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 978-0-9831592-3-0 @*
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.
1351 @cindex shell escape
1352 @item shell @var{command-string}
1353 @itemx !@var{command-string}
1354 Invoke a standard shell to execute @var{command-string}.
1355 Note that no space is needed between @code{!} and @var{command-string}.
1356 If it exists, the environment variable @code{SHELL} determines which
1357 shell to run. Otherwise @value{GDBN} uses the default shell
1358 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1361 The utility @code{make} is often needed in development environments.
1362 You do not have to use the @code{shell} command for this purpose in
1367 @cindex calling make
1368 @item make @var{make-args}
1369 Execute the @code{make} program with the specified
1370 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1373 @node Logging Output
1374 @section Logging Output
1375 @cindex logging @value{GDBN} output
1376 @cindex save @value{GDBN} output to a file
1378 You may want to save the output of @value{GDBN} commands to a file.
1379 There are several commands to control @value{GDBN}'s logging.
1383 @item set logging on
1385 @item set logging off
1387 @cindex logging file name
1388 @item set logging file @var{file}
1389 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1390 @item set logging overwrite [on|off]
1391 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1392 you want @code{set logging on} to overwrite the logfile instead.
1393 @item set logging redirect [on|off]
1394 By default, @value{GDBN} output will go to both the terminal and the logfile.
1395 Set @code{redirect} if you want output to go only to the log file.
1396 @kindex show logging
1398 Show the current values of the logging settings.
1402 @chapter @value{GDBN} Commands
1404 You can abbreviate a @value{GDBN} command to the first few letters of the command
1405 name, if that abbreviation is unambiguous; and you can repeat certain
1406 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1407 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1408 show you the alternatives available, if there is more than one possibility).
1411 * Command Syntax:: How to give commands to @value{GDBN}
1412 * Completion:: Command completion
1413 * Help:: How to ask @value{GDBN} for help
1416 @node Command Syntax
1417 @section Command Syntax
1419 A @value{GDBN} command is a single line of input. There is no limit on
1420 how long it can be. It starts with a command name, which is followed by
1421 arguments whose meaning depends on the command name. For example, the
1422 command @code{step} accepts an argument which is the number of times to
1423 step, as in @samp{step 5}. You can also use the @code{step} command
1424 with no arguments. Some commands do not allow any arguments.
1426 @cindex abbreviation
1427 @value{GDBN} command names may always be truncated if that abbreviation is
1428 unambiguous. Other possible command abbreviations are listed in the
1429 documentation for individual commands. In some cases, even ambiguous
1430 abbreviations are allowed; for example, @code{s} is specially defined as
1431 equivalent to @code{step} even though there are other commands whose
1432 names start with @code{s}. You can test abbreviations by using them as
1433 arguments to the @code{help} command.
1435 @cindex repeating commands
1436 @kindex RET @r{(repeat last command)}
1437 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1438 repeat the previous command. Certain commands (for example, @code{run})
1439 will not repeat this way; these are commands whose unintentional
1440 repetition might cause trouble and which you are unlikely to want to
1441 repeat. User-defined commands can disable this feature; see
1442 @ref{Define, dont-repeat}.
1444 The @code{list} and @code{x} commands, when you repeat them with
1445 @key{RET}, construct new arguments rather than repeating
1446 exactly as typed. This permits easy scanning of source or memory.
1448 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1449 output, in a way similar to the common utility @code{more}
1450 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1451 @key{RET} too many in this situation, @value{GDBN} disables command
1452 repetition after any command that generates this sort of display.
1454 @kindex # @r{(a comment)}
1456 Any text from a @kbd{#} to the end of the line is a comment; it does
1457 nothing. This is useful mainly in command files (@pxref{Command
1458 Files,,Command Files}).
1460 @cindex repeating command sequences
1461 @kindex Ctrl-o @r{(operate-and-get-next)}
1462 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1463 commands. This command accepts the current line, like @key{RET}, and
1464 then fetches the next line relative to the current line from the history
1468 @section Command Completion
1471 @cindex word completion
1472 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1473 only one possibility; it can also show you what the valid possibilities
1474 are for the next word in a command, at any time. This works for @value{GDBN}
1475 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1477 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1478 of a word. If there is only one possibility, @value{GDBN} fills in the
1479 word, and waits for you to finish the command (or press @key{RET} to
1480 enter it). For example, if you type
1482 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1483 @c complete accuracy in these examples; space introduced for clarity.
1484 @c If texinfo enhancements make it unnecessary, it would be nice to
1485 @c replace " @key" by "@key" in the following...
1487 (@value{GDBP}) info bre @key{TAB}
1491 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1492 the only @code{info} subcommand beginning with @samp{bre}:
1495 (@value{GDBP}) info breakpoints
1499 You can either press @key{RET} at this point, to run the @code{info
1500 breakpoints} command, or backspace and enter something else, if
1501 @samp{breakpoints} does not look like the command you expected. (If you
1502 were sure you wanted @code{info breakpoints} in the first place, you
1503 might as well just type @key{RET} immediately after @samp{info bre},
1504 to exploit command abbreviations rather than command completion).
1506 If there is more than one possibility for the next word when you press
1507 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1508 characters and try again, or just press @key{TAB} a second time;
1509 @value{GDBN} displays all the possible completions for that word. For
1510 example, you might want to set a breakpoint on a subroutine whose name
1511 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1512 just sounds the bell. Typing @key{TAB} again displays all the
1513 function names in your program that begin with those characters, for
1517 (@value{GDBP}) b make_ @key{TAB}
1518 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1519 make_a_section_from_file make_environ
1520 make_abs_section make_function_type
1521 make_blockvector make_pointer_type
1522 make_cleanup make_reference_type
1523 make_command make_symbol_completion_list
1524 (@value{GDBP}) b make_
1528 After displaying the available possibilities, @value{GDBN} copies your
1529 partial input (@samp{b make_} in the example) so you can finish the
1532 If you just want to see the list of alternatives in the first place, you
1533 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1534 means @kbd{@key{META} ?}. You can type this either by holding down a
1535 key designated as the @key{META} shift on your keyboard (if there is
1536 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1538 @cindex quotes in commands
1539 @cindex completion of quoted strings
1540 Sometimes the string you need, while logically a ``word'', may contain
1541 parentheses or other characters that @value{GDBN} normally excludes from
1542 its notion of a word. To permit word completion to work in this
1543 situation, you may enclose words in @code{'} (single quote marks) in
1544 @value{GDBN} commands.
1546 The most likely situation where you might need this is in typing the
1547 name of a C@t{++} function. This is because C@t{++} allows function
1548 overloading (multiple definitions of the same function, distinguished
1549 by argument type). For example, when you want to set a breakpoint you
1550 may need to distinguish whether you mean the version of @code{name}
1551 that takes an @code{int} parameter, @code{name(int)}, or the version
1552 that takes a @code{float} parameter, @code{name(float)}. To use the
1553 word-completion facilities in this situation, type a single quote
1554 @code{'} at the beginning of the function name. This alerts
1555 @value{GDBN} that it may need to consider more information than usual
1556 when you press @key{TAB} or @kbd{M-?} to request word completion:
1559 (@value{GDBP}) b 'bubble( @kbd{M-?}
1560 bubble(double,double) bubble(int,int)
1561 (@value{GDBP}) b 'bubble(
1564 In some cases, @value{GDBN} can tell that completing a name requires using
1565 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1566 completing as much as it can) if you do not type the quote in the first
1570 (@value{GDBP}) b bub @key{TAB}
1571 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1572 (@value{GDBP}) b 'bubble(
1576 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1577 you have not yet started typing the argument list when you ask for
1578 completion on an overloaded symbol.
1580 For more information about overloaded functions, see @ref{C Plus Plus
1581 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1582 overload-resolution off} to disable overload resolution;
1583 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1585 @cindex completion of structure field names
1586 @cindex structure field name completion
1587 @cindex completion of union field names
1588 @cindex union field name completion
1589 When completing in an expression which looks up a field in a
1590 structure, @value{GDBN} also tries@footnote{The completer can be
1591 confused by certain kinds of invalid expressions. Also, it only
1592 examines the static type of the expression, not the dynamic type.} to
1593 limit completions to the field names available in the type of the
1597 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1598 magic to_fputs to_rewind
1599 to_data to_isatty to_write
1600 to_delete to_put to_write_async_safe
1605 This is because the @code{gdb_stdout} is a variable of the type
1606 @code{struct ui_file} that is defined in @value{GDBN} sources as
1613 ui_file_flush_ftype *to_flush;
1614 ui_file_write_ftype *to_write;
1615 ui_file_write_async_safe_ftype *to_write_async_safe;
1616 ui_file_fputs_ftype *to_fputs;
1617 ui_file_read_ftype *to_read;
1618 ui_file_delete_ftype *to_delete;
1619 ui_file_isatty_ftype *to_isatty;
1620 ui_file_rewind_ftype *to_rewind;
1621 ui_file_put_ftype *to_put;
1628 @section Getting Help
1629 @cindex online documentation
1632 You can always ask @value{GDBN} itself for information on its commands,
1633 using the command @code{help}.
1636 @kindex h @r{(@code{help})}
1639 You can use @code{help} (abbreviated @code{h}) with no arguments to
1640 display a short list of named classes of commands:
1644 List of classes of commands:
1646 aliases -- Aliases of other commands
1647 breakpoints -- Making program stop at certain points
1648 data -- Examining data
1649 files -- Specifying and examining files
1650 internals -- Maintenance commands
1651 obscure -- Obscure features
1652 running -- Running the program
1653 stack -- Examining the stack
1654 status -- Status inquiries
1655 support -- Support facilities
1656 tracepoints -- Tracing of program execution without
1657 stopping the program
1658 user-defined -- User-defined commands
1660 Type "help" followed by a class name for a list of
1661 commands in that class.
1662 Type "help" followed by command name for full
1664 Command name abbreviations are allowed if unambiguous.
1667 @c the above line break eliminates huge line overfull...
1669 @item help @var{class}
1670 Using one of the general help classes as an argument, you can get a
1671 list of the individual commands in that class. For example, here is the
1672 help display for the class @code{status}:
1675 (@value{GDBP}) help status
1680 @c Line break in "show" line falsifies real output, but needed
1681 @c to fit in smallbook page size.
1682 info -- Generic command for showing things
1683 about the program being debugged
1684 show -- Generic command for showing things
1687 Type "help" followed by command name for full
1689 Command name abbreviations are allowed if unambiguous.
1693 @item help @var{command}
1694 With a command name as @code{help} argument, @value{GDBN} displays a
1695 short paragraph on how to use that command.
1698 @item apropos @var{args}
1699 The @code{apropos} command searches through all of the @value{GDBN}
1700 commands, and their documentation, for the regular expression specified in
1701 @var{args}. It prints out all matches found. For example:
1712 set symbol-reloading -- Set dynamic symbol table reloading
1713 multiple times in one run
1714 show symbol-reloading -- Show dynamic symbol table reloading
1715 multiple times in one run
1720 @item complete @var{args}
1721 The @code{complete @var{args}} command lists all the possible completions
1722 for the beginning of a command. Use @var{args} to specify the beginning of the
1723 command you want completed. For example:
1729 @noindent results in:
1740 @noindent This is intended for use by @sc{gnu} Emacs.
1743 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1744 and @code{show} to inquire about the state of your program, or the state
1745 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1746 manual introduces each of them in the appropriate context. The listings
1747 under @code{info} and under @code{show} in the Index point to
1748 all the sub-commands. @xref{Index}.
1753 @kindex i @r{(@code{info})}
1755 This command (abbreviated @code{i}) is for describing the state of your
1756 program. For example, you can show the arguments passed to a function
1757 with @code{info args}, list the registers currently in use with @code{info
1758 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1759 You can get a complete list of the @code{info} sub-commands with
1760 @w{@code{help info}}.
1764 You can assign the result of an expression to an environment variable with
1765 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1766 @code{set prompt $}.
1770 In contrast to @code{info}, @code{show} is for describing the state of
1771 @value{GDBN} itself.
1772 You can change most of the things you can @code{show}, by using the
1773 related command @code{set}; for example, you can control what number
1774 system is used for displays with @code{set radix}, or simply inquire
1775 which is currently in use with @code{show radix}.
1778 To display all the settable parameters and their current
1779 values, you can use @code{show} with no arguments; you may also use
1780 @code{info set}. Both commands produce the same display.
1781 @c FIXME: "info set" violates the rule that "info" is for state of
1782 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1783 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1787 Here are three miscellaneous @code{show} subcommands, all of which are
1788 exceptional in lacking corresponding @code{set} commands:
1791 @kindex show version
1792 @cindex @value{GDBN} version number
1794 Show what version of @value{GDBN} is running. You should include this
1795 information in @value{GDBN} bug-reports. If multiple versions of
1796 @value{GDBN} are in use at your site, you may need to determine which
1797 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1798 commands are introduced, and old ones may wither away. Also, many
1799 system vendors ship variant versions of @value{GDBN}, and there are
1800 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1801 The version number is the same as the one announced when you start
1804 @kindex show copying
1805 @kindex info copying
1806 @cindex display @value{GDBN} copyright
1809 Display information about permission for copying @value{GDBN}.
1811 @kindex show warranty
1812 @kindex info warranty
1814 @itemx info warranty
1815 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1816 if your version of @value{GDBN} comes with one.
1821 @chapter Running Programs Under @value{GDBN}
1823 When you run a program under @value{GDBN}, you must first generate
1824 debugging information when you compile it.
1826 You may start @value{GDBN} with its arguments, if any, in an environment
1827 of your choice. If you are doing native debugging, you may redirect
1828 your program's input and output, debug an already running process, or
1829 kill a child process.
1832 * Compilation:: Compiling for debugging
1833 * Starting:: Starting your program
1834 * Arguments:: Your program's arguments
1835 * Environment:: Your program's environment
1837 * Working Directory:: Your program's working directory
1838 * Input/Output:: Your program's input and output
1839 * Attach:: Debugging an already-running process
1840 * Kill Process:: Killing the child process
1842 * Inferiors and Programs:: Debugging multiple inferiors and programs
1843 * Threads:: Debugging programs with multiple threads
1844 * Forks:: Debugging forks
1845 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1849 @section Compiling for Debugging
1851 In order to debug a program effectively, you need to generate
1852 debugging information when you compile it. This debugging information
1853 is stored in the object file; it describes the data type of each
1854 variable or function and the correspondence between source line numbers
1855 and addresses in the executable code.
1857 To request debugging information, specify the @samp{-g} option when you run
1860 Programs that are to be shipped to your customers are compiled with
1861 optimizations, using the @samp{-O} compiler option. However, some
1862 compilers are unable to handle the @samp{-g} and @samp{-O} options
1863 together. Using those compilers, you cannot generate optimized
1864 executables containing debugging information.
1866 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1867 without @samp{-O}, making it possible to debug optimized code. We
1868 recommend that you @emph{always} use @samp{-g} whenever you compile a
1869 program. You may think your program is correct, but there is no sense
1870 in pushing your luck. For more information, see @ref{Optimized Code}.
1872 Older versions of the @sc{gnu} C compiler permitted a variant option
1873 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1874 format; if your @sc{gnu} C compiler has this option, do not use it.
1876 @value{GDBN} knows about preprocessor macros and can show you their
1877 expansion (@pxref{Macros}). Most compilers do not include information
1878 about preprocessor macros in the debugging information if you specify
1879 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1880 the @sc{gnu} C compiler, provides macro information if you are using
1881 the DWARF debugging format, and specify the option @option{-g3}.
1883 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1884 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1885 information on @value{NGCC} options affecting debug information.
1887 You will have the best debugging experience if you use the latest
1888 version of the DWARF debugging format that your compiler supports.
1889 DWARF is currently the most expressive and best supported debugging
1890 format in @value{GDBN}.
1894 @section Starting your Program
1900 @kindex r @r{(@code{run})}
1903 Use the @code{run} command to start your program under @value{GDBN}.
1904 You must first specify the program name (except on VxWorks) with an
1905 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1906 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1907 (@pxref{Files, ,Commands to Specify Files}).
1911 If you are running your program in an execution environment that
1912 supports processes, @code{run} creates an inferior process and makes
1913 that process run your program. In some environments without processes,
1914 @code{run} jumps to the start of your program. Other targets,
1915 like @samp{remote}, are always running. If you get an error
1916 message like this one:
1919 The "remote" target does not support "run".
1920 Try "help target" or "continue".
1924 then use @code{continue} to run your program. You may need @code{load}
1925 first (@pxref{load}).
1927 The execution of a program is affected by certain information it
1928 receives from its superior. @value{GDBN} provides ways to specify this
1929 information, which you must do @emph{before} starting your program. (You
1930 can change it after starting your program, but such changes only affect
1931 your program the next time you start it.) This information may be
1932 divided into four categories:
1935 @item The @emph{arguments.}
1936 Specify the arguments to give your program as the arguments of the
1937 @code{run} command. If a shell is available on your target, the shell
1938 is used to pass the arguments, so that you may use normal conventions
1939 (such as wildcard expansion or variable substitution) in describing
1941 In Unix systems, you can control which shell is used with the
1942 @code{SHELL} environment variable.
1943 @xref{Arguments, ,Your Program's Arguments}.
1945 @item The @emph{environment.}
1946 Your program normally inherits its environment from @value{GDBN}, but you can
1947 use the @value{GDBN} commands @code{set environment} and @code{unset
1948 environment} to change parts of the environment that affect
1949 your program. @xref{Environment, ,Your Program's Environment}.
1951 @item The @emph{working directory.}
1952 Your program inherits its working directory from @value{GDBN}. You can set
1953 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1954 @xref{Working Directory, ,Your Program's Working Directory}.
1956 @item The @emph{standard input and output.}
1957 Your program normally uses the same device for standard input and
1958 standard output as @value{GDBN} is using. You can redirect input and output
1959 in the @code{run} command line, or you can use the @code{tty} command to
1960 set a different device for your program.
1961 @xref{Input/Output, ,Your Program's Input and Output}.
1964 @emph{Warning:} While input and output redirection work, you cannot use
1965 pipes to pass the output of the program you are debugging to another
1966 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1970 When you issue the @code{run} command, your program begins to execute
1971 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1972 of how to arrange for your program to stop. Once your program has
1973 stopped, you may call functions in your program, using the @code{print}
1974 or @code{call} commands. @xref{Data, ,Examining Data}.
1976 If the modification time of your symbol file has changed since the last
1977 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1978 table, and reads it again. When it does this, @value{GDBN} tries to retain
1979 your current breakpoints.
1984 @cindex run to main procedure
1985 The name of the main procedure can vary from language to language.
1986 With C or C@t{++}, the main procedure name is always @code{main}, but
1987 other languages such as Ada do not require a specific name for their
1988 main procedure. The debugger provides a convenient way to start the
1989 execution of the program and to stop at the beginning of the main
1990 procedure, depending on the language used.
1992 The @samp{start} command does the equivalent of setting a temporary
1993 breakpoint at the beginning of the main procedure and then invoking
1994 the @samp{run} command.
1996 @cindex elaboration phase
1997 Some programs contain an @dfn{elaboration} phase where some startup code is
1998 executed before the main procedure is called. This depends on the
1999 languages used to write your program. In C@t{++}, for instance,
2000 constructors for static and global objects are executed before
2001 @code{main} is called. It is therefore possible that the debugger stops
2002 before reaching the main procedure. However, the temporary breakpoint
2003 will remain to halt execution.
2005 Specify the arguments to give to your program as arguments to the
2006 @samp{start} command. These arguments will be given verbatim to the
2007 underlying @samp{run} command. Note that the same arguments will be
2008 reused if no argument is provided during subsequent calls to
2009 @samp{start} or @samp{run}.
2011 It is sometimes necessary to debug the program during elaboration. In
2012 these cases, using the @code{start} command would stop the execution of
2013 your program too late, as the program would have already completed the
2014 elaboration phase. Under these circumstances, insert breakpoints in your
2015 elaboration code before running your program.
2017 @kindex set exec-wrapper
2018 @item set exec-wrapper @var{wrapper}
2019 @itemx show exec-wrapper
2020 @itemx unset exec-wrapper
2021 When @samp{exec-wrapper} is set, the specified wrapper is used to
2022 launch programs for debugging. @value{GDBN} starts your program
2023 with a shell command of the form @kbd{exec @var{wrapper}
2024 @var{program}}. Quoting is added to @var{program} and its
2025 arguments, but not to @var{wrapper}, so you should add quotes if
2026 appropriate for your shell. The wrapper runs until it executes
2027 your program, and then @value{GDBN} takes control.
2029 You can use any program that eventually calls @code{execve} with
2030 its arguments as a wrapper. Several standard Unix utilities do
2031 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2032 with @code{exec "$@@"} will also work.
2034 For example, you can use @code{env} to pass an environment variable to
2035 the debugged program, without setting the variable in your shell's
2039 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2043 This command is available when debugging locally on most targets, excluding
2044 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2046 @kindex set disable-randomization
2047 @item set disable-randomization
2048 @itemx set disable-randomization on
2049 This option (enabled by default in @value{GDBN}) will turn off the native
2050 randomization of the virtual address space of the started program. This option
2051 is useful for multiple debugging sessions to make the execution better
2052 reproducible and memory addresses reusable across debugging sessions.
2054 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2055 On @sc{gnu}/Linux you can get the same behavior using
2058 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2061 @item set disable-randomization off
2062 Leave the behavior of the started executable unchanged. Some bugs rear their
2063 ugly heads only when the program is loaded at certain addresses. If your bug
2064 disappears when you run the program under @value{GDBN}, that might be because
2065 @value{GDBN} by default disables the address randomization on platforms, such
2066 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2067 disable-randomization off} to try to reproduce such elusive bugs.
2069 On targets where it is available, virtual address space randomization
2070 protects the programs against certain kinds of security attacks. In these
2071 cases the attacker needs to know the exact location of a concrete executable
2072 code. Randomizing its location makes it impossible to inject jumps misusing
2073 a code at its expected addresses.
2075 Prelinking shared libraries provides a startup performance advantage but it
2076 makes addresses in these libraries predictable for privileged processes by
2077 having just unprivileged access at the target system. Reading the shared
2078 library binary gives enough information for assembling the malicious code
2079 misusing it. Still even a prelinked shared library can get loaded at a new
2080 random address just requiring the regular relocation process during the
2081 startup. Shared libraries not already prelinked are always loaded at
2082 a randomly chosen address.
2084 Position independent executables (PIE) contain position independent code
2085 similar to the shared libraries and therefore such executables get loaded at
2086 a randomly chosen address upon startup. PIE executables always load even
2087 already prelinked shared libraries at a random address. You can build such
2088 executable using @command{gcc -fPIE -pie}.
2090 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2091 (as long as the randomization is enabled).
2093 @item show disable-randomization
2094 Show the current setting of the explicit disable of the native randomization of
2095 the virtual address space of the started program.
2100 @section Your Program's Arguments
2102 @cindex arguments (to your program)
2103 The arguments to your program can be specified by the arguments of the
2105 They are passed to a shell, which expands wildcard characters and
2106 performs redirection of I/O, and thence to your program. Your
2107 @code{SHELL} environment variable (if it exists) specifies what shell
2108 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2109 the default shell (@file{/bin/sh} on Unix).
2111 On non-Unix systems, the program is usually invoked directly by
2112 @value{GDBN}, which emulates I/O redirection via the appropriate system
2113 calls, and the wildcard characters are expanded by the startup code of
2114 the program, not by the shell.
2116 @code{run} with no arguments uses the same arguments used by the previous
2117 @code{run}, or those set by the @code{set args} command.
2122 Specify the arguments to be used the next time your program is run. If
2123 @code{set args} has no arguments, @code{run} executes your program
2124 with no arguments. Once you have run your program with arguments,
2125 using @code{set args} before the next @code{run} is the only way to run
2126 it again without arguments.
2130 Show the arguments to give your program when it is started.
2134 @section Your Program's Environment
2136 @cindex environment (of your program)
2137 The @dfn{environment} consists of a set of environment variables and
2138 their values. Environment variables conventionally record such things as
2139 your user name, your home directory, your terminal type, and your search
2140 path for programs to run. Usually you set up environment variables with
2141 the shell and they are inherited by all the other programs you run. When
2142 debugging, it can be useful to try running your program with a modified
2143 environment without having to start @value{GDBN} over again.
2147 @item path @var{directory}
2148 Add @var{directory} to the front of the @code{PATH} environment variable
2149 (the search path for executables) that will be passed to your program.
2150 The value of @code{PATH} used by @value{GDBN} does not change.
2151 You may specify several directory names, separated by whitespace or by a
2152 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2153 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2154 is moved to the front, so it is searched sooner.
2156 You can use the string @samp{$cwd} to refer to whatever is the current
2157 working directory at the time @value{GDBN} searches the path. If you
2158 use @samp{.} instead, it refers to the directory where you executed the
2159 @code{path} command. @value{GDBN} replaces @samp{.} in the
2160 @var{directory} argument (with the current path) before adding
2161 @var{directory} to the search path.
2162 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2163 @c document that, since repeating it would be a no-op.
2167 Display the list of search paths for executables (the @code{PATH}
2168 environment variable).
2170 @kindex show environment
2171 @item show environment @r{[}@var{varname}@r{]}
2172 Print the value of environment variable @var{varname} to be given to
2173 your program when it starts. If you do not supply @var{varname},
2174 print the names and values of all environment variables to be given to
2175 your program. You can abbreviate @code{environment} as @code{env}.
2177 @kindex set environment
2178 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2179 Set environment variable @var{varname} to @var{value}. The value
2180 changes for your program only, not for @value{GDBN} itself. @var{value} may
2181 be any string; the values of environment variables are just strings, and
2182 any interpretation is supplied by your program itself. The @var{value}
2183 parameter is optional; if it is eliminated, the variable is set to a
2185 @c "any string" here does not include leading, trailing
2186 @c blanks. Gnu asks: does anyone care?
2188 For example, this command:
2195 tells the debugged program, when subsequently run, that its user is named
2196 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2197 are not actually required.)
2199 @kindex unset environment
2200 @item unset environment @var{varname}
2201 Remove variable @var{varname} from the environment to be passed to your
2202 program. This is different from @samp{set env @var{varname} =};
2203 @code{unset environment} removes the variable from the environment,
2204 rather than assigning it an empty value.
2207 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2209 by your @code{SHELL} environment variable if it exists (or
2210 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2211 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2212 @file{.bashrc} for BASH---any variables you set in that file affect
2213 your program. You may wish to move setting of environment variables to
2214 files that are only run when you sign on, such as @file{.login} or
2217 @node Working Directory
2218 @section Your Program's Working Directory
2220 @cindex working directory (of your program)
2221 Each time you start your program with @code{run}, it inherits its
2222 working directory from the current working directory of @value{GDBN}.
2223 The @value{GDBN} working directory is initially whatever it inherited
2224 from its parent process (typically the shell), but you can specify a new
2225 working directory in @value{GDBN} with the @code{cd} command.
2227 The @value{GDBN} working directory also serves as a default for the commands
2228 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2233 @cindex change working directory
2234 @item cd @var{directory}
2235 Set the @value{GDBN} working directory to @var{directory}.
2239 Print the @value{GDBN} working directory.
2242 It is generally impossible to find the current working directory of
2243 the process being debugged (since a program can change its directory
2244 during its run). If you work on a system where @value{GDBN} is
2245 configured with the @file{/proc} support, you can use the @code{info
2246 proc} command (@pxref{SVR4 Process Information}) to find out the
2247 current working directory of the debuggee.
2250 @section Your Program's Input and Output
2255 By default, the program you run under @value{GDBN} does input and output to
2256 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2257 to its own terminal modes to interact with you, but it records the terminal
2258 modes your program was using and switches back to them when you continue
2259 running your program.
2262 @kindex info terminal
2264 Displays information recorded by @value{GDBN} about the terminal modes your
2268 You can redirect your program's input and/or output using shell
2269 redirection with the @code{run} command. For example,
2276 starts your program, diverting its output to the file @file{outfile}.
2279 @cindex controlling terminal
2280 Another way to specify where your program should do input and output is
2281 with the @code{tty} command. This command accepts a file name as
2282 argument, and causes this file to be the default for future @code{run}
2283 commands. It also resets the controlling terminal for the child
2284 process, for future @code{run} commands. For example,
2291 directs that processes started with subsequent @code{run} commands
2292 default to do input and output on the terminal @file{/dev/ttyb} and have
2293 that as their controlling terminal.
2295 An explicit redirection in @code{run} overrides the @code{tty} command's
2296 effect on the input/output device, but not its effect on the controlling
2299 When you use the @code{tty} command or redirect input in the @code{run}
2300 command, only the input @emph{for your program} is affected. The input
2301 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2302 for @code{set inferior-tty}.
2304 @cindex inferior tty
2305 @cindex set inferior controlling terminal
2306 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2307 display the name of the terminal that will be used for future runs of your
2311 @item set inferior-tty /dev/ttyb
2312 @kindex set inferior-tty
2313 Set the tty for the program being debugged to /dev/ttyb.
2315 @item show inferior-tty
2316 @kindex show inferior-tty
2317 Show the current tty for the program being debugged.
2321 @section Debugging an Already-running Process
2326 @item attach @var{process-id}
2327 This command attaches to a running process---one that was started
2328 outside @value{GDBN}. (@code{info files} shows your active
2329 targets.) The command takes as argument a process ID. The usual way to
2330 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2331 or with the @samp{jobs -l} shell command.
2333 @code{attach} does not repeat if you press @key{RET} a second time after
2334 executing the command.
2337 To use @code{attach}, your program must be running in an environment
2338 which supports processes; for example, @code{attach} does not work for
2339 programs on bare-board targets that lack an operating system. You must
2340 also have permission to send the process a signal.
2342 When you use @code{attach}, the debugger finds the program running in
2343 the process first by looking in the current working directory, then (if
2344 the program is not found) by using the source file search path
2345 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2346 the @code{file} command to load the program. @xref{Files, ,Commands to
2349 The first thing @value{GDBN} does after arranging to debug the specified
2350 process is to stop it. You can examine and modify an attached process
2351 with all the @value{GDBN} commands that are ordinarily available when
2352 you start processes with @code{run}. You can insert breakpoints; you
2353 can step and continue; you can modify storage. If you would rather the
2354 process continue running, you may use the @code{continue} command after
2355 attaching @value{GDBN} to the process.
2360 When you have finished debugging the attached process, you can use the
2361 @code{detach} command to release it from @value{GDBN} control. Detaching
2362 the process continues its execution. After the @code{detach} command,
2363 that process and @value{GDBN} become completely independent once more, and you
2364 are ready to @code{attach} another process or start one with @code{run}.
2365 @code{detach} does not repeat if you press @key{RET} again after
2366 executing the command.
2369 If you exit @value{GDBN} while you have an attached process, you detach
2370 that process. If you use the @code{run} command, you kill that process.
2371 By default, @value{GDBN} asks for confirmation if you try to do either of these
2372 things; you can control whether or not you need to confirm by using the
2373 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2377 @section Killing the Child Process
2382 Kill the child process in which your program is running under @value{GDBN}.
2385 This command is useful if you wish to debug a core dump instead of a
2386 running process. @value{GDBN} ignores any core dump file while your program
2389 On some operating systems, a program cannot be executed outside @value{GDBN}
2390 while you have breakpoints set on it inside @value{GDBN}. You can use the
2391 @code{kill} command in this situation to permit running your program
2392 outside the debugger.
2394 The @code{kill} command is also useful if you wish to recompile and
2395 relink your program, since on many systems it is impossible to modify an
2396 executable file while it is running in a process. In this case, when you
2397 next type @code{run}, @value{GDBN} notices that the file has changed, and
2398 reads the symbol table again (while trying to preserve your current
2399 breakpoint settings).
2401 @node Inferiors and Programs
2402 @section Debugging Multiple Inferiors and Programs
2404 @value{GDBN} lets you run and debug multiple programs in a single
2405 session. In addition, @value{GDBN} on some systems may let you run
2406 several programs simultaneously (otherwise you have to exit from one
2407 before starting another). In the most general case, you can have
2408 multiple threads of execution in each of multiple processes, launched
2409 from multiple executables.
2412 @value{GDBN} represents the state of each program execution with an
2413 object called an @dfn{inferior}. An inferior typically corresponds to
2414 a process, but is more general and applies also to targets that do not
2415 have processes. Inferiors may be created before a process runs, and
2416 may be retained after a process exits. Inferiors have unique
2417 identifiers that are different from process ids. Usually each
2418 inferior will also have its own distinct address space, although some
2419 embedded targets may have several inferiors running in different parts
2420 of a single address space. Each inferior may in turn have multiple
2421 threads running in it.
2423 To find out what inferiors exist at any moment, use @w{@code{info
2427 @kindex info inferiors
2428 @item info inferiors
2429 Print a list of all inferiors currently being managed by @value{GDBN}.
2431 @value{GDBN} displays for each inferior (in this order):
2435 the inferior number assigned by @value{GDBN}
2438 the target system's inferior identifier
2441 the name of the executable the inferior is running.
2446 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2447 indicates the current inferior.
2451 @c end table here to get a little more width for example
2454 (@value{GDBP}) info inferiors
2455 Num Description Executable
2456 2 process 2307 hello
2457 * 1 process 3401 goodbye
2460 To switch focus between inferiors, use the @code{inferior} command:
2463 @kindex inferior @var{infno}
2464 @item inferior @var{infno}
2465 Make inferior number @var{infno} the current inferior. The argument
2466 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2467 in the first field of the @samp{info inferiors} display.
2471 You can get multiple executables into a debugging session via the
2472 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2473 systems @value{GDBN} can add inferiors to the debug session
2474 automatically by following calls to @code{fork} and @code{exec}. To
2475 remove inferiors from the debugging session use the
2476 @w{@code{remove-inferiors}} command.
2479 @kindex add-inferior
2480 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2481 Adds @var{n} inferiors to be run using @var{executable} as the
2482 executable. @var{n} defaults to 1. If no executable is specified,
2483 the inferiors begins empty, with no program. You can still assign or
2484 change the program assigned to the inferior at any time by using the
2485 @code{file} command with the executable name as its argument.
2487 @kindex clone-inferior
2488 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2489 Adds @var{n} inferiors ready to execute the same program as inferior
2490 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2491 number of the current inferior. This is a convenient command when you
2492 want to run another instance of the inferior you are debugging.
2495 (@value{GDBP}) info inferiors
2496 Num Description Executable
2497 * 1 process 29964 helloworld
2498 (@value{GDBP}) clone-inferior
2501 (@value{GDBP}) info inferiors
2502 Num Description Executable
2504 * 1 process 29964 helloworld
2507 You can now simply switch focus to inferior 2 and run it.
2509 @kindex remove-inferiors
2510 @item remove-inferiors @var{infno}@dots{}
2511 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2512 possible to remove an inferior that is running with this command. For
2513 those, use the @code{kill} or @code{detach} command first.
2517 To quit debugging one of the running inferiors that is not the current
2518 inferior, you can either detach from it by using the @w{@code{detach
2519 inferior}} command (allowing it to run independently), or kill it
2520 using the @w{@code{kill inferiors}} command:
2523 @kindex detach inferiors @var{infno}@dots{}
2524 @item detach inferior @var{infno}@dots{}
2525 Detach from the inferior or inferiors identified by @value{GDBN}
2526 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2527 still stays on the list of inferiors shown by @code{info inferiors},
2528 but its Description will show @samp{<null>}.
2530 @kindex kill inferiors @var{infno}@dots{}
2531 @item kill inferiors @var{infno}@dots{}
2532 Kill the inferior or inferiors identified by @value{GDBN} inferior
2533 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2534 stays on the list of inferiors shown by @code{info inferiors}, but its
2535 Description will show @samp{<null>}.
2538 After the successful completion of a command such as @code{detach},
2539 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2540 a normal process exit, the inferior is still valid and listed with
2541 @code{info inferiors}, ready to be restarted.
2544 To be notified when inferiors are started or exit under @value{GDBN}'s
2545 control use @w{@code{set print inferior-events}}:
2548 @kindex set print inferior-events
2549 @cindex print messages on inferior start and exit
2550 @item set print inferior-events
2551 @itemx set print inferior-events on
2552 @itemx set print inferior-events off
2553 The @code{set print inferior-events} command allows you to enable or
2554 disable printing of messages when @value{GDBN} notices that new
2555 inferiors have started or that inferiors have exited or have been
2556 detached. By default, these messages will not be printed.
2558 @kindex show print inferior-events
2559 @item show print inferior-events
2560 Show whether messages will be printed when @value{GDBN} detects that
2561 inferiors have started, exited or have been detached.
2564 Many commands will work the same with multiple programs as with a
2565 single program: e.g., @code{print myglobal} will simply display the
2566 value of @code{myglobal} in the current inferior.
2569 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2570 get more info about the relationship of inferiors, programs, address
2571 spaces in a debug session. You can do that with the @w{@code{maint
2572 info program-spaces}} command.
2575 @kindex maint info program-spaces
2576 @item maint info program-spaces
2577 Print a list of all program spaces currently being managed by
2580 @value{GDBN} displays for each program space (in this order):
2584 the program space number assigned by @value{GDBN}
2587 the name of the executable loaded into the program space, with e.g.,
2588 the @code{file} command.
2593 An asterisk @samp{*} preceding the @value{GDBN} program space number
2594 indicates the current program space.
2596 In addition, below each program space line, @value{GDBN} prints extra
2597 information that isn't suitable to display in tabular form. For
2598 example, the list of inferiors bound to the program space.
2601 (@value{GDBP}) maint info program-spaces
2604 Bound inferiors: ID 1 (process 21561)
2608 Here we can see that no inferior is running the program @code{hello},
2609 while @code{process 21561} is running the program @code{goodbye}. On
2610 some targets, it is possible that multiple inferiors are bound to the
2611 same program space. The most common example is that of debugging both
2612 the parent and child processes of a @code{vfork} call. For example,
2615 (@value{GDBP}) maint info program-spaces
2618 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2621 Here, both inferior 2 and inferior 1 are running in the same program
2622 space as a result of inferior 1 having executed a @code{vfork} call.
2626 @section Debugging Programs with Multiple Threads
2628 @cindex threads of execution
2629 @cindex multiple threads
2630 @cindex switching threads
2631 In some operating systems, such as HP-UX and Solaris, a single program
2632 may have more than one @dfn{thread} of execution. The precise semantics
2633 of threads differ from one operating system to another, but in general
2634 the threads of a single program are akin to multiple processes---except
2635 that they share one address space (that is, they can all examine and
2636 modify the same variables). On the other hand, each thread has its own
2637 registers and execution stack, and perhaps private memory.
2639 @value{GDBN} provides these facilities for debugging multi-thread
2643 @item automatic notification of new threads
2644 @item @samp{thread @var{threadno}}, a command to switch among threads
2645 @item @samp{info threads}, a command to inquire about existing threads
2646 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2647 a command to apply a command to a list of threads
2648 @item thread-specific breakpoints
2649 @item @samp{set print thread-events}, which controls printing of
2650 messages on thread start and exit.
2651 @item @samp{set libthread-db-search-path @var{path}}, which lets
2652 the user specify which @code{libthread_db} to use if the default choice
2653 isn't compatible with the program.
2657 @emph{Warning:} These facilities are not yet available on every
2658 @value{GDBN} configuration where the operating system supports threads.
2659 If your @value{GDBN} does not support threads, these commands have no
2660 effect. For example, a system without thread support shows no output
2661 from @samp{info threads}, and always rejects the @code{thread} command,
2665 (@value{GDBP}) info threads
2666 (@value{GDBP}) thread 1
2667 Thread ID 1 not known. Use the "info threads" command to
2668 see the IDs of currently known threads.
2670 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2671 @c doesn't support threads"?
2674 @cindex focus of debugging
2675 @cindex current thread
2676 The @value{GDBN} thread debugging facility allows you to observe all
2677 threads while your program runs---but whenever @value{GDBN} takes
2678 control, one thread in particular is always the focus of debugging.
2679 This thread is called the @dfn{current thread}. Debugging commands show
2680 program information from the perspective of the current thread.
2682 @cindex @code{New} @var{systag} message
2683 @cindex thread identifier (system)
2684 @c FIXME-implementors!! It would be more helpful if the [New...] message
2685 @c included GDB's numeric thread handle, so you could just go to that
2686 @c thread without first checking `info threads'.
2687 Whenever @value{GDBN} detects a new thread in your program, it displays
2688 the target system's identification for the thread with a message in the
2689 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2690 whose form varies depending on the particular system. For example, on
2691 @sc{gnu}/Linux, you might see
2694 [New Thread 0x41e02940 (LWP 25582)]
2698 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2699 the @var{systag} is simply something like @samp{process 368}, with no
2702 @c FIXME!! (1) Does the [New...] message appear even for the very first
2703 @c thread of a program, or does it only appear for the
2704 @c second---i.e.@: when it becomes obvious we have a multithread
2706 @c (2) *Is* there necessarily a first thread always? Or do some
2707 @c multithread systems permit starting a program with multiple
2708 @c threads ab initio?
2710 @cindex thread number
2711 @cindex thread identifier (GDB)
2712 For debugging purposes, @value{GDBN} associates its own thread
2713 number---always a single integer---with each thread in your program.
2716 @kindex info threads
2717 @item info threads @r{[}@var{id}@dots{}@r{]}
2718 Display a summary of all threads currently in your program. Optional
2719 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2720 means to print information only about the specified thread or threads.
2721 @value{GDBN} displays for each thread (in this order):
2725 the thread number assigned by @value{GDBN}
2728 the target system's thread identifier (@var{systag})
2731 the thread's name, if one is known. A thread can either be named by
2732 the user (see @code{thread name}, below), or, in some cases, by the
2736 the current stack frame summary for that thread
2740 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2741 indicates the current thread.
2745 @c end table here to get a little more width for example
2748 (@value{GDBP}) info threads
2750 3 process 35 thread 27 0x34e5 in sigpause ()
2751 2 process 35 thread 23 0x34e5 in sigpause ()
2752 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2756 On Solaris, you can display more information about user threads with a
2757 Solaris-specific command:
2760 @item maint info sol-threads
2761 @kindex maint info sol-threads
2762 @cindex thread info (Solaris)
2763 Display info on Solaris user threads.
2767 @kindex thread @var{threadno}
2768 @item thread @var{threadno}
2769 Make thread number @var{threadno} the current thread. The command
2770 argument @var{threadno} is the internal @value{GDBN} thread number, as
2771 shown in the first field of the @samp{info threads} display.
2772 @value{GDBN} responds by displaying the system identifier of the thread
2773 you selected, and its current stack frame summary:
2776 (@value{GDBP}) thread 2
2777 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2778 #0 some_function (ignore=0x0) at example.c:8
2779 8 printf ("hello\n");
2783 As with the @samp{[New @dots{}]} message, the form of the text after
2784 @samp{Switching to} depends on your system's conventions for identifying
2787 @vindex $_thread@r{, convenience variable}
2788 The debugger convenience variable @samp{$_thread} contains the number
2789 of the current thread. You may find this useful in writing breakpoint
2790 conditional expressions, command scripts, and so forth. See
2791 @xref{Convenience Vars,, Convenience Variables}, for general
2792 information on convenience variables.
2794 @kindex thread apply
2795 @cindex apply command to several threads
2796 @item thread apply [@var{threadno} | all] @var{command}
2797 The @code{thread apply} command allows you to apply the named
2798 @var{command} to one or more threads. Specify the numbers of the
2799 threads that you want affected with the command argument
2800 @var{threadno}. It can be a single thread number, one of the numbers
2801 shown in the first field of the @samp{info threads} display; or it
2802 could be a range of thread numbers, as in @code{2-4}. To apply a
2803 command to all threads, type @kbd{thread apply all @var{command}}.
2806 @cindex name a thread
2807 @item thread name [@var{name}]
2808 This command assigns a name to the current thread. If no argument is
2809 given, any existing user-specified name is removed. The thread name
2810 appears in the @samp{info threads} display.
2812 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2813 determine the name of the thread as given by the OS. On these
2814 systems, a name specified with @samp{thread name} will override the
2815 system-give name, and removing the user-specified name will cause
2816 @value{GDBN} to once again display the system-specified name.
2819 @cindex search for a thread
2820 @item thread find [@var{regexp}]
2821 Search for and display thread ids whose name or @var{systag}
2822 matches the supplied regular expression.
2824 As well as being the complement to the @samp{thread name} command,
2825 this command also allows you to identify a thread by its target
2826 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2830 (@value{GDBN}) thread find 26688
2831 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2832 (@value{GDBN}) info thread 4
2834 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2837 @kindex set print thread-events
2838 @cindex print messages on thread start and exit
2839 @item set print thread-events
2840 @itemx set print thread-events on
2841 @itemx set print thread-events off
2842 The @code{set print thread-events} command allows you to enable or
2843 disable printing of messages when @value{GDBN} notices that new threads have
2844 started or that threads have exited. By default, these messages will
2845 be printed if detection of these events is supported by the target.
2846 Note that these messages cannot be disabled on all targets.
2848 @kindex show print thread-events
2849 @item show print thread-events
2850 Show whether messages will be printed when @value{GDBN} detects that threads
2851 have started and exited.
2854 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2855 more information about how @value{GDBN} behaves when you stop and start
2856 programs with multiple threads.
2858 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2859 watchpoints in programs with multiple threads.
2862 @kindex set libthread-db-search-path
2863 @cindex search path for @code{libthread_db}
2864 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2865 If this variable is set, @var{path} is a colon-separated list of
2866 directories @value{GDBN} will use to search for @code{libthread_db}.
2867 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2868 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2869 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2872 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2873 @code{libthread_db} library to obtain information about threads in the
2874 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2875 to find @code{libthread_db}.
2877 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2878 refers to the default system directories that are
2879 normally searched for loading shared libraries.
2881 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2882 refers to the directory from which @code{libpthread}
2883 was loaded in the inferior process.
2885 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2886 @value{GDBN} attempts to initialize it with the current inferior process.
2887 If this initialization fails (which could happen because of a version
2888 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2889 will unload @code{libthread_db}, and continue with the next directory.
2890 If none of @code{libthread_db} libraries initialize successfully,
2891 @value{GDBN} will issue a warning and thread debugging will be disabled.
2893 Setting @code{libthread-db-search-path} is currently implemented
2894 only on some platforms.
2896 @kindex show libthread-db-search-path
2897 @item show libthread-db-search-path
2898 Display current libthread_db search path.
2900 @kindex set debug libthread-db
2901 @kindex show debug libthread-db
2902 @cindex debugging @code{libthread_db}
2903 @item set debug libthread-db
2904 @itemx show debug libthread-db
2905 Turns on or off display of @code{libthread_db}-related events.
2906 Use @code{1} to enable, @code{0} to disable.
2910 @section Debugging Forks
2912 @cindex fork, debugging programs which call
2913 @cindex multiple processes
2914 @cindex processes, multiple
2915 On most systems, @value{GDBN} has no special support for debugging
2916 programs which create additional processes using the @code{fork}
2917 function. When a program forks, @value{GDBN} will continue to debug the
2918 parent process and the child process will run unimpeded. If you have
2919 set a breakpoint in any code which the child then executes, the child
2920 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2921 will cause it to terminate.
2923 However, if you want to debug the child process there is a workaround
2924 which isn't too painful. Put a call to @code{sleep} in the code which
2925 the child process executes after the fork. It may be useful to sleep
2926 only if a certain environment variable is set, or a certain file exists,
2927 so that the delay need not occur when you don't want to run @value{GDBN}
2928 on the child. While the child is sleeping, use the @code{ps} program to
2929 get its process ID. Then tell @value{GDBN} (a new invocation of
2930 @value{GDBN} if you are also debugging the parent process) to attach to
2931 the child process (@pxref{Attach}). From that point on you can debug
2932 the child process just like any other process which you attached to.
2934 On some systems, @value{GDBN} provides support for debugging programs that
2935 create additional processes using the @code{fork} or @code{vfork} functions.
2936 Currently, the only platforms with this feature are HP-UX (11.x and later
2937 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2939 By default, when a program forks, @value{GDBN} will continue to debug
2940 the parent process and the child process will run unimpeded.
2942 If you want to follow the child process instead of the parent process,
2943 use the command @w{@code{set follow-fork-mode}}.
2946 @kindex set follow-fork-mode
2947 @item set follow-fork-mode @var{mode}
2948 Set the debugger response to a program call of @code{fork} or
2949 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2950 process. The @var{mode} argument can be:
2954 The original process is debugged after a fork. The child process runs
2955 unimpeded. This is the default.
2958 The new process is debugged after a fork. The parent process runs
2963 @kindex show follow-fork-mode
2964 @item show follow-fork-mode
2965 Display the current debugger response to a @code{fork} or @code{vfork} call.
2968 @cindex debugging multiple processes
2969 On Linux, if you want to debug both the parent and child processes, use the
2970 command @w{@code{set detach-on-fork}}.
2973 @kindex set detach-on-fork
2974 @item set detach-on-fork @var{mode}
2975 Tells gdb whether to detach one of the processes after a fork, or
2976 retain debugger control over them both.
2980 The child process (or parent process, depending on the value of
2981 @code{follow-fork-mode}) will be detached and allowed to run
2982 independently. This is the default.
2985 Both processes will be held under the control of @value{GDBN}.
2986 One process (child or parent, depending on the value of
2987 @code{follow-fork-mode}) is debugged as usual, while the other
2992 @kindex show detach-on-fork
2993 @item show detach-on-fork
2994 Show whether detach-on-fork mode is on/off.
2997 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2998 will retain control of all forked processes (including nested forks).
2999 You can list the forked processes under the control of @value{GDBN} by
3000 using the @w{@code{info inferiors}} command, and switch from one fork
3001 to another by using the @code{inferior} command (@pxref{Inferiors and
3002 Programs, ,Debugging Multiple Inferiors and Programs}).
3004 To quit debugging one of the forked processes, you can either detach
3005 from it by using the @w{@code{detach inferiors}} command (allowing it
3006 to run independently), or kill it using the @w{@code{kill inferiors}}
3007 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3010 If you ask to debug a child process and a @code{vfork} is followed by an
3011 @code{exec}, @value{GDBN} executes the new target up to the first
3012 breakpoint in the new target. If you have a breakpoint set on
3013 @code{main} in your original program, the breakpoint will also be set on
3014 the child process's @code{main}.
3016 On some systems, when a child process is spawned by @code{vfork}, you
3017 cannot debug the child or parent until an @code{exec} call completes.
3019 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3020 call executes, the new target restarts. To restart the parent
3021 process, use the @code{file} command with the parent executable name
3022 as its argument. By default, after an @code{exec} call executes,
3023 @value{GDBN} discards the symbols of the previous executable image.
3024 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3028 @kindex set follow-exec-mode
3029 @item set follow-exec-mode @var{mode}
3031 Set debugger response to a program call of @code{exec}. An
3032 @code{exec} call replaces the program image of a process.
3034 @code{follow-exec-mode} can be:
3038 @value{GDBN} creates a new inferior and rebinds the process to this
3039 new inferior. The program the process was running before the
3040 @code{exec} call can be restarted afterwards by restarting the
3046 (@value{GDBP}) info inferiors
3048 Id Description Executable
3051 process 12020 is executing new program: prog2
3052 Program exited normally.
3053 (@value{GDBP}) info inferiors
3054 Id Description Executable
3060 @value{GDBN} keeps the process bound to the same inferior. The new
3061 executable image replaces the previous executable loaded in the
3062 inferior. Restarting the inferior after the @code{exec} call, with
3063 e.g., the @code{run} command, restarts the executable the process was
3064 running after the @code{exec} call. This is the default mode.
3069 (@value{GDBP}) info inferiors
3070 Id Description Executable
3073 process 12020 is executing new program: prog2
3074 Program exited normally.
3075 (@value{GDBP}) info inferiors
3076 Id Description Executable
3083 You can use the @code{catch} command to make @value{GDBN} stop whenever
3084 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3085 Catchpoints, ,Setting Catchpoints}.
3087 @node Checkpoint/Restart
3088 @section Setting a @emph{Bookmark} to Return to Later
3093 @cindex snapshot of a process
3094 @cindex rewind program state
3096 On certain operating systems@footnote{Currently, only
3097 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3098 program's state, called a @dfn{checkpoint}, and come back to it
3101 Returning to a checkpoint effectively undoes everything that has
3102 happened in the program since the @code{checkpoint} was saved. This
3103 includes changes in memory, registers, and even (within some limits)
3104 system state. Effectively, it is like going back in time to the
3105 moment when the checkpoint was saved.
3107 Thus, if you're stepping thru a program and you think you're
3108 getting close to the point where things go wrong, you can save
3109 a checkpoint. Then, if you accidentally go too far and miss
3110 the critical statement, instead of having to restart your program
3111 from the beginning, you can just go back to the checkpoint and
3112 start again from there.
3114 This can be especially useful if it takes a lot of time or
3115 steps to reach the point where you think the bug occurs.
3117 To use the @code{checkpoint}/@code{restart} method of debugging:
3122 Save a snapshot of the debugged program's current execution state.
3123 The @code{checkpoint} command takes no arguments, but each checkpoint
3124 is assigned a small integer id, similar to a breakpoint id.
3126 @kindex info checkpoints
3127 @item info checkpoints
3128 List the checkpoints that have been saved in the current debugging
3129 session. For each checkpoint, the following information will be
3136 @item Source line, or label
3139 @kindex restart @var{checkpoint-id}
3140 @item restart @var{checkpoint-id}
3141 Restore the program state that was saved as checkpoint number
3142 @var{checkpoint-id}. All program variables, registers, stack frames
3143 etc.@: will be returned to the values that they had when the checkpoint
3144 was saved. In essence, gdb will ``wind back the clock'' to the point
3145 in time when the checkpoint was saved.
3147 Note that breakpoints, @value{GDBN} variables, command history etc.
3148 are not affected by restoring a checkpoint. In general, a checkpoint
3149 only restores things that reside in the program being debugged, not in
3152 @kindex delete checkpoint @var{checkpoint-id}
3153 @item delete checkpoint @var{checkpoint-id}
3154 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3158 Returning to a previously saved checkpoint will restore the user state
3159 of the program being debugged, plus a significant subset of the system
3160 (OS) state, including file pointers. It won't ``un-write'' data from
3161 a file, but it will rewind the file pointer to the previous location,
3162 so that the previously written data can be overwritten. For files
3163 opened in read mode, the pointer will also be restored so that the
3164 previously read data can be read again.
3166 Of course, characters that have been sent to a printer (or other
3167 external device) cannot be ``snatched back'', and characters received
3168 from eg.@: a serial device can be removed from internal program buffers,
3169 but they cannot be ``pushed back'' into the serial pipeline, ready to
3170 be received again. Similarly, the actual contents of files that have
3171 been changed cannot be restored (at this time).
3173 However, within those constraints, you actually can ``rewind'' your
3174 program to a previously saved point in time, and begin debugging it
3175 again --- and you can change the course of events so as to debug a
3176 different execution path this time.
3178 @cindex checkpoints and process id
3179 Finally, there is one bit of internal program state that will be
3180 different when you return to a checkpoint --- the program's process
3181 id. Each checkpoint will have a unique process id (or @var{pid}),
3182 and each will be different from the program's original @var{pid}.
3183 If your program has saved a local copy of its process id, this could
3184 potentially pose a problem.
3186 @subsection A Non-obvious Benefit of Using Checkpoints
3188 On some systems such as @sc{gnu}/Linux, address space randomization
3189 is performed on new processes for security reasons. This makes it
3190 difficult or impossible to set a breakpoint, or watchpoint, on an
3191 absolute address if you have to restart the program, since the
3192 absolute location of a symbol will change from one execution to the
3195 A checkpoint, however, is an @emph{identical} copy of a process.
3196 Therefore if you create a checkpoint at (eg.@:) the start of main,
3197 and simply return to that checkpoint instead of restarting the
3198 process, you can avoid the effects of address randomization and
3199 your symbols will all stay in the same place.
3202 @chapter Stopping and Continuing
3204 The principal purposes of using a debugger are so that you can stop your
3205 program before it terminates; or so that, if your program runs into
3206 trouble, you can investigate and find out why.
3208 Inside @value{GDBN}, your program may stop for any of several reasons,
3209 such as a signal, a breakpoint, or reaching a new line after a
3210 @value{GDBN} command such as @code{step}. You may then examine and
3211 change variables, set new breakpoints or remove old ones, and then
3212 continue execution. Usually, the messages shown by @value{GDBN} provide
3213 ample explanation of the status of your program---but you can also
3214 explicitly request this information at any time.
3217 @kindex info program
3219 Display information about the status of your program: whether it is
3220 running or not, what process it is, and why it stopped.
3224 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3225 * Continuing and Stepping:: Resuming execution
3226 * Skipping Over Functions and Files::
3227 Skipping over functions and files
3229 * Thread Stops:: Stopping and starting multi-thread programs
3233 @section Breakpoints, Watchpoints, and Catchpoints
3236 A @dfn{breakpoint} makes your program stop whenever a certain point in
3237 the program is reached. For each breakpoint, you can add conditions to
3238 control in finer detail whether your program stops. You can set
3239 breakpoints with the @code{break} command and its variants (@pxref{Set
3240 Breaks, ,Setting Breakpoints}), to specify the place where your program
3241 should stop by line number, function name or exact address in the
3244 On some systems, you can set breakpoints in shared libraries before
3245 the executable is run. There is a minor limitation on HP-UX systems:
3246 you must wait until the executable is run in order to set breakpoints
3247 in shared library routines that are not called directly by the program
3248 (for example, routines that are arguments in a @code{pthread_create}
3252 @cindex data breakpoints
3253 @cindex memory tracing
3254 @cindex breakpoint on memory address
3255 @cindex breakpoint on variable modification
3256 A @dfn{watchpoint} is a special breakpoint that stops your program
3257 when the value of an expression changes. The expression may be a value
3258 of a variable, or it could involve values of one or more variables
3259 combined by operators, such as @samp{a + b}. This is sometimes called
3260 @dfn{data breakpoints}. You must use a different command to set
3261 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3262 from that, you can manage a watchpoint like any other breakpoint: you
3263 enable, disable, and delete both breakpoints and watchpoints using the
3266 You can arrange to have values from your program displayed automatically
3267 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3271 @cindex breakpoint on events
3272 A @dfn{catchpoint} is another special breakpoint that stops your program
3273 when a certain kind of event occurs, such as the throwing of a C@t{++}
3274 exception or the loading of a library. As with watchpoints, you use a
3275 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3276 Catchpoints}), but aside from that, you can manage a catchpoint like any
3277 other breakpoint. (To stop when your program receives a signal, use the
3278 @code{handle} command; see @ref{Signals, ,Signals}.)
3280 @cindex breakpoint numbers
3281 @cindex numbers for breakpoints
3282 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3283 catchpoint when you create it; these numbers are successive integers
3284 starting with one. In many of the commands for controlling various
3285 features of breakpoints you use the breakpoint number to say which
3286 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3287 @dfn{disabled}; if disabled, it has no effect on your program until you
3290 @cindex breakpoint ranges
3291 @cindex ranges of breakpoints
3292 Some @value{GDBN} commands accept a range of breakpoints on which to
3293 operate. A breakpoint range is either a single breakpoint number, like
3294 @samp{5}, or two such numbers, in increasing order, separated by a
3295 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3296 all breakpoints in that range are operated on.
3299 * Set Breaks:: Setting breakpoints
3300 * Set Watchpoints:: Setting watchpoints
3301 * Set Catchpoints:: Setting catchpoints
3302 * Delete Breaks:: Deleting breakpoints
3303 * Disabling:: Disabling breakpoints
3304 * Conditions:: Break conditions
3305 * Break Commands:: Breakpoint command lists
3306 * Save Breakpoints:: How to save breakpoints in a file
3307 * Error in Breakpoints:: ``Cannot insert breakpoints''
3308 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3312 @subsection Setting Breakpoints
3314 @c FIXME LMB what does GDB do if no code on line of breakpt?
3315 @c consider in particular declaration with/without initialization.
3317 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3320 @kindex b @r{(@code{break})}
3321 @vindex $bpnum@r{, convenience variable}
3322 @cindex latest breakpoint
3323 Breakpoints are set with the @code{break} command (abbreviated
3324 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3325 number of the breakpoint you've set most recently; see @ref{Convenience
3326 Vars,, Convenience Variables}, for a discussion of what you can do with
3327 convenience variables.
3330 @item break @var{location}
3331 Set a breakpoint at the given @var{location}, which can specify a
3332 function name, a line number, or an address of an instruction.
3333 (@xref{Specify Location}, for a list of all the possible ways to
3334 specify a @var{location}.) The breakpoint will stop your program just
3335 before it executes any of the code in the specified @var{location}.
3337 When using source languages that permit overloading of symbols, such as
3338 C@t{++}, a function name may refer to more than one possible place to break.
3339 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3342 It is also possible to insert a breakpoint that will stop the program
3343 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3344 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3347 When called without any arguments, @code{break} sets a breakpoint at
3348 the next instruction to be executed in the selected stack frame
3349 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3350 innermost, this makes your program stop as soon as control
3351 returns to that frame. This is similar to the effect of a
3352 @code{finish} command in the frame inside the selected frame---except
3353 that @code{finish} does not leave an active breakpoint. If you use
3354 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3355 the next time it reaches the current location; this may be useful
3358 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3359 least one instruction has been executed. If it did not do this, you
3360 would be unable to proceed past a breakpoint without first disabling the
3361 breakpoint. This rule applies whether or not the breakpoint already
3362 existed when your program stopped.
3364 @item break @dots{} if @var{cond}
3365 Set a breakpoint with condition @var{cond}; evaluate the expression
3366 @var{cond} each time the breakpoint is reached, and stop only if the
3367 value is nonzero---that is, if @var{cond} evaluates as true.
3368 @samp{@dots{}} stands for one of the possible arguments described
3369 above (or no argument) specifying where to break. @xref{Conditions,
3370 ,Break Conditions}, for more information on breakpoint conditions.
3373 @item tbreak @var{args}
3374 Set a breakpoint enabled only for one stop. @var{args} are the
3375 same as for the @code{break} command, and the breakpoint is set in the same
3376 way, but the breakpoint is automatically deleted after the first time your
3377 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3380 @cindex hardware breakpoints
3381 @item hbreak @var{args}
3382 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3383 @code{break} command and the breakpoint is set in the same way, but the
3384 breakpoint requires hardware support and some target hardware may not
3385 have this support. The main purpose of this is EPROM/ROM code
3386 debugging, so you can set a breakpoint at an instruction without
3387 changing the instruction. This can be used with the new trap-generation
3388 provided by SPARClite DSU and most x86-based targets. These targets
3389 will generate traps when a program accesses some data or instruction
3390 address that is assigned to the debug registers. However the hardware
3391 breakpoint registers can take a limited number of breakpoints. For
3392 example, on the DSU, only two data breakpoints can be set at a time, and
3393 @value{GDBN} will reject this command if more than two are used. Delete
3394 or disable unused hardware breakpoints before setting new ones
3395 (@pxref{Disabling, ,Disabling Breakpoints}).
3396 @xref{Conditions, ,Break Conditions}.
3397 For remote targets, you can restrict the number of hardware
3398 breakpoints @value{GDBN} will use, see @ref{set remote
3399 hardware-breakpoint-limit}.
3402 @item thbreak @var{args}
3403 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3404 are the same as for the @code{hbreak} command and the breakpoint is set in
3405 the same way. However, like the @code{tbreak} command,
3406 the breakpoint is automatically deleted after the
3407 first time your program stops there. Also, like the @code{hbreak}
3408 command, the breakpoint requires hardware support and some target hardware
3409 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3410 See also @ref{Conditions, ,Break Conditions}.
3413 @cindex regular expression
3414 @cindex breakpoints at functions matching a regexp
3415 @cindex set breakpoints in many functions
3416 @item rbreak @var{regex}
3417 Set breakpoints on all functions matching the regular expression
3418 @var{regex}. This command sets an unconditional breakpoint on all
3419 matches, printing a list of all breakpoints it set. Once these
3420 breakpoints are set, they are treated just like the breakpoints set with
3421 the @code{break} command. You can delete them, disable them, or make
3422 them conditional the same way as any other breakpoint.
3424 The syntax of the regular expression is the standard one used with tools
3425 like @file{grep}. Note that this is different from the syntax used by
3426 shells, so for instance @code{foo*} matches all functions that include
3427 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3428 @code{.*} leading and trailing the regular expression you supply, so to
3429 match only functions that begin with @code{foo}, use @code{^foo}.
3431 @cindex non-member C@t{++} functions, set breakpoint in
3432 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3433 breakpoints on overloaded functions that are not members of any special
3436 @cindex set breakpoints on all functions
3437 The @code{rbreak} command can be used to set breakpoints in
3438 @strong{all} the functions in a program, like this:
3441 (@value{GDBP}) rbreak .
3444 @item rbreak @var{file}:@var{regex}
3445 If @code{rbreak} is called with a filename qualification, it limits
3446 the search for functions matching the given regular expression to the
3447 specified @var{file}. This can be used, for example, to set breakpoints on
3448 every function in a given file:
3451 (@value{GDBP}) rbreak file.c:.
3454 The colon separating the filename qualifier from the regex may
3455 optionally be surrounded by spaces.
3457 @kindex info breakpoints
3458 @cindex @code{$_} and @code{info breakpoints}
3459 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3460 @itemx info break @r{[}@var{n}@dots{}@r{]}
3461 Print a table of all breakpoints, watchpoints, and catchpoints set and
3462 not deleted. Optional argument @var{n} means print information only
3463 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3464 For each breakpoint, following columns are printed:
3467 @item Breakpoint Numbers
3469 Breakpoint, watchpoint, or catchpoint.
3471 Whether the breakpoint is marked to be disabled or deleted when hit.
3472 @item Enabled or Disabled
3473 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3474 that are not enabled.
3476 Where the breakpoint is in your program, as a memory address. For a
3477 pending breakpoint whose address is not yet known, this field will
3478 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3479 library that has the symbol or line referred by breakpoint is loaded.
3480 See below for details. A breakpoint with several locations will
3481 have @samp{<MULTIPLE>} in this field---see below for details.
3483 Where the breakpoint is in the source for your program, as a file and
3484 line number. For a pending breakpoint, the original string passed to
3485 the breakpoint command will be listed as it cannot be resolved until
3486 the appropriate shared library is loaded in the future.
3490 If a breakpoint is conditional, @code{info break} shows the condition on
3491 the line following the affected breakpoint; breakpoint commands, if any,
3492 are listed after that. A pending breakpoint is allowed to have a condition
3493 specified for it. The condition is not parsed for validity until a shared
3494 library is loaded that allows the pending breakpoint to resolve to a
3498 @code{info break} with a breakpoint
3499 number @var{n} as argument lists only that breakpoint. The
3500 convenience variable @code{$_} and the default examining-address for
3501 the @code{x} command are set to the address of the last breakpoint
3502 listed (@pxref{Memory, ,Examining Memory}).
3505 @code{info break} displays a count of the number of times the breakpoint
3506 has been hit. This is especially useful in conjunction with the
3507 @code{ignore} command. You can ignore a large number of breakpoint
3508 hits, look at the breakpoint info to see how many times the breakpoint
3509 was hit, and then run again, ignoring one less than that number. This
3510 will get you quickly to the last hit of that breakpoint.
3513 @value{GDBN} allows you to set any number of breakpoints at the same place in
3514 your program. There is nothing silly or meaningless about this. When
3515 the breakpoints are conditional, this is even useful
3516 (@pxref{Conditions, ,Break Conditions}).
3518 @cindex multiple locations, breakpoints
3519 @cindex breakpoints, multiple locations
3520 It is possible that a breakpoint corresponds to several locations
3521 in your program. Examples of this situation are:
3525 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3526 instances of the function body, used in different cases.
3529 For a C@t{++} template function, a given line in the function can
3530 correspond to any number of instantiations.
3533 For an inlined function, a given source line can correspond to
3534 several places where that function is inlined.
3537 In all those cases, @value{GDBN} will insert a breakpoint at all
3538 the relevant locations@footnote{
3539 As of this writing, multiple-location breakpoints work only if there's
3540 line number information for all the locations. This means that they
3541 will generally not work in system libraries, unless you have debug
3542 info with line numbers for them.}.
3544 A breakpoint with multiple locations is displayed in the breakpoint
3545 table using several rows---one header row, followed by one row for
3546 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3547 address column. The rows for individual locations contain the actual
3548 addresses for locations, and show the functions to which those
3549 locations belong. The number column for a location is of the form
3550 @var{breakpoint-number}.@var{location-number}.
3555 Num Type Disp Enb Address What
3556 1 breakpoint keep y <MULTIPLE>
3558 breakpoint already hit 1 time
3559 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3560 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3563 Each location can be individually enabled or disabled by passing
3564 @var{breakpoint-number}.@var{location-number} as argument to the
3565 @code{enable} and @code{disable} commands. Note that you cannot
3566 delete the individual locations from the list, you can only delete the
3567 entire list of locations that belong to their parent breakpoint (with
3568 the @kbd{delete @var{num}} command, where @var{num} is the number of
3569 the parent breakpoint, 1 in the above example). Disabling or enabling
3570 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3571 that belong to that breakpoint.
3573 @cindex pending breakpoints
3574 It's quite common to have a breakpoint inside a shared library.
3575 Shared libraries can be loaded and unloaded explicitly,
3576 and possibly repeatedly, as the program is executed. To support
3577 this use case, @value{GDBN} updates breakpoint locations whenever
3578 any shared library is loaded or unloaded. Typically, you would
3579 set a breakpoint in a shared library at the beginning of your
3580 debugging session, when the library is not loaded, and when the
3581 symbols from the library are not available. When you try to set
3582 breakpoint, @value{GDBN} will ask you if you want to set
3583 a so called @dfn{pending breakpoint}---breakpoint whose address
3584 is not yet resolved.
3586 After the program is run, whenever a new shared library is loaded,
3587 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3588 shared library contains the symbol or line referred to by some
3589 pending breakpoint, that breakpoint is resolved and becomes an
3590 ordinary breakpoint. When a library is unloaded, all breakpoints
3591 that refer to its symbols or source lines become pending again.
3593 This logic works for breakpoints with multiple locations, too. For
3594 example, if you have a breakpoint in a C@t{++} template function, and
3595 a newly loaded shared library has an instantiation of that template,
3596 a new location is added to the list of locations for the breakpoint.
3598 Except for having unresolved address, pending breakpoints do not
3599 differ from regular breakpoints. You can set conditions or commands,
3600 enable and disable them and perform other breakpoint operations.
3602 @value{GDBN} provides some additional commands for controlling what
3603 happens when the @samp{break} command cannot resolve breakpoint
3604 address specification to an address:
3606 @kindex set breakpoint pending
3607 @kindex show breakpoint pending
3609 @item set breakpoint pending auto
3610 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3611 location, it queries you whether a pending breakpoint should be created.
3613 @item set breakpoint pending on
3614 This indicates that an unrecognized breakpoint location should automatically
3615 result in a pending breakpoint being created.
3617 @item set breakpoint pending off
3618 This indicates that pending breakpoints are not to be created. Any
3619 unrecognized breakpoint location results in an error. This setting does
3620 not affect any pending breakpoints previously created.
3622 @item show breakpoint pending
3623 Show the current behavior setting for creating pending breakpoints.
3626 The settings above only affect the @code{break} command and its
3627 variants. Once breakpoint is set, it will be automatically updated
3628 as shared libraries are loaded and unloaded.
3630 @cindex automatic hardware breakpoints
3631 For some targets, @value{GDBN} can automatically decide if hardware or
3632 software breakpoints should be used, depending on whether the
3633 breakpoint address is read-only or read-write. This applies to
3634 breakpoints set with the @code{break} command as well as to internal
3635 breakpoints set by commands like @code{next} and @code{finish}. For
3636 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3639 You can control this automatic behaviour with the following commands::
3641 @kindex set breakpoint auto-hw
3642 @kindex show breakpoint auto-hw
3644 @item set breakpoint auto-hw on
3645 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3646 will try to use the target memory map to decide if software or hardware
3647 breakpoint must be used.
3649 @item set breakpoint auto-hw off
3650 This indicates @value{GDBN} should not automatically select breakpoint
3651 type. If the target provides a memory map, @value{GDBN} will warn when
3652 trying to set software breakpoint at a read-only address.
3655 @value{GDBN} normally implements breakpoints by replacing the program code
3656 at the breakpoint address with a special instruction, which, when
3657 executed, given control to the debugger. By default, the program
3658 code is so modified only when the program is resumed. As soon as
3659 the program stops, @value{GDBN} restores the original instructions. This
3660 behaviour guards against leaving breakpoints inserted in the
3661 target should gdb abrubptly disconnect. However, with slow remote
3662 targets, inserting and removing breakpoint can reduce the performance.
3663 This behavior can be controlled with the following commands::
3665 @kindex set breakpoint always-inserted
3666 @kindex show breakpoint always-inserted
3668 @item set breakpoint always-inserted off
3669 All breakpoints, including newly added by the user, are inserted in
3670 the target only when the target is resumed. All breakpoints are
3671 removed from the target when it stops.
3673 @item set breakpoint always-inserted on
3674 Causes all breakpoints to be inserted in the target at all times. If
3675 the user adds a new breakpoint, or changes an existing breakpoint, the
3676 breakpoints in the target are updated immediately. A breakpoint is
3677 removed from the target only when breakpoint itself is removed.
3679 @cindex non-stop mode, and @code{breakpoint always-inserted}
3680 @item set breakpoint always-inserted auto
3681 This is the default mode. If @value{GDBN} is controlling the inferior
3682 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3683 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3684 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3685 @code{breakpoint always-inserted} mode is off.
3688 @cindex negative breakpoint numbers
3689 @cindex internal @value{GDBN} breakpoints
3690 @value{GDBN} itself sometimes sets breakpoints in your program for
3691 special purposes, such as proper handling of @code{longjmp} (in C
3692 programs). These internal breakpoints are assigned negative numbers,
3693 starting with @code{-1}; @samp{info breakpoints} does not display them.
3694 You can see these breakpoints with the @value{GDBN} maintenance command
3695 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3698 @node Set Watchpoints
3699 @subsection Setting Watchpoints
3701 @cindex setting watchpoints
3702 You can use a watchpoint to stop execution whenever the value of an
3703 expression changes, without having to predict a particular place where
3704 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3705 The expression may be as simple as the value of a single variable, or
3706 as complex as many variables combined by operators. Examples include:
3710 A reference to the value of a single variable.
3713 An address cast to an appropriate data type. For example,
3714 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3715 address (assuming an @code{int} occupies 4 bytes).
3718 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3719 expression can use any operators valid in the program's native
3720 language (@pxref{Languages}).
3723 You can set a watchpoint on an expression even if the expression can
3724 not be evaluated yet. For instance, you can set a watchpoint on
3725 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3726 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3727 the expression produces a valid value. If the expression becomes
3728 valid in some other way than changing a variable (e.g.@: if the memory
3729 pointed to by @samp{*global_ptr} becomes readable as the result of a
3730 @code{malloc} call), @value{GDBN} may not stop until the next time
3731 the expression changes.
3733 @cindex software watchpoints
3734 @cindex hardware watchpoints
3735 Depending on your system, watchpoints may be implemented in software or
3736 hardware. @value{GDBN} does software watchpointing by single-stepping your
3737 program and testing the variable's value each time, which is hundreds of
3738 times slower than normal execution. (But this may still be worth it, to
3739 catch errors where you have no clue what part of your program is the
3742 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3743 x86-based targets, @value{GDBN} includes support for hardware
3744 watchpoints, which do not slow down the running of your program.
3748 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3749 Set a watchpoint for an expression. @value{GDBN} will break when the
3750 expression @var{expr} is written into by the program and its value
3751 changes. The simplest (and the most popular) use of this command is
3752 to watch the value of a single variable:
3755 (@value{GDBP}) watch foo
3758 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3759 argument, @value{GDBN} breaks only when the thread identified by
3760 @var{threadnum} changes the value of @var{expr}. If any other threads
3761 change the value of @var{expr}, @value{GDBN} will not break. Note
3762 that watchpoints restricted to a single thread in this way only work
3763 with Hardware Watchpoints.
3765 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3766 (see below). The @code{-location} argument tells @value{GDBN} to
3767 instead watch the memory referred to by @var{expr}. In this case,
3768 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3769 and watch the memory at that address. The type of the result is used
3770 to determine the size of the watched memory. If the expression's
3771 result does not have an address, then @value{GDBN} will print an
3774 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3775 of masked watchpoints, if the current architecture supports this
3776 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3777 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3778 to an address to watch. The mask specifies that some bits of an address
3779 (the bits which are reset in the mask) should be ignored when matching
3780 the address accessed by the inferior against the watchpoint address.
3781 Thus, a masked watchpoint watches many addresses simultaneously---those
3782 addresses whose unmasked bits are identical to the unmasked bits in the
3783 watchpoint address. The @code{mask} argument implies @code{-location}.
3787 (@value{GDBP}) watch foo mask 0xffff00ff
3788 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3792 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3793 Set a watchpoint that will break when the value of @var{expr} is read
3797 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3798 Set a watchpoint that will break when @var{expr} is either read from
3799 or written into by the program.
3801 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3802 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3803 This command prints a list of watchpoints, using the same format as
3804 @code{info break} (@pxref{Set Breaks}).
3807 If you watch for a change in a numerically entered address you need to
3808 dereference it, as the address itself is just a constant number which will
3809 never change. @value{GDBN} refuses to create a watchpoint that watches
3810 a never-changing value:
3813 (@value{GDBP}) watch 0x600850
3814 Cannot watch constant value 0x600850.
3815 (@value{GDBP}) watch *(int *) 0x600850
3816 Watchpoint 1: *(int *) 6293584
3819 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3820 watchpoints execute very quickly, and the debugger reports a change in
3821 value at the exact instruction where the change occurs. If @value{GDBN}
3822 cannot set a hardware watchpoint, it sets a software watchpoint, which
3823 executes more slowly and reports the change in value at the next
3824 @emph{statement}, not the instruction, after the change occurs.
3826 @cindex use only software watchpoints
3827 You can force @value{GDBN} to use only software watchpoints with the
3828 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3829 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3830 the underlying system supports them. (Note that hardware-assisted
3831 watchpoints that were set @emph{before} setting
3832 @code{can-use-hw-watchpoints} to zero will still use the hardware
3833 mechanism of watching expression values.)
3836 @item set can-use-hw-watchpoints
3837 @kindex set can-use-hw-watchpoints
3838 Set whether or not to use hardware watchpoints.
3840 @item show can-use-hw-watchpoints
3841 @kindex show can-use-hw-watchpoints
3842 Show the current mode of using hardware watchpoints.
3845 For remote targets, you can restrict the number of hardware
3846 watchpoints @value{GDBN} will use, see @ref{set remote
3847 hardware-breakpoint-limit}.
3849 When you issue the @code{watch} command, @value{GDBN} reports
3852 Hardware watchpoint @var{num}: @var{expr}
3856 if it was able to set a hardware watchpoint.
3858 Currently, the @code{awatch} and @code{rwatch} commands can only set
3859 hardware watchpoints, because accesses to data that don't change the
3860 value of the watched expression cannot be detected without examining
3861 every instruction as it is being executed, and @value{GDBN} does not do
3862 that currently. If @value{GDBN} finds that it is unable to set a
3863 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3864 will print a message like this:
3867 Expression cannot be implemented with read/access watchpoint.
3870 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3871 data type of the watched expression is wider than what a hardware
3872 watchpoint on the target machine can handle. For example, some systems
3873 can only watch regions that are up to 4 bytes wide; on such systems you
3874 cannot set hardware watchpoints for an expression that yields a
3875 double-precision floating-point number (which is typically 8 bytes
3876 wide). As a work-around, it might be possible to break the large region
3877 into a series of smaller ones and watch them with separate watchpoints.
3879 If you set too many hardware watchpoints, @value{GDBN} might be unable
3880 to insert all of them when you resume the execution of your program.
3881 Since the precise number of active watchpoints is unknown until such
3882 time as the program is about to be resumed, @value{GDBN} might not be
3883 able to warn you about this when you set the watchpoints, and the
3884 warning will be printed only when the program is resumed:
3887 Hardware watchpoint @var{num}: Could not insert watchpoint
3891 If this happens, delete or disable some of the watchpoints.
3893 Watching complex expressions that reference many variables can also
3894 exhaust the resources available for hardware-assisted watchpoints.
3895 That's because @value{GDBN} needs to watch every variable in the
3896 expression with separately allocated resources.
3898 If you call a function interactively using @code{print} or @code{call},
3899 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3900 kind of breakpoint or the call completes.
3902 @value{GDBN} automatically deletes watchpoints that watch local
3903 (automatic) variables, or expressions that involve such variables, when
3904 they go out of scope, that is, when the execution leaves the block in
3905 which these variables were defined. In particular, when the program
3906 being debugged terminates, @emph{all} local variables go out of scope,
3907 and so only watchpoints that watch global variables remain set. If you
3908 rerun the program, you will need to set all such watchpoints again. One
3909 way of doing that would be to set a code breakpoint at the entry to the
3910 @code{main} function and when it breaks, set all the watchpoints.
3912 @cindex watchpoints and threads
3913 @cindex threads and watchpoints
3914 In multi-threaded programs, watchpoints will detect changes to the
3915 watched expression from every thread.
3918 @emph{Warning:} In multi-threaded programs, software watchpoints
3919 have only limited usefulness. If @value{GDBN} creates a software
3920 watchpoint, it can only watch the value of an expression @emph{in a
3921 single thread}. If you are confident that the expression can only
3922 change due to the current thread's activity (and if you are also
3923 confident that no other thread can become current), then you can use
3924 software watchpoints as usual. However, @value{GDBN} may not notice
3925 when a non-current thread's activity changes the expression. (Hardware
3926 watchpoints, in contrast, watch an expression in all threads.)
3929 @xref{set remote hardware-watchpoint-limit}.
3931 @node Set Catchpoints
3932 @subsection Setting Catchpoints
3933 @cindex catchpoints, setting
3934 @cindex exception handlers
3935 @cindex event handling
3937 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3938 kinds of program events, such as C@t{++} exceptions or the loading of a
3939 shared library. Use the @code{catch} command to set a catchpoint.
3943 @item catch @var{event}
3944 Stop when @var{event} occurs. @var{event} can be any of the following:
3947 @cindex stop on C@t{++} exceptions
3948 The throwing of a C@t{++} exception.
3951 The catching of a C@t{++} exception.
3954 @cindex Ada exception catching
3955 @cindex catch Ada exceptions
3956 An Ada exception being raised. If an exception name is specified
3957 at the end of the command (eg @code{catch exception Program_Error}),
3958 the debugger will stop only when this specific exception is raised.
3959 Otherwise, the debugger stops execution when any Ada exception is raised.
3961 When inserting an exception catchpoint on a user-defined exception whose
3962 name is identical to one of the exceptions defined by the language, the
3963 fully qualified name must be used as the exception name. Otherwise,
3964 @value{GDBN} will assume that it should stop on the pre-defined exception
3965 rather than the user-defined one. For instance, assuming an exception
3966 called @code{Constraint_Error} is defined in package @code{Pck}, then
3967 the command to use to catch such exceptions is @kbd{catch exception
3968 Pck.Constraint_Error}.
3970 @item exception unhandled
3971 An exception that was raised but is not handled by the program.
3974 A failed Ada assertion.
3977 @cindex break on fork/exec
3978 A call to @code{exec}. This is currently only available for HP-UX
3982 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3983 @cindex break on a system call.
3984 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3985 syscall is a mechanism for application programs to request a service
3986 from the operating system (OS) or one of the OS system services.
3987 @value{GDBN} can catch some or all of the syscalls issued by the
3988 debuggee, and show the related information for each syscall. If no
3989 argument is specified, calls to and returns from all system calls
3992 @var{name} can be any system call name that is valid for the
3993 underlying OS. Just what syscalls are valid depends on the OS. On
3994 GNU and Unix systems, you can find the full list of valid syscall
3995 names on @file{/usr/include/asm/unistd.h}.
3997 @c For MS-Windows, the syscall names and the corresponding numbers
3998 @c can be found, e.g., on this URL:
3999 @c http://www.metasploit.com/users/opcode/syscalls.html
4000 @c but we don't support Windows syscalls yet.
4002 Normally, @value{GDBN} knows in advance which syscalls are valid for
4003 each OS, so you can use the @value{GDBN} command-line completion
4004 facilities (@pxref{Completion,, command completion}) to list the
4007 You may also specify the system call numerically. A syscall's
4008 number is the value passed to the OS's syscall dispatcher to
4009 identify the requested service. When you specify the syscall by its
4010 name, @value{GDBN} uses its database of syscalls to convert the name
4011 into the corresponding numeric code, but using the number directly
4012 may be useful if @value{GDBN}'s database does not have the complete
4013 list of syscalls on your system (e.g., because @value{GDBN} lags
4014 behind the OS upgrades).
4016 The example below illustrates how this command works if you don't provide
4020 (@value{GDBP}) catch syscall
4021 Catchpoint 1 (syscall)
4023 Starting program: /tmp/catch-syscall
4025 Catchpoint 1 (call to syscall 'close'), \
4026 0xffffe424 in __kernel_vsyscall ()
4030 Catchpoint 1 (returned from syscall 'close'), \
4031 0xffffe424 in __kernel_vsyscall ()
4035 Here is an example of catching a system call by name:
4038 (@value{GDBP}) catch syscall chroot
4039 Catchpoint 1 (syscall 'chroot' [61])
4041 Starting program: /tmp/catch-syscall
4043 Catchpoint 1 (call to syscall 'chroot'), \
4044 0xffffe424 in __kernel_vsyscall ()
4048 Catchpoint 1 (returned from syscall 'chroot'), \
4049 0xffffe424 in __kernel_vsyscall ()
4053 An example of specifying a system call numerically. In the case
4054 below, the syscall number has a corresponding entry in the XML
4055 file, so @value{GDBN} finds its name and prints it:
4058 (@value{GDBP}) catch syscall 252
4059 Catchpoint 1 (syscall(s) 'exit_group')
4061 Starting program: /tmp/catch-syscall
4063 Catchpoint 1 (call to syscall 'exit_group'), \
4064 0xffffe424 in __kernel_vsyscall ()
4068 Program exited normally.
4072 However, there can be situations when there is no corresponding name
4073 in XML file for that syscall number. In this case, @value{GDBN} prints
4074 a warning message saying that it was not able to find the syscall name,
4075 but the catchpoint will be set anyway. See the example below:
4078 (@value{GDBP}) catch syscall 764
4079 warning: The number '764' does not represent a known syscall.
4080 Catchpoint 2 (syscall 764)
4084 If you configure @value{GDBN} using the @samp{--without-expat} option,
4085 it will not be able to display syscall names. Also, if your
4086 architecture does not have an XML file describing its system calls,
4087 you will not be able to see the syscall names. It is important to
4088 notice that these two features are used for accessing the syscall
4089 name database. In either case, you will see a warning like this:
4092 (@value{GDBP}) catch syscall
4093 warning: Could not open "syscalls/i386-linux.xml"
4094 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4095 GDB will not be able to display syscall names.
4096 Catchpoint 1 (syscall)
4100 Of course, the file name will change depending on your architecture and system.
4102 Still using the example above, you can also try to catch a syscall by its
4103 number. In this case, you would see something like:
4106 (@value{GDBP}) catch syscall 252
4107 Catchpoint 1 (syscall(s) 252)
4110 Again, in this case @value{GDBN} would not be able to display syscall's names.
4113 A call to @code{fork}. This is currently only available for HP-UX
4117 A call to @code{vfork}. This is currently only available for HP-UX
4122 @item tcatch @var{event}
4123 Set a catchpoint that is enabled only for one stop. The catchpoint is
4124 automatically deleted after the first time the event is caught.
4128 Use the @code{info break} command to list the current catchpoints.
4130 There are currently some limitations to C@t{++} exception handling
4131 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4135 If you call a function interactively, @value{GDBN} normally returns
4136 control to you when the function has finished executing. If the call
4137 raises an exception, however, the call may bypass the mechanism that
4138 returns control to you and cause your program either to abort or to
4139 simply continue running until it hits a breakpoint, catches a signal
4140 that @value{GDBN} is listening for, or exits. This is the case even if
4141 you set a catchpoint for the exception; catchpoints on exceptions are
4142 disabled within interactive calls.
4145 You cannot raise an exception interactively.
4148 You cannot install an exception handler interactively.
4151 @cindex raise exceptions
4152 Sometimes @code{catch} is not the best way to debug exception handling:
4153 if you need to know exactly where an exception is raised, it is better to
4154 stop @emph{before} the exception handler is called, since that way you
4155 can see the stack before any unwinding takes place. If you set a
4156 breakpoint in an exception handler instead, it may not be easy to find
4157 out where the exception was raised.
4159 To stop just before an exception handler is called, you need some
4160 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4161 raised by calling a library function named @code{__raise_exception}
4162 which has the following ANSI C interface:
4165 /* @var{addr} is where the exception identifier is stored.
4166 @var{id} is the exception identifier. */
4167 void __raise_exception (void **addr, void *id);
4171 To make the debugger catch all exceptions before any stack
4172 unwinding takes place, set a breakpoint on @code{__raise_exception}
4173 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4175 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4176 that depends on the value of @var{id}, you can stop your program when
4177 a specific exception is raised. You can use multiple conditional
4178 breakpoints to stop your program when any of a number of exceptions are
4183 @subsection Deleting Breakpoints
4185 @cindex clearing breakpoints, watchpoints, catchpoints
4186 @cindex deleting breakpoints, watchpoints, catchpoints
4187 It is often necessary to eliminate a breakpoint, watchpoint, or
4188 catchpoint once it has done its job and you no longer want your program
4189 to stop there. This is called @dfn{deleting} the breakpoint. A
4190 breakpoint that has been deleted no longer exists; it is forgotten.
4192 With the @code{clear} command you can delete breakpoints according to
4193 where they are in your program. With the @code{delete} command you can
4194 delete individual breakpoints, watchpoints, or catchpoints by specifying
4195 their breakpoint numbers.
4197 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4198 automatically ignores breakpoints on the first instruction to be executed
4199 when you continue execution without changing the execution address.
4204 Delete any breakpoints at the next instruction to be executed in the
4205 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4206 the innermost frame is selected, this is a good way to delete a
4207 breakpoint where your program just stopped.
4209 @item clear @var{location}
4210 Delete any breakpoints set at the specified @var{location}.
4211 @xref{Specify Location}, for the various forms of @var{location}; the
4212 most useful ones are listed below:
4215 @item clear @var{function}
4216 @itemx clear @var{filename}:@var{function}
4217 Delete any breakpoints set at entry to the named @var{function}.
4219 @item clear @var{linenum}
4220 @itemx clear @var{filename}:@var{linenum}
4221 Delete any breakpoints set at or within the code of the specified
4222 @var{linenum} of the specified @var{filename}.
4225 @cindex delete breakpoints
4227 @kindex d @r{(@code{delete})}
4228 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4229 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4230 ranges specified as arguments. If no argument is specified, delete all
4231 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4232 confirm off}). You can abbreviate this command as @code{d}.
4236 @subsection Disabling Breakpoints
4238 @cindex enable/disable a breakpoint
4239 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4240 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4241 it had been deleted, but remembers the information on the breakpoint so
4242 that you can @dfn{enable} it again later.
4244 You disable and enable breakpoints, watchpoints, and catchpoints with
4245 the @code{enable} and @code{disable} commands, optionally specifying
4246 one or more breakpoint numbers as arguments. Use @code{info break} to
4247 print a list of all breakpoints, watchpoints, and catchpoints if you
4248 do not know which numbers to use.
4250 Disabling and enabling a breakpoint that has multiple locations
4251 affects all of its locations.
4253 A breakpoint, watchpoint, or catchpoint can have any of four different
4254 states of enablement:
4258 Enabled. The breakpoint stops your program. A breakpoint set
4259 with the @code{break} command starts out in this state.
4261 Disabled. The breakpoint has no effect on your program.
4263 Enabled once. The breakpoint stops your program, but then becomes
4266 Enabled for deletion. The breakpoint stops your program, but
4267 immediately after it does so it is deleted permanently. A breakpoint
4268 set with the @code{tbreak} command starts out in this state.
4271 You can use the following commands to enable or disable breakpoints,
4272 watchpoints, and catchpoints:
4276 @kindex dis @r{(@code{disable})}
4277 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4278 Disable the specified breakpoints---or all breakpoints, if none are
4279 listed. A disabled breakpoint has no effect but is not forgotten. All
4280 options such as ignore-counts, conditions and commands are remembered in
4281 case the breakpoint is enabled again later. You may abbreviate
4282 @code{disable} as @code{dis}.
4285 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4286 Enable the specified breakpoints (or all defined breakpoints). They
4287 become effective once again in stopping your program.
4289 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4290 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4291 of these breakpoints immediately after stopping your program.
4293 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4294 Enable the specified breakpoints to work once, then die. @value{GDBN}
4295 deletes any of these breakpoints as soon as your program stops there.
4296 Breakpoints set by the @code{tbreak} command start out in this state.
4299 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4300 @c confusing: tbreak is also initially enabled.
4301 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4302 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4303 subsequently, they become disabled or enabled only when you use one of
4304 the commands above. (The command @code{until} can set and delete a
4305 breakpoint of its own, but it does not change the state of your other
4306 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4310 @subsection Break Conditions
4311 @cindex conditional breakpoints
4312 @cindex breakpoint conditions
4314 @c FIXME what is scope of break condition expr? Context where wanted?
4315 @c in particular for a watchpoint?
4316 The simplest sort of breakpoint breaks every time your program reaches a
4317 specified place. You can also specify a @dfn{condition} for a
4318 breakpoint. A condition is just a Boolean expression in your
4319 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4320 a condition evaluates the expression each time your program reaches it,
4321 and your program stops only if the condition is @emph{true}.
4323 This is the converse of using assertions for program validation; in that
4324 situation, you want to stop when the assertion is violated---that is,
4325 when the condition is false. In C, if you want to test an assertion expressed
4326 by the condition @var{assert}, you should set the condition
4327 @samp{! @var{assert}} on the appropriate breakpoint.
4329 Conditions are also accepted for watchpoints; you may not need them,
4330 since a watchpoint is inspecting the value of an expression anyhow---but
4331 it might be simpler, say, to just set a watchpoint on a variable name,
4332 and specify a condition that tests whether the new value is an interesting
4335 Break conditions can have side effects, and may even call functions in
4336 your program. This can be useful, for example, to activate functions
4337 that log program progress, or to use your own print functions to
4338 format special data structures. The effects are completely predictable
4339 unless there is another enabled breakpoint at the same address. (In
4340 that case, @value{GDBN} might see the other breakpoint first and stop your
4341 program without checking the condition of this one.) Note that
4342 breakpoint commands are usually more convenient and flexible than break
4344 purpose of performing side effects when a breakpoint is reached
4345 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4347 Break conditions can be specified when a breakpoint is set, by using
4348 @samp{if} in the arguments to the @code{break} command. @xref{Set
4349 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4350 with the @code{condition} command.
4352 You can also use the @code{if} keyword with the @code{watch} command.
4353 The @code{catch} command does not recognize the @code{if} keyword;
4354 @code{condition} is the only way to impose a further condition on a
4359 @item condition @var{bnum} @var{expression}
4360 Specify @var{expression} as the break condition for breakpoint,
4361 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4362 breakpoint @var{bnum} stops your program only if the value of
4363 @var{expression} is true (nonzero, in C). When you use
4364 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4365 syntactic correctness, and to determine whether symbols in it have
4366 referents in the context of your breakpoint. If @var{expression} uses
4367 symbols not referenced in the context of the breakpoint, @value{GDBN}
4368 prints an error message:
4371 No symbol "foo" in current context.
4376 not actually evaluate @var{expression} at the time the @code{condition}
4377 command (or a command that sets a breakpoint with a condition, like
4378 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4380 @item condition @var{bnum}
4381 Remove the condition from breakpoint number @var{bnum}. It becomes
4382 an ordinary unconditional breakpoint.
4385 @cindex ignore count (of breakpoint)
4386 A special case of a breakpoint condition is to stop only when the
4387 breakpoint has been reached a certain number of times. This is so
4388 useful that there is a special way to do it, using the @dfn{ignore
4389 count} of the breakpoint. Every breakpoint has an ignore count, which
4390 is an integer. Most of the time, the ignore count is zero, and
4391 therefore has no effect. But if your program reaches a breakpoint whose
4392 ignore count is positive, then instead of stopping, it just decrements
4393 the ignore count by one and continues. As a result, if the ignore count
4394 value is @var{n}, the breakpoint does not stop the next @var{n} times
4395 your program reaches it.
4399 @item ignore @var{bnum} @var{count}
4400 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4401 The next @var{count} times the breakpoint is reached, your program's
4402 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4405 To make the breakpoint stop the next time it is reached, specify
4408 When you use @code{continue} to resume execution of your program from a
4409 breakpoint, you can specify an ignore count directly as an argument to
4410 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4411 Stepping,,Continuing and Stepping}.
4413 If a breakpoint has a positive ignore count and a condition, the
4414 condition is not checked. Once the ignore count reaches zero,
4415 @value{GDBN} resumes checking the condition.
4417 You could achieve the effect of the ignore count with a condition such
4418 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4419 is decremented each time. @xref{Convenience Vars, ,Convenience
4423 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4426 @node Break Commands
4427 @subsection Breakpoint Command Lists
4429 @cindex breakpoint commands
4430 You can give any breakpoint (or watchpoint or catchpoint) a series of
4431 commands to execute when your program stops due to that breakpoint. For
4432 example, you might want to print the values of certain expressions, or
4433 enable other breakpoints.
4437 @kindex end@r{ (breakpoint commands)}
4438 @item commands @r{[}@var{range}@dots{}@r{]}
4439 @itemx @dots{} @var{command-list} @dots{}
4441 Specify a list of commands for the given breakpoints. The commands
4442 themselves appear on the following lines. Type a line containing just
4443 @code{end} to terminate the commands.
4445 To remove all commands from a breakpoint, type @code{commands} and
4446 follow it immediately with @code{end}; that is, give no commands.
4448 With no argument, @code{commands} refers to the last breakpoint,
4449 watchpoint, or catchpoint set (not to the breakpoint most recently
4450 encountered). If the most recent breakpoints were set with a single
4451 command, then the @code{commands} will apply to all the breakpoints
4452 set by that command. This applies to breakpoints set by
4453 @code{rbreak}, and also applies when a single @code{break} command
4454 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4458 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4459 disabled within a @var{command-list}.
4461 You can use breakpoint commands to start your program up again. Simply
4462 use the @code{continue} command, or @code{step}, or any other command
4463 that resumes execution.
4465 Any other commands in the command list, after a command that resumes
4466 execution, are ignored. This is because any time you resume execution
4467 (even with a simple @code{next} or @code{step}), you may encounter
4468 another breakpoint---which could have its own command list, leading to
4469 ambiguities about which list to execute.
4472 If the first command you specify in a command list is @code{silent}, the
4473 usual message about stopping at a breakpoint is not printed. This may
4474 be desirable for breakpoints that are to print a specific message and
4475 then continue. If none of the remaining commands print anything, you
4476 see no sign that the breakpoint was reached. @code{silent} is
4477 meaningful only at the beginning of a breakpoint command list.
4479 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4480 print precisely controlled output, and are often useful in silent
4481 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4483 For example, here is how you could use breakpoint commands to print the
4484 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4490 printf "x is %d\n",x
4495 One application for breakpoint commands is to compensate for one bug so
4496 you can test for another. Put a breakpoint just after the erroneous line
4497 of code, give it a condition to detect the case in which something
4498 erroneous has been done, and give it commands to assign correct values
4499 to any variables that need them. End with the @code{continue} command
4500 so that your program does not stop, and start with the @code{silent}
4501 command so that no output is produced. Here is an example:
4512 @node Save Breakpoints
4513 @subsection How to save breakpoints to a file
4515 To save breakpoint definitions to a file use the @w{@code{save
4516 breakpoints}} command.
4519 @kindex save breakpoints
4520 @cindex save breakpoints to a file for future sessions
4521 @item save breakpoints [@var{filename}]
4522 This command saves all current breakpoint definitions together with
4523 their commands and ignore counts, into a file @file{@var{filename}}
4524 suitable for use in a later debugging session. This includes all
4525 types of breakpoints (breakpoints, watchpoints, catchpoints,
4526 tracepoints). To read the saved breakpoint definitions, use the
4527 @code{source} command (@pxref{Command Files}). Note that watchpoints
4528 with expressions involving local variables may fail to be recreated
4529 because it may not be possible to access the context where the
4530 watchpoint is valid anymore. Because the saved breakpoint definitions
4531 are simply a sequence of @value{GDBN} commands that recreate the
4532 breakpoints, you can edit the file in your favorite editing program,
4533 and remove the breakpoint definitions you're not interested in, or
4534 that can no longer be recreated.
4537 @c @ifclear BARETARGET
4538 @node Error in Breakpoints
4539 @subsection ``Cannot insert breakpoints''
4541 If you request too many active hardware-assisted breakpoints and
4542 watchpoints, you will see this error message:
4544 @c FIXME: the precise wording of this message may change; the relevant
4545 @c source change is not committed yet (Sep 3, 1999).
4547 Stopped; cannot insert breakpoints.
4548 You may have requested too many hardware breakpoints and watchpoints.
4552 This message is printed when you attempt to resume the program, since
4553 only then @value{GDBN} knows exactly how many hardware breakpoints and
4554 watchpoints it needs to insert.
4556 When this message is printed, you need to disable or remove some of the
4557 hardware-assisted breakpoints and watchpoints, and then continue.
4559 @node Breakpoint-related Warnings
4560 @subsection ``Breakpoint address adjusted...''
4561 @cindex breakpoint address adjusted
4563 Some processor architectures place constraints on the addresses at
4564 which breakpoints may be placed. For architectures thus constrained,
4565 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4566 with the constraints dictated by the architecture.
4568 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4569 a VLIW architecture in which a number of RISC-like instructions may be
4570 bundled together for parallel execution. The FR-V architecture
4571 constrains the location of a breakpoint instruction within such a
4572 bundle to the instruction with the lowest address. @value{GDBN}
4573 honors this constraint by adjusting a breakpoint's address to the
4574 first in the bundle.
4576 It is not uncommon for optimized code to have bundles which contain
4577 instructions from different source statements, thus it may happen that
4578 a breakpoint's address will be adjusted from one source statement to
4579 another. Since this adjustment may significantly alter @value{GDBN}'s
4580 breakpoint related behavior from what the user expects, a warning is
4581 printed when the breakpoint is first set and also when the breakpoint
4584 A warning like the one below is printed when setting a breakpoint
4585 that's been subject to address adjustment:
4588 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4591 Such warnings are printed both for user settable and @value{GDBN}'s
4592 internal breakpoints. If you see one of these warnings, you should
4593 verify that a breakpoint set at the adjusted address will have the
4594 desired affect. If not, the breakpoint in question may be removed and
4595 other breakpoints may be set which will have the desired behavior.
4596 E.g., it may be sufficient to place the breakpoint at a later
4597 instruction. A conditional breakpoint may also be useful in some
4598 cases to prevent the breakpoint from triggering too often.
4600 @value{GDBN} will also issue a warning when stopping at one of these
4601 adjusted breakpoints:
4604 warning: Breakpoint 1 address previously adjusted from 0x00010414
4608 When this warning is encountered, it may be too late to take remedial
4609 action except in cases where the breakpoint is hit earlier or more
4610 frequently than expected.
4612 @node Continuing and Stepping
4613 @section Continuing and Stepping
4617 @cindex resuming execution
4618 @dfn{Continuing} means resuming program execution until your program
4619 completes normally. In contrast, @dfn{stepping} means executing just
4620 one more ``step'' of your program, where ``step'' may mean either one
4621 line of source code, or one machine instruction (depending on what
4622 particular command you use). Either when continuing or when stepping,
4623 your program may stop even sooner, due to a breakpoint or a signal. (If
4624 it stops due to a signal, you may want to use @code{handle}, or use
4625 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4629 @kindex c @r{(@code{continue})}
4630 @kindex fg @r{(resume foreground execution)}
4631 @item continue @r{[}@var{ignore-count}@r{]}
4632 @itemx c @r{[}@var{ignore-count}@r{]}
4633 @itemx fg @r{[}@var{ignore-count}@r{]}
4634 Resume program execution, at the address where your program last stopped;
4635 any breakpoints set at that address are bypassed. The optional argument
4636 @var{ignore-count} allows you to specify a further number of times to
4637 ignore a breakpoint at this location; its effect is like that of
4638 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4640 The argument @var{ignore-count} is meaningful only when your program
4641 stopped due to a breakpoint. At other times, the argument to
4642 @code{continue} is ignored.
4644 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4645 debugged program is deemed to be the foreground program) are provided
4646 purely for convenience, and have exactly the same behavior as
4650 To resume execution at a different place, you can use @code{return}
4651 (@pxref{Returning, ,Returning from a Function}) to go back to the
4652 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4653 Different Address}) to go to an arbitrary location in your program.
4655 A typical technique for using stepping is to set a breakpoint
4656 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4657 beginning of the function or the section of your program where a problem
4658 is believed to lie, run your program until it stops at that breakpoint,
4659 and then step through the suspect area, examining the variables that are
4660 interesting, until you see the problem happen.
4664 @kindex s @r{(@code{step})}
4666 Continue running your program until control reaches a different source
4667 line, then stop it and return control to @value{GDBN}. This command is
4668 abbreviated @code{s}.
4671 @c "without debugging information" is imprecise; actually "without line
4672 @c numbers in the debugging information". (gcc -g1 has debugging info but
4673 @c not line numbers). But it seems complex to try to make that
4674 @c distinction here.
4675 @emph{Warning:} If you use the @code{step} command while control is
4676 within a function that was compiled without debugging information,
4677 execution proceeds until control reaches a function that does have
4678 debugging information. Likewise, it will not step into a function which
4679 is compiled without debugging information. To step through functions
4680 without debugging information, use the @code{stepi} command, described
4684 The @code{step} command only stops at the first instruction of a source
4685 line. This prevents the multiple stops that could otherwise occur in
4686 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4687 to stop if a function that has debugging information is called within
4688 the line. In other words, @code{step} @emph{steps inside} any functions
4689 called within the line.
4691 Also, the @code{step} command only enters a function if there is line
4692 number information for the function. Otherwise it acts like the
4693 @code{next} command. This avoids problems when using @code{cc -gl}
4694 on MIPS machines. Previously, @code{step} entered subroutines if there
4695 was any debugging information about the routine.
4697 @item step @var{count}
4698 Continue running as in @code{step}, but do so @var{count} times. If a
4699 breakpoint is reached, or a signal not related to stepping occurs before
4700 @var{count} steps, stepping stops right away.
4703 @kindex n @r{(@code{next})}
4704 @item next @r{[}@var{count}@r{]}
4705 Continue to the next source line in the current (innermost) stack frame.
4706 This is similar to @code{step}, but function calls that appear within
4707 the line of code are executed without stopping. Execution stops when
4708 control reaches a different line of code at the original stack level
4709 that was executing when you gave the @code{next} command. This command
4710 is abbreviated @code{n}.
4712 An argument @var{count} is a repeat count, as for @code{step}.
4715 @c FIX ME!! Do we delete this, or is there a way it fits in with
4716 @c the following paragraph? --- Vctoria
4718 @c @code{next} within a function that lacks debugging information acts like
4719 @c @code{step}, but any function calls appearing within the code of the
4720 @c function are executed without stopping.
4722 The @code{next} command only stops at the first instruction of a
4723 source line. This prevents multiple stops that could otherwise occur in
4724 @code{switch} statements, @code{for} loops, etc.
4726 @kindex set step-mode
4728 @cindex functions without line info, and stepping
4729 @cindex stepping into functions with no line info
4730 @itemx set step-mode on
4731 The @code{set step-mode on} command causes the @code{step} command to
4732 stop at the first instruction of a function which contains no debug line
4733 information rather than stepping over it.
4735 This is useful in cases where you may be interested in inspecting the
4736 machine instructions of a function which has no symbolic info and do not
4737 want @value{GDBN} to automatically skip over this function.
4739 @item set step-mode off
4740 Causes the @code{step} command to step over any functions which contains no
4741 debug information. This is the default.
4743 @item show step-mode
4744 Show whether @value{GDBN} will stop in or step over functions without
4745 source line debug information.
4748 @kindex fin @r{(@code{finish})}
4750 Continue running until just after function in the selected stack frame
4751 returns. Print the returned value (if any). This command can be
4752 abbreviated as @code{fin}.
4754 Contrast this with the @code{return} command (@pxref{Returning,
4755 ,Returning from a Function}).
4758 @kindex u @r{(@code{until})}
4759 @cindex run until specified location
4762 Continue running until a source line past the current line, in the
4763 current stack frame, is reached. This command is used to avoid single
4764 stepping through a loop more than once. It is like the @code{next}
4765 command, except that when @code{until} encounters a jump, it
4766 automatically continues execution until the program counter is greater
4767 than the address of the jump.
4769 This means that when you reach the end of a loop after single stepping
4770 though it, @code{until} makes your program continue execution until it
4771 exits the loop. In contrast, a @code{next} command at the end of a loop
4772 simply steps back to the beginning of the loop, which forces you to step
4773 through the next iteration.
4775 @code{until} always stops your program if it attempts to exit the current
4778 @code{until} may produce somewhat counterintuitive results if the order
4779 of machine code does not match the order of the source lines. For
4780 example, in the following excerpt from a debugging session, the @code{f}
4781 (@code{frame}) command shows that execution is stopped at line
4782 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4786 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4788 (@value{GDBP}) until
4789 195 for ( ; argc > 0; NEXTARG) @{
4792 This happened because, for execution efficiency, the compiler had
4793 generated code for the loop closure test at the end, rather than the
4794 start, of the loop---even though the test in a C @code{for}-loop is
4795 written before the body of the loop. The @code{until} command appeared
4796 to step back to the beginning of the loop when it advanced to this
4797 expression; however, it has not really gone to an earlier
4798 statement---not in terms of the actual machine code.
4800 @code{until} with no argument works by means of single
4801 instruction stepping, and hence is slower than @code{until} with an
4804 @item until @var{location}
4805 @itemx u @var{location}
4806 Continue running your program until either the specified location is
4807 reached, or the current stack frame returns. @var{location} is any of
4808 the forms described in @ref{Specify Location}.
4809 This form of the command uses temporary breakpoints, and
4810 hence is quicker than @code{until} without an argument. The specified
4811 location is actually reached only if it is in the current frame. This
4812 implies that @code{until} can be used to skip over recursive function
4813 invocations. For instance in the code below, if the current location is
4814 line @code{96}, issuing @code{until 99} will execute the program up to
4815 line @code{99} in the same invocation of factorial, i.e., after the inner
4816 invocations have returned.
4819 94 int factorial (int value)
4821 96 if (value > 1) @{
4822 97 value *= factorial (value - 1);
4829 @kindex advance @var{location}
4830 @itemx advance @var{location}
4831 Continue running the program up to the given @var{location}. An argument is
4832 required, which should be of one of the forms described in
4833 @ref{Specify Location}.
4834 Execution will also stop upon exit from the current stack
4835 frame. This command is similar to @code{until}, but @code{advance} will
4836 not skip over recursive function calls, and the target location doesn't
4837 have to be in the same frame as the current one.
4841 @kindex si @r{(@code{stepi})}
4843 @itemx stepi @var{arg}
4845 Execute one machine instruction, then stop and return to the debugger.
4847 It is often useful to do @samp{display/i $pc} when stepping by machine
4848 instructions. This makes @value{GDBN} automatically display the next
4849 instruction to be executed, each time your program stops. @xref{Auto
4850 Display,, Automatic Display}.
4852 An argument is a repeat count, as in @code{step}.
4856 @kindex ni @r{(@code{nexti})}
4858 @itemx nexti @var{arg}
4860 Execute one machine instruction, but if it is a function call,
4861 proceed until the function returns.
4863 An argument is a repeat count, as in @code{next}.
4866 @node Skipping Over Functions and Files
4867 @section Skipping Over Functions and Files
4868 @cindex skipping over functions and files
4870 The program you are debugging may contain some functions which are
4871 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4872 skip a function or all functions in a file when stepping.
4874 For example, consider the following C function:
4885 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4886 are not interested in stepping through @code{boring}. If you run @code{step}
4887 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4888 step over both @code{foo} and @code{boring}!
4890 One solution is to @code{step} into @code{boring} and use the @code{finish}
4891 command to immediately exit it. But this can become tedious if @code{boring}
4892 is called from many places.
4894 A more flexible solution is to execute @kbd{skip boring}. This instructs
4895 @value{GDBN} never to step into @code{boring}. Now when you execute
4896 @code{step} at line 103, you'll step over @code{boring} and directly into
4899 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4900 example, @code{skip file boring.c}.
4903 @kindex skip function
4904 @item skip @r{[}@var{linespec}@r{]}
4905 @itemx skip function @r{[}@var{linespec}@r{]}
4906 After running this command, the function named by @var{linespec} or the
4907 function containing the line named by @var{linespec} will be skipped over when
4908 stepping. @xref{Specify Location}.
4910 If you do not specify @var{linespec}, the function you're currently debugging
4913 (If you have a function called @code{file} that you want to skip, use
4914 @kbd{skip function file}.)
4917 @item skip file @r{[}@var{filename}@r{]}
4918 After running this command, any function whose source lives in @var{filename}
4919 will be skipped over when stepping.
4921 If you do not specify @var{filename}, functions whose source lives in the file
4922 you're currently debugging will be skipped.
4925 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4926 These are the commands for managing your list of skips:
4930 @item info skip @r{[}@var{range}@r{]}
4931 Print details about the specified skip(s). If @var{range} is not specified,
4932 print a table with details about all functions and files marked for skipping.
4933 @code{info skip} prints the following information about each skip:
4937 A number identifying this skip.
4939 The type of this skip, either @samp{function} or @samp{file}.
4940 @item Enabled or Disabled
4941 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4943 For function skips, this column indicates the address in memory of the function
4944 being skipped. If you've set a function skip on a function which has not yet
4945 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4946 which has the function is loaded, @code{info skip} will show the function's
4949 For file skips, this field contains the filename being skipped. For functions
4950 skips, this field contains the function name and its line number in the file
4951 where it is defined.
4955 @item skip delete @r{[}@var{range}@r{]}
4956 Delete the specified skip(s). If @var{range} is not specified, delete all
4960 @item skip enable @r{[}@var{range}@r{]}
4961 Enable the specified skip(s). If @var{range} is not specified, enable all
4964 @kindex skip disable
4965 @item skip disable @r{[}@var{range}@r{]}
4966 Disable the specified skip(s). If @var{range} is not specified, disable all
4975 A signal is an asynchronous event that can happen in a program. The
4976 operating system defines the possible kinds of signals, and gives each
4977 kind a name and a number. For example, in Unix @code{SIGINT} is the
4978 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4979 @code{SIGSEGV} is the signal a program gets from referencing a place in
4980 memory far away from all the areas in use; @code{SIGALRM} occurs when
4981 the alarm clock timer goes off (which happens only if your program has
4982 requested an alarm).
4984 @cindex fatal signals
4985 Some signals, including @code{SIGALRM}, are a normal part of the
4986 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4987 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4988 program has not specified in advance some other way to handle the signal.
4989 @code{SIGINT} does not indicate an error in your program, but it is normally
4990 fatal so it can carry out the purpose of the interrupt: to kill the program.
4992 @value{GDBN} has the ability to detect any occurrence of a signal in your
4993 program. You can tell @value{GDBN} in advance what to do for each kind of
4996 @cindex handling signals
4997 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4998 @code{SIGALRM} be silently passed to your program
4999 (so as not to interfere with their role in the program's functioning)
5000 but to stop your program immediately whenever an error signal happens.
5001 You can change these settings with the @code{handle} command.
5004 @kindex info signals
5008 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5009 handle each one. You can use this to see the signal numbers of all
5010 the defined types of signals.
5012 @item info signals @var{sig}
5013 Similar, but print information only about the specified signal number.
5015 @code{info handle} is an alias for @code{info signals}.
5018 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5019 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5020 can be the number of a signal or its name (with or without the
5021 @samp{SIG} at the beginning); a list of signal numbers of the form
5022 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5023 known signals. Optional arguments @var{keywords}, described below,
5024 say what change to make.
5028 The keywords allowed by the @code{handle} command can be abbreviated.
5029 Their full names are:
5033 @value{GDBN} should not stop your program when this signal happens. It may
5034 still print a message telling you that the signal has come in.
5037 @value{GDBN} should stop your program when this signal happens. This implies
5038 the @code{print} keyword as well.
5041 @value{GDBN} should print a message when this signal happens.
5044 @value{GDBN} should not mention the occurrence of the signal at all. This
5045 implies the @code{nostop} keyword as well.
5049 @value{GDBN} should allow your program to see this signal; your program
5050 can handle the signal, or else it may terminate if the signal is fatal
5051 and not handled. @code{pass} and @code{noignore} are synonyms.
5055 @value{GDBN} should not allow your program to see this signal.
5056 @code{nopass} and @code{ignore} are synonyms.
5060 When a signal stops your program, the signal is not visible to the
5062 continue. Your program sees the signal then, if @code{pass} is in
5063 effect for the signal in question @emph{at that time}. In other words,
5064 after @value{GDBN} reports a signal, you can use the @code{handle}
5065 command with @code{pass} or @code{nopass} to control whether your
5066 program sees that signal when you continue.
5068 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5069 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5070 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5073 You can also use the @code{signal} command to prevent your program from
5074 seeing a signal, or cause it to see a signal it normally would not see,
5075 or to give it any signal at any time. For example, if your program stopped
5076 due to some sort of memory reference error, you might store correct
5077 values into the erroneous variables and continue, hoping to see more
5078 execution; but your program would probably terminate immediately as
5079 a result of the fatal signal once it saw the signal. To prevent this,
5080 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5083 @cindex extra signal information
5084 @anchor{extra signal information}
5086 On some targets, @value{GDBN} can inspect extra signal information
5087 associated with the intercepted signal, before it is actually
5088 delivered to the program being debugged. This information is exported
5089 by the convenience variable @code{$_siginfo}, and consists of data
5090 that is passed by the kernel to the signal handler at the time of the
5091 receipt of a signal. The data type of the information itself is
5092 target dependent. You can see the data type using the @code{ptype
5093 $_siginfo} command. On Unix systems, it typically corresponds to the
5094 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5097 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5098 referenced address that raised a segmentation fault.
5102 (@value{GDBP}) continue
5103 Program received signal SIGSEGV, Segmentation fault.
5104 0x0000000000400766 in main ()
5106 (@value{GDBP}) ptype $_siginfo
5113 struct @{...@} _kill;
5114 struct @{...@} _timer;
5116 struct @{...@} _sigchld;
5117 struct @{...@} _sigfault;
5118 struct @{...@} _sigpoll;
5121 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5125 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5126 $1 = (void *) 0x7ffff7ff7000
5130 Depending on target support, @code{$_siginfo} may also be writable.
5133 @section Stopping and Starting Multi-thread Programs
5135 @cindex stopped threads
5136 @cindex threads, stopped
5138 @cindex continuing threads
5139 @cindex threads, continuing
5141 @value{GDBN} supports debugging programs with multiple threads
5142 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5143 are two modes of controlling execution of your program within the
5144 debugger. In the default mode, referred to as @dfn{all-stop mode},
5145 when any thread in your program stops (for example, at a breakpoint
5146 or while being stepped), all other threads in the program are also stopped by
5147 @value{GDBN}. On some targets, @value{GDBN} also supports
5148 @dfn{non-stop mode}, in which other threads can continue to run freely while
5149 you examine the stopped thread in the debugger.
5152 * All-Stop Mode:: All threads stop when GDB takes control
5153 * Non-Stop Mode:: Other threads continue to execute
5154 * Background Execution:: Running your program asynchronously
5155 * Thread-Specific Breakpoints:: Controlling breakpoints
5156 * Interrupted System Calls:: GDB may interfere with system calls
5157 * Observer Mode:: GDB does not alter program behavior
5161 @subsection All-Stop Mode
5163 @cindex all-stop mode
5165 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5166 @emph{all} threads of execution stop, not just the current thread. This
5167 allows you to examine the overall state of the program, including
5168 switching between threads, without worrying that things may change
5171 Conversely, whenever you restart the program, @emph{all} threads start
5172 executing. @emph{This is true even when single-stepping} with commands
5173 like @code{step} or @code{next}.
5175 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5176 Since thread scheduling is up to your debugging target's operating
5177 system (not controlled by @value{GDBN}), other threads may
5178 execute more than one statement while the current thread completes a
5179 single step. Moreover, in general other threads stop in the middle of a
5180 statement, rather than at a clean statement boundary, when the program
5183 You might even find your program stopped in another thread after
5184 continuing or even single-stepping. This happens whenever some other
5185 thread runs into a breakpoint, a signal, or an exception before the
5186 first thread completes whatever you requested.
5188 @cindex automatic thread selection
5189 @cindex switching threads automatically
5190 @cindex threads, automatic switching
5191 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5192 signal, it automatically selects the thread where that breakpoint or
5193 signal happened. @value{GDBN} alerts you to the context switch with a
5194 message such as @samp{[Switching to Thread @var{n}]} to identify the
5197 On some OSes, you can modify @value{GDBN}'s default behavior by
5198 locking the OS scheduler to allow only a single thread to run.
5201 @item set scheduler-locking @var{mode}
5202 @cindex scheduler locking mode
5203 @cindex lock scheduler
5204 Set the scheduler locking mode. If it is @code{off}, then there is no
5205 locking and any thread may run at any time. If @code{on}, then only the
5206 current thread may run when the inferior is resumed. The @code{step}
5207 mode optimizes for single-stepping; it prevents other threads
5208 from preempting the current thread while you are stepping, so that
5209 the focus of debugging does not change unexpectedly.
5210 Other threads only rarely (or never) get a chance to run
5211 when you step. They are more likely to run when you @samp{next} over a
5212 function call, and they are completely free to run when you use commands
5213 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5214 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5215 the current thread away from the thread that you are debugging.
5217 @item show scheduler-locking
5218 Display the current scheduler locking mode.
5221 @cindex resume threads of multiple processes simultaneously
5222 By default, when you issue one of the execution commands such as
5223 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5224 threads of the current inferior to run. For example, if @value{GDBN}
5225 is attached to two inferiors, each with two threads, the
5226 @code{continue} command resumes only the two threads of the current
5227 inferior. This is useful, for example, when you debug a program that
5228 forks and you want to hold the parent stopped (so that, for instance,
5229 it doesn't run to exit), while you debug the child. In other
5230 situations, you may not be interested in inspecting the current state
5231 of any of the processes @value{GDBN} is attached to, and you may want
5232 to resume them all until some breakpoint is hit. In the latter case,
5233 you can instruct @value{GDBN} to allow all threads of all the
5234 inferiors to run with the @w{@code{set schedule-multiple}} command.
5237 @kindex set schedule-multiple
5238 @item set schedule-multiple
5239 Set the mode for allowing threads of multiple processes to be resumed
5240 when an execution command is issued. When @code{on}, all threads of
5241 all processes are allowed to run. When @code{off}, only the threads
5242 of the current process are resumed. The default is @code{off}. The
5243 @code{scheduler-locking} mode takes precedence when set to @code{on},
5244 or while you are stepping and set to @code{step}.
5246 @item show schedule-multiple
5247 Display the current mode for resuming the execution of threads of
5252 @subsection Non-Stop Mode
5254 @cindex non-stop mode
5256 @c This section is really only a place-holder, and needs to be expanded
5257 @c with more details.
5259 For some multi-threaded targets, @value{GDBN} supports an optional
5260 mode of operation in which you can examine stopped program threads in
5261 the debugger while other threads continue to execute freely. This
5262 minimizes intrusion when debugging live systems, such as programs
5263 where some threads have real-time constraints or must continue to
5264 respond to external events. This is referred to as @dfn{non-stop} mode.
5266 In non-stop mode, when a thread stops to report a debugging event,
5267 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5268 threads as well, in contrast to the all-stop mode behavior. Additionally,
5269 execution commands such as @code{continue} and @code{step} apply by default
5270 only to the current thread in non-stop mode, rather than all threads as
5271 in all-stop mode. This allows you to control threads explicitly in
5272 ways that are not possible in all-stop mode --- for example, stepping
5273 one thread while allowing others to run freely, stepping
5274 one thread while holding all others stopped, or stepping several threads
5275 independently and simultaneously.
5277 To enter non-stop mode, use this sequence of commands before you run
5278 or attach to your program:
5281 # Enable the async interface.
5284 # If using the CLI, pagination breaks non-stop.
5287 # Finally, turn it on!
5291 You can use these commands to manipulate the non-stop mode setting:
5294 @kindex set non-stop
5295 @item set non-stop on
5296 Enable selection of non-stop mode.
5297 @item set non-stop off
5298 Disable selection of non-stop mode.
5299 @kindex show non-stop
5301 Show the current non-stop enablement setting.
5304 Note these commands only reflect whether non-stop mode is enabled,
5305 not whether the currently-executing program is being run in non-stop mode.
5306 In particular, the @code{set non-stop} preference is only consulted when
5307 @value{GDBN} starts or connects to the target program, and it is generally
5308 not possible to switch modes once debugging has started. Furthermore,
5309 since not all targets support non-stop mode, even when you have enabled
5310 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5313 In non-stop mode, all execution commands apply only to the current thread
5314 by default. That is, @code{continue} only continues one thread.
5315 To continue all threads, issue @code{continue -a} or @code{c -a}.
5317 You can use @value{GDBN}'s background execution commands
5318 (@pxref{Background Execution}) to run some threads in the background
5319 while you continue to examine or step others from @value{GDBN}.
5320 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5321 always executed asynchronously in non-stop mode.
5323 Suspending execution is done with the @code{interrupt} command when
5324 running in the background, or @kbd{Ctrl-c} during foreground execution.
5325 In all-stop mode, this stops the whole process;
5326 but in non-stop mode the interrupt applies only to the current thread.
5327 To stop the whole program, use @code{interrupt -a}.
5329 Other execution commands do not currently support the @code{-a} option.
5331 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5332 that thread current, as it does in all-stop mode. This is because the
5333 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5334 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5335 changed to a different thread just as you entered a command to operate on the
5336 previously current thread.
5338 @node Background Execution
5339 @subsection Background Execution
5341 @cindex foreground execution
5342 @cindex background execution
5343 @cindex asynchronous execution
5344 @cindex execution, foreground, background and asynchronous
5346 @value{GDBN}'s execution commands have two variants: the normal
5347 foreground (synchronous) behavior, and a background
5348 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5349 the program to report that some thread has stopped before prompting for
5350 another command. In background execution, @value{GDBN} immediately gives
5351 a command prompt so that you can issue other commands while your program runs.
5353 You need to explicitly enable asynchronous mode before you can use
5354 background execution commands. You can use these commands to
5355 manipulate the asynchronous mode setting:
5358 @kindex set target-async
5359 @item set target-async on
5360 Enable asynchronous mode.
5361 @item set target-async off
5362 Disable asynchronous mode.
5363 @kindex show target-async
5364 @item show target-async
5365 Show the current target-async setting.
5368 If the target doesn't support async mode, @value{GDBN} issues an error
5369 message if you attempt to use the background execution commands.
5371 To specify background execution, add a @code{&} to the command. For example,
5372 the background form of the @code{continue} command is @code{continue&}, or
5373 just @code{c&}. The execution commands that accept background execution
5379 @xref{Starting, , Starting your Program}.
5383 @xref{Attach, , Debugging an Already-running Process}.
5387 @xref{Continuing and Stepping, step}.
5391 @xref{Continuing and Stepping, stepi}.
5395 @xref{Continuing and Stepping, next}.
5399 @xref{Continuing and Stepping, nexti}.
5403 @xref{Continuing and Stepping, continue}.
5407 @xref{Continuing and Stepping, finish}.
5411 @xref{Continuing and Stepping, until}.
5415 Background execution is especially useful in conjunction with non-stop
5416 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5417 However, you can also use these commands in the normal all-stop mode with
5418 the restriction that you cannot issue another execution command until the
5419 previous one finishes. Examples of commands that are valid in all-stop
5420 mode while the program is running include @code{help} and @code{info break}.
5422 You can interrupt your program while it is running in the background by
5423 using the @code{interrupt} command.
5430 Suspend execution of the running program. In all-stop mode,
5431 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5432 only the current thread. To stop the whole program in non-stop mode,
5433 use @code{interrupt -a}.
5436 @node Thread-Specific Breakpoints
5437 @subsection Thread-Specific Breakpoints
5439 When your program has multiple threads (@pxref{Threads,, Debugging
5440 Programs with Multiple Threads}), you can choose whether to set
5441 breakpoints on all threads, or on a particular thread.
5444 @cindex breakpoints and threads
5445 @cindex thread breakpoints
5446 @kindex break @dots{} thread @var{threadno}
5447 @item break @var{linespec} thread @var{threadno}
5448 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5449 @var{linespec} specifies source lines; there are several ways of
5450 writing them (@pxref{Specify Location}), but the effect is always to
5451 specify some source line.
5453 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5454 to specify that you only want @value{GDBN} to stop the program when a
5455 particular thread reaches this breakpoint. @var{threadno} is one of the
5456 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5457 column of the @samp{info threads} display.
5459 If you do not specify @samp{thread @var{threadno}} when you set a
5460 breakpoint, the breakpoint applies to @emph{all} threads of your
5463 You can use the @code{thread} qualifier on conditional breakpoints as
5464 well; in this case, place @samp{thread @var{threadno}} before or
5465 after the breakpoint condition, like this:
5468 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5473 @node Interrupted System Calls
5474 @subsection Interrupted System Calls
5476 @cindex thread breakpoints and system calls
5477 @cindex system calls and thread breakpoints
5478 @cindex premature return from system calls
5479 There is an unfortunate side effect when using @value{GDBN} to debug
5480 multi-threaded programs. If one thread stops for a
5481 breakpoint, or for some other reason, and another thread is blocked in a
5482 system call, then the system call may return prematurely. This is a
5483 consequence of the interaction between multiple threads and the signals
5484 that @value{GDBN} uses to implement breakpoints and other events that
5487 To handle this problem, your program should check the return value of
5488 each system call and react appropriately. This is good programming
5491 For example, do not write code like this:
5497 The call to @code{sleep} will return early if a different thread stops
5498 at a breakpoint or for some other reason.
5500 Instead, write this:
5505 unslept = sleep (unslept);
5508 A system call is allowed to return early, so the system is still
5509 conforming to its specification. But @value{GDBN} does cause your
5510 multi-threaded program to behave differently than it would without
5513 Also, @value{GDBN} uses internal breakpoints in the thread library to
5514 monitor certain events such as thread creation and thread destruction.
5515 When such an event happens, a system call in another thread may return
5516 prematurely, even though your program does not appear to stop.
5519 @subsection Observer Mode
5521 If you want to build on non-stop mode and observe program behavior
5522 without any chance of disruption by @value{GDBN}, you can set
5523 variables to disable all of the debugger's attempts to modify state,
5524 whether by writing memory, inserting breakpoints, etc. These operate
5525 at a low level, intercepting operations from all commands.
5527 When all of these are set to @code{off}, then @value{GDBN} is said to
5528 be @dfn{observer mode}. As a convenience, the variable
5529 @code{observer} can be set to disable these, plus enable non-stop
5532 Note that @value{GDBN} will not prevent you from making nonsensical
5533 combinations of these settings. For instance, if you have enabled
5534 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5535 then breakpoints that work by writing trap instructions into the code
5536 stream will still not be able to be placed.
5541 @item set observer on
5542 @itemx set observer off
5543 When set to @code{on}, this disables all the permission variables
5544 below (except for @code{insert-fast-tracepoints}), plus enables
5545 non-stop debugging. Setting this to @code{off} switches back to
5546 normal debugging, though remaining in non-stop mode.
5549 Show whether observer mode is on or off.
5551 @kindex may-write-registers
5552 @item set may-write-registers on
5553 @itemx set may-write-registers off
5554 This controls whether @value{GDBN} will attempt to alter the values of
5555 registers, such as with assignment expressions in @code{print}, or the
5556 @code{jump} command. It defaults to @code{on}.
5558 @item show may-write-registers
5559 Show the current permission to write registers.
5561 @kindex may-write-memory
5562 @item set may-write-memory on
5563 @itemx set may-write-memory off
5564 This controls whether @value{GDBN} will attempt to alter the contents
5565 of memory, such as with assignment expressions in @code{print}. It
5566 defaults to @code{on}.
5568 @item show may-write-memory
5569 Show the current permission to write memory.
5571 @kindex may-insert-breakpoints
5572 @item set may-insert-breakpoints on
5573 @itemx set may-insert-breakpoints off
5574 This controls whether @value{GDBN} will attempt to insert breakpoints.
5575 This affects all breakpoints, including internal breakpoints defined
5576 by @value{GDBN}. It defaults to @code{on}.
5578 @item show may-insert-breakpoints
5579 Show the current permission to insert breakpoints.
5581 @kindex may-insert-tracepoints
5582 @item set may-insert-tracepoints on
5583 @itemx set may-insert-tracepoints off
5584 This controls whether @value{GDBN} will attempt to insert (regular)
5585 tracepoints at the beginning of a tracing experiment. It affects only
5586 non-fast tracepoints, fast tracepoints being under the control of
5587 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5589 @item show may-insert-tracepoints
5590 Show the current permission to insert tracepoints.
5592 @kindex may-insert-fast-tracepoints
5593 @item set may-insert-fast-tracepoints on
5594 @itemx set may-insert-fast-tracepoints off
5595 This controls whether @value{GDBN} will attempt to insert fast
5596 tracepoints at the beginning of a tracing experiment. It affects only
5597 fast tracepoints, regular (non-fast) tracepoints being under the
5598 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5600 @item show may-insert-fast-tracepoints
5601 Show the current permission to insert fast tracepoints.
5603 @kindex may-interrupt
5604 @item set may-interrupt on
5605 @itemx set may-interrupt off
5606 This controls whether @value{GDBN} will attempt to interrupt or stop
5607 program execution. When this variable is @code{off}, the
5608 @code{interrupt} command will have no effect, nor will
5609 @kbd{Ctrl-c}. It defaults to @code{on}.
5611 @item show may-interrupt
5612 Show the current permission to interrupt or stop the program.
5616 @node Reverse Execution
5617 @chapter Running programs backward
5618 @cindex reverse execution
5619 @cindex running programs backward
5621 When you are debugging a program, it is not unusual to realize that
5622 you have gone too far, and some event of interest has already happened.
5623 If the target environment supports it, @value{GDBN} can allow you to
5624 ``rewind'' the program by running it backward.
5626 A target environment that supports reverse execution should be able
5627 to ``undo'' the changes in machine state that have taken place as the
5628 program was executing normally. Variables, registers etc.@: should
5629 revert to their previous values. Obviously this requires a great
5630 deal of sophistication on the part of the target environment; not
5631 all target environments can support reverse execution.
5633 When a program is executed in reverse, the instructions that
5634 have most recently been executed are ``un-executed'', in reverse
5635 order. The program counter runs backward, following the previous
5636 thread of execution in reverse. As each instruction is ``un-executed'',
5637 the values of memory and/or registers that were changed by that
5638 instruction are reverted to their previous states. After executing
5639 a piece of source code in reverse, all side effects of that code
5640 should be ``undone'', and all variables should be returned to their
5641 prior values@footnote{
5642 Note that some side effects are easier to undo than others. For instance,
5643 memory and registers are relatively easy, but device I/O is hard. Some
5644 targets may be able undo things like device I/O, and some may not.
5646 The contract between @value{GDBN} and the reverse executing target
5647 requires only that the target do something reasonable when
5648 @value{GDBN} tells it to execute backwards, and then report the
5649 results back to @value{GDBN}. Whatever the target reports back to
5650 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5651 assumes that the memory and registers that the target reports are in a
5652 consistant state, but @value{GDBN} accepts whatever it is given.
5655 If you are debugging in a target environment that supports
5656 reverse execution, @value{GDBN} provides the following commands.
5659 @kindex reverse-continue
5660 @kindex rc @r{(@code{reverse-continue})}
5661 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5662 @itemx rc @r{[}@var{ignore-count}@r{]}
5663 Beginning at the point where your program last stopped, start executing
5664 in reverse. Reverse execution will stop for breakpoints and synchronous
5665 exceptions (signals), just like normal execution. Behavior of
5666 asynchronous signals depends on the target environment.
5668 @kindex reverse-step
5669 @kindex rs @r{(@code{step})}
5670 @item reverse-step @r{[}@var{count}@r{]}
5671 Run the program backward until control reaches the start of a
5672 different source line; then stop it, and return control to @value{GDBN}.
5674 Like the @code{step} command, @code{reverse-step} will only stop
5675 at the beginning of a source line. It ``un-executes'' the previously
5676 executed source line. If the previous source line included calls to
5677 debuggable functions, @code{reverse-step} will step (backward) into
5678 the called function, stopping at the beginning of the @emph{last}
5679 statement in the called function (typically a return statement).
5681 Also, as with the @code{step} command, if non-debuggable functions are
5682 called, @code{reverse-step} will run thru them backward without stopping.
5684 @kindex reverse-stepi
5685 @kindex rsi @r{(@code{reverse-stepi})}
5686 @item reverse-stepi @r{[}@var{count}@r{]}
5687 Reverse-execute one machine instruction. Note that the instruction
5688 to be reverse-executed is @emph{not} the one pointed to by the program
5689 counter, but the instruction executed prior to that one. For instance,
5690 if the last instruction was a jump, @code{reverse-stepi} will take you
5691 back from the destination of the jump to the jump instruction itself.
5693 @kindex reverse-next
5694 @kindex rn @r{(@code{reverse-next})}
5695 @item reverse-next @r{[}@var{count}@r{]}
5696 Run backward to the beginning of the previous line executed in
5697 the current (innermost) stack frame. If the line contains function
5698 calls, they will be ``un-executed'' without stopping. Starting from
5699 the first line of a function, @code{reverse-next} will take you back
5700 to the caller of that function, @emph{before} the function was called,
5701 just as the normal @code{next} command would take you from the last
5702 line of a function back to its return to its caller
5703 @footnote{Unless the code is too heavily optimized.}.
5705 @kindex reverse-nexti
5706 @kindex rni @r{(@code{reverse-nexti})}
5707 @item reverse-nexti @r{[}@var{count}@r{]}
5708 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5709 in reverse, except that called functions are ``un-executed'' atomically.
5710 That is, if the previously executed instruction was a return from
5711 another function, @code{reverse-nexti} will continue to execute
5712 in reverse until the call to that function (from the current stack
5715 @kindex reverse-finish
5716 @item reverse-finish
5717 Just as the @code{finish} command takes you to the point where the
5718 current function returns, @code{reverse-finish} takes you to the point
5719 where it was called. Instead of ending up at the end of the current
5720 function invocation, you end up at the beginning.
5722 @kindex set exec-direction
5723 @item set exec-direction
5724 Set the direction of target execution.
5725 @itemx set exec-direction reverse
5726 @cindex execute forward or backward in time
5727 @value{GDBN} will perform all execution commands in reverse, until the
5728 exec-direction mode is changed to ``forward''. Affected commands include
5729 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5730 command cannot be used in reverse mode.
5731 @item set exec-direction forward
5732 @value{GDBN} will perform all execution commands in the normal fashion.
5733 This is the default.
5737 @node Process Record and Replay
5738 @chapter Recording Inferior's Execution and Replaying It
5739 @cindex process record and replay
5740 @cindex recording inferior's execution and replaying it
5742 On some platforms, @value{GDBN} provides a special @dfn{process record
5743 and replay} target that can record a log of the process execution, and
5744 replay it later with both forward and reverse execution commands.
5747 When this target is in use, if the execution log includes the record
5748 for the next instruction, @value{GDBN} will debug in @dfn{replay
5749 mode}. In the replay mode, the inferior does not really execute code
5750 instructions. Instead, all the events that normally happen during
5751 code execution are taken from the execution log. While code is not
5752 really executed in replay mode, the values of registers (including the
5753 program counter register) and the memory of the inferior are still
5754 changed as they normally would. Their contents are taken from the
5758 If the record for the next instruction is not in the execution log,
5759 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5760 inferior executes normally, and @value{GDBN} records the execution log
5763 The process record and replay target supports reverse execution
5764 (@pxref{Reverse Execution}), even if the platform on which the
5765 inferior runs does not. However, the reverse execution is limited in
5766 this case by the range of the instructions recorded in the execution
5767 log. In other words, reverse execution on platforms that don't
5768 support it directly can only be done in the replay mode.
5770 When debugging in the reverse direction, @value{GDBN} will work in
5771 replay mode as long as the execution log includes the record for the
5772 previous instruction; otherwise, it will work in record mode, if the
5773 platform supports reverse execution, or stop if not.
5775 For architecture environments that support process record and replay,
5776 @value{GDBN} provides the following commands:
5779 @kindex target record
5783 This command starts the process record and replay target. The process
5784 record and replay target can only debug a process that is already
5785 running. Therefore, you need first to start the process with the
5786 @kbd{run} or @kbd{start} commands, and then start the recording with
5787 the @kbd{target record} command.
5789 Both @code{record} and @code{rec} are aliases of @code{target record}.
5791 @cindex displaced stepping, and process record and replay
5792 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5793 will be automatically disabled when process record and replay target
5794 is started. That's because the process record and replay target
5795 doesn't support displaced stepping.
5797 @cindex non-stop mode, and process record and replay
5798 @cindex asynchronous execution, and process record and replay
5799 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5800 the asynchronous execution mode (@pxref{Background Execution}), the
5801 process record and replay target cannot be started because it doesn't
5802 support these two modes.
5807 Stop the process record and replay target. When process record and
5808 replay target stops, the entire execution log will be deleted and the
5809 inferior will either be terminated, or will remain in its final state.
5811 When you stop the process record and replay target in record mode (at
5812 the end of the execution log), the inferior will be stopped at the
5813 next instruction that would have been recorded. In other words, if
5814 you record for a while and then stop recording, the inferior process
5815 will be left in the same state as if the recording never happened.
5817 On the other hand, if the process record and replay target is stopped
5818 while in replay mode (that is, not at the end of the execution log,
5819 but at some earlier point), the inferior process will become ``live''
5820 at that earlier state, and it will then be possible to continue the
5821 usual ``live'' debugging of the process from that state.
5823 When the inferior process exits, or @value{GDBN} detaches from it,
5824 process record and replay target will automatically stop itself.
5827 @item record save @var{filename}
5828 Save the execution log to a file @file{@var{filename}}.
5829 Default filename is @file{gdb_record.@var{process_id}}, where
5830 @var{process_id} is the process ID of the inferior.
5832 @kindex record restore
5833 @item record restore @var{filename}
5834 Restore the execution log from a file @file{@var{filename}}.
5835 File must have been created with @code{record save}.
5837 @kindex set record insn-number-max
5838 @item set record insn-number-max @var{limit}
5839 Set the limit of instructions to be recorded. Default value is 200000.
5841 If @var{limit} is a positive number, then @value{GDBN} will start
5842 deleting instructions from the log once the number of the record
5843 instructions becomes greater than @var{limit}. For every new recorded
5844 instruction, @value{GDBN} will delete the earliest recorded
5845 instruction to keep the number of recorded instructions at the limit.
5846 (Since deleting recorded instructions loses information, @value{GDBN}
5847 lets you control what happens when the limit is reached, by means of
5848 the @code{stop-at-limit} option, described below.)
5850 If @var{limit} is zero, @value{GDBN} will never delete recorded
5851 instructions from the execution log. The number of recorded
5852 instructions is unlimited in this case.
5854 @kindex show record insn-number-max
5855 @item show record insn-number-max
5856 Show the limit of instructions to be recorded.
5858 @kindex set record stop-at-limit
5859 @item set record stop-at-limit
5860 Control the behavior when the number of recorded instructions reaches
5861 the limit. If ON (the default), @value{GDBN} will stop when the limit
5862 is reached for the first time and ask you whether you want to stop the
5863 inferior or continue running it and recording the execution log. If
5864 you decide to continue recording, each new recorded instruction will
5865 cause the oldest one to be deleted.
5867 If this option is OFF, @value{GDBN} will automatically delete the
5868 oldest record to make room for each new one, without asking.
5870 @kindex show record stop-at-limit
5871 @item show record stop-at-limit
5872 Show the current setting of @code{stop-at-limit}.
5874 @kindex set record memory-query
5875 @item set record memory-query
5876 Control the behavior when @value{GDBN} is unable to record memory
5877 changes caused by an instruction. If ON, @value{GDBN} will query
5878 whether to stop the inferior in that case.
5880 If this option is OFF (the default), @value{GDBN} will automatically
5881 ignore the effect of such instructions on memory. Later, when
5882 @value{GDBN} replays this execution log, it will mark the log of this
5883 instruction as not accessible, and it will not affect the replay
5886 @kindex show record memory-query
5887 @item show record memory-query
5888 Show the current setting of @code{memory-query}.
5892 Show various statistics about the state of process record and its
5893 in-memory execution log buffer, including:
5897 Whether in record mode or replay mode.
5899 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5901 Highest recorded instruction number.
5903 Current instruction about to be replayed (if in replay mode).
5905 Number of instructions contained in the execution log.
5907 Maximum number of instructions that may be contained in the execution log.
5910 @kindex record delete
5913 When record target runs in replay mode (``in the past''), delete the
5914 subsequent execution log and begin to record a new execution log starting
5915 from the current address. This means you will abandon the previously
5916 recorded ``future'' and begin recording a new ``future''.
5921 @chapter Examining the Stack
5923 When your program has stopped, the first thing you need to know is where it
5924 stopped and how it got there.
5927 Each time your program performs a function call, information about the call
5929 That information includes the location of the call in your program,
5930 the arguments of the call,
5931 and the local variables of the function being called.
5932 The information is saved in a block of data called a @dfn{stack frame}.
5933 The stack frames are allocated in a region of memory called the @dfn{call
5936 When your program stops, the @value{GDBN} commands for examining the
5937 stack allow you to see all of this information.
5939 @cindex selected frame
5940 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5941 @value{GDBN} commands refer implicitly to the selected frame. In
5942 particular, whenever you ask @value{GDBN} for the value of a variable in
5943 your program, the value is found in the selected frame. There are
5944 special @value{GDBN} commands to select whichever frame you are
5945 interested in. @xref{Selection, ,Selecting a Frame}.
5947 When your program stops, @value{GDBN} automatically selects the
5948 currently executing frame and describes it briefly, similar to the
5949 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5952 * Frames:: Stack frames
5953 * Backtrace:: Backtraces
5954 * Selection:: Selecting a frame
5955 * Frame Info:: Information on a frame
5960 @section Stack Frames
5962 @cindex frame, definition
5964 The call stack is divided up into contiguous pieces called @dfn{stack
5965 frames}, or @dfn{frames} for short; each frame is the data associated
5966 with one call to one function. The frame contains the arguments given
5967 to the function, the function's local variables, and the address at
5968 which the function is executing.
5970 @cindex initial frame
5971 @cindex outermost frame
5972 @cindex innermost frame
5973 When your program is started, the stack has only one frame, that of the
5974 function @code{main}. This is called the @dfn{initial} frame or the
5975 @dfn{outermost} frame. Each time a function is called, a new frame is
5976 made. Each time a function returns, the frame for that function invocation
5977 is eliminated. If a function is recursive, there can be many frames for
5978 the same function. The frame for the function in which execution is
5979 actually occurring is called the @dfn{innermost} frame. This is the most
5980 recently created of all the stack frames that still exist.
5982 @cindex frame pointer
5983 Inside your program, stack frames are identified by their addresses. A
5984 stack frame consists of many bytes, each of which has its own address; each
5985 kind of computer has a convention for choosing one byte whose
5986 address serves as the address of the frame. Usually this address is kept
5987 in a register called the @dfn{frame pointer register}
5988 (@pxref{Registers, $fp}) while execution is going on in that frame.
5990 @cindex frame number
5991 @value{GDBN} assigns numbers to all existing stack frames, starting with
5992 zero for the innermost frame, one for the frame that called it,
5993 and so on upward. These numbers do not really exist in your program;
5994 they are assigned by @value{GDBN} to give you a way of designating stack
5995 frames in @value{GDBN} commands.
5997 @c The -fomit-frame-pointer below perennially causes hbox overflow
5998 @c underflow problems.
5999 @cindex frameless execution
6000 Some compilers provide a way to compile functions so that they operate
6001 without stack frames. (For example, the @value{NGCC} option
6003 @samp{-fomit-frame-pointer}
6005 generates functions without a frame.)
6006 This is occasionally done with heavily used library functions to save
6007 the frame setup time. @value{GDBN} has limited facilities for dealing
6008 with these function invocations. If the innermost function invocation
6009 has no stack frame, @value{GDBN} nevertheless regards it as though
6010 it had a separate frame, which is numbered zero as usual, allowing
6011 correct tracing of the function call chain. However, @value{GDBN} has
6012 no provision for frameless functions elsewhere in the stack.
6015 @kindex frame@r{, command}
6016 @cindex current stack frame
6017 @item frame @var{args}
6018 The @code{frame} command allows you to move from one stack frame to another,
6019 and to print the stack frame you select. @var{args} may be either the
6020 address of the frame or the stack frame number. Without an argument,
6021 @code{frame} prints the current stack frame.
6023 @kindex select-frame
6024 @cindex selecting frame silently
6026 The @code{select-frame} command allows you to move from one stack frame
6027 to another without printing the frame. This is the silent version of
6035 @cindex call stack traces
6036 A backtrace is a summary of how your program got where it is. It shows one
6037 line per frame, for many frames, starting with the currently executing
6038 frame (frame zero), followed by its caller (frame one), and on up the
6043 @kindex bt @r{(@code{backtrace})}
6046 Print a backtrace of the entire stack: one line per frame for all
6047 frames in the stack.
6049 You can stop the backtrace at any time by typing the system interrupt
6050 character, normally @kbd{Ctrl-c}.
6052 @item backtrace @var{n}
6054 Similar, but print only the innermost @var{n} frames.
6056 @item backtrace -@var{n}
6058 Similar, but print only the outermost @var{n} frames.
6060 @item backtrace full
6062 @itemx bt full @var{n}
6063 @itemx bt full -@var{n}
6064 Print the values of the local variables also. @var{n} specifies the
6065 number of frames to print, as described above.
6070 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6071 are additional aliases for @code{backtrace}.
6073 @cindex multiple threads, backtrace
6074 In a multi-threaded program, @value{GDBN} by default shows the
6075 backtrace only for the current thread. To display the backtrace for
6076 several or all of the threads, use the command @code{thread apply}
6077 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6078 apply all backtrace}, @value{GDBN} will display the backtrace for all
6079 the threads; this is handy when you debug a core dump of a
6080 multi-threaded program.
6082 Each line in the backtrace shows the frame number and the function name.
6083 The program counter value is also shown---unless you use @code{set
6084 print address off}. The backtrace also shows the source file name and
6085 line number, as well as the arguments to the function. The program
6086 counter value is omitted if it is at the beginning of the code for that
6089 Here is an example of a backtrace. It was made with the command
6090 @samp{bt 3}, so it shows the innermost three frames.
6094 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6096 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6097 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6099 (More stack frames follow...)
6104 The display for frame zero does not begin with a program counter
6105 value, indicating that your program has stopped at the beginning of the
6106 code for line @code{993} of @code{builtin.c}.
6109 The value of parameter @code{data} in frame 1 has been replaced by
6110 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6111 only if it is a scalar (integer, pointer, enumeration, etc). See command
6112 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6113 on how to configure the way function parameter values are printed.
6115 @cindex optimized out, in backtrace
6116 @cindex function call arguments, optimized out
6117 If your program was compiled with optimizations, some compilers will
6118 optimize away arguments passed to functions if those arguments are
6119 never used after the call. Such optimizations generate code that
6120 passes arguments through registers, but doesn't store those arguments
6121 in the stack frame. @value{GDBN} has no way of displaying such
6122 arguments in stack frames other than the innermost one. Here's what
6123 such a backtrace might look like:
6127 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6129 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6130 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6132 (More stack frames follow...)
6137 The values of arguments that were not saved in their stack frames are
6138 shown as @samp{<optimized out>}.
6140 If you need to display the values of such optimized-out arguments,
6141 either deduce that from other variables whose values depend on the one
6142 you are interested in, or recompile without optimizations.
6144 @cindex backtrace beyond @code{main} function
6145 @cindex program entry point
6146 @cindex startup code, and backtrace
6147 Most programs have a standard user entry point---a place where system
6148 libraries and startup code transition into user code. For C this is
6149 @code{main}@footnote{
6150 Note that embedded programs (the so-called ``free-standing''
6151 environment) are not required to have a @code{main} function as the
6152 entry point. They could even have multiple entry points.}.
6153 When @value{GDBN} finds the entry function in a backtrace
6154 it will terminate the backtrace, to avoid tracing into highly
6155 system-specific (and generally uninteresting) code.
6157 If you need to examine the startup code, or limit the number of levels
6158 in a backtrace, you can change this behavior:
6161 @item set backtrace past-main
6162 @itemx set backtrace past-main on
6163 @kindex set backtrace
6164 Backtraces will continue past the user entry point.
6166 @item set backtrace past-main off
6167 Backtraces will stop when they encounter the user entry point. This is the
6170 @item show backtrace past-main
6171 @kindex show backtrace
6172 Display the current user entry point backtrace policy.
6174 @item set backtrace past-entry
6175 @itemx set backtrace past-entry on
6176 Backtraces will continue past the internal entry point of an application.
6177 This entry point is encoded by the linker when the application is built,
6178 and is likely before the user entry point @code{main} (or equivalent) is called.
6180 @item set backtrace past-entry off
6181 Backtraces will stop when they encounter the internal entry point of an
6182 application. This is the default.
6184 @item show backtrace past-entry
6185 Display the current internal entry point backtrace policy.
6187 @item set backtrace limit @var{n}
6188 @itemx set backtrace limit 0
6189 @cindex backtrace limit
6190 Limit the backtrace to @var{n} levels. A value of zero means
6193 @item show backtrace limit
6194 Display the current limit on backtrace levels.
6198 @section Selecting a Frame
6200 Most commands for examining the stack and other data in your program work on
6201 whichever stack frame is selected at the moment. Here are the commands for
6202 selecting a stack frame; all of them finish by printing a brief description
6203 of the stack frame just selected.
6206 @kindex frame@r{, selecting}
6207 @kindex f @r{(@code{frame})}
6210 Select frame number @var{n}. Recall that frame zero is the innermost
6211 (currently executing) frame, frame one is the frame that called the
6212 innermost one, and so on. The highest-numbered frame is the one for
6215 @item frame @var{addr}
6217 Select the frame at address @var{addr}. This is useful mainly if the
6218 chaining of stack frames has been damaged by a bug, making it
6219 impossible for @value{GDBN} to assign numbers properly to all frames. In
6220 addition, this can be useful when your program has multiple stacks and
6221 switches between them.
6223 On the SPARC architecture, @code{frame} needs two addresses to
6224 select an arbitrary frame: a frame pointer and a stack pointer.
6226 On the MIPS and Alpha architecture, it needs two addresses: a stack
6227 pointer and a program counter.
6229 On the 29k architecture, it needs three addresses: a register stack
6230 pointer, a program counter, and a memory stack pointer.
6234 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6235 advances toward the outermost frame, to higher frame numbers, to frames
6236 that have existed longer. @var{n} defaults to one.
6239 @kindex do @r{(@code{down})}
6241 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6242 advances toward the innermost frame, to lower frame numbers, to frames
6243 that were created more recently. @var{n} defaults to one. You may
6244 abbreviate @code{down} as @code{do}.
6247 All of these commands end by printing two lines of output describing the
6248 frame. The first line shows the frame number, the function name, the
6249 arguments, and the source file and line number of execution in that
6250 frame. The second line shows the text of that source line.
6258 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6260 10 read_input_file (argv[i]);
6264 After such a printout, the @code{list} command with no arguments
6265 prints ten lines centered on the point of execution in the frame.
6266 You can also edit the program at the point of execution with your favorite
6267 editing program by typing @code{edit}.
6268 @xref{List, ,Printing Source Lines},
6272 @kindex down-silently
6274 @item up-silently @var{n}
6275 @itemx down-silently @var{n}
6276 These two commands are variants of @code{up} and @code{down},
6277 respectively; they differ in that they do their work silently, without
6278 causing display of the new frame. They are intended primarily for use
6279 in @value{GDBN} command scripts, where the output might be unnecessary and
6284 @section Information About a Frame
6286 There are several other commands to print information about the selected
6292 When used without any argument, this command does not change which
6293 frame is selected, but prints a brief description of the currently
6294 selected stack frame. It can be abbreviated @code{f}. With an
6295 argument, this command is used to select a stack frame.
6296 @xref{Selection, ,Selecting a Frame}.
6299 @kindex info f @r{(@code{info frame})}
6302 This command prints a verbose description of the selected stack frame,
6307 the address of the frame
6309 the address of the next frame down (called by this frame)
6311 the address of the next frame up (caller of this frame)
6313 the language in which the source code corresponding to this frame is written
6315 the address of the frame's arguments
6317 the address of the frame's local variables
6319 the program counter saved in it (the address of execution in the caller frame)
6321 which registers were saved in the frame
6324 @noindent The verbose description is useful when
6325 something has gone wrong that has made the stack format fail to fit
6326 the usual conventions.
6328 @item info frame @var{addr}
6329 @itemx info f @var{addr}
6330 Print a verbose description of the frame at address @var{addr}, without
6331 selecting that frame. The selected frame remains unchanged by this
6332 command. This requires the same kind of address (more than one for some
6333 architectures) that you specify in the @code{frame} command.
6334 @xref{Selection, ,Selecting a Frame}.
6338 Print the arguments of the selected frame, each on a separate line.
6342 Print the local variables of the selected frame, each on a separate
6343 line. These are all variables (declared either static or automatic)
6344 accessible at the point of execution of the selected frame.
6347 @cindex catch exceptions, list active handlers
6348 @cindex exception handlers, how to list
6350 Print a list of all the exception handlers that are active in the
6351 current stack frame at the current point of execution. To see other
6352 exception handlers, visit the associated frame (using the @code{up},
6353 @code{down}, or @code{frame} commands); then type @code{info catch}.
6354 @xref{Set Catchpoints, , Setting Catchpoints}.
6360 @chapter Examining Source Files
6362 @value{GDBN} can print parts of your program's source, since the debugging
6363 information recorded in the program tells @value{GDBN} what source files were
6364 used to build it. When your program stops, @value{GDBN} spontaneously prints
6365 the line where it stopped. Likewise, when you select a stack frame
6366 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6367 execution in that frame has stopped. You can print other portions of
6368 source files by explicit command.
6370 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6371 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6372 @value{GDBN} under @sc{gnu} Emacs}.
6375 * List:: Printing source lines
6376 * Specify Location:: How to specify code locations
6377 * Edit:: Editing source files
6378 * Search:: Searching source files
6379 * Source Path:: Specifying source directories
6380 * Machine Code:: Source and machine code
6384 @section Printing Source Lines
6387 @kindex l @r{(@code{list})}
6388 To print lines from a source file, use the @code{list} command
6389 (abbreviated @code{l}). By default, ten lines are printed.
6390 There are several ways to specify what part of the file you want to
6391 print; see @ref{Specify Location}, for the full list.
6393 Here are the forms of the @code{list} command most commonly used:
6396 @item list @var{linenum}
6397 Print lines centered around line number @var{linenum} in the
6398 current source file.
6400 @item list @var{function}
6401 Print lines centered around the beginning of function
6405 Print more lines. If the last lines printed were printed with a
6406 @code{list} command, this prints lines following the last lines
6407 printed; however, if the last line printed was a solitary line printed
6408 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6409 Stack}), this prints lines centered around that line.
6412 Print lines just before the lines last printed.
6415 @cindex @code{list}, how many lines to display
6416 By default, @value{GDBN} prints ten source lines with any of these forms of
6417 the @code{list} command. You can change this using @code{set listsize}:
6420 @kindex set listsize
6421 @item set listsize @var{count}
6422 Make the @code{list} command display @var{count} source lines (unless
6423 the @code{list} argument explicitly specifies some other number).
6425 @kindex show listsize
6427 Display the number of lines that @code{list} prints.
6430 Repeating a @code{list} command with @key{RET} discards the argument,
6431 so it is equivalent to typing just @code{list}. This is more useful
6432 than listing the same lines again. An exception is made for an
6433 argument of @samp{-}; that argument is preserved in repetition so that
6434 each repetition moves up in the source file.
6436 In general, the @code{list} command expects you to supply zero, one or two
6437 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6438 of writing them (@pxref{Specify Location}), but the effect is always
6439 to specify some source line.
6441 Here is a complete description of the possible arguments for @code{list}:
6444 @item list @var{linespec}
6445 Print lines centered around the line specified by @var{linespec}.
6447 @item list @var{first},@var{last}
6448 Print lines from @var{first} to @var{last}. Both arguments are
6449 linespecs. When a @code{list} command has two linespecs, and the
6450 source file of the second linespec is omitted, this refers to
6451 the same source file as the first linespec.
6453 @item list ,@var{last}
6454 Print lines ending with @var{last}.
6456 @item list @var{first},
6457 Print lines starting with @var{first}.
6460 Print lines just after the lines last printed.
6463 Print lines just before the lines last printed.
6466 As described in the preceding table.
6469 @node Specify Location
6470 @section Specifying a Location
6471 @cindex specifying location
6474 Several @value{GDBN} commands accept arguments that specify a location
6475 of your program's code. Since @value{GDBN} is a source-level
6476 debugger, a location usually specifies some line in the source code;
6477 for that reason, locations are also known as @dfn{linespecs}.
6479 Here are all the different ways of specifying a code location that
6480 @value{GDBN} understands:
6484 Specifies the line number @var{linenum} of the current source file.
6487 @itemx +@var{offset}
6488 Specifies the line @var{offset} lines before or after the @dfn{current
6489 line}. For the @code{list} command, the current line is the last one
6490 printed; for the breakpoint commands, this is the line at which
6491 execution stopped in the currently selected @dfn{stack frame}
6492 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6493 used as the second of the two linespecs in a @code{list} command,
6494 this specifies the line @var{offset} lines up or down from the first
6497 @item @var{filename}:@var{linenum}
6498 Specifies the line @var{linenum} in the source file @var{filename}.
6500 @item @var{function}
6501 Specifies the line that begins the body of the function @var{function}.
6502 For example, in C, this is the line with the open brace.
6504 @item @var{function}:@var{label}
6505 Specifies the line where @var{label} appears in @var{function}.
6507 @item @var{filename}:@var{function}
6508 Specifies the line that begins the body of the function @var{function}
6509 in the file @var{filename}. You only need the file name with a
6510 function name to avoid ambiguity when there are identically named
6511 functions in different source files.
6514 Specifies the line at which the label named @var{label} appears.
6515 @value{GDBN} searches for the label in the function corresponding to
6516 the currently selected stack frame. If there is no current selected
6517 stack frame (for instance, if the inferior is not running), then
6518 @value{GDBN} will not search for a label.
6520 @item *@var{address}
6521 Specifies the program address @var{address}. For line-oriented
6522 commands, such as @code{list} and @code{edit}, this specifies a source
6523 line that contains @var{address}. For @code{break} and other
6524 breakpoint oriented commands, this can be used to set breakpoints in
6525 parts of your program which do not have debugging information or
6528 Here @var{address} may be any expression valid in the current working
6529 language (@pxref{Languages, working language}) that specifies a code
6530 address. In addition, as a convenience, @value{GDBN} extends the
6531 semantics of expressions used in locations to cover the situations
6532 that frequently happen during debugging. Here are the various forms
6536 @item @var{expression}
6537 Any expression valid in the current working language.
6539 @item @var{funcaddr}
6540 An address of a function or procedure derived from its name. In C,
6541 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6542 simply the function's name @var{function} (and actually a special case
6543 of a valid expression). In Pascal and Modula-2, this is
6544 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6545 (although the Pascal form also works).
6547 This form specifies the address of the function's first instruction,
6548 before the stack frame and arguments have been set up.
6550 @item '@var{filename}'::@var{funcaddr}
6551 Like @var{funcaddr} above, but also specifies the name of the source
6552 file explicitly. This is useful if the name of the function does not
6553 specify the function unambiguously, e.g., if there are several
6554 functions with identical names in different source files.
6561 @section Editing Source Files
6562 @cindex editing source files
6565 @kindex e @r{(@code{edit})}
6566 To edit the lines in a source file, use the @code{edit} command.
6567 The editing program of your choice
6568 is invoked with the current line set to
6569 the active line in the program.
6570 Alternatively, there are several ways to specify what part of the file you
6571 want to print if you want to see other parts of the program:
6574 @item edit @var{location}
6575 Edit the source file specified by @code{location}. Editing starts at
6576 that @var{location}, e.g., at the specified source line of the
6577 specified file. @xref{Specify Location}, for all the possible forms
6578 of the @var{location} argument; here are the forms of the @code{edit}
6579 command most commonly used:
6582 @item edit @var{number}
6583 Edit the current source file with @var{number} as the active line number.
6585 @item edit @var{function}
6586 Edit the file containing @var{function} at the beginning of its definition.
6591 @subsection Choosing your Editor
6592 You can customize @value{GDBN} to use any editor you want
6594 The only restriction is that your editor (say @code{ex}), recognizes the
6595 following command-line syntax:
6597 ex +@var{number} file
6599 The optional numeric value +@var{number} specifies the number of the line in
6600 the file where to start editing.}.
6601 By default, it is @file{@value{EDITOR}}, but you can change this
6602 by setting the environment variable @code{EDITOR} before using
6603 @value{GDBN}. For example, to configure @value{GDBN} to use the
6604 @code{vi} editor, you could use these commands with the @code{sh} shell:
6610 or in the @code{csh} shell,
6612 setenv EDITOR /usr/bin/vi
6617 @section Searching Source Files
6618 @cindex searching source files
6620 There are two commands for searching through the current source file for a
6625 @kindex forward-search
6626 @item forward-search @var{regexp}
6627 @itemx search @var{regexp}
6628 The command @samp{forward-search @var{regexp}} checks each line,
6629 starting with the one following the last line listed, for a match for
6630 @var{regexp}. It lists the line that is found. You can use the
6631 synonym @samp{search @var{regexp}} or abbreviate the command name as
6634 @kindex reverse-search
6635 @item reverse-search @var{regexp}
6636 The command @samp{reverse-search @var{regexp}} checks each line, starting
6637 with the one before the last line listed and going backward, for a match
6638 for @var{regexp}. It lists the line that is found. You can abbreviate
6639 this command as @code{rev}.
6643 @section Specifying Source Directories
6646 @cindex directories for source files
6647 Executable programs sometimes do not record the directories of the source
6648 files from which they were compiled, just the names. Even when they do,
6649 the directories could be moved between the compilation and your debugging
6650 session. @value{GDBN} has a list of directories to search for source files;
6651 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6652 it tries all the directories in the list, in the order they are present
6653 in the list, until it finds a file with the desired name.
6655 For example, suppose an executable references the file
6656 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6657 @file{/mnt/cross}. The file is first looked up literally; if this
6658 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6659 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6660 message is printed. @value{GDBN} does not look up the parts of the
6661 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6662 Likewise, the subdirectories of the source path are not searched: if
6663 the source path is @file{/mnt/cross}, and the binary refers to
6664 @file{foo.c}, @value{GDBN} would not find it under
6665 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6667 Plain file names, relative file names with leading directories, file
6668 names containing dots, etc.@: are all treated as described above; for
6669 instance, if the source path is @file{/mnt/cross}, and the source file
6670 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6671 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6672 that---@file{/mnt/cross/foo.c}.
6674 Note that the executable search path is @emph{not} used to locate the
6677 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6678 any information it has cached about where source files are found and where
6679 each line is in the file.
6683 When you start @value{GDBN}, its source path includes only @samp{cdir}
6684 and @samp{cwd}, in that order.
6685 To add other directories, use the @code{directory} command.
6687 The search path is used to find both program source files and @value{GDBN}
6688 script files (read using the @samp{-command} option and @samp{source} command).
6690 In addition to the source path, @value{GDBN} provides a set of commands
6691 that manage a list of source path substitution rules. A @dfn{substitution
6692 rule} specifies how to rewrite source directories stored in the program's
6693 debug information in case the sources were moved to a different
6694 directory between compilation and debugging. A rule is made of
6695 two strings, the first specifying what needs to be rewritten in
6696 the path, and the second specifying how it should be rewritten.
6697 In @ref{set substitute-path}, we name these two parts @var{from} and
6698 @var{to} respectively. @value{GDBN} does a simple string replacement
6699 of @var{from} with @var{to} at the start of the directory part of the
6700 source file name, and uses that result instead of the original file
6701 name to look up the sources.
6703 Using the previous example, suppose the @file{foo-1.0} tree has been
6704 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6705 @value{GDBN} to replace @file{/usr/src} in all source path names with
6706 @file{/mnt/cross}. The first lookup will then be
6707 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6708 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6709 substitution rule, use the @code{set substitute-path} command
6710 (@pxref{set substitute-path}).
6712 To avoid unexpected substitution results, a rule is applied only if the
6713 @var{from} part of the directory name ends at a directory separator.
6714 For instance, a rule substituting @file{/usr/source} into
6715 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6716 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6717 is applied only at the beginning of the directory name, this rule will
6718 not be applied to @file{/root/usr/source/baz.c} either.
6720 In many cases, you can achieve the same result using the @code{directory}
6721 command. However, @code{set substitute-path} can be more efficient in
6722 the case where the sources are organized in a complex tree with multiple
6723 subdirectories. With the @code{directory} command, you need to add each
6724 subdirectory of your project. If you moved the entire tree while
6725 preserving its internal organization, then @code{set substitute-path}
6726 allows you to direct the debugger to all the sources with one single
6729 @code{set substitute-path} is also more than just a shortcut command.
6730 The source path is only used if the file at the original location no
6731 longer exists. On the other hand, @code{set substitute-path} modifies
6732 the debugger behavior to look at the rewritten location instead. So, if
6733 for any reason a source file that is not relevant to your executable is
6734 located at the original location, a substitution rule is the only
6735 method available to point @value{GDBN} at the new location.
6737 @cindex @samp{--with-relocated-sources}
6738 @cindex default source path substitution
6739 You can configure a default source path substitution rule by
6740 configuring @value{GDBN} with the
6741 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6742 should be the name of a directory under @value{GDBN}'s configured
6743 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6744 directory names in debug information under @var{dir} will be adjusted
6745 automatically if the installed @value{GDBN} is moved to a new
6746 location. This is useful if @value{GDBN}, libraries or executables
6747 with debug information and corresponding source code are being moved
6751 @item directory @var{dirname} @dots{}
6752 @item dir @var{dirname} @dots{}
6753 Add directory @var{dirname} to the front of the source path. Several
6754 directory names may be given to this command, separated by @samp{:}
6755 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6756 part of absolute file names) or
6757 whitespace. You may specify a directory that is already in the source
6758 path; this moves it forward, so @value{GDBN} searches it sooner.
6762 @vindex $cdir@r{, convenience variable}
6763 @vindex $cwd@r{, convenience variable}
6764 @cindex compilation directory
6765 @cindex current directory
6766 @cindex working directory
6767 @cindex directory, current
6768 @cindex directory, compilation
6769 You can use the string @samp{$cdir} to refer to the compilation
6770 directory (if one is recorded), and @samp{$cwd} to refer to the current
6771 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6772 tracks the current working directory as it changes during your @value{GDBN}
6773 session, while the latter is immediately expanded to the current
6774 directory at the time you add an entry to the source path.
6777 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6779 @c RET-repeat for @code{directory} is explicitly disabled, but since
6780 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6782 @item set directories @var{path-list}
6783 @kindex set directories
6784 Set the source path to @var{path-list}.
6785 @samp{$cdir:$cwd} are added if missing.
6787 @item show directories
6788 @kindex show directories
6789 Print the source path: show which directories it contains.
6791 @anchor{set substitute-path}
6792 @item set substitute-path @var{from} @var{to}
6793 @kindex set substitute-path
6794 Define a source path substitution rule, and add it at the end of the
6795 current list of existing substitution rules. If a rule with the same
6796 @var{from} was already defined, then the old rule is also deleted.
6798 For example, if the file @file{/foo/bar/baz.c} was moved to
6799 @file{/mnt/cross/baz.c}, then the command
6802 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6806 will tell @value{GDBN} to replace @samp{/usr/src} with
6807 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6808 @file{baz.c} even though it was moved.
6810 In the case when more than one substitution rule have been defined,
6811 the rules are evaluated one by one in the order where they have been
6812 defined. The first one matching, if any, is selected to perform
6815 For instance, if we had entered the following commands:
6818 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6819 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6823 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6824 @file{/mnt/include/defs.h} by using the first rule. However, it would
6825 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6826 @file{/mnt/src/lib/foo.c}.
6829 @item unset substitute-path [path]
6830 @kindex unset substitute-path
6831 If a path is specified, search the current list of substitution rules
6832 for a rule that would rewrite that path. Delete that rule if found.
6833 A warning is emitted by the debugger if no rule could be found.
6835 If no path is specified, then all substitution rules are deleted.
6837 @item show substitute-path [path]
6838 @kindex show substitute-path
6839 If a path is specified, then print the source path substitution rule
6840 which would rewrite that path, if any.
6842 If no path is specified, then print all existing source path substitution
6847 If your source path is cluttered with directories that are no longer of
6848 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6849 versions of source. You can correct the situation as follows:
6853 Use @code{directory} with no argument to reset the source path to its default value.
6856 Use @code{directory} with suitable arguments to reinstall the
6857 directories you want in the source path. You can add all the
6858 directories in one command.
6862 @section Source and Machine Code
6863 @cindex source line and its code address
6865 You can use the command @code{info line} to map source lines to program
6866 addresses (and vice versa), and the command @code{disassemble} to display
6867 a range of addresses as machine instructions. You can use the command
6868 @code{set disassemble-next-line} to set whether to disassemble next
6869 source line when execution stops. When run under @sc{gnu} Emacs
6870 mode, the @code{info line} command causes the arrow to point to the
6871 line specified. Also, @code{info line} prints addresses in symbolic form as
6876 @item info line @var{linespec}
6877 Print the starting and ending addresses of the compiled code for
6878 source line @var{linespec}. You can specify source lines in any of
6879 the ways documented in @ref{Specify Location}.
6882 For example, we can use @code{info line} to discover the location of
6883 the object code for the first line of function
6884 @code{m4_changequote}:
6886 @c FIXME: I think this example should also show the addresses in
6887 @c symbolic form, as they usually would be displayed.
6889 (@value{GDBP}) info line m4_changequote
6890 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6894 @cindex code address and its source line
6895 We can also inquire (using @code{*@var{addr}} as the form for
6896 @var{linespec}) what source line covers a particular address:
6898 (@value{GDBP}) info line *0x63ff
6899 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6902 @cindex @code{$_} and @code{info line}
6903 @cindex @code{x} command, default address
6904 @kindex x@r{(examine), and} info line
6905 After @code{info line}, the default address for the @code{x} command
6906 is changed to the starting address of the line, so that @samp{x/i} is
6907 sufficient to begin examining the machine code (@pxref{Memory,
6908 ,Examining Memory}). Also, this address is saved as the value of the
6909 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6914 @cindex assembly instructions
6915 @cindex instructions, assembly
6916 @cindex machine instructions
6917 @cindex listing machine instructions
6919 @itemx disassemble /m
6920 @itemx disassemble /r
6921 This specialized command dumps a range of memory as machine
6922 instructions. It can also print mixed source+disassembly by specifying
6923 the @code{/m} modifier and print the raw instructions in hex as well as
6924 in symbolic form by specifying the @code{/r}.
6925 The default memory range is the function surrounding the
6926 program counter of the selected frame. A single argument to this
6927 command is a program counter value; @value{GDBN} dumps the function
6928 surrounding this value. When two arguments are given, they should
6929 be separated by a comma, possibly surrounded by whitespace. The
6930 arguments specify a range of addresses to dump, in one of two forms:
6933 @item @var{start},@var{end}
6934 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6935 @item @var{start},+@var{length}
6936 the addresses from @var{start} (inclusive) to
6937 @code{@var{start}+@var{length}} (exclusive).
6941 When 2 arguments are specified, the name of the function is also
6942 printed (since there could be several functions in the given range).
6944 The argument(s) can be any expression yielding a numeric value, such as
6945 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6947 If the range of memory being disassembled contains current program counter,
6948 the instruction at that location is shown with a @code{=>} marker.
6951 The following example shows the disassembly of a range of addresses of
6952 HP PA-RISC 2.0 code:
6955 (@value{GDBP}) disas 0x32c4, 0x32e4
6956 Dump of assembler code from 0x32c4 to 0x32e4:
6957 0x32c4 <main+204>: addil 0,dp
6958 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6959 0x32cc <main+212>: ldil 0x3000,r31
6960 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6961 0x32d4 <main+220>: ldo 0(r31),rp
6962 0x32d8 <main+224>: addil -0x800,dp
6963 0x32dc <main+228>: ldo 0x588(r1),r26
6964 0x32e0 <main+232>: ldil 0x3000,r31
6965 End of assembler dump.
6968 Here is an example showing mixed source+assembly for Intel x86, when the
6969 program is stopped just after function prologue:
6972 (@value{GDBP}) disas /m main
6973 Dump of assembler code for function main:
6975 0x08048330 <+0>: push %ebp
6976 0x08048331 <+1>: mov %esp,%ebp
6977 0x08048333 <+3>: sub $0x8,%esp
6978 0x08048336 <+6>: and $0xfffffff0,%esp
6979 0x08048339 <+9>: sub $0x10,%esp
6981 6 printf ("Hello.\n");
6982 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6983 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6987 0x08048348 <+24>: mov $0x0,%eax
6988 0x0804834d <+29>: leave
6989 0x0804834e <+30>: ret
6991 End of assembler dump.
6994 Here is another example showing raw instructions in hex for AMD x86-64,
6997 (gdb) disas /r 0x400281,+10
6998 Dump of assembler code from 0x400281 to 0x40028b:
6999 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7000 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7001 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7002 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7003 End of assembler dump.
7006 Some architectures have more than one commonly-used set of instruction
7007 mnemonics or other syntax.
7009 For programs that were dynamically linked and use shared libraries,
7010 instructions that call functions or branch to locations in the shared
7011 libraries might show a seemingly bogus location---it's actually a
7012 location of the relocation table. On some architectures, @value{GDBN}
7013 might be able to resolve these to actual function names.
7016 @kindex set disassembly-flavor
7017 @cindex Intel disassembly flavor
7018 @cindex AT&T disassembly flavor
7019 @item set disassembly-flavor @var{instruction-set}
7020 Select the instruction set to use when disassembling the
7021 program via the @code{disassemble} or @code{x/i} commands.
7023 Currently this command is only defined for the Intel x86 family. You
7024 can set @var{instruction-set} to either @code{intel} or @code{att}.
7025 The default is @code{att}, the AT&T flavor used by default by Unix
7026 assemblers for x86-based targets.
7028 @kindex show disassembly-flavor
7029 @item show disassembly-flavor
7030 Show the current setting of the disassembly flavor.
7034 @kindex set disassemble-next-line
7035 @kindex show disassemble-next-line
7036 @item set disassemble-next-line
7037 @itemx show disassemble-next-line
7038 Control whether or not @value{GDBN} will disassemble the next source
7039 line or instruction when execution stops. If ON, @value{GDBN} will
7040 display disassembly of the next source line when execution of the
7041 program being debugged stops. This is @emph{in addition} to
7042 displaying the source line itself, which @value{GDBN} always does if
7043 possible. If the next source line cannot be displayed for some reason
7044 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7045 info in the debug info), @value{GDBN} will display disassembly of the
7046 next @emph{instruction} instead of showing the next source line. If
7047 AUTO, @value{GDBN} will display disassembly of next instruction only
7048 if the source line cannot be displayed. This setting causes
7049 @value{GDBN} to display some feedback when you step through a function
7050 with no line info or whose source file is unavailable. The default is
7051 OFF, which means never display the disassembly of the next line or
7057 @chapter Examining Data
7059 @cindex printing data
7060 @cindex examining data
7063 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7064 @c document because it is nonstandard... Under Epoch it displays in a
7065 @c different window or something like that.
7066 The usual way to examine data in your program is with the @code{print}
7067 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7068 evaluates and prints the value of an expression of the language your
7069 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7070 Different Languages}). It may also print the expression using a
7071 Python-based pretty-printer (@pxref{Pretty Printing}).
7074 @item print @var{expr}
7075 @itemx print /@var{f} @var{expr}
7076 @var{expr} is an expression (in the source language). By default the
7077 value of @var{expr} is printed in a format appropriate to its data type;
7078 you can choose a different format by specifying @samp{/@var{f}}, where
7079 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7083 @itemx print /@var{f}
7084 @cindex reprint the last value
7085 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7086 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7087 conveniently inspect the same value in an alternative format.
7090 A more low-level way of examining data is with the @code{x} command.
7091 It examines data in memory at a specified address and prints it in a
7092 specified format. @xref{Memory, ,Examining Memory}.
7094 If you are interested in information about types, or about how the
7095 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7096 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7100 * Expressions:: Expressions
7101 * Ambiguous Expressions:: Ambiguous Expressions
7102 * Variables:: Program variables
7103 * Arrays:: Artificial arrays
7104 * Output Formats:: Output formats
7105 * Memory:: Examining memory
7106 * Auto Display:: Automatic display
7107 * Print Settings:: Print settings
7108 * Pretty Printing:: Python pretty printing
7109 * Value History:: Value history
7110 * Convenience Vars:: Convenience variables
7111 * Registers:: Registers
7112 * Floating Point Hardware:: Floating point hardware
7113 * Vector Unit:: Vector Unit
7114 * OS Information:: Auxiliary data provided by operating system
7115 * Memory Region Attributes:: Memory region attributes
7116 * Dump/Restore Files:: Copy between memory and a file
7117 * Core File Generation:: Cause a program dump its core
7118 * Character Sets:: Debugging programs that use a different
7119 character set than GDB does
7120 * Caching Remote Data:: Data caching for remote targets
7121 * Searching Memory:: Searching memory for a sequence of bytes
7125 @section Expressions
7128 @code{print} and many other @value{GDBN} commands accept an expression and
7129 compute its value. Any kind of constant, variable or operator defined
7130 by the programming language you are using is valid in an expression in
7131 @value{GDBN}. This includes conditional expressions, function calls,
7132 casts, and string constants. It also includes preprocessor macros, if
7133 you compiled your program to include this information; see
7136 @cindex arrays in expressions
7137 @value{GDBN} supports array constants in expressions input by
7138 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7139 you can use the command @code{print @{1, 2, 3@}} to create an array
7140 of three integers. If you pass an array to a function or assign it
7141 to a program variable, @value{GDBN} copies the array to memory that
7142 is @code{malloc}ed in the target program.
7144 Because C is so widespread, most of the expressions shown in examples in
7145 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7146 Languages}, for information on how to use expressions in other
7149 In this section, we discuss operators that you can use in @value{GDBN}
7150 expressions regardless of your programming language.
7152 @cindex casts, in expressions
7153 Casts are supported in all languages, not just in C, because it is so
7154 useful to cast a number into a pointer in order to examine a structure
7155 at that address in memory.
7156 @c FIXME: casts supported---Mod2 true?
7158 @value{GDBN} supports these operators, in addition to those common
7159 to programming languages:
7163 @samp{@@} is a binary operator for treating parts of memory as arrays.
7164 @xref{Arrays, ,Artificial Arrays}, for more information.
7167 @samp{::} allows you to specify a variable in terms of the file or
7168 function where it is defined. @xref{Variables, ,Program Variables}.
7170 @cindex @{@var{type}@}
7171 @cindex type casting memory
7172 @cindex memory, viewing as typed object
7173 @cindex casts, to view memory
7174 @item @{@var{type}@} @var{addr}
7175 Refers to an object of type @var{type} stored at address @var{addr} in
7176 memory. @var{addr} may be any expression whose value is an integer or
7177 pointer (but parentheses are required around binary operators, just as in
7178 a cast). This construct is allowed regardless of what kind of data is
7179 normally supposed to reside at @var{addr}.
7182 @node Ambiguous Expressions
7183 @section Ambiguous Expressions
7184 @cindex ambiguous expressions
7186 Expressions can sometimes contain some ambiguous elements. For instance,
7187 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7188 a single function name to be defined several times, for application in
7189 different contexts. This is called @dfn{overloading}. Another example
7190 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7191 templates and is typically instantiated several times, resulting in
7192 the same function name being defined in different contexts.
7194 In some cases and depending on the language, it is possible to adjust
7195 the expression to remove the ambiguity. For instance in C@t{++}, you
7196 can specify the signature of the function you want to break on, as in
7197 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7198 qualified name of your function often makes the expression unambiguous
7201 When an ambiguity that needs to be resolved is detected, the debugger
7202 has the capability to display a menu of numbered choices for each
7203 possibility, and then waits for the selection with the prompt @samp{>}.
7204 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7205 aborts the current command. If the command in which the expression was
7206 used allows more than one choice to be selected, the next option in the
7207 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7210 For example, the following session excerpt shows an attempt to set a
7211 breakpoint at the overloaded symbol @code{String::after}.
7212 We choose three particular definitions of that function name:
7214 @c FIXME! This is likely to change to show arg type lists, at least
7217 (@value{GDBP}) b String::after
7220 [2] file:String.cc; line number:867
7221 [3] file:String.cc; line number:860
7222 [4] file:String.cc; line number:875
7223 [5] file:String.cc; line number:853
7224 [6] file:String.cc; line number:846
7225 [7] file:String.cc; line number:735
7227 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7228 Breakpoint 2 at 0xb344: file String.cc, line 875.
7229 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7230 Multiple breakpoints were set.
7231 Use the "delete" command to delete unwanted
7238 @kindex set multiple-symbols
7239 @item set multiple-symbols @var{mode}
7240 @cindex multiple-symbols menu
7242 This option allows you to adjust the debugger behavior when an expression
7245 By default, @var{mode} is set to @code{all}. If the command with which
7246 the expression is used allows more than one choice, then @value{GDBN}
7247 automatically selects all possible choices. For instance, inserting
7248 a breakpoint on a function using an ambiguous name results in a breakpoint
7249 inserted on each possible match. However, if a unique choice must be made,
7250 then @value{GDBN} uses the menu to help you disambiguate the expression.
7251 For instance, printing the address of an overloaded function will result
7252 in the use of the menu.
7254 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7255 when an ambiguity is detected.
7257 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7258 an error due to the ambiguity and the command is aborted.
7260 @kindex show multiple-symbols
7261 @item show multiple-symbols
7262 Show the current value of the @code{multiple-symbols} setting.
7266 @section Program Variables
7268 The most common kind of expression to use is the name of a variable
7271 Variables in expressions are understood in the selected stack frame
7272 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7276 global (or file-static)
7283 visible according to the scope rules of the
7284 programming language from the point of execution in that frame
7287 @noindent This means that in the function
7302 you can examine and use the variable @code{a} whenever your program is
7303 executing within the function @code{foo}, but you can only use or
7304 examine the variable @code{b} while your program is executing inside
7305 the block where @code{b} is declared.
7307 @cindex variable name conflict
7308 There is an exception: you can refer to a variable or function whose
7309 scope is a single source file even if the current execution point is not
7310 in this file. But it is possible to have more than one such variable or
7311 function with the same name (in different source files). If that
7312 happens, referring to that name has unpredictable effects. If you wish,
7313 you can specify a static variable in a particular function or file,
7314 using the colon-colon (@code{::}) notation:
7316 @cindex colon-colon, context for variables/functions
7318 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7319 @cindex @code{::}, context for variables/functions
7322 @var{file}::@var{variable}
7323 @var{function}::@var{variable}
7327 Here @var{file} or @var{function} is the name of the context for the
7328 static @var{variable}. In the case of file names, you can use quotes to
7329 make sure @value{GDBN} parses the file name as a single word---for example,
7330 to print a global value of @code{x} defined in @file{f2.c}:
7333 (@value{GDBP}) p 'f2.c'::x
7336 @cindex C@t{++} scope resolution
7337 This use of @samp{::} is very rarely in conflict with the very similar
7338 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7339 scope resolution operator in @value{GDBN} expressions.
7340 @c FIXME: Um, so what happens in one of those rare cases where it's in
7343 @cindex wrong values
7344 @cindex variable values, wrong
7345 @cindex function entry/exit, wrong values of variables
7346 @cindex optimized code, wrong values of variables
7348 @emph{Warning:} Occasionally, a local variable may appear to have the
7349 wrong value at certain points in a function---just after entry to a new
7350 scope, and just before exit.
7352 You may see this problem when you are stepping by machine instructions.
7353 This is because, on most machines, it takes more than one instruction to
7354 set up a stack frame (including local variable definitions); if you are
7355 stepping by machine instructions, variables may appear to have the wrong
7356 values until the stack frame is completely built. On exit, it usually
7357 also takes more than one machine instruction to destroy a stack frame;
7358 after you begin stepping through that group of instructions, local
7359 variable definitions may be gone.
7361 This may also happen when the compiler does significant optimizations.
7362 To be sure of always seeing accurate values, turn off all optimization
7365 @cindex ``No symbol "foo" in current context''
7366 Another possible effect of compiler optimizations is to optimize
7367 unused variables out of existence, or assign variables to registers (as
7368 opposed to memory addresses). Depending on the support for such cases
7369 offered by the debug info format used by the compiler, @value{GDBN}
7370 might not be able to display values for such local variables. If that
7371 happens, @value{GDBN} will print a message like this:
7374 No symbol "foo" in current context.
7377 To solve such problems, either recompile without optimizations, or use a
7378 different debug info format, if the compiler supports several such
7379 formats. @xref{Compilation}, for more information on choosing compiler
7380 options. @xref{C, ,C and C@t{++}}, for more information about debug
7381 info formats that are best suited to C@t{++} programs.
7383 If you ask to print an object whose contents are unknown to
7384 @value{GDBN}, e.g., because its data type is not completely specified
7385 by the debug information, @value{GDBN} will say @samp{<incomplete
7386 type>}. @xref{Symbols, incomplete type}, for more about this.
7388 If you append @kbd{@@entry} string to a function parameter name you get its
7389 value at the time the function got called. If the value is not available an
7390 error message is printed. Entry values are available only with some compilers.
7391 Entry values are normally also printed at the function parameter list according
7392 to @ref{set print entry-values}.
7395 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7401 (gdb) print i@@entry
7405 Strings are identified as arrays of @code{char} values without specified
7406 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7407 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7408 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7409 defines literal string type @code{"char"} as @code{char} without a sign.
7414 signed char var1[] = "A";
7417 You get during debugging
7422 $2 = @{65 'A', 0 '\0'@}
7426 @section Artificial Arrays
7428 @cindex artificial array
7430 @kindex @@@r{, referencing memory as an array}
7431 It is often useful to print out several successive objects of the
7432 same type in memory; a section of an array, or an array of
7433 dynamically determined size for which only a pointer exists in the
7436 You can do this by referring to a contiguous span of memory as an
7437 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7438 operand of @samp{@@} should be the first element of the desired array
7439 and be an individual object. The right operand should be the desired length
7440 of the array. The result is an array value whose elements are all of
7441 the type of the left argument. The first element is actually the left
7442 argument; the second element comes from bytes of memory immediately
7443 following those that hold the first element, and so on. Here is an
7444 example. If a program says
7447 int *array = (int *) malloc (len * sizeof (int));
7451 you can print the contents of @code{array} with
7457 The left operand of @samp{@@} must reside in memory. Array values made
7458 with @samp{@@} in this way behave just like other arrays in terms of
7459 subscripting, and are coerced to pointers when used in expressions.
7460 Artificial arrays most often appear in expressions via the value history
7461 (@pxref{Value History, ,Value History}), after printing one out.
7463 Another way to create an artificial array is to use a cast.
7464 This re-interprets a value as if it were an array.
7465 The value need not be in memory:
7467 (@value{GDBP}) p/x (short[2])0x12345678
7468 $1 = @{0x1234, 0x5678@}
7471 As a convenience, if you leave the array length out (as in
7472 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7473 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7475 (@value{GDBP}) p/x (short[])0x12345678
7476 $2 = @{0x1234, 0x5678@}
7479 Sometimes the artificial array mechanism is not quite enough; in
7480 moderately complex data structures, the elements of interest may not
7481 actually be adjacent---for example, if you are interested in the values
7482 of pointers in an array. One useful work-around in this situation is
7483 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7484 Variables}) as a counter in an expression that prints the first
7485 interesting value, and then repeat that expression via @key{RET}. For
7486 instance, suppose you have an array @code{dtab} of pointers to
7487 structures, and you are interested in the values of a field @code{fv}
7488 in each structure. Here is an example of what you might type:
7498 @node Output Formats
7499 @section Output Formats
7501 @cindex formatted output
7502 @cindex output formats
7503 By default, @value{GDBN} prints a value according to its data type. Sometimes
7504 this is not what you want. For example, you might want to print a number
7505 in hex, or a pointer in decimal. Or you might want to view data in memory
7506 at a certain address as a character string or as an instruction. To do
7507 these things, specify an @dfn{output format} when you print a value.
7509 The simplest use of output formats is to say how to print a value
7510 already computed. This is done by starting the arguments of the
7511 @code{print} command with a slash and a format letter. The format
7512 letters supported are:
7516 Regard the bits of the value as an integer, and print the integer in
7520 Print as integer in signed decimal.
7523 Print as integer in unsigned decimal.
7526 Print as integer in octal.
7529 Print as integer in binary. The letter @samp{t} stands for ``two''.
7530 @footnote{@samp{b} cannot be used because these format letters are also
7531 used with the @code{x} command, where @samp{b} stands for ``byte'';
7532 see @ref{Memory,,Examining Memory}.}
7535 @cindex unknown address, locating
7536 @cindex locate address
7537 Print as an address, both absolute in hexadecimal and as an offset from
7538 the nearest preceding symbol. You can use this format used to discover
7539 where (in what function) an unknown address is located:
7542 (@value{GDBP}) p/a 0x54320
7543 $3 = 0x54320 <_initialize_vx+396>
7547 The command @code{info symbol 0x54320} yields similar results.
7548 @xref{Symbols, info symbol}.
7551 Regard as an integer and print it as a character constant. This
7552 prints both the numerical value and its character representation. The
7553 character representation is replaced with the octal escape @samp{\nnn}
7554 for characters outside the 7-bit @sc{ascii} range.
7556 Without this format, @value{GDBN} displays @code{char},
7557 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7558 constants. Single-byte members of vectors are displayed as integer
7562 Regard the bits of the value as a floating point number and print
7563 using typical floating point syntax.
7566 @cindex printing strings
7567 @cindex printing byte arrays
7568 Regard as a string, if possible. With this format, pointers to single-byte
7569 data are displayed as null-terminated strings and arrays of single-byte data
7570 are displayed as fixed-length strings. Other values are displayed in their
7573 Without this format, @value{GDBN} displays pointers to and arrays of
7574 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7575 strings. Single-byte members of a vector are displayed as an integer
7579 @cindex raw printing
7580 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7581 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7582 Printing}). This typically results in a higher-level display of the
7583 value's contents. The @samp{r} format bypasses any Python
7584 pretty-printer which might exist.
7587 For example, to print the program counter in hex (@pxref{Registers}), type
7594 Note that no space is required before the slash; this is because command
7595 names in @value{GDBN} cannot contain a slash.
7597 To reprint the last value in the value history with a different format,
7598 you can use the @code{print} command with just a format and no
7599 expression. For example, @samp{p/x} reprints the last value in hex.
7602 @section Examining Memory
7604 You can use the command @code{x} (for ``examine'') to examine memory in
7605 any of several formats, independently of your program's data types.
7607 @cindex examining memory
7609 @kindex x @r{(examine memory)}
7610 @item x/@var{nfu} @var{addr}
7613 Use the @code{x} command to examine memory.
7616 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7617 much memory to display and how to format it; @var{addr} is an
7618 expression giving the address where you want to start displaying memory.
7619 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7620 Several commands set convenient defaults for @var{addr}.
7623 @item @var{n}, the repeat count
7624 The repeat count is a decimal integer; the default is 1. It specifies
7625 how much memory (counting by units @var{u}) to display.
7626 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7629 @item @var{f}, the display format
7630 The display format is one of the formats used by @code{print}
7631 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7632 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7633 The default is @samp{x} (hexadecimal) initially. The default changes
7634 each time you use either @code{x} or @code{print}.
7636 @item @var{u}, the unit size
7637 The unit size is any of
7643 Halfwords (two bytes).
7645 Words (four bytes). This is the initial default.
7647 Giant words (eight bytes).
7650 Each time you specify a unit size with @code{x}, that size becomes the
7651 default unit the next time you use @code{x}. For the @samp{i} format,
7652 the unit size is ignored and is normally not written. For the @samp{s} format,
7653 the unit size defaults to @samp{b}, unless it is explicitly given.
7654 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7655 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7656 Note that the results depend on the programming language of the
7657 current compilation unit. If the language is C, the @samp{s}
7658 modifier will use the UTF-16 encoding while @samp{w} will use
7659 UTF-32. The encoding is set by the programming language and cannot
7662 @item @var{addr}, starting display address
7663 @var{addr} is the address where you want @value{GDBN} to begin displaying
7664 memory. The expression need not have a pointer value (though it may);
7665 it is always interpreted as an integer address of a byte of memory.
7666 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7667 @var{addr} is usually just after the last address examined---but several
7668 other commands also set the default address: @code{info breakpoints} (to
7669 the address of the last breakpoint listed), @code{info line} (to the
7670 starting address of a line), and @code{print} (if you use it to display
7671 a value from memory).
7674 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7675 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7676 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7677 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7678 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7680 Since the letters indicating unit sizes are all distinct from the
7681 letters specifying output formats, you do not have to remember whether
7682 unit size or format comes first; either order works. The output
7683 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7684 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7686 Even though the unit size @var{u} is ignored for the formats @samp{s}
7687 and @samp{i}, you might still want to use a count @var{n}; for example,
7688 @samp{3i} specifies that you want to see three machine instructions,
7689 including any operands. For convenience, especially when used with
7690 the @code{display} command, the @samp{i} format also prints branch delay
7691 slot instructions, if any, beyond the count specified, which immediately
7692 follow the last instruction that is within the count. The command
7693 @code{disassemble} gives an alternative way of inspecting machine
7694 instructions; see @ref{Machine Code,,Source and Machine Code}.
7696 All the defaults for the arguments to @code{x} are designed to make it
7697 easy to continue scanning memory with minimal specifications each time
7698 you use @code{x}. For example, after you have inspected three machine
7699 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7700 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7701 the repeat count @var{n} is used again; the other arguments default as
7702 for successive uses of @code{x}.
7704 When examining machine instructions, the instruction at current program
7705 counter is shown with a @code{=>} marker. For example:
7708 (@value{GDBP}) x/5i $pc-6
7709 0x804837f <main+11>: mov %esp,%ebp
7710 0x8048381 <main+13>: push %ecx
7711 0x8048382 <main+14>: sub $0x4,%esp
7712 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7713 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7716 @cindex @code{$_}, @code{$__}, and value history
7717 The addresses and contents printed by the @code{x} command are not saved
7718 in the value history because there is often too much of them and they
7719 would get in the way. Instead, @value{GDBN} makes these values available for
7720 subsequent use in expressions as values of the convenience variables
7721 @code{$_} and @code{$__}. After an @code{x} command, the last address
7722 examined is available for use in expressions in the convenience variable
7723 @code{$_}. The contents of that address, as examined, are available in
7724 the convenience variable @code{$__}.
7726 If the @code{x} command has a repeat count, the address and contents saved
7727 are from the last memory unit printed; this is not the same as the last
7728 address printed if several units were printed on the last line of output.
7730 @cindex remote memory comparison
7731 @cindex verify remote memory image
7732 When you are debugging a program running on a remote target machine
7733 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7734 remote machine's memory against the executable file you downloaded to
7735 the target. The @code{compare-sections} command is provided for such
7739 @kindex compare-sections
7740 @item compare-sections @r{[}@var{section-name}@r{]}
7741 Compare the data of a loadable section @var{section-name} in the
7742 executable file of the program being debugged with the same section in
7743 the remote machine's memory, and report any mismatches. With no
7744 arguments, compares all loadable sections. This command's
7745 availability depends on the target's support for the @code{"qCRC"}
7750 @section Automatic Display
7751 @cindex automatic display
7752 @cindex display of expressions
7754 If you find that you want to print the value of an expression frequently
7755 (to see how it changes), you might want to add it to the @dfn{automatic
7756 display list} so that @value{GDBN} prints its value each time your program stops.
7757 Each expression added to the list is given a number to identify it;
7758 to remove an expression from the list, you specify that number.
7759 The automatic display looks like this:
7763 3: bar[5] = (struct hack *) 0x3804
7767 This display shows item numbers, expressions and their current values. As with
7768 displays you request manually using @code{x} or @code{print}, you can
7769 specify the output format you prefer; in fact, @code{display} decides
7770 whether to use @code{print} or @code{x} depending your format
7771 specification---it uses @code{x} if you specify either the @samp{i}
7772 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7776 @item display @var{expr}
7777 Add the expression @var{expr} to the list of expressions to display
7778 each time your program stops. @xref{Expressions, ,Expressions}.
7780 @code{display} does not repeat if you press @key{RET} again after using it.
7782 @item display/@var{fmt} @var{expr}
7783 For @var{fmt} specifying only a display format and not a size or
7784 count, add the expression @var{expr} to the auto-display list but
7785 arrange to display it each time in the specified format @var{fmt}.
7786 @xref{Output Formats,,Output Formats}.
7788 @item display/@var{fmt} @var{addr}
7789 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7790 number of units, add the expression @var{addr} as a memory address to
7791 be examined each time your program stops. Examining means in effect
7792 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7795 For example, @samp{display/i $pc} can be helpful, to see the machine
7796 instruction about to be executed each time execution stops (@samp{$pc}
7797 is a common name for the program counter; @pxref{Registers, ,Registers}).
7800 @kindex delete display
7802 @item undisplay @var{dnums}@dots{}
7803 @itemx delete display @var{dnums}@dots{}
7804 Remove items from the list of expressions to display. Specify the
7805 numbers of the displays that you want affected with the command
7806 argument @var{dnums}. It can be a single display number, one of the
7807 numbers shown in the first field of the @samp{info display} display;
7808 or it could be a range of display numbers, as in @code{2-4}.
7810 @code{undisplay} does not repeat if you press @key{RET} after using it.
7811 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7813 @kindex disable display
7814 @item disable display @var{dnums}@dots{}
7815 Disable the display of item numbers @var{dnums}. A disabled display
7816 item is not printed automatically, but is not forgotten. It may be
7817 enabled again later. Specify the numbers of the displays that you
7818 want affected with the command argument @var{dnums}. It can be a
7819 single display number, one of the numbers shown in the first field of
7820 the @samp{info display} display; or it could be a range of display
7821 numbers, as in @code{2-4}.
7823 @kindex enable display
7824 @item enable display @var{dnums}@dots{}
7825 Enable display of item numbers @var{dnums}. It becomes effective once
7826 again in auto display of its expression, until you specify otherwise.
7827 Specify the numbers of the displays that you want affected with the
7828 command argument @var{dnums}. It can be a single display number, one
7829 of the numbers shown in the first field of the @samp{info display}
7830 display; or it could be a range of display numbers, as in @code{2-4}.
7833 Display the current values of the expressions on the list, just as is
7834 done when your program stops.
7836 @kindex info display
7838 Print the list of expressions previously set up to display
7839 automatically, each one with its item number, but without showing the
7840 values. This includes disabled expressions, which are marked as such.
7841 It also includes expressions which would not be displayed right now
7842 because they refer to automatic variables not currently available.
7845 @cindex display disabled out of scope
7846 If a display expression refers to local variables, then it does not make
7847 sense outside the lexical context for which it was set up. Such an
7848 expression is disabled when execution enters a context where one of its
7849 variables is not defined. For example, if you give the command
7850 @code{display last_char} while inside a function with an argument
7851 @code{last_char}, @value{GDBN} displays this argument while your program
7852 continues to stop inside that function. When it stops elsewhere---where
7853 there is no variable @code{last_char}---the display is disabled
7854 automatically. The next time your program stops where @code{last_char}
7855 is meaningful, you can enable the display expression once again.
7857 @node Print Settings
7858 @section Print Settings
7860 @cindex format options
7861 @cindex print settings
7862 @value{GDBN} provides the following ways to control how arrays, structures,
7863 and symbols are printed.
7866 These settings are useful for debugging programs in any language:
7870 @item set print address
7871 @itemx set print address on
7872 @cindex print/don't print memory addresses
7873 @value{GDBN} prints memory addresses showing the location of stack
7874 traces, structure values, pointer values, breakpoints, and so forth,
7875 even when it also displays the contents of those addresses. The default
7876 is @code{on}. For example, this is what a stack frame display looks like with
7877 @code{set print address on}:
7882 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7884 530 if (lquote != def_lquote)
7888 @item set print address off
7889 Do not print addresses when displaying their contents. For example,
7890 this is the same stack frame displayed with @code{set print address off}:
7894 (@value{GDBP}) set print addr off
7896 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7897 530 if (lquote != def_lquote)
7901 You can use @samp{set print address off} to eliminate all machine
7902 dependent displays from the @value{GDBN} interface. For example, with
7903 @code{print address off}, you should get the same text for backtraces on
7904 all machines---whether or not they involve pointer arguments.
7907 @item show print address
7908 Show whether or not addresses are to be printed.
7911 When @value{GDBN} prints a symbolic address, it normally prints the
7912 closest earlier symbol plus an offset. If that symbol does not uniquely
7913 identify the address (for example, it is a name whose scope is a single
7914 source file), you may need to clarify. One way to do this is with
7915 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7916 you can set @value{GDBN} to print the source file and line number when
7917 it prints a symbolic address:
7920 @item set print symbol-filename on
7921 @cindex source file and line of a symbol
7922 @cindex symbol, source file and line
7923 Tell @value{GDBN} to print the source file name and line number of a
7924 symbol in the symbolic form of an address.
7926 @item set print symbol-filename off
7927 Do not print source file name and line number of a symbol. This is the
7930 @item show print symbol-filename
7931 Show whether or not @value{GDBN} will print the source file name and
7932 line number of a symbol in the symbolic form of an address.
7935 Another situation where it is helpful to show symbol filenames and line
7936 numbers is when disassembling code; @value{GDBN} shows you the line
7937 number and source file that corresponds to each instruction.
7939 Also, you may wish to see the symbolic form only if the address being
7940 printed is reasonably close to the closest earlier symbol:
7943 @item set print max-symbolic-offset @var{max-offset}
7944 @cindex maximum value for offset of closest symbol
7945 Tell @value{GDBN} to only display the symbolic form of an address if the
7946 offset between the closest earlier symbol and the address is less than
7947 @var{max-offset}. The default is 0, which tells @value{GDBN}
7948 to always print the symbolic form of an address if any symbol precedes it.
7950 @item show print max-symbolic-offset
7951 Ask how large the maximum offset is that @value{GDBN} prints in a
7955 @cindex wild pointer, interpreting
7956 @cindex pointer, finding referent
7957 If you have a pointer and you are not sure where it points, try
7958 @samp{set print symbol-filename on}. Then you can determine the name
7959 and source file location of the variable where it points, using
7960 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7961 For example, here @value{GDBN} shows that a variable @code{ptt} points
7962 at another variable @code{t}, defined in @file{hi2.c}:
7965 (@value{GDBP}) set print symbol-filename on
7966 (@value{GDBP}) p/a ptt
7967 $4 = 0xe008 <t in hi2.c>
7971 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7972 does not show the symbol name and filename of the referent, even with
7973 the appropriate @code{set print} options turned on.
7976 Other settings control how different kinds of objects are printed:
7979 @item set print array
7980 @itemx set print array on
7981 @cindex pretty print arrays
7982 Pretty print arrays. This format is more convenient to read,
7983 but uses more space. The default is off.
7985 @item set print array off
7986 Return to compressed format for arrays.
7988 @item show print array
7989 Show whether compressed or pretty format is selected for displaying
7992 @cindex print array indexes
7993 @item set print array-indexes
7994 @itemx set print array-indexes on
7995 Print the index of each element when displaying arrays. May be more
7996 convenient to locate a given element in the array or quickly find the
7997 index of a given element in that printed array. The default is off.
7999 @item set print array-indexes off
8000 Stop printing element indexes when displaying arrays.
8002 @item show print array-indexes
8003 Show whether the index of each element is printed when displaying
8006 @item set print elements @var{number-of-elements}
8007 @cindex number of array elements to print
8008 @cindex limit on number of printed array elements
8009 Set a limit on how many elements of an array @value{GDBN} will print.
8010 If @value{GDBN} is printing a large array, it stops printing after it has
8011 printed the number of elements set by the @code{set print elements} command.
8012 This limit also applies to the display of strings.
8013 When @value{GDBN} starts, this limit is set to 200.
8014 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8016 @item show print elements
8017 Display the number of elements of a large array that @value{GDBN} will print.
8018 If the number is 0, then the printing is unlimited.
8020 @item set print frame-arguments @var{value}
8021 @kindex set print frame-arguments
8022 @cindex printing frame argument values
8023 @cindex print all frame argument values
8024 @cindex print frame argument values for scalars only
8025 @cindex do not print frame argument values
8026 This command allows to control how the values of arguments are printed
8027 when the debugger prints a frame (@pxref{Frames}). The possible
8032 The values of all arguments are printed.
8035 Print the value of an argument only if it is a scalar. The value of more
8036 complex arguments such as arrays, structures, unions, etc, is replaced
8037 by @code{@dots{}}. This is the default. Here is an example where
8038 only scalar arguments are shown:
8041 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8046 None of the argument values are printed. Instead, the value of each argument
8047 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8050 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8055 By default, only scalar arguments are printed. This command can be used
8056 to configure the debugger to print the value of all arguments, regardless
8057 of their type. However, it is often advantageous to not print the value
8058 of more complex parameters. For instance, it reduces the amount of
8059 information printed in each frame, making the backtrace more readable.
8060 Also, it improves performance when displaying Ada frames, because
8061 the computation of large arguments can sometimes be CPU-intensive,
8062 especially in large applications. Setting @code{print frame-arguments}
8063 to @code{scalars} (the default) or @code{none} avoids this computation,
8064 thus speeding up the display of each Ada frame.
8066 @item show print frame-arguments
8067 Show how the value of arguments should be displayed when printing a frame.
8069 @anchor{set print entry-values}
8070 @item set print entry-values @var{value}
8071 @kindex set print entry-values
8072 Set printing of frame argument values at function entry. In some cases
8073 @value{GDBN} can determine the value of function argument which was passed by
8074 the function caller, even if the value was modified inside the called function
8075 and therefore is different. With optimized code, the current value could be
8076 unavailable, but the entry value may still be known.
8078 The default value is @code{default} (see below for its description). Older
8079 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8080 this feature will behave in the @code{default} setting the same way as with the
8083 This functionality is currently supported only by DWARF 2 debugging format and
8084 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8085 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8088 The @var{value} parameter can be one of the following:
8092 Print only actual parameter values, never print values from function entry
8096 #0 different (val=6)
8097 #0 lost (val=<optimized out>)
8099 #0 invalid (val=<optimized out>)
8103 Print only parameter values from function entry point. The actual parameter
8104 values are never printed.
8106 #0 equal (val@@entry=5)
8107 #0 different (val@@entry=5)
8108 #0 lost (val@@entry=5)
8109 #0 born (val@@entry=<optimized out>)
8110 #0 invalid (val@@entry=<optimized out>)
8114 Print only parameter values from function entry point. If value from function
8115 entry point is not known while the actual value is known, print the actual
8116 value for such parameter.
8118 #0 equal (val@@entry=5)
8119 #0 different (val@@entry=5)
8120 #0 lost (val@@entry=5)
8122 #0 invalid (val@@entry=<optimized out>)
8126 Print actual parameter values. If actual parameter value is not known while
8127 value from function entry point is known, print the entry point value for such
8131 #0 different (val=6)
8132 #0 lost (val@@entry=5)
8134 #0 invalid (val=<optimized out>)
8138 Always print both the actual parameter value and its value from function entry
8139 point, even if values of one or both are not available due to compiler
8142 #0 equal (val=5, val@@entry=5)
8143 #0 different (val=6, val@@entry=5)
8144 #0 lost (val=<optimized out>, val@@entry=5)
8145 #0 born (val=10, val@@entry=<optimized out>)
8146 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8150 Print the actual parameter value if it is known and also its value from
8151 function entry point if it is known. If neither is known, print for the actual
8152 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8153 values are known and identical, print the shortened
8154 @code{param=param@@entry=VALUE} notation.
8156 #0 equal (val=val@@entry=5)
8157 #0 different (val=6, val@@entry=5)
8158 #0 lost (val@@entry=5)
8160 #0 invalid (val=<optimized out>)
8164 Always print the actual parameter value. Print also its value from function
8165 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8166 if both values are known and identical, print the shortened
8167 @code{param=param@@entry=VALUE} notation.
8169 #0 equal (val=val@@entry=5)
8170 #0 different (val=6, val@@entry=5)
8171 #0 lost (val=<optimized out>, val@@entry=5)
8173 #0 invalid (val=<optimized out>)
8177 For analysis messages on possible failures of frame argument values at function
8178 entry resolution see @ref{set debug entry-values}.
8180 @item show print entry-values
8181 Show the method being used for printing of frame argument values at function
8184 @item set print repeats
8185 @cindex repeated array elements
8186 Set the threshold for suppressing display of repeated array
8187 elements. When the number of consecutive identical elements of an
8188 array exceeds the threshold, @value{GDBN} prints the string
8189 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8190 identical repetitions, instead of displaying the identical elements
8191 themselves. Setting the threshold to zero will cause all elements to
8192 be individually printed. The default threshold is 10.
8194 @item show print repeats
8195 Display the current threshold for printing repeated identical
8198 @item set print null-stop
8199 @cindex @sc{null} elements in arrays
8200 Cause @value{GDBN} to stop printing the characters of an array when the first
8201 @sc{null} is encountered. This is useful when large arrays actually
8202 contain only short strings.
8205 @item show print null-stop
8206 Show whether @value{GDBN} stops printing an array on the first
8207 @sc{null} character.
8209 @item set print pretty on
8210 @cindex print structures in indented form
8211 @cindex indentation in structure display
8212 Cause @value{GDBN} to print structures in an indented format with one member
8213 per line, like this:
8228 @item set print pretty off
8229 Cause @value{GDBN} to print structures in a compact format, like this:
8233 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8234 meat = 0x54 "Pork"@}
8239 This is the default format.
8241 @item show print pretty
8242 Show which format @value{GDBN} is using to print structures.
8244 @item set print sevenbit-strings on
8245 @cindex eight-bit characters in strings
8246 @cindex octal escapes in strings
8247 Print using only seven-bit characters; if this option is set,
8248 @value{GDBN} displays any eight-bit characters (in strings or
8249 character values) using the notation @code{\}@var{nnn}. This setting is
8250 best if you are working in English (@sc{ascii}) and you use the
8251 high-order bit of characters as a marker or ``meta'' bit.
8253 @item set print sevenbit-strings off
8254 Print full eight-bit characters. This allows the use of more
8255 international character sets, and is the default.
8257 @item show print sevenbit-strings
8258 Show whether or not @value{GDBN} is printing only seven-bit characters.
8260 @item set print union on
8261 @cindex unions in structures, printing
8262 Tell @value{GDBN} to print unions which are contained in structures
8263 and other unions. This is the default setting.
8265 @item set print union off
8266 Tell @value{GDBN} not to print unions which are contained in
8267 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8270 @item show print union
8271 Ask @value{GDBN} whether or not it will print unions which are contained in
8272 structures and other unions.
8274 For example, given the declarations
8277 typedef enum @{Tree, Bug@} Species;
8278 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8279 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8290 struct thing foo = @{Tree, @{Acorn@}@};
8294 with @code{set print union on} in effect @samp{p foo} would print
8297 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8301 and with @code{set print union off} in effect it would print
8304 $1 = @{it = Tree, form = @{...@}@}
8308 @code{set print union} affects programs written in C-like languages
8314 These settings are of interest when debugging C@t{++} programs:
8317 @cindex demangling C@t{++} names
8318 @item set print demangle
8319 @itemx set print demangle on
8320 Print C@t{++} names in their source form rather than in the encoded
8321 (``mangled'') form passed to the assembler and linker for type-safe
8322 linkage. The default is on.
8324 @item show print demangle
8325 Show whether C@t{++} names are printed in mangled or demangled form.
8327 @item set print asm-demangle
8328 @itemx set print asm-demangle on
8329 Print C@t{++} names in their source form rather than their mangled form, even
8330 in assembler code printouts such as instruction disassemblies.
8333 @item show print asm-demangle
8334 Show whether C@t{++} names in assembly listings are printed in mangled
8337 @cindex C@t{++} symbol decoding style
8338 @cindex symbol decoding style, C@t{++}
8339 @kindex set demangle-style
8340 @item set demangle-style @var{style}
8341 Choose among several encoding schemes used by different compilers to
8342 represent C@t{++} names. The choices for @var{style} are currently:
8346 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8349 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8350 This is the default.
8353 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8356 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8359 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8360 @strong{Warning:} this setting alone is not sufficient to allow
8361 debugging @code{cfront}-generated executables. @value{GDBN} would
8362 require further enhancement to permit that.
8365 If you omit @var{style}, you will see a list of possible formats.
8367 @item show demangle-style
8368 Display the encoding style currently in use for decoding C@t{++} symbols.
8370 @item set print object
8371 @itemx set print object on
8372 @cindex derived type of an object, printing
8373 @cindex display derived types
8374 When displaying a pointer to an object, identify the @emph{actual}
8375 (derived) type of the object rather than the @emph{declared} type, using
8376 the virtual function table. Note that the virtual function table is
8377 required---this feature can only work for objects that have run-time
8378 type identification; a single virtual method in the object's declared
8381 @item set print object off
8382 Display only the declared type of objects, without reference to the
8383 virtual function table. This is the default setting.
8385 @item show print object
8386 Show whether actual, or declared, object types are displayed.
8388 @item set print static-members
8389 @itemx set print static-members on
8390 @cindex static members of C@t{++} objects
8391 Print static members when displaying a C@t{++} object. The default is on.
8393 @item set print static-members off
8394 Do not print static members when displaying a C@t{++} object.
8396 @item show print static-members
8397 Show whether C@t{++} static members are printed or not.
8399 @item set print pascal_static-members
8400 @itemx set print pascal_static-members on
8401 @cindex static members of Pascal objects
8402 @cindex Pascal objects, static members display
8403 Print static members when displaying a Pascal object. The default is on.
8405 @item set print pascal_static-members off
8406 Do not print static members when displaying a Pascal object.
8408 @item show print pascal_static-members
8409 Show whether Pascal static members are printed or not.
8411 @c These don't work with HP ANSI C++ yet.
8412 @item set print vtbl
8413 @itemx set print vtbl on
8414 @cindex pretty print C@t{++} virtual function tables
8415 @cindex virtual functions (C@t{++}) display
8416 @cindex VTBL display
8417 Pretty print C@t{++} virtual function tables. The default is off.
8418 (The @code{vtbl} commands do not work on programs compiled with the HP
8419 ANSI C@t{++} compiler (@code{aCC}).)
8421 @item set print vtbl off
8422 Do not pretty print C@t{++} virtual function tables.
8424 @item show print vtbl
8425 Show whether C@t{++} virtual function tables are pretty printed, or not.
8428 @node Pretty Printing
8429 @section Pretty Printing
8431 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8432 Python code. It greatly simplifies the display of complex objects. This
8433 mechanism works for both MI and the CLI.
8436 * Pretty-Printer Introduction:: Introduction to pretty-printers
8437 * Pretty-Printer Example:: An example pretty-printer
8438 * Pretty-Printer Commands:: Pretty-printer commands
8441 @node Pretty-Printer Introduction
8442 @subsection Pretty-Printer Introduction
8444 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8445 registered for the value. If there is then @value{GDBN} invokes the
8446 pretty-printer to print the value. Otherwise the value is printed normally.
8448 Pretty-printers are normally named. This makes them easy to manage.
8449 The @samp{info pretty-printer} command will list all the installed
8450 pretty-printers with their names.
8451 If a pretty-printer can handle multiple data types, then its
8452 @dfn{subprinters} are the printers for the individual data types.
8453 Each such subprinter has its own name.
8454 The format of the name is @var{printer-name};@var{subprinter-name}.
8456 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8457 Typically they are automatically loaded and registered when the corresponding
8458 debug information is loaded, thus making them available without having to
8459 do anything special.
8461 There are three places where a pretty-printer can be registered.
8465 Pretty-printers registered globally are available when debugging
8469 Pretty-printers registered with a program space are available only
8470 when debugging that program.
8471 @xref{Progspaces In Python}, for more details on program spaces in Python.
8474 Pretty-printers registered with an objfile are loaded and unloaded
8475 with the corresponding objfile (e.g., shared library).
8476 @xref{Objfiles In Python}, for more details on objfiles in Python.
8479 @xref{Selecting Pretty-Printers}, for further information on how
8480 pretty-printers are selected,
8482 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8485 @node Pretty-Printer Example
8486 @subsection Pretty-Printer Example
8488 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8491 (@value{GDBP}) print s
8493 static npos = 4294967295,
8495 <std::allocator<char>> = @{
8496 <__gnu_cxx::new_allocator<char>> = @{
8497 <No data fields>@}, <No data fields>
8499 members of std::basic_string<char, std::char_traits<char>,
8500 std::allocator<char> >::_Alloc_hider:
8501 _M_p = 0x804a014 "abcd"
8506 With a pretty-printer for @code{std::string} only the contents are printed:
8509 (@value{GDBP}) print s
8513 @node Pretty-Printer Commands
8514 @subsection Pretty-Printer Commands
8515 @cindex pretty-printer commands
8518 @kindex info pretty-printer
8519 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8520 Print the list of installed pretty-printers.
8521 This includes disabled pretty-printers, which are marked as such.
8523 @var{object-regexp} is a regular expression matching the objects
8524 whose pretty-printers to list.
8525 Objects can be @code{global}, the program space's file
8526 (@pxref{Progspaces In Python}),
8527 and the object files within that program space (@pxref{Objfiles In Python}).
8528 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8529 looks up a printer from these three objects.
8531 @var{name-regexp} is a regular expression matching the name of the printers
8534 @kindex disable pretty-printer
8535 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8536 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8537 A disabled pretty-printer is not forgotten, it may be enabled again later.
8539 @kindex enable pretty-printer
8540 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8541 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8546 Suppose we have three pretty-printers installed: one from library1.so
8547 named @code{foo} that prints objects of type @code{foo}, and
8548 another from library2.so named @code{bar} that prints two types of objects,
8549 @code{bar1} and @code{bar2}.
8552 (gdb) info pretty-printer
8559 (gdb) info pretty-printer library2
8564 (gdb) disable pretty-printer library1
8566 2 of 3 printers enabled
8567 (gdb) info pretty-printer
8574 (gdb) disable pretty-printer library2 bar:bar1
8576 1 of 3 printers enabled
8577 (gdb) info pretty-printer library2
8584 (gdb) disable pretty-printer library2 bar
8586 0 of 3 printers enabled
8587 (gdb) info pretty-printer library2
8596 Note that for @code{bar} the entire printer can be disabled,
8597 as can each individual subprinter.
8600 @section Value History
8602 @cindex value history
8603 @cindex history of values printed by @value{GDBN}
8604 Values printed by the @code{print} command are saved in the @value{GDBN}
8605 @dfn{value history}. This allows you to refer to them in other expressions.
8606 Values are kept until the symbol table is re-read or discarded
8607 (for example with the @code{file} or @code{symbol-file} commands).
8608 When the symbol table changes, the value history is discarded,
8609 since the values may contain pointers back to the types defined in the
8614 @cindex history number
8615 The values printed are given @dfn{history numbers} by which you can
8616 refer to them. These are successive integers starting with one.
8617 @code{print} shows you the history number assigned to a value by
8618 printing @samp{$@var{num} = } before the value; here @var{num} is the
8621 To refer to any previous value, use @samp{$} followed by the value's
8622 history number. The way @code{print} labels its output is designed to
8623 remind you of this. Just @code{$} refers to the most recent value in
8624 the history, and @code{$$} refers to the value before that.
8625 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8626 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8627 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8629 For example, suppose you have just printed a pointer to a structure and
8630 want to see the contents of the structure. It suffices to type
8636 If you have a chain of structures where the component @code{next} points
8637 to the next one, you can print the contents of the next one with this:
8644 You can print successive links in the chain by repeating this
8645 command---which you can do by just typing @key{RET}.
8647 Note that the history records values, not expressions. If the value of
8648 @code{x} is 4 and you type these commands:
8656 then the value recorded in the value history by the @code{print} command
8657 remains 4 even though the value of @code{x} has changed.
8662 Print the last ten values in the value history, with their item numbers.
8663 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8664 values} does not change the history.
8666 @item show values @var{n}
8667 Print ten history values centered on history item number @var{n}.
8670 Print ten history values just after the values last printed. If no more
8671 values are available, @code{show values +} produces no display.
8674 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8675 same effect as @samp{show values +}.
8677 @node Convenience Vars
8678 @section Convenience Variables
8680 @cindex convenience variables
8681 @cindex user-defined variables
8682 @value{GDBN} provides @dfn{convenience variables} that you can use within
8683 @value{GDBN} to hold on to a value and refer to it later. These variables
8684 exist entirely within @value{GDBN}; they are not part of your program, and
8685 setting a convenience variable has no direct effect on further execution
8686 of your program. That is why you can use them freely.
8688 Convenience variables are prefixed with @samp{$}. Any name preceded by
8689 @samp{$} can be used for a convenience variable, unless it is one of
8690 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8691 (Value history references, in contrast, are @emph{numbers} preceded
8692 by @samp{$}. @xref{Value History, ,Value History}.)
8694 You can save a value in a convenience variable with an assignment
8695 expression, just as you would set a variable in your program.
8699 set $foo = *object_ptr
8703 would save in @code{$foo} the value contained in the object pointed to by
8706 Using a convenience variable for the first time creates it, but its
8707 value is @code{void} until you assign a new value. You can alter the
8708 value with another assignment at any time.
8710 Convenience variables have no fixed types. You can assign a convenience
8711 variable any type of value, including structures and arrays, even if
8712 that variable already has a value of a different type. The convenience
8713 variable, when used as an expression, has the type of its current value.
8716 @kindex show convenience
8717 @cindex show all user variables
8718 @item show convenience
8719 Print a list of convenience variables used so far, and their values.
8720 Abbreviated @code{show conv}.
8722 @kindex init-if-undefined
8723 @cindex convenience variables, initializing
8724 @item init-if-undefined $@var{variable} = @var{expression}
8725 Set a convenience variable if it has not already been set. This is useful
8726 for user-defined commands that keep some state. It is similar, in concept,
8727 to using local static variables with initializers in C (except that
8728 convenience variables are global). It can also be used to allow users to
8729 override default values used in a command script.
8731 If the variable is already defined then the expression is not evaluated so
8732 any side-effects do not occur.
8735 One of the ways to use a convenience variable is as a counter to be
8736 incremented or a pointer to be advanced. For example, to print
8737 a field from successive elements of an array of structures:
8741 print bar[$i++]->contents
8745 Repeat that command by typing @key{RET}.
8747 Some convenience variables are created automatically by @value{GDBN} and given
8748 values likely to be useful.
8751 @vindex $_@r{, convenience variable}
8753 The variable @code{$_} is automatically set by the @code{x} command to
8754 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8755 commands which provide a default address for @code{x} to examine also
8756 set @code{$_} to that address; these commands include @code{info line}
8757 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8758 except when set by the @code{x} command, in which case it is a pointer
8759 to the type of @code{$__}.
8761 @vindex $__@r{, convenience variable}
8763 The variable @code{$__} is automatically set by the @code{x} command
8764 to the value found in the last address examined. Its type is chosen
8765 to match the format in which the data was printed.
8768 @vindex $_exitcode@r{, convenience variable}
8769 The variable @code{$_exitcode} is automatically set to the exit code when
8770 the program being debugged terminates.
8773 @vindex $_sdata@r{, inspect, convenience variable}
8774 The variable @code{$_sdata} contains extra collected static tracepoint
8775 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8776 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8777 if extra static tracepoint data has not been collected.
8780 @vindex $_siginfo@r{, convenience variable}
8781 The variable @code{$_siginfo} contains extra signal information
8782 (@pxref{extra signal information}). Note that @code{$_siginfo}
8783 could be empty, if the application has not yet received any signals.
8784 For example, it will be empty before you execute the @code{run} command.
8787 @vindex $_tlb@r{, convenience variable}
8788 The variable @code{$_tlb} is automatically set when debugging
8789 applications running on MS-Windows in native mode or connected to
8790 gdbserver that supports the @code{qGetTIBAddr} request.
8791 @xref{General Query Packets}.
8792 This variable contains the address of the thread information block.
8796 On HP-UX systems, if you refer to a function or variable name that
8797 begins with a dollar sign, @value{GDBN} searches for a user or system
8798 name first, before it searches for a convenience variable.
8800 @cindex convenience functions
8801 @value{GDBN} also supplies some @dfn{convenience functions}. These
8802 have a syntax similar to convenience variables. A convenience
8803 function can be used in an expression just like an ordinary function;
8804 however, a convenience function is implemented internally to
8809 @kindex help function
8810 @cindex show all convenience functions
8811 Print a list of all convenience functions.
8818 You can refer to machine register contents, in expressions, as variables
8819 with names starting with @samp{$}. The names of registers are different
8820 for each machine; use @code{info registers} to see the names used on
8824 @kindex info registers
8825 @item info registers
8826 Print the names and values of all registers except floating-point
8827 and vector registers (in the selected stack frame).
8829 @kindex info all-registers
8830 @cindex floating point registers
8831 @item info all-registers
8832 Print the names and values of all registers, including floating-point
8833 and vector registers (in the selected stack frame).
8835 @item info registers @var{regname} @dots{}
8836 Print the @dfn{relativized} value of each specified register @var{regname}.
8837 As discussed in detail below, register values are normally relative to
8838 the selected stack frame. @var{regname} may be any register name valid on
8839 the machine you are using, with or without the initial @samp{$}.
8842 @cindex stack pointer register
8843 @cindex program counter register
8844 @cindex process status register
8845 @cindex frame pointer register
8846 @cindex standard registers
8847 @value{GDBN} has four ``standard'' register names that are available (in
8848 expressions) on most machines---whenever they do not conflict with an
8849 architecture's canonical mnemonics for registers. The register names
8850 @code{$pc} and @code{$sp} are used for the program counter register and
8851 the stack pointer. @code{$fp} is used for a register that contains a
8852 pointer to the current stack frame, and @code{$ps} is used for a
8853 register that contains the processor status. For example,
8854 you could print the program counter in hex with
8861 or print the instruction to be executed next with
8868 or add four to the stack pointer@footnote{This is a way of removing
8869 one word from the stack, on machines where stacks grow downward in
8870 memory (most machines, nowadays). This assumes that the innermost
8871 stack frame is selected; setting @code{$sp} is not allowed when other
8872 stack frames are selected. To pop entire frames off the stack,
8873 regardless of machine architecture, use @code{return};
8874 see @ref{Returning, ,Returning from a Function}.} with
8880 Whenever possible, these four standard register names are available on
8881 your machine even though the machine has different canonical mnemonics,
8882 so long as there is no conflict. The @code{info registers} command
8883 shows the canonical names. For example, on the SPARC, @code{info
8884 registers} displays the processor status register as @code{$psr} but you
8885 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8886 is an alias for the @sc{eflags} register.
8888 @value{GDBN} always considers the contents of an ordinary register as an
8889 integer when the register is examined in this way. Some machines have
8890 special registers which can hold nothing but floating point; these
8891 registers are considered to have floating point values. There is no way
8892 to refer to the contents of an ordinary register as floating point value
8893 (although you can @emph{print} it as a floating point value with
8894 @samp{print/f $@var{regname}}).
8896 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8897 means that the data format in which the register contents are saved by
8898 the operating system is not the same one that your program normally
8899 sees. For example, the registers of the 68881 floating point
8900 coprocessor are always saved in ``extended'' (raw) format, but all C
8901 programs expect to work with ``double'' (virtual) format. In such
8902 cases, @value{GDBN} normally works with the virtual format only (the format
8903 that makes sense for your program), but the @code{info registers} command
8904 prints the data in both formats.
8906 @cindex SSE registers (x86)
8907 @cindex MMX registers (x86)
8908 Some machines have special registers whose contents can be interpreted
8909 in several different ways. For example, modern x86-based machines
8910 have SSE and MMX registers that can hold several values packed
8911 together in several different formats. @value{GDBN} refers to such
8912 registers in @code{struct} notation:
8915 (@value{GDBP}) print $xmm1
8917 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8918 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8919 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8920 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8921 v4_int32 = @{0, 20657912, 11, 13@},
8922 v2_int64 = @{88725056443645952, 55834574859@},
8923 uint128 = 0x0000000d0000000b013b36f800000000
8928 To set values of such registers, you need to tell @value{GDBN} which
8929 view of the register you wish to change, as if you were assigning
8930 value to a @code{struct} member:
8933 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8936 Normally, register values are relative to the selected stack frame
8937 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8938 value that the register would contain if all stack frames farther in
8939 were exited and their saved registers restored. In order to see the
8940 true contents of hardware registers, you must select the innermost
8941 frame (with @samp{frame 0}).
8943 However, @value{GDBN} must deduce where registers are saved, from the machine
8944 code generated by your compiler. If some registers are not saved, or if
8945 @value{GDBN} is unable to locate the saved registers, the selected stack
8946 frame makes no difference.
8948 @node Floating Point Hardware
8949 @section Floating Point Hardware
8950 @cindex floating point
8952 Depending on the configuration, @value{GDBN} may be able to give
8953 you more information about the status of the floating point hardware.
8958 Display hardware-dependent information about the floating
8959 point unit. The exact contents and layout vary depending on the
8960 floating point chip. Currently, @samp{info float} is supported on
8961 the ARM and x86 machines.
8965 @section Vector Unit
8968 Depending on the configuration, @value{GDBN} may be able to give you
8969 more information about the status of the vector unit.
8974 Display information about the vector unit. The exact contents and
8975 layout vary depending on the hardware.
8978 @node OS Information
8979 @section Operating System Auxiliary Information
8980 @cindex OS information
8982 @value{GDBN} provides interfaces to useful OS facilities that can help
8983 you debug your program.
8985 @cindex @code{ptrace} system call
8986 @cindex @code{struct user} contents
8987 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8988 machines), it interfaces with the inferior via the @code{ptrace}
8989 system call. The operating system creates a special sata structure,
8990 called @code{struct user}, for this interface. You can use the
8991 command @code{info udot} to display the contents of this data
8997 Display the contents of the @code{struct user} maintained by the OS
8998 kernel for the program being debugged. @value{GDBN} displays the
8999 contents of @code{struct user} as a list of hex numbers, similar to
9000 the @code{examine} command.
9003 @cindex auxiliary vector
9004 @cindex vector, auxiliary
9005 Some operating systems supply an @dfn{auxiliary vector} to programs at
9006 startup. This is akin to the arguments and environment that you
9007 specify for a program, but contains a system-dependent variety of
9008 binary values that tell system libraries important details about the
9009 hardware, operating system, and process. Each value's purpose is
9010 identified by an integer tag; the meanings are well-known but system-specific.
9011 Depending on the configuration and operating system facilities,
9012 @value{GDBN} may be able to show you this information. For remote
9013 targets, this functionality may further depend on the remote stub's
9014 support of the @samp{qXfer:auxv:read} packet, see
9015 @ref{qXfer auxiliary vector read}.
9020 Display the auxiliary vector of the inferior, which can be either a
9021 live process or a core dump file. @value{GDBN} prints each tag value
9022 numerically, and also shows names and text descriptions for recognized
9023 tags. Some values in the vector are numbers, some bit masks, and some
9024 pointers to strings or other data. @value{GDBN} displays each value in the
9025 most appropriate form for a recognized tag, and in hexadecimal for
9026 an unrecognized tag.
9029 On some targets, @value{GDBN} can access operating-system-specific information
9030 and display it to user, without interpretation. For remote targets,
9031 this functionality depends on the remote stub's support of the
9032 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9037 List the types of OS information available for the target. If the
9038 target does not return a list of possible types, this command will
9041 @kindex info os processes
9042 @item info os processes
9043 Display the list of processes on the target. For each process,
9044 @value{GDBN} prints the process identifier, the name of the user, and
9045 the command corresponding to the process.
9048 @node Memory Region Attributes
9049 @section Memory Region Attributes
9050 @cindex memory region attributes
9052 @dfn{Memory region attributes} allow you to describe special handling
9053 required by regions of your target's memory. @value{GDBN} uses
9054 attributes to determine whether to allow certain types of memory
9055 accesses; whether to use specific width accesses; and whether to cache
9056 target memory. By default the description of memory regions is
9057 fetched from the target (if the current target supports this), but the
9058 user can override the fetched regions.
9060 Defined memory regions can be individually enabled and disabled. When a
9061 memory region is disabled, @value{GDBN} uses the default attributes when
9062 accessing memory in that region. Similarly, if no memory regions have
9063 been defined, @value{GDBN} uses the default attributes when accessing
9066 When a memory region is defined, it is given a number to identify it;
9067 to enable, disable, or remove a memory region, you specify that number.
9071 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9072 Define a memory region bounded by @var{lower} and @var{upper} with
9073 attributes @var{attributes}@dots{}, and add it to the list of regions
9074 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9075 case: it is treated as the target's maximum memory address.
9076 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9079 Discard any user changes to the memory regions and use target-supplied
9080 regions, if available, or no regions if the target does not support.
9083 @item delete mem @var{nums}@dots{}
9084 Remove memory regions @var{nums}@dots{} from the list of regions
9085 monitored by @value{GDBN}.
9088 @item disable mem @var{nums}@dots{}
9089 Disable monitoring of memory regions @var{nums}@dots{}.
9090 A disabled memory region is not forgotten.
9091 It may be enabled again later.
9094 @item enable mem @var{nums}@dots{}
9095 Enable monitoring of memory regions @var{nums}@dots{}.
9099 Print a table of all defined memory regions, with the following columns
9103 @item Memory Region Number
9104 @item Enabled or Disabled.
9105 Enabled memory regions are marked with @samp{y}.
9106 Disabled memory regions are marked with @samp{n}.
9109 The address defining the inclusive lower bound of the memory region.
9112 The address defining the exclusive upper bound of the memory region.
9115 The list of attributes set for this memory region.
9120 @subsection Attributes
9122 @subsubsection Memory Access Mode
9123 The access mode attributes set whether @value{GDBN} may make read or
9124 write accesses to a memory region.
9126 While these attributes prevent @value{GDBN} from performing invalid
9127 memory accesses, they do nothing to prevent the target system, I/O DMA,
9128 etc.@: from accessing memory.
9132 Memory is read only.
9134 Memory is write only.
9136 Memory is read/write. This is the default.
9139 @subsubsection Memory Access Size
9140 The access size attribute tells @value{GDBN} to use specific sized
9141 accesses in the memory region. Often memory mapped device registers
9142 require specific sized accesses. If no access size attribute is
9143 specified, @value{GDBN} may use accesses of any size.
9147 Use 8 bit memory accesses.
9149 Use 16 bit memory accesses.
9151 Use 32 bit memory accesses.
9153 Use 64 bit memory accesses.
9156 @c @subsubsection Hardware/Software Breakpoints
9157 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9158 @c will use hardware or software breakpoints for the internal breakpoints
9159 @c used by the step, next, finish, until, etc. commands.
9163 @c Always use hardware breakpoints
9164 @c @item swbreak (default)
9167 @subsubsection Data Cache
9168 The data cache attributes set whether @value{GDBN} will cache target
9169 memory. While this generally improves performance by reducing debug
9170 protocol overhead, it can lead to incorrect results because @value{GDBN}
9171 does not know about volatile variables or memory mapped device
9176 Enable @value{GDBN} to cache target memory.
9178 Disable @value{GDBN} from caching target memory. This is the default.
9181 @subsection Memory Access Checking
9182 @value{GDBN} can be instructed to refuse accesses to memory that is
9183 not explicitly described. This can be useful if accessing such
9184 regions has undesired effects for a specific target, or to provide
9185 better error checking. The following commands control this behaviour.
9188 @kindex set mem inaccessible-by-default
9189 @item set mem inaccessible-by-default [on|off]
9190 If @code{on} is specified, make @value{GDBN} treat memory not
9191 explicitly described by the memory ranges as non-existent and refuse accesses
9192 to such memory. The checks are only performed if there's at least one
9193 memory range defined. If @code{off} is specified, make @value{GDBN}
9194 treat the memory not explicitly described by the memory ranges as RAM.
9195 The default value is @code{on}.
9196 @kindex show mem inaccessible-by-default
9197 @item show mem inaccessible-by-default
9198 Show the current handling of accesses to unknown memory.
9202 @c @subsubsection Memory Write Verification
9203 @c The memory write verification attributes set whether @value{GDBN}
9204 @c will re-reads data after each write to verify the write was successful.
9208 @c @item noverify (default)
9211 @node Dump/Restore Files
9212 @section Copy Between Memory and a File
9213 @cindex dump/restore files
9214 @cindex append data to a file
9215 @cindex dump data to a file
9216 @cindex restore data from a file
9218 You can use the commands @code{dump}, @code{append}, and
9219 @code{restore} to copy data between target memory and a file. The
9220 @code{dump} and @code{append} commands write data to a file, and the
9221 @code{restore} command reads data from a file back into the inferior's
9222 memory. Files may be in binary, Motorola S-record, Intel hex, or
9223 Tektronix Hex format; however, @value{GDBN} can only append to binary
9229 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9230 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9231 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9232 or the value of @var{expr}, to @var{filename} in the given format.
9234 The @var{format} parameter may be any one of:
9241 Motorola S-record format.
9243 Tektronix Hex format.
9246 @value{GDBN} uses the same definitions of these formats as the
9247 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9248 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9252 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9253 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9254 Append the contents of memory from @var{start_addr} to @var{end_addr},
9255 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9256 (@value{GDBN} can only append data to files in raw binary form.)
9259 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9260 Restore the contents of file @var{filename} into memory. The
9261 @code{restore} command can automatically recognize any known @sc{bfd}
9262 file format, except for raw binary. To restore a raw binary file you
9263 must specify the optional keyword @code{binary} after the filename.
9265 If @var{bias} is non-zero, its value will be added to the addresses
9266 contained in the file. Binary files always start at address zero, so
9267 they will be restored at address @var{bias}. Other bfd files have
9268 a built-in location; they will be restored at offset @var{bias}
9271 If @var{start} and/or @var{end} are non-zero, then only data between
9272 file offset @var{start} and file offset @var{end} will be restored.
9273 These offsets are relative to the addresses in the file, before
9274 the @var{bias} argument is applied.
9278 @node Core File Generation
9279 @section How to Produce a Core File from Your Program
9280 @cindex dump core from inferior
9282 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9283 image of a running process and its process status (register values
9284 etc.). Its primary use is post-mortem debugging of a program that
9285 crashed while it ran outside a debugger. A program that crashes
9286 automatically produces a core file, unless this feature is disabled by
9287 the user. @xref{Files}, for information on invoking @value{GDBN} in
9288 the post-mortem debugging mode.
9290 Occasionally, you may wish to produce a core file of the program you
9291 are debugging in order to preserve a snapshot of its state.
9292 @value{GDBN} has a special command for that.
9296 @kindex generate-core-file
9297 @item generate-core-file [@var{file}]
9298 @itemx gcore [@var{file}]
9299 Produce a core dump of the inferior process. The optional argument
9300 @var{file} specifies the file name where to put the core dump. If not
9301 specified, the file name defaults to @file{core.@var{pid}}, where
9302 @var{pid} is the inferior process ID.
9304 Note that this command is implemented only for some systems (as of
9305 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9308 @node Character Sets
9309 @section Character Sets
9310 @cindex character sets
9312 @cindex translating between character sets
9313 @cindex host character set
9314 @cindex target character set
9316 If the program you are debugging uses a different character set to
9317 represent characters and strings than the one @value{GDBN} uses itself,
9318 @value{GDBN} can automatically translate between the character sets for
9319 you. The character set @value{GDBN} uses we call the @dfn{host
9320 character set}; the one the inferior program uses we call the
9321 @dfn{target character set}.
9323 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9324 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9325 remote protocol (@pxref{Remote Debugging}) to debug a program
9326 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9327 then the host character set is Latin-1, and the target character set is
9328 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9329 target-charset EBCDIC-US}, then @value{GDBN} translates between
9330 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9331 character and string literals in expressions.
9333 @value{GDBN} has no way to automatically recognize which character set
9334 the inferior program uses; you must tell it, using the @code{set
9335 target-charset} command, described below.
9337 Here are the commands for controlling @value{GDBN}'s character set
9341 @item set target-charset @var{charset}
9342 @kindex set target-charset
9343 Set the current target character set to @var{charset}. To display the
9344 list of supported target character sets, type
9345 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9347 @item set host-charset @var{charset}
9348 @kindex set host-charset
9349 Set the current host character set to @var{charset}.
9351 By default, @value{GDBN} uses a host character set appropriate to the
9352 system it is running on; you can override that default using the
9353 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9354 automatically determine the appropriate host character set. In this
9355 case, @value{GDBN} uses @samp{UTF-8}.
9357 @value{GDBN} can only use certain character sets as its host character
9358 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9359 @value{GDBN} will list the host character sets it supports.
9361 @item set charset @var{charset}
9363 Set the current host and target character sets to @var{charset}. As
9364 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9365 @value{GDBN} will list the names of the character sets that can be used
9366 for both host and target.
9369 @kindex show charset
9370 Show the names of the current host and target character sets.
9372 @item show host-charset
9373 @kindex show host-charset
9374 Show the name of the current host character set.
9376 @item show target-charset
9377 @kindex show target-charset
9378 Show the name of the current target character set.
9380 @item set target-wide-charset @var{charset}
9381 @kindex set target-wide-charset
9382 Set the current target's wide character set to @var{charset}. This is
9383 the character set used by the target's @code{wchar_t} type. To
9384 display the list of supported wide character sets, type
9385 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9387 @item show target-wide-charset
9388 @kindex show target-wide-charset
9389 Show the name of the current target's wide character set.
9392 Here is an example of @value{GDBN}'s character set support in action.
9393 Assume that the following source code has been placed in the file
9394 @file{charset-test.c}:
9400 = @{72, 101, 108, 108, 111, 44, 32, 119,
9401 111, 114, 108, 100, 33, 10, 0@};
9402 char ibm1047_hello[]
9403 = @{200, 133, 147, 147, 150, 107, 64, 166,
9404 150, 153, 147, 132, 90, 37, 0@};
9408 printf ("Hello, world!\n");
9412 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9413 containing the string @samp{Hello, world!} followed by a newline,
9414 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9416 We compile the program, and invoke the debugger on it:
9419 $ gcc -g charset-test.c -o charset-test
9420 $ gdb -nw charset-test
9421 GNU gdb 2001-12-19-cvs
9422 Copyright 2001 Free Software Foundation, Inc.
9427 We can use the @code{show charset} command to see what character sets
9428 @value{GDBN} is currently using to interpret and display characters and
9432 (@value{GDBP}) show charset
9433 The current host and target character set is `ISO-8859-1'.
9437 For the sake of printing this manual, let's use @sc{ascii} as our
9438 initial character set:
9440 (@value{GDBP}) set charset ASCII
9441 (@value{GDBP}) show charset
9442 The current host and target character set is `ASCII'.
9446 Let's assume that @sc{ascii} is indeed the correct character set for our
9447 host system --- in other words, let's assume that if @value{GDBN} prints
9448 characters using the @sc{ascii} character set, our terminal will display
9449 them properly. Since our current target character set is also
9450 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9453 (@value{GDBP}) print ascii_hello
9454 $1 = 0x401698 "Hello, world!\n"
9455 (@value{GDBP}) print ascii_hello[0]
9460 @value{GDBN} uses the target character set for character and string
9461 literals you use in expressions:
9464 (@value{GDBP}) print '+'
9469 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9472 @value{GDBN} relies on the user to tell it which character set the
9473 target program uses. If we print @code{ibm1047_hello} while our target
9474 character set is still @sc{ascii}, we get jibberish:
9477 (@value{GDBP}) print ibm1047_hello
9478 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9479 (@value{GDBP}) print ibm1047_hello[0]
9484 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9485 @value{GDBN} tells us the character sets it supports:
9488 (@value{GDBP}) set target-charset
9489 ASCII EBCDIC-US IBM1047 ISO-8859-1
9490 (@value{GDBP}) set target-charset
9493 We can select @sc{ibm1047} as our target character set, and examine the
9494 program's strings again. Now the @sc{ascii} string is wrong, but
9495 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9496 target character set, @sc{ibm1047}, to the host character set,
9497 @sc{ascii}, and they display correctly:
9500 (@value{GDBP}) set target-charset IBM1047
9501 (@value{GDBP}) show charset
9502 The current host character set is `ASCII'.
9503 The current target character set is `IBM1047'.
9504 (@value{GDBP}) print ascii_hello
9505 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9506 (@value{GDBP}) print ascii_hello[0]
9508 (@value{GDBP}) print ibm1047_hello
9509 $8 = 0x4016a8 "Hello, world!\n"
9510 (@value{GDBP}) print ibm1047_hello[0]
9515 As above, @value{GDBN} uses the target character set for character and
9516 string literals you use in expressions:
9519 (@value{GDBP}) print '+'
9524 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9527 @node Caching Remote Data
9528 @section Caching Data of Remote Targets
9529 @cindex caching data of remote targets
9531 @value{GDBN} caches data exchanged between the debugger and a
9532 remote target (@pxref{Remote Debugging}). Such caching generally improves
9533 performance, because it reduces the overhead of the remote protocol by
9534 bundling memory reads and writes into large chunks. Unfortunately, simply
9535 caching everything would lead to incorrect results, since @value{GDBN}
9536 does not necessarily know anything about volatile values, memory-mapped I/O
9537 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9538 memory can be changed @emph{while} a gdb command is executing.
9539 Therefore, by default, @value{GDBN} only caches data
9540 known to be on the stack@footnote{In non-stop mode, it is moderately
9541 rare for a running thread to modify the stack of a stopped thread
9542 in a way that would interfere with a backtrace, and caching of
9543 stack reads provides a significant speed up of remote backtraces.}.
9544 Other regions of memory can be explicitly marked as
9545 cacheable; see @pxref{Memory Region Attributes}.
9548 @kindex set remotecache
9549 @item set remotecache on
9550 @itemx set remotecache off
9551 This option no longer does anything; it exists for compatibility
9554 @kindex show remotecache
9555 @item show remotecache
9556 Show the current state of the obsolete remotecache flag.
9558 @kindex set stack-cache
9559 @item set stack-cache on
9560 @itemx set stack-cache off
9561 Enable or disable caching of stack accesses. When @code{ON}, use
9562 caching. By default, this option is @code{ON}.
9564 @kindex show stack-cache
9565 @item show stack-cache
9566 Show the current state of data caching for memory accesses.
9569 @item info dcache @r{[}line@r{]}
9570 Print the information about the data cache performance. The
9571 information displayed includes the dcache width and depth, and for
9572 each cache line, its number, address, and how many times it was
9573 referenced. This command is useful for debugging the data cache
9576 If a line number is specified, the contents of that line will be
9579 @item set dcache size @var{size}
9581 @kindex set dcache size
9582 Set maximum number of entries in dcache (dcache depth above).
9584 @item set dcache line-size @var{line-size}
9585 @cindex dcache line-size
9586 @kindex set dcache line-size
9587 Set number of bytes each dcache entry caches (dcache width above).
9588 Must be a power of 2.
9590 @item show dcache size
9591 @kindex show dcache size
9592 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9594 @item show dcache line-size
9595 @kindex show dcache line-size
9596 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9600 @node Searching Memory
9601 @section Search Memory
9602 @cindex searching memory
9604 Memory can be searched for a particular sequence of bytes with the
9605 @code{find} command.
9609 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9610 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9611 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9612 etc. The search begins at address @var{start_addr} and continues for either
9613 @var{len} bytes or through to @var{end_addr} inclusive.
9616 @var{s} and @var{n} are optional parameters.
9617 They may be specified in either order, apart or together.
9620 @item @var{s}, search query size
9621 The size of each search query value.
9627 halfwords (two bytes)
9631 giant words (eight bytes)
9634 All values are interpreted in the current language.
9635 This means, for example, that if the current source language is C/C@t{++}
9636 then searching for the string ``hello'' includes the trailing '\0'.
9638 If the value size is not specified, it is taken from the
9639 value's type in the current language.
9640 This is useful when one wants to specify the search
9641 pattern as a mixture of types.
9642 Note that this means, for example, that in the case of C-like languages
9643 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9644 which is typically four bytes.
9646 @item @var{n}, maximum number of finds
9647 The maximum number of matches to print. The default is to print all finds.
9650 You can use strings as search values. Quote them with double-quotes
9652 The string value is copied into the search pattern byte by byte,
9653 regardless of the endianness of the target and the size specification.
9655 The address of each match found is printed as well as a count of the
9656 number of matches found.
9658 The address of the last value found is stored in convenience variable
9660 A count of the number of matches is stored in @samp{$numfound}.
9662 For example, if stopped at the @code{printf} in this function:
9668 static char hello[] = "hello-hello";
9669 static struct @{ char c; short s; int i; @}
9670 __attribute__ ((packed)) mixed
9671 = @{ 'c', 0x1234, 0x87654321 @};
9672 printf ("%s\n", hello);
9677 you get during debugging:
9680 (gdb) find &hello[0], +sizeof(hello), "hello"
9681 0x804956d <hello.1620+6>
9683 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9684 0x8049567 <hello.1620>
9685 0x804956d <hello.1620+6>
9687 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9688 0x8049567 <hello.1620>
9690 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9691 0x8049560 <mixed.1625>
9693 (gdb) print $numfound
9696 $2 = (void *) 0x8049560
9699 @node Optimized Code
9700 @chapter Debugging Optimized Code
9701 @cindex optimized code, debugging
9702 @cindex debugging optimized code
9704 Almost all compilers support optimization. With optimization
9705 disabled, the compiler generates assembly code that corresponds
9706 directly to your source code, in a simplistic way. As the compiler
9707 applies more powerful optimizations, the generated assembly code
9708 diverges from your original source code. With help from debugging
9709 information generated by the compiler, @value{GDBN} can map from
9710 the running program back to constructs from your original source.
9712 @value{GDBN} is more accurate with optimization disabled. If you
9713 can recompile without optimization, it is easier to follow the
9714 progress of your program during debugging. But, there are many cases
9715 where you may need to debug an optimized version.
9717 When you debug a program compiled with @samp{-g -O}, remember that the
9718 optimizer has rearranged your code; the debugger shows you what is
9719 really there. Do not be too surprised when the execution path does not
9720 exactly match your source file! An extreme example: if you define a
9721 variable, but never use it, @value{GDBN} never sees that
9722 variable---because the compiler optimizes it out of existence.
9724 Some things do not work as well with @samp{-g -O} as with just
9725 @samp{-g}, particularly on machines with instruction scheduling. If in
9726 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9727 please report it to us as a bug (including a test case!).
9728 @xref{Variables}, for more information about debugging optimized code.
9731 * Inline Functions:: How @value{GDBN} presents inlining
9732 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9735 @node Inline Functions
9736 @section Inline Functions
9737 @cindex inline functions, debugging
9739 @dfn{Inlining} is an optimization that inserts a copy of the function
9740 body directly at each call site, instead of jumping to a shared
9741 routine. @value{GDBN} displays inlined functions just like
9742 non-inlined functions. They appear in backtraces. You can view their
9743 arguments and local variables, step into them with @code{step}, skip
9744 them with @code{next}, and escape from them with @code{finish}.
9745 You can check whether a function was inlined by using the
9746 @code{info frame} command.
9748 For @value{GDBN} to support inlined functions, the compiler must
9749 record information about inlining in the debug information ---
9750 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9751 other compilers do also. @value{GDBN} only supports inlined functions
9752 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9753 do not emit two required attributes (@samp{DW_AT_call_file} and
9754 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9755 function calls with earlier versions of @value{NGCC}. It instead
9756 displays the arguments and local variables of inlined functions as
9757 local variables in the caller.
9759 The body of an inlined function is directly included at its call site;
9760 unlike a non-inlined function, there are no instructions devoted to
9761 the call. @value{GDBN} still pretends that the call site and the
9762 start of the inlined function are different instructions. Stepping to
9763 the call site shows the call site, and then stepping again shows
9764 the first line of the inlined function, even though no additional
9765 instructions are executed.
9767 This makes source-level debugging much clearer; you can see both the
9768 context of the call and then the effect of the call. Only stepping by
9769 a single instruction using @code{stepi} or @code{nexti} does not do
9770 this; single instruction steps always show the inlined body.
9772 There are some ways that @value{GDBN} does not pretend that inlined
9773 function calls are the same as normal calls:
9777 You cannot set breakpoints on inlined functions. @value{GDBN}
9778 either reports that there is no symbol with that name, or else sets the
9779 breakpoint only on non-inlined copies of the function. This limitation
9780 will be removed in a future version of @value{GDBN}; until then,
9781 set a breakpoint by line number on the first line of the inlined
9785 Setting breakpoints at the call site of an inlined function may not
9786 work, because the call site does not contain any code. @value{GDBN}
9787 may incorrectly move the breakpoint to the next line of the enclosing
9788 function, after the call. This limitation will be removed in a future
9789 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9790 or inside the inlined function instead.
9793 @value{GDBN} cannot locate the return value of inlined calls after
9794 using the @code{finish} command. This is a limitation of compiler-generated
9795 debugging information; after @code{finish}, you can step to the next line
9796 and print a variable where your program stored the return value.
9800 @node Tail Call Frames
9801 @section Tail Call Frames
9802 @cindex tail call frames, debugging
9804 Function @code{B} can call function @code{C} in its very last statement. In
9805 unoptimized compilation the call of @code{C} is immediately followed by return
9806 instruction at the end of @code{B} code. Optimizing compiler may replace the
9807 call and return in function @code{B} into one jump to function @code{C}
9808 instead. Such use of a jump instruction is called @dfn{tail call}.
9810 During execution of function @code{C}, there will be no indication in the
9811 function call stack frames that it was tail-called from @code{B}. If function
9812 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9813 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9814 some cases @value{GDBN} can determine that @code{C} was tail-called from
9815 @code{B}, and it will then create fictitious call frame for that, with the
9816 return address set up as if @code{B} called @code{C} normally.
9818 This functionality is currently supported only by DWARF 2 debugging format and
9819 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9820 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9823 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9824 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9828 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9830 Stack level 1, frame at 0x7fffffffda30:
9831 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9832 tail call frame, caller of frame at 0x7fffffffda30
9833 source language c++.
9834 Arglist at unknown address.
9835 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9838 The detection of all the possible code path executions can find them ambiguous.
9839 There is no execution history stored (possible @ref{Reverse Execution} is never
9840 used for this purpose) and the last known caller could have reached the known
9841 callee by multiple different jump sequences. In such case @value{GDBN} still
9842 tries to show at least all the unambiguous top tail callers and all the
9843 unambiguous bottom tail calees, if any.
9846 @anchor{set debug entry-values}
9847 @item set debug entry-values
9848 @kindex set debug entry-values
9849 When set to on, enables printing of analysis messages for both frame argument
9850 values at function entry and tail calls. It will show all the possible valid
9851 tail calls code paths it has considered. It will also print the intersection
9852 of them with the final unambiguous (possibly partial or even empty) code path
9855 @item show debug entry-values
9856 @kindex show debug entry-values
9857 Show the current state of analysis messages printing for both frame argument
9858 values at function entry and tail calls.
9861 The analysis messages for tail calls can for example show why the virtual tail
9862 call frame for function @code{c} has not been recognized (due to the indirect
9863 reference by variable @code{x}):
9866 static void __attribute__((noinline, noclone)) c (void);
9867 void (*x) (void) = c;
9868 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9869 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9870 int main (void) @{ x (); return 0; @}
9872 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9873 DW_TAG_GNU_call_site 0x40039a in main
9875 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9878 #1 0x000000000040039a in main () at t.c:5
9881 Another possibility is an ambiguous virtual tail call frames resolution:
9885 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9886 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9887 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9888 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9889 static void __attribute__((noinline, noclone)) b (void)
9890 @{ if (i) c (); else e (); @}
9891 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9892 int main (void) @{ a (); return 0; @}
9894 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9895 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9896 tailcall: reduced: 0x4004d2(a) |
9899 #1 0x00000000004004d2 in a () at t.c:8
9900 #2 0x0000000000400395 in main () at t.c:9
9903 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9904 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9906 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9907 @ifset HAVE_MAKEINFO_CLICK
9909 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9910 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9912 @ifclear HAVE_MAKEINFO_CLICK
9914 @set CALLSEQ1B @value{CALLSEQ1A}
9915 @set CALLSEQ2B @value{CALLSEQ2A}
9918 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9919 The code can have possible execution paths @value{CALLSEQ1B} or
9920 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9922 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9923 has found. It then finds another possible calling sequcen - that one is
9924 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9925 printed as the @code{reduced:} calling sequence. That one could have many
9926 futher @code{compare:} and @code{reduced:} statements as long as there remain
9927 any non-ambiguous sequence entries.
9929 For the frame of function @code{b} in both cases there are different possible
9930 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9931 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9932 therefore this one is displayed to the user while the ambiguous frames are
9935 There can be also reasons why printing of frame argument values at function
9940 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9941 static void __attribute__((noinline, noclone)) a (int i);
9942 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9943 static void __attribute__((noinline, noclone)) a (int i)
9944 @{ if (i) b (i - 1); else c (0); @}
9945 int main (void) @{ a (5); return 0; @}
9948 #0 c (i=i@@entry=0) at t.c:2
9949 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9950 function "a" at 0x400420 can call itself via tail calls
9951 i=<optimized out>) at t.c:6
9952 #2 0x000000000040036e in main () at t.c:7
9955 @value{GDBN} cannot find out from the inferior state if and how many times did
9956 function @code{a} call itself (via function @code{b}) as these calls would be
9957 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9958 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9959 prints @code{<optimized out>} instead.
9962 @chapter C Preprocessor Macros
9964 Some languages, such as C and C@t{++}, provide a way to define and invoke
9965 ``preprocessor macros'' which expand into strings of tokens.
9966 @value{GDBN} can evaluate expressions containing macro invocations, show
9967 the result of macro expansion, and show a macro's definition, including
9968 where it was defined.
9970 You may need to compile your program specially to provide @value{GDBN}
9971 with information about preprocessor macros. Most compilers do not
9972 include macros in their debugging information, even when you compile
9973 with the @option{-g} flag. @xref{Compilation}.
9975 A program may define a macro at one point, remove that definition later,
9976 and then provide a different definition after that. Thus, at different
9977 points in the program, a macro may have different definitions, or have
9978 no definition at all. If there is a current stack frame, @value{GDBN}
9979 uses the macros in scope at that frame's source code line. Otherwise,
9980 @value{GDBN} uses the macros in scope at the current listing location;
9983 Whenever @value{GDBN} evaluates an expression, it always expands any
9984 macro invocations present in the expression. @value{GDBN} also provides
9985 the following commands for working with macros explicitly.
9989 @kindex macro expand
9990 @cindex macro expansion, showing the results of preprocessor
9991 @cindex preprocessor macro expansion, showing the results of
9992 @cindex expanding preprocessor macros
9993 @item macro expand @var{expression}
9994 @itemx macro exp @var{expression}
9995 Show the results of expanding all preprocessor macro invocations in
9996 @var{expression}. Since @value{GDBN} simply expands macros, but does
9997 not parse the result, @var{expression} need not be a valid expression;
9998 it can be any string of tokens.
10001 @item macro expand-once @var{expression}
10002 @itemx macro exp1 @var{expression}
10003 @cindex expand macro once
10004 @i{(This command is not yet implemented.)} Show the results of
10005 expanding those preprocessor macro invocations that appear explicitly in
10006 @var{expression}. Macro invocations appearing in that expansion are
10007 left unchanged. This command allows you to see the effect of a
10008 particular macro more clearly, without being confused by further
10009 expansions. Since @value{GDBN} simply expands macros, but does not
10010 parse the result, @var{expression} need not be a valid expression; it
10011 can be any string of tokens.
10014 @cindex macro definition, showing
10015 @cindex definition of a macro, showing
10016 @cindex macros, from debug info
10017 @item info macro [-a|-all] [--] @var{macro}
10018 Show the current definition or all definitions of the named @var{macro},
10019 and describe the source location or compiler command-line where that
10020 definition was established. The optional double dash is to signify the end of
10021 argument processing and the beginning of @var{macro} for non C-like macros where
10022 the macro may begin with a hyphen.
10024 @kindex info macros
10025 @item info macros @var{linespec}
10026 Show all macro definitions that are in effect at the location specified
10027 by @var{linespec}, and describe the source location or compiler
10028 command-line where those definitions were established.
10030 @kindex macro define
10031 @cindex user-defined macros
10032 @cindex defining macros interactively
10033 @cindex macros, user-defined
10034 @item macro define @var{macro} @var{replacement-list}
10035 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10036 Introduce a definition for a preprocessor macro named @var{macro},
10037 invocations of which are replaced by the tokens given in
10038 @var{replacement-list}. The first form of this command defines an
10039 ``object-like'' macro, which takes no arguments; the second form
10040 defines a ``function-like'' macro, which takes the arguments given in
10043 A definition introduced by this command is in scope in every
10044 expression evaluated in @value{GDBN}, until it is removed with the
10045 @code{macro undef} command, described below. The definition overrides
10046 all definitions for @var{macro} present in the program being debugged,
10047 as well as any previous user-supplied definition.
10049 @kindex macro undef
10050 @item macro undef @var{macro}
10051 Remove any user-supplied definition for the macro named @var{macro}.
10052 This command only affects definitions provided with the @code{macro
10053 define} command, described above; it cannot remove definitions present
10054 in the program being debugged.
10058 List all the macros defined using the @code{macro define} command.
10061 @cindex macros, example of debugging with
10062 Here is a transcript showing the above commands in action. First, we
10063 show our source files:
10068 #include "sample.h"
10071 #define ADD(x) (M + x)
10076 printf ("Hello, world!\n");
10078 printf ("We're so creative.\n");
10080 printf ("Goodbye, world!\n");
10087 Now, we compile the program using the @sc{gnu} C compiler,
10088 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10089 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10090 and @option{-gdwarf-4}; we recommend always choosing the most recent
10091 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10092 includes information about preprocessor macros in the debugging
10096 $ gcc -gdwarf-2 -g3 sample.c -o sample
10100 Now, we start @value{GDBN} on our sample program:
10104 GNU gdb 2002-05-06-cvs
10105 Copyright 2002 Free Software Foundation, Inc.
10106 GDB is free software, @dots{}
10110 We can expand macros and examine their definitions, even when the
10111 program is not running. @value{GDBN} uses the current listing position
10112 to decide which macro definitions are in scope:
10115 (@value{GDBP}) list main
10118 5 #define ADD(x) (M + x)
10123 10 printf ("Hello, world!\n");
10125 12 printf ("We're so creative.\n");
10126 (@value{GDBP}) info macro ADD
10127 Defined at /home/jimb/gdb/macros/play/sample.c:5
10128 #define ADD(x) (M + x)
10129 (@value{GDBP}) info macro Q
10130 Defined at /home/jimb/gdb/macros/play/sample.h:1
10131 included at /home/jimb/gdb/macros/play/sample.c:2
10133 (@value{GDBP}) macro expand ADD(1)
10134 expands to: (42 + 1)
10135 (@value{GDBP}) macro expand-once ADD(1)
10136 expands to: once (M + 1)
10140 In the example above, note that @code{macro expand-once} expands only
10141 the macro invocation explicit in the original text --- the invocation of
10142 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10143 which was introduced by @code{ADD}.
10145 Once the program is running, @value{GDBN} uses the macro definitions in
10146 force at the source line of the current stack frame:
10149 (@value{GDBP}) break main
10150 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10152 Starting program: /home/jimb/gdb/macros/play/sample
10154 Breakpoint 1, main () at sample.c:10
10155 10 printf ("Hello, world!\n");
10159 At line 10, the definition of the macro @code{N} at line 9 is in force:
10162 (@value{GDBP}) info macro N
10163 Defined at /home/jimb/gdb/macros/play/sample.c:9
10165 (@value{GDBP}) macro expand N Q M
10166 expands to: 28 < 42
10167 (@value{GDBP}) print N Q M
10172 As we step over directives that remove @code{N}'s definition, and then
10173 give it a new definition, @value{GDBN} finds the definition (or lack
10174 thereof) in force at each point:
10177 (@value{GDBP}) next
10179 12 printf ("We're so creative.\n");
10180 (@value{GDBP}) info macro N
10181 The symbol `N' has no definition as a C/C++ preprocessor macro
10182 at /home/jimb/gdb/macros/play/sample.c:12
10183 (@value{GDBP}) next
10185 14 printf ("Goodbye, world!\n");
10186 (@value{GDBP}) info macro N
10187 Defined at /home/jimb/gdb/macros/play/sample.c:13
10189 (@value{GDBP}) macro expand N Q M
10190 expands to: 1729 < 42
10191 (@value{GDBP}) print N Q M
10196 In addition to source files, macros can be defined on the compilation command
10197 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10198 such a way, @value{GDBN} displays the location of their definition as line zero
10199 of the source file submitted to the compiler.
10202 (@value{GDBP}) info macro __STDC__
10203 Defined at /home/jimb/gdb/macros/play/sample.c:0
10210 @chapter Tracepoints
10211 @c This chapter is based on the documentation written by Michael
10212 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10214 @cindex tracepoints
10215 In some applications, it is not feasible for the debugger to interrupt
10216 the program's execution long enough for the developer to learn
10217 anything helpful about its behavior. If the program's correctness
10218 depends on its real-time behavior, delays introduced by a debugger
10219 might cause the program to change its behavior drastically, or perhaps
10220 fail, even when the code itself is correct. It is useful to be able
10221 to observe the program's behavior without interrupting it.
10223 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10224 specify locations in the program, called @dfn{tracepoints}, and
10225 arbitrary expressions to evaluate when those tracepoints are reached.
10226 Later, using the @code{tfind} command, you can examine the values
10227 those expressions had when the program hit the tracepoints. The
10228 expressions may also denote objects in memory---structures or arrays,
10229 for example---whose values @value{GDBN} should record; while visiting
10230 a particular tracepoint, you may inspect those objects as if they were
10231 in memory at that moment. However, because @value{GDBN} records these
10232 values without interacting with you, it can do so quickly and
10233 unobtrusively, hopefully not disturbing the program's behavior.
10235 The tracepoint facility is currently available only for remote
10236 targets. @xref{Targets}. In addition, your remote target must know
10237 how to collect trace data. This functionality is implemented in the
10238 remote stub; however, none of the stubs distributed with @value{GDBN}
10239 support tracepoints as of this writing. The format of the remote
10240 packets used to implement tracepoints are described in @ref{Tracepoint
10243 It is also possible to get trace data from a file, in a manner reminiscent
10244 of corefiles; you specify the filename, and use @code{tfind} to search
10245 through the file. @xref{Trace Files}, for more details.
10247 This chapter describes the tracepoint commands and features.
10250 * Set Tracepoints::
10251 * Analyze Collected Data::
10252 * Tracepoint Variables::
10256 @node Set Tracepoints
10257 @section Commands to Set Tracepoints
10259 Before running such a @dfn{trace experiment}, an arbitrary number of
10260 tracepoints can be set. A tracepoint is actually a special type of
10261 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10262 standard breakpoint commands. For instance, as with breakpoints,
10263 tracepoint numbers are successive integers starting from one, and many
10264 of the commands associated with tracepoints take the tracepoint number
10265 as their argument, to identify which tracepoint to work on.
10267 For each tracepoint, you can specify, in advance, some arbitrary set
10268 of data that you want the target to collect in the trace buffer when
10269 it hits that tracepoint. The collected data can include registers,
10270 local variables, or global data. Later, you can use @value{GDBN}
10271 commands to examine the values these data had at the time the
10272 tracepoint was hit.
10274 Tracepoints do not support every breakpoint feature. Ignore counts on
10275 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10276 commands when they are hit. Tracepoints may not be thread-specific
10279 @cindex fast tracepoints
10280 Some targets may support @dfn{fast tracepoints}, which are inserted in
10281 a different way (such as with a jump instead of a trap), that is
10282 faster but possibly restricted in where they may be installed.
10284 @cindex static tracepoints
10285 @cindex markers, static tracepoints
10286 @cindex probing markers, static tracepoints
10287 Regular and fast tracepoints are dynamic tracing facilities, meaning
10288 that they can be used to insert tracepoints at (almost) any location
10289 in the target. Some targets may also support controlling @dfn{static
10290 tracepoints} from @value{GDBN}. With static tracing, a set of
10291 instrumentation points, also known as @dfn{markers}, are embedded in
10292 the target program, and can be activated or deactivated by name or
10293 address. These are usually placed at locations which facilitate
10294 investigating what the target is actually doing. @value{GDBN}'s
10295 support for static tracing includes being able to list instrumentation
10296 points, and attach them with @value{GDBN} defined high level
10297 tracepoints that expose the whole range of convenience of
10298 @value{GDBN}'s tracepoints support. Namely, support for collecting
10299 registers values and values of global or local (to the instrumentation
10300 point) variables; tracepoint conditions and trace state variables.
10301 The act of installing a @value{GDBN} static tracepoint on an
10302 instrumentation point, or marker, is referred to as @dfn{probing} a
10303 static tracepoint marker.
10305 @code{gdbserver} supports tracepoints on some target systems.
10306 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10308 This section describes commands to set tracepoints and associated
10309 conditions and actions.
10312 * Create and Delete Tracepoints::
10313 * Enable and Disable Tracepoints::
10314 * Tracepoint Passcounts::
10315 * Tracepoint Conditions::
10316 * Trace State Variables::
10317 * Tracepoint Actions::
10318 * Listing Tracepoints::
10319 * Listing Static Tracepoint Markers::
10320 * Starting and Stopping Trace Experiments::
10321 * Tracepoint Restrictions::
10324 @node Create and Delete Tracepoints
10325 @subsection Create and Delete Tracepoints
10328 @cindex set tracepoint
10330 @item trace @var{location}
10331 The @code{trace} command is very similar to the @code{break} command.
10332 Its argument @var{location} can be a source line, a function name, or
10333 an address in the target program. @xref{Specify Location}. The
10334 @code{trace} command defines a tracepoint, which is a point in the
10335 target program where the debugger will briefly stop, collect some
10336 data, and then allow the program to continue. Setting a tracepoint or
10337 changing its actions takes effect immediately if the remote stub
10338 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10340 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10341 these changes don't take effect until the next @code{tstart}
10342 command, and once a trace experiment is running, further changes will
10343 not have any effect until the next trace experiment starts. In addition,
10344 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10345 address is not yet resolved. (This is similar to pending breakpoints.)
10346 Pending tracepoints are not downloaded to the target and not installed
10347 until they are resolved. The resolution of pending tracepoints requires
10348 @value{GDBN} support---when debugging with the remote target, and
10349 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10350 tracing}), pending tracepoints can not be resolved (and downloaded to
10351 the remote stub) while @value{GDBN} is disconnected.
10353 Here are some examples of using the @code{trace} command:
10356 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10358 (@value{GDBP}) @b{trace +2} // 2 lines forward
10360 (@value{GDBP}) @b{trace my_function} // first source line of function
10362 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10364 (@value{GDBP}) @b{trace *0x2117c4} // an address
10368 You can abbreviate @code{trace} as @code{tr}.
10370 @item trace @var{location} if @var{cond}
10371 Set a tracepoint with condition @var{cond}; evaluate the expression
10372 @var{cond} each time the tracepoint is reached, and collect data only
10373 if the value is nonzero---that is, if @var{cond} evaluates as true.
10374 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10375 information on tracepoint conditions.
10377 @item ftrace @var{location} [ if @var{cond} ]
10378 @cindex set fast tracepoint
10379 @cindex fast tracepoints, setting
10381 The @code{ftrace} command sets a fast tracepoint. For targets that
10382 support them, fast tracepoints will use a more efficient but possibly
10383 less general technique to trigger data collection, such as a jump
10384 instruction instead of a trap, or some sort of hardware support. It
10385 may not be possible to create a fast tracepoint at the desired
10386 location, in which case the command will exit with an explanatory
10389 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10392 On 32-bit x86-architecture systems, fast tracepoints normally need to
10393 be placed at an instruction that is 5 bytes or longer, but can be
10394 placed at 4-byte instructions if the low 64K of memory of the target
10395 program is available to install trampolines. Some Unix-type systems,
10396 such as @sc{gnu}/Linux, exclude low addresses from the program's
10397 address space; but for instance with the Linux kernel it is possible
10398 to let @value{GDBN} use this area by doing a @command{sysctl} command
10399 to set the @code{mmap_min_addr} kernel parameter, as in
10402 sudo sysctl -w vm.mmap_min_addr=32768
10406 which sets the low address to 32K, which leaves plenty of room for
10407 trampolines. The minimum address should be set to a page boundary.
10409 @item strace @var{location} [ if @var{cond} ]
10410 @cindex set static tracepoint
10411 @cindex static tracepoints, setting
10412 @cindex probe static tracepoint marker
10414 The @code{strace} command sets a static tracepoint. For targets that
10415 support it, setting a static tracepoint probes a static
10416 instrumentation point, or marker, found at @var{location}. It may not
10417 be possible to set a static tracepoint at the desired location, in
10418 which case the command will exit with an explanatory message.
10420 @value{GDBN} handles arguments to @code{strace} exactly as for
10421 @code{trace}, with the addition that the user can also specify
10422 @code{-m @var{marker}} as @var{location}. This probes the marker
10423 identified by the @var{marker} string identifier. This identifier
10424 depends on the static tracepoint backend library your program is
10425 using. You can find all the marker identifiers in the @samp{ID} field
10426 of the @code{info static-tracepoint-markers} command output.
10427 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10428 Markers}. For example, in the following small program using the UST
10434 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10439 the marker id is composed of joining the first two arguments to the
10440 @code{trace_mark} call with a slash, which translates to:
10443 (@value{GDBP}) info static-tracepoint-markers
10444 Cnt Enb ID Address What
10445 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10451 so you may probe the marker above with:
10454 (@value{GDBP}) strace -m ust/bar33
10457 Static tracepoints accept an extra collect action --- @code{collect
10458 $_sdata}. This collects arbitrary user data passed in the probe point
10459 call to the tracing library. In the UST example above, you'll see
10460 that the third argument to @code{trace_mark} is a printf-like format
10461 string. The user data is then the result of running that formating
10462 string against the following arguments. Note that @code{info
10463 static-tracepoint-markers} command output lists that format string in
10464 the @samp{Data:} field.
10466 You can inspect this data when analyzing the trace buffer, by printing
10467 the $_sdata variable like any other variable available to
10468 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10471 @cindex last tracepoint number
10472 @cindex recent tracepoint number
10473 @cindex tracepoint number
10474 The convenience variable @code{$tpnum} records the tracepoint number
10475 of the most recently set tracepoint.
10477 @kindex delete tracepoint
10478 @cindex tracepoint deletion
10479 @item delete tracepoint @r{[}@var{num}@r{]}
10480 Permanently delete one or more tracepoints. With no argument, the
10481 default is to delete all tracepoints. Note that the regular
10482 @code{delete} command can remove tracepoints also.
10487 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10489 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10493 You can abbreviate this command as @code{del tr}.
10496 @node Enable and Disable Tracepoints
10497 @subsection Enable and Disable Tracepoints
10499 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10502 @kindex disable tracepoint
10503 @item disable tracepoint @r{[}@var{num}@r{]}
10504 Disable tracepoint @var{num}, or all tracepoints if no argument
10505 @var{num} is given. A disabled tracepoint will have no effect during
10506 a trace experiment, but it is not forgotten. You can re-enable
10507 a disabled tracepoint using the @code{enable tracepoint} command.
10508 If the command is issued during a trace experiment and the debug target
10509 has support for disabling tracepoints during a trace experiment, then the
10510 change will be effective immediately. Otherwise, it will be applied to the
10511 next trace experiment.
10513 @kindex enable tracepoint
10514 @item enable tracepoint @r{[}@var{num}@r{]}
10515 Enable tracepoint @var{num}, or all tracepoints. If this command is
10516 issued during a trace experiment and the debug target supports enabling
10517 tracepoints during a trace experiment, then the enabled tracepoints will
10518 become effective immediately. Otherwise, they will become effective the
10519 next time a trace experiment is run.
10522 @node Tracepoint Passcounts
10523 @subsection Tracepoint Passcounts
10527 @cindex tracepoint pass count
10528 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10529 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10530 automatically stop a trace experiment. If a tracepoint's passcount is
10531 @var{n}, then the trace experiment will be automatically stopped on
10532 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10533 @var{num} is not specified, the @code{passcount} command sets the
10534 passcount of the most recently defined tracepoint. If no passcount is
10535 given, the trace experiment will run until stopped explicitly by the
10541 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10542 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10544 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10545 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10546 (@value{GDBP}) @b{trace foo}
10547 (@value{GDBP}) @b{pass 3}
10548 (@value{GDBP}) @b{trace bar}
10549 (@value{GDBP}) @b{pass 2}
10550 (@value{GDBP}) @b{trace baz}
10551 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10552 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10553 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10554 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10558 @node Tracepoint Conditions
10559 @subsection Tracepoint Conditions
10560 @cindex conditional tracepoints
10561 @cindex tracepoint conditions
10563 The simplest sort of tracepoint collects data every time your program
10564 reaches a specified place. You can also specify a @dfn{condition} for
10565 a tracepoint. A condition is just a Boolean expression in your
10566 programming language (@pxref{Expressions, ,Expressions}). A
10567 tracepoint with a condition evaluates the expression each time your
10568 program reaches it, and data collection happens only if the condition
10571 Tracepoint conditions can be specified when a tracepoint is set, by
10572 using @samp{if} in the arguments to the @code{trace} command.
10573 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10574 also be set or changed at any time with the @code{condition} command,
10575 just as with breakpoints.
10577 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10578 the conditional expression itself. Instead, @value{GDBN} encodes the
10579 expression into an agent expression (@pxref{Agent Expressions})
10580 suitable for execution on the target, independently of @value{GDBN}.
10581 Global variables become raw memory locations, locals become stack
10582 accesses, and so forth.
10584 For instance, suppose you have a function that is usually called
10585 frequently, but should not be called after an error has occurred. You
10586 could use the following tracepoint command to collect data about calls
10587 of that function that happen while the error code is propagating
10588 through the program; an unconditional tracepoint could end up
10589 collecting thousands of useless trace frames that you would have to
10593 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10596 @node Trace State Variables
10597 @subsection Trace State Variables
10598 @cindex trace state variables
10600 A @dfn{trace state variable} is a special type of variable that is
10601 created and managed by target-side code. The syntax is the same as
10602 that for GDB's convenience variables (a string prefixed with ``$''),
10603 but they are stored on the target. They must be created explicitly,
10604 using a @code{tvariable} command. They are always 64-bit signed
10607 Trace state variables are remembered by @value{GDBN}, and downloaded
10608 to the target along with tracepoint information when the trace
10609 experiment starts. There are no intrinsic limits on the number of
10610 trace state variables, beyond memory limitations of the target.
10612 @cindex convenience variables, and trace state variables
10613 Although trace state variables are managed by the target, you can use
10614 them in print commands and expressions as if they were convenience
10615 variables; @value{GDBN} will get the current value from the target
10616 while the trace experiment is running. Trace state variables share
10617 the same namespace as other ``$'' variables, which means that you
10618 cannot have trace state variables with names like @code{$23} or
10619 @code{$pc}, nor can you have a trace state variable and a convenience
10620 variable with the same name.
10624 @item tvariable $@var{name} [ = @var{expression} ]
10626 The @code{tvariable} command creates a new trace state variable named
10627 @code{$@var{name}}, and optionally gives it an initial value of
10628 @var{expression}. @var{expression} is evaluated when this command is
10629 entered; the result will be converted to an integer if possible,
10630 otherwise @value{GDBN} will report an error. A subsequent
10631 @code{tvariable} command specifying the same name does not create a
10632 variable, but instead assigns the supplied initial value to the
10633 existing variable of that name, overwriting any previous initial
10634 value. The default initial value is 0.
10636 @item info tvariables
10637 @kindex info tvariables
10638 List all the trace state variables along with their initial values.
10639 Their current values may also be displayed, if the trace experiment is
10642 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10643 @kindex delete tvariable
10644 Delete the given trace state variables, or all of them if no arguments
10649 @node Tracepoint Actions
10650 @subsection Tracepoint Action Lists
10654 @cindex tracepoint actions
10655 @item actions @r{[}@var{num}@r{]}
10656 This command will prompt for a list of actions to be taken when the
10657 tracepoint is hit. If the tracepoint number @var{num} is not
10658 specified, this command sets the actions for the one that was most
10659 recently defined (so that you can define a tracepoint and then say
10660 @code{actions} without bothering about its number). You specify the
10661 actions themselves on the following lines, one action at a time, and
10662 terminate the actions list with a line containing just @code{end}. So
10663 far, the only defined actions are @code{collect}, @code{teval}, and
10664 @code{while-stepping}.
10666 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10667 Commands, ,Breakpoint Command Lists}), except that only the defined
10668 actions are allowed; any other @value{GDBN} command is rejected.
10670 @cindex remove actions from a tracepoint
10671 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10672 and follow it immediately with @samp{end}.
10675 (@value{GDBP}) @b{collect @var{data}} // collect some data
10677 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10679 (@value{GDBP}) @b{end} // signals the end of actions.
10682 In the following example, the action list begins with @code{collect}
10683 commands indicating the things to be collected when the tracepoint is
10684 hit. Then, in order to single-step and collect additional data
10685 following the tracepoint, a @code{while-stepping} command is used,
10686 followed by the list of things to be collected after each step in a
10687 sequence of single steps. The @code{while-stepping} command is
10688 terminated by its own separate @code{end} command. Lastly, the action
10689 list is terminated by an @code{end} command.
10692 (@value{GDBP}) @b{trace foo}
10693 (@value{GDBP}) @b{actions}
10694 Enter actions for tracepoint 1, one per line:
10697 > while-stepping 12
10698 > collect $pc, arr[i]
10703 @kindex collect @r{(tracepoints)}
10704 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10705 Collect values of the given expressions when the tracepoint is hit.
10706 This command accepts a comma-separated list of any valid expressions.
10707 In addition to global, static, or local variables, the following
10708 special arguments are supported:
10712 Collect all registers.
10715 Collect all function arguments.
10718 Collect all local variables.
10721 Collect the return address. This is helpful if you want to see more
10725 @vindex $_sdata@r{, collect}
10726 Collect static tracepoint marker specific data. Only available for
10727 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10728 Lists}. On the UST static tracepoints library backend, an
10729 instrumentation point resembles a @code{printf} function call. The
10730 tracing library is able to collect user specified data formatted to a
10731 character string using the format provided by the programmer that
10732 instrumented the program. Other backends have similar mechanisms.
10733 Here's an example of a UST marker call:
10736 const char master_name[] = "$your_name";
10737 trace_mark(channel1, marker1, "hello %s", master_name)
10740 In this case, collecting @code{$_sdata} collects the string
10741 @samp{hello $yourname}. When analyzing the trace buffer, you can
10742 inspect @samp{$_sdata} like any other variable available to
10746 You can give several consecutive @code{collect} commands, each one
10747 with a single argument, or one @code{collect} command with several
10748 arguments separated by commas; the effect is the same.
10750 The optional @var{mods} changes the usual handling of the arguments.
10751 @code{s} requests that pointers to chars be handled as strings, in
10752 particular collecting the contents of the memory being pointed at, up
10753 to the first zero. The upper bound is by default the value of the
10754 @code{print elements} variable; if @code{s} is followed by a decimal
10755 number, that is the upper bound instead. So for instance
10756 @samp{collect/s25 mystr} collects as many as 25 characters at
10759 The command @code{info scope} (@pxref{Symbols, info scope}) is
10760 particularly useful for figuring out what data to collect.
10762 @kindex teval @r{(tracepoints)}
10763 @item teval @var{expr1}, @var{expr2}, @dots{}
10764 Evaluate the given expressions when the tracepoint is hit. This
10765 command accepts a comma-separated list of expressions. The results
10766 are discarded, so this is mainly useful for assigning values to trace
10767 state variables (@pxref{Trace State Variables}) without adding those
10768 values to the trace buffer, as would be the case if the @code{collect}
10771 @kindex while-stepping @r{(tracepoints)}
10772 @item while-stepping @var{n}
10773 Perform @var{n} single-step instruction traces after the tracepoint,
10774 collecting new data after each step. The @code{while-stepping}
10775 command is followed by the list of what to collect while stepping
10776 (followed by its own @code{end} command):
10779 > while-stepping 12
10780 > collect $regs, myglobal
10786 Note that @code{$pc} is not automatically collected by
10787 @code{while-stepping}; you need to explicitly collect that register if
10788 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10791 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10792 @kindex set default-collect
10793 @cindex default collection action
10794 This variable is a list of expressions to collect at each tracepoint
10795 hit. It is effectively an additional @code{collect} action prepended
10796 to every tracepoint action list. The expressions are parsed
10797 individually for each tracepoint, so for instance a variable named
10798 @code{xyz} may be interpreted as a global for one tracepoint, and a
10799 local for another, as appropriate to the tracepoint's location.
10801 @item show default-collect
10802 @kindex show default-collect
10803 Show the list of expressions that are collected by default at each
10808 @node Listing Tracepoints
10809 @subsection Listing Tracepoints
10812 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10813 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10814 @cindex information about tracepoints
10815 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10816 Display information about the tracepoint @var{num}. If you don't
10817 specify a tracepoint number, displays information about all the
10818 tracepoints defined so far. The format is similar to that used for
10819 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10820 command, simply restricting itself to tracepoints.
10822 A tracepoint's listing may include additional information specific to
10827 its passcount as given by the @code{passcount @var{n}} command
10831 (@value{GDBP}) @b{info trace}
10832 Num Type Disp Enb Address What
10833 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10835 collect globfoo, $regs
10844 This command can be abbreviated @code{info tp}.
10847 @node Listing Static Tracepoint Markers
10848 @subsection Listing Static Tracepoint Markers
10851 @kindex info static-tracepoint-markers
10852 @cindex information about static tracepoint markers
10853 @item info static-tracepoint-markers
10854 Display information about all static tracepoint markers defined in the
10857 For each marker, the following columns are printed:
10861 An incrementing counter, output to help readability. This is not a
10864 The marker ID, as reported by the target.
10865 @item Enabled or Disabled
10866 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10867 that are not enabled.
10869 Where the marker is in your program, as a memory address.
10871 Where the marker is in the source for your program, as a file and line
10872 number. If the debug information included in the program does not
10873 allow @value{GDBN} to locate the source of the marker, this column
10874 will be left blank.
10878 In addition, the following information may be printed for each marker:
10882 User data passed to the tracing library by the marker call. In the
10883 UST backend, this is the format string passed as argument to the
10885 @item Static tracepoints probing the marker
10886 The list of static tracepoints attached to the marker.
10890 (@value{GDBP}) info static-tracepoint-markers
10891 Cnt ID Enb Address What
10892 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10893 Data: number1 %d number2 %d
10894 Probed by static tracepoints: #2
10895 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10901 @node Starting and Stopping Trace Experiments
10902 @subsection Starting and Stopping Trace Experiments
10905 @kindex tstart [ @var{notes} ]
10906 @cindex start a new trace experiment
10907 @cindex collected data discarded
10909 This command starts the trace experiment, and begins collecting data.
10910 It has the side effect of discarding all the data collected in the
10911 trace buffer during the previous trace experiment. If any arguments
10912 are supplied, they are taken as a note and stored with the trace
10913 experiment's state. The notes may be arbitrary text, and are
10914 especially useful with disconnected tracing in a multi-user context;
10915 the notes can explain what the trace is doing, supply user contact
10916 information, and so forth.
10918 @kindex tstop [ @var{notes} ]
10919 @cindex stop a running trace experiment
10921 This command stops the trace experiment. If any arguments are
10922 supplied, they are recorded with the experiment as a note. This is
10923 useful if you are stopping a trace started by someone else, for
10924 instance if the trace is interfering with the system's behavior and
10925 needs to be stopped quickly.
10927 @strong{Note}: a trace experiment and data collection may stop
10928 automatically if any tracepoint's passcount is reached
10929 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10932 @cindex status of trace data collection
10933 @cindex trace experiment, status of
10935 This command displays the status of the current trace data
10939 Here is an example of the commands we described so far:
10942 (@value{GDBP}) @b{trace gdb_c_test}
10943 (@value{GDBP}) @b{actions}
10944 Enter actions for tracepoint #1, one per line.
10945 > collect $regs,$locals,$args
10946 > while-stepping 11
10950 (@value{GDBP}) @b{tstart}
10951 [time passes @dots{}]
10952 (@value{GDBP}) @b{tstop}
10955 @anchor{disconnected tracing}
10956 @cindex disconnected tracing
10957 You can choose to continue running the trace experiment even if
10958 @value{GDBN} disconnects from the target, voluntarily or
10959 involuntarily. For commands such as @code{detach}, the debugger will
10960 ask what you want to do with the trace. But for unexpected
10961 terminations (@value{GDBN} crash, network outage), it would be
10962 unfortunate to lose hard-won trace data, so the variable
10963 @code{disconnected-tracing} lets you decide whether the trace should
10964 continue running without @value{GDBN}.
10967 @item set disconnected-tracing on
10968 @itemx set disconnected-tracing off
10969 @kindex set disconnected-tracing
10970 Choose whether a tracing run should continue to run if @value{GDBN}
10971 has disconnected from the target. Note that @code{detach} or
10972 @code{quit} will ask you directly what to do about a running trace no
10973 matter what this variable's setting, so the variable is mainly useful
10974 for handling unexpected situations, such as loss of the network.
10976 @item show disconnected-tracing
10977 @kindex show disconnected-tracing
10978 Show the current choice for disconnected tracing.
10982 When you reconnect to the target, the trace experiment may or may not
10983 still be running; it might have filled the trace buffer in the
10984 meantime, or stopped for one of the other reasons. If it is running,
10985 it will continue after reconnection.
10987 Upon reconnection, the target will upload information about the
10988 tracepoints in effect. @value{GDBN} will then compare that
10989 information to the set of tracepoints currently defined, and attempt
10990 to match them up, allowing for the possibility that the numbers may
10991 have changed due to creation and deletion in the meantime. If one of
10992 the target's tracepoints does not match any in @value{GDBN}, the
10993 debugger will create a new tracepoint, so that you have a number with
10994 which to specify that tracepoint. This matching-up process is
10995 necessarily heuristic, and it may result in useless tracepoints being
10996 created; you may simply delete them if they are of no use.
10998 @cindex circular trace buffer
10999 If your target agent supports a @dfn{circular trace buffer}, then you
11000 can run a trace experiment indefinitely without filling the trace
11001 buffer; when space runs out, the agent deletes already-collected trace
11002 frames, oldest first, until there is enough room to continue
11003 collecting. This is especially useful if your tracepoints are being
11004 hit too often, and your trace gets terminated prematurely because the
11005 buffer is full. To ask for a circular trace buffer, simply set
11006 @samp{circular-trace-buffer} to on. You can set this at any time,
11007 including during tracing; if the agent can do it, it will change
11008 buffer handling on the fly, otherwise it will not take effect until
11012 @item set circular-trace-buffer on
11013 @itemx set circular-trace-buffer off
11014 @kindex set circular-trace-buffer
11015 Choose whether a tracing run should use a linear or circular buffer
11016 for trace data. A linear buffer will not lose any trace data, but may
11017 fill up prematurely, while a circular buffer will discard old trace
11018 data, but it will have always room for the latest tracepoint hits.
11020 @item show circular-trace-buffer
11021 @kindex show circular-trace-buffer
11022 Show the current choice for the trace buffer. Note that this may not
11023 match the agent's current buffer handling, nor is it guaranteed to
11024 match the setting that might have been in effect during a past run,
11025 for instance if you are looking at frames from a trace file.
11030 @item set trace-user @var{text}
11031 @kindex set trace-user
11033 @item show trace-user
11034 @kindex show trace-user
11036 @item set trace-notes @var{text}
11037 @kindex set trace-notes
11038 Set the trace run's notes.
11040 @item show trace-notes
11041 @kindex show trace-notes
11042 Show the trace run's notes.
11044 @item set trace-stop-notes @var{text}
11045 @kindex set trace-stop-notes
11046 Set the trace run's stop notes. The handling of the note is as for
11047 @code{tstop} arguments; the set command is convenient way to fix a
11048 stop note that is mistaken or incomplete.
11050 @item show trace-stop-notes
11051 @kindex show trace-stop-notes
11052 Show the trace run's stop notes.
11056 @node Tracepoint Restrictions
11057 @subsection Tracepoint Restrictions
11059 @cindex tracepoint restrictions
11060 There are a number of restrictions on the use of tracepoints. As
11061 described above, tracepoint data gathering occurs on the target
11062 without interaction from @value{GDBN}. Thus the full capabilities of
11063 the debugger are not available during data gathering, and then at data
11064 examination time, you will be limited by only having what was
11065 collected. The following items describe some common problems, but it
11066 is not exhaustive, and you may run into additional difficulties not
11072 Tracepoint expressions are intended to gather objects (lvalues). Thus
11073 the full flexibility of GDB's expression evaluator is not available.
11074 You cannot call functions, cast objects to aggregate types, access
11075 convenience variables or modify values (except by assignment to trace
11076 state variables). Some language features may implicitly call
11077 functions (for instance Objective-C fields with accessors), and therefore
11078 cannot be collected either.
11081 Collection of local variables, either individually or in bulk with
11082 @code{$locals} or @code{$args}, during @code{while-stepping} may
11083 behave erratically. The stepping action may enter a new scope (for
11084 instance by stepping into a function), or the location of the variable
11085 may change (for instance it is loaded into a register). The
11086 tracepoint data recorded uses the location information for the
11087 variables that is correct for the tracepoint location. When the
11088 tracepoint is created, it is not possible, in general, to determine
11089 where the steps of a @code{while-stepping} sequence will advance the
11090 program---particularly if a conditional branch is stepped.
11093 Collection of an incompletely-initialized or partially-destroyed object
11094 may result in something that @value{GDBN} cannot display, or displays
11095 in a misleading way.
11098 When @value{GDBN} displays a pointer to character it automatically
11099 dereferences the pointer to also display characters of the string
11100 being pointed to. However, collecting the pointer during tracing does
11101 not automatically collect the string. You need to explicitly
11102 dereference the pointer and provide size information if you want to
11103 collect not only the pointer, but the memory pointed to. For example,
11104 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11108 It is not possible to collect a complete stack backtrace at a
11109 tracepoint. Instead, you may collect the registers and a few hundred
11110 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11111 (adjust to use the name of the actual stack pointer register on your
11112 target architecture, and the amount of stack you wish to capture).
11113 Then the @code{backtrace} command will show a partial backtrace when
11114 using a trace frame. The number of stack frames that can be examined
11115 depends on the sizes of the frames in the collected stack. Note that
11116 if you ask for a block so large that it goes past the bottom of the
11117 stack, the target agent may report an error trying to read from an
11121 If you do not collect registers at a tracepoint, @value{GDBN} can
11122 infer that the value of @code{$pc} must be the same as the address of
11123 the tracepoint and use that when you are looking at a trace frame
11124 for that tracepoint. However, this cannot work if the tracepoint has
11125 multiple locations (for instance if it was set in a function that was
11126 inlined), or if it has a @code{while-stepping} loop. In those cases
11127 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11132 @node Analyze Collected Data
11133 @section Using the Collected Data
11135 After the tracepoint experiment ends, you use @value{GDBN} commands
11136 for examining the trace data. The basic idea is that each tracepoint
11137 collects a trace @dfn{snapshot} every time it is hit and another
11138 snapshot every time it single-steps. All these snapshots are
11139 consecutively numbered from zero and go into a buffer, and you can
11140 examine them later. The way you examine them is to @dfn{focus} on a
11141 specific trace snapshot. When the remote stub is focused on a trace
11142 snapshot, it will respond to all @value{GDBN} requests for memory and
11143 registers by reading from the buffer which belongs to that snapshot,
11144 rather than from @emph{real} memory or registers of the program being
11145 debugged. This means that @strong{all} @value{GDBN} commands
11146 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11147 behave as if we were currently debugging the program state as it was
11148 when the tracepoint occurred. Any requests for data that are not in
11149 the buffer will fail.
11152 * tfind:: How to select a trace snapshot
11153 * tdump:: How to display all data for a snapshot
11154 * save tracepoints:: How to save tracepoints for a future run
11158 @subsection @code{tfind @var{n}}
11161 @cindex select trace snapshot
11162 @cindex find trace snapshot
11163 The basic command for selecting a trace snapshot from the buffer is
11164 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11165 counting from zero. If no argument @var{n} is given, the next
11166 snapshot is selected.
11168 Here are the various forms of using the @code{tfind} command.
11172 Find the first snapshot in the buffer. This is a synonym for
11173 @code{tfind 0} (since 0 is the number of the first snapshot).
11176 Stop debugging trace snapshots, resume @emph{live} debugging.
11179 Same as @samp{tfind none}.
11182 No argument means find the next trace snapshot.
11185 Find the previous trace snapshot before the current one. This permits
11186 retracing earlier steps.
11188 @item tfind tracepoint @var{num}
11189 Find the next snapshot associated with tracepoint @var{num}. Search
11190 proceeds forward from the last examined trace snapshot. If no
11191 argument @var{num} is given, it means find the next snapshot collected
11192 for the same tracepoint as the current snapshot.
11194 @item tfind pc @var{addr}
11195 Find the next snapshot associated with the value @var{addr} of the
11196 program counter. Search proceeds forward from the last examined trace
11197 snapshot. If no argument @var{addr} is given, it means find the next
11198 snapshot with the same value of PC as the current snapshot.
11200 @item tfind outside @var{addr1}, @var{addr2}
11201 Find the next snapshot whose PC is outside the given range of
11202 addresses (exclusive).
11204 @item tfind range @var{addr1}, @var{addr2}
11205 Find the next snapshot whose PC is between @var{addr1} and
11206 @var{addr2} (inclusive).
11208 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11209 Find the next snapshot associated with the source line @var{n}. If
11210 the optional argument @var{file} is given, refer to line @var{n} in
11211 that source file. Search proceeds forward from the last examined
11212 trace snapshot. If no argument @var{n} is given, it means find the
11213 next line other than the one currently being examined; thus saying
11214 @code{tfind line} repeatedly can appear to have the same effect as
11215 stepping from line to line in a @emph{live} debugging session.
11218 The default arguments for the @code{tfind} commands are specifically
11219 designed to make it easy to scan through the trace buffer. For
11220 instance, @code{tfind} with no argument selects the next trace
11221 snapshot, and @code{tfind -} with no argument selects the previous
11222 trace snapshot. So, by giving one @code{tfind} command, and then
11223 simply hitting @key{RET} repeatedly you can examine all the trace
11224 snapshots in order. Or, by saying @code{tfind -} and then hitting
11225 @key{RET} repeatedly you can examine the snapshots in reverse order.
11226 The @code{tfind line} command with no argument selects the snapshot
11227 for the next source line executed. The @code{tfind pc} command with
11228 no argument selects the next snapshot with the same program counter
11229 (PC) as the current frame. The @code{tfind tracepoint} command with
11230 no argument selects the next trace snapshot collected by the same
11231 tracepoint as the current one.
11233 In addition to letting you scan through the trace buffer manually,
11234 these commands make it easy to construct @value{GDBN} scripts that
11235 scan through the trace buffer and print out whatever collected data
11236 you are interested in. Thus, if we want to examine the PC, FP, and SP
11237 registers from each trace frame in the buffer, we can say this:
11240 (@value{GDBP}) @b{tfind start}
11241 (@value{GDBP}) @b{while ($trace_frame != -1)}
11242 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11243 $trace_frame, $pc, $sp, $fp
11247 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11248 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11249 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11250 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11251 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11252 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11253 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11254 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11255 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11256 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11257 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11260 Or, if we want to examine the variable @code{X} at each source line in
11264 (@value{GDBP}) @b{tfind start}
11265 (@value{GDBP}) @b{while ($trace_frame != -1)}
11266 > printf "Frame %d, X == %d\n", $trace_frame, X
11276 @subsection @code{tdump}
11278 @cindex dump all data collected at tracepoint
11279 @cindex tracepoint data, display
11281 This command takes no arguments. It prints all the data collected at
11282 the current trace snapshot.
11285 (@value{GDBP}) @b{trace 444}
11286 (@value{GDBP}) @b{actions}
11287 Enter actions for tracepoint #2, one per line:
11288 > collect $regs, $locals, $args, gdb_long_test
11291 (@value{GDBP}) @b{tstart}
11293 (@value{GDBP}) @b{tfind line 444}
11294 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11296 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11298 (@value{GDBP}) @b{tdump}
11299 Data collected at tracepoint 2, trace frame 1:
11300 d0 0xc4aa0085 -995491707
11304 d4 0x71aea3d 119204413
11307 d7 0x380035 3670069
11308 a0 0x19e24a 1696330
11309 a1 0x3000668 50333288
11311 a3 0x322000 3284992
11312 a4 0x3000698 50333336
11313 a5 0x1ad3cc 1758156
11314 fp 0x30bf3c 0x30bf3c
11315 sp 0x30bf34 0x30bf34
11317 pc 0x20b2c8 0x20b2c8
11321 p = 0x20e5b4 "gdb-test"
11328 gdb_long_test = 17 '\021'
11333 @code{tdump} works by scanning the tracepoint's current collection
11334 actions and printing the value of each expression listed. So
11335 @code{tdump} can fail, if after a run, you change the tracepoint's
11336 actions to mention variables that were not collected during the run.
11338 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11339 uses the collected value of @code{$pc} to distinguish between trace
11340 frames that were collected at the tracepoint hit, and frames that were
11341 collected while stepping. This allows it to correctly choose whether
11342 to display the basic list of collections, or the collections from the
11343 body of the while-stepping loop. However, if @code{$pc} was not collected,
11344 then @code{tdump} will always attempt to dump using the basic collection
11345 list, and may fail if a while-stepping frame does not include all the
11346 same data that is collected at the tracepoint hit.
11347 @c This is getting pretty arcane, example would be good.
11349 @node save tracepoints
11350 @subsection @code{save tracepoints @var{filename}}
11351 @kindex save tracepoints
11352 @kindex save-tracepoints
11353 @cindex save tracepoints for future sessions
11355 This command saves all current tracepoint definitions together with
11356 their actions and passcounts, into a file @file{@var{filename}}
11357 suitable for use in a later debugging session. To read the saved
11358 tracepoint definitions, use the @code{source} command (@pxref{Command
11359 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11360 alias for @w{@code{save tracepoints}}
11362 @node Tracepoint Variables
11363 @section Convenience Variables for Tracepoints
11364 @cindex tracepoint variables
11365 @cindex convenience variables for tracepoints
11368 @vindex $trace_frame
11369 @item (int) $trace_frame
11370 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11371 snapshot is selected.
11373 @vindex $tracepoint
11374 @item (int) $tracepoint
11375 The tracepoint for the current trace snapshot.
11377 @vindex $trace_line
11378 @item (int) $trace_line
11379 The line number for the current trace snapshot.
11381 @vindex $trace_file
11382 @item (char []) $trace_file
11383 The source file for the current trace snapshot.
11385 @vindex $trace_func
11386 @item (char []) $trace_func
11387 The name of the function containing @code{$tracepoint}.
11390 Note: @code{$trace_file} is not suitable for use in @code{printf},
11391 use @code{output} instead.
11393 Here's a simple example of using these convenience variables for
11394 stepping through all the trace snapshots and printing some of their
11395 data. Note that these are not the same as trace state variables,
11396 which are managed by the target.
11399 (@value{GDBP}) @b{tfind start}
11401 (@value{GDBP}) @b{while $trace_frame != -1}
11402 > output $trace_file
11403 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11409 @section Using Trace Files
11410 @cindex trace files
11412 In some situations, the target running a trace experiment may no
11413 longer be available; perhaps it crashed, or the hardware was needed
11414 for a different activity. To handle these cases, you can arrange to
11415 dump the trace data into a file, and later use that file as a source
11416 of trace data, via the @code{target tfile} command.
11421 @item tsave [ -r ] @var{filename}
11422 Save the trace data to @var{filename}. By default, this command
11423 assumes that @var{filename} refers to the host filesystem, so if
11424 necessary @value{GDBN} will copy raw trace data up from the target and
11425 then save it. If the target supports it, you can also supply the
11426 optional argument @code{-r} (``remote'') to direct the target to save
11427 the data directly into @var{filename} in its own filesystem, which may be
11428 more efficient if the trace buffer is very large. (Note, however, that
11429 @code{target tfile} can only read from files accessible to the host.)
11431 @kindex target tfile
11433 @item target tfile @var{filename}
11434 Use the file named @var{filename} as a source of trace data. Commands
11435 that examine data work as they do with a live target, but it is not
11436 possible to run any new trace experiments. @code{tstatus} will report
11437 the state of the trace run at the moment the data was saved, as well
11438 as the current trace frame you are examining. @var{filename} must be
11439 on a filesystem accessible to the host.
11444 @chapter Debugging Programs That Use Overlays
11447 If your program is too large to fit completely in your target system's
11448 memory, you can sometimes use @dfn{overlays} to work around this
11449 problem. @value{GDBN} provides some support for debugging programs that
11453 * How Overlays Work:: A general explanation of overlays.
11454 * Overlay Commands:: Managing overlays in @value{GDBN}.
11455 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11456 mapped by asking the inferior.
11457 * Overlay Sample Program:: A sample program using overlays.
11460 @node How Overlays Work
11461 @section How Overlays Work
11462 @cindex mapped overlays
11463 @cindex unmapped overlays
11464 @cindex load address, overlay's
11465 @cindex mapped address
11466 @cindex overlay area
11468 Suppose you have a computer whose instruction address space is only 64
11469 kilobytes long, but which has much more memory which can be accessed by
11470 other means: special instructions, segment registers, or memory
11471 management hardware, for example. Suppose further that you want to
11472 adapt a program which is larger than 64 kilobytes to run on this system.
11474 One solution is to identify modules of your program which are relatively
11475 independent, and need not call each other directly; call these modules
11476 @dfn{overlays}. Separate the overlays from the main program, and place
11477 their machine code in the larger memory. Place your main program in
11478 instruction memory, but leave at least enough space there to hold the
11479 largest overlay as well.
11481 Now, to call a function located in an overlay, you must first copy that
11482 overlay's machine code from the large memory into the space set aside
11483 for it in the instruction memory, and then jump to its entry point
11486 @c NB: In the below the mapped area's size is greater or equal to the
11487 @c size of all overlays. This is intentional to remind the developer
11488 @c that overlays don't necessarily need to be the same size.
11492 Data Instruction Larger
11493 Address Space Address Space Address Space
11494 +-----------+ +-----------+ +-----------+
11496 +-----------+ +-----------+ +-----------+<-- overlay 1
11497 | program | | main | .----| overlay 1 | load address
11498 | variables | | program | | +-----------+
11499 | and heap | | | | | |
11500 +-----------+ | | | +-----------+<-- overlay 2
11501 | | +-----------+ | | | load address
11502 +-----------+ | | | .-| overlay 2 |
11504 mapped --->+-----------+ | | +-----------+
11505 address | | | | | |
11506 | overlay | <-' | | |
11507 | area | <---' +-----------+<-- overlay 3
11508 | | <---. | | load address
11509 +-----------+ `--| overlay 3 |
11516 @anchor{A code overlay}A code overlay
11520 The diagram (@pxref{A code overlay}) shows a system with separate data
11521 and instruction address spaces. To map an overlay, the program copies
11522 its code from the larger address space to the instruction address space.
11523 Since the overlays shown here all use the same mapped address, only one
11524 may be mapped at a time. For a system with a single address space for
11525 data and instructions, the diagram would be similar, except that the
11526 program variables and heap would share an address space with the main
11527 program and the overlay area.
11529 An overlay loaded into instruction memory and ready for use is called a
11530 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11531 instruction memory. An overlay not present (or only partially present)
11532 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11533 is its address in the larger memory. The mapped address is also called
11534 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11535 called the @dfn{load memory address}, or @dfn{LMA}.
11537 Unfortunately, overlays are not a completely transparent way to adapt a
11538 program to limited instruction memory. They introduce a new set of
11539 global constraints you must keep in mind as you design your program:
11544 Before calling or returning to a function in an overlay, your program
11545 must make sure that overlay is actually mapped. Otherwise, the call or
11546 return will transfer control to the right address, but in the wrong
11547 overlay, and your program will probably crash.
11550 If the process of mapping an overlay is expensive on your system, you
11551 will need to choose your overlays carefully to minimize their effect on
11552 your program's performance.
11555 The executable file you load onto your system must contain each
11556 overlay's instructions, appearing at the overlay's load address, not its
11557 mapped address. However, each overlay's instructions must be relocated
11558 and its symbols defined as if the overlay were at its mapped address.
11559 You can use GNU linker scripts to specify different load and relocation
11560 addresses for pieces of your program; see @ref{Overlay Description,,,
11561 ld.info, Using ld: the GNU linker}.
11564 The procedure for loading executable files onto your system must be able
11565 to load their contents into the larger address space as well as the
11566 instruction and data spaces.
11570 The overlay system described above is rather simple, and could be
11571 improved in many ways:
11576 If your system has suitable bank switch registers or memory management
11577 hardware, you could use those facilities to make an overlay's load area
11578 contents simply appear at their mapped address in instruction space.
11579 This would probably be faster than copying the overlay to its mapped
11580 area in the usual way.
11583 If your overlays are small enough, you could set aside more than one
11584 overlay area, and have more than one overlay mapped at a time.
11587 You can use overlays to manage data, as well as instructions. In
11588 general, data overlays are even less transparent to your design than
11589 code overlays: whereas code overlays only require care when you call or
11590 return to functions, data overlays require care every time you access
11591 the data. Also, if you change the contents of a data overlay, you
11592 must copy its contents back out to its load address before you can copy a
11593 different data overlay into the same mapped area.
11598 @node Overlay Commands
11599 @section Overlay Commands
11601 To use @value{GDBN}'s overlay support, each overlay in your program must
11602 correspond to a separate section of the executable file. The section's
11603 virtual memory address and load memory address must be the overlay's
11604 mapped and load addresses. Identifying overlays with sections allows
11605 @value{GDBN} to determine the appropriate address of a function or
11606 variable, depending on whether the overlay is mapped or not.
11608 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11609 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11614 Disable @value{GDBN}'s overlay support. When overlay support is
11615 disabled, @value{GDBN} assumes that all functions and variables are
11616 always present at their mapped addresses. By default, @value{GDBN}'s
11617 overlay support is disabled.
11619 @item overlay manual
11620 @cindex manual overlay debugging
11621 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11622 relies on you to tell it which overlays are mapped, and which are not,
11623 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11624 commands described below.
11626 @item overlay map-overlay @var{overlay}
11627 @itemx overlay map @var{overlay}
11628 @cindex map an overlay
11629 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11630 be the name of the object file section containing the overlay. When an
11631 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11632 functions and variables at their mapped addresses. @value{GDBN} assumes
11633 that any other overlays whose mapped ranges overlap that of
11634 @var{overlay} are now unmapped.
11636 @item overlay unmap-overlay @var{overlay}
11637 @itemx overlay unmap @var{overlay}
11638 @cindex unmap an overlay
11639 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11640 must be the name of the object file section containing the overlay.
11641 When an overlay is unmapped, @value{GDBN} assumes it can find the
11642 overlay's functions and variables at their load addresses.
11645 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11646 consults a data structure the overlay manager maintains in the inferior
11647 to see which overlays are mapped. For details, see @ref{Automatic
11648 Overlay Debugging}.
11650 @item overlay load-target
11651 @itemx overlay load
11652 @cindex reloading the overlay table
11653 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11654 re-reads the table @value{GDBN} automatically each time the inferior
11655 stops, so this command should only be necessary if you have changed the
11656 overlay mapping yourself using @value{GDBN}. This command is only
11657 useful when using automatic overlay debugging.
11659 @item overlay list-overlays
11660 @itemx overlay list
11661 @cindex listing mapped overlays
11662 Display a list of the overlays currently mapped, along with their mapped
11663 addresses, load addresses, and sizes.
11667 Normally, when @value{GDBN} prints a code address, it includes the name
11668 of the function the address falls in:
11671 (@value{GDBP}) print main
11672 $3 = @{int ()@} 0x11a0 <main>
11675 When overlay debugging is enabled, @value{GDBN} recognizes code in
11676 unmapped overlays, and prints the names of unmapped functions with
11677 asterisks around them. For example, if @code{foo} is a function in an
11678 unmapped overlay, @value{GDBN} prints it this way:
11681 (@value{GDBP}) overlay list
11682 No sections are mapped.
11683 (@value{GDBP}) print foo
11684 $5 = @{int (int)@} 0x100000 <*foo*>
11687 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11691 (@value{GDBP}) overlay list
11692 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11693 mapped at 0x1016 - 0x104a
11694 (@value{GDBP}) print foo
11695 $6 = @{int (int)@} 0x1016 <foo>
11698 When overlay debugging is enabled, @value{GDBN} can find the correct
11699 address for functions and variables in an overlay, whether or not the
11700 overlay is mapped. This allows most @value{GDBN} commands, like
11701 @code{break} and @code{disassemble}, to work normally, even on unmapped
11702 code. However, @value{GDBN}'s breakpoint support has some limitations:
11706 @cindex breakpoints in overlays
11707 @cindex overlays, setting breakpoints in
11708 You can set breakpoints in functions in unmapped overlays, as long as
11709 @value{GDBN} can write to the overlay at its load address.
11711 @value{GDBN} can not set hardware or simulator-based breakpoints in
11712 unmapped overlays. However, if you set a breakpoint at the end of your
11713 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11714 you are using manual overlay management), @value{GDBN} will re-set its
11715 breakpoints properly.
11719 @node Automatic Overlay Debugging
11720 @section Automatic Overlay Debugging
11721 @cindex automatic overlay debugging
11723 @value{GDBN} can automatically track which overlays are mapped and which
11724 are not, given some simple co-operation from the overlay manager in the
11725 inferior. If you enable automatic overlay debugging with the
11726 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11727 looks in the inferior's memory for certain variables describing the
11728 current state of the overlays.
11730 Here are the variables your overlay manager must define to support
11731 @value{GDBN}'s automatic overlay debugging:
11735 @item @code{_ovly_table}:
11736 This variable must be an array of the following structures:
11741 /* The overlay's mapped address. */
11744 /* The size of the overlay, in bytes. */
11745 unsigned long size;
11747 /* The overlay's load address. */
11750 /* Non-zero if the overlay is currently mapped;
11752 unsigned long mapped;
11756 @item @code{_novlys}:
11757 This variable must be a four-byte signed integer, holding the total
11758 number of elements in @code{_ovly_table}.
11762 To decide whether a particular overlay is mapped or not, @value{GDBN}
11763 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11764 @code{lma} members equal the VMA and LMA of the overlay's section in the
11765 executable file. When @value{GDBN} finds a matching entry, it consults
11766 the entry's @code{mapped} member to determine whether the overlay is
11769 In addition, your overlay manager may define a function called
11770 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11771 will silently set a breakpoint there. If the overlay manager then
11772 calls this function whenever it has changed the overlay table, this
11773 will enable @value{GDBN} to accurately keep track of which overlays
11774 are in program memory, and update any breakpoints that may be set
11775 in overlays. This will allow breakpoints to work even if the
11776 overlays are kept in ROM or other non-writable memory while they
11777 are not being executed.
11779 @node Overlay Sample Program
11780 @section Overlay Sample Program
11781 @cindex overlay example program
11783 When linking a program which uses overlays, you must place the overlays
11784 at their load addresses, while relocating them to run at their mapped
11785 addresses. To do this, you must write a linker script (@pxref{Overlay
11786 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11787 since linker scripts are specific to a particular host system, target
11788 architecture, and target memory layout, this manual cannot provide
11789 portable sample code demonstrating @value{GDBN}'s overlay support.
11791 However, the @value{GDBN} source distribution does contain an overlaid
11792 program, with linker scripts for a few systems, as part of its test
11793 suite. The program consists of the following files from
11794 @file{gdb/testsuite/gdb.base}:
11798 The main program file.
11800 A simple overlay manager, used by @file{overlays.c}.
11805 Overlay modules, loaded and used by @file{overlays.c}.
11808 Linker scripts for linking the test program on the @code{d10v-elf}
11809 and @code{m32r-elf} targets.
11812 You can build the test program using the @code{d10v-elf} GCC
11813 cross-compiler like this:
11816 $ d10v-elf-gcc -g -c overlays.c
11817 $ d10v-elf-gcc -g -c ovlymgr.c
11818 $ d10v-elf-gcc -g -c foo.c
11819 $ d10v-elf-gcc -g -c bar.c
11820 $ d10v-elf-gcc -g -c baz.c
11821 $ d10v-elf-gcc -g -c grbx.c
11822 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11823 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11826 The build process is identical for any other architecture, except that
11827 you must substitute the appropriate compiler and linker script for the
11828 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11832 @chapter Using @value{GDBN} with Different Languages
11835 Although programming languages generally have common aspects, they are
11836 rarely expressed in the same manner. For instance, in ANSI C,
11837 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11838 Modula-2, it is accomplished by @code{p^}. Values can also be
11839 represented (and displayed) differently. Hex numbers in C appear as
11840 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11842 @cindex working language
11843 Language-specific information is built into @value{GDBN} for some languages,
11844 allowing you to express operations like the above in your program's
11845 native language, and allowing @value{GDBN} to output values in a manner
11846 consistent with the syntax of your program's native language. The
11847 language you use to build expressions is called the @dfn{working
11851 * Setting:: Switching between source languages
11852 * Show:: Displaying the language
11853 * Checks:: Type and range checks
11854 * Supported Languages:: Supported languages
11855 * Unsupported Languages:: Unsupported languages
11859 @section Switching Between Source Languages
11861 There are two ways to control the working language---either have @value{GDBN}
11862 set it automatically, or select it manually yourself. You can use the
11863 @code{set language} command for either purpose. On startup, @value{GDBN}
11864 defaults to setting the language automatically. The working language is
11865 used to determine how expressions you type are interpreted, how values
11868 In addition to the working language, every source file that
11869 @value{GDBN} knows about has its own working language. For some object
11870 file formats, the compiler might indicate which language a particular
11871 source file is in. However, most of the time @value{GDBN} infers the
11872 language from the name of the file. The language of a source file
11873 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11874 show each frame appropriately for its own language. There is no way to
11875 set the language of a source file from within @value{GDBN}, but you can
11876 set the language associated with a filename extension. @xref{Show, ,
11877 Displaying the Language}.
11879 This is most commonly a problem when you use a program, such
11880 as @code{cfront} or @code{f2c}, that generates C but is written in
11881 another language. In that case, make the
11882 program use @code{#line} directives in its C output; that way
11883 @value{GDBN} will know the correct language of the source code of the original
11884 program, and will display that source code, not the generated C code.
11887 * Filenames:: Filename extensions and languages.
11888 * Manually:: Setting the working language manually
11889 * Automatically:: Having @value{GDBN} infer the source language
11893 @subsection List of Filename Extensions and Languages
11895 If a source file name ends in one of the following extensions, then
11896 @value{GDBN} infers that its language is the one indicated.
11914 C@t{++} source file
11920 Objective-C source file
11924 Fortran source file
11927 Modula-2 source file
11931 Assembler source file. This actually behaves almost like C, but
11932 @value{GDBN} does not skip over function prologues when stepping.
11935 In addition, you may set the language associated with a filename
11936 extension. @xref{Show, , Displaying the Language}.
11939 @subsection Setting the Working Language
11941 If you allow @value{GDBN} to set the language automatically,
11942 expressions are interpreted the same way in your debugging session and
11945 @kindex set language
11946 If you wish, you may set the language manually. To do this, issue the
11947 command @samp{set language @var{lang}}, where @var{lang} is the name of
11948 a language, such as
11949 @code{c} or @code{modula-2}.
11950 For a list of the supported languages, type @samp{set language}.
11952 Setting the language manually prevents @value{GDBN} from updating the working
11953 language automatically. This can lead to confusion if you try
11954 to debug a program when the working language is not the same as the
11955 source language, when an expression is acceptable to both
11956 languages---but means different things. For instance, if the current
11957 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11965 might not have the effect you intended. In C, this means to add
11966 @code{b} and @code{c} and place the result in @code{a}. The result
11967 printed would be the value of @code{a}. In Modula-2, this means to compare
11968 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11970 @node Automatically
11971 @subsection Having @value{GDBN} Infer the Source Language
11973 To have @value{GDBN} set the working language automatically, use
11974 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11975 then infers the working language. That is, when your program stops in a
11976 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11977 working language to the language recorded for the function in that
11978 frame. If the language for a frame is unknown (that is, if the function
11979 or block corresponding to the frame was defined in a source file that
11980 does not have a recognized extension), the current working language is
11981 not changed, and @value{GDBN} issues a warning.
11983 This may not seem necessary for most programs, which are written
11984 entirely in one source language. However, program modules and libraries
11985 written in one source language can be used by a main program written in
11986 a different source language. Using @samp{set language auto} in this
11987 case frees you from having to set the working language manually.
11990 @section Displaying the Language
11992 The following commands help you find out which language is the
11993 working language, and also what language source files were written in.
11996 @item show language
11997 @kindex show language
11998 Display the current working language. This is the
11999 language you can use with commands such as @code{print} to
12000 build and compute expressions that may involve variables in your program.
12003 @kindex info frame@r{, show the source language}
12004 Display the source language for this frame. This language becomes the
12005 working language if you use an identifier from this frame.
12006 @xref{Frame Info, ,Information about a Frame}, to identify the other
12007 information listed here.
12010 @kindex info source@r{, show the source language}
12011 Display the source language of this source file.
12012 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12013 information listed here.
12016 In unusual circumstances, you may have source files with extensions
12017 not in the standard list. You can then set the extension associated
12018 with a language explicitly:
12021 @item set extension-language @var{ext} @var{language}
12022 @kindex set extension-language
12023 Tell @value{GDBN} that source files with extension @var{ext} are to be
12024 assumed as written in the source language @var{language}.
12026 @item info extensions
12027 @kindex info extensions
12028 List all the filename extensions and the associated languages.
12032 @section Type and Range Checking
12035 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12036 checking are included, but they do not yet have any effect. This
12037 section documents the intended facilities.
12039 @c FIXME remove warning when type/range code added
12041 Some languages are designed to guard you against making seemingly common
12042 errors through a series of compile- and run-time checks. These include
12043 checking the type of arguments to functions and operators, and making
12044 sure mathematical overflows are caught at run time. Checks such as
12045 these help to ensure a program's correctness once it has been compiled
12046 by eliminating type mismatches, and providing active checks for range
12047 errors when your program is running.
12049 @value{GDBN} can check for conditions like the above if you wish.
12050 Although @value{GDBN} does not check the statements in your program,
12051 it can check expressions entered directly into @value{GDBN} for
12052 evaluation via the @code{print} command, for example. As with the
12053 working language, @value{GDBN} can also decide whether or not to check
12054 automatically based on your program's source language.
12055 @xref{Supported Languages, ,Supported Languages}, for the default
12056 settings of supported languages.
12059 * Type Checking:: An overview of type checking
12060 * Range Checking:: An overview of range checking
12063 @cindex type checking
12064 @cindex checks, type
12065 @node Type Checking
12066 @subsection An Overview of Type Checking
12068 Some languages, such as Modula-2, are strongly typed, meaning that the
12069 arguments to operators and functions have to be of the correct type,
12070 otherwise an error occurs. These checks prevent type mismatch
12071 errors from ever causing any run-time problems. For example,
12079 The second example fails because the @code{CARDINAL} 1 is not
12080 type-compatible with the @code{REAL} 2.3.
12082 For the expressions you use in @value{GDBN} commands, you can tell the
12083 @value{GDBN} type checker to skip checking;
12084 to treat any mismatches as errors and abandon the expression;
12085 or to only issue warnings when type mismatches occur,
12086 but evaluate the expression anyway. When you choose the last of
12087 these, @value{GDBN} evaluates expressions like the second example above, but
12088 also issues a warning.
12090 Even if you turn type checking off, there may be other reasons
12091 related to type that prevent @value{GDBN} from evaluating an expression.
12092 For instance, @value{GDBN} does not know how to add an @code{int} and
12093 a @code{struct foo}. These particular type errors have nothing to do
12094 with the language in use, and usually arise from expressions, such as
12095 the one described above, which make little sense to evaluate anyway.
12097 Each language defines to what degree it is strict about type. For
12098 instance, both Modula-2 and C require the arguments to arithmetical
12099 operators to be numbers. In C, enumerated types and pointers can be
12100 represented as numbers, so that they are valid arguments to mathematical
12101 operators. @xref{Supported Languages, ,Supported Languages}, for further
12102 details on specific languages.
12104 @value{GDBN} provides some additional commands for controlling the type checker:
12106 @kindex set check type
12107 @kindex show check type
12109 @item set check type auto
12110 Set type checking on or off based on the current working language.
12111 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12114 @item set check type on
12115 @itemx set check type off
12116 Set type checking on or off, overriding the default setting for the
12117 current working language. Issue a warning if the setting does not
12118 match the language default. If any type mismatches occur in
12119 evaluating an expression while type checking is on, @value{GDBN} prints a
12120 message and aborts evaluation of the expression.
12122 @item set check type warn
12123 Cause the type checker to issue warnings, but to always attempt to
12124 evaluate the expression. Evaluating the expression may still
12125 be impossible for other reasons. For example, @value{GDBN} cannot add
12126 numbers and structures.
12129 Show the current setting of the type checker, and whether or not @value{GDBN}
12130 is setting it automatically.
12133 @cindex range checking
12134 @cindex checks, range
12135 @node Range Checking
12136 @subsection An Overview of Range Checking
12138 In some languages (such as Modula-2), it is an error to exceed the
12139 bounds of a type; this is enforced with run-time checks. Such range
12140 checking is meant to ensure program correctness by making sure
12141 computations do not overflow, or indices on an array element access do
12142 not exceed the bounds of the array.
12144 For expressions you use in @value{GDBN} commands, you can tell
12145 @value{GDBN} to treat range errors in one of three ways: ignore them,
12146 always treat them as errors and abandon the expression, or issue
12147 warnings but evaluate the expression anyway.
12149 A range error can result from numerical overflow, from exceeding an
12150 array index bound, or when you type a constant that is not a member
12151 of any type. Some languages, however, do not treat overflows as an
12152 error. In many implementations of C, mathematical overflow causes the
12153 result to ``wrap around'' to lower values---for example, if @var{m} is
12154 the largest integer value, and @var{s} is the smallest, then
12157 @var{m} + 1 @result{} @var{s}
12160 This, too, is specific to individual languages, and in some cases
12161 specific to individual compilers or machines. @xref{Supported Languages, ,
12162 Supported Languages}, for further details on specific languages.
12164 @value{GDBN} provides some additional commands for controlling the range checker:
12166 @kindex set check range
12167 @kindex show check range
12169 @item set check range auto
12170 Set range checking on or off based on the current working language.
12171 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12174 @item set check range on
12175 @itemx set check range off
12176 Set range checking on or off, overriding the default setting for the
12177 current working language. A warning is issued if the setting does not
12178 match the language default. If a range error occurs and range checking is on,
12179 then a message is printed and evaluation of the expression is aborted.
12181 @item set check range warn
12182 Output messages when the @value{GDBN} range checker detects a range error,
12183 but attempt to evaluate the expression anyway. Evaluating the
12184 expression may still be impossible for other reasons, such as accessing
12185 memory that the process does not own (a typical example from many Unix
12189 Show the current setting of the range checker, and whether or not it is
12190 being set automatically by @value{GDBN}.
12193 @node Supported Languages
12194 @section Supported Languages
12196 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12197 assembly, Modula-2, and Ada.
12198 @c This is false ...
12199 Some @value{GDBN} features may be used in expressions regardless of the
12200 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12201 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12202 ,Expressions}) can be used with the constructs of any supported
12205 The following sections detail to what degree each source language is
12206 supported by @value{GDBN}. These sections are not meant to be language
12207 tutorials or references, but serve only as a reference guide to what the
12208 @value{GDBN} expression parser accepts, and what input and output
12209 formats should look like for different languages. There are many good
12210 books written on each of these languages; please look to these for a
12211 language reference or tutorial.
12214 * C:: C and C@t{++}
12216 * Objective-C:: Objective-C
12217 * OpenCL C:: OpenCL C
12218 * Fortran:: Fortran
12220 * Modula-2:: Modula-2
12225 @subsection C and C@t{++}
12227 @cindex C and C@t{++}
12228 @cindex expressions in C or C@t{++}
12230 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12231 to both languages. Whenever this is the case, we discuss those languages
12235 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12236 @cindex @sc{gnu} C@t{++}
12237 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12238 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12239 effectively, you must compile your C@t{++} programs with a supported
12240 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12241 compiler (@code{aCC}).
12244 * C Operators:: C and C@t{++} operators
12245 * C Constants:: C and C@t{++} constants
12246 * C Plus Plus Expressions:: C@t{++} expressions
12247 * C Defaults:: Default settings for C and C@t{++}
12248 * C Checks:: C and C@t{++} type and range checks
12249 * Debugging C:: @value{GDBN} and C
12250 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12251 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12255 @subsubsection C and C@t{++} Operators
12257 @cindex C and C@t{++} operators
12259 Operators must be defined on values of specific types. For instance,
12260 @code{+} is defined on numbers, but not on structures. Operators are
12261 often defined on groups of types.
12263 For the purposes of C and C@t{++}, the following definitions hold:
12268 @emph{Integral types} include @code{int} with any of its storage-class
12269 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12272 @emph{Floating-point types} include @code{float}, @code{double}, and
12273 @code{long double} (if supported by the target platform).
12276 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12279 @emph{Scalar types} include all of the above.
12284 The following operators are supported. They are listed here
12285 in order of increasing precedence:
12289 The comma or sequencing operator. Expressions in a comma-separated list
12290 are evaluated from left to right, with the result of the entire
12291 expression being the last expression evaluated.
12294 Assignment. The value of an assignment expression is the value
12295 assigned. Defined on scalar types.
12298 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12299 and translated to @w{@code{@var{a} = @var{a op b}}}.
12300 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12301 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12302 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12305 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12306 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12310 Logical @sc{or}. Defined on integral types.
12313 Logical @sc{and}. Defined on integral types.
12316 Bitwise @sc{or}. Defined on integral types.
12319 Bitwise exclusive-@sc{or}. Defined on integral types.
12322 Bitwise @sc{and}. Defined on integral types.
12325 Equality and inequality. Defined on scalar types. The value of these
12326 expressions is 0 for false and non-zero for true.
12328 @item <@r{, }>@r{, }<=@r{, }>=
12329 Less than, greater than, less than or equal, greater than or equal.
12330 Defined on scalar types. The value of these expressions is 0 for false
12331 and non-zero for true.
12334 left shift, and right shift. Defined on integral types.
12337 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12340 Addition and subtraction. Defined on integral types, floating-point types and
12343 @item *@r{, }/@r{, }%
12344 Multiplication, division, and modulus. Multiplication and division are
12345 defined on integral and floating-point types. Modulus is defined on
12349 Increment and decrement. When appearing before a variable, the
12350 operation is performed before the variable is used in an expression;
12351 when appearing after it, the variable's value is used before the
12352 operation takes place.
12355 Pointer dereferencing. Defined on pointer types. Same precedence as
12359 Address operator. Defined on variables. Same precedence as @code{++}.
12361 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12362 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12363 to examine the address
12364 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12368 Negative. Defined on integral and floating-point types. Same
12369 precedence as @code{++}.
12372 Logical negation. Defined on integral types. Same precedence as
12376 Bitwise complement operator. Defined on integral types. Same precedence as
12381 Structure member, and pointer-to-structure member. For convenience,
12382 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12383 pointer based on the stored type information.
12384 Defined on @code{struct} and @code{union} data.
12387 Dereferences of pointers to members.
12390 Array indexing. @code{@var{a}[@var{i}]} is defined as
12391 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12394 Function parameter list. Same precedence as @code{->}.
12397 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12398 and @code{class} types.
12401 Doubled colons also represent the @value{GDBN} scope operator
12402 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12406 If an operator is redefined in the user code, @value{GDBN} usually
12407 attempts to invoke the redefined version instead of using the operator's
12408 predefined meaning.
12411 @subsubsection C and C@t{++} Constants
12413 @cindex C and C@t{++} constants
12415 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12420 Integer constants are a sequence of digits. Octal constants are
12421 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12422 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12423 @samp{l}, specifying that the constant should be treated as a
12427 Floating point constants are a sequence of digits, followed by a decimal
12428 point, followed by a sequence of digits, and optionally followed by an
12429 exponent. An exponent is of the form:
12430 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12431 sequence of digits. The @samp{+} is optional for positive exponents.
12432 A floating-point constant may also end with a letter @samp{f} or
12433 @samp{F}, specifying that the constant should be treated as being of
12434 the @code{float} (as opposed to the default @code{double}) type; or with
12435 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12439 Enumerated constants consist of enumerated identifiers, or their
12440 integral equivalents.
12443 Character constants are a single character surrounded by single quotes
12444 (@code{'}), or a number---the ordinal value of the corresponding character
12445 (usually its @sc{ascii} value). Within quotes, the single character may
12446 be represented by a letter or by @dfn{escape sequences}, which are of
12447 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12448 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12449 @samp{@var{x}} is a predefined special character---for example,
12450 @samp{\n} for newline.
12452 Wide character constants can be written by prefixing a character
12453 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12454 form of @samp{x}. The target wide character set is used when
12455 computing the value of this constant (@pxref{Character Sets}).
12458 String constants are a sequence of character constants surrounded by
12459 double quotes (@code{"}). Any valid character constant (as described
12460 above) may appear. Double quotes within the string must be preceded by
12461 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12464 Wide string constants can be written by prefixing a string constant
12465 with @samp{L}, as in C. The target wide character set is used when
12466 computing the value of this constant (@pxref{Character Sets}).
12469 Pointer constants are an integral value. You can also write pointers
12470 to constants using the C operator @samp{&}.
12473 Array constants are comma-separated lists surrounded by braces @samp{@{}
12474 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12475 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12476 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12479 @node C Plus Plus Expressions
12480 @subsubsection C@t{++} Expressions
12482 @cindex expressions in C@t{++}
12483 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12485 @cindex debugging C@t{++} programs
12486 @cindex C@t{++} compilers
12487 @cindex debug formats and C@t{++}
12488 @cindex @value{NGCC} and C@t{++}
12490 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12491 the proper compiler and the proper debug format. Currently,
12492 @value{GDBN} works best when debugging C@t{++} code that is compiled
12493 with the most recent version of @value{NGCC} possible. The DWARF
12494 debugging format is preferred; @value{NGCC} defaults to this on most
12495 popular platforms. Other compilers and/or debug formats are likely to
12496 work badly or not at all when using @value{GDBN} to debug C@t{++}
12497 code. @xref{Compilation}.
12502 @cindex member functions
12504 Member function calls are allowed; you can use expressions like
12507 count = aml->GetOriginal(x, y)
12510 @vindex this@r{, inside C@t{++} member functions}
12511 @cindex namespace in C@t{++}
12513 While a member function is active (in the selected stack frame), your
12514 expressions have the same namespace available as the member function;
12515 that is, @value{GDBN} allows implicit references to the class instance
12516 pointer @code{this} following the same rules as C@t{++}. @code{using}
12517 declarations in the current scope are also respected by @value{GDBN}.
12519 @cindex call overloaded functions
12520 @cindex overloaded functions, calling
12521 @cindex type conversions in C@t{++}
12523 You can call overloaded functions; @value{GDBN} resolves the function
12524 call to the right definition, with some restrictions. @value{GDBN} does not
12525 perform overload resolution involving user-defined type conversions,
12526 calls to constructors, or instantiations of templates that do not exist
12527 in the program. It also cannot handle ellipsis argument lists or
12530 It does perform integral conversions and promotions, floating-point
12531 promotions, arithmetic conversions, pointer conversions, conversions of
12532 class objects to base classes, and standard conversions such as those of
12533 functions or arrays to pointers; it requires an exact match on the
12534 number of function arguments.
12536 Overload resolution is always performed, unless you have specified
12537 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12538 ,@value{GDBN} Features for C@t{++}}.
12540 You must specify @code{set overload-resolution off} in order to use an
12541 explicit function signature to call an overloaded function, as in
12543 p 'foo(char,int)'('x', 13)
12546 The @value{GDBN} command-completion facility can simplify this;
12547 see @ref{Completion, ,Command Completion}.
12549 @cindex reference declarations
12551 @value{GDBN} understands variables declared as C@t{++} references; you can use
12552 them in expressions just as you do in C@t{++} source---they are automatically
12555 In the parameter list shown when @value{GDBN} displays a frame, the values of
12556 reference variables are not displayed (unlike other variables); this
12557 avoids clutter, since references are often used for large structures.
12558 The @emph{address} of a reference variable is always shown, unless
12559 you have specified @samp{set print address off}.
12562 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12563 expressions can use it just as expressions in your program do. Since
12564 one scope may be defined in another, you can use @code{::} repeatedly if
12565 necessary, for example in an expression like
12566 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12567 resolving name scope by reference to source files, in both C and C@t{++}
12568 debugging (@pxref{Variables, ,Program Variables}).
12571 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12576 @subsubsection C and C@t{++} Defaults
12578 @cindex C and C@t{++} defaults
12580 If you allow @value{GDBN} to set type and range checking automatically, they
12581 both default to @code{off} whenever the working language changes to
12582 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12583 selects the working language.
12585 If you allow @value{GDBN} to set the language automatically, it
12586 recognizes source files whose names end with @file{.c}, @file{.C}, or
12587 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12588 these files, it sets the working language to C or C@t{++}.
12589 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12590 for further details.
12592 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12593 @c unimplemented. If (b) changes, it might make sense to let this node
12594 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12597 @subsubsection C and C@t{++} Type and Range Checks
12599 @cindex C and C@t{++} checks
12601 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12602 is not used. However, if you turn type checking on, @value{GDBN}
12603 considers two variables type equivalent if:
12607 The two variables are structured and have the same structure, union, or
12611 The two variables have the same type name, or types that have been
12612 declared equivalent through @code{typedef}.
12615 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12618 The two @code{struct}, @code{union}, or @code{enum} variables are
12619 declared in the same declaration. (Note: this may not be true for all C
12624 Range checking, if turned on, is done on mathematical operations. Array
12625 indices are not checked, since they are often used to index a pointer
12626 that is not itself an array.
12629 @subsubsection @value{GDBN} and C
12631 The @code{set print union} and @code{show print union} commands apply to
12632 the @code{union} type. When set to @samp{on}, any @code{union} that is
12633 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12634 appears as @samp{@{...@}}.
12636 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12637 with pointers and a memory allocation function. @xref{Expressions,
12640 @node Debugging C Plus Plus
12641 @subsubsection @value{GDBN} Features for C@t{++}
12643 @cindex commands for C@t{++}
12645 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12646 designed specifically for use with C@t{++}. Here is a summary:
12649 @cindex break in overloaded functions
12650 @item @r{breakpoint menus}
12651 When you want a breakpoint in a function whose name is overloaded,
12652 @value{GDBN} has the capability to display a menu of possible breakpoint
12653 locations to help you specify which function definition you want.
12654 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12656 @cindex overloading in C@t{++}
12657 @item rbreak @var{regex}
12658 Setting breakpoints using regular expressions is helpful for setting
12659 breakpoints on overloaded functions that are not members of any special
12661 @xref{Set Breaks, ,Setting Breakpoints}.
12663 @cindex C@t{++} exception handling
12666 Debug C@t{++} exception handling using these commands. @xref{Set
12667 Catchpoints, , Setting Catchpoints}.
12669 @cindex inheritance
12670 @item ptype @var{typename}
12671 Print inheritance relationships as well as other information for type
12673 @xref{Symbols, ,Examining the Symbol Table}.
12675 @cindex C@t{++} symbol display
12676 @item set print demangle
12677 @itemx show print demangle
12678 @itemx set print asm-demangle
12679 @itemx show print asm-demangle
12680 Control whether C@t{++} symbols display in their source form, both when
12681 displaying code as C@t{++} source and when displaying disassemblies.
12682 @xref{Print Settings, ,Print Settings}.
12684 @item set print object
12685 @itemx show print object
12686 Choose whether to print derived (actual) or declared types of objects.
12687 @xref{Print Settings, ,Print Settings}.
12689 @item set print vtbl
12690 @itemx show print vtbl
12691 Control the format for printing virtual function tables.
12692 @xref{Print Settings, ,Print Settings}.
12693 (The @code{vtbl} commands do not work on programs compiled with the HP
12694 ANSI C@t{++} compiler (@code{aCC}).)
12696 @kindex set overload-resolution
12697 @cindex overloaded functions, overload resolution
12698 @item set overload-resolution on
12699 Enable overload resolution for C@t{++} expression evaluation. The default
12700 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12701 and searches for a function whose signature matches the argument types,
12702 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12703 Expressions, ,C@t{++} Expressions}, for details).
12704 If it cannot find a match, it emits a message.
12706 @item set overload-resolution off
12707 Disable overload resolution for C@t{++} expression evaluation. For
12708 overloaded functions that are not class member functions, @value{GDBN}
12709 chooses the first function of the specified name that it finds in the
12710 symbol table, whether or not its arguments are of the correct type. For
12711 overloaded functions that are class member functions, @value{GDBN}
12712 searches for a function whose signature @emph{exactly} matches the
12715 @kindex show overload-resolution
12716 @item show overload-resolution
12717 Show the current setting of overload resolution.
12719 @item @r{Overloaded symbol names}
12720 You can specify a particular definition of an overloaded symbol, using
12721 the same notation that is used to declare such symbols in C@t{++}: type
12722 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12723 also use the @value{GDBN} command-line word completion facilities to list the
12724 available choices, or to finish the type list for you.
12725 @xref{Completion,, Command Completion}, for details on how to do this.
12728 @node Decimal Floating Point
12729 @subsubsection Decimal Floating Point format
12730 @cindex decimal floating point format
12732 @value{GDBN} can examine, set and perform computations with numbers in
12733 decimal floating point format, which in the C language correspond to the
12734 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12735 specified by the extension to support decimal floating-point arithmetic.
12737 There are two encodings in use, depending on the architecture: BID (Binary
12738 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12739 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12742 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12743 to manipulate decimal floating point numbers, it is not possible to convert
12744 (using a cast, for example) integers wider than 32-bit to decimal float.
12746 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12747 point computations, error checking in decimal float operations ignores
12748 underflow, overflow and divide by zero exceptions.
12750 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12751 to inspect @code{_Decimal128} values stored in floating point registers.
12752 See @ref{PowerPC,,PowerPC} for more details.
12758 @value{GDBN} can be used to debug programs written in D and compiled with
12759 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12760 specific feature --- dynamic arrays.
12763 @subsection Objective-C
12765 @cindex Objective-C
12766 This section provides information about some commands and command
12767 options that are useful for debugging Objective-C code. See also
12768 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12769 few more commands specific to Objective-C support.
12772 * Method Names in Commands::
12773 * The Print Command with Objective-C::
12776 @node Method Names in Commands
12777 @subsubsection Method Names in Commands
12779 The following commands have been extended to accept Objective-C method
12780 names as line specifications:
12782 @kindex clear@r{, and Objective-C}
12783 @kindex break@r{, and Objective-C}
12784 @kindex info line@r{, and Objective-C}
12785 @kindex jump@r{, and Objective-C}
12786 @kindex list@r{, and Objective-C}
12790 @item @code{info line}
12795 A fully qualified Objective-C method name is specified as
12798 -[@var{Class} @var{methodName}]
12801 where the minus sign is used to indicate an instance method and a
12802 plus sign (not shown) is used to indicate a class method. The class
12803 name @var{Class} and method name @var{methodName} are enclosed in
12804 brackets, similar to the way messages are specified in Objective-C
12805 source code. For example, to set a breakpoint at the @code{create}
12806 instance method of class @code{Fruit} in the program currently being
12810 break -[Fruit create]
12813 To list ten program lines around the @code{initialize} class method,
12817 list +[NSText initialize]
12820 In the current version of @value{GDBN}, the plus or minus sign is
12821 required. In future versions of @value{GDBN}, the plus or minus
12822 sign will be optional, but you can use it to narrow the search. It
12823 is also possible to specify just a method name:
12829 You must specify the complete method name, including any colons. If
12830 your program's source files contain more than one @code{create} method,
12831 you'll be presented with a numbered list of classes that implement that
12832 method. Indicate your choice by number, or type @samp{0} to exit if
12835 As another example, to clear a breakpoint established at the
12836 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12839 clear -[NSWindow makeKeyAndOrderFront:]
12842 @node The Print Command with Objective-C
12843 @subsubsection The Print Command With Objective-C
12844 @cindex Objective-C, print objects
12845 @kindex print-object
12846 @kindex po @r{(@code{print-object})}
12848 The print command has also been extended to accept methods. For example:
12851 print -[@var{object} hash]
12854 @cindex print an Objective-C object description
12855 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12857 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12858 and print the result. Also, an additional command has been added,
12859 @code{print-object} or @code{po} for short, which is meant to print
12860 the description of an object. However, this command may only work
12861 with certain Objective-C libraries that have a particular hook
12862 function, @code{_NSPrintForDebugger}, defined.
12865 @subsection OpenCL C
12868 This section provides information about @value{GDBN}s OpenCL C support.
12871 * OpenCL C Datatypes::
12872 * OpenCL C Expressions::
12873 * OpenCL C Operators::
12876 @node OpenCL C Datatypes
12877 @subsubsection OpenCL C Datatypes
12879 @cindex OpenCL C Datatypes
12880 @value{GDBN} supports the builtin scalar and vector datatypes specified
12881 by OpenCL 1.1. In addition the half- and double-precision floating point
12882 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12883 extensions are also known to @value{GDBN}.
12885 @node OpenCL C Expressions
12886 @subsubsection OpenCL C Expressions
12888 @cindex OpenCL C Expressions
12889 @value{GDBN} supports accesses to vector components including the access as
12890 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12891 supported by @value{GDBN} can be used as well.
12893 @node OpenCL C Operators
12894 @subsubsection OpenCL C Operators
12896 @cindex OpenCL C Operators
12897 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12901 @subsection Fortran
12902 @cindex Fortran-specific support in @value{GDBN}
12904 @value{GDBN} can be used to debug programs written in Fortran, but it
12905 currently supports only the features of Fortran 77 language.
12907 @cindex trailing underscore, in Fortran symbols
12908 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12909 among them) append an underscore to the names of variables and
12910 functions. When you debug programs compiled by those compilers, you
12911 will need to refer to variables and functions with a trailing
12915 * Fortran Operators:: Fortran operators and expressions
12916 * Fortran Defaults:: Default settings for Fortran
12917 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12920 @node Fortran Operators
12921 @subsubsection Fortran Operators and Expressions
12923 @cindex Fortran operators and expressions
12925 Operators must be defined on values of specific types. For instance,
12926 @code{+} is defined on numbers, but not on characters or other non-
12927 arithmetic types. Operators are often defined on groups of types.
12931 The exponentiation operator. It raises the first operand to the power
12935 The range operator. Normally used in the form of array(low:high) to
12936 represent a section of array.
12939 The access component operator. Normally used to access elements in derived
12940 types. Also suitable for unions. As unions aren't part of regular Fortran,
12941 this can only happen when accessing a register that uses a gdbarch-defined
12945 @node Fortran Defaults
12946 @subsubsection Fortran Defaults
12948 @cindex Fortran Defaults
12950 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12951 default uses case-insensitive matches for Fortran symbols. You can
12952 change that with the @samp{set case-insensitive} command, see
12953 @ref{Symbols}, for the details.
12955 @node Special Fortran Commands
12956 @subsubsection Special Fortran Commands
12958 @cindex Special Fortran commands
12960 @value{GDBN} has some commands to support Fortran-specific features,
12961 such as displaying common blocks.
12964 @cindex @code{COMMON} blocks, Fortran
12965 @kindex info common
12966 @item info common @r{[}@var{common-name}@r{]}
12967 This command prints the values contained in the Fortran @code{COMMON}
12968 block whose name is @var{common-name}. With no argument, the names of
12969 all @code{COMMON} blocks visible at the current program location are
12976 @cindex Pascal support in @value{GDBN}, limitations
12977 Debugging Pascal programs which use sets, subranges, file variables, or
12978 nested functions does not currently work. @value{GDBN} does not support
12979 entering expressions, printing values, or similar features using Pascal
12982 The Pascal-specific command @code{set print pascal_static-members}
12983 controls whether static members of Pascal objects are displayed.
12984 @xref{Print Settings, pascal_static-members}.
12987 @subsection Modula-2
12989 @cindex Modula-2, @value{GDBN} support
12991 The extensions made to @value{GDBN} to support Modula-2 only support
12992 output from the @sc{gnu} Modula-2 compiler (which is currently being
12993 developed). Other Modula-2 compilers are not currently supported, and
12994 attempting to debug executables produced by them is most likely
12995 to give an error as @value{GDBN} reads in the executable's symbol
12998 @cindex expressions in Modula-2
13000 * M2 Operators:: Built-in operators
13001 * Built-In Func/Proc:: Built-in functions and procedures
13002 * M2 Constants:: Modula-2 constants
13003 * M2 Types:: Modula-2 types
13004 * M2 Defaults:: Default settings for Modula-2
13005 * Deviations:: Deviations from standard Modula-2
13006 * M2 Checks:: Modula-2 type and range checks
13007 * M2 Scope:: The scope operators @code{::} and @code{.}
13008 * GDB/M2:: @value{GDBN} and Modula-2
13012 @subsubsection Operators
13013 @cindex Modula-2 operators
13015 Operators must be defined on values of specific types. For instance,
13016 @code{+} is defined on numbers, but not on structures. Operators are
13017 often defined on groups of types. For the purposes of Modula-2, the
13018 following definitions hold:
13023 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13027 @emph{Character types} consist of @code{CHAR} and its subranges.
13030 @emph{Floating-point types} consist of @code{REAL}.
13033 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13037 @emph{Scalar types} consist of all of the above.
13040 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13043 @emph{Boolean types} consist of @code{BOOLEAN}.
13047 The following operators are supported, and appear in order of
13048 increasing precedence:
13052 Function argument or array index separator.
13055 Assignment. The value of @var{var} @code{:=} @var{value} is
13059 Less than, greater than on integral, floating-point, or enumerated
13063 Less than or equal to, greater than or equal to
13064 on integral, floating-point and enumerated types, or set inclusion on
13065 set types. Same precedence as @code{<}.
13067 @item =@r{, }<>@r{, }#
13068 Equality and two ways of expressing inequality, valid on scalar types.
13069 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13070 available for inequality, since @code{#} conflicts with the script
13074 Set membership. Defined on set types and the types of their members.
13075 Same precedence as @code{<}.
13078 Boolean disjunction. Defined on boolean types.
13081 Boolean conjunction. Defined on boolean types.
13084 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13087 Addition and subtraction on integral and floating-point types, or union
13088 and difference on set types.
13091 Multiplication on integral and floating-point types, or set intersection
13095 Division on floating-point types, or symmetric set difference on set
13096 types. Same precedence as @code{*}.
13099 Integer division and remainder. Defined on integral types. Same
13100 precedence as @code{*}.
13103 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13106 Pointer dereferencing. Defined on pointer types.
13109 Boolean negation. Defined on boolean types. Same precedence as
13113 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13114 precedence as @code{^}.
13117 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13120 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13124 @value{GDBN} and Modula-2 scope operators.
13128 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13129 treats the use of the operator @code{IN}, or the use of operators
13130 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13131 @code{<=}, and @code{>=} on sets as an error.
13135 @node Built-In Func/Proc
13136 @subsubsection Built-in Functions and Procedures
13137 @cindex Modula-2 built-ins
13139 Modula-2 also makes available several built-in procedures and functions.
13140 In describing these, the following metavariables are used:
13145 represents an @code{ARRAY} variable.
13148 represents a @code{CHAR} constant or variable.
13151 represents a variable or constant of integral type.
13154 represents an identifier that belongs to a set. Generally used in the
13155 same function with the metavariable @var{s}. The type of @var{s} should
13156 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13159 represents a variable or constant of integral or floating-point type.
13162 represents a variable or constant of floating-point type.
13168 represents a variable.
13171 represents a variable or constant of one of many types. See the
13172 explanation of the function for details.
13175 All Modula-2 built-in procedures also return a result, described below.
13179 Returns the absolute value of @var{n}.
13182 If @var{c} is a lower case letter, it returns its upper case
13183 equivalent, otherwise it returns its argument.
13186 Returns the character whose ordinal value is @var{i}.
13189 Decrements the value in the variable @var{v} by one. Returns the new value.
13191 @item DEC(@var{v},@var{i})
13192 Decrements the value in the variable @var{v} by @var{i}. Returns the
13195 @item EXCL(@var{m},@var{s})
13196 Removes the element @var{m} from the set @var{s}. Returns the new
13199 @item FLOAT(@var{i})
13200 Returns the floating point equivalent of the integer @var{i}.
13202 @item HIGH(@var{a})
13203 Returns the index of the last member of @var{a}.
13206 Increments the value in the variable @var{v} by one. Returns the new value.
13208 @item INC(@var{v},@var{i})
13209 Increments the value in the variable @var{v} by @var{i}. Returns the
13212 @item INCL(@var{m},@var{s})
13213 Adds the element @var{m} to the set @var{s} if it is not already
13214 there. Returns the new set.
13217 Returns the maximum value of the type @var{t}.
13220 Returns the minimum value of the type @var{t}.
13223 Returns boolean TRUE if @var{i} is an odd number.
13226 Returns the ordinal value of its argument. For example, the ordinal
13227 value of a character is its @sc{ascii} value (on machines supporting the
13228 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13229 integral, character and enumerated types.
13231 @item SIZE(@var{x})
13232 Returns the size of its argument. @var{x} can be a variable or a type.
13234 @item TRUNC(@var{r})
13235 Returns the integral part of @var{r}.
13237 @item TSIZE(@var{x})
13238 Returns the size of its argument. @var{x} can be a variable or a type.
13240 @item VAL(@var{t},@var{i})
13241 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13245 @emph{Warning:} Sets and their operations are not yet supported, so
13246 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13250 @cindex Modula-2 constants
13252 @subsubsection Constants
13254 @value{GDBN} allows you to express the constants of Modula-2 in the following
13260 Integer constants are simply a sequence of digits. When used in an
13261 expression, a constant is interpreted to be type-compatible with the
13262 rest of the expression. Hexadecimal integers are specified by a
13263 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13266 Floating point constants appear as a sequence of digits, followed by a
13267 decimal point and another sequence of digits. An optional exponent can
13268 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13269 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13270 digits of the floating point constant must be valid decimal (base 10)
13274 Character constants consist of a single character enclosed by a pair of
13275 like quotes, either single (@code{'}) or double (@code{"}). They may
13276 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13277 followed by a @samp{C}.
13280 String constants consist of a sequence of characters enclosed by a
13281 pair of like quotes, either single (@code{'}) or double (@code{"}).
13282 Escape sequences in the style of C are also allowed. @xref{C
13283 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13287 Enumerated constants consist of an enumerated identifier.
13290 Boolean constants consist of the identifiers @code{TRUE} and
13294 Pointer constants consist of integral values only.
13297 Set constants are not yet supported.
13301 @subsubsection Modula-2 Types
13302 @cindex Modula-2 types
13304 Currently @value{GDBN} can print the following data types in Modula-2
13305 syntax: array types, record types, set types, pointer types, procedure
13306 types, enumerated types, subrange types and base types. You can also
13307 print the contents of variables declared using these type.
13308 This section gives a number of simple source code examples together with
13309 sample @value{GDBN} sessions.
13311 The first example contains the following section of code:
13320 and you can request @value{GDBN} to interrogate the type and value of
13321 @code{r} and @code{s}.
13324 (@value{GDBP}) print s
13326 (@value{GDBP}) ptype s
13328 (@value{GDBP}) print r
13330 (@value{GDBP}) ptype r
13335 Likewise if your source code declares @code{s} as:
13339 s: SET ['A'..'Z'] ;
13343 then you may query the type of @code{s} by:
13346 (@value{GDBP}) ptype s
13347 type = SET ['A'..'Z']
13351 Note that at present you cannot interactively manipulate set
13352 expressions using the debugger.
13354 The following example shows how you might declare an array in Modula-2
13355 and how you can interact with @value{GDBN} to print its type and contents:
13359 s: ARRAY [-10..10] OF CHAR ;
13363 (@value{GDBP}) ptype s
13364 ARRAY [-10..10] OF CHAR
13367 Note that the array handling is not yet complete and although the type
13368 is printed correctly, expression handling still assumes that all
13369 arrays have a lower bound of zero and not @code{-10} as in the example
13372 Here are some more type related Modula-2 examples:
13376 colour = (blue, red, yellow, green) ;
13377 t = [blue..yellow] ;
13385 The @value{GDBN} interaction shows how you can query the data type
13386 and value of a variable.
13389 (@value{GDBP}) print s
13391 (@value{GDBP}) ptype t
13392 type = [blue..yellow]
13396 In this example a Modula-2 array is declared and its contents
13397 displayed. Observe that the contents are written in the same way as
13398 their @code{C} counterparts.
13402 s: ARRAY [1..5] OF CARDINAL ;
13408 (@value{GDBP}) print s
13409 $1 = @{1, 0, 0, 0, 0@}
13410 (@value{GDBP}) ptype s
13411 type = ARRAY [1..5] OF CARDINAL
13414 The Modula-2 language interface to @value{GDBN} also understands
13415 pointer types as shown in this example:
13419 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13426 and you can request that @value{GDBN} describes the type of @code{s}.
13429 (@value{GDBP}) ptype s
13430 type = POINTER TO ARRAY [1..5] OF CARDINAL
13433 @value{GDBN} handles compound types as we can see in this example.
13434 Here we combine array types, record types, pointer types and subrange
13445 myarray = ARRAY myrange OF CARDINAL ;
13446 myrange = [-2..2] ;
13448 s: POINTER TO ARRAY myrange OF foo ;
13452 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13456 (@value{GDBP}) ptype s
13457 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13460 f3 : ARRAY [-2..2] OF CARDINAL;
13465 @subsubsection Modula-2 Defaults
13466 @cindex Modula-2 defaults
13468 If type and range checking are set automatically by @value{GDBN}, they
13469 both default to @code{on} whenever the working language changes to
13470 Modula-2. This happens regardless of whether you or @value{GDBN}
13471 selected the working language.
13473 If you allow @value{GDBN} to set the language automatically, then entering
13474 code compiled from a file whose name ends with @file{.mod} sets the
13475 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13476 Infer the Source Language}, for further details.
13479 @subsubsection Deviations from Standard Modula-2
13480 @cindex Modula-2, deviations from
13482 A few changes have been made to make Modula-2 programs easier to debug.
13483 This is done primarily via loosening its type strictness:
13487 Unlike in standard Modula-2, pointer constants can be formed by
13488 integers. This allows you to modify pointer variables during
13489 debugging. (In standard Modula-2, the actual address contained in a
13490 pointer variable is hidden from you; it can only be modified
13491 through direct assignment to another pointer variable or expression that
13492 returned a pointer.)
13495 C escape sequences can be used in strings and characters to represent
13496 non-printable characters. @value{GDBN} prints out strings with these
13497 escape sequences embedded. Single non-printable characters are
13498 printed using the @samp{CHR(@var{nnn})} format.
13501 The assignment operator (@code{:=}) returns the value of its right-hand
13505 All built-in procedures both modify @emph{and} return their argument.
13509 @subsubsection Modula-2 Type and Range Checks
13510 @cindex Modula-2 checks
13513 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13516 @c FIXME remove warning when type/range checks added
13518 @value{GDBN} considers two Modula-2 variables type equivalent if:
13522 They are of types that have been declared equivalent via a @code{TYPE
13523 @var{t1} = @var{t2}} statement
13526 They have been declared on the same line. (Note: This is true of the
13527 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13530 As long as type checking is enabled, any attempt to combine variables
13531 whose types are not equivalent is an error.
13533 Range checking is done on all mathematical operations, assignment, array
13534 index bounds, and all built-in functions and procedures.
13537 @subsubsection The Scope Operators @code{::} and @code{.}
13539 @cindex @code{.}, Modula-2 scope operator
13540 @cindex colon, doubled as scope operator
13542 @vindex colon-colon@r{, in Modula-2}
13543 @c Info cannot handle :: but TeX can.
13546 @vindex ::@r{, in Modula-2}
13549 There are a few subtle differences between the Modula-2 scope operator
13550 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13555 @var{module} . @var{id}
13556 @var{scope} :: @var{id}
13560 where @var{scope} is the name of a module or a procedure,
13561 @var{module} the name of a module, and @var{id} is any declared
13562 identifier within your program, except another module.
13564 Using the @code{::} operator makes @value{GDBN} search the scope
13565 specified by @var{scope} for the identifier @var{id}. If it is not
13566 found in the specified scope, then @value{GDBN} searches all scopes
13567 enclosing the one specified by @var{scope}.
13569 Using the @code{.} operator makes @value{GDBN} search the current scope for
13570 the identifier specified by @var{id} that was imported from the
13571 definition module specified by @var{module}. With this operator, it is
13572 an error if the identifier @var{id} was not imported from definition
13573 module @var{module}, or if @var{id} is not an identifier in
13577 @subsubsection @value{GDBN} and Modula-2
13579 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13580 Five subcommands of @code{set print} and @code{show print} apply
13581 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13582 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13583 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13584 analogue in Modula-2.
13586 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13587 with any language, is not useful with Modula-2. Its
13588 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13589 created in Modula-2 as they can in C or C@t{++}. However, because an
13590 address can be specified by an integral constant, the construct
13591 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13593 @cindex @code{#} in Modula-2
13594 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13595 interpreted as the beginning of a comment. Use @code{<>} instead.
13601 The extensions made to @value{GDBN} for Ada only support
13602 output from the @sc{gnu} Ada (GNAT) compiler.
13603 Other Ada compilers are not currently supported, and
13604 attempting to debug executables produced by them is most likely
13608 @cindex expressions in Ada
13610 * Ada Mode Intro:: General remarks on the Ada syntax
13611 and semantics supported by Ada mode
13613 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13614 * Additions to Ada:: Extensions of the Ada expression syntax.
13615 * Stopping Before Main Program:: Debugging the program during elaboration.
13616 * Ada Tasks:: Listing and setting breakpoints in tasks.
13617 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13618 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13620 * Ada Glitches:: Known peculiarities of Ada mode.
13623 @node Ada Mode Intro
13624 @subsubsection Introduction
13625 @cindex Ada mode, general
13627 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13628 syntax, with some extensions.
13629 The philosophy behind the design of this subset is
13633 That @value{GDBN} should provide basic literals and access to operations for
13634 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13635 leaving more sophisticated computations to subprograms written into the
13636 program (which therefore may be called from @value{GDBN}).
13639 That type safety and strict adherence to Ada language restrictions
13640 are not particularly important to the @value{GDBN} user.
13643 That brevity is important to the @value{GDBN} user.
13646 Thus, for brevity, the debugger acts as if all names declared in
13647 user-written packages are directly visible, even if they are not visible
13648 according to Ada rules, thus making it unnecessary to fully qualify most
13649 names with their packages, regardless of context. Where this causes
13650 ambiguity, @value{GDBN} asks the user's intent.
13652 The debugger will start in Ada mode if it detects an Ada main program.
13653 As for other languages, it will enter Ada mode when stopped in a program that
13654 was translated from an Ada source file.
13656 While in Ada mode, you may use `@t{--}' for comments. This is useful
13657 mostly for documenting command files. The standard @value{GDBN} comment
13658 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13659 middle (to allow based literals).
13661 The debugger supports limited overloading. Given a subprogram call in which
13662 the function symbol has multiple definitions, it will use the number of
13663 actual parameters and some information about their types to attempt to narrow
13664 the set of definitions. It also makes very limited use of context, preferring
13665 procedures to functions in the context of the @code{call} command, and
13666 functions to procedures elsewhere.
13668 @node Omissions from Ada
13669 @subsubsection Omissions from Ada
13670 @cindex Ada, omissions from
13672 Here are the notable omissions from the subset:
13676 Only a subset of the attributes are supported:
13680 @t{'First}, @t{'Last}, and @t{'Length}
13681 on array objects (not on types and subtypes).
13684 @t{'Min} and @t{'Max}.
13687 @t{'Pos} and @t{'Val}.
13693 @t{'Range} on array objects (not subtypes), but only as the right
13694 operand of the membership (@code{in}) operator.
13697 @t{'Access}, @t{'Unchecked_Access}, and
13698 @t{'Unrestricted_Access} (a GNAT extension).
13706 @code{Characters.Latin_1} are not available and
13707 concatenation is not implemented. Thus, escape characters in strings are
13708 not currently available.
13711 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13712 equality of representations. They will generally work correctly
13713 for strings and arrays whose elements have integer or enumeration types.
13714 They may not work correctly for arrays whose element
13715 types have user-defined equality, for arrays of real values
13716 (in particular, IEEE-conformant floating point, because of negative
13717 zeroes and NaNs), and for arrays whose elements contain unused bits with
13718 indeterminate values.
13721 The other component-by-component array operations (@code{and}, @code{or},
13722 @code{xor}, @code{not}, and relational tests other than equality)
13723 are not implemented.
13726 @cindex array aggregates (Ada)
13727 @cindex record aggregates (Ada)
13728 @cindex aggregates (Ada)
13729 There is limited support for array and record aggregates. They are
13730 permitted only on the right sides of assignments, as in these examples:
13733 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13734 (@value{GDBP}) set An_Array := (1, others => 0)
13735 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13736 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13737 (@value{GDBP}) set A_Record := (1, "Peter", True);
13738 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13742 discriminant's value by assigning an aggregate has an
13743 undefined effect if that discriminant is used within the record.
13744 However, you can first modify discriminants by directly assigning to
13745 them (which normally would not be allowed in Ada), and then performing an
13746 aggregate assignment. For example, given a variable @code{A_Rec}
13747 declared to have a type such as:
13750 type Rec (Len : Small_Integer := 0) is record
13752 Vals : IntArray (1 .. Len);
13756 you can assign a value with a different size of @code{Vals} with two
13760 (@value{GDBP}) set A_Rec.Len := 4
13761 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13764 As this example also illustrates, @value{GDBN} is very loose about the usual
13765 rules concerning aggregates. You may leave out some of the
13766 components of an array or record aggregate (such as the @code{Len}
13767 component in the assignment to @code{A_Rec} above); they will retain their
13768 original values upon assignment. You may freely use dynamic values as
13769 indices in component associations. You may even use overlapping or
13770 redundant component associations, although which component values are
13771 assigned in such cases is not defined.
13774 Calls to dispatching subprograms are not implemented.
13777 The overloading algorithm is much more limited (i.e., less selective)
13778 than that of real Ada. It makes only limited use of the context in
13779 which a subexpression appears to resolve its meaning, and it is much
13780 looser in its rules for allowing type matches. As a result, some
13781 function calls will be ambiguous, and the user will be asked to choose
13782 the proper resolution.
13785 The @code{new} operator is not implemented.
13788 Entry calls are not implemented.
13791 Aside from printing, arithmetic operations on the native VAX floating-point
13792 formats are not supported.
13795 It is not possible to slice a packed array.
13798 The names @code{True} and @code{False}, when not part of a qualified name,
13799 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13801 Should your program
13802 redefine these names in a package or procedure (at best a dubious practice),
13803 you will have to use fully qualified names to access their new definitions.
13806 @node Additions to Ada
13807 @subsubsection Additions to Ada
13808 @cindex Ada, deviations from
13810 As it does for other languages, @value{GDBN} makes certain generic
13811 extensions to Ada (@pxref{Expressions}):
13815 If the expression @var{E} is a variable residing in memory (typically
13816 a local variable or array element) and @var{N} is a positive integer,
13817 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13818 @var{N}-1 adjacent variables following it in memory as an array. In
13819 Ada, this operator is generally not necessary, since its prime use is
13820 in displaying parts of an array, and slicing will usually do this in
13821 Ada. However, there are occasional uses when debugging programs in
13822 which certain debugging information has been optimized away.
13825 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13826 appears in function or file @var{B}.'' When @var{B} is a file name,
13827 you must typically surround it in single quotes.
13830 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13831 @var{type} that appears at address @var{addr}.''
13834 A name starting with @samp{$} is a convenience variable
13835 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13838 In addition, @value{GDBN} provides a few other shortcuts and outright
13839 additions specific to Ada:
13843 The assignment statement is allowed as an expression, returning
13844 its right-hand operand as its value. Thus, you may enter
13847 (@value{GDBP}) set x := y + 3
13848 (@value{GDBP}) print A(tmp := y + 1)
13852 The semicolon is allowed as an ``operator,'' returning as its value
13853 the value of its right-hand operand.
13854 This allows, for example,
13855 complex conditional breaks:
13858 (@value{GDBP}) break f
13859 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13863 Rather than use catenation and symbolic character names to introduce special
13864 characters into strings, one may instead use a special bracket notation,
13865 which is also used to print strings. A sequence of characters of the form
13866 @samp{["@var{XX}"]} within a string or character literal denotes the
13867 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13868 sequence of characters @samp{["""]} also denotes a single quotation mark
13869 in strings. For example,
13871 "One line.["0a"]Next line.["0a"]"
13874 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13878 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13879 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13883 (@value{GDBP}) print 'max(x, y)
13887 When printing arrays, @value{GDBN} uses positional notation when the
13888 array has a lower bound of 1, and uses a modified named notation otherwise.
13889 For example, a one-dimensional array of three integers with a lower bound
13890 of 3 might print as
13897 That is, in contrast to valid Ada, only the first component has a @code{=>}
13901 You may abbreviate attributes in expressions with any unique,
13902 multi-character subsequence of
13903 their names (an exact match gets preference).
13904 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13905 in place of @t{a'length}.
13908 @cindex quoting Ada internal identifiers
13909 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13910 to lower case. The GNAT compiler uses upper-case characters for
13911 some of its internal identifiers, which are normally of no interest to users.
13912 For the rare occasions when you actually have to look at them,
13913 enclose them in angle brackets to avoid the lower-case mapping.
13916 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13920 Printing an object of class-wide type or dereferencing an
13921 access-to-class-wide value will display all the components of the object's
13922 specific type (as indicated by its run-time tag). Likewise, component
13923 selection on such a value will operate on the specific type of the
13928 @node Stopping Before Main Program
13929 @subsubsection Stopping at the Very Beginning
13931 @cindex breakpointing Ada elaboration code
13932 It is sometimes necessary to debug the program during elaboration, and
13933 before reaching the main procedure.
13934 As defined in the Ada Reference
13935 Manual, the elaboration code is invoked from a procedure called
13936 @code{adainit}. To run your program up to the beginning of
13937 elaboration, simply use the following two commands:
13938 @code{tbreak adainit} and @code{run}.
13941 @subsubsection Extensions for Ada Tasks
13942 @cindex Ada, tasking
13944 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13945 @value{GDBN} provides the following task-related commands:
13950 This command shows a list of current Ada tasks, as in the following example:
13957 (@value{GDBP}) info tasks
13958 ID TID P-ID Pri State Name
13959 1 8088000 0 15 Child Activation Wait main_task
13960 2 80a4000 1 15 Accept Statement b
13961 3 809a800 1 15 Child Activation Wait a
13962 * 4 80ae800 3 15 Runnable c
13967 In this listing, the asterisk before the last task indicates it to be the
13968 task currently being inspected.
13972 Represents @value{GDBN}'s internal task number.
13978 The parent's task ID (@value{GDBN}'s internal task number).
13981 The base priority of the task.
13984 Current state of the task.
13988 The task has been created but has not been activated. It cannot be
13992 The task is not blocked for any reason known to Ada. (It may be waiting
13993 for a mutex, though.) It is conceptually "executing" in normal mode.
13996 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13997 that were waiting on terminate alternatives have been awakened and have
13998 terminated themselves.
14000 @item Child Activation Wait
14001 The task is waiting for created tasks to complete activation.
14003 @item Accept Statement
14004 The task is waiting on an accept or selective wait statement.
14006 @item Waiting on entry call
14007 The task is waiting on an entry call.
14009 @item Async Select Wait
14010 The task is waiting to start the abortable part of an asynchronous
14014 The task is waiting on a select statement with only a delay
14017 @item Child Termination Wait
14018 The task is sleeping having completed a master within itself, and is
14019 waiting for the tasks dependent on that master to become terminated or
14020 waiting on a terminate Phase.
14022 @item Wait Child in Term Alt
14023 The task is sleeping waiting for tasks on terminate alternatives to
14024 finish terminating.
14026 @item Accepting RV with @var{taskno}
14027 The task is accepting a rendez-vous with the task @var{taskno}.
14031 Name of the task in the program.
14035 @kindex info task @var{taskno}
14036 @item info task @var{taskno}
14037 This command shows detailled informations on the specified task, as in
14038 the following example:
14043 (@value{GDBP}) info tasks
14044 ID TID P-ID Pri State Name
14045 1 8077880 0 15 Child Activation Wait main_task
14046 * 2 807c468 1 15 Runnable task_1
14047 (@value{GDBP}) info task 2
14048 Ada Task: 0x807c468
14051 Parent: 1 (main_task)
14057 @kindex task@r{ (Ada)}
14058 @cindex current Ada task ID
14059 This command prints the ID of the current task.
14065 (@value{GDBP}) info tasks
14066 ID TID P-ID Pri State Name
14067 1 8077870 0 15 Child Activation Wait main_task
14068 * 2 807c458 1 15 Runnable t
14069 (@value{GDBP}) task
14070 [Current task is 2]
14073 @item task @var{taskno}
14074 @cindex Ada task switching
14075 This command is like the @code{thread @var{threadno}}
14076 command (@pxref{Threads}). It switches the context of debugging
14077 from the current task to the given task.
14083 (@value{GDBP}) info tasks
14084 ID TID P-ID Pri State Name
14085 1 8077870 0 15 Child Activation Wait main_task
14086 * 2 807c458 1 15 Runnable t
14087 (@value{GDBP}) task 1
14088 [Switching to task 1]
14089 #0 0x8067726 in pthread_cond_wait ()
14091 #0 0x8067726 in pthread_cond_wait ()
14092 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14093 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14094 #3 0x806153e in system.tasking.stages.activate_tasks ()
14095 #4 0x804aacc in un () at un.adb:5
14098 @item break @var{linespec} task @var{taskno}
14099 @itemx break @var{linespec} task @var{taskno} if @dots{}
14100 @cindex breakpoints and tasks, in Ada
14101 @cindex task breakpoints, in Ada
14102 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14103 These commands are like the @code{break @dots{} thread @dots{}}
14104 command (@pxref{Thread Stops}).
14105 @var{linespec} specifies source lines, as described
14106 in @ref{Specify Location}.
14108 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14109 to specify that you only want @value{GDBN} to stop the program when a
14110 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14111 numeric task identifiers assigned by @value{GDBN}, shown in the first
14112 column of the @samp{info tasks} display.
14114 If you do not specify @samp{task @var{taskno}} when you set a
14115 breakpoint, the breakpoint applies to @emph{all} tasks of your
14118 You can use the @code{task} qualifier on conditional breakpoints as
14119 well; in this case, place @samp{task @var{taskno}} before the
14120 breakpoint condition (before the @code{if}).
14128 (@value{GDBP}) info tasks
14129 ID TID P-ID Pri State Name
14130 1 140022020 0 15 Child Activation Wait main_task
14131 2 140045060 1 15 Accept/Select Wait t2
14132 3 140044840 1 15 Runnable t1
14133 * 4 140056040 1 15 Runnable t3
14134 (@value{GDBP}) b 15 task 2
14135 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14136 (@value{GDBP}) cont
14141 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14143 (@value{GDBP}) info tasks
14144 ID TID P-ID Pri State Name
14145 1 140022020 0 15 Child Activation Wait main_task
14146 * 2 140045060 1 15 Runnable t2
14147 3 140044840 1 15 Runnable t1
14148 4 140056040 1 15 Delay Sleep t3
14152 @node Ada Tasks and Core Files
14153 @subsubsection Tasking Support when Debugging Core Files
14154 @cindex Ada tasking and core file debugging
14156 When inspecting a core file, as opposed to debugging a live program,
14157 tasking support may be limited or even unavailable, depending on
14158 the platform being used.
14159 For instance, on x86-linux, the list of tasks is available, but task
14160 switching is not supported. On Tru64, however, task switching will work
14163 On certain platforms, including Tru64, the debugger needs to perform some
14164 memory writes in order to provide Ada tasking support. When inspecting
14165 a core file, this means that the core file must be opened with read-write
14166 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14167 Under these circumstances, you should make a backup copy of the core
14168 file before inspecting it with @value{GDBN}.
14170 @node Ravenscar Profile
14171 @subsubsection Tasking Support when using the Ravenscar Profile
14172 @cindex Ravenscar Profile
14174 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14175 specifically designed for systems with safety-critical real-time
14179 @kindex set ravenscar task-switching on
14180 @cindex task switching with program using Ravenscar Profile
14181 @item set ravenscar task-switching on
14182 Allows task switching when debugging a program that uses the Ravenscar
14183 Profile. This is the default.
14185 @kindex set ravenscar task-switching off
14186 @item set ravenscar task-switching off
14187 Turn off task switching when debugging a program that uses the Ravenscar
14188 Profile. This is mostly intended to disable the code that adds support
14189 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14190 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14191 To be effective, this command should be run before the program is started.
14193 @kindex show ravenscar task-switching
14194 @item show ravenscar task-switching
14195 Show whether it is possible to switch from task to task in a program
14196 using the Ravenscar Profile.
14201 @subsubsection Known Peculiarities of Ada Mode
14202 @cindex Ada, problems
14204 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14205 we know of several problems with and limitations of Ada mode in
14207 some of which will be fixed with planned future releases of the debugger
14208 and the GNU Ada compiler.
14212 Static constants that the compiler chooses not to materialize as objects in
14213 storage are invisible to the debugger.
14216 Named parameter associations in function argument lists are ignored (the
14217 argument lists are treated as positional).
14220 Many useful library packages are currently invisible to the debugger.
14223 Fixed-point arithmetic, conversions, input, and output is carried out using
14224 floating-point arithmetic, and may give results that only approximate those on
14228 The GNAT compiler never generates the prefix @code{Standard} for any of
14229 the standard symbols defined by the Ada language. @value{GDBN} knows about
14230 this: it will strip the prefix from names when you use it, and will never
14231 look for a name you have so qualified among local symbols, nor match against
14232 symbols in other packages or subprograms. If you have
14233 defined entities anywhere in your program other than parameters and
14234 local variables whose simple names match names in @code{Standard},
14235 GNAT's lack of qualification here can cause confusion. When this happens,
14236 you can usually resolve the confusion
14237 by qualifying the problematic names with package
14238 @code{Standard} explicitly.
14241 Older versions of the compiler sometimes generate erroneous debugging
14242 information, resulting in the debugger incorrectly printing the value
14243 of affected entities. In some cases, the debugger is able to work
14244 around an issue automatically. In other cases, the debugger is able
14245 to work around the issue, but the work-around has to be specifically
14248 @kindex set ada trust-PAD-over-XVS
14249 @kindex show ada trust-PAD-over-XVS
14252 @item set ada trust-PAD-over-XVS on
14253 Configure GDB to strictly follow the GNAT encoding when computing the
14254 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14255 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14256 a complete description of the encoding used by the GNAT compiler).
14257 This is the default.
14259 @item set ada trust-PAD-over-XVS off
14260 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14261 sometimes prints the wrong value for certain entities, changing @code{ada
14262 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14263 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14264 @code{off}, but this incurs a slight performance penalty, so it is
14265 recommended to leave this setting to @code{on} unless necessary.
14269 @node Unsupported Languages
14270 @section Unsupported Languages
14272 @cindex unsupported languages
14273 @cindex minimal language
14274 In addition to the other fully-supported programming languages,
14275 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14276 It does not represent a real programming language, but provides a set
14277 of capabilities close to what the C or assembly languages provide.
14278 This should allow most simple operations to be performed while debugging
14279 an application that uses a language currently not supported by @value{GDBN}.
14281 If the language is set to @code{auto}, @value{GDBN} will automatically
14282 select this language if the current frame corresponds to an unsupported
14286 @chapter Examining the Symbol Table
14288 The commands described in this chapter allow you to inquire about the
14289 symbols (names of variables, functions and types) defined in your
14290 program. This information is inherent in the text of your program and
14291 does not change as your program executes. @value{GDBN} finds it in your
14292 program's symbol table, in the file indicated when you started @value{GDBN}
14293 (@pxref{File Options, ,Choosing Files}), or by one of the
14294 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14296 @cindex symbol names
14297 @cindex names of symbols
14298 @cindex quoting names
14299 Occasionally, you may need to refer to symbols that contain unusual
14300 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14301 most frequent case is in referring to static variables in other
14302 source files (@pxref{Variables,,Program Variables}). File names
14303 are recorded in object files as debugging symbols, but @value{GDBN} would
14304 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14305 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14306 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14313 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14316 @cindex case-insensitive symbol names
14317 @cindex case sensitivity in symbol names
14318 @kindex set case-sensitive
14319 @item set case-sensitive on
14320 @itemx set case-sensitive off
14321 @itemx set case-sensitive auto
14322 Normally, when @value{GDBN} looks up symbols, it matches their names
14323 with case sensitivity determined by the current source language.
14324 Occasionally, you may wish to control that. The command @code{set
14325 case-sensitive} lets you do that by specifying @code{on} for
14326 case-sensitive matches or @code{off} for case-insensitive ones. If
14327 you specify @code{auto}, case sensitivity is reset to the default
14328 suitable for the source language. The default is case-sensitive
14329 matches for all languages except for Fortran, for which the default is
14330 case-insensitive matches.
14332 @kindex show case-sensitive
14333 @item show case-sensitive
14334 This command shows the current setting of case sensitivity for symbols
14337 @kindex info address
14338 @cindex address of a symbol
14339 @item info address @var{symbol}
14340 Describe where the data for @var{symbol} is stored. For a register
14341 variable, this says which register it is kept in. For a non-register
14342 local variable, this prints the stack-frame offset at which the variable
14345 Note the contrast with @samp{print &@var{symbol}}, which does not work
14346 at all for a register variable, and for a stack local variable prints
14347 the exact address of the current instantiation of the variable.
14349 @kindex info symbol
14350 @cindex symbol from address
14351 @cindex closest symbol and offset for an address
14352 @item info symbol @var{addr}
14353 Print the name of a symbol which is stored at the address @var{addr}.
14354 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14355 nearest symbol and an offset from it:
14358 (@value{GDBP}) info symbol 0x54320
14359 _initialize_vx + 396 in section .text
14363 This is the opposite of the @code{info address} command. You can use
14364 it to find out the name of a variable or a function given its address.
14366 For dynamically linked executables, the name of executable or shared
14367 library containing the symbol is also printed:
14370 (@value{GDBP}) info symbol 0x400225
14371 _start + 5 in section .text of /tmp/a.out
14372 (@value{GDBP}) info symbol 0x2aaaac2811cf
14373 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14377 @item whatis [@var{arg}]
14378 Print the data type of @var{arg}, which can be either an expression
14379 or a name of a data type. With no argument, print the data type of
14380 @code{$}, the last value in the value history.
14382 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14383 is not actually evaluated, and any side-effecting operations (such as
14384 assignments or function calls) inside it do not take place.
14386 If @var{arg} is a variable or an expression, @code{whatis} prints its
14387 literal type as it is used in the source code. If the type was
14388 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14389 the data type underlying the @code{typedef}. If the type of the
14390 variable or the expression is a compound data type, such as
14391 @code{struct} or @code{class}, @code{whatis} never prints their
14392 fields or methods. It just prints the @code{struct}/@code{class}
14393 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14394 such a compound data type, use @code{ptype}.
14396 If @var{arg} is a type name that was defined using @code{typedef},
14397 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14398 Unrolling means that @code{whatis} will show the underlying type used
14399 in the @code{typedef} declaration of @var{arg}. However, if that
14400 underlying type is also a @code{typedef}, @code{whatis} will not
14403 For C code, the type names may also have the form @samp{class
14404 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14405 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14408 @item ptype [@var{arg}]
14409 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14410 detailed description of the type, instead of just the name of the type.
14411 @xref{Expressions, ,Expressions}.
14413 Contrary to @code{whatis}, @code{ptype} always unrolls any
14414 @code{typedef}s in its argument declaration, whether the argument is
14415 a variable, expression, or a data type. This means that @code{ptype}
14416 of a variable or an expression will not print literally its type as
14417 present in the source code---use @code{whatis} for that. @code{typedef}s at
14418 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14419 fields, methods and inner @code{class typedef}s of @code{struct}s,
14420 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14422 For example, for this variable declaration:
14425 typedef double real_t;
14426 struct complex @{ real_t real; double imag; @};
14427 typedef struct complex complex_t;
14429 real_t *real_pointer_var;
14433 the two commands give this output:
14437 (@value{GDBP}) whatis var
14439 (@value{GDBP}) ptype var
14440 type = struct complex @{
14444 (@value{GDBP}) whatis complex_t
14445 type = struct complex
14446 (@value{GDBP}) whatis struct complex
14447 type = struct complex
14448 (@value{GDBP}) ptype struct complex
14449 type = struct complex @{
14453 (@value{GDBP}) whatis real_pointer_var
14455 (@value{GDBP}) ptype real_pointer_var
14461 As with @code{whatis}, using @code{ptype} without an argument refers to
14462 the type of @code{$}, the last value in the value history.
14464 @cindex incomplete type
14465 Sometimes, programs use opaque data types or incomplete specifications
14466 of complex data structure. If the debug information included in the
14467 program does not allow @value{GDBN} to display a full declaration of
14468 the data type, it will say @samp{<incomplete type>}. For example,
14469 given these declarations:
14473 struct foo *fooptr;
14477 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14480 (@value{GDBP}) ptype foo
14481 $1 = <incomplete type>
14485 ``Incomplete type'' is C terminology for data types that are not
14486 completely specified.
14489 @item info types @var{regexp}
14491 Print a brief description of all types whose names match the regular
14492 expression @var{regexp} (or all types in your program, if you supply
14493 no argument). Each complete typename is matched as though it were a
14494 complete line; thus, @samp{i type value} gives information on all
14495 types in your program whose names include the string @code{value}, but
14496 @samp{i type ^value$} gives information only on types whose complete
14497 name is @code{value}.
14499 This command differs from @code{ptype} in two ways: first, like
14500 @code{whatis}, it does not print a detailed description; second, it
14501 lists all source files where a type is defined.
14504 @cindex local variables
14505 @item info scope @var{location}
14506 List all the variables local to a particular scope. This command
14507 accepts a @var{location} argument---a function name, a source line, or
14508 an address preceded by a @samp{*}, and prints all the variables local
14509 to the scope defined by that location. (@xref{Specify Location}, for
14510 details about supported forms of @var{location}.) For example:
14513 (@value{GDBP}) @b{info scope command_line_handler}
14514 Scope for command_line_handler:
14515 Symbol rl is an argument at stack/frame offset 8, length 4.
14516 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14517 Symbol linelength is in static storage at address 0x150a1c, length 4.
14518 Symbol p is a local variable in register $esi, length 4.
14519 Symbol p1 is a local variable in register $ebx, length 4.
14520 Symbol nline is a local variable in register $edx, length 4.
14521 Symbol repeat is a local variable at frame offset -8, length 4.
14525 This command is especially useful for determining what data to collect
14526 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14529 @kindex info source
14531 Show information about the current source file---that is, the source file for
14532 the function containing the current point of execution:
14535 the name of the source file, and the directory containing it,
14537 the directory it was compiled in,
14539 its length, in lines,
14541 which programming language it is written in,
14543 whether the executable includes debugging information for that file, and
14544 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14546 whether the debugging information includes information about
14547 preprocessor macros.
14551 @kindex info sources
14553 Print the names of all source files in your program for which there is
14554 debugging information, organized into two lists: files whose symbols
14555 have already been read, and files whose symbols will be read when needed.
14557 @kindex info functions
14558 @item info functions
14559 Print the names and data types of all defined functions.
14561 @item info functions @var{regexp}
14562 Print the names and data types of all defined functions
14563 whose names contain a match for regular expression @var{regexp}.
14564 Thus, @samp{info fun step} finds all functions whose names
14565 include @code{step}; @samp{info fun ^step} finds those whose names
14566 start with @code{step}. If a function name contains characters
14567 that conflict with the regular expression language (e.g.@:
14568 @samp{operator*()}), they may be quoted with a backslash.
14570 @kindex info variables
14571 @item info variables
14572 Print the names and data types of all variables that are defined
14573 outside of functions (i.e.@: excluding local variables).
14575 @item info variables @var{regexp}
14576 Print the names and data types of all variables (except for local
14577 variables) whose names contain a match for regular expression
14580 @kindex info classes
14581 @cindex Objective-C, classes and selectors
14583 @itemx info classes @var{regexp}
14584 Display all Objective-C classes in your program, or
14585 (with the @var{regexp} argument) all those matching a particular regular
14588 @kindex info selectors
14589 @item info selectors
14590 @itemx info selectors @var{regexp}
14591 Display all Objective-C selectors in your program, or
14592 (with the @var{regexp} argument) all those matching a particular regular
14596 This was never implemented.
14597 @kindex info methods
14599 @itemx info methods @var{regexp}
14600 The @code{info methods} command permits the user to examine all defined
14601 methods within C@t{++} program, or (with the @var{regexp} argument) a
14602 specific set of methods found in the various C@t{++} classes. Many
14603 C@t{++} classes provide a large number of methods. Thus, the output
14604 from the @code{ptype} command can be overwhelming and hard to use. The
14605 @code{info-methods} command filters the methods, printing only those
14606 which match the regular-expression @var{regexp}.
14609 @cindex reloading symbols
14610 Some systems allow individual object files that make up your program to
14611 be replaced without stopping and restarting your program. For example,
14612 in VxWorks you can simply recompile a defective object file and keep on
14613 running. If you are running on one of these systems, you can allow
14614 @value{GDBN} to reload the symbols for automatically relinked modules:
14617 @kindex set symbol-reloading
14618 @item set symbol-reloading on
14619 Replace symbol definitions for the corresponding source file when an
14620 object file with a particular name is seen again.
14622 @item set symbol-reloading off
14623 Do not replace symbol definitions when encountering object files of the
14624 same name more than once. This is the default state; if you are not
14625 running on a system that permits automatic relinking of modules, you
14626 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14627 may discard symbols when linking large programs, that may contain
14628 several modules (from different directories or libraries) with the same
14631 @kindex show symbol-reloading
14632 @item show symbol-reloading
14633 Show the current @code{on} or @code{off} setting.
14636 @cindex opaque data types
14637 @kindex set opaque-type-resolution
14638 @item set opaque-type-resolution on
14639 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14640 declared as a pointer to a @code{struct}, @code{class}, or
14641 @code{union}---for example, @code{struct MyType *}---that is used in one
14642 source file although the full declaration of @code{struct MyType} is in
14643 another source file. The default is on.
14645 A change in the setting of this subcommand will not take effect until
14646 the next time symbols for a file are loaded.
14648 @item set opaque-type-resolution off
14649 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14650 is printed as follows:
14652 @{<no data fields>@}
14655 @kindex show opaque-type-resolution
14656 @item show opaque-type-resolution
14657 Show whether opaque types are resolved or not.
14659 @kindex maint print symbols
14660 @cindex symbol dump
14661 @kindex maint print psymbols
14662 @cindex partial symbol dump
14663 @item maint print symbols @var{filename}
14664 @itemx maint print psymbols @var{filename}
14665 @itemx maint print msymbols @var{filename}
14666 Write a dump of debugging symbol data into the file @var{filename}.
14667 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14668 symbols with debugging data are included. If you use @samp{maint print
14669 symbols}, @value{GDBN} includes all the symbols for which it has already
14670 collected full details: that is, @var{filename} reflects symbols for
14671 only those files whose symbols @value{GDBN} has read. You can use the
14672 command @code{info sources} to find out which files these are. If you
14673 use @samp{maint print psymbols} instead, the dump shows information about
14674 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14675 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14676 @samp{maint print msymbols} dumps just the minimal symbol information
14677 required for each object file from which @value{GDBN} has read some symbols.
14678 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14679 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14681 @kindex maint info symtabs
14682 @kindex maint info psymtabs
14683 @cindex listing @value{GDBN}'s internal symbol tables
14684 @cindex symbol tables, listing @value{GDBN}'s internal
14685 @cindex full symbol tables, listing @value{GDBN}'s internal
14686 @cindex partial symbol tables, listing @value{GDBN}'s internal
14687 @item maint info symtabs @r{[} @var{regexp} @r{]}
14688 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14690 List the @code{struct symtab} or @code{struct partial_symtab}
14691 structures whose names match @var{regexp}. If @var{regexp} is not
14692 given, list them all. The output includes expressions which you can
14693 copy into a @value{GDBN} debugging this one to examine a particular
14694 structure in more detail. For example:
14697 (@value{GDBP}) maint info psymtabs dwarf2read
14698 @{ objfile /home/gnu/build/gdb/gdb
14699 ((struct objfile *) 0x82e69d0)
14700 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14701 ((struct partial_symtab *) 0x8474b10)
14704 text addresses 0x814d3c8 -- 0x8158074
14705 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14706 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14707 dependencies (none)
14710 (@value{GDBP}) maint info symtabs
14714 We see that there is one partial symbol table whose filename contains
14715 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14716 and we see that @value{GDBN} has not read in any symtabs yet at all.
14717 If we set a breakpoint on a function, that will cause @value{GDBN} to
14718 read the symtab for the compilation unit containing that function:
14721 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14722 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14724 (@value{GDBP}) maint info symtabs
14725 @{ objfile /home/gnu/build/gdb/gdb
14726 ((struct objfile *) 0x82e69d0)
14727 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14728 ((struct symtab *) 0x86c1f38)
14731 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14732 linetable ((struct linetable *) 0x8370fa0)
14733 debugformat DWARF 2
14742 @chapter Altering Execution
14744 Once you think you have found an error in your program, you might want to
14745 find out for certain whether correcting the apparent error would lead to
14746 correct results in the rest of the run. You can find the answer by
14747 experiment, using the @value{GDBN} features for altering execution of the
14750 For example, you can store new values into variables or memory
14751 locations, give your program a signal, restart it at a different
14752 address, or even return prematurely from a function.
14755 * Assignment:: Assignment to variables
14756 * Jumping:: Continuing at a different address
14757 * Signaling:: Giving your program a signal
14758 * Returning:: Returning from a function
14759 * Calling:: Calling your program's functions
14760 * Patching:: Patching your program
14764 @section Assignment to Variables
14767 @cindex setting variables
14768 To alter the value of a variable, evaluate an assignment expression.
14769 @xref{Expressions, ,Expressions}. For example,
14776 stores the value 4 into the variable @code{x}, and then prints the
14777 value of the assignment expression (which is 4).
14778 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14779 information on operators in supported languages.
14781 @kindex set variable
14782 @cindex variables, setting
14783 If you are not interested in seeing the value of the assignment, use the
14784 @code{set} command instead of the @code{print} command. @code{set} is
14785 really the same as @code{print} except that the expression's value is
14786 not printed and is not put in the value history (@pxref{Value History,
14787 ,Value History}). The expression is evaluated only for its effects.
14789 If the beginning of the argument string of the @code{set} command
14790 appears identical to a @code{set} subcommand, use the @code{set
14791 variable} command instead of just @code{set}. This command is identical
14792 to @code{set} except for its lack of subcommands. For example, if your
14793 program has a variable @code{width}, you get an error if you try to set
14794 a new value with just @samp{set width=13}, because @value{GDBN} has the
14795 command @code{set width}:
14798 (@value{GDBP}) whatis width
14800 (@value{GDBP}) p width
14802 (@value{GDBP}) set width=47
14803 Invalid syntax in expression.
14807 The invalid expression, of course, is @samp{=47}. In
14808 order to actually set the program's variable @code{width}, use
14811 (@value{GDBP}) set var width=47
14814 Because the @code{set} command has many subcommands that can conflict
14815 with the names of program variables, it is a good idea to use the
14816 @code{set variable} command instead of just @code{set}. For example, if
14817 your program has a variable @code{g}, you run into problems if you try
14818 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14819 the command @code{set gnutarget}, abbreviated @code{set g}:
14823 (@value{GDBP}) whatis g
14827 (@value{GDBP}) set g=4
14831 The program being debugged has been started already.
14832 Start it from the beginning? (y or n) y
14833 Starting program: /home/smith/cc_progs/a.out
14834 "/home/smith/cc_progs/a.out": can't open to read symbols:
14835 Invalid bfd target.
14836 (@value{GDBP}) show g
14837 The current BFD target is "=4".
14842 The program variable @code{g} did not change, and you silently set the
14843 @code{gnutarget} to an invalid value. In order to set the variable
14847 (@value{GDBP}) set var g=4
14850 @value{GDBN} allows more implicit conversions in assignments than C; you can
14851 freely store an integer value into a pointer variable or vice versa,
14852 and you can convert any structure to any other structure that is the
14853 same length or shorter.
14854 @comment FIXME: how do structs align/pad in these conversions?
14855 @comment /doc@cygnus.com 18dec1990
14857 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14858 construct to generate a value of specified type at a specified address
14859 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14860 to memory location @code{0x83040} as an integer (which implies a certain size
14861 and representation in memory), and
14864 set @{int@}0x83040 = 4
14868 stores the value 4 into that memory location.
14871 @section Continuing at a Different Address
14873 Ordinarily, when you continue your program, you do so at the place where
14874 it stopped, with the @code{continue} command. You can instead continue at
14875 an address of your own choosing, with the following commands:
14879 @item jump @var{linespec}
14880 @itemx jump @var{location}
14881 Resume execution at line @var{linespec} or at address given by
14882 @var{location}. Execution stops again immediately if there is a
14883 breakpoint there. @xref{Specify Location}, for a description of the
14884 different forms of @var{linespec} and @var{location}. It is common
14885 practice to use the @code{tbreak} command in conjunction with
14886 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14888 The @code{jump} command does not change the current stack frame, or
14889 the stack pointer, or the contents of any memory location or any
14890 register other than the program counter. If line @var{linespec} is in
14891 a different function from the one currently executing, the results may
14892 be bizarre if the two functions expect different patterns of arguments or
14893 of local variables. For this reason, the @code{jump} command requests
14894 confirmation if the specified line is not in the function currently
14895 executing. However, even bizarre results are predictable if you are
14896 well acquainted with the machine-language code of your program.
14899 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14900 On many systems, you can get much the same effect as the @code{jump}
14901 command by storing a new value into the register @code{$pc}. The
14902 difference is that this does not start your program running; it only
14903 changes the address of where it @emph{will} run when you continue. For
14911 makes the next @code{continue} command or stepping command execute at
14912 address @code{0x485}, rather than at the address where your program stopped.
14913 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14915 The most common occasion to use the @code{jump} command is to back
14916 up---perhaps with more breakpoints set---over a portion of a program
14917 that has already executed, in order to examine its execution in more
14922 @section Giving your Program a Signal
14923 @cindex deliver a signal to a program
14927 @item signal @var{signal}
14928 Resume execution where your program stopped, but immediately give it the
14929 signal @var{signal}. @var{signal} can be the name or the number of a
14930 signal. For example, on many systems @code{signal 2} and @code{signal
14931 SIGINT} are both ways of sending an interrupt signal.
14933 Alternatively, if @var{signal} is zero, continue execution without
14934 giving a signal. This is useful when your program stopped on account of
14935 a signal and would ordinary see the signal when resumed with the
14936 @code{continue} command; @samp{signal 0} causes it to resume without a
14939 @code{signal} does not repeat when you press @key{RET} a second time
14940 after executing the command.
14944 Invoking the @code{signal} command is not the same as invoking the
14945 @code{kill} utility from the shell. Sending a signal with @code{kill}
14946 causes @value{GDBN} to decide what to do with the signal depending on
14947 the signal handling tables (@pxref{Signals}). The @code{signal} command
14948 passes the signal directly to your program.
14952 @section Returning from a Function
14955 @cindex returning from a function
14958 @itemx return @var{expression}
14959 You can cancel execution of a function call with the @code{return}
14960 command. If you give an
14961 @var{expression} argument, its value is used as the function's return
14965 When you use @code{return}, @value{GDBN} discards the selected stack frame
14966 (and all frames within it). You can think of this as making the
14967 discarded frame return prematurely. If you wish to specify a value to
14968 be returned, give that value as the argument to @code{return}.
14970 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14971 Frame}), and any other frames inside of it, leaving its caller as the
14972 innermost remaining frame. That frame becomes selected. The
14973 specified value is stored in the registers used for returning values
14976 The @code{return} command does not resume execution; it leaves the
14977 program stopped in the state that would exist if the function had just
14978 returned. In contrast, the @code{finish} command (@pxref{Continuing
14979 and Stepping, ,Continuing and Stepping}) resumes execution until the
14980 selected stack frame returns naturally.
14982 @value{GDBN} needs to know how the @var{expression} argument should be set for
14983 the inferior. The concrete registers assignment depends on the OS ABI and the
14984 type being returned by the selected stack frame. For example it is common for
14985 OS ABI to return floating point values in FPU registers while integer values in
14986 CPU registers. Still some ABIs return even floating point values in CPU
14987 registers. Larger integer widths (such as @code{long long int}) also have
14988 specific placement rules. @value{GDBN} already knows the OS ABI from its
14989 current target so it needs to find out also the type being returned to make the
14990 assignment into the right register(s).
14992 Normally, the selected stack frame has debug info. @value{GDBN} will always
14993 use the debug info instead of the implicit type of @var{expression} when the
14994 debug info is available. For example, if you type @kbd{return -1}, and the
14995 function in the current stack frame is declared to return a @code{long long
14996 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14997 into a @code{long long int}:
15000 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15002 (@value{GDBP}) return -1
15003 Make func return now? (y or n) y
15004 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15005 43 printf ("result=%lld\n", func ());
15009 However, if the selected stack frame does not have a debug info, e.g., if the
15010 function was compiled without debug info, @value{GDBN} has to find out the type
15011 to return from user. Specifying a different type by mistake may set the value
15012 in different inferior registers than the caller code expects. For example,
15013 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15014 of a @code{long long int} result for a debug info less function (on 32-bit
15015 architectures). Therefore the user is required to specify the return type by
15016 an appropriate cast explicitly:
15019 Breakpoint 2, 0x0040050b in func ()
15020 (@value{GDBP}) return -1
15021 Return value type not available for selected stack frame.
15022 Please use an explicit cast of the value to return.
15023 (@value{GDBP}) return (long long int) -1
15024 Make selected stack frame return now? (y or n) y
15025 #0 0x00400526 in main ()
15030 @section Calling Program Functions
15033 @cindex calling functions
15034 @cindex inferior functions, calling
15035 @item print @var{expr}
15036 Evaluate the expression @var{expr} and display the resulting value.
15037 @var{expr} may include calls to functions in the program being
15041 @item call @var{expr}
15042 Evaluate the expression @var{expr} without displaying @code{void}
15045 You can use this variant of the @code{print} command if you want to
15046 execute a function from your program that does not return anything
15047 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15048 with @code{void} returned values that @value{GDBN} will otherwise
15049 print. If the result is not void, it is printed and saved in the
15053 It is possible for the function you call via the @code{print} or
15054 @code{call} command to generate a signal (e.g., if there's a bug in
15055 the function, or if you passed it incorrect arguments). What happens
15056 in that case is controlled by the @code{set unwindonsignal} command.
15058 Similarly, with a C@t{++} program it is possible for the function you
15059 call via the @code{print} or @code{call} command to generate an
15060 exception that is not handled due to the constraints of the dummy
15061 frame. In this case, any exception that is raised in the frame, but has
15062 an out-of-frame exception handler will not be found. GDB builds a
15063 dummy-frame for the inferior function call, and the unwinder cannot
15064 seek for exception handlers outside of this dummy-frame. What happens
15065 in that case is controlled by the
15066 @code{set unwind-on-terminating-exception} command.
15069 @item set unwindonsignal
15070 @kindex set unwindonsignal
15071 @cindex unwind stack in called functions
15072 @cindex call dummy stack unwinding
15073 Set unwinding of the stack if a signal is received while in a function
15074 that @value{GDBN} called in the program being debugged. If set to on,
15075 @value{GDBN} unwinds the stack it created for the call and restores
15076 the context to what it was before the call. If set to off (the
15077 default), @value{GDBN} stops in the frame where the signal was
15080 @item show unwindonsignal
15081 @kindex show unwindonsignal
15082 Show the current setting of stack unwinding in the functions called by
15085 @item set unwind-on-terminating-exception
15086 @kindex set unwind-on-terminating-exception
15087 @cindex unwind stack in called functions with unhandled exceptions
15088 @cindex call dummy stack unwinding on unhandled exception.
15089 Set unwinding of the stack if a C@t{++} exception is raised, but left
15090 unhandled while in a function that @value{GDBN} called in the program being
15091 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15092 it created for the call and restores the context to what it was before
15093 the call. If set to off, @value{GDBN} the exception is delivered to
15094 the default C@t{++} exception handler and the inferior terminated.
15096 @item show unwind-on-terminating-exception
15097 @kindex show unwind-on-terminating-exception
15098 Show the current setting of stack unwinding in the functions called by
15103 @cindex weak alias functions
15104 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15105 for another function. In such case, @value{GDBN} might not pick up
15106 the type information, including the types of the function arguments,
15107 which causes @value{GDBN} to call the inferior function incorrectly.
15108 As a result, the called function will function erroneously and may
15109 even crash. A solution to that is to use the name of the aliased
15113 @section Patching Programs
15115 @cindex patching binaries
15116 @cindex writing into executables
15117 @cindex writing into corefiles
15119 By default, @value{GDBN} opens the file containing your program's
15120 executable code (or the corefile) read-only. This prevents accidental
15121 alterations to machine code; but it also prevents you from intentionally
15122 patching your program's binary.
15124 If you'd like to be able to patch the binary, you can specify that
15125 explicitly with the @code{set write} command. For example, you might
15126 want to turn on internal debugging flags, or even to make emergency
15132 @itemx set write off
15133 If you specify @samp{set write on}, @value{GDBN} opens executable and
15134 core files for both reading and writing; if you specify @kbd{set write
15135 off} (the default), @value{GDBN} opens them read-only.
15137 If you have already loaded a file, you must load it again (using the
15138 @code{exec-file} or @code{core-file} command) after changing @code{set
15139 write}, for your new setting to take effect.
15143 Display whether executable files and core files are opened for writing
15144 as well as reading.
15148 @chapter @value{GDBN} Files
15150 @value{GDBN} needs to know the file name of the program to be debugged,
15151 both in order to read its symbol table and in order to start your
15152 program. To debug a core dump of a previous run, you must also tell
15153 @value{GDBN} the name of the core dump file.
15156 * Files:: Commands to specify files
15157 * Separate Debug Files:: Debugging information in separate files
15158 * Index Files:: Index files speed up GDB
15159 * Symbol Errors:: Errors reading symbol files
15160 * Data Files:: GDB data files
15164 @section Commands to Specify Files
15166 @cindex symbol table
15167 @cindex core dump file
15169 You may want to specify executable and core dump file names. The usual
15170 way to do this is at start-up time, using the arguments to
15171 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15172 Out of @value{GDBN}}).
15174 Occasionally it is necessary to change to a different file during a
15175 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15176 specify a file you want to use. Or you are debugging a remote target
15177 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15178 Program}). In these situations the @value{GDBN} commands to specify
15179 new files are useful.
15182 @cindex executable file
15184 @item file @var{filename}
15185 Use @var{filename} as the program to be debugged. It is read for its
15186 symbols and for the contents of pure memory. It is also the program
15187 executed when you use the @code{run} command. If you do not specify a
15188 directory and the file is not found in the @value{GDBN} working directory,
15189 @value{GDBN} uses the environment variable @code{PATH} as a list of
15190 directories to search, just as the shell does when looking for a program
15191 to run. You can change the value of this variable, for both @value{GDBN}
15192 and your program, using the @code{path} command.
15194 @cindex unlinked object files
15195 @cindex patching object files
15196 You can load unlinked object @file{.o} files into @value{GDBN} using
15197 the @code{file} command. You will not be able to ``run'' an object
15198 file, but you can disassemble functions and inspect variables. Also,
15199 if the underlying BFD functionality supports it, you could use
15200 @kbd{gdb -write} to patch object files using this technique. Note
15201 that @value{GDBN} can neither interpret nor modify relocations in this
15202 case, so branches and some initialized variables will appear to go to
15203 the wrong place. But this feature is still handy from time to time.
15206 @code{file} with no argument makes @value{GDBN} discard any information it
15207 has on both executable file and the symbol table.
15210 @item exec-file @r{[} @var{filename} @r{]}
15211 Specify that the program to be run (but not the symbol table) is found
15212 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15213 if necessary to locate your program. Omitting @var{filename} means to
15214 discard information on the executable file.
15216 @kindex symbol-file
15217 @item symbol-file @r{[} @var{filename} @r{]}
15218 Read symbol table information from file @var{filename}. @code{PATH} is
15219 searched when necessary. Use the @code{file} command to get both symbol
15220 table and program to run from the same file.
15222 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15223 program's symbol table.
15225 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15226 some breakpoints and auto-display expressions. This is because they may
15227 contain pointers to the internal data recording symbols and data types,
15228 which are part of the old symbol table data being discarded inside
15231 @code{symbol-file} does not repeat if you press @key{RET} again after
15234 When @value{GDBN} is configured for a particular environment, it
15235 understands debugging information in whatever format is the standard
15236 generated for that environment; you may use either a @sc{gnu} compiler, or
15237 other compilers that adhere to the local conventions.
15238 Best results are usually obtained from @sc{gnu} compilers; for example,
15239 using @code{@value{NGCC}} you can generate debugging information for
15242 For most kinds of object files, with the exception of old SVR3 systems
15243 using COFF, the @code{symbol-file} command does not normally read the
15244 symbol table in full right away. Instead, it scans the symbol table
15245 quickly to find which source files and which symbols are present. The
15246 details are read later, one source file at a time, as they are needed.
15248 The purpose of this two-stage reading strategy is to make @value{GDBN}
15249 start up faster. For the most part, it is invisible except for
15250 occasional pauses while the symbol table details for a particular source
15251 file are being read. (The @code{set verbose} command can turn these
15252 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15253 Warnings and Messages}.)
15255 We have not implemented the two-stage strategy for COFF yet. When the
15256 symbol table is stored in COFF format, @code{symbol-file} reads the
15257 symbol table data in full right away. Note that ``stabs-in-COFF''
15258 still does the two-stage strategy, since the debug info is actually
15262 @cindex reading symbols immediately
15263 @cindex symbols, reading immediately
15264 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15265 @itemx file @r{[} -readnow @r{]} @var{filename}
15266 You can override the @value{GDBN} two-stage strategy for reading symbol
15267 tables by using the @samp{-readnow} option with any of the commands that
15268 load symbol table information, if you want to be sure @value{GDBN} has the
15269 entire symbol table available.
15271 @c FIXME: for now no mention of directories, since this seems to be in
15272 @c flux. 13mar1992 status is that in theory GDB would look either in
15273 @c current dir or in same dir as myprog; but issues like competing
15274 @c GDB's, or clutter in system dirs, mean that in practice right now
15275 @c only current dir is used. FFish says maybe a special GDB hierarchy
15276 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15280 @item core-file @r{[}@var{filename}@r{]}
15282 Specify the whereabouts of a core dump file to be used as the ``contents
15283 of memory''. Traditionally, core files contain only some parts of the
15284 address space of the process that generated them; @value{GDBN} can access the
15285 executable file itself for other parts.
15287 @code{core-file} with no argument specifies that no core file is
15290 Note that the core file is ignored when your program is actually running
15291 under @value{GDBN}. So, if you have been running your program and you
15292 wish to debug a core file instead, you must kill the subprocess in which
15293 the program is running. To do this, use the @code{kill} command
15294 (@pxref{Kill Process, ,Killing the Child Process}).
15296 @kindex add-symbol-file
15297 @cindex dynamic linking
15298 @item add-symbol-file @var{filename} @var{address}
15299 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15300 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15301 The @code{add-symbol-file} command reads additional symbol table
15302 information from the file @var{filename}. You would use this command
15303 when @var{filename} has been dynamically loaded (by some other means)
15304 into the program that is running. @var{address} should be the memory
15305 address at which the file has been loaded; @value{GDBN} cannot figure
15306 this out for itself. You can additionally specify an arbitrary number
15307 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15308 section name and base address for that section. You can specify any
15309 @var{address} as an expression.
15311 The symbol table of the file @var{filename} is added to the symbol table
15312 originally read with the @code{symbol-file} command. You can use the
15313 @code{add-symbol-file} command any number of times; the new symbol data
15314 thus read keeps adding to the old. To discard all old symbol data
15315 instead, use the @code{symbol-file} command without any arguments.
15317 @cindex relocatable object files, reading symbols from
15318 @cindex object files, relocatable, reading symbols from
15319 @cindex reading symbols from relocatable object files
15320 @cindex symbols, reading from relocatable object files
15321 @cindex @file{.o} files, reading symbols from
15322 Although @var{filename} is typically a shared library file, an
15323 executable file, or some other object file which has been fully
15324 relocated for loading into a process, you can also load symbolic
15325 information from relocatable @file{.o} files, as long as:
15329 the file's symbolic information refers only to linker symbols defined in
15330 that file, not to symbols defined by other object files,
15332 every section the file's symbolic information refers to has actually
15333 been loaded into the inferior, as it appears in the file, and
15335 you can determine the address at which every section was loaded, and
15336 provide these to the @code{add-symbol-file} command.
15340 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15341 relocatable files into an already running program; such systems
15342 typically make the requirements above easy to meet. However, it's
15343 important to recognize that many native systems use complex link
15344 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15345 assembly, for example) that make the requirements difficult to meet. In
15346 general, one cannot assume that using @code{add-symbol-file} to read a
15347 relocatable object file's symbolic information will have the same effect
15348 as linking the relocatable object file into the program in the normal
15351 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15353 @kindex add-symbol-file-from-memory
15354 @cindex @code{syscall DSO}
15355 @cindex load symbols from memory
15356 @item add-symbol-file-from-memory @var{address}
15357 Load symbols from the given @var{address} in a dynamically loaded
15358 object file whose image is mapped directly into the inferior's memory.
15359 For example, the Linux kernel maps a @code{syscall DSO} into each
15360 process's address space; this DSO provides kernel-specific code for
15361 some system calls. The argument can be any expression whose
15362 evaluation yields the address of the file's shared object file header.
15363 For this command to work, you must have used @code{symbol-file} or
15364 @code{exec-file} commands in advance.
15366 @kindex add-shared-symbol-files
15368 @item add-shared-symbol-files @var{library-file}
15369 @itemx assf @var{library-file}
15370 The @code{add-shared-symbol-files} command can currently be used only
15371 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15372 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15373 @value{GDBN} automatically looks for shared libraries, however if
15374 @value{GDBN} does not find yours, you can invoke
15375 @code{add-shared-symbol-files}. It takes one argument: the shared
15376 library's file name. @code{assf} is a shorthand alias for
15377 @code{add-shared-symbol-files}.
15380 @item section @var{section} @var{addr}
15381 The @code{section} command changes the base address of the named
15382 @var{section} of the exec file to @var{addr}. This can be used if the
15383 exec file does not contain section addresses, (such as in the
15384 @code{a.out} format), or when the addresses specified in the file
15385 itself are wrong. Each section must be changed separately. The
15386 @code{info files} command, described below, lists all the sections and
15390 @kindex info target
15393 @code{info files} and @code{info target} are synonymous; both print the
15394 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15395 including the names of the executable and core dump files currently in
15396 use by @value{GDBN}, and the files from which symbols were loaded. The
15397 command @code{help target} lists all possible targets rather than
15400 @kindex maint info sections
15401 @item maint info sections
15402 Another command that can give you extra information about program sections
15403 is @code{maint info sections}. In addition to the section information
15404 displayed by @code{info files}, this command displays the flags and file
15405 offset of each section in the executable and core dump files. In addition,
15406 @code{maint info sections} provides the following command options (which
15407 may be arbitrarily combined):
15411 Display sections for all loaded object files, including shared libraries.
15412 @item @var{sections}
15413 Display info only for named @var{sections}.
15414 @item @var{section-flags}
15415 Display info only for sections for which @var{section-flags} are true.
15416 The section flags that @value{GDBN} currently knows about are:
15419 Section will have space allocated in the process when loaded.
15420 Set for all sections except those containing debug information.
15422 Section will be loaded from the file into the child process memory.
15423 Set for pre-initialized code and data, clear for @code{.bss} sections.
15425 Section needs to be relocated before loading.
15427 Section cannot be modified by the child process.
15429 Section contains executable code only.
15431 Section contains data only (no executable code).
15433 Section will reside in ROM.
15435 Section contains data for constructor/destructor lists.
15437 Section is not empty.
15439 An instruction to the linker to not output the section.
15440 @item COFF_SHARED_LIBRARY
15441 A notification to the linker that the section contains
15442 COFF shared library information.
15444 Section contains common symbols.
15447 @kindex set trust-readonly-sections
15448 @cindex read-only sections
15449 @item set trust-readonly-sections on
15450 Tell @value{GDBN} that readonly sections in your object file
15451 really are read-only (i.e.@: that their contents will not change).
15452 In that case, @value{GDBN} can fetch values from these sections
15453 out of the object file, rather than from the target program.
15454 For some targets (notably embedded ones), this can be a significant
15455 enhancement to debugging performance.
15457 The default is off.
15459 @item set trust-readonly-sections off
15460 Tell @value{GDBN} not to trust readonly sections. This means that
15461 the contents of the section might change while the program is running,
15462 and must therefore be fetched from the target when needed.
15464 @item show trust-readonly-sections
15465 Show the current setting of trusting readonly sections.
15468 All file-specifying commands allow both absolute and relative file names
15469 as arguments. @value{GDBN} always converts the file name to an absolute file
15470 name and remembers it that way.
15472 @cindex shared libraries
15473 @anchor{Shared Libraries}
15474 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15475 and IBM RS/6000 AIX shared libraries.
15477 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15478 shared libraries. @xref{Expat}.
15480 @value{GDBN} automatically loads symbol definitions from shared libraries
15481 when you use the @code{run} command, or when you examine a core file.
15482 (Before you issue the @code{run} command, @value{GDBN} does not understand
15483 references to a function in a shared library, however---unless you are
15484 debugging a core file).
15486 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15487 automatically loads the symbols at the time of the @code{shl_load} call.
15489 @c FIXME: some @value{GDBN} release may permit some refs to undef
15490 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15491 @c FIXME...lib; check this from time to time when updating manual
15493 There are times, however, when you may wish to not automatically load
15494 symbol definitions from shared libraries, such as when they are
15495 particularly large or there are many of them.
15497 To control the automatic loading of shared library symbols, use the
15501 @kindex set auto-solib-add
15502 @item set auto-solib-add @var{mode}
15503 If @var{mode} is @code{on}, symbols from all shared object libraries
15504 will be loaded automatically when the inferior begins execution, you
15505 attach to an independently started inferior, or when the dynamic linker
15506 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15507 is @code{off}, symbols must be loaded manually, using the
15508 @code{sharedlibrary} command. The default value is @code{on}.
15510 @cindex memory used for symbol tables
15511 If your program uses lots of shared libraries with debug info that
15512 takes large amounts of memory, you can decrease the @value{GDBN}
15513 memory footprint by preventing it from automatically loading the
15514 symbols from shared libraries. To that end, type @kbd{set
15515 auto-solib-add off} before running the inferior, then load each
15516 library whose debug symbols you do need with @kbd{sharedlibrary
15517 @var{regexp}}, where @var{regexp} is a regular expression that matches
15518 the libraries whose symbols you want to be loaded.
15520 @kindex show auto-solib-add
15521 @item show auto-solib-add
15522 Display the current autoloading mode.
15525 @cindex load shared library
15526 To explicitly load shared library symbols, use the @code{sharedlibrary}
15530 @kindex info sharedlibrary
15532 @item info share @var{regex}
15533 @itemx info sharedlibrary @var{regex}
15534 Print the names of the shared libraries which are currently loaded
15535 that match @var{regex}. If @var{regex} is omitted then print
15536 all shared libraries that are loaded.
15538 @kindex sharedlibrary
15540 @item sharedlibrary @var{regex}
15541 @itemx share @var{regex}
15542 Load shared object library symbols for files matching a
15543 Unix regular expression.
15544 As with files loaded automatically, it only loads shared libraries
15545 required by your program for a core file or after typing @code{run}. If
15546 @var{regex} is omitted all shared libraries required by your program are
15549 @item nosharedlibrary
15550 @kindex nosharedlibrary
15551 @cindex unload symbols from shared libraries
15552 Unload all shared object library symbols. This discards all symbols
15553 that have been loaded from all shared libraries. Symbols from shared
15554 libraries that were loaded by explicit user requests are not
15558 Sometimes you may wish that @value{GDBN} stops and gives you control
15559 when any of shared library events happen. Use the @code{set
15560 stop-on-solib-events} command for this:
15563 @item set stop-on-solib-events
15564 @kindex set stop-on-solib-events
15565 This command controls whether @value{GDBN} should give you control
15566 when the dynamic linker notifies it about some shared library event.
15567 The most common event of interest is loading or unloading of a new
15570 @item show stop-on-solib-events
15571 @kindex show stop-on-solib-events
15572 Show whether @value{GDBN} stops and gives you control when shared
15573 library events happen.
15576 Shared libraries are also supported in many cross or remote debugging
15577 configurations. @value{GDBN} needs to have access to the target's libraries;
15578 this can be accomplished either by providing copies of the libraries
15579 on the host system, or by asking @value{GDBN} to automatically retrieve the
15580 libraries from the target. If copies of the target libraries are
15581 provided, they need to be the same as the target libraries, although the
15582 copies on the target can be stripped as long as the copies on the host are
15585 @cindex where to look for shared libraries
15586 For remote debugging, you need to tell @value{GDBN} where the target
15587 libraries are, so that it can load the correct copies---otherwise, it
15588 may try to load the host's libraries. @value{GDBN} has two variables
15589 to specify the search directories for target libraries.
15592 @cindex prefix for shared library file names
15593 @cindex system root, alternate
15594 @kindex set solib-absolute-prefix
15595 @kindex set sysroot
15596 @item set sysroot @var{path}
15597 Use @var{path} as the system root for the program being debugged. Any
15598 absolute shared library paths will be prefixed with @var{path}; many
15599 runtime loaders store the absolute paths to the shared library in the
15600 target program's memory. If you use @code{set sysroot} to find shared
15601 libraries, they need to be laid out in the same way that they are on
15602 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15605 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15606 retrieve the target libraries from the remote system. This is only
15607 supported when using a remote target that supports the @code{remote get}
15608 command (@pxref{File Transfer,,Sending files to a remote system}).
15609 The part of @var{path} following the initial @file{remote:}
15610 (if present) is used as system root prefix on the remote file system.
15611 @footnote{If you want to specify a local system root using a directory
15612 that happens to be named @file{remote:}, you need to use some equivalent
15613 variant of the name like @file{./remote:}.}
15615 For targets with an MS-DOS based filesystem, such as MS-Windows and
15616 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15617 absolute file name with @var{path}. But first, on Unix hosts,
15618 @value{GDBN} converts all backslash directory separators into forward
15619 slashes, because the backslash is not a directory separator on Unix:
15622 c:\foo\bar.dll @result{} c:/foo/bar.dll
15625 Then, @value{GDBN} attempts prefixing the target file name with
15626 @var{path}, and looks for the resulting file name in the host file
15630 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15633 If that does not find the shared library, @value{GDBN} tries removing
15634 the @samp{:} character from the drive spec, both for convenience, and,
15635 for the case of the host file system not supporting file names with
15639 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15642 This makes it possible to have a system root that mirrors a target
15643 with more than one drive. E.g., you may want to setup your local
15644 copies of the target system shared libraries like so (note @samp{c} vs
15648 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15649 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15650 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15654 and point the system root at @file{/path/to/sysroot}, so that
15655 @value{GDBN} can find the correct copies of both
15656 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15658 If that still does not find the shared library, @value{GDBN} tries
15659 removing the whole drive spec from the target file name:
15662 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15665 This last lookup makes it possible to not care about the drive name,
15666 if you don't want or need to.
15668 The @code{set solib-absolute-prefix} command is an alias for @code{set
15671 @cindex default system root
15672 @cindex @samp{--with-sysroot}
15673 You can set the default system root by using the configure-time
15674 @samp{--with-sysroot} option. If the system root is inside
15675 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15676 @samp{--exec-prefix}), then the default system root will be updated
15677 automatically if the installed @value{GDBN} is moved to a new
15680 @kindex show sysroot
15682 Display the current shared library prefix.
15684 @kindex set solib-search-path
15685 @item set solib-search-path @var{path}
15686 If this variable is set, @var{path} is a colon-separated list of
15687 directories to search for shared libraries. @samp{solib-search-path}
15688 is used after @samp{sysroot} fails to locate the library, or if the
15689 path to the library is relative instead of absolute. If you want to
15690 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15691 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15692 finding your host's libraries. @samp{sysroot} is preferred; setting
15693 it to a nonexistent directory may interfere with automatic loading
15694 of shared library symbols.
15696 @kindex show solib-search-path
15697 @item show solib-search-path
15698 Display the current shared library search path.
15700 @cindex DOS file-name semantics of file names.
15701 @kindex set target-file-system-kind (unix|dos-based|auto)
15702 @kindex show target-file-system-kind
15703 @item set target-file-system-kind @var{kind}
15704 Set assumed file system kind for target reported file names.
15706 Shared library file names as reported by the target system may not
15707 make sense as is on the system @value{GDBN} is running on. For
15708 example, when remote debugging a target that has MS-DOS based file
15709 system semantics, from a Unix host, the target may be reporting to
15710 @value{GDBN} a list of loaded shared libraries with file names such as
15711 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15712 drive letters, so the @samp{c:\} prefix is not normally understood as
15713 indicating an absolute file name, and neither is the backslash
15714 normally considered a directory separator character. In that case,
15715 the native file system would interpret this whole absolute file name
15716 as a relative file name with no directory components. This would make
15717 it impossible to point @value{GDBN} at a copy of the remote target's
15718 shared libraries on the host using @code{set sysroot}, and impractical
15719 with @code{set solib-search-path}. Setting
15720 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15721 to interpret such file names similarly to how the target would, and to
15722 map them to file names valid on @value{GDBN}'s native file system
15723 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15724 to one of the supported file system kinds. In that case, @value{GDBN}
15725 tries to determine the appropriate file system variant based on the
15726 current target's operating system (@pxref{ABI, ,Configuring the
15727 Current ABI}). The supported file system settings are:
15731 Instruct @value{GDBN} to assume the target file system is of Unix
15732 kind. Only file names starting the forward slash (@samp{/}) character
15733 are considered absolute, and the directory separator character is also
15737 Instruct @value{GDBN} to assume the target file system is DOS based.
15738 File names starting with either a forward slash, or a drive letter
15739 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15740 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15741 considered directory separators.
15744 Instruct @value{GDBN} to use the file system kind associated with the
15745 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15746 This is the default.
15750 @cindex file name canonicalization
15751 @cindex base name differences
15752 When processing file names provided by the user, @value{GDBN}
15753 frequently needs to compare them to the file names recorded in the
15754 program's debug info. Normally, @value{GDBN} compares just the
15755 @dfn{base names} of the files as strings, which is reasonably fast
15756 even for very large programs. (The base name of a file is the last
15757 portion of its name, after stripping all the leading directories.)
15758 This shortcut in comparison is based upon the assumption that files
15759 cannot have more than one base name. This is usually true, but
15760 references to files that use symlinks or similar filesystem
15761 facilities violate that assumption. If your program records files
15762 using such facilities, or if you provide file names to @value{GDBN}
15763 using symlinks etc., you can set @code{basenames-may-differ} to
15764 @code{true} to instruct @value{GDBN} to completely canonicalize each
15765 pair of file names it needs to compare. This will make file-name
15766 comparisons accurate, but at a price of a significant slowdown.
15769 @item set basenames-may-differ
15770 @kindex set basenames-may-differ
15771 Set whether a source file may have multiple base names.
15773 @item show basenames-may-differ
15774 @kindex show basenames-may-differ
15775 Show whether a source file may have multiple base names.
15778 @node Separate Debug Files
15779 @section Debugging Information in Separate Files
15780 @cindex separate debugging information files
15781 @cindex debugging information in separate files
15782 @cindex @file{.debug} subdirectories
15783 @cindex debugging information directory, global
15784 @cindex global debugging information directory
15785 @cindex build ID, and separate debugging files
15786 @cindex @file{.build-id} directory
15788 @value{GDBN} allows you to put a program's debugging information in a
15789 file separate from the executable itself, in a way that allows
15790 @value{GDBN} to find and load the debugging information automatically.
15791 Since debugging information can be very large---sometimes larger
15792 than the executable code itself---some systems distribute debugging
15793 information for their executables in separate files, which users can
15794 install only when they need to debug a problem.
15796 @value{GDBN} supports two ways of specifying the separate debug info
15801 The executable contains a @dfn{debug link} that specifies the name of
15802 the separate debug info file. The separate debug file's name is
15803 usually @file{@var{executable}.debug}, where @var{executable} is the
15804 name of the corresponding executable file without leading directories
15805 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15806 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15807 checksum for the debug file, which @value{GDBN} uses to validate that
15808 the executable and the debug file came from the same build.
15811 The executable contains a @dfn{build ID}, a unique bit string that is
15812 also present in the corresponding debug info file. (This is supported
15813 only on some operating systems, notably those which use the ELF format
15814 for binary files and the @sc{gnu} Binutils.) For more details about
15815 this feature, see the description of the @option{--build-id}
15816 command-line option in @ref{Options, , Command Line Options, ld.info,
15817 The GNU Linker}. The debug info file's name is not specified
15818 explicitly by the build ID, but can be computed from the build ID, see
15822 Depending on the way the debug info file is specified, @value{GDBN}
15823 uses two different methods of looking for the debug file:
15827 For the ``debug link'' method, @value{GDBN} looks up the named file in
15828 the directory of the executable file, then in a subdirectory of that
15829 directory named @file{.debug}, and finally under the global debug
15830 directory, in a subdirectory whose name is identical to the leading
15831 directories of the executable's absolute file name.
15834 For the ``build ID'' method, @value{GDBN} looks in the
15835 @file{.build-id} subdirectory of the global debug directory for a file
15836 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15837 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15838 are the rest of the bit string. (Real build ID strings are 32 or more
15839 hex characters, not 10.)
15842 So, for example, suppose you ask @value{GDBN} to debug
15843 @file{/usr/bin/ls}, which has a debug link that specifies the
15844 file @file{ls.debug}, and a build ID whose value in hex is
15845 @code{abcdef1234}. If the global debug directory is
15846 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15847 debug information files, in the indicated order:
15851 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15853 @file{/usr/bin/ls.debug}
15855 @file{/usr/bin/.debug/ls.debug}
15857 @file{/usr/lib/debug/usr/bin/ls.debug}.
15860 You can set the global debugging info directory's name, and view the
15861 name @value{GDBN} is currently using.
15865 @kindex set debug-file-directory
15866 @item set debug-file-directory @var{directories}
15867 Set the directories which @value{GDBN} searches for separate debugging
15868 information files to @var{directory}. Multiple directory components can be set
15869 concatenating them by a directory separator.
15871 @kindex show debug-file-directory
15872 @item show debug-file-directory
15873 Show the directories @value{GDBN} searches for separate debugging
15878 @cindex @code{.gnu_debuglink} sections
15879 @cindex debug link sections
15880 A debug link is a special section of the executable file named
15881 @code{.gnu_debuglink}. The section must contain:
15885 A filename, with any leading directory components removed, followed by
15888 zero to three bytes of padding, as needed to reach the next four-byte
15889 boundary within the section, and
15891 a four-byte CRC checksum, stored in the same endianness used for the
15892 executable file itself. The checksum is computed on the debugging
15893 information file's full contents by the function given below, passing
15894 zero as the @var{crc} argument.
15897 Any executable file format can carry a debug link, as long as it can
15898 contain a section named @code{.gnu_debuglink} with the contents
15901 @cindex @code{.note.gnu.build-id} sections
15902 @cindex build ID sections
15903 The build ID is a special section in the executable file (and in other
15904 ELF binary files that @value{GDBN} may consider). This section is
15905 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15906 It contains unique identification for the built files---the ID remains
15907 the same across multiple builds of the same build tree. The default
15908 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15909 content for the build ID string. The same section with an identical
15910 value is present in the original built binary with symbols, in its
15911 stripped variant, and in the separate debugging information file.
15913 The debugging information file itself should be an ordinary
15914 executable, containing a full set of linker symbols, sections, and
15915 debugging information. The sections of the debugging information file
15916 should have the same names, addresses, and sizes as the original file,
15917 but they need not contain any data---much like a @code{.bss} section
15918 in an ordinary executable.
15920 The @sc{gnu} binary utilities (Binutils) package includes the
15921 @samp{objcopy} utility that can produce
15922 the separated executable / debugging information file pairs using the
15923 following commands:
15926 @kbd{objcopy --only-keep-debug foo foo.debug}
15931 These commands remove the debugging
15932 information from the executable file @file{foo} and place it in the file
15933 @file{foo.debug}. You can use the first, second or both methods to link the
15938 The debug link method needs the following additional command to also leave
15939 behind a debug link in @file{foo}:
15942 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15945 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15946 a version of the @code{strip} command such that the command @kbd{strip foo -f
15947 foo.debug} has the same functionality as the two @code{objcopy} commands and
15948 the @code{ln -s} command above, together.
15951 Build ID gets embedded into the main executable using @code{ld --build-id} or
15952 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15953 compatibility fixes for debug files separation are present in @sc{gnu} binary
15954 utilities (Binutils) package since version 2.18.
15959 @cindex CRC algorithm definition
15960 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15961 IEEE 802.3 using the polynomial:
15963 @c TexInfo requires naked braces for multi-digit exponents for Tex
15964 @c output, but this causes HTML output to barf. HTML has to be set using
15965 @c raw commands. So we end up having to specify this equation in 2
15970 <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>
15971 + <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
15977 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15978 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15982 The function is computed byte at a time, taking the least
15983 significant bit of each byte first. The initial pattern
15984 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15985 the final result is inverted to ensure trailing zeros also affect the
15988 @emph{Note:} This is the same CRC polynomial as used in handling the
15989 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15990 , @value{GDBN} Remote Serial Protocol}). However in the
15991 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15992 significant bit first, and the result is not inverted, so trailing
15993 zeros have no effect on the CRC value.
15995 To complete the description, we show below the code of the function
15996 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15997 initially supplied @code{crc} argument means that an initial call to
15998 this function passing in zero will start computing the CRC using
16001 @kindex gnu_debuglink_crc32
16004 gnu_debuglink_crc32 (unsigned long crc,
16005 unsigned char *buf, size_t len)
16007 static const unsigned long crc32_table[256] =
16009 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16010 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16011 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16012 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16013 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16014 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16015 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16016 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16017 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16018 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16019 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16020 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16021 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16022 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16023 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16024 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16025 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16026 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16027 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16028 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16029 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16030 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16031 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16032 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16033 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16034 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16035 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16036 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16037 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16038 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16039 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16040 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16041 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16042 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16043 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16044 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16045 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16046 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16047 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16048 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16049 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16050 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16051 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16052 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16053 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16054 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16055 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16056 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16057 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16058 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16059 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16062 unsigned char *end;
16064 crc = ~crc & 0xffffffff;
16065 for (end = buf + len; buf < end; ++buf)
16066 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16067 return ~crc & 0xffffffff;
16072 This computation does not apply to the ``build ID'' method.
16076 @section Index Files Speed Up @value{GDBN}
16077 @cindex index files
16078 @cindex @samp{.gdb_index} section
16080 When @value{GDBN} finds a symbol file, it scans the symbols in the
16081 file in order to construct an internal symbol table. This lets most
16082 @value{GDBN} operations work quickly---at the cost of a delay early
16083 on. For large programs, this delay can be quite lengthy, so
16084 @value{GDBN} provides a way to build an index, which speeds up
16087 The index is stored as a section in the symbol file. @value{GDBN} can
16088 write the index to a file, then you can put it into the symbol file
16089 using @command{objcopy}.
16091 To create an index file, use the @code{save gdb-index} command:
16094 @item save gdb-index @var{directory}
16095 @kindex save gdb-index
16096 Create an index file for each symbol file currently known by
16097 @value{GDBN}. Each file is named after its corresponding symbol file,
16098 with @samp{.gdb-index} appended, and is written into the given
16102 Once you have created an index file you can merge it into your symbol
16103 file, here named @file{symfile}, using @command{objcopy}:
16106 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16107 --set-section-flags .gdb_index=readonly symfile symfile
16110 There are currently some limitation on indices. They only work when
16111 for DWARF debugging information, not stabs. And, they do not
16112 currently work for programs using Ada.
16114 @node Symbol Errors
16115 @section Errors Reading Symbol Files
16117 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16118 such as symbol types it does not recognize, or known bugs in compiler
16119 output. By default, @value{GDBN} does not notify you of such problems, since
16120 they are relatively common and primarily of interest to people
16121 debugging compilers. If you are interested in seeing information
16122 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16123 only one message about each such type of problem, no matter how many
16124 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16125 to see how many times the problems occur, with the @code{set
16126 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16129 The messages currently printed, and their meanings, include:
16132 @item inner block not inside outer block in @var{symbol}
16134 The symbol information shows where symbol scopes begin and end
16135 (such as at the start of a function or a block of statements). This
16136 error indicates that an inner scope block is not fully contained
16137 in its outer scope blocks.
16139 @value{GDBN} circumvents the problem by treating the inner block as if it had
16140 the same scope as the outer block. In the error message, @var{symbol}
16141 may be shown as ``@code{(don't know)}'' if the outer block is not a
16144 @item block at @var{address} out of order
16146 The symbol information for symbol scope blocks should occur in
16147 order of increasing addresses. This error indicates that it does not
16150 @value{GDBN} does not circumvent this problem, and has trouble
16151 locating symbols in the source file whose symbols it is reading. (You
16152 can often determine what source file is affected by specifying
16153 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16156 @item bad block start address patched
16158 The symbol information for a symbol scope block has a start address
16159 smaller than the address of the preceding source line. This is known
16160 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16162 @value{GDBN} circumvents the problem by treating the symbol scope block as
16163 starting on the previous source line.
16165 @item bad string table offset in symbol @var{n}
16168 Symbol number @var{n} contains a pointer into the string table which is
16169 larger than the size of the string table.
16171 @value{GDBN} circumvents the problem by considering the symbol to have the
16172 name @code{foo}, which may cause other problems if many symbols end up
16175 @item unknown symbol type @code{0x@var{nn}}
16177 The symbol information contains new data types that @value{GDBN} does
16178 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16179 uncomprehended information, in hexadecimal.
16181 @value{GDBN} circumvents the error by ignoring this symbol information.
16182 This usually allows you to debug your program, though certain symbols
16183 are not accessible. If you encounter such a problem and feel like
16184 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16185 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16186 and examine @code{*bufp} to see the symbol.
16188 @item stub type has NULL name
16190 @value{GDBN} could not find the full definition for a struct or class.
16192 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16193 The symbol information for a C@t{++} member function is missing some
16194 information that recent versions of the compiler should have output for
16197 @item info mismatch between compiler and debugger
16199 @value{GDBN} could not parse a type specification output by the compiler.
16204 @section GDB Data Files
16206 @cindex prefix for data files
16207 @value{GDBN} will sometimes read an auxiliary data file. These files
16208 are kept in a directory known as the @dfn{data directory}.
16210 You can set the data directory's name, and view the name @value{GDBN}
16211 is currently using.
16214 @kindex set data-directory
16215 @item set data-directory @var{directory}
16216 Set the directory which @value{GDBN} searches for auxiliary data files
16217 to @var{directory}.
16219 @kindex show data-directory
16220 @item show data-directory
16221 Show the directory @value{GDBN} searches for auxiliary data files.
16224 @cindex default data directory
16225 @cindex @samp{--with-gdb-datadir}
16226 You can set the default data directory by using the configure-time
16227 @samp{--with-gdb-datadir} option. If the data directory is inside
16228 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16229 @samp{--exec-prefix}), then the default data directory will be updated
16230 automatically if the installed @value{GDBN} is moved to a new
16233 The data directory may also be specified with the
16234 @code{--data-directory} command line option.
16235 @xref{Mode Options}.
16238 @chapter Specifying a Debugging Target
16240 @cindex debugging target
16241 A @dfn{target} is the execution environment occupied by your program.
16243 Often, @value{GDBN} runs in the same host environment as your program;
16244 in that case, the debugging target is specified as a side effect when
16245 you use the @code{file} or @code{core} commands. When you need more
16246 flexibility---for example, running @value{GDBN} on a physically separate
16247 host, or controlling a standalone system over a serial port or a
16248 realtime system over a TCP/IP connection---you can use the @code{target}
16249 command to specify one of the target types configured for @value{GDBN}
16250 (@pxref{Target Commands, ,Commands for Managing Targets}).
16252 @cindex target architecture
16253 It is possible to build @value{GDBN} for several different @dfn{target
16254 architectures}. When @value{GDBN} is built like that, you can choose
16255 one of the available architectures with the @kbd{set architecture}
16259 @kindex set architecture
16260 @kindex show architecture
16261 @item set architecture @var{arch}
16262 This command sets the current target architecture to @var{arch}. The
16263 value of @var{arch} can be @code{"auto"}, in addition to one of the
16264 supported architectures.
16266 @item show architecture
16267 Show the current target architecture.
16269 @item set processor
16271 @kindex set processor
16272 @kindex show processor
16273 These are alias commands for, respectively, @code{set architecture}
16274 and @code{show architecture}.
16278 * Active Targets:: Active targets
16279 * Target Commands:: Commands for managing targets
16280 * Byte Order:: Choosing target byte order
16283 @node Active Targets
16284 @section Active Targets
16286 @cindex stacking targets
16287 @cindex active targets
16288 @cindex multiple targets
16290 There are multiple classes of targets such as: processes, executable files or
16291 recording sessions. Core files belong to the process class, making core file
16292 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16293 on multiple active targets, one in each class. This allows you to (for
16294 example) start a process and inspect its activity, while still having access to
16295 the executable file after the process finishes. Or if you start process
16296 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16297 presented a virtual layer of the recording target, while the process target
16298 remains stopped at the chronologically last point of the process execution.
16300 Use the @code{core-file} and @code{exec-file} commands to select a new core
16301 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16302 specify as a target a process that is already running, use the @code{attach}
16303 command (@pxref{Attach, ,Debugging an Already-running Process}).
16305 @node Target Commands
16306 @section Commands for Managing Targets
16309 @item target @var{type} @var{parameters}
16310 Connects the @value{GDBN} host environment to a target machine or
16311 process. A target is typically a protocol for talking to debugging
16312 facilities. You use the argument @var{type} to specify the type or
16313 protocol of the target machine.
16315 Further @var{parameters} are interpreted by the target protocol, but
16316 typically include things like device names or host names to connect
16317 with, process numbers, and baud rates.
16319 The @code{target} command does not repeat if you press @key{RET} again
16320 after executing the command.
16322 @kindex help target
16324 Displays the names of all targets available. To display targets
16325 currently selected, use either @code{info target} or @code{info files}
16326 (@pxref{Files, ,Commands to Specify Files}).
16328 @item help target @var{name}
16329 Describe a particular target, including any parameters necessary to
16332 @kindex set gnutarget
16333 @item set gnutarget @var{args}
16334 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16335 knows whether it is reading an @dfn{executable},
16336 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16337 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16338 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16341 @emph{Warning:} To specify a file format with @code{set gnutarget},
16342 you must know the actual BFD name.
16346 @xref{Files, , Commands to Specify Files}.
16348 @kindex show gnutarget
16349 @item show gnutarget
16350 Use the @code{show gnutarget} command to display what file format
16351 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16352 @value{GDBN} will determine the file format for each file automatically,
16353 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16356 @cindex common targets
16357 Here are some common targets (available, or not, depending on the GDB
16362 @item target exec @var{program}
16363 @cindex executable file target
16364 An executable file. @samp{target exec @var{program}} is the same as
16365 @samp{exec-file @var{program}}.
16367 @item target core @var{filename}
16368 @cindex core dump file target
16369 A core dump file. @samp{target core @var{filename}} is the same as
16370 @samp{core-file @var{filename}}.
16372 @item target remote @var{medium}
16373 @cindex remote target
16374 A remote system connected to @value{GDBN} via a serial line or network
16375 connection. This command tells @value{GDBN} to use its own remote
16376 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16378 For example, if you have a board connected to @file{/dev/ttya} on the
16379 machine running @value{GDBN}, you could say:
16382 target remote /dev/ttya
16385 @code{target remote} supports the @code{load} command. This is only
16386 useful if you have some other way of getting the stub to the target
16387 system, and you can put it somewhere in memory where it won't get
16388 clobbered by the download.
16390 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16391 @cindex built-in simulator target
16392 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16400 works; however, you cannot assume that a specific memory map, device
16401 drivers, or even basic I/O is available, although some simulators do
16402 provide these. For info about any processor-specific simulator details,
16403 see the appropriate section in @ref{Embedded Processors, ,Embedded
16408 Some configurations may include these targets as well:
16412 @item target nrom @var{dev}
16413 @cindex NetROM ROM emulator target
16414 NetROM ROM emulator. This target only supports downloading.
16418 Different targets are available on different configurations of @value{GDBN};
16419 your configuration may have more or fewer targets.
16421 Many remote targets require you to download the executable's code once
16422 you've successfully established a connection. You may wish to control
16423 various aspects of this process.
16428 @kindex set hash@r{, for remote monitors}
16429 @cindex hash mark while downloading
16430 This command controls whether a hash mark @samp{#} is displayed while
16431 downloading a file to the remote monitor. If on, a hash mark is
16432 displayed after each S-record is successfully downloaded to the
16436 @kindex show hash@r{, for remote monitors}
16437 Show the current status of displaying the hash mark.
16439 @item set debug monitor
16440 @kindex set debug monitor
16441 @cindex display remote monitor communications
16442 Enable or disable display of communications messages between
16443 @value{GDBN} and the remote monitor.
16445 @item show debug monitor
16446 @kindex show debug monitor
16447 Show the current status of displaying communications between
16448 @value{GDBN} and the remote monitor.
16453 @kindex load @var{filename}
16454 @item load @var{filename}
16456 Depending on what remote debugging facilities are configured into
16457 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16458 is meant to make @var{filename} (an executable) available for debugging
16459 on the remote system---by downloading, or dynamic linking, for example.
16460 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16461 the @code{add-symbol-file} command.
16463 If your @value{GDBN} does not have a @code{load} command, attempting to
16464 execute it gets the error message ``@code{You can't do that when your
16465 target is @dots{}}''
16467 The file is loaded at whatever address is specified in the executable.
16468 For some object file formats, you can specify the load address when you
16469 link the program; for other formats, like a.out, the object file format
16470 specifies a fixed address.
16471 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16473 Depending on the remote side capabilities, @value{GDBN} may be able to
16474 load programs into flash memory.
16476 @code{load} does not repeat if you press @key{RET} again after using it.
16480 @section Choosing Target Byte Order
16482 @cindex choosing target byte order
16483 @cindex target byte order
16485 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16486 offer the ability to run either big-endian or little-endian byte
16487 orders. Usually the executable or symbol will include a bit to
16488 designate the endian-ness, and you will not need to worry about
16489 which to use. However, you may still find it useful to adjust
16490 @value{GDBN}'s idea of processor endian-ness manually.
16494 @item set endian big
16495 Instruct @value{GDBN} to assume the target is big-endian.
16497 @item set endian little
16498 Instruct @value{GDBN} to assume the target is little-endian.
16500 @item set endian auto
16501 Instruct @value{GDBN} to use the byte order associated with the
16505 Display @value{GDBN}'s current idea of the target byte order.
16509 Note that these commands merely adjust interpretation of symbolic
16510 data on the host, and that they have absolutely no effect on the
16514 @node Remote Debugging
16515 @chapter Debugging Remote Programs
16516 @cindex remote debugging
16518 If you are trying to debug a program running on a machine that cannot run
16519 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16520 For example, you might use remote debugging on an operating system kernel,
16521 or on a small system which does not have a general purpose operating system
16522 powerful enough to run a full-featured debugger.
16524 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16525 to make this work with particular debugging targets. In addition,
16526 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16527 but not specific to any particular target system) which you can use if you
16528 write the remote stubs---the code that runs on the remote system to
16529 communicate with @value{GDBN}.
16531 Other remote targets may be available in your
16532 configuration of @value{GDBN}; use @code{help target} to list them.
16535 * Connecting:: Connecting to a remote target
16536 * File Transfer:: Sending files to a remote system
16537 * Server:: Using the gdbserver program
16538 * Remote Configuration:: Remote configuration
16539 * Remote Stub:: Implementing a remote stub
16543 @section Connecting to a Remote Target
16545 On the @value{GDBN} host machine, you will need an unstripped copy of
16546 your program, since @value{GDBN} needs symbol and debugging information.
16547 Start up @value{GDBN} as usual, using the name of the local copy of your
16548 program as the first argument.
16550 @cindex @code{target remote}
16551 @value{GDBN} can communicate with the target over a serial line, or
16552 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16553 each case, @value{GDBN} uses the same protocol for debugging your
16554 program; only the medium carrying the debugging packets varies. The
16555 @code{target remote} command establishes a connection to the target.
16556 Its arguments indicate which medium to use:
16560 @item target remote @var{serial-device}
16561 @cindex serial line, @code{target remote}
16562 Use @var{serial-device} to communicate with the target. For example,
16563 to use a serial line connected to the device named @file{/dev/ttyb}:
16566 target remote /dev/ttyb
16569 If you're using a serial line, you may want to give @value{GDBN} the
16570 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16571 (@pxref{Remote Configuration, set remotebaud}) before the
16572 @code{target} command.
16574 @item target remote @code{@var{host}:@var{port}}
16575 @itemx target remote @code{tcp:@var{host}:@var{port}}
16576 @cindex @acronym{TCP} port, @code{target remote}
16577 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16578 The @var{host} may be either a host name or a numeric @acronym{IP}
16579 address; @var{port} must be a decimal number. The @var{host} could be
16580 the target machine itself, if it is directly connected to the net, or
16581 it might be a terminal server which in turn has a serial line to the
16584 For example, to connect to port 2828 on a terminal server named
16588 target remote manyfarms:2828
16591 If your remote target is actually running on the same machine as your
16592 debugger session (e.g.@: a simulator for your target running on the
16593 same host), you can omit the hostname. For example, to connect to
16594 port 1234 on your local machine:
16597 target remote :1234
16601 Note that the colon is still required here.
16603 @item target remote @code{udp:@var{host}:@var{port}}
16604 @cindex @acronym{UDP} port, @code{target remote}
16605 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16606 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16609 target remote udp:manyfarms:2828
16612 When using a @acronym{UDP} connection for remote debugging, you should
16613 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16614 can silently drop packets on busy or unreliable networks, which will
16615 cause havoc with your debugging session.
16617 @item target remote | @var{command}
16618 @cindex pipe, @code{target remote} to
16619 Run @var{command} in the background and communicate with it using a
16620 pipe. The @var{command} is a shell command, to be parsed and expanded
16621 by the system's command shell, @code{/bin/sh}; it should expect remote
16622 protocol packets on its standard input, and send replies on its
16623 standard output. You could use this to run a stand-alone simulator
16624 that speaks the remote debugging protocol, to make net connections
16625 using programs like @code{ssh}, or for other similar tricks.
16627 If @var{command} closes its standard output (perhaps by exiting),
16628 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16629 program has already exited, this will have no effect.)
16633 Once the connection has been established, you can use all the usual
16634 commands to examine and change data. The remote program is already
16635 running; you can use @kbd{step} and @kbd{continue}, and you do not
16636 need to use @kbd{run}.
16638 @cindex interrupting remote programs
16639 @cindex remote programs, interrupting
16640 Whenever @value{GDBN} is waiting for the remote program, if you type the
16641 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16642 program. This may or may not succeed, depending in part on the hardware
16643 and the serial drivers the remote system uses. If you type the
16644 interrupt character once again, @value{GDBN} displays this prompt:
16647 Interrupted while waiting for the program.
16648 Give up (and stop debugging it)? (y or n)
16651 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16652 (If you decide you want to try again later, you can use @samp{target
16653 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16654 goes back to waiting.
16657 @kindex detach (remote)
16659 When you have finished debugging the remote program, you can use the
16660 @code{detach} command to release it from @value{GDBN} control.
16661 Detaching from the target normally resumes its execution, but the results
16662 will depend on your particular remote stub. After the @code{detach}
16663 command, @value{GDBN} is free to connect to another target.
16667 The @code{disconnect} command behaves like @code{detach}, except that
16668 the target is generally not resumed. It will wait for @value{GDBN}
16669 (this instance or another one) to connect and continue debugging. After
16670 the @code{disconnect} command, @value{GDBN} is again free to connect to
16673 @cindex send command to remote monitor
16674 @cindex extend @value{GDBN} for remote targets
16675 @cindex add new commands for external monitor
16677 @item monitor @var{cmd}
16678 This command allows you to send arbitrary commands directly to the
16679 remote monitor. Since @value{GDBN} doesn't care about the commands it
16680 sends like this, this command is the way to extend @value{GDBN}---you
16681 can add new commands that only the external monitor will understand
16685 @node File Transfer
16686 @section Sending files to a remote system
16687 @cindex remote target, file transfer
16688 @cindex file transfer
16689 @cindex sending files to remote systems
16691 Some remote targets offer the ability to transfer files over the same
16692 connection used to communicate with @value{GDBN}. This is convenient
16693 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16694 running @code{gdbserver} over a network interface. For other targets,
16695 e.g.@: embedded devices with only a single serial port, this may be
16696 the only way to upload or download files.
16698 Not all remote targets support these commands.
16702 @item remote put @var{hostfile} @var{targetfile}
16703 Copy file @var{hostfile} from the host system (the machine running
16704 @value{GDBN}) to @var{targetfile} on the target system.
16707 @item remote get @var{targetfile} @var{hostfile}
16708 Copy file @var{targetfile} from the target system to @var{hostfile}
16709 on the host system.
16711 @kindex remote delete
16712 @item remote delete @var{targetfile}
16713 Delete @var{targetfile} from the target system.
16718 @section Using the @code{gdbserver} Program
16721 @cindex remote connection without stubs
16722 @code{gdbserver} is a control program for Unix-like systems, which
16723 allows you to connect your program with a remote @value{GDBN} via
16724 @code{target remote}---but without linking in the usual debugging stub.
16726 @code{gdbserver} is not a complete replacement for the debugging stubs,
16727 because it requires essentially the same operating-system facilities
16728 that @value{GDBN} itself does. In fact, a system that can run
16729 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16730 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16731 because it is a much smaller program than @value{GDBN} itself. It is
16732 also easier to port than all of @value{GDBN}, so you may be able to get
16733 started more quickly on a new system by using @code{gdbserver}.
16734 Finally, if you develop code for real-time systems, you may find that
16735 the tradeoffs involved in real-time operation make it more convenient to
16736 do as much development work as possible on another system, for example
16737 by cross-compiling. You can use @code{gdbserver} to make a similar
16738 choice for debugging.
16740 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16741 or a TCP connection, using the standard @value{GDBN} remote serial
16745 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16746 Do not run @code{gdbserver} connected to any public network; a
16747 @value{GDBN} connection to @code{gdbserver} provides access to the
16748 target system with the same privileges as the user running
16752 @subsection Running @code{gdbserver}
16753 @cindex arguments, to @code{gdbserver}
16754 @cindex @code{gdbserver}, command-line arguments
16756 Run @code{gdbserver} on the target system. You need a copy of the
16757 program you want to debug, including any libraries it requires.
16758 @code{gdbserver} does not need your program's symbol table, so you can
16759 strip the program if necessary to save space. @value{GDBN} on the host
16760 system does all the symbol handling.
16762 To use the server, you must tell it how to communicate with @value{GDBN};
16763 the name of your program; and the arguments for your program. The usual
16767 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16770 @var{comm} is either a device name (to use a serial line) or a TCP
16771 hostname and portnumber. For example, to debug Emacs with the argument
16772 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16776 target> gdbserver /dev/com1 emacs foo.txt
16779 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16782 To use a TCP connection instead of a serial line:
16785 target> gdbserver host:2345 emacs foo.txt
16788 The only difference from the previous example is the first argument,
16789 specifying that you are communicating with the host @value{GDBN} via
16790 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16791 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16792 (Currently, the @samp{host} part is ignored.) You can choose any number
16793 you want for the port number as long as it does not conflict with any
16794 TCP ports already in use on the target system (for example, @code{23} is
16795 reserved for @code{telnet}).@footnote{If you choose a port number that
16796 conflicts with another service, @code{gdbserver} prints an error message
16797 and exits.} You must use the same port number with the host @value{GDBN}
16798 @code{target remote} command.
16800 @subsubsection Attaching to a Running Program
16801 @cindex attach to a program, @code{gdbserver}
16802 @cindex @option{--attach}, @code{gdbserver} option
16804 On some targets, @code{gdbserver} can also attach to running programs.
16805 This is accomplished via the @code{--attach} argument. The syntax is:
16808 target> gdbserver --attach @var{comm} @var{pid}
16811 @var{pid} is the process ID of a currently running process. It isn't necessary
16812 to point @code{gdbserver} at a binary for the running process.
16815 You can debug processes by name instead of process ID if your target has the
16816 @code{pidof} utility:
16819 target> gdbserver --attach @var{comm} `pidof @var{program}`
16822 In case more than one copy of @var{program} is running, or @var{program}
16823 has multiple threads, most versions of @code{pidof} support the
16824 @code{-s} option to only return the first process ID.
16826 @subsubsection Multi-Process Mode for @code{gdbserver}
16827 @cindex @code{gdbserver}, multiple processes
16828 @cindex multiple processes with @code{gdbserver}
16830 When you connect to @code{gdbserver} using @code{target remote},
16831 @code{gdbserver} debugs the specified program only once. When the
16832 program exits, or you detach from it, @value{GDBN} closes the connection
16833 and @code{gdbserver} exits.
16835 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16836 enters multi-process mode. When the debugged program exits, or you
16837 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16838 though no program is running. The @code{run} and @code{attach}
16839 commands instruct @code{gdbserver} to run or attach to a new program.
16840 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16841 remote exec-file}) to select the program to run. Command line
16842 arguments are supported, except for wildcard expansion and I/O
16843 redirection (@pxref{Arguments}).
16845 @cindex @option{--multi}, @code{gdbserver} option
16846 To start @code{gdbserver} without supplying an initial command to run
16847 or process ID to attach, use the @option{--multi} command line option.
16848 Then you can connect using @kbd{target extended-remote} and start
16849 the program you want to debug.
16851 In multi-process mode @code{gdbserver} does not automatically exit unless you
16852 use the option @option{--once}. You can terminate it by using
16853 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16854 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16855 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16856 @option{--multi} option to @code{gdbserver} has no influence on that.
16858 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16860 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16862 @code{gdbserver} normally terminates after all of its debugged processes have
16863 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16864 extended-remote}, @code{gdbserver} stays running even with no processes left.
16865 @value{GDBN} normally terminates the spawned debugged process on its exit,
16866 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16867 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16868 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16869 stays running even in the @kbd{target remote} mode.
16871 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16872 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16873 completeness, at most one @value{GDBN} can be connected at a time.
16875 @cindex @option{--once}, @code{gdbserver} option
16876 By default, @code{gdbserver} keeps the listening TCP port open, so that
16877 additional connections are possible. However, if you start @code{gdbserver}
16878 with the @option{--once} option, it will stop listening for any further
16879 connection attempts after connecting to the first @value{GDBN} session. This
16880 means no further connections to @code{gdbserver} will be possible after the
16881 first one. It also means @code{gdbserver} will terminate after the first
16882 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16883 connections and even in the @kbd{target extended-remote} mode. The
16884 @option{--once} option allows reusing the same port number for connecting to
16885 multiple instances of @code{gdbserver} running on the same host, since each
16886 instance closes its port after the first connection.
16888 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16890 @cindex @option{--debug}, @code{gdbserver} option
16891 The @option{--debug} option tells @code{gdbserver} to display extra
16892 status information about the debugging process.
16893 @cindex @option{--remote-debug}, @code{gdbserver} option
16894 The @option{--remote-debug} option tells @code{gdbserver} to display
16895 remote protocol debug output. These options are intended for
16896 @code{gdbserver} development and for bug reports to the developers.
16898 @cindex @option{--wrapper}, @code{gdbserver} option
16899 The @option{--wrapper} option specifies a wrapper to launch programs
16900 for debugging. The option should be followed by the name of the
16901 wrapper, then any command-line arguments to pass to the wrapper, then
16902 @kbd{--} indicating the end of the wrapper arguments.
16904 @code{gdbserver} runs the specified wrapper program with a combined
16905 command line including the wrapper arguments, then the name of the
16906 program to debug, then any arguments to the program. The wrapper
16907 runs until it executes your program, and then @value{GDBN} gains control.
16909 You can use any program that eventually calls @code{execve} with
16910 its arguments as a wrapper. Several standard Unix utilities do
16911 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16912 with @code{exec "$@@"} will also work.
16914 For example, you can use @code{env} to pass an environment variable to
16915 the debugged program, without setting the variable in @code{gdbserver}'s
16919 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16922 @subsection Connecting to @code{gdbserver}
16924 Run @value{GDBN} on the host system.
16926 First make sure you have the necessary symbol files. Load symbols for
16927 your application using the @code{file} command before you connect. Use
16928 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16929 was compiled with the correct sysroot using @code{--with-sysroot}).
16931 The symbol file and target libraries must exactly match the executable
16932 and libraries on the target, with one exception: the files on the host
16933 system should not be stripped, even if the files on the target system
16934 are. Mismatched or missing files will lead to confusing results
16935 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16936 files may also prevent @code{gdbserver} from debugging multi-threaded
16939 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16940 For TCP connections, you must start up @code{gdbserver} prior to using
16941 the @code{target remote} command. Otherwise you may get an error whose
16942 text depends on the host system, but which usually looks something like
16943 @samp{Connection refused}. Don't use the @code{load}
16944 command in @value{GDBN} when using @code{gdbserver}, since the program is
16945 already on the target.
16947 @subsection Monitor Commands for @code{gdbserver}
16948 @cindex monitor commands, for @code{gdbserver}
16949 @anchor{Monitor Commands for gdbserver}
16951 During a @value{GDBN} session using @code{gdbserver}, you can use the
16952 @code{monitor} command to send special requests to @code{gdbserver}.
16953 Here are the available commands.
16957 List the available monitor commands.
16959 @item monitor set debug 0
16960 @itemx monitor set debug 1
16961 Disable or enable general debugging messages.
16963 @item monitor set remote-debug 0
16964 @itemx monitor set remote-debug 1
16965 Disable or enable specific debugging messages associated with the remote
16966 protocol (@pxref{Remote Protocol}).
16968 @item monitor set libthread-db-search-path [PATH]
16969 @cindex gdbserver, search path for @code{libthread_db}
16970 When this command is issued, @var{path} is a colon-separated list of
16971 directories to search for @code{libthread_db} (@pxref{Threads,,set
16972 libthread-db-search-path}). If you omit @var{path},
16973 @samp{libthread-db-search-path} will be reset to its default value.
16975 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16976 not supported in @code{gdbserver}.
16979 Tell gdbserver to exit immediately. This command should be followed by
16980 @code{disconnect} to close the debugging session. @code{gdbserver} will
16981 detach from any attached processes and kill any processes it created.
16982 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16983 of a multi-process mode debug session.
16987 @subsection Tracepoints support in @code{gdbserver}
16988 @cindex tracepoints support in @code{gdbserver}
16990 On some targets, @code{gdbserver} supports tracepoints, fast
16991 tracepoints and static tracepoints.
16993 For fast or static tracepoints to work, a special library called the
16994 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16995 This library is built and distributed as an integral part of
16996 @code{gdbserver}. In addition, support for static tracepoints
16997 requires building the in-process agent library with static tracepoints
16998 support. At present, the UST (LTTng Userspace Tracer,
16999 @url{http://lttng.org/ust}) tracing engine is supported. This support
17000 is automatically available if UST development headers are found in the
17001 standard include path when @code{gdbserver} is built, or if
17002 @code{gdbserver} was explicitly configured using @option{--with-ust}
17003 to point at such headers. You can explicitly disable the support
17004 using @option{--with-ust=no}.
17006 There are several ways to load the in-process agent in your program:
17009 @item Specifying it as dependency at link time
17011 You can link your program dynamically with the in-process agent
17012 library. On most systems, this is accomplished by adding
17013 @code{-linproctrace} to the link command.
17015 @item Using the system's preloading mechanisms
17017 You can force loading the in-process agent at startup time by using
17018 your system's support for preloading shared libraries. Many Unixes
17019 support the concept of preloading user defined libraries. In most
17020 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17021 in the environment. See also the description of @code{gdbserver}'s
17022 @option{--wrapper} command line option.
17024 @item Using @value{GDBN} to force loading the agent at run time
17026 On some systems, you can force the inferior to load a shared library,
17027 by calling a dynamic loader function in the inferior that takes care
17028 of dynamically looking up and loading a shared library. On most Unix
17029 systems, the function is @code{dlopen}. You'll use the @code{call}
17030 command for that. For example:
17033 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17036 Note that on most Unix systems, for the @code{dlopen} function to be
17037 available, the program needs to be linked with @code{-ldl}.
17040 On systems that have a userspace dynamic loader, like most Unix
17041 systems, when you connect to @code{gdbserver} using @code{target
17042 remote}, you'll find that the program is stopped at the dynamic
17043 loader's entry point, and no shared library has been loaded in the
17044 program's address space yet, including the in-process agent. In that
17045 case, before being able to use any of the fast or static tracepoints
17046 features, you need to let the loader run and load the shared
17047 libraries. The simplest way to do that is to run the program to the
17048 main procedure. E.g., if debugging a C or C@t{++} program, start
17049 @code{gdbserver} like so:
17052 $ gdbserver :9999 myprogram
17055 Start GDB and connect to @code{gdbserver} like so, and run to main:
17059 (@value{GDBP}) target remote myhost:9999
17060 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17061 (@value{GDBP}) b main
17062 (@value{GDBP}) continue
17065 The in-process tracing agent library should now be loaded into the
17066 process; you can confirm it with the @code{info sharedlibrary}
17067 command, which will list @file{libinproctrace.so} as loaded in the
17068 process. You are now ready to install fast tracepoints, list static
17069 tracepoint markers, probe static tracepoints markers, and start
17072 @node Remote Configuration
17073 @section Remote Configuration
17076 @kindex show remote
17077 This section documents the configuration options available when
17078 debugging remote programs. For the options related to the File I/O
17079 extensions of the remote protocol, see @ref{system,
17080 system-call-allowed}.
17083 @item set remoteaddresssize @var{bits}
17084 @cindex address size for remote targets
17085 @cindex bits in remote address
17086 Set the maximum size of address in a memory packet to the specified
17087 number of bits. @value{GDBN} will mask off the address bits above
17088 that number, when it passes addresses to the remote target. The
17089 default value is the number of bits in the target's address.
17091 @item show remoteaddresssize
17092 Show the current value of remote address size in bits.
17094 @item set remotebaud @var{n}
17095 @cindex baud rate for remote targets
17096 Set the baud rate for the remote serial I/O to @var{n} baud. The
17097 value is used to set the speed of the serial port used for debugging
17100 @item show remotebaud
17101 Show the current speed of the remote connection.
17103 @item set remotebreak
17104 @cindex interrupt remote programs
17105 @cindex BREAK signal instead of Ctrl-C
17106 @anchor{set remotebreak}
17107 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17108 when you type @kbd{Ctrl-c} to interrupt the program running
17109 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17110 character instead. The default is off, since most remote systems
17111 expect to see @samp{Ctrl-C} as the interrupt signal.
17113 @item show remotebreak
17114 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17115 interrupt the remote program.
17117 @item set remoteflow on
17118 @itemx set remoteflow off
17119 @kindex set remoteflow
17120 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17121 on the serial port used to communicate to the remote target.
17123 @item show remoteflow
17124 @kindex show remoteflow
17125 Show the current setting of hardware flow control.
17127 @item set remotelogbase @var{base}
17128 Set the base (a.k.a.@: radix) of logging serial protocol
17129 communications to @var{base}. Supported values of @var{base} are:
17130 @code{ascii}, @code{octal}, and @code{hex}. The default is
17133 @item show remotelogbase
17134 Show the current setting of the radix for logging remote serial
17137 @item set remotelogfile @var{file}
17138 @cindex record serial communications on file
17139 Record remote serial communications on the named @var{file}. The
17140 default is not to record at all.
17142 @item show remotelogfile.
17143 Show the current setting of the file name on which to record the
17144 serial communications.
17146 @item set remotetimeout @var{num}
17147 @cindex timeout for serial communications
17148 @cindex remote timeout
17149 Set the timeout limit to wait for the remote target to respond to
17150 @var{num} seconds. The default is 2 seconds.
17152 @item show remotetimeout
17153 Show the current number of seconds to wait for the remote target
17156 @cindex limit hardware breakpoints and watchpoints
17157 @cindex remote target, limit break- and watchpoints
17158 @anchor{set remote hardware-watchpoint-limit}
17159 @anchor{set remote hardware-breakpoint-limit}
17160 @item set remote hardware-watchpoint-limit @var{limit}
17161 @itemx set remote hardware-breakpoint-limit @var{limit}
17162 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17163 watchpoints. A limit of -1, the default, is treated as unlimited.
17165 @cindex limit hardware watchpoints length
17166 @cindex remote target, limit watchpoints length
17167 @anchor{set remote hardware-watchpoint-length-limit}
17168 @item set remote hardware-watchpoint-length-limit @var{limit}
17169 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17170 a remote hardware watchpoint. A limit of -1, the default, is treated
17173 @item show remote hardware-watchpoint-length-limit
17174 Show the current limit (in bytes) of the maximum length of
17175 a remote hardware watchpoint.
17177 @item set remote exec-file @var{filename}
17178 @itemx show remote exec-file
17179 @anchor{set remote exec-file}
17180 @cindex executable file, for remote target
17181 Select the file used for @code{run} with @code{target
17182 extended-remote}. This should be set to a filename valid on the
17183 target system. If it is not set, the target will use a default
17184 filename (e.g.@: the last program run).
17186 @item set remote interrupt-sequence
17187 @cindex interrupt remote programs
17188 @cindex select Ctrl-C, BREAK or BREAK-g
17189 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17190 @samp{BREAK-g} as the
17191 sequence to the remote target in order to interrupt the execution.
17192 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17193 is high level of serial line for some certain time.
17194 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17195 It is @code{BREAK} signal followed by character @code{g}.
17197 @item show interrupt-sequence
17198 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17199 is sent by @value{GDBN} to interrupt the remote program.
17200 @code{BREAK-g} is BREAK signal followed by @code{g} and
17201 also known as Magic SysRq g.
17203 @item set remote interrupt-on-connect
17204 @cindex send interrupt-sequence on start
17205 Specify whether interrupt-sequence is sent to remote target when
17206 @value{GDBN} connects to it. This is mostly needed when you debug
17207 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17208 which is known as Magic SysRq g in order to connect @value{GDBN}.
17210 @item show interrupt-on-connect
17211 Show whether interrupt-sequence is sent
17212 to remote target when @value{GDBN} connects to it.
17216 @item set tcp auto-retry on
17217 @cindex auto-retry, for remote TCP target
17218 Enable auto-retry for remote TCP connections. This is useful if the remote
17219 debugging agent is launched in parallel with @value{GDBN}; there is a race
17220 condition because the agent may not become ready to accept the connection
17221 before @value{GDBN} attempts to connect. When auto-retry is
17222 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17223 to establish the connection using the timeout specified by
17224 @code{set tcp connect-timeout}.
17226 @item set tcp auto-retry off
17227 Do not auto-retry failed TCP connections.
17229 @item show tcp auto-retry
17230 Show the current auto-retry setting.
17232 @item set tcp connect-timeout @var{seconds}
17233 @cindex connection timeout, for remote TCP target
17234 @cindex timeout, for remote target connection
17235 Set the timeout for establishing a TCP connection to the remote target to
17236 @var{seconds}. The timeout affects both polling to retry failed connections
17237 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17238 that are merely slow to complete, and represents an approximate cumulative
17241 @item show tcp connect-timeout
17242 Show the current connection timeout setting.
17245 @cindex remote packets, enabling and disabling
17246 The @value{GDBN} remote protocol autodetects the packets supported by
17247 your debugging stub. If you need to override the autodetection, you
17248 can use these commands to enable or disable individual packets. Each
17249 packet can be set to @samp{on} (the remote target supports this
17250 packet), @samp{off} (the remote target does not support this packet),
17251 or @samp{auto} (detect remote target support for this packet). They
17252 all default to @samp{auto}. For more information about each packet,
17253 see @ref{Remote Protocol}.
17255 During normal use, you should not have to use any of these commands.
17256 If you do, that may be a bug in your remote debugging stub, or a bug
17257 in @value{GDBN}. You may want to report the problem to the
17258 @value{GDBN} developers.
17260 For each packet @var{name}, the command to enable or disable the
17261 packet is @code{set remote @var{name}-packet}. The available settings
17264 @multitable @columnfractions 0.28 0.32 0.25
17267 @tab Related Features
17269 @item @code{fetch-register}
17271 @tab @code{info registers}
17273 @item @code{set-register}
17277 @item @code{binary-download}
17279 @tab @code{load}, @code{set}
17281 @item @code{read-aux-vector}
17282 @tab @code{qXfer:auxv:read}
17283 @tab @code{info auxv}
17285 @item @code{symbol-lookup}
17286 @tab @code{qSymbol}
17287 @tab Detecting multiple threads
17289 @item @code{attach}
17290 @tab @code{vAttach}
17293 @item @code{verbose-resume}
17295 @tab Stepping or resuming multiple threads
17301 @item @code{software-breakpoint}
17305 @item @code{hardware-breakpoint}
17309 @item @code{write-watchpoint}
17313 @item @code{read-watchpoint}
17317 @item @code{access-watchpoint}
17321 @item @code{target-features}
17322 @tab @code{qXfer:features:read}
17323 @tab @code{set architecture}
17325 @item @code{library-info}
17326 @tab @code{qXfer:libraries:read}
17327 @tab @code{info sharedlibrary}
17329 @item @code{memory-map}
17330 @tab @code{qXfer:memory-map:read}
17331 @tab @code{info mem}
17333 @item @code{read-sdata-object}
17334 @tab @code{qXfer:sdata:read}
17335 @tab @code{print $_sdata}
17337 @item @code{read-spu-object}
17338 @tab @code{qXfer:spu:read}
17339 @tab @code{info spu}
17341 @item @code{write-spu-object}
17342 @tab @code{qXfer:spu:write}
17343 @tab @code{info spu}
17345 @item @code{read-siginfo-object}
17346 @tab @code{qXfer:siginfo:read}
17347 @tab @code{print $_siginfo}
17349 @item @code{write-siginfo-object}
17350 @tab @code{qXfer:siginfo:write}
17351 @tab @code{set $_siginfo}
17353 @item @code{threads}
17354 @tab @code{qXfer:threads:read}
17355 @tab @code{info threads}
17357 @item @code{get-thread-local-@*storage-address}
17358 @tab @code{qGetTLSAddr}
17359 @tab Displaying @code{__thread} variables
17361 @item @code{get-thread-information-block-address}
17362 @tab @code{qGetTIBAddr}
17363 @tab Display MS-Windows Thread Information Block.
17365 @item @code{search-memory}
17366 @tab @code{qSearch:memory}
17369 @item @code{supported-packets}
17370 @tab @code{qSupported}
17371 @tab Remote communications parameters
17373 @item @code{pass-signals}
17374 @tab @code{QPassSignals}
17375 @tab @code{handle @var{signal}}
17377 @item @code{hostio-close-packet}
17378 @tab @code{vFile:close}
17379 @tab @code{remote get}, @code{remote put}
17381 @item @code{hostio-open-packet}
17382 @tab @code{vFile:open}
17383 @tab @code{remote get}, @code{remote put}
17385 @item @code{hostio-pread-packet}
17386 @tab @code{vFile:pread}
17387 @tab @code{remote get}, @code{remote put}
17389 @item @code{hostio-pwrite-packet}
17390 @tab @code{vFile:pwrite}
17391 @tab @code{remote get}, @code{remote put}
17393 @item @code{hostio-unlink-packet}
17394 @tab @code{vFile:unlink}
17395 @tab @code{remote delete}
17397 @item @code{noack-packet}
17398 @tab @code{QStartNoAckMode}
17399 @tab Packet acknowledgment
17401 @item @code{osdata}
17402 @tab @code{qXfer:osdata:read}
17403 @tab @code{info os}
17405 @item @code{query-attached}
17406 @tab @code{qAttached}
17407 @tab Querying remote process attach state.
17409 @item @code{traceframe-info}
17410 @tab @code{qXfer:traceframe-info:read}
17411 @tab Traceframe info
17413 @item @code{install-in-trace}
17414 @tab @code{InstallInTrace}
17415 @tab Install tracepoint in tracing
17417 @item @code{disable-randomization}
17418 @tab @code{QDisableRandomization}
17419 @tab @code{set disable-randomization}
17423 @section Implementing a Remote Stub
17425 @cindex debugging stub, example
17426 @cindex remote stub, example
17427 @cindex stub example, remote debugging
17428 The stub files provided with @value{GDBN} implement the target side of the
17429 communication protocol, and the @value{GDBN} side is implemented in the
17430 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17431 these subroutines to communicate, and ignore the details. (If you're
17432 implementing your own stub file, you can still ignore the details: start
17433 with one of the existing stub files. @file{sparc-stub.c} is the best
17434 organized, and therefore the easiest to read.)
17436 @cindex remote serial debugging, overview
17437 To debug a program running on another machine (the debugging
17438 @dfn{target} machine), you must first arrange for all the usual
17439 prerequisites for the program to run by itself. For example, for a C
17444 A startup routine to set up the C runtime environment; these usually
17445 have a name like @file{crt0}. The startup routine may be supplied by
17446 your hardware supplier, or you may have to write your own.
17449 A C subroutine library to support your program's
17450 subroutine calls, notably managing input and output.
17453 A way of getting your program to the other machine---for example, a
17454 download program. These are often supplied by the hardware
17455 manufacturer, but you may have to write your own from hardware
17459 The next step is to arrange for your program to use a serial port to
17460 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17461 machine). In general terms, the scheme looks like this:
17465 @value{GDBN} already understands how to use this protocol; when everything
17466 else is set up, you can simply use the @samp{target remote} command
17467 (@pxref{Targets,,Specifying a Debugging Target}).
17469 @item On the target,
17470 you must link with your program a few special-purpose subroutines that
17471 implement the @value{GDBN} remote serial protocol. The file containing these
17472 subroutines is called a @dfn{debugging stub}.
17474 On certain remote targets, you can use an auxiliary program
17475 @code{gdbserver} instead of linking a stub into your program.
17476 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17479 The debugging stub is specific to the architecture of the remote
17480 machine; for example, use @file{sparc-stub.c} to debug programs on
17483 @cindex remote serial stub list
17484 These working remote stubs are distributed with @value{GDBN}:
17489 @cindex @file{i386-stub.c}
17492 For Intel 386 and compatible architectures.
17495 @cindex @file{m68k-stub.c}
17496 @cindex Motorola 680x0
17498 For Motorola 680x0 architectures.
17501 @cindex @file{sh-stub.c}
17504 For Renesas SH architectures.
17507 @cindex @file{sparc-stub.c}
17509 For @sc{sparc} architectures.
17511 @item sparcl-stub.c
17512 @cindex @file{sparcl-stub.c}
17515 For Fujitsu @sc{sparclite} architectures.
17519 The @file{README} file in the @value{GDBN} distribution may list other
17520 recently added stubs.
17523 * Stub Contents:: What the stub can do for you
17524 * Bootstrapping:: What you must do for the stub
17525 * Debug Session:: Putting it all together
17528 @node Stub Contents
17529 @subsection What the Stub Can Do for You
17531 @cindex remote serial stub
17532 The debugging stub for your architecture supplies these three
17536 @item set_debug_traps
17537 @findex set_debug_traps
17538 @cindex remote serial stub, initialization
17539 This routine arranges for @code{handle_exception} to run when your
17540 program stops. You must call this subroutine explicitly near the
17541 beginning of your program.
17543 @item handle_exception
17544 @findex handle_exception
17545 @cindex remote serial stub, main routine
17546 This is the central workhorse, but your program never calls it
17547 explicitly---the setup code arranges for @code{handle_exception} to
17548 run when a trap is triggered.
17550 @code{handle_exception} takes control when your program stops during
17551 execution (for example, on a breakpoint), and mediates communications
17552 with @value{GDBN} on the host machine. This is where the communications
17553 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17554 representative on the target machine. It begins by sending summary
17555 information on the state of your program, then continues to execute,
17556 retrieving and transmitting any information @value{GDBN} needs, until you
17557 execute a @value{GDBN} command that makes your program resume; at that point,
17558 @code{handle_exception} returns control to your own code on the target
17562 @cindex @code{breakpoint} subroutine, remote
17563 Use this auxiliary subroutine to make your program contain a
17564 breakpoint. Depending on the particular situation, this may be the only
17565 way for @value{GDBN} to get control. For instance, if your target
17566 machine has some sort of interrupt button, you won't need to call this;
17567 pressing the interrupt button transfers control to
17568 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17569 simply receiving characters on the serial port may also trigger a trap;
17570 again, in that situation, you don't need to call @code{breakpoint} from
17571 your own program---simply running @samp{target remote} from the host
17572 @value{GDBN} session gets control.
17574 Call @code{breakpoint} if none of these is true, or if you simply want
17575 to make certain your program stops at a predetermined point for the
17576 start of your debugging session.
17579 @node Bootstrapping
17580 @subsection What You Must Do for the Stub
17582 @cindex remote stub, support routines
17583 The debugging stubs that come with @value{GDBN} are set up for a particular
17584 chip architecture, but they have no information about the rest of your
17585 debugging target machine.
17587 First of all you need to tell the stub how to communicate with the
17591 @item int getDebugChar()
17592 @findex getDebugChar
17593 Write this subroutine to read a single character from the serial port.
17594 It may be identical to @code{getchar} for your target system; a
17595 different name is used to allow you to distinguish the two if you wish.
17597 @item void putDebugChar(int)
17598 @findex putDebugChar
17599 Write this subroutine to write a single character to the serial port.
17600 It may be identical to @code{putchar} for your target system; a
17601 different name is used to allow you to distinguish the two if you wish.
17604 @cindex control C, and remote debugging
17605 @cindex interrupting remote targets
17606 If you want @value{GDBN} to be able to stop your program while it is
17607 running, you need to use an interrupt-driven serial driver, and arrange
17608 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17609 character). That is the character which @value{GDBN} uses to tell the
17610 remote system to stop.
17612 Getting the debugging target to return the proper status to @value{GDBN}
17613 probably requires changes to the standard stub; one quick and dirty way
17614 is to just execute a breakpoint instruction (the ``dirty'' part is that
17615 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17617 Other routines you need to supply are:
17620 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17621 @findex exceptionHandler
17622 Write this function to install @var{exception_address} in the exception
17623 handling tables. You need to do this because the stub does not have any
17624 way of knowing what the exception handling tables on your target system
17625 are like (for example, the processor's table might be in @sc{rom},
17626 containing entries which point to a table in @sc{ram}).
17627 @var{exception_number} is the exception number which should be changed;
17628 its meaning is architecture-dependent (for example, different numbers
17629 might represent divide by zero, misaligned access, etc). When this
17630 exception occurs, control should be transferred directly to
17631 @var{exception_address}, and the processor state (stack, registers,
17632 and so on) should be just as it is when a processor exception occurs. So if
17633 you want to use a jump instruction to reach @var{exception_address}, it
17634 should be a simple jump, not a jump to subroutine.
17636 For the 386, @var{exception_address} should be installed as an interrupt
17637 gate so that interrupts are masked while the handler runs. The gate
17638 should be at privilege level 0 (the most privileged level). The
17639 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17640 help from @code{exceptionHandler}.
17642 @item void flush_i_cache()
17643 @findex flush_i_cache
17644 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17645 instruction cache, if any, on your target machine. If there is no
17646 instruction cache, this subroutine may be a no-op.
17648 On target machines that have instruction caches, @value{GDBN} requires this
17649 function to make certain that the state of your program is stable.
17653 You must also make sure this library routine is available:
17656 @item void *memset(void *, int, int)
17658 This is the standard library function @code{memset} that sets an area of
17659 memory to a known value. If you have one of the free versions of
17660 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17661 either obtain it from your hardware manufacturer, or write your own.
17664 If you do not use the GNU C compiler, you may need other standard
17665 library subroutines as well; this varies from one stub to another,
17666 but in general the stubs are likely to use any of the common library
17667 subroutines which @code{@value{NGCC}} generates as inline code.
17670 @node Debug Session
17671 @subsection Putting it All Together
17673 @cindex remote serial debugging summary
17674 In summary, when your program is ready to debug, you must follow these
17679 Make sure you have defined the supporting low-level routines
17680 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17682 @code{getDebugChar}, @code{putDebugChar},
17683 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17687 Insert these lines near the top of your program:
17695 For the 680x0 stub only, you need to provide a variable called
17696 @code{exceptionHook}. Normally you just use:
17699 void (*exceptionHook)() = 0;
17703 but if before calling @code{set_debug_traps}, you set it to point to a
17704 function in your program, that function is called when
17705 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17706 error). The function indicated by @code{exceptionHook} is called with
17707 one parameter: an @code{int} which is the exception number.
17710 Compile and link together: your program, the @value{GDBN} debugging stub for
17711 your target architecture, and the supporting subroutines.
17714 Make sure you have a serial connection between your target machine and
17715 the @value{GDBN} host, and identify the serial port on the host.
17718 @c The "remote" target now provides a `load' command, so we should
17719 @c document that. FIXME.
17720 Download your program to your target machine (or get it there by
17721 whatever means the manufacturer provides), and start it.
17724 Start @value{GDBN} on the host, and connect to the target
17725 (@pxref{Connecting,,Connecting to a Remote Target}).
17729 @node Configurations
17730 @chapter Configuration-Specific Information
17732 While nearly all @value{GDBN} commands are available for all native and
17733 cross versions of the debugger, there are some exceptions. This chapter
17734 describes things that are only available in certain configurations.
17736 There are three major categories of configurations: native
17737 configurations, where the host and target are the same, embedded
17738 operating system configurations, which are usually the same for several
17739 different processor architectures, and bare embedded processors, which
17740 are quite different from each other.
17745 * Embedded Processors::
17752 This section describes details specific to particular native
17757 * BSD libkvm Interface:: Debugging BSD kernel memory images
17758 * SVR4 Process Information:: SVR4 process information
17759 * DJGPP Native:: Features specific to the DJGPP port
17760 * Cygwin Native:: Features specific to the Cygwin port
17761 * Hurd Native:: Features specific to @sc{gnu} Hurd
17762 * Neutrino:: Features specific to QNX Neutrino
17763 * Darwin:: Features specific to Darwin
17769 On HP-UX systems, if you refer to a function or variable name that
17770 begins with a dollar sign, @value{GDBN} searches for a user or system
17771 name first, before it searches for a convenience variable.
17774 @node BSD libkvm Interface
17775 @subsection BSD libkvm Interface
17778 @cindex kernel memory image
17779 @cindex kernel crash dump
17781 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17782 interface that provides a uniform interface for accessing kernel virtual
17783 memory images, including live systems and crash dumps. @value{GDBN}
17784 uses this interface to allow you to debug live kernels and kernel crash
17785 dumps on many native BSD configurations. This is implemented as a
17786 special @code{kvm} debugging target. For debugging a live system, load
17787 the currently running kernel into @value{GDBN} and connect to the
17791 (@value{GDBP}) @b{target kvm}
17794 For debugging crash dumps, provide the file name of the crash dump as an
17798 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17801 Once connected to the @code{kvm} target, the following commands are
17807 Set current context from the @dfn{Process Control Block} (PCB) address.
17810 Set current context from proc address. This command isn't available on
17811 modern FreeBSD systems.
17814 @node SVR4 Process Information
17815 @subsection SVR4 Process Information
17817 @cindex examine process image
17818 @cindex process info via @file{/proc}
17820 Many versions of SVR4 and compatible systems provide a facility called
17821 @samp{/proc} that can be used to examine the image of a running
17822 process using file-system subroutines. If @value{GDBN} is configured
17823 for an operating system with this facility, the command @code{info
17824 proc} is available to report information about the process running
17825 your program, or about any process running on your system. @code{info
17826 proc} works only on SVR4 systems that include the @code{procfs} code.
17827 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17828 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17834 @itemx info proc @var{process-id}
17835 Summarize available information about any running process. If a
17836 process ID is specified by @var{process-id}, display information about
17837 that process; otherwise display information about the program being
17838 debugged. The summary includes the debugged process ID, the command
17839 line used to invoke it, its current working directory, and its
17840 executable file's absolute file name.
17842 On some systems, @var{process-id} can be of the form
17843 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17844 within a process. If the optional @var{pid} part is missing, it means
17845 a thread from the process being debugged (the leading @samp{/} still
17846 needs to be present, or else @value{GDBN} will interpret the number as
17847 a process ID rather than a thread ID).
17849 @item info proc mappings
17850 @cindex memory address space mappings
17851 Report the memory address space ranges accessible in the program, with
17852 information on whether the process has read, write, or execute access
17853 rights to each range. On @sc{gnu}/Linux systems, each memory range
17854 includes the object file which is mapped to that range, instead of the
17855 memory access rights to that range.
17857 @item info proc stat
17858 @itemx info proc status
17859 @cindex process detailed status information
17860 These subcommands are specific to @sc{gnu}/Linux systems. They show
17861 the process-related information, including the user ID and group ID;
17862 how many threads are there in the process; its virtual memory usage;
17863 the signals that are pending, blocked, and ignored; its TTY; its
17864 consumption of system and user time; its stack size; its @samp{nice}
17865 value; etc. For more information, see the @samp{proc} man page
17866 (type @kbd{man 5 proc} from your shell prompt).
17868 @item info proc all
17869 Show all the information about the process described under all of the
17870 above @code{info proc} subcommands.
17873 @comment These sub-options of 'info proc' were not included when
17874 @comment procfs.c was re-written. Keep their descriptions around
17875 @comment against the day when someone finds the time to put them back in.
17876 @kindex info proc times
17877 @item info proc times
17878 Starting time, user CPU time, and system CPU time for your program and
17881 @kindex info proc id
17883 Report on the process IDs related to your program: its own process ID,
17884 the ID of its parent, the process group ID, and the session ID.
17887 @item set procfs-trace
17888 @kindex set procfs-trace
17889 @cindex @code{procfs} API calls
17890 This command enables and disables tracing of @code{procfs} API calls.
17892 @item show procfs-trace
17893 @kindex show procfs-trace
17894 Show the current state of @code{procfs} API call tracing.
17896 @item set procfs-file @var{file}
17897 @kindex set procfs-file
17898 Tell @value{GDBN} to write @code{procfs} API trace to the named
17899 @var{file}. @value{GDBN} appends the trace info to the previous
17900 contents of the file. The default is to display the trace on the
17903 @item show procfs-file
17904 @kindex show procfs-file
17905 Show the file to which @code{procfs} API trace is written.
17907 @item proc-trace-entry
17908 @itemx proc-trace-exit
17909 @itemx proc-untrace-entry
17910 @itemx proc-untrace-exit
17911 @kindex proc-trace-entry
17912 @kindex proc-trace-exit
17913 @kindex proc-untrace-entry
17914 @kindex proc-untrace-exit
17915 These commands enable and disable tracing of entries into and exits
17916 from the @code{syscall} interface.
17919 @kindex info pidlist
17920 @cindex process list, QNX Neutrino
17921 For QNX Neutrino only, this command displays the list of all the
17922 processes and all the threads within each process.
17925 @kindex info meminfo
17926 @cindex mapinfo list, QNX Neutrino
17927 For QNX Neutrino only, this command displays the list of all mapinfos.
17931 @subsection Features for Debugging @sc{djgpp} Programs
17932 @cindex @sc{djgpp} debugging
17933 @cindex native @sc{djgpp} debugging
17934 @cindex MS-DOS-specific commands
17937 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17938 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17939 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17940 top of real-mode DOS systems and their emulations.
17942 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17943 defines a few commands specific to the @sc{djgpp} port. This
17944 subsection describes those commands.
17949 This is a prefix of @sc{djgpp}-specific commands which print
17950 information about the target system and important OS structures.
17953 @cindex MS-DOS system info
17954 @cindex free memory information (MS-DOS)
17955 @item info dos sysinfo
17956 This command displays assorted information about the underlying
17957 platform: the CPU type and features, the OS version and flavor, the
17958 DPMI version, and the available conventional and DPMI memory.
17963 @cindex segment descriptor tables
17964 @cindex descriptor tables display
17966 @itemx info dos ldt
17967 @itemx info dos idt
17968 These 3 commands display entries from, respectively, Global, Local,
17969 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17970 tables are data structures which store a descriptor for each segment
17971 that is currently in use. The segment's selector is an index into a
17972 descriptor table; the table entry for that index holds the
17973 descriptor's base address and limit, and its attributes and access
17976 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17977 segment (used for both data and the stack), and a DOS segment (which
17978 allows access to DOS/BIOS data structures and absolute addresses in
17979 conventional memory). However, the DPMI host will usually define
17980 additional segments in order to support the DPMI environment.
17982 @cindex garbled pointers
17983 These commands allow to display entries from the descriptor tables.
17984 Without an argument, all entries from the specified table are
17985 displayed. An argument, which should be an integer expression, means
17986 display a single entry whose index is given by the argument. For
17987 example, here's a convenient way to display information about the
17988 debugged program's data segment:
17991 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17992 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17996 This comes in handy when you want to see whether a pointer is outside
17997 the data segment's limit (i.e.@: @dfn{garbled}).
17999 @cindex page tables display (MS-DOS)
18001 @itemx info dos pte
18002 These two commands display entries from, respectively, the Page
18003 Directory and the Page Tables. Page Directories and Page Tables are
18004 data structures which control how virtual memory addresses are mapped
18005 into physical addresses. A Page Table includes an entry for every
18006 page of memory that is mapped into the program's address space; there
18007 may be several Page Tables, each one holding up to 4096 entries. A
18008 Page Directory has up to 4096 entries, one each for every Page Table
18009 that is currently in use.
18011 Without an argument, @kbd{info dos pde} displays the entire Page
18012 Directory, and @kbd{info dos pte} displays all the entries in all of
18013 the Page Tables. An argument, an integer expression, given to the
18014 @kbd{info dos pde} command means display only that entry from the Page
18015 Directory table. An argument given to the @kbd{info dos pte} command
18016 means display entries from a single Page Table, the one pointed to by
18017 the specified entry in the Page Directory.
18019 @cindex direct memory access (DMA) on MS-DOS
18020 These commands are useful when your program uses @dfn{DMA} (Direct
18021 Memory Access), which needs physical addresses to program the DMA
18024 These commands are supported only with some DPMI servers.
18026 @cindex physical address from linear address
18027 @item info dos address-pte @var{addr}
18028 This command displays the Page Table entry for a specified linear
18029 address. The argument @var{addr} is a linear address which should
18030 already have the appropriate segment's base address added to it,
18031 because this command accepts addresses which may belong to @emph{any}
18032 segment. For example, here's how to display the Page Table entry for
18033 the page where a variable @code{i} is stored:
18036 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18037 @exdent @code{Page Table entry for address 0x11a00d30:}
18038 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18042 This says that @code{i} is stored at offset @code{0xd30} from the page
18043 whose physical base address is @code{0x02698000}, and shows all the
18044 attributes of that page.
18046 Note that you must cast the addresses of variables to a @code{char *},
18047 since otherwise the value of @code{__djgpp_base_address}, the base
18048 address of all variables and functions in a @sc{djgpp} program, will
18049 be added using the rules of C pointer arithmetics: if @code{i} is
18050 declared an @code{int}, @value{GDBN} will add 4 times the value of
18051 @code{__djgpp_base_address} to the address of @code{i}.
18053 Here's another example, it displays the Page Table entry for the
18057 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18058 @exdent @code{Page Table entry for address 0x29110:}
18059 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18063 (The @code{+ 3} offset is because the transfer buffer's address is the
18064 3rd member of the @code{_go32_info_block} structure.) The output
18065 clearly shows that this DPMI server maps the addresses in conventional
18066 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18067 linear (@code{0x29110}) addresses are identical.
18069 This command is supported only with some DPMI servers.
18072 @cindex DOS serial data link, remote debugging
18073 In addition to native debugging, the DJGPP port supports remote
18074 debugging via a serial data link. The following commands are specific
18075 to remote serial debugging in the DJGPP port of @value{GDBN}.
18078 @kindex set com1base
18079 @kindex set com1irq
18080 @kindex set com2base
18081 @kindex set com2irq
18082 @kindex set com3base
18083 @kindex set com3irq
18084 @kindex set com4base
18085 @kindex set com4irq
18086 @item set com1base @var{addr}
18087 This command sets the base I/O port address of the @file{COM1} serial
18090 @item set com1irq @var{irq}
18091 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18092 for the @file{COM1} serial port.
18094 There are similar commands @samp{set com2base}, @samp{set com3irq},
18095 etc.@: for setting the port address and the @code{IRQ} lines for the
18098 @kindex show com1base
18099 @kindex show com1irq
18100 @kindex show com2base
18101 @kindex show com2irq
18102 @kindex show com3base
18103 @kindex show com3irq
18104 @kindex show com4base
18105 @kindex show com4irq
18106 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18107 display the current settings of the base address and the @code{IRQ}
18108 lines used by the COM ports.
18111 @kindex info serial
18112 @cindex DOS serial port status
18113 This command prints the status of the 4 DOS serial ports. For each
18114 port, it prints whether it's active or not, its I/O base address and
18115 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18116 counts of various errors encountered so far.
18120 @node Cygwin Native
18121 @subsection Features for Debugging MS Windows PE Executables
18122 @cindex MS Windows debugging
18123 @cindex native Cygwin debugging
18124 @cindex Cygwin-specific commands
18126 @value{GDBN} supports native debugging of MS Windows programs, including
18127 DLLs with and without symbolic debugging information.
18129 @cindex Ctrl-BREAK, MS-Windows
18130 @cindex interrupt debuggee on MS-Windows
18131 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18132 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18133 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18134 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18135 sequence, which can be used to interrupt the debuggee even if it
18138 There are various additional Cygwin-specific commands, described in
18139 this section. Working with DLLs that have no debugging symbols is
18140 described in @ref{Non-debug DLL Symbols}.
18145 This is a prefix of MS Windows-specific commands which print
18146 information about the target system and important OS structures.
18148 @item info w32 selector
18149 This command displays information returned by
18150 the Win32 API @code{GetThreadSelectorEntry} function.
18151 It takes an optional argument that is evaluated to
18152 a long value to give the information about this given selector.
18153 Without argument, this command displays information
18154 about the six segment registers.
18156 @item info w32 thread-information-block
18157 This command displays thread specific information stored in the
18158 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18159 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18163 This is a Cygwin-specific alias of @code{info shared}.
18165 @kindex dll-symbols
18167 This command loads symbols from a dll similarly to
18168 add-sym command but without the need to specify a base address.
18170 @kindex set cygwin-exceptions
18171 @cindex debugging the Cygwin DLL
18172 @cindex Cygwin DLL, debugging
18173 @item set cygwin-exceptions @var{mode}
18174 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18175 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18176 @value{GDBN} will delay recognition of exceptions, and may ignore some
18177 exceptions which seem to be caused by internal Cygwin DLL
18178 ``bookkeeping''. This option is meant primarily for debugging the
18179 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18180 @value{GDBN} users with false @code{SIGSEGV} signals.
18182 @kindex show cygwin-exceptions
18183 @item show cygwin-exceptions
18184 Displays whether @value{GDBN} will break on exceptions that happen
18185 inside the Cygwin DLL itself.
18187 @kindex set new-console
18188 @item set new-console @var{mode}
18189 If @var{mode} is @code{on} the debuggee will
18190 be started in a new console on next start.
18191 If @var{mode} is @code{off}, the debuggee will
18192 be started in the same console as the debugger.
18194 @kindex show new-console
18195 @item show new-console
18196 Displays whether a new console is used
18197 when the debuggee is started.
18199 @kindex set new-group
18200 @item set new-group @var{mode}
18201 This boolean value controls whether the debuggee should
18202 start a new group or stay in the same group as the debugger.
18203 This affects the way the Windows OS handles
18206 @kindex show new-group
18207 @item show new-group
18208 Displays current value of new-group boolean.
18210 @kindex set debugevents
18211 @item set debugevents
18212 This boolean value adds debug output concerning kernel events related
18213 to the debuggee seen by the debugger. This includes events that
18214 signal thread and process creation and exit, DLL loading and
18215 unloading, console interrupts, and debugging messages produced by the
18216 Windows @code{OutputDebugString} API call.
18218 @kindex set debugexec
18219 @item set debugexec
18220 This boolean value adds debug output concerning execute events
18221 (such as resume thread) seen by the debugger.
18223 @kindex set debugexceptions
18224 @item set debugexceptions
18225 This boolean value adds debug output concerning exceptions in the
18226 debuggee seen by the debugger.
18228 @kindex set debugmemory
18229 @item set debugmemory
18230 This boolean value adds debug output concerning debuggee memory reads
18231 and writes by the debugger.
18235 This boolean values specifies whether the debuggee is called
18236 via a shell or directly (default value is on).
18240 Displays if the debuggee will be started with a shell.
18245 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18248 @node Non-debug DLL Symbols
18249 @subsubsection Support for DLLs without Debugging Symbols
18250 @cindex DLLs with no debugging symbols
18251 @cindex Minimal symbols and DLLs
18253 Very often on windows, some of the DLLs that your program relies on do
18254 not include symbolic debugging information (for example,
18255 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18256 symbols in a DLL, it relies on the minimal amount of symbolic
18257 information contained in the DLL's export table. This section
18258 describes working with such symbols, known internally to @value{GDBN} as
18259 ``minimal symbols''.
18261 Note that before the debugged program has started execution, no DLLs
18262 will have been loaded. The easiest way around this problem is simply to
18263 start the program --- either by setting a breakpoint or letting the
18264 program run once to completion. It is also possible to force
18265 @value{GDBN} to load a particular DLL before starting the executable ---
18266 see the shared library information in @ref{Files}, or the
18267 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18268 explicitly loading symbols from a DLL with no debugging information will
18269 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18270 which may adversely affect symbol lookup performance.
18272 @subsubsection DLL Name Prefixes
18274 In keeping with the naming conventions used by the Microsoft debugging
18275 tools, DLL export symbols are made available with a prefix based on the
18276 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18277 also entered into the symbol table, so @code{CreateFileA} is often
18278 sufficient. In some cases there will be name clashes within a program
18279 (particularly if the executable itself includes full debugging symbols)
18280 necessitating the use of the fully qualified name when referring to the
18281 contents of the DLL. Use single-quotes around the name to avoid the
18282 exclamation mark (``!'') being interpreted as a language operator.
18284 Note that the internal name of the DLL may be all upper-case, even
18285 though the file name of the DLL is lower-case, or vice-versa. Since
18286 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18287 some confusion. If in doubt, try the @code{info functions} and
18288 @code{info variables} commands or even @code{maint print msymbols}
18289 (@pxref{Symbols}). Here's an example:
18292 (@value{GDBP}) info function CreateFileA
18293 All functions matching regular expression "CreateFileA":
18295 Non-debugging symbols:
18296 0x77e885f4 CreateFileA
18297 0x77e885f4 KERNEL32!CreateFileA
18301 (@value{GDBP}) info function !
18302 All functions matching regular expression "!":
18304 Non-debugging symbols:
18305 0x6100114c cygwin1!__assert
18306 0x61004034 cygwin1!_dll_crt0@@0
18307 0x61004240 cygwin1!dll_crt0(per_process *)
18311 @subsubsection Working with Minimal Symbols
18313 Symbols extracted from a DLL's export table do not contain very much
18314 type information. All that @value{GDBN} can do is guess whether a symbol
18315 refers to a function or variable depending on the linker section that
18316 contains the symbol. Also note that the actual contents of the memory
18317 contained in a DLL are not available unless the program is running. This
18318 means that you cannot examine the contents of a variable or disassemble
18319 a function within a DLL without a running program.
18321 Variables are generally treated as pointers and dereferenced
18322 automatically. For this reason, it is often necessary to prefix a
18323 variable name with the address-of operator (``&'') and provide explicit
18324 type information in the command. Here's an example of the type of
18328 (@value{GDBP}) print 'cygwin1!__argv'
18333 (@value{GDBP}) x 'cygwin1!__argv'
18334 0x10021610: "\230y\""
18337 And two possible solutions:
18340 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18341 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18345 (@value{GDBP}) x/2x &'cygwin1!__argv'
18346 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18347 (@value{GDBP}) x/x 0x10021608
18348 0x10021608: 0x0022fd98
18349 (@value{GDBP}) x/s 0x0022fd98
18350 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18353 Setting a break point within a DLL is possible even before the program
18354 starts execution. However, under these circumstances, @value{GDBN} can't
18355 examine the initial instructions of the function in order to skip the
18356 function's frame set-up code. You can work around this by using ``*&''
18357 to set the breakpoint at a raw memory address:
18360 (@value{GDBP}) break *&'python22!PyOS_Readline'
18361 Breakpoint 1 at 0x1e04eff0
18364 The author of these extensions is not entirely convinced that setting a
18365 break point within a shared DLL like @file{kernel32.dll} is completely
18369 @subsection Commands Specific to @sc{gnu} Hurd Systems
18370 @cindex @sc{gnu} Hurd debugging
18372 This subsection describes @value{GDBN} commands specific to the
18373 @sc{gnu} Hurd native debugging.
18378 @kindex set signals@r{, Hurd command}
18379 @kindex set sigs@r{, Hurd command}
18380 This command toggles the state of inferior signal interception by
18381 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18382 affected by this command. @code{sigs} is a shorthand alias for
18387 @kindex show signals@r{, Hurd command}
18388 @kindex show sigs@r{, Hurd command}
18389 Show the current state of intercepting inferior's signals.
18391 @item set signal-thread
18392 @itemx set sigthread
18393 @kindex set signal-thread
18394 @kindex set sigthread
18395 This command tells @value{GDBN} which thread is the @code{libc} signal
18396 thread. That thread is run when a signal is delivered to a running
18397 process. @code{set sigthread} is the shorthand alias of @code{set
18400 @item show signal-thread
18401 @itemx show sigthread
18402 @kindex show signal-thread
18403 @kindex show sigthread
18404 These two commands show which thread will run when the inferior is
18405 delivered a signal.
18408 @kindex set stopped@r{, Hurd command}
18409 This commands tells @value{GDBN} that the inferior process is stopped,
18410 as with the @code{SIGSTOP} signal. The stopped process can be
18411 continued by delivering a signal to it.
18414 @kindex show stopped@r{, Hurd command}
18415 This command shows whether @value{GDBN} thinks the debuggee is
18418 @item set exceptions
18419 @kindex set exceptions@r{, Hurd command}
18420 Use this command to turn off trapping of exceptions in the inferior.
18421 When exception trapping is off, neither breakpoints nor
18422 single-stepping will work. To restore the default, set exception
18425 @item show exceptions
18426 @kindex show exceptions@r{, Hurd command}
18427 Show the current state of trapping exceptions in the inferior.
18429 @item set task pause
18430 @kindex set task@r{, Hurd commands}
18431 @cindex task attributes (@sc{gnu} Hurd)
18432 @cindex pause current task (@sc{gnu} Hurd)
18433 This command toggles task suspension when @value{GDBN} has control.
18434 Setting it to on takes effect immediately, and the task is suspended
18435 whenever @value{GDBN} gets control. Setting it to off will take
18436 effect the next time the inferior is continued. If this option is set
18437 to off, you can use @code{set thread default pause on} or @code{set
18438 thread pause on} (see below) to pause individual threads.
18440 @item show task pause
18441 @kindex show task@r{, Hurd commands}
18442 Show the current state of task suspension.
18444 @item set task detach-suspend-count
18445 @cindex task suspend count
18446 @cindex detach from task, @sc{gnu} Hurd
18447 This command sets the suspend count the task will be left with when
18448 @value{GDBN} detaches from it.
18450 @item show task detach-suspend-count
18451 Show the suspend count the task will be left with when detaching.
18453 @item set task exception-port
18454 @itemx set task excp
18455 @cindex task exception port, @sc{gnu} Hurd
18456 This command sets the task exception port to which @value{GDBN} will
18457 forward exceptions. The argument should be the value of the @dfn{send
18458 rights} of the task. @code{set task excp} is a shorthand alias.
18460 @item set noninvasive
18461 @cindex noninvasive task options
18462 This command switches @value{GDBN} to a mode that is the least
18463 invasive as far as interfering with the inferior is concerned. This
18464 is the same as using @code{set task pause}, @code{set exceptions}, and
18465 @code{set signals} to values opposite to the defaults.
18467 @item info send-rights
18468 @itemx info receive-rights
18469 @itemx info port-rights
18470 @itemx info port-sets
18471 @itemx info dead-names
18474 @cindex send rights, @sc{gnu} Hurd
18475 @cindex receive rights, @sc{gnu} Hurd
18476 @cindex port rights, @sc{gnu} Hurd
18477 @cindex port sets, @sc{gnu} Hurd
18478 @cindex dead names, @sc{gnu} Hurd
18479 These commands display information about, respectively, send rights,
18480 receive rights, port rights, port sets, and dead names of a task.
18481 There are also shorthand aliases: @code{info ports} for @code{info
18482 port-rights} and @code{info psets} for @code{info port-sets}.
18484 @item set thread pause
18485 @kindex set thread@r{, Hurd command}
18486 @cindex thread properties, @sc{gnu} Hurd
18487 @cindex pause current thread (@sc{gnu} Hurd)
18488 This command toggles current thread suspension when @value{GDBN} has
18489 control. Setting it to on takes effect immediately, and the current
18490 thread is suspended whenever @value{GDBN} gets control. Setting it to
18491 off will take effect the next time the inferior is continued.
18492 Normally, this command has no effect, since when @value{GDBN} has
18493 control, the whole task is suspended. However, if you used @code{set
18494 task pause off} (see above), this command comes in handy to suspend
18495 only the current thread.
18497 @item show thread pause
18498 @kindex show thread@r{, Hurd command}
18499 This command shows the state of current thread suspension.
18501 @item set thread run
18502 This command sets whether the current thread is allowed to run.
18504 @item show thread run
18505 Show whether the current thread is allowed to run.
18507 @item set thread detach-suspend-count
18508 @cindex thread suspend count, @sc{gnu} Hurd
18509 @cindex detach from thread, @sc{gnu} Hurd
18510 This command sets the suspend count @value{GDBN} will leave on a
18511 thread when detaching. This number is relative to the suspend count
18512 found by @value{GDBN} when it notices the thread; use @code{set thread
18513 takeover-suspend-count} to force it to an absolute value.
18515 @item show thread detach-suspend-count
18516 Show the suspend count @value{GDBN} will leave on the thread when
18519 @item set thread exception-port
18520 @itemx set thread excp
18521 Set the thread exception port to which to forward exceptions. This
18522 overrides the port set by @code{set task exception-port} (see above).
18523 @code{set thread excp} is the shorthand alias.
18525 @item set thread takeover-suspend-count
18526 Normally, @value{GDBN}'s thread suspend counts are relative to the
18527 value @value{GDBN} finds when it notices each thread. This command
18528 changes the suspend counts to be absolute instead.
18530 @item set thread default
18531 @itemx show thread default
18532 @cindex thread default settings, @sc{gnu} Hurd
18533 Each of the above @code{set thread} commands has a @code{set thread
18534 default} counterpart (e.g., @code{set thread default pause}, @code{set
18535 thread default exception-port}, etc.). The @code{thread default}
18536 variety of commands sets the default thread properties for all
18537 threads; you can then change the properties of individual threads with
18538 the non-default commands.
18543 @subsection QNX Neutrino
18544 @cindex QNX Neutrino
18546 @value{GDBN} provides the following commands specific to the QNX
18550 @item set debug nto-debug
18551 @kindex set debug nto-debug
18552 When set to on, enables debugging messages specific to the QNX
18555 @item show debug nto-debug
18556 @kindex show debug nto-debug
18557 Show the current state of QNX Neutrino messages.
18564 @value{GDBN} provides the following commands specific to the Darwin target:
18567 @item set debug darwin @var{num}
18568 @kindex set debug darwin
18569 When set to a non zero value, enables debugging messages specific to
18570 the Darwin support. Higher values produce more verbose output.
18572 @item show debug darwin
18573 @kindex show debug darwin
18574 Show the current state of Darwin messages.
18576 @item set debug mach-o @var{num}
18577 @kindex set debug mach-o
18578 When set to a non zero value, enables debugging messages while
18579 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18580 file format used on Darwin for object and executable files.) Higher
18581 values produce more verbose output. This is a command to diagnose
18582 problems internal to @value{GDBN} and should not be needed in normal
18585 @item show debug mach-o
18586 @kindex show debug mach-o
18587 Show the current state of Mach-O file messages.
18589 @item set mach-exceptions on
18590 @itemx set mach-exceptions off
18591 @kindex set mach-exceptions
18592 On Darwin, faults are first reported as a Mach exception and are then
18593 mapped to a Posix signal. Use this command to turn on trapping of
18594 Mach exceptions in the inferior. This might be sometimes useful to
18595 better understand the cause of a fault. The default is off.
18597 @item show mach-exceptions
18598 @kindex show mach-exceptions
18599 Show the current state of exceptions trapping.
18604 @section Embedded Operating Systems
18606 This section describes configurations involving the debugging of
18607 embedded operating systems that are available for several different
18611 * VxWorks:: Using @value{GDBN} with VxWorks
18614 @value{GDBN} includes the ability to debug programs running on
18615 various real-time operating systems.
18618 @subsection Using @value{GDBN} with VxWorks
18624 @kindex target vxworks
18625 @item target vxworks @var{machinename}
18626 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18627 is the target system's machine name or IP address.
18631 On VxWorks, @code{load} links @var{filename} dynamically on the
18632 current target system as well as adding its symbols in @value{GDBN}.
18634 @value{GDBN} enables developers to spawn and debug tasks running on networked
18635 VxWorks targets from a Unix host. Already-running tasks spawned from
18636 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18637 both the Unix host and on the VxWorks target. The program
18638 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18639 installed with the name @code{vxgdb}, to distinguish it from a
18640 @value{GDBN} for debugging programs on the host itself.)
18643 @item VxWorks-timeout @var{args}
18644 @kindex vxworks-timeout
18645 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18646 This option is set by the user, and @var{args} represents the number of
18647 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18648 your VxWorks target is a slow software simulator or is on the far side
18649 of a thin network line.
18652 The following information on connecting to VxWorks was current when
18653 this manual was produced; newer releases of VxWorks may use revised
18656 @findex INCLUDE_RDB
18657 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18658 to include the remote debugging interface routines in the VxWorks
18659 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18660 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18661 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18662 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18663 information on configuring and remaking VxWorks, see the manufacturer's
18665 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18667 Once you have included @file{rdb.a} in your VxWorks system image and set
18668 your Unix execution search path to find @value{GDBN}, you are ready to
18669 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18670 @code{vxgdb}, depending on your installation).
18672 @value{GDBN} comes up showing the prompt:
18679 * VxWorks Connection:: Connecting to VxWorks
18680 * VxWorks Download:: VxWorks download
18681 * VxWorks Attach:: Running tasks
18684 @node VxWorks Connection
18685 @subsubsection Connecting to VxWorks
18687 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18688 network. To connect to a target whose host name is ``@code{tt}'', type:
18691 (vxgdb) target vxworks tt
18695 @value{GDBN} displays messages like these:
18698 Attaching remote machine across net...
18703 @value{GDBN} then attempts to read the symbol tables of any object modules
18704 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18705 these files by searching the directories listed in the command search
18706 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18707 to find an object file, it displays a message such as:
18710 prog.o: No such file or directory.
18713 When this happens, add the appropriate directory to the search path with
18714 the @value{GDBN} command @code{path}, and execute the @code{target}
18717 @node VxWorks Download
18718 @subsubsection VxWorks Download
18720 @cindex download to VxWorks
18721 If you have connected to the VxWorks target and you want to debug an
18722 object that has not yet been loaded, you can use the @value{GDBN}
18723 @code{load} command to download a file from Unix to VxWorks
18724 incrementally. The object file given as an argument to the @code{load}
18725 command is actually opened twice: first by the VxWorks target in order
18726 to download the code, then by @value{GDBN} in order to read the symbol
18727 table. This can lead to problems if the current working directories on
18728 the two systems differ. If both systems have NFS mounted the same
18729 filesystems, you can avoid these problems by using absolute paths.
18730 Otherwise, it is simplest to set the working directory on both systems
18731 to the directory in which the object file resides, and then to reference
18732 the file by its name, without any path. For instance, a program
18733 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18734 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18735 program, type this on VxWorks:
18738 -> cd "@var{vxpath}/vw/demo/rdb"
18742 Then, in @value{GDBN}, type:
18745 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18746 (vxgdb) load prog.o
18749 @value{GDBN} displays a response similar to this:
18752 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18755 You can also use the @code{load} command to reload an object module
18756 after editing and recompiling the corresponding source file. Note that
18757 this makes @value{GDBN} delete all currently-defined breakpoints,
18758 auto-displays, and convenience variables, and to clear the value
18759 history. (This is necessary in order to preserve the integrity of
18760 debugger's data structures that reference the target system's symbol
18763 @node VxWorks Attach
18764 @subsubsection Running Tasks
18766 @cindex running VxWorks tasks
18767 You can also attach to an existing task using the @code{attach} command as
18771 (vxgdb) attach @var{task}
18775 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18776 or suspended when you attach to it. Running tasks are suspended at
18777 the time of attachment.
18779 @node Embedded Processors
18780 @section Embedded Processors
18782 This section goes into details specific to particular embedded
18785 @cindex send command to simulator
18786 Whenever a specific embedded processor has a simulator, @value{GDBN}
18787 allows to send an arbitrary command to the simulator.
18790 @item sim @var{command}
18791 @kindex sim@r{, a command}
18792 Send an arbitrary @var{command} string to the simulator. Consult the
18793 documentation for the specific simulator in use for information about
18794 acceptable commands.
18800 * M32R/D:: Renesas M32R/D
18801 * M68K:: Motorola M68K
18802 * MicroBlaze:: Xilinx MicroBlaze
18803 * MIPS Embedded:: MIPS Embedded
18804 * OpenRISC 1000:: OpenRisc 1000
18805 * PA:: HP PA Embedded
18806 * PowerPC Embedded:: PowerPC Embedded
18807 * Sparclet:: Tsqware Sparclet
18808 * Sparclite:: Fujitsu Sparclite
18809 * Z8000:: Zilog Z8000
18812 * Super-H:: Renesas Super-H
18821 @item target rdi @var{dev}
18822 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18823 use this target to communicate with both boards running the Angel
18824 monitor, or with the EmbeddedICE JTAG debug device.
18827 @item target rdp @var{dev}
18832 @value{GDBN} provides the following ARM-specific commands:
18835 @item set arm disassembler
18837 This commands selects from a list of disassembly styles. The
18838 @code{"std"} style is the standard style.
18840 @item show arm disassembler
18842 Show the current disassembly style.
18844 @item set arm apcs32
18845 @cindex ARM 32-bit mode
18846 This command toggles ARM operation mode between 32-bit and 26-bit.
18848 @item show arm apcs32
18849 Display the current usage of the ARM 32-bit mode.
18851 @item set arm fpu @var{fputype}
18852 This command sets the ARM floating-point unit (FPU) type. The
18853 argument @var{fputype} can be one of these:
18857 Determine the FPU type by querying the OS ABI.
18859 Software FPU, with mixed-endian doubles on little-endian ARM
18862 GCC-compiled FPA co-processor.
18864 Software FPU with pure-endian doubles.
18870 Show the current type of the FPU.
18873 This command forces @value{GDBN} to use the specified ABI.
18876 Show the currently used ABI.
18878 @item set arm fallback-mode (arm|thumb|auto)
18879 @value{GDBN} uses the symbol table, when available, to determine
18880 whether instructions are ARM or Thumb. This command controls
18881 @value{GDBN}'s default behavior when the symbol table is not
18882 available. The default is @samp{auto}, which causes @value{GDBN} to
18883 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18886 @item show arm fallback-mode
18887 Show the current fallback instruction mode.
18889 @item set arm force-mode (arm|thumb|auto)
18890 This command overrides use of the symbol table to determine whether
18891 instructions are ARM or Thumb. The default is @samp{auto}, which
18892 causes @value{GDBN} to use the symbol table and then the setting
18893 of @samp{set arm fallback-mode}.
18895 @item show arm force-mode
18896 Show the current forced instruction mode.
18898 @item set debug arm
18899 Toggle whether to display ARM-specific debugging messages from the ARM
18900 target support subsystem.
18902 @item show debug arm
18903 Show whether ARM-specific debugging messages are enabled.
18906 The following commands are available when an ARM target is debugged
18907 using the RDI interface:
18910 @item rdilogfile @r{[}@var{file}@r{]}
18912 @cindex ADP (Angel Debugger Protocol) logging
18913 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18914 With an argument, sets the log file to the specified @var{file}. With
18915 no argument, show the current log file name. The default log file is
18918 @item rdilogenable @r{[}@var{arg}@r{]}
18919 @kindex rdilogenable
18920 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18921 enables logging, with an argument 0 or @code{"no"} disables it. With
18922 no arguments displays the current setting. When logging is enabled,
18923 ADP packets exchanged between @value{GDBN} and the RDI target device
18924 are logged to a file.
18926 @item set rdiromatzero
18927 @kindex set rdiromatzero
18928 @cindex ROM at zero address, RDI
18929 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18930 vector catching is disabled, so that zero address can be used. If off
18931 (the default), vector catching is enabled. For this command to take
18932 effect, it needs to be invoked prior to the @code{target rdi} command.
18934 @item show rdiromatzero
18935 @kindex show rdiromatzero
18936 Show the current setting of ROM at zero address.
18938 @item set rdiheartbeat
18939 @kindex set rdiheartbeat
18940 @cindex RDI heartbeat
18941 Enable or disable RDI heartbeat packets. It is not recommended to
18942 turn on this option, since it confuses ARM and EPI JTAG interface, as
18943 well as the Angel monitor.
18945 @item show rdiheartbeat
18946 @kindex show rdiheartbeat
18947 Show the setting of RDI heartbeat packets.
18951 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18952 The @value{GDBN} ARM simulator accepts the following optional arguments.
18955 @item --swi-support=@var{type}
18956 Tell the simulator which SWI interfaces to support.
18957 @var{type} may be a comma separated list of the following values.
18958 The default value is @code{all}.
18971 @subsection Renesas M32R/D and M32R/SDI
18974 @kindex target m32r
18975 @item target m32r @var{dev}
18976 Renesas M32R/D ROM monitor.
18978 @kindex target m32rsdi
18979 @item target m32rsdi @var{dev}
18980 Renesas M32R SDI server, connected via parallel port to the board.
18983 The following @value{GDBN} commands are specific to the M32R monitor:
18986 @item set download-path @var{path}
18987 @kindex set download-path
18988 @cindex find downloadable @sc{srec} files (M32R)
18989 Set the default path for finding downloadable @sc{srec} files.
18991 @item show download-path
18992 @kindex show download-path
18993 Show the default path for downloadable @sc{srec} files.
18995 @item set board-address @var{addr}
18996 @kindex set board-address
18997 @cindex M32-EVA target board address
18998 Set the IP address for the M32R-EVA target board.
19000 @item show board-address
19001 @kindex show board-address
19002 Show the current IP address of the target board.
19004 @item set server-address @var{addr}
19005 @kindex set server-address
19006 @cindex download server address (M32R)
19007 Set the IP address for the download server, which is the @value{GDBN}'s
19010 @item show server-address
19011 @kindex show server-address
19012 Display the IP address of the download server.
19014 @item upload @r{[}@var{file}@r{]}
19015 @kindex upload@r{, M32R}
19016 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19017 upload capability. If no @var{file} argument is given, the current
19018 executable file is uploaded.
19020 @item tload @r{[}@var{file}@r{]}
19021 @kindex tload@r{, M32R}
19022 Test the @code{upload} command.
19025 The following commands are available for M32R/SDI:
19030 @cindex reset SDI connection, M32R
19031 This command resets the SDI connection.
19035 This command shows the SDI connection status.
19038 @kindex debug_chaos
19039 @cindex M32R/Chaos debugging
19040 Instructs the remote that M32R/Chaos debugging is to be used.
19042 @item use_debug_dma
19043 @kindex use_debug_dma
19044 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19047 @kindex use_mon_code
19048 Instructs the remote to use the MON_CODE method of accessing memory.
19051 @kindex use_ib_break
19052 Instructs the remote to set breakpoints by IB break.
19054 @item use_dbt_break
19055 @kindex use_dbt_break
19056 Instructs the remote to set breakpoints by DBT.
19062 The Motorola m68k configuration includes ColdFire support, and a
19063 target command for the following ROM monitor.
19067 @kindex target dbug
19068 @item target dbug @var{dev}
19069 dBUG ROM monitor for Motorola ColdFire.
19074 @subsection MicroBlaze
19075 @cindex Xilinx MicroBlaze
19076 @cindex XMD, Xilinx Microprocessor Debugger
19078 The MicroBlaze is a soft-core processor supported on various Xilinx
19079 FPGAs, such as Spartan or Virtex series. Boards with these processors
19080 usually have JTAG ports which connect to a host system running the Xilinx
19081 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19082 This host system is used to download the configuration bitstream to
19083 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19084 communicates with the target board using the JTAG interface and
19085 presents a @code{gdbserver} interface to the board. By default
19086 @code{xmd} uses port @code{1234}. (While it is possible to change
19087 this default port, it requires the use of undocumented @code{xmd}
19088 commands. Contact Xilinx support if you need to do this.)
19090 Use these GDB commands to connect to the MicroBlaze target processor.
19093 @item target remote :1234
19094 Use this command to connect to the target if you are running @value{GDBN}
19095 on the same system as @code{xmd}.
19097 @item target remote @var{xmd-host}:1234
19098 Use this command to connect to the target if it is connected to @code{xmd}
19099 running on a different system named @var{xmd-host}.
19102 Use this command to download a program to the MicroBlaze target.
19104 @item set debug microblaze @var{n}
19105 Enable MicroBlaze-specific debugging messages if non-zero.
19107 @item show debug microblaze @var{n}
19108 Show MicroBlaze-specific debugging level.
19111 @node MIPS Embedded
19112 @subsection MIPS Embedded
19114 @cindex MIPS boards
19115 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19116 MIPS board attached to a serial line. This is available when
19117 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19120 Use these @value{GDBN} commands to specify the connection to your target board:
19123 @item target mips @var{port}
19124 @kindex target mips @var{port}
19125 To run a program on the board, start up @code{@value{GDBP}} with the
19126 name of your program as the argument. To connect to the board, use the
19127 command @samp{target mips @var{port}}, where @var{port} is the name of
19128 the serial port connected to the board. If the program has not already
19129 been downloaded to the board, you may use the @code{load} command to
19130 download it. You can then use all the usual @value{GDBN} commands.
19132 For example, this sequence connects to the target board through a serial
19133 port, and loads and runs a program called @var{prog} through the
19137 host$ @value{GDBP} @var{prog}
19138 @value{GDBN} is free software and @dots{}
19139 (@value{GDBP}) target mips /dev/ttyb
19140 (@value{GDBP}) load @var{prog}
19144 @item target mips @var{hostname}:@var{portnumber}
19145 On some @value{GDBN} host configurations, you can specify a TCP
19146 connection (for instance, to a serial line managed by a terminal
19147 concentrator) instead of a serial port, using the syntax
19148 @samp{@var{hostname}:@var{portnumber}}.
19150 @item target pmon @var{port}
19151 @kindex target pmon @var{port}
19154 @item target ddb @var{port}
19155 @kindex target ddb @var{port}
19156 NEC's DDB variant of PMON for Vr4300.
19158 @item target lsi @var{port}
19159 @kindex target lsi @var{port}
19160 LSI variant of PMON.
19162 @kindex target r3900
19163 @item target r3900 @var{dev}
19164 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19166 @kindex target array
19167 @item target array @var{dev}
19168 Array Tech LSI33K RAID controller board.
19174 @value{GDBN} also supports these special commands for MIPS targets:
19177 @item set mipsfpu double
19178 @itemx set mipsfpu single
19179 @itemx set mipsfpu none
19180 @itemx set mipsfpu auto
19181 @itemx show mipsfpu
19182 @kindex set mipsfpu
19183 @kindex show mipsfpu
19184 @cindex MIPS remote floating point
19185 @cindex floating point, MIPS remote
19186 If your target board does not support the MIPS floating point
19187 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19188 need this, you may wish to put the command in your @value{GDBN} init
19189 file). This tells @value{GDBN} how to find the return value of
19190 functions which return floating point values. It also allows
19191 @value{GDBN} to avoid saving the floating point registers when calling
19192 functions on the board. If you are using a floating point coprocessor
19193 with only single precision floating point support, as on the @sc{r4650}
19194 processor, use the command @samp{set mipsfpu single}. The default
19195 double precision floating point coprocessor may be selected using
19196 @samp{set mipsfpu double}.
19198 In previous versions the only choices were double precision or no
19199 floating point, so @samp{set mipsfpu on} will select double precision
19200 and @samp{set mipsfpu off} will select no floating point.
19202 As usual, you can inquire about the @code{mipsfpu} variable with
19203 @samp{show mipsfpu}.
19205 @item set timeout @var{seconds}
19206 @itemx set retransmit-timeout @var{seconds}
19207 @itemx show timeout
19208 @itemx show retransmit-timeout
19209 @cindex @code{timeout}, MIPS protocol
19210 @cindex @code{retransmit-timeout}, MIPS protocol
19211 @kindex set timeout
19212 @kindex show timeout
19213 @kindex set retransmit-timeout
19214 @kindex show retransmit-timeout
19215 You can control the timeout used while waiting for a packet, in the MIPS
19216 remote protocol, with the @code{set timeout @var{seconds}} command. The
19217 default is 5 seconds. Similarly, you can control the timeout used while
19218 waiting for an acknowledgment of a packet with the @code{set
19219 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19220 You can inspect both values with @code{show timeout} and @code{show
19221 retransmit-timeout}. (These commands are @emph{only} available when
19222 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19224 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19225 is waiting for your program to stop. In that case, @value{GDBN} waits
19226 forever because it has no way of knowing how long the program is going
19227 to run before stopping.
19229 @item set syn-garbage-limit @var{num}
19230 @kindex set syn-garbage-limit@r{, MIPS remote}
19231 @cindex synchronize with remote MIPS target
19232 Limit the maximum number of characters @value{GDBN} should ignore when
19233 it tries to synchronize with the remote target. The default is 10
19234 characters. Setting the limit to -1 means there's no limit.
19236 @item show syn-garbage-limit
19237 @kindex show syn-garbage-limit@r{, MIPS remote}
19238 Show the current limit on the number of characters to ignore when
19239 trying to synchronize with the remote system.
19241 @item set monitor-prompt @var{prompt}
19242 @kindex set monitor-prompt@r{, MIPS remote}
19243 @cindex remote monitor prompt
19244 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19245 remote monitor. The default depends on the target:
19255 @item show monitor-prompt
19256 @kindex show monitor-prompt@r{, MIPS remote}
19257 Show the current strings @value{GDBN} expects as the prompt from the
19260 @item set monitor-warnings
19261 @kindex set monitor-warnings@r{, MIPS remote}
19262 Enable or disable monitor warnings about hardware breakpoints. This
19263 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19264 display warning messages whose codes are returned by the @code{lsi}
19265 PMON monitor for breakpoint commands.
19267 @item show monitor-warnings
19268 @kindex show monitor-warnings@r{, MIPS remote}
19269 Show the current setting of printing monitor warnings.
19271 @item pmon @var{command}
19272 @kindex pmon@r{, MIPS remote}
19273 @cindex send PMON command
19274 This command allows sending an arbitrary @var{command} string to the
19275 monitor. The monitor must be in debug mode for this to work.
19278 @node OpenRISC 1000
19279 @subsection OpenRISC 1000
19280 @cindex OpenRISC 1000
19282 @cindex or1k boards
19283 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19284 about platform and commands.
19288 @kindex target jtag
19289 @item target jtag jtag://@var{host}:@var{port}
19291 Connects to remote JTAG server.
19292 JTAG remote server can be either an or1ksim or JTAG server,
19293 connected via parallel port to the board.
19295 Example: @code{target jtag jtag://localhost:9999}
19298 @item or1ksim @var{command}
19299 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19300 Simulator, proprietary commands can be executed.
19302 @kindex info or1k spr
19303 @item info or1k spr
19304 Displays spr groups.
19306 @item info or1k spr @var{group}
19307 @itemx info or1k spr @var{groupno}
19308 Displays register names in selected group.
19310 @item info or1k spr @var{group} @var{register}
19311 @itemx info or1k spr @var{register}
19312 @itemx info or1k spr @var{groupno} @var{registerno}
19313 @itemx info or1k spr @var{registerno}
19314 Shows information about specified spr register.
19317 @item spr @var{group} @var{register} @var{value}
19318 @itemx spr @var{register @var{value}}
19319 @itemx spr @var{groupno} @var{registerno @var{value}}
19320 @itemx spr @var{registerno @var{value}}
19321 Writes @var{value} to specified spr register.
19324 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19325 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19326 program execution and is thus much faster. Hardware breakpoints/watchpoint
19327 triggers can be set using:
19330 Load effective address/data
19332 Store effective address/data
19334 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19339 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19340 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19342 @code{htrace} commands:
19343 @cindex OpenRISC 1000 htrace
19346 @item hwatch @var{conditional}
19347 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19348 or Data. For example:
19350 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19352 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19356 Display information about current HW trace configuration.
19358 @item htrace trigger @var{conditional}
19359 Set starting criteria for HW trace.
19361 @item htrace qualifier @var{conditional}
19362 Set acquisition qualifier for HW trace.
19364 @item htrace stop @var{conditional}
19365 Set HW trace stopping criteria.
19367 @item htrace record [@var{data}]*
19368 Selects the data to be recorded, when qualifier is met and HW trace was
19371 @item htrace enable
19372 @itemx htrace disable
19373 Enables/disables the HW trace.
19375 @item htrace rewind [@var{filename}]
19376 Clears currently recorded trace data.
19378 If filename is specified, new trace file is made and any newly collected data
19379 will be written there.
19381 @item htrace print [@var{start} [@var{len}]]
19382 Prints trace buffer, using current record configuration.
19384 @item htrace mode continuous
19385 Set continuous trace mode.
19387 @item htrace mode suspend
19388 Set suspend trace mode.
19392 @node PowerPC Embedded
19393 @subsection PowerPC Embedded
19395 @cindex DVC register
19396 @value{GDBN} supports using the DVC (Data Value Compare) register to
19397 implement in hardware simple hardware watchpoint conditions of the form:
19400 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19401 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19404 The DVC register will be automatically used when @value{GDBN} detects
19405 such pattern in a condition expression, and the created watchpoint uses one
19406 debug register (either the @code{exact-watchpoints} option is on and the
19407 variable is scalar, or the variable has a length of one byte). This feature
19408 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19411 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19412 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19413 in which case watchpoints using only one debug register are created when
19414 watching variables of scalar types.
19416 You can create an artificial array to watch an arbitrary memory
19417 region using one of the following commands (@pxref{Expressions}):
19420 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19421 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19424 PowerPC embedded processors support masked watchpoints. See the discussion
19425 about the @code{mask} argument in @ref{Set Watchpoints}.
19427 @cindex ranged breakpoint
19428 PowerPC embedded processors support hardware accelerated
19429 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19430 the inferior whenever it executes an instruction at any address within
19431 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19432 use the @code{break-range} command.
19434 @value{GDBN} provides the following PowerPC-specific commands:
19437 @kindex break-range
19438 @item break-range @var{start-location}, @var{end-location}
19439 Set a breakpoint for an address range.
19440 @var{start-location} and @var{end-location} can specify a function name,
19441 a line number, an offset of lines from the current line or from the start
19442 location, or an address of an instruction (see @ref{Specify Location},
19443 for a list of all the possible ways to specify a @var{location}.)
19444 The breakpoint will stop execution of the inferior whenever it
19445 executes an instruction at any address within the specified range,
19446 (including @var{start-location} and @var{end-location}.)
19448 @kindex set powerpc
19449 @item set powerpc soft-float
19450 @itemx show powerpc soft-float
19451 Force @value{GDBN} to use (or not use) a software floating point calling
19452 convention. By default, @value{GDBN} selects the calling convention based
19453 on the selected architecture and the provided executable file.
19455 @item set powerpc vector-abi
19456 @itemx show powerpc vector-abi
19457 Force @value{GDBN} to use the specified calling convention for vector
19458 arguments and return values. The valid options are @samp{auto};
19459 @samp{generic}, to avoid vector registers even if they are present;
19460 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19461 registers. By default, @value{GDBN} selects the calling convention
19462 based on the selected architecture and the provided executable file.
19464 @item set powerpc exact-watchpoints
19465 @itemx show powerpc exact-watchpoints
19466 Allow @value{GDBN} to use only one debug register when watching a variable
19467 of scalar type, thus assuming that the variable is accessed through the
19468 address of its first byte.
19470 @kindex target dink32
19471 @item target dink32 @var{dev}
19472 DINK32 ROM monitor.
19474 @kindex target ppcbug
19475 @item target ppcbug @var{dev}
19476 @kindex target ppcbug1
19477 @item target ppcbug1 @var{dev}
19478 PPCBUG ROM monitor for PowerPC.
19481 @item target sds @var{dev}
19482 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19485 @cindex SDS protocol
19486 The following commands specific to the SDS protocol are supported
19490 @item set sdstimeout @var{nsec}
19491 @kindex set sdstimeout
19492 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19493 default is 2 seconds.
19495 @item show sdstimeout
19496 @kindex show sdstimeout
19497 Show the current value of the SDS timeout.
19499 @item sds @var{command}
19500 @kindex sds@r{, a command}
19501 Send the specified @var{command} string to the SDS monitor.
19506 @subsection HP PA Embedded
19510 @kindex target op50n
19511 @item target op50n @var{dev}
19512 OP50N monitor, running on an OKI HPPA board.
19514 @kindex target w89k
19515 @item target w89k @var{dev}
19516 W89K monitor, running on a Winbond HPPA board.
19521 @subsection Tsqware Sparclet
19525 @value{GDBN} enables developers to debug tasks running on
19526 Sparclet targets from a Unix host.
19527 @value{GDBN} uses code that runs on
19528 both the Unix host and on the Sparclet target. The program
19529 @code{@value{GDBP}} is installed and executed on the Unix host.
19532 @item remotetimeout @var{args}
19533 @kindex remotetimeout
19534 @value{GDBN} supports the option @code{remotetimeout}.
19535 This option is set by the user, and @var{args} represents the number of
19536 seconds @value{GDBN} waits for responses.
19539 @cindex compiling, on Sparclet
19540 When compiling for debugging, include the options @samp{-g} to get debug
19541 information and @samp{-Ttext} to relocate the program to where you wish to
19542 load it on the target. You may also want to add the options @samp{-n} or
19543 @samp{-N} in order to reduce the size of the sections. Example:
19546 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19549 You can use @code{objdump} to verify that the addresses are what you intended:
19552 sparclet-aout-objdump --headers --syms prog
19555 @cindex running, on Sparclet
19557 your Unix execution search path to find @value{GDBN}, you are ready to
19558 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19559 (or @code{sparclet-aout-gdb}, depending on your installation).
19561 @value{GDBN} comes up showing the prompt:
19568 * Sparclet File:: Setting the file to debug
19569 * Sparclet Connection:: Connecting to Sparclet
19570 * Sparclet Download:: Sparclet download
19571 * Sparclet Execution:: Running and debugging
19574 @node Sparclet File
19575 @subsubsection Setting File to Debug
19577 The @value{GDBN} command @code{file} lets you choose with program to debug.
19580 (gdbslet) file prog
19584 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19585 @value{GDBN} locates
19586 the file by searching the directories listed in the command search
19588 If the file was compiled with debug information (option @samp{-g}), source
19589 files will be searched as well.
19590 @value{GDBN} locates
19591 the source files by searching the directories listed in the directory search
19592 path (@pxref{Environment, ,Your Program's Environment}).
19594 to find a file, it displays a message such as:
19597 prog: No such file or directory.
19600 When this happens, add the appropriate directories to the search paths with
19601 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19602 @code{target} command again.
19604 @node Sparclet Connection
19605 @subsubsection Connecting to Sparclet
19607 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19608 To connect to a target on serial port ``@code{ttya}'', type:
19611 (gdbslet) target sparclet /dev/ttya
19612 Remote target sparclet connected to /dev/ttya
19613 main () at ../prog.c:3
19617 @value{GDBN} displays messages like these:
19623 @node Sparclet Download
19624 @subsubsection Sparclet Download
19626 @cindex download to Sparclet
19627 Once connected to the Sparclet target,
19628 you can use the @value{GDBN}
19629 @code{load} command to download the file from the host to the target.
19630 The file name and load offset should be given as arguments to the @code{load}
19632 Since the file format is aout, the program must be loaded to the starting
19633 address. You can use @code{objdump} to find out what this value is. The load
19634 offset is an offset which is added to the VMA (virtual memory address)
19635 of each of the file's sections.
19636 For instance, if the program
19637 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19638 and bss at 0x12010170, in @value{GDBN}, type:
19641 (gdbslet) load prog 0x12010000
19642 Loading section .text, size 0xdb0 vma 0x12010000
19645 If the code is loaded at a different address then what the program was linked
19646 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19647 to tell @value{GDBN} where to map the symbol table.
19649 @node Sparclet Execution
19650 @subsubsection Running and Debugging
19652 @cindex running and debugging Sparclet programs
19653 You can now begin debugging the task using @value{GDBN}'s execution control
19654 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19655 manual for the list of commands.
19659 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19661 Starting program: prog
19662 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19663 3 char *symarg = 0;
19665 4 char *execarg = "hello!";
19670 @subsection Fujitsu Sparclite
19674 @kindex target sparclite
19675 @item target sparclite @var{dev}
19676 Fujitsu sparclite boards, used only for the purpose of loading.
19677 You must use an additional command to debug the program.
19678 For example: target remote @var{dev} using @value{GDBN} standard
19684 @subsection Zilog Z8000
19687 @cindex simulator, Z8000
19688 @cindex Zilog Z8000 simulator
19690 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19693 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19694 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19695 segmented variant). The simulator recognizes which architecture is
19696 appropriate by inspecting the object code.
19699 @item target sim @var{args}
19701 @kindex target sim@r{, with Z8000}
19702 Debug programs on a simulated CPU. If the simulator supports setup
19703 options, specify them via @var{args}.
19707 After specifying this target, you can debug programs for the simulated
19708 CPU in the same style as programs for your host computer; use the
19709 @code{file} command to load a new program image, the @code{run} command
19710 to run your program, and so on.
19712 As well as making available all the usual machine registers
19713 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19714 additional items of information as specially named registers:
19719 Counts clock-ticks in the simulator.
19722 Counts instructions run in the simulator.
19725 Execution time in 60ths of a second.
19729 You can refer to these values in @value{GDBN} expressions with the usual
19730 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19731 conditional breakpoint that suspends only after at least 5000
19732 simulated clock ticks.
19735 @subsection Atmel AVR
19738 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19739 following AVR-specific commands:
19742 @item info io_registers
19743 @kindex info io_registers@r{, AVR}
19744 @cindex I/O registers (Atmel AVR)
19745 This command displays information about the AVR I/O registers. For
19746 each register, @value{GDBN} prints its number and value.
19753 When configured for debugging CRIS, @value{GDBN} provides the
19754 following CRIS-specific commands:
19757 @item set cris-version @var{ver}
19758 @cindex CRIS version
19759 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19760 The CRIS version affects register names and sizes. This command is useful in
19761 case autodetection of the CRIS version fails.
19763 @item show cris-version
19764 Show the current CRIS version.
19766 @item set cris-dwarf2-cfi
19767 @cindex DWARF-2 CFI and CRIS
19768 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19769 Change to @samp{off} when using @code{gcc-cris} whose version is below
19772 @item show cris-dwarf2-cfi
19773 Show the current state of using DWARF-2 CFI.
19775 @item set cris-mode @var{mode}
19777 Set the current CRIS mode to @var{mode}. It should only be changed when
19778 debugging in guru mode, in which case it should be set to
19779 @samp{guru} (the default is @samp{normal}).
19781 @item show cris-mode
19782 Show the current CRIS mode.
19786 @subsection Renesas Super-H
19789 For the Renesas Super-H processor, @value{GDBN} provides these
19794 @kindex regs@r{, Super-H}
19795 Show the values of all Super-H registers.
19797 @item set sh calling-convention @var{convention}
19798 @kindex set sh calling-convention
19799 Set the calling-convention used when calling functions from @value{GDBN}.
19800 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19801 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19802 convention. If the DWARF-2 information of the called function specifies
19803 that the function follows the Renesas calling convention, the function
19804 is called using the Renesas calling convention. If the calling convention
19805 is set to @samp{renesas}, the Renesas calling convention is always used,
19806 regardless of the DWARF-2 information. This can be used to override the
19807 default of @samp{gcc} if debug information is missing, or the compiler
19808 does not emit the DWARF-2 calling convention entry for a function.
19810 @item show sh calling-convention
19811 @kindex show sh calling-convention
19812 Show the current calling convention setting.
19817 @node Architectures
19818 @section Architectures
19820 This section describes characteristics of architectures that affect
19821 all uses of @value{GDBN} with the architecture, both native and cross.
19828 * HPPA:: HP PA architecture
19829 * SPU:: Cell Broadband Engine SPU architecture
19834 @subsection x86 Architecture-specific Issues
19837 @item set struct-convention @var{mode}
19838 @kindex set struct-convention
19839 @cindex struct return convention
19840 @cindex struct/union returned in registers
19841 Set the convention used by the inferior to return @code{struct}s and
19842 @code{union}s from functions to @var{mode}. Possible values of
19843 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19844 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19845 are returned on the stack, while @code{"reg"} means that a
19846 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19847 be returned in a register.
19849 @item show struct-convention
19850 @kindex show struct-convention
19851 Show the current setting of the convention to return @code{struct}s
19860 @kindex set rstack_high_address
19861 @cindex AMD 29K register stack
19862 @cindex register stack, AMD29K
19863 @item set rstack_high_address @var{address}
19864 On AMD 29000 family processors, registers are saved in a separate
19865 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19866 extent of this stack. Normally, @value{GDBN} just assumes that the
19867 stack is ``large enough''. This may result in @value{GDBN} referencing
19868 memory locations that do not exist. If necessary, you can get around
19869 this problem by specifying the ending address of the register stack with
19870 the @code{set rstack_high_address} command. The argument should be an
19871 address, which you probably want to precede with @samp{0x} to specify in
19874 @kindex show rstack_high_address
19875 @item show rstack_high_address
19876 Display the current limit of the register stack, on AMD 29000 family
19884 See the following section.
19889 @cindex stack on Alpha
19890 @cindex stack on MIPS
19891 @cindex Alpha stack
19893 Alpha- and MIPS-based computers use an unusual stack frame, which
19894 sometimes requires @value{GDBN} to search backward in the object code to
19895 find the beginning of a function.
19897 @cindex response time, MIPS debugging
19898 To improve response time (especially for embedded applications, where
19899 @value{GDBN} may be restricted to a slow serial line for this search)
19900 you may want to limit the size of this search, using one of these
19904 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19905 @item set heuristic-fence-post @var{limit}
19906 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19907 search for the beginning of a function. A value of @var{0} (the
19908 default) means there is no limit. However, except for @var{0}, the
19909 larger the limit the more bytes @code{heuristic-fence-post} must search
19910 and therefore the longer it takes to run. You should only need to use
19911 this command when debugging a stripped executable.
19913 @item show heuristic-fence-post
19914 Display the current limit.
19918 These commands are available @emph{only} when @value{GDBN} is configured
19919 for debugging programs on Alpha or MIPS processors.
19921 Several MIPS-specific commands are available when debugging MIPS
19925 @item set mips abi @var{arg}
19926 @kindex set mips abi
19927 @cindex set ABI for MIPS
19928 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19929 values of @var{arg} are:
19933 The default ABI associated with the current binary (this is the
19943 @item show mips abi
19944 @kindex show mips abi
19945 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19948 @itemx show mipsfpu
19949 @xref{MIPS Embedded, set mipsfpu}.
19951 @item set mips mask-address @var{arg}
19952 @kindex set mips mask-address
19953 @cindex MIPS addresses, masking
19954 This command determines whether the most-significant 32 bits of 64-bit
19955 MIPS addresses are masked off. The argument @var{arg} can be
19956 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19957 setting, which lets @value{GDBN} determine the correct value.
19959 @item show mips mask-address
19960 @kindex show mips mask-address
19961 Show whether the upper 32 bits of MIPS addresses are masked off or
19964 @item set remote-mips64-transfers-32bit-regs
19965 @kindex set remote-mips64-transfers-32bit-regs
19966 This command controls compatibility with 64-bit MIPS targets that
19967 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19968 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19969 and 64 bits for other registers, set this option to @samp{on}.
19971 @item show remote-mips64-transfers-32bit-regs
19972 @kindex show remote-mips64-transfers-32bit-regs
19973 Show the current setting of compatibility with older MIPS 64 targets.
19975 @item set debug mips
19976 @kindex set debug mips
19977 This command turns on and off debugging messages for the MIPS-specific
19978 target code in @value{GDBN}.
19980 @item show debug mips
19981 @kindex show debug mips
19982 Show the current setting of MIPS debugging messages.
19988 @cindex HPPA support
19990 When @value{GDBN} is debugging the HP PA architecture, it provides the
19991 following special commands:
19994 @item set debug hppa
19995 @kindex set debug hppa
19996 This command determines whether HPPA architecture-specific debugging
19997 messages are to be displayed.
19999 @item show debug hppa
20000 Show whether HPPA debugging messages are displayed.
20002 @item maint print unwind @var{address}
20003 @kindex maint print unwind@r{, HPPA}
20004 This command displays the contents of the unwind table entry at the
20005 given @var{address}.
20011 @subsection Cell Broadband Engine SPU architecture
20012 @cindex Cell Broadband Engine
20015 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20016 it provides the following special commands:
20019 @item info spu event
20021 Display SPU event facility status. Shows current event mask
20022 and pending event status.
20024 @item info spu signal
20025 Display SPU signal notification facility status. Shows pending
20026 signal-control word and signal notification mode of both signal
20027 notification channels.
20029 @item info spu mailbox
20030 Display SPU mailbox facility status. Shows all pending entries,
20031 in order of processing, in each of the SPU Write Outbound,
20032 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20035 Display MFC DMA status. Shows all pending commands in the MFC
20036 DMA queue. For each entry, opcode, tag, class IDs, effective
20037 and local store addresses and transfer size are shown.
20039 @item info spu proxydma
20040 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20041 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20042 and local store addresses and transfer size are shown.
20046 When @value{GDBN} is debugging a combined PowerPC/SPU application
20047 on the Cell Broadband Engine, it provides in addition the following
20051 @item set spu stop-on-load @var{arg}
20053 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20054 will give control to the user when a new SPE thread enters its @code{main}
20055 function. The default is @code{off}.
20057 @item show spu stop-on-load
20059 Show whether to stop for new SPE threads.
20061 @item set spu auto-flush-cache @var{arg}
20062 Set whether to automatically flush the software-managed cache. When set to
20063 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20064 cache to be flushed whenever SPE execution stops. This provides a consistent
20065 view of PowerPC memory that is accessed via the cache. If an application
20066 does not use the software-managed cache, this option has no effect.
20068 @item show spu auto-flush-cache
20069 Show whether to automatically flush the software-managed cache.
20074 @subsection PowerPC
20075 @cindex PowerPC architecture
20077 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20078 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20079 numbers stored in the floating point registers. These values must be stored
20080 in two consecutive registers, always starting at an even register like
20081 @code{f0} or @code{f2}.
20083 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20084 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20085 @code{f2} and @code{f3} for @code{$dl1} and so on.
20087 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20088 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20091 @node Controlling GDB
20092 @chapter Controlling @value{GDBN}
20094 You can alter the way @value{GDBN} interacts with you by using the
20095 @code{set} command. For commands controlling how @value{GDBN} displays
20096 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20101 * Editing:: Command editing
20102 * Command History:: Command history
20103 * Screen Size:: Screen size
20104 * Numbers:: Numbers
20105 * ABI:: Configuring the current ABI
20106 * Messages/Warnings:: Optional warnings and messages
20107 * Debugging Output:: Optional messages about internal happenings
20108 * Other Misc Settings:: Other Miscellaneous Settings
20116 @value{GDBN} indicates its readiness to read a command by printing a string
20117 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20118 can change the prompt string with the @code{set prompt} command. For
20119 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20120 the prompt in one of the @value{GDBN} sessions so that you can always tell
20121 which one you are talking to.
20123 @emph{Note:} @code{set prompt} does not add a space for you after the
20124 prompt you set. This allows you to set a prompt which ends in a space
20125 or a prompt that does not.
20129 @item set prompt @var{newprompt}
20130 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20132 @kindex show prompt
20134 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20137 Versions of @value{GDBN} that ship with Python scripting enabled have
20138 prompt extensions. The commands for interacting with these extensions
20142 @kindex set extended-prompt
20143 @item set extended-prompt @var{prompt}
20144 Set an extended prompt that allows for substitutions.
20145 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20146 substitution. Any escape sequences specified as part of the prompt
20147 string are replaced with the corresponding strings each time the prompt
20153 set extended-prompt Current working directory: \w (gdb)
20156 Note that when an extended-prompt is set, it takes control of the
20157 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20159 @kindex show extended-prompt
20160 @item show extended-prompt
20161 Prints the extended prompt. Any escape sequences specified as part of
20162 the prompt string with @code{set extended-prompt}, are replaced with the
20163 corresponding strings each time the prompt is displayed.
20167 @section Command Editing
20169 @cindex command line editing
20171 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20172 @sc{gnu} library provides consistent behavior for programs which provide a
20173 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20174 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20175 substitution, and a storage and recall of command history across
20176 debugging sessions.
20178 You may control the behavior of command line editing in @value{GDBN} with the
20179 command @code{set}.
20182 @kindex set editing
20185 @itemx set editing on
20186 Enable command line editing (enabled by default).
20188 @item set editing off
20189 Disable command line editing.
20191 @kindex show editing
20193 Show whether command line editing is enabled.
20196 @ifset SYSTEM_READLINE
20197 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20199 @ifclear SYSTEM_READLINE
20200 @xref{Command Line Editing},
20202 for more details about the Readline
20203 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20204 encouraged to read that chapter.
20206 @node Command History
20207 @section Command History
20208 @cindex command history
20210 @value{GDBN} can keep track of the commands you type during your
20211 debugging sessions, so that you can be certain of precisely what
20212 happened. Use these commands to manage the @value{GDBN} command
20215 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20216 package, to provide the history facility.
20217 @ifset SYSTEM_READLINE
20218 @xref{Using History Interactively, , , history, GNU History Library},
20220 @ifclear SYSTEM_READLINE
20221 @xref{Using History Interactively},
20223 for the detailed description of the History library.
20225 To issue a command to @value{GDBN} without affecting certain aspects of
20226 the state which is seen by users, prefix it with @samp{server }
20227 (@pxref{Server Prefix}). This
20228 means that this command will not affect the command history, nor will it
20229 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20230 pressed on a line by itself.
20232 @cindex @code{server}, command prefix
20233 The server prefix does not affect the recording of values into the value
20234 history; to print a value without recording it into the value history,
20235 use the @code{output} command instead of the @code{print} command.
20237 Here is the description of @value{GDBN} commands related to command
20241 @cindex history substitution
20242 @cindex history file
20243 @kindex set history filename
20244 @cindex @env{GDBHISTFILE}, environment variable
20245 @item set history filename @var{fname}
20246 Set the name of the @value{GDBN} command history file to @var{fname}.
20247 This is the file where @value{GDBN} reads an initial command history
20248 list, and where it writes the command history from this session when it
20249 exits. You can access this list through history expansion or through
20250 the history command editing characters listed below. This file defaults
20251 to the value of the environment variable @code{GDBHISTFILE}, or to
20252 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20255 @cindex save command history
20256 @kindex set history save
20257 @item set history save
20258 @itemx set history save on
20259 Record command history in a file, whose name may be specified with the
20260 @code{set history filename} command. By default, this option is disabled.
20262 @item set history save off
20263 Stop recording command history in a file.
20265 @cindex history size
20266 @kindex set history size
20267 @cindex @env{HISTSIZE}, environment variable
20268 @item set history size @var{size}
20269 Set the number of commands which @value{GDBN} keeps in its history list.
20270 This defaults to the value of the environment variable
20271 @code{HISTSIZE}, or to 256 if this variable is not set.
20274 History expansion assigns special meaning to the character @kbd{!}.
20275 @ifset SYSTEM_READLINE
20276 @xref{Event Designators, , , history, GNU History Library},
20278 @ifclear SYSTEM_READLINE
20279 @xref{Event Designators},
20283 @cindex history expansion, turn on/off
20284 Since @kbd{!} is also the logical not operator in C, history expansion
20285 is off by default. If you decide to enable history expansion with the
20286 @code{set history expansion on} command, you may sometimes need to
20287 follow @kbd{!} (when it is used as logical not, in an expression) with
20288 a space or a tab to prevent it from being expanded. The readline
20289 history facilities do not attempt substitution on the strings
20290 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20292 The commands to control history expansion are:
20295 @item set history expansion on
20296 @itemx set history expansion
20297 @kindex set history expansion
20298 Enable history expansion. History expansion is off by default.
20300 @item set history expansion off
20301 Disable history expansion.
20304 @kindex show history
20306 @itemx show history filename
20307 @itemx show history save
20308 @itemx show history size
20309 @itemx show history expansion
20310 These commands display the state of the @value{GDBN} history parameters.
20311 @code{show history} by itself displays all four states.
20316 @kindex show commands
20317 @cindex show last commands
20318 @cindex display command history
20319 @item show commands
20320 Display the last ten commands in the command history.
20322 @item show commands @var{n}
20323 Print ten commands centered on command number @var{n}.
20325 @item show commands +
20326 Print ten commands just after the commands last printed.
20330 @section Screen Size
20331 @cindex size of screen
20332 @cindex pauses in output
20334 Certain commands to @value{GDBN} may produce large amounts of
20335 information output to the screen. To help you read all of it,
20336 @value{GDBN} pauses and asks you for input at the end of each page of
20337 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20338 to discard the remaining output. Also, the screen width setting
20339 determines when to wrap lines of output. Depending on what is being
20340 printed, @value{GDBN} tries to break the line at a readable place,
20341 rather than simply letting it overflow onto the following line.
20343 Normally @value{GDBN} knows the size of the screen from the terminal
20344 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20345 together with the value of the @code{TERM} environment variable and the
20346 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20347 you can override it with the @code{set height} and @code{set
20354 @kindex show height
20355 @item set height @var{lpp}
20357 @itemx set width @var{cpl}
20359 These @code{set} commands specify a screen height of @var{lpp} lines and
20360 a screen width of @var{cpl} characters. The associated @code{show}
20361 commands display the current settings.
20363 If you specify a height of zero lines, @value{GDBN} does not pause during
20364 output no matter how long the output is. This is useful if output is to a
20365 file or to an editor buffer.
20367 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20368 from wrapping its output.
20370 @item set pagination on
20371 @itemx set pagination off
20372 @kindex set pagination
20373 Turn the output pagination on or off; the default is on. Turning
20374 pagination off is the alternative to @code{set height 0}. Note that
20375 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20376 Options, -batch}) also automatically disables pagination.
20378 @item show pagination
20379 @kindex show pagination
20380 Show the current pagination mode.
20385 @cindex number representation
20386 @cindex entering numbers
20388 You can always enter numbers in octal, decimal, or hexadecimal in
20389 @value{GDBN} by the usual conventions: octal numbers begin with
20390 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20391 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20392 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20393 10; likewise, the default display for numbers---when no particular
20394 format is specified---is base 10. You can change the default base for
20395 both input and output with the commands described below.
20398 @kindex set input-radix
20399 @item set input-radix @var{base}
20400 Set the default base for numeric input. Supported choices
20401 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20402 specified either unambiguously or using the current input radix; for
20406 set input-radix 012
20407 set input-radix 10.
20408 set input-radix 0xa
20412 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20413 leaves the input radix unchanged, no matter what it was, since
20414 @samp{10}, being without any leading or trailing signs of its base, is
20415 interpreted in the current radix. Thus, if the current radix is 16,
20416 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20419 @kindex set output-radix
20420 @item set output-radix @var{base}
20421 Set the default base for numeric display. Supported choices
20422 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20423 specified either unambiguously or using the current input radix.
20425 @kindex show input-radix
20426 @item show input-radix
20427 Display the current default base for numeric input.
20429 @kindex show output-radix
20430 @item show output-radix
20431 Display the current default base for numeric display.
20433 @item set radix @r{[}@var{base}@r{]}
20437 These commands set and show the default base for both input and output
20438 of numbers. @code{set radix} sets the radix of input and output to
20439 the same base; without an argument, it resets the radix back to its
20440 default value of 10.
20445 @section Configuring the Current ABI
20447 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20448 application automatically. However, sometimes you need to override its
20449 conclusions. Use these commands to manage @value{GDBN}'s view of the
20456 One @value{GDBN} configuration can debug binaries for multiple operating
20457 system targets, either via remote debugging or native emulation.
20458 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20459 but you can override its conclusion using the @code{set osabi} command.
20460 One example where this is useful is in debugging of binaries which use
20461 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20462 not have the same identifying marks that the standard C library for your
20467 Show the OS ABI currently in use.
20470 With no argument, show the list of registered available OS ABI's.
20472 @item set osabi @var{abi}
20473 Set the current OS ABI to @var{abi}.
20476 @cindex float promotion
20478 Generally, the way that an argument of type @code{float} is passed to a
20479 function depends on whether the function is prototyped. For a prototyped
20480 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20481 according to the architecture's convention for @code{float}. For unprototyped
20482 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20483 @code{double} and then passed.
20485 Unfortunately, some forms of debug information do not reliably indicate whether
20486 a function is prototyped. If @value{GDBN} calls a function that is not marked
20487 as prototyped, it consults @kbd{set coerce-float-to-double}.
20490 @kindex set coerce-float-to-double
20491 @item set coerce-float-to-double
20492 @itemx set coerce-float-to-double on
20493 Arguments of type @code{float} will be promoted to @code{double} when passed
20494 to an unprototyped function. This is the default setting.
20496 @item set coerce-float-to-double off
20497 Arguments of type @code{float} will be passed directly to unprototyped
20500 @kindex show coerce-float-to-double
20501 @item show coerce-float-to-double
20502 Show the current setting of promoting @code{float} to @code{double}.
20506 @kindex show cp-abi
20507 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20508 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20509 used to build your application. @value{GDBN} only fully supports
20510 programs with a single C@t{++} ABI; if your program contains code using
20511 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20512 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20513 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20514 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20515 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20516 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20521 Show the C@t{++} ABI currently in use.
20524 With no argument, show the list of supported C@t{++} ABI's.
20526 @item set cp-abi @var{abi}
20527 @itemx set cp-abi auto
20528 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20531 @node Messages/Warnings
20532 @section Optional Warnings and Messages
20534 @cindex verbose operation
20535 @cindex optional warnings
20536 By default, @value{GDBN} is silent about its inner workings. If you are
20537 running on a slow machine, you may want to use the @code{set verbose}
20538 command. This makes @value{GDBN} tell you when it does a lengthy
20539 internal operation, so you will not think it has crashed.
20541 Currently, the messages controlled by @code{set verbose} are those
20542 which announce that the symbol table for a source file is being read;
20543 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20546 @kindex set verbose
20547 @item set verbose on
20548 Enables @value{GDBN} output of certain informational messages.
20550 @item set verbose off
20551 Disables @value{GDBN} output of certain informational messages.
20553 @kindex show verbose
20555 Displays whether @code{set verbose} is on or off.
20558 By default, if @value{GDBN} encounters bugs in the symbol table of an
20559 object file, it is silent; but if you are debugging a compiler, you may
20560 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20565 @kindex set complaints
20566 @item set complaints @var{limit}
20567 Permits @value{GDBN} to output @var{limit} complaints about each type of
20568 unusual symbols before becoming silent about the problem. Set
20569 @var{limit} to zero to suppress all complaints; set it to a large number
20570 to prevent complaints from being suppressed.
20572 @kindex show complaints
20573 @item show complaints
20574 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20578 @anchor{confirmation requests}
20579 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20580 lot of stupid questions to confirm certain commands. For example, if
20581 you try to run a program which is already running:
20585 The program being debugged has been started already.
20586 Start it from the beginning? (y or n)
20589 If you are willing to unflinchingly face the consequences of your own
20590 commands, you can disable this ``feature'':
20594 @kindex set confirm
20596 @cindex confirmation
20597 @cindex stupid questions
20598 @item set confirm off
20599 Disables confirmation requests. Note that running @value{GDBN} with
20600 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20601 automatically disables confirmation requests.
20603 @item set confirm on
20604 Enables confirmation requests (the default).
20606 @kindex show confirm
20608 Displays state of confirmation requests.
20612 @cindex command tracing
20613 If you need to debug user-defined commands or sourced files you may find it
20614 useful to enable @dfn{command tracing}. In this mode each command will be
20615 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20616 quantity denoting the call depth of each command.
20619 @kindex set trace-commands
20620 @cindex command scripts, debugging
20621 @item set trace-commands on
20622 Enable command tracing.
20623 @item set trace-commands off
20624 Disable command tracing.
20625 @item show trace-commands
20626 Display the current state of command tracing.
20629 @node Debugging Output
20630 @section Optional Messages about Internal Happenings
20631 @cindex optional debugging messages
20633 @value{GDBN} has commands that enable optional debugging messages from
20634 various @value{GDBN} subsystems; normally these commands are of
20635 interest to @value{GDBN} maintainers, or when reporting a bug. This
20636 section documents those commands.
20639 @kindex set exec-done-display
20640 @item set exec-done-display
20641 Turns on or off the notification of asynchronous commands'
20642 completion. When on, @value{GDBN} will print a message when an
20643 asynchronous command finishes its execution. The default is off.
20644 @kindex show exec-done-display
20645 @item show exec-done-display
20646 Displays the current setting of asynchronous command completion
20649 @cindex gdbarch debugging info
20650 @cindex architecture debugging info
20651 @item set debug arch
20652 Turns on or off display of gdbarch debugging info. The default is off
20654 @item show debug arch
20655 Displays the current state of displaying gdbarch debugging info.
20656 @item set debug aix-thread
20657 @cindex AIX threads
20658 Display debugging messages about inner workings of the AIX thread
20660 @item show debug aix-thread
20661 Show the current state of AIX thread debugging info display.
20662 @item set debug check-physname
20664 Check the results of the ``physname'' computation. When reading DWARF
20665 debugging information for C@t{++}, @value{GDBN} attempts to compute
20666 each entity's name. @value{GDBN} can do this computation in two
20667 different ways, depending on exactly what information is present.
20668 When enabled, this setting causes @value{GDBN} to compute the names
20669 both ways and display any discrepancies.
20670 @item show debug check-physname
20671 Show the current state of ``physname'' checking.
20672 @item set debug dwarf2-die
20673 @cindex DWARF2 DIEs
20674 Dump DWARF2 DIEs after they are read in.
20675 The value is the number of nesting levels to print.
20676 A value of zero turns off the display.
20677 @item show debug dwarf2-die
20678 Show the current state of DWARF2 DIE debugging.
20679 @item set debug displaced
20680 @cindex displaced stepping debugging info
20681 Turns on or off display of @value{GDBN} debugging info for the
20682 displaced stepping support. The default is off.
20683 @item show debug displaced
20684 Displays the current state of displaying @value{GDBN} debugging info
20685 related to displaced stepping.
20686 @item set debug event
20687 @cindex event debugging info
20688 Turns on or off display of @value{GDBN} event debugging info. The
20690 @item show debug event
20691 Displays the current state of displaying @value{GDBN} event debugging
20693 @item set debug expression
20694 @cindex expression debugging info
20695 Turns on or off display of debugging info about @value{GDBN}
20696 expression parsing. The default is off.
20697 @item show debug expression
20698 Displays the current state of displaying debugging info about
20699 @value{GDBN} expression parsing.
20700 @item set debug frame
20701 @cindex frame debugging info
20702 Turns on or off display of @value{GDBN} frame debugging info. The
20704 @item show debug frame
20705 Displays the current state of displaying @value{GDBN} frame debugging
20707 @item set debug gnu-nat
20708 @cindex @sc{gnu}/Hurd debug messages
20709 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20710 @item show debug gnu-nat
20711 Show the current state of @sc{gnu}/Hurd debugging messages.
20712 @item set debug infrun
20713 @cindex inferior debugging info
20714 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20715 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20716 for implementing operations such as single-stepping the inferior.
20717 @item show debug infrun
20718 Displays the current state of @value{GDBN} inferior debugging.
20719 @item set debug jit
20720 @cindex just-in-time compilation, debugging messages
20721 Turns on or off debugging messages from JIT debug support.
20722 @item show debug jit
20723 Displays the current state of @value{GDBN} JIT debugging.
20724 @item set debug lin-lwp
20725 @cindex @sc{gnu}/Linux LWP debug messages
20726 @cindex Linux lightweight processes
20727 Turns on or off debugging messages from the Linux LWP debug support.
20728 @item show debug lin-lwp
20729 Show the current state of Linux LWP debugging messages.
20730 @item set debug observer
20731 @cindex observer debugging info
20732 Turns on or off display of @value{GDBN} observer debugging. This
20733 includes info such as the notification of observable events.
20734 @item show debug observer
20735 Displays the current state of observer debugging.
20736 @item set debug overload
20737 @cindex C@t{++} overload debugging info
20738 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20739 info. This includes info such as ranking of functions, etc. The default
20741 @item show debug overload
20742 Displays the current state of displaying @value{GDBN} C@t{++} overload
20744 @cindex expression parser, debugging info
20745 @cindex debug expression parser
20746 @item set debug parser
20747 Turns on or off the display of expression parser debugging output.
20748 Internally, this sets the @code{yydebug} variable in the expression
20749 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20750 details. The default is off.
20751 @item show debug parser
20752 Show the current state of expression parser debugging.
20753 @cindex packets, reporting on stdout
20754 @cindex serial connections, debugging
20755 @cindex debug remote protocol
20756 @cindex remote protocol debugging
20757 @cindex display remote packets
20758 @item set debug remote
20759 Turns on or off display of reports on all packets sent back and forth across
20760 the serial line to the remote machine. The info is printed on the
20761 @value{GDBN} standard output stream. The default is off.
20762 @item show debug remote
20763 Displays the state of display of remote packets.
20764 @item set debug serial
20765 Turns on or off display of @value{GDBN} serial debugging info. The
20767 @item show debug serial
20768 Displays the current state of displaying @value{GDBN} serial debugging
20770 @item set debug solib-frv
20771 @cindex FR-V shared-library debugging
20772 Turns on or off debugging messages for FR-V shared-library code.
20773 @item show debug solib-frv
20774 Display the current state of FR-V shared-library code debugging
20776 @item set debug target
20777 @cindex target debugging info
20778 Turns on or off display of @value{GDBN} target debugging info. This info
20779 includes what is going on at the target level of GDB, as it happens. The
20780 default is 0. Set it to 1 to track events, and to 2 to also track the
20781 value of large memory transfers. Changes to this flag do not take effect
20782 until the next time you connect to a target or use the @code{run} command.
20783 @item show debug target
20784 Displays the current state of displaying @value{GDBN} target debugging
20786 @item set debug timestamp
20787 @cindex timestampping debugging info
20788 Turns on or off display of timestamps with @value{GDBN} debugging info.
20789 When enabled, seconds and microseconds are displayed before each debugging
20791 @item show debug timestamp
20792 Displays the current state of displaying timestamps with @value{GDBN}
20794 @item set debugvarobj
20795 @cindex variable object debugging info
20796 Turns on or off display of @value{GDBN} variable object debugging
20797 info. The default is off.
20798 @item show debugvarobj
20799 Displays the current state of displaying @value{GDBN} variable object
20801 @item set debug xml
20802 @cindex XML parser debugging
20803 Turns on or off debugging messages for built-in XML parsers.
20804 @item show debug xml
20805 Displays the current state of XML debugging messages.
20808 @node Other Misc Settings
20809 @section Other Miscellaneous Settings
20810 @cindex miscellaneous settings
20813 @kindex set interactive-mode
20814 @item set interactive-mode
20815 If @code{on}, forces @value{GDBN} to assume that GDB was started
20816 in a terminal. In practice, this means that @value{GDBN} should wait
20817 for the user to answer queries generated by commands entered at
20818 the command prompt. If @code{off}, forces @value{GDBN} to operate
20819 in the opposite mode, and it uses the default answers to all queries.
20820 If @code{auto} (the default), @value{GDBN} tries to determine whether
20821 its standard input is a terminal, and works in interactive-mode if it
20822 is, non-interactively otherwise.
20824 In the vast majority of cases, the debugger should be able to guess
20825 correctly which mode should be used. But this setting can be useful
20826 in certain specific cases, such as running a MinGW @value{GDBN}
20827 inside a cygwin window.
20829 @kindex show interactive-mode
20830 @item show interactive-mode
20831 Displays whether the debugger is operating in interactive mode or not.
20834 @node Extending GDB
20835 @chapter Extending @value{GDBN}
20836 @cindex extending GDB
20838 @value{GDBN} provides three mechanisms for extension. The first is based
20839 on composition of @value{GDBN} commands, the second is based on the
20840 Python scripting language, and the third is for defining new aliases of
20843 To facilitate the use of the first two extensions, @value{GDBN} is capable
20844 of evaluating the contents of a file. When doing so, @value{GDBN}
20845 can recognize which scripting language is being used by looking at
20846 the filename extension. Files with an unrecognized filename extension
20847 are always treated as a @value{GDBN} Command Files.
20848 @xref{Command Files,, Command files}.
20850 You can control how @value{GDBN} evaluates these files with the following
20854 @kindex set script-extension
20855 @kindex show script-extension
20856 @item set script-extension off
20857 All scripts are always evaluated as @value{GDBN} Command Files.
20859 @item set script-extension soft
20860 The debugger determines the scripting language based on filename
20861 extension. If this scripting language is supported, @value{GDBN}
20862 evaluates the script using that language. Otherwise, it evaluates
20863 the file as a @value{GDBN} Command File.
20865 @item set script-extension strict
20866 The debugger determines the scripting language based on filename
20867 extension, and evaluates the script using that language. If the
20868 language is not supported, then the evaluation fails.
20870 @item show script-extension
20871 Display the current value of the @code{script-extension} option.
20876 * Sequences:: Canned Sequences of Commands
20877 * Python:: Scripting @value{GDBN} using Python
20878 * Aliases:: Creating new spellings of existing commands
20882 @section Canned Sequences of Commands
20884 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20885 Command Lists}), @value{GDBN} provides two ways to store sequences of
20886 commands for execution as a unit: user-defined commands and command
20890 * Define:: How to define your own commands
20891 * Hooks:: Hooks for user-defined commands
20892 * Command Files:: How to write scripts of commands to be stored in a file
20893 * Output:: Commands for controlled output
20897 @subsection User-defined Commands
20899 @cindex user-defined command
20900 @cindex arguments, to user-defined commands
20901 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20902 which you assign a new name as a command. This is done with the
20903 @code{define} command. User commands may accept up to 10 arguments
20904 separated by whitespace. Arguments are accessed within the user command
20905 via @code{$arg0@dots{}$arg9}. A trivial example:
20909 print $arg0 + $arg1 + $arg2
20914 To execute the command use:
20921 This defines the command @code{adder}, which prints the sum of
20922 its three arguments. Note the arguments are text substitutions, so they may
20923 reference variables, use complex expressions, or even perform inferior
20926 @cindex argument count in user-defined commands
20927 @cindex how many arguments (user-defined commands)
20928 In addition, @code{$argc} may be used to find out how many arguments have
20929 been passed. This expands to a number in the range 0@dots{}10.
20934 print $arg0 + $arg1
20937 print $arg0 + $arg1 + $arg2
20945 @item define @var{commandname}
20946 Define a command named @var{commandname}. If there is already a command
20947 by that name, you are asked to confirm that you want to redefine it.
20948 @var{commandname} may be a bare command name consisting of letters,
20949 numbers, dashes, and underscores. It may also start with any predefined
20950 prefix command. For example, @samp{define target my-target} creates
20951 a user-defined @samp{target my-target} command.
20953 The definition of the command is made up of other @value{GDBN} command lines,
20954 which are given following the @code{define} command. The end of these
20955 commands is marked by a line containing @code{end}.
20958 @kindex end@r{ (user-defined commands)}
20959 @item document @var{commandname}
20960 Document the user-defined command @var{commandname}, so that it can be
20961 accessed by @code{help}. The command @var{commandname} must already be
20962 defined. This command reads lines of documentation just as @code{define}
20963 reads the lines of the command definition, ending with @code{end}.
20964 After the @code{document} command is finished, @code{help} on command
20965 @var{commandname} displays the documentation you have written.
20967 You may use the @code{document} command again to change the
20968 documentation of a command. Redefining the command with @code{define}
20969 does not change the documentation.
20971 @kindex dont-repeat
20972 @cindex don't repeat command
20974 Used inside a user-defined command, this tells @value{GDBN} that this
20975 command should not be repeated when the user hits @key{RET}
20976 (@pxref{Command Syntax, repeat last command}).
20978 @kindex help user-defined
20979 @item help user-defined
20980 List all user-defined commands, with the first line of the documentation
20985 @itemx show user @var{commandname}
20986 Display the @value{GDBN} commands used to define @var{commandname} (but
20987 not its documentation). If no @var{commandname} is given, display the
20988 definitions for all user-defined commands.
20990 @cindex infinite recursion in user-defined commands
20991 @kindex show max-user-call-depth
20992 @kindex set max-user-call-depth
20993 @item show max-user-call-depth
20994 @itemx set max-user-call-depth
20995 The value of @code{max-user-call-depth} controls how many recursion
20996 levels are allowed in user-defined commands before @value{GDBN} suspects an
20997 infinite recursion and aborts the command.
21000 In addition to the above commands, user-defined commands frequently
21001 use control flow commands, described in @ref{Command Files}.
21003 When user-defined commands are executed, the
21004 commands of the definition are not printed. An error in any command
21005 stops execution of the user-defined command.
21007 If used interactively, commands that would ask for confirmation proceed
21008 without asking when used inside a user-defined command. Many @value{GDBN}
21009 commands that normally print messages to say what they are doing omit the
21010 messages when used in a user-defined command.
21013 @subsection User-defined Command Hooks
21014 @cindex command hooks
21015 @cindex hooks, for commands
21016 @cindex hooks, pre-command
21019 You may define @dfn{hooks}, which are a special kind of user-defined
21020 command. Whenever you run the command @samp{foo}, if the user-defined
21021 command @samp{hook-foo} exists, it is executed (with no arguments)
21022 before that command.
21024 @cindex hooks, post-command
21026 A hook may also be defined which is run after the command you executed.
21027 Whenever you run the command @samp{foo}, if the user-defined command
21028 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21029 that command. Post-execution hooks may exist simultaneously with
21030 pre-execution hooks, for the same command.
21032 It is valid for a hook to call the command which it hooks. If this
21033 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21035 @c It would be nice if hookpost could be passed a parameter indicating
21036 @c if the command it hooks executed properly or not. FIXME!
21038 @kindex stop@r{, a pseudo-command}
21039 In addition, a pseudo-command, @samp{stop} exists. Defining
21040 (@samp{hook-stop}) makes the associated commands execute every time
21041 execution stops in your program: before breakpoint commands are run,
21042 displays are printed, or the stack frame is printed.
21044 For example, to ignore @code{SIGALRM} signals while
21045 single-stepping, but treat them normally during normal execution,
21050 handle SIGALRM nopass
21054 handle SIGALRM pass
21057 define hook-continue
21058 handle SIGALRM pass
21062 As a further example, to hook at the beginning and end of the @code{echo}
21063 command, and to add extra text to the beginning and end of the message,
21071 define hookpost-echo
21075 (@value{GDBP}) echo Hello World
21076 <<<---Hello World--->>>
21081 You can define a hook for any single-word command in @value{GDBN}, but
21082 not for command aliases; you should define a hook for the basic command
21083 name, e.g.@: @code{backtrace} rather than @code{bt}.
21084 @c FIXME! So how does Joe User discover whether a command is an alias
21086 You can hook a multi-word command by adding @code{hook-} or
21087 @code{hookpost-} to the last word of the command, e.g.@:
21088 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21090 If an error occurs during the execution of your hook, execution of
21091 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21092 (before the command that you actually typed had a chance to run).
21094 If you try to define a hook which does not match any known command, you
21095 get a warning from the @code{define} command.
21097 @node Command Files
21098 @subsection Command Files
21100 @cindex command files
21101 @cindex scripting commands
21102 A command file for @value{GDBN} is a text file made of lines that are
21103 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21104 also be included. An empty line in a command file does nothing; it
21105 does not mean to repeat the last command, as it would from the
21108 You can request the execution of a command file with the @code{source}
21109 command. Note that the @code{source} command is also used to evaluate
21110 scripts that are not Command Files. The exact behavior can be configured
21111 using the @code{script-extension} setting.
21112 @xref{Extending GDB,, Extending GDB}.
21116 @cindex execute commands from a file
21117 @item source [-s] [-v] @var{filename}
21118 Execute the command file @var{filename}.
21121 The lines in a command file are generally executed sequentially,
21122 unless the order of execution is changed by one of the
21123 @emph{flow-control commands} described below. The commands are not
21124 printed as they are executed. An error in any command terminates
21125 execution of the command file and control is returned to the console.
21127 @value{GDBN} first searches for @var{filename} in the current directory.
21128 If the file is not found there, and @var{filename} does not specify a
21129 directory, then @value{GDBN} also looks for the file on the source search path
21130 (specified with the @samp{directory} command);
21131 except that @file{$cdir} is not searched because the compilation directory
21132 is not relevant to scripts.
21134 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21135 on the search path even if @var{filename} specifies a directory.
21136 The search is done by appending @var{filename} to each element of the
21137 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21138 and the search path contains @file{/home/user} then @value{GDBN} will
21139 look for the script @file{/home/user/mylib/myscript}.
21140 The search is also done if @var{filename} is an absolute path.
21141 For example, if @var{filename} is @file{/tmp/myscript} and
21142 the search path contains @file{/home/user} then @value{GDBN} will
21143 look for the script @file{/home/user/tmp/myscript}.
21144 For DOS-like systems, if @var{filename} contains a drive specification,
21145 it is stripped before concatenation. For example, if @var{filename} is
21146 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21147 will look for the script @file{c:/tmp/myscript}.
21149 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21150 each command as it is executed. The option must be given before
21151 @var{filename}, and is interpreted as part of the filename anywhere else.
21153 Commands that would ask for confirmation if used interactively proceed
21154 without asking when used in a command file. Many @value{GDBN} commands that
21155 normally print messages to say what they are doing omit the messages
21156 when called from command files.
21158 @value{GDBN} also accepts command input from standard input. In this
21159 mode, normal output goes to standard output and error output goes to
21160 standard error. Errors in a command file supplied on standard input do
21161 not terminate execution of the command file---execution continues with
21165 gdb < cmds > log 2>&1
21168 (The syntax above will vary depending on the shell used.) This example
21169 will execute commands from the file @file{cmds}. All output and errors
21170 would be directed to @file{log}.
21172 Since commands stored on command files tend to be more general than
21173 commands typed interactively, they frequently need to deal with
21174 complicated situations, such as different or unexpected values of
21175 variables and symbols, changes in how the program being debugged is
21176 built, etc. @value{GDBN} provides a set of flow-control commands to
21177 deal with these complexities. Using these commands, you can write
21178 complex scripts that loop over data structures, execute commands
21179 conditionally, etc.
21186 This command allows to include in your script conditionally executed
21187 commands. The @code{if} command takes a single argument, which is an
21188 expression to evaluate. It is followed by a series of commands that
21189 are executed only if the expression is true (its value is nonzero).
21190 There can then optionally be an @code{else} line, followed by a series
21191 of commands that are only executed if the expression was false. The
21192 end of the list is marked by a line containing @code{end}.
21196 This command allows to write loops. Its syntax is similar to
21197 @code{if}: the command takes a single argument, which is an expression
21198 to evaluate, and must be followed by the commands to execute, one per
21199 line, terminated by an @code{end}. These commands are called the
21200 @dfn{body} of the loop. The commands in the body of @code{while} are
21201 executed repeatedly as long as the expression evaluates to true.
21205 This command exits the @code{while} loop in whose body it is included.
21206 Execution of the script continues after that @code{while}s @code{end}
21209 @kindex loop_continue
21210 @item loop_continue
21211 This command skips the execution of the rest of the body of commands
21212 in the @code{while} loop in whose body it is included. Execution
21213 branches to the beginning of the @code{while} loop, where it evaluates
21214 the controlling expression.
21216 @kindex end@r{ (if/else/while commands)}
21218 Terminate the block of commands that are the body of @code{if},
21219 @code{else}, or @code{while} flow-control commands.
21224 @subsection Commands for Controlled Output
21226 During the execution of a command file or a user-defined command, normal
21227 @value{GDBN} output is suppressed; the only output that appears is what is
21228 explicitly printed by the commands in the definition. This section
21229 describes three commands useful for generating exactly the output you
21234 @item echo @var{text}
21235 @c I do not consider backslash-space a standard C escape sequence
21236 @c because it is not in ANSI.
21237 Print @var{text}. Nonprinting characters can be included in
21238 @var{text} using C escape sequences, such as @samp{\n} to print a
21239 newline. @strong{No newline is printed unless you specify one.}
21240 In addition to the standard C escape sequences, a backslash followed
21241 by a space stands for a space. This is useful for displaying a
21242 string with spaces at the beginning or the end, since leading and
21243 trailing spaces are otherwise trimmed from all arguments.
21244 To print @samp{@w{ }and foo =@w{ }}, use the command
21245 @samp{echo \@w{ }and foo = \@w{ }}.
21247 A backslash at the end of @var{text} can be used, as in C, to continue
21248 the command onto subsequent lines. For example,
21251 echo This is some text\n\
21252 which is continued\n\
21253 onto several lines.\n
21256 produces the same output as
21259 echo This is some text\n
21260 echo which is continued\n
21261 echo onto several lines.\n
21265 @item output @var{expression}
21266 Print the value of @var{expression} and nothing but that value: no
21267 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21268 value history either. @xref{Expressions, ,Expressions}, for more information
21271 @item output/@var{fmt} @var{expression}
21272 Print the value of @var{expression} in format @var{fmt}. You can use
21273 the same formats as for @code{print}. @xref{Output Formats,,Output
21274 Formats}, for more information.
21277 @item printf @var{template}, @var{expressions}@dots{}
21278 Print the values of one or more @var{expressions} under the control of
21279 the string @var{template}. To print several values, make
21280 @var{expressions} be a comma-separated list of individual expressions,
21281 which may be either numbers or pointers. Their values are printed as
21282 specified by @var{template}, exactly as a C program would do by
21283 executing the code below:
21286 printf (@var{template}, @var{expressions}@dots{});
21289 As in @code{C} @code{printf}, ordinary characters in @var{template}
21290 are printed verbatim, while @dfn{conversion specification} introduced
21291 by the @samp{%} character cause subsequent @var{expressions} to be
21292 evaluated, their values converted and formatted according to type and
21293 style information encoded in the conversion specifications, and then
21296 For example, you can print two values in hex like this:
21299 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21302 @code{printf} supports all the standard @code{C} conversion
21303 specifications, including the flags and modifiers between the @samp{%}
21304 character and the conversion letter, with the following exceptions:
21308 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21311 The modifier @samp{*} is not supported for specifying precision or
21315 The @samp{'} flag (for separation of digits into groups according to
21316 @code{LC_NUMERIC'}) is not supported.
21319 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21323 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21326 The conversion letters @samp{a} and @samp{A} are not supported.
21330 Note that the @samp{ll} type modifier is supported only if the
21331 underlying @code{C} implementation used to build @value{GDBN} supports
21332 the @code{long long int} type, and the @samp{L} type modifier is
21333 supported only if @code{long double} type is available.
21335 As in @code{C}, @code{printf} supports simple backslash-escape
21336 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21337 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21338 single character. Octal and hexadecimal escape sequences are not
21341 Additionally, @code{printf} supports conversion specifications for DFP
21342 (@dfn{Decimal Floating Point}) types using the following length modifiers
21343 together with a floating point specifier.
21348 @samp{H} for printing @code{Decimal32} types.
21351 @samp{D} for printing @code{Decimal64} types.
21354 @samp{DD} for printing @code{Decimal128} types.
21357 If the underlying @code{C} implementation used to build @value{GDBN} has
21358 support for the three length modifiers for DFP types, other modifiers
21359 such as width and precision will also be available for @value{GDBN} to use.
21361 In case there is no such @code{C} support, no additional modifiers will be
21362 available and the value will be printed in the standard way.
21364 Here's an example of printing DFP types using the above conversion letters:
21366 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21370 @item eval @var{template}, @var{expressions}@dots{}
21371 Convert the values of one or more @var{expressions} under the control of
21372 the string @var{template} to a command line, and call it.
21377 @section Scripting @value{GDBN} using Python
21378 @cindex python scripting
21379 @cindex scripting with python
21381 You can script @value{GDBN} using the @uref{http://www.python.org/,
21382 Python programming language}. This feature is available only if
21383 @value{GDBN} was configured using @option{--with-python}.
21385 @cindex python directory
21386 Python scripts used by @value{GDBN} should be installed in
21387 @file{@var{data-directory}/python}, where @var{data-directory} is
21388 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21389 This directory, known as the @dfn{python directory},
21390 is automatically added to the Python Search Path in order to allow
21391 the Python interpreter to locate all scripts installed at this location.
21393 Additionally, @value{GDBN} commands and convenience functions which
21394 are written in Python and are located in the
21395 @file{@var{data-directory}/python/gdb/command} or
21396 @file{@var{data-directory}/python/gdb/function} directories are
21397 automatically imported when @value{GDBN} starts.
21400 * Python Commands:: Accessing Python from @value{GDBN}.
21401 * Python API:: Accessing @value{GDBN} from Python.
21402 * Auto-loading:: Automatically loading Python code.
21403 * Python modules:: Python modules provided by @value{GDBN}.
21406 @node Python Commands
21407 @subsection Python Commands
21408 @cindex python commands
21409 @cindex commands to access python
21411 @value{GDBN} provides one command for accessing the Python interpreter,
21412 and one related setting:
21416 @item python @r{[}@var{code}@r{]}
21417 The @code{python} command can be used to evaluate Python code.
21419 If given an argument, the @code{python} command will evaluate the
21420 argument as a Python command. For example:
21423 (@value{GDBP}) python print 23
21427 If you do not provide an argument to @code{python}, it will act as a
21428 multi-line command, like @code{define}. In this case, the Python
21429 script is made up of subsequent command lines, given after the
21430 @code{python} command. This command list is terminated using a line
21431 containing @code{end}. For example:
21434 (@value{GDBP}) python
21436 End with a line saying just "end".
21442 @kindex maint set python print-stack
21443 @item maint set python print-stack
21444 This command is now deprecated. Instead use @code{set python
21447 @kindex set python print-stack
21448 @item set python print-stack
21449 By default, @value{GDBN} will not print a stack trace when an error
21450 occurs in a Python script. This can be controlled using @code{set
21451 python print-stack}: if @code{on}, then Python stack printing is
21452 enabled; if @code{off}, the default, then Python stack printing is
21456 It is also possible to execute a Python script from the @value{GDBN}
21460 @item source @file{script-name}
21461 The script name must end with @samp{.py} and @value{GDBN} must be configured
21462 to recognize the script language based on filename extension using
21463 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21465 @item python execfile ("script-name")
21466 This method is based on the @code{execfile} Python built-in function,
21467 and thus is always available.
21471 @subsection Python API
21473 @cindex programming in python
21475 @cindex python stdout
21476 @cindex python pagination
21477 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21478 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21479 A Python program which outputs to one of these streams may have its
21480 output interrupted by the user (@pxref{Screen Size}). In this
21481 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21484 * Basic Python:: Basic Python Functions.
21485 * Exception Handling:: How Python exceptions are translated.
21486 * Values From Inferior:: Python representation of values.
21487 * Types In Python:: Python representation of types.
21488 * Pretty Printing API:: Pretty-printing values.
21489 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21490 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21491 * Inferiors In Python:: Python representation of inferiors (processes)
21492 * Events In Python:: Listening for events from @value{GDBN}.
21493 * Threads In Python:: Accessing inferior threads from Python.
21494 * Commands In Python:: Implementing new commands in Python.
21495 * Parameters In Python:: Adding new @value{GDBN} parameters.
21496 * Functions In Python:: Writing new convenience functions.
21497 * Progspaces In Python:: Program spaces.
21498 * Objfiles In Python:: Object files.
21499 * Frames In Python:: Accessing inferior stack frames from Python.
21500 * Blocks In Python:: Accessing frame blocks from Python.
21501 * Symbols In Python:: Python representation of symbols.
21502 * Symbol Tables In Python:: Python representation of symbol tables.
21503 * Lazy Strings In Python:: Python representation of lazy strings.
21504 * Breakpoints In Python:: Manipulating breakpoints using Python.
21508 @subsubsection Basic Python
21510 @cindex python functions
21511 @cindex python module
21513 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21514 methods and classes added by @value{GDBN} are placed in this module.
21515 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21516 use in all scripts evaluated by the @code{python} command.
21518 @findex gdb.PYTHONDIR
21519 @defvar gdb.PYTHONDIR
21520 A string containing the python directory (@pxref{Python}).
21523 @findex gdb.execute
21524 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21525 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21526 If a GDB exception happens while @var{command} runs, it is
21527 translated as described in @ref{Exception Handling,,Exception Handling}.
21529 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21530 command as having originated from the user invoking it interactively.
21531 It must be a boolean value. If omitted, it defaults to @code{False}.
21533 By default, any output produced by @var{command} is sent to
21534 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21535 @code{True}, then output will be collected by @code{gdb.execute} and
21536 returned as a string. The default is @code{False}, in which case the
21537 return value is @code{None}. If @var{to_string} is @code{True}, the
21538 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21539 and height, and its pagination will be disabled; @pxref{Screen Size}.
21542 @findex gdb.breakpoints
21543 @defun gdb.breakpoints ()
21544 Return a sequence holding all of @value{GDBN}'s breakpoints.
21545 @xref{Breakpoints In Python}, for more information.
21548 @findex gdb.parameter
21549 @defun gdb.parameter (parameter)
21550 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21551 string naming the parameter to look up; @var{parameter} may contain
21552 spaces if the parameter has a multi-part name. For example,
21553 @samp{print object} is a valid parameter name.
21555 If the named parameter does not exist, this function throws a
21556 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21557 parameter's value is converted to a Python value of the appropriate
21558 type, and returned.
21561 @findex gdb.history
21562 @defun gdb.history (number)
21563 Return a value from @value{GDBN}'s value history (@pxref{Value
21564 History}). @var{number} indicates which history element to return.
21565 If @var{number} is negative, then @value{GDBN} will take its absolute value
21566 and count backward from the last element (i.e., the most recent element) to
21567 find the value to return. If @var{number} is zero, then @value{GDBN} will
21568 return the most recent element. If the element specified by @var{number}
21569 doesn't exist in the value history, a @code{gdb.error} exception will be
21572 If no exception is raised, the return value is always an instance of
21573 @code{gdb.Value} (@pxref{Values From Inferior}).
21576 @findex gdb.parse_and_eval
21577 @defun gdb.parse_and_eval (expression)
21578 Parse @var{expression} as an expression in the current language,
21579 evaluate it, and return the result as a @code{gdb.Value}.
21580 @var{expression} must be a string.
21582 This function can be useful when implementing a new command
21583 (@pxref{Commands In Python}), as it provides a way to parse the
21584 command's argument as an expression. It is also useful simply to
21585 compute values, for example, it is the only way to get the value of a
21586 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21589 @findex gdb.post_event
21590 @defun gdb.post_event (event)
21591 Put @var{event}, a callable object taking no arguments, into
21592 @value{GDBN}'s internal event queue. This callable will be invoked at
21593 some later point, during @value{GDBN}'s event processing. Events
21594 posted using @code{post_event} will be run in the order in which they
21595 were posted; however, there is no way to know when they will be
21596 processed relative to other events inside @value{GDBN}.
21598 @value{GDBN} is not thread-safe. If your Python program uses multiple
21599 threads, you must be careful to only call @value{GDBN}-specific
21600 functions in the main @value{GDBN} thread. @code{post_event} ensures
21604 (@value{GDBP}) python
21608 > def __init__(self, message):
21609 > self.message = message;
21610 > def __call__(self):
21611 > gdb.write(self.message)
21613 >class MyThread1 (threading.Thread):
21615 > gdb.post_event(Writer("Hello "))
21617 >class MyThread2 (threading.Thread):
21619 > gdb.post_event(Writer("World\n"))
21621 >MyThread1().start()
21622 >MyThread2().start()
21624 (@value{GDBP}) Hello World
21629 @defun gdb.write (string @r{[}, stream{]})
21630 Print a string to @value{GDBN}'s paginated output stream. The
21631 optional @var{stream} determines the stream to print to. The default
21632 stream is @value{GDBN}'s standard output stream. Possible stream
21639 @value{GDBN}'s standard output stream.
21644 @value{GDBN}'s standard error stream.
21649 @value{GDBN}'s log stream (@pxref{Logging Output}).
21652 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21653 call this function and will automatically direct the output to the
21658 @defun gdb.flush ()
21659 Flush the buffer of a @value{GDBN} paginated stream so that the
21660 contents are displayed immediately. @value{GDBN} will flush the
21661 contents of a stream automatically when it encounters a newline in the
21662 buffer. The optional @var{stream} determines the stream to flush. The
21663 default stream is @value{GDBN}'s standard output stream. Possible
21670 @value{GDBN}'s standard output stream.
21675 @value{GDBN}'s standard error stream.
21680 @value{GDBN}'s log stream (@pxref{Logging Output}).
21684 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21685 call this function for the relevant stream.
21688 @findex gdb.target_charset
21689 @defun gdb.target_charset ()
21690 Return the name of the current target character set (@pxref{Character
21691 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21692 that @samp{auto} is never returned.
21695 @findex gdb.target_wide_charset
21696 @defun gdb.target_wide_charset ()
21697 Return the name of the current target wide character set
21698 (@pxref{Character Sets}). This differs from
21699 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21703 @findex gdb.solib_name
21704 @defun gdb.solib_name (address)
21705 Return the name of the shared library holding the given @var{address}
21706 as a string, or @code{None}.
21709 @findex gdb.decode_line
21710 @defun gdb.decode_line @r{[}expression@r{]}
21711 Return locations of the line specified by @var{expression}, or of the
21712 current line if no argument was given. This function returns a Python
21713 tuple containing two elements. The first element contains a string
21714 holding any unparsed section of @var{expression} (or @code{None} if
21715 the expression has been fully parsed). The second element contains
21716 either @code{None} or another tuple that contains all the locations
21717 that match the expression represented as @code{gdb.Symtab_and_line}
21718 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21719 provided, it is decoded the way that @value{GDBN}'s inbuilt
21720 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21723 @defun gdb.prompt_hook (current_prompt)
21724 @anchor{prompt_hook}
21726 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21727 assigned to this operation before a prompt is displayed by
21730 The parameter @code{current_prompt} contains the current @value{GDBN}
21731 prompt. This method must return a Python string, or @code{None}. If
21732 a string is returned, the @value{GDBN} prompt will be set to that
21733 string. If @code{None} is returned, @value{GDBN} will continue to use
21734 the current prompt.
21736 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21737 such as those used by readline for command input, and annotation
21738 related prompts are prohibited from being changed.
21741 @node Exception Handling
21742 @subsubsection Exception Handling
21743 @cindex python exceptions
21744 @cindex exceptions, python
21746 When executing the @code{python} command, Python exceptions
21747 uncaught within the Python code are translated to calls to
21748 @value{GDBN} error-reporting mechanism. If the command that called
21749 @code{python} does not handle the error, @value{GDBN} will
21750 terminate it and print an error message containing the Python
21751 exception name, the associated value, and the Python call stack
21752 backtrace at the point where the exception was raised. Example:
21755 (@value{GDBP}) python print foo
21756 Traceback (most recent call last):
21757 File "<string>", line 1, in <module>
21758 NameError: name 'foo' is not defined
21761 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21762 Python code are converted to Python exceptions. The type of the
21763 Python exception depends on the error.
21767 This is the base class for most exceptions generated by @value{GDBN}.
21768 It is derived from @code{RuntimeError}, for compatibility with earlier
21769 versions of @value{GDBN}.
21771 If an error occurring in @value{GDBN} does not fit into some more
21772 specific category, then the generated exception will have this type.
21774 @item gdb.MemoryError
21775 This is a subclass of @code{gdb.error} which is thrown when an
21776 operation tried to access invalid memory in the inferior.
21778 @item KeyboardInterrupt
21779 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21780 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21783 In all cases, your exception handler will see the @value{GDBN} error
21784 message as its value and the Python call stack backtrace at the Python
21785 statement closest to where the @value{GDBN} error occured as the
21788 @findex gdb.GdbError
21789 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21790 it is useful to be able to throw an exception that doesn't cause a
21791 traceback to be printed. For example, the user may have invoked the
21792 command incorrectly. Use the @code{gdb.GdbError} exception
21793 to handle this case. Example:
21797 >class HelloWorld (gdb.Command):
21798 > """Greet the whole world."""
21799 > def __init__ (self):
21800 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21801 > def invoke (self, args, from_tty):
21802 > argv = gdb.string_to_argv (args)
21803 > if len (argv) != 0:
21804 > raise gdb.GdbError ("hello-world takes no arguments")
21805 > print "Hello, World!"
21808 (gdb) hello-world 42
21809 hello-world takes no arguments
21812 @node Values From Inferior
21813 @subsubsection Values From Inferior
21814 @cindex values from inferior, with Python
21815 @cindex python, working with values from inferior
21817 @cindex @code{gdb.Value}
21818 @value{GDBN} provides values it obtains from the inferior program in
21819 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21820 for its internal bookkeeping of the inferior's values, and for
21821 fetching values when necessary.
21823 Inferior values that are simple scalars can be used directly in
21824 Python expressions that are valid for the value's data type. Here's
21825 an example for an integer or floating-point value @code{some_val}:
21832 As result of this, @code{bar} will also be a @code{gdb.Value} object
21833 whose values are of the same type as those of @code{some_val}.
21835 Inferior values that are structures or instances of some class can
21836 be accessed using the Python @dfn{dictionary syntax}. For example, if
21837 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21838 can access its @code{foo} element with:
21841 bar = some_val['foo']
21844 Again, @code{bar} will also be a @code{gdb.Value} object.
21846 A @code{gdb.Value} that represents a function can be executed via
21847 inferior function call. Any arguments provided to the call must match
21848 the function's prototype, and must be provided in the order specified
21851 For example, @code{some_val} is a @code{gdb.Value} instance
21852 representing a function that takes two integers as arguments. To
21853 execute this function, call it like so:
21856 result = some_val (10,20)
21859 Any values returned from a function call will be stored as a
21862 The following attributes are provided:
21865 @defvar Value.address
21866 If this object is addressable, this read-only attribute holds a
21867 @code{gdb.Value} object representing the address. Otherwise,
21868 this attribute holds @code{None}.
21871 @cindex optimized out value in Python
21872 @defvar Value.is_optimized_out
21873 This read-only boolean attribute is true if the compiler optimized out
21874 this value, thus it is not available for fetching from the inferior.
21878 The type of this @code{gdb.Value}. The value of this attribute is a
21879 @code{gdb.Type} object (@pxref{Types In Python}).
21882 @defvar Value.dynamic_type
21883 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21884 type information (@acronym{RTTI}) to determine the dynamic type of the
21885 value. If this value is of class type, it will return the class in
21886 which the value is embedded, if any. If this value is of pointer or
21887 reference to a class type, it will compute the dynamic type of the
21888 referenced object, and return a pointer or reference to that type,
21889 respectively. In all other cases, it will return the value's static
21892 Note that this feature will only work when debugging a C@t{++} program
21893 that includes @acronym{RTTI} for the object in question. Otherwise,
21894 it will just return the static type of the value as in @kbd{ptype foo}
21895 (@pxref{Symbols, ptype}).
21898 @defvar Value.is_lazy
21899 The value of this read-only boolean attribute is @code{True} if this
21900 @code{gdb.Value} has not yet been fetched from the inferior.
21901 @value{GDBN} does not fetch values until necessary, for efficiency.
21905 myval = gdb.parse_and_eval ('somevar')
21908 The value of @code{somevar} is not fetched at this time. It will be
21909 fetched when the value is needed, or when the @code{fetch_lazy}
21914 The following methods are provided:
21917 @defun Value.__init__ (@var{val})
21918 Many Python values can be converted directly to a @code{gdb.Value} via
21919 this object initializer. Specifically:
21922 @item Python boolean
21923 A Python boolean is converted to the boolean type from the current
21926 @item Python integer
21927 A Python integer is converted to the C @code{long} type for the
21928 current architecture.
21931 A Python long is converted to the C @code{long long} type for the
21932 current architecture.
21935 A Python float is converted to the C @code{double} type for the
21936 current architecture.
21938 @item Python string
21939 A Python string is converted to a target string, using the current
21942 @item @code{gdb.Value}
21943 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21945 @item @code{gdb.LazyString}
21946 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21947 Python}), then the lazy string's @code{value} method is called, and
21948 its result is used.
21952 @defun Value.cast (type)
21953 Return a new instance of @code{gdb.Value} that is the result of
21954 casting this instance to the type described by @var{type}, which must
21955 be a @code{gdb.Type} object. If the cast cannot be performed for some
21956 reason, this method throws an exception.
21959 @defun Value.dereference ()
21960 For pointer data types, this method returns a new @code{gdb.Value} object
21961 whose contents is the object pointed to by the pointer. For example, if
21962 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21969 then you can use the corresponding @code{gdb.Value} to access what
21970 @code{foo} points to like this:
21973 bar = foo.dereference ()
21976 The result @code{bar} will be a @code{gdb.Value} object holding the
21977 value pointed to by @code{foo}.
21980 @defun Value.dynamic_cast (type)
21981 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21982 operator were used. Consult a C@t{++} reference for details.
21985 @defun Value.reinterpret_cast (type)
21986 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21987 operator were used. Consult a C@t{++} reference for details.
21990 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
21991 If this @code{gdb.Value} represents a string, then this method
21992 converts the contents to a Python string. Otherwise, this method will
21993 throw an exception.
21995 Strings are recognized in a language-specific way; whether a given
21996 @code{gdb.Value} represents a string is determined by the current
21999 For C-like languages, a value is a string if it is a pointer to or an
22000 array of characters or ints. The string is assumed to be terminated
22001 by a zero of the appropriate width. However if the optional length
22002 argument is given, the string will be converted to that given length,
22003 ignoring any embedded zeros that the string may contain.
22005 If the optional @var{encoding} argument is given, it must be a string
22006 naming the encoding of the string in the @code{gdb.Value}, such as
22007 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22008 the same encodings as the corresponding argument to Python's
22009 @code{string.decode} method, and the Python codec machinery will be used
22010 to convert the string. If @var{encoding} is not given, or if
22011 @var{encoding} is the empty string, then either the @code{target-charset}
22012 (@pxref{Character Sets}) will be used, or a language-specific encoding
22013 will be used, if the current language is able to supply one.
22015 The optional @var{errors} argument is the same as the corresponding
22016 argument to Python's @code{string.decode} method.
22018 If the optional @var{length} argument is given, the string will be
22019 fetched and converted to the given length.
22022 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22023 If this @code{gdb.Value} represents a string, then this method
22024 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22025 In Python}). Otherwise, this method will throw an exception.
22027 If the optional @var{encoding} argument is given, it must be a string
22028 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22029 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22030 @var{encoding} argument is an encoding that @value{GDBN} does
22031 recognize, @value{GDBN} will raise an error.
22033 When a lazy string is printed, the @value{GDBN} encoding machinery is
22034 used to convert the string during printing. If the optional
22035 @var{encoding} argument is not provided, or is an empty string,
22036 @value{GDBN} will automatically select the encoding most suitable for
22037 the string type. For further information on encoding in @value{GDBN}
22038 please see @ref{Character Sets}.
22040 If the optional @var{length} argument is given, the string will be
22041 fetched and encoded to the length of characters specified. If
22042 the @var{length} argument is not provided, the string will be fetched
22043 and encoded until a null of appropriate width is found.
22046 @defun Value.fetch_lazy ()
22047 If the @code{gdb.Value} object is currently a lazy value
22048 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22049 fetched from the inferior. Any errors that occur in the process
22050 will produce a Python exception.
22052 If the @code{gdb.Value} object is not a lazy value, this method
22055 This method does not return a value.
22060 @node Types In Python
22061 @subsubsection Types In Python
22062 @cindex types in Python
22063 @cindex Python, working with types
22066 @value{GDBN} represents types from the inferior using the class
22069 The following type-related functions are available in the @code{gdb}
22072 @findex gdb.lookup_type
22073 @defun gdb.lookup_type (name @r{[}, block@r{]})
22074 This function looks up a type by name. @var{name} is the name of the
22075 type to look up. It must be a string.
22077 If @var{block} is given, then @var{name} is looked up in that scope.
22078 Otherwise, it is searched for globally.
22080 Ordinarily, this function will return an instance of @code{gdb.Type}.
22081 If the named type cannot be found, it will throw an exception.
22084 If the type is a structure or class type, or an enum type, the fields
22085 of that type can be accessed using the Python @dfn{dictionary syntax}.
22086 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22087 a structure type, you can access its @code{foo} field with:
22090 bar = some_type['foo']
22093 @code{bar} will be a @code{gdb.Field} object; see below under the
22094 description of the @code{Type.fields} method for a description of the
22095 @code{gdb.Field} class.
22097 An instance of @code{Type} has the following attributes:
22101 The type code for this type. The type code will be one of the
22102 @code{TYPE_CODE_} constants defined below.
22105 @defvar Type.sizeof
22106 The size of this type, in target @code{char} units. Usually, a
22107 target's @code{char} type will be an 8-bit byte. However, on some
22108 unusual platforms, this type may have a different size.
22112 The tag name for this type. The tag name is the name after
22113 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22114 languages have this concept. If this type has no tag name, then
22115 @code{None} is returned.
22119 The following methods are provided:
22122 @defun Type.fields ()
22123 For structure and union types, this method returns the fields. Range
22124 types have two fields, the minimum and maximum values. Enum types
22125 have one field per enum constant. Function and method types have one
22126 field per parameter. The base types of C@t{++} classes are also
22127 represented as fields. If the type has no fields, or does not fit
22128 into one of these categories, an empty sequence will be returned.
22130 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22133 This attribute is not available for @code{static} fields (as in
22134 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22135 position of the field. For @code{enum} fields, the value is the
22136 enumeration member's integer representation.
22139 The name of the field, or @code{None} for anonymous fields.
22142 This is @code{True} if the field is artificial, usually meaning that
22143 it was provided by the compiler and not the user. This attribute is
22144 always provided, and is @code{False} if the field is not artificial.
22146 @item is_base_class
22147 This is @code{True} if the field represents a base class of a C@t{++}
22148 structure. This attribute is always provided, and is @code{False}
22149 if the field is not a base class of the type that is the argument of
22150 @code{fields}, or if that type was not a C@t{++} class.
22153 If the field is packed, or is a bitfield, then this will have a
22154 non-zero value, which is the size of the field in bits. Otherwise,
22155 this will be zero; in this case the field's size is given by its type.
22158 The type of the field. This is usually an instance of @code{Type},
22159 but it can be @code{None} in some situations.
22163 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22164 Return a new @code{gdb.Type} object which represents an array of this
22165 type. If one argument is given, it is the inclusive upper bound of
22166 the array; in this case the lower bound is zero. If two arguments are
22167 given, the first argument is the lower bound of the array, and the
22168 second argument is the upper bound of the array. An array's length
22169 must not be negative, but the bounds can be.
22172 @defun Type.const ()
22173 Return a new @code{gdb.Type} object which represents a
22174 @code{const}-qualified variant of this type.
22177 @defun Type.volatile ()
22178 Return a new @code{gdb.Type} object which represents a
22179 @code{volatile}-qualified variant of this type.
22182 @defun Type.unqualified ()
22183 Return a new @code{gdb.Type} object which represents an unqualified
22184 variant of this type. That is, the result is neither @code{const} nor
22188 @defun Type.range ()
22189 Return a Python @code{Tuple} object that contains two elements: the
22190 low bound of the argument type and the high bound of that type. If
22191 the type does not have a range, @value{GDBN} will raise a
22192 @code{gdb.error} exception (@pxref{Exception Handling}).
22195 @defun Type.reference ()
22196 Return a new @code{gdb.Type} object which represents a reference to this
22200 @defun Type.pointer ()
22201 Return a new @code{gdb.Type} object which represents a pointer to this
22205 @defun Type.strip_typedefs ()
22206 Return a new @code{gdb.Type} that represents the real type,
22207 after removing all layers of typedefs.
22210 @defun Type.target ()
22211 Return a new @code{gdb.Type} object which represents the target type
22214 For a pointer type, the target type is the type of the pointed-to
22215 object. For an array type (meaning C-like arrays), the target type is
22216 the type of the elements of the array. For a function or method type,
22217 the target type is the type of the return value. For a complex type,
22218 the target type is the type of the elements. For a typedef, the
22219 target type is the aliased type.
22221 If the type does not have a target, this method will throw an
22225 @defun Type.template_argument (n @r{[}, block@r{]})
22226 If this @code{gdb.Type} is an instantiation of a template, this will
22227 return a new @code{gdb.Type} which represents the type of the
22228 @var{n}th template argument.
22230 If this @code{gdb.Type} is not a template type, this will throw an
22231 exception. Ordinarily, only C@t{++} code will have template types.
22233 If @var{block} is given, then @var{name} is looked up in that scope.
22234 Otherwise, it is searched for globally.
22239 Each type has a code, which indicates what category this type falls
22240 into. The available type categories are represented by constants
22241 defined in the @code{gdb} module:
22244 @findex TYPE_CODE_PTR
22245 @findex gdb.TYPE_CODE_PTR
22246 @item gdb.TYPE_CODE_PTR
22247 The type is a pointer.
22249 @findex TYPE_CODE_ARRAY
22250 @findex gdb.TYPE_CODE_ARRAY
22251 @item gdb.TYPE_CODE_ARRAY
22252 The type is an array.
22254 @findex TYPE_CODE_STRUCT
22255 @findex gdb.TYPE_CODE_STRUCT
22256 @item gdb.TYPE_CODE_STRUCT
22257 The type is a structure.
22259 @findex TYPE_CODE_UNION
22260 @findex gdb.TYPE_CODE_UNION
22261 @item gdb.TYPE_CODE_UNION
22262 The type is a union.
22264 @findex TYPE_CODE_ENUM
22265 @findex gdb.TYPE_CODE_ENUM
22266 @item gdb.TYPE_CODE_ENUM
22267 The type is an enum.
22269 @findex TYPE_CODE_FLAGS
22270 @findex gdb.TYPE_CODE_FLAGS
22271 @item gdb.TYPE_CODE_FLAGS
22272 A bit flags type, used for things such as status registers.
22274 @findex TYPE_CODE_FUNC
22275 @findex gdb.TYPE_CODE_FUNC
22276 @item gdb.TYPE_CODE_FUNC
22277 The type is a function.
22279 @findex TYPE_CODE_INT
22280 @findex gdb.TYPE_CODE_INT
22281 @item gdb.TYPE_CODE_INT
22282 The type is an integer type.
22284 @findex TYPE_CODE_FLT
22285 @findex gdb.TYPE_CODE_FLT
22286 @item gdb.TYPE_CODE_FLT
22287 A floating point type.
22289 @findex TYPE_CODE_VOID
22290 @findex gdb.TYPE_CODE_VOID
22291 @item gdb.TYPE_CODE_VOID
22292 The special type @code{void}.
22294 @findex TYPE_CODE_SET
22295 @findex gdb.TYPE_CODE_SET
22296 @item gdb.TYPE_CODE_SET
22299 @findex TYPE_CODE_RANGE
22300 @findex gdb.TYPE_CODE_RANGE
22301 @item gdb.TYPE_CODE_RANGE
22302 A range type, that is, an integer type with bounds.
22304 @findex TYPE_CODE_STRING
22305 @findex gdb.TYPE_CODE_STRING
22306 @item gdb.TYPE_CODE_STRING
22307 A string type. Note that this is only used for certain languages with
22308 language-defined string types; C strings are not represented this way.
22310 @findex TYPE_CODE_BITSTRING
22311 @findex gdb.TYPE_CODE_BITSTRING
22312 @item gdb.TYPE_CODE_BITSTRING
22315 @findex TYPE_CODE_ERROR
22316 @findex gdb.TYPE_CODE_ERROR
22317 @item gdb.TYPE_CODE_ERROR
22318 An unknown or erroneous type.
22320 @findex TYPE_CODE_METHOD
22321 @findex gdb.TYPE_CODE_METHOD
22322 @item gdb.TYPE_CODE_METHOD
22323 A method type, as found in C@t{++} or Java.
22325 @findex TYPE_CODE_METHODPTR
22326 @findex gdb.TYPE_CODE_METHODPTR
22327 @item gdb.TYPE_CODE_METHODPTR
22328 A pointer-to-member-function.
22330 @findex TYPE_CODE_MEMBERPTR
22331 @findex gdb.TYPE_CODE_MEMBERPTR
22332 @item gdb.TYPE_CODE_MEMBERPTR
22333 A pointer-to-member.
22335 @findex TYPE_CODE_REF
22336 @findex gdb.TYPE_CODE_REF
22337 @item gdb.TYPE_CODE_REF
22340 @findex TYPE_CODE_CHAR
22341 @findex gdb.TYPE_CODE_CHAR
22342 @item gdb.TYPE_CODE_CHAR
22345 @findex TYPE_CODE_BOOL
22346 @findex gdb.TYPE_CODE_BOOL
22347 @item gdb.TYPE_CODE_BOOL
22350 @findex TYPE_CODE_COMPLEX
22351 @findex gdb.TYPE_CODE_COMPLEX
22352 @item gdb.TYPE_CODE_COMPLEX
22353 A complex float type.
22355 @findex TYPE_CODE_TYPEDEF
22356 @findex gdb.TYPE_CODE_TYPEDEF
22357 @item gdb.TYPE_CODE_TYPEDEF
22358 A typedef to some other type.
22360 @findex TYPE_CODE_NAMESPACE
22361 @findex gdb.TYPE_CODE_NAMESPACE
22362 @item gdb.TYPE_CODE_NAMESPACE
22363 A C@t{++} namespace.
22365 @findex TYPE_CODE_DECFLOAT
22366 @findex gdb.TYPE_CODE_DECFLOAT
22367 @item gdb.TYPE_CODE_DECFLOAT
22368 A decimal floating point type.
22370 @findex TYPE_CODE_INTERNAL_FUNCTION
22371 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22372 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22373 A function internal to @value{GDBN}. This is the type used to represent
22374 convenience functions.
22377 Further support for types is provided in the @code{gdb.types}
22378 Python module (@pxref{gdb.types}).
22380 @node Pretty Printing API
22381 @subsubsection Pretty Printing API
22383 An example output is provided (@pxref{Pretty Printing}).
22385 A pretty-printer is just an object that holds a value and implements a
22386 specific interface, defined here.
22388 @defun pretty_printer.children (self)
22389 @value{GDBN} will call this method on a pretty-printer to compute the
22390 children of the pretty-printer's value.
22392 This method must return an object conforming to the Python iterator
22393 protocol. Each item returned by the iterator must be a tuple holding
22394 two elements. The first element is the ``name'' of the child; the
22395 second element is the child's value. The value can be any Python
22396 object which is convertible to a @value{GDBN} value.
22398 This method is optional. If it does not exist, @value{GDBN} will act
22399 as though the value has no children.
22402 @defun pretty_printer.display_hint (self)
22403 The CLI may call this method and use its result to change the
22404 formatting of a value. The result will also be supplied to an MI
22405 consumer as a @samp{displayhint} attribute of the variable being
22408 This method is optional. If it does exist, this method must return a
22411 Some display hints are predefined by @value{GDBN}:
22415 Indicate that the object being printed is ``array-like''. The CLI
22416 uses this to respect parameters such as @code{set print elements} and
22417 @code{set print array}.
22420 Indicate that the object being printed is ``map-like'', and that the
22421 children of this value can be assumed to alternate between keys and
22425 Indicate that the object being printed is ``string-like''. If the
22426 printer's @code{to_string} method returns a Python string of some
22427 kind, then @value{GDBN} will call its internal language-specific
22428 string-printing function to format the string. For the CLI this means
22429 adding quotation marks, possibly escaping some characters, respecting
22430 @code{set print elements}, and the like.
22434 @defun pretty_printer.to_string (self)
22435 @value{GDBN} will call this method to display the string
22436 representation of the value passed to the object's constructor.
22438 When printing from the CLI, if the @code{to_string} method exists,
22439 then @value{GDBN} will prepend its result to the values returned by
22440 @code{children}. Exactly how this formatting is done is dependent on
22441 the display hint, and may change as more hints are added. Also,
22442 depending on the print settings (@pxref{Print Settings}), the CLI may
22443 print just the result of @code{to_string} in a stack trace, omitting
22444 the result of @code{children}.
22446 If this method returns a string, it is printed verbatim.
22448 Otherwise, if this method returns an instance of @code{gdb.Value},
22449 then @value{GDBN} prints this value. This may result in a call to
22450 another pretty-printer.
22452 If instead the method returns a Python value which is convertible to a
22453 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22454 the resulting value. Again, this may result in a call to another
22455 pretty-printer. Python scalars (integers, floats, and booleans) and
22456 strings are convertible to @code{gdb.Value}; other types are not.
22458 Finally, if this method returns @code{None} then no further operations
22459 are peformed in this method and nothing is printed.
22461 If the result is not one of these types, an exception is raised.
22464 @value{GDBN} provides a function which can be used to look up the
22465 default pretty-printer for a @code{gdb.Value}:
22467 @findex gdb.default_visualizer
22468 @defun gdb.default_visualizer (value)
22469 This function takes a @code{gdb.Value} object as an argument. If a
22470 pretty-printer for this value exists, then it is returned. If no such
22471 printer exists, then this returns @code{None}.
22474 @node Selecting Pretty-Printers
22475 @subsubsection Selecting Pretty-Printers
22477 The Python list @code{gdb.pretty_printers} contains an array of
22478 functions or callable objects that have been registered via addition
22479 as a pretty-printer. Printers in this list are called @code{global}
22480 printers, they're available when debugging all inferiors.
22481 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22482 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22485 Each function on these lists is passed a single @code{gdb.Value}
22486 argument and should return a pretty-printer object conforming to the
22487 interface definition above (@pxref{Pretty Printing API}). If a function
22488 cannot create a pretty-printer for the value, it should return
22491 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22492 @code{gdb.Objfile} in the current program space and iteratively calls
22493 each enabled lookup routine in the list for that @code{gdb.Objfile}
22494 until it receives a pretty-printer object.
22495 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22496 searches the pretty-printer list of the current program space,
22497 calling each enabled function until an object is returned.
22498 After these lists have been exhausted, it tries the global
22499 @code{gdb.pretty_printers} list, again calling each enabled function until an
22500 object is returned.
22502 The order in which the objfiles are searched is not specified. For a
22503 given list, functions are always invoked from the head of the list,
22504 and iterated over sequentially until the end of the list, or a printer
22505 object is returned.
22507 For various reasons a pretty-printer may not work.
22508 For example, the underlying data structure may have changed and
22509 the pretty-printer is out of date.
22511 The consequences of a broken pretty-printer are severe enough that
22512 @value{GDBN} provides support for enabling and disabling individual
22513 printers. For example, if @code{print frame-arguments} is on,
22514 a backtrace can become highly illegible if any argument is printed
22515 with a broken printer.
22517 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22518 attribute to the registered function or callable object. If this attribute
22519 is present and its value is @code{False}, the printer is disabled, otherwise
22520 the printer is enabled.
22522 @node Writing a Pretty-Printer
22523 @subsubsection Writing a Pretty-Printer
22524 @cindex writing a pretty-printer
22526 A pretty-printer consists of two parts: a lookup function to detect
22527 if the type is supported, and the printer itself.
22529 Here is an example showing how a @code{std::string} printer might be
22530 written. @xref{Pretty Printing API}, for details on the API this class
22534 class StdStringPrinter(object):
22535 "Print a std::string"
22537 def __init__(self, val):
22540 def to_string(self):
22541 return self.val['_M_dataplus']['_M_p']
22543 def display_hint(self):
22547 And here is an example showing how a lookup function for the printer
22548 example above might be written.
22551 def str_lookup_function(val):
22552 lookup_tag = val.type.tag
22553 if lookup_tag == None:
22555 regex = re.compile("^std::basic_string<char,.*>$")
22556 if regex.match(lookup_tag):
22557 return StdStringPrinter(val)
22561 The example lookup function extracts the value's type, and attempts to
22562 match it to a type that it can pretty-print. If it is a type the
22563 printer can pretty-print, it will return a printer object. If not, it
22564 returns @code{None}.
22566 We recommend that you put your core pretty-printers into a Python
22567 package. If your pretty-printers are for use with a library, we
22568 further recommend embedding a version number into the package name.
22569 This practice will enable @value{GDBN} to load multiple versions of
22570 your pretty-printers at the same time, because they will have
22573 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22574 can be evaluated multiple times without changing its meaning. An
22575 ideal auto-load file will consist solely of @code{import}s of your
22576 printer modules, followed by a call to a register pretty-printers with
22577 the current objfile.
22579 Taken as a whole, this approach will scale nicely to multiple
22580 inferiors, each potentially using a different library version.
22581 Embedding a version number in the Python package name will ensure that
22582 @value{GDBN} is able to load both sets of printers simultaneously.
22583 Then, because the search for pretty-printers is done by objfile, and
22584 because your auto-loaded code took care to register your library's
22585 printers with a specific objfile, @value{GDBN} will find the correct
22586 printers for the specific version of the library used by each
22589 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22590 this code might appear in @code{gdb.libstdcxx.v6}:
22593 def register_printers(objfile):
22594 objfile.pretty_printers.add(str_lookup_function)
22598 And then the corresponding contents of the auto-load file would be:
22601 import gdb.libstdcxx.v6
22602 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22605 The previous example illustrates a basic pretty-printer.
22606 There are a few things that can be improved on.
22607 The printer doesn't have a name, making it hard to identify in a
22608 list of installed printers. The lookup function has a name, but
22609 lookup functions can have arbitrary, even identical, names.
22611 Second, the printer only handles one type, whereas a library typically has
22612 several types. One could install a lookup function for each desired type
22613 in the library, but one could also have a single lookup function recognize
22614 several types. The latter is the conventional way this is handled.
22615 If a pretty-printer can handle multiple data types, then its
22616 @dfn{subprinters} are the printers for the individual data types.
22618 The @code{gdb.printing} module provides a formal way of solving these
22619 problems (@pxref{gdb.printing}).
22620 Here is another example that handles multiple types.
22622 These are the types we are going to pretty-print:
22625 struct foo @{ int a, b; @};
22626 struct bar @{ struct foo x, y; @};
22629 Here are the printers:
22633 """Print a foo object."""
22635 def __init__(self, val):
22638 def to_string(self):
22639 return ("a=<" + str(self.val["a"]) +
22640 "> b=<" + str(self.val["b"]) + ">")
22643 """Print a bar object."""
22645 def __init__(self, val):
22648 def to_string(self):
22649 return ("x=<" + str(self.val["x"]) +
22650 "> y=<" + str(self.val["y"]) + ">")
22653 This example doesn't need a lookup function, that is handled by the
22654 @code{gdb.printing} module. Instead a function is provided to build up
22655 the object that handles the lookup.
22658 import gdb.printing
22660 def build_pretty_printer():
22661 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22663 pp.add_printer('foo', '^foo$', fooPrinter)
22664 pp.add_printer('bar', '^bar$', barPrinter)
22668 And here is the autoload support:
22671 import gdb.printing
22673 gdb.printing.register_pretty_printer(
22674 gdb.current_objfile(),
22675 my_library.build_pretty_printer())
22678 Finally, when this printer is loaded into @value{GDBN}, here is the
22679 corresponding output of @samp{info pretty-printer}:
22682 (gdb) info pretty-printer
22689 @node Inferiors In Python
22690 @subsubsection Inferiors In Python
22691 @cindex inferiors in Python
22693 @findex gdb.Inferior
22694 Programs which are being run under @value{GDBN} are called inferiors
22695 (@pxref{Inferiors and Programs}). Python scripts can access
22696 information about and manipulate inferiors controlled by @value{GDBN}
22697 via objects of the @code{gdb.Inferior} class.
22699 The following inferior-related functions are available in the @code{gdb}
22702 @defun gdb.inferiors ()
22703 Return a tuple containing all inferior objects.
22706 @defun gdb.selected_inferior ()
22707 Return an object representing the current inferior.
22710 A @code{gdb.Inferior} object has the following attributes:
22713 @defvar Inferior.num
22714 ID of inferior, as assigned by GDB.
22717 @defvar Inferior.pid
22718 Process ID of the inferior, as assigned by the underlying operating
22722 @defvar Inferior.was_attached
22723 Boolean signaling whether the inferior was created using `attach', or
22724 started by @value{GDBN} itself.
22728 A @code{gdb.Inferior} object has the following methods:
22731 @defun Inferior.is_valid ()
22732 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22733 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22734 if the inferior no longer exists within @value{GDBN}. All other
22735 @code{gdb.Inferior} methods will throw an exception if it is invalid
22736 at the time the method is called.
22739 @defun Inferior.threads ()
22740 This method returns a tuple holding all the threads which are valid
22741 when it is called. If there are no valid threads, the method will
22742 return an empty tuple.
22745 @findex gdb.read_memory
22746 @defun Inferior.read_memory (address, length)
22747 Read @var{length} bytes of memory from the inferior, starting at
22748 @var{address}. Returns a buffer object, which behaves much like an array
22749 or a string. It can be modified and given to the @code{gdb.write_memory}
22753 @findex gdb.write_memory
22754 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22755 Write the contents of @var{buffer} to the inferior, starting at
22756 @var{address}. The @var{buffer} parameter must be a Python object
22757 which supports the buffer protocol, i.e., a string, an array or the
22758 object returned from @code{gdb.read_memory}. If given, @var{length}
22759 determines the number of bytes from @var{buffer} to be written.
22762 @findex gdb.search_memory
22763 @defun Inferior.search_memory (address, length, pattern)
22764 Search a region of the inferior memory starting at @var{address} with
22765 the given @var{length} using the search pattern supplied in
22766 @var{pattern}. The @var{pattern} parameter must be a Python object
22767 which supports the buffer protocol, i.e., a string, an array or the
22768 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22769 containing the address where the pattern was found, or @code{None} if
22770 the pattern could not be found.
22774 @node Events In Python
22775 @subsubsection Events In Python
22776 @cindex inferior events in Python
22778 @value{GDBN} provides a general event facility so that Python code can be
22779 notified of various state changes, particularly changes that occur in
22782 An @dfn{event} is just an object that describes some state change. The
22783 type of the object and its attributes will vary depending on the details
22784 of the change. All the existing events are described below.
22786 In order to be notified of an event, you must register an event handler
22787 with an @dfn{event registry}. An event registry is an object in the
22788 @code{gdb.events} module which dispatches particular events. A registry
22789 provides methods to register and unregister event handlers:
22792 @defun EventRegistry.connect (object)
22793 Add the given callable @var{object} to the registry. This object will be
22794 called when an event corresponding to this registry occurs.
22797 @defun EventRegistry.disconnect (object)
22798 Remove the given @var{object} from the registry. Once removed, the object
22799 will no longer receive notifications of events.
22803 Here is an example:
22806 def exit_handler (event):
22807 print "event type: exit"
22808 print "exit code: %d" % (event.exit_code)
22810 gdb.events.exited.connect (exit_handler)
22813 In the above example we connect our handler @code{exit_handler} to the
22814 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22815 called when the inferior exits. The argument @dfn{event} in this example is
22816 of type @code{gdb.ExitedEvent}. As you can see in the example the
22817 @code{ExitedEvent} object has an attribute which indicates the exit code of
22820 The following is a listing of the event registries that are available and
22821 details of the events they emit:
22826 Emits @code{gdb.ThreadEvent}.
22828 Some events can be thread specific when @value{GDBN} is running in non-stop
22829 mode. When represented in Python, these events all extend
22830 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22831 events which are emitted by this or other modules might extend this event.
22832 Examples of these events are @code{gdb.BreakpointEvent} and
22833 @code{gdb.ContinueEvent}.
22836 @defvar ThreadEvent.inferior_thread
22837 In non-stop mode this attribute will be set to the specific thread which was
22838 involved in the emitted event. Otherwise, it will be set to @code{None}.
22842 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22844 This event indicates that the inferior has been continued after a stop. For
22845 inherited attribute refer to @code{gdb.ThreadEvent} above.
22847 @item events.exited
22848 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22849 @code{events.ExitedEvent} has two attributes:
22851 @defvar ExitedEvent.exit_code
22852 An integer representing the exit code, if available, which the inferior
22853 has returned. (The exit code could be unavailable if, for example,
22854 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22855 the attribute does not exist.
22857 @defvar ExitedEvent inferior
22858 A reference to the inferior which triggered the @code{exited} event.
22863 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22865 Indicates that the inferior has stopped. All events emitted by this registry
22866 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22867 will indicate the stopped thread when @value{GDBN} is running in non-stop
22868 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22870 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22872 This event indicates that the inferior or one of its threads has received as
22873 signal. @code{gdb.SignalEvent} has the following attributes:
22876 @defvar SignalEvent.stop_signal
22877 A string representing the signal received by the inferior. A list of possible
22878 signal values can be obtained by running the command @code{info signals} in
22879 the @value{GDBN} command prompt.
22883 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22885 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22886 been hit, and has the following attributes:
22889 @defvar BreakpointEvent.breakpoints
22890 A sequence containing references to all the breakpoints (type
22891 @code{gdb.Breakpoint}) that were hit.
22892 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22894 @defvar BreakpointEvent.breakpoint
22895 A reference to the first breakpoint that was hit.
22896 This function is maintained for backward compatibility and is now deprecated
22897 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22901 @item events.new_objfile
22902 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22903 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22906 @defvar NewObjFileEvent.new_objfile
22907 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22908 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22914 @node Threads In Python
22915 @subsubsection Threads In Python
22916 @cindex threads in python
22918 @findex gdb.InferiorThread
22919 Python scripts can access information about, and manipulate inferior threads
22920 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22922 The following thread-related functions are available in the @code{gdb}
22925 @findex gdb.selected_thread
22926 @defun gdb.selected_thread ()
22927 This function returns the thread object for the selected thread. If there
22928 is no selected thread, this will return @code{None}.
22931 A @code{gdb.InferiorThread} object has the following attributes:
22934 @defvar InferiorThread.name
22935 The name of the thread. If the user specified a name using
22936 @code{thread name}, then this returns that name. Otherwise, if an
22937 OS-supplied name is available, then it is returned. Otherwise, this
22938 returns @code{None}.
22940 This attribute can be assigned to. The new value must be a string
22941 object, which sets the new name, or @code{None}, which removes any
22942 user-specified thread name.
22945 @defvar InferiorThread.num
22946 ID of the thread, as assigned by GDB.
22949 @defvar InferiorThread.ptid
22950 ID of the thread, as assigned by the operating system. This attribute is a
22951 tuple containing three integers. The first is the Process ID (PID); the second
22952 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22953 Either the LWPID or TID may be 0, which indicates that the operating system
22954 does not use that identifier.
22958 A @code{gdb.InferiorThread} object has the following methods:
22961 @defun InferiorThread.is_valid ()
22962 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22963 @code{False} if not. A @code{gdb.InferiorThread} object will become
22964 invalid if the thread exits, or the inferior that the thread belongs
22965 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22966 exception if it is invalid at the time the method is called.
22969 @defun InferiorThread.switch ()
22970 This changes @value{GDBN}'s currently selected thread to the one represented
22974 @defun InferiorThread.is_stopped ()
22975 Return a Boolean indicating whether the thread is stopped.
22978 @defun InferiorThread.is_running ()
22979 Return a Boolean indicating whether the thread is running.
22982 @defun InferiorThread.is_exited ()
22983 Return a Boolean indicating whether the thread is exited.
22987 @node Commands In Python
22988 @subsubsection Commands In Python
22990 @cindex commands in python
22991 @cindex python commands
22992 You can implement new @value{GDBN} CLI commands in Python. A CLI
22993 command is implemented using an instance of the @code{gdb.Command}
22994 class, most commonly using a subclass.
22996 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
22997 The object initializer for @code{Command} registers the new command
22998 with @value{GDBN}. This initializer is normally invoked from the
22999 subclass' own @code{__init__} method.
23001 @var{name} is the name of the command. If @var{name} consists of
23002 multiple words, then the initial words are looked for as prefix
23003 commands. In this case, if one of the prefix commands does not exist,
23004 an exception is raised.
23006 There is no support for multi-line commands.
23008 @var{command_class} should be one of the @samp{COMMAND_} constants
23009 defined below. This argument tells @value{GDBN} how to categorize the
23010 new command in the help system.
23012 @var{completer_class} is an optional argument. If given, it should be
23013 one of the @samp{COMPLETE_} constants defined below. This argument
23014 tells @value{GDBN} how to perform completion for this command. If not
23015 given, @value{GDBN} will attempt to complete using the object's
23016 @code{complete} method (see below); if no such method is found, an
23017 error will occur when completion is attempted.
23019 @var{prefix} is an optional argument. If @code{True}, then the new
23020 command is a prefix command; sub-commands of this command may be
23023 The help text for the new command is taken from the Python
23024 documentation string for the command's class, if there is one. If no
23025 documentation string is provided, the default value ``This command is
23026 not documented.'' is used.
23029 @cindex don't repeat Python command
23030 @defun Command.dont_repeat ()
23031 By default, a @value{GDBN} command is repeated when the user enters a
23032 blank line at the command prompt. A command can suppress this
23033 behavior by invoking the @code{dont_repeat} method. This is similar
23034 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23037 @defun Command.invoke (argument, from_tty)
23038 This method is called by @value{GDBN} when this command is invoked.
23040 @var{argument} is a string. It is the argument to the command, after
23041 leading and trailing whitespace has been stripped.
23043 @var{from_tty} is a boolean argument. When true, this means that the
23044 command was entered by the user at the terminal; when false it means
23045 that the command came from elsewhere.
23047 If this method throws an exception, it is turned into a @value{GDBN}
23048 @code{error} call. Otherwise, the return value is ignored.
23050 @findex gdb.string_to_argv
23051 To break @var{argument} up into an argv-like string use
23052 @code{gdb.string_to_argv}. This function behaves identically to
23053 @value{GDBN}'s internal argument lexer @code{buildargv}.
23054 It is recommended to use this for consistency.
23055 Arguments are separated by spaces and may be quoted.
23059 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23060 ['1', '2 "3', '4 "5', "6 '7"]
23065 @cindex completion of Python commands
23066 @defun Command.complete (text, word)
23067 This method is called by @value{GDBN} when the user attempts
23068 completion on this command. All forms of completion are handled by
23069 this method, that is, the @key{TAB} and @key{M-?} key bindings
23070 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23073 The arguments @var{text} and @var{word} are both strings. @var{text}
23074 holds the complete command line up to the cursor's location.
23075 @var{word} holds the last word of the command line; this is computed
23076 using a word-breaking heuristic.
23078 The @code{complete} method can return several values:
23081 If the return value is a sequence, the contents of the sequence are
23082 used as the completions. It is up to @code{complete} to ensure that the
23083 contents actually do complete the word. A zero-length sequence is
23084 allowed, it means that there were no completions available. Only
23085 string elements of the sequence are used; other elements in the
23086 sequence are ignored.
23089 If the return value is one of the @samp{COMPLETE_} constants defined
23090 below, then the corresponding @value{GDBN}-internal completion
23091 function is invoked, and its result is used.
23094 All other results are treated as though there were no available
23099 When a new command is registered, it must be declared as a member of
23100 some general class of commands. This is used to classify top-level
23101 commands in the on-line help system; note that prefix commands are not
23102 listed under their own category but rather that of their top-level
23103 command. The available classifications are represented by constants
23104 defined in the @code{gdb} module:
23107 @findex COMMAND_NONE
23108 @findex gdb.COMMAND_NONE
23109 @item gdb.COMMAND_NONE
23110 The command does not belong to any particular class. A command in
23111 this category will not be displayed in any of the help categories.
23113 @findex COMMAND_RUNNING
23114 @findex gdb.COMMAND_RUNNING
23115 @item gdb.COMMAND_RUNNING
23116 The command is related to running the inferior. For example,
23117 @code{start}, @code{step}, and @code{continue} are in this category.
23118 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23119 commands in this category.
23121 @findex COMMAND_DATA
23122 @findex gdb.COMMAND_DATA
23123 @item gdb.COMMAND_DATA
23124 The command is related to data or variables. For example,
23125 @code{call}, @code{find}, and @code{print} are in this category. Type
23126 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23129 @findex COMMAND_STACK
23130 @findex gdb.COMMAND_STACK
23131 @item gdb.COMMAND_STACK
23132 The command has to do with manipulation of the stack. For example,
23133 @code{backtrace}, @code{frame}, and @code{return} are in this
23134 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23135 list of commands in this category.
23137 @findex COMMAND_FILES
23138 @findex gdb.COMMAND_FILES
23139 @item gdb.COMMAND_FILES
23140 This class is used for file-related commands. For example,
23141 @code{file}, @code{list} and @code{section} are in this category.
23142 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23143 commands in this category.
23145 @findex COMMAND_SUPPORT
23146 @findex gdb.COMMAND_SUPPORT
23147 @item gdb.COMMAND_SUPPORT
23148 This should be used for ``support facilities'', generally meaning
23149 things that are useful to the user when interacting with @value{GDBN},
23150 but not related to the state of the inferior. For example,
23151 @code{help}, @code{make}, and @code{shell} are in this category. Type
23152 @kbd{help support} at the @value{GDBN} prompt to see a list of
23153 commands in this category.
23155 @findex COMMAND_STATUS
23156 @findex gdb.COMMAND_STATUS
23157 @item gdb.COMMAND_STATUS
23158 The command is an @samp{info}-related command, that is, related to the
23159 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23160 and @code{show} are in this category. Type @kbd{help status} at the
23161 @value{GDBN} prompt to see a list of commands in this category.
23163 @findex COMMAND_BREAKPOINTS
23164 @findex gdb.COMMAND_BREAKPOINTS
23165 @item gdb.COMMAND_BREAKPOINTS
23166 The command has to do with breakpoints. For example, @code{break},
23167 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23168 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23171 @findex COMMAND_TRACEPOINTS
23172 @findex gdb.COMMAND_TRACEPOINTS
23173 @item gdb.COMMAND_TRACEPOINTS
23174 The command has to do with tracepoints. For example, @code{trace},
23175 @code{actions}, and @code{tfind} are in this category. Type
23176 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23177 commands in this category.
23179 @findex COMMAND_OBSCURE
23180 @findex gdb.COMMAND_OBSCURE
23181 @item gdb.COMMAND_OBSCURE
23182 The command is only used in unusual circumstances, or is not of
23183 general interest to users. For example, @code{checkpoint},
23184 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23185 obscure} at the @value{GDBN} prompt to see a list of commands in this
23188 @findex COMMAND_MAINTENANCE
23189 @findex gdb.COMMAND_MAINTENANCE
23190 @item gdb.COMMAND_MAINTENANCE
23191 The command is only useful to @value{GDBN} maintainers. The
23192 @code{maintenance} and @code{flushregs} commands are in this category.
23193 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23194 commands in this category.
23197 A new command can use a predefined completion function, either by
23198 specifying it via an argument at initialization, or by returning it
23199 from the @code{complete} method. These predefined completion
23200 constants are all defined in the @code{gdb} module:
23203 @findex COMPLETE_NONE
23204 @findex gdb.COMPLETE_NONE
23205 @item gdb.COMPLETE_NONE
23206 This constant means that no completion should be done.
23208 @findex COMPLETE_FILENAME
23209 @findex gdb.COMPLETE_FILENAME
23210 @item gdb.COMPLETE_FILENAME
23211 This constant means that filename completion should be performed.
23213 @findex COMPLETE_LOCATION
23214 @findex gdb.COMPLETE_LOCATION
23215 @item gdb.COMPLETE_LOCATION
23216 This constant means that location completion should be done.
23217 @xref{Specify Location}.
23219 @findex COMPLETE_COMMAND
23220 @findex gdb.COMPLETE_COMMAND
23221 @item gdb.COMPLETE_COMMAND
23222 This constant means that completion should examine @value{GDBN}
23225 @findex COMPLETE_SYMBOL
23226 @findex gdb.COMPLETE_SYMBOL
23227 @item gdb.COMPLETE_SYMBOL
23228 This constant means that completion should be done using symbol names
23232 The following code snippet shows how a trivial CLI command can be
23233 implemented in Python:
23236 class HelloWorld (gdb.Command):
23237 """Greet the whole world."""
23239 def __init__ (self):
23240 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23242 def invoke (self, arg, from_tty):
23243 print "Hello, World!"
23248 The last line instantiates the class, and is necessary to trigger the
23249 registration of the command with @value{GDBN}. Depending on how the
23250 Python code is read into @value{GDBN}, you may need to import the
23251 @code{gdb} module explicitly.
23253 @node Parameters In Python
23254 @subsubsection Parameters In Python
23256 @cindex parameters in python
23257 @cindex python parameters
23258 @tindex gdb.Parameter
23260 You can implement new @value{GDBN} parameters using Python. A new
23261 parameter is implemented as an instance of the @code{gdb.Parameter}
23264 Parameters are exposed to the user via the @code{set} and
23265 @code{show} commands. @xref{Help}.
23267 There are many parameters that already exist and can be set in
23268 @value{GDBN}. Two examples are: @code{set follow fork} and
23269 @code{set charset}. Setting these parameters influences certain
23270 behavior in @value{GDBN}. Similarly, you can define parameters that
23271 can be used to influence behavior in custom Python scripts and commands.
23273 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23274 The object initializer for @code{Parameter} registers the new
23275 parameter with @value{GDBN}. This initializer is normally invoked
23276 from the subclass' own @code{__init__} method.
23278 @var{name} is the name of the new parameter. If @var{name} consists
23279 of multiple words, then the initial words are looked for as prefix
23280 parameters. An example of this can be illustrated with the
23281 @code{set print} set of parameters. If @var{name} is
23282 @code{print foo}, then @code{print} will be searched as the prefix
23283 parameter. In this case the parameter can subsequently be accessed in
23284 @value{GDBN} as @code{set print foo}.
23286 If @var{name} consists of multiple words, and no prefix parameter group
23287 can be found, an exception is raised.
23289 @var{command-class} should be one of the @samp{COMMAND_} constants
23290 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23291 categorize the new parameter in the help system.
23293 @var{parameter-class} should be one of the @samp{PARAM_} constants
23294 defined below. This argument tells @value{GDBN} the type of the new
23295 parameter; this information is used for input validation and
23298 If @var{parameter-class} is @code{PARAM_ENUM}, then
23299 @var{enum-sequence} must be a sequence of strings. These strings
23300 represent the possible values for the parameter.
23302 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23303 of a fourth argument will cause an exception to be thrown.
23305 The help text for the new parameter is taken from the Python
23306 documentation string for the parameter's class, if there is one. If
23307 there is no documentation string, a default value is used.
23310 @defvar Parameter.set_doc
23311 If this attribute exists, and is a string, then its value is used as
23312 the help text for this parameter's @code{set} command. The value is
23313 examined when @code{Parameter.__init__} is invoked; subsequent changes
23317 @defvar Parameter.show_doc
23318 If this attribute exists, and is a string, then its value is used as
23319 the help text for this parameter's @code{show} command. The value is
23320 examined when @code{Parameter.__init__} is invoked; subsequent changes
23324 @defvar Parameter.value
23325 The @code{value} attribute holds the underlying value of the
23326 parameter. It can be read and assigned to just as any other
23327 attribute. @value{GDBN} does validation when assignments are made.
23330 There are two methods that should be implemented in any
23331 @code{Parameter} class. These are:
23333 @defun Parameter.get_set_string (self)
23334 @value{GDBN} will call this method when a @var{parameter}'s value has
23335 been changed via the @code{set} API (for example, @kbd{set foo off}).
23336 The @code{value} attribute has already been populated with the new
23337 value and may be used in output. This method must return a string.
23340 @defun Parameter.get_show_string (self, svalue)
23341 @value{GDBN} will call this method when a @var{parameter}'s
23342 @code{show} API has been invoked (for example, @kbd{show foo}). The
23343 argument @code{svalue} receives the string representation of the
23344 current value. This method must return a string.
23347 When a new parameter is defined, its type must be specified. The
23348 available types are represented by constants defined in the @code{gdb}
23352 @findex PARAM_BOOLEAN
23353 @findex gdb.PARAM_BOOLEAN
23354 @item gdb.PARAM_BOOLEAN
23355 The value is a plain boolean. The Python boolean values, @code{True}
23356 and @code{False} are the only valid values.
23358 @findex PARAM_AUTO_BOOLEAN
23359 @findex gdb.PARAM_AUTO_BOOLEAN
23360 @item gdb.PARAM_AUTO_BOOLEAN
23361 The value has three possible states: true, false, and @samp{auto}. In
23362 Python, true and false are represented using boolean constants, and
23363 @samp{auto} is represented using @code{None}.
23365 @findex PARAM_UINTEGER
23366 @findex gdb.PARAM_UINTEGER
23367 @item gdb.PARAM_UINTEGER
23368 The value is an unsigned integer. The value of 0 should be
23369 interpreted to mean ``unlimited''.
23371 @findex PARAM_INTEGER
23372 @findex gdb.PARAM_INTEGER
23373 @item gdb.PARAM_INTEGER
23374 The value is a signed integer. The value of 0 should be interpreted
23375 to mean ``unlimited''.
23377 @findex PARAM_STRING
23378 @findex gdb.PARAM_STRING
23379 @item gdb.PARAM_STRING
23380 The value is a string. When the user modifies the string, any escape
23381 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23382 translated into corresponding characters and encoded into the current
23385 @findex PARAM_STRING_NOESCAPE
23386 @findex gdb.PARAM_STRING_NOESCAPE
23387 @item gdb.PARAM_STRING_NOESCAPE
23388 The value is a string. When the user modifies the string, escapes are
23389 passed through untranslated.
23391 @findex PARAM_OPTIONAL_FILENAME
23392 @findex gdb.PARAM_OPTIONAL_FILENAME
23393 @item gdb.PARAM_OPTIONAL_FILENAME
23394 The value is a either a filename (a string), or @code{None}.
23396 @findex PARAM_FILENAME
23397 @findex gdb.PARAM_FILENAME
23398 @item gdb.PARAM_FILENAME
23399 The value is a filename. This is just like
23400 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23402 @findex PARAM_ZINTEGER
23403 @findex gdb.PARAM_ZINTEGER
23404 @item gdb.PARAM_ZINTEGER
23405 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23406 is interpreted as itself.
23409 @findex gdb.PARAM_ENUM
23410 @item gdb.PARAM_ENUM
23411 The value is a string, which must be one of a collection string
23412 constants provided when the parameter is created.
23415 @node Functions In Python
23416 @subsubsection Writing new convenience functions
23418 @cindex writing convenience functions
23419 @cindex convenience functions in python
23420 @cindex python convenience functions
23421 @tindex gdb.Function
23423 You can implement new convenience functions (@pxref{Convenience Vars})
23424 in Python. A convenience function is an instance of a subclass of the
23425 class @code{gdb.Function}.
23427 @defun Function.__init__ (name)
23428 The initializer for @code{Function} registers the new function with
23429 @value{GDBN}. The argument @var{name} is the name of the function,
23430 a string. The function will be visible to the user as a convenience
23431 variable of type @code{internal function}, whose name is the same as
23432 the given @var{name}.
23434 The documentation for the new function is taken from the documentation
23435 string for the new class.
23438 @defun Function.invoke (@var{*args})
23439 When a convenience function is evaluated, its arguments are converted
23440 to instances of @code{gdb.Value}, and then the function's
23441 @code{invoke} method is called. Note that @value{GDBN} does not
23442 predetermine the arity of convenience functions. Instead, all
23443 available arguments are passed to @code{invoke}, following the
23444 standard Python calling convention. In particular, a convenience
23445 function can have default values for parameters without ill effect.
23447 The return value of this method is used as its value in the enclosing
23448 expression. If an ordinary Python value is returned, it is converted
23449 to a @code{gdb.Value} following the usual rules.
23452 The following code snippet shows how a trivial convenience function can
23453 be implemented in Python:
23456 class Greet (gdb.Function):
23457 """Return string to greet someone.
23458 Takes a name as argument."""
23460 def __init__ (self):
23461 super (Greet, self).__init__ ("greet")
23463 def invoke (self, name):
23464 return "Hello, %s!" % name.string ()
23469 The last line instantiates the class, and is necessary to trigger the
23470 registration of the function with @value{GDBN}. Depending on how the
23471 Python code is read into @value{GDBN}, you may need to import the
23472 @code{gdb} module explicitly.
23474 @node Progspaces In Python
23475 @subsubsection Program Spaces In Python
23477 @cindex progspaces in python
23478 @tindex gdb.Progspace
23480 A program space, or @dfn{progspace}, represents a symbolic view
23481 of an address space.
23482 It consists of all of the objfiles of the program.
23483 @xref{Objfiles In Python}.
23484 @xref{Inferiors and Programs, program spaces}, for more details
23485 about program spaces.
23487 The following progspace-related functions are available in the
23490 @findex gdb.current_progspace
23491 @defun gdb.current_progspace ()
23492 This function returns the program space of the currently selected inferior.
23493 @xref{Inferiors and Programs}.
23496 @findex gdb.progspaces
23497 @defun gdb.progspaces ()
23498 Return a sequence of all the progspaces currently known to @value{GDBN}.
23501 Each progspace is represented by an instance of the @code{gdb.Progspace}
23504 @defvar Progspace.filename
23505 The file name of the progspace as a string.
23508 @defvar Progspace.pretty_printers
23509 The @code{pretty_printers} attribute is a list of functions. It is
23510 used to look up pretty-printers. A @code{Value} is passed to each
23511 function in order; if the function returns @code{None}, then the
23512 search continues. Otherwise, the return value should be an object
23513 which is used to format the value. @xref{Pretty Printing API}, for more
23517 @node Objfiles In Python
23518 @subsubsection Objfiles In Python
23520 @cindex objfiles in python
23521 @tindex gdb.Objfile
23523 @value{GDBN} loads symbols for an inferior from various
23524 symbol-containing files (@pxref{Files}). These include the primary
23525 executable file, any shared libraries used by the inferior, and any
23526 separate debug info files (@pxref{Separate Debug Files}).
23527 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23529 The following objfile-related functions are available in the
23532 @findex gdb.current_objfile
23533 @defun gdb.current_objfile ()
23534 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23535 sets the ``current objfile'' to the corresponding objfile. This
23536 function returns the current objfile. If there is no current objfile,
23537 this function returns @code{None}.
23540 @findex gdb.objfiles
23541 @defun gdb.objfiles ()
23542 Return a sequence of all the objfiles current known to @value{GDBN}.
23543 @xref{Objfiles In Python}.
23546 Each objfile is represented by an instance of the @code{gdb.Objfile}
23549 @defvar Objfile.filename
23550 The file name of the objfile as a string.
23553 @defvar Objfile.pretty_printers
23554 The @code{pretty_printers} attribute is a list of functions. It is
23555 used to look up pretty-printers. A @code{Value} is passed to each
23556 function in order; if the function returns @code{None}, then the
23557 search continues. Otherwise, the return value should be an object
23558 which is used to format the value. @xref{Pretty Printing API}, for more
23562 A @code{gdb.Objfile} object has the following methods:
23564 @defun Objfile.is_valid ()
23565 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23566 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23567 if the object file it refers to is not loaded in @value{GDBN} any
23568 longer. All other @code{gdb.Objfile} methods will throw an exception
23569 if it is invalid at the time the method is called.
23572 @node Frames In Python
23573 @subsubsection Accessing inferior stack frames from Python.
23575 @cindex frames in python
23576 When the debugged program stops, @value{GDBN} is able to analyze its call
23577 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23578 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23579 while its corresponding frame exists in the inferior's stack. If you try
23580 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23581 exception (@pxref{Exception Handling}).
23583 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23587 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23591 The following frame-related functions are available in the @code{gdb} module:
23593 @findex gdb.selected_frame
23594 @defun gdb.selected_frame ()
23595 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23598 @findex gdb.newest_frame
23599 @defun gdb.newest_frame ()
23600 Return the newest frame object for the selected thread.
23603 @defun gdb.frame_stop_reason_string (reason)
23604 Return a string explaining the reason why @value{GDBN} stopped unwinding
23605 frames, as expressed by the given @var{reason} code (an integer, see the
23606 @code{unwind_stop_reason} method further down in this section).
23609 A @code{gdb.Frame} object has the following methods:
23612 @defun Frame.is_valid ()
23613 Returns true if the @code{gdb.Frame} object is valid, false if not.
23614 A frame object can become invalid if the frame it refers to doesn't
23615 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23616 an exception if it is invalid at the time the method is called.
23619 @defun Frame.name ()
23620 Returns the function name of the frame, or @code{None} if it can't be
23624 @defun Frame.type ()
23625 Returns the type of the frame. The value can be one of:
23627 @item gdb.NORMAL_FRAME
23628 An ordinary stack frame.
23630 @item gdb.DUMMY_FRAME
23631 A fake stack frame that was created by @value{GDBN} when performing an
23632 inferior function call.
23634 @item gdb.INLINE_FRAME
23635 A frame representing an inlined function. The function was inlined
23636 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23638 @item gdb.TAILCALL_FRAME
23639 A frame representing a tail call. @xref{Tail Call Frames}.
23641 @item gdb.SIGTRAMP_FRAME
23642 A signal trampoline frame. This is the frame created by the OS when
23643 it calls into a signal handler.
23645 @item gdb.ARCH_FRAME
23646 A fake stack frame representing a cross-architecture call.
23648 @item gdb.SENTINEL_FRAME
23649 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23654 @defun Frame.unwind_stop_reason ()
23655 Return an integer representing the reason why it's not possible to find
23656 more frames toward the outermost frame. Use
23657 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23658 function to a string. The value can be one of:
23661 @item gdb.FRAME_UNWIND_NO_REASON
23662 No particular reason (older frames should be available).
23664 @item gdb.FRAME_UNWIND_NULL_ID
23665 The previous frame's analyzer returns an invalid result.
23667 @item gdb.FRAME_UNWIND_OUTERMOST
23668 This frame is the outermost.
23670 @item gdb.FRAME_UNWIND_UNAVAILABLE
23671 Cannot unwind further, because that would require knowing the
23672 values of registers or memory that have not been collected.
23674 @item gdb.FRAME_UNWIND_INNER_ID
23675 This frame ID looks like it ought to belong to a NEXT frame,
23676 but we got it for a PREV frame. Normally, this is a sign of
23677 unwinder failure. It could also indicate stack corruption.
23679 @item gdb.FRAME_UNWIND_SAME_ID
23680 This frame has the same ID as the previous one. That means
23681 that unwinding further would almost certainly give us another
23682 frame with exactly the same ID, so break the chain. Normally,
23683 this is a sign of unwinder failure. It could also indicate
23686 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23687 The frame unwinder did not find any saved PC, but we needed
23688 one to unwind further.
23690 @item gdb.FRAME_UNWIND_FIRST_ERROR
23691 Any stop reason greater or equal to this value indicates some kind
23692 of error. This special value facilitates writing code that tests
23693 for errors in unwinding in a way that will work correctly even if
23694 the list of the other values is modified in future @value{GDBN}
23695 versions. Using it, you could write:
23697 reason = gdb.selected_frame().unwind_stop_reason ()
23698 reason_str = gdb.frame_stop_reason_string (reason)
23699 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23700 print "An error occured: %s" % reason_str
23707 Returns the frame's resume address.
23710 @defun Frame.block ()
23711 Return the frame's code block. @xref{Blocks In Python}.
23714 @defun Frame.function ()
23715 Return the symbol for the function corresponding to this frame.
23716 @xref{Symbols In Python}.
23719 @defun Frame.older ()
23720 Return the frame that called this frame.
23723 @defun Frame.newer ()
23724 Return the frame called by this frame.
23727 @defun Frame.find_sal ()
23728 Return the frame's symtab and line object.
23729 @xref{Symbol Tables In Python}.
23732 @defun Frame.read_var (variable @r{[}, block@r{]})
23733 Return the value of @var{variable} in this frame. If the optional
23734 argument @var{block} is provided, search for the variable from that
23735 block; otherwise start at the frame's current block (which is
23736 determined by the frame's current program counter). @var{variable}
23737 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23738 @code{gdb.Block} object.
23741 @defun Frame.select ()
23742 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23747 @node Blocks In Python
23748 @subsubsection Accessing frame blocks from Python.
23750 @cindex blocks in python
23753 Within each frame, @value{GDBN} maintains information on each block
23754 stored in that frame. These blocks are organized hierarchically, and
23755 are represented individually in Python as a @code{gdb.Block}.
23756 Please see @ref{Frames In Python}, for a more in-depth discussion on
23757 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23758 detailed technical information on @value{GDBN}'s book-keeping of the
23761 The following block-related functions are available in the @code{gdb}
23764 @findex gdb.block_for_pc
23765 @defun gdb.block_for_pc (pc)
23766 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23767 block cannot be found for the @var{pc} value specified, the function
23768 will return @code{None}.
23771 A @code{gdb.Block} object has the following methods:
23774 @defun Block.is_valid ()
23775 Returns @code{True} if the @code{gdb.Block} object is valid,
23776 @code{False} if not. A block object can become invalid if the block it
23777 refers to doesn't exist anymore in the inferior. All other
23778 @code{gdb.Block} methods will throw an exception if it is invalid at
23779 the time the method is called. This method is also made available to
23780 the Python iterator object that @code{gdb.Block} provides in an iteration
23781 context and via the Python @code{iter} built-in function.
23785 A @code{gdb.Block} object has the following attributes:
23788 @defvar Block.start
23789 The start address of the block. This attribute is not writable.
23793 The end address of the block. This attribute is not writable.
23796 @defvar Block.function
23797 The name of the block represented as a @code{gdb.Symbol}. If the
23798 block is not named, then this attribute holds @code{None}. This
23799 attribute is not writable.
23802 @defvar Block.superblock
23803 The block containing this block. If this parent block does not exist,
23804 this attribute holds @code{None}. This attribute is not writable.
23807 @defvar Block.global_block
23808 The global block associated with this block. This attribute is not
23812 @defvar Block.static_block
23813 The static block associated with this block. This attribute is not
23817 @defvar Block.is_global
23818 @code{True} if the @code{gdb.Block} object is a global block,
23819 @code{False} if not. This attribute is not
23823 @defvar Block.is_static
23824 @code{True} if the @code{gdb.Block} object is a static block,
23825 @code{False} if not. This attribute is not writable.
23829 @node Symbols In Python
23830 @subsubsection Python representation of Symbols.
23832 @cindex symbols in python
23835 @value{GDBN} represents every variable, function and type as an
23836 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23837 Similarly, Python represents these symbols in @value{GDBN} with the
23838 @code{gdb.Symbol} object.
23840 The following symbol-related functions are available in the @code{gdb}
23843 @findex gdb.lookup_symbol
23844 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23845 This function searches for a symbol by name. The search scope can be
23846 restricted to the parameters defined in the optional domain and block
23849 @var{name} is the name of the symbol. It must be a string. The
23850 optional @var{block} argument restricts the search to symbols visible
23851 in that @var{block}. The @var{block} argument must be a
23852 @code{gdb.Block} object. If omitted, the block for the current frame
23853 is used. The optional @var{domain} argument restricts
23854 the search to the domain type. The @var{domain} argument must be a
23855 domain constant defined in the @code{gdb} module and described later
23858 The result is a tuple of two elements.
23859 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23861 If the symbol is found, the second element is @code{True} if the symbol
23862 is a field of a method's object (e.g., @code{this} in C@t{++}),
23863 otherwise it is @code{False}.
23864 If the symbol is not found, the second element is @code{False}.
23867 @findex gdb.lookup_global_symbol
23868 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23869 This function searches for a global symbol by name.
23870 The search scope can be restricted to by the domain argument.
23872 @var{name} is the name of the symbol. It must be a string.
23873 The optional @var{domain} argument restricts the search to the domain type.
23874 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23875 module and described later in this chapter.
23877 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23881 A @code{gdb.Symbol} object has the following attributes:
23884 @defvar Symbol.type
23885 The type of the symbol or @code{None} if no type is recorded.
23886 This attribute is represented as a @code{gdb.Type} object.
23887 @xref{Types In Python}. This attribute is not writable.
23890 @defvar Symbol.symtab
23891 The symbol table in which the symbol appears. This attribute is
23892 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23893 Python}. This attribute is not writable.
23896 @defvar Symbol.name
23897 The name of the symbol as a string. This attribute is not writable.
23900 @defvar Symbol.linkage_name
23901 The name of the symbol, as used by the linker (i.e., may be mangled).
23902 This attribute is not writable.
23905 @defvar Symbol.print_name
23906 The name of the symbol in a form suitable for output. This is either
23907 @code{name} or @code{linkage_name}, depending on whether the user
23908 asked @value{GDBN} to display demangled or mangled names.
23911 @defvar Symbol.addr_class
23912 The address class of the symbol. This classifies how to find the value
23913 of a symbol. Each address class is a constant defined in the
23914 @code{gdb} module and described later in this chapter.
23917 @defvar Symbol.is_argument
23918 @code{True} if the symbol is an argument of a function.
23921 @defvar Symbol.is_constant
23922 @code{True} if the symbol is a constant.
23925 @defvar Symbol.is_function
23926 @code{True} if the symbol is a function or a method.
23929 @defvar Symbol.is_variable
23930 @code{True} if the symbol is a variable.
23934 A @code{gdb.Symbol} object has the following methods:
23937 @defun Symbol.is_valid ()
23938 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23939 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23940 the symbol it refers to does not exist in @value{GDBN} any longer.
23941 All other @code{gdb.Symbol} methods will throw an exception if it is
23942 invalid at the time the method is called.
23946 The available domain categories in @code{gdb.Symbol} are represented
23947 as constants in the @code{gdb} module:
23950 @findex SYMBOL_UNDEF_DOMAIN
23951 @findex gdb.SYMBOL_UNDEF_DOMAIN
23952 @item gdb.SYMBOL_UNDEF_DOMAIN
23953 This is used when a domain has not been discovered or none of the
23954 following domains apply. This usually indicates an error either
23955 in the symbol information or in @value{GDBN}'s handling of symbols.
23956 @findex SYMBOL_VAR_DOMAIN
23957 @findex gdb.SYMBOL_VAR_DOMAIN
23958 @item gdb.SYMBOL_VAR_DOMAIN
23959 This domain contains variables, function names, typedef names and enum
23961 @findex SYMBOL_STRUCT_DOMAIN
23962 @findex gdb.SYMBOL_STRUCT_DOMAIN
23963 @item gdb.SYMBOL_STRUCT_DOMAIN
23964 This domain holds struct, union and enum type names.
23965 @findex SYMBOL_LABEL_DOMAIN
23966 @findex gdb.SYMBOL_LABEL_DOMAIN
23967 @item gdb.SYMBOL_LABEL_DOMAIN
23968 This domain contains names of labels (for gotos).
23969 @findex SYMBOL_VARIABLES_DOMAIN
23970 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23971 @item gdb.SYMBOL_VARIABLES_DOMAIN
23972 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23973 contains everything minus functions and types.
23974 @findex SYMBOL_FUNCTIONS_DOMAIN
23975 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23976 @item gdb.SYMBOL_FUNCTION_DOMAIN
23977 This domain contains all functions.
23978 @findex SYMBOL_TYPES_DOMAIN
23979 @findex gdb.SYMBOL_TYPES_DOMAIN
23980 @item gdb.SYMBOL_TYPES_DOMAIN
23981 This domain contains all types.
23984 The available address class categories in @code{gdb.Symbol} are represented
23985 as constants in the @code{gdb} module:
23988 @findex SYMBOL_LOC_UNDEF
23989 @findex gdb.SYMBOL_LOC_UNDEF
23990 @item gdb.SYMBOL_LOC_UNDEF
23991 If this is returned by address class, it indicates an error either in
23992 the symbol information or in @value{GDBN}'s handling of symbols.
23993 @findex SYMBOL_LOC_CONST
23994 @findex gdb.SYMBOL_LOC_CONST
23995 @item gdb.SYMBOL_LOC_CONST
23996 Value is constant int.
23997 @findex SYMBOL_LOC_STATIC
23998 @findex gdb.SYMBOL_LOC_STATIC
23999 @item gdb.SYMBOL_LOC_STATIC
24000 Value is at a fixed address.
24001 @findex SYMBOL_LOC_REGISTER
24002 @findex gdb.SYMBOL_LOC_REGISTER
24003 @item gdb.SYMBOL_LOC_REGISTER
24004 Value is in a register.
24005 @findex SYMBOL_LOC_ARG
24006 @findex gdb.SYMBOL_LOC_ARG
24007 @item gdb.SYMBOL_LOC_ARG
24008 Value is an argument. This value is at the offset stored within the
24009 symbol inside the frame's argument list.
24010 @findex SYMBOL_LOC_REF_ARG
24011 @findex gdb.SYMBOL_LOC_REF_ARG
24012 @item gdb.SYMBOL_LOC_REF_ARG
24013 Value address is stored in the frame's argument list. Just like
24014 @code{LOC_ARG} except that the value's address is stored at the
24015 offset, not the value itself.
24016 @findex SYMBOL_LOC_REGPARM_ADDR
24017 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24018 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24019 Value is a specified register. Just like @code{LOC_REGISTER} except
24020 the register holds the address of the argument instead of the argument
24022 @findex SYMBOL_LOC_LOCAL
24023 @findex gdb.SYMBOL_LOC_LOCAL
24024 @item gdb.SYMBOL_LOC_LOCAL
24025 Value is a local variable.
24026 @findex SYMBOL_LOC_TYPEDEF
24027 @findex gdb.SYMBOL_LOC_TYPEDEF
24028 @item gdb.SYMBOL_LOC_TYPEDEF
24029 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24031 @findex SYMBOL_LOC_BLOCK
24032 @findex gdb.SYMBOL_LOC_BLOCK
24033 @item gdb.SYMBOL_LOC_BLOCK
24035 @findex SYMBOL_LOC_CONST_BYTES
24036 @findex gdb.SYMBOL_LOC_CONST_BYTES
24037 @item gdb.SYMBOL_LOC_CONST_BYTES
24038 Value is a byte-sequence.
24039 @findex SYMBOL_LOC_UNRESOLVED
24040 @findex gdb.SYMBOL_LOC_UNRESOLVED
24041 @item gdb.SYMBOL_LOC_UNRESOLVED
24042 Value is at a fixed address, but the address of the variable has to be
24043 determined from the minimal symbol table whenever the variable is
24045 @findex SYMBOL_LOC_OPTIMIZED_OUT
24046 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24047 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24048 The value does not actually exist in the program.
24049 @findex SYMBOL_LOC_COMPUTED
24050 @findex gdb.SYMBOL_LOC_COMPUTED
24051 @item gdb.SYMBOL_LOC_COMPUTED
24052 The value's address is a computed location.
24055 @node Symbol Tables In Python
24056 @subsubsection Symbol table representation in Python.
24058 @cindex symbol tables in python
24060 @tindex gdb.Symtab_and_line
24062 Access to symbol table data maintained by @value{GDBN} on the inferior
24063 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24064 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24065 from the @code{find_sal} method in @code{gdb.Frame} object.
24066 @xref{Frames In Python}.
24068 For more information on @value{GDBN}'s symbol table management, see
24069 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24071 A @code{gdb.Symtab_and_line} object has the following attributes:
24074 @defvar Symtab_and_line.symtab
24075 The symbol table object (@code{gdb.Symtab}) for this frame.
24076 This attribute is not writable.
24079 @defvar Symtab_and_line.pc
24080 Indicates the current program counter address. This attribute is not
24084 @defvar Symtab_and_line.line
24085 Indicates the current line number for this object. This
24086 attribute is not writable.
24090 A @code{gdb.Symtab_and_line} object has the following methods:
24093 @defun Symtab_and_line.is_valid ()
24094 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24095 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24096 invalid if the Symbol table and line object it refers to does not
24097 exist in @value{GDBN} any longer. All other
24098 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24099 invalid at the time the method is called.
24103 A @code{gdb.Symtab} object has the following attributes:
24106 @defvar Symtab.filename
24107 The symbol table's source filename. This attribute is not writable.
24110 @defvar Symtab.objfile
24111 The symbol table's backing object file. @xref{Objfiles In Python}.
24112 This attribute is not writable.
24116 A @code{gdb.Symtab} object has the following methods:
24119 @defun Symtab.is_valid ()
24120 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24121 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24122 the symbol table it refers to does not exist in @value{GDBN} any
24123 longer. All other @code{gdb.Symtab} methods will throw an exception
24124 if it is invalid at the time the method is called.
24127 @defun Symtab.fullname ()
24128 Return the symbol table's source absolute file name.
24132 @node Breakpoints In Python
24133 @subsubsection Manipulating breakpoints using Python
24135 @cindex breakpoints in python
24136 @tindex gdb.Breakpoint
24138 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24141 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24142 Create a new breakpoint. @var{spec} is a string naming the
24143 location of the breakpoint, or an expression that defines a
24144 watchpoint. The contents can be any location recognized by the
24145 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24146 command. The optional @var{type} denotes the breakpoint to create
24147 from the types defined later in this chapter. This argument can be
24148 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24149 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24150 allows the breakpoint to become invisible to the user. The breakpoint
24151 will neither be reported when created, nor will it be listed in the
24152 output from @code{info breakpoints} (but will be listed with the
24153 @code{maint info breakpoints} command). The optional @var{wp_class}
24154 argument defines the class of watchpoint to create, if @var{type} is
24155 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24156 assumed to be a @code{gdb.WP_WRITE} class.
24159 @defun Breakpoint.stop (self)
24160 The @code{gdb.Breakpoint} class can be sub-classed and, in
24161 particular, you may choose to implement the @code{stop} method.
24162 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24163 it will be called when the inferior reaches any location of a
24164 breakpoint which instantiates that sub-class. If the method returns
24165 @code{True}, the inferior will be stopped at the location of the
24166 breakpoint, otherwise the inferior will continue.
24168 If there are multiple breakpoints at the same location with a
24169 @code{stop} method, each one will be called regardless of the
24170 return status of the previous. This ensures that all @code{stop}
24171 methods have a chance to execute at that location. In this scenario
24172 if one of the methods returns @code{True} but the others return
24173 @code{False}, the inferior will still be stopped.
24175 You should not alter the execution state of the inferior (i.e.@:, step,
24176 next, etc.), alter the current frame context (i.e.@:, change the current
24177 active frame), or alter, add or delete any breakpoint. As a general
24178 rule, you should not alter any data within @value{GDBN} or the inferior
24181 Example @code{stop} implementation:
24184 class MyBreakpoint (gdb.Breakpoint):
24186 inf_val = gdb.parse_and_eval("foo")
24193 The available watchpoint types represented by constants are defined in the
24198 @findex gdb.WP_READ
24200 Read only watchpoint.
24203 @findex gdb.WP_WRITE
24205 Write only watchpoint.
24208 @findex gdb.WP_ACCESS
24209 @item gdb.WP_ACCESS
24210 Read/Write watchpoint.
24213 @defun Breakpoint.is_valid ()
24214 Return @code{True} if this @code{Breakpoint} object is valid,
24215 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24216 if the user deletes the breakpoint. In this case, the object still
24217 exists, but the underlying breakpoint does not. In the cases of
24218 watchpoint scope, the watchpoint remains valid even if execution of the
24219 inferior leaves the scope of that watchpoint.
24222 @defun Breakpoint.delete
24223 Permanently deletes the @value{GDBN} breakpoint. This also
24224 invalidates the Python @code{Breakpoint} object. Any further access
24225 to this object's attributes or methods will raise an error.
24228 @defvar Breakpoint.enabled
24229 This attribute is @code{True} if the breakpoint is enabled, and
24230 @code{False} otherwise. This attribute is writable.
24233 @defvar Breakpoint.silent
24234 This attribute is @code{True} if the breakpoint is silent, and
24235 @code{False} otherwise. This attribute is writable.
24237 Note that a breakpoint can also be silent if it has commands and the
24238 first command is @code{silent}. This is not reported by the
24239 @code{silent} attribute.
24242 @defvar Breakpoint.thread
24243 If the breakpoint is thread-specific, this attribute holds the thread
24244 id. If the breakpoint is not thread-specific, this attribute is
24245 @code{None}. This attribute is writable.
24248 @defvar Breakpoint.task
24249 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24250 id. If the breakpoint is not task-specific (or the underlying
24251 language is not Ada), this attribute is @code{None}. This attribute
24255 @defvar Breakpoint.ignore_count
24256 This attribute holds the ignore count for the breakpoint, an integer.
24257 This attribute is writable.
24260 @defvar Breakpoint.number
24261 This attribute holds the breakpoint's number --- the identifier used by
24262 the user to manipulate the breakpoint. This attribute is not writable.
24265 @defvar Breakpoint.type
24266 This attribute holds the breakpoint's type --- the identifier used to
24267 determine the actual breakpoint type or use-case. This attribute is not
24271 @defvar Breakpoint.visible
24272 This attribute tells whether the breakpoint is visible to the user
24273 when set, or when the @samp{info breakpoints} command is run. This
24274 attribute is not writable.
24277 The available types are represented by constants defined in the @code{gdb}
24281 @findex BP_BREAKPOINT
24282 @findex gdb.BP_BREAKPOINT
24283 @item gdb.BP_BREAKPOINT
24284 Normal code breakpoint.
24286 @findex BP_WATCHPOINT
24287 @findex gdb.BP_WATCHPOINT
24288 @item gdb.BP_WATCHPOINT
24289 Watchpoint breakpoint.
24291 @findex BP_HARDWARE_WATCHPOINT
24292 @findex gdb.BP_HARDWARE_WATCHPOINT
24293 @item gdb.BP_HARDWARE_WATCHPOINT
24294 Hardware assisted watchpoint.
24296 @findex BP_READ_WATCHPOINT
24297 @findex gdb.BP_READ_WATCHPOINT
24298 @item gdb.BP_READ_WATCHPOINT
24299 Hardware assisted read watchpoint.
24301 @findex BP_ACCESS_WATCHPOINT
24302 @findex gdb.BP_ACCESS_WATCHPOINT
24303 @item gdb.BP_ACCESS_WATCHPOINT
24304 Hardware assisted access watchpoint.
24307 @defvar Breakpoint.hit_count
24308 This attribute holds the hit count for the breakpoint, an integer.
24309 This attribute is writable, but currently it can only be set to zero.
24312 @defvar Breakpoint.location
24313 This attribute holds the location of the breakpoint, as specified by
24314 the user. It is a string. If the breakpoint does not have a location
24315 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24316 attribute is not writable.
24319 @defvar Breakpoint.expression
24320 This attribute holds a breakpoint expression, as specified by
24321 the user. It is a string. If the breakpoint does not have an
24322 expression (the breakpoint is not a watchpoint) the attribute's value
24323 is @code{None}. This attribute is not writable.
24326 @defvar Breakpoint.condition
24327 This attribute holds the condition of the breakpoint, as specified by
24328 the user. It is a string. If there is no condition, this attribute's
24329 value is @code{None}. This attribute is writable.
24332 @defvar Breakpoint.commands
24333 This attribute holds the commands attached to the breakpoint. If
24334 there are commands, this attribute's value is a string holding all the
24335 commands, separated by newlines. If there are no commands, this
24336 attribute is @code{None}. This attribute is not writable.
24339 @node Lazy Strings In Python
24340 @subsubsection Python representation of lazy strings.
24342 @cindex lazy strings in python
24343 @tindex gdb.LazyString
24345 A @dfn{lazy string} is a string whose contents is not retrieved or
24346 encoded until it is needed.
24348 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24349 @code{address} that points to a region of memory, an @code{encoding}
24350 that will be used to encode that region of memory, and a @code{length}
24351 to delimit the region of memory that represents the string. The
24352 difference between a @code{gdb.LazyString} and a string wrapped within
24353 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24354 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24355 retrieved and encoded during printing, while a @code{gdb.Value}
24356 wrapping a string is immediately retrieved and encoded on creation.
24358 A @code{gdb.LazyString} object has the following functions:
24360 @defun LazyString.value ()
24361 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24362 will point to the string in memory, but will lose all the delayed
24363 retrieval, encoding and handling that @value{GDBN} applies to a
24364 @code{gdb.LazyString}.
24367 @defvar LazyString.address
24368 This attribute holds the address of the string. This attribute is not
24372 @defvar LazyString.length
24373 This attribute holds the length of the string in characters. If the
24374 length is -1, then the string will be fetched and encoded up to the
24375 first null of appropriate width. This attribute is not writable.
24378 @defvar LazyString.encoding
24379 This attribute holds the encoding that will be applied to the string
24380 when the string is printed by @value{GDBN}. If the encoding is not
24381 set, or contains an empty string, then @value{GDBN} will select the
24382 most appropriate encoding when the string is printed. This attribute
24386 @defvar LazyString.type
24387 This attribute holds the type that is represented by the lazy string's
24388 type. For a lazy string this will always be a pointer type. To
24389 resolve this to the lazy string's character type, use the type's
24390 @code{target} method. @xref{Types In Python}. This attribute is not
24395 @subsection Auto-loading
24396 @cindex auto-loading, Python
24398 When a new object file is read (for example, due to the @code{file}
24399 command, or because the inferior has loaded a shared library),
24400 @value{GDBN} will look for Python support scripts in several ways:
24401 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24404 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24405 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24406 * Which flavor to choose?::
24409 The auto-loading feature is useful for supplying application-specific
24410 debugging commands and scripts.
24412 Auto-loading can be enabled or disabled,
24413 and the list of auto-loaded scripts can be printed.
24416 @kindex set auto-load-scripts
24417 @item set auto-load-scripts [yes|no]
24418 Enable or disable the auto-loading of Python scripts.
24420 @kindex show auto-load-scripts
24421 @item show auto-load-scripts
24422 Show whether auto-loading of Python scripts is enabled or disabled.
24424 @kindex info auto-load-scripts
24425 @cindex print list of auto-loaded scripts
24426 @item info auto-load-scripts [@var{regexp}]
24427 Print the list of all scripts that @value{GDBN} auto-loaded.
24429 Also printed is the list of scripts that were mentioned in
24430 the @code{.debug_gdb_scripts} section and were not found
24431 (@pxref{.debug_gdb_scripts section}).
24432 This is useful because their names are not printed when @value{GDBN}
24433 tries to load them and fails. There may be many of them, and printing
24434 an error message for each one is problematic.
24436 If @var{regexp} is supplied only scripts with matching names are printed.
24441 (gdb) info auto-load-scripts
24443 Yes py-section-script.py
24444 full name: /tmp/py-section-script.py
24445 Missing my-foo-pretty-printers.py
24449 When reading an auto-loaded file, @value{GDBN} sets the
24450 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24451 function (@pxref{Objfiles In Python}). This can be useful for
24452 registering objfile-specific pretty-printers.
24454 @node objfile-gdb.py file
24455 @subsubsection The @file{@var{objfile}-gdb.py} file
24456 @cindex @file{@var{objfile}-gdb.py}
24458 When a new object file is read, @value{GDBN} looks for
24459 a file named @file{@var{objfile}-gdb.py},
24460 where @var{objfile} is the object file's real name, formed by ensuring
24461 that the file name is absolute, following all symlinks, and resolving
24462 @code{.} and @code{..} components. If this file exists and is
24463 readable, @value{GDBN} will evaluate it as a Python script.
24465 If this file does not exist, and if the parameter
24466 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24467 then @value{GDBN} will look for @var{real-name} in all of the
24468 directories mentioned in the value of @code{debug-file-directory}.
24470 Finally, if this file does not exist, then @value{GDBN} will look for
24471 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24472 @var{data-directory} is @value{GDBN}'s data directory (available via
24473 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24474 is the object file's real name, as described above.
24476 @value{GDBN} does not track which files it has already auto-loaded this way.
24477 @value{GDBN} will load the associated script every time the corresponding
24478 @var{objfile} is opened.
24479 So your @file{-gdb.py} file should be careful to avoid errors if it
24480 is evaluated more than once.
24482 @node .debug_gdb_scripts section
24483 @subsubsection The @code{.debug_gdb_scripts} section
24484 @cindex @code{.debug_gdb_scripts} section
24486 For systems using file formats like ELF and COFF,
24487 when @value{GDBN} loads a new object file
24488 it will look for a special section named @samp{.debug_gdb_scripts}.
24489 If this section exists, its contents is a list of names of scripts to load.
24491 @value{GDBN} will look for each specified script file first in the
24492 current directory and then along the source search path
24493 (@pxref{Source Path, ,Specifying Source Directories}),
24494 except that @file{$cdir} is not searched, since the compilation
24495 directory is not relevant to scripts.
24497 Entries can be placed in section @code{.debug_gdb_scripts} with,
24498 for example, this GCC macro:
24501 /* Note: The "MS" section flags are to remove duplicates. */
24502 #define DEFINE_GDB_SCRIPT(script_name) \
24504 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24506 .asciz \"" script_name "\"\n\
24512 Then one can reference the macro in a header or source file like this:
24515 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24518 The script name may include directories if desired.
24520 If the macro is put in a header, any application or library
24521 using this header will get a reference to the specified script.
24523 @node Which flavor to choose?
24524 @subsubsection Which flavor to choose?
24526 Given the multiple ways of auto-loading Python scripts, it might not always
24527 be clear which one to choose. This section provides some guidance.
24529 Benefits of the @file{-gdb.py} way:
24533 Can be used with file formats that don't support multiple sections.
24536 Ease of finding scripts for public libraries.
24538 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24539 in the source search path.
24540 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24541 isn't a source directory in which to find the script.
24544 Doesn't require source code additions.
24547 Benefits of the @code{.debug_gdb_scripts} way:
24551 Works with static linking.
24553 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24554 trigger their loading. When an application is statically linked the only
24555 objfile available is the executable, and it is cumbersome to attach all the
24556 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24559 Works with classes that are entirely inlined.
24561 Some classes can be entirely inlined, and thus there may not be an associated
24562 shared library to attach a @file{-gdb.py} script to.
24565 Scripts needn't be copied out of the source tree.
24567 In some circumstances, apps can be built out of large collections of internal
24568 libraries, and the build infrastructure necessary to install the
24569 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24570 cumbersome. It may be easier to specify the scripts in the
24571 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24572 top of the source tree to the source search path.
24575 @node Python modules
24576 @subsection Python modules
24577 @cindex python modules
24579 @value{GDBN} comes with several modules to assist writing Python code.
24582 * gdb.printing:: Building and registering pretty-printers.
24583 * gdb.types:: Utilities for working with types.
24584 * gdb.prompt:: Utilities for prompt value substitution.
24588 @subsubsection gdb.printing
24589 @cindex gdb.printing
24591 This module provides a collection of utilities for working with
24595 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24596 This class specifies the API that makes @samp{info pretty-printer},
24597 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24598 Pretty-printers should generally inherit from this class.
24600 @item SubPrettyPrinter (@var{name})
24601 For printers that handle multiple types, this class specifies the
24602 corresponding API for the subprinters.
24604 @item RegexpCollectionPrettyPrinter (@var{name})
24605 Utility class for handling multiple printers, all recognized via
24606 regular expressions.
24607 @xref{Writing a Pretty-Printer}, for an example.
24609 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24610 Register @var{printer} with the pretty-printer list of @var{obj}.
24611 If @var{replace} is @code{True} then any existing copy of the printer
24612 is replaced. Otherwise a @code{RuntimeError} exception is raised
24613 if a printer with the same name already exists.
24617 @subsubsection gdb.types
24620 This module provides a collection of utilities for working with
24621 @code{gdb.Types} objects.
24624 @item get_basic_type (@var{type})
24625 Return @var{type} with const and volatile qualifiers stripped,
24626 and with typedefs and C@t{++} references converted to the underlying type.
24631 typedef const int const_int;
24633 const_int& foo_ref (foo);
24634 int main () @{ return 0; @}
24641 (gdb) python import gdb.types
24642 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24643 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24647 @item has_field (@var{type}, @var{field})
24648 Return @code{True} if @var{type}, assumed to be a type with fields
24649 (e.g., a structure or union), has field @var{field}.
24651 @item make_enum_dict (@var{enum_type})
24652 Return a Python @code{dictionary} type produced from @var{enum_type}.
24654 @item deep_items (@var{type})
24655 Returns a Python iterator similar to the standard
24656 @code{gdb.Type.iteritems} method, except that the iterator returned
24657 by @code{deep_items} will recursively traverse anonymous struct or
24658 union fields. For example:
24672 Then in @value{GDBN}:
24674 (@value{GDBP}) python import gdb.types
24675 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24676 (@value{GDBP}) python print struct_a.keys ()
24678 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24679 @{['a', 'b0', 'b1']@}
24685 @subsubsection gdb.prompt
24688 This module provides a method for prompt value-substitution.
24691 @item substitute_prompt (@var{string})
24692 Return @var{string} with escape sequences substituted by values. Some
24693 escape sequences take arguments. You can specify arguments inside
24694 ``@{@}'' immediately following the escape sequence.
24696 The escape sequences you can pass to this function are:
24700 Substitute a backslash.
24702 Substitute an ESC character.
24704 Substitute the selected frame; an argument names a frame parameter.
24706 Substitute a newline.
24708 Substitute a parameter's value; the argument names the parameter.
24710 Substitute a carriage return.
24712 Substitute the selected thread; an argument names a thread parameter.
24714 Substitute the version of GDB.
24716 Substitute the current working directory.
24718 Begin a sequence of non-printing characters. These sequences are
24719 typically used with the ESC character, and are not counted in the string
24720 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24721 blue-colored ``(gdb)'' prompt where the length is five.
24723 End a sequence of non-printing characters.
24729 substitute_prompt (``frame: \f,
24730 print arguments: \p@{print frame-arguments@}'')
24733 @exdent will return the string:
24736 "frame: main, print arguments: scalars"
24741 @section Creating new spellings of existing commands
24742 @cindex aliases for commands
24744 It is often useful to define alternate spellings of existing commands.
24745 For example, if a new @value{GDBN} command defined in Python has
24746 a long name to type, it is handy to have an abbreviated version of it
24747 that involves less typing.
24749 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24750 of the @samp{step} command even though it is otherwise an ambiguous
24751 abbreviation of other commands like @samp{set} and @samp{show}.
24753 Aliases are also used to provide shortened or more common versions
24754 of multi-word commands. For example, @value{GDBN} provides the
24755 @samp{tty} alias of the @samp{set inferior-tty} command.
24757 You can define a new alias with the @samp{alias} command.
24762 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24766 @var{ALIAS} specifies the name of the new alias.
24767 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24770 @var{COMMAND} specifies the name of an existing command
24771 that is being aliased.
24773 The @samp{-a} option specifies that the new alias is an abbreviation
24774 of the command. Abbreviations are not shown in command
24775 lists displayed by the @samp{help} command.
24777 The @samp{--} option specifies the end of options,
24778 and is useful when @var{ALIAS} begins with a dash.
24780 Here is a simple example showing how to make an abbreviation
24781 of a command so that there is less to type.
24782 Suppose you were tired of typing @samp{disas}, the current
24783 shortest unambiguous abbreviation of the @samp{disassemble} command
24784 and you wanted an even shorter version named @samp{di}.
24785 The following will accomplish this.
24788 (gdb) alias -a di = disas
24791 Note that aliases are different from user-defined commands.
24792 With a user-defined command, you also need to write documentation
24793 for it with the @samp{document} command.
24794 An alias automatically picks up the documentation of the existing command.
24796 Here is an example where we make @samp{elms} an abbreviation of
24797 @samp{elements} in the @samp{set print elements} command.
24798 This is to show that you can make an abbreviation of any part
24802 (gdb) alias -a set print elms = set print elements
24803 (gdb) alias -a show print elms = show print elements
24804 (gdb) set p elms 20
24806 Limit on string chars or array elements to print is 200.
24809 Note that if you are defining an alias of a @samp{set} command,
24810 and you want to have an alias for the corresponding @samp{show}
24811 command, then you need to define the latter separately.
24813 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24814 @var{ALIAS}, just as they are normally.
24817 (gdb) alias -a set pr elms = set p ele
24820 Finally, here is an example showing the creation of a one word
24821 alias for a more complex command.
24822 This creates alias @samp{spe} of the command @samp{set print elements}.
24825 (gdb) alias spe = set print elements
24830 @chapter Command Interpreters
24831 @cindex command interpreters
24833 @value{GDBN} supports multiple command interpreters, and some command
24834 infrastructure to allow users or user interface writers to switch
24835 between interpreters or run commands in other interpreters.
24837 @value{GDBN} currently supports two command interpreters, the console
24838 interpreter (sometimes called the command-line interpreter or @sc{cli})
24839 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24840 describes both of these interfaces in great detail.
24842 By default, @value{GDBN} will start with the console interpreter.
24843 However, the user may choose to start @value{GDBN} with another
24844 interpreter by specifying the @option{-i} or @option{--interpreter}
24845 startup options. Defined interpreters include:
24849 @cindex console interpreter
24850 The traditional console or command-line interpreter. This is the most often
24851 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24852 @value{GDBN} will use this interpreter.
24855 @cindex mi interpreter
24856 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24857 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24858 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24862 @cindex mi2 interpreter
24863 The current @sc{gdb/mi} interface.
24866 @cindex mi1 interpreter
24867 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24871 @cindex invoke another interpreter
24872 The interpreter being used by @value{GDBN} may not be dynamically
24873 switched at runtime. Although possible, this could lead to a very
24874 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24875 enters the command "interpreter-set console" in a console view,
24876 @value{GDBN} would switch to using the console interpreter, rendering
24877 the IDE inoperable!
24879 @kindex interpreter-exec
24880 Although you may only choose a single interpreter at startup, you may execute
24881 commands in any interpreter from the current interpreter using the appropriate
24882 command. If you are running the console interpreter, simply use the
24883 @code{interpreter-exec} command:
24886 interpreter-exec mi "-data-list-register-names"
24889 @sc{gdb/mi} has a similar command, although it is only available in versions of
24890 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24893 @chapter @value{GDBN} Text User Interface
24895 @cindex Text User Interface
24898 * TUI Overview:: TUI overview
24899 * TUI Keys:: TUI key bindings
24900 * TUI Single Key Mode:: TUI single key mode
24901 * TUI Commands:: TUI-specific commands
24902 * TUI Configuration:: TUI configuration variables
24905 The @value{GDBN} Text User Interface (TUI) is a terminal
24906 interface which uses the @code{curses} library to show the source
24907 file, the assembly output, the program registers and @value{GDBN}
24908 commands in separate text windows. The TUI mode is supported only
24909 on platforms where a suitable version of the @code{curses} library
24912 @pindex @value{GDBTUI}
24913 The TUI mode is enabled by default when you invoke @value{GDBN} as
24914 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24915 You can also switch in and out of TUI mode while @value{GDBN} runs by
24916 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24917 @xref{TUI Keys, ,TUI Key Bindings}.
24920 @section TUI Overview
24922 In TUI mode, @value{GDBN} can display several text windows:
24926 This window is the @value{GDBN} command window with the @value{GDBN}
24927 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24928 managed using readline.
24931 The source window shows the source file of the program. The current
24932 line and active breakpoints are displayed in this window.
24935 The assembly window shows the disassembly output of the program.
24938 This window shows the processor registers. Registers are highlighted
24939 when their values change.
24942 The source and assembly windows show the current program position
24943 by highlighting the current line and marking it with a @samp{>} marker.
24944 Breakpoints are indicated with two markers. The first marker
24945 indicates the breakpoint type:
24949 Breakpoint which was hit at least once.
24952 Breakpoint which was never hit.
24955 Hardware breakpoint which was hit at least once.
24958 Hardware breakpoint which was never hit.
24961 The second marker indicates whether the breakpoint is enabled or not:
24965 Breakpoint is enabled.
24968 Breakpoint is disabled.
24971 The source, assembly and register windows are updated when the current
24972 thread changes, when the frame changes, or when the program counter
24975 These windows are not all visible at the same time. The command
24976 window is always visible. The others can be arranged in several
24987 source and assembly,
24990 source and registers, or
24993 assembly and registers.
24996 A status line above the command window shows the following information:
25000 Indicates the current @value{GDBN} target.
25001 (@pxref{Targets, ,Specifying a Debugging Target}).
25004 Gives the current process or thread number.
25005 When no process is being debugged, this field is set to @code{No process}.
25008 Gives the current function name for the selected frame.
25009 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25010 When there is no symbol corresponding to the current program counter,
25011 the string @code{??} is displayed.
25014 Indicates the current line number for the selected frame.
25015 When the current line number is not known, the string @code{??} is displayed.
25018 Indicates the current program counter address.
25022 @section TUI Key Bindings
25023 @cindex TUI key bindings
25025 The TUI installs several key bindings in the readline keymaps
25026 @ifset SYSTEM_READLINE
25027 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25029 @ifclear SYSTEM_READLINE
25030 (@pxref{Command Line Editing}).
25032 The following key bindings are installed for both TUI mode and the
25033 @value{GDBN} standard mode.
25042 Enter or leave the TUI mode. When leaving the TUI mode,
25043 the curses window management stops and @value{GDBN} operates using
25044 its standard mode, writing on the terminal directly. When reentering
25045 the TUI mode, control is given back to the curses windows.
25046 The screen is then refreshed.
25050 Use a TUI layout with only one window. The layout will
25051 either be @samp{source} or @samp{assembly}. When the TUI mode
25052 is not active, it will switch to the TUI mode.
25054 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25058 Use a TUI layout with at least two windows. When the current
25059 layout already has two windows, the next layout with two windows is used.
25060 When a new layout is chosen, one window will always be common to the
25061 previous layout and the new one.
25063 Think of it as the Emacs @kbd{C-x 2} binding.
25067 Change the active window. The TUI associates several key bindings
25068 (like scrolling and arrow keys) with the active window. This command
25069 gives the focus to the next TUI window.
25071 Think of it as the Emacs @kbd{C-x o} binding.
25075 Switch in and out of the TUI SingleKey mode that binds single
25076 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25079 The following key bindings only work in the TUI mode:
25084 Scroll the active window one page up.
25088 Scroll the active window one page down.
25092 Scroll the active window one line up.
25096 Scroll the active window one line down.
25100 Scroll the active window one column left.
25104 Scroll the active window one column right.
25108 Refresh the screen.
25111 Because the arrow keys scroll the active window in the TUI mode, they
25112 are not available for their normal use by readline unless the command
25113 window has the focus. When another window is active, you must use
25114 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25115 and @kbd{C-f} to control the command window.
25117 @node TUI Single Key Mode
25118 @section TUI Single Key Mode
25119 @cindex TUI single key mode
25121 The TUI also provides a @dfn{SingleKey} mode, which binds several
25122 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25123 switch into this mode, where the following key bindings are used:
25126 @kindex c @r{(SingleKey TUI key)}
25130 @kindex d @r{(SingleKey TUI key)}
25134 @kindex f @r{(SingleKey TUI key)}
25138 @kindex n @r{(SingleKey TUI key)}
25142 @kindex q @r{(SingleKey TUI key)}
25144 exit the SingleKey mode.
25146 @kindex r @r{(SingleKey TUI key)}
25150 @kindex s @r{(SingleKey TUI key)}
25154 @kindex u @r{(SingleKey TUI key)}
25158 @kindex v @r{(SingleKey TUI key)}
25162 @kindex w @r{(SingleKey TUI key)}
25167 Other keys temporarily switch to the @value{GDBN} command prompt.
25168 The key that was pressed is inserted in the editing buffer so that
25169 it is possible to type most @value{GDBN} commands without interaction
25170 with the TUI SingleKey mode. Once the command is entered the TUI
25171 SingleKey mode is restored. The only way to permanently leave
25172 this mode is by typing @kbd{q} or @kbd{C-x s}.
25176 @section TUI-specific Commands
25177 @cindex TUI commands
25179 The TUI has specific commands to control the text windows.
25180 These commands are always available, even when @value{GDBN} is not in
25181 the TUI mode. When @value{GDBN} is in the standard mode, most
25182 of these commands will automatically switch to the TUI mode.
25184 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25185 terminal, or @value{GDBN} has been started with the machine interface
25186 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25187 these commands will fail with an error, because it would not be
25188 possible or desirable to enable curses window management.
25193 List and give the size of all displayed windows.
25197 Display the next layout.
25200 Display the previous layout.
25203 Display the source window only.
25206 Display the assembly window only.
25209 Display the source and assembly window.
25212 Display the register window together with the source or assembly window.
25216 Make the next window active for scrolling.
25219 Make the previous window active for scrolling.
25222 Make the source window active for scrolling.
25225 Make the assembly window active for scrolling.
25228 Make the register window active for scrolling.
25231 Make the command window active for scrolling.
25235 Refresh the screen. This is similar to typing @kbd{C-L}.
25237 @item tui reg float
25239 Show the floating point registers in the register window.
25241 @item tui reg general
25242 Show the general registers in the register window.
25245 Show the next register group. The list of register groups as well as
25246 their order is target specific. The predefined register groups are the
25247 following: @code{general}, @code{float}, @code{system}, @code{vector},
25248 @code{all}, @code{save}, @code{restore}.
25250 @item tui reg system
25251 Show the system registers in the register window.
25255 Update the source window and the current execution point.
25257 @item winheight @var{name} +@var{count}
25258 @itemx winheight @var{name} -@var{count}
25260 Change the height of the window @var{name} by @var{count}
25261 lines. Positive counts increase the height, while negative counts
25264 @item tabset @var{nchars}
25266 Set the width of tab stops to be @var{nchars} characters.
25269 @node TUI Configuration
25270 @section TUI Configuration Variables
25271 @cindex TUI configuration variables
25273 Several configuration variables control the appearance of TUI windows.
25276 @item set tui border-kind @var{kind}
25277 @kindex set tui border-kind
25278 Select the border appearance for the source, assembly and register windows.
25279 The possible values are the following:
25282 Use a space character to draw the border.
25285 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25288 Use the Alternate Character Set to draw the border. The border is
25289 drawn using character line graphics if the terminal supports them.
25292 @item set tui border-mode @var{mode}
25293 @kindex set tui border-mode
25294 @itemx set tui active-border-mode @var{mode}
25295 @kindex set tui active-border-mode
25296 Select the display attributes for the borders of the inactive windows
25297 or the active window. The @var{mode} can be one of the following:
25300 Use normal attributes to display the border.
25306 Use reverse video mode.
25309 Use half bright mode.
25311 @item half-standout
25312 Use half bright and standout mode.
25315 Use extra bright or bold mode.
25317 @item bold-standout
25318 Use extra bright or bold and standout mode.
25323 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25326 @cindex @sc{gnu} Emacs
25327 A special interface allows you to use @sc{gnu} Emacs to view (and
25328 edit) the source files for the program you are debugging with
25331 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25332 executable file you want to debug as an argument. This command starts
25333 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25334 created Emacs buffer.
25335 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25337 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25342 All ``terminal'' input and output goes through an Emacs buffer, called
25345 This applies both to @value{GDBN} commands and their output, and to the input
25346 and output done by the program you are debugging.
25348 This is useful because it means that you can copy the text of previous
25349 commands and input them again; you can even use parts of the output
25352 All the facilities of Emacs' Shell mode are available for interacting
25353 with your program. In particular, you can send signals the usual
25354 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25358 @value{GDBN} displays source code through Emacs.
25360 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25361 source file for that frame and puts an arrow (@samp{=>}) at the
25362 left margin of the current line. Emacs uses a separate buffer for
25363 source display, and splits the screen to show both your @value{GDBN} session
25366 Explicit @value{GDBN} @code{list} or search commands still produce output as
25367 usual, but you probably have no reason to use them from Emacs.
25370 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25371 a graphical mode, enabled by default, which provides further buffers
25372 that can control the execution and describe the state of your program.
25373 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25375 If you specify an absolute file name when prompted for the @kbd{M-x
25376 gdb} argument, then Emacs sets your current working directory to where
25377 your program resides. If you only specify the file name, then Emacs
25378 sets your current working directory to the directory associated
25379 with the previous buffer. In this case, @value{GDBN} may find your
25380 program by searching your environment's @code{PATH} variable, but on
25381 some operating systems it might not find the source. So, although the
25382 @value{GDBN} input and output session proceeds normally, the auxiliary
25383 buffer does not display the current source and line of execution.
25385 The initial working directory of @value{GDBN} is printed on the top
25386 line of the GUD buffer and this serves as a default for the commands
25387 that specify files for @value{GDBN} to operate on. @xref{Files,
25388 ,Commands to Specify Files}.
25390 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25391 need to call @value{GDBN} by a different name (for example, if you
25392 keep several configurations around, with different names) you can
25393 customize the Emacs variable @code{gud-gdb-command-name} to run the
25396 In the GUD buffer, you can use these special Emacs commands in
25397 addition to the standard Shell mode commands:
25401 Describe the features of Emacs' GUD Mode.
25404 Execute to another source line, like the @value{GDBN} @code{step} command; also
25405 update the display window to show the current file and location.
25408 Execute to next source line in this function, skipping all function
25409 calls, like the @value{GDBN} @code{next} command. Then update the display window
25410 to show the current file and location.
25413 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25414 display window accordingly.
25417 Execute until exit from the selected stack frame, like the @value{GDBN}
25418 @code{finish} command.
25421 Continue execution of your program, like the @value{GDBN} @code{continue}
25425 Go up the number of frames indicated by the numeric argument
25426 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25427 like the @value{GDBN} @code{up} command.
25430 Go down the number of frames indicated by the numeric argument, like the
25431 @value{GDBN} @code{down} command.
25434 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25435 tells @value{GDBN} to set a breakpoint on the source line point is on.
25437 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25438 separate frame which shows a backtrace when the GUD buffer is current.
25439 Move point to any frame in the stack and type @key{RET} to make it
25440 become the current frame and display the associated source in the
25441 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25442 selected frame become the current one. In graphical mode, the
25443 speedbar displays watch expressions.
25445 If you accidentally delete the source-display buffer, an easy way to get
25446 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25447 request a frame display; when you run under Emacs, this recreates
25448 the source buffer if necessary to show you the context of the current
25451 The source files displayed in Emacs are in ordinary Emacs buffers
25452 which are visiting the source files in the usual way. You can edit
25453 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25454 communicates with Emacs in terms of line numbers. If you add or
25455 delete lines from the text, the line numbers that @value{GDBN} knows cease
25456 to correspond properly with the code.
25458 A more detailed description of Emacs' interaction with @value{GDBN} is
25459 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25462 @c The following dropped because Epoch is nonstandard. Reactivate
25463 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25465 @kindex Emacs Epoch environment
25469 Version 18 of @sc{gnu} Emacs has a built-in window system
25470 called the @code{epoch}
25471 environment. Users of this environment can use a new command,
25472 @code{inspect} which performs identically to @code{print} except that
25473 each value is printed in its own window.
25478 @chapter The @sc{gdb/mi} Interface
25480 @unnumberedsec Function and Purpose
25482 @cindex @sc{gdb/mi}, its purpose
25483 @sc{gdb/mi} is a line based machine oriented text interface to
25484 @value{GDBN} and is activated by specifying using the
25485 @option{--interpreter} command line option (@pxref{Mode Options}). It
25486 is specifically intended to support the development of systems which
25487 use the debugger as just one small component of a larger system.
25489 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25490 in the form of a reference manual.
25492 Note that @sc{gdb/mi} is still under construction, so some of the
25493 features described below are incomplete and subject to change
25494 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25496 @unnumberedsec Notation and Terminology
25498 @cindex notational conventions, for @sc{gdb/mi}
25499 This chapter uses the following notation:
25503 @code{|} separates two alternatives.
25506 @code{[ @var{something} ]} indicates that @var{something} is optional:
25507 it may or may not be given.
25510 @code{( @var{group} )*} means that @var{group} inside the parentheses
25511 may repeat zero or more times.
25514 @code{( @var{group} )+} means that @var{group} inside the parentheses
25515 may repeat one or more times.
25518 @code{"@var{string}"} means a literal @var{string}.
25522 @heading Dependencies
25526 * GDB/MI General Design::
25527 * GDB/MI Command Syntax::
25528 * GDB/MI Compatibility with CLI::
25529 * GDB/MI Development and Front Ends::
25530 * GDB/MI Output Records::
25531 * GDB/MI Simple Examples::
25532 * GDB/MI Command Description Format::
25533 * GDB/MI Breakpoint Commands::
25534 * GDB/MI Program Context::
25535 * GDB/MI Thread Commands::
25536 * GDB/MI Ada Tasking Commands::
25537 * GDB/MI Program Execution::
25538 * GDB/MI Stack Manipulation::
25539 * GDB/MI Variable Objects::
25540 * GDB/MI Data Manipulation::
25541 * GDB/MI Tracepoint Commands::
25542 * GDB/MI Symbol Query::
25543 * GDB/MI File Commands::
25545 * GDB/MI Kod Commands::
25546 * GDB/MI Memory Overlay Commands::
25547 * GDB/MI Signal Handling Commands::
25549 * GDB/MI Target Manipulation::
25550 * GDB/MI File Transfer Commands::
25551 * GDB/MI Miscellaneous Commands::
25554 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25555 @node GDB/MI General Design
25556 @section @sc{gdb/mi} General Design
25557 @cindex GDB/MI General Design
25559 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25560 parts---commands sent to @value{GDBN}, responses to those commands
25561 and notifications. Each command results in exactly one response,
25562 indicating either successful completion of the command, or an error.
25563 For the commands that do not resume the target, the response contains the
25564 requested information. For the commands that resume the target, the
25565 response only indicates whether the target was successfully resumed.
25566 Notifications is the mechanism for reporting changes in the state of the
25567 target, or in @value{GDBN} state, that cannot conveniently be associated with
25568 a command and reported as part of that command response.
25570 The important examples of notifications are:
25574 Exec notifications. These are used to report changes in
25575 target state---when a target is resumed, or stopped. It would not
25576 be feasible to include this information in response of resuming
25577 commands, because one resume commands can result in multiple events in
25578 different threads. Also, quite some time may pass before any event
25579 happens in the target, while a frontend needs to know whether the resuming
25580 command itself was successfully executed.
25583 Console output, and status notifications. Console output
25584 notifications are used to report output of CLI commands, as well as
25585 diagnostics for other commands. Status notifications are used to
25586 report the progress of a long-running operation. Naturally, including
25587 this information in command response would mean no output is produced
25588 until the command is finished, which is undesirable.
25591 General notifications. Commands may have various side effects on
25592 the @value{GDBN} or target state beyond their official purpose. For example,
25593 a command may change the selected thread. Although such changes can
25594 be included in command response, using notification allows for more
25595 orthogonal frontend design.
25599 There's no guarantee that whenever an MI command reports an error,
25600 @value{GDBN} or the target are in any specific state, and especially,
25601 the state is not reverted to the state before the MI command was
25602 processed. Therefore, whenever an MI command results in an error,
25603 we recommend that the frontend refreshes all the information shown in
25604 the user interface.
25608 * Context management::
25609 * Asynchronous and non-stop modes::
25613 @node Context management
25614 @subsection Context management
25616 In most cases when @value{GDBN} accesses the target, this access is
25617 done in context of a specific thread and frame (@pxref{Frames}).
25618 Often, even when accessing global data, the target requires that a thread
25619 be specified. The CLI interface maintains the selected thread and frame,
25620 and supplies them to target on each command. This is convenient,
25621 because a command line user would not want to specify that information
25622 explicitly on each command, and because user interacts with
25623 @value{GDBN} via a single terminal, so no confusion is possible as
25624 to what thread and frame are the current ones.
25626 In the case of MI, the concept of selected thread and frame is less
25627 useful. First, a frontend can easily remember this information
25628 itself. Second, a graphical frontend can have more than one window,
25629 each one used for debugging a different thread, and the frontend might
25630 want to access additional threads for internal purposes. This
25631 increases the risk that by relying on implicitly selected thread, the
25632 frontend may be operating on a wrong one. Therefore, each MI command
25633 should explicitly specify which thread and frame to operate on. To
25634 make it possible, each MI command accepts the @samp{--thread} and
25635 @samp{--frame} options, the value to each is @value{GDBN} identifier
25636 for thread and frame to operate on.
25638 Usually, each top-level window in a frontend allows the user to select
25639 a thread and a frame, and remembers the user selection for further
25640 operations. However, in some cases @value{GDBN} may suggest that the
25641 current thread be changed. For example, when stopping on a breakpoint
25642 it is reasonable to switch to the thread where breakpoint is hit. For
25643 another example, if the user issues the CLI @samp{thread} command via
25644 the frontend, it is desirable to change the frontend's selected thread to the
25645 one specified by user. @value{GDBN} communicates the suggestion to
25646 change current thread using the @samp{=thread-selected} notification.
25647 No such notification is available for the selected frame at the moment.
25649 Note that historically, MI shares the selected thread with CLI, so
25650 frontends used the @code{-thread-select} to execute commands in the
25651 right context. However, getting this to work right is cumbersome. The
25652 simplest way is for frontend to emit @code{-thread-select} command
25653 before every command. This doubles the number of commands that need
25654 to be sent. The alternative approach is to suppress @code{-thread-select}
25655 if the selected thread in @value{GDBN} is supposed to be identical to the
25656 thread the frontend wants to operate on. However, getting this
25657 optimization right can be tricky. In particular, if the frontend
25658 sends several commands to @value{GDBN}, and one of the commands changes the
25659 selected thread, then the behaviour of subsequent commands will
25660 change. So, a frontend should either wait for response from such
25661 problematic commands, or explicitly add @code{-thread-select} for
25662 all subsequent commands. No frontend is known to do this exactly
25663 right, so it is suggested to just always pass the @samp{--thread} and
25664 @samp{--frame} options.
25666 @node Asynchronous and non-stop modes
25667 @subsection Asynchronous command execution and non-stop mode
25669 On some targets, @value{GDBN} is capable of processing MI commands
25670 even while the target is running. This is called @dfn{asynchronous
25671 command execution} (@pxref{Background Execution}). The frontend may
25672 specify a preferrence for asynchronous execution using the
25673 @code{-gdb-set target-async 1} command, which should be emitted before
25674 either running the executable or attaching to the target. After the
25675 frontend has started the executable or attached to the target, it can
25676 find if asynchronous execution is enabled using the
25677 @code{-list-target-features} command.
25679 Even if @value{GDBN} can accept a command while target is running,
25680 many commands that access the target do not work when the target is
25681 running. Therefore, asynchronous command execution is most useful
25682 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25683 it is possible to examine the state of one thread, while other threads
25686 When a given thread is running, MI commands that try to access the
25687 target in the context of that thread may not work, or may work only on
25688 some targets. In particular, commands that try to operate on thread's
25689 stack will not work, on any target. Commands that read memory, or
25690 modify breakpoints, may work or not work, depending on the target. Note
25691 that even commands that operate on global state, such as @code{print},
25692 @code{set}, and breakpoint commands, still access the target in the
25693 context of a specific thread, so frontend should try to find a
25694 stopped thread and perform the operation on that thread (using the
25695 @samp{--thread} option).
25697 Which commands will work in the context of a running thread is
25698 highly target dependent. However, the two commands
25699 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25700 to find the state of a thread, will always work.
25702 @node Thread groups
25703 @subsection Thread groups
25704 @value{GDBN} may be used to debug several processes at the same time.
25705 On some platfroms, @value{GDBN} may support debugging of several
25706 hardware systems, each one having several cores with several different
25707 processes running on each core. This section describes the MI
25708 mechanism to support such debugging scenarios.
25710 The key observation is that regardless of the structure of the
25711 target, MI can have a global list of threads, because most commands that
25712 accept the @samp{--thread} option do not need to know what process that
25713 thread belongs to. Therefore, it is not necessary to introduce
25714 neither additional @samp{--process} option, nor an notion of the
25715 current process in the MI interface. The only strictly new feature
25716 that is required is the ability to find how the threads are grouped
25719 To allow the user to discover such grouping, and to support arbitrary
25720 hierarchy of machines/cores/processes, MI introduces the concept of a
25721 @dfn{thread group}. Thread group is a collection of threads and other
25722 thread groups. A thread group always has a string identifier, a type,
25723 and may have additional attributes specific to the type. A new
25724 command, @code{-list-thread-groups}, returns the list of top-level
25725 thread groups, which correspond to processes that @value{GDBN} is
25726 debugging at the moment. By passing an identifier of a thread group
25727 to the @code{-list-thread-groups} command, it is possible to obtain
25728 the members of specific thread group.
25730 To allow the user to easily discover processes, and other objects, he
25731 wishes to debug, a concept of @dfn{available thread group} is
25732 introduced. Available thread group is an thread group that
25733 @value{GDBN} is not debugging, but that can be attached to, using the
25734 @code{-target-attach} command. The list of available top-level thread
25735 groups can be obtained using @samp{-list-thread-groups --available}.
25736 In general, the content of a thread group may be only retrieved only
25737 after attaching to that thread group.
25739 Thread groups are related to inferiors (@pxref{Inferiors and
25740 Programs}). Each inferior corresponds to a thread group of a special
25741 type @samp{process}, and some additional operations are permitted on
25742 such thread groups.
25744 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25745 @node GDB/MI Command Syntax
25746 @section @sc{gdb/mi} Command Syntax
25749 * GDB/MI Input Syntax::
25750 * GDB/MI Output Syntax::
25753 @node GDB/MI Input Syntax
25754 @subsection @sc{gdb/mi} Input Syntax
25756 @cindex input syntax for @sc{gdb/mi}
25757 @cindex @sc{gdb/mi}, input syntax
25759 @item @var{command} @expansion{}
25760 @code{@var{cli-command} | @var{mi-command}}
25762 @item @var{cli-command} @expansion{}
25763 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25764 @var{cli-command} is any existing @value{GDBN} CLI command.
25766 @item @var{mi-command} @expansion{}
25767 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25768 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25770 @item @var{token} @expansion{}
25771 "any sequence of digits"
25773 @item @var{option} @expansion{}
25774 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25776 @item @var{parameter} @expansion{}
25777 @code{@var{non-blank-sequence} | @var{c-string}}
25779 @item @var{operation} @expansion{}
25780 @emph{any of the operations described in this chapter}
25782 @item @var{non-blank-sequence} @expansion{}
25783 @emph{anything, provided it doesn't contain special characters such as
25784 "-", @var{nl}, """ and of course " "}
25786 @item @var{c-string} @expansion{}
25787 @code{""" @var{seven-bit-iso-c-string-content} """}
25789 @item @var{nl} @expansion{}
25798 The CLI commands are still handled by the @sc{mi} interpreter; their
25799 output is described below.
25802 The @code{@var{token}}, when present, is passed back when the command
25806 Some @sc{mi} commands accept optional arguments as part of the parameter
25807 list. Each option is identified by a leading @samp{-} (dash) and may be
25808 followed by an optional argument parameter. Options occur first in the
25809 parameter list and can be delimited from normal parameters using
25810 @samp{--} (this is useful when some parameters begin with a dash).
25817 We want easy access to the existing CLI syntax (for debugging).
25820 We want it to be easy to spot a @sc{mi} operation.
25823 @node GDB/MI Output Syntax
25824 @subsection @sc{gdb/mi} Output Syntax
25826 @cindex output syntax of @sc{gdb/mi}
25827 @cindex @sc{gdb/mi}, output syntax
25828 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25829 followed, optionally, by a single result record. This result record
25830 is for the most recent command. The sequence of output records is
25831 terminated by @samp{(gdb)}.
25833 If an input command was prefixed with a @code{@var{token}} then the
25834 corresponding output for that command will also be prefixed by that same
25838 @item @var{output} @expansion{}
25839 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25841 @item @var{result-record} @expansion{}
25842 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25844 @item @var{out-of-band-record} @expansion{}
25845 @code{@var{async-record} | @var{stream-record}}
25847 @item @var{async-record} @expansion{}
25848 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25850 @item @var{exec-async-output} @expansion{}
25851 @code{[ @var{token} ] "*" @var{async-output}}
25853 @item @var{status-async-output} @expansion{}
25854 @code{[ @var{token} ] "+" @var{async-output}}
25856 @item @var{notify-async-output} @expansion{}
25857 @code{[ @var{token} ] "=" @var{async-output}}
25859 @item @var{async-output} @expansion{}
25860 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25862 @item @var{result-class} @expansion{}
25863 @code{"done" | "running" | "connected" | "error" | "exit"}
25865 @item @var{async-class} @expansion{}
25866 @code{"stopped" | @var{others}} (where @var{others} will be added
25867 depending on the needs---this is still in development).
25869 @item @var{result} @expansion{}
25870 @code{ @var{variable} "=" @var{value}}
25872 @item @var{variable} @expansion{}
25873 @code{ @var{string} }
25875 @item @var{value} @expansion{}
25876 @code{ @var{const} | @var{tuple} | @var{list} }
25878 @item @var{const} @expansion{}
25879 @code{@var{c-string}}
25881 @item @var{tuple} @expansion{}
25882 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25884 @item @var{list} @expansion{}
25885 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25886 @var{result} ( "," @var{result} )* "]" }
25888 @item @var{stream-record} @expansion{}
25889 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25891 @item @var{console-stream-output} @expansion{}
25892 @code{"~" @var{c-string}}
25894 @item @var{target-stream-output} @expansion{}
25895 @code{"@@" @var{c-string}}
25897 @item @var{log-stream-output} @expansion{}
25898 @code{"&" @var{c-string}}
25900 @item @var{nl} @expansion{}
25903 @item @var{token} @expansion{}
25904 @emph{any sequence of digits}.
25912 All output sequences end in a single line containing a period.
25915 The @code{@var{token}} is from the corresponding request. Note that
25916 for all async output, while the token is allowed by the grammar and
25917 may be output by future versions of @value{GDBN} for select async
25918 output messages, it is generally omitted. Frontends should treat
25919 all async output as reporting general changes in the state of the
25920 target and there should be no need to associate async output to any
25924 @cindex status output in @sc{gdb/mi}
25925 @var{status-async-output} contains on-going status information about the
25926 progress of a slow operation. It can be discarded. All status output is
25927 prefixed by @samp{+}.
25930 @cindex async output in @sc{gdb/mi}
25931 @var{exec-async-output} contains asynchronous state change on the target
25932 (stopped, started, disappeared). All async output is prefixed by
25936 @cindex notify output in @sc{gdb/mi}
25937 @var{notify-async-output} contains supplementary information that the
25938 client should handle (e.g., a new breakpoint information). All notify
25939 output is prefixed by @samp{=}.
25942 @cindex console output in @sc{gdb/mi}
25943 @var{console-stream-output} is output that should be displayed as is in the
25944 console. It is the textual response to a CLI command. All the console
25945 output is prefixed by @samp{~}.
25948 @cindex target output in @sc{gdb/mi}
25949 @var{target-stream-output} is the output produced by the target program.
25950 All the target output is prefixed by @samp{@@}.
25953 @cindex log output in @sc{gdb/mi}
25954 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25955 instance messages that should be displayed as part of an error log. All
25956 the log output is prefixed by @samp{&}.
25959 @cindex list output in @sc{gdb/mi}
25960 New @sc{gdb/mi} commands should only output @var{lists} containing
25966 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25967 details about the various output records.
25969 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25970 @node GDB/MI Compatibility with CLI
25971 @section @sc{gdb/mi} Compatibility with CLI
25973 @cindex compatibility, @sc{gdb/mi} and CLI
25974 @cindex @sc{gdb/mi}, compatibility with CLI
25976 For the developers convenience CLI commands can be entered directly,
25977 but there may be some unexpected behaviour. For example, commands
25978 that query the user will behave as if the user replied yes, breakpoint
25979 command lists are not executed and some CLI commands, such as
25980 @code{if}, @code{when} and @code{define}, prompt for further input with
25981 @samp{>}, which is not valid MI output.
25983 This feature may be removed at some stage in the future and it is
25984 recommended that front ends use the @code{-interpreter-exec} command
25985 (@pxref{-interpreter-exec}).
25987 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25988 @node GDB/MI Development and Front Ends
25989 @section @sc{gdb/mi} Development and Front Ends
25990 @cindex @sc{gdb/mi} development
25992 The application which takes the MI output and presents the state of the
25993 program being debugged to the user is called a @dfn{front end}.
25995 Although @sc{gdb/mi} is still incomplete, it is currently being used
25996 by a variety of front ends to @value{GDBN}. This makes it difficult
25997 to introduce new functionality without breaking existing usage. This
25998 section tries to minimize the problems by describing how the protocol
26001 Some changes in MI need not break a carefully designed front end, and
26002 for these the MI version will remain unchanged. The following is a
26003 list of changes that may occur within one level, so front ends should
26004 parse MI output in a way that can handle them:
26008 New MI commands may be added.
26011 New fields may be added to the output of any MI command.
26014 The range of values for fields with specified values, e.g.,
26015 @code{in_scope} (@pxref{-var-update}) may be extended.
26017 @c The format of field's content e.g type prefix, may change so parse it
26018 @c at your own risk. Yes, in general?
26020 @c The order of fields may change? Shouldn't really matter but it might
26021 @c resolve inconsistencies.
26024 If the changes are likely to break front ends, the MI version level
26025 will be increased by one. This will allow the front end to parse the
26026 output according to the MI version. Apart from mi0, new versions of
26027 @value{GDBN} will not support old versions of MI and it will be the
26028 responsibility of the front end to work with the new one.
26030 @c Starting with mi3, add a new command -mi-version that prints the MI
26033 The best way to avoid unexpected changes in MI that might break your front
26034 end is to make your project known to @value{GDBN} developers and
26035 follow development on @email{gdb@@sourceware.org} and
26036 @email{gdb-patches@@sourceware.org}.
26037 @cindex mailing lists
26039 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26040 @node GDB/MI Output Records
26041 @section @sc{gdb/mi} Output Records
26044 * GDB/MI Result Records::
26045 * GDB/MI Stream Records::
26046 * GDB/MI Async Records::
26047 * GDB/MI Frame Information::
26048 * GDB/MI Thread Information::
26049 * GDB/MI Ada Exception Information::
26052 @node GDB/MI Result Records
26053 @subsection @sc{gdb/mi} Result Records
26055 @cindex result records in @sc{gdb/mi}
26056 @cindex @sc{gdb/mi}, result records
26057 In addition to a number of out-of-band notifications, the response to a
26058 @sc{gdb/mi} command includes one of the following result indications:
26062 @item "^done" [ "," @var{results} ]
26063 The synchronous operation was successful, @code{@var{results}} are the return
26068 This result record is equivalent to @samp{^done}. Historically, it
26069 was output instead of @samp{^done} if the command has resumed the
26070 target. This behaviour is maintained for backward compatibility, but
26071 all frontends should treat @samp{^done} and @samp{^running}
26072 identically and rely on the @samp{*running} output record to determine
26073 which threads are resumed.
26077 @value{GDBN} has connected to a remote target.
26079 @item "^error" "," @var{c-string}
26081 The operation failed. The @code{@var{c-string}} contains the corresponding
26086 @value{GDBN} has terminated.
26090 @node GDB/MI Stream Records
26091 @subsection @sc{gdb/mi} Stream Records
26093 @cindex @sc{gdb/mi}, stream records
26094 @cindex stream records in @sc{gdb/mi}
26095 @value{GDBN} internally maintains a number of output streams: the console, the
26096 target, and the log. The output intended for each of these streams is
26097 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26099 Each stream record begins with a unique @dfn{prefix character} which
26100 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26101 Syntax}). In addition to the prefix, each stream record contains a
26102 @code{@var{string-output}}. This is either raw text (with an implicit new
26103 line) or a quoted C string (which does not contain an implicit newline).
26106 @item "~" @var{string-output}
26107 The console output stream contains text that should be displayed in the
26108 CLI console window. It contains the textual responses to CLI commands.
26110 @item "@@" @var{string-output}
26111 The target output stream contains any textual output from the running
26112 target. This is only present when GDB's event loop is truly
26113 asynchronous, which is currently only the case for remote targets.
26115 @item "&" @var{string-output}
26116 The log stream contains debugging messages being produced by @value{GDBN}'s
26120 @node GDB/MI Async Records
26121 @subsection @sc{gdb/mi} Async Records
26123 @cindex async records in @sc{gdb/mi}
26124 @cindex @sc{gdb/mi}, async records
26125 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26126 additional changes that have occurred. Those changes can either be a
26127 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26128 target activity (e.g., target stopped).
26130 The following is the list of possible async records:
26134 @item *running,thread-id="@var{thread}"
26135 The target is now running. The @var{thread} field tells which
26136 specific thread is now running, and can be @samp{all} if all threads
26137 are running. The frontend should assume that no interaction with a
26138 running thread is possible after this notification is produced.
26139 The frontend should not assume that this notification is output
26140 only once for any command. @value{GDBN} may emit this notification
26141 several times, either for different threads, because it cannot resume
26142 all threads together, or even for a single thread, if the thread must
26143 be stepped though some code before letting it run freely.
26145 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26146 The target has stopped. The @var{reason} field can have one of the
26150 @item breakpoint-hit
26151 A breakpoint was reached.
26152 @item watchpoint-trigger
26153 A watchpoint was triggered.
26154 @item read-watchpoint-trigger
26155 A read watchpoint was triggered.
26156 @item access-watchpoint-trigger
26157 An access watchpoint was triggered.
26158 @item function-finished
26159 An -exec-finish or similar CLI command was accomplished.
26160 @item location-reached
26161 An -exec-until or similar CLI command was accomplished.
26162 @item watchpoint-scope
26163 A watchpoint has gone out of scope.
26164 @item end-stepping-range
26165 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26166 similar CLI command was accomplished.
26167 @item exited-signalled
26168 The inferior exited because of a signal.
26170 The inferior exited.
26171 @item exited-normally
26172 The inferior exited normally.
26173 @item signal-received
26174 A signal was received by the inferior.
26177 The @var{id} field identifies the thread that directly caused the stop
26178 -- for example by hitting a breakpoint. Depending on whether all-stop
26179 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26180 stop all threads, or only the thread that directly triggered the stop.
26181 If all threads are stopped, the @var{stopped} field will have the
26182 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26183 field will be a list of thread identifiers. Presently, this list will
26184 always include a single thread, but frontend should be prepared to see
26185 several threads in the list. The @var{core} field reports the
26186 processor core on which the stop event has happened. This field may be absent
26187 if such information is not available.
26189 @item =thread-group-added,id="@var{id}"
26190 @itemx =thread-group-removed,id="@var{id}"
26191 A thread group was either added or removed. The @var{id} field
26192 contains the @value{GDBN} identifier of the thread group. When a thread
26193 group is added, it generally might not be associated with a running
26194 process. When a thread group is removed, its id becomes invalid and
26195 cannot be used in any way.
26197 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26198 A thread group became associated with a running program,
26199 either because the program was just started or the thread group
26200 was attached to a program. The @var{id} field contains the
26201 @value{GDBN} identifier of the thread group. The @var{pid} field
26202 contains process identifier, specific to the operating system.
26204 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26205 A thread group is no longer associated with a running program,
26206 either because the program has exited, or because it was detached
26207 from. The @var{id} field contains the @value{GDBN} identifier of the
26208 thread group. @var{code} is the exit code of the inferior; it exists
26209 only when the inferior exited with some code.
26211 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26212 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26213 A thread either was created, or has exited. The @var{id} field
26214 contains the @value{GDBN} identifier of the thread. The @var{gid}
26215 field identifies the thread group this thread belongs to.
26217 @item =thread-selected,id="@var{id}"
26218 Informs that the selected thread was changed as result of the last
26219 command. This notification is not emitted as result of @code{-thread-select}
26220 command but is emitted whenever an MI command that is not documented
26221 to change the selected thread actually changes it. In particular,
26222 invoking, directly or indirectly (via user-defined command), the CLI
26223 @code{thread} command, will generate this notification.
26225 We suggest that in response to this notification, front ends
26226 highlight the selected thread and cause subsequent commands to apply to
26229 @item =library-loaded,...
26230 Reports that a new library file was loaded by the program. This
26231 notification has 4 fields---@var{id}, @var{target-name},
26232 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26233 opaque identifier of the library. For remote debugging case,
26234 @var{target-name} and @var{host-name} fields give the name of the
26235 library file on the target, and on the host respectively. For native
26236 debugging, both those fields have the same value. The
26237 @var{symbols-loaded} field is emitted only for backward compatibility
26238 and should not be relied on to convey any useful information. The
26239 @var{thread-group} field, if present, specifies the id of the thread
26240 group in whose context the library was loaded. If the field is
26241 absent, it means the library was loaded in the context of all present
26244 @item =library-unloaded,...
26245 Reports that a library was unloaded by the program. This notification
26246 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26247 the same meaning as for the @code{=library-loaded} notification.
26248 The @var{thread-group} field, if present, specifies the id of the
26249 thread group in whose context the library was unloaded. If the field is
26250 absent, it means the library was unloaded in the context of all present
26253 @item =breakpoint-created,bkpt=@{...@}
26254 @itemx =breakpoint-modified,bkpt=@{...@}
26255 @itemx =breakpoint-deleted,bkpt=@{...@}
26256 Reports that a breakpoint was created, modified, or deleted,
26257 respectively. Only user-visible breakpoints are reported to the MI
26260 The @var{bkpt} argument is of the same form as returned by the various
26261 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26263 Note that if a breakpoint is emitted in the result record of a
26264 command, then it will not also be emitted in an async record.
26268 @node GDB/MI Frame Information
26269 @subsection @sc{gdb/mi} Frame Information
26271 Response from many MI commands includes an information about stack
26272 frame. This information is a tuple that may have the following
26277 The level of the stack frame. The innermost frame has the level of
26278 zero. This field is always present.
26281 The name of the function corresponding to the frame. This field may
26282 be absent if @value{GDBN} is unable to determine the function name.
26285 The code address for the frame. This field is always present.
26288 The name of the source files that correspond to the frame's code
26289 address. This field may be absent.
26292 The source line corresponding to the frames' code address. This field
26296 The name of the binary file (either executable or shared library) the
26297 corresponds to the frame's code address. This field may be absent.
26301 @node GDB/MI Thread Information
26302 @subsection @sc{gdb/mi} Thread Information
26304 Whenever @value{GDBN} has to report an information about a thread, it
26305 uses a tuple with the following fields:
26309 The numeric id assigned to the thread by @value{GDBN}. This field is
26313 Target-specific string identifying the thread. This field is always present.
26316 Additional information about the thread provided by the target.
26317 It is supposed to be human-readable and not interpreted by the
26318 frontend. This field is optional.
26321 Either @samp{stopped} or @samp{running}, depending on whether the
26322 thread is presently running. This field is always present.
26325 The value of this field is an integer number of the processor core the
26326 thread was last seen on. This field is optional.
26329 @node GDB/MI Ada Exception Information
26330 @subsection @sc{gdb/mi} Ada Exception Information
26332 Whenever a @code{*stopped} record is emitted because the program
26333 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26334 @value{GDBN} provides the name of the exception that was raised via
26335 the @code{exception-name} field.
26337 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26338 @node GDB/MI Simple Examples
26339 @section Simple Examples of @sc{gdb/mi} Interaction
26340 @cindex @sc{gdb/mi}, simple examples
26342 This subsection presents several simple examples of interaction using
26343 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26344 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26345 the output received from @sc{gdb/mi}.
26347 Note the line breaks shown in the examples are here only for
26348 readability, they don't appear in the real output.
26350 @subheading Setting a Breakpoint
26352 Setting a breakpoint generates synchronous output which contains detailed
26353 information of the breakpoint.
26356 -> -break-insert main
26357 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26358 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26359 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26363 @subheading Program Execution
26365 Program execution generates asynchronous records and MI gives the
26366 reason that execution stopped.
26372 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26373 frame=@{addr="0x08048564",func="main",
26374 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26375 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26380 <- *stopped,reason="exited-normally"
26384 @subheading Quitting @value{GDBN}
26386 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26394 Please note that @samp{^exit} is printed immediately, but it might
26395 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26396 performs necessary cleanups, including killing programs being debugged
26397 or disconnecting from debug hardware, so the frontend should wait till
26398 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26399 fails to exit in reasonable time.
26401 @subheading A Bad Command
26403 Here's what happens if you pass a non-existent command:
26407 <- ^error,msg="Undefined MI command: rubbish"
26412 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26413 @node GDB/MI Command Description Format
26414 @section @sc{gdb/mi} Command Description Format
26416 The remaining sections describe blocks of commands. Each block of
26417 commands is laid out in a fashion similar to this section.
26419 @subheading Motivation
26421 The motivation for this collection of commands.
26423 @subheading Introduction
26425 A brief introduction to this collection of commands as a whole.
26427 @subheading Commands
26429 For each command in the block, the following is described:
26431 @subsubheading Synopsis
26434 -command @var{args}@dots{}
26437 @subsubheading Result
26439 @subsubheading @value{GDBN} Command
26441 The corresponding @value{GDBN} CLI command(s), if any.
26443 @subsubheading Example
26445 Example(s) formatted for readability. Some of the described commands have
26446 not been implemented yet and these are labeled N.A.@: (not available).
26449 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26450 @node GDB/MI Breakpoint Commands
26451 @section @sc{gdb/mi} Breakpoint Commands
26453 @cindex breakpoint commands for @sc{gdb/mi}
26454 @cindex @sc{gdb/mi}, breakpoint commands
26455 This section documents @sc{gdb/mi} commands for manipulating
26458 @subheading The @code{-break-after} Command
26459 @findex -break-after
26461 @subsubheading Synopsis
26464 -break-after @var{number} @var{count}
26467 The breakpoint number @var{number} is not in effect until it has been
26468 hit @var{count} times. To see how this is reflected in the output of
26469 the @samp{-break-list} command, see the description of the
26470 @samp{-break-list} command below.
26472 @subsubheading @value{GDBN} Command
26474 The corresponding @value{GDBN} command is @samp{ignore}.
26476 @subsubheading Example
26481 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26482 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26483 fullname="/home/foo/hello.c",line="5",times="0"@}
26490 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26491 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26492 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26493 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26494 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26495 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26496 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26497 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26498 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26499 line="5",times="0",ignore="3"@}]@}
26504 @subheading The @code{-break-catch} Command
26505 @findex -break-catch
26508 @subheading The @code{-break-commands} Command
26509 @findex -break-commands
26511 @subsubheading Synopsis
26514 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26517 Specifies the CLI commands that should be executed when breakpoint
26518 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26519 are the commands. If no command is specified, any previously-set
26520 commands are cleared. @xref{Break Commands}. Typical use of this
26521 functionality is tracing a program, that is, printing of values of
26522 some variables whenever breakpoint is hit and then continuing.
26524 @subsubheading @value{GDBN} Command
26526 The corresponding @value{GDBN} command is @samp{commands}.
26528 @subsubheading Example
26533 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26534 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26535 fullname="/home/foo/hello.c",line="5",times="0"@}
26537 -break-commands 1 "print v" "continue"
26542 @subheading The @code{-break-condition} Command
26543 @findex -break-condition
26545 @subsubheading Synopsis
26548 -break-condition @var{number} @var{expr}
26551 Breakpoint @var{number} will stop the program only if the condition in
26552 @var{expr} is true. The condition becomes part of the
26553 @samp{-break-list} output (see the description of the @samp{-break-list}
26556 @subsubheading @value{GDBN} Command
26558 The corresponding @value{GDBN} command is @samp{condition}.
26560 @subsubheading Example
26564 -break-condition 1 1
26568 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26569 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26570 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26571 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26572 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26573 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26574 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26575 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26576 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26577 line="5",cond="1",times="0",ignore="3"@}]@}
26581 @subheading The @code{-break-delete} Command
26582 @findex -break-delete
26584 @subsubheading Synopsis
26587 -break-delete ( @var{breakpoint} )+
26590 Delete the breakpoint(s) whose number(s) are specified in the argument
26591 list. This is obviously reflected in the breakpoint list.
26593 @subsubheading @value{GDBN} Command
26595 The corresponding @value{GDBN} command is @samp{delete}.
26597 @subsubheading Example
26605 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26606 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26607 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26608 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26609 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26610 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26611 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26616 @subheading The @code{-break-disable} Command
26617 @findex -break-disable
26619 @subsubheading Synopsis
26622 -break-disable ( @var{breakpoint} )+
26625 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26626 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26628 @subsubheading @value{GDBN} Command
26630 The corresponding @value{GDBN} command is @samp{disable}.
26632 @subsubheading Example
26640 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26641 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26642 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26643 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26644 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26645 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26646 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26647 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26648 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26649 line="5",times="0"@}]@}
26653 @subheading The @code{-break-enable} Command
26654 @findex -break-enable
26656 @subsubheading Synopsis
26659 -break-enable ( @var{breakpoint} )+
26662 Enable (previously disabled) @var{breakpoint}(s).
26664 @subsubheading @value{GDBN} Command
26666 The corresponding @value{GDBN} command is @samp{enable}.
26668 @subsubheading Example
26676 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26677 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26678 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26679 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26680 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26681 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26682 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26683 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26684 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26685 line="5",times="0"@}]@}
26689 @subheading The @code{-break-info} Command
26690 @findex -break-info
26692 @subsubheading Synopsis
26695 -break-info @var{breakpoint}
26699 Get information about a single breakpoint.
26701 @subsubheading @value{GDBN} Command
26703 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26705 @subsubheading Example
26708 @subheading The @code{-break-insert} Command
26709 @findex -break-insert
26711 @subsubheading Synopsis
26714 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26715 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26716 [ -p @var{thread} ] [ @var{location} ]
26720 If specified, @var{location}, can be one of:
26727 @item filename:linenum
26728 @item filename:function
26732 The possible optional parameters of this command are:
26736 Insert a temporary breakpoint.
26738 Insert a hardware breakpoint.
26739 @item -c @var{condition}
26740 Make the breakpoint conditional on @var{condition}.
26741 @item -i @var{ignore-count}
26742 Initialize the @var{ignore-count}.
26744 If @var{location} cannot be parsed (for example if it
26745 refers to unknown files or functions), create a pending
26746 breakpoint. Without this flag, @value{GDBN} will report
26747 an error, and won't create a breakpoint, if @var{location}
26750 Create a disabled breakpoint.
26752 Create a tracepoint. @xref{Tracepoints}. When this parameter
26753 is used together with @samp{-h}, a fast tracepoint is created.
26756 @subsubheading Result
26758 The result is in the form:
26761 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26762 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26763 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26764 times="@var{times}"@}
26768 where @var{number} is the @value{GDBN} number for this breakpoint,
26769 @var{funcname} is the name of the function where the breakpoint was
26770 inserted, @var{filename} is the name of the source file which contains
26771 this function, @var{lineno} is the source line number within that file
26772 and @var{times} the number of times that the breakpoint has been hit
26773 (always 0 for -break-insert but may be greater for -break-info or -break-list
26774 which use the same output).
26776 Note: this format is open to change.
26777 @c An out-of-band breakpoint instead of part of the result?
26779 @subsubheading @value{GDBN} Command
26781 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26782 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26784 @subsubheading Example
26789 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26790 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26792 -break-insert -t foo
26793 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26794 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26797 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26798 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26799 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26800 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26801 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26802 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26803 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26804 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26805 addr="0x0001072c", func="main",file="recursive2.c",
26806 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26807 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26808 addr="0x00010774",func="foo",file="recursive2.c",
26809 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26811 -break-insert -r foo.*
26812 ~int foo(int, int);
26813 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26814 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26818 @subheading The @code{-break-list} Command
26819 @findex -break-list
26821 @subsubheading Synopsis
26827 Displays the list of inserted breakpoints, showing the following fields:
26831 number of the breakpoint
26833 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26835 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26838 is the breakpoint enabled or no: @samp{y} or @samp{n}
26840 memory location at which the breakpoint is set
26842 logical location of the breakpoint, expressed by function name, file
26845 number of times the breakpoint has been hit
26848 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26849 @code{body} field is an empty list.
26851 @subsubheading @value{GDBN} Command
26853 The corresponding @value{GDBN} command is @samp{info break}.
26855 @subsubheading Example
26860 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26861 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26862 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26863 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26864 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26865 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26866 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26867 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26868 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26869 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26870 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26871 line="13",times="0"@}]@}
26875 Here's an example of the result when there are no breakpoints:
26880 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26881 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26882 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26883 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26884 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26885 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26886 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26891 @subheading The @code{-break-passcount} Command
26892 @findex -break-passcount
26894 @subsubheading Synopsis
26897 -break-passcount @var{tracepoint-number} @var{passcount}
26900 Set the passcount for tracepoint @var{tracepoint-number} to
26901 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26902 is not a tracepoint, error is emitted. This corresponds to CLI
26903 command @samp{passcount}.
26905 @subheading The @code{-break-watch} Command
26906 @findex -break-watch
26908 @subsubheading Synopsis
26911 -break-watch [ -a | -r ]
26914 Create a watchpoint. With the @samp{-a} option it will create an
26915 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26916 read from or on a write to the memory location. With the @samp{-r}
26917 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26918 trigger only when the memory location is accessed for reading. Without
26919 either of the options, the watchpoint created is a regular watchpoint,
26920 i.e., it will trigger when the memory location is accessed for writing.
26921 @xref{Set Watchpoints, , Setting Watchpoints}.
26923 Note that @samp{-break-list} will report a single list of watchpoints and
26924 breakpoints inserted.
26926 @subsubheading @value{GDBN} Command
26928 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26931 @subsubheading Example
26933 Setting a watchpoint on a variable in the @code{main} function:
26938 ^done,wpt=@{number="2",exp="x"@}
26943 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26944 value=@{old="-268439212",new="55"@},
26945 frame=@{func="main",args=[],file="recursive2.c",
26946 fullname="/home/foo/bar/recursive2.c",line="5"@}
26950 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26951 the program execution twice: first for the variable changing value, then
26952 for the watchpoint going out of scope.
26957 ^done,wpt=@{number="5",exp="C"@}
26962 *stopped,reason="watchpoint-trigger",
26963 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26964 frame=@{func="callee4",args=[],
26965 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26966 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26971 *stopped,reason="watchpoint-scope",wpnum="5",
26972 frame=@{func="callee3",args=[@{name="strarg",
26973 value="0x11940 \"A string argument.\""@}],
26974 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26975 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26979 Listing breakpoints and watchpoints, at different points in the program
26980 execution. Note that once the watchpoint goes out of scope, it is
26986 ^done,wpt=@{number="2",exp="C"@}
26989 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26990 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26991 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26992 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26993 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26994 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26995 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26996 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26997 addr="0x00010734",func="callee4",
26998 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26999 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27000 bkpt=@{number="2",type="watchpoint",disp="keep",
27001 enabled="y",addr="",what="C",times="0"@}]@}
27006 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27007 value=@{old="-276895068",new="3"@},
27008 frame=@{func="callee4",args=[],
27009 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27010 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27013 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27014 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27015 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27016 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27017 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27018 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27019 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27020 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27021 addr="0x00010734",func="callee4",
27022 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27023 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27024 bkpt=@{number="2",type="watchpoint",disp="keep",
27025 enabled="y",addr="",what="C",times="-5"@}]@}
27029 ^done,reason="watchpoint-scope",wpnum="2",
27030 frame=@{func="callee3",args=[@{name="strarg",
27031 value="0x11940 \"A string argument.\""@}],
27032 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27033 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27036 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27037 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27038 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27039 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27040 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27041 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27042 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27043 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27044 addr="0x00010734",func="callee4",
27045 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27046 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27051 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27052 @node GDB/MI Program Context
27053 @section @sc{gdb/mi} Program Context
27055 @subheading The @code{-exec-arguments} Command
27056 @findex -exec-arguments
27059 @subsubheading Synopsis
27062 -exec-arguments @var{args}
27065 Set the inferior program arguments, to be used in the next
27068 @subsubheading @value{GDBN} Command
27070 The corresponding @value{GDBN} command is @samp{set args}.
27072 @subsubheading Example
27076 -exec-arguments -v word
27083 @subheading The @code{-exec-show-arguments} Command
27084 @findex -exec-show-arguments
27086 @subsubheading Synopsis
27089 -exec-show-arguments
27092 Print the arguments of the program.
27094 @subsubheading @value{GDBN} Command
27096 The corresponding @value{GDBN} command is @samp{show args}.
27098 @subsubheading Example
27103 @subheading The @code{-environment-cd} Command
27104 @findex -environment-cd
27106 @subsubheading Synopsis
27109 -environment-cd @var{pathdir}
27112 Set @value{GDBN}'s working directory.
27114 @subsubheading @value{GDBN} Command
27116 The corresponding @value{GDBN} command is @samp{cd}.
27118 @subsubheading Example
27122 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27128 @subheading The @code{-environment-directory} Command
27129 @findex -environment-directory
27131 @subsubheading Synopsis
27134 -environment-directory [ -r ] [ @var{pathdir} ]+
27137 Add directories @var{pathdir} to beginning of search path for source files.
27138 If the @samp{-r} option is used, the search path is reset to the default
27139 search path. If directories @var{pathdir} are supplied in addition to the
27140 @samp{-r} option, the search path is first reset and then addition
27142 Multiple directories may be specified, separated by blanks. Specifying
27143 multiple directories in a single command
27144 results in the directories added to the beginning of the
27145 search path in the same order they were presented in the command.
27146 If blanks are needed as
27147 part of a directory name, double-quotes should be used around
27148 the name. In the command output, the path will show up separated
27149 by the system directory-separator character. The directory-separator
27150 character must not be used
27151 in any directory name.
27152 If no directories are specified, the current search path is displayed.
27154 @subsubheading @value{GDBN} Command
27156 The corresponding @value{GDBN} command is @samp{dir}.
27158 @subsubheading Example
27162 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27163 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27165 -environment-directory ""
27166 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27168 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27169 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27171 -environment-directory -r
27172 ^done,source-path="$cdir:$cwd"
27177 @subheading The @code{-environment-path} Command
27178 @findex -environment-path
27180 @subsubheading Synopsis
27183 -environment-path [ -r ] [ @var{pathdir} ]+
27186 Add directories @var{pathdir} to beginning of search path for object files.
27187 If the @samp{-r} option is used, the search path is reset to the original
27188 search path that existed at gdb start-up. If directories @var{pathdir} are
27189 supplied in addition to the
27190 @samp{-r} option, the search path is first reset and then addition
27192 Multiple directories may be specified, separated by blanks. Specifying
27193 multiple directories in a single command
27194 results in the directories added to the beginning of the
27195 search path in the same order they were presented in the command.
27196 If blanks are needed as
27197 part of a directory name, double-quotes should be used around
27198 the name. In the command output, the path will show up separated
27199 by the system directory-separator character. The directory-separator
27200 character must not be used
27201 in any directory name.
27202 If no directories are specified, the current path is displayed.
27205 @subsubheading @value{GDBN} Command
27207 The corresponding @value{GDBN} command is @samp{path}.
27209 @subsubheading Example
27214 ^done,path="/usr/bin"
27216 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27217 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27219 -environment-path -r /usr/local/bin
27220 ^done,path="/usr/local/bin:/usr/bin"
27225 @subheading The @code{-environment-pwd} Command
27226 @findex -environment-pwd
27228 @subsubheading Synopsis
27234 Show the current working directory.
27236 @subsubheading @value{GDBN} Command
27238 The corresponding @value{GDBN} command is @samp{pwd}.
27240 @subsubheading Example
27245 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27249 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27250 @node GDB/MI Thread Commands
27251 @section @sc{gdb/mi} Thread Commands
27254 @subheading The @code{-thread-info} Command
27255 @findex -thread-info
27257 @subsubheading Synopsis
27260 -thread-info [ @var{thread-id} ]
27263 Reports information about either a specific thread, if
27264 the @var{thread-id} parameter is present, or about all
27265 threads. When printing information about all threads,
27266 also reports the current thread.
27268 @subsubheading @value{GDBN} Command
27270 The @samp{info thread} command prints the same information
27273 @subsubheading Result
27275 The result is a list of threads. The following attributes are
27276 defined for a given thread:
27280 This field exists only for the current thread. It has the value @samp{*}.
27283 The identifier that @value{GDBN} uses to refer to the thread.
27286 The identifier that the target uses to refer to the thread.
27289 Extra information about the thread, in a target-specific format. This
27293 The name of the thread. If the user specified a name using the
27294 @code{thread name} command, then this name is given. Otherwise, if
27295 @value{GDBN} can extract the thread name from the target, then that
27296 name is given. If @value{GDBN} cannot find the thread name, then this
27300 The stack frame currently executing in the thread.
27303 The thread's state. The @samp{state} field may have the following
27308 The thread is stopped. Frame information is available for stopped
27312 The thread is running. There's no frame information for running
27318 If @value{GDBN} can find the CPU core on which this thread is running,
27319 then this field is the core identifier. This field is optional.
27323 @subsubheading Example
27328 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27329 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27330 args=[]@},state="running"@},
27331 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27332 frame=@{level="0",addr="0x0804891f",func="foo",
27333 args=[@{name="i",value="10"@}],
27334 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27335 state="running"@}],
27336 current-thread-id="1"
27340 @subheading The @code{-thread-list-ids} Command
27341 @findex -thread-list-ids
27343 @subsubheading Synopsis
27349 Produces a list of the currently known @value{GDBN} thread ids. At the
27350 end of the list it also prints the total number of such threads.
27352 This command is retained for historical reasons, the
27353 @code{-thread-info} command should be used instead.
27355 @subsubheading @value{GDBN} Command
27357 Part of @samp{info threads} supplies the same information.
27359 @subsubheading Example
27364 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27365 current-thread-id="1",number-of-threads="3"
27370 @subheading The @code{-thread-select} Command
27371 @findex -thread-select
27373 @subsubheading Synopsis
27376 -thread-select @var{threadnum}
27379 Make @var{threadnum} the current thread. It prints the number of the new
27380 current thread, and the topmost frame for that thread.
27382 This command is deprecated in favor of explicitly using the
27383 @samp{--thread} option to each command.
27385 @subsubheading @value{GDBN} Command
27387 The corresponding @value{GDBN} command is @samp{thread}.
27389 @subsubheading Example
27396 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27397 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27401 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27402 number-of-threads="3"
27405 ^done,new-thread-id="3",
27406 frame=@{level="0",func="vprintf",
27407 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27408 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27412 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27413 @node GDB/MI Ada Tasking Commands
27414 @section @sc{gdb/mi} Ada Tasking Commands
27416 @subheading The @code{-ada-task-info} Command
27417 @findex -ada-task-info
27419 @subsubheading Synopsis
27422 -ada-task-info [ @var{task-id} ]
27425 Reports information about either a specific Ada task, if the
27426 @var{task-id} parameter is present, or about all Ada tasks.
27428 @subsubheading @value{GDBN} Command
27430 The @samp{info tasks} command prints the same information
27431 about all Ada tasks (@pxref{Ada Tasks}).
27433 @subsubheading Result
27435 The result is a table of Ada tasks. The following columns are
27436 defined for each Ada task:
27440 This field exists only for the current thread. It has the value @samp{*}.
27443 The identifier that @value{GDBN} uses to refer to the Ada task.
27446 The identifier that the target uses to refer to the Ada task.
27449 The identifier of the thread corresponding to the Ada task.
27451 This field should always exist, as Ada tasks are always implemented
27452 on top of a thread. But if @value{GDBN} cannot find this corresponding
27453 thread for any reason, the field is omitted.
27456 This field exists only when the task was created by another task.
27457 In this case, it provides the ID of the parent task.
27460 The base priority of the task.
27463 The current state of the task. For a detailed description of the
27464 possible states, see @ref{Ada Tasks}.
27467 The name of the task.
27471 @subsubheading Example
27475 ^done,tasks=@{nr_rows="3",nr_cols="8",
27476 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27477 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27478 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27479 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27480 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27481 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27482 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27483 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27484 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27485 state="Child Termination Wait",name="main_task"@}]@}
27489 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27490 @node GDB/MI Program Execution
27491 @section @sc{gdb/mi} Program Execution
27493 These are the asynchronous commands which generate the out-of-band
27494 record @samp{*stopped}. Currently @value{GDBN} only really executes
27495 asynchronously with remote targets and this interaction is mimicked in
27498 @subheading The @code{-exec-continue} Command
27499 @findex -exec-continue
27501 @subsubheading Synopsis
27504 -exec-continue [--reverse] [--all|--thread-group N]
27507 Resumes the execution of the inferior program, which will continue
27508 to execute until it reaches a debugger stop event. If the
27509 @samp{--reverse} option is specified, execution resumes in reverse until
27510 it reaches a stop event. Stop events may include
27513 breakpoints or watchpoints
27515 signals or exceptions
27517 the end of the process (or its beginning under @samp{--reverse})
27519 the end or beginning of a replay log if one is being used.
27521 In all-stop mode (@pxref{All-Stop
27522 Mode}), may resume only one thread, or all threads, depending on the
27523 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27524 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27525 ignored in all-stop mode. If the @samp{--thread-group} options is
27526 specified, then all threads in that thread group are resumed.
27528 @subsubheading @value{GDBN} Command
27530 The corresponding @value{GDBN} corresponding is @samp{continue}.
27532 @subsubheading Example
27539 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27540 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27546 @subheading The @code{-exec-finish} Command
27547 @findex -exec-finish
27549 @subsubheading Synopsis
27552 -exec-finish [--reverse]
27555 Resumes the execution of the inferior program until the current
27556 function is exited. Displays the results returned by the function.
27557 If the @samp{--reverse} option is specified, resumes the reverse
27558 execution of the inferior program until the point where current
27559 function was called.
27561 @subsubheading @value{GDBN} Command
27563 The corresponding @value{GDBN} command is @samp{finish}.
27565 @subsubheading Example
27567 Function returning @code{void}.
27574 *stopped,reason="function-finished",frame=@{func="main",args=[],
27575 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27579 Function returning other than @code{void}. The name of the internal
27580 @value{GDBN} variable storing the result is printed, together with the
27587 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27588 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27589 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27590 gdb-result-var="$1",return-value="0"
27595 @subheading The @code{-exec-interrupt} Command
27596 @findex -exec-interrupt
27598 @subsubheading Synopsis
27601 -exec-interrupt [--all|--thread-group N]
27604 Interrupts the background execution of the target. Note how the token
27605 associated with the stop message is the one for the execution command
27606 that has been interrupted. The token for the interrupt itself only
27607 appears in the @samp{^done} output. If the user is trying to
27608 interrupt a non-running program, an error message will be printed.
27610 Note that when asynchronous execution is enabled, this command is
27611 asynchronous just like other execution commands. That is, first the
27612 @samp{^done} response will be printed, and the target stop will be
27613 reported after that using the @samp{*stopped} notification.
27615 In non-stop mode, only the context thread is interrupted by default.
27616 All threads (in all inferiors) will be interrupted if the
27617 @samp{--all} option is specified. If the @samp{--thread-group}
27618 option is specified, all threads in that group will be interrupted.
27620 @subsubheading @value{GDBN} Command
27622 The corresponding @value{GDBN} command is @samp{interrupt}.
27624 @subsubheading Example
27635 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27636 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27637 fullname="/home/foo/bar/try.c",line="13"@}
27642 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27646 @subheading The @code{-exec-jump} Command
27649 @subsubheading Synopsis
27652 -exec-jump @var{location}
27655 Resumes execution of the inferior program at the location specified by
27656 parameter. @xref{Specify Location}, for a description of the
27657 different forms of @var{location}.
27659 @subsubheading @value{GDBN} Command
27661 The corresponding @value{GDBN} command is @samp{jump}.
27663 @subsubheading Example
27666 -exec-jump foo.c:10
27667 *running,thread-id="all"
27672 @subheading The @code{-exec-next} Command
27675 @subsubheading Synopsis
27678 -exec-next [--reverse]
27681 Resumes execution of the inferior program, stopping when the beginning
27682 of the next source line is reached.
27684 If the @samp{--reverse} option is specified, resumes reverse execution
27685 of the inferior program, stopping at the beginning of the previous
27686 source line. If you issue this command on the first line of a
27687 function, it will take you back to the caller of that function, to the
27688 source line where the function was called.
27691 @subsubheading @value{GDBN} Command
27693 The corresponding @value{GDBN} command is @samp{next}.
27695 @subsubheading Example
27701 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27706 @subheading The @code{-exec-next-instruction} Command
27707 @findex -exec-next-instruction
27709 @subsubheading Synopsis
27712 -exec-next-instruction [--reverse]
27715 Executes one machine instruction. If the instruction is a function
27716 call, continues until the function returns. If the program stops at an
27717 instruction in the middle of a source line, the address will be
27720 If the @samp{--reverse} option is specified, resumes reverse execution
27721 of the inferior program, stopping at the previous instruction. If the
27722 previously executed instruction was a return from another function,
27723 it will continue to execute in reverse until the call to that function
27724 (from the current stack frame) is reached.
27726 @subsubheading @value{GDBN} Command
27728 The corresponding @value{GDBN} command is @samp{nexti}.
27730 @subsubheading Example
27734 -exec-next-instruction
27738 *stopped,reason="end-stepping-range",
27739 addr="0x000100d4",line="5",file="hello.c"
27744 @subheading The @code{-exec-return} Command
27745 @findex -exec-return
27747 @subsubheading Synopsis
27753 Makes current function return immediately. Doesn't execute the inferior.
27754 Displays the new current frame.
27756 @subsubheading @value{GDBN} Command
27758 The corresponding @value{GDBN} command is @samp{return}.
27760 @subsubheading Example
27764 200-break-insert callee4
27765 200^done,bkpt=@{number="1",addr="0x00010734",
27766 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27771 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27772 frame=@{func="callee4",args=[],
27773 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27774 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27780 111^done,frame=@{level="0",func="callee3",
27781 args=[@{name="strarg",
27782 value="0x11940 \"A string argument.\""@}],
27783 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27784 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27789 @subheading The @code{-exec-run} Command
27792 @subsubheading Synopsis
27795 -exec-run [--all | --thread-group N]
27798 Starts execution of the inferior from the beginning. The inferior
27799 executes until either a breakpoint is encountered or the program
27800 exits. In the latter case the output will include an exit code, if
27801 the program has exited exceptionally.
27803 When no option is specified, the current inferior is started. If the
27804 @samp{--thread-group} option is specified, it should refer to a thread
27805 group of type @samp{process}, and that thread group will be started.
27806 If the @samp{--all} option is specified, then all inferiors will be started.
27808 @subsubheading @value{GDBN} Command
27810 The corresponding @value{GDBN} command is @samp{run}.
27812 @subsubheading Examples
27817 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27822 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27823 frame=@{func="main",args=[],file="recursive2.c",
27824 fullname="/home/foo/bar/recursive2.c",line="4"@}
27829 Program exited normally:
27837 *stopped,reason="exited-normally"
27842 Program exited exceptionally:
27850 *stopped,reason="exited",exit-code="01"
27854 Another way the program can terminate is if it receives a signal such as
27855 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27859 *stopped,reason="exited-signalled",signal-name="SIGINT",
27860 signal-meaning="Interrupt"
27864 @c @subheading -exec-signal
27867 @subheading The @code{-exec-step} Command
27870 @subsubheading Synopsis
27873 -exec-step [--reverse]
27876 Resumes execution of the inferior program, stopping when the beginning
27877 of the next source line is reached, if the next source line is not a
27878 function call. If it is, stop at the first instruction of the called
27879 function. If the @samp{--reverse} option is specified, resumes reverse
27880 execution of the inferior program, stopping at the beginning of the
27881 previously executed source line.
27883 @subsubheading @value{GDBN} Command
27885 The corresponding @value{GDBN} command is @samp{step}.
27887 @subsubheading Example
27889 Stepping into a function:
27895 *stopped,reason="end-stepping-range",
27896 frame=@{func="foo",args=[@{name="a",value="10"@},
27897 @{name="b",value="0"@}],file="recursive2.c",
27898 fullname="/home/foo/bar/recursive2.c",line="11"@}
27908 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27913 @subheading The @code{-exec-step-instruction} Command
27914 @findex -exec-step-instruction
27916 @subsubheading Synopsis
27919 -exec-step-instruction [--reverse]
27922 Resumes the inferior which executes one machine instruction. If the
27923 @samp{--reverse} option is specified, resumes reverse execution of the
27924 inferior program, stopping at the previously executed instruction.
27925 The output, once @value{GDBN} has stopped, will vary depending on
27926 whether we have stopped in the middle of a source line or not. In the
27927 former case, the address at which the program stopped will be printed
27930 @subsubheading @value{GDBN} Command
27932 The corresponding @value{GDBN} command is @samp{stepi}.
27934 @subsubheading Example
27938 -exec-step-instruction
27942 *stopped,reason="end-stepping-range",
27943 frame=@{func="foo",args=[],file="try.c",
27944 fullname="/home/foo/bar/try.c",line="10"@}
27946 -exec-step-instruction
27950 *stopped,reason="end-stepping-range",
27951 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27952 fullname="/home/foo/bar/try.c",line="10"@}
27957 @subheading The @code{-exec-until} Command
27958 @findex -exec-until
27960 @subsubheading Synopsis
27963 -exec-until [ @var{location} ]
27966 Executes the inferior until the @var{location} specified in the
27967 argument is reached. If there is no argument, the inferior executes
27968 until a source line greater than the current one is reached. The
27969 reason for stopping in this case will be @samp{location-reached}.
27971 @subsubheading @value{GDBN} Command
27973 The corresponding @value{GDBN} command is @samp{until}.
27975 @subsubheading Example
27979 -exec-until recursive2.c:6
27983 *stopped,reason="location-reached",frame=@{func="main",args=[],
27984 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27989 @subheading -file-clear
27990 Is this going away????
27993 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27994 @node GDB/MI Stack Manipulation
27995 @section @sc{gdb/mi} Stack Manipulation Commands
27998 @subheading The @code{-stack-info-frame} Command
27999 @findex -stack-info-frame
28001 @subsubheading Synopsis
28007 Get info on the selected frame.
28009 @subsubheading @value{GDBN} Command
28011 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28012 (without arguments).
28014 @subsubheading Example
28019 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28020 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28021 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28025 @subheading The @code{-stack-info-depth} Command
28026 @findex -stack-info-depth
28028 @subsubheading Synopsis
28031 -stack-info-depth [ @var{max-depth} ]
28034 Return the depth of the stack. If the integer argument @var{max-depth}
28035 is specified, do not count beyond @var{max-depth} frames.
28037 @subsubheading @value{GDBN} Command
28039 There's no equivalent @value{GDBN} command.
28041 @subsubheading Example
28043 For a stack with frame levels 0 through 11:
28050 -stack-info-depth 4
28053 -stack-info-depth 12
28056 -stack-info-depth 11
28059 -stack-info-depth 13
28064 @subheading The @code{-stack-list-arguments} Command
28065 @findex -stack-list-arguments
28067 @subsubheading Synopsis
28070 -stack-list-arguments @var{print-values}
28071 [ @var{low-frame} @var{high-frame} ]
28074 Display a list of the arguments for the frames between @var{low-frame}
28075 and @var{high-frame} (inclusive). If @var{low-frame} and
28076 @var{high-frame} are not provided, list the arguments for the whole
28077 call stack. If the two arguments are equal, show the single frame
28078 at the corresponding level. It is an error if @var{low-frame} is
28079 larger than the actual number of frames. On the other hand,
28080 @var{high-frame} may be larger than the actual number of frames, in
28081 which case only existing frames will be returned.
28083 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28084 the variables; if it is 1 or @code{--all-values}, print also their
28085 values; and if it is 2 or @code{--simple-values}, print the name,
28086 type and value for simple data types, and the name and type for arrays,
28087 structures and unions.
28089 Use of this command to obtain arguments in a single frame is
28090 deprecated in favor of the @samp{-stack-list-variables} command.
28092 @subsubheading @value{GDBN} Command
28094 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28095 @samp{gdb_get_args} command which partially overlaps with the
28096 functionality of @samp{-stack-list-arguments}.
28098 @subsubheading Example
28105 frame=@{level="0",addr="0x00010734",func="callee4",
28106 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28107 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28108 frame=@{level="1",addr="0x0001076c",func="callee3",
28109 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28110 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28111 frame=@{level="2",addr="0x0001078c",func="callee2",
28112 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28113 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28114 frame=@{level="3",addr="0x000107b4",func="callee1",
28115 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28116 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28117 frame=@{level="4",addr="0x000107e0",func="main",
28118 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28119 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28121 -stack-list-arguments 0
28124 frame=@{level="0",args=[]@},
28125 frame=@{level="1",args=[name="strarg"]@},
28126 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28127 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28128 frame=@{level="4",args=[]@}]
28130 -stack-list-arguments 1
28133 frame=@{level="0",args=[]@},
28135 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28136 frame=@{level="2",args=[
28137 @{name="intarg",value="2"@},
28138 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28139 @{frame=@{level="3",args=[
28140 @{name="intarg",value="2"@},
28141 @{name="strarg",value="0x11940 \"A string argument.\""@},
28142 @{name="fltarg",value="3.5"@}]@},
28143 frame=@{level="4",args=[]@}]
28145 -stack-list-arguments 0 2 2
28146 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28148 -stack-list-arguments 1 2 2
28149 ^done,stack-args=[frame=@{level="2",
28150 args=[@{name="intarg",value="2"@},
28151 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28155 @c @subheading -stack-list-exception-handlers
28158 @subheading The @code{-stack-list-frames} Command
28159 @findex -stack-list-frames
28161 @subsubheading Synopsis
28164 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28167 List the frames currently on the stack. For each frame it displays the
28172 The frame number, 0 being the topmost frame, i.e., the innermost function.
28174 The @code{$pc} value for that frame.
28178 File name of the source file where the function lives.
28179 @item @var{fullname}
28180 The full file name of the source file where the function lives.
28182 Line number corresponding to the @code{$pc}.
28184 The shared library where this function is defined. This is only given
28185 if the frame's function is not known.
28188 If invoked without arguments, this command prints a backtrace for the
28189 whole stack. If given two integer arguments, it shows the frames whose
28190 levels are between the two arguments (inclusive). If the two arguments
28191 are equal, it shows the single frame at the corresponding level. It is
28192 an error if @var{low-frame} is larger than the actual number of
28193 frames. On the other hand, @var{high-frame} may be larger than the
28194 actual number of frames, in which case only existing frames will be returned.
28196 @subsubheading @value{GDBN} Command
28198 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28200 @subsubheading Example
28202 Full stack backtrace:
28208 [frame=@{level="0",addr="0x0001076c",func="foo",
28209 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28210 frame=@{level="1",addr="0x000107a4",func="foo",
28211 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28212 frame=@{level="2",addr="0x000107a4",func="foo",
28213 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28214 frame=@{level="3",addr="0x000107a4",func="foo",
28215 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28216 frame=@{level="4",addr="0x000107a4",func="foo",
28217 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28218 frame=@{level="5",addr="0x000107a4",func="foo",
28219 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28220 frame=@{level="6",addr="0x000107a4",func="foo",
28221 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28222 frame=@{level="7",addr="0x000107a4",func="foo",
28223 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28224 frame=@{level="8",addr="0x000107a4",func="foo",
28225 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28226 frame=@{level="9",addr="0x000107a4",func="foo",
28227 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28228 frame=@{level="10",addr="0x000107a4",func="foo",
28229 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28230 frame=@{level="11",addr="0x00010738",func="main",
28231 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28235 Show frames between @var{low_frame} and @var{high_frame}:
28239 -stack-list-frames 3 5
28241 [frame=@{level="3",addr="0x000107a4",func="foo",
28242 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28243 frame=@{level="4",addr="0x000107a4",func="foo",
28244 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28245 frame=@{level="5",addr="0x000107a4",func="foo",
28246 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28250 Show a single frame:
28254 -stack-list-frames 3 3
28256 [frame=@{level="3",addr="0x000107a4",func="foo",
28257 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28262 @subheading The @code{-stack-list-locals} Command
28263 @findex -stack-list-locals
28265 @subsubheading Synopsis
28268 -stack-list-locals @var{print-values}
28271 Display the local variable names for the selected frame. If
28272 @var{print-values} is 0 or @code{--no-values}, print only the names of
28273 the variables; if it is 1 or @code{--all-values}, print also their
28274 values; and if it is 2 or @code{--simple-values}, print the name,
28275 type and value for simple data types, and the name and type for arrays,
28276 structures and unions. In this last case, a frontend can immediately
28277 display the value of simple data types and create variable objects for
28278 other data types when the user wishes to explore their values in
28281 This command is deprecated in favor of the
28282 @samp{-stack-list-variables} command.
28284 @subsubheading @value{GDBN} Command
28286 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28288 @subsubheading Example
28292 -stack-list-locals 0
28293 ^done,locals=[name="A",name="B",name="C"]
28295 -stack-list-locals --all-values
28296 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28297 @{name="C",value="@{1, 2, 3@}"@}]
28298 -stack-list-locals --simple-values
28299 ^done,locals=[@{name="A",type="int",value="1"@},
28300 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28304 @subheading The @code{-stack-list-variables} Command
28305 @findex -stack-list-variables
28307 @subsubheading Synopsis
28310 -stack-list-variables @var{print-values}
28313 Display the names of local variables and function arguments for the selected frame. If
28314 @var{print-values} is 0 or @code{--no-values}, print only the names of
28315 the variables; if it is 1 or @code{--all-values}, print also their
28316 values; and if it is 2 or @code{--simple-values}, print the name,
28317 type and value for simple data types, and the name and type for arrays,
28318 structures and unions.
28320 @subsubheading Example
28324 -stack-list-variables --thread 1 --frame 0 --all-values
28325 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28330 @subheading The @code{-stack-select-frame} Command
28331 @findex -stack-select-frame
28333 @subsubheading Synopsis
28336 -stack-select-frame @var{framenum}
28339 Change the selected frame. Select a different frame @var{framenum} on
28342 This command in deprecated in favor of passing the @samp{--frame}
28343 option to every command.
28345 @subsubheading @value{GDBN} Command
28347 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28348 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28350 @subsubheading Example
28354 -stack-select-frame 2
28359 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28360 @node GDB/MI Variable Objects
28361 @section @sc{gdb/mi} Variable Objects
28365 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28367 For the implementation of a variable debugger window (locals, watched
28368 expressions, etc.), we are proposing the adaptation of the existing code
28369 used by @code{Insight}.
28371 The two main reasons for that are:
28375 It has been proven in practice (it is already on its second generation).
28378 It will shorten development time (needless to say how important it is
28382 The original interface was designed to be used by Tcl code, so it was
28383 slightly changed so it could be used through @sc{gdb/mi}. This section
28384 describes the @sc{gdb/mi} operations that will be available and gives some
28385 hints about their use.
28387 @emph{Note}: In addition to the set of operations described here, we
28388 expect the @sc{gui} implementation of a variable window to require, at
28389 least, the following operations:
28392 @item @code{-gdb-show} @code{output-radix}
28393 @item @code{-stack-list-arguments}
28394 @item @code{-stack-list-locals}
28395 @item @code{-stack-select-frame}
28400 @subheading Introduction to Variable Objects
28402 @cindex variable objects in @sc{gdb/mi}
28404 Variable objects are "object-oriented" MI interface for examining and
28405 changing values of expressions. Unlike some other MI interfaces that
28406 work with expressions, variable objects are specifically designed for
28407 simple and efficient presentation in the frontend. A variable object
28408 is identified by string name. When a variable object is created, the
28409 frontend specifies the expression for that variable object. The
28410 expression can be a simple variable, or it can be an arbitrary complex
28411 expression, and can even involve CPU registers. After creating a
28412 variable object, the frontend can invoke other variable object
28413 operations---for example to obtain or change the value of a variable
28414 object, or to change display format.
28416 Variable objects have hierarchical tree structure. Any variable object
28417 that corresponds to a composite type, such as structure in C, has
28418 a number of child variable objects, for example corresponding to each
28419 element of a structure. A child variable object can itself have
28420 children, recursively. Recursion ends when we reach
28421 leaf variable objects, which always have built-in types. Child variable
28422 objects are created only by explicit request, so if a frontend
28423 is not interested in the children of a particular variable object, no
28424 child will be created.
28426 For a leaf variable object it is possible to obtain its value as a
28427 string, or set the value from a string. String value can be also
28428 obtained for a non-leaf variable object, but it's generally a string
28429 that only indicates the type of the object, and does not list its
28430 contents. Assignment to a non-leaf variable object is not allowed.
28432 A frontend does not need to read the values of all variable objects each time
28433 the program stops. Instead, MI provides an update command that lists all
28434 variable objects whose values has changed since the last update
28435 operation. This considerably reduces the amount of data that must
28436 be transferred to the frontend. As noted above, children variable
28437 objects are created on demand, and only leaf variable objects have a
28438 real value. As result, gdb will read target memory only for leaf
28439 variables that frontend has created.
28441 The automatic update is not always desirable. For example, a frontend
28442 might want to keep a value of some expression for future reference,
28443 and never update it. For another example, fetching memory is
28444 relatively slow for embedded targets, so a frontend might want
28445 to disable automatic update for the variables that are either not
28446 visible on the screen, or ``closed''. This is possible using so
28447 called ``frozen variable objects''. Such variable objects are never
28448 implicitly updated.
28450 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28451 fixed variable object, the expression is parsed when the variable
28452 object is created, including associating identifiers to specific
28453 variables. The meaning of expression never changes. For a floating
28454 variable object the values of variables whose names appear in the
28455 expressions are re-evaluated every time in the context of the current
28456 frame. Consider this example:
28461 struct work_state state;
28468 If a fixed variable object for the @code{state} variable is created in
28469 this function, and we enter the recursive call, the variable
28470 object will report the value of @code{state} in the top-level
28471 @code{do_work} invocation. On the other hand, a floating variable
28472 object will report the value of @code{state} in the current frame.
28474 If an expression specified when creating a fixed variable object
28475 refers to a local variable, the variable object becomes bound to the
28476 thread and frame in which the variable object is created. When such
28477 variable object is updated, @value{GDBN} makes sure that the
28478 thread/frame combination the variable object is bound to still exists,
28479 and re-evaluates the variable object in context of that thread/frame.
28481 The following is the complete set of @sc{gdb/mi} operations defined to
28482 access this functionality:
28484 @multitable @columnfractions .4 .6
28485 @item @strong{Operation}
28486 @tab @strong{Description}
28488 @item @code{-enable-pretty-printing}
28489 @tab enable Python-based pretty-printing
28490 @item @code{-var-create}
28491 @tab create a variable object
28492 @item @code{-var-delete}
28493 @tab delete the variable object and/or its children
28494 @item @code{-var-set-format}
28495 @tab set the display format of this variable
28496 @item @code{-var-show-format}
28497 @tab show the display format of this variable
28498 @item @code{-var-info-num-children}
28499 @tab tells how many children this object has
28500 @item @code{-var-list-children}
28501 @tab return a list of the object's children
28502 @item @code{-var-info-type}
28503 @tab show the type of this variable object
28504 @item @code{-var-info-expression}
28505 @tab print parent-relative expression that this variable object represents
28506 @item @code{-var-info-path-expression}
28507 @tab print full expression that this variable object represents
28508 @item @code{-var-show-attributes}
28509 @tab is this variable editable? does it exist here?
28510 @item @code{-var-evaluate-expression}
28511 @tab get the value of this variable
28512 @item @code{-var-assign}
28513 @tab set the value of this variable
28514 @item @code{-var-update}
28515 @tab update the variable and its children
28516 @item @code{-var-set-frozen}
28517 @tab set frozeness attribute
28518 @item @code{-var-set-update-range}
28519 @tab set range of children to display on update
28522 In the next subsection we describe each operation in detail and suggest
28523 how it can be used.
28525 @subheading Description And Use of Operations on Variable Objects
28527 @subheading The @code{-enable-pretty-printing} Command
28528 @findex -enable-pretty-printing
28531 -enable-pretty-printing
28534 @value{GDBN} allows Python-based visualizers to affect the output of the
28535 MI variable object commands. However, because there was no way to
28536 implement this in a fully backward-compatible way, a front end must
28537 request that this functionality be enabled.
28539 Once enabled, this feature cannot be disabled.
28541 Note that if Python support has not been compiled into @value{GDBN},
28542 this command will still succeed (and do nothing).
28544 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28545 may work differently in future versions of @value{GDBN}.
28547 @subheading The @code{-var-create} Command
28548 @findex -var-create
28550 @subsubheading Synopsis
28553 -var-create @{@var{name} | "-"@}
28554 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28557 This operation creates a variable object, which allows the monitoring of
28558 a variable, the result of an expression, a memory cell or a CPU
28561 The @var{name} parameter is the string by which the object can be
28562 referenced. It must be unique. If @samp{-} is specified, the varobj
28563 system will generate a string ``varNNNNNN'' automatically. It will be
28564 unique provided that one does not specify @var{name} of that format.
28565 The command fails if a duplicate name is found.
28567 The frame under which the expression should be evaluated can be
28568 specified by @var{frame-addr}. A @samp{*} indicates that the current
28569 frame should be used. A @samp{@@} indicates that a floating variable
28570 object must be created.
28572 @var{expression} is any expression valid on the current language set (must not
28573 begin with a @samp{*}), or one of the following:
28577 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28580 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28583 @samp{$@var{regname}} --- a CPU register name
28586 @cindex dynamic varobj
28587 A varobj's contents may be provided by a Python-based pretty-printer. In this
28588 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28589 have slightly different semantics in some cases. If the
28590 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28591 will never create a dynamic varobj. This ensures backward
28592 compatibility for existing clients.
28594 @subsubheading Result
28596 This operation returns attributes of the newly-created varobj. These
28601 The name of the varobj.
28604 The number of children of the varobj. This number is not necessarily
28605 reliable for a dynamic varobj. Instead, you must examine the
28606 @samp{has_more} attribute.
28609 The varobj's scalar value. For a varobj whose type is some sort of
28610 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28611 will not be interesting.
28614 The varobj's type. This is a string representation of the type, as
28615 would be printed by the @value{GDBN} CLI.
28618 If a variable object is bound to a specific thread, then this is the
28619 thread's identifier.
28622 For a dynamic varobj, this indicates whether there appear to be any
28623 children available. For a non-dynamic varobj, this will be 0.
28626 This attribute will be present and have the value @samp{1} if the
28627 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28628 then this attribute will not be present.
28631 A dynamic varobj can supply a display hint to the front end. The
28632 value comes directly from the Python pretty-printer object's
28633 @code{display_hint} method. @xref{Pretty Printing API}.
28636 Typical output will look like this:
28639 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28640 has_more="@var{has_more}"
28644 @subheading The @code{-var-delete} Command
28645 @findex -var-delete
28647 @subsubheading Synopsis
28650 -var-delete [ -c ] @var{name}
28653 Deletes a previously created variable object and all of its children.
28654 With the @samp{-c} option, just deletes the children.
28656 Returns an error if the object @var{name} is not found.
28659 @subheading The @code{-var-set-format} Command
28660 @findex -var-set-format
28662 @subsubheading Synopsis
28665 -var-set-format @var{name} @var{format-spec}
28668 Sets the output format for the value of the object @var{name} to be
28671 @anchor{-var-set-format}
28672 The syntax for the @var{format-spec} is as follows:
28675 @var{format-spec} @expansion{}
28676 @{binary | decimal | hexadecimal | octal | natural@}
28679 The natural format is the default format choosen automatically
28680 based on the variable type (like decimal for an @code{int}, hex
28681 for pointers, etc.).
28683 For a variable with children, the format is set only on the
28684 variable itself, and the children are not affected.
28686 @subheading The @code{-var-show-format} Command
28687 @findex -var-show-format
28689 @subsubheading Synopsis
28692 -var-show-format @var{name}
28695 Returns the format used to display the value of the object @var{name}.
28698 @var{format} @expansion{}
28703 @subheading The @code{-var-info-num-children} Command
28704 @findex -var-info-num-children
28706 @subsubheading Synopsis
28709 -var-info-num-children @var{name}
28712 Returns the number of children of a variable object @var{name}:
28718 Note that this number is not completely reliable for a dynamic varobj.
28719 It will return the current number of children, but more children may
28723 @subheading The @code{-var-list-children} Command
28724 @findex -var-list-children
28726 @subsubheading Synopsis
28729 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28731 @anchor{-var-list-children}
28733 Return a list of the children of the specified variable object and
28734 create variable objects for them, if they do not already exist. With
28735 a single argument or if @var{print-values} has a value of 0 or
28736 @code{--no-values}, print only the names of the variables; if
28737 @var{print-values} is 1 or @code{--all-values}, also print their
28738 values; and if it is 2 or @code{--simple-values} print the name and
28739 value for simple data types and just the name for arrays, structures
28742 @var{from} and @var{to}, if specified, indicate the range of children
28743 to report. If @var{from} or @var{to} is less than zero, the range is
28744 reset and all children will be reported. Otherwise, children starting
28745 at @var{from} (zero-based) and up to and excluding @var{to} will be
28748 If a child range is requested, it will only affect the current call to
28749 @code{-var-list-children}, but not future calls to @code{-var-update}.
28750 For this, you must instead use @code{-var-set-update-range}. The
28751 intent of this approach is to enable a front end to implement any
28752 update approach it likes; for example, scrolling a view may cause the
28753 front end to request more children with @code{-var-list-children}, and
28754 then the front end could call @code{-var-set-update-range} with a
28755 different range to ensure that future updates are restricted to just
28758 For each child the following results are returned:
28763 Name of the variable object created for this child.
28766 The expression to be shown to the user by the front end to designate this child.
28767 For example this may be the name of a structure member.
28769 For a dynamic varobj, this value cannot be used to form an
28770 expression. There is no way to do this at all with a dynamic varobj.
28772 For C/C@t{++} structures there are several pseudo children returned to
28773 designate access qualifiers. For these pseudo children @var{exp} is
28774 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28775 type and value are not present.
28777 A dynamic varobj will not report the access qualifying
28778 pseudo-children, regardless of the language. This information is not
28779 available at all with a dynamic varobj.
28782 Number of children this child has. For a dynamic varobj, this will be
28786 The type of the child.
28789 If values were requested, this is the value.
28792 If this variable object is associated with a thread, this is the thread id.
28793 Otherwise this result is not present.
28796 If the variable object is frozen, this variable will be present with a value of 1.
28799 The result may have its own attributes:
28803 A dynamic varobj can supply a display hint to the front end. The
28804 value comes directly from the Python pretty-printer object's
28805 @code{display_hint} method. @xref{Pretty Printing API}.
28808 This is an integer attribute which is nonzero if there are children
28809 remaining after the end of the selected range.
28812 @subsubheading Example
28816 -var-list-children n
28817 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28818 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28820 -var-list-children --all-values n
28821 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28822 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28826 @subheading The @code{-var-info-type} Command
28827 @findex -var-info-type
28829 @subsubheading Synopsis
28832 -var-info-type @var{name}
28835 Returns the type of the specified variable @var{name}. The type is
28836 returned as a string in the same format as it is output by the
28840 type=@var{typename}
28844 @subheading The @code{-var-info-expression} Command
28845 @findex -var-info-expression
28847 @subsubheading Synopsis
28850 -var-info-expression @var{name}
28853 Returns a string that is suitable for presenting this
28854 variable object in user interface. The string is generally
28855 not valid expression in the current language, and cannot be evaluated.
28857 For example, if @code{a} is an array, and variable object
28858 @code{A} was created for @code{a}, then we'll get this output:
28861 (gdb) -var-info-expression A.1
28862 ^done,lang="C",exp="1"
28866 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28868 Note that the output of the @code{-var-list-children} command also
28869 includes those expressions, so the @code{-var-info-expression} command
28872 @subheading The @code{-var-info-path-expression} Command
28873 @findex -var-info-path-expression
28875 @subsubheading Synopsis
28878 -var-info-path-expression @var{name}
28881 Returns an expression that can be evaluated in the current
28882 context and will yield the same value that a variable object has.
28883 Compare this with the @code{-var-info-expression} command, which
28884 result can be used only for UI presentation. Typical use of
28885 the @code{-var-info-path-expression} command is creating a
28886 watchpoint from a variable object.
28888 This command is currently not valid for children of a dynamic varobj,
28889 and will give an error when invoked on one.
28891 For example, suppose @code{C} is a C@t{++} class, derived from class
28892 @code{Base}, and that the @code{Base} class has a member called
28893 @code{m_size}. Assume a variable @code{c} is has the type of
28894 @code{C} and a variable object @code{C} was created for variable
28895 @code{c}. Then, we'll get this output:
28897 (gdb) -var-info-path-expression C.Base.public.m_size
28898 ^done,path_expr=((Base)c).m_size)
28901 @subheading The @code{-var-show-attributes} Command
28902 @findex -var-show-attributes
28904 @subsubheading Synopsis
28907 -var-show-attributes @var{name}
28910 List attributes of the specified variable object @var{name}:
28913 status=@var{attr} [ ( ,@var{attr} )* ]
28917 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28919 @subheading The @code{-var-evaluate-expression} Command
28920 @findex -var-evaluate-expression
28922 @subsubheading Synopsis
28925 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28928 Evaluates the expression that is represented by the specified variable
28929 object and returns its value as a string. The format of the string
28930 can be specified with the @samp{-f} option. The possible values of
28931 this option are the same as for @code{-var-set-format}
28932 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28933 the current display format will be used. The current display format
28934 can be changed using the @code{-var-set-format} command.
28940 Note that one must invoke @code{-var-list-children} for a variable
28941 before the value of a child variable can be evaluated.
28943 @subheading The @code{-var-assign} Command
28944 @findex -var-assign
28946 @subsubheading Synopsis
28949 -var-assign @var{name} @var{expression}
28952 Assigns the value of @var{expression} to the variable object specified
28953 by @var{name}. The object must be @samp{editable}. If the variable's
28954 value is altered by the assign, the variable will show up in any
28955 subsequent @code{-var-update} list.
28957 @subsubheading Example
28965 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28969 @subheading The @code{-var-update} Command
28970 @findex -var-update
28972 @subsubheading Synopsis
28975 -var-update [@var{print-values}] @{@var{name} | "*"@}
28978 Reevaluate the expressions corresponding to the variable object
28979 @var{name} and all its direct and indirect children, and return the
28980 list of variable objects whose values have changed; @var{name} must
28981 be a root variable object. Here, ``changed'' means that the result of
28982 @code{-var-evaluate-expression} before and after the
28983 @code{-var-update} is different. If @samp{*} is used as the variable
28984 object names, all existing variable objects are updated, except
28985 for frozen ones (@pxref{-var-set-frozen}). The option
28986 @var{print-values} determines whether both names and values, or just
28987 names are printed. The possible values of this option are the same
28988 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28989 recommended to use the @samp{--all-values} option, to reduce the
28990 number of MI commands needed on each program stop.
28992 With the @samp{*} parameter, if a variable object is bound to a
28993 currently running thread, it will not be updated, without any
28996 If @code{-var-set-update-range} was previously used on a varobj, then
28997 only the selected range of children will be reported.
28999 @code{-var-update} reports all the changed varobjs in a tuple named
29002 Each item in the change list is itself a tuple holding:
29006 The name of the varobj.
29009 If values were requested for this update, then this field will be
29010 present and will hold the value of the varobj.
29013 @anchor{-var-update}
29014 This field is a string which may take one of three values:
29018 The variable object's current value is valid.
29021 The variable object does not currently hold a valid value but it may
29022 hold one in the future if its associated expression comes back into
29026 The variable object no longer holds a valid value.
29027 This can occur when the executable file being debugged has changed,
29028 either through recompilation or by using the @value{GDBN} @code{file}
29029 command. The front end should normally choose to delete these variable
29033 In the future new values may be added to this list so the front should
29034 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29037 This is only present if the varobj is still valid. If the type
29038 changed, then this will be the string @samp{true}; otherwise it will
29042 If the varobj's type changed, then this field will be present and will
29045 @item new_num_children
29046 For a dynamic varobj, if the number of children changed, or if the
29047 type changed, this will be the new number of children.
29049 The @samp{numchild} field in other varobj responses is generally not
29050 valid for a dynamic varobj -- it will show the number of children that
29051 @value{GDBN} knows about, but because dynamic varobjs lazily
29052 instantiate their children, this will not reflect the number of
29053 children which may be available.
29055 The @samp{new_num_children} attribute only reports changes to the
29056 number of children known by @value{GDBN}. This is the only way to
29057 detect whether an update has removed children (which necessarily can
29058 only happen at the end of the update range).
29061 The display hint, if any.
29064 This is an integer value, which will be 1 if there are more children
29065 available outside the varobj's update range.
29068 This attribute will be present and have the value @samp{1} if the
29069 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29070 then this attribute will not be present.
29073 If new children were added to a dynamic varobj within the selected
29074 update range (as set by @code{-var-set-update-range}), then they will
29075 be listed in this attribute.
29078 @subsubheading Example
29085 -var-update --all-values var1
29086 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29087 type_changed="false"@}]
29091 @subheading The @code{-var-set-frozen} Command
29092 @findex -var-set-frozen
29093 @anchor{-var-set-frozen}
29095 @subsubheading Synopsis
29098 -var-set-frozen @var{name} @var{flag}
29101 Set the frozenness flag on the variable object @var{name}. The
29102 @var{flag} parameter should be either @samp{1} to make the variable
29103 frozen or @samp{0} to make it unfrozen. If a variable object is
29104 frozen, then neither itself, nor any of its children, are
29105 implicitly updated by @code{-var-update} of
29106 a parent variable or by @code{-var-update *}. Only
29107 @code{-var-update} of the variable itself will update its value and
29108 values of its children. After a variable object is unfrozen, it is
29109 implicitly updated by all subsequent @code{-var-update} operations.
29110 Unfreezing a variable does not update it, only subsequent
29111 @code{-var-update} does.
29113 @subsubheading Example
29117 -var-set-frozen V 1
29122 @subheading The @code{-var-set-update-range} command
29123 @findex -var-set-update-range
29124 @anchor{-var-set-update-range}
29126 @subsubheading Synopsis
29129 -var-set-update-range @var{name} @var{from} @var{to}
29132 Set the range of children to be returned by future invocations of
29133 @code{-var-update}.
29135 @var{from} and @var{to} indicate the range of children to report. If
29136 @var{from} or @var{to} is less than zero, the range is reset and all
29137 children will be reported. Otherwise, children starting at @var{from}
29138 (zero-based) and up to and excluding @var{to} will be reported.
29140 @subsubheading Example
29144 -var-set-update-range V 1 2
29148 @subheading The @code{-var-set-visualizer} command
29149 @findex -var-set-visualizer
29150 @anchor{-var-set-visualizer}
29152 @subsubheading Synopsis
29155 -var-set-visualizer @var{name} @var{visualizer}
29158 Set a visualizer for the variable object @var{name}.
29160 @var{visualizer} is the visualizer to use. The special value
29161 @samp{None} means to disable any visualizer in use.
29163 If not @samp{None}, @var{visualizer} must be a Python expression.
29164 This expression must evaluate to a callable object which accepts a
29165 single argument. @value{GDBN} will call this object with the value of
29166 the varobj @var{name} as an argument (this is done so that the same
29167 Python pretty-printing code can be used for both the CLI and MI).
29168 When called, this object must return an object which conforms to the
29169 pretty-printing interface (@pxref{Pretty Printing API}).
29171 The pre-defined function @code{gdb.default_visualizer} may be used to
29172 select a visualizer by following the built-in process
29173 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29174 a varobj is created, and so ordinarily is not needed.
29176 This feature is only available if Python support is enabled. The MI
29177 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29178 can be used to check this.
29180 @subsubheading Example
29182 Resetting the visualizer:
29186 -var-set-visualizer V None
29190 Reselecting the default (type-based) visualizer:
29194 -var-set-visualizer V gdb.default_visualizer
29198 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29199 can be used to instantiate this class for a varobj:
29203 -var-set-visualizer V "lambda val: SomeClass()"
29207 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29208 @node GDB/MI Data Manipulation
29209 @section @sc{gdb/mi} Data Manipulation
29211 @cindex data manipulation, in @sc{gdb/mi}
29212 @cindex @sc{gdb/mi}, data manipulation
29213 This section describes the @sc{gdb/mi} commands that manipulate data:
29214 examine memory and registers, evaluate expressions, etc.
29216 @c REMOVED FROM THE INTERFACE.
29217 @c @subheading -data-assign
29218 @c Change the value of a program variable. Plenty of side effects.
29219 @c @subsubheading GDB Command
29221 @c @subsubheading Example
29224 @subheading The @code{-data-disassemble} Command
29225 @findex -data-disassemble
29227 @subsubheading Synopsis
29231 [ -s @var{start-addr} -e @var{end-addr} ]
29232 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29240 @item @var{start-addr}
29241 is the beginning address (or @code{$pc})
29242 @item @var{end-addr}
29244 @item @var{filename}
29245 is the name of the file to disassemble
29246 @item @var{linenum}
29247 is the line number to disassemble around
29249 is the number of disassembly lines to be produced. If it is -1,
29250 the whole function will be disassembled, in case no @var{end-addr} is
29251 specified. If @var{end-addr} is specified as a non-zero value, and
29252 @var{lines} is lower than the number of disassembly lines between
29253 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29254 displayed; if @var{lines} is higher than the number of lines between
29255 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29258 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29259 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29260 mixed source and disassembly with raw opcodes).
29263 @subsubheading Result
29265 The output for each instruction is composed of four fields:
29274 Note that whatever included in the instruction field, is not manipulated
29275 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29277 @subsubheading @value{GDBN} Command
29279 There's no direct mapping from this command to the CLI.
29281 @subsubheading Example
29283 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29287 -data-disassemble -s $pc -e "$pc + 20" -- 0
29290 @{address="0x000107c0",func-name="main",offset="4",
29291 inst="mov 2, %o0"@},
29292 @{address="0x000107c4",func-name="main",offset="8",
29293 inst="sethi %hi(0x11800), %o2"@},
29294 @{address="0x000107c8",func-name="main",offset="12",
29295 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29296 @{address="0x000107cc",func-name="main",offset="16",
29297 inst="sethi %hi(0x11800), %o2"@},
29298 @{address="0x000107d0",func-name="main",offset="20",
29299 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29303 Disassemble the whole @code{main} function. Line 32 is part of
29307 -data-disassemble -f basics.c -l 32 -- 0
29309 @{address="0x000107bc",func-name="main",offset="0",
29310 inst="save %sp, -112, %sp"@},
29311 @{address="0x000107c0",func-name="main",offset="4",
29312 inst="mov 2, %o0"@},
29313 @{address="0x000107c4",func-name="main",offset="8",
29314 inst="sethi %hi(0x11800), %o2"@},
29316 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29317 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29321 Disassemble 3 instructions from the start of @code{main}:
29325 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29327 @{address="0x000107bc",func-name="main",offset="0",
29328 inst="save %sp, -112, %sp"@},
29329 @{address="0x000107c0",func-name="main",offset="4",
29330 inst="mov 2, %o0"@},
29331 @{address="0x000107c4",func-name="main",offset="8",
29332 inst="sethi %hi(0x11800), %o2"@}]
29336 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29340 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29342 src_and_asm_line=@{line="31",
29343 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29344 testsuite/gdb.mi/basics.c",line_asm_insn=[
29345 @{address="0x000107bc",func-name="main",offset="0",
29346 inst="save %sp, -112, %sp"@}]@},
29347 src_and_asm_line=@{line="32",
29348 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29349 testsuite/gdb.mi/basics.c",line_asm_insn=[
29350 @{address="0x000107c0",func-name="main",offset="4",
29351 inst="mov 2, %o0"@},
29352 @{address="0x000107c4",func-name="main",offset="8",
29353 inst="sethi %hi(0x11800), %o2"@}]@}]
29358 @subheading The @code{-data-evaluate-expression} Command
29359 @findex -data-evaluate-expression
29361 @subsubheading Synopsis
29364 -data-evaluate-expression @var{expr}
29367 Evaluate @var{expr} as an expression. The expression could contain an
29368 inferior function call. The function call will execute synchronously.
29369 If the expression contains spaces, it must be enclosed in double quotes.
29371 @subsubheading @value{GDBN} Command
29373 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29374 @samp{call}. In @code{gdbtk} only, there's a corresponding
29375 @samp{gdb_eval} command.
29377 @subsubheading Example
29379 In the following example, the numbers that precede the commands are the
29380 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29381 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29385 211-data-evaluate-expression A
29388 311-data-evaluate-expression &A
29389 311^done,value="0xefffeb7c"
29391 411-data-evaluate-expression A+3
29394 511-data-evaluate-expression "A + 3"
29400 @subheading The @code{-data-list-changed-registers} Command
29401 @findex -data-list-changed-registers
29403 @subsubheading Synopsis
29406 -data-list-changed-registers
29409 Display a list of the registers that have changed.
29411 @subsubheading @value{GDBN} Command
29413 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29414 has the corresponding command @samp{gdb_changed_register_list}.
29416 @subsubheading Example
29418 On a PPC MBX board:
29426 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29427 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29430 -data-list-changed-registers
29431 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29432 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29433 "24","25","26","27","28","30","31","64","65","66","67","69"]
29438 @subheading The @code{-data-list-register-names} Command
29439 @findex -data-list-register-names
29441 @subsubheading Synopsis
29444 -data-list-register-names [ ( @var{regno} )+ ]
29447 Show a list of register names for the current target. If no arguments
29448 are given, it shows a list of the names of all the registers. If
29449 integer numbers are given as arguments, it will print a list of the
29450 names of the registers corresponding to the arguments. To ensure
29451 consistency between a register name and its number, the output list may
29452 include empty register names.
29454 @subsubheading @value{GDBN} Command
29456 @value{GDBN} does not have a command which corresponds to
29457 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29458 corresponding command @samp{gdb_regnames}.
29460 @subsubheading Example
29462 For the PPC MBX board:
29465 -data-list-register-names
29466 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29467 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29468 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29469 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29470 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29471 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29472 "", "pc","ps","cr","lr","ctr","xer"]
29474 -data-list-register-names 1 2 3
29475 ^done,register-names=["r1","r2","r3"]
29479 @subheading The @code{-data-list-register-values} Command
29480 @findex -data-list-register-values
29482 @subsubheading Synopsis
29485 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29488 Display the registers' contents. @var{fmt} is the format according to
29489 which the registers' contents are to be returned, followed by an optional
29490 list of numbers specifying the registers to display. A missing list of
29491 numbers indicates that the contents of all the registers must be returned.
29493 Allowed formats for @var{fmt} are:
29510 @subsubheading @value{GDBN} Command
29512 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29513 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29515 @subsubheading Example
29517 For a PPC MBX board (note: line breaks are for readability only, they
29518 don't appear in the actual output):
29522 -data-list-register-values r 64 65
29523 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29524 @{number="65",value="0x00029002"@}]
29526 -data-list-register-values x
29527 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29528 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29529 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29530 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29531 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29532 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29533 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29534 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29535 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29536 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29537 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29538 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29539 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29540 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29541 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29542 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29543 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29544 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29545 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29546 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29547 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29548 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29549 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29550 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29551 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29552 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29553 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29554 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29555 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29556 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29557 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29558 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29559 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29560 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29561 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29562 @{number="69",value="0x20002b03"@}]
29567 @subheading The @code{-data-read-memory} Command
29568 @findex -data-read-memory
29570 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29572 @subsubheading Synopsis
29575 -data-read-memory [ -o @var{byte-offset} ]
29576 @var{address} @var{word-format} @var{word-size}
29577 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29584 @item @var{address}
29585 An expression specifying the address of the first memory word to be
29586 read. Complex expressions containing embedded white space should be
29587 quoted using the C convention.
29589 @item @var{word-format}
29590 The format to be used to print the memory words. The notation is the
29591 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29594 @item @var{word-size}
29595 The size of each memory word in bytes.
29597 @item @var{nr-rows}
29598 The number of rows in the output table.
29600 @item @var{nr-cols}
29601 The number of columns in the output table.
29604 If present, indicates that each row should include an @sc{ascii} dump. The
29605 value of @var{aschar} is used as a padding character when a byte is not a
29606 member of the printable @sc{ascii} character set (printable @sc{ascii}
29607 characters are those whose code is between 32 and 126, inclusively).
29609 @item @var{byte-offset}
29610 An offset to add to the @var{address} before fetching memory.
29613 This command displays memory contents as a table of @var{nr-rows} by
29614 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29615 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29616 (returned as @samp{total-bytes}). Should less than the requested number
29617 of bytes be returned by the target, the missing words are identified
29618 using @samp{N/A}. The number of bytes read from the target is returned
29619 in @samp{nr-bytes} and the starting address used to read memory in
29622 The address of the next/previous row or page is available in
29623 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29626 @subsubheading @value{GDBN} Command
29628 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29629 @samp{gdb_get_mem} memory read command.
29631 @subsubheading Example
29633 Read six bytes of memory starting at @code{bytes+6} but then offset by
29634 @code{-6} bytes. Format as three rows of two columns. One byte per
29635 word. Display each word in hex.
29639 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29640 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29641 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29642 prev-page="0x0000138a",memory=[
29643 @{addr="0x00001390",data=["0x00","0x01"]@},
29644 @{addr="0x00001392",data=["0x02","0x03"]@},
29645 @{addr="0x00001394",data=["0x04","0x05"]@}]
29649 Read two bytes of memory starting at address @code{shorts + 64} and
29650 display as a single word formatted in decimal.
29654 5-data-read-memory shorts+64 d 2 1 1
29655 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29656 next-row="0x00001512",prev-row="0x0000150e",
29657 next-page="0x00001512",prev-page="0x0000150e",memory=[
29658 @{addr="0x00001510",data=["128"]@}]
29662 Read thirty two bytes of memory starting at @code{bytes+16} and format
29663 as eight rows of four columns. Include a string encoding with @samp{x}
29664 used as the non-printable character.
29668 4-data-read-memory bytes+16 x 1 8 4 x
29669 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29670 next-row="0x000013c0",prev-row="0x0000139c",
29671 next-page="0x000013c0",prev-page="0x00001380",memory=[
29672 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29673 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29674 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29675 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29676 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29677 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29678 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29679 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29683 @subheading The @code{-data-read-memory-bytes} Command
29684 @findex -data-read-memory-bytes
29686 @subsubheading Synopsis
29689 -data-read-memory-bytes [ -o @var{byte-offset} ]
29690 @var{address} @var{count}
29697 @item @var{address}
29698 An expression specifying the address of the first memory word to be
29699 read. Complex expressions containing embedded white space should be
29700 quoted using the C convention.
29703 The number of bytes to read. This should be an integer literal.
29705 @item @var{byte-offset}
29706 The offsets in bytes relative to @var{address} at which to start
29707 reading. This should be an integer literal. This option is provided
29708 so that a frontend is not required to first evaluate address and then
29709 perform address arithmetics itself.
29713 This command attempts to read all accessible memory regions in the
29714 specified range. First, all regions marked as unreadable in the memory
29715 map (if one is defined) will be skipped. @xref{Memory Region
29716 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29717 regions. For each one, if reading full region results in an errors,
29718 @value{GDBN} will try to read a subset of the region.
29720 In general, every single byte in the region may be readable or not,
29721 and the only way to read every readable byte is to try a read at
29722 every address, which is not practical. Therefore, @value{GDBN} will
29723 attempt to read all accessible bytes at either beginning or the end
29724 of the region, using a binary division scheme. This heuristic works
29725 well for reading accross a memory map boundary. Note that if a region
29726 has a readable range that is neither at the beginning or the end,
29727 @value{GDBN} will not read it.
29729 The result record (@pxref{GDB/MI Result Records}) that is output of
29730 the command includes a field named @samp{memory} whose content is a
29731 list of tuples. Each tuple represent a successfully read memory block
29732 and has the following fields:
29736 The start address of the memory block, as hexadecimal literal.
29739 The end address of the memory block, as hexadecimal literal.
29742 The offset of the memory block, as hexadecimal literal, relative to
29743 the start address passed to @code{-data-read-memory-bytes}.
29746 The contents of the memory block, in hex.
29752 @subsubheading @value{GDBN} Command
29754 The corresponding @value{GDBN} command is @samp{x}.
29756 @subsubheading Example
29760 -data-read-memory-bytes &a 10
29761 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29763 contents="01000000020000000300"@}]
29768 @subheading The @code{-data-write-memory-bytes} Command
29769 @findex -data-write-memory-bytes
29771 @subsubheading Synopsis
29774 -data-write-memory-bytes @var{address} @var{contents}
29781 @item @var{address}
29782 An expression specifying the address of the first memory word to be
29783 read. Complex expressions containing embedded white space should be
29784 quoted using the C convention.
29786 @item @var{contents}
29787 The hex-encoded bytes to write.
29791 @subsubheading @value{GDBN} Command
29793 There's no corresponding @value{GDBN} command.
29795 @subsubheading Example
29799 -data-write-memory-bytes &a "aabbccdd"
29805 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29806 @node GDB/MI Tracepoint Commands
29807 @section @sc{gdb/mi} Tracepoint Commands
29809 The commands defined in this section implement MI support for
29810 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29812 @subheading The @code{-trace-find} Command
29813 @findex -trace-find
29815 @subsubheading Synopsis
29818 -trace-find @var{mode} [@var{parameters}@dots{}]
29821 Find a trace frame using criteria defined by @var{mode} and
29822 @var{parameters}. The following table lists permissible
29823 modes and their parameters. For details of operation, see @ref{tfind}.
29828 No parameters are required. Stops examining trace frames.
29831 An integer is required as parameter. Selects tracepoint frame with
29834 @item tracepoint-number
29835 An integer is required as parameter. Finds next
29836 trace frame that corresponds to tracepoint with the specified number.
29839 An address is required as parameter. Finds
29840 next trace frame that corresponds to any tracepoint at the specified
29843 @item pc-inside-range
29844 Two addresses are required as parameters. Finds next trace
29845 frame that corresponds to a tracepoint at an address inside the
29846 specified range. Both bounds are considered to be inside the range.
29848 @item pc-outside-range
29849 Two addresses are required as parameters. Finds
29850 next trace frame that corresponds to a tracepoint at an address outside
29851 the specified range. Both bounds are considered to be inside the range.
29854 Line specification is required as parameter. @xref{Specify Location}.
29855 Finds next trace frame that corresponds to a tracepoint at
29856 the specified location.
29860 If @samp{none} was passed as @var{mode}, the response does not
29861 have fields. Otherwise, the response may have the following fields:
29865 This field has either @samp{0} or @samp{1} as the value, depending
29866 on whether a matching tracepoint was found.
29869 The index of the found traceframe. This field is present iff
29870 the @samp{found} field has value of @samp{1}.
29873 The index of the found tracepoint. This field is present iff
29874 the @samp{found} field has value of @samp{1}.
29877 The information about the frame corresponding to the found trace
29878 frame. This field is present only if a trace frame was found.
29879 @xref{GDB/MI Frame Information}, for description of this field.
29883 @subsubheading @value{GDBN} Command
29885 The corresponding @value{GDBN} command is @samp{tfind}.
29887 @subheading -trace-define-variable
29888 @findex -trace-define-variable
29890 @subsubheading Synopsis
29893 -trace-define-variable @var{name} [ @var{value} ]
29896 Create trace variable @var{name} if it does not exist. If
29897 @var{value} is specified, sets the initial value of the specified
29898 trace variable to that value. Note that the @var{name} should start
29899 with the @samp{$} character.
29901 @subsubheading @value{GDBN} Command
29903 The corresponding @value{GDBN} command is @samp{tvariable}.
29905 @subheading -trace-list-variables
29906 @findex -trace-list-variables
29908 @subsubheading Synopsis
29911 -trace-list-variables
29914 Return a table of all defined trace variables. Each element of the
29915 table has the following fields:
29919 The name of the trace variable. This field is always present.
29922 The initial value. This is a 64-bit signed integer. This
29923 field is always present.
29926 The value the trace variable has at the moment. This is a 64-bit
29927 signed integer. This field is absent iff current value is
29928 not defined, for example if the trace was never run, or is
29933 @subsubheading @value{GDBN} Command
29935 The corresponding @value{GDBN} command is @samp{tvariables}.
29937 @subsubheading Example
29941 -trace-list-variables
29942 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29943 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29944 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29945 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29946 body=[variable=@{name="$trace_timestamp",initial="0"@}
29947 variable=@{name="$foo",initial="10",current="15"@}]@}
29951 @subheading -trace-save
29952 @findex -trace-save
29954 @subsubheading Synopsis
29957 -trace-save [-r ] @var{filename}
29960 Saves the collected trace data to @var{filename}. Without the
29961 @samp{-r} option, the data is downloaded from the target and saved
29962 in a local file. With the @samp{-r} option the target is asked
29963 to perform the save.
29965 @subsubheading @value{GDBN} Command
29967 The corresponding @value{GDBN} command is @samp{tsave}.
29970 @subheading -trace-start
29971 @findex -trace-start
29973 @subsubheading Synopsis
29979 Starts a tracing experiments. The result of this command does not
29982 @subsubheading @value{GDBN} Command
29984 The corresponding @value{GDBN} command is @samp{tstart}.
29986 @subheading -trace-status
29987 @findex -trace-status
29989 @subsubheading Synopsis
29995 Obtains the status of a tracing experiment. The result may include
29996 the following fields:
30001 May have a value of either @samp{0}, when no tracing operations are
30002 supported, @samp{1}, when all tracing operations are supported, or
30003 @samp{file} when examining trace file. In the latter case, examining
30004 of trace frame is possible but new tracing experiement cannot be
30005 started. This field is always present.
30008 May have a value of either @samp{0} or @samp{1} depending on whether
30009 tracing experiement is in progress on target. This field is present
30010 if @samp{supported} field is not @samp{0}.
30013 Report the reason why the tracing was stopped last time. This field
30014 may be absent iff tracing was never stopped on target yet. The
30015 value of @samp{request} means the tracing was stopped as result of
30016 the @code{-trace-stop} command. The value of @samp{overflow} means
30017 the tracing buffer is full. The value of @samp{disconnection} means
30018 tracing was automatically stopped when @value{GDBN} has disconnected.
30019 The value of @samp{passcount} means tracing was stopped when a
30020 tracepoint was passed a maximal number of times for that tracepoint.
30021 This field is present if @samp{supported} field is not @samp{0}.
30023 @item stopping-tracepoint
30024 The number of tracepoint whose passcount as exceeded. This field is
30025 present iff the @samp{stop-reason} field has the value of
30029 @itemx frames-created
30030 The @samp{frames} field is a count of the total number of trace frames
30031 in the trace buffer, while @samp{frames-created} is the total created
30032 during the run, including ones that were discarded, such as when a
30033 circular trace buffer filled up. Both fields are optional.
30037 These fields tell the current size of the tracing buffer and the
30038 remaining space. These fields are optional.
30041 The value of the circular trace buffer flag. @code{1} means that the
30042 trace buffer is circular and old trace frames will be discarded if
30043 necessary to make room, @code{0} means that the trace buffer is linear
30047 The value of the disconnected tracing flag. @code{1} means that
30048 tracing will continue after @value{GDBN} disconnects, @code{0} means
30049 that the trace run will stop.
30053 @subsubheading @value{GDBN} Command
30055 The corresponding @value{GDBN} command is @samp{tstatus}.
30057 @subheading -trace-stop
30058 @findex -trace-stop
30060 @subsubheading Synopsis
30066 Stops a tracing experiment. The result of this command has the same
30067 fields as @code{-trace-status}, except that the @samp{supported} and
30068 @samp{running} fields are not output.
30070 @subsubheading @value{GDBN} Command
30072 The corresponding @value{GDBN} command is @samp{tstop}.
30075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30076 @node GDB/MI Symbol Query
30077 @section @sc{gdb/mi} Symbol Query Commands
30081 @subheading The @code{-symbol-info-address} Command
30082 @findex -symbol-info-address
30084 @subsubheading Synopsis
30087 -symbol-info-address @var{symbol}
30090 Describe where @var{symbol} is stored.
30092 @subsubheading @value{GDBN} Command
30094 The corresponding @value{GDBN} command is @samp{info address}.
30096 @subsubheading Example
30100 @subheading The @code{-symbol-info-file} Command
30101 @findex -symbol-info-file
30103 @subsubheading Synopsis
30109 Show the file for the symbol.
30111 @subsubheading @value{GDBN} Command
30113 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30114 @samp{gdb_find_file}.
30116 @subsubheading Example
30120 @subheading The @code{-symbol-info-function} Command
30121 @findex -symbol-info-function
30123 @subsubheading Synopsis
30126 -symbol-info-function
30129 Show which function the symbol lives in.
30131 @subsubheading @value{GDBN} Command
30133 @samp{gdb_get_function} in @code{gdbtk}.
30135 @subsubheading Example
30139 @subheading The @code{-symbol-info-line} Command
30140 @findex -symbol-info-line
30142 @subsubheading Synopsis
30148 Show the core addresses of the code for a source line.
30150 @subsubheading @value{GDBN} Command
30152 The corresponding @value{GDBN} command is @samp{info line}.
30153 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30155 @subsubheading Example
30159 @subheading The @code{-symbol-info-symbol} Command
30160 @findex -symbol-info-symbol
30162 @subsubheading Synopsis
30165 -symbol-info-symbol @var{addr}
30168 Describe what symbol is at location @var{addr}.
30170 @subsubheading @value{GDBN} Command
30172 The corresponding @value{GDBN} command is @samp{info symbol}.
30174 @subsubheading Example
30178 @subheading The @code{-symbol-list-functions} Command
30179 @findex -symbol-list-functions
30181 @subsubheading Synopsis
30184 -symbol-list-functions
30187 List the functions in the executable.
30189 @subsubheading @value{GDBN} Command
30191 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30192 @samp{gdb_search} in @code{gdbtk}.
30194 @subsubheading Example
30199 @subheading The @code{-symbol-list-lines} Command
30200 @findex -symbol-list-lines
30202 @subsubheading Synopsis
30205 -symbol-list-lines @var{filename}
30208 Print the list of lines that contain code and their associated program
30209 addresses for the given source filename. The entries are sorted in
30210 ascending PC order.
30212 @subsubheading @value{GDBN} Command
30214 There is no corresponding @value{GDBN} command.
30216 @subsubheading Example
30219 -symbol-list-lines basics.c
30220 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30226 @subheading The @code{-symbol-list-types} Command
30227 @findex -symbol-list-types
30229 @subsubheading Synopsis
30235 List all the type names.
30237 @subsubheading @value{GDBN} Command
30239 The corresponding commands are @samp{info types} in @value{GDBN},
30240 @samp{gdb_search} in @code{gdbtk}.
30242 @subsubheading Example
30246 @subheading The @code{-symbol-list-variables} Command
30247 @findex -symbol-list-variables
30249 @subsubheading Synopsis
30252 -symbol-list-variables
30255 List all the global and static variable names.
30257 @subsubheading @value{GDBN} Command
30259 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30261 @subsubheading Example
30265 @subheading The @code{-symbol-locate} Command
30266 @findex -symbol-locate
30268 @subsubheading Synopsis
30274 @subsubheading @value{GDBN} Command
30276 @samp{gdb_loc} in @code{gdbtk}.
30278 @subsubheading Example
30282 @subheading The @code{-symbol-type} Command
30283 @findex -symbol-type
30285 @subsubheading Synopsis
30288 -symbol-type @var{variable}
30291 Show type of @var{variable}.
30293 @subsubheading @value{GDBN} Command
30295 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30296 @samp{gdb_obj_variable}.
30298 @subsubheading Example
30303 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30304 @node GDB/MI File Commands
30305 @section @sc{gdb/mi} File Commands
30307 This section describes the GDB/MI commands to specify executable file names
30308 and to read in and obtain symbol table information.
30310 @subheading The @code{-file-exec-and-symbols} Command
30311 @findex -file-exec-and-symbols
30313 @subsubheading Synopsis
30316 -file-exec-and-symbols @var{file}
30319 Specify the executable file to be debugged. This file is the one from
30320 which the symbol table is also read. If no file is specified, the
30321 command clears the executable and symbol information. If breakpoints
30322 are set when using this command with no arguments, @value{GDBN} will produce
30323 error messages. Otherwise, no output is produced, except a completion
30326 @subsubheading @value{GDBN} Command
30328 The corresponding @value{GDBN} command is @samp{file}.
30330 @subsubheading Example
30334 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30340 @subheading The @code{-file-exec-file} Command
30341 @findex -file-exec-file
30343 @subsubheading Synopsis
30346 -file-exec-file @var{file}
30349 Specify the executable file to be debugged. Unlike
30350 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30351 from this file. If used without argument, @value{GDBN} clears the information
30352 about the executable file. No output is produced, except a completion
30355 @subsubheading @value{GDBN} Command
30357 The corresponding @value{GDBN} command is @samp{exec-file}.
30359 @subsubheading Example
30363 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30370 @subheading The @code{-file-list-exec-sections} Command
30371 @findex -file-list-exec-sections
30373 @subsubheading Synopsis
30376 -file-list-exec-sections
30379 List the sections of the current executable file.
30381 @subsubheading @value{GDBN} Command
30383 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30384 information as this command. @code{gdbtk} has a corresponding command
30385 @samp{gdb_load_info}.
30387 @subsubheading Example
30392 @subheading The @code{-file-list-exec-source-file} Command
30393 @findex -file-list-exec-source-file
30395 @subsubheading Synopsis
30398 -file-list-exec-source-file
30401 List the line number, the current source file, and the absolute path
30402 to the current source file for the current executable. The macro
30403 information field has a value of @samp{1} or @samp{0} depending on
30404 whether or not the file includes preprocessor macro information.
30406 @subsubheading @value{GDBN} Command
30408 The @value{GDBN} equivalent is @samp{info source}
30410 @subsubheading Example
30414 123-file-list-exec-source-file
30415 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30420 @subheading The @code{-file-list-exec-source-files} Command
30421 @findex -file-list-exec-source-files
30423 @subsubheading Synopsis
30426 -file-list-exec-source-files
30429 List the source files for the current executable.
30431 It will always output the filename, but only when @value{GDBN} can find
30432 the absolute file name of a source file, will it output the fullname.
30434 @subsubheading @value{GDBN} Command
30436 The @value{GDBN} equivalent is @samp{info sources}.
30437 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30439 @subsubheading Example
30442 -file-list-exec-source-files
30444 @{file=foo.c,fullname=/home/foo.c@},
30445 @{file=/home/bar.c,fullname=/home/bar.c@},
30446 @{file=gdb_could_not_find_fullpath.c@}]
30451 @subheading The @code{-file-list-shared-libraries} Command
30452 @findex -file-list-shared-libraries
30454 @subsubheading Synopsis
30457 -file-list-shared-libraries
30460 List the shared libraries in the program.
30462 @subsubheading @value{GDBN} Command
30464 The corresponding @value{GDBN} command is @samp{info shared}.
30466 @subsubheading Example
30470 @subheading The @code{-file-list-symbol-files} Command
30471 @findex -file-list-symbol-files
30473 @subsubheading Synopsis
30476 -file-list-symbol-files
30481 @subsubheading @value{GDBN} Command
30483 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30485 @subsubheading Example
30490 @subheading The @code{-file-symbol-file} Command
30491 @findex -file-symbol-file
30493 @subsubheading Synopsis
30496 -file-symbol-file @var{file}
30499 Read symbol table info from the specified @var{file} argument. When
30500 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30501 produced, except for a completion notification.
30503 @subsubheading @value{GDBN} Command
30505 The corresponding @value{GDBN} command is @samp{symbol-file}.
30507 @subsubheading Example
30511 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30517 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30518 @node GDB/MI Memory Overlay Commands
30519 @section @sc{gdb/mi} Memory Overlay Commands
30521 The memory overlay commands are not implemented.
30523 @c @subheading -overlay-auto
30525 @c @subheading -overlay-list-mapping-state
30527 @c @subheading -overlay-list-overlays
30529 @c @subheading -overlay-map
30531 @c @subheading -overlay-off
30533 @c @subheading -overlay-on
30535 @c @subheading -overlay-unmap
30537 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30538 @node GDB/MI Signal Handling Commands
30539 @section @sc{gdb/mi} Signal Handling Commands
30541 Signal handling commands are not implemented.
30543 @c @subheading -signal-handle
30545 @c @subheading -signal-list-handle-actions
30547 @c @subheading -signal-list-signal-types
30551 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30552 @node GDB/MI Target Manipulation
30553 @section @sc{gdb/mi} Target Manipulation Commands
30556 @subheading The @code{-target-attach} Command
30557 @findex -target-attach
30559 @subsubheading Synopsis
30562 -target-attach @var{pid} | @var{gid} | @var{file}
30565 Attach to a process @var{pid} or a file @var{file} outside of
30566 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30567 group, the id previously returned by
30568 @samp{-list-thread-groups --available} must be used.
30570 @subsubheading @value{GDBN} Command
30572 The corresponding @value{GDBN} command is @samp{attach}.
30574 @subsubheading Example
30578 =thread-created,id="1"
30579 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30585 @subheading The @code{-target-compare-sections} Command
30586 @findex -target-compare-sections
30588 @subsubheading Synopsis
30591 -target-compare-sections [ @var{section} ]
30594 Compare data of section @var{section} on target to the exec file.
30595 Without the argument, all sections are compared.
30597 @subsubheading @value{GDBN} Command
30599 The @value{GDBN} equivalent is @samp{compare-sections}.
30601 @subsubheading Example
30606 @subheading The @code{-target-detach} Command
30607 @findex -target-detach
30609 @subsubheading Synopsis
30612 -target-detach [ @var{pid} | @var{gid} ]
30615 Detach from the remote target which normally resumes its execution.
30616 If either @var{pid} or @var{gid} is specified, detaches from either
30617 the specified process, or specified thread group. There's no output.
30619 @subsubheading @value{GDBN} Command
30621 The corresponding @value{GDBN} command is @samp{detach}.
30623 @subsubheading Example
30633 @subheading The @code{-target-disconnect} Command
30634 @findex -target-disconnect
30636 @subsubheading Synopsis
30642 Disconnect from the remote target. There's no output and the target is
30643 generally not resumed.
30645 @subsubheading @value{GDBN} Command
30647 The corresponding @value{GDBN} command is @samp{disconnect}.
30649 @subsubheading Example
30659 @subheading The @code{-target-download} Command
30660 @findex -target-download
30662 @subsubheading Synopsis
30668 Loads the executable onto the remote target.
30669 It prints out an update message every half second, which includes the fields:
30673 The name of the section.
30675 The size of what has been sent so far for that section.
30677 The size of the section.
30679 The total size of what was sent so far (the current and the previous sections).
30681 The size of the overall executable to download.
30685 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30686 @sc{gdb/mi} Output Syntax}).
30688 In addition, it prints the name and size of the sections, as they are
30689 downloaded. These messages include the following fields:
30693 The name of the section.
30695 The size of the section.
30697 The size of the overall executable to download.
30701 At the end, a summary is printed.
30703 @subsubheading @value{GDBN} Command
30705 The corresponding @value{GDBN} command is @samp{load}.
30707 @subsubheading Example
30709 Note: each status message appears on a single line. Here the messages
30710 have been broken down so that they can fit onto a page.
30715 +download,@{section=".text",section-size="6668",total-size="9880"@}
30716 +download,@{section=".text",section-sent="512",section-size="6668",
30717 total-sent="512",total-size="9880"@}
30718 +download,@{section=".text",section-sent="1024",section-size="6668",
30719 total-sent="1024",total-size="9880"@}
30720 +download,@{section=".text",section-sent="1536",section-size="6668",
30721 total-sent="1536",total-size="9880"@}
30722 +download,@{section=".text",section-sent="2048",section-size="6668",
30723 total-sent="2048",total-size="9880"@}
30724 +download,@{section=".text",section-sent="2560",section-size="6668",
30725 total-sent="2560",total-size="9880"@}
30726 +download,@{section=".text",section-sent="3072",section-size="6668",
30727 total-sent="3072",total-size="9880"@}
30728 +download,@{section=".text",section-sent="3584",section-size="6668",
30729 total-sent="3584",total-size="9880"@}
30730 +download,@{section=".text",section-sent="4096",section-size="6668",
30731 total-sent="4096",total-size="9880"@}
30732 +download,@{section=".text",section-sent="4608",section-size="6668",
30733 total-sent="4608",total-size="9880"@}
30734 +download,@{section=".text",section-sent="5120",section-size="6668",
30735 total-sent="5120",total-size="9880"@}
30736 +download,@{section=".text",section-sent="5632",section-size="6668",
30737 total-sent="5632",total-size="9880"@}
30738 +download,@{section=".text",section-sent="6144",section-size="6668",
30739 total-sent="6144",total-size="9880"@}
30740 +download,@{section=".text",section-sent="6656",section-size="6668",
30741 total-sent="6656",total-size="9880"@}
30742 +download,@{section=".init",section-size="28",total-size="9880"@}
30743 +download,@{section=".fini",section-size="28",total-size="9880"@}
30744 +download,@{section=".data",section-size="3156",total-size="9880"@}
30745 +download,@{section=".data",section-sent="512",section-size="3156",
30746 total-sent="7236",total-size="9880"@}
30747 +download,@{section=".data",section-sent="1024",section-size="3156",
30748 total-sent="7748",total-size="9880"@}
30749 +download,@{section=".data",section-sent="1536",section-size="3156",
30750 total-sent="8260",total-size="9880"@}
30751 +download,@{section=".data",section-sent="2048",section-size="3156",
30752 total-sent="8772",total-size="9880"@}
30753 +download,@{section=".data",section-sent="2560",section-size="3156",
30754 total-sent="9284",total-size="9880"@}
30755 +download,@{section=".data",section-sent="3072",section-size="3156",
30756 total-sent="9796",total-size="9880"@}
30757 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30764 @subheading The @code{-target-exec-status} Command
30765 @findex -target-exec-status
30767 @subsubheading Synopsis
30770 -target-exec-status
30773 Provide information on the state of the target (whether it is running or
30774 not, for instance).
30776 @subsubheading @value{GDBN} Command
30778 There's no equivalent @value{GDBN} command.
30780 @subsubheading Example
30784 @subheading The @code{-target-list-available-targets} Command
30785 @findex -target-list-available-targets
30787 @subsubheading Synopsis
30790 -target-list-available-targets
30793 List the possible targets to connect to.
30795 @subsubheading @value{GDBN} Command
30797 The corresponding @value{GDBN} command is @samp{help target}.
30799 @subsubheading Example
30803 @subheading The @code{-target-list-current-targets} Command
30804 @findex -target-list-current-targets
30806 @subsubheading Synopsis
30809 -target-list-current-targets
30812 Describe the current target.
30814 @subsubheading @value{GDBN} Command
30816 The corresponding information is printed by @samp{info file} (among
30819 @subsubheading Example
30823 @subheading The @code{-target-list-parameters} Command
30824 @findex -target-list-parameters
30826 @subsubheading Synopsis
30829 -target-list-parameters
30835 @subsubheading @value{GDBN} Command
30839 @subsubheading Example
30843 @subheading The @code{-target-select} Command
30844 @findex -target-select
30846 @subsubheading Synopsis
30849 -target-select @var{type} @var{parameters @dots{}}
30852 Connect @value{GDBN} to the remote target. This command takes two args:
30856 The type of target, for instance @samp{remote}, etc.
30857 @item @var{parameters}
30858 Device names, host names and the like. @xref{Target Commands, ,
30859 Commands for Managing Targets}, for more details.
30862 The output is a connection notification, followed by the address at
30863 which the target program is, in the following form:
30866 ^connected,addr="@var{address}",func="@var{function name}",
30867 args=[@var{arg list}]
30870 @subsubheading @value{GDBN} Command
30872 The corresponding @value{GDBN} command is @samp{target}.
30874 @subsubheading Example
30878 -target-select remote /dev/ttya
30879 ^connected,addr="0xfe00a300",func="??",args=[]
30883 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30884 @node GDB/MI File Transfer Commands
30885 @section @sc{gdb/mi} File Transfer Commands
30888 @subheading The @code{-target-file-put} Command
30889 @findex -target-file-put
30891 @subsubheading Synopsis
30894 -target-file-put @var{hostfile} @var{targetfile}
30897 Copy file @var{hostfile} from the host system (the machine running
30898 @value{GDBN}) to @var{targetfile} on the target system.
30900 @subsubheading @value{GDBN} Command
30902 The corresponding @value{GDBN} command is @samp{remote put}.
30904 @subsubheading Example
30908 -target-file-put localfile remotefile
30914 @subheading The @code{-target-file-get} Command
30915 @findex -target-file-get
30917 @subsubheading Synopsis
30920 -target-file-get @var{targetfile} @var{hostfile}
30923 Copy file @var{targetfile} from the target system to @var{hostfile}
30924 on the host system.
30926 @subsubheading @value{GDBN} Command
30928 The corresponding @value{GDBN} command is @samp{remote get}.
30930 @subsubheading Example
30934 -target-file-get remotefile localfile
30940 @subheading The @code{-target-file-delete} Command
30941 @findex -target-file-delete
30943 @subsubheading Synopsis
30946 -target-file-delete @var{targetfile}
30949 Delete @var{targetfile} from the target system.
30951 @subsubheading @value{GDBN} Command
30953 The corresponding @value{GDBN} command is @samp{remote delete}.
30955 @subsubheading Example
30959 -target-file-delete remotefile
30965 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30966 @node GDB/MI Miscellaneous Commands
30967 @section Miscellaneous @sc{gdb/mi} Commands
30969 @c @subheading -gdb-complete
30971 @subheading The @code{-gdb-exit} Command
30974 @subsubheading Synopsis
30980 Exit @value{GDBN} immediately.
30982 @subsubheading @value{GDBN} Command
30984 Approximately corresponds to @samp{quit}.
30986 @subsubheading Example
30996 @subheading The @code{-exec-abort} Command
30997 @findex -exec-abort
30999 @subsubheading Synopsis
31005 Kill the inferior running program.
31007 @subsubheading @value{GDBN} Command
31009 The corresponding @value{GDBN} command is @samp{kill}.
31011 @subsubheading Example
31016 @subheading The @code{-gdb-set} Command
31019 @subsubheading Synopsis
31025 Set an internal @value{GDBN} variable.
31026 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31028 @subsubheading @value{GDBN} Command
31030 The corresponding @value{GDBN} command is @samp{set}.
31032 @subsubheading Example
31042 @subheading The @code{-gdb-show} Command
31045 @subsubheading Synopsis
31051 Show the current value of a @value{GDBN} variable.
31053 @subsubheading @value{GDBN} Command
31055 The corresponding @value{GDBN} command is @samp{show}.
31057 @subsubheading Example
31066 @c @subheading -gdb-source
31069 @subheading The @code{-gdb-version} Command
31070 @findex -gdb-version
31072 @subsubheading Synopsis
31078 Show version information for @value{GDBN}. Used mostly in testing.
31080 @subsubheading @value{GDBN} Command
31082 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31083 default shows this information when you start an interactive session.
31085 @subsubheading Example
31087 @c This example modifies the actual output from GDB to avoid overfull
31093 ~Copyright 2000 Free Software Foundation, Inc.
31094 ~GDB is free software, covered by the GNU General Public License, and
31095 ~you are welcome to change it and/or distribute copies of it under
31096 ~ certain conditions.
31097 ~Type "show copying" to see the conditions.
31098 ~There is absolutely no warranty for GDB. Type "show warranty" for
31100 ~This GDB was configured as
31101 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31106 @subheading The @code{-list-features} Command
31107 @findex -list-features
31109 Returns a list of particular features of the MI protocol that
31110 this version of gdb implements. A feature can be a command,
31111 or a new field in an output of some command, or even an
31112 important bugfix. While a frontend can sometimes detect presence
31113 of a feature at runtime, it is easier to perform detection at debugger
31116 The command returns a list of strings, with each string naming an
31117 available feature. Each returned string is just a name, it does not
31118 have any internal structure. The list of possible feature names
31124 (gdb) -list-features
31125 ^done,result=["feature1","feature2"]
31128 The current list of features is:
31131 @item frozen-varobjs
31132 Indicates support for the @code{-var-set-frozen} command, as well
31133 as possible presense of the @code{frozen} field in the output
31134 of @code{-varobj-create}.
31135 @item pending-breakpoints
31136 Indicates support for the @option{-f} option to the @code{-break-insert}
31139 Indicates Python scripting support, Python-based
31140 pretty-printing commands, and possible presence of the
31141 @samp{display_hint} field in the output of @code{-var-list-children}
31143 Indicates support for the @code{-thread-info} command.
31144 @item data-read-memory-bytes
31145 Indicates support for the @code{-data-read-memory-bytes} and the
31146 @code{-data-write-memory-bytes} commands.
31147 @item breakpoint-notifications
31148 Indicates that changes to breakpoints and breakpoints created via the
31149 CLI will be announced via async records.
31150 @item ada-task-info
31151 Indicates support for the @code{-ada-task-info} command.
31154 @subheading The @code{-list-target-features} Command
31155 @findex -list-target-features
31157 Returns a list of particular features that are supported by the
31158 target. Those features affect the permitted MI commands, but
31159 unlike the features reported by the @code{-list-features} command, the
31160 features depend on which target GDB is using at the moment. Whenever
31161 a target can change, due to commands such as @code{-target-select},
31162 @code{-target-attach} or @code{-exec-run}, the list of target features
31163 may change, and the frontend should obtain it again.
31167 (gdb) -list-features
31168 ^done,result=["async"]
31171 The current list of features is:
31175 Indicates that the target is capable of asynchronous command
31176 execution, which means that @value{GDBN} will accept further commands
31177 while the target is running.
31180 Indicates that the target is capable of reverse execution.
31181 @xref{Reverse Execution}, for more information.
31185 @subheading The @code{-list-thread-groups} Command
31186 @findex -list-thread-groups
31188 @subheading Synopsis
31191 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31194 Lists thread groups (@pxref{Thread groups}). When a single thread
31195 group is passed as the argument, lists the children of that group.
31196 When several thread group are passed, lists information about those
31197 thread groups. Without any parameters, lists information about all
31198 top-level thread groups.
31200 Normally, thread groups that are being debugged are reported.
31201 With the @samp{--available} option, @value{GDBN} reports thread groups
31202 available on the target.
31204 The output of this command may have either a @samp{threads} result or
31205 a @samp{groups} result. The @samp{thread} result has a list of tuples
31206 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31207 Information}). The @samp{groups} result has a list of tuples as value,
31208 each tuple describing a thread group. If top-level groups are
31209 requested (that is, no parameter is passed), or when several groups
31210 are passed, the output always has a @samp{groups} result. The format
31211 of the @samp{group} result is described below.
31213 To reduce the number of roundtrips it's possible to list thread groups
31214 together with their children, by passing the @samp{--recurse} option
31215 and the recursion depth. Presently, only recursion depth of 1 is
31216 permitted. If this option is present, then every reported thread group
31217 will also include its children, either as @samp{group} or
31218 @samp{threads} field.
31220 In general, any combination of option and parameters is permitted, with
31221 the following caveats:
31225 When a single thread group is passed, the output will typically
31226 be the @samp{threads} result. Because threads may not contain
31227 anything, the @samp{recurse} option will be ignored.
31230 When the @samp{--available} option is passed, limited information may
31231 be available. In particular, the list of threads of a process might
31232 be inaccessible. Further, specifying specific thread groups might
31233 not give any performance advantage over listing all thread groups.
31234 The frontend should assume that @samp{-list-thread-groups --available}
31235 is always an expensive operation and cache the results.
31239 The @samp{groups} result is a list of tuples, where each tuple may
31240 have the following fields:
31244 Identifier of the thread group. This field is always present.
31245 The identifier is an opaque string; frontends should not try to
31246 convert it to an integer, even though it might look like one.
31249 The type of the thread group. At present, only @samp{process} is a
31253 The target-specific process identifier. This field is only present
31254 for thread groups of type @samp{process} and only if the process exists.
31257 The number of children this thread group has. This field may be
31258 absent for an available thread group.
31261 This field has a list of tuples as value, each tuple describing a
31262 thread. It may be present if the @samp{--recurse} option is
31263 specified, and it's actually possible to obtain the threads.
31266 This field is a list of integers, each identifying a core that one
31267 thread of the group is running on. This field may be absent if
31268 such information is not available.
31271 The name of the executable file that corresponds to this thread group.
31272 The field is only present for thread groups of type @samp{process},
31273 and only if there is a corresponding executable file.
31277 @subheading Example
31281 -list-thread-groups
31282 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31283 -list-thread-groups 17
31284 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31285 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31286 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31287 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31288 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31289 -list-thread-groups --available
31290 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31291 -list-thread-groups --available --recurse 1
31292 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31293 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31294 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31295 -list-thread-groups --available --recurse 1 17 18
31296 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31297 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31298 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31302 @subheading The @code{-add-inferior} Command
31303 @findex -add-inferior
31305 @subheading Synopsis
31311 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31312 inferior is not associated with any executable. Such association may
31313 be established with the @samp{-file-exec-and-symbols} command
31314 (@pxref{GDB/MI File Commands}). The command response has a single
31315 field, @samp{thread-group}, whose value is the identifier of the
31316 thread group corresponding to the new inferior.
31318 @subheading Example
31323 ^done,thread-group="i3"
31326 @subheading The @code{-interpreter-exec} Command
31327 @findex -interpreter-exec
31329 @subheading Synopsis
31332 -interpreter-exec @var{interpreter} @var{command}
31334 @anchor{-interpreter-exec}
31336 Execute the specified @var{command} in the given @var{interpreter}.
31338 @subheading @value{GDBN} Command
31340 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31342 @subheading Example
31346 -interpreter-exec console "break main"
31347 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31348 &"During symbol reading, bad structure-type format.\n"
31349 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31354 @subheading The @code{-inferior-tty-set} Command
31355 @findex -inferior-tty-set
31357 @subheading Synopsis
31360 -inferior-tty-set /dev/pts/1
31363 Set terminal for future runs of the program being debugged.
31365 @subheading @value{GDBN} Command
31367 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31369 @subheading Example
31373 -inferior-tty-set /dev/pts/1
31378 @subheading The @code{-inferior-tty-show} Command
31379 @findex -inferior-tty-show
31381 @subheading Synopsis
31387 Show terminal for future runs of program being debugged.
31389 @subheading @value{GDBN} Command
31391 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31393 @subheading Example
31397 -inferior-tty-set /dev/pts/1
31401 ^done,inferior_tty_terminal="/dev/pts/1"
31405 @subheading The @code{-enable-timings} Command
31406 @findex -enable-timings
31408 @subheading Synopsis
31411 -enable-timings [yes | no]
31414 Toggle the printing of the wallclock, user and system times for an MI
31415 command as a field in its output. This command is to help frontend
31416 developers optimize the performance of their code. No argument is
31417 equivalent to @samp{yes}.
31419 @subheading @value{GDBN} Command
31423 @subheading Example
31431 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31432 addr="0x080484ed",func="main",file="myprog.c",
31433 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31434 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31442 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31443 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31444 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31445 fullname="/home/nickrob/myprog.c",line="73"@}
31450 @chapter @value{GDBN} Annotations
31452 This chapter describes annotations in @value{GDBN}. Annotations were
31453 designed to interface @value{GDBN} to graphical user interfaces or other
31454 similar programs which want to interact with @value{GDBN} at a
31455 relatively high level.
31457 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31461 This is Edition @value{EDITION}, @value{DATE}.
31465 * Annotations Overview:: What annotations are; the general syntax.
31466 * Server Prefix:: Issuing a command without affecting user state.
31467 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31468 * Errors:: Annotations for error messages.
31469 * Invalidation:: Some annotations describe things now invalid.
31470 * Annotations for Running::
31471 Whether the program is running, how it stopped, etc.
31472 * Source Annotations:: Annotations describing source code.
31475 @node Annotations Overview
31476 @section What is an Annotation?
31477 @cindex annotations
31479 Annotations start with a newline character, two @samp{control-z}
31480 characters, and the name of the annotation. If there is no additional
31481 information associated with this annotation, the name of the annotation
31482 is followed immediately by a newline. If there is additional
31483 information, the name of the annotation is followed by a space, the
31484 additional information, and a newline. The additional information
31485 cannot contain newline characters.
31487 Any output not beginning with a newline and two @samp{control-z}
31488 characters denotes literal output from @value{GDBN}. Currently there is
31489 no need for @value{GDBN} to output a newline followed by two
31490 @samp{control-z} characters, but if there was such a need, the
31491 annotations could be extended with an @samp{escape} annotation which
31492 means those three characters as output.
31494 The annotation @var{level}, which is specified using the
31495 @option{--annotate} command line option (@pxref{Mode Options}), controls
31496 how much information @value{GDBN} prints together with its prompt,
31497 values of expressions, source lines, and other types of output. Level 0
31498 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31499 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31500 for programs that control @value{GDBN}, and level 2 annotations have
31501 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31502 Interface, annotate, GDB's Obsolete Annotations}).
31505 @kindex set annotate
31506 @item set annotate @var{level}
31507 The @value{GDBN} command @code{set annotate} sets the level of
31508 annotations to the specified @var{level}.
31510 @item show annotate
31511 @kindex show annotate
31512 Show the current annotation level.
31515 This chapter describes level 3 annotations.
31517 A simple example of starting up @value{GDBN} with annotations is:
31520 $ @kbd{gdb --annotate=3}
31522 Copyright 2003 Free Software Foundation, Inc.
31523 GDB is free software, covered by the GNU General Public License,
31524 and you are welcome to change it and/or distribute copies of it
31525 under certain conditions.
31526 Type "show copying" to see the conditions.
31527 There is absolutely no warranty for GDB. Type "show warranty"
31529 This GDB was configured as "i386-pc-linux-gnu"
31540 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31541 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31542 denotes a @samp{control-z} character) are annotations; the rest is
31543 output from @value{GDBN}.
31545 @node Server Prefix
31546 @section The Server Prefix
31547 @cindex server prefix
31549 If you prefix a command with @samp{server } then it will not affect
31550 the command history, nor will it affect @value{GDBN}'s notion of which
31551 command to repeat if @key{RET} is pressed on a line by itself. This
31552 means that commands can be run behind a user's back by a front-end in
31553 a transparent manner.
31555 The @code{server } prefix does not affect the recording of values into
31556 the value history; to print a value without recording it into the
31557 value history, use the @code{output} command instead of the
31558 @code{print} command.
31560 Using this prefix also disables confirmation requests
31561 (@pxref{confirmation requests}).
31564 @section Annotation for @value{GDBN} Input
31566 @cindex annotations for prompts
31567 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31568 to know when to send output, when the output from a given command is
31571 Different kinds of input each have a different @dfn{input type}. Each
31572 input type has three annotations: a @code{pre-} annotation, which
31573 denotes the beginning of any prompt which is being output, a plain
31574 annotation, which denotes the end of the prompt, and then a @code{post-}
31575 annotation which denotes the end of any echo which may (or may not) be
31576 associated with the input. For example, the @code{prompt} input type
31577 features the following annotations:
31585 The input types are
31588 @findex pre-prompt annotation
31589 @findex prompt annotation
31590 @findex post-prompt annotation
31592 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31594 @findex pre-commands annotation
31595 @findex commands annotation
31596 @findex post-commands annotation
31598 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31599 command. The annotations are repeated for each command which is input.
31601 @findex pre-overload-choice annotation
31602 @findex overload-choice annotation
31603 @findex post-overload-choice annotation
31604 @item overload-choice
31605 When @value{GDBN} wants the user to select between various overloaded functions.
31607 @findex pre-query annotation
31608 @findex query annotation
31609 @findex post-query annotation
31611 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31613 @findex pre-prompt-for-continue annotation
31614 @findex prompt-for-continue annotation
31615 @findex post-prompt-for-continue annotation
31616 @item prompt-for-continue
31617 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31618 expect this to work well; instead use @code{set height 0} to disable
31619 prompting. This is because the counting of lines is buggy in the
31620 presence of annotations.
31625 @cindex annotations for errors, warnings and interrupts
31627 @findex quit annotation
31632 This annotation occurs right before @value{GDBN} responds to an interrupt.
31634 @findex error annotation
31639 This annotation occurs right before @value{GDBN} responds to an error.
31641 Quit and error annotations indicate that any annotations which @value{GDBN} was
31642 in the middle of may end abruptly. For example, if a
31643 @code{value-history-begin} annotation is followed by a @code{error}, one
31644 cannot expect to receive the matching @code{value-history-end}. One
31645 cannot expect not to receive it either, however; an error annotation
31646 does not necessarily mean that @value{GDBN} is immediately returning all the way
31649 @findex error-begin annotation
31650 A quit or error annotation may be preceded by
31656 Any output between that and the quit or error annotation is the error
31659 Warning messages are not yet annotated.
31660 @c If we want to change that, need to fix warning(), type_error(),
31661 @c range_error(), and possibly other places.
31664 @section Invalidation Notices
31666 @cindex annotations for invalidation messages
31667 The following annotations say that certain pieces of state may have
31671 @findex frames-invalid annotation
31672 @item ^Z^Zframes-invalid
31674 The frames (for example, output from the @code{backtrace} command) may
31677 @findex breakpoints-invalid annotation
31678 @item ^Z^Zbreakpoints-invalid
31680 The breakpoints may have changed. For example, the user just added or
31681 deleted a breakpoint.
31684 @node Annotations for Running
31685 @section Running the Program
31686 @cindex annotations for running programs
31688 @findex starting annotation
31689 @findex stopping annotation
31690 When the program starts executing due to a @value{GDBN} command such as
31691 @code{step} or @code{continue},
31697 is output. When the program stops,
31703 is output. Before the @code{stopped} annotation, a variety of
31704 annotations describe how the program stopped.
31707 @findex exited annotation
31708 @item ^Z^Zexited @var{exit-status}
31709 The program exited, and @var{exit-status} is the exit status (zero for
31710 successful exit, otherwise nonzero).
31712 @findex signalled annotation
31713 @findex signal-name annotation
31714 @findex signal-name-end annotation
31715 @findex signal-string annotation
31716 @findex signal-string-end annotation
31717 @item ^Z^Zsignalled
31718 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31719 annotation continues:
31725 ^Z^Zsignal-name-end
31729 ^Z^Zsignal-string-end
31734 where @var{name} is the name of the signal, such as @code{SIGILL} or
31735 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31736 as @code{Illegal Instruction} or @code{Segmentation fault}.
31737 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31738 user's benefit and have no particular format.
31740 @findex signal annotation
31742 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31743 just saying that the program received the signal, not that it was
31744 terminated with it.
31746 @findex breakpoint annotation
31747 @item ^Z^Zbreakpoint @var{number}
31748 The program hit breakpoint number @var{number}.
31750 @findex watchpoint annotation
31751 @item ^Z^Zwatchpoint @var{number}
31752 The program hit watchpoint number @var{number}.
31755 @node Source Annotations
31756 @section Displaying Source
31757 @cindex annotations for source display
31759 @findex source annotation
31760 The following annotation is used instead of displaying source code:
31763 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31766 where @var{filename} is an absolute file name indicating which source
31767 file, @var{line} is the line number within that file (where 1 is the
31768 first line in the file), @var{character} is the character position
31769 within the file (where 0 is the first character in the file) (for most
31770 debug formats this will necessarily point to the beginning of a line),
31771 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31772 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31773 @var{addr} is the address in the target program associated with the
31774 source which is being displayed. @var{addr} is in the form @samp{0x}
31775 followed by one or more lowercase hex digits (note that this does not
31776 depend on the language).
31778 @node JIT Interface
31779 @chapter JIT Compilation Interface
31780 @cindex just-in-time compilation
31781 @cindex JIT compilation interface
31783 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31784 interface. A JIT compiler is a program or library that generates native
31785 executable code at runtime and executes it, usually in order to achieve good
31786 performance while maintaining platform independence.
31788 Programs that use JIT compilation are normally difficult to debug because
31789 portions of their code are generated at runtime, instead of being loaded from
31790 object files, which is where @value{GDBN} normally finds the program's symbols
31791 and debug information. In order to debug programs that use JIT compilation,
31792 @value{GDBN} has an interface that allows the program to register in-memory
31793 symbol files with @value{GDBN} at runtime.
31795 If you are using @value{GDBN} to debug a program that uses this interface, then
31796 it should work transparently so long as you have not stripped the binary. If
31797 you are developing a JIT compiler, then the interface is documented in the rest
31798 of this chapter. At this time, the only known client of this interface is the
31801 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31802 JIT compiler communicates with @value{GDBN} by writing data into a global
31803 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31804 attaches, it reads a linked list of symbol files from the global variable to
31805 find existing code, and puts a breakpoint in the function so that it can find
31806 out about additional code.
31809 * Declarations:: Relevant C struct declarations
31810 * Registering Code:: Steps to register code
31811 * Unregistering Code:: Steps to unregister code
31812 * Custom Debug Info:: Emit debug information in a custom format
31816 @section JIT Declarations
31818 These are the relevant struct declarations that a C program should include to
31819 implement the interface:
31829 struct jit_code_entry
31831 struct jit_code_entry *next_entry;
31832 struct jit_code_entry *prev_entry;
31833 const char *symfile_addr;
31834 uint64_t symfile_size;
31837 struct jit_descriptor
31840 /* This type should be jit_actions_t, but we use uint32_t
31841 to be explicit about the bitwidth. */
31842 uint32_t action_flag;
31843 struct jit_code_entry *relevant_entry;
31844 struct jit_code_entry *first_entry;
31847 /* GDB puts a breakpoint in this function. */
31848 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31850 /* Make sure to specify the version statically, because the
31851 debugger may check the version before we can set it. */
31852 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31855 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31856 modifications to this global data properly, which can easily be done by putting
31857 a global mutex around modifications to these structures.
31859 @node Registering Code
31860 @section Registering Code
31862 To register code with @value{GDBN}, the JIT should follow this protocol:
31866 Generate an object file in memory with symbols and other desired debug
31867 information. The file must include the virtual addresses of the sections.
31870 Create a code entry for the file, which gives the start and size of the symbol
31874 Add it to the linked list in the JIT descriptor.
31877 Point the relevant_entry field of the descriptor at the entry.
31880 Set @code{action_flag} to @code{JIT_REGISTER} and call
31881 @code{__jit_debug_register_code}.
31884 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31885 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31886 new code. However, the linked list must still be maintained in order to allow
31887 @value{GDBN} to attach to a running process and still find the symbol files.
31889 @node Unregistering Code
31890 @section Unregistering Code
31892 If code is freed, then the JIT should use the following protocol:
31896 Remove the code entry corresponding to the code from the linked list.
31899 Point the @code{relevant_entry} field of the descriptor at the code entry.
31902 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31903 @code{__jit_debug_register_code}.
31906 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31907 and the JIT will leak the memory used for the associated symbol files.
31909 @node Custom Debug Info
31910 @section Custom Debug Info
31911 @cindex custom JIT debug info
31912 @cindex JIT debug info reader
31914 Generating debug information in platform-native file formats (like ELF
31915 or COFF) may be an overkill for JIT compilers; especially if all the
31916 debug info is used for is displaying a meaningful backtrace. The
31917 issue can be resolved by having the JIT writers decide on a debug info
31918 format and also provide a reader that parses the debug info generated
31919 by the JIT compiler. This section gives a brief overview on writing
31920 such a parser. More specific details can be found in the source file
31921 @file{gdb/jit-reader.in}, which is also installed as a header at
31922 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
31924 The reader is implemented as a shared object (so this functionality is
31925 not available on platforms which don't allow loading shared objects at
31926 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
31927 @code{jit-reader-unload} are provided, to be used to load and unload
31928 the readers from a preconfigured directory. Once loaded, the shared
31929 object is used the parse the debug information emitted by the JIT
31933 * Using JIT Debug Info Readers:: How to use supplied readers correctly
31934 * Writing JIT Debug Info Readers:: Creating a debug-info reader
31937 @node Using JIT Debug Info Readers
31938 @subsection Using JIT Debug Info Readers
31939 @kindex jit-reader-load
31940 @kindex jit-reader-unload
31942 Readers can be loaded and unloaded using the @code{jit-reader-load}
31943 and @code{jit-reader-unload} commands.
31946 @item jit-reader-load @var{reader-name}
31947 Load the JIT reader named @var{reader-name}. On a UNIX system, this
31948 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
31949 @var{libdir} is the system library directory, usually
31950 @file{/usr/local/lib}. Only one reader can be active at a time;
31951 trying to load a second reader when one is already loaded will result
31952 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
31953 first unloading the current one using @code{jit-reader-load} and then
31954 invoking @code{jit-reader-load}.
31956 @item jit-reader-unload
31957 Unload the currently loaded JIT reader.
31961 @node Writing JIT Debug Info Readers
31962 @subsection Writing JIT Debug Info Readers
31963 @cindex writing JIT debug info readers
31965 As mentioned, a reader is essentially a shared object conforming to a
31966 certain ABI. This ABI is described in @file{jit-reader.h}.
31968 @file{jit-reader.h} defines the structures, macros and functions
31969 required to write a reader. It is installed (along with
31970 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
31971 the system include directory.
31973 Readers need to be released under a GPL compatible license. A reader
31974 can be declared as released under such a license by placing the macro
31975 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
31977 The entry point for readers is the symbol @code{gdb_init_reader},
31978 which is expected to be a function with the prototype
31980 @findex gdb_init_reader
31982 extern struct gdb_reader_funcs *gdb_init_reader (void);
31985 @cindex @code{struct gdb_reader_funcs}
31987 @code{struct gdb_reader_funcs} contains a set of pointers to callback
31988 functions. These functions are executed to read the debug info
31989 generated by the JIT compiler (@code{read}), to unwind stack frames
31990 (@code{unwind}) and to create canonical frame IDs
31991 (@code{get_Frame_id}). It also has a callback that is called when the
31992 reader is being unloaded (@code{destroy}). The struct looks like this
31995 struct gdb_reader_funcs
31997 /* Must be set to GDB_READER_INTERFACE_VERSION. */
31998 int reader_version;
32000 /* For use by the reader. */
32003 gdb_read_debug_info *read;
32004 gdb_unwind_frame *unwind;
32005 gdb_get_frame_id *get_frame_id;
32006 gdb_destroy_reader *destroy;
32010 @cindex @code{struct gdb_symbol_callbacks}
32011 @cindex @code{struct gdb_unwind_callbacks}
32013 The callbacks are provided with another set of callbacks by
32014 @value{GDBN} to do their job. For @code{read}, these callbacks are
32015 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32016 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32017 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32018 files and new symbol tables inside those object files. @code{struct
32019 gdb_unwind_callbacks} has callbacks to read registers off the current
32020 frame and to write out the values of the registers in the previous
32021 frame. Both have a callback (@code{target_read}) to read bytes off the
32022 target's address space.
32025 @chapter Reporting Bugs in @value{GDBN}
32026 @cindex bugs in @value{GDBN}
32027 @cindex reporting bugs in @value{GDBN}
32029 Your bug reports play an essential role in making @value{GDBN} reliable.
32031 Reporting a bug may help you by bringing a solution to your problem, or it
32032 may not. But in any case the principal function of a bug report is to help
32033 the entire community by making the next version of @value{GDBN} work better. Bug
32034 reports are your contribution to the maintenance of @value{GDBN}.
32036 In order for a bug report to serve its purpose, you must include the
32037 information that enables us to fix the bug.
32040 * Bug Criteria:: Have you found a bug?
32041 * Bug Reporting:: How to report bugs
32045 @section Have You Found a Bug?
32046 @cindex bug criteria
32048 If you are not sure whether you have found a bug, here are some guidelines:
32051 @cindex fatal signal
32052 @cindex debugger crash
32053 @cindex crash of debugger
32055 If the debugger gets a fatal signal, for any input whatever, that is a
32056 @value{GDBN} bug. Reliable debuggers never crash.
32058 @cindex error on valid input
32060 If @value{GDBN} produces an error message for valid input, that is a
32061 bug. (Note that if you're cross debugging, the problem may also be
32062 somewhere in the connection to the target.)
32064 @cindex invalid input
32066 If @value{GDBN} does not produce an error message for invalid input,
32067 that is a bug. However, you should note that your idea of
32068 ``invalid input'' might be our idea of ``an extension'' or ``support
32069 for traditional practice''.
32072 If you are an experienced user of debugging tools, your suggestions
32073 for improvement of @value{GDBN} are welcome in any case.
32076 @node Bug Reporting
32077 @section How to Report Bugs
32078 @cindex bug reports
32079 @cindex @value{GDBN} bugs, reporting
32081 A number of companies and individuals offer support for @sc{gnu} products.
32082 If you obtained @value{GDBN} from a support organization, we recommend you
32083 contact that organization first.
32085 You can find contact information for many support companies and
32086 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32088 @c should add a web page ref...
32091 @ifset BUGURL_DEFAULT
32092 In any event, we also recommend that you submit bug reports for
32093 @value{GDBN}. The preferred method is to submit them directly using
32094 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32095 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32098 @strong{Do not send bug reports to @samp{info-gdb}, or to
32099 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32100 not want to receive bug reports. Those that do have arranged to receive
32103 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32104 serves as a repeater. The mailing list and the newsgroup carry exactly
32105 the same messages. Often people think of posting bug reports to the
32106 newsgroup instead of mailing them. This appears to work, but it has one
32107 problem which can be crucial: a newsgroup posting often lacks a mail
32108 path back to the sender. Thus, if we need to ask for more information,
32109 we may be unable to reach you. For this reason, it is better to send
32110 bug reports to the mailing list.
32112 @ifclear BUGURL_DEFAULT
32113 In any event, we also recommend that you submit bug reports for
32114 @value{GDBN} to @value{BUGURL}.
32118 The fundamental principle of reporting bugs usefully is this:
32119 @strong{report all the facts}. If you are not sure whether to state a
32120 fact or leave it out, state it!
32122 Often people omit facts because they think they know what causes the
32123 problem and assume that some details do not matter. Thus, you might
32124 assume that the name of the variable you use in an example does not matter.
32125 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32126 stray memory reference which happens to fetch from the location where that
32127 name is stored in memory; perhaps, if the name were different, the contents
32128 of that location would fool the debugger into doing the right thing despite
32129 the bug. Play it safe and give a specific, complete example. That is the
32130 easiest thing for you to do, and the most helpful.
32132 Keep in mind that the purpose of a bug report is to enable us to fix the
32133 bug. It may be that the bug has been reported previously, but neither
32134 you nor we can know that unless your bug report is complete and
32137 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32138 bell?'' Those bug reports are useless, and we urge everyone to
32139 @emph{refuse to respond to them} except to chide the sender to report
32142 To enable us to fix the bug, you should include all these things:
32146 The version of @value{GDBN}. @value{GDBN} announces it if you start
32147 with no arguments; you can also print it at any time using @code{show
32150 Without this, we will not know whether there is any point in looking for
32151 the bug in the current version of @value{GDBN}.
32154 The type of machine you are using, and the operating system name and
32158 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32159 ``@value{GCC}--2.8.1''.
32162 What compiler (and its version) was used to compile the program you are
32163 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32164 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32165 to get this information; for other compilers, see the documentation for
32169 The command arguments you gave the compiler to compile your example and
32170 observe the bug. For example, did you use @samp{-O}? To guarantee
32171 you will not omit something important, list them all. A copy of the
32172 Makefile (or the output from make) is sufficient.
32174 If we were to try to guess the arguments, we would probably guess wrong
32175 and then we might not encounter the bug.
32178 A complete input script, and all necessary source files, that will
32182 A description of what behavior you observe that you believe is
32183 incorrect. For example, ``It gets a fatal signal.''
32185 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32186 will certainly notice it. But if the bug is incorrect output, we might
32187 not notice unless it is glaringly wrong. You might as well not give us
32188 a chance to make a mistake.
32190 Even if the problem you experience is a fatal signal, you should still
32191 say so explicitly. Suppose something strange is going on, such as, your
32192 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32193 the C library on your system. (This has happened!) Your copy might
32194 crash and ours would not. If you told us to expect a crash, then when
32195 ours fails to crash, we would know that the bug was not happening for
32196 us. If you had not told us to expect a crash, then we would not be able
32197 to draw any conclusion from our observations.
32200 @cindex recording a session script
32201 To collect all this information, you can use a session recording program
32202 such as @command{script}, which is available on many Unix systems.
32203 Just run your @value{GDBN} session inside @command{script} and then
32204 include the @file{typescript} file with your bug report.
32206 Another way to record a @value{GDBN} session is to run @value{GDBN}
32207 inside Emacs and then save the entire buffer to a file.
32210 If you wish to suggest changes to the @value{GDBN} source, send us context
32211 diffs. If you even discuss something in the @value{GDBN} source, refer to
32212 it by context, not by line number.
32214 The line numbers in our development sources will not match those in your
32215 sources. Your line numbers would convey no useful information to us.
32219 Here are some things that are not necessary:
32223 A description of the envelope of the bug.
32225 Often people who encounter a bug spend a lot of time investigating
32226 which changes to the input file will make the bug go away and which
32227 changes will not affect it.
32229 This is often time consuming and not very useful, because the way we
32230 will find the bug is by running a single example under the debugger
32231 with breakpoints, not by pure deduction from a series of examples.
32232 We recommend that you save your time for something else.
32234 Of course, if you can find a simpler example to report @emph{instead}
32235 of the original one, that is a convenience for us. Errors in the
32236 output will be easier to spot, running under the debugger will take
32237 less time, and so on.
32239 However, simplification is not vital; if you do not want to do this,
32240 report the bug anyway and send us the entire test case you used.
32243 A patch for the bug.
32245 A patch for the bug does help us if it is a good one. But do not omit
32246 the necessary information, such as the test case, on the assumption that
32247 a patch is all we need. We might see problems with your patch and decide
32248 to fix the problem another way, or we might not understand it at all.
32250 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32251 construct an example that will make the program follow a certain path
32252 through the code. If you do not send us the example, we will not be able
32253 to construct one, so we will not be able to verify that the bug is fixed.
32255 And if we cannot understand what bug you are trying to fix, or why your
32256 patch should be an improvement, we will not install it. A test case will
32257 help us to understand.
32260 A guess about what the bug is or what it depends on.
32262 Such guesses are usually wrong. Even we cannot guess right about such
32263 things without first using the debugger to find the facts.
32266 @c The readline documentation is distributed with the readline code
32267 @c and consists of the two following files:
32270 @c Use -I with makeinfo to point to the appropriate directory,
32271 @c environment var TEXINPUTS with TeX.
32272 @ifclear SYSTEM_READLINE
32273 @include rluser.texi
32274 @include hsuser.texi
32278 @appendix In Memoriam
32280 The @value{GDBN} project mourns the loss of the following long-time
32285 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32286 to Free Software in general. Outside of @value{GDBN}, he was known in
32287 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32289 @item Michael Snyder
32290 Michael was one of the Global Maintainers of the @value{GDBN} project,
32291 with contributions recorded as early as 1996, until 2011. In addition
32292 to his day to day participation, he was a large driving force behind
32293 adding Reverse Debugging to @value{GDBN}.
32296 Beyond their technical contributions to the project, they were also
32297 enjoyable members of the Free Software Community. We will miss them.
32299 @node Formatting Documentation
32300 @appendix Formatting Documentation
32302 @cindex @value{GDBN} reference card
32303 @cindex reference card
32304 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32305 for printing with PostScript or Ghostscript, in the @file{gdb}
32306 subdirectory of the main source directory@footnote{In
32307 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32308 release.}. If you can use PostScript or Ghostscript with your printer,
32309 you can print the reference card immediately with @file{refcard.ps}.
32311 The release also includes the source for the reference card. You
32312 can format it, using @TeX{}, by typing:
32318 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32319 mode on US ``letter'' size paper;
32320 that is, on a sheet 11 inches wide by 8.5 inches
32321 high. You will need to specify this form of printing as an option to
32322 your @sc{dvi} output program.
32324 @cindex documentation
32326 All the documentation for @value{GDBN} comes as part of the machine-readable
32327 distribution. The documentation is written in Texinfo format, which is
32328 a documentation system that uses a single source file to produce both
32329 on-line information and a printed manual. You can use one of the Info
32330 formatting commands to create the on-line version of the documentation
32331 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32333 @value{GDBN} includes an already formatted copy of the on-line Info
32334 version of this manual in the @file{gdb} subdirectory. The main Info
32335 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32336 subordinate files matching @samp{gdb.info*} in the same directory. If
32337 necessary, you can print out these files, or read them with any editor;
32338 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32339 Emacs or the standalone @code{info} program, available as part of the
32340 @sc{gnu} Texinfo distribution.
32342 If you want to format these Info files yourself, you need one of the
32343 Info formatting programs, such as @code{texinfo-format-buffer} or
32346 If you have @code{makeinfo} installed, and are in the top level
32347 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32348 version @value{GDBVN}), you can make the Info file by typing:
32355 If you want to typeset and print copies of this manual, you need @TeX{},
32356 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32357 Texinfo definitions file.
32359 @TeX{} is a typesetting program; it does not print files directly, but
32360 produces output files called @sc{dvi} files. To print a typeset
32361 document, you need a program to print @sc{dvi} files. If your system
32362 has @TeX{} installed, chances are it has such a program. The precise
32363 command to use depends on your system; @kbd{lpr -d} is common; another
32364 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32365 require a file name without any extension or a @samp{.dvi} extension.
32367 @TeX{} also requires a macro definitions file called
32368 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32369 written in Texinfo format. On its own, @TeX{} cannot either read or
32370 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32371 and is located in the @file{gdb-@var{version-number}/texinfo}
32374 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32375 typeset and print this manual. First switch to the @file{gdb}
32376 subdirectory of the main source directory (for example, to
32377 @file{gdb-@value{GDBVN}/gdb}) and type:
32383 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32385 @node Installing GDB
32386 @appendix Installing @value{GDBN}
32387 @cindex installation
32390 * Requirements:: Requirements for building @value{GDBN}
32391 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32392 * Separate Objdir:: Compiling @value{GDBN} in another directory
32393 * Config Names:: Specifying names for hosts and targets
32394 * Configure Options:: Summary of options for configure
32395 * System-wide configuration:: Having a system-wide init file
32399 @section Requirements for Building @value{GDBN}
32400 @cindex building @value{GDBN}, requirements for
32402 Building @value{GDBN} requires various tools and packages to be available.
32403 Other packages will be used only if they are found.
32405 @heading Tools/Packages Necessary for Building @value{GDBN}
32407 @item ISO C90 compiler
32408 @value{GDBN} is written in ISO C90. It should be buildable with any
32409 working C90 compiler, e.g.@: GCC.
32413 @heading Tools/Packages Optional for Building @value{GDBN}
32417 @value{GDBN} can use the Expat XML parsing library. This library may be
32418 included with your operating system distribution; if it is not, you
32419 can get the latest version from @url{http://expat.sourceforge.net}.
32420 The @file{configure} script will search for this library in several
32421 standard locations; if it is installed in an unusual path, you can
32422 use the @option{--with-libexpat-prefix} option to specify its location.
32428 Remote protocol memory maps (@pxref{Memory Map Format})
32430 Target descriptions (@pxref{Target Descriptions})
32432 Remote shared library lists (@pxref{Library List Format})
32434 MS-Windows shared libraries (@pxref{Shared Libraries})
32436 Traceframe info (@pxref{Traceframe Info Format})
32440 @cindex compressed debug sections
32441 @value{GDBN} will use the @samp{zlib} library, if available, to read
32442 compressed debug sections. Some linkers, such as GNU gold, are capable
32443 of producing binaries with compressed debug sections. If @value{GDBN}
32444 is compiled with @samp{zlib}, it will be able to read the debug
32445 information in such binaries.
32447 The @samp{zlib} library is likely included with your operating system
32448 distribution; if it is not, you can get the latest version from
32449 @url{http://zlib.net}.
32452 @value{GDBN}'s features related to character sets (@pxref{Character
32453 Sets}) require a functioning @code{iconv} implementation. If you are
32454 on a GNU system, then this is provided by the GNU C Library. Some
32455 other systems also provide a working @code{iconv}.
32457 If @value{GDBN} is using the @code{iconv} program which is installed
32458 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32459 This is done with @option{--with-iconv-bin} which specifies the
32460 directory that contains the @code{iconv} program.
32462 On systems without @code{iconv}, you can install GNU Libiconv. If you
32463 have previously installed Libiconv, you can use the
32464 @option{--with-libiconv-prefix} option to configure.
32466 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32467 arrange to build Libiconv if a directory named @file{libiconv} appears
32468 in the top-most source directory. If Libiconv is built this way, and
32469 if the operating system does not provide a suitable @code{iconv}
32470 implementation, then the just-built library will automatically be used
32471 by @value{GDBN}. One easy way to set this up is to download GNU
32472 Libiconv, unpack it, and then rename the directory holding the
32473 Libiconv source code to @samp{libiconv}.
32476 @node Running Configure
32477 @section Invoking the @value{GDBN} @file{configure} Script
32478 @cindex configuring @value{GDBN}
32479 @value{GDBN} comes with a @file{configure} script that automates the process
32480 of preparing @value{GDBN} for installation; you can then use @code{make} to
32481 build the @code{gdb} program.
32483 @c irrelevant in info file; it's as current as the code it lives with.
32484 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32485 look at the @file{README} file in the sources; we may have improved the
32486 installation procedures since publishing this manual.}
32489 The @value{GDBN} distribution includes all the source code you need for
32490 @value{GDBN} in a single directory, whose name is usually composed by
32491 appending the version number to @samp{gdb}.
32493 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32494 @file{gdb-@value{GDBVN}} directory. That directory contains:
32497 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32498 script for configuring @value{GDBN} and all its supporting libraries
32500 @item gdb-@value{GDBVN}/gdb
32501 the source specific to @value{GDBN} itself
32503 @item gdb-@value{GDBVN}/bfd
32504 source for the Binary File Descriptor library
32506 @item gdb-@value{GDBVN}/include
32507 @sc{gnu} include files
32509 @item gdb-@value{GDBVN}/libiberty
32510 source for the @samp{-liberty} free software library
32512 @item gdb-@value{GDBVN}/opcodes
32513 source for the library of opcode tables and disassemblers
32515 @item gdb-@value{GDBVN}/readline
32516 source for the @sc{gnu} command-line interface
32518 @item gdb-@value{GDBVN}/glob
32519 source for the @sc{gnu} filename pattern-matching subroutine
32521 @item gdb-@value{GDBVN}/mmalloc
32522 source for the @sc{gnu} memory-mapped malloc package
32525 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32526 from the @file{gdb-@var{version-number}} source directory, which in
32527 this example is the @file{gdb-@value{GDBVN}} directory.
32529 First switch to the @file{gdb-@var{version-number}} source directory
32530 if you are not already in it; then run @file{configure}. Pass the
32531 identifier for the platform on which @value{GDBN} will run as an
32537 cd gdb-@value{GDBVN}
32538 ./configure @var{host}
32543 where @var{host} is an identifier such as @samp{sun4} or
32544 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32545 (You can often leave off @var{host}; @file{configure} tries to guess the
32546 correct value by examining your system.)
32548 Running @samp{configure @var{host}} and then running @code{make} builds the
32549 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32550 libraries, then @code{gdb} itself. The configured source files, and the
32551 binaries, are left in the corresponding source directories.
32554 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32555 system does not recognize this automatically when you run a different
32556 shell, you may need to run @code{sh} on it explicitly:
32559 sh configure @var{host}
32562 If you run @file{configure} from a directory that contains source
32563 directories for multiple libraries or programs, such as the
32564 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32566 creates configuration files for every directory level underneath (unless
32567 you tell it not to, with the @samp{--norecursion} option).
32569 You should run the @file{configure} script from the top directory in the
32570 source tree, the @file{gdb-@var{version-number}} directory. If you run
32571 @file{configure} from one of the subdirectories, you will configure only
32572 that subdirectory. That is usually not what you want. In particular,
32573 if you run the first @file{configure} from the @file{gdb} subdirectory
32574 of the @file{gdb-@var{version-number}} directory, you will omit the
32575 configuration of @file{bfd}, @file{readline}, and other sibling
32576 directories of the @file{gdb} subdirectory. This leads to build errors
32577 about missing include files such as @file{bfd/bfd.h}.
32579 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32580 However, you should make sure that the shell on your path (named by
32581 the @samp{SHELL} environment variable) is publicly readable. Remember
32582 that @value{GDBN} uses the shell to start your program---some systems refuse to
32583 let @value{GDBN} debug child processes whose programs are not readable.
32585 @node Separate Objdir
32586 @section Compiling @value{GDBN} in Another Directory
32588 If you want to run @value{GDBN} versions for several host or target machines,
32589 you need a different @code{gdb} compiled for each combination of
32590 host and target. @file{configure} is designed to make this easy by
32591 allowing you to generate each configuration in a separate subdirectory,
32592 rather than in the source directory. If your @code{make} program
32593 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32594 @code{make} in each of these directories builds the @code{gdb}
32595 program specified there.
32597 To build @code{gdb} in a separate directory, run @file{configure}
32598 with the @samp{--srcdir} option to specify where to find the source.
32599 (You also need to specify a path to find @file{configure}
32600 itself from your working directory. If the path to @file{configure}
32601 would be the same as the argument to @samp{--srcdir}, you can leave out
32602 the @samp{--srcdir} option; it is assumed.)
32604 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32605 separate directory for a Sun 4 like this:
32609 cd gdb-@value{GDBVN}
32612 ../gdb-@value{GDBVN}/configure sun4
32617 When @file{configure} builds a configuration using a remote source
32618 directory, it creates a tree for the binaries with the same structure
32619 (and using the same names) as the tree under the source directory. In
32620 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32621 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32622 @file{gdb-sun4/gdb}.
32624 Make sure that your path to the @file{configure} script has just one
32625 instance of @file{gdb} in it. If your path to @file{configure} looks
32626 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32627 one subdirectory of @value{GDBN}, not the whole package. This leads to
32628 build errors about missing include files such as @file{bfd/bfd.h}.
32630 One popular reason to build several @value{GDBN} configurations in separate
32631 directories is to configure @value{GDBN} for cross-compiling (where
32632 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32633 programs that run on another machine---the @dfn{target}).
32634 You specify a cross-debugging target by
32635 giving the @samp{--target=@var{target}} option to @file{configure}.
32637 When you run @code{make} to build a program or library, you must run
32638 it in a configured directory---whatever directory you were in when you
32639 called @file{configure} (or one of its subdirectories).
32641 The @code{Makefile} that @file{configure} generates in each source
32642 directory also runs recursively. If you type @code{make} in a source
32643 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32644 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32645 will build all the required libraries, and then build GDB.
32647 When you have multiple hosts or targets configured in separate
32648 directories, you can run @code{make} on them in parallel (for example,
32649 if they are NFS-mounted on each of the hosts); they will not interfere
32653 @section Specifying Names for Hosts and Targets
32655 The specifications used for hosts and targets in the @file{configure}
32656 script are based on a three-part naming scheme, but some short predefined
32657 aliases are also supported. The full naming scheme encodes three pieces
32658 of information in the following pattern:
32661 @var{architecture}-@var{vendor}-@var{os}
32664 For example, you can use the alias @code{sun4} as a @var{host} argument,
32665 or as the value for @var{target} in a @code{--target=@var{target}}
32666 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32668 The @file{configure} script accompanying @value{GDBN} does not provide
32669 any query facility to list all supported host and target names or
32670 aliases. @file{configure} calls the Bourne shell script
32671 @code{config.sub} to map abbreviations to full names; you can read the
32672 script, if you wish, or you can use it to test your guesses on
32673 abbreviations---for example:
32676 % sh config.sub i386-linux
32678 % sh config.sub alpha-linux
32679 alpha-unknown-linux-gnu
32680 % sh config.sub hp9k700
32682 % sh config.sub sun4
32683 sparc-sun-sunos4.1.1
32684 % sh config.sub sun3
32685 m68k-sun-sunos4.1.1
32686 % sh config.sub i986v
32687 Invalid configuration `i986v': machine `i986v' not recognized
32691 @code{config.sub} is also distributed in the @value{GDBN} source
32692 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32694 @node Configure Options
32695 @section @file{configure} Options
32697 Here is a summary of the @file{configure} options and arguments that
32698 are most often useful for building @value{GDBN}. @file{configure} also has
32699 several other options not listed here. @inforef{What Configure
32700 Does,,configure.info}, for a full explanation of @file{configure}.
32703 configure @r{[}--help@r{]}
32704 @r{[}--prefix=@var{dir}@r{]}
32705 @r{[}--exec-prefix=@var{dir}@r{]}
32706 @r{[}--srcdir=@var{dirname}@r{]}
32707 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32708 @r{[}--target=@var{target}@r{]}
32713 You may introduce options with a single @samp{-} rather than
32714 @samp{--} if you prefer; but you may abbreviate option names if you use
32719 Display a quick summary of how to invoke @file{configure}.
32721 @item --prefix=@var{dir}
32722 Configure the source to install programs and files under directory
32725 @item --exec-prefix=@var{dir}
32726 Configure the source to install programs under directory
32729 @c avoid splitting the warning from the explanation:
32731 @item --srcdir=@var{dirname}
32732 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32733 @code{make} that implements the @code{VPATH} feature.}@*
32734 Use this option to make configurations in directories separate from the
32735 @value{GDBN} source directories. Among other things, you can use this to
32736 build (or maintain) several configurations simultaneously, in separate
32737 directories. @file{configure} writes configuration-specific files in
32738 the current directory, but arranges for them to use the source in the
32739 directory @var{dirname}. @file{configure} creates directories under
32740 the working directory in parallel to the source directories below
32743 @item --norecursion
32744 Configure only the directory level where @file{configure} is executed; do not
32745 propagate configuration to subdirectories.
32747 @item --target=@var{target}
32748 Configure @value{GDBN} for cross-debugging programs running on the specified
32749 @var{target}. Without this option, @value{GDBN} is configured to debug
32750 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32752 There is no convenient way to generate a list of all available targets.
32754 @item @var{host} @dots{}
32755 Configure @value{GDBN} to run on the specified @var{host}.
32757 There is no convenient way to generate a list of all available hosts.
32760 There are many other options available as well, but they are generally
32761 needed for special purposes only.
32763 @node System-wide configuration
32764 @section System-wide configuration and settings
32765 @cindex system-wide init file
32767 @value{GDBN} can be configured to have a system-wide init file;
32768 this file will be read and executed at startup (@pxref{Startup, , What
32769 @value{GDBN} does during startup}).
32771 Here is the corresponding configure option:
32774 @item --with-system-gdbinit=@var{file}
32775 Specify that the default location of the system-wide init file is
32779 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32780 it may be subject to relocation. Two possible cases:
32784 If the default location of this init file contains @file{$prefix},
32785 it will be subject to relocation. Suppose that the configure options
32786 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32787 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32788 init file is looked for as @file{$install/etc/gdbinit} instead of
32789 @file{$prefix/etc/gdbinit}.
32792 By contrast, if the default location does not contain the prefix,
32793 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32794 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32795 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32796 wherever @value{GDBN} is installed.
32799 @node Maintenance Commands
32800 @appendix Maintenance Commands
32801 @cindex maintenance commands
32802 @cindex internal commands
32804 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32805 includes a number of commands intended for @value{GDBN} developers,
32806 that are not documented elsewhere in this manual. These commands are
32807 provided here for reference. (For commands that turn on debugging
32808 messages, see @ref{Debugging Output}.)
32811 @kindex maint agent
32812 @kindex maint agent-eval
32813 @item maint agent @var{expression}
32814 @itemx maint agent-eval @var{expression}
32815 Translate the given @var{expression} into remote agent bytecodes.
32816 This command is useful for debugging the Agent Expression mechanism
32817 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32818 expression useful for data collection, such as by tracepoints, while
32819 @samp{maint agent-eval} produces an expression that evaluates directly
32820 to a result. For instance, a collection expression for @code{globa +
32821 globb} will include bytecodes to record four bytes of memory at each
32822 of the addresses of @code{globa} and @code{globb}, while discarding
32823 the result of the addition, while an evaluation expression will do the
32824 addition and return the sum.
32826 @kindex maint info breakpoints
32827 @item @anchor{maint info breakpoints}maint info breakpoints
32828 Using the same format as @samp{info breakpoints}, display both the
32829 breakpoints you've set explicitly, and those @value{GDBN} is using for
32830 internal purposes. Internal breakpoints are shown with negative
32831 breakpoint numbers. The type column identifies what kind of breakpoint
32836 Normal, explicitly set breakpoint.
32839 Normal, explicitly set watchpoint.
32842 Internal breakpoint, used to handle correctly stepping through
32843 @code{longjmp} calls.
32845 @item longjmp resume
32846 Internal breakpoint at the target of a @code{longjmp}.
32849 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32852 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32855 Shared library events.
32859 @kindex set displaced-stepping
32860 @kindex show displaced-stepping
32861 @cindex displaced stepping support
32862 @cindex out-of-line single-stepping
32863 @item set displaced-stepping
32864 @itemx show displaced-stepping
32865 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32866 if the target supports it. Displaced stepping is a way to single-step
32867 over breakpoints without removing them from the inferior, by executing
32868 an out-of-line copy of the instruction that was originally at the
32869 breakpoint location. It is also known as out-of-line single-stepping.
32872 @item set displaced-stepping on
32873 If the target architecture supports it, @value{GDBN} will use
32874 displaced stepping to step over breakpoints.
32876 @item set displaced-stepping off
32877 @value{GDBN} will not use displaced stepping to step over breakpoints,
32878 even if such is supported by the target architecture.
32880 @cindex non-stop mode, and @samp{set displaced-stepping}
32881 @item set displaced-stepping auto
32882 This is the default mode. @value{GDBN} will use displaced stepping
32883 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32884 architecture supports displaced stepping.
32887 @kindex maint check-symtabs
32888 @item maint check-symtabs
32889 Check the consistency of psymtabs and symtabs.
32891 @kindex maint cplus first_component
32892 @item maint cplus first_component @var{name}
32893 Print the first C@t{++} class/namespace component of @var{name}.
32895 @kindex maint cplus namespace
32896 @item maint cplus namespace
32897 Print the list of possible C@t{++} namespaces.
32899 @kindex maint demangle
32900 @item maint demangle @var{name}
32901 Demangle a C@t{++} or Objective-C mangled @var{name}.
32903 @kindex maint deprecate
32904 @kindex maint undeprecate
32905 @cindex deprecated commands
32906 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
32907 @itemx maint undeprecate @var{command}
32908 Deprecate or undeprecate the named @var{command}. Deprecated commands
32909 cause @value{GDBN} to issue a warning when you use them. The optional
32910 argument @var{replacement} says which newer command should be used in
32911 favor of the deprecated one; if it is given, @value{GDBN} will mention
32912 the replacement as part of the warning.
32914 @kindex maint dump-me
32915 @item maint dump-me
32916 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
32917 Cause a fatal signal in the debugger and force it to dump its core.
32918 This is supported only on systems which support aborting a program
32919 with the @code{SIGQUIT} signal.
32921 @kindex maint internal-error
32922 @kindex maint internal-warning
32923 @item maint internal-error @r{[}@var{message-text}@r{]}
32924 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
32925 Cause @value{GDBN} to call the internal function @code{internal_error}
32926 or @code{internal_warning} and hence behave as though an internal error
32927 or internal warning has been detected. In addition to reporting the
32928 internal problem, these functions give the user the opportunity to
32929 either quit @value{GDBN} or create a core file of the current
32930 @value{GDBN} session.
32932 These commands take an optional parameter @var{message-text} that is
32933 used as the text of the error or warning message.
32935 Here's an example of using @code{internal-error}:
32938 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
32939 @dots{}/maint.c:121: internal-error: testing, 1, 2
32940 A problem internal to GDB has been detected. Further
32941 debugging may prove unreliable.
32942 Quit this debugging session? (y or n) @kbd{n}
32943 Create a core file? (y or n) @kbd{n}
32947 @cindex @value{GDBN} internal error
32948 @cindex internal errors, control of @value{GDBN} behavior
32950 @kindex maint set internal-error
32951 @kindex maint show internal-error
32952 @kindex maint set internal-warning
32953 @kindex maint show internal-warning
32954 @item maint set internal-error @var{action} [ask|yes|no]
32955 @itemx maint show internal-error @var{action}
32956 @itemx maint set internal-warning @var{action} [ask|yes|no]
32957 @itemx maint show internal-warning @var{action}
32958 When @value{GDBN} reports an internal problem (error or warning) it
32959 gives the user the opportunity to both quit @value{GDBN} and create a
32960 core file of the current @value{GDBN} session. These commands let you
32961 override the default behaviour for each particular @var{action},
32962 described in the table below.
32966 You can specify that @value{GDBN} should always (yes) or never (no)
32967 quit. The default is to ask the user what to do.
32970 You can specify that @value{GDBN} should always (yes) or never (no)
32971 create a core file. The default is to ask the user what to do.
32974 @kindex maint packet
32975 @item maint packet @var{text}
32976 If @value{GDBN} is talking to an inferior via the serial protocol,
32977 then this command sends the string @var{text} to the inferior, and
32978 displays the response packet. @value{GDBN} supplies the initial
32979 @samp{$} character, the terminating @samp{#} character, and the
32982 @kindex maint print architecture
32983 @item maint print architecture @r{[}@var{file}@r{]}
32984 Print the entire architecture configuration. The optional argument
32985 @var{file} names the file where the output goes.
32987 @kindex maint print c-tdesc
32988 @item maint print c-tdesc
32989 Print the current target description (@pxref{Target Descriptions}) as
32990 a C source file. The created source file can be used in @value{GDBN}
32991 when an XML parser is not available to parse the description.
32993 @kindex maint print dummy-frames
32994 @item maint print dummy-frames
32995 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
32998 (@value{GDBP}) @kbd{b add}
33000 (@value{GDBP}) @kbd{print add(2,3)}
33001 Breakpoint 2, add (a=2, b=3) at @dots{}
33003 The program being debugged stopped while in a function called from GDB.
33005 (@value{GDBP}) @kbd{maint print dummy-frames}
33006 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33007 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33008 call_lo=0x01014000 call_hi=0x01014001
33012 Takes an optional file parameter.
33014 @kindex maint print registers
33015 @kindex maint print raw-registers
33016 @kindex maint print cooked-registers
33017 @kindex maint print register-groups
33018 @kindex maint print remote-registers
33019 @item maint print registers @r{[}@var{file}@r{]}
33020 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33021 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33022 @itemx maint print register-groups @r{[}@var{file}@r{]}
33023 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33024 Print @value{GDBN}'s internal register data structures.
33026 The command @code{maint print raw-registers} includes the contents of
33027 the raw register cache; the command @code{maint print
33028 cooked-registers} includes the (cooked) value of all registers,
33029 including registers which aren't available on the target nor visible
33030 to user; the command @code{maint print register-groups} includes the
33031 groups that each register is a member of; and the command @code{maint
33032 print remote-registers} includes the remote target's register numbers
33033 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33034 @value{GDBN} Internals}.
33036 These commands take an optional parameter, a file name to which to
33037 write the information.
33039 @kindex maint print reggroups
33040 @item maint print reggroups @r{[}@var{file}@r{]}
33041 Print @value{GDBN}'s internal register group data structures. The
33042 optional argument @var{file} tells to what file to write the
33045 The register groups info looks like this:
33048 (@value{GDBP}) @kbd{maint print reggroups}
33061 This command forces @value{GDBN} to flush its internal register cache.
33063 @kindex maint print objfiles
33064 @cindex info for known object files
33065 @item maint print objfiles
33066 Print a dump of all known object files. For each object file, this
33067 command prints its name, address in memory, and all of its psymtabs
33070 @kindex maint print section-scripts
33071 @cindex info for known .debug_gdb_scripts-loaded scripts
33072 @item maint print section-scripts [@var{regexp}]
33073 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33074 If @var{regexp} is specified, only print scripts loaded by object files
33075 matching @var{regexp}.
33076 For each script, this command prints its name as specified in the objfile,
33077 and the full path if known.
33078 @xref{.debug_gdb_scripts section}.
33080 @kindex maint print statistics
33081 @cindex bcache statistics
33082 @item maint print statistics
33083 This command prints, for each object file in the program, various data
33084 about that object file followed by the byte cache (@dfn{bcache})
33085 statistics for the object file. The objfile data includes the number
33086 of minimal, partial, full, and stabs symbols, the number of types
33087 defined by the objfile, the number of as yet unexpanded psym tables,
33088 the number of line tables and string tables, and the amount of memory
33089 used by the various tables. The bcache statistics include the counts,
33090 sizes, and counts of duplicates of all and unique objects, max,
33091 average, and median entry size, total memory used and its overhead and
33092 savings, and various measures of the hash table size and chain
33095 @kindex maint print target-stack
33096 @cindex target stack description
33097 @item maint print target-stack
33098 A @dfn{target} is an interface between the debugger and a particular
33099 kind of file or process. Targets can be stacked in @dfn{strata},
33100 so that more than one target can potentially respond to a request.
33101 In particular, memory accesses will walk down the stack of targets
33102 until they find a target that is interested in handling that particular
33105 This command prints a short description of each layer that was pushed on
33106 the @dfn{target stack}, starting from the top layer down to the bottom one.
33108 @kindex maint print type
33109 @cindex type chain of a data type
33110 @item maint print type @var{expr}
33111 Print the type chain for a type specified by @var{expr}. The argument
33112 can be either a type name or a symbol. If it is a symbol, the type of
33113 that symbol is described. The type chain produced by this command is
33114 a recursive definition of the data type as stored in @value{GDBN}'s
33115 data structures, including its flags and contained types.
33117 @kindex maint set dwarf2 always-disassemble
33118 @kindex maint show dwarf2 always-disassemble
33119 @item maint set dwarf2 always-disassemble
33120 @item maint show dwarf2 always-disassemble
33121 Control the behavior of @code{info address} when using DWARF debugging
33124 The default is @code{off}, which means that @value{GDBN} should try to
33125 describe a variable's location in an easily readable format. When
33126 @code{on}, @value{GDBN} will instead display the DWARF location
33127 expression in an assembly-like format. Note that some locations are
33128 too complex for @value{GDBN} to describe simply; in this case you will
33129 always see the disassembly form.
33131 Here is an example of the resulting disassembly:
33134 (gdb) info addr argc
33135 Symbol "argc" is a complex DWARF expression:
33139 For more information on these expressions, see
33140 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33142 @kindex maint set dwarf2 max-cache-age
33143 @kindex maint show dwarf2 max-cache-age
33144 @item maint set dwarf2 max-cache-age
33145 @itemx maint show dwarf2 max-cache-age
33146 Control the DWARF 2 compilation unit cache.
33148 @cindex DWARF 2 compilation units cache
33149 In object files with inter-compilation-unit references, such as those
33150 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33151 reader needs to frequently refer to previously read compilation units.
33152 This setting controls how long a compilation unit will remain in the
33153 cache if it is not referenced. A higher limit means that cached
33154 compilation units will be stored in memory longer, and more total
33155 memory will be used. Setting it to zero disables caching, which will
33156 slow down @value{GDBN} startup, but reduce memory consumption.
33158 @kindex maint set profile
33159 @kindex maint show profile
33160 @cindex profiling GDB
33161 @item maint set profile
33162 @itemx maint show profile
33163 Control profiling of @value{GDBN}.
33165 Profiling will be disabled until you use the @samp{maint set profile}
33166 command to enable it. When you enable profiling, the system will begin
33167 collecting timing and execution count data; when you disable profiling or
33168 exit @value{GDBN}, the results will be written to a log file. Remember that
33169 if you use profiling, @value{GDBN} will overwrite the profiling log file
33170 (often called @file{gmon.out}). If you have a record of important profiling
33171 data in a @file{gmon.out} file, be sure to move it to a safe location.
33173 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33174 compiled with the @samp{-pg} compiler option.
33176 @kindex maint set show-debug-regs
33177 @kindex maint show show-debug-regs
33178 @cindex hardware debug registers
33179 @item maint set show-debug-regs
33180 @itemx maint show show-debug-regs
33181 Control whether to show variables that mirror the hardware debug
33182 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33183 enabled, the debug registers values are shown when @value{GDBN} inserts or
33184 removes a hardware breakpoint or watchpoint, and when the inferior
33185 triggers a hardware-assisted breakpoint or watchpoint.
33187 @kindex maint set show-all-tib
33188 @kindex maint show show-all-tib
33189 @item maint set show-all-tib
33190 @itemx maint show show-all-tib
33191 Control whether to show all non zero areas within a 1k block starting
33192 at thread local base, when using the @samp{info w32 thread-information-block}
33195 @kindex maint space
33196 @cindex memory used by commands
33198 Control whether to display memory usage for each command. If set to a
33199 nonzero value, @value{GDBN} will display how much memory each command
33200 took, following the command's own output. This can also be requested
33201 by invoking @value{GDBN} with the @option{--statistics} command-line
33202 switch (@pxref{Mode Options}).
33205 @cindex time of command execution
33207 Control whether to display the execution time of @value{GDBN} for each command.
33208 If set to a nonzero value, @value{GDBN} will display how much time it
33209 took to execute each command, following the command's own output.
33210 Both CPU time and wallclock time are printed.
33211 Printing both is useful when trying to determine whether the cost is
33212 CPU or, e.g., disk/network, latency.
33213 Note that the CPU time printed is for @value{GDBN} only, it does not include
33214 the execution time of the inferior because there's no mechanism currently
33215 to compute how much time was spent by @value{GDBN} and how much time was
33216 spent by the program been debugged.
33217 This can also be requested by invoking @value{GDBN} with the
33218 @option{--statistics} command-line switch (@pxref{Mode Options}).
33220 @kindex maint translate-address
33221 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33222 Find the symbol stored at the location specified by the address
33223 @var{addr} and an optional section name @var{section}. If found,
33224 @value{GDBN} prints the name of the closest symbol and an offset from
33225 the symbol's location to the specified address. This is similar to
33226 the @code{info address} command (@pxref{Symbols}), except that this
33227 command also allows to find symbols in other sections.
33229 If section was not specified, the section in which the symbol was found
33230 is also printed. For dynamically linked executables, the name of
33231 executable or shared library containing the symbol is printed as well.
33235 The following command is useful for non-interactive invocations of
33236 @value{GDBN}, such as in the test suite.
33239 @item set watchdog @var{nsec}
33240 @kindex set watchdog
33241 @cindex watchdog timer
33242 @cindex timeout for commands
33243 Set the maximum number of seconds @value{GDBN} will wait for the
33244 target operation to finish. If this time expires, @value{GDBN}
33245 reports and error and the command is aborted.
33247 @item show watchdog
33248 Show the current setting of the target wait timeout.
33251 @node Remote Protocol
33252 @appendix @value{GDBN} Remote Serial Protocol
33257 * Stop Reply Packets::
33258 * General Query Packets::
33259 * Architecture-Specific Protocol Details::
33260 * Tracepoint Packets::
33261 * Host I/O Packets::
33263 * Notification Packets::
33264 * Remote Non-Stop::
33265 * Packet Acknowledgment::
33267 * File-I/O Remote Protocol Extension::
33268 * Library List Format::
33269 * Memory Map Format::
33270 * Thread List Format::
33271 * Traceframe Info Format::
33277 There may be occasions when you need to know something about the
33278 protocol---for example, if there is only one serial port to your target
33279 machine, you might want your program to do something special if it
33280 recognizes a packet meant for @value{GDBN}.
33282 In the examples below, @samp{->} and @samp{<-} are used to indicate
33283 transmitted and received data, respectively.
33285 @cindex protocol, @value{GDBN} remote serial
33286 @cindex serial protocol, @value{GDBN} remote
33287 @cindex remote serial protocol
33288 All @value{GDBN} commands and responses (other than acknowledgments
33289 and notifications, see @ref{Notification Packets}) are sent as a
33290 @var{packet}. A @var{packet} is introduced with the character
33291 @samp{$}, the actual @var{packet-data}, and the terminating character
33292 @samp{#} followed by a two-digit @var{checksum}:
33295 @code{$}@var{packet-data}@code{#}@var{checksum}
33299 @cindex checksum, for @value{GDBN} remote
33301 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33302 characters between the leading @samp{$} and the trailing @samp{#} (an
33303 eight bit unsigned checksum).
33305 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33306 specification also included an optional two-digit @var{sequence-id}:
33309 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33312 @cindex sequence-id, for @value{GDBN} remote
33314 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33315 has never output @var{sequence-id}s. Stubs that handle packets added
33316 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33318 When either the host or the target machine receives a packet, the first
33319 response expected is an acknowledgment: either @samp{+} (to indicate
33320 the package was received correctly) or @samp{-} (to request
33324 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33329 The @samp{+}/@samp{-} acknowledgments can be disabled
33330 once a connection is established.
33331 @xref{Packet Acknowledgment}, for details.
33333 The host (@value{GDBN}) sends @var{command}s, and the target (the
33334 debugging stub incorporated in your program) sends a @var{response}. In
33335 the case of step and continue @var{command}s, the response is only sent
33336 when the operation has completed, and the target has again stopped all
33337 threads in all attached processes. This is the default all-stop mode
33338 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33339 execution mode; see @ref{Remote Non-Stop}, for details.
33341 @var{packet-data} consists of a sequence of characters with the
33342 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33345 @cindex remote protocol, field separator
33346 Fields within the packet should be separated using @samp{,} @samp{;} or
33347 @samp{:}. Except where otherwise noted all numbers are represented in
33348 @sc{hex} with leading zeros suppressed.
33350 Implementors should note that prior to @value{GDBN} 5.0, the character
33351 @samp{:} could not appear as the third character in a packet (as it
33352 would potentially conflict with the @var{sequence-id}).
33354 @cindex remote protocol, binary data
33355 @anchor{Binary Data}
33356 Binary data in most packets is encoded either as two hexadecimal
33357 digits per byte of binary data. This allowed the traditional remote
33358 protocol to work over connections which were only seven-bit clean.
33359 Some packets designed more recently assume an eight-bit clean
33360 connection, and use a more efficient encoding to send and receive
33363 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33364 as an escape character. Any escaped byte is transmitted as the escape
33365 character followed by the original character XORed with @code{0x20}.
33366 For example, the byte @code{0x7d} would be transmitted as the two
33367 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33368 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33369 @samp{@}}) must always be escaped. Responses sent by the stub
33370 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33371 is not interpreted as the start of a run-length encoded sequence
33374 Response @var{data} can be run-length encoded to save space.
33375 Run-length encoding replaces runs of identical characters with one
33376 instance of the repeated character, followed by a @samp{*} and a
33377 repeat count. The repeat count is itself sent encoded, to avoid
33378 binary characters in @var{data}: a value of @var{n} is sent as
33379 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33380 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33381 code 32) for a repeat count of 3. (This is because run-length
33382 encoding starts to win for counts 3 or more.) Thus, for example,
33383 @samp{0* } is a run-length encoding of ``0000'': the space character
33384 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33387 The printable characters @samp{#} and @samp{$} or with a numeric value
33388 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33389 seven repeats (@samp{$}) can be expanded using a repeat count of only
33390 five (@samp{"}). For example, @samp{00000000} can be encoded as
33393 The error response returned for some packets includes a two character
33394 error number. That number is not well defined.
33396 @cindex empty response, for unsupported packets
33397 For any @var{command} not supported by the stub, an empty response
33398 (@samp{$#00}) should be returned. That way it is possible to extend the
33399 protocol. A newer @value{GDBN} can tell if a packet is supported based
33402 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33403 commands for register access, and the @samp{m} and @samp{M} commands
33404 for memory access. Stubs that only control single-threaded targets
33405 can implement run control with the @samp{c} (continue), and @samp{s}
33406 (step) commands. Stubs that support multi-threading targets should
33407 support the @samp{vCont} command. All other commands are optional.
33412 The following table provides a complete list of all currently defined
33413 @var{command}s and their corresponding response @var{data}.
33414 @xref{File-I/O Remote Protocol Extension}, for details about the File
33415 I/O extension of the remote protocol.
33417 Each packet's description has a template showing the packet's overall
33418 syntax, followed by an explanation of the packet's meaning. We
33419 include spaces in some of the templates for clarity; these are not
33420 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33421 separate its components. For example, a template like @samp{foo
33422 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33423 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33424 @var{baz}. @value{GDBN} does not transmit a space character between the
33425 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33428 @cindex @var{thread-id}, in remote protocol
33429 @anchor{thread-id syntax}
33430 Several packets and replies include a @var{thread-id} field to identify
33431 a thread. Normally these are positive numbers with a target-specific
33432 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33433 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33436 In addition, the remote protocol supports a multiprocess feature in
33437 which the @var{thread-id} syntax is extended to optionally include both
33438 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33439 The @var{pid} (process) and @var{tid} (thread) components each have the
33440 format described above: a positive number with target-specific
33441 interpretation formatted as a big-endian hex string, literal @samp{-1}
33442 to indicate all processes or threads (respectively), or @samp{0} to
33443 indicate an arbitrary process or thread. Specifying just a process, as
33444 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33445 error to specify all processes but a specific thread, such as
33446 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33447 for those packets and replies explicitly documented to include a process
33448 ID, rather than a @var{thread-id}.
33450 The multiprocess @var{thread-id} syntax extensions are only used if both
33451 @value{GDBN} and the stub report support for the @samp{multiprocess}
33452 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33455 Note that all packet forms beginning with an upper- or lower-case
33456 letter, other than those described here, are reserved for future use.
33458 Here are the packet descriptions.
33463 @cindex @samp{!} packet
33464 @anchor{extended mode}
33465 Enable extended mode. In extended mode, the remote server is made
33466 persistent. The @samp{R} packet is used to restart the program being
33472 The remote target both supports and has enabled extended mode.
33476 @cindex @samp{?} packet
33477 Indicate the reason the target halted. The reply is the same as for
33478 step and continue. This packet has a special interpretation when the
33479 target is in non-stop mode; see @ref{Remote Non-Stop}.
33482 @xref{Stop Reply Packets}, for the reply specifications.
33484 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33485 @cindex @samp{A} packet
33486 Initialized @code{argv[]} array passed into program. @var{arglen}
33487 specifies the number of bytes in the hex encoded byte stream
33488 @var{arg}. See @code{gdbserver} for more details.
33493 The arguments were set.
33499 @cindex @samp{b} packet
33500 (Don't use this packet; its behavior is not well-defined.)
33501 Change the serial line speed to @var{baud}.
33503 JTC: @emph{When does the transport layer state change? When it's
33504 received, or after the ACK is transmitted. In either case, there are
33505 problems if the command or the acknowledgment packet is dropped.}
33507 Stan: @emph{If people really wanted to add something like this, and get
33508 it working for the first time, they ought to modify ser-unix.c to send
33509 some kind of out-of-band message to a specially-setup stub and have the
33510 switch happen "in between" packets, so that from remote protocol's point
33511 of view, nothing actually happened.}
33513 @item B @var{addr},@var{mode}
33514 @cindex @samp{B} packet
33515 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33516 breakpoint at @var{addr}.
33518 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33519 (@pxref{insert breakpoint or watchpoint packet}).
33521 @cindex @samp{bc} packet
33524 Backward continue. Execute the target system in reverse. No parameter.
33525 @xref{Reverse Execution}, for more information.
33528 @xref{Stop Reply Packets}, for the reply specifications.
33530 @cindex @samp{bs} packet
33533 Backward single step. Execute one instruction in reverse. No parameter.
33534 @xref{Reverse Execution}, for more information.
33537 @xref{Stop Reply Packets}, for the reply specifications.
33539 @item c @r{[}@var{addr}@r{]}
33540 @cindex @samp{c} packet
33541 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33542 resume at current address.
33544 This packet is deprecated for multi-threading support. @xref{vCont
33548 @xref{Stop Reply Packets}, for the reply specifications.
33550 @item C @var{sig}@r{[};@var{addr}@r{]}
33551 @cindex @samp{C} packet
33552 Continue with signal @var{sig} (hex signal number). If
33553 @samp{;@var{addr}} is omitted, resume at same address.
33555 This packet is deprecated for multi-threading support. @xref{vCont
33559 @xref{Stop Reply Packets}, for the reply specifications.
33562 @cindex @samp{d} packet
33565 Don't use this packet; instead, define a general set packet
33566 (@pxref{General Query Packets}).
33570 @cindex @samp{D} packet
33571 The first form of the packet is used to detach @value{GDBN} from the
33572 remote system. It is sent to the remote target
33573 before @value{GDBN} disconnects via the @code{detach} command.
33575 The second form, including a process ID, is used when multiprocess
33576 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33577 detach only a specific process. The @var{pid} is specified as a
33578 big-endian hex string.
33588 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33589 @cindex @samp{F} packet
33590 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33591 This is part of the File-I/O protocol extension. @xref{File-I/O
33592 Remote Protocol Extension}, for the specification.
33595 @anchor{read registers packet}
33596 @cindex @samp{g} packet
33597 Read general registers.
33601 @item @var{XX@dots{}}
33602 Each byte of register data is described by two hex digits. The bytes
33603 with the register are transmitted in target byte order. The size of
33604 each register and their position within the @samp{g} packet are
33605 determined by the @value{GDBN} internal gdbarch functions
33606 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33607 specification of several standard @samp{g} packets is specified below.
33609 When reading registers from a trace frame (@pxref{Analyze Collected
33610 Data,,Using the Collected Data}), the stub may also return a string of
33611 literal @samp{x}'s in place of the register data digits, to indicate
33612 that the corresponding register has not been collected, thus its value
33613 is unavailable. For example, for an architecture with 4 registers of
33614 4 bytes each, the following reply indicates to @value{GDBN} that
33615 registers 0 and 2 have not been collected, while registers 1 and 3
33616 have been collected, and both have zero value:
33620 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33627 @item G @var{XX@dots{}}
33628 @cindex @samp{G} packet
33629 Write general registers. @xref{read registers packet}, for a
33630 description of the @var{XX@dots{}} data.
33640 @item H @var{op} @var{thread-id}
33641 @cindex @samp{H} packet
33642 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33643 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33644 it should be @samp{c} for step and continue operations (note that this
33645 is deprecated, supporting the @samp{vCont} command is a better
33646 option), @samp{g} for other operations. The thread designator
33647 @var{thread-id} has the format and interpretation described in
33648 @ref{thread-id syntax}.
33659 @c 'H': How restrictive (or permissive) is the thread model. If a
33660 @c thread is selected and stopped, are other threads allowed
33661 @c to continue to execute? As I mentioned above, I think the
33662 @c semantics of each command when a thread is selected must be
33663 @c described. For example:
33665 @c 'g': If the stub supports threads and a specific thread is
33666 @c selected, returns the register block from that thread;
33667 @c otherwise returns current registers.
33669 @c 'G' If the stub supports threads and a specific thread is
33670 @c selected, sets the registers of the register block of
33671 @c that thread; otherwise sets current registers.
33673 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33674 @anchor{cycle step packet}
33675 @cindex @samp{i} packet
33676 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33677 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33678 step starting at that address.
33681 @cindex @samp{I} packet
33682 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33686 @cindex @samp{k} packet
33689 FIXME: @emph{There is no description of how to operate when a specific
33690 thread context has been selected (i.e.@: does 'k' kill only that
33693 @item m @var{addr},@var{length}
33694 @cindex @samp{m} packet
33695 Read @var{length} bytes of memory starting at address @var{addr}.
33696 Note that @var{addr} may not be aligned to any particular boundary.
33698 The stub need not use any particular size or alignment when gathering
33699 data from memory for the response; even if @var{addr} is word-aligned
33700 and @var{length} is a multiple of the word size, the stub is free to
33701 use byte accesses, or not. For this reason, this packet may not be
33702 suitable for accessing memory-mapped I/O devices.
33703 @cindex alignment of remote memory accesses
33704 @cindex size of remote memory accesses
33705 @cindex memory, alignment and size of remote accesses
33709 @item @var{XX@dots{}}
33710 Memory contents; each byte is transmitted as a two-digit hexadecimal
33711 number. The reply may contain fewer bytes than requested if the
33712 server was able to read only part of the region of memory.
33717 @item M @var{addr},@var{length}:@var{XX@dots{}}
33718 @cindex @samp{M} packet
33719 Write @var{length} bytes of memory starting at address @var{addr}.
33720 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33721 hexadecimal number.
33728 for an error (this includes the case where only part of the data was
33733 @cindex @samp{p} packet
33734 Read the value of register @var{n}; @var{n} is in hex.
33735 @xref{read registers packet}, for a description of how the returned
33736 register value is encoded.
33740 @item @var{XX@dots{}}
33741 the register's value
33745 Indicating an unrecognized @var{query}.
33748 @item P @var{n@dots{}}=@var{r@dots{}}
33749 @anchor{write register packet}
33750 @cindex @samp{P} packet
33751 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33752 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33753 digits for each byte in the register (target byte order).
33763 @item q @var{name} @var{params}@dots{}
33764 @itemx Q @var{name} @var{params}@dots{}
33765 @cindex @samp{q} packet
33766 @cindex @samp{Q} packet
33767 General query (@samp{q}) and set (@samp{Q}). These packets are
33768 described fully in @ref{General Query Packets}.
33771 @cindex @samp{r} packet
33772 Reset the entire system.
33774 Don't use this packet; use the @samp{R} packet instead.
33777 @cindex @samp{R} packet
33778 Restart the program being debugged. @var{XX}, while needed, is ignored.
33779 This packet is only available in extended mode (@pxref{extended mode}).
33781 The @samp{R} packet has no reply.
33783 @item s @r{[}@var{addr}@r{]}
33784 @cindex @samp{s} packet
33785 Single step. @var{addr} is the address at which to resume. If
33786 @var{addr} is omitted, resume at same address.
33788 This packet is deprecated for multi-threading support. @xref{vCont
33792 @xref{Stop Reply Packets}, for the reply specifications.
33794 @item S @var{sig}@r{[};@var{addr}@r{]}
33795 @anchor{step with signal packet}
33796 @cindex @samp{S} packet
33797 Step with signal. This is analogous to the @samp{C} packet, but
33798 requests a single-step, rather than a normal resumption of execution.
33800 This packet is deprecated for multi-threading support. @xref{vCont
33804 @xref{Stop Reply Packets}, for the reply specifications.
33806 @item t @var{addr}:@var{PP},@var{MM}
33807 @cindex @samp{t} packet
33808 Search backwards starting at address @var{addr} for a match with pattern
33809 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33810 @var{addr} must be at least 3 digits.
33812 @item T @var{thread-id}
33813 @cindex @samp{T} packet
33814 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33819 thread is still alive
33825 Packets starting with @samp{v} are identified by a multi-letter name,
33826 up to the first @samp{;} or @samp{?} (or the end of the packet).
33828 @item vAttach;@var{pid}
33829 @cindex @samp{vAttach} packet
33830 Attach to a new process with the specified process ID @var{pid}.
33831 The process ID is a
33832 hexadecimal integer identifying the process. In all-stop mode, all
33833 threads in the attached process are stopped; in non-stop mode, it may be
33834 attached without being stopped if that is supported by the target.
33836 @c In non-stop mode, on a successful vAttach, the stub should set the
33837 @c current thread to a thread of the newly-attached process. After
33838 @c attaching, GDB queries for the attached process's thread ID with qC.
33839 @c Also note that, from a user perspective, whether or not the
33840 @c target is stopped on attach in non-stop mode depends on whether you
33841 @c use the foreground or background version of the attach command, not
33842 @c on what vAttach does; GDB does the right thing with respect to either
33843 @c stopping or restarting threads.
33845 This packet is only available in extended mode (@pxref{extended mode}).
33851 @item @r{Any stop packet}
33852 for success in all-stop mode (@pxref{Stop Reply Packets})
33854 for success in non-stop mode (@pxref{Remote Non-Stop})
33857 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33858 @cindex @samp{vCont} packet
33859 @anchor{vCont packet}
33860 Resume the inferior, specifying different actions for each thread.
33861 If an action is specified with no @var{thread-id}, then it is applied to any
33862 threads that don't have a specific action specified; if no default action is
33863 specified then other threads should remain stopped in all-stop mode and
33864 in their current state in non-stop mode.
33865 Specifying multiple
33866 default actions is an error; specifying no actions is also an error.
33867 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33869 Currently supported actions are:
33875 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33879 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33884 The optional argument @var{addr} normally associated with the
33885 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33886 not supported in @samp{vCont}.
33888 The @samp{t} action is only relevant in non-stop mode
33889 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33890 A stop reply should be generated for any affected thread not already stopped.
33891 When a thread is stopped by means of a @samp{t} action,
33892 the corresponding stop reply should indicate that the thread has stopped with
33893 signal @samp{0}, regardless of whether the target uses some other signal
33894 as an implementation detail.
33897 @xref{Stop Reply Packets}, for the reply specifications.
33900 @cindex @samp{vCont?} packet
33901 Request a list of actions supported by the @samp{vCont} packet.
33905 @item vCont@r{[};@var{action}@dots{}@r{]}
33906 The @samp{vCont} packet is supported. Each @var{action} is a supported
33907 command in the @samp{vCont} packet.
33909 The @samp{vCont} packet is not supported.
33912 @item vFile:@var{operation}:@var{parameter}@dots{}
33913 @cindex @samp{vFile} packet
33914 Perform a file operation on the target system. For details,
33915 see @ref{Host I/O Packets}.
33917 @item vFlashErase:@var{addr},@var{length}
33918 @cindex @samp{vFlashErase} packet
33919 Direct the stub to erase @var{length} bytes of flash starting at
33920 @var{addr}. The region may enclose any number of flash blocks, but
33921 its start and end must fall on block boundaries, as indicated by the
33922 flash block size appearing in the memory map (@pxref{Memory Map
33923 Format}). @value{GDBN} groups flash memory programming operations
33924 together, and sends a @samp{vFlashDone} request after each group; the
33925 stub is allowed to delay erase operation until the @samp{vFlashDone}
33926 packet is received.
33928 The stub must support @samp{vCont} if it reports support for
33929 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
33930 this case @samp{vCont} actions can be specified to apply to all threads
33931 in a process by using the @samp{p@var{pid}.-1} form of the
33942 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
33943 @cindex @samp{vFlashWrite} packet
33944 Direct the stub to write data to flash address @var{addr}. The data
33945 is passed in binary form using the same encoding as for the @samp{X}
33946 packet (@pxref{Binary Data}). The memory ranges specified by
33947 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
33948 not overlap, and must appear in order of increasing addresses
33949 (although @samp{vFlashErase} packets for higher addresses may already
33950 have been received; the ordering is guaranteed only between
33951 @samp{vFlashWrite} packets). If a packet writes to an address that was
33952 neither erased by a preceding @samp{vFlashErase} packet nor by some other
33953 target-specific method, the results are unpredictable.
33961 for vFlashWrite addressing non-flash memory
33967 @cindex @samp{vFlashDone} packet
33968 Indicate to the stub that flash programming operation is finished.
33969 The stub is permitted to delay or batch the effects of a group of
33970 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
33971 @samp{vFlashDone} packet is received. The contents of the affected
33972 regions of flash memory are unpredictable until the @samp{vFlashDone}
33973 request is completed.
33975 @item vKill;@var{pid}
33976 @cindex @samp{vKill} packet
33977 Kill the process with the specified process ID. @var{pid} is a
33978 hexadecimal integer identifying the process. This packet is used in
33979 preference to @samp{k} when multiprocess protocol extensions are
33980 supported; see @ref{multiprocess extensions}.
33990 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
33991 @cindex @samp{vRun} packet
33992 Run the program @var{filename}, passing it each @var{argument} on its
33993 command line. The file and arguments are hex-encoded strings. If
33994 @var{filename} is an empty string, the stub may use a default program
33995 (e.g.@: the last program run). The program is created in the stopped
33998 @c FIXME: What about non-stop mode?
34000 This packet is only available in extended mode (@pxref{extended mode}).
34006 @item @r{Any stop packet}
34007 for success (@pxref{Stop Reply Packets})
34011 @anchor{vStopped packet}
34012 @cindex @samp{vStopped} packet
34014 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34015 reply and prompt for the stub to report another one.
34019 @item @r{Any stop packet}
34020 if there is another unreported stop event (@pxref{Stop Reply Packets})
34022 if there are no unreported stop events
34025 @item X @var{addr},@var{length}:@var{XX@dots{}}
34027 @cindex @samp{X} packet
34028 Write data to memory, where the data is transmitted in binary.
34029 @var{addr} is address, @var{length} is number of bytes,
34030 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34040 @item z @var{type},@var{addr},@var{kind}
34041 @itemx Z @var{type},@var{addr},@var{kind}
34042 @anchor{insert breakpoint or watchpoint packet}
34043 @cindex @samp{z} packet
34044 @cindex @samp{Z} packets
34045 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34046 watchpoint starting at address @var{address} of kind @var{kind}.
34048 Each breakpoint and watchpoint packet @var{type} is documented
34051 @emph{Implementation notes: A remote target shall return an empty string
34052 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34053 remote target shall support either both or neither of a given
34054 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34055 avoid potential problems with duplicate packets, the operations should
34056 be implemented in an idempotent way.}
34058 @item z0,@var{addr},@var{kind}
34059 @itemx Z0,@var{addr},@var{kind}
34060 @cindex @samp{z0} packet
34061 @cindex @samp{Z0} packet
34062 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34063 @var{addr} of type @var{kind}.
34065 A memory breakpoint is implemented by replacing the instruction at
34066 @var{addr} with a software breakpoint or trap instruction. The
34067 @var{kind} is target-specific and typically indicates the size of
34068 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34069 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34070 architectures have additional meanings for @var{kind};
34071 see @ref{Architecture-Specific Protocol Details}.
34073 @emph{Implementation note: It is possible for a target to copy or move
34074 code that contains memory breakpoints (e.g., when implementing
34075 overlays). The behavior of this packet, in the presence of such a
34076 target, is not defined.}
34088 @item z1,@var{addr},@var{kind}
34089 @itemx Z1,@var{addr},@var{kind}
34090 @cindex @samp{z1} packet
34091 @cindex @samp{Z1} packet
34092 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34093 address @var{addr}.
34095 A hardware breakpoint is implemented using a mechanism that is not
34096 dependant on being able to modify the target's memory. @var{kind}
34097 has the same meaning as in @samp{Z0} packets.
34099 @emph{Implementation note: A hardware breakpoint is not affected by code
34112 @item z2,@var{addr},@var{kind}
34113 @itemx Z2,@var{addr},@var{kind}
34114 @cindex @samp{z2} packet
34115 @cindex @samp{Z2} packet
34116 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34117 @var{kind} is interpreted as the number of bytes to watch.
34129 @item z3,@var{addr},@var{kind}
34130 @itemx Z3,@var{addr},@var{kind}
34131 @cindex @samp{z3} packet
34132 @cindex @samp{Z3} packet
34133 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34134 @var{kind} is interpreted as the number of bytes to watch.
34146 @item z4,@var{addr},@var{kind}
34147 @itemx Z4,@var{addr},@var{kind}
34148 @cindex @samp{z4} packet
34149 @cindex @samp{Z4} packet
34150 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34151 @var{kind} is interpreted as the number of bytes to watch.
34165 @node Stop Reply Packets
34166 @section Stop Reply Packets
34167 @cindex stop reply packets
34169 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34170 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34171 receive any of the below as a reply. Except for @samp{?}
34172 and @samp{vStopped}, that reply is only returned
34173 when the target halts. In the below the exact meaning of @dfn{signal
34174 number} is defined by the header @file{include/gdb/signals.h} in the
34175 @value{GDBN} source code.
34177 As in the description of request packets, we include spaces in the
34178 reply templates for clarity; these are not part of the reply packet's
34179 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34185 The program received signal number @var{AA} (a two-digit hexadecimal
34186 number). This is equivalent to a @samp{T} response with no
34187 @var{n}:@var{r} pairs.
34189 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34190 @cindex @samp{T} packet reply
34191 The program received signal number @var{AA} (a two-digit hexadecimal
34192 number). This is equivalent to an @samp{S} response, except that the
34193 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34194 and other information directly in the stop reply packet, reducing
34195 round-trip latency. Single-step and breakpoint traps are reported
34196 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34200 If @var{n} is a hexadecimal number, it is a register number, and the
34201 corresponding @var{r} gives that register's value. @var{r} is a
34202 series of bytes in target byte order, with each byte given by a
34203 two-digit hex number.
34206 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34207 the stopped thread, as specified in @ref{thread-id syntax}.
34210 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34211 the core on which the stop event was detected.
34214 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34215 specific event that stopped the target. The currently defined stop
34216 reasons are listed below. @var{aa} should be @samp{05}, the trap
34217 signal. At most one stop reason should be present.
34220 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34221 and go on to the next; this allows us to extend the protocol in the
34225 The currently defined stop reasons are:
34231 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34234 @cindex shared library events, remote reply
34236 The packet indicates that the loaded libraries have changed.
34237 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34238 list of loaded libraries. @var{r} is ignored.
34240 @cindex replay log events, remote reply
34242 The packet indicates that the target cannot continue replaying
34243 logged execution events, because it has reached the end (or the
34244 beginning when executing backward) of the log. The value of @var{r}
34245 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34246 for more information.
34250 @itemx W @var{AA} ; process:@var{pid}
34251 The process exited, and @var{AA} is the exit status. This is only
34252 applicable to certain targets.
34254 The second form of the response, including the process ID of the exited
34255 process, can be used only when @value{GDBN} has reported support for
34256 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34257 The @var{pid} is formatted as a big-endian hex string.
34260 @itemx X @var{AA} ; process:@var{pid}
34261 The process terminated with signal @var{AA}.
34263 The second form of the response, including the process ID of the
34264 terminated process, can be used only when @value{GDBN} has reported
34265 support for multiprocess protocol extensions; see @ref{multiprocess
34266 extensions}. The @var{pid} is formatted as a big-endian hex string.
34268 @item O @var{XX}@dots{}
34269 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34270 written as the program's console output. This can happen at any time
34271 while the program is running and the debugger should continue to wait
34272 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34274 @item F @var{call-id},@var{parameter}@dots{}
34275 @var{call-id} is the identifier which says which host system call should
34276 be called. This is just the name of the function. Translation into the
34277 correct system call is only applicable as it's defined in @value{GDBN}.
34278 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34281 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34282 this very system call.
34284 The target replies with this packet when it expects @value{GDBN} to
34285 call a host system call on behalf of the target. @value{GDBN} replies
34286 with an appropriate @samp{F} packet and keeps up waiting for the next
34287 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34288 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34289 Protocol Extension}, for more details.
34293 @node General Query Packets
34294 @section General Query Packets
34295 @cindex remote query requests
34297 Packets starting with @samp{q} are @dfn{general query packets};
34298 packets starting with @samp{Q} are @dfn{general set packets}. General
34299 query and set packets are a semi-unified form for retrieving and
34300 sending information to and from the stub.
34302 The initial letter of a query or set packet is followed by a name
34303 indicating what sort of thing the packet applies to. For example,
34304 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34305 definitions with the stub. These packet names follow some
34310 The name must not contain commas, colons or semicolons.
34312 Most @value{GDBN} query and set packets have a leading upper case
34315 The names of custom vendor packets should use a company prefix, in
34316 lower case, followed by a period. For example, packets designed at
34317 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34318 foos) or @samp{Qacme.bar} (for setting bars).
34321 The name of a query or set packet should be separated from any
34322 parameters by a @samp{:}; the parameters themselves should be
34323 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34324 full packet name, and check for a separator or the end of the packet,
34325 in case two packet names share a common prefix. New packets should not begin
34326 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34327 packets predate these conventions, and have arguments without any terminator
34328 for the packet name; we suspect they are in widespread use in places that
34329 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34330 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34333 Like the descriptions of the other packets, each description here
34334 has a template showing the packet's overall syntax, followed by an
34335 explanation of the packet's meaning. We include spaces in some of the
34336 templates for clarity; these are not part of the packet's syntax. No
34337 @value{GDBN} packet uses spaces to separate its components.
34339 Here are the currently defined query and set packets:
34343 @item QAllow:@var{op}:@var{val}@dots{}
34344 @cindex @samp{QAllow} packet
34345 Specify which operations @value{GDBN} expects to request of the
34346 target, as a semicolon-separated list of operation name and value
34347 pairs. Possible values for @var{op} include @samp{WriteReg},
34348 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34349 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34350 indicating that @value{GDBN} will not request the operation, or 1,
34351 indicating that it may. (The target can then use this to set up its
34352 own internals optimally, for instance if the debugger never expects to
34353 insert breakpoints, it may not need to install its own trap handler.)
34356 @cindex current thread, remote request
34357 @cindex @samp{qC} packet
34358 Return the current thread ID.
34362 @item QC @var{thread-id}
34363 Where @var{thread-id} is a thread ID as documented in
34364 @ref{thread-id syntax}.
34365 @item @r{(anything else)}
34366 Any other reply implies the old thread ID.
34369 @item qCRC:@var{addr},@var{length}
34370 @cindex CRC of memory block, remote request
34371 @cindex @samp{qCRC} packet
34372 Compute the CRC checksum of a block of memory using CRC-32 defined in
34373 IEEE 802.3. The CRC is computed byte at a time, taking the most
34374 significant bit of each byte first. The initial pattern code
34375 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34377 @emph{Note:} This is the same CRC used in validating separate debug
34378 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34379 Files}). However the algorithm is slightly different. When validating
34380 separate debug files, the CRC is computed taking the @emph{least}
34381 significant bit of each byte first, and the final result is inverted to
34382 detect trailing zeros.
34387 An error (such as memory fault)
34388 @item C @var{crc32}
34389 The specified memory region's checksum is @var{crc32}.
34392 @item QDisableRandomization:@var{value}
34393 @cindex disable address space randomization, remote request
34394 @cindex @samp{QDisableRandomization} packet
34395 Some target operating systems will randomize the virtual address space
34396 of the inferior process as a security feature, but provide a feature
34397 to disable such randomization, e.g.@: to allow for a more deterministic
34398 debugging experience. On such systems, this packet with a @var{value}
34399 of 1 directs the target to disable address space randomization for
34400 processes subsequently started via @samp{vRun} packets, while a packet
34401 with a @var{value} of 0 tells the target to enable address space
34404 This packet is only available in extended mode (@pxref{extended mode}).
34409 The request succeeded.
34412 An error occurred. @var{nn} are hex digits.
34415 An empty reply indicates that @samp{QDisableRandomization} is not supported
34419 This packet is not probed by default; the remote stub must request it,
34420 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34421 This should only be done on targets that actually support disabling
34422 address space randomization.
34425 @itemx qsThreadInfo
34426 @cindex list active threads, remote request
34427 @cindex @samp{qfThreadInfo} packet
34428 @cindex @samp{qsThreadInfo} packet
34429 Obtain a list of all active thread IDs from the target (OS). Since there
34430 may be too many active threads to fit into one reply packet, this query
34431 works iteratively: it may require more than one query/reply sequence to
34432 obtain the entire list of threads. The first query of the sequence will
34433 be the @samp{qfThreadInfo} query; subsequent queries in the
34434 sequence will be the @samp{qsThreadInfo} query.
34436 NOTE: This packet replaces the @samp{qL} query (see below).
34440 @item m @var{thread-id}
34442 @item m @var{thread-id},@var{thread-id}@dots{}
34443 a comma-separated list of thread IDs
34445 (lower case letter @samp{L}) denotes end of list.
34448 In response to each query, the target will reply with a list of one or
34449 more thread IDs, separated by commas.
34450 @value{GDBN} will respond to each reply with a request for more thread
34451 ids (using the @samp{qs} form of the query), until the target responds
34452 with @samp{l} (lower-case ell, for @dfn{last}).
34453 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34456 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34457 @cindex get thread-local storage address, remote request
34458 @cindex @samp{qGetTLSAddr} packet
34459 Fetch the address associated with thread local storage specified
34460 by @var{thread-id}, @var{offset}, and @var{lm}.
34462 @var{thread-id} is the thread ID associated with the
34463 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34465 @var{offset} is the (big endian, hex encoded) offset associated with the
34466 thread local variable. (This offset is obtained from the debug
34467 information associated with the variable.)
34469 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34470 load module associated with the thread local storage. For example,
34471 a @sc{gnu}/Linux system will pass the link map address of the shared
34472 object associated with the thread local storage under consideration.
34473 Other operating environments may choose to represent the load module
34474 differently, so the precise meaning of this parameter will vary.
34478 @item @var{XX}@dots{}
34479 Hex encoded (big endian) bytes representing the address of the thread
34480 local storage requested.
34483 An error occurred. @var{nn} are hex digits.
34486 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34489 @item qGetTIBAddr:@var{thread-id}
34490 @cindex get thread information block address
34491 @cindex @samp{qGetTIBAddr} packet
34492 Fetch address of the Windows OS specific Thread Information Block.
34494 @var{thread-id} is the thread ID associated with the thread.
34498 @item @var{XX}@dots{}
34499 Hex encoded (big endian) bytes representing the linear address of the
34500 thread information block.
34503 An error occured. This means that either the thread was not found, or the
34504 address could not be retrieved.
34507 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34510 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34511 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34512 digit) is one to indicate the first query and zero to indicate a
34513 subsequent query; @var{threadcount} (two hex digits) is the maximum
34514 number of threads the response packet can contain; and @var{nextthread}
34515 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34516 returned in the response as @var{argthread}.
34518 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34522 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34523 Where: @var{count} (two hex digits) is the number of threads being
34524 returned; @var{done} (one hex digit) is zero to indicate more threads
34525 and one indicates no further threads; @var{argthreadid} (eight hex
34526 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34527 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34528 digits). See @code{remote.c:parse_threadlist_response()}.
34532 @cindex section offsets, remote request
34533 @cindex @samp{qOffsets} packet
34534 Get section offsets that the target used when relocating the downloaded
34539 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34540 Relocate the @code{Text} section by @var{xxx} from its original address.
34541 Relocate the @code{Data} section by @var{yyy} from its original address.
34542 If the object file format provides segment information (e.g.@: @sc{elf}
34543 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34544 segments by the supplied offsets.
34546 @emph{Note: while a @code{Bss} offset may be included in the response,
34547 @value{GDBN} ignores this and instead applies the @code{Data} offset
34548 to the @code{Bss} section.}
34550 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34551 Relocate the first segment of the object file, which conventionally
34552 contains program code, to a starting address of @var{xxx}. If
34553 @samp{DataSeg} is specified, relocate the second segment, which
34554 conventionally contains modifiable data, to a starting address of
34555 @var{yyy}. @value{GDBN} will report an error if the object file
34556 does not contain segment information, or does not contain at least
34557 as many segments as mentioned in the reply. Extra segments are
34558 kept at fixed offsets relative to the last relocated segment.
34561 @item qP @var{mode} @var{thread-id}
34562 @cindex thread information, remote request
34563 @cindex @samp{qP} packet
34564 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34565 encoded 32 bit mode; @var{thread-id} is a thread ID
34566 (@pxref{thread-id syntax}).
34568 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34571 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34575 @cindex non-stop mode, remote request
34576 @cindex @samp{QNonStop} packet
34578 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34579 @xref{Remote Non-Stop}, for more information.
34584 The request succeeded.
34587 An error occurred. @var{nn} are hex digits.
34590 An empty reply indicates that @samp{QNonStop} is not supported by
34594 This packet is not probed by default; the remote stub must request it,
34595 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34596 Use of this packet is controlled by the @code{set non-stop} command;
34597 @pxref{Non-Stop Mode}.
34599 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34600 @cindex pass signals to inferior, remote request
34601 @cindex @samp{QPassSignals} packet
34602 @anchor{QPassSignals}
34603 Each listed @var{signal} should be passed directly to the inferior process.
34604 Signals are numbered identically to continue packets and stop replies
34605 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34606 strictly greater than the previous item. These signals do not need to stop
34607 the inferior, or be reported to @value{GDBN}. All other signals should be
34608 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34609 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34610 new list. This packet improves performance when using @samp{handle
34611 @var{signal} nostop noprint pass}.
34616 The request succeeded.
34619 An error occurred. @var{nn} are hex digits.
34622 An empty reply indicates that @samp{QPassSignals} is not supported by
34626 Use of this packet is controlled by the @code{set remote pass-signals}
34627 command (@pxref{Remote Configuration, set remote pass-signals}).
34628 This packet is not probed by default; the remote stub must request it,
34629 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34631 @item qRcmd,@var{command}
34632 @cindex execute remote command, remote request
34633 @cindex @samp{qRcmd} packet
34634 @var{command} (hex encoded) is passed to the local interpreter for
34635 execution. Invalid commands should be reported using the output
34636 string. Before the final result packet, the target may also respond
34637 with a number of intermediate @samp{O@var{output}} console output
34638 packets. @emph{Implementors should note that providing access to a
34639 stubs's interpreter may have security implications}.
34644 A command response with no output.
34646 A command response with the hex encoded output string @var{OUTPUT}.
34648 Indicate a badly formed request.
34650 An empty reply indicates that @samp{qRcmd} is not recognized.
34653 (Note that the @code{qRcmd} packet's name is separated from the
34654 command by a @samp{,}, not a @samp{:}, contrary to the naming
34655 conventions above. Please don't use this packet as a model for new
34658 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34659 @cindex searching memory, in remote debugging
34660 @cindex @samp{qSearch:memory} packet
34661 @anchor{qSearch memory}
34662 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34663 @var{address} and @var{length} are encoded in hex.
34664 @var{search-pattern} is a sequence of bytes, hex encoded.
34669 The pattern was not found.
34671 The pattern was found at @var{address}.
34673 A badly formed request or an error was encountered while searching memory.
34675 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34678 @item QStartNoAckMode
34679 @cindex @samp{QStartNoAckMode} packet
34680 @anchor{QStartNoAckMode}
34681 Request that the remote stub disable the normal @samp{+}/@samp{-}
34682 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34687 The stub has switched to no-acknowledgment mode.
34688 @value{GDBN} acknowledges this reponse,
34689 but neither the stub nor @value{GDBN} shall send or expect further
34690 @samp{+}/@samp{-} acknowledgments in the current connection.
34692 An empty reply indicates that the stub does not support no-acknowledgment mode.
34695 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34696 @cindex supported packets, remote query
34697 @cindex features of the remote protocol
34698 @cindex @samp{qSupported} packet
34699 @anchor{qSupported}
34700 Tell the remote stub about features supported by @value{GDBN}, and
34701 query the stub for features it supports. This packet allows
34702 @value{GDBN} and the remote stub to take advantage of each others'
34703 features. @samp{qSupported} also consolidates multiple feature probes
34704 at startup, to improve @value{GDBN} performance---a single larger
34705 packet performs better than multiple smaller probe packets on
34706 high-latency links. Some features may enable behavior which must not
34707 be on by default, e.g.@: because it would confuse older clients or
34708 stubs. Other features may describe packets which could be
34709 automatically probed for, but are not. These features must be
34710 reported before @value{GDBN} will use them. This ``default
34711 unsupported'' behavior is not appropriate for all packets, but it
34712 helps to keep the initial connection time under control with new
34713 versions of @value{GDBN} which support increasing numbers of packets.
34717 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34718 The stub supports or does not support each returned @var{stubfeature},
34719 depending on the form of each @var{stubfeature} (see below for the
34722 An empty reply indicates that @samp{qSupported} is not recognized,
34723 or that no features needed to be reported to @value{GDBN}.
34726 The allowed forms for each feature (either a @var{gdbfeature} in the
34727 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34731 @item @var{name}=@var{value}
34732 The remote protocol feature @var{name} is supported, and associated
34733 with the specified @var{value}. The format of @var{value} depends
34734 on the feature, but it must not include a semicolon.
34736 The remote protocol feature @var{name} is supported, and does not
34737 need an associated value.
34739 The remote protocol feature @var{name} is not supported.
34741 The remote protocol feature @var{name} may be supported, and
34742 @value{GDBN} should auto-detect support in some other way when it is
34743 needed. This form will not be used for @var{gdbfeature} notifications,
34744 but may be used for @var{stubfeature} responses.
34747 Whenever the stub receives a @samp{qSupported} request, the
34748 supplied set of @value{GDBN} features should override any previous
34749 request. This allows @value{GDBN} to put the stub in a known
34750 state, even if the stub had previously been communicating with
34751 a different version of @value{GDBN}.
34753 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34758 This feature indicates whether @value{GDBN} supports multiprocess
34759 extensions to the remote protocol. @value{GDBN} does not use such
34760 extensions unless the stub also reports that it supports them by
34761 including @samp{multiprocess+} in its @samp{qSupported} reply.
34762 @xref{multiprocess extensions}, for details.
34765 This feature indicates that @value{GDBN} supports the XML target
34766 description. If the stub sees @samp{xmlRegisters=} with target
34767 specific strings separated by a comma, it will report register
34771 This feature indicates whether @value{GDBN} supports the
34772 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34773 instruction reply packet}).
34776 Stubs should ignore any unknown values for
34777 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34778 packet supports receiving packets of unlimited length (earlier
34779 versions of @value{GDBN} may reject overly long responses). Additional values
34780 for @var{gdbfeature} may be defined in the future to let the stub take
34781 advantage of new features in @value{GDBN}, e.g.@: incompatible
34782 improvements in the remote protocol---the @samp{multiprocess} feature is
34783 an example of such a feature. The stub's reply should be independent
34784 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34785 describes all the features it supports, and then the stub replies with
34786 all the features it supports.
34788 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34789 responses, as long as each response uses one of the standard forms.
34791 Some features are flags. A stub which supports a flag feature
34792 should respond with a @samp{+} form response. Other features
34793 require values, and the stub should respond with an @samp{=}
34796 Each feature has a default value, which @value{GDBN} will use if
34797 @samp{qSupported} is not available or if the feature is not mentioned
34798 in the @samp{qSupported} response. The default values are fixed; a
34799 stub is free to omit any feature responses that match the defaults.
34801 Not all features can be probed, but for those which can, the probing
34802 mechanism is useful: in some cases, a stub's internal
34803 architecture may not allow the protocol layer to know some information
34804 about the underlying target in advance. This is especially common in
34805 stubs which may be configured for multiple targets.
34807 These are the currently defined stub features and their properties:
34809 @multitable @columnfractions 0.35 0.2 0.12 0.2
34810 @c NOTE: The first row should be @headitem, but we do not yet require
34811 @c a new enough version of Texinfo (4.7) to use @headitem.
34813 @tab Value Required
34817 @item @samp{PacketSize}
34822 @item @samp{qXfer:auxv:read}
34827 @item @samp{qXfer:features:read}
34832 @item @samp{qXfer:libraries:read}
34837 @item @samp{qXfer:memory-map:read}
34842 @item @samp{qXfer:sdata:read}
34847 @item @samp{qXfer:spu:read}
34852 @item @samp{qXfer:spu:write}
34857 @item @samp{qXfer:siginfo:read}
34862 @item @samp{qXfer:siginfo:write}
34867 @item @samp{qXfer:threads:read}
34872 @item @samp{qXfer:traceframe-info:read}
34877 @item @samp{qXfer:fdpic:read}
34882 @item @samp{QNonStop}
34887 @item @samp{QPassSignals}
34892 @item @samp{QStartNoAckMode}
34897 @item @samp{multiprocess}
34902 @item @samp{ConditionalTracepoints}
34907 @item @samp{ReverseContinue}
34912 @item @samp{ReverseStep}
34917 @item @samp{TracepointSource}
34922 @item @samp{QAllow}
34927 @item @samp{QDisableRandomization}
34932 @item @samp{EnableDisableTracepoints}
34937 @item @samp{tracenz}
34944 These are the currently defined stub features, in more detail:
34947 @cindex packet size, remote protocol
34948 @item PacketSize=@var{bytes}
34949 The remote stub can accept packets up to at least @var{bytes} in
34950 length. @value{GDBN} will send packets up to this size for bulk
34951 transfers, and will never send larger packets. This is a limit on the
34952 data characters in the packet, including the frame and checksum.
34953 There is no trailing NUL byte in a remote protocol packet; if the stub
34954 stores packets in a NUL-terminated format, it should allow an extra
34955 byte in its buffer for the NUL. If this stub feature is not supported,
34956 @value{GDBN} guesses based on the size of the @samp{g} packet response.
34958 @item qXfer:auxv:read
34959 The remote stub understands the @samp{qXfer:auxv:read} packet
34960 (@pxref{qXfer auxiliary vector read}).
34962 @item qXfer:features:read
34963 The remote stub understands the @samp{qXfer:features:read} packet
34964 (@pxref{qXfer target description read}).
34966 @item qXfer:libraries:read
34967 The remote stub understands the @samp{qXfer:libraries:read} packet
34968 (@pxref{qXfer library list read}).
34970 @item qXfer:memory-map:read
34971 The remote stub understands the @samp{qXfer:memory-map:read} packet
34972 (@pxref{qXfer memory map read}).
34974 @item qXfer:sdata:read
34975 The remote stub understands the @samp{qXfer:sdata:read} packet
34976 (@pxref{qXfer sdata read}).
34978 @item qXfer:spu:read
34979 The remote stub understands the @samp{qXfer:spu:read} packet
34980 (@pxref{qXfer spu read}).
34982 @item qXfer:spu:write
34983 The remote stub understands the @samp{qXfer:spu:write} packet
34984 (@pxref{qXfer spu write}).
34986 @item qXfer:siginfo:read
34987 The remote stub understands the @samp{qXfer:siginfo:read} packet
34988 (@pxref{qXfer siginfo read}).
34990 @item qXfer:siginfo:write
34991 The remote stub understands the @samp{qXfer:siginfo:write} packet
34992 (@pxref{qXfer siginfo write}).
34994 @item qXfer:threads:read
34995 The remote stub understands the @samp{qXfer:threads:read} packet
34996 (@pxref{qXfer threads read}).
34998 @item qXfer:traceframe-info:read
34999 The remote stub understands the @samp{qXfer:traceframe-info:read}
35000 packet (@pxref{qXfer traceframe info read}).
35002 @item qXfer:fdpic:read
35003 The remote stub understands the @samp{qXfer:fdpic:read}
35004 packet (@pxref{qXfer fdpic loadmap read}).
35007 The remote stub understands the @samp{QNonStop} packet
35008 (@pxref{QNonStop}).
35011 The remote stub understands the @samp{QPassSignals} packet
35012 (@pxref{QPassSignals}).
35014 @item QStartNoAckMode
35015 The remote stub understands the @samp{QStartNoAckMode} packet and
35016 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35019 @anchor{multiprocess extensions}
35020 @cindex multiprocess extensions, in remote protocol
35021 The remote stub understands the multiprocess extensions to the remote
35022 protocol syntax. The multiprocess extensions affect the syntax of
35023 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35024 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35025 replies. Note that reporting this feature indicates support for the
35026 syntactic extensions only, not that the stub necessarily supports
35027 debugging of more than one process at a time. The stub must not use
35028 multiprocess extensions in packet replies unless @value{GDBN} has also
35029 indicated it supports them in its @samp{qSupported} request.
35031 @item qXfer:osdata:read
35032 The remote stub understands the @samp{qXfer:osdata:read} packet
35033 ((@pxref{qXfer osdata read}).
35035 @item ConditionalTracepoints
35036 The remote stub accepts and implements conditional expressions defined
35037 for tracepoints (@pxref{Tracepoint Conditions}).
35039 @item ReverseContinue
35040 The remote stub accepts and implements the reverse continue packet
35044 The remote stub accepts and implements the reverse step packet
35047 @item TracepointSource
35048 The remote stub understands the @samp{QTDPsrc} packet that supplies
35049 the source form of tracepoint definitions.
35052 The remote stub understands the @samp{QAllow} packet.
35054 @item QDisableRandomization
35055 The remote stub understands the @samp{QDisableRandomization} packet.
35057 @item StaticTracepoint
35058 @cindex static tracepoints, in remote protocol
35059 The remote stub supports static tracepoints.
35061 @item InstallInTrace
35062 @anchor{install tracepoint in tracing}
35063 The remote stub supports installing tracepoint in tracing.
35065 @item EnableDisableTracepoints
35066 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35067 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35068 to be enabled and disabled while a trace experiment is running.
35071 @cindex string tracing, in remote protocol
35072 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35073 See @ref{Bytecode Descriptions} for details about the bytecode.
35078 @cindex symbol lookup, remote request
35079 @cindex @samp{qSymbol} packet
35080 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35081 requests. Accept requests from the target for the values of symbols.
35086 The target does not need to look up any (more) symbols.
35087 @item qSymbol:@var{sym_name}
35088 The target requests the value of symbol @var{sym_name} (hex encoded).
35089 @value{GDBN} may provide the value by using the
35090 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35094 @item qSymbol:@var{sym_value}:@var{sym_name}
35095 Set the value of @var{sym_name} to @var{sym_value}.
35097 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35098 target has previously requested.
35100 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35101 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35107 The target does not need to look up any (more) symbols.
35108 @item qSymbol:@var{sym_name}
35109 The target requests the value of a new symbol @var{sym_name} (hex
35110 encoded). @value{GDBN} will continue to supply the values of symbols
35111 (if available), until the target ceases to request them.
35116 @item QTDisconnected
35123 @itemx qTMinFTPILen
35125 @xref{Tracepoint Packets}.
35127 @item qThreadExtraInfo,@var{thread-id}
35128 @cindex thread attributes info, remote request
35129 @cindex @samp{qThreadExtraInfo} packet
35130 Obtain a printable string description of a thread's attributes from
35131 the target OS. @var{thread-id} is a thread ID;
35132 see @ref{thread-id syntax}. This
35133 string may contain anything that the target OS thinks is interesting
35134 for @value{GDBN} to tell the user about the thread. The string is
35135 displayed in @value{GDBN}'s @code{info threads} display. Some
35136 examples of possible thread extra info strings are @samp{Runnable}, or
35137 @samp{Blocked on Mutex}.
35141 @item @var{XX}@dots{}
35142 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35143 comprising the printable string containing the extra information about
35144 the thread's attributes.
35147 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35148 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35149 conventions above. Please don't use this packet as a model for new
35168 @xref{Tracepoint Packets}.
35170 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35171 @cindex read special object, remote request
35172 @cindex @samp{qXfer} packet
35173 @anchor{qXfer read}
35174 Read uninterpreted bytes from the target's special data area
35175 identified by the keyword @var{object}. Request @var{length} bytes
35176 starting at @var{offset} bytes into the data. The content and
35177 encoding of @var{annex} is specific to @var{object}; it can supply
35178 additional details about what data to access.
35180 Here are the specific requests of this form defined so far. All
35181 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35182 formats, listed below.
35185 @item qXfer:auxv:read::@var{offset},@var{length}
35186 @anchor{qXfer auxiliary vector read}
35187 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35188 auxiliary vector}. Note @var{annex} must be empty.
35190 This packet is not probed by default; the remote stub must request it,
35191 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35193 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35194 @anchor{qXfer target description read}
35195 Access the @dfn{target description}. @xref{Target Descriptions}. The
35196 annex specifies which XML document to access. The main description is
35197 always loaded from the @samp{target.xml} annex.
35199 This packet is not probed by default; the remote stub must request it,
35200 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35202 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35203 @anchor{qXfer library list read}
35204 Access the target's list of loaded libraries. @xref{Library List Format}.
35205 The annex part of the generic @samp{qXfer} packet must be empty
35206 (@pxref{qXfer read}).
35208 Targets which maintain a list of libraries in the program's memory do
35209 not need to implement this packet; it is designed for platforms where
35210 the operating system manages the list of loaded libraries.
35212 This packet is not probed by default; the remote stub must request it,
35213 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35215 @item qXfer:memory-map:read::@var{offset},@var{length}
35216 @anchor{qXfer memory map read}
35217 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35218 annex part of the generic @samp{qXfer} packet must be empty
35219 (@pxref{qXfer read}).
35221 This packet is not probed by default; the remote stub must request it,
35222 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35224 @item qXfer:sdata:read::@var{offset},@var{length}
35225 @anchor{qXfer sdata read}
35227 Read contents of the extra collected static tracepoint marker
35228 information. The annex part of the generic @samp{qXfer} packet must
35229 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35232 This packet is not probed by default; the remote stub must request it,
35233 by supplying an appropriate @samp{qSupported} response
35234 (@pxref{qSupported}).
35236 @item qXfer:siginfo:read::@var{offset},@var{length}
35237 @anchor{qXfer siginfo read}
35238 Read contents of the extra signal information on the target
35239 system. The annex part of the generic @samp{qXfer} packet must be
35240 empty (@pxref{qXfer read}).
35242 This packet is not probed by default; the remote stub must request it,
35243 by supplying an appropriate @samp{qSupported} response
35244 (@pxref{qSupported}).
35246 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35247 @anchor{qXfer spu read}
35248 Read contents of an @code{spufs} file on the target system. The
35249 annex specifies which file to read; it must be of the form
35250 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35251 in the target process, and @var{name} identifes the @code{spufs} file
35252 in that context to be accessed.
35254 This packet is not probed by default; the remote stub must request it,
35255 by supplying an appropriate @samp{qSupported} response
35256 (@pxref{qSupported}).
35258 @item qXfer:threads:read::@var{offset},@var{length}
35259 @anchor{qXfer threads read}
35260 Access the list of threads on target. @xref{Thread List Format}. The
35261 annex part of the generic @samp{qXfer} packet must be empty
35262 (@pxref{qXfer read}).
35264 This packet is not probed by default; the remote stub must request it,
35265 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35267 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35268 @anchor{qXfer traceframe info read}
35270 Return a description of the current traceframe's contents.
35271 @xref{Traceframe Info Format}. The annex part of the generic
35272 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35274 This packet is not probed by default; the remote stub must request it,
35275 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35277 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35278 @anchor{qXfer fdpic loadmap read}
35279 Read contents of @code{loadmap}s on the target system. The
35280 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35281 executable @code{loadmap} or interpreter @code{loadmap} to read.
35283 This packet is not probed by default; the remote stub must request it,
35284 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35286 @item qXfer:osdata:read::@var{offset},@var{length}
35287 @anchor{qXfer osdata read}
35288 Access the target's @dfn{operating system information}.
35289 @xref{Operating System Information}.
35296 Data @var{data} (@pxref{Binary Data}) has been read from the
35297 target. There may be more data at a higher address (although
35298 it is permitted to return @samp{m} even for the last valid
35299 block of data, as long as at least one byte of data was read).
35300 @var{data} may have fewer bytes than the @var{length} in the
35304 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35305 There is no more data to be read. @var{data} may have fewer bytes
35306 than the @var{length} in the request.
35309 The @var{offset} in the request is at the end of the data.
35310 There is no more data to be read.
35313 The request was malformed, or @var{annex} was invalid.
35316 The offset was invalid, or there was an error encountered reading the data.
35317 @var{nn} is a hex-encoded @code{errno} value.
35320 An empty reply indicates the @var{object} string was not recognized by
35321 the stub, or that the object does not support reading.
35324 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35325 @cindex write data into object, remote request
35326 @anchor{qXfer write}
35327 Write uninterpreted bytes into the target's special data area
35328 identified by the keyword @var{object}, starting at @var{offset} bytes
35329 into the data. @var{data}@dots{} is the binary-encoded data
35330 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35331 is specific to @var{object}; it can supply additional details about what data
35334 Here are the specific requests of this form defined so far. All
35335 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35336 formats, listed below.
35339 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35340 @anchor{qXfer siginfo write}
35341 Write @var{data} to the extra signal information on the target system.
35342 The annex part of the generic @samp{qXfer} packet must be
35343 empty (@pxref{qXfer write}).
35345 This packet is not probed by default; the remote stub must request it,
35346 by supplying an appropriate @samp{qSupported} response
35347 (@pxref{qSupported}).
35349 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35350 @anchor{qXfer spu write}
35351 Write @var{data} to an @code{spufs} file on the target system. The
35352 annex specifies which file to write; it must be of the form
35353 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35354 in the target process, and @var{name} identifes the @code{spufs} file
35355 in that context to be accessed.
35357 This packet is not probed by default; the remote stub must request it,
35358 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35364 @var{nn} (hex encoded) is the number of bytes written.
35365 This may be fewer bytes than supplied in the request.
35368 The request was malformed, or @var{annex} was invalid.
35371 The offset was invalid, or there was an error encountered writing the data.
35372 @var{nn} is a hex-encoded @code{errno} value.
35375 An empty reply indicates the @var{object} string was not
35376 recognized by the stub, or that the object does not support writing.
35379 @item qXfer:@var{object}:@var{operation}:@dots{}
35380 Requests of this form may be added in the future. When a stub does
35381 not recognize the @var{object} keyword, or its support for
35382 @var{object} does not recognize the @var{operation} keyword, the stub
35383 must respond with an empty packet.
35385 @item qAttached:@var{pid}
35386 @cindex query attached, remote request
35387 @cindex @samp{qAttached} packet
35388 Return an indication of whether the remote server attached to an
35389 existing process or created a new process. When the multiprocess
35390 protocol extensions are supported (@pxref{multiprocess extensions}),
35391 @var{pid} is an integer in hexadecimal format identifying the target
35392 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35393 the query packet will be simplified as @samp{qAttached}.
35395 This query is used, for example, to know whether the remote process
35396 should be detached or killed when a @value{GDBN} session is ended with
35397 the @code{quit} command.
35402 The remote server attached to an existing process.
35404 The remote server created a new process.
35406 A badly formed request or an error was encountered.
35411 @node Architecture-Specific Protocol Details
35412 @section Architecture-Specific Protocol Details
35414 This section describes how the remote protocol is applied to specific
35415 target architectures. Also see @ref{Standard Target Features}, for
35416 details of XML target descriptions for each architecture.
35420 @subsubsection Breakpoint Kinds
35422 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35427 16-bit Thumb mode breakpoint.
35430 32-bit Thumb mode (Thumb-2) breakpoint.
35433 32-bit ARM mode breakpoint.
35439 @subsubsection Register Packet Format
35441 The following @code{g}/@code{G} packets have previously been defined.
35442 In the below, some thirty-two bit registers are transferred as
35443 sixty-four bits. Those registers should be zero/sign extended (which?)
35444 to fill the space allocated. Register bytes are transferred in target
35445 byte order. The two nibbles within a register byte are transferred
35446 most-significant - least-significant.
35452 All registers are transferred as thirty-two bit quantities in the order:
35453 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35454 registers; fsr; fir; fp.
35458 All registers are transferred as sixty-four bit quantities (including
35459 thirty-two bit registers such as @code{sr}). The ordering is the same
35464 @node Tracepoint Packets
35465 @section Tracepoint Packets
35466 @cindex tracepoint packets
35467 @cindex packets, tracepoint
35469 Here we describe the packets @value{GDBN} uses to implement
35470 tracepoints (@pxref{Tracepoints}).
35474 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35475 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35476 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35477 the tracepoint is disabled. @var{step} is the tracepoint's step
35478 count, and @var{pass} is its pass count. If an @samp{F} is present,
35479 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35480 the number of bytes that the target should copy elsewhere to make room
35481 for the tracepoint. If an @samp{X} is present, it introduces a
35482 tracepoint condition, which consists of a hexadecimal length, followed
35483 by a comma and hex-encoded bytes, in a manner similar to action
35484 encodings as described below. If the trailing @samp{-} is present,
35485 further @samp{QTDP} packets will follow to specify this tracepoint's
35491 The packet was understood and carried out.
35493 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35495 The packet was not recognized.
35498 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35499 Define actions to be taken when a tracepoint is hit. @var{n} and
35500 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35501 this tracepoint. This packet may only be sent immediately after
35502 another @samp{QTDP} packet that ended with a @samp{-}. If the
35503 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35504 specifying more actions for this tracepoint.
35506 In the series of action packets for a given tracepoint, at most one
35507 can have an @samp{S} before its first @var{action}. If such a packet
35508 is sent, it and the following packets define ``while-stepping''
35509 actions. Any prior packets define ordinary actions --- that is, those
35510 taken when the tracepoint is first hit. If no action packet has an
35511 @samp{S}, then all the packets in the series specify ordinary
35512 tracepoint actions.
35514 The @samp{@var{action}@dots{}} portion of the packet is a series of
35515 actions, concatenated without separators. Each action has one of the
35521 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35522 a hexadecimal number whose @var{i}'th bit is set if register number
35523 @var{i} should be collected. (The least significant bit is numbered
35524 zero.) Note that @var{mask} may be any number of digits long; it may
35525 not fit in a 32-bit word.
35527 @item M @var{basereg},@var{offset},@var{len}
35528 Collect @var{len} bytes of memory starting at the address in register
35529 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35530 @samp{-1}, then the range has a fixed address: @var{offset} is the
35531 address of the lowest byte to collect. The @var{basereg},
35532 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35533 values (the @samp{-1} value for @var{basereg} is a special case).
35535 @item X @var{len},@var{expr}
35536 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35537 it directs. @var{expr} is an agent expression, as described in
35538 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35539 two-digit hex number in the packet; @var{len} is the number of bytes
35540 in the expression (and thus one-half the number of hex digits in the
35545 Any number of actions may be packed together in a single @samp{QTDP}
35546 packet, as long as the packet does not exceed the maximum packet
35547 length (400 bytes, for many stubs). There may be only one @samp{R}
35548 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35549 actions. Any registers referred to by @samp{M} and @samp{X} actions
35550 must be collected by a preceding @samp{R} action. (The
35551 ``while-stepping'' actions are treated as if they were attached to a
35552 separate tracepoint, as far as these restrictions are concerned.)
35557 The packet was understood and carried out.
35559 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35561 The packet was not recognized.
35564 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35565 @cindex @samp{QTDPsrc} packet
35566 Specify a source string of tracepoint @var{n} at address @var{addr}.
35567 This is useful to get accurate reproduction of the tracepoints
35568 originally downloaded at the beginning of the trace run. @var{type}
35569 is the name of the tracepoint part, such as @samp{cond} for the
35570 tracepoint's conditional expression (see below for a list of types), while
35571 @var{bytes} is the string, encoded in hexadecimal.
35573 @var{start} is the offset of the @var{bytes} within the overall source
35574 string, while @var{slen} is the total length of the source string.
35575 This is intended for handling source strings that are longer than will
35576 fit in a single packet.
35577 @c Add detailed example when this info is moved into a dedicated
35578 @c tracepoint descriptions section.
35580 The available string types are @samp{at} for the location,
35581 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35582 @value{GDBN} sends a separate packet for each command in the action
35583 list, in the same order in which the commands are stored in the list.
35585 The target does not need to do anything with source strings except
35586 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35589 Although this packet is optional, and @value{GDBN} will only send it
35590 if the target replies with @samp{TracepointSource} @xref{General
35591 Query Packets}, it makes both disconnected tracing and trace files
35592 much easier to use. Otherwise the user must be careful that the
35593 tracepoints in effect while looking at trace frames are identical to
35594 the ones in effect during the trace run; even a small discrepancy
35595 could cause @samp{tdump} not to work, or a particular trace frame not
35598 @item QTDV:@var{n}:@var{value}
35599 @cindex define trace state variable, remote request
35600 @cindex @samp{QTDV} packet
35601 Create a new trace state variable, number @var{n}, with an initial
35602 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35603 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35604 the option of not using this packet for initial values of zero; the
35605 target should simply create the trace state variables as they are
35606 mentioned in expressions.
35608 @item QTFrame:@var{n}
35609 Select the @var{n}'th tracepoint frame from the buffer, and use the
35610 register and memory contents recorded there to answer subsequent
35611 request packets from @value{GDBN}.
35613 A successful reply from the stub indicates that the stub has found the
35614 requested frame. The response is a series of parts, concatenated
35615 without separators, describing the frame we selected. Each part has
35616 one of the following forms:
35620 The selected frame is number @var{n} in the trace frame buffer;
35621 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35622 was no frame matching the criteria in the request packet.
35625 The selected trace frame records a hit of tracepoint number @var{t};
35626 @var{t} is a hexadecimal number.
35630 @item QTFrame:pc:@var{addr}
35631 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35632 currently selected frame whose PC is @var{addr};
35633 @var{addr} is a hexadecimal number.
35635 @item QTFrame:tdp:@var{t}
35636 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35637 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35638 is a hexadecimal number.
35640 @item QTFrame:range:@var{start}:@var{end}
35641 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35642 currently selected frame whose PC is between @var{start} (inclusive)
35643 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35646 @item QTFrame:outside:@var{start}:@var{end}
35647 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35648 frame @emph{outside} the given range of addresses (exclusive).
35651 This packet requests the minimum length of instruction at which a fast
35652 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
35653 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
35654 it depends on the target system being able to create trampolines in
35655 the first 64K of memory, which might or might not be possible for that
35656 system. So the reply to this packet will be 4 if it is able to
35663 The minimum instruction length is currently unknown.
35665 The minimum instruction length is @var{length}, where @var{length} is greater
35666 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
35667 that a fast tracepoint may be placed on any instruction regardless of size.
35669 An error has occurred.
35671 An empty reply indicates that the request is not supported by the stub.
35675 Begin the tracepoint experiment. Begin collecting data from
35676 tracepoint hits in the trace frame buffer. This packet supports the
35677 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35678 instruction reply packet}).
35681 End the tracepoint experiment. Stop collecting trace frames.
35683 @item QTEnable:@var{n}:@var{addr}
35685 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35686 experiment. If the tracepoint was previously disabled, then collection
35687 of data from it will resume.
35689 @item QTDisable:@var{n}:@var{addr}
35691 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35692 experiment. No more data will be collected from the tracepoint unless
35693 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35696 Clear the table of tracepoints, and empty the trace frame buffer.
35698 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35699 Establish the given ranges of memory as ``transparent''. The stub
35700 will answer requests for these ranges from memory's current contents,
35701 if they were not collected as part of the tracepoint hit.
35703 @value{GDBN} uses this to mark read-only regions of memory, like those
35704 containing program code. Since these areas never change, they should
35705 still have the same contents they did when the tracepoint was hit, so
35706 there's no reason for the stub to refuse to provide their contents.
35708 @item QTDisconnected:@var{value}
35709 Set the choice to what to do with the tracing run when @value{GDBN}
35710 disconnects from the target. A @var{value} of 1 directs the target to
35711 continue the tracing run, while 0 tells the target to stop tracing if
35712 @value{GDBN} is no longer in the picture.
35715 Ask the stub if there is a trace experiment running right now.
35717 The reply has the form:
35721 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35722 @var{running} is a single digit @code{1} if the trace is presently
35723 running, or @code{0} if not. It is followed by semicolon-separated
35724 optional fields that an agent may use to report additional status.
35728 If the trace is not running, the agent may report any of several
35729 explanations as one of the optional fields:
35734 No trace has been run yet.
35736 @item tstop[:@var{text}]:0
35737 The trace was stopped by a user-originated stop command. The optional
35738 @var{text} field is a user-supplied string supplied as part of the
35739 stop command (for instance, an explanation of why the trace was
35740 stopped manually). It is hex-encoded.
35743 The trace stopped because the trace buffer filled up.
35745 @item tdisconnected:0
35746 The trace stopped because @value{GDBN} disconnected from the target.
35748 @item tpasscount:@var{tpnum}
35749 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35751 @item terror:@var{text}:@var{tpnum}
35752 The trace stopped because tracepoint @var{tpnum} had an error. The
35753 string @var{text} is available to describe the nature of the error
35754 (for instance, a divide by zero in the condition expression).
35755 @var{text} is hex encoded.
35758 The trace stopped for some other reason.
35762 Additional optional fields supply statistical and other information.
35763 Although not required, they are extremely useful for users monitoring
35764 the progress of a trace run. If a trace has stopped, and these
35765 numbers are reported, they must reflect the state of the just-stopped
35770 @item tframes:@var{n}
35771 The number of trace frames in the buffer.
35773 @item tcreated:@var{n}
35774 The total number of trace frames created during the run. This may
35775 be larger than the trace frame count, if the buffer is circular.
35777 @item tsize:@var{n}
35778 The total size of the trace buffer, in bytes.
35780 @item tfree:@var{n}
35781 The number of bytes still unused in the buffer.
35783 @item circular:@var{n}
35784 The value of the circular trace buffer flag. @code{1} means that the
35785 trace buffer is circular and old trace frames will be discarded if
35786 necessary to make room, @code{0} means that the trace buffer is linear
35789 @item disconn:@var{n}
35790 The value of the disconnected tracing flag. @code{1} means that
35791 tracing will continue after @value{GDBN} disconnects, @code{0} means
35792 that the trace run will stop.
35796 @item qTP:@var{tp}:@var{addr}
35797 @cindex tracepoint status, remote request
35798 @cindex @samp{qTP} packet
35799 Ask the stub for the current state of tracepoint number @var{tp} at
35800 address @var{addr}.
35804 @item V@var{hits}:@var{usage}
35805 The tracepoint has been hit @var{hits} times so far during the trace
35806 run, and accounts for @var{usage} in the trace buffer. Note that
35807 @code{while-stepping} steps are not counted as separate hits, but the
35808 steps' space consumption is added into the usage number.
35812 @item qTV:@var{var}
35813 @cindex trace state variable value, remote request
35814 @cindex @samp{qTV} packet
35815 Ask the stub for the value of the trace state variable number @var{var}.
35820 The value of the variable is @var{value}. This will be the current
35821 value of the variable if the user is examining a running target, or a
35822 saved value if the variable was collected in the trace frame that the
35823 user is looking at. Note that multiple requests may result in
35824 different reply values, such as when requesting values while the
35825 program is running.
35828 The value of the variable is unknown. This would occur, for example,
35829 if the user is examining a trace frame in which the requested variable
35835 These packets request data about tracepoints that are being used by
35836 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35837 of data, and multiple @code{qTsP} to get additional pieces. Replies
35838 to these packets generally take the form of the @code{QTDP} packets
35839 that define tracepoints. (FIXME add detailed syntax)
35843 These packets request data about trace state variables that are on the
35844 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35845 and multiple @code{qTsV} to get additional variables. Replies to
35846 these packets follow the syntax of the @code{QTDV} packets that define
35847 trace state variables.
35851 These packets request data about static tracepoint markers that exist
35852 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35853 first piece of data, and multiple @code{qTsSTM} to get additional
35854 pieces. Replies to these packets take the following form:
35858 @item m @var{address}:@var{id}:@var{extra}
35860 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35861 a comma-separated list of markers
35863 (lower case letter @samp{L}) denotes end of list.
35865 An error occurred. @var{nn} are hex digits.
35867 An empty reply indicates that the request is not supported by the
35871 @var{address} is encoded in hex.
35872 @var{id} and @var{extra} are strings encoded in hex.
35874 In response to each query, the target will reply with a list of one or
35875 more markers, separated by commas. @value{GDBN} will respond to each
35876 reply with a request for more markers (using the @samp{qs} form of the
35877 query), until the target responds with @samp{l} (lower-case ell, for
35880 @item qTSTMat:@var{address}
35881 This packets requests data about static tracepoint markers in the
35882 target program at @var{address}. Replies to this packet follow the
35883 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35884 tracepoint markers.
35886 @item QTSave:@var{filename}
35887 This packet directs the target to save trace data to the file name
35888 @var{filename} in the target's filesystem. @var{filename} is encoded
35889 as a hex string; the interpretation of the file name (relative vs
35890 absolute, wild cards, etc) is up to the target.
35892 @item qTBuffer:@var{offset},@var{len}
35893 Return up to @var{len} bytes of the current contents of trace buffer,
35894 starting at @var{offset}. The trace buffer is treated as if it were
35895 a contiguous collection of traceframes, as per the trace file format.
35896 The reply consists as many hex-encoded bytes as the target can deliver
35897 in a packet; it is not an error to return fewer than were asked for.
35898 A reply consisting of just @code{l} indicates that no bytes are
35901 @item QTBuffer:circular:@var{value}
35902 This packet directs the target to use a circular trace buffer if
35903 @var{value} is 1, or a linear buffer if the value is 0.
35905 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
35906 This packet adds optional textual notes to the trace run. Allowable
35907 types include @code{user}, @code{notes}, and @code{tstop}, the
35908 @var{text} fields are arbitrary strings, hex-encoded.
35912 @subsection Relocate instruction reply packet
35913 When installing fast tracepoints in memory, the target may need to
35914 relocate the instruction currently at the tracepoint address to a
35915 different address in memory. For most instructions, a simple copy is
35916 enough, but, for example, call instructions that implicitly push the
35917 return address on the stack, and relative branches or other
35918 PC-relative instructions require offset adjustment, so that the effect
35919 of executing the instruction at a different address is the same as if
35920 it had executed in the original location.
35922 In response to several of the tracepoint packets, the target may also
35923 respond with a number of intermediate @samp{qRelocInsn} request
35924 packets before the final result packet, to have @value{GDBN} handle
35925 this relocation operation. If a packet supports this mechanism, its
35926 documentation will explicitly say so. See for example the above
35927 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
35928 format of the request is:
35931 @item qRelocInsn:@var{from};@var{to}
35933 This requests @value{GDBN} to copy instruction at address @var{from}
35934 to address @var{to}, possibly adjusted so that executing the
35935 instruction at @var{to} has the same effect as executing it at
35936 @var{from}. @value{GDBN} writes the adjusted instruction to target
35937 memory starting at @var{to}.
35942 @item qRelocInsn:@var{adjusted_size}
35943 Informs the stub the relocation is complete. @var{adjusted_size} is
35944 the length in bytes of resulting relocated instruction sequence.
35946 A badly formed request was detected, or an error was encountered while
35947 relocating the instruction.
35950 @node Host I/O Packets
35951 @section Host I/O Packets
35952 @cindex Host I/O, remote protocol
35953 @cindex file transfer, remote protocol
35955 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
35956 operations on the far side of a remote link. For example, Host I/O is
35957 used to upload and download files to a remote target with its own
35958 filesystem. Host I/O uses the same constant values and data structure
35959 layout as the target-initiated File-I/O protocol. However, the
35960 Host I/O packets are structured differently. The target-initiated
35961 protocol relies on target memory to store parameters and buffers.
35962 Host I/O requests are initiated by @value{GDBN}, and the
35963 target's memory is not involved. @xref{File-I/O Remote Protocol
35964 Extension}, for more details on the target-initiated protocol.
35966 The Host I/O request packets all encode a single operation along with
35967 its arguments. They have this format:
35971 @item vFile:@var{operation}: @var{parameter}@dots{}
35972 @var{operation} is the name of the particular request; the target
35973 should compare the entire packet name up to the second colon when checking
35974 for a supported operation. The format of @var{parameter} depends on
35975 the operation. Numbers are always passed in hexadecimal. Negative
35976 numbers have an explicit minus sign (i.e.@: two's complement is not
35977 used). Strings (e.g.@: filenames) are encoded as a series of
35978 hexadecimal bytes. The last argument to a system call may be a
35979 buffer of escaped binary data (@pxref{Binary Data}).
35983 The valid responses to Host I/O packets are:
35987 @item F @var{result} [, @var{errno}] [; @var{attachment}]
35988 @var{result} is the integer value returned by this operation, usually
35989 non-negative for success and -1 for errors. If an error has occured,
35990 @var{errno} will be included in the result. @var{errno} will have a
35991 value defined by the File-I/O protocol (@pxref{Errno Values}). For
35992 operations which return data, @var{attachment} supplies the data as a
35993 binary buffer. Binary buffers in response packets are escaped in the
35994 normal way (@pxref{Binary Data}). See the individual packet
35995 documentation for the interpretation of @var{result} and
35999 An empty response indicates that this operation is not recognized.
36003 These are the supported Host I/O operations:
36006 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36007 Open a file at @var{pathname} and return a file descriptor for it, or
36008 return -1 if an error occurs. @var{pathname} is a string,
36009 @var{flags} is an integer indicating a mask of open flags
36010 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36011 of mode bits to use if the file is created (@pxref{mode_t Values}).
36012 @xref{open}, for details of the open flags and mode values.
36014 @item vFile:close: @var{fd}
36015 Close the open file corresponding to @var{fd} and return 0, or
36016 -1 if an error occurs.
36018 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36019 Read data from the open file corresponding to @var{fd}. Up to
36020 @var{count} bytes will be read from the file, starting at @var{offset}
36021 relative to the start of the file. The target may read fewer bytes;
36022 common reasons include packet size limits and an end-of-file
36023 condition. The number of bytes read is returned. Zero should only be
36024 returned for a successful read at the end of the file, or if
36025 @var{count} was zero.
36027 The data read should be returned as a binary attachment on success.
36028 If zero bytes were read, the response should include an empty binary
36029 attachment (i.e.@: a trailing semicolon). The return value is the
36030 number of target bytes read; the binary attachment may be longer if
36031 some characters were escaped.
36033 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36034 Write @var{data} (a binary buffer) to the open file corresponding
36035 to @var{fd}. Start the write at @var{offset} from the start of the
36036 file. Unlike many @code{write} system calls, there is no
36037 separate @var{count} argument; the length of @var{data} in the
36038 packet is used. @samp{vFile:write} returns the number of bytes written,
36039 which may be shorter than the length of @var{data}, or -1 if an
36042 @item vFile:unlink: @var{pathname}
36043 Delete the file at @var{pathname} on the target. Return 0,
36044 or -1 if an error occurs. @var{pathname} is a string.
36049 @section Interrupts
36050 @cindex interrupts (remote protocol)
36052 When a program on the remote target is running, @value{GDBN} may
36053 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36054 a @code{BREAK} followed by @code{g},
36055 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36057 The precise meaning of @code{BREAK} is defined by the transport
36058 mechanism and may, in fact, be undefined. @value{GDBN} does not
36059 currently define a @code{BREAK} mechanism for any of the network
36060 interfaces except for TCP, in which case @value{GDBN} sends the
36061 @code{telnet} BREAK sequence.
36063 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36064 transport mechanisms. It is represented by sending the single byte
36065 @code{0x03} without any of the usual packet overhead described in
36066 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36067 transmitted as part of a packet, it is considered to be packet data
36068 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36069 (@pxref{X packet}), used for binary downloads, may include an unescaped
36070 @code{0x03} as part of its packet.
36072 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36073 When Linux kernel receives this sequence from serial port,
36074 it stops execution and connects to gdb.
36076 Stubs are not required to recognize these interrupt mechanisms and the
36077 precise meaning associated with receipt of the interrupt is
36078 implementation defined. If the target supports debugging of multiple
36079 threads and/or processes, it should attempt to interrupt all
36080 currently-executing threads and processes.
36081 If the stub is successful at interrupting the
36082 running program, it should send one of the stop
36083 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36084 of successfully stopping the program in all-stop mode, and a stop reply
36085 for each stopped thread in non-stop mode.
36086 Interrupts received while the
36087 program is stopped are discarded.
36089 @node Notification Packets
36090 @section Notification Packets
36091 @cindex notification packets
36092 @cindex packets, notification
36094 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36095 packets that require no acknowledgment. Both the GDB and the stub
36096 may send notifications (although the only notifications defined at
36097 present are sent by the stub). Notifications carry information
36098 without incurring the round-trip latency of an acknowledgment, and so
36099 are useful for low-impact communications where occasional packet loss
36102 A notification packet has the form @samp{% @var{data} #
36103 @var{checksum}}, where @var{data} is the content of the notification,
36104 and @var{checksum} is a checksum of @var{data}, computed and formatted
36105 as for ordinary @value{GDBN} packets. A notification's @var{data}
36106 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36107 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36108 to acknowledge the notification's receipt or to report its corruption.
36110 Every notification's @var{data} begins with a name, which contains no
36111 colon characters, followed by a colon character.
36113 Recipients should silently ignore corrupted notifications and
36114 notifications they do not understand. Recipients should restart
36115 timeout periods on receipt of a well-formed notification, whether or
36116 not they understand it.
36118 Senders should only send the notifications described here when this
36119 protocol description specifies that they are permitted. In the
36120 future, we may extend the protocol to permit existing notifications in
36121 new contexts; this rule helps older senders avoid confusing newer
36124 (Older versions of @value{GDBN} ignore bytes received until they see
36125 the @samp{$} byte that begins an ordinary packet, so new stubs may
36126 transmit notifications without fear of confusing older clients. There
36127 are no notifications defined for @value{GDBN} to send at the moment, but we
36128 assume that most older stubs would ignore them, as well.)
36130 The following notification packets from the stub to @value{GDBN} are
36134 @item Stop: @var{reply}
36135 Report an asynchronous stop event in non-stop mode.
36136 The @var{reply} has the form of a stop reply, as
36137 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36138 for information on how these notifications are acknowledged by
36142 @node Remote Non-Stop
36143 @section Remote Protocol Support for Non-Stop Mode
36145 @value{GDBN}'s remote protocol supports non-stop debugging of
36146 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36147 supports non-stop mode, it should report that to @value{GDBN} by including
36148 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36150 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36151 establishing a new connection with the stub. Entering non-stop mode
36152 does not alter the state of any currently-running threads, but targets
36153 must stop all threads in any already-attached processes when entering
36154 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36155 probe the target state after a mode change.
36157 In non-stop mode, when an attached process encounters an event that
36158 would otherwise be reported with a stop reply, it uses the
36159 asynchronous notification mechanism (@pxref{Notification Packets}) to
36160 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36161 in all processes are stopped when a stop reply is sent, in non-stop
36162 mode only the thread reporting the stop event is stopped. That is,
36163 when reporting a @samp{S} or @samp{T} response to indicate completion
36164 of a step operation, hitting a breakpoint, or a fault, only the
36165 affected thread is stopped; any other still-running threads continue
36166 to run. When reporting a @samp{W} or @samp{X} response, all running
36167 threads belonging to other attached processes continue to run.
36169 Only one stop reply notification at a time may be pending; if
36170 additional stop events occur before @value{GDBN} has acknowledged the
36171 previous notification, they must be queued by the stub for later
36172 synchronous transmission in response to @samp{vStopped} packets from
36173 @value{GDBN}. Because the notification mechanism is unreliable,
36174 the stub is permitted to resend a stop reply notification
36175 if it believes @value{GDBN} may not have received it. @value{GDBN}
36176 ignores additional stop reply notifications received before it has
36177 finished processing a previous notification and the stub has completed
36178 sending any queued stop events.
36180 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36181 notification at any time. Specifically, they may appear when
36182 @value{GDBN} is not otherwise reading input from the stub, or when
36183 @value{GDBN} is expecting to read a normal synchronous response or a
36184 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36185 Notification packets are distinct from any other communication from
36186 the stub so there is no ambiguity.
36188 After receiving a stop reply notification, @value{GDBN} shall
36189 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36190 as a regular, synchronous request to the stub. Such acknowledgment
36191 is not required to happen immediately, as @value{GDBN} is permitted to
36192 send other, unrelated packets to the stub first, which the stub should
36195 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36196 stop events to report to @value{GDBN}, it shall respond by sending a
36197 normal stop reply response. @value{GDBN} shall then send another
36198 @samp{vStopped} packet to solicit further responses; again, it is
36199 permitted to send other, unrelated packets as well which the stub
36200 should process normally.
36202 If the stub receives a @samp{vStopped} packet and there are no
36203 additional stop events to report, the stub shall return an @samp{OK}
36204 response. At this point, if further stop events occur, the stub shall
36205 send a new stop reply notification, @value{GDBN} shall accept the
36206 notification, and the process shall be repeated.
36208 In non-stop mode, the target shall respond to the @samp{?} packet as
36209 follows. First, any incomplete stop reply notification/@samp{vStopped}
36210 sequence in progress is abandoned. The target must begin a new
36211 sequence reporting stop events for all stopped threads, whether or not
36212 it has previously reported those events to @value{GDBN}. The first
36213 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36214 subsequent stop replies are sent as responses to @samp{vStopped} packets
36215 using the mechanism described above. The target must not send
36216 asynchronous stop reply notifications until the sequence is complete.
36217 If all threads are running when the target receives the @samp{?} packet,
36218 or if the target is not attached to any process, it shall respond
36221 @node Packet Acknowledgment
36222 @section Packet Acknowledgment
36224 @cindex acknowledgment, for @value{GDBN} remote
36225 @cindex packet acknowledgment, for @value{GDBN} remote
36226 By default, when either the host or the target machine receives a packet,
36227 the first response expected is an acknowledgment: either @samp{+} (to indicate
36228 the package was received correctly) or @samp{-} (to request retransmission).
36229 This mechanism allows the @value{GDBN} remote protocol to operate over
36230 unreliable transport mechanisms, such as a serial line.
36232 In cases where the transport mechanism is itself reliable (such as a pipe or
36233 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36234 It may be desirable to disable them in that case to reduce communication
36235 overhead, or for other reasons. This can be accomplished by means of the
36236 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36238 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36239 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36240 and response format still includes the normal checksum, as described in
36241 @ref{Overview}, but the checksum may be ignored by the receiver.
36243 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36244 no-acknowledgment mode, it should report that to @value{GDBN}
36245 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36246 @pxref{qSupported}.
36247 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36248 disabled via the @code{set remote noack-packet off} command
36249 (@pxref{Remote Configuration}),
36250 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36251 Only then may the stub actually turn off packet acknowledgments.
36252 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36253 response, which can be safely ignored by the stub.
36255 Note that @code{set remote noack-packet} command only affects negotiation
36256 between @value{GDBN} and the stub when subsequent connections are made;
36257 it does not affect the protocol acknowledgment state for any current
36259 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36260 new connection is established,
36261 there is also no protocol request to re-enable the acknowledgments
36262 for the current connection, once disabled.
36267 Example sequence of a target being re-started. Notice how the restart
36268 does not get any direct output:
36273 @emph{target restarts}
36276 <- @code{T001:1234123412341234}
36280 Example sequence of a target being stepped by a single instruction:
36283 -> @code{G1445@dots{}}
36288 <- @code{T001:1234123412341234}
36292 <- @code{1455@dots{}}
36296 @node File-I/O Remote Protocol Extension
36297 @section File-I/O Remote Protocol Extension
36298 @cindex File-I/O remote protocol extension
36301 * File-I/O Overview::
36302 * Protocol Basics::
36303 * The F Request Packet::
36304 * The F Reply Packet::
36305 * The Ctrl-C Message::
36307 * List of Supported Calls::
36308 * Protocol-specific Representation of Datatypes::
36310 * File-I/O Examples::
36313 @node File-I/O Overview
36314 @subsection File-I/O Overview
36315 @cindex file-i/o overview
36317 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36318 target to use the host's file system and console I/O to perform various
36319 system calls. System calls on the target system are translated into a
36320 remote protocol packet to the host system, which then performs the needed
36321 actions and returns a response packet to the target system.
36322 This simulates file system operations even on targets that lack file systems.
36324 The protocol is defined to be independent of both the host and target systems.
36325 It uses its own internal representation of datatypes and values. Both
36326 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36327 translating the system-dependent value representations into the internal
36328 protocol representations when data is transmitted.
36330 The communication is synchronous. A system call is possible only when
36331 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36332 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36333 the target is stopped to allow deterministic access to the target's
36334 memory. Therefore File-I/O is not interruptible by target signals. On
36335 the other hand, it is possible to interrupt File-I/O by a user interrupt
36336 (@samp{Ctrl-C}) within @value{GDBN}.
36338 The target's request to perform a host system call does not finish
36339 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36340 after finishing the system call, the target returns to continuing the
36341 previous activity (continue, step). No additional continue or step
36342 request from @value{GDBN} is required.
36345 (@value{GDBP}) continue
36346 <- target requests 'system call X'
36347 target is stopped, @value{GDBN} executes system call
36348 -> @value{GDBN} returns result
36349 ... target continues, @value{GDBN} returns to wait for the target
36350 <- target hits breakpoint and sends a Txx packet
36353 The protocol only supports I/O on the console and to regular files on
36354 the host file system. Character or block special devices, pipes,
36355 named pipes, sockets or any other communication method on the host
36356 system are not supported by this protocol.
36358 File I/O is not supported in non-stop mode.
36360 @node Protocol Basics
36361 @subsection Protocol Basics
36362 @cindex protocol basics, file-i/o
36364 The File-I/O protocol uses the @code{F} packet as the request as well
36365 as reply packet. Since a File-I/O system call can only occur when
36366 @value{GDBN} is waiting for a response from the continuing or stepping target,
36367 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36368 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36369 This @code{F} packet contains all information needed to allow @value{GDBN}
36370 to call the appropriate host system call:
36374 A unique identifier for the requested system call.
36377 All parameters to the system call. Pointers are given as addresses
36378 in the target memory address space. Pointers to strings are given as
36379 pointer/length pair. Numerical values are given as they are.
36380 Numerical control flags are given in a protocol-specific representation.
36384 At this point, @value{GDBN} has to perform the following actions.
36388 If the parameters include pointer values to data needed as input to a
36389 system call, @value{GDBN} requests this data from the target with a
36390 standard @code{m} packet request. This additional communication has to be
36391 expected by the target implementation and is handled as any other @code{m}
36395 @value{GDBN} translates all value from protocol representation to host
36396 representation as needed. Datatypes are coerced into the host types.
36399 @value{GDBN} calls the system call.
36402 It then coerces datatypes back to protocol representation.
36405 If the system call is expected to return data in buffer space specified
36406 by pointer parameters to the call, the data is transmitted to the
36407 target using a @code{M} or @code{X} packet. This packet has to be expected
36408 by the target implementation and is handled as any other @code{M} or @code{X}
36413 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36414 necessary information for the target to continue. This at least contains
36421 @code{errno}, if has been changed by the system call.
36428 After having done the needed type and value coercion, the target continues
36429 the latest continue or step action.
36431 @node The F Request Packet
36432 @subsection The @code{F} Request Packet
36433 @cindex file-i/o request packet
36434 @cindex @code{F} request packet
36436 The @code{F} request packet has the following format:
36439 @item F@var{call-id},@var{parameter@dots{}}
36441 @var{call-id} is the identifier to indicate the host system call to be called.
36442 This is just the name of the function.
36444 @var{parameter@dots{}} are the parameters to the system call.
36445 Parameters are hexadecimal integer values, either the actual values in case
36446 of scalar datatypes, pointers to target buffer space in case of compound
36447 datatypes and unspecified memory areas, or pointer/length pairs in case
36448 of string parameters. These are appended to the @var{call-id} as a
36449 comma-delimited list. All values are transmitted in ASCII
36450 string representation, pointer/length pairs separated by a slash.
36456 @node The F Reply Packet
36457 @subsection The @code{F} Reply Packet
36458 @cindex file-i/o reply packet
36459 @cindex @code{F} reply packet
36461 The @code{F} reply packet has the following format:
36465 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36467 @var{retcode} is the return code of the system call as hexadecimal value.
36469 @var{errno} is the @code{errno} set by the call, in protocol-specific
36471 This parameter can be omitted if the call was successful.
36473 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36474 case, @var{errno} must be sent as well, even if the call was successful.
36475 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36482 or, if the call was interrupted before the host call has been performed:
36489 assuming 4 is the protocol-specific representation of @code{EINTR}.
36494 @node The Ctrl-C Message
36495 @subsection The @samp{Ctrl-C} Message
36496 @cindex ctrl-c message, in file-i/o protocol
36498 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36499 reply packet (@pxref{The F Reply Packet}),
36500 the target should behave as if it had
36501 gotten a break message. The meaning for the target is ``system call
36502 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36503 (as with a break message) and return to @value{GDBN} with a @code{T02}
36506 It's important for the target to know in which
36507 state the system call was interrupted. There are two possible cases:
36511 The system call hasn't been performed on the host yet.
36514 The system call on the host has been finished.
36518 These two states can be distinguished by the target by the value of the
36519 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36520 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36521 on POSIX systems. In any other case, the target may presume that the
36522 system call has been finished --- successfully or not --- and should behave
36523 as if the break message arrived right after the system call.
36525 @value{GDBN} must behave reliably. If the system call has not been called
36526 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36527 @code{errno} in the packet. If the system call on the host has been finished
36528 before the user requests a break, the full action must be finished by
36529 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36530 The @code{F} packet may only be sent when either nothing has happened
36531 or the full action has been completed.
36534 @subsection Console I/O
36535 @cindex console i/o as part of file-i/o
36537 By default and if not explicitly closed by the target system, the file
36538 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36539 on the @value{GDBN} console is handled as any other file output operation
36540 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36541 by @value{GDBN} so that after the target read request from file descriptor
36542 0 all following typing is buffered until either one of the following
36547 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36549 system call is treated as finished.
36552 The user presses @key{RET}. This is treated as end of input with a trailing
36556 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36557 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36561 If the user has typed more characters than fit in the buffer given to
36562 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36563 either another @code{read(0, @dots{})} is requested by the target, or debugging
36564 is stopped at the user's request.
36567 @node List of Supported Calls
36568 @subsection List of Supported Calls
36569 @cindex list of supported file-i/o calls
36586 @unnumberedsubsubsec open
36587 @cindex open, file-i/o system call
36592 int open(const char *pathname, int flags);
36593 int open(const char *pathname, int flags, mode_t mode);
36597 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36600 @var{flags} is the bitwise @code{OR} of the following values:
36604 If the file does not exist it will be created. The host
36605 rules apply as far as file ownership and time stamps
36609 When used with @code{O_CREAT}, if the file already exists it is
36610 an error and open() fails.
36613 If the file already exists and the open mode allows
36614 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36615 truncated to zero length.
36618 The file is opened in append mode.
36621 The file is opened for reading only.
36624 The file is opened for writing only.
36627 The file is opened for reading and writing.
36631 Other bits are silently ignored.
36635 @var{mode} is the bitwise @code{OR} of the following values:
36639 User has read permission.
36642 User has write permission.
36645 Group has read permission.
36648 Group has write permission.
36651 Others have read permission.
36654 Others have write permission.
36658 Other bits are silently ignored.
36661 @item Return value:
36662 @code{open} returns the new file descriptor or -1 if an error
36669 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36672 @var{pathname} refers to a directory.
36675 The requested access is not allowed.
36678 @var{pathname} was too long.
36681 A directory component in @var{pathname} does not exist.
36684 @var{pathname} refers to a device, pipe, named pipe or socket.
36687 @var{pathname} refers to a file on a read-only filesystem and
36688 write access was requested.
36691 @var{pathname} is an invalid pointer value.
36694 No space on device to create the file.
36697 The process already has the maximum number of files open.
36700 The limit on the total number of files open on the system
36704 The call was interrupted by the user.
36710 @unnumberedsubsubsec close
36711 @cindex close, file-i/o system call
36720 @samp{Fclose,@var{fd}}
36722 @item Return value:
36723 @code{close} returns zero on success, or -1 if an error occurred.
36729 @var{fd} isn't a valid open file descriptor.
36732 The call was interrupted by the user.
36738 @unnumberedsubsubsec read
36739 @cindex read, file-i/o system call
36744 int read(int fd, void *buf, unsigned int count);
36748 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36750 @item Return value:
36751 On success, the number of bytes read is returned.
36752 Zero indicates end of file. If count is zero, read
36753 returns zero as well. On error, -1 is returned.
36759 @var{fd} is not a valid file descriptor or is not open for
36763 @var{bufptr} is an invalid pointer value.
36766 The call was interrupted by the user.
36772 @unnumberedsubsubsec write
36773 @cindex write, file-i/o system call
36778 int write(int fd, const void *buf, unsigned int count);
36782 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36784 @item Return value:
36785 On success, the number of bytes written are returned.
36786 Zero indicates nothing was written. On error, -1
36793 @var{fd} is not a valid file descriptor or is not open for
36797 @var{bufptr} is an invalid pointer value.
36800 An attempt was made to write a file that exceeds the
36801 host-specific maximum file size allowed.
36804 No space on device to write the data.
36807 The call was interrupted by the user.
36813 @unnumberedsubsubsec lseek
36814 @cindex lseek, file-i/o system call
36819 long lseek (int fd, long offset, int flag);
36823 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36825 @var{flag} is one of:
36829 The offset is set to @var{offset} bytes.
36832 The offset is set to its current location plus @var{offset}
36836 The offset is set to the size of the file plus @var{offset}
36840 @item Return value:
36841 On success, the resulting unsigned offset in bytes from
36842 the beginning of the file is returned. Otherwise, a
36843 value of -1 is returned.
36849 @var{fd} is not a valid open file descriptor.
36852 @var{fd} is associated with the @value{GDBN} console.
36855 @var{flag} is not a proper value.
36858 The call was interrupted by the user.
36864 @unnumberedsubsubsec rename
36865 @cindex rename, file-i/o system call
36870 int rename(const char *oldpath, const char *newpath);
36874 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36876 @item Return value:
36877 On success, zero is returned. On error, -1 is returned.
36883 @var{newpath} is an existing directory, but @var{oldpath} is not a
36887 @var{newpath} is a non-empty directory.
36890 @var{oldpath} or @var{newpath} is a directory that is in use by some
36894 An attempt was made to make a directory a subdirectory
36898 A component used as a directory in @var{oldpath} or new
36899 path is not a directory. Or @var{oldpath} is a directory
36900 and @var{newpath} exists but is not a directory.
36903 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
36906 No access to the file or the path of the file.
36910 @var{oldpath} or @var{newpath} was too long.
36913 A directory component in @var{oldpath} or @var{newpath} does not exist.
36916 The file is on a read-only filesystem.
36919 The device containing the file has no room for the new
36923 The call was interrupted by the user.
36929 @unnumberedsubsubsec unlink
36930 @cindex unlink, file-i/o system call
36935 int unlink(const char *pathname);
36939 @samp{Funlink,@var{pathnameptr}/@var{len}}
36941 @item Return value:
36942 On success, zero is returned. On error, -1 is returned.
36948 No access to the file or the path of the file.
36951 The system does not allow unlinking of directories.
36954 The file @var{pathname} cannot be unlinked because it's
36955 being used by another process.
36958 @var{pathnameptr} is an invalid pointer value.
36961 @var{pathname} was too long.
36964 A directory component in @var{pathname} does not exist.
36967 A component of the path is not a directory.
36970 The file is on a read-only filesystem.
36973 The call was interrupted by the user.
36979 @unnumberedsubsubsec stat/fstat
36980 @cindex fstat, file-i/o system call
36981 @cindex stat, file-i/o system call
36986 int stat(const char *pathname, struct stat *buf);
36987 int fstat(int fd, struct stat *buf);
36991 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
36992 @samp{Ffstat,@var{fd},@var{bufptr}}
36994 @item Return value:
36995 On success, zero is returned. On error, -1 is returned.
37001 @var{fd} is not a valid open file.
37004 A directory component in @var{pathname} does not exist or the
37005 path is an empty string.
37008 A component of the path is not a directory.
37011 @var{pathnameptr} is an invalid pointer value.
37014 No access to the file or the path of the file.
37017 @var{pathname} was too long.
37020 The call was interrupted by the user.
37026 @unnumberedsubsubsec gettimeofday
37027 @cindex gettimeofday, file-i/o system call
37032 int gettimeofday(struct timeval *tv, void *tz);
37036 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37038 @item Return value:
37039 On success, 0 is returned, -1 otherwise.
37045 @var{tz} is a non-NULL pointer.
37048 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37054 @unnumberedsubsubsec isatty
37055 @cindex isatty, file-i/o system call
37060 int isatty(int fd);
37064 @samp{Fisatty,@var{fd}}
37066 @item Return value:
37067 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37073 The call was interrupted by the user.
37078 Note that the @code{isatty} call is treated as a special case: it returns
37079 1 to the target if the file descriptor is attached
37080 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37081 would require implementing @code{ioctl} and would be more complex than
37086 @unnumberedsubsubsec system
37087 @cindex system, file-i/o system call
37092 int system(const char *command);
37096 @samp{Fsystem,@var{commandptr}/@var{len}}
37098 @item Return value:
37099 If @var{len} is zero, the return value indicates whether a shell is
37100 available. A zero return value indicates a shell is not available.
37101 For non-zero @var{len}, the value returned is -1 on error and the
37102 return status of the command otherwise. Only the exit status of the
37103 command is returned, which is extracted from the host's @code{system}
37104 return value by calling @code{WEXITSTATUS(retval)}. In case
37105 @file{/bin/sh} could not be executed, 127 is returned.
37111 The call was interrupted by the user.
37116 @value{GDBN} takes over the full task of calling the necessary host calls
37117 to perform the @code{system} call. The return value of @code{system} on
37118 the host is simplified before it's returned
37119 to the target. Any termination signal information from the child process
37120 is discarded, and the return value consists
37121 entirely of the exit status of the called command.
37123 Due to security concerns, the @code{system} call is by default refused
37124 by @value{GDBN}. The user has to allow this call explicitly with the
37125 @code{set remote system-call-allowed 1} command.
37128 @item set remote system-call-allowed
37129 @kindex set remote system-call-allowed
37130 Control whether to allow the @code{system} calls in the File I/O
37131 protocol for the remote target. The default is zero (disabled).
37133 @item show remote system-call-allowed
37134 @kindex show remote system-call-allowed
37135 Show whether the @code{system} calls are allowed in the File I/O
37139 @node Protocol-specific Representation of Datatypes
37140 @subsection Protocol-specific Representation of Datatypes
37141 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37144 * Integral Datatypes::
37146 * Memory Transfer::
37151 @node Integral Datatypes
37152 @unnumberedsubsubsec Integral Datatypes
37153 @cindex integral datatypes, in file-i/o protocol
37155 The integral datatypes used in the system calls are @code{int},
37156 @code{unsigned int}, @code{long}, @code{unsigned long},
37157 @code{mode_t}, and @code{time_t}.
37159 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37160 implemented as 32 bit values in this protocol.
37162 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37164 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37165 in @file{limits.h}) to allow range checking on host and target.
37167 @code{time_t} datatypes are defined as seconds since the Epoch.
37169 All integral datatypes transferred as part of a memory read or write of a
37170 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37173 @node Pointer Values
37174 @unnumberedsubsubsec Pointer Values
37175 @cindex pointer values, in file-i/o protocol
37177 Pointers to target data are transmitted as they are. An exception
37178 is made for pointers to buffers for which the length isn't
37179 transmitted as part of the function call, namely strings. Strings
37180 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37187 which is a pointer to data of length 18 bytes at position 0x1aaf.
37188 The length is defined as the full string length in bytes, including
37189 the trailing null byte. For example, the string @code{"hello world"}
37190 at address 0x123456 is transmitted as
37196 @node Memory Transfer
37197 @unnumberedsubsubsec Memory Transfer
37198 @cindex memory transfer, in file-i/o protocol
37200 Structured data which is transferred using a memory read or write (for
37201 example, a @code{struct stat}) is expected to be in a protocol-specific format
37202 with all scalar multibyte datatypes being big endian. Translation to
37203 this representation needs to be done both by the target before the @code{F}
37204 packet is sent, and by @value{GDBN} before
37205 it transfers memory to the target. Transferred pointers to structured
37206 data should point to the already-coerced data at any time.
37210 @unnumberedsubsubsec struct stat
37211 @cindex struct stat, in file-i/o protocol
37213 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37214 is defined as follows:
37218 unsigned int st_dev; /* device */
37219 unsigned int st_ino; /* inode */
37220 mode_t st_mode; /* protection */
37221 unsigned int st_nlink; /* number of hard links */
37222 unsigned int st_uid; /* user ID of owner */
37223 unsigned int st_gid; /* group ID of owner */
37224 unsigned int st_rdev; /* device type (if inode device) */
37225 unsigned long st_size; /* total size, in bytes */
37226 unsigned long st_blksize; /* blocksize for filesystem I/O */
37227 unsigned long st_blocks; /* number of blocks allocated */
37228 time_t st_atime; /* time of last access */
37229 time_t st_mtime; /* time of last modification */
37230 time_t st_ctime; /* time of last change */
37234 The integral datatypes conform to the definitions given in the
37235 appropriate section (see @ref{Integral Datatypes}, for details) so this
37236 structure is of size 64 bytes.
37238 The values of several fields have a restricted meaning and/or
37244 A value of 0 represents a file, 1 the console.
37247 No valid meaning for the target. Transmitted unchanged.
37250 Valid mode bits are described in @ref{Constants}. Any other
37251 bits have currently no meaning for the target.
37256 No valid meaning for the target. Transmitted unchanged.
37261 These values have a host and file system dependent
37262 accuracy. Especially on Windows hosts, the file system may not
37263 support exact timing values.
37266 The target gets a @code{struct stat} of the above representation and is
37267 responsible for coercing it to the target representation before
37270 Note that due to size differences between the host, target, and protocol
37271 representations of @code{struct stat} members, these members could eventually
37272 get truncated on the target.
37274 @node struct timeval
37275 @unnumberedsubsubsec struct timeval
37276 @cindex struct timeval, in file-i/o protocol
37278 The buffer of type @code{struct timeval} used by the File-I/O protocol
37279 is defined as follows:
37283 time_t tv_sec; /* second */
37284 long tv_usec; /* microsecond */
37288 The integral datatypes conform to the definitions given in the
37289 appropriate section (see @ref{Integral Datatypes}, for details) so this
37290 structure is of size 8 bytes.
37293 @subsection Constants
37294 @cindex constants, in file-i/o protocol
37296 The following values are used for the constants inside of the
37297 protocol. @value{GDBN} and target are responsible for translating these
37298 values before and after the call as needed.
37309 @unnumberedsubsubsec Open Flags
37310 @cindex open flags, in file-i/o protocol
37312 All values are given in hexadecimal representation.
37324 @node mode_t Values
37325 @unnumberedsubsubsec mode_t Values
37326 @cindex mode_t values, in file-i/o protocol
37328 All values are given in octal representation.
37345 @unnumberedsubsubsec Errno Values
37346 @cindex errno values, in file-i/o protocol
37348 All values are given in decimal representation.
37373 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37374 any error value not in the list of supported error numbers.
37377 @unnumberedsubsubsec Lseek Flags
37378 @cindex lseek flags, in file-i/o protocol
37387 @unnumberedsubsubsec Limits
37388 @cindex limits, in file-i/o protocol
37390 All values are given in decimal representation.
37393 INT_MIN -2147483648
37395 UINT_MAX 4294967295
37396 LONG_MIN -9223372036854775808
37397 LONG_MAX 9223372036854775807
37398 ULONG_MAX 18446744073709551615
37401 @node File-I/O Examples
37402 @subsection File-I/O Examples
37403 @cindex file-i/o examples
37405 Example sequence of a write call, file descriptor 3, buffer is at target
37406 address 0x1234, 6 bytes should be written:
37409 <- @code{Fwrite,3,1234,6}
37410 @emph{request memory read from target}
37413 @emph{return "6 bytes written"}
37417 Example sequence of a read call, file descriptor 3, buffer is at target
37418 address 0x1234, 6 bytes should be read:
37421 <- @code{Fread,3,1234,6}
37422 @emph{request memory write to target}
37423 -> @code{X1234,6:XXXXXX}
37424 @emph{return "6 bytes read"}
37428 Example sequence of a read call, call fails on the host due to invalid
37429 file descriptor (@code{EBADF}):
37432 <- @code{Fread,3,1234,6}
37436 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37440 <- @code{Fread,3,1234,6}
37445 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37449 <- @code{Fread,3,1234,6}
37450 -> @code{X1234,6:XXXXXX}
37454 @node Library List Format
37455 @section Library List Format
37456 @cindex library list format, remote protocol
37458 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37459 same process as your application to manage libraries. In this case,
37460 @value{GDBN} can use the loader's symbol table and normal memory
37461 operations to maintain a list of shared libraries. On other
37462 platforms, the operating system manages loaded libraries.
37463 @value{GDBN} can not retrieve the list of currently loaded libraries
37464 through memory operations, so it uses the @samp{qXfer:libraries:read}
37465 packet (@pxref{qXfer library list read}) instead. The remote stub
37466 queries the target's operating system and reports which libraries
37469 The @samp{qXfer:libraries:read} packet returns an XML document which
37470 lists loaded libraries and their offsets. Each library has an
37471 associated name and one or more segment or section base addresses,
37472 which report where the library was loaded in memory.
37474 For the common case of libraries that are fully linked binaries, the
37475 library should have a list of segments. If the target supports
37476 dynamic linking of a relocatable object file, its library XML element
37477 should instead include a list of allocated sections. The segment or
37478 section bases are start addresses, not relocation offsets; they do not
37479 depend on the library's link-time base addresses.
37481 @value{GDBN} must be linked with the Expat library to support XML
37482 library lists. @xref{Expat}.
37484 A simple memory map, with one loaded library relocated by a single
37485 offset, looks like this:
37489 <library name="/lib/libc.so.6">
37490 <segment address="0x10000000"/>
37495 Another simple memory map, with one loaded library with three
37496 allocated sections (.text, .data, .bss), looks like this:
37500 <library name="sharedlib.o">
37501 <section address="0x10000000"/>
37502 <section address="0x20000000"/>
37503 <section address="0x30000000"/>
37508 The format of a library list is described by this DTD:
37511 <!-- library-list: Root element with versioning -->
37512 <!ELEMENT library-list (library)*>
37513 <!ATTLIST library-list version CDATA #FIXED "1.0">
37514 <!ELEMENT library (segment*, section*)>
37515 <!ATTLIST library name CDATA #REQUIRED>
37516 <!ELEMENT segment EMPTY>
37517 <!ATTLIST segment address CDATA #REQUIRED>
37518 <!ELEMENT section EMPTY>
37519 <!ATTLIST section address CDATA #REQUIRED>
37522 In addition, segments and section descriptors cannot be mixed within a
37523 single library element, and you must supply at least one segment or
37524 section for each library.
37526 @node Memory Map Format
37527 @section Memory Map Format
37528 @cindex memory map format
37530 To be able to write into flash memory, @value{GDBN} needs to obtain a
37531 memory map from the target. This section describes the format of the
37534 The memory map is obtained using the @samp{qXfer:memory-map:read}
37535 (@pxref{qXfer memory map read}) packet and is an XML document that
37536 lists memory regions.
37538 @value{GDBN} must be linked with the Expat library to support XML
37539 memory maps. @xref{Expat}.
37541 The top-level structure of the document is shown below:
37544 <?xml version="1.0"?>
37545 <!DOCTYPE memory-map
37546 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37547 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37553 Each region can be either:
37558 A region of RAM starting at @var{addr} and extending for @var{length}
37562 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37567 A region of read-only memory:
37570 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37575 A region of flash memory, with erasure blocks @var{blocksize}
37579 <memory type="flash" start="@var{addr}" length="@var{length}">
37580 <property name="blocksize">@var{blocksize}</property>
37586 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37587 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37588 packets to write to addresses in such ranges.
37590 The formal DTD for memory map format is given below:
37593 <!-- ................................................... -->
37594 <!-- Memory Map XML DTD ................................ -->
37595 <!-- File: memory-map.dtd .............................. -->
37596 <!-- .................................... .............. -->
37597 <!-- memory-map.dtd -->
37598 <!-- memory-map: Root element with versioning -->
37599 <!ELEMENT memory-map (memory | property)>
37600 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37601 <!ELEMENT memory (property)>
37602 <!-- memory: Specifies a memory region,
37603 and its type, or device. -->
37604 <!ATTLIST memory type CDATA #REQUIRED
37605 start CDATA #REQUIRED
37606 length CDATA #REQUIRED
37607 device CDATA #IMPLIED>
37608 <!-- property: Generic attribute tag -->
37609 <!ELEMENT property (#PCDATA | property)*>
37610 <!ATTLIST property name CDATA #REQUIRED>
37613 @node Thread List Format
37614 @section Thread List Format
37615 @cindex thread list format
37617 To efficiently update the list of threads and their attributes,
37618 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37619 (@pxref{qXfer threads read}) and obtains the XML document with
37620 the following structure:
37623 <?xml version="1.0"?>
37625 <thread id="id" core="0">
37626 ... description ...
37631 Each @samp{thread} element must have the @samp{id} attribute that
37632 identifies the thread (@pxref{thread-id syntax}). The
37633 @samp{core} attribute, if present, specifies which processor core
37634 the thread was last executing on. The content of the of @samp{thread}
37635 element is interpreted as human-readable auxilliary information.
37637 @node Traceframe Info Format
37638 @section Traceframe Info Format
37639 @cindex traceframe info format
37641 To be able to know which objects in the inferior can be examined when
37642 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37643 memory ranges, registers and trace state variables that have been
37644 collected in a traceframe.
37646 This list is obtained using the @samp{qXfer:traceframe-info:read}
37647 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37649 @value{GDBN} must be linked with the Expat library to support XML
37650 traceframe info discovery. @xref{Expat}.
37652 The top-level structure of the document is shown below:
37655 <?xml version="1.0"?>
37656 <!DOCTYPE traceframe-info
37657 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37658 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37664 Each traceframe block can be either:
37669 A region of collected memory starting at @var{addr} and extending for
37670 @var{length} bytes from there:
37673 <memory start="@var{addr}" length="@var{length}"/>
37678 The formal DTD for the traceframe info format is given below:
37681 <!ELEMENT traceframe-info (memory)* >
37682 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37684 <!ELEMENT memory EMPTY>
37685 <!ATTLIST memory start CDATA #REQUIRED
37686 length CDATA #REQUIRED>
37689 @include agentexpr.texi
37691 @node Target Descriptions
37692 @appendix Target Descriptions
37693 @cindex target descriptions
37695 One of the challenges of using @value{GDBN} to debug embedded systems
37696 is that there are so many minor variants of each processor
37697 architecture in use. It is common practice for vendors to start with
37698 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37699 and then make changes to adapt it to a particular market niche. Some
37700 architectures have hundreds of variants, available from dozens of
37701 vendors. This leads to a number of problems:
37705 With so many different customized processors, it is difficult for
37706 the @value{GDBN} maintainers to keep up with the changes.
37708 Since individual variants may have short lifetimes or limited
37709 audiences, it may not be worthwhile to carry information about every
37710 variant in the @value{GDBN} source tree.
37712 When @value{GDBN} does support the architecture of the embedded system
37713 at hand, the task of finding the correct architecture name to give the
37714 @command{set architecture} command can be error-prone.
37717 To address these problems, the @value{GDBN} remote protocol allows a
37718 target system to not only identify itself to @value{GDBN}, but to
37719 actually describe its own features. This lets @value{GDBN} support
37720 processor variants it has never seen before --- to the extent that the
37721 descriptions are accurate, and that @value{GDBN} understands them.
37723 @value{GDBN} must be linked with the Expat library to support XML
37724 target descriptions. @xref{Expat}.
37727 * Retrieving Descriptions:: How descriptions are fetched from a target.
37728 * Target Description Format:: The contents of a target description.
37729 * Predefined Target Types:: Standard types available for target
37731 * Standard Target Features:: Features @value{GDBN} knows about.
37734 @node Retrieving Descriptions
37735 @section Retrieving Descriptions
37737 Target descriptions can be read from the target automatically, or
37738 specified by the user manually. The default behavior is to read the
37739 description from the target. @value{GDBN} retrieves it via the remote
37740 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37741 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37742 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37743 XML document, of the form described in @ref{Target Description
37746 Alternatively, you can specify a file to read for the target description.
37747 If a file is set, the target will not be queried. The commands to
37748 specify a file are:
37751 @cindex set tdesc filename
37752 @item set tdesc filename @var{path}
37753 Read the target description from @var{path}.
37755 @cindex unset tdesc filename
37756 @item unset tdesc filename
37757 Do not read the XML target description from a file. @value{GDBN}
37758 will use the description supplied by the current target.
37760 @cindex show tdesc filename
37761 @item show tdesc filename
37762 Show the filename to read for a target description, if any.
37766 @node Target Description Format
37767 @section Target Description Format
37768 @cindex target descriptions, XML format
37770 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37771 document which complies with the Document Type Definition provided in
37772 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37773 means you can use generally available tools like @command{xmllint} to
37774 check that your feature descriptions are well-formed and valid.
37775 However, to help people unfamiliar with XML write descriptions for
37776 their targets, we also describe the grammar here.
37778 Target descriptions can identify the architecture of the remote target
37779 and (for some architectures) provide information about custom register
37780 sets. They can also identify the OS ABI of the remote target.
37781 @value{GDBN} can use this information to autoconfigure for your
37782 target, or to warn you if you connect to an unsupported target.
37784 Here is a simple target description:
37787 <target version="1.0">
37788 <architecture>i386:x86-64</architecture>
37793 This minimal description only says that the target uses
37794 the x86-64 architecture.
37796 A target description has the following overall form, with [ ] marking
37797 optional elements and @dots{} marking repeatable elements. The elements
37798 are explained further below.
37801 <?xml version="1.0"?>
37802 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37803 <target version="1.0">
37804 @r{[}@var{architecture}@r{]}
37805 @r{[}@var{osabi}@r{]}
37806 @r{[}@var{compatible}@r{]}
37807 @r{[}@var{feature}@dots{}@r{]}
37812 The description is generally insensitive to whitespace and line
37813 breaks, under the usual common-sense rules. The XML version
37814 declaration and document type declaration can generally be omitted
37815 (@value{GDBN} does not require them), but specifying them may be
37816 useful for XML validation tools. The @samp{version} attribute for
37817 @samp{<target>} may also be omitted, but we recommend
37818 including it; if future versions of @value{GDBN} use an incompatible
37819 revision of @file{gdb-target.dtd}, they will detect and report
37820 the version mismatch.
37822 @subsection Inclusion
37823 @cindex target descriptions, inclusion
37826 @cindex <xi:include>
37829 It can sometimes be valuable to split a target description up into
37830 several different annexes, either for organizational purposes, or to
37831 share files between different possible target descriptions. You can
37832 divide a description into multiple files by replacing any element of
37833 the target description with an inclusion directive of the form:
37836 <xi:include href="@var{document}"/>
37840 When @value{GDBN} encounters an element of this form, it will retrieve
37841 the named XML @var{document}, and replace the inclusion directive with
37842 the contents of that document. If the current description was read
37843 using @samp{qXfer}, then so will be the included document;
37844 @var{document} will be interpreted as the name of an annex. If the
37845 current description was read from a file, @value{GDBN} will look for
37846 @var{document} as a file in the same directory where it found the
37847 original description.
37849 @subsection Architecture
37850 @cindex <architecture>
37852 An @samp{<architecture>} element has this form:
37855 <architecture>@var{arch}</architecture>
37858 @var{arch} is one of the architectures from the set accepted by
37859 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37862 @cindex @code{<osabi>}
37864 This optional field was introduced in @value{GDBN} version 7.0.
37865 Previous versions of @value{GDBN} ignore it.
37867 An @samp{<osabi>} element has this form:
37870 <osabi>@var{abi-name}</osabi>
37873 @var{abi-name} is an OS ABI name from the same selection accepted by
37874 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
37876 @subsection Compatible Architecture
37877 @cindex @code{<compatible>}
37879 This optional field was introduced in @value{GDBN} version 7.0.
37880 Previous versions of @value{GDBN} ignore it.
37882 A @samp{<compatible>} element has this form:
37885 <compatible>@var{arch}</compatible>
37888 @var{arch} is one of the architectures from the set accepted by
37889 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37891 A @samp{<compatible>} element is used to specify that the target
37892 is able to run binaries in some other than the main target architecture
37893 given by the @samp{<architecture>} element. For example, on the
37894 Cell Broadband Engine, the main architecture is @code{powerpc:common}
37895 or @code{powerpc:common64}, but the system is able to run binaries
37896 in the @code{spu} architecture as well. The way to describe this
37897 capability with @samp{<compatible>} is as follows:
37900 <architecture>powerpc:common</architecture>
37901 <compatible>spu</compatible>
37904 @subsection Features
37907 Each @samp{<feature>} describes some logical portion of the target
37908 system. Features are currently used to describe available CPU
37909 registers and the types of their contents. A @samp{<feature>} element
37913 <feature name="@var{name}">
37914 @r{[}@var{type}@dots{}@r{]}
37920 Each feature's name should be unique within the description. The name
37921 of a feature does not matter unless @value{GDBN} has some special
37922 knowledge of the contents of that feature; if it does, the feature
37923 should have its standard name. @xref{Standard Target Features}.
37927 Any register's value is a collection of bits which @value{GDBN} must
37928 interpret. The default interpretation is a two's complement integer,
37929 but other types can be requested by name in the register description.
37930 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
37931 Target Types}), and the description can define additional composite types.
37933 Each type element must have an @samp{id} attribute, which gives
37934 a unique (within the containing @samp{<feature>}) name to the type.
37935 Types must be defined before they are used.
37938 Some targets offer vector registers, which can be treated as arrays
37939 of scalar elements. These types are written as @samp{<vector>} elements,
37940 specifying the array element type, @var{type}, and the number of elements,
37944 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
37948 If a register's value is usefully viewed in multiple ways, define it
37949 with a union type containing the useful representations. The
37950 @samp{<union>} element contains one or more @samp{<field>} elements,
37951 each of which has a @var{name} and a @var{type}:
37954 <union id="@var{id}">
37955 <field name="@var{name}" type="@var{type}"/>
37961 If a register's value is composed from several separate values, define
37962 it with a structure type. There are two forms of the @samp{<struct>}
37963 element; a @samp{<struct>} element must either contain only bitfields
37964 or contain no bitfields. If the structure contains only bitfields,
37965 its total size in bytes must be specified, each bitfield must have an
37966 explicit start and end, and bitfields are automatically assigned an
37967 integer type. The field's @var{start} should be less than or
37968 equal to its @var{end}, and zero represents the least significant bit.
37971 <struct id="@var{id}" size="@var{size}">
37972 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37977 If the structure contains no bitfields, then each field has an
37978 explicit type, and no implicit padding is added.
37981 <struct id="@var{id}">
37982 <field name="@var{name}" type="@var{type}"/>
37988 If a register's value is a series of single-bit flags, define it with
37989 a flags type. The @samp{<flags>} element has an explicit @var{size}
37990 and contains one or more @samp{<field>} elements. Each field has a
37991 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
37995 <flags id="@var{id}" size="@var{size}">
37996 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38001 @subsection Registers
38004 Each register is represented as an element with this form:
38007 <reg name="@var{name}"
38008 bitsize="@var{size}"
38009 @r{[}regnum="@var{num}"@r{]}
38010 @r{[}save-restore="@var{save-restore}"@r{]}
38011 @r{[}type="@var{type}"@r{]}
38012 @r{[}group="@var{group}"@r{]}/>
38016 The components are as follows:
38021 The register's name; it must be unique within the target description.
38024 The register's size, in bits.
38027 The register's number. If omitted, a register's number is one greater
38028 than that of the previous register (either in the current feature or in
38029 a preceding feature); the first register in the target description
38030 defaults to zero. This register number is used to read or write
38031 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38032 packets, and registers appear in the @code{g} and @code{G} packets
38033 in order of increasing register number.
38036 Whether the register should be preserved across inferior function
38037 calls; this must be either @code{yes} or @code{no}. The default is
38038 @code{yes}, which is appropriate for most registers except for
38039 some system control registers; this is not related to the target's
38043 The type of the register. @var{type} may be a predefined type, a type
38044 defined in the current feature, or one of the special types @code{int}
38045 and @code{float}. @code{int} is an integer type of the correct size
38046 for @var{bitsize}, and @code{float} is a floating point type (in the
38047 architecture's normal floating point format) of the correct size for
38048 @var{bitsize}. The default is @code{int}.
38051 The register group to which this register belongs. @var{group} must
38052 be either @code{general}, @code{float}, or @code{vector}. If no
38053 @var{group} is specified, @value{GDBN} will not display the register
38054 in @code{info registers}.
38058 @node Predefined Target Types
38059 @section Predefined Target Types
38060 @cindex target descriptions, predefined types
38062 Type definitions in the self-description can build up composite types
38063 from basic building blocks, but can not define fundamental types. Instead,
38064 standard identifiers are provided by @value{GDBN} for the fundamental
38065 types. The currently supported types are:
38074 Signed integer types holding the specified number of bits.
38081 Unsigned integer types holding the specified number of bits.
38085 Pointers to unspecified code and data. The program counter and
38086 any dedicated return address register may be marked as code
38087 pointers; printing a code pointer converts it into a symbolic
38088 address. The stack pointer and any dedicated address registers
38089 may be marked as data pointers.
38092 Single precision IEEE floating point.
38095 Double precision IEEE floating point.
38098 The 12-byte extended precision format used by ARM FPA registers.
38101 The 10-byte extended precision format used by x87 registers.
38104 32bit @sc{eflags} register used by x86.
38107 32bit @sc{mxcsr} register used by x86.
38111 @node Standard Target Features
38112 @section Standard Target Features
38113 @cindex target descriptions, standard features
38115 A target description must contain either no registers or all the
38116 target's registers. If the description contains no registers, then
38117 @value{GDBN} will assume a default register layout, selected based on
38118 the architecture. If the description contains any registers, the
38119 default layout will not be used; the standard registers must be
38120 described in the target description, in such a way that @value{GDBN}
38121 can recognize them.
38123 This is accomplished by giving specific names to feature elements
38124 which contain standard registers. @value{GDBN} will look for features
38125 with those names and verify that they contain the expected registers;
38126 if any known feature is missing required registers, or if any required
38127 feature is missing, @value{GDBN} will reject the target
38128 description. You can add additional registers to any of the
38129 standard features --- @value{GDBN} will display them just as if
38130 they were added to an unrecognized feature.
38132 This section lists the known features and their expected contents.
38133 Sample XML documents for these features are included in the
38134 @value{GDBN} source tree, in the directory @file{gdb/features}.
38136 Names recognized by @value{GDBN} should include the name of the
38137 company or organization which selected the name, and the overall
38138 architecture to which the feature applies; so e.g.@: the feature
38139 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38141 The names of registers are not case sensitive for the purpose
38142 of recognizing standard features, but @value{GDBN} will only display
38143 registers using the capitalization used in the description.
38150 * PowerPC Features::
38156 @subsection ARM Features
38157 @cindex target descriptions, ARM features
38159 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38161 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38162 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38164 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38165 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38166 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38169 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38170 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38172 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38173 it should contain at least registers @samp{wR0} through @samp{wR15} and
38174 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38175 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38177 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38178 should contain at least registers @samp{d0} through @samp{d15}. If
38179 they are present, @samp{d16} through @samp{d31} should also be included.
38180 @value{GDBN} will synthesize the single-precision registers from
38181 halves of the double-precision registers.
38183 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38184 need to contain registers; it instructs @value{GDBN} to display the
38185 VFP double-precision registers as vectors and to synthesize the
38186 quad-precision registers from pairs of double-precision registers.
38187 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38188 be present and include 32 double-precision registers.
38190 @node i386 Features
38191 @subsection i386 Features
38192 @cindex target descriptions, i386 features
38194 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38195 targets. It should describe the following registers:
38199 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38201 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38203 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38204 @samp{fs}, @samp{gs}
38206 @samp{st0} through @samp{st7}
38208 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38209 @samp{foseg}, @samp{fooff} and @samp{fop}
38212 The register sets may be different, depending on the target.
38214 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38215 describe registers:
38219 @samp{xmm0} through @samp{xmm7} for i386
38221 @samp{xmm0} through @samp{xmm15} for amd64
38226 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38227 @samp{org.gnu.gdb.i386.sse} feature. It should
38228 describe the upper 128 bits of @sc{ymm} registers:
38232 @samp{ymm0h} through @samp{ymm7h} for i386
38234 @samp{ymm0h} through @samp{ymm15h} for amd64
38237 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38238 describe a single register, @samp{orig_eax}.
38240 @node MIPS Features
38241 @subsection MIPS Features
38242 @cindex target descriptions, MIPS features
38244 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38245 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38246 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38249 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38250 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38251 registers. They may be 32-bit or 64-bit depending on the target.
38253 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38254 it may be optional in a future version of @value{GDBN}. It should
38255 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38256 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38258 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38259 contain a single register, @samp{restart}, which is used by the
38260 Linux kernel to control restartable syscalls.
38262 @node M68K Features
38263 @subsection M68K Features
38264 @cindex target descriptions, M68K features
38267 @item @samp{org.gnu.gdb.m68k.core}
38268 @itemx @samp{org.gnu.gdb.coldfire.core}
38269 @itemx @samp{org.gnu.gdb.fido.core}
38270 One of those features must be always present.
38271 The feature that is present determines which flavor of m68k is
38272 used. The feature that is present should contain registers
38273 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38274 @samp{sp}, @samp{ps} and @samp{pc}.
38276 @item @samp{org.gnu.gdb.coldfire.fp}
38277 This feature is optional. If present, it should contain registers
38278 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38282 @node PowerPC Features
38283 @subsection PowerPC Features
38284 @cindex target descriptions, PowerPC features
38286 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38287 targets. It should contain registers @samp{r0} through @samp{r31},
38288 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38289 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38291 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38292 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38294 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38295 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38298 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38299 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38300 will combine these registers with the floating point registers
38301 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38302 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38303 through @samp{vs63}, the set of vector registers for POWER7.
38305 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38306 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38307 @samp{spefscr}. SPE targets should provide 32-bit registers in
38308 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38309 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38310 these to present registers @samp{ev0} through @samp{ev31} to the
38313 @node TIC6x Features
38314 @subsection TMS320C6x Features
38315 @cindex target descriptions, TIC6x features
38316 @cindex target descriptions, TMS320C6x features
38317 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38318 targets. It should contain registers @samp{A0} through @samp{A15},
38319 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38321 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38322 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38323 through @samp{B31}.
38325 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38326 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38328 @node Operating System Information
38329 @appendix Operating System Information
38330 @cindex operating system information
38336 Users of @value{GDBN} often wish to obtain information about the state of
38337 the operating system running on the target---for example the list of
38338 processes, or the list of open files. This section describes the
38339 mechanism that makes it possible. This mechanism is similar to the
38340 target features mechanism (@pxref{Target Descriptions}), but focuses
38341 on a different aspect of target.
38343 Operating system information is retrived from the target via the
38344 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38345 read}). The object name in the request should be @samp{osdata}, and
38346 the @var{annex} identifies the data to be fetched.
38349 @appendixsection Process list
38350 @cindex operating system information, process list
38352 When requesting the process list, the @var{annex} field in the
38353 @samp{qXfer} request should be @samp{processes}. The returned data is
38354 an XML document. The formal syntax of this document is defined in
38355 @file{gdb/features/osdata.dtd}.
38357 An example document is:
38360 <?xml version="1.0"?>
38361 <!DOCTYPE target SYSTEM "osdata.dtd">
38362 <osdata type="processes">
38364 <column name="pid">1</column>
38365 <column name="user">root</column>
38366 <column name="command">/sbin/init</column>
38367 <column name="cores">1,2,3</column>
38372 Each item should include a column whose name is @samp{pid}. The value
38373 of that column should identify the process on the target. The
38374 @samp{user} and @samp{command} columns are optional, and will be
38375 displayed by @value{GDBN}. The @samp{cores} column, if present,
38376 should contain a comma-separated list of cores that this process
38377 is running on. Target may provide additional columns,
38378 which @value{GDBN} currently ignores.
38380 @node Trace File Format
38381 @appendix Trace File Format
38382 @cindex trace file format
38384 The trace file comes in three parts: a header, a textual description
38385 section, and a trace frame section with binary data.
38387 The header has the form @code{\x7fTRACE0\n}. The first byte is
38388 @code{0x7f} so as to indicate that the file contains binary data,
38389 while the @code{0} is a version number that may have different values
38392 The description section consists of multiple lines of @sc{ascii} text
38393 separated by newline characters (@code{0xa}). The lines may include a
38394 variety of optional descriptive or context-setting information, such
38395 as tracepoint definitions or register set size. @value{GDBN} will
38396 ignore any line that it does not recognize. An empty line marks the end
38399 @c FIXME add some specific types of data
38401 The trace frame section consists of a number of consecutive frames.
38402 Each frame begins with a two-byte tracepoint number, followed by a
38403 four-byte size giving the amount of data in the frame. The data in
38404 the frame consists of a number of blocks, each introduced by a
38405 character indicating its type (at least register, memory, and trace
38406 state variable). The data in this section is raw binary, not a
38407 hexadecimal or other encoding; its endianness matches the target's
38410 @c FIXME bi-arch may require endianness/arch info in description section
38413 @item R @var{bytes}
38414 Register block. The number and ordering of bytes matches that of a
38415 @code{g} packet in the remote protocol. Note that these are the
38416 actual bytes, in target order and @value{GDBN} register order, not a
38417 hexadecimal encoding.
38419 @item M @var{address} @var{length} @var{bytes}...
38420 Memory block. This is a contiguous block of memory, at the 8-byte
38421 address @var{address}, with a 2-byte length @var{length}, followed by
38422 @var{length} bytes.
38424 @item V @var{number} @var{value}
38425 Trace state variable block. This records the 8-byte signed value
38426 @var{value} of trace state variable numbered @var{number}.
38430 Future enhancements of the trace file format may include additional types
38433 @node Index Section Format
38434 @appendix @code{.gdb_index} section format
38435 @cindex .gdb_index section format
38436 @cindex index section format
38438 This section documents the index section that is created by @code{save
38439 gdb-index} (@pxref{Index Files}). The index section is
38440 DWARF-specific; some knowledge of DWARF is assumed in this
38443 The mapped index file format is designed to be directly
38444 @code{mmap}able on any architecture. In most cases, a datum is
38445 represented using a little-endian 32-bit integer value, called an
38446 @code{offset_type}. Big endian machines must byte-swap the values
38447 before using them. Exceptions to this rule are noted. The data is
38448 laid out such that alignment is always respected.
38450 A mapped index consists of several areas, laid out in order.
38454 The file header. This is a sequence of values, of @code{offset_type}
38455 unless otherwise noted:
38459 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38460 Version 4 differs by its hashing function.
38463 The offset, from the start of the file, of the CU list.
38466 The offset, from the start of the file, of the types CU list. Note
38467 that this area can be empty, in which case this offset will be equal
38468 to the next offset.
38471 The offset, from the start of the file, of the address area.
38474 The offset, from the start of the file, of the symbol table.
38477 The offset, from the start of the file, of the constant pool.
38481 The CU list. This is a sequence of pairs of 64-bit little-endian
38482 values, sorted by the CU offset. The first element in each pair is
38483 the offset of a CU in the @code{.debug_info} section. The second
38484 element in each pair is the length of that CU. References to a CU
38485 elsewhere in the map are done using a CU index, which is just the
38486 0-based index into this table. Note that if there are type CUs, then
38487 conceptually CUs and type CUs form a single list for the purposes of
38491 The types CU list. This is a sequence of triplets of 64-bit
38492 little-endian values. In a triplet, the first value is the CU offset,
38493 the second value is the type offset in the CU, and the third value is
38494 the type signature. The types CU list is not sorted.
38497 The address area. The address area consists of a sequence of address
38498 entries. Each address entry has three elements:
38502 The low address. This is a 64-bit little-endian value.
38505 The high address. This is a 64-bit little-endian value. Like
38506 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38509 The CU index. This is an @code{offset_type} value.
38513 The symbol table. This is an open-addressed hash table. The size of
38514 the hash table is always a power of 2.
38516 Each slot in the hash table consists of a pair of @code{offset_type}
38517 values. The first value is the offset of the symbol's name in the
38518 constant pool. The second value is the offset of the CU vector in the
38521 If both values are 0, then this slot in the hash table is empty. This
38522 is ok because while 0 is a valid constant pool index, it cannot be a
38523 valid index for both a string and a CU vector.
38525 The hash value for a table entry is computed by applying an
38526 iterative hash function to the symbol's name. Starting with an
38527 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38528 the string is incorporated into the hash using the formula depending on the
38533 The formula is @code{r = r * 67 + c - 113}.
38536 The formula is @code{r = r * 67 + tolower (c) - 113}.
38539 The terminating @samp{\0} is not incorporated into the hash.
38541 The step size used in the hash table is computed via
38542 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38543 value, and @samp{size} is the size of the hash table. The step size
38544 is used to find the next candidate slot when handling a hash
38547 The names of C@t{++} symbols in the hash table are canonicalized. We
38548 don't currently have a simple description of the canonicalization
38549 algorithm; if you intend to create new index sections, you must read
38553 The constant pool. This is simply a bunch of bytes. It is organized
38554 so that alignment is correct: CU vectors are stored first, followed by
38557 A CU vector in the constant pool is a sequence of @code{offset_type}
38558 values. The first value is the number of CU indices in the vector.
38559 Each subsequent value is the index of a CU in the CU list. This
38560 element in the hash table is used to indicate which CUs define the
38563 A string in the constant pool is zero-terminated.
38568 @node GNU Free Documentation License
38569 @appendix GNU Free Documentation License
38578 % I think something like @colophon should be in texinfo. In the
38580 \long\def\colophon{\hbox to0pt{}\vfill
38581 \centerline{The body of this manual is set in}
38582 \centerline{\fontname\tenrm,}
38583 \centerline{with headings in {\bf\fontname\tenbf}}
38584 \centerline{and examples in {\tt\fontname\tentt}.}
38585 \centerline{{\it\fontname\tenit\/},}
38586 \centerline{{\bf\fontname\tenbf}, and}
38587 \centerline{{\sl\fontname\tensl\/}}
38588 \centerline{are used for emphasis.}\vfill}
38590 % Blame: doc@cygnus.com, 1991.