standard shell to execute @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, because this information is rather large.
1877 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1878 provides macro information if you specify the options
1879 @option{-gdwarf-2} and @option{-g3}; the former option requests
1880 debugging information in the Dwarf 2 format, and the latter requests
1881 ``extra information''. In the future, we hope to find more compact
1882 ways to represent macro information, so that it can be included with
1887 @section Starting your Program
1893 @kindex r @r{(@code{run})}
1896 Use the @code{run} command to start your program under @value{GDBN}.
1897 You must first specify the program name (except on VxWorks) with an
1898 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1899 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1900 (@pxref{Files, ,Commands to Specify Files}).
1904 If you are running your program in an execution environment that
1905 supports processes, @code{run} creates an inferior process and makes
1906 that process run your program. In some environments without processes,
1907 @code{run} jumps to the start of your program. Other targets,
1908 like @samp{remote}, are always running. If you get an error
1909 message like this one:
1912 The "remote" target does not support "run".
1913 Try "help target" or "continue".
1917 then use @code{continue} to run your program. You may need @code{load}
1918 first (@pxref{load}).
1920 The execution of a program is affected by certain information it
1921 receives from its superior. @value{GDBN} provides ways to specify this
1922 information, which you must do @emph{before} starting your program. (You
1923 can change it after starting your program, but such changes only affect
1924 your program the next time you start it.) This information may be
1925 divided into four categories:
1928 @item The @emph{arguments.}
1929 Specify the arguments to give your program as the arguments of the
1930 @code{run} command. If a shell is available on your target, the shell
1931 is used to pass the arguments, so that you may use normal conventions
1932 (such as wildcard expansion or variable substitution) in describing
1934 In Unix systems, you can control which shell is used with the
1935 @code{SHELL} environment variable.
1936 @xref{Arguments, ,Your Program's Arguments}.
1938 @item The @emph{environment.}
1939 Your program normally inherits its environment from @value{GDBN}, but you can
1940 use the @value{GDBN} commands @code{set environment} and @code{unset
1941 environment} to change parts of the environment that affect
1942 your program. @xref{Environment, ,Your Program's Environment}.
1944 @item The @emph{working directory.}
1945 Your program inherits its working directory from @value{GDBN}. You can set
1946 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1947 @xref{Working Directory, ,Your Program's Working Directory}.
1949 @item The @emph{standard input and output.}
1950 Your program normally uses the same device for standard input and
1951 standard output as @value{GDBN} is using. You can redirect input and output
1952 in the @code{run} command line, or you can use the @code{tty} command to
1953 set a different device for your program.
1954 @xref{Input/Output, ,Your Program's Input and Output}.
1957 @emph{Warning:} While input and output redirection work, you cannot use
1958 pipes to pass the output of the program you are debugging to another
1959 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1963 When you issue the @code{run} command, your program begins to execute
1964 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1965 of how to arrange for your program to stop. Once your program has
1966 stopped, you may call functions in your program, using the @code{print}
1967 or @code{call} commands. @xref{Data, ,Examining Data}.
1969 If the modification time of your symbol file has changed since the last
1970 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1971 table, and reads it again. When it does this, @value{GDBN} tries to retain
1972 your current breakpoints.
1977 @cindex run to main procedure
1978 The name of the main procedure can vary from language to language.
1979 With C or C@t{++}, the main procedure name is always @code{main}, but
1980 other languages such as Ada do not require a specific name for their
1981 main procedure. The debugger provides a convenient way to start the
1982 execution of the program and to stop at the beginning of the main
1983 procedure, depending on the language used.
1985 The @samp{start} command does the equivalent of setting a temporary
1986 breakpoint at the beginning of the main procedure and then invoking
1987 the @samp{run} command.
1989 @cindex elaboration phase
1990 Some programs contain an @dfn{elaboration} phase where some startup code is
1991 executed before the main procedure is called. This depends on the
1992 languages used to write your program. In C@t{++}, for instance,
1993 constructors for static and global objects are executed before
1994 @code{main} is called. It is therefore possible that the debugger stops
1995 before reaching the main procedure. However, the temporary breakpoint
1996 will remain to halt execution.
1998 Specify the arguments to give to your program as arguments to the
1999 @samp{start} command. These arguments will be given verbatim to the
2000 underlying @samp{run} command. Note that the same arguments will be
2001 reused if no argument is provided during subsequent calls to
2002 @samp{start} or @samp{run}.
2004 It is sometimes necessary to debug the program during elaboration. In
2005 these cases, using the @code{start} command would stop the execution of
2006 your program too late, as the program would have already completed the
2007 elaboration phase. Under these circumstances, insert breakpoints in your
2008 elaboration code before running your program.
2010 @kindex set exec-wrapper
2011 @item set exec-wrapper @var{wrapper}
2012 @itemx show exec-wrapper
2013 @itemx unset exec-wrapper
2014 When @samp{exec-wrapper} is set, the specified wrapper is used to
2015 launch programs for debugging. @value{GDBN} starts your program
2016 with a shell command of the form @kbd{exec @var{wrapper}
2017 @var{program}}. Quoting is added to @var{program} and its
2018 arguments, but not to @var{wrapper}, so you should add quotes if
2019 appropriate for your shell. The wrapper runs until it executes
2020 your program, and then @value{GDBN} takes control.
2022 You can use any program that eventually calls @code{execve} with
2023 its arguments as a wrapper. Several standard Unix utilities do
2024 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2025 with @code{exec "$@@"} will also work.
2027 For example, you can use @code{env} to pass an environment variable to
2028 the debugged program, without setting the variable in your shell's
2032 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2036 This command is available when debugging locally on most targets, excluding
2037 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2039 @kindex set disable-randomization
2040 @item set disable-randomization
2041 @itemx set disable-randomization on
2042 This option (enabled by default in @value{GDBN}) will turn off the native
2043 randomization of the virtual address space of the started program. This option
2044 is useful for multiple debugging sessions to make the execution better
2045 reproducible and memory addresses reusable across debugging sessions.
2047 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2051 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2054 @item set disable-randomization off
2055 Leave the behavior of the started executable unchanged. Some bugs rear their
2056 ugly heads only when the program is loaded at certain addresses. If your bug
2057 disappears when you run the program under @value{GDBN}, that might be because
2058 @value{GDBN} by default disables the address randomization on platforms, such
2059 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2060 disable-randomization off} to try to reproduce such elusive bugs.
2062 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2063 It protects the programs against some kinds of security attacks. In these
2064 cases the attacker needs to know the exact location of a concrete executable
2065 code. Randomizing its location makes it impossible to inject jumps misusing
2066 a code at its expected addresses.
2068 Prelinking shared libraries provides a startup performance advantage but it
2069 makes addresses in these libraries predictable for privileged processes by
2070 having just unprivileged access at the target system. Reading the shared
2071 library binary gives enough information for assembling the malicious code
2072 misusing it. Still even a prelinked shared library can get loaded at a new
2073 random address just requiring the regular relocation process during the
2074 startup. Shared libraries not already prelinked are always loaded at
2075 a randomly chosen address.
2077 Position independent executables (PIE) contain position independent code
2078 similar to the shared libraries and therefore such executables get loaded at
2079 a randomly chosen address upon startup. PIE executables always load even
2080 already prelinked shared libraries at a random address. You can build such
2081 executable using @command{gcc -fPIE -pie}.
2083 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2084 (as long as the randomization is enabled).
2086 @item show disable-randomization
2087 Show the current setting of the explicit disable of the native randomization of
2088 the virtual address space of the started program.
2093 @section Your Program's Arguments
2095 @cindex arguments (to your program)
2096 The arguments to your program can be specified by the arguments of the
2098 They are passed to a shell, which expands wildcard characters and
2099 performs redirection of I/O, and thence to your program. Your
2100 @code{SHELL} environment variable (if it exists) specifies what shell
2101 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2102 the default shell (@file{/bin/sh} on Unix).
2104 On non-Unix systems, the program is usually invoked directly by
2105 @value{GDBN}, which emulates I/O redirection via the appropriate system
2106 calls, and the wildcard characters are expanded by the startup code of
2107 the program, not by the shell.
2109 @code{run} with no arguments uses the same arguments used by the previous
2110 @code{run}, or those set by the @code{set args} command.
2115 Specify the arguments to be used the next time your program is run. If
2116 @code{set args} has no arguments, @code{run} executes your program
2117 with no arguments. Once you have run your program with arguments,
2118 using @code{set args} before the next @code{run} is the only way to run
2119 it again without arguments.
2123 Show the arguments to give your program when it is started.
2127 @section Your Program's Environment
2129 @cindex environment (of your program)
2130 The @dfn{environment} consists of a set of environment variables and
2131 their values. Environment variables conventionally record such things as
2132 your user name, your home directory, your terminal type, and your search
2133 path for programs to run. Usually you set up environment variables with
2134 the shell and they are inherited by all the other programs you run. When
2135 debugging, it can be useful to try running your program with a modified
2136 environment without having to start @value{GDBN} over again.
2140 @item path @var{directory}
2141 Add @var{directory} to the front of the @code{PATH} environment variable
2142 (the search path for executables) that will be passed to your program.
2143 The value of @code{PATH} used by @value{GDBN} does not change.
2144 You may specify several directory names, separated by whitespace or by a
2145 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2146 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2147 is moved to the front, so it is searched sooner.
2149 You can use the string @samp{$cwd} to refer to whatever is the current
2150 working directory at the time @value{GDBN} searches the path. If you
2151 use @samp{.} instead, it refers to the directory where you executed the
2152 @code{path} command. @value{GDBN} replaces @samp{.} in the
2153 @var{directory} argument (with the current path) before adding
2154 @var{directory} to the search path.
2155 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2156 @c document that, since repeating it would be a no-op.
2160 Display the list of search paths for executables (the @code{PATH}
2161 environment variable).
2163 @kindex show environment
2164 @item show environment @r{[}@var{varname}@r{]}
2165 Print the value of environment variable @var{varname} to be given to
2166 your program when it starts. If you do not supply @var{varname},
2167 print the names and values of all environment variables to be given to
2168 your program. You can abbreviate @code{environment} as @code{env}.
2170 @kindex set environment
2171 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2172 Set environment variable @var{varname} to @var{value}. The value
2173 changes for your program only, not for @value{GDBN} itself. @var{value} may
2174 be any string; the values of environment variables are just strings, and
2175 any interpretation is supplied by your program itself. The @var{value}
2176 parameter is optional; if it is eliminated, the variable is set to a
2178 @c "any string" here does not include leading, trailing
2179 @c blanks. Gnu asks: does anyone care?
2181 For example, this command:
2188 tells the debugged program, when subsequently run, that its user is named
2189 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2190 are not actually required.)
2192 @kindex unset environment
2193 @item unset environment @var{varname}
2194 Remove variable @var{varname} from the environment to be passed to your
2195 program. This is different from @samp{set env @var{varname} =};
2196 @code{unset environment} removes the variable from the environment,
2197 rather than assigning it an empty value.
2200 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2202 by your @code{SHELL} environment variable if it exists (or
2203 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2204 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2205 @file{.bashrc} for BASH---any variables you set in that file affect
2206 your program. You may wish to move setting of environment variables to
2207 files that are only run when you sign on, such as @file{.login} or
2210 @node Working Directory
2211 @section Your Program's Working Directory
2213 @cindex working directory (of your program)
2214 Each time you start your program with @code{run}, it inherits its
2215 working directory from the current working directory of @value{GDBN}.
2216 The @value{GDBN} working directory is initially whatever it inherited
2217 from its parent process (typically the shell), but you can specify a new
2218 working directory in @value{GDBN} with the @code{cd} command.
2220 The @value{GDBN} working directory also serves as a default for the commands
2221 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2226 @cindex change working directory
2227 @item cd @var{directory}
2228 Set the @value{GDBN} working directory to @var{directory}.
2232 Print the @value{GDBN} working directory.
2235 It is generally impossible to find the current working directory of
2236 the process being debugged (since a program can change its directory
2237 during its run). If you work on a system where @value{GDBN} is
2238 configured with the @file{/proc} support, you can use the @code{info
2239 proc} command (@pxref{SVR4 Process Information}) to find out the
2240 current working directory of the debuggee.
2243 @section Your Program's Input and Output
2248 By default, the program you run under @value{GDBN} does input and output to
2249 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2250 to its own terminal modes to interact with you, but it records the terminal
2251 modes your program was using and switches back to them when you continue
2252 running your program.
2255 @kindex info terminal
2257 Displays information recorded by @value{GDBN} about the terminal modes your
2261 You can redirect your program's input and/or output using shell
2262 redirection with the @code{run} command. For example,
2269 starts your program, diverting its output to the file @file{outfile}.
2272 @cindex controlling terminal
2273 Another way to specify where your program should do input and output is
2274 with the @code{tty} command. This command accepts a file name as
2275 argument, and causes this file to be the default for future @code{run}
2276 commands. It also resets the controlling terminal for the child
2277 process, for future @code{run} commands. For example,
2284 directs that processes started with subsequent @code{run} commands
2285 default to do input and output on the terminal @file{/dev/ttyb} and have
2286 that as their controlling terminal.
2288 An explicit redirection in @code{run} overrides the @code{tty} command's
2289 effect on the input/output device, but not its effect on the controlling
2292 When you use the @code{tty} command or redirect input in the @code{run}
2293 command, only the input @emph{for your program} is affected. The input
2294 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2295 for @code{set inferior-tty}.
2297 @cindex inferior tty
2298 @cindex set inferior controlling terminal
2299 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2300 display the name of the terminal that will be used for future runs of your
2304 @item set inferior-tty /dev/ttyb
2305 @kindex set inferior-tty
2306 Set the tty for the program being debugged to /dev/ttyb.
2308 @item show inferior-tty
2309 @kindex show inferior-tty
2310 Show the current tty for the program being debugged.
2314 @section Debugging an Already-running Process
2319 @item attach @var{process-id}
2320 This command attaches to a running process---one that was started
2321 outside @value{GDBN}. (@code{info files} shows your active
2322 targets.) The command takes as argument a process ID. The usual way to
2323 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2324 or with the @samp{jobs -l} shell command.
2326 @code{attach} does not repeat if you press @key{RET} a second time after
2327 executing the command.
2330 To use @code{attach}, your program must be running in an environment
2331 which supports processes; for example, @code{attach} does not work for
2332 programs on bare-board targets that lack an operating system. You must
2333 also have permission to send the process a signal.
2335 When you use @code{attach}, the debugger finds the program running in
2336 the process first by looking in the current working directory, then (if
2337 the program is not found) by using the source file search path
2338 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2339 the @code{file} command to load the program. @xref{Files, ,Commands to
2342 The first thing @value{GDBN} does after arranging to debug the specified
2343 process is to stop it. You can examine and modify an attached process
2344 with all the @value{GDBN} commands that are ordinarily available when
2345 you start processes with @code{run}. You can insert breakpoints; you
2346 can step and continue; you can modify storage. If you would rather the
2347 process continue running, you may use the @code{continue} command after
2348 attaching @value{GDBN} to the process.
2353 When you have finished debugging the attached process, you can use the
2354 @code{detach} command to release it from @value{GDBN} control. Detaching
2355 the process continues its execution. After the @code{detach} command,
2356 that process and @value{GDBN} become completely independent once more, and you
2357 are ready to @code{attach} another process or start one with @code{run}.
2358 @code{detach} does not repeat if you press @key{RET} again after
2359 executing the command.
2362 If you exit @value{GDBN} while you have an attached process, you detach
2363 that process. If you use the @code{run} command, you kill that process.
2364 By default, @value{GDBN} asks for confirmation if you try to do either of these
2365 things; you can control whether or not you need to confirm by using the
2366 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2370 @section Killing the Child Process
2375 Kill the child process in which your program is running under @value{GDBN}.
2378 This command is useful if you wish to debug a core dump instead of a
2379 running process. @value{GDBN} ignores any core dump file while your program
2382 On some operating systems, a program cannot be executed outside @value{GDBN}
2383 while you have breakpoints set on it inside @value{GDBN}. You can use the
2384 @code{kill} command in this situation to permit running your program
2385 outside the debugger.
2387 The @code{kill} command is also useful if you wish to recompile and
2388 relink your program, since on many systems it is impossible to modify an
2389 executable file while it is running in a process. In this case, when you
2390 next type @code{run}, @value{GDBN} notices that the file has changed, and
2391 reads the symbol table again (while trying to preserve your current
2392 breakpoint settings).
2394 @node Inferiors and Programs
2395 @section Debugging Multiple Inferiors and Programs
2397 @value{GDBN} lets you run and debug multiple programs in a single
2398 session. In addition, @value{GDBN} on some systems may let you run
2399 several programs simultaneously (otherwise you have to exit from one
2400 before starting another). In the most general case, you can have
2401 multiple threads of execution in each of multiple processes, launched
2402 from multiple executables.
2405 @value{GDBN} represents the state of each program execution with an
2406 object called an @dfn{inferior}. An inferior typically corresponds to
2407 a process, but is more general and applies also to targets that do not
2408 have processes. Inferiors may be created before a process runs, and
2409 may be retained after a process exits. Inferiors have unique
2410 identifiers that are different from process ids. Usually each
2411 inferior will also have its own distinct address space, although some
2412 embedded targets may have several inferiors running in different parts
2413 of a single address space. Each inferior may in turn have multiple
2414 threads running in it.
2416 To find out what inferiors exist at any moment, use @w{@code{info
2420 @kindex info inferiors
2421 @item info inferiors
2422 Print a list of all inferiors currently being managed by @value{GDBN}.
2424 @value{GDBN} displays for each inferior (in this order):
2428 the inferior number assigned by @value{GDBN}
2431 the target system's inferior identifier
2434 the name of the executable the inferior is running.
2439 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2440 indicates the current inferior.
2444 @c end table here to get a little more width for example
2447 (@value{GDBP}) info inferiors
2448 Num Description Executable
2449 2 process 2307 hello
2450 * 1 process 3401 goodbye
2453 To switch focus between inferiors, use the @code{inferior} command:
2456 @kindex inferior @var{infno}
2457 @item inferior @var{infno}
2458 Make inferior number @var{infno} the current inferior. The argument
2459 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2460 in the first field of the @samp{info inferiors} display.
2464 You can get multiple executables into a debugging session via the
2465 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2466 systems @value{GDBN} can add inferiors to the debug session
2467 automatically by following calls to @code{fork} and @code{exec}. To
2468 remove inferiors from the debugging session use the
2469 @w{@code{remove-inferiors}} command.
2472 @kindex add-inferior
2473 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2474 Adds @var{n} inferiors to be run using @var{executable} as the
2475 executable. @var{n} defaults to 1. If no executable is specified,
2476 the inferiors begins empty, with no program. You can still assign or
2477 change the program assigned to the inferior at any time by using the
2478 @code{file} command with the executable name as its argument.
2480 @kindex clone-inferior
2481 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2482 Adds @var{n} inferiors ready to execute the same program as inferior
2483 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2484 number of the current inferior. This is a convenient command when you
2485 want to run another instance of the inferior you are debugging.
2488 (@value{GDBP}) info inferiors
2489 Num Description Executable
2490 * 1 process 29964 helloworld
2491 (@value{GDBP}) clone-inferior
2494 (@value{GDBP}) info inferiors
2495 Num Description Executable
2497 * 1 process 29964 helloworld
2500 You can now simply switch focus to inferior 2 and run it.
2502 @kindex remove-inferiors
2503 @item remove-inferiors @var{infno}@dots{}
2504 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2505 possible to remove an inferior that is running with this command. For
2506 those, use the @code{kill} or @code{detach} command first.
2510 To quit debugging one of the running inferiors that is not the current
2511 inferior, you can either detach from it by using the @w{@code{detach
2512 inferior}} command (allowing it to run independently), or kill it
2513 using the @w{@code{kill inferiors}} command:
2516 @kindex detach inferiors @var{infno}@dots{}
2517 @item detach inferior @var{infno}@dots{}
2518 Detach from the inferior or inferiors identified by @value{GDBN}
2519 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2520 still stays on the list of inferiors shown by @code{info inferiors},
2521 but its Description will show @samp{<null>}.
2523 @kindex kill inferiors @var{infno}@dots{}
2524 @item kill inferiors @var{infno}@dots{}
2525 Kill the inferior or inferiors identified by @value{GDBN} inferior
2526 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2527 stays on the list of inferiors shown by @code{info inferiors}, but its
2528 Description will show @samp{<null>}.
2531 After the successful completion of a command such as @code{detach},
2532 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2533 a normal process exit, the inferior is still valid and listed with
2534 @code{info inferiors}, ready to be restarted.
2537 To be notified when inferiors are started or exit under @value{GDBN}'s
2538 control use @w{@code{set print inferior-events}}:
2541 @kindex set print inferior-events
2542 @cindex print messages on inferior start and exit
2543 @item set print inferior-events
2544 @itemx set print inferior-events on
2545 @itemx set print inferior-events off
2546 The @code{set print inferior-events} command allows you to enable or
2547 disable printing of messages when @value{GDBN} notices that new
2548 inferiors have started or that inferiors have exited or have been
2549 detached. By default, these messages will not be printed.
2551 @kindex show print inferior-events
2552 @item show print inferior-events
2553 Show whether messages will be printed when @value{GDBN} detects that
2554 inferiors have started, exited or have been detached.
2557 Many commands will work the same with multiple programs as with a
2558 single program: e.g., @code{print myglobal} will simply display the
2559 value of @code{myglobal} in the current inferior.
2562 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2563 get more info about the relationship of inferiors, programs, address
2564 spaces in a debug session. You can do that with the @w{@code{maint
2565 info program-spaces}} command.
2568 @kindex maint info program-spaces
2569 @item maint info program-spaces
2570 Print a list of all program spaces currently being managed by
2573 @value{GDBN} displays for each program space (in this order):
2577 the program space number assigned by @value{GDBN}
2580 the name of the executable loaded into the program space, with e.g.,
2581 the @code{file} command.
2586 An asterisk @samp{*} preceding the @value{GDBN} program space number
2587 indicates the current program space.
2589 In addition, below each program space line, @value{GDBN} prints extra
2590 information that isn't suitable to display in tabular form. For
2591 example, the list of inferiors bound to the program space.
2594 (@value{GDBP}) maint info program-spaces
2597 Bound inferiors: ID 1 (process 21561)
2601 Here we can see that no inferior is running the program @code{hello},
2602 while @code{process 21561} is running the program @code{goodbye}. On
2603 some targets, it is possible that multiple inferiors are bound to the
2604 same program space. The most common example is that of debugging both
2605 the parent and child processes of a @code{vfork} call. For example,
2608 (@value{GDBP}) maint info program-spaces
2611 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2614 Here, both inferior 2 and inferior 1 are running in the same program
2615 space as a result of inferior 1 having executed a @code{vfork} call.
2619 @section Debugging Programs with Multiple Threads
2621 @cindex threads of execution
2622 @cindex multiple threads
2623 @cindex switching threads
2624 In some operating systems, such as HP-UX and Solaris, a single program
2625 may have more than one @dfn{thread} of execution. The precise semantics
2626 of threads differ from one operating system to another, but in general
2627 the threads of a single program are akin to multiple processes---except
2628 that they share one address space (that is, they can all examine and
2629 modify the same variables). On the other hand, each thread has its own
2630 registers and execution stack, and perhaps private memory.
2632 @value{GDBN} provides these facilities for debugging multi-thread
2636 @item automatic notification of new threads
2637 @item @samp{thread @var{threadno}}, a command to switch among threads
2638 @item @samp{info threads}, a command to inquire about existing threads
2639 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2640 a command to apply a command to a list of threads
2641 @item thread-specific breakpoints
2642 @item @samp{set print thread-events}, which controls printing of
2643 messages on thread start and exit.
2644 @item @samp{set libthread-db-search-path @var{path}}, which lets
2645 the user specify which @code{libthread_db} to use if the default choice
2646 isn't compatible with the program.
2650 @emph{Warning:} These facilities are not yet available on every
2651 @value{GDBN} configuration where the operating system supports threads.
2652 If your @value{GDBN} does not support threads, these commands have no
2653 effect. For example, a system without thread support shows no output
2654 from @samp{info threads}, and always rejects the @code{thread} command,
2658 (@value{GDBP}) info threads
2659 (@value{GDBP}) thread 1
2660 Thread ID 1 not known. Use the "info threads" command to
2661 see the IDs of currently known threads.
2663 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2664 @c doesn't support threads"?
2667 @cindex focus of debugging
2668 @cindex current thread
2669 The @value{GDBN} thread debugging facility allows you to observe all
2670 threads while your program runs---but whenever @value{GDBN} takes
2671 control, one thread in particular is always the focus of debugging.
2672 This thread is called the @dfn{current thread}. Debugging commands show
2673 program information from the perspective of the current thread.
2675 @cindex @code{New} @var{systag} message
2676 @cindex thread identifier (system)
2677 @c FIXME-implementors!! It would be more helpful if the [New...] message
2678 @c included GDB's numeric thread handle, so you could just go to that
2679 @c thread without first checking `info threads'.
2680 Whenever @value{GDBN} detects a new thread in your program, it displays
2681 the target system's identification for the thread with a message in the
2682 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2683 whose form varies depending on the particular system. For example, on
2684 @sc{gnu}/Linux, you might see
2687 [New Thread 0x41e02940 (LWP 25582)]
2691 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2692 the @var{systag} is simply something like @samp{process 368}, with no
2695 @c FIXME!! (1) Does the [New...] message appear even for the very first
2696 @c thread of a program, or does it only appear for the
2697 @c second---i.e.@: when it becomes obvious we have a multithread
2699 @c (2) *Is* there necessarily a first thread always? Or do some
2700 @c multithread systems permit starting a program with multiple
2701 @c threads ab initio?
2703 @cindex thread number
2704 @cindex thread identifier (GDB)
2705 For debugging purposes, @value{GDBN} associates its own thread
2706 number---always a single integer---with each thread in your program.
2709 @kindex info threads
2710 @item info threads @r{[}@var{id}@dots{}@r{]}
2711 Display a summary of all threads currently in your program. Optional
2712 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2713 means to print information only about the specified thread or threads.
2714 @value{GDBN} displays for each thread (in this order):
2718 the thread number assigned by @value{GDBN}
2721 the target system's thread identifier (@var{systag})
2724 the thread's name, if one is known. A thread can either be named by
2725 the user (see @code{thread name}, below), or, in some cases, by the
2729 the current stack frame summary for that thread
2733 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2734 indicates the current thread.
2738 @c end table here to get a little more width for example
2741 (@value{GDBP}) info threads
2743 3 process 35 thread 27 0x34e5 in sigpause ()
2744 2 process 35 thread 23 0x34e5 in sigpause ()
2745 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2749 On Solaris, you can display more information about user threads with a
2750 Solaris-specific command:
2753 @item maint info sol-threads
2754 @kindex maint info sol-threads
2755 @cindex thread info (Solaris)
2756 Display info on Solaris user threads.
2760 @kindex thread @var{threadno}
2761 @item thread @var{threadno}
2762 Make thread number @var{threadno} the current thread. The command
2763 argument @var{threadno} is the internal @value{GDBN} thread number, as
2764 shown in the first field of the @samp{info threads} display.
2765 @value{GDBN} responds by displaying the system identifier of the thread
2766 you selected, and its current stack frame summary:
2769 (@value{GDBP}) thread 2
2770 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2771 #0 some_function (ignore=0x0) at example.c:8
2772 8 printf ("hello\n");
2776 As with the @samp{[New @dots{}]} message, the form of the text after
2777 @samp{Switching to} depends on your system's conventions for identifying
2780 @vindex $_thread@r{, convenience variable}
2781 The debugger convenience variable @samp{$_thread} contains the number
2782 of the current thread. You may find this useful in writing breakpoint
2783 conditional expressions, command scripts, and so forth. See
2784 @xref{Convenience Vars,, Convenience Variables}, for general
2785 information on convenience variables.
2787 @kindex thread apply
2788 @cindex apply command to several threads
2789 @item thread apply [@var{threadno} | all] @var{command}
2790 The @code{thread apply} command allows you to apply the named
2791 @var{command} to one or more threads. Specify the numbers of the
2792 threads that you want affected with the command argument
2793 @var{threadno}. It can be a single thread number, one of the numbers
2794 shown in the first field of the @samp{info threads} display; or it
2795 could be a range of thread numbers, as in @code{2-4}. To apply a
2796 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @cindex name a thread
2800 @item thread name [@var{name}]
2801 This command assigns a name to the current thread. If no argument is
2802 given, any existing user-specified name is removed. The thread name
2803 appears in the @samp{info threads} display.
2805 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2806 determine the name of the thread as given by the OS. On these
2807 systems, a name specified with @samp{thread name} will override the
2808 system-give name, and removing the user-specified name will cause
2809 @value{GDBN} to once again display the system-specified name.
2812 @cindex search for a thread
2813 @item thread find [@var{regexp}]
2814 Search for and display thread ids whose name or @var{systag}
2815 matches the supplied regular expression.
2817 As well as being the complement to the @samp{thread name} command,
2818 this command also allows you to identify a thread by its target
2819 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2823 (@value{GDBN}) thread find 26688
2824 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2825 (@value{GDBN}) info thread 4
2827 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2830 @kindex set print thread-events
2831 @cindex print messages on thread start and exit
2832 @item set print thread-events
2833 @itemx set print thread-events on
2834 @itemx set print thread-events off
2835 The @code{set print thread-events} command allows you to enable or
2836 disable printing of messages when @value{GDBN} notices that new threads have
2837 started or that threads have exited. By default, these messages will
2838 be printed if detection of these events is supported by the target.
2839 Note that these messages cannot be disabled on all targets.
2841 @kindex show print thread-events
2842 @item show print thread-events
2843 Show whether messages will be printed when @value{GDBN} detects that threads
2844 have started and exited.
2847 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2848 more information about how @value{GDBN} behaves when you stop and start
2849 programs with multiple threads.
2851 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2852 watchpoints in programs with multiple threads.
2855 @kindex set libthread-db-search-path
2856 @cindex search path for @code{libthread_db}
2857 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2858 If this variable is set, @var{path} is a colon-separated list of
2859 directories @value{GDBN} will use to search for @code{libthread_db}.
2860 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2863 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2864 @code{libthread_db} library to obtain information about threads in the
2865 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2866 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2867 with default system shared library directories, and finally the directory
2868 from which @code{libpthread} was loaded in the inferior process.
2870 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2871 @value{GDBN} attempts to initialize it with the current inferior process.
2872 If this initialization fails (which could happen because of a version
2873 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2874 will unload @code{libthread_db}, and continue with the next directory.
2875 If none of @code{libthread_db} libraries initialize successfully,
2876 @value{GDBN} will issue a warning and thread debugging will be disabled.
2878 Setting @code{libthread-db-search-path} is currently implemented
2879 only on some platforms.
2881 @kindex show libthread-db-search-path
2882 @item show libthread-db-search-path
2883 Display current libthread_db search path.
2885 @kindex set debug libthread-db
2886 @kindex show debug libthread-db
2887 @cindex debugging @code{libthread_db}
2888 @item set debug libthread-db
2889 @itemx show debug libthread-db
2890 Turns on or off display of @code{libthread_db}-related events.
2891 Use @code{1} to enable, @code{0} to disable.
2895 @section Debugging Forks
2897 @cindex fork, debugging programs which call
2898 @cindex multiple processes
2899 @cindex processes, multiple
2900 On most systems, @value{GDBN} has no special support for debugging
2901 programs which create additional processes using the @code{fork}
2902 function. When a program forks, @value{GDBN} will continue to debug the
2903 parent process and the child process will run unimpeded. If you have
2904 set a breakpoint in any code which the child then executes, the child
2905 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2906 will cause it to terminate.
2908 However, if you want to debug the child process there is a workaround
2909 which isn't too painful. Put a call to @code{sleep} in the code which
2910 the child process executes after the fork. It may be useful to sleep
2911 only if a certain environment variable is set, or a certain file exists,
2912 so that the delay need not occur when you don't want to run @value{GDBN}
2913 on the child. While the child is sleeping, use the @code{ps} program to
2914 get its process ID. Then tell @value{GDBN} (a new invocation of
2915 @value{GDBN} if you are also debugging the parent process) to attach to
2916 the child process (@pxref{Attach}). From that point on you can debug
2917 the child process just like any other process which you attached to.
2919 On some systems, @value{GDBN} provides support for debugging programs that
2920 create additional processes using the @code{fork} or @code{vfork} functions.
2921 Currently, the only platforms with this feature are HP-UX (11.x and later
2922 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2924 By default, when a program forks, @value{GDBN} will continue to debug
2925 the parent process and the child process will run unimpeded.
2927 If you want to follow the child process instead of the parent process,
2928 use the command @w{@code{set follow-fork-mode}}.
2931 @kindex set follow-fork-mode
2932 @item set follow-fork-mode @var{mode}
2933 Set the debugger response to a program call of @code{fork} or
2934 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2935 process. The @var{mode} argument can be:
2939 The original process is debugged after a fork. The child process runs
2940 unimpeded. This is the default.
2943 The new process is debugged after a fork. The parent process runs
2948 @kindex show follow-fork-mode
2949 @item show follow-fork-mode
2950 Display the current debugger response to a @code{fork} or @code{vfork} call.
2953 @cindex debugging multiple processes
2954 On Linux, if you want to debug both the parent and child processes, use the
2955 command @w{@code{set detach-on-fork}}.
2958 @kindex set detach-on-fork
2959 @item set detach-on-fork @var{mode}
2960 Tells gdb whether to detach one of the processes after a fork, or
2961 retain debugger control over them both.
2965 The child process (or parent process, depending on the value of
2966 @code{follow-fork-mode}) will be detached and allowed to run
2967 independently. This is the default.
2970 Both processes will be held under the control of @value{GDBN}.
2971 One process (child or parent, depending on the value of
2972 @code{follow-fork-mode}) is debugged as usual, while the other
2977 @kindex show detach-on-fork
2978 @item show detach-on-fork
2979 Show whether detach-on-fork mode is on/off.
2982 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2983 will retain control of all forked processes (including nested forks).
2984 You can list the forked processes under the control of @value{GDBN} by
2985 using the @w{@code{info inferiors}} command, and switch from one fork
2986 to another by using the @code{inferior} command (@pxref{Inferiors and
2987 Programs, ,Debugging Multiple Inferiors and Programs}).
2989 To quit debugging one of the forked processes, you can either detach
2990 from it by using the @w{@code{detach inferiors}} command (allowing it
2991 to run independently), or kill it using the @w{@code{kill inferiors}}
2992 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2995 If you ask to debug a child process and a @code{vfork} is followed by an
2996 @code{exec}, @value{GDBN} executes the new target up to the first
2997 breakpoint in the new target. If you have a breakpoint set on
2998 @code{main} in your original program, the breakpoint will also be set on
2999 the child process's @code{main}.
3001 On some systems, when a child process is spawned by @code{vfork}, you
3002 cannot debug the child or parent until an @code{exec} call completes.
3004 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3005 call executes, the new target restarts. To restart the parent
3006 process, use the @code{file} command with the parent executable name
3007 as its argument. By default, after an @code{exec} call executes,
3008 @value{GDBN} discards the symbols of the previous executable image.
3009 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3013 @kindex set follow-exec-mode
3014 @item set follow-exec-mode @var{mode}
3016 Set debugger response to a program call of @code{exec}. An
3017 @code{exec} call replaces the program image of a process.
3019 @code{follow-exec-mode} can be:
3023 @value{GDBN} creates a new inferior and rebinds the process to this
3024 new inferior. The program the process was running before the
3025 @code{exec} call can be restarted afterwards by restarting the
3031 (@value{GDBP}) info inferiors
3033 Id Description Executable
3036 process 12020 is executing new program: prog2
3037 Program exited normally.
3038 (@value{GDBP}) info inferiors
3039 Id Description Executable
3045 @value{GDBN} keeps the process bound to the same inferior. The new
3046 executable image replaces the previous executable loaded in the
3047 inferior. Restarting the inferior after the @code{exec} call, with
3048 e.g., the @code{run} command, restarts the executable the process was
3049 running after the @code{exec} call. This is the default mode.
3054 (@value{GDBP}) info inferiors
3055 Id Description Executable
3058 process 12020 is executing new program: prog2
3059 Program exited normally.
3060 (@value{GDBP}) info inferiors
3061 Id Description Executable
3068 You can use the @code{catch} command to make @value{GDBN} stop whenever
3069 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3070 Catchpoints, ,Setting Catchpoints}.
3072 @node Checkpoint/Restart
3073 @section Setting a @emph{Bookmark} to Return to Later
3078 @cindex snapshot of a process
3079 @cindex rewind program state
3081 On certain operating systems@footnote{Currently, only
3082 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3083 program's state, called a @dfn{checkpoint}, and come back to it
3086 Returning to a checkpoint effectively undoes everything that has
3087 happened in the program since the @code{checkpoint} was saved. This
3088 includes changes in memory, registers, and even (within some limits)
3089 system state. Effectively, it is like going back in time to the
3090 moment when the checkpoint was saved.
3092 Thus, if you're stepping thru a program and you think you're
3093 getting close to the point where things go wrong, you can save
3094 a checkpoint. Then, if you accidentally go too far and miss
3095 the critical statement, instead of having to restart your program
3096 from the beginning, you can just go back to the checkpoint and
3097 start again from there.
3099 This can be especially useful if it takes a lot of time or
3100 steps to reach the point where you think the bug occurs.
3102 To use the @code{checkpoint}/@code{restart} method of debugging:
3107 Save a snapshot of the debugged program's current execution state.
3108 The @code{checkpoint} command takes no arguments, but each checkpoint
3109 is assigned a small integer id, similar to a breakpoint id.
3111 @kindex info checkpoints
3112 @item info checkpoints
3113 List the checkpoints that have been saved in the current debugging
3114 session. For each checkpoint, the following information will be
3121 @item Source line, or label
3124 @kindex restart @var{checkpoint-id}
3125 @item restart @var{checkpoint-id}
3126 Restore the program state that was saved as checkpoint number
3127 @var{checkpoint-id}. All program variables, registers, stack frames
3128 etc.@: will be returned to the values that they had when the checkpoint
3129 was saved. In essence, gdb will ``wind back the clock'' to the point
3130 in time when the checkpoint was saved.
3132 Note that breakpoints, @value{GDBN} variables, command history etc.
3133 are not affected by restoring a checkpoint. In general, a checkpoint
3134 only restores things that reside in the program being debugged, not in
3137 @kindex delete checkpoint @var{checkpoint-id}
3138 @item delete checkpoint @var{checkpoint-id}
3139 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3143 Returning to a previously saved checkpoint will restore the user state
3144 of the program being debugged, plus a significant subset of the system
3145 (OS) state, including file pointers. It won't ``un-write'' data from
3146 a file, but it will rewind the file pointer to the previous location,
3147 so that the previously written data can be overwritten. For files
3148 opened in read mode, the pointer will also be restored so that the
3149 previously read data can be read again.
3151 Of course, characters that have been sent to a printer (or other
3152 external device) cannot be ``snatched back'', and characters received
3153 from eg.@: a serial device can be removed from internal program buffers,
3154 but they cannot be ``pushed back'' into the serial pipeline, ready to
3155 be received again. Similarly, the actual contents of files that have
3156 been changed cannot be restored (at this time).
3158 However, within those constraints, you actually can ``rewind'' your
3159 program to a previously saved point in time, and begin debugging it
3160 again --- and you can change the course of events so as to debug a
3161 different execution path this time.
3163 @cindex checkpoints and process id
3164 Finally, there is one bit of internal program state that will be
3165 different when you return to a checkpoint --- the program's process
3166 id. Each checkpoint will have a unique process id (or @var{pid}),
3167 and each will be different from the program's original @var{pid}.
3168 If your program has saved a local copy of its process id, this could
3169 potentially pose a problem.
3171 @subsection A Non-obvious Benefit of Using Checkpoints
3173 On some systems such as @sc{gnu}/Linux, address space randomization
3174 is performed on new processes for security reasons. This makes it
3175 difficult or impossible to set a breakpoint, or watchpoint, on an
3176 absolute address if you have to restart the program, since the
3177 absolute location of a symbol will change from one execution to the
3180 A checkpoint, however, is an @emph{identical} copy of a process.
3181 Therefore if you create a checkpoint at (eg.@:) the start of main,
3182 and simply return to that checkpoint instead of restarting the
3183 process, you can avoid the effects of address randomization and
3184 your symbols will all stay in the same place.
3187 @chapter Stopping and Continuing
3189 The principal purposes of using a debugger are so that you can stop your
3190 program before it terminates; or so that, if your program runs into
3191 trouble, you can investigate and find out why.
3193 Inside @value{GDBN}, your program may stop for any of several reasons,
3194 such as a signal, a breakpoint, or reaching a new line after a
3195 @value{GDBN} command such as @code{step}. You may then examine and
3196 change variables, set new breakpoints or remove old ones, and then
3197 continue execution. Usually, the messages shown by @value{GDBN} provide
3198 ample explanation of the status of your program---but you can also
3199 explicitly request this information at any time.
3202 @kindex info program
3204 Display information about the status of your program: whether it is
3205 running or not, what process it is, and why it stopped.
3209 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3210 * Continuing and Stepping:: Resuming execution
3212 * Thread Stops:: Stopping and starting multi-thread programs
3216 @section Breakpoints, Watchpoints, and Catchpoints
3219 A @dfn{breakpoint} makes your program stop whenever a certain point in
3220 the program is reached. For each breakpoint, you can add conditions to
3221 control in finer detail whether your program stops. You can set
3222 breakpoints with the @code{break} command and its variants (@pxref{Set
3223 Breaks, ,Setting Breakpoints}), to specify the place where your program
3224 should stop by line number, function name or exact address in the
3227 On some systems, you can set breakpoints in shared libraries before
3228 the executable is run. There is a minor limitation on HP-UX systems:
3229 you must wait until the executable is run in order to set breakpoints
3230 in shared library routines that are not called directly by the program
3231 (for example, routines that are arguments in a @code{pthread_create}
3235 @cindex data breakpoints
3236 @cindex memory tracing
3237 @cindex breakpoint on memory address
3238 @cindex breakpoint on variable modification
3239 A @dfn{watchpoint} is a special breakpoint that stops your program
3240 when the value of an expression changes. The expression may be a value
3241 of a variable, or it could involve values of one or more variables
3242 combined by operators, such as @samp{a + b}. This is sometimes called
3243 @dfn{data breakpoints}. You must use a different command to set
3244 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3245 from that, you can manage a watchpoint like any other breakpoint: you
3246 enable, disable, and delete both breakpoints and watchpoints using the
3249 You can arrange to have values from your program displayed automatically
3250 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3254 @cindex breakpoint on events
3255 A @dfn{catchpoint} is another special breakpoint that stops your program
3256 when a certain kind of event occurs, such as the throwing of a C@t{++}
3257 exception or the loading of a library. As with watchpoints, you use a
3258 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3259 Catchpoints}), but aside from that, you can manage a catchpoint like any
3260 other breakpoint. (To stop when your program receives a signal, use the
3261 @code{handle} command; see @ref{Signals, ,Signals}.)
3263 @cindex breakpoint numbers
3264 @cindex numbers for breakpoints
3265 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3266 catchpoint when you create it; these numbers are successive integers
3267 starting with one. In many of the commands for controlling various
3268 features of breakpoints you use the breakpoint number to say which
3269 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3270 @dfn{disabled}; if disabled, it has no effect on your program until you
3273 @cindex breakpoint ranges
3274 @cindex ranges of breakpoints
3275 Some @value{GDBN} commands accept a range of breakpoints on which to
3276 operate. A breakpoint range is either a single breakpoint number, like
3277 @samp{5}, or two such numbers, in increasing order, separated by a
3278 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3279 all breakpoints in that range are operated on.
3282 * Set Breaks:: Setting breakpoints
3283 * Set Watchpoints:: Setting watchpoints
3284 * Set Catchpoints:: Setting catchpoints
3285 * Delete Breaks:: Deleting breakpoints
3286 * Disabling:: Disabling breakpoints
3287 * Conditions:: Break conditions
3288 * Break Commands:: Breakpoint command lists
3289 * Save Breakpoints:: How to save breakpoints in a file
3290 * Error in Breakpoints:: ``Cannot insert breakpoints''
3291 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3295 @subsection Setting Breakpoints
3297 @c FIXME LMB what does GDB do if no code on line of breakpt?
3298 @c consider in particular declaration with/without initialization.
3300 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3303 @kindex b @r{(@code{break})}
3304 @vindex $bpnum@r{, convenience variable}
3305 @cindex latest breakpoint
3306 Breakpoints are set with the @code{break} command (abbreviated
3307 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3308 number of the breakpoint you've set most recently; see @ref{Convenience
3309 Vars,, Convenience Variables}, for a discussion of what you can do with
3310 convenience variables.
3313 @item break @var{location}
3314 Set a breakpoint at the given @var{location}, which can specify a
3315 function name, a line number, or an address of an instruction.
3316 (@xref{Specify Location}, for a list of all the possible ways to
3317 specify a @var{location}.) The breakpoint will stop your program just
3318 before it executes any of the code in the specified @var{location}.
3320 When using source languages that permit overloading of symbols, such as
3321 C@t{++}, a function name may refer to more than one possible place to break.
3322 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3325 It is also possible to insert a breakpoint that will stop the program
3326 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3327 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3330 When called without any arguments, @code{break} sets a breakpoint at
3331 the next instruction to be executed in the selected stack frame
3332 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3333 innermost, this makes your program stop as soon as control
3334 returns to that frame. This is similar to the effect of a
3335 @code{finish} command in the frame inside the selected frame---except
3336 that @code{finish} does not leave an active breakpoint. If you use
3337 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3338 the next time it reaches the current location; this may be useful
3341 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3342 least one instruction has been executed. If it did not do this, you
3343 would be unable to proceed past a breakpoint without first disabling the
3344 breakpoint. This rule applies whether or not the breakpoint already
3345 existed when your program stopped.
3347 @item break @dots{} if @var{cond}
3348 Set a breakpoint with condition @var{cond}; evaluate the expression
3349 @var{cond} each time the breakpoint is reached, and stop only if the
3350 value is nonzero---that is, if @var{cond} evaluates as true.
3351 @samp{@dots{}} stands for one of the possible arguments described
3352 above (or no argument) specifying where to break. @xref{Conditions,
3353 ,Break Conditions}, for more information on breakpoint conditions.
3356 @item tbreak @var{args}
3357 Set a breakpoint enabled only for one stop. @var{args} are the
3358 same as for the @code{break} command, and the breakpoint is set in the same
3359 way, but the breakpoint is automatically deleted after the first time your
3360 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3363 @cindex hardware breakpoints
3364 @item hbreak @var{args}
3365 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3366 @code{break} command and the breakpoint is set in the same way, but the
3367 breakpoint requires hardware support and some target hardware may not
3368 have this support. The main purpose of this is EPROM/ROM code
3369 debugging, so you can set a breakpoint at an instruction without
3370 changing the instruction. This can be used with the new trap-generation
3371 provided by SPARClite DSU and most x86-based targets. These targets
3372 will generate traps when a program accesses some data or instruction
3373 address that is assigned to the debug registers. However the hardware
3374 breakpoint registers can take a limited number of breakpoints. For
3375 example, on the DSU, only two data breakpoints can be set at a time, and
3376 @value{GDBN} will reject this command if more than two are used. Delete
3377 or disable unused hardware breakpoints before setting new ones
3378 (@pxref{Disabling, ,Disabling Breakpoints}).
3379 @xref{Conditions, ,Break Conditions}.
3380 For remote targets, you can restrict the number of hardware
3381 breakpoints @value{GDBN} will use, see @ref{set remote
3382 hardware-breakpoint-limit}.
3385 @item thbreak @var{args}
3386 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3387 are the same as for the @code{hbreak} command and the breakpoint is set in
3388 the same way. However, like the @code{tbreak} command,
3389 the breakpoint is automatically deleted after the
3390 first time your program stops there. Also, like the @code{hbreak}
3391 command, the breakpoint requires hardware support and some target hardware
3392 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3393 See also @ref{Conditions, ,Break Conditions}.
3396 @cindex regular expression
3397 @cindex breakpoints at functions matching a regexp
3398 @cindex set breakpoints in many functions
3399 @item rbreak @var{regex}
3400 Set breakpoints on all functions matching the regular expression
3401 @var{regex}. This command sets an unconditional breakpoint on all
3402 matches, printing a list of all breakpoints it set. Once these
3403 breakpoints are set, they are treated just like the breakpoints set with
3404 the @code{break} command. You can delete them, disable them, or make
3405 them conditional the same way as any other breakpoint.
3407 The syntax of the regular expression is the standard one used with tools
3408 like @file{grep}. Note that this is different from the syntax used by
3409 shells, so for instance @code{foo*} matches all functions that include
3410 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3411 @code{.*} leading and trailing the regular expression you supply, so to
3412 match only functions that begin with @code{foo}, use @code{^foo}.
3414 @cindex non-member C@t{++} functions, set breakpoint in
3415 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3416 breakpoints on overloaded functions that are not members of any special
3419 @cindex set breakpoints on all functions
3420 The @code{rbreak} command can be used to set breakpoints in
3421 @strong{all} the functions in a program, like this:
3424 (@value{GDBP}) rbreak .
3427 @item rbreak @var{file}:@var{regex}
3428 If @code{rbreak} is called with a filename qualification, it limits
3429 the search for functions matching the given regular expression to the
3430 specified @var{file}. This can be used, for example, to set breakpoints on
3431 every function in a given file:
3434 (@value{GDBP}) rbreak file.c:.
3437 The colon separating the filename qualifier from the regex may
3438 optionally be surrounded by spaces.
3440 @kindex info breakpoints
3441 @cindex @code{$_} and @code{info breakpoints}
3442 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3443 @itemx info break @r{[}@var{n}@dots{}@r{]}
3444 Print a table of all breakpoints, watchpoints, and catchpoints set and
3445 not deleted. Optional argument @var{n} means print information only
3446 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3447 For each breakpoint, following columns are printed:
3450 @item Breakpoint Numbers
3452 Breakpoint, watchpoint, or catchpoint.
3454 Whether the breakpoint is marked to be disabled or deleted when hit.
3455 @item Enabled or Disabled
3456 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3457 that are not enabled.
3459 Where the breakpoint is in your program, as a memory address. For a
3460 pending breakpoint whose address is not yet known, this field will
3461 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3462 library that has the symbol or line referred by breakpoint is loaded.
3463 See below for details. A breakpoint with several locations will
3464 have @samp{<MULTIPLE>} in this field---see below for details.
3466 Where the breakpoint is in the source for your program, as a file and
3467 line number. For a pending breakpoint, the original string passed to
3468 the breakpoint command will be listed as it cannot be resolved until
3469 the appropriate shared library is loaded in the future.
3473 If a breakpoint is conditional, @code{info break} shows the condition on
3474 the line following the affected breakpoint; breakpoint commands, if any,
3475 are listed after that. A pending breakpoint is allowed to have a condition
3476 specified for it. The condition is not parsed for validity until a shared
3477 library is loaded that allows the pending breakpoint to resolve to a
3481 @code{info break} with a breakpoint
3482 number @var{n} as argument lists only that breakpoint. The
3483 convenience variable @code{$_} and the default examining-address for
3484 the @code{x} command are set to the address of the last breakpoint
3485 listed (@pxref{Memory, ,Examining Memory}).
3488 @code{info break} displays a count of the number of times the breakpoint
3489 has been hit. This is especially useful in conjunction with the
3490 @code{ignore} command. You can ignore a large number of breakpoint
3491 hits, look at the breakpoint info to see how many times the breakpoint
3492 was hit, and then run again, ignoring one less than that number. This
3493 will get you quickly to the last hit of that breakpoint.
3496 @value{GDBN} allows you to set any number of breakpoints at the same place in
3497 your program. There is nothing silly or meaningless about this. When
3498 the breakpoints are conditional, this is even useful
3499 (@pxref{Conditions, ,Break Conditions}).
3501 @cindex multiple locations, breakpoints
3502 @cindex breakpoints, multiple locations
3503 It is possible that a breakpoint corresponds to several locations
3504 in your program. Examples of this situation are:
3508 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3509 instances of the function body, used in different cases.
3512 For a C@t{++} template function, a given line in the function can
3513 correspond to any number of instantiations.
3516 For an inlined function, a given source line can correspond to
3517 several places where that function is inlined.
3520 In all those cases, @value{GDBN} will insert a breakpoint at all
3521 the relevant locations@footnote{
3522 As of this writing, multiple-location breakpoints work only if there's
3523 line number information for all the locations. This means that they
3524 will generally not work in system libraries, unless you have debug
3525 info with line numbers for them.}.
3527 A breakpoint with multiple locations is displayed in the breakpoint
3528 table using several rows---one header row, followed by one row for
3529 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3530 address column. The rows for individual locations contain the actual
3531 addresses for locations, and show the functions to which those
3532 locations belong. The number column for a location is of the form
3533 @var{breakpoint-number}.@var{location-number}.
3538 Num Type Disp Enb Address What
3539 1 breakpoint keep y <MULTIPLE>
3541 breakpoint already hit 1 time
3542 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3543 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3546 Each location can be individually enabled or disabled by passing
3547 @var{breakpoint-number}.@var{location-number} as argument to the
3548 @code{enable} and @code{disable} commands. Note that you cannot
3549 delete the individual locations from the list, you can only delete the
3550 entire list of locations that belong to their parent breakpoint (with
3551 the @kbd{delete @var{num}} command, where @var{num} is the number of
3552 the parent breakpoint, 1 in the above example). Disabling or enabling
3553 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3554 that belong to that breakpoint.
3556 @cindex pending breakpoints
3557 It's quite common to have a breakpoint inside a shared library.
3558 Shared libraries can be loaded and unloaded explicitly,
3559 and possibly repeatedly, as the program is executed. To support
3560 this use case, @value{GDBN} updates breakpoint locations whenever
3561 any shared library is loaded or unloaded. Typically, you would
3562 set a breakpoint in a shared library at the beginning of your
3563 debugging session, when the library is not loaded, and when the
3564 symbols from the library are not available. When you try to set
3565 breakpoint, @value{GDBN} will ask you if you want to set
3566 a so called @dfn{pending breakpoint}---breakpoint whose address
3567 is not yet resolved.
3569 After the program is run, whenever a new shared library is loaded,
3570 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3571 shared library contains the symbol or line referred to by some
3572 pending breakpoint, that breakpoint is resolved and becomes an
3573 ordinary breakpoint. When a library is unloaded, all breakpoints
3574 that refer to its symbols or source lines become pending again.
3576 This logic works for breakpoints with multiple locations, too. For
3577 example, if you have a breakpoint in a C@t{++} template function, and
3578 a newly loaded shared library has an instantiation of that template,
3579 a new location is added to the list of locations for the breakpoint.
3581 Except for having unresolved address, pending breakpoints do not
3582 differ from regular breakpoints. You can set conditions or commands,
3583 enable and disable them and perform other breakpoint operations.
3585 @value{GDBN} provides some additional commands for controlling what
3586 happens when the @samp{break} command cannot resolve breakpoint
3587 address specification to an address:
3589 @kindex set breakpoint pending
3590 @kindex show breakpoint pending
3592 @item set breakpoint pending auto
3593 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3594 location, it queries you whether a pending breakpoint should be created.
3596 @item set breakpoint pending on
3597 This indicates that an unrecognized breakpoint location should automatically
3598 result in a pending breakpoint being created.
3600 @item set breakpoint pending off
3601 This indicates that pending breakpoints are not to be created. Any
3602 unrecognized breakpoint location results in an error. This setting does
3603 not affect any pending breakpoints previously created.
3605 @item show breakpoint pending
3606 Show the current behavior setting for creating pending breakpoints.
3609 The settings above only affect the @code{break} command and its
3610 variants. Once breakpoint is set, it will be automatically updated
3611 as shared libraries are loaded and unloaded.
3613 @cindex automatic hardware breakpoints
3614 For some targets, @value{GDBN} can automatically decide if hardware or
3615 software breakpoints should be used, depending on whether the
3616 breakpoint address is read-only or read-write. This applies to
3617 breakpoints set with the @code{break} command as well as to internal
3618 breakpoints set by commands like @code{next} and @code{finish}. For
3619 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3622 You can control this automatic behaviour with the following commands::
3624 @kindex set breakpoint auto-hw
3625 @kindex show breakpoint auto-hw
3627 @item set breakpoint auto-hw on
3628 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3629 will try to use the target memory map to decide if software or hardware
3630 breakpoint must be used.
3632 @item set breakpoint auto-hw off
3633 This indicates @value{GDBN} should not automatically select breakpoint
3634 type. If the target provides a memory map, @value{GDBN} will warn when
3635 trying to set software breakpoint at a read-only address.
3638 @value{GDBN} normally implements breakpoints by replacing the program code
3639 at the breakpoint address with a special instruction, which, when
3640 executed, given control to the debugger. By default, the program
3641 code is so modified only when the program is resumed. As soon as
3642 the program stops, @value{GDBN} restores the original instructions. This
3643 behaviour guards against leaving breakpoints inserted in the
3644 target should gdb abrubptly disconnect. However, with slow remote
3645 targets, inserting and removing breakpoint can reduce the performance.
3646 This behavior can be controlled with the following commands::
3648 @kindex set breakpoint always-inserted
3649 @kindex show breakpoint always-inserted
3651 @item set breakpoint always-inserted off
3652 All breakpoints, including newly added by the user, are inserted in
3653 the target only when the target is resumed. All breakpoints are
3654 removed from the target when it stops.
3656 @item set breakpoint always-inserted on
3657 Causes all breakpoints to be inserted in the target at all times. If
3658 the user adds a new breakpoint, or changes an existing breakpoint, the
3659 breakpoints in the target are updated immediately. A breakpoint is
3660 removed from the target only when breakpoint itself is removed.
3662 @cindex non-stop mode, and @code{breakpoint always-inserted}
3663 @item set breakpoint always-inserted auto
3664 This is the default mode. If @value{GDBN} is controlling the inferior
3665 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3666 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3667 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3668 @code{breakpoint always-inserted} mode is off.
3671 @cindex negative breakpoint numbers
3672 @cindex internal @value{GDBN} breakpoints
3673 @value{GDBN} itself sometimes sets breakpoints in your program for
3674 special purposes, such as proper handling of @code{longjmp} (in C
3675 programs). These internal breakpoints are assigned negative numbers,
3676 starting with @code{-1}; @samp{info breakpoints} does not display them.
3677 You can see these breakpoints with the @value{GDBN} maintenance command
3678 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3681 @node Set Watchpoints
3682 @subsection Setting Watchpoints
3684 @cindex setting watchpoints
3685 You can use a watchpoint to stop execution whenever the value of an
3686 expression changes, without having to predict a particular place where
3687 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3688 The expression may be as simple as the value of a single variable, or
3689 as complex as many variables combined by operators. Examples include:
3693 A reference to the value of a single variable.
3696 An address cast to an appropriate data type. For example,
3697 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3698 address (assuming an @code{int} occupies 4 bytes).
3701 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3702 expression can use any operators valid in the program's native
3703 language (@pxref{Languages}).
3706 You can set a watchpoint on an expression even if the expression can
3707 not be evaluated yet. For instance, you can set a watchpoint on
3708 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3709 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3710 the expression produces a valid value. If the expression becomes
3711 valid in some other way than changing a variable (e.g.@: if the memory
3712 pointed to by @samp{*global_ptr} becomes readable as the result of a
3713 @code{malloc} call), @value{GDBN} may not stop until the next time
3714 the expression changes.
3716 @cindex software watchpoints
3717 @cindex hardware watchpoints
3718 Depending on your system, watchpoints may be implemented in software or
3719 hardware. @value{GDBN} does software watchpointing by single-stepping your
3720 program and testing the variable's value each time, which is hundreds of
3721 times slower than normal execution. (But this may still be worth it, to
3722 catch errors where you have no clue what part of your program is the
3725 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3726 x86-based targets, @value{GDBN} includes support for hardware
3727 watchpoints, which do not slow down the running of your program.
3731 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3732 Set a watchpoint for an expression. @value{GDBN} will break when the
3733 expression @var{expr} is written into by the program and its value
3734 changes. The simplest (and the most popular) use of this command is
3735 to watch the value of a single variable:
3738 (@value{GDBP}) watch foo
3741 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3742 argument, @value{GDBN} breaks only when the thread identified by
3743 @var{threadnum} changes the value of @var{expr}. If any other threads
3744 change the value of @var{expr}, @value{GDBN} will not break. Note
3745 that watchpoints restricted to a single thread in this way only work
3746 with Hardware Watchpoints.
3748 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3749 (see below). The @code{-location} argument tells @value{GDBN} to
3750 instead watch the memory referred to by @var{expr}. In this case,
3751 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3752 and watch the memory at that address. The type of the result is used
3753 to determine the size of the watched memory. If the expression's
3754 result does not have an address, then @value{GDBN} will print an
3757 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3758 of masked watchpoints, if the current architecture supports this
3759 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3760 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3761 to an address to watch. The mask specifies that some bits of an address
3762 (the bits which are reset in the mask) should be ignored when matching
3763 the address accessed by the inferior against the watchpoint address.
3764 Thus, a masked watchpoint watches many addresses simultaneously---those
3765 addresses whose unmasked bits are identical to the unmasked bits in the
3766 watchpoint address. The @code{mask} argument implies @code{-location}.
3770 (@value{GDBP}) watch foo mask 0xffff00ff
3771 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3775 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3776 Set a watchpoint that will break when the value of @var{expr} is read
3780 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3781 Set a watchpoint that will break when @var{expr} is either read from
3782 or written into by the program.
3784 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3785 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3786 This command prints a list of watchpoints, using the same format as
3787 @code{info break} (@pxref{Set Breaks}).
3790 If you watch for a change in a numerically entered address you need to
3791 dereference it, as the address itself is just a constant number which will
3792 never change. @value{GDBN} refuses to create a watchpoint that watches
3793 a never-changing value:
3796 (@value{GDBP}) watch 0x600850
3797 Cannot watch constant value 0x600850.
3798 (@value{GDBP}) watch *(int *) 0x600850
3799 Watchpoint 1: *(int *) 6293584
3802 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3803 watchpoints execute very quickly, and the debugger reports a change in
3804 value at the exact instruction where the change occurs. If @value{GDBN}
3805 cannot set a hardware watchpoint, it sets a software watchpoint, which
3806 executes more slowly and reports the change in value at the next
3807 @emph{statement}, not the instruction, after the change occurs.
3809 @cindex use only software watchpoints
3810 You can force @value{GDBN} to use only software watchpoints with the
3811 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3812 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3813 the underlying system supports them. (Note that hardware-assisted
3814 watchpoints that were set @emph{before} setting
3815 @code{can-use-hw-watchpoints} to zero will still use the hardware
3816 mechanism of watching expression values.)
3819 @item set can-use-hw-watchpoints
3820 @kindex set can-use-hw-watchpoints
3821 Set whether or not to use hardware watchpoints.
3823 @item show can-use-hw-watchpoints
3824 @kindex show can-use-hw-watchpoints
3825 Show the current mode of using hardware watchpoints.
3828 For remote targets, you can restrict the number of hardware
3829 watchpoints @value{GDBN} will use, see @ref{set remote
3830 hardware-breakpoint-limit}.
3832 When you issue the @code{watch} command, @value{GDBN} reports
3835 Hardware watchpoint @var{num}: @var{expr}
3839 if it was able to set a hardware watchpoint.
3841 Currently, the @code{awatch} and @code{rwatch} commands can only set
3842 hardware watchpoints, because accesses to data that don't change the
3843 value of the watched expression cannot be detected without examining
3844 every instruction as it is being executed, and @value{GDBN} does not do
3845 that currently. If @value{GDBN} finds that it is unable to set a
3846 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3847 will print a message like this:
3850 Expression cannot be implemented with read/access watchpoint.
3853 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3854 data type of the watched expression is wider than what a hardware
3855 watchpoint on the target machine can handle. For example, some systems
3856 can only watch regions that are up to 4 bytes wide; on such systems you
3857 cannot set hardware watchpoints for an expression that yields a
3858 double-precision floating-point number (which is typically 8 bytes
3859 wide). As a work-around, it might be possible to break the large region
3860 into a series of smaller ones and watch them with separate watchpoints.
3862 If you set too many hardware watchpoints, @value{GDBN} might be unable
3863 to insert all of them when you resume the execution of your program.
3864 Since the precise number of active watchpoints is unknown until such
3865 time as the program is about to be resumed, @value{GDBN} might not be
3866 able to warn you about this when you set the watchpoints, and the
3867 warning will be printed only when the program is resumed:
3870 Hardware watchpoint @var{num}: Could not insert watchpoint
3874 If this happens, delete or disable some of the watchpoints.
3876 Watching complex expressions that reference many variables can also
3877 exhaust the resources available for hardware-assisted watchpoints.
3878 That's because @value{GDBN} needs to watch every variable in the
3879 expression with separately allocated resources.
3881 If you call a function interactively using @code{print} or @code{call},
3882 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3883 kind of breakpoint or the call completes.
3885 @value{GDBN} automatically deletes watchpoints that watch local
3886 (automatic) variables, or expressions that involve such variables, when
3887 they go out of scope, that is, when the execution leaves the block in
3888 which these variables were defined. In particular, when the program
3889 being debugged terminates, @emph{all} local variables go out of scope,
3890 and so only watchpoints that watch global variables remain set. If you
3891 rerun the program, you will need to set all such watchpoints again. One
3892 way of doing that would be to set a code breakpoint at the entry to the
3893 @code{main} function and when it breaks, set all the watchpoints.
3895 @cindex watchpoints and threads
3896 @cindex threads and watchpoints
3897 In multi-threaded programs, watchpoints will detect changes to the
3898 watched expression from every thread.
3901 @emph{Warning:} In multi-threaded programs, software watchpoints
3902 have only limited usefulness. If @value{GDBN} creates a software
3903 watchpoint, it can only watch the value of an expression @emph{in a
3904 single thread}. If you are confident that the expression can only
3905 change due to the current thread's activity (and if you are also
3906 confident that no other thread can become current), then you can use
3907 software watchpoints as usual. However, @value{GDBN} may not notice
3908 when a non-current thread's activity changes the expression. (Hardware
3909 watchpoints, in contrast, watch an expression in all threads.)
3912 @xref{set remote hardware-watchpoint-limit}.
3914 @node Set Catchpoints
3915 @subsection Setting Catchpoints
3916 @cindex catchpoints, setting
3917 @cindex exception handlers
3918 @cindex event handling
3920 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3921 kinds of program events, such as C@t{++} exceptions or the loading of a
3922 shared library. Use the @code{catch} command to set a catchpoint.
3926 @item catch @var{event}
3927 Stop when @var{event} occurs. @var{event} can be any of the following:
3930 @cindex stop on C@t{++} exceptions
3931 The throwing of a C@t{++} exception.
3934 The catching of a C@t{++} exception.
3937 @cindex Ada exception catching
3938 @cindex catch Ada exceptions
3939 An Ada exception being raised. If an exception name is specified
3940 at the end of the command (eg @code{catch exception Program_Error}),
3941 the debugger will stop only when this specific exception is raised.
3942 Otherwise, the debugger stops execution when any Ada exception is raised.
3944 When inserting an exception catchpoint on a user-defined exception whose
3945 name is identical to one of the exceptions defined by the language, the
3946 fully qualified name must be used as the exception name. Otherwise,
3947 @value{GDBN} will assume that it should stop on the pre-defined exception
3948 rather than the user-defined one. For instance, assuming an exception
3949 called @code{Constraint_Error} is defined in package @code{Pck}, then
3950 the command to use to catch such exceptions is @kbd{catch exception
3951 Pck.Constraint_Error}.
3953 @item exception unhandled
3954 An exception that was raised but is not handled by the program.
3957 A failed Ada assertion.
3960 @cindex break on fork/exec
3961 A call to @code{exec}. This is currently only available for HP-UX
3965 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3966 @cindex break on a system call.
3967 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3968 syscall is a mechanism for application programs to request a service
3969 from the operating system (OS) or one of the OS system services.
3970 @value{GDBN} can catch some or all of the syscalls issued by the
3971 debuggee, and show the related information for each syscall. If no
3972 argument is specified, calls to and returns from all system calls
3975 @var{name} can be any system call name that is valid for the
3976 underlying OS. Just what syscalls are valid depends on the OS. On
3977 GNU and Unix systems, you can find the full list of valid syscall
3978 names on @file{/usr/include/asm/unistd.h}.
3980 @c For MS-Windows, the syscall names and the corresponding numbers
3981 @c can be found, e.g., on this URL:
3982 @c http://www.metasploit.com/users/opcode/syscalls.html
3983 @c but we don't support Windows syscalls yet.
3985 Normally, @value{GDBN} knows in advance which syscalls are valid for
3986 each OS, so you can use the @value{GDBN} command-line completion
3987 facilities (@pxref{Completion,, command completion}) to list the
3990 You may also specify the system call numerically. A syscall's
3991 number is the value passed to the OS's syscall dispatcher to
3992 identify the requested service. When you specify the syscall by its
3993 name, @value{GDBN} uses its database of syscalls to convert the name
3994 into the corresponding numeric code, but using the number directly
3995 may be useful if @value{GDBN}'s database does not have the complete
3996 list of syscalls on your system (e.g., because @value{GDBN} lags
3997 behind the OS upgrades).
3999 The example below illustrates how this command works if you don't provide
4003 (@value{GDBP}) catch syscall
4004 Catchpoint 1 (syscall)
4006 Starting program: /tmp/catch-syscall
4008 Catchpoint 1 (call to syscall 'close'), \
4009 0xffffe424 in __kernel_vsyscall ()
4013 Catchpoint 1 (returned from syscall 'close'), \
4014 0xffffe424 in __kernel_vsyscall ()
4018 Here is an example of catching a system call by name:
4021 (@value{GDBP}) catch syscall chroot
4022 Catchpoint 1 (syscall 'chroot' [61])
4024 Starting program: /tmp/catch-syscall
4026 Catchpoint 1 (call to syscall 'chroot'), \
4027 0xffffe424 in __kernel_vsyscall ()
4031 Catchpoint 1 (returned from syscall 'chroot'), \
4032 0xffffe424 in __kernel_vsyscall ()
4036 An example of specifying a system call numerically. In the case
4037 below, the syscall number has a corresponding entry in the XML
4038 file, so @value{GDBN} finds its name and prints it:
4041 (@value{GDBP}) catch syscall 252
4042 Catchpoint 1 (syscall(s) 'exit_group')
4044 Starting program: /tmp/catch-syscall
4046 Catchpoint 1 (call to syscall 'exit_group'), \
4047 0xffffe424 in __kernel_vsyscall ()
4051 Program exited normally.
4055 However, there can be situations when there is no corresponding name
4056 in XML file for that syscall number. In this case, @value{GDBN} prints
4057 a warning message saying that it was not able to find the syscall name,
4058 but the catchpoint will be set anyway. See the example below:
4061 (@value{GDBP}) catch syscall 764
4062 warning: The number '764' does not represent a known syscall.
4063 Catchpoint 2 (syscall 764)
4067 If you configure @value{GDBN} using the @samp{--without-expat} option,
4068 it will not be able to display syscall names. Also, if your
4069 architecture does not have an XML file describing its system calls,
4070 you will not be able to see the syscall names. It is important to
4071 notice that these two features are used for accessing the syscall
4072 name database. In either case, you will see a warning like this:
4075 (@value{GDBP}) catch syscall
4076 warning: Could not open "syscalls/i386-linux.xml"
4077 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4078 GDB will not be able to display syscall names.
4079 Catchpoint 1 (syscall)
4083 Of course, the file name will change depending on your architecture and system.
4085 Still using the example above, you can also try to catch a syscall by its
4086 number. In this case, you would see something like:
4089 (@value{GDBP}) catch syscall 252
4090 Catchpoint 1 (syscall(s) 252)
4093 Again, in this case @value{GDBN} would not be able to display syscall's names.
4096 A call to @code{fork}. This is currently only available for HP-UX
4100 A call to @code{vfork}. This is currently only available for HP-UX
4105 @item tcatch @var{event}
4106 Set a catchpoint that is enabled only for one stop. The catchpoint is
4107 automatically deleted after the first time the event is caught.
4111 Use the @code{info break} command to list the current catchpoints.
4113 There are currently some limitations to C@t{++} exception handling
4114 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4118 If you call a function interactively, @value{GDBN} normally returns
4119 control to you when the function has finished executing. If the call
4120 raises an exception, however, the call may bypass the mechanism that
4121 returns control to you and cause your program either to abort or to
4122 simply continue running until it hits a breakpoint, catches a signal
4123 that @value{GDBN} is listening for, or exits. This is the case even if
4124 you set a catchpoint for the exception; catchpoints on exceptions are
4125 disabled within interactive calls.
4128 You cannot raise an exception interactively.
4131 You cannot install an exception handler interactively.
4134 @cindex raise exceptions
4135 Sometimes @code{catch} is not the best way to debug exception handling:
4136 if you need to know exactly where an exception is raised, it is better to
4137 stop @emph{before} the exception handler is called, since that way you
4138 can see the stack before any unwinding takes place. If you set a
4139 breakpoint in an exception handler instead, it may not be easy to find
4140 out where the exception was raised.
4142 To stop just before an exception handler is called, you need some
4143 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4144 raised by calling a library function named @code{__raise_exception}
4145 which has the following ANSI C interface:
4148 /* @var{addr} is where the exception identifier is stored.
4149 @var{id} is the exception identifier. */
4150 void __raise_exception (void **addr, void *id);
4154 To make the debugger catch all exceptions before any stack
4155 unwinding takes place, set a breakpoint on @code{__raise_exception}
4156 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4158 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4159 that depends on the value of @var{id}, you can stop your program when
4160 a specific exception is raised. You can use multiple conditional
4161 breakpoints to stop your program when any of a number of exceptions are
4166 @subsection Deleting Breakpoints
4168 @cindex clearing breakpoints, watchpoints, catchpoints
4169 @cindex deleting breakpoints, watchpoints, catchpoints
4170 It is often necessary to eliminate a breakpoint, watchpoint, or
4171 catchpoint once it has done its job and you no longer want your program
4172 to stop there. This is called @dfn{deleting} the breakpoint. A
4173 breakpoint that has been deleted no longer exists; it is forgotten.
4175 With the @code{clear} command you can delete breakpoints according to
4176 where they are in your program. With the @code{delete} command you can
4177 delete individual breakpoints, watchpoints, or catchpoints by specifying
4178 their breakpoint numbers.
4180 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4181 automatically ignores breakpoints on the first instruction to be executed
4182 when you continue execution without changing the execution address.
4187 Delete any breakpoints at the next instruction to be executed in the
4188 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4189 the innermost frame is selected, this is a good way to delete a
4190 breakpoint where your program just stopped.
4192 @item clear @var{location}
4193 Delete any breakpoints set at the specified @var{location}.
4194 @xref{Specify Location}, for the various forms of @var{location}; the
4195 most useful ones are listed below:
4198 @item clear @var{function}
4199 @itemx clear @var{filename}:@var{function}
4200 Delete any breakpoints set at entry to the named @var{function}.
4202 @item clear @var{linenum}
4203 @itemx clear @var{filename}:@var{linenum}
4204 Delete any breakpoints set at or within the code of the specified
4205 @var{linenum} of the specified @var{filename}.
4208 @cindex delete breakpoints
4210 @kindex d @r{(@code{delete})}
4211 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4212 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4213 ranges specified as arguments. If no argument is specified, delete all
4214 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4215 confirm off}). You can abbreviate this command as @code{d}.
4219 @subsection Disabling Breakpoints
4221 @cindex enable/disable a breakpoint
4222 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4223 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4224 it had been deleted, but remembers the information on the breakpoint so
4225 that you can @dfn{enable} it again later.
4227 You disable and enable breakpoints, watchpoints, and catchpoints with
4228 the @code{enable} and @code{disable} commands, optionally specifying
4229 one or more breakpoint numbers as arguments. Use @code{info break} to
4230 print a list of all breakpoints, watchpoints, and catchpoints if you
4231 do not know which numbers to use.
4233 Disabling and enabling a breakpoint that has multiple locations
4234 affects all of its locations.
4236 A breakpoint, watchpoint, or catchpoint can have any of four different
4237 states of enablement:
4241 Enabled. The breakpoint stops your program. A breakpoint set
4242 with the @code{break} command starts out in this state.
4244 Disabled. The breakpoint has no effect on your program.
4246 Enabled once. The breakpoint stops your program, but then becomes
4249 Enabled for deletion. The breakpoint stops your program, but
4250 immediately after it does so it is deleted permanently. A breakpoint
4251 set with the @code{tbreak} command starts out in this state.
4254 You can use the following commands to enable or disable breakpoints,
4255 watchpoints, and catchpoints:
4259 @kindex dis @r{(@code{disable})}
4260 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4261 Disable the specified breakpoints---or all breakpoints, if none are
4262 listed. A disabled breakpoint has no effect but is not forgotten. All
4263 options such as ignore-counts, conditions and commands are remembered in
4264 case the breakpoint is enabled again later. You may abbreviate
4265 @code{disable} as @code{dis}.
4268 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4269 Enable the specified breakpoints (or all defined breakpoints). They
4270 become effective once again in stopping your program.
4272 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4273 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4274 of these breakpoints immediately after stopping your program.
4276 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4277 Enable the specified breakpoints to work once, then die. @value{GDBN}
4278 deletes any of these breakpoints as soon as your program stops there.
4279 Breakpoints set by the @code{tbreak} command start out in this state.
4282 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4283 @c confusing: tbreak is also initially enabled.
4284 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4285 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4286 subsequently, they become disabled or enabled only when you use one of
4287 the commands above. (The command @code{until} can set and delete a
4288 breakpoint of its own, but it does not change the state of your other
4289 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4293 @subsection Break Conditions
4294 @cindex conditional breakpoints
4295 @cindex breakpoint conditions
4297 @c FIXME what is scope of break condition expr? Context where wanted?
4298 @c in particular for a watchpoint?
4299 The simplest sort of breakpoint breaks every time your program reaches a
4300 specified place. You can also specify a @dfn{condition} for a
4301 breakpoint. A condition is just a Boolean expression in your
4302 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4303 a condition evaluates the expression each time your program reaches it,
4304 and your program stops only if the condition is @emph{true}.
4306 This is the converse of using assertions for program validation; in that
4307 situation, you want to stop when the assertion is violated---that is,
4308 when the condition is false. In C, if you want to test an assertion expressed
4309 by the condition @var{assert}, you should set the condition
4310 @samp{! @var{assert}} on the appropriate breakpoint.
4312 Conditions are also accepted for watchpoints; you may not need them,
4313 since a watchpoint is inspecting the value of an expression anyhow---but
4314 it might be simpler, say, to just set a watchpoint on a variable name,
4315 and specify a condition that tests whether the new value is an interesting
4318 Break conditions can have side effects, and may even call functions in
4319 your program. This can be useful, for example, to activate functions
4320 that log program progress, or to use your own print functions to
4321 format special data structures. The effects are completely predictable
4322 unless there is another enabled breakpoint at the same address. (In
4323 that case, @value{GDBN} might see the other breakpoint first and stop your
4324 program without checking the condition of this one.) Note that
4325 breakpoint commands are usually more convenient and flexible than break
4327 purpose of performing side effects when a breakpoint is reached
4328 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4330 Break conditions can be specified when a breakpoint is set, by using
4331 @samp{if} in the arguments to the @code{break} command. @xref{Set
4332 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4333 with the @code{condition} command.
4335 You can also use the @code{if} keyword with the @code{watch} command.
4336 The @code{catch} command does not recognize the @code{if} keyword;
4337 @code{condition} is the only way to impose a further condition on a
4342 @item condition @var{bnum} @var{expression}
4343 Specify @var{expression} as the break condition for breakpoint,
4344 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4345 breakpoint @var{bnum} stops your program only if the value of
4346 @var{expression} is true (nonzero, in C). When you use
4347 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4348 syntactic correctness, and to determine whether symbols in it have
4349 referents in the context of your breakpoint. If @var{expression} uses
4350 symbols not referenced in the context of the breakpoint, @value{GDBN}
4351 prints an error message:
4354 No symbol "foo" in current context.
4359 not actually evaluate @var{expression} at the time the @code{condition}
4360 command (or a command that sets a breakpoint with a condition, like
4361 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4363 @item condition @var{bnum}
4364 Remove the condition from breakpoint number @var{bnum}. It becomes
4365 an ordinary unconditional breakpoint.
4368 @cindex ignore count (of breakpoint)
4369 A special case of a breakpoint condition is to stop only when the
4370 breakpoint has been reached a certain number of times. This is so
4371 useful that there is a special way to do it, using the @dfn{ignore
4372 count} of the breakpoint. Every breakpoint has an ignore count, which
4373 is an integer. Most of the time, the ignore count is zero, and
4374 therefore has no effect. But if your program reaches a breakpoint whose
4375 ignore count is positive, then instead of stopping, it just decrements
4376 the ignore count by one and continues. As a result, if the ignore count
4377 value is @var{n}, the breakpoint does not stop the next @var{n} times
4378 your program reaches it.
4382 @item ignore @var{bnum} @var{count}
4383 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4384 The next @var{count} times the breakpoint is reached, your program's
4385 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4388 To make the breakpoint stop the next time it is reached, specify
4391 When you use @code{continue} to resume execution of your program from a
4392 breakpoint, you can specify an ignore count directly as an argument to
4393 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4394 Stepping,,Continuing and Stepping}.
4396 If a breakpoint has a positive ignore count and a condition, the
4397 condition is not checked. Once the ignore count reaches zero,
4398 @value{GDBN} resumes checking the condition.
4400 You could achieve the effect of the ignore count with a condition such
4401 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4402 is decremented each time. @xref{Convenience Vars, ,Convenience
4406 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4409 @node Break Commands
4410 @subsection Breakpoint Command Lists
4412 @cindex breakpoint commands
4413 You can give any breakpoint (or watchpoint or catchpoint) a series of
4414 commands to execute when your program stops due to that breakpoint. For
4415 example, you might want to print the values of certain expressions, or
4416 enable other breakpoints.
4420 @kindex end@r{ (breakpoint commands)}
4421 @item commands @r{[}@var{range}@dots{}@r{]}
4422 @itemx @dots{} @var{command-list} @dots{}
4424 Specify a list of commands for the given breakpoints. The commands
4425 themselves appear on the following lines. Type a line containing just
4426 @code{end} to terminate the commands.
4428 To remove all commands from a breakpoint, type @code{commands} and
4429 follow it immediately with @code{end}; that is, give no commands.
4431 With no argument, @code{commands} refers to the last breakpoint,
4432 watchpoint, or catchpoint set (not to the breakpoint most recently
4433 encountered). If the most recent breakpoints were set with a single
4434 command, then the @code{commands} will apply to all the breakpoints
4435 set by that command. This applies to breakpoints set by
4436 @code{rbreak}, and also applies when a single @code{break} command
4437 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4441 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4442 disabled within a @var{command-list}.
4444 You can use breakpoint commands to start your program up again. Simply
4445 use the @code{continue} command, or @code{step}, or any other command
4446 that resumes execution.
4448 Any other commands in the command list, after a command that resumes
4449 execution, are ignored. This is because any time you resume execution
4450 (even with a simple @code{next} or @code{step}), you may encounter
4451 another breakpoint---which could have its own command list, leading to
4452 ambiguities about which list to execute.
4455 If the first command you specify in a command list is @code{silent}, the
4456 usual message about stopping at a breakpoint is not printed. This may
4457 be desirable for breakpoints that are to print a specific message and
4458 then continue. If none of the remaining commands print anything, you
4459 see no sign that the breakpoint was reached. @code{silent} is
4460 meaningful only at the beginning of a breakpoint command list.
4462 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4463 print precisely controlled output, and are often useful in silent
4464 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4466 For example, here is how you could use breakpoint commands to print the
4467 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4473 printf "x is %d\n",x
4478 One application for breakpoint commands is to compensate for one bug so
4479 you can test for another. Put a breakpoint just after the erroneous line
4480 of code, give it a condition to detect the case in which something
4481 erroneous has been done, and give it commands to assign correct values
4482 to any variables that need them. End with the @code{continue} command
4483 so that your program does not stop, and start with the @code{silent}
4484 command so that no output is produced. Here is an example:
4495 @node Save Breakpoints
4496 @subsection How to save breakpoints to a file
4498 To save breakpoint definitions to a file use the @w{@code{save
4499 breakpoints}} command.
4502 @kindex save breakpoints
4503 @cindex save breakpoints to a file for future sessions
4504 @item save breakpoints [@var{filename}]
4505 This command saves all current breakpoint definitions together with
4506 their commands and ignore counts, into a file @file{@var{filename}}
4507 suitable for use in a later debugging session. This includes all
4508 types of breakpoints (breakpoints, watchpoints, catchpoints,
4509 tracepoints). To read the saved breakpoint definitions, use the
4510 @code{source} command (@pxref{Command Files}). Note that watchpoints
4511 with expressions involving local variables may fail to be recreated
4512 because it may not be possible to access the context where the
4513 watchpoint is valid anymore. Because the saved breakpoint definitions
4514 are simply a sequence of @value{GDBN} commands that recreate the
4515 breakpoints, you can edit the file in your favorite editing program,
4516 and remove the breakpoint definitions you're not interested in, or
4517 that can no longer be recreated.
4520 @c @ifclear BARETARGET
4521 @node Error in Breakpoints
4522 @subsection ``Cannot insert breakpoints''
4524 If you request too many active hardware-assisted breakpoints and
4525 watchpoints, you will see this error message:
4527 @c FIXME: the precise wording of this message may change; the relevant
4528 @c source change is not committed yet (Sep 3, 1999).
4530 Stopped; cannot insert breakpoints.
4531 You may have requested too many hardware breakpoints and watchpoints.
4535 This message is printed when you attempt to resume the program, since
4536 only then @value{GDBN} knows exactly how many hardware breakpoints and
4537 watchpoints it needs to insert.
4539 When this message is printed, you need to disable or remove some of the
4540 hardware-assisted breakpoints and watchpoints, and then continue.
4542 @node Breakpoint-related Warnings
4543 @subsection ``Breakpoint address adjusted...''
4544 @cindex breakpoint address adjusted
4546 Some processor architectures place constraints on the addresses at
4547 which breakpoints may be placed. For architectures thus constrained,
4548 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4549 with the constraints dictated by the architecture.
4551 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4552 a VLIW architecture in which a number of RISC-like instructions may be
4553 bundled together for parallel execution. The FR-V architecture
4554 constrains the location of a breakpoint instruction within such a
4555 bundle to the instruction with the lowest address. @value{GDBN}
4556 honors this constraint by adjusting a breakpoint's address to the
4557 first in the bundle.
4559 It is not uncommon for optimized code to have bundles which contain
4560 instructions from different source statements, thus it may happen that
4561 a breakpoint's address will be adjusted from one source statement to
4562 another. Since this adjustment may significantly alter @value{GDBN}'s
4563 breakpoint related behavior from what the user expects, a warning is
4564 printed when the breakpoint is first set and also when the breakpoint
4567 A warning like the one below is printed when setting a breakpoint
4568 that's been subject to address adjustment:
4571 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4574 Such warnings are printed both for user settable and @value{GDBN}'s
4575 internal breakpoints. If you see one of these warnings, you should
4576 verify that a breakpoint set at the adjusted address will have the
4577 desired affect. If not, the breakpoint in question may be removed and
4578 other breakpoints may be set which will have the desired behavior.
4579 E.g., it may be sufficient to place the breakpoint at a later
4580 instruction. A conditional breakpoint may also be useful in some
4581 cases to prevent the breakpoint from triggering too often.
4583 @value{GDBN} will also issue a warning when stopping at one of these
4584 adjusted breakpoints:
4587 warning: Breakpoint 1 address previously adjusted from 0x00010414
4591 When this warning is encountered, it may be too late to take remedial
4592 action except in cases where the breakpoint is hit earlier or more
4593 frequently than expected.
4595 @node Continuing and Stepping
4596 @section Continuing and Stepping
4600 @cindex resuming execution
4601 @dfn{Continuing} means resuming program execution until your program
4602 completes normally. In contrast, @dfn{stepping} means executing just
4603 one more ``step'' of your program, where ``step'' may mean either one
4604 line of source code, or one machine instruction (depending on what
4605 particular command you use). Either when continuing or when stepping,
4606 your program may stop even sooner, due to a breakpoint or a signal. (If
4607 it stops due to a signal, you may want to use @code{handle}, or use
4608 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4612 @kindex c @r{(@code{continue})}
4613 @kindex fg @r{(resume foreground execution)}
4614 @item continue @r{[}@var{ignore-count}@r{]}
4615 @itemx c @r{[}@var{ignore-count}@r{]}
4616 @itemx fg @r{[}@var{ignore-count}@r{]}
4617 Resume program execution, at the address where your program last stopped;
4618 any breakpoints set at that address are bypassed. The optional argument
4619 @var{ignore-count} allows you to specify a further number of times to
4620 ignore a breakpoint at this location; its effect is like that of
4621 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4623 The argument @var{ignore-count} is meaningful only when your program
4624 stopped due to a breakpoint. At other times, the argument to
4625 @code{continue} is ignored.
4627 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4628 debugged program is deemed to be the foreground program) are provided
4629 purely for convenience, and have exactly the same behavior as
4633 To resume execution at a different place, you can use @code{return}
4634 (@pxref{Returning, ,Returning from a Function}) to go back to the
4635 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4636 Different Address}) to go to an arbitrary location in your program.
4638 A typical technique for using stepping is to set a breakpoint
4639 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4640 beginning of the function or the section of your program where a problem
4641 is believed to lie, run your program until it stops at that breakpoint,
4642 and then step through the suspect area, examining the variables that are
4643 interesting, until you see the problem happen.
4647 @kindex s @r{(@code{step})}
4649 Continue running your program until control reaches a different source
4650 line, then stop it and return control to @value{GDBN}. This command is
4651 abbreviated @code{s}.
4654 @c "without debugging information" is imprecise; actually "without line
4655 @c numbers in the debugging information". (gcc -g1 has debugging info but
4656 @c not line numbers). But it seems complex to try to make that
4657 @c distinction here.
4658 @emph{Warning:} If you use the @code{step} command while control is
4659 within a function that was compiled without debugging information,
4660 execution proceeds until control reaches a function that does have
4661 debugging information. Likewise, it will not step into a function which
4662 is compiled without debugging information. To step through functions
4663 without debugging information, use the @code{stepi} command, described
4667 The @code{step} command only stops at the first instruction of a source
4668 line. This prevents the multiple stops that could otherwise occur in
4669 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4670 to stop if a function that has debugging information is called within
4671 the line. In other words, @code{step} @emph{steps inside} any functions
4672 called within the line.
4674 Also, the @code{step} command only enters a function if there is line
4675 number information for the function. Otherwise it acts like the
4676 @code{next} command. This avoids problems when using @code{cc -gl}
4677 on MIPS machines. Previously, @code{step} entered subroutines if there
4678 was any debugging information about the routine.
4680 @item step @var{count}
4681 Continue running as in @code{step}, but do so @var{count} times. If a
4682 breakpoint is reached, or a signal not related to stepping occurs before
4683 @var{count} steps, stepping stops right away.
4686 @kindex n @r{(@code{next})}
4687 @item next @r{[}@var{count}@r{]}
4688 Continue to the next source line in the current (innermost) stack frame.
4689 This is similar to @code{step}, but function calls that appear within
4690 the line of code are executed without stopping. Execution stops when
4691 control reaches a different line of code at the original stack level
4692 that was executing when you gave the @code{next} command. This command
4693 is abbreviated @code{n}.
4695 An argument @var{count} is a repeat count, as for @code{step}.
4698 @c FIX ME!! Do we delete this, or is there a way it fits in with
4699 @c the following paragraph? --- Vctoria
4701 @c @code{next} within a function that lacks debugging information acts like
4702 @c @code{step}, but any function calls appearing within the code of the
4703 @c function are executed without stopping.
4705 The @code{next} command only stops at the first instruction of a
4706 source line. This prevents multiple stops that could otherwise occur in
4707 @code{switch} statements, @code{for} loops, etc.
4709 @kindex set step-mode
4711 @cindex functions without line info, and stepping
4712 @cindex stepping into functions with no line info
4713 @itemx set step-mode on
4714 The @code{set step-mode on} command causes the @code{step} command to
4715 stop at the first instruction of a function which contains no debug line
4716 information rather than stepping over it.
4718 This is useful in cases where you may be interested in inspecting the
4719 machine instructions of a function which has no symbolic info and do not
4720 want @value{GDBN} to automatically skip over this function.
4722 @item set step-mode off
4723 Causes the @code{step} command to step over any functions which contains no
4724 debug information. This is the default.
4726 @item show step-mode
4727 Show whether @value{GDBN} will stop in or step over functions without
4728 source line debug information.
4731 @kindex fin @r{(@code{finish})}
4733 Continue running until just after function in the selected stack frame
4734 returns. Print the returned value (if any). This command can be
4735 abbreviated as @code{fin}.
4737 Contrast this with the @code{return} command (@pxref{Returning,
4738 ,Returning from a Function}).
4741 @kindex u @r{(@code{until})}
4742 @cindex run until specified location
4745 Continue running until a source line past the current line, in the
4746 current stack frame, is reached. This command is used to avoid single
4747 stepping through a loop more than once. It is like the @code{next}
4748 command, except that when @code{until} encounters a jump, it
4749 automatically continues execution until the program counter is greater
4750 than the address of the jump.
4752 This means that when you reach the end of a loop after single stepping
4753 though it, @code{until} makes your program continue execution until it
4754 exits the loop. In contrast, a @code{next} command at the end of a loop
4755 simply steps back to the beginning of the loop, which forces you to step
4756 through the next iteration.
4758 @code{until} always stops your program if it attempts to exit the current
4761 @code{until} may produce somewhat counterintuitive results if the order
4762 of machine code does not match the order of the source lines. For
4763 example, in the following excerpt from a debugging session, the @code{f}
4764 (@code{frame}) command shows that execution is stopped at line
4765 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4769 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4771 (@value{GDBP}) until
4772 195 for ( ; argc > 0; NEXTARG) @{
4775 This happened because, for execution efficiency, the compiler had
4776 generated code for the loop closure test at the end, rather than the
4777 start, of the loop---even though the test in a C @code{for}-loop is
4778 written before the body of the loop. The @code{until} command appeared
4779 to step back to the beginning of the loop when it advanced to this
4780 expression; however, it has not really gone to an earlier
4781 statement---not in terms of the actual machine code.
4783 @code{until} with no argument works by means of single
4784 instruction stepping, and hence is slower than @code{until} with an
4787 @item until @var{location}
4788 @itemx u @var{location}
4789 Continue running your program until either the specified location is
4790 reached, or the current stack frame returns. @var{location} is any of
4791 the forms described in @ref{Specify Location}.
4792 This form of the command uses temporary breakpoints, and
4793 hence is quicker than @code{until} without an argument. The specified
4794 location is actually reached only if it is in the current frame. This
4795 implies that @code{until} can be used to skip over recursive function
4796 invocations. For instance in the code below, if the current location is
4797 line @code{96}, issuing @code{until 99} will execute the program up to
4798 line @code{99} in the same invocation of factorial, i.e., after the inner
4799 invocations have returned.
4802 94 int factorial (int value)
4804 96 if (value > 1) @{
4805 97 value *= factorial (value - 1);
4812 @kindex advance @var{location}
4813 @itemx advance @var{location}
4814 Continue running the program up to the given @var{location}. An argument is
4815 required, which should be of one of the forms described in
4816 @ref{Specify Location}.
4817 Execution will also stop upon exit from the current stack
4818 frame. This command is similar to @code{until}, but @code{advance} will
4819 not skip over recursive function calls, and the target location doesn't
4820 have to be in the same frame as the current one.
4824 @kindex si @r{(@code{stepi})}
4826 @itemx stepi @var{arg}
4828 Execute one machine instruction, then stop and return to the debugger.
4830 It is often useful to do @samp{display/i $pc} when stepping by machine
4831 instructions. This makes @value{GDBN} automatically display the next
4832 instruction to be executed, each time your program stops. @xref{Auto
4833 Display,, Automatic Display}.
4835 An argument is a repeat count, as in @code{step}.
4839 @kindex ni @r{(@code{nexti})}
4841 @itemx nexti @var{arg}
4843 Execute one machine instruction, but if it is a function call,
4844 proceed until the function returns.
4846 An argument is a repeat count, as in @code{next}.
4853 A signal is an asynchronous event that can happen in a program. The
4854 operating system defines the possible kinds of signals, and gives each
4855 kind a name and a number. For example, in Unix @code{SIGINT} is the
4856 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4857 @code{SIGSEGV} is the signal a program gets from referencing a place in
4858 memory far away from all the areas in use; @code{SIGALRM} occurs when
4859 the alarm clock timer goes off (which happens only if your program has
4860 requested an alarm).
4862 @cindex fatal signals
4863 Some signals, including @code{SIGALRM}, are a normal part of the
4864 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4865 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4866 program has not specified in advance some other way to handle the signal.
4867 @code{SIGINT} does not indicate an error in your program, but it is normally
4868 fatal so it can carry out the purpose of the interrupt: to kill the program.
4870 @value{GDBN} has the ability to detect any occurrence of a signal in your
4871 program. You can tell @value{GDBN} in advance what to do for each kind of
4874 @cindex handling signals
4875 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4876 @code{SIGALRM} be silently passed to your program
4877 (so as not to interfere with their role in the program's functioning)
4878 but to stop your program immediately whenever an error signal happens.
4879 You can change these settings with the @code{handle} command.
4882 @kindex info signals
4886 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4887 handle each one. You can use this to see the signal numbers of all
4888 the defined types of signals.
4890 @item info signals @var{sig}
4891 Similar, but print information only about the specified signal number.
4893 @code{info handle} is an alias for @code{info signals}.
4896 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4897 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4898 can be the number of a signal or its name (with or without the
4899 @samp{SIG} at the beginning); a list of signal numbers of the form
4900 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4901 known signals. Optional arguments @var{keywords}, described below,
4902 say what change to make.
4906 The keywords allowed by the @code{handle} command can be abbreviated.
4907 Their full names are:
4911 @value{GDBN} should not stop your program when this signal happens. It may
4912 still print a message telling you that the signal has come in.
4915 @value{GDBN} should stop your program when this signal happens. This implies
4916 the @code{print} keyword as well.
4919 @value{GDBN} should print a message when this signal happens.
4922 @value{GDBN} should not mention the occurrence of the signal at all. This
4923 implies the @code{nostop} keyword as well.
4927 @value{GDBN} should allow your program to see this signal; your program
4928 can handle the signal, or else it may terminate if the signal is fatal
4929 and not handled. @code{pass} and @code{noignore} are synonyms.
4933 @value{GDBN} should not allow your program to see this signal.
4934 @code{nopass} and @code{ignore} are synonyms.
4938 When a signal stops your program, the signal is not visible to the
4940 continue. Your program sees the signal then, if @code{pass} is in
4941 effect for the signal in question @emph{at that time}. In other words,
4942 after @value{GDBN} reports a signal, you can use the @code{handle}
4943 command with @code{pass} or @code{nopass} to control whether your
4944 program sees that signal when you continue.
4946 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4947 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4948 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4951 You can also use the @code{signal} command to prevent your program from
4952 seeing a signal, or cause it to see a signal it normally would not see,
4953 or to give it any signal at any time. For example, if your program stopped
4954 due to some sort of memory reference error, you might store correct
4955 values into the erroneous variables and continue, hoping to see more
4956 execution; but your program would probably terminate immediately as
4957 a result of the fatal signal once it saw the signal. To prevent this,
4958 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4961 @cindex extra signal information
4962 @anchor{extra signal information}
4964 On some targets, @value{GDBN} can inspect extra signal information
4965 associated with the intercepted signal, before it is actually
4966 delivered to the program being debugged. This information is exported
4967 by the convenience variable @code{$_siginfo}, and consists of data
4968 that is passed by the kernel to the signal handler at the time of the
4969 receipt of a signal. The data type of the information itself is
4970 target dependent. You can see the data type using the @code{ptype
4971 $_siginfo} command. On Unix systems, it typically corresponds to the
4972 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4975 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4976 referenced address that raised a segmentation fault.
4980 (@value{GDBP}) continue
4981 Program received signal SIGSEGV, Segmentation fault.
4982 0x0000000000400766 in main ()
4984 (@value{GDBP}) ptype $_siginfo
4991 struct @{...@} _kill;
4992 struct @{...@} _timer;
4994 struct @{...@} _sigchld;
4995 struct @{...@} _sigfault;
4996 struct @{...@} _sigpoll;
4999 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5003 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5004 $1 = (void *) 0x7ffff7ff7000
5008 Depending on target support, @code{$_siginfo} may also be writable.
5011 @section Stopping and Starting Multi-thread Programs
5013 @cindex stopped threads
5014 @cindex threads, stopped
5016 @cindex continuing threads
5017 @cindex threads, continuing
5019 @value{GDBN} supports debugging programs with multiple threads
5020 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5021 are two modes of controlling execution of your program within the
5022 debugger. In the default mode, referred to as @dfn{all-stop mode},
5023 when any thread in your program stops (for example, at a breakpoint
5024 or while being stepped), all other threads in the program are also stopped by
5025 @value{GDBN}. On some targets, @value{GDBN} also supports
5026 @dfn{non-stop mode}, in which other threads can continue to run freely while
5027 you examine the stopped thread in the debugger.
5030 * All-Stop Mode:: All threads stop when GDB takes control
5031 * Non-Stop Mode:: Other threads continue to execute
5032 * Background Execution:: Running your program asynchronously
5033 * Thread-Specific Breakpoints:: Controlling breakpoints
5034 * Interrupted System Calls:: GDB may interfere with system calls
5035 * Observer Mode:: GDB does not alter program behavior
5039 @subsection All-Stop Mode
5041 @cindex all-stop mode
5043 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5044 @emph{all} threads of execution stop, not just the current thread. This
5045 allows you to examine the overall state of the program, including
5046 switching between threads, without worrying that things may change
5049 Conversely, whenever you restart the program, @emph{all} threads start
5050 executing. @emph{This is true even when single-stepping} with commands
5051 like @code{step} or @code{next}.
5053 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5054 Since thread scheduling is up to your debugging target's operating
5055 system (not controlled by @value{GDBN}), other threads may
5056 execute more than one statement while the current thread completes a
5057 single step. Moreover, in general other threads stop in the middle of a
5058 statement, rather than at a clean statement boundary, when the program
5061 You might even find your program stopped in another thread after
5062 continuing or even single-stepping. This happens whenever some other
5063 thread runs into a breakpoint, a signal, or an exception before the
5064 first thread completes whatever you requested.
5066 @cindex automatic thread selection
5067 @cindex switching threads automatically
5068 @cindex threads, automatic switching
5069 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5070 signal, it automatically selects the thread where that breakpoint or
5071 signal happened. @value{GDBN} alerts you to the context switch with a
5072 message such as @samp{[Switching to Thread @var{n}]} to identify the
5075 On some OSes, you can modify @value{GDBN}'s default behavior by
5076 locking the OS scheduler to allow only a single thread to run.
5079 @item set scheduler-locking @var{mode}
5080 @cindex scheduler locking mode
5081 @cindex lock scheduler
5082 Set the scheduler locking mode. If it is @code{off}, then there is no
5083 locking and any thread may run at any time. If @code{on}, then only the
5084 current thread may run when the inferior is resumed. The @code{step}
5085 mode optimizes for single-stepping; it prevents other threads
5086 from preempting the current thread while you are stepping, so that
5087 the focus of debugging does not change unexpectedly.
5088 Other threads only rarely (or never) get a chance to run
5089 when you step. They are more likely to run when you @samp{next} over a
5090 function call, and they are completely free to run when you use commands
5091 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5092 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5093 the current thread away from the thread that you are debugging.
5095 @item show scheduler-locking
5096 Display the current scheduler locking mode.
5099 @cindex resume threads of multiple processes simultaneously
5100 By default, when you issue one of the execution commands such as
5101 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5102 threads of the current inferior to run. For example, if @value{GDBN}
5103 is attached to two inferiors, each with two threads, the
5104 @code{continue} command resumes only the two threads of the current
5105 inferior. This is useful, for example, when you debug a program that
5106 forks and you want to hold the parent stopped (so that, for instance,
5107 it doesn't run to exit), while you debug the child. In other
5108 situations, you may not be interested in inspecting the current state
5109 of any of the processes @value{GDBN} is attached to, and you may want
5110 to resume them all until some breakpoint is hit. In the latter case,
5111 you can instruct @value{GDBN} to allow all threads of all the
5112 inferiors to run with the @w{@code{set schedule-multiple}} command.
5115 @kindex set schedule-multiple
5116 @item set schedule-multiple
5117 Set the mode for allowing threads of multiple processes to be resumed
5118 when an execution command is issued. When @code{on}, all threads of
5119 all processes are allowed to run. When @code{off}, only the threads
5120 of the current process are resumed. The default is @code{off}. The
5121 @code{scheduler-locking} mode takes precedence when set to @code{on},
5122 or while you are stepping and set to @code{step}.
5124 @item show schedule-multiple
5125 Display the current mode for resuming the execution of threads of
5130 @subsection Non-Stop Mode
5132 @cindex non-stop mode
5134 @c This section is really only a place-holder, and needs to be expanded
5135 @c with more details.
5137 For some multi-threaded targets, @value{GDBN} supports an optional
5138 mode of operation in which you can examine stopped program threads in
5139 the debugger while other threads continue to execute freely. This
5140 minimizes intrusion when debugging live systems, such as programs
5141 where some threads have real-time constraints or must continue to
5142 respond to external events. This is referred to as @dfn{non-stop} mode.
5144 In non-stop mode, when a thread stops to report a debugging event,
5145 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5146 threads as well, in contrast to the all-stop mode behavior. Additionally,
5147 execution commands such as @code{continue} and @code{step} apply by default
5148 only to the current thread in non-stop mode, rather than all threads as
5149 in all-stop mode. This allows you to control threads explicitly in
5150 ways that are not possible in all-stop mode --- for example, stepping
5151 one thread while allowing others to run freely, stepping
5152 one thread while holding all others stopped, or stepping several threads
5153 independently and simultaneously.
5155 To enter non-stop mode, use this sequence of commands before you run
5156 or attach to your program:
5159 # Enable the async interface.
5162 # If using the CLI, pagination breaks non-stop.
5165 # Finally, turn it on!
5169 You can use these commands to manipulate the non-stop mode setting:
5172 @kindex set non-stop
5173 @item set non-stop on
5174 Enable selection of non-stop mode.
5175 @item set non-stop off
5176 Disable selection of non-stop mode.
5177 @kindex show non-stop
5179 Show the current non-stop enablement setting.
5182 Note these commands only reflect whether non-stop mode is enabled,
5183 not whether the currently-executing program is being run in non-stop mode.
5184 In particular, the @code{set non-stop} preference is only consulted when
5185 @value{GDBN} starts or connects to the target program, and it is generally
5186 not possible to switch modes once debugging has started. Furthermore,
5187 since not all targets support non-stop mode, even when you have enabled
5188 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5191 In non-stop mode, all execution commands apply only to the current thread
5192 by default. That is, @code{continue} only continues one thread.
5193 To continue all threads, issue @code{continue -a} or @code{c -a}.
5195 You can use @value{GDBN}'s background execution commands
5196 (@pxref{Background Execution}) to run some threads in the background
5197 while you continue to examine or step others from @value{GDBN}.
5198 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5199 always executed asynchronously in non-stop mode.
5201 Suspending execution is done with the @code{interrupt} command when
5202 running in the background, or @kbd{Ctrl-c} during foreground execution.
5203 In all-stop mode, this stops the whole process;
5204 but in non-stop mode the interrupt applies only to the current thread.
5205 To stop the whole program, use @code{interrupt -a}.
5207 Other execution commands do not currently support the @code{-a} option.
5209 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5210 that thread current, as it does in all-stop mode. This is because the
5211 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5212 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5213 changed to a different thread just as you entered a command to operate on the
5214 previously current thread.
5216 @node Background Execution
5217 @subsection Background Execution
5219 @cindex foreground execution
5220 @cindex background execution
5221 @cindex asynchronous execution
5222 @cindex execution, foreground, background and asynchronous
5224 @value{GDBN}'s execution commands have two variants: the normal
5225 foreground (synchronous) behavior, and a background
5226 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5227 the program to report that some thread has stopped before prompting for
5228 another command. In background execution, @value{GDBN} immediately gives
5229 a command prompt so that you can issue other commands while your program runs.
5231 You need to explicitly enable asynchronous mode before you can use
5232 background execution commands. You can use these commands to
5233 manipulate the asynchronous mode setting:
5236 @kindex set target-async
5237 @item set target-async on
5238 Enable asynchronous mode.
5239 @item set target-async off
5240 Disable asynchronous mode.
5241 @kindex show target-async
5242 @item show target-async
5243 Show the current target-async setting.
5246 If the target doesn't support async mode, @value{GDBN} issues an error
5247 message if you attempt to use the background execution commands.
5249 To specify background execution, add a @code{&} to the command. For example,
5250 the background form of the @code{continue} command is @code{continue&}, or
5251 just @code{c&}. The execution commands that accept background execution
5257 @xref{Starting, , Starting your Program}.
5261 @xref{Attach, , Debugging an Already-running Process}.
5265 @xref{Continuing and Stepping, step}.
5269 @xref{Continuing and Stepping, stepi}.
5273 @xref{Continuing and Stepping, next}.
5277 @xref{Continuing and Stepping, nexti}.
5281 @xref{Continuing and Stepping, continue}.
5285 @xref{Continuing and Stepping, finish}.
5289 @xref{Continuing and Stepping, until}.
5293 Background execution is especially useful in conjunction with non-stop
5294 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5295 However, you can also use these commands in the normal all-stop mode with
5296 the restriction that you cannot issue another execution command until the
5297 previous one finishes. Examples of commands that are valid in all-stop
5298 mode while the program is running include @code{help} and @code{info break}.
5300 You can interrupt your program while it is running in the background by
5301 using the @code{interrupt} command.
5308 Suspend execution of the running program. In all-stop mode,
5309 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5310 only the current thread. To stop the whole program in non-stop mode,
5311 use @code{interrupt -a}.
5314 @node Thread-Specific Breakpoints
5315 @subsection Thread-Specific Breakpoints
5317 When your program has multiple threads (@pxref{Threads,, Debugging
5318 Programs with Multiple Threads}), you can choose whether to set
5319 breakpoints on all threads, or on a particular thread.
5322 @cindex breakpoints and threads
5323 @cindex thread breakpoints
5324 @kindex break @dots{} thread @var{threadno}
5325 @item break @var{linespec} thread @var{threadno}
5326 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5327 @var{linespec} specifies source lines; there are several ways of
5328 writing them (@pxref{Specify Location}), but the effect is always to
5329 specify some source line.
5331 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5332 to specify that you only want @value{GDBN} to stop the program when a
5333 particular thread reaches this breakpoint. @var{threadno} is one of the
5334 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5335 column of the @samp{info threads} display.
5337 If you do not specify @samp{thread @var{threadno}} when you set a
5338 breakpoint, the breakpoint applies to @emph{all} threads of your
5341 You can use the @code{thread} qualifier on conditional breakpoints as
5342 well; in this case, place @samp{thread @var{threadno}} before or
5343 after the breakpoint condition, like this:
5346 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5351 @node Interrupted System Calls
5352 @subsection Interrupted System Calls
5354 @cindex thread breakpoints and system calls
5355 @cindex system calls and thread breakpoints
5356 @cindex premature return from system calls
5357 There is an unfortunate side effect when using @value{GDBN} to debug
5358 multi-threaded programs. If one thread stops for a
5359 breakpoint, or for some other reason, and another thread is blocked in a
5360 system call, then the system call may return prematurely. This is a
5361 consequence of the interaction between multiple threads and the signals
5362 that @value{GDBN} uses to implement breakpoints and other events that
5365 To handle this problem, your program should check the return value of
5366 each system call and react appropriately. This is good programming
5369 For example, do not write code like this:
5375 The call to @code{sleep} will return early if a different thread stops
5376 at a breakpoint or for some other reason.
5378 Instead, write this:
5383 unslept = sleep (unslept);
5386 A system call is allowed to return early, so the system is still
5387 conforming to its specification. But @value{GDBN} does cause your
5388 multi-threaded program to behave differently than it would without
5391 Also, @value{GDBN} uses internal breakpoints in the thread library to
5392 monitor certain events such as thread creation and thread destruction.
5393 When such an event happens, a system call in another thread may return
5394 prematurely, even though your program does not appear to stop.
5397 @subsection Observer Mode
5399 If you want to build on non-stop mode and observe program behavior
5400 without any chance of disruption by @value{GDBN}, you can set
5401 variables to disable all of the debugger's attempts to modify state,
5402 whether by writing memory, inserting breakpoints, etc. These operate
5403 at a low level, intercepting operations from all commands.
5405 When all of these are set to @code{off}, then @value{GDBN} is said to
5406 be @dfn{observer mode}. As a convenience, the variable
5407 @code{observer} can be set to disable these, plus enable non-stop
5410 Note that @value{GDBN} will not prevent you from making nonsensical
5411 combinations of these settings. For instance, if you have enabled
5412 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5413 then breakpoints that work by writing trap instructions into the code
5414 stream will still not be able to be placed.
5419 @item set observer on
5420 @itemx set observer off
5421 When set to @code{on}, this disables all the permission variables
5422 below (except for @code{insert-fast-tracepoints}), plus enables
5423 non-stop debugging. Setting this to @code{off} switches back to
5424 normal debugging, though remaining in non-stop mode.
5427 Show whether observer mode is on or off.
5429 @kindex may-write-registers
5430 @item set may-write-registers on
5431 @itemx set may-write-registers off
5432 This controls whether @value{GDBN} will attempt to alter the values of
5433 registers, such as with assignment expressions in @code{print}, or the
5434 @code{jump} command. It defaults to @code{on}.
5436 @item show may-write-registers
5437 Show the current permission to write registers.
5439 @kindex may-write-memory
5440 @item set may-write-memory on
5441 @itemx set may-write-memory off
5442 This controls whether @value{GDBN} will attempt to alter the contents
5443 of memory, such as with assignment expressions in @code{print}. It
5444 defaults to @code{on}.
5446 @item show may-write-memory
5447 Show the current permission to write memory.
5449 @kindex may-insert-breakpoints
5450 @item set may-insert-breakpoints on
5451 @itemx set may-insert-breakpoints off
5452 This controls whether @value{GDBN} will attempt to insert breakpoints.
5453 This affects all breakpoints, including internal breakpoints defined
5454 by @value{GDBN}. It defaults to @code{on}.
5456 @item show may-insert-breakpoints
5457 Show the current permission to insert breakpoints.
5459 @kindex may-insert-tracepoints
5460 @item set may-insert-tracepoints on
5461 @itemx set may-insert-tracepoints off
5462 This controls whether @value{GDBN} will attempt to insert (regular)
5463 tracepoints at the beginning of a tracing experiment. It affects only
5464 non-fast tracepoints, fast tracepoints being under the control of
5465 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5467 @item show may-insert-tracepoints
5468 Show the current permission to insert tracepoints.
5470 @kindex may-insert-fast-tracepoints
5471 @item set may-insert-fast-tracepoints on
5472 @itemx set may-insert-fast-tracepoints off
5473 This controls whether @value{GDBN} will attempt to insert fast
5474 tracepoints at the beginning of a tracing experiment. It affects only
5475 fast tracepoints, regular (non-fast) tracepoints being under the
5476 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5478 @item show may-insert-fast-tracepoints
5479 Show the current permission to insert fast tracepoints.
5481 @kindex may-interrupt
5482 @item set may-interrupt on
5483 @itemx set may-interrupt off
5484 This controls whether @value{GDBN} will attempt to interrupt or stop
5485 program execution. When this variable is @code{off}, the
5486 @code{interrupt} command will have no effect, nor will
5487 @kbd{Ctrl-c}. It defaults to @code{on}.
5489 @item show may-interrupt
5490 Show the current permission to interrupt or stop the program.
5494 @node Reverse Execution
5495 @chapter Running programs backward
5496 @cindex reverse execution
5497 @cindex running programs backward
5499 When you are debugging a program, it is not unusual to realize that
5500 you have gone too far, and some event of interest has already happened.
5501 If the target environment supports it, @value{GDBN} can allow you to
5502 ``rewind'' the program by running it backward.
5504 A target environment that supports reverse execution should be able
5505 to ``undo'' the changes in machine state that have taken place as the
5506 program was executing normally. Variables, registers etc.@: should
5507 revert to their previous values. Obviously this requires a great
5508 deal of sophistication on the part of the target environment; not
5509 all target environments can support reverse execution.
5511 When a program is executed in reverse, the instructions that
5512 have most recently been executed are ``un-executed'', in reverse
5513 order. The program counter runs backward, following the previous
5514 thread of execution in reverse. As each instruction is ``un-executed'',
5515 the values of memory and/or registers that were changed by that
5516 instruction are reverted to their previous states. After executing
5517 a piece of source code in reverse, all side effects of that code
5518 should be ``undone'', and all variables should be returned to their
5519 prior values@footnote{
5520 Note that some side effects are easier to undo than others. For instance,
5521 memory and registers are relatively easy, but device I/O is hard. Some
5522 targets may be able undo things like device I/O, and some may not.
5524 The contract between @value{GDBN} and the reverse executing target
5525 requires only that the target do something reasonable when
5526 @value{GDBN} tells it to execute backwards, and then report the
5527 results back to @value{GDBN}. Whatever the target reports back to
5528 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5529 assumes that the memory and registers that the target reports are in a
5530 consistant state, but @value{GDBN} accepts whatever it is given.
5533 If you are debugging in a target environment that supports
5534 reverse execution, @value{GDBN} provides the following commands.
5537 @kindex reverse-continue
5538 @kindex rc @r{(@code{reverse-continue})}
5539 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5540 @itemx rc @r{[}@var{ignore-count}@r{]}
5541 Beginning at the point where your program last stopped, start executing
5542 in reverse. Reverse execution will stop for breakpoints and synchronous
5543 exceptions (signals), just like normal execution. Behavior of
5544 asynchronous signals depends on the target environment.
5546 @kindex reverse-step
5547 @kindex rs @r{(@code{step})}
5548 @item reverse-step @r{[}@var{count}@r{]}
5549 Run the program backward until control reaches the start of a
5550 different source line; then stop it, and return control to @value{GDBN}.
5552 Like the @code{step} command, @code{reverse-step} will only stop
5553 at the beginning of a source line. It ``un-executes'' the previously
5554 executed source line. If the previous source line included calls to
5555 debuggable functions, @code{reverse-step} will step (backward) into
5556 the called function, stopping at the beginning of the @emph{last}
5557 statement in the called function (typically a return statement).
5559 Also, as with the @code{step} command, if non-debuggable functions are
5560 called, @code{reverse-step} will run thru them backward without stopping.
5562 @kindex reverse-stepi
5563 @kindex rsi @r{(@code{reverse-stepi})}
5564 @item reverse-stepi @r{[}@var{count}@r{]}
5565 Reverse-execute one machine instruction. Note that the instruction
5566 to be reverse-executed is @emph{not} the one pointed to by the program
5567 counter, but the instruction executed prior to that one. For instance,
5568 if the last instruction was a jump, @code{reverse-stepi} will take you
5569 back from the destination of the jump to the jump instruction itself.
5571 @kindex reverse-next
5572 @kindex rn @r{(@code{reverse-next})}
5573 @item reverse-next @r{[}@var{count}@r{]}
5574 Run backward to the beginning of the previous line executed in
5575 the current (innermost) stack frame. If the line contains function
5576 calls, they will be ``un-executed'' without stopping. Starting from
5577 the first line of a function, @code{reverse-next} will take you back
5578 to the caller of that function, @emph{before} the function was called,
5579 just as the normal @code{next} command would take you from the last
5580 line of a function back to its return to its caller
5581 @footnote{Unless the code is too heavily optimized.}.
5583 @kindex reverse-nexti
5584 @kindex rni @r{(@code{reverse-nexti})}
5585 @item reverse-nexti @r{[}@var{count}@r{]}
5586 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5587 in reverse, except that called functions are ``un-executed'' atomically.
5588 That is, if the previously executed instruction was a return from
5589 another function, @code{reverse-nexti} will continue to execute
5590 in reverse until the call to that function (from the current stack
5593 @kindex reverse-finish
5594 @item reverse-finish
5595 Just as the @code{finish} command takes you to the point where the
5596 current function returns, @code{reverse-finish} takes you to the point
5597 where it was called. Instead of ending up at the end of the current
5598 function invocation, you end up at the beginning.
5600 @kindex set exec-direction
5601 @item set exec-direction
5602 Set the direction of target execution.
5603 @itemx set exec-direction reverse
5604 @cindex execute forward or backward in time
5605 @value{GDBN} will perform all execution commands in reverse, until the
5606 exec-direction mode is changed to ``forward''. Affected commands include
5607 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5608 command cannot be used in reverse mode.
5609 @item set exec-direction forward
5610 @value{GDBN} will perform all execution commands in the normal fashion.
5611 This is the default.
5615 @node Process Record and Replay
5616 @chapter Recording Inferior's Execution and Replaying It
5617 @cindex process record and replay
5618 @cindex recording inferior's execution and replaying it
5620 On some platforms, @value{GDBN} provides a special @dfn{process record
5621 and replay} target that can record a log of the process execution, and
5622 replay it later with both forward and reverse execution commands.
5625 When this target is in use, if the execution log includes the record
5626 for the next instruction, @value{GDBN} will debug in @dfn{replay
5627 mode}. In the replay mode, the inferior does not really execute code
5628 instructions. Instead, all the events that normally happen during
5629 code execution are taken from the execution log. While code is not
5630 really executed in replay mode, the values of registers (including the
5631 program counter register) and the memory of the inferior are still
5632 changed as they normally would. Their contents are taken from the
5636 If the record for the next instruction is not in the execution log,
5637 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5638 inferior executes normally, and @value{GDBN} records the execution log
5641 The process record and replay target supports reverse execution
5642 (@pxref{Reverse Execution}), even if the platform on which the
5643 inferior runs does not. However, the reverse execution is limited in
5644 this case by the range of the instructions recorded in the execution
5645 log. In other words, reverse execution on platforms that don't
5646 support it directly can only be done in the replay mode.
5648 When debugging in the reverse direction, @value{GDBN} will work in
5649 replay mode as long as the execution log includes the record for the
5650 previous instruction; otherwise, it will work in record mode, if the
5651 platform supports reverse execution, or stop if not.
5653 For architecture environments that support process record and replay,
5654 @value{GDBN} provides the following commands:
5657 @kindex target record
5661 This command starts the process record and replay target. The process
5662 record and replay target can only debug a process that is already
5663 running. Therefore, you need first to start the process with the
5664 @kbd{run} or @kbd{start} commands, and then start the recording with
5665 the @kbd{target record} command.
5667 Both @code{record} and @code{rec} are aliases of @code{target record}.
5669 @cindex displaced stepping, and process record and replay
5670 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5671 will be automatically disabled when process record and replay target
5672 is started. That's because the process record and replay target
5673 doesn't support displaced stepping.
5675 @cindex non-stop mode, and process record and replay
5676 @cindex asynchronous execution, and process record and replay
5677 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5678 the asynchronous execution mode (@pxref{Background Execution}), the
5679 process record and replay target cannot be started because it doesn't
5680 support these two modes.
5685 Stop the process record and replay target. When process record and
5686 replay target stops, the entire execution log will be deleted and the
5687 inferior will either be terminated, or will remain in its final state.
5689 When you stop the process record and replay target in record mode (at
5690 the end of the execution log), the inferior will be stopped at the
5691 next instruction that would have been recorded. In other words, if
5692 you record for a while and then stop recording, the inferior process
5693 will be left in the same state as if the recording never happened.
5695 On the other hand, if the process record and replay target is stopped
5696 while in replay mode (that is, not at the end of the execution log,
5697 but at some earlier point), the inferior process will become ``live''
5698 at that earlier state, and it will then be possible to continue the
5699 usual ``live'' debugging of the process from that state.
5701 When the inferior process exits, or @value{GDBN} detaches from it,
5702 process record and replay target will automatically stop itself.
5705 @item record save @var{filename}
5706 Save the execution log to a file @file{@var{filename}}.
5707 Default filename is @file{gdb_record.@var{process_id}}, where
5708 @var{process_id} is the process ID of the inferior.
5710 @kindex record restore
5711 @item record restore @var{filename}
5712 Restore the execution log from a file @file{@var{filename}}.
5713 File must have been created with @code{record save}.
5715 @kindex set record insn-number-max
5716 @item set record insn-number-max @var{limit}
5717 Set the limit of instructions to be recorded. Default value is 200000.
5719 If @var{limit} is a positive number, then @value{GDBN} will start
5720 deleting instructions from the log once the number of the record
5721 instructions becomes greater than @var{limit}. For every new recorded
5722 instruction, @value{GDBN} will delete the earliest recorded
5723 instruction to keep the number of recorded instructions at the limit.
5724 (Since deleting recorded instructions loses information, @value{GDBN}
5725 lets you control what happens when the limit is reached, by means of
5726 the @code{stop-at-limit} option, described below.)
5728 If @var{limit} is zero, @value{GDBN} will never delete recorded
5729 instructions from the execution log. The number of recorded
5730 instructions is unlimited in this case.
5732 @kindex show record insn-number-max
5733 @item show record insn-number-max
5734 Show the limit of instructions to be recorded.
5736 @kindex set record stop-at-limit
5737 @item set record stop-at-limit
5738 Control the behavior when the number of recorded instructions reaches
5739 the limit. If ON (the default), @value{GDBN} will stop when the limit
5740 is reached for the first time and ask you whether you want to stop the
5741 inferior or continue running it and recording the execution log. If
5742 you decide to continue recording, each new recorded instruction will
5743 cause the oldest one to be deleted.
5745 If this option is OFF, @value{GDBN} will automatically delete the
5746 oldest record to make room for each new one, without asking.
5748 @kindex show record stop-at-limit
5749 @item show record stop-at-limit
5750 Show the current setting of @code{stop-at-limit}.
5752 @kindex set record memory-query
5753 @item set record memory-query
5754 Control the behavior when @value{GDBN} is unable to record memory
5755 changes caused by an instruction. If ON, @value{GDBN} will query
5756 whether to stop the inferior in that case.
5758 If this option is OFF (the default), @value{GDBN} will automatically
5759 ignore the effect of such instructions on memory. Later, when
5760 @value{GDBN} replays this execution log, it will mark the log of this
5761 instruction as not accessible, and it will not affect the replay
5764 @kindex show record memory-query
5765 @item show record memory-query
5766 Show the current setting of @code{memory-query}.
5770 Show various statistics about the state of process record and its
5771 in-memory execution log buffer, including:
5775 Whether in record mode or replay mode.
5777 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5779 Highest recorded instruction number.
5781 Current instruction about to be replayed (if in replay mode).
5783 Number of instructions contained in the execution log.
5785 Maximum number of instructions that may be contained in the execution log.
5788 @kindex record delete
5791 When record target runs in replay mode (``in the past''), delete the
5792 subsequent execution log and begin to record a new execution log starting
5793 from the current address. This means you will abandon the previously
5794 recorded ``future'' and begin recording a new ``future''.
5799 @chapter Examining the Stack
5801 When your program has stopped, the first thing you need to know is where it
5802 stopped and how it got there.
5805 Each time your program performs a function call, information about the call
5807 That information includes the location of the call in your program,
5808 the arguments of the call,
5809 and the local variables of the function being called.
5810 The information is saved in a block of data called a @dfn{stack frame}.
5811 The stack frames are allocated in a region of memory called the @dfn{call
5814 When your program stops, the @value{GDBN} commands for examining the
5815 stack allow you to see all of this information.
5817 @cindex selected frame
5818 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5819 @value{GDBN} commands refer implicitly to the selected frame. In
5820 particular, whenever you ask @value{GDBN} for the value of a variable in
5821 your program, the value is found in the selected frame. There are
5822 special @value{GDBN} commands to select whichever frame you are
5823 interested in. @xref{Selection, ,Selecting a Frame}.
5825 When your program stops, @value{GDBN} automatically selects the
5826 currently executing frame and describes it briefly, similar to the
5827 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5830 * Frames:: Stack frames
5831 * Backtrace:: Backtraces
5832 * Selection:: Selecting a frame
5833 * Frame Info:: Information on a frame
5838 @section Stack Frames
5840 @cindex frame, definition
5842 The call stack is divided up into contiguous pieces called @dfn{stack
5843 frames}, or @dfn{frames} for short; each frame is the data associated
5844 with one call to one function. The frame contains the arguments given
5845 to the function, the function's local variables, and the address at
5846 which the function is executing.
5848 @cindex initial frame
5849 @cindex outermost frame
5850 @cindex innermost frame
5851 When your program is started, the stack has only one frame, that of the
5852 function @code{main}. This is called the @dfn{initial} frame or the
5853 @dfn{outermost} frame. Each time a function is called, a new frame is
5854 made. Each time a function returns, the frame for that function invocation
5855 is eliminated. If a function is recursive, there can be many frames for
5856 the same function. The frame for the function in which execution is
5857 actually occurring is called the @dfn{innermost} frame. This is the most
5858 recently created of all the stack frames that still exist.
5860 @cindex frame pointer
5861 Inside your program, stack frames are identified by their addresses. A
5862 stack frame consists of many bytes, each of which has its own address; each
5863 kind of computer has a convention for choosing one byte whose
5864 address serves as the address of the frame. Usually this address is kept
5865 in a register called the @dfn{frame pointer register}
5866 (@pxref{Registers, $fp}) while execution is going on in that frame.
5868 @cindex frame number
5869 @value{GDBN} assigns numbers to all existing stack frames, starting with
5870 zero for the innermost frame, one for the frame that called it,
5871 and so on upward. These numbers do not really exist in your program;
5872 they are assigned by @value{GDBN} to give you a way of designating stack
5873 frames in @value{GDBN} commands.
5875 @c The -fomit-frame-pointer below perennially causes hbox overflow
5876 @c underflow problems.
5877 @cindex frameless execution
5878 Some compilers provide a way to compile functions so that they operate
5879 without stack frames. (For example, the @value{NGCC} option
5881 @samp{-fomit-frame-pointer}
5883 generates functions without a frame.)
5884 This is occasionally done with heavily used library functions to save
5885 the frame setup time. @value{GDBN} has limited facilities for dealing
5886 with these function invocations. If the innermost function invocation
5887 has no stack frame, @value{GDBN} nevertheless regards it as though
5888 it had a separate frame, which is numbered zero as usual, allowing
5889 correct tracing of the function call chain. However, @value{GDBN} has
5890 no provision for frameless functions elsewhere in the stack.
5893 @kindex frame@r{, command}
5894 @cindex current stack frame
5895 @item frame @var{args}
5896 The @code{frame} command allows you to move from one stack frame to another,
5897 and to print the stack frame you select. @var{args} may be either the
5898 address of the frame or the stack frame number. Without an argument,
5899 @code{frame} prints the current stack frame.
5901 @kindex select-frame
5902 @cindex selecting frame silently
5904 The @code{select-frame} command allows you to move from one stack frame
5905 to another without printing the frame. This is the silent version of
5913 @cindex call stack traces
5914 A backtrace is a summary of how your program got where it is. It shows one
5915 line per frame, for many frames, starting with the currently executing
5916 frame (frame zero), followed by its caller (frame one), and on up the
5921 @kindex bt @r{(@code{backtrace})}
5924 Print a backtrace of the entire stack: one line per frame for all
5925 frames in the stack.
5927 You can stop the backtrace at any time by typing the system interrupt
5928 character, normally @kbd{Ctrl-c}.
5930 @item backtrace @var{n}
5932 Similar, but print only the innermost @var{n} frames.
5934 @item backtrace -@var{n}
5936 Similar, but print only the outermost @var{n} frames.
5938 @item backtrace full
5940 @itemx bt full @var{n}
5941 @itemx bt full -@var{n}
5942 Print the values of the local variables also. @var{n} specifies the
5943 number of frames to print, as described above.
5948 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5949 are additional aliases for @code{backtrace}.
5951 @cindex multiple threads, backtrace
5952 In a multi-threaded program, @value{GDBN} by default shows the
5953 backtrace only for the current thread. To display the backtrace for
5954 several or all of the threads, use the command @code{thread apply}
5955 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5956 apply all backtrace}, @value{GDBN} will display the backtrace for all
5957 the threads; this is handy when you debug a core dump of a
5958 multi-threaded program.
5960 Each line in the backtrace shows the frame number and the function name.
5961 The program counter value is also shown---unless you use @code{set
5962 print address off}. The backtrace also shows the source file name and
5963 line number, as well as the arguments to the function. The program
5964 counter value is omitted if it is at the beginning of the code for that
5967 Here is an example of a backtrace. It was made with the command
5968 @samp{bt 3}, so it shows the innermost three frames.
5972 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5974 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5975 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5977 (More stack frames follow...)
5982 The display for frame zero does not begin with a program counter
5983 value, indicating that your program has stopped at the beginning of the
5984 code for line @code{993} of @code{builtin.c}.
5987 The value of parameter @code{data} in frame 1 has been replaced by
5988 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5989 only if it is a scalar (integer, pointer, enumeration, etc). See command
5990 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5991 on how to configure the way function parameter values are printed.
5993 @cindex optimized out, in backtrace
5994 @cindex function call arguments, optimized out
5995 If your program was compiled with optimizations, some compilers will
5996 optimize away arguments passed to functions if those arguments are
5997 never used after the call. Such optimizations generate code that
5998 passes arguments through registers, but doesn't store those arguments
5999 in the stack frame. @value{GDBN} has no way of displaying such
6000 arguments in stack frames other than the innermost one. Here's what
6001 such a backtrace might look like:
6005 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6007 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6008 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6010 (More stack frames follow...)
6015 The values of arguments that were not saved in their stack frames are
6016 shown as @samp{<optimized out>}.
6018 If you need to display the values of such optimized-out arguments,
6019 either deduce that from other variables whose values depend on the one
6020 you are interested in, or recompile without optimizations.
6022 @cindex backtrace beyond @code{main} function
6023 @cindex program entry point
6024 @cindex startup code, and backtrace
6025 Most programs have a standard user entry point---a place where system
6026 libraries and startup code transition into user code. For C this is
6027 @code{main}@footnote{
6028 Note that embedded programs (the so-called ``free-standing''
6029 environment) are not required to have a @code{main} function as the
6030 entry point. They could even have multiple entry points.}.
6031 When @value{GDBN} finds the entry function in a backtrace
6032 it will terminate the backtrace, to avoid tracing into highly
6033 system-specific (and generally uninteresting) code.
6035 If you need to examine the startup code, or limit the number of levels
6036 in a backtrace, you can change this behavior:
6039 @item set backtrace past-main
6040 @itemx set backtrace past-main on
6041 @kindex set backtrace
6042 Backtraces will continue past the user entry point.
6044 @item set backtrace past-main off
6045 Backtraces will stop when they encounter the user entry point. This is the
6048 @item show backtrace past-main
6049 @kindex show backtrace
6050 Display the current user entry point backtrace policy.
6052 @item set backtrace past-entry
6053 @itemx set backtrace past-entry on
6054 Backtraces will continue past the internal entry point of an application.
6055 This entry point is encoded by the linker when the application is built,
6056 and is likely before the user entry point @code{main} (or equivalent) is called.
6058 @item set backtrace past-entry off
6059 Backtraces will stop when they encounter the internal entry point of an
6060 application. This is the default.
6062 @item show backtrace past-entry
6063 Display the current internal entry point backtrace policy.
6065 @item set backtrace limit @var{n}
6066 @itemx set backtrace limit 0
6067 @cindex backtrace limit
6068 Limit the backtrace to @var{n} levels. A value of zero means
6071 @item show backtrace limit
6072 Display the current limit on backtrace levels.
6076 @section Selecting a Frame
6078 Most commands for examining the stack and other data in your program work on
6079 whichever stack frame is selected at the moment. Here are the commands for
6080 selecting a stack frame; all of them finish by printing a brief description
6081 of the stack frame just selected.
6084 @kindex frame@r{, selecting}
6085 @kindex f @r{(@code{frame})}
6088 Select frame number @var{n}. Recall that frame zero is the innermost
6089 (currently executing) frame, frame one is the frame that called the
6090 innermost one, and so on. The highest-numbered frame is the one for
6093 @item frame @var{addr}
6095 Select the frame at address @var{addr}. This is useful mainly if the
6096 chaining of stack frames has been damaged by a bug, making it
6097 impossible for @value{GDBN} to assign numbers properly to all frames. In
6098 addition, this can be useful when your program has multiple stacks and
6099 switches between them.
6101 On the SPARC architecture, @code{frame} needs two addresses to
6102 select an arbitrary frame: a frame pointer and a stack pointer.
6104 On the MIPS and Alpha architecture, it needs two addresses: a stack
6105 pointer and a program counter.
6107 On the 29k architecture, it needs three addresses: a register stack
6108 pointer, a program counter, and a memory stack pointer.
6112 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6113 advances toward the outermost frame, to higher frame numbers, to frames
6114 that have existed longer. @var{n} defaults to one.
6117 @kindex do @r{(@code{down})}
6119 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6120 advances toward the innermost frame, to lower frame numbers, to frames
6121 that were created more recently. @var{n} defaults to one. You may
6122 abbreviate @code{down} as @code{do}.
6125 All of these commands end by printing two lines of output describing the
6126 frame. The first line shows the frame number, the function name, the
6127 arguments, and the source file and line number of execution in that
6128 frame. The second line shows the text of that source line.
6136 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6138 10 read_input_file (argv[i]);
6142 After such a printout, the @code{list} command with no arguments
6143 prints ten lines centered on the point of execution in the frame.
6144 You can also edit the program at the point of execution with your favorite
6145 editing program by typing @code{edit}.
6146 @xref{List, ,Printing Source Lines},
6150 @kindex down-silently
6152 @item up-silently @var{n}
6153 @itemx down-silently @var{n}
6154 These two commands are variants of @code{up} and @code{down},
6155 respectively; they differ in that they do their work silently, without
6156 causing display of the new frame. They are intended primarily for use
6157 in @value{GDBN} command scripts, where the output might be unnecessary and
6162 @section Information About a Frame
6164 There are several other commands to print information about the selected
6170 When used without any argument, this command does not change which
6171 frame is selected, but prints a brief description of the currently
6172 selected stack frame. It can be abbreviated @code{f}. With an
6173 argument, this command is used to select a stack frame.
6174 @xref{Selection, ,Selecting a Frame}.
6177 @kindex info f @r{(@code{info frame})}
6180 This command prints a verbose description of the selected stack frame,
6185 the address of the frame
6187 the address of the next frame down (called by this frame)
6189 the address of the next frame up (caller of this frame)
6191 the language in which the source code corresponding to this frame is written
6193 the address of the frame's arguments
6195 the address of the frame's local variables
6197 the program counter saved in it (the address of execution in the caller frame)
6199 which registers were saved in the frame
6202 @noindent The verbose description is useful when
6203 something has gone wrong that has made the stack format fail to fit
6204 the usual conventions.
6206 @item info frame @var{addr}
6207 @itemx info f @var{addr}
6208 Print a verbose description of the frame at address @var{addr}, without
6209 selecting that frame. The selected frame remains unchanged by this
6210 command. This requires the same kind of address (more than one for some
6211 architectures) that you specify in the @code{frame} command.
6212 @xref{Selection, ,Selecting a Frame}.
6216 Print the arguments of the selected frame, each on a separate line.
6220 Print the local variables of the selected frame, each on a separate
6221 line. These are all variables (declared either static or automatic)
6222 accessible at the point of execution of the selected frame.
6225 @cindex catch exceptions, list active handlers
6226 @cindex exception handlers, how to list
6228 Print a list of all the exception handlers that are active in the
6229 current stack frame at the current point of execution. To see other
6230 exception handlers, visit the associated frame (using the @code{up},
6231 @code{down}, or @code{frame} commands); then type @code{info catch}.
6232 @xref{Set Catchpoints, , Setting Catchpoints}.
6238 @chapter Examining Source Files
6240 @value{GDBN} can print parts of your program's source, since the debugging
6241 information recorded in the program tells @value{GDBN} what source files were
6242 used to build it. When your program stops, @value{GDBN} spontaneously prints
6243 the line where it stopped. Likewise, when you select a stack frame
6244 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6245 execution in that frame has stopped. You can print other portions of
6246 source files by explicit command.
6248 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6249 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6250 @value{GDBN} under @sc{gnu} Emacs}.
6253 * List:: Printing source lines
6254 * Specify Location:: How to specify code locations
6255 * Edit:: Editing source files
6256 * Search:: Searching source files
6257 * Source Path:: Specifying source directories
6258 * Machine Code:: Source and machine code
6262 @section Printing Source Lines
6265 @kindex l @r{(@code{list})}
6266 To print lines from a source file, use the @code{list} command
6267 (abbreviated @code{l}). By default, ten lines are printed.
6268 There are several ways to specify what part of the file you want to
6269 print; see @ref{Specify Location}, for the full list.
6271 Here are the forms of the @code{list} command most commonly used:
6274 @item list @var{linenum}
6275 Print lines centered around line number @var{linenum} in the
6276 current source file.
6278 @item list @var{function}
6279 Print lines centered around the beginning of function
6283 Print more lines. If the last lines printed were printed with a
6284 @code{list} command, this prints lines following the last lines
6285 printed; however, if the last line printed was a solitary line printed
6286 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6287 Stack}), this prints lines centered around that line.
6290 Print lines just before the lines last printed.
6293 @cindex @code{list}, how many lines to display
6294 By default, @value{GDBN} prints ten source lines with any of these forms of
6295 the @code{list} command. You can change this using @code{set listsize}:
6298 @kindex set listsize
6299 @item set listsize @var{count}
6300 Make the @code{list} command display @var{count} source lines (unless
6301 the @code{list} argument explicitly specifies some other number).
6303 @kindex show listsize
6305 Display the number of lines that @code{list} prints.
6308 Repeating a @code{list} command with @key{RET} discards the argument,
6309 so it is equivalent to typing just @code{list}. This is more useful
6310 than listing the same lines again. An exception is made for an
6311 argument of @samp{-}; that argument is preserved in repetition so that
6312 each repetition moves up in the source file.
6314 In general, the @code{list} command expects you to supply zero, one or two
6315 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6316 of writing them (@pxref{Specify Location}), but the effect is always
6317 to specify some source line.
6319 Here is a complete description of the possible arguments for @code{list}:
6322 @item list @var{linespec}
6323 Print lines centered around the line specified by @var{linespec}.
6325 @item list @var{first},@var{last}
6326 Print lines from @var{first} to @var{last}. Both arguments are
6327 linespecs. When a @code{list} command has two linespecs, and the
6328 source file of the second linespec is omitted, this refers to
6329 the same source file as the first linespec.
6331 @item list ,@var{last}
6332 Print lines ending with @var{last}.
6334 @item list @var{first},
6335 Print lines starting with @var{first}.
6338 Print lines just after the lines last printed.
6341 Print lines just before the lines last printed.
6344 As described in the preceding table.
6347 @node Specify Location
6348 @section Specifying a Location
6349 @cindex specifying location
6352 Several @value{GDBN} commands accept arguments that specify a location
6353 of your program's code. Since @value{GDBN} is a source-level
6354 debugger, a location usually specifies some line in the source code;
6355 for that reason, locations are also known as @dfn{linespecs}.
6357 Here are all the different ways of specifying a code location that
6358 @value{GDBN} understands:
6362 Specifies the line number @var{linenum} of the current source file.
6365 @itemx +@var{offset}
6366 Specifies the line @var{offset} lines before or after the @dfn{current
6367 line}. For the @code{list} command, the current line is the last one
6368 printed; for the breakpoint commands, this is the line at which
6369 execution stopped in the currently selected @dfn{stack frame}
6370 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6371 used as the second of the two linespecs in a @code{list} command,
6372 this specifies the line @var{offset} lines up or down from the first
6375 @item @var{filename}:@var{linenum}
6376 Specifies the line @var{linenum} in the source file @var{filename}.
6378 @item @var{function}
6379 Specifies the line that begins the body of the function @var{function}.
6380 For example, in C, this is the line with the open brace.
6382 @item @var{function}:@var{label}
6383 Specifies the line where @var{label} appears in @var{function}.
6385 @item @var{filename}:@var{function}
6386 Specifies the line that begins the body of the function @var{function}
6387 in the file @var{filename}. You only need the file name with a
6388 function name to avoid ambiguity when there are identically named
6389 functions in different source files.
6392 Specifies the line at which the label named @var{label} appears.
6393 @value{GDBN} searches for the label in the function corresponding to
6394 the currently selected stack frame. If there is no current selected
6395 stack frame (for instance, if the inferior is not running), then
6396 @value{GDBN} will not search for a label.
6398 @item *@var{address}
6399 Specifies the program address @var{address}. For line-oriented
6400 commands, such as @code{list} and @code{edit}, this specifies a source
6401 line that contains @var{address}. For @code{break} and other
6402 breakpoint oriented commands, this can be used to set breakpoints in
6403 parts of your program which do not have debugging information or
6406 Here @var{address} may be any expression valid in the current working
6407 language (@pxref{Languages, working language}) that specifies a code
6408 address. In addition, as a convenience, @value{GDBN} extends the
6409 semantics of expressions used in locations to cover the situations
6410 that frequently happen during debugging. Here are the various forms
6414 @item @var{expression}
6415 Any expression valid in the current working language.
6417 @item @var{funcaddr}
6418 An address of a function or procedure derived from its name. In C,
6419 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6420 simply the function's name @var{function} (and actually a special case
6421 of a valid expression). In Pascal and Modula-2, this is
6422 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6423 (although the Pascal form also works).
6425 This form specifies the address of the function's first instruction,
6426 before the stack frame and arguments have been set up.
6428 @item '@var{filename}'::@var{funcaddr}
6429 Like @var{funcaddr} above, but also specifies the name of the source
6430 file explicitly. This is useful if the name of the function does not
6431 specify the function unambiguously, e.g., if there are several
6432 functions with identical names in different source files.
6439 @section Editing Source Files
6440 @cindex editing source files
6443 @kindex e @r{(@code{edit})}
6444 To edit the lines in a source file, use the @code{edit} command.
6445 The editing program of your choice
6446 is invoked with the current line set to
6447 the active line in the program.
6448 Alternatively, there are several ways to specify what part of the file you
6449 want to print if you want to see other parts of the program:
6452 @item edit @var{location}
6453 Edit the source file specified by @code{location}. Editing starts at
6454 that @var{location}, e.g., at the specified source line of the
6455 specified file. @xref{Specify Location}, for all the possible forms
6456 of the @var{location} argument; here are the forms of the @code{edit}
6457 command most commonly used:
6460 @item edit @var{number}
6461 Edit the current source file with @var{number} as the active line number.
6463 @item edit @var{function}
6464 Edit the file containing @var{function} at the beginning of its definition.
6469 @subsection Choosing your Editor
6470 You can customize @value{GDBN} to use any editor you want
6472 The only restriction is that your editor (say @code{ex}), recognizes the
6473 following command-line syntax:
6475 ex +@var{number} file
6477 The optional numeric value +@var{number} specifies the number of the line in
6478 the file where to start editing.}.
6479 By default, it is @file{@value{EDITOR}}, but you can change this
6480 by setting the environment variable @code{EDITOR} before using
6481 @value{GDBN}. For example, to configure @value{GDBN} to use the
6482 @code{vi} editor, you could use these commands with the @code{sh} shell:
6488 or in the @code{csh} shell,
6490 setenv EDITOR /usr/bin/vi
6495 @section Searching Source Files
6496 @cindex searching source files
6498 There are two commands for searching through the current source file for a
6503 @kindex forward-search
6504 @item forward-search @var{regexp}
6505 @itemx search @var{regexp}
6506 The command @samp{forward-search @var{regexp}} checks each line,
6507 starting with the one following the last line listed, for a match for
6508 @var{regexp}. It lists the line that is found. You can use the
6509 synonym @samp{search @var{regexp}} or abbreviate the command name as
6512 @kindex reverse-search
6513 @item reverse-search @var{regexp}
6514 The command @samp{reverse-search @var{regexp}} checks each line, starting
6515 with the one before the last line listed and going backward, for a match
6516 for @var{regexp}. It lists the line that is found. You can abbreviate
6517 this command as @code{rev}.
6521 @section Specifying Source Directories
6524 @cindex directories for source files
6525 Executable programs sometimes do not record the directories of the source
6526 files from which they were compiled, just the names. Even when they do,
6527 the directories could be moved between the compilation and your debugging
6528 session. @value{GDBN} has a list of directories to search for source files;
6529 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6530 it tries all the directories in the list, in the order they are present
6531 in the list, until it finds a file with the desired name.
6533 For example, suppose an executable references the file
6534 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6535 @file{/mnt/cross}. The file is first looked up literally; if this
6536 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6537 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6538 message is printed. @value{GDBN} does not look up the parts of the
6539 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6540 Likewise, the subdirectories of the source path are not searched: if
6541 the source path is @file{/mnt/cross}, and the binary refers to
6542 @file{foo.c}, @value{GDBN} would not find it under
6543 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6545 Plain file names, relative file names with leading directories, file
6546 names containing dots, etc.@: are all treated as described above; for
6547 instance, if the source path is @file{/mnt/cross}, and the source file
6548 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6549 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6550 that---@file{/mnt/cross/foo.c}.
6552 Note that the executable search path is @emph{not} used to locate the
6555 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6556 any information it has cached about where source files are found and where
6557 each line is in the file.
6561 When you start @value{GDBN}, its source path includes only @samp{cdir}
6562 and @samp{cwd}, in that order.
6563 To add other directories, use the @code{directory} command.
6565 The search path is used to find both program source files and @value{GDBN}
6566 script files (read using the @samp{-command} option and @samp{source} command).
6568 In addition to the source path, @value{GDBN} provides a set of commands
6569 that manage a list of source path substitution rules. A @dfn{substitution
6570 rule} specifies how to rewrite source directories stored in the program's
6571 debug information in case the sources were moved to a different
6572 directory between compilation and debugging. A rule is made of
6573 two strings, the first specifying what needs to be rewritten in
6574 the path, and the second specifying how it should be rewritten.
6575 In @ref{set substitute-path}, we name these two parts @var{from} and
6576 @var{to} respectively. @value{GDBN} does a simple string replacement
6577 of @var{from} with @var{to} at the start of the directory part of the
6578 source file name, and uses that result instead of the original file
6579 name to look up the sources.
6581 Using the previous example, suppose the @file{foo-1.0} tree has been
6582 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6583 @value{GDBN} to replace @file{/usr/src} in all source path names with
6584 @file{/mnt/cross}. The first lookup will then be
6585 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6586 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6587 substitution rule, use the @code{set substitute-path} command
6588 (@pxref{set substitute-path}).
6590 To avoid unexpected substitution results, a rule is applied only if the
6591 @var{from} part of the directory name ends at a directory separator.
6592 For instance, a rule substituting @file{/usr/source} into
6593 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6594 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6595 is applied only at the beginning of the directory name, this rule will
6596 not be applied to @file{/root/usr/source/baz.c} either.
6598 In many cases, you can achieve the same result using the @code{directory}
6599 command. However, @code{set substitute-path} can be more efficient in
6600 the case where the sources are organized in a complex tree with multiple
6601 subdirectories. With the @code{directory} command, you need to add each
6602 subdirectory of your project. If you moved the entire tree while
6603 preserving its internal organization, then @code{set substitute-path}
6604 allows you to direct the debugger to all the sources with one single
6607 @code{set substitute-path} is also more than just a shortcut command.
6608 The source path is only used if the file at the original location no
6609 longer exists. On the other hand, @code{set substitute-path} modifies
6610 the debugger behavior to look at the rewritten location instead. So, if
6611 for any reason a source file that is not relevant to your executable is
6612 located at the original location, a substitution rule is the only
6613 method available to point @value{GDBN} at the new location.
6615 @cindex @samp{--with-relocated-sources}
6616 @cindex default source path substitution
6617 You can configure a default source path substitution rule by
6618 configuring @value{GDBN} with the
6619 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6620 should be the name of a directory under @value{GDBN}'s configured
6621 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6622 directory names in debug information under @var{dir} will be adjusted
6623 automatically if the installed @value{GDBN} is moved to a new
6624 location. This is useful if @value{GDBN}, libraries or executables
6625 with debug information and corresponding source code are being moved
6629 @item directory @var{dirname} @dots{}
6630 @item dir @var{dirname} @dots{}
6631 Add directory @var{dirname} to the front of the source path. Several
6632 directory names may be given to this command, separated by @samp{:}
6633 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6634 part of absolute file names) or
6635 whitespace. You may specify a directory that is already in the source
6636 path; this moves it forward, so @value{GDBN} searches it sooner.
6640 @vindex $cdir@r{, convenience variable}
6641 @vindex $cwd@r{, convenience variable}
6642 @cindex compilation directory
6643 @cindex current directory
6644 @cindex working directory
6645 @cindex directory, current
6646 @cindex directory, compilation
6647 You can use the string @samp{$cdir} to refer to the compilation
6648 directory (if one is recorded), and @samp{$cwd} to refer to the current
6649 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6650 tracks the current working directory as it changes during your @value{GDBN}
6651 session, while the latter is immediately expanded to the current
6652 directory at the time you add an entry to the source path.
6655 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6657 @c RET-repeat for @code{directory} is explicitly disabled, but since
6658 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6660 @item set directories @var{path-list}
6661 @kindex set directories
6662 Set the source path to @var{path-list}.
6663 @samp{$cdir:$cwd} are added if missing.
6665 @item show directories
6666 @kindex show directories
6667 Print the source path: show which directories it contains.
6669 @anchor{set substitute-path}
6670 @item set substitute-path @var{from} @var{to}
6671 @kindex set substitute-path
6672 Define a source path substitution rule, and add it at the end of the
6673 current list of existing substitution rules. If a rule with the same
6674 @var{from} was already defined, then the old rule is also deleted.
6676 For example, if the file @file{/foo/bar/baz.c} was moved to
6677 @file{/mnt/cross/baz.c}, then the command
6680 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6684 will tell @value{GDBN} to replace @samp{/usr/src} with
6685 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6686 @file{baz.c} even though it was moved.
6688 In the case when more than one substitution rule have been defined,
6689 the rules are evaluated one by one in the order where they have been
6690 defined. The first one matching, if any, is selected to perform
6693 For instance, if we had entered the following commands:
6696 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6697 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6701 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6702 @file{/mnt/include/defs.h} by using the first rule. However, it would
6703 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6704 @file{/mnt/src/lib/foo.c}.
6707 @item unset substitute-path [path]
6708 @kindex unset substitute-path
6709 If a path is specified, search the current list of substitution rules
6710 for a rule that would rewrite that path. Delete that rule if found.
6711 A warning is emitted by the debugger if no rule could be found.
6713 If no path is specified, then all substitution rules are deleted.
6715 @item show substitute-path [path]
6716 @kindex show substitute-path
6717 If a path is specified, then print the source path substitution rule
6718 which would rewrite that path, if any.
6720 If no path is specified, then print all existing source path substitution
6725 If your source path is cluttered with directories that are no longer of
6726 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6727 versions of source. You can correct the situation as follows:
6731 Use @code{directory} with no argument to reset the source path to its default value.
6734 Use @code{directory} with suitable arguments to reinstall the
6735 directories you want in the source path. You can add all the
6736 directories in one command.
6740 @section Source and Machine Code
6741 @cindex source line and its code address
6743 You can use the command @code{info line} to map source lines to program
6744 addresses (and vice versa), and the command @code{disassemble} to display
6745 a range of addresses as machine instructions. You can use the command
6746 @code{set disassemble-next-line} to set whether to disassemble next
6747 source line when execution stops. When run under @sc{gnu} Emacs
6748 mode, the @code{info line} command causes the arrow to point to the
6749 line specified. Also, @code{info line} prints addresses in symbolic form as
6754 @item info line @var{linespec}
6755 Print the starting and ending addresses of the compiled code for
6756 source line @var{linespec}. You can specify source lines in any of
6757 the ways documented in @ref{Specify Location}.
6760 For example, we can use @code{info line} to discover the location of
6761 the object code for the first line of function
6762 @code{m4_changequote}:
6764 @c FIXME: I think this example should also show the addresses in
6765 @c symbolic form, as they usually would be displayed.
6767 (@value{GDBP}) info line m4_changequote
6768 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6772 @cindex code address and its source line
6773 We can also inquire (using @code{*@var{addr}} as the form for
6774 @var{linespec}) what source line covers a particular address:
6776 (@value{GDBP}) info line *0x63ff
6777 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6780 @cindex @code{$_} and @code{info line}
6781 @cindex @code{x} command, default address
6782 @kindex x@r{(examine), and} info line
6783 After @code{info line}, the default address for the @code{x} command
6784 is changed to the starting address of the line, so that @samp{x/i} is
6785 sufficient to begin examining the machine code (@pxref{Memory,
6786 ,Examining Memory}). Also, this address is saved as the value of the
6787 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6792 @cindex assembly instructions
6793 @cindex instructions, assembly
6794 @cindex machine instructions
6795 @cindex listing machine instructions
6797 @itemx disassemble /m
6798 @itemx disassemble /r
6799 This specialized command dumps a range of memory as machine
6800 instructions. It can also print mixed source+disassembly by specifying
6801 the @code{/m} modifier and print the raw instructions in hex as well as
6802 in symbolic form by specifying the @code{/r}.
6803 The default memory range is the function surrounding the
6804 program counter of the selected frame. A single argument to this
6805 command is a program counter value; @value{GDBN} dumps the function
6806 surrounding this value. When two arguments are given, they should
6807 be separated by a comma, possibly surrounded by whitespace. The
6808 arguments specify a range of addresses to dump, in one of two forms:
6811 @item @var{start},@var{end}
6812 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6813 @item @var{start},+@var{length}
6814 the addresses from @var{start} (inclusive) to
6815 @code{@var{start}+@var{length}} (exclusive).
6819 When 2 arguments are specified, the name of the function is also
6820 printed (since there could be several functions in the given range).
6822 The argument(s) can be any expression yielding a numeric value, such as
6823 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6825 If the range of memory being disassembled contains current program counter,
6826 the instruction at that location is shown with a @code{=>} marker.
6829 The following example shows the disassembly of a range of addresses of
6830 HP PA-RISC 2.0 code:
6833 (@value{GDBP}) disas 0x32c4, 0x32e4
6834 Dump of assembler code from 0x32c4 to 0x32e4:
6835 0x32c4 <main+204>: addil 0,dp
6836 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6837 0x32cc <main+212>: ldil 0x3000,r31
6838 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6839 0x32d4 <main+220>: ldo 0(r31),rp
6840 0x32d8 <main+224>: addil -0x800,dp
6841 0x32dc <main+228>: ldo 0x588(r1),r26
6842 0x32e0 <main+232>: ldil 0x3000,r31
6843 End of assembler dump.
6846 Here is an example showing mixed source+assembly for Intel x86, when the
6847 program is stopped just after function prologue:
6850 (@value{GDBP}) disas /m main
6851 Dump of assembler code for function main:
6853 0x08048330 <+0>: push %ebp
6854 0x08048331 <+1>: mov %esp,%ebp
6855 0x08048333 <+3>: sub $0x8,%esp
6856 0x08048336 <+6>: and $0xfffffff0,%esp
6857 0x08048339 <+9>: sub $0x10,%esp
6859 6 printf ("Hello.\n");
6860 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6861 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6865 0x08048348 <+24>: mov $0x0,%eax
6866 0x0804834d <+29>: leave
6867 0x0804834e <+30>: ret
6869 End of assembler dump.
6872 Here is another example showing raw instructions in hex for AMD x86-64,
6875 (gdb) disas /r 0x400281,+10
6876 Dump of assembler code from 0x400281 to 0x40028b:
6877 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6878 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6879 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6880 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6881 End of assembler dump.
6884 Some architectures have more than one commonly-used set of instruction
6885 mnemonics or other syntax.
6887 For programs that were dynamically linked and use shared libraries,
6888 instructions that call functions or branch to locations in the shared
6889 libraries might show a seemingly bogus location---it's actually a
6890 location of the relocation table. On some architectures, @value{GDBN}
6891 might be able to resolve these to actual function names.
6894 @kindex set disassembly-flavor
6895 @cindex Intel disassembly flavor
6896 @cindex AT&T disassembly flavor
6897 @item set disassembly-flavor @var{instruction-set}
6898 Select the instruction set to use when disassembling the
6899 program via the @code{disassemble} or @code{x/i} commands.
6901 Currently this command is only defined for the Intel x86 family. You
6902 can set @var{instruction-set} to either @code{intel} or @code{att}.
6903 The default is @code{att}, the AT&T flavor used by default by Unix
6904 assemblers for x86-based targets.
6906 @kindex show disassembly-flavor
6907 @item show disassembly-flavor
6908 Show the current setting of the disassembly flavor.
6912 @kindex set disassemble-next-line
6913 @kindex show disassemble-next-line
6914 @item set disassemble-next-line
6915 @itemx show disassemble-next-line
6916 Control whether or not @value{GDBN} will disassemble the next source
6917 line or instruction when execution stops. If ON, @value{GDBN} will
6918 display disassembly of the next source line when execution of the
6919 program being debugged stops. This is @emph{in addition} to
6920 displaying the source line itself, which @value{GDBN} always does if
6921 possible. If the next source line cannot be displayed for some reason
6922 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6923 info in the debug info), @value{GDBN} will display disassembly of the
6924 next @emph{instruction} instead of showing the next source line. If
6925 AUTO, @value{GDBN} will display disassembly of next instruction only
6926 if the source line cannot be displayed. This setting causes
6927 @value{GDBN} to display some feedback when you step through a function
6928 with no line info or whose source file is unavailable. The default is
6929 OFF, which means never display the disassembly of the next line or
6935 @chapter Examining Data
6937 @cindex printing data
6938 @cindex examining data
6941 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6942 @c document because it is nonstandard... Under Epoch it displays in a
6943 @c different window or something like that.
6944 The usual way to examine data in your program is with the @code{print}
6945 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6946 evaluates and prints the value of an expression of the language your
6947 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6948 Different Languages}). It may also print the expression using a
6949 Python-based pretty-printer (@pxref{Pretty Printing}).
6952 @item print @var{expr}
6953 @itemx print /@var{f} @var{expr}
6954 @var{expr} is an expression (in the source language). By default the
6955 value of @var{expr} is printed in a format appropriate to its data type;
6956 you can choose a different format by specifying @samp{/@var{f}}, where
6957 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6961 @itemx print /@var{f}
6962 @cindex reprint the last value
6963 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6964 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6965 conveniently inspect the same value in an alternative format.
6968 A more low-level way of examining data is with the @code{x} command.
6969 It examines data in memory at a specified address and prints it in a
6970 specified format. @xref{Memory, ,Examining Memory}.
6972 If you are interested in information about types, or about how the
6973 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6974 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6978 * Expressions:: Expressions
6979 * Ambiguous Expressions:: Ambiguous Expressions
6980 * Variables:: Program variables
6981 * Arrays:: Artificial arrays
6982 * Output Formats:: Output formats
6983 * Memory:: Examining memory
6984 * Auto Display:: Automatic display
6985 * Print Settings:: Print settings
6986 * Pretty Printing:: Python pretty printing
6987 * Value History:: Value history
6988 * Convenience Vars:: Convenience variables
6989 * Registers:: Registers
6990 * Floating Point Hardware:: Floating point hardware
6991 * Vector Unit:: Vector Unit
6992 * OS Information:: Auxiliary data provided by operating system
6993 * Memory Region Attributes:: Memory region attributes
6994 * Dump/Restore Files:: Copy between memory and a file
6995 * Core File Generation:: Cause a program dump its core
6996 * Character Sets:: Debugging programs that use a different
6997 character set than GDB does
6998 * Caching Remote Data:: Data caching for remote targets
6999 * Searching Memory:: Searching memory for a sequence of bytes
7003 @section Expressions
7006 @code{print} and many other @value{GDBN} commands accept an expression and
7007 compute its value. Any kind of constant, variable or operator defined
7008 by the programming language you are using is valid in an expression in
7009 @value{GDBN}. This includes conditional expressions, function calls,
7010 casts, and string constants. It also includes preprocessor macros, if
7011 you compiled your program to include this information; see
7014 @cindex arrays in expressions
7015 @value{GDBN} supports array constants in expressions input by
7016 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7017 you can use the command @code{print @{1, 2, 3@}} to create an array
7018 of three integers. If you pass an array to a function or assign it
7019 to a program variable, @value{GDBN} copies the array to memory that
7020 is @code{malloc}ed in the target program.
7022 Because C is so widespread, most of the expressions shown in examples in
7023 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7024 Languages}, for information on how to use expressions in other
7027 In this section, we discuss operators that you can use in @value{GDBN}
7028 expressions regardless of your programming language.
7030 @cindex casts, in expressions
7031 Casts are supported in all languages, not just in C, because it is so
7032 useful to cast a number into a pointer in order to examine a structure
7033 at that address in memory.
7034 @c FIXME: casts supported---Mod2 true?
7036 @value{GDBN} supports these operators, in addition to those common
7037 to programming languages:
7041 @samp{@@} is a binary operator for treating parts of memory as arrays.
7042 @xref{Arrays, ,Artificial Arrays}, for more information.
7045 @samp{::} allows you to specify a variable in terms of the file or
7046 function where it is defined. @xref{Variables, ,Program Variables}.
7048 @cindex @{@var{type}@}
7049 @cindex type casting memory
7050 @cindex memory, viewing as typed object
7051 @cindex casts, to view memory
7052 @item @{@var{type}@} @var{addr}
7053 Refers to an object of type @var{type} stored at address @var{addr} in
7054 memory. @var{addr} may be any expression whose value is an integer or
7055 pointer (but parentheses are required around binary operators, just as in
7056 a cast). This construct is allowed regardless of what kind of data is
7057 normally supposed to reside at @var{addr}.
7060 @node Ambiguous Expressions
7061 @section Ambiguous Expressions
7062 @cindex ambiguous expressions
7064 Expressions can sometimes contain some ambiguous elements. For instance,
7065 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7066 a single function name to be defined several times, for application in
7067 different contexts. This is called @dfn{overloading}. Another example
7068 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7069 templates and is typically instantiated several times, resulting in
7070 the same function name being defined in different contexts.
7072 In some cases and depending on the language, it is possible to adjust
7073 the expression to remove the ambiguity. For instance in C@t{++}, you
7074 can specify the signature of the function you want to break on, as in
7075 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7076 qualified name of your function often makes the expression unambiguous
7079 When an ambiguity that needs to be resolved is detected, the debugger
7080 has the capability to display a menu of numbered choices for each
7081 possibility, and then waits for the selection with the prompt @samp{>}.
7082 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7083 aborts the current command. If the command in which the expression was
7084 used allows more than one choice to be selected, the next option in the
7085 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7088 For example, the following session excerpt shows an attempt to set a
7089 breakpoint at the overloaded symbol @code{String::after}.
7090 We choose three particular definitions of that function name:
7092 @c FIXME! This is likely to change to show arg type lists, at least
7095 (@value{GDBP}) b String::after
7098 [2] file:String.cc; line number:867
7099 [3] file:String.cc; line number:860
7100 [4] file:String.cc; line number:875
7101 [5] file:String.cc; line number:853
7102 [6] file:String.cc; line number:846
7103 [7] file:String.cc; line number:735
7105 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7106 Breakpoint 2 at 0xb344: file String.cc, line 875.
7107 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7108 Multiple breakpoints were set.
7109 Use the "delete" command to delete unwanted
7116 @kindex set multiple-symbols
7117 @item set multiple-symbols @var{mode}
7118 @cindex multiple-symbols menu
7120 This option allows you to adjust the debugger behavior when an expression
7123 By default, @var{mode} is set to @code{all}. If the command with which
7124 the expression is used allows more than one choice, then @value{GDBN}
7125 automatically selects all possible choices. For instance, inserting
7126 a breakpoint on a function using an ambiguous name results in a breakpoint
7127 inserted on each possible match. However, if a unique choice must be made,
7128 then @value{GDBN} uses the menu to help you disambiguate the expression.
7129 For instance, printing the address of an overloaded function will result
7130 in the use of the menu.
7132 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7133 when an ambiguity is detected.
7135 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7136 an error due to the ambiguity and the command is aborted.
7138 @kindex show multiple-symbols
7139 @item show multiple-symbols
7140 Show the current value of the @code{multiple-symbols} setting.
7144 @section Program Variables
7146 The most common kind of expression to use is the name of a variable
7149 Variables in expressions are understood in the selected stack frame
7150 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7154 global (or file-static)
7161 visible according to the scope rules of the
7162 programming language from the point of execution in that frame
7165 @noindent This means that in the function
7180 you can examine and use the variable @code{a} whenever your program is
7181 executing within the function @code{foo}, but you can only use or
7182 examine the variable @code{b} while your program is executing inside
7183 the block where @code{b} is declared.
7185 @cindex variable name conflict
7186 There is an exception: you can refer to a variable or function whose
7187 scope is a single source file even if the current execution point is not
7188 in this file. But it is possible to have more than one such variable or
7189 function with the same name (in different source files). If that
7190 happens, referring to that name has unpredictable effects. If you wish,
7191 you can specify a static variable in a particular function or file,
7192 using the colon-colon (@code{::}) notation:
7194 @cindex colon-colon, context for variables/functions
7196 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7197 @cindex @code{::}, context for variables/functions
7200 @var{file}::@var{variable}
7201 @var{function}::@var{variable}
7205 Here @var{file} or @var{function} is the name of the context for the
7206 static @var{variable}. In the case of file names, you can use quotes to
7207 make sure @value{GDBN} parses the file name as a single word---for example,
7208 to print a global value of @code{x} defined in @file{f2.c}:
7211 (@value{GDBP}) p 'f2.c'::x
7214 @cindex C@t{++} scope resolution
7215 This use of @samp{::} is very rarely in conflict with the very similar
7216 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7217 scope resolution operator in @value{GDBN} expressions.
7218 @c FIXME: Um, so what happens in one of those rare cases where it's in
7221 @cindex wrong values
7222 @cindex variable values, wrong
7223 @cindex function entry/exit, wrong values of variables
7224 @cindex optimized code, wrong values of variables
7226 @emph{Warning:} Occasionally, a local variable may appear to have the
7227 wrong value at certain points in a function---just after entry to a new
7228 scope, and just before exit.
7230 You may see this problem when you are stepping by machine instructions.
7231 This is because, on most machines, it takes more than one instruction to
7232 set up a stack frame (including local variable definitions); if you are
7233 stepping by machine instructions, variables may appear to have the wrong
7234 values until the stack frame is completely built. On exit, it usually
7235 also takes more than one machine instruction to destroy a stack frame;
7236 after you begin stepping through that group of instructions, local
7237 variable definitions may be gone.
7239 This may also happen when the compiler does significant optimizations.
7240 To be sure of always seeing accurate values, turn off all optimization
7243 @cindex ``No symbol "foo" in current context''
7244 Another possible effect of compiler optimizations is to optimize
7245 unused variables out of existence, or assign variables to registers (as
7246 opposed to memory addresses). Depending on the support for such cases
7247 offered by the debug info format used by the compiler, @value{GDBN}
7248 might not be able to display values for such local variables. If that
7249 happens, @value{GDBN} will print a message like this:
7252 No symbol "foo" in current context.
7255 To solve such problems, either recompile without optimizations, or use a
7256 different debug info format, if the compiler supports several such
7257 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7258 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7259 produces debug info in a format that is superior to formats such as
7260 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7261 an effective form for debug info. @xref{Debugging Options,,Options
7262 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7263 Compiler Collection (GCC)}.
7264 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7265 that are best suited to C@t{++} programs.
7267 If you ask to print an object whose contents are unknown to
7268 @value{GDBN}, e.g., because its data type is not completely specified
7269 by the debug information, @value{GDBN} will say @samp{<incomplete
7270 type>}. @xref{Symbols, incomplete type}, for more about this.
7272 Strings are identified as arrays of @code{char} values without specified
7273 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7274 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7275 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7276 defines literal string type @code{"char"} as @code{char} without a sign.
7281 signed char var1[] = "A";
7284 You get during debugging
7289 $2 = @{65 'A', 0 '\0'@}
7293 @section Artificial Arrays
7295 @cindex artificial array
7297 @kindex @@@r{, referencing memory as an array}
7298 It is often useful to print out several successive objects of the
7299 same type in memory; a section of an array, or an array of
7300 dynamically determined size for which only a pointer exists in the
7303 You can do this by referring to a contiguous span of memory as an
7304 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7305 operand of @samp{@@} should be the first element of the desired array
7306 and be an individual object. The right operand should be the desired length
7307 of the array. The result is an array value whose elements are all of
7308 the type of the left argument. The first element is actually the left
7309 argument; the second element comes from bytes of memory immediately
7310 following those that hold the first element, and so on. Here is an
7311 example. If a program says
7314 int *array = (int *) malloc (len * sizeof (int));
7318 you can print the contents of @code{array} with
7324 The left operand of @samp{@@} must reside in memory. Array values made
7325 with @samp{@@} in this way behave just like other arrays in terms of
7326 subscripting, and are coerced to pointers when used in expressions.
7327 Artificial arrays most often appear in expressions via the value history
7328 (@pxref{Value History, ,Value History}), after printing one out.
7330 Another way to create an artificial array is to use a cast.
7331 This re-interprets a value as if it were an array.
7332 The value need not be in memory:
7334 (@value{GDBP}) p/x (short[2])0x12345678
7335 $1 = @{0x1234, 0x5678@}
7338 As a convenience, if you leave the array length out (as in
7339 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7340 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7342 (@value{GDBP}) p/x (short[])0x12345678
7343 $2 = @{0x1234, 0x5678@}
7346 Sometimes the artificial array mechanism is not quite enough; in
7347 moderately complex data structures, the elements of interest may not
7348 actually be adjacent---for example, if you are interested in the values
7349 of pointers in an array. One useful work-around in this situation is
7350 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7351 Variables}) as a counter in an expression that prints the first
7352 interesting value, and then repeat that expression via @key{RET}. For
7353 instance, suppose you have an array @code{dtab} of pointers to
7354 structures, and you are interested in the values of a field @code{fv}
7355 in each structure. Here is an example of what you might type:
7365 @node Output Formats
7366 @section Output Formats
7368 @cindex formatted output
7369 @cindex output formats
7370 By default, @value{GDBN} prints a value according to its data type. Sometimes
7371 this is not what you want. For example, you might want to print a number
7372 in hex, or a pointer in decimal. Or you might want to view data in memory
7373 at a certain address as a character string or as an instruction. To do
7374 these things, specify an @dfn{output format} when you print a value.
7376 The simplest use of output formats is to say how to print a value
7377 already computed. This is done by starting the arguments of the
7378 @code{print} command with a slash and a format letter. The format
7379 letters supported are:
7383 Regard the bits of the value as an integer, and print the integer in
7387 Print as integer in signed decimal.
7390 Print as integer in unsigned decimal.
7393 Print as integer in octal.
7396 Print as integer in binary. The letter @samp{t} stands for ``two''.
7397 @footnote{@samp{b} cannot be used because these format letters are also
7398 used with the @code{x} command, where @samp{b} stands for ``byte'';
7399 see @ref{Memory,,Examining Memory}.}
7402 @cindex unknown address, locating
7403 @cindex locate address
7404 Print as an address, both absolute in hexadecimal and as an offset from
7405 the nearest preceding symbol. You can use this format used to discover
7406 where (in what function) an unknown address is located:
7409 (@value{GDBP}) p/a 0x54320
7410 $3 = 0x54320 <_initialize_vx+396>
7414 The command @code{info symbol 0x54320} yields similar results.
7415 @xref{Symbols, info symbol}.
7418 Regard as an integer and print it as a character constant. This
7419 prints both the numerical value and its character representation. The
7420 character representation is replaced with the octal escape @samp{\nnn}
7421 for characters outside the 7-bit @sc{ascii} range.
7423 Without this format, @value{GDBN} displays @code{char},
7424 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7425 constants. Single-byte members of vectors are displayed as integer
7429 Regard the bits of the value as a floating point number and print
7430 using typical floating point syntax.
7433 @cindex printing strings
7434 @cindex printing byte arrays
7435 Regard as a string, if possible. With this format, pointers to single-byte
7436 data are displayed as null-terminated strings and arrays of single-byte data
7437 are displayed as fixed-length strings. Other values are displayed in their
7440 Without this format, @value{GDBN} displays pointers to and arrays of
7441 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7442 strings. Single-byte members of a vector are displayed as an integer
7446 @cindex raw printing
7447 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7448 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7449 Printing}). This typically results in a higher-level display of the
7450 value's contents. The @samp{r} format bypasses any Python
7451 pretty-printer which might exist.
7454 For example, to print the program counter in hex (@pxref{Registers}), type
7461 Note that no space is required before the slash; this is because command
7462 names in @value{GDBN} cannot contain a slash.
7464 To reprint the last value in the value history with a different format,
7465 you can use the @code{print} command with just a format and no
7466 expression. For example, @samp{p/x} reprints the last value in hex.
7469 @section Examining Memory
7471 You can use the command @code{x} (for ``examine'') to examine memory in
7472 any of several formats, independently of your program's data types.
7474 @cindex examining memory
7476 @kindex x @r{(examine memory)}
7477 @item x/@var{nfu} @var{addr}
7480 Use the @code{x} command to examine memory.
7483 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7484 much memory to display and how to format it; @var{addr} is an
7485 expression giving the address where you want to start displaying memory.
7486 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7487 Several commands set convenient defaults for @var{addr}.
7490 @item @var{n}, the repeat count
7491 The repeat count is a decimal integer; the default is 1. It specifies
7492 how much memory (counting by units @var{u}) to display.
7493 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7496 @item @var{f}, the display format
7497 The display format is one of the formats used by @code{print}
7498 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7499 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7500 The default is @samp{x} (hexadecimal) initially. The default changes
7501 each time you use either @code{x} or @code{print}.
7503 @item @var{u}, the unit size
7504 The unit size is any of
7510 Halfwords (two bytes).
7512 Words (four bytes). This is the initial default.
7514 Giant words (eight bytes).
7517 Each time you specify a unit size with @code{x}, that size becomes the
7518 default unit the next time you use @code{x}. For the @samp{i} format,
7519 the unit size is ignored and is normally not written. For the @samp{s} format,
7520 the unit size defaults to @samp{b}, unless it is explicitly given.
7521 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7522 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7523 Note that the results depend on the programming language of the
7524 current compilation unit. If the language is C, the @samp{s}
7525 modifier will use the UTF-16 encoding while @samp{w} will use
7526 UTF-32. The encoding is set by the programming language and cannot
7529 @item @var{addr}, starting display address
7530 @var{addr} is the address where you want @value{GDBN} to begin displaying
7531 memory. The expression need not have a pointer value (though it may);
7532 it is always interpreted as an integer address of a byte of memory.
7533 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7534 @var{addr} is usually just after the last address examined---but several
7535 other commands also set the default address: @code{info breakpoints} (to
7536 the address of the last breakpoint listed), @code{info line} (to the
7537 starting address of a line), and @code{print} (if you use it to display
7538 a value from memory).
7541 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7542 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7543 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7544 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7545 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7547 Since the letters indicating unit sizes are all distinct from the
7548 letters specifying output formats, you do not have to remember whether
7549 unit size or format comes first; either order works. The output
7550 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7551 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7553 Even though the unit size @var{u} is ignored for the formats @samp{s}
7554 and @samp{i}, you might still want to use a count @var{n}; for example,
7555 @samp{3i} specifies that you want to see three machine instructions,
7556 including any operands. For convenience, especially when used with
7557 the @code{display} command, the @samp{i} format also prints branch delay
7558 slot instructions, if any, beyond the count specified, which immediately
7559 follow the last instruction that is within the count. The command
7560 @code{disassemble} gives an alternative way of inspecting machine
7561 instructions; see @ref{Machine Code,,Source and Machine Code}.
7563 All the defaults for the arguments to @code{x} are designed to make it
7564 easy to continue scanning memory with minimal specifications each time
7565 you use @code{x}. For example, after you have inspected three machine
7566 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7567 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7568 the repeat count @var{n} is used again; the other arguments default as
7569 for successive uses of @code{x}.
7571 When examining machine instructions, the instruction at current program
7572 counter is shown with a @code{=>} marker. For example:
7575 (@value{GDBP}) x/5i $pc-6
7576 0x804837f <main+11>: mov %esp,%ebp
7577 0x8048381 <main+13>: push %ecx
7578 0x8048382 <main+14>: sub $0x4,%esp
7579 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7580 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7583 @cindex @code{$_}, @code{$__}, and value history
7584 The addresses and contents printed by the @code{x} command are not saved
7585 in the value history because there is often too much of them and they
7586 would get in the way. Instead, @value{GDBN} makes these values available for
7587 subsequent use in expressions as values of the convenience variables
7588 @code{$_} and @code{$__}. After an @code{x} command, the last address
7589 examined is available for use in expressions in the convenience variable
7590 @code{$_}. The contents of that address, as examined, are available in
7591 the convenience variable @code{$__}.
7593 If the @code{x} command has a repeat count, the address and contents saved
7594 are from the last memory unit printed; this is not the same as the last
7595 address printed if several units were printed on the last line of output.
7597 @cindex remote memory comparison
7598 @cindex verify remote memory image
7599 When you are debugging a program running on a remote target machine
7600 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7601 remote machine's memory against the executable file you downloaded to
7602 the target. The @code{compare-sections} command is provided for such
7606 @kindex compare-sections
7607 @item compare-sections @r{[}@var{section-name}@r{]}
7608 Compare the data of a loadable section @var{section-name} in the
7609 executable file of the program being debugged with the same section in
7610 the remote machine's memory, and report any mismatches. With no
7611 arguments, compares all loadable sections. This command's
7612 availability depends on the target's support for the @code{"qCRC"}
7617 @section Automatic Display
7618 @cindex automatic display
7619 @cindex display of expressions
7621 If you find that you want to print the value of an expression frequently
7622 (to see how it changes), you might want to add it to the @dfn{automatic
7623 display list} so that @value{GDBN} prints its value each time your program stops.
7624 Each expression added to the list is given a number to identify it;
7625 to remove an expression from the list, you specify that number.
7626 The automatic display looks like this:
7630 3: bar[5] = (struct hack *) 0x3804
7634 This display shows item numbers, expressions and their current values. As with
7635 displays you request manually using @code{x} or @code{print}, you can
7636 specify the output format you prefer; in fact, @code{display} decides
7637 whether to use @code{print} or @code{x} depending your format
7638 specification---it uses @code{x} if you specify either the @samp{i}
7639 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7643 @item display @var{expr}
7644 Add the expression @var{expr} to the list of expressions to display
7645 each time your program stops. @xref{Expressions, ,Expressions}.
7647 @code{display} does not repeat if you press @key{RET} again after using it.
7649 @item display/@var{fmt} @var{expr}
7650 For @var{fmt} specifying only a display format and not a size or
7651 count, add the expression @var{expr} to the auto-display list but
7652 arrange to display it each time in the specified format @var{fmt}.
7653 @xref{Output Formats,,Output Formats}.
7655 @item display/@var{fmt} @var{addr}
7656 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7657 number of units, add the expression @var{addr} as a memory address to
7658 be examined each time your program stops. Examining means in effect
7659 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7662 For example, @samp{display/i $pc} can be helpful, to see the machine
7663 instruction about to be executed each time execution stops (@samp{$pc}
7664 is a common name for the program counter; @pxref{Registers, ,Registers}).
7667 @kindex delete display
7669 @item undisplay @var{dnums}@dots{}
7670 @itemx delete display @var{dnums}@dots{}
7671 Remove items from the list of expressions to display. Specify the
7672 numbers of the displays that you want affected with the command
7673 argument @var{dnums}. It can be a single display number, one of the
7674 numbers shown in the first field of the @samp{info display} display;
7675 or it could be a range of display numbers, as in @code{2-4}.
7677 @code{undisplay} does not repeat if you press @key{RET} after using it.
7678 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7680 @kindex disable display
7681 @item disable display @var{dnums}@dots{}
7682 Disable the display of item numbers @var{dnums}. A disabled display
7683 item is not printed automatically, but is not forgotten. It may be
7684 enabled again later. Specify the numbers of the displays that you
7685 want affected with the command argument @var{dnums}. It can be a
7686 single display number, one of the numbers shown in the first field of
7687 the @samp{info display} display; or it could be a range of display
7688 numbers, as in @code{2-4}.
7690 @kindex enable display
7691 @item enable display @var{dnums}@dots{}
7692 Enable display of item numbers @var{dnums}. It becomes effective once
7693 again in auto display of its expression, until you specify otherwise.
7694 Specify the numbers of the displays that you want affected with the
7695 command argument @var{dnums}. It can be a single display number, one
7696 of the numbers shown in the first field of the @samp{info display}
7697 display; or it could be a range of display numbers, as in @code{2-4}.
7700 Display the current values of the expressions on the list, just as is
7701 done when your program stops.
7703 @kindex info display
7705 Print the list of expressions previously set up to display
7706 automatically, each one with its item number, but without showing the
7707 values. This includes disabled expressions, which are marked as such.
7708 It also includes expressions which would not be displayed right now
7709 because they refer to automatic variables not currently available.
7712 @cindex display disabled out of scope
7713 If a display expression refers to local variables, then it does not make
7714 sense outside the lexical context for which it was set up. Such an
7715 expression is disabled when execution enters a context where one of its
7716 variables is not defined. For example, if you give the command
7717 @code{display last_char} while inside a function with an argument
7718 @code{last_char}, @value{GDBN} displays this argument while your program
7719 continues to stop inside that function. When it stops elsewhere---where
7720 there is no variable @code{last_char}---the display is disabled
7721 automatically. The next time your program stops where @code{last_char}
7722 is meaningful, you can enable the display expression once again.
7724 @node Print Settings
7725 @section Print Settings
7727 @cindex format options
7728 @cindex print settings
7729 @value{GDBN} provides the following ways to control how arrays, structures,
7730 and symbols are printed.
7733 These settings are useful for debugging programs in any language:
7737 @item set print address
7738 @itemx set print address on
7739 @cindex print/don't print memory addresses
7740 @value{GDBN} prints memory addresses showing the location of stack
7741 traces, structure values, pointer values, breakpoints, and so forth,
7742 even when it also displays the contents of those addresses. The default
7743 is @code{on}. For example, this is what a stack frame display looks like with
7744 @code{set print address on}:
7749 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7751 530 if (lquote != def_lquote)
7755 @item set print address off
7756 Do not print addresses when displaying their contents. For example,
7757 this is the same stack frame displayed with @code{set print address off}:
7761 (@value{GDBP}) set print addr off
7763 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7764 530 if (lquote != def_lquote)
7768 You can use @samp{set print address off} to eliminate all machine
7769 dependent displays from the @value{GDBN} interface. For example, with
7770 @code{print address off}, you should get the same text for backtraces on
7771 all machines---whether or not they involve pointer arguments.
7774 @item show print address
7775 Show whether or not addresses are to be printed.
7778 When @value{GDBN} prints a symbolic address, it normally prints the
7779 closest earlier symbol plus an offset. If that symbol does not uniquely
7780 identify the address (for example, it is a name whose scope is a single
7781 source file), you may need to clarify. One way to do this is with
7782 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7783 you can set @value{GDBN} to print the source file and line number when
7784 it prints a symbolic address:
7787 @item set print symbol-filename on
7788 @cindex source file and line of a symbol
7789 @cindex symbol, source file and line
7790 Tell @value{GDBN} to print the source file name and line number of a
7791 symbol in the symbolic form of an address.
7793 @item set print symbol-filename off
7794 Do not print source file name and line number of a symbol. This is the
7797 @item show print symbol-filename
7798 Show whether or not @value{GDBN} will print the source file name and
7799 line number of a symbol in the symbolic form of an address.
7802 Another situation where it is helpful to show symbol filenames and line
7803 numbers is when disassembling code; @value{GDBN} shows you the line
7804 number and source file that corresponds to each instruction.
7806 Also, you may wish to see the symbolic form only if the address being
7807 printed is reasonably close to the closest earlier symbol:
7810 @item set print max-symbolic-offset @var{max-offset}
7811 @cindex maximum value for offset of closest symbol
7812 Tell @value{GDBN} to only display the symbolic form of an address if the
7813 offset between the closest earlier symbol and the address is less than
7814 @var{max-offset}. The default is 0, which tells @value{GDBN}
7815 to always print the symbolic form of an address if any symbol precedes it.
7817 @item show print max-symbolic-offset
7818 Ask how large the maximum offset is that @value{GDBN} prints in a
7822 @cindex wild pointer, interpreting
7823 @cindex pointer, finding referent
7824 If you have a pointer and you are not sure where it points, try
7825 @samp{set print symbol-filename on}. Then you can determine the name
7826 and source file location of the variable where it points, using
7827 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7828 For example, here @value{GDBN} shows that a variable @code{ptt} points
7829 at another variable @code{t}, defined in @file{hi2.c}:
7832 (@value{GDBP}) set print symbol-filename on
7833 (@value{GDBP}) p/a ptt
7834 $4 = 0xe008 <t in hi2.c>
7838 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7839 does not show the symbol name and filename of the referent, even with
7840 the appropriate @code{set print} options turned on.
7843 Other settings control how different kinds of objects are printed:
7846 @item set print array
7847 @itemx set print array on
7848 @cindex pretty print arrays
7849 Pretty print arrays. This format is more convenient to read,
7850 but uses more space. The default is off.
7852 @item set print array off
7853 Return to compressed format for arrays.
7855 @item show print array
7856 Show whether compressed or pretty format is selected for displaying
7859 @cindex print array indexes
7860 @item set print array-indexes
7861 @itemx set print array-indexes on
7862 Print the index of each element when displaying arrays. May be more
7863 convenient to locate a given element in the array or quickly find the
7864 index of a given element in that printed array. The default is off.
7866 @item set print array-indexes off
7867 Stop printing element indexes when displaying arrays.
7869 @item show print array-indexes
7870 Show whether the index of each element is printed when displaying
7873 @item set print elements @var{number-of-elements}
7874 @cindex number of array elements to print
7875 @cindex limit on number of printed array elements
7876 Set a limit on how many elements of an array @value{GDBN} will print.
7877 If @value{GDBN} is printing a large array, it stops printing after it has
7878 printed the number of elements set by the @code{set print elements} command.
7879 This limit also applies to the display of strings.
7880 When @value{GDBN} starts, this limit is set to 200.
7881 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7883 @item show print elements
7884 Display the number of elements of a large array that @value{GDBN} will print.
7885 If the number is 0, then the printing is unlimited.
7887 @item set print frame-arguments @var{value}
7888 @kindex set print frame-arguments
7889 @cindex printing frame argument values
7890 @cindex print all frame argument values
7891 @cindex print frame argument values for scalars only
7892 @cindex do not print frame argument values
7893 This command allows to control how the values of arguments are printed
7894 when the debugger prints a frame (@pxref{Frames}). The possible
7899 The values of all arguments are printed.
7902 Print the value of an argument only if it is a scalar. The value of more
7903 complex arguments such as arrays, structures, unions, etc, is replaced
7904 by @code{@dots{}}. This is the default. Here is an example where
7905 only scalar arguments are shown:
7908 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7913 None of the argument values are printed. Instead, the value of each argument
7914 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7917 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7922 By default, only scalar arguments are printed. This command can be used
7923 to configure the debugger to print the value of all arguments, regardless
7924 of their type. However, it is often advantageous to not print the value
7925 of more complex parameters. For instance, it reduces the amount of
7926 information printed in each frame, making the backtrace more readable.
7927 Also, it improves performance when displaying Ada frames, because
7928 the computation of large arguments can sometimes be CPU-intensive,
7929 especially in large applications. Setting @code{print frame-arguments}
7930 to @code{scalars} (the default) or @code{none} avoids this computation,
7931 thus speeding up the display of each Ada frame.
7933 @item show print frame-arguments
7934 Show how the value of arguments should be displayed when printing a frame.
7936 @item set print repeats
7937 @cindex repeated array elements
7938 Set the threshold for suppressing display of repeated array
7939 elements. When the number of consecutive identical elements of an
7940 array exceeds the threshold, @value{GDBN} prints the string
7941 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7942 identical repetitions, instead of displaying the identical elements
7943 themselves. Setting the threshold to zero will cause all elements to
7944 be individually printed. The default threshold is 10.
7946 @item show print repeats
7947 Display the current threshold for printing repeated identical
7950 @item set print null-stop
7951 @cindex @sc{null} elements in arrays
7952 Cause @value{GDBN} to stop printing the characters of an array when the first
7953 @sc{null} is encountered. This is useful when large arrays actually
7954 contain only short strings.
7957 @item show print null-stop
7958 Show whether @value{GDBN} stops printing an array on the first
7959 @sc{null} character.
7961 @item set print pretty on
7962 @cindex print structures in indented form
7963 @cindex indentation in structure display
7964 Cause @value{GDBN} to print structures in an indented format with one member
7965 per line, like this:
7980 @item set print pretty off
7981 Cause @value{GDBN} to print structures in a compact format, like this:
7985 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7986 meat = 0x54 "Pork"@}
7991 This is the default format.
7993 @item show print pretty
7994 Show which format @value{GDBN} is using to print structures.
7996 @item set print sevenbit-strings on
7997 @cindex eight-bit characters in strings
7998 @cindex octal escapes in strings
7999 Print using only seven-bit characters; if this option is set,
8000 @value{GDBN} displays any eight-bit characters (in strings or
8001 character values) using the notation @code{\}@var{nnn}. This setting is
8002 best if you are working in English (@sc{ascii}) and you use the
8003 high-order bit of characters as a marker or ``meta'' bit.
8005 @item set print sevenbit-strings off
8006 Print full eight-bit characters. This allows the use of more
8007 international character sets, and is the default.
8009 @item show print sevenbit-strings
8010 Show whether or not @value{GDBN} is printing only seven-bit characters.
8012 @item set print union on
8013 @cindex unions in structures, printing
8014 Tell @value{GDBN} to print unions which are contained in structures
8015 and other unions. This is the default setting.
8017 @item set print union off
8018 Tell @value{GDBN} not to print unions which are contained in
8019 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8022 @item show print union
8023 Ask @value{GDBN} whether or not it will print unions which are contained in
8024 structures and other unions.
8026 For example, given the declarations
8029 typedef enum @{Tree, Bug@} Species;
8030 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8031 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8042 struct thing foo = @{Tree, @{Acorn@}@};
8046 with @code{set print union on} in effect @samp{p foo} would print
8049 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8053 and with @code{set print union off} in effect it would print
8056 $1 = @{it = Tree, form = @{...@}@}
8060 @code{set print union} affects programs written in C-like languages
8066 These settings are of interest when debugging C@t{++} programs:
8069 @cindex demangling C@t{++} names
8070 @item set print demangle
8071 @itemx set print demangle on
8072 Print C@t{++} names in their source form rather than in the encoded
8073 (``mangled'') form passed to the assembler and linker for type-safe
8074 linkage. The default is on.
8076 @item show print demangle
8077 Show whether C@t{++} names are printed in mangled or demangled form.
8079 @item set print asm-demangle
8080 @itemx set print asm-demangle on
8081 Print C@t{++} names in their source form rather than their mangled form, even
8082 in assembler code printouts such as instruction disassemblies.
8085 @item show print asm-demangle
8086 Show whether C@t{++} names in assembly listings are printed in mangled
8089 @cindex C@t{++} symbol decoding style
8090 @cindex symbol decoding style, C@t{++}
8091 @kindex set demangle-style
8092 @item set demangle-style @var{style}
8093 Choose among several encoding schemes used by different compilers to
8094 represent C@t{++} names. The choices for @var{style} are currently:
8098 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8101 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8102 This is the default.
8105 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8108 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8111 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8112 @strong{Warning:} this setting alone is not sufficient to allow
8113 debugging @code{cfront}-generated executables. @value{GDBN} would
8114 require further enhancement to permit that.
8117 If you omit @var{style}, you will see a list of possible formats.
8119 @item show demangle-style
8120 Display the encoding style currently in use for decoding C@t{++} symbols.
8122 @item set print object
8123 @itemx set print object on
8124 @cindex derived type of an object, printing
8125 @cindex display derived types
8126 When displaying a pointer to an object, identify the @emph{actual}
8127 (derived) type of the object rather than the @emph{declared} type, using
8128 the virtual function table.
8130 @item set print object off
8131 Display only the declared type of objects, without reference to the
8132 virtual function table. This is the default setting.
8134 @item show print object
8135 Show whether actual, or declared, object types are displayed.
8137 @item set print static-members
8138 @itemx set print static-members on
8139 @cindex static members of C@t{++} objects
8140 Print static members when displaying a C@t{++} object. The default is on.
8142 @item set print static-members off
8143 Do not print static members when displaying a C@t{++} object.
8145 @item show print static-members
8146 Show whether C@t{++} static members are printed or not.
8148 @item set print pascal_static-members
8149 @itemx set print pascal_static-members on
8150 @cindex static members of Pascal objects
8151 @cindex Pascal objects, static members display
8152 Print static members when displaying a Pascal object. The default is on.
8154 @item set print pascal_static-members off
8155 Do not print static members when displaying a Pascal object.
8157 @item show print pascal_static-members
8158 Show whether Pascal static members are printed or not.
8160 @c These don't work with HP ANSI C++ yet.
8161 @item set print vtbl
8162 @itemx set print vtbl on
8163 @cindex pretty print C@t{++} virtual function tables
8164 @cindex virtual functions (C@t{++}) display
8165 @cindex VTBL display
8166 Pretty print C@t{++} virtual function tables. The default is off.
8167 (The @code{vtbl} commands do not work on programs compiled with the HP
8168 ANSI C@t{++} compiler (@code{aCC}).)
8170 @item set print vtbl off
8171 Do not pretty print C@t{++} virtual function tables.
8173 @item show print vtbl
8174 Show whether C@t{++} virtual function tables are pretty printed, or not.
8177 @node Pretty Printing
8178 @section Pretty Printing
8180 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8181 Python code. It greatly simplifies the display of complex objects. This
8182 mechanism works for both MI and the CLI.
8185 * Pretty-Printer Introduction:: Introduction to pretty-printers
8186 * Pretty-Printer Example:: An example pretty-printer
8187 * Pretty-Printer Commands:: Pretty-printer commands
8190 @node Pretty-Printer Introduction
8191 @subsection Pretty-Printer Introduction
8193 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8194 registered for the value. If there is then @value{GDBN} invokes the
8195 pretty-printer to print the value. Otherwise the value is printed normally.
8197 Pretty-printers are normally named. This makes them easy to manage.
8198 The @samp{info pretty-printer} command will list all the installed
8199 pretty-printers with their names.
8200 If a pretty-printer can handle multiple data types, then its
8201 @dfn{subprinters} are the printers for the individual data types.
8202 Each such subprinter has its own name.
8203 The format of the name is @var{printer-name};@var{subprinter-name}.
8205 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8206 Typically they are automatically loaded and registered when the corresponding
8207 debug information is loaded, thus making them available without having to
8208 do anything special.
8210 There are three places where a pretty-printer can be registered.
8214 Pretty-printers registered globally are available when debugging
8218 Pretty-printers registered with a program space are available only
8219 when debugging that program.
8220 @xref{Progspaces In Python}, for more details on program spaces in Python.
8223 Pretty-printers registered with an objfile are loaded and unloaded
8224 with the corresponding objfile (e.g., shared library).
8225 @xref{Objfiles In Python}, for more details on objfiles in Python.
8228 @xref{Selecting Pretty-Printers}, for further information on how
8229 pretty-printers are selected,
8231 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8234 @node Pretty-Printer Example
8235 @subsection Pretty-Printer Example
8237 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8240 (@value{GDBP}) print s
8242 static npos = 4294967295,
8244 <std::allocator<char>> = @{
8245 <__gnu_cxx::new_allocator<char>> = @{
8246 <No data fields>@}, <No data fields>
8248 members of std::basic_string<char, std::char_traits<char>,
8249 std::allocator<char> >::_Alloc_hider:
8250 _M_p = 0x804a014 "abcd"
8255 With a pretty-printer for @code{std::string} only the contents are printed:
8258 (@value{GDBP}) print s
8262 @node Pretty-Printer Commands
8263 @subsection Pretty-Printer Commands
8264 @cindex pretty-printer commands
8267 @kindex info pretty-printer
8268 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8269 Print the list of installed pretty-printers.
8270 This includes disabled pretty-printers, which are marked as such.
8272 @var{object-regexp} is a regular expression matching the objects
8273 whose pretty-printers to list.
8274 Objects can be @code{global}, the program space's file
8275 (@pxref{Progspaces In Python}),
8276 and the object files within that program space (@pxref{Objfiles In Python}).
8277 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8278 looks up a printer from these three objects.
8280 @var{name-regexp} is a regular expression matching the name of the printers
8283 @kindex disable pretty-printer
8284 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8285 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8286 A disabled pretty-printer is not forgotten, it may be enabled again later.
8288 @kindex enable pretty-printer
8289 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8290 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8295 Suppose we have three pretty-printers installed: one from library1.so
8296 named @code{foo} that prints objects of type @code{foo}, and
8297 another from library2.so named @code{bar} that prints two types of objects,
8298 @code{bar1} and @code{bar2}.
8301 (gdb) info pretty-printer
8308 (gdb) info pretty-printer library2
8313 (gdb) disable pretty-printer library1
8315 2 of 3 printers enabled
8316 (gdb) info pretty-printer
8323 (gdb) disable pretty-printer library2 bar:bar1
8325 1 of 3 printers enabled
8326 (gdb) info pretty-printer library2
8333 (gdb) disable pretty-printer library2 bar
8335 0 of 3 printers enabled
8336 (gdb) info pretty-printer library2
8345 Note that for @code{bar} the entire printer can be disabled,
8346 as can each individual subprinter.
8349 @section Value History
8351 @cindex value history
8352 @cindex history of values printed by @value{GDBN}
8353 Values printed by the @code{print} command are saved in the @value{GDBN}
8354 @dfn{value history}. This allows you to refer to them in other expressions.
8355 Values are kept until the symbol table is re-read or discarded
8356 (for example with the @code{file} or @code{symbol-file} commands).
8357 When the symbol table changes, the value history is discarded,
8358 since the values may contain pointers back to the types defined in the
8363 @cindex history number
8364 The values printed are given @dfn{history numbers} by which you can
8365 refer to them. These are successive integers starting with one.
8366 @code{print} shows you the history number assigned to a value by
8367 printing @samp{$@var{num} = } before the value; here @var{num} is the
8370 To refer to any previous value, use @samp{$} followed by the value's
8371 history number. The way @code{print} labels its output is designed to
8372 remind you of this. Just @code{$} refers to the most recent value in
8373 the history, and @code{$$} refers to the value before that.
8374 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8375 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8376 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8378 For example, suppose you have just printed a pointer to a structure and
8379 want to see the contents of the structure. It suffices to type
8385 If you have a chain of structures where the component @code{next} points
8386 to the next one, you can print the contents of the next one with this:
8393 You can print successive links in the chain by repeating this
8394 command---which you can do by just typing @key{RET}.
8396 Note that the history records values, not expressions. If the value of
8397 @code{x} is 4 and you type these commands:
8405 then the value recorded in the value history by the @code{print} command
8406 remains 4 even though the value of @code{x} has changed.
8411 Print the last ten values in the value history, with their item numbers.
8412 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8413 values} does not change the history.
8415 @item show values @var{n}
8416 Print ten history values centered on history item number @var{n}.
8419 Print ten history values just after the values last printed. If no more
8420 values are available, @code{show values +} produces no display.
8423 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8424 same effect as @samp{show values +}.
8426 @node Convenience Vars
8427 @section Convenience Variables
8429 @cindex convenience variables
8430 @cindex user-defined variables
8431 @value{GDBN} provides @dfn{convenience variables} that you can use within
8432 @value{GDBN} to hold on to a value and refer to it later. These variables
8433 exist entirely within @value{GDBN}; they are not part of your program, and
8434 setting a convenience variable has no direct effect on further execution
8435 of your program. That is why you can use them freely.
8437 Convenience variables are prefixed with @samp{$}. Any name preceded by
8438 @samp{$} can be used for a convenience variable, unless it is one of
8439 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8440 (Value history references, in contrast, are @emph{numbers} preceded
8441 by @samp{$}. @xref{Value History, ,Value History}.)
8443 You can save a value in a convenience variable with an assignment
8444 expression, just as you would set a variable in your program.
8448 set $foo = *object_ptr
8452 would save in @code{$foo} the value contained in the object pointed to by
8455 Using a convenience variable for the first time creates it, but its
8456 value is @code{void} until you assign a new value. You can alter the
8457 value with another assignment at any time.
8459 Convenience variables have no fixed types. You can assign a convenience
8460 variable any type of value, including structures and arrays, even if
8461 that variable already has a value of a different type. The convenience
8462 variable, when used as an expression, has the type of its current value.
8465 @kindex show convenience
8466 @cindex show all user variables
8467 @item show convenience
8468 Print a list of convenience variables used so far, and their values.
8469 Abbreviated @code{show conv}.
8471 @kindex init-if-undefined
8472 @cindex convenience variables, initializing
8473 @item init-if-undefined $@var{variable} = @var{expression}
8474 Set a convenience variable if it has not already been set. This is useful
8475 for user-defined commands that keep some state. It is similar, in concept,
8476 to using local static variables with initializers in C (except that
8477 convenience variables are global). It can also be used to allow users to
8478 override default values used in a command script.
8480 If the variable is already defined then the expression is not evaluated so
8481 any side-effects do not occur.
8484 One of the ways to use a convenience variable is as a counter to be
8485 incremented or a pointer to be advanced. For example, to print
8486 a field from successive elements of an array of structures:
8490 print bar[$i++]->contents
8494 Repeat that command by typing @key{RET}.
8496 Some convenience variables are created automatically by @value{GDBN} and given
8497 values likely to be useful.
8500 @vindex $_@r{, convenience variable}
8502 The variable @code{$_} is automatically set by the @code{x} command to
8503 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8504 commands which provide a default address for @code{x} to examine also
8505 set @code{$_} to that address; these commands include @code{info line}
8506 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8507 except when set by the @code{x} command, in which case it is a pointer
8508 to the type of @code{$__}.
8510 @vindex $__@r{, convenience variable}
8512 The variable @code{$__} is automatically set by the @code{x} command
8513 to the value found in the last address examined. Its type is chosen
8514 to match the format in which the data was printed.
8517 @vindex $_exitcode@r{, convenience variable}
8518 The variable @code{$_exitcode} is automatically set to the exit code when
8519 the program being debugged terminates.
8522 @vindex $_sdata@r{, inspect, convenience variable}
8523 The variable @code{$_sdata} contains extra collected static tracepoint
8524 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8525 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8526 if extra static tracepoint data has not been collected.
8529 @vindex $_siginfo@r{, convenience variable}
8530 The variable @code{$_siginfo} contains extra signal information
8531 (@pxref{extra signal information}). Note that @code{$_siginfo}
8532 could be empty, if the application has not yet received any signals.
8533 For example, it will be empty before you execute the @code{run} command.
8536 @vindex $_tlb@r{, convenience variable}
8537 The variable @code{$_tlb} is automatically set when debugging
8538 applications running on MS-Windows in native mode or connected to
8539 gdbserver that supports the @code{qGetTIBAddr} request.
8540 @xref{General Query Packets}.
8541 This variable contains the address of the thread information block.
8545 On HP-UX systems, if you refer to a function or variable name that
8546 begins with a dollar sign, @value{GDBN} searches for a user or system
8547 name first, before it searches for a convenience variable.
8549 @cindex convenience functions
8550 @value{GDBN} also supplies some @dfn{convenience functions}. These
8551 have a syntax similar to convenience variables. A convenience
8552 function can be used in an expression just like an ordinary function;
8553 however, a convenience function is implemented internally to
8558 @kindex help function
8559 @cindex show all convenience functions
8560 Print a list of all convenience functions.
8567 You can refer to machine register contents, in expressions, as variables
8568 with names starting with @samp{$}. The names of registers are different
8569 for each machine; use @code{info registers} to see the names used on
8573 @kindex info registers
8574 @item info registers
8575 Print the names and values of all registers except floating-point
8576 and vector registers (in the selected stack frame).
8578 @kindex info all-registers
8579 @cindex floating point registers
8580 @item info all-registers
8581 Print the names and values of all registers, including floating-point
8582 and vector registers (in the selected stack frame).
8584 @item info registers @var{regname} @dots{}
8585 Print the @dfn{relativized} value of each specified register @var{regname}.
8586 As discussed in detail below, register values are normally relative to
8587 the selected stack frame. @var{regname} may be any register name valid on
8588 the machine you are using, with or without the initial @samp{$}.
8591 @cindex stack pointer register
8592 @cindex program counter register
8593 @cindex process status register
8594 @cindex frame pointer register
8595 @cindex standard registers
8596 @value{GDBN} has four ``standard'' register names that are available (in
8597 expressions) on most machines---whenever they do not conflict with an
8598 architecture's canonical mnemonics for registers. The register names
8599 @code{$pc} and @code{$sp} are used for the program counter register and
8600 the stack pointer. @code{$fp} is used for a register that contains a
8601 pointer to the current stack frame, and @code{$ps} is used for a
8602 register that contains the processor status. For example,
8603 you could print the program counter in hex with
8610 or print the instruction to be executed next with
8617 or add four to the stack pointer@footnote{This is a way of removing
8618 one word from the stack, on machines where stacks grow downward in
8619 memory (most machines, nowadays). This assumes that the innermost
8620 stack frame is selected; setting @code{$sp} is not allowed when other
8621 stack frames are selected. To pop entire frames off the stack,
8622 regardless of machine architecture, use @code{return};
8623 see @ref{Returning, ,Returning from a Function}.} with
8629 Whenever possible, these four standard register names are available on
8630 your machine even though the machine has different canonical mnemonics,
8631 so long as there is no conflict. The @code{info registers} command
8632 shows the canonical names. For example, on the SPARC, @code{info
8633 registers} displays the processor status register as @code{$psr} but you
8634 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8635 is an alias for the @sc{eflags} register.
8637 @value{GDBN} always considers the contents of an ordinary register as an
8638 integer when the register is examined in this way. Some machines have
8639 special registers which can hold nothing but floating point; these
8640 registers are considered to have floating point values. There is no way
8641 to refer to the contents of an ordinary register as floating point value
8642 (although you can @emph{print} it as a floating point value with
8643 @samp{print/f $@var{regname}}).
8645 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8646 means that the data format in which the register contents are saved by
8647 the operating system is not the same one that your program normally
8648 sees. For example, the registers of the 68881 floating point
8649 coprocessor are always saved in ``extended'' (raw) format, but all C
8650 programs expect to work with ``double'' (virtual) format. In such
8651 cases, @value{GDBN} normally works with the virtual format only (the format
8652 that makes sense for your program), but the @code{info registers} command
8653 prints the data in both formats.
8655 @cindex SSE registers (x86)
8656 @cindex MMX registers (x86)
8657 Some machines have special registers whose contents can be interpreted
8658 in several different ways. For example, modern x86-based machines
8659 have SSE and MMX registers that can hold several values packed
8660 together in several different formats. @value{GDBN} refers to such
8661 registers in @code{struct} notation:
8664 (@value{GDBP}) print $xmm1
8666 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8667 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8668 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8669 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8670 v4_int32 = @{0, 20657912, 11, 13@},
8671 v2_int64 = @{88725056443645952, 55834574859@},
8672 uint128 = 0x0000000d0000000b013b36f800000000
8677 To set values of such registers, you need to tell @value{GDBN} which
8678 view of the register you wish to change, as if you were assigning
8679 value to a @code{struct} member:
8682 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8685 Normally, register values are relative to the selected stack frame
8686 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8687 value that the register would contain if all stack frames farther in
8688 were exited and their saved registers restored. In order to see the
8689 true contents of hardware registers, you must select the innermost
8690 frame (with @samp{frame 0}).
8692 However, @value{GDBN} must deduce where registers are saved, from the machine
8693 code generated by your compiler. If some registers are not saved, or if
8694 @value{GDBN} is unable to locate the saved registers, the selected stack
8695 frame makes no difference.
8697 @node Floating Point Hardware
8698 @section Floating Point Hardware
8699 @cindex floating point
8701 Depending on the configuration, @value{GDBN} may be able to give
8702 you more information about the status of the floating point hardware.
8707 Display hardware-dependent information about the floating
8708 point unit. The exact contents and layout vary depending on the
8709 floating point chip. Currently, @samp{info float} is supported on
8710 the ARM and x86 machines.
8714 @section Vector Unit
8717 Depending on the configuration, @value{GDBN} may be able to give you
8718 more information about the status of the vector unit.
8723 Display information about the vector unit. The exact contents and
8724 layout vary depending on the hardware.
8727 @node OS Information
8728 @section Operating System Auxiliary Information
8729 @cindex OS information
8731 @value{GDBN} provides interfaces to useful OS facilities that can help
8732 you debug your program.
8734 @cindex @code{ptrace} system call
8735 @cindex @code{struct user} contents
8736 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8737 machines), it interfaces with the inferior via the @code{ptrace}
8738 system call. The operating system creates a special sata structure,
8739 called @code{struct user}, for this interface. You can use the
8740 command @code{info udot} to display the contents of this data
8746 Display the contents of the @code{struct user} maintained by the OS
8747 kernel for the program being debugged. @value{GDBN} displays the
8748 contents of @code{struct user} as a list of hex numbers, similar to
8749 the @code{examine} command.
8752 @cindex auxiliary vector
8753 @cindex vector, auxiliary
8754 Some operating systems supply an @dfn{auxiliary vector} to programs at
8755 startup. This is akin to the arguments and environment that you
8756 specify for a program, but contains a system-dependent variety of
8757 binary values that tell system libraries important details about the
8758 hardware, operating system, and process. Each value's purpose is
8759 identified by an integer tag; the meanings are well-known but system-specific.
8760 Depending on the configuration and operating system facilities,
8761 @value{GDBN} may be able to show you this information. For remote
8762 targets, this functionality may further depend on the remote stub's
8763 support of the @samp{qXfer:auxv:read} packet, see
8764 @ref{qXfer auxiliary vector read}.
8769 Display the auxiliary vector of the inferior, which can be either a
8770 live process or a core dump file. @value{GDBN} prints each tag value
8771 numerically, and also shows names and text descriptions for recognized
8772 tags. Some values in the vector are numbers, some bit masks, and some
8773 pointers to strings or other data. @value{GDBN} displays each value in the
8774 most appropriate form for a recognized tag, and in hexadecimal for
8775 an unrecognized tag.
8778 On some targets, @value{GDBN} can access operating-system-specific information
8779 and display it to user, without interpretation. For remote targets,
8780 this functionality depends on the remote stub's support of the
8781 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8786 List the types of OS information available for the target. If the
8787 target does not return a list of possible types, this command will
8790 @kindex info os processes
8791 @item info os processes
8792 Display the list of processes on the target. For each process,
8793 @value{GDBN} prints the process identifier, the name of the user, and
8794 the command corresponding to the process.
8797 @node Memory Region Attributes
8798 @section Memory Region Attributes
8799 @cindex memory region attributes
8801 @dfn{Memory region attributes} allow you to describe special handling
8802 required by regions of your target's memory. @value{GDBN} uses
8803 attributes to determine whether to allow certain types of memory
8804 accesses; whether to use specific width accesses; and whether to cache
8805 target memory. By default the description of memory regions is
8806 fetched from the target (if the current target supports this), but the
8807 user can override the fetched regions.
8809 Defined memory regions can be individually enabled and disabled. When a
8810 memory region is disabled, @value{GDBN} uses the default attributes when
8811 accessing memory in that region. Similarly, if no memory regions have
8812 been defined, @value{GDBN} uses the default attributes when accessing
8815 When a memory region is defined, it is given a number to identify it;
8816 to enable, disable, or remove a memory region, you specify that number.
8820 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8821 Define a memory region bounded by @var{lower} and @var{upper} with
8822 attributes @var{attributes}@dots{}, and add it to the list of regions
8823 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8824 case: it is treated as the target's maximum memory address.
8825 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8828 Discard any user changes to the memory regions and use target-supplied
8829 regions, if available, or no regions if the target does not support.
8832 @item delete mem @var{nums}@dots{}
8833 Remove memory regions @var{nums}@dots{} from the list of regions
8834 monitored by @value{GDBN}.
8837 @item disable mem @var{nums}@dots{}
8838 Disable monitoring of memory regions @var{nums}@dots{}.
8839 A disabled memory region is not forgotten.
8840 It may be enabled again later.
8843 @item enable mem @var{nums}@dots{}
8844 Enable monitoring of memory regions @var{nums}@dots{}.
8848 Print a table of all defined memory regions, with the following columns
8852 @item Memory Region Number
8853 @item Enabled or Disabled.
8854 Enabled memory regions are marked with @samp{y}.
8855 Disabled memory regions are marked with @samp{n}.
8858 The address defining the inclusive lower bound of the memory region.
8861 The address defining the exclusive upper bound of the memory region.
8864 The list of attributes set for this memory region.
8869 @subsection Attributes
8871 @subsubsection Memory Access Mode
8872 The access mode attributes set whether @value{GDBN} may make read or
8873 write accesses to a memory region.
8875 While these attributes prevent @value{GDBN} from performing invalid
8876 memory accesses, they do nothing to prevent the target system, I/O DMA,
8877 etc.@: from accessing memory.
8881 Memory is read only.
8883 Memory is write only.
8885 Memory is read/write. This is the default.
8888 @subsubsection Memory Access Size
8889 The access size attribute tells @value{GDBN} to use specific sized
8890 accesses in the memory region. Often memory mapped device registers
8891 require specific sized accesses. If no access size attribute is
8892 specified, @value{GDBN} may use accesses of any size.
8896 Use 8 bit memory accesses.
8898 Use 16 bit memory accesses.
8900 Use 32 bit memory accesses.
8902 Use 64 bit memory accesses.
8905 @c @subsubsection Hardware/Software Breakpoints
8906 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8907 @c will use hardware or software breakpoints for the internal breakpoints
8908 @c used by the step, next, finish, until, etc. commands.
8912 @c Always use hardware breakpoints
8913 @c @item swbreak (default)
8916 @subsubsection Data Cache
8917 The data cache attributes set whether @value{GDBN} will cache target
8918 memory. While this generally improves performance by reducing debug
8919 protocol overhead, it can lead to incorrect results because @value{GDBN}
8920 does not know about volatile variables or memory mapped device
8925 Enable @value{GDBN} to cache target memory.
8927 Disable @value{GDBN} from caching target memory. This is the default.
8930 @subsection Memory Access Checking
8931 @value{GDBN} can be instructed to refuse accesses to memory that is
8932 not explicitly described. This can be useful if accessing such
8933 regions has undesired effects for a specific target, or to provide
8934 better error checking. The following commands control this behaviour.
8937 @kindex set mem inaccessible-by-default
8938 @item set mem inaccessible-by-default [on|off]
8939 If @code{on} is specified, make @value{GDBN} treat memory not
8940 explicitly described by the memory ranges as non-existent and refuse accesses
8941 to such memory. The checks are only performed if there's at least one
8942 memory range defined. If @code{off} is specified, make @value{GDBN}
8943 treat the memory not explicitly described by the memory ranges as RAM.
8944 The default value is @code{on}.
8945 @kindex show mem inaccessible-by-default
8946 @item show mem inaccessible-by-default
8947 Show the current handling of accesses to unknown memory.
8951 @c @subsubsection Memory Write Verification
8952 @c The memory write verification attributes set whether @value{GDBN}
8953 @c will re-reads data after each write to verify the write was successful.
8957 @c @item noverify (default)
8960 @node Dump/Restore Files
8961 @section Copy Between Memory and a File
8962 @cindex dump/restore files
8963 @cindex append data to a file
8964 @cindex dump data to a file
8965 @cindex restore data from a file
8967 You can use the commands @code{dump}, @code{append}, and
8968 @code{restore} to copy data between target memory and a file. The
8969 @code{dump} and @code{append} commands write data to a file, and the
8970 @code{restore} command reads data from a file back into the inferior's
8971 memory. Files may be in binary, Motorola S-record, Intel hex, or
8972 Tektronix Hex format; however, @value{GDBN} can only append to binary
8978 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8979 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8980 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8981 or the value of @var{expr}, to @var{filename} in the given format.
8983 The @var{format} parameter may be any one of:
8990 Motorola S-record format.
8992 Tektronix Hex format.
8995 @value{GDBN} uses the same definitions of these formats as the
8996 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8997 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9001 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9002 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9003 Append the contents of memory from @var{start_addr} to @var{end_addr},
9004 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9005 (@value{GDBN} can only append data to files in raw binary form.)
9008 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9009 Restore the contents of file @var{filename} into memory. The
9010 @code{restore} command can automatically recognize any known @sc{bfd}
9011 file format, except for raw binary. To restore a raw binary file you
9012 must specify the optional keyword @code{binary} after the filename.
9014 If @var{bias} is non-zero, its value will be added to the addresses
9015 contained in the file. Binary files always start at address zero, so
9016 they will be restored at address @var{bias}. Other bfd files have
9017 a built-in location; they will be restored at offset @var{bias}
9020 If @var{start} and/or @var{end} are non-zero, then only data between
9021 file offset @var{start} and file offset @var{end} will be restored.
9022 These offsets are relative to the addresses in the file, before
9023 the @var{bias} argument is applied.
9027 @node Core File Generation
9028 @section How to Produce a Core File from Your Program
9029 @cindex dump core from inferior
9031 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9032 image of a running process and its process status (register values
9033 etc.). Its primary use is post-mortem debugging of a program that
9034 crashed while it ran outside a debugger. A program that crashes
9035 automatically produces a core file, unless this feature is disabled by
9036 the user. @xref{Files}, for information on invoking @value{GDBN} in
9037 the post-mortem debugging mode.
9039 Occasionally, you may wish to produce a core file of the program you
9040 are debugging in order to preserve a snapshot of its state.
9041 @value{GDBN} has a special command for that.
9045 @kindex generate-core-file
9046 @item generate-core-file [@var{file}]
9047 @itemx gcore [@var{file}]
9048 Produce a core dump of the inferior process. The optional argument
9049 @var{file} specifies the file name where to put the core dump. If not
9050 specified, the file name defaults to @file{core.@var{pid}}, where
9051 @var{pid} is the inferior process ID.
9053 Note that this command is implemented only for some systems (as of
9054 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9057 @node Character Sets
9058 @section Character Sets
9059 @cindex character sets
9061 @cindex translating between character sets
9062 @cindex host character set
9063 @cindex target character set
9065 If the program you are debugging uses a different character set to
9066 represent characters and strings than the one @value{GDBN} uses itself,
9067 @value{GDBN} can automatically translate between the character sets for
9068 you. The character set @value{GDBN} uses we call the @dfn{host
9069 character set}; the one the inferior program uses we call the
9070 @dfn{target character set}.
9072 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9073 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9074 remote protocol (@pxref{Remote Debugging}) to debug a program
9075 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9076 then the host character set is Latin-1, and the target character set is
9077 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9078 target-charset EBCDIC-US}, then @value{GDBN} translates between
9079 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9080 character and string literals in expressions.
9082 @value{GDBN} has no way to automatically recognize which character set
9083 the inferior program uses; you must tell it, using the @code{set
9084 target-charset} command, described below.
9086 Here are the commands for controlling @value{GDBN}'s character set
9090 @item set target-charset @var{charset}
9091 @kindex set target-charset
9092 Set the current target character set to @var{charset}. To display the
9093 list of supported target character sets, type
9094 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9096 @item set host-charset @var{charset}
9097 @kindex set host-charset
9098 Set the current host character set to @var{charset}.
9100 By default, @value{GDBN} uses a host character set appropriate to the
9101 system it is running on; you can override that default using the
9102 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9103 automatically determine the appropriate host character set. In this
9104 case, @value{GDBN} uses @samp{UTF-8}.
9106 @value{GDBN} can only use certain character sets as its host character
9107 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9108 @value{GDBN} will list the host character sets it supports.
9110 @item set charset @var{charset}
9112 Set the current host and target character sets to @var{charset}. As
9113 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9114 @value{GDBN} will list the names of the character sets that can be used
9115 for both host and target.
9118 @kindex show charset
9119 Show the names of the current host and target character sets.
9121 @item show host-charset
9122 @kindex show host-charset
9123 Show the name of the current host character set.
9125 @item show target-charset
9126 @kindex show target-charset
9127 Show the name of the current target character set.
9129 @item set target-wide-charset @var{charset}
9130 @kindex set target-wide-charset
9131 Set the current target's wide character set to @var{charset}. This is
9132 the character set used by the target's @code{wchar_t} type. To
9133 display the list of supported wide character sets, type
9134 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9136 @item show target-wide-charset
9137 @kindex show target-wide-charset
9138 Show the name of the current target's wide character set.
9141 Here is an example of @value{GDBN}'s character set support in action.
9142 Assume that the following source code has been placed in the file
9143 @file{charset-test.c}:
9149 = @{72, 101, 108, 108, 111, 44, 32, 119,
9150 111, 114, 108, 100, 33, 10, 0@};
9151 char ibm1047_hello[]
9152 = @{200, 133, 147, 147, 150, 107, 64, 166,
9153 150, 153, 147, 132, 90, 37, 0@};
9157 printf ("Hello, world!\n");
9161 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9162 containing the string @samp{Hello, world!} followed by a newline,
9163 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9165 We compile the program, and invoke the debugger on it:
9168 $ gcc -g charset-test.c -o charset-test
9169 $ gdb -nw charset-test
9170 GNU gdb 2001-12-19-cvs
9171 Copyright 2001 Free Software Foundation, Inc.
9176 We can use the @code{show charset} command to see what character sets
9177 @value{GDBN} is currently using to interpret and display characters and
9181 (@value{GDBP}) show charset
9182 The current host and target character set is `ISO-8859-1'.
9186 For the sake of printing this manual, let's use @sc{ascii} as our
9187 initial character set:
9189 (@value{GDBP}) set charset ASCII
9190 (@value{GDBP}) show charset
9191 The current host and target character set is `ASCII'.
9195 Let's assume that @sc{ascii} is indeed the correct character set for our
9196 host system --- in other words, let's assume that if @value{GDBN} prints
9197 characters using the @sc{ascii} character set, our terminal will display
9198 them properly. Since our current target character set is also
9199 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9202 (@value{GDBP}) print ascii_hello
9203 $1 = 0x401698 "Hello, world!\n"
9204 (@value{GDBP}) print ascii_hello[0]
9209 @value{GDBN} uses the target character set for character and string
9210 literals you use in expressions:
9213 (@value{GDBP}) print '+'
9218 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9221 @value{GDBN} relies on the user to tell it which character set the
9222 target program uses. If we print @code{ibm1047_hello} while our target
9223 character set is still @sc{ascii}, we get jibberish:
9226 (@value{GDBP}) print ibm1047_hello
9227 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9228 (@value{GDBP}) print ibm1047_hello[0]
9233 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9234 @value{GDBN} tells us the character sets it supports:
9237 (@value{GDBP}) set target-charset
9238 ASCII EBCDIC-US IBM1047 ISO-8859-1
9239 (@value{GDBP}) set target-charset
9242 We can select @sc{ibm1047} as our target character set, and examine the
9243 program's strings again. Now the @sc{ascii} string is wrong, but
9244 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9245 target character set, @sc{ibm1047}, to the host character set,
9246 @sc{ascii}, and they display correctly:
9249 (@value{GDBP}) set target-charset IBM1047
9250 (@value{GDBP}) show charset
9251 The current host character set is `ASCII'.
9252 The current target character set is `IBM1047'.
9253 (@value{GDBP}) print ascii_hello
9254 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9255 (@value{GDBP}) print ascii_hello[0]
9257 (@value{GDBP}) print ibm1047_hello
9258 $8 = 0x4016a8 "Hello, world!\n"
9259 (@value{GDBP}) print ibm1047_hello[0]
9264 As above, @value{GDBN} uses the target character set for character and
9265 string literals you use in expressions:
9268 (@value{GDBP}) print '+'
9273 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9276 @node Caching Remote Data
9277 @section Caching Data of Remote Targets
9278 @cindex caching data of remote targets
9280 @value{GDBN} caches data exchanged between the debugger and a
9281 remote target (@pxref{Remote Debugging}). Such caching generally improves
9282 performance, because it reduces the overhead of the remote protocol by
9283 bundling memory reads and writes into large chunks. Unfortunately, simply
9284 caching everything would lead to incorrect results, since @value{GDBN}
9285 does not necessarily know anything about volatile values, memory-mapped I/O
9286 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9287 memory can be changed @emph{while} a gdb command is executing.
9288 Therefore, by default, @value{GDBN} only caches data
9289 known to be on the stack@footnote{In non-stop mode, it is moderately
9290 rare for a running thread to modify the stack of a stopped thread
9291 in a way that would interfere with a backtrace, and caching of
9292 stack reads provides a significant speed up of remote backtraces.}.
9293 Other regions of memory can be explicitly marked as
9294 cacheable; see @pxref{Memory Region Attributes}.
9297 @kindex set remotecache
9298 @item set remotecache on
9299 @itemx set remotecache off
9300 This option no longer does anything; it exists for compatibility
9303 @kindex show remotecache
9304 @item show remotecache
9305 Show the current state of the obsolete remotecache flag.
9307 @kindex set stack-cache
9308 @item set stack-cache on
9309 @itemx set stack-cache off
9310 Enable or disable caching of stack accesses. When @code{ON}, use
9311 caching. By default, this option is @code{ON}.
9313 @kindex show stack-cache
9314 @item show stack-cache
9315 Show the current state of data caching for memory accesses.
9318 @item info dcache @r{[}line@r{]}
9319 Print the information about the data cache performance. The
9320 information displayed includes the dcache width and depth, and for
9321 each cache line, its number, address, and how many times it was
9322 referenced. This command is useful for debugging the data cache
9325 If a line number is specified, the contents of that line will be
9329 @node Searching Memory
9330 @section Search Memory
9331 @cindex searching memory
9333 Memory can be searched for a particular sequence of bytes with the
9334 @code{find} command.
9338 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9339 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9340 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9341 etc. The search begins at address @var{start_addr} and continues for either
9342 @var{len} bytes or through to @var{end_addr} inclusive.
9345 @var{s} and @var{n} are optional parameters.
9346 They may be specified in either order, apart or together.
9349 @item @var{s}, search query size
9350 The size of each search query value.
9356 halfwords (two bytes)
9360 giant words (eight bytes)
9363 All values are interpreted in the current language.
9364 This means, for example, that if the current source language is C/C@t{++}
9365 then searching for the string ``hello'' includes the trailing '\0'.
9367 If the value size is not specified, it is taken from the
9368 value's type in the current language.
9369 This is useful when one wants to specify the search
9370 pattern as a mixture of types.
9371 Note that this means, for example, that in the case of C-like languages
9372 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9373 which is typically four bytes.
9375 @item @var{n}, maximum number of finds
9376 The maximum number of matches to print. The default is to print all finds.
9379 You can use strings as search values. Quote them with double-quotes
9381 The string value is copied into the search pattern byte by byte,
9382 regardless of the endianness of the target and the size specification.
9384 The address of each match found is printed as well as a count of the
9385 number of matches found.
9387 The address of the last value found is stored in convenience variable
9389 A count of the number of matches is stored in @samp{$numfound}.
9391 For example, if stopped at the @code{printf} in this function:
9397 static char hello[] = "hello-hello";
9398 static struct @{ char c; short s; int i; @}
9399 __attribute__ ((packed)) mixed
9400 = @{ 'c', 0x1234, 0x87654321 @};
9401 printf ("%s\n", hello);
9406 you get during debugging:
9409 (gdb) find &hello[0], +sizeof(hello), "hello"
9410 0x804956d <hello.1620+6>
9412 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9413 0x8049567 <hello.1620>
9414 0x804956d <hello.1620+6>
9416 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9417 0x8049567 <hello.1620>
9419 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9420 0x8049560 <mixed.1625>
9422 (gdb) print $numfound
9425 $2 = (void *) 0x8049560
9428 @node Optimized Code
9429 @chapter Debugging Optimized Code
9430 @cindex optimized code, debugging
9431 @cindex debugging optimized code
9433 Almost all compilers support optimization. With optimization
9434 disabled, the compiler generates assembly code that corresponds
9435 directly to your source code, in a simplistic way. As the compiler
9436 applies more powerful optimizations, the generated assembly code
9437 diverges from your original source code. With help from debugging
9438 information generated by the compiler, @value{GDBN} can map from
9439 the running program back to constructs from your original source.
9441 @value{GDBN} is more accurate with optimization disabled. If you
9442 can recompile without optimization, it is easier to follow the
9443 progress of your program during debugging. But, there are many cases
9444 where you may need to debug an optimized version.
9446 When you debug a program compiled with @samp{-g -O}, remember that the
9447 optimizer has rearranged your code; the debugger shows you what is
9448 really there. Do not be too surprised when the execution path does not
9449 exactly match your source file! An extreme example: if you define a
9450 variable, but never use it, @value{GDBN} never sees that
9451 variable---because the compiler optimizes it out of existence.
9453 Some things do not work as well with @samp{-g -O} as with just
9454 @samp{-g}, particularly on machines with instruction scheduling. If in
9455 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9456 please report it to us as a bug (including a test case!).
9457 @xref{Variables}, for more information about debugging optimized code.
9460 * Inline Functions:: How @value{GDBN} presents inlining
9463 @node Inline Functions
9464 @section Inline Functions
9465 @cindex inline functions, debugging
9467 @dfn{Inlining} is an optimization that inserts a copy of the function
9468 body directly at each call site, instead of jumping to a shared
9469 routine. @value{GDBN} displays inlined functions just like
9470 non-inlined functions. They appear in backtraces. You can view their
9471 arguments and local variables, step into them with @code{step}, skip
9472 them with @code{next}, and escape from them with @code{finish}.
9473 You can check whether a function was inlined by using the
9474 @code{info frame} command.
9476 For @value{GDBN} to support inlined functions, the compiler must
9477 record information about inlining in the debug information ---
9478 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9479 other compilers do also. @value{GDBN} only supports inlined functions
9480 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9481 do not emit two required attributes (@samp{DW_AT_call_file} and
9482 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9483 function calls with earlier versions of @value{NGCC}. It instead
9484 displays the arguments and local variables of inlined functions as
9485 local variables in the caller.
9487 The body of an inlined function is directly included at its call site;
9488 unlike a non-inlined function, there are no instructions devoted to
9489 the call. @value{GDBN} still pretends that the call site and the
9490 start of the inlined function are different instructions. Stepping to
9491 the call site shows the call site, and then stepping again shows
9492 the first line of the inlined function, even though no additional
9493 instructions are executed.
9495 This makes source-level debugging much clearer; you can see both the
9496 context of the call and then the effect of the call. Only stepping by
9497 a single instruction using @code{stepi} or @code{nexti} does not do
9498 this; single instruction steps always show the inlined body.
9500 There are some ways that @value{GDBN} does not pretend that inlined
9501 function calls are the same as normal calls:
9505 You cannot set breakpoints on inlined functions. @value{GDBN}
9506 either reports that there is no symbol with that name, or else sets the
9507 breakpoint only on non-inlined copies of the function. This limitation
9508 will be removed in a future version of @value{GDBN}; until then,
9509 set a breakpoint by line number on the first line of the inlined
9513 Setting breakpoints at the call site of an inlined function may not
9514 work, because the call site does not contain any code. @value{GDBN}
9515 may incorrectly move the breakpoint to the next line of the enclosing
9516 function, after the call. This limitation will be removed in a future
9517 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9518 or inside the inlined function instead.
9521 @value{GDBN} cannot locate the return value of inlined calls after
9522 using the @code{finish} command. This is a limitation of compiler-generated
9523 debugging information; after @code{finish}, you can step to the next line
9524 and print a variable where your program stored the return value.
9530 @chapter C Preprocessor Macros
9532 Some languages, such as C and C@t{++}, provide a way to define and invoke
9533 ``preprocessor macros'' which expand into strings of tokens.
9534 @value{GDBN} can evaluate expressions containing macro invocations, show
9535 the result of macro expansion, and show a macro's definition, including
9536 where it was defined.
9538 You may need to compile your program specially to provide @value{GDBN}
9539 with information about preprocessor macros. Most compilers do not
9540 include macros in their debugging information, even when you compile
9541 with the @option{-g} flag. @xref{Compilation}.
9543 A program may define a macro at one point, remove that definition later,
9544 and then provide a different definition after that. Thus, at different
9545 points in the program, a macro may have different definitions, or have
9546 no definition at all. If there is a current stack frame, @value{GDBN}
9547 uses the macros in scope at that frame's source code line. Otherwise,
9548 @value{GDBN} uses the macros in scope at the current listing location;
9551 Whenever @value{GDBN} evaluates an expression, it always expands any
9552 macro invocations present in the expression. @value{GDBN} also provides
9553 the following commands for working with macros explicitly.
9557 @kindex macro expand
9558 @cindex macro expansion, showing the results of preprocessor
9559 @cindex preprocessor macro expansion, showing the results of
9560 @cindex expanding preprocessor macros
9561 @item macro expand @var{expression}
9562 @itemx macro exp @var{expression}
9563 Show the results of expanding all preprocessor macro invocations in
9564 @var{expression}. Since @value{GDBN} simply expands macros, but does
9565 not parse the result, @var{expression} need not be a valid expression;
9566 it can be any string of tokens.
9569 @item macro expand-once @var{expression}
9570 @itemx macro exp1 @var{expression}
9571 @cindex expand macro once
9572 @i{(This command is not yet implemented.)} Show the results of
9573 expanding those preprocessor macro invocations that appear explicitly in
9574 @var{expression}. Macro invocations appearing in that expansion are
9575 left unchanged. This command allows you to see the effect of a
9576 particular macro more clearly, without being confused by further
9577 expansions. Since @value{GDBN} simply expands macros, but does not
9578 parse the result, @var{expression} need not be a valid expression; it
9579 can be any string of tokens.
9582 @cindex macro definition, showing
9583 @cindex definition, showing a macro's
9584 @item info macro @var{macro}
9585 Show the definition of the macro named @var{macro}, and describe the
9586 source location or compiler command-line where that definition was established.
9588 @kindex macro define
9589 @cindex user-defined macros
9590 @cindex defining macros interactively
9591 @cindex macros, user-defined
9592 @item macro define @var{macro} @var{replacement-list}
9593 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9594 Introduce a definition for a preprocessor macro named @var{macro},
9595 invocations of which are replaced by the tokens given in
9596 @var{replacement-list}. The first form of this command defines an
9597 ``object-like'' macro, which takes no arguments; the second form
9598 defines a ``function-like'' macro, which takes the arguments given in
9601 A definition introduced by this command is in scope in every
9602 expression evaluated in @value{GDBN}, until it is removed with the
9603 @code{macro undef} command, described below. The definition overrides
9604 all definitions for @var{macro} present in the program being debugged,
9605 as well as any previous user-supplied definition.
9608 @item macro undef @var{macro}
9609 Remove any user-supplied definition for the macro named @var{macro}.
9610 This command only affects definitions provided with the @code{macro
9611 define} command, described above; it cannot remove definitions present
9612 in the program being debugged.
9616 List all the macros defined using the @code{macro define} command.
9619 @cindex macros, example of debugging with
9620 Here is a transcript showing the above commands in action. First, we
9621 show our source files:
9629 #define ADD(x) (M + x)
9634 printf ("Hello, world!\n");
9636 printf ("We're so creative.\n");
9638 printf ("Goodbye, world!\n");
9645 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9646 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9647 compiler includes information about preprocessor macros in the debugging
9651 $ gcc -gdwarf-2 -g3 sample.c -o sample
9655 Now, we start @value{GDBN} on our sample program:
9659 GNU gdb 2002-05-06-cvs
9660 Copyright 2002 Free Software Foundation, Inc.
9661 GDB is free software, @dots{}
9665 We can expand macros and examine their definitions, even when the
9666 program is not running. @value{GDBN} uses the current listing position
9667 to decide which macro definitions are in scope:
9670 (@value{GDBP}) list main
9673 5 #define ADD(x) (M + x)
9678 10 printf ("Hello, world!\n");
9680 12 printf ("We're so creative.\n");
9681 (@value{GDBP}) info macro ADD
9682 Defined at /home/jimb/gdb/macros/play/sample.c:5
9683 #define ADD(x) (M + x)
9684 (@value{GDBP}) info macro Q
9685 Defined at /home/jimb/gdb/macros/play/sample.h:1
9686 included at /home/jimb/gdb/macros/play/sample.c:2
9688 (@value{GDBP}) macro expand ADD(1)
9689 expands to: (42 + 1)
9690 (@value{GDBP}) macro expand-once ADD(1)
9691 expands to: once (M + 1)
9695 In the example above, note that @code{macro expand-once} expands only
9696 the macro invocation explicit in the original text --- the invocation of
9697 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9698 which was introduced by @code{ADD}.
9700 Once the program is running, @value{GDBN} uses the macro definitions in
9701 force at the source line of the current stack frame:
9704 (@value{GDBP}) break main
9705 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9707 Starting program: /home/jimb/gdb/macros/play/sample
9709 Breakpoint 1, main () at sample.c:10
9710 10 printf ("Hello, world!\n");
9714 At line 10, the definition of the macro @code{N} at line 9 is in force:
9717 (@value{GDBP}) info macro N
9718 Defined at /home/jimb/gdb/macros/play/sample.c:9
9720 (@value{GDBP}) macro expand N Q M
9722 (@value{GDBP}) print N Q M
9727 As we step over directives that remove @code{N}'s definition, and then
9728 give it a new definition, @value{GDBN} finds the definition (or lack
9729 thereof) in force at each point:
9734 12 printf ("We're so creative.\n");
9735 (@value{GDBP}) info macro N
9736 The symbol `N' has no definition as a C/C++ preprocessor macro
9737 at /home/jimb/gdb/macros/play/sample.c:12
9740 14 printf ("Goodbye, world!\n");
9741 (@value{GDBP}) info macro N
9742 Defined at /home/jimb/gdb/macros/play/sample.c:13
9744 (@value{GDBP}) macro expand N Q M
9745 expands to: 1729 < 42
9746 (@value{GDBP}) print N Q M
9751 In addition to source files, macros can be defined on the compilation command
9752 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9753 such a way, @value{GDBN} displays the location of their definition as line zero
9754 of the source file submitted to the compiler.
9757 (@value{GDBP}) info macro __STDC__
9758 Defined at /home/jimb/gdb/macros/play/sample.c:0
9765 @chapter Tracepoints
9766 @c This chapter is based on the documentation written by Michael
9767 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9770 In some applications, it is not feasible for the debugger to interrupt
9771 the program's execution long enough for the developer to learn
9772 anything helpful about its behavior. If the program's correctness
9773 depends on its real-time behavior, delays introduced by a debugger
9774 might cause the program to change its behavior drastically, or perhaps
9775 fail, even when the code itself is correct. It is useful to be able
9776 to observe the program's behavior without interrupting it.
9778 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9779 specify locations in the program, called @dfn{tracepoints}, and
9780 arbitrary expressions to evaluate when those tracepoints are reached.
9781 Later, using the @code{tfind} command, you can examine the values
9782 those expressions had when the program hit the tracepoints. The
9783 expressions may also denote objects in memory---structures or arrays,
9784 for example---whose values @value{GDBN} should record; while visiting
9785 a particular tracepoint, you may inspect those objects as if they were
9786 in memory at that moment. However, because @value{GDBN} records these
9787 values without interacting with you, it can do so quickly and
9788 unobtrusively, hopefully not disturbing the program's behavior.
9790 The tracepoint facility is currently available only for remote
9791 targets. @xref{Targets}. In addition, your remote target must know
9792 how to collect trace data. This functionality is implemented in the
9793 remote stub; however, none of the stubs distributed with @value{GDBN}
9794 support tracepoints as of this writing. The format of the remote
9795 packets used to implement tracepoints are described in @ref{Tracepoint
9798 It is also possible to get trace data from a file, in a manner reminiscent
9799 of corefiles; you specify the filename, and use @code{tfind} to search
9800 through the file. @xref{Trace Files}, for more details.
9802 This chapter describes the tracepoint commands and features.
9806 * Analyze Collected Data::
9807 * Tracepoint Variables::
9811 @node Set Tracepoints
9812 @section Commands to Set Tracepoints
9814 Before running such a @dfn{trace experiment}, an arbitrary number of
9815 tracepoints can be set. A tracepoint is actually a special type of
9816 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9817 standard breakpoint commands. For instance, as with breakpoints,
9818 tracepoint numbers are successive integers starting from one, and many
9819 of the commands associated with tracepoints take the tracepoint number
9820 as their argument, to identify which tracepoint to work on.
9822 For each tracepoint, you can specify, in advance, some arbitrary set
9823 of data that you want the target to collect in the trace buffer when
9824 it hits that tracepoint. The collected data can include registers,
9825 local variables, or global data. Later, you can use @value{GDBN}
9826 commands to examine the values these data had at the time the
9829 Tracepoints do not support every breakpoint feature. Ignore counts on
9830 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9831 commands when they are hit. Tracepoints may not be thread-specific
9834 @cindex fast tracepoints
9835 Some targets may support @dfn{fast tracepoints}, which are inserted in
9836 a different way (such as with a jump instead of a trap), that is
9837 faster but possibly restricted in where they may be installed.
9839 @cindex static tracepoints
9840 @cindex markers, static tracepoints
9841 @cindex probing markers, static tracepoints
9842 Regular and fast tracepoints are dynamic tracing facilities, meaning
9843 that they can be used to insert tracepoints at (almost) any location
9844 in the target. Some targets may also support controlling @dfn{static
9845 tracepoints} from @value{GDBN}. With static tracing, a set of
9846 instrumentation points, also known as @dfn{markers}, are embedded in
9847 the target program, and can be activated or deactivated by name or
9848 address. These are usually placed at locations which facilitate
9849 investigating what the target is actually doing. @value{GDBN}'s
9850 support for static tracing includes being able to list instrumentation
9851 points, and attach them with @value{GDBN} defined high level
9852 tracepoints that expose the whole range of convenience of
9853 @value{GDBN}'s tracepoints support. Namely, support for collecting
9854 registers values and values of global or local (to the instrumentation
9855 point) variables; tracepoint conditions and trace state variables.
9856 The act of installing a @value{GDBN} static tracepoint on an
9857 instrumentation point, or marker, is referred to as @dfn{probing} a
9858 static tracepoint marker.
9860 @code{gdbserver} supports tracepoints on some target systems.
9861 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9863 This section describes commands to set tracepoints and associated
9864 conditions and actions.
9867 * Create and Delete Tracepoints::
9868 * Enable and Disable Tracepoints::
9869 * Tracepoint Passcounts::
9870 * Tracepoint Conditions::
9871 * Trace State Variables::
9872 * Tracepoint Actions::
9873 * Listing Tracepoints::
9874 * Listing Static Tracepoint Markers::
9875 * Starting and Stopping Trace Experiments::
9876 * Tracepoint Restrictions::
9879 @node Create and Delete Tracepoints
9880 @subsection Create and Delete Tracepoints
9883 @cindex set tracepoint
9885 @item trace @var{location}
9886 The @code{trace} command is very similar to the @code{break} command.
9887 Its argument @var{location} can be a source line, a function name, or
9888 an address in the target program. @xref{Specify Location}. The
9889 @code{trace} command defines a tracepoint, which is a point in the
9890 target program where the debugger will briefly stop, collect some
9891 data, and then allow the program to continue. Setting a tracepoint or
9892 changing its actions doesn't take effect until the next @code{tstart}
9893 command, and once a trace experiment is running, further changes will
9894 not have any effect until the next trace experiment starts.
9896 Here are some examples of using the @code{trace} command:
9899 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9901 (@value{GDBP}) @b{trace +2} // 2 lines forward
9903 (@value{GDBP}) @b{trace my_function} // first source line of function
9905 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9907 (@value{GDBP}) @b{trace *0x2117c4} // an address
9911 You can abbreviate @code{trace} as @code{tr}.
9913 @item trace @var{location} if @var{cond}
9914 Set a tracepoint with condition @var{cond}; evaluate the expression
9915 @var{cond} each time the tracepoint is reached, and collect data only
9916 if the value is nonzero---that is, if @var{cond} evaluates as true.
9917 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9918 information on tracepoint conditions.
9920 @item ftrace @var{location} [ if @var{cond} ]
9921 @cindex set fast tracepoint
9922 @cindex fast tracepoints, setting
9924 The @code{ftrace} command sets a fast tracepoint. For targets that
9925 support them, fast tracepoints will use a more efficient but possibly
9926 less general technique to trigger data collection, such as a jump
9927 instruction instead of a trap, or some sort of hardware support. It
9928 may not be possible to create a fast tracepoint at the desired
9929 location, in which case the command will exit with an explanatory
9932 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9935 @item strace @var{location} [ if @var{cond} ]
9936 @cindex set static tracepoint
9937 @cindex static tracepoints, setting
9938 @cindex probe static tracepoint marker
9940 The @code{strace} command sets a static tracepoint. For targets that
9941 support it, setting a static tracepoint probes a static
9942 instrumentation point, or marker, found at @var{location}. It may not
9943 be possible to set a static tracepoint at the desired location, in
9944 which case the command will exit with an explanatory message.
9946 @value{GDBN} handles arguments to @code{strace} exactly as for
9947 @code{trace}, with the addition that the user can also specify
9948 @code{-m @var{marker}} as @var{location}. This probes the marker
9949 identified by the @var{marker} string identifier. This identifier
9950 depends on the static tracepoint backend library your program is
9951 using. You can find all the marker identifiers in the @samp{ID} field
9952 of the @code{info static-tracepoint-markers} command output.
9953 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9954 Markers}. For example, in the following small program using the UST
9960 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9965 the marker id is composed of joining the first two arguments to the
9966 @code{trace_mark} call with a slash, which translates to:
9969 (@value{GDBP}) info static-tracepoint-markers
9970 Cnt Enb ID Address What
9971 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9977 so you may probe the marker above with:
9980 (@value{GDBP}) strace -m ust/bar33
9983 Static tracepoints accept an extra collect action --- @code{collect
9984 $_sdata}. This collects arbitrary user data passed in the probe point
9985 call to the tracing library. In the UST example above, you'll see
9986 that the third argument to @code{trace_mark} is a printf-like format
9987 string. The user data is then the result of running that formating
9988 string against the following arguments. Note that @code{info
9989 static-tracepoint-markers} command output lists that format string in
9990 the @samp{Data:} field.
9992 You can inspect this data when analyzing the trace buffer, by printing
9993 the $_sdata variable like any other variable available to
9994 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9997 @cindex last tracepoint number
9998 @cindex recent tracepoint number
9999 @cindex tracepoint number
10000 The convenience variable @code{$tpnum} records the tracepoint number
10001 of the most recently set tracepoint.
10003 @kindex delete tracepoint
10004 @cindex tracepoint deletion
10005 @item delete tracepoint @r{[}@var{num}@r{]}
10006 Permanently delete one or more tracepoints. With no argument, the
10007 default is to delete all tracepoints. Note that the regular
10008 @code{delete} command can remove tracepoints also.
10013 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10015 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10019 You can abbreviate this command as @code{del tr}.
10022 @node Enable and Disable Tracepoints
10023 @subsection Enable and Disable Tracepoints
10025 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10028 @kindex disable tracepoint
10029 @item disable tracepoint @r{[}@var{num}@r{]}
10030 Disable tracepoint @var{num}, or all tracepoints if no argument
10031 @var{num} is given. A disabled tracepoint will have no effect during
10032 a trace experiment, but it is not forgotten. You can re-enable
10033 a disabled tracepoint using the @code{enable tracepoint} command.
10034 If the command is issued during a trace experiment and the debug target
10035 has support for disabling tracepoints during a trace experiment, then the
10036 change will be effective immediately. Otherwise, it will be applied to the
10037 next trace experiment.
10039 @kindex enable tracepoint
10040 @item enable tracepoint @r{[}@var{num}@r{]}
10041 Enable tracepoint @var{num}, or all tracepoints. If this command is
10042 issued during a trace experiment and the debug target supports enabling
10043 tracepoints during a trace experiment, then the enabled tracepoints will
10044 become effective immediately. Otherwise, they will become effective the
10045 next time a trace experiment is run.
10048 @node Tracepoint Passcounts
10049 @subsection Tracepoint Passcounts
10053 @cindex tracepoint pass count
10054 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10055 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10056 automatically stop a trace experiment. If a tracepoint's passcount is
10057 @var{n}, then the trace experiment will be automatically stopped on
10058 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10059 @var{num} is not specified, the @code{passcount} command sets the
10060 passcount of the most recently defined tracepoint. If no passcount is
10061 given, the trace experiment will run until stopped explicitly by the
10067 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10068 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10070 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10071 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10072 (@value{GDBP}) @b{trace foo}
10073 (@value{GDBP}) @b{pass 3}
10074 (@value{GDBP}) @b{trace bar}
10075 (@value{GDBP}) @b{pass 2}
10076 (@value{GDBP}) @b{trace baz}
10077 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10078 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10079 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10080 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10084 @node Tracepoint Conditions
10085 @subsection Tracepoint Conditions
10086 @cindex conditional tracepoints
10087 @cindex tracepoint conditions
10089 The simplest sort of tracepoint collects data every time your program
10090 reaches a specified place. You can also specify a @dfn{condition} for
10091 a tracepoint. A condition is just a Boolean expression in your
10092 programming language (@pxref{Expressions, ,Expressions}). A
10093 tracepoint with a condition evaluates the expression each time your
10094 program reaches it, and data collection happens only if the condition
10097 Tracepoint conditions can be specified when a tracepoint is set, by
10098 using @samp{if} in the arguments to the @code{trace} command.
10099 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10100 also be set or changed at any time with the @code{condition} command,
10101 just as with breakpoints.
10103 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10104 the conditional expression itself. Instead, @value{GDBN} encodes the
10105 expression into an agent expression (@pxref{Agent Expressions})
10106 suitable for execution on the target, independently of @value{GDBN}.
10107 Global variables become raw memory locations, locals become stack
10108 accesses, and so forth.
10110 For instance, suppose you have a function that is usually called
10111 frequently, but should not be called after an error has occurred. You
10112 could use the following tracepoint command to collect data about calls
10113 of that function that happen while the error code is propagating
10114 through the program; an unconditional tracepoint could end up
10115 collecting thousands of useless trace frames that you would have to
10119 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10122 @node Trace State Variables
10123 @subsection Trace State Variables
10124 @cindex trace state variables
10126 A @dfn{trace state variable} is a special type of variable that is
10127 created and managed by target-side code. The syntax is the same as
10128 that for GDB's convenience variables (a string prefixed with ``$''),
10129 but they are stored on the target. They must be created explicitly,
10130 using a @code{tvariable} command. They are always 64-bit signed
10133 Trace state variables are remembered by @value{GDBN}, and downloaded
10134 to the target along with tracepoint information when the trace
10135 experiment starts. There are no intrinsic limits on the number of
10136 trace state variables, beyond memory limitations of the target.
10138 @cindex convenience variables, and trace state variables
10139 Although trace state variables are managed by the target, you can use
10140 them in print commands and expressions as if they were convenience
10141 variables; @value{GDBN} will get the current value from the target
10142 while the trace experiment is running. Trace state variables share
10143 the same namespace as other ``$'' variables, which means that you
10144 cannot have trace state variables with names like @code{$23} or
10145 @code{$pc}, nor can you have a trace state variable and a convenience
10146 variable with the same name.
10150 @item tvariable $@var{name} [ = @var{expression} ]
10152 The @code{tvariable} command creates a new trace state variable named
10153 @code{$@var{name}}, and optionally gives it an initial value of
10154 @var{expression}. @var{expression} is evaluated when this command is
10155 entered; the result will be converted to an integer if possible,
10156 otherwise @value{GDBN} will report an error. A subsequent
10157 @code{tvariable} command specifying the same name does not create a
10158 variable, but instead assigns the supplied initial value to the
10159 existing variable of that name, overwriting any previous initial
10160 value. The default initial value is 0.
10162 @item info tvariables
10163 @kindex info tvariables
10164 List all the trace state variables along with their initial values.
10165 Their current values may also be displayed, if the trace experiment is
10168 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10169 @kindex delete tvariable
10170 Delete the given trace state variables, or all of them if no arguments
10175 @node Tracepoint Actions
10176 @subsection Tracepoint Action Lists
10180 @cindex tracepoint actions
10181 @item actions @r{[}@var{num}@r{]}
10182 This command will prompt for a list of actions to be taken when the
10183 tracepoint is hit. If the tracepoint number @var{num} is not
10184 specified, this command sets the actions for the one that was most
10185 recently defined (so that you can define a tracepoint and then say
10186 @code{actions} without bothering about its number). You specify the
10187 actions themselves on the following lines, one action at a time, and
10188 terminate the actions list with a line containing just @code{end}. So
10189 far, the only defined actions are @code{collect}, @code{teval}, and
10190 @code{while-stepping}.
10192 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10193 Commands, ,Breakpoint Command Lists}), except that only the defined
10194 actions are allowed; any other @value{GDBN} command is rejected.
10196 @cindex remove actions from a tracepoint
10197 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10198 and follow it immediately with @samp{end}.
10201 (@value{GDBP}) @b{collect @var{data}} // collect some data
10203 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10205 (@value{GDBP}) @b{end} // signals the end of actions.
10208 In the following example, the action list begins with @code{collect}
10209 commands indicating the things to be collected when the tracepoint is
10210 hit. Then, in order to single-step and collect additional data
10211 following the tracepoint, a @code{while-stepping} command is used,
10212 followed by the list of things to be collected after each step in a
10213 sequence of single steps. The @code{while-stepping} command is
10214 terminated by its own separate @code{end} command. Lastly, the action
10215 list is terminated by an @code{end} command.
10218 (@value{GDBP}) @b{trace foo}
10219 (@value{GDBP}) @b{actions}
10220 Enter actions for tracepoint 1, one per line:
10223 > while-stepping 12
10224 > collect $pc, arr[i]
10229 @kindex collect @r{(tracepoints)}
10230 @item collect @var{expr1}, @var{expr2}, @dots{}
10231 Collect values of the given expressions when the tracepoint is hit.
10232 This command accepts a comma-separated list of any valid expressions.
10233 In addition to global, static, or local variables, the following
10234 special arguments are supported:
10238 Collect all registers.
10241 Collect all function arguments.
10244 Collect all local variables.
10247 @vindex $_sdata@r{, collect}
10248 Collect static tracepoint marker specific data. Only available for
10249 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10250 Lists}. On the UST static tracepoints library backend, an
10251 instrumentation point resembles a @code{printf} function call. The
10252 tracing library is able to collect user specified data formatted to a
10253 character string using the format provided by the programmer that
10254 instrumented the program. Other backends have similar mechanisms.
10255 Here's an example of a UST marker call:
10258 const char master_name[] = "$your_name";
10259 trace_mark(channel1, marker1, "hello %s", master_name)
10262 In this case, collecting @code{$_sdata} collects the string
10263 @samp{hello $yourname}. When analyzing the trace buffer, you can
10264 inspect @samp{$_sdata} like any other variable available to
10268 You can give several consecutive @code{collect} commands, each one
10269 with a single argument, or one @code{collect} command with several
10270 arguments separated by commas; the effect is the same.
10272 The command @code{info scope} (@pxref{Symbols, info scope}) is
10273 particularly useful for figuring out what data to collect.
10275 @kindex teval @r{(tracepoints)}
10276 @item teval @var{expr1}, @var{expr2}, @dots{}
10277 Evaluate the given expressions when the tracepoint is hit. This
10278 command accepts a comma-separated list of expressions. The results
10279 are discarded, so this is mainly useful for assigning values to trace
10280 state variables (@pxref{Trace State Variables}) without adding those
10281 values to the trace buffer, as would be the case if the @code{collect}
10284 @kindex while-stepping @r{(tracepoints)}
10285 @item while-stepping @var{n}
10286 Perform @var{n} single-step instruction traces after the tracepoint,
10287 collecting new data after each step. The @code{while-stepping}
10288 command is followed by the list of what to collect while stepping
10289 (followed by its own @code{end} command):
10292 > while-stepping 12
10293 > collect $regs, myglobal
10299 Note that @code{$pc} is not automatically collected by
10300 @code{while-stepping}; you need to explicitly collect that register if
10301 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10304 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10305 @kindex set default-collect
10306 @cindex default collection action
10307 This variable is a list of expressions to collect at each tracepoint
10308 hit. It is effectively an additional @code{collect} action prepended
10309 to every tracepoint action list. The expressions are parsed
10310 individually for each tracepoint, so for instance a variable named
10311 @code{xyz} may be interpreted as a global for one tracepoint, and a
10312 local for another, as appropriate to the tracepoint's location.
10314 @item show default-collect
10315 @kindex show default-collect
10316 Show the list of expressions that are collected by default at each
10321 @node Listing Tracepoints
10322 @subsection Listing Tracepoints
10325 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10326 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10327 @cindex information about tracepoints
10328 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10329 Display information about the tracepoint @var{num}. If you don't
10330 specify a tracepoint number, displays information about all the
10331 tracepoints defined so far. The format is similar to that used for
10332 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10333 command, simply restricting itself to tracepoints.
10335 A tracepoint's listing may include additional information specific to
10340 its passcount as given by the @code{passcount @var{n}} command
10344 (@value{GDBP}) @b{info trace}
10345 Num Type Disp Enb Address What
10346 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10348 collect globfoo, $regs
10357 This command can be abbreviated @code{info tp}.
10360 @node Listing Static Tracepoint Markers
10361 @subsection Listing Static Tracepoint Markers
10364 @kindex info static-tracepoint-markers
10365 @cindex information about static tracepoint markers
10366 @item info static-tracepoint-markers
10367 Display information about all static tracepoint markers defined in the
10370 For each marker, the following columns are printed:
10374 An incrementing counter, output to help readability. This is not a
10377 The marker ID, as reported by the target.
10378 @item Enabled or Disabled
10379 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10380 that are not enabled.
10382 Where the marker is in your program, as a memory address.
10384 Where the marker is in the source for your program, as a file and line
10385 number. If the debug information included in the program does not
10386 allow @value{GDBN} to locate the source of the marker, this column
10387 will be left blank.
10391 In addition, the following information may be printed for each marker:
10395 User data passed to the tracing library by the marker call. In the
10396 UST backend, this is the format string passed as argument to the
10398 @item Static tracepoints probing the marker
10399 The list of static tracepoints attached to the marker.
10403 (@value{GDBP}) info static-tracepoint-markers
10404 Cnt ID Enb Address What
10405 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10406 Data: number1 %d number2 %d
10407 Probed by static tracepoints: #2
10408 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10414 @node Starting and Stopping Trace Experiments
10415 @subsection Starting and Stopping Trace Experiments
10419 @cindex start a new trace experiment
10420 @cindex collected data discarded
10422 This command takes no arguments. It starts the trace experiment, and
10423 begins collecting data. This has the side effect of discarding all
10424 the data collected in the trace buffer during the previous trace
10428 @cindex stop a running trace experiment
10430 This command takes no arguments. It ends the trace experiment, and
10431 stops collecting data.
10433 @strong{Note}: a trace experiment and data collection may stop
10434 automatically if any tracepoint's passcount is reached
10435 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10438 @cindex status of trace data collection
10439 @cindex trace experiment, status of
10441 This command displays the status of the current trace data
10445 Here is an example of the commands we described so far:
10448 (@value{GDBP}) @b{trace gdb_c_test}
10449 (@value{GDBP}) @b{actions}
10450 Enter actions for tracepoint #1, one per line.
10451 > collect $regs,$locals,$args
10452 > while-stepping 11
10456 (@value{GDBP}) @b{tstart}
10457 [time passes @dots{}]
10458 (@value{GDBP}) @b{tstop}
10461 @anchor{disconnected tracing}
10462 @cindex disconnected tracing
10463 You can choose to continue running the trace experiment even if
10464 @value{GDBN} disconnects from the target, voluntarily or
10465 involuntarily. For commands such as @code{detach}, the debugger will
10466 ask what you want to do with the trace. But for unexpected
10467 terminations (@value{GDBN} crash, network outage), it would be
10468 unfortunate to lose hard-won trace data, so the variable
10469 @code{disconnected-tracing} lets you decide whether the trace should
10470 continue running without @value{GDBN}.
10473 @item set disconnected-tracing on
10474 @itemx set disconnected-tracing off
10475 @kindex set disconnected-tracing
10476 Choose whether a tracing run should continue to run if @value{GDBN}
10477 has disconnected from the target. Note that @code{detach} or
10478 @code{quit} will ask you directly what to do about a running trace no
10479 matter what this variable's setting, so the variable is mainly useful
10480 for handling unexpected situations, such as loss of the network.
10482 @item show disconnected-tracing
10483 @kindex show disconnected-tracing
10484 Show the current choice for disconnected tracing.
10488 When you reconnect to the target, the trace experiment may or may not
10489 still be running; it might have filled the trace buffer in the
10490 meantime, or stopped for one of the other reasons. If it is running,
10491 it will continue after reconnection.
10493 Upon reconnection, the target will upload information about the
10494 tracepoints in effect. @value{GDBN} will then compare that
10495 information to the set of tracepoints currently defined, and attempt
10496 to match them up, allowing for the possibility that the numbers may
10497 have changed due to creation and deletion in the meantime. If one of
10498 the target's tracepoints does not match any in @value{GDBN}, the
10499 debugger will create a new tracepoint, so that you have a number with
10500 which to specify that tracepoint. This matching-up process is
10501 necessarily heuristic, and it may result in useless tracepoints being
10502 created; you may simply delete them if they are of no use.
10504 @cindex circular trace buffer
10505 If your target agent supports a @dfn{circular trace buffer}, then you
10506 can run a trace experiment indefinitely without filling the trace
10507 buffer; when space runs out, the agent deletes already-collected trace
10508 frames, oldest first, until there is enough room to continue
10509 collecting. This is especially useful if your tracepoints are being
10510 hit too often, and your trace gets terminated prematurely because the
10511 buffer is full. To ask for a circular trace buffer, simply set
10512 @samp{circular-trace-buffer} to on. You can set this at any time,
10513 including during tracing; if the agent can do it, it will change
10514 buffer handling on the fly, otherwise it will not take effect until
10518 @item set circular-trace-buffer on
10519 @itemx set circular-trace-buffer off
10520 @kindex set circular-trace-buffer
10521 Choose whether a tracing run should use a linear or circular buffer
10522 for trace data. A linear buffer will not lose any trace data, but may
10523 fill up prematurely, while a circular buffer will discard old trace
10524 data, but it will have always room for the latest tracepoint hits.
10526 @item show circular-trace-buffer
10527 @kindex show circular-trace-buffer
10528 Show the current choice for the trace buffer. Note that this may not
10529 match the agent's current buffer handling, nor is it guaranteed to
10530 match the setting that might have been in effect during a past run,
10531 for instance if you are looking at frames from a trace file.
10535 @node Tracepoint Restrictions
10536 @subsection Tracepoint Restrictions
10538 @cindex tracepoint restrictions
10539 There are a number of restrictions on the use of tracepoints. As
10540 described above, tracepoint data gathering occurs on the target
10541 without interaction from @value{GDBN}. Thus the full capabilities of
10542 the debugger are not available during data gathering, and then at data
10543 examination time, you will be limited by only having what was
10544 collected. The following items describe some common problems, but it
10545 is not exhaustive, and you may run into additional difficulties not
10551 Tracepoint expressions are intended to gather objects (lvalues). Thus
10552 the full flexibility of GDB's expression evaluator is not available.
10553 You cannot call functions, cast objects to aggregate types, access
10554 convenience variables or modify values (except by assignment to trace
10555 state variables). Some language features may implicitly call
10556 functions (for instance Objective-C fields with accessors), and therefore
10557 cannot be collected either.
10560 Collection of local variables, either individually or in bulk with
10561 @code{$locals} or @code{$args}, during @code{while-stepping} may
10562 behave erratically. The stepping action may enter a new scope (for
10563 instance by stepping into a function), or the location of the variable
10564 may change (for instance it is loaded into a register). The
10565 tracepoint data recorded uses the location information for the
10566 variables that is correct for the tracepoint location. When the
10567 tracepoint is created, it is not possible, in general, to determine
10568 where the steps of a @code{while-stepping} sequence will advance the
10569 program---particularly if a conditional branch is stepped.
10572 Collection of an incompletely-initialized or partially-destroyed object
10573 may result in something that @value{GDBN} cannot display, or displays
10574 in a misleading way.
10577 When @value{GDBN} displays a pointer to character it automatically
10578 dereferences the pointer to also display characters of the string
10579 being pointed to. However, collecting the pointer during tracing does
10580 not automatically collect the string. You need to explicitly
10581 dereference the pointer and provide size information if you want to
10582 collect not only the pointer, but the memory pointed to. For example,
10583 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10587 It is not possible to collect a complete stack backtrace at a
10588 tracepoint. Instead, you may collect the registers and a few hundred
10589 bytes from the stack pointer with something like @code{*$esp@@300}
10590 (adjust to use the name of the actual stack pointer register on your
10591 target architecture, and the amount of stack you wish to capture).
10592 Then the @code{backtrace} command will show a partial backtrace when
10593 using a trace frame. The number of stack frames that can be examined
10594 depends on the sizes of the frames in the collected stack. Note that
10595 if you ask for a block so large that it goes past the bottom of the
10596 stack, the target agent may report an error trying to read from an
10600 If you do not collect registers at a tracepoint, @value{GDBN} can
10601 infer that the value of @code{$pc} must be the same as the address of
10602 the tracepoint and use that when you are looking at a trace frame
10603 for that tracepoint. However, this cannot work if the tracepoint has
10604 multiple locations (for instance if it was set in a function that was
10605 inlined), or if it has a @code{while-stepping} loop. In those cases
10606 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10611 @node Analyze Collected Data
10612 @section Using the Collected Data
10614 After the tracepoint experiment ends, you use @value{GDBN} commands
10615 for examining the trace data. The basic idea is that each tracepoint
10616 collects a trace @dfn{snapshot} every time it is hit and another
10617 snapshot every time it single-steps. All these snapshots are
10618 consecutively numbered from zero and go into a buffer, and you can
10619 examine them later. The way you examine them is to @dfn{focus} on a
10620 specific trace snapshot. When the remote stub is focused on a trace
10621 snapshot, it will respond to all @value{GDBN} requests for memory and
10622 registers by reading from the buffer which belongs to that snapshot,
10623 rather than from @emph{real} memory or registers of the program being
10624 debugged. This means that @strong{all} @value{GDBN} commands
10625 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10626 behave as if we were currently debugging the program state as it was
10627 when the tracepoint occurred. Any requests for data that are not in
10628 the buffer will fail.
10631 * tfind:: How to select a trace snapshot
10632 * tdump:: How to display all data for a snapshot
10633 * save tracepoints:: How to save tracepoints for a future run
10637 @subsection @code{tfind @var{n}}
10640 @cindex select trace snapshot
10641 @cindex find trace snapshot
10642 The basic command for selecting a trace snapshot from the buffer is
10643 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10644 counting from zero. If no argument @var{n} is given, the next
10645 snapshot is selected.
10647 Here are the various forms of using the @code{tfind} command.
10651 Find the first snapshot in the buffer. This is a synonym for
10652 @code{tfind 0} (since 0 is the number of the first snapshot).
10655 Stop debugging trace snapshots, resume @emph{live} debugging.
10658 Same as @samp{tfind none}.
10661 No argument means find the next trace snapshot.
10664 Find the previous trace snapshot before the current one. This permits
10665 retracing earlier steps.
10667 @item tfind tracepoint @var{num}
10668 Find the next snapshot associated with tracepoint @var{num}. Search
10669 proceeds forward from the last examined trace snapshot. If no
10670 argument @var{num} is given, it means find the next snapshot collected
10671 for the same tracepoint as the current snapshot.
10673 @item tfind pc @var{addr}
10674 Find the next snapshot associated with the value @var{addr} of the
10675 program counter. Search proceeds forward from the last examined trace
10676 snapshot. If no argument @var{addr} is given, it means find the next
10677 snapshot with the same value of PC as the current snapshot.
10679 @item tfind outside @var{addr1}, @var{addr2}
10680 Find the next snapshot whose PC is outside the given range of
10681 addresses (exclusive).
10683 @item tfind range @var{addr1}, @var{addr2}
10684 Find the next snapshot whose PC is between @var{addr1} and
10685 @var{addr2} (inclusive).
10687 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10688 Find the next snapshot associated with the source line @var{n}. If
10689 the optional argument @var{file} is given, refer to line @var{n} in
10690 that source file. Search proceeds forward from the last examined
10691 trace snapshot. If no argument @var{n} is given, it means find the
10692 next line other than the one currently being examined; thus saying
10693 @code{tfind line} repeatedly can appear to have the same effect as
10694 stepping from line to line in a @emph{live} debugging session.
10697 The default arguments for the @code{tfind} commands are specifically
10698 designed to make it easy to scan through the trace buffer. For
10699 instance, @code{tfind} with no argument selects the next trace
10700 snapshot, and @code{tfind -} with no argument selects the previous
10701 trace snapshot. So, by giving one @code{tfind} command, and then
10702 simply hitting @key{RET} repeatedly you can examine all the trace
10703 snapshots in order. Or, by saying @code{tfind -} and then hitting
10704 @key{RET} repeatedly you can examine the snapshots in reverse order.
10705 The @code{tfind line} command with no argument selects the snapshot
10706 for the next source line executed. The @code{tfind pc} command with
10707 no argument selects the next snapshot with the same program counter
10708 (PC) as the current frame. The @code{tfind tracepoint} command with
10709 no argument selects the next trace snapshot collected by the same
10710 tracepoint as the current one.
10712 In addition to letting you scan through the trace buffer manually,
10713 these commands make it easy to construct @value{GDBN} scripts that
10714 scan through the trace buffer and print out whatever collected data
10715 you are interested in. Thus, if we want to examine the PC, FP, and SP
10716 registers from each trace frame in the buffer, we can say this:
10719 (@value{GDBP}) @b{tfind start}
10720 (@value{GDBP}) @b{while ($trace_frame != -1)}
10721 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10722 $trace_frame, $pc, $sp, $fp
10726 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10727 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10728 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10729 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10730 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10731 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10732 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10733 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10734 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10735 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10736 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10739 Or, if we want to examine the variable @code{X} at each source line in
10743 (@value{GDBP}) @b{tfind start}
10744 (@value{GDBP}) @b{while ($trace_frame != -1)}
10745 > printf "Frame %d, X == %d\n", $trace_frame, X
10755 @subsection @code{tdump}
10757 @cindex dump all data collected at tracepoint
10758 @cindex tracepoint data, display
10760 This command takes no arguments. It prints all the data collected at
10761 the current trace snapshot.
10764 (@value{GDBP}) @b{trace 444}
10765 (@value{GDBP}) @b{actions}
10766 Enter actions for tracepoint #2, one per line:
10767 > collect $regs, $locals, $args, gdb_long_test
10770 (@value{GDBP}) @b{tstart}
10772 (@value{GDBP}) @b{tfind line 444}
10773 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10775 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10777 (@value{GDBP}) @b{tdump}
10778 Data collected at tracepoint 2, trace frame 1:
10779 d0 0xc4aa0085 -995491707
10783 d4 0x71aea3d 119204413
10786 d7 0x380035 3670069
10787 a0 0x19e24a 1696330
10788 a1 0x3000668 50333288
10790 a3 0x322000 3284992
10791 a4 0x3000698 50333336
10792 a5 0x1ad3cc 1758156
10793 fp 0x30bf3c 0x30bf3c
10794 sp 0x30bf34 0x30bf34
10796 pc 0x20b2c8 0x20b2c8
10800 p = 0x20e5b4 "gdb-test"
10807 gdb_long_test = 17 '\021'
10812 @code{tdump} works by scanning the tracepoint's current collection
10813 actions and printing the value of each expression listed. So
10814 @code{tdump} can fail, if after a run, you change the tracepoint's
10815 actions to mention variables that were not collected during the run.
10817 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10818 uses the collected value of @code{$pc} to distinguish between trace
10819 frames that were collected at the tracepoint hit, and frames that were
10820 collected while stepping. This allows it to correctly choose whether
10821 to display the basic list of collections, or the collections from the
10822 body of the while-stepping loop. However, if @code{$pc} was not collected,
10823 then @code{tdump} will always attempt to dump using the basic collection
10824 list, and may fail if a while-stepping frame does not include all the
10825 same data that is collected at the tracepoint hit.
10826 @c This is getting pretty arcane, example would be good.
10828 @node save tracepoints
10829 @subsection @code{save tracepoints @var{filename}}
10830 @kindex save tracepoints
10831 @kindex save-tracepoints
10832 @cindex save tracepoints for future sessions
10834 This command saves all current tracepoint definitions together with
10835 their actions and passcounts, into a file @file{@var{filename}}
10836 suitable for use in a later debugging session. To read the saved
10837 tracepoint definitions, use the @code{source} command (@pxref{Command
10838 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10839 alias for @w{@code{save tracepoints}}
10841 @node Tracepoint Variables
10842 @section Convenience Variables for Tracepoints
10843 @cindex tracepoint variables
10844 @cindex convenience variables for tracepoints
10847 @vindex $trace_frame
10848 @item (int) $trace_frame
10849 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10850 snapshot is selected.
10852 @vindex $tracepoint
10853 @item (int) $tracepoint
10854 The tracepoint for the current trace snapshot.
10856 @vindex $trace_line
10857 @item (int) $trace_line
10858 The line number for the current trace snapshot.
10860 @vindex $trace_file
10861 @item (char []) $trace_file
10862 The source file for the current trace snapshot.
10864 @vindex $trace_func
10865 @item (char []) $trace_func
10866 The name of the function containing @code{$tracepoint}.
10869 Note: @code{$trace_file} is not suitable for use in @code{printf},
10870 use @code{output} instead.
10872 Here's a simple example of using these convenience variables for
10873 stepping through all the trace snapshots and printing some of their
10874 data. Note that these are not the same as trace state variables,
10875 which are managed by the target.
10878 (@value{GDBP}) @b{tfind start}
10880 (@value{GDBP}) @b{while $trace_frame != -1}
10881 > output $trace_file
10882 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10888 @section Using Trace Files
10889 @cindex trace files
10891 In some situations, the target running a trace experiment may no
10892 longer be available; perhaps it crashed, or the hardware was needed
10893 for a different activity. To handle these cases, you can arrange to
10894 dump the trace data into a file, and later use that file as a source
10895 of trace data, via the @code{target tfile} command.
10900 @item tsave [ -r ] @var{filename}
10901 Save the trace data to @var{filename}. By default, this command
10902 assumes that @var{filename} refers to the host filesystem, so if
10903 necessary @value{GDBN} will copy raw trace data up from the target and
10904 then save it. If the target supports it, you can also supply the
10905 optional argument @code{-r} (``remote'') to direct the target to save
10906 the data directly into @var{filename} in its own filesystem, which may be
10907 more efficient if the trace buffer is very large. (Note, however, that
10908 @code{target tfile} can only read from files accessible to the host.)
10910 @kindex target tfile
10912 @item target tfile @var{filename}
10913 Use the file named @var{filename} as a source of trace data. Commands
10914 that examine data work as they do with a live target, but it is not
10915 possible to run any new trace experiments. @code{tstatus} will report
10916 the state of the trace run at the moment the data was saved, as well
10917 as the current trace frame you are examining. @var{filename} must be
10918 on a filesystem accessible to the host.
10923 @chapter Debugging Programs That Use Overlays
10926 If your program is too large to fit completely in your target system's
10927 memory, you can sometimes use @dfn{overlays} to work around this
10928 problem. @value{GDBN} provides some support for debugging programs that
10932 * How Overlays Work:: A general explanation of overlays.
10933 * Overlay Commands:: Managing overlays in @value{GDBN}.
10934 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10935 mapped by asking the inferior.
10936 * Overlay Sample Program:: A sample program using overlays.
10939 @node How Overlays Work
10940 @section How Overlays Work
10941 @cindex mapped overlays
10942 @cindex unmapped overlays
10943 @cindex load address, overlay's
10944 @cindex mapped address
10945 @cindex overlay area
10947 Suppose you have a computer whose instruction address space is only 64
10948 kilobytes long, but which has much more memory which can be accessed by
10949 other means: special instructions, segment registers, or memory
10950 management hardware, for example. Suppose further that you want to
10951 adapt a program which is larger than 64 kilobytes to run on this system.
10953 One solution is to identify modules of your program which are relatively
10954 independent, and need not call each other directly; call these modules
10955 @dfn{overlays}. Separate the overlays from the main program, and place
10956 their machine code in the larger memory. Place your main program in
10957 instruction memory, but leave at least enough space there to hold the
10958 largest overlay as well.
10960 Now, to call a function located in an overlay, you must first copy that
10961 overlay's machine code from the large memory into the space set aside
10962 for it in the instruction memory, and then jump to its entry point
10965 @c NB: In the below the mapped area's size is greater or equal to the
10966 @c size of all overlays. This is intentional to remind the developer
10967 @c that overlays don't necessarily need to be the same size.
10971 Data Instruction Larger
10972 Address Space Address Space Address Space
10973 +-----------+ +-----------+ +-----------+
10975 +-----------+ +-----------+ +-----------+<-- overlay 1
10976 | program | | main | .----| overlay 1 | load address
10977 | variables | | program | | +-----------+
10978 | and heap | | | | | |
10979 +-----------+ | | | +-----------+<-- overlay 2
10980 | | +-----------+ | | | load address
10981 +-----------+ | | | .-| overlay 2 |
10983 mapped --->+-----------+ | | +-----------+
10984 address | | | | | |
10985 | overlay | <-' | | |
10986 | area | <---' +-----------+<-- overlay 3
10987 | | <---. | | load address
10988 +-----------+ `--| overlay 3 |
10995 @anchor{A code overlay}A code overlay
10999 The diagram (@pxref{A code overlay}) shows a system with separate data
11000 and instruction address spaces. To map an overlay, the program copies
11001 its code from the larger address space to the instruction address space.
11002 Since the overlays shown here all use the same mapped address, only one
11003 may be mapped at a time. For a system with a single address space for
11004 data and instructions, the diagram would be similar, except that the
11005 program variables and heap would share an address space with the main
11006 program and the overlay area.
11008 An overlay loaded into instruction memory and ready for use is called a
11009 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11010 instruction memory. An overlay not present (or only partially present)
11011 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11012 is its address in the larger memory. The mapped address is also called
11013 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11014 called the @dfn{load memory address}, or @dfn{LMA}.
11016 Unfortunately, overlays are not a completely transparent way to adapt a
11017 program to limited instruction memory. They introduce a new set of
11018 global constraints you must keep in mind as you design your program:
11023 Before calling or returning to a function in an overlay, your program
11024 must make sure that overlay is actually mapped. Otherwise, the call or
11025 return will transfer control to the right address, but in the wrong
11026 overlay, and your program will probably crash.
11029 If the process of mapping an overlay is expensive on your system, you
11030 will need to choose your overlays carefully to minimize their effect on
11031 your program's performance.
11034 The executable file you load onto your system must contain each
11035 overlay's instructions, appearing at the overlay's load address, not its
11036 mapped address. However, each overlay's instructions must be relocated
11037 and its symbols defined as if the overlay were at its mapped address.
11038 You can use GNU linker scripts to specify different load and relocation
11039 addresses for pieces of your program; see @ref{Overlay Description,,,
11040 ld.info, Using ld: the GNU linker}.
11043 The procedure for loading executable files onto your system must be able
11044 to load their contents into the larger address space as well as the
11045 instruction and data spaces.
11049 The overlay system described above is rather simple, and could be
11050 improved in many ways:
11055 If your system has suitable bank switch registers or memory management
11056 hardware, you could use those facilities to make an overlay's load area
11057 contents simply appear at their mapped address in instruction space.
11058 This would probably be faster than copying the overlay to its mapped
11059 area in the usual way.
11062 If your overlays are small enough, you could set aside more than one
11063 overlay area, and have more than one overlay mapped at a time.
11066 You can use overlays to manage data, as well as instructions. In
11067 general, data overlays are even less transparent to your design than
11068 code overlays: whereas code overlays only require care when you call or
11069 return to functions, data overlays require care every time you access
11070 the data. Also, if you change the contents of a data overlay, you
11071 must copy its contents back out to its load address before you can copy a
11072 different data overlay into the same mapped area.
11077 @node Overlay Commands
11078 @section Overlay Commands
11080 To use @value{GDBN}'s overlay support, each overlay in your program must
11081 correspond to a separate section of the executable file. The section's
11082 virtual memory address and load memory address must be the overlay's
11083 mapped and load addresses. Identifying overlays with sections allows
11084 @value{GDBN} to determine the appropriate address of a function or
11085 variable, depending on whether the overlay is mapped or not.
11087 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11088 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11093 Disable @value{GDBN}'s overlay support. When overlay support is
11094 disabled, @value{GDBN} assumes that all functions and variables are
11095 always present at their mapped addresses. By default, @value{GDBN}'s
11096 overlay support is disabled.
11098 @item overlay manual
11099 @cindex manual overlay debugging
11100 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11101 relies on you to tell it which overlays are mapped, and which are not,
11102 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11103 commands described below.
11105 @item overlay map-overlay @var{overlay}
11106 @itemx overlay map @var{overlay}
11107 @cindex map an overlay
11108 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11109 be the name of the object file section containing the overlay. When an
11110 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11111 functions and variables at their mapped addresses. @value{GDBN} assumes
11112 that any other overlays whose mapped ranges overlap that of
11113 @var{overlay} are now unmapped.
11115 @item overlay unmap-overlay @var{overlay}
11116 @itemx overlay unmap @var{overlay}
11117 @cindex unmap an overlay
11118 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11119 must be the name of the object file section containing the overlay.
11120 When an overlay is unmapped, @value{GDBN} assumes it can find the
11121 overlay's functions and variables at their load addresses.
11124 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11125 consults a data structure the overlay manager maintains in the inferior
11126 to see which overlays are mapped. For details, see @ref{Automatic
11127 Overlay Debugging}.
11129 @item overlay load-target
11130 @itemx overlay load
11131 @cindex reloading the overlay table
11132 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11133 re-reads the table @value{GDBN} automatically each time the inferior
11134 stops, so this command should only be necessary if you have changed the
11135 overlay mapping yourself using @value{GDBN}. This command is only
11136 useful when using automatic overlay debugging.
11138 @item overlay list-overlays
11139 @itemx overlay list
11140 @cindex listing mapped overlays
11141 Display a list of the overlays currently mapped, along with their mapped
11142 addresses, load addresses, and sizes.
11146 Normally, when @value{GDBN} prints a code address, it includes the name
11147 of the function the address falls in:
11150 (@value{GDBP}) print main
11151 $3 = @{int ()@} 0x11a0 <main>
11154 When overlay debugging is enabled, @value{GDBN} recognizes code in
11155 unmapped overlays, and prints the names of unmapped functions with
11156 asterisks around them. For example, if @code{foo} is a function in an
11157 unmapped overlay, @value{GDBN} prints it this way:
11160 (@value{GDBP}) overlay list
11161 No sections are mapped.
11162 (@value{GDBP}) print foo
11163 $5 = @{int (int)@} 0x100000 <*foo*>
11166 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11170 (@value{GDBP}) overlay list
11171 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11172 mapped at 0x1016 - 0x104a
11173 (@value{GDBP}) print foo
11174 $6 = @{int (int)@} 0x1016 <foo>
11177 When overlay debugging is enabled, @value{GDBN} can find the correct
11178 address for functions and variables in an overlay, whether or not the
11179 overlay is mapped. This allows most @value{GDBN} commands, like
11180 @code{break} and @code{disassemble}, to work normally, even on unmapped
11181 code. However, @value{GDBN}'s breakpoint support has some limitations:
11185 @cindex breakpoints in overlays
11186 @cindex overlays, setting breakpoints in
11187 You can set breakpoints in functions in unmapped overlays, as long as
11188 @value{GDBN} can write to the overlay at its load address.
11190 @value{GDBN} can not set hardware or simulator-based breakpoints in
11191 unmapped overlays. However, if you set a breakpoint at the end of your
11192 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11193 you are using manual overlay management), @value{GDBN} will re-set its
11194 breakpoints properly.
11198 @node Automatic Overlay Debugging
11199 @section Automatic Overlay Debugging
11200 @cindex automatic overlay debugging
11202 @value{GDBN} can automatically track which overlays are mapped and which
11203 are not, given some simple co-operation from the overlay manager in the
11204 inferior. If you enable automatic overlay debugging with the
11205 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11206 looks in the inferior's memory for certain variables describing the
11207 current state of the overlays.
11209 Here are the variables your overlay manager must define to support
11210 @value{GDBN}'s automatic overlay debugging:
11214 @item @code{_ovly_table}:
11215 This variable must be an array of the following structures:
11220 /* The overlay's mapped address. */
11223 /* The size of the overlay, in bytes. */
11224 unsigned long size;
11226 /* The overlay's load address. */
11229 /* Non-zero if the overlay is currently mapped;
11231 unsigned long mapped;
11235 @item @code{_novlys}:
11236 This variable must be a four-byte signed integer, holding the total
11237 number of elements in @code{_ovly_table}.
11241 To decide whether a particular overlay is mapped or not, @value{GDBN}
11242 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11243 @code{lma} members equal the VMA and LMA of the overlay's section in the
11244 executable file. When @value{GDBN} finds a matching entry, it consults
11245 the entry's @code{mapped} member to determine whether the overlay is
11248 In addition, your overlay manager may define a function called
11249 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11250 will silently set a breakpoint there. If the overlay manager then
11251 calls this function whenever it has changed the overlay table, this
11252 will enable @value{GDBN} to accurately keep track of which overlays
11253 are in program memory, and update any breakpoints that may be set
11254 in overlays. This will allow breakpoints to work even if the
11255 overlays are kept in ROM or other non-writable memory while they
11256 are not being executed.
11258 @node Overlay Sample Program
11259 @section Overlay Sample Program
11260 @cindex overlay example program
11262 When linking a program which uses overlays, you must place the overlays
11263 at their load addresses, while relocating them to run at their mapped
11264 addresses. To do this, you must write a linker script (@pxref{Overlay
11265 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11266 since linker scripts are specific to a particular host system, target
11267 architecture, and target memory layout, this manual cannot provide
11268 portable sample code demonstrating @value{GDBN}'s overlay support.
11270 However, the @value{GDBN} source distribution does contain an overlaid
11271 program, with linker scripts for a few systems, as part of its test
11272 suite. The program consists of the following files from
11273 @file{gdb/testsuite/gdb.base}:
11277 The main program file.
11279 A simple overlay manager, used by @file{overlays.c}.
11284 Overlay modules, loaded and used by @file{overlays.c}.
11287 Linker scripts for linking the test program on the @code{d10v-elf}
11288 and @code{m32r-elf} targets.
11291 You can build the test program using the @code{d10v-elf} GCC
11292 cross-compiler like this:
11295 $ d10v-elf-gcc -g -c overlays.c
11296 $ d10v-elf-gcc -g -c ovlymgr.c
11297 $ d10v-elf-gcc -g -c foo.c
11298 $ d10v-elf-gcc -g -c bar.c
11299 $ d10v-elf-gcc -g -c baz.c
11300 $ d10v-elf-gcc -g -c grbx.c
11301 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11302 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11305 The build process is identical for any other architecture, except that
11306 you must substitute the appropriate compiler and linker script for the
11307 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11311 @chapter Using @value{GDBN} with Different Languages
11314 Although programming languages generally have common aspects, they are
11315 rarely expressed in the same manner. For instance, in ANSI C,
11316 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11317 Modula-2, it is accomplished by @code{p^}. Values can also be
11318 represented (and displayed) differently. Hex numbers in C appear as
11319 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11321 @cindex working language
11322 Language-specific information is built into @value{GDBN} for some languages,
11323 allowing you to express operations like the above in your program's
11324 native language, and allowing @value{GDBN} to output values in a manner
11325 consistent with the syntax of your program's native language. The
11326 language you use to build expressions is called the @dfn{working
11330 * Setting:: Switching between source languages
11331 * Show:: Displaying the language
11332 * Checks:: Type and range checks
11333 * Supported Languages:: Supported languages
11334 * Unsupported Languages:: Unsupported languages
11338 @section Switching Between Source Languages
11340 There are two ways to control the working language---either have @value{GDBN}
11341 set it automatically, or select it manually yourself. You can use the
11342 @code{set language} command for either purpose. On startup, @value{GDBN}
11343 defaults to setting the language automatically. The working language is
11344 used to determine how expressions you type are interpreted, how values
11347 In addition to the working language, every source file that
11348 @value{GDBN} knows about has its own working language. For some object
11349 file formats, the compiler might indicate which language a particular
11350 source file is in. However, most of the time @value{GDBN} infers the
11351 language from the name of the file. The language of a source file
11352 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11353 show each frame appropriately for its own language. There is no way to
11354 set the language of a source file from within @value{GDBN}, but you can
11355 set the language associated with a filename extension. @xref{Show, ,
11356 Displaying the Language}.
11358 This is most commonly a problem when you use a program, such
11359 as @code{cfront} or @code{f2c}, that generates C but is written in
11360 another language. In that case, make the
11361 program use @code{#line} directives in its C output; that way
11362 @value{GDBN} will know the correct language of the source code of the original
11363 program, and will display that source code, not the generated C code.
11366 * Filenames:: Filename extensions and languages.
11367 * Manually:: Setting the working language manually
11368 * Automatically:: Having @value{GDBN} infer the source language
11372 @subsection List of Filename Extensions and Languages
11374 If a source file name ends in one of the following extensions, then
11375 @value{GDBN} infers that its language is the one indicated.
11393 C@t{++} source file
11399 Objective-C source file
11403 Fortran source file
11406 Modula-2 source file
11410 Assembler source file. This actually behaves almost like C, but
11411 @value{GDBN} does not skip over function prologues when stepping.
11414 In addition, you may set the language associated with a filename
11415 extension. @xref{Show, , Displaying the Language}.
11418 @subsection Setting the Working Language
11420 If you allow @value{GDBN} to set the language automatically,
11421 expressions are interpreted the same way in your debugging session and
11424 @kindex set language
11425 If you wish, you may set the language manually. To do this, issue the
11426 command @samp{set language @var{lang}}, where @var{lang} is the name of
11427 a language, such as
11428 @code{c} or @code{modula-2}.
11429 For a list of the supported languages, type @samp{set language}.
11431 Setting the language manually prevents @value{GDBN} from updating the working
11432 language automatically. This can lead to confusion if you try
11433 to debug a program when the working language is not the same as the
11434 source language, when an expression is acceptable to both
11435 languages---but means different things. For instance, if the current
11436 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11444 might not have the effect you intended. In C, this means to add
11445 @code{b} and @code{c} and place the result in @code{a}. The result
11446 printed would be the value of @code{a}. In Modula-2, this means to compare
11447 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11449 @node Automatically
11450 @subsection Having @value{GDBN} Infer the Source Language
11452 To have @value{GDBN} set the working language automatically, use
11453 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11454 then infers the working language. That is, when your program stops in a
11455 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11456 working language to the language recorded for the function in that
11457 frame. If the language for a frame is unknown (that is, if the function
11458 or block corresponding to the frame was defined in a source file that
11459 does not have a recognized extension), the current working language is
11460 not changed, and @value{GDBN} issues a warning.
11462 This may not seem necessary for most programs, which are written
11463 entirely in one source language. However, program modules and libraries
11464 written in one source language can be used by a main program written in
11465 a different source language. Using @samp{set language auto} in this
11466 case frees you from having to set the working language manually.
11469 @section Displaying the Language
11471 The following commands help you find out which language is the
11472 working language, and also what language source files were written in.
11475 @item show language
11476 @kindex show language
11477 Display the current working language. This is the
11478 language you can use with commands such as @code{print} to
11479 build and compute expressions that may involve variables in your program.
11482 @kindex info frame@r{, show the source language}
11483 Display the source language for this frame. This language becomes the
11484 working language if you use an identifier from this frame.
11485 @xref{Frame Info, ,Information about a Frame}, to identify the other
11486 information listed here.
11489 @kindex info source@r{, show the source language}
11490 Display the source language of this source file.
11491 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11492 information listed here.
11495 In unusual circumstances, you may have source files with extensions
11496 not in the standard list. You can then set the extension associated
11497 with a language explicitly:
11500 @item set extension-language @var{ext} @var{language}
11501 @kindex set extension-language
11502 Tell @value{GDBN} that source files with extension @var{ext} are to be
11503 assumed as written in the source language @var{language}.
11505 @item info extensions
11506 @kindex info extensions
11507 List all the filename extensions and the associated languages.
11511 @section Type and Range Checking
11514 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11515 checking are included, but they do not yet have any effect. This
11516 section documents the intended facilities.
11518 @c FIXME remove warning when type/range code added
11520 Some languages are designed to guard you against making seemingly common
11521 errors through a series of compile- and run-time checks. These include
11522 checking the type of arguments to functions and operators, and making
11523 sure mathematical overflows are caught at run time. Checks such as
11524 these help to ensure a program's correctness once it has been compiled
11525 by eliminating type mismatches, and providing active checks for range
11526 errors when your program is running.
11528 @value{GDBN} can check for conditions like the above if you wish.
11529 Although @value{GDBN} does not check the statements in your program,
11530 it can check expressions entered directly into @value{GDBN} for
11531 evaluation via the @code{print} command, for example. As with the
11532 working language, @value{GDBN} can also decide whether or not to check
11533 automatically based on your program's source language.
11534 @xref{Supported Languages, ,Supported Languages}, for the default
11535 settings of supported languages.
11538 * Type Checking:: An overview of type checking
11539 * Range Checking:: An overview of range checking
11542 @cindex type checking
11543 @cindex checks, type
11544 @node Type Checking
11545 @subsection An Overview of Type Checking
11547 Some languages, such as Modula-2, are strongly typed, meaning that the
11548 arguments to operators and functions have to be of the correct type,
11549 otherwise an error occurs. These checks prevent type mismatch
11550 errors from ever causing any run-time problems. For example,
11558 The second example fails because the @code{CARDINAL} 1 is not
11559 type-compatible with the @code{REAL} 2.3.
11561 For the expressions you use in @value{GDBN} commands, you can tell the
11562 @value{GDBN} type checker to skip checking;
11563 to treat any mismatches as errors and abandon the expression;
11564 or to only issue warnings when type mismatches occur,
11565 but evaluate the expression anyway. When you choose the last of
11566 these, @value{GDBN} evaluates expressions like the second example above, but
11567 also issues a warning.
11569 Even if you turn type checking off, there may be other reasons
11570 related to type that prevent @value{GDBN} from evaluating an expression.
11571 For instance, @value{GDBN} does not know how to add an @code{int} and
11572 a @code{struct foo}. These particular type errors have nothing to do
11573 with the language in use, and usually arise from expressions, such as
11574 the one described above, which make little sense to evaluate anyway.
11576 Each language defines to what degree it is strict about type. For
11577 instance, both Modula-2 and C require the arguments to arithmetical
11578 operators to be numbers. In C, enumerated types and pointers can be
11579 represented as numbers, so that they are valid arguments to mathematical
11580 operators. @xref{Supported Languages, ,Supported Languages}, for further
11581 details on specific languages.
11583 @value{GDBN} provides some additional commands for controlling the type checker:
11585 @kindex set check type
11586 @kindex show check type
11588 @item set check type auto
11589 Set type checking on or off based on the current working language.
11590 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11593 @item set check type on
11594 @itemx set check type off
11595 Set type checking on or off, overriding the default setting for the
11596 current working language. Issue a warning if the setting does not
11597 match the language default. If any type mismatches occur in
11598 evaluating an expression while type checking is on, @value{GDBN} prints a
11599 message and aborts evaluation of the expression.
11601 @item set check type warn
11602 Cause the type checker to issue warnings, but to always attempt to
11603 evaluate the expression. Evaluating the expression may still
11604 be impossible for other reasons. For example, @value{GDBN} cannot add
11605 numbers and structures.
11608 Show the current setting of the type checker, and whether or not @value{GDBN}
11609 is setting it automatically.
11612 @cindex range checking
11613 @cindex checks, range
11614 @node Range Checking
11615 @subsection An Overview of Range Checking
11617 In some languages (such as Modula-2), it is an error to exceed the
11618 bounds of a type; this is enforced with run-time checks. Such range
11619 checking is meant to ensure program correctness by making sure
11620 computations do not overflow, or indices on an array element access do
11621 not exceed the bounds of the array.
11623 For expressions you use in @value{GDBN} commands, you can tell
11624 @value{GDBN} to treat range errors in one of three ways: ignore them,
11625 always treat them as errors and abandon the expression, or issue
11626 warnings but evaluate the expression anyway.
11628 A range error can result from numerical overflow, from exceeding an
11629 array index bound, or when you type a constant that is not a member
11630 of any type. Some languages, however, do not treat overflows as an
11631 error. In many implementations of C, mathematical overflow causes the
11632 result to ``wrap around'' to lower values---for example, if @var{m} is
11633 the largest integer value, and @var{s} is the smallest, then
11636 @var{m} + 1 @result{} @var{s}
11639 This, too, is specific to individual languages, and in some cases
11640 specific to individual compilers or machines. @xref{Supported Languages, ,
11641 Supported Languages}, for further details on specific languages.
11643 @value{GDBN} provides some additional commands for controlling the range checker:
11645 @kindex set check range
11646 @kindex show check range
11648 @item set check range auto
11649 Set range checking on or off based on the current working language.
11650 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11653 @item set check range on
11654 @itemx set check range off
11655 Set range checking on or off, overriding the default setting for the
11656 current working language. A warning is issued if the setting does not
11657 match the language default. If a range error occurs and range checking is on,
11658 then a message is printed and evaluation of the expression is aborted.
11660 @item set check range warn
11661 Output messages when the @value{GDBN} range checker detects a range error,
11662 but attempt to evaluate the expression anyway. Evaluating the
11663 expression may still be impossible for other reasons, such as accessing
11664 memory that the process does not own (a typical example from many Unix
11668 Show the current setting of the range checker, and whether or not it is
11669 being set automatically by @value{GDBN}.
11672 @node Supported Languages
11673 @section Supported Languages
11675 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11676 assembly, Modula-2, and Ada.
11677 @c This is false ...
11678 Some @value{GDBN} features may be used in expressions regardless of the
11679 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11680 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11681 ,Expressions}) can be used with the constructs of any supported
11684 The following sections detail to what degree each source language is
11685 supported by @value{GDBN}. These sections are not meant to be language
11686 tutorials or references, but serve only as a reference guide to what the
11687 @value{GDBN} expression parser accepts, and what input and output
11688 formats should look like for different languages. There are many good
11689 books written on each of these languages; please look to these for a
11690 language reference or tutorial.
11693 * C:: C and C@t{++}
11695 * Objective-C:: Objective-C
11696 * OpenCL C:: OpenCL C
11697 * Fortran:: Fortran
11699 * Modula-2:: Modula-2
11704 @subsection C and C@t{++}
11706 @cindex C and C@t{++}
11707 @cindex expressions in C or C@t{++}
11709 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11710 to both languages. Whenever this is the case, we discuss those languages
11714 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11715 @cindex @sc{gnu} C@t{++}
11716 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11717 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11718 effectively, you must compile your C@t{++} programs with a supported
11719 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11720 compiler (@code{aCC}).
11722 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11723 format; if it doesn't work on your system, try the stabs+ debugging
11724 format. You can select those formats explicitly with the @code{g++}
11725 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11726 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11727 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11730 * C Operators:: C and C@t{++} operators
11731 * C Constants:: C and C@t{++} constants
11732 * C Plus Plus Expressions:: C@t{++} expressions
11733 * C Defaults:: Default settings for C and C@t{++}
11734 * C Checks:: C and C@t{++} type and range checks
11735 * Debugging C:: @value{GDBN} and C
11736 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11737 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11741 @subsubsection C and C@t{++} Operators
11743 @cindex C and C@t{++} operators
11745 Operators must be defined on values of specific types. For instance,
11746 @code{+} is defined on numbers, but not on structures. Operators are
11747 often defined on groups of types.
11749 For the purposes of C and C@t{++}, the following definitions hold:
11754 @emph{Integral types} include @code{int} with any of its storage-class
11755 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11758 @emph{Floating-point types} include @code{float}, @code{double}, and
11759 @code{long double} (if supported by the target platform).
11762 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11765 @emph{Scalar types} include all of the above.
11770 The following operators are supported. They are listed here
11771 in order of increasing precedence:
11775 The comma or sequencing operator. Expressions in a comma-separated list
11776 are evaluated from left to right, with the result of the entire
11777 expression being the last expression evaluated.
11780 Assignment. The value of an assignment expression is the value
11781 assigned. Defined on scalar types.
11784 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11785 and translated to @w{@code{@var{a} = @var{a op b}}}.
11786 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11787 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11788 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11791 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11792 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11796 Logical @sc{or}. Defined on integral types.
11799 Logical @sc{and}. Defined on integral types.
11802 Bitwise @sc{or}. Defined on integral types.
11805 Bitwise exclusive-@sc{or}. Defined on integral types.
11808 Bitwise @sc{and}. Defined on integral types.
11811 Equality and inequality. Defined on scalar types. The value of these
11812 expressions is 0 for false and non-zero for true.
11814 @item <@r{, }>@r{, }<=@r{, }>=
11815 Less than, greater than, less than or equal, greater than or equal.
11816 Defined on scalar types. The value of these expressions is 0 for false
11817 and non-zero for true.
11820 left shift, and right shift. Defined on integral types.
11823 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11826 Addition and subtraction. Defined on integral types, floating-point types and
11829 @item *@r{, }/@r{, }%
11830 Multiplication, division, and modulus. Multiplication and division are
11831 defined on integral and floating-point types. Modulus is defined on
11835 Increment and decrement. When appearing before a variable, the
11836 operation is performed before the variable is used in an expression;
11837 when appearing after it, the variable's value is used before the
11838 operation takes place.
11841 Pointer dereferencing. Defined on pointer types. Same precedence as
11845 Address operator. Defined on variables. Same precedence as @code{++}.
11847 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11848 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11849 to examine the address
11850 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11854 Negative. Defined on integral and floating-point types. Same
11855 precedence as @code{++}.
11858 Logical negation. Defined on integral types. Same precedence as
11862 Bitwise complement operator. Defined on integral types. Same precedence as
11867 Structure member, and pointer-to-structure member. For convenience,
11868 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11869 pointer based on the stored type information.
11870 Defined on @code{struct} and @code{union} data.
11873 Dereferences of pointers to members.
11876 Array indexing. @code{@var{a}[@var{i}]} is defined as
11877 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11880 Function parameter list. Same precedence as @code{->}.
11883 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11884 and @code{class} types.
11887 Doubled colons also represent the @value{GDBN} scope operator
11888 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11892 If an operator is redefined in the user code, @value{GDBN} usually
11893 attempts to invoke the redefined version instead of using the operator's
11894 predefined meaning.
11897 @subsubsection C and C@t{++} Constants
11899 @cindex C and C@t{++} constants
11901 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11906 Integer constants are a sequence of digits. Octal constants are
11907 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11908 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11909 @samp{l}, specifying that the constant should be treated as a
11913 Floating point constants are a sequence of digits, followed by a decimal
11914 point, followed by a sequence of digits, and optionally followed by an
11915 exponent. An exponent is of the form:
11916 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11917 sequence of digits. The @samp{+} is optional for positive exponents.
11918 A floating-point constant may also end with a letter @samp{f} or
11919 @samp{F}, specifying that the constant should be treated as being of
11920 the @code{float} (as opposed to the default @code{double}) type; or with
11921 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11925 Enumerated constants consist of enumerated identifiers, or their
11926 integral equivalents.
11929 Character constants are a single character surrounded by single quotes
11930 (@code{'}), or a number---the ordinal value of the corresponding character
11931 (usually its @sc{ascii} value). Within quotes, the single character may
11932 be represented by a letter or by @dfn{escape sequences}, which are of
11933 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11934 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11935 @samp{@var{x}} is a predefined special character---for example,
11936 @samp{\n} for newline.
11939 String constants are a sequence of character constants surrounded by
11940 double quotes (@code{"}). Any valid character constant (as described
11941 above) may appear. Double quotes within the string must be preceded by
11942 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11946 Pointer constants are an integral value. You can also write pointers
11947 to constants using the C operator @samp{&}.
11950 Array constants are comma-separated lists surrounded by braces @samp{@{}
11951 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11952 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11953 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11956 @node C Plus Plus Expressions
11957 @subsubsection C@t{++} Expressions
11959 @cindex expressions in C@t{++}
11960 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11962 @cindex debugging C@t{++} programs
11963 @cindex C@t{++} compilers
11964 @cindex debug formats and C@t{++}
11965 @cindex @value{NGCC} and C@t{++}
11967 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11968 proper compiler and the proper debug format. Currently, @value{GDBN}
11969 works best when debugging C@t{++} code that is compiled with
11970 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11971 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11972 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11973 stabs+ as their default debug format, so you usually don't need to
11974 specify a debug format explicitly. Other compilers and/or debug formats
11975 are likely to work badly or not at all when using @value{GDBN} to debug
11981 @cindex member functions
11983 Member function calls are allowed; you can use expressions like
11986 count = aml->GetOriginal(x, y)
11989 @vindex this@r{, inside C@t{++} member functions}
11990 @cindex namespace in C@t{++}
11992 While a member function is active (in the selected stack frame), your
11993 expressions have the same namespace available as the member function;
11994 that is, @value{GDBN} allows implicit references to the class instance
11995 pointer @code{this} following the same rules as C@t{++}.
11997 @cindex call overloaded functions
11998 @cindex overloaded functions, calling
11999 @cindex type conversions in C@t{++}
12001 You can call overloaded functions; @value{GDBN} resolves the function
12002 call to the right definition, with some restrictions. @value{GDBN} does not
12003 perform overload resolution involving user-defined type conversions,
12004 calls to constructors, or instantiations of templates that do not exist
12005 in the program. It also cannot handle ellipsis argument lists or
12008 It does perform integral conversions and promotions, floating-point
12009 promotions, arithmetic conversions, pointer conversions, conversions of
12010 class objects to base classes, and standard conversions such as those of
12011 functions or arrays to pointers; it requires an exact match on the
12012 number of function arguments.
12014 Overload resolution is always performed, unless you have specified
12015 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12016 ,@value{GDBN} Features for C@t{++}}.
12018 You must specify @code{set overload-resolution off} in order to use an
12019 explicit function signature to call an overloaded function, as in
12021 p 'foo(char,int)'('x', 13)
12024 The @value{GDBN} command-completion facility can simplify this;
12025 see @ref{Completion, ,Command Completion}.
12027 @cindex reference declarations
12029 @value{GDBN} understands variables declared as C@t{++} references; you can use
12030 them in expressions just as you do in C@t{++} source---they are automatically
12033 In the parameter list shown when @value{GDBN} displays a frame, the values of
12034 reference variables are not displayed (unlike other variables); this
12035 avoids clutter, since references are often used for large structures.
12036 The @emph{address} of a reference variable is always shown, unless
12037 you have specified @samp{set print address off}.
12040 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12041 expressions can use it just as expressions in your program do. Since
12042 one scope may be defined in another, you can use @code{::} repeatedly if
12043 necessary, for example in an expression like
12044 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12045 resolving name scope by reference to source files, in both C and C@t{++}
12046 debugging (@pxref{Variables, ,Program Variables}).
12049 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12050 calling virtual functions correctly, printing out virtual bases of
12051 objects, calling functions in a base subobject, casting objects, and
12052 invoking user-defined operators.
12055 @subsubsection C and C@t{++} Defaults
12057 @cindex C and C@t{++} defaults
12059 If you allow @value{GDBN} to set type and range checking automatically, they
12060 both default to @code{off} whenever the working language changes to
12061 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12062 selects the working language.
12064 If you allow @value{GDBN} to set the language automatically, it
12065 recognizes source files whose names end with @file{.c}, @file{.C}, or
12066 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12067 these files, it sets the working language to C or C@t{++}.
12068 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12069 for further details.
12071 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12072 @c unimplemented. If (b) changes, it might make sense to let this node
12073 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12076 @subsubsection C and C@t{++} Type and Range Checks
12078 @cindex C and C@t{++} checks
12080 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12081 is not used. However, if you turn type checking on, @value{GDBN}
12082 considers two variables type equivalent if:
12086 The two variables are structured and have the same structure, union, or
12090 The two variables have the same type name, or types that have been
12091 declared equivalent through @code{typedef}.
12094 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12097 The two @code{struct}, @code{union}, or @code{enum} variables are
12098 declared in the same declaration. (Note: this may not be true for all C
12103 Range checking, if turned on, is done on mathematical operations. Array
12104 indices are not checked, since they are often used to index a pointer
12105 that is not itself an array.
12108 @subsubsection @value{GDBN} and C
12110 The @code{set print union} and @code{show print union} commands apply to
12111 the @code{union} type. When set to @samp{on}, any @code{union} that is
12112 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12113 appears as @samp{@{...@}}.
12115 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12116 with pointers and a memory allocation function. @xref{Expressions,
12119 @node Debugging C Plus Plus
12120 @subsubsection @value{GDBN} Features for C@t{++}
12122 @cindex commands for C@t{++}
12124 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12125 designed specifically for use with C@t{++}. Here is a summary:
12128 @cindex break in overloaded functions
12129 @item @r{breakpoint menus}
12130 When you want a breakpoint in a function whose name is overloaded,
12131 @value{GDBN} has the capability to display a menu of possible breakpoint
12132 locations to help you specify which function definition you want.
12133 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12135 @cindex overloading in C@t{++}
12136 @item rbreak @var{regex}
12137 Setting breakpoints using regular expressions is helpful for setting
12138 breakpoints on overloaded functions that are not members of any special
12140 @xref{Set Breaks, ,Setting Breakpoints}.
12142 @cindex C@t{++} exception handling
12145 Debug C@t{++} exception handling using these commands. @xref{Set
12146 Catchpoints, , Setting Catchpoints}.
12148 @cindex inheritance
12149 @item ptype @var{typename}
12150 Print inheritance relationships as well as other information for type
12152 @xref{Symbols, ,Examining the Symbol Table}.
12154 @cindex C@t{++} symbol display
12155 @item set print demangle
12156 @itemx show print demangle
12157 @itemx set print asm-demangle
12158 @itemx show print asm-demangle
12159 Control whether C@t{++} symbols display in their source form, both when
12160 displaying code as C@t{++} source and when displaying disassemblies.
12161 @xref{Print Settings, ,Print Settings}.
12163 @item set print object
12164 @itemx show print object
12165 Choose whether to print derived (actual) or declared types of objects.
12166 @xref{Print Settings, ,Print Settings}.
12168 @item set print vtbl
12169 @itemx show print vtbl
12170 Control the format for printing virtual function tables.
12171 @xref{Print Settings, ,Print Settings}.
12172 (The @code{vtbl} commands do not work on programs compiled with the HP
12173 ANSI C@t{++} compiler (@code{aCC}).)
12175 @kindex set overload-resolution
12176 @cindex overloaded functions, overload resolution
12177 @item set overload-resolution on
12178 Enable overload resolution for C@t{++} expression evaluation. The default
12179 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12180 and searches for a function whose signature matches the argument types,
12181 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12182 Expressions, ,C@t{++} Expressions}, for details).
12183 If it cannot find a match, it emits a message.
12185 @item set overload-resolution off
12186 Disable overload resolution for C@t{++} expression evaluation. For
12187 overloaded functions that are not class member functions, @value{GDBN}
12188 chooses the first function of the specified name that it finds in the
12189 symbol table, whether or not its arguments are of the correct type. For
12190 overloaded functions that are class member functions, @value{GDBN}
12191 searches for a function whose signature @emph{exactly} matches the
12194 @kindex show overload-resolution
12195 @item show overload-resolution
12196 Show the current setting of overload resolution.
12198 @item @r{Overloaded symbol names}
12199 You can specify a particular definition of an overloaded symbol, using
12200 the same notation that is used to declare such symbols in C@t{++}: type
12201 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12202 also use the @value{GDBN} command-line word completion facilities to list the
12203 available choices, or to finish the type list for you.
12204 @xref{Completion,, Command Completion}, for details on how to do this.
12207 @node Decimal Floating Point
12208 @subsubsection Decimal Floating Point format
12209 @cindex decimal floating point format
12211 @value{GDBN} can examine, set and perform computations with numbers in
12212 decimal floating point format, which in the C language correspond to the
12213 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12214 specified by the extension to support decimal floating-point arithmetic.
12216 There are two encodings in use, depending on the architecture: BID (Binary
12217 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12218 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12221 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12222 to manipulate decimal floating point numbers, it is not possible to convert
12223 (using a cast, for example) integers wider than 32-bit to decimal float.
12225 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12226 point computations, error checking in decimal float operations ignores
12227 underflow, overflow and divide by zero exceptions.
12229 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12230 to inspect @code{_Decimal128} values stored in floating point registers.
12231 See @ref{PowerPC,,PowerPC} for more details.
12237 @value{GDBN} can be used to debug programs written in D and compiled with
12238 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12239 specific feature --- dynamic arrays.
12242 @subsection Objective-C
12244 @cindex Objective-C
12245 This section provides information about some commands and command
12246 options that are useful for debugging Objective-C code. See also
12247 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12248 few more commands specific to Objective-C support.
12251 * Method Names in Commands::
12252 * The Print Command with Objective-C::
12255 @node Method Names in Commands
12256 @subsubsection Method Names in Commands
12258 The following commands have been extended to accept Objective-C method
12259 names as line specifications:
12261 @kindex clear@r{, and Objective-C}
12262 @kindex break@r{, and Objective-C}
12263 @kindex info line@r{, and Objective-C}
12264 @kindex jump@r{, and Objective-C}
12265 @kindex list@r{, and Objective-C}
12269 @item @code{info line}
12274 A fully qualified Objective-C method name is specified as
12277 -[@var{Class} @var{methodName}]
12280 where the minus sign is used to indicate an instance method and a
12281 plus sign (not shown) is used to indicate a class method. The class
12282 name @var{Class} and method name @var{methodName} are enclosed in
12283 brackets, similar to the way messages are specified in Objective-C
12284 source code. For example, to set a breakpoint at the @code{create}
12285 instance method of class @code{Fruit} in the program currently being
12289 break -[Fruit create]
12292 To list ten program lines around the @code{initialize} class method,
12296 list +[NSText initialize]
12299 In the current version of @value{GDBN}, the plus or minus sign is
12300 required. In future versions of @value{GDBN}, the plus or minus
12301 sign will be optional, but you can use it to narrow the search. It
12302 is also possible to specify just a method name:
12308 You must specify the complete method name, including any colons. If
12309 your program's source files contain more than one @code{create} method,
12310 you'll be presented with a numbered list of classes that implement that
12311 method. Indicate your choice by number, or type @samp{0} to exit if
12314 As another example, to clear a breakpoint established at the
12315 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12318 clear -[NSWindow makeKeyAndOrderFront:]
12321 @node The Print Command with Objective-C
12322 @subsubsection The Print Command With Objective-C
12323 @cindex Objective-C, print objects
12324 @kindex print-object
12325 @kindex po @r{(@code{print-object})}
12327 The print command has also been extended to accept methods. For example:
12330 print -[@var{object} hash]
12333 @cindex print an Objective-C object description
12334 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12336 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12337 and print the result. Also, an additional command has been added,
12338 @code{print-object} or @code{po} for short, which is meant to print
12339 the description of an object. However, this command may only work
12340 with certain Objective-C libraries that have a particular hook
12341 function, @code{_NSPrintForDebugger}, defined.
12344 @subsection OpenCL C
12347 This section provides information about @value{GDBN}s OpenCL C support.
12350 * OpenCL C Datatypes::
12351 * OpenCL C Expressions::
12352 * OpenCL C Operators::
12355 @node OpenCL C Datatypes
12356 @subsubsection OpenCL C Datatypes
12358 @cindex OpenCL C Datatypes
12359 @value{GDBN} supports the builtin scalar and vector datatypes specified
12360 by OpenCL 1.1. In addition the half- and double-precision floating point
12361 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12362 extensions are also known to @value{GDBN}.
12364 @node OpenCL C Expressions
12365 @subsubsection OpenCL C Expressions
12367 @cindex OpenCL C Expressions
12368 @value{GDBN} supports accesses to vector components including the access as
12369 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12370 supported by @value{GDBN} can be used as well.
12372 @node OpenCL C Operators
12373 @subsubsection OpenCL C Operators
12375 @cindex OpenCL C Operators
12376 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12380 @subsection Fortran
12381 @cindex Fortran-specific support in @value{GDBN}
12383 @value{GDBN} can be used to debug programs written in Fortran, but it
12384 currently supports only the features of Fortran 77 language.
12386 @cindex trailing underscore, in Fortran symbols
12387 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12388 among them) append an underscore to the names of variables and
12389 functions. When you debug programs compiled by those compilers, you
12390 will need to refer to variables and functions with a trailing
12394 * Fortran Operators:: Fortran operators and expressions
12395 * Fortran Defaults:: Default settings for Fortran
12396 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12399 @node Fortran Operators
12400 @subsubsection Fortran Operators and Expressions
12402 @cindex Fortran operators and expressions
12404 Operators must be defined on values of specific types. For instance,
12405 @code{+} is defined on numbers, but not on characters or other non-
12406 arithmetic types. Operators are often defined on groups of types.
12410 The exponentiation operator. It raises the first operand to the power
12414 The range operator. Normally used in the form of array(low:high) to
12415 represent a section of array.
12418 The access component operator. Normally used to access elements in derived
12419 types. Also suitable for unions. As unions aren't part of regular Fortran,
12420 this can only happen when accessing a register that uses a gdbarch-defined
12424 @node Fortran Defaults
12425 @subsubsection Fortran Defaults
12427 @cindex Fortran Defaults
12429 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12430 default uses case-insensitive matches for Fortran symbols. You can
12431 change that with the @samp{set case-insensitive} command, see
12432 @ref{Symbols}, for the details.
12434 @node Special Fortran Commands
12435 @subsubsection Special Fortran Commands
12437 @cindex Special Fortran commands
12439 @value{GDBN} has some commands to support Fortran-specific features,
12440 such as displaying common blocks.
12443 @cindex @code{COMMON} blocks, Fortran
12444 @kindex info common
12445 @item info common @r{[}@var{common-name}@r{]}
12446 This command prints the values contained in the Fortran @code{COMMON}
12447 block whose name is @var{common-name}. With no argument, the names of
12448 all @code{COMMON} blocks visible at the current program location are
12455 @cindex Pascal support in @value{GDBN}, limitations
12456 Debugging Pascal programs which use sets, subranges, file variables, or
12457 nested functions does not currently work. @value{GDBN} does not support
12458 entering expressions, printing values, or similar features using Pascal
12461 The Pascal-specific command @code{set print pascal_static-members}
12462 controls whether static members of Pascal objects are displayed.
12463 @xref{Print Settings, pascal_static-members}.
12466 @subsection Modula-2
12468 @cindex Modula-2, @value{GDBN} support
12470 The extensions made to @value{GDBN} to support Modula-2 only support
12471 output from the @sc{gnu} Modula-2 compiler (which is currently being
12472 developed). Other Modula-2 compilers are not currently supported, and
12473 attempting to debug executables produced by them is most likely
12474 to give an error as @value{GDBN} reads in the executable's symbol
12477 @cindex expressions in Modula-2
12479 * M2 Operators:: Built-in operators
12480 * Built-In Func/Proc:: Built-in functions and procedures
12481 * M2 Constants:: Modula-2 constants
12482 * M2 Types:: Modula-2 types
12483 * M2 Defaults:: Default settings for Modula-2
12484 * Deviations:: Deviations from standard Modula-2
12485 * M2 Checks:: Modula-2 type and range checks
12486 * M2 Scope:: The scope operators @code{::} and @code{.}
12487 * GDB/M2:: @value{GDBN} and Modula-2
12491 @subsubsection Operators
12492 @cindex Modula-2 operators
12494 Operators must be defined on values of specific types. For instance,
12495 @code{+} is defined on numbers, but not on structures. Operators are
12496 often defined on groups of types. For the purposes of Modula-2, the
12497 following definitions hold:
12502 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12506 @emph{Character types} consist of @code{CHAR} and its subranges.
12509 @emph{Floating-point types} consist of @code{REAL}.
12512 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12516 @emph{Scalar types} consist of all of the above.
12519 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12522 @emph{Boolean types} consist of @code{BOOLEAN}.
12526 The following operators are supported, and appear in order of
12527 increasing precedence:
12531 Function argument or array index separator.
12534 Assignment. The value of @var{var} @code{:=} @var{value} is
12538 Less than, greater than on integral, floating-point, or enumerated
12542 Less than or equal to, greater than or equal to
12543 on integral, floating-point and enumerated types, or set inclusion on
12544 set types. Same precedence as @code{<}.
12546 @item =@r{, }<>@r{, }#
12547 Equality and two ways of expressing inequality, valid on scalar types.
12548 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12549 available for inequality, since @code{#} conflicts with the script
12553 Set membership. Defined on set types and the types of their members.
12554 Same precedence as @code{<}.
12557 Boolean disjunction. Defined on boolean types.
12560 Boolean conjunction. Defined on boolean types.
12563 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12566 Addition and subtraction on integral and floating-point types, or union
12567 and difference on set types.
12570 Multiplication on integral and floating-point types, or set intersection
12574 Division on floating-point types, or symmetric set difference on set
12575 types. Same precedence as @code{*}.
12578 Integer division and remainder. Defined on integral types. Same
12579 precedence as @code{*}.
12582 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12585 Pointer dereferencing. Defined on pointer types.
12588 Boolean negation. Defined on boolean types. Same precedence as
12592 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12593 precedence as @code{^}.
12596 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12599 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12603 @value{GDBN} and Modula-2 scope operators.
12607 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12608 treats the use of the operator @code{IN}, or the use of operators
12609 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12610 @code{<=}, and @code{>=} on sets as an error.
12614 @node Built-In Func/Proc
12615 @subsubsection Built-in Functions and Procedures
12616 @cindex Modula-2 built-ins
12618 Modula-2 also makes available several built-in procedures and functions.
12619 In describing these, the following metavariables are used:
12624 represents an @code{ARRAY} variable.
12627 represents a @code{CHAR} constant or variable.
12630 represents a variable or constant of integral type.
12633 represents an identifier that belongs to a set. Generally used in the
12634 same function with the metavariable @var{s}. The type of @var{s} should
12635 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12638 represents a variable or constant of integral or floating-point type.
12641 represents a variable or constant of floating-point type.
12647 represents a variable.
12650 represents a variable or constant of one of many types. See the
12651 explanation of the function for details.
12654 All Modula-2 built-in procedures also return a result, described below.
12658 Returns the absolute value of @var{n}.
12661 If @var{c} is a lower case letter, it returns its upper case
12662 equivalent, otherwise it returns its argument.
12665 Returns the character whose ordinal value is @var{i}.
12668 Decrements the value in the variable @var{v} by one. Returns the new value.
12670 @item DEC(@var{v},@var{i})
12671 Decrements the value in the variable @var{v} by @var{i}. Returns the
12674 @item EXCL(@var{m},@var{s})
12675 Removes the element @var{m} from the set @var{s}. Returns the new
12678 @item FLOAT(@var{i})
12679 Returns the floating point equivalent of the integer @var{i}.
12681 @item HIGH(@var{a})
12682 Returns the index of the last member of @var{a}.
12685 Increments the value in the variable @var{v} by one. Returns the new value.
12687 @item INC(@var{v},@var{i})
12688 Increments the value in the variable @var{v} by @var{i}. Returns the
12691 @item INCL(@var{m},@var{s})
12692 Adds the element @var{m} to the set @var{s} if it is not already
12693 there. Returns the new set.
12696 Returns the maximum value of the type @var{t}.
12699 Returns the minimum value of the type @var{t}.
12702 Returns boolean TRUE if @var{i} is an odd number.
12705 Returns the ordinal value of its argument. For example, the ordinal
12706 value of a character is its @sc{ascii} value (on machines supporting the
12707 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12708 integral, character and enumerated types.
12710 @item SIZE(@var{x})
12711 Returns the size of its argument. @var{x} can be a variable or a type.
12713 @item TRUNC(@var{r})
12714 Returns the integral part of @var{r}.
12716 @item TSIZE(@var{x})
12717 Returns the size of its argument. @var{x} can be a variable or a type.
12719 @item VAL(@var{t},@var{i})
12720 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12724 @emph{Warning:} Sets and their operations are not yet supported, so
12725 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12729 @cindex Modula-2 constants
12731 @subsubsection Constants
12733 @value{GDBN} allows you to express the constants of Modula-2 in the following
12739 Integer constants are simply a sequence of digits. When used in an
12740 expression, a constant is interpreted to be type-compatible with the
12741 rest of the expression. Hexadecimal integers are specified by a
12742 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12745 Floating point constants appear as a sequence of digits, followed by a
12746 decimal point and another sequence of digits. An optional exponent can
12747 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12748 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12749 digits of the floating point constant must be valid decimal (base 10)
12753 Character constants consist of a single character enclosed by a pair of
12754 like quotes, either single (@code{'}) or double (@code{"}). They may
12755 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12756 followed by a @samp{C}.
12759 String constants consist of a sequence of characters enclosed by a
12760 pair of like quotes, either single (@code{'}) or double (@code{"}).
12761 Escape sequences in the style of C are also allowed. @xref{C
12762 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12766 Enumerated constants consist of an enumerated identifier.
12769 Boolean constants consist of the identifiers @code{TRUE} and
12773 Pointer constants consist of integral values only.
12776 Set constants are not yet supported.
12780 @subsubsection Modula-2 Types
12781 @cindex Modula-2 types
12783 Currently @value{GDBN} can print the following data types in Modula-2
12784 syntax: array types, record types, set types, pointer types, procedure
12785 types, enumerated types, subrange types and base types. You can also
12786 print the contents of variables declared using these type.
12787 This section gives a number of simple source code examples together with
12788 sample @value{GDBN} sessions.
12790 The first example contains the following section of code:
12799 and you can request @value{GDBN} to interrogate the type and value of
12800 @code{r} and @code{s}.
12803 (@value{GDBP}) print s
12805 (@value{GDBP}) ptype s
12807 (@value{GDBP}) print r
12809 (@value{GDBP}) ptype r
12814 Likewise if your source code declares @code{s} as:
12818 s: SET ['A'..'Z'] ;
12822 then you may query the type of @code{s} by:
12825 (@value{GDBP}) ptype s
12826 type = SET ['A'..'Z']
12830 Note that at present you cannot interactively manipulate set
12831 expressions using the debugger.
12833 The following example shows how you might declare an array in Modula-2
12834 and how you can interact with @value{GDBN} to print its type and contents:
12838 s: ARRAY [-10..10] OF CHAR ;
12842 (@value{GDBP}) ptype s
12843 ARRAY [-10..10] OF CHAR
12846 Note that the array handling is not yet complete and although the type
12847 is printed correctly, expression handling still assumes that all
12848 arrays have a lower bound of zero and not @code{-10} as in the example
12851 Here are some more type related Modula-2 examples:
12855 colour = (blue, red, yellow, green) ;
12856 t = [blue..yellow] ;
12864 The @value{GDBN} interaction shows how you can query the data type
12865 and value of a variable.
12868 (@value{GDBP}) print s
12870 (@value{GDBP}) ptype t
12871 type = [blue..yellow]
12875 In this example a Modula-2 array is declared and its contents
12876 displayed. Observe that the contents are written in the same way as
12877 their @code{C} counterparts.
12881 s: ARRAY [1..5] OF CARDINAL ;
12887 (@value{GDBP}) print s
12888 $1 = @{1, 0, 0, 0, 0@}
12889 (@value{GDBP}) ptype s
12890 type = ARRAY [1..5] OF CARDINAL
12893 The Modula-2 language interface to @value{GDBN} also understands
12894 pointer types as shown in this example:
12898 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12905 and you can request that @value{GDBN} describes the type of @code{s}.
12908 (@value{GDBP}) ptype s
12909 type = POINTER TO ARRAY [1..5] OF CARDINAL
12912 @value{GDBN} handles compound types as we can see in this example.
12913 Here we combine array types, record types, pointer types and subrange
12924 myarray = ARRAY myrange OF CARDINAL ;
12925 myrange = [-2..2] ;
12927 s: POINTER TO ARRAY myrange OF foo ;
12931 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12935 (@value{GDBP}) ptype s
12936 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12939 f3 : ARRAY [-2..2] OF CARDINAL;
12944 @subsubsection Modula-2 Defaults
12945 @cindex Modula-2 defaults
12947 If type and range checking are set automatically by @value{GDBN}, they
12948 both default to @code{on} whenever the working language changes to
12949 Modula-2. This happens regardless of whether you or @value{GDBN}
12950 selected the working language.
12952 If you allow @value{GDBN} to set the language automatically, then entering
12953 code compiled from a file whose name ends with @file{.mod} sets the
12954 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12955 Infer the Source Language}, for further details.
12958 @subsubsection Deviations from Standard Modula-2
12959 @cindex Modula-2, deviations from
12961 A few changes have been made to make Modula-2 programs easier to debug.
12962 This is done primarily via loosening its type strictness:
12966 Unlike in standard Modula-2, pointer constants can be formed by
12967 integers. This allows you to modify pointer variables during
12968 debugging. (In standard Modula-2, the actual address contained in a
12969 pointer variable is hidden from you; it can only be modified
12970 through direct assignment to another pointer variable or expression that
12971 returned a pointer.)
12974 C escape sequences can be used in strings and characters to represent
12975 non-printable characters. @value{GDBN} prints out strings with these
12976 escape sequences embedded. Single non-printable characters are
12977 printed using the @samp{CHR(@var{nnn})} format.
12980 The assignment operator (@code{:=}) returns the value of its right-hand
12984 All built-in procedures both modify @emph{and} return their argument.
12988 @subsubsection Modula-2 Type and Range Checks
12989 @cindex Modula-2 checks
12992 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12995 @c FIXME remove warning when type/range checks added
12997 @value{GDBN} considers two Modula-2 variables type equivalent if:
13001 They are of types that have been declared equivalent via a @code{TYPE
13002 @var{t1} = @var{t2}} statement
13005 They have been declared on the same line. (Note: This is true of the
13006 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13009 As long as type checking is enabled, any attempt to combine variables
13010 whose types are not equivalent is an error.
13012 Range checking is done on all mathematical operations, assignment, array
13013 index bounds, and all built-in functions and procedures.
13016 @subsubsection The Scope Operators @code{::} and @code{.}
13018 @cindex @code{.}, Modula-2 scope operator
13019 @cindex colon, doubled as scope operator
13021 @vindex colon-colon@r{, in Modula-2}
13022 @c Info cannot handle :: but TeX can.
13025 @vindex ::@r{, in Modula-2}
13028 There are a few subtle differences between the Modula-2 scope operator
13029 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13034 @var{module} . @var{id}
13035 @var{scope} :: @var{id}
13039 where @var{scope} is the name of a module or a procedure,
13040 @var{module} the name of a module, and @var{id} is any declared
13041 identifier within your program, except another module.
13043 Using the @code{::} operator makes @value{GDBN} search the scope
13044 specified by @var{scope} for the identifier @var{id}. If it is not
13045 found in the specified scope, then @value{GDBN} searches all scopes
13046 enclosing the one specified by @var{scope}.
13048 Using the @code{.} operator makes @value{GDBN} search the current scope for
13049 the identifier specified by @var{id} that was imported from the
13050 definition module specified by @var{module}. With this operator, it is
13051 an error if the identifier @var{id} was not imported from definition
13052 module @var{module}, or if @var{id} is not an identifier in
13056 @subsubsection @value{GDBN} and Modula-2
13058 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13059 Five subcommands of @code{set print} and @code{show print} apply
13060 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13061 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13062 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13063 analogue in Modula-2.
13065 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13066 with any language, is not useful with Modula-2. Its
13067 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13068 created in Modula-2 as they can in C or C@t{++}. However, because an
13069 address can be specified by an integral constant, the construct
13070 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13072 @cindex @code{#} in Modula-2
13073 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13074 interpreted as the beginning of a comment. Use @code{<>} instead.
13080 The extensions made to @value{GDBN} for Ada only support
13081 output from the @sc{gnu} Ada (GNAT) compiler.
13082 Other Ada compilers are not currently supported, and
13083 attempting to debug executables produced by them is most likely
13087 @cindex expressions in Ada
13089 * Ada Mode Intro:: General remarks on the Ada syntax
13090 and semantics supported by Ada mode
13092 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13093 * Additions to Ada:: Extensions of the Ada expression syntax.
13094 * Stopping Before Main Program:: Debugging the program during elaboration.
13095 * Ada Tasks:: Listing and setting breakpoints in tasks.
13096 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13097 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13099 * Ada Glitches:: Known peculiarities of Ada mode.
13102 @node Ada Mode Intro
13103 @subsubsection Introduction
13104 @cindex Ada mode, general
13106 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13107 syntax, with some extensions.
13108 The philosophy behind the design of this subset is
13112 That @value{GDBN} should provide basic literals and access to operations for
13113 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13114 leaving more sophisticated computations to subprograms written into the
13115 program (which therefore may be called from @value{GDBN}).
13118 That type safety and strict adherence to Ada language restrictions
13119 are not particularly important to the @value{GDBN} user.
13122 That brevity is important to the @value{GDBN} user.
13125 Thus, for brevity, the debugger acts as if all names declared in
13126 user-written packages are directly visible, even if they are not visible
13127 according to Ada rules, thus making it unnecessary to fully qualify most
13128 names with their packages, regardless of context. Where this causes
13129 ambiguity, @value{GDBN} asks the user's intent.
13131 The debugger will start in Ada mode if it detects an Ada main program.
13132 As for other languages, it will enter Ada mode when stopped in a program that
13133 was translated from an Ada source file.
13135 While in Ada mode, you may use `@t{--}' for comments. This is useful
13136 mostly for documenting command files. The standard @value{GDBN} comment
13137 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13138 middle (to allow based literals).
13140 The debugger supports limited overloading. Given a subprogram call in which
13141 the function symbol has multiple definitions, it will use the number of
13142 actual parameters and some information about their types to attempt to narrow
13143 the set of definitions. It also makes very limited use of context, preferring
13144 procedures to functions in the context of the @code{call} command, and
13145 functions to procedures elsewhere.
13147 @node Omissions from Ada
13148 @subsubsection Omissions from Ada
13149 @cindex Ada, omissions from
13151 Here are the notable omissions from the subset:
13155 Only a subset of the attributes are supported:
13159 @t{'First}, @t{'Last}, and @t{'Length}
13160 on array objects (not on types and subtypes).
13163 @t{'Min} and @t{'Max}.
13166 @t{'Pos} and @t{'Val}.
13172 @t{'Range} on array objects (not subtypes), but only as the right
13173 operand of the membership (@code{in}) operator.
13176 @t{'Access}, @t{'Unchecked_Access}, and
13177 @t{'Unrestricted_Access} (a GNAT extension).
13185 @code{Characters.Latin_1} are not available and
13186 concatenation is not implemented. Thus, escape characters in strings are
13187 not currently available.
13190 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13191 equality of representations. They will generally work correctly
13192 for strings and arrays whose elements have integer or enumeration types.
13193 They may not work correctly for arrays whose element
13194 types have user-defined equality, for arrays of real values
13195 (in particular, IEEE-conformant floating point, because of negative
13196 zeroes and NaNs), and for arrays whose elements contain unused bits with
13197 indeterminate values.
13200 The other component-by-component array operations (@code{and}, @code{or},
13201 @code{xor}, @code{not}, and relational tests other than equality)
13202 are not implemented.
13205 @cindex array aggregates (Ada)
13206 @cindex record aggregates (Ada)
13207 @cindex aggregates (Ada)
13208 There is limited support for array and record aggregates. They are
13209 permitted only on the right sides of assignments, as in these examples:
13212 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13213 (@value{GDBP}) set An_Array := (1, others => 0)
13214 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13215 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13216 (@value{GDBP}) set A_Record := (1, "Peter", True);
13217 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13221 discriminant's value by assigning an aggregate has an
13222 undefined effect if that discriminant is used within the record.
13223 However, you can first modify discriminants by directly assigning to
13224 them (which normally would not be allowed in Ada), and then performing an
13225 aggregate assignment. For example, given a variable @code{A_Rec}
13226 declared to have a type such as:
13229 type Rec (Len : Small_Integer := 0) is record
13231 Vals : IntArray (1 .. Len);
13235 you can assign a value with a different size of @code{Vals} with two
13239 (@value{GDBP}) set A_Rec.Len := 4
13240 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13243 As this example also illustrates, @value{GDBN} is very loose about the usual
13244 rules concerning aggregates. You may leave out some of the
13245 components of an array or record aggregate (such as the @code{Len}
13246 component in the assignment to @code{A_Rec} above); they will retain their
13247 original values upon assignment. You may freely use dynamic values as
13248 indices in component associations. You may even use overlapping or
13249 redundant component associations, although which component values are
13250 assigned in such cases is not defined.
13253 Calls to dispatching subprograms are not implemented.
13256 The overloading algorithm is much more limited (i.e., less selective)
13257 than that of real Ada. It makes only limited use of the context in
13258 which a subexpression appears to resolve its meaning, and it is much
13259 looser in its rules for allowing type matches. As a result, some
13260 function calls will be ambiguous, and the user will be asked to choose
13261 the proper resolution.
13264 The @code{new} operator is not implemented.
13267 Entry calls are not implemented.
13270 Aside from printing, arithmetic operations on the native VAX floating-point
13271 formats are not supported.
13274 It is not possible to slice a packed array.
13277 The names @code{True} and @code{False}, when not part of a qualified name,
13278 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13280 Should your program
13281 redefine these names in a package or procedure (at best a dubious practice),
13282 you will have to use fully qualified names to access their new definitions.
13285 @node Additions to Ada
13286 @subsubsection Additions to Ada
13287 @cindex Ada, deviations from
13289 As it does for other languages, @value{GDBN} makes certain generic
13290 extensions to Ada (@pxref{Expressions}):
13294 If the expression @var{E} is a variable residing in memory (typically
13295 a local variable or array element) and @var{N} is a positive integer,
13296 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13297 @var{N}-1 adjacent variables following it in memory as an array. In
13298 Ada, this operator is generally not necessary, since its prime use is
13299 in displaying parts of an array, and slicing will usually do this in
13300 Ada. However, there are occasional uses when debugging programs in
13301 which certain debugging information has been optimized away.
13304 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13305 appears in function or file @var{B}.'' When @var{B} is a file name,
13306 you must typically surround it in single quotes.
13309 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13310 @var{type} that appears at address @var{addr}.''
13313 A name starting with @samp{$} is a convenience variable
13314 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13317 In addition, @value{GDBN} provides a few other shortcuts and outright
13318 additions specific to Ada:
13322 The assignment statement is allowed as an expression, returning
13323 its right-hand operand as its value. Thus, you may enter
13326 (@value{GDBP}) set x := y + 3
13327 (@value{GDBP}) print A(tmp := y + 1)
13331 The semicolon is allowed as an ``operator,'' returning as its value
13332 the value of its right-hand operand.
13333 This allows, for example,
13334 complex conditional breaks:
13337 (@value{GDBP}) break f
13338 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13342 Rather than use catenation and symbolic character names to introduce special
13343 characters into strings, one may instead use a special bracket notation,
13344 which is also used to print strings. A sequence of characters of the form
13345 @samp{["@var{XX}"]} within a string or character literal denotes the
13346 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13347 sequence of characters @samp{["""]} also denotes a single quotation mark
13348 in strings. For example,
13350 "One line.["0a"]Next line.["0a"]"
13353 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13357 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13358 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13362 (@value{GDBP}) print 'max(x, y)
13366 When printing arrays, @value{GDBN} uses positional notation when the
13367 array has a lower bound of 1, and uses a modified named notation otherwise.
13368 For example, a one-dimensional array of three integers with a lower bound
13369 of 3 might print as
13376 That is, in contrast to valid Ada, only the first component has a @code{=>}
13380 You may abbreviate attributes in expressions with any unique,
13381 multi-character subsequence of
13382 their names (an exact match gets preference).
13383 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13384 in place of @t{a'length}.
13387 @cindex quoting Ada internal identifiers
13388 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13389 to lower case. The GNAT compiler uses upper-case characters for
13390 some of its internal identifiers, which are normally of no interest to users.
13391 For the rare occasions when you actually have to look at them,
13392 enclose them in angle brackets to avoid the lower-case mapping.
13395 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13399 Printing an object of class-wide type or dereferencing an
13400 access-to-class-wide value will display all the components of the object's
13401 specific type (as indicated by its run-time tag). Likewise, component
13402 selection on such a value will operate on the specific type of the
13407 @node Stopping Before Main Program
13408 @subsubsection Stopping at the Very Beginning
13410 @cindex breakpointing Ada elaboration code
13411 It is sometimes necessary to debug the program during elaboration, and
13412 before reaching the main procedure.
13413 As defined in the Ada Reference
13414 Manual, the elaboration code is invoked from a procedure called
13415 @code{adainit}. To run your program up to the beginning of
13416 elaboration, simply use the following two commands:
13417 @code{tbreak adainit} and @code{run}.
13420 @subsubsection Extensions for Ada Tasks
13421 @cindex Ada, tasking
13423 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13424 @value{GDBN} provides the following task-related commands:
13429 This command shows a list of current Ada tasks, as in the following example:
13436 (@value{GDBP}) info tasks
13437 ID TID P-ID Pri State Name
13438 1 8088000 0 15 Child Activation Wait main_task
13439 2 80a4000 1 15 Accept Statement b
13440 3 809a800 1 15 Child Activation Wait a
13441 * 4 80ae800 3 15 Runnable c
13446 In this listing, the asterisk before the last task indicates it to be the
13447 task currently being inspected.
13451 Represents @value{GDBN}'s internal task number.
13457 The parent's task ID (@value{GDBN}'s internal task number).
13460 The base priority of the task.
13463 Current state of the task.
13467 The task has been created but has not been activated. It cannot be
13471 The task is not blocked for any reason known to Ada. (It may be waiting
13472 for a mutex, though.) It is conceptually "executing" in normal mode.
13475 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13476 that were waiting on terminate alternatives have been awakened and have
13477 terminated themselves.
13479 @item Child Activation Wait
13480 The task is waiting for created tasks to complete activation.
13482 @item Accept Statement
13483 The task is waiting on an accept or selective wait statement.
13485 @item Waiting on entry call
13486 The task is waiting on an entry call.
13488 @item Async Select Wait
13489 The task is waiting to start the abortable part of an asynchronous
13493 The task is waiting on a select statement with only a delay
13496 @item Child Termination Wait
13497 The task is sleeping having completed a master within itself, and is
13498 waiting for the tasks dependent on that master to become terminated or
13499 waiting on a terminate Phase.
13501 @item Wait Child in Term Alt
13502 The task is sleeping waiting for tasks on terminate alternatives to
13503 finish terminating.
13505 @item Accepting RV with @var{taskno}
13506 The task is accepting a rendez-vous with the task @var{taskno}.
13510 Name of the task in the program.
13514 @kindex info task @var{taskno}
13515 @item info task @var{taskno}
13516 This command shows detailled informations on the specified task, as in
13517 the following example:
13522 (@value{GDBP}) info tasks
13523 ID TID P-ID Pri State Name
13524 1 8077880 0 15 Child Activation Wait main_task
13525 * 2 807c468 1 15 Runnable task_1
13526 (@value{GDBP}) info task 2
13527 Ada Task: 0x807c468
13530 Parent: 1 (main_task)
13536 @kindex task@r{ (Ada)}
13537 @cindex current Ada task ID
13538 This command prints the ID of the current task.
13544 (@value{GDBP}) info tasks
13545 ID TID P-ID Pri State Name
13546 1 8077870 0 15 Child Activation Wait main_task
13547 * 2 807c458 1 15 Runnable t
13548 (@value{GDBP}) task
13549 [Current task is 2]
13552 @item task @var{taskno}
13553 @cindex Ada task switching
13554 This command is like the @code{thread @var{threadno}}
13555 command (@pxref{Threads}). It switches the context of debugging
13556 from the current task to the given task.
13562 (@value{GDBP}) info tasks
13563 ID TID P-ID Pri State Name
13564 1 8077870 0 15 Child Activation Wait main_task
13565 * 2 807c458 1 15 Runnable t
13566 (@value{GDBP}) task 1
13567 [Switching to task 1]
13568 #0 0x8067726 in pthread_cond_wait ()
13570 #0 0x8067726 in pthread_cond_wait ()
13571 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13572 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13573 #3 0x806153e in system.tasking.stages.activate_tasks ()
13574 #4 0x804aacc in un () at un.adb:5
13577 @item break @var{linespec} task @var{taskno}
13578 @itemx break @var{linespec} task @var{taskno} if @dots{}
13579 @cindex breakpoints and tasks, in Ada
13580 @cindex task breakpoints, in Ada
13581 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13582 These commands are like the @code{break @dots{} thread @dots{}}
13583 command (@pxref{Thread Stops}).
13584 @var{linespec} specifies source lines, as described
13585 in @ref{Specify Location}.
13587 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13588 to specify that you only want @value{GDBN} to stop the program when a
13589 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13590 numeric task identifiers assigned by @value{GDBN}, shown in the first
13591 column of the @samp{info tasks} display.
13593 If you do not specify @samp{task @var{taskno}} when you set a
13594 breakpoint, the breakpoint applies to @emph{all} tasks of your
13597 You can use the @code{task} qualifier on conditional breakpoints as
13598 well; in this case, place @samp{task @var{taskno}} before the
13599 breakpoint condition (before the @code{if}).
13607 (@value{GDBP}) info tasks
13608 ID TID P-ID Pri State Name
13609 1 140022020 0 15 Child Activation Wait main_task
13610 2 140045060 1 15 Accept/Select Wait t2
13611 3 140044840 1 15 Runnable t1
13612 * 4 140056040 1 15 Runnable t3
13613 (@value{GDBP}) b 15 task 2
13614 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13615 (@value{GDBP}) cont
13620 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13622 (@value{GDBP}) info tasks
13623 ID TID P-ID Pri State Name
13624 1 140022020 0 15 Child Activation Wait main_task
13625 * 2 140045060 1 15 Runnable t2
13626 3 140044840 1 15 Runnable t1
13627 4 140056040 1 15 Delay Sleep t3
13631 @node Ada Tasks and Core Files
13632 @subsubsection Tasking Support when Debugging Core Files
13633 @cindex Ada tasking and core file debugging
13635 When inspecting a core file, as opposed to debugging a live program,
13636 tasking support may be limited or even unavailable, depending on
13637 the platform being used.
13638 For instance, on x86-linux, the list of tasks is available, but task
13639 switching is not supported. On Tru64, however, task switching will work
13642 On certain platforms, including Tru64, the debugger needs to perform some
13643 memory writes in order to provide Ada tasking support. When inspecting
13644 a core file, this means that the core file must be opened with read-write
13645 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13646 Under these circumstances, you should make a backup copy of the core
13647 file before inspecting it with @value{GDBN}.
13649 @node Ravenscar Profile
13650 @subsubsection Tasking Support when using the Ravenscar Profile
13651 @cindex Ravenscar Profile
13653 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13654 specifically designed for systems with safety-critical real-time
13658 @kindex set ravenscar task-switching on
13659 @cindex task switching with program using Ravenscar Profile
13660 @item set ravenscar task-switching on
13661 Allows task switching when debugging a program that uses the Ravenscar
13662 Profile. This is the default.
13664 @kindex set ravenscar task-switching off
13665 @item set ravenscar task-switching off
13666 Turn off task switching when debugging a program that uses the Ravenscar
13667 Profile. This is mostly intended to disable the code that adds support
13668 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13669 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13670 To be effective, this command should be run before the program is started.
13672 @kindex show ravenscar task-switching
13673 @item show ravenscar task-switching
13674 Show whether it is possible to switch from task to task in a program
13675 using the Ravenscar Profile.
13680 @subsubsection Known Peculiarities of Ada Mode
13681 @cindex Ada, problems
13683 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13684 we know of several problems with and limitations of Ada mode in
13686 some of which will be fixed with planned future releases of the debugger
13687 and the GNU Ada compiler.
13691 Static constants that the compiler chooses not to materialize as objects in
13692 storage are invisible to the debugger.
13695 Named parameter associations in function argument lists are ignored (the
13696 argument lists are treated as positional).
13699 Many useful library packages are currently invisible to the debugger.
13702 Fixed-point arithmetic, conversions, input, and output is carried out using
13703 floating-point arithmetic, and may give results that only approximate those on
13707 The GNAT compiler never generates the prefix @code{Standard} for any of
13708 the standard symbols defined by the Ada language. @value{GDBN} knows about
13709 this: it will strip the prefix from names when you use it, and will never
13710 look for a name you have so qualified among local symbols, nor match against
13711 symbols in other packages or subprograms. If you have
13712 defined entities anywhere in your program other than parameters and
13713 local variables whose simple names match names in @code{Standard},
13714 GNAT's lack of qualification here can cause confusion. When this happens,
13715 you can usually resolve the confusion
13716 by qualifying the problematic names with package
13717 @code{Standard} explicitly.
13720 Older versions of the compiler sometimes generate erroneous debugging
13721 information, resulting in the debugger incorrectly printing the value
13722 of affected entities. In some cases, the debugger is able to work
13723 around an issue automatically. In other cases, the debugger is able
13724 to work around the issue, but the work-around has to be specifically
13727 @kindex set ada trust-PAD-over-XVS
13728 @kindex show ada trust-PAD-over-XVS
13731 @item set ada trust-PAD-over-XVS on
13732 Configure GDB to strictly follow the GNAT encoding when computing the
13733 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13734 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13735 a complete description of the encoding used by the GNAT compiler).
13736 This is the default.
13738 @item set ada trust-PAD-over-XVS off
13739 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13740 sometimes prints the wrong value for certain entities, changing @code{ada
13741 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13742 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13743 @code{off}, but this incurs a slight performance penalty, so it is
13744 recommended to leave this setting to @code{on} unless necessary.
13748 @node Unsupported Languages
13749 @section Unsupported Languages
13751 @cindex unsupported languages
13752 @cindex minimal language
13753 In addition to the other fully-supported programming languages,
13754 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13755 It does not represent a real programming language, but provides a set
13756 of capabilities close to what the C or assembly languages provide.
13757 This should allow most simple operations to be performed while debugging
13758 an application that uses a language currently not supported by @value{GDBN}.
13760 If the language is set to @code{auto}, @value{GDBN} will automatically
13761 select this language if the current frame corresponds to an unsupported
13765 @chapter Examining the Symbol Table
13767 The commands described in this chapter allow you to inquire about the
13768 symbols (names of variables, functions and types) defined in your
13769 program. This information is inherent in the text of your program and
13770 does not change as your program executes. @value{GDBN} finds it in your
13771 program's symbol table, in the file indicated when you started @value{GDBN}
13772 (@pxref{File Options, ,Choosing Files}), or by one of the
13773 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13775 @cindex symbol names
13776 @cindex names of symbols
13777 @cindex quoting names
13778 Occasionally, you may need to refer to symbols that contain unusual
13779 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13780 most frequent case is in referring to static variables in other
13781 source files (@pxref{Variables,,Program Variables}). File names
13782 are recorded in object files as debugging symbols, but @value{GDBN} would
13783 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13784 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13785 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13792 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13795 @cindex case-insensitive symbol names
13796 @cindex case sensitivity in symbol names
13797 @kindex set case-sensitive
13798 @item set case-sensitive on
13799 @itemx set case-sensitive off
13800 @itemx set case-sensitive auto
13801 Normally, when @value{GDBN} looks up symbols, it matches their names
13802 with case sensitivity determined by the current source language.
13803 Occasionally, you may wish to control that. The command @code{set
13804 case-sensitive} lets you do that by specifying @code{on} for
13805 case-sensitive matches or @code{off} for case-insensitive ones. If
13806 you specify @code{auto}, case sensitivity is reset to the default
13807 suitable for the source language. The default is case-sensitive
13808 matches for all languages except for Fortran, for which the default is
13809 case-insensitive matches.
13811 @kindex show case-sensitive
13812 @item show case-sensitive
13813 This command shows the current setting of case sensitivity for symbols
13816 @kindex info address
13817 @cindex address of a symbol
13818 @item info address @var{symbol}
13819 Describe where the data for @var{symbol} is stored. For a register
13820 variable, this says which register it is kept in. For a non-register
13821 local variable, this prints the stack-frame offset at which the variable
13824 Note the contrast with @samp{print &@var{symbol}}, which does not work
13825 at all for a register variable, and for a stack local variable prints
13826 the exact address of the current instantiation of the variable.
13828 @kindex info symbol
13829 @cindex symbol from address
13830 @cindex closest symbol and offset for an address
13831 @item info symbol @var{addr}
13832 Print the name of a symbol which is stored at the address @var{addr}.
13833 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13834 nearest symbol and an offset from it:
13837 (@value{GDBP}) info symbol 0x54320
13838 _initialize_vx + 396 in section .text
13842 This is the opposite of the @code{info address} command. You can use
13843 it to find out the name of a variable or a function given its address.
13845 For dynamically linked executables, the name of executable or shared
13846 library containing the symbol is also printed:
13849 (@value{GDBP}) info symbol 0x400225
13850 _start + 5 in section .text of /tmp/a.out
13851 (@value{GDBP}) info symbol 0x2aaaac2811cf
13852 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13856 @item whatis [@var{arg}]
13857 Print the data type of @var{arg}, which can be either an expression or
13858 a data type. With no argument, print the data type of @code{$}, the
13859 last value in the value history. If @var{arg} is an expression, it is
13860 not actually evaluated, and any side-effecting operations (such as
13861 assignments or function calls) inside it do not take place. If
13862 @var{arg} is a type name, it may be the name of a type or typedef, or
13863 for C code it may have the form @samp{class @var{class-name}},
13864 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13865 @samp{enum @var{enum-tag}}.
13866 @xref{Expressions, ,Expressions}.
13869 @item ptype [@var{arg}]
13870 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13871 detailed description of the type, instead of just the name of the type.
13872 @xref{Expressions, ,Expressions}.
13874 For example, for this variable declaration:
13877 struct complex @{double real; double imag;@} v;
13881 the two commands give this output:
13885 (@value{GDBP}) whatis v
13886 type = struct complex
13887 (@value{GDBP}) ptype v
13888 type = struct complex @{
13896 As with @code{whatis}, using @code{ptype} without an argument refers to
13897 the type of @code{$}, the last value in the value history.
13899 @cindex incomplete type
13900 Sometimes, programs use opaque data types or incomplete specifications
13901 of complex data structure. If the debug information included in the
13902 program does not allow @value{GDBN} to display a full declaration of
13903 the data type, it will say @samp{<incomplete type>}. For example,
13904 given these declarations:
13908 struct foo *fooptr;
13912 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13915 (@value{GDBP}) ptype foo
13916 $1 = <incomplete type>
13920 ``Incomplete type'' is C terminology for data types that are not
13921 completely specified.
13924 @item info types @var{regexp}
13926 Print a brief description of all types whose names match the regular
13927 expression @var{regexp} (or all types in your program, if you supply
13928 no argument). Each complete typename is matched as though it were a
13929 complete line; thus, @samp{i type value} gives information on all
13930 types in your program whose names include the string @code{value}, but
13931 @samp{i type ^value$} gives information only on types whose complete
13932 name is @code{value}.
13934 This command differs from @code{ptype} in two ways: first, like
13935 @code{whatis}, it does not print a detailed description; second, it
13936 lists all source files where a type is defined.
13939 @cindex local variables
13940 @item info scope @var{location}
13941 List all the variables local to a particular scope. This command
13942 accepts a @var{location} argument---a function name, a source line, or
13943 an address preceded by a @samp{*}, and prints all the variables local
13944 to the scope defined by that location. (@xref{Specify Location}, for
13945 details about supported forms of @var{location}.) For example:
13948 (@value{GDBP}) @b{info scope command_line_handler}
13949 Scope for command_line_handler:
13950 Symbol rl is an argument at stack/frame offset 8, length 4.
13951 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13952 Symbol linelength is in static storage at address 0x150a1c, length 4.
13953 Symbol p is a local variable in register $esi, length 4.
13954 Symbol p1 is a local variable in register $ebx, length 4.
13955 Symbol nline is a local variable in register $edx, length 4.
13956 Symbol repeat is a local variable at frame offset -8, length 4.
13960 This command is especially useful for determining what data to collect
13961 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13964 @kindex info source
13966 Show information about the current source file---that is, the source file for
13967 the function containing the current point of execution:
13970 the name of the source file, and the directory containing it,
13972 the directory it was compiled in,
13974 its length, in lines,
13976 which programming language it is written in,
13978 whether the executable includes debugging information for that file, and
13979 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13981 whether the debugging information includes information about
13982 preprocessor macros.
13986 @kindex info sources
13988 Print the names of all source files in your program for which there is
13989 debugging information, organized into two lists: files whose symbols
13990 have already been read, and files whose symbols will be read when needed.
13992 @kindex info functions
13993 @item info functions
13994 Print the names and data types of all defined functions.
13996 @item info functions @var{regexp}
13997 Print the names and data types of all defined functions
13998 whose names contain a match for regular expression @var{regexp}.
13999 Thus, @samp{info fun step} finds all functions whose names
14000 include @code{step}; @samp{info fun ^step} finds those whose names
14001 start with @code{step}. If a function name contains characters
14002 that conflict with the regular expression language (e.g.@:
14003 @samp{operator*()}), they may be quoted with a backslash.
14005 @kindex info variables
14006 @item info variables
14007 Print the names and data types of all variables that are defined
14008 outside of functions (i.e.@: excluding local variables).
14010 @item info variables @var{regexp}
14011 Print the names and data types of all variables (except for local
14012 variables) whose names contain a match for regular expression
14015 @kindex info classes
14016 @cindex Objective-C, classes and selectors
14018 @itemx info classes @var{regexp}
14019 Display all Objective-C classes in your program, or
14020 (with the @var{regexp} argument) all those matching a particular regular
14023 @kindex info selectors
14024 @item info selectors
14025 @itemx info selectors @var{regexp}
14026 Display all Objective-C selectors in your program, or
14027 (with the @var{regexp} argument) all those matching a particular regular
14031 This was never implemented.
14032 @kindex info methods
14034 @itemx info methods @var{regexp}
14035 The @code{info methods} command permits the user to examine all defined
14036 methods within C@t{++} program, or (with the @var{regexp} argument) a
14037 specific set of methods found in the various C@t{++} classes. Many
14038 C@t{++} classes provide a large number of methods. Thus, the output
14039 from the @code{ptype} command can be overwhelming and hard to use. The
14040 @code{info-methods} command filters the methods, printing only those
14041 which match the regular-expression @var{regexp}.
14044 @cindex reloading symbols
14045 Some systems allow individual object files that make up your program to
14046 be replaced without stopping and restarting your program. For example,
14047 in VxWorks you can simply recompile a defective object file and keep on
14048 running. If you are running on one of these systems, you can allow
14049 @value{GDBN} to reload the symbols for automatically relinked modules:
14052 @kindex set symbol-reloading
14053 @item set symbol-reloading on
14054 Replace symbol definitions for the corresponding source file when an
14055 object file with a particular name is seen again.
14057 @item set symbol-reloading off
14058 Do not replace symbol definitions when encountering object files of the
14059 same name more than once. This is the default state; if you are not
14060 running on a system that permits automatic relinking of modules, you
14061 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14062 may discard symbols when linking large programs, that may contain
14063 several modules (from different directories or libraries) with the same
14066 @kindex show symbol-reloading
14067 @item show symbol-reloading
14068 Show the current @code{on} or @code{off} setting.
14071 @cindex opaque data types
14072 @kindex set opaque-type-resolution
14073 @item set opaque-type-resolution on
14074 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14075 declared as a pointer to a @code{struct}, @code{class}, or
14076 @code{union}---for example, @code{struct MyType *}---that is used in one
14077 source file although the full declaration of @code{struct MyType} is in
14078 another source file. The default is on.
14080 A change in the setting of this subcommand will not take effect until
14081 the next time symbols for a file are loaded.
14083 @item set opaque-type-resolution off
14084 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14085 is printed as follows:
14087 @{<no data fields>@}
14090 @kindex show opaque-type-resolution
14091 @item show opaque-type-resolution
14092 Show whether opaque types are resolved or not.
14094 @kindex maint print symbols
14095 @cindex symbol dump
14096 @kindex maint print psymbols
14097 @cindex partial symbol dump
14098 @item maint print symbols @var{filename}
14099 @itemx maint print psymbols @var{filename}
14100 @itemx maint print msymbols @var{filename}
14101 Write a dump of debugging symbol data into the file @var{filename}.
14102 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14103 symbols with debugging data are included. If you use @samp{maint print
14104 symbols}, @value{GDBN} includes all the symbols for which it has already
14105 collected full details: that is, @var{filename} reflects symbols for
14106 only those files whose symbols @value{GDBN} has read. You can use the
14107 command @code{info sources} to find out which files these are. If you
14108 use @samp{maint print psymbols} instead, the dump shows information about
14109 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14110 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14111 @samp{maint print msymbols} dumps just the minimal symbol information
14112 required for each object file from which @value{GDBN} has read some symbols.
14113 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14114 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14116 @kindex maint info symtabs
14117 @kindex maint info psymtabs
14118 @cindex listing @value{GDBN}'s internal symbol tables
14119 @cindex symbol tables, listing @value{GDBN}'s internal
14120 @cindex full symbol tables, listing @value{GDBN}'s internal
14121 @cindex partial symbol tables, listing @value{GDBN}'s internal
14122 @item maint info symtabs @r{[} @var{regexp} @r{]}
14123 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14125 List the @code{struct symtab} or @code{struct partial_symtab}
14126 structures whose names match @var{regexp}. If @var{regexp} is not
14127 given, list them all. The output includes expressions which you can
14128 copy into a @value{GDBN} debugging this one to examine a particular
14129 structure in more detail. For example:
14132 (@value{GDBP}) maint info psymtabs dwarf2read
14133 @{ objfile /home/gnu/build/gdb/gdb
14134 ((struct objfile *) 0x82e69d0)
14135 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14136 ((struct partial_symtab *) 0x8474b10)
14139 text addresses 0x814d3c8 -- 0x8158074
14140 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14141 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14142 dependencies (none)
14145 (@value{GDBP}) maint info symtabs
14149 We see that there is one partial symbol table whose filename contains
14150 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14151 and we see that @value{GDBN} has not read in any symtabs yet at all.
14152 If we set a breakpoint on a function, that will cause @value{GDBN} to
14153 read the symtab for the compilation unit containing that function:
14156 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14157 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14159 (@value{GDBP}) maint info symtabs
14160 @{ objfile /home/gnu/build/gdb/gdb
14161 ((struct objfile *) 0x82e69d0)
14162 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14163 ((struct symtab *) 0x86c1f38)
14166 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14167 linetable ((struct linetable *) 0x8370fa0)
14168 debugformat DWARF 2
14177 @chapter Altering Execution
14179 Once you think you have found an error in your program, you might want to
14180 find out for certain whether correcting the apparent error would lead to
14181 correct results in the rest of the run. You can find the answer by
14182 experiment, using the @value{GDBN} features for altering execution of the
14185 For example, you can store new values into variables or memory
14186 locations, give your program a signal, restart it at a different
14187 address, or even return prematurely from a function.
14190 * Assignment:: Assignment to variables
14191 * Jumping:: Continuing at a different address
14192 * Signaling:: Giving your program a signal
14193 * Returning:: Returning from a function
14194 * Calling:: Calling your program's functions
14195 * Patching:: Patching your program
14199 @section Assignment to Variables
14202 @cindex setting variables
14203 To alter the value of a variable, evaluate an assignment expression.
14204 @xref{Expressions, ,Expressions}. For example,
14211 stores the value 4 into the variable @code{x}, and then prints the
14212 value of the assignment expression (which is 4).
14213 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14214 information on operators in supported languages.
14216 @kindex set variable
14217 @cindex variables, setting
14218 If you are not interested in seeing the value of the assignment, use the
14219 @code{set} command instead of the @code{print} command. @code{set} is
14220 really the same as @code{print} except that the expression's value is
14221 not printed and is not put in the value history (@pxref{Value History,
14222 ,Value History}). The expression is evaluated only for its effects.
14224 If the beginning of the argument string of the @code{set} command
14225 appears identical to a @code{set} subcommand, use the @code{set
14226 variable} command instead of just @code{set}. This command is identical
14227 to @code{set} except for its lack of subcommands. For example, if your
14228 program has a variable @code{width}, you get an error if you try to set
14229 a new value with just @samp{set width=13}, because @value{GDBN} has the
14230 command @code{set width}:
14233 (@value{GDBP}) whatis width
14235 (@value{GDBP}) p width
14237 (@value{GDBP}) set width=47
14238 Invalid syntax in expression.
14242 The invalid expression, of course, is @samp{=47}. In
14243 order to actually set the program's variable @code{width}, use
14246 (@value{GDBP}) set var width=47
14249 Because the @code{set} command has many subcommands that can conflict
14250 with the names of program variables, it is a good idea to use the
14251 @code{set variable} command instead of just @code{set}. For example, if
14252 your program has a variable @code{g}, you run into problems if you try
14253 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14254 the command @code{set gnutarget}, abbreviated @code{set g}:
14258 (@value{GDBP}) whatis g
14262 (@value{GDBP}) set g=4
14266 The program being debugged has been started already.
14267 Start it from the beginning? (y or n) y
14268 Starting program: /home/smith/cc_progs/a.out
14269 "/home/smith/cc_progs/a.out": can't open to read symbols:
14270 Invalid bfd target.
14271 (@value{GDBP}) show g
14272 The current BFD target is "=4".
14277 The program variable @code{g} did not change, and you silently set the
14278 @code{gnutarget} to an invalid value. In order to set the variable
14282 (@value{GDBP}) set var g=4
14285 @value{GDBN} allows more implicit conversions in assignments than C; you can
14286 freely store an integer value into a pointer variable or vice versa,
14287 and you can convert any structure to any other structure that is the
14288 same length or shorter.
14289 @comment FIXME: how do structs align/pad in these conversions?
14290 @comment /doc@cygnus.com 18dec1990
14292 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14293 construct to generate a value of specified type at a specified address
14294 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14295 to memory location @code{0x83040} as an integer (which implies a certain size
14296 and representation in memory), and
14299 set @{int@}0x83040 = 4
14303 stores the value 4 into that memory location.
14306 @section Continuing at a Different Address
14308 Ordinarily, when you continue your program, you do so at the place where
14309 it stopped, with the @code{continue} command. You can instead continue at
14310 an address of your own choosing, with the following commands:
14314 @item jump @var{linespec}
14315 @itemx jump @var{location}
14316 Resume execution at line @var{linespec} or at address given by
14317 @var{location}. Execution stops again immediately if there is a
14318 breakpoint there. @xref{Specify Location}, for a description of the
14319 different forms of @var{linespec} and @var{location}. It is common
14320 practice to use the @code{tbreak} command in conjunction with
14321 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14323 The @code{jump} command does not change the current stack frame, or
14324 the stack pointer, or the contents of any memory location or any
14325 register other than the program counter. If line @var{linespec} is in
14326 a different function from the one currently executing, the results may
14327 be bizarre if the two functions expect different patterns of arguments or
14328 of local variables. For this reason, the @code{jump} command requests
14329 confirmation if the specified line is not in the function currently
14330 executing. However, even bizarre results are predictable if you are
14331 well acquainted with the machine-language code of your program.
14334 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14335 On many systems, you can get much the same effect as the @code{jump}
14336 command by storing a new value into the register @code{$pc}. The
14337 difference is that this does not start your program running; it only
14338 changes the address of where it @emph{will} run when you continue. For
14346 makes the next @code{continue} command or stepping command execute at
14347 address @code{0x485}, rather than at the address where your program stopped.
14348 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14350 The most common occasion to use the @code{jump} command is to back
14351 up---perhaps with more breakpoints set---over a portion of a program
14352 that has already executed, in order to examine its execution in more
14357 @section Giving your Program a Signal
14358 @cindex deliver a signal to a program
14362 @item signal @var{signal}
14363 Resume execution where your program stopped, but immediately give it the
14364 signal @var{signal}. @var{signal} can be the name or the number of a
14365 signal. For example, on many systems @code{signal 2} and @code{signal
14366 SIGINT} are both ways of sending an interrupt signal.
14368 Alternatively, if @var{signal} is zero, continue execution without
14369 giving a signal. This is useful when your program stopped on account of
14370 a signal and would ordinary see the signal when resumed with the
14371 @code{continue} command; @samp{signal 0} causes it to resume without a
14374 @code{signal} does not repeat when you press @key{RET} a second time
14375 after executing the command.
14379 Invoking the @code{signal} command is not the same as invoking the
14380 @code{kill} utility from the shell. Sending a signal with @code{kill}
14381 causes @value{GDBN} to decide what to do with the signal depending on
14382 the signal handling tables (@pxref{Signals}). The @code{signal} command
14383 passes the signal directly to your program.
14387 @section Returning from a Function
14390 @cindex returning from a function
14393 @itemx return @var{expression}
14394 You can cancel execution of a function call with the @code{return}
14395 command. If you give an
14396 @var{expression} argument, its value is used as the function's return
14400 When you use @code{return}, @value{GDBN} discards the selected stack frame
14401 (and all frames within it). You can think of this as making the
14402 discarded frame return prematurely. If you wish to specify a value to
14403 be returned, give that value as the argument to @code{return}.
14405 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14406 Frame}), and any other frames inside of it, leaving its caller as the
14407 innermost remaining frame. That frame becomes selected. The
14408 specified value is stored in the registers used for returning values
14411 The @code{return} command does not resume execution; it leaves the
14412 program stopped in the state that would exist if the function had just
14413 returned. In contrast, the @code{finish} command (@pxref{Continuing
14414 and Stepping, ,Continuing and Stepping}) resumes execution until the
14415 selected stack frame returns naturally.
14417 @value{GDBN} needs to know how the @var{expression} argument should be set for
14418 the inferior. The concrete registers assignment depends on the OS ABI and the
14419 type being returned by the selected stack frame. For example it is common for
14420 OS ABI to return floating point values in FPU registers while integer values in
14421 CPU registers. Still some ABIs return even floating point values in CPU
14422 registers. Larger integer widths (such as @code{long long int}) also have
14423 specific placement rules. @value{GDBN} already knows the OS ABI from its
14424 current target so it needs to find out also the type being returned to make the
14425 assignment into the right register(s).
14427 Normally, the selected stack frame has debug info. @value{GDBN} will always
14428 use the debug info instead of the implicit type of @var{expression} when the
14429 debug info is available. For example, if you type @kbd{return -1}, and the
14430 function in the current stack frame is declared to return a @code{long long
14431 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14432 into a @code{long long int}:
14435 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14437 (@value{GDBP}) return -1
14438 Make func return now? (y or n) y
14439 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14440 43 printf ("result=%lld\n", func ());
14444 However, if the selected stack frame does not have a debug info, e.g., if the
14445 function was compiled without debug info, @value{GDBN} has to find out the type
14446 to return from user. Specifying a different type by mistake may set the value
14447 in different inferior registers than the caller code expects. For example,
14448 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14449 of a @code{long long int} result for a debug info less function (on 32-bit
14450 architectures). Therefore the user is required to specify the return type by
14451 an appropriate cast explicitly:
14454 Breakpoint 2, 0x0040050b in func ()
14455 (@value{GDBP}) return -1
14456 Return value type not available for selected stack frame.
14457 Please use an explicit cast of the value to return.
14458 (@value{GDBP}) return (long long int) -1
14459 Make selected stack frame return now? (y or n) y
14460 #0 0x00400526 in main ()
14465 @section Calling Program Functions
14468 @cindex calling functions
14469 @cindex inferior functions, calling
14470 @item print @var{expr}
14471 Evaluate the expression @var{expr} and display the resulting value.
14472 @var{expr} may include calls to functions in the program being
14476 @item call @var{expr}
14477 Evaluate the expression @var{expr} without displaying @code{void}
14480 You can use this variant of the @code{print} command if you want to
14481 execute a function from your program that does not return anything
14482 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14483 with @code{void} returned values that @value{GDBN} will otherwise
14484 print. If the result is not void, it is printed and saved in the
14488 It is possible for the function you call via the @code{print} or
14489 @code{call} command to generate a signal (e.g., if there's a bug in
14490 the function, or if you passed it incorrect arguments). What happens
14491 in that case is controlled by the @code{set unwindonsignal} command.
14493 Similarly, with a C@t{++} program it is possible for the function you
14494 call via the @code{print} or @code{call} command to generate an
14495 exception that is not handled due to the constraints of the dummy
14496 frame. In this case, any exception that is raised in the frame, but has
14497 an out-of-frame exception handler will not be found. GDB builds a
14498 dummy-frame for the inferior function call, and the unwinder cannot
14499 seek for exception handlers outside of this dummy-frame. What happens
14500 in that case is controlled by the
14501 @code{set unwind-on-terminating-exception} command.
14504 @item set unwindonsignal
14505 @kindex set unwindonsignal
14506 @cindex unwind stack in called functions
14507 @cindex call dummy stack unwinding
14508 Set unwinding of the stack if a signal is received while in a function
14509 that @value{GDBN} called in the program being debugged. If set to on,
14510 @value{GDBN} unwinds the stack it created for the call and restores
14511 the context to what it was before the call. If set to off (the
14512 default), @value{GDBN} stops in the frame where the signal was
14515 @item show unwindonsignal
14516 @kindex show unwindonsignal
14517 Show the current setting of stack unwinding in the functions called by
14520 @item set unwind-on-terminating-exception
14521 @kindex set unwind-on-terminating-exception
14522 @cindex unwind stack in called functions with unhandled exceptions
14523 @cindex call dummy stack unwinding on unhandled exception.
14524 Set unwinding of the stack if a C@t{++} exception is raised, but left
14525 unhandled while in a function that @value{GDBN} called in the program being
14526 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14527 it created for the call and restores the context to what it was before
14528 the call. If set to off, @value{GDBN} the exception is delivered to
14529 the default C@t{++} exception handler and the inferior terminated.
14531 @item show unwind-on-terminating-exception
14532 @kindex show unwind-on-terminating-exception
14533 Show the current setting of stack unwinding in the functions called by
14538 @cindex weak alias functions
14539 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14540 for another function. In such case, @value{GDBN} might not pick up
14541 the type information, including the types of the function arguments,
14542 which causes @value{GDBN} to call the inferior function incorrectly.
14543 As a result, the called function will function erroneously and may
14544 even crash. A solution to that is to use the name of the aliased
14548 @section Patching Programs
14550 @cindex patching binaries
14551 @cindex writing into executables
14552 @cindex writing into corefiles
14554 By default, @value{GDBN} opens the file containing your program's
14555 executable code (or the corefile) read-only. This prevents accidental
14556 alterations to machine code; but it also prevents you from intentionally
14557 patching your program's binary.
14559 If you'd like to be able to patch the binary, you can specify that
14560 explicitly with the @code{set write} command. For example, you might
14561 want to turn on internal debugging flags, or even to make emergency
14567 @itemx set write off
14568 If you specify @samp{set write on}, @value{GDBN} opens executable and
14569 core files for both reading and writing; if you specify @kbd{set write
14570 off} (the default), @value{GDBN} opens them read-only.
14572 If you have already loaded a file, you must load it again (using the
14573 @code{exec-file} or @code{core-file} command) after changing @code{set
14574 write}, for your new setting to take effect.
14578 Display whether executable files and core files are opened for writing
14579 as well as reading.
14583 @chapter @value{GDBN} Files
14585 @value{GDBN} needs to know the file name of the program to be debugged,
14586 both in order to read its symbol table and in order to start your
14587 program. To debug a core dump of a previous run, you must also tell
14588 @value{GDBN} the name of the core dump file.
14591 * Files:: Commands to specify files
14592 * Separate Debug Files:: Debugging information in separate files
14593 * Index Files:: Index files speed up GDB
14594 * Symbol Errors:: Errors reading symbol files
14595 * Data Files:: GDB data files
14599 @section Commands to Specify Files
14601 @cindex symbol table
14602 @cindex core dump file
14604 You may want to specify executable and core dump file names. The usual
14605 way to do this is at start-up time, using the arguments to
14606 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14607 Out of @value{GDBN}}).
14609 Occasionally it is necessary to change to a different file during a
14610 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14611 specify a file you want to use. Or you are debugging a remote target
14612 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14613 Program}). In these situations the @value{GDBN} commands to specify
14614 new files are useful.
14617 @cindex executable file
14619 @item file @var{filename}
14620 Use @var{filename} as the program to be debugged. It is read for its
14621 symbols and for the contents of pure memory. It is also the program
14622 executed when you use the @code{run} command. If you do not specify a
14623 directory and the file is not found in the @value{GDBN} working directory,
14624 @value{GDBN} uses the environment variable @code{PATH} as a list of
14625 directories to search, just as the shell does when looking for a program
14626 to run. You can change the value of this variable, for both @value{GDBN}
14627 and your program, using the @code{path} command.
14629 @cindex unlinked object files
14630 @cindex patching object files
14631 You can load unlinked object @file{.o} files into @value{GDBN} using
14632 the @code{file} command. You will not be able to ``run'' an object
14633 file, but you can disassemble functions and inspect variables. Also,
14634 if the underlying BFD functionality supports it, you could use
14635 @kbd{gdb -write} to patch object files using this technique. Note
14636 that @value{GDBN} can neither interpret nor modify relocations in this
14637 case, so branches and some initialized variables will appear to go to
14638 the wrong place. But this feature is still handy from time to time.
14641 @code{file} with no argument makes @value{GDBN} discard any information it
14642 has on both executable file and the symbol table.
14645 @item exec-file @r{[} @var{filename} @r{]}
14646 Specify that the program to be run (but not the symbol table) is found
14647 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14648 if necessary to locate your program. Omitting @var{filename} means to
14649 discard information on the executable file.
14651 @kindex symbol-file
14652 @item symbol-file @r{[} @var{filename} @r{]}
14653 Read symbol table information from file @var{filename}. @code{PATH} is
14654 searched when necessary. Use the @code{file} command to get both symbol
14655 table and program to run from the same file.
14657 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14658 program's symbol table.
14660 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14661 some breakpoints and auto-display expressions. This is because they may
14662 contain pointers to the internal data recording symbols and data types,
14663 which are part of the old symbol table data being discarded inside
14666 @code{symbol-file} does not repeat if you press @key{RET} again after
14669 When @value{GDBN} is configured for a particular environment, it
14670 understands debugging information in whatever format is the standard
14671 generated for that environment; you may use either a @sc{gnu} compiler, or
14672 other compilers that adhere to the local conventions.
14673 Best results are usually obtained from @sc{gnu} compilers; for example,
14674 using @code{@value{NGCC}} you can generate debugging information for
14677 For most kinds of object files, with the exception of old SVR3 systems
14678 using COFF, the @code{symbol-file} command does not normally read the
14679 symbol table in full right away. Instead, it scans the symbol table
14680 quickly to find which source files and which symbols are present. The
14681 details are read later, one source file at a time, as they are needed.
14683 The purpose of this two-stage reading strategy is to make @value{GDBN}
14684 start up faster. For the most part, it is invisible except for
14685 occasional pauses while the symbol table details for a particular source
14686 file are being read. (The @code{set verbose} command can turn these
14687 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14688 Warnings and Messages}.)
14690 We have not implemented the two-stage strategy for COFF yet. When the
14691 symbol table is stored in COFF format, @code{symbol-file} reads the
14692 symbol table data in full right away. Note that ``stabs-in-COFF''
14693 still does the two-stage strategy, since the debug info is actually
14697 @cindex reading symbols immediately
14698 @cindex symbols, reading immediately
14699 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14700 @itemx file @r{[} -readnow @r{]} @var{filename}
14701 You can override the @value{GDBN} two-stage strategy for reading symbol
14702 tables by using the @samp{-readnow} option with any of the commands that
14703 load symbol table information, if you want to be sure @value{GDBN} has the
14704 entire symbol table available.
14706 @c FIXME: for now no mention of directories, since this seems to be in
14707 @c flux. 13mar1992 status is that in theory GDB would look either in
14708 @c current dir or in same dir as myprog; but issues like competing
14709 @c GDB's, or clutter in system dirs, mean that in practice right now
14710 @c only current dir is used. FFish says maybe a special GDB hierarchy
14711 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14715 @item core-file @r{[}@var{filename}@r{]}
14717 Specify the whereabouts of a core dump file to be used as the ``contents
14718 of memory''. Traditionally, core files contain only some parts of the
14719 address space of the process that generated them; @value{GDBN} can access the
14720 executable file itself for other parts.
14722 @code{core-file} with no argument specifies that no core file is
14725 Note that the core file is ignored when your program is actually running
14726 under @value{GDBN}. So, if you have been running your program and you
14727 wish to debug a core file instead, you must kill the subprocess in which
14728 the program is running. To do this, use the @code{kill} command
14729 (@pxref{Kill Process, ,Killing the Child Process}).
14731 @kindex add-symbol-file
14732 @cindex dynamic linking
14733 @item add-symbol-file @var{filename} @var{address}
14734 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14735 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14736 The @code{add-symbol-file} command reads additional symbol table
14737 information from the file @var{filename}. You would use this command
14738 when @var{filename} has been dynamically loaded (by some other means)
14739 into the program that is running. @var{address} should be the memory
14740 address at which the file has been loaded; @value{GDBN} cannot figure
14741 this out for itself. You can additionally specify an arbitrary number
14742 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14743 section name and base address for that section. You can specify any
14744 @var{address} as an expression.
14746 The symbol table of the file @var{filename} is added to the symbol table
14747 originally read with the @code{symbol-file} command. You can use the
14748 @code{add-symbol-file} command any number of times; the new symbol data
14749 thus read keeps adding to the old. To discard all old symbol data
14750 instead, use the @code{symbol-file} command without any arguments.
14752 @cindex relocatable object files, reading symbols from
14753 @cindex object files, relocatable, reading symbols from
14754 @cindex reading symbols from relocatable object files
14755 @cindex symbols, reading from relocatable object files
14756 @cindex @file{.o} files, reading symbols from
14757 Although @var{filename} is typically a shared library file, an
14758 executable file, or some other object file which has been fully
14759 relocated for loading into a process, you can also load symbolic
14760 information from relocatable @file{.o} files, as long as:
14764 the file's symbolic information refers only to linker symbols defined in
14765 that file, not to symbols defined by other object files,
14767 every section the file's symbolic information refers to has actually
14768 been loaded into the inferior, as it appears in the file, and
14770 you can determine the address at which every section was loaded, and
14771 provide these to the @code{add-symbol-file} command.
14775 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14776 relocatable files into an already running program; such systems
14777 typically make the requirements above easy to meet. However, it's
14778 important to recognize that many native systems use complex link
14779 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14780 assembly, for example) that make the requirements difficult to meet. In
14781 general, one cannot assume that using @code{add-symbol-file} to read a
14782 relocatable object file's symbolic information will have the same effect
14783 as linking the relocatable object file into the program in the normal
14786 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14788 @kindex add-symbol-file-from-memory
14789 @cindex @code{syscall DSO}
14790 @cindex load symbols from memory
14791 @item add-symbol-file-from-memory @var{address}
14792 Load symbols from the given @var{address} in a dynamically loaded
14793 object file whose image is mapped directly into the inferior's memory.
14794 For example, the Linux kernel maps a @code{syscall DSO} into each
14795 process's address space; this DSO provides kernel-specific code for
14796 some system calls. The argument can be any expression whose
14797 evaluation yields the address of the file's shared object file header.
14798 For this command to work, you must have used @code{symbol-file} or
14799 @code{exec-file} commands in advance.
14801 @kindex add-shared-symbol-files
14803 @item add-shared-symbol-files @var{library-file}
14804 @itemx assf @var{library-file}
14805 The @code{add-shared-symbol-files} command can currently be used only
14806 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14807 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14808 @value{GDBN} automatically looks for shared libraries, however if
14809 @value{GDBN} does not find yours, you can invoke
14810 @code{add-shared-symbol-files}. It takes one argument: the shared
14811 library's file name. @code{assf} is a shorthand alias for
14812 @code{add-shared-symbol-files}.
14815 @item section @var{section} @var{addr}
14816 The @code{section} command changes the base address of the named
14817 @var{section} of the exec file to @var{addr}. This can be used if the
14818 exec file does not contain section addresses, (such as in the
14819 @code{a.out} format), or when the addresses specified in the file
14820 itself are wrong. Each section must be changed separately. The
14821 @code{info files} command, described below, lists all the sections and
14825 @kindex info target
14828 @code{info files} and @code{info target} are synonymous; both print the
14829 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14830 including the names of the executable and core dump files currently in
14831 use by @value{GDBN}, and the files from which symbols were loaded. The
14832 command @code{help target} lists all possible targets rather than
14835 @kindex maint info sections
14836 @item maint info sections
14837 Another command that can give you extra information about program sections
14838 is @code{maint info sections}. In addition to the section information
14839 displayed by @code{info files}, this command displays the flags and file
14840 offset of each section in the executable and core dump files. In addition,
14841 @code{maint info sections} provides the following command options (which
14842 may be arbitrarily combined):
14846 Display sections for all loaded object files, including shared libraries.
14847 @item @var{sections}
14848 Display info only for named @var{sections}.
14849 @item @var{section-flags}
14850 Display info only for sections for which @var{section-flags} are true.
14851 The section flags that @value{GDBN} currently knows about are:
14854 Section will have space allocated in the process when loaded.
14855 Set for all sections except those containing debug information.
14857 Section will be loaded from the file into the child process memory.
14858 Set for pre-initialized code and data, clear for @code{.bss} sections.
14860 Section needs to be relocated before loading.
14862 Section cannot be modified by the child process.
14864 Section contains executable code only.
14866 Section contains data only (no executable code).
14868 Section will reside in ROM.
14870 Section contains data for constructor/destructor lists.
14872 Section is not empty.
14874 An instruction to the linker to not output the section.
14875 @item COFF_SHARED_LIBRARY
14876 A notification to the linker that the section contains
14877 COFF shared library information.
14879 Section contains common symbols.
14882 @kindex set trust-readonly-sections
14883 @cindex read-only sections
14884 @item set trust-readonly-sections on
14885 Tell @value{GDBN} that readonly sections in your object file
14886 really are read-only (i.e.@: that their contents will not change).
14887 In that case, @value{GDBN} can fetch values from these sections
14888 out of the object file, rather than from the target program.
14889 For some targets (notably embedded ones), this can be a significant
14890 enhancement to debugging performance.
14892 The default is off.
14894 @item set trust-readonly-sections off
14895 Tell @value{GDBN} not to trust readonly sections. This means that
14896 the contents of the section might change while the program is running,
14897 and must therefore be fetched from the target when needed.
14899 @item show trust-readonly-sections
14900 Show the current setting of trusting readonly sections.
14903 All file-specifying commands allow both absolute and relative file names
14904 as arguments. @value{GDBN} always converts the file name to an absolute file
14905 name and remembers it that way.
14907 @cindex shared libraries
14908 @anchor{Shared Libraries}
14909 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14910 and IBM RS/6000 AIX shared libraries.
14912 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14913 shared libraries. @xref{Expat}.
14915 @value{GDBN} automatically loads symbol definitions from shared libraries
14916 when you use the @code{run} command, or when you examine a core file.
14917 (Before you issue the @code{run} command, @value{GDBN} does not understand
14918 references to a function in a shared library, however---unless you are
14919 debugging a core file).
14921 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14922 automatically loads the symbols at the time of the @code{shl_load} call.
14924 @c FIXME: some @value{GDBN} release may permit some refs to undef
14925 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14926 @c FIXME...lib; check this from time to time when updating manual
14928 There are times, however, when you may wish to not automatically load
14929 symbol definitions from shared libraries, such as when they are
14930 particularly large or there are many of them.
14932 To control the automatic loading of shared library symbols, use the
14936 @kindex set auto-solib-add
14937 @item set auto-solib-add @var{mode}
14938 If @var{mode} is @code{on}, symbols from all shared object libraries
14939 will be loaded automatically when the inferior begins execution, you
14940 attach to an independently started inferior, or when the dynamic linker
14941 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14942 is @code{off}, symbols must be loaded manually, using the
14943 @code{sharedlibrary} command. The default value is @code{on}.
14945 @cindex memory used for symbol tables
14946 If your program uses lots of shared libraries with debug info that
14947 takes large amounts of memory, you can decrease the @value{GDBN}
14948 memory footprint by preventing it from automatically loading the
14949 symbols from shared libraries. To that end, type @kbd{set
14950 auto-solib-add off} before running the inferior, then load each
14951 library whose debug symbols you do need with @kbd{sharedlibrary
14952 @var{regexp}}, where @var{regexp} is a regular expression that matches
14953 the libraries whose symbols you want to be loaded.
14955 @kindex show auto-solib-add
14956 @item show auto-solib-add
14957 Display the current autoloading mode.
14960 @cindex load shared library
14961 To explicitly load shared library symbols, use the @code{sharedlibrary}
14965 @kindex info sharedlibrary
14967 @item info share @var{regex}
14968 @itemx info sharedlibrary @var{regex}
14969 Print the names of the shared libraries which are currently loaded
14970 that match @var{regex}. If @var{regex} is omitted then print
14971 all shared libraries that are loaded.
14973 @kindex sharedlibrary
14975 @item sharedlibrary @var{regex}
14976 @itemx share @var{regex}
14977 Load shared object library symbols for files matching a
14978 Unix regular expression.
14979 As with files loaded automatically, it only loads shared libraries
14980 required by your program for a core file or after typing @code{run}. If
14981 @var{regex} is omitted all shared libraries required by your program are
14984 @item nosharedlibrary
14985 @kindex nosharedlibrary
14986 @cindex unload symbols from shared libraries
14987 Unload all shared object library symbols. This discards all symbols
14988 that have been loaded from all shared libraries. Symbols from shared
14989 libraries that were loaded by explicit user requests are not
14993 Sometimes you may wish that @value{GDBN} stops and gives you control
14994 when any of shared library events happen. Use the @code{set
14995 stop-on-solib-events} command for this:
14998 @item set stop-on-solib-events
14999 @kindex set stop-on-solib-events
15000 This command controls whether @value{GDBN} should give you control
15001 when the dynamic linker notifies it about some shared library event.
15002 The most common event of interest is loading or unloading of a new
15005 @item show stop-on-solib-events
15006 @kindex show stop-on-solib-events
15007 Show whether @value{GDBN} stops and gives you control when shared
15008 library events happen.
15011 Shared libraries are also supported in many cross or remote debugging
15012 configurations. @value{GDBN} needs to have access to the target's libraries;
15013 this can be accomplished either by providing copies of the libraries
15014 on the host system, or by asking @value{GDBN} to automatically retrieve the
15015 libraries from the target. If copies of the target libraries are
15016 provided, they need to be the same as the target libraries, although the
15017 copies on the target can be stripped as long as the copies on the host are
15020 @cindex where to look for shared libraries
15021 For remote debugging, you need to tell @value{GDBN} where the target
15022 libraries are, so that it can load the correct copies---otherwise, it
15023 may try to load the host's libraries. @value{GDBN} has two variables
15024 to specify the search directories for target libraries.
15027 @cindex prefix for shared library file names
15028 @cindex system root, alternate
15029 @kindex set solib-absolute-prefix
15030 @kindex set sysroot
15031 @item set sysroot @var{path}
15032 Use @var{path} as the system root for the program being debugged. Any
15033 absolute shared library paths will be prefixed with @var{path}; many
15034 runtime loaders store the absolute paths to the shared library in the
15035 target program's memory. If you use @code{set sysroot} to find shared
15036 libraries, they need to be laid out in the same way that they are on
15037 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15040 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15041 retrieve the target libraries from the remote system. This is only
15042 supported when using a remote target that supports the @code{remote get}
15043 command (@pxref{File Transfer,,Sending files to a remote system}).
15044 The part of @var{path} following the initial @file{remote:}
15045 (if present) is used as system root prefix on the remote file system.
15046 @footnote{If you want to specify a local system root using a directory
15047 that happens to be named @file{remote:}, you need to use some equivalent
15048 variant of the name like @file{./remote:}.}
15050 For targets with an MS-DOS based filesystem, such as MS-Windows and
15051 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15052 absolute file name with @var{path}. But first, on Unix hosts,
15053 @value{GDBN} converts all backslash directory separators into forward
15054 slashes, because the backslash is not a directory separator on Unix:
15057 c:\foo\bar.dll @result{} c:/foo/bar.dll
15060 Then, @value{GDBN} attempts prefixing the target file name with
15061 @var{path}, and looks for the resulting file name in the host file
15065 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15068 If that does not find the shared library, @value{GDBN} tries removing
15069 the @samp{:} character from the drive spec, both for convenience, and,
15070 for the case of the host file system not supporting file names with
15074 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15077 This makes it possible to have a system root that mirrors a target
15078 with more than one drive. E.g., you may want to setup your local
15079 copies of the target system shared libraries like so (note @samp{c} vs
15083 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15084 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15085 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15089 and point the system root at @file{/path/to/sysroot}, so that
15090 @value{GDBN} can find the correct copies of both
15091 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15093 If that still does not find the shared library, @value{GDBN} tries
15094 removing the whole drive spec from the target file name:
15097 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15100 This last lookup makes it possible to not care about the drive name,
15101 if you don't want or need to.
15103 The @code{set solib-absolute-prefix} command is an alias for @code{set
15106 @cindex default system root
15107 @cindex @samp{--with-sysroot}
15108 You can set the default system root by using the configure-time
15109 @samp{--with-sysroot} option. If the system root is inside
15110 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15111 @samp{--exec-prefix}), then the default system root will be updated
15112 automatically if the installed @value{GDBN} is moved to a new
15115 @kindex show sysroot
15117 Display the current shared library prefix.
15119 @kindex set solib-search-path
15120 @item set solib-search-path @var{path}
15121 If this variable is set, @var{path} is a colon-separated list of
15122 directories to search for shared libraries. @samp{solib-search-path}
15123 is used after @samp{sysroot} fails to locate the library, or if the
15124 path to the library is relative instead of absolute. If you want to
15125 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15126 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15127 finding your host's libraries. @samp{sysroot} is preferred; setting
15128 it to a nonexistent directory may interfere with automatic loading
15129 of shared library symbols.
15131 @kindex show solib-search-path
15132 @item show solib-search-path
15133 Display the current shared library search path.
15135 @cindex DOS file-name semantics of file names.
15136 @kindex set target-file-system-kind (unix|dos-based|auto)
15137 @kindex show target-file-system-kind
15138 @item set target-file-system-kind @var{kind}
15139 Set assumed file system kind for target reported file names.
15141 Shared library file names as reported by the target system may not
15142 make sense as is on the system @value{GDBN} is running on. For
15143 example, when remote debugging a target that has MS-DOS based file
15144 system semantics, from a Unix host, the target may be reporting to
15145 @value{GDBN} a list of loaded shared libraries with file names such as
15146 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15147 drive letters, so the @samp{c:\} prefix is not normally understood as
15148 indicating an absolute file name, and neither is the backslash
15149 normally considered a directory separator character. In that case,
15150 the native file system would interpret this whole absolute file name
15151 as a relative file name with no directory components. This would make
15152 it impossible to point @value{GDBN} at a copy of the remote target's
15153 shared libraries on the host using @code{set sysroot}, and impractical
15154 with @code{set solib-search-path}. Setting
15155 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15156 to interpret such file names similarly to how the target would, and to
15157 map them to file names valid on @value{GDBN}'s native file system
15158 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15159 to one of the supported file system kinds. In that case, @value{GDBN}
15160 tries to determine the appropriate file system variant based on the
15161 current target's operating system (@pxref{ABI, ,Configuring the
15162 Current ABI}). The supported file system settings are:
15166 Instruct @value{GDBN} to assume the target file system is of Unix
15167 kind. Only file names starting the forward slash (@samp{/}) character
15168 are considered absolute, and the directory separator character is also
15172 Instruct @value{GDBN} to assume the target file system is DOS based.
15173 File names starting with either a forward slash, or a drive letter
15174 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15175 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15176 considered directory separators.
15179 Instruct @value{GDBN} to use the file system kind associated with the
15180 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15181 This is the default.
15186 @node Separate Debug Files
15187 @section Debugging Information in Separate Files
15188 @cindex separate debugging information files
15189 @cindex debugging information in separate files
15190 @cindex @file{.debug} subdirectories
15191 @cindex debugging information directory, global
15192 @cindex global debugging information directory
15193 @cindex build ID, and separate debugging files
15194 @cindex @file{.build-id} directory
15196 @value{GDBN} allows you to put a program's debugging information in a
15197 file separate from the executable itself, in a way that allows
15198 @value{GDBN} to find and load the debugging information automatically.
15199 Since debugging information can be very large---sometimes larger
15200 than the executable code itself---some systems distribute debugging
15201 information for their executables in separate files, which users can
15202 install only when they need to debug a problem.
15204 @value{GDBN} supports two ways of specifying the separate debug info
15209 The executable contains a @dfn{debug link} that specifies the name of
15210 the separate debug info file. The separate debug file's name is
15211 usually @file{@var{executable}.debug}, where @var{executable} is the
15212 name of the corresponding executable file without leading directories
15213 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15214 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15215 checksum for the debug file, which @value{GDBN} uses to validate that
15216 the executable and the debug file came from the same build.
15219 The executable contains a @dfn{build ID}, a unique bit string that is
15220 also present in the corresponding debug info file. (This is supported
15221 only on some operating systems, notably those which use the ELF format
15222 for binary files and the @sc{gnu} Binutils.) For more details about
15223 this feature, see the description of the @option{--build-id}
15224 command-line option in @ref{Options, , Command Line Options, ld.info,
15225 The GNU Linker}. The debug info file's name is not specified
15226 explicitly by the build ID, but can be computed from the build ID, see
15230 Depending on the way the debug info file is specified, @value{GDBN}
15231 uses two different methods of looking for the debug file:
15235 For the ``debug link'' method, @value{GDBN} looks up the named file in
15236 the directory of the executable file, then in a subdirectory of that
15237 directory named @file{.debug}, and finally under the global debug
15238 directory, in a subdirectory whose name is identical to the leading
15239 directories of the executable's absolute file name.
15242 For the ``build ID'' method, @value{GDBN} looks in the
15243 @file{.build-id} subdirectory of the global debug directory for a file
15244 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15245 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15246 are the rest of the bit string. (Real build ID strings are 32 or more
15247 hex characters, not 10.)
15250 So, for example, suppose you ask @value{GDBN} to debug
15251 @file{/usr/bin/ls}, which has a debug link that specifies the
15252 file @file{ls.debug}, and a build ID whose value in hex is
15253 @code{abcdef1234}. If the global debug directory is
15254 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15255 debug information files, in the indicated order:
15259 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15261 @file{/usr/bin/ls.debug}
15263 @file{/usr/bin/.debug/ls.debug}
15265 @file{/usr/lib/debug/usr/bin/ls.debug}.
15268 You can set the global debugging info directory's name, and view the
15269 name @value{GDBN} is currently using.
15273 @kindex set debug-file-directory
15274 @item set debug-file-directory @var{directories}
15275 Set the directories which @value{GDBN} searches for separate debugging
15276 information files to @var{directory}. Multiple directory components can be set
15277 concatenating them by a directory separator.
15279 @kindex show debug-file-directory
15280 @item show debug-file-directory
15281 Show the directories @value{GDBN} searches for separate debugging
15286 @cindex @code{.gnu_debuglink} sections
15287 @cindex debug link sections
15288 A debug link is a special section of the executable file named
15289 @code{.gnu_debuglink}. The section must contain:
15293 A filename, with any leading directory components removed, followed by
15296 zero to three bytes of padding, as needed to reach the next four-byte
15297 boundary within the section, and
15299 a four-byte CRC checksum, stored in the same endianness used for the
15300 executable file itself. The checksum is computed on the debugging
15301 information file's full contents by the function given below, passing
15302 zero as the @var{crc} argument.
15305 Any executable file format can carry a debug link, as long as it can
15306 contain a section named @code{.gnu_debuglink} with the contents
15309 @cindex @code{.note.gnu.build-id} sections
15310 @cindex build ID sections
15311 The build ID is a special section in the executable file (and in other
15312 ELF binary files that @value{GDBN} may consider). This section is
15313 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15314 It contains unique identification for the built files---the ID remains
15315 the same across multiple builds of the same build tree. The default
15316 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15317 content for the build ID string. The same section with an identical
15318 value is present in the original built binary with symbols, in its
15319 stripped variant, and in the separate debugging information file.
15321 The debugging information file itself should be an ordinary
15322 executable, containing a full set of linker symbols, sections, and
15323 debugging information. The sections of the debugging information file
15324 should have the same names, addresses, and sizes as the original file,
15325 but they need not contain any data---much like a @code{.bss} section
15326 in an ordinary executable.
15328 The @sc{gnu} binary utilities (Binutils) package includes the
15329 @samp{objcopy} utility that can produce
15330 the separated executable / debugging information file pairs using the
15331 following commands:
15334 @kbd{objcopy --only-keep-debug foo foo.debug}
15339 These commands remove the debugging
15340 information from the executable file @file{foo} and place it in the file
15341 @file{foo.debug}. You can use the first, second or both methods to link the
15346 The debug link method needs the following additional command to also leave
15347 behind a debug link in @file{foo}:
15350 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15353 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15354 a version of the @code{strip} command such that the command @kbd{strip foo -f
15355 foo.debug} has the same functionality as the two @code{objcopy} commands and
15356 the @code{ln -s} command above, together.
15359 Build ID gets embedded into the main executable using @code{ld --build-id} or
15360 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15361 compatibility fixes for debug files separation are present in @sc{gnu} binary
15362 utilities (Binutils) package since version 2.18.
15367 @cindex CRC algorithm definition
15368 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15369 IEEE 802.3 using the polynomial:
15371 @c TexInfo requires naked braces for multi-digit exponents for Tex
15372 @c output, but this causes HTML output to barf. HTML has to be set using
15373 @c raw commands. So we end up having to specify this equation in 2
15378 <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>
15379 + <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
15385 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15386 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15390 The function is computed byte at a time, taking the least
15391 significant bit of each byte first. The initial pattern
15392 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15393 the final result is inverted to ensure trailing zeros also affect the
15396 @emph{Note:} This is the same CRC polynomial as used in handling the
15397 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15398 , @value{GDBN} Remote Serial Protocol}). However in the
15399 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15400 significant bit first, and the result is not inverted, so trailing
15401 zeros have no effect on the CRC value.
15403 To complete the description, we show below the code of the function
15404 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15405 initially supplied @code{crc} argument means that an initial call to
15406 this function passing in zero will start computing the CRC using
15409 @kindex gnu_debuglink_crc32
15412 gnu_debuglink_crc32 (unsigned long crc,
15413 unsigned char *buf, size_t len)
15415 static const unsigned long crc32_table[256] =
15417 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15418 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15419 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15420 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15421 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15422 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15423 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15424 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15425 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15426 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15427 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15428 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15429 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15430 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15431 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15432 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15433 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15434 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15435 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15436 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15437 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15438 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15439 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15440 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15441 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15442 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15443 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15444 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15445 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15446 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15447 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15448 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15449 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15450 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15451 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15452 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15453 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15454 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15455 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15456 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15457 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15458 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15459 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15460 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15461 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15462 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15463 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15464 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15465 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15466 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15467 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15470 unsigned char *end;
15472 crc = ~crc & 0xffffffff;
15473 for (end = buf + len; buf < end; ++buf)
15474 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15475 return ~crc & 0xffffffff;
15480 This computation does not apply to the ``build ID'' method.
15484 @section Index Files Speed Up @value{GDBN}
15485 @cindex index files
15486 @cindex @samp{.gdb_index} section
15488 When @value{GDBN} finds a symbol file, it scans the symbols in the
15489 file in order to construct an internal symbol table. This lets most
15490 @value{GDBN} operations work quickly---at the cost of a delay early
15491 on. For large programs, this delay can be quite lengthy, so
15492 @value{GDBN} provides a way to build an index, which speeds up
15495 The index is stored as a section in the symbol file. @value{GDBN} can
15496 write the index to a file, then you can put it into the symbol file
15497 using @command{objcopy}.
15499 To create an index file, use the @code{save gdb-index} command:
15502 @item save gdb-index @var{directory}
15503 @kindex save gdb-index
15504 Create an index file for each symbol file currently known by
15505 @value{GDBN}. Each file is named after its corresponding symbol file,
15506 with @samp{.gdb-index} appended, and is written into the given
15510 Once you have created an index file you can merge it into your symbol
15511 file, here named @file{symfile}, using @command{objcopy}:
15514 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15515 --set-section-flags .gdb_index=readonly symfile symfile
15518 There are currently some limitation on indices. They only work when
15519 for DWARF debugging information, not stabs. And, they do not
15520 currently work for programs using Ada.
15522 @node Symbol Errors
15523 @section Errors Reading Symbol Files
15525 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15526 such as symbol types it does not recognize, or known bugs in compiler
15527 output. By default, @value{GDBN} does not notify you of such problems, since
15528 they are relatively common and primarily of interest to people
15529 debugging compilers. If you are interested in seeing information
15530 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15531 only one message about each such type of problem, no matter how many
15532 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15533 to see how many times the problems occur, with the @code{set
15534 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15537 The messages currently printed, and their meanings, include:
15540 @item inner block not inside outer block in @var{symbol}
15542 The symbol information shows where symbol scopes begin and end
15543 (such as at the start of a function or a block of statements). This
15544 error indicates that an inner scope block is not fully contained
15545 in its outer scope blocks.
15547 @value{GDBN} circumvents the problem by treating the inner block as if it had
15548 the same scope as the outer block. In the error message, @var{symbol}
15549 may be shown as ``@code{(don't know)}'' if the outer block is not a
15552 @item block at @var{address} out of order
15554 The symbol information for symbol scope blocks should occur in
15555 order of increasing addresses. This error indicates that it does not
15558 @value{GDBN} does not circumvent this problem, and has trouble
15559 locating symbols in the source file whose symbols it is reading. (You
15560 can often determine what source file is affected by specifying
15561 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15564 @item bad block start address patched
15566 The symbol information for a symbol scope block has a start address
15567 smaller than the address of the preceding source line. This is known
15568 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15570 @value{GDBN} circumvents the problem by treating the symbol scope block as
15571 starting on the previous source line.
15573 @item bad string table offset in symbol @var{n}
15576 Symbol number @var{n} contains a pointer into the string table which is
15577 larger than the size of the string table.
15579 @value{GDBN} circumvents the problem by considering the symbol to have the
15580 name @code{foo}, which may cause other problems if many symbols end up
15583 @item unknown symbol type @code{0x@var{nn}}
15585 The symbol information contains new data types that @value{GDBN} does
15586 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15587 uncomprehended information, in hexadecimal.
15589 @value{GDBN} circumvents the error by ignoring this symbol information.
15590 This usually allows you to debug your program, though certain symbols
15591 are not accessible. If you encounter such a problem and feel like
15592 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15593 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15594 and examine @code{*bufp} to see the symbol.
15596 @item stub type has NULL name
15598 @value{GDBN} could not find the full definition for a struct or class.
15600 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15601 The symbol information for a C@t{++} member function is missing some
15602 information that recent versions of the compiler should have output for
15605 @item info mismatch between compiler and debugger
15607 @value{GDBN} could not parse a type specification output by the compiler.
15612 @section GDB Data Files
15614 @cindex prefix for data files
15615 @value{GDBN} will sometimes read an auxiliary data file. These files
15616 are kept in a directory known as the @dfn{data directory}.
15618 You can set the data directory's name, and view the name @value{GDBN}
15619 is currently using.
15622 @kindex set data-directory
15623 @item set data-directory @var{directory}
15624 Set the directory which @value{GDBN} searches for auxiliary data files
15625 to @var{directory}.
15627 @kindex show data-directory
15628 @item show data-directory
15629 Show the directory @value{GDBN} searches for auxiliary data files.
15632 @cindex default data directory
15633 @cindex @samp{--with-gdb-datadir}
15634 You can set the default data directory by using the configure-time
15635 @samp{--with-gdb-datadir} option. If the data directory is inside
15636 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15637 @samp{--exec-prefix}), then the default data directory will be updated
15638 automatically if the installed @value{GDBN} is moved to a new
15641 The data directory may also be specified with the
15642 @code{--data-directory} command line option.
15643 @xref{Mode Options}.
15646 @chapter Specifying a Debugging Target
15648 @cindex debugging target
15649 A @dfn{target} is the execution environment occupied by your program.
15651 Often, @value{GDBN} runs in the same host environment as your program;
15652 in that case, the debugging target is specified as a side effect when
15653 you use the @code{file} or @code{core} commands. When you need more
15654 flexibility---for example, running @value{GDBN} on a physically separate
15655 host, or controlling a standalone system over a serial port or a
15656 realtime system over a TCP/IP connection---you can use the @code{target}
15657 command to specify one of the target types configured for @value{GDBN}
15658 (@pxref{Target Commands, ,Commands for Managing Targets}).
15660 @cindex target architecture
15661 It is possible to build @value{GDBN} for several different @dfn{target
15662 architectures}. When @value{GDBN} is built like that, you can choose
15663 one of the available architectures with the @kbd{set architecture}
15667 @kindex set architecture
15668 @kindex show architecture
15669 @item set architecture @var{arch}
15670 This command sets the current target architecture to @var{arch}. The
15671 value of @var{arch} can be @code{"auto"}, in addition to one of the
15672 supported architectures.
15674 @item show architecture
15675 Show the current target architecture.
15677 @item set processor
15679 @kindex set processor
15680 @kindex show processor
15681 These are alias commands for, respectively, @code{set architecture}
15682 and @code{show architecture}.
15686 * Active Targets:: Active targets
15687 * Target Commands:: Commands for managing targets
15688 * Byte Order:: Choosing target byte order
15691 @node Active Targets
15692 @section Active Targets
15694 @cindex stacking targets
15695 @cindex active targets
15696 @cindex multiple targets
15698 There are multiple classes of targets such as: processes, executable files or
15699 recording sessions. Core files belong to the process class, making core file
15700 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15701 on multiple active targets, one in each class. This allows you to (for
15702 example) start a process and inspect its activity, while still having access to
15703 the executable file after the process finishes. Or if you start process
15704 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15705 presented a virtual layer of the recording target, while the process target
15706 remains stopped at the chronologically last point of the process execution.
15708 Use the @code{core-file} and @code{exec-file} commands to select a new core
15709 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15710 specify as a target a process that is already running, use the @code{attach}
15711 command (@pxref{Attach, ,Debugging an Already-running Process}).
15713 @node Target Commands
15714 @section Commands for Managing Targets
15717 @item target @var{type} @var{parameters}
15718 Connects the @value{GDBN} host environment to a target machine or
15719 process. A target is typically a protocol for talking to debugging
15720 facilities. You use the argument @var{type} to specify the type or
15721 protocol of the target machine.
15723 Further @var{parameters} are interpreted by the target protocol, but
15724 typically include things like device names or host names to connect
15725 with, process numbers, and baud rates.
15727 The @code{target} command does not repeat if you press @key{RET} again
15728 after executing the command.
15730 @kindex help target
15732 Displays the names of all targets available. To display targets
15733 currently selected, use either @code{info target} or @code{info files}
15734 (@pxref{Files, ,Commands to Specify Files}).
15736 @item help target @var{name}
15737 Describe a particular target, including any parameters necessary to
15740 @kindex set gnutarget
15741 @item set gnutarget @var{args}
15742 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15743 knows whether it is reading an @dfn{executable},
15744 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15745 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15746 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15749 @emph{Warning:} To specify a file format with @code{set gnutarget},
15750 you must know the actual BFD name.
15754 @xref{Files, , Commands to Specify Files}.
15756 @kindex show gnutarget
15757 @item show gnutarget
15758 Use the @code{show gnutarget} command to display what file format
15759 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15760 @value{GDBN} will determine the file format for each file automatically,
15761 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15764 @cindex common targets
15765 Here are some common targets (available, or not, depending on the GDB
15770 @item target exec @var{program}
15771 @cindex executable file target
15772 An executable file. @samp{target exec @var{program}} is the same as
15773 @samp{exec-file @var{program}}.
15775 @item target core @var{filename}
15776 @cindex core dump file target
15777 A core dump file. @samp{target core @var{filename}} is the same as
15778 @samp{core-file @var{filename}}.
15780 @item target remote @var{medium}
15781 @cindex remote target
15782 A remote system connected to @value{GDBN} via a serial line or network
15783 connection. This command tells @value{GDBN} to use its own remote
15784 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15786 For example, if you have a board connected to @file{/dev/ttya} on the
15787 machine running @value{GDBN}, you could say:
15790 target remote /dev/ttya
15793 @code{target remote} supports the @code{load} command. This is only
15794 useful if you have some other way of getting the stub to the target
15795 system, and you can put it somewhere in memory where it won't get
15796 clobbered by the download.
15798 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15799 @cindex built-in simulator target
15800 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15808 works; however, you cannot assume that a specific memory map, device
15809 drivers, or even basic I/O is available, although some simulators do
15810 provide these. For info about any processor-specific simulator details,
15811 see the appropriate section in @ref{Embedded Processors, ,Embedded
15816 Some configurations may include these targets as well:
15820 @item target nrom @var{dev}
15821 @cindex NetROM ROM emulator target
15822 NetROM ROM emulator. This target only supports downloading.
15826 Different targets are available on different configurations of @value{GDBN};
15827 your configuration may have more or fewer targets.
15829 Many remote targets require you to download the executable's code once
15830 you've successfully established a connection. You may wish to control
15831 various aspects of this process.
15836 @kindex set hash@r{, for remote monitors}
15837 @cindex hash mark while downloading
15838 This command controls whether a hash mark @samp{#} is displayed while
15839 downloading a file to the remote monitor. If on, a hash mark is
15840 displayed after each S-record is successfully downloaded to the
15844 @kindex show hash@r{, for remote monitors}
15845 Show the current status of displaying the hash mark.
15847 @item set debug monitor
15848 @kindex set debug monitor
15849 @cindex display remote monitor communications
15850 Enable or disable display of communications messages between
15851 @value{GDBN} and the remote monitor.
15853 @item show debug monitor
15854 @kindex show debug monitor
15855 Show the current status of displaying communications between
15856 @value{GDBN} and the remote monitor.
15861 @kindex load @var{filename}
15862 @item load @var{filename}
15864 Depending on what remote debugging facilities are configured into
15865 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15866 is meant to make @var{filename} (an executable) available for debugging
15867 on the remote system---by downloading, or dynamic linking, for example.
15868 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15869 the @code{add-symbol-file} command.
15871 If your @value{GDBN} does not have a @code{load} command, attempting to
15872 execute it gets the error message ``@code{You can't do that when your
15873 target is @dots{}}''
15875 The file is loaded at whatever address is specified in the executable.
15876 For some object file formats, you can specify the load address when you
15877 link the program; for other formats, like a.out, the object file format
15878 specifies a fixed address.
15879 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15881 Depending on the remote side capabilities, @value{GDBN} may be able to
15882 load programs into flash memory.
15884 @code{load} does not repeat if you press @key{RET} again after using it.
15888 @section Choosing Target Byte Order
15890 @cindex choosing target byte order
15891 @cindex target byte order
15893 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15894 offer the ability to run either big-endian or little-endian byte
15895 orders. Usually the executable or symbol will include a bit to
15896 designate the endian-ness, and you will not need to worry about
15897 which to use. However, you may still find it useful to adjust
15898 @value{GDBN}'s idea of processor endian-ness manually.
15902 @item set endian big
15903 Instruct @value{GDBN} to assume the target is big-endian.
15905 @item set endian little
15906 Instruct @value{GDBN} to assume the target is little-endian.
15908 @item set endian auto
15909 Instruct @value{GDBN} to use the byte order associated with the
15913 Display @value{GDBN}'s current idea of the target byte order.
15917 Note that these commands merely adjust interpretation of symbolic
15918 data on the host, and that they have absolutely no effect on the
15922 @node Remote Debugging
15923 @chapter Debugging Remote Programs
15924 @cindex remote debugging
15926 If you are trying to debug a program running on a machine that cannot run
15927 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15928 For example, you might use remote debugging on an operating system kernel,
15929 or on a small system which does not have a general purpose operating system
15930 powerful enough to run a full-featured debugger.
15932 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15933 to make this work with particular debugging targets. In addition,
15934 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15935 but not specific to any particular target system) which you can use if you
15936 write the remote stubs---the code that runs on the remote system to
15937 communicate with @value{GDBN}.
15939 Other remote targets may be available in your
15940 configuration of @value{GDBN}; use @code{help target} to list them.
15943 * Connecting:: Connecting to a remote target
15944 * File Transfer:: Sending files to a remote system
15945 * Server:: Using the gdbserver program
15946 * Remote Configuration:: Remote configuration
15947 * Remote Stub:: Implementing a remote stub
15951 @section Connecting to a Remote Target
15953 On the @value{GDBN} host machine, you will need an unstripped copy of
15954 your program, since @value{GDBN} needs symbol and debugging information.
15955 Start up @value{GDBN} as usual, using the name of the local copy of your
15956 program as the first argument.
15958 @cindex @code{target remote}
15959 @value{GDBN} can communicate with the target over a serial line, or
15960 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15961 each case, @value{GDBN} uses the same protocol for debugging your
15962 program; only the medium carrying the debugging packets varies. The
15963 @code{target remote} command establishes a connection to the target.
15964 Its arguments indicate which medium to use:
15968 @item target remote @var{serial-device}
15969 @cindex serial line, @code{target remote}
15970 Use @var{serial-device} to communicate with the target. For example,
15971 to use a serial line connected to the device named @file{/dev/ttyb}:
15974 target remote /dev/ttyb
15977 If you're using a serial line, you may want to give @value{GDBN} the
15978 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15979 (@pxref{Remote Configuration, set remotebaud}) before the
15980 @code{target} command.
15982 @item target remote @code{@var{host}:@var{port}}
15983 @itemx target remote @code{tcp:@var{host}:@var{port}}
15984 @cindex @acronym{TCP} port, @code{target remote}
15985 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15986 The @var{host} may be either a host name or a numeric @acronym{IP}
15987 address; @var{port} must be a decimal number. The @var{host} could be
15988 the target machine itself, if it is directly connected to the net, or
15989 it might be a terminal server which in turn has a serial line to the
15992 For example, to connect to port 2828 on a terminal server named
15996 target remote manyfarms:2828
15999 If your remote target is actually running on the same machine as your
16000 debugger session (e.g.@: a simulator for your target running on the
16001 same host), you can omit the hostname. For example, to connect to
16002 port 1234 on your local machine:
16005 target remote :1234
16009 Note that the colon is still required here.
16011 @item target remote @code{udp:@var{host}:@var{port}}
16012 @cindex @acronym{UDP} port, @code{target remote}
16013 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16014 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16017 target remote udp:manyfarms:2828
16020 When using a @acronym{UDP} connection for remote debugging, you should
16021 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16022 can silently drop packets on busy or unreliable networks, which will
16023 cause havoc with your debugging session.
16025 @item target remote | @var{command}
16026 @cindex pipe, @code{target remote} to
16027 Run @var{command} in the background and communicate with it using a
16028 pipe. The @var{command} is a shell command, to be parsed and expanded
16029 by the system's command shell, @code{/bin/sh}; it should expect remote
16030 protocol packets on its standard input, and send replies on its
16031 standard output. You could use this to run a stand-alone simulator
16032 that speaks the remote debugging protocol, to make net connections
16033 using programs like @code{ssh}, or for other similar tricks.
16035 If @var{command} closes its standard output (perhaps by exiting),
16036 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16037 program has already exited, this will have no effect.)
16041 Once the connection has been established, you can use all the usual
16042 commands to examine and change data. The remote program is already
16043 running; you can use @kbd{step} and @kbd{continue}, and you do not
16044 need to use @kbd{run}.
16046 @cindex interrupting remote programs
16047 @cindex remote programs, interrupting
16048 Whenever @value{GDBN} is waiting for the remote program, if you type the
16049 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16050 program. This may or may not succeed, depending in part on the hardware
16051 and the serial drivers the remote system uses. If you type the
16052 interrupt character once again, @value{GDBN} displays this prompt:
16055 Interrupted while waiting for the program.
16056 Give up (and stop debugging it)? (y or n)
16059 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16060 (If you decide you want to try again later, you can use @samp{target
16061 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16062 goes back to waiting.
16065 @kindex detach (remote)
16067 When you have finished debugging the remote program, you can use the
16068 @code{detach} command to release it from @value{GDBN} control.
16069 Detaching from the target normally resumes its execution, but the results
16070 will depend on your particular remote stub. After the @code{detach}
16071 command, @value{GDBN} is free to connect to another target.
16075 The @code{disconnect} command behaves like @code{detach}, except that
16076 the target is generally not resumed. It will wait for @value{GDBN}
16077 (this instance or another one) to connect and continue debugging. After
16078 the @code{disconnect} command, @value{GDBN} is again free to connect to
16081 @cindex send command to remote monitor
16082 @cindex extend @value{GDBN} for remote targets
16083 @cindex add new commands for external monitor
16085 @item monitor @var{cmd}
16086 This command allows you to send arbitrary commands directly to the
16087 remote monitor. Since @value{GDBN} doesn't care about the commands it
16088 sends like this, this command is the way to extend @value{GDBN}---you
16089 can add new commands that only the external monitor will understand
16093 @node File Transfer
16094 @section Sending files to a remote system
16095 @cindex remote target, file transfer
16096 @cindex file transfer
16097 @cindex sending files to remote systems
16099 Some remote targets offer the ability to transfer files over the same
16100 connection used to communicate with @value{GDBN}. This is convenient
16101 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16102 running @code{gdbserver} over a network interface. For other targets,
16103 e.g.@: embedded devices with only a single serial port, this may be
16104 the only way to upload or download files.
16106 Not all remote targets support these commands.
16110 @item remote put @var{hostfile} @var{targetfile}
16111 Copy file @var{hostfile} from the host system (the machine running
16112 @value{GDBN}) to @var{targetfile} on the target system.
16115 @item remote get @var{targetfile} @var{hostfile}
16116 Copy file @var{targetfile} from the target system to @var{hostfile}
16117 on the host system.
16119 @kindex remote delete
16120 @item remote delete @var{targetfile}
16121 Delete @var{targetfile} from the target system.
16126 @section Using the @code{gdbserver} Program
16129 @cindex remote connection without stubs
16130 @code{gdbserver} is a control program for Unix-like systems, which
16131 allows you to connect your program with a remote @value{GDBN} via
16132 @code{target remote}---but without linking in the usual debugging stub.
16134 @code{gdbserver} is not a complete replacement for the debugging stubs,
16135 because it requires essentially the same operating-system facilities
16136 that @value{GDBN} itself does. In fact, a system that can run
16137 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16138 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16139 because it is a much smaller program than @value{GDBN} itself. It is
16140 also easier to port than all of @value{GDBN}, so you may be able to get
16141 started more quickly on a new system by using @code{gdbserver}.
16142 Finally, if you develop code for real-time systems, you may find that
16143 the tradeoffs involved in real-time operation make it more convenient to
16144 do as much development work as possible on another system, for example
16145 by cross-compiling. You can use @code{gdbserver} to make a similar
16146 choice for debugging.
16148 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16149 or a TCP connection, using the standard @value{GDBN} remote serial
16153 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16154 Do not run @code{gdbserver} connected to any public network; a
16155 @value{GDBN} connection to @code{gdbserver} provides access to the
16156 target system with the same privileges as the user running
16160 @subsection Running @code{gdbserver}
16161 @cindex arguments, to @code{gdbserver}
16162 @cindex @code{gdbserver}, command-line arguments
16164 Run @code{gdbserver} on the target system. You need a copy of the
16165 program you want to debug, including any libraries it requires.
16166 @code{gdbserver} does not need your program's symbol table, so you can
16167 strip the program if necessary to save space. @value{GDBN} on the host
16168 system does all the symbol handling.
16170 To use the server, you must tell it how to communicate with @value{GDBN};
16171 the name of your program; and the arguments for your program. The usual
16175 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16178 @var{comm} is either a device name (to use a serial line) or a TCP
16179 hostname and portnumber. For example, to debug Emacs with the argument
16180 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16184 target> gdbserver /dev/com1 emacs foo.txt
16187 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16190 To use a TCP connection instead of a serial line:
16193 target> gdbserver host:2345 emacs foo.txt
16196 The only difference from the previous example is the first argument,
16197 specifying that you are communicating with the host @value{GDBN} via
16198 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16199 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16200 (Currently, the @samp{host} part is ignored.) You can choose any number
16201 you want for the port number as long as it does not conflict with any
16202 TCP ports already in use on the target system (for example, @code{23} is
16203 reserved for @code{telnet}).@footnote{If you choose a port number that
16204 conflicts with another service, @code{gdbserver} prints an error message
16205 and exits.} You must use the same port number with the host @value{GDBN}
16206 @code{target remote} command.
16208 @subsubsection Attaching to a Running Program
16209 @cindex attach to a program, @code{gdbserver}
16210 @cindex @option{--attach}, @code{gdbserver} option
16212 On some targets, @code{gdbserver} can also attach to running programs.
16213 This is accomplished via the @code{--attach} argument. The syntax is:
16216 target> gdbserver --attach @var{comm} @var{pid}
16219 @var{pid} is the process ID of a currently running process. It isn't necessary
16220 to point @code{gdbserver} at a binary for the running process.
16223 You can debug processes by name instead of process ID if your target has the
16224 @code{pidof} utility:
16227 target> gdbserver --attach @var{comm} `pidof @var{program}`
16230 In case more than one copy of @var{program} is running, or @var{program}
16231 has multiple threads, most versions of @code{pidof} support the
16232 @code{-s} option to only return the first process ID.
16234 @subsubsection Multi-Process Mode for @code{gdbserver}
16235 @cindex @code{gdbserver}, multiple processes
16236 @cindex multiple processes with @code{gdbserver}
16238 When you connect to @code{gdbserver} using @code{target remote},
16239 @code{gdbserver} debugs the specified program only once. When the
16240 program exits, or you detach from it, @value{GDBN} closes the connection
16241 and @code{gdbserver} exits.
16243 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16244 enters multi-process mode. When the debugged program exits, or you
16245 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16246 though no program is running. The @code{run} and @code{attach}
16247 commands instruct @code{gdbserver} to run or attach to a new program.
16248 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16249 remote exec-file}) to select the program to run. Command line
16250 arguments are supported, except for wildcard expansion and I/O
16251 redirection (@pxref{Arguments}).
16253 @cindex @option{--multi}, @code{gdbserver} option
16254 To start @code{gdbserver} without supplying an initial command to run
16255 or process ID to attach, use the @option{--multi} command line option.
16256 Then you can connect using @kbd{target extended-remote} and start
16257 the program you want to debug.
16259 In multi-process mode @code{gdbserver} does not automatically exit unless you
16260 use the option @option{--once}. You can terminate it by using
16261 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16262 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16263 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16264 @option{--multi} option to @code{gdbserver} has no influence on that.
16266 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16268 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16270 @code{gdbserver} normally terminates after all of its debugged processes have
16271 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16272 extended-remote}, @code{gdbserver} stays running even with no processes left.
16273 @value{GDBN} normally terminates the spawned debugged process on its exit,
16274 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16275 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16276 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16277 stays running even in the @kbd{target remote} mode.
16279 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16280 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16281 completeness, at most one @value{GDBN} can be connected at a time.
16283 @cindex @option{--once}, @code{gdbserver} option
16284 By default, @code{gdbserver} keeps the listening TCP port open, so that
16285 additional connections are possible. However, if you start @code{gdbserver}
16286 with the @option{--once} option, it will stop listening for any further
16287 connection attempts after connecting to the first @value{GDBN} session. This
16288 means no further connections to @code{gdbserver} will be possible after the
16289 first one. It also means @code{gdbserver} will terminate after the first
16290 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16291 connections and even in the @kbd{target extended-remote} mode. The
16292 @option{--once} option allows reusing the same port number for connecting to
16293 multiple instances of @code{gdbserver} running on the same host, since each
16294 instance closes its port after the first connection.
16296 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16298 @cindex @option{--debug}, @code{gdbserver} option
16299 The @option{--debug} option tells @code{gdbserver} to display extra
16300 status information about the debugging process.
16301 @cindex @option{--remote-debug}, @code{gdbserver} option
16302 The @option{--remote-debug} option tells @code{gdbserver} to display
16303 remote protocol debug output. These options are intended for
16304 @code{gdbserver} development and for bug reports to the developers.
16306 @cindex @option{--wrapper}, @code{gdbserver} option
16307 The @option{--wrapper} option specifies a wrapper to launch programs
16308 for debugging. The option should be followed by the name of the
16309 wrapper, then any command-line arguments to pass to the wrapper, then
16310 @kbd{--} indicating the end of the wrapper arguments.
16312 @code{gdbserver} runs the specified wrapper program with a combined
16313 command line including the wrapper arguments, then the name of the
16314 program to debug, then any arguments to the program. The wrapper
16315 runs until it executes your program, and then @value{GDBN} gains control.
16317 You can use any program that eventually calls @code{execve} with
16318 its arguments as a wrapper. Several standard Unix utilities do
16319 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16320 with @code{exec "$@@"} will also work.
16322 For example, you can use @code{env} to pass an environment variable to
16323 the debugged program, without setting the variable in @code{gdbserver}'s
16327 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16330 @subsection Connecting to @code{gdbserver}
16332 Run @value{GDBN} on the host system.
16334 First make sure you have the necessary symbol files. Load symbols for
16335 your application using the @code{file} command before you connect. Use
16336 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16337 was compiled with the correct sysroot using @code{--with-sysroot}).
16339 The symbol file and target libraries must exactly match the executable
16340 and libraries on the target, with one exception: the files on the host
16341 system should not be stripped, even if the files on the target system
16342 are. Mismatched or missing files will lead to confusing results
16343 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16344 files may also prevent @code{gdbserver} from debugging multi-threaded
16347 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16348 For TCP connections, you must start up @code{gdbserver} prior to using
16349 the @code{target remote} command. Otherwise you may get an error whose
16350 text depends on the host system, but which usually looks something like
16351 @samp{Connection refused}. Don't use the @code{load}
16352 command in @value{GDBN} when using @code{gdbserver}, since the program is
16353 already on the target.
16355 @subsection Monitor Commands for @code{gdbserver}
16356 @cindex monitor commands, for @code{gdbserver}
16357 @anchor{Monitor Commands for gdbserver}
16359 During a @value{GDBN} session using @code{gdbserver}, you can use the
16360 @code{monitor} command to send special requests to @code{gdbserver}.
16361 Here are the available commands.
16365 List the available monitor commands.
16367 @item monitor set debug 0
16368 @itemx monitor set debug 1
16369 Disable or enable general debugging messages.
16371 @item monitor set remote-debug 0
16372 @itemx monitor set remote-debug 1
16373 Disable or enable specific debugging messages associated with the remote
16374 protocol (@pxref{Remote Protocol}).
16376 @item monitor set libthread-db-search-path [PATH]
16377 @cindex gdbserver, search path for @code{libthread_db}
16378 When this command is issued, @var{path} is a colon-separated list of
16379 directories to search for @code{libthread_db} (@pxref{Threads,,set
16380 libthread-db-search-path}). If you omit @var{path},
16381 @samp{libthread-db-search-path} will be reset to its default value.
16384 Tell gdbserver to exit immediately. This command should be followed by
16385 @code{disconnect} to close the debugging session. @code{gdbserver} will
16386 detach from any attached processes and kill any processes it created.
16387 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16388 of a multi-process mode debug session.
16392 @subsection Tracepoints support in @code{gdbserver}
16393 @cindex tracepoints support in @code{gdbserver}
16395 On some targets, @code{gdbserver} supports tracepoints, fast
16396 tracepoints and static tracepoints.
16398 For fast or static tracepoints to work, a special library called the
16399 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16400 This library is built and distributed as an integral part of
16401 @code{gdbserver}. In addition, support for static tracepoints
16402 requires building the in-process agent library with static tracepoints
16403 support. At present, the UST (LTTng Userspace Tracer,
16404 @url{http://lttng.org/ust}) tracing engine is supported. This support
16405 is automatically available if UST development headers are found in the
16406 standard include path when @code{gdbserver} is built, or if
16407 @code{gdbserver} was explicitly configured using @option{--with-ust}
16408 to point at such headers. You can explicitly disable the support
16409 using @option{--with-ust=no}.
16411 There are several ways to load the in-process agent in your program:
16414 @item Specifying it as dependency at link time
16416 You can link your program dynamically with the in-process agent
16417 library. On most systems, this is accomplished by adding
16418 @code{-linproctrace} to the link command.
16420 @item Using the system's preloading mechanisms
16422 You can force loading the in-process agent at startup time by using
16423 your system's support for preloading shared libraries. Many Unixes
16424 support the concept of preloading user defined libraries. In most
16425 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16426 in the environment. See also the description of @code{gdbserver}'s
16427 @option{--wrapper} command line option.
16429 @item Using @value{GDBN} to force loading the agent at run time
16431 On some systems, you can force the inferior to load a shared library,
16432 by calling a dynamic loader function in the inferior that takes care
16433 of dynamically looking up and loading a shared library. On most Unix
16434 systems, the function is @code{dlopen}. You'll use the @code{call}
16435 command for that. For example:
16438 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16441 Note that on most Unix systems, for the @code{dlopen} function to be
16442 available, the program needs to be linked with @code{-ldl}.
16445 On systems that have a userspace dynamic loader, like most Unix
16446 systems, when you connect to @code{gdbserver} using @code{target
16447 remote}, you'll find that the program is stopped at the dynamic
16448 loader's entry point, and no shared library has been loaded in the
16449 program's address space yet, including the in-process agent. In that
16450 case, before being able to use any of the fast or static tracepoints
16451 features, you need to let the loader run and load the shared
16452 libraries. The simplest way to do that is to run the program to the
16453 main procedure. E.g., if debugging a C or C@t{++} program, start
16454 @code{gdbserver} like so:
16457 $ gdbserver :9999 myprogram
16460 Start GDB and connect to @code{gdbserver} like so, and run to main:
16464 (@value{GDBP}) target remote myhost:9999
16465 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16466 (@value{GDBP}) b main
16467 (@value{GDBP}) continue
16470 The in-process tracing agent library should now be loaded into the
16471 process; you can confirm it with the @code{info sharedlibrary}
16472 command, which will list @file{libinproctrace.so} as loaded in the
16473 process. You are now ready to install fast tracepoints, list static
16474 tracepoint markers, probe static tracepoints markers, and start
16477 @node Remote Configuration
16478 @section Remote Configuration
16481 @kindex show remote
16482 This section documents the configuration options available when
16483 debugging remote programs. For the options related to the File I/O
16484 extensions of the remote protocol, see @ref{system,
16485 system-call-allowed}.
16488 @item set remoteaddresssize @var{bits}
16489 @cindex address size for remote targets
16490 @cindex bits in remote address
16491 Set the maximum size of address in a memory packet to the specified
16492 number of bits. @value{GDBN} will mask off the address bits above
16493 that number, when it passes addresses to the remote target. The
16494 default value is the number of bits in the target's address.
16496 @item show remoteaddresssize
16497 Show the current value of remote address size in bits.
16499 @item set remotebaud @var{n}
16500 @cindex baud rate for remote targets
16501 Set the baud rate for the remote serial I/O to @var{n} baud. The
16502 value is used to set the speed of the serial port used for debugging
16505 @item show remotebaud
16506 Show the current speed of the remote connection.
16508 @item set remotebreak
16509 @cindex interrupt remote programs
16510 @cindex BREAK signal instead of Ctrl-C
16511 @anchor{set remotebreak}
16512 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16513 when you type @kbd{Ctrl-c} to interrupt the program running
16514 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16515 character instead. The default is off, since most remote systems
16516 expect to see @samp{Ctrl-C} as the interrupt signal.
16518 @item show remotebreak
16519 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16520 interrupt the remote program.
16522 @item set remoteflow on
16523 @itemx set remoteflow off
16524 @kindex set remoteflow
16525 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16526 on the serial port used to communicate to the remote target.
16528 @item show remoteflow
16529 @kindex show remoteflow
16530 Show the current setting of hardware flow control.
16532 @item set remotelogbase @var{base}
16533 Set the base (a.k.a.@: radix) of logging serial protocol
16534 communications to @var{base}. Supported values of @var{base} are:
16535 @code{ascii}, @code{octal}, and @code{hex}. The default is
16538 @item show remotelogbase
16539 Show the current setting of the radix for logging remote serial
16542 @item set remotelogfile @var{file}
16543 @cindex record serial communications on file
16544 Record remote serial communications on the named @var{file}. The
16545 default is not to record at all.
16547 @item show remotelogfile.
16548 Show the current setting of the file name on which to record the
16549 serial communications.
16551 @item set remotetimeout @var{num}
16552 @cindex timeout for serial communications
16553 @cindex remote timeout
16554 Set the timeout limit to wait for the remote target to respond to
16555 @var{num} seconds. The default is 2 seconds.
16557 @item show remotetimeout
16558 Show the current number of seconds to wait for the remote target
16561 @cindex limit hardware breakpoints and watchpoints
16562 @cindex remote target, limit break- and watchpoints
16563 @anchor{set remote hardware-watchpoint-limit}
16564 @anchor{set remote hardware-breakpoint-limit}
16565 @item set remote hardware-watchpoint-limit @var{limit}
16566 @itemx set remote hardware-breakpoint-limit @var{limit}
16567 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16568 watchpoints. A limit of -1, the default, is treated as unlimited.
16570 @item set remote exec-file @var{filename}
16571 @itemx show remote exec-file
16572 @anchor{set remote exec-file}
16573 @cindex executable file, for remote target
16574 Select the file used for @code{run} with @code{target
16575 extended-remote}. This should be set to a filename valid on the
16576 target system. If it is not set, the target will use a default
16577 filename (e.g.@: the last program run).
16579 @item set remote interrupt-sequence
16580 @cindex interrupt remote programs
16581 @cindex select Ctrl-C, BREAK or BREAK-g
16582 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16583 @samp{BREAK-g} as the
16584 sequence to the remote target in order to interrupt the execution.
16585 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16586 is high level of serial line for some certain time.
16587 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16588 It is @code{BREAK} signal followed by character @code{g}.
16590 @item show interrupt-sequence
16591 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16592 is sent by @value{GDBN} to interrupt the remote program.
16593 @code{BREAK-g} is BREAK signal followed by @code{g} and
16594 also known as Magic SysRq g.
16596 @item set remote interrupt-on-connect
16597 @cindex send interrupt-sequence on start
16598 Specify whether interrupt-sequence is sent to remote target when
16599 @value{GDBN} connects to it. This is mostly needed when you debug
16600 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16601 which is known as Magic SysRq g in order to connect @value{GDBN}.
16603 @item show interrupt-on-connect
16604 Show whether interrupt-sequence is sent
16605 to remote target when @value{GDBN} connects to it.
16609 @item set tcp auto-retry on
16610 @cindex auto-retry, for remote TCP target
16611 Enable auto-retry for remote TCP connections. This is useful if the remote
16612 debugging agent is launched in parallel with @value{GDBN}; there is a race
16613 condition because the agent may not become ready to accept the connection
16614 before @value{GDBN} attempts to connect. When auto-retry is
16615 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16616 to establish the connection using the timeout specified by
16617 @code{set tcp connect-timeout}.
16619 @item set tcp auto-retry off
16620 Do not auto-retry failed TCP connections.
16622 @item show tcp auto-retry
16623 Show the current auto-retry setting.
16625 @item set tcp connect-timeout @var{seconds}
16626 @cindex connection timeout, for remote TCP target
16627 @cindex timeout, for remote target connection
16628 Set the timeout for establishing a TCP connection to the remote target to
16629 @var{seconds}. The timeout affects both polling to retry failed connections
16630 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16631 that are merely slow to complete, and represents an approximate cumulative
16634 @item show tcp connect-timeout
16635 Show the current connection timeout setting.
16638 @cindex remote packets, enabling and disabling
16639 The @value{GDBN} remote protocol autodetects the packets supported by
16640 your debugging stub. If you need to override the autodetection, you
16641 can use these commands to enable or disable individual packets. Each
16642 packet can be set to @samp{on} (the remote target supports this
16643 packet), @samp{off} (the remote target does not support this packet),
16644 or @samp{auto} (detect remote target support for this packet). They
16645 all default to @samp{auto}. For more information about each packet,
16646 see @ref{Remote Protocol}.
16648 During normal use, you should not have to use any of these commands.
16649 If you do, that may be a bug in your remote debugging stub, or a bug
16650 in @value{GDBN}. You may want to report the problem to the
16651 @value{GDBN} developers.
16653 For each packet @var{name}, the command to enable or disable the
16654 packet is @code{set remote @var{name}-packet}. The available settings
16657 @multitable @columnfractions 0.28 0.32 0.25
16660 @tab Related Features
16662 @item @code{fetch-register}
16664 @tab @code{info registers}
16666 @item @code{set-register}
16670 @item @code{binary-download}
16672 @tab @code{load}, @code{set}
16674 @item @code{read-aux-vector}
16675 @tab @code{qXfer:auxv:read}
16676 @tab @code{info auxv}
16678 @item @code{symbol-lookup}
16679 @tab @code{qSymbol}
16680 @tab Detecting multiple threads
16682 @item @code{attach}
16683 @tab @code{vAttach}
16686 @item @code{verbose-resume}
16688 @tab Stepping or resuming multiple threads
16694 @item @code{software-breakpoint}
16698 @item @code{hardware-breakpoint}
16702 @item @code{write-watchpoint}
16706 @item @code{read-watchpoint}
16710 @item @code{access-watchpoint}
16714 @item @code{target-features}
16715 @tab @code{qXfer:features:read}
16716 @tab @code{set architecture}
16718 @item @code{library-info}
16719 @tab @code{qXfer:libraries:read}
16720 @tab @code{info sharedlibrary}
16722 @item @code{memory-map}
16723 @tab @code{qXfer:memory-map:read}
16724 @tab @code{info mem}
16726 @item @code{read-sdata-object}
16727 @tab @code{qXfer:sdata:read}
16728 @tab @code{print $_sdata}
16730 @item @code{read-spu-object}
16731 @tab @code{qXfer:spu:read}
16732 @tab @code{info spu}
16734 @item @code{write-spu-object}
16735 @tab @code{qXfer:spu:write}
16736 @tab @code{info spu}
16738 @item @code{read-siginfo-object}
16739 @tab @code{qXfer:siginfo:read}
16740 @tab @code{print $_siginfo}
16742 @item @code{write-siginfo-object}
16743 @tab @code{qXfer:siginfo:write}
16744 @tab @code{set $_siginfo}
16746 @item @code{threads}
16747 @tab @code{qXfer:threads:read}
16748 @tab @code{info threads}
16750 @item @code{get-thread-local-@*storage-address}
16751 @tab @code{qGetTLSAddr}
16752 @tab Displaying @code{__thread} variables
16754 @item @code{get-thread-information-block-address}
16755 @tab @code{qGetTIBAddr}
16756 @tab Display MS-Windows Thread Information Block.
16758 @item @code{search-memory}
16759 @tab @code{qSearch:memory}
16762 @item @code{supported-packets}
16763 @tab @code{qSupported}
16764 @tab Remote communications parameters
16766 @item @code{pass-signals}
16767 @tab @code{QPassSignals}
16768 @tab @code{handle @var{signal}}
16770 @item @code{hostio-close-packet}
16771 @tab @code{vFile:close}
16772 @tab @code{remote get}, @code{remote put}
16774 @item @code{hostio-open-packet}
16775 @tab @code{vFile:open}
16776 @tab @code{remote get}, @code{remote put}
16778 @item @code{hostio-pread-packet}
16779 @tab @code{vFile:pread}
16780 @tab @code{remote get}, @code{remote put}
16782 @item @code{hostio-pwrite-packet}
16783 @tab @code{vFile:pwrite}
16784 @tab @code{remote get}, @code{remote put}
16786 @item @code{hostio-unlink-packet}
16787 @tab @code{vFile:unlink}
16788 @tab @code{remote delete}
16790 @item @code{noack-packet}
16791 @tab @code{QStartNoAckMode}
16792 @tab Packet acknowledgment
16794 @item @code{osdata}
16795 @tab @code{qXfer:osdata:read}
16796 @tab @code{info os}
16798 @item @code{query-attached}
16799 @tab @code{qAttached}
16800 @tab Querying remote process attach state.
16802 @item @code{traceframe-info}
16803 @tab @code{qXfer:traceframe-info:read}
16804 @tab Traceframe info
16808 @section Implementing a Remote Stub
16810 @cindex debugging stub, example
16811 @cindex remote stub, example
16812 @cindex stub example, remote debugging
16813 The stub files provided with @value{GDBN} implement the target side of the
16814 communication protocol, and the @value{GDBN} side is implemented in the
16815 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16816 these subroutines to communicate, and ignore the details. (If you're
16817 implementing your own stub file, you can still ignore the details: start
16818 with one of the existing stub files. @file{sparc-stub.c} is the best
16819 organized, and therefore the easiest to read.)
16821 @cindex remote serial debugging, overview
16822 To debug a program running on another machine (the debugging
16823 @dfn{target} machine), you must first arrange for all the usual
16824 prerequisites for the program to run by itself. For example, for a C
16829 A startup routine to set up the C runtime environment; these usually
16830 have a name like @file{crt0}. The startup routine may be supplied by
16831 your hardware supplier, or you may have to write your own.
16834 A C subroutine library to support your program's
16835 subroutine calls, notably managing input and output.
16838 A way of getting your program to the other machine---for example, a
16839 download program. These are often supplied by the hardware
16840 manufacturer, but you may have to write your own from hardware
16844 The next step is to arrange for your program to use a serial port to
16845 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16846 machine). In general terms, the scheme looks like this:
16850 @value{GDBN} already understands how to use this protocol; when everything
16851 else is set up, you can simply use the @samp{target remote} command
16852 (@pxref{Targets,,Specifying a Debugging Target}).
16854 @item On the target,
16855 you must link with your program a few special-purpose subroutines that
16856 implement the @value{GDBN} remote serial protocol. The file containing these
16857 subroutines is called a @dfn{debugging stub}.
16859 On certain remote targets, you can use an auxiliary program
16860 @code{gdbserver} instead of linking a stub into your program.
16861 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16864 The debugging stub is specific to the architecture of the remote
16865 machine; for example, use @file{sparc-stub.c} to debug programs on
16868 @cindex remote serial stub list
16869 These working remote stubs are distributed with @value{GDBN}:
16874 @cindex @file{i386-stub.c}
16877 For Intel 386 and compatible architectures.
16880 @cindex @file{m68k-stub.c}
16881 @cindex Motorola 680x0
16883 For Motorola 680x0 architectures.
16886 @cindex @file{sh-stub.c}
16889 For Renesas SH architectures.
16892 @cindex @file{sparc-stub.c}
16894 For @sc{sparc} architectures.
16896 @item sparcl-stub.c
16897 @cindex @file{sparcl-stub.c}
16900 For Fujitsu @sc{sparclite} architectures.
16904 The @file{README} file in the @value{GDBN} distribution may list other
16905 recently added stubs.
16908 * Stub Contents:: What the stub can do for you
16909 * Bootstrapping:: What you must do for the stub
16910 * Debug Session:: Putting it all together
16913 @node Stub Contents
16914 @subsection What the Stub Can Do for You
16916 @cindex remote serial stub
16917 The debugging stub for your architecture supplies these three
16921 @item set_debug_traps
16922 @findex set_debug_traps
16923 @cindex remote serial stub, initialization
16924 This routine arranges for @code{handle_exception} to run when your
16925 program stops. You must call this subroutine explicitly near the
16926 beginning of your program.
16928 @item handle_exception
16929 @findex handle_exception
16930 @cindex remote serial stub, main routine
16931 This is the central workhorse, but your program never calls it
16932 explicitly---the setup code arranges for @code{handle_exception} to
16933 run when a trap is triggered.
16935 @code{handle_exception} takes control when your program stops during
16936 execution (for example, on a breakpoint), and mediates communications
16937 with @value{GDBN} on the host machine. This is where the communications
16938 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16939 representative on the target machine. It begins by sending summary
16940 information on the state of your program, then continues to execute,
16941 retrieving and transmitting any information @value{GDBN} needs, until you
16942 execute a @value{GDBN} command that makes your program resume; at that point,
16943 @code{handle_exception} returns control to your own code on the target
16947 @cindex @code{breakpoint} subroutine, remote
16948 Use this auxiliary subroutine to make your program contain a
16949 breakpoint. Depending on the particular situation, this may be the only
16950 way for @value{GDBN} to get control. For instance, if your target
16951 machine has some sort of interrupt button, you won't need to call this;
16952 pressing the interrupt button transfers control to
16953 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16954 simply receiving characters on the serial port may also trigger a trap;
16955 again, in that situation, you don't need to call @code{breakpoint} from
16956 your own program---simply running @samp{target remote} from the host
16957 @value{GDBN} session gets control.
16959 Call @code{breakpoint} if none of these is true, or if you simply want
16960 to make certain your program stops at a predetermined point for the
16961 start of your debugging session.
16964 @node Bootstrapping
16965 @subsection What You Must Do for the Stub
16967 @cindex remote stub, support routines
16968 The debugging stubs that come with @value{GDBN} are set up for a particular
16969 chip architecture, but they have no information about the rest of your
16970 debugging target machine.
16972 First of all you need to tell the stub how to communicate with the
16976 @item int getDebugChar()
16977 @findex getDebugChar
16978 Write this subroutine to read a single character from the serial port.
16979 It may be identical to @code{getchar} for your target system; a
16980 different name is used to allow you to distinguish the two if you wish.
16982 @item void putDebugChar(int)
16983 @findex putDebugChar
16984 Write this subroutine to write a single character to the serial port.
16985 It may be identical to @code{putchar} for your target system; a
16986 different name is used to allow you to distinguish the two if you wish.
16989 @cindex control C, and remote debugging
16990 @cindex interrupting remote targets
16991 If you want @value{GDBN} to be able to stop your program while it is
16992 running, you need to use an interrupt-driven serial driver, and arrange
16993 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16994 character). That is the character which @value{GDBN} uses to tell the
16995 remote system to stop.
16997 Getting the debugging target to return the proper status to @value{GDBN}
16998 probably requires changes to the standard stub; one quick and dirty way
16999 is to just execute a breakpoint instruction (the ``dirty'' part is that
17000 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17002 Other routines you need to supply are:
17005 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17006 @findex exceptionHandler
17007 Write this function to install @var{exception_address} in the exception
17008 handling tables. You need to do this because the stub does not have any
17009 way of knowing what the exception handling tables on your target system
17010 are like (for example, the processor's table might be in @sc{rom},
17011 containing entries which point to a table in @sc{ram}).
17012 @var{exception_number} is the exception number which should be changed;
17013 its meaning is architecture-dependent (for example, different numbers
17014 might represent divide by zero, misaligned access, etc). When this
17015 exception occurs, control should be transferred directly to
17016 @var{exception_address}, and the processor state (stack, registers,
17017 and so on) should be just as it is when a processor exception occurs. So if
17018 you want to use a jump instruction to reach @var{exception_address}, it
17019 should be a simple jump, not a jump to subroutine.
17021 For the 386, @var{exception_address} should be installed as an interrupt
17022 gate so that interrupts are masked while the handler runs. The gate
17023 should be at privilege level 0 (the most privileged level). The
17024 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17025 help from @code{exceptionHandler}.
17027 @item void flush_i_cache()
17028 @findex flush_i_cache
17029 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17030 instruction cache, if any, on your target machine. If there is no
17031 instruction cache, this subroutine may be a no-op.
17033 On target machines that have instruction caches, @value{GDBN} requires this
17034 function to make certain that the state of your program is stable.
17038 You must also make sure this library routine is available:
17041 @item void *memset(void *, int, int)
17043 This is the standard library function @code{memset} that sets an area of
17044 memory to a known value. If you have one of the free versions of
17045 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17046 either obtain it from your hardware manufacturer, or write your own.
17049 If you do not use the GNU C compiler, you may need other standard
17050 library subroutines as well; this varies from one stub to another,
17051 but in general the stubs are likely to use any of the common library
17052 subroutines which @code{@value{NGCC}} generates as inline code.
17055 @node Debug Session
17056 @subsection Putting it All Together
17058 @cindex remote serial debugging summary
17059 In summary, when your program is ready to debug, you must follow these
17064 Make sure you have defined the supporting low-level routines
17065 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17067 @code{getDebugChar}, @code{putDebugChar},
17068 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17072 Insert these lines near the top of your program:
17080 For the 680x0 stub only, you need to provide a variable called
17081 @code{exceptionHook}. Normally you just use:
17084 void (*exceptionHook)() = 0;
17088 but if before calling @code{set_debug_traps}, you set it to point to a
17089 function in your program, that function is called when
17090 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17091 error). The function indicated by @code{exceptionHook} is called with
17092 one parameter: an @code{int} which is the exception number.
17095 Compile and link together: your program, the @value{GDBN} debugging stub for
17096 your target architecture, and the supporting subroutines.
17099 Make sure you have a serial connection between your target machine and
17100 the @value{GDBN} host, and identify the serial port on the host.
17103 @c The "remote" target now provides a `load' command, so we should
17104 @c document that. FIXME.
17105 Download your program to your target machine (or get it there by
17106 whatever means the manufacturer provides), and start it.
17109 Start @value{GDBN} on the host, and connect to the target
17110 (@pxref{Connecting,,Connecting to a Remote Target}).
17114 @node Configurations
17115 @chapter Configuration-Specific Information
17117 While nearly all @value{GDBN} commands are available for all native and
17118 cross versions of the debugger, there are some exceptions. This chapter
17119 describes things that are only available in certain configurations.
17121 There are three major categories of configurations: native
17122 configurations, where the host and target are the same, embedded
17123 operating system configurations, which are usually the same for several
17124 different processor architectures, and bare embedded processors, which
17125 are quite different from each other.
17130 * Embedded Processors::
17137 This section describes details specific to particular native
17142 * BSD libkvm Interface:: Debugging BSD kernel memory images
17143 * SVR4 Process Information:: SVR4 process information
17144 * DJGPP Native:: Features specific to the DJGPP port
17145 * Cygwin Native:: Features specific to the Cygwin port
17146 * Hurd Native:: Features specific to @sc{gnu} Hurd
17147 * Neutrino:: Features specific to QNX Neutrino
17148 * Darwin:: Features specific to Darwin
17154 On HP-UX systems, if you refer to a function or variable name that
17155 begins with a dollar sign, @value{GDBN} searches for a user or system
17156 name first, before it searches for a convenience variable.
17159 @node BSD libkvm Interface
17160 @subsection BSD libkvm Interface
17163 @cindex kernel memory image
17164 @cindex kernel crash dump
17166 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17167 interface that provides a uniform interface for accessing kernel virtual
17168 memory images, including live systems and crash dumps. @value{GDBN}
17169 uses this interface to allow you to debug live kernels and kernel crash
17170 dumps on many native BSD configurations. This is implemented as a
17171 special @code{kvm} debugging target. For debugging a live system, load
17172 the currently running kernel into @value{GDBN} and connect to the
17176 (@value{GDBP}) @b{target kvm}
17179 For debugging crash dumps, provide the file name of the crash dump as an
17183 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17186 Once connected to the @code{kvm} target, the following commands are
17192 Set current context from the @dfn{Process Control Block} (PCB) address.
17195 Set current context from proc address. This command isn't available on
17196 modern FreeBSD systems.
17199 @node SVR4 Process Information
17200 @subsection SVR4 Process Information
17202 @cindex examine process image
17203 @cindex process info via @file{/proc}
17205 Many versions of SVR4 and compatible systems provide a facility called
17206 @samp{/proc} that can be used to examine the image of a running
17207 process using file-system subroutines. If @value{GDBN} is configured
17208 for an operating system with this facility, the command @code{info
17209 proc} is available to report information about the process running
17210 your program, or about any process running on your system. @code{info
17211 proc} works only on SVR4 systems that include the @code{procfs} code.
17212 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17213 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17219 @itemx info proc @var{process-id}
17220 Summarize available information about any running process. If a
17221 process ID is specified by @var{process-id}, display information about
17222 that process; otherwise display information about the program being
17223 debugged. The summary includes the debugged process ID, the command
17224 line used to invoke it, its current working directory, and its
17225 executable file's absolute file name.
17227 On some systems, @var{process-id} can be of the form
17228 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17229 within a process. If the optional @var{pid} part is missing, it means
17230 a thread from the process being debugged (the leading @samp{/} still
17231 needs to be present, or else @value{GDBN} will interpret the number as
17232 a process ID rather than a thread ID).
17234 @item info proc mappings
17235 @cindex memory address space mappings
17236 Report the memory address space ranges accessible in the program, with
17237 information on whether the process has read, write, or execute access
17238 rights to each range. On @sc{gnu}/Linux systems, each memory range
17239 includes the object file which is mapped to that range, instead of the
17240 memory access rights to that range.
17242 @item info proc stat
17243 @itemx info proc status
17244 @cindex process detailed status information
17245 These subcommands are specific to @sc{gnu}/Linux systems. They show
17246 the process-related information, including the user ID and group ID;
17247 how many threads are there in the process; its virtual memory usage;
17248 the signals that are pending, blocked, and ignored; its TTY; its
17249 consumption of system and user time; its stack size; its @samp{nice}
17250 value; etc. For more information, see the @samp{proc} man page
17251 (type @kbd{man 5 proc} from your shell prompt).
17253 @item info proc all
17254 Show all the information about the process described under all of the
17255 above @code{info proc} subcommands.
17258 @comment These sub-options of 'info proc' were not included when
17259 @comment procfs.c was re-written. Keep their descriptions around
17260 @comment against the day when someone finds the time to put them back in.
17261 @kindex info proc times
17262 @item info proc times
17263 Starting time, user CPU time, and system CPU time for your program and
17266 @kindex info proc id
17268 Report on the process IDs related to your program: its own process ID,
17269 the ID of its parent, the process group ID, and the session ID.
17272 @item set procfs-trace
17273 @kindex set procfs-trace
17274 @cindex @code{procfs} API calls
17275 This command enables and disables tracing of @code{procfs} API calls.
17277 @item show procfs-trace
17278 @kindex show procfs-trace
17279 Show the current state of @code{procfs} API call tracing.
17281 @item set procfs-file @var{file}
17282 @kindex set procfs-file
17283 Tell @value{GDBN} to write @code{procfs} API trace to the named
17284 @var{file}. @value{GDBN} appends the trace info to the previous
17285 contents of the file. The default is to display the trace on the
17288 @item show procfs-file
17289 @kindex show procfs-file
17290 Show the file to which @code{procfs} API trace is written.
17292 @item proc-trace-entry
17293 @itemx proc-trace-exit
17294 @itemx proc-untrace-entry
17295 @itemx proc-untrace-exit
17296 @kindex proc-trace-entry
17297 @kindex proc-trace-exit
17298 @kindex proc-untrace-entry
17299 @kindex proc-untrace-exit
17300 These commands enable and disable tracing of entries into and exits
17301 from the @code{syscall} interface.
17304 @kindex info pidlist
17305 @cindex process list, QNX Neutrino
17306 For QNX Neutrino only, this command displays the list of all the
17307 processes and all the threads within each process.
17310 @kindex info meminfo
17311 @cindex mapinfo list, QNX Neutrino
17312 For QNX Neutrino only, this command displays the list of all mapinfos.
17316 @subsection Features for Debugging @sc{djgpp} Programs
17317 @cindex @sc{djgpp} debugging
17318 @cindex native @sc{djgpp} debugging
17319 @cindex MS-DOS-specific commands
17322 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17323 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17324 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17325 top of real-mode DOS systems and their emulations.
17327 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17328 defines a few commands specific to the @sc{djgpp} port. This
17329 subsection describes those commands.
17334 This is a prefix of @sc{djgpp}-specific commands which print
17335 information about the target system and important OS structures.
17338 @cindex MS-DOS system info
17339 @cindex free memory information (MS-DOS)
17340 @item info dos sysinfo
17341 This command displays assorted information about the underlying
17342 platform: the CPU type and features, the OS version and flavor, the
17343 DPMI version, and the available conventional and DPMI memory.
17348 @cindex segment descriptor tables
17349 @cindex descriptor tables display
17351 @itemx info dos ldt
17352 @itemx info dos idt
17353 These 3 commands display entries from, respectively, Global, Local,
17354 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17355 tables are data structures which store a descriptor for each segment
17356 that is currently in use. The segment's selector is an index into a
17357 descriptor table; the table entry for that index holds the
17358 descriptor's base address and limit, and its attributes and access
17361 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17362 segment (used for both data and the stack), and a DOS segment (which
17363 allows access to DOS/BIOS data structures and absolute addresses in
17364 conventional memory). However, the DPMI host will usually define
17365 additional segments in order to support the DPMI environment.
17367 @cindex garbled pointers
17368 These commands allow to display entries from the descriptor tables.
17369 Without an argument, all entries from the specified table are
17370 displayed. An argument, which should be an integer expression, means
17371 display a single entry whose index is given by the argument. For
17372 example, here's a convenient way to display information about the
17373 debugged program's data segment:
17376 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17377 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17381 This comes in handy when you want to see whether a pointer is outside
17382 the data segment's limit (i.e.@: @dfn{garbled}).
17384 @cindex page tables display (MS-DOS)
17386 @itemx info dos pte
17387 These two commands display entries from, respectively, the Page
17388 Directory and the Page Tables. Page Directories and Page Tables are
17389 data structures which control how virtual memory addresses are mapped
17390 into physical addresses. A Page Table includes an entry for every
17391 page of memory that is mapped into the program's address space; there
17392 may be several Page Tables, each one holding up to 4096 entries. A
17393 Page Directory has up to 4096 entries, one each for every Page Table
17394 that is currently in use.
17396 Without an argument, @kbd{info dos pde} displays the entire Page
17397 Directory, and @kbd{info dos pte} displays all the entries in all of
17398 the Page Tables. An argument, an integer expression, given to the
17399 @kbd{info dos pde} command means display only that entry from the Page
17400 Directory table. An argument given to the @kbd{info dos pte} command
17401 means display entries from a single Page Table, the one pointed to by
17402 the specified entry in the Page Directory.
17404 @cindex direct memory access (DMA) on MS-DOS
17405 These commands are useful when your program uses @dfn{DMA} (Direct
17406 Memory Access), which needs physical addresses to program the DMA
17409 These commands are supported only with some DPMI servers.
17411 @cindex physical address from linear address
17412 @item info dos address-pte @var{addr}
17413 This command displays the Page Table entry for a specified linear
17414 address. The argument @var{addr} is a linear address which should
17415 already have the appropriate segment's base address added to it,
17416 because this command accepts addresses which may belong to @emph{any}
17417 segment. For example, here's how to display the Page Table entry for
17418 the page where a variable @code{i} is stored:
17421 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17422 @exdent @code{Page Table entry for address 0x11a00d30:}
17423 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17427 This says that @code{i} is stored at offset @code{0xd30} from the page
17428 whose physical base address is @code{0x02698000}, and shows all the
17429 attributes of that page.
17431 Note that you must cast the addresses of variables to a @code{char *},
17432 since otherwise the value of @code{__djgpp_base_address}, the base
17433 address of all variables and functions in a @sc{djgpp} program, will
17434 be added using the rules of C pointer arithmetics: if @code{i} is
17435 declared an @code{int}, @value{GDBN} will add 4 times the value of
17436 @code{__djgpp_base_address} to the address of @code{i}.
17438 Here's another example, it displays the Page Table entry for the
17442 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17443 @exdent @code{Page Table entry for address 0x29110:}
17444 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17448 (The @code{+ 3} offset is because the transfer buffer's address is the
17449 3rd member of the @code{_go32_info_block} structure.) The output
17450 clearly shows that this DPMI server maps the addresses in conventional
17451 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17452 linear (@code{0x29110}) addresses are identical.
17454 This command is supported only with some DPMI servers.
17457 @cindex DOS serial data link, remote debugging
17458 In addition to native debugging, the DJGPP port supports remote
17459 debugging via a serial data link. The following commands are specific
17460 to remote serial debugging in the DJGPP port of @value{GDBN}.
17463 @kindex set com1base
17464 @kindex set com1irq
17465 @kindex set com2base
17466 @kindex set com2irq
17467 @kindex set com3base
17468 @kindex set com3irq
17469 @kindex set com4base
17470 @kindex set com4irq
17471 @item set com1base @var{addr}
17472 This command sets the base I/O port address of the @file{COM1} serial
17475 @item set com1irq @var{irq}
17476 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17477 for the @file{COM1} serial port.
17479 There are similar commands @samp{set com2base}, @samp{set com3irq},
17480 etc.@: for setting the port address and the @code{IRQ} lines for the
17483 @kindex show com1base
17484 @kindex show com1irq
17485 @kindex show com2base
17486 @kindex show com2irq
17487 @kindex show com3base
17488 @kindex show com3irq
17489 @kindex show com4base
17490 @kindex show com4irq
17491 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17492 display the current settings of the base address and the @code{IRQ}
17493 lines used by the COM ports.
17496 @kindex info serial
17497 @cindex DOS serial port status
17498 This command prints the status of the 4 DOS serial ports. For each
17499 port, it prints whether it's active or not, its I/O base address and
17500 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17501 counts of various errors encountered so far.
17505 @node Cygwin Native
17506 @subsection Features for Debugging MS Windows PE Executables
17507 @cindex MS Windows debugging
17508 @cindex native Cygwin debugging
17509 @cindex Cygwin-specific commands
17511 @value{GDBN} supports native debugging of MS Windows programs, including
17512 DLLs with and without symbolic debugging information.
17514 @cindex Ctrl-BREAK, MS-Windows
17515 @cindex interrupt debuggee on MS-Windows
17516 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17517 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17518 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17519 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17520 sequence, which can be used to interrupt the debuggee even if it
17523 There are various additional Cygwin-specific commands, described in
17524 this section. Working with DLLs that have no debugging symbols is
17525 described in @ref{Non-debug DLL Symbols}.
17530 This is a prefix of MS Windows-specific commands which print
17531 information about the target system and important OS structures.
17533 @item info w32 selector
17534 This command displays information returned by
17535 the Win32 API @code{GetThreadSelectorEntry} function.
17536 It takes an optional argument that is evaluated to
17537 a long value to give the information about this given selector.
17538 Without argument, this command displays information
17539 about the six segment registers.
17541 @item info w32 thread-information-block
17542 This command displays thread specific information stored in the
17543 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17544 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17548 This is a Cygwin-specific alias of @code{info shared}.
17550 @kindex dll-symbols
17552 This command loads symbols from a dll similarly to
17553 add-sym command but without the need to specify a base address.
17555 @kindex set cygwin-exceptions
17556 @cindex debugging the Cygwin DLL
17557 @cindex Cygwin DLL, debugging
17558 @item set cygwin-exceptions @var{mode}
17559 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17560 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17561 @value{GDBN} will delay recognition of exceptions, and may ignore some
17562 exceptions which seem to be caused by internal Cygwin DLL
17563 ``bookkeeping''. This option is meant primarily for debugging the
17564 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17565 @value{GDBN} users with false @code{SIGSEGV} signals.
17567 @kindex show cygwin-exceptions
17568 @item show cygwin-exceptions
17569 Displays whether @value{GDBN} will break on exceptions that happen
17570 inside the Cygwin DLL itself.
17572 @kindex set new-console
17573 @item set new-console @var{mode}
17574 If @var{mode} is @code{on} the debuggee will
17575 be started in a new console on next start.
17576 If @var{mode} is @code{off}, the debuggee will
17577 be started in the same console as the debugger.
17579 @kindex show new-console
17580 @item show new-console
17581 Displays whether a new console is used
17582 when the debuggee is started.
17584 @kindex set new-group
17585 @item set new-group @var{mode}
17586 This boolean value controls whether the debuggee should
17587 start a new group or stay in the same group as the debugger.
17588 This affects the way the Windows OS handles
17591 @kindex show new-group
17592 @item show new-group
17593 Displays current value of new-group boolean.
17595 @kindex set debugevents
17596 @item set debugevents
17597 This boolean value adds debug output concerning kernel events related
17598 to the debuggee seen by the debugger. This includes events that
17599 signal thread and process creation and exit, DLL loading and
17600 unloading, console interrupts, and debugging messages produced by the
17601 Windows @code{OutputDebugString} API call.
17603 @kindex set debugexec
17604 @item set debugexec
17605 This boolean value adds debug output concerning execute events
17606 (such as resume thread) seen by the debugger.
17608 @kindex set debugexceptions
17609 @item set debugexceptions
17610 This boolean value adds debug output concerning exceptions in the
17611 debuggee seen by the debugger.
17613 @kindex set debugmemory
17614 @item set debugmemory
17615 This boolean value adds debug output concerning debuggee memory reads
17616 and writes by the debugger.
17620 This boolean values specifies whether the debuggee is called
17621 via a shell or directly (default value is on).
17625 Displays if the debuggee will be started with a shell.
17630 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17633 @node Non-debug DLL Symbols
17634 @subsubsection Support for DLLs without Debugging Symbols
17635 @cindex DLLs with no debugging symbols
17636 @cindex Minimal symbols and DLLs
17638 Very often on windows, some of the DLLs that your program relies on do
17639 not include symbolic debugging information (for example,
17640 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17641 symbols in a DLL, it relies on the minimal amount of symbolic
17642 information contained in the DLL's export table. This section
17643 describes working with such symbols, known internally to @value{GDBN} as
17644 ``minimal symbols''.
17646 Note that before the debugged program has started execution, no DLLs
17647 will have been loaded. The easiest way around this problem is simply to
17648 start the program --- either by setting a breakpoint or letting the
17649 program run once to completion. It is also possible to force
17650 @value{GDBN} to load a particular DLL before starting the executable ---
17651 see the shared library information in @ref{Files}, or the
17652 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17653 explicitly loading symbols from a DLL with no debugging information will
17654 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17655 which may adversely affect symbol lookup performance.
17657 @subsubsection DLL Name Prefixes
17659 In keeping with the naming conventions used by the Microsoft debugging
17660 tools, DLL export symbols are made available with a prefix based on the
17661 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17662 also entered into the symbol table, so @code{CreateFileA} is often
17663 sufficient. In some cases there will be name clashes within a program
17664 (particularly if the executable itself includes full debugging symbols)
17665 necessitating the use of the fully qualified name when referring to the
17666 contents of the DLL. Use single-quotes around the name to avoid the
17667 exclamation mark (``!'') being interpreted as a language operator.
17669 Note that the internal name of the DLL may be all upper-case, even
17670 though the file name of the DLL is lower-case, or vice-versa. Since
17671 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17672 some confusion. If in doubt, try the @code{info functions} and
17673 @code{info variables} commands or even @code{maint print msymbols}
17674 (@pxref{Symbols}). Here's an example:
17677 (@value{GDBP}) info function CreateFileA
17678 All functions matching regular expression "CreateFileA":
17680 Non-debugging symbols:
17681 0x77e885f4 CreateFileA
17682 0x77e885f4 KERNEL32!CreateFileA
17686 (@value{GDBP}) info function !
17687 All functions matching regular expression "!":
17689 Non-debugging symbols:
17690 0x6100114c cygwin1!__assert
17691 0x61004034 cygwin1!_dll_crt0@@0
17692 0x61004240 cygwin1!dll_crt0(per_process *)
17696 @subsubsection Working with Minimal Symbols
17698 Symbols extracted from a DLL's export table do not contain very much
17699 type information. All that @value{GDBN} can do is guess whether a symbol
17700 refers to a function or variable depending on the linker section that
17701 contains the symbol. Also note that the actual contents of the memory
17702 contained in a DLL are not available unless the program is running. This
17703 means that you cannot examine the contents of a variable or disassemble
17704 a function within a DLL without a running program.
17706 Variables are generally treated as pointers and dereferenced
17707 automatically. For this reason, it is often necessary to prefix a
17708 variable name with the address-of operator (``&'') and provide explicit
17709 type information in the command. Here's an example of the type of
17713 (@value{GDBP}) print 'cygwin1!__argv'
17718 (@value{GDBP}) x 'cygwin1!__argv'
17719 0x10021610: "\230y\""
17722 And two possible solutions:
17725 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17726 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17730 (@value{GDBP}) x/2x &'cygwin1!__argv'
17731 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17732 (@value{GDBP}) x/x 0x10021608
17733 0x10021608: 0x0022fd98
17734 (@value{GDBP}) x/s 0x0022fd98
17735 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17738 Setting a break point within a DLL is possible even before the program
17739 starts execution. However, under these circumstances, @value{GDBN} can't
17740 examine the initial instructions of the function in order to skip the
17741 function's frame set-up code. You can work around this by using ``*&''
17742 to set the breakpoint at a raw memory address:
17745 (@value{GDBP}) break *&'python22!PyOS_Readline'
17746 Breakpoint 1 at 0x1e04eff0
17749 The author of these extensions is not entirely convinced that setting a
17750 break point within a shared DLL like @file{kernel32.dll} is completely
17754 @subsection Commands Specific to @sc{gnu} Hurd Systems
17755 @cindex @sc{gnu} Hurd debugging
17757 This subsection describes @value{GDBN} commands specific to the
17758 @sc{gnu} Hurd native debugging.
17763 @kindex set signals@r{, Hurd command}
17764 @kindex set sigs@r{, Hurd command}
17765 This command toggles the state of inferior signal interception by
17766 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17767 affected by this command. @code{sigs} is a shorthand alias for
17772 @kindex show signals@r{, Hurd command}
17773 @kindex show sigs@r{, Hurd command}
17774 Show the current state of intercepting inferior's signals.
17776 @item set signal-thread
17777 @itemx set sigthread
17778 @kindex set signal-thread
17779 @kindex set sigthread
17780 This command tells @value{GDBN} which thread is the @code{libc} signal
17781 thread. That thread is run when a signal is delivered to a running
17782 process. @code{set sigthread} is the shorthand alias of @code{set
17785 @item show signal-thread
17786 @itemx show sigthread
17787 @kindex show signal-thread
17788 @kindex show sigthread
17789 These two commands show which thread will run when the inferior is
17790 delivered a signal.
17793 @kindex set stopped@r{, Hurd command}
17794 This commands tells @value{GDBN} that the inferior process is stopped,
17795 as with the @code{SIGSTOP} signal. The stopped process can be
17796 continued by delivering a signal to it.
17799 @kindex show stopped@r{, Hurd command}
17800 This command shows whether @value{GDBN} thinks the debuggee is
17803 @item set exceptions
17804 @kindex set exceptions@r{, Hurd command}
17805 Use this command to turn off trapping of exceptions in the inferior.
17806 When exception trapping is off, neither breakpoints nor
17807 single-stepping will work. To restore the default, set exception
17810 @item show exceptions
17811 @kindex show exceptions@r{, Hurd command}
17812 Show the current state of trapping exceptions in the inferior.
17814 @item set task pause
17815 @kindex set task@r{, Hurd commands}
17816 @cindex task attributes (@sc{gnu} Hurd)
17817 @cindex pause current task (@sc{gnu} Hurd)
17818 This command toggles task suspension when @value{GDBN} has control.
17819 Setting it to on takes effect immediately, and the task is suspended
17820 whenever @value{GDBN} gets control. Setting it to off will take
17821 effect the next time the inferior is continued. If this option is set
17822 to off, you can use @code{set thread default pause on} or @code{set
17823 thread pause on} (see below) to pause individual threads.
17825 @item show task pause
17826 @kindex show task@r{, Hurd commands}
17827 Show the current state of task suspension.
17829 @item set task detach-suspend-count
17830 @cindex task suspend count
17831 @cindex detach from task, @sc{gnu} Hurd
17832 This command sets the suspend count the task will be left with when
17833 @value{GDBN} detaches from it.
17835 @item show task detach-suspend-count
17836 Show the suspend count the task will be left with when detaching.
17838 @item set task exception-port
17839 @itemx set task excp
17840 @cindex task exception port, @sc{gnu} Hurd
17841 This command sets the task exception port to which @value{GDBN} will
17842 forward exceptions. The argument should be the value of the @dfn{send
17843 rights} of the task. @code{set task excp} is a shorthand alias.
17845 @item set noninvasive
17846 @cindex noninvasive task options
17847 This command switches @value{GDBN} to a mode that is the least
17848 invasive as far as interfering with the inferior is concerned. This
17849 is the same as using @code{set task pause}, @code{set exceptions}, and
17850 @code{set signals} to values opposite to the defaults.
17852 @item info send-rights
17853 @itemx info receive-rights
17854 @itemx info port-rights
17855 @itemx info port-sets
17856 @itemx info dead-names
17859 @cindex send rights, @sc{gnu} Hurd
17860 @cindex receive rights, @sc{gnu} Hurd
17861 @cindex port rights, @sc{gnu} Hurd
17862 @cindex port sets, @sc{gnu} Hurd
17863 @cindex dead names, @sc{gnu} Hurd
17864 These commands display information about, respectively, send rights,
17865 receive rights, port rights, port sets, and dead names of a task.
17866 There are also shorthand aliases: @code{info ports} for @code{info
17867 port-rights} and @code{info psets} for @code{info port-sets}.
17869 @item set thread pause
17870 @kindex set thread@r{, Hurd command}
17871 @cindex thread properties, @sc{gnu} Hurd
17872 @cindex pause current thread (@sc{gnu} Hurd)
17873 This command toggles current thread suspension when @value{GDBN} has
17874 control. Setting it to on takes effect immediately, and the current
17875 thread is suspended whenever @value{GDBN} gets control. Setting it to
17876 off will take effect the next time the inferior is continued.
17877 Normally, this command has no effect, since when @value{GDBN} has
17878 control, the whole task is suspended. However, if you used @code{set
17879 task pause off} (see above), this command comes in handy to suspend
17880 only the current thread.
17882 @item show thread pause
17883 @kindex show thread@r{, Hurd command}
17884 This command shows the state of current thread suspension.
17886 @item set thread run
17887 This command sets whether the current thread is allowed to run.
17889 @item show thread run
17890 Show whether the current thread is allowed to run.
17892 @item set thread detach-suspend-count
17893 @cindex thread suspend count, @sc{gnu} Hurd
17894 @cindex detach from thread, @sc{gnu} Hurd
17895 This command sets the suspend count @value{GDBN} will leave on a
17896 thread when detaching. This number is relative to the suspend count
17897 found by @value{GDBN} when it notices the thread; use @code{set thread
17898 takeover-suspend-count} to force it to an absolute value.
17900 @item show thread detach-suspend-count
17901 Show the suspend count @value{GDBN} will leave on the thread when
17904 @item set thread exception-port
17905 @itemx set thread excp
17906 Set the thread exception port to which to forward exceptions. This
17907 overrides the port set by @code{set task exception-port} (see above).
17908 @code{set thread excp} is the shorthand alias.
17910 @item set thread takeover-suspend-count
17911 Normally, @value{GDBN}'s thread suspend counts are relative to the
17912 value @value{GDBN} finds when it notices each thread. This command
17913 changes the suspend counts to be absolute instead.
17915 @item set thread default
17916 @itemx show thread default
17917 @cindex thread default settings, @sc{gnu} Hurd
17918 Each of the above @code{set thread} commands has a @code{set thread
17919 default} counterpart (e.g., @code{set thread default pause}, @code{set
17920 thread default exception-port}, etc.). The @code{thread default}
17921 variety of commands sets the default thread properties for all
17922 threads; you can then change the properties of individual threads with
17923 the non-default commands.
17928 @subsection QNX Neutrino
17929 @cindex QNX Neutrino
17931 @value{GDBN} provides the following commands specific to the QNX
17935 @item set debug nto-debug
17936 @kindex set debug nto-debug
17937 When set to on, enables debugging messages specific to the QNX
17940 @item show debug nto-debug
17941 @kindex show debug nto-debug
17942 Show the current state of QNX Neutrino messages.
17949 @value{GDBN} provides the following commands specific to the Darwin target:
17952 @item set debug darwin @var{num}
17953 @kindex set debug darwin
17954 When set to a non zero value, enables debugging messages specific to
17955 the Darwin support. Higher values produce more verbose output.
17957 @item show debug darwin
17958 @kindex show debug darwin
17959 Show the current state of Darwin messages.
17961 @item set debug mach-o @var{num}
17962 @kindex set debug mach-o
17963 When set to a non zero value, enables debugging messages while
17964 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17965 file format used on Darwin for object and executable files.) Higher
17966 values produce more verbose output. This is a command to diagnose
17967 problems internal to @value{GDBN} and should not be needed in normal
17970 @item show debug mach-o
17971 @kindex show debug mach-o
17972 Show the current state of Mach-O file messages.
17974 @item set mach-exceptions on
17975 @itemx set mach-exceptions off
17976 @kindex set mach-exceptions
17977 On Darwin, faults are first reported as a Mach exception and are then
17978 mapped to a Posix signal. Use this command to turn on trapping of
17979 Mach exceptions in the inferior. This might be sometimes useful to
17980 better understand the cause of a fault. The default is off.
17982 @item show mach-exceptions
17983 @kindex show mach-exceptions
17984 Show the current state of exceptions trapping.
17989 @section Embedded Operating Systems
17991 This section describes configurations involving the debugging of
17992 embedded operating systems that are available for several different
17996 * VxWorks:: Using @value{GDBN} with VxWorks
17999 @value{GDBN} includes the ability to debug programs running on
18000 various real-time operating systems.
18003 @subsection Using @value{GDBN} with VxWorks
18009 @kindex target vxworks
18010 @item target vxworks @var{machinename}
18011 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18012 is the target system's machine name or IP address.
18016 On VxWorks, @code{load} links @var{filename} dynamically on the
18017 current target system as well as adding its symbols in @value{GDBN}.
18019 @value{GDBN} enables developers to spawn and debug tasks running on networked
18020 VxWorks targets from a Unix host. Already-running tasks spawned from
18021 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18022 both the Unix host and on the VxWorks target. The program
18023 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18024 installed with the name @code{vxgdb}, to distinguish it from a
18025 @value{GDBN} for debugging programs on the host itself.)
18028 @item VxWorks-timeout @var{args}
18029 @kindex vxworks-timeout
18030 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18031 This option is set by the user, and @var{args} represents the number of
18032 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18033 your VxWorks target is a slow software simulator or is on the far side
18034 of a thin network line.
18037 The following information on connecting to VxWorks was current when
18038 this manual was produced; newer releases of VxWorks may use revised
18041 @findex INCLUDE_RDB
18042 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18043 to include the remote debugging interface routines in the VxWorks
18044 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18045 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18046 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18047 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18048 information on configuring and remaking VxWorks, see the manufacturer's
18050 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18052 Once you have included @file{rdb.a} in your VxWorks system image and set
18053 your Unix execution search path to find @value{GDBN}, you are ready to
18054 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18055 @code{vxgdb}, depending on your installation).
18057 @value{GDBN} comes up showing the prompt:
18064 * VxWorks Connection:: Connecting to VxWorks
18065 * VxWorks Download:: VxWorks download
18066 * VxWorks Attach:: Running tasks
18069 @node VxWorks Connection
18070 @subsubsection Connecting to VxWorks
18072 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18073 network. To connect to a target whose host name is ``@code{tt}'', type:
18076 (vxgdb) target vxworks tt
18080 @value{GDBN} displays messages like these:
18083 Attaching remote machine across net...
18088 @value{GDBN} then attempts to read the symbol tables of any object modules
18089 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18090 these files by searching the directories listed in the command search
18091 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18092 to find an object file, it displays a message such as:
18095 prog.o: No such file or directory.
18098 When this happens, add the appropriate directory to the search path with
18099 the @value{GDBN} command @code{path}, and execute the @code{target}
18102 @node VxWorks Download
18103 @subsubsection VxWorks Download
18105 @cindex download to VxWorks
18106 If you have connected to the VxWorks target and you want to debug an
18107 object that has not yet been loaded, you can use the @value{GDBN}
18108 @code{load} command to download a file from Unix to VxWorks
18109 incrementally. The object file given as an argument to the @code{load}
18110 command is actually opened twice: first by the VxWorks target in order
18111 to download the code, then by @value{GDBN} in order to read the symbol
18112 table. This can lead to problems if the current working directories on
18113 the two systems differ. If both systems have NFS mounted the same
18114 filesystems, you can avoid these problems by using absolute paths.
18115 Otherwise, it is simplest to set the working directory on both systems
18116 to the directory in which the object file resides, and then to reference
18117 the file by its name, without any path. For instance, a program
18118 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18119 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18120 program, type this on VxWorks:
18123 -> cd "@var{vxpath}/vw/demo/rdb"
18127 Then, in @value{GDBN}, type:
18130 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18131 (vxgdb) load prog.o
18134 @value{GDBN} displays a response similar to this:
18137 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18140 You can also use the @code{load} command to reload an object module
18141 after editing and recompiling the corresponding source file. Note that
18142 this makes @value{GDBN} delete all currently-defined breakpoints,
18143 auto-displays, and convenience variables, and to clear the value
18144 history. (This is necessary in order to preserve the integrity of
18145 debugger's data structures that reference the target system's symbol
18148 @node VxWorks Attach
18149 @subsubsection Running Tasks
18151 @cindex running VxWorks tasks
18152 You can also attach to an existing task using the @code{attach} command as
18156 (vxgdb) attach @var{task}
18160 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18161 or suspended when you attach to it. Running tasks are suspended at
18162 the time of attachment.
18164 @node Embedded Processors
18165 @section Embedded Processors
18167 This section goes into details specific to particular embedded
18170 @cindex send command to simulator
18171 Whenever a specific embedded processor has a simulator, @value{GDBN}
18172 allows to send an arbitrary command to the simulator.
18175 @item sim @var{command}
18176 @kindex sim@r{, a command}
18177 Send an arbitrary @var{command} string to the simulator. Consult the
18178 documentation for the specific simulator in use for information about
18179 acceptable commands.
18185 * M32R/D:: Renesas M32R/D
18186 * M68K:: Motorola M68K
18187 * MicroBlaze:: Xilinx MicroBlaze
18188 * MIPS Embedded:: MIPS Embedded
18189 * OpenRISC 1000:: OpenRisc 1000
18190 * PA:: HP PA Embedded
18191 * PowerPC Embedded:: PowerPC Embedded
18192 * Sparclet:: Tsqware Sparclet
18193 * Sparclite:: Fujitsu Sparclite
18194 * Z8000:: Zilog Z8000
18197 * Super-H:: Renesas Super-H
18206 @item target rdi @var{dev}
18207 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18208 use this target to communicate with both boards running the Angel
18209 monitor, or with the EmbeddedICE JTAG debug device.
18212 @item target rdp @var{dev}
18217 @value{GDBN} provides the following ARM-specific commands:
18220 @item set arm disassembler
18222 This commands selects from a list of disassembly styles. The
18223 @code{"std"} style is the standard style.
18225 @item show arm disassembler
18227 Show the current disassembly style.
18229 @item set arm apcs32
18230 @cindex ARM 32-bit mode
18231 This command toggles ARM operation mode between 32-bit and 26-bit.
18233 @item show arm apcs32
18234 Display the current usage of the ARM 32-bit mode.
18236 @item set arm fpu @var{fputype}
18237 This command sets the ARM floating-point unit (FPU) type. The
18238 argument @var{fputype} can be one of these:
18242 Determine the FPU type by querying the OS ABI.
18244 Software FPU, with mixed-endian doubles on little-endian ARM
18247 GCC-compiled FPA co-processor.
18249 Software FPU with pure-endian doubles.
18255 Show the current type of the FPU.
18258 This command forces @value{GDBN} to use the specified ABI.
18261 Show the currently used ABI.
18263 @item set arm fallback-mode (arm|thumb|auto)
18264 @value{GDBN} uses the symbol table, when available, to determine
18265 whether instructions are ARM or Thumb. This command controls
18266 @value{GDBN}'s default behavior when the symbol table is not
18267 available. The default is @samp{auto}, which causes @value{GDBN} to
18268 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18271 @item show arm fallback-mode
18272 Show the current fallback instruction mode.
18274 @item set arm force-mode (arm|thumb|auto)
18275 This command overrides use of the symbol table to determine whether
18276 instructions are ARM or Thumb. The default is @samp{auto}, which
18277 causes @value{GDBN} to use the symbol table and then the setting
18278 of @samp{set arm fallback-mode}.
18280 @item show arm force-mode
18281 Show the current forced instruction mode.
18283 @item set debug arm
18284 Toggle whether to display ARM-specific debugging messages from the ARM
18285 target support subsystem.
18287 @item show debug arm
18288 Show whether ARM-specific debugging messages are enabled.
18291 The following commands are available when an ARM target is debugged
18292 using the RDI interface:
18295 @item rdilogfile @r{[}@var{file}@r{]}
18297 @cindex ADP (Angel Debugger Protocol) logging
18298 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18299 With an argument, sets the log file to the specified @var{file}. With
18300 no argument, show the current log file name. The default log file is
18303 @item rdilogenable @r{[}@var{arg}@r{]}
18304 @kindex rdilogenable
18305 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18306 enables logging, with an argument 0 or @code{"no"} disables it. With
18307 no arguments displays the current setting. When logging is enabled,
18308 ADP packets exchanged between @value{GDBN} and the RDI target device
18309 are logged to a file.
18311 @item set rdiromatzero
18312 @kindex set rdiromatzero
18313 @cindex ROM at zero address, RDI
18314 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18315 vector catching is disabled, so that zero address can be used. If off
18316 (the default), vector catching is enabled. For this command to take
18317 effect, it needs to be invoked prior to the @code{target rdi} command.
18319 @item show rdiromatzero
18320 @kindex show rdiromatzero
18321 Show the current setting of ROM at zero address.
18323 @item set rdiheartbeat
18324 @kindex set rdiheartbeat
18325 @cindex RDI heartbeat
18326 Enable or disable RDI heartbeat packets. It is not recommended to
18327 turn on this option, since it confuses ARM and EPI JTAG interface, as
18328 well as the Angel monitor.
18330 @item show rdiheartbeat
18331 @kindex show rdiheartbeat
18332 Show the setting of RDI heartbeat packets.
18336 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18337 The @value{GDBN} ARM simulator accepts the following optional arguments.
18340 @item --swi-support=@var{type}
18341 Tell the simulator which SWI interfaces to support.
18342 @var{type} may be a comma separated list of the following values.
18343 The default value is @code{all}.
18356 @subsection Renesas M32R/D and M32R/SDI
18359 @kindex target m32r
18360 @item target m32r @var{dev}
18361 Renesas M32R/D ROM monitor.
18363 @kindex target m32rsdi
18364 @item target m32rsdi @var{dev}
18365 Renesas M32R SDI server, connected via parallel port to the board.
18368 The following @value{GDBN} commands are specific to the M32R monitor:
18371 @item set download-path @var{path}
18372 @kindex set download-path
18373 @cindex find downloadable @sc{srec} files (M32R)
18374 Set the default path for finding downloadable @sc{srec} files.
18376 @item show download-path
18377 @kindex show download-path
18378 Show the default path for downloadable @sc{srec} files.
18380 @item set board-address @var{addr}
18381 @kindex set board-address
18382 @cindex M32-EVA target board address
18383 Set the IP address for the M32R-EVA target board.
18385 @item show board-address
18386 @kindex show board-address
18387 Show the current IP address of the target board.
18389 @item set server-address @var{addr}
18390 @kindex set server-address
18391 @cindex download server address (M32R)
18392 Set the IP address for the download server, which is the @value{GDBN}'s
18395 @item show server-address
18396 @kindex show server-address
18397 Display the IP address of the download server.
18399 @item upload @r{[}@var{file}@r{]}
18400 @kindex upload@r{, M32R}
18401 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18402 upload capability. If no @var{file} argument is given, the current
18403 executable file is uploaded.
18405 @item tload @r{[}@var{file}@r{]}
18406 @kindex tload@r{, M32R}
18407 Test the @code{upload} command.
18410 The following commands are available for M32R/SDI:
18415 @cindex reset SDI connection, M32R
18416 This command resets the SDI connection.
18420 This command shows the SDI connection status.
18423 @kindex debug_chaos
18424 @cindex M32R/Chaos debugging
18425 Instructs the remote that M32R/Chaos debugging is to be used.
18427 @item use_debug_dma
18428 @kindex use_debug_dma
18429 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18432 @kindex use_mon_code
18433 Instructs the remote to use the MON_CODE method of accessing memory.
18436 @kindex use_ib_break
18437 Instructs the remote to set breakpoints by IB break.
18439 @item use_dbt_break
18440 @kindex use_dbt_break
18441 Instructs the remote to set breakpoints by DBT.
18447 The Motorola m68k configuration includes ColdFire support, and a
18448 target command for the following ROM monitor.
18452 @kindex target dbug
18453 @item target dbug @var{dev}
18454 dBUG ROM monitor for Motorola ColdFire.
18459 @subsection MicroBlaze
18460 @cindex Xilinx MicroBlaze
18461 @cindex XMD, Xilinx Microprocessor Debugger
18463 The MicroBlaze is a soft-core processor supported on various Xilinx
18464 FPGAs, such as Spartan or Virtex series. Boards with these processors
18465 usually have JTAG ports which connect to a host system running the Xilinx
18466 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18467 This host system is used to download the configuration bitstream to
18468 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18469 communicates with the target board using the JTAG interface and
18470 presents a @code{gdbserver} interface to the board. By default
18471 @code{xmd} uses port @code{1234}. (While it is possible to change
18472 this default port, it requires the use of undocumented @code{xmd}
18473 commands. Contact Xilinx support if you need to do this.)
18475 Use these GDB commands to connect to the MicroBlaze target processor.
18478 @item target remote :1234
18479 Use this command to connect to the target if you are running @value{GDBN}
18480 on the same system as @code{xmd}.
18482 @item target remote @var{xmd-host}:1234
18483 Use this command to connect to the target if it is connected to @code{xmd}
18484 running on a different system named @var{xmd-host}.
18487 Use this command to download a program to the MicroBlaze target.
18489 @item set debug microblaze @var{n}
18490 Enable MicroBlaze-specific debugging messages if non-zero.
18492 @item show debug microblaze @var{n}
18493 Show MicroBlaze-specific debugging level.
18496 @node MIPS Embedded
18497 @subsection MIPS Embedded
18499 @cindex MIPS boards
18500 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18501 MIPS board attached to a serial line. This is available when
18502 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18505 Use these @value{GDBN} commands to specify the connection to your target board:
18508 @item target mips @var{port}
18509 @kindex target mips @var{port}
18510 To run a program on the board, start up @code{@value{GDBP}} with the
18511 name of your program as the argument. To connect to the board, use the
18512 command @samp{target mips @var{port}}, where @var{port} is the name of
18513 the serial port connected to the board. If the program has not already
18514 been downloaded to the board, you may use the @code{load} command to
18515 download it. You can then use all the usual @value{GDBN} commands.
18517 For example, this sequence connects to the target board through a serial
18518 port, and loads and runs a program called @var{prog} through the
18522 host$ @value{GDBP} @var{prog}
18523 @value{GDBN} is free software and @dots{}
18524 (@value{GDBP}) target mips /dev/ttyb
18525 (@value{GDBP}) load @var{prog}
18529 @item target mips @var{hostname}:@var{portnumber}
18530 On some @value{GDBN} host configurations, you can specify a TCP
18531 connection (for instance, to a serial line managed by a terminal
18532 concentrator) instead of a serial port, using the syntax
18533 @samp{@var{hostname}:@var{portnumber}}.
18535 @item target pmon @var{port}
18536 @kindex target pmon @var{port}
18539 @item target ddb @var{port}
18540 @kindex target ddb @var{port}
18541 NEC's DDB variant of PMON for Vr4300.
18543 @item target lsi @var{port}
18544 @kindex target lsi @var{port}
18545 LSI variant of PMON.
18547 @kindex target r3900
18548 @item target r3900 @var{dev}
18549 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18551 @kindex target array
18552 @item target array @var{dev}
18553 Array Tech LSI33K RAID controller board.
18559 @value{GDBN} also supports these special commands for MIPS targets:
18562 @item set mipsfpu double
18563 @itemx set mipsfpu single
18564 @itemx set mipsfpu none
18565 @itemx set mipsfpu auto
18566 @itemx show mipsfpu
18567 @kindex set mipsfpu
18568 @kindex show mipsfpu
18569 @cindex MIPS remote floating point
18570 @cindex floating point, MIPS remote
18571 If your target board does not support the MIPS floating point
18572 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18573 need this, you may wish to put the command in your @value{GDBN} init
18574 file). This tells @value{GDBN} how to find the return value of
18575 functions which return floating point values. It also allows
18576 @value{GDBN} to avoid saving the floating point registers when calling
18577 functions on the board. If you are using a floating point coprocessor
18578 with only single precision floating point support, as on the @sc{r4650}
18579 processor, use the command @samp{set mipsfpu single}. The default
18580 double precision floating point coprocessor may be selected using
18581 @samp{set mipsfpu double}.
18583 In previous versions the only choices were double precision or no
18584 floating point, so @samp{set mipsfpu on} will select double precision
18585 and @samp{set mipsfpu off} will select no floating point.
18587 As usual, you can inquire about the @code{mipsfpu} variable with
18588 @samp{show mipsfpu}.
18590 @item set timeout @var{seconds}
18591 @itemx set retransmit-timeout @var{seconds}
18592 @itemx show timeout
18593 @itemx show retransmit-timeout
18594 @cindex @code{timeout}, MIPS protocol
18595 @cindex @code{retransmit-timeout}, MIPS protocol
18596 @kindex set timeout
18597 @kindex show timeout
18598 @kindex set retransmit-timeout
18599 @kindex show retransmit-timeout
18600 You can control the timeout used while waiting for a packet, in the MIPS
18601 remote protocol, with the @code{set timeout @var{seconds}} command. The
18602 default is 5 seconds. Similarly, you can control the timeout used while
18603 waiting for an acknowledgment of a packet with the @code{set
18604 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18605 You can inspect both values with @code{show timeout} and @code{show
18606 retransmit-timeout}. (These commands are @emph{only} available when
18607 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18609 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18610 is waiting for your program to stop. In that case, @value{GDBN} waits
18611 forever because it has no way of knowing how long the program is going
18612 to run before stopping.
18614 @item set syn-garbage-limit @var{num}
18615 @kindex set syn-garbage-limit@r{, MIPS remote}
18616 @cindex synchronize with remote MIPS target
18617 Limit the maximum number of characters @value{GDBN} should ignore when
18618 it tries to synchronize with the remote target. The default is 10
18619 characters. Setting the limit to -1 means there's no limit.
18621 @item show syn-garbage-limit
18622 @kindex show syn-garbage-limit@r{, MIPS remote}
18623 Show the current limit on the number of characters to ignore when
18624 trying to synchronize with the remote system.
18626 @item set monitor-prompt @var{prompt}
18627 @kindex set monitor-prompt@r{, MIPS remote}
18628 @cindex remote monitor prompt
18629 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18630 remote monitor. The default depends on the target:
18640 @item show monitor-prompt
18641 @kindex show monitor-prompt@r{, MIPS remote}
18642 Show the current strings @value{GDBN} expects as the prompt from the
18645 @item set monitor-warnings
18646 @kindex set monitor-warnings@r{, MIPS remote}
18647 Enable or disable monitor warnings about hardware breakpoints. This
18648 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18649 display warning messages whose codes are returned by the @code{lsi}
18650 PMON monitor for breakpoint commands.
18652 @item show monitor-warnings
18653 @kindex show monitor-warnings@r{, MIPS remote}
18654 Show the current setting of printing monitor warnings.
18656 @item pmon @var{command}
18657 @kindex pmon@r{, MIPS remote}
18658 @cindex send PMON command
18659 This command allows sending an arbitrary @var{command} string to the
18660 monitor. The monitor must be in debug mode for this to work.
18663 @node OpenRISC 1000
18664 @subsection OpenRISC 1000
18665 @cindex OpenRISC 1000
18667 @cindex or1k boards
18668 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18669 about platform and commands.
18673 @kindex target jtag
18674 @item target jtag jtag://@var{host}:@var{port}
18676 Connects to remote JTAG server.
18677 JTAG remote server can be either an or1ksim or JTAG server,
18678 connected via parallel port to the board.
18680 Example: @code{target jtag jtag://localhost:9999}
18683 @item or1ksim @var{command}
18684 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18685 Simulator, proprietary commands can be executed.
18687 @kindex info or1k spr
18688 @item info or1k spr
18689 Displays spr groups.
18691 @item info or1k spr @var{group}
18692 @itemx info or1k spr @var{groupno}
18693 Displays register names in selected group.
18695 @item info or1k spr @var{group} @var{register}
18696 @itemx info or1k spr @var{register}
18697 @itemx info or1k spr @var{groupno} @var{registerno}
18698 @itemx info or1k spr @var{registerno}
18699 Shows information about specified spr register.
18702 @item spr @var{group} @var{register} @var{value}
18703 @itemx spr @var{register @var{value}}
18704 @itemx spr @var{groupno} @var{registerno @var{value}}
18705 @itemx spr @var{registerno @var{value}}
18706 Writes @var{value} to specified spr register.
18709 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18710 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18711 program execution and is thus much faster. Hardware breakpoints/watchpoint
18712 triggers can be set using:
18715 Load effective address/data
18717 Store effective address/data
18719 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18724 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18725 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18727 @code{htrace} commands:
18728 @cindex OpenRISC 1000 htrace
18731 @item hwatch @var{conditional}
18732 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18733 or Data. For example:
18735 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18737 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18741 Display information about current HW trace configuration.
18743 @item htrace trigger @var{conditional}
18744 Set starting criteria for HW trace.
18746 @item htrace qualifier @var{conditional}
18747 Set acquisition qualifier for HW trace.
18749 @item htrace stop @var{conditional}
18750 Set HW trace stopping criteria.
18752 @item htrace record [@var{data}]*
18753 Selects the data to be recorded, when qualifier is met and HW trace was
18756 @item htrace enable
18757 @itemx htrace disable
18758 Enables/disables the HW trace.
18760 @item htrace rewind [@var{filename}]
18761 Clears currently recorded trace data.
18763 If filename is specified, new trace file is made and any newly collected data
18764 will be written there.
18766 @item htrace print [@var{start} [@var{len}]]
18767 Prints trace buffer, using current record configuration.
18769 @item htrace mode continuous
18770 Set continuous trace mode.
18772 @item htrace mode suspend
18773 Set suspend trace mode.
18777 @node PowerPC Embedded
18778 @subsection PowerPC Embedded
18780 @cindex DVC register
18781 @value{GDBN} supports using the DVC (Data Value Compare) register to
18782 implement in hardware simple hardware watchpoint conditions of the form:
18785 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18786 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18789 The DVC register will be automatically used when @value{GDBN} detects
18790 such pattern in a condition expression, and the created watchpoint uses one
18791 debug register (either the @code{exact-watchpoints} option is on and the
18792 variable is scalar, or the variable has a length of one byte). This feature
18793 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
18796 When running on PowerPC embedded processors, @value{GDBN} automatically uses
18797 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
18798 in which case watchpoints using only one debug register are created when
18799 watching variables of scalar types.
18801 You can create an artificial array to watch an arbitrary memory
18802 region using one of the following commands (@pxref{Expressions}):
18805 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
18806 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
18809 PowerPC embedded processors support masked watchpoints. See the discussion
18810 about the @code{mask} argument in @ref{Set Watchpoints}.
18812 @cindex ranged breakpoint
18813 PowerPC embedded processors support hardware accelerated
18814 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
18815 the inferior whenever it executes an instruction at any address within
18816 the range it specifies. To set a ranged breakpoint in @value{GDBN},
18817 use the @code{break-range} command.
18819 @value{GDBN} provides the following PowerPC-specific commands:
18822 @kindex break-range
18823 @item break-range @var{start-location}, @var{end-location}
18824 Set a breakpoint for an address range.
18825 @var{start-location} and @var{end-location} can specify a function name,
18826 a line number, an offset of lines from the current line or from the start
18827 location, or an address of an instruction (see @ref{Specify Location},
18828 for a list of all the possible ways to specify a @var{location}.)
18829 The breakpoint will stop execution of the inferior whenever it
18830 executes an instruction at any address within the specified range,
18831 (including @var{start-location} and @var{end-location}.)
18833 @kindex set powerpc
18834 @item set powerpc soft-float
18835 @itemx show powerpc soft-float
18836 Force @value{GDBN} to use (or not use) a software floating point calling
18837 convention. By default, @value{GDBN} selects the calling convention based
18838 on the selected architecture and the provided executable file.
18840 @item set powerpc vector-abi
18841 @itemx show powerpc vector-abi
18842 Force @value{GDBN} to use the specified calling convention for vector
18843 arguments and return values. The valid options are @samp{auto};
18844 @samp{generic}, to avoid vector registers even if they are present;
18845 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18846 registers. By default, @value{GDBN} selects the calling convention
18847 based on the selected architecture and the provided executable file.
18849 @item set powerpc exact-watchpoints
18850 @itemx show powerpc exact-watchpoints
18851 Allow @value{GDBN} to use only one debug register when watching a variable
18852 of scalar type, thus assuming that the variable is accessed through the
18853 address of its first byte.
18855 @kindex target dink32
18856 @item target dink32 @var{dev}
18857 DINK32 ROM monitor.
18859 @kindex target ppcbug
18860 @item target ppcbug @var{dev}
18861 @kindex target ppcbug1
18862 @item target ppcbug1 @var{dev}
18863 PPCBUG ROM monitor for PowerPC.
18866 @item target sds @var{dev}
18867 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18870 @cindex SDS protocol
18871 The following commands specific to the SDS protocol are supported
18875 @item set sdstimeout @var{nsec}
18876 @kindex set sdstimeout
18877 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18878 default is 2 seconds.
18880 @item show sdstimeout
18881 @kindex show sdstimeout
18882 Show the current value of the SDS timeout.
18884 @item sds @var{command}
18885 @kindex sds@r{, a command}
18886 Send the specified @var{command} string to the SDS monitor.
18891 @subsection HP PA Embedded
18895 @kindex target op50n
18896 @item target op50n @var{dev}
18897 OP50N monitor, running on an OKI HPPA board.
18899 @kindex target w89k
18900 @item target w89k @var{dev}
18901 W89K monitor, running on a Winbond HPPA board.
18906 @subsection Tsqware Sparclet
18910 @value{GDBN} enables developers to debug tasks running on
18911 Sparclet targets from a Unix host.
18912 @value{GDBN} uses code that runs on
18913 both the Unix host and on the Sparclet target. The program
18914 @code{@value{GDBP}} is installed and executed on the Unix host.
18917 @item remotetimeout @var{args}
18918 @kindex remotetimeout
18919 @value{GDBN} supports the option @code{remotetimeout}.
18920 This option is set by the user, and @var{args} represents the number of
18921 seconds @value{GDBN} waits for responses.
18924 @cindex compiling, on Sparclet
18925 When compiling for debugging, include the options @samp{-g} to get debug
18926 information and @samp{-Ttext} to relocate the program to where you wish to
18927 load it on the target. You may also want to add the options @samp{-n} or
18928 @samp{-N} in order to reduce the size of the sections. Example:
18931 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18934 You can use @code{objdump} to verify that the addresses are what you intended:
18937 sparclet-aout-objdump --headers --syms prog
18940 @cindex running, on Sparclet
18942 your Unix execution search path to find @value{GDBN}, you are ready to
18943 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18944 (or @code{sparclet-aout-gdb}, depending on your installation).
18946 @value{GDBN} comes up showing the prompt:
18953 * Sparclet File:: Setting the file to debug
18954 * Sparclet Connection:: Connecting to Sparclet
18955 * Sparclet Download:: Sparclet download
18956 * Sparclet Execution:: Running and debugging
18959 @node Sparclet File
18960 @subsubsection Setting File to Debug
18962 The @value{GDBN} command @code{file} lets you choose with program to debug.
18965 (gdbslet) file prog
18969 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18970 @value{GDBN} locates
18971 the file by searching the directories listed in the command search
18973 If the file was compiled with debug information (option @samp{-g}), source
18974 files will be searched as well.
18975 @value{GDBN} locates
18976 the source files by searching the directories listed in the directory search
18977 path (@pxref{Environment, ,Your Program's Environment}).
18979 to find a file, it displays a message such as:
18982 prog: No such file or directory.
18985 When this happens, add the appropriate directories to the search paths with
18986 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18987 @code{target} command again.
18989 @node Sparclet Connection
18990 @subsubsection Connecting to Sparclet
18992 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18993 To connect to a target on serial port ``@code{ttya}'', type:
18996 (gdbslet) target sparclet /dev/ttya
18997 Remote target sparclet connected to /dev/ttya
18998 main () at ../prog.c:3
19002 @value{GDBN} displays messages like these:
19008 @node Sparclet Download
19009 @subsubsection Sparclet Download
19011 @cindex download to Sparclet
19012 Once connected to the Sparclet target,
19013 you can use the @value{GDBN}
19014 @code{load} command to download the file from the host to the target.
19015 The file name and load offset should be given as arguments to the @code{load}
19017 Since the file format is aout, the program must be loaded to the starting
19018 address. You can use @code{objdump} to find out what this value is. The load
19019 offset is an offset which is added to the VMA (virtual memory address)
19020 of each of the file's sections.
19021 For instance, if the program
19022 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19023 and bss at 0x12010170, in @value{GDBN}, type:
19026 (gdbslet) load prog 0x12010000
19027 Loading section .text, size 0xdb0 vma 0x12010000
19030 If the code is loaded at a different address then what the program was linked
19031 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19032 to tell @value{GDBN} where to map the symbol table.
19034 @node Sparclet Execution
19035 @subsubsection Running and Debugging
19037 @cindex running and debugging Sparclet programs
19038 You can now begin debugging the task using @value{GDBN}'s execution control
19039 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19040 manual for the list of commands.
19044 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19046 Starting program: prog
19047 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19048 3 char *symarg = 0;
19050 4 char *execarg = "hello!";
19055 @subsection Fujitsu Sparclite
19059 @kindex target sparclite
19060 @item target sparclite @var{dev}
19061 Fujitsu sparclite boards, used only for the purpose of loading.
19062 You must use an additional command to debug the program.
19063 For example: target remote @var{dev} using @value{GDBN} standard
19069 @subsection Zilog Z8000
19072 @cindex simulator, Z8000
19073 @cindex Zilog Z8000 simulator
19075 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19078 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19079 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19080 segmented variant). The simulator recognizes which architecture is
19081 appropriate by inspecting the object code.
19084 @item target sim @var{args}
19086 @kindex target sim@r{, with Z8000}
19087 Debug programs on a simulated CPU. If the simulator supports setup
19088 options, specify them via @var{args}.
19092 After specifying this target, you can debug programs for the simulated
19093 CPU in the same style as programs for your host computer; use the
19094 @code{file} command to load a new program image, the @code{run} command
19095 to run your program, and so on.
19097 As well as making available all the usual machine registers
19098 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19099 additional items of information as specially named registers:
19104 Counts clock-ticks in the simulator.
19107 Counts instructions run in the simulator.
19110 Execution time in 60ths of a second.
19114 You can refer to these values in @value{GDBN} expressions with the usual
19115 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19116 conditional breakpoint that suspends only after at least 5000
19117 simulated clock ticks.
19120 @subsection Atmel AVR
19123 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19124 following AVR-specific commands:
19127 @item info io_registers
19128 @kindex info io_registers@r{, AVR}
19129 @cindex I/O registers (Atmel AVR)
19130 This command displays information about the AVR I/O registers. For
19131 each register, @value{GDBN} prints its number and value.
19138 When configured for debugging CRIS, @value{GDBN} provides the
19139 following CRIS-specific commands:
19142 @item set cris-version @var{ver}
19143 @cindex CRIS version
19144 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19145 The CRIS version affects register names and sizes. This command is useful in
19146 case autodetection of the CRIS version fails.
19148 @item show cris-version
19149 Show the current CRIS version.
19151 @item set cris-dwarf2-cfi
19152 @cindex DWARF-2 CFI and CRIS
19153 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19154 Change to @samp{off} when using @code{gcc-cris} whose version is below
19157 @item show cris-dwarf2-cfi
19158 Show the current state of using DWARF-2 CFI.
19160 @item set cris-mode @var{mode}
19162 Set the current CRIS mode to @var{mode}. It should only be changed when
19163 debugging in guru mode, in which case it should be set to
19164 @samp{guru} (the default is @samp{normal}).
19166 @item show cris-mode
19167 Show the current CRIS mode.
19171 @subsection Renesas Super-H
19174 For the Renesas Super-H processor, @value{GDBN} provides these
19179 @kindex regs@r{, Super-H}
19180 Show the values of all Super-H registers.
19182 @item set sh calling-convention @var{convention}
19183 @kindex set sh calling-convention
19184 Set the calling-convention used when calling functions from @value{GDBN}.
19185 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19186 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19187 convention. If the DWARF-2 information of the called function specifies
19188 that the function follows the Renesas calling convention, the function
19189 is called using the Renesas calling convention. If the calling convention
19190 is set to @samp{renesas}, the Renesas calling convention is always used,
19191 regardless of the DWARF-2 information. This can be used to override the
19192 default of @samp{gcc} if debug information is missing, or the compiler
19193 does not emit the DWARF-2 calling convention entry for a function.
19195 @item show sh calling-convention
19196 @kindex show sh calling-convention
19197 Show the current calling convention setting.
19202 @node Architectures
19203 @section Architectures
19205 This section describes characteristics of architectures that affect
19206 all uses of @value{GDBN} with the architecture, both native and cross.
19213 * HPPA:: HP PA architecture
19214 * SPU:: Cell Broadband Engine SPU architecture
19219 @subsection x86 Architecture-specific Issues
19222 @item set struct-convention @var{mode}
19223 @kindex set struct-convention
19224 @cindex struct return convention
19225 @cindex struct/union returned in registers
19226 Set the convention used by the inferior to return @code{struct}s and
19227 @code{union}s from functions to @var{mode}. Possible values of
19228 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19229 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19230 are returned on the stack, while @code{"reg"} means that a
19231 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19232 be returned in a register.
19234 @item show struct-convention
19235 @kindex show struct-convention
19236 Show the current setting of the convention to return @code{struct}s
19245 @kindex set rstack_high_address
19246 @cindex AMD 29K register stack
19247 @cindex register stack, AMD29K
19248 @item set rstack_high_address @var{address}
19249 On AMD 29000 family processors, registers are saved in a separate
19250 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19251 extent of this stack. Normally, @value{GDBN} just assumes that the
19252 stack is ``large enough''. This may result in @value{GDBN} referencing
19253 memory locations that do not exist. If necessary, you can get around
19254 this problem by specifying the ending address of the register stack with
19255 the @code{set rstack_high_address} command. The argument should be an
19256 address, which you probably want to precede with @samp{0x} to specify in
19259 @kindex show rstack_high_address
19260 @item show rstack_high_address
19261 Display the current limit of the register stack, on AMD 29000 family
19269 See the following section.
19274 @cindex stack on Alpha
19275 @cindex stack on MIPS
19276 @cindex Alpha stack
19278 Alpha- and MIPS-based computers use an unusual stack frame, which
19279 sometimes requires @value{GDBN} to search backward in the object code to
19280 find the beginning of a function.
19282 @cindex response time, MIPS debugging
19283 To improve response time (especially for embedded applications, where
19284 @value{GDBN} may be restricted to a slow serial line for this search)
19285 you may want to limit the size of this search, using one of these
19289 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19290 @item set heuristic-fence-post @var{limit}
19291 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19292 search for the beginning of a function. A value of @var{0} (the
19293 default) means there is no limit. However, except for @var{0}, the
19294 larger the limit the more bytes @code{heuristic-fence-post} must search
19295 and therefore the longer it takes to run. You should only need to use
19296 this command when debugging a stripped executable.
19298 @item show heuristic-fence-post
19299 Display the current limit.
19303 These commands are available @emph{only} when @value{GDBN} is configured
19304 for debugging programs on Alpha or MIPS processors.
19306 Several MIPS-specific commands are available when debugging MIPS
19310 @item set mips abi @var{arg}
19311 @kindex set mips abi
19312 @cindex set ABI for MIPS
19313 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19314 values of @var{arg} are:
19318 The default ABI associated with the current binary (this is the
19329 @item show mips abi
19330 @kindex show mips abi
19331 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19334 @itemx show mipsfpu
19335 @xref{MIPS Embedded, set mipsfpu}.
19337 @item set mips mask-address @var{arg}
19338 @kindex set mips mask-address
19339 @cindex MIPS addresses, masking
19340 This command determines whether the most-significant 32 bits of 64-bit
19341 MIPS addresses are masked off. The argument @var{arg} can be
19342 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19343 setting, which lets @value{GDBN} determine the correct value.
19345 @item show mips mask-address
19346 @kindex show mips mask-address
19347 Show whether the upper 32 bits of MIPS addresses are masked off or
19350 @item set remote-mips64-transfers-32bit-regs
19351 @kindex set remote-mips64-transfers-32bit-regs
19352 This command controls compatibility with 64-bit MIPS targets that
19353 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19354 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19355 and 64 bits for other registers, set this option to @samp{on}.
19357 @item show remote-mips64-transfers-32bit-regs
19358 @kindex show remote-mips64-transfers-32bit-regs
19359 Show the current setting of compatibility with older MIPS 64 targets.
19361 @item set debug mips
19362 @kindex set debug mips
19363 This command turns on and off debugging messages for the MIPS-specific
19364 target code in @value{GDBN}.
19366 @item show debug mips
19367 @kindex show debug mips
19368 Show the current setting of MIPS debugging messages.
19374 @cindex HPPA support
19376 When @value{GDBN} is debugging the HP PA architecture, it provides the
19377 following special commands:
19380 @item set debug hppa
19381 @kindex set debug hppa
19382 This command determines whether HPPA architecture-specific debugging
19383 messages are to be displayed.
19385 @item show debug hppa
19386 Show whether HPPA debugging messages are displayed.
19388 @item maint print unwind @var{address}
19389 @kindex maint print unwind@r{, HPPA}
19390 This command displays the contents of the unwind table entry at the
19391 given @var{address}.
19397 @subsection Cell Broadband Engine SPU architecture
19398 @cindex Cell Broadband Engine
19401 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19402 it provides the following special commands:
19405 @item info spu event
19407 Display SPU event facility status. Shows current event mask
19408 and pending event status.
19410 @item info spu signal
19411 Display SPU signal notification facility status. Shows pending
19412 signal-control word and signal notification mode of both signal
19413 notification channels.
19415 @item info spu mailbox
19416 Display SPU mailbox facility status. Shows all pending entries,
19417 in order of processing, in each of the SPU Write Outbound,
19418 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19421 Display MFC DMA status. Shows all pending commands in the MFC
19422 DMA queue. For each entry, opcode, tag, class IDs, effective
19423 and local store addresses and transfer size are shown.
19425 @item info spu proxydma
19426 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19427 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19428 and local store addresses and transfer size are shown.
19432 When @value{GDBN} is debugging a combined PowerPC/SPU application
19433 on the Cell Broadband Engine, it provides in addition the following
19437 @item set spu stop-on-load @var{arg}
19439 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19440 will give control to the user when a new SPE thread enters its @code{main}
19441 function. The default is @code{off}.
19443 @item show spu stop-on-load
19445 Show whether to stop for new SPE threads.
19447 @item set spu auto-flush-cache @var{arg}
19448 Set whether to automatically flush the software-managed cache. When set to
19449 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19450 cache to be flushed whenever SPE execution stops. This provides a consistent
19451 view of PowerPC memory that is accessed via the cache. If an application
19452 does not use the software-managed cache, this option has no effect.
19454 @item show spu auto-flush-cache
19455 Show whether to automatically flush the software-managed cache.
19460 @subsection PowerPC
19461 @cindex PowerPC architecture
19463 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19464 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19465 numbers stored in the floating point registers. These values must be stored
19466 in two consecutive registers, always starting at an even register like
19467 @code{f0} or @code{f2}.
19469 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19470 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19471 @code{f2} and @code{f3} for @code{$dl1} and so on.
19473 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19474 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19477 @node Controlling GDB
19478 @chapter Controlling @value{GDBN}
19480 You can alter the way @value{GDBN} interacts with you by using the
19481 @code{set} command. For commands controlling how @value{GDBN} displays
19482 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19487 * Editing:: Command editing
19488 * Command History:: Command history
19489 * Screen Size:: Screen size
19490 * Numbers:: Numbers
19491 * ABI:: Configuring the current ABI
19492 * Messages/Warnings:: Optional warnings and messages
19493 * Debugging Output:: Optional messages about internal happenings
19494 * Other Misc Settings:: Other Miscellaneous Settings
19502 @value{GDBN} indicates its readiness to read a command by printing a string
19503 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19504 can change the prompt string with the @code{set prompt} command. For
19505 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19506 the prompt in one of the @value{GDBN} sessions so that you can always tell
19507 which one you are talking to.
19509 @emph{Note:} @code{set prompt} does not add a space for you after the
19510 prompt you set. This allows you to set a prompt which ends in a space
19511 or a prompt that does not.
19515 @item set prompt @var{newprompt}
19516 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19518 @kindex show prompt
19520 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19524 @section Command Editing
19526 @cindex command line editing
19528 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19529 @sc{gnu} library provides consistent behavior for programs which provide a
19530 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19531 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19532 substitution, and a storage and recall of command history across
19533 debugging sessions.
19535 You may control the behavior of command line editing in @value{GDBN} with the
19536 command @code{set}.
19539 @kindex set editing
19542 @itemx set editing on
19543 Enable command line editing (enabled by default).
19545 @item set editing off
19546 Disable command line editing.
19548 @kindex show editing
19550 Show whether command line editing is enabled.
19553 @ifset SYSTEM_READLINE
19554 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19556 @ifclear SYSTEM_READLINE
19557 @xref{Command Line Editing},
19559 for more details about the Readline
19560 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19561 encouraged to read that chapter.
19563 @node Command History
19564 @section Command History
19565 @cindex command history
19567 @value{GDBN} can keep track of the commands you type during your
19568 debugging sessions, so that you can be certain of precisely what
19569 happened. Use these commands to manage the @value{GDBN} command
19572 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19573 package, to provide the history facility.
19574 @ifset SYSTEM_READLINE
19575 @xref{Using History Interactively, , , history, GNU History Library},
19577 @ifclear SYSTEM_READLINE
19578 @xref{Using History Interactively},
19580 for the detailed description of the History library.
19582 To issue a command to @value{GDBN} without affecting certain aspects of
19583 the state which is seen by users, prefix it with @samp{server }
19584 (@pxref{Server Prefix}). This
19585 means that this command will not affect the command history, nor will it
19586 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19587 pressed on a line by itself.
19589 @cindex @code{server}, command prefix
19590 The server prefix does not affect the recording of values into the value
19591 history; to print a value without recording it into the value history,
19592 use the @code{output} command instead of the @code{print} command.
19594 Here is the description of @value{GDBN} commands related to command
19598 @cindex history substitution
19599 @cindex history file
19600 @kindex set history filename
19601 @cindex @env{GDBHISTFILE}, environment variable
19602 @item set history filename @var{fname}
19603 Set the name of the @value{GDBN} command history file to @var{fname}.
19604 This is the file where @value{GDBN} reads an initial command history
19605 list, and where it writes the command history from this session when it
19606 exits. You can access this list through history expansion or through
19607 the history command editing characters listed below. This file defaults
19608 to the value of the environment variable @code{GDBHISTFILE}, or to
19609 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19612 @cindex save command history
19613 @kindex set history save
19614 @item set history save
19615 @itemx set history save on
19616 Record command history in a file, whose name may be specified with the
19617 @code{set history filename} command. By default, this option is disabled.
19619 @item set history save off
19620 Stop recording command history in a file.
19622 @cindex history size
19623 @kindex set history size
19624 @cindex @env{HISTSIZE}, environment variable
19625 @item set history size @var{size}
19626 Set the number of commands which @value{GDBN} keeps in its history list.
19627 This defaults to the value of the environment variable
19628 @code{HISTSIZE}, or to 256 if this variable is not set.
19631 History expansion assigns special meaning to the character @kbd{!}.
19632 @ifset SYSTEM_READLINE
19633 @xref{Event Designators, , , history, GNU History Library},
19635 @ifclear SYSTEM_READLINE
19636 @xref{Event Designators},
19640 @cindex history expansion, turn on/off
19641 Since @kbd{!} is also the logical not operator in C, history expansion
19642 is off by default. If you decide to enable history expansion with the
19643 @code{set history expansion on} command, you may sometimes need to
19644 follow @kbd{!} (when it is used as logical not, in an expression) with
19645 a space or a tab to prevent it from being expanded. The readline
19646 history facilities do not attempt substitution on the strings
19647 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19649 The commands to control history expansion are:
19652 @item set history expansion on
19653 @itemx set history expansion
19654 @kindex set history expansion
19655 Enable history expansion. History expansion is off by default.
19657 @item set history expansion off
19658 Disable history expansion.
19661 @kindex show history
19663 @itemx show history filename
19664 @itemx show history save
19665 @itemx show history size
19666 @itemx show history expansion
19667 These commands display the state of the @value{GDBN} history parameters.
19668 @code{show history} by itself displays all four states.
19673 @kindex show commands
19674 @cindex show last commands
19675 @cindex display command history
19676 @item show commands
19677 Display the last ten commands in the command history.
19679 @item show commands @var{n}
19680 Print ten commands centered on command number @var{n}.
19682 @item show commands +
19683 Print ten commands just after the commands last printed.
19687 @section Screen Size
19688 @cindex size of screen
19689 @cindex pauses in output
19691 Certain commands to @value{GDBN} may produce large amounts of
19692 information output to the screen. To help you read all of it,
19693 @value{GDBN} pauses and asks you for input at the end of each page of
19694 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19695 to discard the remaining output. Also, the screen width setting
19696 determines when to wrap lines of output. Depending on what is being
19697 printed, @value{GDBN} tries to break the line at a readable place,
19698 rather than simply letting it overflow onto the following line.
19700 Normally @value{GDBN} knows the size of the screen from the terminal
19701 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19702 together with the value of the @code{TERM} environment variable and the
19703 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19704 you can override it with the @code{set height} and @code{set
19711 @kindex show height
19712 @item set height @var{lpp}
19714 @itemx set width @var{cpl}
19716 These @code{set} commands specify a screen height of @var{lpp} lines and
19717 a screen width of @var{cpl} characters. The associated @code{show}
19718 commands display the current settings.
19720 If you specify a height of zero lines, @value{GDBN} does not pause during
19721 output no matter how long the output is. This is useful if output is to a
19722 file or to an editor buffer.
19724 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19725 from wrapping its output.
19727 @item set pagination on
19728 @itemx set pagination off
19729 @kindex set pagination
19730 Turn the output pagination on or off; the default is on. Turning
19731 pagination off is the alternative to @code{set height 0}. Note that
19732 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19733 Options, -batch}) also automatically disables pagination.
19735 @item show pagination
19736 @kindex show pagination
19737 Show the current pagination mode.
19742 @cindex number representation
19743 @cindex entering numbers
19745 You can always enter numbers in octal, decimal, or hexadecimal in
19746 @value{GDBN} by the usual conventions: octal numbers begin with
19747 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19748 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19749 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19750 10; likewise, the default display for numbers---when no particular
19751 format is specified---is base 10. You can change the default base for
19752 both input and output with the commands described below.
19755 @kindex set input-radix
19756 @item set input-radix @var{base}
19757 Set the default base for numeric input. Supported choices
19758 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19759 specified either unambiguously or using the current input radix; for
19763 set input-radix 012
19764 set input-radix 10.
19765 set input-radix 0xa
19769 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19770 leaves the input radix unchanged, no matter what it was, since
19771 @samp{10}, being without any leading or trailing signs of its base, is
19772 interpreted in the current radix. Thus, if the current radix is 16,
19773 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19776 @kindex set output-radix
19777 @item set output-radix @var{base}
19778 Set the default base for numeric display. Supported choices
19779 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19780 specified either unambiguously or using the current input radix.
19782 @kindex show input-radix
19783 @item show input-radix
19784 Display the current default base for numeric input.
19786 @kindex show output-radix
19787 @item show output-radix
19788 Display the current default base for numeric display.
19790 @item set radix @r{[}@var{base}@r{]}
19794 These commands set and show the default base for both input and output
19795 of numbers. @code{set radix} sets the radix of input and output to
19796 the same base; without an argument, it resets the radix back to its
19797 default value of 10.
19802 @section Configuring the Current ABI
19804 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19805 application automatically. However, sometimes you need to override its
19806 conclusions. Use these commands to manage @value{GDBN}'s view of the
19813 One @value{GDBN} configuration can debug binaries for multiple operating
19814 system targets, either via remote debugging or native emulation.
19815 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19816 but you can override its conclusion using the @code{set osabi} command.
19817 One example where this is useful is in debugging of binaries which use
19818 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19819 not have the same identifying marks that the standard C library for your
19824 Show the OS ABI currently in use.
19827 With no argument, show the list of registered available OS ABI's.
19829 @item set osabi @var{abi}
19830 Set the current OS ABI to @var{abi}.
19833 @cindex float promotion
19835 Generally, the way that an argument of type @code{float} is passed to a
19836 function depends on whether the function is prototyped. For a prototyped
19837 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19838 according to the architecture's convention for @code{float}. For unprototyped
19839 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19840 @code{double} and then passed.
19842 Unfortunately, some forms of debug information do not reliably indicate whether
19843 a function is prototyped. If @value{GDBN} calls a function that is not marked
19844 as prototyped, it consults @kbd{set coerce-float-to-double}.
19847 @kindex set coerce-float-to-double
19848 @item set coerce-float-to-double
19849 @itemx set coerce-float-to-double on
19850 Arguments of type @code{float} will be promoted to @code{double} when passed
19851 to an unprototyped function. This is the default setting.
19853 @item set coerce-float-to-double off
19854 Arguments of type @code{float} will be passed directly to unprototyped
19857 @kindex show coerce-float-to-double
19858 @item show coerce-float-to-double
19859 Show the current setting of promoting @code{float} to @code{double}.
19863 @kindex show cp-abi
19864 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19865 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19866 used to build your application. @value{GDBN} only fully supports
19867 programs with a single C@t{++} ABI; if your program contains code using
19868 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19869 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19870 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19871 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19872 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19873 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19878 Show the C@t{++} ABI currently in use.
19881 With no argument, show the list of supported C@t{++} ABI's.
19883 @item set cp-abi @var{abi}
19884 @itemx set cp-abi auto
19885 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19888 @node Messages/Warnings
19889 @section Optional Warnings and Messages
19891 @cindex verbose operation
19892 @cindex optional warnings
19893 By default, @value{GDBN} is silent about its inner workings. If you are
19894 running on a slow machine, you may want to use the @code{set verbose}
19895 command. This makes @value{GDBN} tell you when it does a lengthy
19896 internal operation, so you will not think it has crashed.
19898 Currently, the messages controlled by @code{set verbose} are those
19899 which announce that the symbol table for a source file is being read;
19900 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19903 @kindex set verbose
19904 @item set verbose on
19905 Enables @value{GDBN} output of certain informational messages.
19907 @item set verbose off
19908 Disables @value{GDBN} output of certain informational messages.
19910 @kindex show verbose
19912 Displays whether @code{set verbose} is on or off.
19915 By default, if @value{GDBN} encounters bugs in the symbol table of an
19916 object file, it is silent; but if you are debugging a compiler, you may
19917 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19922 @kindex set complaints
19923 @item set complaints @var{limit}
19924 Permits @value{GDBN} to output @var{limit} complaints about each type of
19925 unusual symbols before becoming silent about the problem. Set
19926 @var{limit} to zero to suppress all complaints; set it to a large number
19927 to prevent complaints from being suppressed.
19929 @kindex show complaints
19930 @item show complaints
19931 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19935 @anchor{confirmation requests}
19936 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19937 lot of stupid questions to confirm certain commands. For example, if
19938 you try to run a program which is already running:
19942 The program being debugged has been started already.
19943 Start it from the beginning? (y or n)
19946 If you are willing to unflinchingly face the consequences of your own
19947 commands, you can disable this ``feature'':
19951 @kindex set confirm
19953 @cindex confirmation
19954 @cindex stupid questions
19955 @item set confirm off
19956 Disables confirmation requests. Note that running @value{GDBN} with
19957 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19958 automatically disables confirmation requests.
19960 @item set confirm on
19961 Enables confirmation requests (the default).
19963 @kindex show confirm
19965 Displays state of confirmation requests.
19969 @cindex command tracing
19970 If you need to debug user-defined commands or sourced files you may find it
19971 useful to enable @dfn{command tracing}. In this mode each command will be
19972 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19973 quantity denoting the call depth of each command.
19976 @kindex set trace-commands
19977 @cindex command scripts, debugging
19978 @item set trace-commands on
19979 Enable command tracing.
19980 @item set trace-commands off
19981 Disable command tracing.
19982 @item show trace-commands
19983 Display the current state of command tracing.
19986 @node Debugging Output
19987 @section Optional Messages about Internal Happenings
19988 @cindex optional debugging messages
19990 @value{GDBN} has commands that enable optional debugging messages from
19991 various @value{GDBN} subsystems; normally these commands are of
19992 interest to @value{GDBN} maintainers, or when reporting a bug. This
19993 section documents those commands.
19996 @kindex set exec-done-display
19997 @item set exec-done-display
19998 Turns on or off the notification of asynchronous commands'
19999 completion. When on, @value{GDBN} will print a message when an
20000 asynchronous command finishes its execution. The default is off.
20001 @kindex show exec-done-display
20002 @item show exec-done-display
20003 Displays the current setting of asynchronous command completion
20006 @cindex gdbarch debugging info
20007 @cindex architecture debugging info
20008 @item set debug arch
20009 Turns on or off display of gdbarch debugging info. The default is off
20011 @item show debug arch
20012 Displays the current state of displaying gdbarch debugging info.
20013 @item set debug aix-thread
20014 @cindex AIX threads
20015 Display debugging messages about inner workings of the AIX thread
20017 @item show debug aix-thread
20018 Show the current state of AIX thread debugging info display.
20019 @item set debug dwarf2-die
20020 @cindex DWARF2 DIEs
20021 Dump DWARF2 DIEs after they are read in.
20022 The value is the number of nesting levels to print.
20023 A value of zero turns off the display.
20024 @item show debug dwarf2-die
20025 Show the current state of DWARF2 DIE debugging.
20026 @item set debug displaced
20027 @cindex displaced stepping debugging info
20028 Turns on or off display of @value{GDBN} debugging info for the
20029 displaced stepping support. The default is off.
20030 @item show debug displaced
20031 Displays the current state of displaying @value{GDBN} debugging info
20032 related to displaced stepping.
20033 @item set debug event
20034 @cindex event debugging info
20035 Turns on or off display of @value{GDBN} event debugging info. The
20037 @item show debug event
20038 Displays the current state of displaying @value{GDBN} event debugging
20040 @item set debug expression
20041 @cindex expression debugging info
20042 Turns on or off display of debugging info about @value{GDBN}
20043 expression parsing. The default is off.
20044 @item show debug expression
20045 Displays the current state of displaying debugging info about
20046 @value{GDBN} expression parsing.
20047 @item set debug frame
20048 @cindex frame debugging info
20049 Turns on or off display of @value{GDBN} frame debugging info. The
20051 @item show debug frame
20052 Displays the current state of displaying @value{GDBN} frame debugging
20054 @item set debug gnu-nat
20055 @cindex @sc{gnu}/Hurd debug messages
20056 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20057 @item show debug gnu-nat
20058 Show the current state of @sc{gnu}/Hurd debugging messages.
20059 @item set debug infrun
20060 @cindex inferior debugging info
20061 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20062 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20063 for implementing operations such as single-stepping the inferior.
20064 @item show debug infrun
20065 Displays the current state of @value{GDBN} inferior debugging.
20066 @item set debug jit
20067 @cindex just-in-time compilation, debugging messages
20068 Turns on or off debugging messages from JIT debug support.
20069 @item show debug jit
20070 Displays the current state of @value{GDBN} JIT debugging.
20071 @item set debug lin-lwp
20072 @cindex @sc{gnu}/Linux LWP debug messages
20073 @cindex Linux lightweight processes
20074 Turns on or off debugging messages from the Linux LWP debug support.
20075 @item show debug lin-lwp
20076 Show the current state of Linux LWP debugging messages.
20077 @item set debug observer
20078 @cindex observer debugging info
20079 Turns on or off display of @value{GDBN} observer debugging. This
20080 includes info such as the notification of observable events.
20081 @item show debug observer
20082 Displays the current state of observer debugging.
20083 @item set debug overload
20084 @cindex C@t{++} overload debugging info
20085 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20086 info. This includes info such as ranking of functions, etc. The default
20088 @item show debug overload
20089 Displays the current state of displaying @value{GDBN} C@t{++} overload
20091 @cindex expression parser, debugging info
20092 @cindex debug expression parser
20093 @item set debug parser
20094 Turns on or off the display of expression parser debugging output.
20095 Internally, this sets the @code{yydebug} variable in the expression
20096 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20097 details. The default is off.
20098 @item show debug parser
20099 Show the current state of expression parser debugging.
20100 @cindex packets, reporting on stdout
20101 @cindex serial connections, debugging
20102 @cindex debug remote protocol
20103 @cindex remote protocol debugging
20104 @cindex display remote packets
20105 @item set debug remote
20106 Turns on or off display of reports on all packets sent back and forth across
20107 the serial line to the remote machine. The info is printed on the
20108 @value{GDBN} standard output stream. The default is off.
20109 @item show debug remote
20110 Displays the state of display of remote packets.
20111 @item set debug serial
20112 Turns on or off display of @value{GDBN} serial debugging info. The
20114 @item show debug serial
20115 Displays the current state of displaying @value{GDBN} serial debugging
20117 @item set debug solib-frv
20118 @cindex FR-V shared-library debugging
20119 Turns on or off debugging messages for FR-V shared-library code.
20120 @item show debug solib-frv
20121 Display the current state of FR-V shared-library code debugging
20123 @item set debug target
20124 @cindex target debugging info
20125 Turns on or off display of @value{GDBN} target debugging info. This info
20126 includes what is going on at the target level of GDB, as it happens. The
20127 default is 0. Set it to 1 to track events, and to 2 to also track the
20128 value of large memory transfers. Changes to this flag do not take effect
20129 until the next time you connect to a target or use the @code{run} command.
20130 @item show debug target
20131 Displays the current state of displaying @value{GDBN} target debugging
20133 @item set debug timestamp
20134 @cindex timestampping debugging info
20135 Turns on or off display of timestamps with @value{GDBN} debugging info.
20136 When enabled, seconds and microseconds are displayed before each debugging
20138 @item show debug timestamp
20139 Displays the current state of displaying timestamps with @value{GDBN}
20141 @item set debugvarobj
20142 @cindex variable object debugging info
20143 Turns on or off display of @value{GDBN} variable object debugging
20144 info. The default is off.
20145 @item show debugvarobj
20146 Displays the current state of displaying @value{GDBN} variable object
20148 @item set debug xml
20149 @cindex XML parser debugging
20150 Turns on or off debugging messages for built-in XML parsers.
20151 @item show debug xml
20152 Displays the current state of XML debugging messages.
20155 @node Other Misc Settings
20156 @section Other Miscellaneous Settings
20157 @cindex miscellaneous settings
20160 @kindex set interactive-mode
20161 @item set interactive-mode
20162 If @code{on}, forces @value{GDBN} to assume that GDB was started
20163 in a terminal. In practice, this means that @value{GDBN} should wait
20164 for the user to answer queries generated by commands entered at
20165 the command prompt. If @code{off}, forces @value{GDBN} to operate
20166 in the opposite mode, and it uses the default answers to all queries.
20167 If @code{auto} (the default), @value{GDBN} tries to determine whether
20168 its standard input is a terminal, and works in interactive-mode if it
20169 is, non-interactively otherwise.
20171 In the vast majority of cases, the debugger should be able to guess
20172 correctly which mode should be used. But this setting can be useful
20173 in certain specific cases, such as running a MinGW @value{GDBN}
20174 inside a cygwin window.
20176 @kindex show interactive-mode
20177 @item show interactive-mode
20178 Displays whether the debugger is operating in interactive mode or not.
20181 @node Extending GDB
20182 @chapter Extending @value{GDBN}
20183 @cindex extending GDB
20185 @value{GDBN} provides two mechanisms for extension. The first is based
20186 on composition of @value{GDBN} commands, and the second is based on the
20187 Python scripting language.
20189 To facilitate the use of these extensions, @value{GDBN} is capable
20190 of evaluating the contents of a file. When doing so, @value{GDBN}
20191 can recognize which scripting language is being used by looking at
20192 the filename extension. Files with an unrecognized filename extension
20193 are always treated as a @value{GDBN} Command Files.
20194 @xref{Command Files,, Command files}.
20196 You can control how @value{GDBN} evaluates these files with the following
20200 @kindex set script-extension
20201 @kindex show script-extension
20202 @item set script-extension off
20203 All scripts are always evaluated as @value{GDBN} Command Files.
20205 @item set script-extension soft
20206 The debugger determines the scripting language based on filename
20207 extension. If this scripting language is supported, @value{GDBN}
20208 evaluates the script using that language. Otherwise, it evaluates
20209 the file as a @value{GDBN} Command File.
20211 @item set script-extension strict
20212 The debugger determines the scripting language based on filename
20213 extension, and evaluates the script using that language. If the
20214 language is not supported, then the evaluation fails.
20216 @item show script-extension
20217 Display the current value of the @code{script-extension} option.
20222 * Sequences:: Canned Sequences of Commands
20223 * Python:: Scripting @value{GDBN} using Python
20227 @section Canned Sequences of Commands
20229 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20230 Command Lists}), @value{GDBN} provides two ways to store sequences of
20231 commands for execution as a unit: user-defined commands and command
20235 * Define:: How to define your own commands
20236 * Hooks:: Hooks for user-defined commands
20237 * Command Files:: How to write scripts of commands to be stored in a file
20238 * Output:: Commands for controlled output
20242 @subsection User-defined Commands
20244 @cindex user-defined command
20245 @cindex arguments, to user-defined commands
20246 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20247 which you assign a new name as a command. This is done with the
20248 @code{define} command. User commands may accept up to 10 arguments
20249 separated by whitespace. Arguments are accessed within the user command
20250 via @code{$arg0@dots{}$arg9}. A trivial example:
20254 print $arg0 + $arg1 + $arg2
20259 To execute the command use:
20266 This defines the command @code{adder}, which prints the sum of
20267 its three arguments. Note the arguments are text substitutions, so they may
20268 reference variables, use complex expressions, or even perform inferior
20271 @cindex argument count in user-defined commands
20272 @cindex how many arguments (user-defined commands)
20273 In addition, @code{$argc} may be used to find out how many arguments have
20274 been passed. This expands to a number in the range 0@dots{}10.
20279 print $arg0 + $arg1
20282 print $arg0 + $arg1 + $arg2
20290 @item define @var{commandname}
20291 Define a command named @var{commandname}. If there is already a command
20292 by that name, you are asked to confirm that you want to redefine it.
20293 @var{commandname} may be a bare command name consisting of letters,
20294 numbers, dashes, and underscores. It may also start with any predefined
20295 prefix command. For example, @samp{define target my-target} creates
20296 a user-defined @samp{target my-target} command.
20298 The definition of the command is made up of other @value{GDBN} command lines,
20299 which are given following the @code{define} command. The end of these
20300 commands is marked by a line containing @code{end}.
20303 @kindex end@r{ (user-defined commands)}
20304 @item document @var{commandname}
20305 Document the user-defined command @var{commandname}, so that it can be
20306 accessed by @code{help}. The command @var{commandname} must already be
20307 defined. This command reads lines of documentation just as @code{define}
20308 reads the lines of the command definition, ending with @code{end}.
20309 After the @code{document} command is finished, @code{help} on command
20310 @var{commandname} displays the documentation you have written.
20312 You may use the @code{document} command again to change the
20313 documentation of a command. Redefining the command with @code{define}
20314 does not change the documentation.
20316 @kindex dont-repeat
20317 @cindex don't repeat command
20319 Used inside a user-defined command, this tells @value{GDBN} that this
20320 command should not be repeated when the user hits @key{RET}
20321 (@pxref{Command Syntax, repeat last command}).
20323 @kindex help user-defined
20324 @item help user-defined
20325 List all user-defined commands, with the first line of the documentation
20330 @itemx show user @var{commandname}
20331 Display the @value{GDBN} commands used to define @var{commandname} (but
20332 not its documentation). If no @var{commandname} is given, display the
20333 definitions for all user-defined commands.
20335 @cindex infinite recursion in user-defined commands
20336 @kindex show max-user-call-depth
20337 @kindex set max-user-call-depth
20338 @item show max-user-call-depth
20339 @itemx set max-user-call-depth
20340 The value of @code{max-user-call-depth} controls how many recursion
20341 levels are allowed in user-defined commands before @value{GDBN} suspects an
20342 infinite recursion and aborts the command.
20345 In addition to the above commands, user-defined commands frequently
20346 use control flow commands, described in @ref{Command Files}.
20348 When user-defined commands are executed, the
20349 commands of the definition are not printed. An error in any command
20350 stops execution of the user-defined command.
20352 If used interactively, commands that would ask for confirmation proceed
20353 without asking when used inside a user-defined command. Many @value{GDBN}
20354 commands that normally print messages to say what they are doing omit the
20355 messages when used in a user-defined command.
20358 @subsection User-defined Command Hooks
20359 @cindex command hooks
20360 @cindex hooks, for commands
20361 @cindex hooks, pre-command
20364 You may define @dfn{hooks}, which are a special kind of user-defined
20365 command. Whenever you run the command @samp{foo}, if the user-defined
20366 command @samp{hook-foo} exists, it is executed (with no arguments)
20367 before that command.
20369 @cindex hooks, post-command
20371 A hook may also be defined which is run after the command you executed.
20372 Whenever you run the command @samp{foo}, if the user-defined command
20373 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20374 that command. Post-execution hooks may exist simultaneously with
20375 pre-execution hooks, for the same command.
20377 It is valid for a hook to call the command which it hooks. If this
20378 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20380 @c It would be nice if hookpost could be passed a parameter indicating
20381 @c if the command it hooks executed properly or not. FIXME!
20383 @kindex stop@r{, a pseudo-command}
20384 In addition, a pseudo-command, @samp{stop} exists. Defining
20385 (@samp{hook-stop}) makes the associated commands execute every time
20386 execution stops in your program: before breakpoint commands are run,
20387 displays are printed, or the stack frame is printed.
20389 For example, to ignore @code{SIGALRM} signals while
20390 single-stepping, but treat them normally during normal execution,
20395 handle SIGALRM nopass
20399 handle SIGALRM pass
20402 define hook-continue
20403 handle SIGALRM pass
20407 As a further example, to hook at the beginning and end of the @code{echo}
20408 command, and to add extra text to the beginning and end of the message,
20416 define hookpost-echo
20420 (@value{GDBP}) echo Hello World
20421 <<<---Hello World--->>>
20426 You can define a hook for any single-word command in @value{GDBN}, but
20427 not for command aliases; you should define a hook for the basic command
20428 name, e.g.@: @code{backtrace} rather than @code{bt}.
20429 @c FIXME! So how does Joe User discover whether a command is an alias
20431 You can hook a multi-word command by adding @code{hook-} or
20432 @code{hookpost-} to the last word of the command, e.g.@:
20433 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20435 If an error occurs during the execution of your hook, execution of
20436 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20437 (before the command that you actually typed had a chance to run).
20439 If you try to define a hook which does not match any known command, you
20440 get a warning from the @code{define} command.
20442 @node Command Files
20443 @subsection Command Files
20445 @cindex command files
20446 @cindex scripting commands
20447 A command file for @value{GDBN} is a text file made of lines that are
20448 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20449 also be included. An empty line in a command file does nothing; it
20450 does not mean to repeat the last command, as it would from the
20453 You can request the execution of a command file with the @code{source}
20454 command. Note that the @code{source} command is also used to evaluate
20455 scripts that are not Command Files. The exact behavior can be configured
20456 using the @code{script-extension} setting.
20457 @xref{Extending GDB,, Extending GDB}.
20461 @cindex execute commands from a file
20462 @item source [-s] [-v] @var{filename}
20463 Execute the command file @var{filename}.
20466 The lines in a command file are generally executed sequentially,
20467 unless the order of execution is changed by one of the
20468 @emph{flow-control commands} described below. The commands are not
20469 printed as they are executed. An error in any command terminates
20470 execution of the command file and control is returned to the console.
20472 @value{GDBN} first searches for @var{filename} in the current directory.
20473 If the file is not found there, and @var{filename} does not specify a
20474 directory, then @value{GDBN} also looks for the file on the source search path
20475 (specified with the @samp{directory} command);
20476 except that @file{$cdir} is not searched because the compilation directory
20477 is not relevant to scripts.
20479 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20480 on the search path even if @var{filename} specifies a directory.
20481 The search is done by appending @var{filename} to each element of the
20482 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20483 and the search path contains @file{/home/user} then @value{GDBN} will
20484 look for the script @file{/home/user/mylib/myscript}.
20485 The search is also done if @var{filename} is an absolute path.
20486 For example, if @var{filename} is @file{/tmp/myscript} and
20487 the search path contains @file{/home/user} then @value{GDBN} will
20488 look for the script @file{/home/user/tmp/myscript}.
20489 For DOS-like systems, if @var{filename} contains a drive specification,
20490 it is stripped before concatenation. For example, if @var{filename} is
20491 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20492 will look for the script @file{c:/tmp/myscript}.
20494 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20495 each command as it is executed. The option must be given before
20496 @var{filename}, and is interpreted as part of the filename anywhere else.
20498 Commands that would ask for confirmation if used interactively proceed
20499 without asking when used in a command file. Many @value{GDBN} commands that
20500 normally print messages to say what they are doing omit the messages
20501 when called from command files.
20503 @value{GDBN} also accepts command input from standard input. In this
20504 mode, normal output goes to standard output and error output goes to
20505 standard error. Errors in a command file supplied on standard input do
20506 not terminate execution of the command file---execution continues with
20510 gdb < cmds > log 2>&1
20513 (The syntax above will vary depending on the shell used.) This example
20514 will execute commands from the file @file{cmds}. All output and errors
20515 would be directed to @file{log}.
20517 Since commands stored on command files tend to be more general than
20518 commands typed interactively, they frequently need to deal with
20519 complicated situations, such as different or unexpected values of
20520 variables and symbols, changes in how the program being debugged is
20521 built, etc. @value{GDBN} provides a set of flow-control commands to
20522 deal with these complexities. Using these commands, you can write
20523 complex scripts that loop over data structures, execute commands
20524 conditionally, etc.
20531 This command allows to include in your script conditionally executed
20532 commands. The @code{if} command takes a single argument, which is an
20533 expression to evaluate. It is followed by a series of commands that
20534 are executed only if the expression is true (its value is nonzero).
20535 There can then optionally be an @code{else} line, followed by a series
20536 of commands that are only executed if the expression was false. The
20537 end of the list is marked by a line containing @code{end}.
20541 This command allows to write loops. Its syntax is similar to
20542 @code{if}: the command takes a single argument, which is an expression
20543 to evaluate, and must be followed by the commands to execute, one per
20544 line, terminated by an @code{end}. These commands are called the
20545 @dfn{body} of the loop. The commands in the body of @code{while} are
20546 executed repeatedly as long as the expression evaluates to true.
20550 This command exits the @code{while} loop in whose body it is included.
20551 Execution of the script continues after that @code{while}s @code{end}
20554 @kindex loop_continue
20555 @item loop_continue
20556 This command skips the execution of the rest of the body of commands
20557 in the @code{while} loop in whose body it is included. Execution
20558 branches to the beginning of the @code{while} loop, where it evaluates
20559 the controlling expression.
20561 @kindex end@r{ (if/else/while commands)}
20563 Terminate the block of commands that are the body of @code{if},
20564 @code{else}, or @code{while} flow-control commands.
20569 @subsection Commands for Controlled Output
20571 During the execution of a command file or a user-defined command, normal
20572 @value{GDBN} output is suppressed; the only output that appears is what is
20573 explicitly printed by the commands in the definition. This section
20574 describes three commands useful for generating exactly the output you
20579 @item echo @var{text}
20580 @c I do not consider backslash-space a standard C escape sequence
20581 @c because it is not in ANSI.
20582 Print @var{text}. Nonprinting characters can be included in
20583 @var{text} using C escape sequences, such as @samp{\n} to print a
20584 newline. @strong{No newline is printed unless you specify one.}
20585 In addition to the standard C escape sequences, a backslash followed
20586 by a space stands for a space. This is useful for displaying a
20587 string with spaces at the beginning or the end, since leading and
20588 trailing spaces are otherwise trimmed from all arguments.
20589 To print @samp{@w{ }and foo =@w{ }}, use the command
20590 @samp{echo \@w{ }and foo = \@w{ }}.
20592 A backslash at the end of @var{text} can be used, as in C, to continue
20593 the command onto subsequent lines. For example,
20596 echo This is some text\n\
20597 which is continued\n\
20598 onto several lines.\n
20601 produces the same output as
20604 echo This is some text\n
20605 echo which is continued\n
20606 echo onto several lines.\n
20610 @item output @var{expression}
20611 Print the value of @var{expression} and nothing but that value: no
20612 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20613 value history either. @xref{Expressions, ,Expressions}, for more information
20616 @item output/@var{fmt} @var{expression}
20617 Print the value of @var{expression} in format @var{fmt}. You can use
20618 the same formats as for @code{print}. @xref{Output Formats,,Output
20619 Formats}, for more information.
20622 @item printf @var{template}, @var{expressions}@dots{}
20623 Print the values of one or more @var{expressions} under the control of
20624 the string @var{template}. To print several values, make
20625 @var{expressions} be a comma-separated list of individual expressions,
20626 which may be either numbers or pointers. Their values are printed as
20627 specified by @var{template}, exactly as a C program would do by
20628 executing the code below:
20631 printf (@var{template}, @var{expressions}@dots{});
20634 As in @code{C} @code{printf}, ordinary characters in @var{template}
20635 are printed verbatim, while @dfn{conversion specification} introduced
20636 by the @samp{%} character cause subsequent @var{expressions} to be
20637 evaluated, their values converted and formatted according to type and
20638 style information encoded in the conversion specifications, and then
20641 For example, you can print two values in hex like this:
20644 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20647 @code{printf} supports all the standard @code{C} conversion
20648 specifications, including the flags and modifiers between the @samp{%}
20649 character and the conversion letter, with the following exceptions:
20653 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20656 The modifier @samp{*} is not supported for specifying precision or
20660 The @samp{'} flag (for separation of digits into groups according to
20661 @code{LC_NUMERIC'}) is not supported.
20664 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20668 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20671 The conversion letters @samp{a} and @samp{A} are not supported.
20675 Note that the @samp{ll} type modifier is supported only if the
20676 underlying @code{C} implementation used to build @value{GDBN} supports
20677 the @code{long long int} type, and the @samp{L} type modifier is
20678 supported only if @code{long double} type is available.
20680 As in @code{C}, @code{printf} supports simple backslash-escape
20681 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20682 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20683 single character. Octal and hexadecimal escape sequences are not
20686 Additionally, @code{printf} supports conversion specifications for DFP
20687 (@dfn{Decimal Floating Point}) types using the following length modifiers
20688 together with a floating point specifier.
20693 @samp{H} for printing @code{Decimal32} types.
20696 @samp{D} for printing @code{Decimal64} types.
20699 @samp{DD} for printing @code{Decimal128} types.
20702 If the underlying @code{C} implementation used to build @value{GDBN} has
20703 support for the three length modifiers for DFP types, other modifiers
20704 such as width and precision will also be available for @value{GDBN} to use.
20706 In case there is no such @code{C} support, no additional modifiers will be
20707 available and the value will be printed in the standard way.
20709 Here's an example of printing DFP types using the above conversion letters:
20711 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20715 @item eval @var{template}, @var{expressions}@dots{}
20716 Convert the values of one or more @var{expressions} under the control of
20717 the string @var{template} to a command line, and call it.
20722 @section Scripting @value{GDBN} using Python
20723 @cindex python scripting
20724 @cindex scripting with python
20726 You can script @value{GDBN} using the @uref{http://www.python.org/,
20727 Python programming language}. This feature is available only if
20728 @value{GDBN} was configured using @option{--with-python}.
20730 @cindex python directory
20731 Python scripts used by @value{GDBN} should be installed in
20732 @file{@var{data-directory}/python}, where @var{data-directory} is
20733 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20734 This directory, known as the @dfn{python directory},
20735 is automatically added to the Python Search Path in order to allow
20736 the Python interpreter to locate all scripts installed at this location.
20739 * Python Commands:: Accessing Python from @value{GDBN}.
20740 * Python API:: Accessing @value{GDBN} from Python.
20741 * Auto-loading:: Automatically loading Python code.
20742 * Python modules:: Python modules provided by @value{GDBN}.
20745 @node Python Commands
20746 @subsection Python Commands
20747 @cindex python commands
20748 @cindex commands to access python
20750 @value{GDBN} provides one command for accessing the Python interpreter,
20751 and one related setting:
20755 @item python @r{[}@var{code}@r{]}
20756 The @code{python} command can be used to evaluate Python code.
20758 If given an argument, the @code{python} command will evaluate the
20759 argument as a Python command. For example:
20762 (@value{GDBP}) python print 23
20766 If you do not provide an argument to @code{python}, it will act as a
20767 multi-line command, like @code{define}. In this case, the Python
20768 script is made up of subsequent command lines, given after the
20769 @code{python} command. This command list is terminated using a line
20770 containing @code{end}. For example:
20773 (@value{GDBP}) python
20775 End with a line saying just "end".
20781 @kindex maint set python print-stack
20782 @item maint set python print-stack
20783 By default, @value{GDBN} will print a stack trace when an error occurs
20784 in a Python script. This can be controlled using @code{maint set
20785 python print-stack}: if @code{on}, the default, then Python stack
20786 printing is enabled; if @code{off}, then Python stack printing is
20790 It is also possible to execute a Python script from the @value{GDBN}
20794 @item source @file{script-name}
20795 The script name must end with @samp{.py} and @value{GDBN} must be configured
20796 to recognize the script language based on filename extension using
20797 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20799 @item python execfile ("script-name")
20800 This method is based on the @code{execfile} Python built-in function,
20801 and thus is always available.
20805 @subsection Python API
20807 @cindex programming in python
20809 @cindex python stdout
20810 @cindex python pagination
20811 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20812 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20813 A Python program which outputs to one of these streams may have its
20814 output interrupted by the user (@pxref{Screen Size}). In this
20815 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20818 * Basic Python:: Basic Python Functions.
20819 * Exception Handling:: How Python exceptions are translated.
20820 * Values From Inferior:: Python representation of values.
20821 * Types In Python:: Python representation of types.
20822 * Pretty Printing API:: Pretty-printing values.
20823 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20824 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20825 * Inferiors In Python:: Python representation of inferiors (processes)
20826 * Events In Python:: Listening for events from @value{GDBN}.
20827 * Threads In Python:: Accessing inferior threads from Python.
20828 * Commands In Python:: Implementing new commands in Python.
20829 * Parameters In Python:: Adding new @value{GDBN} parameters.
20830 * Functions In Python:: Writing new convenience functions.
20831 * Progspaces In Python:: Program spaces.
20832 * Objfiles In Python:: Object files.
20833 * Frames In Python:: Accessing inferior stack frames from Python.
20834 * Blocks In Python:: Accessing frame blocks from Python.
20835 * Symbols In Python:: Python representation of symbols.
20836 * Symbol Tables In Python:: Python representation of symbol tables.
20837 * Lazy Strings In Python:: Python representation of lazy strings.
20838 * Breakpoints In Python:: Manipulating breakpoints using Python.
20842 @subsubsection Basic Python
20844 @cindex python functions
20845 @cindex python module
20847 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20848 methods and classes added by @value{GDBN} are placed in this module.
20849 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20850 use in all scripts evaluated by the @code{python} command.
20852 @findex gdb.PYTHONDIR
20854 A string containing the python directory (@pxref{Python}).
20857 @findex gdb.execute
20858 @defun execute command [from_tty] [to_string]
20859 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20860 If a GDB exception happens while @var{command} runs, it is
20861 translated as described in @ref{Exception Handling,,Exception Handling}.
20863 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20864 command as having originated from the user invoking it interactively.
20865 It must be a boolean value. If omitted, it defaults to @code{False}.
20867 By default, any output produced by @var{command} is sent to
20868 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20869 @code{True}, then output will be collected by @code{gdb.execute} and
20870 returned as a string. The default is @code{False}, in which case the
20871 return value is @code{None}. If @var{to_string} is @code{True}, the
20872 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20873 and height, and its pagination will be disabled; @pxref{Screen Size}.
20876 @findex gdb.breakpoints
20878 Return a sequence holding all of @value{GDBN}'s breakpoints.
20879 @xref{Breakpoints In Python}, for more information.
20882 @findex gdb.parameter
20883 @defun parameter parameter
20884 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20885 string naming the parameter to look up; @var{parameter} may contain
20886 spaces if the parameter has a multi-part name. For example,
20887 @samp{print object} is a valid parameter name.
20889 If the named parameter does not exist, this function throws a
20890 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
20891 parameter's value is converted to a Python value of the appropriate
20892 type, and returned.
20895 @findex gdb.history
20896 @defun history number
20897 Return a value from @value{GDBN}'s value history (@pxref{Value
20898 History}). @var{number} indicates which history element to return.
20899 If @var{number} is negative, then @value{GDBN} will take its absolute value
20900 and count backward from the last element (i.e., the most recent element) to
20901 find the value to return. If @var{number} is zero, then @value{GDBN} will
20902 return the most recent element. If the element specified by @var{number}
20903 doesn't exist in the value history, a @code{gdb.error} exception will be
20906 If no exception is raised, the return value is always an instance of
20907 @code{gdb.Value} (@pxref{Values From Inferior}).
20910 @findex gdb.parse_and_eval
20911 @defun parse_and_eval expression
20912 Parse @var{expression} as an expression in the current language,
20913 evaluate it, and return the result as a @code{gdb.Value}.
20914 @var{expression} must be a string.
20916 This function can be useful when implementing a new command
20917 (@pxref{Commands In Python}), as it provides a way to parse the
20918 command's argument as an expression. It is also useful simply to
20919 compute values, for example, it is the only way to get the value of a
20920 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20923 @findex gdb.post_event
20924 @defun post_event event
20925 Put @var{event}, a callable object taking no arguments, into
20926 @value{GDBN}'s internal event queue. This callable will be invoked at
20927 some later point, during @value{GDBN}'s event processing. Events
20928 posted using @code{post_event} will be run in the order in which they
20929 were posted; however, there is no way to know when they will be
20930 processed relative to other events inside @value{GDBN}.
20932 @value{GDBN} is not thread-safe. If your Python program uses multiple
20933 threads, you must be careful to only call @value{GDBN}-specific
20934 functions in the main @value{GDBN} thread. @code{post_event} ensures
20938 (@value{GDBP}) python
20942 > def __init__(self, message):
20943 > self.message = message;
20944 > def __call__(self):
20945 > gdb.write(self.message)
20947 >class MyThread1 (threading.Thread):
20949 > gdb.post_event(Writer("Hello "))
20951 >class MyThread2 (threading.Thread):
20953 > gdb.post_event(Writer("World\n"))
20955 >MyThread1().start()
20956 >MyThread2().start()
20958 (@value{GDBP}) Hello World
20963 @defun write string @r{[}stream{]}
20964 Print a string to @value{GDBN}'s paginated output stream. The
20965 optional @var{stream} determines the stream to print to. The default
20966 stream is @value{GDBN}'s standard output stream. Possible stream
20973 @value{GDBN}'s standard output stream.
20978 @value{GDBN}'s standard error stream.
20983 @value{GDBN}'s log stream (@pxref{Logging Output}).
20986 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20987 call this function and will automatically direct the output to the
20993 Flush the buffer of a @value{GDBN} paginated stream so that the
20994 contents are displayed immediately. @value{GDBN} will flush the
20995 contents of a stream automatically when it encounters a newline in the
20996 buffer. The optional @var{stream} determines the stream to flush. The
20997 default stream is @value{GDBN}'s standard output stream. Possible
21004 @value{GDBN}'s standard output stream.
21009 @value{GDBN}'s standard error stream.
21014 @value{GDBN}'s log stream (@pxref{Logging Output}).
21018 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21019 call this function for the relevant stream.
21022 @findex gdb.target_charset
21023 @defun target_charset
21024 Return the name of the current target character set (@pxref{Character
21025 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21026 that @samp{auto} is never returned.
21029 @findex gdb.target_wide_charset
21030 @defun target_wide_charset
21031 Return the name of the current target wide character set
21032 (@pxref{Character Sets}). This differs from
21033 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21037 @findex gdb.solib_name
21038 @defun solib_name address
21039 Return the name of the shared library holding the given @var{address}
21040 as a string, or @code{None}.
21043 @findex gdb.decode_line
21044 @defun decode_line @r{[}expression@r{]}
21045 Return locations of the line specified by @var{expression}, or of the
21046 current line if no argument was given. This function returns a Python
21047 tuple containing two elements. The first element contains a string
21048 holding any unparsed section of @var{expression} (or @code{None} if
21049 the expression has been fully parsed). The second element contains
21050 either @code{None} or another tuple that contains all the locations
21051 that match the expression represented as @code{gdb.Symtab_and_line}
21052 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21053 provided, it is decoded the way that @value{GDBN}'s inbuilt
21054 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21057 @node Exception Handling
21058 @subsubsection Exception Handling
21059 @cindex python exceptions
21060 @cindex exceptions, python
21062 When executing the @code{python} command, Python exceptions
21063 uncaught within the Python code are translated to calls to
21064 @value{GDBN} error-reporting mechanism. If the command that called
21065 @code{python} does not handle the error, @value{GDBN} will
21066 terminate it and print an error message containing the Python
21067 exception name, the associated value, and the Python call stack
21068 backtrace at the point where the exception was raised. Example:
21071 (@value{GDBP}) python print foo
21072 Traceback (most recent call last):
21073 File "<string>", line 1, in <module>
21074 NameError: name 'foo' is not defined
21077 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21078 Python code are converted to Python exceptions. The type of the
21079 Python exception depends on the error.
21083 This is the base class for most exceptions generated by @value{GDBN}.
21084 It is derived from @code{RuntimeError}, for compatibility with earlier
21085 versions of @value{GDBN}.
21087 If an error occurring in @value{GDBN} does not fit into some more
21088 specific category, then the generated exception will have this type.
21090 @item gdb.MemoryError
21091 This is a subclass of @code{gdb.error} which is thrown when an
21092 operation tried to access invalid memory in the inferior.
21094 @item KeyboardInterrupt
21095 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21096 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21099 In all cases, your exception handler will see the @value{GDBN} error
21100 message as its value and the Python call stack backtrace at the Python
21101 statement closest to where the @value{GDBN} error occured as the
21104 @findex gdb.GdbError
21105 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21106 it is useful to be able to throw an exception that doesn't cause a
21107 traceback to be printed. For example, the user may have invoked the
21108 command incorrectly. Use the @code{gdb.GdbError} exception
21109 to handle this case. Example:
21113 >class HelloWorld (gdb.Command):
21114 > """Greet the whole world."""
21115 > def __init__ (self):
21116 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21117 > def invoke (self, args, from_tty):
21118 > argv = gdb.string_to_argv (args)
21119 > if len (argv) != 0:
21120 > raise gdb.GdbError ("hello-world takes no arguments")
21121 > print "Hello, World!"
21124 (gdb) hello-world 42
21125 hello-world takes no arguments
21128 @node Values From Inferior
21129 @subsubsection Values From Inferior
21130 @cindex values from inferior, with Python
21131 @cindex python, working with values from inferior
21133 @cindex @code{gdb.Value}
21134 @value{GDBN} provides values it obtains from the inferior program in
21135 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21136 for its internal bookkeeping of the inferior's values, and for
21137 fetching values when necessary.
21139 Inferior values that are simple scalars can be used directly in
21140 Python expressions that are valid for the value's data type. Here's
21141 an example for an integer or floating-point value @code{some_val}:
21148 As result of this, @code{bar} will also be a @code{gdb.Value} object
21149 whose values are of the same type as those of @code{some_val}.
21151 Inferior values that are structures or instances of some class can
21152 be accessed using the Python @dfn{dictionary syntax}. For example, if
21153 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21154 can access its @code{foo} element with:
21157 bar = some_val['foo']
21160 Again, @code{bar} will also be a @code{gdb.Value} object.
21162 A @code{gdb.Value} that represents a function can be executed via
21163 inferior function call. Any arguments provided to the call must match
21164 the function's prototype, and must be provided in the order specified
21167 For example, @code{some_val} is a @code{gdb.Value} instance
21168 representing a function that takes two integers as arguments. To
21169 execute this function, call it like so:
21172 result = some_val (10,20)
21175 Any values returned from a function call will be stored as a
21178 The following attributes are provided:
21181 @defivar Value address
21182 If this object is addressable, this read-only attribute holds a
21183 @code{gdb.Value} object representing the address. Otherwise,
21184 this attribute holds @code{None}.
21187 @cindex optimized out value in Python
21188 @defivar Value is_optimized_out
21189 This read-only boolean attribute is true if the compiler optimized out
21190 this value, thus it is not available for fetching from the inferior.
21193 @defivar Value type
21194 The type of this @code{gdb.Value}. The value of this attribute is a
21195 @code{gdb.Type} object (@pxref{Types In Python}).
21198 @defivar Value dynamic_type
21199 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21200 type information (@acronym{RTTI}) to determine the dynamic type of the
21201 value. If this value is of class type, it will return the class in
21202 which the value is embedded, if any. If this value is of pointer or
21203 reference to a class type, it will compute the dynamic type of the
21204 referenced object, and return a pointer or reference to that type,
21205 respectively. In all other cases, it will return the value's static
21208 Note that this feature will only work when debugging a C@t{++} program
21209 that includes @acronym{RTTI} for the object in question. Otherwise,
21210 it will just return the static type of the value as in @kbd{ptype foo}
21211 (@pxref{Symbols, ptype}).
21215 The following methods are provided:
21218 @defmethod Value __init__ @var{val}
21219 Many Python values can be converted directly to a @code{gdb.Value} via
21220 this object initializer. Specifically:
21223 @item Python boolean
21224 A Python boolean is converted to the boolean type from the current
21227 @item Python integer
21228 A Python integer is converted to the C @code{long} type for the
21229 current architecture.
21232 A Python long is converted to the C @code{long long} type for the
21233 current architecture.
21236 A Python float is converted to the C @code{double} type for the
21237 current architecture.
21239 @item Python string
21240 A Python string is converted to a target string, using the current
21243 @item @code{gdb.Value}
21244 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21246 @item @code{gdb.LazyString}
21247 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21248 Python}), then the lazy string's @code{value} method is called, and
21249 its result is used.
21253 @defmethod Value cast type
21254 Return a new instance of @code{gdb.Value} that is the result of
21255 casting this instance to the type described by @var{type}, which must
21256 be a @code{gdb.Type} object. If the cast cannot be performed for some
21257 reason, this method throws an exception.
21260 @defmethod Value dereference
21261 For pointer data types, this method returns a new @code{gdb.Value} object
21262 whose contents is the object pointed to by the pointer. For example, if
21263 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21270 then you can use the corresponding @code{gdb.Value} to access what
21271 @code{foo} points to like this:
21274 bar = foo.dereference ()
21277 The result @code{bar} will be a @code{gdb.Value} object holding the
21278 value pointed to by @code{foo}.
21281 @defmethod Value dynamic_cast type
21282 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21283 operator were used. Consult a C@t{++} reference for details.
21286 @defmethod Value reinterpret_cast type
21287 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21288 operator were used. Consult a C@t{++} reference for details.
21291 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21292 If this @code{gdb.Value} represents a string, then this method
21293 converts the contents to a Python string. Otherwise, this method will
21294 throw an exception.
21296 Strings are recognized in a language-specific way; whether a given
21297 @code{gdb.Value} represents a string is determined by the current
21300 For C-like languages, a value is a string if it is a pointer to or an
21301 array of characters or ints. The string is assumed to be terminated
21302 by a zero of the appropriate width. However if the optional length
21303 argument is given, the string will be converted to that given length,
21304 ignoring any embedded zeros that the string may contain.
21306 If the optional @var{encoding} argument is given, it must be a string
21307 naming the encoding of the string in the @code{gdb.Value}, such as
21308 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21309 the same encodings as the corresponding argument to Python's
21310 @code{string.decode} method, and the Python codec machinery will be used
21311 to convert the string. If @var{encoding} is not given, or if
21312 @var{encoding} is the empty string, then either the @code{target-charset}
21313 (@pxref{Character Sets}) will be used, or a language-specific encoding
21314 will be used, if the current language is able to supply one.
21316 The optional @var{errors} argument is the same as the corresponding
21317 argument to Python's @code{string.decode} method.
21319 If the optional @var{length} argument is given, the string will be
21320 fetched and converted to the given length.
21323 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21324 If this @code{gdb.Value} represents a string, then this method
21325 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21326 In Python}). Otherwise, this method will throw an exception.
21328 If the optional @var{encoding} argument is given, it must be a string
21329 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21330 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21331 @var{encoding} argument is an encoding that @value{GDBN} does
21332 recognize, @value{GDBN} will raise an error.
21334 When a lazy string is printed, the @value{GDBN} encoding machinery is
21335 used to convert the string during printing. If the optional
21336 @var{encoding} argument is not provided, or is an empty string,
21337 @value{GDBN} will automatically select the encoding most suitable for
21338 the string type. For further information on encoding in @value{GDBN}
21339 please see @ref{Character Sets}.
21341 If the optional @var{length} argument is given, the string will be
21342 fetched and encoded to the length of characters specified. If
21343 the @var{length} argument is not provided, the string will be fetched
21344 and encoded until a null of appropriate width is found.
21348 @node Types In Python
21349 @subsubsection Types In Python
21350 @cindex types in Python
21351 @cindex Python, working with types
21354 @value{GDBN} represents types from the inferior using the class
21357 The following type-related functions are available in the @code{gdb}
21360 @findex gdb.lookup_type
21361 @defun lookup_type name [block]
21362 This function looks up a type by name. @var{name} is the name of the
21363 type to look up. It must be a string.
21365 If @var{block} is given, then @var{name} is looked up in that scope.
21366 Otherwise, it is searched for globally.
21368 Ordinarily, this function will return an instance of @code{gdb.Type}.
21369 If the named type cannot be found, it will throw an exception.
21372 An instance of @code{Type} has the following attributes:
21376 The type code for this type. The type code will be one of the
21377 @code{TYPE_CODE_} constants defined below.
21380 @defivar Type sizeof
21381 The size of this type, in target @code{char} units. Usually, a
21382 target's @code{char} type will be an 8-bit byte. However, on some
21383 unusual platforms, this type may have a different size.
21387 The tag name for this type. The tag name is the name after
21388 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21389 languages have this concept. If this type has no tag name, then
21390 @code{None} is returned.
21394 The following methods are provided:
21397 @defmethod Type fields
21398 For structure and union types, this method returns the fields. Range
21399 types have two fields, the minimum and maximum values. Enum types
21400 have one field per enum constant. Function and method types have one
21401 field per parameter. The base types of C@t{++} classes are also
21402 represented as fields. If the type has no fields, or does not fit
21403 into one of these categories, an empty sequence will be returned.
21405 Each field is an object, with some pre-defined attributes:
21408 This attribute is not available for @code{static} fields (as in
21409 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21410 position of the field.
21413 The name of the field, or @code{None} for anonymous fields.
21416 This is @code{True} if the field is artificial, usually meaning that
21417 it was provided by the compiler and not the user. This attribute is
21418 always provided, and is @code{False} if the field is not artificial.
21420 @item is_base_class
21421 This is @code{True} if the field represents a base class of a C@t{++}
21422 structure. This attribute is always provided, and is @code{False}
21423 if the field is not a base class of the type that is the argument of
21424 @code{fields}, or if that type was not a C@t{++} class.
21427 If the field is packed, or is a bitfield, then this will have a
21428 non-zero value, which is the size of the field in bits. Otherwise,
21429 this will be zero; in this case the field's size is given by its type.
21432 The type of the field. This is usually an instance of @code{Type},
21433 but it can be @code{None} in some situations.
21437 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21438 Return a new @code{gdb.Type} object which represents an array of this
21439 type. If one argument is given, it is the inclusive upper bound of
21440 the array; in this case the lower bound is zero. If two arguments are
21441 given, the first argument is the lower bound of the array, and the
21442 second argument is the upper bound of the array. An array's length
21443 must not be negative, but the bounds can be.
21446 @defmethod Type const
21447 Return a new @code{gdb.Type} object which represents a
21448 @code{const}-qualified variant of this type.
21451 @defmethod Type volatile
21452 Return a new @code{gdb.Type} object which represents a
21453 @code{volatile}-qualified variant of this type.
21456 @defmethod Type unqualified
21457 Return a new @code{gdb.Type} object which represents an unqualified
21458 variant of this type. That is, the result is neither @code{const} nor
21462 @defmethod Type range
21463 Return a Python @code{Tuple} object that contains two elements: the
21464 low bound of the argument type and the high bound of that type. If
21465 the type does not have a range, @value{GDBN} will raise a
21466 @code{gdb.error} exception (@pxref{Exception Handling}).
21469 @defmethod Type reference
21470 Return a new @code{gdb.Type} object which represents a reference to this
21474 @defmethod Type pointer
21475 Return a new @code{gdb.Type} object which represents a pointer to this
21479 @defmethod Type strip_typedefs
21480 Return a new @code{gdb.Type} that represents the real type,
21481 after removing all layers of typedefs.
21484 @defmethod Type target
21485 Return a new @code{gdb.Type} object which represents the target type
21488 For a pointer type, the target type is the type of the pointed-to
21489 object. For an array type (meaning C-like arrays), the target type is
21490 the type of the elements of the array. For a function or method type,
21491 the target type is the type of the return value. For a complex type,
21492 the target type is the type of the elements. For a typedef, the
21493 target type is the aliased type.
21495 If the type does not have a target, this method will throw an
21499 @defmethod Type template_argument n [block]
21500 If this @code{gdb.Type} is an instantiation of a template, this will
21501 return a new @code{gdb.Type} which represents the type of the
21502 @var{n}th template argument.
21504 If this @code{gdb.Type} is not a template type, this will throw an
21505 exception. Ordinarily, only C@t{++} code will have template types.
21507 If @var{block} is given, then @var{name} is looked up in that scope.
21508 Otherwise, it is searched for globally.
21513 Each type has a code, which indicates what category this type falls
21514 into. The available type categories are represented by constants
21515 defined in the @code{gdb} module:
21518 @findex TYPE_CODE_PTR
21519 @findex gdb.TYPE_CODE_PTR
21520 @item TYPE_CODE_PTR
21521 The type is a pointer.
21523 @findex TYPE_CODE_ARRAY
21524 @findex gdb.TYPE_CODE_ARRAY
21525 @item TYPE_CODE_ARRAY
21526 The type is an array.
21528 @findex TYPE_CODE_STRUCT
21529 @findex gdb.TYPE_CODE_STRUCT
21530 @item TYPE_CODE_STRUCT
21531 The type is a structure.
21533 @findex TYPE_CODE_UNION
21534 @findex gdb.TYPE_CODE_UNION
21535 @item TYPE_CODE_UNION
21536 The type is a union.
21538 @findex TYPE_CODE_ENUM
21539 @findex gdb.TYPE_CODE_ENUM
21540 @item TYPE_CODE_ENUM
21541 The type is an enum.
21543 @findex TYPE_CODE_FLAGS
21544 @findex gdb.TYPE_CODE_FLAGS
21545 @item TYPE_CODE_FLAGS
21546 A bit flags type, used for things such as status registers.
21548 @findex TYPE_CODE_FUNC
21549 @findex gdb.TYPE_CODE_FUNC
21550 @item TYPE_CODE_FUNC
21551 The type is a function.
21553 @findex TYPE_CODE_INT
21554 @findex gdb.TYPE_CODE_INT
21555 @item TYPE_CODE_INT
21556 The type is an integer type.
21558 @findex TYPE_CODE_FLT
21559 @findex gdb.TYPE_CODE_FLT
21560 @item TYPE_CODE_FLT
21561 A floating point type.
21563 @findex TYPE_CODE_VOID
21564 @findex gdb.TYPE_CODE_VOID
21565 @item TYPE_CODE_VOID
21566 The special type @code{void}.
21568 @findex TYPE_CODE_SET
21569 @findex gdb.TYPE_CODE_SET
21570 @item TYPE_CODE_SET
21573 @findex TYPE_CODE_RANGE
21574 @findex gdb.TYPE_CODE_RANGE
21575 @item TYPE_CODE_RANGE
21576 A range type, that is, an integer type with bounds.
21578 @findex TYPE_CODE_STRING
21579 @findex gdb.TYPE_CODE_STRING
21580 @item TYPE_CODE_STRING
21581 A string type. Note that this is only used for certain languages with
21582 language-defined string types; C strings are not represented this way.
21584 @findex TYPE_CODE_BITSTRING
21585 @findex gdb.TYPE_CODE_BITSTRING
21586 @item TYPE_CODE_BITSTRING
21589 @findex TYPE_CODE_ERROR
21590 @findex gdb.TYPE_CODE_ERROR
21591 @item TYPE_CODE_ERROR
21592 An unknown or erroneous type.
21594 @findex TYPE_CODE_METHOD
21595 @findex gdb.TYPE_CODE_METHOD
21596 @item TYPE_CODE_METHOD
21597 A method type, as found in C@t{++} or Java.
21599 @findex TYPE_CODE_METHODPTR
21600 @findex gdb.TYPE_CODE_METHODPTR
21601 @item TYPE_CODE_METHODPTR
21602 A pointer-to-member-function.
21604 @findex TYPE_CODE_MEMBERPTR
21605 @findex gdb.TYPE_CODE_MEMBERPTR
21606 @item TYPE_CODE_MEMBERPTR
21607 A pointer-to-member.
21609 @findex TYPE_CODE_REF
21610 @findex gdb.TYPE_CODE_REF
21611 @item TYPE_CODE_REF
21614 @findex TYPE_CODE_CHAR
21615 @findex gdb.TYPE_CODE_CHAR
21616 @item TYPE_CODE_CHAR
21619 @findex TYPE_CODE_BOOL
21620 @findex gdb.TYPE_CODE_BOOL
21621 @item TYPE_CODE_BOOL
21624 @findex TYPE_CODE_COMPLEX
21625 @findex gdb.TYPE_CODE_COMPLEX
21626 @item TYPE_CODE_COMPLEX
21627 A complex float type.
21629 @findex TYPE_CODE_TYPEDEF
21630 @findex gdb.TYPE_CODE_TYPEDEF
21631 @item TYPE_CODE_TYPEDEF
21632 A typedef to some other type.
21634 @findex TYPE_CODE_NAMESPACE
21635 @findex gdb.TYPE_CODE_NAMESPACE
21636 @item TYPE_CODE_NAMESPACE
21637 A C@t{++} namespace.
21639 @findex TYPE_CODE_DECFLOAT
21640 @findex gdb.TYPE_CODE_DECFLOAT
21641 @item TYPE_CODE_DECFLOAT
21642 A decimal floating point type.
21644 @findex TYPE_CODE_INTERNAL_FUNCTION
21645 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21646 @item TYPE_CODE_INTERNAL_FUNCTION
21647 A function internal to @value{GDBN}. This is the type used to represent
21648 convenience functions.
21651 Further support for types is provided in the @code{gdb.types}
21652 Python module (@pxref{gdb.types}).
21654 @node Pretty Printing API
21655 @subsubsection Pretty Printing API
21657 An example output is provided (@pxref{Pretty Printing}).
21659 A pretty-printer is just an object that holds a value and implements a
21660 specific interface, defined here.
21662 @defop Operation {pretty printer} children (self)
21663 @value{GDBN} will call this method on a pretty-printer to compute the
21664 children of the pretty-printer's value.
21666 This method must return an object conforming to the Python iterator
21667 protocol. Each item returned by the iterator must be a tuple holding
21668 two elements. The first element is the ``name'' of the child; the
21669 second element is the child's value. The value can be any Python
21670 object which is convertible to a @value{GDBN} value.
21672 This method is optional. If it does not exist, @value{GDBN} will act
21673 as though the value has no children.
21676 @defop Operation {pretty printer} display_hint (self)
21677 The CLI may call this method and use its result to change the
21678 formatting of a value. The result will also be supplied to an MI
21679 consumer as a @samp{displayhint} attribute of the variable being
21682 This method is optional. If it does exist, this method must return a
21685 Some display hints are predefined by @value{GDBN}:
21689 Indicate that the object being printed is ``array-like''. The CLI
21690 uses this to respect parameters such as @code{set print elements} and
21691 @code{set print array}.
21694 Indicate that the object being printed is ``map-like'', and that the
21695 children of this value can be assumed to alternate between keys and
21699 Indicate that the object being printed is ``string-like''. If the
21700 printer's @code{to_string} method returns a Python string of some
21701 kind, then @value{GDBN} will call its internal language-specific
21702 string-printing function to format the string. For the CLI this means
21703 adding quotation marks, possibly escaping some characters, respecting
21704 @code{set print elements}, and the like.
21708 @defop Operation {pretty printer} to_string (self)
21709 @value{GDBN} will call this method to display the string
21710 representation of the value passed to the object's constructor.
21712 When printing from the CLI, if the @code{to_string} method exists,
21713 then @value{GDBN} will prepend its result to the values returned by
21714 @code{children}. Exactly how this formatting is done is dependent on
21715 the display hint, and may change as more hints are added. Also,
21716 depending on the print settings (@pxref{Print Settings}), the CLI may
21717 print just the result of @code{to_string} in a stack trace, omitting
21718 the result of @code{children}.
21720 If this method returns a string, it is printed verbatim.
21722 Otherwise, if this method returns an instance of @code{gdb.Value},
21723 then @value{GDBN} prints this value. This may result in a call to
21724 another pretty-printer.
21726 If instead the method returns a Python value which is convertible to a
21727 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21728 the resulting value. Again, this may result in a call to another
21729 pretty-printer. Python scalars (integers, floats, and booleans) and
21730 strings are convertible to @code{gdb.Value}; other types are not.
21732 Finally, if this method returns @code{None} then no further operations
21733 are peformed in this method and nothing is printed.
21735 If the result is not one of these types, an exception is raised.
21738 @value{GDBN} provides a function which can be used to look up the
21739 default pretty-printer for a @code{gdb.Value}:
21741 @findex gdb.default_visualizer
21742 @defun default_visualizer value
21743 This function takes a @code{gdb.Value} object as an argument. If a
21744 pretty-printer for this value exists, then it is returned. If no such
21745 printer exists, then this returns @code{None}.
21748 @node Selecting Pretty-Printers
21749 @subsubsection Selecting Pretty-Printers
21751 The Python list @code{gdb.pretty_printers} contains an array of
21752 functions or callable objects that have been registered via addition
21753 as a pretty-printer. Printers in this list are called @code{global}
21754 printers, they're available when debugging all inferiors.
21755 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21756 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21759 Each function on these lists is passed a single @code{gdb.Value}
21760 argument and should return a pretty-printer object conforming to the
21761 interface definition above (@pxref{Pretty Printing API}). If a function
21762 cannot create a pretty-printer for the value, it should return
21765 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21766 @code{gdb.Objfile} in the current program space and iteratively calls
21767 each enabled lookup routine in the list for that @code{gdb.Objfile}
21768 until it receives a pretty-printer object.
21769 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21770 searches the pretty-printer list of the current program space,
21771 calling each enabled function until an object is returned.
21772 After these lists have been exhausted, it tries the global
21773 @code{gdb.pretty_printers} list, again calling each enabled function until an
21774 object is returned.
21776 The order in which the objfiles are searched is not specified. For a
21777 given list, functions are always invoked from the head of the list,
21778 and iterated over sequentially until the end of the list, or a printer
21779 object is returned.
21781 For various reasons a pretty-printer may not work.
21782 For example, the underlying data structure may have changed and
21783 the pretty-printer is out of date.
21785 The consequences of a broken pretty-printer are severe enough that
21786 @value{GDBN} provides support for enabling and disabling individual
21787 printers. For example, if @code{print frame-arguments} is on,
21788 a backtrace can become highly illegible if any argument is printed
21789 with a broken printer.
21791 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21792 attribute to the registered function or callable object. If this attribute
21793 is present and its value is @code{False}, the printer is disabled, otherwise
21794 the printer is enabled.
21796 @node Writing a Pretty-Printer
21797 @subsubsection Writing a Pretty-Printer
21798 @cindex writing a pretty-printer
21800 A pretty-printer consists of two parts: a lookup function to detect
21801 if the type is supported, and the printer itself.
21803 Here is an example showing how a @code{std::string} printer might be
21804 written. @xref{Pretty Printing API}, for details on the API this class
21808 class StdStringPrinter(object):
21809 "Print a std::string"
21811 def __init__(self, val):
21814 def to_string(self):
21815 return self.val['_M_dataplus']['_M_p']
21817 def display_hint(self):
21821 And here is an example showing how a lookup function for the printer
21822 example above might be written.
21825 def str_lookup_function(val):
21826 lookup_tag = val.type.tag
21827 if lookup_tag == None:
21829 regex = re.compile("^std::basic_string<char,.*>$")
21830 if regex.match(lookup_tag):
21831 return StdStringPrinter(val)
21835 The example lookup function extracts the value's type, and attempts to
21836 match it to a type that it can pretty-print. If it is a type the
21837 printer can pretty-print, it will return a printer object. If not, it
21838 returns @code{None}.
21840 We recommend that you put your core pretty-printers into a Python
21841 package. If your pretty-printers are for use with a library, we
21842 further recommend embedding a version number into the package name.
21843 This practice will enable @value{GDBN} to load multiple versions of
21844 your pretty-printers at the same time, because they will have
21847 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21848 can be evaluated multiple times without changing its meaning. An
21849 ideal auto-load file will consist solely of @code{import}s of your
21850 printer modules, followed by a call to a register pretty-printers with
21851 the current objfile.
21853 Taken as a whole, this approach will scale nicely to multiple
21854 inferiors, each potentially using a different library version.
21855 Embedding a version number in the Python package name will ensure that
21856 @value{GDBN} is able to load both sets of printers simultaneously.
21857 Then, because the search for pretty-printers is done by objfile, and
21858 because your auto-loaded code took care to register your library's
21859 printers with a specific objfile, @value{GDBN} will find the correct
21860 printers for the specific version of the library used by each
21863 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21864 this code might appear in @code{gdb.libstdcxx.v6}:
21867 def register_printers(objfile):
21868 objfile.pretty_printers.add(str_lookup_function)
21872 And then the corresponding contents of the auto-load file would be:
21875 import gdb.libstdcxx.v6
21876 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21879 The previous example illustrates a basic pretty-printer.
21880 There are a few things that can be improved on.
21881 The printer doesn't have a name, making it hard to identify in a
21882 list of installed printers. The lookup function has a name, but
21883 lookup functions can have arbitrary, even identical, names.
21885 Second, the printer only handles one type, whereas a library typically has
21886 several types. One could install a lookup function for each desired type
21887 in the library, but one could also have a single lookup function recognize
21888 several types. The latter is the conventional way this is handled.
21889 If a pretty-printer can handle multiple data types, then its
21890 @dfn{subprinters} are the printers for the individual data types.
21892 The @code{gdb.printing} module provides a formal way of solving these
21893 problems (@pxref{gdb.printing}).
21894 Here is another example that handles multiple types.
21896 These are the types we are going to pretty-print:
21899 struct foo @{ int a, b; @};
21900 struct bar @{ struct foo x, y; @};
21903 Here are the printers:
21907 """Print a foo object."""
21909 def __init__(self, val):
21912 def to_string(self):
21913 return ("a=<" + str(self.val["a"]) +
21914 "> b=<" + str(self.val["b"]) + ">")
21917 """Print a bar object."""
21919 def __init__(self, val):
21922 def to_string(self):
21923 return ("x=<" + str(self.val["x"]) +
21924 "> y=<" + str(self.val["y"]) + ">")
21927 This example doesn't need a lookup function, that is handled by the
21928 @code{gdb.printing} module. Instead a function is provided to build up
21929 the object that handles the lookup.
21932 import gdb.printing
21934 def build_pretty_printer():
21935 pp = gdb.printing.RegexpCollectionPrettyPrinter(
21937 pp.add_printer('foo', '^foo$', fooPrinter)
21938 pp.add_printer('bar', '^bar$', barPrinter)
21942 And here is the autoload support:
21945 import gdb.printing
21947 gdb.printing.register_pretty_printer(
21948 gdb.current_objfile(),
21949 my_library.build_pretty_printer())
21952 Finally, when this printer is loaded into @value{GDBN}, here is the
21953 corresponding output of @samp{info pretty-printer}:
21956 (gdb) info pretty-printer
21963 @node Inferiors In Python
21964 @subsubsection Inferiors In Python
21965 @cindex inferiors in Python
21967 @findex gdb.Inferior
21968 Programs which are being run under @value{GDBN} are called inferiors
21969 (@pxref{Inferiors and Programs}). Python scripts can access
21970 information about and manipulate inferiors controlled by @value{GDBN}
21971 via objects of the @code{gdb.Inferior} class.
21973 The following inferior-related functions are available in the @code{gdb}
21977 Return a tuple containing all inferior objects.
21980 A @code{gdb.Inferior} object has the following attributes:
21983 @defivar Inferior num
21984 ID of inferior, as assigned by GDB.
21987 @defivar Inferior pid
21988 Process ID of the inferior, as assigned by the underlying operating
21992 @defivar Inferior was_attached
21993 Boolean signaling whether the inferior was created using `attach', or
21994 started by @value{GDBN} itself.
21998 A @code{gdb.Inferior} object has the following methods:
22001 @defmethod Inferior is_valid
22002 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22003 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22004 if the inferior no longer exists within @value{GDBN}. All other
22005 @code{gdb.Inferior} methods will throw an exception if it is invalid
22006 at the time the method is called.
22009 @defmethod Inferior threads
22010 This method returns a tuple holding all the threads which are valid
22011 when it is called. If there are no valid threads, the method will
22012 return an empty tuple.
22015 @findex gdb.read_memory
22016 @defmethod Inferior read_memory address length
22017 Read @var{length} bytes of memory from the inferior, starting at
22018 @var{address}. Returns a buffer object, which behaves much like an array
22019 or a string. It can be modified and given to the @code{gdb.write_memory}
22023 @findex gdb.write_memory
22024 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
22025 Write the contents of @var{buffer} to the inferior, starting at
22026 @var{address}. The @var{buffer} parameter must be a Python object
22027 which supports the buffer protocol, i.e., a string, an array or the
22028 object returned from @code{gdb.read_memory}. If given, @var{length}
22029 determines the number of bytes from @var{buffer} to be written.
22032 @findex gdb.search_memory
22033 @defmethod Inferior search_memory address length pattern
22034 Search a region of the inferior memory starting at @var{address} with
22035 the given @var{length} using the search pattern supplied in
22036 @var{pattern}. The @var{pattern} parameter must be a Python object
22037 which supports the buffer protocol, i.e., a string, an array or the
22038 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22039 containing the address where the pattern was found, or @code{None} if
22040 the pattern could not be found.
22044 @node Events In Python
22045 @subsubsection Events In Python
22046 @cindex inferior events in Python
22048 @value{GDBN} provides a general event facility so that Python code can be
22049 notified of various state changes, particularly changes that occur in
22052 An @dfn{event} is just an object that describes some state change. The
22053 type of the object and its attributes will vary depending on the details
22054 of the change. All the existing events are described below.
22056 In order to be notified of an event, you must register an event handler
22057 with an @dfn{event registry}. An event registry is an object in the
22058 @code{gdb.events} module which dispatches particular events. A registry
22059 provides methods to register and unregister event handlers:
22062 @defmethod EventRegistry connect object
22063 Add the given callable @var{object} to the registry. This object will be
22064 called when an event corresponding to this registry occurs.
22067 @defmethod EventRegistry disconnect object
22068 Remove the given @var{object} from the registry. Once removed, the object
22069 will no longer receive notifications of events.
22073 Here is an example:
22076 def exit_handler (event):
22077 print "event type: exit"
22078 print "exit code: %d" % (event.exit_code)
22080 gdb.events.exited.connect (exit_handler)
22083 In the above example we connect our handler @code{exit_handler} to the
22084 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22085 called when the inferior exits. The argument @dfn{event} in this example is
22086 of type @code{gdb.ExitedEvent}. As you can see in the example the
22087 @code{ExitedEvent} object has an attribute which indicates the exit code of
22090 The following is a listing of the event registries that are available and
22091 details of the events they emit:
22096 Emits @code{gdb.ThreadEvent}.
22098 Some events can be thread specific when @value{GDBN} is running in non-stop
22099 mode. When represented in Python, these events all extend
22100 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22101 events which are emitted by this or other modules might extend this event.
22102 Examples of these events are @code{gdb.BreakpointEvent} and
22103 @code{gdb.ContinueEvent}.
22106 @defivar ThreadEvent inferior_thread
22107 In non-stop mode this attribute will be set to the specific thread which was
22108 involved in the emitted event. Otherwise, it will be set to @code{None}.
22112 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22114 This event indicates that the inferior has been continued after a stop. For
22115 inherited attribute refer to @code{gdb.ThreadEvent} above.
22117 @item events.exited
22118 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22119 @code{events.ExitedEvent} has one attribute:
22121 @defivar ExitedEvent exit_code
22122 An integer representing the exit code which the inferior has returned.
22127 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22129 Indicates that the inferior has stopped. All events emitted by this registry
22130 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22131 will indicate the stopped thread when @value{GDBN} is running in non-stop
22132 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22134 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22136 This event indicates that the inferior or one of its threads has received as
22137 signal. @code{gdb.SignalEvent} has the following attributes:
22140 @defivar SignalEvent stop_signal
22141 A string representing the signal received by the inferior. A list of possible
22142 signal values can be obtained by running the command @code{info signals} in
22143 the @value{GDBN} command prompt.
22147 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22149 @code{gdb.BreakpointEvent} event indicates that a breakpoint has been hit, and
22150 has the following attributes:
22153 @defivar BreakpointEvent breakpoint
22154 A reference to the breakpoint that was hit of type @code{gdb.Breakpoint}.
22155 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22161 @node Threads In Python
22162 @subsubsection Threads In Python
22163 @cindex threads in python
22165 @findex gdb.InferiorThread
22166 Python scripts can access information about, and manipulate inferior threads
22167 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22169 The following thread-related functions are available in the @code{gdb}
22172 @findex gdb.selected_thread
22173 @defun selected_thread
22174 This function returns the thread object for the selected thread. If there
22175 is no selected thread, this will return @code{None}.
22178 A @code{gdb.InferiorThread} object has the following attributes:
22181 @defivar InferiorThread name
22182 The name of the thread. If the user specified a name using
22183 @code{thread name}, then this returns that name. Otherwise, if an
22184 OS-supplied name is available, then it is returned. Otherwise, this
22185 returns @code{None}.
22187 This attribute can be assigned to. The new value must be a string
22188 object, which sets the new name, or @code{None}, which removes any
22189 user-specified thread name.
22192 @defivar InferiorThread num
22193 ID of the thread, as assigned by GDB.
22196 @defivar InferiorThread ptid
22197 ID of the thread, as assigned by the operating system. This attribute is a
22198 tuple containing three integers. The first is the Process ID (PID); the second
22199 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22200 Either the LWPID or TID may be 0, which indicates that the operating system
22201 does not use that identifier.
22205 A @code{gdb.InferiorThread} object has the following methods:
22208 @defmethod InferiorThread is_valid
22209 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22210 @code{False} if not. A @code{gdb.InferiorThread} object will become
22211 invalid if the thread exits, or the inferior that the thread belongs
22212 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22213 exception if it is invalid at the time the method is called.
22216 @defmethod InferiorThread switch
22217 This changes @value{GDBN}'s currently selected thread to the one represented
22221 @defmethod InferiorThread is_stopped
22222 Return a Boolean indicating whether the thread is stopped.
22225 @defmethod InferiorThread is_running
22226 Return a Boolean indicating whether the thread is running.
22229 @defmethod InferiorThread is_exited
22230 Return a Boolean indicating whether the thread is exited.
22234 @node Commands In Python
22235 @subsubsection Commands In Python
22237 @cindex commands in python
22238 @cindex python commands
22239 You can implement new @value{GDBN} CLI commands in Python. A CLI
22240 command is implemented using an instance of the @code{gdb.Command}
22241 class, most commonly using a subclass.
22243 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
22244 The object initializer for @code{Command} registers the new command
22245 with @value{GDBN}. This initializer is normally invoked from the
22246 subclass' own @code{__init__} method.
22248 @var{name} is the name of the command. If @var{name} consists of
22249 multiple words, then the initial words are looked for as prefix
22250 commands. In this case, if one of the prefix commands does not exist,
22251 an exception is raised.
22253 There is no support for multi-line commands.
22255 @var{command_class} should be one of the @samp{COMMAND_} constants
22256 defined below. This argument tells @value{GDBN} how to categorize the
22257 new command in the help system.
22259 @var{completer_class} is an optional argument. If given, it should be
22260 one of the @samp{COMPLETE_} constants defined below. This argument
22261 tells @value{GDBN} how to perform completion for this command. If not
22262 given, @value{GDBN} will attempt to complete using the object's
22263 @code{complete} method (see below); if no such method is found, an
22264 error will occur when completion is attempted.
22266 @var{prefix} is an optional argument. If @code{True}, then the new
22267 command is a prefix command; sub-commands of this command may be
22270 The help text for the new command is taken from the Python
22271 documentation string for the command's class, if there is one. If no
22272 documentation string is provided, the default value ``This command is
22273 not documented.'' is used.
22276 @cindex don't repeat Python command
22277 @defmethod Command dont_repeat
22278 By default, a @value{GDBN} command is repeated when the user enters a
22279 blank line at the command prompt. A command can suppress this
22280 behavior by invoking the @code{dont_repeat} method. This is similar
22281 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22284 @defmethod Command invoke argument from_tty
22285 This method is called by @value{GDBN} when this command is invoked.
22287 @var{argument} is a string. It is the argument to the command, after
22288 leading and trailing whitespace has been stripped.
22290 @var{from_tty} is a boolean argument. When true, this means that the
22291 command was entered by the user at the terminal; when false it means
22292 that the command came from elsewhere.
22294 If this method throws an exception, it is turned into a @value{GDBN}
22295 @code{error} call. Otherwise, the return value is ignored.
22297 @findex gdb.string_to_argv
22298 To break @var{argument} up into an argv-like string use
22299 @code{gdb.string_to_argv}. This function behaves identically to
22300 @value{GDBN}'s internal argument lexer @code{buildargv}.
22301 It is recommended to use this for consistency.
22302 Arguments are separated by spaces and may be quoted.
22306 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22307 ['1', '2 "3', '4 "5', "6 '7"]
22312 @cindex completion of Python commands
22313 @defmethod Command complete text word
22314 This method is called by @value{GDBN} when the user attempts
22315 completion on this command. All forms of completion are handled by
22316 this method, that is, the @key{TAB} and @key{M-?} key bindings
22317 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22320 The arguments @var{text} and @var{word} are both strings. @var{text}
22321 holds the complete command line up to the cursor's location.
22322 @var{word} holds the last word of the command line; this is computed
22323 using a word-breaking heuristic.
22325 The @code{complete} method can return several values:
22328 If the return value is a sequence, the contents of the sequence are
22329 used as the completions. It is up to @code{complete} to ensure that the
22330 contents actually do complete the word. A zero-length sequence is
22331 allowed, it means that there were no completions available. Only
22332 string elements of the sequence are used; other elements in the
22333 sequence are ignored.
22336 If the return value is one of the @samp{COMPLETE_} constants defined
22337 below, then the corresponding @value{GDBN}-internal completion
22338 function is invoked, and its result is used.
22341 All other results are treated as though there were no available
22346 When a new command is registered, it must be declared as a member of
22347 some general class of commands. This is used to classify top-level
22348 commands in the on-line help system; note that prefix commands are not
22349 listed under their own category but rather that of their top-level
22350 command. The available classifications are represented by constants
22351 defined in the @code{gdb} module:
22354 @findex COMMAND_NONE
22355 @findex gdb.COMMAND_NONE
22357 The command does not belong to any particular class. A command in
22358 this category will not be displayed in any of the help categories.
22360 @findex COMMAND_RUNNING
22361 @findex gdb.COMMAND_RUNNING
22362 @item COMMAND_RUNNING
22363 The command is related to running the inferior. For example,
22364 @code{start}, @code{step}, and @code{continue} are in this category.
22365 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22366 commands in this category.
22368 @findex COMMAND_DATA
22369 @findex gdb.COMMAND_DATA
22371 The command is related to data or variables. For example,
22372 @code{call}, @code{find}, and @code{print} are in this category. Type
22373 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22376 @findex COMMAND_STACK
22377 @findex gdb.COMMAND_STACK
22378 @item COMMAND_STACK
22379 The command has to do with manipulation of the stack. For example,
22380 @code{backtrace}, @code{frame}, and @code{return} are in this
22381 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22382 list of commands in this category.
22384 @findex COMMAND_FILES
22385 @findex gdb.COMMAND_FILES
22386 @item COMMAND_FILES
22387 This class is used for file-related commands. For example,
22388 @code{file}, @code{list} and @code{section} are in this category.
22389 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22390 commands in this category.
22392 @findex COMMAND_SUPPORT
22393 @findex gdb.COMMAND_SUPPORT
22394 @item COMMAND_SUPPORT
22395 This should be used for ``support facilities'', generally meaning
22396 things that are useful to the user when interacting with @value{GDBN},
22397 but not related to the state of the inferior. For example,
22398 @code{help}, @code{make}, and @code{shell} are in this category. Type
22399 @kbd{help support} at the @value{GDBN} prompt to see a list of
22400 commands in this category.
22402 @findex COMMAND_STATUS
22403 @findex gdb.COMMAND_STATUS
22404 @item COMMAND_STATUS
22405 The command is an @samp{info}-related command, that is, related to the
22406 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22407 and @code{show} are in this category. Type @kbd{help status} at the
22408 @value{GDBN} prompt to see a list of commands in this category.
22410 @findex COMMAND_BREAKPOINTS
22411 @findex gdb.COMMAND_BREAKPOINTS
22412 @item COMMAND_BREAKPOINTS
22413 The command has to do with breakpoints. For example, @code{break},
22414 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22415 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22418 @findex COMMAND_TRACEPOINTS
22419 @findex gdb.COMMAND_TRACEPOINTS
22420 @item COMMAND_TRACEPOINTS
22421 The command has to do with tracepoints. For example, @code{trace},
22422 @code{actions}, and @code{tfind} are in this category. Type
22423 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22424 commands in this category.
22426 @findex COMMAND_OBSCURE
22427 @findex gdb.COMMAND_OBSCURE
22428 @item COMMAND_OBSCURE
22429 The command is only used in unusual circumstances, or is not of
22430 general interest to users. For example, @code{checkpoint},
22431 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22432 obscure} at the @value{GDBN} prompt to see a list of commands in this
22435 @findex COMMAND_MAINTENANCE
22436 @findex gdb.COMMAND_MAINTENANCE
22437 @item COMMAND_MAINTENANCE
22438 The command is only useful to @value{GDBN} maintainers. The
22439 @code{maintenance} and @code{flushregs} commands are in this category.
22440 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22441 commands in this category.
22444 A new command can use a predefined completion function, either by
22445 specifying it via an argument at initialization, or by returning it
22446 from the @code{complete} method. These predefined completion
22447 constants are all defined in the @code{gdb} module:
22450 @findex COMPLETE_NONE
22451 @findex gdb.COMPLETE_NONE
22452 @item COMPLETE_NONE
22453 This constant means that no completion should be done.
22455 @findex COMPLETE_FILENAME
22456 @findex gdb.COMPLETE_FILENAME
22457 @item COMPLETE_FILENAME
22458 This constant means that filename completion should be performed.
22460 @findex COMPLETE_LOCATION
22461 @findex gdb.COMPLETE_LOCATION
22462 @item COMPLETE_LOCATION
22463 This constant means that location completion should be done.
22464 @xref{Specify Location}.
22466 @findex COMPLETE_COMMAND
22467 @findex gdb.COMPLETE_COMMAND
22468 @item COMPLETE_COMMAND
22469 This constant means that completion should examine @value{GDBN}
22472 @findex COMPLETE_SYMBOL
22473 @findex gdb.COMPLETE_SYMBOL
22474 @item COMPLETE_SYMBOL
22475 This constant means that completion should be done using symbol names
22479 The following code snippet shows how a trivial CLI command can be
22480 implemented in Python:
22483 class HelloWorld (gdb.Command):
22484 """Greet the whole world."""
22486 def __init__ (self):
22487 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22489 def invoke (self, arg, from_tty):
22490 print "Hello, World!"
22495 The last line instantiates the class, and is necessary to trigger the
22496 registration of the command with @value{GDBN}. Depending on how the
22497 Python code is read into @value{GDBN}, you may need to import the
22498 @code{gdb} module explicitly.
22500 @node Parameters In Python
22501 @subsubsection Parameters In Python
22503 @cindex parameters in python
22504 @cindex python parameters
22505 @tindex gdb.Parameter
22507 You can implement new @value{GDBN} parameters using Python. A new
22508 parameter is implemented as an instance of the @code{gdb.Parameter}
22511 Parameters are exposed to the user via the @code{set} and
22512 @code{show} commands. @xref{Help}.
22514 There are many parameters that already exist and can be set in
22515 @value{GDBN}. Two examples are: @code{set follow fork} and
22516 @code{set charset}. Setting these parameters influences certain
22517 behavior in @value{GDBN}. Similarly, you can define parameters that
22518 can be used to influence behavior in custom Python scripts and commands.
22520 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22521 The object initializer for @code{Parameter} registers the new
22522 parameter with @value{GDBN}. This initializer is normally invoked
22523 from the subclass' own @code{__init__} method.
22525 @var{name} is the name of the new parameter. If @var{name} consists
22526 of multiple words, then the initial words are looked for as prefix
22527 parameters. An example of this can be illustrated with the
22528 @code{set print} set of parameters. If @var{name} is
22529 @code{print foo}, then @code{print} will be searched as the prefix
22530 parameter. In this case the parameter can subsequently be accessed in
22531 @value{GDBN} as @code{set print foo}.
22533 If @var{name} consists of multiple words, and no prefix parameter group
22534 can be found, an exception is raised.
22536 @var{command-class} should be one of the @samp{COMMAND_} constants
22537 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22538 categorize the new parameter in the help system.
22540 @var{parameter-class} should be one of the @samp{PARAM_} constants
22541 defined below. This argument tells @value{GDBN} the type of the new
22542 parameter; this information is used for input validation and
22545 If @var{parameter-class} is @code{PARAM_ENUM}, then
22546 @var{enum-sequence} must be a sequence of strings. These strings
22547 represent the possible values for the parameter.
22549 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22550 of a fourth argument will cause an exception to be thrown.
22552 The help text for the new parameter is taken from the Python
22553 documentation string for the parameter's class, if there is one. If
22554 there is no documentation string, a default value is used.
22557 @defivar Parameter set_doc
22558 If this attribute exists, and is a string, then its value is used as
22559 the help text for this parameter's @code{set} command. The value is
22560 examined when @code{Parameter.__init__} is invoked; subsequent changes
22564 @defivar Parameter show_doc
22565 If this attribute exists, and is a string, then its value is used as
22566 the help text for this parameter's @code{show} command. The value is
22567 examined when @code{Parameter.__init__} is invoked; subsequent changes
22571 @defivar Parameter value
22572 The @code{value} attribute holds the underlying value of the
22573 parameter. It can be read and assigned to just as any other
22574 attribute. @value{GDBN} does validation when assignments are made.
22577 There are two methods that should be implemented in any
22578 @code{Parameter} class. These are:
22580 @defop Operation {parameter} get_set_string self
22581 @value{GDBN} will call this method when a @var{parameter}'s value has
22582 been changed via the @code{set} API (for example, @kbd{set foo off}).
22583 The @code{value} attribute has already been populated with the new
22584 value and may be used in output. This method must return a string.
22587 @defop Operation {parameter} get_show_string self svalue
22588 @value{GDBN} will call this method when a @var{parameter}'s
22589 @code{show} API has been invoked (for example, @kbd{show foo}). The
22590 argument @code{svalue} receives the string representation of the
22591 current value. This method must return a string.
22594 When a new parameter is defined, its type must be specified. The
22595 available types are represented by constants defined in the @code{gdb}
22599 @findex PARAM_BOOLEAN
22600 @findex gdb.PARAM_BOOLEAN
22601 @item PARAM_BOOLEAN
22602 The value is a plain boolean. The Python boolean values, @code{True}
22603 and @code{False} are the only valid values.
22605 @findex PARAM_AUTO_BOOLEAN
22606 @findex gdb.PARAM_AUTO_BOOLEAN
22607 @item PARAM_AUTO_BOOLEAN
22608 The value has three possible states: true, false, and @samp{auto}. In
22609 Python, true and false are represented using boolean constants, and
22610 @samp{auto} is represented using @code{None}.
22612 @findex PARAM_UINTEGER
22613 @findex gdb.PARAM_UINTEGER
22614 @item PARAM_UINTEGER
22615 The value is an unsigned integer. The value of 0 should be
22616 interpreted to mean ``unlimited''.
22618 @findex PARAM_INTEGER
22619 @findex gdb.PARAM_INTEGER
22620 @item PARAM_INTEGER
22621 The value is a signed integer. The value of 0 should be interpreted
22622 to mean ``unlimited''.
22624 @findex PARAM_STRING
22625 @findex gdb.PARAM_STRING
22627 The value is a string. When the user modifies the string, any escape
22628 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22629 translated into corresponding characters and encoded into the current
22632 @findex PARAM_STRING_NOESCAPE
22633 @findex gdb.PARAM_STRING_NOESCAPE
22634 @item PARAM_STRING_NOESCAPE
22635 The value is a string. When the user modifies the string, escapes are
22636 passed through untranslated.
22638 @findex PARAM_OPTIONAL_FILENAME
22639 @findex gdb.PARAM_OPTIONAL_FILENAME
22640 @item PARAM_OPTIONAL_FILENAME
22641 The value is a either a filename (a string), or @code{None}.
22643 @findex PARAM_FILENAME
22644 @findex gdb.PARAM_FILENAME
22645 @item PARAM_FILENAME
22646 The value is a filename. This is just like
22647 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22649 @findex PARAM_ZINTEGER
22650 @findex gdb.PARAM_ZINTEGER
22651 @item PARAM_ZINTEGER
22652 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22653 is interpreted as itself.
22656 @findex gdb.PARAM_ENUM
22658 The value is a string, which must be one of a collection string
22659 constants provided when the parameter is created.
22662 @node Functions In Python
22663 @subsubsection Writing new convenience functions
22665 @cindex writing convenience functions
22666 @cindex convenience functions in python
22667 @cindex python convenience functions
22668 @tindex gdb.Function
22670 You can implement new convenience functions (@pxref{Convenience Vars})
22671 in Python. A convenience function is an instance of a subclass of the
22672 class @code{gdb.Function}.
22674 @defmethod Function __init__ name
22675 The initializer for @code{Function} registers the new function with
22676 @value{GDBN}. The argument @var{name} is the name of the function,
22677 a string. The function will be visible to the user as a convenience
22678 variable of type @code{internal function}, whose name is the same as
22679 the given @var{name}.
22681 The documentation for the new function is taken from the documentation
22682 string for the new class.
22685 @defmethod Function invoke @var{*args}
22686 When a convenience function is evaluated, its arguments are converted
22687 to instances of @code{gdb.Value}, and then the function's
22688 @code{invoke} method is called. Note that @value{GDBN} does not
22689 predetermine the arity of convenience functions. Instead, all
22690 available arguments are passed to @code{invoke}, following the
22691 standard Python calling convention. In particular, a convenience
22692 function can have default values for parameters without ill effect.
22694 The return value of this method is used as its value in the enclosing
22695 expression. If an ordinary Python value is returned, it is converted
22696 to a @code{gdb.Value} following the usual rules.
22699 The following code snippet shows how a trivial convenience function can
22700 be implemented in Python:
22703 class Greet (gdb.Function):
22704 """Return string to greet someone.
22705 Takes a name as argument."""
22707 def __init__ (self):
22708 super (Greet, self).__init__ ("greet")
22710 def invoke (self, name):
22711 return "Hello, %s!" % name.string ()
22716 The last line instantiates the class, and is necessary to trigger the
22717 registration of the function with @value{GDBN}. Depending on how the
22718 Python code is read into @value{GDBN}, you may need to import the
22719 @code{gdb} module explicitly.
22721 @node Progspaces In Python
22722 @subsubsection Program Spaces In Python
22724 @cindex progspaces in python
22725 @tindex gdb.Progspace
22727 A program space, or @dfn{progspace}, represents a symbolic view
22728 of an address space.
22729 It consists of all of the objfiles of the program.
22730 @xref{Objfiles In Python}.
22731 @xref{Inferiors and Programs, program spaces}, for more details
22732 about program spaces.
22734 The following progspace-related functions are available in the
22737 @findex gdb.current_progspace
22738 @defun current_progspace
22739 This function returns the program space of the currently selected inferior.
22740 @xref{Inferiors and Programs}.
22743 @findex gdb.progspaces
22745 Return a sequence of all the progspaces currently known to @value{GDBN}.
22748 Each progspace is represented by an instance of the @code{gdb.Progspace}
22751 @defivar Progspace filename
22752 The file name of the progspace as a string.
22755 @defivar Progspace pretty_printers
22756 The @code{pretty_printers} attribute is a list of functions. It is
22757 used to look up pretty-printers. A @code{Value} is passed to each
22758 function in order; if the function returns @code{None}, then the
22759 search continues. Otherwise, the return value should be an object
22760 which is used to format the value. @xref{Pretty Printing API}, for more
22764 @node Objfiles In Python
22765 @subsubsection Objfiles In Python
22767 @cindex objfiles in python
22768 @tindex gdb.Objfile
22770 @value{GDBN} loads symbols for an inferior from various
22771 symbol-containing files (@pxref{Files}). These include the primary
22772 executable file, any shared libraries used by the inferior, and any
22773 separate debug info files (@pxref{Separate Debug Files}).
22774 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22776 The following objfile-related functions are available in the
22779 @findex gdb.current_objfile
22780 @defun current_objfile
22781 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22782 sets the ``current objfile'' to the corresponding objfile. This
22783 function returns the current objfile. If there is no current objfile,
22784 this function returns @code{None}.
22787 @findex gdb.objfiles
22789 Return a sequence of all the objfiles current known to @value{GDBN}.
22790 @xref{Objfiles In Python}.
22793 Each objfile is represented by an instance of the @code{gdb.Objfile}
22796 @defivar Objfile filename
22797 The file name of the objfile as a string.
22800 @defivar Objfile pretty_printers
22801 The @code{pretty_printers} attribute is a list of functions. It is
22802 used to look up pretty-printers. A @code{Value} is passed to each
22803 function in order; if the function returns @code{None}, then the
22804 search continues. Otherwise, the return value should be an object
22805 which is used to format the value. @xref{Pretty Printing API}, for more
22809 A @code{gdb.Objfile} object has the following methods:
22811 @defmethod Objfile is_valid
22812 Returns @code{True} if the @code{gdb.Objfile} object is valid,
22813 @code{False} if not. A @code{gdb.Objfile} object can become invalid
22814 if the object file it refers to is not loaded in @value{GDBN} any
22815 longer. All other @code{gdb.Objfile} methods will throw an exception
22816 if it is invalid at the time the method is called.
22819 @node Frames In Python
22820 @subsubsection Accessing inferior stack frames from Python.
22822 @cindex frames in python
22823 When the debugged program stops, @value{GDBN} is able to analyze its call
22824 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22825 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22826 while its corresponding frame exists in the inferior's stack. If you try
22827 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
22828 exception (@pxref{Exception Handling}).
22830 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22834 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22838 The following frame-related functions are available in the @code{gdb} module:
22840 @findex gdb.selected_frame
22841 @defun selected_frame
22842 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22845 @findex gdb.newest_frame
22846 @defun newest_frame
22847 Return the newest frame object for the selected thread.
22850 @defun frame_stop_reason_string reason
22851 Return a string explaining the reason why @value{GDBN} stopped unwinding
22852 frames, as expressed by the given @var{reason} code (an integer, see the
22853 @code{unwind_stop_reason} method further down in this section).
22856 A @code{gdb.Frame} object has the following methods:
22859 @defmethod Frame is_valid
22860 Returns true if the @code{gdb.Frame} object is valid, false if not.
22861 A frame object can become invalid if the frame it refers to doesn't
22862 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22863 an exception if it is invalid at the time the method is called.
22866 @defmethod Frame name
22867 Returns the function name of the frame, or @code{None} if it can't be
22871 @defmethod Frame type
22872 Returns the type of the frame. The value can be one of:
22874 @item gdb.NORMAL_FRAME
22875 An ordinary stack frame.
22877 @item gdb.DUMMY_FRAME
22878 A fake stack frame that was created by @value{GDBN} when performing an
22879 inferior function call.
22881 @item gdb.INLINE_FRAME
22882 A frame representing an inlined function. The function was inlined
22883 into a @code{gdb.NORMAL_FRAME} that is older than this one.
22885 @item gdb.SIGTRAMP_FRAME
22886 A signal trampoline frame. This is the frame created by the OS when
22887 it calls into a signal handler.
22889 @item gdb.ARCH_FRAME
22890 A fake stack frame representing a cross-architecture call.
22892 @item gdb.SENTINEL_FRAME
22893 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
22898 @defmethod Frame unwind_stop_reason
22899 Return an integer representing the reason why it's not possible to find
22900 more frames toward the outermost frame. Use
22901 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22902 function to a string.
22905 @defmethod Frame pc
22906 Returns the frame's resume address.
22909 @defmethod Frame block
22910 Return the frame's code block. @xref{Blocks In Python}.
22913 @defmethod Frame function
22914 Return the symbol for the function corresponding to this frame.
22915 @xref{Symbols In Python}.
22918 @defmethod Frame older
22919 Return the frame that called this frame.
22922 @defmethod Frame newer
22923 Return the frame called by this frame.
22926 @defmethod Frame find_sal
22927 Return the frame's symtab and line object.
22928 @xref{Symbol Tables In Python}.
22931 @defmethod Frame read_var variable @r{[}block@r{]}
22932 Return the value of @var{variable} in this frame. If the optional
22933 argument @var{block} is provided, search for the variable from that
22934 block; otherwise start at the frame's current block (which is
22935 determined by the frame's current program counter). @var{variable}
22936 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22937 @code{gdb.Block} object.
22940 @defmethod Frame select
22941 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22946 @node Blocks In Python
22947 @subsubsection Accessing frame blocks from Python.
22949 @cindex blocks in python
22952 Within each frame, @value{GDBN} maintains information on each block
22953 stored in that frame. These blocks are organized hierarchically, and
22954 are represented individually in Python as a @code{gdb.Block}.
22955 Please see @ref{Frames In Python}, for a more in-depth discussion on
22956 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22957 detailed technical information on @value{GDBN}'s book-keeping of the
22960 The following block-related functions are available in the @code{gdb}
22963 @findex gdb.block_for_pc
22964 @defun block_for_pc pc
22965 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22966 block cannot be found for the @var{pc} value specified, the function
22967 will return @code{None}.
22970 A @code{gdb.Block} object has the following methods:
22973 @defmethod Block is_valid
22974 Returns @code{True} if the @code{gdb.Block} object is valid,
22975 @code{False} if not. A block object can become invalid if the block it
22976 refers to doesn't exist anymore in the inferior. All other
22977 @code{gdb.Block} methods will throw an exception if it is invalid at
22978 the time the method is called. This method is also made available to
22979 the Python iterator object that @code{gdb.Block} provides in an iteration
22980 context and via the Python @code{iter} built-in function.
22984 A @code{gdb.Block} object has the following attributes:
22987 @defivar Block start
22988 The start address of the block. This attribute is not writable.
22992 The end address of the block. This attribute is not writable.
22995 @defivar Block function
22996 The name of the block represented as a @code{gdb.Symbol}. If the
22997 block is not named, then this attribute holds @code{None}. This
22998 attribute is not writable.
23001 @defivar Block superblock
23002 The block containing this block. If this parent block does not exist,
23003 this attribute holds @code{None}. This attribute is not writable.
23007 @node Symbols In Python
23008 @subsubsection Python representation of Symbols.
23010 @cindex symbols in python
23013 @value{GDBN} represents every variable, function and type as an
23014 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23015 Similarly, Python represents these symbols in @value{GDBN} with the
23016 @code{gdb.Symbol} object.
23018 The following symbol-related functions are available in the @code{gdb}
23021 @findex gdb.lookup_symbol
23022 @defun lookup_symbol name @r{[}block@r{]} @r{[}domain@r{]}
23023 This function searches for a symbol by name. The search scope can be
23024 restricted to the parameters defined in the optional domain and block
23027 @var{name} is the name of the symbol. It must be a string. The
23028 optional @var{block} argument restricts the search to symbols visible
23029 in that @var{block}. The @var{block} argument must be a
23030 @code{gdb.Block} object. If omitted, the block for the current frame
23031 is used. The optional @var{domain} argument restricts
23032 the search to the domain type. The @var{domain} argument must be a
23033 domain constant defined in the @code{gdb} module and described later
23036 The result is a tuple of two elements.
23037 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23039 If the symbol is found, the second element is @code{True} if the symbol
23040 is a field of a method's object (e.g., @code{this} in C@t{++}),
23041 otherwise it is @code{False}.
23042 If the symbol is not found, the second element is @code{False}.
23045 @findex gdb.lookup_global_symbol
23046 @defun lookup_global_symbol name @r{[}domain@r{]}
23047 This function searches for a global symbol by name.
23048 The search scope can be restricted to by the domain argument.
23050 @var{name} is the name of the symbol. It must be a string.
23051 The optional @var{domain} argument restricts the search to the domain type.
23052 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23053 module and described later in this chapter.
23055 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23059 A @code{gdb.Symbol} object has the following attributes:
23062 @defivar Symbol symtab
23063 The symbol table in which the symbol appears. This attribute is
23064 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23065 Python}. This attribute is not writable.
23068 @defivar Symbol name
23069 The name of the symbol as a string. This attribute is not writable.
23072 @defivar Symbol linkage_name
23073 The name of the symbol, as used by the linker (i.e., may be mangled).
23074 This attribute is not writable.
23077 @defivar Symbol print_name
23078 The name of the symbol in a form suitable for output. This is either
23079 @code{name} or @code{linkage_name}, depending on whether the user
23080 asked @value{GDBN} to display demangled or mangled names.
23083 @defivar Symbol addr_class
23084 The address class of the symbol. This classifies how to find the value
23085 of a symbol. Each address class is a constant defined in the
23086 @code{gdb} module and described later in this chapter.
23089 @defivar Symbol is_argument
23090 @code{True} if the symbol is an argument of a function.
23093 @defivar Symbol is_constant
23094 @code{True} if the symbol is a constant.
23097 @defivar Symbol is_function
23098 @code{True} if the symbol is a function or a method.
23101 @defivar Symbol is_variable
23102 @code{True} if the symbol is a variable.
23106 A @code{gdb.Symbol} object has the following methods:
23109 @defmethod Symbol is_valid
23110 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23111 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23112 the symbol it refers to does not exist in @value{GDBN} any longer.
23113 All other @code{gdb.Symbol} methods will throw an exception if it is
23114 invalid at the time the method is called.
23118 The available domain categories in @code{gdb.Symbol} are represented
23119 as constants in the @code{gdb} module:
23122 @findex SYMBOL_UNDEF_DOMAIN
23123 @findex gdb.SYMBOL_UNDEF_DOMAIN
23124 @item SYMBOL_UNDEF_DOMAIN
23125 This is used when a domain has not been discovered or none of the
23126 following domains apply. This usually indicates an error either
23127 in the symbol information or in @value{GDBN}'s handling of symbols.
23128 @findex SYMBOL_VAR_DOMAIN
23129 @findex gdb.SYMBOL_VAR_DOMAIN
23130 @item SYMBOL_VAR_DOMAIN
23131 This domain contains variables, function names, typedef names and enum
23133 @findex SYMBOL_STRUCT_DOMAIN
23134 @findex gdb.SYMBOL_STRUCT_DOMAIN
23135 @item SYMBOL_STRUCT_DOMAIN
23136 This domain holds struct, union and enum type names.
23137 @findex SYMBOL_LABEL_DOMAIN
23138 @findex gdb.SYMBOL_LABEL_DOMAIN
23139 @item SYMBOL_LABEL_DOMAIN
23140 This domain contains names of labels (for gotos).
23141 @findex SYMBOL_VARIABLES_DOMAIN
23142 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23143 @item SYMBOL_VARIABLES_DOMAIN
23144 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23145 contains everything minus functions and types.
23146 @findex SYMBOL_FUNCTIONS_DOMAIN
23147 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23148 @item SYMBOL_FUNCTION_DOMAIN
23149 This domain contains all functions.
23150 @findex SYMBOL_TYPES_DOMAIN
23151 @findex gdb.SYMBOL_TYPES_DOMAIN
23152 @item SYMBOL_TYPES_DOMAIN
23153 This domain contains all types.
23156 The available address class categories in @code{gdb.Symbol} are represented
23157 as constants in the @code{gdb} module:
23160 @findex SYMBOL_LOC_UNDEF
23161 @findex gdb.SYMBOL_LOC_UNDEF
23162 @item SYMBOL_LOC_UNDEF
23163 If this is returned by address class, it indicates an error either in
23164 the symbol information or in @value{GDBN}'s handling of symbols.
23165 @findex SYMBOL_LOC_CONST
23166 @findex gdb.SYMBOL_LOC_CONST
23167 @item SYMBOL_LOC_CONST
23168 Value is constant int.
23169 @findex SYMBOL_LOC_STATIC
23170 @findex gdb.SYMBOL_LOC_STATIC
23171 @item SYMBOL_LOC_STATIC
23172 Value is at a fixed address.
23173 @findex SYMBOL_LOC_REGISTER
23174 @findex gdb.SYMBOL_LOC_REGISTER
23175 @item SYMBOL_LOC_REGISTER
23176 Value is in a register.
23177 @findex SYMBOL_LOC_ARG
23178 @findex gdb.SYMBOL_LOC_ARG
23179 @item SYMBOL_LOC_ARG
23180 Value is an argument. This value is at the offset stored within the
23181 symbol inside the frame's argument list.
23182 @findex SYMBOL_LOC_REF_ARG
23183 @findex gdb.SYMBOL_LOC_REF_ARG
23184 @item SYMBOL_LOC_REF_ARG
23185 Value address is stored in the frame's argument list. Just like
23186 @code{LOC_ARG} except that the value's address is stored at the
23187 offset, not the value itself.
23188 @findex SYMBOL_LOC_REGPARM_ADDR
23189 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23190 @item SYMBOL_LOC_REGPARM_ADDR
23191 Value is a specified register. Just like @code{LOC_REGISTER} except
23192 the register holds the address of the argument instead of the argument
23194 @findex SYMBOL_LOC_LOCAL
23195 @findex gdb.SYMBOL_LOC_LOCAL
23196 @item SYMBOL_LOC_LOCAL
23197 Value is a local variable.
23198 @findex SYMBOL_LOC_TYPEDEF
23199 @findex gdb.SYMBOL_LOC_TYPEDEF
23200 @item SYMBOL_LOC_TYPEDEF
23201 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23203 @findex SYMBOL_LOC_BLOCK
23204 @findex gdb.SYMBOL_LOC_BLOCK
23205 @item SYMBOL_LOC_BLOCK
23207 @findex SYMBOL_LOC_CONST_BYTES
23208 @findex gdb.SYMBOL_LOC_CONST_BYTES
23209 @item SYMBOL_LOC_CONST_BYTES
23210 Value is a byte-sequence.
23211 @findex SYMBOL_LOC_UNRESOLVED
23212 @findex gdb.SYMBOL_LOC_UNRESOLVED
23213 @item SYMBOL_LOC_UNRESOLVED
23214 Value is at a fixed address, but the address of the variable has to be
23215 determined from the minimal symbol table whenever the variable is
23217 @findex SYMBOL_LOC_OPTIMIZED_OUT
23218 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23219 @item SYMBOL_LOC_OPTIMIZED_OUT
23220 The value does not actually exist in the program.
23221 @findex SYMBOL_LOC_COMPUTED
23222 @findex gdb.SYMBOL_LOC_COMPUTED
23223 @item SYMBOL_LOC_COMPUTED
23224 The value's address is a computed location.
23227 @node Symbol Tables In Python
23228 @subsubsection Symbol table representation in Python.
23230 @cindex symbol tables in python
23232 @tindex gdb.Symtab_and_line
23234 Access to symbol table data maintained by @value{GDBN} on the inferior
23235 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23236 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23237 from the @code{find_sal} method in @code{gdb.Frame} object.
23238 @xref{Frames In Python}.
23240 For more information on @value{GDBN}'s symbol table management, see
23241 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23243 A @code{gdb.Symtab_and_line} object has the following attributes:
23246 @defivar Symtab_and_line symtab
23247 The symbol table object (@code{gdb.Symtab}) for this frame.
23248 This attribute is not writable.
23251 @defivar Symtab_and_line pc
23252 Indicates the current program counter address. This attribute is not
23256 @defivar Symtab_and_line line
23257 Indicates the current line number for this object. This
23258 attribute is not writable.
23262 A @code{gdb.Symtab_and_line} object has the following methods:
23265 @defmethod Symtab_and_line is_valid
23266 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23267 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23268 invalid if the Symbol table and line object it refers to does not
23269 exist in @value{GDBN} any longer. All other
23270 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23271 invalid at the time the method is called.
23275 A @code{gdb.Symtab} object has the following attributes:
23278 @defivar Symtab filename
23279 The symbol table's source filename. This attribute is not writable.
23282 @defivar Symtab objfile
23283 The symbol table's backing object file. @xref{Objfiles In Python}.
23284 This attribute is not writable.
23288 A @code{gdb.Symtab} object has the following methods:
23291 @defmethod Symtab is_valid
23292 Returns @code{True} if the @code{gdb.Symtab} object is valid,
23293 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
23294 the symbol table it refers to does not exist in @value{GDBN} any
23295 longer. All other @code{gdb.Symtab} methods will throw an exception
23296 if it is invalid at the time the method is called.
23299 @defmethod Symtab fullname
23300 Return the symbol table's source absolute file name.
23304 @node Breakpoints In Python
23305 @subsubsection Manipulating breakpoints using Python
23307 @cindex breakpoints in python
23308 @tindex gdb.Breakpoint
23310 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23313 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]} @r{[}internal@r{]}
23314 Create a new breakpoint. @var{spec} is a string naming the
23315 location of the breakpoint, or an expression that defines a
23316 watchpoint. The contents can be any location recognized by the
23317 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23318 command. The optional @var{type} denotes the breakpoint to create
23319 from the types defined later in this chapter. This argument can be
23320 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
23321 defaults to @code{BP_BREAKPOINT}. The optional @var{internal} argument
23322 allows the breakpoint to become invisible to the user. The breakpoint
23323 will neither be reported when created, nor will it be listed in the
23324 output from @code{info breakpoints} (but will be listed with the
23325 @code{maint info breakpoints} command). The optional @var{wp_class}
23326 argument defines the class of watchpoint to create, if @var{type} is
23327 @code{BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23328 assumed to be a @var{WP_WRITE} class.
23331 @defop Operation {gdb.Breakpoint} stop (self)
23332 The @code{gdb.Breakpoint} class can be sub-classed and, in
23333 particular, you may choose to implement the @code{stop} method.
23334 If this method is defined as a sub-class of @code{gdb.Breakpoint},
23335 it will be called when the inferior reaches any location of a
23336 breakpoint which instantiates that sub-class. If the method returns
23337 @code{True}, the inferior will be stopped at the location of the
23338 breakpoint, otherwise the inferior will continue.
23340 If there are multiple breakpoints at the same location with a
23341 @code{stop} method, each one will be called regardless of the
23342 return status of the previous. This ensures that all @code{stop}
23343 methods have a chance to execute at that location. In this scenario
23344 if one of the methods returns @code{True} but the others return
23345 @code{False}, the inferior will still be stopped.
23347 Example @code{stop} implementation:
23350 class MyBreakpoint (gdb.Breakpoint):
23352 inf_val = gdb.parse_and_eval("foo")
23359 The available watchpoint types represented by constants are defined in the
23364 @findex gdb.WP_READ
23366 Read only watchpoint.
23369 @findex gdb.WP_WRITE
23371 Write only watchpoint.
23374 @findex gdb.WP_ACCESS
23376 Read/Write watchpoint.
23379 @defmethod Breakpoint is_valid
23380 Return @code{True} if this @code{Breakpoint} object is valid,
23381 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23382 if the user deletes the breakpoint. In this case, the object still
23383 exists, but the underlying breakpoint does not. In the cases of
23384 watchpoint scope, the watchpoint remains valid even if execution of the
23385 inferior leaves the scope of that watchpoint.
23388 @defmethod Breakpoint delete
23389 Permanently deletes the @value{GDBN} breakpoint. This also
23390 invalidates the Python @code{Breakpoint} object. Any further access
23391 to this object's attributes or methods will raise an error.
23394 @defivar Breakpoint enabled
23395 This attribute is @code{True} if the breakpoint is enabled, and
23396 @code{False} otherwise. This attribute is writable.
23399 @defivar Breakpoint silent
23400 This attribute is @code{True} if the breakpoint is silent, and
23401 @code{False} otherwise. This attribute is writable.
23403 Note that a breakpoint can also be silent if it has commands and the
23404 first command is @code{silent}. This is not reported by the
23405 @code{silent} attribute.
23408 @defivar Breakpoint thread
23409 If the breakpoint is thread-specific, this attribute holds the thread
23410 id. If the breakpoint is not thread-specific, this attribute is
23411 @code{None}. This attribute is writable.
23414 @defivar Breakpoint task
23415 If the breakpoint is Ada task-specific, this attribute holds the Ada task
23416 id. If the breakpoint is not task-specific (or the underlying
23417 language is not Ada), this attribute is @code{None}. This attribute
23421 @defivar Breakpoint ignore_count
23422 This attribute holds the ignore count for the breakpoint, an integer.
23423 This attribute is writable.
23426 @defivar Breakpoint number
23427 This attribute holds the breakpoint's number --- the identifier used by
23428 the user to manipulate the breakpoint. This attribute is not writable.
23431 @defivar Breakpoint type
23432 This attribute holds the breakpoint's type --- the identifier used to
23433 determine the actual breakpoint type or use-case. This attribute is not
23437 @defivar Breakpoint visible
23438 This attribute tells whether the breakpoint is visible to the user
23439 when set, or when the @samp{info breakpoints} command is run. This
23440 attribute is not writable.
23443 The available types are represented by constants defined in the @code{gdb}
23447 @findex BP_BREAKPOINT
23448 @findex gdb.BP_BREAKPOINT
23449 @item BP_BREAKPOINT
23450 Normal code breakpoint.
23452 @findex BP_WATCHPOINT
23453 @findex gdb.BP_WATCHPOINT
23454 @item BP_WATCHPOINT
23455 Watchpoint breakpoint.
23457 @findex BP_HARDWARE_WATCHPOINT
23458 @findex gdb.BP_HARDWARE_WATCHPOINT
23459 @item BP_HARDWARE_WATCHPOINT
23460 Hardware assisted watchpoint.
23462 @findex BP_READ_WATCHPOINT
23463 @findex gdb.BP_READ_WATCHPOINT
23464 @item BP_READ_WATCHPOINT
23465 Hardware assisted read watchpoint.
23467 @findex BP_ACCESS_WATCHPOINT
23468 @findex gdb.BP_ACCESS_WATCHPOINT
23469 @item BP_ACCESS_WATCHPOINT
23470 Hardware assisted access watchpoint.
23473 @defivar Breakpoint hit_count
23474 This attribute holds the hit count for the breakpoint, an integer.
23475 This attribute is writable, but currently it can only be set to zero.
23478 @defivar Breakpoint location
23479 This attribute holds the location of the breakpoint, as specified by
23480 the user. It is a string. If the breakpoint does not have a location
23481 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23482 attribute is not writable.
23485 @defivar Breakpoint expression
23486 This attribute holds a breakpoint expression, as specified by
23487 the user. It is a string. If the breakpoint does not have an
23488 expression (the breakpoint is not a watchpoint) the attribute's value
23489 is @code{None}. This attribute is not writable.
23492 @defivar Breakpoint condition
23493 This attribute holds the condition of the breakpoint, as specified by
23494 the user. It is a string. If there is no condition, this attribute's
23495 value is @code{None}. This attribute is writable.
23498 @defivar Breakpoint commands
23499 This attribute holds the commands attached to the breakpoint. If
23500 there are commands, this attribute's value is a string holding all the
23501 commands, separated by newlines. If there are no commands, this
23502 attribute is @code{None}. This attribute is not writable.
23505 @node Lazy Strings In Python
23506 @subsubsection Python representation of lazy strings.
23508 @cindex lazy strings in python
23509 @tindex gdb.LazyString
23511 A @dfn{lazy string} is a string whose contents is not retrieved or
23512 encoded until it is needed.
23514 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23515 @code{address} that points to a region of memory, an @code{encoding}
23516 that will be used to encode that region of memory, and a @code{length}
23517 to delimit the region of memory that represents the string. The
23518 difference between a @code{gdb.LazyString} and a string wrapped within
23519 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23520 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23521 retrieved and encoded during printing, while a @code{gdb.Value}
23522 wrapping a string is immediately retrieved and encoded on creation.
23524 A @code{gdb.LazyString} object has the following functions:
23526 @defmethod LazyString value
23527 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23528 will point to the string in memory, but will lose all the delayed
23529 retrieval, encoding and handling that @value{GDBN} applies to a
23530 @code{gdb.LazyString}.
23533 @defivar LazyString address
23534 This attribute holds the address of the string. This attribute is not
23538 @defivar LazyString length
23539 This attribute holds the length of the string in characters. If the
23540 length is -1, then the string will be fetched and encoded up to the
23541 first null of appropriate width. This attribute is not writable.
23544 @defivar LazyString encoding
23545 This attribute holds the encoding that will be applied to the string
23546 when the string is printed by @value{GDBN}. If the encoding is not
23547 set, or contains an empty string, then @value{GDBN} will select the
23548 most appropriate encoding when the string is printed. This attribute
23552 @defivar LazyString type
23553 This attribute holds the type that is represented by the lazy string's
23554 type. For a lazy string this will always be a pointer type. To
23555 resolve this to the lazy string's character type, use the type's
23556 @code{target} method. @xref{Types In Python}. This attribute is not
23561 @subsection Auto-loading
23562 @cindex auto-loading, Python
23564 When a new object file is read (for example, due to the @code{file}
23565 command, or because the inferior has loaded a shared library),
23566 @value{GDBN} will look for Python support scripts in several ways:
23567 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23570 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23571 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23572 * Which flavor to choose?::
23575 The auto-loading feature is useful for supplying application-specific
23576 debugging commands and scripts.
23578 Auto-loading can be enabled or disabled.
23581 @kindex set auto-load-scripts
23582 @item set auto-load-scripts [yes|no]
23583 Enable or disable the auto-loading of Python scripts.
23585 @kindex show auto-load-scripts
23586 @item show auto-load-scripts
23587 Show whether auto-loading of Python scripts is enabled or disabled.
23590 When reading an auto-loaded file, @value{GDBN} sets the
23591 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23592 function (@pxref{Objfiles In Python}). This can be useful for
23593 registering objfile-specific pretty-printers.
23595 @node objfile-gdb.py file
23596 @subsubsection The @file{@var{objfile}-gdb.py} file
23597 @cindex @file{@var{objfile}-gdb.py}
23599 When a new object file is read, @value{GDBN} looks for
23600 a file named @file{@var{objfile}-gdb.py},
23601 where @var{objfile} is the object file's real name, formed by ensuring
23602 that the file name is absolute, following all symlinks, and resolving
23603 @code{.} and @code{..} components. If this file exists and is
23604 readable, @value{GDBN} will evaluate it as a Python script.
23606 If this file does not exist, and if the parameter
23607 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23608 then @value{GDBN} will look for @var{real-name} in all of the
23609 directories mentioned in the value of @code{debug-file-directory}.
23611 Finally, if this file does not exist, then @value{GDBN} will look for
23612 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23613 @var{data-directory} is @value{GDBN}'s data directory (available via
23614 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23615 is the object file's real name, as described above.
23617 @value{GDBN} does not track which files it has already auto-loaded this way.
23618 @value{GDBN} will load the associated script every time the corresponding
23619 @var{objfile} is opened.
23620 So your @file{-gdb.py} file should be careful to avoid errors if it
23621 is evaluated more than once.
23623 @node .debug_gdb_scripts section
23624 @subsubsection The @code{.debug_gdb_scripts} section
23625 @cindex @code{.debug_gdb_scripts} section
23627 For systems using file formats like ELF and COFF,
23628 when @value{GDBN} loads a new object file
23629 it will look for a special section named @samp{.debug_gdb_scripts}.
23630 If this section exists, its contents is a list of names of scripts to load.
23632 @value{GDBN} will look for each specified script file first in the
23633 current directory and then along the source search path
23634 (@pxref{Source Path, ,Specifying Source Directories}),
23635 except that @file{$cdir} is not searched, since the compilation
23636 directory is not relevant to scripts.
23638 Entries can be placed in section @code{.debug_gdb_scripts} with,
23639 for example, this GCC macro:
23642 /* Note: The "MS" section flags are to remove duplicates. */
23643 #define DEFINE_GDB_SCRIPT(script_name) \
23645 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23647 .asciz \"" script_name "\"\n\
23653 Then one can reference the macro in a header or source file like this:
23656 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23659 The script name may include directories if desired.
23661 If the macro is put in a header, any application or library
23662 using this header will get a reference to the specified script.
23664 @node Which flavor to choose?
23665 @subsubsection Which flavor to choose?
23667 Given the multiple ways of auto-loading Python scripts, it might not always
23668 be clear which one to choose. This section provides some guidance.
23670 Benefits of the @file{-gdb.py} way:
23674 Can be used with file formats that don't support multiple sections.
23677 Ease of finding scripts for public libraries.
23679 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23680 in the source search path.
23681 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23682 isn't a source directory in which to find the script.
23685 Doesn't require source code additions.
23688 Benefits of the @code{.debug_gdb_scripts} way:
23692 Works with static linking.
23694 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23695 trigger their loading. When an application is statically linked the only
23696 objfile available is the executable, and it is cumbersome to attach all the
23697 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23700 Works with classes that are entirely inlined.
23702 Some classes can be entirely inlined, and thus there may not be an associated
23703 shared library to attach a @file{-gdb.py} script to.
23706 Scripts needn't be copied out of the source tree.
23708 In some circumstances, apps can be built out of large collections of internal
23709 libraries, and the build infrastructure necessary to install the
23710 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23711 cumbersome. It may be easier to specify the scripts in the
23712 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23713 top of the source tree to the source search path.
23716 @node Python modules
23717 @subsection Python modules
23718 @cindex python modules
23720 @value{GDBN} comes with a module to assist writing Python code.
23723 * gdb.printing:: Building and registering pretty-printers.
23724 * gdb.types:: Utilities for working with types.
23728 @subsubsection gdb.printing
23729 @cindex gdb.printing
23731 This module provides a collection of utilities for working with
23735 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23736 This class specifies the API that makes @samp{info pretty-printer},
23737 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23738 Pretty-printers should generally inherit from this class.
23740 @item SubPrettyPrinter (@var{name})
23741 For printers that handle multiple types, this class specifies the
23742 corresponding API for the subprinters.
23744 @item RegexpCollectionPrettyPrinter (@var{name})
23745 Utility class for handling multiple printers, all recognized via
23746 regular expressions.
23747 @xref{Writing a Pretty-Printer}, for an example.
23749 @item register_pretty_printer (@var{obj}, @var{printer})
23750 Register @var{printer} with the pretty-printer list of @var{obj}.
23754 @subsubsection gdb.types
23757 This module provides a collection of utilities for working with
23758 @code{gdb.Types} objects.
23761 @item get_basic_type (@var{type})
23762 Return @var{type} with const and volatile qualifiers stripped,
23763 and with typedefs and C@t{++} references converted to the underlying type.
23768 typedef const int const_int;
23770 const_int& foo_ref (foo);
23771 int main () @{ return 0; @}
23778 (gdb) python import gdb.types
23779 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23780 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23784 @item has_field (@var{type}, @var{field})
23785 Return @code{True} if @var{type}, assumed to be a type with fields
23786 (e.g., a structure or union), has field @var{field}.
23788 @item make_enum_dict (@var{enum_type})
23789 Return a Python @code{dictionary} type produced from @var{enum_type}.
23793 @chapter Command Interpreters
23794 @cindex command interpreters
23796 @value{GDBN} supports multiple command interpreters, and some command
23797 infrastructure to allow users or user interface writers to switch
23798 between interpreters or run commands in other interpreters.
23800 @value{GDBN} currently supports two command interpreters, the console
23801 interpreter (sometimes called the command-line interpreter or @sc{cli})
23802 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23803 describes both of these interfaces in great detail.
23805 By default, @value{GDBN} will start with the console interpreter.
23806 However, the user may choose to start @value{GDBN} with another
23807 interpreter by specifying the @option{-i} or @option{--interpreter}
23808 startup options. Defined interpreters include:
23812 @cindex console interpreter
23813 The traditional console or command-line interpreter. This is the most often
23814 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23815 @value{GDBN} will use this interpreter.
23818 @cindex mi interpreter
23819 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23820 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23821 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23825 @cindex mi2 interpreter
23826 The current @sc{gdb/mi} interface.
23829 @cindex mi1 interpreter
23830 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23834 @cindex invoke another interpreter
23835 The interpreter being used by @value{GDBN} may not be dynamically
23836 switched at runtime. Although possible, this could lead to a very
23837 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23838 enters the command "interpreter-set console" in a console view,
23839 @value{GDBN} would switch to using the console interpreter, rendering
23840 the IDE inoperable!
23842 @kindex interpreter-exec
23843 Although you may only choose a single interpreter at startup, you may execute
23844 commands in any interpreter from the current interpreter using the appropriate
23845 command. If you are running the console interpreter, simply use the
23846 @code{interpreter-exec} command:
23849 interpreter-exec mi "-data-list-register-names"
23852 @sc{gdb/mi} has a similar command, although it is only available in versions of
23853 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23856 @chapter @value{GDBN} Text User Interface
23858 @cindex Text User Interface
23861 * TUI Overview:: TUI overview
23862 * TUI Keys:: TUI key bindings
23863 * TUI Single Key Mode:: TUI single key mode
23864 * TUI Commands:: TUI-specific commands
23865 * TUI Configuration:: TUI configuration variables
23868 The @value{GDBN} Text User Interface (TUI) is a terminal
23869 interface which uses the @code{curses} library to show the source
23870 file, the assembly output, the program registers and @value{GDBN}
23871 commands in separate text windows. The TUI mode is supported only
23872 on platforms where a suitable version of the @code{curses} library
23875 @pindex @value{GDBTUI}
23876 The TUI mode is enabled by default when you invoke @value{GDBN} as
23877 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23878 You can also switch in and out of TUI mode while @value{GDBN} runs by
23879 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23880 @xref{TUI Keys, ,TUI Key Bindings}.
23883 @section TUI Overview
23885 In TUI mode, @value{GDBN} can display several text windows:
23889 This window is the @value{GDBN} command window with the @value{GDBN}
23890 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23891 managed using readline.
23894 The source window shows the source file of the program. The current
23895 line and active breakpoints are displayed in this window.
23898 The assembly window shows the disassembly output of the program.
23901 This window shows the processor registers. Registers are highlighted
23902 when their values change.
23905 The source and assembly windows show the current program position
23906 by highlighting the current line and marking it with a @samp{>} marker.
23907 Breakpoints are indicated with two markers. The first marker
23908 indicates the breakpoint type:
23912 Breakpoint which was hit at least once.
23915 Breakpoint which was never hit.
23918 Hardware breakpoint which was hit at least once.
23921 Hardware breakpoint which was never hit.
23924 The second marker indicates whether the breakpoint is enabled or not:
23928 Breakpoint is enabled.
23931 Breakpoint is disabled.
23934 The source, assembly and register windows are updated when the current
23935 thread changes, when the frame changes, or when the program counter
23938 These windows are not all visible at the same time. The command
23939 window is always visible. The others can be arranged in several
23950 source and assembly,
23953 source and registers, or
23956 assembly and registers.
23959 A status line above the command window shows the following information:
23963 Indicates the current @value{GDBN} target.
23964 (@pxref{Targets, ,Specifying a Debugging Target}).
23967 Gives the current process or thread number.
23968 When no process is being debugged, this field is set to @code{No process}.
23971 Gives the current function name for the selected frame.
23972 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23973 When there is no symbol corresponding to the current program counter,
23974 the string @code{??} is displayed.
23977 Indicates the current line number for the selected frame.
23978 When the current line number is not known, the string @code{??} is displayed.
23981 Indicates the current program counter address.
23985 @section TUI Key Bindings
23986 @cindex TUI key bindings
23988 The TUI installs several key bindings in the readline keymaps
23989 @ifset SYSTEM_READLINE
23990 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
23992 @ifclear SYSTEM_READLINE
23993 (@pxref{Command Line Editing}).
23995 The following key bindings are installed for both TUI mode and the
23996 @value{GDBN} standard mode.
24005 Enter or leave the TUI mode. When leaving the TUI mode,
24006 the curses window management stops and @value{GDBN} operates using
24007 its standard mode, writing on the terminal directly. When reentering
24008 the TUI mode, control is given back to the curses windows.
24009 The screen is then refreshed.
24013 Use a TUI layout with only one window. The layout will
24014 either be @samp{source} or @samp{assembly}. When the TUI mode
24015 is not active, it will switch to the TUI mode.
24017 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24021 Use a TUI layout with at least two windows. When the current
24022 layout already has two windows, the next layout with two windows is used.
24023 When a new layout is chosen, one window will always be common to the
24024 previous layout and the new one.
24026 Think of it as the Emacs @kbd{C-x 2} binding.
24030 Change the active window. The TUI associates several key bindings
24031 (like scrolling and arrow keys) with the active window. This command
24032 gives the focus to the next TUI window.
24034 Think of it as the Emacs @kbd{C-x o} binding.
24038 Switch in and out of the TUI SingleKey mode that binds single
24039 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24042 The following key bindings only work in the TUI mode:
24047 Scroll the active window one page up.
24051 Scroll the active window one page down.
24055 Scroll the active window one line up.
24059 Scroll the active window one line down.
24063 Scroll the active window one column left.
24067 Scroll the active window one column right.
24071 Refresh the screen.
24074 Because the arrow keys scroll the active window in the TUI mode, they
24075 are not available for their normal use by readline unless the command
24076 window has the focus. When another window is active, you must use
24077 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24078 and @kbd{C-f} to control the command window.
24080 @node TUI Single Key Mode
24081 @section TUI Single Key Mode
24082 @cindex TUI single key mode
24084 The TUI also provides a @dfn{SingleKey} mode, which binds several
24085 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24086 switch into this mode, where the following key bindings are used:
24089 @kindex c @r{(SingleKey TUI key)}
24093 @kindex d @r{(SingleKey TUI key)}
24097 @kindex f @r{(SingleKey TUI key)}
24101 @kindex n @r{(SingleKey TUI key)}
24105 @kindex q @r{(SingleKey TUI key)}
24107 exit the SingleKey mode.
24109 @kindex r @r{(SingleKey TUI key)}
24113 @kindex s @r{(SingleKey TUI key)}
24117 @kindex u @r{(SingleKey TUI key)}
24121 @kindex v @r{(SingleKey TUI key)}
24125 @kindex w @r{(SingleKey TUI key)}
24130 Other keys temporarily switch to the @value{GDBN} command prompt.
24131 The key that was pressed is inserted in the editing buffer so that
24132 it is possible to type most @value{GDBN} commands without interaction
24133 with the TUI SingleKey mode. Once the command is entered the TUI
24134 SingleKey mode is restored. The only way to permanently leave
24135 this mode is by typing @kbd{q} or @kbd{C-x s}.
24139 @section TUI-specific Commands
24140 @cindex TUI commands
24142 The TUI has specific commands to control the text windows.
24143 These commands are always available, even when @value{GDBN} is not in
24144 the TUI mode. When @value{GDBN} is in the standard mode, most
24145 of these commands will automatically switch to the TUI mode.
24147 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24148 terminal, or @value{GDBN} has been started with the machine interface
24149 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24150 these commands will fail with an error, because it would not be
24151 possible or desirable to enable curses window management.
24156 List and give the size of all displayed windows.
24160 Display the next layout.
24163 Display the previous layout.
24166 Display the source window only.
24169 Display the assembly window only.
24172 Display the source and assembly window.
24175 Display the register window together with the source or assembly window.
24179 Make the next window active for scrolling.
24182 Make the previous window active for scrolling.
24185 Make the source window active for scrolling.
24188 Make the assembly window active for scrolling.
24191 Make the register window active for scrolling.
24194 Make the command window active for scrolling.
24198 Refresh the screen. This is similar to typing @kbd{C-L}.
24200 @item tui reg float
24202 Show the floating point registers in the register window.
24204 @item tui reg general
24205 Show the general registers in the register window.
24208 Show the next register group. The list of register groups as well as
24209 their order is target specific. The predefined register groups are the
24210 following: @code{general}, @code{float}, @code{system}, @code{vector},
24211 @code{all}, @code{save}, @code{restore}.
24213 @item tui reg system
24214 Show the system registers in the register window.
24218 Update the source window and the current execution point.
24220 @item winheight @var{name} +@var{count}
24221 @itemx winheight @var{name} -@var{count}
24223 Change the height of the window @var{name} by @var{count}
24224 lines. Positive counts increase the height, while negative counts
24227 @item tabset @var{nchars}
24229 Set the width of tab stops to be @var{nchars} characters.
24232 @node TUI Configuration
24233 @section TUI Configuration Variables
24234 @cindex TUI configuration variables
24236 Several configuration variables control the appearance of TUI windows.
24239 @item set tui border-kind @var{kind}
24240 @kindex set tui border-kind
24241 Select the border appearance for the source, assembly and register windows.
24242 The possible values are the following:
24245 Use a space character to draw the border.
24248 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24251 Use the Alternate Character Set to draw the border. The border is
24252 drawn using character line graphics if the terminal supports them.
24255 @item set tui border-mode @var{mode}
24256 @kindex set tui border-mode
24257 @itemx set tui active-border-mode @var{mode}
24258 @kindex set tui active-border-mode
24259 Select the display attributes for the borders of the inactive windows
24260 or the active window. The @var{mode} can be one of the following:
24263 Use normal attributes to display the border.
24269 Use reverse video mode.
24272 Use half bright mode.
24274 @item half-standout
24275 Use half bright and standout mode.
24278 Use extra bright or bold mode.
24280 @item bold-standout
24281 Use extra bright or bold and standout mode.
24286 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24289 @cindex @sc{gnu} Emacs
24290 A special interface allows you to use @sc{gnu} Emacs to view (and
24291 edit) the source files for the program you are debugging with
24294 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24295 executable file you want to debug as an argument. This command starts
24296 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24297 created Emacs buffer.
24298 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24300 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24305 All ``terminal'' input and output goes through an Emacs buffer, called
24308 This applies both to @value{GDBN} commands and their output, and to the input
24309 and output done by the program you are debugging.
24311 This is useful because it means that you can copy the text of previous
24312 commands and input them again; you can even use parts of the output
24315 All the facilities of Emacs' Shell mode are available for interacting
24316 with your program. In particular, you can send signals the usual
24317 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24321 @value{GDBN} displays source code through Emacs.
24323 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24324 source file for that frame and puts an arrow (@samp{=>}) at the
24325 left margin of the current line. Emacs uses a separate buffer for
24326 source display, and splits the screen to show both your @value{GDBN} session
24329 Explicit @value{GDBN} @code{list} or search commands still produce output as
24330 usual, but you probably have no reason to use them from Emacs.
24333 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24334 a graphical mode, enabled by default, which provides further buffers
24335 that can control the execution and describe the state of your program.
24336 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24338 If you specify an absolute file name when prompted for the @kbd{M-x
24339 gdb} argument, then Emacs sets your current working directory to where
24340 your program resides. If you only specify the file name, then Emacs
24341 sets your current working directory to the directory associated
24342 with the previous buffer. In this case, @value{GDBN} may find your
24343 program by searching your environment's @code{PATH} variable, but on
24344 some operating systems it might not find the source. So, although the
24345 @value{GDBN} input and output session proceeds normally, the auxiliary
24346 buffer does not display the current source and line of execution.
24348 The initial working directory of @value{GDBN} is printed on the top
24349 line of the GUD buffer and this serves as a default for the commands
24350 that specify files for @value{GDBN} to operate on. @xref{Files,
24351 ,Commands to Specify Files}.
24353 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24354 need to call @value{GDBN} by a different name (for example, if you
24355 keep several configurations around, with different names) you can
24356 customize the Emacs variable @code{gud-gdb-command-name} to run the
24359 In the GUD buffer, you can use these special Emacs commands in
24360 addition to the standard Shell mode commands:
24364 Describe the features of Emacs' GUD Mode.
24367 Execute to another source line, like the @value{GDBN} @code{step} command; also
24368 update the display window to show the current file and location.
24371 Execute to next source line in this function, skipping all function
24372 calls, like the @value{GDBN} @code{next} command. Then update the display window
24373 to show the current file and location.
24376 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24377 display window accordingly.
24380 Execute until exit from the selected stack frame, like the @value{GDBN}
24381 @code{finish} command.
24384 Continue execution of your program, like the @value{GDBN} @code{continue}
24388 Go up the number of frames indicated by the numeric argument
24389 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24390 like the @value{GDBN} @code{up} command.
24393 Go down the number of frames indicated by the numeric argument, like the
24394 @value{GDBN} @code{down} command.
24397 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24398 tells @value{GDBN} to set a breakpoint on the source line point is on.
24400 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24401 separate frame which shows a backtrace when the GUD buffer is current.
24402 Move point to any frame in the stack and type @key{RET} to make it
24403 become the current frame and display the associated source in the
24404 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24405 selected frame become the current one. In graphical mode, the
24406 speedbar displays watch expressions.
24408 If you accidentally delete the source-display buffer, an easy way to get
24409 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24410 request a frame display; when you run under Emacs, this recreates
24411 the source buffer if necessary to show you the context of the current
24414 The source files displayed in Emacs are in ordinary Emacs buffers
24415 which are visiting the source files in the usual way. You can edit
24416 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24417 communicates with Emacs in terms of line numbers. If you add or
24418 delete lines from the text, the line numbers that @value{GDBN} knows cease
24419 to correspond properly with the code.
24421 A more detailed description of Emacs' interaction with @value{GDBN} is
24422 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24425 @c The following dropped because Epoch is nonstandard. Reactivate
24426 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
24428 @kindex Emacs Epoch environment
24432 Version 18 of @sc{gnu} Emacs has a built-in window system
24433 called the @code{epoch}
24434 environment. Users of this environment can use a new command,
24435 @code{inspect} which performs identically to @code{print} except that
24436 each value is printed in its own window.
24441 @chapter The @sc{gdb/mi} Interface
24443 @unnumberedsec Function and Purpose
24445 @cindex @sc{gdb/mi}, its purpose
24446 @sc{gdb/mi} is a line based machine oriented text interface to
24447 @value{GDBN} and is activated by specifying using the
24448 @option{--interpreter} command line option (@pxref{Mode Options}). It
24449 is specifically intended to support the development of systems which
24450 use the debugger as just one small component of a larger system.
24452 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24453 in the form of a reference manual.
24455 Note that @sc{gdb/mi} is still under construction, so some of the
24456 features described below are incomplete and subject to change
24457 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24459 @unnumberedsec Notation and Terminology
24461 @cindex notational conventions, for @sc{gdb/mi}
24462 This chapter uses the following notation:
24466 @code{|} separates two alternatives.
24469 @code{[ @var{something} ]} indicates that @var{something} is optional:
24470 it may or may not be given.
24473 @code{( @var{group} )*} means that @var{group} inside the parentheses
24474 may repeat zero or more times.
24477 @code{( @var{group} )+} means that @var{group} inside the parentheses
24478 may repeat one or more times.
24481 @code{"@var{string}"} means a literal @var{string}.
24485 @heading Dependencies
24489 * GDB/MI General Design::
24490 * GDB/MI Command Syntax::
24491 * GDB/MI Compatibility with CLI::
24492 * GDB/MI Development and Front Ends::
24493 * GDB/MI Output Records::
24494 * GDB/MI Simple Examples::
24495 * GDB/MI Command Description Format::
24496 * GDB/MI Breakpoint Commands::
24497 * GDB/MI Program Context::
24498 * GDB/MI Thread Commands::
24499 * GDB/MI Program Execution::
24500 * GDB/MI Stack Manipulation::
24501 * GDB/MI Variable Objects::
24502 * GDB/MI Data Manipulation::
24503 * GDB/MI Tracepoint Commands::
24504 * GDB/MI Symbol Query::
24505 * GDB/MI File Commands::
24507 * GDB/MI Kod Commands::
24508 * GDB/MI Memory Overlay Commands::
24509 * GDB/MI Signal Handling Commands::
24511 * GDB/MI Target Manipulation::
24512 * GDB/MI File Transfer Commands::
24513 * GDB/MI Miscellaneous Commands::
24516 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24517 @node GDB/MI General Design
24518 @section @sc{gdb/mi} General Design
24519 @cindex GDB/MI General Design
24521 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24522 parts---commands sent to @value{GDBN}, responses to those commands
24523 and notifications. Each command results in exactly one response,
24524 indicating either successful completion of the command, or an error.
24525 For the commands that do not resume the target, the response contains the
24526 requested information. For the commands that resume the target, the
24527 response only indicates whether the target was successfully resumed.
24528 Notifications is the mechanism for reporting changes in the state of the
24529 target, or in @value{GDBN} state, that cannot conveniently be associated with
24530 a command and reported as part of that command response.
24532 The important examples of notifications are:
24536 Exec notifications. These are used to report changes in
24537 target state---when a target is resumed, or stopped. It would not
24538 be feasible to include this information in response of resuming
24539 commands, because one resume commands can result in multiple events in
24540 different threads. Also, quite some time may pass before any event
24541 happens in the target, while a frontend needs to know whether the resuming
24542 command itself was successfully executed.
24545 Console output, and status notifications. Console output
24546 notifications are used to report output of CLI commands, as well as
24547 diagnostics for other commands. Status notifications are used to
24548 report the progress of a long-running operation. Naturally, including
24549 this information in command response would mean no output is produced
24550 until the command is finished, which is undesirable.
24553 General notifications. Commands may have various side effects on
24554 the @value{GDBN} or target state beyond their official purpose. For example,
24555 a command may change the selected thread. Although such changes can
24556 be included in command response, using notification allows for more
24557 orthogonal frontend design.
24561 There's no guarantee that whenever an MI command reports an error,
24562 @value{GDBN} or the target are in any specific state, and especially,
24563 the state is not reverted to the state before the MI command was
24564 processed. Therefore, whenever an MI command results in an error,
24565 we recommend that the frontend refreshes all the information shown in
24566 the user interface.
24570 * Context management::
24571 * Asynchronous and non-stop modes::
24575 @node Context management
24576 @subsection Context management
24578 In most cases when @value{GDBN} accesses the target, this access is
24579 done in context of a specific thread and frame (@pxref{Frames}).
24580 Often, even when accessing global data, the target requires that a thread
24581 be specified. The CLI interface maintains the selected thread and frame,
24582 and supplies them to target on each command. This is convenient,
24583 because a command line user would not want to specify that information
24584 explicitly on each command, and because user interacts with
24585 @value{GDBN} via a single terminal, so no confusion is possible as
24586 to what thread and frame are the current ones.
24588 In the case of MI, the concept of selected thread and frame is less
24589 useful. First, a frontend can easily remember this information
24590 itself. Second, a graphical frontend can have more than one window,
24591 each one used for debugging a different thread, and the frontend might
24592 want to access additional threads for internal purposes. This
24593 increases the risk that by relying on implicitly selected thread, the
24594 frontend may be operating on a wrong one. Therefore, each MI command
24595 should explicitly specify which thread and frame to operate on. To
24596 make it possible, each MI command accepts the @samp{--thread} and
24597 @samp{--frame} options, the value to each is @value{GDBN} identifier
24598 for thread and frame to operate on.
24600 Usually, each top-level window in a frontend allows the user to select
24601 a thread and a frame, and remembers the user selection for further
24602 operations. However, in some cases @value{GDBN} may suggest that the
24603 current thread be changed. For example, when stopping on a breakpoint
24604 it is reasonable to switch to the thread where breakpoint is hit. For
24605 another example, if the user issues the CLI @samp{thread} command via
24606 the frontend, it is desirable to change the frontend's selected thread to the
24607 one specified by user. @value{GDBN} communicates the suggestion to
24608 change current thread using the @samp{=thread-selected} notification.
24609 No such notification is available for the selected frame at the moment.
24611 Note that historically, MI shares the selected thread with CLI, so
24612 frontends used the @code{-thread-select} to execute commands in the
24613 right context. However, getting this to work right is cumbersome. The
24614 simplest way is for frontend to emit @code{-thread-select} command
24615 before every command. This doubles the number of commands that need
24616 to be sent. The alternative approach is to suppress @code{-thread-select}
24617 if the selected thread in @value{GDBN} is supposed to be identical to the
24618 thread the frontend wants to operate on. However, getting this
24619 optimization right can be tricky. In particular, if the frontend
24620 sends several commands to @value{GDBN}, and one of the commands changes the
24621 selected thread, then the behaviour of subsequent commands will
24622 change. So, a frontend should either wait for response from such
24623 problematic commands, or explicitly add @code{-thread-select} for
24624 all subsequent commands. No frontend is known to do this exactly
24625 right, so it is suggested to just always pass the @samp{--thread} and
24626 @samp{--frame} options.
24628 @node Asynchronous and non-stop modes
24629 @subsection Asynchronous command execution and non-stop mode
24631 On some targets, @value{GDBN} is capable of processing MI commands
24632 even while the target is running. This is called @dfn{asynchronous
24633 command execution} (@pxref{Background Execution}). The frontend may
24634 specify a preferrence for asynchronous execution using the
24635 @code{-gdb-set target-async 1} command, which should be emitted before
24636 either running the executable or attaching to the target. After the
24637 frontend has started the executable or attached to the target, it can
24638 find if asynchronous execution is enabled using the
24639 @code{-list-target-features} command.
24641 Even if @value{GDBN} can accept a command while target is running,
24642 many commands that access the target do not work when the target is
24643 running. Therefore, asynchronous command execution is most useful
24644 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24645 it is possible to examine the state of one thread, while other threads
24648 When a given thread is running, MI commands that try to access the
24649 target in the context of that thread may not work, or may work only on
24650 some targets. In particular, commands that try to operate on thread's
24651 stack will not work, on any target. Commands that read memory, or
24652 modify breakpoints, may work or not work, depending on the target. Note
24653 that even commands that operate on global state, such as @code{print},
24654 @code{set}, and breakpoint commands, still access the target in the
24655 context of a specific thread, so frontend should try to find a
24656 stopped thread and perform the operation on that thread (using the
24657 @samp{--thread} option).
24659 Which commands will work in the context of a running thread is
24660 highly target dependent. However, the two commands
24661 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24662 to find the state of a thread, will always work.
24664 @node Thread groups
24665 @subsection Thread groups
24666 @value{GDBN} may be used to debug several processes at the same time.
24667 On some platfroms, @value{GDBN} may support debugging of several
24668 hardware systems, each one having several cores with several different
24669 processes running on each core. This section describes the MI
24670 mechanism to support such debugging scenarios.
24672 The key observation is that regardless of the structure of the
24673 target, MI can have a global list of threads, because most commands that
24674 accept the @samp{--thread} option do not need to know what process that
24675 thread belongs to. Therefore, it is not necessary to introduce
24676 neither additional @samp{--process} option, nor an notion of the
24677 current process in the MI interface. The only strictly new feature
24678 that is required is the ability to find how the threads are grouped
24681 To allow the user to discover such grouping, and to support arbitrary
24682 hierarchy of machines/cores/processes, MI introduces the concept of a
24683 @dfn{thread group}. Thread group is a collection of threads and other
24684 thread groups. A thread group always has a string identifier, a type,
24685 and may have additional attributes specific to the type. A new
24686 command, @code{-list-thread-groups}, returns the list of top-level
24687 thread groups, which correspond to processes that @value{GDBN} is
24688 debugging at the moment. By passing an identifier of a thread group
24689 to the @code{-list-thread-groups} command, it is possible to obtain
24690 the members of specific thread group.
24692 To allow the user to easily discover processes, and other objects, he
24693 wishes to debug, a concept of @dfn{available thread group} is
24694 introduced. Available thread group is an thread group that
24695 @value{GDBN} is not debugging, but that can be attached to, using the
24696 @code{-target-attach} command. The list of available top-level thread
24697 groups can be obtained using @samp{-list-thread-groups --available}.
24698 In general, the content of a thread group may be only retrieved only
24699 after attaching to that thread group.
24701 Thread groups are related to inferiors (@pxref{Inferiors and
24702 Programs}). Each inferior corresponds to a thread group of a special
24703 type @samp{process}, and some additional operations are permitted on
24704 such thread groups.
24706 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24707 @node GDB/MI Command Syntax
24708 @section @sc{gdb/mi} Command Syntax
24711 * GDB/MI Input Syntax::
24712 * GDB/MI Output Syntax::
24715 @node GDB/MI Input Syntax
24716 @subsection @sc{gdb/mi} Input Syntax
24718 @cindex input syntax for @sc{gdb/mi}
24719 @cindex @sc{gdb/mi}, input syntax
24721 @item @var{command} @expansion{}
24722 @code{@var{cli-command} | @var{mi-command}}
24724 @item @var{cli-command} @expansion{}
24725 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24726 @var{cli-command} is any existing @value{GDBN} CLI command.
24728 @item @var{mi-command} @expansion{}
24729 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24730 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24732 @item @var{token} @expansion{}
24733 "any sequence of digits"
24735 @item @var{option} @expansion{}
24736 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24738 @item @var{parameter} @expansion{}
24739 @code{@var{non-blank-sequence} | @var{c-string}}
24741 @item @var{operation} @expansion{}
24742 @emph{any of the operations described in this chapter}
24744 @item @var{non-blank-sequence} @expansion{}
24745 @emph{anything, provided it doesn't contain special characters such as
24746 "-", @var{nl}, """ and of course " "}
24748 @item @var{c-string} @expansion{}
24749 @code{""" @var{seven-bit-iso-c-string-content} """}
24751 @item @var{nl} @expansion{}
24760 The CLI commands are still handled by the @sc{mi} interpreter; their
24761 output is described below.
24764 The @code{@var{token}}, when present, is passed back when the command
24768 Some @sc{mi} commands accept optional arguments as part of the parameter
24769 list. Each option is identified by a leading @samp{-} (dash) and may be
24770 followed by an optional argument parameter. Options occur first in the
24771 parameter list and can be delimited from normal parameters using
24772 @samp{--} (this is useful when some parameters begin with a dash).
24779 We want easy access to the existing CLI syntax (for debugging).
24782 We want it to be easy to spot a @sc{mi} operation.
24785 @node GDB/MI Output Syntax
24786 @subsection @sc{gdb/mi} Output Syntax
24788 @cindex output syntax of @sc{gdb/mi}
24789 @cindex @sc{gdb/mi}, output syntax
24790 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24791 followed, optionally, by a single result record. This result record
24792 is for the most recent command. The sequence of output records is
24793 terminated by @samp{(gdb)}.
24795 If an input command was prefixed with a @code{@var{token}} then the
24796 corresponding output for that command will also be prefixed by that same
24800 @item @var{output} @expansion{}
24801 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24803 @item @var{result-record} @expansion{}
24804 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24806 @item @var{out-of-band-record} @expansion{}
24807 @code{@var{async-record} | @var{stream-record}}
24809 @item @var{async-record} @expansion{}
24810 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24812 @item @var{exec-async-output} @expansion{}
24813 @code{[ @var{token} ] "*" @var{async-output}}
24815 @item @var{status-async-output} @expansion{}
24816 @code{[ @var{token} ] "+" @var{async-output}}
24818 @item @var{notify-async-output} @expansion{}
24819 @code{[ @var{token} ] "=" @var{async-output}}
24821 @item @var{async-output} @expansion{}
24822 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24824 @item @var{result-class} @expansion{}
24825 @code{"done" | "running" | "connected" | "error" | "exit"}
24827 @item @var{async-class} @expansion{}
24828 @code{"stopped" | @var{others}} (where @var{others} will be added
24829 depending on the needs---this is still in development).
24831 @item @var{result} @expansion{}
24832 @code{ @var{variable} "=" @var{value}}
24834 @item @var{variable} @expansion{}
24835 @code{ @var{string} }
24837 @item @var{value} @expansion{}
24838 @code{ @var{const} | @var{tuple} | @var{list} }
24840 @item @var{const} @expansion{}
24841 @code{@var{c-string}}
24843 @item @var{tuple} @expansion{}
24844 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24846 @item @var{list} @expansion{}
24847 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24848 @var{result} ( "," @var{result} )* "]" }
24850 @item @var{stream-record} @expansion{}
24851 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24853 @item @var{console-stream-output} @expansion{}
24854 @code{"~" @var{c-string}}
24856 @item @var{target-stream-output} @expansion{}
24857 @code{"@@" @var{c-string}}
24859 @item @var{log-stream-output} @expansion{}
24860 @code{"&" @var{c-string}}
24862 @item @var{nl} @expansion{}
24865 @item @var{token} @expansion{}
24866 @emph{any sequence of digits}.
24874 All output sequences end in a single line containing a period.
24877 The @code{@var{token}} is from the corresponding request. Note that
24878 for all async output, while the token is allowed by the grammar and
24879 may be output by future versions of @value{GDBN} for select async
24880 output messages, it is generally omitted. Frontends should treat
24881 all async output as reporting general changes in the state of the
24882 target and there should be no need to associate async output to any
24886 @cindex status output in @sc{gdb/mi}
24887 @var{status-async-output} contains on-going status information about the
24888 progress of a slow operation. It can be discarded. All status output is
24889 prefixed by @samp{+}.
24892 @cindex async output in @sc{gdb/mi}
24893 @var{exec-async-output} contains asynchronous state change on the target
24894 (stopped, started, disappeared). All async output is prefixed by
24898 @cindex notify output in @sc{gdb/mi}
24899 @var{notify-async-output} contains supplementary information that the
24900 client should handle (e.g., a new breakpoint information). All notify
24901 output is prefixed by @samp{=}.
24904 @cindex console output in @sc{gdb/mi}
24905 @var{console-stream-output} is output that should be displayed as is in the
24906 console. It is the textual response to a CLI command. All the console
24907 output is prefixed by @samp{~}.
24910 @cindex target output in @sc{gdb/mi}
24911 @var{target-stream-output} is the output produced by the target program.
24912 All the target output is prefixed by @samp{@@}.
24915 @cindex log output in @sc{gdb/mi}
24916 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24917 instance messages that should be displayed as part of an error log. All
24918 the log output is prefixed by @samp{&}.
24921 @cindex list output in @sc{gdb/mi}
24922 New @sc{gdb/mi} commands should only output @var{lists} containing
24928 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24929 details about the various output records.
24931 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24932 @node GDB/MI Compatibility with CLI
24933 @section @sc{gdb/mi} Compatibility with CLI
24935 @cindex compatibility, @sc{gdb/mi} and CLI
24936 @cindex @sc{gdb/mi}, compatibility with CLI
24938 For the developers convenience CLI commands can be entered directly,
24939 but there may be some unexpected behaviour. For example, commands
24940 that query the user will behave as if the user replied yes, breakpoint
24941 command lists are not executed and some CLI commands, such as
24942 @code{if}, @code{when} and @code{define}, prompt for further input with
24943 @samp{>}, which is not valid MI output.
24945 This feature may be removed at some stage in the future and it is
24946 recommended that front ends use the @code{-interpreter-exec} command
24947 (@pxref{-interpreter-exec}).
24949 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24950 @node GDB/MI Development and Front Ends
24951 @section @sc{gdb/mi} Development and Front Ends
24952 @cindex @sc{gdb/mi} development
24954 The application which takes the MI output and presents the state of the
24955 program being debugged to the user is called a @dfn{front end}.
24957 Although @sc{gdb/mi} is still incomplete, it is currently being used
24958 by a variety of front ends to @value{GDBN}. This makes it difficult
24959 to introduce new functionality without breaking existing usage. This
24960 section tries to minimize the problems by describing how the protocol
24963 Some changes in MI need not break a carefully designed front end, and
24964 for these the MI version will remain unchanged. The following is a
24965 list of changes that may occur within one level, so front ends should
24966 parse MI output in a way that can handle them:
24970 New MI commands may be added.
24973 New fields may be added to the output of any MI command.
24976 The range of values for fields with specified values, e.g.,
24977 @code{in_scope} (@pxref{-var-update}) may be extended.
24979 @c The format of field's content e.g type prefix, may change so parse it
24980 @c at your own risk. Yes, in general?
24982 @c The order of fields may change? Shouldn't really matter but it might
24983 @c resolve inconsistencies.
24986 If the changes are likely to break front ends, the MI version level
24987 will be increased by one. This will allow the front end to parse the
24988 output according to the MI version. Apart from mi0, new versions of
24989 @value{GDBN} will not support old versions of MI and it will be the
24990 responsibility of the front end to work with the new one.
24992 @c Starting with mi3, add a new command -mi-version that prints the MI
24995 The best way to avoid unexpected changes in MI that might break your front
24996 end is to make your project known to @value{GDBN} developers and
24997 follow development on @email{gdb@@sourceware.org} and
24998 @email{gdb-patches@@sourceware.org}.
24999 @cindex mailing lists
25001 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25002 @node GDB/MI Output Records
25003 @section @sc{gdb/mi} Output Records
25006 * GDB/MI Result Records::
25007 * GDB/MI Stream Records::
25008 * GDB/MI Async Records::
25009 * GDB/MI Frame Information::
25010 * GDB/MI Thread Information::
25011 * GDB/MI Ada Exception Information::
25014 @node GDB/MI Result Records
25015 @subsection @sc{gdb/mi} Result Records
25017 @cindex result records in @sc{gdb/mi}
25018 @cindex @sc{gdb/mi}, result records
25019 In addition to a number of out-of-band notifications, the response to a
25020 @sc{gdb/mi} command includes one of the following result indications:
25024 @item "^done" [ "," @var{results} ]
25025 The synchronous operation was successful, @code{@var{results}} are the return
25030 This result record is equivalent to @samp{^done}. Historically, it
25031 was output instead of @samp{^done} if the command has resumed the
25032 target. This behaviour is maintained for backward compatibility, but
25033 all frontends should treat @samp{^done} and @samp{^running}
25034 identically and rely on the @samp{*running} output record to determine
25035 which threads are resumed.
25039 @value{GDBN} has connected to a remote target.
25041 @item "^error" "," @var{c-string}
25043 The operation failed. The @code{@var{c-string}} contains the corresponding
25048 @value{GDBN} has terminated.
25052 @node GDB/MI Stream Records
25053 @subsection @sc{gdb/mi} Stream Records
25055 @cindex @sc{gdb/mi}, stream records
25056 @cindex stream records in @sc{gdb/mi}
25057 @value{GDBN} internally maintains a number of output streams: the console, the
25058 target, and the log. The output intended for each of these streams is
25059 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25061 Each stream record begins with a unique @dfn{prefix character} which
25062 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25063 Syntax}). In addition to the prefix, each stream record contains a
25064 @code{@var{string-output}}. This is either raw text (with an implicit new
25065 line) or a quoted C string (which does not contain an implicit newline).
25068 @item "~" @var{string-output}
25069 The console output stream contains text that should be displayed in the
25070 CLI console window. It contains the textual responses to CLI commands.
25072 @item "@@" @var{string-output}
25073 The target output stream contains any textual output from the running
25074 target. This is only present when GDB's event loop is truly
25075 asynchronous, which is currently only the case for remote targets.
25077 @item "&" @var{string-output}
25078 The log stream contains debugging messages being produced by @value{GDBN}'s
25082 @node GDB/MI Async Records
25083 @subsection @sc{gdb/mi} Async Records
25085 @cindex async records in @sc{gdb/mi}
25086 @cindex @sc{gdb/mi}, async records
25087 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25088 additional changes that have occurred. Those changes can either be a
25089 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25090 target activity (e.g., target stopped).
25092 The following is the list of possible async records:
25096 @item *running,thread-id="@var{thread}"
25097 The target is now running. The @var{thread} field tells which
25098 specific thread is now running, and can be @samp{all} if all threads
25099 are running. The frontend should assume that no interaction with a
25100 running thread is possible after this notification is produced.
25101 The frontend should not assume that this notification is output
25102 only once for any command. @value{GDBN} may emit this notification
25103 several times, either for different threads, because it cannot resume
25104 all threads together, or even for a single thread, if the thread must
25105 be stepped though some code before letting it run freely.
25107 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25108 The target has stopped. The @var{reason} field can have one of the
25112 @item breakpoint-hit
25113 A breakpoint was reached.
25114 @item watchpoint-trigger
25115 A watchpoint was triggered.
25116 @item read-watchpoint-trigger
25117 A read watchpoint was triggered.
25118 @item access-watchpoint-trigger
25119 An access watchpoint was triggered.
25120 @item function-finished
25121 An -exec-finish or similar CLI command was accomplished.
25122 @item location-reached
25123 An -exec-until or similar CLI command was accomplished.
25124 @item watchpoint-scope
25125 A watchpoint has gone out of scope.
25126 @item end-stepping-range
25127 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25128 similar CLI command was accomplished.
25129 @item exited-signalled
25130 The inferior exited because of a signal.
25132 The inferior exited.
25133 @item exited-normally
25134 The inferior exited normally.
25135 @item signal-received
25136 A signal was received by the inferior.
25139 The @var{id} field identifies the thread that directly caused the stop
25140 -- for example by hitting a breakpoint. Depending on whether all-stop
25141 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25142 stop all threads, or only the thread that directly triggered the stop.
25143 If all threads are stopped, the @var{stopped} field will have the
25144 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25145 field will be a list of thread identifiers. Presently, this list will
25146 always include a single thread, but frontend should be prepared to see
25147 several threads in the list. The @var{core} field reports the
25148 processor core on which the stop event has happened. This field may be absent
25149 if such information is not available.
25151 @item =thread-group-added,id="@var{id}"
25152 @itemx =thread-group-removed,id="@var{id}"
25153 A thread group was either added or removed. The @var{id} field
25154 contains the @value{GDBN} identifier of the thread group. When a thread
25155 group is added, it generally might not be associated with a running
25156 process. When a thread group is removed, its id becomes invalid and
25157 cannot be used in any way.
25159 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25160 A thread group became associated with a running program,
25161 either because the program was just started or the thread group
25162 was attached to a program. The @var{id} field contains the
25163 @value{GDBN} identifier of the thread group. The @var{pid} field
25164 contains process identifier, specific to the operating system.
25166 @itemx =thread-group-exited,id="@var{id}"
25167 A thread group is no longer associated with a running program,
25168 either because the program has exited, or because it was detached
25169 from. The @var{id} field contains the @value{GDBN} identifier of the
25172 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25173 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25174 A thread either was created, or has exited. The @var{id} field
25175 contains the @value{GDBN} identifier of the thread. The @var{gid}
25176 field identifies the thread group this thread belongs to.
25178 @item =thread-selected,id="@var{id}"
25179 Informs that the selected thread was changed as result of the last
25180 command. This notification is not emitted as result of @code{-thread-select}
25181 command but is emitted whenever an MI command that is not documented
25182 to change the selected thread actually changes it. In particular,
25183 invoking, directly or indirectly (via user-defined command), the CLI
25184 @code{thread} command, will generate this notification.
25186 We suggest that in response to this notification, front ends
25187 highlight the selected thread and cause subsequent commands to apply to
25190 @item =library-loaded,...
25191 Reports that a new library file was loaded by the program. This
25192 notification has 4 fields---@var{id}, @var{target-name},
25193 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25194 opaque identifier of the library. For remote debugging case,
25195 @var{target-name} and @var{host-name} fields give the name of the
25196 library file on the target, and on the host respectively. For native
25197 debugging, both those fields have the same value. The
25198 @var{symbols-loaded} field is emitted only for backward compatibility
25199 and should not be relied on to convey any useful information. The
25200 @var{thread-group} field, if present, specifies the id of the thread
25201 group in whose context the library was loaded. If the field is
25202 absent, it means the library was loaded in the context of all present
25205 @item =library-unloaded,...
25206 Reports that a library was unloaded by the program. This notification
25207 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25208 the same meaning as for the @code{=library-loaded} notification.
25209 The @var{thread-group} field, if present, specifies the id of the
25210 thread group in whose context the library was unloaded. If the field is
25211 absent, it means the library was unloaded in the context of all present
25214 @item =breakpoint-created,bkpt=@{...@}
25215 @itemx =breakpoint-modified,bkpt=@{...@}
25216 @itemx =breakpoint-deleted,bkpt=@{...@}
25217 Reports that a breakpoint was created, modified, or deleted,
25218 respectively. Only user-visible breakpoints are reported to the MI
25221 The @var{bkpt} argument is of the same form as returned by the various
25222 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
25224 Note that if a breakpoint is emitted in the result record of a
25225 command, then it will not also be emitted in an async record.
25229 @node GDB/MI Frame Information
25230 @subsection @sc{gdb/mi} Frame Information
25232 Response from many MI commands includes an information about stack
25233 frame. This information is a tuple that may have the following
25238 The level of the stack frame. The innermost frame has the level of
25239 zero. This field is always present.
25242 The name of the function corresponding to the frame. This field may
25243 be absent if @value{GDBN} is unable to determine the function name.
25246 The code address for the frame. This field is always present.
25249 The name of the source files that correspond to the frame's code
25250 address. This field may be absent.
25253 The source line corresponding to the frames' code address. This field
25257 The name of the binary file (either executable or shared library) the
25258 corresponds to the frame's code address. This field may be absent.
25262 @node GDB/MI Thread Information
25263 @subsection @sc{gdb/mi} Thread Information
25265 Whenever @value{GDBN} has to report an information about a thread, it
25266 uses a tuple with the following fields:
25270 The numeric id assigned to the thread by @value{GDBN}. This field is
25274 Target-specific string identifying the thread. This field is always present.
25277 Additional information about the thread provided by the target.
25278 It is supposed to be human-readable and not interpreted by the
25279 frontend. This field is optional.
25282 Either @samp{stopped} or @samp{running}, depending on whether the
25283 thread is presently running. This field is always present.
25286 The value of this field is an integer number of the processor core the
25287 thread was last seen on. This field is optional.
25290 @node GDB/MI Ada Exception Information
25291 @subsection @sc{gdb/mi} Ada Exception Information
25293 Whenever a @code{*stopped} record is emitted because the program
25294 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25295 @value{GDBN} provides the name of the exception that was raised via
25296 the @code{exception-name} field.
25298 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25299 @node GDB/MI Simple Examples
25300 @section Simple Examples of @sc{gdb/mi} Interaction
25301 @cindex @sc{gdb/mi}, simple examples
25303 This subsection presents several simple examples of interaction using
25304 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25305 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25306 the output received from @sc{gdb/mi}.
25308 Note the line breaks shown in the examples are here only for
25309 readability, they don't appear in the real output.
25311 @subheading Setting a Breakpoint
25313 Setting a breakpoint generates synchronous output which contains detailed
25314 information of the breakpoint.
25317 -> -break-insert main
25318 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25319 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25320 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
25324 @subheading Program Execution
25326 Program execution generates asynchronous records and MI gives the
25327 reason that execution stopped.
25333 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25334 frame=@{addr="0x08048564",func="main",
25335 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25336 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25341 <- *stopped,reason="exited-normally"
25345 @subheading Quitting @value{GDBN}
25347 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25355 Please note that @samp{^exit} is printed immediately, but it might
25356 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25357 performs necessary cleanups, including killing programs being debugged
25358 or disconnecting from debug hardware, so the frontend should wait till
25359 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25360 fails to exit in reasonable time.
25362 @subheading A Bad Command
25364 Here's what happens if you pass a non-existent command:
25368 <- ^error,msg="Undefined MI command: rubbish"
25373 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25374 @node GDB/MI Command Description Format
25375 @section @sc{gdb/mi} Command Description Format
25377 The remaining sections describe blocks of commands. Each block of
25378 commands is laid out in a fashion similar to this section.
25380 @subheading Motivation
25382 The motivation for this collection of commands.
25384 @subheading Introduction
25386 A brief introduction to this collection of commands as a whole.
25388 @subheading Commands
25390 For each command in the block, the following is described:
25392 @subsubheading Synopsis
25395 -command @var{args}@dots{}
25398 @subsubheading Result
25400 @subsubheading @value{GDBN} Command
25402 The corresponding @value{GDBN} CLI command(s), if any.
25404 @subsubheading Example
25406 Example(s) formatted for readability. Some of the described commands have
25407 not been implemented yet and these are labeled N.A.@: (not available).
25410 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25411 @node GDB/MI Breakpoint Commands
25412 @section @sc{gdb/mi} Breakpoint Commands
25414 @cindex breakpoint commands for @sc{gdb/mi}
25415 @cindex @sc{gdb/mi}, breakpoint commands
25416 This section documents @sc{gdb/mi} commands for manipulating
25419 @subheading The @code{-break-after} Command
25420 @findex -break-after
25422 @subsubheading Synopsis
25425 -break-after @var{number} @var{count}
25428 The breakpoint number @var{number} is not in effect until it has been
25429 hit @var{count} times. To see how this is reflected in the output of
25430 the @samp{-break-list} command, see the description of the
25431 @samp{-break-list} command below.
25433 @subsubheading @value{GDBN} Command
25435 The corresponding @value{GDBN} command is @samp{ignore}.
25437 @subsubheading Example
25442 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25443 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25444 fullname="/home/foo/hello.c",line="5",times="0"@}
25451 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25452 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25453 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25454 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25455 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25456 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25457 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25458 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25459 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25460 line="5",times="0",ignore="3"@}]@}
25465 @subheading The @code{-break-catch} Command
25466 @findex -break-catch
25469 @subheading The @code{-break-commands} Command
25470 @findex -break-commands
25472 @subsubheading Synopsis
25475 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25478 Specifies the CLI commands that should be executed when breakpoint
25479 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25480 are the commands. If no command is specified, any previously-set
25481 commands are cleared. @xref{Break Commands}. Typical use of this
25482 functionality is tracing a program, that is, printing of values of
25483 some variables whenever breakpoint is hit and then continuing.
25485 @subsubheading @value{GDBN} Command
25487 The corresponding @value{GDBN} command is @samp{commands}.
25489 @subsubheading Example
25494 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25495 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25496 fullname="/home/foo/hello.c",line="5",times="0"@}
25498 -break-commands 1 "print v" "continue"
25503 @subheading The @code{-break-condition} Command
25504 @findex -break-condition
25506 @subsubheading Synopsis
25509 -break-condition @var{number} @var{expr}
25512 Breakpoint @var{number} will stop the program only if the condition in
25513 @var{expr} is true. The condition becomes part of the
25514 @samp{-break-list} output (see the description of the @samp{-break-list}
25517 @subsubheading @value{GDBN} Command
25519 The corresponding @value{GDBN} command is @samp{condition}.
25521 @subsubheading Example
25525 -break-condition 1 1
25529 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25530 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25531 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25532 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25533 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25534 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25535 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25536 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25537 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25538 line="5",cond="1",times="0",ignore="3"@}]@}
25542 @subheading The @code{-break-delete} Command
25543 @findex -break-delete
25545 @subsubheading Synopsis
25548 -break-delete ( @var{breakpoint} )+
25551 Delete the breakpoint(s) whose number(s) are specified in the argument
25552 list. This is obviously reflected in the breakpoint list.
25554 @subsubheading @value{GDBN} Command
25556 The corresponding @value{GDBN} command is @samp{delete}.
25558 @subsubheading Example
25566 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25567 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25568 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25569 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25570 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25571 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25572 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25577 @subheading The @code{-break-disable} Command
25578 @findex -break-disable
25580 @subsubheading Synopsis
25583 -break-disable ( @var{breakpoint} )+
25586 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25587 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25589 @subsubheading @value{GDBN} Command
25591 The corresponding @value{GDBN} command is @samp{disable}.
25593 @subsubheading Example
25601 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25602 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25603 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25604 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25605 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25606 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25607 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25608 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25609 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25610 line="5",times="0"@}]@}
25614 @subheading The @code{-break-enable} Command
25615 @findex -break-enable
25617 @subsubheading Synopsis
25620 -break-enable ( @var{breakpoint} )+
25623 Enable (previously disabled) @var{breakpoint}(s).
25625 @subsubheading @value{GDBN} Command
25627 The corresponding @value{GDBN} command is @samp{enable}.
25629 @subsubheading Example
25637 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25638 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25639 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25640 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25641 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25642 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25643 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25644 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25645 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25646 line="5",times="0"@}]@}
25650 @subheading The @code{-break-info} Command
25651 @findex -break-info
25653 @subsubheading Synopsis
25656 -break-info @var{breakpoint}
25660 Get information about a single breakpoint.
25662 @subsubheading @value{GDBN} Command
25664 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25666 @subsubheading Example
25669 @subheading The @code{-break-insert} Command
25670 @findex -break-insert
25672 @subsubheading Synopsis
25675 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25676 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25677 [ -p @var{thread} ] [ @var{location} ]
25681 If specified, @var{location}, can be one of:
25688 @item filename:linenum
25689 @item filename:function
25693 The possible optional parameters of this command are:
25697 Insert a temporary breakpoint.
25699 Insert a hardware breakpoint.
25700 @item -c @var{condition}
25701 Make the breakpoint conditional on @var{condition}.
25702 @item -i @var{ignore-count}
25703 Initialize the @var{ignore-count}.
25705 If @var{location} cannot be parsed (for example if it
25706 refers to unknown files or functions), create a pending
25707 breakpoint. Without this flag, @value{GDBN} will report
25708 an error, and won't create a breakpoint, if @var{location}
25711 Create a disabled breakpoint.
25713 Create a tracepoint. @xref{Tracepoints}. When this parameter
25714 is used together with @samp{-h}, a fast tracepoint is created.
25717 @subsubheading Result
25719 The result is in the form:
25722 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25723 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25724 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25725 times="@var{times}"@}
25729 where @var{number} is the @value{GDBN} number for this breakpoint,
25730 @var{funcname} is the name of the function where the breakpoint was
25731 inserted, @var{filename} is the name of the source file which contains
25732 this function, @var{lineno} is the source line number within that file
25733 and @var{times} the number of times that the breakpoint has been hit
25734 (always 0 for -break-insert but may be greater for -break-info or -break-list
25735 which use the same output).
25737 Note: this format is open to change.
25738 @c An out-of-band breakpoint instead of part of the result?
25740 @subsubheading @value{GDBN} Command
25742 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25743 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25745 @subsubheading Example
25750 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25751 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25753 -break-insert -t foo
25754 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25755 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25758 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25759 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25760 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25761 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25762 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25763 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25764 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25765 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25766 addr="0x0001072c", func="main",file="recursive2.c",
25767 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25768 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25769 addr="0x00010774",func="foo",file="recursive2.c",
25770 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25772 -break-insert -r foo.*
25773 ~int foo(int, int);
25774 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25775 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25779 @subheading The @code{-break-list} Command
25780 @findex -break-list
25782 @subsubheading Synopsis
25788 Displays the list of inserted breakpoints, showing the following fields:
25792 number of the breakpoint
25794 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25796 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25799 is the breakpoint enabled or no: @samp{y} or @samp{n}
25801 memory location at which the breakpoint is set
25803 logical location of the breakpoint, expressed by function name, file
25806 number of times the breakpoint has been hit
25809 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25810 @code{body} field is an empty list.
25812 @subsubheading @value{GDBN} Command
25814 The corresponding @value{GDBN} command is @samp{info break}.
25816 @subsubheading Example
25821 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25822 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25823 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25824 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25825 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25826 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25827 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25828 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25829 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25830 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25831 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25832 line="13",times="0"@}]@}
25836 Here's an example of the result when there are no breakpoints:
25841 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25842 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25843 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25844 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25845 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25846 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25847 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25852 @subheading The @code{-break-passcount} Command
25853 @findex -break-passcount
25855 @subsubheading Synopsis
25858 -break-passcount @var{tracepoint-number} @var{passcount}
25861 Set the passcount for tracepoint @var{tracepoint-number} to
25862 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25863 is not a tracepoint, error is emitted. This corresponds to CLI
25864 command @samp{passcount}.
25866 @subheading The @code{-break-watch} Command
25867 @findex -break-watch
25869 @subsubheading Synopsis
25872 -break-watch [ -a | -r ]
25875 Create a watchpoint. With the @samp{-a} option it will create an
25876 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25877 read from or on a write to the memory location. With the @samp{-r}
25878 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25879 trigger only when the memory location is accessed for reading. Without
25880 either of the options, the watchpoint created is a regular watchpoint,
25881 i.e., it will trigger when the memory location is accessed for writing.
25882 @xref{Set Watchpoints, , Setting Watchpoints}.
25884 Note that @samp{-break-list} will report a single list of watchpoints and
25885 breakpoints inserted.
25887 @subsubheading @value{GDBN} Command
25889 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25892 @subsubheading Example
25894 Setting a watchpoint on a variable in the @code{main} function:
25899 ^done,wpt=@{number="2",exp="x"@}
25904 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25905 value=@{old="-268439212",new="55"@},
25906 frame=@{func="main",args=[],file="recursive2.c",
25907 fullname="/home/foo/bar/recursive2.c",line="5"@}
25911 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25912 the program execution twice: first for the variable changing value, then
25913 for the watchpoint going out of scope.
25918 ^done,wpt=@{number="5",exp="C"@}
25923 *stopped,reason="watchpoint-trigger",
25924 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25925 frame=@{func="callee4",args=[],
25926 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25927 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25932 *stopped,reason="watchpoint-scope",wpnum="5",
25933 frame=@{func="callee3",args=[@{name="strarg",
25934 value="0x11940 \"A string argument.\""@}],
25935 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25936 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25940 Listing breakpoints and watchpoints, at different points in the program
25941 execution. Note that once the watchpoint goes out of scope, it is
25947 ^done,wpt=@{number="2",exp="C"@}
25950 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25951 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25952 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25953 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25954 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25955 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25956 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25957 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25958 addr="0x00010734",func="callee4",
25959 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25960 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25961 bkpt=@{number="2",type="watchpoint",disp="keep",
25962 enabled="y",addr="",what="C",times="0"@}]@}
25967 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25968 value=@{old="-276895068",new="3"@},
25969 frame=@{func="callee4",args=[],
25970 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25971 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25974 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25975 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25976 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25977 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25978 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25979 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25980 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25981 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25982 addr="0x00010734",func="callee4",
25983 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25984 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25985 bkpt=@{number="2",type="watchpoint",disp="keep",
25986 enabled="y",addr="",what="C",times="-5"@}]@}
25990 ^done,reason="watchpoint-scope",wpnum="2",
25991 frame=@{func="callee3",args=[@{name="strarg",
25992 value="0x11940 \"A string argument.\""@}],
25993 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25994 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25997 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25998 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25999 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26000 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26001 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26002 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26003 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26004 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26005 addr="0x00010734",func="callee4",
26006 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26007 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26012 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26013 @node GDB/MI Program Context
26014 @section @sc{gdb/mi} Program Context
26016 @subheading The @code{-exec-arguments} Command
26017 @findex -exec-arguments
26020 @subsubheading Synopsis
26023 -exec-arguments @var{args}
26026 Set the inferior program arguments, to be used in the next
26029 @subsubheading @value{GDBN} Command
26031 The corresponding @value{GDBN} command is @samp{set args}.
26033 @subsubheading Example
26037 -exec-arguments -v word
26044 @subheading The @code{-exec-show-arguments} Command
26045 @findex -exec-show-arguments
26047 @subsubheading Synopsis
26050 -exec-show-arguments
26053 Print the arguments of the program.
26055 @subsubheading @value{GDBN} Command
26057 The corresponding @value{GDBN} command is @samp{show args}.
26059 @subsubheading Example
26064 @subheading The @code{-environment-cd} Command
26065 @findex -environment-cd
26067 @subsubheading Synopsis
26070 -environment-cd @var{pathdir}
26073 Set @value{GDBN}'s working directory.
26075 @subsubheading @value{GDBN} Command
26077 The corresponding @value{GDBN} command is @samp{cd}.
26079 @subsubheading Example
26083 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26089 @subheading The @code{-environment-directory} Command
26090 @findex -environment-directory
26092 @subsubheading Synopsis
26095 -environment-directory [ -r ] [ @var{pathdir} ]+
26098 Add directories @var{pathdir} to beginning of search path for source files.
26099 If the @samp{-r} option is used, the search path is reset to the default
26100 search path. If directories @var{pathdir} are supplied in addition to the
26101 @samp{-r} option, the search path is first reset and then addition
26103 Multiple directories may be specified, separated by blanks. Specifying
26104 multiple directories in a single command
26105 results in the directories added to the beginning of the
26106 search path in the same order they were presented in the command.
26107 If blanks are needed as
26108 part of a directory name, double-quotes should be used around
26109 the name. In the command output, the path will show up separated
26110 by the system directory-separator character. The directory-separator
26111 character must not be used
26112 in any directory name.
26113 If no directories are specified, the current search path is displayed.
26115 @subsubheading @value{GDBN} Command
26117 The corresponding @value{GDBN} command is @samp{dir}.
26119 @subsubheading Example
26123 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26124 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26126 -environment-directory ""
26127 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26129 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26130 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26132 -environment-directory -r
26133 ^done,source-path="$cdir:$cwd"
26138 @subheading The @code{-environment-path} Command
26139 @findex -environment-path
26141 @subsubheading Synopsis
26144 -environment-path [ -r ] [ @var{pathdir} ]+
26147 Add directories @var{pathdir} to beginning of search path for object files.
26148 If the @samp{-r} option is used, the search path is reset to the original
26149 search path that existed at gdb start-up. If directories @var{pathdir} are
26150 supplied in addition to the
26151 @samp{-r} option, the search path is first reset and then addition
26153 Multiple directories may be specified, separated by blanks. Specifying
26154 multiple directories in a single command
26155 results in the directories added to the beginning of the
26156 search path in the same order they were presented in the command.
26157 If blanks are needed as
26158 part of a directory name, double-quotes should be used around
26159 the name. In the command output, the path will show up separated
26160 by the system directory-separator character. The directory-separator
26161 character must not be used
26162 in any directory name.
26163 If no directories are specified, the current path is displayed.
26166 @subsubheading @value{GDBN} Command
26168 The corresponding @value{GDBN} command is @samp{path}.
26170 @subsubheading Example
26175 ^done,path="/usr/bin"
26177 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26178 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26180 -environment-path -r /usr/local/bin
26181 ^done,path="/usr/local/bin:/usr/bin"
26186 @subheading The @code{-environment-pwd} Command
26187 @findex -environment-pwd
26189 @subsubheading Synopsis
26195 Show the current working directory.
26197 @subsubheading @value{GDBN} Command
26199 The corresponding @value{GDBN} command is @samp{pwd}.
26201 @subsubheading Example
26206 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26210 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26211 @node GDB/MI Thread Commands
26212 @section @sc{gdb/mi} Thread Commands
26215 @subheading The @code{-thread-info} Command
26216 @findex -thread-info
26218 @subsubheading Synopsis
26221 -thread-info [ @var{thread-id} ]
26224 Reports information about either a specific thread, if
26225 the @var{thread-id} parameter is present, or about all
26226 threads. When printing information about all threads,
26227 also reports the current thread.
26229 @subsubheading @value{GDBN} Command
26231 The @samp{info thread} command prints the same information
26234 @subsubheading Result
26236 The result is a list of threads. The following attributes are
26237 defined for a given thread:
26241 This field exists only for the current thread. It has the value @samp{*}.
26244 The identifier that @value{GDBN} uses to refer to the thread.
26247 The identifier that the target uses to refer to the thread.
26250 Extra information about the thread, in a target-specific format. This
26254 The name of the thread. If the user specified a name using the
26255 @code{thread name} command, then this name is given. Otherwise, if
26256 @value{GDBN} can extract the thread name from the target, then that
26257 name is given. If @value{GDBN} cannot find the thread name, then this
26261 The stack frame currently executing in the thread.
26264 The thread's state. The @samp{state} field may have the following
26269 The thread is stopped. Frame information is available for stopped
26273 The thread is running. There's no frame information for running
26279 If @value{GDBN} can find the CPU core on which this thread is running,
26280 then this field is the core identifier. This field is optional.
26284 @subsubheading Example
26289 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26290 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26291 args=[]@},state="running"@},
26292 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26293 frame=@{level="0",addr="0x0804891f",func="foo",
26294 args=[@{name="i",value="10"@}],
26295 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26296 state="running"@}],
26297 current-thread-id="1"
26301 @subheading The @code{-thread-list-ids} Command
26302 @findex -thread-list-ids
26304 @subsubheading Synopsis
26310 Produces a list of the currently known @value{GDBN} thread ids. At the
26311 end of the list it also prints the total number of such threads.
26313 This command is retained for historical reasons, the
26314 @code{-thread-info} command should be used instead.
26316 @subsubheading @value{GDBN} Command
26318 Part of @samp{info threads} supplies the same information.
26320 @subsubheading Example
26325 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26326 current-thread-id="1",number-of-threads="3"
26331 @subheading The @code{-thread-select} Command
26332 @findex -thread-select
26334 @subsubheading Synopsis
26337 -thread-select @var{threadnum}
26340 Make @var{threadnum} the current thread. It prints the number of the new
26341 current thread, and the topmost frame for that thread.
26343 This command is deprecated in favor of explicitly using the
26344 @samp{--thread} option to each command.
26346 @subsubheading @value{GDBN} Command
26348 The corresponding @value{GDBN} command is @samp{thread}.
26350 @subsubheading Example
26357 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26358 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26362 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26363 number-of-threads="3"
26366 ^done,new-thread-id="3",
26367 frame=@{level="0",func="vprintf",
26368 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26369 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26373 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26374 @node GDB/MI Program Execution
26375 @section @sc{gdb/mi} Program Execution
26377 These are the asynchronous commands which generate the out-of-band
26378 record @samp{*stopped}. Currently @value{GDBN} only really executes
26379 asynchronously with remote targets and this interaction is mimicked in
26382 @subheading The @code{-exec-continue} Command
26383 @findex -exec-continue
26385 @subsubheading Synopsis
26388 -exec-continue [--reverse] [--all|--thread-group N]
26391 Resumes the execution of the inferior program, which will continue
26392 to execute until it reaches a debugger stop event. If the
26393 @samp{--reverse} option is specified, execution resumes in reverse until
26394 it reaches a stop event. Stop events may include
26397 breakpoints or watchpoints
26399 signals or exceptions
26401 the end of the process (or its beginning under @samp{--reverse})
26403 the end or beginning of a replay log if one is being used.
26405 In all-stop mode (@pxref{All-Stop
26406 Mode}), may resume only one thread, or all threads, depending on the
26407 value of the @samp{scheduler-locking} variable. If @samp{--all} is
26408 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
26409 ignored in all-stop mode. If the @samp{--thread-group} options is
26410 specified, then all threads in that thread group are resumed.
26412 @subsubheading @value{GDBN} Command
26414 The corresponding @value{GDBN} corresponding is @samp{continue}.
26416 @subsubheading Example
26423 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
26424 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
26430 @subheading The @code{-exec-finish} Command
26431 @findex -exec-finish
26433 @subsubheading Synopsis
26436 -exec-finish [--reverse]
26439 Resumes the execution of the inferior program until the current
26440 function is exited. Displays the results returned by the function.
26441 If the @samp{--reverse} option is specified, resumes the reverse
26442 execution of the inferior program until the point where current
26443 function was called.
26445 @subsubheading @value{GDBN} Command
26447 The corresponding @value{GDBN} command is @samp{finish}.
26449 @subsubheading Example
26451 Function returning @code{void}.
26458 *stopped,reason="function-finished",frame=@{func="main",args=[],
26459 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
26463 Function returning other than @code{void}. The name of the internal
26464 @value{GDBN} variable storing the result is printed, together with the
26471 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
26472 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
26473 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26474 gdb-result-var="$1",return-value="0"
26479 @subheading The @code{-exec-interrupt} Command
26480 @findex -exec-interrupt
26482 @subsubheading Synopsis
26485 -exec-interrupt [--all|--thread-group N]
26488 Interrupts the background execution of the target. Note how the token
26489 associated with the stop message is the one for the execution command
26490 that has been interrupted. The token for the interrupt itself only
26491 appears in the @samp{^done} output. If the user is trying to
26492 interrupt a non-running program, an error message will be printed.
26494 Note that when asynchronous execution is enabled, this command is
26495 asynchronous just like other execution commands. That is, first the
26496 @samp{^done} response will be printed, and the target stop will be
26497 reported after that using the @samp{*stopped} notification.
26499 In non-stop mode, only the context thread is interrupted by default.
26500 All threads (in all inferiors) will be interrupted if the
26501 @samp{--all} option is specified. If the @samp{--thread-group}
26502 option is specified, all threads in that group will be interrupted.
26504 @subsubheading @value{GDBN} Command
26506 The corresponding @value{GDBN} command is @samp{interrupt}.
26508 @subsubheading Example
26519 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
26520 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
26521 fullname="/home/foo/bar/try.c",line="13"@}
26526 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
26530 @subheading The @code{-exec-jump} Command
26533 @subsubheading Synopsis
26536 -exec-jump @var{location}
26539 Resumes execution of the inferior program at the location specified by
26540 parameter. @xref{Specify Location}, for a description of the
26541 different forms of @var{location}.
26543 @subsubheading @value{GDBN} Command
26545 The corresponding @value{GDBN} command is @samp{jump}.
26547 @subsubheading Example
26550 -exec-jump foo.c:10
26551 *running,thread-id="all"
26556 @subheading The @code{-exec-next} Command
26559 @subsubheading Synopsis
26562 -exec-next [--reverse]
26565 Resumes execution of the inferior program, stopping when the beginning
26566 of the next source line is reached.
26568 If the @samp{--reverse} option is specified, resumes reverse execution
26569 of the inferior program, stopping at the beginning of the previous
26570 source line. If you issue this command on the first line of a
26571 function, it will take you back to the caller of that function, to the
26572 source line where the function was called.
26575 @subsubheading @value{GDBN} Command
26577 The corresponding @value{GDBN} command is @samp{next}.
26579 @subsubheading Example
26585 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26590 @subheading The @code{-exec-next-instruction} Command
26591 @findex -exec-next-instruction
26593 @subsubheading Synopsis
26596 -exec-next-instruction [--reverse]
26599 Executes one machine instruction. If the instruction is a function
26600 call, continues until the function returns. If the program stops at an
26601 instruction in the middle of a source line, the address will be
26604 If the @samp{--reverse} option is specified, resumes reverse execution
26605 of the inferior program, stopping at the previous instruction. If the
26606 previously executed instruction was a return from another function,
26607 it will continue to execute in reverse until the call to that function
26608 (from the current stack frame) is reached.
26610 @subsubheading @value{GDBN} Command
26612 The corresponding @value{GDBN} command is @samp{nexti}.
26614 @subsubheading Example
26618 -exec-next-instruction
26622 *stopped,reason="end-stepping-range",
26623 addr="0x000100d4",line="5",file="hello.c"
26628 @subheading The @code{-exec-return} Command
26629 @findex -exec-return
26631 @subsubheading Synopsis
26637 Makes current function return immediately. Doesn't execute the inferior.
26638 Displays the new current frame.
26640 @subsubheading @value{GDBN} Command
26642 The corresponding @value{GDBN} command is @samp{return}.
26644 @subsubheading Example
26648 200-break-insert callee4
26649 200^done,bkpt=@{number="1",addr="0x00010734",
26650 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26655 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26656 frame=@{func="callee4",args=[],
26657 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26658 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26664 111^done,frame=@{level="0",func="callee3",
26665 args=[@{name="strarg",
26666 value="0x11940 \"A string argument.\""@}],
26667 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26668 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26673 @subheading The @code{-exec-run} Command
26676 @subsubheading Synopsis
26679 -exec-run [--all | --thread-group N]
26682 Starts execution of the inferior from the beginning. The inferior
26683 executes until either a breakpoint is encountered or the program
26684 exits. In the latter case the output will include an exit code, if
26685 the program has exited exceptionally.
26687 When no option is specified, the current inferior is started. If the
26688 @samp{--thread-group} option is specified, it should refer to a thread
26689 group of type @samp{process}, and that thread group will be started.
26690 If the @samp{--all} option is specified, then all inferiors will be started.
26692 @subsubheading @value{GDBN} Command
26694 The corresponding @value{GDBN} command is @samp{run}.
26696 @subsubheading Examples
26701 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26706 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26707 frame=@{func="main",args=[],file="recursive2.c",
26708 fullname="/home/foo/bar/recursive2.c",line="4"@}
26713 Program exited normally:
26721 *stopped,reason="exited-normally"
26726 Program exited exceptionally:
26734 *stopped,reason="exited",exit-code="01"
26738 Another way the program can terminate is if it receives a signal such as
26739 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26743 *stopped,reason="exited-signalled",signal-name="SIGINT",
26744 signal-meaning="Interrupt"
26748 @c @subheading -exec-signal
26751 @subheading The @code{-exec-step} Command
26754 @subsubheading Synopsis
26757 -exec-step [--reverse]
26760 Resumes execution of the inferior program, stopping when the beginning
26761 of the next source line is reached, if the next source line is not a
26762 function call. If it is, stop at the first instruction of the called
26763 function. If the @samp{--reverse} option is specified, resumes reverse
26764 execution of the inferior program, stopping at the beginning of the
26765 previously executed source line.
26767 @subsubheading @value{GDBN} Command
26769 The corresponding @value{GDBN} command is @samp{step}.
26771 @subsubheading Example
26773 Stepping into a function:
26779 *stopped,reason="end-stepping-range",
26780 frame=@{func="foo",args=[@{name="a",value="10"@},
26781 @{name="b",value="0"@}],file="recursive2.c",
26782 fullname="/home/foo/bar/recursive2.c",line="11"@}
26792 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26797 @subheading The @code{-exec-step-instruction} Command
26798 @findex -exec-step-instruction
26800 @subsubheading Synopsis
26803 -exec-step-instruction [--reverse]
26806 Resumes the inferior which executes one machine instruction. If the
26807 @samp{--reverse} option is specified, resumes reverse execution of the
26808 inferior program, stopping at the previously executed instruction.
26809 The output, once @value{GDBN} has stopped, will vary depending on
26810 whether we have stopped in the middle of a source line or not. In the
26811 former case, the address at which the program stopped will be printed
26814 @subsubheading @value{GDBN} Command
26816 The corresponding @value{GDBN} command is @samp{stepi}.
26818 @subsubheading Example
26822 -exec-step-instruction
26826 *stopped,reason="end-stepping-range",
26827 frame=@{func="foo",args=[],file="try.c",
26828 fullname="/home/foo/bar/try.c",line="10"@}
26830 -exec-step-instruction
26834 *stopped,reason="end-stepping-range",
26835 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26836 fullname="/home/foo/bar/try.c",line="10"@}
26841 @subheading The @code{-exec-until} Command
26842 @findex -exec-until
26844 @subsubheading Synopsis
26847 -exec-until [ @var{location} ]
26850 Executes the inferior until the @var{location} specified in the
26851 argument is reached. If there is no argument, the inferior executes
26852 until a source line greater than the current one is reached. The
26853 reason for stopping in this case will be @samp{location-reached}.
26855 @subsubheading @value{GDBN} Command
26857 The corresponding @value{GDBN} command is @samp{until}.
26859 @subsubheading Example
26863 -exec-until recursive2.c:6
26867 *stopped,reason="location-reached",frame=@{func="main",args=[],
26868 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26873 @subheading -file-clear
26874 Is this going away????
26877 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26878 @node GDB/MI Stack Manipulation
26879 @section @sc{gdb/mi} Stack Manipulation Commands
26882 @subheading The @code{-stack-info-frame} Command
26883 @findex -stack-info-frame
26885 @subsubheading Synopsis
26891 Get info on the selected frame.
26893 @subsubheading @value{GDBN} Command
26895 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26896 (without arguments).
26898 @subsubheading Example
26903 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26904 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26905 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26909 @subheading The @code{-stack-info-depth} Command
26910 @findex -stack-info-depth
26912 @subsubheading Synopsis
26915 -stack-info-depth [ @var{max-depth} ]
26918 Return the depth of the stack. If the integer argument @var{max-depth}
26919 is specified, do not count beyond @var{max-depth} frames.
26921 @subsubheading @value{GDBN} Command
26923 There's no equivalent @value{GDBN} command.
26925 @subsubheading Example
26927 For a stack with frame levels 0 through 11:
26934 -stack-info-depth 4
26937 -stack-info-depth 12
26940 -stack-info-depth 11
26943 -stack-info-depth 13
26948 @subheading The @code{-stack-list-arguments} Command
26949 @findex -stack-list-arguments
26951 @subsubheading Synopsis
26954 -stack-list-arguments @var{print-values}
26955 [ @var{low-frame} @var{high-frame} ]
26958 Display a list of the arguments for the frames between @var{low-frame}
26959 and @var{high-frame} (inclusive). If @var{low-frame} and
26960 @var{high-frame} are not provided, list the arguments for the whole
26961 call stack. If the two arguments are equal, show the single frame
26962 at the corresponding level. It is an error if @var{low-frame} is
26963 larger than the actual number of frames. On the other hand,
26964 @var{high-frame} may be larger than the actual number of frames, in
26965 which case only existing frames will be returned.
26967 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26968 the variables; if it is 1 or @code{--all-values}, print also their
26969 values; and if it is 2 or @code{--simple-values}, print the name,
26970 type and value for simple data types, and the name and type for arrays,
26971 structures and unions.
26973 Use of this command to obtain arguments in a single frame is
26974 deprecated in favor of the @samp{-stack-list-variables} command.
26976 @subsubheading @value{GDBN} Command
26978 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26979 @samp{gdb_get_args} command which partially overlaps with the
26980 functionality of @samp{-stack-list-arguments}.
26982 @subsubheading Example
26989 frame=@{level="0",addr="0x00010734",func="callee4",
26990 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26991 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26992 frame=@{level="1",addr="0x0001076c",func="callee3",
26993 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26994 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26995 frame=@{level="2",addr="0x0001078c",func="callee2",
26996 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26997 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26998 frame=@{level="3",addr="0x000107b4",func="callee1",
26999 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27000 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27001 frame=@{level="4",addr="0x000107e0",func="main",
27002 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27003 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27005 -stack-list-arguments 0
27008 frame=@{level="0",args=[]@},
27009 frame=@{level="1",args=[name="strarg"]@},
27010 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27011 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27012 frame=@{level="4",args=[]@}]
27014 -stack-list-arguments 1
27017 frame=@{level="0",args=[]@},
27019 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27020 frame=@{level="2",args=[
27021 @{name="intarg",value="2"@},
27022 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27023 @{frame=@{level="3",args=[
27024 @{name="intarg",value="2"@},
27025 @{name="strarg",value="0x11940 \"A string argument.\""@},
27026 @{name="fltarg",value="3.5"@}]@},
27027 frame=@{level="4",args=[]@}]
27029 -stack-list-arguments 0 2 2
27030 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27032 -stack-list-arguments 1 2 2
27033 ^done,stack-args=[frame=@{level="2",
27034 args=[@{name="intarg",value="2"@},
27035 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27039 @c @subheading -stack-list-exception-handlers
27042 @subheading The @code{-stack-list-frames} Command
27043 @findex -stack-list-frames
27045 @subsubheading Synopsis
27048 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
27051 List the frames currently on the stack. For each frame it displays the
27056 The frame number, 0 being the topmost frame, i.e., the innermost function.
27058 The @code{$pc} value for that frame.
27062 File name of the source file where the function lives.
27063 @item @var{fullname}
27064 The full file name of the source file where the function lives.
27066 Line number corresponding to the @code{$pc}.
27068 The shared library where this function is defined. This is only given
27069 if the frame's function is not known.
27072 If invoked without arguments, this command prints a backtrace for the
27073 whole stack. If given two integer arguments, it shows the frames whose
27074 levels are between the two arguments (inclusive). If the two arguments
27075 are equal, it shows the single frame at the corresponding level. It is
27076 an error if @var{low-frame} is larger than the actual number of
27077 frames. On the other hand, @var{high-frame} may be larger than the
27078 actual number of frames, in which case only existing frames will be returned.
27080 @subsubheading @value{GDBN} Command
27082 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27084 @subsubheading Example
27086 Full stack backtrace:
27092 [frame=@{level="0",addr="0x0001076c",func="foo",
27093 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27094 frame=@{level="1",addr="0x000107a4",func="foo",
27095 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27096 frame=@{level="2",addr="0x000107a4",func="foo",
27097 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27098 frame=@{level="3",addr="0x000107a4",func="foo",
27099 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27100 frame=@{level="4",addr="0x000107a4",func="foo",
27101 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27102 frame=@{level="5",addr="0x000107a4",func="foo",
27103 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27104 frame=@{level="6",addr="0x000107a4",func="foo",
27105 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27106 frame=@{level="7",addr="0x000107a4",func="foo",
27107 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27108 frame=@{level="8",addr="0x000107a4",func="foo",
27109 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27110 frame=@{level="9",addr="0x000107a4",func="foo",
27111 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27112 frame=@{level="10",addr="0x000107a4",func="foo",
27113 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27114 frame=@{level="11",addr="0x00010738",func="main",
27115 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27119 Show frames between @var{low_frame} and @var{high_frame}:
27123 -stack-list-frames 3 5
27125 [frame=@{level="3",addr="0x000107a4",func="foo",
27126 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27127 frame=@{level="4",addr="0x000107a4",func="foo",
27128 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27129 frame=@{level="5",addr="0x000107a4",func="foo",
27130 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27134 Show a single frame:
27138 -stack-list-frames 3 3
27140 [frame=@{level="3",addr="0x000107a4",func="foo",
27141 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27146 @subheading The @code{-stack-list-locals} Command
27147 @findex -stack-list-locals
27149 @subsubheading Synopsis
27152 -stack-list-locals @var{print-values}
27155 Display the local variable names for the selected frame. If
27156 @var{print-values} is 0 or @code{--no-values}, print only the names of
27157 the variables; if it is 1 or @code{--all-values}, print also their
27158 values; and if it is 2 or @code{--simple-values}, print the name,
27159 type and value for simple data types, and the name and type for arrays,
27160 structures and unions. In this last case, a frontend can immediately
27161 display the value of simple data types and create variable objects for
27162 other data types when the user wishes to explore their values in
27165 This command is deprecated in favor of the
27166 @samp{-stack-list-variables} command.
27168 @subsubheading @value{GDBN} Command
27170 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27172 @subsubheading Example
27176 -stack-list-locals 0
27177 ^done,locals=[name="A",name="B",name="C"]
27179 -stack-list-locals --all-values
27180 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27181 @{name="C",value="@{1, 2, 3@}"@}]
27182 -stack-list-locals --simple-values
27183 ^done,locals=[@{name="A",type="int",value="1"@},
27184 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27188 @subheading The @code{-stack-list-variables} Command
27189 @findex -stack-list-variables
27191 @subsubheading Synopsis
27194 -stack-list-variables @var{print-values}
27197 Display the names of local variables and function arguments for the selected frame. If
27198 @var{print-values} is 0 or @code{--no-values}, print only the names of
27199 the variables; if it is 1 or @code{--all-values}, print also their
27200 values; and if it is 2 or @code{--simple-values}, print the name,
27201 type and value for simple data types, and the name and type for arrays,
27202 structures and unions.
27204 @subsubheading Example
27208 -stack-list-variables --thread 1 --frame 0 --all-values
27209 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27214 @subheading The @code{-stack-select-frame} Command
27215 @findex -stack-select-frame
27217 @subsubheading Synopsis
27220 -stack-select-frame @var{framenum}
27223 Change the selected frame. Select a different frame @var{framenum} on
27226 This command in deprecated in favor of passing the @samp{--frame}
27227 option to every command.
27229 @subsubheading @value{GDBN} Command
27231 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27232 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27234 @subsubheading Example
27238 -stack-select-frame 2
27243 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27244 @node GDB/MI Variable Objects
27245 @section @sc{gdb/mi} Variable Objects
27249 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27251 For the implementation of a variable debugger window (locals, watched
27252 expressions, etc.), we are proposing the adaptation of the existing code
27253 used by @code{Insight}.
27255 The two main reasons for that are:
27259 It has been proven in practice (it is already on its second generation).
27262 It will shorten development time (needless to say how important it is
27266 The original interface was designed to be used by Tcl code, so it was
27267 slightly changed so it could be used through @sc{gdb/mi}. This section
27268 describes the @sc{gdb/mi} operations that will be available and gives some
27269 hints about their use.
27271 @emph{Note}: In addition to the set of operations described here, we
27272 expect the @sc{gui} implementation of a variable window to require, at
27273 least, the following operations:
27276 @item @code{-gdb-show} @code{output-radix}
27277 @item @code{-stack-list-arguments}
27278 @item @code{-stack-list-locals}
27279 @item @code{-stack-select-frame}
27284 @subheading Introduction to Variable Objects
27286 @cindex variable objects in @sc{gdb/mi}
27288 Variable objects are "object-oriented" MI interface for examining and
27289 changing values of expressions. Unlike some other MI interfaces that
27290 work with expressions, variable objects are specifically designed for
27291 simple and efficient presentation in the frontend. A variable object
27292 is identified by string name. When a variable object is created, the
27293 frontend specifies the expression for that variable object. The
27294 expression can be a simple variable, or it can be an arbitrary complex
27295 expression, and can even involve CPU registers. After creating a
27296 variable object, the frontend can invoke other variable object
27297 operations---for example to obtain or change the value of a variable
27298 object, or to change display format.
27300 Variable objects have hierarchical tree structure. Any variable object
27301 that corresponds to a composite type, such as structure in C, has
27302 a number of child variable objects, for example corresponding to each
27303 element of a structure. A child variable object can itself have
27304 children, recursively. Recursion ends when we reach
27305 leaf variable objects, which always have built-in types. Child variable
27306 objects are created only by explicit request, so if a frontend
27307 is not interested in the children of a particular variable object, no
27308 child will be created.
27310 For a leaf variable object it is possible to obtain its value as a
27311 string, or set the value from a string. String value can be also
27312 obtained for a non-leaf variable object, but it's generally a string
27313 that only indicates the type of the object, and does not list its
27314 contents. Assignment to a non-leaf variable object is not allowed.
27316 A frontend does not need to read the values of all variable objects each time
27317 the program stops. Instead, MI provides an update command that lists all
27318 variable objects whose values has changed since the last update
27319 operation. This considerably reduces the amount of data that must
27320 be transferred to the frontend. As noted above, children variable
27321 objects are created on demand, and only leaf variable objects have a
27322 real value. As result, gdb will read target memory only for leaf
27323 variables that frontend has created.
27325 The automatic update is not always desirable. For example, a frontend
27326 might want to keep a value of some expression for future reference,
27327 and never update it. For another example, fetching memory is
27328 relatively slow for embedded targets, so a frontend might want
27329 to disable automatic update for the variables that are either not
27330 visible on the screen, or ``closed''. This is possible using so
27331 called ``frozen variable objects''. Such variable objects are never
27332 implicitly updated.
27334 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
27335 fixed variable object, the expression is parsed when the variable
27336 object is created, including associating identifiers to specific
27337 variables. The meaning of expression never changes. For a floating
27338 variable object the values of variables whose names appear in the
27339 expressions are re-evaluated every time in the context of the current
27340 frame. Consider this example:
27345 struct work_state state;
27352 If a fixed variable object for the @code{state} variable is created in
27353 this function, and we enter the recursive call, the variable
27354 object will report the value of @code{state} in the top-level
27355 @code{do_work} invocation. On the other hand, a floating variable
27356 object will report the value of @code{state} in the current frame.
27358 If an expression specified when creating a fixed variable object
27359 refers to a local variable, the variable object becomes bound to the
27360 thread and frame in which the variable object is created. When such
27361 variable object is updated, @value{GDBN} makes sure that the
27362 thread/frame combination the variable object is bound to still exists,
27363 and re-evaluates the variable object in context of that thread/frame.
27365 The following is the complete set of @sc{gdb/mi} operations defined to
27366 access this functionality:
27368 @multitable @columnfractions .4 .6
27369 @item @strong{Operation}
27370 @tab @strong{Description}
27372 @item @code{-enable-pretty-printing}
27373 @tab enable Python-based pretty-printing
27374 @item @code{-var-create}
27375 @tab create a variable object
27376 @item @code{-var-delete}
27377 @tab delete the variable object and/or its children
27378 @item @code{-var-set-format}
27379 @tab set the display format of this variable
27380 @item @code{-var-show-format}
27381 @tab show the display format of this variable
27382 @item @code{-var-info-num-children}
27383 @tab tells how many children this object has
27384 @item @code{-var-list-children}
27385 @tab return a list of the object's children
27386 @item @code{-var-info-type}
27387 @tab show the type of this variable object
27388 @item @code{-var-info-expression}
27389 @tab print parent-relative expression that this variable object represents
27390 @item @code{-var-info-path-expression}
27391 @tab print full expression that this variable object represents
27392 @item @code{-var-show-attributes}
27393 @tab is this variable editable? does it exist here?
27394 @item @code{-var-evaluate-expression}
27395 @tab get the value of this variable
27396 @item @code{-var-assign}
27397 @tab set the value of this variable
27398 @item @code{-var-update}
27399 @tab update the variable and its children
27400 @item @code{-var-set-frozen}
27401 @tab set frozeness attribute
27402 @item @code{-var-set-update-range}
27403 @tab set range of children to display on update
27406 In the next subsection we describe each operation in detail and suggest
27407 how it can be used.
27409 @subheading Description And Use of Operations on Variable Objects
27411 @subheading The @code{-enable-pretty-printing} Command
27412 @findex -enable-pretty-printing
27415 -enable-pretty-printing
27418 @value{GDBN} allows Python-based visualizers to affect the output of the
27419 MI variable object commands. However, because there was no way to
27420 implement this in a fully backward-compatible way, a front end must
27421 request that this functionality be enabled.
27423 Once enabled, this feature cannot be disabled.
27425 Note that if Python support has not been compiled into @value{GDBN},
27426 this command will still succeed (and do nothing).
27428 This feature is currently (as of @value{GDBN} 7.0) experimental, and
27429 may work differently in future versions of @value{GDBN}.
27431 @subheading The @code{-var-create} Command
27432 @findex -var-create
27434 @subsubheading Synopsis
27437 -var-create @{@var{name} | "-"@}
27438 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
27441 This operation creates a variable object, which allows the monitoring of
27442 a variable, the result of an expression, a memory cell or a CPU
27445 The @var{name} parameter is the string by which the object can be
27446 referenced. It must be unique. If @samp{-} is specified, the varobj
27447 system will generate a string ``varNNNNNN'' automatically. It will be
27448 unique provided that one does not specify @var{name} of that format.
27449 The command fails if a duplicate name is found.
27451 The frame under which the expression should be evaluated can be
27452 specified by @var{frame-addr}. A @samp{*} indicates that the current
27453 frame should be used. A @samp{@@} indicates that a floating variable
27454 object must be created.
27456 @var{expression} is any expression valid on the current language set (must not
27457 begin with a @samp{*}), or one of the following:
27461 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
27464 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
27467 @samp{$@var{regname}} --- a CPU register name
27470 @cindex dynamic varobj
27471 A varobj's contents may be provided by a Python-based pretty-printer. In this
27472 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
27473 have slightly different semantics in some cases. If the
27474 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
27475 will never create a dynamic varobj. This ensures backward
27476 compatibility for existing clients.
27478 @subsubheading Result
27480 This operation returns attributes of the newly-created varobj. These
27485 The name of the varobj.
27488 The number of children of the varobj. This number is not necessarily
27489 reliable for a dynamic varobj. Instead, you must examine the
27490 @samp{has_more} attribute.
27493 The varobj's scalar value. For a varobj whose type is some sort of
27494 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
27495 will not be interesting.
27498 The varobj's type. This is a string representation of the type, as
27499 would be printed by the @value{GDBN} CLI.
27502 If a variable object is bound to a specific thread, then this is the
27503 thread's identifier.
27506 For a dynamic varobj, this indicates whether there appear to be any
27507 children available. For a non-dynamic varobj, this will be 0.
27510 This attribute will be present and have the value @samp{1} if the
27511 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27512 then this attribute will not be present.
27515 A dynamic varobj can supply a display hint to the front end. The
27516 value comes directly from the Python pretty-printer object's
27517 @code{display_hint} method. @xref{Pretty Printing API}.
27520 Typical output will look like this:
27523 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
27524 has_more="@var{has_more}"
27528 @subheading The @code{-var-delete} Command
27529 @findex -var-delete
27531 @subsubheading Synopsis
27534 -var-delete [ -c ] @var{name}
27537 Deletes a previously created variable object and all of its children.
27538 With the @samp{-c} option, just deletes the children.
27540 Returns an error if the object @var{name} is not found.
27543 @subheading The @code{-var-set-format} Command
27544 @findex -var-set-format
27546 @subsubheading Synopsis
27549 -var-set-format @var{name} @var{format-spec}
27552 Sets the output format for the value of the object @var{name} to be
27555 @anchor{-var-set-format}
27556 The syntax for the @var{format-spec} is as follows:
27559 @var{format-spec} @expansion{}
27560 @{binary | decimal | hexadecimal | octal | natural@}
27563 The natural format is the default format choosen automatically
27564 based on the variable type (like decimal for an @code{int}, hex
27565 for pointers, etc.).
27567 For a variable with children, the format is set only on the
27568 variable itself, and the children are not affected.
27570 @subheading The @code{-var-show-format} Command
27571 @findex -var-show-format
27573 @subsubheading Synopsis
27576 -var-show-format @var{name}
27579 Returns the format used to display the value of the object @var{name}.
27582 @var{format} @expansion{}
27587 @subheading The @code{-var-info-num-children} Command
27588 @findex -var-info-num-children
27590 @subsubheading Synopsis
27593 -var-info-num-children @var{name}
27596 Returns the number of children of a variable object @var{name}:
27602 Note that this number is not completely reliable for a dynamic varobj.
27603 It will return the current number of children, but more children may
27607 @subheading The @code{-var-list-children} Command
27608 @findex -var-list-children
27610 @subsubheading Synopsis
27613 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27615 @anchor{-var-list-children}
27617 Return a list of the children of the specified variable object and
27618 create variable objects for them, if they do not already exist. With
27619 a single argument or if @var{print-values} has a value of 0 or
27620 @code{--no-values}, print only the names of the variables; if
27621 @var{print-values} is 1 or @code{--all-values}, also print their
27622 values; and if it is 2 or @code{--simple-values} print the name and
27623 value for simple data types and just the name for arrays, structures
27626 @var{from} and @var{to}, if specified, indicate the range of children
27627 to report. If @var{from} or @var{to} is less than zero, the range is
27628 reset and all children will be reported. Otherwise, children starting
27629 at @var{from} (zero-based) and up to and excluding @var{to} will be
27632 If a child range is requested, it will only affect the current call to
27633 @code{-var-list-children}, but not future calls to @code{-var-update}.
27634 For this, you must instead use @code{-var-set-update-range}. The
27635 intent of this approach is to enable a front end to implement any
27636 update approach it likes; for example, scrolling a view may cause the
27637 front end to request more children with @code{-var-list-children}, and
27638 then the front end could call @code{-var-set-update-range} with a
27639 different range to ensure that future updates are restricted to just
27642 For each child the following results are returned:
27647 Name of the variable object created for this child.
27650 The expression to be shown to the user by the front end to designate this child.
27651 For example this may be the name of a structure member.
27653 For a dynamic varobj, this value cannot be used to form an
27654 expression. There is no way to do this at all with a dynamic varobj.
27656 For C/C@t{++} structures there are several pseudo children returned to
27657 designate access qualifiers. For these pseudo children @var{exp} is
27658 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27659 type and value are not present.
27661 A dynamic varobj will not report the access qualifying
27662 pseudo-children, regardless of the language. This information is not
27663 available at all with a dynamic varobj.
27666 Number of children this child has. For a dynamic varobj, this will be
27670 The type of the child.
27673 If values were requested, this is the value.
27676 If this variable object is associated with a thread, this is the thread id.
27677 Otherwise this result is not present.
27680 If the variable object is frozen, this variable will be present with a value of 1.
27683 The result may have its own attributes:
27687 A dynamic varobj can supply a display hint to the front end. The
27688 value comes directly from the Python pretty-printer object's
27689 @code{display_hint} method. @xref{Pretty Printing API}.
27692 This is an integer attribute which is nonzero if there are children
27693 remaining after the end of the selected range.
27696 @subsubheading Example
27700 -var-list-children n
27701 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27702 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27704 -var-list-children --all-values n
27705 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27706 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27710 @subheading The @code{-var-info-type} Command
27711 @findex -var-info-type
27713 @subsubheading Synopsis
27716 -var-info-type @var{name}
27719 Returns the type of the specified variable @var{name}. The type is
27720 returned as a string in the same format as it is output by the
27724 type=@var{typename}
27728 @subheading The @code{-var-info-expression} Command
27729 @findex -var-info-expression
27731 @subsubheading Synopsis
27734 -var-info-expression @var{name}
27737 Returns a string that is suitable for presenting this
27738 variable object in user interface. The string is generally
27739 not valid expression in the current language, and cannot be evaluated.
27741 For example, if @code{a} is an array, and variable object
27742 @code{A} was created for @code{a}, then we'll get this output:
27745 (gdb) -var-info-expression A.1
27746 ^done,lang="C",exp="1"
27750 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27752 Note that the output of the @code{-var-list-children} command also
27753 includes those expressions, so the @code{-var-info-expression} command
27756 @subheading The @code{-var-info-path-expression} Command
27757 @findex -var-info-path-expression
27759 @subsubheading Synopsis
27762 -var-info-path-expression @var{name}
27765 Returns an expression that can be evaluated in the current
27766 context and will yield the same value that a variable object has.
27767 Compare this with the @code{-var-info-expression} command, which
27768 result can be used only for UI presentation. Typical use of
27769 the @code{-var-info-path-expression} command is creating a
27770 watchpoint from a variable object.
27772 This command is currently not valid for children of a dynamic varobj,
27773 and will give an error when invoked on one.
27775 For example, suppose @code{C} is a C@t{++} class, derived from class
27776 @code{Base}, and that the @code{Base} class has a member called
27777 @code{m_size}. Assume a variable @code{c} is has the type of
27778 @code{C} and a variable object @code{C} was created for variable
27779 @code{c}. Then, we'll get this output:
27781 (gdb) -var-info-path-expression C.Base.public.m_size
27782 ^done,path_expr=((Base)c).m_size)
27785 @subheading The @code{-var-show-attributes} Command
27786 @findex -var-show-attributes
27788 @subsubheading Synopsis
27791 -var-show-attributes @var{name}
27794 List attributes of the specified variable object @var{name}:
27797 status=@var{attr} [ ( ,@var{attr} )* ]
27801 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27803 @subheading The @code{-var-evaluate-expression} Command
27804 @findex -var-evaluate-expression
27806 @subsubheading Synopsis
27809 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27812 Evaluates the expression that is represented by the specified variable
27813 object and returns its value as a string. The format of the string
27814 can be specified with the @samp{-f} option. The possible values of
27815 this option are the same as for @code{-var-set-format}
27816 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27817 the current display format will be used. The current display format
27818 can be changed using the @code{-var-set-format} command.
27824 Note that one must invoke @code{-var-list-children} for a variable
27825 before the value of a child variable can be evaluated.
27827 @subheading The @code{-var-assign} Command
27828 @findex -var-assign
27830 @subsubheading Synopsis
27833 -var-assign @var{name} @var{expression}
27836 Assigns the value of @var{expression} to the variable object specified
27837 by @var{name}. The object must be @samp{editable}. If the variable's
27838 value is altered by the assign, the variable will show up in any
27839 subsequent @code{-var-update} list.
27841 @subsubheading Example
27849 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27853 @subheading The @code{-var-update} Command
27854 @findex -var-update
27856 @subsubheading Synopsis
27859 -var-update [@var{print-values}] @{@var{name} | "*"@}
27862 Reevaluate the expressions corresponding to the variable object
27863 @var{name} and all its direct and indirect children, and return the
27864 list of variable objects whose values have changed; @var{name} must
27865 be a root variable object. Here, ``changed'' means that the result of
27866 @code{-var-evaluate-expression} before and after the
27867 @code{-var-update} is different. If @samp{*} is used as the variable
27868 object names, all existing variable objects are updated, except
27869 for frozen ones (@pxref{-var-set-frozen}). The option
27870 @var{print-values} determines whether both names and values, or just
27871 names are printed. The possible values of this option are the same
27872 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27873 recommended to use the @samp{--all-values} option, to reduce the
27874 number of MI commands needed on each program stop.
27876 With the @samp{*} parameter, if a variable object is bound to a
27877 currently running thread, it will not be updated, without any
27880 If @code{-var-set-update-range} was previously used on a varobj, then
27881 only the selected range of children will be reported.
27883 @code{-var-update} reports all the changed varobjs in a tuple named
27886 Each item in the change list is itself a tuple holding:
27890 The name of the varobj.
27893 If values were requested for this update, then this field will be
27894 present and will hold the value of the varobj.
27897 @anchor{-var-update}
27898 This field is a string which may take one of three values:
27902 The variable object's current value is valid.
27905 The variable object does not currently hold a valid value but it may
27906 hold one in the future if its associated expression comes back into
27910 The variable object no longer holds a valid value.
27911 This can occur when the executable file being debugged has changed,
27912 either through recompilation or by using the @value{GDBN} @code{file}
27913 command. The front end should normally choose to delete these variable
27917 In the future new values may be added to this list so the front should
27918 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27921 This is only present if the varobj is still valid. If the type
27922 changed, then this will be the string @samp{true}; otherwise it will
27926 If the varobj's type changed, then this field will be present and will
27929 @item new_num_children
27930 For a dynamic varobj, if the number of children changed, or if the
27931 type changed, this will be the new number of children.
27933 The @samp{numchild} field in other varobj responses is generally not
27934 valid for a dynamic varobj -- it will show the number of children that
27935 @value{GDBN} knows about, but because dynamic varobjs lazily
27936 instantiate their children, this will not reflect the number of
27937 children which may be available.
27939 The @samp{new_num_children} attribute only reports changes to the
27940 number of children known by @value{GDBN}. This is the only way to
27941 detect whether an update has removed children (which necessarily can
27942 only happen at the end of the update range).
27945 The display hint, if any.
27948 This is an integer value, which will be 1 if there are more children
27949 available outside the varobj's update range.
27952 This attribute will be present and have the value @samp{1} if the
27953 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27954 then this attribute will not be present.
27957 If new children were added to a dynamic varobj within the selected
27958 update range (as set by @code{-var-set-update-range}), then they will
27959 be listed in this attribute.
27962 @subsubheading Example
27969 -var-update --all-values var1
27970 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27971 type_changed="false"@}]
27975 @subheading The @code{-var-set-frozen} Command
27976 @findex -var-set-frozen
27977 @anchor{-var-set-frozen}
27979 @subsubheading Synopsis
27982 -var-set-frozen @var{name} @var{flag}
27985 Set the frozenness flag on the variable object @var{name}. The
27986 @var{flag} parameter should be either @samp{1} to make the variable
27987 frozen or @samp{0} to make it unfrozen. If a variable object is
27988 frozen, then neither itself, nor any of its children, are
27989 implicitly updated by @code{-var-update} of
27990 a parent variable or by @code{-var-update *}. Only
27991 @code{-var-update} of the variable itself will update its value and
27992 values of its children. After a variable object is unfrozen, it is
27993 implicitly updated by all subsequent @code{-var-update} operations.
27994 Unfreezing a variable does not update it, only subsequent
27995 @code{-var-update} does.
27997 @subsubheading Example
28001 -var-set-frozen V 1
28006 @subheading The @code{-var-set-update-range} command
28007 @findex -var-set-update-range
28008 @anchor{-var-set-update-range}
28010 @subsubheading Synopsis
28013 -var-set-update-range @var{name} @var{from} @var{to}
28016 Set the range of children to be returned by future invocations of
28017 @code{-var-update}.
28019 @var{from} and @var{to} indicate the range of children to report. If
28020 @var{from} or @var{to} is less than zero, the range is reset and all
28021 children will be reported. Otherwise, children starting at @var{from}
28022 (zero-based) and up to and excluding @var{to} will be reported.
28024 @subsubheading Example
28028 -var-set-update-range V 1 2
28032 @subheading The @code{-var-set-visualizer} command
28033 @findex -var-set-visualizer
28034 @anchor{-var-set-visualizer}
28036 @subsubheading Synopsis
28039 -var-set-visualizer @var{name} @var{visualizer}
28042 Set a visualizer for the variable object @var{name}.
28044 @var{visualizer} is the visualizer to use. The special value
28045 @samp{None} means to disable any visualizer in use.
28047 If not @samp{None}, @var{visualizer} must be a Python expression.
28048 This expression must evaluate to a callable object which accepts a
28049 single argument. @value{GDBN} will call this object with the value of
28050 the varobj @var{name} as an argument (this is done so that the same
28051 Python pretty-printing code can be used for both the CLI and MI).
28052 When called, this object must return an object which conforms to the
28053 pretty-printing interface (@pxref{Pretty Printing API}).
28055 The pre-defined function @code{gdb.default_visualizer} may be used to
28056 select a visualizer by following the built-in process
28057 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28058 a varobj is created, and so ordinarily is not needed.
28060 This feature is only available if Python support is enabled. The MI
28061 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
28062 can be used to check this.
28064 @subsubheading Example
28066 Resetting the visualizer:
28070 -var-set-visualizer V None
28074 Reselecting the default (type-based) visualizer:
28078 -var-set-visualizer V gdb.default_visualizer
28082 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28083 can be used to instantiate this class for a varobj:
28087 -var-set-visualizer V "lambda val: SomeClass()"
28091 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28092 @node GDB/MI Data Manipulation
28093 @section @sc{gdb/mi} Data Manipulation
28095 @cindex data manipulation, in @sc{gdb/mi}
28096 @cindex @sc{gdb/mi}, data manipulation
28097 This section describes the @sc{gdb/mi} commands that manipulate data:
28098 examine memory and registers, evaluate expressions, etc.
28100 @c REMOVED FROM THE INTERFACE.
28101 @c @subheading -data-assign
28102 @c Change the value of a program variable. Plenty of side effects.
28103 @c @subsubheading GDB Command
28105 @c @subsubheading Example
28108 @subheading The @code{-data-disassemble} Command
28109 @findex -data-disassemble
28111 @subsubheading Synopsis
28115 [ -s @var{start-addr} -e @var{end-addr} ]
28116 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28124 @item @var{start-addr}
28125 is the beginning address (or @code{$pc})
28126 @item @var{end-addr}
28128 @item @var{filename}
28129 is the name of the file to disassemble
28130 @item @var{linenum}
28131 is the line number to disassemble around
28133 is the number of disassembly lines to be produced. If it is -1,
28134 the whole function will be disassembled, in case no @var{end-addr} is
28135 specified. If @var{end-addr} is specified as a non-zero value, and
28136 @var{lines} is lower than the number of disassembly lines between
28137 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28138 displayed; if @var{lines} is higher than the number of lines between
28139 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28142 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28143 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28144 mixed source and disassembly with raw opcodes).
28147 @subsubheading Result
28149 The output for each instruction is composed of four fields:
28158 Note that whatever included in the instruction field, is not manipulated
28159 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
28161 @subsubheading @value{GDBN} Command
28163 There's no direct mapping from this command to the CLI.
28165 @subsubheading Example
28167 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28171 -data-disassemble -s $pc -e "$pc + 20" -- 0
28174 @{address="0x000107c0",func-name="main",offset="4",
28175 inst="mov 2, %o0"@},
28176 @{address="0x000107c4",func-name="main",offset="8",
28177 inst="sethi %hi(0x11800), %o2"@},
28178 @{address="0x000107c8",func-name="main",offset="12",
28179 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28180 @{address="0x000107cc",func-name="main",offset="16",
28181 inst="sethi %hi(0x11800), %o2"@},
28182 @{address="0x000107d0",func-name="main",offset="20",
28183 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28187 Disassemble the whole @code{main} function. Line 32 is part of
28191 -data-disassemble -f basics.c -l 32 -- 0
28193 @{address="0x000107bc",func-name="main",offset="0",
28194 inst="save %sp, -112, %sp"@},
28195 @{address="0x000107c0",func-name="main",offset="4",
28196 inst="mov 2, %o0"@},
28197 @{address="0x000107c4",func-name="main",offset="8",
28198 inst="sethi %hi(0x11800), %o2"@},
28200 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
28201 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
28205 Disassemble 3 instructions from the start of @code{main}:
28209 -data-disassemble -f basics.c -l 32 -n 3 -- 0
28211 @{address="0x000107bc",func-name="main",offset="0",
28212 inst="save %sp, -112, %sp"@},
28213 @{address="0x000107c0",func-name="main",offset="4",
28214 inst="mov 2, %o0"@},
28215 @{address="0x000107c4",func-name="main",offset="8",
28216 inst="sethi %hi(0x11800), %o2"@}]
28220 Disassemble 3 instructions from the start of @code{main} in mixed mode:
28224 -data-disassemble -f basics.c -l 32 -n 3 -- 1
28226 src_and_asm_line=@{line="31",
28227 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28228 testsuite/gdb.mi/basics.c",line_asm_insn=[
28229 @{address="0x000107bc",func-name="main",offset="0",
28230 inst="save %sp, -112, %sp"@}]@},
28231 src_and_asm_line=@{line="32",
28232 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28233 testsuite/gdb.mi/basics.c",line_asm_insn=[
28234 @{address="0x000107c0",func-name="main",offset="4",
28235 inst="mov 2, %o0"@},
28236 @{address="0x000107c4",func-name="main",offset="8",
28237 inst="sethi %hi(0x11800), %o2"@}]@}]
28242 @subheading The @code{-data-evaluate-expression} Command
28243 @findex -data-evaluate-expression
28245 @subsubheading Synopsis
28248 -data-evaluate-expression @var{expr}
28251 Evaluate @var{expr} as an expression. The expression could contain an
28252 inferior function call. The function call will execute synchronously.
28253 If the expression contains spaces, it must be enclosed in double quotes.
28255 @subsubheading @value{GDBN} Command
28257 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
28258 @samp{call}. In @code{gdbtk} only, there's a corresponding
28259 @samp{gdb_eval} command.
28261 @subsubheading Example
28263 In the following example, the numbers that precede the commands are the
28264 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
28265 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
28269 211-data-evaluate-expression A
28272 311-data-evaluate-expression &A
28273 311^done,value="0xefffeb7c"
28275 411-data-evaluate-expression A+3
28278 511-data-evaluate-expression "A + 3"
28284 @subheading The @code{-data-list-changed-registers} Command
28285 @findex -data-list-changed-registers
28287 @subsubheading Synopsis
28290 -data-list-changed-registers
28293 Display a list of the registers that have changed.
28295 @subsubheading @value{GDBN} Command
28297 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
28298 has the corresponding command @samp{gdb_changed_register_list}.
28300 @subsubheading Example
28302 On a PPC MBX board:
28310 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
28311 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
28314 -data-list-changed-registers
28315 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
28316 "10","11","13","14","15","16","17","18","19","20","21","22","23",
28317 "24","25","26","27","28","30","31","64","65","66","67","69"]
28322 @subheading The @code{-data-list-register-names} Command
28323 @findex -data-list-register-names
28325 @subsubheading Synopsis
28328 -data-list-register-names [ ( @var{regno} )+ ]
28331 Show a list of register names for the current target. If no arguments
28332 are given, it shows a list of the names of all the registers. If
28333 integer numbers are given as arguments, it will print a list of the
28334 names of the registers corresponding to the arguments. To ensure
28335 consistency between a register name and its number, the output list may
28336 include empty register names.
28338 @subsubheading @value{GDBN} Command
28340 @value{GDBN} does not have a command which corresponds to
28341 @samp{-data-list-register-names}. In @code{gdbtk} there is a
28342 corresponding command @samp{gdb_regnames}.
28344 @subsubheading Example
28346 For the PPC MBX board:
28349 -data-list-register-names
28350 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
28351 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
28352 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
28353 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
28354 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
28355 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
28356 "", "pc","ps","cr","lr","ctr","xer"]
28358 -data-list-register-names 1 2 3
28359 ^done,register-names=["r1","r2","r3"]
28363 @subheading The @code{-data-list-register-values} Command
28364 @findex -data-list-register-values
28366 @subsubheading Synopsis
28369 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
28372 Display the registers' contents. @var{fmt} is the format according to
28373 which the registers' contents are to be returned, followed by an optional
28374 list of numbers specifying the registers to display. A missing list of
28375 numbers indicates that the contents of all the registers must be returned.
28377 Allowed formats for @var{fmt} are:
28394 @subsubheading @value{GDBN} Command
28396 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
28397 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
28399 @subsubheading Example
28401 For a PPC MBX board (note: line breaks are for readability only, they
28402 don't appear in the actual output):
28406 -data-list-register-values r 64 65
28407 ^done,register-values=[@{number="64",value="0xfe00a300"@},
28408 @{number="65",value="0x00029002"@}]
28410 -data-list-register-values x
28411 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
28412 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
28413 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
28414 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
28415 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
28416 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
28417 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
28418 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
28419 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
28420 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
28421 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
28422 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
28423 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
28424 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
28425 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
28426 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
28427 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
28428 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
28429 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
28430 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
28431 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
28432 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
28433 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
28434 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
28435 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
28436 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
28437 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
28438 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
28439 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
28440 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
28441 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
28442 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
28443 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
28444 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
28445 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
28446 @{number="69",value="0x20002b03"@}]
28451 @subheading The @code{-data-read-memory} Command
28452 @findex -data-read-memory
28454 This command is deprecated, use @code{-data-read-memory-bytes} instead.
28456 @subsubheading Synopsis
28459 -data-read-memory [ -o @var{byte-offset} ]
28460 @var{address} @var{word-format} @var{word-size}
28461 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
28468 @item @var{address}
28469 An expression specifying the address of the first memory word to be
28470 read. Complex expressions containing embedded white space should be
28471 quoted using the C convention.
28473 @item @var{word-format}
28474 The format to be used to print the memory words. The notation is the
28475 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
28478 @item @var{word-size}
28479 The size of each memory word in bytes.
28481 @item @var{nr-rows}
28482 The number of rows in the output table.
28484 @item @var{nr-cols}
28485 The number of columns in the output table.
28488 If present, indicates that each row should include an @sc{ascii} dump. The
28489 value of @var{aschar} is used as a padding character when a byte is not a
28490 member of the printable @sc{ascii} character set (printable @sc{ascii}
28491 characters are those whose code is between 32 and 126, inclusively).
28493 @item @var{byte-offset}
28494 An offset to add to the @var{address} before fetching memory.
28497 This command displays memory contents as a table of @var{nr-rows} by
28498 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
28499 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
28500 (returned as @samp{total-bytes}). Should less than the requested number
28501 of bytes be returned by the target, the missing words are identified
28502 using @samp{N/A}. The number of bytes read from the target is returned
28503 in @samp{nr-bytes} and the starting address used to read memory in
28506 The address of the next/previous row or page is available in
28507 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
28510 @subsubheading @value{GDBN} Command
28512 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
28513 @samp{gdb_get_mem} memory read command.
28515 @subsubheading Example
28517 Read six bytes of memory starting at @code{bytes+6} but then offset by
28518 @code{-6} bytes. Format as three rows of two columns. One byte per
28519 word. Display each word in hex.
28523 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
28524 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
28525 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
28526 prev-page="0x0000138a",memory=[
28527 @{addr="0x00001390",data=["0x00","0x01"]@},
28528 @{addr="0x00001392",data=["0x02","0x03"]@},
28529 @{addr="0x00001394",data=["0x04","0x05"]@}]
28533 Read two bytes of memory starting at address @code{shorts + 64} and
28534 display as a single word formatted in decimal.
28538 5-data-read-memory shorts+64 d 2 1 1
28539 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28540 next-row="0x00001512",prev-row="0x0000150e",
28541 next-page="0x00001512",prev-page="0x0000150e",memory=[
28542 @{addr="0x00001510",data=["128"]@}]
28546 Read thirty two bytes of memory starting at @code{bytes+16} and format
28547 as eight rows of four columns. Include a string encoding with @samp{x}
28548 used as the non-printable character.
28552 4-data-read-memory bytes+16 x 1 8 4 x
28553 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28554 next-row="0x000013c0",prev-row="0x0000139c",
28555 next-page="0x000013c0",prev-page="0x00001380",memory=[
28556 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28557 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28558 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28559 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28560 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28561 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28562 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28563 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28567 @subheading The @code{-data-read-memory-bytes} Command
28568 @findex -data-read-memory-bytes
28570 @subsubheading Synopsis
28573 -data-read-memory-bytes [ -o @var{byte-offset} ]
28574 @var{address} @var{count}
28581 @item @var{address}
28582 An expression specifying the address of the first memory word to be
28583 read. Complex expressions containing embedded white space should be
28584 quoted using the C convention.
28587 The number of bytes to read. This should be an integer literal.
28589 @item @var{byte-offset}
28590 The offsets in bytes relative to @var{address} at which to start
28591 reading. This should be an integer literal. This option is provided
28592 so that a frontend is not required to first evaluate address and then
28593 perform address arithmetics itself.
28597 This command attempts to read all accessible memory regions in the
28598 specified range. First, all regions marked as unreadable in the memory
28599 map (if one is defined) will be skipped. @xref{Memory Region
28600 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28601 regions. For each one, if reading full region results in an errors,
28602 @value{GDBN} will try to read a subset of the region.
28604 In general, every single byte in the region may be readable or not,
28605 and the only way to read every readable byte is to try a read at
28606 every address, which is not practical. Therefore, @value{GDBN} will
28607 attempt to read all accessible bytes at either beginning or the end
28608 of the region, using a binary division scheme. This heuristic works
28609 well for reading accross a memory map boundary. Note that if a region
28610 has a readable range that is neither at the beginning or the end,
28611 @value{GDBN} will not read it.
28613 The result record (@pxref{GDB/MI Result Records}) that is output of
28614 the command includes a field named @samp{memory} whose content is a
28615 list of tuples. Each tuple represent a successfully read memory block
28616 and has the following fields:
28620 The start address of the memory block, as hexadecimal literal.
28623 The end address of the memory block, as hexadecimal literal.
28626 The offset of the memory block, as hexadecimal literal, relative to
28627 the start address passed to @code{-data-read-memory-bytes}.
28630 The contents of the memory block, in hex.
28636 @subsubheading @value{GDBN} Command
28638 The corresponding @value{GDBN} command is @samp{x}.
28640 @subsubheading Example
28644 -data-read-memory-bytes &a 10
28645 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28647 contents="01000000020000000300"@}]
28652 @subheading The @code{-data-write-memory-bytes} Command
28653 @findex -data-write-memory-bytes
28655 @subsubheading Synopsis
28658 -data-write-memory-bytes @var{address} @var{contents}
28665 @item @var{address}
28666 An expression specifying the address of the first memory word to be
28667 read. Complex expressions containing embedded white space should be
28668 quoted using the C convention.
28670 @item @var{contents}
28671 The hex-encoded bytes to write.
28675 @subsubheading @value{GDBN} Command
28677 There's no corresponding @value{GDBN} command.
28679 @subsubheading Example
28683 -data-write-memory-bytes &a "aabbccdd"
28689 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28690 @node GDB/MI Tracepoint Commands
28691 @section @sc{gdb/mi} Tracepoint Commands
28693 The commands defined in this section implement MI support for
28694 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28696 @subheading The @code{-trace-find} Command
28697 @findex -trace-find
28699 @subsubheading Synopsis
28702 -trace-find @var{mode} [@var{parameters}@dots{}]
28705 Find a trace frame using criteria defined by @var{mode} and
28706 @var{parameters}. The following table lists permissible
28707 modes and their parameters. For details of operation, see @ref{tfind}.
28712 No parameters are required. Stops examining trace frames.
28715 An integer is required as parameter. Selects tracepoint frame with
28718 @item tracepoint-number
28719 An integer is required as parameter. Finds next
28720 trace frame that corresponds to tracepoint with the specified number.
28723 An address is required as parameter. Finds
28724 next trace frame that corresponds to any tracepoint at the specified
28727 @item pc-inside-range
28728 Two addresses are required as parameters. Finds next trace
28729 frame that corresponds to a tracepoint at an address inside the
28730 specified range. Both bounds are considered to be inside the range.
28732 @item pc-outside-range
28733 Two addresses are required as parameters. Finds
28734 next trace frame that corresponds to a tracepoint at an address outside
28735 the specified range. Both bounds are considered to be inside the range.
28738 Line specification is required as parameter. @xref{Specify Location}.
28739 Finds next trace frame that corresponds to a tracepoint at
28740 the specified location.
28744 If @samp{none} was passed as @var{mode}, the response does not
28745 have fields. Otherwise, the response may have the following fields:
28749 This field has either @samp{0} or @samp{1} as the value, depending
28750 on whether a matching tracepoint was found.
28753 The index of the found traceframe. This field is present iff
28754 the @samp{found} field has value of @samp{1}.
28757 The index of the found tracepoint. This field is present iff
28758 the @samp{found} field has value of @samp{1}.
28761 The information about the frame corresponding to the found trace
28762 frame. This field is present only if a trace frame was found.
28763 @xref{GDB/MI Frame Information}, for description of this field.
28767 @subsubheading @value{GDBN} Command
28769 The corresponding @value{GDBN} command is @samp{tfind}.
28771 @subheading -trace-define-variable
28772 @findex -trace-define-variable
28774 @subsubheading Synopsis
28777 -trace-define-variable @var{name} [ @var{value} ]
28780 Create trace variable @var{name} if it does not exist. If
28781 @var{value} is specified, sets the initial value of the specified
28782 trace variable to that value. Note that the @var{name} should start
28783 with the @samp{$} character.
28785 @subsubheading @value{GDBN} Command
28787 The corresponding @value{GDBN} command is @samp{tvariable}.
28789 @subheading -trace-list-variables
28790 @findex -trace-list-variables
28792 @subsubheading Synopsis
28795 -trace-list-variables
28798 Return a table of all defined trace variables. Each element of the
28799 table has the following fields:
28803 The name of the trace variable. This field is always present.
28806 The initial value. This is a 64-bit signed integer. This
28807 field is always present.
28810 The value the trace variable has at the moment. This is a 64-bit
28811 signed integer. This field is absent iff current value is
28812 not defined, for example if the trace was never run, or is
28817 @subsubheading @value{GDBN} Command
28819 The corresponding @value{GDBN} command is @samp{tvariables}.
28821 @subsubheading Example
28825 -trace-list-variables
28826 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28827 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28828 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28829 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28830 body=[variable=@{name="$trace_timestamp",initial="0"@}
28831 variable=@{name="$foo",initial="10",current="15"@}]@}
28835 @subheading -trace-save
28836 @findex -trace-save
28838 @subsubheading Synopsis
28841 -trace-save [-r ] @var{filename}
28844 Saves the collected trace data to @var{filename}. Without the
28845 @samp{-r} option, the data is downloaded from the target and saved
28846 in a local file. With the @samp{-r} option the target is asked
28847 to perform the save.
28849 @subsubheading @value{GDBN} Command
28851 The corresponding @value{GDBN} command is @samp{tsave}.
28854 @subheading -trace-start
28855 @findex -trace-start
28857 @subsubheading Synopsis
28863 Starts a tracing experiments. The result of this command does not
28866 @subsubheading @value{GDBN} Command
28868 The corresponding @value{GDBN} command is @samp{tstart}.
28870 @subheading -trace-status
28871 @findex -trace-status
28873 @subsubheading Synopsis
28879 Obtains the status of a tracing experiment. The result may include
28880 the following fields:
28885 May have a value of either @samp{0}, when no tracing operations are
28886 supported, @samp{1}, when all tracing operations are supported, or
28887 @samp{file} when examining trace file. In the latter case, examining
28888 of trace frame is possible but new tracing experiement cannot be
28889 started. This field is always present.
28892 May have a value of either @samp{0} or @samp{1} depending on whether
28893 tracing experiement is in progress on target. This field is present
28894 if @samp{supported} field is not @samp{0}.
28897 Report the reason why the tracing was stopped last time. This field
28898 may be absent iff tracing was never stopped on target yet. The
28899 value of @samp{request} means the tracing was stopped as result of
28900 the @code{-trace-stop} command. The value of @samp{overflow} means
28901 the tracing buffer is full. The value of @samp{disconnection} means
28902 tracing was automatically stopped when @value{GDBN} has disconnected.
28903 The value of @samp{passcount} means tracing was stopped when a
28904 tracepoint was passed a maximal number of times for that tracepoint.
28905 This field is present if @samp{supported} field is not @samp{0}.
28907 @item stopping-tracepoint
28908 The number of tracepoint whose passcount as exceeded. This field is
28909 present iff the @samp{stop-reason} field has the value of
28913 @itemx frames-created
28914 The @samp{frames} field is a count of the total number of trace frames
28915 in the trace buffer, while @samp{frames-created} is the total created
28916 during the run, including ones that were discarded, such as when a
28917 circular trace buffer filled up. Both fields are optional.
28921 These fields tell the current size of the tracing buffer and the
28922 remaining space. These fields are optional.
28925 The value of the circular trace buffer flag. @code{1} means that the
28926 trace buffer is circular and old trace frames will be discarded if
28927 necessary to make room, @code{0} means that the trace buffer is linear
28931 The value of the disconnected tracing flag. @code{1} means that
28932 tracing will continue after @value{GDBN} disconnects, @code{0} means
28933 that the trace run will stop.
28937 @subsubheading @value{GDBN} Command
28939 The corresponding @value{GDBN} command is @samp{tstatus}.
28941 @subheading -trace-stop
28942 @findex -trace-stop
28944 @subsubheading Synopsis
28950 Stops a tracing experiment. The result of this command has the same
28951 fields as @code{-trace-status}, except that the @samp{supported} and
28952 @samp{running} fields are not output.
28954 @subsubheading @value{GDBN} Command
28956 The corresponding @value{GDBN} command is @samp{tstop}.
28959 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28960 @node GDB/MI Symbol Query
28961 @section @sc{gdb/mi} Symbol Query Commands
28965 @subheading The @code{-symbol-info-address} Command
28966 @findex -symbol-info-address
28968 @subsubheading Synopsis
28971 -symbol-info-address @var{symbol}
28974 Describe where @var{symbol} is stored.
28976 @subsubheading @value{GDBN} Command
28978 The corresponding @value{GDBN} command is @samp{info address}.
28980 @subsubheading Example
28984 @subheading The @code{-symbol-info-file} Command
28985 @findex -symbol-info-file
28987 @subsubheading Synopsis
28993 Show the file for the symbol.
28995 @subsubheading @value{GDBN} Command
28997 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28998 @samp{gdb_find_file}.
29000 @subsubheading Example
29004 @subheading The @code{-symbol-info-function} Command
29005 @findex -symbol-info-function
29007 @subsubheading Synopsis
29010 -symbol-info-function
29013 Show which function the symbol lives in.
29015 @subsubheading @value{GDBN} Command
29017 @samp{gdb_get_function} in @code{gdbtk}.
29019 @subsubheading Example
29023 @subheading The @code{-symbol-info-line} Command
29024 @findex -symbol-info-line
29026 @subsubheading Synopsis
29032 Show the core addresses of the code for a source line.
29034 @subsubheading @value{GDBN} Command
29036 The corresponding @value{GDBN} command is @samp{info line}.
29037 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29039 @subsubheading Example
29043 @subheading The @code{-symbol-info-symbol} Command
29044 @findex -symbol-info-symbol
29046 @subsubheading Synopsis
29049 -symbol-info-symbol @var{addr}
29052 Describe what symbol is at location @var{addr}.
29054 @subsubheading @value{GDBN} Command
29056 The corresponding @value{GDBN} command is @samp{info symbol}.
29058 @subsubheading Example
29062 @subheading The @code{-symbol-list-functions} Command
29063 @findex -symbol-list-functions
29065 @subsubheading Synopsis
29068 -symbol-list-functions
29071 List the functions in the executable.
29073 @subsubheading @value{GDBN} Command
29075 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29076 @samp{gdb_search} in @code{gdbtk}.
29078 @subsubheading Example
29083 @subheading The @code{-symbol-list-lines} Command
29084 @findex -symbol-list-lines
29086 @subsubheading Synopsis
29089 -symbol-list-lines @var{filename}
29092 Print the list of lines that contain code and their associated program
29093 addresses for the given source filename. The entries are sorted in
29094 ascending PC order.
29096 @subsubheading @value{GDBN} Command
29098 There is no corresponding @value{GDBN} command.
29100 @subsubheading Example
29103 -symbol-list-lines basics.c
29104 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29110 @subheading The @code{-symbol-list-types} Command
29111 @findex -symbol-list-types
29113 @subsubheading Synopsis
29119 List all the type names.
29121 @subsubheading @value{GDBN} Command
29123 The corresponding commands are @samp{info types} in @value{GDBN},
29124 @samp{gdb_search} in @code{gdbtk}.
29126 @subsubheading Example
29130 @subheading The @code{-symbol-list-variables} Command
29131 @findex -symbol-list-variables
29133 @subsubheading Synopsis
29136 -symbol-list-variables
29139 List all the global and static variable names.
29141 @subsubheading @value{GDBN} Command
29143 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
29145 @subsubheading Example
29149 @subheading The @code{-symbol-locate} Command
29150 @findex -symbol-locate
29152 @subsubheading Synopsis
29158 @subsubheading @value{GDBN} Command
29160 @samp{gdb_loc} in @code{gdbtk}.
29162 @subsubheading Example
29166 @subheading The @code{-symbol-type} Command
29167 @findex -symbol-type
29169 @subsubheading Synopsis
29172 -symbol-type @var{variable}
29175 Show type of @var{variable}.
29177 @subsubheading @value{GDBN} Command
29179 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
29180 @samp{gdb_obj_variable}.
29182 @subsubheading Example
29187 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29188 @node GDB/MI File Commands
29189 @section @sc{gdb/mi} File Commands
29191 This section describes the GDB/MI commands to specify executable file names
29192 and to read in and obtain symbol table information.
29194 @subheading The @code{-file-exec-and-symbols} Command
29195 @findex -file-exec-and-symbols
29197 @subsubheading Synopsis
29200 -file-exec-and-symbols @var{file}
29203 Specify the executable file to be debugged. This file is the one from
29204 which the symbol table is also read. If no file is specified, the
29205 command clears the executable and symbol information. If breakpoints
29206 are set when using this command with no arguments, @value{GDBN} will produce
29207 error messages. Otherwise, no output is produced, except a completion
29210 @subsubheading @value{GDBN} Command
29212 The corresponding @value{GDBN} command is @samp{file}.
29214 @subsubheading Example
29218 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29224 @subheading The @code{-file-exec-file} Command
29225 @findex -file-exec-file
29227 @subsubheading Synopsis
29230 -file-exec-file @var{file}
29233 Specify the executable file to be debugged. Unlike
29234 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
29235 from this file. If used without argument, @value{GDBN} clears the information
29236 about the executable file. No output is produced, except a completion
29239 @subsubheading @value{GDBN} Command
29241 The corresponding @value{GDBN} command is @samp{exec-file}.
29243 @subsubheading Example
29247 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29254 @subheading The @code{-file-list-exec-sections} Command
29255 @findex -file-list-exec-sections
29257 @subsubheading Synopsis
29260 -file-list-exec-sections
29263 List the sections of the current executable file.
29265 @subsubheading @value{GDBN} Command
29267 The @value{GDBN} command @samp{info file} shows, among the rest, the same
29268 information as this command. @code{gdbtk} has a corresponding command
29269 @samp{gdb_load_info}.
29271 @subsubheading Example
29276 @subheading The @code{-file-list-exec-source-file} Command
29277 @findex -file-list-exec-source-file
29279 @subsubheading Synopsis
29282 -file-list-exec-source-file
29285 List the line number, the current source file, and the absolute path
29286 to the current source file for the current executable. The macro
29287 information field has a value of @samp{1} or @samp{0} depending on
29288 whether or not the file includes preprocessor macro information.
29290 @subsubheading @value{GDBN} Command
29292 The @value{GDBN} equivalent is @samp{info source}
29294 @subsubheading Example
29298 123-file-list-exec-source-file
29299 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
29304 @subheading The @code{-file-list-exec-source-files} Command
29305 @findex -file-list-exec-source-files
29307 @subsubheading Synopsis
29310 -file-list-exec-source-files
29313 List the source files for the current executable.
29315 It will always output the filename, but only when @value{GDBN} can find
29316 the absolute file name of a source file, will it output the fullname.
29318 @subsubheading @value{GDBN} Command
29320 The @value{GDBN} equivalent is @samp{info sources}.
29321 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
29323 @subsubheading Example
29326 -file-list-exec-source-files
29328 @{file=foo.c,fullname=/home/foo.c@},
29329 @{file=/home/bar.c,fullname=/home/bar.c@},
29330 @{file=gdb_could_not_find_fullpath.c@}]
29335 @subheading The @code{-file-list-shared-libraries} Command
29336 @findex -file-list-shared-libraries
29338 @subsubheading Synopsis
29341 -file-list-shared-libraries
29344 List the shared libraries in the program.
29346 @subsubheading @value{GDBN} Command
29348 The corresponding @value{GDBN} command is @samp{info shared}.
29350 @subsubheading Example
29354 @subheading The @code{-file-list-symbol-files} Command
29355 @findex -file-list-symbol-files
29357 @subsubheading Synopsis
29360 -file-list-symbol-files
29365 @subsubheading @value{GDBN} Command
29367 The corresponding @value{GDBN} command is @samp{info file} (part of it).
29369 @subsubheading Example
29374 @subheading The @code{-file-symbol-file} Command
29375 @findex -file-symbol-file
29377 @subsubheading Synopsis
29380 -file-symbol-file @var{file}
29383 Read symbol table info from the specified @var{file} argument. When
29384 used without arguments, clears @value{GDBN}'s symbol table info. No output is
29385 produced, except for a completion notification.
29387 @subsubheading @value{GDBN} Command
29389 The corresponding @value{GDBN} command is @samp{symbol-file}.
29391 @subsubheading Example
29395 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29401 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29402 @node GDB/MI Memory Overlay Commands
29403 @section @sc{gdb/mi} Memory Overlay Commands
29405 The memory overlay commands are not implemented.
29407 @c @subheading -overlay-auto
29409 @c @subheading -overlay-list-mapping-state
29411 @c @subheading -overlay-list-overlays
29413 @c @subheading -overlay-map
29415 @c @subheading -overlay-off
29417 @c @subheading -overlay-on
29419 @c @subheading -overlay-unmap
29421 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29422 @node GDB/MI Signal Handling Commands
29423 @section @sc{gdb/mi} Signal Handling Commands
29425 Signal handling commands are not implemented.
29427 @c @subheading -signal-handle
29429 @c @subheading -signal-list-handle-actions
29431 @c @subheading -signal-list-signal-types
29435 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29436 @node GDB/MI Target Manipulation
29437 @section @sc{gdb/mi} Target Manipulation Commands
29440 @subheading The @code{-target-attach} Command
29441 @findex -target-attach
29443 @subsubheading Synopsis
29446 -target-attach @var{pid} | @var{gid} | @var{file}
29449 Attach to a process @var{pid} or a file @var{file} outside of
29450 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
29451 group, the id previously returned by
29452 @samp{-list-thread-groups --available} must be used.
29454 @subsubheading @value{GDBN} Command
29456 The corresponding @value{GDBN} command is @samp{attach}.
29458 @subsubheading Example
29462 =thread-created,id="1"
29463 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
29469 @subheading The @code{-target-compare-sections} Command
29470 @findex -target-compare-sections
29472 @subsubheading Synopsis
29475 -target-compare-sections [ @var{section} ]
29478 Compare data of section @var{section} on target to the exec file.
29479 Without the argument, all sections are compared.
29481 @subsubheading @value{GDBN} Command
29483 The @value{GDBN} equivalent is @samp{compare-sections}.
29485 @subsubheading Example
29490 @subheading The @code{-target-detach} Command
29491 @findex -target-detach
29493 @subsubheading Synopsis
29496 -target-detach [ @var{pid} | @var{gid} ]
29499 Detach from the remote target which normally resumes its execution.
29500 If either @var{pid} or @var{gid} is specified, detaches from either
29501 the specified process, or specified thread group. There's no output.
29503 @subsubheading @value{GDBN} Command
29505 The corresponding @value{GDBN} command is @samp{detach}.
29507 @subsubheading Example
29517 @subheading The @code{-target-disconnect} Command
29518 @findex -target-disconnect
29520 @subsubheading Synopsis
29526 Disconnect from the remote target. There's no output and the target is
29527 generally not resumed.
29529 @subsubheading @value{GDBN} Command
29531 The corresponding @value{GDBN} command is @samp{disconnect}.
29533 @subsubheading Example
29543 @subheading The @code{-target-download} Command
29544 @findex -target-download
29546 @subsubheading Synopsis
29552 Loads the executable onto the remote target.
29553 It prints out an update message every half second, which includes the fields:
29557 The name of the section.
29559 The size of what has been sent so far for that section.
29561 The size of the section.
29563 The total size of what was sent so far (the current and the previous sections).
29565 The size of the overall executable to download.
29569 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29570 @sc{gdb/mi} Output Syntax}).
29572 In addition, it prints the name and size of the sections, as they are
29573 downloaded. These messages include the following fields:
29577 The name of the section.
29579 The size of the section.
29581 The size of the overall executable to download.
29585 At the end, a summary is printed.
29587 @subsubheading @value{GDBN} Command
29589 The corresponding @value{GDBN} command is @samp{load}.
29591 @subsubheading Example
29593 Note: each status message appears on a single line. Here the messages
29594 have been broken down so that they can fit onto a page.
29599 +download,@{section=".text",section-size="6668",total-size="9880"@}
29600 +download,@{section=".text",section-sent="512",section-size="6668",
29601 total-sent="512",total-size="9880"@}
29602 +download,@{section=".text",section-sent="1024",section-size="6668",
29603 total-sent="1024",total-size="9880"@}
29604 +download,@{section=".text",section-sent="1536",section-size="6668",
29605 total-sent="1536",total-size="9880"@}
29606 +download,@{section=".text",section-sent="2048",section-size="6668",
29607 total-sent="2048",total-size="9880"@}
29608 +download,@{section=".text",section-sent="2560",section-size="6668",
29609 total-sent="2560",total-size="9880"@}
29610 +download,@{section=".text",section-sent="3072",section-size="6668",
29611 total-sent="3072",total-size="9880"@}
29612 +download,@{section=".text",section-sent="3584",section-size="6668",
29613 total-sent="3584",total-size="9880"@}
29614 +download,@{section=".text",section-sent="4096",section-size="6668",
29615 total-sent="4096",total-size="9880"@}
29616 +download,@{section=".text",section-sent="4608",section-size="6668",
29617 total-sent="4608",total-size="9880"@}
29618 +download,@{section=".text",section-sent="5120",section-size="6668",
29619 total-sent="5120",total-size="9880"@}
29620 +download,@{section=".text",section-sent="5632",section-size="6668",
29621 total-sent="5632",total-size="9880"@}
29622 +download,@{section=".text",section-sent="6144",section-size="6668",
29623 total-sent="6144",total-size="9880"@}
29624 +download,@{section=".text",section-sent="6656",section-size="6668",
29625 total-sent="6656",total-size="9880"@}
29626 +download,@{section=".init",section-size="28",total-size="9880"@}
29627 +download,@{section=".fini",section-size="28",total-size="9880"@}
29628 +download,@{section=".data",section-size="3156",total-size="9880"@}
29629 +download,@{section=".data",section-sent="512",section-size="3156",
29630 total-sent="7236",total-size="9880"@}
29631 +download,@{section=".data",section-sent="1024",section-size="3156",
29632 total-sent="7748",total-size="9880"@}
29633 +download,@{section=".data",section-sent="1536",section-size="3156",
29634 total-sent="8260",total-size="9880"@}
29635 +download,@{section=".data",section-sent="2048",section-size="3156",
29636 total-sent="8772",total-size="9880"@}
29637 +download,@{section=".data",section-sent="2560",section-size="3156",
29638 total-sent="9284",total-size="9880"@}
29639 +download,@{section=".data",section-sent="3072",section-size="3156",
29640 total-sent="9796",total-size="9880"@}
29641 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29648 @subheading The @code{-target-exec-status} Command
29649 @findex -target-exec-status
29651 @subsubheading Synopsis
29654 -target-exec-status
29657 Provide information on the state of the target (whether it is running or
29658 not, for instance).
29660 @subsubheading @value{GDBN} Command
29662 There's no equivalent @value{GDBN} command.
29664 @subsubheading Example
29668 @subheading The @code{-target-list-available-targets} Command
29669 @findex -target-list-available-targets
29671 @subsubheading Synopsis
29674 -target-list-available-targets
29677 List the possible targets to connect to.
29679 @subsubheading @value{GDBN} Command
29681 The corresponding @value{GDBN} command is @samp{help target}.
29683 @subsubheading Example
29687 @subheading The @code{-target-list-current-targets} Command
29688 @findex -target-list-current-targets
29690 @subsubheading Synopsis
29693 -target-list-current-targets
29696 Describe the current target.
29698 @subsubheading @value{GDBN} Command
29700 The corresponding information is printed by @samp{info file} (among
29703 @subsubheading Example
29707 @subheading The @code{-target-list-parameters} Command
29708 @findex -target-list-parameters
29710 @subsubheading Synopsis
29713 -target-list-parameters
29719 @subsubheading @value{GDBN} Command
29723 @subsubheading Example
29727 @subheading The @code{-target-select} Command
29728 @findex -target-select
29730 @subsubheading Synopsis
29733 -target-select @var{type} @var{parameters @dots{}}
29736 Connect @value{GDBN} to the remote target. This command takes two args:
29740 The type of target, for instance @samp{remote}, etc.
29741 @item @var{parameters}
29742 Device names, host names and the like. @xref{Target Commands, ,
29743 Commands for Managing Targets}, for more details.
29746 The output is a connection notification, followed by the address at
29747 which the target program is, in the following form:
29750 ^connected,addr="@var{address}",func="@var{function name}",
29751 args=[@var{arg list}]
29754 @subsubheading @value{GDBN} Command
29756 The corresponding @value{GDBN} command is @samp{target}.
29758 @subsubheading Example
29762 -target-select remote /dev/ttya
29763 ^connected,addr="0xfe00a300",func="??",args=[]
29767 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29768 @node GDB/MI File Transfer Commands
29769 @section @sc{gdb/mi} File Transfer Commands
29772 @subheading The @code{-target-file-put} Command
29773 @findex -target-file-put
29775 @subsubheading Synopsis
29778 -target-file-put @var{hostfile} @var{targetfile}
29781 Copy file @var{hostfile} from the host system (the machine running
29782 @value{GDBN}) to @var{targetfile} on the target system.
29784 @subsubheading @value{GDBN} Command
29786 The corresponding @value{GDBN} command is @samp{remote put}.
29788 @subsubheading Example
29792 -target-file-put localfile remotefile
29798 @subheading The @code{-target-file-get} Command
29799 @findex -target-file-get
29801 @subsubheading Synopsis
29804 -target-file-get @var{targetfile} @var{hostfile}
29807 Copy file @var{targetfile} from the target system to @var{hostfile}
29808 on the host system.
29810 @subsubheading @value{GDBN} Command
29812 The corresponding @value{GDBN} command is @samp{remote get}.
29814 @subsubheading Example
29818 -target-file-get remotefile localfile
29824 @subheading The @code{-target-file-delete} Command
29825 @findex -target-file-delete
29827 @subsubheading Synopsis
29830 -target-file-delete @var{targetfile}
29833 Delete @var{targetfile} from the target system.
29835 @subsubheading @value{GDBN} Command
29837 The corresponding @value{GDBN} command is @samp{remote delete}.
29839 @subsubheading Example
29843 -target-file-delete remotefile
29849 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29850 @node GDB/MI Miscellaneous Commands
29851 @section Miscellaneous @sc{gdb/mi} Commands
29853 @c @subheading -gdb-complete
29855 @subheading The @code{-gdb-exit} Command
29858 @subsubheading Synopsis
29864 Exit @value{GDBN} immediately.
29866 @subsubheading @value{GDBN} Command
29868 Approximately corresponds to @samp{quit}.
29870 @subsubheading Example
29880 @subheading The @code{-exec-abort} Command
29881 @findex -exec-abort
29883 @subsubheading Synopsis
29889 Kill the inferior running program.
29891 @subsubheading @value{GDBN} Command
29893 The corresponding @value{GDBN} command is @samp{kill}.
29895 @subsubheading Example
29900 @subheading The @code{-gdb-set} Command
29903 @subsubheading Synopsis
29909 Set an internal @value{GDBN} variable.
29910 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29912 @subsubheading @value{GDBN} Command
29914 The corresponding @value{GDBN} command is @samp{set}.
29916 @subsubheading Example
29926 @subheading The @code{-gdb-show} Command
29929 @subsubheading Synopsis
29935 Show the current value of a @value{GDBN} variable.
29937 @subsubheading @value{GDBN} Command
29939 The corresponding @value{GDBN} command is @samp{show}.
29941 @subsubheading Example
29950 @c @subheading -gdb-source
29953 @subheading The @code{-gdb-version} Command
29954 @findex -gdb-version
29956 @subsubheading Synopsis
29962 Show version information for @value{GDBN}. Used mostly in testing.
29964 @subsubheading @value{GDBN} Command
29966 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29967 default shows this information when you start an interactive session.
29969 @subsubheading Example
29971 @c This example modifies the actual output from GDB to avoid overfull
29977 ~Copyright 2000 Free Software Foundation, Inc.
29978 ~GDB is free software, covered by the GNU General Public License, and
29979 ~you are welcome to change it and/or distribute copies of it under
29980 ~ certain conditions.
29981 ~Type "show copying" to see the conditions.
29982 ~There is absolutely no warranty for GDB. Type "show warranty" for
29984 ~This GDB was configured as
29985 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29990 @subheading The @code{-list-features} Command
29991 @findex -list-features
29993 Returns a list of particular features of the MI protocol that
29994 this version of gdb implements. A feature can be a command,
29995 or a new field in an output of some command, or even an
29996 important bugfix. While a frontend can sometimes detect presence
29997 of a feature at runtime, it is easier to perform detection at debugger
30000 The command returns a list of strings, with each string naming an
30001 available feature. Each returned string is just a name, it does not
30002 have any internal structure. The list of possible feature names
30008 (gdb) -list-features
30009 ^done,result=["feature1","feature2"]
30012 The current list of features is:
30015 @item frozen-varobjs
30016 Indicates presence of the @code{-var-set-frozen} command, as well
30017 as possible presense of the @code{frozen} field in the output
30018 of @code{-varobj-create}.
30019 @item pending-breakpoints
30020 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
30022 Indicates presence of Python scripting support, Python-based
30023 pretty-printing commands, and possible presence of the
30024 @samp{display_hint} field in the output of @code{-var-list-children}
30026 Indicates presence of the @code{-thread-info} command.
30027 @item data-read-memory-bytes
30028 Indicates presense of the @code{-data-read-memory-bytes} and the
30029 @code{-data-write-memory-bytes} commands.
30033 @subheading The @code{-list-target-features} Command
30034 @findex -list-target-features
30036 Returns a list of particular features that are supported by the
30037 target. Those features affect the permitted MI commands, but
30038 unlike the features reported by the @code{-list-features} command, the
30039 features depend on which target GDB is using at the moment. Whenever
30040 a target can change, due to commands such as @code{-target-select},
30041 @code{-target-attach} or @code{-exec-run}, the list of target features
30042 may change, and the frontend should obtain it again.
30046 (gdb) -list-features
30047 ^done,result=["async"]
30050 The current list of features is:
30054 Indicates that the target is capable of asynchronous command
30055 execution, which means that @value{GDBN} will accept further commands
30056 while the target is running.
30059 Indicates that the target is capable of reverse execution.
30060 @xref{Reverse Execution}, for more information.
30064 @subheading The @code{-list-thread-groups} Command
30065 @findex -list-thread-groups
30067 @subheading Synopsis
30070 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
30073 Lists thread groups (@pxref{Thread groups}). When a single thread
30074 group is passed as the argument, lists the children of that group.
30075 When several thread group are passed, lists information about those
30076 thread groups. Without any parameters, lists information about all
30077 top-level thread groups.
30079 Normally, thread groups that are being debugged are reported.
30080 With the @samp{--available} option, @value{GDBN} reports thread groups
30081 available on the target.
30083 The output of this command may have either a @samp{threads} result or
30084 a @samp{groups} result. The @samp{thread} result has a list of tuples
30085 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
30086 Information}). The @samp{groups} result has a list of tuples as value,
30087 each tuple describing a thread group. If top-level groups are
30088 requested (that is, no parameter is passed), or when several groups
30089 are passed, the output always has a @samp{groups} result. The format
30090 of the @samp{group} result is described below.
30092 To reduce the number of roundtrips it's possible to list thread groups
30093 together with their children, by passing the @samp{--recurse} option
30094 and the recursion depth. Presently, only recursion depth of 1 is
30095 permitted. If this option is present, then every reported thread group
30096 will also include its children, either as @samp{group} or
30097 @samp{threads} field.
30099 In general, any combination of option and parameters is permitted, with
30100 the following caveats:
30104 When a single thread group is passed, the output will typically
30105 be the @samp{threads} result. Because threads may not contain
30106 anything, the @samp{recurse} option will be ignored.
30109 When the @samp{--available} option is passed, limited information may
30110 be available. In particular, the list of threads of a process might
30111 be inaccessible. Further, specifying specific thread groups might
30112 not give any performance advantage over listing all thread groups.
30113 The frontend should assume that @samp{-list-thread-groups --available}
30114 is always an expensive operation and cache the results.
30118 The @samp{groups} result is a list of tuples, where each tuple may
30119 have the following fields:
30123 Identifier of the thread group. This field is always present.
30124 The identifier is an opaque string; frontends should not try to
30125 convert it to an integer, even though it might look like one.
30128 The type of the thread group. At present, only @samp{process} is a
30132 The target-specific process identifier. This field is only present
30133 for thread groups of type @samp{process} and only if the process exists.
30136 The number of children this thread group has. This field may be
30137 absent for an available thread group.
30140 This field has a list of tuples as value, each tuple describing a
30141 thread. It may be present if the @samp{--recurse} option is
30142 specified, and it's actually possible to obtain the threads.
30145 This field is a list of integers, each identifying a core that one
30146 thread of the group is running on. This field may be absent if
30147 such information is not available.
30150 The name of the executable file that corresponds to this thread group.
30151 The field is only present for thread groups of type @samp{process},
30152 and only if there is a corresponding executable file.
30156 @subheading Example
30160 -list-thread-groups
30161 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
30162 -list-thread-groups 17
30163 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30164 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
30165 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30166 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
30167 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
30168 -list-thread-groups --available
30169 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
30170 -list-thread-groups --available --recurse 1
30171 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30172 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30173 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
30174 -list-thread-groups --available --recurse 1 17 18
30175 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30176 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30177 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
30181 @subheading The @code{-add-inferior} Command
30182 @findex -add-inferior
30184 @subheading Synopsis
30190 Creates a new inferior (@pxref{Inferiors and Programs}). The created
30191 inferior is not associated with any executable. Such association may
30192 be established with the @samp{-file-exec-and-symbols} command
30193 (@pxref{GDB/MI File Commands}). The command response has a single
30194 field, @samp{thread-group}, whose value is the identifier of the
30195 thread group corresponding to the new inferior.
30197 @subheading Example
30202 ^done,thread-group="i3"
30205 @subheading The @code{-interpreter-exec} Command
30206 @findex -interpreter-exec
30208 @subheading Synopsis
30211 -interpreter-exec @var{interpreter} @var{command}
30213 @anchor{-interpreter-exec}
30215 Execute the specified @var{command} in the given @var{interpreter}.
30217 @subheading @value{GDBN} Command
30219 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
30221 @subheading Example
30225 -interpreter-exec console "break main"
30226 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
30227 &"During symbol reading, bad structure-type format.\n"
30228 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
30233 @subheading The @code{-inferior-tty-set} Command
30234 @findex -inferior-tty-set
30236 @subheading Synopsis
30239 -inferior-tty-set /dev/pts/1
30242 Set terminal for future runs of the program being debugged.
30244 @subheading @value{GDBN} Command
30246 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
30248 @subheading Example
30252 -inferior-tty-set /dev/pts/1
30257 @subheading The @code{-inferior-tty-show} Command
30258 @findex -inferior-tty-show
30260 @subheading Synopsis
30266 Show terminal for future runs of program being debugged.
30268 @subheading @value{GDBN} Command
30270 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
30272 @subheading Example
30276 -inferior-tty-set /dev/pts/1
30280 ^done,inferior_tty_terminal="/dev/pts/1"
30284 @subheading The @code{-enable-timings} Command
30285 @findex -enable-timings
30287 @subheading Synopsis
30290 -enable-timings [yes | no]
30293 Toggle the printing of the wallclock, user and system times for an MI
30294 command as a field in its output. This command is to help frontend
30295 developers optimize the performance of their code. No argument is
30296 equivalent to @samp{yes}.
30298 @subheading @value{GDBN} Command
30302 @subheading Example
30310 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30311 addr="0x080484ed",func="main",file="myprog.c",
30312 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
30313 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
30321 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30322 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
30323 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
30324 fullname="/home/nickrob/myprog.c",line="73"@}
30329 @chapter @value{GDBN} Annotations
30331 This chapter describes annotations in @value{GDBN}. Annotations were
30332 designed to interface @value{GDBN} to graphical user interfaces or other
30333 similar programs which want to interact with @value{GDBN} at a
30334 relatively high level.
30336 The annotation mechanism has largely been superseded by @sc{gdb/mi}
30340 This is Edition @value{EDITION}, @value{DATE}.
30344 * Annotations Overview:: What annotations are; the general syntax.
30345 * Server Prefix:: Issuing a command without affecting user state.
30346 * Prompting:: Annotations marking @value{GDBN}'s need for input.
30347 * Errors:: Annotations for error messages.
30348 * Invalidation:: Some annotations describe things now invalid.
30349 * Annotations for Running::
30350 Whether the program is running, how it stopped, etc.
30351 * Source Annotations:: Annotations describing source code.
30354 @node Annotations Overview
30355 @section What is an Annotation?
30356 @cindex annotations
30358 Annotations start with a newline character, two @samp{control-z}
30359 characters, and the name of the annotation. If there is no additional
30360 information associated with this annotation, the name of the annotation
30361 is followed immediately by a newline. If there is additional
30362 information, the name of the annotation is followed by a space, the
30363 additional information, and a newline. The additional information
30364 cannot contain newline characters.
30366 Any output not beginning with a newline and two @samp{control-z}
30367 characters denotes literal output from @value{GDBN}. Currently there is
30368 no need for @value{GDBN} to output a newline followed by two
30369 @samp{control-z} characters, but if there was such a need, the
30370 annotations could be extended with an @samp{escape} annotation which
30371 means those three characters as output.
30373 The annotation @var{level}, which is specified using the
30374 @option{--annotate} command line option (@pxref{Mode Options}), controls
30375 how much information @value{GDBN} prints together with its prompt,
30376 values of expressions, source lines, and other types of output. Level 0
30377 is for no annotations, level 1 is for use when @value{GDBN} is run as a
30378 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
30379 for programs that control @value{GDBN}, and level 2 annotations have
30380 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
30381 Interface, annotate, GDB's Obsolete Annotations}).
30384 @kindex set annotate
30385 @item set annotate @var{level}
30386 The @value{GDBN} command @code{set annotate} sets the level of
30387 annotations to the specified @var{level}.
30389 @item show annotate
30390 @kindex show annotate
30391 Show the current annotation level.
30394 This chapter describes level 3 annotations.
30396 A simple example of starting up @value{GDBN} with annotations is:
30399 $ @kbd{gdb --annotate=3}
30401 Copyright 2003 Free Software Foundation, Inc.
30402 GDB is free software, covered by the GNU General Public License,
30403 and you are welcome to change it and/or distribute copies of it
30404 under certain conditions.
30405 Type "show copying" to see the conditions.
30406 There is absolutely no warranty for GDB. Type "show warranty"
30408 This GDB was configured as "i386-pc-linux-gnu"
30419 Here @samp{quit} is input to @value{GDBN}; the rest is output from
30420 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
30421 denotes a @samp{control-z} character) are annotations; the rest is
30422 output from @value{GDBN}.
30424 @node Server Prefix
30425 @section The Server Prefix
30426 @cindex server prefix
30428 If you prefix a command with @samp{server } then it will not affect
30429 the command history, nor will it affect @value{GDBN}'s notion of which
30430 command to repeat if @key{RET} is pressed on a line by itself. This
30431 means that commands can be run behind a user's back by a front-end in
30432 a transparent manner.
30434 The @code{server } prefix does not affect the recording of values into
30435 the value history; to print a value without recording it into the
30436 value history, use the @code{output} command instead of the
30437 @code{print} command.
30439 Using this prefix also disables confirmation requests
30440 (@pxref{confirmation requests}).
30443 @section Annotation for @value{GDBN} Input
30445 @cindex annotations for prompts
30446 When @value{GDBN} prompts for input, it annotates this fact so it is possible
30447 to know when to send output, when the output from a given command is
30450 Different kinds of input each have a different @dfn{input type}. Each
30451 input type has three annotations: a @code{pre-} annotation, which
30452 denotes the beginning of any prompt which is being output, a plain
30453 annotation, which denotes the end of the prompt, and then a @code{post-}
30454 annotation which denotes the end of any echo which may (or may not) be
30455 associated with the input. For example, the @code{prompt} input type
30456 features the following annotations:
30464 The input types are
30467 @findex pre-prompt annotation
30468 @findex prompt annotation
30469 @findex post-prompt annotation
30471 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
30473 @findex pre-commands annotation
30474 @findex commands annotation
30475 @findex post-commands annotation
30477 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
30478 command. The annotations are repeated for each command which is input.
30480 @findex pre-overload-choice annotation
30481 @findex overload-choice annotation
30482 @findex post-overload-choice annotation
30483 @item overload-choice
30484 When @value{GDBN} wants the user to select between various overloaded functions.
30486 @findex pre-query annotation
30487 @findex query annotation
30488 @findex post-query annotation
30490 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
30492 @findex pre-prompt-for-continue annotation
30493 @findex prompt-for-continue annotation
30494 @findex post-prompt-for-continue annotation
30495 @item prompt-for-continue
30496 When @value{GDBN} is asking the user to press return to continue. Note: Don't
30497 expect this to work well; instead use @code{set height 0} to disable
30498 prompting. This is because the counting of lines is buggy in the
30499 presence of annotations.
30504 @cindex annotations for errors, warnings and interrupts
30506 @findex quit annotation
30511 This annotation occurs right before @value{GDBN} responds to an interrupt.
30513 @findex error annotation
30518 This annotation occurs right before @value{GDBN} responds to an error.
30520 Quit and error annotations indicate that any annotations which @value{GDBN} was
30521 in the middle of may end abruptly. For example, if a
30522 @code{value-history-begin} annotation is followed by a @code{error}, one
30523 cannot expect to receive the matching @code{value-history-end}. One
30524 cannot expect not to receive it either, however; an error annotation
30525 does not necessarily mean that @value{GDBN} is immediately returning all the way
30528 @findex error-begin annotation
30529 A quit or error annotation may be preceded by
30535 Any output between that and the quit or error annotation is the error
30538 Warning messages are not yet annotated.
30539 @c If we want to change that, need to fix warning(), type_error(),
30540 @c range_error(), and possibly other places.
30543 @section Invalidation Notices
30545 @cindex annotations for invalidation messages
30546 The following annotations say that certain pieces of state may have
30550 @findex frames-invalid annotation
30551 @item ^Z^Zframes-invalid
30553 The frames (for example, output from the @code{backtrace} command) may
30556 @findex breakpoints-invalid annotation
30557 @item ^Z^Zbreakpoints-invalid
30559 The breakpoints may have changed. For example, the user just added or
30560 deleted a breakpoint.
30563 @node Annotations for Running
30564 @section Running the Program
30565 @cindex annotations for running programs
30567 @findex starting annotation
30568 @findex stopping annotation
30569 When the program starts executing due to a @value{GDBN} command such as
30570 @code{step} or @code{continue},
30576 is output. When the program stops,
30582 is output. Before the @code{stopped} annotation, a variety of
30583 annotations describe how the program stopped.
30586 @findex exited annotation
30587 @item ^Z^Zexited @var{exit-status}
30588 The program exited, and @var{exit-status} is the exit status (zero for
30589 successful exit, otherwise nonzero).
30591 @findex signalled annotation
30592 @findex signal-name annotation
30593 @findex signal-name-end annotation
30594 @findex signal-string annotation
30595 @findex signal-string-end annotation
30596 @item ^Z^Zsignalled
30597 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30598 annotation continues:
30604 ^Z^Zsignal-name-end
30608 ^Z^Zsignal-string-end
30613 where @var{name} is the name of the signal, such as @code{SIGILL} or
30614 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30615 as @code{Illegal Instruction} or @code{Segmentation fault}.
30616 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30617 user's benefit and have no particular format.
30619 @findex signal annotation
30621 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30622 just saying that the program received the signal, not that it was
30623 terminated with it.
30625 @findex breakpoint annotation
30626 @item ^Z^Zbreakpoint @var{number}
30627 The program hit breakpoint number @var{number}.
30629 @findex watchpoint annotation
30630 @item ^Z^Zwatchpoint @var{number}
30631 The program hit watchpoint number @var{number}.
30634 @node Source Annotations
30635 @section Displaying Source
30636 @cindex annotations for source display
30638 @findex source annotation
30639 The following annotation is used instead of displaying source code:
30642 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30645 where @var{filename} is an absolute file name indicating which source
30646 file, @var{line} is the line number within that file (where 1 is the
30647 first line in the file), @var{character} is the character position
30648 within the file (where 0 is the first character in the file) (for most
30649 debug formats this will necessarily point to the beginning of a line),
30650 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30651 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30652 @var{addr} is the address in the target program associated with the
30653 source which is being displayed. @var{addr} is in the form @samp{0x}
30654 followed by one or more lowercase hex digits (note that this does not
30655 depend on the language).
30657 @node JIT Interface
30658 @chapter JIT Compilation Interface
30659 @cindex just-in-time compilation
30660 @cindex JIT compilation interface
30662 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30663 interface. A JIT compiler is a program or library that generates native
30664 executable code at runtime and executes it, usually in order to achieve good
30665 performance while maintaining platform independence.
30667 Programs that use JIT compilation are normally difficult to debug because
30668 portions of their code are generated at runtime, instead of being loaded from
30669 object files, which is where @value{GDBN} normally finds the program's symbols
30670 and debug information. In order to debug programs that use JIT compilation,
30671 @value{GDBN} has an interface that allows the program to register in-memory
30672 symbol files with @value{GDBN} at runtime.
30674 If you are using @value{GDBN} to debug a program that uses this interface, then
30675 it should work transparently so long as you have not stripped the binary. If
30676 you are developing a JIT compiler, then the interface is documented in the rest
30677 of this chapter. At this time, the only known client of this interface is the
30680 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30681 JIT compiler communicates with @value{GDBN} by writing data into a global
30682 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30683 attaches, it reads a linked list of symbol files from the global variable to
30684 find existing code, and puts a breakpoint in the function so that it can find
30685 out about additional code.
30688 * Declarations:: Relevant C struct declarations
30689 * Registering Code:: Steps to register code
30690 * Unregistering Code:: Steps to unregister code
30694 @section JIT Declarations
30696 These are the relevant struct declarations that a C program should include to
30697 implement the interface:
30707 struct jit_code_entry
30709 struct jit_code_entry *next_entry;
30710 struct jit_code_entry *prev_entry;
30711 const char *symfile_addr;
30712 uint64_t symfile_size;
30715 struct jit_descriptor
30718 /* This type should be jit_actions_t, but we use uint32_t
30719 to be explicit about the bitwidth. */
30720 uint32_t action_flag;
30721 struct jit_code_entry *relevant_entry;
30722 struct jit_code_entry *first_entry;
30725 /* GDB puts a breakpoint in this function. */
30726 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30728 /* Make sure to specify the version statically, because the
30729 debugger may check the version before we can set it. */
30730 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30733 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30734 modifications to this global data properly, which can easily be done by putting
30735 a global mutex around modifications to these structures.
30737 @node Registering Code
30738 @section Registering Code
30740 To register code with @value{GDBN}, the JIT should follow this protocol:
30744 Generate an object file in memory with symbols and other desired debug
30745 information. The file must include the virtual addresses of the sections.
30748 Create a code entry for the file, which gives the start and size of the symbol
30752 Add it to the linked list in the JIT descriptor.
30755 Point the relevant_entry field of the descriptor at the entry.
30758 Set @code{action_flag} to @code{JIT_REGISTER} and call
30759 @code{__jit_debug_register_code}.
30762 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30763 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30764 new code. However, the linked list must still be maintained in order to allow
30765 @value{GDBN} to attach to a running process and still find the symbol files.
30767 @node Unregistering Code
30768 @section Unregistering Code
30770 If code is freed, then the JIT should use the following protocol:
30774 Remove the code entry corresponding to the code from the linked list.
30777 Point the @code{relevant_entry} field of the descriptor at the code entry.
30780 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30781 @code{__jit_debug_register_code}.
30784 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30785 and the JIT will leak the memory used for the associated symbol files.
30788 @chapter Reporting Bugs in @value{GDBN}
30789 @cindex bugs in @value{GDBN}
30790 @cindex reporting bugs in @value{GDBN}
30792 Your bug reports play an essential role in making @value{GDBN} reliable.
30794 Reporting a bug may help you by bringing a solution to your problem, or it
30795 may not. But in any case the principal function of a bug report is to help
30796 the entire community by making the next version of @value{GDBN} work better. Bug
30797 reports are your contribution to the maintenance of @value{GDBN}.
30799 In order for a bug report to serve its purpose, you must include the
30800 information that enables us to fix the bug.
30803 * Bug Criteria:: Have you found a bug?
30804 * Bug Reporting:: How to report bugs
30808 @section Have You Found a Bug?
30809 @cindex bug criteria
30811 If you are not sure whether you have found a bug, here are some guidelines:
30814 @cindex fatal signal
30815 @cindex debugger crash
30816 @cindex crash of debugger
30818 If the debugger gets a fatal signal, for any input whatever, that is a
30819 @value{GDBN} bug. Reliable debuggers never crash.
30821 @cindex error on valid input
30823 If @value{GDBN} produces an error message for valid input, that is a
30824 bug. (Note that if you're cross debugging, the problem may also be
30825 somewhere in the connection to the target.)
30827 @cindex invalid input
30829 If @value{GDBN} does not produce an error message for invalid input,
30830 that is a bug. However, you should note that your idea of
30831 ``invalid input'' might be our idea of ``an extension'' or ``support
30832 for traditional practice''.
30835 If you are an experienced user of debugging tools, your suggestions
30836 for improvement of @value{GDBN} are welcome in any case.
30839 @node Bug Reporting
30840 @section How to Report Bugs
30841 @cindex bug reports
30842 @cindex @value{GDBN} bugs, reporting
30844 A number of companies and individuals offer support for @sc{gnu} products.
30845 If you obtained @value{GDBN} from a support organization, we recommend you
30846 contact that organization first.
30848 You can find contact information for many support companies and
30849 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30851 @c should add a web page ref...
30854 @ifset BUGURL_DEFAULT
30855 In any event, we also recommend that you submit bug reports for
30856 @value{GDBN}. The preferred method is to submit them directly using
30857 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30858 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30861 @strong{Do not send bug reports to @samp{info-gdb}, or to
30862 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30863 not want to receive bug reports. Those that do have arranged to receive
30866 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30867 serves as a repeater. The mailing list and the newsgroup carry exactly
30868 the same messages. Often people think of posting bug reports to the
30869 newsgroup instead of mailing them. This appears to work, but it has one
30870 problem which can be crucial: a newsgroup posting often lacks a mail
30871 path back to the sender. Thus, if we need to ask for more information,
30872 we may be unable to reach you. For this reason, it is better to send
30873 bug reports to the mailing list.
30875 @ifclear BUGURL_DEFAULT
30876 In any event, we also recommend that you submit bug reports for
30877 @value{GDBN} to @value{BUGURL}.
30881 The fundamental principle of reporting bugs usefully is this:
30882 @strong{report all the facts}. If you are not sure whether to state a
30883 fact or leave it out, state it!
30885 Often people omit facts because they think they know what causes the
30886 problem and assume that some details do not matter. Thus, you might
30887 assume that the name of the variable you use in an example does not matter.
30888 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30889 stray memory reference which happens to fetch from the location where that
30890 name is stored in memory; perhaps, if the name were different, the contents
30891 of that location would fool the debugger into doing the right thing despite
30892 the bug. Play it safe and give a specific, complete example. That is the
30893 easiest thing for you to do, and the most helpful.
30895 Keep in mind that the purpose of a bug report is to enable us to fix the
30896 bug. It may be that the bug has been reported previously, but neither
30897 you nor we can know that unless your bug report is complete and
30900 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30901 bell?'' Those bug reports are useless, and we urge everyone to
30902 @emph{refuse to respond to them} except to chide the sender to report
30905 To enable us to fix the bug, you should include all these things:
30909 The version of @value{GDBN}. @value{GDBN} announces it if you start
30910 with no arguments; you can also print it at any time using @code{show
30913 Without this, we will not know whether there is any point in looking for
30914 the bug in the current version of @value{GDBN}.
30917 The type of machine you are using, and the operating system name and
30921 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30922 ``@value{GCC}--2.8.1''.
30925 What compiler (and its version) was used to compile the program you are
30926 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30927 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30928 to get this information; for other compilers, see the documentation for
30932 The command arguments you gave the compiler to compile your example and
30933 observe the bug. For example, did you use @samp{-O}? To guarantee
30934 you will not omit something important, list them all. A copy of the
30935 Makefile (or the output from make) is sufficient.
30937 If we were to try to guess the arguments, we would probably guess wrong
30938 and then we might not encounter the bug.
30941 A complete input script, and all necessary source files, that will
30945 A description of what behavior you observe that you believe is
30946 incorrect. For example, ``It gets a fatal signal.''
30948 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30949 will certainly notice it. But if the bug is incorrect output, we might
30950 not notice unless it is glaringly wrong. You might as well not give us
30951 a chance to make a mistake.
30953 Even if the problem you experience is a fatal signal, you should still
30954 say so explicitly. Suppose something strange is going on, such as, your
30955 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30956 the C library on your system. (This has happened!) Your copy might
30957 crash and ours would not. If you told us to expect a crash, then when
30958 ours fails to crash, we would know that the bug was not happening for
30959 us. If you had not told us to expect a crash, then we would not be able
30960 to draw any conclusion from our observations.
30963 @cindex recording a session script
30964 To collect all this information, you can use a session recording program
30965 such as @command{script}, which is available on many Unix systems.
30966 Just run your @value{GDBN} session inside @command{script} and then
30967 include the @file{typescript} file with your bug report.
30969 Another way to record a @value{GDBN} session is to run @value{GDBN}
30970 inside Emacs and then save the entire buffer to a file.
30973 If you wish to suggest changes to the @value{GDBN} source, send us context
30974 diffs. If you even discuss something in the @value{GDBN} source, refer to
30975 it by context, not by line number.
30977 The line numbers in our development sources will not match those in your
30978 sources. Your line numbers would convey no useful information to us.
30982 Here are some things that are not necessary:
30986 A description of the envelope of the bug.
30988 Often people who encounter a bug spend a lot of time investigating
30989 which changes to the input file will make the bug go away and which
30990 changes will not affect it.
30992 This is often time consuming and not very useful, because the way we
30993 will find the bug is by running a single example under the debugger
30994 with breakpoints, not by pure deduction from a series of examples.
30995 We recommend that you save your time for something else.
30997 Of course, if you can find a simpler example to report @emph{instead}
30998 of the original one, that is a convenience for us. Errors in the
30999 output will be easier to spot, running under the debugger will take
31000 less time, and so on.
31002 However, simplification is not vital; if you do not want to do this,
31003 report the bug anyway and send us the entire test case you used.
31006 A patch for the bug.
31008 A patch for the bug does help us if it is a good one. But do not omit
31009 the necessary information, such as the test case, on the assumption that
31010 a patch is all we need. We might see problems with your patch and decide
31011 to fix the problem another way, or we might not understand it at all.
31013 Sometimes with a program as complicated as @value{GDBN} it is very hard to
31014 construct an example that will make the program follow a certain path
31015 through the code. If you do not send us the example, we will not be able
31016 to construct one, so we will not be able to verify that the bug is fixed.
31018 And if we cannot understand what bug you are trying to fix, or why your
31019 patch should be an improvement, we will not install it. A test case will
31020 help us to understand.
31023 A guess about what the bug is or what it depends on.
31025 Such guesses are usually wrong. Even we cannot guess right about such
31026 things without first using the debugger to find the facts.
31029 @c The readline documentation is distributed with the readline code
31030 @c and consists of the two following files:
31033 @c Use -I with makeinfo to point to the appropriate directory,
31034 @c environment var TEXINPUTS with TeX.
31035 @ifclear SYSTEM_READLINE
31036 @include rluser.texi
31037 @include hsuser.texi
31041 @appendix In Memoriam
31043 The @value{GDBN} project mourns the loss of the following long-time
31048 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
31049 to Free Software in general. Outside of @value{GDBN}, he was known in
31050 the Amiga world for his series of Fish Disks, and the GeekGadget project.
31052 @item Michael Snyder
31053 Michael was one of the Global Maintainers of the @value{GDBN} project,
31054 with contributions recorded as early as 1996, until 2011. In addition
31055 to his day to day participation, he was a large driving force behind
31056 adding Reverse Debugging to @value{GDBN}.
31059 Beyond their technical contributions to the project, they were also
31060 enjoyable members of the Free Software Community. We will miss them.
31062 @node Formatting Documentation
31063 @appendix Formatting Documentation
31065 @cindex @value{GDBN} reference card
31066 @cindex reference card
31067 The @value{GDBN} 4 release includes an already-formatted reference card, ready
31068 for printing with PostScript or Ghostscript, in the @file{gdb}
31069 subdirectory of the main source directory@footnote{In
31070 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
31071 release.}. If you can use PostScript or Ghostscript with your printer,
31072 you can print the reference card immediately with @file{refcard.ps}.
31074 The release also includes the source for the reference card. You
31075 can format it, using @TeX{}, by typing:
31081 The @value{GDBN} reference card is designed to print in @dfn{landscape}
31082 mode on US ``letter'' size paper;
31083 that is, on a sheet 11 inches wide by 8.5 inches
31084 high. You will need to specify this form of printing as an option to
31085 your @sc{dvi} output program.
31087 @cindex documentation
31089 All the documentation for @value{GDBN} comes as part of the machine-readable
31090 distribution. The documentation is written in Texinfo format, which is
31091 a documentation system that uses a single source file to produce both
31092 on-line information and a printed manual. You can use one of the Info
31093 formatting commands to create the on-line version of the documentation
31094 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
31096 @value{GDBN} includes an already formatted copy of the on-line Info
31097 version of this manual in the @file{gdb} subdirectory. The main Info
31098 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
31099 subordinate files matching @samp{gdb.info*} in the same directory. If
31100 necessary, you can print out these files, or read them with any editor;
31101 but they are easier to read using the @code{info} subsystem in @sc{gnu}
31102 Emacs or the standalone @code{info} program, available as part of the
31103 @sc{gnu} Texinfo distribution.
31105 If you want to format these Info files yourself, you need one of the
31106 Info formatting programs, such as @code{texinfo-format-buffer} or
31109 If you have @code{makeinfo} installed, and are in the top level
31110 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
31111 version @value{GDBVN}), you can make the Info file by typing:
31118 If you want to typeset and print copies of this manual, you need @TeX{},
31119 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
31120 Texinfo definitions file.
31122 @TeX{} is a typesetting program; it does not print files directly, but
31123 produces output files called @sc{dvi} files. To print a typeset
31124 document, you need a program to print @sc{dvi} files. If your system
31125 has @TeX{} installed, chances are it has such a program. The precise
31126 command to use depends on your system; @kbd{lpr -d} is common; another
31127 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
31128 require a file name without any extension or a @samp{.dvi} extension.
31130 @TeX{} also requires a macro definitions file called
31131 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
31132 written in Texinfo format. On its own, @TeX{} cannot either read or
31133 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
31134 and is located in the @file{gdb-@var{version-number}/texinfo}
31137 If you have @TeX{} and a @sc{dvi} printer program installed, you can
31138 typeset and print this manual. First switch to the @file{gdb}
31139 subdirectory of the main source directory (for example, to
31140 @file{gdb-@value{GDBVN}/gdb}) and type:
31146 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
31148 @node Installing GDB
31149 @appendix Installing @value{GDBN}
31150 @cindex installation
31153 * Requirements:: Requirements for building @value{GDBN}
31154 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
31155 * Separate Objdir:: Compiling @value{GDBN} in another directory
31156 * Config Names:: Specifying names for hosts and targets
31157 * Configure Options:: Summary of options for configure
31158 * System-wide configuration:: Having a system-wide init file
31162 @section Requirements for Building @value{GDBN}
31163 @cindex building @value{GDBN}, requirements for
31165 Building @value{GDBN} requires various tools and packages to be available.
31166 Other packages will be used only if they are found.
31168 @heading Tools/Packages Necessary for Building @value{GDBN}
31170 @item ISO C90 compiler
31171 @value{GDBN} is written in ISO C90. It should be buildable with any
31172 working C90 compiler, e.g.@: GCC.
31176 @heading Tools/Packages Optional for Building @value{GDBN}
31180 @value{GDBN} can use the Expat XML parsing library. This library may be
31181 included with your operating system distribution; if it is not, you
31182 can get the latest version from @url{http://expat.sourceforge.net}.
31183 The @file{configure} script will search for this library in several
31184 standard locations; if it is installed in an unusual path, you can
31185 use the @option{--with-libexpat-prefix} option to specify its location.
31191 Remote protocol memory maps (@pxref{Memory Map Format})
31193 Target descriptions (@pxref{Target Descriptions})
31195 Remote shared library lists (@pxref{Library List Format})
31197 MS-Windows shared libraries (@pxref{Shared Libraries})
31199 Traceframe info (@pxref{Traceframe Info Format})
31203 @cindex compressed debug sections
31204 @value{GDBN} will use the @samp{zlib} library, if available, to read
31205 compressed debug sections. Some linkers, such as GNU gold, are capable
31206 of producing binaries with compressed debug sections. If @value{GDBN}
31207 is compiled with @samp{zlib}, it will be able to read the debug
31208 information in such binaries.
31210 The @samp{zlib} library is likely included with your operating system
31211 distribution; if it is not, you can get the latest version from
31212 @url{http://zlib.net}.
31215 @value{GDBN}'s features related to character sets (@pxref{Character
31216 Sets}) require a functioning @code{iconv} implementation. If you are
31217 on a GNU system, then this is provided by the GNU C Library. Some
31218 other systems also provide a working @code{iconv}.
31220 If @value{GDBN} is using the @code{iconv} program which is installed
31221 in a non-standard place, you will need to tell @value{GDBN} where to find it.
31222 This is done with @option{--with-iconv-bin} which specifies the
31223 directory that contains the @code{iconv} program.
31225 On systems without @code{iconv}, you can install GNU Libiconv. If you
31226 have previously installed Libiconv, you can use the
31227 @option{--with-libiconv-prefix} option to configure.
31229 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
31230 arrange to build Libiconv if a directory named @file{libiconv} appears
31231 in the top-most source directory. If Libiconv is built this way, and
31232 if the operating system does not provide a suitable @code{iconv}
31233 implementation, then the just-built library will automatically be used
31234 by @value{GDBN}. One easy way to set this up is to download GNU
31235 Libiconv, unpack it, and then rename the directory holding the
31236 Libiconv source code to @samp{libiconv}.
31239 @node Running Configure
31240 @section Invoking the @value{GDBN} @file{configure} Script
31241 @cindex configuring @value{GDBN}
31242 @value{GDBN} comes with a @file{configure} script that automates the process
31243 of preparing @value{GDBN} for installation; you can then use @code{make} to
31244 build the @code{gdb} program.
31246 @c irrelevant in info file; it's as current as the code it lives with.
31247 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
31248 look at the @file{README} file in the sources; we may have improved the
31249 installation procedures since publishing this manual.}
31252 The @value{GDBN} distribution includes all the source code you need for
31253 @value{GDBN} in a single directory, whose name is usually composed by
31254 appending the version number to @samp{gdb}.
31256 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
31257 @file{gdb-@value{GDBVN}} directory. That directory contains:
31260 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
31261 script for configuring @value{GDBN} and all its supporting libraries
31263 @item gdb-@value{GDBVN}/gdb
31264 the source specific to @value{GDBN} itself
31266 @item gdb-@value{GDBVN}/bfd
31267 source for the Binary File Descriptor library
31269 @item gdb-@value{GDBVN}/include
31270 @sc{gnu} include files
31272 @item gdb-@value{GDBVN}/libiberty
31273 source for the @samp{-liberty} free software library
31275 @item gdb-@value{GDBVN}/opcodes
31276 source for the library of opcode tables and disassemblers
31278 @item gdb-@value{GDBVN}/readline
31279 source for the @sc{gnu} command-line interface
31281 @item gdb-@value{GDBVN}/glob
31282 source for the @sc{gnu} filename pattern-matching subroutine
31284 @item gdb-@value{GDBVN}/mmalloc
31285 source for the @sc{gnu} memory-mapped malloc package
31288 The simplest way to configure and build @value{GDBN} is to run @file{configure}
31289 from the @file{gdb-@var{version-number}} source directory, which in
31290 this example is the @file{gdb-@value{GDBVN}} directory.
31292 First switch to the @file{gdb-@var{version-number}} source directory
31293 if you are not already in it; then run @file{configure}. Pass the
31294 identifier for the platform on which @value{GDBN} will run as an
31300 cd gdb-@value{GDBVN}
31301 ./configure @var{host}
31306 where @var{host} is an identifier such as @samp{sun4} or
31307 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
31308 (You can often leave off @var{host}; @file{configure} tries to guess the
31309 correct value by examining your system.)
31311 Running @samp{configure @var{host}} and then running @code{make} builds the
31312 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
31313 libraries, then @code{gdb} itself. The configured source files, and the
31314 binaries, are left in the corresponding source directories.
31317 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
31318 system does not recognize this automatically when you run a different
31319 shell, you may need to run @code{sh} on it explicitly:
31322 sh configure @var{host}
31325 If you run @file{configure} from a directory that contains source
31326 directories for multiple libraries or programs, such as the
31327 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
31329 creates configuration files for every directory level underneath (unless
31330 you tell it not to, with the @samp{--norecursion} option).
31332 You should run the @file{configure} script from the top directory in the
31333 source tree, the @file{gdb-@var{version-number}} directory. If you run
31334 @file{configure} from one of the subdirectories, you will configure only
31335 that subdirectory. That is usually not what you want. In particular,
31336 if you run the first @file{configure} from the @file{gdb} subdirectory
31337 of the @file{gdb-@var{version-number}} directory, you will omit the
31338 configuration of @file{bfd}, @file{readline}, and other sibling
31339 directories of the @file{gdb} subdirectory. This leads to build errors
31340 about missing include files such as @file{bfd/bfd.h}.
31342 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
31343 However, you should make sure that the shell on your path (named by
31344 the @samp{SHELL} environment variable) is publicly readable. Remember
31345 that @value{GDBN} uses the shell to start your program---some systems refuse to
31346 let @value{GDBN} debug child processes whose programs are not readable.
31348 @node Separate Objdir
31349 @section Compiling @value{GDBN} in Another Directory
31351 If you want to run @value{GDBN} versions for several host or target machines,
31352 you need a different @code{gdb} compiled for each combination of
31353 host and target. @file{configure} is designed to make this easy by
31354 allowing you to generate each configuration in a separate subdirectory,
31355 rather than in the source directory. If your @code{make} program
31356 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
31357 @code{make} in each of these directories builds the @code{gdb}
31358 program specified there.
31360 To build @code{gdb} in a separate directory, run @file{configure}
31361 with the @samp{--srcdir} option to specify where to find the source.
31362 (You also need to specify a path to find @file{configure}
31363 itself from your working directory. If the path to @file{configure}
31364 would be the same as the argument to @samp{--srcdir}, you can leave out
31365 the @samp{--srcdir} option; it is assumed.)
31367 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
31368 separate directory for a Sun 4 like this:
31372 cd gdb-@value{GDBVN}
31375 ../gdb-@value{GDBVN}/configure sun4
31380 When @file{configure} builds a configuration using a remote source
31381 directory, it creates a tree for the binaries with the same structure
31382 (and using the same names) as the tree under the source directory. In
31383 the example, you'd find the Sun 4 library @file{libiberty.a} in the
31384 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
31385 @file{gdb-sun4/gdb}.
31387 Make sure that your path to the @file{configure} script has just one
31388 instance of @file{gdb} in it. If your path to @file{configure} looks
31389 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
31390 one subdirectory of @value{GDBN}, not the whole package. This leads to
31391 build errors about missing include files such as @file{bfd/bfd.h}.
31393 One popular reason to build several @value{GDBN} configurations in separate
31394 directories is to configure @value{GDBN} for cross-compiling (where
31395 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
31396 programs that run on another machine---the @dfn{target}).
31397 You specify a cross-debugging target by
31398 giving the @samp{--target=@var{target}} option to @file{configure}.
31400 When you run @code{make} to build a program or library, you must run
31401 it in a configured directory---whatever directory you were in when you
31402 called @file{configure} (or one of its subdirectories).
31404 The @code{Makefile} that @file{configure} generates in each source
31405 directory also runs recursively. If you type @code{make} in a source
31406 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
31407 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
31408 will build all the required libraries, and then build GDB.
31410 When you have multiple hosts or targets configured in separate
31411 directories, you can run @code{make} on them in parallel (for example,
31412 if they are NFS-mounted on each of the hosts); they will not interfere
31416 @section Specifying Names for Hosts and Targets
31418 The specifications used for hosts and targets in the @file{configure}
31419 script are based on a three-part naming scheme, but some short predefined
31420 aliases are also supported. The full naming scheme encodes three pieces
31421 of information in the following pattern:
31424 @var{architecture}-@var{vendor}-@var{os}
31427 For example, you can use the alias @code{sun4} as a @var{host} argument,
31428 or as the value for @var{target} in a @code{--target=@var{target}}
31429 option. The equivalent full name is @samp{sparc-sun-sunos4}.
31431 The @file{configure} script accompanying @value{GDBN} does not provide
31432 any query facility to list all supported host and target names or
31433 aliases. @file{configure} calls the Bourne shell script
31434 @code{config.sub} to map abbreviations to full names; you can read the
31435 script, if you wish, or you can use it to test your guesses on
31436 abbreviations---for example:
31439 % sh config.sub i386-linux
31441 % sh config.sub alpha-linux
31442 alpha-unknown-linux-gnu
31443 % sh config.sub hp9k700
31445 % sh config.sub sun4
31446 sparc-sun-sunos4.1.1
31447 % sh config.sub sun3
31448 m68k-sun-sunos4.1.1
31449 % sh config.sub i986v
31450 Invalid configuration `i986v': machine `i986v' not recognized
31454 @code{config.sub} is also distributed in the @value{GDBN} source
31455 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
31457 @node Configure Options
31458 @section @file{configure} Options
31460 Here is a summary of the @file{configure} options and arguments that
31461 are most often useful for building @value{GDBN}. @file{configure} also has
31462 several other options not listed here. @inforef{What Configure
31463 Does,,configure.info}, for a full explanation of @file{configure}.
31466 configure @r{[}--help@r{]}
31467 @r{[}--prefix=@var{dir}@r{]}
31468 @r{[}--exec-prefix=@var{dir}@r{]}
31469 @r{[}--srcdir=@var{dirname}@r{]}
31470 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
31471 @r{[}--target=@var{target}@r{]}
31476 You may introduce options with a single @samp{-} rather than
31477 @samp{--} if you prefer; but you may abbreviate option names if you use
31482 Display a quick summary of how to invoke @file{configure}.
31484 @item --prefix=@var{dir}
31485 Configure the source to install programs and files under directory
31488 @item --exec-prefix=@var{dir}
31489 Configure the source to install programs under directory
31492 @c avoid splitting the warning from the explanation:
31494 @item --srcdir=@var{dirname}
31495 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
31496 @code{make} that implements the @code{VPATH} feature.}@*
31497 Use this option to make configurations in directories separate from the
31498 @value{GDBN} source directories. Among other things, you can use this to
31499 build (or maintain) several configurations simultaneously, in separate
31500 directories. @file{configure} writes configuration-specific files in
31501 the current directory, but arranges for them to use the source in the
31502 directory @var{dirname}. @file{configure} creates directories under
31503 the working directory in parallel to the source directories below
31506 @item --norecursion
31507 Configure only the directory level where @file{configure} is executed; do not
31508 propagate configuration to subdirectories.
31510 @item --target=@var{target}
31511 Configure @value{GDBN} for cross-debugging programs running on the specified
31512 @var{target}. Without this option, @value{GDBN} is configured to debug
31513 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
31515 There is no convenient way to generate a list of all available targets.
31517 @item @var{host} @dots{}
31518 Configure @value{GDBN} to run on the specified @var{host}.
31520 There is no convenient way to generate a list of all available hosts.
31523 There are many other options available as well, but they are generally
31524 needed for special purposes only.
31526 @node System-wide configuration
31527 @section System-wide configuration and settings
31528 @cindex system-wide init file
31530 @value{GDBN} can be configured to have a system-wide init file;
31531 this file will be read and executed at startup (@pxref{Startup, , What
31532 @value{GDBN} does during startup}).
31534 Here is the corresponding configure option:
31537 @item --with-system-gdbinit=@var{file}
31538 Specify that the default location of the system-wide init file is
31542 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
31543 it may be subject to relocation. Two possible cases:
31547 If the default location of this init file contains @file{$prefix},
31548 it will be subject to relocation. Suppose that the configure options
31549 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
31550 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
31551 init file is looked for as @file{$install/etc/gdbinit} instead of
31552 @file{$prefix/etc/gdbinit}.
31555 By contrast, if the default location does not contain the prefix,
31556 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
31557 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
31558 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
31559 wherever @value{GDBN} is installed.
31562 @node Maintenance Commands
31563 @appendix Maintenance Commands
31564 @cindex maintenance commands
31565 @cindex internal commands
31567 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31568 includes a number of commands intended for @value{GDBN} developers,
31569 that are not documented elsewhere in this manual. These commands are
31570 provided here for reference. (For commands that turn on debugging
31571 messages, see @ref{Debugging Output}.)
31574 @kindex maint agent
31575 @kindex maint agent-eval
31576 @item maint agent @var{expression}
31577 @itemx maint agent-eval @var{expression}
31578 Translate the given @var{expression} into remote agent bytecodes.
31579 This command is useful for debugging the Agent Expression mechanism
31580 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31581 expression useful for data collection, such as by tracepoints, while
31582 @samp{maint agent-eval} produces an expression that evaluates directly
31583 to a result. For instance, a collection expression for @code{globa +
31584 globb} will include bytecodes to record four bytes of memory at each
31585 of the addresses of @code{globa} and @code{globb}, while discarding
31586 the result of the addition, while an evaluation expression will do the
31587 addition and return the sum.
31589 @kindex maint info breakpoints
31590 @item @anchor{maint info breakpoints}maint info breakpoints
31591 Using the same format as @samp{info breakpoints}, display both the
31592 breakpoints you've set explicitly, and those @value{GDBN} is using for
31593 internal purposes. Internal breakpoints are shown with negative
31594 breakpoint numbers. The type column identifies what kind of breakpoint
31599 Normal, explicitly set breakpoint.
31602 Normal, explicitly set watchpoint.
31605 Internal breakpoint, used to handle correctly stepping through
31606 @code{longjmp} calls.
31608 @item longjmp resume
31609 Internal breakpoint at the target of a @code{longjmp}.
31612 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31615 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31618 Shared library events.
31622 @kindex set displaced-stepping
31623 @kindex show displaced-stepping
31624 @cindex displaced stepping support
31625 @cindex out-of-line single-stepping
31626 @item set displaced-stepping
31627 @itemx show displaced-stepping
31628 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31629 if the target supports it. Displaced stepping is a way to single-step
31630 over breakpoints without removing them from the inferior, by executing
31631 an out-of-line copy of the instruction that was originally at the
31632 breakpoint location. It is also known as out-of-line single-stepping.
31635 @item set displaced-stepping on
31636 If the target architecture supports it, @value{GDBN} will use
31637 displaced stepping to step over breakpoints.
31639 @item set displaced-stepping off
31640 @value{GDBN} will not use displaced stepping to step over breakpoints,
31641 even if such is supported by the target architecture.
31643 @cindex non-stop mode, and @samp{set displaced-stepping}
31644 @item set displaced-stepping auto
31645 This is the default mode. @value{GDBN} will use displaced stepping
31646 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31647 architecture supports displaced stepping.
31650 @kindex maint check-symtabs
31651 @item maint check-symtabs
31652 Check the consistency of psymtabs and symtabs.
31654 @kindex maint cplus first_component
31655 @item maint cplus first_component @var{name}
31656 Print the first C@t{++} class/namespace component of @var{name}.
31658 @kindex maint cplus namespace
31659 @item maint cplus namespace
31660 Print the list of possible C@t{++} namespaces.
31662 @kindex maint demangle
31663 @item maint demangle @var{name}
31664 Demangle a C@t{++} or Objective-C mangled @var{name}.
31666 @kindex maint deprecate
31667 @kindex maint undeprecate
31668 @cindex deprecated commands
31669 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31670 @itemx maint undeprecate @var{command}
31671 Deprecate or undeprecate the named @var{command}. Deprecated commands
31672 cause @value{GDBN} to issue a warning when you use them. The optional
31673 argument @var{replacement} says which newer command should be used in
31674 favor of the deprecated one; if it is given, @value{GDBN} will mention
31675 the replacement as part of the warning.
31677 @kindex maint dump-me
31678 @item maint dump-me
31679 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31680 Cause a fatal signal in the debugger and force it to dump its core.
31681 This is supported only on systems which support aborting a program
31682 with the @code{SIGQUIT} signal.
31684 @kindex maint internal-error
31685 @kindex maint internal-warning
31686 @item maint internal-error @r{[}@var{message-text}@r{]}
31687 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31688 Cause @value{GDBN} to call the internal function @code{internal_error}
31689 or @code{internal_warning} and hence behave as though an internal error
31690 or internal warning has been detected. In addition to reporting the
31691 internal problem, these functions give the user the opportunity to
31692 either quit @value{GDBN} or create a core file of the current
31693 @value{GDBN} session.
31695 These commands take an optional parameter @var{message-text} that is
31696 used as the text of the error or warning message.
31698 Here's an example of using @code{internal-error}:
31701 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31702 @dots{}/maint.c:121: internal-error: testing, 1, 2
31703 A problem internal to GDB has been detected. Further
31704 debugging may prove unreliable.
31705 Quit this debugging session? (y or n) @kbd{n}
31706 Create a core file? (y or n) @kbd{n}
31710 @cindex @value{GDBN} internal error
31711 @cindex internal errors, control of @value{GDBN} behavior
31713 @kindex maint set internal-error
31714 @kindex maint show internal-error
31715 @kindex maint set internal-warning
31716 @kindex maint show internal-warning
31717 @item maint set internal-error @var{action} [ask|yes|no]
31718 @itemx maint show internal-error @var{action}
31719 @itemx maint set internal-warning @var{action} [ask|yes|no]
31720 @itemx maint show internal-warning @var{action}
31721 When @value{GDBN} reports an internal problem (error or warning) it
31722 gives the user the opportunity to both quit @value{GDBN} and create a
31723 core file of the current @value{GDBN} session. These commands let you
31724 override the default behaviour for each particular @var{action},
31725 described in the table below.
31729 You can specify that @value{GDBN} should always (yes) or never (no)
31730 quit. The default is to ask the user what to do.
31733 You can specify that @value{GDBN} should always (yes) or never (no)
31734 create a core file. The default is to ask the user what to do.
31737 @kindex maint packet
31738 @item maint packet @var{text}
31739 If @value{GDBN} is talking to an inferior via the serial protocol,
31740 then this command sends the string @var{text} to the inferior, and
31741 displays the response packet. @value{GDBN} supplies the initial
31742 @samp{$} character, the terminating @samp{#} character, and the
31745 @kindex maint print architecture
31746 @item maint print architecture @r{[}@var{file}@r{]}
31747 Print the entire architecture configuration. The optional argument
31748 @var{file} names the file where the output goes.
31750 @kindex maint print c-tdesc
31751 @item maint print c-tdesc
31752 Print the current target description (@pxref{Target Descriptions}) as
31753 a C source file. The created source file can be used in @value{GDBN}
31754 when an XML parser is not available to parse the description.
31756 @kindex maint print dummy-frames
31757 @item maint print dummy-frames
31758 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31761 (@value{GDBP}) @kbd{b add}
31763 (@value{GDBP}) @kbd{print add(2,3)}
31764 Breakpoint 2, add (a=2, b=3) at @dots{}
31766 The program being debugged stopped while in a function called from GDB.
31768 (@value{GDBP}) @kbd{maint print dummy-frames}
31769 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31770 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31771 call_lo=0x01014000 call_hi=0x01014001
31775 Takes an optional file parameter.
31777 @kindex maint print registers
31778 @kindex maint print raw-registers
31779 @kindex maint print cooked-registers
31780 @kindex maint print register-groups
31781 @kindex maint print remote-registers
31782 @item maint print registers @r{[}@var{file}@r{]}
31783 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31784 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31785 @itemx maint print register-groups @r{[}@var{file}@r{]}
31786 @itemx maint print remote-registers @r{[}@var{file}@r{]}
31787 Print @value{GDBN}'s internal register data structures.
31789 The command @code{maint print raw-registers} includes the contents of
31790 the raw register cache; the command @code{maint print
31791 cooked-registers} includes the (cooked) value of all registers,
31792 including registers which aren't available on the target nor visible
31793 to user; the command @code{maint print register-groups} includes the
31794 groups that each register is a member of; and the command @code{maint
31795 print remote-registers} includes the remote target's register numbers
31796 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
31797 @value{GDBN} Internals}.
31799 These commands take an optional parameter, a file name to which to
31800 write the information.
31802 @kindex maint print reggroups
31803 @item maint print reggroups @r{[}@var{file}@r{]}
31804 Print @value{GDBN}'s internal register group data structures. The
31805 optional argument @var{file} tells to what file to write the
31808 The register groups info looks like this:
31811 (@value{GDBP}) @kbd{maint print reggroups}
31824 This command forces @value{GDBN} to flush its internal register cache.
31826 @kindex maint print objfiles
31827 @cindex info for known object files
31828 @item maint print objfiles
31829 Print a dump of all known object files. For each object file, this
31830 command prints its name, address in memory, and all of its psymtabs
31833 @kindex maint print section-scripts
31834 @cindex info for known .debug_gdb_scripts-loaded scripts
31835 @item maint print section-scripts [@var{regexp}]
31836 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31837 If @var{regexp} is specified, only print scripts loaded by object files
31838 matching @var{regexp}.
31839 For each script, this command prints its name as specified in the objfile,
31840 and the full path if known.
31841 @xref{.debug_gdb_scripts section}.
31843 @kindex maint print statistics
31844 @cindex bcache statistics
31845 @item maint print statistics
31846 This command prints, for each object file in the program, various data
31847 about that object file followed by the byte cache (@dfn{bcache})
31848 statistics for the object file. The objfile data includes the number
31849 of minimal, partial, full, and stabs symbols, the number of types
31850 defined by the objfile, the number of as yet unexpanded psym tables,
31851 the number of line tables and string tables, and the amount of memory
31852 used by the various tables. The bcache statistics include the counts,
31853 sizes, and counts of duplicates of all and unique objects, max,
31854 average, and median entry size, total memory used and its overhead and
31855 savings, and various measures of the hash table size and chain
31858 @kindex maint print target-stack
31859 @cindex target stack description
31860 @item maint print target-stack
31861 A @dfn{target} is an interface between the debugger and a particular
31862 kind of file or process. Targets can be stacked in @dfn{strata},
31863 so that more than one target can potentially respond to a request.
31864 In particular, memory accesses will walk down the stack of targets
31865 until they find a target that is interested in handling that particular
31868 This command prints a short description of each layer that was pushed on
31869 the @dfn{target stack}, starting from the top layer down to the bottom one.
31871 @kindex maint print type
31872 @cindex type chain of a data type
31873 @item maint print type @var{expr}
31874 Print the type chain for a type specified by @var{expr}. The argument
31875 can be either a type name or a symbol. If it is a symbol, the type of
31876 that symbol is described. The type chain produced by this command is
31877 a recursive definition of the data type as stored in @value{GDBN}'s
31878 data structures, including its flags and contained types.
31880 @kindex maint set dwarf2 always-disassemble
31881 @kindex maint show dwarf2 always-disassemble
31882 @item maint set dwarf2 always-disassemble
31883 @item maint show dwarf2 always-disassemble
31884 Control the behavior of @code{info address} when using DWARF debugging
31887 The default is @code{off}, which means that @value{GDBN} should try to
31888 describe a variable's location in an easily readable format. When
31889 @code{on}, @value{GDBN} will instead display the DWARF location
31890 expression in an assembly-like format. Note that some locations are
31891 too complex for @value{GDBN} to describe simply; in this case you will
31892 always see the disassembly form.
31894 Here is an example of the resulting disassembly:
31897 (gdb) info addr argc
31898 Symbol "argc" is a complex DWARF expression:
31902 For more information on these expressions, see
31903 @uref{http://www.dwarfstd.org/, the DWARF standard}.
31905 @kindex maint set dwarf2 max-cache-age
31906 @kindex maint show dwarf2 max-cache-age
31907 @item maint set dwarf2 max-cache-age
31908 @itemx maint show dwarf2 max-cache-age
31909 Control the DWARF 2 compilation unit cache.
31911 @cindex DWARF 2 compilation units cache
31912 In object files with inter-compilation-unit references, such as those
31913 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
31914 reader needs to frequently refer to previously read compilation units.
31915 This setting controls how long a compilation unit will remain in the
31916 cache if it is not referenced. A higher limit means that cached
31917 compilation units will be stored in memory longer, and more total
31918 memory will be used. Setting it to zero disables caching, which will
31919 slow down @value{GDBN} startup, but reduce memory consumption.
31921 @kindex maint set profile
31922 @kindex maint show profile
31923 @cindex profiling GDB
31924 @item maint set profile
31925 @itemx maint show profile
31926 Control profiling of @value{GDBN}.
31928 Profiling will be disabled until you use the @samp{maint set profile}
31929 command to enable it. When you enable profiling, the system will begin
31930 collecting timing and execution count data; when you disable profiling or
31931 exit @value{GDBN}, the results will be written to a log file. Remember that
31932 if you use profiling, @value{GDBN} will overwrite the profiling log file
31933 (often called @file{gmon.out}). If you have a record of important profiling
31934 data in a @file{gmon.out} file, be sure to move it to a safe location.
31936 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31937 compiled with the @samp{-pg} compiler option.
31939 @kindex maint set show-debug-regs
31940 @kindex maint show show-debug-regs
31941 @cindex hardware debug registers
31942 @item maint set show-debug-regs
31943 @itemx maint show show-debug-regs
31944 Control whether to show variables that mirror the hardware debug
31945 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31946 enabled, the debug registers values are shown when @value{GDBN} inserts or
31947 removes a hardware breakpoint or watchpoint, and when the inferior
31948 triggers a hardware-assisted breakpoint or watchpoint.
31950 @kindex maint set show-all-tib
31951 @kindex maint show show-all-tib
31952 @item maint set show-all-tib
31953 @itemx maint show show-all-tib
31954 Control whether to show all non zero areas within a 1k block starting
31955 at thread local base, when using the @samp{info w32 thread-information-block}
31958 @kindex maint space
31959 @cindex memory used by commands
31961 Control whether to display memory usage for each command. If set to a
31962 nonzero value, @value{GDBN} will display how much memory each command
31963 took, following the command's own output. This can also be requested
31964 by invoking @value{GDBN} with the @option{--statistics} command-line
31965 switch (@pxref{Mode Options}).
31968 @cindex time of command execution
31970 Control whether to display the execution time for each command. If
31971 set to a nonzero value, @value{GDBN} will display how much time it
31972 took to execute each command, following the command's own output.
31973 The time is not printed for the commands that run the target, since
31974 there's no mechanism currently to compute how much time was spend
31975 by @value{GDBN} and how much time was spend by the program been debugged.
31976 it's not possibly currently
31977 This can also be requested by invoking @value{GDBN} with the
31978 @option{--statistics} command-line switch (@pxref{Mode Options}).
31980 @kindex maint translate-address
31981 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31982 Find the symbol stored at the location specified by the address
31983 @var{addr} and an optional section name @var{section}. If found,
31984 @value{GDBN} prints the name of the closest symbol and an offset from
31985 the symbol's location to the specified address. This is similar to
31986 the @code{info address} command (@pxref{Symbols}), except that this
31987 command also allows to find symbols in other sections.
31989 If section was not specified, the section in which the symbol was found
31990 is also printed. For dynamically linked executables, the name of
31991 executable or shared library containing the symbol is printed as well.
31995 The following command is useful for non-interactive invocations of
31996 @value{GDBN}, such as in the test suite.
31999 @item set watchdog @var{nsec}
32000 @kindex set watchdog
32001 @cindex watchdog timer
32002 @cindex timeout for commands
32003 Set the maximum number of seconds @value{GDBN} will wait for the
32004 target operation to finish. If this time expires, @value{GDBN}
32005 reports and error and the command is aborted.
32007 @item show watchdog
32008 Show the current setting of the target wait timeout.
32011 @node Remote Protocol
32012 @appendix @value{GDBN} Remote Serial Protocol
32017 * Stop Reply Packets::
32018 * General Query Packets::
32019 * Architecture-Specific Protocol Details::
32020 * Tracepoint Packets::
32021 * Host I/O Packets::
32023 * Notification Packets::
32024 * Remote Non-Stop::
32025 * Packet Acknowledgment::
32027 * File-I/O Remote Protocol Extension::
32028 * Library List Format::
32029 * Memory Map Format::
32030 * Thread List Format::
32031 * Traceframe Info Format::
32037 There may be occasions when you need to know something about the
32038 protocol---for example, if there is only one serial port to your target
32039 machine, you might want your program to do something special if it
32040 recognizes a packet meant for @value{GDBN}.
32042 In the examples below, @samp{->} and @samp{<-} are used to indicate
32043 transmitted and received data, respectively.
32045 @cindex protocol, @value{GDBN} remote serial
32046 @cindex serial protocol, @value{GDBN} remote
32047 @cindex remote serial protocol
32048 All @value{GDBN} commands and responses (other than acknowledgments
32049 and notifications, see @ref{Notification Packets}) are sent as a
32050 @var{packet}. A @var{packet} is introduced with the character
32051 @samp{$}, the actual @var{packet-data}, and the terminating character
32052 @samp{#} followed by a two-digit @var{checksum}:
32055 @code{$}@var{packet-data}@code{#}@var{checksum}
32059 @cindex checksum, for @value{GDBN} remote
32061 The two-digit @var{checksum} is computed as the modulo 256 sum of all
32062 characters between the leading @samp{$} and the trailing @samp{#} (an
32063 eight bit unsigned checksum).
32065 Implementors should note that prior to @value{GDBN} 5.0 the protocol
32066 specification also included an optional two-digit @var{sequence-id}:
32069 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
32072 @cindex sequence-id, for @value{GDBN} remote
32074 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
32075 has never output @var{sequence-id}s. Stubs that handle packets added
32076 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
32078 When either the host or the target machine receives a packet, the first
32079 response expected is an acknowledgment: either @samp{+} (to indicate
32080 the package was received correctly) or @samp{-} (to request
32084 -> @code{$}@var{packet-data}@code{#}@var{checksum}
32089 The @samp{+}/@samp{-} acknowledgments can be disabled
32090 once a connection is established.
32091 @xref{Packet Acknowledgment}, for details.
32093 The host (@value{GDBN}) sends @var{command}s, and the target (the
32094 debugging stub incorporated in your program) sends a @var{response}. In
32095 the case of step and continue @var{command}s, the response is only sent
32096 when the operation has completed, and the target has again stopped all
32097 threads in all attached processes. This is the default all-stop mode
32098 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
32099 execution mode; see @ref{Remote Non-Stop}, for details.
32101 @var{packet-data} consists of a sequence of characters with the
32102 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
32105 @cindex remote protocol, field separator
32106 Fields within the packet should be separated using @samp{,} @samp{;} or
32107 @samp{:}. Except where otherwise noted all numbers are represented in
32108 @sc{hex} with leading zeros suppressed.
32110 Implementors should note that prior to @value{GDBN} 5.0, the character
32111 @samp{:} could not appear as the third character in a packet (as it
32112 would potentially conflict with the @var{sequence-id}).
32114 @cindex remote protocol, binary data
32115 @anchor{Binary Data}
32116 Binary data in most packets is encoded either as two hexadecimal
32117 digits per byte of binary data. This allowed the traditional remote
32118 protocol to work over connections which were only seven-bit clean.
32119 Some packets designed more recently assume an eight-bit clean
32120 connection, and use a more efficient encoding to send and receive
32123 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
32124 as an escape character. Any escaped byte is transmitted as the escape
32125 character followed by the original character XORed with @code{0x20}.
32126 For example, the byte @code{0x7d} would be transmitted as the two
32127 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
32128 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
32129 @samp{@}}) must always be escaped. Responses sent by the stub
32130 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
32131 is not interpreted as the start of a run-length encoded sequence
32134 Response @var{data} can be run-length encoded to save space.
32135 Run-length encoding replaces runs of identical characters with one
32136 instance of the repeated character, followed by a @samp{*} and a
32137 repeat count. The repeat count is itself sent encoded, to avoid
32138 binary characters in @var{data}: a value of @var{n} is sent as
32139 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
32140 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
32141 code 32) for a repeat count of 3. (This is because run-length
32142 encoding starts to win for counts 3 or more.) Thus, for example,
32143 @samp{0* } is a run-length encoding of ``0000'': the space character
32144 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
32147 The printable characters @samp{#} and @samp{$} or with a numeric value
32148 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
32149 seven repeats (@samp{$}) can be expanded using a repeat count of only
32150 five (@samp{"}). For example, @samp{00000000} can be encoded as
32153 The error response returned for some packets includes a two character
32154 error number. That number is not well defined.
32156 @cindex empty response, for unsupported packets
32157 For any @var{command} not supported by the stub, an empty response
32158 (@samp{$#00}) should be returned. That way it is possible to extend the
32159 protocol. A newer @value{GDBN} can tell if a packet is supported based
32162 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
32163 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
32169 The following table provides a complete list of all currently defined
32170 @var{command}s and their corresponding response @var{data}.
32171 @xref{File-I/O Remote Protocol Extension}, for details about the File
32172 I/O extension of the remote protocol.
32174 Each packet's description has a template showing the packet's overall
32175 syntax, followed by an explanation of the packet's meaning. We
32176 include spaces in some of the templates for clarity; these are not
32177 part of the packet's syntax. No @value{GDBN} packet uses spaces to
32178 separate its components. For example, a template like @samp{foo
32179 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
32180 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
32181 @var{baz}. @value{GDBN} does not transmit a space character between the
32182 @samp{foo} and the @var{bar}, or between the @var{bar} and the
32185 @cindex @var{thread-id}, in remote protocol
32186 @anchor{thread-id syntax}
32187 Several packets and replies include a @var{thread-id} field to identify
32188 a thread. Normally these are positive numbers with a target-specific
32189 interpretation, formatted as big-endian hex strings. A @var{thread-id}
32190 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
32193 In addition, the remote protocol supports a multiprocess feature in
32194 which the @var{thread-id} syntax is extended to optionally include both
32195 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
32196 The @var{pid} (process) and @var{tid} (thread) components each have the
32197 format described above: a positive number with target-specific
32198 interpretation formatted as a big-endian hex string, literal @samp{-1}
32199 to indicate all processes or threads (respectively), or @samp{0} to
32200 indicate an arbitrary process or thread. Specifying just a process, as
32201 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
32202 error to specify all processes but a specific thread, such as
32203 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
32204 for those packets and replies explicitly documented to include a process
32205 ID, rather than a @var{thread-id}.
32207 The multiprocess @var{thread-id} syntax extensions are only used if both
32208 @value{GDBN} and the stub report support for the @samp{multiprocess}
32209 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
32212 Note that all packet forms beginning with an upper- or lower-case
32213 letter, other than those described here, are reserved for future use.
32215 Here are the packet descriptions.
32220 @cindex @samp{!} packet
32221 @anchor{extended mode}
32222 Enable extended mode. In extended mode, the remote server is made
32223 persistent. The @samp{R} packet is used to restart the program being
32229 The remote target both supports and has enabled extended mode.
32233 @cindex @samp{?} packet
32234 Indicate the reason the target halted. The reply is the same as for
32235 step and continue. This packet has a special interpretation when the
32236 target is in non-stop mode; see @ref{Remote Non-Stop}.
32239 @xref{Stop Reply Packets}, for the reply specifications.
32241 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
32242 @cindex @samp{A} packet
32243 Initialized @code{argv[]} array passed into program. @var{arglen}
32244 specifies the number of bytes in the hex encoded byte stream
32245 @var{arg}. See @code{gdbserver} for more details.
32250 The arguments were set.
32256 @cindex @samp{b} packet
32257 (Don't use this packet; its behavior is not well-defined.)
32258 Change the serial line speed to @var{baud}.
32260 JTC: @emph{When does the transport layer state change? When it's
32261 received, or after the ACK is transmitted. In either case, there are
32262 problems if the command or the acknowledgment packet is dropped.}
32264 Stan: @emph{If people really wanted to add something like this, and get
32265 it working for the first time, they ought to modify ser-unix.c to send
32266 some kind of out-of-band message to a specially-setup stub and have the
32267 switch happen "in between" packets, so that from remote protocol's point
32268 of view, nothing actually happened.}
32270 @item B @var{addr},@var{mode}
32271 @cindex @samp{B} packet
32272 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
32273 breakpoint at @var{addr}.
32275 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
32276 (@pxref{insert breakpoint or watchpoint packet}).
32278 @cindex @samp{bc} packet
32281 Backward continue. Execute the target system in reverse. No parameter.
32282 @xref{Reverse Execution}, for more information.
32285 @xref{Stop Reply Packets}, for the reply specifications.
32287 @cindex @samp{bs} packet
32290 Backward single step. Execute one instruction in reverse. No parameter.
32291 @xref{Reverse Execution}, for more information.
32294 @xref{Stop Reply Packets}, for the reply specifications.
32296 @item c @r{[}@var{addr}@r{]}
32297 @cindex @samp{c} packet
32298 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
32299 resume at current address.
32302 @xref{Stop Reply Packets}, for the reply specifications.
32304 @item C @var{sig}@r{[};@var{addr}@r{]}
32305 @cindex @samp{C} packet
32306 Continue with signal @var{sig} (hex signal number). If
32307 @samp{;@var{addr}} is omitted, resume at same address.
32310 @xref{Stop Reply Packets}, for the reply specifications.
32313 @cindex @samp{d} packet
32316 Don't use this packet; instead, define a general set packet
32317 (@pxref{General Query Packets}).
32321 @cindex @samp{D} packet
32322 The first form of the packet is used to detach @value{GDBN} from the
32323 remote system. It is sent to the remote target
32324 before @value{GDBN} disconnects via the @code{detach} command.
32326 The second form, including a process ID, is used when multiprocess
32327 protocol extensions are enabled (@pxref{multiprocess extensions}), to
32328 detach only a specific process. The @var{pid} is specified as a
32329 big-endian hex string.
32339 @item F @var{RC},@var{EE},@var{CF};@var{XX}
32340 @cindex @samp{F} packet
32341 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
32342 This is part of the File-I/O protocol extension. @xref{File-I/O
32343 Remote Protocol Extension}, for the specification.
32346 @anchor{read registers packet}
32347 @cindex @samp{g} packet
32348 Read general registers.
32352 @item @var{XX@dots{}}
32353 Each byte of register data is described by two hex digits. The bytes
32354 with the register are transmitted in target byte order. The size of
32355 each register and their position within the @samp{g} packet are
32356 determined by the @value{GDBN} internal gdbarch functions
32357 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
32358 specification of several standard @samp{g} packets is specified below.
32360 When reading registers from a trace frame (@pxref{Analyze Collected
32361 Data,,Using the Collected Data}), the stub may also return a string of
32362 literal @samp{x}'s in place of the register data digits, to indicate
32363 that the corresponding register has not been collected, thus its value
32364 is unavailable. For example, for an architecture with 4 registers of
32365 4 bytes each, the following reply indicates to @value{GDBN} that
32366 registers 0 and 2 have not been collected, while registers 1 and 3
32367 have been collected, and both have zero value:
32371 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
32378 @item G @var{XX@dots{}}
32379 @cindex @samp{G} packet
32380 Write general registers. @xref{read registers packet}, for a
32381 description of the @var{XX@dots{}} data.
32391 @item H @var{c} @var{thread-id}
32392 @cindex @samp{H} packet
32393 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
32394 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
32395 should be @samp{c} for step and continue operations, @samp{g} for other
32396 operations. The thread designator @var{thread-id} has the format and
32397 interpretation described in @ref{thread-id syntax}.
32408 @c 'H': How restrictive (or permissive) is the thread model. If a
32409 @c thread is selected and stopped, are other threads allowed
32410 @c to continue to execute? As I mentioned above, I think the
32411 @c semantics of each command when a thread is selected must be
32412 @c described. For example:
32414 @c 'g': If the stub supports threads and a specific thread is
32415 @c selected, returns the register block from that thread;
32416 @c otherwise returns current registers.
32418 @c 'G' If the stub supports threads and a specific thread is
32419 @c selected, sets the registers of the register block of
32420 @c that thread; otherwise sets current registers.
32422 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
32423 @anchor{cycle step packet}
32424 @cindex @samp{i} packet
32425 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
32426 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
32427 step starting at that address.
32430 @cindex @samp{I} packet
32431 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
32435 @cindex @samp{k} packet
32438 FIXME: @emph{There is no description of how to operate when a specific
32439 thread context has been selected (i.e.@: does 'k' kill only that
32442 @item m @var{addr},@var{length}
32443 @cindex @samp{m} packet
32444 Read @var{length} bytes of memory starting at address @var{addr}.
32445 Note that @var{addr} may not be aligned to any particular boundary.
32447 The stub need not use any particular size or alignment when gathering
32448 data from memory for the response; even if @var{addr} is word-aligned
32449 and @var{length} is a multiple of the word size, the stub is free to
32450 use byte accesses, or not. For this reason, this packet may not be
32451 suitable for accessing memory-mapped I/O devices.
32452 @cindex alignment of remote memory accesses
32453 @cindex size of remote memory accesses
32454 @cindex memory, alignment and size of remote accesses
32458 @item @var{XX@dots{}}
32459 Memory contents; each byte is transmitted as a two-digit hexadecimal
32460 number. The reply may contain fewer bytes than requested if the
32461 server was able to read only part of the region of memory.
32466 @item M @var{addr},@var{length}:@var{XX@dots{}}
32467 @cindex @samp{M} packet
32468 Write @var{length} bytes of memory starting at address @var{addr}.
32469 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
32470 hexadecimal number.
32477 for an error (this includes the case where only part of the data was
32482 @cindex @samp{p} packet
32483 Read the value of register @var{n}; @var{n} is in hex.
32484 @xref{read registers packet}, for a description of how the returned
32485 register value is encoded.
32489 @item @var{XX@dots{}}
32490 the register's value
32494 Indicating an unrecognized @var{query}.
32497 @item P @var{n@dots{}}=@var{r@dots{}}
32498 @anchor{write register packet}
32499 @cindex @samp{P} packet
32500 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
32501 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
32502 digits for each byte in the register (target byte order).
32512 @item q @var{name} @var{params}@dots{}
32513 @itemx Q @var{name} @var{params}@dots{}
32514 @cindex @samp{q} packet
32515 @cindex @samp{Q} packet
32516 General query (@samp{q}) and set (@samp{Q}). These packets are
32517 described fully in @ref{General Query Packets}.
32520 @cindex @samp{r} packet
32521 Reset the entire system.
32523 Don't use this packet; use the @samp{R} packet instead.
32526 @cindex @samp{R} packet
32527 Restart the program being debugged. @var{XX}, while needed, is ignored.
32528 This packet is only available in extended mode (@pxref{extended mode}).
32530 The @samp{R} packet has no reply.
32532 @item s @r{[}@var{addr}@r{]}
32533 @cindex @samp{s} packet
32534 Single step. @var{addr} is the address at which to resume. If
32535 @var{addr} is omitted, resume at same address.
32538 @xref{Stop Reply Packets}, for the reply specifications.
32540 @item S @var{sig}@r{[};@var{addr}@r{]}
32541 @anchor{step with signal packet}
32542 @cindex @samp{S} packet
32543 Step with signal. This is analogous to the @samp{C} packet, but
32544 requests a single-step, rather than a normal resumption of execution.
32547 @xref{Stop Reply Packets}, for the reply specifications.
32549 @item t @var{addr}:@var{PP},@var{MM}
32550 @cindex @samp{t} packet
32551 Search backwards starting at address @var{addr} for a match with pattern
32552 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
32553 @var{addr} must be at least 3 digits.
32555 @item T @var{thread-id}
32556 @cindex @samp{T} packet
32557 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
32562 thread is still alive
32568 Packets starting with @samp{v} are identified by a multi-letter name,
32569 up to the first @samp{;} or @samp{?} (or the end of the packet).
32571 @item vAttach;@var{pid}
32572 @cindex @samp{vAttach} packet
32573 Attach to a new process with the specified process ID @var{pid}.
32574 The process ID is a
32575 hexadecimal integer identifying the process. In all-stop mode, all
32576 threads in the attached process are stopped; in non-stop mode, it may be
32577 attached without being stopped if that is supported by the target.
32579 @c In non-stop mode, on a successful vAttach, the stub should set the
32580 @c current thread to a thread of the newly-attached process. After
32581 @c attaching, GDB queries for the attached process's thread ID with qC.
32582 @c Also note that, from a user perspective, whether or not the
32583 @c target is stopped on attach in non-stop mode depends on whether you
32584 @c use the foreground or background version of the attach command, not
32585 @c on what vAttach does; GDB does the right thing with respect to either
32586 @c stopping or restarting threads.
32588 This packet is only available in extended mode (@pxref{extended mode}).
32594 @item @r{Any stop packet}
32595 for success in all-stop mode (@pxref{Stop Reply Packets})
32597 for success in non-stop mode (@pxref{Remote Non-Stop})
32600 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32601 @cindex @samp{vCont} packet
32602 Resume the inferior, specifying different actions for each thread.
32603 If an action is specified with no @var{thread-id}, then it is applied to any
32604 threads that don't have a specific action specified; if no default action is
32605 specified then other threads should remain stopped in all-stop mode and
32606 in their current state in non-stop mode.
32607 Specifying multiple
32608 default actions is an error; specifying no actions is also an error.
32609 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32611 Currently supported actions are:
32617 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32621 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32626 The optional argument @var{addr} normally associated with the
32627 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32628 not supported in @samp{vCont}.
32630 The @samp{t} action is only relevant in non-stop mode
32631 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32632 A stop reply should be generated for any affected thread not already stopped.
32633 When a thread is stopped by means of a @samp{t} action,
32634 the corresponding stop reply should indicate that the thread has stopped with
32635 signal @samp{0}, regardless of whether the target uses some other signal
32636 as an implementation detail.
32639 @xref{Stop Reply Packets}, for the reply specifications.
32642 @cindex @samp{vCont?} packet
32643 Request a list of actions supported by the @samp{vCont} packet.
32647 @item vCont@r{[};@var{action}@dots{}@r{]}
32648 The @samp{vCont} packet is supported. Each @var{action} is a supported
32649 command in the @samp{vCont} packet.
32651 The @samp{vCont} packet is not supported.
32654 @item vFile:@var{operation}:@var{parameter}@dots{}
32655 @cindex @samp{vFile} packet
32656 Perform a file operation on the target system. For details,
32657 see @ref{Host I/O Packets}.
32659 @item vFlashErase:@var{addr},@var{length}
32660 @cindex @samp{vFlashErase} packet
32661 Direct the stub to erase @var{length} bytes of flash starting at
32662 @var{addr}. The region may enclose any number of flash blocks, but
32663 its start and end must fall on block boundaries, as indicated by the
32664 flash block size appearing in the memory map (@pxref{Memory Map
32665 Format}). @value{GDBN} groups flash memory programming operations
32666 together, and sends a @samp{vFlashDone} request after each group; the
32667 stub is allowed to delay erase operation until the @samp{vFlashDone}
32668 packet is received.
32670 The stub must support @samp{vCont} if it reports support for
32671 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32672 this case @samp{vCont} actions can be specified to apply to all threads
32673 in a process by using the @samp{p@var{pid}.-1} form of the
32684 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32685 @cindex @samp{vFlashWrite} packet
32686 Direct the stub to write data to flash address @var{addr}. The data
32687 is passed in binary form using the same encoding as for the @samp{X}
32688 packet (@pxref{Binary Data}). The memory ranges specified by
32689 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32690 not overlap, and must appear in order of increasing addresses
32691 (although @samp{vFlashErase} packets for higher addresses may already
32692 have been received; the ordering is guaranteed only between
32693 @samp{vFlashWrite} packets). If a packet writes to an address that was
32694 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32695 target-specific method, the results are unpredictable.
32703 for vFlashWrite addressing non-flash memory
32709 @cindex @samp{vFlashDone} packet
32710 Indicate to the stub that flash programming operation is finished.
32711 The stub is permitted to delay or batch the effects of a group of
32712 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32713 @samp{vFlashDone} packet is received. The contents of the affected
32714 regions of flash memory are unpredictable until the @samp{vFlashDone}
32715 request is completed.
32717 @item vKill;@var{pid}
32718 @cindex @samp{vKill} packet
32719 Kill the process with the specified process ID. @var{pid} is a
32720 hexadecimal integer identifying the process. This packet is used in
32721 preference to @samp{k} when multiprocess protocol extensions are
32722 supported; see @ref{multiprocess extensions}.
32732 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32733 @cindex @samp{vRun} packet
32734 Run the program @var{filename}, passing it each @var{argument} on its
32735 command line. The file and arguments are hex-encoded strings. If
32736 @var{filename} is an empty string, the stub may use a default program
32737 (e.g.@: the last program run). The program is created in the stopped
32740 @c FIXME: What about non-stop mode?
32742 This packet is only available in extended mode (@pxref{extended mode}).
32748 @item @r{Any stop packet}
32749 for success (@pxref{Stop Reply Packets})
32753 @anchor{vStopped packet}
32754 @cindex @samp{vStopped} packet
32756 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32757 reply and prompt for the stub to report another one.
32761 @item @r{Any stop packet}
32762 if there is another unreported stop event (@pxref{Stop Reply Packets})
32764 if there are no unreported stop events
32767 @item X @var{addr},@var{length}:@var{XX@dots{}}
32769 @cindex @samp{X} packet
32770 Write data to memory, where the data is transmitted in binary.
32771 @var{addr} is address, @var{length} is number of bytes,
32772 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32782 @item z @var{type},@var{addr},@var{kind}
32783 @itemx Z @var{type},@var{addr},@var{kind}
32784 @anchor{insert breakpoint or watchpoint packet}
32785 @cindex @samp{z} packet
32786 @cindex @samp{Z} packets
32787 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32788 watchpoint starting at address @var{address} of kind @var{kind}.
32790 Each breakpoint and watchpoint packet @var{type} is documented
32793 @emph{Implementation notes: A remote target shall return an empty string
32794 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32795 remote target shall support either both or neither of a given
32796 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32797 avoid potential problems with duplicate packets, the operations should
32798 be implemented in an idempotent way.}
32800 @item z0,@var{addr},@var{kind}
32801 @itemx Z0,@var{addr},@var{kind}
32802 @cindex @samp{z0} packet
32803 @cindex @samp{Z0} packet
32804 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32805 @var{addr} of type @var{kind}.
32807 A memory breakpoint is implemented by replacing the instruction at
32808 @var{addr} with a software breakpoint or trap instruction. The
32809 @var{kind} is target-specific and typically indicates the size of
32810 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32811 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32812 architectures have additional meanings for @var{kind};
32813 see @ref{Architecture-Specific Protocol Details}.
32815 @emph{Implementation note: It is possible for a target to copy or move
32816 code that contains memory breakpoints (e.g., when implementing
32817 overlays). The behavior of this packet, in the presence of such a
32818 target, is not defined.}
32830 @item z1,@var{addr},@var{kind}
32831 @itemx Z1,@var{addr},@var{kind}
32832 @cindex @samp{z1} packet
32833 @cindex @samp{Z1} packet
32834 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32835 address @var{addr}.
32837 A hardware breakpoint is implemented using a mechanism that is not
32838 dependant on being able to modify the target's memory. @var{kind}
32839 has the same meaning as in @samp{Z0} packets.
32841 @emph{Implementation note: A hardware breakpoint is not affected by code
32854 @item z2,@var{addr},@var{kind}
32855 @itemx Z2,@var{addr},@var{kind}
32856 @cindex @samp{z2} packet
32857 @cindex @samp{Z2} packet
32858 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32859 @var{kind} is interpreted as the number of bytes to watch.
32871 @item z3,@var{addr},@var{kind}
32872 @itemx Z3,@var{addr},@var{kind}
32873 @cindex @samp{z3} packet
32874 @cindex @samp{Z3} packet
32875 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
32876 @var{kind} is interpreted as the number of bytes to watch.
32888 @item z4,@var{addr},@var{kind}
32889 @itemx Z4,@var{addr},@var{kind}
32890 @cindex @samp{z4} packet
32891 @cindex @samp{Z4} packet
32892 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
32893 @var{kind} is interpreted as the number of bytes to watch.
32907 @node Stop Reply Packets
32908 @section Stop Reply Packets
32909 @cindex stop reply packets
32911 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
32912 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
32913 receive any of the below as a reply. Except for @samp{?}
32914 and @samp{vStopped}, that reply is only returned
32915 when the target halts. In the below the exact meaning of @dfn{signal
32916 number} is defined by the header @file{include/gdb/signals.h} in the
32917 @value{GDBN} source code.
32919 As in the description of request packets, we include spaces in the
32920 reply templates for clarity; these are not part of the reply packet's
32921 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
32927 The program received signal number @var{AA} (a two-digit hexadecimal
32928 number). This is equivalent to a @samp{T} response with no
32929 @var{n}:@var{r} pairs.
32931 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
32932 @cindex @samp{T} packet reply
32933 The program received signal number @var{AA} (a two-digit hexadecimal
32934 number). This is equivalent to an @samp{S} response, except that the
32935 @samp{@var{n}:@var{r}} pairs can carry values of important registers
32936 and other information directly in the stop reply packet, reducing
32937 round-trip latency. Single-step and breakpoint traps are reported
32938 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
32942 If @var{n} is a hexadecimal number, it is a register number, and the
32943 corresponding @var{r} gives that register's value. @var{r} is a
32944 series of bytes in target byte order, with each byte given by a
32945 two-digit hex number.
32948 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32949 the stopped thread, as specified in @ref{thread-id syntax}.
32952 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32953 the core on which the stop event was detected.
32956 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32957 specific event that stopped the target. The currently defined stop
32958 reasons are listed below. @var{aa} should be @samp{05}, the trap
32959 signal. At most one stop reason should be present.
32962 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32963 and go on to the next; this allows us to extend the protocol in the
32967 The currently defined stop reasons are:
32973 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32976 @cindex shared library events, remote reply
32978 The packet indicates that the loaded libraries have changed.
32979 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32980 list of loaded libraries. @var{r} is ignored.
32982 @cindex replay log events, remote reply
32984 The packet indicates that the target cannot continue replaying
32985 logged execution events, because it has reached the end (or the
32986 beginning when executing backward) of the log. The value of @var{r}
32987 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32988 for more information.
32992 @itemx W @var{AA} ; process:@var{pid}
32993 The process exited, and @var{AA} is the exit status. This is only
32994 applicable to certain targets.
32996 The second form of the response, including the process ID of the exited
32997 process, can be used only when @value{GDBN} has reported support for
32998 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32999 The @var{pid} is formatted as a big-endian hex string.
33002 @itemx X @var{AA} ; process:@var{pid}
33003 The process terminated with signal @var{AA}.
33005 The second form of the response, including the process ID of the
33006 terminated process, can be used only when @value{GDBN} has reported
33007 support for multiprocess protocol extensions; see @ref{multiprocess
33008 extensions}. The @var{pid} is formatted as a big-endian hex string.
33010 @item O @var{XX}@dots{}
33011 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
33012 written as the program's console output. This can happen at any time
33013 while the program is running and the debugger should continue to wait
33014 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
33016 @item F @var{call-id},@var{parameter}@dots{}
33017 @var{call-id} is the identifier which says which host system call should
33018 be called. This is just the name of the function. Translation into the
33019 correct system call is only applicable as it's defined in @value{GDBN}.
33020 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
33023 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
33024 this very system call.
33026 The target replies with this packet when it expects @value{GDBN} to
33027 call a host system call on behalf of the target. @value{GDBN} replies
33028 with an appropriate @samp{F} packet and keeps up waiting for the next
33029 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
33030 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
33031 Protocol Extension}, for more details.
33035 @node General Query Packets
33036 @section General Query Packets
33037 @cindex remote query requests
33039 Packets starting with @samp{q} are @dfn{general query packets};
33040 packets starting with @samp{Q} are @dfn{general set packets}. General
33041 query and set packets are a semi-unified form for retrieving and
33042 sending information to and from the stub.
33044 The initial letter of a query or set packet is followed by a name
33045 indicating what sort of thing the packet applies to. For example,
33046 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
33047 definitions with the stub. These packet names follow some
33052 The name must not contain commas, colons or semicolons.
33054 Most @value{GDBN} query and set packets have a leading upper case
33057 The names of custom vendor packets should use a company prefix, in
33058 lower case, followed by a period. For example, packets designed at
33059 the Acme Corporation might begin with @samp{qacme.foo} (for querying
33060 foos) or @samp{Qacme.bar} (for setting bars).
33063 The name of a query or set packet should be separated from any
33064 parameters by a @samp{:}; the parameters themselves should be
33065 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
33066 full packet name, and check for a separator or the end of the packet,
33067 in case two packet names share a common prefix. New packets should not begin
33068 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
33069 packets predate these conventions, and have arguments without any terminator
33070 for the packet name; we suspect they are in widespread use in places that
33071 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
33072 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
33075 Like the descriptions of the other packets, each description here
33076 has a template showing the packet's overall syntax, followed by an
33077 explanation of the packet's meaning. We include spaces in some of the
33078 templates for clarity; these are not part of the packet's syntax. No
33079 @value{GDBN} packet uses spaces to separate its components.
33081 Here are the currently defined query and set packets:
33085 @item QAllow:@var{op}:@var{val}@dots{}
33086 @cindex @samp{QAllow} packet
33087 Specify which operations @value{GDBN} expects to request of the
33088 target, as a semicolon-separated list of operation name and value
33089 pairs. Possible values for @var{op} include @samp{WriteReg},
33090 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
33091 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
33092 indicating that @value{GDBN} will not request the operation, or 1,
33093 indicating that it may. (The target can then use this to set up its
33094 own internals optimally, for instance if the debugger never expects to
33095 insert breakpoints, it may not need to install its own trap handler.)
33098 @cindex current thread, remote request
33099 @cindex @samp{qC} packet
33100 Return the current thread ID.
33104 @item QC @var{thread-id}
33105 Where @var{thread-id} is a thread ID as documented in
33106 @ref{thread-id syntax}.
33107 @item @r{(anything else)}
33108 Any other reply implies the old thread ID.
33111 @item qCRC:@var{addr},@var{length}
33112 @cindex CRC of memory block, remote request
33113 @cindex @samp{qCRC} packet
33114 Compute the CRC checksum of a block of memory using CRC-32 defined in
33115 IEEE 802.3. The CRC is computed byte at a time, taking the most
33116 significant bit of each byte first. The initial pattern code
33117 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
33119 @emph{Note:} This is the same CRC used in validating separate debug
33120 files (@pxref{Separate Debug Files, , Debugging Information in Separate
33121 Files}). However the algorithm is slightly different. When validating
33122 separate debug files, the CRC is computed taking the @emph{least}
33123 significant bit of each byte first, and the final result is inverted to
33124 detect trailing zeros.
33129 An error (such as memory fault)
33130 @item C @var{crc32}
33131 The specified memory region's checksum is @var{crc32}.
33135 @itemx qsThreadInfo
33136 @cindex list active threads, remote request
33137 @cindex @samp{qfThreadInfo} packet
33138 @cindex @samp{qsThreadInfo} packet
33139 Obtain a list of all active thread IDs from the target (OS). Since there
33140 may be too many active threads to fit into one reply packet, this query
33141 works iteratively: it may require more than one query/reply sequence to
33142 obtain the entire list of threads. The first query of the sequence will
33143 be the @samp{qfThreadInfo} query; subsequent queries in the
33144 sequence will be the @samp{qsThreadInfo} query.
33146 NOTE: This packet replaces the @samp{qL} query (see below).
33150 @item m @var{thread-id}
33152 @item m @var{thread-id},@var{thread-id}@dots{}
33153 a comma-separated list of thread IDs
33155 (lower case letter @samp{L}) denotes end of list.
33158 In response to each query, the target will reply with a list of one or
33159 more thread IDs, separated by commas.
33160 @value{GDBN} will respond to each reply with a request for more thread
33161 ids (using the @samp{qs} form of the query), until the target responds
33162 with @samp{l} (lower-case ell, for @dfn{last}).
33163 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
33166 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
33167 @cindex get thread-local storage address, remote request
33168 @cindex @samp{qGetTLSAddr} packet
33169 Fetch the address associated with thread local storage specified
33170 by @var{thread-id}, @var{offset}, and @var{lm}.
33172 @var{thread-id} is the thread ID associated with the
33173 thread for which to fetch the TLS address. @xref{thread-id syntax}.
33175 @var{offset} is the (big endian, hex encoded) offset associated with the
33176 thread local variable. (This offset is obtained from the debug
33177 information associated with the variable.)
33179 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
33180 load module associated with the thread local storage. For example,
33181 a @sc{gnu}/Linux system will pass the link map address of the shared
33182 object associated with the thread local storage under consideration.
33183 Other operating environments may choose to represent the load module
33184 differently, so the precise meaning of this parameter will vary.
33188 @item @var{XX}@dots{}
33189 Hex encoded (big endian) bytes representing the address of the thread
33190 local storage requested.
33193 An error occurred. @var{nn} are hex digits.
33196 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
33199 @item qGetTIBAddr:@var{thread-id}
33200 @cindex get thread information block address
33201 @cindex @samp{qGetTIBAddr} packet
33202 Fetch address of the Windows OS specific Thread Information Block.
33204 @var{thread-id} is the thread ID associated with the thread.
33208 @item @var{XX}@dots{}
33209 Hex encoded (big endian) bytes representing the linear address of the
33210 thread information block.
33213 An error occured. This means that either the thread was not found, or the
33214 address could not be retrieved.
33217 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
33220 @item qL @var{startflag} @var{threadcount} @var{nextthread}
33221 Obtain thread information from RTOS. Where: @var{startflag} (one hex
33222 digit) is one to indicate the first query and zero to indicate a
33223 subsequent query; @var{threadcount} (two hex digits) is the maximum
33224 number of threads the response packet can contain; and @var{nextthread}
33225 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
33226 returned in the response as @var{argthread}.
33228 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
33232 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
33233 Where: @var{count} (two hex digits) is the number of threads being
33234 returned; @var{done} (one hex digit) is zero to indicate more threads
33235 and one indicates no further threads; @var{argthreadid} (eight hex
33236 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
33237 is a sequence of thread IDs from the target. @var{threadid} (eight hex
33238 digits). See @code{remote.c:parse_threadlist_response()}.
33242 @cindex section offsets, remote request
33243 @cindex @samp{qOffsets} packet
33244 Get section offsets that the target used when relocating the downloaded
33249 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
33250 Relocate the @code{Text} section by @var{xxx} from its original address.
33251 Relocate the @code{Data} section by @var{yyy} from its original address.
33252 If the object file format provides segment information (e.g.@: @sc{elf}
33253 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
33254 segments by the supplied offsets.
33256 @emph{Note: while a @code{Bss} offset may be included in the response,
33257 @value{GDBN} ignores this and instead applies the @code{Data} offset
33258 to the @code{Bss} section.}
33260 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
33261 Relocate the first segment of the object file, which conventionally
33262 contains program code, to a starting address of @var{xxx}. If
33263 @samp{DataSeg} is specified, relocate the second segment, which
33264 conventionally contains modifiable data, to a starting address of
33265 @var{yyy}. @value{GDBN} will report an error if the object file
33266 does not contain segment information, or does not contain at least
33267 as many segments as mentioned in the reply. Extra segments are
33268 kept at fixed offsets relative to the last relocated segment.
33271 @item qP @var{mode} @var{thread-id}
33272 @cindex thread information, remote request
33273 @cindex @samp{qP} packet
33274 Returns information on @var{thread-id}. Where: @var{mode} is a hex
33275 encoded 32 bit mode; @var{thread-id} is a thread ID
33276 (@pxref{thread-id syntax}).
33278 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
33281 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
33285 @cindex non-stop mode, remote request
33286 @cindex @samp{QNonStop} packet
33288 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
33289 @xref{Remote Non-Stop}, for more information.
33294 The request succeeded.
33297 An error occurred. @var{nn} are hex digits.
33300 An empty reply indicates that @samp{QNonStop} is not supported by
33304 This packet is not probed by default; the remote stub must request it,
33305 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33306 Use of this packet is controlled by the @code{set non-stop} command;
33307 @pxref{Non-Stop Mode}.
33309 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
33310 @cindex pass signals to inferior, remote request
33311 @cindex @samp{QPassSignals} packet
33312 @anchor{QPassSignals}
33313 Each listed @var{signal} should be passed directly to the inferior process.
33314 Signals are numbered identically to continue packets and stop replies
33315 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
33316 strictly greater than the previous item. These signals do not need to stop
33317 the inferior, or be reported to @value{GDBN}. All other signals should be
33318 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
33319 combine; any earlier @samp{QPassSignals} list is completely replaced by the
33320 new list. This packet improves performance when using @samp{handle
33321 @var{signal} nostop noprint pass}.
33326 The request succeeded.
33329 An error occurred. @var{nn} are hex digits.
33332 An empty reply indicates that @samp{QPassSignals} is not supported by
33336 Use of this packet is controlled by the @code{set remote pass-signals}
33337 command (@pxref{Remote Configuration, set remote pass-signals}).
33338 This packet is not probed by default; the remote stub must request it,
33339 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33341 @item qRcmd,@var{command}
33342 @cindex execute remote command, remote request
33343 @cindex @samp{qRcmd} packet
33344 @var{command} (hex encoded) is passed to the local interpreter for
33345 execution. Invalid commands should be reported using the output
33346 string. Before the final result packet, the target may also respond
33347 with a number of intermediate @samp{O@var{output}} console output
33348 packets. @emph{Implementors should note that providing access to a
33349 stubs's interpreter may have security implications}.
33354 A command response with no output.
33356 A command response with the hex encoded output string @var{OUTPUT}.
33358 Indicate a badly formed request.
33360 An empty reply indicates that @samp{qRcmd} is not recognized.
33363 (Note that the @code{qRcmd} packet's name is separated from the
33364 command by a @samp{,}, not a @samp{:}, contrary to the naming
33365 conventions above. Please don't use this packet as a model for new
33368 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
33369 @cindex searching memory, in remote debugging
33370 @cindex @samp{qSearch:memory} packet
33371 @anchor{qSearch memory}
33372 Search @var{length} bytes at @var{address} for @var{search-pattern}.
33373 @var{address} and @var{length} are encoded in hex.
33374 @var{search-pattern} is a sequence of bytes, hex encoded.
33379 The pattern was not found.
33381 The pattern was found at @var{address}.
33383 A badly formed request or an error was encountered while searching memory.
33385 An empty reply indicates that @samp{qSearch:memory} is not recognized.
33388 @item QStartNoAckMode
33389 @cindex @samp{QStartNoAckMode} packet
33390 @anchor{QStartNoAckMode}
33391 Request that the remote stub disable the normal @samp{+}/@samp{-}
33392 protocol acknowledgments (@pxref{Packet Acknowledgment}).
33397 The stub has switched to no-acknowledgment mode.
33398 @value{GDBN} acknowledges this reponse,
33399 but neither the stub nor @value{GDBN} shall send or expect further
33400 @samp{+}/@samp{-} acknowledgments in the current connection.
33402 An empty reply indicates that the stub does not support no-acknowledgment mode.
33405 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
33406 @cindex supported packets, remote query
33407 @cindex features of the remote protocol
33408 @cindex @samp{qSupported} packet
33409 @anchor{qSupported}
33410 Tell the remote stub about features supported by @value{GDBN}, and
33411 query the stub for features it supports. This packet allows
33412 @value{GDBN} and the remote stub to take advantage of each others'
33413 features. @samp{qSupported} also consolidates multiple feature probes
33414 at startup, to improve @value{GDBN} performance---a single larger
33415 packet performs better than multiple smaller probe packets on
33416 high-latency links. Some features may enable behavior which must not
33417 be on by default, e.g.@: because it would confuse older clients or
33418 stubs. Other features may describe packets which could be
33419 automatically probed for, but are not. These features must be
33420 reported before @value{GDBN} will use them. This ``default
33421 unsupported'' behavior is not appropriate for all packets, but it
33422 helps to keep the initial connection time under control with new
33423 versions of @value{GDBN} which support increasing numbers of packets.
33427 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
33428 The stub supports or does not support each returned @var{stubfeature},
33429 depending on the form of each @var{stubfeature} (see below for the
33432 An empty reply indicates that @samp{qSupported} is not recognized,
33433 or that no features needed to be reported to @value{GDBN}.
33436 The allowed forms for each feature (either a @var{gdbfeature} in the
33437 @samp{qSupported} packet, or a @var{stubfeature} in the response)
33441 @item @var{name}=@var{value}
33442 The remote protocol feature @var{name} is supported, and associated
33443 with the specified @var{value}. The format of @var{value} depends
33444 on the feature, but it must not include a semicolon.
33446 The remote protocol feature @var{name} is supported, and does not
33447 need an associated value.
33449 The remote protocol feature @var{name} is not supported.
33451 The remote protocol feature @var{name} may be supported, and
33452 @value{GDBN} should auto-detect support in some other way when it is
33453 needed. This form will not be used for @var{gdbfeature} notifications,
33454 but may be used for @var{stubfeature} responses.
33457 Whenever the stub receives a @samp{qSupported} request, the
33458 supplied set of @value{GDBN} features should override any previous
33459 request. This allows @value{GDBN} to put the stub in a known
33460 state, even if the stub had previously been communicating with
33461 a different version of @value{GDBN}.
33463 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
33468 This feature indicates whether @value{GDBN} supports multiprocess
33469 extensions to the remote protocol. @value{GDBN} does not use such
33470 extensions unless the stub also reports that it supports them by
33471 including @samp{multiprocess+} in its @samp{qSupported} reply.
33472 @xref{multiprocess extensions}, for details.
33475 This feature indicates that @value{GDBN} supports the XML target
33476 description. If the stub sees @samp{xmlRegisters=} with target
33477 specific strings separated by a comma, it will report register
33481 This feature indicates whether @value{GDBN} supports the
33482 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
33483 instruction reply packet}).
33486 Stubs should ignore any unknown values for
33487 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
33488 packet supports receiving packets of unlimited length (earlier
33489 versions of @value{GDBN} may reject overly long responses). Additional values
33490 for @var{gdbfeature} may be defined in the future to let the stub take
33491 advantage of new features in @value{GDBN}, e.g.@: incompatible
33492 improvements in the remote protocol---the @samp{multiprocess} feature is
33493 an example of such a feature. The stub's reply should be independent
33494 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
33495 describes all the features it supports, and then the stub replies with
33496 all the features it supports.
33498 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
33499 responses, as long as each response uses one of the standard forms.
33501 Some features are flags. A stub which supports a flag feature
33502 should respond with a @samp{+} form response. Other features
33503 require values, and the stub should respond with an @samp{=}
33506 Each feature has a default value, which @value{GDBN} will use if
33507 @samp{qSupported} is not available or if the feature is not mentioned
33508 in the @samp{qSupported} response. The default values are fixed; a
33509 stub is free to omit any feature responses that match the defaults.
33511 Not all features can be probed, but for those which can, the probing
33512 mechanism is useful: in some cases, a stub's internal
33513 architecture may not allow the protocol layer to know some information
33514 about the underlying target in advance. This is especially common in
33515 stubs which may be configured for multiple targets.
33517 These are the currently defined stub features and their properties:
33519 @multitable @columnfractions 0.35 0.2 0.12 0.2
33520 @c NOTE: The first row should be @headitem, but we do not yet require
33521 @c a new enough version of Texinfo (4.7) to use @headitem.
33523 @tab Value Required
33527 @item @samp{PacketSize}
33532 @item @samp{qXfer:auxv:read}
33537 @item @samp{qXfer:features:read}
33542 @item @samp{qXfer:libraries:read}
33547 @item @samp{qXfer:memory-map:read}
33552 @item @samp{qXfer:sdata:read}
33557 @item @samp{qXfer:spu:read}
33562 @item @samp{qXfer:spu:write}
33567 @item @samp{qXfer:siginfo:read}
33572 @item @samp{qXfer:siginfo:write}
33577 @item @samp{qXfer:threads:read}
33582 @item @samp{qXfer:traceframe-info:read}
33588 @item @samp{QNonStop}
33593 @item @samp{QPassSignals}
33598 @item @samp{QStartNoAckMode}
33603 @item @samp{multiprocess}
33608 @item @samp{ConditionalTracepoints}
33613 @item @samp{ReverseContinue}
33618 @item @samp{ReverseStep}
33623 @item @samp{TracepointSource}
33628 @item @samp{QAllow}
33633 @item @samp{EnableDisableTracepoints}
33640 These are the currently defined stub features, in more detail:
33643 @cindex packet size, remote protocol
33644 @item PacketSize=@var{bytes}
33645 The remote stub can accept packets up to at least @var{bytes} in
33646 length. @value{GDBN} will send packets up to this size for bulk
33647 transfers, and will never send larger packets. This is a limit on the
33648 data characters in the packet, including the frame and checksum.
33649 There is no trailing NUL byte in a remote protocol packet; if the stub
33650 stores packets in a NUL-terminated format, it should allow an extra
33651 byte in its buffer for the NUL. If this stub feature is not supported,
33652 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33654 @item qXfer:auxv:read
33655 The remote stub understands the @samp{qXfer:auxv:read} packet
33656 (@pxref{qXfer auxiliary vector read}).
33658 @item qXfer:features:read
33659 The remote stub understands the @samp{qXfer:features:read} packet
33660 (@pxref{qXfer target description read}).
33662 @item qXfer:libraries:read
33663 The remote stub understands the @samp{qXfer:libraries:read} packet
33664 (@pxref{qXfer library list read}).
33666 @item qXfer:memory-map:read
33667 The remote stub understands the @samp{qXfer:memory-map:read} packet
33668 (@pxref{qXfer memory map read}).
33670 @item qXfer:sdata:read
33671 The remote stub understands the @samp{qXfer:sdata:read} packet
33672 (@pxref{qXfer sdata read}).
33674 @item qXfer:spu:read
33675 The remote stub understands the @samp{qXfer:spu:read} packet
33676 (@pxref{qXfer spu read}).
33678 @item qXfer:spu:write
33679 The remote stub understands the @samp{qXfer:spu:write} packet
33680 (@pxref{qXfer spu write}).
33682 @item qXfer:siginfo:read
33683 The remote stub understands the @samp{qXfer:siginfo:read} packet
33684 (@pxref{qXfer siginfo read}).
33686 @item qXfer:siginfo:write
33687 The remote stub understands the @samp{qXfer:siginfo:write} packet
33688 (@pxref{qXfer siginfo write}).
33690 @item qXfer:threads:read
33691 The remote stub understands the @samp{qXfer:threads:read} packet
33692 (@pxref{qXfer threads read}).
33694 @item qXfer:traceframe-info:read
33695 The remote stub understands the @samp{qXfer:traceframe-info:read}
33696 packet (@pxref{qXfer traceframe info read}).
33699 The remote stub understands the @samp{QNonStop} packet
33700 (@pxref{QNonStop}).
33703 The remote stub understands the @samp{QPassSignals} packet
33704 (@pxref{QPassSignals}).
33706 @item QStartNoAckMode
33707 The remote stub understands the @samp{QStartNoAckMode} packet and
33708 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33711 @anchor{multiprocess extensions}
33712 @cindex multiprocess extensions, in remote protocol
33713 The remote stub understands the multiprocess extensions to the remote
33714 protocol syntax. The multiprocess extensions affect the syntax of
33715 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33716 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33717 replies. Note that reporting this feature indicates support for the
33718 syntactic extensions only, not that the stub necessarily supports
33719 debugging of more than one process at a time. The stub must not use
33720 multiprocess extensions in packet replies unless @value{GDBN} has also
33721 indicated it supports them in its @samp{qSupported} request.
33723 @item qXfer:osdata:read
33724 The remote stub understands the @samp{qXfer:osdata:read} packet
33725 ((@pxref{qXfer osdata read}).
33727 @item ConditionalTracepoints
33728 The remote stub accepts and implements conditional expressions defined
33729 for tracepoints (@pxref{Tracepoint Conditions}).
33731 @item ReverseContinue
33732 The remote stub accepts and implements the reverse continue packet
33736 The remote stub accepts and implements the reverse step packet
33739 @item TracepointSource
33740 The remote stub understands the @samp{QTDPsrc} packet that supplies
33741 the source form of tracepoint definitions.
33744 The remote stub understands the @samp{QAllow} packet.
33746 @item StaticTracepoint
33747 @cindex static tracepoints, in remote protocol
33748 The remote stub supports static tracepoints.
33750 @item EnableDisableTracepoints
33751 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
33752 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
33753 to be enabled and disabled while a trace experiment is running.
33758 @cindex symbol lookup, remote request
33759 @cindex @samp{qSymbol} packet
33760 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33761 requests. Accept requests from the target for the values of symbols.
33766 The target does not need to look up any (more) symbols.
33767 @item qSymbol:@var{sym_name}
33768 The target requests the value of symbol @var{sym_name} (hex encoded).
33769 @value{GDBN} may provide the value by using the
33770 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33774 @item qSymbol:@var{sym_value}:@var{sym_name}
33775 Set the value of @var{sym_name} to @var{sym_value}.
33777 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33778 target has previously requested.
33780 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33781 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33787 The target does not need to look up any (more) symbols.
33788 @item qSymbol:@var{sym_name}
33789 The target requests the value of a new symbol @var{sym_name} (hex
33790 encoded). @value{GDBN} will continue to supply the values of symbols
33791 (if available), until the target ceases to request them.
33796 @item QTDisconnected
33803 @xref{Tracepoint Packets}.
33805 @item qThreadExtraInfo,@var{thread-id}
33806 @cindex thread attributes info, remote request
33807 @cindex @samp{qThreadExtraInfo} packet
33808 Obtain a printable string description of a thread's attributes from
33809 the target OS. @var{thread-id} is a thread ID;
33810 see @ref{thread-id syntax}. This
33811 string may contain anything that the target OS thinks is interesting
33812 for @value{GDBN} to tell the user about the thread. The string is
33813 displayed in @value{GDBN}'s @code{info threads} display. Some
33814 examples of possible thread extra info strings are @samp{Runnable}, or
33815 @samp{Blocked on Mutex}.
33819 @item @var{XX}@dots{}
33820 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33821 comprising the printable string containing the extra information about
33822 the thread's attributes.
33825 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33826 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33827 conventions above. Please don't use this packet as a model for new
33844 @xref{Tracepoint Packets}.
33846 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33847 @cindex read special object, remote request
33848 @cindex @samp{qXfer} packet
33849 @anchor{qXfer read}
33850 Read uninterpreted bytes from the target's special data area
33851 identified by the keyword @var{object}. Request @var{length} bytes
33852 starting at @var{offset} bytes into the data. The content and
33853 encoding of @var{annex} is specific to @var{object}; it can supply
33854 additional details about what data to access.
33856 Here are the specific requests of this form defined so far. All
33857 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33858 formats, listed below.
33861 @item qXfer:auxv:read::@var{offset},@var{length}
33862 @anchor{qXfer auxiliary vector read}
33863 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33864 auxiliary vector}. Note @var{annex} must be empty.
33866 This packet is not probed by default; the remote stub must request it,
33867 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33869 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33870 @anchor{qXfer target description read}
33871 Access the @dfn{target description}. @xref{Target Descriptions}. The
33872 annex specifies which XML document to access. The main description is
33873 always loaded from the @samp{target.xml} annex.
33875 This packet is not probed by default; the remote stub must request it,
33876 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33878 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
33879 @anchor{qXfer library list read}
33880 Access the target's list of loaded libraries. @xref{Library List Format}.
33881 The annex part of the generic @samp{qXfer} packet must be empty
33882 (@pxref{qXfer read}).
33884 Targets which maintain a list of libraries in the program's memory do
33885 not need to implement this packet; it is designed for platforms where
33886 the operating system manages the list of loaded libraries.
33888 This packet is not probed by default; the remote stub must request it,
33889 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33891 @item qXfer:memory-map:read::@var{offset},@var{length}
33892 @anchor{qXfer memory map read}
33893 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
33894 annex part of the generic @samp{qXfer} packet must be empty
33895 (@pxref{qXfer read}).
33897 This packet is not probed by default; the remote stub must request it,
33898 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33900 @item qXfer:sdata:read::@var{offset},@var{length}
33901 @anchor{qXfer sdata read}
33903 Read contents of the extra collected static tracepoint marker
33904 information. The annex part of the generic @samp{qXfer} packet must
33905 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
33908 This packet is not probed by default; the remote stub must request it,
33909 by supplying an appropriate @samp{qSupported} response
33910 (@pxref{qSupported}).
33912 @item qXfer:siginfo:read::@var{offset},@var{length}
33913 @anchor{qXfer siginfo read}
33914 Read contents of the extra signal information on the target
33915 system. The annex part of the generic @samp{qXfer} packet must be
33916 empty (@pxref{qXfer read}).
33918 This packet is not probed by default; the remote stub must request it,
33919 by supplying an appropriate @samp{qSupported} response
33920 (@pxref{qSupported}).
33922 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
33923 @anchor{qXfer spu read}
33924 Read contents of an @code{spufs} file on the target system. The
33925 annex specifies which file to read; it must be of the form
33926 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33927 in the target process, and @var{name} identifes the @code{spufs} file
33928 in that context to be accessed.
33930 This packet is not probed by default; the remote stub must request it,
33931 by supplying an appropriate @samp{qSupported} response
33932 (@pxref{qSupported}).
33934 @item qXfer:threads:read::@var{offset},@var{length}
33935 @anchor{qXfer threads read}
33936 Access the list of threads on target. @xref{Thread List Format}. The
33937 annex part of the generic @samp{qXfer} packet must be empty
33938 (@pxref{qXfer read}).
33940 This packet is not probed by default; the remote stub must request it,
33941 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33943 @item qXfer:traceframe-info:read::@var{offset},@var{length}
33944 @anchor{qXfer traceframe info read}
33946 Return a description of the current traceframe's contents.
33947 @xref{Traceframe Info Format}. The annex part of the generic
33948 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
33950 This packet is not probed by default; the remote stub must request it,
33951 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33953 @item qXfer:osdata:read::@var{offset},@var{length}
33954 @anchor{qXfer osdata read}
33955 Access the target's @dfn{operating system information}.
33956 @xref{Operating System Information}.
33963 Data @var{data} (@pxref{Binary Data}) has been read from the
33964 target. There may be more data at a higher address (although
33965 it is permitted to return @samp{m} even for the last valid
33966 block of data, as long as at least one byte of data was read).
33967 @var{data} may have fewer bytes than the @var{length} in the
33971 Data @var{data} (@pxref{Binary Data}) has been read from the target.
33972 There is no more data to be read. @var{data} may have fewer bytes
33973 than the @var{length} in the request.
33976 The @var{offset} in the request is at the end of the data.
33977 There is no more data to be read.
33980 The request was malformed, or @var{annex} was invalid.
33983 The offset was invalid, or there was an error encountered reading the data.
33984 @var{nn} is a hex-encoded @code{errno} value.
33987 An empty reply indicates the @var{object} string was not recognized by
33988 the stub, or that the object does not support reading.
33991 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33992 @cindex write data into object, remote request
33993 @anchor{qXfer write}
33994 Write uninterpreted bytes into the target's special data area
33995 identified by the keyword @var{object}, starting at @var{offset} bytes
33996 into the data. @var{data}@dots{} is the binary-encoded data
33997 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33998 is specific to @var{object}; it can supply additional details about what data
34001 Here are the specific requests of this form defined so far. All
34002 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
34003 formats, listed below.
34006 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
34007 @anchor{qXfer siginfo write}
34008 Write @var{data} to the extra signal information on the target system.
34009 The annex part of the generic @samp{qXfer} packet must be
34010 empty (@pxref{qXfer write}).
34012 This packet is not probed by default; the remote stub must request it,
34013 by supplying an appropriate @samp{qSupported} response
34014 (@pxref{qSupported}).
34016 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
34017 @anchor{qXfer spu write}
34018 Write @var{data} to an @code{spufs} file on the target system. The
34019 annex specifies which file to write; it must be of the form
34020 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34021 in the target process, and @var{name} identifes the @code{spufs} file
34022 in that context to be accessed.
34024 This packet is not probed by default; the remote stub must request it,
34025 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34031 @var{nn} (hex encoded) is the number of bytes written.
34032 This may be fewer bytes than supplied in the request.
34035 The request was malformed, or @var{annex} was invalid.
34038 The offset was invalid, or there was an error encountered writing the data.
34039 @var{nn} is a hex-encoded @code{errno} value.
34042 An empty reply indicates the @var{object} string was not
34043 recognized by the stub, or that the object does not support writing.
34046 @item qXfer:@var{object}:@var{operation}:@dots{}
34047 Requests of this form may be added in the future. When a stub does
34048 not recognize the @var{object} keyword, or its support for
34049 @var{object} does not recognize the @var{operation} keyword, the stub
34050 must respond with an empty packet.
34052 @item qAttached:@var{pid}
34053 @cindex query attached, remote request
34054 @cindex @samp{qAttached} packet
34055 Return an indication of whether the remote server attached to an
34056 existing process or created a new process. When the multiprocess
34057 protocol extensions are supported (@pxref{multiprocess extensions}),
34058 @var{pid} is an integer in hexadecimal format identifying the target
34059 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
34060 the query packet will be simplified as @samp{qAttached}.
34062 This query is used, for example, to know whether the remote process
34063 should be detached or killed when a @value{GDBN} session is ended with
34064 the @code{quit} command.
34069 The remote server attached to an existing process.
34071 The remote server created a new process.
34073 A badly formed request or an error was encountered.
34078 @node Architecture-Specific Protocol Details
34079 @section Architecture-Specific Protocol Details
34081 This section describes how the remote protocol is applied to specific
34082 target architectures. Also see @ref{Standard Target Features}, for
34083 details of XML target descriptions for each architecture.
34087 @subsubsection Breakpoint Kinds
34089 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
34094 16-bit Thumb mode breakpoint.
34097 32-bit Thumb mode (Thumb-2) breakpoint.
34100 32-bit ARM mode breakpoint.
34106 @subsubsection Register Packet Format
34108 The following @code{g}/@code{G} packets have previously been defined.
34109 In the below, some thirty-two bit registers are transferred as
34110 sixty-four bits. Those registers should be zero/sign extended (which?)
34111 to fill the space allocated. Register bytes are transferred in target
34112 byte order. The two nibbles within a register byte are transferred
34113 most-significant - least-significant.
34119 All registers are transferred as thirty-two bit quantities in the order:
34120 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
34121 registers; fsr; fir; fp.
34125 All registers are transferred as sixty-four bit quantities (including
34126 thirty-two bit registers such as @code{sr}). The ordering is the same
34131 @node Tracepoint Packets
34132 @section Tracepoint Packets
34133 @cindex tracepoint packets
34134 @cindex packets, tracepoint
34136 Here we describe the packets @value{GDBN} uses to implement
34137 tracepoints (@pxref{Tracepoints}).
34141 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
34142 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
34143 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
34144 the tracepoint is disabled. @var{step} is the tracepoint's step
34145 count, and @var{pass} is its pass count. If an @samp{F} is present,
34146 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
34147 the number of bytes that the target should copy elsewhere to make room
34148 for the tracepoint. If an @samp{X} is present, it introduces a
34149 tracepoint condition, which consists of a hexadecimal length, followed
34150 by a comma and hex-encoded bytes, in a manner similar to action
34151 encodings as described below. If the trailing @samp{-} is present,
34152 further @samp{QTDP} packets will follow to specify this tracepoint's
34158 The packet was understood and carried out.
34160 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34162 The packet was not recognized.
34165 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
34166 Define actions to be taken when a tracepoint is hit. @var{n} and
34167 @var{addr} must be the same as in the initial @samp{QTDP} packet for
34168 this tracepoint. This packet may only be sent immediately after
34169 another @samp{QTDP} packet that ended with a @samp{-}. If the
34170 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
34171 specifying more actions for this tracepoint.
34173 In the series of action packets for a given tracepoint, at most one
34174 can have an @samp{S} before its first @var{action}. If such a packet
34175 is sent, it and the following packets define ``while-stepping''
34176 actions. Any prior packets define ordinary actions --- that is, those
34177 taken when the tracepoint is first hit. If no action packet has an
34178 @samp{S}, then all the packets in the series specify ordinary
34179 tracepoint actions.
34181 The @samp{@var{action}@dots{}} portion of the packet is a series of
34182 actions, concatenated without separators. Each action has one of the
34188 Collect the registers whose bits are set in @var{mask}. @var{mask} is
34189 a hexadecimal number whose @var{i}'th bit is set if register number
34190 @var{i} should be collected. (The least significant bit is numbered
34191 zero.) Note that @var{mask} may be any number of digits long; it may
34192 not fit in a 32-bit word.
34194 @item M @var{basereg},@var{offset},@var{len}
34195 Collect @var{len} bytes of memory starting at the address in register
34196 number @var{basereg}, plus @var{offset}. If @var{basereg} is
34197 @samp{-1}, then the range has a fixed address: @var{offset} is the
34198 address of the lowest byte to collect. The @var{basereg},
34199 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
34200 values (the @samp{-1} value for @var{basereg} is a special case).
34202 @item X @var{len},@var{expr}
34203 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
34204 it directs. @var{expr} is an agent expression, as described in
34205 @ref{Agent Expressions}. Each byte of the expression is encoded as a
34206 two-digit hex number in the packet; @var{len} is the number of bytes
34207 in the expression (and thus one-half the number of hex digits in the
34212 Any number of actions may be packed together in a single @samp{QTDP}
34213 packet, as long as the packet does not exceed the maximum packet
34214 length (400 bytes, for many stubs). There may be only one @samp{R}
34215 action per tracepoint, and it must precede any @samp{M} or @samp{X}
34216 actions. Any registers referred to by @samp{M} and @samp{X} actions
34217 must be collected by a preceding @samp{R} action. (The
34218 ``while-stepping'' actions are treated as if they were attached to a
34219 separate tracepoint, as far as these restrictions are concerned.)
34224 The packet was understood and carried out.
34226 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34228 The packet was not recognized.
34231 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
34232 @cindex @samp{QTDPsrc} packet
34233 Specify a source string of tracepoint @var{n} at address @var{addr}.
34234 This is useful to get accurate reproduction of the tracepoints
34235 originally downloaded at the beginning of the trace run. @var{type}
34236 is the name of the tracepoint part, such as @samp{cond} for the
34237 tracepoint's conditional expression (see below for a list of types), while
34238 @var{bytes} is the string, encoded in hexadecimal.
34240 @var{start} is the offset of the @var{bytes} within the overall source
34241 string, while @var{slen} is the total length of the source string.
34242 This is intended for handling source strings that are longer than will
34243 fit in a single packet.
34244 @c Add detailed example when this info is moved into a dedicated
34245 @c tracepoint descriptions section.
34247 The available string types are @samp{at} for the location,
34248 @samp{cond} for the conditional, and @samp{cmd} for an action command.
34249 @value{GDBN} sends a separate packet for each command in the action
34250 list, in the same order in which the commands are stored in the list.
34252 The target does not need to do anything with source strings except
34253 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
34256 Although this packet is optional, and @value{GDBN} will only send it
34257 if the target replies with @samp{TracepointSource} @xref{General
34258 Query Packets}, it makes both disconnected tracing and trace files
34259 much easier to use. Otherwise the user must be careful that the
34260 tracepoints in effect while looking at trace frames are identical to
34261 the ones in effect during the trace run; even a small discrepancy
34262 could cause @samp{tdump} not to work, or a particular trace frame not
34265 @item QTDV:@var{n}:@var{value}
34266 @cindex define trace state variable, remote request
34267 @cindex @samp{QTDV} packet
34268 Create a new trace state variable, number @var{n}, with an initial
34269 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
34270 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
34271 the option of not using this packet for initial values of zero; the
34272 target should simply create the trace state variables as they are
34273 mentioned in expressions.
34275 @item QTFrame:@var{n}
34276 Select the @var{n}'th tracepoint frame from the buffer, and use the
34277 register and memory contents recorded there to answer subsequent
34278 request packets from @value{GDBN}.
34280 A successful reply from the stub indicates that the stub has found the
34281 requested frame. The response is a series of parts, concatenated
34282 without separators, describing the frame we selected. Each part has
34283 one of the following forms:
34287 The selected frame is number @var{n} in the trace frame buffer;
34288 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
34289 was no frame matching the criteria in the request packet.
34292 The selected trace frame records a hit of tracepoint number @var{t};
34293 @var{t} is a hexadecimal number.
34297 @item QTFrame:pc:@var{addr}
34298 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34299 currently selected frame whose PC is @var{addr};
34300 @var{addr} is a hexadecimal number.
34302 @item QTFrame:tdp:@var{t}
34303 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34304 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
34305 is a hexadecimal number.
34307 @item QTFrame:range:@var{start}:@var{end}
34308 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34309 currently selected frame whose PC is between @var{start} (inclusive)
34310 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
34313 @item QTFrame:outside:@var{start}:@var{end}
34314 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
34315 frame @emph{outside} the given range of addresses (exclusive).
34318 Begin the tracepoint experiment. Begin collecting data from
34319 tracepoint hits in the trace frame buffer. This packet supports the
34320 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
34321 instruction reply packet}).
34324 End the tracepoint experiment. Stop collecting trace frames.
34326 @item QTEnable:@var{n}:@var{addr}
34328 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
34329 experiment. If the tracepoint was previously disabled, then collection
34330 of data from it will resume.
34332 @item QTDisable:@var{n}:@var{addr}
34334 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
34335 experiment. No more data will be collected from the tracepoint unless
34336 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
34339 Clear the table of tracepoints, and empty the trace frame buffer.
34341 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
34342 Establish the given ranges of memory as ``transparent''. The stub
34343 will answer requests for these ranges from memory's current contents,
34344 if they were not collected as part of the tracepoint hit.
34346 @value{GDBN} uses this to mark read-only regions of memory, like those
34347 containing program code. Since these areas never change, they should
34348 still have the same contents they did when the tracepoint was hit, so
34349 there's no reason for the stub to refuse to provide their contents.
34351 @item QTDisconnected:@var{value}
34352 Set the choice to what to do with the tracing run when @value{GDBN}
34353 disconnects from the target. A @var{value} of 1 directs the target to
34354 continue the tracing run, while 0 tells the target to stop tracing if
34355 @value{GDBN} is no longer in the picture.
34358 Ask the stub if there is a trace experiment running right now.
34360 The reply has the form:
34364 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
34365 @var{running} is a single digit @code{1} if the trace is presently
34366 running, or @code{0} if not. It is followed by semicolon-separated
34367 optional fields that an agent may use to report additional status.
34371 If the trace is not running, the agent may report any of several
34372 explanations as one of the optional fields:
34377 No trace has been run yet.
34380 The trace was stopped by a user-originated stop command.
34383 The trace stopped because the trace buffer filled up.
34385 @item tdisconnected:0
34386 The trace stopped because @value{GDBN} disconnected from the target.
34388 @item tpasscount:@var{tpnum}
34389 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
34391 @item terror:@var{text}:@var{tpnum}
34392 The trace stopped because tracepoint @var{tpnum} had an error. The
34393 string @var{text} is available to describe the nature of the error
34394 (for instance, a divide by zero in the condition expression).
34395 @var{text} is hex encoded.
34398 The trace stopped for some other reason.
34402 Additional optional fields supply statistical and other information.
34403 Although not required, they are extremely useful for users monitoring
34404 the progress of a trace run. If a trace has stopped, and these
34405 numbers are reported, they must reflect the state of the just-stopped
34410 @item tframes:@var{n}
34411 The number of trace frames in the buffer.
34413 @item tcreated:@var{n}
34414 The total number of trace frames created during the run. This may
34415 be larger than the trace frame count, if the buffer is circular.
34417 @item tsize:@var{n}
34418 The total size of the trace buffer, in bytes.
34420 @item tfree:@var{n}
34421 The number of bytes still unused in the buffer.
34423 @item circular:@var{n}
34424 The value of the circular trace buffer flag. @code{1} means that the
34425 trace buffer is circular and old trace frames will be discarded if
34426 necessary to make room, @code{0} means that the trace buffer is linear
34429 @item disconn:@var{n}
34430 The value of the disconnected tracing flag. @code{1} means that
34431 tracing will continue after @value{GDBN} disconnects, @code{0} means
34432 that the trace run will stop.
34436 @item qTV:@var{var}
34437 @cindex trace state variable value, remote request
34438 @cindex @samp{qTV} packet
34439 Ask the stub for the value of the trace state variable number @var{var}.
34444 The value of the variable is @var{value}. This will be the current
34445 value of the variable if the user is examining a running target, or a
34446 saved value if the variable was collected in the trace frame that the
34447 user is looking at. Note that multiple requests may result in
34448 different reply values, such as when requesting values while the
34449 program is running.
34452 The value of the variable is unknown. This would occur, for example,
34453 if the user is examining a trace frame in which the requested variable
34459 These packets request data about tracepoints that are being used by
34460 the target. @value{GDBN} sends @code{qTfP} to get the first piece
34461 of data, and multiple @code{qTsP} to get additional pieces. Replies
34462 to these packets generally take the form of the @code{QTDP} packets
34463 that define tracepoints. (FIXME add detailed syntax)
34467 These packets request data about trace state variables that are on the
34468 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
34469 and multiple @code{qTsV} to get additional variables. Replies to
34470 these packets follow the syntax of the @code{QTDV} packets that define
34471 trace state variables.
34475 These packets request data about static tracepoint markers that exist
34476 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
34477 first piece of data, and multiple @code{qTsSTM} to get additional
34478 pieces. Replies to these packets take the following form:
34482 @item m @var{address}:@var{id}:@var{extra}
34484 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
34485 a comma-separated list of markers
34487 (lower case letter @samp{L}) denotes end of list.
34489 An error occurred. @var{nn} are hex digits.
34491 An empty reply indicates that the request is not supported by the
34495 @var{address} is encoded in hex.
34496 @var{id} and @var{extra} are strings encoded in hex.
34498 In response to each query, the target will reply with a list of one or
34499 more markers, separated by commas. @value{GDBN} will respond to each
34500 reply with a request for more markers (using the @samp{qs} form of the
34501 query), until the target responds with @samp{l} (lower-case ell, for
34504 @item qTSTMat:@var{address}
34505 This packets requests data about static tracepoint markers in the
34506 target program at @var{address}. Replies to this packet follow the
34507 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
34508 tracepoint markers.
34510 @item QTSave:@var{filename}
34511 This packet directs the target to save trace data to the file name
34512 @var{filename} in the target's filesystem. @var{filename} is encoded
34513 as a hex string; the interpretation of the file name (relative vs
34514 absolute, wild cards, etc) is up to the target.
34516 @item qTBuffer:@var{offset},@var{len}
34517 Return up to @var{len} bytes of the current contents of trace buffer,
34518 starting at @var{offset}. The trace buffer is treated as if it were
34519 a contiguous collection of traceframes, as per the trace file format.
34520 The reply consists as many hex-encoded bytes as the target can deliver
34521 in a packet; it is not an error to return fewer than were asked for.
34522 A reply consisting of just @code{l} indicates that no bytes are
34525 @item QTBuffer:circular:@var{value}
34526 This packet directs the target to use a circular trace buffer if
34527 @var{value} is 1, or a linear buffer if the value is 0.
34531 @subsection Relocate instruction reply packet
34532 When installing fast tracepoints in memory, the target may need to
34533 relocate the instruction currently at the tracepoint address to a
34534 different address in memory. For most instructions, a simple copy is
34535 enough, but, for example, call instructions that implicitly push the
34536 return address on the stack, and relative branches or other
34537 PC-relative instructions require offset adjustment, so that the effect
34538 of executing the instruction at a different address is the same as if
34539 it had executed in the original location.
34541 In response to several of the tracepoint packets, the target may also
34542 respond with a number of intermediate @samp{qRelocInsn} request
34543 packets before the final result packet, to have @value{GDBN} handle
34544 this relocation operation. If a packet supports this mechanism, its
34545 documentation will explicitly say so. See for example the above
34546 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
34547 format of the request is:
34550 @item qRelocInsn:@var{from};@var{to}
34552 This requests @value{GDBN} to copy instruction at address @var{from}
34553 to address @var{to}, possibly adjusted so that executing the
34554 instruction at @var{to} has the same effect as executing it at
34555 @var{from}. @value{GDBN} writes the adjusted instruction to target
34556 memory starting at @var{to}.
34561 @item qRelocInsn:@var{adjusted_size}
34562 Informs the stub the relocation is complete. @var{adjusted_size} is
34563 the length in bytes of resulting relocated instruction sequence.
34565 A badly formed request was detected, or an error was encountered while
34566 relocating the instruction.
34569 @node Host I/O Packets
34570 @section Host I/O Packets
34571 @cindex Host I/O, remote protocol
34572 @cindex file transfer, remote protocol
34574 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
34575 operations on the far side of a remote link. For example, Host I/O is
34576 used to upload and download files to a remote target with its own
34577 filesystem. Host I/O uses the same constant values and data structure
34578 layout as the target-initiated File-I/O protocol. However, the
34579 Host I/O packets are structured differently. The target-initiated
34580 protocol relies on target memory to store parameters and buffers.
34581 Host I/O requests are initiated by @value{GDBN}, and the
34582 target's memory is not involved. @xref{File-I/O Remote Protocol
34583 Extension}, for more details on the target-initiated protocol.
34585 The Host I/O request packets all encode a single operation along with
34586 its arguments. They have this format:
34590 @item vFile:@var{operation}: @var{parameter}@dots{}
34591 @var{operation} is the name of the particular request; the target
34592 should compare the entire packet name up to the second colon when checking
34593 for a supported operation. The format of @var{parameter} depends on
34594 the operation. Numbers are always passed in hexadecimal. Negative
34595 numbers have an explicit minus sign (i.e.@: two's complement is not
34596 used). Strings (e.g.@: filenames) are encoded as a series of
34597 hexadecimal bytes. The last argument to a system call may be a
34598 buffer of escaped binary data (@pxref{Binary Data}).
34602 The valid responses to Host I/O packets are:
34606 @item F @var{result} [, @var{errno}] [; @var{attachment}]
34607 @var{result} is the integer value returned by this operation, usually
34608 non-negative for success and -1 for errors. If an error has occured,
34609 @var{errno} will be included in the result. @var{errno} will have a
34610 value defined by the File-I/O protocol (@pxref{Errno Values}). For
34611 operations which return data, @var{attachment} supplies the data as a
34612 binary buffer. Binary buffers in response packets are escaped in the
34613 normal way (@pxref{Binary Data}). See the individual packet
34614 documentation for the interpretation of @var{result} and
34618 An empty response indicates that this operation is not recognized.
34622 These are the supported Host I/O operations:
34625 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
34626 Open a file at @var{pathname} and return a file descriptor for it, or
34627 return -1 if an error occurs. @var{pathname} is a string,
34628 @var{flags} is an integer indicating a mask of open flags
34629 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34630 of mode bits to use if the file is created (@pxref{mode_t Values}).
34631 @xref{open}, for details of the open flags and mode values.
34633 @item vFile:close: @var{fd}
34634 Close the open file corresponding to @var{fd} and return 0, or
34635 -1 if an error occurs.
34637 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34638 Read data from the open file corresponding to @var{fd}. Up to
34639 @var{count} bytes will be read from the file, starting at @var{offset}
34640 relative to the start of the file. The target may read fewer bytes;
34641 common reasons include packet size limits and an end-of-file
34642 condition. The number of bytes read is returned. Zero should only be
34643 returned for a successful read at the end of the file, or if
34644 @var{count} was zero.
34646 The data read should be returned as a binary attachment on success.
34647 If zero bytes were read, the response should include an empty binary
34648 attachment (i.e.@: a trailing semicolon). The return value is the
34649 number of target bytes read; the binary attachment may be longer if
34650 some characters were escaped.
34652 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34653 Write @var{data} (a binary buffer) to the open file corresponding
34654 to @var{fd}. Start the write at @var{offset} from the start of the
34655 file. Unlike many @code{write} system calls, there is no
34656 separate @var{count} argument; the length of @var{data} in the
34657 packet is used. @samp{vFile:write} returns the number of bytes written,
34658 which may be shorter than the length of @var{data}, or -1 if an
34661 @item vFile:unlink: @var{pathname}
34662 Delete the file at @var{pathname} on the target. Return 0,
34663 or -1 if an error occurs. @var{pathname} is a string.
34668 @section Interrupts
34669 @cindex interrupts (remote protocol)
34671 When a program on the remote target is running, @value{GDBN} may
34672 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34673 a @code{BREAK} followed by @code{g},
34674 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34676 The precise meaning of @code{BREAK} is defined by the transport
34677 mechanism and may, in fact, be undefined. @value{GDBN} does not
34678 currently define a @code{BREAK} mechanism for any of the network
34679 interfaces except for TCP, in which case @value{GDBN} sends the
34680 @code{telnet} BREAK sequence.
34682 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34683 transport mechanisms. It is represented by sending the single byte
34684 @code{0x03} without any of the usual packet overhead described in
34685 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34686 transmitted as part of a packet, it is considered to be packet data
34687 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34688 (@pxref{X packet}), used for binary downloads, may include an unescaped
34689 @code{0x03} as part of its packet.
34691 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
34692 When Linux kernel receives this sequence from serial port,
34693 it stops execution and connects to gdb.
34695 Stubs are not required to recognize these interrupt mechanisms and the
34696 precise meaning associated with receipt of the interrupt is
34697 implementation defined. If the target supports debugging of multiple
34698 threads and/or processes, it should attempt to interrupt all
34699 currently-executing threads and processes.
34700 If the stub is successful at interrupting the
34701 running program, it should send one of the stop
34702 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
34703 of successfully stopping the program in all-stop mode, and a stop reply
34704 for each stopped thread in non-stop mode.
34705 Interrupts received while the
34706 program is stopped are discarded.
34708 @node Notification Packets
34709 @section Notification Packets
34710 @cindex notification packets
34711 @cindex packets, notification
34713 The @value{GDBN} remote serial protocol includes @dfn{notifications},
34714 packets that require no acknowledgment. Both the GDB and the stub
34715 may send notifications (although the only notifications defined at
34716 present are sent by the stub). Notifications carry information
34717 without incurring the round-trip latency of an acknowledgment, and so
34718 are useful for low-impact communications where occasional packet loss
34721 A notification packet has the form @samp{% @var{data} #
34722 @var{checksum}}, where @var{data} is the content of the notification,
34723 and @var{checksum} is a checksum of @var{data}, computed and formatted
34724 as for ordinary @value{GDBN} packets. A notification's @var{data}
34725 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
34726 receiving a notification, the recipient sends no @samp{+} or @samp{-}
34727 to acknowledge the notification's receipt or to report its corruption.
34729 Every notification's @var{data} begins with a name, which contains no
34730 colon characters, followed by a colon character.
34732 Recipients should silently ignore corrupted notifications and
34733 notifications they do not understand. Recipients should restart
34734 timeout periods on receipt of a well-formed notification, whether or
34735 not they understand it.
34737 Senders should only send the notifications described here when this
34738 protocol description specifies that they are permitted. In the
34739 future, we may extend the protocol to permit existing notifications in
34740 new contexts; this rule helps older senders avoid confusing newer
34743 (Older versions of @value{GDBN} ignore bytes received until they see
34744 the @samp{$} byte that begins an ordinary packet, so new stubs may
34745 transmit notifications without fear of confusing older clients. There
34746 are no notifications defined for @value{GDBN} to send at the moment, but we
34747 assume that most older stubs would ignore them, as well.)
34749 The following notification packets from the stub to @value{GDBN} are
34753 @item Stop: @var{reply}
34754 Report an asynchronous stop event in non-stop mode.
34755 The @var{reply} has the form of a stop reply, as
34756 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34757 for information on how these notifications are acknowledged by
34761 @node Remote Non-Stop
34762 @section Remote Protocol Support for Non-Stop Mode
34764 @value{GDBN}'s remote protocol supports non-stop debugging of
34765 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34766 supports non-stop mode, it should report that to @value{GDBN} by including
34767 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34769 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34770 establishing a new connection with the stub. Entering non-stop mode
34771 does not alter the state of any currently-running threads, but targets
34772 must stop all threads in any already-attached processes when entering
34773 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34774 probe the target state after a mode change.
34776 In non-stop mode, when an attached process encounters an event that
34777 would otherwise be reported with a stop reply, it uses the
34778 asynchronous notification mechanism (@pxref{Notification Packets}) to
34779 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34780 in all processes are stopped when a stop reply is sent, in non-stop
34781 mode only the thread reporting the stop event is stopped. That is,
34782 when reporting a @samp{S} or @samp{T} response to indicate completion
34783 of a step operation, hitting a breakpoint, or a fault, only the
34784 affected thread is stopped; any other still-running threads continue
34785 to run. When reporting a @samp{W} or @samp{X} response, all running
34786 threads belonging to other attached processes continue to run.
34788 Only one stop reply notification at a time may be pending; if
34789 additional stop events occur before @value{GDBN} has acknowledged the
34790 previous notification, they must be queued by the stub for later
34791 synchronous transmission in response to @samp{vStopped} packets from
34792 @value{GDBN}. Because the notification mechanism is unreliable,
34793 the stub is permitted to resend a stop reply notification
34794 if it believes @value{GDBN} may not have received it. @value{GDBN}
34795 ignores additional stop reply notifications received before it has
34796 finished processing a previous notification and the stub has completed
34797 sending any queued stop events.
34799 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34800 notification at any time. Specifically, they may appear when
34801 @value{GDBN} is not otherwise reading input from the stub, or when
34802 @value{GDBN} is expecting to read a normal synchronous response or a
34803 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34804 Notification packets are distinct from any other communication from
34805 the stub so there is no ambiguity.
34807 After receiving a stop reply notification, @value{GDBN} shall
34808 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34809 as a regular, synchronous request to the stub. Such acknowledgment
34810 is not required to happen immediately, as @value{GDBN} is permitted to
34811 send other, unrelated packets to the stub first, which the stub should
34814 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34815 stop events to report to @value{GDBN}, it shall respond by sending a
34816 normal stop reply response. @value{GDBN} shall then send another
34817 @samp{vStopped} packet to solicit further responses; again, it is
34818 permitted to send other, unrelated packets as well which the stub
34819 should process normally.
34821 If the stub receives a @samp{vStopped} packet and there are no
34822 additional stop events to report, the stub shall return an @samp{OK}
34823 response. At this point, if further stop events occur, the stub shall
34824 send a new stop reply notification, @value{GDBN} shall accept the
34825 notification, and the process shall be repeated.
34827 In non-stop mode, the target shall respond to the @samp{?} packet as
34828 follows. First, any incomplete stop reply notification/@samp{vStopped}
34829 sequence in progress is abandoned. The target must begin a new
34830 sequence reporting stop events for all stopped threads, whether or not
34831 it has previously reported those events to @value{GDBN}. The first
34832 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34833 subsequent stop replies are sent as responses to @samp{vStopped} packets
34834 using the mechanism described above. The target must not send
34835 asynchronous stop reply notifications until the sequence is complete.
34836 If all threads are running when the target receives the @samp{?} packet,
34837 or if the target is not attached to any process, it shall respond
34840 @node Packet Acknowledgment
34841 @section Packet Acknowledgment
34843 @cindex acknowledgment, for @value{GDBN} remote
34844 @cindex packet acknowledgment, for @value{GDBN} remote
34845 By default, when either the host or the target machine receives a packet,
34846 the first response expected is an acknowledgment: either @samp{+} (to indicate
34847 the package was received correctly) or @samp{-} (to request retransmission).
34848 This mechanism allows the @value{GDBN} remote protocol to operate over
34849 unreliable transport mechanisms, such as a serial line.
34851 In cases where the transport mechanism is itself reliable (such as a pipe or
34852 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34853 It may be desirable to disable them in that case to reduce communication
34854 overhead, or for other reasons. This can be accomplished by means of the
34855 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34857 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34858 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34859 and response format still includes the normal checksum, as described in
34860 @ref{Overview}, but the checksum may be ignored by the receiver.
34862 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34863 no-acknowledgment mode, it should report that to @value{GDBN}
34864 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34865 @pxref{qSupported}.
34866 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34867 disabled via the @code{set remote noack-packet off} command
34868 (@pxref{Remote Configuration}),
34869 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34870 Only then may the stub actually turn off packet acknowledgments.
34871 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34872 response, which can be safely ignored by the stub.
34874 Note that @code{set remote noack-packet} command only affects negotiation
34875 between @value{GDBN} and the stub when subsequent connections are made;
34876 it does not affect the protocol acknowledgment state for any current
34878 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
34879 new connection is established,
34880 there is also no protocol request to re-enable the acknowledgments
34881 for the current connection, once disabled.
34886 Example sequence of a target being re-started. Notice how the restart
34887 does not get any direct output:
34892 @emph{target restarts}
34895 <- @code{T001:1234123412341234}
34899 Example sequence of a target being stepped by a single instruction:
34902 -> @code{G1445@dots{}}
34907 <- @code{T001:1234123412341234}
34911 <- @code{1455@dots{}}
34915 @node File-I/O Remote Protocol Extension
34916 @section File-I/O Remote Protocol Extension
34917 @cindex File-I/O remote protocol extension
34920 * File-I/O Overview::
34921 * Protocol Basics::
34922 * The F Request Packet::
34923 * The F Reply Packet::
34924 * The Ctrl-C Message::
34926 * List of Supported Calls::
34927 * Protocol-specific Representation of Datatypes::
34929 * File-I/O Examples::
34932 @node File-I/O Overview
34933 @subsection File-I/O Overview
34934 @cindex file-i/o overview
34936 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
34937 target to use the host's file system and console I/O to perform various
34938 system calls. System calls on the target system are translated into a
34939 remote protocol packet to the host system, which then performs the needed
34940 actions and returns a response packet to the target system.
34941 This simulates file system operations even on targets that lack file systems.
34943 The protocol is defined to be independent of both the host and target systems.
34944 It uses its own internal representation of datatypes and values. Both
34945 @value{GDBN} and the target's @value{GDBN} stub are responsible for
34946 translating the system-dependent value representations into the internal
34947 protocol representations when data is transmitted.
34949 The communication is synchronous. A system call is possible only when
34950 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
34951 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
34952 the target is stopped to allow deterministic access to the target's
34953 memory. Therefore File-I/O is not interruptible by target signals. On
34954 the other hand, it is possible to interrupt File-I/O by a user interrupt
34955 (@samp{Ctrl-C}) within @value{GDBN}.
34957 The target's request to perform a host system call does not finish
34958 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
34959 after finishing the system call, the target returns to continuing the
34960 previous activity (continue, step). No additional continue or step
34961 request from @value{GDBN} is required.
34964 (@value{GDBP}) continue
34965 <- target requests 'system call X'
34966 target is stopped, @value{GDBN} executes system call
34967 -> @value{GDBN} returns result
34968 ... target continues, @value{GDBN} returns to wait for the target
34969 <- target hits breakpoint and sends a Txx packet
34972 The protocol only supports I/O on the console and to regular files on
34973 the host file system. Character or block special devices, pipes,
34974 named pipes, sockets or any other communication method on the host
34975 system are not supported by this protocol.
34977 File I/O is not supported in non-stop mode.
34979 @node Protocol Basics
34980 @subsection Protocol Basics
34981 @cindex protocol basics, file-i/o
34983 The File-I/O protocol uses the @code{F} packet as the request as well
34984 as reply packet. Since a File-I/O system call can only occur when
34985 @value{GDBN} is waiting for a response from the continuing or stepping target,
34986 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34987 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34988 This @code{F} packet contains all information needed to allow @value{GDBN}
34989 to call the appropriate host system call:
34993 A unique identifier for the requested system call.
34996 All parameters to the system call. Pointers are given as addresses
34997 in the target memory address space. Pointers to strings are given as
34998 pointer/length pair. Numerical values are given as they are.
34999 Numerical control flags are given in a protocol-specific representation.
35003 At this point, @value{GDBN} has to perform the following actions.
35007 If the parameters include pointer values to data needed as input to a
35008 system call, @value{GDBN} requests this data from the target with a
35009 standard @code{m} packet request. This additional communication has to be
35010 expected by the target implementation and is handled as any other @code{m}
35014 @value{GDBN} translates all value from protocol representation to host
35015 representation as needed. Datatypes are coerced into the host types.
35018 @value{GDBN} calls the system call.
35021 It then coerces datatypes back to protocol representation.
35024 If the system call is expected to return data in buffer space specified
35025 by pointer parameters to the call, the data is transmitted to the
35026 target using a @code{M} or @code{X} packet. This packet has to be expected
35027 by the target implementation and is handled as any other @code{M} or @code{X}
35032 Eventually @value{GDBN} replies with another @code{F} packet which contains all
35033 necessary information for the target to continue. This at least contains
35040 @code{errno}, if has been changed by the system call.
35047 After having done the needed type and value coercion, the target continues
35048 the latest continue or step action.
35050 @node The F Request Packet
35051 @subsection The @code{F} Request Packet
35052 @cindex file-i/o request packet
35053 @cindex @code{F} request packet
35055 The @code{F} request packet has the following format:
35058 @item F@var{call-id},@var{parameter@dots{}}
35060 @var{call-id} is the identifier to indicate the host system call to be called.
35061 This is just the name of the function.
35063 @var{parameter@dots{}} are the parameters to the system call.
35064 Parameters are hexadecimal integer values, either the actual values in case
35065 of scalar datatypes, pointers to target buffer space in case of compound
35066 datatypes and unspecified memory areas, or pointer/length pairs in case
35067 of string parameters. These are appended to the @var{call-id} as a
35068 comma-delimited list. All values are transmitted in ASCII
35069 string representation, pointer/length pairs separated by a slash.
35075 @node The F Reply Packet
35076 @subsection The @code{F} Reply Packet
35077 @cindex file-i/o reply packet
35078 @cindex @code{F} reply packet
35080 The @code{F} reply packet has the following format:
35084 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
35086 @var{retcode} is the return code of the system call as hexadecimal value.
35088 @var{errno} is the @code{errno} set by the call, in protocol-specific
35090 This parameter can be omitted if the call was successful.
35092 @var{Ctrl-C flag} is only sent if the user requested a break. In this
35093 case, @var{errno} must be sent as well, even if the call was successful.
35094 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
35101 or, if the call was interrupted before the host call has been performed:
35108 assuming 4 is the protocol-specific representation of @code{EINTR}.
35113 @node The Ctrl-C Message
35114 @subsection The @samp{Ctrl-C} Message
35115 @cindex ctrl-c message, in file-i/o protocol
35117 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
35118 reply packet (@pxref{The F Reply Packet}),
35119 the target should behave as if it had
35120 gotten a break message. The meaning for the target is ``system call
35121 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
35122 (as with a break message) and return to @value{GDBN} with a @code{T02}
35125 It's important for the target to know in which
35126 state the system call was interrupted. There are two possible cases:
35130 The system call hasn't been performed on the host yet.
35133 The system call on the host has been finished.
35137 These two states can be distinguished by the target by the value of the
35138 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
35139 call hasn't been performed. This is equivalent to the @code{EINTR} handling
35140 on POSIX systems. In any other case, the target may presume that the
35141 system call has been finished --- successfully or not --- and should behave
35142 as if the break message arrived right after the system call.
35144 @value{GDBN} must behave reliably. If the system call has not been called
35145 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
35146 @code{errno} in the packet. If the system call on the host has been finished
35147 before the user requests a break, the full action must be finished by
35148 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
35149 The @code{F} packet may only be sent when either nothing has happened
35150 or the full action has been completed.
35153 @subsection Console I/O
35154 @cindex console i/o as part of file-i/o
35156 By default and if not explicitly closed by the target system, the file
35157 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
35158 on the @value{GDBN} console is handled as any other file output operation
35159 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
35160 by @value{GDBN} so that after the target read request from file descriptor
35161 0 all following typing is buffered until either one of the following
35166 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
35168 system call is treated as finished.
35171 The user presses @key{RET}. This is treated as end of input with a trailing
35175 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
35176 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
35180 If the user has typed more characters than fit in the buffer given to
35181 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
35182 either another @code{read(0, @dots{})} is requested by the target, or debugging
35183 is stopped at the user's request.
35186 @node List of Supported Calls
35187 @subsection List of Supported Calls
35188 @cindex list of supported file-i/o calls
35205 @unnumberedsubsubsec open
35206 @cindex open, file-i/o system call
35211 int open(const char *pathname, int flags);
35212 int open(const char *pathname, int flags, mode_t mode);
35216 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
35219 @var{flags} is the bitwise @code{OR} of the following values:
35223 If the file does not exist it will be created. The host
35224 rules apply as far as file ownership and time stamps
35228 When used with @code{O_CREAT}, if the file already exists it is
35229 an error and open() fails.
35232 If the file already exists and the open mode allows
35233 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
35234 truncated to zero length.
35237 The file is opened in append mode.
35240 The file is opened for reading only.
35243 The file is opened for writing only.
35246 The file is opened for reading and writing.
35250 Other bits are silently ignored.
35254 @var{mode} is the bitwise @code{OR} of the following values:
35258 User has read permission.
35261 User has write permission.
35264 Group has read permission.
35267 Group has write permission.
35270 Others have read permission.
35273 Others have write permission.
35277 Other bits are silently ignored.
35280 @item Return value:
35281 @code{open} returns the new file descriptor or -1 if an error
35288 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
35291 @var{pathname} refers to a directory.
35294 The requested access is not allowed.
35297 @var{pathname} was too long.
35300 A directory component in @var{pathname} does not exist.
35303 @var{pathname} refers to a device, pipe, named pipe or socket.
35306 @var{pathname} refers to a file on a read-only filesystem and
35307 write access was requested.
35310 @var{pathname} is an invalid pointer value.
35313 No space on device to create the file.
35316 The process already has the maximum number of files open.
35319 The limit on the total number of files open on the system
35323 The call was interrupted by the user.
35329 @unnumberedsubsubsec close
35330 @cindex close, file-i/o system call
35339 @samp{Fclose,@var{fd}}
35341 @item Return value:
35342 @code{close} returns zero on success, or -1 if an error occurred.
35348 @var{fd} isn't a valid open file descriptor.
35351 The call was interrupted by the user.
35357 @unnumberedsubsubsec read
35358 @cindex read, file-i/o system call
35363 int read(int fd, void *buf, unsigned int count);
35367 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
35369 @item Return value:
35370 On success, the number of bytes read is returned.
35371 Zero indicates end of file. If count is zero, read
35372 returns zero as well. On error, -1 is returned.
35378 @var{fd} is not a valid file descriptor or is not open for
35382 @var{bufptr} is an invalid pointer value.
35385 The call was interrupted by the user.
35391 @unnumberedsubsubsec write
35392 @cindex write, file-i/o system call
35397 int write(int fd, const void *buf, unsigned int count);
35401 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
35403 @item Return value:
35404 On success, the number of bytes written are returned.
35405 Zero indicates nothing was written. On error, -1
35412 @var{fd} is not a valid file descriptor or is not open for
35416 @var{bufptr} is an invalid pointer value.
35419 An attempt was made to write a file that exceeds the
35420 host-specific maximum file size allowed.
35423 No space on device to write the data.
35426 The call was interrupted by the user.
35432 @unnumberedsubsubsec lseek
35433 @cindex lseek, file-i/o system call
35438 long lseek (int fd, long offset, int flag);
35442 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
35444 @var{flag} is one of:
35448 The offset is set to @var{offset} bytes.
35451 The offset is set to its current location plus @var{offset}
35455 The offset is set to the size of the file plus @var{offset}
35459 @item Return value:
35460 On success, the resulting unsigned offset in bytes from
35461 the beginning of the file is returned. Otherwise, a
35462 value of -1 is returned.
35468 @var{fd} is not a valid open file descriptor.
35471 @var{fd} is associated with the @value{GDBN} console.
35474 @var{flag} is not a proper value.
35477 The call was interrupted by the user.
35483 @unnumberedsubsubsec rename
35484 @cindex rename, file-i/o system call
35489 int rename(const char *oldpath, const char *newpath);
35493 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
35495 @item Return value:
35496 On success, zero is returned. On error, -1 is returned.
35502 @var{newpath} is an existing directory, but @var{oldpath} is not a
35506 @var{newpath} is a non-empty directory.
35509 @var{oldpath} or @var{newpath} is a directory that is in use by some
35513 An attempt was made to make a directory a subdirectory
35517 A component used as a directory in @var{oldpath} or new
35518 path is not a directory. Or @var{oldpath} is a directory
35519 and @var{newpath} exists but is not a directory.
35522 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
35525 No access to the file or the path of the file.
35529 @var{oldpath} or @var{newpath} was too long.
35532 A directory component in @var{oldpath} or @var{newpath} does not exist.
35535 The file is on a read-only filesystem.
35538 The device containing the file has no room for the new
35542 The call was interrupted by the user.
35548 @unnumberedsubsubsec unlink
35549 @cindex unlink, file-i/o system call
35554 int unlink(const char *pathname);
35558 @samp{Funlink,@var{pathnameptr}/@var{len}}
35560 @item Return value:
35561 On success, zero is returned. On error, -1 is returned.
35567 No access to the file or the path of the file.
35570 The system does not allow unlinking of directories.
35573 The file @var{pathname} cannot be unlinked because it's
35574 being used by another process.
35577 @var{pathnameptr} is an invalid pointer value.
35580 @var{pathname} was too long.
35583 A directory component in @var{pathname} does not exist.
35586 A component of the path is not a directory.
35589 The file is on a read-only filesystem.
35592 The call was interrupted by the user.
35598 @unnumberedsubsubsec stat/fstat
35599 @cindex fstat, file-i/o system call
35600 @cindex stat, file-i/o system call
35605 int stat(const char *pathname, struct stat *buf);
35606 int fstat(int fd, struct stat *buf);
35610 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
35611 @samp{Ffstat,@var{fd},@var{bufptr}}
35613 @item Return value:
35614 On success, zero is returned. On error, -1 is returned.
35620 @var{fd} is not a valid open file.
35623 A directory component in @var{pathname} does not exist or the
35624 path is an empty string.
35627 A component of the path is not a directory.
35630 @var{pathnameptr} is an invalid pointer value.
35633 No access to the file or the path of the file.
35636 @var{pathname} was too long.
35639 The call was interrupted by the user.
35645 @unnumberedsubsubsec gettimeofday
35646 @cindex gettimeofday, file-i/o system call
35651 int gettimeofday(struct timeval *tv, void *tz);
35655 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35657 @item Return value:
35658 On success, 0 is returned, -1 otherwise.
35664 @var{tz} is a non-NULL pointer.
35667 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35673 @unnumberedsubsubsec isatty
35674 @cindex isatty, file-i/o system call
35679 int isatty(int fd);
35683 @samp{Fisatty,@var{fd}}
35685 @item Return value:
35686 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
35692 The call was interrupted by the user.
35697 Note that the @code{isatty} call is treated as a special case: it returns
35698 1 to the target if the file descriptor is attached
35699 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
35700 would require implementing @code{ioctl} and would be more complex than
35705 @unnumberedsubsubsec system
35706 @cindex system, file-i/o system call
35711 int system(const char *command);
35715 @samp{Fsystem,@var{commandptr}/@var{len}}
35717 @item Return value:
35718 If @var{len} is zero, the return value indicates whether a shell is
35719 available. A zero return value indicates a shell is not available.
35720 For non-zero @var{len}, the value returned is -1 on error and the
35721 return status of the command otherwise. Only the exit status of the
35722 command is returned, which is extracted from the host's @code{system}
35723 return value by calling @code{WEXITSTATUS(retval)}. In case
35724 @file{/bin/sh} could not be executed, 127 is returned.
35730 The call was interrupted by the user.
35735 @value{GDBN} takes over the full task of calling the necessary host calls
35736 to perform the @code{system} call. The return value of @code{system} on
35737 the host is simplified before it's returned
35738 to the target. Any termination signal information from the child process
35739 is discarded, and the return value consists
35740 entirely of the exit status of the called command.
35742 Due to security concerns, the @code{system} call is by default refused
35743 by @value{GDBN}. The user has to allow this call explicitly with the
35744 @code{set remote system-call-allowed 1} command.
35747 @item set remote system-call-allowed
35748 @kindex set remote system-call-allowed
35749 Control whether to allow the @code{system} calls in the File I/O
35750 protocol for the remote target. The default is zero (disabled).
35752 @item show remote system-call-allowed
35753 @kindex show remote system-call-allowed
35754 Show whether the @code{system} calls are allowed in the File I/O
35758 @node Protocol-specific Representation of Datatypes
35759 @subsection Protocol-specific Representation of Datatypes
35760 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35763 * Integral Datatypes::
35765 * Memory Transfer::
35770 @node Integral Datatypes
35771 @unnumberedsubsubsec Integral Datatypes
35772 @cindex integral datatypes, in file-i/o protocol
35774 The integral datatypes used in the system calls are @code{int},
35775 @code{unsigned int}, @code{long}, @code{unsigned long},
35776 @code{mode_t}, and @code{time_t}.
35778 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35779 implemented as 32 bit values in this protocol.
35781 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35783 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35784 in @file{limits.h}) to allow range checking on host and target.
35786 @code{time_t} datatypes are defined as seconds since the Epoch.
35788 All integral datatypes transferred as part of a memory read or write of a
35789 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35792 @node Pointer Values
35793 @unnumberedsubsubsec Pointer Values
35794 @cindex pointer values, in file-i/o protocol
35796 Pointers to target data are transmitted as they are. An exception
35797 is made for pointers to buffers for which the length isn't
35798 transmitted as part of the function call, namely strings. Strings
35799 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35806 which is a pointer to data of length 18 bytes at position 0x1aaf.
35807 The length is defined as the full string length in bytes, including
35808 the trailing null byte. For example, the string @code{"hello world"}
35809 at address 0x123456 is transmitted as
35815 @node Memory Transfer
35816 @unnumberedsubsubsec Memory Transfer
35817 @cindex memory transfer, in file-i/o protocol
35819 Structured data which is transferred using a memory read or write (for
35820 example, a @code{struct stat}) is expected to be in a protocol-specific format
35821 with all scalar multibyte datatypes being big endian. Translation to
35822 this representation needs to be done both by the target before the @code{F}
35823 packet is sent, and by @value{GDBN} before
35824 it transfers memory to the target. Transferred pointers to structured
35825 data should point to the already-coerced data at any time.
35829 @unnumberedsubsubsec struct stat
35830 @cindex struct stat, in file-i/o protocol
35832 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35833 is defined as follows:
35837 unsigned int st_dev; /* device */
35838 unsigned int st_ino; /* inode */
35839 mode_t st_mode; /* protection */
35840 unsigned int st_nlink; /* number of hard links */
35841 unsigned int st_uid; /* user ID of owner */
35842 unsigned int st_gid; /* group ID of owner */
35843 unsigned int st_rdev; /* device type (if inode device) */
35844 unsigned long st_size; /* total size, in bytes */
35845 unsigned long st_blksize; /* blocksize for filesystem I/O */
35846 unsigned long st_blocks; /* number of blocks allocated */
35847 time_t st_atime; /* time of last access */
35848 time_t st_mtime; /* time of last modification */
35849 time_t st_ctime; /* time of last change */
35853 The integral datatypes conform to the definitions given in the
35854 appropriate section (see @ref{Integral Datatypes}, for details) so this
35855 structure is of size 64 bytes.
35857 The values of several fields have a restricted meaning and/or
35863 A value of 0 represents a file, 1 the console.
35866 No valid meaning for the target. Transmitted unchanged.
35869 Valid mode bits are described in @ref{Constants}. Any other
35870 bits have currently no meaning for the target.
35875 No valid meaning for the target. Transmitted unchanged.
35880 These values have a host and file system dependent
35881 accuracy. Especially on Windows hosts, the file system may not
35882 support exact timing values.
35885 The target gets a @code{struct stat} of the above representation and is
35886 responsible for coercing it to the target representation before
35889 Note that due to size differences between the host, target, and protocol
35890 representations of @code{struct stat} members, these members could eventually
35891 get truncated on the target.
35893 @node struct timeval
35894 @unnumberedsubsubsec struct timeval
35895 @cindex struct timeval, in file-i/o protocol
35897 The buffer of type @code{struct timeval} used by the File-I/O protocol
35898 is defined as follows:
35902 time_t tv_sec; /* second */
35903 long tv_usec; /* microsecond */
35907 The integral datatypes conform to the definitions given in the
35908 appropriate section (see @ref{Integral Datatypes}, for details) so this
35909 structure is of size 8 bytes.
35912 @subsection Constants
35913 @cindex constants, in file-i/o protocol
35915 The following values are used for the constants inside of the
35916 protocol. @value{GDBN} and target are responsible for translating these
35917 values before and after the call as needed.
35928 @unnumberedsubsubsec Open Flags
35929 @cindex open flags, in file-i/o protocol
35931 All values are given in hexadecimal representation.
35943 @node mode_t Values
35944 @unnumberedsubsubsec mode_t Values
35945 @cindex mode_t values, in file-i/o protocol
35947 All values are given in octal representation.
35964 @unnumberedsubsubsec Errno Values
35965 @cindex errno values, in file-i/o protocol
35967 All values are given in decimal representation.
35992 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35993 any error value not in the list of supported error numbers.
35996 @unnumberedsubsubsec Lseek Flags
35997 @cindex lseek flags, in file-i/o protocol
36006 @unnumberedsubsubsec Limits
36007 @cindex limits, in file-i/o protocol
36009 All values are given in decimal representation.
36012 INT_MIN -2147483648
36014 UINT_MAX 4294967295
36015 LONG_MIN -9223372036854775808
36016 LONG_MAX 9223372036854775807
36017 ULONG_MAX 18446744073709551615
36020 @node File-I/O Examples
36021 @subsection File-I/O Examples
36022 @cindex file-i/o examples
36024 Example sequence of a write call, file descriptor 3, buffer is at target
36025 address 0x1234, 6 bytes should be written:
36028 <- @code{Fwrite,3,1234,6}
36029 @emph{request memory read from target}
36032 @emph{return "6 bytes written"}
36036 Example sequence of a read call, file descriptor 3, buffer is at target
36037 address 0x1234, 6 bytes should be read:
36040 <- @code{Fread,3,1234,6}
36041 @emph{request memory write to target}
36042 -> @code{X1234,6:XXXXXX}
36043 @emph{return "6 bytes read"}
36047 Example sequence of a read call, call fails on the host due to invalid
36048 file descriptor (@code{EBADF}):
36051 <- @code{Fread,3,1234,6}
36055 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
36059 <- @code{Fread,3,1234,6}
36064 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
36068 <- @code{Fread,3,1234,6}
36069 -> @code{X1234,6:XXXXXX}
36073 @node Library List Format
36074 @section Library List Format
36075 @cindex library list format, remote protocol
36077 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
36078 same process as your application to manage libraries. In this case,
36079 @value{GDBN} can use the loader's symbol table and normal memory
36080 operations to maintain a list of shared libraries. On other
36081 platforms, the operating system manages loaded libraries.
36082 @value{GDBN} can not retrieve the list of currently loaded libraries
36083 through memory operations, so it uses the @samp{qXfer:libraries:read}
36084 packet (@pxref{qXfer library list read}) instead. The remote stub
36085 queries the target's operating system and reports which libraries
36088 The @samp{qXfer:libraries:read} packet returns an XML document which
36089 lists loaded libraries and their offsets. Each library has an
36090 associated name and one or more segment or section base addresses,
36091 which report where the library was loaded in memory.
36093 For the common case of libraries that are fully linked binaries, the
36094 library should have a list of segments. If the target supports
36095 dynamic linking of a relocatable object file, its library XML element
36096 should instead include a list of allocated sections. The segment or
36097 section bases are start addresses, not relocation offsets; they do not
36098 depend on the library's link-time base addresses.
36100 @value{GDBN} must be linked with the Expat library to support XML
36101 library lists. @xref{Expat}.
36103 A simple memory map, with one loaded library relocated by a single
36104 offset, looks like this:
36108 <library name="/lib/libc.so.6">
36109 <segment address="0x10000000"/>
36114 Another simple memory map, with one loaded library with three
36115 allocated sections (.text, .data, .bss), looks like this:
36119 <library name="sharedlib.o">
36120 <section address="0x10000000"/>
36121 <section address="0x20000000"/>
36122 <section address="0x30000000"/>
36127 The format of a library list is described by this DTD:
36130 <!-- library-list: Root element with versioning -->
36131 <!ELEMENT library-list (library)*>
36132 <!ATTLIST library-list version CDATA #FIXED "1.0">
36133 <!ELEMENT library (segment*, section*)>
36134 <!ATTLIST library name CDATA #REQUIRED>
36135 <!ELEMENT segment EMPTY>
36136 <!ATTLIST segment address CDATA #REQUIRED>
36137 <!ELEMENT section EMPTY>
36138 <!ATTLIST section address CDATA #REQUIRED>
36141 In addition, segments and section descriptors cannot be mixed within a
36142 single library element, and you must supply at least one segment or
36143 section for each library.
36145 @node Memory Map Format
36146 @section Memory Map Format
36147 @cindex memory map format
36149 To be able to write into flash memory, @value{GDBN} needs to obtain a
36150 memory map from the target. This section describes the format of the
36153 The memory map is obtained using the @samp{qXfer:memory-map:read}
36154 (@pxref{qXfer memory map read}) packet and is an XML document that
36155 lists memory regions.
36157 @value{GDBN} must be linked with the Expat library to support XML
36158 memory maps. @xref{Expat}.
36160 The top-level structure of the document is shown below:
36163 <?xml version="1.0"?>
36164 <!DOCTYPE memory-map
36165 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36166 "http://sourceware.org/gdb/gdb-memory-map.dtd">
36172 Each region can be either:
36177 A region of RAM starting at @var{addr} and extending for @var{length}
36181 <memory type="ram" start="@var{addr}" length="@var{length}"/>
36186 A region of read-only memory:
36189 <memory type="rom" start="@var{addr}" length="@var{length}"/>
36194 A region of flash memory, with erasure blocks @var{blocksize}
36198 <memory type="flash" start="@var{addr}" length="@var{length}">
36199 <property name="blocksize">@var{blocksize}</property>
36205 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
36206 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
36207 packets to write to addresses in such ranges.
36209 The formal DTD for memory map format is given below:
36212 <!-- ................................................... -->
36213 <!-- Memory Map XML DTD ................................ -->
36214 <!-- File: memory-map.dtd .............................. -->
36215 <!-- .................................... .............. -->
36216 <!-- memory-map.dtd -->
36217 <!-- memory-map: Root element with versioning -->
36218 <!ELEMENT memory-map (memory | property)>
36219 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
36220 <!ELEMENT memory (property)>
36221 <!-- memory: Specifies a memory region,
36222 and its type, or device. -->
36223 <!ATTLIST memory type CDATA #REQUIRED
36224 start CDATA #REQUIRED
36225 length CDATA #REQUIRED
36226 device CDATA #IMPLIED>
36227 <!-- property: Generic attribute tag -->
36228 <!ELEMENT property (#PCDATA | property)*>
36229 <!ATTLIST property name CDATA #REQUIRED>
36232 @node Thread List Format
36233 @section Thread List Format
36234 @cindex thread list format
36236 To efficiently update the list of threads and their attributes,
36237 @value{GDBN} issues the @samp{qXfer:threads:read} packet
36238 (@pxref{qXfer threads read}) and obtains the XML document with
36239 the following structure:
36242 <?xml version="1.0"?>
36244 <thread id="id" core="0">
36245 ... description ...
36250 Each @samp{thread} element must have the @samp{id} attribute that
36251 identifies the thread (@pxref{thread-id syntax}). The
36252 @samp{core} attribute, if present, specifies which processor core
36253 the thread was last executing on. The content of the of @samp{thread}
36254 element is interpreted as human-readable auxilliary information.
36256 @node Traceframe Info Format
36257 @section Traceframe Info Format
36258 @cindex traceframe info format
36260 To be able to know which objects in the inferior can be examined when
36261 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
36262 memory ranges, registers and trace state variables that have been
36263 collected in a traceframe.
36265 This list is obtained using the @samp{qXfer:traceframe-info:read}
36266 (@pxref{qXfer traceframe info read}) packet and is an XML document.
36268 @value{GDBN} must be linked with the Expat library to support XML
36269 traceframe info discovery. @xref{Expat}.
36271 The top-level structure of the document is shown below:
36274 <?xml version="1.0"?>
36275 <!DOCTYPE traceframe-info
36276 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36277 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
36283 Each traceframe block can be either:
36288 A region of collected memory starting at @var{addr} and extending for
36289 @var{length} bytes from there:
36292 <memory start="@var{addr}" length="@var{length}"/>
36297 The formal DTD for the traceframe info format is given below:
36300 <!ELEMENT traceframe-info (memory)* >
36301 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
36303 <!ELEMENT memory EMPTY>
36304 <!ATTLIST memory start CDATA #REQUIRED
36305 length CDATA #REQUIRED>
36308 @include agentexpr.texi
36310 @node Target Descriptions
36311 @appendix Target Descriptions
36312 @cindex target descriptions
36314 @strong{Warning:} target descriptions are still under active development,
36315 and the contents and format may change between @value{GDBN} releases.
36316 The format is expected to stabilize in the future.
36318 One of the challenges of using @value{GDBN} to debug embedded systems
36319 is that there are so many minor variants of each processor
36320 architecture in use. It is common practice for vendors to start with
36321 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
36322 and then make changes to adapt it to a particular market niche. Some
36323 architectures have hundreds of variants, available from dozens of
36324 vendors. This leads to a number of problems:
36328 With so many different customized processors, it is difficult for
36329 the @value{GDBN} maintainers to keep up with the changes.
36331 Since individual variants may have short lifetimes or limited
36332 audiences, it may not be worthwhile to carry information about every
36333 variant in the @value{GDBN} source tree.
36335 When @value{GDBN} does support the architecture of the embedded system
36336 at hand, the task of finding the correct architecture name to give the
36337 @command{set architecture} command can be error-prone.
36340 To address these problems, the @value{GDBN} remote protocol allows a
36341 target system to not only identify itself to @value{GDBN}, but to
36342 actually describe its own features. This lets @value{GDBN} support
36343 processor variants it has never seen before --- to the extent that the
36344 descriptions are accurate, and that @value{GDBN} understands them.
36346 @value{GDBN} must be linked with the Expat library to support XML
36347 target descriptions. @xref{Expat}.
36350 * Retrieving Descriptions:: How descriptions are fetched from a target.
36351 * Target Description Format:: The contents of a target description.
36352 * Predefined Target Types:: Standard types available for target
36354 * Standard Target Features:: Features @value{GDBN} knows about.
36357 @node Retrieving Descriptions
36358 @section Retrieving Descriptions
36360 Target descriptions can be read from the target automatically, or
36361 specified by the user manually. The default behavior is to read the
36362 description from the target. @value{GDBN} retrieves it via the remote
36363 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
36364 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
36365 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
36366 XML document, of the form described in @ref{Target Description
36369 Alternatively, you can specify a file to read for the target description.
36370 If a file is set, the target will not be queried. The commands to
36371 specify a file are:
36374 @cindex set tdesc filename
36375 @item set tdesc filename @var{path}
36376 Read the target description from @var{path}.
36378 @cindex unset tdesc filename
36379 @item unset tdesc filename
36380 Do not read the XML target description from a file. @value{GDBN}
36381 will use the description supplied by the current target.
36383 @cindex show tdesc filename
36384 @item show tdesc filename
36385 Show the filename to read for a target description, if any.
36389 @node Target Description Format
36390 @section Target Description Format
36391 @cindex target descriptions, XML format
36393 A target description annex is an @uref{http://www.w3.org/XML/, XML}
36394 document which complies with the Document Type Definition provided in
36395 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
36396 means you can use generally available tools like @command{xmllint} to
36397 check that your feature descriptions are well-formed and valid.
36398 However, to help people unfamiliar with XML write descriptions for
36399 their targets, we also describe the grammar here.
36401 Target descriptions can identify the architecture of the remote target
36402 and (for some architectures) provide information about custom register
36403 sets. They can also identify the OS ABI of the remote target.
36404 @value{GDBN} can use this information to autoconfigure for your
36405 target, or to warn you if you connect to an unsupported target.
36407 Here is a simple target description:
36410 <target version="1.0">
36411 <architecture>i386:x86-64</architecture>
36416 This minimal description only says that the target uses
36417 the x86-64 architecture.
36419 A target description has the following overall form, with [ ] marking
36420 optional elements and @dots{} marking repeatable elements. The elements
36421 are explained further below.
36424 <?xml version="1.0"?>
36425 <!DOCTYPE target SYSTEM "gdb-target.dtd">
36426 <target version="1.0">
36427 @r{[}@var{architecture}@r{]}
36428 @r{[}@var{osabi}@r{]}
36429 @r{[}@var{compatible}@r{]}
36430 @r{[}@var{feature}@dots{}@r{]}
36435 The description is generally insensitive to whitespace and line
36436 breaks, under the usual common-sense rules. The XML version
36437 declaration and document type declaration can generally be omitted
36438 (@value{GDBN} does not require them), but specifying them may be
36439 useful for XML validation tools. The @samp{version} attribute for
36440 @samp{<target>} may also be omitted, but we recommend
36441 including it; if future versions of @value{GDBN} use an incompatible
36442 revision of @file{gdb-target.dtd}, they will detect and report
36443 the version mismatch.
36445 @subsection Inclusion
36446 @cindex target descriptions, inclusion
36449 @cindex <xi:include>
36452 It can sometimes be valuable to split a target description up into
36453 several different annexes, either for organizational purposes, or to
36454 share files between different possible target descriptions. You can
36455 divide a description into multiple files by replacing any element of
36456 the target description with an inclusion directive of the form:
36459 <xi:include href="@var{document}"/>
36463 When @value{GDBN} encounters an element of this form, it will retrieve
36464 the named XML @var{document}, and replace the inclusion directive with
36465 the contents of that document. If the current description was read
36466 using @samp{qXfer}, then so will be the included document;
36467 @var{document} will be interpreted as the name of an annex. If the
36468 current description was read from a file, @value{GDBN} will look for
36469 @var{document} as a file in the same directory where it found the
36470 original description.
36472 @subsection Architecture
36473 @cindex <architecture>
36475 An @samp{<architecture>} element has this form:
36478 <architecture>@var{arch}</architecture>
36481 @var{arch} is one of the architectures from the set accepted by
36482 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36485 @cindex @code{<osabi>}
36487 This optional field was introduced in @value{GDBN} version 7.0.
36488 Previous versions of @value{GDBN} ignore it.
36490 An @samp{<osabi>} element has this form:
36493 <osabi>@var{abi-name}</osabi>
36496 @var{abi-name} is an OS ABI name from the same selection accepted by
36497 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
36499 @subsection Compatible Architecture
36500 @cindex @code{<compatible>}
36502 This optional field was introduced in @value{GDBN} version 7.0.
36503 Previous versions of @value{GDBN} ignore it.
36505 A @samp{<compatible>} element has this form:
36508 <compatible>@var{arch}</compatible>
36511 @var{arch} is one of the architectures from the set accepted by
36512 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36514 A @samp{<compatible>} element is used to specify that the target
36515 is able to run binaries in some other than the main target architecture
36516 given by the @samp{<architecture>} element. For example, on the
36517 Cell Broadband Engine, the main architecture is @code{powerpc:common}
36518 or @code{powerpc:common64}, but the system is able to run binaries
36519 in the @code{spu} architecture as well. The way to describe this
36520 capability with @samp{<compatible>} is as follows:
36523 <architecture>powerpc:common</architecture>
36524 <compatible>spu</compatible>
36527 @subsection Features
36530 Each @samp{<feature>} describes some logical portion of the target
36531 system. Features are currently used to describe available CPU
36532 registers and the types of their contents. A @samp{<feature>} element
36536 <feature name="@var{name}">
36537 @r{[}@var{type}@dots{}@r{]}
36543 Each feature's name should be unique within the description. The name
36544 of a feature does not matter unless @value{GDBN} has some special
36545 knowledge of the contents of that feature; if it does, the feature
36546 should have its standard name. @xref{Standard Target Features}.
36550 Any register's value is a collection of bits which @value{GDBN} must
36551 interpret. The default interpretation is a two's complement integer,
36552 but other types can be requested by name in the register description.
36553 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
36554 Target Types}), and the description can define additional composite types.
36556 Each type element must have an @samp{id} attribute, which gives
36557 a unique (within the containing @samp{<feature>}) name to the type.
36558 Types must be defined before they are used.
36561 Some targets offer vector registers, which can be treated as arrays
36562 of scalar elements. These types are written as @samp{<vector>} elements,
36563 specifying the array element type, @var{type}, and the number of elements,
36567 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
36571 If a register's value is usefully viewed in multiple ways, define it
36572 with a union type containing the useful representations. The
36573 @samp{<union>} element contains one or more @samp{<field>} elements,
36574 each of which has a @var{name} and a @var{type}:
36577 <union id="@var{id}">
36578 <field name="@var{name}" type="@var{type}"/>
36584 If a register's value is composed from several separate values, define
36585 it with a structure type. There are two forms of the @samp{<struct>}
36586 element; a @samp{<struct>} element must either contain only bitfields
36587 or contain no bitfields. If the structure contains only bitfields,
36588 its total size in bytes must be specified, each bitfield must have an
36589 explicit start and end, and bitfields are automatically assigned an
36590 integer type. The field's @var{start} should be less than or
36591 equal to its @var{end}, and zero represents the least significant bit.
36594 <struct id="@var{id}" size="@var{size}">
36595 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36600 If the structure contains no bitfields, then each field has an
36601 explicit type, and no implicit padding is added.
36604 <struct id="@var{id}">
36605 <field name="@var{name}" type="@var{type}"/>
36611 If a register's value is a series of single-bit flags, define it with
36612 a flags type. The @samp{<flags>} element has an explicit @var{size}
36613 and contains one or more @samp{<field>} elements. Each field has a
36614 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
36618 <flags id="@var{id}" size="@var{size}">
36619 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36624 @subsection Registers
36627 Each register is represented as an element with this form:
36630 <reg name="@var{name}"
36631 bitsize="@var{size}"
36632 @r{[}regnum="@var{num}"@r{]}
36633 @r{[}save-restore="@var{save-restore}"@r{]}
36634 @r{[}type="@var{type}"@r{]}
36635 @r{[}group="@var{group}"@r{]}/>
36639 The components are as follows:
36644 The register's name; it must be unique within the target description.
36647 The register's size, in bits.
36650 The register's number. If omitted, a register's number is one greater
36651 than that of the previous register (either in the current feature or in
36652 a preceeding feature); the first register in the target description
36653 defaults to zero. This register number is used to read or write
36654 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36655 packets, and registers appear in the @code{g} and @code{G} packets
36656 in order of increasing register number.
36659 Whether the register should be preserved across inferior function
36660 calls; this must be either @code{yes} or @code{no}. The default is
36661 @code{yes}, which is appropriate for most registers except for
36662 some system control registers; this is not related to the target's
36666 The type of the register. @var{type} may be a predefined type, a type
36667 defined in the current feature, or one of the special types @code{int}
36668 and @code{float}. @code{int} is an integer type of the correct size
36669 for @var{bitsize}, and @code{float} is a floating point type (in the
36670 architecture's normal floating point format) of the correct size for
36671 @var{bitsize}. The default is @code{int}.
36674 The register group to which this register belongs. @var{group} must
36675 be either @code{general}, @code{float}, or @code{vector}. If no
36676 @var{group} is specified, @value{GDBN} will not display the register
36677 in @code{info registers}.
36681 @node Predefined Target Types
36682 @section Predefined Target Types
36683 @cindex target descriptions, predefined types
36685 Type definitions in the self-description can build up composite types
36686 from basic building blocks, but can not define fundamental types. Instead,
36687 standard identifiers are provided by @value{GDBN} for the fundamental
36688 types. The currently supported types are:
36697 Signed integer types holding the specified number of bits.
36704 Unsigned integer types holding the specified number of bits.
36708 Pointers to unspecified code and data. The program counter and
36709 any dedicated return address register may be marked as code
36710 pointers; printing a code pointer converts it into a symbolic
36711 address. The stack pointer and any dedicated address registers
36712 may be marked as data pointers.
36715 Single precision IEEE floating point.
36718 Double precision IEEE floating point.
36721 The 12-byte extended precision format used by ARM FPA registers.
36724 The 10-byte extended precision format used by x87 registers.
36727 32bit @sc{eflags} register used by x86.
36730 32bit @sc{mxcsr} register used by x86.
36734 @node Standard Target Features
36735 @section Standard Target Features
36736 @cindex target descriptions, standard features
36738 A target description must contain either no registers or all the
36739 target's registers. If the description contains no registers, then
36740 @value{GDBN} will assume a default register layout, selected based on
36741 the architecture. If the description contains any registers, the
36742 default layout will not be used; the standard registers must be
36743 described in the target description, in such a way that @value{GDBN}
36744 can recognize them.
36746 This is accomplished by giving specific names to feature elements
36747 which contain standard registers. @value{GDBN} will look for features
36748 with those names and verify that they contain the expected registers;
36749 if any known feature is missing required registers, or if any required
36750 feature is missing, @value{GDBN} will reject the target
36751 description. You can add additional registers to any of the
36752 standard features --- @value{GDBN} will display them just as if
36753 they were added to an unrecognized feature.
36755 This section lists the known features and their expected contents.
36756 Sample XML documents for these features are included in the
36757 @value{GDBN} source tree, in the directory @file{gdb/features}.
36759 Names recognized by @value{GDBN} should include the name of the
36760 company or organization which selected the name, and the overall
36761 architecture to which the feature applies; so e.g.@: the feature
36762 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36764 The names of registers are not case sensitive for the purpose
36765 of recognizing standard features, but @value{GDBN} will only display
36766 registers using the capitalization used in the description.
36773 * PowerPC Features::
36778 @subsection ARM Features
36779 @cindex target descriptions, ARM features
36781 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36783 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36784 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36786 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36787 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36788 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36791 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36792 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36794 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36795 it should contain at least registers @samp{wR0} through @samp{wR15} and
36796 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36797 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36799 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36800 should contain at least registers @samp{d0} through @samp{d15}. If
36801 they are present, @samp{d16} through @samp{d31} should also be included.
36802 @value{GDBN} will synthesize the single-precision registers from
36803 halves of the double-precision registers.
36805 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36806 need to contain registers; it instructs @value{GDBN} to display the
36807 VFP double-precision registers as vectors and to synthesize the
36808 quad-precision registers from pairs of double-precision registers.
36809 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36810 be present and include 32 double-precision registers.
36812 @node i386 Features
36813 @subsection i386 Features
36814 @cindex target descriptions, i386 features
36816 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36817 targets. It should describe the following registers:
36821 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36823 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36825 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36826 @samp{fs}, @samp{gs}
36828 @samp{st0} through @samp{st7}
36830 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36831 @samp{foseg}, @samp{fooff} and @samp{fop}
36834 The register sets may be different, depending on the target.
36836 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36837 describe registers:
36841 @samp{xmm0} through @samp{xmm7} for i386
36843 @samp{xmm0} through @samp{xmm15} for amd64
36848 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36849 @samp{org.gnu.gdb.i386.sse} feature. It should
36850 describe the upper 128 bits of @sc{ymm} registers:
36854 @samp{ymm0h} through @samp{ymm7h} for i386
36856 @samp{ymm0h} through @samp{ymm15h} for amd64
36859 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36860 describe a single register, @samp{orig_eax}.
36862 @node MIPS Features
36863 @subsection MIPS Features
36864 @cindex target descriptions, MIPS features
36866 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36867 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36868 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36871 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36872 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36873 registers. They may be 32-bit or 64-bit depending on the target.
36875 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36876 it may be optional in a future version of @value{GDBN}. It should
36877 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36878 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
36880 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
36881 contain a single register, @samp{restart}, which is used by the
36882 Linux kernel to control restartable syscalls.
36884 @node M68K Features
36885 @subsection M68K Features
36886 @cindex target descriptions, M68K features
36889 @item @samp{org.gnu.gdb.m68k.core}
36890 @itemx @samp{org.gnu.gdb.coldfire.core}
36891 @itemx @samp{org.gnu.gdb.fido.core}
36892 One of those features must be always present.
36893 The feature that is present determines which flavor of m68k is
36894 used. The feature that is present should contain registers
36895 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
36896 @samp{sp}, @samp{ps} and @samp{pc}.
36898 @item @samp{org.gnu.gdb.coldfire.fp}
36899 This feature is optional. If present, it should contain registers
36900 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
36904 @node PowerPC Features
36905 @subsection PowerPC Features
36906 @cindex target descriptions, PowerPC features
36908 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
36909 targets. It should contain registers @samp{r0} through @samp{r31},
36910 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
36911 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
36913 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
36914 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
36916 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
36917 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
36920 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
36921 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
36922 will combine these registers with the floating point registers
36923 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
36924 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
36925 through @samp{vs63}, the set of vector registers for POWER7.
36927 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
36928 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
36929 @samp{spefscr}. SPE targets should provide 32-bit registers in
36930 @samp{org.gnu.gdb.power.core} and provide the upper halves in
36931 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
36932 these to present registers @samp{ev0} through @samp{ev31} to the
36935 @node Operating System Information
36936 @appendix Operating System Information
36937 @cindex operating system information
36943 Users of @value{GDBN} often wish to obtain information about the state of
36944 the operating system running on the target---for example the list of
36945 processes, or the list of open files. This section describes the
36946 mechanism that makes it possible. This mechanism is similar to the
36947 target features mechanism (@pxref{Target Descriptions}), but focuses
36948 on a different aspect of target.
36950 Operating system information is retrived from the target via the
36951 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
36952 read}). The object name in the request should be @samp{osdata}, and
36953 the @var{annex} identifies the data to be fetched.
36956 @appendixsection Process list
36957 @cindex operating system information, process list
36959 When requesting the process list, the @var{annex} field in the
36960 @samp{qXfer} request should be @samp{processes}. The returned data is
36961 an XML document. The formal syntax of this document is defined in
36962 @file{gdb/features/osdata.dtd}.
36964 An example document is:
36967 <?xml version="1.0"?>
36968 <!DOCTYPE target SYSTEM "osdata.dtd">
36969 <osdata type="processes">
36971 <column name="pid">1</column>
36972 <column name="user">root</column>
36973 <column name="command">/sbin/init</column>
36974 <column name="cores">1,2,3</column>
36979 Each item should include a column whose name is @samp{pid}. The value
36980 of that column should identify the process on the target. The
36981 @samp{user} and @samp{command} columns are optional, and will be
36982 displayed by @value{GDBN}. The @samp{cores} column, if present,
36983 should contain a comma-separated list of cores that this process
36984 is running on. Target may provide additional columns,
36985 which @value{GDBN} currently ignores.
36987 @node Trace File Format
36988 @appendix Trace File Format
36989 @cindex trace file format
36991 The trace file comes in three parts: a header, a textual description
36992 section, and a trace frame section with binary data.
36994 The header has the form @code{\x7fTRACE0\n}. The first byte is
36995 @code{0x7f} so as to indicate that the file contains binary data,
36996 while the @code{0} is a version number that may have different values
36999 The description section consists of multiple lines of @sc{ascii} text
37000 separated by newline characters (@code{0xa}). The lines may include a
37001 variety of optional descriptive or context-setting information, such
37002 as tracepoint definitions or register set size. @value{GDBN} will
37003 ignore any line that it does not recognize. An empty line marks the end
37006 @c FIXME add some specific types of data
37008 The trace frame section consists of a number of consecutive frames.
37009 Each frame begins with a two-byte tracepoint number, followed by a
37010 four-byte size giving the amount of data in the frame. The data in
37011 the frame consists of a number of blocks, each introduced by a
37012 character indicating its type (at least register, memory, and trace
37013 state variable). The data in this section is raw binary, not a
37014 hexadecimal or other encoding; its endianness matches the target's
37017 @c FIXME bi-arch may require endianness/arch info in description section
37020 @item R @var{bytes}
37021 Register block. The number and ordering of bytes matches that of a
37022 @code{g} packet in the remote protocol. Note that these are the
37023 actual bytes, in target order and @value{GDBN} register order, not a
37024 hexadecimal encoding.
37026 @item M @var{address} @var{length} @var{bytes}...
37027 Memory block. This is a contiguous block of memory, at the 8-byte
37028 address @var{address}, with a 2-byte length @var{length}, followed by
37029 @var{length} bytes.
37031 @item V @var{number} @var{value}
37032 Trace state variable block. This records the 8-byte signed value
37033 @var{value} of trace state variable numbered @var{number}.
37037 Future enhancements of the trace file format may include additional types
37040 @node Index Section Format
37041 @appendix @code{.gdb_index} section format
37042 @cindex .gdb_index section format
37043 @cindex index section format
37045 This section documents the index section that is created by @code{save
37046 gdb-index} (@pxref{Index Files}). The index section is
37047 DWARF-specific; some knowledge of DWARF is assumed in this
37050 The mapped index file format is designed to be directly
37051 @code{mmap}able on any architecture. In most cases, a datum is
37052 represented using a little-endian 32-bit integer value, called an
37053 @code{offset_type}. Big endian machines must byte-swap the values
37054 before using them. Exceptions to this rule are noted. The data is
37055 laid out such that alignment is always respected.
37057 A mapped index consists of several areas, laid out in order.
37061 The file header. This is a sequence of values, of @code{offset_type}
37062 unless otherwise noted:
37066 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
37067 Version 4 differs by its hashing function.
37070 The offset, from the start of the file, of the CU list.
37073 The offset, from the start of the file, of the types CU list. Note
37074 that this area can be empty, in which case this offset will be equal
37075 to the next offset.
37078 The offset, from the start of the file, of the address area.
37081 The offset, from the start of the file, of the symbol table.
37084 The offset, from the start of the file, of the constant pool.
37088 The CU list. This is a sequence of pairs of 64-bit little-endian
37089 values, sorted by the CU offset. The first element in each pair is
37090 the offset of a CU in the @code{.debug_info} section. The second
37091 element in each pair is the length of that CU. References to a CU
37092 elsewhere in the map are done using a CU index, which is just the
37093 0-based index into this table. Note that if there are type CUs, then
37094 conceptually CUs and type CUs form a single list for the purposes of
37098 The types CU list. This is a sequence of triplets of 64-bit
37099 little-endian values. In a triplet, the first value is the CU offset,
37100 the second value is the type offset in the CU, and the third value is
37101 the type signature. The types CU list is not sorted.
37104 The address area. The address area consists of a sequence of address
37105 entries. Each address entry has three elements:
37109 The low address. This is a 64-bit little-endian value.
37112 The high address. This is a 64-bit little-endian value. Like
37113 @code{DW_AT_high_pc}, the value is one byte beyond the end.
37116 The CU index. This is an @code{offset_type} value.
37120 The symbol table. This is an open-addressed hash table. The size of
37121 the hash table is always a power of 2.
37123 Each slot in the hash table consists of a pair of @code{offset_type}
37124 values. The first value is the offset of the symbol's name in the
37125 constant pool. The second value is the offset of the CU vector in the
37128 If both values are 0, then this slot in the hash table is empty. This
37129 is ok because while 0 is a valid constant pool index, it cannot be a
37130 valid index for both a string and a CU vector.
37132 The hash value for a table entry is computed by applying an
37133 iterative hash function to the symbol's name. Starting with an
37134 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
37135 the string is incorporated into the hash using the formula depending on the
37140 The formula is @code{r = r * 67 + c - 113}.
37143 The formula is @code{r = r * 67 + tolower (c) - 113}.
37146 The terminating @samp{\0} is not incorporated into the hash.
37148 The step size used in the hash table is computed via
37149 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
37150 value, and @samp{size} is the size of the hash table. The step size
37151 is used to find the next candidate slot when handling a hash
37154 The names of C@t{++} symbols in the hash table are canonicalized. We
37155 don't currently have a simple description of the canonicalization
37156 algorithm; if you intend to create new index sections, you must read
37160 The constant pool. This is simply a bunch of bytes. It is organized
37161 so that alignment is correct: CU vectors are stored first, followed by
37164 A CU vector in the constant pool is a sequence of @code{offset_type}
37165 values. The first value is the number of CU indices in the vector.
37166 Each subsequent value is the index of a CU in the CU list. This
37167 element in the hash table is used to indicate which CUs define the
37170 A string in the constant pool is zero-terminated.
37175 @node GNU Free Documentation License
37176 @appendix GNU Free Documentation License
37185 % I think something like @colophon should be in texinfo. In the
37187 \long\def\colophon{\hbox to0pt{}\vfill
37188 \centerline{The body of this manual is set in}
37189 \centerline{\fontname\tenrm,}
37190 \centerline{with headings in {\bf\fontname\tenbf}}
37191 \centerline{and examples in {\tt\fontname\tentt}.}
37192 \centerline{{\it\fontname\tenit\/},}
37193 \centerline{{\bf\fontname\tenbf}, and}
37194 \centerline{{\sl\fontname\tensl\/}}
37195 \centerline{are used for emphasis.}\vfill}
37197 % Blame: doc@cygnus.com, 1991.