1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
3 @c 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 @c 2010, 2011 Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
107 @node Top, Summary, (dir), (dir)
109 @top Debugging with @value{GDBN}
111 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
113 This is the @value{EDITION} Edition, for @value{GDBN}
114 @ifset VERSION_PACKAGE
115 @value{VERSION_PACKAGE}
117 Version @value{GDBVN}.
119 Copyright (C) 1988-2010 Free Software Foundation, Inc.
121 This edition of the GDB manual is dedicated to the memory of Fred
122 Fish. Fred was a long-standing contributor to GDB and to Free
123 software in general. We will miss him.
126 * Summary:: Summary of @value{GDBN}
127 * Sample Session:: A sample @value{GDBN} session
129 * Invocation:: Getting in and out of @value{GDBN}
130 * Commands:: @value{GDBN} commands
131 * Running:: Running programs under @value{GDBN}
132 * Stopping:: Stopping and continuing
133 * Reverse Execution:: Running programs backward
134 * Process Record and Replay:: Recording inferior's execution and replaying it
135 * Stack:: Examining the stack
136 * Source:: Examining source files
137 * Data:: Examining data
138 * Optimized Code:: Debugging optimized code
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Extending GDB:: Extending @value{GDBN}
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
158 * JIT Interface:: Using the JIT debugging interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 @ifset SYSTEM_READLINE
163 * Command Line Editing: (rluserman). Command Line Editing
164 * Using History Interactively: (history). Using History Interactively
166 @ifclear SYSTEM_READLINE
167 * Command Line Editing:: Command Line Editing
168 * Using History Interactively:: Using History Interactively
170 * In Memoriam:: In Memoriam
171 * Formatting Documentation:: How to format and print @value{GDBN} documentation
172 * Installing GDB:: Installing GDB
173 * Maintenance Commands:: Maintenance Commands
174 * Remote Protocol:: GDB Remote Serial Protocol
175 * Agent Expressions:: The GDB Agent Expression Mechanism
176 * Target Descriptions:: How targets can describe themselves to
178 * Operating System Information:: Getting additional information from
180 * Trace File Format:: GDB trace file format
181 * Index Section Format:: .gdb_index section format
182 * Copying:: GNU General Public License says
183 how you can copy and share GDB
184 * GNU Free Documentation License:: The license for this documentation
193 @unnumbered Summary of @value{GDBN}
195 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
196 going on ``inside'' another program while it executes---or what another
197 program was doing at the moment it crashed.
199 @value{GDBN} can do four main kinds of things (plus other things in support of
200 these) to help you catch bugs in the act:
204 Start your program, specifying anything that might affect its behavior.
207 Make your program stop on specified conditions.
210 Examine what has happened, when your program has stopped.
213 Change things in your program, so you can experiment with correcting the
214 effects of one bug and go on to learn about another.
217 You can use @value{GDBN} to debug programs written in C and C@t{++}.
218 For more information, see @ref{Supported Languages,,Supported Languages}.
219 For more information, see @ref{C,,C and C++}.
221 Support for D is partial. For information on D, see
225 Support for Modula-2 is partial. For information on Modula-2, see
226 @ref{Modula-2,,Modula-2}.
228 Support for OpenCL C is partial. For information on OpenCL C, see
229 @ref{OpenCL C,,OpenCL C}.
232 Debugging Pascal programs which use sets, subranges, file variables, or
233 nested functions does not currently work. @value{GDBN} does not support
234 entering expressions, printing values, or similar features using Pascal
238 @value{GDBN} can be used to debug programs written in Fortran, although
239 it may be necessary to refer to some variables with a trailing
242 @value{GDBN} can be used to debug programs written in Objective-C,
243 using either the Apple/NeXT or the GNU Objective-C runtime.
246 * Free Software:: Freely redistributable software
247 * Contributors:: Contributors to GDB
251 @unnumberedsec Free Software
253 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
254 General Public License
255 (GPL). The GPL gives you the freedom to copy or adapt a licensed
256 program---but every person getting a copy also gets with it the
257 freedom to modify that copy (which means that they must get access to
258 the source code), and the freedom to distribute further copies.
259 Typical software companies use copyrights to limit your freedoms; the
260 Free Software Foundation uses the GPL to preserve these freedoms.
262 Fundamentally, the General Public License is a license which says that
263 you have these freedoms and that you cannot take these freedoms away
266 @unnumberedsec Free Software Needs Free Documentation
268 The biggest deficiency in the free software community today is not in
269 the software---it is the lack of good free documentation that we can
270 include with the free software. Many of our most important
271 programs do not come with free reference manuals and free introductory
272 texts. Documentation is an essential part of any software package;
273 when an important free software package does not come with a free
274 manual and a free tutorial, that is a major gap. We have many such
277 Consider Perl, for instance. The tutorial manuals that people
278 normally use are non-free. How did this come about? Because the
279 authors of those manuals published them with restrictive terms---no
280 copying, no modification, source files not available---which exclude
281 them from the free software world.
283 That wasn't the first time this sort of thing happened, and it was far
284 from the last. Many times we have heard a GNU user eagerly describe a
285 manual that he is writing, his intended contribution to the community,
286 only to learn that he had ruined everything by signing a publication
287 contract to make it non-free.
289 Free documentation, like free software, is a matter of freedom, not
290 price. The problem with the non-free manual is not that publishers
291 charge a price for printed copies---that in itself is fine. (The Free
292 Software Foundation sells printed copies of manuals, too.) The
293 problem is the restrictions on the use of the manual. Free manuals
294 are available in source code form, and give you permission to copy and
295 modify. Non-free manuals do not allow this.
297 The criteria of freedom for a free manual are roughly the same as for
298 free software. Redistribution (including the normal kinds of
299 commercial redistribution) must be permitted, so that the manual can
300 accompany every copy of the program, both on-line and on paper.
302 Permission for modification of the technical content is crucial too.
303 When people modify the software, adding or changing features, if they
304 are conscientious they will change the manual too---so they can
305 provide accurate and clear documentation for the modified program. A
306 manual that leaves you no choice but to write a new manual to document
307 a changed version of the program is not really available to our
310 Some kinds of limits on the way modification is handled are
311 acceptable. For example, requirements to preserve the original
312 author's copyright notice, the distribution terms, or the list of
313 authors, are ok. It is also no problem to require modified versions
314 to include notice that they were modified. Even entire sections that
315 may not be deleted or changed are acceptable, as long as they deal
316 with nontechnical topics (like this one). These kinds of restrictions
317 are acceptable because they don't obstruct the community's normal use
320 However, it must be possible to modify all the @emph{technical}
321 content of the manual, and then distribute the result in all the usual
322 media, through all the usual channels. Otherwise, the restrictions
323 obstruct the use of the manual, it is not free, and we need another
324 manual to replace it.
326 Please spread the word about this issue. Our community continues to
327 lose manuals to proprietary publishing. If we spread the word that
328 free software needs free reference manuals and free tutorials, perhaps
329 the next person who wants to contribute by writing documentation will
330 realize, before it is too late, that only free manuals contribute to
331 the free software community.
333 If you are writing documentation, please insist on publishing it under
334 the GNU Free Documentation License or another free documentation
335 license. Remember that this decision requires your approval---you
336 don't have to let the publisher decide. Some commercial publishers
337 will use a free license if you insist, but they will not propose the
338 option; it is up to you to raise the issue and say firmly that this is
339 what you want. If the publisher you are dealing with refuses, please
340 try other publishers. If you're not sure whether a proposed license
341 is free, write to @email{licensing@@gnu.org}.
343 You can encourage commercial publishers to sell more free, copylefted
344 manuals and tutorials by buying them, and particularly by buying
345 copies from the publishers that paid for their writing or for major
346 improvements. Meanwhile, try to avoid buying non-free documentation
347 at all. Check the distribution terms of a manual before you buy it,
348 and insist that whoever seeks your business must respect your freedom.
349 Check the history of the book, and try to reward the publishers that
350 have paid or pay the authors to work on it.
352 The Free Software Foundation maintains a list of free documentation
353 published by other publishers, at
354 @url{http://www.fsf.org/doc/other-free-books.html}.
357 @unnumberedsec Contributors to @value{GDBN}
359 Richard Stallman was the original author of @value{GDBN}, and of many
360 other @sc{gnu} programs. Many others have contributed to its
361 development. This section attempts to credit major contributors. One
362 of the virtues of free software is that everyone is free to contribute
363 to it; with regret, we cannot actually acknowledge everyone here. The
364 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
365 blow-by-blow account.
367 Changes much prior to version 2.0 are lost in the mists of time.
370 @emph{Plea:} Additions to this section are particularly welcome. If you
371 or your friends (or enemies, to be evenhanded) have been unfairly
372 omitted from this list, we would like to add your names!
375 So that they may not regard their many labors as thankless, we
376 particularly thank those who shepherded @value{GDBN} through major
378 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
379 Jim Blandy (release 4.18);
380 Jason Molenda (release 4.17);
381 Stan Shebs (release 4.14);
382 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
383 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
384 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
385 Jim Kingdon (releases 3.5, 3.4, and 3.3);
386 and Randy Smith (releases 3.2, 3.1, and 3.0).
388 Richard Stallman, assisted at various times by Peter TerMaat, Chris
389 Hanson, and Richard Mlynarik, handled releases through 2.8.
391 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
392 in @value{GDBN}, with significant additional contributions from Per
393 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
394 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
395 much general update work leading to release 3.0).
397 @value{GDBN} uses the BFD subroutine library to examine multiple
398 object-file formats; BFD was a joint project of David V.
399 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
401 David Johnson wrote the original COFF support; Pace Willison did
402 the original support for encapsulated COFF.
404 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
406 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
407 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
409 Jean-Daniel Fekete contributed Sun 386i support.
410 Chris Hanson improved the HP9000 support.
411 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
412 David Johnson contributed Encore Umax support.
413 Jyrki Kuoppala contributed Altos 3068 support.
414 Jeff Law contributed HP PA and SOM support.
415 Keith Packard contributed NS32K support.
416 Doug Rabson contributed Acorn Risc Machine support.
417 Bob Rusk contributed Harris Nighthawk CX-UX support.
418 Chris Smith contributed Convex support (and Fortran debugging).
419 Jonathan Stone contributed Pyramid support.
420 Michael Tiemann contributed SPARC support.
421 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
422 Pace Willison contributed Intel 386 support.
423 Jay Vosburgh contributed Symmetry support.
424 Marko Mlinar contributed OpenRISC 1000 support.
426 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
428 Rich Schaefer and Peter Schauer helped with support of SunOS shared
431 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
432 about several machine instruction sets.
434 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
435 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
436 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
437 and RDI targets, respectively.
439 Brian Fox is the author of the readline libraries providing
440 command-line editing and command history.
442 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
443 Modula-2 support, and contributed the Languages chapter of this manual.
445 Fred Fish wrote most of the support for Unix System Vr4.
446 He also enhanced the command-completion support to cover C@t{++} overloaded
449 Hitachi America (now Renesas America), Ltd. sponsored the support for
450 H8/300, H8/500, and Super-H processors.
452 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
454 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
457 Toshiba sponsored the support for the TX39 Mips processor.
459 Matsushita sponsored the support for the MN10200 and MN10300 processors.
461 Fujitsu sponsored the support for SPARClite and FR30 processors.
463 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
466 Michael Snyder added support for tracepoints.
468 Stu Grossman wrote gdbserver.
470 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
471 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
473 The following people at the Hewlett-Packard Company contributed
474 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
475 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
476 compiler, and the Text User Interface (nee Terminal User Interface):
477 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
478 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
479 provided HP-specific information in this manual.
481 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
482 Robert Hoehne made significant contributions to the DJGPP port.
484 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
485 development since 1991. Cygnus engineers who have worked on @value{GDBN}
486 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
487 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
488 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
489 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
490 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
491 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
492 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
493 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
494 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
495 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
496 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
497 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
498 Zuhn have made contributions both large and small.
500 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
501 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
503 Jim Blandy added support for preprocessor macros, while working for Red
506 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
507 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
508 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
509 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
510 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
511 with the migration of old architectures to this new framework.
513 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
514 unwinder framework, this consisting of a fresh new design featuring
515 frame IDs, independent frame sniffers, and the sentinel frame. Mark
516 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
517 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
518 trad unwinders. The architecture-specific changes, each involving a
519 complete rewrite of the architecture's frame code, were carried out by
520 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
521 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
522 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
523 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
526 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
527 Tensilica, Inc.@: contributed support for Xtensa processors. Others
528 who have worked on the Xtensa port of @value{GDBN} in the past include
529 Steve Tjiang, John Newlin, and Scott Foehner.
531 Michael Eager and staff of Xilinx, Inc., contributed support for the
532 Xilinx MicroBlaze architecture.
535 @chapter A Sample @value{GDBN} Session
537 You can use this manual at your leisure to read all about @value{GDBN}.
538 However, a handful of commands are enough to get started using the
539 debugger. This chapter illustrates those commands.
542 In this sample session, we emphasize user input like this: @b{input},
543 to make it easier to pick out from the surrounding output.
546 @c FIXME: this example may not be appropriate for some configs, where
547 @c FIXME...primary interest is in remote use.
549 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
550 processor) exhibits the following bug: sometimes, when we change its
551 quote strings from the default, the commands used to capture one macro
552 definition within another stop working. In the following short @code{m4}
553 session, we define a macro @code{foo} which expands to @code{0000}; we
554 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
555 same thing. However, when we change the open quote string to
556 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
557 procedure fails to define a new synonym @code{baz}:
566 @b{define(bar,defn(`foo'))}
570 @b{changequote(<QUOTE>,<UNQUOTE>)}
572 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
575 m4: End of input: 0: fatal error: EOF in string
579 Let us use @value{GDBN} to try to see what is going on.
582 $ @b{@value{GDBP} m4}
583 @c FIXME: this falsifies the exact text played out, to permit smallbook
584 @c FIXME... format to come out better.
585 @value{GDBN} is free software and you are welcome to distribute copies
586 of it under certain conditions; type "show copying" to see
588 There is absolutely no warranty for @value{GDBN}; type "show warranty"
591 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
596 @value{GDBN} reads only enough symbol data to know where to find the
597 rest when needed; as a result, the first prompt comes up very quickly.
598 We now tell @value{GDBN} to use a narrower display width than usual, so
599 that examples fit in this manual.
602 (@value{GDBP}) @b{set width 70}
606 We need to see how the @code{m4} built-in @code{changequote} works.
607 Having looked at the source, we know the relevant subroutine is
608 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
609 @code{break} command.
612 (@value{GDBP}) @b{break m4_changequote}
613 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
617 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
618 control; as long as control does not reach the @code{m4_changequote}
619 subroutine, the program runs as usual:
622 (@value{GDBP}) @b{run}
623 Starting program: /work/Editorial/gdb/gnu/m4/m4
631 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
632 suspends execution of @code{m4}, displaying information about the
633 context where it stops.
636 @b{changequote(<QUOTE>,<UNQUOTE>)}
638 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
640 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
644 Now we use the command @code{n} (@code{next}) to advance execution to
645 the next line of the current function.
649 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
654 @code{set_quotes} looks like a promising subroutine. We can go into it
655 by using the command @code{s} (@code{step}) instead of @code{next}.
656 @code{step} goes to the next line to be executed in @emph{any}
657 subroutine, so it steps into @code{set_quotes}.
661 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
663 530 if (lquote != def_lquote)
667 The display that shows the subroutine where @code{m4} is now
668 suspended (and its arguments) is called a stack frame display. It
669 shows a summary of the stack. We can use the @code{backtrace}
670 command (which can also be spelled @code{bt}), to see where we are
671 in the stack as a whole: the @code{backtrace} command displays a
672 stack frame for each active subroutine.
675 (@value{GDBP}) @b{bt}
676 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
680 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
681 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
683 #4 0x79dc in expand_input () at macro.c:40
684 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
688 We step through a few more lines to see what happens. The first two
689 times, we can use @samp{s}; the next two times we use @code{n} to avoid
690 falling into the @code{xstrdup} subroutine.
694 0x3b5c 532 if (rquote != def_rquote)
696 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
697 def_lquote : xstrdup(lq);
699 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
702 538 len_lquote = strlen(rquote);
706 The last line displayed looks a little odd; we can examine the variables
707 @code{lquote} and @code{rquote} to see if they are in fact the new left
708 and right quotes we specified. We use the command @code{p}
709 (@code{print}) to see their values.
712 (@value{GDBP}) @b{p lquote}
713 $1 = 0x35d40 "<QUOTE>"
714 (@value{GDBP}) @b{p rquote}
715 $2 = 0x35d50 "<UNQUOTE>"
719 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
720 To look at some context, we can display ten lines of source
721 surrounding the current line with the @code{l} (@code{list}) command.
727 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
733 539 len_rquote = strlen(lquote);
740 Let us step past the two lines that set @code{len_lquote} and
741 @code{len_rquote}, and then examine the values of those variables.
745 539 len_rquote = strlen(lquote);
748 (@value{GDBP}) @b{p len_lquote}
750 (@value{GDBP}) @b{p len_rquote}
755 That certainly looks wrong, assuming @code{len_lquote} and
756 @code{len_rquote} are meant to be the lengths of @code{lquote} and
757 @code{rquote} respectively. We can set them to better values using
758 the @code{p} command, since it can print the value of
759 any expression---and that expression can include subroutine calls and
763 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
765 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
770 Is that enough to fix the problem of using the new quotes with the
771 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
772 executing with the @code{c} (@code{continue}) command, and then try the
773 example that caused trouble initially:
779 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
786 Success! The new quotes now work just as well as the default ones. The
787 problem seems to have been just the two typos defining the wrong
788 lengths. We allow @code{m4} exit by giving it an EOF as input:
792 Program exited normally.
796 The message @samp{Program exited normally.} is from @value{GDBN}; it
797 indicates @code{m4} has finished executing. We can end our @value{GDBN}
798 session with the @value{GDBN} @code{quit} command.
801 (@value{GDBP}) @b{quit}
805 @chapter Getting In and Out of @value{GDBN}
807 This chapter discusses how to start @value{GDBN}, and how to get out of it.
811 type @samp{@value{GDBP}} to start @value{GDBN}.
813 type @kbd{quit} or @kbd{Ctrl-d} to exit.
817 * Invoking GDB:: How to start @value{GDBN}
818 * Quitting GDB:: How to quit @value{GDBN}
819 * Shell Commands:: How to use shell commands inside @value{GDBN}
820 * Logging Output:: How to log @value{GDBN}'s output to a file
824 @section Invoking @value{GDBN}
826 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
827 @value{GDBN} reads commands from the terminal until you tell it to exit.
829 You can also run @code{@value{GDBP}} with a variety of arguments and options,
830 to specify more of your debugging environment at the outset.
832 The command-line options described here are designed
833 to cover a variety of situations; in some environments, some of these
834 options may effectively be unavailable.
836 The most usual way to start @value{GDBN} is with one argument,
837 specifying an executable program:
840 @value{GDBP} @var{program}
844 You can also start with both an executable program and a core file
848 @value{GDBP} @var{program} @var{core}
851 You can, instead, specify a process ID as a second argument, if you want
852 to debug a running process:
855 @value{GDBP} @var{program} 1234
859 would attach @value{GDBN} to process @code{1234} (unless you also have a file
860 named @file{1234}; @value{GDBN} does check for a core file first).
862 Taking advantage of the second command-line argument requires a fairly
863 complete operating system; when you use @value{GDBN} as a remote
864 debugger attached to a bare board, there may not be any notion of
865 ``process'', and there is often no way to get a core dump. @value{GDBN}
866 will warn you if it is unable to attach or to read core dumps.
868 You can optionally have @code{@value{GDBP}} pass any arguments after the
869 executable file to the inferior using @code{--args}. This option stops
872 @value{GDBP} --args gcc -O2 -c foo.c
874 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
875 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
877 You can run @code{@value{GDBP}} without printing the front material, which describes
878 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
885 You can further control how @value{GDBN} starts up by using command-line
886 options. @value{GDBN} itself can remind you of the options available.
896 to display all available options and briefly describe their use
897 (@samp{@value{GDBP} -h} is a shorter equivalent).
899 All options and command line arguments you give are processed
900 in sequential order. The order makes a difference when the
901 @samp{-x} option is used.
905 * File Options:: Choosing files
906 * Mode Options:: Choosing modes
907 * Startup:: What @value{GDBN} does during startup
911 @subsection Choosing Files
913 When @value{GDBN} starts, it reads any arguments other than options as
914 specifying an executable file and core file (or process ID). This is
915 the same as if the arguments were specified by the @samp{-se} and
916 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
917 first argument that does not have an associated option flag as
918 equivalent to the @samp{-se} option followed by that argument; and the
919 second argument that does not have an associated option flag, if any, as
920 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
921 If the second argument begins with a decimal digit, @value{GDBN} will
922 first attempt to attach to it as a process, and if that fails, attempt
923 to open it as a corefile. If you have a corefile whose name begins with
924 a digit, you can prevent @value{GDBN} from treating it as a pid by
925 prefixing it with @file{./}, e.g.@: @file{./12345}.
927 If @value{GDBN} has not been configured to included core file support,
928 such as for most embedded targets, then it will complain about a second
929 argument and ignore it.
931 Many options have both long and short forms; both are shown in the
932 following list. @value{GDBN} also recognizes the long forms if you truncate
933 them, so long as enough of the option is present to be unambiguous.
934 (If you prefer, you can flag option arguments with @samp{--} rather
935 than @samp{-}, though we illustrate the more usual convention.)
937 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
938 @c way, both those who look for -foo and --foo in the index, will find
942 @item -symbols @var{file}
944 @cindex @code{--symbols}
946 Read symbol table from file @var{file}.
948 @item -exec @var{file}
950 @cindex @code{--exec}
952 Use file @var{file} as the executable file to execute when appropriate,
953 and for examining pure data in conjunction with a core dump.
957 Read symbol table from file @var{file} and use it as the executable
960 @item -core @var{file}
962 @cindex @code{--core}
964 Use file @var{file} as a core dump to examine.
966 @item -pid @var{number}
967 @itemx -p @var{number}
970 Connect to process ID @var{number}, as with the @code{attach} command.
972 @item -command @var{file}
974 @cindex @code{--command}
976 Execute commands from file @var{file}. The contents of this file is
977 evaluated exactly as the @code{source} command would.
978 @xref{Command Files,, Command files}.
980 @item -eval-command @var{command}
981 @itemx -ex @var{command}
982 @cindex @code{--eval-command}
984 Execute a single @value{GDBN} command.
986 This option may be used multiple times to call multiple commands. It may
987 also be interleaved with @samp{-command} as required.
990 @value{GDBP} -ex 'target sim' -ex 'load' \
991 -x setbreakpoints -ex 'run' a.out
994 @item -directory @var{directory}
995 @itemx -d @var{directory}
996 @cindex @code{--directory}
998 Add @var{directory} to the path to search for source and script files.
1002 @cindex @code{--readnow}
1004 Read each symbol file's entire symbol table immediately, rather than
1005 the default, which is to read it incrementally as it is needed.
1006 This makes startup slower, but makes future operations faster.
1011 @subsection Choosing Modes
1013 You can run @value{GDBN} in various alternative modes---for example, in
1014 batch mode or quiet mode.
1021 Do not execute commands found in any initialization files. Normally,
1022 @value{GDBN} executes the commands in these files after all the command
1023 options and arguments have been processed. @xref{Command Files,,Command
1029 @cindex @code{--quiet}
1030 @cindex @code{--silent}
1032 ``Quiet''. Do not print the introductory and copyright messages. These
1033 messages are also suppressed in batch mode.
1036 @cindex @code{--batch}
1037 Run in batch mode. Exit with status @code{0} after processing all the
1038 command files specified with @samp{-x} (and all commands from
1039 initialization files, if not inhibited with @samp{-n}). Exit with
1040 nonzero status if an error occurs in executing the @value{GDBN} commands
1041 in the command files. Batch mode also disables pagination, sets unlimited
1042 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1043 off} were in effect (@pxref{Messages/Warnings}).
1045 Batch mode may be useful for running @value{GDBN} as a filter, for
1046 example to download and run a program on another computer; in order to
1047 make this more useful, the message
1050 Program exited normally.
1054 (which is ordinarily issued whenever a program running under
1055 @value{GDBN} control terminates) is not issued when running in batch
1059 @cindex @code{--batch-silent}
1060 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1061 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1062 unaffected). This is much quieter than @samp{-silent} and would be useless
1063 for an interactive session.
1065 This is particularly useful when using targets that give @samp{Loading section}
1066 messages, for example.
1068 Note that targets that give their output via @value{GDBN}, as opposed to
1069 writing directly to @code{stdout}, will also be made silent.
1071 @item -return-child-result
1072 @cindex @code{--return-child-result}
1073 The return code from @value{GDBN} will be the return code from the child
1074 process (the process being debugged), with the following exceptions:
1078 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1079 internal error. In this case the exit code is the same as it would have been
1080 without @samp{-return-child-result}.
1082 The user quits with an explicit value. E.g., @samp{quit 1}.
1084 The child process never runs, or is not allowed to terminate, in which case
1085 the exit code will be -1.
1088 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1089 when @value{GDBN} is being used as a remote program loader or simulator
1094 @cindex @code{--nowindows}
1096 ``No windows''. If @value{GDBN} comes with a graphical user interface
1097 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1098 interface. If no GUI is available, this option has no effect.
1102 @cindex @code{--windows}
1104 If @value{GDBN} includes a GUI, then this option requires it to be
1107 @item -cd @var{directory}
1109 Run @value{GDBN} using @var{directory} as its working directory,
1110 instead of the current directory.
1112 @item -data-directory @var{directory}
1113 @cindex @code{--data-directory}
1114 Run @value{GDBN} using @var{directory} as its data directory.
1115 The data directory is where @value{GDBN} searches for its
1116 auxiliary files. @xref{Data Files}.
1120 @cindex @code{--fullname}
1122 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1123 subprocess. It tells @value{GDBN} to output the full file name and line
1124 number in a standard, recognizable fashion each time a stack frame is
1125 displayed (which includes each time your program stops). This
1126 recognizable format looks like two @samp{\032} characters, followed by
1127 the file name, line number and character position separated by colons,
1128 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1129 @samp{\032} characters as a signal to display the source code for the
1133 @cindex @code{--epoch}
1134 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1135 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1136 routines so as to allow Epoch to display values of expressions in a
1139 @item -annotate @var{level}
1140 @cindex @code{--annotate}
1141 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1142 effect is identical to using @samp{set annotate @var{level}}
1143 (@pxref{Annotations}). The annotation @var{level} controls how much
1144 information @value{GDBN} prints together with its prompt, values of
1145 expressions, source lines, and other types of output. Level 0 is the
1146 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1147 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1148 that control @value{GDBN}, and level 2 has been deprecated.
1150 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1154 @cindex @code{--args}
1155 Change interpretation of command line so that arguments following the
1156 executable file are passed as command line arguments to the inferior.
1157 This option stops option processing.
1159 @item -baud @var{bps}
1161 @cindex @code{--baud}
1163 Set the line speed (baud rate or bits per second) of any serial
1164 interface used by @value{GDBN} for remote debugging.
1166 @item -l @var{timeout}
1168 Set the timeout (in seconds) of any communication used by @value{GDBN}
1169 for remote debugging.
1171 @item -tty @var{device}
1172 @itemx -t @var{device}
1173 @cindex @code{--tty}
1175 Run using @var{device} for your program's standard input and output.
1176 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1178 @c resolve the situation of these eventually
1180 @cindex @code{--tui}
1181 Activate the @dfn{Text User Interface} when starting. The Text User
1182 Interface manages several text windows on the terminal, showing
1183 source, assembly, registers and @value{GDBN} command outputs
1184 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1185 Text User Interface can be enabled by invoking the program
1186 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1187 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1190 @c @cindex @code{--xdb}
1191 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1192 @c For information, see the file @file{xdb_trans.html}, which is usually
1193 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1196 @item -interpreter @var{interp}
1197 @cindex @code{--interpreter}
1198 Use the interpreter @var{interp} for interface with the controlling
1199 program or device. This option is meant to be set by programs which
1200 communicate with @value{GDBN} using it as a back end.
1201 @xref{Interpreters, , Command Interpreters}.
1203 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1204 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1205 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1206 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1207 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1208 @sc{gdb/mi} interfaces are no longer supported.
1211 @cindex @code{--write}
1212 Open the executable and core files for both reading and writing. This
1213 is equivalent to the @samp{set write on} command inside @value{GDBN}
1217 @cindex @code{--statistics}
1218 This option causes @value{GDBN} to print statistics about time and
1219 memory usage after it completes each command and returns to the prompt.
1222 @cindex @code{--version}
1223 This option causes @value{GDBN} to print its version number and
1224 no-warranty blurb, and exit.
1229 @subsection What @value{GDBN} Does During Startup
1230 @cindex @value{GDBN} startup
1232 Here's the description of what @value{GDBN} does during session startup:
1236 Sets up the command interpreter as specified by the command line
1237 (@pxref{Mode Options, interpreter}).
1241 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1242 used when building @value{GDBN}; @pxref{System-wide configuration,
1243 ,System-wide configuration and settings}) and executes all the commands in
1247 Reads the init file (if any) in your home directory@footnote{On
1248 DOS/Windows systems, the home directory is the one pointed to by the
1249 @code{HOME} environment variable.} and executes all the commands in
1253 Processes command line options and operands.
1256 Reads and executes the commands from init file (if any) in the current
1257 working directory. This is only done if the current directory is
1258 different from your home directory. Thus, you can have more than one
1259 init file, one generic in your home directory, and another, specific
1260 to the program you are debugging, in the directory where you invoke
1264 If the command line specified a program to debug, or a process to
1265 attach to, or a core file, @value{GDBN} loads any auto-loaded
1266 scripts provided for the program or for its loaded shared libraries.
1267 @xref{Auto-loading}.
1269 If you wish to disable the auto-loading during startup,
1270 you must do something like the following:
1273 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1276 The following does not work because the auto-loading is turned off too late:
1279 $ gdb -ex "set auto-load-scripts off" myprogram
1283 Reads command files specified by the @samp{-x} option. @xref{Command
1284 Files}, for more details about @value{GDBN} command files.
1287 Reads the command history recorded in the @dfn{history file}.
1288 @xref{Command History}, for more details about the command history and the
1289 files where @value{GDBN} records it.
1292 Init files use the same syntax as @dfn{command files} (@pxref{Command
1293 Files}) and are processed by @value{GDBN} in the same way. The init
1294 file in your home directory can set options (such as @samp{set
1295 complaints}) that affect subsequent processing of command line options
1296 and operands. Init files are not executed if you use the @samp{-nx}
1297 option (@pxref{Mode Options, ,Choosing Modes}).
1299 To display the list of init files loaded by gdb at startup, you
1300 can use @kbd{gdb --help}.
1302 @cindex init file name
1303 @cindex @file{.gdbinit}
1304 @cindex @file{gdb.ini}
1305 The @value{GDBN} init files are normally called @file{.gdbinit}.
1306 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1307 the limitations of file names imposed by DOS filesystems. The Windows
1308 ports of @value{GDBN} use the standard name, but if they find a
1309 @file{gdb.ini} file, they warn you about that and suggest to rename
1310 the file to the standard name.
1314 @section Quitting @value{GDBN}
1315 @cindex exiting @value{GDBN}
1316 @cindex leaving @value{GDBN}
1319 @kindex quit @r{[}@var{expression}@r{]}
1320 @kindex q @r{(@code{quit})}
1321 @item quit @r{[}@var{expression}@r{]}
1323 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1324 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1325 do not supply @var{expression}, @value{GDBN} will terminate normally;
1326 otherwise it will terminate using the result of @var{expression} as the
1331 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1332 terminates the action of any @value{GDBN} command that is in progress and
1333 returns to @value{GDBN} command level. It is safe to type the interrupt
1334 character at any time because @value{GDBN} does not allow it to take effect
1335 until a time when it is safe.
1337 If you have been using @value{GDBN} to control an attached process or
1338 device, you can release it with the @code{detach} command
1339 (@pxref{Attach, ,Debugging an Already-running Process}).
1341 @node Shell Commands
1342 @section Shell Commands
1344 If you need to execute occasional shell commands during your
1345 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1346 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command string}
1352 Invoke a standard shell to execute @var{command string}.
1353 If it exists, the environment variable @code{SHELL} determines which
1354 shell to run. Otherwise @value{GDBN} uses the default shell
1355 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1358 The utility @code{make} is often needed in development environments.
1359 You do not have to use the @code{shell} command for this purpose in
1364 @cindex calling make
1365 @item make @var{make-args}
1366 Execute the @code{make} program with the specified
1367 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1370 @node Logging Output
1371 @section Logging Output
1372 @cindex logging @value{GDBN} output
1373 @cindex save @value{GDBN} output to a file
1375 You may want to save the output of @value{GDBN} commands to a file.
1376 There are several commands to control @value{GDBN}'s logging.
1380 @item set logging on
1382 @item set logging off
1384 @cindex logging file name
1385 @item set logging file @var{file}
1386 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1387 @item set logging overwrite [on|off]
1388 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1389 you want @code{set logging on} to overwrite the logfile instead.
1390 @item set logging redirect [on|off]
1391 By default, @value{GDBN} output will go to both the terminal and the logfile.
1392 Set @code{redirect} if you want output to go only to the log file.
1393 @kindex show logging
1395 Show the current values of the logging settings.
1399 @chapter @value{GDBN} Commands
1401 You can abbreviate a @value{GDBN} command to the first few letters of the command
1402 name, if that abbreviation is unambiguous; and you can repeat certain
1403 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1404 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1405 show you the alternatives available, if there is more than one possibility).
1408 * Command Syntax:: How to give commands to @value{GDBN}
1409 * Completion:: Command completion
1410 * Help:: How to ask @value{GDBN} for help
1413 @node Command Syntax
1414 @section Command Syntax
1416 A @value{GDBN} command is a single line of input. There is no limit on
1417 how long it can be. It starts with a command name, which is followed by
1418 arguments whose meaning depends on the command name. For example, the
1419 command @code{step} accepts an argument which is the number of times to
1420 step, as in @samp{step 5}. You can also use the @code{step} command
1421 with no arguments. Some commands do not allow any arguments.
1423 @cindex abbreviation
1424 @value{GDBN} command names may always be truncated if that abbreviation is
1425 unambiguous. Other possible command abbreviations are listed in the
1426 documentation for individual commands. In some cases, even ambiguous
1427 abbreviations are allowed; for example, @code{s} is specially defined as
1428 equivalent to @code{step} even though there are other commands whose
1429 names start with @code{s}. You can test abbreviations by using them as
1430 arguments to the @code{help} command.
1432 @cindex repeating commands
1433 @kindex RET @r{(repeat last command)}
1434 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1435 repeat the previous command. Certain commands (for example, @code{run})
1436 will not repeat this way; these are commands whose unintentional
1437 repetition might cause trouble and which you are unlikely to want to
1438 repeat. User-defined commands can disable this feature; see
1439 @ref{Define, dont-repeat}.
1441 The @code{list} and @code{x} commands, when you repeat them with
1442 @key{RET}, construct new arguments rather than repeating
1443 exactly as typed. This permits easy scanning of source or memory.
1445 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1446 output, in a way similar to the common utility @code{more}
1447 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1448 @key{RET} too many in this situation, @value{GDBN} disables command
1449 repetition after any command that generates this sort of display.
1451 @kindex # @r{(a comment)}
1453 Any text from a @kbd{#} to the end of the line is a comment; it does
1454 nothing. This is useful mainly in command files (@pxref{Command
1455 Files,,Command Files}).
1457 @cindex repeating command sequences
1458 @kindex Ctrl-o @r{(operate-and-get-next)}
1459 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1460 commands. This command accepts the current line, like @key{RET}, and
1461 then fetches the next line relative to the current line from the history
1465 @section Command Completion
1468 @cindex word completion
1469 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1470 only one possibility; it can also show you what the valid possibilities
1471 are for the next word in a command, at any time. This works for @value{GDBN}
1472 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1474 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1475 of a word. If there is only one possibility, @value{GDBN} fills in the
1476 word, and waits for you to finish the command (or press @key{RET} to
1477 enter it). For example, if you type
1479 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1480 @c complete accuracy in these examples; space introduced for clarity.
1481 @c If texinfo enhancements make it unnecessary, it would be nice to
1482 @c replace " @key" by "@key" in the following...
1484 (@value{GDBP}) info bre @key{TAB}
1488 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1489 the only @code{info} subcommand beginning with @samp{bre}:
1492 (@value{GDBP}) info breakpoints
1496 You can either press @key{RET} at this point, to run the @code{info
1497 breakpoints} command, or backspace and enter something else, if
1498 @samp{breakpoints} does not look like the command you expected. (If you
1499 were sure you wanted @code{info breakpoints} in the first place, you
1500 might as well just type @key{RET} immediately after @samp{info bre},
1501 to exploit command abbreviations rather than command completion).
1503 If there is more than one possibility for the next word when you press
1504 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1505 characters and try again, or just press @key{TAB} a second time;
1506 @value{GDBN} displays all the possible completions for that word. For
1507 example, you might want to set a breakpoint on a subroutine whose name
1508 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1509 just sounds the bell. Typing @key{TAB} again displays all the
1510 function names in your program that begin with those characters, for
1514 (@value{GDBP}) b make_ @key{TAB}
1515 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1516 make_a_section_from_file make_environ
1517 make_abs_section make_function_type
1518 make_blockvector make_pointer_type
1519 make_cleanup make_reference_type
1520 make_command make_symbol_completion_list
1521 (@value{GDBP}) b make_
1525 After displaying the available possibilities, @value{GDBN} copies your
1526 partial input (@samp{b make_} in the example) so you can finish the
1529 If you just want to see the list of alternatives in the first place, you
1530 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1531 means @kbd{@key{META} ?}. You can type this either by holding down a
1532 key designated as the @key{META} shift on your keyboard (if there is
1533 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1535 @cindex quotes in commands
1536 @cindex completion of quoted strings
1537 Sometimes the string you need, while logically a ``word'', may contain
1538 parentheses or other characters that @value{GDBN} normally excludes from
1539 its notion of a word. To permit word completion to work in this
1540 situation, you may enclose words in @code{'} (single quote marks) in
1541 @value{GDBN} commands.
1543 The most likely situation where you might need this is in typing the
1544 name of a C@t{++} function. This is because C@t{++} allows function
1545 overloading (multiple definitions of the same function, distinguished
1546 by argument type). For example, when you want to set a breakpoint you
1547 may need to distinguish whether you mean the version of @code{name}
1548 that takes an @code{int} parameter, @code{name(int)}, or the version
1549 that takes a @code{float} parameter, @code{name(float)}. To use the
1550 word-completion facilities in this situation, type a single quote
1551 @code{'} at the beginning of the function name. This alerts
1552 @value{GDBN} that it may need to consider more information than usual
1553 when you press @key{TAB} or @kbd{M-?} to request word completion:
1556 (@value{GDBP}) b 'bubble( @kbd{M-?}
1557 bubble(double,double) bubble(int,int)
1558 (@value{GDBP}) b 'bubble(
1561 In some cases, @value{GDBN} can tell that completing a name requires using
1562 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1563 completing as much as it can) if you do not type the quote in the first
1567 (@value{GDBP}) b bub @key{TAB}
1568 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1569 (@value{GDBP}) b 'bubble(
1573 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1574 you have not yet started typing the argument list when you ask for
1575 completion on an overloaded symbol.
1577 For more information about overloaded functions, see @ref{C Plus Plus
1578 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1579 overload-resolution off} to disable overload resolution;
1580 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1582 @cindex completion of structure field names
1583 @cindex structure field name completion
1584 @cindex completion of union field names
1585 @cindex union field name completion
1586 When completing in an expression which looks up a field in a
1587 structure, @value{GDBN} also tries@footnote{The completer can be
1588 confused by certain kinds of invalid expressions. Also, it only
1589 examines the static type of the expression, not the dynamic type.} to
1590 limit completions to the field names available in the type of the
1594 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1595 magic to_delete to_fputs to_put to_rewind
1596 to_data to_flush to_isatty to_read to_write
1600 This is because the @code{gdb_stdout} is a variable of the type
1601 @code{struct ui_file} that is defined in @value{GDBN} sources as
1608 ui_file_flush_ftype *to_flush;
1609 ui_file_write_ftype *to_write;
1610 ui_file_fputs_ftype *to_fputs;
1611 ui_file_read_ftype *to_read;
1612 ui_file_delete_ftype *to_delete;
1613 ui_file_isatty_ftype *to_isatty;
1614 ui_file_rewind_ftype *to_rewind;
1615 ui_file_put_ftype *to_put;
1622 @section Getting Help
1623 @cindex online documentation
1626 You can always ask @value{GDBN} itself for information on its commands,
1627 using the command @code{help}.
1630 @kindex h @r{(@code{help})}
1633 You can use @code{help} (abbreviated @code{h}) with no arguments to
1634 display a short list of named classes of commands:
1638 List of classes of commands:
1640 aliases -- Aliases of other commands
1641 breakpoints -- Making program stop at certain points
1642 data -- Examining data
1643 files -- Specifying and examining files
1644 internals -- Maintenance commands
1645 obscure -- Obscure features
1646 running -- Running the program
1647 stack -- Examining the stack
1648 status -- Status inquiries
1649 support -- Support facilities
1650 tracepoints -- Tracing of program execution without
1651 stopping the program
1652 user-defined -- User-defined commands
1654 Type "help" followed by a class name for a list of
1655 commands in that class.
1656 Type "help" followed by command name for full
1658 Command name abbreviations are allowed if unambiguous.
1661 @c the above line break eliminates huge line overfull...
1663 @item help @var{class}
1664 Using one of the general help classes as an argument, you can get a
1665 list of the individual commands in that class. For example, here is the
1666 help display for the class @code{status}:
1669 (@value{GDBP}) help status
1674 @c Line break in "show" line falsifies real output, but needed
1675 @c to fit in smallbook page size.
1676 info -- Generic command for showing things
1677 about the program being debugged
1678 show -- Generic command for showing things
1681 Type "help" followed by command name for full
1683 Command name abbreviations are allowed if unambiguous.
1687 @item help @var{command}
1688 With a command name as @code{help} argument, @value{GDBN} displays a
1689 short paragraph on how to use that command.
1692 @item apropos @var{args}
1693 The @code{apropos} command searches through all of the @value{GDBN}
1694 commands, and their documentation, for the regular expression specified in
1695 @var{args}. It prints out all matches found. For example:
1706 set symbol-reloading -- Set dynamic symbol table reloading
1707 multiple times in one run
1708 show symbol-reloading -- Show dynamic symbol table reloading
1709 multiple times in one run
1714 @item complete @var{args}
1715 The @code{complete @var{args}} command lists all the possible completions
1716 for the beginning of a command. Use @var{args} to specify the beginning of the
1717 command you want completed. For example:
1723 @noindent results in:
1734 @noindent This is intended for use by @sc{gnu} Emacs.
1737 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1738 and @code{show} to inquire about the state of your program, or the state
1739 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1740 manual introduces each of them in the appropriate context. The listings
1741 under @code{info} and under @code{show} in the Index point to
1742 all the sub-commands. @xref{Index}.
1747 @kindex i @r{(@code{info})}
1749 This command (abbreviated @code{i}) is for describing the state of your
1750 program. For example, you can show the arguments passed to a function
1751 with @code{info args}, list the registers currently in use with @code{info
1752 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1753 You can get a complete list of the @code{info} sub-commands with
1754 @w{@code{help info}}.
1758 You can assign the result of an expression to an environment variable with
1759 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1760 @code{set prompt $}.
1764 In contrast to @code{info}, @code{show} is for describing the state of
1765 @value{GDBN} itself.
1766 You can change most of the things you can @code{show}, by using the
1767 related command @code{set}; for example, you can control what number
1768 system is used for displays with @code{set radix}, or simply inquire
1769 which is currently in use with @code{show radix}.
1772 To display all the settable parameters and their current
1773 values, you can use @code{show} with no arguments; you may also use
1774 @code{info set}. Both commands produce the same display.
1775 @c FIXME: "info set" violates the rule that "info" is for state of
1776 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1777 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1781 Here are three miscellaneous @code{show} subcommands, all of which are
1782 exceptional in lacking corresponding @code{set} commands:
1785 @kindex show version
1786 @cindex @value{GDBN} version number
1788 Show what version of @value{GDBN} is running. You should include this
1789 information in @value{GDBN} bug-reports. If multiple versions of
1790 @value{GDBN} are in use at your site, you may need to determine which
1791 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1792 commands are introduced, and old ones may wither away. Also, many
1793 system vendors ship variant versions of @value{GDBN}, and there are
1794 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1795 The version number is the same as the one announced when you start
1798 @kindex show copying
1799 @kindex info copying
1800 @cindex display @value{GDBN} copyright
1803 Display information about permission for copying @value{GDBN}.
1805 @kindex show warranty
1806 @kindex info warranty
1808 @itemx info warranty
1809 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1810 if your version of @value{GDBN} comes with one.
1815 @chapter Running Programs Under @value{GDBN}
1817 When you run a program under @value{GDBN}, you must first generate
1818 debugging information when you compile it.
1820 You may start @value{GDBN} with its arguments, if any, in an environment
1821 of your choice. If you are doing native debugging, you may redirect
1822 your program's input and output, debug an already running process, or
1823 kill a child process.
1826 * Compilation:: Compiling for debugging
1827 * Starting:: Starting your program
1828 * Arguments:: Your program's arguments
1829 * Environment:: Your program's environment
1831 * Working Directory:: Your program's working directory
1832 * Input/Output:: Your program's input and output
1833 * Attach:: Debugging an already-running process
1834 * Kill Process:: Killing the child process
1836 * Inferiors and Programs:: Debugging multiple inferiors and programs
1837 * Threads:: Debugging programs with multiple threads
1838 * Forks:: Debugging forks
1839 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1843 @section Compiling for Debugging
1845 In order to debug a program effectively, you need to generate
1846 debugging information when you compile it. This debugging information
1847 is stored in the object file; it describes the data type of each
1848 variable or function and the correspondence between source line numbers
1849 and addresses in the executable code.
1851 To request debugging information, specify the @samp{-g} option when you run
1854 Programs that are to be shipped to your customers are compiled with
1855 optimizations, using the @samp{-O} compiler option. However, some
1856 compilers are unable to handle the @samp{-g} and @samp{-O} options
1857 together. Using those compilers, you cannot generate optimized
1858 executables containing debugging information.
1860 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1861 without @samp{-O}, making it possible to debug optimized code. We
1862 recommend that you @emph{always} use @samp{-g} whenever you compile a
1863 program. You may think your program is correct, but there is no sense
1864 in pushing your luck. For more information, see @ref{Optimized Code}.
1866 Older versions of the @sc{gnu} C compiler permitted a variant option
1867 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1868 format; if your @sc{gnu} C compiler has this option, do not use it.
1870 @value{GDBN} knows about preprocessor macros and can show you their
1871 expansion (@pxref{Macros}). Most compilers do not include information
1872 about preprocessor macros in the debugging information if you specify
1873 the @option{-g} flag alone, because this information is rather large.
1874 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1875 provides macro information if you specify the options
1876 @option{-gdwarf-2} and @option{-g3}; the former option requests
1877 debugging information in the Dwarf 2 format, and the latter requests
1878 ``extra information''. In the future, we hope to find more compact
1879 ways to represent macro information, so that it can be included with
1884 @section Starting your Program
1890 @kindex r @r{(@code{run})}
1893 Use the @code{run} command to start your program under @value{GDBN}.
1894 You must first specify the program name (except on VxWorks) with an
1895 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1896 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1897 (@pxref{Files, ,Commands to Specify Files}).
1901 If you are running your program in an execution environment that
1902 supports processes, @code{run} creates an inferior process and makes
1903 that process run your program. In some environments without processes,
1904 @code{run} jumps to the start of your program. Other targets,
1905 like @samp{remote}, are always running. If you get an error
1906 message like this one:
1909 The "remote" target does not support "run".
1910 Try "help target" or "continue".
1914 then use @code{continue} to run your program. You may need @code{load}
1915 first (@pxref{load}).
1917 The execution of a program is affected by certain information it
1918 receives from its superior. @value{GDBN} provides ways to specify this
1919 information, which you must do @emph{before} starting your program. (You
1920 can change it after starting your program, but such changes only affect
1921 your program the next time you start it.) This information may be
1922 divided into four categories:
1925 @item The @emph{arguments.}
1926 Specify the arguments to give your program as the arguments of the
1927 @code{run} command. If a shell is available on your target, the shell
1928 is used to pass the arguments, so that you may use normal conventions
1929 (such as wildcard expansion or variable substitution) in describing
1931 In Unix systems, you can control which shell is used with the
1932 @code{SHELL} environment variable.
1933 @xref{Arguments, ,Your Program's Arguments}.
1935 @item The @emph{environment.}
1936 Your program normally inherits its environment from @value{GDBN}, but you can
1937 use the @value{GDBN} commands @code{set environment} and @code{unset
1938 environment} to change parts of the environment that affect
1939 your program. @xref{Environment, ,Your Program's Environment}.
1941 @item The @emph{working directory.}
1942 Your program inherits its working directory from @value{GDBN}. You can set
1943 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1944 @xref{Working Directory, ,Your Program's Working Directory}.
1946 @item The @emph{standard input and output.}
1947 Your program normally uses the same device for standard input and
1948 standard output as @value{GDBN} is using. You can redirect input and output
1949 in the @code{run} command line, or you can use the @code{tty} command to
1950 set a different device for your program.
1951 @xref{Input/Output, ,Your Program's Input and Output}.
1954 @emph{Warning:} While input and output redirection work, you cannot use
1955 pipes to pass the output of the program you are debugging to another
1956 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1960 When you issue the @code{run} command, your program begins to execute
1961 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1962 of how to arrange for your program to stop. Once your program has
1963 stopped, you may call functions in your program, using the @code{print}
1964 or @code{call} commands. @xref{Data, ,Examining Data}.
1966 If the modification time of your symbol file has changed since the last
1967 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1968 table, and reads it again. When it does this, @value{GDBN} tries to retain
1969 your current breakpoints.
1974 @cindex run to main procedure
1975 The name of the main procedure can vary from language to language.
1976 With C or C@t{++}, the main procedure name is always @code{main}, but
1977 other languages such as Ada do not require a specific name for their
1978 main procedure. The debugger provides a convenient way to start the
1979 execution of the program and to stop at the beginning of the main
1980 procedure, depending on the language used.
1982 The @samp{start} command does the equivalent of setting a temporary
1983 breakpoint at the beginning of the main procedure and then invoking
1984 the @samp{run} command.
1986 @cindex elaboration phase
1987 Some programs contain an @dfn{elaboration} phase where some startup code is
1988 executed before the main procedure is called. This depends on the
1989 languages used to write your program. In C@t{++}, for instance,
1990 constructors for static and global objects are executed before
1991 @code{main} is called. It is therefore possible that the debugger stops
1992 before reaching the main procedure. However, the temporary breakpoint
1993 will remain to halt execution.
1995 Specify the arguments to give to your program as arguments to the
1996 @samp{start} command. These arguments will be given verbatim to the
1997 underlying @samp{run} command. Note that the same arguments will be
1998 reused if no argument is provided during subsequent calls to
1999 @samp{start} or @samp{run}.
2001 It is sometimes necessary to debug the program during elaboration. In
2002 these cases, using the @code{start} command would stop the execution of
2003 your program too late, as the program would have already completed the
2004 elaboration phase. Under these circumstances, insert breakpoints in your
2005 elaboration code before running your program.
2007 @kindex set exec-wrapper
2008 @item set exec-wrapper @var{wrapper}
2009 @itemx show exec-wrapper
2010 @itemx unset exec-wrapper
2011 When @samp{exec-wrapper} is set, the specified wrapper is used to
2012 launch programs for debugging. @value{GDBN} starts your program
2013 with a shell command of the form @kbd{exec @var{wrapper}
2014 @var{program}}. Quoting is added to @var{program} and its
2015 arguments, but not to @var{wrapper}, so you should add quotes if
2016 appropriate for your shell. The wrapper runs until it executes
2017 your program, and then @value{GDBN} takes control.
2019 You can use any program that eventually calls @code{execve} with
2020 its arguments as a wrapper. Several standard Unix utilities do
2021 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2022 with @code{exec "$@@"} will also work.
2024 For example, you can use @code{env} to pass an environment variable to
2025 the debugged program, without setting the variable in your shell's
2029 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2033 This command is available when debugging locally on most targets, excluding
2034 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2036 @kindex set disable-randomization
2037 @item set disable-randomization
2038 @itemx set disable-randomization on
2039 This option (enabled by default in @value{GDBN}) will turn off the native
2040 randomization of the virtual address space of the started program. This option
2041 is useful for multiple debugging sessions to make the execution better
2042 reproducible and memory addresses reusable across debugging sessions.
2044 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2048 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2051 @item set disable-randomization off
2052 Leave the behavior of the started executable unchanged. Some bugs rear their
2053 ugly heads only when the program is loaded at certain addresses. If your bug
2054 disappears when you run the program under @value{GDBN}, that might be because
2055 @value{GDBN} by default disables the address randomization on platforms, such
2056 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2057 disable-randomization off} to try to reproduce such elusive bugs.
2059 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2060 It protects the programs against some kinds of security attacks. In these
2061 cases the attacker needs to know the exact location of a concrete executable
2062 code. Randomizing its location makes it impossible to inject jumps misusing
2063 a code at its expected addresses.
2065 Prelinking shared libraries provides a startup performance advantage but it
2066 makes addresses in these libraries predictable for privileged processes by
2067 having just unprivileged access at the target system. Reading the shared
2068 library binary gives enough information for assembling the malicious code
2069 misusing it. Still even a prelinked shared library can get loaded at a new
2070 random address just requiring the regular relocation process during the
2071 startup. Shared libraries not already prelinked are always loaded at
2072 a randomly chosen address.
2074 Position independent executables (PIE) contain position independent code
2075 similar to the shared libraries and therefore such executables get loaded at
2076 a randomly chosen address upon startup. PIE executables always load even
2077 already prelinked shared libraries at a random address. You can build such
2078 executable using @command{gcc -fPIE -pie}.
2080 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2081 (as long as the randomization is enabled).
2083 @item show disable-randomization
2084 Show the current setting of the explicit disable of the native randomization of
2085 the virtual address space of the started program.
2090 @section Your Program's Arguments
2092 @cindex arguments (to your program)
2093 The arguments to your program can be specified by the arguments of the
2095 They are passed to a shell, which expands wildcard characters and
2096 performs redirection of I/O, and thence to your program. Your
2097 @code{SHELL} environment variable (if it exists) specifies what shell
2098 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2099 the default shell (@file{/bin/sh} on Unix).
2101 On non-Unix systems, the program is usually invoked directly by
2102 @value{GDBN}, which emulates I/O redirection via the appropriate system
2103 calls, and the wildcard characters are expanded by the startup code of
2104 the program, not by the shell.
2106 @code{run} with no arguments uses the same arguments used by the previous
2107 @code{run}, or those set by the @code{set args} command.
2112 Specify the arguments to be used the next time your program is run. If
2113 @code{set args} has no arguments, @code{run} executes your program
2114 with no arguments. Once you have run your program with arguments,
2115 using @code{set args} before the next @code{run} is the only way to run
2116 it again without arguments.
2120 Show the arguments to give your program when it is started.
2124 @section Your Program's Environment
2126 @cindex environment (of your program)
2127 The @dfn{environment} consists of a set of environment variables and
2128 their values. Environment variables conventionally record such things as
2129 your user name, your home directory, your terminal type, and your search
2130 path for programs to run. Usually you set up environment variables with
2131 the shell and they are inherited by all the other programs you run. When
2132 debugging, it can be useful to try running your program with a modified
2133 environment without having to start @value{GDBN} over again.
2137 @item path @var{directory}
2138 Add @var{directory} to the front of the @code{PATH} environment variable
2139 (the search path for executables) that will be passed to your program.
2140 The value of @code{PATH} used by @value{GDBN} does not change.
2141 You may specify several directory names, separated by whitespace or by a
2142 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2143 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2144 is moved to the front, so it is searched sooner.
2146 You can use the string @samp{$cwd} to refer to whatever is the current
2147 working directory at the time @value{GDBN} searches the path. If you
2148 use @samp{.} instead, it refers to the directory where you executed the
2149 @code{path} command. @value{GDBN} replaces @samp{.} in the
2150 @var{directory} argument (with the current path) before adding
2151 @var{directory} to the search path.
2152 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2153 @c document that, since repeating it would be a no-op.
2157 Display the list of search paths for executables (the @code{PATH}
2158 environment variable).
2160 @kindex show environment
2161 @item show environment @r{[}@var{varname}@r{]}
2162 Print the value of environment variable @var{varname} to be given to
2163 your program when it starts. If you do not supply @var{varname},
2164 print the names and values of all environment variables to be given to
2165 your program. You can abbreviate @code{environment} as @code{env}.
2167 @kindex set environment
2168 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2169 Set environment variable @var{varname} to @var{value}. The value
2170 changes for your program only, not for @value{GDBN} itself. @var{value} may
2171 be any string; the values of environment variables are just strings, and
2172 any interpretation is supplied by your program itself. The @var{value}
2173 parameter is optional; if it is eliminated, the variable is set to a
2175 @c "any string" here does not include leading, trailing
2176 @c blanks. Gnu asks: does anyone care?
2178 For example, this command:
2185 tells the debugged program, when subsequently run, that its user is named
2186 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2187 are not actually required.)
2189 @kindex unset environment
2190 @item unset environment @var{varname}
2191 Remove variable @var{varname} from the environment to be passed to your
2192 program. This is different from @samp{set env @var{varname} =};
2193 @code{unset environment} removes the variable from the environment,
2194 rather than assigning it an empty value.
2197 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2199 by your @code{SHELL} environment variable if it exists (or
2200 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2201 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2202 @file{.bashrc} for BASH---any variables you set in that file affect
2203 your program. You may wish to move setting of environment variables to
2204 files that are only run when you sign on, such as @file{.login} or
2207 @node Working Directory
2208 @section Your Program's Working Directory
2210 @cindex working directory (of your program)
2211 Each time you start your program with @code{run}, it inherits its
2212 working directory from the current working directory of @value{GDBN}.
2213 The @value{GDBN} working directory is initially whatever it inherited
2214 from its parent process (typically the shell), but you can specify a new
2215 working directory in @value{GDBN} with the @code{cd} command.
2217 The @value{GDBN} working directory also serves as a default for the commands
2218 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2223 @cindex change working directory
2224 @item cd @var{directory}
2225 Set the @value{GDBN} working directory to @var{directory}.
2229 Print the @value{GDBN} working directory.
2232 It is generally impossible to find the current working directory of
2233 the process being debugged (since a program can change its directory
2234 during its run). If you work on a system where @value{GDBN} is
2235 configured with the @file{/proc} support, you can use the @code{info
2236 proc} command (@pxref{SVR4 Process Information}) to find out the
2237 current working directory of the debuggee.
2240 @section Your Program's Input and Output
2245 By default, the program you run under @value{GDBN} does input and output to
2246 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2247 to its own terminal modes to interact with you, but it records the terminal
2248 modes your program was using and switches back to them when you continue
2249 running your program.
2252 @kindex info terminal
2254 Displays information recorded by @value{GDBN} about the terminal modes your
2258 You can redirect your program's input and/or output using shell
2259 redirection with the @code{run} command. For example,
2266 starts your program, diverting its output to the file @file{outfile}.
2269 @cindex controlling terminal
2270 Another way to specify where your program should do input and output is
2271 with the @code{tty} command. This command accepts a file name as
2272 argument, and causes this file to be the default for future @code{run}
2273 commands. It also resets the controlling terminal for the child
2274 process, for future @code{run} commands. For example,
2281 directs that processes started with subsequent @code{run} commands
2282 default to do input and output on the terminal @file{/dev/ttyb} and have
2283 that as their controlling terminal.
2285 An explicit redirection in @code{run} overrides the @code{tty} command's
2286 effect on the input/output device, but not its effect on the controlling
2289 When you use the @code{tty} command or redirect input in the @code{run}
2290 command, only the input @emph{for your program} is affected. The input
2291 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2292 for @code{set inferior-tty}.
2294 @cindex inferior tty
2295 @cindex set inferior controlling terminal
2296 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2297 display the name of the terminal that will be used for future runs of your
2301 @item set inferior-tty /dev/ttyb
2302 @kindex set inferior-tty
2303 Set the tty for the program being debugged to /dev/ttyb.
2305 @item show inferior-tty
2306 @kindex show inferior-tty
2307 Show the current tty for the program being debugged.
2311 @section Debugging an Already-running Process
2316 @item attach @var{process-id}
2317 This command attaches to a running process---one that was started
2318 outside @value{GDBN}. (@code{info files} shows your active
2319 targets.) The command takes as argument a process ID. The usual way to
2320 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2321 or with the @samp{jobs -l} shell command.
2323 @code{attach} does not repeat if you press @key{RET} a second time after
2324 executing the command.
2327 To use @code{attach}, your program must be running in an environment
2328 which supports processes; for example, @code{attach} does not work for
2329 programs on bare-board targets that lack an operating system. You must
2330 also have permission to send the process a signal.
2332 When you use @code{attach}, the debugger finds the program running in
2333 the process first by looking in the current working directory, then (if
2334 the program is not found) by using the source file search path
2335 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2336 the @code{file} command to load the program. @xref{Files, ,Commands to
2339 The first thing @value{GDBN} does after arranging to debug the specified
2340 process is to stop it. You can examine and modify an attached process
2341 with all the @value{GDBN} commands that are ordinarily available when
2342 you start processes with @code{run}. You can insert breakpoints; you
2343 can step and continue; you can modify storage. If you would rather the
2344 process continue running, you may use the @code{continue} command after
2345 attaching @value{GDBN} to the process.
2350 When you have finished debugging the attached process, you can use the
2351 @code{detach} command to release it from @value{GDBN} control. Detaching
2352 the process continues its execution. After the @code{detach} command,
2353 that process and @value{GDBN} become completely independent once more, and you
2354 are ready to @code{attach} another process or start one with @code{run}.
2355 @code{detach} does not repeat if you press @key{RET} again after
2356 executing the command.
2359 If you exit @value{GDBN} while you have an attached process, you detach
2360 that process. If you use the @code{run} command, you kill that process.
2361 By default, @value{GDBN} asks for confirmation if you try to do either of these
2362 things; you can control whether or not you need to confirm by using the
2363 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2367 @section Killing the Child Process
2372 Kill the child process in which your program is running under @value{GDBN}.
2375 This command is useful if you wish to debug a core dump instead of a
2376 running process. @value{GDBN} ignores any core dump file while your program
2379 On some operating systems, a program cannot be executed outside @value{GDBN}
2380 while you have breakpoints set on it inside @value{GDBN}. You can use the
2381 @code{kill} command in this situation to permit running your program
2382 outside the debugger.
2384 The @code{kill} command is also useful if you wish to recompile and
2385 relink your program, since on many systems it is impossible to modify an
2386 executable file while it is running in a process. In this case, when you
2387 next type @code{run}, @value{GDBN} notices that the file has changed, and
2388 reads the symbol table again (while trying to preserve your current
2389 breakpoint settings).
2391 @node Inferiors and Programs
2392 @section Debugging Multiple Inferiors and Programs
2394 @value{GDBN} lets you run and debug multiple programs in a single
2395 session. In addition, @value{GDBN} on some systems may let you run
2396 several programs simultaneously (otherwise you have to exit from one
2397 before starting another). In the most general case, you can have
2398 multiple threads of execution in each of multiple processes, launched
2399 from multiple executables.
2402 @value{GDBN} represents the state of each program execution with an
2403 object called an @dfn{inferior}. An inferior typically corresponds to
2404 a process, but is more general and applies also to targets that do not
2405 have processes. Inferiors may be created before a process runs, and
2406 may be retained after a process exits. Inferiors have unique
2407 identifiers that are different from process ids. Usually each
2408 inferior will also have its own distinct address space, although some
2409 embedded targets may have several inferiors running in different parts
2410 of a single address space. Each inferior may in turn have multiple
2411 threads running in it.
2413 To find out what inferiors exist at any moment, use @w{@code{info
2417 @kindex info inferiors
2418 @item info inferiors
2419 Print a list of all inferiors currently being managed by @value{GDBN}.
2421 @value{GDBN} displays for each inferior (in this order):
2425 the inferior number assigned by @value{GDBN}
2428 the target system's inferior identifier
2431 the name of the executable the inferior is running.
2436 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2437 indicates the current inferior.
2441 @c end table here to get a little more width for example
2444 (@value{GDBP}) info inferiors
2445 Num Description Executable
2446 2 process 2307 hello
2447 * 1 process 3401 goodbye
2450 To switch focus between inferiors, use the @code{inferior} command:
2453 @kindex inferior @var{infno}
2454 @item inferior @var{infno}
2455 Make inferior number @var{infno} the current inferior. The argument
2456 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2457 in the first field of the @samp{info inferiors} display.
2461 You can get multiple executables into a debugging session via the
2462 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2463 systems @value{GDBN} can add inferiors to the debug session
2464 automatically by following calls to @code{fork} and @code{exec}. To
2465 remove inferiors from the debugging session use the
2466 @w{@code{remove-inferiors}} command.
2469 @kindex add-inferior
2470 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2471 Adds @var{n} inferiors to be run using @var{executable} as the
2472 executable. @var{n} defaults to 1. If no executable is specified,
2473 the inferiors begins empty, with no program. You can still assign or
2474 change the program assigned to the inferior at any time by using the
2475 @code{file} command with the executable name as its argument.
2477 @kindex clone-inferior
2478 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2479 Adds @var{n} inferiors ready to execute the same program as inferior
2480 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2481 number of the current inferior. This is a convenient command when you
2482 want to run another instance of the inferior you are debugging.
2485 (@value{GDBP}) info inferiors
2486 Num Description Executable
2487 * 1 process 29964 helloworld
2488 (@value{GDBP}) clone-inferior
2491 (@value{GDBP}) info inferiors
2492 Num Description Executable
2494 * 1 process 29964 helloworld
2497 You can now simply switch focus to inferior 2 and run it.
2499 @kindex remove-inferiors
2500 @item remove-inferiors @var{infno}@dots{}
2501 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2502 possible to remove an inferior that is running with this command. For
2503 those, use the @code{kill} or @code{detach} command first.
2507 To quit debugging one of the running inferiors that is not the current
2508 inferior, you can either detach from it by using the @w{@code{detach
2509 inferior}} command (allowing it to run independently), or kill it
2510 using the @w{@code{kill inferiors}} command:
2513 @kindex detach inferiors @var{infno}@dots{}
2514 @item detach inferior @var{infno}@dots{}
2515 Detach from the inferior or inferiors identified by @value{GDBN}
2516 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2517 still stays on the list of inferiors shown by @code{info inferiors},
2518 but its Description will show @samp{<null>}.
2520 @kindex kill inferiors @var{infno}@dots{}
2521 @item kill inferiors @var{infno}@dots{}
2522 Kill the inferior or inferiors identified by @value{GDBN} inferior
2523 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2524 stays on the list of inferiors shown by @code{info inferiors}, but its
2525 Description will show @samp{<null>}.
2528 After the successful completion of a command such as @code{detach},
2529 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2530 a normal process exit, the inferior is still valid and listed with
2531 @code{info inferiors}, ready to be restarted.
2534 To be notified when inferiors are started or exit under @value{GDBN}'s
2535 control use @w{@code{set print inferior-events}}:
2538 @kindex set print inferior-events
2539 @cindex print messages on inferior start and exit
2540 @item set print inferior-events
2541 @itemx set print inferior-events on
2542 @itemx set print inferior-events off
2543 The @code{set print inferior-events} command allows you to enable or
2544 disable printing of messages when @value{GDBN} notices that new
2545 inferiors have started or that inferiors have exited or have been
2546 detached. By default, these messages will not be printed.
2548 @kindex show print inferior-events
2549 @item show print inferior-events
2550 Show whether messages will be printed when @value{GDBN} detects that
2551 inferiors have started, exited or have been detached.
2554 Many commands will work the same with multiple programs as with a
2555 single program: e.g., @code{print myglobal} will simply display the
2556 value of @code{myglobal} in the current inferior.
2559 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2560 get more info about the relationship of inferiors, programs, address
2561 spaces in a debug session. You can do that with the @w{@code{maint
2562 info program-spaces}} command.
2565 @kindex maint info program-spaces
2566 @item maint info program-spaces
2567 Print a list of all program spaces currently being managed by
2570 @value{GDBN} displays for each program space (in this order):
2574 the program space number assigned by @value{GDBN}
2577 the name of the executable loaded into the program space, with e.g.,
2578 the @code{file} command.
2583 An asterisk @samp{*} preceding the @value{GDBN} program space number
2584 indicates the current program space.
2586 In addition, below each program space line, @value{GDBN} prints extra
2587 information that isn't suitable to display in tabular form. For
2588 example, the list of inferiors bound to the program space.
2591 (@value{GDBP}) maint info program-spaces
2594 Bound inferiors: ID 1 (process 21561)
2598 Here we can see that no inferior is running the program @code{hello},
2599 while @code{process 21561} is running the program @code{goodbye}. On
2600 some targets, it is possible that multiple inferiors are bound to the
2601 same program space. The most common example is that of debugging both
2602 the parent and child processes of a @code{vfork} call. For example,
2605 (@value{GDBP}) maint info program-spaces
2608 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2611 Here, both inferior 2 and inferior 1 are running in the same program
2612 space as a result of inferior 1 having executed a @code{vfork} call.
2616 @section Debugging Programs with Multiple Threads
2618 @cindex threads of execution
2619 @cindex multiple threads
2620 @cindex switching threads
2621 In some operating systems, such as HP-UX and Solaris, a single program
2622 may have more than one @dfn{thread} of execution. The precise semantics
2623 of threads differ from one operating system to another, but in general
2624 the threads of a single program are akin to multiple processes---except
2625 that they share one address space (that is, they can all examine and
2626 modify the same variables). On the other hand, each thread has its own
2627 registers and execution stack, and perhaps private memory.
2629 @value{GDBN} provides these facilities for debugging multi-thread
2633 @item automatic notification of new threads
2634 @item @samp{thread @var{threadno}}, a command to switch among threads
2635 @item @samp{info threads}, a command to inquire about existing threads
2636 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2637 a command to apply a command to a list of threads
2638 @item thread-specific breakpoints
2639 @item @samp{set print thread-events}, which controls printing of
2640 messages on thread start and exit.
2641 @item @samp{set libthread-db-search-path @var{path}}, which lets
2642 the user specify which @code{libthread_db} to use if the default choice
2643 isn't compatible with the program.
2647 @emph{Warning:} These facilities are not yet available on every
2648 @value{GDBN} configuration where the operating system supports threads.
2649 If your @value{GDBN} does not support threads, these commands have no
2650 effect. For example, a system without thread support shows no output
2651 from @samp{info threads}, and always rejects the @code{thread} command,
2655 (@value{GDBP}) info threads
2656 (@value{GDBP}) thread 1
2657 Thread ID 1 not known. Use the "info threads" command to
2658 see the IDs of currently known threads.
2660 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2661 @c doesn't support threads"?
2664 @cindex focus of debugging
2665 @cindex current thread
2666 The @value{GDBN} thread debugging facility allows you to observe all
2667 threads while your program runs---but whenever @value{GDBN} takes
2668 control, one thread in particular is always the focus of debugging.
2669 This thread is called the @dfn{current thread}. Debugging commands show
2670 program information from the perspective of the current thread.
2672 @cindex @code{New} @var{systag} message
2673 @cindex thread identifier (system)
2674 @c FIXME-implementors!! It would be more helpful if the [New...] message
2675 @c included GDB's numeric thread handle, so you could just go to that
2676 @c thread without first checking `info threads'.
2677 Whenever @value{GDBN} detects a new thread in your program, it displays
2678 the target system's identification for the thread with a message in the
2679 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2680 whose form varies depending on the particular system. For example, on
2681 @sc{gnu}/Linux, you might see
2684 [New Thread 0x41e02940 (LWP 25582)]
2688 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2689 the @var{systag} is simply something like @samp{process 368}, with no
2692 @c FIXME!! (1) Does the [New...] message appear even for the very first
2693 @c thread of a program, or does it only appear for the
2694 @c second---i.e.@: when it becomes obvious we have a multithread
2696 @c (2) *Is* there necessarily a first thread always? Or do some
2697 @c multithread systems permit starting a program with multiple
2698 @c threads ab initio?
2700 @cindex thread number
2701 @cindex thread identifier (GDB)
2702 For debugging purposes, @value{GDBN} associates its own thread
2703 number---always a single integer---with each thread in your program.
2706 @kindex info threads
2707 @item info threads @r{[}@var{id}@dots{}@r{]}
2708 Display a summary of all threads currently in your program. Optional
2709 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2710 means to print information only about the specified thread or threads.
2711 @value{GDBN} displays for each thread (in this order):
2715 the thread number assigned by @value{GDBN}
2718 the target system's thread identifier (@var{systag})
2721 the thread's name, if one is known. A thread can either be named by
2722 the user (see @code{thread name}, below), or, in some cases, by the
2726 the current stack frame summary for that thread
2730 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2731 indicates the current thread.
2735 @c end table here to get a little more width for example
2738 (@value{GDBP}) info threads
2740 3 process 35 thread 27 0x34e5 in sigpause ()
2741 2 process 35 thread 23 0x34e5 in sigpause ()
2742 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2746 On Solaris, you can display more information about user threads with a
2747 Solaris-specific command:
2750 @item maint info sol-threads
2751 @kindex maint info sol-threads
2752 @cindex thread info (Solaris)
2753 Display info on Solaris user threads.
2757 @kindex thread @var{threadno}
2758 @item thread @var{threadno}
2759 Make thread number @var{threadno} the current thread. The command
2760 argument @var{threadno} is the internal @value{GDBN} thread number, as
2761 shown in the first field of the @samp{info threads} display.
2762 @value{GDBN} responds by displaying the system identifier of the thread
2763 you selected, and its current stack frame summary:
2766 (@value{GDBP}) thread 2
2767 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2768 #0 some_function (ignore=0x0) at example.c:8
2769 8 printf ("hello\n");
2773 As with the @samp{[New @dots{}]} message, the form of the text after
2774 @samp{Switching to} depends on your system's conventions for identifying
2777 @vindex $_thread@r{, convenience variable}
2778 The debugger convenience variable @samp{$_thread} contains the number
2779 of the current thread. You may find this useful in writing breakpoint
2780 conditional expressions, command scripts, and so forth. See
2781 @xref{Convenience Vars,, Convenience Variables}, for general
2782 information on convenience variables.
2784 @kindex thread apply
2785 @cindex apply command to several threads
2786 @item thread apply [@var{threadno} | all] @var{command}
2787 The @code{thread apply} command allows you to apply the named
2788 @var{command} to one or more threads. Specify the numbers of the
2789 threads that you want affected with the command argument
2790 @var{threadno}. It can be a single thread number, one of the numbers
2791 shown in the first field of the @samp{info threads} display; or it
2792 could be a range of thread numbers, as in @code{2-4}. To apply a
2793 command to all threads, type @kbd{thread apply all @var{command}}.
2796 @cindex name a thread
2797 @item thread name [@var{name}]
2798 This command assigns a name to the current thread. If no argument is
2799 given, any existing user-specified name is removed. The thread name
2800 appears in the @samp{info threads} display.
2802 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2803 determine the name of the thread as given by the OS. On these
2804 systems, a name specified with @samp{thread name} will override the
2805 system-give name, and removing the user-specified name will cause
2806 @value{GDBN} to once again display the system-specified name.
2809 @cindex search for a thread
2810 @item thread find [@var{regexp}]
2811 Search for and display thread ids whose name or @var{systag}
2812 matches the supplied regular expression.
2814 As well as being the complement to the @samp{thread name} command,
2815 this command also allows you to identify a thread by its target
2816 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2820 (@value{GDBN}) thread find 26688
2821 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2822 (@value{GDBN}) info thread 4
2824 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2827 @kindex set print thread-events
2828 @cindex print messages on thread start and exit
2829 @item set print thread-events
2830 @itemx set print thread-events on
2831 @itemx set print thread-events off
2832 The @code{set print thread-events} command allows you to enable or
2833 disable printing of messages when @value{GDBN} notices that new threads have
2834 started or that threads have exited. By default, these messages will
2835 be printed if detection of these events is supported by the target.
2836 Note that these messages cannot be disabled on all targets.
2838 @kindex show print thread-events
2839 @item show print thread-events
2840 Show whether messages will be printed when @value{GDBN} detects that threads
2841 have started and exited.
2844 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2845 more information about how @value{GDBN} behaves when you stop and start
2846 programs with multiple threads.
2848 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2849 watchpoints in programs with multiple threads.
2852 @kindex set libthread-db-search-path
2853 @cindex search path for @code{libthread_db}
2854 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2855 If this variable is set, @var{path} is a colon-separated list of
2856 directories @value{GDBN} will use to search for @code{libthread_db}.
2857 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2860 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2861 @code{libthread_db} library to obtain information about threads in the
2862 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2863 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2864 with default system shared library directories, and finally the directory
2865 from which @code{libpthread} was loaded in the inferior process.
2867 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2868 @value{GDBN} attempts to initialize it with the current inferior process.
2869 If this initialization fails (which could happen because of a version
2870 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2871 will unload @code{libthread_db}, and continue with the next directory.
2872 If none of @code{libthread_db} libraries initialize successfully,
2873 @value{GDBN} will issue a warning and thread debugging will be disabled.
2875 Setting @code{libthread-db-search-path} is currently implemented
2876 only on some platforms.
2878 @kindex show libthread-db-search-path
2879 @item show libthread-db-search-path
2880 Display current libthread_db search path.
2882 @kindex set debug libthread-db
2883 @kindex show debug libthread-db
2884 @cindex debugging @code{libthread_db}
2885 @item set debug libthread-db
2886 @itemx show debug libthread-db
2887 Turns on or off display of @code{libthread_db}-related events.
2888 Use @code{1} to enable, @code{0} to disable.
2892 @section Debugging Forks
2894 @cindex fork, debugging programs which call
2895 @cindex multiple processes
2896 @cindex processes, multiple
2897 On most systems, @value{GDBN} has no special support for debugging
2898 programs which create additional processes using the @code{fork}
2899 function. When a program forks, @value{GDBN} will continue to debug the
2900 parent process and the child process will run unimpeded. If you have
2901 set a breakpoint in any code which the child then executes, the child
2902 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2903 will cause it to terminate.
2905 However, if you want to debug the child process there is a workaround
2906 which isn't too painful. Put a call to @code{sleep} in the code which
2907 the child process executes after the fork. It may be useful to sleep
2908 only if a certain environment variable is set, or a certain file exists,
2909 so that the delay need not occur when you don't want to run @value{GDBN}
2910 on the child. While the child is sleeping, use the @code{ps} program to
2911 get its process ID. Then tell @value{GDBN} (a new invocation of
2912 @value{GDBN} if you are also debugging the parent process) to attach to
2913 the child process (@pxref{Attach}). From that point on you can debug
2914 the child process just like any other process which you attached to.
2916 On some systems, @value{GDBN} provides support for debugging programs that
2917 create additional processes using the @code{fork} or @code{vfork} functions.
2918 Currently, the only platforms with this feature are HP-UX (11.x and later
2919 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2921 By default, when a program forks, @value{GDBN} will continue to debug
2922 the parent process and the child process will run unimpeded.
2924 If you want to follow the child process instead of the parent process,
2925 use the command @w{@code{set follow-fork-mode}}.
2928 @kindex set follow-fork-mode
2929 @item set follow-fork-mode @var{mode}
2930 Set the debugger response to a program call of @code{fork} or
2931 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2932 process. The @var{mode} argument can be:
2936 The original process is debugged after a fork. The child process runs
2937 unimpeded. This is the default.
2940 The new process is debugged after a fork. The parent process runs
2945 @kindex show follow-fork-mode
2946 @item show follow-fork-mode
2947 Display the current debugger response to a @code{fork} or @code{vfork} call.
2950 @cindex debugging multiple processes
2951 On Linux, if you want to debug both the parent and child processes, use the
2952 command @w{@code{set detach-on-fork}}.
2955 @kindex set detach-on-fork
2956 @item set detach-on-fork @var{mode}
2957 Tells gdb whether to detach one of the processes after a fork, or
2958 retain debugger control over them both.
2962 The child process (or parent process, depending on the value of
2963 @code{follow-fork-mode}) will be detached and allowed to run
2964 independently. This is the default.
2967 Both processes will be held under the control of @value{GDBN}.
2968 One process (child or parent, depending on the value of
2969 @code{follow-fork-mode}) is debugged as usual, while the other
2974 @kindex show detach-on-fork
2975 @item show detach-on-fork
2976 Show whether detach-on-fork mode is on/off.
2979 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2980 will retain control of all forked processes (including nested forks).
2981 You can list the forked processes under the control of @value{GDBN} by
2982 using the @w{@code{info inferiors}} command, and switch from one fork
2983 to another by using the @code{inferior} command (@pxref{Inferiors and
2984 Programs, ,Debugging Multiple Inferiors and Programs}).
2986 To quit debugging one of the forked processes, you can either detach
2987 from it by using the @w{@code{detach inferiors}} command (allowing it
2988 to run independently), or kill it using the @w{@code{kill inferiors}}
2989 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2992 If you ask to debug a child process and a @code{vfork} is followed by an
2993 @code{exec}, @value{GDBN} executes the new target up to the first
2994 breakpoint in the new target. If you have a breakpoint set on
2995 @code{main} in your original program, the breakpoint will also be set on
2996 the child process's @code{main}.
2998 On some systems, when a child process is spawned by @code{vfork}, you
2999 cannot debug the child or parent until an @code{exec} call completes.
3001 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3002 call executes, the new target restarts. To restart the parent
3003 process, use the @code{file} command with the parent executable name
3004 as its argument. By default, after an @code{exec} call executes,
3005 @value{GDBN} discards the symbols of the previous executable image.
3006 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3010 @kindex set follow-exec-mode
3011 @item set follow-exec-mode @var{mode}
3013 Set debugger response to a program call of @code{exec}. An
3014 @code{exec} call replaces the program image of a process.
3016 @code{follow-exec-mode} can be:
3020 @value{GDBN} creates a new inferior and rebinds the process to this
3021 new inferior. The program the process was running before the
3022 @code{exec} call can be restarted afterwards by restarting the
3028 (@value{GDBP}) info inferiors
3030 Id Description Executable
3033 process 12020 is executing new program: prog2
3034 Program exited normally.
3035 (@value{GDBP}) info inferiors
3036 Id Description Executable
3042 @value{GDBN} keeps the process bound to the same inferior. The new
3043 executable image replaces the previous executable loaded in the
3044 inferior. Restarting the inferior after the @code{exec} call, with
3045 e.g., the @code{run} command, restarts the executable the process was
3046 running after the @code{exec} call. This is the default mode.
3051 (@value{GDBP}) info inferiors
3052 Id Description Executable
3055 process 12020 is executing new program: prog2
3056 Program exited normally.
3057 (@value{GDBP}) info inferiors
3058 Id Description Executable
3065 You can use the @code{catch} command to make @value{GDBN} stop whenever
3066 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3067 Catchpoints, ,Setting Catchpoints}.
3069 @node Checkpoint/Restart
3070 @section Setting a @emph{Bookmark} to Return to Later
3075 @cindex snapshot of a process
3076 @cindex rewind program state
3078 On certain operating systems@footnote{Currently, only
3079 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3080 program's state, called a @dfn{checkpoint}, and come back to it
3083 Returning to a checkpoint effectively undoes everything that has
3084 happened in the program since the @code{checkpoint} was saved. This
3085 includes changes in memory, registers, and even (within some limits)
3086 system state. Effectively, it is like going back in time to the
3087 moment when the checkpoint was saved.
3089 Thus, if you're stepping thru a program and you think you're
3090 getting close to the point where things go wrong, you can save
3091 a checkpoint. Then, if you accidentally go too far and miss
3092 the critical statement, instead of having to restart your program
3093 from the beginning, you can just go back to the checkpoint and
3094 start again from there.
3096 This can be especially useful if it takes a lot of time or
3097 steps to reach the point where you think the bug occurs.
3099 To use the @code{checkpoint}/@code{restart} method of debugging:
3104 Save a snapshot of the debugged program's current execution state.
3105 The @code{checkpoint} command takes no arguments, but each checkpoint
3106 is assigned a small integer id, similar to a breakpoint id.
3108 @kindex info checkpoints
3109 @item info checkpoints
3110 List the checkpoints that have been saved in the current debugging
3111 session. For each checkpoint, the following information will be
3118 @item Source line, or label
3121 @kindex restart @var{checkpoint-id}
3122 @item restart @var{checkpoint-id}
3123 Restore the program state that was saved as checkpoint number
3124 @var{checkpoint-id}. All program variables, registers, stack frames
3125 etc.@: will be returned to the values that they had when the checkpoint
3126 was saved. In essence, gdb will ``wind back the clock'' to the point
3127 in time when the checkpoint was saved.
3129 Note that breakpoints, @value{GDBN} variables, command history etc.
3130 are not affected by restoring a checkpoint. In general, a checkpoint
3131 only restores things that reside in the program being debugged, not in
3134 @kindex delete checkpoint @var{checkpoint-id}
3135 @item delete checkpoint @var{checkpoint-id}
3136 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3140 Returning to a previously saved checkpoint will restore the user state
3141 of the program being debugged, plus a significant subset of the system
3142 (OS) state, including file pointers. It won't ``un-write'' data from
3143 a file, but it will rewind the file pointer to the previous location,
3144 so that the previously written data can be overwritten. For files
3145 opened in read mode, the pointer will also be restored so that the
3146 previously read data can be read again.
3148 Of course, characters that have been sent to a printer (or other
3149 external device) cannot be ``snatched back'', and characters received
3150 from eg.@: a serial device can be removed from internal program buffers,
3151 but they cannot be ``pushed back'' into the serial pipeline, ready to
3152 be received again. Similarly, the actual contents of files that have
3153 been changed cannot be restored (at this time).
3155 However, within those constraints, you actually can ``rewind'' your
3156 program to a previously saved point in time, and begin debugging it
3157 again --- and you can change the course of events so as to debug a
3158 different execution path this time.
3160 @cindex checkpoints and process id
3161 Finally, there is one bit of internal program state that will be
3162 different when you return to a checkpoint --- the program's process
3163 id. Each checkpoint will have a unique process id (or @var{pid}),
3164 and each will be different from the program's original @var{pid}.
3165 If your program has saved a local copy of its process id, this could
3166 potentially pose a problem.
3168 @subsection A Non-obvious Benefit of Using Checkpoints
3170 On some systems such as @sc{gnu}/Linux, address space randomization
3171 is performed on new processes for security reasons. This makes it
3172 difficult or impossible to set a breakpoint, or watchpoint, on an
3173 absolute address if you have to restart the program, since the
3174 absolute location of a symbol will change from one execution to the
3177 A checkpoint, however, is an @emph{identical} copy of a process.
3178 Therefore if you create a checkpoint at (eg.@:) the start of main,
3179 and simply return to that checkpoint instead of restarting the
3180 process, you can avoid the effects of address randomization and
3181 your symbols will all stay in the same place.
3184 @chapter Stopping and Continuing
3186 The principal purposes of using a debugger are so that you can stop your
3187 program before it terminates; or so that, if your program runs into
3188 trouble, you can investigate and find out why.
3190 Inside @value{GDBN}, your program may stop for any of several reasons,
3191 such as a signal, a breakpoint, or reaching a new line after a
3192 @value{GDBN} command such as @code{step}. You may then examine and
3193 change variables, set new breakpoints or remove old ones, and then
3194 continue execution. Usually, the messages shown by @value{GDBN} provide
3195 ample explanation of the status of your program---but you can also
3196 explicitly request this information at any time.
3199 @kindex info program
3201 Display information about the status of your program: whether it is
3202 running or not, what process it is, and why it stopped.
3206 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3207 * Continuing and Stepping:: Resuming execution
3209 * Thread Stops:: Stopping and starting multi-thread programs
3213 @section Breakpoints, Watchpoints, and Catchpoints
3216 A @dfn{breakpoint} makes your program stop whenever a certain point in
3217 the program is reached. For each breakpoint, you can add conditions to
3218 control in finer detail whether your program stops. You can set
3219 breakpoints with the @code{break} command and its variants (@pxref{Set
3220 Breaks, ,Setting Breakpoints}), to specify the place where your program
3221 should stop by line number, function name or exact address in the
3224 On some systems, you can set breakpoints in shared libraries before
3225 the executable is run. There is a minor limitation on HP-UX systems:
3226 you must wait until the executable is run in order to set breakpoints
3227 in shared library routines that are not called directly by the program
3228 (for example, routines that are arguments in a @code{pthread_create}
3232 @cindex data breakpoints
3233 @cindex memory tracing
3234 @cindex breakpoint on memory address
3235 @cindex breakpoint on variable modification
3236 A @dfn{watchpoint} is a special breakpoint that stops your program
3237 when the value of an expression changes. The expression may be a value
3238 of a variable, or it could involve values of one or more variables
3239 combined by operators, such as @samp{a + b}. This is sometimes called
3240 @dfn{data breakpoints}. You must use a different command to set
3241 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3242 from that, you can manage a watchpoint like any other breakpoint: you
3243 enable, disable, and delete both breakpoints and watchpoints using the
3246 You can arrange to have values from your program displayed automatically
3247 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3251 @cindex breakpoint on events
3252 A @dfn{catchpoint} is another special breakpoint that stops your program
3253 when a certain kind of event occurs, such as the throwing of a C@t{++}
3254 exception or the loading of a library. As with watchpoints, you use a
3255 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3256 Catchpoints}), but aside from that, you can manage a catchpoint like any
3257 other breakpoint. (To stop when your program receives a signal, use the
3258 @code{handle} command; see @ref{Signals, ,Signals}.)
3260 @cindex breakpoint numbers
3261 @cindex numbers for breakpoints
3262 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3263 catchpoint when you create it; these numbers are successive integers
3264 starting with one. In many of the commands for controlling various
3265 features of breakpoints you use the breakpoint number to say which
3266 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3267 @dfn{disabled}; if disabled, it has no effect on your program until you
3270 @cindex breakpoint ranges
3271 @cindex ranges of breakpoints
3272 Some @value{GDBN} commands accept a range of breakpoints on which to
3273 operate. A breakpoint range is either a single breakpoint number, like
3274 @samp{5}, or two such numbers, in increasing order, separated by a
3275 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3276 all breakpoints in that range are operated on.
3279 * Set Breaks:: Setting breakpoints
3280 * Set Watchpoints:: Setting watchpoints
3281 * Set Catchpoints:: Setting catchpoints
3282 * Delete Breaks:: Deleting breakpoints
3283 * Disabling:: Disabling breakpoints
3284 * Conditions:: Break conditions
3285 * Break Commands:: Breakpoint command lists
3286 * Save Breakpoints:: How to save breakpoints in a file
3287 * Error in Breakpoints:: ``Cannot insert breakpoints''
3288 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3292 @subsection Setting Breakpoints
3294 @c FIXME LMB what does GDB do if no code on line of breakpt?
3295 @c consider in particular declaration with/without initialization.
3297 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3300 @kindex b @r{(@code{break})}
3301 @vindex $bpnum@r{, convenience variable}
3302 @cindex latest breakpoint
3303 Breakpoints are set with the @code{break} command (abbreviated
3304 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3305 number of the breakpoint you've set most recently; see @ref{Convenience
3306 Vars,, Convenience Variables}, for a discussion of what you can do with
3307 convenience variables.
3310 @item break @var{location}
3311 Set a breakpoint at the given @var{location}, which can specify a
3312 function name, a line number, or an address of an instruction.
3313 (@xref{Specify Location}, for a list of all the possible ways to
3314 specify a @var{location}.) The breakpoint will stop your program just
3315 before it executes any of the code in the specified @var{location}.
3317 When using source languages that permit overloading of symbols, such as
3318 C@t{++}, a function name may refer to more than one possible place to break.
3319 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3322 It is also possible to insert a breakpoint that will stop the program
3323 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3324 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3327 When called without any arguments, @code{break} sets a breakpoint at
3328 the next instruction to be executed in the selected stack frame
3329 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3330 innermost, this makes your program stop as soon as control
3331 returns to that frame. This is similar to the effect of a
3332 @code{finish} command in the frame inside the selected frame---except
3333 that @code{finish} does not leave an active breakpoint. If you use
3334 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3335 the next time it reaches the current location; this may be useful
3338 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3339 least one instruction has been executed. If it did not do this, you
3340 would be unable to proceed past a breakpoint without first disabling the
3341 breakpoint. This rule applies whether or not the breakpoint already
3342 existed when your program stopped.
3344 @item break @dots{} if @var{cond}
3345 Set a breakpoint with condition @var{cond}; evaluate the expression
3346 @var{cond} each time the breakpoint is reached, and stop only if the
3347 value is nonzero---that is, if @var{cond} evaluates as true.
3348 @samp{@dots{}} stands for one of the possible arguments described
3349 above (or no argument) specifying where to break. @xref{Conditions,
3350 ,Break Conditions}, for more information on breakpoint conditions.
3353 @item tbreak @var{args}
3354 Set a breakpoint enabled only for one stop. @var{args} are the
3355 same as for the @code{break} command, and the breakpoint is set in the same
3356 way, but the breakpoint is automatically deleted after the first time your
3357 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3360 @cindex hardware breakpoints
3361 @item hbreak @var{args}
3362 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3363 @code{break} command and the breakpoint is set in the same way, but the
3364 breakpoint requires hardware support and some target hardware may not
3365 have this support. The main purpose of this is EPROM/ROM code
3366 debugging, so you can set a breakpoint at an instruction without
3367 changing the instruction. This can be used with the new trap-generation
3368 provided by SPARClite DSU and most x86-based targets. These targets
3369 will generate traps when a program accesses some data or instruction
3370 address that is assigned to the debug registers. However the hardware
3371 breakpoint registers can take a limited number of breakpoints. For
3372 example, on the DSU, only two data breakpoints can be set at a time, and
3373 @value{GDBN} will reject this command if more than two are used. Delete
3374 or disable unused hardware breakpoints before setting new ones
3375 (@pxref{Disabling, ,Disabling Breakpoints}).
3376 @xref{Conditions, ,Break Conditions}.
3377 For remote targets, you can restrict the number of hardware
3378 breakpoints @value{GDBN} will use, see @ref{set remote
3379 hardware-breakpoint-limit}.
3382 @item thbreak @var{args}
3383 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3384 are the same as for the @code{hbreak} command and the breakpoint is set in
3385 the same way. However, like the @code{tbreak} command,
3386 the breakpoint is automatically deleted after the
3387 first time your program stops there. Also, like the @code{hbreak}
3388 command, the breakpoint requires hardware support and some target hardware
3389 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3390 See also @ref{Conditions, ,Break Conditions}.
3393 @cindex regular expression
3394 @cindex breakpoints at functions matching a regexp
3395 @cindex set breakpoints in many functions
3396 @item rbreak @var{regex}
3397 Set breakpoints on all functions matching the regular expression
3398 @var{regex}. This command sets an unconditional breakpoint on all
3399 matches, printing a list of all breakpoints it set. Once these
3400 breakpoints are set, they are treated just like the breakpoints set with
3401 the @code{break} command. You can delete them, disable them, or make
3402 them conditional the same way as any other breakpoint.
3404 The syntax of the regular expression is the standard one used with tools
3405 like @file{grep}. Note that this is different from the syntax used by
3406 shells, so for instance @code{foo*} matches all functions that include
3407 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3408 @code{.*} leading and trailing the regular expression you supply, so to
3409 match only functions that begin with @code{foo}, use @code{^foo}.
3411 @cindex non-member C@t{++} functions, set breakpoint in
3412 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3413 breakpoints on overloaded functions that are not members of any special
3416 @cindex set breakpoints on all functions
3417 The @code{rbreak} command can be used to set breakpoints in
3418 @strong{all} the functions in a program, like this:
3421 (@value{GDBP}) rbreak .
3424 @item rbreak @var{file}:@var{regex}
3425 If @code{rbreak} is called with a filename qualification, it limits
3426 the search for functions matching the given regular expression to the
3427 specified @var{file}. This can be used, for example, to set breakpoints on
3428 every function in a given file:
3431 (@value{GDBP}) rbreak file.c:.
3434 The colon separating the filename qualifier from the regex may
3435 optionally be surrounded by spaces.
3437 @kindex info breakpoints
3438 @cindex @code{$_} and @code{info breakpoints}
3439 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3440 @itemx info break @r{[}@var{n}@dots{}@r{]}
3441 Print a table of all breakpoints, watchpoints, and catchpoints set and
3442 not deleted. Optional argument @var{n} means print information only
3443 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3444 For each breakpoint, following columns are printed:
3447 @item Breakpoint Numbers
3449 Breakpoint, watchpoint, or catchpoint.
3451 Whether the breakpoint is marked to be disabled or deleted when hit.
3452 @item Enabled or Disabled
3453 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3454 that are not enabled.
3456 Where the breakpoint is in your program, as a memory address. For a
3457 pending breakpoint whose address is not yet known, this field will
3458 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3459 library that has the symbol or line referred by breakpoint is loaded.
3460 See below for details. A breakpoint with several locations will
3461 have @samp{<MULTIPLE>} in this field---see below for details.
3463 Where the breakpoint is in the source for your program, as a file and
3464 line number. For a pending breakpoint, the original string passed to
3465 the breakpoint command will be listed as it cannot be resolved until
3466 the appropriate shared library is loaded in the future.
3470 If a breakpoint is conditional, @code{info break} shows the condition on
3471 the line following the affected breakpoint; breakpoint commands, if any,
3472 are listed after that. A pending breakpoint is allowed to have a condition
3473 specified for it. The condition is not parsed for validity until a shared
3474 library is loaded that allows the pending breakpoint to resolve to a
3478 @code{info break} with a breakpoint
3479 number @var{n} as argument lists only that breakpoint. The
3480 convenience variable @code{$_} and the default examining-address for
3481 the @code{x} command are set to the address of the last breakpoint
3482 listed (@pxref{Memory, ,Examining Memory}).
3485 @code{info break} displays a count of the number of times the breakpoint
3486 has been hit. This is especially useful in conjunction with the
3487 @code{ignore} command. You can ignore a large number of breakpoint
3488 hits, look at the breakpoint info to see how many times the breakpoint
3489 was hit, and then run again, ignoring one less than that number. This
3490 will get you quickly to the last hit of that breakpoint.
3493 @value{GDBN} allows you to set any number of breakpoints at the same place in
3494 your program. There is nothing silly or meaningless about this. When
3495 the breakpoints are conditional, this is even useful
3496 (@pxref{Conditions, ,Break Conditions}).
3498 @cindex multiple locations, breakpoints
3499 @cindex breakpoints, multiple locations
3500 It is possible that a breakpoint corresponds to several locations
3501 in your program. Examples of this situation are:
3505 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3506 instances of the function body, used in different cases.
3509 For a C@t{++} template function, a given line in the function can
3510 correspond to any number of instantiations.
3513 For an inlined function, a given source line can correspond to
3514 several places where that function is inlined.
3517 In all those cases, @value{GDBN} will insert a breakpoint at all
3518 the relevant locations@footnote{
3519 As of this writing, multiple-location breakpoints work only if there's
3520 line number information for all the locations. This means that they
3521 will generally not work in system libraries, unless you have debug
3522 info with line numbers for them.}.
3524 A breakpoint with multiple locations is displayed in the breakpoint
3525 table using several rows---one header row, followed by one row for
3526 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3527 address column. The rows for individual locations contain the actual
3528 addresses for locations, and show the functions to which those
3529 locations belong. The number column for a location is of the form
3530 @var{breakpoint-number}.@var{location-number}.
3535 Num Type Disp Enb Address What
3536 1 breakpoint keep y <MULTIPLE>
3538 breakpoint already hit 1 time
3539 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3540 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3543 Each location can be individually enabled or disabled by passing
3544 @var{breakpoint-number}.@var{location-number} as argument to the
3545 @code{enable} and @code{disable} commands. Note that you cannot
3546 delete the individual locations from the list, you can only delete the
3547 entire list of locations that belong to their parent breakpoint (with
3548 the @kbd{delete @var{num}} command, where @var{num} is the number of
3549 the parent breakpoint, 1 in the above example). Disabling or enabling
3550 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3551 that belong to that breakpoint.
3553 @cindex pending breakpoints
3554 It's quite common to have a breakpoint inside a shared library.
3555 Shared libraries can be loaded and unloaded explicitly,
3556 and possibly repeatedly, as the program is executed. To support
3557 this use case, @value{GDBN} updates breakpoint locations whenever
3558 any shared library is loaded or unloaded. Typically, you would
3559 set a breakpoint in a shared library at the beginning of your
3560 debugging session, when the library is not loaded, and when the
3561 symbols from the library are not available. When you try to set
3562 breakpoint, @value{GDBN} will ask you if you want to set
3563 a so called @dfn{pending breakpoint}---breakpoint whose address
3564 is not yet resolved.
3566 After the program is run, whenever a new shared library is loaded,
3567 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3568 shared library contains the symbol or line referred to by some
3569 pending breakpoint, that breakpoint is resolved and becomes an
3570 ordinary breakpoint. When a library is unloaded, all breakpoints
3571 that refer to its symbols or source lines become pending again.
3573 This logic works for breakpoints with multiple locations, too. For
3574 example, if you have a breakpoint in a C@t{++} template function, and
3575 a newly loaded shared library has an instantiation of that template,
3576 a new location is added to the list of locations for the breakpoint.
3578 Except for having unresolved address, pending breakpoints do not
3579 differ from regular breakpoints. You can set conditions or commands,
3580 enable and disable them and perform other breakpoint operations.
3582 @value{GDBN} provides some additional commands for controlling what
3583 happens when the @samp{break} command cannot resolve breakpoint
3584 address specification to an address:
3586 @kindex set breakpoint pending
3587 @kindex show breakpoint pending
3589 @item set breakpoint pending auto
3590 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3591 location, it queries you whether a pending breakpoint should be created.
3593 @item set breakpoint pending on
3594 This indicates that an unrecognized breakpoint location should automatically
3595 result in a pending breakpoint being created.
3597 @item set breakpoint pending off
3598 This indicates that pending breakpoints are not to be created. Any
3599 unrecognized breakpoint location results in an error. This setting does
3600 not affect any pending breakpoints previously created.
3602 @item show breakpoint pending
3603 Show the current behavior setting for creating pending breakpoints.
3606 The settings above only affect the @code{break} command and its
3607 variants. Once breakpoint is set, it will be automatically updated
3608 as shared libraries are loaded and unloaded.
3610 @cindex automatic hardware breakpoints
3611 For some targets, @value{GDBN} can automatically decide if hardware or
3612 software breakpoints should be used, depending on whether the
3613 breakpoint address is read-only or read-write. This applies to
3614 breakpoints set with the @code{break} command as well as to internal
3615 breakpoints set by commands like @code{next} and @code{finish}. For
3616 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3619 You can control this automatic behaviour with the following commands::
3621 @kindex set breakpoint auto-hw
3622 @kindex show breakpoint auto-hw
3624 @item set breakpoint auto-hw on
3625 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3626 will try to use the target memory map to decide if software or hardware
3627 breakpoint must be used.
3629 @item set breakpoint auto-hw off
3630 This indicates @value{GDBN} should not automatically select breakpoint
3631 type. If the target provides a memory map, @value{GDBN} will warn when
3632 trying to set software breakpoint at a read-only address.
3635 @value{GDBN} normally implements breakpoints by replacing the program code
3636 at the breakpoint address with a special instruction, which, when
3637 executed, given control to the debugger. By default, the program
3638 code is so modified only when the program is resumed. As soon as
3639 the program stops, @value{GDBN} restores the original instructions. This
3640 behaviour guards against leaving breakpoints inserted in the
3641 target should gdb abrubptly disconnect. However, with slow remote
3642 targets, inserting and removing breakpoint can reduce the performance.
3643 This behavior can be controlled with the following commands::
3645 @kindex set breakpoint always-inserted
3646 @kindex show breakpoint always-inserted
3648 @item set breakpoint always-inserted off
3649 All breakpoints, including newly added by the user, are inserted in
3650 the target only when the target is resumed. All breakpoints are
3651 removed from the target when it stops.
3653 @item set breakpoint always-inserted on
3654 Causes all breakpoints to be inserted in the target at all times. If
3655 the user adds a new breakpoint, or changes an existing breakpoint, the
3656 breakpoints in the target are updated immediately. A breakpoint is
3657 removed from the target only when breakpoint itself is removed.
3659 @cindex non-stop mode, and @code{breakpoint always-inserted}
3660 @item set breakpoint always-inserted auto
3661 This is the default mode. If @value{GDBN} is controlling the inferior
3662 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3663 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3664 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3665 @code{breakpoint always-inserted} mode is off.
3668 @cindex negative breakpoint numbers
3669 @cindex internal @value{GDBN} breakpoints
3670 @value{GDBN} itself sometimes sets breakpoints in your program for
3671 special purposes, such as proper handling of @code{longjmp} (in C
3672 programs). These internal breakpoints are assigned negative numbers,
3673 starting with @code{-1}; @samp{info breakpoints} does not display them.
3674 You can see these breakpoints with the @value{GDBN} maintenance command
3675 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3678 @node Set Watchpoints
3679 @subsection Setting Watchpoints
3681 @cindex setting watchpoints
3682 You can use a watchpoint to stop execution whenever the value of an
3683 expression changes, without having to predict a particular place where
3684 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3685 The expression may be as simple as the value of a single variable, or
3686 as complex as many variables combined by operators. Examples include:
3690 A reference to the value of a single variable.
3693 An address cast to an appropriate data type. For example,
3694 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3695 address (assuming an @code{int} occupies 4 bytes).
3698 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3699 expression can use any operators valid in the program's native
3700 language (@pxref{Languages}).
3703 You can set a watchpoint on an expression even if the expression can
3704 not be evaluated yet. For instance, you can set a watchpoint on
3705 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3706 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3707 the expression produces a valid value. If the expression becomes
3708 valid in some other way than changing a variable (e.g.@: if the memory
3709 pointed to by @samp{*global_ptr} becomes readable as the result of a
3710 @code{malloc} call), @value{GDBN} may not stop until the next time
3711 the expression changes.
3713 @cindex software watchpoints
3714 @cindex hardware watchpoints
3715 Depending on your system, watchpoints may be implemented in software or
3716 hardware. @value{GDBN} does software watchpointing by single-stepping your
3717 program and testing the variable's value each time, which is hundreds of
3718 times slower than normal execution. (But this may still be worth it, to
3719 catch errors where you have no clue what part of your program is the
3722 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3723 x86-based targets, @value{GDBN} includes support for hardware
3724 watchpoints, which do not slow down the running of your program.
3728 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3729 Set a watchpoint for an expression. @value{GDBN} will break when the
3730 expression @var{expr} is written into by the program and its value
3731 changes. The simplest (and the most popular) use of this command is
3732 to watch the value of a single variable:
3735 (@value{GDBP}) watch foo
3738 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3739 clause, @value{GDBN} breaks only when the thread identified by
3740 @var{threadnum} changes the value of @var{expr}. If any other threads
3741 change the value of @var{expr}, @value{GDBN} will not break. Note
3742 that watchpoints restricted to a single thread in this way only work
3743 with Hardware Watchpoints.
3745 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3746 (see below). The @code{-location} argument tells @value{GDBN} to
3747 instead watch the memory referred to by @var{expr}. In this case,
3748 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3749 and watch the memory at that address. The type of the result is used
3750 to determine the size of the watched memory. If the expression's
3751 result does not have an address, then @value{GDBN} will print an
3755 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3756 Set a watchpoint that will break when the value of @var{expr} is read
3760 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3761 Set a watchpoint that will break when @var{expr} is either read from
3762 or written into by the program.
3764 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3765 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3766 This command prints a list of watchpoints, using the same format as
3767 @code{info break} (@pxref{Set Breaks}).
3770 If you watch for a change in a numerically entered address you need to
3771 dereference it, as the address itself is just a constant number which will
3772 never change. @value{GDBN} refuses to create a watchpoint that watches
3773 a never-changing value:
3776 (@value{GDBP}) watch 0x600850
3777 Cannot watch constant value 0x600850.
3778 (@value{GDBP}) watch *(int *) 0x600850
3779 Watchpoint 1: *(int *) 6293584
3782 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3783 watchpoints execute very quickly, and the debugger reports a change in
3784 value at the exact instruction where the change occurs. If @value{GDBN}
3785 cannot set a hardware watchpoint, it sets a software watchpoint, which
3786 executes more slowly and reports the change in value at the next
3787 @emph{statement}, not the instruction, after the change occurs.
3789 @cindex use only software watchpoints
3790 You can force @value{GDBN} to use only software watchpoints with the
3791 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3792 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3793 the underlying system supports them. (Note that hardware-assisted
3794 watchpoints that were set @emph{before} setting
3795 @code{can-use-hw-watchpoints} to zero will still use the hardware
3796 mechanism of watching expression values.)
3799 @item set can-use-hw-watchpoints
3800 @kindex set can-use-hw-watchpoints
3801 Set whether or not to use hardware watchpoints.
3803 @item show can-use-hw-watchpoints
3804 @kindex show can-use-hw-watchpoints
3805 Show the current mode of using hardware watchpoints.
3808 For remote targets, you can restrict the number of hardware
3809 watchpoints @value{GDBN} will use, see @ref{set remote
3810 hardware-breakpoint-limit}.
3812 When you issue the @code{watch} command, @value{GDBN} reports
3815 Hardware watchpoint @var{num}: @var{expr}
3819 if it was able to set a hardware watchpoint.
3821 Currently, the @code{awatch} and @code{rwatch} commands can only set
3822 hardware watchpoints, because accesses to data that don't change the
3823 value of the watched expression cannot be detected without examining
3824 every instruction as it is being executed, and @value{GDBN} does not do
3825 that currently. If @value{GDBN} finds that it is unable to set a
3826 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3827 will print a message like this:
3830 Expression cannot be implemented with read/access watchpoint.
3833 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3834 data type of the watched expression is wider than what a hardware
3835 watchpoint on the target machine can handle. For example, some systems
3836 can only watch regions that are up to 4 bytes wide; on such systems you
3837 cannot set hardware watchpoints for an expression that yields a
3838 double-precision floating-point number (which is typically 8 bytes
3839 wide). As a work-around, it might be possible to break the large region
3840 into a series of smaller ones and watch them with separate watchpoints.
3842 If you set too many hardware watchpoints, @value{GDBN} might be unable
3843 to insert all of them when you resume the execution of your program.
3844 Since the precise number of active watchpoints is unknown until such
3845 time as the program is about to be resumed, @value{GDBN} might not be
3846 able to warn you about this when you set the watchpoints, and the
3847 warning will be printed only when the program is resumed:
3850 Hardware watchpoint @var{num}: Could not insert watchpoint
3854 If this happens, delete or disable some of the watchpoints.
3856 Watching complex expressions that reference many variables can also
3857 exhaust the resources available for hardware-assisted watchpoints.
3858 That's because @value{GDBN} needs to watch every variable in the
3859 expression with separately allocated resources.
3861 If you call a function interactively using @code{print} or @code{call},
3862 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3863 kind of breakpoint or the call completes.
3865 @value{GDBN} automatically deletes watchpoints that watch local
3866 (automatic) variables, or expressions that involve such variables, when
3867 they go out of scope, that is, when the execution leaves the block in
3868 which these variables were defined. In particular, when the program
3869 being debugged terminates, @emph{all} local variables go out of scope,
3870 and so only watchpoints that watch global variables remain set. If you
3871 rerun the program, you will need to set all such watchpoints again. One
3872 way of doing that would be to set a code breakpoint at the entry to the
3873 @code{main} function and when it breaks, set all the watchpoints.
3875 @cindex watchpoints and threads
3876 @cindex threads and watchpoints
3877 In multi-threaded programs, watchpoints will detect changes to the
3878 watched expression from every thread.
3881 @emph{Warning:} In multi-threaded programs, software watchpoints
3882 have only limited usefulness. If @value{GDBN} creates a software
3883 watchpoint, it can only watch the value of an expression @emph{in a
3884 single thread}. If you are confident that the expression can only
3885 change due to the current thread's activity (and if you are also
3886 confident that no other thread can become current), then you can use
3887 software watchpoints as usual. However, @value{GDBN} may not notice
3888 when a non-current thread's activity changes the expression. (Hardware
3889 watchpoints, in contrast, watch an expression in all threads.)
3892 @xref{set remote hardware-watchpoint-limit}.
3894 @node Set Catchpoints
3895 @subsection Setting Catchpoints
3896 @cindex catchpoints, setting
3897 @cindex exception handlers
3898 @cindex event handling
3900 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3901 kinds of program events, such as C@t{++} exceptions or the loading of a
3902 shared library. Use the @code{catch} command to set a catchpoint.
3906 @item catch @var{event}
3907 Stop when @var{event} occurs. @var{event} can be any of the following:
3910 @cindex stop on C@t{++} exceptions
3911 The throwing of a C@t{++} exception.
3914 The catching of a C@t{++} exception.
3917 @cindex Ada exception catching
3918 @cindex catch Ada exceptions
3919 An Ada exception being raised. If an exception name is specified
3920 at the end of the command (eg @code{catch exception Program_Error}),
3921 the debugger will stop only when this specific exception is raised.
3922 Otherwise, the debugger stops execution when any Ada exception is raised.
3924 When inserting an exception catchpoint on a user-defined exception whose
3925 name is identical to one of the exceptions defined by the language, the
3926 fully qualified name must be used as the exception name. Otherwise,
3927 @value{GDBN} will assume that it should stop on the pre-defined exception
3928 rather than the user-defined one. For instance, assuming an exception
3929 called @code{Constraint_Error} is defined in package @code{Pck}, then
3930 the command to use to catch such exceptions is @kbd{catch exception
3931 Pck.Constraint_Error}.
3933 @item exception unhandled
3934 An exception that was raised but is not handled by the program.
3937 A failed Ada assertion.
3940 @cindex break on fork/exec
3941 A call to @code{exec}. This is currently only available for HP-UX
3945 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3946 @cindex break on a system call.
3947 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3948 syscall is a mechanism for application programs to request a service
3949 from the operating system (OS) or one of the OS system services.
3950 @value{GDBN} can catch some or all of the syscalls issued by the
3951 debuggee, and show the related information for each syscall. If no
3952 argument is specified, calls to and returns from all system calls
3955 @var{name} can be any system call name that is valid for the
3956 underlying OS. Just what syscalls are valid depends on the OS. On
3957 GNU and Unix systems, you can find the full list of valid syscall
3958 names on @file{/usr/include/asm/unistd.h}.
3960 @c For MS-Windows, the syscall names and the corresponding numbers
3961 @c can be found, e.g., on this URL:
3962 @c http://www.metasploit.com/users/opcode/syscalls.html
3963 @c but we don't support Windows syscalls yet.
3965 Normally, @value{GDBN} knows in advance which syscalls are valid for
3966 each OS, so you can use the @value{GDBN} command-line completion
3967 facilities (@pxref{Completion,, command completion}) to list the
3970 You may also specify the system call numerically. A syscall's
3971 number is the value passed to the OS's syscall dispatcher to
3972 identify the requested service. When you specify the syscall by its
3973 name, @value{GDBN} uses its database of syscalls to convert the name
3974 into the corresponding numeric code, but using the number directly
3975 may be useful if @value{GDBN}'s database does not have the complete
3976 list of syscalls on your system (e.g., because @value{GDBN} lags
3977 behind the OS upgrades).
3979 The example below illustrates how this command works if you don't provide
3983 (@value{GDBP}) catch syscall
3984 Catchpoint 1 (syscall)
3986 Starting program: /tmp/catch-syscall
3988 Catchpoint 1 (call to syscall 'close'), \
3989 0xffffe424 in __kernel_vsyscall ()
3993 Catchpoint 1 (returned from syscall 'close'), \
3994 0xffffe424 in __kernel_vsyscall ()
3998 Here is an example of catching a system call by name:
4001 (@value{GDBP}) catch syscall chroot
4002 Catchpoint 1 (syscall 'chroot' [61])
4004 Starting program: /tmp/catch-syscall
4006 Catchpoint 1 (call to syscall 'chroot'), \
4007 0xffffe424 in __kernel_vsyscall ()
4011 Catchpoint 1 (returned from syscall 'chroot'), \
4012 0xffffe424 in __kernel_vsyscall ()
4016 An example of specifying a system call numerically. In the case
4017 below, the syscall number has a corresponding entry in the XML
4018 file, so @value{GDBN} finds its name and prints it:
4021 (@value{GDBP}) catch syscall 252
4022 Catchpoint 1 (syscall(s) 'exit_group')
4024 Starting program: /tmp/catch-syscall
4026 Catchpoint 1 (call to syscall 'exit_group'), \
4027 0xffffe424 in __kernel_vsyscall ()
4031 Program exited normally.
4035 However, there can be situations when there is no corresponding name
4036 in XML file for that syscall number. In this case, @value{GDBN} prints
4037 a warning message saying that it was not able to find the syscall name,
4038 but the catchpoint will be set anyway. See the example below:
4041 (@value{GDBP}) catch syscall 764
4042 warning: The number '764' does not represent a known syscall.
4043 Catchpoint 2 (syscall 764)
4047 If you configure @value{GDBN} using the @samp{--without-expat} option,
4048 it will not be able to display syscall names. Also, if your
4049 architecture does not have an XML file describing its system calls,
4050 you will not be able to see the syscall names. It is important to
4051 notice that these two features are used for accessing the syscall
4052 name database. In either case, you will see a warning like this:
4055 (@value{GDBP}) catch syscall
4056 warning: Could not open "syscalls/i386-linux.xml"
4057 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4058 GDB will not be able to display syscall names.
4059 Catchpoint 1 (syscall)
4063 Of course, the file name will change depending on your architecture and system.
4065 Still using the example above, you can also try to catch a syscall by its
4066 number. In this case, you would see something like:
4069 (@value{GDBP}) catch syscall 252
4070 Catchpoint 1 (syscall(s) 252)
4073 Again, in this case @value{GDBN} would not be able to display syscall's names.
4076 A call to @code{fork}. This is currently only available for HP-UX
4080 A call to @code{vfork}. This is currently only available for HP-UX
4085 @item tcatch @var{event}
4086 Set a catchpoint that is enabled only for one stop. The catchpoint is
4087 automatically deleted after the first time the event is caught.
4091 Use the @code{info break} command to list the current catchpoints.
4093 There are currently some limitations to C@t{++} exception handling
4094 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4098 If you call a function interactively, @value{GDBN} normally returns
4099 control to you when the function has finished executing. If the call
4100 raises an exception, however, the call may bypass the mechanism that
4101 returns control to you and cause your program either to abort or to
4102 simply continue running until it hits a breakpoint, catches a signal
4103 that @value{GDBN} is listening for, or exits. This is the case even if
4104 you set a catchpoint for the exception; catchpoints on exceptions are
4105 disabled within interactive calls.
4108 You cannot raise an exception interactively.
4111 You cannot install an exception handler interactively.
4114 @cindex raise exceptions
4115 Sometimes @code{catch} is not the best way to debug exception handling:
4116 if you need to know exactly where an exception is raised, it is better to
4117 stop @emph{before} the exception handler is called, since that way you
4118 can see the stack before any unwinding takes place. If you set a
4119 breakpoint in an exception handler instead, it may not be easy to find
4120 out where the exception was raised.
4122 To stop just before an exception handler is called, you need some
4123 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4124 raised by calling a library function named @code{__raise_exception}
4125 which has the following ANSI C interface:
4128 /* @var{addr} is where the exception identifier is stored.
4129 @var{id} is the exception identifier. */
4130 void __raise_exception (void **addr, void *id);
4134 To make the debugger catch all exceptions before any stack
4135 unwinding takes place, set a breakpoint on @code{__raise_exception}
4136 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4138 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4139 that depends on the value of @var{id}, you can stop your program when
4140 a specific exception is raised. You can use multiple conditional
4141 breakpoints to stop your program when any of a number of exceptions are
4146 @subsection Deleting Breakpoints
4148 @cindex clearing breakpoints, watchpoints, catchpoints
4149 @cindex deleting breakpoints, watchpoints, catchpoints
4150 It is often necessary to eliminate a breakpoint, watchpoint, or
4151 catchpoint once it has done its job and you no longer want your program
4152 to stop there. This is called @dfn{deleting} the breakpoint. A
4153 breakpoint that has been deleted no longer exists; it is forgotten.
4155 With the @code{clear} command you can delete breakpoints according to
4156 where they are in your program. With the @code{delete} command you can
4157 delete individual breakpoints, watchpoints, or catchpoints by specifying
4158 their breakpoint numbers.
4160 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4161 automatically ignores breakpoints on the first instruction to be executed
4162 when you continue execution without changing the execution address.
4167 Delete any breakpoints at the next instruction to be executed in the
4168 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4169 the innermost frame is selected, this is a good way to delete a
4170 breakpoint where your program just stopped.
4172 @item clear @var{location}
4173 Delete any breakpoints set at the specified @var{location}.
4174 @xref{Specify Location}, for the various forms of @var{location}; the
4175 most useful ones are listed below:
4178 @item clear @var{function}
4179 @itemx clear @var{filename}:@var{function}
4180 Delete any breakpoints set at entry to the named @var{function}.
4182 @item clear @var{linenum}
4183 @itemx clear @var{filename}:@var{linenum}
4184 Delete any breakpoints set at or within the code of the specified
4185 @var{linenum} of the specified @var{filename}.
4188 @cindex delete breakpoints
4190 @kindex d @r{(@code{delete})}
4191 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4192 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4193 ranges specified as arguments. If no argument is specified, delete all
4194 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4195 confirm off}). You can abbreviate this command as @code{d}.
4199 @subsection Disabling Breakpoints
4201 @cindex enable/disable a breakpoint
4202 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4203 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4204 it had been deleted, but remembers the information on the breakpoint so
4205 that you can @dfn{enable} it again later.
4207 You disable and enable breakpoints, watchpoints, and catchpoints with
4208 the @code{enable} and @code{disable} commands, optionally specifying
4209 one or more breakpoint numbers as arguments. Use @code{info break} to
4210 print a list of all breakpoints, watchpoints, and catchpoints if you
4211 do not know which numbers to use.
4213 Disabling and enabling a breakpoint that has multiple locations
4214 affects all of its locations.
4216 A breakpoint, watchpoint, or catchpoint can have any of four different
4217 states of enablement:
4221 Enabled. The breakpoint stops your program. A breakpoint set
4222 with the @code{break} command starts out in this state.
4224 Disabled. The breakpoint has no effect on your program.
4226 Enabled once. The breakpoint stops your program, but then becomes
4229 Enabled for deletion. The breakpoint stops your program, but
4230 immediately after it does so it is deleted permanently. A breakpoint
4231 set with the @code{tbreak} command starts out in this state.
4234 You can use the following commands to enable or disable breakpoints,
4235 watchpoints, and catchpoints:
4239 @kindex dis @r{(@code{disable})}
4240 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4241 Disable the specified breakpoints---or all breakpoints, if none are
4242 listed. A disabled breakpoint has no effect but is not forgotten. All
4243 options such as ignore-counts, conditions and commands are remembered in
4244 case the breakpoint is enabled again later. You may abbreviate
4245 @code{disable} as @code{dis}.
4248 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4249 Enable the specified breakpoints (or all defined breakpoints). They
4250 become effective once again in stopping your program.
4252 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4253 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4254 of these breakpoints immediately after stopping your program.
4256 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4257 Enable the specified breakpoints to work once, then die. @value{GDBN}
4258 deletes any of these breakpoints as soon as your program stops there.
4259 Breakpoints set by the @code{tbreak} command start out in this state.
4262 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4263 @c confusing: tbreak is also initially enabled.
4264 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4265 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4266 subsequently, they become disabled or enabled only when you use one of
4267 the commands above. (The command @code{until} can set and delete a
4268 breakpoint of its own, but it does not change the state of your other
4269 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4273 @subsection Break Conditions
4274 @cindex conditional breakpoints
4275 @cindex breakpoint conditions
4277 @c FIXME what is scope of break condition expr? Context where wanted?
4278 @c in particular for a watchpoint?
4279 The simplest sort of breakpoint breaks every time your program reaches a
4280 specified place. You can also specify a @dfn{condition} for a
4281 breakpoint. A condition is just a Boolean expression in your
4282 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4283 a condition evaluates the expression each time your program reaches it,
4284 and your program stops only if the condition is @emph{true}.
4286 This is the converse of using assertions for program validation; in that
4287 situation, you want to stop when the assertion is violated---that is,
4288 when the condition is false. In C, if you want to test an assertion expressed
4289 by the condition @var{assert}, you should set the condition
4290 @samp{! @var{assert}} on the appropriate breakpoint.
4292 Conditions are also accepted for watchpoints; you may not need them,
4293 since a watchpoint is inspecting the value of an expression anyhow---but
4294 it might be simpler, say, to just set a watchpoint on a variable name,
4295 and specify a condition that tests whether the new value is an interesting
4298 Break conditions can have side effects, and may even call functions in
4299 your program. This can be useful, for example, to activate functions
4300 that log program progress, or to use your own print functions to
4301 format special data structures. The effects are completely predictable
4302 unless there is another enabled breakpoint at the same address. (In
4303 that case, @value{GDBN} might see the other breakpoint first and stop your
4304 program without checking the condition of this one.) Note that
4305 breakpoint commands are usually more convenient and flexible than break
4307 purpose of performing side effects when a breakpoint is reached
4308 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4310 Break conditions can be specified when a breakpoint is set, by using
4311 @samp{if} in the arguments to the @code{break} command. @xref{Set
4312 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4313 with the @code{condition} command.
4315 You can also use the @code{if} keyword with the @code{watch} command.
4316 The @code{catch} command does not recognize the @code{if} keyword;
4317 @code{condition} is the only way to impose a further condition on a
4322 @item condition @var{bnum} @var{expression}
4323 Specify @var{expression} as the break condition for breakpoint,
4324 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4325 breakpoint @var{bnum} stops your program only if the value of
4326 @var{expression} is true (nonzero, in C). When you use
4327 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4328 syntactic correctness, and to determine whether symbols in it have
4329 referents in the context of your breakpoint. If @var{expression} uses
4330 symbols not referenced in the context of the breakpoint, @value{GDBN}
4331 prints an error message:
4334 No symbol "foo" in current context.
4339 not actually evaluate @var{expression} at the time the @code{condition}
4340 command (or a command that sets a breakpoint with a condition, like
4341 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4343 @item condition @var{bnum}
4344 Remove the condition from breakpoint number @var{bnum}. It becomes
4345 an ordinary unconditional breakpoint.
4348 @cindex ignore count (of breakpoint)
4349 A special case of a breakpoint condition is to stop only when the
4350 breakpoint has been reached a certain number of times. This is so
4351 useful that there is a special way to do it, using the @dfn{ignore
4352 count} of the breakpoint. Every breakpoint has an ignore count, which
4353 is an integer. Most of the time, the ignore count is zero, and
4354 therefore has no effect. But if your program reaches a breakpoint whose
4355 ignore count is positive, then instead of stopping, it just decrements
4356 the ignore count by one and continues. As a result, if the ignore count
4357 value is @var{n}, the breakpoint does not stop the next @var{n} times
4358 your program reaches it.
4362 @item ignore @var{bnum} @var{count}
4363 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4364 The next @var{count} times the breakpoint is reached, your program's
4365 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4368 To make the breakpoint stop the next time it is reached, specify
4371 When you use @code{continue} to resume execution of your program from a
4372 breakpoint, you can specify an ignore count directly as an argument to
4373 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4374 Stepping,,Continuing and Stepping}.
4376 If a breakpoint has a positive ignore count and a condition, the
4377 condition is not checked. Once the ignore count reaches zero,
4378 @value{GDBN} resumes checking the condition.
4380 You could achieve the effect of the ignore count with a condition such
4381 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4382 is decremented each time. @xref{Convenience Vars, ,Convenience
4386 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4389 @node Break Commands
4390 @subsection Breakpoint Command Lists
4392 @cindex breakpoint commands
4393 You can give any breakpoint (or watchpoint or catchpoint) a series of
4394 commands to execute when your program stops due to that breakpoint. For
4395 example, you might want to print the values of certain expressions, or
4396 enable other breakpoints.
4400 @kindex end@r{ (breakpoint commands)}
4401 @item commands @r{[}@var{range}@dots{}@r{]}
4402 @itemx @dots{} @var{command-list} @dots{}
4404 Specify a list of commands for the given breakpoints. The commands
4405 themselves appear on the following lines. Type a line containing just
4406 @code{end} to terminate the commands.
4408 To remove all commands from a breakpoint, type @code{commands} and
4409 follow it immediately with @code{end}; that is, give no commands.
4411 With no argument, @code{commands} refers to the last breakpoint,
4412 watchpoint, or catchpoint set (not to the breakpoint most recently
4413 encountered). If the most recent breakpoints were set with a single
4414 command, then the @code{commands} will apply to all the breakpoints
4415 set by that command. This applies to breakpoints set by
4416 @code{rbreak}, and also applies when a single @code{break} command
4417 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4421 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4422 disabled within a @var{command-list}.
4424 You can use breakpoint commands to start your program up again. Simply
4425 use the @code{continue} command, or @code{step}, or any other command
4426 that resumes execution.
4428 Any other commands in the command list, after a command that resumes
4429 execution, are ignored. This is because any time you resume execution
4430 (even with a simple @code{next} or @code{step}), you may encounter
4431 another breakpoint---which could have its own command list, leading to
4432 ambiguities about which list to execute.
4435 If the first command you specify in a command list is @code{silent}, the
4436 usual message about stopping at a breakpoint is not printed. This may
4437 be desirable for breakpoints that are to print a specific message and
4438 then continue. If none of the remaining commands print anything, you
4439 see no sign that the breakpoint was reached. @code{silent} is
4440 meaningful only at the beginning of a breakpoint command list.
4442 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4443 print precisely controlled output, and are often useful in silent
4444 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4446 For example, here is how you could use breakpoint commands to print the
4447 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4453 printf "x is %d\n",x
4458 One application for breakpoint commands is to compensate for one bug so
4459 you can test for another. Put a breakpoint just after the erroneous line
4460 of code, give it a condition to detect the case in which something
4461 erroneous has been done, and give it commands to assign correct values
4462 to any variables that need them. End with the @code{continue} command
4463 so that your program does not stop, and start with the @code{silent}
4464 command so that no output is produced. Here is an example:
4475 @node Save Breakpoints
4476 @subsection How to save breakpoints to a file
4478 To save breakpoint definitions to a file use the @w{@code{save
4479 breakpoints}} command.
4482 @kindex save breakpoints
4483 @cindex save breakpoints to a file for future sessions
4484 @item save breakpoints [@var{filename}]
4485 This command saves all current breakpoint definitions together with
4486 their commands and ignore counts, into a file @file{@var{filename}}
4487 suitable for use in a later debugging session. This includes all
4488 types of breakpoints (breakpoints, watchpoints, catchpoints,
4489 tracepoints). To read the saved breakpoint definitions, use the
4490 @code{source} command (@pxref{Command Files}). Note that watchpoints
4491 with expressions involving local variables may fail to be recreated
4492 because it may not be possible to access the context where the
4493 watchpoint is valid anymore. Because the saved breakpoint definitions
4494 are simply a sequence of @value{GDBN} commands that recreate the
4495 breakpoints, you can edit the file in your favorite editing program,
4496 and remove the breakpoint definitions you're not interested in, or
4497 that can no longer be recreated.
4500 @c @ifclear BARETARGET
4501 @node Error in Breakpoints
4502 @subsection ``Cannot insert breakpoints''
4504 If you request too many active hardware-assisted breakpoints and
4505 watchpoints, you will see this error message:
4507 @c FIXME: the precise wording of this message may change; the relevant
4508 @c source change is not committed yet (Sep 3, 1999).
4510 Stopped; cannot insert breakpoints.
4511 You may have requested too many hardware breakpoints and watchpoints.
4515 This message is printed when you attempt to resume the program, since
4516 only then @value{GDBN} knows exactly how many hardware breakpoints and
4517 watchpoints it needs to insert.
4519 When this message is printed, you need to disable or remove some of the
4520 hardware-assisted breakpoints and watchpoints, and then continue.
4522 @node Breakpoint-related Warnings
4523 @subsection ``Breakpoint address adjusted...''
4524 @cindex breakpoint address adjusted
4526 Some processor architectures place constraints on the addresses at
4527 which breakpoints may be placed. For architectures thus constrained,
4528 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4529 with the constraints dictated by the architecture.
4531 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4532 a VLIW architecture in which a number of RISC-like instructions may be
4533 bundled together for parallel execution. The FR-V architecture
4534 constrains the location of a breakpoint instruction within such a
4535 bundle to the instruction with the lowest address. @value{GDBN}
4536 honors this constraint by adjusting a breakpoint's address to the
4537 first in the bundle.
4539 It is not uncommon for optimized code to have bundles which contain
4540 instructions from different source statements, thus it may happen that
4541 a breakpoint's address will be adjusted from one source statement to
4542 another. Since this adjustment may significantly alter @value{GDBN}'s
4543 breakpoint related behavior from what the user expects, a warning is
4544 printed when the breakpoint is first set and also when the breakpoint
4547 A warning like the one below is printed when setting a breakpoint
4548 that's been subject to address adjustment:
4551 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4554 Such warnings are printed both for user settable and @value{GDBN}'s
4555 internal breakpoints. If you see one of these warnings, you should
4556 verify that a breakpoint set at the adjusted address will have the
4557 desired affect. If not, the breakpoint in question may be removed and
4558 other breakpoints may be set which will have the desired behavior.
4559 E.g., it may be sufficient to place the breakpoint at a later
4560 instruction. A conditional breakpoint may also be useful in some
4561 cases to prevent the breakpoint from triggering too often.
4563 @value{GDBN} will also issue a warning when stopping at one of these
4564 adjusted breakpoints:
4567 warning: Breakpoint 1 address previously adjusted from 0x00010414
4571 When this warning is encountered, it may be too late to take remedial
4572 action except in cases where the breakpoint is hit earlier or more
4573 frequently than expected.
4575 @node Continuing and Stepping
4576 @section Continuing and Stepping
4580 @cindex resuming execution
4581 @dfn{Continuing} means resuming program execution until your program
4582 completes normally. In contrast, @dfn{stepping} means executing just
4583 one more ``step'' of your program, where ``step'' may mean either one
4584 line of source code, or one machine instruction (depending on what
4585 particular command you use). Either when continuing or when stepping,
4586 your program may stop even sooner, due to a breakpoint or a signal. (If
4587 it stops due to a signal, you may want to use @code{handle}, or use
4588 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4592 @kindex c @r{(@code{continue})}
4593 @kindex fg @r{(resume foreground execution)}
4594 @item continue @r{[}@var{ignore-count}@r{]}
4595 @itemx c @r{[}@var{ignore-count}@r{]}
4596 @itemx fg @r{[}@var{ignore-count}@r{]}
4597 Resume program execution, at the address where your program last stopped;
4598 any breakpoints set at that address are bypassed. The optional argument
4599 @var{ignore-count} allows you to specify a further number of times to
4600 ignore a breakpoint at this location; its effect is like that of
4601 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4603 The argument @var{ignore-count} is meaningful only when your program
4604 stopped due to a breakpoint. At other times, the argument to
4605 @code{continue} is ignored.
4607 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4608 debugged program is deemed to be the foreground program) are provided
4609 purely for convenience, and have exactly the same behavior as
4613 To resume execution at a different place, you can use @code{return}
4614 (@pxref{Returning, ,Returning from a Function}) to go back to the
4615 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4616 Different Address}) to go to an arbitrary location in your program.
4618 A typical technique for using stepping is to set a breakpoint
4619 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4620 beginning of the function or the section of your program where a problem
4621 is believed to lie, run your program until it stops at that breakpoint,
4622 and then step through the suspect area, examining the variables that are
4623 interesting, until you see the problem happen.
4627 @kindex s @r{(@code{step})}
4629 Continue running your program until control reaches a different source
4630 line, then stop it and return control to @value{GDBN}. This command is
4631 abbreviated @code{s}.
4634 @c "without debugging information" is imprecise; actually "without line
4635 @c numbers in the debugging information". (gcc -g1 has debugging info but
4636 @c not line numbers). But it seems complex to try to make that
4637 @c distinction here.
4638 @emph{Warning:} If you use the @code{step} command while control is
4639 within a function that was compiled without debugging information,
4640 execution proceeds until control reaches a function that does have
4641 debugging information. Likewise, it will not step into a function which
4642 is compiled without debugging information. To step through functions
4643 without debugging information, use the @code{stepi} command, described
4647 The @code{step} command only stops at the first instruction of a source
4648 line. This prevents the multiple stops that could otherwise occur in
4649 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4650 to stop if a function that has debugging information is called within
4651 the line. In other words, @code{step} @emph{steps inside} any functions
4652 called within the line.
4654 Also, the @code{step} command only enters a function if there is line
4655 number information for the function. Otherwise it acts like the
4656 @code{next} command. This avoids problems when using @code{cc -gl}
4657 on MIPS machines. Previously, @code{step} entered subroutines if there
4658 was any debugging information about the routine.
4660 @item step @var{count}
4661 Continue running as in @code{step}, but do so @var{count} times. If a
4662 breakpoint is reached, or a signal not related to stepping occurs before
4663 @var{count} steps, stepping stops right away.
4666 @kindex n @r{(@code{next})}
4667 @item next @r{[}@var{count}@r{]}
4668 Continue to the next source line in the current (innermost) stack frame.
4669 This is similar to @code{step}, but function calls that appear within
4670 the line of code are executed without stopping. Execution stops when
4671 control reaches a different line of code at the original stack level
4672 that was executing when you gave the @code{next} command. This command
4673 is abbreviated @code{n}.
4675 An argument @var{count} is a repeat count, as for @code{step}.
4678 @c FIX ME!! Do we delete this, or is there a way it fits in with
4679 @c the following paragraph? --- Vctoria
4681 @c @code{next} within a function that lacks debugging information acts like
4682 @c @code{step}, but any function calls appearing within the code of the
4683 @c function are executed without stopping.
4685 The @code{next} command only stops at the first instruction of a
4686 source line. This prevents multiple stops that could otherwise occur in
4687 @code{switch} statements, @code{for} loops, etc.
4689 @kindex set step-mode
4691 @cindex functions without line info, and stepping
4692 @cindex stepping into functions with no line info
4693 @itemx set step-mode on
4694 The @code{set step-mode on} command causes the @code{step} command to
4695 stop at the first instruction of a function which contains no debug line
4696 information rather than stepping over it.
4698 This is useful in cases where you may be interested in inspecting the
4699 machine instructions of a function which has no symbolic info and do not
4700 want @value{GDBN} to automatically skip over this function.
4702 @item set step-mode off
4703 Causes the @code{step} command to step over any functions which contains no
4704 debug information. This is the default.
4706 @item show step-mode
4707 Show whether @value{GDBN} will stop in or step over functions without
4708 source line debug information.
4711 @kindex fin @r{(@code{finish})}
4713 Continue running until just after function in the selected stack frame
4714 returns. Print the returned value (if any). This command can be
4715 abbreviated as @code{fin}.
4717 Contrast this with the @code{return} command (@pxref{Returning,
4718 ,Returning from a Function}).
4721 @kindex u @r{(@code{until})}
4722 @cindex run until specified location
4725 Continue running until a source line past the current line, in the
4726 current stack frame, is reached. This command is used to avoid single
4727 stepping through a loop more than once. It is like the @code{next}
4728 command, except that when @code{until} encounters a jump, it
4729 automatically continues execution until the program counter is greater
4730 than the address of the jump.
4732 This means that when you reach the end of a loop after single stepping
4733 though it, @code{until} makes your program continue execution until it
4734 exits the loop. In contrast, a @code{next} command at the end of a loop
4735 simply steps back to the beginning of the loop, which forces you to step
4736 through the next iteration.
4738 @code{until} always stops your program if it attempts to exit the current
4741 @code{until} may produce somewhat counterintuitive results if the order
4742 of machine code does not match the order of the source lines. For
4743 example, in the following excerpt from a debugging session, the @code{f}
4744 (@code{frame}) command shows that execution is stopped at line
4745 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4749 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4751 (@value{GDBP}) until
4752 195 for ( ; argc > 0; NEXTARG) @{
4755 This happened because, for execution efficiency, the compiler had
4756 generated code for the loop closure test at the end, rather than the
4757 start, of the loop---even though the test in a C @code{for}-loop is
4758 written before the body of the loop. The @code{until} command appeared
4759 to step back to the beginning of the loop when it advanced to this
4760 expression; however, it has not really gone to an earlier
4761 statement---not in terms of the actual machine code.
4763 @code{until} with no argument works by means of single
4764 instruction stepping, and hence is slower than @code{until} with an
4767 @item until @var{location}
4768 @itemx u @var{location}
4769 Continue running your program until either the specified location is
4770 reached, or the current stack frame returns. @var{location} is any of
4771 the forms described in @ref{Specify Location}.
4772 This form of the command uses temporary breakpoints, and
4773 hence is quicker than @code{until} without an argument. The specified
4774 location is actually reached only if it is in the current frame. This
4775 implies that @code{until} can be used to skip over recursive function
4776 invocations. For instance in the code below, if the current location is
4777 line @code{96}, issuing @code{until 99} will execute the program up to
4778 line @code{99} in the same invocation of factorial, i.e., after the inner
4779 invocations have returned.
4782 94 int factorial (int value)
4784 96 if (value > 1) @{
4785 97 value *= factorial (value - 1);
4792 @kindex advance @var{location}
4793 @itemx advance @var{location}
4794 Continue running the program up to the given @var{location}. An argument is
4795 required, which should be of one of the forms described in
4796 @ref{Specify Location}.
4797 Execution will also stop upon exit from the current stack
4798 frame. This command is similar to @code{until}, but @code{advance} will
4799 not skip over recursive function calls, and the target location doesn't
4800 have to be in the same frame as the current one.
4804 @kindex si @r{(@code{stepi})}
4806 @itemx stepi @var{arg}
4808 Execute one machine instruction, then stop and return to the debugger.
4810 It is often useful to do @samp{display/i $pc} when stepping by machine
4811 instructions. This makes @value{GDBN} automatically display the next
4812 instruction to be executed, each time your program stops. @xref{Auto
4813 Display,, Automatic Display}.
4815 An argument is a repeat count, as in @code{step}.
4819 @kindex ni @r{(@code{nexti})}
4821 @itemx nexti @var{arg}
4823 Execute one machine instruction, but if it is a function call,
4824 proceed until the function returns.
4826 An argument is a repeat count, as in @code{next}.
4833 A signal is an asynchronous event that can happen in a program. The
4834 operating system defines the possible kinds of signals, and gives each
4835 kind a name and a number. For example, in Unix @code{SIGINT} is the
4836 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4837 @code{SIGSEGV} is the signal a program gets from referencing a place in
4838 memory far away from all the areas in use; @code{SIGALRM} occurs when
4839 the alarm clock timer goes off (which happens only if your program has
4840 requested an alarm).
4842 @cindex fatal signals
4843 Some signals, including @code{SIGALRM}, are a normal part of the
4844 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4845 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4846 program has not specified in advance some other way to handle the signal.
4847 @code{SIGINT} does not indicate an error in your program, but it is normally
4848 fatal so it can carry out the purpose of the interrupt: to kill the program.
4850 @value{GDBN} has the ability to detect any occurrence of a signal in your
4851 program. You can tell @value{GDBN} in advance what to do for each kind of
4854 @cindex handling signals
4855 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4856 @code{SIGALRM} be silently passed to your program
4857 (so as not to interfere with their role in the program's functioning)
4858 but to stop your program immediately whenever an error signal happens.
4859 You can change these settings with the @code{handle} command.
4862 @kindex info signals
4866 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4867 handle each one. You can use this to see the signal numbers of all
4868 the defined types of signals.
4870 @item info signals @var{sig}
4871 Similar, but print information only about the specified signal number.
4873 @code{info handle} is an alias for @code{info signals}.
4876 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4877 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4878 can be the number of a signal or its name (with or without the
4879 @samp{SIG} at the beginning); a list of signal numbers of the form
4880 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4881 known signals. Optional arguments @var{keywords}, described below,
4882 say what change to make.
4886 The keywords allowed by the @code{handle} command can be abbreviated.
4887 Their full names are:
4891 @value{GDBN} should not stop your program when this signal happens. It may
4892 still print a message telling you that the signal has come in.
4895 @value{GDBN} should stop your program when this signal happens. This implies
4896 the @code{print} keyword as well.
4899 @value{GDBN} should print a message when this signal happens.
4902 @value{GDBN} should not mention the occurrence of the signal at all. This
4903 implies the @code{nostop} keyword as well.
4907 @value{GDBN} should allow your program to see this signal; your program
4908 can handle the signal, or else it may terminate if the signal is fatal
4909 and not handled. @code{pass} and @code{noignore} are synonyms.
4913 @value{GDBN} should not allow your program to see this signal.
4914 @code{nopass} and @code{ignore} are synonyms.
4918 When a signal stops your program, the signal is not visible to the
4920 continue. Your program sees the signal then, if @code{pass} is in
4921 effect for the signal in question @emph{at that time}. In other words,
4922 after @value{GDBN} reports a signal, you can use the @code{handle}
4923 command with @code{pass} or @code{nopass} to control whether your
4924 program sees that signal when you continue.
4926 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4927 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4928 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4931 You can also use the @code{signal} command to prevent your program from
4932 seeing a signal, or cause it to see a signal it normally would not see,
4933 or to give it any signal at any time. For example, if your program stopped
4934 due to some sort of memory reference error, you might store correct
4935 values into the erroneous variables and continue, hoping to see more
4936 execution; but your program would probably terminate immediately as
4937 a result of the fatal signal once it saw the signal. To prevent this,
4938 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4941 @cindex extra signal information
4942 @anchor{extra signal information}
4944 On some targets, @value{GDBN} can inspect extra signal information
4945 associated with the intercepted signal, before it is actually
4946 delivered to the program being debugged. This information is exported
4947 by the convenience variable @code{$_siginfo}, and consists of data
4948 that is passed by the kernel to the signal handler at the time of the
4949 receipt of a signal. The data type of the information itself is
4950 target dependent. You can see the data type using the @code{ptype
4951 $_siginfo} command. On Unix systems, it typically corresponds to the
4952 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4955 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4956 referenced address that raised a segmentation fault.
4960 (@value{GDBP}) continue
4961 Program received signal SIGSEGV, Segmentation fault.
4962 0x0000000000400766 in main ()
4964 (@value{GDBP}) ptype $_siginfo
4971 struct @{...@} _kill;
4972 struct @{...@} _timer;
4974 struct @{...@} _sigchld;
4975 struct @{...@} _sigfault;
4976 struct @{...@} _sigpoll;
4979 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4983 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4984 $1 = (void *) 0x7ffff7ff7000
4988 Depending on target support, @code{$_siginfo} may also be writable.
4991 @section Stopping and Starting Multi-thread Programs
4993 @cindex stopped threads
4994 @cindex threads, stopped
4996 @cindex continuing threads
4997 @cindex threads, continuing
4999 @value{GDBN} supports debugging programs with multiple threads
5000 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5001 are two modes of controlling execution of your program within the
5002 debugger. In the default mode, referred to as @dfn{all-stop mode},
5003 when any thread in your program stops (for example, at a breakpoint
5004 or while being stepped), all other threads in the program are also stopped by
5005 @value{GDBN}. On some targets, @value{GDBN} also supports
5006 @dfn{non-stop mode}, in which other threads can continue to run freely while
5007 you examine the stopped thread in the debugger.
5010 * All-Stop Mode:: All threads stop when GDB takes control
5011 * Non-Stop Mode:: Other threads continue to execute
5012 * Background Execution:: Running your program asynchronously
5013 * Thread-Specific Breakpoints:: Controlling breakpoints
5014 * Interrupted System Calls:: GDB may interfere with system calls
5015 * Observer Mode:: GDB does not alter program behavior
5019 @subsection All-Stop Mode
5021 @cindex all-stop mode
5023 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5024 @emph{all} threads of execution stop, not just the current thread. This
5025 allows you to examine the overall state of the program, including
5026 switching between threads, without worrying that things may change
5029 Conversely, whenever you restart the program, @emph{all} threads start
5030 executing. @emph{This is true even when single-stepping} with commands
5031 like @code{step} or @code{next}.
5033 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5034 Since thread scheduling is up to your debugging target's operating
5035 system (not controlled by @value{GDBN}), other threads may
5036 execute more than one statement while the current thread completes a
5037 single step. Moreover, in general other threads stop in the middle of a
5038 statement, rather than at a clean statement boundary, when the program
5041 You might even find your program stopped in another thread after
5042 continuing or even single-stepping. This happens whenever some other
5043 thread runs into a breakpoint, a signal, or an exception before the
5044 first thread completes whatever you requested.
5046 @cindex automatic thread selection
5047 @cindex switching threads automatically
5048 @cindex threads, automatic switching
5049 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5050 signal, it automatically selects the thread where that breakpoint or
5051 signal happened. @value{GDBN} alerts you to the context switch with a
5052 message such as @samp{[Switching to Thread @var{n}]} to identify the
5055 On some OSes, you can modify @value{GDBN}'s default behavior by
5056 locking the OS scheduler to allow only a single thread to run.
5059 @item set scheduler-locking @var{mode}
5060 @cindex scheduler locking mode
5061 @cindex lock scheduler
5062 Set the scheduler locking mode. If it is @code{off}, then there is no
5063 locking and any thread may run at any time. If @code{on}, then only the
5064 current thread may run when the inferior is resumed. The @code{step}
5065 mode optimizes for single-stepping; it prevents other threads
5066 from preempting the current thread while you are stepping, so that
5067 the focus of debugging does not change unexpectedly.
5068 Other threads only rarely (or never) get a chance to run
5069 when you step. They are more likely to run when you @samp{next} over a
5070 function call, and they are completely free to run when you use commands
5071 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5072 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5073 the current thread away from the thread that you are debugging.
5075 @item show scheduler-locking
5076 Display the current scheduler locking mode.
5079 @cindex resume threads of multiple processes simultaneously
5080 By default, when you issue one of the execution commands such as
5081 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5082 threads of the current inferior to run. For example, if @value{GDBN}
5083 is attached to two inferiors, each with two threads, the
5084 @code{continue} command resumes only the two threads of the current
5085 inferior. This is useful, for example, when you debug a program that
5086 forks and you want to hold the parent stopped (so that, for instance,
5087 it doesn't run to exit), while you debug the child. In other
5088 situations, you may not be interested in inspecting the current state
5089 of any of the processes @value{GDBN} is attached to, and you may want
5090 to resume them all until some breakpoint is hit. In the latter case,
5091 you can instruct @value{GDBN} to allow all threads of all the
5092 inferiors to run with the @w{@code{set schedule-multiple}} command.
5095 @kindex set schedule-multiple
5096 @item set schedule-multiple
5097 Set the mode for allowing threads of multiple processes to be resumed
5098 when an execution command is issued. When @code{on}, all threads of
5099 all processes are allowed to run. When @code{off}, only the threads
5100 of the current process are resumed. The default is @code{off}. The
5101 @code{scheduler-locking} mode takes precedence when set to @code{on},
5102 or while you are stepping and set to @code{step}.
5104 @item show schedule-multiple
5105 Display the current mode for resuming the execution of threads of
5110 @subsection Non-Stop Mode
5112 @cindex non-stop mode
5114 @c This section is really only a place-holder, and needs to be expanded
5115 @c with more details.
5117 For some multi-threaded targets, @value{GDBN} supports an optional
5118 mode of operation in which you can examine stopped program threads in
5119 the debugger while other threads continue to execute freely. This
5120 minimizes intrusion when debugging live systems, such as programs
5121 where some threads have real-time constraints or must continue to
5122 respond to external events. This is referred to as @dfn{non-stop} mode.
5124 In non-stop mode, when a thread stops to report a debugging event,
5125 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5126 threads as well, in contrast to the all-stop mode behavior. Additionally,
5127 execution commands such as @code{continue} and @code{step} apply by default
5128 only to the current thread in non-stop mode, rather than all threads as
5129 in all-stop mode. This allows you to control threads explicitly in
5130 ways that are not possible in all-stop mode --- for example, stepping
5131 one thread while allowing others to run freely, stepping
5132 one thread while holding all others stopped, or stepping several threads
5133 independently and simultaneously.
5135 To enter non-stop mode, use this sequence of commands before you run
5136 or attach to your program:
5139 # Enable the async interface.
5142 # If using the CLI, pagination breaks non-stop.
5145 # Finally, turn it on!
5149 You can use these commands to manipulate the non-stop mode setting:
5152 @kindex set non-stop
5153 @item set non-stop on
5154 Enable selection of non-stop mode.
5155 @item set non-stop off
5156 Disable selection of non-stop mode.
5157 @kindex show non-stop
5159 Show the current non-stop enablement setting.
5162 Note these commands only reflect whether non-stop mode is enabled,
5163 not whether the currently-executing program is being run in non-stop mode.
5164 In particular, the @code{set non-stop} preference is only consulted when
5165 @value{GDBN} starts or connects to the target program, and it is generally
5166 not possible to switch modes once debugging has started. Furthermore,
5167 since not all targets support non-stop mode, even when you have enabled
5168 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5171 In non-stop mode, all execution commands apply only to the current thread
5172 by default. That is, @code{continue} only continues one thread.
5173 To continue all threads, issue @code{continue -a} or @code{c -a}.
5175 You can use @value{GDBN}'s background execution commands
5176 (@pxref{Background Execution}) to run some threads in the background
5177 while you continue to examine or step others from @value{GDBN}.
5178 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5179 always executed asynchronously in non-stop mode.
5181 Suspending execution is done with the @code{interrupt} command when
5182 running in the background, or @kbd{Ctrl-c} during foreground execution.
5183 In all-stop mode, this stops the whole process;
5184 but in non-stop mode the interrupt applies only to the current thread.
5185 To stop the whole program, use @code{interrupt -a}.
5187 Other execution commands do not currently support the @code{-a} option.
5189 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5190 that thread current, as it does in all-stop mode. This is because the
5191 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5192 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5193 changed to a different thread just as you entered a command to operate on the
5194 previously current thread.
5196 @node Background Execution
5197 @subsection Background Execution
5199 @cindex foreground execution
5200 @cindex background execution
5201 @cindex asynchronous execution
5202 @cindex execution, foreground, background and asynchronous
5204 @value{GDBN}'s execution commands have two variants: the normal
5205 foreground (synchronous) behavior, and a background
5206 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5207 the program to report that some thread has stopped before prompting for
5208 another command. In background execution, @value{GDBN} immediately gives
5209 a command prompt so that you can issue other commands while your program runs.
5211 You need to explicitly enable asynchronous mode before you can use
5212 background execution commands. You can use these commands to
5213 manipulate the asynchronous mode setting:
5216 @kindex set target-async
5217 @item set target-async on
5218 Enable asynchronous mode.
5219 @item set target-async off
5220 Disable asynchronous mode.
5221 @kindex show target-async
5222 @item show target-async
5223 Show the current target-async setting.
5226 If the target doesn't support async mode, @value{GDBN} issues an error
5227 message if you attempt to use the background execution commands.
5229 To specify background execution, add a @code{&} to the command. For example,
5230 the background form of the @code{continue} command is @code{continue&}, or
5231 just @code{c&}. The execution commands that accept background execution
5237 @xref{Starting, , Starting your Program}.
5241 @xref{Attach, , Debugging an Already-running Process}.
5245 @xref{Continuing and Stepping, step}.
5249 @xref{Continuing and Stepping, stepi}.
5253 @xref{Continuing and Stepping, next}.
5257 @xref{Continuing and Stepping, nexti}.
5261 @xref{Continuing and Stepping, continue}.
5265 @xref{Continuing and Stepping, finish}.
5269 @xref{Continuing and Stepping, until}.
5273 Background execution is especially useful in conjunction with non-stop
5274 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5275 However, you can also use these commands in the normal all-stop mode with
5276 the restriction that you cannot issue another execution command until the
5277 previous one finishes. Examples of commands that are valid in all-stop
5278 mode while the program is running include @code{help} and @code{info break}.
5280 You can interrupt your program while it is running in the background by
5281 using the @code{interrupt} command.
5288 Suspend execution of the running program. In all-stop mode,
5289 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5290 only the current thread. To stop the whole program in non-stop mode,
5291 use @code{interrupt -a}.
5294 @node Thread-Specific Breakpoints
5295 @subsection Thread-Specific Breakpoints
5297 When your program has multiple threads (@pxref{Threads,, Debugging
5298 Programs with Multiple Threads}), you can choose whether to set
5299 breakpoints on all threads, or on a particular thread.
5302 @cindex breakpoints and threads
5303 @cindex thread breakpoints
5304 @kindex break @dots{} thread @var{threadno}
5305 @item break @var{linespec} thread @var{threadno}
5306 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5307 @var{linespec} specifies source lines; there are several ways of
5308 writing them (@pxref{Specify Location}), but the effect is always to
5309 specify some source line.
5311 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5312 to specify that you only want @value{GDBN} to stop the program when a
5313 particular thread reaches this breakpoint. @var{threadno} is one of the
5314 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5315 column of the @samp{info threads} display.
5317 If you do not specify @samp{thread @var{threadno}} when you set a
5318 breakpoint, the breakpoint applies to @emph{all} threads of your
5321 You can use the @code{thread} qualifier on conditional breakpoints as
5322 well; in this case, place @samp{thread @var{threadno}} before or
5323 after the breakpoint condition, like this:
5326 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5331 @node Interrupted System Calls
5332 @subsection Interrupted System Calls
5334 @cindex thread breakpoints and system calls
5335 @cindex system calls and thread breakpoints
5336 @cindex premature return from system calls
5337 There is an unfortunate side effect when using @value{GDBN} to debug
5338 multi-threaded programs. If one thread stops for a
5339 breakpoint, or for some other reason, and another thread is blocked in a
5340 system call, then the system call may return prematurely. This is a
5341 consequence of the interaction between multiple threads and the signals
5342 that @value{GDBN} uses to implement breakpoints and other events that
5345 To handle this problem, your program should check the return value of
5346 each system call and react appropriately. This is good programming
5349 For example, do not write code like this:
5355 The call to @code{sleep} will return early if a different thread stops
5356 at a breakpoint or for some other reason.
5358 Instead, write this:
5363 unslept = sleep (unslept);
5366 A system call is allowed to return early, so the system is still
5367 conforming to its specification. But @value{GDBN} does cause your
5368 multi-threaded program to behave differently than it would without
5371 Also, @value{GDBN} uses internal breakpoints in the thread library to
5372 monitor certain events such as thread creation and thread destruction.
5373 When such an event happens, a system call in another thread may return
5374 prematurely, even though your program does not appear to stop.
5377 @subsection Observer Mode
5379 If you want to build on non-stop mode and observe program behavior
5380 without any chance of disruption by @value{GDBN}, you can set
5381 variables to disable all of the debugger's attempts to modify state,
5382 whether by writing memory, inserting breakpoints, etc. These operate
5383 at a low level, intercepting operations from all commands.
5385 When all of these are set to @code{off}, then @value{GDBN} is said to
5386 be @dfn{observer mode}. As a convenience, the variable
5387 @code{observer} can be set to disable these, plus enable non-stop
5390 Note that @value{GDBN} will not prevent you from making nonsensical
5391 combinations of these settings. For instance, if you have enabled
5392 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5393 then breakpoints that work by writing trap instructions into the code
5394 stream will still not be able to be placed.
5399 @item set observer on
5400 @itemx set observer off
5401 When set to @code{on}, this disables all the permission variables
5402 below (except for @code{insert-fast-tracepoints}), plus enables
5403 non-stop debugging. Setting this to @code{off} switches back to
5404 normal debugging, though remaining in non-stop mode.
5407 Show whether observer mode is on or off.
5409 @kindex may-write-registers
5410 @item set may-write-registers on
5411 @itemx set may-write-registers off
5412 This controls whether @value{GDBN} will attempt to alter the values of
5413 registers, such as with assignment expressions in @code{print}, or the
5414 @code{jump} command. It defaults to @code{on}.
5416 @item show may-write-registers
5417 Show the current permission to write registers.
5419 @kindex may-write-memory
5420 @item set may-write-memory on
5421 @itemx set may-write-memory off
5422 This controls whether @value{GDBN} will attempt to alter the contents
5423 of memory, such as with assignment expressions in @code{print}. It
5424 defaults to @code{on}.
5426 @item show may-write-memory
5427 Show the current permission to write memory.
5429 @kindex may-insert-breakpoints
5430 @item set may-insert-breakpoints on
5431 @itemx set may-insert-breakpoints off
5432 This controls whether @value{GDBN} will attempt to insert breakpoints.
5433 This affects all breakpoints, including internal breakpoints defined
5434 by @value{GDBN}. It defaults to @code{on}.
5436 @item show may-insert-breakpoints
5437 Show the current permission to insert breakpoints.
5439 @kindex may-insert-tracepoints
5440 @item set may-insert-tracepoints on
5441 @itemx set may-insert-tracepoints off
5442 This controls whether @value{GDBN} will attempt to insert (regular)
5443 tracepoints at the beginning of a tracing experiment. It affects only
5444 non-fast tracepoints, fast tracepoints being under the control of
5445 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5447 @item show may-insert-tracepoints
5448 Show the current permission to insert tracepoints.
5450 @kindex may-insert-fast-tracepoints
5451 @item set may-insert-fast-tracepoints on
5452 @itemx set may-insert-fast-tracepoints off
5453 This controls whether @value{GDBN} will attempt to insert fast
5454 tracepoints at the beginning of a tracing experiment. It affects only
5455 fast tracepoints, regular (non-fast) tracepoints being under the
5456 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5458 @item show may-insert-fast-tracepoints
5459 Show the current permission to insert fast tracepoints.
5461 @kindex may-interrupt
5462 @item set may-interrupt on
5463 @itemx set may-interrupt off
5464 This controls whether @value{GDBN} will attempt to interrupt or stop
5465 program execution. When this variable is @code{off}, the
5466 @code{interrupt} command will have no effect, nor will
5467 @kbd{Ctrl-c}. It defaults to @code{on}.
5469 @item show may-interrupt
5470 Show the current permission to interrupt or stop the program.
5474 @node Reverse Execution
5475 @chapter Running programs backward
5476 @cindex reverse execution
5477 @cindex running programs backward
5479 When you are debugging a program, it is not unusual to realize that
5480 you have gone too far, and some event of interest has already happened.
5481 If the target environment supports it, @value{GDBN} can allow you to
5482 ``rewind'' the program by running it backward.
5484 A target environment that supports reverse execution should be able
5485 to ``undo'' the changes in machine state that have taken place as the
5486 program was executing normally. Variables, registers etc.@: should
5487 revert to their previous values. Obviously this requires a great
5488 deal of sophistication on the part of the target environment; not
5489 all target environments can support reverse execution.
5491 When a program is executed in reverse, the instructions that
5492 have most recently been executed are ``un-executed'', in reverse
5493 order. The program counter runs backward, following the previous
5494 thread of execution in reverse. As each instruction is ``un-executed'',
5495 the values of memory and/or registers that were changed by that
5496 instruction are reverted to their previous states. After executing
5497 a piece of source code in reverse, all side effects of that code
5498 should be ``undone'', and all variables should be returned to their
5499 prior values@footnote{
5500 Note that some side effects are easier to undo than others. For instance,
5501 memory and registers are relatively easy, but device I/O is hard. Some
5502 targets may be able undo things like device I/O, and some may not.
5504 The contract between @value{GDBN} and the reverse executing target
5505 requires only that the target do something reasonable when
5506 @value{GDBN} tells it to execute backwards, and then report the
5507 results back to @value{GDBN}. Whatever the target reports back to
5508 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5509 assumes that the memory and registers that the target reports are in a
5510 consistant state, but @value{GDBN} accepts whatever it is given.
5513 If you are debugging in a target environment that supports
5514 reverse execution, @value{GDBN} provides the following commands.
5517 @kindex reverse-continue
5518 @kindex rc @r{(@code{reverse-continue})}
5519 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5520 @itemx rc @r{[}@var{ignore-count}@r{]}
5521 Beginning at the point where your program last stopped, start executing
5522 in reverse. Reverse execution will stop for breakpoints and synchronous
5523 exceptions (signals), just like normal execution. Behavior of
5524 asynchronous signals depends on the target environment.
5526 @kindex reverse-step
5527 @kindex rs @r{(@code{step})}
5528 @item reverse-step @r{[}@var{count}@r{]}
5529 Run the program backward until control reaches the start of a
5530 different source line; then stop it, and return control to @value{GDBN}.
5532 Like the @code{step} command, @code{reverse-step} will only stop
5533 at the beginning of a source line. It ``un-executes'' the previously
5534 executed source line. If the previous source line included calls to
5535 debuggable functions, @code{reverse-step} will step (backward) into
5536 the called function, stopping at the beginning of the @emph{last}
5537 statement in the called function (typically a return statement).
5539 Also, as with the @code{step} command, if non-debuggable functions are
5540 called, @code{reverse-step} will run thru them backward without stopping.
5542 @kindex reverse-stepi
5543 @kindex rsi @r{(@code{reverse-stepi})}
5544 @item reverse-stepi @r{[}@var{count}@r{]}
5545 Reverse-execute one machine instruction. Note that the instruction
5546 to be reverse-executed is @emph{not} the one pointed to by the program
5547 counter, but the instruction executed prior to that one. For instance,
5548 if the last instruction was a jump, @code{reverse-stepi} will take you
5549 back from the destination of the jump to the jump instruction itself.
5551 @kindex reverse-next
5552 @kindex rn @r{(@code{reverse-next})}
5553 @item reverse-next @r{[}@var{count}@r{]}
5554 Run backward to the beginning of the previous line executed in
5555 the current (innermost) stack frame. If the line contains function
5556 calls, they will be ``un-executed'' without stopping. Starting from
5557 the first line of a function, @code{reverse-next} will take you back
5558 to the caller of that function, @emph{before} the function was called,
5559 just as the normal @code{next} command would take you from the last
5560 line of a function back to its return to its caller
5561 @footnote{Unless the code is too heavily optimized.}.
5563 @kindex reverse-nexti
5564 @kindex rni @r{(@code{reverse-nexti})}
5565 @item reverse-nexti @r{[}@var{count}@r{]}
5566 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5567 in reverse, except that called functions are ``un-executed'' atomically.
5568 That is, if the previously executed instruction was a return from
5569 another function, @code{reverse-nexti} will continue to execute
5570 in reverse until the call to that function (from the current stack
5573 @kindex reverse-finish
5574 @item reverse-finish
5575 Just as the @code{finish} command takes you to the point where the
5576 current function returns, @code{reverse-finish} takes you to the point
5577 where it was called. Instead of ending up at the end of the current
5578 function invocation, you end up at the beginning.
5580 @kindex set exec-direction
5581 @item set exec-direction
5582 Set the direction of target execution.
5583 @itemx set exec-direction reverse
5584 @cindex execute forward or backward in time
5585 @value{GDBN} will perform all execution commands in reverse, until the
5586 exec-direction mode is changed to ``forward''. Affected commands include
5587 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5588 command cannot be used in reverse mode.
5589 @item set exec-direction forward
5590 @value{GDBN} will perform all execution commands in the normal fashion.
5591 This is the default.
5595 @node Process Record and Replay
5596 @chapter Recording Inferior's Execution and Replaying It
5597 @cindex process record and replay
5598 @cindex recording inferior's execution and replaying it
5600 On some platforms, @value{GDBN} provides a special @dfn{process record
5601 and replay} target that can record a log of the process execution, and
5602 replay it later with both forward and reverse execution commands.
5605 When this target is in use, if the execution log includes the record
5606 for the next instruction, @value{GDBN} will debug in @dfn{replay
5607 mode}. In the replay mode, the inferior does not really execute code
5608 instructions. Instead, all the events that normally happen during
5609 code execution are taken from the execution log. While code is not
5610 really executed in replay mode, the values of registers (including the
5611 program counter register) and the memory of the inferior are still
5612 changed as they normally would. Their contents are taken from the
5616 If the record for the next instruction is not in the execution log,
5617 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5618 inferior executes normally, and @value{GDBN} records the execution log
5621 The process record and replay target supports reverse execution
5622 (@pxref{Reverse Execution}), even if the platform on which the
5623 inferior runs does not. However, the reverse execution is limited in
5624 this case by the range of the instructions recorded in the execution
5625 log. In other words, reverse execution on platforms that don't
5626 support it directly can only be done in the replay mode.
5628 When debugging in the reverse direction, @value{GDBN} will work in
5629 replay mode as long as the execution log includes the record for the
5630 previous instruction; otherwise, it will work in record mode, if the
5631 platform supports reverse execution, or stop if not.
5633 For architecture environments that support process record and replay,
5634 @value{GDBN} provides the following commands:
5637 @kindex target record
5641 This command starts the process record and replay target. The process
5642 record and replay target can only debug a process that is already
5643 running. Therefore, you need first to start the process with the
5644 @kbd{run} or @kbd{start} commands, and then start the recording with
5645 the @kbd{target record} command.
5647 Both @code{record} and @code{rec} are aliases of @code{target record}.
5649 @cindex displaced stepping, and process record and replay
5650 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5651 will be automatically disabled when process record and replay target
5652 is started. That's because the process record and replay target
5653 doesn't support displaced stepping.
5655 @cindex non-stop mode, and process record and replay
5656 @cindex asynchronous execution, and process record and replay
5657 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5658 the asynchronous execution mode (@pxref{Background Execution}), the
5659 process record and replay target cannot be started because it doesn't
5660 support these two modes.
5665 Stop the process record and replay target. When process record and
5666 replay target stops, the entire execution log will be deleted and the
5667 inferior will either be terminated, or will remain in its final state.
5669 When you stop the process record and replay target in record mode (at
5670 the end of the execution log), the inferior will be stopped at the
5671 next instruction that would have been recorded. In other words, if
5672 you record for a while and then stop recording, the inferior process
5673 will be left in the same state as if the recording never happened.
5675 On the other hand, if the process record and replay target is stopped
5676 while in replay mode (that is, not at the end of the execution log,
5677 but at some earlier point), the inferior process will become ``live''
5678 at that earlier state, and it will then be possible to continue the
5679 usual ``live'' debugging of the process from that state.
5681 When the inferior process exits, or @value{GDBN} detaches from it,
5682 process record and replay target will automatically stop itself.
5685 @item record save @var{filename}
5686 Save the execution log to a file @file{@var{filename}}.
5687 Default filename is @file{gdb_record.@var{process_id}}, where
5688 @var{process_id} is the process ID of the inferior.
5690 @kindex record restore
5691 @item record restore @var{filename}
5692 Restore the execution log from a file @file{@var{filename}}.
5693 File must have been created with @code{record save}.
5695 @kindex set record insn-number-max
5696 @item set record insn-number-max @var{limit}
5697 Set the limit of instructions to be recorded. Default value is 200000.
5699 If @var{limit} is a positive number, then @value{GDBN} will start
5700 deleting instructions from the log once the number of the record
5701 instructions becomes greater than @var{limit}. For every new recorded
5702 instruction, @value{GDBN} will delete the earliest recorded
5703 instruction to keep the number of recorded instructions at the limit.
5704 (Since deleting recorded instructions loses information, @value{GDBN}
5705 lets you control what happens when the limit is reached, by means of
5706 the @code{stop-at-limit} option, described below.)
5708 If @var{limit} is zero, @value{GDBN} will never delete recorded
5709 instructions from the execution log. The number of recorded
5710 instructions is unlimited in this case.
5712 @kindex show record insn-number-max
5713 @item show record insn-number-max
5714 Show the limit of instructions to be recorded.
5716 @kindex set record stop-at-limit
5717 @item set record stop-at-limit
5718 Control the behavior when the number of recorded instructions reaches
5719 the limit. If ON (the default), @value{GDBN} will stop when the limit
5720 is reached for the first time and ask you whether you want to stop the
5721 inferior or continue running it and recording the execution log. If
5722 you decide to continue recording, each new recorded instruction will
5723 cause the oldest one to be deleted.
5725 If this option is OFF, @value{GDBN} will automatically delete the
5726 oldest record to make room for each new one, without asking.
5728 @kindex show record stop-at-limit
5729 @item show record stop-at-limit
5730 Show the current setting of @code{stop-at-limit}.
5732 @kindex set record memory-query
5733 @item set record memory-query
5734 Control the behavior when @value{GDBN} is unable to record memory
5735 changes caused by an instruction. If ON, @value{GDBN} will query
5736 whether to stop the inferior in that case.
5738 If this option is OFF (the default), @value{GDBN} will automatically
5739 ignore the effect of such instructions on memory. Later, when
5740 @value{GDBN} replays this execution log, it will mark the log of this
5741 instruction as not accessible, and it will not affect the replay
5744 @kindex show record memory-query
5745 @item show record memory-query
5746 Show the current setting of @code{memory-query}.
5750 Show various statistics about the state of process record and its
5751 in-memory execution log buffer, including:
5755 Whether in record mode or replay mode.
5757 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5759 Highest recorded instruction number.
5761 Current instruction about to be replayed (if in replay mode).
5763 Number of instructions contained in the execution log.
5765 Maximum number of instructions that may be contained in the execution log.
5768 @kindex record delete
5771 When record target runs in replay mode (``in the past''), delete the
5772 subsequent execution log and begin to record a new execution log starting
5773 from the current address. This means you will abandon the previously
5774 recorded ``future'' and begin recording a new ``future''.
5779 @chapter Examining the Stack
5781 When your program has stopped, the first thing you need to know is where it
5782 stopped and how it got there.
5785 Each time your program performs a function call, information about the call
5787 That information includes the location of the call in your program,
5788 the arguments of the call,
5789 and the local variables of the function being called.
5790 The information is saved in a block of data called a @dfn{stack frame}.
5791 The stack frames are allocated in a region of memory called the @dfn{call
5794 When your program stops, the @value{GDBN} commands for examining the
5795 stack allow you to see all of this information.
5797 @cindex selected frame
5798 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5799 @value{GDBN} commands refer implicitly to the selected frame. In
5800 particular, whenever you ask @value{GDBN} for the value of a variable in
5801 your program, the value is found in the selected frame. There are
5802 special @value{GDBN} commands to select whichever frame you are
5803 interested in. @xref{Selection, ,Selecting a Frame}.
5805 When your program stops, @value{GDBN} automatically selects the
5806 currently executing frame and describes it briefly, similar to the
5807 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5810 * Frames:: Stack frames
5811 * Backtrace:: Backtraces
5812 * Selection:: Selecting a frame
5813 * Frame Info:: Information on a frame
5818 @section Stack Frames
5820 @cindex frame, definition
5822 The call stack is divided up into contiguous pieces called @dfn{stack
5823 frames}, or @dfn{frames} for short; each frame is the data associated
5824 with one call to one function. The frame contains the arguments given
5825 to the function, the function's local variables, and the address at
5826 which the function is executing.
5828 @cindex initial frame
5829 @cindex outermost frame
5830 @cindex innermost frame
5831 When your program is started, the stack has only one frame, that of the
5832 function @code{main}. This is called the @dfn{initial} frame or the
5833 @dfn{outermost} frame. Each time a function is called, a new frame is
5834 made. Each time a function returns, the frame for that function invocation
5835 is eliminated. If a function is recursive, there can be many frames for
5836 the same function. The frame for the function in which execution is
5837 actually occurring is called the @dfn{innermost} frame. This is the most
5838 recently created of all the stack frames that still exist.
5840 @cindex frame pointer
5841 Inside your program, stack frames are identified by their addresses. A
5842 stack frame consists of many bytes, each of which has its own address; each
5843 kind of computer has a convention for choosing one byte whose
5844 address serves as the address of the frame. Usually this address is kept
5845 in a register called the @dfn{frame pointer register}
5846 (@pxref{Registers, $fp}) while execution is going on in that frame.
5848 @cindex frame number
5849 @value{GDBN} assigns numbers to all existing stack frames, starting with
5850 zero for the innermost frame, one for the frame that called it,
5851 and so on upward. These numbers do not really exist in your program;
5852 they are assigned by @value{GDBN} to give you a way of designating stack
5853 frames in @value{GDBN} commands.
5855 @c The -fomit-frame-pointer below perennially causes hbox overflow
5856 @c underflow problems.
5857 @cindex frameless execution
5858 Some compilers provide a way to compile functions so that they operate
5859 without stack frames. (For example, the @value{NGCC} option
5861 @samp{-fomit-frame-pointer}
5863 generates functions without a frame.)
5864 This is occasionally done with heavily used library functions to save
5865 the frame setup time. @value{GDBN} has limited facilities for dealing
5866 with these function invocations. If the innermost function invocation
5867 has no stack frame, @value{GDBN} nevertheless regards it as though
5868 it had a separate frame, which is numbered zero as usual, allowing
5869 correct tracing of the function call chain. However, @value{GDBN} has
5870 no provision for frameless functions elsewhere in the stack.
5873 @kindex frame@r{, command}
5874 @cindex current stack frame
5875 @item frame @var{args}
5876 The @code{frame} command allows you to move from one stack frame to another,
5877 and to print the stack frame you select. @var{args} may be either the
5878 address of the frame or the stack frame number. Without an argument,
5879 @code{frame} prints the current stack frame.
5881 @kindex select-frame
5882 @cindex selecting frame silently
5884 The @code{select-frame} command allows you to move from one stack frame
5885 to another without printing the frame. This is the silent version of
5893 @cindex call stack traces
5894 A backtrace is a summary of how your program got where it is. It shows one
5895 line per frame, for many frames, starting with the currently executing
5896 frame (frame zero), followed by its caller (frame one), and on up the
5901 @kindex bt @r{(@code{backtrace})}
5904 Print a backtrace of the entire stack: one line per frame for all
5905 frames in the stack.
5907 You can stop the backtrace at any time by typing the system interrupt
5908 character, normally @kbd{Ctrl-c}.
5910 @item backtrace @var{n}
5912 Similar, but print only the innermost @var{n} frames.
5914 @item backtrace -@var{n}
5916 Similar, but print only the outermost @var{n} frames.
5918 @item backtrace full
5920 @itemx bt full @var{n}
5921 @itemx bt full -@var{n}
5922 Print the values of the local variables also. @var{n} specifies the
5923 number of frames to print, as described above.
5928 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5929 are additional aliases for @code{backtrace}.
5931 @cindex multiple threads, backtrace
5932 In a multi-threaded program, @value{GDBN} by default shows the
5933 backtrace only for the current thread. To display the backtrace for
5934 several or all of the threads, use the command @code{thread apply}
5935 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5936 apply all backtrace}, @value{GDBN} will display the backtrace for all
5937 the threads; this is handy when you debug a core dump of a
5938 multi-threaded program.
5940 Each line in the backtrace shows the frame number and the function name.
5941 The program counter value is also shown---unless you use @code{set
5942 print address off}. The backtrace also shows the source file name and
5943 line number, as well as the arguments to the function. The program
5944 counter value is omitted if it is at the beginning of the code for that
5947 Here is an example of a backtrace. It was made with the command
5948 @samp{bt 3}, so it shows the innermost three frames.
5952 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5954 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5955 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5957 (More stack frames follow...)
5962 The display for frame zero does not begin with a program counter
5963 value, indicating that your program has stopped at the beginning of the
5964 code for line @code{993} of @code{builtin.c}.
5967 The value of parameter @code{data} in frame 1 has been replaced by
5968 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5969 only if it is a scalar (integer, pointer, enumeration, etc). See command
5970 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5971 on how to configure the way function parameter values are printed.
5973 @cindex optimized out, in backtrace
5974 @cindex function call arguments, optimized out
5975 If your program was compiled with optimizations, some compilers will
5976 optimize away arguments passed to functions if those arguments are
5977 never used after the call. Such optimizations generate code that
5978 passes arguments through registers, but doesn't store those arguments
5979 in the stack frame. @value{GDBN} has no way of displaying such
5980 arguments in stack frames other than the innermost one. Here's what
5981 such a backtrace might look like:
5985 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5987 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
5988 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
5990 (More stack frames follow...)
5995 The values of arguments that were not saved in their stack frames are
5996 shown as @samp{<optimized out>}.
5998 If you need to display the values of such optimized-out arguments,
5999 either deduce that from other variables whose values depend on the one
6000 you are interested in, or recompile without optimizations.
6002 @cindex backtrace beyond @code{main} function
6003 @cindex program entry point
6004 @cindex startup code, and backtrace
6005 Most programs have a standard user entry point---a place where system
6006 libraries and startup code transition into user code. For C this is
6007 @code{main}@footnote{
6008 Note that embedded programs (the so-called ``free-standing''
6009 environment) are not required to have a @code{main} function as the
6010 entry point. They could even have multiple entry points.}.
6011 When @value{GDBN} finds the entry function in a backtrace
6012 it will terminate the backtrace, to avoid tracing into highly
6013 system-specific (and generally uninteresting) code.
6015 If you need to examine the startup code, or limit the number of levels
6016 in a backtrace, you can change this behavior:
6019 @item set backtrace past-main
6020 @itemx set backtrace past-main on
6021 @kindex set backtrace
6022 Backtraces will continue past the user entry point.
6024 @item set backtrace past-main off
6025 Backtraces will stop when they encounter the user entry point. This is the
6028 @item show backtrace past-main
6029 @kindex show backtrace
6030 Display the current user entry point backtrace policy.
6032 @item set backtrace past-entry
6033 @itemx set backtrace past-entry on
6034 Backtraces will continue past the internal entry point of an application.
6035 This entry point is encoded by the linker when the application is built,
6036 and is likely before the user entry point @code{main} (or equivalent) is called.
6038 @item set backtrace past-entry off
6039 Backtraces will stop when they encounter the internal entry point of an
6040 application. This is the default.
6042 @item show backtrace past-entry
6043 Display the current internal entry point backtrace policy.
6045 @item set backtrace limit @var{n}
6046 @itemx set backtrace limit 0
6047 @cindex backtrace limit
6048 Limit the backtrace to @var{n} levels. A value of zero means
6051 @item show backtrace limit
6052 Display the current limit on backtrace levels.
6056 @section Selecting a Frame
6058 Most commands for examining the stack and other data in your program work on
6059 whichever stack frame is selected at the moment. Here are the commands for
6060 selecting a stack frame; all of them finish by printing a brief description
6061 of the stack frame just selected.
6064 @kindex frame@r{, selecting}
6065 @kindex f @r{(@code{frame})}
6068 Select frame number @var{n}. Recall that frame zero is the innermost
6069 (currently executing) frame, frame one is the frame that called the
6070 innermost one, and so on. The highest-numbered frame is the one for
6073 @item frame @var{addr}
6075 Select the frame at address @var{addr}. This is useful mainly if the
6076 chaining of stack frames has been damaged by a bug, making it
6077 impossible for @value{GDBN} to assign numbers properly to all frames. In
6078 addition, this can be useful when your program has multiple stacks and
6079 switches between them.
6081 On the SPARC architecture, @code{frame} needs two addresses to
6082 select an arbitrary frame: a frame pointer and a stack pointer.
6084 On the MIPS and Alpha architecture, it needs two addresses: a stack
6085 pointer and a program counter.
6087 On the 29k architecture, it needs three addresses: a register stack
6088 pointer, a program counter, and a memory stack pointer.
6092 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6093 advances toward the outermost frame, to higher frame numbers, to frames
6094 that have existed longer. @var{n} defaults to one.
6097 @kindex do @r{(@code{down})}
6099 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6100 advances toward the innermost frame, to lower frame numbers, to frames
6101 that were created more recently. @var{n} defaults to one. You may
6102 abbreviate @code{down} as @code{do}.
6105 All of these commands end by printing two lines of output describing the
6106 frame. The first line shows the frame number, the function name, the
6107 arguments, and the source file and line number of execution in that
6108 frame. The second line shows the text of that source line.
6116 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6118 10 read_input_file (argv[i]);
6122 After such a printout, the @code{list} command with no arguments
6123 prints ten lines centered on the point of execution in the frame.
6124 You can also edit the program at the point of execution with your favorite
6125 editing program by typing @code{edit}.
6126 @xref{List, ,Printing Source Lines},
6130 @kindex down-silently
6132 @item up-silently @var{n}
6133 @itemx down-silently @var{n}
6134 These two commands are variants of @code{up} and @code{down},
6135 respectively; they differ in that they do their work silently, without
6136 causing display of the new frame. They are intended primarily for use
6137 in @value{GDBN} command scripts, where the output might be unnecessary and
6142 @section Information About a Frame
6144 There are several other commands to print information about the selected
6150 When used without any argument, this command does not change which
6151 frame is selected, but prints a brief description of the currently
6152 selected stack frame. It can be abbreviated @code{f}. With an
6153 argument, this command is used to select a stack frame.
6154 @xref{Selection, ,Selecting a Frame}.
6157 @kindex info f @r{(@code{info frame})}
6160 This command prints a verbose description of the selected stack frame,
6165 the address of the frame
6167 the address of the next frame down (called by this frame)
6169 the address of the next frame up (caller of this frame)
6171 the language in which the source code corresponding to this frame is written
6173 the address of the frame's arguments
6175 the address of the frame's local variables
6177 the program counter saved in it (the address of execution in the caller frame)
6179 which registers were saved in the frame
6182 @noindent The verbose description is useful when
6183 something has gone wrong that has made the stack format fail to fit
6184 the usual conventions.
6186 @item info frame @var{addr}
6187 @itemx info f @var{addr}
6188 Print a verbose description of the frame at address @var{addr}, without
6189 selecting that frame. The selected frame remains unchanged by this
6190 command. This requires the same kind of address (more than one for some
6191 architectures) that you specify in the @code{frame} command.
6192 @xref{Selection, ,Selecting a Frame}.
6196 Print the arguments of the selected frame, each on a separate line.
6200 Print the local variables of the selected frame, each on a separate
6201 line. These are all variables (declared either static or automatic)
6202 accessible at the point of execution of the selected frame.
6205 @cindex catch exceptions, list active handlers
6206 @cindex exception handlers, how to list
6208 Print a list of all the exception handlers that are active in the
6209 current stack frame at the current point of execution. To see other
6210 exception handlers, visit the associated frame (using the @code{up},
6211 @code{down}, or @code{frame} commands); then type @code{info catch}.
6212 @xref{Set Catchpoints, , Setting Catchpoints}.
6218 @chapter Examining Source Files
6220 @value{GDBN} can print parts of your program's source, since the debugging
6221 information recorded in the program tells @value{GDBN} what source files were
6222 used to build it. When your program stops, @value{GDBN} spontaneously prints
6223 the line where it stopped. Likewise, when you select a stack frame
6224 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6225 execution in that frame has stopped. You can print other portions of
6226 source files by explicit command.
6228 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6229 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6230 @value{GDBN} under @sc{gnu} Emacs}.
6233 * List:: Printing source lines
6234 * Specify Location:: How to specify code locations
6235 * Edit:: Editing source files
6236 * Search:: Searching source files
6237 * Source Path:: Specifying source directories
6238 * Machine Code:: Source and machine code
6242 @section Printing Source Lines
6245 @kindex l @r{(@code{list})}
6246 To print lines from a source file, use the @code{list} command
6247 (abbreviated @code{l}). By default, ten lines are printed.
6248 There are several ways to specify what part of the file you want to
6249 print; see @ref{Specify Location}, for the full list.
6251 Here are the forms of the @code{list} command most commonly used:
6254 @item list @var{linenum}
6255 Print lines centered around line number @var{linenum} in the
6256 current source file.
6258 @item list @var{function}
6259 Print lines centered around the beginning of function
6263 Print more lines. If the last lines printed were printed with a
6264 @code{list} command, this prints lines following the last lines
6265 printed; however, if the last line printed was a solitary line printed
6266 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6267 Stack}), this prints lines centered around that line.
6270 Print lines just before the lines last printed.
6273 @cindex @code{list}, how many lines to display
6274 By default, @value{GDBN} prints ten source lines with any of these forms of
6275 the @code{list} command. You can change this using @code{set listsize}:
6278 @kindex set listsize
6279 @item set listsize @var{count}
6280 Make the @code{list} command display @var{count} source lines (unless
6281 the @code{list} argument explicitly specifies some other number).
6283 @kindex show listsize
6285 Display the number of lines that @code{list} prints.
6288 Repeating a @code{list} command with @key{RET} discards the argument,
6289 so it is equivalent to typing just @code{list}. This is more useful
6290 than listing the same lines again. An exception is made for an
6291 argument of @samp{-}; that argument is preserved in repetition so that
6292 each repetition moves up in the source file.
6294 In general, the @code{list} command expects you to supply zero, one or two
6295 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6296 of writing them (@pxref{Specify Location}), but the effect is always
6297 to specify some source line.
6299 Here is a complete description of the possible arguments for @code{list}:
6302 @item list @var{linespec}
6303 Print lines centered around the line specified by @var{linespec}.
6305 @item list @var{first},@var{last}
6306 Print lines from @var{first} to @var{last}. Both arguments are
6307 linespecs. When a @code{list} command has two linespecs, and the
6308 source file of the second linespec is omitted, this refers to
6309 the same source file as the first linespec.
6311 @item list ,@var{last}
6312 Print lines ending with @var{last}.
6314 @item list @var{first},
6315 Print lines starting with @var{first}.
6318 Print lines just after the lines last printed.
6321 Print lines just before the lines last printed.
6324 As described in the preceding table.
6327 @node Specify Location
6328 @section Specifying a Location
6329 @cindex specifying location
6332 Several @value{GDBN} commands accept arguments that specify a location
6333 of your program's code. Since @value{GDBN} is a source-level
6334 debugger, a location usually specifies some line in the source code;
6335 for that reason, locations are also known as @dfn{linespecs}.
6337 Here are all the different ways of specifying a code location that
6338 @value{GDBN} understands:
6342 Specifies the line number @var{linenum} of the current source file.
6345 @itemx +@var{offset}
6346 Specifies the line @var{offset} lines before or after the @dfn{current
6347 line}. For the @code{list} command, the current line is the last one
6348 printed; for the breakpoint commands, this is the line at which
6349 execution stopped in the currently selected @dfn{stack frame}
6350 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6351 used as the second of the two linespecs in a @code{list} command,
6352 this specifies the line @var{offset} lines up or down from the first
6355 @item @var{filename}:@var{linenum}
6356 Specifies the line @var{linenum} in the source file @var{filename}.
6358 @item @var{function}
6359 Specifies the line that begins the body of the function @var{function}.
6360 For example, in C, this is the line with the open brace.
6362 @item @var{function}:@var{label}
6363 Specifies the line where @var{label} appears in @var{function}.
6365 @item @var{filename}:@var{function}
6366 Specifies the line that begins the body of the function @var{function}
6367 in the file @var{filename}. You only need the file name with a
6368 function name to avoid ambiguity when there are identically named
6369 functions in different source files.
6372 Specifies the line at which the label named @var{label} appears.
6373 @value{GDBN} searches for the label in the function corresponding to
6374 the currently selected stack frame. If there is no current selected
6375 stack frame (for instance, if the inferior is not running), then
6376 @value{GDBN} will not search for a label.
6378 @item *@var{address}
6379 Specifies the program address @var{address}. For line-oriented
6380 commands, such as @code{list} and @code{edit}, this specifies a source
6381 line that contains @var{address}. For @code{break} and other
6382 breakpoint oriented commands, this can be used to set breakpoints in
6383 parts of your program which do not have debugging information or
6386 Here @var{address} may be any expression valid in the current working
6387 language (@pxref{Languages, working language}) that specifies a code
6388 address. In addition, as a convenience, @value{GDBN} extends the
6389 semantics of expressions used in locations to cover the situations
6390 that frequently happen during debugging. Here are the various forms
6394 @item @var{expression}
6395 Any expression valid in the current working language.
6397 @item @var{funcaddr}
6398 An address of a function or procedure derived from its name. In C,
6399 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6400 simply the function's name @var{function} (and actually a special case
6401 of a valid expression). In Pascal and Modula-2, this is
6402 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6403 (although the Pascal form also works).
6405 This form specifies the address of the function's first instruction,
6406 before the stack frame and arguments have been set up.
6408 @item '@var{filename}'::@var{funcaddr}
6409 Like @var{funcaddr} above, but also specifies the name of the source
6410 file explicitly. This is useful if the name of the function does not
6411 specify the function unambiguously, e.g., if there are several
6412 functions with identical names in different source files.
6419 @section Editing Source Files
6420 @cindex editing source files
6423 @kindex e @r{(@code{edit})}
6424 To edit the lines in a source file, use the @code{edit} command.
6425 The editing program of your choice
6426 is invoked with the current line set to
6427 the active line in the program.
6428 Alternatively, there are several ways to specify what part of the file you
6429 want to print if you want to see other parts of the program:
6432 @item edit @var{location}
6433 Edit the source file specified by @code{location}. Editing starts at
6434 that @var{location}, e.g., at the specified source line of the
6435 specified file. @xref{Specify Location}, for all the possible forms
6436 of the @var{location} argument; here are the forms of the @code{edit}
6437 command most commonly used:
6440 @item edit @var{number}
6441 Edit the current source file with @var{number} as the active line number.
6443 @item edit @var{function}
6444 Edit the file containing @var{function} at the beginning of its definition.
6449 @subsection Choosing your Editor
6450 You can customize @value{GDBN} to use any editor you want
6452 The only restriction is that your editor (say @code{ex}), recognizes the
6453 following command-line syntax:
6455 ex +@var{number} file
6457 The optional numeric value +@var{number} specifies the number of the line in
6458 the file where to start editing.}.
6459 By default, it is @file{@value{EDITOR}}, but you can change this
6460 by setting the environment variable @code{EDITOR} before using
6461 @value{GDBN}. For example, to configure @value{GDBN} to use the
6462 @code{vi} editor, you could use these commands with the @code{sh} shell:
6468 or in the @code{csh} shell,
6470 setenv EDITOR /usr/bin/vi
6475 @section Searching Source Files
6476 @cindex searching source files
6478 There are two commands for searching through the current source file for a
6483 @kindex forward-search
6484 @item forward-search @var{regexp}
6485 @itemx search @var{regexp}
6486 The command @samp{forward-search @var{regexp}} checks each line,
6487 starting with the one following the last line listed, for a match for
6488 @var{regexp}. It lists the line that is found. You can use the
6489 synonym @samp{search @var{regexp}} or abbreviate the command name as
6492 @kindex reverse-search
6493 @item reverse-search @var{regexp}
6494 The command @samp{reverse-search @var{regexp}} checks each line, starting
6495 with the one before the last line listed and going backward, for a match
6496 for @var{regexp}. It lists the line that is found. You can abbreviate
6497 this command as @code{rev}.
6501 @section Specifying Source Directories
6504 @cindex directories for source files
6505 Executable programs sometimes do not record the directories of the source
6506 files from which they were compiled, just the names. Even when they do,
6507 the directories could be moved between the compilation and your debugging
6508 session. @value{GDBN} has a list of directories to search for source files;
6509 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6510 it tries all the directories in the list, in the order they are present
6511 in the list, until it finds a file with the desired name.
6513 For example, suppose an executable references the file
6514 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6515 @file{/mnt/cross}. The file is first looked up literally; if this
6516 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6517 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6518 message is printed. @value{GDBN} does not look up the parts of the
6519 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6520 Likewise, the subdirectories of the source path are not searched: if
6521 the source path is @file{/mnt/cross}, and the binary refers to
6522 @file{foo.c}, @value{GDBN} would not find it under
6523 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6525 Plain file names, relative file names with leading directories, file
6526 names containing dots, etc.@: are all treated as described above; for
6527 instance, if the source path is @file{/mnt/cross}, and the source file
6528 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6529 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6530 that---@file{/mnt/cross/foo.c}.
6532 Note that the executable search path is @emph{not} used to locate the
6535 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6536 any information it has cached about where source files are found and where
6537 each line is in the file.
6541 When you start @value{GDBN}, its source path includes only @samp{cdir}
6542 and @samp{cwd}, in that order.
6543 To add other directories, use the @code{directory} command.
6545 The search path is used to find both program source files and @value{GDBN}
6546 script files (read using the @samp{-command} option and @samp{source} command).
6548 In addition to the source path, @value{GDBN} provides a set of commands
6549 that manage a list of source path substitution rules. A @dfn{substitution
6550 rule} specifies how to rewrite source directories stored in the program's
6551 debug information in case the sources were moved to a different
6552 directory between compilation and debugging. A rule is made of
6553 two strings, the first specifying what needs to be rewritten in
6554 the path, and the second specifying how it should be rewritten.
6555 In @ref{set substitute-path}, we name these two parts @var{from} and
6556 @var{to} respectively. @value{GDBN} does a simple string replacement
6557 of @var{from} with @var{to} at the start of the directory part of the
6558 source file name, and uses that result instead of the original file
6559 name to look up the sources.
6561 Using the previous example, suppose the @file{foo-1.0} tree has been
6562 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6563 @value{GDBN} to replace @file{/usr/src} in all source path names with
6564 @file{/mnt/cross}. The first lookup will then be
6565 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6566 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6567 substitution rule, use the @code{set substitute-path} command
6568 (@pxref{set substitute-path}).
6570 To avoid unexpected substitution results, a rule is applied only if the
6571 @var{from} part of the directory name ends at a directory separator.
6572 For instance, a rule substituting @file{/usr/source} into
6573 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6574 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6575 is applied only at the beginning of the directory name, this rule will
6576 not be applied to @file{/root/usr/source/baz.c} either.
6578 In many cases, you can achieve the same result using the @code{directory}
6579 command. However, @code{set substitute-path} can be more efficient in
6580 the case where the sources are organized in a complex tree with multiple
6581 subdirectories. With the @code{directory} command, you need to add each
6582 subdirectory of your project. If you moved the entire tree while
6583 preserving its internal organization, then @code{set substitute-path}
6584 allows you to direct the debugger to all the sources with one single
6587 @code{set substitute-path} is also more than just a shortcut command.
6588 The source path is only used if the file at the original location no
6589 longer exists. On the other hand, @code{set substitute-path} modifies
6590 the debugger behavior to look at the rewritten location instead. So, if
6591 for any reason a source file that is not relevant to your executable is
6592 located at the original location, a substitution rule is the only
6593 method available to point @value{GDBN} at the new location.
6595 @cindex @samp{--with-relocated-sources}
6596 @cindex default source path substitution
6597 You can configure a default source path substitution rule by
6598 configuring @value{GDBN} with the
6599 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6600 should be the name of a directory under @value{GDBN}'s configured
6601 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6602 directory names in debug information under @var{dir} will be adjusted
6603 automatically if the installed @value{GDBN} is moved to a new
6604 location. This is useful if @value{GDBN}, libraries or executables
6605 with debug information and corresponding source code are being moved
6609 @item directory @var{dirname} @dots{}
6610 @item dir @var{dirname} @dots{}
6611 Add directory @var{dirname} to the front of the source path. Several
6612 directory names may be given to this command, separated by @samp{:}
6613 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6614 part of absolute file names) or
6615 whitespace. You may specify a directory that is already in the source
6616 path; this moves it forward, so @value{GDBN} searches it sooner.
6620 @vindex $cdir@r{, convenience variable}
6621 @vindex $cwd@r{, convenience variable}
6622 @cindex compilation directory
6623 @cindex current directory
6624 @cindex working directory
6625 @cindex directory, current
6626 @cindex directory, compilation
6627 You can use the string @samp{$cdir} to refer to the compilation
6628 directory (if one is recorded), and @samp{$cwd} to refer to the current
6629 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6630 tracks the current working directory as it changes during your @value{GDBN}
6631 session, while the latter is immediately expanded to the current
6632 directory at the time you add an entry to the source path.
6635 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6637 @c RET-repeat for @code{directory} is explicitly disabled, but since
6638 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6640 @item set directories @var{path-list}
6641 @kindex set directories
6642 Set the source path to @var{path-list}.
6643 @samp{$cdir:$cwd} are added if missing.
6645 @item show directories
6646 @kindex show directories
6647 Print the source path: show which directories it contains.
6649 @anchor{set substitute-path}
6650 @item set substitute-path @var{from} @var{to}
6651 @kindex set substitute-path
6652 Define a source path substitution rule, and add it at the end of the
6653 current list of existing substitution rules. If a rule with the same
6654 @var{from} was already defined, then the old rule is also deleted.
6656 For example, if the file @file{/foo/bar/baz.c} was moved to
6657 @file{/mnt/cross/baz.c}, then the command
6660 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6664 will tell @value{GDBN} to replace @samp{/usr/src} with
6665 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6666 @file{baz.c} even though it was moved.
6668 In the case when more than one substitution rule have been defined,
6669 the rules are evaluated one by one in the order where they have been
6670 defined. The first one matching, if any, is selected to perform
6673 For instance, if we had entered the following commands:
6676 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6677 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6681 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6682 @file{/mnt/include/defs.h} by using the first rule. However, it would
6683 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6684 @file{/mnt/src/lib/foo.c}.
6687 @item unset substitute-path [path]
6688 @kindex unset substitute-path
6689 If a path is specified, search the current list of substitution rules
6690 for a rule that would rewrite that path. Delete that rule if found.
6691 A warning is emitted by the debugger if no rule could be found.
6693 If no path is specified, then all substitution rules are deleted.
6695 @item show substitute-path [path]
6696 @kindex show substitute-path
6697 If a path is specified, then print the source path substitution rule
6698 which would rewrite that path, if any.
6700 If no path is specified, then print all existing source path substitution
6705 If your source path is cluttered with directories that are no longer of
6706 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6707 versions of source. You can correct the situation as follows:
6711 Use @code{directory} with no argument to reset the source path to its default value.
6714 Use @code{directory} with suitable arguments to reinstall the
6715 directories you want in the source path. You can add all the
6716 directories in one command.
6720 @section Source and Machine Code
6721 @cindex source line and its code address
6723 You can use the command @code{info line} to map source lines to program
6724 addresses (and vice versa), and the command @code{disassemble} to display
6725 a range of addresses as machine instructions. You can use the command
6726 @code{set disassemble-next-line} to set whether to disassemble next
6727 source line when execution stops. When run under @sc{gnu} Emacs
6728 mode, the @code{info line} command causes the arrow to point to the
6729 line specified. Also, @code{info line} prints addresses in symbolic form as
6734 @item info line @var{linespec}
6735 Print the starting and ending addresses of the compiled code for
6736 source line @var{linespec}. You can specify source lines in any of
6737 the ways documented in @ref{Specify Location}.
6740 For example, we can use @code{info line} to discover the location of
6741 the object code for the first line of function
6742 @code{m4_changequote}:
6744 @c FIXME: I think this example should also show the addresses in
6745 @c symbolic form, as they usually would be displayed.
6747 (@value{GDBP}) info line m4_changequote
6748 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6752 @cindex code address and its source line
6753 We can also inquire (using @code{*@var{addr}} as the form for
6754 @var{linespec}) what source line covers a particular address:
6756 (@value{GDBP}) info line *0x63ff
6757 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6760 @cindex @code{$_} and @code{info line}
6761 @cindex @code{x} command, default address
6762 @kindex x@r{(examine), and} info line
6763 After @code{info line}, the default address for the @code{x} command
6764 is changed to the starting address of the line, so that @samp{x/i} is
6765 sufficient to begin examining the machine code (@pxref{Memory,
6766 ,Examining Memory}). Also, this address is saved as the value of the
6767 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6772 @cindex assembly instructions
6773 @cindex instructions, assembly
6774 @cindex machine instructions
6775 @cindex listing machine instructions
6777 @itemx disassemble /m
6778 @itemx disassemble /r
6779 This specialized command dumps a range of memory as machine
6780 instructions. It can also print mixed source+disassembly by specifying
6781 the @code{/m} modifier and print the raw instructions in hex as well as
6782 in symbolic form by specifying the @code{/r}.
6783 The default memory range is the function surrounding the
6784 program counter of the selected frame. A single argument to this
6785 command is a program counter value; @value{GDBN} dumps the function
6786 surrounding this value. When two arguments are given, they should
6787 be separated by a comma, possibly surrounded by whitespace. The
6788 arguments specify a range of addresses to dump, in one of two forms:
6791 @item @var{start},@var{end}
6792 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6793 @item @var{start},+@var{length}
6794 the addresses from @var{start} (inclusive) to
6795 @code{@var{start}+@var{length}} (exclusive).
6799 When 2 arguments are specified, the name of the function is also
6800 printed (since there could be several functions in the given range).
6802 The argument(s) can be any expression yielding a numeric value, such as
6803 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6805 If the range of memory being disassembled contains current program counter,
6806 the instruction at that location is shown with a @code{=>} marker.
6809 The following example shows the disassembly of a range of addresses of
6810 HP PA-RISC 2.0 code:
6813 (@value{GDBP}) disas 0x32c4, 0x32e4
6814 Dump of assembler code from 0x32c4 to 0x32e4:
6815 0x32c4 <main+204>: addil 0,dp
6816 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6817 0x32cc <main+212>: ldil 0x3000,r31
6818 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6819 0x32d4 <main+220>: ldo 0(r31),rp
6820 0x32d8 <main+224>: addil -0x800,dp
6821 0x32dc <main+228>: ldo 0x588(r1),r26
6822 0x32e0 <main+232>: ldil 0x3000,r31
6823 End of assembler dump.
6826 Here is an example showing mixed source+assembly for Intel x86, when the
6827 program is stopped just after function prologue:
6830 (@value{GDBP}) disas /m main
6831 Dump of assembler code for function main:
6833 0x08048330 <+0>: push %ebp
6834 0x08048331 <+1>: mov %esp,%ebp
6835 0x08048333 <+3>: sub $0x8,%esp
6836 0x08048336 <+6>: and $0xfffffff0,%esp
6837 0x08048339 <+9>: sub $0x10,%esp
6839 6 printf ("Hello.\n");
6840 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6841 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6845 0x08048348 <+24>: mov $0x0,%eax
6846 0x0804834d <+29>: leave
6847 0x0804834e <+30>: ret
6849 End of assembler dump.
6852 Here is another example showing raw instructions in hex for AMD x86-64,
6855 (gdb) disas /r 0x400281,+10
6856 Dump of assembler code from 0x400281 to 0x40028b:
6857 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6858 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6859 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6860 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6861 End of assembler dump.
6864 Some architectures have more than one commonly-used set of instruction
6865 mnemonics or other syntax.
6867 For programs that were dynamically linked and use shared libraries,
6868 instructions that call functions or branch to locations in the shared
6869 libraries might show a seemingly bogus location---it's actually a
6870 location of the relocation table. On some architectures, @value{GDBN}
6871 might be able to resolve these to actual function names.
6874 @kindex set disassembly-flavor
6875 @cindex Intel disassembly flavor
6876 @cindex AT&T disassembly flavor
6877 @item set disassembly-flavor @var{instruction-set}
6878 Select the instruction set to use when disassembling the
6879 program via the @code{disassemble} or @code{x/i} commands.
6881 Currently this command is only defined for the Intel x86 family. You
6882 can set @var{instruction-set} to either @code{intel} or @code{att}.
6883 The default is @code{att}, the AT&T flavor used by default by Unix
6884 assemblers for x86-based targets.
6886 @kindex show disassembly-flavor
6887 @item show disassembly-flavor
6888 Show the current setting of the disassembly flavor.
6892 @kindex set disassemble-next-line
6893 @kindex show disassemble-next-line
6894 @item set disassemble-next-line
6895 @itemx show disassemble-next-line
6896 Control whether or not @value{GDBN} will disassemble the next source
6897 line or instruction when execution stops. If ON, @value{GDBN} will
6898 display disassembly of the next source line when execution of the
6899 program being debugged stops. This is @emph{in addition} to
6900 displaying the source line itself, which @value{GDBN} always does if
6901 possible. If the next source line cannot be displayed for some reason
6902 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6903 info in the debug info), @value{GDBN} will display disassembly of the
6904 next @emph{instruction} instead of showing the next source line. If
6905 AUTO, @value{GDBN} will display disassembly of next instruction only
6906 if the source line cannot be displayed. This setting causes
6907 @value{GDBN} to display some feedback when you step through a function
6908 with no line info or whose source file is unavailable. The default is
6909 OFF, which means never display the disassembly of the next line or
6915 @chapter Examining Data
6917 @cindex printing data
6918 @cindex examining data
6921 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6922 @c document because it is nonstandard... Under Epoch it displays in a
6923 @c different window or something like that.
6924 The usual way to examine data in your program is with the @code{print}
6925 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6926 evaluates and prints the value of an expression of the language your
6927 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6928 Different Languages}). It may also print the expression using a
6929 Python-based pretty-printer (@pxref{Pretty Printing}).
6932 @item print @var{expr}
6933 @itemx print /@var{f} @var{expr}
6934 @var{expr} is an expression (in the source language). By default the
6935 value of @var{expr} is printed in a format appropriate to its data type;
6936 you can choose a different format by specifying @samp{/@var{f}}, where
6937 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6941 @itemx print /@var{f}
6942 @cindex reprint the last value
6943 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6944 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6945 conveniently inspect the same value in an alternative format.
6948 A more low-level way of examining data is with the @code{x} command.
6949 It examines data in memory at a specified address and prints it in a
6950 specified format. @xref{Memory, ,Examining Memory}.
6952 If you are interested in information about types, or about how the
6953 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6954 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6958 * Expressions:: Expressions
6959 * Ambiguous Expressions:: Ambiguous Expressions
6960 * Variables:: Program variables
6961 * Arrays:: Artificial arrays
6962 * Output Formats:: Output formats
6963 * Memory:: Examining memory
6964 * Auto Display:: Automatic display
6965 * Print Settings:: Print settings
6966 * Pretty Printing:: Python pretty printing
6967 * Value History:: Value history
6968 * Convenience Vars:: Convenience variables
6969 * Registers:: Registers
6970 * Floating Point Hardware:: Floating point hardware
6971 * Vector Unit:: Vector Unit
6972 * OS Information:: Auxiliary data provided by operating system
6973 * Memory Region Attributes:: Memory region attributes
6974 * Dump/Restore Files:: Copy between memory and a file
6975 * Core File Generation:: Cause a program dump its core
6976 * Character Sets:: Debugging programs that use a different
6977 character set than GDB does
6978 * Caching Remote Data:: Data caching for remote targets
6979 * Searching Memory:: Searching memory for a sequence of bytes
6983 @section Expressions
6986 @code{print} and many other @value{GDBN} commands accept an expression and
6987 compute its value. Any kind of constant, variable or operator defined
6988 by the programming language you are using is valid in an expression in
6989 @value{GDBN}. This includes conditional expressions, function calls,
6990 casts, and string constants. It also includes preprocessor macros, if
6991 you compiled your program to include this information; see
6994 @cindex arrays in expressions
6995 @value{GDBN} supports array constants in expressions input by
6996 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6997 you can use the command @code{print @{1, 2, 3@}} to create an array
6998 of three integers. If you pass an array to a function or assign it
6999 to a program variable, @value{GDBN} copies the array to memory that
7000 is @code{malloc}ed in the target program.
7002 Because C is so widespread, most of the expressions shown in examples in
7003 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7004 Languages}, for information on how to use expressions in other
7007 In this section, we discuss operators that you can use in @value{GDBN}
7008 expressions regardless of your programming language.
7010 @cindex casts, in expressions
7011 Casts are supported in all languages, not just in C, because it is so
7012 useful to cast a number into a pointer in order to examine a structure
7013 at that address in memory.
7014 @c FIXME: casts supported---Mod2 true?
7016 @value{GDBN} supports these operators, in addition to those common
7017 to programming languages:
7021 @samp{@@} is a binary operator for treating parts of memory as arrays.
7022 @xref{Arrays, ,Artificial Arrays}, for more information.
7025 @samp{::} allows you to specify a variable in terms of the file or
7026 function where it is defined. @xref{Variables, ,Program Variables}.
7028 @cindex @{@var{type}@}
7029 @cindex type casting memory
7030 @cindex memory, viewing as typed object
7031 @cindex casts, to view memory
7032 @item @{@var{type}@} @var{addr}
7033 Refers to an object of type @var{type} stored at address @var{addr} in
7034 memory. @var{addr} may be any expression whose value is an integer or
7035 pointer (but parentheses are required around binary operators, just as in
7036 a cast). This construct is allowed regardless of what kind of data is
7037 normally supposed to reside at @var{addr}.
7040 @node Ambiguous Expressions
7041 @section Ambiguous Expressions
7042 @cindex ambiguous expressions
7044 Expressions can sometimes contain some ambiguous elements. For instance,
7045 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7046 a single function name to be defined several times, for application in
7047 different contexts. This is called @dfn{overloading}. Another example
7048 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7049 templates and is typically instantiated several times, resulting in
7050 the same function name being defined in different contexts.
7052 In some cases and depending on the language, it is possible to adjust
7053 the expression to remove the ambiguity. For instance in C@t{++}, you
7054 can specify the signature of the function you want to break on, as in
7055 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7056 qualified name of your function often makes the expression unambiguous
7059 When an ambiguity that needs to be resolved is detected, the debugger
7060 has the capability to display a menu of numbered choices for each
7061 possibility, and then waits for the selection with the prompt @samp{>}.
7062 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7063 aborts the current command. If the command in which the expression was
7064 used allows more than one choice to be selected, the next option in the
7065 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7068 For example, the following session excerpt shows an attempt to set a
7069 breakpoint at the overloaded symbol @code{String::after}.
7070 We choose three particular definitions of that function name:
7072 @c FIXME! This is likely to change to show arg type lists, at least
7075 (@value{GDBP}) b String::after
7078 [2] file:String.cc; line number:867
7079 [3] file:String.cc; line number:860
7080 [4] file:String.cc; line number:875
7081 [5] file:String.cc; line number:853
7082 [6] file:String.cc; line number:846
7083 [7] file:String.cc; line number:735
7085 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7086 Breakpoint 2 at 0xb344: file String.cc, line 875.
7087 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7088 Multiple breakpoints were set.
7089 Use the "delete" command to delete unwanted
7096 @kindex set multiple-symbols
7097 @item set multiple-symbols @var{mode}
7098 @cindex multiple-symbols menu
7100 This option allows you to adjust the debugger behavior when an expression
7103 By default, @var{mode} is set to @code{all}. If the command with which
7104 the expression is used allows more than one choice, then @value{GDBN}
7105 automatically selects all possible choices. For instance, inserting
7106 a breakpoint on a function using an ambiguous name results in a breakpoint
7107 inserted on each possible match. However, if a unique choice must be made,
7108 then @value{GDBN} uses the menu to help you disambiguate the expression.
7109 For instance, printing the address of an overloaded function will result
7110 in the use of the menu.
7112 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7113 when an ambiguity is detected.
7115 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7116 an error due to the ambiguity and the command is aborted.
7118 @kindex show multiple-symbols
7119 @item show multiple-symbols
7120 Show the current value of the @code{multiple-symbols} setting.
7124 @section Program Variables
7126 The most common kind of expression to use is the name of a variable
7129 Variables in expressions are understood in the selected stack frame
7130 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7134 global (or file-static)
7141 visible according to the scope rules of the
7142 programming language from the point of execution in that frame
7145 @noindent This means that in the function
7160 you can examine and use the variable @code{a} whenever your program is
7161 executing within the function @code{foo}, but you can only use or
7162 examine the variable @code{b} while your program is executing inside
7163 the block where @code{b} is declared.
7165 @cindex variable name conflict
7166 There is an exception: you can refer to a variable or function whose
7167 scope is a single source file even if the current execution point is not
7168 in this file. But it is possible to have more than one such variable or
7169 function with the same name (in different source files). If that
7170 happens, referring to that name has unpredictable effects. If you wish,
7171 you can specify a static variable in a particular function or file,
7172 using the colon-colon (@code{::}) notation:
7174 @cindex colon-colon, context for variables/functions
7176 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7177 @cindex @code{::}, context for variables/functions
7180 @var{file}::@var{variable}
7181 @var{function}::@var{variable}
7185 Here @var{file} or @var{function} is the name of the context for the
7186 static @var{variable}. In the case of file names, you can use quotes to
7187 make sure @value{GDBN} parses the file name as a single word---for example,
7188 to print a global value of @code{x} defined in @file{f2.c}:
7191 (@value{GDBP}) p 'f2.c'::x
7194 @cindex C@t{++} scope resolution
7195 This use of @samp{::} is very rarely in conflict with the very similar
7196 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7197 scope resolution operator in @value{GDBN} expressions.
7198 @c FIXME: Um, so what happens in one of those rare cases where it's in
7201 @cindex wrong values
7202 @cindex variable values, wrong
7203 @cindex function entry/exit, wrong values of variables
7204 @cindex optimized code, wrong values of variables
7206 @emph{Warning:} Occasionally, a local variable may appear to have the
7207 wrong value at certain points in a function---just after entry to a new
7208 scope, and just before exit.
7210 You may see this problem when you are stepping by machine instructions.
7211 This is because, on most machines, it takes more than one instruction to
7212 set up a stack frame (including local variable definitions); if you are
7213 stepping by machine instructions, variables may appear to have the wrong
7214 values until the stack frame is completely built. On exit, it usually
7215 also takes more than one machine instruction to destroy a stack frame;
7216 after you begin stepping through that group of instructions, local
7217 variable definitions may be gone.
7219 This may also happen when the compiler does significant optimizations.
7220 To be sure of always seeing accurate values, turn off all optimization
7223 @cindex ``No symbol "foo" in current context''
7224 Another possible effect of compiler optimizations is to optimize
7225 unused variables out of existence, or assign variables to registers (as
7226 opposed to memory addresses). Depending on the support for such cases
7227 offered by the debug info format used by the compiler, @value{GDBN}
7228 might not be able to display values for such local variables. If that
7229 happens, @value{GDBN} will print a message like this:
7232 No symbol "foo" in current context.
7235 To solve such problems, either recompile without optimizations, or use a
7236 different debug info format, if the compiler supports several such
7237 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7238 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7239 produces debug info in a format that is superior to formats such as
7240 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7241 an effective form for debug info. @xref{Debugging Options,,Options
7242 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7243 Compiler Collection (GCC)}.
7244 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7245 that are best suited to C@t{++} programs.
7247 If you ask to print an object whose contents are unknown to
7248 @value{GDBN}, e.g., because its data type is not completely specified
7249 by the debug information, @value{GDBN} will say @samp{<incomplete
7250 type>}. @xref{Symbols, incomplete type}, for more about this.
7252 Strings are identified as arrays of @code{char} values without specified
7253 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7254 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7255 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7256 defines literal string type @code{"char"} as @code{char} without a sign.
7261 signed char var1[] = "A";
7264 You get during debugging
7269 $2 = @{65 'A', 0 '\0'@}
7273 @section Artificial Arrays
7275 @cindex artificial array
7277 @kindex @@@r{, referencing memory as an array}
7278 It is often useful to print out several successive objects of the
7279 same type in memory; a section of an array, or an array of
7280 dynamically determined size for which only a pointer exists in the
7283 You can do this by referring to a contiguous span of memory as an
7284 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7285 operand of @samp{@@} should be the first element of the desired array
7286 and be an individual object. The right operand should be the desired length
7287 of the array. The result is an array value whose elements are all of
7288 the type of the left argument. The first element is actually the left
7289 argument; the second element comes from bytes of memory immediately
7290 following those that hold the first element, and so on. Here is an
7291 example. If a program says
7294 int *array = (int *) malloc (len * sizeof (int));
7298 you can print the contents of @code{array} with
7304 The left operand of @samp{@@} must reside in memory. Array values made
7305 with @samp{@@} in this way behave just like other arrays in terms of
7306 subscripting, and are coerced to pointers when used in expressions.
7307 Artificial arrays most often appear in expressions via the value history
7308 (@pxref{Value History, ,Value History}), after printing one out.
7310 Another way to create an artificial array is to use a cast.
7311 This re-interprets a value as if it were an array.
7312 The value need not be in memory:
7314 (@value{GDBP}) p/x (short[2])0x12345678
7315 $1 = @{0x1234, 0x5678@}
7318 As a convenience, if you leave the array length out (as in
7319 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7320 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7322 (@value{GDBP}) p/x (short[])0x12345678
7323 $2 = @{0x1234, 0x5678@}
7326 Sometimes the artificial array mechanism is not quite enough; in
7327 moderately complex data structures, the elements of interest may not
7328 actually be adjacent---for example, if you are interested in the values
7329 of pointers in an array. One useful work-around in this situation is
7330 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7331 Variables}) as a counter in an expression that prints the first
7332 interesting value, and then repeat that expression via @key{RET}. For
7333 instance, suppose you have an array @code{dtab} of pointers to
7334 structures, and you are interested in the values of a field @code{fv}
7335 in each structure. Here is an example of what you might type:
7345 @node Output Formats
7346 @section Output Formats
7348 @cindex formatted output
7349 @cindex output formats
7350 By default, @value{GDBN} prints a value according to its data type. Sometimes
7351 this is not what you want. For example, you might want to print a number
7352 in hex, or a pointer in decimal. Or you might want to view data in memory
7353 at a certain address as a character string or as an instruction. To do
7354 these things, specify an @dfn{output format} when you print a value.
7356 The simplest use of output formats is to say how to print a value
7357 already computed. This is done by starting the arguments of the
7358 @code{print} command with a slash and a format letter. The format
7359 letters supported are:
7363 Regard the bits of the value as an integer, and print the integer in
7367 Print as integer in signed decimal.
7370 Print as integer in unsigned decimal.
7373 Print as integer in octal.
7376 Print as integer in binary. The letter @samp{t} stands for ``two''.
7377 @footnote{@samp{b} cannot be used because these format letters are also
7378 used with the @code{x} command, where @samp{b} stands for ``byte'';
7379 see @ref{Memory,,Examining Memory}.}
7382 @cindex unknown address, locating
7383 @cindex locate address
7384 Print as an address, both absolute in hexadecimal and as an offset from
7385 the nearest preceding symbol. You can use this format used to discover
7386 where (in what function) an unknown address is located:
7389 (@value{GDBP}) p/a 0x54320
7390 $3 = 0x54320 <_initialize_vx+396>
7394 The command @code{info symbol 0x54320} yields similar results.
7395 @xref{Symbols, info symbol}.
7398 Regard as an integer and print it as a character constant. This
7399 prints both the numerical value and its character representation. The
7400 character representation is replaced with the octal escape @samp{\nnn}
7401 for characters outside the 7-bit @sc{ascii} range.
7403 Without this format, @value{GDBN} displays @code{char},
7404 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7405 constants. Single-byte members of vectors are displayed as integer
7409 Regard the bits of the value as a floating point number and print
7410 using typical floating point syntax.
7413 @cindex printing strings
7414 @cindex printing byte arrays
7415 Regard as a string, if possible. With this format, pointers to single-byte
7416 data are displayed as null-terminated strings and arrays of single-byte data
7417 are displayed as fixed-length strings. Other values are displayed in their
7420 Without this format, @value{GDBN} displays pointers to and arrays of
7421 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7422 strings. Single-byte members of a vector are displayed as an integer
7426 @cindex raw printing
7427 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7428 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7429 Printing}). This typically results in a higher-level display of the
7430 value's contents. The @samp{r} format bypasses any Python
7431 pretty-printer which might exist.
7434 For example, to print the program counter in hex (@pxref{Registers}), type
7441 Note that no space is required before the slash; this is because command
7442 names in @value{GDBN} cannot contain a slash.
7444 To reprint the last value in the value history with a different format,
7445 you can use the @code{print} command with just a format and no
7446 expression. For example, @samp{p/x} reprints the last value in hex.
7449 @section Examining Memory
7451 You can use the command @code{x} (for ``examine'') to examine memory in
7452 any of several formats, independently of your program's data types.
7454 @cindex examining memory
7456 @kindex x @r{(examine memory)}
7457 @item x/@var{nfu} @var{addr}
7460 Use the @code{x} command to examine memory.
7463 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7464 much memory to display and how to format it; @var{addr} is an
7465 expression giving the address where you want to start displaying memory.
7466 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7467 Several commands set convenient defaults for @var{addr}.
7470 @item @var{n}, the repeat count
7471 The repeat count is a decimal integer; the default is 1. It specifies
7472 how much memory (counting by units @var{u}) to display.
7473 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7476 @item @var{f}, the display format
7477 The display format is one of the formats used by @code{print}
7478 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7479 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7480 The default is @samp{x} (hexadecimal) initially. The default changes
7481 each time you use either @code{x} or @code{print}.
7483 @item @var{u}, the unit size
7484 The unit size is any of
7490 Halfwords (two bytes).
7492 Words (four bytes). This is the initial default.
7494 Giant words (eight bytes).
7497 Each time you specify a unit size with @code{x}, that size becomes the
7498 default unit the next time you use @code{x}. For the @samp{i} format,
7499 the unit size is ignored and is normally not written. For the @samp{s} format,
7500 the unit size defaults to @samp{b}, unless it is explicitly given.
7501 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7502 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7503 Note that the results depend on the programming language of the
7504 current compilation unit. If the language is C, the @samp{s}
7505 modifier will use the UTF-16 encoding while @samp{w} will use
7506 UTF-32. The encoding is set by the programming language and cannot
7509 @item @var{addr}, starting display address
7510 @var{addr} is the address where you want @value{GDBN} to begin displaying
7511 memory. The expression need not have a pointer value (though it may);
7512 it is always interpreted as an integer address of a byte of memory.
7513 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7514 @var{addr} is usually just after the last address examined---but several
7515 other commands also set the default address: @code{info breakpoints} (to
7516 the address of the last breakpoint listed), @code{info line} (to the
7517 starting address of a line), and @code{print} (if you use it to display
7518 a value from memory).
7521 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7522 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7523 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7524 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7525 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7527 Since the letters indicating unit sizes are all distinct from the
7528 letters specifying output formats, you do not have to remember whether
7529 unit size or format comes first; either order works. The output
7530 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7531 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7533 Even though the unit size @var{u} is ignored for the formats @samp{s}
7534 and @samp{i}, you might still want to use a count @var{n}; for example,
7535 @samp{3i} specifies that you want to see three machine instructions,
7536 including any operands. For convenience, especially when used with
7537 the @code{display} command, the @samp{i} format also prints branch delay
7538 slot instructions, if any, beyond the count specified, which immediately
7539 follow the last instruction that is within the count. The command
7540 @code{disassemble} gives an alternative way of inspecting machine
7541 instructions; see @ref{Machine Code,,Source and Machine Code}.
7543 All the defaults for the arguments to @code{x} are designed to make it
7544 easy to continue scanning memory with minimal specifications each time
7545 you use @code{x}. For example, after you have inspected three machine
7546 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7547 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7548 the repeat count @var{n} is used again; the other arguments default as
7549 for successive uses of @code{x}.
7551 When examining machine instructions, the instruction at current program
7552 counter is shown with a @code{=>} marker. For example:
7555 (@value{GDBP}) x/5i $pc-6
7556 0x804837f <main+11>: mov %esp,%ebp
7557 0x8048381 <main+13>: push %ecx
7558 0x8048382 <main+14>: sub $0x4,%esp
7559 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7560 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7563 @cindex @code{$_}, @code{$__}, and value history
7564 The addresses and contents printed by the @code{x} command are not saved
7565 in the value history because there is often too much of them and they
7566 would get in the way. Instead, @value{GDBN} makes these values available for
7567 subsequent use in expressions as values of the convenience variables
7568 @code{$_} and @code{$__}. After an @code{x} command, the last address
7569 examined is available for use in expressions in the convenience variable
7570 @code{$_}. The contents of that address, as examined, are available in
7571 the convenience variable @code{$__}.
7573 If the @code{x} command has a repeat count, the address and contents saved
7574 are from the last memory unit printed; this is not the same as the last
7575 address printed if several units were printed on the last line of output.
7577 @cindex remote memory comparison
7578 @cindex verify remote memory image
7579 When you are debugging a program running on a remote target machine
7580 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7581 remote machine's memory against the executable file you downloaded to
7582 the target. The @code{compare-sections} command is provided for such
7586 @kindex compare-sections
7587 @item compare-sections @r{[}@var{section-name}@r{]}
7588 Compare the data of a loadable section @var{section-name} in the
7589 executable file of the program being debugged with the same section in
7590 the remote machine's memory, and report any mismatches. With no
7591 arguments, compares all loadable sections. This command's
7592 availability depends on the target's support for the @code{"qCRC"}
7597 @section Automatic Display
7598 @cindex automatic display
7599 @cindex display of expressions
7601 If you find that you want to print the value of an expression frequently
7602 (to see how it changes), you might want to add it to the @dfn{automatic
7603 display list} so that @value{GDBN} prints its value each time your program stops.
7604 Each expression added to the list is given a number to identify it;
7605 to remove an expression from the list, you specify that number.
7606 The automatic display looks like this:
7610 3: bar[5] = (struct hack *) 0x3804
7614 This display shows item numbers, expressions and their current values. As with
7615 displays you request manually using @code{x} or @code{print}, you can
7616 specify the output format you prefer; in fact, @code{display} decides
7617 whether to use @code{print} or @code{x} depending your format
7618 specification---it uses @code{x} if you specify either the @samp{i}
7619 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7623 @item display @var{expr}
7624 Add the expression @var{expr} to the list of expressions to display
7625 each time your program stops. @xref{Expressions, ,Expressions}.
7627 @code{display} does not repeat if you press @key{RET} again after using it.
7629 @item display/@var{fmt} @var{expr}
7630 For @var{fmt} specifying only a display format and not a size or
7631 count, add the expression @var{expr} to the auto-display list but
7632 arrange to display it each time in the specified format @var{fmt}.
7633 @xref{Output Formats,,Output Formats}.
7635 @item display/@var{fmt} @var{addr}
7636 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7637 number of units, add the expression @var{addr} as a memory address to
7638 be examined each time your program stops. Examining means in effect
7639 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7642 For example, @samp{display/i $pc} can be helpful, to see the machine
7643 instruction about to be executed each time execution stops (@samp{$pc}
7644 is a common name for the program counter; @pxref{Registers, ,Registers}).
7647 @kindex delete display
7649 @item undisplay @var{dnums}@dots{}
7650 @itemx delete display @var{dnums}@dots{}
7651 Remove items from the list of expressions to display. Specify the
7652 numbers of the displays that you want affected with the command
7653 argument @var{dnums}. It can be a single display number, one of the
7654 numbers shown in the first field of the @samp{info display} display;
7655 or it could be a range of display numbers, as in @code{2-4}.
7657 @code{undisplay} does not repeat if you press @key{RET} after using it.
7658 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7660 @kindex disable display
7661 @item disable display @var{dnums}@dots{}
7662 Disable the display of item numbers @var{dnums}. A disabled display
7663 item is not printed automatically, but is not forgotten. It may be
7664 enabled again later. Specify the numbers of the displays that you
7665 want affected with the command argument @var{dnums}. It can be a
7666 single display number, one of the numbers shown in the first field of
7667 the @samp{info display} display; or it could be a range of display
7668 numbers, as in @code{2-4}.
7670 @kindex enable display
7671 @item enable display @var{dnums}@dots{}
7672 Enable display of item numbers @var{dnums}. It becomes effective once
7673 again in auto display of its expression, until you specify otherwise.
7674 Specify the numbers of the displays that you want affected with the
7675 command argument @var{dnums}. It can be a single display number, one
7676 of the numbers shown in the first field of the @samp{info display}
7677 display; or it could be a range of display numbers, as in @code{2-4}.
7680 Display the current values of the expressions on the list, just as is
7681 done when your program stops.
7683 @kindex info display
7685 Print the list of expressions previously set up to display
7686 automatically, each one with its item number, but without showing the
7687 values. This includes disabled expressions, which are marked as such.
7688 It also includes expressions which would not be displayed right now
7689 because they refer to automatic variables not currently available.
7692 @cindex display disabled out of scope
7693 If a display expression refers to local variables, then it does not make
7694 sense outside the lexical context for which it was set up. Such an
7695 expression is disabled when execution enters a context where one of its
7696 variables is not defined. For example, if you give the command
7697 @code{display last_char} while inside a function with an argument
7698 @code{last_char}, @value{GDBN} displays this argument while your program
7699 continues to stop inside that function. When it stops elsewhere---where
7700 there is no variable @code{last_char}---the display is disabled
7701 automatically. The next time your program stops where @code{last_char}
7702 is meaningful, you can enable the display expression once again.
7704 @node Print Settings
7705 @section Print Settings
7707 @cindex format options
7708 @cindex print settings
7709 @value{GDBN} provides the following ways to control how arrays, structures,
7710 and symbols are printed.
7713 These settings are useful for debugging programs in any language:
7717 @item set print address
7718 @itemx set print address on
7719 @cindex print/don't print memory addresses
7720 @value{GDBN} prints memory addresses showing the location of stack
7721 traces, structure values, pointer values, breakpoints, and so forth,
7722 even when it also displays the contents of those addresses. The default
7723 is @code{on}. For example, this is what a stack frame display looks like with
7724 @code{set print address on}:
7729 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7731 530 if (lquote != def_lquote)
7735 @item set print address off
7736 Do not print addresses when displaying their contents. For example,
7737 this is the same stack frame displayed with @code{set print address off}:
7741 (@value{GDBP}) set print addr off
7743 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7744 530 if (lquote != def_lquote)
7748 You can use @samp{set print address off} to eliminate all machine
7749 dependent displays from the @value{GDBN} interface. For example, with
7750 @code{print address off}, you should get the same text for backtraces on
7751 all machines---whether or not they involve pointer arguments.
7754 @item show print address
7755 Show whether or not addresses are to be printed.
7758 When @value{GDBN} prints a symbolic address, it normally prints the
7759 closest earlier symbol plus an offset. If that symbol does not uniquely
7760 identify the address (for example, it is a name whose scope is a single
7761 source file), you may need to clarify. One way to do this is with
7762 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7763 you can set @value{GDBN} to print the source file and line number when
7764 it prints a symbolic address:
7767 @item set print symbol-filename on
7768 @cindex source file and line of a symbol
7769 @cindex symbol, source file and line
7770 Tell @value{GDBN} to print the source file name and line number of a
7771 symbol in the symbolic form of an address.
7773 @item set print symbol-filename off
7774 Do not print source file name and line number of a symbol. This is the
7777 @item show print symbol-filename
7778 Show whether or not @value{GDBN} will print the source file name and
7779 line number of a symbol in the symbolic form of an address.
7782 Another situation where it is helpful to show symbol filenames and line
7783 numbers is when disassembling code; @value{GDBN} shows you the line
7784 number and source file that corresponds to each instruction.
7786 Also, you may wish to see the symbolic form only if the address being
7787 printed is reasonably close to the closest earlier symbol:
7790 @item set print max-symbolic-offset @var{max-offset}
7791 @cindex maximum value for offset of closest symbol
7792 Tell @value{GDBN} to only display the symbolic form of an address if the
7793 offset between the closest earlier symbol and the address is less than
7794 @var{max-offset}. The default is 0, which tells @value{GDBN}
7795 to always print the symbolic form of an address if any symbol precedes it.
7797 @item show print max-symbolic-offset
7798 Ask how large the maximum offset is that @value{GDBN} prints in a
7802 @cindex wild pointer, interpreting
7803 @cindex pointer, finding referent
7804 If you have a pointer and you are not sure where it points, try
7805 @samp{set print symbol-filename on}. Then you can determine the name
7806 and source file location of the variable where it points, using
7807 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7808 For example, here @value{GDBN} shows that a variable @code{ptt} points
7809 at another variable @code{t}, defined in @file{hi2.c}:
7812 (@value{GDBP}) set print symbol-filename on
7813 (@value{GDBP}) p/a ptt
7814 $4 = 0xe008 <t in hi2.c>
7818 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7819 does not show the symbol name and filename of the referent, even with
7820 the appropriate @code{set print} options turned on.
7823 Other settings control how different kinds of objects are printed:
7826 @item set print array
7827 @itemx set print array on
7828 @cindex pretty print arrays
7829 Pretty print arrays. This format is more convenient to read,
7830 but uses more space. The default is off.
7832 @item set print array off
7833 Return to compressed format for arrays.
7835 @item show print array
7836 Show whether compressed or pretty format is selected for displaying
7839 @cindex print array indexes
7840 @item set print array-indexes
7841 @itemx set print array-indexes on
7842 Print the index of each element when displaying arrays. May be more
7843 convenient to locate a given element in the array or quickly find the
7844 index of a given element in that printed array. The default is off.
7846 @item set print array-indexes off
7847 Stop printing element indexes when displaying arrays.
7849 @item show print array-indexes
7850 Show whether the index of each element is printed when displaying
7853 @item set print elements @var{number-of-elements}
7854 @cindex number of array elements to print
7855 @cindex limit on number of printed array elements
7856 Set a limit on how many elements of an array @value{GDBN} will print.
7857 If @value{GDBN} is printing a large array, it stops printing after it has
7858 printed the number of elements set by the @code{set print elements} command.
7859 This limit also applies to the display of strings.
7860 When @value{GDBN} starts, this limit is set to 200.
7861 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7863 @item show print elements
7864 Display the number of elements of a large array that @value{GDBN} will print.
7865 If the number is 0, then the printing is unlimited.
7867 @item set print frame-arguments @var{value}
7868 @kindex set print frame-arguments
7869 @cindex printing frame argument values
7870 @cindex print all frame argument values
7871 @cindex print frame argument values for scalars only
7872 @cindex do not print frame argument values
7873 This command allows to control how the values of arguments are printed
7874 when the debugger prints a frame (@pxref{Frames}). The possible
7879 The values of all arguments are printed.
7882 Print the value of an argument only if it is a scalar. The value of more
7883 complex arguments such as arrays, structures, unions, etc, is replaced
7884 by @code{@dots{}}. This is the default. Here is an example where
7885 only scalar arguments are shown:
7888 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7893 None of the argument values are printed. Instead, the value of each argument
7894 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7897 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7902 By default, only scalar arguments are printed. This command can be used
7903 to configure the debugger to print the value of all arguments, regardless
7904 of their type. However, it is often advantageous to not print the value
7905 of more complex parameters. For instance, it reduces the amount of
7906 information printed in each frame, making the backtrace more readable.
7907 Also, it improves performance when displaying Ada frames, because
7908 the computation of large arguments can sometimes be CPU-intensive,
7909 especially in large applications. Setting @code{print frame-arguments}
7910 to @code{scalars} (the default) or @code{none} avoids this computation,
7911 thus speeding up the display of each Ada frame.
7913 @item show print frame-arguments
7914 Show how the value of arguments should be displayed when printing a frame.
7916 @item set print repeats
7917 @cindex repeated array elements
7918 Set the threshold for suppressing display of repeated array
7919 elements. When the number of consecutive identical elements of an
7920 array exceeds the threshold, @value{GDBN} prints the string
7921 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7922 identical repetitions, instead of displaying the identical elements
7923 themselves. Setting the threshold to zero will cause all elements to
7924 be individually printed. The default threshold is 10.
7926 @item show print repeats
7927 Display the current threshold for printing repeated identical
7930 @item set print null-stop
7931 @cindex @sc{null} elements in arrays
7932 Cause @value{GDBN} to stop printing the characters of an array when the first
7933 @sc{null} is encountered. This is useful when large arrays actually
7934 contain only short strings.
7937 @item show print null-stop
7938 Show whether @value{GDBN} stops printing an array on the first
7939 @sc{null} character.
7941 @item set print pretty on
7942 @cindex print structures in indented form
7943 @cindex indentation in structure display
7944 Cause @value{GDBN} to print structures in an indented format with one member
7945 per line, like this:
7960 @item set print pretty off
7961 Cause @value{GDBN} to print structures in a compact format, like this:
7965 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7966 meat = 0x54 "Pork"@}
7971 This is the default format.
7973 @item show print pretty
7974 Show which format @value{GDBN} is using to print structures.
7976 @item set print sevenbit-strings on
7977 @cindex eight-bit characters in strings
7978 @cindex octal escapes in strings
7979 Print using only seven-bit characters; if this option is set,
7980 @value{GDBN} displays any eight-bit characters (in strings or
7981 character values) using the notation @code{\}@var{nnn}. This setting is
7982 best if you are working in English (@sc{ascii}) and you use the
7983 high-order bit of characters as a marker or ``meta'' bit.
7985 @item set print sevenbit-strings off
7986 Print full eight-bit characters. This allows the use of more
7987 international character sets, and is the default.
7989 @item show print sevenbit-strings
7990 Show whether or not @value{GDBN} is printing only seven-bit characters.
7992 @item set print union on
7993 @cindex unions in structures, printing
7994 Tell @value{GDBN} to print unions which are contained in structures
7995 and other unions. This is the default setting.
7997 @item set print union off
7998 Tell @value{GDBN} not to print unions which are contained in
7999 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8002 @item show print union
8003 Ask @value{GDBN} whether or not it will print unions which are contained in
8004 structures and other unions.
8006 For example, given the declarations
8009 typedef enum @{Tree, Bug@} Species;
8010 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8011 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8022 struct thing foo = @{Tree, @{Acorn@}@};
8026 with @code{set print union on} in effect @samp{p foo} would print
8029 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8033 and with @code{set print union off} in effect it would print
8036 $1 = @{it = Tree, form = @{...@}@}
8040 @code{set print union} affects programs written in C-like languages
8046 These settings are of interest when debugging C@t{++} programs:
8049 @cindex demangling C@t{++} names
8050 @item set print demangle
8051 @itemx set print demangle on
8052 Print C@t{++} names in their source form rather than in the encoded
8053 (``mangled'') form passed to the assembler and linker for type-safe
8054 linkage. The default is on.
8056 @item show print demangle
8057 Show whether C@t{++} names are printed in mangled or demangled form.
8059 @item set print asm-demangle
8060 @itemx set print asm-demangle on
8061 Print C@t{++} names in their source form rather than their mangled form, even
8062 in assembler code printouts such as instruction disassemblies.
8065 @item show print asm-demangle
8066 Show whether C@t{++} names in assembly listings are printed in mangled
8069 @cindex C@t{++} symbol decoding style
8070 @cindex symbol decoding style, C@t{++}
8071 @kindex set demangle-style
8072 @item set demangle-style @var{style}
8073 Choose among several encoding schemes used by different compilers to
8074 represent C@t{++} names. The choices for @var{style} are currently:
8078 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8081 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8082 This is the default.
8085 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8088 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8091 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8092 @strong{Warning:} this setting alone is not sufficient to allow
8093 debugging @code{cfront}-generated executables. @value{GDBN} would
8094 require further enhancement to permit that.
8097 If you omit @var{style}, you will see a list of possible formats.
8099 @item show demangle-style
8100 Display the encoding style currently in use for decoding C@t{++} symbols.
8102 @item set print object
8103 @itemx set print object on
8104 @cindex derived type of an object, printing
8105 @cindex display derived types
8106 When displaying a pointer to an object, identify the @emph{actual}
8107 (derived) type of the object rather than the @emph{declared} type, using
8108 the virtual function table.
8110 @item set print object off
8111 Display only the declared type of objects, without reference to the
8112 virtual function table. This is the default setting.
8114 @item show print object
8115 Show whether actual, or declared, object types are displayed.
8117 @item set print static-members
8118 @itemx set print static-members on
8119 @cindex static members of C@t{++} objects
8120 Print static members when displaying a C@t{++} object. The default is on.
8122 @item set print static-members off
8123 Do not print static members when displaying a C@t{++} object.
8125 @item show print static-members
8126 Show whether C@t{++} static members are printed or not.
8128 @item set print pascal_static-members
8129 @itemx set print pascal_static-members on
8130 @cindex static members of Pascal objects
8131 @cindex Pascal objects, static members display
8132 Print static members when displaying a Pascal object. The default is on.
8134 @item set print pascal_static-members off
8135 Do not print static members when displaying a Pascal object.
8137 @item show print pascal_static-members
8138 Show whether Pascal static members are printed or not.
8140 @c These don't work with HP ANSI C++ yet.
8141 @item set print vtbl
8142 @itemx set print vtbl on
8143 @cindex pretty print C@t{++} virtual function tables
8144 @cindex virtual functions (C@t{++}) display
8145 @cindex VTBL display
8146 Pretty print C@t{++} virtual function tables. The default is off.
8147 (The @code{vtbl} commands do not work on programs compiled with the HP
8148 ANSI C@t{++} compiler (@code{aCC}).)
8150 @item set print vtbl off
8151 Do not pretty print C@t{++} virtual function tables.
8153 @item show print vtbl
8154 Show whether C@t{++} virtual function tables are pretty printed, or not.
8157 @node Pretty Printing
8158 @section Pretty Printing
8160 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8161 Python code. It greatly simplifies the display of complex objects. This
8162 mechanism works for both MI and the CLI.
8165 * Pretty-Printer Introduction:: Introduction to pretty-printers
8166 * Pretty-Printer Example:: An example pretty-printer
8167 * Pretty-Printer Commands:: Pretty-printer commands
8170 @node Pretty-Printer Introduction
8171 @subsection Pretty-Printer Introduction
8173 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8174 registered for the value. If there is then @value{GDBN} invokes the
8175 pretty-printer to print the value. Otherwise the value is printed normally.
8177 Pretty-printers are normally named. This makes them easy to manage.
8178 The @samp{info pretty-printer} command will list all the installed
8179 pretty-printers with their names.
8180 If a pretty-printer can handle multiple data types, then its
8181 @dfn{subprinters} are the printers for the individual data types.
8182 Each such subprinter has its own name.
8183 The format of the name is @var{printer-name};@var{subprinter-name}.
8185 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8186 Typically they are automatically loaded and registered when the corresponding
8187 debug information is loaded, thus making them available without having to
8188 do anything special.
8190 There are three places where a pretty-printer can be registered.
8194 Pretty-printers registered globally are available when debugging
8198 Pretty-printers registered with a program space are available only
8199 when debugging that program.
8200 @xref{Progspaces In Python}, for more details on program spaces in Python.
8203 Pretty-printers registered with an objfile are loaded and unloaded
8204 with the corresponding objfile (e.g., shared library).
8205 @xref{Objfiles In Python}, for more details on objfiles in Python.
8208 @xref{Selecting Pretty-Printers}, for further information on how
8209 pretty-printers are selected,
8211 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8214 @node Pretty-Printer Example
8215 @subsection Pretty-Printer Example
8217 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8220 (@value{GDBP}) print s
8222 static npos = 4294967295,
8224 <std::allocator<char>> = @{
8225 <__gnu_cxx::new_allocator<char>> = @{
8226 <No data fields>@}, <No data fields>
8228 members of std::basic_string<char, std::char_traits<char>,
8229 std::allocator<char> >::_Alloc_hider:
8230 _M_p = 0x804a014 "abcd"
8235 With a pretty-printer for @code{std::string} only the contents are printed:
8238 (@value{GDBP}) print s
8242 @node Pretty-Printer Commands
8243 @subsection Pretty-Printer Commands
8244 @cindex pretty-printer commands
8247 @kindex info pretty-printer
8248 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8249 Print the list of installed pretty-printers.
8250 This includes disabled pretty-printers, which are marked as such.
8252 @var{object-regexp} is a regular expression matching the objects
8253 whose pretty-printers to list.
8254 Objects can be @code{global}, the program space's file
8255 (@pxref{Progspaces In Python}),
8256 and the object files within that program space (@pxref{Objfiles In Python}).
8257 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8258 looks up a printer from these three objects.
8260 @var{name-regexp} is a regular expression matching the name of the printers
8263 @kindex disable pretty-printer
8264 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8265 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8266 A disabled pretty-printer is not forgotten, it may be enabled again later.
8268 @kindex enable pretty-printer
8269 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8270 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8275 Suppose we have three pretty-printers installed: one from library1.so
8276 named @code{foo} that prints objects of type @code{foo}, and
8277 another from library2.so named @code{bar} that prints two types of objects,
8278 @code{bar1} and @code{bar2}.
8281 (gdb) info pretty-printer
8288 (gdb) info pretty-printer library2
8293 (gdb) disable pretty-printer library1
8295 2 of 3 printers enabled
8296 (gdb) info pretty-printer
8303 (gdb) disable pretty-printer library2 bar:bar1
8305 1 of 3 printers enabled
8306 (gdb) info pretty-printer library2
8313 (gdb) disable pretty-printer library2 bar
8315 0 of 3 printers enabled
8316 (gdb) info pretty-printer library2
8325 Note that for @code{bar} the entire printer can be disabled,
8326 as can each individual subprinter.
8329 @section Value History
8331 @cindex value history
8332 @cindex history of values printed by @value{GDBN}
8333 Values printed by the @code{print} command are saved in the @value{GDBN}
8334 @dfn{value history}. This allows you to refer to them in other expressions.
8335 Values are kept until the symbol table is re-read or discarded
8336 (for example with the @code{file} or @code{symbol-file} commands).
8337 When the symbol table changes, the value history is discarded,
8338 since the values may contain pointers back to the types defined in the
8343 @cindex history number
8344 The values printed are given @dfn{history numbers} by which you can
8345 refer to them. These are successive integers starting with one.
8346 @code{print} shows you the history number assigned to a value by
8347 printing @samp{$@var{num} = } before the value; here @var{num} is the
8350 To refer to any previous value, use @samp{$} followed by the value's
8351 history number. The way @code{print} labels its output is designed to
8352 remind you of this. Just @code{$} refers to the most recent value in
8353 the history, and @code{$$} refers to the value before that.
8354 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8355 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8356 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8358 For example, suppose you have just printed a pointer to a structure and
8359 want to see the contents of the structure. It suffices to type
8365 If you have a chain of structures where the component @code{next} points
8366 to the next one, you can print the contents of the next one with this:
8373 You can print successive links in the chain by repeating this
8374 command---which you can do by just typing @key{RET}.
8376 Note that the history records values, not expressions. If the value of
8377 @code{x} is 4 and you type these commands:
8385 then the value recorded in the value history by the @code{print} command
8386 remains 4 even though the value of @code{x} has changed.
8391 Print the last ten values in the value history, with their item numbers.
8392 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8393 values} does not change the history.
8395 @item show values @var{n}
8396 Print ten history values centered on history item number @var{n}.
8399 Print ten history values just after the values last printed. If no more
8400 values are available, @code{show values +} produces no display.
8403 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8404 same effect as @samp{show values +}.
8406 @node Convenience Vars
8407 @section Convenience Variables
8409 @cindex convenience variables
8410 @cindex user-defined variables
8411 @value{GDBN} provides @dfn{convenience variables} that you can use within
8412 @value{GDBN} to hold on to a value and refer to it later. These variables
8413 exist entirely within @value{GDBN}; they are not part of your program, and
8414 setting a convenience variable has no direct effect on further execution
8415 of your program. That is why you can use them freely.
8417 Convenience variables are prefixed with @samp{$}. Any name preceded by
8418 @samp{$} can be used for a convenience variable, unless it is one of
8419 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8420 (Value history references, in contrast, are @emph{numbers} preceded
8421 by @samp{$}. @xref{Value History, ,Value History}.)
8423 You can save a value in a convenience variable with an assignment
8424 expression, just as you would set a variable in your program.
8428 set $foo = *object_ptr
8432 would save in @code{$foo} the value contained in the object pointed to by
8435 Using a convenience variable for the first time creates it, but its
8436 value is @code{void} until you assign a new value. You can alter the
8437 value with another assignment at any time.
8439 Convenience variables have no fixed types. You can assign a convenience
8440 variable any type of value, including structures and arrays, even if
8441 that variable already has a value of a different type. The convenience
8442 variable, when used as an expression, has the type of its current value.
8445 @kindex show convenience
8446 @cindex show all user variables
8447 @item show convenience
8448 Print a list of convenience variables used so far, and their values.
8449 Abbreviated @code{show conv}.
8451 @kindex init-if-undefined
8452 @cindex convenience variables, initializing
8453 @item init-if-undefined $@var{variable} = @var{expression}
8454 Set a convenience variable if it has not already been set. This is useful
8455 for user-defined commands that keep some state. It is similar, in concept,
8456 to using local static variables with initializers in C (except that
8457 convenience variables are global). It can also be used to allow users to
8458 override default values used in a command script.
8460 If the variable is already defined then the expression is not evaluated so
8461 any side-effects do not occur.
8464 One of the ways to use a convenience variable is as a counter to be
8465 incremented or a pointer to be advanced. For example, to print
8466 a field from successive elements of an array of structures:
8470 print bar[$i++]->contents
8474 Repeat that command by typing @key{RET}.
8476 Some convenience variables are created automatically by @value{GDBN} and given
8477 values likely to be useful.
8480 @vindex $_@r{, convenience variable}
8482 The variable @code{$_} is automatically set by the @code{x} command to
8483 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8484 commands which provide a default address for @code{x} to examine also
8485 set @code{$_} to that address; these commands include @code{info line}
8486 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8487 except when set by the @code{x} command, in which case it is a pointer
8488 to the type of @code{$__}.
8490 @vindex $__@r{, convenience variable}
8492 The variable @code{$__} is automatically set by the @code{x} command
8493 to the value found in the last address examined. Its type is chosen
8494 to match the format in which the data was printed.
8497 @vindex $_exitcode@r{, convenience variable}
8498 The variable @code{$_exitcode} is automatically set to the exit code when
8499 the program being debugged terminates.
8502 @vindex $_sdata@r{, inspect, convenience variable}
8503 The variable @code{$_sdata} contains extra collected static tracepoint
8504 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8505 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8506 if extra static tracepoint data has not been collected.
8509 @vindex $_siginfo@r{, convenience variable}
8510 The variable @code{$_siginfo} contains extra signal information
8511 (@pxref{extra signal information}). Note that @code{$_siginfo}
8512 could be empty, if the application has not yet received any signals.
8513 For example, it will be empty before you execute the @code{run} command.
8516 @vindex $_tlb@r{, convenience variable}
8517 The variable @code{$_tlb} is automatically set when debugging
8518 applications running on MS-Windows in native mode or connected to
8519 gdbserver that supports the @code{qGetTIBAddr} request.
8520 @xref{General Query Packets}.
8521 This variable contains the address of the thread information block.
8525 On HP-UX systems, if you refer to a function or variable name that
8526 begins with a dollar sign, @value{GDBN} searches for a user or system
8527 name first, before it searches for a convenience variable.
8529 @cindex convenience functions
8530 @value{GDBN} also supplies some @dfn{convenience functions}. These
8531 have a syntax similar to convenience variables. A convenience
8532 function can be used in an expression just like an ordinary function;
8533 however, a convenience function is implemented internally to
8538 @kindex help function
8539 @cindex show all convenience functions
8540 Print a list of all convenience functions.
8547 You can refer to machine register contents, in expressions, as variables
8548 with names starting with @samp{$}. The names of registers are different
8549 for each machine; use @code{info registers} to see the names used on
8553 @kindex info registers
8554 @item info registers
8555 Print the names and values of all registers except floating-point
8556 and vector registers (in the selected stack frame).
8558 @kindex info all-registers
8559 @cindex floating point registers
8560 @item info all-registers
8561 Print the names and values of all registers, including floating-point
8562 and vector registers (in the selected stack frame).
8564 @item info registers @var{regname} @dots{}
8565 Print the @dfn{relativized} value of each specified register @var{regname}.
8566 As discussed in detail below, register values are normally relative to
8567 the selected stack frame. @var{regname} may be any register name valid on
8568 the machine you are using, with or without the initial @samp{$}.
8571 @cindex stack pointer register
8572 @cindex program counter register
8573 @cindex process status register
8574 @cindex frame pointer register
8575 @cindex standard registers
8576 @value{GDBN} has four ``standard'' register names that are available (in
8577 expressions) on most machines---whenever they do not conflict with an
8578 architecture's canonical mnemonics for registers. The register names
8579 @code{$pc} and @code{$sp} are used for the program counter register and
8580 the stack pointer. @code{$fp} is used for a register that contains a
8581 pointer to the current stack frame, and @code{$ps} is used for a
8582 register that contains the processor status. For example,
8583 you could print the program counter in hex with
8590 or print the instruction to be executed next with
8597 or add four to the stack pointer@footnote{This is a way of removing
8598 one word from the stack, on machines where stacks grow downward in
8599 memory (most machines, nowadays). This assumes that the innermost
8600 stack frame is selected; setting @code{$sp} is not allowed when other
8601 stack frames are selected. To pop entire frames off the stack,
8602 regardless of machine architecture, use @code{return};
8603 see @ref{Returning, ,Returning from a Function}.} with
8609 Whenever possible, these four standard register names are available on
8610 your machine even though the machine has different canonical mnemonics,
8611 so long as there is no conflict. The @code{info registers} command
8612 shows the canonical names. For example, on the SPARC, @code{info
8613 registers} displays the processor status register as @code{$psr} but you
8614 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8615 is an alias for the @sc{eflags} register.
8617 @value{GDBN} always considers the contents of an ordinary register as an
8618 integer when the register is examined in this way. Some machines have
8619 special registers which can hold nothing but floating point; these
8620 registers are considered to have floating point values. There is no way
8621 to refer to the contents of an ordinary register as floating point value
8622 (although you can @emph{print} it as a floating point value with
8623 @samp{print/f $@var{regname}}).
8625 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8626 means that the data format in which the register contents are saved by
8627 the operating system is not the same one that your program normally
8628 sees. For example, the registers of the 68881 floating point
8629 coprocessor are always saved in ``extended'' (raw) format, but all C
8630 programs expect to work with ``double'' (virtual) format. In such
8631 cases, @value{GDBN} normally works with the virtual format only (the format
8632 that makes sense for your program), but the @code{info registers} command
8633 prints the data in both formats.
8635 @cindex SSE registers (x86)
8636 @cindex MMX registers (x86)
8637 Some machines have special registers whose contents can be interpreted
8638 in several different ways. For example, modern x86-based machines
8639 have SSE and MMX registers that can hold several values packed
8640 together in several different formats. @value{GDBN} refers to such
8641 registers in @code{struct} notation:
8644 (@value{GDBP}) print $xmm1
8646 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8647 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8648 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8649 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8650 v4_int32 = @{0, 20657912, 11, 13@},
8651 v2_int64 = @{88725056443645952, 55834574859@},
8652 uint128 = 0x0000000d0000000b013b36f800000000
8657 To set values of such registers, you need to tell @value{GDBN} which
8658 view of the register you wish to change, as if you were assigning
8659 value to a @code{struct} member:
8662 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8665 Normally, register values are relative to the selected stack frame
8666 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8667 value that the register would contain if all stack frames farther in
8668 were exited and their saved registers restored. In order to see the
8669 true contents of hardware registers, you must select the innermost
8670 frame (with @samp{frame 0}).
8672 However, @value{GDBN} must deduce where registers are saved, from the machine
8673 code generated by your compiler. If some registers are not saved, or if
8674 @value{GDBN} is unable to locate the saved registers, the selected stack
8675 frame makes no difference.
8677 @node Floating Point Hardware
8678 @section Floating Point Hardware
8679 @cindex floating point
8681 Depending on the configuration, @value{GDBN} may be able to give
8682 you more information about the status of the floating point hardware.
8687 Display hardware-dependent information about the floating
8688 point unit. The exact contents and layout vary depending on the
8689 floating point chip. Currently, @samp{info float} is supported on
8690 the ARM and x86 machines.
8694 @section Vector Unit
8697 Depending on the configuration, @value{GDBN} may be able to give you
8698 more information about the status of the vector unit.
8703 Display information about the vector unit. The exact contents and
8704 layout vary depending on the hardware.
8707 @node OS Information
8708 @section Operating System Auxiliary Information
8709 @cindex OS information
8711 @value{GDBN} provides interfaces to useful OS facilities that can help
8712 you debug your program.
8714 @cindex @code{ptrace} system call
8715 @cindex @code{struct user} contents
8716 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8717 machines), it interfaces with the inferior via the @code{ptrace}
8718 system call. The operating system creates a special sata structure,
8719 called @code{struct user}, for this interface. You can use the
8720 command @code{info udot} to display the contents of this data
8726 Display the contents of the @code{struct user} maintained by the OS
8727 kernel for the program being debugged. @value{GDBN} displays the
8728 contents of @code{struct user} as a list of hex numbers, similar to
8729 the @code{examine} command.
8732 @cindex auxiliary vector
8733 @cindex vector, auxiliary
8734 Some operating systems supply an @dfn{auxiliary vector} to programs at
8735 startup. This is akin to the arguments and environment that you
8736 specify for a program, but contains a system-dependent variety of
8737 binary values that tell system libraries important details about the
8738 hardware, operating system, and process. Each value's purpose is
8739 identified by an integer tag; the meanings are well-known but system-specific.
8740 Depending on the configuration and operating system facilities,
8741 @value{GDBN} may be able to show you this information. For remote
8742 targets, this functionality may further depend on the remote stub's
8743 support of the @samp{qXfer:auxv:read} packet, see
8744 @ref{qXfer auxiliary vector read}.
8749 Display the auxiliary vector of the inferior, which can be either a
8750 live process or a core dump file. @value{GDBN} prints each tag value
8751 numerically, and also shows names and text descriptions for recognized
8752 tags. Some values in the vector are numbers, some bit masks, and some
8753 pointers to strings or other data. @value{GDBN} displays each value in the
8754 most appropriate form for a recognized tag, and in hexadecimal for
8755 an unrecognized tag.
8758 On some targets, @value{GDBN} can access operating-system-specific information
8759 and display it to user, without interpretation. For remote targets,
8760 this functionality depends on the remote stub's support of the
8761 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8766 List the types of OS information available for the target. If the
8767 target does not return a list of possible types, this command will
8770 @kindex info os processes
8771 @item info os processes
8772 Display the list of processes on the target. For each process,
8773 @value{GDBN} prints the process identifier, the name of the user, and
8774 the command corresponding to the process.
8777 @node Memory Region Attributes
8778 @section Memory Region Attributes
8779 @cindex memory region attributes
8781 @dfn{Memory region attributes} allow you to describe special handling
8782 required by regions of your target's memory. @value{GDBN} uses
8783 attributes to determine whether to allow certain types of memory
8784 accesses; whether to use specific width accesses; and whether to cache
8785 target memory. By default the description of memory regions is
8786 fetched from the target (if the current target supports this), but the
8787 user can override the fetched regions.
8789 Defined memory regions can be individually enabled and disabled. When a
8790 memory region is disabled, @value{GDBN} uses the default attributes when
8791 accessing memory in that region. Similarly, if no memory regions have
8792 been defined, @value{GDBN} uses the default attributes when accessing
8795 When a memory region is defined, it is given a number to identify it;
8796 to enable, disable, or remove a memory region, you specify that number.
8800 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8801 Define a memory region bounded by @var{lower} and @var{upper} with
8802 attributes @var{attributes}@dots{}, and add it to the list of regions
8803 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8804 case: it is treated as the target's maximum memory address.
8805 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8808 Discard any user changes to the memory regions and use target-supplied
8809 regions, if available, or no regions if the target does not support.
8812 @item delete mem @var{nums}@dots{}
8813 Remove memory regions @var{nums}@dots{} from the list of regions
8814 monitored by @value{GDBN}.
8817 @item disable mem @var{nums}@dots{}
8818 Disable monitoring of memory regions @var{nums}@dots{}.
8819 A disabled memory region is not forgotten.
8820 It may be enabled again later.
8823 @item enable mem @var{nums}@dots{}
8824 Enable monitoring of memory regions @var{nums}@dots{}.
8828 Print a table of all defined memory regions, with the following columns
8832 @item Memory Region Number
8833 @item Enabled or Disabled.
8834 Enabled memory regions are marked with @samp{y}.
8835 Disabled memory regions are marked with @samp{n}.
8838 The address defining the inclusive lower bound of the memory region.
8841 The address defining the exclusive upper bound of the memory region.
8844 The list of attributes set for this memory region.
8849 @subsection Attributes
8851 @subsubsection Memory Access Mode
8852 The access mode attributes set whether @value{GDBN} may make read or
8853 write accesses to a memory region.
8855 While these attributes prevent @value{GDBN} from performing invalid
8856 memory accesses, they do nothing to prevent the target system, I/O DMA,
8857 etc.@: from accessing memory.
8861 Memory is read only.
8863 Memory is write only.
8865 Memory is read/write. This is the default.
8868 @subsubsection Memory Access Size
8869 The access size attribute tells @value{GDBN} to use specific sized
8870 accesses in the memory region. Often memory mapped device registers
8871 require specific sized accesses. If no access size attribute is
8872 specified, @value{GDBN} may use accesses of any size.
8876 Use 8 bit memory accesses.
8878 Use 16 bit memory accesses.
8880 Use 32 bit memory accesses.
8882 Use 64 bit memory accesses.
8885 @c @subsubsection Hardware/Software Breakpoints
8886 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8887 @c will use hardware or software breakpoints for the internal breakpoints
8888 @c used by the step, next, finish, until, etc. commands.
8892 @c Always use hardware breakpoints
8893 @c @item swbreak (default)
8896 @subsubsection Data Cache
8897 The data cache attributes set whether @value{GDBN} will cache target
8898 memory. While this generally improves performance by reducing debug
8899 protocol overhead, it can lead to incorrect results because @value{GDBN}
8900 does not know about volatile variables or memory mapped device
8905 Enable @value{GDBN} to cache target memory.
8907 Disable @value{GDBN} from caching target memory. This is the default.
8910 @subsection Memory Access Checking
8911 @value{GDBN} can be instructed to refuse accesses to memory that is
8912 not explicitly described. This can be useful if accessing such
8913 regions has undesired effects for a specific target, or to provide
8914 better error checking. The following commands control this behaviour.
8917 @kindex set mem inaccessible-by-default
8918 @item set mem inaccessible-by-default [on|off]
8919 If @code{on} is specified, make @value{GDBN} treat memory not
8920 explicitly described by the memory ranges as non-existent and refuse accesses
8921 to such memory. The checks are only performed if there's at least one
8922 memory range defined. If @code{off} is specified, make @value{GDBN}
8923 treat the memory not explicitly described by the memory ranges as RAM.
8924 The default value is @code{on}.
8925 @kindex show mem inaccessible-by-default
8926 @item show mem inaccessible-by-default
8927 Show the current handling of accesses to unknown memory.
8931 @c @subsubsection Memory Write Verification
8932 @c The memory write verification attributes set whether @value{GDBN}
8933 @c will re-reads data after each write to verify the write was successful.
8937 @c @item noverify (default)
8940 @node Dump/Restore Files
8941 @section Copy Between Memory and a File
8942 @cindex dump/restore files
8943 @cindex append data to a file
8944 @cindex dump data to a file
8945 @cindex restore data from a file
8947 You can use the commands @code{dump}, @code{append}, and
8948 @code{restore} to copy data between target memory and a file. The
8949 @code{dump} and @code{append} commands write data to a file, and the
8950 @code{restore} command reads data from a file back into the inferior's
8951 memory. Files may be in binary, Motorola S-record, Intel hex, or
8952 Tektronix Hex format; however, @value{GDBN} can only append to binary
8958 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8959 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8960 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8961 or the value of @var{expr}, to @var{filename} in the given format.
8963 The @var{format} parameter may be any one of:
8970 Motorola S-record format.
8972 Tektronix Hex format.
8975 @value{GDBN} uses the same definitions of these formats as the
8976 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8977 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8981 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8982 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8983 Append the contents of memory from @var{start_addr} to @var{end_addr},
8984 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8985 (@value{GDBN} can only append data to files in raw binary form.)
8988 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8989 Restore the contents of file @var{filename} into memory. The
8990 @code{restore} command can automatically recognize any known @sc{bfd}
8991 file format, except for raw binary. To restore a raw binary file you
8992 must specify the optional keyword @code{binary} after the filename.
8994 If @var{bias} is non-zero, its value will be added to the addresses
8995 contained in the file. Binary files always start at address zero, so
8996 they will be restored at address @var{bias}. Other bfd files have
8997 a built-in location; they will be restored at offset @var{bias}
9000 If @var{start} and/or @var{end} are non-zero, then only data between
9001 file offset @var{start} and file offset @var{end} will be restored.
9002 These offsets are relative to the addresses in the file, before
9003 the @var{bias} argument is applied.
9007 @node Core File Generation
9008 @section How to Produce a Core File from Your Program
9009 @cindex dump core from inferior
9011 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9012 image of a running process and its process status (register values
9013 etc.). Its primary use is post-mortem debugging of a program that
9014 crashed while it ran outside a debugger. A program that crashes
9015 automatically produces a core file, unless this feature is disabled by
9016 the user. @xref{Files}, for information on invoking @value{GDBN} in
9017 the post-mortem debugging mode.
9019 Occasionally, you may wish to produce a core file of the program you
9020 are debugging in order to preserve a snapshot of its state.
9021 @value{GDBN} has a special command for that.
9025 @kindex generate-core-file
9026 @item generate-core-file [@var{file}]
9027 @itemx gcore [@var{file}]
9028 Produce a core dump of the inferior process. The optional argument
9029 @var{file} specifies the file name where to put the core dump. If not
9030 specified, the file name defaults to @file{core.@var{pid}}, where
9031 @var{pid} is the inferior process ID.
9033 Note that this command is implemented only for some systems (as of
9034 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9037 @node Character Sets
9038 @section Character Sets
9039 @cindex character sets
9041 @cindex translating between character sets
9042 @cindex host character set
9043 @cindex target character set
9045 If the program you are debugging uses a different character set to
9046 represent characters and strings than the one @value{GDBN} uses itself,
9047 @value{GDBN} can automatically translate between the character sets for
9048 you. The character set @value{GDBN} uses we call the @dfn{host
9049 character set}; the one the inferior program uses we call the
9050 @dfn{target character set}.
9052 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9053 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9054 remote protocol (@pxref{Remote Debugging}) to debug a program
9055 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9056 then the host character set is Latin-1, and the target character set is
9057 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9058 target-charset EBCDIC-US}, then @value{GDBN} translates between
9059 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9060 character and string literals in expressions.
9062 @value{GDBN} has no way to automatically recognize which character set
9063 the inferior program uses; you must tell it, using the @code{set
9064 target-charset} command, described below.
9066 Here are the commands for controlling @value{GDBN}'s character set
9070 @item set target-charset @var{charset}
9071 @kindex set target-charset
9072 Set the current target character set to @var{charset}. To display the
9073 list of supported target character sets, type
9074 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9076 @item set host-charset @var{charset}
9077 @kindex set host-charset
9078 Set the current host character set to @var{charset}.
9080 By default, @value{GDBN} uses a host character set appropriate to the
9081 system it is running on; you can override that default using the
9082 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9083 automatically determine the appropriate host character set. In this
9084 case, @value{GDBN} uses @samp{UTF-8}.
9086 @value{GDBN} can only use certain character sets as its host character
9087 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9088 @value{GDBN} will list the host character sets it supports.
9090 @item set charset @var{charset}
9092 Set the current host and target character sets to @var{charset}. As
9093 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9094 @value{GDBN} will list the names of the character sets that can be used
9095 for both host and target.
9098 @kindex show charset
9099 Show the names of the current host and target character sets.
9101 @item show host-charset
9102 @kindex show host-charset
9103 Show the name of the current host character set.
9105 @item show target-charset
9106 @kindex show target-charset
9107 Show the name of the current target character set.
9109 @item set target-wide-charset @var{charset}
9110 @kindex set target-wide-charset
9111 Set the current target's wide character set to @var{charset}. This is
9112 the character set used by the target's @code{wchar_t} type. To
9113 display the list of supported wide character sets, type
9114 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9116 @item show target-wide-charset
9117 @kindex show target-wide-charset
9118 Show the name of the current target's wide character set.
9121 Here is an example of @value{GDBN}'s character set support in action.
9122 Assume that the following source code has been placed in the file
9123 @file{charset-test.c}:
9129 = @{72, 101, 108, 108, 111, 44, 32, 119,
9130 111, 114, 108, 100, 33, 10, 0@};
9131 char ibm1047_hello[]
9132 = @{200, 133, 147, 147, 150, 107, 64, 166,
9133 150, 153, 147, 132, 90, 37, 0@};
9137 printf ("Hello, world!\n");
9141 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9142 containing the string @samp{Hello, world!} followed by a newline,
9143 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9145 We compile the program, and invoke the debugger on it:
9148 $ gcc -g charset-test.c -o charset-test
9149 $ gdb -nw charset-test
9150 GNU gdb 2001-12-19-cvs
9151 Copyright 2001 Free Software Foundation, Inc.
9156 We can use the @code{show charset} command to see what character sets
9157 @value{GDBN} is currently using to interpret and display characters and
9161 (@value{GDBP}) show charset
9162 The current host and target character set is `ISO-8859-1'.
9166 For the sake of printing this manual, let's use @sc{ascii} as our
9167 initial character set:
9169 (@value{GDBP}) set charset ASCII
9170 (@value{GDBP}) show charset
9171 The current host and target character set is `ASCII'.
9175 Let's assume that @sc{ascii} is indeed the correct character set for our
9176 host system --- in other words, let's assume that if @value{GDBN} prints
9177 characters using the @sc{ascii} character set, our terminal will display
9178 them properly. Since our current target character set is also
9179 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9182 (@value{GDBP}) print ascii_hello
9183 $1 = 0x401698 "Hello, world!\n"
9184 (@value{GDBP}) print ascii_hello[0]
9189 @value{GDBN} uses the target character set for character and string
9190 literals you use in expressions:
9193 (@value{GDBP}) print '+'
9198 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9201 @value{GDBN} relies on the user to tell it which character set the
9202 target program uses. If we print @code{ibm1047_hello} while our target
9203 character set is still @sc{ascii}, we get jibberish:
9206 (@value{GDBP}) print ibm1047_hello
9207 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9208 (@value{GDBP}) print ibm1047_hello[0]
9213 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9214 @value{GDBN} tells us the character sets it supports:
9217 (@value{GDBP}) set target-charset
9218 ASCII EBCDIC-US IBM1047 ISO-8859-1
9219 (@value{GDBP}) set target-charset
9222 We can select @sc{ibm1047} as our target character set, and examine the
9223 program's strings again. Now the @sc{ascii} string is wrong, but
9224 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9225 target character set, @sc{ibm1047}, to the host character set,
9226 @sc{ascii}, and they display correctly:
9229 (@value{GDBP}) set target-charset IBM1047
9230 (@value{GDBP}) show charset
9231 The current host character set is `ASCII'.
9232 The current target character set is `IBM1047'.
9233 (@value{GDBP}) print ascii_hello
9234 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9235 (@value{GDBP}) print ascii_hello[0]
9237 (@value{GDBP}) print ibm1047_hello
9238 $8 = 0x4016a8 "Hello, world!\n"
9239 (@value{GDBP}) print ibm1047_hello[0]
9244 As above, @value{GDBN} uses the target character set for character and
9245 string literals you use in expressions:
9248 (@value{GDBP}) print '+'
9253 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9256 @node Caching Remote Data
9257 @section Caching Data of Remote Targets
9258 @cindex caching data of remote targets
9260 @value{GDBN} caches data exchanged between the debugger and a
9261 remote target (@pxref{Remote Debugging}). Such caching generally improves
9262 performance, because it reduces the overhead of the remote protocol by
9263 bundling memory reads and writes into large chunks. Unfortunately, simply
9264 caching everything would lead to incorrect results, since @value{GDBN}
9265 does not necessarily know anything about volatile values, memory-mapped I/O
9266 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9267 memory can be changed @emph{while} a gdb command is executing.
9268 Therefore, by default, @value{GDBN} only caches data
9269 known to be on the stack@footnote{In non-stop mode, it is moderately
9270 rare for a running thread to modify the stack of a stopped thread
9271 in a way that would interfere with a backtrace, and caching of
9272 stack reads provides a significant speed up of remote backtraces.}.
9273 Other regions of memory can be explicitly marked as
9274 cacheable; see @pxref{Memory Region Attributes}.
9277 @kindex set remotecache
9278 @item set remotecache on
9279 @itemx set remotecache off
9280 This option no longer does anything; it exists for compatibility
9283 @kindex show remotecache
9284 @item show remotecache
9285 Show the current state of the obsolete remotecache flag.
9287 @kindex set stack-cache
9288 @item set stack-cache on
9289 @itemx set stack-cache off
9290 Enable or disable caching of stack accesses. When @code{ON}, use
9291 caching. By default, this option is @code{ON}.
9293 @kindex show stack-cache
9294 @item show stack-cache
9295 Show the current state of data caching for memory accesses.
9298 @item info dcache @r{[}line@r{]}
9299 Print the information about the data cache performance. The
9300 information displayed includes the dcache width and depth, and for
9301 each cache line, its number, address, and how many times it was
9302 referenced. This command is useful for debugging the data cache
9305 If a line number is specified, the contents of that line will be
9309 @node Searching Memory
9310 @section Search Memory
9311 @cindex searching memory
9313 Memory can be searched for a particular sequence of bytes with the
9314 @code{find} command.
9318 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9319 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9320 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9321 etc. The search begins at address @var{start_addr} and continues for either
9322 @var{len} bytes or through to @var{end_addr} inclusive.
9325 @var{s} and @var{n} are optional parameters.
9326 They may be specified in either order, apart or together.
9329 @item @var{s}, search query size
9330 The size of each search query value.
9336 halfwords (two bytes)
9340 giant words (eight bytes)
9343 All values are interpreted in the current language.
9344 This means, for example, that if the current source language is C/C@t{++}
9345 then searching for the string ``hello'' includes the trailing '\0'.
9347 If the value size is not specified, it is taken from the
9348 value's type in the current language.
9349 This is useful when one wants to specify the search
9350 pattern as a mixture of types.
9351 Note that this means, for example, that in the case of C-like languages
9352 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9353 which is typically four bytes.
9355 @item @var{n}, maximum number of finds
9356 The maximum number of matches to print. The default is to print all finds.
9359 You can use strings as search values. Quote them with double-quotes
9361 The string value is copied into the search pattern byte by byte,
9362 regardless of the endianness of the target and the size specification.
9364 The address of each match found is printed as well as a count of the
9365 number of matches found.
9367 The address of the last value found is stored in convenience variable
9369 A count of the number of matches is stored in @samp{$numfound}.
9371 For example, if stopped at the @code{printf} in this function:
9377 static char hello[] = "hello-hello";
9378 static struct @{ char c; short s; int i; @}
9379 __attribute__ ((packed)) mixed
9380 = @{ 'c', 0x1234, 0x87654321 @};
9381 printf ("%s\n", hello);
9386 you get during debugging:
9389 (gdb) find &hello[0], +sizeof(hello), "hello"
9390 0x804956d <hello.1620+6>
9392 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9393 0x8049567 <hello.1620>
9394 0x804956d <hello.1620+6>
9396 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9397 0x8049567 <hello.1620>
9399 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9400 0x8049560 <mixed.1625>
9402 (gdb) print $numfound
9405 $2 = (void *) 0x8049560
9408 @node Optimized Code
9409 @chapter Debugging Optimized Code
9410 @cindex optimized code, debugging
9411 @cindex debugging optimized code
9413 Almost all compilers support optimization. With optimization
9414 disabled, the compiler generates assembly code that corresponds
9415 directly to your source code, in a simplistic way. As the compiler
9416 applies more powerful optimizations, the generated assembly code
9417 diverges from your original source code. With help from debugging
9418 information generated by the compiler, @value{GDBN} can map from
9419 the running program back to constructs from your original source.
9421 @value{GDBN} is more accurate with optimization disabled. If you
9422 can recompile without optimization, it is easier to follow the
9423 progress of your program during debugging. But, there are many cases
9424 where you may need to debug an optimized version.
9426 When you debug a program compiled with @samp{-g -O}, remember that the
9427 optimizer has rearranged your code; the debugger shows you what is
9428 really there. Do not be too surprised when the execution path does not
9429 exactly match your source file! An extreme example: if you define a
9430 variable, but never use it, @value{GDBN} never sees that
9431 variable---because the compiler optimizes it out of existence.
9433 Some things do not work as well with @samp{-g -O} as with just
9434 @samp{-g}, particularly on machines with instruction scheduling. If in
9435 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9436 please report it to us as a bug (including a test case!).
9437 @xref{Variables}, for more information about debugging optimized code.
9440 * Inline Functions:: How @value{GDBN} presents inlining
9443 @node Inline Functions
9444 @section Inline Functions
9445 @cindex inline functions, debugging
9447 @dfn{Inlining} is an optimization that inserts a copy of the function
9448 body directly at each call site, instead of jumping to a shared
9449 routine. @value{GDBN} displays inlined functions just like
9450 non-inlined functions. They appear in backtraces. You can view their
9451 arguments and local variables, step into them with @code{step}, skip
9452 them with @code{next}, and escape from them with @code{finish}.
9453 You can check whether a function was inlined by using the
9454 @code{info frame} command.
9456 For @value{GDBN} to support inlined functions, the compiler must
9457 record information about inlining in the debug information ---
9458 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9459 other compilers do also. @value{GDBN} only supports inlined functions
9460 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9461 do not emit two required attributes (@samp{DW_AT_call_file} and
9462 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9463 function calls with earlier versions of @value{NGCC}. It instead
9464 displays the arguments and local variables of inlined functions as
9465 local variables in the caller.
9467 The body of an inlined function is directly included at its call site;
9468 unlike a non-inlined function, there are no instructions devoted to
9469 the call. @value{GDBN} still pretends that the call site and the
9470 start of the inlined function are different instructions. Stepping to
9471 the call site shows the call site, and then stepping again shows
9472 the first line of the inlined function, even though no additional
9473 instructions are executed.
9475 This makes source-level debugging much clearer; you can see both the
9476 context of the call and then the effect of the call. Only stepping by
9477 a single instruction using @code{stepi} or @code{nexti} does not do
9478 this; single instruction steps always show the inlined body.
9480 There are some ways that @value{GDBN} does not pretend that inlined
9481 function calls are the same as normal calls:
9485 You cannot set breakpoints on inlined functions. @value{GDBN}
9486 either reports that there is no symbol with that name, or else sets the
9487 breakpoint only on non-inlined copies of the function. This limitation
9488 will be removed in a future version of @value{GDBN}; until then,
9489 set a breakpoint by line number on the first line of the inlined
9493 Setting breakpoints at the call site of an inlined function may not
9494 work, because the call site does not contain any code. @value{GDBN}
9495 may incorrectly move the breakpoint to the next line of the enclosing
9496 function, after the call. This limitation will be removed in a future
9497 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9498 or inside the inlined function instead.
9501 @value{GDBN} cannot locate the return value of inlined calls after
9502 using the @code{finish} command. This is a limitation of compiler-generated
9503 debugging information; after @code{finish}, you can step to the next line
9504 and print a variable where your program stored the return value.
9510 @chapter C Preprocessor Macros
9512 Some languages, such as C and C@t{++}, provide a way to define and invoke
9513 ``preprocessor macros'' which expand into strings of tokens.
9514 @value{GDBN} can evaluate expressions containing macro invocations, show
9515 the result of macro expansion, and show a macro's definition, including
9516 where it was defined.
9518 You may need to compile your program specially to provide @value{GDBN}
9519 with information about preprocessor macros. Most compilers do not
9520 include macros in their debugging information, even when you compile
9521 with the @option{-g} flag. @xref{Compilation}.
9523 A program may define a macro at one point, remove that definition later,
9524 and then provide a different definition after that. Thus, at different
9525 points in the program, a macro may have different definitions, or have
9526 no definition at all. If there is a current stack frame, @value{GDBN}
9527 uses the macros in scope at that frame's source code line. Otherwise,
9528 @value{GDBN} uses the macros in scope at the current listing location;
9531 Whenever @value{GDBN} evaluates an expression, it always expands any
9532 macro invocations present in the expression. @value{GDBN} also provides
9533 the following commands for working with macros explicitly.
9537 @kindex macro expand
9538 @cindex macro expansion, showing the results of preprocessor
9539 @cindex preprocessor macro expansion, showing the results of
9540 @cindex expanding preprocessor macros
9541 @item macro expand @var{expression}
9542 @itemx macro exp @var{expression}
9543 Show the results of expanding all preprocessor macro invocations in
9544 @var{expression}. Since @value{GDBN} simply expands macros, but does
9545 not parse the result, @var{expression} need not be a valid expression;
9546 it can be any string of tokens.
9549 @item macro expand-once @var{expression}
9550 @itemx macro exp1 @var{expression}
9551 @cindex expand macro once
9552 @i{(This command is not yet implemented.)} Show the results of
9553 expanding those preprocessor macro invocations that appear explicitly in
9554 @var{expression}. Macro invocations appearing in that expansion are
9555 left unchanged. This command allows you to see the effect of a
9556 particular macro more clearly, without being confused by further
9557 expansions. Since @value{GDBN} simply expands macros, but does not
9558 parse the result, @var{expression} need not be a valid expression; it
9559 can be any string of tokens.
9562 @cindex macro definition, showing
9563 @cindex definition, showing a macro's
9564 @item info macro @var{macro}
9565 Show the definition of the macro named @var{macro}, and describe the
9566 source location or compiler command-line where that definition was established.
9568 @kindex macro define
9569 @cindex user-defined macros
9570 @cindex defining macros interactively
9571 @cindex macros, user-defined
9572 @item macro define @var{macro} @var{replacement-list}
9573 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9574 Introduce a definition for a preprocessor macro named @var{macro},
9575 invocations of which are replaced by the tokens given in
9576 @var{replacement-list}. The first form of this command defines an
9577 ``object-like'' macro, which takes no arguments; the second form
9578 defines a ``function-like'' macro, which takes the arguments given in
9581 A definition introduced by this command is in scope in every
9582 expression evaluated in @value{GDBN}, until it is removed with the
9583 @code{macro undef} command, described below. The definition overrides
9584 all definitions for @var{macro} present in the program being debugged,
9585 as well as any previous user-supplied definition.
9588 @item macro undef @var{macro}
9589 Remove any user-supplied definition for the macro named @var{macro}.
9590 This command only affects definitions provided with the @code{macro
9591 define} command, described above; it cannot remove definitions present
9592 in the program being debugged.
9596 List all the macros defined using the @code{macro define} command.
9599 @cindex macros, example of debugging with
9600 Here is a transcript showing the above commands in action. First, we
9601 show our source files:
9609 #define ADD(x) (M + x)
9614 printf ("Hello, world!\n");
9616 printf ("We're so creative.\n");
9618 printf ("Goodbye, world!\n");
9625 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9626 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9627 compiler includes information about preprocessor macros in the debugging
9631 $ gcc -gdwarf-2 -g3 sample.c -o sample
9635 Now, we start @value{GDBN} on our sample program:
9639 GNU gdb 2002-05-06-cvs
9640 Copyright 2002 Free Software Foundation, Inc.
9641 GDB is free software, @dots{}
9645 We can expand macros and examine their definitions, even when the
9646 program is not running. @value{GDBN} uses the current listing position
9647 to decide which macro definitions are in scope:
9650 (@value{GDBP}) list main
9653 5 #define ADD(x) (M + x)
9658 10 printf ("Hello, world!\n");
9660 12 printf ("We're so creative.\n");
9661 (@value{GDBP}) info macro ADD
9662 Defined at /home/jimb/gdb/macros/play/sample.c:5
9663 #define ADD(x) (M + x)
9664 (@value{GDBP}) info macro Q
9665 Defined at /home/jimb/gdb/macros/play/sample.h:1
9666 included at /home/jimb/gdb/macros/play/sample.c:2
9668 (@value{GDBP}) macro expand ADD(1)
9669 expands to: (42 + 1)
9670 (@value{GDBP}) macro expand-once ADD(1)
9671 expands to: once (M + 1)
9675 In the example above, note that @code{macro expand-once} expands only
9676 the macro invocation explicit in the original text --- the invocation of
9677 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9678 which was introduced by @code{ADD}.
9680 Once the program is running, @value{GDBN} uses the macro definitions in
9681 force at the source line of the current stack frame:
9684 (@value{GDBP}) break main
9685 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9687 Starting program: /home/jimb/gdb/macros/play/sample
9689 Breakpoint 1, main () at sample.c:10
9690 10 printf ("Hello, world!\n");
9694 At line 10, the definition of the macro @code{N} at line 9 is in force:
9697 (@value{GDBP}) info macro N
9698 Defined at /home/jimb/gdb/macros/play/sample.c:9
9700 (@value{GDBP}) macro expand N Q M
9702 (@value{GDBP}) print N Q M
9707 As we step over directives that remove @code{N}'s definition, and then
9708 give it a new definition, @value{GDBN} finds the definition (or lack
9709 thereof) in force at each point:
9714 12 printf ("We're so creative.\n");
9715 (@value{GDBP}) info macro N
9716 The symbol `N' has no definition as a C/C++ preprocessor macro
9717 at /home/jimb/gdb/macros/play/sample.c:12
9720 14 printf ("Goodbye, world!\n");
9721 (@value{GDBP}) info macro N
9722 Defined at /home/jimb/gdb/macros/play/sample.c:13
9724 (@value{GDBP}) macro expand N Q M
9725 expands to: 1729 < 42
9726 (@value{GDBP}) print N Q M
9731 In addition to source files, macros can be defined on the compilation command
9732 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9733 such a way, @value{GDBN} displays the location of their definition as line zero
9734 of the source file submitted to the compiler.
9737 (@value{GDBP}) info macro __STDC__
9738 Defined at /home/jimb/gdb/macros/play/sample.c:0
9745 @chapter Tracepoints
9746 @c This chapter is based on the documentation written by Michael
9747 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9750 In some applications, it is not feasible for the debugger to interrupt
9751 the program's execution long enough for the developer to learn
9752 anything helpful about its behavior. If the program's correctness
9753 depends on its real-time behavior, delays introduced by a debugger
9754 might cause the program to change its behavior drastically, or perhaps
9755 fail, even when the code itself is correct. It is useful to be able
9756 to observe the program's behavior without interrupting it.
9758 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9759 specify locations in the program, called @dfn{tracepoints}, and
9760 arbitrary expressions to evaluate when those tracepoints are reached.
9761 Later, using the @code{tfind} command, you can examine the values
9762 those expressions had when the program hit the tracepoints. The
9763 expressions may also denote objects in memory---structures or arrays,
9764 for example---whose values @value{GDBN} should record; while visiting
9765 a particular tracepoint, you may inspect those objects as if they were
9766 in memory at that moment. However, because @value{GDBN} records these
9767 values without interacting with you, it can do so quickly and
9768 unobtrusively, hopefully not disturbing the program's behavior.
9770 The tracepoint facility is currently available only for remote
9771 targets. @xref{Targets}. In addition, your remote target must know
9772 how to collect trace data. This functionality is implemented in the
9773 remote stub; however, none of the stubs distributed with @value{GDBN}
9774 support tracepoints as of this writing. The format of the remote
9775 packets used to implement tracepoints are described in @ref{Tracepoint
9778 It is also possible to get trace data from a file, in a manner reminiscent
9779 of corefiles; you specify the filename, and use @code{tfind} to search
9780 through the file. @xref{Trace Files}, for more details.
9782 This chapter describes the tracepoint commands and features.
9786 * Analyze Collected Data::
9787 * Tracepoint Variables::
9791 @node Set Tracepoints
9792 @section Commands to Set Tracepoints
9794 Before running such a @dfn{trace experiment}, an arbitrary number of
9795 tracepoints can be set. A tracepoint is actually a special type of
9796 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9797 standard breakpoint commands. For instance, as with breakpoints,
9798 tracepoint numbers are successive integers starting from one, and many
9799 of the commands associated with tracepoints take the tracepoint number
9800 as their argument, to identify which tracepoint to work on.
9802 For each tracepoint, you can specify, in advance, some arbitrary set
9803 of data that you want the target to collect in the trace buffer when
9804 it hits that tracepoint. The collected data can include registers,
9805 local variables, or global data. Later, you can use @value{GDBN}
9806 commands to examine the values these data had at the time the
9809 Tracepoints do not support every breakpoint feature. Ignore counts on
9810 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9811 commands when they are hit. Tracepoints may not be thread-specific
9814 @cindex fast tracepoints
9815 Some targets may support @dfn{fast tracepoints}, which are inserted in
9816 a different way (such as with a jump instead of a trap), that is
9817 faster but possibly restricted in where they may be installed.
9819 @cindex static tracepoints
9820 @cindex markers, static tracepoints
9821 @cindex probing markers, static tracepoints
9822 Regular and fast tracepoints are dynamic tracing facilities, meaning
9823 that they can be used to insert tracepoints at (almost) any location
9824 in the target. Some targets may also support controlling @dfn{static
9825 tracepoints} from @value{GDBN}. With static tracing, a set of
9826 instrumentation points, also known as @dfn{markers}, are embedded in
9827 the target program, and can be activated or deactivated by name or
9828 address. These are usually placed at locations which facilitate
9829 investigating what the target is actually doing. @value{GDBN}'s
9830 support for static tracing includes being able to list instrumentation
9831 points, and attach them with @value{GDBN} defined high level
9832 tracepoints that expose the whole range of convenience of
9833 @value{GDBN}'s tracepoints support. Namely, support for collecting
9834 registers values and values of global or local (to the instrumentation
9835 point) variables; tracepoint conditions and trace state variables.
9836 The act of installing a @value{GDBN} static tracepoint on an
9837 instrumentation point, or marker, is referred to as @dfn{probing} a
9838 static tracepoint marker.
9840 @code{gdbserver} supports tracepoints on some target systems.
9841 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9843 This section describes commands to set tracepoints and associated
9844 conditions and actions.
9847 * Create and Delete Tracepoints::
9848 * Enable and Disable Tracepoints::
9849 * Tracepoint Passcounts::
9850 * Tracepoint Conditions::
9851 * Trace State Variables::
9852 * Tracepoint Actions::
9853 * Listing Tracepoints::
9854 * Listing Static Tracepoint Markers::
9855 * Starting and Stopping Trace Experiments::
9856 * Tracepoint Restrictions::
9859 @node Create and Delete Tracepoints
9860 @subsection Create and Delete Tracepoints
9863 @cindex set tracepoint
9865 @item trace @var{location}
9866 The @code{trace} command is very similar to the @code{break} command.
9867 Its argument @var{location} can be a source line, a function name, or
9868 an address in the target program. @xref{Specify Location}. The
9869 @code{trace} command defines a tracepoint, which is a point in the
9870 target program where the debugger will briefly stop, collect some
9871 data, and then allow the program to continue. Setting a tracepoint or
9872 changing its actions doesn't take effect until the next @code{tstart}
9873 command, and once a trace experiment is running, further changes will
9874 not have any effect until the next trace experiment starts.
9876 Here are some examples of using the @code{trace} command:
9879 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9881 (@value{GDBP}) @b{trace +2} // 2 lines forward
9883 (@value{GDBP}) @b{trace my_function} // first source line of function
9885 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9887 (@value{GDBP}) @b{trace *0x2117c4} // an address
9891 You can abbreviate @code{trace} as @code{tr}.
9893 @item trace @var{location} if @var{cond}
9894 Set a tracepoint with condition @var{cond}; evaluate the expression
9895 @var{cond} each time the tracepoint is reached, and collect data only
9896 if the value is nonzero---that is, if @var{cond} evaluates as true.
9897 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9898 information on tracepoint conditions.
9900 @item ftrace @var{location} [ if @var{cond} ]
9901 @cindex set fast tracepoint
9902 @cindex fast tracepoints, setting
9904 The @code{ftrace} command sets a fast tracepoint. For targets that
9905 support them, fast tracepoints will use a more efficient but possibly
9906 less general technique to trigger data collection, such as a jump
9907 instruction instead of a trap, or some sort of hardware support. It
9908 may not be possible to create a fast tracepoint at the desired
9909 location, in which case the command will exit with an explanatory
9912 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9915 @item strace @var{location} [ if @var{cond} ]
9916 @cindex set static tracepoint
9917 @cindex static tracepoints, setting
9918 @cindex probe static tracepoint marker
9920 The @code{strace} command sets a static tracepoint. For targets that
9921 support it, setting a static tracepoint probes a static
9922 instrumentation point, or marker, found at @var{location}. It may not
9923 be possible to set a static tracepoint at the desired location, in
9924 which case the command will exit with an explanatory message.
9926 @value{GDBN} handles arguments to @code{strace} exactly as for
9927 @code{trace}, with the addition that the user can also specify
9928 @code{-m @var{marker}} as @var{location}. This probes the marker
9929 identified by the @var{marker} string identifier. This identifier
9930 depends on the static tracepoint backend library your program is
9931 using. You can find all the marker identifiers in the @samp{ID} field
9932 of the @code{info static-tracepoint-markers} command output.
9933 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9934 Markers}. For example, in the following small program using the UST
9940 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9945 the marker id is composed of joining the first two arguments to the
9946 @code{trace_mark} call with a slash, which translates to:
9949 (@value{GDBP}) info static-tracepoint-markers
9950 Cnt Enb ID Address What
9951 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9957 so you may probe the marker above with:
9960 (@value{GDBP}) strace -m ust/bar33
9963 Static tracepoints accept an extra collect action --- @code{collect
9964 $_sdata}. This collects arbitrary user data passed in the probe point
9965 call to the tracing library. In the UST example above, you'll see
9966 that the third argument to @code{trace_mark} is a printf-like format
9967 string. The user data is then the result of running that formating
9968 string against the following arguments. Note that @code{info
9969 static-tracepoint-markers} command output lists that format string in
9970 the @samp{Data:} field.
9972 You can inspect this data when analyzing the trace buffer, by printing
9973 the $_sdata variable like any other variable available to
9974 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9977 @cindex last tracepoint number
9978 @cindex recent tracepoint number
9979 @cindex tracepoint number
9980 The convenience variable @code{$tpnum} records the tracepoint number
9981 of the most recently set tracepoint.
9983 @kindex delete tracepoint
9984 @cindex tracepoint deletion
9985 @item delete tracepoint @r{[}@var{num}@r{]}
9986 Permanently delete one or more tracepoints. With no argument, the
9987 default is to delete all tracepoints. Note that the regular
9988 @code{delete} command can remove tracepoints also.
9993 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9995 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9999 You can abbreviate this command as @code{del tr}.
10002 @node Enable and Disable Tracepoints
10003 @subsection Enable and Disable Tracepoints
10005 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10008 @kindex disable tracepoint
10009 @item disable tracepoint @r{[}@var{num}@r{]}
10010 Disable tracepoint @var{num}, or all tracepoints if no argument
10011 @var{num} is given. A disabled tracepoint will have no effect during
10012 the next trace experiment, but it is not forgotten. You can re-enable
10013 a disabled tracepoint using the @code{enable tracepoint} command.
10015 @kindex enable tracepoint
10016 @item enable tracepoint @r{[}@var{num}@r{]}
10017 Enable tracepoint @var{num}, or all tracepoints. The enabled
10018 tracepoints will become effective the next time a trace experiment is
10022 @node Tracepoint Passcounts
10023 @subsection Tracepoint Passcounts
10027 @cindex tracepoint pass count
10028 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10029 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10030 automatically stop a trace experiment. If a tracepoint's passcount is
10031 @var{n}, then the trace experiment will be automatically stopped on
10032 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10033 @var{num} is not specified, the @code{passcount} command sets the
10034 passcount of the most recently defined tracepoint. If no passcount is
10035 given, the trace experiment will run until stopped explicitly by the
10041 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10042 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10044 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10045 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10046 (@value{GDBP}) @b{trace foo}
10047 (@value{GDBP}) @b{pass 3}
10048 (@value{GDBP}) @b{trace bar}
10049 (@value{GDBP}) @b{pass 2}
10050 (@value{GDBP}) @b{trace baz}
10051 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10052 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10053 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10054 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10058 @node Tracepoint Conditions
10059 @subsection Tracepoint Conditions
10060 @cindex conditional tracepoints
10061 @cindex tracepoint conditions
10063 The simplest sort of tracepoint collects data every time your program
10064 reaches a specified place. You can also specify a @dfn{condition} for
10065 a tracepoint. A condition is just a Boolean expression in your
10066 programming language (@pxref{Expressions, ,Expressions}). A
10067 tracepoint with a condition evaluates the expression each time your
10068 program reaches it, and data collection happens only if the condition
10071 Tracepoint conditions can be specified when a tracepoint is set, by
10072 using @samp{if} in the arguments to the @code{trace} command.
10073 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10074 also be set or changed at any time with the @code{condition} command,
10075 just as with breakpoints.
10077 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10078 the conditional expression itself. Instead, @value{GDBN} encodes the
10079 expression into an agent expression (@pxref{Agent Expressions})
10080 suitable for execution on the target, independently of @value{GDBN}.
10081 Global variables become raw memory locations, locals become stack
10082 accesses, and so forth.
10084 For instance, suppose you have a function that is usually called
10085 frequently, but should not be called after an error has occurred. You
10086 could use the following tracepoint command to collect data about calls
10087 of that function that happen while the error code is propagating
10088 through the program; an unconditional tracepoint could end up
10089 collecting thousands of useless trace frames that you would have to
10093 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10096 @node Trace State Variables
10097 @subsection Trace State Variables
10098 @cindex trace state variables
10100 A @dfn{trace state variable} is a special type of variable that is
10101 created and managed by target-side code. The syntax is the same as
10102 that for GDB's convenience variables (a string prefixed with ``$''),
10103 but they are stored on the target. They must be created explicitly,
10104 using a @code{tvariable} command. They are always 64-bit signed
10107 Trace state variables are remembered by @value{GDBN}, and downloaded
10108 to the target along with tracepoint information when the trace
10109 experiment starts. There are no intrinsic limits on the number of
10110 trace state variables, beyond memory limitations of the target.
10112 @cindex convenience variables, and trace state variables
10113 Although trace state variables are managed by the target, you can use
10114 them in print commands and expressions as if they were convenience
10115 variables; @value{GDBN} will get the current value from the target
10116 while the trace experiment is running. Trace state variables share
10117 the same namespace as other ``$'' variables, which means that you
10118 cannot have trace state variables with names like @code{$23} or
10119 @code{$pc}, nor can you have a trace state variable and a convenience
10120 variable with the same name.
10124 @item tvariable $@var{name} [ = @var{expression} ]
10126 The @code{tvariable} command creates a new trace state variable named
10127 @code{$@var{name}}, and optionally gives it an initial value of
10128 @var{expression}. @var{expression} is evaluated when this command is
10129 entered; the result will be converted to an integer if possible,
10130 otherwise @value{GDBN} will report an error. A subsequent
10131 @code{tvariable} command specifying the same name does not create a
10132 variable, but instead assigns the supplied initial value to the
10133 existing variable of that name, overwriting any previous initial
10134 value. The default initial value is 0.
10136 @item info tvariables
10137 @kindex info tvariables
10138 List all the trace state variables along with their initial values.
10139 Their current values may also be displayed, if the trace experiment is
10142 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10143 @kindex delete tvariable
10144 Delete the given trace state variables, or all of them if no arguments
10149 @node Tracepoint Actions
10150 @subsection Tracepoint Action Lists
10154 @cindex tracepoint actions
10155 @item actions @r{[}@var{num}@r{]}
10156 This command will prompt for a list of actions to be taken when the
10157 tracepoint is hit. If the tracepoint number @var{num} is not
10158 specified, this command sets the actions for the one that was most
10159 recently defined (so that you can define a tracepoint and then say
10160 @code{actions} without bothering about its number). You specify the
10161 actions themselves on the following lines, one action at a time, and
10162 terminate the actions list with a line containing just @code{end}. So
10163 far, the only defined actions are @code{collect}, @code{teval}, and
10164 @code{while-stepping}.
10166 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10167 Commands, ,Breakpoint Command Lists}), except that only the defined
10168 actions are allowed; any other @value{GDBN} command is rejected.
10170 @cindex remove actions from a tracepoint
10171 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10172 and follow it immediately with @samp{end}.
10175 (@value{GDBP}) @b{collect @var{data}} // collect some data
10177 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10179 (@value{GDBP}) @b{end} // signals the end of actions.
10182 In the following example, the action list begins with @code{collect}
10183 commands indicating the things to be collected when the tracepoint is
10184 hit. Then, in order to single-step and collect additional data
10185 following the tracepoint, a @code{while-stepping} command is used,
10186 followed by the list of things to be collected after each step in a
10187 sequence of single steps. The @code{while-stepping} command is
10188 terminated by its own separate @code{end} command. Lastly, the action
10189 list is terminated by an @code{end} command.
10192 (@value{GDBP}) @b{trace foo}
10193 (@value{GDBP}) @b{actions}
10194 Enter actions for tracepoint 1, one per line:
10197 > while-stepping 12
10198 > collect $pc, arr[i]
10203 @kindex collect @r{(tracepoints)}
10204 @item collect @var{expr1}, @var{expr2}, @dots{}
10205 Collect values of the given expressions when the tracepoint is hit.
10206 This command accepts a comma-separated list of any valid expressions.
10207 In addition to global, static, or local variables, the following
10208 special arguments are supported:
10212 Collect all registers.
10215 Collect all function arguments.
10218 Collect all local variables.
10221 @vindex $_sdata@r{, collect}
10222 Collect static tracepoint marker specific data. Only available for
10223 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10224 Lists}. On the UST static tracepoints library backend, an
10225 instrumentation point resembles a @code{printf} function call. The
10226 tracing library is able to collect user specified data formatted to a
10227 character string using the format provided by the programmer that
10228 instrumented the program. Other backends have similar mechanisms.
10229 Here's an example of a UST marker call:
10232 const char master_name[] = "$your_name";
10233 trace_mark(channel1, marker1, "hello %s", master_name)
10236 In this case, collecting @code{$_sdata} collects the string
10237 @samp{hello $yourname}. When analyzing the trace buffer, you can
10238 inspect @samp{$_sdata} like any other variable available to
10242 You can give several consecutive @code{collect} commands, each one
10243 with a single argument, or one @code{collect} command with several
10244 arguments separated by commas; the effect is the same.
10246 The command @code{info scope} (@pxref{Symbols, info scope}) is
10247 particularly useful for figuring out what data to collect.
10249 @kindex teval @r{(tracepoints)}
10250 @item teval @var{expr1}, @var{expr2}, @dots{}
10251 Evaluate the given expressions when the tracepoint is hit. This
10252 command accepts a comma-separated list of expressions. The results
10253 are discarded, so this is mainly useful for assigning values to trace
10254 state variables (@pxref{Trace State Variables}) without adding those
10255 values to the trace buffer, as would be the case if the @code{collect}
10258 @kindex while-stepping @r{(tracepoints)}
10259 @item while-stepping @var{n}
10260 Perform @var{n} single-step instruction traces after the tracepoint,
10261 collecting new data after each step. The @code{while-stepping}
10262 command is followed by the list of what to collect while stepping
10263 (followed by its own @code{end} command):
10266 > while-stepping 12
10267 > collect $regs, myglobal
10273 Note that @code{$pc} is not automatically collected by
10274 @code{while-stepping}; you need to explicitly collect that register if
10275 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10278 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10279 @kindex set default-collect
10280 @cindex default collection action
10281 This variable is a list of expressions to collect at each tracepoint
10282 hit. It is effectively an additional @code{collect} action prepended
10283 to every tracepoint action list. The expressions are parsed
10284 individually for each tracepoint, so for instance a variable named
10285 @code{xyz} may be interpreted as a global for one tracepoint, and a
10286 local for another, as appropriate to the tracepoint's location.
10288 @item show default-collect
10289 @kindex show default-collect
10290 Show the list of expressions that are collected by default at each
10295 @node Listing Tracepoints
10296 @subsection Listing Tracepoints
10299 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10300 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10301 @cindex information about tracepoints
10302 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10303 Display information about the tracepoint @var{num}. If you don't
10304 specify a tracepoint number, displays information about all the
10305 tracepoints defined so far. The format is similar to that used for
10306 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10307 command, simply restricting itself to tracepoints.
10309 A tracepoint's listing may include additional information specific to
10314 its passcount as given by the @code{passcount @var{n}} command
10318 (@value{GDBP}) @b{info trace}
10319 Num Type Disp Enb Address What
10320 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10322 collect globfoo, $regs
10331 This command can be abbreviated @code{info tp}.
10334 @node Listing Static Tracepoint Markers
10335 @subsection Listing Static Tracepoint Markers
10338 @kindex info static-tracepoint-markers
10339 @cindex information about static tracepoint markers
10340 @item info static-tracepoint-markers
10341 Display information about all static tracepoint markers defined in the
10344 For each marker, the following columns are printed:
10348 An incrementing counter, output to help readability. This is not a
10351 The marker ID, as reported by the target.
10352 @item Enabled or Disabled
10353 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10354 that are not enabled.
10356 Where the marker is in your program, as a memory address.
10358 Where the marker is in the source for your program, as a file and line
10359 number. If the debug information included in the program does not
10360 allow @value{GDBN} to locate the source of the marker, this column
10361 will be left blank.
10365 In addition, the following information may be printed for each marker:
10369 User data passed to the tracing library by the marker call. In the
10370 UST backend, this is the format string passed as argument to the
10372 @item Static tracepoints probing the marker
10373 The list of static tracepoints attached to the marker.
10377 (@value{GDBP}) info static-tracepoint-markers
10378 Cnt ID Enb Address What
10379 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10380 Data: number1 %d number2 %d
10381 Probed by static tracepoints: #2
10382 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10388 @node Starting and Stopping Trace Experiments
10389 @subsection Starting and Stopping Trace Experiments
10393 @cindex start a new trace experiment
10394 @cindex collected data discarded
10396 This command takes no arguments. It starts the trace experiment, and
10397 begins collecting data. This has the side effect of discarding all
10398 the data collected in the trace buffer during the previous trace
10402 @cindex stop a running trace experiment
10404 This command takes no arguments. It ends the trace experiment, and
10405 stops collecting data.
10407 @strong{Note}: a trace experiment and data collection may stop
10408 automatically if any tracepoint's passcount is reached
10409 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10412 @cindex status of trace data collection
10413 @cindex trace experiment, status of
10415 This command displays the status of the current trace data
10419 Here is an example of the commands we described so far:
10422 (@value{GDBP}) @b{trace gdb_c_test}
10423 (@value{GDBP}) @b{actions}
10424 Enter actions for tracepoint #1, one per line.
10425 > collect $regs,$locals,$args
10426 > while-stepping 11
10430 (@value{GDBP}) @b{tstart}
10431 [time passes @dots{}]
10432 (@value{GDBP}) @b{tstop}
10435 @anchor{disconnected tracing}
10436 @cindex disconnected tracing
10437 You can choose to continue running the trace experiment even if
10438 @value{GDBN} disconnects from the target, voluntarily or
10439 involuntarily. For commands such as @code{detach}, the debugger will
10440 ask what you want to do with the trace. But for unexpected
10441 terminations (@value{GDBN} crash, network outage), it would be
10442 unfortunate to lose hard-won trace data, so the variable
10443 @code{disconnected-tracing} lets you decide whether the trace should
10444 continue running without @value{GDBN}.
10447 @item set disconnected-tracing on
10448 @itemx set disconnected-tracing off
10449 @kindex set disconnected-tracing
10450 Choose whether a tracing run should continue to run if @value{GDBN}
10451 has disconnected from the target. Note that @code{detach} or
10452 @code{quit} will ask you directly what to do about a running trace no
10453 matter what this variable's setting, so the variable is mainly useful
10454 for handling unexpected situations, such as loss of the network.
10456 @item show disconnected-tracing
10457 @kindex show disconnected-tracing
10458 Show the current choice for disconnected tracing.
10462 When you reconnect to the target, the trace experiment may or may not
10463 still be running; it might have filled the trace buffer in the
10464 meantime, or stopped for one of the other reasons. If it is running,
10465 it will continue after reconnection.
10467 Upon reconnection, the target will upload information about the
10468 tracepoints in effect. @value{GDBN} will then compare that
10469 information to the set of tracepoints currently defined, and attempt
10470 to match them up, allowing for the possibility that the numbers may
10471 have changed due to creation and deletion in the meantime. If one of
10472 the target's tracepoints does not match any in @value{GDBN}, the
10473 debugger will create a new tracepoint, so that you have a number with
10474 which to specify that tracepoint. This matching-up process is
10475 necessarily heuristic, and it may result in useless tracepoints being
10476 created; you may simply delete them if they are of no use.
10478 @cindex circular trace buffer
10479 If your target agent supports a @dfn{circular trace buffer}, then you
10480 can run a trace experiment indefinitely without filling the trace
10481 buffer; when space runs out, the agent deletes already-collected trace
10482 frames, oldest first, until there is enough room to continue
10483 collecting. This is especially useful if your tracepoints are being
10484 hit too often, and your trace gets terminated prematurely because the
10485 buffer is full. To ask for a circular trace buffer, simply set
10486 @samp{circular-trace-buffer} to on. You can set this at any time,
10487 including during tracing; if the agent can do it, it will change
10488 buffer handling on the fly, otherwise it will not take effect until
10492 @item set circular-trace-buffer on
10493 @itemx set circular-trace-buffer off
10494 @kindex set circular-trace-buffer
10495 Choose whether a tracing run should use a linear or circular buffer
10496 for trace data. A linear buffer will not lose any trace data, but may
10497 fill up prematurely, while a circular buffer will discard old trace
10498 data, but it will have always room for the latest tracepoint hits.
10500 @item show circular-trace-buffer
10501 @kindex show circular-trace-buffer
10502 Show the current choice for the trace buffer. Note that this may not
10503 match the agent's current buffer handling, nor is it guaranteed to
10504 match the setting that might have been in effect during a past run,
10505 for instance if you are looking at frames from a trace file.
10509 @node Tracepoint Restrictions
10510 @subsection Tracepoint Restrictions
10512 @cindex tracepoint restrictions
10513 There are a number of restrictions on the use of tracepoints. As
10514 described above, tracepoint data gathering occurs on the target
10515 without interaction from @value{GDBN}. Thus the full capabilities of
10516 the debugger are not available during data gathering, and then at data
10517 examination time, you will be limited by only having what was
10518 collected. The following items describe some common problems, but it
10519 is not exhaustive, and you may run into additional difficulties not
10525 Tracepoint expressions are intended to gather objects (lvalues). Thus
10526 the full flexibility of GDB's expression evaluator is not available.
10527 You cannot call functions, cast objects to aggregate types, access
10528 convenience variables or modify values (except by assignment to trace
10529 state variables). Some language features may implicitly call
10530 functions (for instance Objective-C fields with accessors), and therefore
10531 cannot be collected either.
10534 Collection of local variables, either individually or in bulk with
10535 @code{$locals} or @code{$args}, during @code{while-stepping} may
10536 behave erratically. The stepping action may enter a new scope (for
10537 instance by stepping into a function), or the location of the variable
10538 may change (for instance it is loaded into a register). The
10539 tracepoint data recorded uses the location information for the
10540 variables that is correct for the tracepoint location. When the
10541 tracepoint is created, it is not possible, in general, to determine
10542 where the steps of a @code{while-stepping} sequence will advance the
10543 program---particularly if a conditional branch is stepped.
10546 Collection of an incompletely-initialized or partially-destroyed object
10547 may result in something that @value{GDBN} cannot display, or displays
10548 in a misleading way.
10551 When @value{GDBN} displays a pointer to character it automatically
10552 dereferences the pointer to also display characters of the string
10553 being pointed to. However, collecting the pointer during tracing does
10554 not automatically collect the string. You need to explicitly
10555 dereference the pointer and provide size information if you want to
10556 collect not only the pointer, but the memory pointed to. For example,
10557 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10561 It is not possible to collect a complete stack backtrace at a
10562 tracepoint. Instead, you may collect the registers and a few hundred
10563 bytes from the stack pointer with something like @code{*$esp@@300}
10564 (adjust to use the name of the actual stack pointer register on your
10565 target architecture, and the amount of stack you wish to capture).
10566 Then the @code{backtrace} command will show a partial backtrace when
10567 using a trace frame. The number of stack frames that can be examined
10568 depends on the sizes of the frames in the collected stack. Note that
10569 if you ask for a block so large that it goes past the bottom of the
10570 stack, the target agent may report an error trying to read from an
10574 If you do not collect registers at a tracepoint, @value{GDBN} can
10575 infer that the value of @code{$pc} must be the same as the address of
10576 the tracepoint and use that when you are looking at a trace frame
10577 for that tracepoint. However, this cannot work if the tracepoint has
10578 multiple locations (for instance if it was set in a function that was
10579 inlined), or if it has a @code{while-stepping} loop. In those cases
10580 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10585 @node Analyze Collected Data
10586 @section Using the Collected Data
10588 After the tracepoint experiment ends, you use @value{GDBN} commands
10589 for examining the trace data. The basic idea is that each tracepoint
10590 collects a trace @dfn{snapshot} every time it is hit and another
10591 snapshot every time it single-steps. All these snapshots are
10592 consecutively numbered from zero and go into a buffer, and you can
10593 examine them later. The way you examine them is to @dfn{focus} on a
10594 specific trace snapshot. When the remote stub is focused on a trace
10595 snapshot, it will respond to all @value{GDBN} requests for memory and
10596 registers by reading from the buffer which belongs to that snapshot,
10597 rather than from @emph{real} memory or registers of the program being
10598 debugged. This means that @strong{all} @value{GDBN} commands
10599 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10600 behave as if we were currently debugging the program state as it was
10601 when the tracepoint occurred. Any requests for data that are not in
10602 the buffer will fail.
10605 * tfind:: How to select a trace snapshot
10606 * tdump:: How to display all data for a snapshot
10607 * save tracepoints:: How to save tracepoints for a future run
10611 @subsection @code{tfind @var{n}}
10614 @cindex select trace snapshot
10615 @cindex find trace snapshot
10616 The basic command for selecting a trace snapshot from the buffer is
10617 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10618 counting from zero. If no argument @var{n} is given, the next
10619 snapshot is selected.
10621 Here are the various forms of using the @code{tfind} command.
10625 Find the first snapshot in the buffer. This is a synonym for
10626 @code{tfind 0} (since 0 is the number of the first snapshot).
10629 Stop debugging trace snapshots, resume @emph{live} debugging.
10632 Same as @samp{tfind none}.
10635 No argument means find the next trace snapshot.
10638 Find the previous trace snapshot before the current one. This permits
10639 retracing earlier steps.
10641 @item tfind tracepoint @var{num}
10642 Find the next snapshot associated with tracepoint @var{num}. Search
10643 proceeds forward from the last examined trace snapshot. If no
10644 argument @var{num} is given, it means find the next snapshot collected
10645 for the same tracepoint as the current snapshot.
10647 @item tfind pc @var{addr}
10648 Find the next snapshot associated with the value @var{addr} of the
10649 program counter. Search proceeds forward from the last examined trace
10650 snapshot. If no argument @var{addr} is given, it means find the next
10651 snapshot with the same value of PC as the current snapshot.
10653 @item tfind outside @var{addr1}, @var{addr2}
10654 Find the next snapshot whose PC is outside the given range of
10655 addresses (exclusive).
10657 @item tfind range @var{addr1}, @var{addr2}
10658 Find the next snapshot whose PC is between @var{addr1} and
10659 @var{addr2} (inclusive).
10661 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10662 Find the next snapshot associated with the source line @var{n}. If
10663 the optional argument @var{file} is given, refer to line @var{n} in
10664 that source file. Search proceeds forward from the last examined
10665 trace snapshot. If no argument @var{n} is given, it means find the
10666 next line other than the one currently being examined; thus saying
10667 @code{tfind line} repeatedly can appear to have the same effect as
10668 stepping from line to line in a @emph{live} debugging session.
10671 The default arguments for the @code{tfind} commands are specifically
10672 designed to make it easy to scan through the trace buffer. For
10673 instance, @code{tfind} with no argument selects the next trace
10674 snapshot, and @code{tfind -} with no argument selects the previous
10675 trace snapshot. So, by giving one @code{tfind} command, and then
10676 simply hitting @key{RET} repeatedly you can examine all the trace
10677 snapshots in order. Or, by saying @code{tfind -} and then hitting
10678 @key{RET} repeatedly you can examine the snapshots in reverse order.
10679 The @code{tfind line} command with no argument selects the snapshot
10680 for the next source line executed. The @code{tfind pc} command with
10681 no argument selects the next snapshot with the same program counter
10682 (PC) as the current frame. The @code{tfind tracepoint} command with
10683 no argument selects the next trace snapshot collected by the same
10684 tracepoint as the current one.
10686 In addition to letting you scan through the trace buffer manually,
10687 these commands make it easy to construct @value{GDBN} scripts that
10688 scan through the trace buffer and print out whatever collected data
10689 you are interested in. Thus, if we want to examine the PC, FP, and SP
10690 registers from each trace frame in the buffer, we can say this:
10693 (@value{GDBP}) @b{tfind start}
10694 (@value{GDBP}) @b{while ($trace_frame != -1)}
10695 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10696 $trace_frame, $pc, $sp, $fp
10700 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10701 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10702 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10703 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10704 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10705 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10706 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10707 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10708 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10709 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10710 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10713 Or, if we want to examine the variable @code{X} at each source line in
10717 (@value{GDBP}) @b{tfind start}
10718 (@value{GDBP}) @b{while ($trace_frame != -1)}
10719 > printf "Frame %d, X == %d\n", $trace_frame, X
10729 @subsection @code{tdump}
10731 @cindex dump all data collected at tracepoint
10732 @cindex tracepoint data, display
10734 This command takes no arguments. It prints all the data collected at
10735 the current trace snapshot.
10738 (@value{GDBP}) @b{trace 444}
10739 (@value{GDBP}) @b{actions}
10740 Enter actions for tracepoint #2, one per line:
10741 > collect $regs, $locals, $args, gdb_long_test
10744 (@value{GDBP}) @b{tstart}
10746 (@value{GDBP}) @b{tfind line 444}
10747 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10749 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10751 (@value{GDBP}) @b{tdump}
10752 Data collected at tracepoint 2, trace frame 1:
10753 d0 0xc4aa0085 -995491707
10757 d4 0x71aea3d 119204413
10760 d7 0x380035 3670069
10761 a0 0x19e24a 1696330
10762 a1 0x3000668 50333288
10764 a3 0x322000 3284992
10765 a4 0x3000698 50333336
10766 a5 0x1ad3cc 1758156
10767 fp 0x30bf3c 0x30bf3c
10768 sp 0x30bf34 0x30bf34
10770 pc 0x20b2c8 0x20b2c8
10774 p = 0x20e5b4 "gdb-test"
10781 gdb_long_test = 17 '\021'
10786 @code{tdump} works by scanning the tracepoint's current collection
10787 actions and printing the value of each expression listed. So
10788 @code{tdump} can fail, if after a run, you change the tracepoint's
10789 actions to mention variables that were not collected during the run.
10791 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10792 uses the collected value of @code{$pc} to distinguish between trace
10793 frames that were collected at the tracepoint hit, and frames that were
10794 collected while stepping. This allows it to correctly choose whether
10795 to display the basic list of collections, or the collections from the
10796 body of the while-stepping loop. However, if @code{$pc} was not collected,
10797 then @code{tdump} will always attempt to dump using the basic collection
10798 list, and may fail if a while-stepping frame does not include all the
10799 same data that is collected at the tracepoint hit.
10800 @c This is getting pretty arcane, example would be good.
10802 @node save tracepoints
10803 @subsection @code{save tracepoints @var{filename}}
10804 @kindex save tracepoints
10805 @kindex save-tracepoints
10806 @cindex save tracepoints for future sessions
10808 This command saves all current tracepoint definitions together with
10809 their actions and passcounts, into a file @file{@var{filename}}
10810 suitable for use in a later debugging session. To read the saved
10811 tracepoint definitions, use the @code{source} command (@pxref{Command
10812 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10813 alias for @w{@code{save tracepoints}}
10815 @node Tracepoint Variables
10816 @section Convenience Variables for Tracepoints
10817 @cindex tracepoint variables
10818 @cindex convenience variables for tracepoints
10821 @vindex $trace_frame
10822 @item (int) $trace_frame
10823 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10824 snapshot is selected.
10826 @vindex $tracepoint
10827 @item (int) $tracepoint
10828 The tracepoint for the current trace snapshot.
10830 @vindex $trace_line
10831 @item (int) $trace_line
10832 The line number for the current trace snapshot.
10834 @vindex $trace_file
10835 @item (char []) $trace_file
10836 The source file for the current trace snapshot.
10838 @vindex $trace_func
10839 @item (char []) $trace_func
10840 The name of the function containing @code{$tracepoint}.
10843 Note: @code{$trace_file} is not suitable for use in @code{printf},
10844 use @code{output} instead.
10846 Here's a simple example of using these convenience variables for
10847 stepping through all the trace snapshots and printing some of their
10848 data. Note that these are not the same as trace state variables,
10849 which are managed by the target.
10852 (@value{GDBP}) @b{tfind start}
10854 (@value{GDBP}) @b{while $trace_frame != -1}
10855 > output $trace_file
10856 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10862 @section Using Trace Files
10863 @cindex trace files
10865 In some situations, the target running a trace experiment may no
10866 longer be available; perhaps it crashed, or the hardware was needed
10867 for a different activity. To handle these cases, you can arrange to
10868 dump the trace data into a file, and later use that file as a source
10869 of trace data, via the @code{target tfile} command.
10874 @item tsave [ -r ] @var{filename}
10875 Save the trace data to @var{filename}. By default, this command
10876 assumes that @var{filename} refers to the host filesystem, so if
10877 necessary @value{GDBN} will copy raw trace data up from the target and
10878 then save it. If the target supports it, you can also supply the
10879 optional argument @code{-r} (``remote'') to direct the target to save
10880 the data directly into @var{filename} in its own filesystem, which may be
10881 more efficient if the trace buffer is very large. (Note, however, that
10882 @code{target tfile} can only read from files accessible to the host.)
10884 @kindex target tfile
10886 @item target tfile @var{filename}
10887 Use the file named @var{filename} as a source of trace data. Commands
10888 that examine data work as they do with a live target, but it is not
10889 possible to run any new trace experiments. @code{tstatus} will report
10890 the state of the trace run at the moment the data was saved, as well
10891 as the current trace frame you are examining. @var{filename} must be
10892 on a filesystem accessible to the host.
10897 @chapter Debugging Programs That Use Overlays
10900 If your program is too large to fit completely in your target system's
10901 memory, you can sometimes use @dfn{overlays} to work around this
10902 problem. @value{GDBN} provides some support for debugging programs that
10906 * How Overlays Work:: A general explanation of overlays.
10907 * Overlay Commands:: Managing overlays in @value{GDBN}.
10908 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10909 mapped by asking the inferior.
10910 * Overlay Sample Program:: A sample program using overlays.
10913 @node How Overlays Work
10914 @section How Overlays Work
10915 @cindex mapped overlays
10916 @cindex unmapped overlays
10917 @cindex load address, overlay's
10918 @cindex mapped address
10919 @cindex overlay area
10921 Suppose you have a computer whose instruction address space is only 64
10922 kilobytes long, but which has much more memory which can be accessed by
10923 other means: special instructions, segment registers, or memory
10924 management hardware, for example. Suppose further that you want to
10925 adapt a program which is larger than 64 kilobytes to run on this system.
10927 One solution is to identify modules of your program which are relatively
10928 independent, and need not call each other directly; call these modules
10929 @dfn{overlays}. Separate the overlays from the main program, and place
10930 their machine code in the larger memory. Place your main program in
10931 instruction memory, but leave at least enough space there to hold the
10932 largest overlay as well.
10934 Now, to call a function located in an overlay, you must first copy that
10935 overlay's machine code from the large memory into the space set aside
10936 for it in the instruction memory, and then jump to its entry point
10939 @c NB: In the below the mapped area's size is greater or equal to the
10940 @c size of all overlays. This is intentional to remind the developer
10941 @c that overlays don't necessarily need to be the same size.
10945 Data Instruction Larger
10946 Address Space Address Space Address Space
10947 +-----------+ +-----------+ +-----------+
10949 +-----------+ +-----------+ +-----------+<-- overlay 1
10950 | program | | main | .----| overlay 1 | load address
10951 | variables | | program | | +-----------+
10952 | and heap | | | | | |
10953 +-----------+ | | | +-----------+<-- overlay 2
10954 | | +-----------+ | | | load address
10955 +-----------+ | | | .-| overlay 2 |
10957 mapped --->+-----------+ | | +-----------+
10958 address | | | | | |
10959 | overlay | <-' | | |
10960 | area | <---' +-----------+<-- overlay 3
10961 | | <---. | | load address
10962 +-----------+ `--| overlay 3 |
10969 @anchor{A code overlay}A code overlay
10973 The diagram (@pxref{A code overlay}) shows a system with separate data
10974 and instruction address spaces. To map an overlay, the program copies
10975 its code from the larger address space to the instruction address space.
10976 Since the overlays shown here all use the same mapped address, only one
10977 may be mapped at a time. For a system with a single address space for
10978 data and instructions, the diagram would be similar, except that the
10979 program variables and heap would share an address space with the main
10980 program and the overlay area.
10982 An overlay loaded into instruction memory and ready for use is called a
10983 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10984 instruction memory. An overlay not present (or only partially present)
10985 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10986 is its address in the larger memory. The mapped address is also called
10987 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10988 called the @dfn{load memory address}, or @dfn{LMA}.
10990 Unfortunately, overlays are not a completely transparent way to adapt a
10991 program to limited instruction memory. They introduce a new set of
10992 global constraints you must keep in mind as you design your program:
10997 Before calling or returning to a function in an overlay, your program
10998 must make sure that overlay is actually mapped. Otherwise, the call or
10999 return will transfer control to the right address, but in the wrong
11000 overlay, and your program will probably crash.
11003 If the process of mapping an overlay is expensive on your system, you
11004 will need to choose your overlays carefully to minimize their effect on
11005 your program's performance.
11008 The executable file you load onto your system must contain each
11009 overlay's instructions, appearing at the overlay's load address, not its
11010 mapped address. However, each overlay's instructions must be relocated
11011 and its symbols defined as if the overlay were at its mapped address.
11012 You can use GNU linker scripts to specify different load and relocation
11013 addresses for pieces of your program; see @ref{Overlay Description,,,
11014 ld.info, Using ld: the GNU linker}.
11017 The procedure for loading executable files onto your system must be able
11018 to load their contents into the larger address space as well as the
11019 instruction and data spaces.
11023 The overlay system described above is rather simple, and could be
11024 improved in many ways:
11029 If your system has suitable bank switch registers or memory management
11030 hardware, you could use those facilities to make an overlay's load area
11031 contents simply appear at their mapped address in instruction space.
11032 This would probably be faster than copying the overlay to its mapped
11033 area in the usual way.
11036 If your overlays are small enough, you could set aside more than one
11037 overlay area, and have more than one overlay mapped at a time.
11040 You can use overlays to manage data, as well as instructions. In
11041 general, data overlays are even less transparent to your design than
11042 code overlays: whereas code overlays only require care when you call or
11043 return to functions, data overlays require care every time you access
11044 the data. Also, if you change the contents of a data overlay, you
11045 must copy its contents back out to its load address before you can copy a
11046 different data overlay into the same mapped area.
11051 @node Overlay Commands
11052 @section Overlay Commands
11054 To use @value{GDBN}'s overlay support, each overlay in your program must
11055 correspond to a separate section of the executable file. The section's
11056 virtual memory address and load memory address must be the overlay's
11057 mapped and load addresses. Identifying overlays with sections allows
11058 @value{GDBN} to determine the appropriate address of a function or
11059 variable, depending on whether the overlay is mapped or not.
11061 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11062 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11067 Disable @value{GDBN}'s overlay support. When overlay support is
11068 disabled, @value{GDBN} assumes that all functions and variables are
11069 always present at their mapped addresses. By default, @value{GDBN}'s
11070 overlay support is disabled.
11072 @item overlay manual
11073 @cindex manual overlay debugging
11074 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11075 relies on you to tell it which overlays are mapped, and which are not,
11076 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11077 commands described below.
11079 @item overlay map-overlay @var{overlay}
11080 @itemx overlay map @var{overlay}
11081 @cindex map an overlay
11082 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11083 be the name of the object file section containing the overlay. When an
11084 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11085 functions and variables at their mapped addresses. @value{GDBN} assumes
11086 that any other overlays whose mapped ranges overlap that of
11087 @var{overlay} are now unmapped.
11089 @item overlay unmap-overlay @var{overlay}
11090 @itemx overlay unmap @var{overlay}
11091 @cindex unmap an overlay
11092 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11093 must be the name of the object file section containing the overlay.
11094 When an overlay is unmapped, @value{GDBN} assumes it can find the
11095 overlay's functions and variables at their load addresses.
11098 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11099 consults a data structure the overlay manager maintains in the inferior
11100 to see which overlays are mapped. For details, see @ref{Automatic
11101 Overlay Debugging}.
11103 @item overlay load-target
11104 @itemx overlay load
11105 @cindex reloading the overlay table
11106 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11107 re-reads the table @value{GDBN} automatically each time the inferior
11108 stops, so this command should only be necessary if you have changed the
11109 overlay mapping yourself using @value{GDBN}. This command is only
11110 useful when using automatic overlay debugging.
11112 @item overlay list-overlays
11113 @itemx overlay list
11114 @cindex listing mapped overlays
11115 Display a list of the overlays currently mapped, along with their mapped
11116 addresses, load addresses, and sizes.
11120 Normally, when @value{GDBN} prints a code address, it includes the name
11121 of the function the address falls in:
11124 (@value{GDBP}) print main
11125 $3 = @{int ()@} 0x11a0 <main>
11128 When overlay debugging is enabled, @value{GDBN} recognizes code in
11129 unmapped overlays, and prints the names of unmapped functions with
11130 asterisks around them. For example, if @code{foo} is a function in an
11131 unmapped overlay, @value{GDBN} prints it this way:
11134 (@value{GDBP}) overlay list
11135 No sections are mapped.
11136 (@value{GDBP}) print foo
11137 $5 = @{int (int)@} 0x100000 <*foo*>
11140 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11144 (@value{GDBP}) overlay list
11145 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11146 mapped at 0x1016 - 0x104a
11147 (@value{GDBP}) print foo
11148 $6 = @{int (int)@} 0x1016 <foo>
11151 When overlay debugging is enabled, @value{GDBN} can find the correct
11152 address for functions and variables in an overlay, whether or not the
11153 overlay is mapped. This allows most @value{GDBN} commands, like
11154 @code{break} and @code{disassemble}, to work normally, even on unmapped
11155 code. However, @value{GDBN}'s breakpoint support has some limitations:
11159 @cindex breakpoints in overlays
11160 @cindex overlays, setting breakpoints in
11161 You can set breakpoints in functions in unmapped overlays, as long as
11162 @value{GDBN} can write to the overlay at its load address.
11164 @value{GDBN} can not set hardware or simulator-based breakpoints in
11165 unmapped overlays. However, if you set a breakpoint at the end of your
11166 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11167 you are using manual overlay management), @value{GDBN} will re-set its
11168 breakpoints properly.
11172 @node Automatic Overlay Debugging
11173 @section Automatic Overlay Debugging
11174 @cindex automatic overlay debugging
11176 @value{GDBN} can automatically track which overlays are mapped and which
11177 are not, given some simple co-operation from the overlay manager in the
11178 inferior. If you enable automatic overlay debugging with the
11179 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11180 looks in the inferior's memory for certain variables describing the
11181 current state of the overlays.
11183 Here are the variables your overlay manager must define to support
11184 @value{GDBN}'s automatic overlay debugging:
11188 @item @code{_ovly_table}:
11189 This variable must be an array of the following structures:
11194 /* The overlay's mapped address. */
11197 /* The size of the overlay, in bytes. */
11198 unsigned long size;
11200 /* The overlay's load address. */
11203 /* Non-zero if the overlay is currently mapped;
11205 unsigned long mapped;
11209 @item @code{_novlys}:
11210 This variable must be a four-byte signed integer, holding the total
11211 number of elements in @code{_ovly_table}.
11215 To decide whether a particular overlay is mapped or not, @value{GDBN}
11216 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11217 @code{lma} members equal the VMA and LMA of the overlay's section in the
11218 executable file. When @value{GDBN} finds a matching entry, it consults
11219 the entry's @code{mapped} member to determine whether the overlay is
11222 In addition, your overlay manager may define a function called
11223 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11224 will silently set a breakpoint there. If the overlay manager then
11225 calls this function whenever it has changed the overlay table, this
11226 will enable @value{GDBN} to accurately keep track of which overlays
11227 are in program memory, and update any breakpoints that may be set
11228 in overlays. This will allow breakpoints to work even if the
11229 overlays are kept in ROM or other non-writable memory while they
11230 are not being executed.
11232 @node Overlay Sample Program
11233 @section Overlay Sample Program
11234 @cindex overlay example program
11236 When linking a program which uses overlays, you must place the overlays
11237 at their load addresses, while relocating them to run at their mapped
11238 addresses. To do this, you must write a linker script (@pxref{Overlay
11239 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11240 since linker scripts are specific to a particular host system, target
11241 architecture, and target memory layout, this manual cannot provide
11242 portable sample code demonstrating @value{GDBN}'s overlay support.
11244 However, the @value{GDBN} source distribution does contain an overlaid
11245 program, with linker scripts for a few systems, as part of its test
11246 suite. The program consists of the following files from
11247 @file{gdb/testsuite/gdb.base}:
11251 The main program file.
11253 A simple overlay manager, used by @file{overlays.c}.
11258 Overlay modules, loaded and used by @file{overlays.c}.
11261 Linker scripts for linking the test program on the @code{d10v-elf}
11262 and @code{m32r-elf} targets.
11265 You can build the test program using the @code{d10v-elf} GCC
11266 cross-compiler like this:
11269 $ d10v-elf-gcc -g -c overlays.c
11270 $ d10v-elf-gcc -g -c ovlymgr.c
11271 $ d10v-elf-gcc -g -c foo.c
11272 $ d10v-elf-gcc -g -c bar.c
11273 $ d10v-elf-gcc -g -c baz.c
11274 $ d10v-elf-gcc -g -c grbx.c
11275 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11276 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11279 The build process is identical for any other architecture, except that
11280 you must substitute the appropriate compiler and linker script for the
11281 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11285 @chapter Using @value{GDBN} with Different Languages
11288 Although programming languages generally have common aspects, they are
11289 rarely expressed in the same manner. For instance, in ANSI C,
11290 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11291 Modula-2, it is accomplished by @code{p^}. Values can also be
11292 represented (and displayed) differently. Hex numbers in C appear as
11293 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11295 @cindex working language
11296 Language-specific information is built into @value{GDBN} for some languages,
11297 allowing you to express operations like the above in your program's
11298 native language, and allowing @value{GDBN} to output values in a manner
11299 consistent with the syntax of your program's native language. The
11300 language you use to build expressions is called the @dfn{working
11304 * Setting:: Switching between source languages
11305 * Show:: Displaying the language
11306 * Checks:: Type and range checks
11307 * Supported Languages:: Supported languages
11308 * Unsupported Languages:: Unsupported languages
11312 @section Switching Between Source Languages
11314 There are two ways to control the working language---either have @value{GDBN}
11315 set it automatically, or select it manually yourself. You can use the
11316 @code{set language} command for either purpose. On startup, @value{GDBN}
11317 defaults to setting the language automatically. The working language is
11318 used to determine how expressions you type are interpreted, how values
11321 In addition to the working language, every source file that
11322 @value{GDBN} knows about has its own working language. For some object
11323 file formats, the compiler might indicate which language a particular
11324 source file is in. However, most of the time @value{GDBN} infers the
11325 language from the name of the file. The language of a source file
11326 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11327 show each frame appropriately for its own language. There is no way to
11328 set the language of a source file from within @value{GDBN}, but you can
11329 set the language associated with a filename extension. @xref{Show, ,
11330 Displaying the Language}.
11332 This is most commonly a problem when you use a program, such
11333 as @code{cfront} or @code{f2c}, that generates C but is written in
11334 another language. In that case, make the
11335 program use @code{#line} directives in its C output; that way
11336 @value{GDBN} will know the correct language of the source code of the original
11337 program, and will display that source code, not the generated C code.
11340 * Filenames:: Filename extensions and languages.
11341 * Manually:: Setting the working language manually
11342 * Automatically:: Having @value{GDBN} infer the source language
11346 @subsection List of Filename Extensions and Languages
11348 If a source file name ends in one of the following extensions, then
11349 @value{GDBN} infers that its language is the one indicated.
11367 C@t{++} source file
11373 Objective-C source file
11377 Fortran source file
11380 Modula-2 source file
11384 Assembler source file. This actually behaves almost like C, but
11385 @value{GDBN} does not skip over function prologues when stepping.
11388 In addition, you may set the language associated with a filename
11389 extension. @xref{Show, , Displaying the Language}.
11392 @subsection Setting the Working Language
11394 If you allow @value{GDBN} to set the language automatically,
11395 expressions are interpreted the same way in your debugging session and
11398 @kindex set language
11399 If you wish, you may set the language manually. To do this, issue the
11400 command @samp{set language @var{lang}}, where @var{lang} is the name of
11401 a language, such as
11402 @code{c} or @code{modula-2}.
11403 For a list of the supported languages, type @samp{set language}.
11405 Setting the language manually prevents @value{GDBN} from updating the working
11406 language automatically. This can lead to confusion if you try
11407 to debug a program when the working language is not the same as the
11408 source language, when an expression is acceptable to both
11409 languages---but means different things. For instance, if the current
11410 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11418 might not have the effect you intended. In C, this means to add
11419 @code{b} and @code{c} and place the result in @code{a}. The result
11420 printed would be the value of @code{a}. In Modula-2, this means to compare
11421 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11423 @node Automatically
11424 @subsection Having @value{GDBN} Infer the Source Language
11426 To have @value{GDBN} set the working language automatically, use
11427 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11428 then infers the working language. That is, when your program stops in a
11429 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11430 working language to the language recorded for the function in that
11431 frame. If the language for a frame is unknown (that is, if the function
11432 or block corresponding to the frame was defined in a source file that
11433 does not have a recognized extension), the current working language is
11434 not changed, and @value{GDBN} issues a warning.
11436 This may not seem necessary for most programs, which are written
11437 entirely in one source language. However, program modules and libraries
11438 written in one source language can be used by a main program written in
11439 a different source language. Using @samp{set language auto} in this
11440 case frees you from having to set the working language manually.
11443 @section Displaying the Language
11445 The following commands help you find out which language is the
11446 working language, and also what language source files were written in.
11449 @item show language
11450 @kindex show language
11451 Display the current working language. This is the
11452 language you can use with commands such as @code{print} to
11453 build and compute expressions that may involve variables in your program.
11456 @kindex info frame@r{, show the source language}
11457 Display the source language for this frame. This language becomes the
11458 working language if you use an identifier from this frame.
11459 @xref{Frame Info, ,Information about a Frame}, to identify the other
11460 information listed here.
11463 @kindex info source@r{, show the source language}
11464 Display the source language of this source file.
11465 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11466 information listed here.
11469 In unusual circumstances, you may have source files with extensions
11470 not in the standard list. You can then set the extension associated
11471 with a language explicitly:
11474 @item set extension-language @var{ext} @var{language}
11475 @kindex set extension-language
11476 Tell @value{GDBN} that source files with extension @var{ext} are to be
11477 assumed as written in the source language @var{language}.
11479 @item info extensions
11480 @kindex info extensions
11481 List all the filename extensions and the associated languages.
11485 @section Type and Range Checking
11488 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11489 checking are included, but they do not yet have any effect. This
11490 section documents the intended facilities.
11492 @c FIXME remove warning when type/range code added
11494 Some languages are designed to guard you against making seemingly common
11495 errors through a series of compile- and run-time checks. These include
11496 checking the type of arguments to functions and operators, and making
11497 sure mathematical overflows are caught at run time. Checks such as
11498 these help to ensure a program's correctness once it has been compiled
11499 by eliminating type mismatches, and providing active checks for range
11500 errors when your program is running.
11502 @value{GDBN} can check for conditions like the above if you wish.
11503 Although @value{GDBN} does not check the statements in your program,
11504 it can check expressions entered directly into @value{GDBN} for
11505 evaluation via the @code{print} command, for example. As with the
11506 working language, @value{GDBN} can also decide whether or not to check
11507 automatically based on your program's source language.
11508 @xref{Supported Languages, ,Supported Languages}, for the default
11509 settings of supported languages.
11512 * Type Checking:: An overview of type checking
11513 * Range Checking:: An overview of range checking
11516 @cindex type checking
11517 @cindex checks, type
11518 @node Type Checking
11519 @subsection An Overview of Type Checking
11521 Some languages, such as Modula-2, are strongly typed, meaning that the
11522 arguments to operators and functions have to be of the correct type,
11523 otherwise an error occurs. These checks prevent type mismatch
11524 errors from ever causing any run-time problems. For example,
11532 The second example fails because the @code{CARDINAL} 1 is not
11533 type-compatible with the @code{REAL} 2.3.
11535 For the expressions you use in @value{GDBN} commands, you can tell the
11536 @value{GDBN} type checker to skip checking;
11537 to treat any mismatches as errors and abandon the expression;
11538 or to only issue warnings when type mismatches occur,
11539 but evaluate the expression anyway. When you choose the last of
11540 these, @value{GDBN} evaluates expressions like the second example above, but
11541 also issues a warning.
11543 Even if you turn type checking off, there may be other reasons
11544 related to type that prevent @value{GDBN} from evaluating an expression.
11545 For instance, @value{GDBN} does not know how to add an @code{int} and
11546 a @code{struct foo}. These particular type errors have nothing to do
11547 with the language in use, and usually arise from expressions, such as
11548 the one described above, which make little sense to evaluate anyway.
11550 Each language defines to what degree it is strict about type. For
11551 instance, both Modula-2 and C require the arguments to arithmetical
11552 operators to be numbers. In C, enumerated types and pointers can be
11553 represented as numbers, so that they are valid arguments to mathematical
11554 operators. @xref{Supported Languages, ,Supported Languages}, for further
11555 details on specific languages.
11557 @value{GDBN} provides some additional commands for controlling the type checker:
11559 @kindex set check type
11560 @kindex show check type
11562 @item set check type auto
11563 Set type checking on or off based on the current working language.
11564 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11567 @item set check type on
11568 @itemx set check type off
11569 Set type checking on or off, overriding the default setting for the
11570 current working language. Issue a warning if the setting does not
11571 match the language default. If any type mismatches occur in
11572 evaluating an expression while type checking is on, @value{GDBN} prints a
11573 message and aborts evaluation of the expression.
11575 @item set check type warn
11576 Cause the type checker to issue warnings, but to always attempt to
11577 evaluate the expression. Evaluating the expression may still
11578 be impossible for other reasons. For example, @value{GDBN} cannot add
11579 numbers and structures.
11582 Show the current setting of the type checker, and whether or not @value{GDBN}
11583 is setting it automatically.
11586 @cindex range checking
11587 @cindex checks, range
11588 @node Range Checking
11589 @subsection An Overview of Range Checking
11591 In some languages (such as Modula-2), it is an error to exceed the
11592 bounds of a type; this is enforced with run-time checks. Such range
11593 checking is meant to ensure program correctness by making sure
11594 computations do not overflow, or indices on an array element access do
11595 not exceed the bounds of the array.
11597 For expressions you use in @value{GDBN} commands, you can tell
11598 @value{GDBN} to treat range errors in one of three ways: ignore them,
11599 always treat them as errors and abandon the expression, or issue
11600 warnings but evaluate the expression anyway.
11602 A range error can result from numerical overflow, from exceeding an
11603 array index bound, or when you type a constant that is not a member
11604 of any type. Some languages, however, do not treat overflows as an
11605 error. In many implementations of C, mathematical overflow causes the
11606 result to ``wrap around'' to lower values---for example, if @var{m} is
11607 the largest integer value, and @var{s} is the smallest, then
11610 @var{m} + 1 @result{} @var{s}
11613 This, too, is specific to individual languages, and in some cases
11614 specific to individual compilers or machines. @xref{Supported Languages, ,
11615 Supported Languages}, for further details on specific languages.
11617 @value{GDBN} provides some additional commands for controlling the range checker:
11619 @kindex set check range
11620 @kindex show check range
11622 @item set check range auto
11623 Set range checking on or off based on the current working language.
11624 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11627 @item set check range on
11628 @itemx set check range off
11629 Set range checking on or off, overriding the default setting for the
11630 current working language. A warning is issued if the setting does not
11631 match the language default. If a range error occurs and range checking is on,
11632 then a message is printed and evaluation of the expression is aborted.
11634 @item set check range warn
11635 Output messages when the @value{GDBN} range checker detects a range error,
11636 but attempt to evaluate the expression anyway. Evaluating the
11637 expression may still be impossible for other reasons, such as accessing
11638 memory that the process does not own (a typical example from many Unix
11642 Show the current setting of the range checker, and whether or not it is
11643 being set automatically by @value{GDBN}.
11646 @node Supported Languages
11647 @section Supported Languages
11649 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11650 assembly, Modula-2, and Ada.
11651 @c This is false ...
11652 Some @value{GDBN} features may be used in expressions regardless of the
11653 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11654 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11655 ,Expressions}) can be used with the constructs of any supported
11658 The following sections detail to what degree each source language is
11659 supported by @value{GDBN}. These sections are not meant to be language
11660 tutorials or references, but serve only as a reference guide to what the
11661 @value{GDBN} expression parser accepts, and what input and output
11662 formats should look like for different languages. There are many good
11663 books written on each of these languages; please look to these for a
11664 language reference or tutorial.
11667 * C:: C and C@t{++}
11669 * Objective-C:: Objective-C
11670 * OpenCL C:: OpenCL C
11671 * Fortran:: Fortran
11673 * Modula-2:: Modula-2
11678 @subsection C and C@t{++}
11680 @cindex C and C@t{++}
11681 @cindex expressions in C or C@t{++}
11683 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11684 to both languages. Whenever this is the case, we discuss those languages
11688 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11689 @cindex @sc{gnu} C@t{++}
11690 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11691 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11692 effectively, you must compile your C@t{++} programs with a supported
11693 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11694 compiler (@code{aCC}).
11696 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11697 format; if it doesn't work on your system, try the stabs+ debugging
11698 format. You can select those formats explicitly with the @code{g++}
11699 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11700 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11701 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11704 * C Operators:: C and C@t{++} operators
11705 * C Constants:: C and C@t{++} constants
11706 * C Plus Plus Expressions:: C@t{++} expressions
11707 * C Defaults:: Default settings for C and C@t{++}
11708 * C Checks:: C and C@t{++} type and range checks
11709 * Debugging C:: @value{GDBN} and C
11710 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11711 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11715 @subsubsection C and C@t{++} Operators
11717 @cindex C and C@t{++} operators
11719 Operators must be defined on values of specific types. For instance,
11720 @code{+} is defined on numbers, but not on structures. Operators are
11721 often defined on groups of types.
11723 For the purposes of C and C@t{++}, the following definitions hold:
11728 @emph{Integral types} include @code{int} with any of its storage-class
11729 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11732 @emph{Floating-point types} include @code{float}, @code{double}, and
11733 @code{long double} (if supported by the target platform).
11736 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11739 @emph{Scalar types} include all of the above.
11744 The following operators are supported. They are listed here
11745 in order of increasing precedence:
11749 The comma or sequencing operator. Expressions in a comma-separated list
11750 are evaluated from left to right, with the result of the entire
11751 expression being the last expression evaluated.
11754 Assignment. The value of an assignment expression is the value
11755 assigned. Defined on scalar types.
11758 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11759 and translated to @w{@code{@var{a} = @var{a op b}}}.
11760 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11761 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11762 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11765 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11766 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11770 Logical @sc{or}. Defined on integral types.
11773 Logical @sc{and}. Defined on integral types.
11776 Bitwise @sc{or}. Defined on integral types.
11779 Bitwise exclusive-@sc{or}. Defined on integral types.
11782 Bitwise @sc{and}. Defined on integral types.
11785 Equality and inequality. Defined on scalar types. The value of these
11786 expressions is 0 for false and non-zero for true.
11788 @item <@r{, }>@r{, }<=@r{, }>=
11789 Less than, greater than, less than or equal, greater than or equal.
11790 Defined on scalar types. The value of these expressions is 0 for false
11791 and non-zero for true.
11794 left shift, and right shift. Defined on integral types.
11797 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11800 Addition and subtraction. Defined on integral types, floating-point types and
11803 @item *@r{, }/@r{, }%
11804 Multiplication, division, and modulus. Multiplication and division are
11805 defined on integral and floating-point types. Modulus is defined on
11809 Increment and decrement. When appearing before a variable, the
11810 operation is performed before the variable is used in an expression;
11811 when appearing after it, the variable's value is used before the
11812 operation takes place.
11815 Pointer dereferencing. Defined on pointer types. Same precedence as
11819 Address operator. Defined on variables. Same precedence as @code{++}.
11821 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11822 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11823 to examine the address
11824 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11828 Negative. Defined on integral and floating-point types. Same
11829 precedence as @code{++}.
11832 Logical negation. Defined on integral types. Same precedence as
11836 Bitwise complement operator. Defined on integral types. Same precedence as
11841 Structure member, and pointer-to-structure member. For convenience,
11842 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11843 pointer based on the stored type information.
11844 Defined on @code{struct} and @code{union} data.
11847 Dereferences of pointers to members.
11850 Array indexing. @code{@var{a}[@var{i}]} is defined as
11851 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11854 Function parameter list. Same precedence as @code{->}.
11857 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11858 and @code{class} types.
11861 Doubled colons also represent the @value{GDBN} scope operator
11862 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11866 If an operator is redefined in the user code, @value{GDBN} usually
11867 attempts to invoke the redefined version instead of using the operator's
11868 predefined meaning.
11871 @subsubsection C and C@t{++} Constants
11873 @cindex C and C@t{++} constants
11875 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11880 Integer constants are a sequence of digits. Octal constants are
11881 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11882 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11883 @samp{l}, specifying that the constant should be treated as a
11887 Floating point constants are a sequence of digits, followed by a decimal
11888 point, followed by a sequence of digits, and optionally followed by an
11889 exponent. An exponent is of the form:
11890 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11891 sequence of digits. The @samp{+} is optional for positive exponents.
11892 A floating-point constant may also end with a letter @samp{f} or
11893 @samp{F}, specifying that the constant should be treated as being of
11894 the @code{float} (as opposed to the default @code{double}) type; or with
11895 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11899 Enumerated constants consist of enumerated identifiers, or their
11900 integral equivalents.
11903 Character constants are a single character surrounded by single quotes
11904 (@code{'}), or a number---the ordinal value of the corresponding character
11905 (usually its @sc{ascii} value). Within quotes, the single character may
11906 be represented by a letter or by @dfn{escape sequences}, which are of
11907 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11908 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11909 @samp{@var{x}} is a predefined special character---for example,
11910 @samp{\n} for newline.
11913 String constants are a sequence of character constants surrounded by
11914 double quotes (@code{"}). Any valid character constant (as described
11915 above) may appear. Double quotes within the string must be preceded by
11916 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11920 Pointer constants are an integral value. You can also write pointers
11921 to constants using the C operator @samp{&}.
11924 Array constants are comma-separated lists surrounded by braces @samp{@{}
11925 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11926 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11927 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11930 @node C Plus Plus Expressions
11931 @subsubsection C@t{++} Expressions
11933 @cindex expressions in C@t{++}
11934 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11936 @cindex debugging C@t{++} programs
11937 @cindex C@t{++} compilers
11938 @cindex debug formats and C@t{++}
11939 @cindex @value{NGCC} and C@t{++}
11941 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11942 proper compiler and the proper debug format. Currently, @value{GDBN}
11943 works best when debugging C@t{++} code that is compiled with
11944 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11945 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11946 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11947 stabs+ as their default debug format, so you usually don't need to
11948 specify a debug format explicitly. Other compilers and/or debug formats
11949 are likely to work badly or not at all when using @value{GDBN} to debug
11955 @cindex member functions
11957 Member function calls are allowed; you can use expressions like
11960 count = aml->GetOriginal(x, y)
11963 @vindex this@r{, inside C@t{++} member functions}
11964 @cindex namespace in C@t{++}
11966 While a member function is active (in the selected stack frame), your
11967 expressions have the same namespace available as the member function;
11968 that is, @value{GDBN} allows implicit references to the class instance
11969 pointer @code{this} following the same rules as C@t{++}.
11971 @cindex call overloaded functions
11972 @cindex overloaded functions, calling
11973 @cindex type conversions in C@t{++}
11975 You can call overloaded functions; @value{GDBN} resolves the function
11976 call to the right definition, with some restrictions. @value{GDBN} does not
11977 perform overload resolution involving user-defined type conversions,
11978 calls to constructors, or instantiations of templates that do not exist
11979 in the program. It also cannot handle ellipsis argument lists or
11982 It does perform integral conversions and promotions, floating-point
11983 promotions, arithmetic conversions, pointer conversions, conversions of
11984 class objects to base classes, and standard conversions such as those of
11985 functions or arrays to pointers; it requires an exact match on the
11986 number of function arguments.
11988 Overload resolution is always performed, unless you have specified
11989 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11990 ,@value{GDBN} Features for C@t{++}}.
11992 You must specify @code{set overload-resolution off} in order to use an
11993 explicit function signature to call an overloaded function, as in
11995 p 'foo(char,int)'('x', 13)
11998 The @value{GDBN} command-completion facility can simplify this;
11999 see @ref{Completion, ,Command Completion}.
12001 @cindex reference declarations
12003 @value{GDBN} understands variables declared as C@t{++} references; you can use
12004 them in expressions just as you do in C@t{++} source---they are automatically
12007 In the parameter list shown when @value{GDBN} displays a frame, the values of
12008 reference variables are not displayed (unlike other variables); this
12009 avoids clutter, since references are often used for large structures.
12010 The @emph{address} of a reference variable is always shown, unless
12011 you have specified @samp{set print address off}.
12014 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12015 expressions can use it just as expressions in your program do. Since
12016 one scope may be defined in another, you can use @code{::} repeatedly if
12017 necessary, for example in an expression like
12018 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12019 resolving name scope by reference to source files, in both C and C@t{++}
12020 debugging (@pxref{Variables, ,Program Variables}).
12023 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12024 calling virtual functions correctly, printing out virtual bases of
12025 objects, calling functions in a base subobject, casting objects, and
12026 invoking user-defined operators.
12029 @subsubsection C and C@t{++} Defaults
12031 @cindex C and C@t{++} defaults
12033 If you allow @value{GDBN} to set type and range checking automatically, they
12034 both default to @code{off} whenever the working language changes to
12035 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12036 selects the working language.
12038 If you allow @value{GDBN} to set the language automatically, it
12039 recognizes source files whose names end with @file{.c}, @file{.C}, or
12040 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12041 these files, it sets the working language to C or C@t{++}.
12042 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12043 for further details.
12045 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12046 @c unimplemented. If (b) changes, it might make sense to let this node
12047 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12050 @subsubsection C and C@t{++} Type and Range Checks
12052 @cindex C and C@t{++} checks
12054 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12055 is not used. However, if you turn type checking on, @value{GDBN}
12056 considers two variables type equivalent if:
12060 The two variables are structured and have the same structure, union, or
12064 The two variables have the same type name, or types that have been
12065 declared equivalent through @code{typedef}.
12068 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12071 The two @code{struct}, @code{union}, or @code{enum} variables are
12072 declared in the same declaration. (Note: this may not be true for all C
12077 Range checking, if turned on, is done on mathematical operations. Array
12078 indices are not checked, since they are often used to index a pointer
12079 that is not itself an array.
12082 @subsubsection @value{GDBN} and C
12084 The @code{set print union} and @code{show print union} commands apply to
12085 the @code{union} type. When set to @samp{on}, any @code{union} that is
12086 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12087 appears as @samp{@{...@}}.
12089 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12090 with pointers and a memory allocation function. @xref{Expressions,
12093 @node Debugging C Plus Plus
12094 @subsubsection @value{GDBN} Features for C@t{++}
12096 @cindex commands for C@t{++}
12098 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12099 designed specifically for use with C@t{++}. Here is a summary:
12102 @cindex break in overloaded functions
12103 @item @r{breakpoint menus}
12104 When you want a breakpoint in a function whose name is overloaded,
12105 @value{GDBN} has the capability to display a menu of possible breakpoint
12106 locations to help you specify which function definition you want.
12107 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12109 @cindex overloading in C@t{++}
12110 @item rbreak @var{regex}
12111 Setting breakpoints using regular expressions is helpful for setting
12112 breakpoints on overloaded functions that are not members of any special
12114 @xref{Set Breaks, ,Setting Breakpoints}.
12116 @cindex C@t{++} exception handling
12119 Debug C@t{++} exception handling using these commands. @xref{Set
12120 Catchpoints, , Setting Catchpoints}.
12122 @cindex inheritance
12123 @item ptype @var{typename}
12124 Print inheritance relationships as well as other information for type
12126 @xref{Symbols, ,Examining the Symbol Table}.
12128 @cindex C@t{++} symbol display
12129 @item set print demangle
12130 @itemx show print demangle
12131 @itemx set print asm-demangle
12132 @itemx show print asm-demangle
12133 Control whether C@t{++} symbols display in their source form, both when
12134 displaying code as C@t{++} source and when displaying disassemblies.
12135 @xref{Print Settings, ,Print Settings}.
12137 @item set print object
12138 @itemx show print object
12139 Choose whether to print derived (actual) or declared types of objects.
12140 @xref{Print Settings, ,Print Settings}.
12142 @item set print vtbl
12143 @itemx show print vtbl
12144 Control the format for printing virtual function tables.
12145 @xref{Print Settings, ,Print Settings}.
12146 (The @code{vtbl} commands do not work on programs compiled with the HP
12147 ANSI C@t{++} compiler (@code{aCC}).)
12149 @kindex set overload-resolution
12150 @cindex overloaded functions, overload resolution
12151 @item set overload-resolution on
12152 Enable overload resolution for C@t{++} expression evaluation. The default
12153 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12154 and searches for a function whose signature matches the argument types,
12155 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12156 Expressions, ,C@t{++} Expressions}, for details).
12157 If it cannot find a match, it emits a message.
12159 @item set overload-resolution off
12160 Disable overload resolution for C@t{++} expression evaluation. For
12161 overloaded functions that are not class member functions, @value{GDBN}
12162 chooses the first function of the specified name that it finds in the
12163 symbol table, whether or not its arguments are of the correct type. For
12164 overloaded functions that are class member functions, @value{GDBN}
12165 searches for a function whose signature @emph{exactly} matches the
12168 @kindex show overload-resolution
12169 @item show overload-resolution
12170 Show the current setting of overload resolution.
12172 @item @r{Overloaded symbol names}
12173 You can specify a particular definition of an overloaded symbol, using
12174 the same notation that is used to declare such symbols in C@t{++}: type
12175 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12176 also use the @value{GDBN} command-line word completion facilities to list the
12177 available choices, or to finish the type list for you.
12178 @xref{Completion,, Command Completion}, for details on how to do this.
12181 @node Decimal Floating Point
12182 @subsubsection Decimal Floating Point format
12183 @cindex decimal floating point format
12185 @value{GDBN} can examine, set and perform computations with numbers in
12186 decimal floating point format, which in the C language correspond to the
12187 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12188 specified by the extension to support decimal floating-point arithmetic.
12190 There are two encodings in use, depending on the architecture: BID (Binary
12191 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12192 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12195 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12196 to manipulate decimal floating point numbers, it is not possible to convert
12197 (using a cast, for example) integers wider than 32-bit to decimal float.
12199 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12200 point computations, error checking in decimal float operations ignores
12201 underflow, overflow and divide by zero exceptions.
12203 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12204 to inspect @code{_Decimal128} values stored in floating point registers.
12205 See @ref{PowerPC,,PowerPC} for more details.
12211 @value{GDBN} can be used to debug programs written in D and compiled with
12212 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12213 specific feature --- dynamic arrays.
12216 @subsection Objective-C
12218 @cindex Objective-C
12219 This section provides information about some commands and command
12220 options that are useful for debugging Objective-C code. See also
12221 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12222 few more commands specific to Objective-C support.
12225 * Method Names in Commands::
12226 * The Print Command with Objective-C::
12229 @node Method Names in Commands
12230 @subsubsection Method Names in Commands
12232 The following commands have been extended to accept Objective-C method
12233 names as line specifications:
12235 @kindex clear@r{, and Objective-C}
12236 @kindex break@r{, and Objective-C}
12237 @kindex info line@r{, and Objective-C}
12238 @kindex jump@r{, and Objective-C}
12239 @kindex list@r{, and Objective-C}
12243 @item @code{info line}
12248 A fully qualified Objective-C method name is specified as
12251 -[@var{Class} @var{methodName}]
12254 where the minus sign is used to indicate an instance method and a
12255 plus sign (not shown) is used to indicate a class method. The class
12256 name @var{Class} and method name @var{methodName} are enclosed in
12257 brackets, similar to the way messages are specified in Objective-C
12258 source code. For example, to set a breakpoint at the @code{create}
12259 instance method of class @code{Fruit} in the program currently being
12263 break -[Fruit create]
12266 To list ten program lines around the @code{initialize} class method,
12270 list +[NSText initialize]
12273 In the current version of @value{GDBN}, the plus or minus sign is
12274 required. In future versions of @value{GDBN}, the plus or minus
12275 sign will be optional, but you can use it to narrow the search. It
12276 is also possible to specify just a method name:
12282 You must specify the complete method name, including any colons. If
12283 your program's source files contain more than one @code{create} method,
12284 you'll be presented with a numbered list of classes that implement that
12285 method. Indicate your choice by number, or type @samp{0} to exit if
12288 As another example, to clear a breakpoint established at the
12289 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12292 clear -[NSWindow makeKeyAndOrderFront:]
12295 @node The Print Command with Objective-C
12296 @subsubsection The Print Command With Objective-C
12297 @cindex Objective-C, print objects
12298 @kindex print-object
12299 @kindex po @r{(@code{print-object})}
12301 The print command has also been extended to accept methods. For example:
12304 print -[@var{object} hash]
12307 @cindex print an Objective-C object description
12308 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12310 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12311 and print the result. Also, an additional command has been added,
12312 @code{print-object} or @code{po} for short, which is meant to print
12313 the description of an object. However, this command may only work
12314 with certain Objective-C libraries that have a particular hook
12315 function, @code{_NSPrintForDebugger}, defined.
12318 @subsection OpenCL C
12321 This section provides information about @value{GDBN}s OpenCL C support.
12324 * OpenCL C Datatypes::
12325 * OpenCL C Expressions::
12326 * OpenCL C Operators::
12329 @node OpenCL C Datatypes
12330 @subsubsection OpenCL C Datatypes
12332 @cindex OpenCL C Datatypes
12333 @value{GDBN} supports the builtin scalar and vector datatypes specified
12334 by OpenCL 1.1. In addition the half- and double-precision floating point
12335 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12336 extensions are also known to @value{GDBN}.
12338 @node OpenCL C Expressions
12339 @subsubsection OpenCL C Expressions
12341 @cindex OpenCL C Expressions
12342 @value{GDBN} supports accesses to vector components including the access as
12343 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12344 supported by @value{GDBN} can be used as well.
12346 @node OpenCL C Operators
12347 @subsubsection OpenCL C Operators
12349 @cindex OpenCL C Operators
12350 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12354 @subsection Fortran
12355 @cindex Fortran-specific support in @value{GDBN}
12357 @value{GDBN} can be used to debug programs written in Fortran, but it
12358 currently supports only the features of Fortran 77 language.
12360 @cindex trailing underscore, in Fortran symbols
12361 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12362 among them) append an underscore to the names of variables and
12363 functions. When you debug programs compiled by those compilers, you
12364 will need to refer to variables and functions with a trailing
12368 * Fortran Operators:: Fortran operators and expressions
12369 * Fortran Defaults:: Default settings for Fortran
12370 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12373 @node Fortran Operators
12374 @subsubsection Fortran Operators and Expressions
12376 @cindex Fortran operators and expressions
12378 Operators must be defined on values of specific types. For instance,
12379 @code{+} is defined on numbers, but not on characters or other non-
12380 arithmetic types. Operators are often defined on groups of types.
12384 The exponentiation operator. It raises the first operand to the power
12388 The range operator. Normally used in the form of array(low:high) to
12389 represent a section of array.
12392 The access component operator. Normally used to access elements in derived
12393 types. Also suitable for unions. As unions aren't part of regular Fortran,
12394 this can only happen when accessing a register that uses a gdbarch-defined
12398 @node Fortran Defaults
12399 @subsubsection Fortran Defaults
12401 @cindex Fortran Defaults
12403 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12404 default uses case-insensitive matches for Fortran symbols. You can
12405 change that with the @samp{set case-insensitive} command, see
12406 @ref{Symbols}, for the details.
12408 @node Special Fortran Commands
12409 @subsubsection Special Fortran Commands
12411 @cindex Special Fortran commands
12413 @value{GDBN} has some commands to support Fortran-specific features,
12414 such as displaying common blocks.
12417 @cindex @code{COMMON} blocks, Fortran
12418 @kindex info common
12419 @item info common @r{[}@var{common-name}@r{]}
12420 This command prints the values contained in the Fortran @code{COMMON}
12421 block whose name is @var{common-name}. With no argument, the names of
12422 all @code{COMMON} blocks visible at the current program location are
12429 @cindex Pascal support in @value{GDBN}, limitations
12430 Debugging Pascal programs which use sets, subranges, file variables, or
12431 nested functions does not currently work. @value{GDBN} does not support
12432 entering expressions, printing values, or similar features using Pascal
12435 The Pascal-specific command @code{set print pascal_static-members}
12436 controls whether static members of Pascal objects are displayed.
12437 @xref{Print Settings, pascal_static-members}.
12440 @subsection Modula-2
12442 @cindex Modula-2, @value{GDBN} support
12444 The extensions made to @value{GDBN} to support Modula-2 only support
12445 output from the @sc{gnu} Modula-2 compiler (which is currently being
12446 developed). Other Modula-2 compilers are not currently supported, and
12447 attempting to debug executables produced by them is most likely
12448 to give an error as @value{GDBN} reads in the executable's symbol
12451 @cindex expressions in Modula-2
12453 * M2 Operators:: Built-in operators
12454 * Built-In Func/Proc:: Built-in functions and procedures
12455 * M2 Constants:: Modula-2 constants
12456 * M2 Types:: Modula-2 types
12457 * M2 Defaults:: Default settings for Modula-2
12458 * Deviations:: Deviations from standard Modula-2
12459 * M2 Checks:: Modula-2 type and range checks
12460 * M2 Scope:: The scope operators @code{::} and @code{.}
12461 * GDB/M2:: @value{GDBN} and Modula-2
12465 @subsubsection Operators
12466 @cindex Modula-2 operators
12468 Operators must be defined on values of specific types. For instance,
12469 @code{+} is defined on numbers, but not on structures. Operators are
12470 often defined on groups of types. For the purposes of Modula-2, the
12471 following definitions hold:
12476 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12480 @emph{Character types} consist of @code{CHAR} and its subranges.
12483 @emph{Floating-point types} consist of @code{REAL}.
12486 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12490 @emph{Scalar types} consist of all of the above.
12493 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12496 @emph{Boolean types} consist of @code{BOOLEAN}.
12500 The following operators are supported, and appear in order of
12501 increasing precedence:
12505 Function argument or array index separator.
12508 Assignment. The value of @var{var} @code{:=} @var{value} is
12512 Less than, greater than on integral, floating-point, or enumerated
12516 Less than or equal to, greater than or equal to
12517 on integral, floating-point and enumerated types, or set inclusion on
12518 set types. Same precedence as @code{<}.
12520 @item =@r{, }<>@r{, }#
12521 Equality and two ways of expressing inequality, valid on scalar types.
12522 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12523 available for inequality, since @code{#} conflicts with the script
12527 Set membership. Defined on set types and the types of their members.
12528 Same precedence as @code{<}.
12531 Boolean disjunction. Defined on boolean types.
12534 Boolean conjunction. Defined on boolean types.
12537 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12540 Addition and subtraction on integral and floating-point types, or union
12541 and difference on set types.
12544 Multiplication on integral and floating-point types, or set intersection
12548 Division on floating-point types, or symmetric set difference on set
12549 types. Same precedence as @code{*}.
12552 Integer division and remainder. Defined on integral types. Same
12553 precedence as @code{*}.
12556 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12559 Pointer dereferencing. Defined on pointer types.
12562 Boolean negation. Defined on boolean types. Same precedence as
12566 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12567 precedence as @code{^}.
12570 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12573 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12577 @value{GDBN} and Modula-2 scope operators.
12581 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12582 treats the use of the operator @code{IN}, or the use of operators
12583 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12584 @code{<=}, and @code{>=} on sets as an error.
12588 @node Built-In Func/Proc
12589 @subsubsection Built-in Functions and Procedures
12590 @cindex Modula-2 built-ins
12592 Modula-2 also makes available several built-in procedures and functions.
12593 In describing these, the following metavariables are used:
12598 represents an @code{ARRAY} variable.
12601 represents a @code{CHAR} constant or variable.
12604 represents a variable or constant of integral type.
12607 represents an identifier that belongs to a set. Generally used in the
12608 same function with the metavariable @var{s}. The type of @var{s} should
12609 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12612 represents a variable or constant of integral or floating-point type.
12615 represents a variable or constant of floating-point type.
12621 represents a variable.
12624 represents a variable or constant of one of many types. See the
12625 explanation of the function for details.
12628 All Modula-2 built-in procedures also return a result, described below.
12632 Returns the absolute value of @var{n}.
12635 If @var{c} is a lower case letter, it returns its upper case
12636 equivalent, otherwise it returns its argument.
12639 Returns the character whose ordinal value is @var{i}.
12642 Decrements the value in the variable @var{v} by one. Returns the new value.
12644 @item DEC(@var{v},@var{i})
12645 Decrements the value in the variable @var{v} by @var{i}. Returns the
12648 @item EXCL(@var{m},@var{s})
12649 Removes the element @var{m} from the set @var{s}. Returns the new
12652 @item FLOAT(@var{i})
12653 Returns the floating point equivalent of the integer @var{i}.
12655 @item HIGH(@var{a})
12656 Returns the index of the last member of @var{a}.
12659 Increments the value in the variable @var{v} by one. Returns the new value.
12661 @item INC(@var{v},@var{i})
12662 Increments the value in the variable @var{v} by @var{i}. Returns the
12665 @item INCL(@var{m},@var{s})
12666 Adds the element @var{m} to the set @var{s} if it is not already
12667 there. Returns the new set.
12670 Returns the maximum value of the type @var{t}.
12673 Returns the minimum value of the type @var{t}.
12676 Returns boolean TRUE if @var{i} is an odd number.
12679 Returns the ordinal value of its argument. For example, the ordinal
12680 value of a character is its @sc{ascii} value (on machines supporting the
12681 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12682 integral, character and enumerated types.
12684 @item SIZE(@var{x})
12685 Returns the size of its argument. @var{x} can be a variable or a type.
12687 @item TRUNC(@var{r})
12688 Returns the integral part of @var{r}.
12690 @item TSIZE(@var{x})
12691 Returns the size of its argument. @var{x} can be a variable or a type.
12693 @item VAL(@var{t},@var{i})
12694 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12698 @emph{Warning:} Sets and their operations are not yet supported, so
12699 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12703 @cindex Modula-2 constants
12705 @subsubsection Constants
12707 @value{GDBN} allows you to express the constants of Modula-2 in the following
12713 Integer constants are simply a sequence of digits. When used in an
12714 expression, a constant is interpreted to be type-compatible with the
12715 rest of the expression. Hexadecimal integers are specified by a
12716 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12719 Floating point constants appear as a sequence of digits, followed by a
12720 decimal point and another sequence of digits. An optional exponent can
12721 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12722 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12723 digits of the floating point constant must be valid decimal (base 10)
12727 Character constants consist of a single character enclosed by a pair of
12728 like quotes, either single (@code{'}) or double (@code{"}). They may
12729 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12730 followed by a @samp{C}.
12733 String constants consist of a sequence of characters enclosed by a
12734 pair of like quotes, either single (@code{'}) or double (@code{"}).
12735 Escape sequences in the style of C are also allowed. @xref{C
12736 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12740 Enumerated constants consist of an enumerated identifier.
12743 Boolean constants consist of the identifiers @code{TRUE} and
12747 Pointer constants consist of integral values only.
12750 Set constants are not yet supported.
12754 @subsubsection Modula-2 Types
12755 @cindex Modula-2 types
12757 Currently @value{GDBN} can print the following data types in Modula-2
12758 syntax: array types, record types, set types, pointer types, procedure
12759 types, enumerated types, subrange types and base types. You can also
12760 print the contents of variables declared using these type.
12761 This section gives a number of simple source code examples together with
12762 sample @value{GDBN} sessions.
12764 The first example contains the following section of code:
12773 and you can request @value{GDBN} to interrogate the type and value of
12774 @code{r} and @code{s}.
12777 (@value{GDBP}) print s
12779 (@value{GDBP}) ptype s
12781 (@value{GDBP}) print r
12783 (@value{GDBP}) ptype r
12788 Likewise if your source code declares @code{s} as:
12792 s: SET ['A'..'Z'] ;
12796 then you may query the type of @code{s} by:
12799 (@value{GDBP}) ptype s
12800 type = SET ['A'..'Z']
12804 Note that at present you cannot interactively manipulate set
12805 expressions using the debugger.
12807 The following example shows how you might declare an array in Modula-2
12808 and how you can interact with @value{GDBN} to print its type and contents:
12812 s: ARRAY [-10..10] OF CHAR ;
12816 (@value{GDBP}) ptype s
12817 ARRAY [-10..10] OF CHAR
12820 Note that the array handling is not yet complete and although the type
12821 is printed correctly, expression handling still assumes that all
12822 arrays have a lower bound of zero and not @code{-10} as in the example
12825 Here are some more type related Modula-2 examples:
12829 colour = (blue, red, yellow, green) ;
12830 t = [blue..yellow] ;
12838 The @value{GDBN} interaction shows how you can query the data type
12839 and value of a variable.
12842 (@value{GDBP}) print s
12844 (@value{GDBP}) ptype t
12845 type = [blue..yellow]
12849 In this example a Modula-2 array is declared and its contents
12850 displayed. Observe that the contents are written in the same way as
12851 their @code{C} counterparts.
12855 s: ARRAY [1..5] OF CARDINAL ;
12861 (@value{GDBP}) print s
12862 $1 = @{1, 0, 0, 0, 0@}
12863 (@value{GDBP}) ptype s
12864 type = ARRAY [1..5] OF CARDINAL
12867 The Modula-2 language interface to @value{GDBN} also understands
12868 pointer types as shown in this example:
12872 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12879 and you can request that @value{GDBN} describes the type of @code{s}.
12882 (@value{GDBP}) ptype s
12883 type = POINTER TO ARRAY [1..5] OF CARDINAL
12886 @value{GDBN} handles compound types as we can see in this example.
12887 Here we combine array types, record types, pointer types and subrange
12898 myarray = ARRAY myrange OF CARDINAL ;
12899 myrange = [-2..2] ;
12901 s: POINTER TO ARRAY myrange OF foo ;
12905 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12909 (@value{GDBP}) ptype s
12910 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12913 f3 : ARRAY [-2..2] OF CARDINAL;
12918 @subsubsection Modula-2 Defaults
12919 @cindex Modula-2 defaults
12921 If type and range checking are set automatically by @value{GDBN}, they
12922 both default to @code{on} whenever the working language changes to
12923 Modula-2. This happens regardless of whether you or @value{GDBN}
12924 selected the working language.
12926 If you allow @value{GDBN} to set the language automatically, then entering
12927 code compiled from a file whose name ends with @file{.mod} sets the
12928 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12929 Infer the Source Language}, for further details.
12932 @subsubsection Deviations from Standard Modula-2
12933 @cindex Modula-2, deviations from
12935 A few changes have been made to make Modula-2 programs easier to debug.
12936 This is done primarily via loosening its type strictness:
12940 Unlike in standard Modula-2, pointer constants can be formed by
12941 integers. This allows you to modify pointer variables during
12942 debugging. (In standard Modula-2, the actual address contained in a
12943 pointer variable is hidden from you; it can only be modified
12944 through direct assignment to another pointer variable or expression that
12945 returned a pointer.)
12948 C escape sequences can be used in strings and characters to represent
12949 non-printable characters. @value{GDBN} prints out strings with these
12950 escape sequences embedded. Single non-printable characters are
12951 printed using the @samp{CHR(@var{nnn})} format.
12954 The assignment operator (@code{:=}) returns the value of its right-hand
12958 All built-in procedures both modify @emph{and} return their argument.
12962 @subsubsection Modula-2 Type and Range Checks
12963 @cindex Modula-2 checks
12966 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12969 @c FIXME remove warning when type/range checks added
12971 @value{GDBN} considers two Modula-2 variables type equivalent if:
12975 They are of types that have been declared equivalent via a @code{TYPE
12976 @var{t1} = @var{t2}} statement
12979 They have been declared on the same line. (Note: This is true of the
12980 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12983 As long as type checking is enabled, any attempt to combine variables
12984 whose types are not equivalent is an error.
12986 Range checking is done on all mathematical operations, assignment, array
12987 index bounds, and all built-in functions and procedures.
12990 @subsubsection The Scope Operators @code{::} and @code{.}
12992 @cindex @code{.}, Modula-2 scope operator
12993 @cindex colon, doubled as scope operator
12995 @vindex colon-colon@r{, in Modula-2}
12996 @c Info cannot handle :: but TeX can.
12999 @vindex ::@r{, in Modula-2}
13002 There are a few subtle differences between the Modula-2 scope operator
13003 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13008 @var{module} . @var{id}
13009 @var{scope} :: @var{id}
13013 where @var{scope} is the name of a module or a procedure,
13014 @var{module} the name of a module, and @var{id} is any declared
13015 identifier within your program, except another module.
13017 Using the @code{::} operator makes @value{GDBN} search the scope
13018 specified by @var{scope} for the identifier @var{id}. If it is not
13019 found in the specified scope, then @value{GDBN} searches all scopes
13020 enclosing the one specified by @var{scope}.
13022 Using the @code{.} operator makes @value{GDBN} search the current scope for
13023 the identifier specified by @var{id} that was imported from the
13024 definition module specified by @var{module}. With this operator, it is
13025 an error if the identifier @var{id} was not imported from definition
13026 module @var{module}, or if @var{id} is not an identifier in
13030 @subsubsection @value{GDBN} and Modula-2
13032 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13033 Five subcommands of @code{set print} and @code{show print} apply
13034 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13035 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13036 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13037 analogue in Modula-2.
13039 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13040 with any language, is not useful with Modula-2. Its
13041 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13042 created in Modula-2 as they can in C or C@t{++}. However, because an
13043 address can be specified by an integral constant, the construct
13044 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13046 @cindex @code{#} in Modula-2
13047 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13048 interpreted as the beginning of a comment. Use @code{<>} instead.
13054 The extensions made to @value{GDBN} for Ada only support
13055 output from the @sc{gnu} Ada (GNAT) compiler.
13056 Other Ada compilers are not currently supported, and
13057 attempting to debug executables produced by them is most likely
13061 @cindex expressions in Ada
13063 * Ada Mode Intro:: General remarks on the Ada syntax
13064 and semantics supported by Ada mode
13066 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13067 * Additions to Ada:: Extensions of the Ada expression syntax.
13068 * Stopping Before Main Program:: Debugging the program during elaboration.
13069 * Ada Tasks:: Listing and setting breakpoints in tasks.
13070 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13071 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13073 * Ada Glitches:: Known peculiarities of Ada mode.
13076 @node Ada Mode Intro
13077 @subsubsection Introduction
13078 @cindex Ada mode, general
13080 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13081 syntax, with some extensions.
13082 The philosophy behind the design of this subset is
13086 That @value{GDBN} should provide basic literals and access to operations for
13087 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13088 leaving more sophisticated computations to subprograms written into the
13089 program (which therefore may be called from @value{GDBN}).
13092 That type safety and strict adherence to Ada language restrictions
13093 are not particularly important to the @value{GDBN} user.
13096 That brevity is important to the @value{GDBN} user.
13099 Thus, for brevity, the debugger acts as if all names declared in
13100 user-written packages are directly visible, even if they are not visible
13101 according to Ada rules, thus making it unnecessary to fully qualify most
13102 names with their packages, regardless of context. Where this causes
13103 ambiguity, @value{GDBN} asks the user's intent.
13105 The debugger will start in Ada mode if it detects an Ada main program.
13106 As for other languages, it will enter Ada mode when stopped in a program that
13107 was translated from an Ada source file.
13109 While in Ada mode, you may use `@t{--}' for comments. This is useful
13110 mostly for documenting command files. The standard @value{GDBN} comment
13111 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13112 middle (to allow based literals).
13114 The debugger supports limited overloading. Given a subprogram call in which
13115 the function symbol has multiple definitions, it will use the number of
13116 actual parameters and some information about their types to attempt to narrow
13117 the set of definitions. It also makes very limited use of context, preferring
13118 procedures to functions in the context of the @code{call} command, and
13119 functions to procedures elsewhere.
13121 @node Omissions from Ada
13122 @subsubsection Omissions from Ada
13123 @cindex Ada, omissions from
13125 Here are the notable omissions from the subset:
13129 Only a subset of the attributes are supported:
13133 @t{'First}, @t{'Last}, and @t{'Length}
13134 on array objects (not on types and subtypes).
13137 @t{'Min} and @t{'Max}.
13140 @t{'Pos} and @t{'Val}.
13146 @t{'Range} on array objects (not subtypes), but only as the right
13147 operand of the membership (@code{in}) operator.
13150 @t{'Access}, @t{'Unchecked_Access}, and
13151 @t{'Unrestricted_Access} (a GNAT extension).
13159 @code{Characters.Latin_1} are not available and
13160 concatenation is not implemented. Thus, escape characters in strings are
13161 not currently available.
13164 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13165 equality of representations. They will generally work correctly
13166 for strings and arrays whose elements have integer or enumeration types.
13167 They may not work correctly for arrays whose element
13168 types have user-defined equality, for arrays of real values
13169 (in particular, IEEE-conformant floating point, because of negative
13170 zeroes and NaNs), and for arrays whose elements contain unused bits with
13171 indeterminate values.
13174 The other component-by-component array operations (@code{and}, @code{or},
13175 @code{xor}, @code{not}, and relational tests other than equality)
13176 are not implemented.
13179 @cindex array aggregates (Ada)
13180 @cindex record aggregates (Ada)
13181 @cindex aggregates (Ada)
13182 There is limited support for array and record aggregates. They are
13183 permitted only on the right sides of assignments, as in these examples:
13186 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13187 (@value{GDBP}) set An_Array := (1, others => 0)
13188 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13189 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13190 (@value{GDBP}) set A_Record := (1, "Peter", True);
13191 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13195 discriminant's value by assigning an aggregate has an
13196 undefined effect if that discriminant is used within the record.
13197 However, you can first modify discriminants by directly assigning to
13198 them (which normally would not be allowed in Ada), and then performing an
13199 aggregate assignment. For example, given a variable @code{A_Rec}
13200 declared to have a type such as:
13203 type Rec (Len : Small_Integer := 0) is record
13205 Vals : IntArray (1 .. Len);
13209 you can assign a value with a different size of @code{Vals} with two
13213 (@value{GDBP}) set A_Rec.Len := 4
13214 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13217 As this example also illustrates, @value{GDBN} is very loose about the usual
13218 rules concerning aggregates. You may leave out some of the
13219 components of an array or record aggregate (such as the @code{Len}
13220 component in the assignment to @code{A_Rec} above); they will retain their
13221 original values upon assignment. You may freely use dynamic values as
13222 indices in component associations. You may even use overlapping or
13223 redundant component associations, although which component values are
13224 assigned in such cases is not defined.
13227 Calls to dispatching subprograms are not implemented.
13230 The overloading algorithm is much more limited (i.e., less selective)
13231 than that of real Ada. It makes only limited use of the context in
13232 which a subexpression appears to resolve its meaning, and it is much
13233 looser in its rules for allowing type matches. As a result, some
13234 function calls will be ambiguous, and the user will be asked to choose
13235 the proper resolution.
13238 The @code{new} operator is not implemented.
13241 Entry calls are not implemented.
13244 Aside from printing, arithmetic operations on the native VAX floating-point
13245 formats are not supported.
13248 It is not possible to slice a packed array.
13251 The names @code{True} and @code{False}, when not part of a qualified name,
13252 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13254 Should your program
13255 redefine these names in a package or procedure (at best a dubious practice),
13256 you will have to use fully qualified names to access their new definitions.
13259 @node Additions to Ada
13260 @subsubsection Additions to Ada
13261 @cindex Ada, deviations from
13263 As it does for other languages, @value{GDBN} makes certain generic
13264 extensions to Ada (@pxref{Expressions}):
13268 If the expression @var{E} is a variable residing in memory (typically
13269 a local variable or array element) and @var{N} is a positive integer,
13270 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13271 @var{N}-1 adjacent variables following it in memory as an array. In
13272 Ada, this operator is generally not necessary, since its prime use is
13273 in displaying parts of an array, and slicing will usually do this in
13274 Ada. However, there are occasional uses when debugging programs in
13275 which certain debugging information has been optimized away.
13278 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13279 appears in function or file @var{B}.'' When @var{B} is a file name,
13280 you must typically surround it in single quotes.
13283 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13284 @var{type} that appears at address @var{addr}.''
13287 A name starting with @samp{$} is a convenience variable
13288 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13291 In addition, @value{GDBN} provides a few other shortcuts and outright
13292 additions specific to Ada:
13296 The assignment statement is allowed as an expression, returning
13297 its right-hand operand as its value. Thus, you may enter
13300 (@value{GDBP}) set x := y + 3
13301 (@value{GDBP}) print A(tmp := y + 1)
13305 The semicolon is allowed as an ``operator,'' returning as its value
13306 the value of its right-hand operand.
13307 This allows, for example,
13308 complex conditional breaks:
13311 (@value{GDBP}) break f
13312 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13316 Rather than use catenation and symbolic character names to introduce special
13317 characters into strings, one may instead use a special bracket notation,
13318 which is also used to print strings. A sequence of characters of the form
13319 @samp{["@var{XX}"]} within a string or character literal denotes the
13320 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13321 sequence of characters @samp{["""]} also denotes a single quotation mark
13322 in strings. For example,
13324 "One line.["0a"]Next line.["0a"]"
13327 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13331 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13332 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13336 (@value{GDBP}) print 'max(x, y)
13340 When printing arrays, @value{GDBN} uses positional notation when the
13341 array has a lower bound of 1, and uses a modified named notation otherwise.
13342 For example, a one-dimensional array of three integers with a lower bound
13343 of 3 might print as
13350 That is, in contrast to valid Ada, only the first component has a @code{=>}
13354 You may abbreviate attributes in expressions with any unique,
13355 multi-character subsequence of
13356 their names (an exact match gets preference).
13357 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13358 in place of @t{a'length}.
13361 @cindex quoting Ada internal identifiers
13362 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13363 to lower case. The GNAT compiler uses upper-case characters for
13364 some of its internal identifiers, which are normally of no interest to users.
13365 For the rare occasions when you actually have to look at them,
13366 enclose them in angle brackets to avoid the lower-case mapping.
13369 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13373 Printing an object of class-wide type or dereferencing an
13374 access-to-class-wide value will display all the components of the object's
13375 specific type (as indicated by its run-time tag). Likewise, component
13376 selection on such a value will operate on the specific type of the
13381 @node Stopping Before Main Program
13382 @subsubsection Stopping at the Very Beginning
13384 @cindex breakpointing Ada elaboration code
13385 It is sometimes necessary to debug the program during elaboration, and
13386 before reaching the main procedure.
13387 As defined in the Ada Reference
13388 Manual, the elaboration code is invoked from a procedure called
13389 @code{adainit}. To run your program up to the beginning of
13390 elaboration, simply use the following two commands:
13391 @code{tbreak adainit} and @code{run}.
13394 @subsubsection Extensions for Ada Tasks
13395 @cindex Ada, tasking
13397 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13398 @value{GDBN} provides the following task-related commands:
13403 This command shows a list of current Ada tasks, as in the following example:
13410 (@value{GDBP}) info tasks
13411 ID TID P-ID Pri State Name
13412 1 8088000 0 15 Child Activation Wait main_task
13413 2 80a4000 1 15 Accept Statement b
13414 3 809a800 1 15 Child Activation Wait a
13415 * 4 80ae800 3 15 Runnable c
13420 In this listing, the asterisk before the last task indicates it to be the
13421 task currently being inspected.
13425 Represents @value{GDBN}'s internal task number.
13431 The parent's task ID (@value{GDBN}'s internal task number).
13434 The base priority of the task.
13437 Current state of the task.
13441 The task has been created but has not been activated. It cannot be
13445 The task is not blocked for any reason known to Ada. (It may be waiting
13446 for a mutex, though.) It is conceptually "executing" in normal mode.
13449 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13450 that were waiting on terminate alternatives have been awakened and have
13451 terminated themselves.
13453 @item Child Activation Wait
13454 The task is waiting for created tasks to complete activation.
13456 @item Accept Statement
13457 The task is waiting on an accept or selective wait statement.
13459 @item Waiting on entry call
13460 The task is waiting on an entry call.
13462 @item Async Select Wait
13463 The task is waiting to start the abortable part of an asynchronous
13467 The task is waiting on a select statement with only a delay
13470 @item Child Termination Wait
13471 The task is sleeping having completed a master within itself, and is
13472 waiting for the tasks dependent on that master to become terminated or
13473 waiting on a terminate Phase.
13475 @item Wait Child in Term Alt
13476 The task is sleeping waiting for tasks on terminate alternatives to
13477 finish terminating.
13479 @item Accepting RV with @var{taskno}
13480 The task is accepting a rendez-vous with the task @var{taskno}.
13484 Name of the task in the program.
13488 @kindex info task @var{taskno}
13489 @item info task @var{taskno}
13490 This command shows detailled informations on the specified task, as in
13491 the following example:
13496 (@value{GDBP}) info tasks
13497 ID TID P-ID Pri State Name
13498 1 8077880 0 15 Child Activation Wait main_task
13499 * 2 807c468 1 15 Runnable task_1
13500 (@value{GDBP}) info task 2
13501 Ada Task: 0x807c468
13504 Parent: 1 (main_task)
13510 @kindex task@r{ (Ada)}
13511 @cindex current Ada task ID
13512 This command prints the ID of the current task.
13518 (@value{GDBP}) info tasks
13519 ID TID P-ID Pri State Name
13520 1 8077870 0 15 Child Activation Wait main_task
13521 * 2 807c458 1 15 Runnable t
13522 (@value{GDBP}) task
13523 [Current task is 2]
13526 @item task @var{taskno}
13527 @cindex Ada task switching
13528 This command is like the @code{thread @var{threadno}}
13529 command (@pxref{Threads}). It switches the context of debugging
13530 from the current task to the given task.
13536 (@value{GDBP}) info tasks
13537 ID TID P-ID Pri State Name
13538 1 8077870 0 15 Child Activation Wait main_task
13539 * 2 807c458 1 15 Runnable t
13540 (@value{GDBP}) task 1
13541 [Switching to task 1]
13542 #0 0x8067726 in pthread_cond_wait ()
13544 #0 0x8067726 in pthread_cond_wait ()
13545 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13546 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13547 #3 0x806153e in system.tasking.stages.activate_tasks ()
13548 #4 0x804aacc in un () at un.adb:5
13551 @item break @var{linespec} task @var{taskno}
13552 @itemx break @var{linespec} task @var{taskno} if @dots{}
13553 @cindex breakpoints and tasks, in Ada
13554 @cindex task breakpoints, in Ada
13555 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13556 These commands are like the @code{break @dots{} thread @dots{}}
13557 command (@pxref{Thread Stops}).
13558 @var{linespec} specifies source lines, as described
13559 in @ref{Specify Location}.
13561 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13562 to specify that you only want @value{GDBN} to stop the program when a
13563 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13564 numeric task identifiers assigned by @value{GDBN}, shown in the first
13565 column of the @samp{info tasks} display.
13567 If you do not specify @samp{task @var{taskno}} when you set a
13568 breakpoint, the breakpoint applies to @emph{all} tasks of your
13571 You can use the @code{task} qualifier on conditional breakpoints as
13572 well; in this case, place @samp{task @var{taskno}} before the
13573 breakpoint condition (before the @code{if}).
13581 (@value{GDBP}) info tasks
13582 ID TID P-ID Pri State Name
13583 1 140022020 0 15 Child Activation Wait main_task
13584 2 140045060 1 15 Accept/Select Wait t2
13585 3 140044840 1 15 Runnable t1
13586 * 4 140056040 1 15 Runnable t3
13587 (@value{GDBP}) b 15 task 2
13588 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13589 (@value{GDBP}) cont
13594 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13596 (@value{GDBP}) info tasks
13597 ID TID P-ID Pri State Name
13598 1 140022020 0 15 Child Activation Wait main_task
13599 * 2 140045060 1 15 Runnable t2
13600 3 140044840 1 15 Runnable t1
13601 4 140056040 1 15 Delay Sleep t3
13605 @node Ada Tasks and Core Files
13606 @subsubsection Tasking Support when Debugging Core Files
13607 @cindex Ada tasking and core file debugging
13609 When inspecting a core file, as opposed to debugging a live program,
13610 tasking support may be limited or even unavailable, depending on
13611 the platform being used.
13612 For instance, on x86-linux, the list of tasks is available, but task
13613 switching is not supported. On Tru64, however, task switching will work
13616 On certain platforms, including Tru64, the debugger needs to perform some
13617 memory writes in order to provide Ada tasking support. When inspecting
13618 a core file, this means that the core file must be opened with read-write
13619 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13620 Under these circumstances, you should make a backup copy of the core
13621 file before inspecting it with @value{GDBN}.
13623 @node Ravenscar Profile
13624 @subsubsection Tasking Support when using the Ravenscar Profile
13625 @cindex Ravenscar Profile
13627 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13628 specifically designed for systems with safety-critical real-time
13632 @kindex set ravenscar task-switching on
13633 @cindex task switching with program using Ravenscar Profile
13634 @item set ravenscar task-switching on
13635 Allows task switching when debugging a program that uses the Ravenscar
13636 Profile. This is the default.
13638 @kindex set ravenscar task-switching off
13639 @item set ravenscar task-switching off
13640 Turn off task switching when debugging a program that uses the Ravenscar
13641 Profile. This is mostly intended to disable the code that adds support
13642 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13643 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13644 To be effective, this command should be run before the program is started.
13646 @kindex show ravenscar task-switching
13647 @item show ravenscar task-switching
13648 Show whether it is possible to switch from task to task in a program
13649 using the Ravenscar Profile.
13654 @subsubsection Known Peculiarities of Ada Mode
13655 @cindex Ada, problems
13657 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13658 we know of several problems with and limitations of Ada mode in
13660 some of which will be fixed with planned future releases of the debugger
13661 and the GNU Ada compiler.
13665 Static constants that the compiler chooses not to materialize as objects in
13666 storage are invisible to the debugger.
13669 Named parameter associations in function argument lists are ignored (the
13670 argument lists are treated as positional).
13673 Many useful library packages are currently invisible to the debugger.
13676 Fixed-point arithmetic, conversions, input, and output is carried out using
13677 floating-point arithmetic, and may give results that only approximate those on
13681 The GNAT compiler never generates the prefix @code{Standard} for any of
13682 the standard symbols defined by the Ada language. @value{GDBN} knows about
13683 this: it will strip the prefix from names when you use it, and will never
13684 look for a name you have so qualified among local symbols, nor match against
13685 symbols in other packages or subprograms. If you have
13686 defined entities anywhere in your program other than parameters and
13687 local variables whose simple names match names in @code{Standard},
13688 GNAT's lack of qualification here can cause confusion. When this happens,
13689 you can usually resolve the confusion
13690 by qualifying the problematic names with package
13691 @code{Standard} explicitly.
13694 Older versions of the compiler sometimes generate erroneous debugging
13695 information, resulting in the debugger incorrectly printing the value
13696 of affected entities. In some cases, the debugger is able to work
13697 around an issue automatically. In other cases, the debugger is able
13698 to work around the issue, but the work-around has to be specifically
13701 @kindex set ada trust-PAD-over-XVS
13702 @kindex show ada trust-PAD-over-XVS
13705 @item set ada trust-PAD-over-XVS on
13706 Configure GDB to strictly follow the GNAT encoding when computing the
13707 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13708 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13709 a complete description of the encoding used by the GNAT compiler).
13710 This is the default.
13712 @item set ada trust-PAD-over-XVS off
13713 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13714 sometimes prints the wrong value for certain entities, changing @code{ada
13715 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13716 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13717 @code{off}, but this incurs a slight performance penalty, so it is
13718 recommended to leave this setting to @code{on} unless necessary.
13722 @node Unsupported Languages
13723 @section Unsupported Languages
13725 @cindex unsupported languages
13726 @cindex minimal language
13727 In addition to the other fully-supported programming languages,
13728 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13729 It does not represent a real programming language, but provides a set
13730 of capabilities close to what the C or assembly languages provide.
13731 This should allow most simple operations to be performed while debugging
13732 an application that uses a language currently not supported by @value{GDBN}.
13734 If the language is set to @code{auto}, @value{GDBN} will automatically
13735 select this language if the current frame corresponds to an unsupported
13739 @chapter Examining the Symbol Table
13741 The commands described in this chapter allow you to inquire about the
13742 symbols (names of variables, functions and types) defined in your
13743 program. This information is inherent in the text of your program and
13744 does not change as your program executes. @value{GDBN} finds it in your
13745 program's symbol table, in the file indicated when you started @value{GDBN}
13746 (@pxref{File Options, ,Choosing Files}), or by one of the
13747 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13749 @cindex symbol names
13750 @cindex names of symbols
13751 @cindex quoting names
13752 Occasionally, you may need to refer to symbols that contain unusual
13753 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13754 most frequent case is in referring to static variables in other
13755 source files (@pxref{Variables,,Program Variables}). File names
13756 are recorded in object files as debugging symbols, but @value{GDBN} would
13757 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13758 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13759 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13766 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13769 @cindex case-insensitive symbol names
13770 @cindex case sensitivity in symbol names
13771 @kindex set case-sensitive
13772 @item set case-sensitive on
13773 @itemx set case-sensitive off
13774 @itemx set case-sensitive auto
13775 Normally, when @value{GDBN} looks up symbols, it matches their names
13776 with case sensitivity determined by the current source language.
13777 Occasionally, you may wish to control that. The command @code{set
13778 case-sensitive} lets you do that by specifying @code{on} for
13779 case-sensitive matches or @code{off} for case-insensitive ones. If
13780 you specify @code{auto}, case sensitivity is reset to the default
13781 suitable for the source language. The default is case-sensitive
13782 matches for all languages except for Fortran, for which the default is
13783 case-insensitive matches.
13785 @kindex show case-sensitive
13786 @item show case-sensitive
13787 This command shows the current setting of case sensitivity for symbols
13790 @kindex info address
13791 @cindex address of a symbol
13792 @item info address @var{symbol}
13793 Describe where the data for @var{symbol} is stored. For a register
13794 variable, this says which register it is kept in. For a non-register
13795 local variable, this prints the stack-frame offset at which the variable
13798 Note the contrast with @samp{print &@var{symbol}}, which does not work
13799 at all for a register variable, and for a stack local variable prints
13800 the exact address of the current instantiation of the variable.
13802 @kindex info symbol
13803 @cindex symbol from address
13804 @cindex closest symbol and offset for an address
13805 @item info symbol @var{addr}
13806 Print the name of a symbol which is stored at the address @var{addr}.
13807 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13808 nearest symbol and an offset from it:
13811 (@value{GDBP}) info symbol 0x54320
13812 _initialize_vx + 396 in section .text
13816 This is the opposite of the @code{info address} command. You can use
13817 it to find out the name of a variable or a function given its address.
13819 For dynamically linked executables, the name of executable or shared
13820 library containing the symbol is also printed:
13823 (@value{GDBP}) info symbol 0x400225
13824 _start + 5 in section .text of /tmp/a.out
13825 (@value{GDBP}) info symbol 0x2aaaac2811cf
13826 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13830 @item whatis [@var{arg}]
13831 Print the data type of @var{arg}, which can be either an expression or
13832 a data type. With no argument, print the data type of @code{$}, the
13833 last value in the value history. If @var{arg} is an expression, it is
13834 not actually evaluated, and any side-effecting operations (such as
13835 assignments or function calls) inside it do not take place. If
13836 @var{arg} is a type name, it may be the name of a type or typedef, or
13837 for C code it may have the form @samp{class @var{class-name}},
13838 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13839 @samp{enum @var{enum-tag}}.
13840 @xref{Expressions, ,Expressions}.
13843 @item ptype [@var{arg}]
13844 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13845 detailed description of the type, instead of just the name of the type.
13846 @xref{Expressions, ,Expressions}.
13848 For example, for this variable declaration:
13851 struct complex @{double real; double imag;@} v;
13855 the two commands give this output:
13859 (@value{GDBP}) whatis v
13860 type = struct complex
13861 (@value{GDBP}) ptype v
13862 type = struct complex @{
13870 As with @code{whatis}, using @code{ptype} without an argument refers to
13871 the type of @code{$}, the last value in the value history.
13873 @cindex incomplete type
13874 Sometimes, programs use opaque data types or incomplete specifications
13875 of complex data structure. If the debug information included in the
13876 program does not allow @value{GDBN} to display a full declaration of
13877 the data type, it will say @samp{<incomplete type>}. For example,
13878 given these declarations:
13882 struct foo *fooptr;
13886 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13889 (@value{GDBP}) ptype foo
13890 $1 = <incomplete type>
13894 ``Incomplete type'' is C terminology for data types that are not
13895 completely specified.
13898 @item info types @var{regexp}
13900 Print a brief description of all types whose names match the regular
13901 expression @var{regexp} (or all types in your program, if you supply
13902 no argument). Each complete typename is matched as though it were a
13903 complete line; thus, @samp{i type value} gives information on all
13904 types in your program whose names include the string @code{value}, but
13905 @samp{i type ^value$} gives information only on types whose complete
13906 name is @code{value}.
13908 This command differs from @code{ptype} in two ways: first, like
13909 @code{whatis}, it does not print a detailed description; second, it
13910 lists all source files where a type is defined.
13913 @cindex local variables
13914 @item info scope @var{location}
13915 List all the variables local to a particular scope. This command
13916 accepts a @var{location} argument---a function name, a source line, or
13917 an address preceded by a @samp{*}, and prints all the variables local
13918 to the scope defined by that location. (@xref{Specify Location}, for
13919 details about supported forms of @var{location}.) For example:
13922 (@value{GDBP}) @b{info scope command_line_handler}
13923 Scope for command_line_handler:
13924 Symbol rl is an argument at stack/frame offset 8, length 4.
13925 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13926 Symbol linelength is in static storage at address 0x150a1c, length 4.
13927 Symbol p is a local variable in register $esi, length 4.
13928 Symbol p1 is a local variable in register $ebx, length 4.
13929 Symbol nline is a local variable in register $edx, length 4.
13930 Symbol repeat is a local variable at frame offset -8, length 4.
13934 This command is especially useful for determining what data to collect
13935 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13938 @kindex info source
13940 Show information about the current source file---that is, the source file for
13941 the function containing the current point of execution:
13944 the name of the source file, and the directory containing it,
13946 the directory it was compiled in,
13948 its length, in lines,
13950 which programming language it is written in,
13952 whether the executable includes debugging information for that file, and
13953 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13955 whether the debugging information includes information about
13956 preprocessor macros.
13960 @kindex info sources
13962 Print the names of all source files in your program for which there is
13963 debugging information, organized into two lists: files whose symbols
13964 have already been read, and files whose symbols will be read when needed.
13966 @kindex info functions
13967 @item info functions
13968 Print the names and data types of all defined functions.
13970 @item info functions @var{regexp}
13971 Print the names and data types of all defined functions
13972 whose names contain a match for regular expression @var{regexp}.
13973 Thus, @samp{info fun step} finds all functions whose names
13974 include @code{step}; @samp{info fun ^step} finds those whose names
13975 start with @code{step}. If a function name contains characters
13976 that conflict with the regular expression language (e.g.@:
13977 @samp{operator*()}), they may be quoted with a backslash.
13979 @kindex info variables
13980 @item info variables
13981 Print the names and data types of all variables that are defined
13982 outside of functions (i.e.@: excluding local variables).
13984 @item info variables @var{regexp}
13985 Print the names and data types of all variables (except for local
13986 variables) whose names contain a match for regular expression
13989 @kindex info classes
13990 @cindex Objective-C, classes and selectors
13992 @itemx info classes @var{regexp}
13993 Display all Objective-C classes in your program, or
13994 (with the @var{regexp} argument) all those matching a particular regular
13997 @kindex info selectors
13998 @item info selectors
13999 @itemx info selectors @var{regexp}
14000 Display all Objective-C selectors in your program, or
14001 (with the @var{regexp} argument) all those matching a particular regular
14005 This was never implemented.
14006 @kindex info methods
14008 @itemx info methods @var{regexp}
14009 The @code{info methods} command permits the user to examine all defined
14010 methods within C@t{++} program, or (with the @var{regexp} argument) a
14011 specific set of methods found in the various C@t{++} classes. Many
14012 C@t{++} classes provide a large number of methods. Thus, the output
14013 from the @code{ptype} command can be overwhelming and hard to use. The
14014 @code{info-methods} command filters the methods, printing only those
14015 which match the regular-expression @var{regexp}.
14018 @cindex reloading symbols
14019 Some systems allow individual object files that make up your program to
14020 be replaced without stopping and restarting your program. For example,
14021 in VxWorks you can simply recompile a defective object file and keep on
14022 running. If you are running on one of these systems, you can allow
14023 @value{GDBN} to reload the symbols for automatically relinked modules:
14026 @kindex set symbol-reloading
14027 @item set symbol-reloading on
14028 Replace symbol definitions for the corresponding source file when an
14029 object file with a particular name is seen again.
14031 @item set symbol-reloading off
14032 Do not replace symbol definitions when encountering object files of the
14033 same name more than once. This is the default state; if you are not
14034 running on a system that permits automatic relinking of modules, you
14035 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14036 may discard symbols when linking large programs, that may contain
14037 several modules (from different directories or libraries) with the same
14040 @kindex show symbol-reloading
14041 @item show symbol-reloading
14042 Show the current @code{on} or @code{off} setting.
14045 @cindex opaque data types
14046 @kindex set opaque-type-resolution
14047 @item set opaque-type-resolution on
14048 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14049 declared as a pointer to a @code{struct}, @code{class}, or
14050 @code{union}---for example, @code{struct MyType *}---that is used in one
14051 source file although the full declaration of @code{struct MyType} is in
14052 another source file. The default is on.
14054 A change in the setting of this subcommand will not take effect until
14055 the next time symbols for a file are loaded.
14057 @item set opaque-type-resolution off
14058 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14059 is printed as follows:
14061 @{<no data fields>@}
14064 @kindex show opaque-type-resolution
14065 @item show opaque-type-resolution
14066 Show whether opaque types are resolved or not.
14068 @kindex maint print symbols
14069 @cindex symbol dump
14070 @kindex maint print psymbols
14071 @cindex partial symbol dump
14072 @item maint print symbols @var{filename}
14073 @itemx maint print psymbols @var{filename}
14074 @itemx maint print msymbols @var{filename}
14075 Write a dump of debugging symbol data into the file @var{filename}.
14076 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14077 symbols with debugging data are included. If you use @samp{maint print
14078 symbols}, @value{GDBN} includes all the symbols for which it has already
14079 collected full details: that is, @var{filename} reflects symbols for
14080 only those files whose symbols @value{GDBN} has read. You can use the
14081 command @code{info sources} to find out which files these are. If you
14082 use @samp{maint print psymbols} instead, the dump shows information about
14083 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14084 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14085 @samp{maint print msymbols} dumps just the minimal symbol information
14086 required for each object file from which @value{GDBN} has read some symbols.
14087 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14088 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14090 @kindex maint info symtabs
14091 @kindex maint info psymtabs
14092 @cindex listing @value{GDBN}'s internal symbol tables
14093 @cindex symbol tables, listing @value{GDBN}'s internal
14094 @cindex full symbol tables, listing @value{GDBN}'s internal
14095 @cindex partial symbol tables, listing @value{GDBN}'s internal
14096 @item maint info symtabs @r{[} @var{regexp} @r{]}
14097 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14099 List the @code{struct symtab} or @code{struct partial_symtab}
14100 structures whose names match @var{regexp}. If @var{regexp} is not
14101 given, list them all. The output includes expressions which you can
14102 copy into a @value{GDBN} debugging this one to examine a particular
14103 structure in more detail. For example:
14106 (@value{GDBP}) maint info psymtabs dwarf2read
14107 @{ objfile /home/gnu/build/gdb/gdb
14108 ((struct objfile *) 0x82e69d0)
14109 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14110 ((struct partial_symtab *) 0x8474b10)
14113 text addresses 0x814d3c8 -- 0x8158074
14114 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14115 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14116 dependencies (none)
14119 (@value{GDBP}) maint info symtabs
14123 We see that there is one partial symbol table whose filename contains
14124 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14125 and we see that @value{GDBN} has not read in any symtabs yet at all.
14126 If we set a breakpoint on a function, that will cause @value{GDBN} to
14127 read the symtab for the compilation unit containing that function:
14130 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14131 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14133 (@value{GDBP}) maint info symtabs
14134 @{ objfile /home/gnu/build/gdb/gdb
14135 ((struct objfile *) 0x82e69d0)
14136 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14137 ((struct symtab *) 0x86c1f38)
14140 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14141 linetable ((struct linetable *) 0x8370fa0)
14142 debugformat DWARF 2
14151 @chapter Altering Execution
14153 Once you think you have found an error in your program, you might want to
14154 find out for certain whether correcting the apparent error would lead to
14155 correct results in the rest of the run. You can find the answer by
14156 experiment, using the @value{GDBN} features for altering execution of the
14159 For example, you can store new values into variables or memory
14160 locations, give your program a signal, restart it at a different
14161 address, or even return prematurely from a function.
14164 * Assignment:: Assignment to variables
14165 * Jumping:: Continuing at a different address
14166 * Signaling:: Giving your program a signal
14167 * Returning:: Returning from a function
14168 * Calling:: Calling your program's functions
14169 * Patching:: Patching your program
14173 @section Assignment to Variables
14176 @cindex setting variables
14177 To alter the value of a variable, evaluate an assignment expression.
14178 @xref{Expressions, ,Expressions}. For example,
14185 stores the value 4 into the variable @code{x}, and then prints the
14186 value of the assignment expression (which is 4).
14187 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14188 information on operators in supported languages.
14190 @kindex set variable
14191 @cindex variables, setting
14192 If you are not interested in seeing the value of the assignment, use the
14193 @code{set} command instead of the @code{print} command. @code{set} is
14194 really the same as @code{print} except that the expression's value is
14195 not printed and is not put in the value history (@pxref{Value History,
14196 ,Value History}). The expression is evaluated only for its effects.
14198 If the beginning of the argument string of the @code{set} command
14199 appears identical to a @code{set} subcommand, use the @code{set
14200 variable} command instead of just @code{set}. This command is identical
14201 to @code{set} except for its lack of subcommands. For example, if your
14202 program has a variable @code{width}, you get an error if you try to set
14203 a new value with just @samp{set width=13}, because @value{GDBN} has the
14204 command @code{set width}:
14207 (@value{GDBP}) whatis width
14209 (@value{GDBP}) p width
14211 (@value{GDBP}) set width=47
14212 Invalid syntax in expression.
14216 The invalid expression, of course, is @samp{=47}. In
14217 order to actually set the program's variable @code{width}, use
14220 (@value{GDBP}) set var width=47
14223 Because the @code{set} command has many subcommands that can conflict
14224 with the names of program variables, it is a good idea to use the
14225 @code{set variable} command instead of just @code{set}. For example, if
14226 your program has a variable @code{g}, you run into problems if you try
14227 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14228 the command @code{set gnutarget}, abbreviated @code{set g}:
14232 (@value{GDBP}) whatis g
14236 (@value{GDBP}) set g=4
14240 The program being debugged has been started already.
14241 Start it from the beginning? (y or n) y
14242 Starting program: /home/smith/cc_progs/a.out
14243 "/home/smith/cc_progs/a.out": can't open to read symbols:
14244 Invalid bfd target.
14245 (@value{GDBP}) show g
14246 The current BFD target is "=4".
14251 The program variable @code{g} did not change, and you silently set the
14252 @code{gnutarget} to an invalid value. In order to set the variable
14256 (@value{GDBP}) set var g=4
14259 @value{GDBN} allows more implicit conversions in assignments than C; you can
14260 freely store an integer value into a pointer variable or vice versa,
14261 and you can convert any structure to any other structure that is the
14262 same length or shorter.
14263 @comment FIXME: how do structs align/pad in these conversions?
14264 @comment /doc@cygnus.com 18dec1990
14266 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14267 construct to generate a value of specified type at a specified address
14268 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14269 to memory location @code{0x83040} as an integer (which implies a certain size
14270 and representation in memory), and
14273 set @{int@}0x83040 = 4
14277 stores the value 4 into that memory location.
14280 @section Continuing at a Different Address
14282 Ordinarily, when you continue your program, you do so at the place where
14283 it stopped, with the @code{continue} command. You can instead continue at
14284 an address of your own choosing, with the following commands:
14288 @item jump @var{linespec}
14289 @itemx jump @var{location}
14290 Resume execution at line @var{linespec} or at address given by
14291 @var{location}. Execution stops again immediately if there is a
14292 breakpoint there. @xref{Specify Location}, for a description of the
14293 different forms of @var{linespec} and @var{location}. It is common
14294 practice to use the @code{tbreak} command in conjunction with
14295 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14297 The @code{jump} command does not change the current stack frame, or
14298 the stack pointer, or the contents of any memory location or any
14299 register other than the program counter. If line @var{linespec} is in
14300 a different function from the one currently executing, the results may
14301 be bizarre if the two functions expect different patterns of arguments or
14302 of local variables. For this reason, the @code{jump} command requests
14303 confirmation if the specified line is not in the function currently
14304 executing. However, even bizarre results are predictable if you are
14305 well acquainted with the machine-language code of your program.
14308 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14309 On many systems, you can get much the same effect as the @code{jump}
14310 command by storing a new value into the register @code{$pc}. The
14311 difference is that this does not start your program running; it only
14312 changes the address of where it @emph{will} run when you continue. For
14320 makes the next @code{continue} command or stepping command execute at
14321 address @code{0x485}, rather than at the address where your program stopped.
14322 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14324 The most common occasion to use the @code{jump} command is to back
14325 up---perhaps with more breakpoints set---over a portion of a program
14326 that has already executed, in order to examine its execution in more
14331 @section Giving your Program a Signal
14332 @cindex deliver a signal to a program
14336 @item signal @var{signal}
14337 Resume execution where your program stopped, but immediately give it the
14338 signal @var{signal}. @var{signal} can be the name or the number of a
14339 signal. For example, on many systems @code{signal 2} and @code{signal
14340 SIGINT} are both ways of sending an interrupt signal.
14342 Alternatively, if @var{signal} is zero, continue execution without
14343 giving a signal. This is useful when your program stopped on account of
14344 a signal and would ordinary see the signal when resumed with the
14345 @code{continue} command; @samp{signal 0} causes it to resume without a
14348 @code{signal} does not repeat when you press @key{RET} a second time
14349 after executing the command.
14353 Invoking the @code{signal} command is not the same as invoking the
14354 @code{kill} utility from the shell. Sending a signal with @code{kill}
14355 causes @value{GDBN} to decide what to do with the signal depending on
14356 the signal handling tables (@pxref{Signals}). The @code{signal} command
14357 passes the signal directly to your program.
14361 @section Returning from a Function
14364 @cindex returning from a function
14367 @itemx return @var{expression}
14368 You can cancel execution of a function call with the @code{return}
14369 command. If you give an
14370 @var{expression} argument, its value is used as the function's return
14374 When you use @code{return}, @value{GDBN} discards the selected stack frame
14375 (and all frames within it). You can think of this as making the
14376 discarded frame return prematurely. If you wish to specify a value to
14377 be returned, give that value as the argument to @code{return}.
14379 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14380 Frame}), and any other frames inside of it, leaving its caller as the
14381 innermost remaining frame. That frame becomes selected. The
14382 specified value is stored in the registers used for returning values
14385 The @code{return} command does not resume execution; it leaves the
14386 program stopped in the state that would exist if the function had just
14387 returned. In contrast, the @code{finish} command (@pxref{Continuing
14388 and Stepping, ,Continuing and Stepping}) resumes execution until the
14389 selected stack frame returns naturally.
14391 @value{GDBN} needs to know how the @var{expression} argument should be set for
14392 the inferior. The concrete registers assignment depends on the OS ABI and the
14393 type being returned by the selected stack frame. For example it is common for
14394 OS ABI to return floating point values in FPU registers while integer values in
14395 CPU registers. Still some ABIs return even floating point values in CPU
14396 registers. Larger integer widths (such as @code{long long int}) also have
14397 specific placement rules. @value{GDBN} already knows the OS ABI from its
14398 current target so it needs to find out also the type being returned to make the
14399 assignment into the right register(s).
14401 Normally, the selected stack frame has debug info. @value{GDBN} will always
14402 use the debug info instead of the implicit type of @var{expression} when the
14403 debug info is available. For example, if you type @kbd{return -1}, and the
14404 function in the current stack frame is declared to return a @code{long long
14405 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14406 into a @code{long long int}:
14409 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14411 (@value{GDBP}) return -1
14412 Make func return now? (y or n) y
14413 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14414 43 printf ("result=%lld\n", func ());
14418 However, if the selected stack frame does not have a debug info, e.g., if the
14419 function was compiled without debug info, @value{GDBN} has to find out the type
14420 to return from user. Specifying a different type by mistake may set the value
14421 in different inferior registers than the caller code expects. For example,
14422 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14423 of a @code{long long int} result for a debug info less function (on 32-bit
14424 architectures). Therefore the user is required to specify the return type by
14425 an appropriate cast explicitly:
14428 Breakpoint 2, 0x0040050b in func ()
14429 (@value{GDBP}) return -1
14430 Return value type not available for selected stack frame.
14431 Please use an explicit cast of the value to return.
14432 (@value{GDBP}) return (long long int) -1
14433 Make selected stack frame return now? (y or n) y
14434 #0 0x00400526 in main ()
14439 @section Calling Program Functions
14442 @cindex calling functions
14443 @cindex inferior functions, calling
14444 @item print @var{expr}
14445 Evaluate the expression @var{expr} and display the resulting value.
14446 @var{expr} may include calls to functions in the program being
14450 @item call @var{expr}
14451 Evaluate the expression @var{expr} without displaying @code{void}
14454 You can use this variant of the @code{print} command if you want to
14455 execute a function from your program that does not return anything
14456 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14457 with @code{void} returned values that @value{GDBN} will otherwise
14458 print. If the result is not void, it is printed and saved in the
14462 It is possible for the function you call via the @code{print} or
14463 @code{call} command to generate a signal (e.g., if there's a bug in
14464 the function, or if you passed it incorrect arguments). What happens
14465 in that case is controlled by the @code{set unwindonsignal} command.
14467 Similarly, with a C@t{++} program it is possible for the function you
14468 call via the @code{print} or @code{call} command to generate an
14469 exception that is not handled due to the constraints of the dummy
14470 frame. In this case, any exception that is raised in the frame, but has
14471 an out-of-frame exception handler will not be found. GDB builds a
14472 dummy-frame for the inferior function call, and the unwinder cannot
14473 seek for exception handlers outside of this dummy-frame. What happens
14474 in that case is controlled by the
14475 @code{set unwind-on-terminating-exception} command.
14478 @item set unwindonsignal
14479 @kindex set unwindonsignal
14480 @cindex unwind stack in called functions
14481 @cindex call dummy stack unwinding
14482 Set unwinding of the stack if a signal is received while in a function
14483 that @value{GDBN} called in the program being debugged. If set to on,
14484 @value{GDBN} unwinds the stack it created for the call and restores
14485 the context to what it was before the call. If set to off (the
14486 default), @value{GDBN} stops in the frame where the signal was
14489 @item show unwindonsignal
14490 @kindex show unwindonsignal
14491 Show the current setting of stack unwinding in the functions called by
14494 @item set unwind-on-terminating-exception
14495 @kindex set unwind-on-terminating-exception
14496 @cindex unwind stack in called functions with unhandled exceptions
14497 @cindex call dummy stack unwinding on unhandled exception.
14498 Set unwinding of the stack if a C@t{++} exception is raised, but left
14499 unhandled while in a function that @value{GDBN} called in the program being
14500 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14501 it created for the call and restores the context to what it was before
14502 the call. If set to off, @value{GDBN} the exception is delivered to
14503 the default C@t{++} exception handler and the inferior terminated.
14505 @item show unwind-on-terminating-exception
14506 @kindex show unwind-on-terminating-exception
14507 Show the current setting of stack unwinding in the functions called by
14512 @cindex weak alias functions
14513 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14514 for another function. In such case, @value{GDBN} might not pick up
14515 the type information, including the types of the function arguments,
14516 which causes @value{GDBN} to call the inferior function incorrectly.
14517 As a result, the called function will function erroneously and may
14518 even crash. A solution to that is to use the name of the aliased
14522 @section Patching Programs
14524 @cindex patching binaries
14525 @cindex writing into executables
14526 @cindex writing into corefiles
14528 By default, @value{GDBN} opens the file containing your program's
14529 executable code (or the corefile) read-only. This prevents accidental
14530 alterations to machine code; but it also prevents you from intentionally
14531 patching your program's binary.
14533 If you'd like to be able to patch the binary, you can specify that
14534 explicitly with the @code{set write} command. For example, you might
14535 want to turn on internal debugging flags, or even to make emergency
14541 @itemx set write off
14542 If you specify @samp{set write on}, @value{GDBN} opens executable and
14543 core files for both reading and writing; if you specify @kbd{set write
14544 off} (the default), @value{GDBN} opens them read-only.
14546 If you have already loaded a file, you must load it again (using the
14547 @code{exec-file} or @code{core-file} command) after changing @code{set
14548 write}, for your new setting to take effect.
14552 Display whether executable files and core files are opened for writing
14553 as well as reading.
14557 @chapter @value{GDBN} Files
14559 @value{GDBN} needs to know the file name of the program to be debugged,
14560 both in order to read its symbol table and in order to start your
14561 program. To debug a core dump of a previous run, you must also tell
14562 @value{GDBN} the name of the core dump file.
14565 * Files:: Commands to specify files
14566 * Separate Debug Files:: Debugging information in separate files
14567 * Index Files:: Index files speed up GDB
14568 * Symbol Errors:: Errors reading symbol files
14569 * Data Files:: GDB data files
14573 @section Commands to Specify Files
14575 @cindex symbol table
14576 @cindex core dump file
14578 You may want to specify executable and core dump file names. The usual
14579 way to do this is at start-up time, using the arguments to
14580 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14581 Out of @value{GDBN}}).
14583 Occasionally it is necessary to change to a different file during a
14584 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14585 specify a file you want to use. Or you are debugging a remote target
14586 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14587 Program}). In these situations the @value{GDBN} commands to specify
14588 new files are useful.
14591 @cindex executable file
14593 @item file @var{filename}
14594 Use @var{filename} as the program to be debugged. It is read for its
14595 symbols and for the contents of pure memory. It is also the program
14596 executed when you use the @code{run} command. If you do not specify a
14597 directory and the file is not found in the @value{GDBN} working directory,
14598 @value{GDBN} uses the environment variable @code{PATH} as a list of
14599 directories to search, just as the shell does when looking for a program
14600 to run. You can change the value of this variable, for both @value{GDBN}
14601 and your program, using the @code{path} command.
14603 @cindex unlinked object files
14604 @cindex patching object files
14605 You can load unlinked object @file{.o} files into @value{GDBN} using
14606 the @code{file} command. You will not be able to ``run'' an object
14607 file, but you can disassemble functions and inspect variables. Also,
14608 if the underlying BFD functionality supports it, you could use
14609 @kbd{gdb -write} to patch object files using this technique. Note
14610 that @value{GDBN} can neither interpret nor modify relocations in this
14611 case, so branches and some initialized variables will appear to go to
14612 the wrong place. But this feature is still handy from time to time.
14615 @code{file} with no argument makes @value{GDBN} discard any information it
14616 has on both executable file and the symbol table.
14619 @item exec-file @r{[} @var{filename} @r{]}
14620 Specify that the program to be run (but not the symbol table) is found
14621 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14622 if necessary to locate your program. Omitting @var{filename} means to
14623 discard information on the executable file.
14625 @kindex symbol-file
14626 @item symbol-file @r{[} @var{filename} @r{]}
14627 Read symbol table information from file @var{filename}. @code{PATH} is
14628 searched when necessary. Use the @code{file} command to get both symbol
14629 table and program to run from the same file.
14631 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14632 program's symbol table.
14634 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14635 some breakpoints and auto-display expressions. This is because they may
14636 contain pointers to the internal data recording symbols and data types,
14637 which are part of the old symbol table data being discarded inside
14640 @code{symbol-file} does not repeat if you press @key{RET} again after
14643 When @value{GDBN} is configured for a particular environment, it
14644 understands debugging information in whatever format is the standard
14645 generated for that environment; you may use either a @sc{gnu} compiler, or
14646 other compilers that adhere to the local conventions.
14647 Best results are usually obtained from @sc{gnu} compilers; for example,
14648 using @code{@value{NGCC}} you can generate debugging information for
14651 For most kinds of object files, with the exception of old SVR3 systems
14652 using COFF, the @code{symbol-file} command does not normally read the
14653 symbol table in full right away. Instead, it scans the symbol table
14654 quickly to find which source files and which symbols are present. The
14655 details are read later, one source file at a time, as they are needed.
14657 The purpose of this two-stage reading strategy is to make @value{GDBN}
14658 start up faster. For the most part, it is invisible except for
14659 occasional pauses while the symbol table details for a particular source
14660 file are being read. (The @code{set verbose} command can turn these
14661 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14662 Warnings and Messages}.)
14664 We have not implemented the two-stage strategy for COFF yet. When the
14665 symbol table is stored in COFF format, @code{symbol-file} reads the
14666 symbol table data in full right away. Note that ``stabs-in-COFF''
14667 still does the two-stage strategy, since the debug info is actually
14671 @cindex reading symbols immediately
14672 @cindex symbols, reading immediately
14673 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14674 @itemx file @r{[} -readnow @r{]} @var{filename}
14675 You can override the @value{GDBN} two-stage strategy for reading symbol
14676 tables by using the @samp{-readnow} option with any of the commands that
14677 load symbol table information, if you want to be sure @value{GDBN} has the
14678 entire symbol table available.
14680 @c FIXME: for now no mention of directories, since this seems to be in
14681 @c flux. 13mar1992 status is that in theory GDB would look either in
14682 @c current dir or in same dir as myprog; but issues like competing
14683 @c GDB's, or clutter in system dirs, mean that in practice right now
14684 @c only current dir is used. FFish says maybe a special GDB hierarchy
14685 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14689 @item core-file @r{[}@var{filename}@r{]}
14691 Specify the whereabouts of a core dump file to be used as the ``contents
14692 of memory''. Traditionally, core files contain only some parts of the
14693 address space of the process that generated them; @value{GDBN} can access the
14694 executable file itself for other parts.
14696 @code{core-file} with no argument specifies that no core file is
14699 Note that the core file is ignored when your program is actually running
14700 under @value{GDBN}. So, if you have been running your program and you
14701 wish to debug a core file instead, you must kill the subprocess in which
14702 the program is running. To do this, use the @code{kill} command
14703 (@pxref{Kill Process, ,Killing the Child Process}).
14705 @kindex add-symbol-file
14706 @cindex dynamic linking
14707 @item add-symbol-file @var{filename} @var{address}
14708 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14709 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14710 The @code{add-symbol-file} command reads additional symbol table
14711 information from the file @var{filename}. You would use this command
14712 when @var{filename} has been dynamically loaded (by some other means)
14713 into the program that is running. @var{address} should be the memory
14714 address at which the file has been loaded; @value{GDBN} cannot figure
14715 this out for itself. You can additionally specify an arbitrary number
14716 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14717 section name and base address for that section. You can specify any
14718 @var{address} as an expression.
14720 The symbol table of the file @var{filename} is added to the symbol table
14721 originally read with the @code{symbol-file} command. You can use the
14722 @code{add-symbol-file} command any number of times; the new symbol data
14723 thus read keeps adding to the old. To discard all old symbol data
14724 instead, use the @code{symbol-file} command without any arguments.
14726 @cindex relocatable object files, reading symbols from
14727 @cindex object files, relocatable, reading symbols from
14728 @cindex reading symbols from relocatable object files
14729 @cindex symbols, reading from relocatable object files
14730 @cindex @file{.o} files, reading symbols from
14731 Although @var{filename} is typically a shared library file, an
14732 executable file, or some other object file which has been fully
14733 relocated for loading into a process, you can also load symbolic
14734 information from relocatable @file{.o} files, as long as:
14738 the file's symbolic information refers only to linker symbols defined in
14739 that file, not to symbols defined by other object files,
14741 every section the file's symbolic information refers to has actually
14742 been loaded into the inferior, as it appears in the file, and
14744 you can determine the address at which every section was loaded, and
14745 provide these to the @code{add-symbol-file} command.
14749 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14750 relocatable files into an already running program; such systems
14751 typically make the requirements above easy to meet. However, it's
14752 important to recognize that many native systems use complex link
14753 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14754 assembly, for example) that make the requirements difficult to meet. In
14755 general, one cannot assume that using @code{add-symbol-file} to read a
14756 relocatable object file's symbolic information will have the same effect
14757 as linking the relocatable object file into the program in the normal
14760 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14762 @kindex add-symbol-file-from-memory
14763 @cindex @code{syscall DSO}
14764 @cindex load symbols from memory
14765 @item add-symbol-file-from-memory @var{address}
14766 Load symbols from the given @var{address} in a dynamically loaded
14767 object file whose image is mapped directly into the inferior's memory.
14768 For example, the Linux kernel maps a @code{syscall DSO} into each
14769 process's address space; this DSO provides kernel-specific code for
14770 some system calls. The argument can be any expression whose
14771 evaluation yields the address of the file's shared object file header.
14772 For this command to work, you must have used @code{symbol-file} or
14773 @code{exec-file} commands in advance.
14775 @kindex add-shared-symbol-files
14777 @item add-shared-symbol-files @var{library-file}
14778 @itemx assf @var{library-file}
14779 The @code{add-shared-symbol-files} command can currently be used only
14780 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14781 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14782 @value{GDBN} automatically looks for shared libraries, however if
14783 @value{GDBN} does not find yours, you can invoke
14784 @code{add-shared-symbol-files}. It takes one argument: the shared
14785 library's file name. @code{assf} is a shorthand alias for
14786 @code{add-shared-symbol-files}.
14789 @item section @var{section} @var{addr}
14790 The @code{section} command changes the base address of the named
14791 @var{section} of the exec file to @var{addr}. This can be used if the
14792 exec file does not contain section addresses, (such as in the
14793 @code{a.out} format), or when the addresses specified in the file
14794 itself are wrong. Each section must be changed separately. The
14795 @code{info files} command, described below, lists all the sections and
14799 @kindex info target
14802 @code{info files} and @code{info target} are synonymous; both print the
14803 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14804 including the names of the executable and core dump files currently in
14805 use by @value{GDBN}, and the files from which symbols were loaded. The
14806 command @code{help target} lists all possible targets rather than
14809 @kindex maint info sections
14810 @item maint info sections
14811 Another command that can give you extra information about program sections
14812 is @code{maint info sections}. In addition to the section information
14813 displayed by @code{info files}, this command displays the flags and file
14814 offset of each section in the executable and core dump files. In addition,
14815 @code{maint info sections} provides the following command options (which
14816 may be arbitrarily combined):
14820 Display sections for all loaded object files, including shared libraries.
14821 @item @var{sections}
14822 Display info only for named @var{sections}.
14823 @item @var{section-flags}
14824 Display info only for sections for which @var{section-flags} are true.
14825 The section flags that @value{GDBN} currently knows about are:
14828 Section will have space allocated in the process when loaded.
14829 Set for all sections except those containing debug information.
14831 Section will be loaded from the file into the child process memory.
14832 Set for pre-initialized code and data, clear for @code{.bss} sections.
14834 Section needs to be relocated before loading.
14836 Section cannot be modified by the child process.
14838 Section contains executable code only.
14840 Section contains data only (no executable code).
14842 Section will reside in ROM.
14844 Section contains data for constructor/destructor lists.
14846 Section is not empty.
14848 An instruction to the linker to not output the section.
14849 @item COFF_SHARED_LIBRARY
14850 A notification to the linker that the section contains
14851 COFF shared library information.
14853 Section contains common symbols.
14856 @kindex set trust-readonly-sections
14857 @cindex read-only sections
14858 @item set trust-readonly-sections on
14859 Tell @value{GDBN} that readonly sections in your object file
14860 really are read-only (i.e.@: that their contents will not change).
14861 In that case, @value{GDBN} can fetch values from these sections
14862 out of the object file, rather than from the target program.
14863 For some targets (notably embedded ones), this can be a significant
14864 enhancement to debugging performance.
14866 The default is off.
14868 @item set trust-readonly-sections off
14869 Tell @value{GDBN} not to trust readonly sections. This means that
14870 the contents of the section might change while the program is running,
14871 and must therefore be fetched from the target when needed.
14873 @item show trust-readonly-sections
14874 Show the current setting of trusting readonly sections.
14877 All file-specifying commands allow both absolute and relative file names
14878 as arguments. @value{GDBN} always converts the file name to an absolute file
14879 name and remembers it that way.
14881 @cindex shared libraries
14882 @anchor{Shared Libraries}
14883 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14884 and IBM RS/6000 AIX shared libraries.
14886 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14887 shared libraries. @xref{Expat}.
14889 @value{GDBN} automatically loads symbol definitions from shared libraries
14890 when you use the @code{run} command, or when you examine a core file.
14891 (Before you issue the @code{run} command, @value{GDBN} does not understand
14892 references to a function in a shared library, however---unless you are
14893 debugging a core file).
14895 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14896 automatically loads the symbols at the time of the @code{shl_load} call.
14898 @c FIXME: some @value{GDBN} release may permit some refs to undef
14899 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14900 @c FIXME...lib; check this from time to time when updating manual
14902 There are times, however, when you may wish to not automatically load
14903 symbol definitions from shared libraries, such as when they are
14904 particularly large or there are many of them.
14906 To control the automatic loading of shared library symbols, use the
14910 @kindex set auto-solib-add
14911 @item set auto-solib-add @var{mode}
14912 If @var{mode} is @code{on}, symbols from all shared object libraries
14913 will be loaded automatically when the inferior begins execution, you
14914 attach to an independently started inferior, or when the dynamic linker
14915 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14916 is @code{off}, symbols must be loaded manually, using the
14917 @code{sharedlibrary} command. The default value is @code{on}.
14919 @cindex memory used for symbol tables
14920 If your program uses lots of shared libraries with debug info that
14921 takes large amounts of memory, you can decrease the @value{GDBN}
14922 memory footprint by preventing it from automatically loading the
14923 symbols from shared libraries. To that end, type @kbd{set
14924 auto-solib-add off} before running the inferior, then load each
14925 library whose debug symbols you do need with @kbd{sharedlibrary
14926 @var{regexp}}, where @var{regexp} is a regular expression that matches
14927 the libraries whose symbols you want to be loaded.
14929 @kindex show auto-solib-add
14930 @item show auto-solib-add
14931 Display the current autoloading mode.
14934 @cindex load shared library
14935 To explicitly load shared library symbols, use the @code{sharedlibrary}
14939 @kindex info sharedlibrary
14941 @item info share @var{regex}
14942 @itemx info sharedlibrary @var{regex}
14943 Print the names of the shared libraries which are currently loaded
14944 that match @var{regex}. If @var{regex} is omitted then print
14945 all shared libraries that are loaded.
14947 @kindex sharedlibrary
14949 @item sharedlibrary @var{regex}
14950 @itemx share @var{regex}
14951 Load shared object library symbols for files matching a
14952 Unix regular expression.
14953 As with files loaded automatically, it only loads shared libraries
14954 required by your program for a core file or after typing @code{run}. If
14955 @var{regex} is omitted all shared libraries required by your program are
14958 @item nosharedlibrary
14959 @kindex nosharedlibrary
14960 @cindex unload symbols from shared libraries
14961 Unload all shared object library symbols. This discards all symbols
14962 that have been loaded from all shared libraries. Symbols from shared
14963 libraries that were loaded by explicit user requests are not
14967 Sometimes you may wish that @value{GDBN} stops and gives you control
14968 when any of shared library events happen. Use the @code{set
14969 stop-on-solib-events} command for this:
14972 @item set stop-on-solib-events
14973 @kindex set stop-on-solib-events
14974 This command controls whether @value{GDBN} should give you control
14975 when the dynamic linker notifies it about some shared library event.
14976 The most common event of interest is loading or unloading of a new
14979 @item show stop-on-solib-events
14980 @kindex show stop-on-solib-events
14981 Show whether @value{GDBN} stops and gives you control when shared
14982 library events happen.
14985 Shared libraries are also supported in many cross or remote debugging
14986 configurations. @value{GDBN} needs to have access to the target's libraries;
14987 this can be accomplished either by providing copies of the libraries
14988 on the host system, or by asking @value{GDBN} to automatically retrieve the
14989 libraries from the target. If copies of the target libraries are
14990 provided, they need to be the same as the target libraries, although the
14991 copies on the target can be stripped as long as the copies on the host are
14994 @cindex where to look for shared libraries
14995 For remote debugging, you need to tell @value{GDBN} where the target
14996 libraries are, so that it can load the correct copies---otherwise, it
14997 may try to load the host's libraries. @value{GDBN} has two variables
14998 to specify the search directories for target libraries.
15001 @cindex prefix for shared library file names
15002 @cindex system root, alternate
15003 @kindex set solib-absolute-prefix
15004 @kindex set sysroot
15005 @item set sysroot @var{path}
15006 Use @var{path} as the system root for the program being debugged. Any
15007 absolute shared library paths will be prefixed with @var{path}; many
15008 runtime loaders store the absolute paths to the shared library in the
15009 target program's memory. If you use @code{set sysroot} to find shared
15010 libraries, they need to be laid out in the same way that they are on
15011 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15014 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15015 retrieve the target libraries from the remote system. This is only
15016 supported when using a remote target that supports the @code{remote get}
15017 command (@pxref{File Transfer,,Sending files to a remote system}).
15018 The part of @var{path} following the initial @file{remote:}
15019 (if present) is used as system root prefix on the remote file system.
15020 @footnote{If you want to specify a local system root using a directory
15021 that happens to be named @file{remote:}, you need to use some equivalent
15022 variant of the name like @file{./remote:}.}
15024 For targets with an MS-DOS based filesystem, such as MS-Windows and
15025 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15026 absolute file name with @var{path}. But first, on Unix hosts,
15027 @value{GDBN} converts all backslash directory separators into forward
15028 slashes, because the backslash is not a directory separator on Unix:
15031 c:\foo\bar.dll @result{} c:/foo/bar.dll
15034 Then, @value{GDBN} attempts prefixing the target file name with
15035 @var{path}, and looks for the resulting file name in the host file
15039 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15042 If that does not find the shared library, @value{GDBN} tries removing
15043 the @samp{:} character from the drive spec, both for convenience, and,
15044 for the case of the host file system not supporting file names with
15048 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15051 This makes it possible to have a system root that mirrors a target
15052 with more than one drive. E.g., you may want to setup your local
15053 copies of the target system shared libraries like so (note @samp{c} vs
15057 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15058 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15059 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15063 and point the system root at @file{/path/to/sysroot}, so that
15064 @value{GDBN} can find the correct copies of both
15065 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15067 If that still does not find the shared library, @value{GDBN} tries
15068 removing the whole drive spec from the target file name:
15071 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15074 This last lookup makes it possible to not care about the drive name,
15075 if you don't want or need to.
15077 The @code{set solib-absolute-prefix} command is an alias for @code{set
15080 @cindex default system root
15081 @cindex @samp{--with-sysroot}
15082 You can set the default system root by using the configure-time
15083 @samp{--with-sysroot} option. If the system root is inside
15084 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15085 @samp{--exec-prefix}), then the default system root will be updated
15086 automatically if the installed @value{GDBN} is moved to a new
15089 @kindex show sysroot
15091 Display the current shared library prefix.
15093 @kindex set solib-search-path
15094 @item set solib-search-path @var{path}
15095 If this variable is set, @var{path} is a colon-separated list of
15096 directories to search for shared libraries. @samp{solib-search-path}
15097 is used after @samp{sysroot} fails to locate the library, or if the
15098 path to the library is relative instead of absolute. If you want to
15099 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15100 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15101 finding your host's libraries. @samp{sysroot} is preferred; setting
15102 it to a nonexistent directory may interfere with automatic loading
15103 of shared library symbols.
15105 @kindex show solib-search-path
15106 @item show solib-search-path
15107 Display the current shared library search path.
15109 @cindex DOS file-name semantics of file names.
15110 @kindex set target-file-system-kind (unix|dos-based|auto)
15111 @kindex show target-file-system-kind
15112 @item set target-file-system-kind @var{kind}
15113 Set assumed file system kind for target reported file names.
15115 Shared library file names as reported by the target system may not
15116 make sense as is on the system @value{GDBN} is running on. For
15117 example, when remote debugging a target that has MS-DOS based file
15118 system semantics, from a Unix host, the target may be reporting to
15119 @value{GDBN} a list of loaded shared libraries with file names such as
15120 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15121 drive letters, so the @samp{c:\} prefix is not normally understood as
15122 indicating an absolute file name, and neither is the backslash
15123 normally considered a directory separator character. In that case,
15124 the native file system would interpret this whole absolute file name
15125 as a relative file name with no directory components. This would make
15126 it impossible to point @value{GDBN} at a copy of the remote target's
15127 shared libraries on the host using @code{set sysroot}, and impractical
15128 with @code{set solib-search-path}. Setting
15129 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15130 to interpret such file names similarly to how the target would, and to
15131 map them to file names valid on @value{GDBN}'s native file system
15132 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15133 to one of the supported file system kinds. In that case, @value{GDBN}
15134 tries to determine the appropriate file system variant based on the
15135 current target's operating system (@pxref{ABI, ,Configuring the
15136 Current ABI}). The supported file system settings are:
15140 Instruct @value{GDBN} to assume the target file system is of Unix
15141 kind. Only file names starting the forward slash (@samp{/}) character
15142 are considered absolute, and the directory separator character is also
15146 Instruct @value{GDBN} to assume the target file system is DOS based.
15147 File names starting with either a forward slash, or a drive letter
15148 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15149 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15150 considered directory separators.
15153 Instruct @value{GDBN} to use the file system kind associated with the
15154 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15155 This is the default.
15160 @node Separate Debug Files
15161 @section Debugging Information in Separate Files
15162 @cindex separate debugging information files
15163 @cindex debugging information in separate files
15164 @cindex @file{.debug} subdirectories
15165 @cindex debugging information directory, global
15166 @cindex global debugging information directory
15167 @cindex build ID, and separate debugging files
15168 @cindex @file{.build-id} directory
15170 @value{GDBN} allows you to put a program's debugging information in a
15171 file separate from the executable itself, in a way that allows
15172 @value{GDBN} to find and load the debugging information automatically.
15173 Since debugging information can be very large---sometimes larger
15174 than the executable code itself---some systems distribute debugging
15175 information for their executables in separate files, which users can
15176 install only when they need to debug a problem.
15178 @value{GDBN} supports two ways of specifying the separate debug info
15183 The executable contains a @dfn{debug link} that specifies the name of
15184 the separate debug info file. The separate debug file's name is
15185 usually @file{@var{executable}.debug}, where @var{executable} is the
15186 name of the corresponding executable file without leading directories
15187 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15188 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15189 checksum for the debug file, which @value{GDBN} uses to validate that
15190 the executable and the debug file came from the same build.
15193 The executable contains a @dfn{build ID}, a unique bit string that is
15194 also present in the corresponding debug info file. (This is supported
15195 only on some operating systems, notably those which use the ELF format
15196 for binary files and the @sc{gnu} Binutils.) For more details about
15197 this feature, see the description of the @option{--build-id}
15198 command-line option in @ref{Options, , Command Line Options, ld.info,
15199 The GNU Linker}. The debug info file's name is not specified
15200 explicitly by the build ID, but can be computed from the build ID, see
15204 Depending on the way the debug info file is specified, @value{GDBN}
15205 uses two different methods of looking for the debug file:
15209 For the ``debug link'' method, @value{GDBN} looks up the named file in
15210 the directory of the executable file, then in a subdirectory of that
15211 directory named @file{.debug}, and finally under the global debug
15212 directory, in a subdirectory whose name is identical to the leading
15213 directories of the executable's absolute file name.
15216 For the ``build ID'' method, @value{GDBN} looks in the
15217 @file{.build-id} subdirectory of the global debug directory for a file
15218 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15219 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15220 are the rest of the bit string. (Real build ID strings are 32 or more
15221 hex characters, not 10.)
15224 So, for example, suppose you ask @value{GDBN} to debug
15225 @file{/usr/bin/ls}, which has a debug link that specifies the
15226 file @file{ls.debug}, and a build ID whose value in hex is
15227 @code{abcdef1234}. If the global debug directory is
15228 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15229 debug information files, in the indicated order:
15233 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15235 @file{/usr/bin/ls.debug}
15237 @file{/usr/bin/.debug/ls.debug}
15239 @file{/usr/lib/debug/usr/bin/ls.debug}.
15242 You can set the global debugging info directory's name, and view the
15243 name @value{GDBN} is currently using.
15247 @kindex set debug-file-directory
15248 @item set debug-file-directory @var{directories}
15249 Set the directories which @value{GDBN} searches for separate debugging
15250 information files to @var{directory}. Multiple directory components can be set
15251 concatenating them by a directory separator.
15253 @kindex show debug-file-directory
15254 @item show debug-file-directory
15255 Show the directories @value{GDBN} searches for separate debugging
15260 @cindex @code{.gnu_debuglink} sections
15261 @cindex debug link sections
15262 A debug link is a special section of the executable file named
15263 @code{.gnu_debuglink}. The section must contain:
15267 A filename, with any leading directory components removed, followed by
15270 zero to three bytes of padding, as needed to reach the next four-byte
15271 boundary within the section, and
15273 a four-byte CRC checksum, stored in the same endianness used for the
15274 executable file itself. The checksum is computed on the debugging
15275 information file's full contents by the function given below, passing
15276 zero as the @var{crc} argument.
15279 Any executable file format can carry a debug link, as long as it can
15280 contain a section named @code{.gnu_debuglink} with the contents
15283 @cindex @code{.note.gnu.build-id} sections
15284 @cindex build ID sections
15285 The build ID is a special section in the executable file (and in other
15286 ELF binary files that @value{GDBN} may consider). This section is
15287 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15288 It contains unique identification for the built files---the ID remains
15289 the same across multiple builds of the same build tree. The default
15290 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15291 content for the build ID string. The same section with an identical
15292 value is present in the original built binary with symbols, in its
15293 stripped variant, and in the separate debugging information file.
15295 The debugging information file itself should be an ordinary
15296 executable, containing a full set of linker symbols, sections, and
15297 debugging information. The sections of the debugging information file
15298 should have the same names, addresses, and sizes as the original file,
15299 but they need not contain any data---much like a @code{.bss} section
15300 in an ordinary executable.
15302 The @sc{gnu} binary utilities (Binutils) package includes the
15303 @samp{objcopy} utility that can produce
15304 the separated executable / debugging information file pairs using the
15305 following commands:
15308 @kbd{objcopy --only-keep-debug foo foo.debug}
15313 These commands remove the debugging
15314 information from the executable file @file{foo} and place it in the file
15315 @file{foo.debug}. You can use the first, second or both methods to link the
15320 The debug link method needs the following additional command to also leave
15321 behind a debug link in @file{foo}:
15324 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15327 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15328 a version of the @code{strip} command such that the command @kbd{strip foo -f
15329 foo.debug} has the same functionality as the two @code{objcopy} commands and
15330 the @code{ln -s} command above, together.
15333 Build ID gets embedded into the main executable using @code{ld --build-id} or
15334 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15335 compatibility fixes for debug files separation are present in @sc{gnu} binary
15336 utilities (Binutils) package since version 2.18.
15341 @cindex CRC algorithm definition
15342 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15343 IEEE 802.3 using the polynomial:
15345 @c TexInfo requires naked braces for multi-digit exponents for Tex
15346 @c output, but this causes HTML output to barf. HTML has to be set using
15347 @c raw commands. So we end up having to specify this equation in 2
15352 <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>
15353 + <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
15359 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15360 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15364 The function is computed byte at a time, taking the least
15365 significant bit of each byte first. The initial pattern
15366 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15367 the final result is inverted to ensure trailing zeros also affect the
15370 @emph{Note:} This is the same CRC polynomial as used in handling the
15371 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15372 , @value{GDBN} Remote Serial Protocol}). However in the
15373 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15374 significant bit first, and the result is not inverted, so trailing
15375 zeros have no effect on the CRC value.
15377 To complete the description, we show below the code of the function
15378 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15379 initially supplied @code{crc} argument means that an initial call to
15380 this function passing in zero will start computing the CRC using
15383 @kindex gnu_debuglink_crc32
15386 gnu_debuglink_crc32 (unsigned long crc,
15387 unsigned char *buf, size_t len)
15389 static const unsigned long crc32_table[256] =
15391 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15392 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15393 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15394 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15395 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15396 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15397 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15398 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15399 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15400 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15401 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15402 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15403 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15404 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15405 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15406 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15407 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15408 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15409 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15410 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15411 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15412 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15413 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15414 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15415 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15416 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15417 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15418 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15419 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15420 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15421 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15422 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15423 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15424 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15425 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15426 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15427 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15428 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15429 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15430 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15431 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15432 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15433 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15434 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15435 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15436 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15437 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15438 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15439 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15440 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15441 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15444 unsigned char *end;
15446 crc = ~crc & 0xffffffff;
15447 for (end = buf + len; buf < end; ++buf)
15448 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15449 return ~crc & 0xffffffff;
15454 This computation does not apply to the ``build ID'' method.
15458 @section Index Files Speed Up @value{GDBN}
15459 @cindex index files
15460 @cindex @samp{.gdb_index} section
15462 When @value{GDBN} finds a symbol file, it scans the symbols in the
15463 file in order to construct an internal symbol table. This lets most
15464 @value{GDBN} operations work quickly---at the cost of a delay early
15465 on. For large programs, this delay can be quite lengthy, so
15466 @value{GDBN} provides a way to build an index, which speeds up
15469 The index is stored as a section in the symbol file. @value{GDBN} can
15470 write the index to a file, then you can put it into the symbol file
15471 using @command{objcopy}.
15473 To create an index file, use the @code{save gdb-index} command:
15476 @item save gdb-index @var{directory}
15477 @kindex save gdb-index
15478 Create an index file for each symbol file currently known by
15479 @value{GDBN}. Each file is named after its corresponding symbol file,
15480 with @samp{.gdb-index} appended, and is written into the given
15484 Once you have created an index file you can merge it into your symbol
15485 file, here named @file{symfile}, using @command{objcopy}:
15488 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15489 --set-section-flags .gdb_index=readonly symfile symfile
15492 There are currently some limitation on indices. They only work when
15493 for DWARF debugging information, not stabs. And, they do not
15494 currently work for programs using Ada.
15496 @node Symbol Errors
15497 @section Errors Reading Symbol Files
15499 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15500 such as symbol types it does not recognize, or known bugs in compiler
15501 output. By default, @value{GDBN} does not notify you of such problems, since
15502 they are relatively common and primarily of interest to people
15503 debugging compilers. If you are interested in seeing information
15504 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15505 only one message about each such type of problem, no matter how many
15506 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15507 to see how many times the problems occur, with the @code{set
15508 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15511 The messages currently printed, and their meanings, include:
15514 @item inner block not inside outer block in @var{symbol}
15516 The symbol information shows where symbol scopes begin and end
15517 (such as at the start of a function or a block of statements). This
15518 error indicates that an inner scope block is not fully contained
15519 in its outer scope blocks.
15521 @value{GDBN} circumvents the problem by treating the inner block as if it had
15522 the same scope as the outer block. In the error message, @var{symbol}
15523 may be shown as ``@code{(don't know)}'' if the outer block is not a
15526 @item block at @var{address} out of order
15528 The symbol information for symbol scope blocks should occur in
15529 order of increasing addresses. This error indicates that it does not
15532 @value{GDBN} does not circumvent this problem, and has trouble
15533 locating symbols in the source file whose symbols it is reading. (You
15534 can often determine what source file is affected by specifying
15535 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15538 @item bad block start address patched
15540 The symbol information for a symbol scope block has a start address
15541 smaller than the address of the preceding source line. This is known
15542 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15544 @value{GDBN} circumvents the problem by treating the symbol scope block as
15545 starting on the previous source line.
15547 @item bad string table offset in symbol @var{n}
15550 Symbol number @var{n} contains a pointer into the string table which is
15551 larger than the size of the string table.
15553 @value{GDBN} circumvents the problem by considering the symbol to have the
15554 name @code{foo}, which may cause other problems if many symbols end up
15557 @item unknown symbol type @code{0x@var{nn}}
15559 The symbol information contains new data types that @value{GDBN} does
15560 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15561 uncomprehended information, in hexadecimal.
15563 @value{GDBN} circumvents the error by ignoring this symbol information.
15564 This usually allows you to debug your program, though certain symbols
15565 are not accessible. If you encounter such a problem and feel like
15566 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15567 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15568 and examine @code{*bufp} to see the symbol.
15570 @item stub type has NULL name
15572 @value{GDBN} could not find the full definition for a struct or class.
15574 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15575 The symbol information for a C@t{++} member function is missing some
15576 information that recent versions of the compiler should have output for
15579 @item info mismatch between compiler and debugger
15581 @value{GDBN} could not parse a type specification output by the compiler.
15586 @section GDB Data Files
15588 @cindex prefix for data files
15589 @value{GDBN} will sometimes read an auxiliary data file. These files
15590 are kept in a directory known as the @dfn{data directory}.
15592 You can set the data directory's name, and view the name @value{GDBN}
15593 is currently using.
15596 @kindex set data-directory
15597 @item set data-directory @var{directory}
15598 Set the directory which @value{GDBN} searches for auxiliary data files
15599 to @var{directory}.
15601 @kindex show data-directory
15602 @item show data-directory
15603 Show the directory @value{GDBN} searches for auxiliary data files.
15606 @cindex default data directory
15607 @cindex @samp{--with-gdb-datadir}
15608 You can set the default data directory by using the configure-time
15609 @samp{--with-gdb-datadir} option. If the data directory is inside
15610 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15611 @samp{--exec-prefix}), then the default data directory will be updated
15612 automatically if the installed @value{GDBN} is moved to a new
15615 The data directory may also be specified with the
15616 @code{--data-directory} command line option.
15617 @xref{Mode Options}.
15620 @chapter Specifying a Debugging Target
15622 @cindex debugging target
15623 A @dfn{target} is the execution environment occupied by your program.
15625 Often, @value{GDBN} runs in the same host environment as your program;
15626 in that case, the debugging target is specified as a side effect when
15627 you use the @code{file} or @code{core} commands. When you need more
15628 flexibility---for example, running @value{GDBN} on a physically separate
15629 host, or controlling a standalone system over a serial port or a
15630 realtime system over a TCP/IP connection---you can use the @code{target}
15631 command to specify one of the target types configured for @value{GDBN}
15632 (@pxref{Target Commands, ,Commands for Managing Targets}).
15634 @cindex target architecture
15635 It is possible to build @value{GDBN} for several different @dfn{target
15636 architectures}. When @value{GDBN} is built like that, you can choose
15637 one of the available architectures with the @kbd{set architecture}
15641 @kindex set architecture
15642 @kindex show architecture
15643 @item set architecture @var{arch}
15644 This command sets the current target architecture to @var{arch}. The
15645 value of @var{arch} can be @code{"auto"}, in addition to one of the
15646 supported architectures.
15648 @item show architecture
15649 Show the current target architecture.
15651 @item set processor
15653 @kindex set processor
15654 @kindex show processor
15655 These are alias commands for, respectively, @code{set architecture}
15656 and @code{show architecture}.
15660 * Active Targets:: Active targets
15661 * Target Commands:: Commands for managing targets
15662 * Byte Order:: Choosing target byte order
15665 @node Active Targets
15666 @section Active Targets
15668 @cindex stacking targets
15669 @cindex active targets
15670 @cindex multiple targets
15672 There are multiple classes of targets such as: processes, executable files or
15673 recording sessions. Core files belong to the process class, making core file
15674 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15675 on multiple active targets, one in each class. This allows you to (for
15676 example) start a process and inspect its activity, while still having access to
15677 the executable file after the process finishes. Or if you start process
15678 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15679 presented a virtual layer of the recording target, while the process target
15680 remains stopped at the chronologically last point of the process execution.
15682 Use the @code{core-file} and @code{exec-file} commands to select a new core
15683 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15684 specify as a target a process that is already running, use the @code{attach}
15685 command (@pxref{Attach, ,Debugging an Already-running Process}).
15687 @node Target Commands
15688 @section Commands for Managing Targets
15691 @item target @var{type} @var{parameters}
15692 Connects the @value{GDBN} host environment to a target machine or
15693 process. A target is typically a protocol for talking to debugging
15694 facilities. You use the argument @var{type} to specify the type or
15695 protocol of the target machine.
15697 Further @var{parameters} are interpreted by the target protocol, but
15698 typically include things like device names or host names to connect
15699 with, process numbers, and baud rates.
15701 The @code{target} command does not repeat if you press @key{RET} again
15702 after executing the command.
15704 @kindex help target
15706 Displays the names of all targets available. To display targets
15707 currently selected, use either @code{info target} or @code{info files}
15708 (@pxref{Files, ,Commands to Specify Files}).
15710 @item help target @var{name}
15711 Describe a particular target, including any parameters necessary to
15714 @kindex set gnutarget
15715 @item set gnutarget @var{args}
15716 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15717 knows whether it is reading an @dfn{executable},
15718 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15719 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15720 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15723 @emph{Warning:} To specify a file format with @code{set gnutarget},
15724 you must know the actual BFD name.
15728 @xref{Files, , Commands to Specify Files}.
15730 @kindex show gnutarget
15731 @item show gnutarget
15732 Use the @code{show gnutarget} command to display what file format
15733 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15734 @value{GDBN} will determine the file format for each file automatically,
15735 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15738 @cindex common targets
15739 Here are some common targets (available, or not, depending on the GDB
15744 @item target exec @var{program}
15745 @cindex executable file target
15746 An executable file. @samp{target exec @var{program}} is the same as
15747 @samp{exec-file @var{program}}.
15749 @item target core @var{filename}
15750 @cindex core dump file target
15751 A core dump file. @samp{target core @var{filename}} is the same as
15752 @samp{core-file @var{filename}}.
15754 @item target remote @var{medium}
15755 @cindex remote target
15756 A remote system connected to @value{GDBN} via a serial line or network
15757 connection. This command tells @value{GDBN} to use its own remote
15758 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15760 For example, if you have a board connected to @file{/dev/ttya} on the
15761 machine running @value{GDBN}, you could say:
15764 target remote /dev/ttya
15767 @code{target remote} supports the @code{load} command. This is only
15768 useful if you have some other way of getting the stub to the target
15769 system, and you can put it somewhere in memory where it won't get
15770 clobbered by the download.
15772 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15773 @cindex built-in simulator target
15774 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15782 works; however, you cannot assume that a specific memory map, device
15783 drivers, or even basic I/O is available, although some simulators do
15784 provide these. For info about any processor-specific simulator details,
15785 see the appropriate section in @ref{Embedded Processors, ,Embedded
15790 Some configurations may include these targets as well:
15794 @item target nrom @var{dev}
15795 @cindex NetROM ROM emulator target
15796 NetROM ROM emulator. This target only supports downloading.
15800 Different targets are available on different configurations of @value{GDBN};
15801 your configuration may have more or fewer targets.
15803 Many remote targets require you to download the executable's code once
15804 you've successfully established a connection. You may wish to control
15805 various aspects of this process.
15810 @kindex set hash@r{, for remote monitors}
15811 @cindex hash mark while downloading
15812 This command controls whether a hash mark @samp{#} is displayed while
15813 downloading a file to the remote monitor. If on, a hash mark is
15814 displayed after each S-record is successfully downloaded to the
15818 @kindex show hash@r{, for remote monitors}
15819 Show the current status of displaying the hash mark.
15821 @item set debug monitor
15822 @kindex set debug monitor
15823 @cindex display remote monitor communications
15824 Enable or disable display of communications messages between
15825 @value{GDBN} and the remote monitor.
15827 @item show debug monitor
15828 @kindex show debug monitor
15829 Show the current status of displaying communications between
15830 @value{GDBN} and the remote monitor.
15835 @kindex load @var{filename}
15836 @item load @var{filename}
15838 Depending on what remote debugging facilities are configured into
15839 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15840 is meant to make @var{filename} (an executable) available for debugging
15841 on the remote system---by downloading, or dynamic linking, for example.
15842 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15843 the @code{add-symbol-file} command.
15845 If your @value{GDBN} does not have a @code{load} command, attempting to
15846 execute it gets the error message ``@code{You can't do that when your
15847 target is @dots{}}''
15849 The file is loaded at whatever address is specified in the executable.
15850 For some object file formats, you can specify the load address when you
15851 link the program; for other formats, like a.out, the object file format
15852 specifies a fixed address.
15853 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15855 Depending on the remote side capabilities, @value{GDBN} may be able to
15856 load programs into flash memory.
15858 @code{load} does not repeat if you press @key{RET} again after using it.
15862 @section Choosing Target Byte Order
15864 @cindex choosing target byte order
15865 @cindex target byte order
15867 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15868 offer the ability to run either big-endian or little-endian byte
15869 orders. Usually the executable or symbol will include a bit to
15870 designate the endian-ness, and you will not need to worry about
15871 which to use. However, you may still find it useful to adjust
15872 @value{GDBN}'s idea of processor endian-ness manually.
15876 @item set endian big
15877 Instruct @value{GDBN} to assume the target is big-endian.
15879 @item set endian little
15880 Instruct @value{GDBN} to assume the target is little-endian.
15882 @item set endian auto
15883 Instruct @value{GDBN} to use the byte order associated with the
15887 Display @value{GDBN}'s current idea of the target byte order.
15891 Note that these commands merely adjust interpretation of symbolic
15892 data on the host, and that they have absolutely no effect on the
15896 @node Remote Debugging
15897 @chapter Debugging Remote Programs
15898 @cindex remote debugging
15900 If you are trying to debug a program running on a machine that cannot run
15901 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15902 For example, you might use remote debugging on an operating system kernel,
15903 or on a small system which does not have a general purpose operating system
15904 powerful enough to run a full-featured debugger.
15906 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15907 to make this work with particular debugging targets. In addition,
15908 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15909 but not specific to any particular target system) which you can use if you
15910 write the remote stubs---the code that runs on the remote system to
15911 communicate with @value{GDBN}.
15913 Other remote targets may be available in your
15914 configuration of @value{GDBN}; use @code{help target} to list them.
15917 * Connecting:: Connecting to a remote target
15918 * File Transfer:: Sending files to a remote system
15919 * Server:: Using the gdbserver program
15920 * Remote Configuration:: Remote configuration
15921 * Remote Stub:: Implementing a remote stub
15925 @section Connecting to a Remote Target
15927 On the @value{GDBN} host machine, you will need an unstripped copy of
15928 your program, since @value{GDBN} needs symbol and debugging information.
15929 Start up @value{GDBN} as usual, using the name of the local copy of your
15930 program as the first argument.
15932 @cindex @code{target remote}
15933 @value{GDBN} can communicate with the target over a serial line, or
15934 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15935 each case, @value{GDBN} uses the same protocol for debugging your
15936 program; only the medium carrying the debugging packets varies. The
15937 @code{target remote} command establishes a connection to the target.
15938 Its arguments indicate which medium to use:
15942 @item target remote @var{serial-device}
15943 @cindex serial line, @code{target remote}
15944 Use @var{serial-device} to communicate with the target. For example,
15945 to use a serial line connected to the device named @file{/dev/ttyb}:
15948 target remote /dev/ttyb
15951 If you're using a serial line, you may want to give @value{GDBN} the
15952 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15953 (@pxref{Remote Configuration, set remotebaud}) before the
15954 @code{target} command.
15956 @item target remote @code{@var{host}:@var{port}}
15957 @itemx target remote @code{tcp:@var{host}:@var{port}}
15958 @cindex @acronym{TCP} port, @code{target remote}
15959 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15960 The @var{host} may be either a host name or a numeric @acronym{IP}
15961 address; @var{port} must be a decimal number. The @var{host} could be
15962 the target machine itself, if it is directly connected to the net, or
15963 it might be a terminal server which in turn has a serial line to the
15966 For example, to connect to port 2828 on a terminal server named
15970 target remote manyfarms:2828
15973 If your remote target is actually running on the same machine as your
15974 debugger session (e.g.@: a simulator for your target running on the
15975 same host), you can omit the hostname. For example, to connect to
15976 port 1234 on your local machine:
15979 target remote :1234
15983 Note that the colon is still required here.
15985 @item target remote @code{udp:@var{host}:@var{port}}
15986 @cindex @acronym{UDP} port, @code{target remote}
15987 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15988 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15991 target remote udp:manyfarms:2828
15994 When using a @acronym{UDP} connection for remote debugging, you should
15995 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15996 can silently drop packets on busy or unreliable networks, which will
15997 cause havoc with your debugging session.
15999 @item target remote | @var{command}
16000 @cindex pipe, @code{target remote} to
16001 Run @var{command} in the background and communicate with it using a
16002 pipe. The @var{command} is a shell command, to be parsed and expanded
16003 by the system's command shell, @code{/bin/sh}; it should expect remote
16004 protocol packets on its standard input, and send replies on its
16005 standard output. You could use this to run a stand-alone simulator
16006 that speaks the remote debugging protocol, to make net connections
16007 using programs like @code{ssh}, or for other similar tricks.
16009 If @var{command} closes its standard output (perhaps by exiting),
16010 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16011 program has already exited, this will have no effect.)
16015 Once the connection has been established, you can use all the usual
16016 commands to examine and change data. The remote program is already
16017 running; you can use @kbd{step} and @kbd{continue}, and you do not
16018 need to use @kbd{run}.
16020 @cindex interrupting remote programs
16021 @cindex remote programs, interrupting
16022 Whenever @value{GDBN} is waiting for the remote program, if you type the
16023 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16024 program. This may or may not succeed, depending in part on the hardware
16025 and the serial drivers the remote system uses. If you type the
16026 interrupt character once again, @value{GDBN} displays this prompt:
16029 Interrupted while waiting for the program.
16030 Give up (and stop debugging it)? (y or n)
16033 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16034 (If you decide you want to try again later, you can use @samp{target
16035 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16036 goes back to waiting.
16039 @kindex detach (remote)
16041 When you have finished debugging the remote program, you can use the
16042 @code{detach} command to release it from @value{GDBN} control.
16043 Detaching from the target normally resumes its execution, but the results
16044 will depend on your particular remote stub. After the @code{detach}
16045 command, @value{GDBN} is free to connect to another target.
16049 The @code{disconnect} command behaves like @code{detach}, except that
16050 the target is generally not resumed. It will wait for @value{GDBN}
16051 (this instance or another one) to connect and continue debugging. After
16052 the @code{disconnect} command, @value{GDBN} is again free to connect to
16055 @cindex send command to remote monitor
16056 @cindex extend @value{GDBN} for remote targets
16057 @cindex add new commands for external monitor
16059 @item monitor @var{cmd}
16060 This command allows you to send arbitrary commands directly to the
16061 remote monitor. Since @value{GDBN} doesn't care about the commands it
16062 sends like this, this command is the way to extend @value{GDBN}---you
16063 can add new commands that only the external monitor will understand
16067 @node File Transfer
16068 @section Sending files to a remote system
16069 @cindex remote target, file transfer
16070 @cindex file transfer
16071 @cindex sending files to remote systems
16073 Some remote targets offer the ability to transfer files over the same
16074 connection used to communicate with @value{GDBN}. This is convenient
16075 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16076 running @code{gdbserver} over a network interface. For other targets,
16077 e.g.@: embedded devices with only a single serial port, this may be
16078 the only way to upload or download files.
16080 Not all remote targets support these commands.
16084 @item remote put @var{hostfile} @var{targetfile}
16085 Copy file @var{hostfile} from the host system (the machine running
16086 @value{GDBN}) to @var{targetfile} on the target system.
16089 @item remote get @var{targetfile} @var{hostfile}
16090 Copy file @var{targetfile} from the target system to @var{hostfile}
16091 on the host system.
16093 @kindex remote delete
16094 @item remote delete @var{targetfile}
16095 Delete @var{targetfile} from the target system.
16100 @section Using the @code{gdbserver} Program
16103 @cindex remote connection without stubs
16104 @code{gdbserver} is a control program for Unix-like systems, which
16105 allows you to connect your program with a remote @value{GDBN} via
16106 @code{target remote}---but without linking in the usual debugging stub.
16108 @code{gdbserver} is not a complete replacement for the debugging stubs,
16109 because it requires essentially the same operating-system facilities
16110 that @value{GDBN} itself does. In fact, a system that can run
16111 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16112 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16113 because it is a much smaller program than @value{GDBN} itself. It is
16114 also easier to port than all of @value{GDBN}, so you may be able to get
16115 started more quickly on a new system by using @code{gdbserver}.
16116 Finally, if you develop code for real-time systems, you may find that
16117 the tradeoffs involved in real-time operation make it more convenient to
16118 do as much development work as possible on another system, for example
16119 by cross-compiling. You can use @code{gdbserver} to make a similar
16120 choice for debugging.
16122 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16123 or a TCP connection, using the standard @value{GDBN} remote serial
16127 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16128 Do not run @code{gdbserver} connected to any public network; a
16129 @value{GDBN} connection to @code{gdbserver} provides access to the
16130 target system with the same privileges as the user running
16134 @subsection Running @code{gdbserver}
16135 @cindex arguments, to @code{gdbserver}
16136 @cindex @code{gdbserver}, command-line arguments
16138 Run @code{gdbserver} on the target system. You need a copy of the
16139 program you want to debug, including any libraries it requires.
16140 @code{gdbserver} does not need your program's symbol table, so you can
16141 strip the program if necessary to save space. @value{GDBN} on the host
16142 system does all the symbol handling.
16144 To use the server, you must tell it how to communicate with @value{GDBN};
16145 the name of your program; and the arguments for your program. The usual
16149 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16152 @var{comm} is either a device name (to use a serial line) or a TCP
16153 hostname and portnumber. For example, to debug Emacs with the argument
16154 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16158 target> gdbserver /dev/com1 emacs foo.txt
16161 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16164 To use a TCP connection instead of a serial line:
16167 target> gdbserver host:2345 emacs foo.txt
16170 The only difference from the previous example is the first argument,
16171 specifying that you are communicating with the host @value{GDBN} via
16172 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16173 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16174 (Currently, the @samp{host} part is ignored.) You can choose any number
16175 you want for the port number as long as it does not conflict with any
16176 TCP ports already in use on the target system (for example, @code{23} is
16177 reserved for @code{telnet}).@footnote{If you choose a port number that
16178 conflicts with another service, @code{gdbserver} prints an error message
16179 and exits.} You must use the same port number with the host @value{GDBN}
16180 @code{target remote} command.
16182 @subsubsection Attaching to a Running Program
16183 @cindex attach to a program, @code{gdbserver}
16184 @cindex @option{--attach}, @code{gdbserver} option
16186 On some targets, @code{gdbserver} can also attach to running programs.
16187 This is accomplished via the @code{--attach} argument. The syntax is:
16190 target> gdbserver --attach @var{comm} @var{pid}
16193 @var{pid} is the process ID of a currently running process. It isn't necessary
16194 to point @code{gdbserver} at a binary for the running process.
16197 You can debug processes by name instead of process ID if your target has the
16198 @code{pidof} utility:
16201 target> gdbserver --attach @var{comm} `pidof @var{program}`
16204 In case more than one copy of @var{program} is running, or @var{program}
16205 has multiple threads, most versions of @code{pidof} support the
16206 @code{-s} option to only return the first process ID.
16208 @subsubsection Multi-Process Mode for @code{gdbserver}
16209 @cindex @code{gdbserver}, multiple processes
16210 @cindex multiple processes with @code{gdbserver}
16212 When you connect to @code{gdbserver} using @code{target remote},
16213 @code{gdbserver} debugs the specified program only once. When the
16214 program exits, or you detach from it, @value{GDBN} closes the connection
16215 and @code{gdbserver} exits.
16217 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16218 enters multi-process mode. When the debugged program exits, or you
16219 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16220 though no program is running. The @code{run} and @code{attach}
16221 commands instruct @code{gdbserver} to run or attach to a new program.
16222 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16223 remote exec-file}) to select the program to run. Command line
16224 arguments are supported, except for wildcard expansion and I/O
16225 redirection (@pxref{Arguments}).
16227 @cindex @option{--multi}, @code{gdbserver} option
16228 To start @code{gdbserver} without supplying an initial command to run
16229 or process ID to attach, use the @option{--multi} command line option.
16230 Then you can connect using @kbd{target extended-remote} and start
16231 the program you want to debug.
16233 In multi-process mode @code{gdbserver} does not automatically exit unless you
16234 use the option @option{--once}. You can terminate it by using
16235 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16236 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16237 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16238 @option{--multi} option to @code{gdbserver} has no influence on that.
16240 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16242 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16244 @code{gdbserver} normally terminates after all of its debugged processes have
16245 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16246 extended-remote}, @code{gdbserver} stays running even with no processes left.
16247 @value{GDBN} normally terminates the spawned debugged process on its exit,
16248 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16249 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16250 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16251 stays running even in the @kbd{target remote} mode.
16253 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16254 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16255 completeness, at most one @value{GDBN} can be connected at a time.
16257 @cindex @option{--once}, @code{gdbserver} option
16258 By default, @code{gdbserver} keeps the listening TCP port open, so that
16259 additional connections are possible. However, if you start @code{gdbserver}
16260 with the @option{--once} option, it will stop listening for any further
16261 connection attempts after connecting to the first @value{GDBN} session. This
16262 means no further connections to @code{gdbserver} will be possible after the
16263 first one. It also means @code{gdbserver} will terminate after the first
16264 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16265 connections and even in the @kbd{target extended-remote} mode. The
16266 @option{--once} option allows reusing the same port number for connecting to
16267 multiple instances of @code{gdbserver} running on the same host, since each
16268 instance closes its port after the first connection.
16270 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16272 @cindex @option{--debug}, @code{gdbserver} option
16273 The @option{--debug} option tells @code{gdbserver} to display extra
16274 status information about the debugging process.
16275 @cindex @option{--remote-debug}, @code{gdbserver} option
16276 The @option{--remote-debug} option tells @code{gdbserver} to display
16277 remote protocol debug output. These options are intended for
16278 @code{gdbserver} development and for bug reports to the developers.
16280 @cindex @option{--wrapper}, @code{gdbserver} option
16281 The @option{--wrapper} option specifies a wrapper to launch programs
16282 for debugging. The option should be followed by the name of the
16283 wrapper, then any command-line arguments to pass to the wrapper, then
16284 @kbd{--} indicating the end of the wrapper arguments.
16286 @code{gdbserver} runs the specified wrapper program with a combined
16287 command line including the wrapper arguments, then the name of the
16288 program to debug, then any arguments to the program. The wrapper
16289 runs until it executes your program, and then @value{GDBN} gains control.
16291 You can use any program that eventually calls @code{execve} with
16292 its arguments as a wrapper. Several standard Unix utilities do
16293 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16294 with @code{exec "$@@"} will also work.
16296 For example, you can use @code{env} to pass an environment variable to
16297 the debugged program, without setting the variable in @code{gdbserver}'s
16301 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16304 @subsection Connecting to @code{gdbserver}
16306 Run @value{GDBN} on the host system.
16308 First make sure you have the necessary symbol files. Load symbols for
16309 your application using the @code{file} command before you connect. Use
16310 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16311 was compiled with the correct sysroot using @code{--with-sysroot}).
16313 The symbol file and target libraries must exactly match the executable
16314 and libraries on the target, with one exception: the files on the host
16315 system should not be stripped, even if the files on the target system
16316 are. Mismatched or missing files will lead to confusing results
16317 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16318 files may also prevent @code{gdbserver} from debugging multi-threaded
16321 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16322 For TCP connections, you must start up @code{gdbserver} prior to using
16323 the @code{target remote} command. Otherwise you may get an error whose
16324 text depends on the host system, but which usually looks something like
16325 @samp{Connection refused}. Don't use the @code{load}
16326 command in @value{GDBN} when using @code{gdbserver}, since the program is
16327 already on the target.
16329 @subsection Monitor Commands for @code{gdbserver}
16330 @cindex monitor commands, for @code{gdbserver}
16331 @anchor{Monitor Commands for gdbserver}
16333 During a @value{GDBN} session using @code{gdbserver}, you can use the
16334 @code{monitor} command to send special requests to @code{gdbserver}.
16335 Here are the available commands.
16339 List the available monitor commands.
16341 @item monitor set debug 0
16342 @itemx monitor set debug 1
16343 Disable or enable general debugging messages.
16345 @item monitor set remote-debug 0
16346 @itemx monitor set remote-debug 1
16347 Disable or enable specific debugging messages associated with the remote
16348 protocol (@pxref{Remote Protocol}).
16350 @item monitor set libthread-db-search-path [PATH]
16351 @cindex gdbserver, search path for @code{libthread_db}
16352 When this command is issued, @var{path} is a colon-separated list of
16353 directories to search for @code{libthread_db} (@pxref{Threads,,set
16354 libthread-db-search-path}). If you omit @var{path},
16355 @samp{libthread-db-search-path} will be reset to an empty list.
16358 Tell gdbserver to exit immediately. This command should be followed by
16359 @code{disconnect} to close the debugging session. @code{gdbserver} will
16360 detach from any attached processes and kill any processes it created.
16361 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16362 of a multi-process mode debug session.
16366 @subsection Tracepoints support in @code{gdbserver}
16367 @cindex tracepoints support in @code{gdbserver}
16369 On some targets, @code{gdbserver} supports tracepoints, fast
16370 tracepoints and static tracepoints.
16372 For fast or static tracepoints to work, a special library called the
16373 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16374 This library is built and distributed as an integral part of
16375 @code{gdbserver}. In addition, support for static tracepoints
16376 requires building the in-process agent library with static tracepoints
16377 support. At present, the UST (LTTng Userspace Tracer,
16378 @url{http://lttng.org/ust}) tracing engine is supported. This support
16379 is automatically available if UST development headers are found in the
16380 standard include path when @code{gdbserver} is built, or if
16381 @code{gdbserver} was explicitly configured using @option{--with-ust}
16382 to point at such headers. You can explicitly disable the support
16383 using @option{--with-ust=no}.
16385 There are several ways to load the in-process agent in your program:
16388 @item Specifying it as dependency at link time
16390 You can link your program dynamically with the in-process agent
16391 library. On most systems, this is accomplished by adding
16392 @code{-linproctrace} to the link command.
16394 @item Using the system's preloading mechanisms
16396 You can force loading the in-process agent at startup time by using
16397 your system's support for preloading shared libraries. Many Unixes
16398 support the concept of preloading user defined libraries. In most
16399 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16400 in the environment. See also the description of @code{gdbserver}'s
16401 @option{--wrapper} command line option.
16403 @item Using @value{GDBN} to force loading the agent at run time
16405 On some systems, you can force the inferior to load a shared library,
16406 by calling a dynamic loader function in the inferior that takes care
16407 of dynamically looking up and loading a shared library. On most Unix
16408 systems, the function is @code{dlopen}. You'll use the @code{call}
16409 command for that. For example:
16412 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16415 Note that on most Unix systems, for the @code{dlopen} function to be
16416 available, the program needs to be linked with @code{-ldl}.
16419 On systems that have a userspace dynamic loader, like most Unix
16420 systems, when you connect to @code{gdbserver} using @code{target
16421 remote}, you'll find that the program is stopped at the dynamic
16422 loader's entry point, and no shared library has been loaded in the
16423 program's address space yet, including the in-process agent. In that
16424 case, before being able to use any of the fast or static tracepoints
16425 features, you need to let the loader run and load the shared
16426 libraries. The simplest way to do that is to run the program to the
16427 main procedure. E.g., if debugging a C or C@t{++} program, start
16428 @code{gdbserver} like so:
16431 $ gdbserver :9999 myprogram
16434 Start GDB and connect to @code{gdbserver} like so, and run to main:
16438 (@value{GDBP}) target remote myhost:9999
16439 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16440 (@value{GDBP}) b main
16441 (@value{GDBP}) continue
16444 The in-process tracing agent library should now be loaded into the
16445 process; you can confirm it with the @code{info sharedlibrary}
16446 command, which will list @file{libinproctrace.so} as loaded in the
16447 process. You are now ready to install fast tracepoints, list static
16448 tracepoint markers, probe static tracepoints markers, and start
16451 @node Remote Configuration
16452 @section Remote Configuration
16455 @kindex show remote
16456 This section documents the configuration options available when
16457 debugging remote programs. For the options related to the File I/O
16458 extensions of the remote protocol, see @ref{system,
16459 system-call-allowed}.
16462 @item set remoteaddresssize @var{bits}
16463 @cindex address size for remote targets
16464 @cindex bits in remote address
16465 Set the maximum size of address in a memory packet to the specified
16466 number of bits. @value{GDBN} will mask off the address bits above
16467 that number, when it passes addresses to the remote target. The
16468 default value is the number of bits in the target's address.
16470 @item show remoteaddresssize
16471 Show the current value of remote address size in bits.
16473 @item set remotebaud @var{n}
16474 @cindex baud rate for remote targets
16475 Set the baud rate for the remote serial I/O to @var{n} baud. The
16476 value is used to set the speed of the serial port used for debugging
16479 @item show remotebaud
16480 Show the current speed of the remote connection.
16482 @item set remotebreak
16483 @cindex interrupt remote programs
16484 @cindex BREAK signal instead of Ctrl-C
16485 @anchor{set remotebreak}
16486 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16487 when you type @kbd{Ctrl-c} to interrupt the program running
16488 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16489 character instead. The default is off, since most remote systems
16490 expect to see @samp{Ctrl-C} as the interrupt signal.
16492 @item show remotebreak
16493 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16494 interrupt the remote program.
16496 @item set remoteflow on
16497 @itemx set remoteflow off
16498 @kindex set remoteflow
16499 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16500 on the serial port used to communicate to the remote target.
16502 @item show remoteflow
16503 @kindex show remoteflow
16504 Show the current setting of hardware flow control.
16506 @item set remotelogbase @var{base}
16507 Set the base (a.k.a.@: radix) of logging serial protocol
16508 communications to @var{base}. Supported values of @var{base} are:
16509 @code{ascii}, @code{octal}, and @code{hex}. The default is
16512 @item show remotelogbase
16513 Show the current setting of the radix for logging remote serial
16516 @item set remotelogfile @var{file}
16517 @cindex record serial communications on file
16518 Record remote serial communications on the named @var{file}. The
16519 default is not to record at all.
16521 @item show remotelogfile.
16522 Show the current setting of the file name on which to record the
16523 serial communications.
16525 @item set remotetimeout @var{num}
16526 @cindex timeout for serial communications
16527 @cindex remote timeout
16528 Set the timeout limit to wait for the remote target to respond to
16529 @var{num} seconds. The default is 2 seconds.
16531 @item show remotetimeout
16532 Show the current number of seconds to wait for the remote target
16535 @cindex limit hardware breakpoints and watchpoints
16536 @cindex remote target, limit break- and watchpoints
16537 @anchor{set remote hardware-watchpoint-limit}
16538 @anchor{set remote hardware-breakpoint-limit}
16539 @item set remote hardware-watchpoint-limit @var{limit}
16540 @itemx set remote hardware-breakpoint-limit @var{limit}
16541 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16542 watchpoints. A limit of -1, the default, is treated as unlimited.
16544 @item set remote exec-file @var{filename}
16545 @itemx show remote exec-file
16546 @anchor{set remote exec-file}
16547 @cindex executable file, for remote target
16548 Select the file used for @code{run} with @code{target
16549 extended-remote}. This should be set to a filename valid on the
16550 target system. If it is not set, the target will use a default
16551 filename (e.g.@: the last program run).
16553 @item set remote interrupt-sequence
16554 @cindex interrupt remote programs
16555 @cindex select Ctrl-C, BREAK or BREAK-g
16556 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16557 @samp{BREAK-g} as the
16558 sequence to the remote target in order to interrupt the execution.
16559 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16560 is high level of serial line for some certain time.
16561 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16562 It is @code{BREAK} signal followed by character @code{g}.
16564 @item show interrupt-sequence
16565 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16566 is sent by @value{GDBN} to interrupt the remote program.
16567 @code{BREAK-g} is BREAK signal followed by @code{g} and
16568 also known as Magic SysRq g.
16570 @item set remote interrupt-on-connect
16571 @cindex send interrupt-sequence on start
16572 Specify whether interrupt-sequence is sent to remote target when
16573 @value{GDBN} connects to it. This is mostly needed when you debug
16574 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16575 which is known as Magic SysRq g in order to connect @value{GDBN}.
16577 @item show interrupt-on-connect
16578 Show whether interrupt-sequence is sent
16579 to remote target when @value{GDBN} connects to it.
16583 @item set tcp auto-retry on
16584 @cindex auto-retry, for remote TCP target
16585 Enable auto-retry for remote TCP connections. This is useful if the remote
16586 debugging agent is launched in parallel with @value{GDBN}; there is a race
16587 condition because the agent may not become ready to accept the connection
16588 before @value{GDBN} attempts to connect. When auto-retry is
16589 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16590 to establish the connection using the timeout specified by
16591 @code{set tcp connect-timeout}.
16593 @item set tcp auto-retry off
16594 Do not auto-retry failed TCP connections.
16596 @item show tcp auto-retry
16597 Show the current auto-retry setting.
16599 @item set tcp connect-timeout @var{seconds}
16600 @cindex connection timeout, for remote TCP target
16601 @cindex timeout, for remote target connection
16602 Set the timeout for establishing a TCP connection to the remote target to
16603 @var{seconds}. The timeout affects both polling to retry failed connections
16604 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16605 that are merely slow to complete, and represents an approximate cumulative
16608 @item show tcp connect-timeout
16609 Show the current connection timeout setting.
16612 @cindex remote packets, enabling and disabling
16613 The @value{GDBN} remote protocol autodetects the packets supported by
16614 your debugging stub. If you need to override the autodetection, you
16615 can use these commands to enable or disable individual packets. Each
16616 packet can be set to @samp{on} (the remote target supports this
16617 packet), @samp{off} (the remote target does not support this packet),
16618 or @samp{auto} (detect remote target support for this packet). They
16619 all default to @samp{auto}. For more information about each packet,
16620 see @ref{Remote Protocol}.
16622 During normal use, you should not have to use any of these commands.
16623 If you do, that may be a bug in your remote debugging stub, or a bug
16624 in @value{GDBN}. You may want to report the problem to the
16625 @value{GDBN} developers.
16627 For each packet @var{name}, the command to enable or disable the
16628 packet is @code{set remote @var{name}-packet}. The available settings
16631 @multitable @columnfractions 0.28 0.32 0.25
16634 @tab Related Features
16636 @item @code{fetch-register}
16638 @tab @code{info registers}
16640 @item @code{set-register}
16644 @item @code{binary-download}
16646 @tab @code{load}, @code{set}
16648 @item @code{read-aux-vector}
16649 @tab @code{qXfer:auxv:read}
16650 @tab @code{info auxv}
16652 @item @code{symbol-lookup}
16653 @tab @code{qSymbol}
16654 @tab Detecting multiple threads
16656 @item @code{attach}
16657 @tab @code{vAttach}
16660 @item @code{verbose-resume}
16662 @tab Stepping or resuming multiple threads
16668 @item @code{software-breakpoint}
16672 @item @code{hardware-breakpoint}
16676 @item @code{write-watchpoint}
16680 @item @code{read-watchpoint}
16684 @item @code{access-watchpoint}
16688 @item @code{target-features}
16689 @tab @code{qXfer:features:read}
16690 @tab @code{set architecture}
16692 @item @code{library-info}
16693 @tab @code{qXfer:libraries:read}
16694 @tab @code{info sharedlibrary}
16696 @item @code{memory-map}
16697 @tab @code{qXfer:memory-map:read}
16698 @tab @code{info mem}
16700 @item @code{read-sdata-object}
16701 @tab @code{qXfer:sdata:read}
16702 @tab @code{print $_sdata}
16704 @item @code{read-spu-object}
16705 @tab @code{qXfer:spu:read}
16706 @tab @code{info spu}
16708 @item @code{write-spu-object}
16709 @tab @code{qXfer:spu:write}
16710 @tab @code{info spu}
16712 @item @code{read-siginfo-object}
16713 @tab @code{qXfer:siginfo:read}
16714 @tab @code{print $_siginfo}
16716 @item @code{write-siginfo-object}
16717 @tab @code{qXfer:siginfo:write}
16718 @tab @code{set $_siginfo}
16720 @item @code{threads}
16721 @tab @code{qXfer:threads:read}
16722 @tab @code{info threads}
16724 @item @code{get-thread-local-@*storage-address}
16725 @tab @code{qGetTLSAddr}
16726 @tab Displaying @code{__thread} variables
16728 @item @code{get-thread-information-block-address}
16729 @tab @code{qGetTIBAddr}
16730 @tab Display MS-Windows Thread Information Block.
16732 @item @code{search-memory}
16733 @tab @code{qSearch:memory}
16736 @item @code{supported-packets}
16737 @tab @code{qSupported}
16738 @tab Remote communications parameters
16740 @item @code{pass-signals}
16741 @tab @code{QPassSignals}
16742 @tab @code{handle @var{signal}}
16744 @item @code{hostio-close-packet}
16745 @tab @code{vFile:close}
16746 @tab @code{remote get}, @code{remote put}
16748 @item @code{hostio-open-packet}
16749 @tab @code{vFile:open}
16750 @tab @code{remote get}, @code{remote put}
16752 @item @code{hostio-pread-packet}
16753 @tab @code{vFile:pread}
16754 @tab @code{remote get}, @code{remote put}
16756 @item @code{hostio-pwrite-packet}
16757 @tab @code{vFile:pwrite}
16758 @tab @code{remote get}, @code{remote put}
16760 @item @code{hostio-unlink-packet}
16761 @tab @code{vFile:unlink}
16762 @tab @code{remote delete}
16764 @item @code{noack-packet}
16765 @tab @code{QStartNoAckMode}
16766 @tab Packet acknowledgment
16768 @item @code{osdata}
16769 @tab @code{qXfer:osdata:read}
16770 @tab @code{info os}
16772 @item @code{query-attached}
16773 @tab @code{qAttached}
16774 @tab Querying remote process attach state.
16776 @item @code{traceframe-info}
16777 @tab @code{qXfer:traceframe-info:read}
16778 @tab Traceframe info
16782 @section Implementing a Remote Stub
16784 @cindex debugging stub, example
16785 @cindex remote stub, example
16786 @cindex stub example, remote debugging
16787 The stub files provided with @value{GDBN} implement the target side of the
16788 communication protocol, and the @value{GDBN} side is implemented in the
16789 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16790 these subroutines to communicate, and ignore the details. (If you're
16791 implementing your own stub file, you can still ignore the details: start
16792 with one of the existing stub files. @file{sparc-stub.c} is the best
16793 organized, and therefore the easiest to read.)
16795 @cindex remote serial debugging, overview
16796 To debug a program running on another machine (the debugging
16797 @dfn{target} machine), you must first arrange for all the usual
16798 prerequisites for the program to run by itself. For example, for a C
16803 A startup routine to set up the C runtime environment; these usually
16804 have a name like @file{crt0}. The startup routine may be supplied by
16805 your hardware supplier, or you may have to write your own.
16808 A C subroutine library to support your program's
16809 subroutine calls, notably managing input and output.
16812 A way of getting your program to the other machine---for example, a
16813 download program. These are often supplied by the hardware
16814 manufacturer, but you may have to write your own from hardware
16818 The next step is to arrange for your program to use a serial port to
16819 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16820 machine). In general terms, the scheme looks like this:
16824 @value{GDBN} already understands how to use this protocol; when everything
16825 else is set up, you can simply use the @samp{target remote} command
16826 (@pxref{Targets,,Specifying a Debugging Target}).
16828 @item On the target,
16829 you must link with your program a few special-purpose subroutines that
16830 implement the @value{GDBN} remote serial protocol. The file containing these
16831 subroutines is called a @dfn{debugging stub}.
16833 On certain remote targets, you can use an auxiliary program
16834 @code{gdbserver} instead of linking a stub into your program.
16835 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16838 The debugging stub is specific to the architecture of the remote
16839 machine; for example, use @file{sparc-stub.c} to debug programs on
16842 @cindex remote serial stub list
16843 These working remote stubs are distributed with @value{GDBN}:
16848 @cindex @file{i386-stub.c}
16851 For Intel 386 and compatible architectures.
16854 @cindex @file{m68k-stub.c}
16855 @cindex Motorola 680x0
16857 For Motorola 680x0 architectures.
16860 @cindex @file{sh-stub.c}
16863 For Renesas SH architectures.
16866 @cindex @file{sparc-stub.c}
16868 For @sc{sparc} architectures.
16870 @item sparcl-stub.c
16871 @cindex @file{sparcl-stub.c}
16874 For Fujitsu @sc{sparclite} architectures.
16878 The @file{README} file in the @value{GDBN} distribution may list other
16879 recently added stubs.
16882 * Stub Contents:: What the stub can do for you
16883 * Bootstrapping:: What you must do for the stub
16884 * Debug Session:: Putting it all together
16887 @node Stub Contents
16888 @subsection What the Stub Can Do for You
16890 @cindex remote serial stub
16891 The debugging stub for your architecture supplies these three
16895 @item set_debug_traps
16896 @findex set_debug_traps
16897 @cindex remote serial stub, initialization
16898 This routine arranges for @code{handle_exception} to run when your
16899 program stops. You must call this subroutine explicitly near the
16900 beginning of your program.
16902 @item handle_exception
16903 @findex handle_exception
16904 @cindex remote serial stub, main routine
16905 This is the central workhorse, but your program never calls it
16906 explicitly---the setup code arranges for @code{handle_exception} to
16907 run when a trap is triggered.
16909 @code{handle_exception} takes control when your program stops during
16910 execution (for example, on a breakpoint), and mediates communications
16911 with @value{GDBN} on the host machine. This is where the communications
16912 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16913 representative on the target machine. It begins by sending summary
16914 information on the state of your program, then continues to execute,
16915 retrieving and transmitting any information @value{GDBN} needs, until you
16916 execute a @value{GDBN} command that makes your program resume; at that point,
16917 @code{handle_exception} returns control to your own code on the target
16921 @cindex @code{breakpoint} subroutine, remote
16922 Use this auxiliary subroutine to make your program contain a
16923 breakpoint. Depending on the particular situation, this may be the only
16924 way for @value{GDBN} to get control. For instance, if your target
16925 machine has some sort of interrupt button, you won't need to call this;
16926 pressing the interrupt button transfers control to
16927 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16928 simply receiving characters on the serial port may also trigger a trap;
16929 again, in that situation, you don't need to call @code{breakpoint} from
16930 your own program---simply running @samp{target remote} from the host
16931 @value{GDBN} session gets control.
16933 Call @code{breakpoint} if none of these is true, or if you simply want
16934 to make certain your program stops at a predetermined point for the
16935 start of your debugging session.
16938 @node Bootstrapping
16939 @subsection What You Must Do for the Stub
16941 @cindex remote stub, support routines
16942 The debugging stubs that come with @value{GDBN} are set up for a particular
16943 chip architecture, but they have no information about the rest of your
16944 debugging target machine.
16946 First of all you need to tell the stub how to communicate with the
16950 @item int getDebugChar()
16951 @findex getDebugChar
16952 Write this subroutine to read a single character from the serial port.
16953 It may be identical to @code{getchar} for your target system; a
16954 different name is used to allow you to distinguish the two if you wish.
16956 @item void putDebugChar(int)
16957 @findex putDebugChar
16958 Write this subroutine to write a single character to the serial port.
16959 It may be identical to @code{putchar} for your target system; a
16960 different name is used to allow you to distinguish the two if you wish.
16963 @cindex control C, and remote debugging
16964 @cindex interrupting remote targets
16965 If you want @value{GDBN} to be able to stop your program while it is
16966 running, you need to use an interrupt-driven serial driver, and arrange
16967 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16968 character). That is the character which @value{GDBN} uses to tell the
16969 remote system to stop.
16971 Getting the debugging target to return the proper status to @value{GDBN}
16972 probably requires changes to the standard stub; one quick and dirty way
16973 is to just execute a breakpoint instruction (the ``dirty'' part is that
16974 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16976 Other routines you need to supply are:
16979 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16980 @findex exceptionHandler
16981 Write this function to install @var{exception_address} in the exception
16982 handling tables. You need to do this because the stub does not have any
16983 way of knowing what the exception handling tables on your target system
16984 are like (for example, the processor's table might be in @sc{rom},
16985 containing entries which point to a table in @sc{ram}).
16986 @var{exception_number} is the exception number which should be changed;
16987 its meaning is architecture-dependent (for example, different numbers
16988 might represent divide by zero, misaligned access, etc). When this
16989 exception occurs, control should be transferred directly to
16990 @var{exception_address}, and the processor state (stack, registers,
16991 and so on) should be just as it is when a processor exception occurs. So if
16992 you want to use a jump instruction to reach @var{exception_address}, it
16993 should be a simple jump, not a jump to subroutine.
16995 For the 386, @var{exception_address} should be installed as an interrupt
16996 gate so that interrupts are masked while the handler runs. The gate
16997 should be at privilege level 0 (the most privileged level). The
16998 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16999 help from @code{exceptionHandler}.
17001 @item void flush_i_cache()
17002 @findex flush_i_cache
17003 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17004 instruction cache, if any, on your target machine. If there is no
17005 instruction cache, this subroutine may be a no-op.
17007 On target machines that have instruction caches, @value{GDBN} requires this
17008 function to make certain that the state of your program is stable.
17012 You must also make sure this library routine is available:
17015 @item void *memset(void *, int, int)
17017 This is the standard library function @code{memset} that sets an area of
17018 memory to a known value. If you have one of the free versions of
17019 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17020 either obtain it from your hardware manufacturer, or write your own.
17023 If you do not use the GNU C compiler, you may need other standard
17024 library subroutines as well; this varies from one stub to another,
17025 but in general the stubs are likely to use any of the common library
17026 subroutines which @code{@value{NGCC}} generates as inline code.
17029 @node Debug Session
17030 @subsection Putting it All Together
17032 @cindex remote serial debugging summary
17033 In summary, when your program is ready to debug, you must follow these
17038 Make sure you have defined the supporting low-level routines
17039 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17041 @code{getDebugChar}, @code{putDebugChar},
17042 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17046 Insert these lines near the top of your program:
17054 For the 680x0 stub only, you need to provide a variable called
17055 @code{exceptionHook}. Normally you just use:
17058 void (*exceptionHook)() = 0;
17062 but if before calling @code{set_debug_traps}, you set it to point to a
17063 function in your program, that function is called when
17064 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17065 error). The function indicated by @code{exceptionHook} is called with
17066 one parameter: an @code{int} which is the exception number.
17069 Compile and link together: your program, the @value{GDBN} debugging stub for
17070 your target architecture, and the supporting subroutines.
17073 Make sure you have a serial connection between your target machine and
17074 the @value{GDBN} host, and identify the serial port on the host.
17077 @c The "remote" target now provides a `load' command, so we should
17078 @c document that. FIXME.
17079 Download your program to your target machine (or get it there by
17080 whatever means the manufacturer provides), and start it.
17083 Start @value{GDBN} on the host, and connect to the target
17084 (@pxref{Connecting,,Connecting to a Remote Target}).
17088 @node Configurations
17089 @chapter Configuration-Specific Information
17091 While nearly all @value{GDBN} commands are available for all native and
17092 cross versions of the debugger, there are some exceptions. This chapter
17093 describes things that are only available in certain configurations.
17095 There are three major categories of configurations: native
17096 configurations, where the host and target are the same, embedded
17097 operating system configurations, which are usually the same for several
17098 different processor architectures, and bare embedded processors, which
17099 are quite different from each other.
17104 * Embedded Processors::
17111 This section describes details specific to particular native
17116 * BSD libkvm Interface:: Debugging BSD kernel memory images
17117 * SVR4 Process Information:: SVR4 process information
17118 * DJGPP Native:: Features specific to the DJGPP port
17119 * Cygwin Native:: Features specific to the Cygwin port
17120 * Hurd Native:: Features specific to @sc{gnu} Hurd
17121 * Neutrino:: Features specific to QNX Neutrino
17122 * Darwin:: Features specific to Darwin
17128 On HP-UX systems, if you refer to a function or variable name that
17129 begins with a dollar sign, @value{GDBN} searches for a user or system
17130 name first, before it searches for a convenience variable.
17133 @node BSD libkvm Interface
17134 @subsection BSD libkvm Interface
17137 @cindex kernel memory image
17138 @cindex kernel crash dump
17140 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17141 interface that provides a uniform interface for accessing kernel virtual
17142 memory images, including live systems and crash dumps. @value{GDBN}
17143 uses this interface to allow you to debug live kernels and kernel crash
17144 dumps on many native BSD configurations. This is implemented as a
17145 special @code{kvm} debugging target. For debugging a live system, load
17146 the currently running kernel into @value{GDBN} and connect to the
17150 (@value{GDBP}) @b{target kvm}
17153 For debugging crash dumps, provide the file name of the crash dump as an
17157 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17160 Once connected to the @code{kvm} target, the following commands are
17166 Set current context from the @dfn{Process Control Block} (PCB) address.
17169 Set current context from proc address. This command isn't available on
17170 modern FreeBSD systems.
17173 @node SVR4 Process Information
17174 @subsection SVR4 Process Information
17176 @cindex examine process image
17177 @cindex process info via @file{/proc}
17179 Many versions of SVR4 and compatible systems provide a facility called
17180 @samp{/proc} that can be used to examine the image of a running
17181 process using file-system subroutines. If @value{GDBN} is configured
17182 for an operating system with this facility, the command @code{info
17183 proc} is available to report information about the process running
17184 your program, or about any process running on your system. @code{info
17185 proc} works only on SVR4 systems that include the @code{procfs} code.
17186 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17187 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17193 @itemx info proc @var{process-id}
17194 Summarize available information about any running process. If a
17195 process ID is specified by @var{process-id}, display information about
17196 that process; otherwise display information about the program being
17197 debugged. The summary includes the debugged process ID, the command
17198 line used to invoke it, its current working directory, and its
17199 executable file's absolute file name.
17201 On some systems, @var{process-id} can be of the form
17202 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17203 within a process. If the optional @var{pid} part is missing, it means
17204 a thread from the process being debugged (the leading @samp{/} still
17205 needs to be present, or else @value{GDBN} will interpret the number as
17206 a process ID rather than a thread ID).
17208 @item info proc mappings
17209 @cindex memory address space mappings
17210 Report the memory address space ranges accessible in the program, with
17211 information on whether the process has read, write, or execute access
17212 rights to each range. On @sc{gnu}/Linux systems, each memory range
17213 includes the object file which is mapped to that range, instead of the
17214 memory access rights to that range.
17216 @item info proc stat
17217 @itemx info proc status
17218 @cindex process detailed status information
17219 These subcommands are specific to @sc{gnu}/Linux systems. They show
17220 the process-related information, including the user ID and group ID;
17221 how many threads are there in the process; its virtual memory usage;
17222 the signals that are pending, blocked, and ignored; its TTY; its
17223 consumption of system and user time; its stack size; its @samp{nice}
17224 value; etc. For more information, see the @samp{proc} man page
17225 (type @kbd{man 5 proc} from your shell prompt).
17227 @item info proc all
17228 Show all the information about the process described under all of the
17229 above @code{info proc} subcommands.
17232 @comment These sub-options of 'info proc' were not included when
17233 @comment procfs.c was re-written. Keep their descriptions around
17234 @comment against the day when someone finds the time to put them back in.
17235 @kindex info proc times
17236 @item info proc times
17237 Starting time, user CPU time, and system CPU time for your program and
17240 @kindex info proc id
17242 Report on the process IDs related to your program: its own process ID,
17243 the ID of its parent, the process group ID, and the session ID.
17246 @item set procfs-trace
17247 @kindex set procfs-trace
17248 @cindex @code{procfs} API calls
17249 This command enables and disables tracing of @code{procfs} API calls.
17251 @item show procfs-trace
17252 @kindex show procfs-trace
17253 Show the current state of @code{procfs} API call tracing.
17255 @item set procfs-file @var{file}
17256 @kindex set procfs-file
17257 Tell @value{GDBN} to write @code{procfs} API trace to the named
17258 @var{file}. @value{GDBN} appends the trace info to the previous
17259 contents of the file. The default is to display the trace on the
17262 @item show procfs-file
17263 @kindex show procfs-file
17264 Show the file to which @code{procfs} API trace is written.
17266 @item proc-trace-entry
17267 @itemx proc-trace-exit
17268 @itemx proc-untrace-entry
17269 @itemx proc-untrace-exit
17270 @kindex proc-trace-entry
17271 @kindex proc-trace-exit
17272 @kindex proc-untrace-entry
17273 @kindex proc-untrace-exit
17274 These commands enable and disable tracing of entries into and exits
17275 from the @code{syscall} interface.
17278 @kindex info pidlist
17279 @cindex process list, QNX Neutrino
17280 For QNX Neutrino only, this command displays the list of all the
17281 processes and all the threads within each process.
17284 @kindex info meminfo
17285 @cindex mapinfo list, QNX Neutrino
17286 For QNX Neutrino only, this command displays the list of all mapinfos.
17290 @subsection Features for Debugging @sc{djgpp} Programs
17291 @cindex @sc{djgpp} debugging
17292 @cindex native @sc{djgpp} debugging
17293 @cindex MS-DOS-specific commands
17296 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17297 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17298 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17299 top of real-mode DOS systems and their emulations.
17301 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17302 defines a few commands specific to the @sc{djgpp} port. This
17303 subsection describes those commands.
17308 This is a prefix of @sc{djgpp}-specific commands which print
17309 information about the target system and important OS structures.
17312 @cindex MS-DOS system info
17313 @cindex free memory information (MS-DOS)
17314 @item info dos sysinfo
17315 This command displays assorted information about the underlying
17316 platform: the CPU type and features, the OS version and flavor, the
17317 DPMI version, and the available conventional and DPMI memory.
17322 @cindex segment descriptor tables
17323 @cindex descriptor tables display
17325 @itemx info dos ldt
17326 @itemx info dos idt
17327 These 3 commands display entries from, respectively, Global, Local,
17328 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17329 tables are data structures which store a descriptor for each segment
17330 that is currently in use. The segment's selector is an index into a
17331 descriptor table; the table entry for that index holds the
17332 descriptor's base address and limit, and its attributes and access
17335 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17336 segment (used for both data and the stack), and a DOS segment (which
17337 allows access to DOS/BIOS data structures and absolute addresses in
17338 conventional memory). However, the DPMI host will usually define
17339 additional segments in order to support the DPMI environment.
17341 @cindex garbled pointers
17342 These commands allow to display entries from the descriptor tables.
17343 Without an argument, all entries from the specified table are
17344 displayed. An argument, which should be an integer expression, means
17345 display a single entry whose index is given by the argument. For
17346 example, here's a convenient way to display information about the
17347 debugged program's data segment:
17350 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17351 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17355 This comes in handy when you want to see whether a pointer is outside
17356 the data segment's limit (i.e.@: @dfn{garbled}).
17358 @cindex page tables display (MS-DOS)
17360 @itemx info dos pte
17361 These two commands display entries from, respectively, the Page
17362 Directory and the Page Tables. Page Directories and Page Tables are
17363 data structures which control how virtual memory addresses are mapped
17364 into physical addresses. A Page Table includes an entry for every
17365 page of memory that is mapped into the program's address space; there
17366 may be several Page Tables, each one holding up to 4096 entries. A
17367 Page Directory has up to 4096 entries, one each for every Page Table
17368 that is currently in use.
17370 Without an argument, @kbd{info dos pde} displays the entire Page
17371 Directory, and @kbd{info dos pte} displays all the entries in all of
17372 the Page Tables. An argument, an integer expression, given to the
17373 @kbd{info dos pde} command means display only that entry from the Page
17374 Directory table. An argument given to the @kbd{info dos pte} command
17375 means display entries from a single Page Table, the one pointed to by
17376 the specified entry in the Page Directory.
17378 @cindex direct memory access (DMA) on MS-DOS
17379 These commands are useful when your program uses @dfn{DMA} (Direct
17380 Memory Access), which needs physical addresses to program the DMA
17383 These commands are supported only with some DPMI servers.
17385 @cindex physical address from linear address
17386 @item info dos address-pte @var{addr}
17387 This command displays the Page Table entry for a specified linear
17388 address. The argument @var{addr} is a linear address which should
17389 already have the appropriate segment's base address added to it,
17390 because this command accepts addresses which may belong to @emph{any}
17391 segment. For example, here's how to display the Page Table entry for
17392 the page where a variable @code{i} is stored:
17395 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17396 @exdent @code{Page Table entry for address 0x11a00d30:}
17397 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17401 This says that @code{i} is stored at offset @code{0xd30} from the page
17402 whose physical base address is @code{0x02698000}, and shows all the
17403 attributes of that page.
17405 Note that you must cast the addresses of variables to a @code{char *},
17406 since otherwise the value of @code{__djgpp_base_address}, the base
17407 address of all variables and functions in a @sc{djgpp} program, will
17408 be added using the rules of C pointer arithmetics: if @code{i} is
17409 declared an @code{int}, @value{GDBN} will add 4 times the value of
17410 @code{__djgpp_base_address} to the address of @code{i}.
17412 Here's another example, it displays the Page Table entry for the
17416 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17417 @exdent @code{Page Table entry for address 0x29110:}
17418 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17422 (The @code{+ 3} offset is because the transfer buffer's address is the
17423 3rd member of the @code{_go32_info_block} structure.) The output
17424 clearly shows that this DPMI server maps the addresses in conventional
17425 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17426 linear (@code{0x29110}) addresses are identical.
17428 This command is supported only with some DPMI servers.
17431 @cindex DOS serial data link, remote debugging
17432 In addition to native debugging, the DJGPP port supports remote
17433 debugging via a serial data link. The following commands are specific
17434 to remote serial debugging in the DJGPP port of @value{GDBN}.
17437 @kindex set com1base
17438 @kindex set com1irq
17439 @kindex set com2base
17440 @kindex set com2irq
17441 @kindex set com3base
17442 @kindex set com3irq
17443 @kindex set com4base
17444 @kindex set com4irq
17445 @item set com1base @var{addr}
17446 This command sets the base I/O port address of the @file{COM1} serial
17449 @item set com1irq @var{irq}
17450 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17451 for the @file{COM1} serial port.
17453 There are similar commands @samp{set com2base}, @samp{set com3irq},
17454 etc.@: for setting the port address and the @code{IRQ} lines for the
17457 @kindex show com1base
17458 @kindex show com1irq
17459 @kindex show com2base
17460 @kindex show com2irq
17461 @kindex show com3base
17462 @kindex show com3irq
17463 @kindex show com4base
17464 @kindex show com4irq
17465 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17466 display the current settings of the base address and the @code{IRQ}
17467 lines used by the COM ports.
17470 @kindex info serial
17471 @cindex DOS serial port status
17472 This command prints the status of the 4 DOS serial ports. For each
17473 port, it prints whether it's active or not, its I/O base address and
17474 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17475 counts of various errors encountered so far.
17479 @node Cygwin Native
17480 @subsection Features for Debugging MS Windows PE Executables
17481 @cindex MS Windows debugging
17482 @cindex native Cygwin debugging
17483 @cindex Cygwin-specific commands
17485 @value{GDBN} supports native debugging of MS Windows programs, including
17486 DLLs with and without symbolic debugging information.
17488 @cindex Ctrl-BREAK, MS-Windows
17489 @cindex interrupt debuggee on MS-Windows
17490 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17491 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17492 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17493 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17494 sequence, which can be used to interrupt the debuggee even if it
17497 There are various additional Cygwin-specific commands, described in
17498 this section. Working with DLLs that have no debugging symbols is
17499 described in @ref{Non-debug DLL Symbols}.
17504 This is a prefix of MS Windows-specific commands which print
17505 information about the target system and important OS structures.
17507 @item info w32 selector
17508 This command displays information returned by
17509 the Win32 API @code{GetThreadSelectorEntry} function.
17510 It takes an optional argument that is evaluated to
17511 a long value to give the information about this given selector.
17512 Without argument, this command displays information
17513 about the six segment registers.
17515 @item info w32 thread-information-block
17516 This command displays thread specific information stored in the
17517 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17518 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17522 This is a Cygwin-specific alias of @code{info shared}.
17524 @kindex dll-symbols
17526 This command loads symbols from a dll similarly to
17527 add-sym command but without the need to specify a base address.
17529 @kindex set cygwin-exceptions
17530 @cindex debugging the Cygwin DLL
17531 @cindex Cygwin DLL, debugging
17532 @item set cygwin-exceptions @var{mode}
17533 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17534 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17535 @value{GDBN} will delay recognition of exceptions, and may ignore some
17536 exceptions which seem to be caused by internal Cygwin DLL
17537 ``bookkeeping''. This option is meant primarily for debugging the
17538 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17539 @value{GDBN} users with false @code{SIGSEGV} signals.
17541 @kindex show cygwin-exceptions
17542 @item show cygwin-exceptions
17543 Displays whether @value{GDBN} will break on exceptions that happen
17544 inside the Cygwin DLL itself.
17546 @kindex set new-console
17547 @item set new-console @var{mode}
17548 If @var{mode} is @code{on} the debuggee will
17549 be started in a new console on next start.
17550 If @var{mode} is @code{off}, the debuggee will
17551 be started in the same console as the debugger.
17553 @kindex show new-console
17554 @item show new-console
17555 Displays whether a new console is used
17556 when the debuggee is started.
17558 @kindex set new-group
17559 @item set new-group @var{mode}
17560 This boolean value controls whether the debuggee should
17561 start a new group or stay in the same group as the debugger.
17562 This affects the way the Windows OS handles
17565 @kindex show new-group
17566 @item show new-group
17567 Displays current value of new-group boolean.
17569 @kindex set debugevents
17570 @item set debugevents
17571 This boolean value adds debug output concerning kernel events related
17572 to the debuggee seen by the debugger. This includes events that
17573 signal thread and process creation and exit, DLL loading and
17574 unloading, console interrupts, and debugging messages produced by the
17575 Windows @code{OutputDebugString} API call.
17577 @kindex set debugexec
17578 @item set debugexec
17579 This boolean value adds debug output concerning execute events
17580 (such as resume thread) seen by the debugger.
17582 @kindex set debugexceptions
17583 @item set debugexceptions
17584 This boolean value adds debug output concerning exceptions in the
17585 debuggee seen by the debugger.
17587 @kindex set debugmemory
17588 @item set debugmemory
17589 This boolean value adds debug output concerning debuggee memory reads
17590 and writes by the debugger.
17594 This boolean values specifies whether the debuggee is called
17595 via a shell or directly (default value is on).
17599 Displays if the debuggee will be started with a shell.
17604 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17607 @node Non-debug DLL Symbols
17608 @subsubsection Support for DLLs without Debugging Symbols
17609 @cindex DLLs with no debugging symbols
17610 @cindex Minimal symbols and DLLs
17612 Very often on windows, some of the DLLs that your program relies on do
17613 not include symbolic debugging information (for example,
17614 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17615 symbols in a DLL, it relies on the minimal amount of symbolic
17616 information contained in the DLL's export table. This section
17617 describes working with such symbols, known internally to @value{GDBN} as
17618 ``minimal symbols''.
17620 Note that before the debugged program has started execution, no DLLs
17621 will have been loaded. The easiest way around this problem is simply to
17622 start the program --- either by setting a breakpoint or letting the
17623 program run once to completion. It is also possible to force
17624 @value{GDBN} to load a particular DLL before starting the executable ---
17625 see the shared library information in @ref{Files}, or the
17626 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17627 explicitly loading symbols from a DLL with no debugging information will
17628 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17629 which may adversely affect symbol lookup performance.
17631 @subsubsection DLL Name Prefixes
17633 In keeping with the naming conventions used by the Microsoft debugging
17634 tools, DLL export symbols are made available with a prefix based on the
17635 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17636 also entered into the symbol table, so @code{CreateFileA} is often
17637 sufficient. In some cases there will be name clashes within a program
17638 (particularly if the executable itself includes full debugging symbols)
17639 necessitating the use of the fully qualified name when referring to the
17640 contents of the DLL. Use single-quotes around the name to avoid the
17641 exclamation mark (``!'') being interpreted as a language operator.
17643 Note that the internal name of the DLL may be all upper-case, even
17644 though the file name of the DLL is lower-case, or vice-versa. Since
17645 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17646 some confusion. If in doubt, try the @code{info functions} and
17647 @code{info variables} commands or even @code{maint print msymbols}
17648 (@pxref{Symbols}). Here's an example:
17651 (@value{GDBP}) info function CreateFileA
17652 All functions matching regular expression "CreateFileA":
17654 Non-debugging symbols:
17655 0x77e885f4 CreateFileA
17656 0x77e885f4 KERNEL32!CreateFileA
17660 (@value{GDBP}) info function !
17661 All functions matching regular expression "!":
17663 Non-debugging symbols:
17664 0x6100114c cygwin1!__assert
17665 0x61004034 cygwin1!_dll_crt0@@0
17666 0x61004240 cygwin1!dll_crt0(per_process *)
17670 @subsubsection Working with Minimal Symbols
17672 Symbols extracted from a DLL's export table do not contain very much
17673 type information. All that @value{GDBN} can do is guess whether a symbol
17674 refers to a function or variable depending on the linker section that
17675 contains the symbol. Also note that the actual contents of the memory
17676 contained in a DLL are not available unless the program is running. This
17677 means that you cannot examine the contents of a variable or disassemble
17678 a function within a DLL without a running program.
17680 Variables are generally treated as pointers and dereferenced
17681 automatically. For this reason, it is often necessary to prefix a
17682 variable name with the address-of operator (``&'') and provide explicit
17683 type information in the command. Here's an example of the type of
17687 (@value{GDBP}) print 'cygwin1!__argv'
17692 (@value{GDBP}) x 'cygwin1!__argv'
17693 0x10021610: "\230y\""
17696 And two possible solutions:
17699 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17700 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17704 (@value{GDBP}) x/2x &'cygwin1!__argv'
17705 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17706 (@value{GDBP}) x/x 0x10021608
17707 0x10021608: 0x0022fd98
17708 (@value{GDBP}) x/s 0x0022fd98
17709 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17712 Setting a break point within a DLL is possible even before the program
17713 starts execution. However, under these circumstances, @value{GDBN} can't
17714 examine the initial instructions of the function in order to skip the
17715 function's frame set-up code. You can work around this by using ``*&''
17716 to set the breakpoint at a raw memory address:
17719 (@value{GDBP}) break *&'python22!PyOS_Readline'
17720 Breakpoint 1 at 0x1e04eff0
17723 The author of these extensions is not entirely convinced that setting a
17724 break point within a shared DLL like @file{kernel32.dll} is completely
17728 @subsection Commands Specific to @sc{gnu} Hurd Systems
17729 @cindex @sc{gnu} Hurd debugging
17731 This subsection describes @value{GDBN} commands specific to the
17732 @sc{gnu} Hurd native debugging.
17737 @kindex set signals@r{, Hurd command}
17738 @kindex set sigs@r{, Hurd command}
17739 This command toggles the state of inferior signal interception by
17740 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17741 affected by this command. @code{sigs} is a shorthand alias for
17746 @kindex show signals@r{, Hurd command}
17747 @kindex show sigs@r{, Hurd command}
17748 Show the current state of intercepting inferior's signals.
17750 @item set signal-thread
17751 @itemx set sigthread
17752 @kindex set signal-thread
17753 @kindex set sigthread
17754 This command tells @value{GDBN} which thread is the @code{libc} signal
17755 thread. That thread is run when a signal is delivered to a running
17756 process. @code{set sigthread} is the shorthand alias of @code{set
17759 @item show signal-thread
17760 @itemx show sigthread
17761 @kindex show signal-thread
17762 @kindex show sigthread
17763 These two commands show which thread will run when the inferior is
17764 delivered a signal.
17767 @kindex set stopped@r{, Hurd command}
17768 This commands tells @value{GDBN} that the inferior process is stopped,
17769 as with the @code{SIGSTOP} signal. The stopped process can be
17770 continued by delivering a signal to it.
17773 @kindex show stopped@r{, Hurd command}
17774 This command shows whether @value{GDBN} thinks the debuggee is
17777 @item set exceptions
17778 @kindex set exceptions@r{, Hurd command}
17779 Use this command to turn off trapping of exceptions in the inferior.
17780 When exception trapping is off, neither breakpoints nor
17781 single-stepping will work. To restore the default, set exception
17784 @item show exceptions
17785 @kindex show exceptions@r{, Hurd command}
17786 Show the current state of trapping exceptions in the inferior.
17788 @item set task pause
17789 @kindex set task@r{, Hurd commands}
17790 @cindex task attributes (@sc{gnu} Hurd)
17791 @cindex pause current task (@sc{gnu} Hurd)
17792 This command toggles task suspension when @value{GDBN} has control.
17793 Setting it to on takes effect immediately, and the task is suspended
17794 whenever @value{GDBN} gets control. Setting it to off will take
17795 effect the next time the inferior is continued. If this option is set
17796 to off, you can use @code{set thread default pause on} or @code{set
17797 thread pause on} (see below) to pause individual threads.
17799 @item show task pause
17800 @kindex show task@r{, Hurd commands}
17801 Show the current state of task suspension.
17803 @item set task detach-suspend-count
17804 @cindex task suspend count
17805 @cindex detach from task, @sc{gnu} Hurd
17806 This command sets the suspend count the task will be left with when
17807 @value{GDBN} detaches from it.
17809 @item show task detach-suspend-count
17810 Show the suspend count the task will be left with when detaching.
17812 @item set task exception-port
17813 @itemx set task excp
17814 @cindex task exception port, @sc{gnu} Hurd
17815 This command sets the task exception port to which @value{GDBN} will
17816 forward exceptions. The argument should be the value of the @dfn{send
17817 rights} of the task. @code{set task excp} is a shorthand alias.
17819 @item set noninvasive
17820 @cindex noninvasive task options
17821 This command switches @value{GDBN} to a mode that is the least
17822 invasive as far as interfering with the inferior is concerned. This
17823 is the same as using @code{set task pause}, @code{set exceptions}, and
17824 @code{set signals} to values opposite to the defaults.
17826 @item info send-rights
17827 @itemx info receive-rights
17828 @itemx info port-rights
17829 @itemx info port-sets
17830 @itemx info dead-names
17833 @cindex send rights, @sc{gnu} Hurd
17834 @cindex receive rights, @sc{gnu} Hurd
17835 @cindex port rights, @sc{gnu} Hurd
17836 @cindex port sets, @sc{gnu} Hurd
17837 @cindex dead names, @sc{gnu} Hurd
17838 These commands display information about, respectively, send rights,
17839 receive rights, port rights, port sets, and dead names of a task.
17840 There are also shorthand aliases: @code{info ports} for @code{info
17841 port-rights} and @code{info psets} for @code{info port-sets}.
17843 @item set thread pause
17844 @kindex set thread@r{, Hurd command}
17845 @cindex thread properties, @sc{gnu} Hurd
17846 @cindex pause current thread (@sc{gnu} Hurd)
17847 This command toggles current thread suspension when @value{GDBN} has
17848 control. Setting it to on takes effect immediately, and the current
17849 thread is suspended whenever @value{GDBN} gets control. Setting it to
17850 off will take effect the next time the inferior is continued.
17851 Normally, this command has no effect, since when @value{GDBN} has
17852 control, the whole task is suspended. However, if you used @code{set
17853 task pause off} (see above), this command comes in handy to suspend
17854 only the current thread.
17856 @item show thread pause
17857 @kindex show thread@r{, Hurd command}
17858 This command shows the state of current thread suspension.
17860 @item set thread run
17861 This command sets whether the current thread is allowed to run.
17863 @item show thread run
17864 Show whether the current thread is allowed to run.
17866 @item set thread detach-suspend-count
17867 @cindex thread suspend count, @sc{gnu} Hurd
17868 @cindex detach from thread, @sc{gnu} Hurd
17869 This command sets the suspend count @value{GDBN} will leave on a
17870 thread when detaching. This number is relative to the suspend count
17871 found by @value{GDBN} when it notices the thread; use @code{set thread
17872 takeover-suspend-count} to force it to an absolute value.
17874 @item show thread detach-suspend-count
17875 Show the suspend count @value{GDBN} will leave on the thread when
17878 @item set thread exception-port
17879 @itemx set thread excp
17880 Set the thread exception port to which to forward exceptions. This
17881 overrides the port set by @code{set task exception-port} (see above).
17882 @code{set thread excp} is the shorthand alias.
17884 @item set thread takeover-suspend-count
17885 Normally, @value{GDBN}'s thread suspend counts are relative to the
17886 value @value{GDBN} finds when it notices each thread. This command
17887 changes the suspend counts to be absolute instead.
17889 @item set thread default
17890 @itemx show thread default
17891 @cindex thread default settings, @sc{gnu} Hurd
17892 Each of the above @code{set thread} commands has a @code{set thread
17893 default} counterpart (e.g., @code{set thread default pause}, @code{set
17894 thread default exception-port}, etc.). The @code{thread default}
17895 variety of commands sets the default thread properties for all
17896 threads; you can then change the properties of individual threads with
17897 the non-default commands.
17902 @subsection QNX Neutrino
17903 @cindex QNX Neutrino
17905 @value{GDBN} provides the following commands specific to the QNX
17909 @item set debug nto-debug
17910 @kindex set debug nto-debug
17911 When set to on, enables debugging messages specific to the QNX
17914 @item show debug nto-debug
17915 @kindex show debug nto-debug
17916 Show the current state of QNX Neutrino messages.
17923 @value{GDBN} provides the following commands specific to the Darwin target:
17926 @item set debug darwin @var{num}
17927 @kindex set debug darwin
17928 When set to a non zero value, enables debugging messages specific to
17929 the Darwin support. Higher values produce more verbose output.
17931 @item show debug darwin
17932 @kindex show debug darwin
17933 Show the current state of Darwin messages.
17935 @item set debug mach-o @var{num}
17936 @kindex set debug mach-o
17937 When set to a non zero value, enables debugging messages while
17938 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17939 file format used on Darwin for object and executable files.) Higher
17940 values produce more verbose output. This is a command to diagnose
17941 problems internal to @value{GDBN} and should not be needed in normal
17944 @item show debug mach-o
17945 @kindex show debug mach-o
17946 Show the current state of Mach-O file messages.
17948 @item set mach-exceptions on
17949 @itemx set mach-exceptions off
17950 @kindex set mach-exceptions
17951 On Darwin, faults are first reported as a Mach exception and are then
17952 mapped to a Posix signal. Use this command to turn on trapping of
17953 Mach exceptions in the inferior. This might be sometimes useful to
17954 better understand the cause of a fault. The default is off.
17956 @item show mach-exceptions
17957 @kindex show mach-exceptions
17958 Show the current state of exceptions trapping.
17963 @section Embedded Operating Systems
17965 This section describes configurations involving the debugging of
17966 embedded operating systems that are available for several different
17970 * VxWorks:: Using @value{GDBN} with VxWorks
17973 @value{GDBN} includes the ability to debug programs running on
17974 various real-time operating systems.
17977 @subsection Using @value{GDBN} with VxWorks
17983 @kindex target vxworks
17984 @item target vxworks @var{machinename}
17985 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17986 is the target system's machine name or IP address.
17990 On VxWorks, @code{load} links @var{filename} dynamically on the
17991 current target system as well as adding its symbols in @value{GDBN}.
17993 @value{GDBN} enables developers to spawn and debug tasks running on networked
17994 VxWorks targets from a Unix host. Already-running tasks spawned from
17995 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17996 both the Unix host and on the VxWorks target. The program
17997 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17998 installed with the name @code{vxgdb}, to distinguish it from a
17999 @value{GDBN} for debugging programs on the host itself.)
18002 @item VxWorks-timeout @var{args}
18003 @kindex vxworks-timeout
18004 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18005 This option is set by the user, and @var{args} represents the number of
18006 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18007 your VxWorks target is a slow software simulator or is on the far side
18008 of a thin network line.
18011 The following information on connecting to VxWorks was current when
18012 this manual was produced; newer releases of VxWorks may use revised
18015 @findex INCLUDE_RDB
18016 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18017 to include the remote debugging interface routines in the VxWorks
18018 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18019 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18020 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18021 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18022 information on configuring and remaking VxWorks, see the manufacturer's
18024 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18026 Once you have included @file{rdb.a} in your VxWorks system image and set
18027 your Unix execution search path to find @value{GDBN}, you are ready to
18028 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18029 @code{vxgdb}, depending on your installation).
18031 @value{GDBN} comes up showing the prompt:
18038 * VxWorks Connection:: Connecting to VxWorks
18039 * VxWorks Download:: VxWorks download
18040 * VxWorks Attach:: Running tasks
18043 @node VxWorks Connection
18044 @subsubsection Connecting to VxWorks
18046 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18047 network. To connect to a target whose host name is ``@code{tt}'', type:
18050 (vxgdb) target vxworks tt
18054 @value{GDBN} displays messages like these:
18057 Attaching remote machine across net...
18062 @value{GDBN} then attempts to read the symbol tables of any object modules
18063 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18064 these files by searching the directories listed in the command search
18065 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18066 to find an object file, it displays a message such as:
18069 prog.o: No such file or directory.
18072 When this happens, add the appropriate directory to the search path with
18073 the @value{GDBN} command @code{path}, and execute the @code{target}
18076 @node VxWorks Download
18077 @subsubsection VxWorks Download
18079 @cindex download to VxWorks
18080 If you have connected to the VxWorks target and you want to debug an
18081 object that has not yet been loaded, you can use the @value{GDBN}
18082 @code{load} command to download a file from Unix to VxWorks
18083 incrementally. The object file given as an argument to the @code{load}
18084 command is actually opened twice: first by the VxWorks target in order
18085 to download the code, then by @value{GDBN} in order to read the symbol
18086 table. This can lead to problems if the current working directories on
18087 the two systems differ. If both systems have NFS mounted the same
18088 filesystems, you can avoid these problems by using absolute paths.
18089 Otherwise, it is simplest to set the working directory on both systems
18090 to the directory in which the object file resides, and then to reference
18091 the file by its name, without any path. For instance, a program
18092 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18093 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18094 program, type this on VxWorks:
18097 -> cd "@var{vxpath}/vw/demo/rdb"
18101 Then, in @value{GDBN}, type:
18104 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18105 (vxgdb) load prog.o
18108 @value{GDBN} displays a response similar to this:
18111 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18114 You can also use the @code{load} command to reload an object module
18115 after editing and recompiling the corresponding source file. Note that
18116 this makes @value{GDBN} delete all currently-defined breakpoints,
18117 auto-displays, and convenience variables, and to clear the value
18118 history. (This is necessary in order to preserve the integrity of
18119 debugger's data structures that reference the target system's symbol
18122 @node VxWorks Attach
18123 @subsubsection Running Tasks
18125 @cindex running VxWorks tasks
18126 You can also attach to an existing task using the @code{attach} command as
18130 (vxgdb) attach @var{task}
18134 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18135 or suspended when you attach to it. Running tasks are suspended at
18136 the time of attachment.
18138 @node Embedded Processors
18139 @section Embedded Processors
18141 This section goes into details specific to particular embedded
18144 @cindex send command to simulator
18145 Whenever a specific embedded processor has a simulator, @value{GDBN}
18146 allows to send an arbitrary command to the simulator.
18149 @item sim @var{command}
18150 @kindex sim@r{, a command}
18151 Send an arbitrary @var{command} string to the simulator. Consult the
18152 documentation for the specific simulator in use for information about
18153 acceptable commands.
18159 * M32R/D:: Renesas M32R/D
18160 * M68K:: Motorola M68K
18161 * MicroBlaze:: Xilinx MicroBlaze
18162 * MIPS Embedded:: MIPS Embedded
18163 * OpenRISC 1000:: OpenRisc 1000
18164 * PA:: HP PA Embedded
18165 * PowerPC Embedded:: PowerPC Embedded
18166 * Sparclet:: Tsqware Sparclet
18167 * Sparclite:: Fujitsu Sparclite
18168 * Z8000:: Zilog Z8000
18171 * Super-H:: Renesas Super-H
18180 @item target rdi @var{dev}
18181 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18182 use this target to communicate with both boards running the Angel
18183 monitor, or with the EmbeddedICE JTAG debug device.
18186 @item target rdp @var{dev}
18191 @value{GDBN} provides the following ARM-specific commands:
18194 @item set arm disassembler
18196 This commands selects from a list of disassembly styles. The
18197 @code{"std"} style is the standard style.
18199 @item show arm disassembler
18201 Show the current disassembly style.
18203 @item set arm apcs32
18204 @cindex ARM 32-bit mode
18205 This command toggles ARM operation mode between 32-bit and 26-bit.
18207 @item show arm apcs32
18208 Display the current usage of the ARM 32-bit mode.
18210 @item set arm fpu @var{fputype}
18211 This command sets the ARM floating-point unit (FPU) type. The
18212 argument @var{fputype} can be one of these:
18216 Determine the FPU type by querying the OS ABI.
18218 Software FPU, with mixed-endian doubles on little-endian ARM
18221 GCC-compiled FPA co-processor.
18223 Software FPU with pure-endian doubles.
18229 Show the current type of the FPU.
18232 This command forces @value{GDBN} to use the specified ABI.
18235 Show the currently used ABI.
18237 @item set arm fallback-mode (arm|thumb|auto)
18238 @value{GDBN} uses the symbol table, when available, to determine
18239 whether instructions are ARM or Thumb. This command controls
18240 @value{GDBN}'s default behavior when the symbol table is not
18241 available. The default is @samp{auto}, which causes @value{GDBN} to
18242 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18245 @item show arm fallback-mode
18246 Show the current fallback instruction mode.
18248 @item set arm force-mode (arm|thumb|auto)
18249 This command overrides use of the symbol table to determine whether
18250 instructions are ARM or Thumb. The default is @samp{auto}, which
18251 causes @value{GDBN} to use the symbol table and then the setting
18252 of @samp{set arm fallback-mode}.
18254 @item show arm force-mode
18255 Show the current forced instruction mode.
18257 @item set debug arm
18258 Toggle whether to display ARM-specific debugging messages from the ARM
18259 target support subsystem.
18261 @item show debug arm
18262 Show whether ARM-specific debugging messages are enabled.
18265 The following commands are available when an ARM target is debugged
18266 using the RDI interface:
18269 @item rdilogfile @r{[}@var{file}@r{]}
18271 @cindex ADP (Angel Debugger Protocol) logging
18272 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18273 With an argument, sets the log file to the specified @var{file}. With
18274 no argument, show the current log file name. The default log file is
18277 @item rdilogenable @r{[}@var{arg}@r{]}
18278 @kindex rdilogenable
18279 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18280 enables logging, with an argument 0 or @code{"no"} disables it. With
18281 no arguments displays the current setting. When logging is enabled,
18282 ADP packets exchanged between @value{GDBN} and the RDI target device
18283 are logged to a file.
18285 @item set rdiromatzero
18286 @kindex set rdiromatzero
18287 @cindex ROM at zero address, RDI
18288 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18289 vector catching is disabled, so that zero address can be used. If off
18290 (the default), vector catching is enabled. For this command to take
18291 effect, it needs to be invoked prior to the @code{target rdi} command.
18293 @item show rdiromatzero
18294 @kindex show rdiromatzero
18295 Show the current setting of ROM at zero address.
18297 @item set rdiheartbeat
18298 @kindex set rdiheartbeat
18299 @cindex RDI heartbeat
18300 Enable or disable RDI heartbeat packets. It is not recommended to
18301 turn on this option, since it confuses ARM and EPI JTAG interface, as
18302 well as the Angel monitor.
18304 @item show rdiheartbeat
18305 @kindex show rdiheartbeat
18306 Show the setting of RDI heartbeat packets.
18310 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18311 The @value{GDBN} ARM simulator accepts the following optional arguments.
18314 @item --swi-support=@var{type}
18315 Tell the simulator which SWI interfaces to support.
18316 @var{type} may be a comma separated list of the following values.
18317 The default value is @code{all}.
18330 @subsection Renesas M32R/D and M32R/SDI
18333 @kindex target m32r
18334 @item target m32r @var{dev}
18335 Renesas M32R/D ROM monitor.
18337 @kindex target m32rsdi
18338 @item target m32rsdi @var{dev}
18339 Renesas M32R SDI server, connected via parallel port to the board.
18342 The following @value{GDBN} commands are specific to the M32R monitor:
18345 @item set download-path @var{path}
18346 @kindex set download-path
18347 @cindex find downloadable @sc{srec} files (M32R)
18348 Set the default path for finding downloadable @sc{srec} files.
18350 @item show download-path
18351 @kindex show download-path
18352 Show the default path for downloadable @sc{srec} files.
18354 @item set board-address @var{addr}
18355 @kindex set board-address
18356 @cindex M32-EVA target board address
18357 Set the IP address for the M32R-EVA target board.
18359 @item show board-address
18360 @kindex show board-address
18361 Show the current IP address of the target board.
18363 @item set server-address @var{addr}
18364 @kindex set server-address
18365 @cindex download server address (M32R)
18366 Set the IP address for the download server, which is the @value{GDBN}'s
18369 @item show server-address
18370 @kindex show server-address
18371 Display the IP address of the download server.
18373 @item upload @r{[}@var{file}@r{]}
18374 @kindex upload@r{, M32R}
18375 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18376 upload capability. If no @var{file} argument is given, the current
18377 executable file is uploaded.
18379 @item tload @r{[}@var{file}@r{]}
18380 @kindex tload@r{, M32R}
18381 Test the @code{upload} command.
18384 The following commands are available for M32R/SDI:
18389 @cindex reset SDI connection, M32R
18390 This command resets the SDI connection.
18394 This command shows the SDI connection status.
18397 @kindex debug_chaos
18398 @cindex M32R/Chaos debugging
18399 Instructs the remote that M32R/Chaos debugging is to be used.
18401 @item use_debug_dma
18402 @kindex use_debug_dma
18403 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18406 @kindex use_mon_code
18407 Instructs the remote to use the MON_CODE method of accessing memory.
18410 @kindex use_ib_break
18411 Instructs the remote to set breakpoints by IB break.
18413 @item use_dbt_break
18414 @kindex use_dbt_break
18415 Instructs the remote to set breakpoints by DBT.
18421 The Motorola m68k configuration includes ColdFire support, and a
18422 target command for the following ROM monitor.
18426 @kindex target dbug
18427 @item target dbug @var{dev}
18428 dBUG ROM monitor for Motorola ColdFire.
18433 @subsection MicroBlaze
18434 @cindex Xilinx MicroBlaze
18435 @cindex XMD, Xilinx Microprocessor Debugger
18437 The MicroBlaze is a soft-core processor supported on various Xilinx
18438 FPGAs, such as Spartan or Virtex series. Boards with these processors
18439 usually have JTAG ports which connect to a host system running the Xilinx
18440 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18441 This host system is used to download the configuration bitstream to
18442 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18443 communicates with the target board using the JTAG interface and
18444 presents a @code{gdbserver} interface to the board. By default
18445 @code{xmd} uses port @code{1234}. (While it is possible to change
18446 this default port, it requires the use of undocumented @code{xmd}
18447 commands. Contact Xilinx support if you need to do this.)
18449 Use these GDB commands to connect to the MicroBlaze target processor.
18452 @item target remote :1234
18453 Use this command to connect to the target if you are running @value{GDBN}
18454 on the same system as @code{xmd}.
18456 @item target remote @var{xmd-host}:1234
18457 Use this command to connect to the target if it is connected to @code{xmd}
18458 running on a different system named @var{xmd-host}.
18461 Use this command to download a program to the MicroBlaze target.
18463 @item set debug microblaze @var{n}
18464 Enable MicroBlaze-specific debugging messages if non-zero.
18466 @item show debug microblaze @var{n}
18467 Show MicroBlaze-specific debugging level.
18470 @node MIPS Embedded
18471 @subsection MIPS Embedded
18473 @cindex MIPS boards
18474 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18475 MIPS board attached to a serial line. This is available when
18476 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18479 Use these @value{GDBN} commands to specify the connection to your target board:
18482 @item target mips @var{port}
18483 @kindex target mips @var{port}
18484 To run a program on the board, start up @code{@value{GDBP}} with the
18485 name of your program as the argument. To connect to the board, use the
18486 command @samp{target mips @var{port}}, where @var{port} is the name of
18487 the serial port connected to the board. If the program has not already
18488 been downloaded to the board, you may use the @code{load} command to
18489 download it. You can then use all the usual @value{GDBN} commands.
18491 For example, this sequence connects to the target board through a serial
18492 port, and loads and runs a program called @var{prog} through the
18496 host$ @value{GDBP} @var{prog}
18497 @value{GDBN} is free software and @dots{}
18498 (@value{GDBP}) target mips /dev/ttyb
18499 (@value{GDBP}) load @var{prog}
18503 @item target mips @var{hostname}:@var{portnumber}
18504 On some @value{GDBN} host configurations, you can specify a TCP
18505 connection (for instance, to a serial line managed by a terminal
18506 concentrator) instead of a serial port, using the syntax
18507 @samp{@var{hostname}:@var{portnumber}}.
18509 @item target pmon @var{port}
18510 @kindex target pmon @var{port}
18513 @item target ddb @var{port}
18514 @kindex target ddb @var{port}
18515 NEC's DDB variant of PMON for Vr4300.
18517 @item target lsi @var{port}
18518 @kindex target lsi @var{port}
18519 LSI variant of PMON.
18521 @kindex target r3900
18522 @item target r3900 @var{dev}
18523 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18525 @kindex target array
18526 @item target array @var{dev}
18527 Array Tech LSI33K RAID controller board.
18533 @value{GDBN} also supports these special commands for MIPS targets:
18536 @item set mipsfpu double
18537 @itemx set mipsfpu single
18538 @itemx set mipsfpu none
18539 @itemx set mipsfpu auto
18540 @itemx show mipsfpu
18541 @kindex set mipsfpu
18542 @kindex show mipsfpu
18543 @cindex MIPS remote floating point
18544 @cindex floating point, MIPS remote
18545 If your target board does not support the MIPS floating point
18546 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18547 need this, you may wish to put the command in your @value{GDBN} init
18548 file). This tells @value{GDBN} how to find the return value of
18549 functions which return floating point values. It also allows
18550 @value{GDBN} to avoid saving the floating point registers when calling
18551 functions on the board. If you are using a floating point coprocessor
18552 with only single precision floating point support, as on the @sc{r4650}
18553 processor, use the command @samp{set mipsfpu single}. The default
18554 double precision floating point coprocessor may be selected using
18555 @samp{set mipsfpu double}.
18557 In previous versions the only choices were double precision or no
18558 floating point, so @samp{set mipsfpu on} will select double precision
18559 and @samp{set mipsfpu off} will select no floating point.
18561 As usual, you can inquire about the @code{mipsfpu} variable with
18562 @samp{show mipsfpu}.
18564 @item set timeout @var{seconds}
18565 @itemx set retransmit-timeout @var{seconds}
18566 @itemx show timeout
18567 @itemx show retransmit-timeout
18568 @cindex @code{timeout}, MIPS protocol
18569 @cindex @code{retransmit-timeout}, MIPS protocol
18570 @kindex set timeout
18571 @kindex show timeout
18572 @kindex set retransmit-timeout
18573 @kindex show retransmit-timeout
18574 You can control the timeout used while waiting for a packet, in the MIPS
18575 remote protocol, with the @code{set timeout @var{seconds}} command. The
18576 default is 5 seconds. Similarly, you can control the timeout used while
18577 waiting for an acknowledgment of a packet with the @code{set
18578 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18579 You can inspect both values with @code{show timeout} and @code{show
18580 retransmit-timeout}. (These commands are @emph{only} available when
18581 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18583 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18584 is waiting for your program to stop. In that case, @value{GDBN} waits
18585 forever because it has no way of knowing how long the program is going
18586 to run before stopping.
18588 @item set syn-garbage-limit @var{num}
18589 @kindex set syn-garbage-limit@r{, MIPS remote}
18590 @cindex synchronize with remote MIPS target
18591 Limit the maximum number of characters @value{GDBN} should ignore when
18592 it tries to synchronize with the remote target. The default is 10
18593 characters. Setting the limit to -1 means there's no limit.
18595 @item show syn-garbage-limit
18596 @kindex show syn-garbage-limit@r{, MIPS remote}
18597 Show the current limit on the number of characters to ignore when
18598 trying to synchronize with the remote system.
18600 @item set monitor-prompt @var{prompt}
18601 @kindex set monitor-prompt@r{, MIPS remote}
18602 @cindex remote monitor prompt
18603 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18604 remote monitor. The default depends on the target:
18614 @item show monitor-prompt
18615 @kindex show monitor-prompt@r{, MIPS remote}
18616 Show the current strings @value{GDBN} expects as the prompt from the
18619 @item set monitor-warnings
18620 @kindex set monitor-warnings@r{, MIPS remote}
18621 Enable or disable monitor warnings about hardware breakpoints. This
18622 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18623 display warning messages whose codes are returned by the @code{lsi}
18624 PMON monitor for breakpoint commands.
18626 @item show monitor-warnings
18627 @kindex show monitor-warnings@r{, MIPS remote}
18628 Show the current setting of printing monitor warnings.
18630 @item pmon @var{command}
18631 @kindex pmon@r{, MIPS remote}
18632 @cindex send PMON command
18633 This command allows sending an arbitrary @var{command} string to the
18634 monitor. The monitor must be in debug mode for this to work.
18637 @node OpenRISC 1000
18638 @subsection OpenRISC 1000
18639 @cindex OpenRISC 1000
18641 @cindex or1k boards
18642 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18643 about platform and commands.
18647 @kindex target jtag
18648 @item target jtag jtag://@var{host}:@var{port}
18650 Connects to remote JTAG server.
18651 JTAG remote server can be either an or1ksim or JTAG server,
18652 connected via parallel port to the board.
18654 Example: @code{target jtag jtag://localhost:9999}
18657 @item or1ksim @var{command}
18658 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18659 Simulator, proprietary commands can be executed.
18661 @kindex info or1k spr
18662 @item info or1k spr
18663 Displays spr groups.
18665 @item info or1k spr @var{group}
18666 @itemx info or1k spr @var{groupno}
18667 Displays register names in selected group.
18669 @item info or1k spr @var{group} @var{register}
18670 @itemx info or1k spr @var{register}
18671 @itemx info or1k spr @var{groupno} @var{registerno}
18672 @itemx info or1k spr @var{registerno}
18673 Shows information about specified spr register.
18676 @item spr @var{group} @var{register} @var{value}
18677 @itemx spr @var{register @var{value}}
18678 @itemx spr @var{groupno} @var{registerno @var{value}}
18679 @itemx spr @var{registerno @var{value}}
18680 Writes @var{value} to specified spr register.
18683 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18684 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18685 program execution and is thus much faster. Hardware breakpoints/watchpoint
18686 triggers can be set using:
18689 Load effective address/data
18691 Store effective address/data
18693 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18698 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18699 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18701 @code{htrace} commands:
18702 @cindex OpenRISC 1000 htrace
18705 @item hwatch @var{conditional}
18706 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18707 or Data. For example:
18709 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18711 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18715 Display information about current HW trace configuration.
18717 @item htrace trigger @var{conditional}
18718 Set starting criteria for HW trace.
18720 @item htrace qualifier @var{conditional}
18721 Set acquisition qualifier for HW trace.
18723 @item htrace stop @var{conditional}
18724 Set HW trace stopping criteria.
18726 @item htrace record [@var{data}]*
18727 Selects the data to be recorded, when qualifier is met and HW trace was
18730 @item htrace enable
18731 @itemx htrace disable
18732 Enables/disables the HW trace.
18734 @item htrace rewind [@var{filename}]
18735 Clears currently recorded trace data.
18737 If filename is specified, new trace file is made and any newly collected data
18738 will be written there.
18740 @item htrace print [@var{start} [@var{len}]]
18741 Prints trace buffer, using current record configuration.
18743 @item htrace mode continuous
18744 Set continuous trace mode.
18746 @item htrace mode suspend
18747 Set suspend trace mode.
18751 @node PowerPC Embedded
18752 @subsection PowerPC Embedded
18754 @cindex DVC register
18755 @value{GDBN} supports using the DVC (Data Value Compare) register to
18756 implement in hardware simple hardware watchpoint conditions of the form:
18759 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18760 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18763 The DVC register will be automatically used when @value{GDBN} detects
18764 such pattern in a condition expression, and the created watchpoint uses one
18765 debug register (either the @code{exact-watchpoints} option is on and the
18766 variable is scalar, or the variable has a length of one byte). This feature
18767 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
18770 When running on PowerPC embedded processors, @value{GDBN} automatically uses
18771 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
18772 in which case watchpoints using only one debug register are created when
18773 watching variables of scalar types.
18775 You can create an artificial array to watch an arbitrary memory
18776 region using one of the following commands (@pxref{Expressions}):
18779 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
18780 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
18783 @cindex ranged breakpoint
18784 PowerPC embedded processors support hardware accelerated
18785 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
18786 the inferior whenever it executes an instruction at any address within
18787 the range it specifies. To set a ranged breakpoint in @value{GDBN},
18788 use the @code{break-range} command.
18790 @value{GDBN} provides the following PowerPC-specific commands:
18793 @kindex break-range
18794 @item break-range @var{start-location}, @var{end-location}
18795 Set a breakpoint for an address range.
18796 @var{start-location} and @var{end-location} can specify a function name,
18797 a line number, an offset of lines from the current line or from the start
18798 location, or an address of an instruction (see @ref{Specify Location},
18799 for a list of all the possible ways to specify a @var{location}.)
18800 The breakpoint will stop execution of the inferior whenever it
18801 executes an instruction at any address within the specified range,
18802 (including @var{start-location} and @var{end-location}.)
18804 @kindex set powerpc
18805 @item set powerpc soft-float
18806 @itemx show powerpc soft-float
18807 Force @value{GDBN} to use (or not use) a software floating point calling
18808 convention. By default, @value{GDBN} selects the calling convention based
18809 on the selected architecture and the provided executable file.
18811 @item set powerpc vector-abi
18812 @itemx show powerpc vector-abi
18813 Force @value{GDBN} to use the specified calling convention for vector
18814 arguments and return values. The valid options are @samp{auto};
18815 @samp{generic}, to avoid vector registers even if they are present;
18816 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18817 registers. By default, @value{GDBN} selects the calling convention
18818 based on the selected architecture and the provided executable file.
18820 @item set powerpc exact-watchpoints
18821 @itemx show powerpc exact-watchpoints
18822 Allow @value{GDBN} to use only one debug register when watching a variable
18823 of scalar type, thus assuming that the variable is accessed through the
18824 address of its first byte.
18826 @kindex target dink32
18827 @item target dink32 @var{dev}
18828 DINK32 ROM monitor.
18830 @kindex target ppcbug
18831 @item target ppcbug @var{dev}
18832 @kindex target ppcbug1
18833 @item target ppcbug1 @var{dev}
18834 PPCBUG ROM monitor for PowerPC.
18837 @item target sds @var{dev}
18838 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18841 @cindex SDS protocol
18842 The following commands specific to the SDS protocol are supported
18846 @item set sdstimeout @var{nsec}
18847 @kindex set sdstimeout
18848 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18849 default is 2 seconds.
18851 @item show sdstimeout
18852 @kindex show sdstimeout
18853 Show the current value of the SDS timeout.
18855 @item sds @var{command}
18856 @kindex sds@r{, a command}
18857 Send the specified @var{command} string to the SDS monitor.
18862 @subsection HP PA Embedded
18866 @kindex target op50n
18867 @item target op50n @var{dev}
18868 OP50N monitor, running on an OKI HPPA board.
18870 @kindex target w89k
18871 @item target w89k @var{dev}
18872 W89K monitor, running on a Winbond HPPA board.
18877 @subsection Tsqware Sparclet
18881 @value{GDBN} enables developers to debug tasks running on
18882 Sparclet targets from a Unix host.
18883 @value{GDBN} uses code that runs on
18884 both the Unix host and on the Sparclet target. The program
18885 @code{@value{GDBP}} is installed and executed on the Unix host.
18888 @item remotetimeout @var{args}
18889 @kindex remotetimeout
18890 @value{GDBN} supports the option @code{remotetimeout}.
18891 This option is set by the user, and @var{args} represents the number of
18892 seconds @value{GDBN} waits for responses.
18895 @cindex compiling, on Sparclet
18896 When compiling for debugging, include the options @samp{-g} to get debug
18897 information and @samp{-Ttext} to relocate the program to where you wish to
18898 load it on the target. You may also want to add the options @samp{-n} or
18899 @samp{-N} in order to reduce the size of the sections. Example:
18902 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18905 You can use @code{objdump} to verify that the addresses are what you intended:
18908 sparclet-aout-objdump --headers --syms prog
18911 @cindex running, on Sparclet
18913 your Unix execution search path to find @value{GDBN}, you are ready to
18914 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18915 (or @code{sparclet-aout-gdb}, depending on your installation).
18917 @value{GDBN} comes up showing the prompt:
18924 * Sparclet File:: Setting the file to debug
18925 * Sparclet Connection:: Connecting to Sparclet
18926 * Sparclet Download:: Sparclet download
18927 * Sparclet Execution:: Running and debugging
18930 @node Sparclet File
18931 @subsubsection Setting File to Debug
18933 The @value{GDBN} command @code{file} lets you choose with program to debug.
18936 (gdbslet) file prog
18940 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18941 @value{GDBN} locates
18942 the file by searching the directories listed in the command search
18944 If the file was compiled with debug information (option @samp{-g}), source
18945 files will be searched as well.
18946 @value{GDBN} locates
18947 the source files by searching the directories listed in the directory search
18948 path (@pxref{Environment, ,Your Program's Environment}).
18950 to find a file, it displays a message such as:
18953 prog: No such file or directory.
18956 When this happens, add the appropriate directories to the search paths with
18957 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18958 @code{target} command again.
18960 @node Sparclet Connection
18961 @subsubsection Connecting to Sparclet
18963 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18964 To connect to a target on serial port ``@code{ttya}'', type:
18967 (gdbslet) target sparclet /dev/ttya
18968 Remote target sparclet connected to /dev/ttya
18969 main () at ../prog.c:3
18973 @value{GDBN} displays messages like these:
18979 @node Sparclet Download
18980 @subsubsection Sparclet Download
18982 @cindex download to Sparclet
18983 Once connected to the Sparclet target,
18984 you can use the @value{GDBN}
18985 @code{load} command to download the file from the host to the target.
18986 The file name and load offset should be given as arguments to the @code{load}
18988 Since the file format is aout, the program must be loaded to the starting
18989 address. You can use @code{objdump} to find out what this value is. The load
18990 offset is an offset which is added to the VMA (virtual memory address)
18991 of each of the file's sections.
18992 For instance, if the program
18993 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18994 and bss at 0x12010170, in @value{GDBN}, type:
18997 (gdbslet) load prog 0x12010000
18998 Loading section .text, size 0xdb0 vma 0x12010000
19001 If the code is loaded at a different address then what the program was linked
19002 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19003 to tell @value{GDBN} where to map the symbol table.
19005 @node Sparclet Execution
19006 @subsubsection Running and Debugging
19008 @cindex running and debugging Sparclet programs
19009 You can now begin debugging the task using @value{GDBN}'s execution control
19010 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19011 manual for the list of commands.
19015 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19017 Starting program: prog
19018 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19019 3 char *symarg = 0;
19021 4 char *execarg = "hello!";
19026 @subsection Fujitsu Sparclite
19030 @kindex target sparclite
19031 @item target sparclite @var{dev}
19032 Fujitsu sparclite boards, used only for the purpose of loading.
19033 You must use an additional command to debug the program.
19034 For example: target remote @var{dev} using @value{GDBN} standard
19040 @subsection Zilog Z8000
19043 @cindex simulator, Z8000
19044 @cindex Zilog Z8000 simulator
19046 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19049 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19050 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19051 segmented variant). The simulator recognizes which architecture is
19052 appropriate by inspecting the object code.
19055 @item target sim @var{args}
19057 @kindex target sim@r{, with Z8000}
19058 Debug programs on a simulated CPU. If the simulator supports setup
19059 options, specify them via @var{args}.
19063 After specifying this target, you can debug programs for the simulated
19064 CPU in the same style as programs for your host computer; use the
19065 @code{file} command to load a new program image, the @code{run} command
19066 to run your program, and so on.
19068 As well as making available all the usual machine registers
19069 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19070 additional items of information as specially named registers:
19075 Counts clock-ticks in the simulator.
19078 Counts instructions run in the simulator.
19081 Execution time in 60ths of a second.
19085 You can refer to these values in @value{GDBN} expressions with the usual
19086 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19087 conditional breakpoint that suspends only after at least 5000
19088 simulated clock ticks.
19091 @subsection Atmel AVR
19094 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19095 following AVR-specific commands:
19098 @item info io_registers
19099 @kindex info io_registers@r{, AVR}
19100 @cindex I/O registers (Atmel AVR)
19101 This command displays information about the AVR I/O registers. For
19102 each register, @value{GDBN} prints its number and value.
19109 When configured for debugging CRIS, @value{GDBN} provides the
19110 following CRIS-specific commands:
19113 @item set cris-version @var{ver}
19114 @cindex CRIS version
19115 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19116 The CRIS version affects register names and sizes. This command is useful in
19117 case autodetection of the CRIS version fails.
19119 @item show cris-version
19120 Show the current CRIS version.
19122 @item set cris-dwarf2-cfi
19123 @cindex DWARF-2 CFI and CRIS
19124 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19125 Change to @samp{off} when using @code{gcc-cris} whose version is below
19128 @item show cris-dwarf2-cfi
19129 Show the current state of using DWARF-2 CFI.
19131 @item set cris-mode @var{mode}
19133 Set the current CRIS mode to @var{mode}. It should only be changed when
19134 debugging in guru mode, in which case it should be set to
19135 @samp{guru} (the default is @samp{normal}).
19137 @item show cris-mode
19138 Show the current CRIS mode.
19142 @subsection Renesas Super-H
19145 For the Renesas Super-H processor, @value{GDBN} provides these
19150 @kindex regs@r{, Super-H}
19151 Show the values of all Super-H registers.
19153 @item set sh calling-convention @var{convention}
19154 @kindex set sh calling-convention
19155 Set the calling-convention used when calling functions from @value{GDBN}.
19156 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19157 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19158 convention. If the DWARF-2 information of the called function specifies
19159 that the function follows the Renesas calling convention, the function
19160 is called using the Renesas calling convention. If the calling convention
19161 is set to @samp{renesas}, the Renesas calling convention is always used,
19162 regardless of the DWARF-2 information. This can be used to override the
19163 default of @samp{gcc} if debug information is missing, or the compiler
19164 does not emit the DWARF-2 calling convention entry for a function.
19166 @item show sh calling-convention
19167 @kindex show sh calling-convention
19168 Show the current calling convention setting.
19173 @node Architectures
19174 @section Architectures
19176 This section describes characteristics of architectures that affect
19177 all uses of @value{GDBN} with the architecture, both native and cross.
19184 * HPPA:: HP PA architecture
19185 * SPU:: Cell Broadband Engine SPU architecture
19190 @subsection x86 Architecture-specific Issues
19193 @item set struct-convention @var{mode}
19194 @kindex set struct-convention
19195 @cindex struct return convention
19196 @cindex struct/union returned in registers
19197 Set the convention used by the inferior to return @code{struct}s and
19198 @code{union}s from functions to @var{mode}. Possible values of
19199 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19200 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19201 are returned on the stack, while @code{"reg"} means that a
19202 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19203 be returned in a register.
19205 @item show struct-convention
19206 @kindex show struct-convention
19207 Show the current setting of the convention to return @code{struct}s
19216 @kindex set rstack_high_address
19217 @cindex AMD 29K register stack
19218 @cindex register stack, AMD29K
19219 @item set rstack_high_address @var{address}
19220 On AMD 29000 family processors, registers are saved in a separate
19221 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19222 extent of this stack. Normally, @value{GDBN} just assumes that the
19223 stack is ``large enough''. This may result in @value{GDBN} referencing
19224 memory locations that do not exist. If necessary, you can get around
19225 this problem by specifying the ending address of the register stack with
19226 the @code{set rstack_high_address} command. The argument should be an
19227 address, which you probably want to precede with @samp{0x} to specify in
19230 @kindex show rstack_high_address
19231 @item show rstack_high_address
19232 Display the current limit of the register stack, on AMD 29000 family
19240 See the following section.
19245 @cindex stack on Alpha
19246 @cindex stack on MIPS
19247 @cindex Alpha stack
19249 Alpha- and MIPS-based computers use an unusual stack frame, which
19250 sometimes requires @value{GDBN} to search backward in the object code to
19251 find the beginning of a function.
19253 @cindex response time, MIPS debugging
19254 To improve response time (especially for embedded applications, where
19255 @value{GDBN} may be restricted to a slow serial line for this search)
19256 you may want to limit the size of this search, using one of these
19260 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19261 @item set heuristic-fence-post @var{limit}
19262 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19263 search for the beginning of a function. A value of @var{0} (the
19264 default) means there is no limit. However, except for @var{0}, the
19265 larger the limit the more bytes @code{heuristic-fence-post} must search
19266 and therefore the longer it takes to run. You should only need to use
19267 this command when debugging a stripped executable.
19269 @item show heuristic-fence-post
19270 Display the current limit.
19274 These commands are available @emph{only} when @value{GDBN} is configured
19275 for debugging programs on Alpha or MIPS processors.
19277 Several MIPS-specific commands are available when debugging MIPS
19281 @item set mips abi @var{arg}
19282 @kindex set mips abi
19283 @cindex set ABI for MIPS
19284 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19285 values of @var{arg} are:
19289 The default ABI associated with the current binary (this is the
19300 @item show mips abi
19301 @kindex show mips abi
19302 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19305 @itemx show mipsfpu
19306 @xref{MIPS Embedded, set mipsfpu}.
19308 @item set mips mask-address @var{arg}
19309 @kindex set mips mask-address
19310 @cindex MIPS addresses, masking
19311 This command determines whether the most-significant 32 bits of 64-bit
19312 MIPS addresses are masked off. The argument @var{arg} can be
19313 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19314 setting, which lets @value{GDBN} determine the correct value.
19316 @item show mips mask-address
19317 @kindex show mips mask-address
19318 Show whether the upper 32 bits of MIPS addresses are masked off or
19321 @item set remote-mips64-transfers-32bit-regs
19322 @kindex set remote-mips64-transfers-32bit-regs
19323 This command controls compatibility with 64-bit MIPS targets that
19324 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19325 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19326 and 64 bits for other registers, set this option to @samp{on}.
19328 @item show remote-mips64-transfers-32bit-regs
19329 @kindex show remote-mips64-transfers-32bit-regs
19330 Show the current setting of compatibility with older MIPS 64 targets.
19332 @item set debug mips
19333 @kindex set debug mips
19334 This command turns on and off debugging messages for the MIPS-specific
19335 target code in @value{GDBN}.
19337 @item show debug mips
19338 @kindex show debug mips
19339 Show the current setting of MIPS debugging messages.
19345 @cindex HPPA support
19347 When @value{GDBN} is debugging the HP PA architecture, it provides the
19348 following special commands:
19351 @item set debug hppa
19352 @kindex set debug hppa
19353 This command determines whether HPPA architecture-specific debugging
19354 messages are to be displayed.
19356 @item show debug hppa
19357 Show whether HPPA debugging messages are displayed.
19359 @item maint print unwind @var{address}
19360 @kindex maint print unwind@r{, HPPA}
19361 This command displays the contents of the unwind table entry at the
19362 given @var{address}.
19368 @subsection Cell Broadband Engine SPU architecture
19369 @cindex Cell Broadband Engine
19372 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19373 it provides the following special commands:
19376 @item info spu event
19378 Display SPU event facility status. Shows current event mask
19379 and pending event status.
19381 @item info spu signal
19382 Display SPU signal notification facility status. Shows pending
19383 signal-control word and signal notification mode of both signal
19384 notification channels.
19386 @item info spu mailbox
19387 Display SPU mailbox facility status. Shows all pending entries,
19388 in order of processing, in each of the SPU Write Outbound,
19389 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19392 Display MFC DMA status. Shows all pending commands in the MFC
19393 DMA queue. For each entry, opcode, tag, class IDs, effective
19394 and local store addresses and transfer size are shown.
19396 @item info spu proxydma
19397 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19398 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19399 and local store addresses and transfer size are shown.
19403 When @value{GDBN} is debugging a combined PowerPC/SPU application
19404 on the Cell Broadband Engine, it provides in addition the following
19408 @item set spu stop-on-load @var{arg}
19410 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19411 will give control to the user when a new SPE thread enters its @code{main}
19412 function. The default is @code{off}.
19414 @item show spu stop-on-load
19416 Show whether to stop for new SPE threads.
19418 @item set spu auto-flush-cache @var{arg}
19419 Set whether to automatically flush the software-managed cache. When set to
19420 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19421 cache to be flushed whenever SPE execution stops. This provides a consistent
19422 view of PowerPC memory that is accessed via the cache. If an application
19423 does not use the software-managed cache, this option has no effect.
19425 @item show spu auto-flush-cache
19426 Show whether to automatically flush the software-managed cache.
19431 @subsection PowerPC
19432 @cindex PowerPC architecture
19434 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19435 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19436 numbers stored in the floating point registers. These values must be stored
19437 in two consecutive registers, always starting at an even register like
19438 @code{f0} or @code{f2}.
19440 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19441 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19442 @code{f2} and @code{f3} for @code{$dl1} and so on.
19444 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19445 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19448 @node Controlling GDB
19449 @chapter Controlling @value{GDBN}
19451 You can alter the way @value{GDBN} interacts with you by using the
19452 @code{set} command. For commands controlling how @value{GDBN} displays
19453 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19458 * Editing:: Command editing
19459 * Command History:: Command history
19460 * Screen Size:: Screen size
19461 * Numbers:: Numbers
19462 * ABI:: Configuring the current ABI
19463 * Messages/Warnings:: Optional warnings and messages
19464 * Debugging Output:: Optional messages about internal happenings
19465 * Other Misc Settings:: Other Miscellaneous Settings
19473 @value{GDBN} indicates its readiness to read a command by printing a string
19474 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19475 can change the prompt string with the @code{set prompt} command. For
19476 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19477 the prompt in one of the @value{GDBN} sessions so that you can always tell
19478 which one you are talking to.
19480 @emph{Note:} @code{set prompt} does not add a space for you after the
19481 prompt you set. This allows you to set a prompt which ends in a space
19482 or a prompt that does not.
19486 @item set prompt @var{newprompt}
19487 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19489 @kindex show prompt
19491 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19495 @section Command Editing
19497 @cindex command line editing
19499 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19500 @sc{gnu} library provides consistent behavior for programs which provide a
19501 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19502 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19503 substitution, and a storage and recall of command history across
19504 debugging sessions.
19506 You may control the behavior of command line editing in @value{GDBN} with the
19507 command @code{set}.
19510 @kindex set editing
19513 @itemx set editing on
19514 Enable command line editing (enabled by default).
19516 @item set editing off
19517 Disable command line editing.
19519 @kindex show editing
19521 Show whether command line editing is enabled.
19524 @ifset SYSTEM_READLINE
19525 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19527 @ifclear SYSTEM_READLINE
19528 @xref{Command Line Editing},
19530 for more details about the Readline
19531 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19532 encouraged to read that chapter.
19534 @node Command History
19535 @section Command History
19536 @cindex command history
19538 @value{GDBN} can keep track of the commands you type during your
19539 debugging sessions, so that you can be certain of precisely what
19540 happened. Use these commands to manage the @value{GDBN} command
19543 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19544 package, to provide the history facility.
19545 @ifset SYSTEM_READLINE
19546 @xref{Using History Interactively, , , history, GNU History Library},
19548 @ifclear SYSTEM_READLINE
19549 @xref{Using History Interactively},
19551 for the detailed description of the History library.
19553 To issue a command to @value{GDBN} without affecting certain aspects of
19554 the state which is seen by users, prefix it with @samp{server }
19555 (@pxref{Server Prefix}). This
19556 means that this command will not affect the command history, nor will it
19557 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19558 pressed on a line by itself.
19560 @cindex @code{server}, command prefix
19561 The server prefix does not affect the recording of values into the value
19562 history; to print a value without recording it into the value history,
19563 use the @code{output} command instead of the @code{print} command.
19565 Here is the description of @value{GDBN} commands related to command
19569 @cindex history substitution
19570 @cindex history file
19571 @kindex set history filename
19572 @cindex @env{GDBHISTFILE}, environment variable
19573 @item set history filename @var{fname}
19574 Set the name of the @value{GDBN} command history file to @var{fname}.
19575 This is the file where @value{GDBN} reads an initial command history
19576 list, and where it writes the command history from this session when it
19577 exits. You can access this list through history expansion or through
19578 the history command editing characters listed below. This file defaults
19579 to the value of the environment variable @code{GDBHISTFILE}, or to
19580 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19583 @cindex save command history
19584 @kindex set history save
19585 @item set history save
19586 @itemx set history save on
19587 Record command history in a file, whose name may be specified with the
19588 @code{set history filename} command. By default, this option is disabled.
19590 @item set history save off
19591 Stop recording command history in a file.
19593 @cindex history size
19594 @kindex set history size
19595 @cindex @env{HISTSIZE}, environment variable
19596 @item set history size @var{size}
19597 Set the number of commands which @value{GDBN} keeps in its history list.
19598 This defaults to the value of the environment variable
19599 @code{HISTSIZE}, or to 256 if this variable is not set.
19602 History expansion assigns special meaning to the character @kbd{!}.
19603 @ifset SYSTEM_READLINE
19604 @xref{Event Designators, , , history, GNU History Library},
19606 @ifclear SYSTEM_READLINE
19607 @xref{Event Designators},
19611 @cindex history expansion, turn on/off
19612 Since @kbd{!} is also the logical not operator in C, history expansion
19613 is off by default. If you decide to enable history expansion with the
19614 @code{set history expansion on} command, you may sometimes need to
19615 follow @kbd{!} (when it is used as logical not, in an expression) with
19616 a space or a tab to prevent it from being expanded. The readline
19617 history facilities do not attempt substitution on the strings
19618 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19620 The commands to control history expansion are:
19623 @item set history expansion on
19624 @itemx set history expansion
19625 @kindex set history expansion
19626 Enable history expansion. History expansion is off by default.
19628 @item set history expansion off
19629 Disable history expansion.
19632 @kindex show history
19634 @itemx show history filename
19635 @itemx show history save
19636 @itemx show history size
19637 @itemx show history expansion
19638 These commands display the state of the @value{GDBN} history parameters.
19639 @code{show history} by itself displays all four states.
19644 @kindex show commands
19645 @cindex show last commands
19646 @cindex display command history
19647 @item show commands
19648 Display the last ten commands in the command history.
19650 @item show commands @var{n}
19651 Print ten commands centered on command number @var{n}.
19653 @item show commands +
19654 Print ten commands just after the commands last printed.
19658 @section Screen Size
19659 @cindex size of screen
19660 @cindex pauses in output
19662 Certain commands to @value{GDBN} may produce large amounts of
19663 information output to the screen. To help you read all of it,
19664 @value{GDBN} pauses and asks you for input at the end of each page of
19665 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19666 to discard the remaining output. Also, the screen width setting
19667 determines when to wrap lines of output. Depending on what is being
19668 printed, @value{GDBN} tries to break the line at a readable place,
19669 rather than simply letting it overflow onto the following line.
19671 Normally @value{GDBN} knows the size of the screen from the terminal
19672 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19673 together with the value of the @code{TERM} environment variable and the
19674 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19675 you can override it with the @code{set height} and @code{set
19682 @kindex show height
19683 @item set height @var{lpp}
19685 @itemx set width @var{cpl}
19687 These @code{set} commands specify a screen height of @var{lpp} lines and
19688 a screen width of @var{cpl} characters. The associated @code{show}
19689 commands display the current settings.
19691 If you specify a height of zero lines, @value{GDBN} does not pause during
19692 output no matter how long the output is. This is useful if output is to a
19693 file or to an editor buffer.
19695 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19696 from wrapping its output.
19698 @item set pagination on
19699 @itemx set pagination off
19700 @kindex set pagination
19701 Turn the output pagination on or off; the default is on. Turning
19702 pagination off is the alternative to @code{set height 0}. Note that
19703 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19704 Options, -batch}) also automatically disables pagination.
19706 @item show pagination
19707 @kindex show pagination
19708 Show the current pagination mode.
19713 @cindex number representation
19714 @cindex entering numbers
19716 You can always enter numbers in octal, decimal, or hexadecimal in
19717 @value{GDBN} by the usual conventions: octal numbers begin with
19718 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19719 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19720 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19721 10; likewise, the default display for numbers---when no particular
19722 format is specified---is base 10. You can change the default base for
19723 both input and output with the commands described below.
19726 @kindex set input-radix
19727 @item set input-radix @var{base}
19728 Set the default base for numeric input. Supported choices
19729 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19730 specified either unambiguously or using the current input radix; for
19734 set input-radix 012
19735 set input-radix 10.
19736 set input-radix 0xa
19740 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19741 leaves the input radix unchanged, no matter what it was, since
19742 @samp{10}, being without any leading or trailing signs of its base, is
19743 interpreted in the current radix. Thus, if the current radix is 16,
19744 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19747 @kindex set output-radix
19748 @item set output-radix @var{base}
19749 Set the default base for numeric display. Supported choices
19750 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19751 specified either unambiguously or using the current input radix.
19753 @kindex show input-radix
19754 @item show input-radix
19755 Display the current default base for numeric input.
19757 @kindex show output-radix
19758 @item show output-radix
19759 Display the current default base for numeric display.
19761 @item set radix @r{[}@var{base}@r{]}
19765 These commands set and show the default base for both input and output
19766 of numbers. @code{set radix} sets the radix of input and output to
19767 the same base; without an argument, it resets the radix back to its
19768 default value of 10.
19773 @section Configuring the Current ABI
19775 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19776 application automatically. However, sometimes you need to override its
19777 conclusions. Use these commands to manage @value{GDBN}'s view of the
19784 One @value{GDBN} configuration can debug binaries for multiple operating
19785 system targets, either via remote debugging or native emulation.
19786 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19787 but you can override its conclusion using the @code{set osabi} command.
19788 One example where this is useful is in debugging of binaries which use
19789 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19790 not have the same identifying marks that the standard C library for your
19795 Show the OS ABI currently in use.
19798 With no argument, show the list of registered available OS ABI's.
19800 @item set osabi @var{abi}
19801 Set the current OS ABI to @var{abi}.
19804 @cindex float promotion
19806 Generally, the way that an argument of type @code{float} is passed to a
19807 function depends on whether the function is prototyped. For a prototyped
19808 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19809 according to the architecture's convention for @code{float}. For unprototyped
19810 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19811 @code{double} and then passed.
19813 Unfortunately, some forms of debug information do not reliably indicate whether
19814 a function is prototyped. If @value{GDBN} calls a function that is not marked
19815 as prototyped, it consults @kbd{set coerce-float-to-double}.
19818 @kindex set coerce-float-to-double
19819 @item set coerce-float-to-double
19820 @itemx set coerce-float-to-double on
19821 Arguments of type @code{float} will be promoted to @code{double} when passed
19822 to an unprototyped function. This is the default setting.
19824 @item set coerce-float-to-double off
19825 Arguments of type @code{float} will be passed directly to unprototyped
19828 @kindex show coerce-float-to-double
19829 @item show coerce-float-to-double
19830 Show the current setting of promoting @code{float} to @code{double}.
19834 @kindex show cp-abi
19835 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19836 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19837 used to build your application. @value{GDBN} only fully supports
19838 programs with a single C@t{++} ABI; if your program contains code using
19839 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19840 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19841 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19842 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19843 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19844 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19849 Show the C@t{++} ABI currently in use.
19852 With no argument, show the list of supported C@t{++} ABI's.
19854 @item set cp-abi @var{abi}
19855 @itemx set cp-abi auto
19856 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19859 @node Messages/Warnings
19860 @section Optional Warnings and Messages
19862 @cindex verbose operation
19863 @cindex optional warnings
19864 By default, @value{GDBN} is silent about its inner workings. If you are
19865 running on a slow machine, you may want to use the @code{set verbose}
19866 command. This makes @value{GDBN} tell you when it does a lengthy
19867 internal operation, so you will not think it has crashed.
19869 Currently, the messages controlled by @code{set verbose} are those
19870 which announce that the symbol table for a source file is being read;
19871 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19874 @kindex set verbose
19875 @item set verbose on
19876 Enables @value{GDBN} output of certain informational messages.
19878 @item set verbose off
19879 Disables @value{GDBN} output of certain informational messages.
19881 @kindex show verbose
19883 Displays whether @code{set verbose} is on or off.
19886 By default, if @value{GDBN} encounters bugs in the symbol table of an
19887 object file, it is silent; but if you are debugging a compiler, you may
19888 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19893 @kindex set complaints
19894 @item set complaints @var{limit}
19895 Permits @value{GDBN} to output @var{limit} complaints about each type of
19896 unusual symbols before becoming silent about the problem. Set
19897 @var{limit} to zero to suppress all complaints; set it to a large number
19898 to prevent complaints from being suppressed.
19900 @kindex show complaints
19901 @item show complaints
19902 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19906 @anchor{confirmation requests}
19907 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19908 lot of stupid questions to confirm certain commands. For example, if
19909 you try to run a program which is already running:
19913 The program being debugged has been started already.
19914 Start it from the beginning? (y or n)
19917 If you are willing to unflinchingly face the consequences of your own
19918 commands, you can disable this ``feature'':
19922 @kindex set confirm
19924 @cindex confirmation
19925 @cindex stupid questions
19926 @item set confirm off
19927 Disables confirmation requests. Note that running @value{GDBN} with
19928 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19929 automatically disables confirmation requests.
19931 @item set confirm on
19932 Enables confirmation requests (the default).
19934 @kindex show confirm
19936 Displays state of confirmation requests.
19940 @cindex command tracing
19941 If you need to debug user-defined commands or sourced files you may find it
19942 useful to enable @dfn{command tracing}. In this mode each command will be
19943 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19944 quantity denoting the call depth of each command.
19947 @kindex set trace-commands
19948 @cindex command scripts, debugging
19949 @item set trace-commands on
19950 Enable command tracing.
19951 @item set trace-commands off
19952 Disable command tracing.
19953 @item show trace-commands
19954 Display the current state of command tracing.
19957 @node Debugging Output
19958 @section Optional Messages about Internal Happenings
19959 @cindex optional debugging messages
19961 @value{GDBN} has commands that enable optional debugging messages from
19962 various @value{GDBN} subsystems; normally these commands are of
19963 interest to @value{GDBN} maintainers, or when reporting a bug. This
19964 section documents those commands.
19967 @kindex set exec-done-display
19968 @item set exec-done-display
19969 Turns on or off the notification of asynchronous commands'
19970 completion. When on, @value{GDBN} will print a message when an
19971 asynchronous command finishes its execution. The default is off.
19972 @kindex show exec-done-display
19973 @item show exec-done-display
19974 Displays the current setting of asynchronous command completion
19977 @cindex gdbarch debugging info
19978 @cindex architecture debugging info
19979 @item set debug arch
19980 Turns on or off display of gdbarch debugging info. The default is off
19982 @item show debug arch
19983 Displays the current state of displaying gdbarch debugging info.
19984 @item set debug aix-thread
19985 @cindex AIX threads
19986 Display debugging messages about inner workings of the AIX thread
19988 @item show debug aix-thread
19989 Show the current state of AIX thread debugging info display.
19990 @item set debug dwarf2-die
19991 @cindex DWARF2 DIEs
19992 Dump DWARF2 DIEs after they are read in.
19993 The value is the number of nesting levels to print.
19994 A value of zero turns off the display.
19995 @item show debug dwarf2-die
19996 Show the current state of DWARF2 DIE debugging.
19997 @item set debug displaced
19998 @cindex displaced stepping debugging info
19999 Turns on or off display of @value{GDBN} debugging info for the
20000 displaced stepping support. The default is off.
20001 @item show debug displaced
20002 Displays the current state of displaying @value{GDBN} debugging info
20003 related to displaced stepping.
20004 @item set debug event
20005 @cindex event debugging info
20006 Turns on or off display of @value{GDBN} event debugging info. The
20008 @item show debug event
20009 Displays the current state of displaying @value{GDBN} event debugging
20011 @item set debug expression
20012 @cindex expression debugging info
20013 Turns on or off display of debugging info about @value{GDBN}
20014 expression parsing. The default is off.
20015 @item show debug expression
20016 Displays the current state of displaying debugging info about
20017 @value{GDBN} expression parsing.
20018 @item set debug frame
20019 @cindex frame debugging info
20020 Turns on or off display of @value{GDBN} frame debugging info. The
20022 @item show debug frame
20023 Displays the current state of displaying @value{GDBN} frame debugging
20025 @item set debug gnu-nat
20026 @cindex @sc{gnu}/Hurd debug messages
20027 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20028 @item show debug gnu-nat
20029 Show the current state of @sc{gnu}/Hurd debugging messages.
20030 @item set debug infrun
20031 @cindex inferior debugging info
20032 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20033 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20034 for implementing operations such as single-stepping the inferior.
20035 @item show debug infrun
20036 Displays the current state of @value{GDBN} inferior debugging.
20037 @item set debug jit
20038 @cindex just-in-time compilation, debugging messages
20039 Turns on or off debugging messages from JIT debug support.
20040 @item show debug jit
20041 Displays the current state of @value{GDBN} JIT debugging.
20042 @item set debug lin-lwp
20043 @cindex @sc{gnu}/Linux LWP debug messages
20044 @cindex Linux lightweight processes
20045 Turns on or off debugging messages from the Linux LWP debug support.
20046 @item show debug lin-lwp
20047 Show the current state of Linux LWP debugging messages.
20048 @item set debug lin-lwp-async
20049 @cindex @sc{gnu}/Linux LWP async debug messages
20050 @cindex Linux lightweight processes
20051 Turns on or off debugging messages from the Linux LWP async debug support.
20052 @item show debug lin-lwp-async
20053 Show the current state of Linux LWP async debugging messages.
20054 @item set debug observer
20055 @cindex observer debugging info
20056 Turns on or off display of @value{GDBN} observer debugging. This
20057 includes info such as the notification of observable events.
20058 @item show debug observer
20059 Displays the current state of observer debugging.
20060 @item set debug overload
20061 @cindex C@t{++} overload debugging info
20062 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20063 info. This includes info such as ranking of functions, etc. The default
20065 @item show debug overload
20066 Displays the current state of displaying @value{GDBN} C@t{++} overload
20068 @cindex expression parser, debugging info
20069 @cindex debug expression parser
20070 @item set debug parser
20071 Turns on or off the display of expression parser debugging output.
20072 Internally, this sets the @code{yydebug} variable in the expression
20073 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20074 details. The default is off.
20075 @item show debug parser
20076 Show the current state of expression parser debugging.
20077 @cindex packets, reporting on stdout
20078 @cindex serial connections, debugging
20079 @cindex debug remote protocol
20080 @cindex remote protocol debugging
20081 @cindex display remote packets
20082 @item set debug remote
20083 Turns on or off display of reports on all packets sent back and forth across
20084 the serial line to the remote machine. The info is printed on the
20085 @value{GDBN} standard output stream. The default is off.
20086 @item show debug remote
20087 Displays the state of display of remote packets.
20088 @item set debug serial
20089 Turns on or off display of @value{GDBN} serial debugging info. The
20091 @item show debug serial
20092 Displays the current state of displaying @value{GDBN} serial debugging
20094 @item set debug solib-frv
20095 @cindex FR-V shared-library debugging
20096 Turns on or off debugging messages for FR-V shared-library code.
20097 @item show debug solib-frv
20098 Display the current state of FR-V shared-library code debugging
20100 @item set debug target
20101 @cindex target debugging info
20102 Turns on or off display of @value{GDBN} target debugging info. This info
20103 includes what is going on at the target level of GDB, as it happens. The
20104 default is 0. Set it to 1 to track events, and to 2 to also track the
20105 value of large memory transfers. Changes to this flag do not take effect
20106 until the next time you connect to a target or use the @code{run} command.
20107 @item show debug target
20108 Displays the current state of displaying @value{GDBN} target debugging
20110 @item set debug timestamp
20111 @cindex timestampping debugging info
20112 Turns on or off display of timestamps with @value{GDBN} debugging info.
20113 When enabled, seconds and microseconds are displayed before each debugging
20115 @item show debug timestamp
20116 Displays the current state of displaying timestamps with @value{GDBN}
20118 @item set debugvarobj
20119 @cindex variable object debugging info
20120 Turns on or off display of @value{GDBN} variable object debugging
20121 info. The default is off.
20122 @item show debugvarobj
20123 Displays the current state of displaying @value{GDBN} variable object
20125 @item set debug xml
20126 @cindex XML parser debugging
20127 Turns on or off debugging messages for built-in XML parsers.
20128 @item show debug xml
20129 Displays the current state of XML debugging messages.
20132 @node Other Misc Settings
20133 @section Other Miscellaneous Settings
20134 @cindex miscellaneous settings
20137 @kindex set interactive-mode
20138 @item set interactive-mode
20139 If @code{on}, forces @value{GDBN} to assume that GDB was started
20140 in a terminal. In practice, this means that @value{GDBN} should wait
20141 for the user to answer queries generated by commands entered at
20142 the command prompt. If @code{off}, forces @value{GDBN} to operate
20143 in the opposite mode, and it uses the default answers to all queries.
20144 If @code{auto} (the default), @value{GDBN} tries to determine whether
20145 its standard input is a terminal, and works in interactive-mode if it
20146 is, non-interactively otherwise.
20148 In the vast majority of cases, the debugger should be able to guess
20149 correctly which mode should be used. But this setting can be useful
20150 in certain specific cases, such as running a MinGW @value{GDBN}
20151 inside a cygwin window.
20153 @kindex show interactive-mode
20154 @item show interactive-mode
20155 Displays whether the debugger is operating in interactive mode or not.
20158 @node Extending GDB
20159 @chapter Extending @value{GDBN}
20160 @cindex extending GDB
20162 @value{GDBN} provides two mechanisms for extension. The first is based
20163 on composition of @value{GDBN} commands, and the second is based on the
20164 Python scripting language.
20166 To facilitate the use of these extensions, @value{GDBN} is capable
20167 of evaluating the contents of a file. When doing so, @value{GDBN}
20168 can recognize which scripting language is being used by looking at
20169 the filename extension. Files with an unrecognized filename extension
20170 are always treated as a @value{GDBN} Command Files.
20171 @xref{Command Files,, Command files}.
20173 You can control how @value{GDBN} evaluates these files with the following
20177 @kindex set script-extension
20178 @kindex show script-extension
20179 @item set script-extension off
20180 All scripts are always evaluated as @value{GDBN} Command Files.
20182 @item set script-extension soft
20183 The debugger determines the scripting language based on filename
20184 extension. If this scripting language is supported, @value{GDBN}
20185 evaluates the script using that language. Otherwise, it evaluates
20186 the file as a @value{GDBN} Command File.
20188 @item set script-extension strict
20189 The debugger determines the scripting language based on filename
20190 extension, and evaluates the script using that language. If the
20191 language is not supported, then the evaluation fails.
20193 @item show script-extension
20194 Display the current value of the @code{script-extension} option.
20199 * Sequences:: Canned Sequences of Commands
20200 * Python:: Scripting @value{GDBN} using Python
20204 @section Canned Sequences of Commands
20206 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20207 Command Lists}), @value{GDBN} provides two ways to store sequences of
20208 commands for execution as a unit: user-defined commands and command
20212 * Define:: How to define your own commands
20213 * Hooks:: Hooks for user-defined commands
20214 * Command Files:: How to write scripts of commands to be stored in a file
20215 * Output:: Commands for controlled output
20219 @subsection User-defined Commands
20221 @cindex user-defined command
20222 @cindex arguments, to user-defined commands
20223 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20224 which you assign a new name as a command. This is done with the
20225 @code{define} command. User commands may accept up to 10 arguments
20226 separated by whitespace. Arguments are accessed within the user command
20227 via @code{$arg0@dots{}$arg9}. A trivial example:
20231 print $arg0 + $arg1 + $arg2
20236 To execute the command use:
20243 This defines the command @code{adder}, which prints the sum of
20244 its three arguments. Note the arguments are text substitutions, so they may
20245 reference variables, use complex expressions, or even perform inferior
20248 @cindex argument count in user-defined commands
20249 @cindex how many arguments (user-defined commands)
20250 In addition, @code{$argc} may be used to find out how many arguments have
20251 been passed. This expands to a number in the range 0@dots{}10.
20256 print $arg0 + $arg1
20259 print $arg0 + $arg1 + $arg2
20267 @item define @var{commandname}
20268 Define a command named @var{commandname}. If there is already a command
20269 by that name, you are asked to confirm that you want to redefine it.
20270 @var{commandname} may be a bare command name consisting of letters,
20271 numbers, dashes, and underscores. It may also start with any predefined
20272 prefix command. For example, @samp{define target my-target} creates
20273 a user-defined @samp{target my-target} command.
20275 The definition of the command is made up of other @value{GDBN} command lines,
20276 which are given following the @code{define} command. The end of these
20277 commands is marked by a line containing @code{end}.
20280 @kindex end@r{ (user-defined commands)}
20281 @item document @var{commandname}
20282 Document the user-defined command @var{commandname}, so that it can be
20283 accessed by @code{help}. The command @var{commandname} must already be
20284 defined. This command reads lines of documentation just as @code{define}
20285 reads the lines of the command definition, ending with @code{end}.
20286 After the @code{document} command is finished, @code{help} on command
20287 @var{commandname} displays the documentation you have written.
20289 You may use the @code{document} command again to change the
20290 documentation of a command. Redefining the command with @code{define}
20291 does not change the documentation.
20293 @kindex dont-repeat
20294 @cindex don't repeat command
20296 Used inside a user-defined command, this tells @value{GDBN} that this
20297 command should not be repeated when the user hits @key{RET}
20298 (@pxref{Command Syntax, repeat last command}).
20300 @kindex help user-defined
20301 @item help user-defined
20302 List all user-defined commands, with the first line of the documentation
20307 @itemx show user @var{commandname}
20308 Display the @value{GDBN} commands used to define @var{commandname} (but
20309 not its documentation). If no @var{commandname} is given, display the
20310 definitions for all user-defined commands.
20312 @cindex infinite recursion in user-defined commands
20313 @kindex show max-user-call-depth
20314 @kindex set max-user-call-depth
20315 @item show max-user-call-depth
20316 @itemx set max-user-call-depth
20317 The value of @code{max-user-call-depth} controls how many recursion
20318 levels are allowed in user-defined commands before @value{GDBN} suspects an
20319 infinite recursion and aborts the command.
20322 In addition to the above commands, user-defined commands frequently
20323 use control flow commands, described in @ref{Command Files}.
20325 When user-defined commands are executed, the
20326 commands of the definition are not printed. An error in any command
20327 stops execution of the user-defined command.
20329 If used interactively, commands that would ask for confirmation proceed
20330 without asking when used inside a user-defined command. Many @value{GDBN}
20331 commands that normally print messages to say what they are doing omit the
20332 messages when used in a user-defined command.
20335 @subsection User-defined Command Hooks
20336 @cindex command hooks
20337 @cindex hooks, for commands
20338 @cindex hooks, pre-command
20341 You may define @dfn{hooks}, which are a special kind of user-defined
20342 command. Whenever you run the command @samp{foo}, if the user-defined
20343 command @samp{hook-foo} exists, it is executed (with no arguments)
20344 before that command.
20346 @cindex hooks, post-command
20348 A hook may also be defined which is run after the command you executed.
20349 Whenever you run the command @samp{foo}, if the user-defined command
20350 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20351 that command. Post-execution hooks may exist simultaneously with
20352 pre-execution hooks, for the same command.
20354 It is valid for a hook to call the command which it hooks. If this
20355 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20357 @c It would be nice if hookpost could be passed a parameter indicating
20358 @c if the command it hooks executed properly or not. FIXME!
20360 @kindex stop@r{, a pseudo-command}
20361 In addition, a pseudo-command, @samp{stop} exists. Defining
20362 (@samp{hook-stop}) makes the associated commands execute every time
20363 execution stops in your program: before breakpoint commands are run,
20364 displays are printed, or the stack frame is printed.
20366 For example, to ignore @code{SIGALRM} signals while
20367 single-stepping, but treat them normally during normal execution,
20372 handle SIGALRM nopass
20376 handle SIGALRM pass
20379 define hook-continue
20380 handle SIGALRM pass
20384 As a further example, to hook at the beginning and end of the @code{echo}
20385 command, and to add extra text to the beginning and end of the message,
20393 define hookpost-echo
20397 (@value{GDBP}) echo Hello World
20398 <<<---Hello World--->>>
20403 You can define a hook for any single-word command in @value{GDBN}, but
20404 not for command aliases; you should define a hook for the basic command
20405 name, e.g.@: @code{backtrace} rather than @code{bt}.
20406 @c FIXME! So how does Joe User discover whether a command is an alias
20408 You can hook a multi-word command by adding @code{hook-} or
20409 @code{hookpost-} to the last word of the command, e.g.@:
20410 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20412 If an error occurs during the execution of your hook, execution of
20413 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20414 (before the command that you actually typed had a chance to run).
20416 If you try to define a hook which does not match any known command, you
20417 get a warning from the @code{define} command.
20419 @node Command Files
20420 @subsection Command Files
20422 @cindex command files
20423 @cindex scripting commands
20424 A command file for @value{GDBN} is a text file made of lines that are
20425 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20426 also be included. An empty line in a command file does nothing; it
20427 does not mean to repeat the last command, as it would from the
20430 You can request the execution of a command file with the @code{source}
20431 command. Note that the @code{source} command is also used to evaluate
20432 scripts that are not Command Files. The exact behavior can be configured
20433 using the @code{script-extension} setting.
20434 @xref{Extending GDB,, Extending GDB}.
20438 @cindex execute commands from a file
20439 @item source [-s] [-v] @var{filename}
20440 Execute the command file @var{filename}.
20443 The lines in a command file are generally executed sequentially,
20444 unless the order of execution is changed by one of the
20445 @emph{flow-control commands} described below. The commands are not
20446 printed as they are executed. An error in any command terminates
20447 execution of the command file and control is returned to the console.
20449 @value{GDBN} first searches for @var{filename} in the current directory.
20450 If the file is not found there, and @var{filename} does not specify a
20451 directory, then @value{GDBN} also looks for the file on the source search path
20452 (specified with the @samp{directory} command);
20453 except that @file{$cdir} is not searched because the compilation directory
20454 is not relevant to scripts.
20456 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20457 on the search path even if @var{filename} specifies a directory.
20458 The search is done by appending @var{filename} to each element of the
20459 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20460 and the search path contains @file{/home/user} then @value{GDBN} will
20461 look for the script @file{/home/user/mylib/myscript}.
20462 The search is also done if @var{filename} is an absolute path.
20463 For example, if @var{filename} is @file{/tmp/myscript} and
20464 the search path contains @file{/home/user} then @value{GDBN} will
20465 look for the script @file{/home/user/tmp/myscript}.
20466 For DOS-like systems, if @var{filename} contains a drive specification,
20467 it is stripped before concatenation. For example, if @var{filename} is
20468 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20469 will look for the script @file{c:/tmp/myscript}.
20471 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20472 each command as it is executed. The option must be given before
20473 @var{filename}, and is interpreted as part of the filename anywhere else.
20475 Commands that would ask for confirmation if used interactively proceed
20476 without asking when used in a command file. Many @value{GDBN} commands that
20477 normally print messages to say what they are doing omit the messages
20478 when called from command files.
20480 @value{GDBN} also accepts command input from standard input. In this
20481 mode, normal output goes to standard output and error output goes to
20482 standard error. Errors in a command file supplied on standard input do
20483 not terminate execution of the command file---execution continues with
20487 gdb < cmds > log 2>&1
20490 (The syntax above will vary depending on the shell used.) This example
20491 will execute commands from the file @file{cmds}. All output and errors
20492 would be directed to @file{log}.
20494 Since commands stored on command files tend to be more general than
20495 commands typed interactively, they frequently need to deal with
20496 complicated situations, such as different or unexpected values of
20497 variables and symbols, changes in how the program being debugged is
20498 built, etc. @value{GDBN} provides a set of flow-control commands to
20499 deal with these complexities. Using these commands, you can write
20500 complex scripts that loop over data structures, execute commands
20501 conditionally, etc.
20508 This command allows to include in your script conditionally executed
20509 commands. The @code{if} command takes a single argument, which is an
20510 expression to evaluate. It is followed by a series of commands that
20511 are executed only if the expression is true (its value is nonzero).
20512 There can then optionally be an @code{else} line, followed by a series
20513 of commands that are only executed if the expression was false. The
20514 end of the list is marked by a line containing @code{end}.
20518 This command allows to write loops. Its syntax is similar to
20519 @code{if}: the command takes a single argument, which is an expression
20520 to evaluate, and must be followed by the commands to execute, one per
20521 line, terminated by an @code{end}. These commands are called the
20522 @dfn{body} of the loop. The commands in the body of @code{while} are
20523 executed repeatedly as long as the expression evaluates to true.
20527 This command exits the @code{while} loop in whose body it is included.
20528 Execution of the script continues after that @code{while}s @code{end}
20531 @kindex loop_continue
20532 @item loop_continue
20533 This command skips the execution of the rest of the body of commands
20534 in the @code{while} loop in whose body it is included. Execution
20535 branches to the beginning of the @code{while} loop, where it evaluates
20536 the controlling expression.
20538 @kindex end@r{ (if/else/while commands)}
20540 Terminate the block of commands that are the body of @code{if},
20541 @code{else}, or @code{while} flow-control commands.
20546 @subsection Commands for Controlled Output
20548 During the execution of a command file or a user-defined command, normal
20549 @value{GDBN} output is suppressed; the only output that appears is what is
20550 explicitly printed by the commands in the definition. This section
20551 describes three commands useful for generating exactly the output you
20556 @item echo @var{text}
20557 @c I do not consider backslash-space a standard C escape sequence
20558 @c because it is not in ANSI.
20559 Print @var{text}. Nonprinting characters can be included in
20560 @var{text} using C escape sequences, such as @samp{\n} to print a
20561 newline. @strong{No newline is printed unless you specify one.}
20562 In addition to the standard C escape sequences, a backslash followed
20563 by a space stands for a space. This is useful for displaying a
20564 string with spaces at the beginning or the end, since leading and
20565 trailing spaces are otherwise trimmed from all arguments.
20566 To print @samp{@w{ }and foo =@w{ }}, use the command
20567 @samp{echo \@w{ }and foo = \@w{ }}.
20569 A backslash at the end of @var{text} can be used, as in C, to continue
20570 the command onto subsequent lines. For example,
20573 echo This is some text\n\
20574 which is continued\n\
20575 onto several lines.\n
20578 produces the same output as
20581 echo This is some text\n
20582 echo which is continued\n
20583 echo onto several lines.\n
20587 @item output @var{expression}
20588 Print the value of @var{expression} and nothing but that value: no
20589 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20590 value history either. @xref{Expressions, ,Expressions}, for more information
20593 @item output/@var{fmt} @var{expression}
20594 Print the value of @var{expression} in format @var{fmt}. You can use
20595 the same formats as for @code{print}. @xref{Output Formats,,Output
20596 Formats}, for more information.
20599 @item printf @var{template}, @var{expressions}@dots{}
20600 Print the values of one or more @var{expressions} under the control of
20601 the string @var{template}. To print several values, make
20602 @var{expressions} be a comma-separated list of individual expressions,
20603 which may be either numbers or pointers. Their values are printed as
20604 specified by @var{template}, exactly as a C program would do by
20605 executing the code below:
20608 printf (@var{template}, @var{expressions}@dots{});
20611 As in @code{C} @code{printf}, ordinary characters in @var{template}
20612 are printed verbatim, while @dfn{conversion specification} introduced
20613 by the @samp{%} character cause subsequent @var{expressions} to be
20614 evaluated, their values converted and formatted according to type and
20615 style information encoded in the conversion specifications, and then
20618 For example, you can print two values in hex like this:
20621 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20624 @code{printf} supports all the standard @code{C} conversion
20625 specifications, including the flags and modifiers between the @samp{%}
20626 character and the conversion letter, with the following exceptions:
20630 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20633 The modifier @samp{*} is not supported for specifying precision or
20637 The @samp{'} flag (for separation of digits into groups according to
20638 @code{LC_NUMERIC'}) is not supported.
20641 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20645 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20648 The conversion letters @samp{a} and @samp{A} are not supported.
20652 Note that the @samp{ll} type modifier is supported only if the
20653 underlying @code{C} implementation used to build @value{GDBN} supports
20654 the @code{long long int} type, and the @samp{L} type modifier is
20655 supported only if @code{long double} type is available.
20657 As in @code{C}, @code{printf} supports simple backslash-escape
20658 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20659 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20660 single character. Octal and hexadecimal escape sequences are not
20663 Additionally, @code{printf} supports conversion specifications for DFP
20664 (@dfn{Decimal Floating Point}) types using the following length modifiers
20665 together with a floating point specifier.
20670 @samp{H} for printing @code{Decimal32} types.
20673 @samp{D} for printing @code{Decimal64} types.
20676 @samp{DD} for printing @code{Decimal128} types.
20679 If the underlying @code{C} implementation used to build @value{GDBN} has
20680 support for the three length modifiers for DFP types, other modifiers
20681 such as width and precision will also be available for @value{GDBN} to use.
20683 In case there is no such @code{C} support, no additional modifiers will be
20684 available and the value will be printed in the standard way.
20686 Here's an example of printing DFP types using the above conversion letters:
20688 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20692 @item eval @var{template}, @var{expressions}@dots{}
20693 Convert the values of one or more @var{expressions} under the control of
20694 the string @var{template} to a command line, and call it.
20699 @section Scripting @value{GDBN} using Python
20700 @cindex python scripting
20701 @cindex scripting with python
20703 You can script @value{GDBN} using the @uref{http://www.python.org/,
20704 Python programming language}. This feature is available only if
20705 @value{GDBN} was configured using @option{--with-python}.
20707 @cindex python directory
20708 Python scripts used by @value{GDBN} should be installed in
20709 @file{@var{data-directory}/python}, where @var{data-directory} is
20710 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20711 This directory, known as the @dfn{python directory},
20712 is automatically added to the Python Search Path in order to allow
20713 the Python interpreter to locate all scripts installed at this location.
20716 * Python Commands:: Accessing Python from @value{GDBN}.
20717 * Python API:: Accessing @value{GDBN} from Python.
20718 * Auto-loading:: Automatically loading Python code.
20719 * Python modules:: Python modules provided by @value{GDBN}.
20722 @node Python Commands
20723 @subsection Python Commands
20724 @cindex python commands
20725 @cindex commands to access python
20727 @value{GDBN} provides one command for accessing the Python interpreter,
20728 and one related setting:
20732 @item python @r{[}@var{code}@r{]}
20733 The @code{python} command can be used to evaluate Python code.
20735 If given an argument, the @code{python} command will evaluate the
20736 argument as a Python command. For example:
20739 (@value{GDBP}) python print 23
20743 If you do not provide an argument to @code{python}, it will act as a
20744 multi-line command, like @code{define}. In this case, the Python
20745 script is made up of subsequent command lines, given after the
20746 @code{python} command. This command list is terminated using a line
20747 containing @code{end}. For example:
20750 (@value{GDBP}) python
20752 End with a line saying just "end".
20758 @kindex maint set python print-stack
20759 @item maint set python print-stack
20760 By default, @value{GDBN} will print a stack trace when an error occurs
20761 in a Python script. This can be controlled using @code{maint set
20762 python print-stack}: if @code{on}, the default, then Python stack
20763 printing is enabled; if @code{off}, then Python stack printing is
20767 It is also possible to execute a Python script from the @value{GDBN}
20771 @item source @file{script-name}
20772 The script name must end with @samp{.py} and @value{GDBN} must be configured
20773 to recognize the script language based on filename extension using
20774 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20776 @item python execfile ("script-name")
20777 This method is based on the @code{execfile} Python built-in function,
20778 and thus is always available.
20782 @subsection Python API
20784 @cindex programming in python
20786 @cindex python stdout
20787 @cindex python pagination
20788 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20789 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20790 A Python program which outputs to one of these streams may have its
20791 output interrupted by the user (@pxref{Screen Size}). In this
20792 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20795 * Basic Python:: Basic Python Functions.
20796 * Exception Handling:: How Python exceptions are translated.
20797 * Values From Inferior:: Python representation of values.
20798 * Types In Python:: Python representation of types.
20799 * Pretty Printing API:: Pretty-printing values.
20800 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20801 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20802 * Inferiors In Python:: Python representation of inferiors (processes)
20803 * Events In Python:: Listening for events from @value{GDBN}.
20804 * Threads In Python:: Accessing inferior threads from Python.
20805 * Commands In Python:: Implementing new commands in Python.
20806 * Parameters In Python:: Adding new @value{GDBN} parameters.
20807 * Functions In Python:: Writing new convenience functions.
20808 * Progspaces In Python:: Program spaces.
20809 * Objfiles In Python:: Object files.
20810 * Frames In Python:: Accessing inferior stack frames from Python.
20811 * Blocks In Python:: Accessing frame blocks from Python.
20812 * Symbols In Python:: Python representation of symbols.
20813 * Symbol Tables In Python:: Python representation of symbol tables.
20814 * Lazy Strings In Python:: Python representation of lazy strings.
20815 * Breakpoints In Python:: Manipulating breakpoints using Python.
20819 @subsubsection Basic Python
20821 @cindex python functions
20822 @cindex python module
20824 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20825 methods and classes added by @value{GDBN} are placed in this module.
20826 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20827 use in all scripts evaluated by the @code{python} command.
20829 @findex gdb.PYTHONDIR
20831 A string containing the python directory (@pxref{Python}).
20834 @findex gdb.execute
20835 @defun execute command [from_tty] [to_string]
20836 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20837 If a GDB exception happens while @var{command} runs, it is
20838 translated as described in @ref{Exception Handling,,Exception Handling}.
20840 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20841 command as having originated from the user invoking it interactively.
20842 It must be a boolean value. If omitted, it defaults to @code{False}.
20844 By default, any output produced by @var{command} is sent to
20845 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20846 @code{True}, then output will be collected by @code{gdb.execute} and
20847 returned as a string. The default is @code{False}, in which case the
20848 return value is @code{None}. If @var{to_string} is @code{True}, the
20849 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20850 and height, and its pagination will be disabled; @pxref{Screen Size}.
20853 @findex gdb.breakpoints
20855 Return a sequence holding all of @value{GDBN}'s breakpoints.
20856 @xref{Breakpoints In Python}, for more information.
20859 @findex gdb.parameter
20860 @defun parameter parameter
20861 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20862 string naming the parameter to look up; @var{parameter} may contain
20863 spaces if the parameter has a multi-part name. For example,
20864 @samp{print object} is a valid parameter name.
20866 If the named parameter does not exist, this function throws a
20867 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
20868 parameter's value is converted to a Python value of the appropriate
20869 type, and returned.
20872 @findex gdb.history
20873 @defun history number
20874 Return a value from @value{GDBN}'s value history (@pxref{Value
20875 History}). @var{number} indicates which history element to return.
20876 If @var{number} is negative, then @value{GDBN} will take its absolute value
20877 and count backward from the last element (i.e., the most recent element) to
20878 find the value to return. If @var{number} is zero, then @value{GDBN} will
20879 return the most recent element. If the element specified by @var{number}
20880 doesn't exist in the value history, a @code{gdb.error} exception will be
20883 If no exception is raised, the return value is always an instance of
20884 @code{gdb.Value} (@pxref{Values From Inferior}).
20887 @findex gdb.parse_and_eval
20888 @defun parse_and_eval expression
20889 Parse @var{expression} as an expression in the current language,
20890 evaluate it, and return the result as a @code{gdb.Value}.
20891 @var{expression} must be a string.
20893 This function can be useful when implementing a new command
20894 (@pxref{Commands In Python}), as it provides a way to parse the
20895 command's argument as an expression. It is also useful simply to
20896 compute values, for example, it is the only way to get the value of a
20897 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20900 @findex gdb.post_event
20901 @defun post_event event
20902 Put @var{event}, a callable object taking no arguments, into
20903 @value{GDBN}'s internal event queue. This callable will be invoked at
20904 some later point, during @value{GDBN}'s event processing. Events
20905 posted using @code{post_event} will be run in the order in which they
20906 were posted; however, there is no way to know when they will be
20907 processed relative to other events inside @value{GDBN}.
20909 @value{GDBN} is not thread-safe. If your Python program uses multiple
20910 threads, you must be careful to only call @value{GDBN}-specific
20911 functions in the main @value{GDBN} thread. @code{post_event} ensures
20915 (@value{GDBP}) python
20919 > def __init__(self, message):
20920 > self.message = message;
20921 > def __call__(self):
20922 > gdb.write(self.message)
20924 >class MyThread1 (threading.Thread):
20926 > gdb.post_event(Writer("Hello "))
20928 >class MyThread2 (threading.Thread):
20930 > gdb.post_event(Writer("World\n"))
20932 >MyThread1().start()
20933 >MyThread2().start()
20935 (@value{GDBP}) Hello World
20940 @defun write string @r{[}stream{]}
20941 Print a string to @value{GDBN}'s paginated output stream. The
20942 optional @var{stream} determines the stream to print to. The default
20943 stream is @value{GDBN}'s standard output stream. Possible stream
20950 @value{GDBN}'s standard output stream.
20955 @value{GDBN}'s standard error stream.
20960 @value{GDBN}'s log stream (@pxref{Logging Output}).
20963 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20964 call this function and will automatically direct the output to the
20970 Flush the buffer of a @value{GDBN} paginated stream so that the
20971 contents are displayed immediately. @value{GDBN} will flush the
20972 contents of a stream automatically when it encounters a newline in the
20973 buffer. The optional @var{stream} determines the stream to flush. The
20974 default stream is @value{GDBN}'s standard output stream. Possible
20981 @value{GDBN}'s standard output stream.
20986 @value{GDBN}'s standard error stream.
20991 @value{GDBN}'s log stream (@pxref{Logging Output}).
20995 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
20996 call this function for the relevant stream.
20999 @findex gdb.target_charset
21000 @defun target_charset
21001 Return the name of the current target character set (@pxref{Character
21002 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21003 that @samp{auto} is never returned.
21006 @findex gdb.target_wide_charset
21007 @defun target_wide_charset
21008 Return the name of the current target wide character set
21009 (@pxref{Character Sets}). This differs from
21010 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21014 @findex gdb.solib_name
21015 @defun solib_name address
21016 Return the name of the shared library holding the given @var{address}
21017 as a string, or @code{None}.
21020 @findex gdb.decode_line
21021 @defun decode_line @r{[}expression@r{]}
21022 Return locations of the line specified by @var{expression}, or of the
21023 current line if no argument was given. This function returns a Python
21024 tuple containing two elements. The first element contains a string
21025 holding any unparsed section of @var{expression} (or @code{None} if
21026 the expression has been fully parsed). The second element contains
21027 either @code{None} or another tuple that contains all the locations
21028 that match the expression represented as @code{gdb.Symtab_and_line}
21029 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21030 provided, it is decoded the way that @value{GDBN}'s inbuilt
21031 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21034 @node Exception Handling
21035 @subsubsection Exception Handling
21036 @cindex python exceptions
21037 @cindex exceptions, python
21039 When executing the @code{python} command, Python exceptions
21040 uncaught within the Python code are translated to calls to
21041 @value{GDBN} error-reporting mechanism. If the command that called
21042 @code{python} does not handle the error, @value{GDBN} will
21043 terminate it and print an error message containing the Python
21044 exception name, the associated value, and the Python call stack
21045 backtrace at the point where the exception was raised. Example:
21048 (@value{GDBP}) python print foo
21049 Traceback (most recent call last):
21050 File "<string>", line 1, in <module>
21051 NameError: name 'foo' is not defined
21054 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21055 Python code are converted to Python exceptions. The type of the
21056 Python exception depends on the error.
21060 This is the base class for most exceptions generated by @value{GDBN}.
21061 It is derived from @code{RuntimeError}, for compatibility with earlier
21062 versions of @value{GDBN}.
21064 If an error occurring in @value{GDBN} does not fit into some more
21065 specific category, then the generated exception will have this type.
21067 @item gdb.MemoryError
21068 This is a subclass of @code{gdb.error} which is thrown when an
21069 operation tried to access invalid memory in the inferior.
21071 @item KeyboardInterrupt
21072 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21073 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21076 In all cases, your exception handler will see the @value{GDBN} error
21077 message as its value and the Python call stack backtrace at the Python
21078 statement closest to where the @value{GDBN} error occured as the
21081 @findex gdb.GdbError
21082 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21083 it is useful to be able to throw an exception that doesn't cause a
21084 traceback to be printed. For example, the user may have invoked the
21085 command incorrectly. Use the @code{gdb.GdbError} exception
21086 to handle this case. Example:
21090 >class HelloWorld (gdb.Command):
21091 > """Greet the whole world."""
21092 > def __init__ (self):
21093 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21094 > def invoke (self, args, from_tty):
21095 > argv = gdb.string_to_argv (args)
21096 > if len (argv) != 0:
21097 > raise gdb.GdbError ("hello-world takes no arguments")
21098 > print "Hello, World!"
21101 (gdb) hello-world 42
21102 hello-world takes no arguments
21105 @node Values From Inferior
21106 @subsubsection Values From Inferior
21107 @cindex values from inferior, with Python
21108 @cindex python, working with values from inferior
21110 @cindex @code{gdb.Value}
21111 @value{GDBN} provides values it obtains from the inferior program in
21112 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21113 for its internal bookkeeping of the inferior's values, and for
21114 fetching values when necessary.
21116 Inferior values that are simple scalars can be used directly in
21117 Python expressions that are valid for the value's data type. Here's
21118 an example for an integer or floating-point value @code{some_val}:
21125 As result of this, @code{bar} will also be a @code{gdb.Value} object
21126 whose values are of the same type as those of @code{some_val}.
21128 Inferior values that are structures or instances of some class can
21129 be accessed using the Python @dfn{dictionary syntax}. For example, if
21130 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21131 can access its @code{foo} element with:
21134 bar = some_val['foo']
21137 Again, @code{bar} will also be a @code{gdb.Value} object.
21139 A @code{gdb.Value} that represents a function can be executed via
21140 inferior function call. Any arguments provided to the call must match
21141 the function's prototype, and must be provided in the order specified
21144 For example, @code{some_val} is a @code{gdb.Value} instance
21145 representing a function that takes two integers as arguments. To
21146 execute this function, call it like so:
21149 result = some_val (10,20)
21152 Any values returned from a function call will be stored as a
21155 The following attributes are provided:
21158 @defivar Value address
21159 If this object is addressable, this read-only attribute holds a
21160 @code{gdb.Value} object representing the address. Otherwise,
21161 this attribute holds @code{None}.
21164 @cindex optimized out value in Python
21165 @defivar Value is_optimized_out
21166 This read-only boolean attribute is true if the compiler optimized out
21167 this value, thus it is not available for fetching from the inferior.
21170 @defivar Value type
21171 The type of this @code{gdb.Value}. The value of this attribute is a
21172 @code{gdb.Type} object (@pxref{Types In Python}).
21175 @defivar Value dynamic_type
21176 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21177 type information (@acronym{RTTI}) to determine the dynamic type of the
21178 value. If this value is of class type, it will return the class in
21179 which the value is embedded, if any. If this value is of pointer or
21180 reference to a class type, it will compute the dynamic type of the
21181 referenced object, and return a pointer or reference to that type,
21182 respectively. In all other cases, it will return the value's static
21185 Note that this feature will only work when debugging a C@t{++} program
21186 that includes @acronym{RTTI} for the object in question. Otherwise,
21187 it will just return the static type of the value as in @kbd{ptype foo}
21188 (@pxref{Symbols, ptype}).
21192 The following methods are provided:
21195 @defmethod Value __init__ @var{val}
21196 Many Python values can be converted directly to a @code{gdb.Value} via
21197 this object initializer. Specifically:
21200 @item Python boolean
21201 A Python boolean is converted to the boolean type from the current
21204 @item Python integer
21205 A Python integer is converted to the C @code{long} type for the
21206 current architecture.
21209 A Python long is converted to the C @code{long long} type for the
21210 current architecture.
21213 A Python float is converted to the C @code{double} type for the
21214 current architecture.
21216 @item Python string
21217 A Python string is converted to a target string, using the current
21220 @item @code{gdb.Value}
21221 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21223 @item @code{gdb.LazyString}
21224 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21225 Python}), then the lazy string's @code{value} method is called, and
21226 its result is used.
21230 @defmethod Value cast type
21231 Return a new instance of @code{gdb.Value} that is the result of
21232 casting this instance to the type described by @var{type}, which must
21233 be a @code{gdb.Type} object. If the cast cannot be performed for some
21234 reason, this method throws an exception.
21237 @defmethod Value dereference
21238 For pointer data types, this method returns a new @code{gdb.Value} object
21239 whose contents is the object pointed to by the pointer. For example, if
21240 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21247 then you can use the corresponding @code{gdb.Value} to access what
21248 @code{foo} points to like this:
21251 bar = foo.dereference ()
21254 The result @code{bar} will be a @code{gdb.Value} object holding the
21255 value pointed to by @code{foo}.
21258 @defmethod Value dynamic_cast type
21259 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21260 operator were used. Consult a C@t{++} reference for details.
21263 @defmethod Value reinterpret_cast type
21264 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21265 operator were used. Consult a C@t{++} reference for details.
21268 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21269 If this @code{gdb.Value} represents a string, then this method
21270 converts the contents to a Python string. Otherwise, this method will
21271 throw an exception.
21273 Strings are recognized in a language-specific way; whether a given
21274 @code{gdb.Value} represents a string is determined by the current
21277 For C-like languages, a value is a string if it is a pointer to or an
21278 array of characters or ints. The string is assumed to be terminated
21279 by a zero of the appropriate width. However if the optional length
21280 argument is given, the string will be converted to that given length,
21281 ignoring any embedded zeros that the string may contain.
21283 If the optional @var{encoding} argument is given, it must be a string
21284 naming the encoding of the string in the @code{gdb.Value}, such as
21285 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21286 the same encodings as the corresponding argument to Python's
21287 @code{string.decode} method, and the Python codec machinery will be used
21288 to convert the string. If @var{encoding} is not given, or if
21289 @var{encoding} is the empty string, then either the @code{target-charset}
21290 (@pxref{Character Sets}) will be used, or a language-specific encoding
21291 will be used, if the current language is able to supply one.
21293 The optional @var{errors} argument is the same as the corresponding
21294 argument to Python's @code{string.decode} method.
21296 If the optional @var{length} argument is given, the string will be
21297 fetched and converted to the given length.
21300 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21301 If this @code{gdb.Value} represents a string, then this method
21302 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21303 In Python}). Otherwise, this method will throw an exception.
21305 If the optional @var{encoding} argument is given, it must be a string
21306 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21307 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21308 @var{encoding} argument is an encoding that @value{GDBN} does
21309 recognize, @value{GDBN} will raise an error.
21311 When a lazy string is printed, the @value{GDBN} encoding machinery is
21312 used to convert the string during printing. If the optional
21313 @var{encoding} argument is not provided, or is an empty string,
21314 @value{GDBN} will automatically select the encoding most suitable for
21315 the string type. For further information on encoding in @value{GDBN}
21316 please see @ref{Character Sets}.
21318 If the optional @var{length} argument is given, the string will be
21319 fetched and encoded to the length of characters specified. If
21320 the @var{length} argument is not provided, the string will be fetched
21321 and encoded until a null of appropriate width is found.
21325 @node Types In Python
21326 @subsubsection Types In Python
21327 @cindex types in Python
21328 @cindex Python, working with types
21331 @value{GDBN} represents types from the inferior using the class
21334 The following type-related functions are available in the @code{gdb}
21337 @findex gdb.lookup_type
21338 @defun lookup_type name [block]
21339 This function looks up a type by name. @var{name} is the name of the
21340 type to look up. It must be a string.
21342 If @var{block} is given, then @var{name} is looked up in that scope.
21343 Otherwise, it is searched for globally.
21345 Ordinarily, this function will return an instance of @code{gdb.Type}.
21346 If the named type cannot be found, it will throw an exception.
21349 An instance of @code{Type} has the following attributes:
21353 The type code for this type. The type code will be one of the
21354 @code{TYPE_CODE_} constants defined below.
21357 @defivar Type sizeof
21358 The size of this type, in target @code{char} units. Usually, a
21359 target's @code{char} type will be an 8-bit byte. However, on some
21360 unusual platforms, this type may have a different size.
21364 The tag name for this type. The tag name is the name after
21365 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21366 languages have this concept. If this type has no tag name, then
21367 @code{None} is returned.
21371 The following methods are provided:
21374 @defmethod Type fields
21375 For structure and union types, this method returns the fields. Range
21376 types have two fields, the minimum and maximum values. Enum types
21377 have one field per enum constant. Function and method types have one
21378 field per parameter. The base types of C@t{++} classes are also
21379 represented as fields. If the type has no fields, or does not fit
21380 into one of these categories, an empty sequence will be returned.
21382 Each field is an object, with some pre-defined attributes:
21385 This attribute is not available for @code{static} fields (as in
21386 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21387 position of the field.
21390 The name of the field, or @code{None} for anonymous fields.
21393 This is @code{True} if the field is artificial, usually meaning that
21394 it was provided by the compiler and not the user. This attribute is
21395 always provided, and is @code{False} if the field is not artificial.
21397 @item is_base_class
21398 This is @code{True} if the field represents a base class of a C@t{++}
21399 structure. This attribute is always provided, and is @code{False}
21400 if the field is not a base class of the type that is the argument of
21401 @code{fields}, or if that type was not a C@t{++} class.
21404 If the field is packed, or is a bitfield, then this will have a
21405 non-zero value, which is the size of the field in bits. Otherwise,
21406 this will be zero; in this case the field's size is given by its type.
21409 The type of the field. This is usually an instance of @code{Type},
21410 but it can be @code{None} in some situations.
21414 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21415 Return a new @code{gdb.Type} object which represents an array of this
21416 type. If one argument is given, it is the inclusive upper bound of
21417 the array; in this case the lower bound is zero. If two arguments are
21418 given, the first argument is the lower bound of the array, and the
21419 second argument is the upper bound of the array. An array's length
21420 must not be negative, but the bounds can be.
21423 @defmethod Type const
21424 Return a new @code{gdb.Type} object which represents a
21425 @code{const}-qualified variant of this type.
21428 @defmethod Type volatile
21429 Return a new @code{gdb.Type} object which represents a
21430 @code{volatile}-qualified variant of this type.
21433 @defmethod Type unqualified
21434 Return a new @code{gdb.Type} object which represents an unqualified
21435 variant of this type. That is, the result is neither @code{const} nor
21439 @defmethod Type range
21440 Return a Python @code{Tuple} object that contains two elements: the
21441 low bound of the argument type and the high bound of that type. If
21442 the type does not have a range, @value{GDBN} will raise a
21443 @code{gdb.error} exception (@pxref{Exception Handling}).
21446 @defmethod Type reference
21447 Return a new @code{gdb.Type} object which represents a reference to this
21451 @defmethod Type pointer
21452 Return a new @code{gdb.Type} object which represents a pointer to this
21456 @defmethod Type strip_typedefs
21457 Return a new @code{gdb.Type} that represents the real type,
21458 after removing all layers of typedefs.
21461 @defmethod Type target
21462 Return a new @code{gdb.Type} object which represents the target type
21465 For a pointer type, the target type is the type of the pointed-to
21466 object. For an array type (meaning C-like arrays), the target type is
21467 the type of the elements of the array. For a function or method type,
21468 the target type is the type of the return value. For a complex type,
21469 the target type is the type of the elements. For a typedef, the
21470 target type is the aliased type.
21472 If the type does not have a target, this method will throw an
21476 @defmethod Type template_argument n [block]
21477 If this @code{gdb.Type} is an instantiation of a template, this will
21478 return a new @code{gdb.Type} which represents the type of the
21479 @var{n}th template argument.
21481 If this @code{gdb.Type} is not a template type, this will throw an
21482 exception. Ordinarily, only C@t{++} code will have template types.
21484 If @var{block} is given, then @var{name} is looked up in that scope.
21485 Otherwise, it is searched for globally.
21490 Each type has a code, which indicates what category this type falls
21491 into. The available type categories are represented by constants
21492 defined in the @code{gdb} module:
21495 @findex TYPE_CODE_PTR
21496 @findex gdb.TYPE_CODE_PTR
21497 @item TYPE_CODE_PTR
21498 The type is a pointer.
21500 @findex TYPE_CODE_ARRAY
21501 @findex gdb.TYPE_CODE_ARRAY
21502 @item TYPE_CODE_ARRAY
21503 The type is an array.
21505 @findex TYPE_CODE_STRUCT
21506 @findex gdb.TYPE_CODE_STRUCT
21507 @item TYPE_CODE_STRUCT
21508 The type is a structure.
21510 @findex TYPE_CODE_UNION
21511 @findex gdb.TYPE_CODE_UNION
21512 @item TYPE_CODE_UNION
21513 The type is a union.
21515 @findex TYPE_CODE_ENUM
21516 @findex gdb.TYPE_CODE_ENUM
21517 @item TYPE_CODE_ENUM
21518 The type is an enum.
21520 @findex TYPE_CODE_FLAGS
21521 @findex gdb.TYPE_CODE_FLAGS
21522 @item TYPE_CODE_FLAGS
21523 A bit flags type, used for things such as status registers.
21525 @findex TYPE_CODE_FUNC
21526 @findex gdb.TYPE_CODE_FUNC
21527 @item TYPE_CODE_FUNC
21528 The type is a function.
21530 @findex TYPE_CODE_INT
21531 @findex gdb.TYPE_CODE_INT
21532 @item TYPE_CODE_INT
21533 The type is an integer type.
21535 @findex TYPE_CODE_FLT
21536 @findex gdb.TYPE_CODE_FLT
21537 @item TYPE_CODE_FLT
21538 A floating point type.
21540 @findex TYPE_CODE_VOID
21541 @findex gdb.TYPE_CODE_VOID
21542 @item TYPE_CODE_VOID
21543 The special type @code{void}.
21545 @findex TYPE_CODE_SET
21546 @findex gdb.TYPE_CODE_SET
21547 @item TYPE_CODE_SET
21550 @findex TYPE_CODE_RANGE
21551 @findex gdb.TYPE_CODE_RANGE
21552 @item TYPE_CODE_RANGE
21553 A range type, that is, an integer type with bounds.
21555 @findex TYPE_CODE_STRING
21556 @findex gdb.TYPE_CODE_STRING
21557 @item TYPE_CODE_STRING
21558 A string type. Note that this is only used for certain languages with
21559 language-defined string types; C strings are not represented this way.
21561 @findex TYPE_CODE_BITSTRING
21562 @findex gdb.TYPE_CODE_BITSTRING
21563 @item TYPE_CODE_BITSTRING
21566 @findex TYPE_CODE_ERROR
21567 @findex gdb.TYPE_CODE_ERROR
21568 @item TYPE_CODE_ERROR
21569 An unknown or erroneous type.
21571 @findex TYPE_CODE_METHOD
21572 @findex gdb.TYPE_CODE_METHOD
21573 @item TYPE_CODE_METHOD
21574 A method type, as found in C@t{++} or Java.
21576 @findex TYPE_CODE_METHODPTR
21577 @findex gdb.TYPE_CODE_METHODPTR
21578 @item TYPE_CODE_METHODPTR
21579 A pointer-to-member-function.
21581 @findex TYPE_CODE_MEMBERPTR
21582 @findex gdb.TYPE_CODE_MEMBERPTR
21583 @item TYPE_CODE_MEMBERPTR
21584 A pointer-to-member.
21586 @findex TYPE_CODE_REF
21587 @findex gdb.TYPE_CODE_REF
21588 @item TYPE_CODE_REF
21591 @findex TYPE_CODE_CHAR
21592 @findex gdb.TYPE_CODE_CHAR
21593 @item TYPE_CODE_CHAR
21596 @findex TYPE_CODE_BOOL
21597 @findex gdb.TYPE_CODE_BOOL
21598 @item TYPE_CODE_BOOL
21601 @findex TYPE_CODE_COMPLEX
21602 @findex gdb.TYPE_CODE_COMPLEX
21603 @item TYPE_CODE_COMPLEX
21604 A complex float type.
21606 @findex TYPE_CODE_TYPEDEF
21607 @findex gdb.TYPE_CODE_TYPEDEF
21608 @item TYPE_CODE_TYPEDEF
21609 A typedef to some other type.
21611 @findex TYPE_CODE_NAMESPACE
21612 @findex gdb.TYPE_CODE_NAMESPACE
21613 @item TYPE_CODE_NAMESPACE
21614 A C@t{++} namespace.
21616 @findex TYPE_CODE_DECFLOAT
21617 @findex gdb.TYPE_CODE_DECFLOAT
21618 @item TYPE_CODE_DECFLOAT
21619 A decimal floating point type.
21621 @findex TYPE_CODE_INTERNAL_FUNCTION
21622 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21623 @item TYPE_CODE_INTERNAL_FUNCTION
21624 A function internal to @value{GDBN}. This is the type used to represent
21625 convenience functions.
21628 Further support for types is provided in the @code{gdb.types}
21629 Python module (@pxref{gdb.types}).
21631 @node Pretty Printing API
21632 @subsubsection Pretty Printing API
21634 An example output is provided (@pxref{Pretty Printing}).
21636 A pretty-printer is just an object that holds a value and implements a
21637 specific interface, defined here.
21639 @defop Operation {pretty printer} children (self)
21640 @value{GDBN} will call this method on a pretty-printer to compute the
21641 children of the pretty-printer's value.
21643 This method must return an object conforming to the Python iterator
21644 protocol. Each item returned by the iterator must be a tuple holding
21645 two elements. The first element is the ``name'' of the child; the
21646 second element is the child's value. The value can be any Python
21647 object which is convertible to a @value{GDBN} value.
21649 This method is optional. If it does not exist, @value{GDBN} will act
21650 as though the value has no children.
21653 @defop Operation {pretty printer} display_hint (self)
21654 The CLI may call this method and use its result to change the
21655 formatting of a value. The result will also be supplied to an MI
21656 consumer as a @samp{displayhint} attribute of the variable being
21659 This method is optional. If it does exist, this method must return a
21662 Some display hints are predefined by @value{GDBN}:
21666 Indicate that the object being printed is ``array-like''. The CLI
21667 uses this to respect parameters such as @code{set print elements} and
21668 @code{set print array}.
21671 Indicate that the object being printed is ``map-like'', and that the
21672 children of this value can be assumed to alternate between keys and
21676 Indicate that the object being printed is ``string-like''. If the
21677 printer's @code{to_string} method returns a Python string of some
21678 kind, then @value{GDBN} will call its internal language-specific
21679 string-printing function to format the string. For the CLI this means
21680 adding quotation marks, possibly escaping some characters, respecting
21681 @code{set print elements}, and the like.
21685 @defop Operation {pretty printer} to_string (self)
21686 @value{GDBN} will call this method to display the string
21687 representation of the value passed to the object's constructor.
21689 When printing from the CLI, if the @code{to_string} method exists,
21690 then @value{GDBN} will prepend its result to the values returned by
21691 @code{children}. Exactly how this formatting is done is dependent on
21692 the display hint, and may change as more hints are added. Also,
21693 depending on the print settings (@pxref{Print Settings}), the CLI may
21694 print just the result of @code{to_string} in a stack trace, omitting
21695 the result of @code{children}.
21697 If this method returns a string, it is printed verbatim.
21699 Otherwise, if this method returns an instance of @code{gdb.Value},
21700 then @value{GDBN} prints this value. This may result in a call to
21701 another pretty-printer.
21703 If instead the method returns a Python value which is convertible to a
21704 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21705 the resulting value. Again, this may result in a call to another
21706 pretty-printer. Python scalars (integers, floats, and booleans) and
21707 strings are convertible to @code{gdb.Value}; other types are not.
21709 Finally, if this method returns @code{None} then no further operations
21710 are peformed in this method and nothing is printed.
21712 If the result is not one of these types, an exception is raised.
21715 @value{GDBN} provides a function which can be used to look up the
21716 default pretty-printer for a @code{gdb.Value}:
21718 @findex gdb.default_visualizer
21719 @defun default_visualizer value
21720 This function takes a @code{gdb.Value} object as an argument. If a
21721 pretty-printer for this value exists, then it is returned. If no such
21722 printer exists, then this returns @code{None}.
21725 @node Selecting Pretty-Printers
21726 @subsubsection Selecting Pretty-Printers
21728 The Python list @code{gdb.pretty_printers} contains an array of
21729 functions or callable objects that have been registered via addition
21730 as a pretty-printer. Printers in this list are called @code{global}
21731 printers, they're available when debugging all inferiors.
21732 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21733 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21736 Each function on these lists is passed a single @code{gdb.Value}
21737 argument and should return a pretty-printer object conforming to the
21738 interface definition above (@pxref{Pretty Printing API}). If a function
21739 cannot create a pretty-printer for the value, it should return
21742 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21743 @code{gdb.Objfile} in the current program space and iteratively calls
21744 each enabled lookup routine in the list for that @code{gdb.Objfile}
21745 until it receives a pretty-printer object.
21746 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21747 searches the pretty-printer list of the current program space,
21748 calling each enabled function until an object is returned.
21749 After these lists have been exhausted, it tries the global
21750 @code{gdb.pretty_printers} list, again calling each enabled function until an
21751 object is returned.
21753 The order in which the objfiles are searched is not specified. For a
21754 given list, functions are always invoked from the head of the list,
21755 and iterated over sequentially until the end of the list, or a printer
21756 object is returned.
21758 For various reasons a pretty-printer may not work.
21759 For example, the underlying data structure may have changed and
21760 the pretty-printer is out of date.
21762 The consequences of a broken pretty-printer are severe enough that
21763 @value{GDBN} provides support for enabling and disabling individual
21764 printers. For example, if @code{print frame-arguments} is on,
21765 a backtrace can become highly illegible if any argument is printed
21766 with a broken printer.
21768 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21769 attribute to the registered function or callable object. If this attribute
21770 is present and its value is @code{False}, the printer is disabled, otherwise
21771 the printer is enabled.
21773 @node Writing a Pretty-Printer
21774 @subsubsection Writing a Pretty-Printer
21775 @cindex writing a pretty-printer
21777 A pretty-printer consists of two parts: a lookup function to detect
21778 if the type is supported, and the printer itself.
21780 Here is an example showing how a @code{std::string} printer might be
21781 written. @xref{Pretty Printing API}, for details on the API this class
21785 class StdStringPrinter(object):
21786 "Print a std::string"
21788 def __init__(self, val):
21791 def to_string(self):
21792 return self.val['_M_dataplus']['_M_p']
21794 def display_hint(self):
21798 And here is an example showing how a lookup function for the printer
21799 example above might be written.
21802 def str_lookup_function(val):
21803 lookup_tag = val.type.tag
21804 if lookup_tag == None:
21806 regex = re.compile("^std::basic_string<char,.*>$")
21807 if regex.match(lookup_tag):
21808 return StdStringPrinter(val)
21812 The example lookup function extracts the value's type, and attempts to
21813 match it to a type that it can pretty-print. If it is a type the
21814 printer can pretty-print, it will return a printer object. If not, it
21815 returns @code{None}.
21817 We recommend that you put your core pretty-printers into a Python
21818 package. If your pretty-printers are for use with a library, we
21819 further recommend embedding a version number into the package name.
21820 This practice will enable @value{GDBN} to load multiple versions of
21821 your pretty-printers at the same time, because they will have
21824 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21825 can be evaluated multiple times without changing its meaning. An
21826 ideal auto-load file will consist solely of @code{import}s of your
21827 printer modules, followed by a call to a register pretty-printers with
21828 the current objfile.
21830 Taken as a whole, this approach will scale nicely to multiple
21831 inferiors, each potentially using a different library version.
21832 Embedding a version number in the Python package name will ensure that
21833 @value{GDBN} is able to load both sets of printers simultaneously.
21834 Then, because the search for pretty-printers is done by objfile, and
21835 because your auto-loaded code took care to register your library's
21836 printers with a specific objfile, @value{GDBN} will find the correct
21837 printers for the specific version of the library used by each
21840 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21841 this code might appear in @code{gdb.libstdcxx.v6}:
21844 def register_printers(objfile):
21845 objfile.pretty_printers.add(str_lookup_function)
21849 And then the corresponding contents of the auto-load file would be:
21852 import gdb.libstdcxx.v6
21853 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21856 The previous example illustrates a basic pretty-printer.
21857 There are a few things that can be improved on.
21858 The printer doesn't have a name, making it hard to identify in a
21859 list of installed printers. The lookup function has a name, but
21860 lookup functions can have arbitrary, even identical, names.
21862 Second, the printer only handles one type, whereas a library typically has
21863 several types. One could install a lookup function for each desired type
21864 in the library, but one could also have a single lookup function recognize
21865 several types. The latter is the conventional way this is handled.
21866 If a pretty-printer can handle multiple data types, then its
21867 @dfn{subprinters} are the printers for the individual data types.
21869 The @code{gdb.printing} module provides a formal way of solving these
21870 problems (@pxref{gdb.printing}).
21871 Here is another example that handles multiple types.
21873 These are the types we are going to pretty-print:
21876 struct foo @{ int a, b; @};
21877 struct bar @{ struct foo x, y; @};
21880 Here are the printers:
21884 """Print a foo object."""
21886 def __init__(self, val):
21889 def to_string(self):
21890 return ("a=<" + str(self.val["a"]) +
21891 "> b=<" + str(self.val["b"]) + ">")
21894 """Print a bar object."""
21896 def __init__(self, val):
21899 def to_string(self):
21900 return ("x=<" + str(self.val["x"]) +
21901 "> y=<" + str(self.val["y"]) + ">")
21904 This example doesn't need a lookup function, that is handled by the
21905 @code{gdb.printing} module. Instead a function is provided to build up
21906 the object that handles the lookup.
21909 import gdb.printing
21911 def build_pretty_printer():
21912 pp = gdb.printing.RegexpCollectionPrettyPrinter(
21914 pp.add_printer('foo', '^foo$', fooPrinter)
21915 pp.add_printer('bar', '^bar$', barPrinter)
21919 And here is the autoload support:
21922 import gdb.printing
21924 gdb.printing.register_pretty_printer(
21925 gdb.current_objfile(),
21926 my_library.build_pretty_printer())
21929 Finally, when this printer is loaded into @value{GDBN}, here is the
21930 corresponding output of @samp{info pretty-printer}:
21933 (gdb) info pretty-printer
21940 @node Inferiors In Python
21941 @subsubsection Inferiors In Python
21942 @cindex inferiors in Python
21944 @findex gdb.Inferior
21945 Programs which are being run under @value{GDBN} are called inferiors
21946 (@pxref{Inferiors and Programs}). Python scripts can access
21947 information about and manipulate inferiors controlled by @value{GDBN}
21948 via objects of the @code{gdb.Inferior} class.
21950 The following inferior-related functions are available in the @code{gdb}
21954 Return a tuple containing all inferior objects.
21957 A @code{gdb.Inferior} object has the following attributes:
21960 @defivar Inferior num
21961 ID of inferior, as assigned by GDB.
21964 @defivar Inferior pid
21965 Process ID of the inferior, as assigned by the underlying operating
21969 @defivar Inferior was_attached
21970 Boolean signaling whether the inferior was created using `attach', or
21971 started by @value{GDBN} itself.
21975 A @code{gdb.Inferior} object has the following methods:
21978 @defmethod Inferior is_valid
21979 Returns @code{True} if the @code{gdb.Inferior} object is valid,
21980 @code{False} if not. A @code{gdb.Inferior} object will become invalid
21981 if the inferior no longer exists within @value{GDBN}. All other
21982 @code{gdb.Inferior} methods will throw an exception if it is invalid
21983 at the time the method is called.
21986 @defmethod Inferior threads
21987 This method returns a tuple holding all the threads which are valid
21988 when it is called. If there are no valid threads, the method will
21989 return an empty tuple.
21992 @findex gdb.read_memory
21993 @defmethod Inferior read_memory address length
21994 Read @var{length} bytes of memory from the inferior, starting at
21995 @var{address}. Returns a buffer object, which behaves much like an array
21996 or a string. It can be modified and given to the @code{gdb.write_memory}
22000 @findex gdb.write_memory
22001 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
22002 Write the contents of @var{buffer} to the inferior, starting at
22003 @var{address}. The @var{buffer} parameter must be a Python object
22004 which supports the buffer protocol, i.e., a string, an array or the
22005 object returned from @code{gdb.read_memory}. If given, @var{length}
22006 determines the number of bytes from @var{buffer} to be written.
22009 @findex gdb.search_memory
22010 @defmethod Inferior search_memory address length pattern
22011 Search a region of the inferior memory starting at @var{address} with
22012 the given @var{length} using the search pattern supplied in
22013 @var{pattern}. The @var{pattern} parameter must be a Python object
22014 which supports the buffer protocol, i.e., a string, an array or the
22015 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22016 containing the address where the pattern was found, or @code{None} if
22017 the pattern could not be found.
22021 @node Events In Python
22022 @subsubsection Events In Python
22023 @cindex inferior events in Python
22025 @value{GDBN} provides a general event facility so that Python code can be
22026 notified of various state changes, particularly changes that occur in
22029 An @dfn{event} is just an object that describes some state change. The
22030 type of the object and its attributes will vary depending on the details
22031 of the change. All the existing events are described below.
22033 In order to be notified of an event, you must register an event handler
22034 with an @dfn{event registry}. An event registry is an object in the
22035 @code{gdb.events} module which dispatches particular events. A registry
22036 provides methods to register and unregister event handlers:
22039 @defmethod EventRegistry connect object
22040 Add the given callable @var{object} to the registry. This object will be
22041 called when an event corresponding to this registry occurs.
22044 @defmethod EventRegistry disconnect object
22045 Remove the given @var{object} from the registry. Once removed, the object
22046 will no longer receive notifications of events.
22050 Here is an example:
22053 def exit_handler (event):
22054 print "event type: exit"
22055 print "exit code: %d" % (event.exit_code)
22057 gdb.events.exited.connect (exit_handler)
22060 In the above example we connect our handler @code{exit_handler} to the
22061 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22062 called when the inferior exits. The argument @dfn{event} in this example is
22063 of type @code{gdb.ExitedEvent}. As you can see in the example the
22064 @code{ExitedEvent} object has an attribute which indicates the exit code of
22067 The following is a listing of the event registries that are available and
22068 details of the events they emit:
22073 Emits @code{gdb.ThreadEvent}.
22075 Some events can be thread specific when @value{GDBN} is running in non-stop
22076 mode. When represented in Python, these events all extend
22077 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22078 events which are emitted by this or other modules might extend this event.
22079 Examples of these events are @code{gdb.BreakpointEvent} and
22080 @code{gdb.ContinueEvent}.
22083 @defivar ThreadEvent inferior_thread
22084 In non-stop mode this attribute will be set to the specific thread which was
22085 involved in the emitted event. Otherwise, it will be set to @code{None}.
22089 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22091 This event indicates that the inferior has been continued after a stop. For
22092 inherited attribute refer to @code{gdb.ThreadEvent} above.
22094 @item events.exited
22095 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22096 @code{events.ExitedEvent} has one attribute:
22098 @defivar ExitedEvent exit_code
22099 An integer representing the exit code which the inferior has returned.
22104 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22106 Indicates that the inferior has stopped. All events emitted by this registry
22107 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22108 will indicate the stopped thread when @value{GDBN} is running in non-stop
22109 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22111 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22113 This event indicates that the inferior or one of its threads has received as
22114 signal. @code{gdb.SignalEvent} has the following attributes:
22117 @defivar SignalEvent stop_signal
22118 A string representing the signal received by the inferior. A list of possible
22119 signal values can be obtained by running the command @code{info signals} in
22120 the @value{GDBN} command prompt.
22124 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22126 @code{gdb.BreakpointEvent} event indicates that a breakpoint has been hit, and
22127 has the following attributes:
22130 @defivar BreakpointEvent breakpoint
22131 A reference to the breakpoint that was hit of type @code{gdb.Breakpoint}.
22132 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22138 @node Threads In Python
22139 @subsubsection Threads In Python
22140 @cindex threads in python
22142 @findex gdb.InferiorThread
22143 Python scripts can access information about, and manipulate inferior threads
22144 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22146 The following thread-related functions are available in the @code{gdb}
22149 @findex gdb.selected_thread
22150 @defun selected_thread
22151 This function returns the thread object for the selected thread. If there
22152 is no selected thread, this will return @code{None}.
22155 A @code{gdb.InferiorThread} object has the following attributes:
22158 @defivar InferiorThread name
22159 The name of the thread. If the user specified a name using
22160 @code{thread name}, then this returns that name. Otherwise, if an
22161 OS-supplied name is available, then it is returned. Otherwise, this
22162 returns @code{None}.
22164 This attribute can be assigned to. The new value must be a string
22165 object, which sets the new name, or @code{None}, which removes any
22166 user-specified thread name.
22169 @defivar InferiorThread num
22170 ID of the thread, as assigned by GDB.
22173 @defivar InferiorThread ptid
22174 ID of the thread, as assigned by the operating system. This attribute is a
22175 tuple containing three integers. The first is the Process ID (PID); the second
22176 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22177 Either the LWPID or TID may be 0, which indicates that the operating system
22178 does not use that identifier.
22182 A @code{gdb.InferiorThread} object has the following methods:
22185 @defmethod InferiorThread is_valid
22186 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22187 @code{False} if not. A @code{gdb.InferiorThread} object will become
22188 invalid if the thread exits, or the inferior that the thread belongs
22189 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22190 exception if it is invalid at the time the method is called.
22193 @defmethod InferiorThread switch
22194 This changes @value{GDBN}'s currently selected thread to the one represented
22198 @defmethod InferiorThread is_stopped
22199 Return a Boolean indicating whether the thread is stopped.
22202 @defmethod InferiorThread is_running
22203 Return a Boolean indicating whether the thread is running.
22206 @defmethod InferiorThread is_exited
22207 Return a Boolean indicating whether the thread is exited.
22211 @node Commands In Python
22212 @subsubsection Commands In Python
22214 @cindex commands in python
22215 @cindex python commands
22216 You can implement new @value{GDBN} CLI commands in Python. A CLI
22217 command is implemented using an instance of the @code{gdb.Command}
22218 class, most commonly using a subclass.
22220 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
22221 The object initializer for @code{Command} registers the new command
22222 with @value{GDBN}. This initializer is normally invoked from the
22223 subclass' own @code{__init__} method.
22225 @var{name} is the name of the command. If @var{name} consists of
22226 multiple words, then the initial words are looked for as prefix
22227 commands. In this case, if one of the prefix commands does not exist,
22228 an exception is raised.
22230 There is no support for multi-line commands.
22232 @var{command_class} should be one of the @samp{COMMAND_} constants
22233 defined below. This argument tells @value{GDBN} how to categorize the
22234 new command in the help system.
22236 @var{completer_class} is an optional argument. If given, it should be
22237 one of the @samp{COMPLETE_} constants defined below. This argument
22238 tells @value{GDBN} how to perform completion for this command. If not
22239 given, @value{GDBN} will attempt to complete using the object's
22240 @code{complete} method (see below); if no such method is found, an
22241 error will occur when completion is attempted.
22243 @var{prefix} is an optional argument. If @code{True}, then the new
22244 command is a prefix command; sub-commands of this command may be
22247 The help text for the new command is taken from the Python
22248 documentation string for the command's class, if there is one. If no
22249 documentation string is provided, the default value ``This command is
22250 not documented.'' is used.
22253 @cindex don't repeat Python command
22254 @defmethod Command dont_repeat
22255 By default, a @value{GDBN} command is repeated when the user enters a
22256 blank line at the command prompt. A command can suppress this
22257 behavior by invoking the @code{dont_repeat} method. This is similar
22258 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22261 @defmethod Command invoke argument from_tty
22262 This method is called by @value{GDBN} when this command is invoked.
22264 @var{argument} is a string. It is the argument to the command, after
22265 leading and trailing whitespace has been stripped.
22267 @var{from_tty} is a boolean argument. When true, this means that the
22268 command was entered by the user at the terminal; when false it means
22269 that the command came from elsewhere.
22271 If this method throws an exception, it is turned into a @value{GDBN}
22272 @code{error} call. Otherwise, the return value is ignored.
22274 @findex gdb.string_to_argv
22275 To break @var{argument} up into an argv-like string use
22276 @code{gdb.string_to_argv}. This function behaves identically to
22277 @value{GDBN}'s internal argument lexer @code{buildargv}.
22278 It is recommended to use this for consistency.
22279 Arguments are separated by spaces and may be quoted.
22283 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22284 ['1', '2 "3', '4 "5', "6 '7"]
22289 @cindex completion of Python commands
22290 @defmethod Command complete text word
22291 This method is called by @value{GDBN} when the user attempts
22292 completion on this command. All forms of completion are handled by
22293 this method, that is, the @key{TAB} and @key{M-?} key bindings
22294 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22297 The arguments @var{text} and @var{word} are both strings. @var{text}
22298 holds the complete command line up to the cursor's location.
22299 @var{word} holds the last word of the command line; this is computed
22300 using a word-breaking heuristic.
22302 The @code{complete} method can return several values:
22305 If the return value is a sequence, the contents of the sequence are
22306 used as the completions. It is up to @code{complete} to ensure that the
22307 contents actually do complete the word. A zero-length sequence is
22308 allowed, it means that there were no completions available. Only
22309 string elements of the sequence are used; other elements in the
22310 sequence are ignored.
22313 If the return value is one of the @samp{COMPLETE_} constants defined
22314 below, then the corresponding @value{GDBN}-internal completion
22315 function is invoked, and its result is used.
22318 All other results are treated as though there were no available
22323 When a new command is registered, it must be declared as a member of
22324 some general class of commands. This is used to classify top-level
22325 commands in the on-line help system; note that prefix commands are not
22326 listed under their own category but rather that of their top-level
22327 command. The available classifications are represented by constants
22328 defined in the @code{gdb} module:
22331 @findex COMMAND_NONE
22332 @findex gdb.COMMAND_NONE
22334 The command does not belong to any particular class. A command in
22335 this category will not be displayed in any of the help categories.
22337 @findex COMMAND_RUNNING
22338 @findex gdb.COMMAND_RUNNING
22339 @item COMMAND_RUNNING
22340 The command is related to running the inferior. For example,
22341 @code{start}, @code{step}, and @code{continue} are in this category.
22342 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22343 commands in this category.
22345 @findex COMMAND_DATA
22346 @findex gdb.COMMAND_DATA
22348 The command is related to data or variables. For example,
22349 @code{call}, @code{find}, and @code{print} are in this category. Type
22350 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22353 @findex COMMAND_STACK
22354 @findex gdb.COMMAND_STACK
22355 @item COMMAND_STACK
22356 The command has to do with manipulation of the stack. For example,
22357 @code{backtrace}, @code{frame}, and @code{return} are in this
22358 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22359 list of commands in this category.
22361 @findex COMMAND_FILES
22362 @findex gdb.COMMAND_FILES
22363 @item COMMAND_FILES
22364 This class is used for file-related commands. For example,
22365 @code{file}, @code{list} and @code{section} are in this category.
22366 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22367 commands in this category.
22369 @findex COMMAND_SUPPORT
22370 @findex gdb.COMMAND_SUPPORT
22371 @item COMMAND_SUPPORT
22372 This should be used for ``support facilities'', generally meaning
22373 things that are useful to the user when interacting with @value{GDBN},
22374 but not related to the state of the inferior. For example,
22375 @code{help}, @code{make}, and @code{shell} are in this category. Type
22376 @kbd{help support} at the @value{GDBN} prompt to see a list of
22377 commands in this category.
22379 @findex COMMAND_STATUS
22380 @findex gdb.COMMAND_STATUS
22381 @item COMMAND_STATUS
22382 The command is an @samp{info}-related command, that is, related to the
22383 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22384 and @code{show} are in this category. Type @kbd{help status} at the
22385 @value{GDBN} prompt to see a list of commands in this category.
22387 @findex COMMAND_BREAKPOINTS
22388 @findex gdb.COMMAND_BREAKPOINTS
22389 @item COMMAND_BREAKPOINTS
22390 The command has to do with breakpoints. For example, @code{break},
22391 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22392 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22395 @findex COMMAND_TRACEPOINTS
22396 @findex gdb.COMMAND_TRACEPOINTS
22397 @item COMMAND_TRACEPOINTS
22398 The command has to do with tracepoints. For example, @code{trace},
22399 @code{actions}, and @code{tfind} are in this category. Type
22400 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22401 commands in this category.
22403 @findex COMMAND_OBSCURE
22404 @findex gdb.COMMAND_OBSCURE
22405 @item COMMAND_OBSCURE
22406 The command is only used in unusual circumstances, or is not of
22407 general interest to users. For example, @code{checkpoint},
22408 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22409 obscure} at the @value{GDBN} prompt to see a list of commands in this
22412 @findex COMMAND_MAINTENANCE
22413 @findex gdb.COMMAND_MAINTENANCE
22414 @item COMMAND_MAINTENANCE
22415 The command is only useful to @value{GDBN} maintainers. The
22416 @code{maintenance} and @code{flushregs} commands are in this category.
22417 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22418 commands in this category.
22421 A new command can use a predefined completion function, either by
22422 specifying it via an argument at initialization, or by returning it
22423 from the @code{complete} method. These predefined completion
22424 constants are all defined in the @code{gdb} module:
22427 @findex COMPLETE_NONE
22428 @findex gdb.COMPLETE_NONE
22429 @item COMPLETE_NONE
22430 This constant means that no completion should be done.
22432 @findex COMPLETE_FILENAME
22433 @findex gdb.COMPLETE_FILENAME
22434 @item COMPLETE_FILENAME
22435 This constant means that filename completion should be performed.
22437 @findex COMPLETE_LOCATION
22438 @findex gdb.COMPLETE_LOCATION
22439 @item COMPLETE_LOCATION
22440 This constant means that location completion should be done.
22441 @xref{Specify Location}.
22443 @findex COMPLETE_COMMAND
22444 @findex gdb.COMPLETE_COMMAND
22445 @item COMPLETE_COMMAND
22446 This constant means that completion should examine @value{GDBN}
22449 @findex COMPLETE_SYMBOL
22450 @findex gdb.COMPLETE_SYMBOL
22451 @item COMPLETE_SYMBOL
22452 This constant means that completion should be done using symbol names
22456 The following code snippet shows how a trivial CLI command can be
22457 implemented in Python:
22460 class HelloWorld (gdb.Command):
22461 """Greet the whole world."""
22463 def __init__ (self):
22464 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22466 def invoke (self, arg, from_tty):
22467 print "Hello, World!"
22472 The last line instantiates the class, and is necessary to trigger the
22473 registration of the command with @value{GDBN}. Depending on how the
22474 Python code is read into @value{GDBN}, you may need to import the
22475 @code{gdb} module explicitly.
22477 @node Parameters In Python
22478 @subsubsection Parameters In Python
22480 @cindex parameters in python
22481 @cindex python parameters
22482 @tindex gdb.Parameter
22484 You can implement new @value{GDBN} parameters using Python. A new
22485 parameter is implemented as an instance of the @code{gdb.Parameter}
22488 Parameters are exposed to the user via the @code{set} and
22489 @code{show} commands. @xref{Help}.
22491 There are many parameters that already exist and can be set in
22492 @value{GDBN}. Two examples are: @code{set follow fork} and
22493 @code{set charset}. Setting these parameters influences certain
22494 behavior in @value{GDBN}. Similarly, you can define parameters that
22495 can be used to influence behavior in custom Python scripts and commands.
22497 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22498 The object initializer for @code{Parameter} registers the new
22499 parameter with @value{GDBN}. This initializer is normally invoked
22500 from the subclass' own @code{__init__} method.
22502 @var{name} is the name of the new parameter. If @var{name} consists
22503 of multiple words, then the initial words are looked for as prefix
22504 parameters. An example of this can be illustrated with the
22505 @code{set print} set of parameters. If @var{name} is
22506 @code{print foo}, then @code{print} will be searched as the prefix
22507 parameter. In this case the parameter can subsequently be accessed in
22508 @value{GDBN} as @code{set print foo}.
22510 If @var{name} consists of multiple words, and no prefix parameter group
22511 can be found, an exception is raised.
22513 @var{command-class} should be one of the @samp{COMMAND_} constants
22514 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22515 categorize the new parameter in the help system.
22517 @var{parameter-class} should be one of the @samp{PARAM_} constants
22518 defined below. This argument tells @value{GDBN} the type of the new
22519 parameter; this information is used for input validation and
22522 If @var{parameter-class} is @code{PARAM_ENUM}, then
22523 @var{enum-sequence} must be a sequence of strings. These strings
22524 represent the possible values for the parameter.
22526 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22527 of a fourth argument will cause an exception to be thrown.
22529 The help text for the new parameter is taken from the Python
22530 documentation string for the parameter's class, if there is one. If
22531 there is no documentation string, a default value is used.
22534 @defivar Parameter set_doc
22535 If this attribute exists, and is a string, then its value is used as
22536 the help text for this parameter's @code{set} command. The value is
22537 examined when @code{Parameter.__init__} is invoked; subsequent changes
22541 @defivar Parameter show_doc
22542 If this attribute exists, and is a string, then its value is used as
22543 the help text for this parameter's @code{show} command. The value is
22544 examined when @code{Parameter.__init__} is invoked; subsequent changes
22548 @defivar Parameter value
22549 The @code{value} attribute holds the underlying value of the
22550 parameter. It can be read and assigned to just as any other
22551 attribute. @value{GDBN} does validation when assignments are made.
22554 There are two methods that should be implemented in any
22555 @code{Parameter} class. These are:
22557 @defop Operation {parameter} get_set_string self
22558 @value{GDBN} will call this method when a @var{parameter}'s value has
22559 been changed via the @code{set} API (for example, @kbd{set foo off}).
22560 The @code{value} attribute has already been populated with the new
22561 value and may be used in output. This method must return a string.
22564 @defop Operation {parameter} get_show_string self svalue
22565 @value{GDBN} will call this method when a @var{parameter}'s
22566 @code{show} API has been invoked (for example, @kbd{show foo}). The
22567 argument @code{svalue} receives the string representation of the
22568 current value. This method must return a string.
22571 When a new parameter is defined, its type must be specified. The
22572 available types are represented by constants defined in the @code{gdb}
22576 @findex PARAM_BOOLEAN
22577 @findex gdb.PARAM_BOOLEAN
22578 @item PARAM_BOOLEAN
22579 The value is a plain boolean. The Python boolean values, @code{True}
22580 and @code{False} are the only valid values.
22582 @findex PARAM_AUTO_BOOLEAN
22583 @findex gdb.PARAM_AUTO_BOOLEAN
22584 @item PARAM_AUTO_BOOLEAN
22585 The value has three possible states: true, false, and @samp{auto}. In
22586 Python, true and false are represented using boolean constants, and
22587 @samp{auto} is represented using @code{None}.
22589 @findex PARAM_UINTEGER
22590 @findex gdb.PARAM_UINTEGER
22591 @item PARAM_UINTEGER
22592 The value is an unsigned integer. The value of 0 should be
22593 interpreted to mean ``unlimited''.
22595 @findex PARAM_INTEGER
22596 @findex gdb.PARAM_INTEGER
22597 @item PARAM_INTEGER
22598 The value is a signed integer. The value of 0 should be interpreted
22599 to mean ``unlimited''.
22601 @findex PARAM_STRING
22602 @findex gdb.PARAM_STRING
22604 The value is a string. When the user modifies the string, any escape
22605 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22606 translated into corresponding characters and encoded into the current
22609 @findex PARAM_STRING_NOESCAPE
22610 @findex gdb.PARAM_STRING_NOESCAPE
22611 @item PARAM_STRING_NOESCAPE
22612 The value is a string. When the user modifies the string, escapes are
22613 passed through untranslated.
22615 @findex PARAM_OPTIONAL_FILENAME
22616 @findex gdb.PARAM_OPTIONAL_FILENAME
22617 @item PARAM_OPTIONAL_FILENAME
22618 The value is a either a filename (a string), or @code{None}.
22620 @findex PARAM_FILENAME
22621 @findex gdb.PARAM_FILENAME
22622 @item PARAM_FILENAME
22623 The value is a filename. This is just like
22624 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22626 @findex PARAM_ZINTEGER
22627 @findex gdb.PARAM_ZINTEGER
22628 @item PARAM_ZINTEGER
22629 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22630 is interpreted as itself.
22633 @findex gdb.PARAM_ENUM
22635 The value is a string, which must be one of a collection string
22636 constants provided when the parameter is created.
22639 @node Functions In Python
22640 @subsubsection Writing new convenience functions
22642 @cindex writing convenience functions
22643 @cindex convenience functions in python
22644 @cindex python convenience functions
22645 @tindex gdb.Function
22647 You can implement new convenience functions (@pxref{Convenience Vars})
22648 in Python. A convenience function is an instance of a subclass of the
22649 class @code{gdb.Function}.
22651 @defmethod Function __init__ name
22652 The initializer for @code{Function} registers the new function with
22653 @value{GDBN}. The argument @var{name} is the name of the function,
22654 a string. The function will be visible to the user as a convenience
22655 variable of type @code{internal function}, whose name is the same as
22656 the given @var{name}.
22658 The documentation for the new function is taken from the documentation
22659 string for the new class.
22662 @defmethod Function invoke @var{*args}
22663 When a convenience function is evaluated, its arguments are converted
22664 to instances of @code{gdb.Value}, and then the function's
22665 @code{invoke} method is called. Note that @value{GDBN} does not
22666 predetermine the arity of convenience functions. Instead, all
22667 available arguments are passed to @code{invoke}, following the
22668 standard Python calling convention. In particular, a convenience
22669 function can have default values for parameters without ill effect.
22671 The return value of this method is used as its value in the enclosing
22672 expression. If an ordinary Python value is returned, it is converted
22673 to a @code{gdb.Value} following the usual rules.
22676 The following code snippet shows how a trivial convenience function can
22677 be implemented in Python:
22680 class Greet (gdb.Function):
22681 """Return string to greet someone.
22682 Takes a name as argument."""
22684 def __init__ (self):
22685 super (Greet, self).__init__ ("greet")
22687 def invoke (self, name):
22688 return "Hello, %s!" % name.string ()
22693 The last line instantiates the class, and is necessary to trigger the
22694 registration of the function with @value{GDBN}. Depending on how the
22695 Python code is read into @value{GDBN}, you may need to import the
22696 @code{gdb} module explicitly.
22698 @node Progspaces In Python
22699 @subsubsection Program Spaces In Python
22701 @cindex progspaces in python
22702 @tindex gdb.Progspace
22704 A program space, or @dfn{progspace}, represents a symbolic view
22705 of an address space.
22706 It consists of all of the objfiles of the program.
22707 @xref{Objfiles In Python}.
22708 @xref{Inferiors and Programs, program spaces}, for more details
22709 about program spaces.
22711 The following progspace-related functions are available in the
22714 @findex gdb.current_progspace
22715 @defun current_progspace
22716 This function returns the program space of the currently selected inferior.
22717 @xref{Inferiors and Programs}.
22720 @findex gdb.progspaces
22722 Return a sequence of all the progspaces currently known to @value{GDBN}.
22725 Each progspace is represented by an instance of the @code{gdb.Progspace}
22728 @defivar Progspace filename
22729 The file name of the progspace as a string.
22732 @defivar Progspace pretty_printers
22733 The @code{pretty_printers} attribute is a list of functions. It is
22734 used to look up pretty-printers. A @code{Value} is passed to each
22735 function in order; if the function returns @code{None}, then the
22736 search continues. Otherwise, the return value should be an object
22737 which is used to format the value. @xref{Pretty Printing API}, for more
22741 @node Objfiles In Python
22742 @subsubsection Objfiles In Python
22744 @cindex objfiles in python
22745 @tindex gdb.Objfile
22747 @value{GDBN} loads symbols for an inferior from various
22748 symbol-containing files (@pxref{Files}). These include the primary
22749 executable file, any shared libraries used by the inferior, and any
22750 separate debug info files (@pxref{Separate Debug Files}).
22751 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22753 The following objfile-related functions are available in the
22756 @findex gdb.current_objfile
22757 @defun current_objfile
22758 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22759 sets the ``current objfile'' to the corresponding objfile. This
22760 function returns the current objfile. If there is no current objfile,
22761 this function returns @code{None}.
22764 @findex gdb.objfiles
22766 Return a sequence of all the objfiles current known to @value{GDBN}.
22767 @xref{Objfiles In Python}.
22770 Each objfile is represented by an instance of the @code{gdb.Objfile}
22773 @defivar Objfile filename
22774 The file name of the objfile as a string.
22777 @defivar Objfile pretty_printers
22778 The @code{pretty_printers} attribute is a list of functions. It is
22779 used to look up pretty-printers. A @code{Value} is passed to each
22780 function in order; if the function returns @code{None}, then the
22781 search continues. Otherwise, the return value should be an object
22782 which is used to format the value. @xref{Pretty Printing API}, for more
22786 A @code{gdb.Objfile} object has the following methods:
22788 @defmethod Objfile is_valid
22789 Returns @code{True} if the @code{gdb.Objfile} object is valid,
22790 @code{False} if not. A @code{gdb.Objfile} object can become invalid
22791 if the object file it refers to is not loaded in @value{GDBN} any
22792 longer. All other @code{gdb.Objfile} methods will throw an exception
22793 if it is invalid at the time the method is called.
22796 @node Frames In Python
22797 @subsubsection Accessing inferior stack frames from Python.
22799 @cindex frames in python
22800 When the debugged program stops, @value{GDBN} is able to analyze its call
22801 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22802 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22803 while its corresponding frame exists in the inferior's stack. If you try
22804 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
22805 exception (@pxref{Exception Handling}).
22807 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22811 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22815 The following frame-related functions are available in the @code{gdb} module:
22817 @findex gdb.selected_frame
22818 @defun selected_frame
22819 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22822 @findex gdb.newest_frame
22823 @defun newest_frame
22824 Return the newest frame object for the selected thread.
22827 @defun frame_stop_reason_string reason
22828 Return a string explaining the reason why @value{GDBN} stopped unwinding
22829 frames, as expressed by the given @var{reason} code (an integer, see the
22830 @code{unwind_stop_reason} method further down in this section).
22833 A @code{gdb.Frame} object has the following methods:
22836 @defmethod Frame is_valid
22837 Returns true if the @code{gdb.Frame} object is valid, false if not.
22838 A frame object can become invalid if the frame it refers to doesn't
22839 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22840 an exception if it is invalid at the time the method is called.
22843 @defmethod Frame name
22844 Returns the function name of the frame, or @code{None} if it can't be
22848 @defmethod Frame type
22849 Returns the type of the frame. The value can be one of:
22851 @item gdb.NORMAL_FRAME
22852 An ordinary stack frame.
22854 @item gdb.DUMMY_FRAME
22855 A fake stack frame that was created by @value{GDBN} when performing an
22856 inferior function call.
22858 @item gdb.INLINE_FRAME
22859 A frame representing an inlined function. The function was inlined
22860 into a @code{gdb.NORMAL_FRAME} that is older than this one.
22862 @item gdb.SIGTRAMP_FRAME
22863 A signal trampoline frame. This is the frame created by the OS when
22864 it calls into a signal handler.
22866 @item gdb.ARCH_FRAME
22867 A fake stack frame representing a cross-architecture call.
22869 @item gdb.SENTINEL_FRAME
22870 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
22875 @defmethod Frame unwind_stop_reason
22876 Return an integer representing the reason why it's not possible to find
22877 more frames toward the outermost frame. Use
22878 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22879 function to a string.
22882 @defmethod Frame pc
22883 Returns the frame's resume address.
22886 @defmethod Frame block
22887 Return the frame's code block. @xref{Blocks In Python}.
22890 @defmethod Frame function
22891 Return the symbol for the function corresponding to this frame.
22892 @xref{Symbols In Python}.
22895 @defmethod Frame older
22896 Return the frame that called this frame.
22899 @defmethod Frame newer
22900 Return the frame called by this frame.
22903 @defmethod Frame find_sal
22904 Return the frame's symtab and line object.
22905 @xref{Symbol Tables In Python}.
22908 @defmethod Frame read_var variable @r{[}block@r{]}
22909 Return the value of @var{variable} in this frame. If the optional
22910 argument @var{block} is provided, search for the variable from that
22911 block; otherwise start at the frame's current block (which is
22912 determined by the frame's current program counter). @var{variable}
22913 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22914 @code{gdb.Block} object.
22917 @defmethod Frame select
22918 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22923 @node Blocks In Python
22924 @subsubsection Accessing frame blocks from Python.
22926 @cindex blocks in python
22929 Within each frame, @value{GDBN} maintains information on each block
22930 stored in that frame. These blocks are organized hierarchically, and
22931 are represented individually in Python as a @code{gdb.Block}.
22932 Please see @ref{Frames In Python}, for a more in-depth discussion on
22933 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22934 detailed technical information on @value{GDBN}'s book-keeping of the
22937 The following block-related functions are available in the @code{gdb}
22940 @findex gdb.block_for_pc
22941 @defun block_for_pc pc
22942 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22943 block cannot be found for the @var{pc} value specified, the function
22944 will return @code{None}.
22947 A @code{gdb.Block} object has the following methods:
22950 @defmethod Block is_valid
22951 Returns @code{True} if the @code{gdb.Block} object is valid,
22952 @code{False} if not. A block object can become invalid if the block it
22953 refers to doesn't exist anymore in the inferior. All other
22954 @code{gdb.Block} methods will throw an exception if it is invalid at
22955 the time the method is called. This method is also made available to
22956 the Python iterator object that @code{gdb.Block} provides in an iteration
22957 context and via the Python @code{iter} built-in function.
22961 A @code{gdb.Block} object has the following attributes:
22964 @defivar Block start
22965 The start address of the block. This attribute is not writable.
22969 The end address of the block. This attribute is not writable.
22972 @defivar Block function
22973 The name of the block represented as a @code{gdb.Symbol}. If the
22974 block is not named, then this attribute holds @code{None}. This
22975 attribute is not writable.
22978 @defivar Block superblock
22979 The block containing this block. If this parent block does not exist,
22980 this attribute holds @code{None}. This attribute is not writable.
22984 @node Symbols In Python
22985 @subsubsection Python representation of Symbols.
22987 @cindex symbols in python
22990 @value{GDBN} represents every variable, function and type as an
22991 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22992 Similarly, Python represents these symbols in @value{GDBN} with the
22993 @code{gdb.Symbol} object.
22995 The following symbol-related functions are available in the @code{gdb}
22998 @findex gdb.lookup_symbol
22999 @defun lookup_symbol name @r{[}block@r{]} @r{[}domain@r{]}
23000 This function searches for a symbol by name. The search scope can be
23001 restricted to the parameters defined in the optional domain and block
23004 @var{name} is the name of the symbol. It must be a string. The
23005 optional @var{block} argument restricts the search to symbols visible
23006 in that @var{block}. The @var{block} argument must be a
23007 @code{gdb.Block} object. If omitted, the block for the current frame
23008 is used. The optional @var{domain} argument restricts
23009 the search to the domain type. The @var{domain} argument must be a
23010 domain constant defined in the @code{gdb} module and described later
23013 The result is a tuple of two elements.
23014 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23016 If the symbol is found, the second element is @code{True} if the symbol
23017 is a field of a method's object (e.g., @code{this} in C@t{++}),
23018 otherwise it is @code{False}.
23019 If the symbol is not found, the second element is @code{False}.
23022 @findex gdb.lookup_global_symbol
23023 @defun lookup_global_symbol name @r{[}domain@r{]}
23024 This function searches for a global symbol by name.
23025 The search scope can be restricted to by the domain argument.
23027 @var{name} is the name of the symbol. It must be a string.
23028 The optional @var{domain} argument restricts the search to the domain type.
23029 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23030 module and described later in this chapter.
23032 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23036 A @code{gdb.Symbol} object has the following attributes:
23039 @defivar Symbol symtab
23040 The symbol table in which the symbol appears. This attribute is
23041 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23042 Python}. This attribute is not writable.
23045 @defivar Symbol name
23046 The name of the symbol as a string. This attribute is not writable.
23049 @defivar Symbol linkage_name
23050 The name of the symbol, as used by the linker (i.e., may be mangled).
23051 This attribute is not writable.
23054 @defivar Symbol print_name
23055 The name of the symbol in a form suitable for output. This is either
23056 @code{name} or @code{linkage_name}, depending on whether the user
23057 asked @value{GDBN} to display demangled or mangled names.
23060 @defivar Symbol addr_class
23061 The address class of the symbol. This classifies how to find the value
23062 of a symbol. Each address class is a constant defined in the
23063 @code{gdb} module and described later in this chapter.
23066 @defivar Symbol is_argument
23067 @code{True} if the symbol is an argument of a function.
23070 @defivar Symbol is_constant
23071 @code{True} if the symbol is a constant.
23074 @defivar Symbol is_function
23075 @code{True} if the symbol is a function or a method.
23078 @defivar Symbol is_variable
23079 @code{True} if the symbol is a variable.
23083 A @code{gdb.Symbol} object has the following methods:
23086 @defmethod Symbol is_valid
23087 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23088 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23089 the symbol it refers to does not exist in @value{GDBN} any longer.
23090 All other @code{gdb.Symbol} methods will throw an exception if it is
23091 invalid at the time the method is called.
23095 The available domain categories in @code{gdb.Symbol} are represented
23096 as constants in the @code{gdb} module:
23099 @findex SYMBOL_UNDEF_DOMAIN
23100 @findex gdb.SYMBOL_UNDEF_DOMAIN
23101 @item SYMBOL_UNDEF_DOMAIN
23102 This is used when a domain has not been discovered or none of the
23103 following domains apply. This usually indicates an error either
23104 in the symbol information or in @value{GDBN}'s handling of symbols.
23105 @findex SYMBOL_VAR_DOMAIN
23106 @findex gdb.SYMBOL_VAR_DOMAIN
23107 @item SYMBOL_VAR_DOMAIN
23108 This domain contains variables, function names, typedef names and enum
23110 @findex SYMBOL_STRUCT_DOMAIN
23111 @findex gdb.SYMBOL_STRUCT_DOMAIN
23112 @item SYMBOL_STRUCT_DOMAIN
23113 This domain holds struct, union and enum type names.
23114 @findex SYMBOL_LABEL_DOMAIN
23115 @findex gdb.SYMBOL_LABEL_DOMAIN
23116 @item SYMBOL_LABEL_DOMAIN
23117 This domain contains names of labels (for gotos).
23118 @findex SYMBOL_VARIABLES_DOMAIN
23119 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23120 @item SYMBOL_VARIABLES_DOMAIN
23121 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23122 contains everything minus functions and types.
23123 @findex SYMBOL_FUNCTIONS_DOMAIN
23124 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23125 @item SYMBOL_FUNCTION_DOMAIN
23126 This domain contains all functions.
23127 @findex SYMBOL_TYPES_DOMAIN
23128 @findex gdb.SYMBOL_TYPES_DOMAIN
23129 @item SYMBOL_TYPES_DOMAIN
23130 This domain contains all types.
23133 The available address class categories in @code{gdb.Symbol} are represented
23134 as constants in the @code{gdb} module:
23137 @findex SYMBOL_LOC_UNDEF
23138 @findex gdb.SYMBOL_LOC_UNDEF
23139 @item SYMBOL_LOC_UNDEF
23140 If this is returned by address class, it indicates an error either in
23141 the symbol information or in @value{GDBN}'s handling of symbols.
23142 @findex SYMBOL_LOC_CONST
23143 @findex gdb.SYMBOL_LOC_CONST
23144 @item SYMBOL_LOC_CONST
23145 Value is constant int.
23146 @findex SYMBOL_LOC_STATIC
23147 @findex gdb.SYMBOL_LOC_STATIC
23148 @item SYMBOL_LOC_STATIC
23149 Value is at a fixed address.
23150 @findex SYMBOL_LOC_REGISTER
23151 @findex gdb.SYMBOL_LOC_REGISTER
23152 @item SYMBOL_LOC_REGISTER
23153 Value is in a register.
23154 @findex SYMBOL_LOC_ARG
23155 @findex gdb.SYMBOL_LOC_ARG
23156 @item SYMBOL_LOC_ARG
23157 Value is an argument. This value is at the offset stored within the
23158 symbol inside the frame's argument list.
23159 @findex SYMBOL_LOC_REF_ARG
23160 @findex gdb.SYMBOL_LOC_REF_ARG
23161 @item SYMBOL_LOC_REF_ARG
23162 Value address is stored in the frame's argument list. Just like
23163 @code{LOC_ARG} except that the value's address is stored at the
23164 offset, not the value itself.
23165 @findex SYMBOL_LOC_REGPARM_ADDR
23166 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23167 @item SYMBOL_LOC_REGPARM_ADDR
23168 Value is a specified register. Just like @code{LOC_REGISTER} except
23169 the register holds the address of the argument instead of the argument
23171 @findex SYMBOL_LOC_LOCAL
23172 @findex gdb.SYMBOL_LOC_LOCAL
23173 @item SYMBOL_LOC_LOCAL
23174 Value is a local variable.
23175 @findex SYMBOL_LOC_TYPEDEF
23176 @findex gdb.SYMBOL_LOC_TYPEDEF
23177 @item SYMBOL_LOC_TYPEDEF
23178 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23180 @findex SYMBOL_LOC_BLOCK
23181 @findex gdb.SYMBOL_LOC_BLOCK
23182 @item SYMBOL_LOC_BLOCK
23184 @findex SYMBOL_LOC_CONST_BYTES
23185 @findex gdb.SYMBOL_LOC_CONST_BYTES
23186 @item SYMBOL_LOC_CONST_BYTES
23187 Value is a byte-sequence.
23188 @findex SYMBOL_LOC_UNRESOLVED
23189 @findex gdb.SYMBOL_LOC_UNRESOLVED
23190 @item SYMBOL_LOC_UNRESOLVED
23191 Value is at a fixed address, but the address of the variable has to be
23192 determined from the minimal symbol table whenever the variable is
23194 @findex SYMBOL_LOC_OPTIMIZED_OUT
23195 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23196 @item SYMBOL_LOC_OPTIMIZED_OUT
23197 The value does not actually exist in the program.
23198 @findex SYMBOL_LOC_COMPUTED
23199 @findex gdb.SYMBOL_LOC_COMPUTED
23200 @item SYMBOL_LOC_COMPUTED
23201 The value's address is a computed location.
23204 @node Symbol Tables In Python
23205 @subsubsection Symbol table representation in Python.
23207 @cindex symbol tables in python
23209 @tindex gdb.Symtab_and_line
23211 Access to symbol table data maintained by @value{GDBN} on the inferior
23212 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23213 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23214 from the @code{find_sal} method in @code{gdb.Frame} object.
23215 @xref{Frames In Python}.
23217 For more information on @value{GDBN}'s symbol table management, see
23218 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23220 A @code{gdb.Symtab_and_line} object has the following attributes:
23223 @defivar Symtab_and_line symtab
23224 The symbol table object (@code{gdb.Symtab}) for this frame.
23225 This attribute is not writable.
23228 @defivar Symtab_and_line pc
23229 Indicates the current program counter address. This attribute is not
23233 @defivar Symtab_and_line line
23234 Indicates the current line number for this object. This
23235 attribute is not writable.
23239 A @code{gdb.Symtab_and_line} object has the following methods:
23242 @defmethod Symtab_and_line is_valid
23243 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23244 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23245 invalid if the Symbol table and line object it refers to does not
23246 exist in @value{GDBN} any longer. All other
23247 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23248 invalid at the time the method is called.
23252 A @code{gdb.Symtab} object has the following attributes:
23255 @defivar Symtab filename
23256 The symbol table's source filename. This attribute is not writable.
23259 @defivar Symtab objfile
23260 The symbol table's backing object file. @xref{Objfiles In Python}.
23261 This attribute is not writable.
23265 A @code{gdb.Symtab} object has the following methods:
23268 @defmethod Symtab is_valid
23269 Returns @code{True} if the @code{gdb.Symtab} object is valid,
23270 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
23271 the symbol table it refers to does not exist in @value{GDBN} any
23272 longer. All other @code{gdb.Symtab} methods will throw an exception
23273 if it is invalid at the time the method is called.
23276 @defmethod Symtab fullname
23277 Return the symbol table's source absolute file name.
23281 @node Breakpoints In Python
23282 @subsubsection Manipulating breakpoints using Python
23284 @cindex breakpoints in python
23285 @tindex gdb.Breakpoint
23287 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23290 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]} @r{[}internal@r{]}
23291 Create a new breakpoint. @var{spec} is a string naming the
23292 location of the breakpoint, or an expression that defines a
23293 watchpoint. The contents can be any location recognized by the
23294 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23295 command. The optional @var{type} denotes the breakpoint to create
23296 from the types defined later in this chapter. This argument can be
23297 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
23298 defaults to @code{BP_BREAKPOINT}. The optional @var{internal} argument
23299 allows the breakpoint to become invisible to the user. The breakpoint
23300 will neither be reported when created, nor will it be listed in the
23301 output from @code{info breakpoints} (but will be listed with the
23302 @code{maint info breakpoints} command). The optional @var{wp_class}
23303 argument defines the class of watchpoint to create, if @var{type} is
23304 @code{BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23305 assumed to be a @var{WP_WRITE} class.
23308 @defop Operation {gdb.Breakpoint} stop (self)
23309 The @code{gdb.Breakpoint} class can be sub-classed and, in
23310 particular, you may choose to implement the @code{stop} method.
23311 If this method is defined as a sub-class of @code{gdb.Breakpoint},
23312 it will be called when the inferior reaches any location of a
23313 breakpoint which instantiates that sub-class. If the method returns
23314 @code{True}, the inferior will be stopped at the location of the
23315 breakpoint, otherwise the inferior will continue.
23317 If there are multiple breakpoints at the same location with a
23318 @code{stop} method, each one will be called regardless of the
23319 return status of the previous. This ensures that all @code{stop}
23320 methods have a chance to execute at that location. In this scenario
23321 if one of the methods returns @code{True} but the others return
23322 @code{False}, the inferior will still be stopped.
23324 Example @code{stop} implementation:
23327 class MyBreakpoint (gdb.Breakpoint):
23329 inf_val = gdb.parse_and_eval("foo")
23336 The available watchpoint types represented by constants are defined in the
23341 @findex gdb.WP_READ
23343 Read only watchpoint.
23346 @findex gdb.WP_WRITE
23348 Write only watchpoint.
23351 @findex gdb.WP_ACCESS
23353 Read/Write watchpoint.
23356 @defmethod Breakpoint is_valid
23357 Return @code{True} if this @code{Breakpoint} object is valid,
23358 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23359 if the user deletes the breakpoint. In this case, the object still
23360 exists, but the underlying breakpoint does not. In the cases of
23361 watchpoint scope, the watchpoint remains valid even if execution of the
23362 inferior leaves the scope of that watchpoint.
23365 @defmethod Breakpoint delete
23366 Permanently deletes the @value{GDBN} breakpoint. This also
23367 invalidates the Python @code{Breakpoint} object. Any further access
23368 to this object's attributes or methods will raise an error.
23371 @defivar Breakpoint enabled
23372 This attribute is @code{True} if the breakpoint is enabled, and
23373 @code{False} otherwise. This attribute is writable.
23376 @defivar Breakpoint silent
23377 This attribute is @code{True} if the breakpoint is silent, and
23378 @code{False} otherwise. This attribute is writable.
23380 Note that a breakpoint can also be silent if it has commands and the
23381 first command is @code{silent}. This is not reported by the
23382 @code{silent} attribute.
23385 @defivar Breakpoint thread
23386 If the breakpoint is thread-specific, this attribute holds the thread
23387 id. If the breakpoint is not thread-specific, this attribute is
23388 @code{None}. This attribute is writable.
23391 @defivar Breakpoint task
23392 If the breakpoint is Ada task-specific, this attribute holds the Ada task
23393 id. If the breakpoint is not task-specific (or the underlying
23394 language is not Ada), this attribute is @code{None}. This attribute
23398 @defivar Breakpoint ignore_count
23399 This attribute holds the ignore count for the breakpoint, an integer.
23400 This attribute is writable.
23403 @defivar Breakpoint number
23404 This attribute holds the breakpoint's number --- the identifier used by
23405 the user to manipulate the breakpoint. This attribute is not writable.
23408 @defivar Breakpoint type
23409 This attribute holds the breakpoint's type --- the identifier used to
23410 determine the actual breakpoint type or use-case. This attribute is not
23414 @defivar Breakpoint visible
23415 This attribute tells whether the breakpoint is visible to the user
23416 when set, or when the @samp{info breakpoints} command is run. This
23417 attribute is not writable.
23420 The available types are represented by constants defined in the @code{gdb}
23424 @findex BP_BREAKPOINT
23425 @findex gdb.BP_BREAKPOINT
23426 @item BP_BREAKPOINT
23427 Normal code breakpoint.
23429 @findex BP_WATCHPOINT
23430 @findex gdb.BP_WATCHPOINT
23431 @item BP_WATCHPOINT
23432 Watchpoint breakpoint.
23434 @findex BP_HARDWARE_WATCHPOINT
23435 @findex gdb.BP_HARDWARE_WATCHPOINT
23436 @item BP_HARDWARE_WATCHPOINT
23437 Hardware assisted watchpoint.
23439 @findex BP_READ_WATCHPOINT
23440 @findex gdb.BP_READ_WATCHPOINT
23441 @item BP_READ_WATCHPOINT
23442 Hardware assisted read watchpoint.
23444 @findex BP_ACCESS_WATCHPOINT
23445 @findex gdb.BP_ACCESS_WATCHPOINT
23446 @item BP_ACCESS_WATCHPOINT
23447 Hardware assisted access watchpoint.
23450 @defivar Breakpoint hit_count
23451 This attribute holds the hit count for the breakpoint, an integer.
23452 This attribute is writable, but currently it can only be set to zero.
23455 @defivar Breakpoint location
23456 This attribute holds the location of the breakpoint, as specified by
23457 the user. It is a string. If the breakpoint does not have a location
23458 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23459 attribute is not writable.
23462 @defivar Breakpoint expression
23463 This attribute holds a breakpoint expression, as specified by
23464 the user. It is a string. If the breakpoint does not have an
23465 expression (the breakpoint is not a watchpoint) the attribute's value
23466 is @code{None}. This attribute is not writable.
23469 @defivar Breakpoint condition
23470 This attribute holds the condition of the breakpoint, as specified by
23471 the user. It is a string. If there is no condition, this attribute's
23472 value is @code{None}. This attribute is writable.
23475 @defivar Breakpoint commands
23476 This attribute holds the commands attached to the breakpoint. If
23477 there are commands, this attribute's value is a string holding all the
23478 commands, separated by newlines. If there are no commands, this
23479 attribute is @code{None}. This attribute is not writable.
23482 @node Lazy Strings In Python
23483 @subsubsection Python representation of lazy strings.
23485 @cindex lazy strings in python
23486 @tindex gdb.LazyString
23488 A @dfn{lazy string} is a string whose contents is not retrieved or
23489 encoded until it is needed.
23491 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23492 @code{address} that points to a region of memory, an @code{encoding}
23493 that will be used to encode that region of memory, and a @code{length}
23494 to delimit the region of memory that represents the string. The
23495 difference between a @code{gdb.LazyString} and a string wrapped within
23496 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23497 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23498 retrieved and encoded during printing, while a @code{gdb.Value}
23499 wrapping a string is immediately retrieved and encoded on creation.
23501 A @code{gdb.LazyString} object has the following functions:
23503 @defmethod LazyString value
23504 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23505 will point to the string in memory, but will lose all the delayed
23506 retrieval, encoding and handling that @value{GDBN} applies to a
23507 @code{gdb.LazyString}.
23510 @defivar LazyString address
23511 This attribute holds the address of the string. This attribute is not
23515 @defivar LazyString length
23516 This attribute holds the length of the string in characters. If the
23517 length is -1, then the string will be fetched and encoded up to the
23518 first null of appropriate width. This attribute is not writable.
23521 @defivar LazyString encoding
23522 This attribute holds the encoding that will be applied to the string
23523 when the string is printed by @value{GDBN}. If the encoding is not
23524 set, or contains an empty string, then @value{GDBN} will select the
23525 most appropriate encoding when the string is printed. This attribute
23529 @defivar LazyString type
23530 This attribute holds the type that is represented by the lazy string's
23531 type. For a lazy string this will always be a pointer type. To
23532 resolve this to the lazy string's character type, use the type's
23533 @code{target} method. @xref{Types In Python}. This attribute is not
23538 @subsection Auto-loading
23539 @cindex auto-loading, Python
23541 When a new object file is read (for example, due to the @code{file}
23542 command, or because the inferior has loaded a shared library),
23543 @value{GDBN} will look for Python support scripts in several ways:
23544 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23547 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23548 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23549 * Which flavor to choose?::
23552 The auto-loading feature is useful for supplying application-specific
23553 debugging commands and scripts.
23555 Auto-loading can be enabled or disabled.
23558 @kindex set auto-load-scripts
23559 @item set auto-load-scripts [yes|no]
23560 Enable or disable the auto-loading of Python scripts.
23562 @kindex show auto-load-scripts
23563 @item show auto-load-scripts
23564 Show whether auto-loading of Python scripts is enabled or disabled.
23567 When reading an auto-loaded file, @value{GDBN} sets the
23568 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23569 function (@pxref{Objfiles In Python}). This can be useful for
23570 registering objfile-specific pretty-printers.
23572 @node objfile-gdb.py file
23573 @subsubsection The @file{@var{objfile}-gdb.py} file
23574 @cindex @file{@var{objfile}-gdb.py}
23576 When a new object file is read, @value{GDBN} looks for
23577 a file named @file{@var{objfile}-gdb.py},
23578 where @var{objfile} is the object file's real name, formed by ensuring
23579 that the file name is absolute, following all symlinks, and resolving
23580 @code{.} and @code{..} components. If this file exists and is
23581 readable, @value{GDBN} will evaluate it as a Python script.
23583 If this file does not exist, and if the parameter
23584 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23585 then @value{GDBN} will look for @var{real-name} in all of the
23586 directories mentioned in the value of @code{debug-file-directory}.
23588 Finally, if this file does not exist, then @value{GDBN} will look for
23589 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23590 @var{data-directory} is @value{GDBN}'s data directory (available via
23591 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23592 is the object file's real name, as described above.
23594 @value{GDBN} does not track which files it has already auto-loaded this way.
23595 @value{GDBN} will load the associated script every time the corresponding
23596 @var{objfile} is opened.
23597 So your @file{-gdb.py} file should be careful to avoid errors if it
23598 is evaluated more than once.
23600 @node .debug_gdb_scripts section
23601 @subsubsection The @code{.debug_gdb_scripts} section
23602 @cindex @code{.debug_gdb_scripts} section
23604 For systems using file formats like ELF and COFF,
23605 when @value{GDBN} loads a new object file
23606 it will look for a special section named @samp{.debug_gdb_scripts}.
23607 If this section exists, its contents is a list of names of scripts to load.
23609 @value{GDBN} will look for each specified script file first in the
23610 current directory and then along the source search path
23611 (@pxref{Source Path, ,Specifying Source Directories}),
23612 except that @file{$cdir} is not searched, since the compilation
23613 directory is not relevant to scripts.
23615 Entries can be placed in section @code{.debug_gdb_scripts} with,
23616 for example, this GCC macro:
23619 /* Note: The "MS" section flags are to remove duplicates. */
23620 #define DEFINE_GDB_SCRIPT(script_name) \
23622 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23624 .asciz \"" script_name "\"\n\
23630 Then one can reference the macro in a header or source file like this:
23633 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23636 The script name may include directories if desired.
23638 If the macro is put in a header, any application or library
23639 using this header will get a reference to the specified script.
23641 @node Which flavor to choose?
23642 @subsubsection Which flavor to choose?
23644 Given the multiple ways of auto-loading Python scripts, it might not always
23645 be clear which one to choose. This section provides some guidance.
23647 Benefits of the @file{-gdb.py} way:
23651 Can be used with file formats that don't support multiple sections.
23654 Ease of finding scripts for public libraries.
23656 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23657 in the source search path.
23658 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23659 isn't a source directory in which to find the script.
23662 Doesn't require source code additions.
23665 Benefits of the @code{.debug_gdb_scripts} way:
23669 Works with static linking.
23671 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23672 trigger their loading. When an application is statically linked the only
23673 objfile available is the executable, and it is cumbersome to attach all the
23674 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23677 Works with classes that are entirely inlined.
23679 Some classes can be entirely inlined, and thus there may not be an associated
23680 shared library to attach a @file{-gdb.py} script to.
23683 Scripts needn't be copied out of the source tree.
23685 In some circumstances, apps can be built out of large collections of internal
23686 libraries, and the build infrastructure necessary to install the
23687 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23688 cumbersome. It may be easier to specify the scripts in the
23689 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23690 top of the source tree to the source search path.
23693 @node Python modules
23694 @subsection Python modules
23695 @cindex python modules
23697 @value{GDBN} comes with a module to assist writing Python code.
23700 * gdb.printing:: Building and registering pretty-printers.
23701 * gdb.types:: Utilities for working with types.
23705 @subsubsection gdb.printing
23706 @cindex gdb.printing
23708 This module provides a collection of utilities for working with
23712 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23713 This class specifies the API that makes @samp{info pretty-printer},
23714 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23715 Pretty-printers should generally inherit from this class.
23717 @item SubPrettyPrinter (@var{name})
23718 For printers that handle multiple types, this class specifies the
23719 corresponding API for the subprinters.
23721 @item RegexpCollectionPrettyPrinter (@var{name})
23722 Utility class for handling multiple printers, all recognized via
23723 regular expressions.
23724 @xref{Writing a Pretty-Printer}, for an example.
23726 @item register_pretty_printer (@var{obj}, @var{printer})
23727 Register @var{printer} with the pretty-printer list of @var{obj}.
23731 @subsubsection gdb.types
23734 This module provides a collection of utilities for working with
23735 @code{gdb.Types} objects.
23738 @item get_basic_type (@var{type})
23739 Return @var{type} with const and volatile qualifiers stripped,
23740 and with typedefs and C@t{++} references converted to the underlying type.
23745 typedef const int const_int;
23747 const_int& foo_ref (foo);
23748 int main () @{ return 0; @}
23755 (gdb) python import gdb.types
23756 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23757 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23761 @item has_field (@var{type}, @var{field})
23762 Return @code{True} if @var{type}, assumed to be a type with fields
23763 (e.g., a structure or union), has field @var{field}.
23765 @item make_enum_dict (@var{enum_type})
23766 Return a Python @code{dictionary} type produced from @var{enum_type}.
23770 @chapter Command Interpreters
23771 @cindex command interpreters
23773 @value{GDBN} supports multiple command interpreters, and some command
23774 infrastructure to allow users or user interface writers to switch
23775 between interpreters or run commands in other interpreters.
23777 @value{GDBN} currently supports two command interpreters, the console
23778 interpreter (sometimes called the command-line interpreter or @sc{cli})
23779 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23780 describes both of these interfaces in great detail.
23782 By default, @value{GDBN} will start with the console interpreter.
23783 However, the user may choose to start @value{GDBN} with another
23784 interpreter by specifying the @option{-i} or @option{--interpreter}
23785 startup options. Defined interpreters include:
23789 @cindex console interpreter
23790 The traditional console or command-line interpreter. This is the most often
23791 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23792 @value{GDBN} will use this interpreter.
23795 @cindex mi interpreter
23796 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23797 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23798 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23802 @cindex mi2 interpreter
23803 The current @sc{gdb/mi} interface.
23806 @cindex mi1 interpreter
23807 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23811 @cindex invoke another interpreter
23812 The interpreter being used by @value{GDBN} may not be dynamically
23813 switched at runtime. Although possible, this could lead to a very
23814 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23815 enters the command "interpreter-set console" in a console view,
23816 @value{GDBN} would switch to using the console interpreter, rendering
23817 the IDE inoperable!
23819 @kindex interpreter-exec
23820 Although you may only choose a single interpreter at startup, you may execute
23821 commands in any interpreter from the current interpreter using the appropriate
23822 command. If you are running the console interpreter, simply use the
23823 @code{interpreter-exec} command:
23826 interpreter-exec mi "-data-list-register-names"
23829 @sc{gdb/mi} has a similar command, although it is only available in versions of
23830 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23833 @chapter @value{GDBN} Text User Interface
23835 @cindex Text User Interface
23838 * TUI Overview:: TUI overview
23839 * TUI Keys:: TUI key bindings
23840 * TUI Single Key Mode:: TUI single key mode
23841 * TUI Commands:: TUI-specific commands
23842 * TUI Configuration:: TUI configuration variables
23845 The @value{GDBN} Text User Interface (TUI) is a terminal
23846 interface which uses the @code{curses} library to show the source
23847 file, the assembly output, the program registers and @value{GDBN}
23848 commands in separate text windows. The TUI mode is supported only
23849 on platforms where a suitable version of the @code{curses} library
23852 @pindex @value{GDBTUI}
23853 The TUI mode is enabled by default when you invoke @value{GDBN} as
23854 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23855 You can also switch in and out of TUI mode while @value{GDBN} runs by
23856 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23857 @xref{TUI Keys, ,TUI Key Bindings}.
23860 @section TUI Overview
23862 In TUI mode, @value{GDBN} can display several text windows:
23866 This window is the @value{GDBN} command window with the @value{GDBN}
23867 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23868 managed using readline.
23871 The source window shows the source file of the program. The current
23872 line and active breakpoints are displayed in this window.
23875 The assembly window shows the disassembly output of the program.
23878 This window shows the processor registers. Registers are highlighted
23879 when their values change.
23882 The source and assembly windows show the current program position
23883 by highlighting the current line and marking it with a @samp{>} marker.
23884 Breakpoints are indicated with two markers. The first marker
23885 indicates the breakpoint type:
23889 Breakpoint which was hit at least once.
23892 Breakpoint which was never hit.
23895 Hardware breakpoint which was hit at least once.
23898 Hardware breakpoint which was never hit.
23901 The second marker indicates whether the breakpoint is enabled or not:
23905 Breakpoint is enabled.
23908 Breakpoint is disabled.
23911 The source, assembly and register windows are updated when the current
23912 thread changes, when the frame changes, or when the program counter
23915 These windows are not all visible at the same time. The command
23916 window is always visible. The others can be arranged in several
23927 source and assembly,
23930 source and registers, or
23933 assembly and registers.
23936 A status line above the command window shows the following information:
23940 Indicates the current @value{GDBN} target.
23941 (@pxref{Targets, ,Specifying a Debugging Target}).
23944 Gives the current process or thread number.
23945 When no process is being debugged, this field is set to @code{No process}.
23948 Gives the current function name for the selected frame.
23949 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23950 When there is no symbol corresponding to the current program counter,
23951 the string @code{??} is displayed.
23954 Indicates the current line number for the selected frame.
23955 When the current line number is not known, the string @code{??} is displayed.
23958 Indicates the current program counter address.
23962 @section TUI Key Bindings
23963 @cindex TUI key bindings
23965 The TUI installs several key bindings in the readline keymaps
23966 @ifset SYSTEM_READLINE
23967 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
23969 @ifclear SYSTEM_READLINE
23970 (@pxref{Command Line Editing}).
23972 The following key bindings are installed for both TUI mode and the
23973 @value{GDBN} standard mode.
23982 Enter or leave the TUI mode. When leaving the TUI mode,
23983 the curses window management stops and @value{GDBN} operates using
23984 its standard mode, writing on the terminal directly. When reentering
23985 the TUI mode, control is given back to the curses windows.
23986 The screen is then refreshed.
23990 Use a TUI layout with only one window. The layout will
23991 either be @samp{source} or @samp{assembly}. When the TUI mode
23992 is not active, it will switch to the TUI mode.
23994 Think of this key binding as the Emacs @kbd{C-x 1} binding.
23998 Use a TUI layout with at least two windows. When the current
23999 layout already has two windows, the next layout with two windows is used.
24000 When a new layout is chosen, one window will always be common to the
24001 previous layout and the new one.
24003 Think of it as the Emacs @kbd{C-x 2} binding.
24007 Change the active window. The TUI associates several key bindings
24008 (like scrolling and arrow keys) with the active window. This command
24009 gives the focus to the next TUI window.
24011 Think of it as the Emacs @kbd{C-x o} binding.
24015 Switch in and out of the TUI SingleKey mode that binds single
24016 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24019 The following key bindings only work in the TUI mode:
24024 Scroll the active window one page up.
24028 Scroll the active window one page down.
24032 Scroll the active window one line up.
24036 Scroll the active window one line down.
24040 Scroll the active window one column left.
24044 Scroll the active window one column right.
24048 Refresh the screen.
24051 Because the arrow keys scroll the active window in the TUI mode, they
24052 are not available for their normal use by readline unless the command
24053 window has the focus. When another window is active, you must use
24054 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24055 and @kbd{C-f} to control the command window.
24057 @node TUI Single Key Mode
24058 @section TUI Single Key Mode
24059 @cindex TUI single key mode
24061 The TUI also provides a @dfn{SingleKey} mode, which binds several
24062 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24063 switch into this mode, where the following key bindings are used:
24066 @kindex c @r{(SingleKey TUI key)}
24070 @kindex d @r{(SingleKey TUI key)}
24074 @kindex f @r{(SingleKey TUI key)}
24078 @kindex n @r{(SingleKey TUI key)}
24082 @kindex q @r{(SingleKey TUI key)}
24084 exit the SingleKey mode.
24086 @kindex r @r{(SingleKey TUI key)}
24090 @kindex s @r{(SingleKey TUI key)}
24094 @kindex u @r{(SingleKey TUI key)}
24098 @kindex v @r{(SingleKey TUI key)}
24102 @kindex w @r{(SingleKey TUI key)}
24107 Other keys temporarily switch to the @value{GDBN} command prompt.
24108 The key that was pressed is inserted in the editing buffer so that
24109 it is possible to type most @value{GDBN} commands without interaction
24110 with the TUI SingleKey mode. Once the command is entered the TUI
24111 SingleKey mode is restored. The only way to permanently leave
24112 this mode is by typing @kbd{q} or @kbd{C-x s}.
24116 @section TUI-specific Commands
24117 @cindex TUI commands
24119 The TUI has specific commands to control the text windows.
24120 These commands are always available, even when @value{GDBN} is not in
24121 the TUI mode. When @value{GDBN} is in the standard mode, most
24122 of these commands will automatically switch to the TUI mode.
24124 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24125 terminal, or @value{GDBN} has been started with the machine interface
24126 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24127 these commands will fail with an error, because it would not be
24128 possible or desirable to enable curses window management.
24133 List and give the size of all displayed windows.
24137 Display the next layout.
24140 Display the previous layout.
24143 Display the source window only.
24146 Display the assembly window only.
24149 Display the source and assembly window.
24152 Display the register window together with the source or assembly window.
24156 Make the next window active for scrolling.
24159 Make the previous window active for scrolling.
24162 Make the source window active for scrolling.
24165 Make the assembly window active for scrolling.
24168 Make the register window active for scrolling.
24171 Make the command window active for scrolling.
24175 Refresh the screen. This is similar to typing @kbd{C-L}.
24177 @item tui reg float
24179 Show the floating point registers in the register window.
24181 @item tui reg general
24182 Show the general registers in the register window.
24185 Show the next register group. The list of register groups as well as
24186 their order is target specific. The predefined register groups are the
24187 following: @code{general}, @code{float}, @code{system}, @code{vector},
24188 @code{all}, @code{save}, @code{restore}.
24190 @item tui reg system
24191 Show the system registers in the register window.
24195 Update the source window and the current execution point.
24197 @item winheight @var{name} +@var{count}
24198 @itemx winheight @var{name} -@var{count}
24200 Change the height of the window @var{name} by @var{count}
24201 lines. Positive counts increase the height, while negative counts
24204 @item tabset @var{nchars}
24206 Set the width of tab stops to be @var{nchars} characters.
24209 @node TUI Configuration
24210 @section TUI Configuration Variables
24211 @cindex TUI configuration variables
24213 Several configuration variables control the appearance of TUI windows.
24216 @item set tui border-kind @var{kind}
24217 @kindex set tui border-kind
24218 Select the border appearance for the source, assembly and register windows.
24219 The possible values are the following:
24222 Use a space character to draw the border.
24225 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24228 Use the Alternate Character Set to draw the border. The border is
24229 drawn using character line graphics if the terminal supports them.
24232 @item set tui border-mode @var{mode}
24233 @kindex set tui border-mode
24234 @itemx set tui active-border-mode @var{mode}
24235 @kindex set tui active-border-mode
24236 Select the display attributes for the borders of the inactive windows
24237 or the active window. The @var{mode} can be one of the following:
24240 Use normal attributes to display the border.
24246 Use reverse video mode.
24249 Use half bright mode.
24251 @item half-standout
24252 Use half bright and standout mode.
24255 Use extra bright or bold mode.
24257 @item bold-standout
24258 Use extra bright or bold and standout mode.
24263 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24266 @cindex @sc{gnu} Emacs
24267 A special interface allows you to use @sc{gnu} Emacs to view (and
24268 edit) the source files for the program you are debugging with
24271 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24272 executable file you want to debug as an argument. This command starts
24273 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24274 created Emacs buffer.
24275 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24277 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24282 All ``terminal'' input and output goes through an Emacs buffer, called
24285 This applies both to @value{GDBN} commands and their output, and to the input
24286 and output done by the program you are debugging.
24288 This is useful because it means that you can copy the text of previous
24289 commands and input them again; you can even use parts of the output
24292 All the facilities of Emacs' Shell mode are available for interacting
24293 with your program. In particular, you can send signals the usual
24294 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24298 @value{GDBN} displays source code through Emacs.
24300 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24301 source file for that frame and puts an arrow (@samp{=>}) at the
24302 left margin of the current line. Emacs uses a separate buffer for
24303 source display, and splits the screen to show both your @value{GDBN} session
24306 Explicit @value{GDBN} @code{list} or search commands still produce output as
24307 usual, but you probably have no reason to use them from Emacs.
24310 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24311 a graphical mode, enabled by default, which provides further buffers
24312 that can control the execution and describe the state of your program.
24313 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24315 If you specify an absolute file name when prompted for the @kbd{M-x
24316 gdb} argument, then Emacs sets your current working directory to where
24317 your program resides. If you only specify the file name, then Emacs
24318 sets your current working directory to the directory associated
24319 with the previous buffer. In this case, @value{GDBN} may find your
24320 program by searching your environment's @code{PATH} variable, but on
24321 some operating systems it might not find the source. So, although the
24322 @value{GDBN} input and output session proceeds normally, the auxiliary
24323 buffer does not display the current source and line of execution.
24325 The initial working directory of @value{GDBN} is printed on the top
24326 line of the GUD buffer and this serves as a default for the commands
24327 that specify files for @value{GDBN} to operate on. @xref{Files,
24328 ,Commands to Specify Files}.
24330 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24331 need to call @value{GDBN} by a different name (for example, if you
24332 keep several configurations around, with different names) you can
24333 customize the Emacs variable @code{gud-gdb-command-name} to run the
24336 In the GUD buffer, you can use these special Emacs commands in
24337 addition to the standard Shell mode commands:
24341 Describe the features of Emacs' GUD Mode.
24344 Execute to another source line, like the @value{GDBN} @code{step} command; also
24345 update the display window to show the current file and location.
24348 Execute to next source line in this function, skipping all function
24349 calls, like the @value{GDBN} @code{next} command. Then update the display window
24350 to show the current file and location.
24353 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24354 display window accordingly.
24357 Execute until exit from the selected stack frame, like the @value{GDBN}
24358 @code{finish} command.
24361 Continue execution of your program, like the @value{GDBN} @code{continue}
24365 Go up the number of frames indicated by the numeric argument
24366 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24367 like the @value{GDBN} @code{up} command.
24370 Go down the number of frames indicated by the numeric argument, like the
24371 @value{GDBN} @code{down} command.
24374 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24375 tells @value{GDBN} to set a breakpoint on the source line point is on.
24377 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24378 separate frame which shows a backtrace when the GUD buffer is current.
24379 Move point to any frame in the stack and type @key{RET} to make it
24380 become the current frame and display the associated source in the
24381 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24382 selected frame become the current one. In graphical mode, the
24383 speedbar displays watch expressions.
24385 If you accidentally delete the source-display buffer, an easy way to get
24386 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24387 request a frame display; when you run under Emacs, this recreates
24388 the source buffer if necessary to show you the context of the current
24391 The source files displayed in Emacs are in ordinary Emacs buffers
24392 which are visiting the source files in the usual way. You can edit
24393 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24394 communicates with Emacs in terms of line numbers. If you add or
24395 delete lines from the text, the line numbers that @value{GDBN} knows cease
24396 to correspond properly with the code.
24398 A more detailed description of Emacs' interaction with @value{GDBN} is
24399 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24402 @c The following dropped because Epoch is nonstandard. Reactivate
24403 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
24405 @kindex Emacs Epoch environment
24409 Version 18 of @sc{gnu} Emacs has a built-in window system
24410 called the @code{epoch}
24411 environment. Users of this environment can use a new command,
24412 @code{inspect} which performs identically to @code{print} except that
24413 each value is printed in its own window.
24418 @chapter The @sc{gdb/mi} Interface
24420 @unnumberedsec Function and Purpose
24422 @cindex @sc{gdb/mi}, its purpose
24423 @sc{gdb/mi} is a line based machine oriented text interface to
24424 @value{GDBN} and is activated by specifying using the
24425 @option{--interpreter} command line option (@pxref{Mode Options}). It
24426 is specifically intended to support the development of systems which
24427 use the debugger as just one small component of a larger system.
24429 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24430 in the form of a reference manual.
24432 Note that @sc{gdb/mi} is still under construction, so some of the
24433 features described below are incomplete and subject to change
24434 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24436 @unnumberedsec Notation and Terminology
24438 @cindex notational conventions, for @sc{gdb/mi}
24439 This chapter uses the following notation:
24443 @code{|} separates two alternatives.
24446 @code{[ @var{something} ]} indicates that @var{something} is optional:
24447 it may or may not be given.
24450 @code{( @var{group} )*} means that @var{group} inside the parentheses
24451 may repeat zero or more times.
24454 @code{( @var{group} )+} means that @var{group} inside the parentheses
24455 may repeat one or more times.
24458 @code{"@var{string}"} means a literal @var{string}.
24462 @heading Dependencies
24466 * GDB/MI General Design::
24467 * GDB/MI Command Syntax::
24468 * GDB/MI Compatibility with CLI::
24469 * GDB/MI Development and Front Ends::
24470 * GDB/MI Output Records::
24471 * GDB/MI Simple Examples::
24472 * GDB/MI Command Description Format::
24473 * GDB/MI Breakpoint Commands::
24474 * GDB/MI Program Context::
24475 * GDB/MI Thread Commands::
24476 * GDB/MI Program Execution::
24477 * GDB/MI Stack Manipulation::
24478 * GDB/MI Variable Objects::
24479 * GDB/MI Data Manipulation::
24480 * GDB/MI Tracepoint Commands::
24481 * GDB/MI Symbol Query::
24482 * GDB/MI File Commands::
24484 * GDB/MI Kod Commands::
24485 * GDB/MI Memory Overlay Commands::
24486 * GDB/MI Signal Handling Commands::
24488 * GDB/MI Target Manipulation::
24489 * GDB/MI File Transfer Commands::
24490 * GDB/MI Miscellaneous Commands::
24493 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24494 @node GDB/MI General Design
24495 @section @sc{gdb/mi} General Design
24496 @cindex GDB/MI General Design
24498 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24499 parts---commands sent to @value{GDBN}, responses to those commands
24500 and notifications. Each command results in exactly one response,
24501 indicating either successful completion of the command, or an error.
24502 For the commands that do not resume the target, the response contains the
24503 requested information. For the commands that resume the target, the
24504 response only indicates whether the target was successfully resumed.
24505 Notifications is the mechanism for reporting changes in the state of the
24506 target, or in @value{GDBN} state, that cannot conveniently be associated with
24507 a command and reported as part of that command response.
24509 The important examples of notifications are:
24513 Exec notifications. These are used to report changes in
24514 target state---when a target is resumed, or stopped. It would not
24515 be feasible to include this information in response of resuming
24516 commands, because one resume commands can result in multiple events in
24517 different threads. Also, quite some time may pass before any event
24518 happens in the target, while a frontend needs to know whether the resuming
24519 command itself was successfully executed.
24522 Console output, and status notifications. Console output
24523 notifications are used to report output of CLI commands, as well as
24524 diagnostics for other commands. Status notifications are used to
24525 report the progress of a long-running operation. Naturally, including
24526 this information in command response would mean no output is produced
24527 until the command is finished, which is undesirable.
24530 General notifications. Commands may have various side effects on
24531 the @value{GDBN} or target state beyond their official purpose. For example,
24532 a command may change the selected thread. Although such changes can
24533 be included in command response, using notification allows for more
24534 orthogonal frontend design.
24538 There's no guarantee that whenever an MI command reports an error,
24539 @value{GDBN} or the target are in any specific state, and especially,
24540 the state is not reverted to the state before the MI command was
24541 processed. Therefore, whenever an MI command results in an error,
24542 we recommend that the frontend refreshes all the information shown in
24543 the user interface.
24547 * Context management::
24548 * Asynchronous and non-stop modes::
24552 @node Context management
24553 @subsection Context management
24555 In most cases when @value{GDBN} accesses the target, this access is
24556 done in context of a specific thread and frame (@pxref{Frames}).
24557 Often, even when accessing global data, the target requires that a thread
24558 be specified. The CLI interface maintains the selected thread and frame,
24559 and supplies them to target on each command. This is convenient,
24560 because a command line user would not want to specify that information
24561 explicitly on each command, and because user interacts with
24562 @value{GDBN} via a single terminal, so no confusion is possible as
24563 to what thread and frame are the current ones.
24565 In the case of MI, the concept of selected thread and frame is less
24566 useful. First, a frontend can easily remember this information
24567 itself. Second, a graphical frontend can have more than one window,
24568 each one used for debugging a different thread, and the frontend might
24569 want to access additional threads for internal purposes. This
24570 increases the risk that by relying on implicitly selected thread, the
24571 frontend may be operating on a wrong one. Therefore, each MI command
24572 should explicitly specify which thread and frame to operate on. To
24573 make it possible, each MI command accepts the @samp{--thread} and
24574 @samp{--frame} options, the value to each is @value{GDBN} identifier
24575 for thread and frame to operate on.
24577 Usually, each top-level window in a frontend allows the user to select
24578 a thread and a frame, and remembers the user selection for further
24579 operations. However, in some cases @value{GDBN} may suggest that the
24580 current thread be changed. For example, when stopping on a breakpoint
24581 it is reasonable to switch to the thread where breakpoint is hit. For
24582 another example, if the user issues the CLI @samp{thread} command via
24583 the frontend, it is desirable to change the frontend's selected thread to the
24584 one specified by user. @value{GDBN} communicates the suggestion to
24585 change current thread using the @samp{=thread-selected} notification.
24586 No such notification is available for the selected frame at the moment.
24588 Note that historically, MI shares the selected thread with CLI, so
24589 frontends used the @code{-thread-select} to execute commands in the
24590 right context. However, getting this to work right is cumbersome. The
24591 simplest way is for frontend to emit @code{-thread-select} command
24592 before every command. This doubles the number of commands that need
24593 to be sent. The alternative approach is to suppress @code{-thread-select}
24594 if the selected thread in @value{GDBN} is supposed to be identical to the
24595 thread the frontend wants to operate on. However, getting this
24596 optimization right can be tricky. In particular, if the frontend
24597 sends several commands to @value{GDBN}, and one of the commands changes the
24598 selected thread, then the behaviour of subsequent commands will
24599 change. So, a frontend should either wait for response from such
24600 problematic commands, or explicitly add @code{-thread-select} for
24601 all subsequent commands. No frontend is known to do this exactly
24602 right, so it is suggested to just always pass the @samp{--thread} and
24603 @samp{--frame} options.
24605 @node Asynchronous and non-stop modes
24606 @subsection Asynchronous command execution and non-stop mode
24608 On some targets, @value{GDBN} is capable of processing MI commands
24609 even while the target is running. This is called @dfn{asynchronous
24610 command execution} (@pxref{Background Execution}). The frontend may
24611 specify a preferrence for asynchronous execution using the
24612 @code{-gdb-set target-async 1} command, which should be emitted before
24613 either running the executable or attaching to the target. After the
24614 frontend has started the executable or attached to the target, it can
24615 find if asynchronous execution is enabled using the
24616 @code{-list-target-features} command.
24618 Even if @value{GDBN} can accept a command while target is running,
24619 many commands that access the target do not work when the target is
24620 running. Therefore, asynchronous command execution is most useful
24621 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24622 it is possible to examine the state of one thread, while other threads
24625 When a given thread is running, MI commands that try to access the
24626 target in the context of that thread may not work, or may work only on
24627 some targets. In particular, commands that try to operate on thread's
24628 stack will not work, on any target. Commands that read memory, or
24629 modify breakpoints, may work or not work, depending on the target. Note
24630 that even commands that operate on global state, such as @code{print},
24631 @code{set}, and breakpoint commands, still access the target in the
24632 context of a specific thread, so frontend should try to find a
24633 stopped thread and perform the operation on that thread (using the
24634 @samp{--thread} option).
24636 Which commands will work in the context of a running thread is
24637 highly target dependent. However, the two commands
24638 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24639 to find the state of a thread, will always work.
24641 @node Thread groups
24642 @subsection Thread groups
24643 @value{GDBN} may be used to debug several processes at the same time.
24644 On some platfroms, @value{GDBN} may support debugging of several
24645 hardware systems, each one having several cores with several different
24646 processes running on each core. This section describes the MI
24647 mechanism to support such debugging scenarios.
24649 The key observation is that regardless of the structure of the
24650 target, MI can have a global list of threads, because most commands that
24651 accept the @samp{--thread} option do not need to know what process that
24652 thread belongs to. Therefore, it is not necessary to introduce
24653 neither additional @samp{--process} option, nor an notion of the
24654 current process in the MI interface. The only strictly new feature
24655 that is required is the ability to find how the threads are grouped
24658 To allow the user to discover such grouping, and to support arbitrary
24659 hierarchy of machines/cores/processes, MI introduces the concept of a
24660 @dfn{thread group}. Thread group is a collection of threads and other
24661 thread groups. A thread group always has a string identifier, a type,
24662 and may have additional attributes specific to the type. A new
24663 command, @code{-list-thread-groups}, returns the list of top-level
24664 thread groups, which correspond to processes that @value{GDBN} is
24665 debugging at the moment. By passing an identifier of a thread group
24666 to the @code{-list-thread-groups} command, it is possible to obtain
24667 the members of specific thread group.
24669 To allow the user to easily discover processes, and other objects, he
24670 wishes to debug, a concept of @dfn{available thread group} is
24671 introduced. Available thread group is an thread group that
24672 @value{GDBN} is not debugging, but that can be attached to, using the
24673 @code{-target-attach} command. The list of available top-level thread
24674 groups can be obtained using @samp{-list-thread-groups --available}.
24675 In general, the content of a thread group may be only retrieved only
24676 after attaching to that thread group.
24678 Thread groups are related to inferiors (@pxref{Inferiors and
24679 Programs}). Each inferior corresponds to a thread group of a special
24680 type @samp{process}, and some additional operations are permitted on
24681 such thread groups.
24683 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24684 @node GDB/MI Command Syntax
24685 @section @sc{gdb/mi} Command Syntax
24688 * GDB/MI Input Syntax::
24689 * GDB/MI Output Syntax::
24692 @node GDB/MI Input Syntax
24693 @subsection @sc{gdb/mi} Input Syntax
24695 @cindex input syntax for @sc{gdb/mi}
24696 @cindex @sc{gdb/mi}, input syntax
24698 @item @var{command} @expansion{}
24699 @code{@var{cli-command} | @var{mi-command}}
24701 @item @var{cli-command} @expansion{}
24702 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24703 @var{cli-command} is any existing @value{GDBN} CLI command.
24705 @item @var{mi-command} @expansion{}
24706 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24707 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24709 @item @var{token} @expansion{}
24710 "any sequence of digits"
24712 @item @var{option} @expansion{}
24713 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24715 @item @var{parameter} @expansion{}
24716 @code{@var{non-blank-sequence} | @var{c-string}}
24718 @item @var{operation} @expansion{}
24719 @emph{any of the operations described in this chapter}
24721 @item @var{non-blank-sequence} @expansion{}
24722 @emph{anything, provided it doesn't contain special characters such as
24723 "-", @var{nl}, """ and of course " "}
24725 @item @var{c-string} @expansion{}
24726 @code{""" @var{seven-bit-iso-c-string-content} """}
24728 @item @var{nl} @expansion{}
24737 The CLI commands are still handled by the @sc{mi} interpreter; their
24738 output is described below.
24741 The @code{@var{token}}, when present, is passed back when the command
24745 Some @sc{mi} commands accept optional arguments as part of the parameter
24746 list. Each option is identified by a leading @samp{-} (dash) and may be
24747 followed by an optional argument parameter. Options occur first in the
24748 parameter list and can be delimited from normal parameters using
24749 @samp{--} (this is useful when some parameters begin with a dash).
24756 We want easy access to the existing CLI syntax (for debugging).
24759 We want it to be easy to spot a @sc{mi} operation.
24762 @node GDB/MI Output Syntax
24763 @subsection @sc{gdb/mi} Output Syntax
24765 @cindex output syntax of @sc{gdb/mi}
24766 @cindex @sc{gdb/mi}, output syntax
24767 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24768 followed, optionally, by a single result record. This result record
24769 is for the most recent command. The sequence of output records is
24770 terminated by @samp{(gdb)}.
24772 If an input command was prefixed with a @code{@var{token}} then the
24773 corresponding output for that command will also be prefixed by that same
24777 @item @var{output} @expansion{}
24778 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24780 @item @var{result-record} @expansion{}
24781 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24783 @item @var{out-of-band-record} @expansion{}
24784 @code{@var{async-record} | @var{stream-record}}
24786 @item @var{async-record} @expansion{}
24787 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24789 @item @var{exec-async-output} @expansion{}
24790 @code{[ @var{token} ] "*" @var{async-output}}
24792 @item @var{status-async-output} @expansion{}
24793 @code{[ @var{token} ] "+" @var{async-output}}
24795 @item @var{notify-async-output} @expansion{}
24796 @code{[ @var{token} ] "=" @var{async-output}}
24798 @item @var{async-output} @expansion{}
24799 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24801 @item @var{result-class} @expansion{}
24802 @code{"done" | "running" | "connected" | "error" | "exit"}
24804 @item @var{async-class} @expansion{}
24805 @code{"stopped" | @var{others}} (where @var{others} will be added
24806 depending on the needs---this is still in development).
24808 @item @var{result} @expansion{}
24809 @code{ @var{variable} "=" @var{value}}
24811 @item @var{variable} @expansion{}
24812 @code{ @var{string} }
24814 @item @var{value} @expansion{}
24815 @code{ @var{const} | @var{tuple} | @var{list} }
24817 @item @var{const} @expansion{}
24818 @code{@var{c-string}}
24820 @item @var{tuple} @expansion{}
24821 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24823 @item @var{list} @expansion{}
24824 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24825 @var{result} ( "," @var{result} )* "]" }
24827 @item @var{stream-record} @expansion{}
24828 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24830 @item @var{console-stream-output} @expansion{}
24831 @code{"~" @var{c-string}}
24833 @item @var{target-stream-output} @expansion{}
24834 @code{"@@" @var{c-string}}
24836 @item @var{log-stream-output} @expansion{}
24837 @code{"&" @var{c-string}}
24839 @item @var{nl} @expansion{}
24842 @item @var{token} @expansion{}
24843 @emph{any sequence of digits}.
24851 All output sequences end in a single line containing a period.
24854 The @code{@var{token}} is from the corresponding request. Note that
24855 for all async output, while the token is allowed by the grammar and
24856 may be output by future versions of @value{GDBN} for select async
24857 output messages, it is generally omitted. Frontends should treat
24858 all async output as reporting general changes in the state of the
24859 target and there should be no need to associate async output to any
24863 @cindex status output in @sc{gdb/mi}
24864 @var{status-async-output} contains on-going status information about the
24865 progress of a slow operation. It can be discarded. All status output is
24866 prefixed by @samp{+}.
24869 @cindex async output in @sc{gdb/mi}
24870 @var{exec-async-output} contains asynchronous state change on the target
24871 (stopped, started, disappeared). All async output is prefixed by
24875 @cindex notify output in @sc{gdb/mi}
24876 @var{notify-async-output} contains supplementary information that the
24877 client should handle (e.g., a new breakpoint information). All notify
24878 output is prefixed by @samp{=}.
24881 @cindex console output in @sc{gdb/mi}
24882 @var{console-stream-output} is output that should be displayed as is in the
24883 console. It is the textual response to a CLI command. All the console
24884 output is prefixed by @samp{~}.
24887 @cindex target output in @sc{gdb/mi}
24888 @var{target-stream-output} is the output produced by the target program.
24889 All the target output is prefixed by @samp{@@}.
24892 @cindex log output in @sc{gdb/mi}
24893 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24894 instance messages that should be displayed as part of an error log. All
24895 the log output is prefixed by @samp{&}.
24898 @cindex list output in @sc{gdb/mi}
24899 New @sc{gdb/mi} commands should only output @var{lists} containing
24905 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24906 details about the various output records.
24908 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24909 @node GDB/MI Compatibility with CLI
24910 @section @sc{gdb/mi} Compatibility with CLI
24912 @cindex compatibility, @sc{gdb/mi} and CLI
24913 @cindex @sc{gdb/mi}, compatibility with CLI
24915 For the developers convenience CLI commands can be entered directly,
24916 but there may be some unexpected behaviour. For example, commands
24917 that query the user will behave as if the user replied yes, breakpoint
24918 command lists are not executed and some CLI commands, such as
24919 @code{if}, @code{when} and @code{define}, prompt for further input with
24920 @samp{>}, which is not valid MI output.
24922 This feature may be removed at some stage in the future and it is
24923 recommended that front ends use the @code{-interpreter-exec} command
24924 (@pxref{-interpreter-exec}).
24926 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24927 @node GDB/MI Development and Front Ends
24928 @section @sc{gdb/mi} Development and Front Ends
24929 @cindex @sc{gdb/mi} development
24931 The application which takes the MI output and presents the state of the
24932 program being debugged to the user is called a @dfn{front end}.
24934 Although @sc{gdb/mi} is still incomplete, it is currently being used
24935 by a variety of front ends to @value{GDBN}. This makes it difficult
24936 to introduce new functionality without breaking existing usage. This
24937 section tries to minimize the problems by describing how the protocol
24940 Some changes in MI need not break a carefully designed front end, and
24941 for these the MI version will remain unchanged. The following is a
24942 list of changes that may occur within one level, so front ends should
24943 parse MI output in a way that can handle them:
24947 New MI commands may be added.
24950 New fields may be added to the output of any MI command.
24953 The range of values for fields with specified values, e.g.,
24954 @code{in_scope} (@pxref{-var-update}) may be extended.
24956 @c The format of field's content e.g type prefix, may change so parse it
24957 @c at your own risk. Yes, in general?
24959 @c The order of fields may change? Shouldn't really matter but it might
24960 @c resolve inconsistencies.
24963 If the changes are likely to break front ends, the MI version level
24964 will be increased by one. This will allow the front end to parse the
24965 output according to the MI version. Apart from mi0, new versions of
24966 @value{GDBN} will not support old versions of MI and it will be the
24967 responsibility of the front end to work with the new one.
24969 @c Starting with mi3, add a new command -mi-version that prints the MI
24972 The best way to avoid unexpected changes in MI that might break your front
24973 end is to make your project known to @value{GDBN} developers and
24974 follow development on @email{gdb@@sourceware.org} and
24975 @email{gdb-patches@@sourceware.org}.
24976 @cindex mailing lists
24978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24979 @node GDB/MI Output Records
24980 @section @sc{gdb/mi} Output Records
24983 * GDB/MI Result Records::
24984 * GDB/MI Stream Records::
24985 * GDB/MI Async Records::
24986 * GDB/MI Frame Information::
24987 * GDB/MI Thread Information::
24988 * GDB/MI Ada Exception Information::
24991 @node GDB/MI Result Records
24992 @subsection @sc{gdb/mi} Result Records
24994 @cindex result records in @sc{gdb/mi}
24995 @cindex @sc{gdb/mi}, result records
24996 In addition to a number of out-of-band notifications, the response to a
24997 @sc{gdb/mi} command includes one of the following result indications:
25001 @item "^done" [ "," @var{results} ]
25002 The synchronous operation was successful, @code{@var{results}} are the return
25007 This result record is equivalent to @samp{^done}. Historically, it
25008 was output instead of @samp{^done} if the command has resumed the
25009 target. This behaviour is maintained for backward compatibility, but
25010 all frontends should treat @samp{^done} and @samp{^running}
25011 identically and rely on the @samp{*running} output record to determine
25012 which threads are resumed.
25016 @value{GDBN} has connected to a remote target.
25018 @item "^error" "," @var{c-string}
25020 The operation failed. The @code{@var{c-string}} contains the corresponding
25025 @value{GDBN} has terminated.
25029 @node GDB/MI Stream Records
25030 @subsection @sc{gdb/mi} Stream Records
25032 @cindex @sc{gdb/mi}, stream records
25033 @cindex stream records in @sc{gdb/mi}
25034 @value{GDBN} internally maintains a number of output streams: the console, the
25035 target, and the log. The output intended for each of these streams is
25036 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25038 Each stream record begins with a unique @dfn{prefix character} which
25039 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25040 Syntax}). In addition to the prefix, each stream record contains a
25041 @code{@var{string-output}}. This is either raw text (with an implicit new
25042 line) or a quoted C string (which does not contain an implicit newline).
25045 @item "~" @var{string-output}
25046 The console output stream contains text that should be displayed in the
25047 CLI console window. It contains the textual responses to CLI commands.
25049 @item "@@" @var{string-output}
25050 The target output stream contains any textual output from the running
25051 target. This is only present when GDB's event loop is truly
25052 asynchronous, which is currently only the case for remote targets.
25054 @item "&" @var{string-output}
25055 The log stream contains debugging messages being produced by @value{GDBN}'s
25059 @node GDB/MI Async Records
25060 @subsection @sc{gdb/mi} Async Records
25062 @cindex async records in @sc{gdb/mi}
25063 @cindex @sc{gdb/mi}, async records
25064 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25065 additional changes that have occurred. Those changes can either be a
25066 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25067 target activity (e.g., target stopped).
25069 The following is the list of possible async records:
25073 @item *running,thread-id="@var{thread}"
25074 The target is now running. The @var{thread} field tells which
25075 specific thread is now running, and can be @samp{all} if all threads
25076 are running. The frontend should assume that no interaction with a
25077 running thread is possible after this notification is produced.
25078 The frontend should not assume that this notification is output
25079 only once for any command. @value{GDBN} may emit this notification
25080 several times, either for different threads, because it cannot resume
25081 all threads together, or even for a single thread, if the thread must
25082 be stepped though some code before letting it run freely.
25084 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25085 The target has stopped. The @var{reason} field can have one of the
25089 @item breakpoint-hit
25090 A breakpoint was reached.
25091 @item watchpoint-trigger
25092 A watchpoint was triggered.
25093 @item read-watchpoint-trigger
25094 A read watchpoint was triggered.
25095 @item access-watchpoint-trigger
25096 An access watchpoint was triggered.
25097 @item function-finished
25098 An -exec-finish or similar CLI command was accomplished.
25099 @item location-reached
25100 An -exec-until or similar CLI command was accomplished.
25101 @item watchpoint-scope
25102 A watchpoint has gone out of scope.
25103 @item end-stepping-range
25104 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25105 similar CLI command was accomplished.
25106 @item exited-signalled
25107 The inferior exited because of a signal.
25109 The inferior exited.
25110 @item exited-normally
25111 The inferior exited normally.
25112 @item signal-received
25113 A signal was received by the inferior.
25116 The @var{id} field identifies the thread that directly caused the stop
25117 -- for example by hitting a breakpoint. Depending on whether all-stop
25118 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25119 stop all threads, or only the thread that directly triggered the stop.
25120 If all threads are stopped, the @var{stopped} field will have the
25121 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25122 field will be a list of thread identifiers. Presently, this list will
25123 always include a single thread, but frontend should be prepared to see
25124 several threads in the list. The @var{core} field reports the
25125 processor core on which the stop event has happened. This field may be absent
25126 if such information is not available.
25128 @item =thread-group-added,id="@var{id}"
25129 @itemx =thread-group-removed,id="@var{id}"
25130 A thread group was either added or removed. The @var{id} field
25131 contains the @value{GDBN} identifier of the thread group. When a thread
25132 group is added, it generally might not be associated with a running
25133 process. When a thread group is removed, its id becomes invalid and
25134 cannot be used in any way.
25136 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25137 A thread group became associated with a running program,
25138 either because the program was just started or the thread group
25139 was attached to a program. The @var{id} field contains the
25140 @value{GDBN} identifier of the thread group. The @var{pid} field
25141 contains process identifier, specific to the operating system.
25143 @itemx =thread-group-exited,id="@var{id}"
25144 A thread group is no longer associated with a running program,
25145 either because the program has exited, or because it was detached
25146 from. The @var{id} field contains the @value{GDBN} identifier of the
25149 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25150 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25151 A thread either was created, or has exited. The @var{id} field
25152 contains the @value{GDBN} identifier of the thread. The @var{gid}
25153 field identifies the thread group this thread belongs to.
25155 @item =thread-selected,id="@var{id}"
25156 Informs that the selected thread was changed as result of the last
25157 command. This notification is not emitted as result of @code{-thread-select}
25158 command but is emitted whenever an MI command that is not documented
25159 to change the selected thread actually changes it. In particular,
25160 invoking, directly or indirectly (via user-defined command), the CLI
25161 @code{thread} command, will generate this notification.
25163 We suggest that in response to this notification, front ends
25164 highlight the selected thread and cause subsequent commands to apply to
25167 @item =library-loaded,...
25168 Reports that a new library file was loaded by the program. This
25169 notification has 4 fields---@var{id}, @var{target-name},
25170 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25171 opaque identifier of the library. For remote debugging case,
25172 @var{target-name} and @var{host-name} fields give the name of the
25173 library file on the target, and on the host respectively. For native
25174 debugging, both those fields have the same value. The
25175 @var{symbols-loaded} field is emitted only for backward compatibility
25176 and should not be relied on to convey any useful information. The
25177 @var{thread-group} field, if present, specifies the id of the thread
25178 group in whose context the library was loaded. If the field is
25179 absent, it means the library was loaded in the context of all present
25182 @item =library-unloaded,...
25183 Reports that a library was unloaded by the program. This notification
25184 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25185 the same meaning as for the @code{=library-loaded} notification.
25186 The @var{thread-group} field, if present, specifies the id of the
25187 thread group in whose context the library was unloaded. If the field is
25188 absent, it means the library was unloaded in the context of all present
25191 @item =breakpoint-created,bkpt=@{...@}
25192 @itemx =breakpoint-modified,bkpt=@{...@}
25193 @itemx =breakpoint-deleted,bkpt=@{...@}
25194 Reports that a breakpoint was created, modified, or deleted,
25195 respectively. Only user-visible breakpoints are reported to the MI
25198 The @var{bkpt} argument is of the same form as returned by the various
25199 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
25201 Note that if a breakpoint is emitted in the result record of a
25202 command, then it will not also be emitted in an async record.
25206 @node GDB/MI Frame Information
25207 @subsection @sc{gdb/mi} Frame Information
25209 Response from many MI commands includes an information about stack
25210 frame. This information is a tuple that may have the following
25215 The level of the stack frame. The innermost frame has the level of
25216 zero. This field is always present.
25219 The name of the function corresponding to the frame. This field may
25220 be absent if @value{GDBN} is unable to determine the function name.
25223 The code address for the frame. This field is always present.
25226 The name of the source files that correspond to the frame's code
25227 address. This field may be absent.
25230 The source line corresponding to the frames' code address. This field
25234 The name of the binary file (either executable or shared library) the
25235 corresponds to the frame's code address. This field may be absent.
25239 @node GDB/MI Thread Information
25240 @subsection @sc{gdb/mi} Thread Information
25242 Whenever @value{GDBN} has to report an information about a thread, it
25243 uses a tuple with the following fields:
25247 The numeric id assigned to the thread by @value{GDBN}. This field is
25251 Target-specific string identifying the thread. This field is always present.
25254 Additional information about the thread provided by the target.
25255 It is supposed to be human-readable and not interpreted by the
25256 frontend. This field is optional.
25259 Either @samp{stopped} or @samp{running}, depending on whether the
25260 thread is presently running. This field is always present.
25263 The value of this field is an integer number of the processor core the
25264 thread was last seen on. This field is optional.
25267 @node GDB/MI Ada Exception Information
25268 @subsection @sc{gdb/mi} Ada Exception Information
25270 Whenever a @code{*stopped} record is emitted because the program
25271 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25272 @value{GDBN} provides the name of the exception that was raised via
25273 the @code{exception-name} field.
25275 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25276 @node GDB/MI Simple Examples
25277 @section Simple Examples of @sc{gdb/mi} Interaction
25278 @cindex @sc{gdb/mi}, simple examples
25280 This subsection presents several simple examples of interaction using
25281 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25282 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25283 the output received from @sc{gdb/mi}.
25285 Note the line breaks shown in the examples are here only for
25286 readability, they don't appear in the real output.
25288 @subheading Setting a Breakpoint
25290 Setting a breakpoint generates synchronous output which contains detailed
25291 information of the breakpoint.
25294 -> -break-insert main
25295 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25296 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25297 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
25301 @subheading Program Execution
25303 Program execution generates asynchronous records and MI gives the
25304 reason that execution stopped.
25310 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25311 frame=@{addr="0x08048564",func="main",
25312 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25313 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25318 <- *stopped,reason="exited-normally"
25322 @subheading Quitting @value{GDBN}
25324 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25332 Please note that @samp{^exit} is printed immediately, but it might
25333 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25334 performs necessary cleanups, including killing programs being debugged
25335 or disconnecting from debug hardware, so the frontend should wait till
25336 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25337 fails to exit in reasonable time.
25339 @subheading A Bad Command
25341 Here's what happens if you pass a non-existent command:
25345 <- ^error,msg="Undefined MI command: rubbish"
25350 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25351 @node GDB/MI Command Description Format
25352 @section @sc{gdb/mi} Command Description Format
25354 The remaining sections describe blocks of commands. Each block of
25355 commands is laid out in a fashion similar to this section.
25357 @subheading Motivation
25359 The motivation for this collection of commands.
25361 @subheading Introduction
25363 A brief introduction to this collection of commands as a whole.
25365 @subheading Commands
25367 For each command in the block, the following is described:
25369 @subsubheading Synopsis
25372 -command @var{args}@dots{}
25375 @subsubheading Result
25377 @subsubheading @value{GDBN} Command
25379 The corresponding @value{GDBN} CLI command(s), if any.
25381 @subsubheading Example
25383 Example(s) formatted for readability. Some of the described commands have
25384 not been implemented yet and these are labeled N.A.@: (not available).
25387 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25388 @node GDB/MI Breakpoint Commands
25389 @section @sc{gdb/mi} Breakpoint Commands
25391 @cindex breakpoint commands for @sc{gdb/mi}
25392 @cindex @sc{gdb/mi}, breakpoint commands
25393 This section documents @sc{gdb/mi} commands for manipulating
25396 @subheading The @code{-break-after} Command
25397 @findex -break-after
25399 @subsubheading Synopsis
25402 -break-after @var{number} @var{count}
25405 The breakpoint number @var{number} is not in effect until it has been
25406 hit @var{count} times. To see how this is reflected in the output of
25407 the @samp{-break-list} command, see the description of the
25408 @samp{-break-list} command below.
25410 @subsubheading @value{GDBN} Command
25412 The corresponding @value{GDBN} command is @samp{ignore}.
25414 @subsubheading Example
25419 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25420 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25421 fullname="/home/foo/hello.c",line="5",times="0"@}
25428 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25429 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25430 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25431 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25432 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25433 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25434 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25435 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25436 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25437 line="5",times="0",ignore="3"@}]@}
25442 @subheading The @code{-break-catch} Command
25443 @findex -break-catch
25446 @subheading The @code{-break-commands} Command
25447 @findex -break-commands
25449 @subsubheading Synopsis
25452 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25455 Specifies the CLI commands that should be executed when breakpoint
25456 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25457 are the commands. If no command is specified, any previously-set
25458 commands are cleared. @xref{Break Commands}. Typical use of this
25459 functionality is tracing a program, that is, printing of values of
25460 some variables whenever breakpoint is hit and then continuing.
25462 @subsubheading @value{GDBN} Command
25464 The corresponding @value{GDBN} command is @samp{commands}.
25466 @subsubheading Example
25471 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25472 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25473 fullname="/home/foo/hello.c",line="5",times="0"@}
25475 -break-commands 1 "print v" "continue"
25480 @subheading The @code{-break-condition} Command
25481 @findex -break-condition
25483 @subsubheading Synopsis
25486 -break-condition @var{number} @var{expr}
25489 Breakpoint @var{number} will stop the program only if the condition in
25490 @var{expr} is true. The condition becomes part of the
25491 @samp{-break-list} output (see the description of the @samp{-break-list}
25494 @subsubheading @value{GDBN} Command
25496 The corresponding @value{GDBN} command is @samp{condition}.
25498 @subsubheading Example
25502 -break-condition 1 1
25506 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25507 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25508 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25509 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25510 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25511 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25512 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25513 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25514 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25515 line="5",cond="1",times="0",ignore="3"@}]@}
25519 @subheading The @code{-break-delete} Command
25520 @findex -break-delete
25522 @subsubheading Synopsis
25525 -break-delete ( @var{breakpoint} )+
25528 Delete the breakpoint(s) whose number(s) are specified in the argument
25529 list. This is obviously reflected in the breakpoint list.
25531 @subsubheading @value{GDBN} Command
25533 The corresponding @value{GDBN} command is @samp{delete}.
25535 @subsubheading Example
25543 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25544 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25545 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25546 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25547 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25548 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25549 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25554 @subheading The @code{-break-disable} Command
25555 @findex -break-disable
25557 @subsubheading Synopsis
25560 -break-disable ( @var{breakpoint} )+
25563 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25564 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25566 @subsubheading @value{GDBN} Command
25568 The corresponding @value{GDBN} command is @samp{disable}.
25570 @subsubheading Example
25578 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25579 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25580 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25581 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25582 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25583 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25584 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25585 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25586 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25587 line="5",times="0"@}]@}
25591 @subheading The @code{-break-enable} Command
25592 @findex -break-enable
25594 @subsubheading Synopsis
25597 -break-enable ( @var{breakpoint} )+
25600 Enable (previously disabled) @var{breakpoint}(s).
25602 @subsubheading @value{GDBN} Command
25604 The corresponding @value{GDBN} command is @samp{enable}.
25606 @subsubheading Example
25614 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25615 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25616 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25617 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25618 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25619 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25620 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25621 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25622 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25623 line="5",times="0"@}]@}
25627 @subheading The @code{-break-info} Command
25628 @findex -break-info
25630 @subsubheading Synopsis
25633 -break-info @var{breakpoint}
25637 Get information about a single breakpoint.
25639 @subsubheading @value{GDBN} Command
25641 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25643 @subsubheading Example
25646 @subheading The @code{-break-insert} Command
25647 @findex -break-insert
25649 @subsubheading Synopsis
25652 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25653 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25654 [ -p @var{thread} ] [ @var{location} ]
25658 If specified, @var{location}, can be one of:
25665 @item filename:linenum
25666 @item filename:function
25670 The possible optional parameters of this command are:
25674 Insert a temporary breakpoint.
25676 Insert a hardware breakpoint.
25677 @item -c @var{condition}
25678 Make the breakpoint conditional on @var{condition}.
25679 @item -i @var{ignore-count}
25680 Initialize the @var{ignore-count}.
25682 If @var{location} cannot be parsed (for example if it
25683 refers to unknown files or functions), create a pending
25684 breakpoint. Without this flag, @value{GDBN} will report
25685 an error, and won't create a breakpoint, if @var{location}
25688 Create a disabled breakpoint.
25690 Create a tracepoint. @xref{Tracepoints}. When this parameter
25691 is used together with @samp{-h}, a fast tracepoint is created.
25694 @subsubheading Result
25696 The result is in the form:
25699 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25700 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25701 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25702 times="@var{times}"@}
25706 where @var{number} is the @value{GDBN} number for this breakpoint,
25707 @var{funcname} is the name of the function where the breakpoint was
25708 inserted, @var{filename} is the name of the source file which contains
25709 this function, @var{lineno} is the source line number within that file
25710 and @var{times} the number of times that the breakpoint has been hit
25711 (always 0 for -break-insert but may be greater for -break-info or -break-list
25712 which use the same output).
25714 Note: this format is open to change.
25715 @c An out-of-band breakpoint instead of part of the result?
25717 @subsubheading @value{GDBN} Command
25719 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25720 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25722 @subsubheading Example
25727 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25728 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25730 -break-insert -t foo
25731 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25732 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25735 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25736 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25737 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25738 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25739 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25740 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25741 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25742 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25743 addr="0x0001072c", func="main",file="recursive2.c",
25744 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25745 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25746 addr="0x00010774",func="foo",file="recursive2.c",
25747 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25749 -break-insert -r foo.*
25750 ~int foo(int, int);
25751 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25752 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25756 @subheading The @code{-break-list} Command
25757 @findex -break-list
25759 @subsubheading Synopsis
25765 Displays the list of inserted breakpoints, showing the following fields:
25769 number of the breakpoint
25771 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25773 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25776 is the breakpoint enabled or no: @samp{y} or @samp{n}
25778 memory location at which the breakpoint is set
25780 logical location of the breakpoint, expressed by function name, file
25783 number of times the breakpoint has been hit
25786 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25787 @code{body} field is an empty list.
25789 @subsubheading @value{GDBN} Command
25791 The corresponding @value{GDBN} command is @samp{info break}.
25793 @subsubheading Example
25798 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25799 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25800 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25801 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25802 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25803 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25804 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25805 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25806 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25807 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25808 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25809 line="13",times="0"@}]@}
25813 Here's an example of the result when there are no breakpoints:
25818 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25819 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25820 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25821 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25822 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25823 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25824 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25829 @subheading The @code{-break-passcount} Command
25830 @findex -break-passcount
25832 @subsubheading Synopsis
25835 -break-passcount @var{tracepoint-number} @var{passcount}
25838 Set the passcount for tracepoint @var{tracepoint-number} to
25839 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25840 is not a tracepoint, error is emitted. This corresponds to CLI
25841 command @samp{passcount}.
25843 @subheading The @code{-break-watch} Command
25844 @findex -break-watch
25846 @subsubheading Synopsis
25849 -break-watch [ -a | -r ]
25852 Create a watchpoint. With the @samp{-a} option it will create an
25853 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25854 read from or on a write to the memory location. With the @samp{-r}
25855 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25856 trigger only when the memory location is accessed for reading. Without
25857 either of the options, the watchpoint created is a regular watchpoint,
25858 i.e., it will trigger when the memory location is accessed for writing.
25859 @xref{Set Watchpoints, , Setting Watchpoints}.
25861 Note that @samp{-break-list} will report a single list of watchpoints and
25862 breakpoints inserted.
25864 @subsubheading @value{GDBN} Command
25866 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25869 @subsubheading Example
25871 Setting a watchpoint on a variable in the @code{main} function:
25876 ^done,wpt=@{number="2",exp="x"@}
25881 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25882 value=@{old="-268439212",new="55"@},
25883 frame=@{func="main",args=[],file="recursive2.c",
25884 fullname="/home/foo/bar/recursive2.c",line="5"@}
25888 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25889 the program execution twice: first for the variable changing value, then
25890 for the watchpoint going out of scope.
25895 ^done,wpt=@{number="5",exp="C"@}
25900 *stopped,reason="watchpoint-trigger",
25901 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25902 frame=@{func="callee4",args=[],
25903 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25904 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25909 *stopped,reason="watchpoint-scope",wpnum="5",
25910 frame=@{func="callee3",args=[@{name="strarg",
25911 value="0x11940 \"A string argument.\""@}],
25912 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25913 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25917 Listing breakpoints and watchpoints, at different points in the program
25918 execution. Note that once the watchpoint goes out of scope, it is
25924 ^done,wpt=@{number="2",exp="C"@}
25927 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25928 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25929 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25930 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25931 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25932 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25933 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25934 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25935 addr="0x00010734",func="callee4",
25936 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25937 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25938 bkpt=@{number="2",type="watchpoint",disp="keep",
25939 enabled="y",addr="",what="C",times="0"@}]@}
25944 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25945 value=@{old="-276895068",new="3"@},
25946 frame=@{func="callee4",args=[],
25947 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25948 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25951 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25952 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25953 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25954 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25955 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25956 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25957 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25958 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25959 addr="0x00010734",func="callee4",
25960 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25961 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25962 bkpt=@{number="2",type="watchpoint",disp="keep",
25963 enabled="y",addr="",what="C",times="-5"@}]@}
25967 ^done,reason="watchpoint-scope",wpnum="2",
25968 frame=@{func="callee3",args=[@{name="strarg",
25969 value="0x11940 \"A string argument.\""@}],
25970 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25971 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25974 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25975 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25976 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25977 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25978 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25979 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25980 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25981 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25982 addr="0x00010734",func="callee4",
25983 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25984 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
25989 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25990 @node GDB/MI Program Context
25991 @section @sc{gdb/mi} Program Context
25993 @subheading The @code{-exec-arguments} Command
25994 @findex -exec-arguments
25997 @subsubheading Synopsis
26000 -exec-arguments @var{args}
26003 Set the inferior program arguments, to be used in the next
26006 @subsubheading @value{GDBN} Command
26008 The corresponding @value{GDBN} command is @samp{set args}.
26010 @subsubheading Example
26014 -exec-arguments -v word
26021 @subheading The @code{-exec-show-arguments} Command
26022 @findex -exec-show-arguments
26024 @subsubheading Synopsis
26027 -exec-show-arguments
26030 Print the arguments of the program.
26032 @subsubheading @value{GDBN} Command
26034 The corresponding @value{GDBN} command is @samp{show args}.
26036 @subsubheading Example
26041 @subheading The @code{-environment-cd} Command
26042 @findex -environment-cd
26044 @subsubheading Synopsis
26047 -environment-cd @var{pathdir}
26050 Set @value{GDBN}'s working directory.
26052 @subsubheading @value{GDBN} Command
26054 The corresponding @value{GDBN} command is @samp{cd}.
26056 @subsubheading Example
26060 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26066 @subheading The @code{-environment-directory} Command
26067 @findex -environment-directory
26069 @subsubheading Synopsis
26072 -environment-directory [ -r ] [ @var{pathdir} ]+
26075 Add directories @var{pathdir} to beginning of search path for source files.
26076 If the @samp{-r} option is used, the search path is reset to the default
26077 search path. If directories @var{pathdir} are supplied in addition to the
26078 @samp{-r} option, the search path is first reset and then addition
26080 Multiple directories may be specified, separated by blanks. Specifying
26081 multiple directories in a single command
26082 results in the directories added to the beginning of the
26083 search path in the same order they were presented in the command.
26084 If blanks are needed as
26085 part of a directory name, double-quotes should be used around
26086 the name. In the command output, the path will show up separated
26087 by the system directory-separator character. The directory-separator
26088 character must not be used
26089 in any directory name.
26090 If no directories are specified, the current search path is displayed.
26092 @subsubheading @value{GDBN} Command
26094 The corresponding @value{GDBN} command is @samp{dir}.
26096 @subsubheading Example
26100 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26101 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26103 -environment-directory ""
26104 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26106 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26107 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26109 -environment-directory -r
26110 ^done,source-path="$cdir:$cwd"
26115 @subheading The @code{-environment-path} Command
26116 @findex -environment-path
26118 @subsubheading Synopsis
26121 -environment-path [ -r ] [ @var{pathdir} ]+
26124 Add directories @var{pathdir} to beginning of search path for object files.
26125 If the @samp{-r} option is used, the search path is reset to the original
26126 search path that existed at gdb start-up. If directories @var{pathdir} are
26127 supplied in addition to the
26128 @samp{-r} option, the search path is first reset and then addition
26130 Multiple directories may be specified, separated by blanks. Specifying
26131 multiple directories in a single command
26132 results in the directories added to the beginning of the
26133 search path in the same order they were presented in the command.
26134 If blanks are needed as
26135 part of a directory name, double-quotes should be used around
26136 the name. In the command output, the path will show up separated
26137 by the system directory-separator character. The directory-separator
26138 character must not be used
26139 in any directory name.
26140 If no directories are specified, the current path is displayed.
26143 @subsubheading @value{GDBN} Command
26145 The corresponding @value{GDBN} command is @samp{path}.
26147 @subsubheading Example
26152 ^done,path="/usr/bin"
26154 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26155 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26157 -environment-path -r /usr/local/bin
26158 ^done,path="/usr/local/bin:/usr/bin"
26163 @subheading The @code{-environment-pwd} Command
26164 @findex -environment-pwd
26166 @subsubheading Synopsis
26172 Show the current working directory.
26174 @subsubheading @value{GDBN} Command
26176 The corresponding @value{GDBN} command is @samp{pwd}.
26178 @subsubheading Example
26183 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26187 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26188 @node GDB/MI Thread Commands
26189 @section @sc{gdb/mi} Thread Commands
26192 @subheading The @code{-thread-info} Command
26193 @findex -thread-info
26195 @subsubheading Synopsis
26198 -thread-info [ @var{thread-id} ]
26201 Reports information about either a specific thread, if
26202 the @var{thread-id} parameter is present, or about all
26203 threads. When printing information about all threads,
26204 also reports the current thread.
26206 @subsubheading @value{GDBN} Command
26208 The @samp{info thread} command prints the same information
26211 @subsubheading Result
26213 The result is a list of threads. The following attributes are
26214 defined for a given thread:
26218 This field exists only for the current thread. It has the value @samp{*}.
26221 The identifier that @value{GDBN} uses to refer to the thread.
26224 The identifier that the target uses to refer to the thread.
26227 Extra information about the thread, in a target-specific format. This
26231 The name of the thread. If the user specified a name using the
26232 @code{thread name} command, then this name is given. Otherwise, if
26233 @value{GDBN} can extract the thread name from the target, then that
26234 name is given. If @value{GDBN} cannot find the thread name, then this
26238 The stack frame currently executing in the thread.
26241 The thread's state. The @samp{state} field may have the following
26246 The thread is stopped. Frame information is available for stopped
26250 The thread is running. There's no frame information for running
26256 If @value{GDBN} can find the CPU core on which this thread is running,
26257 then this field is the core identifier. This field is optional.
26261 @subsubheading Example
26266 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26267 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26268 args=[]@},state="running"@},
26269 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26270 frame=@{level="0",addr="0x0804891f",func="foo",
26271 args=[@{name="i",value="10"@}],
26272 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26273 state="running"@}],
26274 current-thread-id="1"
26278 @subheading The @code{-thread-list-ids} Command
26279 @findex -thread-list-ids
26281 @subsubheading Synopsis
26287 Produces a list of the currently known @value{GDBN} thread ids. At the
26288 end of the list it also prints the total number of such threads.
26290 This command is retained for historical reasons, the
26291 @code{-thread-info} command should be used instead.
26293 @subsubheading @value{GDBN} Command
26295 Part of @samp{info threads} supplies the same information.
26297 @subsubheading Example
26302 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26303 current-thread-id="1",number-of-threads="3"
26308 @subheading The @code{-thread-select} Command
26309 @findex -thread-select
26311 @subsubheading Synopsis
26314 -thread-select @var{threadnum}
26317 Make @var{threadnum} the current thread. It prints the number of the new
26318 current thread, and the topmost frame for that thread.
26320 This command is deprecated in favor of explicitly using the
26321 @samp{--thread} option to each command.
26323 @subsubheading @value{GDBN} Command
26325 The corresponding @value{GDBN} command is @samp{thread}.
26327 @subsubheading Example
26334 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26335 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26339 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26340 number-of-threads="3"
26343 ^done,new-thread-id="3",
26344 frame=@{level="0",func="vprintf",
26345 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26346 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26350 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26351 @node GDB/MI Program Execution
26352 @section @sc{gdb/mi} Program Execution
26354 These are the asynchronous commands which generate the out-of-band
26355 record @samp{*stopped}. Currently @value{GDBN} only really executes
26356 asynchronously with remote targets and this interaction is mimicked in
26359 @subheading The @code{-exec-continue} Command
26360 @findex -exec-continue
26362 @subsubheading Synopsis
26365 -exec-continue [--reverse] [--all|--thread-group N]
26368 Resumes the execution of the inferior program, which will continue
26369 to execute until it reaches a debugger stop event. If the
26370 @samp{--reverse} option is specified, execution resumes in reverse until
26371 it reaches a stop event. Stop events may include
26374 breakpoints or watchpoints
26376 signals or exceptions
26378 the end of the process (or its beginning under @samp{--reverse})
26380 the end or beginning of a replay log if one is being used.
26382 In all-stop mode (@pxref{All-Stop
26383 Mode}), may resume only one thread, or all threads, depending on the
26384 value of the @samp{scheduler-locking} variable. If @samp{--all} is
26385 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
26386 ignored in all-stop mode. If the @samp{--thread-group} options is
26387 specified, then all threads in that thread group are resumed.
26389 @subsubheading @value{GDBN} Command
26391 The corresponding @value{GDBN} corresponding is @samp{continue}.
26393 @subsubheading Example
26400 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
26401 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
26407 @subheading The @code{-exec-finish} Command
26408 @findex -exec-finish
26410 @subsubheading Synopsis
26413 -exec-finish [--reverse]
26416 Resumes the execution of the inferior program until the current
26417 function is exited. Displays the results returned by the function.
26418 If the @samp{--reverse} option is specified, resumes the reverse
26419 execution of the inferior program until the point where current
26420 function was called.
26422 @subsubheading @value{GDBN} Command
26424 The corresponding @value{GDBN} command is @samp{finish}.
26426 @subsubheading Example
26428 Function returning @code{void}.
26435 *stopped,reason="function-finished",frame=@{func="main",args=[],
26436 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
26440 Function returning other than @code{void}. The name of the internal
26441 @value{GDBN} variable storing the result is printed, together with the
26448 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
26449 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
26450 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26451 gdb-result-var="$1",return-value="0"
26456 @subheading The @code{-exec-interrupt} Command
26457 @findex -exec-interrupt
26459 @subsubheading Synopsis
26462 -exec-interrupt [--all|--thread-group N]
26465 Interrupts the background execution of the target. Note how the token
26466 associated with the stop message is the one for the execution command
26467 that has been interrupted. The token for the interrupt itself only
26468 appears in the @samp{^done} output. If the user is trying to
26469 interrupt a non-running program, an error message will be printed.
26471 Note that when asynchronous execution is enabled, this command is
26472 asynchronous just like other execution commands. That is, first the
26473 @samp{^done} response will be printed, and the target stop will be
26474 reported after that using the @samp{*stopped} notification.
26476 In non-stop mode, only the context thread is interrupted by default.
26477 All threads (in all inferiors) will be interrupted if the
26478 @samp{--all} option is specified. If the @samp{--thread-group}
26479 option is specified, all threads in that group will be interrupted.
26481 @subsubheading @value{GDBN} Command
26483 The corresponding @value{GDBN} command is @samp{interrupt}.
26485 @subsubheading Example
26496 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
26497 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
26498 fullname="/home/foo/bar/try.c",line="13"@}
26503 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
26507 @subheading The @code{-exec-jump} Command
26510 @subsubheading Synopsis
26513 -exec-jump @var{location}
26516 Resumes execution of the inferior program at the location specified by
26517 parameter. @xref{Specify Location}, for a description of the
26518 different forms of @var{location}.
26520 @subsubheading @value{GDBN} Command
26522 The corresponding @value{GDBN} command is @samp{jump}.
26524 @subsubheading Example
26527 -exec-jump foo.c:10
26528 *running,thread-id="all"
26533 @subheading The @code{-exec-next} Command
26536 @subsubheading Synopsis
26539 -exec-next [--reverse]
26542 Resumes execution of the inferior program, stopping when the beginning
26543 of the next source line is reached.
26545 If the @samp{--reverse} option is specified, resumes reverse execution
26546 of the inferior program, stopping at the beginning of the previous
26547 source line. If you issue this command on the first line of a
26548 function, it will take you back to the caller of that function, to the
26549 source line where the function was called.
26552 @subsubheading @value{GDBN} Command
26554 The corresponding @value{GDBN} command is @samp{next}.
26556 @subsubheading Example
26562 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26567 @subheading The @code{-exec-next-instruction} Command
26568 @findex -exec-next-instruction
26570 @subsubheading Synopsis
26573 -exec-next-instruction [--reverse]
26576 Executes one machine instruction. If the instruction is a function
26577 call, continues until the function returns. If the program stops at an
26578 instruction in the middle of a source line, the address will be
26581 If the @samp{--reverse} option is specified, resumes reverse execution
26582 of the inferior program, stopping at the previous instruction. If the
26583 previously executed instruction was a return from another function,
26584 it will continue to execute in reverse until the call to that function
26585 (from the current stack frame) is reached.
26587 @subsubheading @value{GDBN} Command
26589 The corresponding @value{GDBN} command is @samp{nexti}.
26591 @subsubheading Example
26595 -exec-next-instruction
26599 *stopped,reason="end-stepping-range",
26600 addr="0x000100d4",line="5",file="hello.c"
26605 @subheading The @code{-exec-return} Command
26606 @findex -exec-return
26608 @subsubheading Synopsis
26614 Makes current function return immediately. Doesn't execute the inferior.
26615 Displays the new current frame.
26617 @subsubheading @value{GDBN} Command
26619 The corresponding @value{GDBN} command is @samp{return}.
26621 @subsubheading Example
26625 200-break-insert callee4
26626 200^done,bkpt=@{number="1",addr="0x00010734",
26627 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26632 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26633 frame=@{func="callee4",args=[],
26634 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26635 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26641 111^done,frame=@{level="0",func="callee3",
26642 args=[@{name="strarg",
26643 value="0x11940 \"A string argument.\""@}],
26644 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26645 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26650 @subheading The @code{-exec-run} Command
26653 @subsubheading Synopsis
26656 -exec-run [--all | --thread-group N]
26659 Starts execution of the inferior from the beginning. The inferior
26660 executes until either a breakpoint is encountered or the program
26661 exits. In the latter case the output will include an exit code, if
26662 the program has exited exceptionally.
26664 When no option is specified, the current inferior is started. If the
26665 @samp{--thread-group} option is specified, it should refer to a thread
26666 group of type @samp{process}, and that thread group will be started.
26667 If the @samp{--all} option is specified, then all inferiors will be started.
26669 @subsubheading @value{GDBN} Command
26671 The corresponding @value{GDBN} command is @samp{run}.
26673 @subsubheading Examples
26678 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26683 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26684 frame=@{func="main",args=[],file="recursive2.c",
26685 fullname="/home/foo/bar/recursive2.c",line="4"@}
26690 Program exited normally:
26698 *stopped,reason="exited-normally"
26703 Program exited exceptionally:
26711 *stopped,reason="exited",exit-code="01"
26715 Another way the program can terminate is if it receives a signal such as
26716 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26720 *stopped,reason="exited-signalled",signal-name="SIGINT",
26721 signal-meaning="Interrupt"
26725 @c @subheading -exec-signal
26728 @subheading The @code{-exec-step} Command
26731 @subsubheading Synopsis
26734 -exec-step [--reverse]
26737 Resumes execution of the inferior program, stopping when the beginning
26738 of the next source line is reached, if the next source line is not a
26739 function call. If it is, stop at the first instruction of the called
26740 function. If the @samp{--reverse} option is specified, resumes reverse
26741 execution of the inferior program, stopping at the beginning of the
26742 previously executed source line.
26744 @subsubheading @value{GDBN} Command
26746 The corresponding @value{GDBN} command is @samp{step}.
26748 @subsubheading Example
26750 Stepping into a function:
26756 *stopped,reason="end-stepping-range",
26757 frame=@{func="foo",args=[@{name="a",value="10"@},
26758 @{name="b",value="0"@}],file="recursive2.c",
26759 fullname="/home/foo/bar/recursive2.c",line="11"@}
26769 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26774 @subheading The @code{-exec-step-instruction} Command
26775 @findex -exec-step-instruction
26777 @subsubheading Synopsis
26780 -exec-step-instruction [--reverse]
26783 Resumes the inferior which executes one machine instruction. If the
26784 @samp{--reverse} option is specified, resumes reverse execution of the
26785 inferior program, stopping at the previously executed instruction.
26786 The output, once @value{GDBN} has stopped, will vary depending on
26787 whether we have stopped in the middle of a source line or not. In the
26788 former case, the address at which the program stopped will be printed
26791 @subsubheading @value{GDBN} Command
26793 The corresponding @value{GDBN} command is @samp{stepi}.
26795 @subsubheading Example
26799 -exec-step-instruction
26803 *stopped,reason="end-stepping-range",
26804 frame=@{func="foo",args=[],file="try.c",
26805 fullname="/home/foo/bar/try.c",line="10"@}
26807 -exec-step-instruction
26811 *stopped,reason="end-stepping-range",
26812 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26813 fullname="/home/foo/bar/try.c",line="10"@}
26818 @subheading The @code{-exec-until} Command
26819 @findex -exec-until
26821 @subsubheading Synopsis
26824 -exec-until [ @var{location} ]
26827 Executes the inferior until the @var{location} specified in the
26828 argument is reached. If there is no argument, the inferior executes
26829 until a source line greater than the current one is reached. The
26830 reason for stopping in this case will be @samp{location-reached}.
26832 @subsubheading @value{GDBN} Command
26834 The corresponding @value{GDBN} command is @samp{until}.
26836 @subsubheading Example
26840 -exec-until recursive2.c:6
26844 *stopped,reason="location-reached",frame=@{func="main",args=[],
26845 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26850 @subheading -file-clear
26851 Is this going away????
26854 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26855 @node GDB/MI Stack Manipulation
26856 @section @sc{gdb/mi} Stack Manipulation Commands
26859 @subheading The @code{-stack-info-frame} Command
26860 @findex -stack-info-frame
26862 @subsubheading Synopsis
26868 Get info on the selected frame.
26870 @subsubheading @value{GDBN} Command
26872 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26873 (without arguments).
26875 @subsubheading Example
26880 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26881 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26882 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26886 @subheading The @code{-stack-info-depth} Command
26887 @findex -stack-info-depth
26889 @subsubheading Synopsis
26892 -stack-info-depth [ @var{max-depth} ]
26895 Return the depth of the stack. If the integer argument @var{max-depth}
26896 is specified, do not count beyond @var{max-depth} frames.
26898 @subsubheading @value{GDBN} Command
26900 There's no equivalent @value{GDBN} command.
26902 @subsubheading Example
26904 For a stack with frame levels 0 through 11:
26911 -stack-info-depth 4
26914 -stack-info-depth 12
26917 -stack-info-depth 11
26920 -stack-info-depth 13
26925 @subheading The @code{-stack-list-arguments} Command
26926 @findex -stack-list-arguments
26928 @subsubheading Synopsis
26931 -stack-list-arguments @var{print-values}
26932 [ @var{low-frame} @var{high-frame} ]
26935 Display a list of the arguments for the frames between @var{low-frame}
26936 and @var{high-frame} (inclusive). If @var{low-frame} and
26937 @var{high-frame} are not provided, list the arguments for the whole
26938 call stack. If the two arguments are equal, show the single frame
26939 at the corresponding level. It is an error if @var{low-frame} is
26940 larger than the actual number of frames. On the other hand,
26941 @var{high-frame} may be larger than the actual number of frames, in
26942 which case only existing frames will be returned.
26944 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26945 the variables; if it is 1 or @code{--all-values}, print also their
26946 values; and if it is 2 or @code{--simple-values}, print the name,
26947 type and value for simple data types, and the name and type for arrays,
26948 structures and unions.
26950 Use of this command to obtain arguments in a single frame is
26951 deprecated in favor of the @samp{-stack-list-variables} command.
26953 @subsubheading @value{GDBN} Command
26955 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26956 @samp{gdb_get_args} command which partially overlaps with the
26957 functionality of @samp{-stack-list-arguments}.
26959 @subsubheading Example
26966 frame=@{level="0",addr="0x00010734",func="callee4",
26967 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26968 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26969 frame=@{level="1",addr="0x0001076c",func="callee3",
26970 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26971 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26972 frame=@{level="2",addr="0x0001078c",func="callee2",
26973 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26974 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26975 frame=@{level="3",addr="0x000107b4",func="callee1",
26976 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26977 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
26978 frame=@{level="4",addr="0x000107e0",func="main",
26979 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26980 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
26982 -stack-list-arguments 0
26985 frame=@{level="0",args=[]@},
26986 frame=@{level="1",args=[name="strarg"]@},
26987 frame=@{level="2",args=[name="intarg",name="strarg"]@},
26988 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
26989 frame=@{level="4",args=[]@}]
26991 -stack-list-arguments 1
26994 frame=@{level="0",args=[]@},
26996 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26997 frame=@{level="2",args=[
26998 @{name="intarg",value="2"@},
26999 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27000 @{frame=@{level="3",args=[
27001 @{name="intarg",value="2"@},
27002 @{name="strarg",value="0x11940 \"A string argument.\""@},
27003 @{name="fltarg",value="3.5"@}]@},
27004 frame=@{level="4",args=[]@}]
27006 -stack-list-arguments 0 2 2
27007 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27009 -stack-list-arguments 1 2 2
27010 ^done,stack-args=[frame=@{level="2",
27011 args=[@{name="intarg",value="2"@},
27012 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27016 @c @subheading -stack-list-exception-handlers
27019 @subheading The @code{-stack-list-frames} Command
27020 @findex -stack-list-frames
27022 @subsubheading Synopsis
27025 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
27028 List the frames currently on the stack. For each frame it displays the
27033 The frame number, 0 being the topmost frame, i.e., the innermost function.
27035 The @code{$pc} value for that frame.
27039 File name of the source file where the function lives.
27040 @item @var{fullname}
27041 The full file name of the source file where the function lives.
27043 Line number corresponding to the @code{$pc}.
27045 The shared library where this function is defined. This is only given
27046 if the frame's function is not known.
27049 If invoked without arguments, this command prints a backtrace for the
27050 whole stack. If given two integer arguments, it shows the frames whose
27051 levels are between the two arguments (inclusive). If the two arguments
27052 are equal, it shows the single frame at the corresponding level. It is
27053 an error if @var{low-frame} is larger than the actual number of
27054 frames. On the other hand, @var{high-frame} may be larger than the
27055 actual number of frames, in which case only existing frames will be returned.
27057 @subsubheading @value{GDBN} Command
27059 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27061 @subsubheading Example
27063 Full stack backtrace:
27069 [frame=@{level="0",addr="0x0001076c",func="foo",
27070 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27071 frame=@{level="1",addr="0x000107a4",func="foo",
27072 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27073 frame=@{level="2",addr="0x000107a4",func="foo",
27074 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27075 frame=@{level="3",addr="0x000107a4",func="foo",
27076 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27077 frame=@{level="4",addr="0x000107a4",func="foo",
27078 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27079 frame=@{level="5",addr="0x000107a4",func="foo",
27080 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27081 frame=@{level="6",addr="0x000107a4",func="foo",
27082 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27083 frame=@{level="7",addr="0x000107a4",func="foo",
27084 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27085 frame=@{level="8",addr="0x000107a4",func="foo",
27086 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27087 frame=@{level="9",addr="0x000107a4",func="foo",
27088 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27089 frame=@{level="10",addr="0x000107a4",func="foo",
27090 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27091 frame=@{level="11",addr="0x00010738",func="main",
27092 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27096 Show frames between @var{low_frame} and @var{high_frame}:
27100 -stack-list-frames 3 5
27102 [frame=@{level="3",addr="0x000107a4",func="foo",
27103 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27104 frame=@{level="4",addr="0x000107a4",func="foo",
27105 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27106 frame=@{level="5",addr="0x000107a4",func="foo",
27107 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27111 Show a single frame:
27115 -stack-list-frames 3 3
27117 [frame=@{level="3",addr="0x000107a4",func="foo",
27118 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27123 @subheading The @code{-stack-list-locals} Command
27124 @findex -stack-list-locals
27126 @subsubheading Synopsis
27129 -stack-list-locals @var{print-values}
27132 Display the local variable names for the selected frame. If
27133 @var{print-values} is 0 or @code{--no-values}, print only the names of
27134 the variables; if it is 1 or @code{--all-values}, print also their
27135 values; and if it is 2 or @code{--simple-values}, print the name,
27136 type and value for simple data types, and the name and type for arrays,
27137 structures and unions. In this last case, a frontend can immediately
27138 display the value of simple data types and create variable objects for
27139 other data types when the user wishes to explore their values in
27142 This command is deprecated in favor of the
27143 @samp{-stack-list-variables} command.
27145 @subsubheading @value{GDBN} Command
27147 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27149 @subsubheading Example
27153 -stack-list-locals 0
27154 ^done,locals=[name="A",name="B",name="C"]
27156 -stack-list-locals --all-values
27157 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27158 @{name="C",value="@{1, 2, 3@}"@}]
27159 -stack-list-locals --simple-values
27160 ^done,locals=[@{name="A",type="int",value="1"@},
27161 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27165 @subheading The @code{-stack-list-variables} Command
27166 @findex -stack-list-variables
27168 @subsubheading Synopsis
27171 -stack-list-variables @var{print-values}
27174 Display the names of local variables and function arguments for the selected frame. If
27175 @var{print-values} is 0 or @code{--no-values}, print only the names of
27176 the variables; if it is 1 or @code{--all-values}, print also their
27177 values; and if it is 2 or @code{--simple-values}, print the name,
27178 type and value for simple data types, and the name and type for arrays,
27179 structures and unions.
27181 @subsubheading Example
27185 -stack-list-variables --thread 1 --frame 0 --all-values
27186 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27191 @subheading The @code{-stack-select-frame} Command
27192 @findex -stack-select-frame
27194 @subsubheading Synopsis
27197 -stack-select-frame @var{framenum}
27200 Change the selected frame. Select a different frame @var{framenum} on
27203 This command in deprecated in favor of passing the @samp{--frame}
27204 option to every command.
27206 @subsubheading @value{GDBN} Command
27208 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27209 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27211 @subsubheading Example
27215 -stack-select-frame 2
27220 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27221 @node GDB/MI Variable Objects
27222 @section @sc{gdb/mi} Variable Objects
27226 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27228 For the implementation of a variable debugger window (locals, watched
27229 expressions, etc.), we are proposing the adaptation of the existing code
27230 used by @code{Insight}.
27232 The two main reasons for that are:
27236 It has been proven in practice (it is already on its second generation).
27239 It will shorten development time (needless to say how important it is
27243 The original interface was designed to be used by Tcl code, so it was
27244 slightly changed so it could be used through @sc{gdb/mi}. This section
27245 describes the @sc{gdb/mi} operations that will be available and gives some
27246 hints about their use.
27248 @emph{Note}: In addition to the set of operations described here, we
27249 expect the @sc{gui} implementation of a variable window to require, at
27250 least, the following operations:
27253 @item @code{-gdb-show} @code{output-radix}
27254 @item @code{-stack-list-arguments}
27255 @item @code{-stack-list-locals}
27256 @item @code{-stack-select-frame}
27261 @subheading Introduction to Variable Objects
27263 @cindex variable objects in @sc{gdb/mi}
27265 Variable objects are "object-oriented" MI interface for examining and
27266 changing values of expressions. Unlike some other MI interfaces that
27267 work with expressions, variable objects are specifically designed for
27268 simple and efficient presentation in the frontend. A variable object
27269 is identified by string name. When a variable object is created, the
27270 frontend specifies the expression for that variable object. The
27271 expression can be a simple variable, or it can be an arbitrary complex
27272 expression, and can even involve CPU registers. After creating a
27273 variable object, the frontend can invoke other variable object
27274 operations---for example to obtain or change the value of a variable
27275 object, or to change display format.
27277 Variable objects have hierarchical tree structure. Any variable object
27278 that corresponds to a composite type, such as structure in C, has
27279 a number of child variable objects, for example corresponding to each
27280 element of a structure. A child variable object can itself have
27281 children, recursively. Recursion ends when we reach
27282 leaf variable objects, which always have built-in types. Child variable
27283 objects are created only by explicit request, so if a frontend
27284 is not interested in the children of a particular variable object, no
27285 child will be created.
27287 For a leaf variable object it is possible to obtain its value as a
27288 string, or set the value from a string. String value can be also
27289 obtained for a non-leaf variable object, but it's generally a string
27290 that only indicates the type of the object, and does not list its
27291 contents. Assignment to a non-leaf variable object is not allowed.
27293 A frontend does not need to read the values of all variable objects each time
27294 the program stops. Instead, MI provides an update command that lists all
27295 variable objects whose values has changed since the last update
27296 operation. This considerably reduces the amount of data that must
27297 be transferred to the frontend. As noted above, children variable
27298 objects are created on demand, and only leaf variable objects have a
27299 real value. As result, gdb will read target memory only for leaf
27300 variables that frontend has created.
27302 The automatic update is not always desirable. For example, a frontend
27303 might want to keep a value of some expression for future reference,
27304 and never update it. For another example, fetching memory is
27305 relatively slow for embedded targets, so a frontend might want
27306 to disable automatic update for the variables that are either not
27307 visible on the screen, or ``closed''. This is possible using so
27308 called ``frozen variable objects''. Such variable objects are never
27309 implicitly updated.
27311 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
27312 fixed variable object, the expression is parsed when the variable
27313 object is created, including associating identifiers to specific
27314 variables. The meaning of expression never changes. For a floating
27315 variable object the values of variables whose names appear in the
27316 expressions are re-evaluated every time in the context of the current
27317 frame. Consider this example:
27322 struct work_state state;
27329 If a fixed variable object for the @code{state} variable is created in
27330 this function, and we enter the recursive call, the variable
27331 object will report the value of @code{state} in the top-level
27332 @code{do_work} invocation. On the other hand, a floating variable
27333 object will report the value of @code{state} in the current frame.
27335 If an expression specified when creating a fixed variable object
27336 refers to a local variable, the variable object becomes bound to the
27337 thread and frame in which the variable object is created. When such
27338 variable object is updated, @value{GDBN} makes sure that the
27339 thread/frame combination the variable object is bound to still exists,
27340 and re-evaluates the variable object in context of that thread/frame.
27342 The following is the complete set of @sc{gdb/mi} operations defined to
27343 access this functionality:
27345 @multitable @columnfractions .4 .6
27346 @item @strong{Operation}
27347 @tab @strong{Description}
27349 @item @code{-enable-pretty-printing}
27350 @tab enable Python-based pretty-printing
27351 @item @code{-var-create}
27352 @tab create a variable object
27353 @item @code{-var-delete}
27354 @tab delete the variable object and/or its children
27355 @item @code{-var-set-format}
27356 @tab set the display format of this variable
27357 @item @code{-var-show-format}
27358 @tab show the display format of this variable
27359 @item @code{-var-info-num-children}
27360 @tab tells how many children this object has
27361 @item @code{-var-list-children}
27362 @tab return a list of the object's children
27363 @item @code{-var-info-type}
27364 @tab show the type of this variable object
27365 @item @code{-var-info-expression}
27366 @tab print parent-relative expression that this variable object represents
27367 @item @code{-var-info-path-expression}
27368 @tab print full expression that this variable object represents
27369 @item @code{-var-show-attributes}
27370 @tab is this variable editable? does it exist here?
27371 @item @code{-var-evaluate-expression}
27372 @tab get the value of this variable
27373 @item @code{-var-assign}
27374 @tab set the value of this variable
27375 @item @code{-var-update}
27376 @tab update the variable and its children
27377 @item @code{-var-set-frozen}
27378 @tab set frozeness attribute
27379 @item @code{-var-set-update-range}
27380 @tab set range of children to display on update
27383 In the next subsection we describe each operation in detail and suggest
27384 how it can be used.
27386 @subheading Description And Use of Operations on Variable Objects
27388 @subheading The @code{-enable-pretty-printing} Command
27389 @findex -enable-pretty-printing
27392 -enable-pretty-printing
27395 @value{GDBN} allows Python-based visualizers to affect the output of the
27396 MI variable object commands. However, because there was no way to
27397 implement this in a fully backward-compatible way, a front end must
27398 request that this functionality be enabled.
27400 Once enabled, this feature cannot be disabled.
27402 Note that if Python support has not been compiled into @value{GDBN},
27403 this command will still succeed (and do nothing).
27405 This feature is currently (as of @value{GDBN} 7.0) experimental, and
27406 may work differently in future versions of @value{GDBN}.
27408 @subheading The @code{-var-create} Command
27409 @findex -var-create
27411 @subsubheading Synopsis
27414 -var-create @{@var{name} | "-"@}
27415 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
27418 This operation creates a variable object, which allows the monitoring of
27419 a variable, the result of an expression, a memory cell or a CPU
27422 The @var{name} parameter is the string by which the object can be
27423 referenced. It must be unique. If @samp{-} is specified, the varobj
27424 system will generate a string ``varNNNNNN'' automatically. It will be
27425 unique provided that one does not specify @var{name} of that format.
27426 The command fails if a duplicate name is found.
27428 The frame under which the expression should be evaluated can be
27429 specified by @var{frame-addr}. A @samp{*} indicates that the current
27430 frame should be used. A @samp{@@} indicates that a floating variable
27431 object must be created.
27433 @var{expression} is any expression valid on the current language set (must not
27434 begin with a @samp{*}), or one of the following:
27438 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
27441 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
27444 @samp{$@var{regname}} --- a CPU register name
27447 @cindex dynamic varobj
27448 A varobj's contents may be provided by a Python-based pretty-printer. In this
27449 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
27450 have slightly different semantics in some cases. If the
27451 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
27452 will never create a dynamic varobj. This ensures backward
27453 compatibility for existing clients.
27455 @subsubheading Result
27457 This operation returns attributes of the newly-created varobj. These
27462 The name of the varobj.
27465 The number of children of the varobj. This number is not necessarily
27466 reliable for a dynamic varobj. Instead, you must examine the
27467 @samp{has_more} attribute.
27470 The varobj's scalar value. For a varobj whose type is some sort of
27471 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
27472 will not be interesting.
27475 The varobj's type. This is a string representation of the type, as
27476 would be printed by the @value{GDBN} CLI.
27479 If a variable object is bound to a specific thread, then this is the
27480 thread's identifier.
27483 For a dynamic varobj, this indicates whether there appear to be any
27484 children available. For a non-dynamic varobj, this will be 0.
27487 This attribute will be present and have the value @samp{1} if the
27488 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27489 then this attribute will not be present.
27492 A dynamic varobj can supply a display hint to the front end. The
27493 value comes directly from the Python pretty-printer object's
27494 @code{display_hint} method. @xref{Pretty Printing API}.
27497 Typical output will look like this:
27500 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
27501 has_more="@var{has_more}"
27505 @subheading The @code{-var-delete} Command
27506 @findex -var-delete
27508 @subsubheading Synopsis
27511 -var-delete [ -c ] @var{name}
27514 Deletes a previously created variable object and all of its children.
27515 With the @samp{-c} option, just deletes the children.
27517 Returns an error if the object @var{name} is not found.
27520 @subheading The @code{-var-set-format} Command
27521 @findex -var-set-format
27523 @subsubheading Synopsis
27526 -var-set-format @var{name} @var{format-spec}
27529 Sets the output format for the value of the object @var{name} to be
27532 @anchor{-var-set-format}
27533 The syntax for the @var{format-spec} is as follows:
27536 @var{format-spec} @expansion{}
27537 @{binary | decimal | hexadecimal | octal | natural@}
27540 The natural format is the default format choosen automatically
27541 based on the variable type (like decimal for an @code{int}, hex
27542 for pointers, etc.).
27544 For a variable with children, the format is set only on the
27545 variable itself, and the children are not affected.
27547 @subheading The @code{-var-show-format} Command
27548 @findex -var-show-format
27550 @subsubheading Synopsis
27553 -var-show-format @var{name}
27556 Returns the format used to display the value of the object @var{name}.
27559 @var{format} @expansion{}
27564 @subheading The @code{-var-info-num-children} Command
27565 @findex -var-info-num-children
27567 @subsubheading Synopsis
27570 -var-info-num-children @var{name}
27573 Returns the number of children of a variable object @var{name}:
27579 Note that this number is not completely reliable for a dynamic varobj.
27580 It will return the current number of children, but more children may
27584 @subheading The @code{-var-list-children} Command
27585 @findex -var-list-children
27587 @subsubheading Synopsis
27590 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27592 @anchor{-var-list-children}
27594 Return a list of the children of the specified variable object and
27595 create variable objects for them, if they do not already exist. With
27596 a single argument or if @var{print-values} has a value of 0 or
27597 @code{--no-values}, print only the names of the variables; if
27598 @var{print-values} is 1 or @code{--all-values}, also print their
27599 values; and if it is 2 or @code{--simple-values} print the name and
27600 value for simple data types and just the name for arrays, structures
27603 @var{from} and @var{to}, if specified, indicate the range of children
27604 to report. If @var{from} or @var{to} is less than zero, the range is
27605 reset and all children will be reported. Otherwise, children starting
27606 at @var{from} (zero-based) and up to and excluding @var{to} will be
27609 If a child range is requested, it will only affect the current call to
27610 @code{-var-list-children}, but not future calls to @code{-var-update}.
27611 For this, you must instead use @code{-var-set-update-range}. The
27612 intent of this approach is to enable a front end to implement any
27613 update approach it likes; for example, scrolling a view may cause the
27614 front end to request more children with @code{-var-list-children}, and
27615 then the front end could call @code{-var-set-update-range} with a
27616 different range to ensure that future updates are restricted to just
27619 For each child the following results are returned:
27624 Name of the variable object created for this child.
27627 The expression to be shown to the user by the front end to designate this child.
27628 For example this may be the name of a structure member.
27630 For a dynamic varobj, this value cannot be used to form an
27631 expression. There is no way to do this at all with a dynamic varobj.
27633 For C/C@t{++} structures there are several pseudo children returned to
27634 designate access qualifiers. For these pseudo children @var{exp} is
27635 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27636 type and value are not present.
27638 A dynamic varobj will not report the access qualifying
27639 pseudo-children, regardless of the language. This information is not
27640 available at all with a dynamic varobj.
27643 Number of children this child has. For a dynamic varobj, this will be
27647 The type of the child.
27650 If values were requested, this is the value.
27653 If this variable object is associated with a thread, this is the thread id.
27654 Otherwise this result is not present.
27657 If the variable object is frozen, this variable will be present with a value of 1.
27660 The result may have its own attributes:
27664 A dynamic varobj can supply a display hint to the front end. The
27665 value comes directly from the Python pretty-printer object's
27666 @code{display_hint} method. @xref{Pretty Printing API}.
27669 This is an integer attribute which is nonzero if there are children
27670 remaining after the end of the selected range.
27673 @subsubheading Example
27677 -var-list-children n
27678 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27679 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27681 -var-list-children --all-values n
27682 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27683 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27687 @subheading The @code{-var-info-type} Command
27688 @findex -var-info-type
27690 @subsubheading Synopsis
27693 -var-info-type @var{name}
27696 Returns the type of the specified variable @var{name}. The type is
27697 returned as a string in the same format as it is output by the
27701 type=@var{typename}
27705 @subheading The @code{-var-info-expression} Command
27706 @findex -var-info-expression
27708 @subsubheading Synopsis
27711 -var-info-expression @var{name}
27714 Returns a string that is suitable for presenting this
27715 variable object in user interface. The string is generally
27716 not valid expression in the current language, and cannot be evaluated.
27718 For example, if @code{a} is an array, and variable object
27719 @code{A} was created for @code{a}, then we'll get this output:
27722 (gdb) -var-info-expression A.1
27723 ^done,lang="C",exp="1"
27727 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27729 Note that the output of the @code{-var-list-children} command also
27730 includes those expressions, so the @code{-var-info-expression} command
27733 @subheading The @code{-var-info-path-expression} Command
27734 @findex -var-info-path-expression
27736 @subsubheading Synopsis
27739 -var-info-path-expression @var{name}
27742 Returns an expression that can be evaluated in the current
27743 context and will yield the same value that a variable object has.
27744 Compare this with the @code{-var-info-expression} command, which
27745 result can be used only for UI presentation. Typical use of
27746 the @code{-var-info-path-expression} command is creating a
27747 watchpoint from a variable object.
27749 This command is currently not valid for children of a dynamic varobj,
27750 and will give an error when invoked on one.
27752 For example, suppose @code{C} is a C@t{++} class, derived from class
27753 @code{Base}, and that the @code{Base} class has a member called
27754 @code{m_size}. Assume a variable @code{c} is has the type of
27755 @code{C} and a variable object @code{C} was created for variable
27756 @code{c}. Then, we'll get this output:
27758 (gdb) -var-info-path-expression C.Base.public.m_size
27759 ^done,path_expr=((Base)c).m_size)
27762 @subheading The @code{-var-show-attributes} Command
27763 @findex -var-show-attributes
27765 @subsubheading Synopsis
27768 -var-show-attributes @var{name}
27771 List attributes of the specified variable object @var{name}:
27774 status=@var{attr} [ ( ,@var{attr} )* ]
27778 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27780 @subheading The @code{-var-evaluate-expression} Command
27781 @findex -var-evaluate-expression
27783 @subsubheading Synopsis
27786 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27789 Evaluates the expression that is represented by the specified variable
27790 object and returns its value as a string. The format of the string
27791 can be specified with the @samp{-f} option. The possible values of
27792 this option are the same as for @code{-var-set-format}
27793 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27794 the current display format will be used. The current display format
27795 can be changed using the @code{-var-set-format} command.
27801 Note that one must invoke @code{-var-list-children} for a variable
27802 before the value of a child variable can be evaluated.
27804 @subheading The @code{-var-assign} Command
27805 @findex -var-assign
27807 @subsubheading Synopsis
27810 -var-assign @var{name} @var{expression}
27813 Assigns the value of @var{expression} to the variable object specified
27814 by @var{name}. The object must be @samp{editable}. If the variable's
27815 value is altered by the assign, the variable will show up in any
27816 subsequent @code{-var-update} list.
27818 @subsubheading Example
27826 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27830 @subheading The @code{-var-update} Command
27831 @findex -var-update
27833 @subsubheading Synopsis
27836 -var-update [@var{print-values}] @{@var{name} | "*"@}
27839 Reevaluate the expressions corresponding to the variable object
27840 @var{name} and all its direct and indirect children, and return the
27841 list of variable objects whose values have changed; @var{name} must
27842 be a root variable object. Here, ``changed'' means that the result of
27843 @code{-var-evaluate-expression} before and after the
27844 @code{-var-update} is different. If @samp{*} is used as the variable
27845 object names, all existing variable objects are updated, except
27846 for frozen ones (@pxref{-var-set-frozen}). The option
27847 @var{print-values} determines whether both names and values, or just
27848 names are printed. The possible values of this option are the same
27849 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27850 recommended to use the @samp{--all-values} option, to reduce the
27851 number of MI commands needed on each program stop.
27853 With the @samp{*} parameter, if a variable object is bound to a
27854 currently running thread, it will not be updated, without any
27857 If @code{-var-set-update-range} was previously used on a varobj, then
27858 only the selected range of children will be reported.
27860 @code{-var-update} reports all the changed varobjs in a tuple named
27863 Each item in the change list is itself a tuple holding:
27867 The name of the varobj.
27870 If values were requested for this update, then this field will be
27871 present and will hold the value of the varobj.
27874 @anchor{-var-update}
27875 This field is a string which may take one of three values:
27879 The variable object's current value is valid.
27882 The variable object does not currently hold a valid value but it may
27883 hold one in the future if its associated expression comes back into
27887 The variable object no longer holds a valid value.
27888 This can occur when the executable file being debugged has changed,
27889 either through recompilation or by using the @value{GDBN} @code{file}
27890 command. The front end should normally choose to delete these variable
27894 In the future new values may be added to this list so the front should
27895 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27898 This is only present if the varobj is still valid. If the type
27899 changed, then this will be the string @samp{true}; otherwise it will
27903 If the varobj's type changed, then this field will be present and will
27906 @item new_num_children
27907 For a dynamic varobj, if the number of children changed, or if the
27908 type changed, this will be the new number of children.
27910 The @samp{numchild} field in other varobj responses is generally not
27911 valid for a dynamic varobj -- it will show the number of children that
27912 @value{GDBN} knows about, but because dynamic varobjs lazily
27913 instantiate their children, this will not reflect the number of
27914 children which may be available.
27916 The @samp{new_num_children} attribute only reports changes to the
27917 number of children known by @value{GDBN}. This is the only way to
27918 detect whether an update has removed children (which necessarily can
27919 only happen at the end of the update range).
27922 The display hint, if any.
27925 This is an integer value, which will be 1 if there are more children
27926 available outside the varobj's update range.
27929 This attribute will be present and have the value @samp{1} if the
27930 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27931 then this attribute will not be present.
27934 If new children were added to a dynamic varobj within the selected
27935 update range (as set by @code{-var-set-update-range}), then they will
27936 be listed in this attribute.
27939 @subsubheading Example
27946 -var-update --all-values var1
27947 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27948 type_changed="false"@}]
27952 @subheading The @code{-var-set-frozen} Command
27953 @findex -var-set-frozen
27954 @anchor{-var-set-frozen}
27956 @subsubheading Synopsis
27959 -var-set-frozen @var{name} @var{flag}
27962 Set the frozenness flag on the variable object @var{name}. The
27963 @var{flag} parameter should be either @samp{1} to make the variable
27964 frozen or @samp{0} to make it unfrozen. If a variable object is
27965 frozen, then neither itself, nor any of its children, are
27966 implicitly updated by @code{-var-update} of
27967 a parent variable or by @code{-var-update *}. Only
27968 @code{-var-update} of the variable itself will update its value and
27969 values of its children. After a variable object is unfrozen, it is
27970 implicitly updated by all subsequent @code{-var-update} operations.
27971 Unfreezing a variable does not update it, only subsequent
27972 @code{-var-update} does.
27974 @subsubheading Example
27978 -var-set-frozen V 1
27983 @subheading The @code{-var-set-update-range} command
27984 @findex -var-set-update-range
27985 @anchor{-var-set-update-range}
27987 @subsubheading Synopsis
27990 -var-set-update-range @var{name} @var{from} @var{to}
27993 Set the range of children to be returned by future invocations of
27994 @code{-var-update}.
27996 @var{from} and @var{to} indicate the range of children to report. If
27997 @var{from} or @var{to} is less than zero, the range is reset and all
27998 children will be reported. Otherwise, children starting at @var{from}
27999 (zero-based) and up to and excluding @var{to} will be reported.
28001 @subsubheading Example
28005 -var-set-update-range V 1 2
28009 @subheading The @code{-var-set-visualizer} command
28010 @findex -var-set-visualizer
28011 @anchor{-var-set-visualizer}
28013 @subsubheading Synopsis
28016 -var-set-visualizer @var{name} @var{visualizer}
28019 Set a visualizer for the variable object @var{name}.
28021 @var{visualizer} is the visualizer to use. The special value
28022 @samp{None} means to disable any visualizer in use.
28024 If not @samp{None}, @var{visualizer} must be a Python expression.
28025 This expression must evaluate to a callable object which accepts a
28026 single argument. @value{GDBN} will call this object with the value of
28027 the varobj @var{name} as an argument (this is done so that the same
28028 Python pretty-printing code can be used for both the CLI and MI).
28029 When called, this object must return an object which conforms to the
28030 pretty-printing interface (@pxref{Pretty Printing API}).
28032 The pre-defined function @code{gdb.default_visualizer} may be used to
28033 select a visualizer by following the built-in process
28034 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28035 a varobj is created, and so ordinarily is not needed.
28037 This feature is only available if Python support is enabled. The MI
28038 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
28039 can be used to check this.
28041 @subsubheading Example
28043 Resetting the visualizer:
28047 -var-set-visualizer V None
28051 Reselecting the default (type-based) visualizer:
28055 -var-set-visualizer V gdb.default_visualizer
28059 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28060 can be used to instantiate this class for a varobj:
28064 -var-set-visualizer V "lambda val: SomeClass()"
28068 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28069 @node GDB/MI Data Manipulation
28070 @section @sc{gdb/mi} Data Manipulation
28072 @cindex data manipulation, in @sc{gdb/mi}
28073 @cindex @sc{gdb/mi}, data manipulation
28074 This section describes the @sc{gdb/mi} commands that manipulate data:
28075 examine memory and registers, evaluate expressions, etc.
28077 @c REMOVED FROM THE INTERFACE.
28078 @c @subheading -data-assign
28079 @c Change the value of a program variable. Plenty of side effects.
28080 @c @subsubheading GDB Command
28082 @c @subsubheading Example
28085 @subheading The @code{-data-disassemble} Command
28086 @findex -data-disassemble
28088 @subsubheading Synopsis
28092 [ -s @var{start-addr} -e @var{end-addr} ]
28093 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28101 @item @var{start-addr}
28102 is the beginning address (or @code{$pc})
28103 @item @var{end-addr}
28105 @item @var{filename}
28106 is the name of the file to disassemble
28107 @item @var{linenum}
28108 is the line number to disassemble around
28110 is the number of disassembly lines to be produced. If it is -1,
28111 the whole function will be disassembled, in case no @var{end-addr} is
28112 specified. If @var{end-addr} is specified as a non-zero value, and
28113 @var{lines} is lower than the number of disassembly lines between
28114 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28115 displayed; if @var{lines} is higher than the number of lines between
28116 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28119 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28120 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28121 mixed source and disassembly with raw opcodes).
28124 @subsubheading Result
28126 The output for each instruction is composed of four fields:
28135 Note that whatever included in the instruction field, is not manipulated
28136 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
28138 @subsubheading @value{GDBN} Command
28140 There's no direct mapping from this command to the CLI.
28142 @subsubheading Example
28144 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28148 -data-disassemble -s $pc -e "$pc + 20" -- 0
28151 @{address="0x000107c0",func-name="main",offset="4",
28152 inst="mov 2, %o0"@},
28153 @{address="0x000107c4",func-name="main",offset="8",
28154 inst="sethi %hi(0x11800), %o2"@},
28155 @{address="0x000107c8",func-name="main",offset="12",
28156 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28157 @{address="0x000107cc",func-name="main",offset="16",
28158 inst="sethi %hi(0x11800), %o2"@},
28159 @{address="0x000107d0",func-name="main",offset="20",
28160 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28164 Disassemble the whole @code{main} function. Line 32 is part of
28168 -data-disassemble -f basics.c -l 32 -- 0
28170 @{address="0x000107bc",func-name="main",offset="0",
28171 inst="save %sp, -112, %sp"@},
28172 @{address="0x000107c0",func-name="main",offset="4",
28173 inst="mov 2, %o0"@},
28174 @{address="0x000107c4",func-name="main",offset="8",
28175 inst="sethi %hi(0x11800), %o2"@},
28177 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
28178 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
28182 Disassemble 3 instructions from the start of @code{main}:
28186 -data-disassemble -f basics.c -l 32 -n 3 -- 0
28188 @{address="0x000107bc",func-name="main",offset="0",
28189 inst="save %sp, -112, %sp"@},
28190 @{address="0x000107c0",func-name="main",offset="4",
28191 inst="mov 2, %o0"@},
28192 @{address="0x000107c4",func-name="main",offset="8",
28193 inst="sethi %hi(0x11800), %o2"@}]
28197 Disassemble 3 instructions from the start of @code{main} in mixed mode:
28201 -data-disassemble -f basics.c -l 32 -n 3 -- 1
28203 src_and_asm_line=@{line="31",
28204 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28205 testsuite/gdb.mi/basics.c",line_asm_insn=[
28206 @{address="0x000107bc",func-name="main",offset="0",
28207 inst="save %sp, -112, %sp"@}]@},
28208 src_and_asm_line=@{line="32",
28209 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28210 testsuite/gdb.mi/basics.c",line_asm_insn=[
28211 @{address="0x000107c0",func-name="main",offset="4",
28212 inst="mov 2, %o0"@},
28213 @{address="0x000107c4",func-name="main",offset="8",
28214 inst="sethi %hi(0x11800), %o2"@}]@}]
28219 @subheading The @code{-data-evaluate-expression} Command
28220 @findex -data-evaluate-expression
28222 @subsubheading Synopsis
28225 -data-evaluate-expression @var{expr}
28228 Evaluate @var{expr} as an expression. The expression could contain an
28229 inferior function call. The function call will execute synchronously.
28230 If the expression contains spaces, it must be enclosed in double quotes.
28232 @subsubheading @value{GDBN} Command
28234 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
28235 @samp{call}. In @code{gdbtk} only, there's a corresponding
28236 @samp{gdb_eval} command.
28238 @subsubheading Example
28240 In the following example, the numbers that precede the commands are the
28241 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
28242 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
28246 211-data-evaluate-expression A
28249 311-data-evaluate-expression &A
28250 311^done,value="0xefffeb7c"
28252 411-data-evaluate-expression A+3
28255 511-data-evaluate-expression "A + 3"
28261 @subheading The @code{-data-list-changed-registers} Command
28262 @findex -data-list-changed-registers
28264 @subsubheading Synopsis
28267 -data-list-changed-registers
28270 Display a list of the registers that have changed.
28272 @subsubheading @value{GDBN} Command
28274 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
28275 has the corresponding command @samp{gdb_changed_register_list}.
28277 @subsubheading Example
28279 On a PPC MBX board:
28287 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
28288 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
28291 -data-list-changed-registers
28292 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
28293 "10","11","13","14","15","16","17","18","19","20","21","22","23",
28294 "24","25","26","27","28","30","31","64","65","66","67","69"]
28299 @subheading The @code{-data-list-register-names} Command
28300 @findex -data-list-register-names
28302 @subsubheading Synopsis
28305 -data-list-register-names [ ( @var{regno} )+ ]
28308 Show a list of register names for the current target. If no arguments
28309 are given, it shows a list of the names of all the registers. If
28310 integer numbers are given as arguments, it will print a list of the
28311 names of the registers corresponding to the arguments. To ensure
28312 consistency between a register name and its number, the output list may
28313 include empty register names.
28315 @subsubheading @value{GDBN} Command
28317 @value{GDBN} does not have a command which corresponds to
28318 @samp{-data-list-register-names}. In @code{gdbtk} there is a
28319 corresponding command @samp{gdb_regnames}.
28321 @subsubheading Example
28323 For the PPC MBX board:
28326 -data-list-register-names
28327 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
28328 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
28329 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
28330 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
28331 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
28332 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
28333 "", "pc","ps","cr","lr","ctr","xer"]
28335 -data-list-register-names 1 2 3
28336 ^done,register-names=["r1","r2","r3"]
28340 @subheading The @code{-data-list-register-values} Command
28341 @findex -data-list-register-values
28343 @subsubheading Synopsis
28346 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
28349 Display the registers' contents. @var{fmt} is the format according to
28350 which the registers' contents are to be returned, followed by an optional
28351 list of numbers specifying the registers to display. A missing list of
28352 numbers indicates that the contents of all the registers must be returned.
28354 Allowed formats for @var{fmt} are:
28371 @subsubheading @value{GDBN} Command
28373 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
28374 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
28376 @subsubheading Example
28378 For a PPC MBX board (note: line breaks are for readability only, they
28379 don't appear in the actual output):
28383 -data-list-register-values r 64 65
28384 ^done,register-values=[@{number="64",value="0xfe00a300"@},
28385 @{number="65",value="0x00029002"@}]
28387 -data-list-register-values x
28388 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
28389 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
28390 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
28391 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
28392 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
28393 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
28394 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
28395 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
28396 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
28397 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
28398 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
28399 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
28400 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
28401 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
28402 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
28403 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
28404 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
28405 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
28406 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
28407 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
28408 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
28409 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
28410 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
28411 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
28412 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
28413 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
28414 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
28415 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
28416 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
28417 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
28418 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
28419 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
28420 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
28421 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
28422 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
28423 @{number="69",value="0x20002b03"@}]
28428 @subheading The @code{-data-read-memory} Command
28429 @findex -data-read-memory
28431 This command is deprecated, use @code{-data-read-memory-bytes} instead.
28433 @subsubheading Synopsis
28436 -data-read-memory [ -o @var{byte-offset} ]
28437 @var{address} @var{word-format} @var{word-size}
28438 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
28445 @item @var{address}
28446 An expression specifying the address of the first memory word to be
28447 read. Complex expressions containing embedded white space should be
28448 quoted using the C convention.
28450 @item @var{word-format}
28451 The format to be used to print the memory words. The notation is the
28452 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
28455 @item @var{word-size}
28456 The size of each memory word in bytes.
28458 @item @var{nr-rows}
28459 The number of rows in the output table.
28461 @item @var{nr-cols}
28462 The number of columns in the output table.
28465 If present, indicates that each row should include an @sc{ascii} dump. The
28466 value of @var{aschar} is used as a padding character when a byte is not a
28467 member of the printable @sc{ascii} character set (printable @sc{ascii}
28468 characters are those whose code is between 32 and 126, inclusively).
28470 @item @var{byte-offset}
28471 An offset to add to the @var{address} before fetching memory.
28474 This command displays memory contents as a table of @var{nr-rows} by
28475 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
28476 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
28477 (returned as @samp{total-bytes}). Should less than the requested number
28478 of bytes be returned by the target, the missing words are identified
28479 using @samp{N/A}. The number of bytes read from the target is returned
28480 in @samp{nr-bytes} and the starting address used to read memory in
28483 The address of the next/previous row or page is available in
28484 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
28487 @subsubheading @value{GDBN} Command
28489 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
28490 @samp{gdb_get_mem} memory read command.
28492 @subsubheading Example
28494 Read six bytes of memory starting at @code{bytes+6} but then offset by
28495 @code{-6} bytes. Format as three rows of two columns. One byte per
28496 word. Display each word in hex.
28500 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
28501 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
28502 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
28503 prev-page="0x0000138a",memory=[
28504 @{addr="0x00001390",data=["0x00","0x01"]@},
28505 @{addr="0x00001392",data=["0x02","0x03"]@},
28506 @{addr="0x00001394",data=["0x04","0x05"]@}]
28510 Read two bytes of memory starting at address @code{shorts + 64} and
28511 display as a single word formatted in decimal.
28515 5-data-read-memory shorts+64 d 2 1 1
28516 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28517 next-row="0x00001512",prev-row="0x0000150e",
28518 next-page="0x00001512",prev-page="0x0000150e",memory=[
28519 @{addr="0x00001510",data=["128"]@}]
28523 Read thirty two bytes of memory starting at @code{bytes+16} and format
28524 as eight rows of four columns. Include a string encoding with @samp{x}
28525 used as the non-printable character.
28529 4-data-read-memory bytes+16 x 1 8 4 x
28530 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28531 next-row="0x000013c0",prev-row="0x0000139c",
28532 next-page="0x000013c0",prev-page="0x00001380",memory=[
28533 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28534 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28535 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28536 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28537 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28538 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28539 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28540 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28544 @subheading The @code{-data-read-memory-bytes} Command
28545 @findex -data-read-memory-bytes
28547 @subsubheading Synopsis
28550 -data-read-memory-bytes [ -o @var{byte-offset} ]
28551 @var{address} @var{count}
28558 @item @var{address}
28559 An expression specifying the address of the first memory word to be
28560 read. Complex expressions containing embedded white space should be
28561 quoted using the C convention.
28564 The number of bytes to read. This should be an integer literal.
28566 @item @var{byte-offset}
28567 The offsets in bytes relative to @var{address} at which to start
28568 reading. This should be an integer literal. This option is provided
28569 so that a frontend is not required to first evaluate address and then
28570 perform address arithmetics itself.
28574 This command attempts to read all accessible memory regions in the
28575 specified range. First, all regions marked as unreadable in the memory
28576 map (if one is defined) will be skipped. @xref{Memory Region
28577 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28578 regions. For each one, if reading full region results in an errors,
28579 @value{GDBN} will try to read a subset of the region.
28581 In general, every single byte in the region may be readable or not,
28582 and the only way to read every readable byte is to try a read at
28583 every address, which is not practical. Therefore, @value{GDBN} will
28584 attempt to read all accessible bytes at either beginning or the end
28585 of the region, using a binary division scheme. This heuristic works
28586 well for reading accross a memory map boundary. Note that if a region
28587 has a readable range that is neither at the beginning or the end,
28588 @value{GDBN} will not read it.
28590 The result record (@pxref{GDB/MI Result Records}) that is output of
28591 the command includes a field named @samp{memory} whose content is a
28592 list of tuples. Each tuple represent a successfully read memory block
28593 and has the following fields:
28597 The start address of the memory block, as hexadecimal literal.
28600 The end address of the memory block, as hexadecimal literal.
28603 The offset of the memory block, as hexadecimal literal, relative to
28604 the start address passed to @code{-data-read-memory-bytes}.
28607 The contents of the memory block, in hex.
28613 @subsubheading @value{GDBN} Command
28615 The corresponding @value{GDBN} command is @samp{x}.
28617 @subsubheading Example
28621 -data-read-memory-bytes &a 10
28622 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28624 contents="01000000020000000300"@}]
28629 @subheading The @code{-data-write-memory-bytes} Command
28630 @findex -data-write-memory-bytes
28632 @subsubheading Synopsis
28635 -data-write-memory-bytes @var{address} @var{contents}
28642 @item @var{address}
28643 An expression specifying the address of the first memory word to be
28644 read. Complex expressions containing embedded white space should be
28645 quoted using the C convention.
28647 @item @var{contents}
28648 The hex-encoded bytes to write.
28652 @subsubheading @value{GDBN} Command
28654 There's no corresponding @value{GDBN} command.
28656 @subsubheading Example
28660 -data-write-memory-bytes &a "aabbccdd"
28666 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28667 @node GDB/MI Tracepoint Commands
28668 @section @sc{gdb/mi} Tracepoint Commands
28670 The commands defined in this section implement MI support for
28671 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28673 @subheading The @code{-trace-find} Command
28674 @findex -trace-find
28676 @subsubheading Synopsis
28679 -trace-find @var{mode} [@var{parameters}@dots{}]
28682 Find a trace frame using criteria defined by @var{mode} and
28683 @var{parameters}. The following table lists permissible
28684 modes and their parameters. For details of operation, see @ref{tfind}.
28689 No parameters are required. Stops examining trace frames.
28692 An integer is required as parameter. Selects tracepoint frame with
28695 @item tracepoint-number
28696 An integer is required as parameter. Finds next
28697 trace frame that corresponds to tracepoint with the specified number.
28700 An address is required as parameter. Finds
28701 next trace frame that corresponds to any tracepoint at the specified
28704 @item pc-inside-range
28705 Two addresses are required as parameters. Finds next trace
28706 frame that corresponds to a tracepoint at an address inside the
28707 specified range. Both bounds are considered to be inside the range.
28709 @item pc-outside-range
28710 Two addresses are required as parameters. Finds
28711 next trace frame that corresponds to a tracepoint at an address outside
28712 the specified range. Both bounds are considered to be inside the range.
28715 Line specification is required as parameter. @xref{Specify Location}.
28716 Finds next trace frame that corresponds to a tracepoint at
28717 the specified location.
28721 If @samp{none} was passed as @var{mode}, the response does not
28722 have fields. Otherwise, the response may have the following fields:
28726 This field has either @samp{0} or @samp{1} as the value, depending
28727 on whether a matching tracepoint was found.
28730 The index of the found traceframe. This field is present iff
28731 the @samp{found} field has value of @samp{1}.
28734 The index of the found tracepoint. This field is present iff
28735 the @samp{found} field has value of @samp{1}.
28738 The information about the frame corresponding to the found trace
28739 frame. This field is present only if a trace frame was found.
28740 @xref{GDB/MI Frame Information}, for description of this field.
28744 @subsubheading @value{GDBN} Command
28746 The corresponding @value{GDBN} command is @samp{tfind}.
28748 @subheading -trace-define-variable
28749 @findex -trace-define-variable
28751 @subsubheading Synopsis
28754 -trace-define-variable @var{name} [ @var{value} ]
28757 Create trace variable @var{name} if it does not exist. If
28758 @var{value} is specified, sets the initial value of the specified
28759 trace variable to that value. Note that the @var{name} should start
28760 with the @samp{$} character.
28762 @subsubheading @value{GDBN} Command
28764 The corresponding @value{GDBN} command is @samp{tvariable}.
28766 @subheading -trace-list-variables
28767 @findex -trace-list-variables
28769 @subsubheading Synopsis
28772 -trace-list-variables
28775 Return a table of all defined trace variables. Each element of the
28776 table has the following fields:
28780 The name of the trace variable. This field is always present.
28783 The initial value. This is a 64-bit signed integer. This
28784 field is always present.
28787 The value the trace variable has at the moment. This is a 64-bit
28788 signed integer. This field is absent iff current value is
28789 not defined, for example if the trace was never run, or is
28794 @subsubheading @value{GDBN} Command
28796 The corresponding @value{GDBN} command is @samp{tvariables}.
28798 @subsubheading Example
28802 -trace-list-variables
28803 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28804 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28805 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28806 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28807 body=[variable=@{name="$trace_timestamp",initial="0"@}
28808 variable=@{name="$foo",initial="10",current="15"@}]@}
28812 @subheading -trace-save
28813 @findex -trace-save
28815 @subsubheading Synopsis
28818 -trace-save [-r ] @var{filename}
28821 Saves the collected trace data to @var{filename}. Without the
28822 @samp{-r} option, the data is downloaded from the target and saved
28823 in a local file. With the @samp{-r} option the target is asked
28824 to perform the save.
28826 @subsubheading @value{GDBN} Command
28828 The corresponding @value{GDBN} command is @samp{tsave}.
28831 @subheading -trace-start
28832 @findex -trace-start
28834 @subsubheading Synopsis
28840 Starts a tracing experiments. The result of this command does not
28843 @subsubheading @value{GDBN} Command
28845 The corresponding @value{GDBN} command is @samp{tstart}.
28847 @subheading -trace-status
28848 @findex -trace-status
28850 @subsubheading Synopsis
28856 Obtains the status of a tracing experiment. The result may include
28857 the following fields:
28862 May have a value of either @samp{0}, when no tracing operations are
28863 supported, @samp{1}, when all tracing operations are supported, or
28864 @samp{file} when examining trace file. In the latter case, examining
28865 of trace frame is possible but new tracing experiement cannot be
28866 started. This field is always present.
28869 May have a value of either @samp{0} or @samp{1} depending on whether
28870 tracing experiement is in progress on target. This field is present
28871 if @samp{supported} field is not @samp{0}.
28874 Report the reason why the tracing was stopped last time. This field
28875 may be absent iff tracing was never stopped on target yet. The
28876 value of @samp{request} means the tracing was stopped as result of
28877 the @code{-trace-stop} command. The value of @samp{overflow} means
28878 the tracing buffer is full. The value of @samp{disconnection} means
28879 tracing was automatically stopped when @value{GDBN} has disconnected.
28880 The value of @samp{passcount} means tracing was stopped when a
28881 tracepoint was passed a maximal number of times for that tracepoint.
28882 This field is present if @samp{supported} field is not @samp{0}.
28884 @item stopping-tracepoint
28885 The number of tracepoint whose passcount as exceeded. This field is
28886 present iff the @samp{stop-reason} field has the value of
28890 @itemx frames-created
28891 The @samp{frames} field is a count of the total number of trace frames
28892 in the trace buffer, while @samp{frames-created} is the total created
28893 during the run, including ones that were discarded, such as when a
28894 circular trace buffer filled up. Both fields are optional.
28898 These fields tell the current size of the tracing buffer and the
28899 remaining space. These fields are optional.
28902 The value of the circular trace buffer flag. @code{1} means that the
28903 trace buffer is circular and old trace frames will be discarded if
28904 necessary to make room, @code{0} means that the trace buffer is linear
28908 The value of the disconnected tracing flag. @code{1} means that
28909 tracing will continue after @value{GDBN} disconnects, @code{0} means
28910 that the trace run will stop.
28914 @subsubheading @value{GDBN} Command
28916 The corresponding @value{GDBN} command is @samp{tstatus}.
28918 @subheading -trace-stop
28919 @findex -trace-stop
28921 @subsubheading Synopsis
28927 Stops a tracing experiment. The result of this command has the same
28928 fields as @code{-trace-status}, except that the @samp{supported} and
28929 @samp{running} fields are not output.
28931 @subsubheading @value{GDBN} Command
28933 The corresponding @value{GDBN} command is @samp{tstop}.
28936 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28937 @node GDB/MI Symbol Query
28938 @section @sc{gdb/mi} Symbol Query Commands
28942 @subheading The @code{-symbol-info-address} Command
28943 @findex -symbol-info-address
28945 @subsubheading Synopsis
28948 -symbol-info-address @var{symbol}
28951 Describe where @var{symbol} is stored.
28953 @subsubheading @value{GDBN} Command
28955 The corresponding @value{GDBN} command is @samp{info address}.
28957 @subsubheading Example
28961 @subheading The @code{-symbol-info-file} Command
28962 @findex -symbol-info-file
28964 @subsubheading Synopsis
28970 Show the file for the symbol.
28972 @subsubheading @value{GDBN} Command
28974 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28975 @samp{gdb_find_file}.
28977 @subsubheading Example
28981 @subheading The @code{-symbol-info-function} Command
28982 @findex -symbol-info-function
28984 @subsubheading Synopsis
28987 -symbol-info-function
28990 Show which function the symbol lives in.
28992 @subsubheading @value{GDBN} Command
28994 @samp{gdb_get_function} in @code{gdbtk}.
28996 @subsubheading Example
29000 @subheading The @code{-symbol-info-line} Command
29001 @findex -symbol-info-line
29003 @subsubheading Synopsis
29009 Show the core addresses of the code for a source line.
29011 @subsubheading @value{GDBN} Command
29013 The corresponding @value{GDBN} command is @samp{info line}.
29014 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29016 @subsubheading Example
29020 @subheading The @code{-symbol-info-symbol} Command
29021 @findex -symbol-info-symbol
29023 @subsubheading Synopsis
29026 -symbol-info-symbol @var{addr}
29029 Describe what symbol is at location @var{addr}.
29031 @subsubheading @value{GDBN} Command
29033 The corresponding @value{GDBN} command is @samp{info symbol}.
29035 @subsubheading Example
29039 @subheading The @code{-symbol-list-functions} Command
29040 @findex -symbol-list-functions
29042 @subsubheading Synopsis
29045 -symbol-list-functions
29048 List the functions in the executable.
29050 @subsubheading @value{GDBN} Command
29052 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29053 @samp{gdb_search} in @code{gdbtk}.
29055 @subsubheading Example
29060 @subheading The @code{-symbol-list-lines} Command
29061 @findex -symbol-list-lines
29063 @subsubheading Synopsis
29066 -symbol-list-lines @var{filename}
29069 Print the list of lines that contain code and their associated program
29070 addresses for the given source filename. The entries are sorted in
29071 ascending PC order.
29073 @subsubheading @value{GDBN} Command
29075 There is no corresponding @value{GDBN} command.
29077 @subsubheading Example
29080 -symbol-list-lines basics.c
29081 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29087 @subheading The @code{-symbol-list-types} Command
29088 @findex -symbol-list-types
29090 @subsubheading Synopsis
29096 List all the type names.
29098 @subsubheading @value{GDBN} Command
29100 The corresponding commands are @samp{info types} in @value{GDBN},
29101 @samp{gdb_search} in @code{gdbtk}.
29103 @subsubheading Example
29107 @subheading The @code{-symbol-list-variables} Command
29108 @findex -symbol-list-variables
29110 @subsubheading Synopsis
29113 -symbol-list-variables
29116 List all the global and static variable names.
29118 @subsubheading @value{GDBN} Command
29120 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
29122 @subsubheading Example
29126 @subheading The @code{-symbol-locate} Command
29127 @findex -symbol-locate
29129 @subsubheading Synopsis
29135 @subsubheading @value{GDBN} Command
29137 @samp{gdb_loc} in @code{gdbtk}.
29139 @subsubheading Example
29143 @subheading The @code{-symbol-type} Command
29144 @findex -symbol-type
29146 @subsubheading Synopsis
29149 -symbol-type @var{variable}
29152 Show type of @var{variable}.
29154 @subsubheading @value{GDBN} Command
29156 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
29157 @samp{gdb_obj_variable}.
29159 @subsubheading Example
29164 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29165 @node GDB/MI File Commands
29166 @section @sc{gdb/mi} File Commands
29168 This section describes the GDB/MI commands to specify executable file names
29169 and to read in and obtain symbol table information.
29171 @subheading The @code{-file-exec-and-symbols} Command
29172 @findex -file-exec-and-symbols
29174 @subsubheading Synopsis
29177 -file-exec-and-symbols @var{file}
29180 Specify the executable file to be debugged. This file is the one from
29181 which the symbol table is also read. If no file is specified, the
29182 command clears the executable and symbol information. If breakpoints
29183 are set when using this command with no arguments, @value{GDBN} will produce
29184 error messages. Otherwise, no output is produced, except a completion
29187 @subsubheading @value{GDBN} Command
29189 The corresponding @value{GDBN} command is @samp{file}.
29191 @subsubheading Example
29195 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29201 @subheading The @code{-file-exec-file} Command
29202 @findex -file-exec-file
29204 @subsubheading Synopsis
29207 -file-exec-file @var{file}
29210 Specify the executable file to be debugged. Unlike
29211 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
29212 from this file. If used without argument, @value{GDBN} clears the information
29213 about the executable file. No output is produced, except a completion
29216 @subsubheading @value{GDBN} Command
29218 The corresponding @value{GDBN} command is @samp{exec-file}.
29220 @subsubheading Example
29224 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29231 @subheading The @code{-file-list-exec-sections} Command
29232 @findex -file-list-exec-sections
29234 @subsubheading Synopsis
29237 -file-list-exec-sections
29240 List the sections of the current executable file.
29242 @subsubheading @value{GDBN} Command
29244 The @value{GDBN} command @samp{info file} shows, among the rest, the same
29245 information as this command. @code{gdbtk} has a corresponding command
29246 @samp{gdb_load_info}.
29248 @subsubheading Example
29253 @subheading The @code{-file-list-exec-source-file} Command
29254 @findex -file-list-exec-source-file
29256 @subsubheading Synopsis
29259 -file-list-exec-source-file
29262 List the line number, the current source file, and the absolute path
29263 to the current source file for the current executable. The macro
29264 information field has a value of @samp{1} or @samp{0} depending on
29265 whether or not the file includes preprocessor macro information.
29267 @subsubheading @value{GDBN} Command
29269 The @value{GDBN} equivalent is @samp{info source}
29271 @subsubheading Example
29275 123-file-list-exec-source-file
29276 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
29281 @subheading The @code{-file-list-exec-source-files} Command
29282 @findex -file-list-exec-source-files
29284 @subsubheading Synopsis
29287 -file-list-exec-source-files
29290 List the source files for the current executable.
29292 It will always output the filename, but only when @value{GDBN} can find
29293 the absolute file name of a source file, will it output the fullname.
29295 @subsubheading @value{GDBN} Command
29297 The @value{GDBN} equivalent is @samp{info sources}.
29298 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
29300 @subsubheading Example
29303 -file-list-exec-source-files
29305 @{file=foo.c,fullname=/home/foo.c@},
29306 @{file=/home/bar.c,fullname=/home/bar.c@},
29307 @{file=gdb_could_not_find_fullpath.c@}]
29312 @subheading The @code{-file-list-shared-libraries} Command
29313 @findex -file-list-shared-libraries
29315 @subsubheading Synopsis
29318 -file-list-shared-libraries
29321 List the shared libraries in the program.
29323 @subsubheading @value{GDBN} Command
29325 The corresponding @value{GDBN} command is @samp{info shared}.
29327 @subsubheading Example
29331 @subheading The @code{-file-list-symbol-files} Command
29332 @findex -file-list-symbol-files
29334 @subsubheading Synopsis
29337 -file-list-symbol-files
29342 @subsubheading @value{GDBN} Command
29344 The corresponding @value{GDBN} command is @samp{info file} (part of it).
29346 @subsubheading Example
29351 @subheading The @code{-file-symbol-file} Command
29352 @findex -file-symbol-file
29354 @subsubheading Synopsis
29357 -file-symbol-file @var{file}
29360 Read symbol table info from the specified @var{file} argument. When
29361 used without arguments, clears @value{GDBN}'s symbol table info. No output is
29362 produced, except for a completion notification.
29364 @subsubheading @value{GDBN} Command
29366 The corresponding @value{GDBN} command is @samp{symbol-file}.
29368 @subsubheading Example
29372 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29378 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29379 @node GDB/MI Memory Overlay Commands
29380 @section @sc{gdb/mi} Memory Overlay Commands
29382 The memory overlay commands are not implemented.
29384 @c @subheading -overlay-auto
29386 @c @subheading -overlay-list-mapping-state
29388 @c @subheading -overlay-list-overlays
29390 @c @subheading -overlay-map
29392 @c @subheading -overlay-off
29394 @c @subheading -overlay-on
29396 @c @subheading -overlay-unmap
29398 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29399 @node GDB/MI Signal Handling Commands
29400 @section @sc{gdb/mi} Signal Handling Commands
29402 Signal handling commands are not implemented.
29404 @c @subheading -signal-handle
29406 @c @subheading -signal-list-handle-actions
29408 @c @subheading -signal-list-signal-types
29412 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29413 @node GDB/MI Target Manipulation
29414 @section @sc{gdb/mi} Target Manipulation Commands
29417 @subheading The @code{-target-attach} Command
29418 @findex -target-attach
29420 @subsubheading Synopsis
29423 -target-attach @var{pid} | @var{gid} | @var{file}
29426 Attach to a process @var{pid} or a file @var{file} outside of
29427 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
29428 group, the id previously returned by
29429 @samp{-list-thread-groups --available} must be used.
29431 @subsubheading @value{GDBN} Command
29433 The corresponding @value{GDBN} command is @samp{attach}.
29435 @subsubheading Example
29439 =thread-created,id="1"
29440 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
29446 @subheading The @code{-target-compare-sections} Command
29447 @findex -target-compare-sections
29449 @subsubheading Synopsis
29452 -target-compare-sections [ @var{section} ]
29455 Compare data of section @var{section} on target to the exec file.
29456 Without the argument, all sections are compared.
29458 @subsubheading @value{GDBN} Command
29460 The @value{GDBN} equivalent is @samp{compare-sections}.
29462 @subsubheading Example
29467 @subheading The @code{-target-detach} Command
29468 @findex -target-detach
29470 @subsubheading Synopsis
29473 -target-detach [ @var{pid} | @var{gid} ]
29476 Detach from the remote target which normally resumes its execution.
29477 If either @var{pid} or @var{gid} is specified, detaches from either
29478 the specified process, or specified thread group. There's no output.
29480 @subsubheading @value{GDBN} Command
29482 The corresponding @value{GDBN} command is @samp{detach}.
29484 @subsubheading Example
29494 @subheading The @code{-target-disconnect} Command
29495 @findex -target-disconnect
29497 @subsubheading Synopsis
29503 Disconnect from the remote target. There's no output and the target is
29504 generally not resumed.
29506 @subsubheading @value{GDBN} Command
29508 The corresponding @value{GDBN} command is @samp{disconnect}.
29510 @subsubheading Example
29520 @subheading The @code{-target-download} Command
29521 @findex -target-download
29523 @subsubheading Synopsis
29529 Loads the executable onto the remote target.
29530 It prints out an update message every half second, which includes the fields:
29534 The name of the section.
29536 The size of what has been sent so far for that section.
29538 The size of the section.
29540 The total size of what was sent so far (the current and the previous sections).
29542 The size of the overall executable to download.
29546 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29547 @sc{gdb/mi} Output Syntax}).
29549 In addition, it prints the name and size of the sections, as they are
29550 downloaded. These messages include the following fields:
29554 The name of the section.
29556 The size of the section.
29558 The size of the overall executable to download.
29562 At the end, a summary is printed.
29564 @subsubheading @value{GDBN} Command
29566 The corresponding @value{GDBN} command is @samp{load}.
29568 @subsubheading Example
29570 Note: each status message appears on a single line. Here the messages
29571 have been broken down so that they can fit onto a page.
29576 +download,@{section=".text",section-size="6668",total-size="9880"@}
29577 +download,@{section=".text",section-sent="512",section-size="6668",
29578 total-sent="512",total-size="9880"@}
29579 +download,@{section=".text",section-sent="1024",section-size="6668",
29580 total-sent="1024",total-size="9880"@}
29581 +download,@{section=".text",section-sent="1536",section-size="6668",
29582 total-sent="1536",total-size="9880"@}
29583 +download,@{section=".text",section-sent="2048",section-size="6668",
29584 total-sent="2048",total-size="9880"@}
29585 +download,@{section=".text",section-sent="2560",section-size="6668",
29586 total-sent="2560",total-size="9880"@}
29587 +download,@{section=".text",section-sent="3072",section-size="6668",
29588 total-sent="3072",total-size="9880"@}
29589 +download,@{section=".text",section-sent="3584",section-size="6668",
29590 total-sent="3584",total-size="9880"@}
29591 +download,@{section=".text",section-sent="4096",section-size="6668",
29592 total-sent="4096",total-size="9880"@}
29593 +download,@{section=".text",section-sent="4608",section-size="6668",
29594 total-sent="4608",total-size="9880"@}
29595 +download,@{section=".text",section-sent="5120",section-size="6668",
29596 total-sent="5120",total-size="9880"@}
29597 +download,@{section=".text",section-sent="5632",section-size="6668",
29598 total-sent="5632",total-size="9880"@}
29599 +download,@{section=".text",section-sent="6144",section-size="6668",
29600 total-sent="6144",total-size="9880"@}
29601 +download,@{section=".text",section-sent="6656",section-size="6668",
29602 total-sent="6656",total-size="9880"@}
29603 +download,@{section=".init",section-size="28",total-size="9880"@}
29604 +download,@{section=".fini",section-size="28",total-size="9880"@}
29605 +download,@{section=".data",section-size="3156",total-size="9880"@}
29606 +download,@{section=".data",section-sent="512",section-size="3156",
29607 total-sent="7236",total-size="9880"@}
29608 +download,@{section=".data",section-sent="1024",section-size="3156",
29609 total-sent="7748",total-size="9880"@}
29610 +download,@{section=".data",section-sent="1536",section-size="3156",
29611 total-sent="8260",total-size="9880"@}
29612 +download,@{section=".data",section-sent="2048",section-size="3156",
29613 total-sent="8772",total-size="9880"@}
29614 +download,@{section=".data",section-sent="2560",section-size="3156",
29615 total-sent="9284",total-size="9880"@}
29616 +download,@{section=".data",section-sent="3072",section-size="3156",
29617 total-sent="9796",total-size="9880"@}
29618 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29625 @subheading The @code{-target-exec-status} Command
29626 @findex -target-exec-status
29628 @subsubheading Synopsis
29631 -target-exec-status
29634 Provide information on the state of the target (whether it is running or
29635 not, for instance).
29637 @subsubheading @value{GDBN} Command
29639 There's no equivalent @value{GDBN} command.
29641 @subsubheading Example
29645 @subheading The @code{-target-list-available-targets} Command
29646 @findex -target-list-available-targets
29648 @subsubheading Synopsis
29651 -target-list-available-targets
29654 List the possible targets to connect to.
29656 @subsubheading @value{GDBN} Command
29658 The corresponding @value{GDBN} command is @samp{help target}.
29660 @subsubheading Example
29664 @subheading The @code{-target-list-current-targets} Command
29665 @findex -target-list-current-targets
29667 @subsubheading Synopsis
29670 -target-list-current-targets
29673 Describe the current target.
29675 @subsubheading @value{GDBN} Command
29677 The corresponding information is printed by @samp{info file} (among
29680 @subsubheading Example
29684 @subheading The @code{-target-list-parameters} Command
29685 @findex -target-list-parameters
29687 @subsubheading Synopsis
29690 -target-list-parameters
29696 @subsubheading @value{GDBN} Command
29700 @subsubheading Example
29704 @subheading The @code{-target-select} Command
29705 @findex -target-select
29707 @subsubheading Synopsis
29710 -target-select @var{type} @var{parameters @dots{}}
29713 Connect @value{GDBN} to the remote target. This command takes two args:
29717 The type of target, for instance @samp{remote}, etc.
29718 @item @var{parameters}
29719 Device names, host names and the like. @xref{Target Commands, ,
29720 Commands for Managing Targets}, for more details.
29723 The output is a connection notification, followed by the address at
29724 which the target program is, in the following form:
29727 ^connected,addr="@var{address}",func="@var{function name}",
29728 args=[@var{arg list}]
29731 @subsubheading @value{GDBN} Command
29733 The corresponding @value{GDBN} command is @samp{target}.
29735 @subsubheading Example
29739 -target-select remote /dev/ttya
29740 ^connected,addr="0xfe00a300",func="??",args=[]
29744 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29745 @node GDB/MI File Transfer Commands
29746 @section @sc{gdb/mi} File Transfer Commands
29749 @subheading The @code{-target-file-put} Command
29750 @findex -target-file-put
29752 @subsubheading Synopsis
29755 -target-file-put @var{hostfile} @var{targetfile}
29758 Copy file @var{hostfile} from the host system (the machine running
29759 @value{GDBN}) to @var{targetfile} on the target system.
29761 @subsubheading @value{GDBN} Command
29763 The corresponding @value{GDBN} command is @samp{remote put}.
29765 @subsubheading Example
29769 -target-file-put localfile remotefile
29775 @subheading The @code{-target-file-get} Command
29776 @findex -target-file-get
29778 @subsubheading Synopsis
29781 -target-file-get @var{targetfile} @var{hostfile}
29784 Copy file @var{targetfile} from the target system to @var{hostfile}
29785 on the host system.
29787 @subsubheading @value{GDBN} Command
29789 The corresponding @value{GDBN} command is @samp{remote get}.
29791 @subsubheading Example
29795 -target-file-get remotefile localfile
29801 @subheading The @code{-target-file-delete} Command
29802 @findex -target-file-delete
29804 @subsubheading Synopsis
29807 -target-file-delete @var{targetfile}
29810 Delete @var{targetfile} from the target system.
29812 @subsubheading @value{GDBN} Command
29814 The corresponding @value{GDBN} command is @samp{remote delete}.
29816 @subsubheading Example
29820 -target-file-delete remotefile
29826 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29827 @node GDB/MI Miscellaneous Commands
29828 @section Miscellaneous @sc{gdb/mi} Commands
29830 @c @subheading -gdb-complete
29832 @subheading The @code{-gdb-exit} Command
29835 @subsubheading Synopsis
29841 Exit @value{GDBN} immediately.
29843 @subsubheading @value{GDBN} Command
29845 Approximately corresponds to @samp{quit}.
29847 @subsubheading Example
29857 @subheading The @code{-exec-abort} Command
29858 @findex -exec-abort
29860 @subsubheading Synopsis
29866 Kill the inferior running program.
29868 @subsubheading @value{GDBN} Command
29870 The corresponding @value{GDBN} command is @samp{kill}.
29872 @subsubheading Example
29877 @subheading The @code{-gdb-set} Command
29880 @subsubheading Synopsis
29886 Set an internal @value{GDBN} variable.
29887 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29889 @subsubheading @value{GDBN} Command
29891 The corresponding @value{GDBN} command is @samp{set}.
29893 @subsubheading Example
29903 @subheading The @code{-gdb-show} Command
29906 @subsubheading Synopsis
29912 Show the current value of a @value{GDBN} variable.
29914 @subsubheading @value{GDBN} Command
29916 The corresponding @value{GDBN} command is @samp{show}.
29918 @subsubheading Example
29927 @c @subheading -gdb-source
29930 @subheading The @code{-gdb-version} Command
29931 @findex -gdb-version
29933 @subsubheading Synopsis
29939 Show version information for @value{GDBN}. Used mostly in testing.
29941 @subsubheading @value{GDBN} Command
29943 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29944 default shows this information when you start an interactive session.
29946 @subsubheading Example
29948 @c This example modifies the actual output from GDB to avoid overfull
29954 ~Copyright 2000 Free Software Foundation, Inc.
29955 ~GDB is free software, covered by the GNU General Public License, and
29956 ~you are welcome to change it and/or distribute copies of it under
29957 ~ certain conditions.
29958 ~Type "show copying" to see the conditions.
29959 ~There is absolutely no warranty for GDB. Type "show warranty" for
29961 ~This GDB was configured as
29962 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29967 @subheading The @code{-list-features} Command
29968 @findex -list-features
29970 Returns a list of particular features of the MI protocol that
29971 this version of gdb implements. A feature can be a command,
29972 or a new field in an output of some command, or even an
29973 important bugfix. While a frontend can sometimes detect presence
29974 of a feature at runtime, it is easier to perform detection at debugger
29977 The command returns a list of strings, with each string naming an
29978 available feature. Each returned string is just a name, it does not
29979 have any internal structure. The list of possible feature names
29985 (gdb) -list-features
29986 ^done,result=["feature1","feature2"]
29989 The current list of features is:
29992 @item frozen-varobjs
29993 Indicates presence of the @code{-var-set-frozen} command, as well
29994 as possible presense of the @code{frozen} field in the output
29995 of @code{-varobj-create}.
29996 @item pending-breakpoints
29997 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
29999 Indicates presence of Python scripting support, Python-based
30000 pretty-printing commands, and possible presence of the
30001 @samp{display_hint} field in the output of @code{-var-list-children}
30003 Indicates presence of the @code{-thread-info} command.
30004 @item data-read-memory-bytes
30005 Indicates presense of the @code{-data-read-memory-bytes} and the
30006 @code{-data-write-memory-bytes} commands.
30010 @subheading The @code{-list-target-features} Command
30011 @findex -list-target-features
30013 Returns a list of particular features that are supported by the
30014 target. Those features affect the permitted MI commands, but
30015 unlike the features reported by the @code{-list-features} command, the
30016 features depend on which target GDB is using at the moment. Whenever
30017 a target can change, due to commands such as @code{-target-select},
30018 @code{-target-attach} or @code{-exec-run}, the list of target features
30019 may change, and the frontend should obtain it again.
30023 (gdb) -list-features
30024 ^done,result=["async"]
30027 The current list of features is:
30031 Indicates that the target is capable of asynchronous command
30032 execution, which means that @value{GDBN} will accept further commands
30033 while the target is running.
30036 Indicates that the target is capable of reverse execution.
30037 @xref{Reverse Execution}, for more information.
30041 @subheading The @code{-list-thread-groups} Command
30042 @findex -list-thread-groups
30044 @subheading Synopsis
30047 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
30050 Lists thread groups (@pxref{Thread groups}). When a single thread
30051 group is passed as the argument, lists the children of that group.
30052 When several thread group are passed, lists information about those
30053 thread groups. Without any parameters, lists information about all
30054 top-level thread groups.
30056 Normally, thread groups that are being debugged are reported.
30057 With the @samp{--available} option, @value{GDBN} reports thread groups
30058 available on the target.
30060 The output of this command may have either a @samp{threads} result or
30061 a @samp{groups} result. The @samp{thread} result has a list of tuples
30062 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
30063 Information}). The @samp{groups} result has a list of tuples as value,
30064 each tuple describing a thread group. If top-level groups are
30065 requested (that is, no parameter is passed), or when several groups
30066 are passed, the output always has a @samp{groups} result. The format
30067 of the @samp{group} result is described below.
30069 To reduce the number of roundtrips it's possible to list thread groups
30070 together with their children, by passing the @samp{--recurse} option
30071 and the recursion depth. Presently, only recursion depth of 1 is
30072 permitted. If this option is present, then every reported thread group
30073 will also include its children, either as @samp{group} or
30074 @samp{threads} field.
30076 In general, any combination of option and parameters is permitted, with
30077 the following caveats:
30081 When a single thread group is passed, the output will typically
30082 be the @samp{threads} result. Because threads may not contain
30083 anything, the @samp{recurse} option will be ignored.
30086 When the @samp{--available} option is passed, limited information may
30087 be available. In particular, the list of threads of a process might
30088 be inaccessible. Further, specifying specific thread groups might
30089 not give any performance advantage over listing all thread groups.
30090 The frontend should assume that @samp{-list-thread-groups --available}
30091 is always an expensive operation and cache the results.
30095 The @samp{groups} result is a list of tuples, where each tuple may
30096 have the following fields:
30100 Identifier of the thread group. This field is always present.
30101 The identifier is an opaque string; frontends should not try to
30102 convert it to an integer, even though it might look like one.
30105 The type of the thread group. At present, only @samp{process} is a
30109 The target-specific process identifier. This field is only present
30110 for thread groups of type @samp{process} and only if the process exists.
30113 The number of children this thread group has. This field may be
30114 absent for an available thread group.
30117 This field has a list of tuples as value, each tuple describing a
30118 thread. It may be present if the @samp{--recurse} option is
30119 specified, and it's actually possible to obtain the threads.
30122 This field is a list of integers, each identifying a core that one
30123 thread of the group is running on. This field may be absent if
30124 such information is not available.
30127 The name of the executable file that corresponds to this thread group.
30128 The field is only present for thread groups of type @samp{process},
30129 and only if there is a corresponding executable file.
30133 @subheading Example
30137 -list-thread-groups
30138 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
30139 -list-thread-groups 17
30140 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30141 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
30142 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30143 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
30144 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
30145 -list-thread-groups --available
30146 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
30147 -list-thread-groups --available --recurse 1
30148 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30149 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30150 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
30151 -list-thread-groups --available --recurse 1 17 18
30152 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30153 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30154 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
30158 @subheading The @code{-add-inferior} Command
30159 @findex -add-inferior
30161 @subheading Synopsis
30167 Creates a new inferior (@pxref{Inferiors and Programs}). The created
30168 inferior is not associated with any executable. Such association may
30169 be established with the @samp{-file-exec-and-symbols} command
30170 (@pxref{GDB/MI File Commands}). The command response has a single
30171 field, @samp{thread-group}, whose value is the identifier of the
30172 thread group corresponding to the new inferior.
30174 @subheading Example
30179 ^done,thread-group="i3"
30182 @subheading The @code{-interpreter-exec} Command
30183 @findex -interpreter-exec
30185 @subheading Synopsis
30188 -interpreter-exec @var{interpreter} @var{command}
30190 @anchor{-interpreter-exec}
30192 Execute the specified @var{command} in the given @var{interpreter}.
30194 @subheading @value{GDBN} Command
30196 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
30198 @subheading Example
30202 -interpreter-exec console "break main"
30203 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
30204 &"During symbol reading, bad structure-type format.\n"
30205 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
30210 @subheading The @code{-inferior-tty-set} Command
30211 @findex -inferior-tty-set
30213 @subheading Synopsis
30216 -inferior-tty-set /dev/pts/1
30219 Set terminal for future runs of the program being debugged.
30221 @subheading @value{GDBN} Command
30223 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
30225 @subheading Example
30229 -inferior-tty-set /dev/pts/1
30234 @subheading The @code{-inferior-tty-show} Command
30235 @findex -inferior-tty-show
30237 @subheading Synopsis
30243 Show terminal for future runs of program being debugged.
30245 @subheading @value{GDBN} Command
30247 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
30249 @subheading Example
30253 -inferior-tty-set /dev/pts/1
30257 ^done,inferior_tty_terminal="/dev/pts/1"
30261 @subheading The @code{-enable-timings} Command
30262 @findex -enable-timings
30264 @subheading Synopsis
30267 -enable-timings [yes | no]
30270 Toggle the printing of the wallclock, user and system times for an MI
30271 command as a field in its output. This command is to help frontend
30272 developers optimize the performance of their code. No argument is
30273 equivalent to @samp{yes}.
30275 @subheading @value{GDBN} Command
30279 @subheading Example
30287 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30288 addr="0x080484ed",func="main",file="myprog.c",
30289 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
30290 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
30298 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30299 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
30300 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
30301 fullname="/home/nickrob/myprog.c",line="73"@}
30306 @chapter @value{GDBN} Annotations
30308 This chapter describes annotations in @value{GDBN}. Annotations were
30309 designed to interface @value{GDBN} to graphical user interfaces or other
30310 similar programs which want to interact with @value{GDBN} at a
30311 relatively high level.
30313 The annotation mechanism has largely been superseded by @sc{gdb/mi}
30317 This is Edition @value{EDITION}, @value{DATE}.
30321 * Annotations Overview:: What annotations are; the general syntax.
30322 * Server Prefix:: Issuing a command without affecting user state.
30323 * Prompting:: Annotations marking @value{GDBN}'s need for input.
30324 * Errors:: Annotations for error messages.
30325 * Invalidation:: Some annotations describe things now invalid.
30326 * Annotations for Running::
30327 Whether the program is running, how it stopped, etc.
30328 * Source Annotations:: Annotations describing source code.
30331 @node Annotations Overview
30332 @section What is an Annotation?
30333 @cindex annotations
30335 Annotations start with a newline character, two @samp{control-z}
30336 characters, and the name of the annotation. If there is no additional
30337 information associated with this annotation, the name of the annotation
30338 is followed immediately by a newline. If there is additional
30339 information, the name of the annotation is followed by a space, the
30340 additional information, and a newline. The additional information
30341 cannot contain newline characters.
30343 Any output not beginning with a newline and two @samp{control-z}
30344 characters denotes literal output from @value{GDBN}. Currently there is
30345 no need for @value{GDBN} to output a newline followed by two
30346 @samp{control-z} characters, but if there was such a need, the
30347 annotations could be extended with an @samp{escape} annotation which
30348 means those three characters as output.
30350 The annotation @var{level}, which is specified using the
30351 @option{--annotate} command line option (@pxref{Mode Options}), controls
30352 how much information @value{GDBN} prints together with its prompt,
30353 values of expressions, source lines, and other types of output. Level 0
30354 is for no annotations, level 1 is for use when @value{GDBN} is run as a
30355 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
30356 for programs that control @value{GDBN}, and level 2 annotations have
30357 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
30358 Interface, annotate, GDB's Obsolete Annotations}).
30361 @kindex set annotate
30362 @item set annotate @var{level}
30363 The @value{GDBN} command @code{set annotate} sets the level of
30364 annotations to the specified @var{level}.
30366 @item show annotate
30367 @kindex show annotate
30368 Show the current annotation level.
30371 This chapter describes level 3 annotations.
30373 A simple example of starting up @value{GDBN} with annotations is:
30376 $ @kbd{gdb --annotate=3}
30378 Copyright 2003 Free Software Foundation, Inc.
30379 GDB is free software, covered by the GNU General Public License,
30380 and you are welcome to change it and/or distribute copies of it
30381 under certain conditions.
30382 Type "show copying" to see the conditions.
30383 There is absolutely no warranty for GDB. Type "show warranty"
30385 This GDB was configured as "i386-pc-linux-gnu"
30396 Here @samp{quit} is input to @value{GDBN}; the rest is output from
30397 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
30398 denotes a @samp{control-z} character) are annotations; the rest is
30399 output from @value{GDBN}.
30401 @node Server Prefix
30402 @section The Server Prefix
30403 @cindex server prefix
30405 If you prefix a command with @samp{server } then it will not affect
30406 the command history, nor will it affect @value{GDBN}'s notion of which
30407 command to repeat if @key{RET} is pressed on a line by itself. This
30408 means that commands can be run behind a user's back by a front-end in
30409 a transparent manner.
30411 The @code{server } prefix does not affect the recording of values into
30412 the value history; to print a value without recording it into the
30413 value history, use the @code{output} command instead of the
30414 @code{print} command.
30416 Using this prefix also disables confirmation requests
30417 (@pxref{confirmation requests}).
30420 @section Annotation for @value{GDBN} Input
30422 @cindex annotations for prompts
30423 When @value{GDBN} prompts for input, it annotates this fact so it is possible
30424 to know when to send output, when the output from a given command is
30427 Different kinds of input each have a different @dfn{input type}. Each
30428 input type has three annotations: a @code{pre-} annotation, which
30429 denotes the beginning of any prompt which is being output, a plain
30430 annotation, which denotes the end of the prompt, and then a @code{post-}
30431 annotation which denotes the end of any echo which may (or may not) be
30432 associated with the input. For example, the @code{prompt} input type
30433 features the following annotations:
30441 The input types are
30444 @findex pre-prompt annotation
30445 @findex prompt annotation
30446 @findex post-prompt annotation
30448 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
30450 @findex pre-commands annotation
30451 @findex commands annotation
30452 @findex post-commands annotation
30454 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
30455 command. The annotations are repeated for each command which is input.
30457 @findex pre-overload-choice annotation
30458 @findex overload-choice annotation
30459 @findex post-overload-choice annotation
30460 @item overload-choice
30461 When @value{GDBN} wants the user to select between various overloaded functions.
30463 @findex pre-query annotation
30464 @findex query annotation
30465 @findex post-query annotation
30467 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
30469 @findex pre-prompt-for-continue annotation
30470 @findex prompt-for-continue annotation
30471 @findex post-prompt-for-continue annotation
30472 @item prompt-for-continue
30473 When @value{GDBN} is asking the user to press return to continue. Note: Don't
30474 expect this to work well; instead use @code{set height 0} to disable
30475 prompting. This is because the counting of lines is buggy in the
30476 presence of annotations.
30481 @cindex annotations for errors, warnings and interrupts
30483 @findex quit annotation
30488 This annotation occurs right before @value{GDBN} responds to an interrupt.
30490 @findex error annotation
30495 This annotation occurs right before @value{GDBN} responds to an error.
30497 Quit and error annotations indicate that any annotations which @value{GDBN} was
30498 in the middle of may end abruptly. For example, if a
30499 @code{value-history-begin} annotation is followed by a @code{error}, one
30500 cannot expect to receive the matching @code{value-history-end}. One
30501 cannot expect not to receive it either, however; an error annotation
30502 does not necessarily mean that @value{GDBN} is immediately returning all the way
30505 @findex error-begin annotation
30506 A quit or error annotation may be preceded by
30512 Any output between that and the quit or error annotation is the error
30515 Warning messages are not yet annotated.
30516 @c If we want to change that, need to fix warning(), type_error(),
30517 @c range_error(), and possibly other places.
30520 @section Invalidation Notices
30522 @cindex annotations for invalidation messages
30523 The following annotations say that certain pieces of state may have
30527 @findex frames-invalid annotation
30528 @item ^Z^Zframes-invalid
30530 The frames (for example, output from the @code{backtrace} command) may
30533 @findex breakpoints-invalid annotation
30534 @item ^Z^Zbreakpoints-invalid
30536 The breakpoints may have changed. For example, the user just added or
30537 deleted a breakpoint.
30540 @node Annotations for Running
30541 @section Running the Program
30542 @cindex annotations for running programs
30544 @findex starting annotation
30545 @findex stopping annotation
30546 When the program starts executing due to a @value{GDBN} command such as
30547 @code{step} or @code{continue},
30553 is output. When the program stops,
30559 is output. Before the @code{stopped} annotation, a variety of
30560 annotations describe how the program stopped.
30563 @findex exited annotation
30564 @item ^Z^Zexited @var{exit-status}
30565 The program exited, and @var{exit-status} is the exit status (zero for
30566 successful exit, otherwise nonzero).
30568 @findex signalled annotation
30569 @findex signal-name annotation
30570 @findex signal-name-end annotation
30571 @findex signal-string annotation
30572 @findex signal-string-end annotation
30573 @item ^Z^Zsignalled
30574 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30575 annotation continues:
30581 ^Z^Zsignal-name-end
30585 ^Z^Zsignal-string-end
30590 where @var{name} is the name of the signal, such as @code{SIGILL} or
30591 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30592 as @code{Illegal Instruction} or @code{Segmentation fault}.
30593 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30594 user's benefit and have no particular format.
30596 @findex signal annotation
30598 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30599 just saying that the program received the signal, not that it was
30600 terminated with it.
30602 @findex breakpoint annotation
30603 @item ^Z^Zbreakpoint @var{number}
30604 The program hit breakpoint number @var{number}.
30606 @findex watchpoint annotation
30607 @item ^Z^Zwatchpoint @var{number}
30608 The program hit watchpoint number @var{number}.
30611 @node Source Annotations
30612 @section Displaying Source
30613 @cindex annotations for source display
30615 @findex source annotation
30616 The following annotation is used instead of displaying source code:
30619 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30622 where @var{filename} is an absolute file name indicating which source
30623 file, @var{line} is the line number within that file (where 1 is the
30624 first line in the file), @var{character} is the character position
30625 within the file (where 0 is the first character in the file) (for most
30626 debug formats this will necessarily point to the beginning of a line),
30627 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30628 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30629 @var{addr} is the address in the target program associated with the
30630 source which is being displayed. @var{addr} is in the form @samp{0x}
30631 followed by one or more lowercase hex digits (note that this does not
30632 depend on the language).
30634 @node JIT Interface
30635 @chapter JIT Compilation Interface
30636 @cindex just-in-time compilation
30637 @cindex JIT compilation interface
30639 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30640 interface. A JIT compiler is a program or library that generates native
30641 executable code at runtime and executes it, usually in order to achieve good
30642 performance while maintaining platform independence.
30644 Programs that use JIT compilation are normally difficult to debug because
30645 portions of their code are generated at runtime, instead of being loaded from
30646 object files, which is where @value{GDBN} normally finds the program's symbols
30647 and debug information. In order to debug programs that use JIT compilation,
30648 @value{GDBN} has an interface that allows the program to register in-memory
30649 symbol files with @value{GDBN} at runtime.
30651 If you are using @value{GDBN} to debug a program that uses this interface, then
30652 it should work transparently so long as you have not stripped the binary. If
30653 you are developing a JIT compiler, then the interface is documented in the rest
30654 of this chapter. At this time, the only known client of this interface is the
30657 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30658 JIT compiler communicates with @value{GDBN} by writing data into a global
30659 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30660 attaches, it reads a linked list of symbol files from the global variable to
30661 find existing code, and puts a breakpoint in the function so that it can find
30662 out about additional code.
30665 * Declarations:: Relevant C struct declarations
30666 * Registering Code:: Steps to register code
30667 * Unregistering Code:: Steps to unregister code
30671 @section JIT Declarations
30673 These are the relevant struct declarations that a C program should include to
30674 implement the interface:
30684 struct jit_code_entry
30686 struct jit_code_entry *next_entry;
30687 struct jit_code_entry *prev_entry;
30688 const char *symfile_addr;
30689 uint64_t symfile_size;
30692 struct jit_descriptor
30695 /* This type should be jit_actions_t, but we use uint32_t
30696 to be explicit about the bitwidth. */
30697 uint32_t action_flag;
30698 struct jit_code_entry *relevant_entry;
30699 struct jit_code_entry *first_entry;
30702 /* GDB puts a breakpoint in this function. */
30703 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30705 /* Make sure to specify the version statically, because the
30706 debugger may check the version before we can set it. */
30707 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30710 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30711 modifications to this global data properly, which can easily be done by putting
30712 a global mutex around modifications to these structures.
30714 @node Registering Code
30715 @section Registering Code
30717 To register code with @value{GDBN}, the JIT should follow this protocol:
30721 Generate an object file in memory with symbols and other desired debug
30722 information. The file must include the virtual addresses of the sections.
30725 Create a code entry for the file, which gives the start and size of the symbol
30729 Add it to the linked list in the JIT descriptor.
30732 Point the relevant_entry field of the descriptor at the entry.
30735 Set @code{action_flag} to @code{JIT_REGISTER} and call
30736 @code{__jit_debug_register_code}.
30739 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30740 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30741 new code. However, the linked list must still be maintained in order to allow
30742 @value{GDBN} to attach to a running process and still find the symbol files.
30744 @node Unregistering Code
30745 @section Unregistering Code
30747 If code is freed, then the JIT should use the following protocol:
30751 Remove the code entry corresponding to the code from the linked list.
30754 Point the @code{relevant_entry} field of the descriptor at the code entry.
30757 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30758 @code{__jit_debug_register_code}.
30761 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30762 and the JIT will leak the memory used for the associated symbol files.
30765 @chapter Reporting Bugs in @value{GDBN}
30766 @cindex bugs in @value{GDBN}
30767 @cindex reporting bugs in @value{GDBN}
30769 Your bug reports play an essential role in making @value{GDBN} reliable.
30771 Reporting a bug may help you by bringing a solution to your problem, or it
30772 may not. But in any case the principal function of a bug report is to help
30773 the entire community by making the next version of @value{GDBN} work better. Bug
30774 reports are your contribution to the maintenance of @value{GDBN}.
30776 In order for a bug report to serve its purpose, you must include the
30777 information that enables us to fix the bug.
30780 * Bug Criteria:: Have you found a bug?
30781 * Bug Reporting:: How to report bugs
30785 @section Have You Found a Bug?
30786 @cindex bug criteria
30788 If you are not sure whether you have found a bug, here are some guidelines:
30791 @cindex fatal signal
30792 @cindex debugger crash
30793 @cindex crash of debugger
30795 If the debugger gets a fatal signal, for any input whatever, that is a
30796 @value{GDBN} bug. Reliable debuggers never crash.
30798 @cindex error on valid input
30800 If @value{GDBN} produces an error message for valid input, that is a
30801 bug. (Note that if you're cross debugging, the problem may also be
30802 somewhere in the connection to the target.)
30804 @cindex invalid input
30806 If @value{GDBN} does not produce an error message for invalid input,
30807 that is a bug. However, you should note that your idea of
30808 ``invalid input'' might be our idea of ``an extension'' or ``support
30809 for traditional practice''.
30812 If you are an experienced user of debugging tools, your suggestions
30813 for improvement of @value{GDBN} are welcome in any case.
30816 @node Bug Reporting
30817 @section How to Report Bugs
30818 @cindex bug reports
30819 @cindex @value{GDBN} bugs, reporting
30821 A number of companies and individuals offer support for @sc{gnu} products.
30822 If you obtained @value{GDBN} from a support organization, we recommend you
30823 contact that organization first.
30825 You can find contact information for many support companies and
30826 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30828 @c should add a web page ref...
30831 @ifset BUGURL_DEFAULT
30832 In any event, we also recommend that you submit bug reports for
30833 @value{GDBN}. The preferred method is to submit them directly using
30834 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30835 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30838 @strong{Do not send bug reports to @samp{info-gdb}, or to
30839 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30840 not want to receive bug reports. Those that do have arranged to receive
30843 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30844 serves as a repeater. The mailing list and the newsgroup carry exactly
30845 the same messages. Often people think of posting bug reports to the
30846 newsgroup instead of mailing them. This appears to work, but it has one
30847 problem which can be crucial: a newsgroup posting often lacks a mail
30848 path back to the sender. Thus, if we need to ask for more information,
30849 we may be unable to reach you. For this reason, it is better to send
30850 bug reports to the mailing list.
30852 @ifclear BUGURL_DEFAULT
30853 In any event, we also recommend that you submit bug reports for
30854 @value{GDBN} to @value{BUGURL}.
30858 The fundamental principle of reporting bugs usefully is this:
30859 @strong{report all the facts}. If you are not sure whether to state a
30860 fact or leave it out, state it!
30862 Often people omit facts because they think they know what causes the
30863 problem and assume that some details do not matter. Thus, you might
30864 assume that the name of the variable you use in an example does not matter.
30865 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30866 stray memory reference which happens to fetch from the location where that
30867 name is stored in memory; perhaps, if the name were different, the contents
30868 of that location would fool the debugger into doing the right thing despite
30869 the bug. Play it safe and give a specific, complete example. That is the
30870 easiest thing for you to do, and the most helpful.
30872 Keep in mind that the purpose of a bug report is to enable us to fix the
30873 bug. It may be that the bug has been reported previously, but neither
30874 you nor we can know that unless your bug report is complete and
30877 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30878 bell?'' Those bug reports are useless, and we urge everyone to
30879 @emph{refuse to respond to them} except to chide the sender to report
30882 To enable us to fix the bug, you should include all these things:
30886 The version of @value{GDBN}. @value{GDBN} announces it if you start
30887 with no arguments; you can also print it at any time using @code{show
30890 Without this, we will not know whether there is any point in looking for
30891 the bug in the current version of @value{GDBN}.
30894 The type of machine you are using, and the operating system name and
30898 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30899 ``@value{GCC}--2.8.1''.
30902 What compiler (and its version) was used to compile the program you are
30903 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30904 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30905 to get this information; for other compilers, see the documentation for
30909 The command arguments you gave the compiler to compile your example and
30910 observe the bug. For example, did you use @samp{-O}? To guarantee
30911 you will not omit something important, list them all. A copy of the
30912 Makefile (or the output from make) is sufficient.
30914 If we were to try to guess the arguments, we would probably guess wrong
30915 and then we might not encounter the bug.
30918 A complete input script, and all necessary source files, that will
30922 A description of what behavior you observe that you believe is
30923 incorrect. For example, ``It gets a fatal signal.''
30925 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30926 will certainly notice it. But if the bug is incorrect output, we might
30927 not notice unless it is glaringly wrong. You might as well not give us
30928 a chance to make a mistake.
30930 Even if the problem you experience is a fatal signal, you should still
30931 say so explicitly. Suppose something strange is going on, such as, your
30932 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30933 the C library on your system. (This has happened!) Your copy might
30934 crash and ours would not. If you told us to expect a crash, then when
30935 ours fails to crash, we would know that the bug was not happening for
30936 us. If you had not told us to expect a crash, then we would not be able
30937 to draw any conclusion from our observations.
30940 @cindex recording a session script
30941 To collect all this information, you can use a session recording program
30942 such as @command{script}, which is available on many Unix systems.
30943 Just run your @value{GDBN} session inside @command{script} and then
30944 include the @file{typescript} file with your bug report.
30946 Another way to record a @value{GDBN} session is to run @value{GDBN}
30947 inside Emacs and then save the entire buffer to a file.
30950 If you wish to suggest changes to the @value{GDBN} source, send us context
30951 diffs. If you even discuss something in the @value{GDBN} source, refer to
30952 it by context, not by line number.
30954 The line numbers in our development sources will not match those in your
30955 sources. Your line numbers would convey no useful information to us.
30959 Here are some things that are not necessary:
30963 A description of the envelope of the bug.
30965 Often people who encounter a bug spend a lot of time investigating
30966 which changes to the input file will make the bug go away and which
30967 changes will not affect it.
30969 This is often time consuming and not very useful, because the way we
30970 will find the bug is by running a single example under the debugger
30971 with breakpoints, not by pure deduction from a series of examples.
30972 We recommend that you save your time for something else.
30974 Of course, if you can find a simpler example to report @emph{instead}
30975 of the original one, that is a convenience for us. Errors in the
30976 output will be easier to spot, running under the debugger will take
30977 less time, and so on.
30979 However, simplification is not vital; if you do not want to do this,
30980 report the bug anyway and send us the entire test case you used.
30983 A patch for the bug.
30985 A patch for the bug does help us if it is a good one. But do not omit
30986 the necessary information, such as the test case, on the assumption that
30987 a patch is all we need. We might see problems with your patch and decide
30988 to fix the problem another way, or we might not understand it at all.
30990 Sometimes with a program as complicated as @value{GDBN} it is very hard to
30991 construct an example that will make the program follow a certain path
30992 through the code. If you do not send us the example, we will not be able
30993 to construct one, so we will not be able to verify that the bug is fixed.
30995 And if we cannot understand what bug you are trying to fix, or why your
30996 patch should be an improvement, we will not install it. A test case will
30997 help us to understand.
31000 A guess about what the bug is or what it depends on.
31002 Such guesses are usually wrong. Even we cannot guess right about such
31003 things without first using the debugger to find the facts.
31006 @c The readline documentation is distributed with the readline code
31007 @c and consists of the two following files:
31009 @c inc-hist.texinfo
31010 @c Use -I with makeinfo to point to the appropriate directory,
31011 @c environment var TEXINPUTS with TeX.
31012 @ifclear SYSTEM_READLINE
31013 @include rluser.texi
31014 @include inc-hist.texinfo
31018 @appendix In Memoriam
31020 The GDB project mourns the loss of the following long-time contributors:
31024 Fred was a long-standing contributor to GDB (1991-2006), and to Free
31025 Software in general. Outside of GDB, he was known in the Amiga world
31026 for his series of Fish Disks, and the GeekGadget project.
31028 @item Michael Snyder
31029 Michael was one of the Global Maintainers of the GDB project, with
31030 contributions recorded as early as 1996, until 2011. In addition to
31031 his day to day participation, he was a large driving force behind
31032 adding Reverse Debugging to GDB.
31035 Beyond their technical contributions to the project, they were also
31036 enjoyable members of the Free Software Community. We will miss them.
31038 @node Formatting Documentation
31039 @appendix Formatting Documentation
31041 @cindex @value{GDBN} reference card
31042 @cindex reference card
31043 The @value{GDBN} 4 release includes an already-formatted reference card, ready
31044 for printing with PostScript or Ghostscript, in the @file{gdb}
31045 subdirectory of the main source directory@footnote{In
31046 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
31047 release.}. If you can use PostScript or Ghostscript with your printer,
31048 you can print the reference card immediately with @file{refcard.ps}.
31050 The release also includes the source for the reference card. You
31051 can format it, using @TeX{}, by typing:
31057 The @value{GDBN} reference card is designed to print in @dfn{landscape}
31058 mode on US ``letter'' size paper;
31059 that is, on a sheet 11 inches wide by 8.5 inches
31060 high. You will need to specify this form of printing as an option to
31061 your @sc{dvi} output program.
31063 @cindex documentation
31065 All the documentation for @value{GDBN} comes as part of the machine-readable
31066 distribution. The documentation is written in Texinfo format, which is
31067 a documentation system that uses a single source file to produce both
31068 on-line information and a printed manual. You can use one of the Info
31069 formatting commands to create the on-line version of the documentation
31070 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
31072 @value{GDBN} includes an already formatted copy of the on-line Info
31073 version of this manual in the @file{gdb} subdirectory. The main Info
31074 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
31075 subordinate files matching @samp{gdb.info*} in the same directory. If
31076 necessary, you can print out these files, or read them with any editor;
31077 but they are easier to read using the @code{info} subsystem in @sc{gnu}
31078 Emacs or the standalone @code{info} program, available as part of the
31079 @sc{gnu} Texinfo distribution.
31081 If you want to format these Info files yourself, you need one of the
31082 Info formatting programs, such as @code{texinfo-format-buffer} or
31085 If you have @code{makeinfo} installed, and are in the top level
31086 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
31087 version @value{GDBVN}), you can make the Info file by typing:
31094 If you want to typeset and print copies of this manual, you need @TeX{},
31095 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
31096 Texinfo definitions file.
31098 @TeX{} is a typesetting program; it does not print files directly, but
31099 produces output files called @sc{dvi} files. To print a typeset
31100 document, you need a program to print @sc{dvi} files. If your system
31101 has @TeX{} installed, chances are it has such a program. The precise
31102 command to use depends on your system; @kbd{lpr -d} is common; another
31103 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
31104 require a file name without any extension or a @samp{.dvi} extension.
31106 @TeX{} also requires a macro definitions file called
31107 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
31108 written in Texinfo format. On its own, @TeX{} cannot either read or
31109 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
31110 and is located in the @file{gdb-@var{version-number}/texinfo}
31113 If you have @TeX{} and a @sc{dvi} printer program installed, you can
31114 typeset and print this manual. First switch to the @file{gdb}
31115 subdirectory of the main source directory (for example, to
31116 @file{gdb-@value{GDBVN}/gdb}) and type:
31122 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
31124 @node Installing GDB
31125 @appendix Installing @value{GDBN}
31126 @cindex installation
31129 * Requirements:: Requirements for building @value{GDBN}
31130 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
31131 * Separate Objdir:: Compiling @value{GDBN} in another directory
31132 * Config Names:: Specifying names for hosts and targets
31133 * Configure Options:: Summary of options for configure
31134 * System-wide configuration:: Having a system-wide init file
31138 @section Requirements for Building @value{GDBN}
31139 @cindex building @value{GDBN}, requirements for
31141 Building @value{GDBN} requires various tools and packages to be available.
31142 Other packages will be used only if they are found.
31144 @heading Tools/Packages Necessary for Building @value{GDBN}
31146 @item ISO C90 compiler
31147 @value{GDBN} is written in ISO C90. It should be buildable with any
31148 working C90 compiler, e.g.@: GCC.
31152 @heading Tools/Packages Optional for Building @value{GDBN}
31156 @value{GDBN} can use the Expat XML parsing library. This library may be
31157 included with your operating system distribution; if it is not, you
31158 can get the latest version from @url{http://expat.sourceforge.net}.
31159 The @file{configure} script will search for this library in several
31160 standard locations; if it is installed in an unusual path, you can
31161 use the @option{--with-libexpat-prefix} option to specify its location.
31167 Remote protocol memory maps (@pxref{Memory Map Format})
31169 Target descriptions (@pxref{Target Descriptions})
31171 Remote shared library lists (@pxref{Library List Format})
31173 MS-Windows shared libraries (@pxref{Shared Libraries})
31175 Traceframe info (@pxref{Traceframe Info Format})
31179 @cindex compressed debug sections
31180 @value{GDBN} will use the @samp{zlib} library, if available, to read
31181 compressed debug sections. Some linkers, such as GNU gold, are capable
31182 of producing binaries with compressed debug sections. If @value{GDBN}
31183 is compiled with @samp{zlib}, it will be able to read the debug
31184 information in such binaries.
31186 The @samp{zlib} library is likely included with your operating system
31187 distribution; if it is not, you can get the latest version from
31188 @url{http://zlib.net}.
31191 @value{GDBN}'s features related to character sets (@pxref{Character
31192 Sets}) require a functioning @code{iconv} implementation. If you are
31193 on a GNU system, then this is provided by the GNU C Library. Some
31194 other systems also provide a working @code{iconv}.
31196 On systems with @code{iconv}, you can install GNU Libiconv. If you
31197 have previously installed Libiconv, you can use the
31198 @option{--with-libiconv-prefix} option to configure.
31200 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
31201 arrange to build Libiconv if a directory named @file{libiconv} appears
31202 in the top-most source directory. If Libiconv is built this way, and
31203 if the operating system does not provide a suitable @code{iconv}
31204 implementation, then the just-built library will automatically be used
31205 by @value{GDBN}. One easy way to set this up is to download GNU
31206 Libiconv, unpack it, and then rename the directory holding the
31207 Libiconv source code to @samp{libiconv}.
31210 @node Running Configure
31211 @section Invoking the @value{GDBN} @file{configure} Script
31212 @cindex configuring @value{GDBN}
31213 @value{GDBN} comes with a @file{configure} script that automates the process
31214 of preparing @value{GDBN} for installation; you can then use @code{make} to
31215 build the @code{gdb} program.
31217 @c irrelevant in info file; it's as current as the code it lives with.
31218 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
31219 look at the @file{README} file in the sources; we may have improved the
31220 installation procedures since publishing this manual.}
31223 The @value{GDBN} distribution includes all the source code you need for
31224 @value{GDBN} in a single directory, whose name is usually composed by
31225 appending the version number to @samp{gdb}.
31227 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
31228 @file{gdb-@value{GDBVN}} directory. That directory contains:
31231 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
31232 script for configuring @value{GDBN} and all its supporting libraries
31234 @item gdb-@value{GDBVN}/gdb
31235 the source specific to @value{GDBN} itself
31237 @item gdb-@value{GDBVN}/bfd
31238 source for the Binary File Descriptor library
31240 @item gdb-@value{GDBVN}/include
31241 @sc{gnu} include files
31243 @item gdb-@value{GDBVN}/libiberty
31244 source for the @samp{-liberty} free software library
31246 @item gdb-@value{GDBVN}/opcodes
31247 source for the library of opcode tables and disassemblers
31249 @item gdb-@value{GDBVN}/readline
31250 source for the @sc{gnu} command-line interface
31252 @item gdb-@value{GDBVN}/glob
31253 source for the @sc{gnu} filename pattern-matching subroutine
31255 @item gdb-@value{GDBVN}/mmalloc
31256 source for the @sc{gnu} memory-mapped malloc package
31259 The simplest way to configure and build @value{GDBN} is to run @file{configure}
31260 from the @file{gdb-@var{version-number}} source directory, which in
31261 this example is the @file{gdb-@value{GDBVN}} directory.
31263 First switch to the @file{gdb-@var{version-number}} source directory
31264 if you are not already in it; then run @file{configure}. Pass the
31265 identifier for the platform on which @value{GDBN} will run as an
31271 cd gdb-@value{GDBVN}
31272 ./configure @var{host}
31277 where @var{host} is an identifier such as @samp{sun4} or
31278 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
31279 (You can often leave off @var{host}; @file{configure} tries to guess the
31280 correct value by examining your system.)
31282 Running @samp{configure @var{host}} and then running @code{make} builds the
31283 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
31284 libraries, then @code{gdb} itself. The configured source files, and the
31285 binaries, are left in the corresponding source directories.
31288 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
31289 system does not recognize this automatically when you run a different
31290 shell, you may need to run @code{sh} on it explicitly:
31293 sh configure @var{host}
31296 If you run @file{configure} from a directory that contains source
31297 directories for multiple libraries or programs, such as the
31298 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
31300 creates configuration files for every directory level underneath (unless
31301 you tell it not to, with the @samp{--norecursion} option).
31303 You should run the @file{configure} script from the top directory in the
31304 source tree, the @file{gdb-@var{version-number}} directory. If you run
31305 @file{configure} from one of the subdirectories, you will configure only
31306 that subdirectory. That is usually not what you want. In particular,
31307 if you run the first @file{configure} from the @file{gdb} subdirectory
31308 of the @file{gdb-@var{version-number}} directory, you will omit the
31309 configuration of @file{bfd}, @file{readline}, and other sibling
31310 directories of the @file{gdb} subdirectory. This leads to build errors
31311 about missing include files such as @file{bfd/bfd.h}.
31313 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
31314 However, you should make sure that the shell on your path (named by
31315 the @samp{SHELL} environment variable) is publicly readable. Remember
31316 that @value{GDBN} uses the shell to start your program---some systems refuse to
31317 let @value{GDBN} debug child processes whose programs are not readable.
31319 @node Separate Objdir
31320 @section Compiling @value{GDBN} in Another Directory
31322 If you want to run @value{GDBN} versions for several host or target machines,
31323 you need a different @code{gdb} compiled for each combination of
31324 host and target. @file{configure} is designed to make this easy by
31325 allowing you to generate each configuration in a separate subdirectory,
31326 rather than in the source directory. If your @code{make} program
31327 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
31328 @code{make} in each of these directories builds the @code{gdb}
31329 program specified there.
31331 To build @code{gdb} in a separate directory, run @file{configure}
31332 with the @samp{--srcdir} option to specify where to find the source.
31333 (You also need to specify a path to find @file{configure}
31334 itself from your working directory. If the path to @file{configure}
31335 would be the same as the argument to @samp{--srcdir}, you can leave out
31336 the @samp{--srcdir} option; it is assumed.)
31338 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
31339 separate directory for a Sun 4 like this:
31343 cd gdb-@value{GDBVN}
31346 ../gdb-@value{GDBVN}/configure sun4
31351 When @file{configure} builds a configuration using a remote source
31352 directory, it creates a tree for the binaries with the same structure
31353 (and using the same names) as the tree under the source directory. In
31354 the example, you'd find the Sun 4 library @file{libiberty.a} in the
31355 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
31356 @file{gdb-sun4/gdb}.
31358 Make sure that your path to the @file{configure} script has just one
31359 instance of @file{gdb} in it. If your path to @file{configure} looks
31360 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
31361 one subdirectory of @value{GDBN}, not the whole package. This leads to
31362 build errors about missing include files such as @file{bfd/bfd.h}.
31364 One popular reason to build several @value{GDBN} configurations in separate
31365 directories is to configure @value{GDBN} for cross-compiling (where
31366 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
31367 programs that run on another machine---the @dfn{target}).
31368 You specify a cross-debugging target by
31369 giving the @samp{--target=@var{target}} option to @file{configure}.
31371 When you run @code{make} to build a program or library, you must run
31372 it in a configured directory---whatever directory you were in when you
31373 called @file{configure} (or one of its subdirectories).
31375 The @code{Makefile} that @file{configure} generates in each source
31376 directory also runs recursively. If you type @code{make} in a source
31377 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
31378 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
31379 will build all the required libraries, and then build GDB.
31381 When you have multiple hosts or targets configured in separate
31382 directories, you can run @code{make} on them in parallel (for example,
31383 if they are NFS-mounted on each of the hosts); they will not interfere
31387 @section Specifying Names for Hosts and Targets
31389 The specifications used for hosts and targets in the @file{configure}
31390 script are based on a three-part naming scheme, but some short predefined
31391 aliases are also supported. The full naming scheme encodes three pieces
31392 of information in the following pattern:
31395 @var{architecture}-@var{vendor}-@var{os}
31398 For example, you can use the alias @code{sun4} as a @var{host} argument,
31399 or as the value for @var{target} in a @code{--target=@var{target}}
31400 option. The equivalent full name is @samp{sparc-sun-sunos4}.
31402 The @file{configure} script accompanying @value{GDBN} does not provide
31403 any query facility to list all supported host and target names or
31404 aliases. @file{configure} calls the Bourne shell script
31405 @code{config.sub} to map abbreviations to full names; you can read the
31406 script, if you wish, or you can use it to test your guesses on
31407 abbreviations---for example:
31410 % sh config.sub i386-linux
31412 % sh config.sub alpha-linux
31413 alpha-unknown-linux-gnu
31414 % sh config.sub hp9k700
31416 % sh config.sub sun4
31417 sparc-sun-sunos4.1.1
31418 % sh config.sub sun3
31419 m68k-sun-sunos4.1.1
31420 % sh config.sub i986v
31421 Invalid configuration `i986v': machine `i986v' not recognized
31425 @code{config.sub} is also distributed in the @value{GDBN} source
31426 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
31428 @node Configure Options
31429 @section @file{configure} Options
31431 Here is a summary of the @file{configure} options and arguments that
31432 are most often useful for building @value{GDBN}. @file{configure} also has
31433 several other options not listed here. @inforef{What Configure
31434 Does,,configure.info}, for a full explanation of @file{configure}.
31437 configure @r{[}--help@r{]}
31438 @r{[}--prefix=@var{dir}@r{]}
31439 @r{[}--exec-prefix=@var{dir}@r{]}
31440 @r{[}--srcdir=@var{dirname}@r{]}
31441 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
31442 @r{[}--target=@var{target}@r{]}
31447 You may introduce options with a single @samp{-} rather than
31448 @samp{--} if you prefer; but you may abbreviate option names if you use
31453 Display a quick summary of how to invoke @file{configure}.
31455 @item --prefix=@var{dir}
31456 Configure the source to install programs and files under directory
31459 @item --exec-prefix=@var{dir}
31460 Configure the source to install programs under directory
31463 @c avoid splitting the warning from the explanation:
31465 @item --srcdir=@var{dirname}
31466 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
31467 @code{make} that implements the @code{VPATH} feature.}@*
31468 Use this option to make configurations in directories separate from the
31469 @value{GDBN} source directories. Among other things, you can use this to
31470 build (or maintain) several configurations simultaneously, in separate
31471 directories. @file{configure} writes configuration-specific files in
31472 the current directory, but arranges for them to use the source in the
31473 directory @var{dirname}. @file{configure} creates directories under
31474 the working directory in parallel to the source directories below
31477 @item --norecursion
31478 Configure only the directory level where @file{configure} is executed; do not
31479 propagate configuration to subdirectories.
31481 @item --target=@var{target}
31482 Configure @value{GDBN} for cross-debugging programs running on the specified
31483 @var{target}. Without this option, @value{GDBN} is configured to debug
31484 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
31486 There is no convenient way to generate a list of all available targets.
31488 @item @var{host} @dots{}
31489 Configure @value{GDBN} to run on the specified @var{host}.
31491 There is no convenient way to generate a list of all available hosts.
31494 There are many other options available as well, but they are generally
31495 needed for special purposes only.
31497 @node System-wide configuration
31498 @section System-wide configuration and settings
31499 @cindex system-wide init file
31501 @value{GDBN} can be configured to have a system-wide init file;
31502 this file will be read and executed at startup (@pxref{Startup, , What
31503 @value{GDBN} does during startup}).
31505 Here is the corresponding configure option:
31508 @item --with-system-gdbinit=@var{file}
31509 Specify that the default location of the system-wide init file is
31513 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
31514 it may be subject to relocation. Two possible cases:
31518 If the default location of this init file contains @file{$prefix},
31519 it will be subject to relocation. Suppose that the configure options
31520 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
31521 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
31522 init file is looked for as @file{$install/etc/gdbinit} instead of
31523 @file{$prefix/etc/gdbinit}.
31526 By contrast, if the default location does not contain the prefix,
31527 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
31528 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
31529 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
31530 wherever @value{GDBN} is installed.
31533 @node Maintenance Commands
31534 @appendix Maintenance Commands
31535 @cindex maintenance commands
31536 @cindex internal commands
31538 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31539 includes a number of commands intended for @value{GDBN} developers,
31540 that are not documented elsewhere in this manual. These commands are
31541 provided here for reference. (For commands that turn on debugging
31542 messages, see @ref{Debugging Output}.)
31545 @kindex maint agent
31546 @kindex maint agent-eval
31547 @item maint agent @var{expression}
31548 @itemx maint agent-eval @var{expression}
31549 Translate the given @var{expression} into remote agent bytecodes.
31550 This command is useful for debugging the Agent Expression mechanism
31551 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31552 expression useful for data collection, such as by tracepoints, while
31553 @samp{maint agent-eval} produces an expression that evaluates directly
31554 to a result. For instance, a collection expression for @code{globa +
31555 globb} will include bytecodes to record four bytes of memory at each
31556 of the addresses of @code{globa} and @code{globb}, while discarding
31557 the result of the addition, while an evaluation expression will do the
31558 addition and return the sum.
31560 @kindex maint info breakpoints
31561 @item @anchor{maint info breakpoints}maint info breakpoints
31562 Using the same format as @samp{info breakpoints}, display both the
31563 breakpoints you've set explicitly, and those @value{GDBN} is using for
31564 internal purposes. Internal breakpoints are shown with negative
31565 breakpoint numbers. The type column identifies what kind of breakpoint
31570 Normal, explicitly set breakpoint.
31573 Normal, explicitly set watchpoint.
31576 Internal breakpoint, used to handle correctly stepping through
31577 @code{longjmp} calls.
31579 @item longjmp resume
31580 Internal breakpoint at the target of a @code{longjmp}.
31583 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31586 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31589 Shared library events.
31593 @kindex set displaced-stepping
31594 @kindex show displaced-stepping
31595 @cindex displaced stepping support
31596 @cindex out-of-line single-stepping
31597 @item set displaced-stepping
31598 @itemx show displaced-stepping
31599 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31600 if the target supports it. Displaced stepping is a way to single-step
31601 over breakpoints without removing them from the inferior, by executing
31602 an out-of-line copy of the instruction that was originally at the
31603 breakpoint location. It is also known as out-of-line single-stepping.
31606 @item set displaced-stepping on
31607 If the target architecture supports it, @value{GDBN} will use
31608 displaced stepping to step over breakpoints.
31610 @item set displaced-stepping off
31611 @value{GDBN} will not use displaced stepping to step over breakpoints,
31612 even if such is supported by the target architecture.
31614 @cindex non-stop mode, and @samp{set displaced-stepping}
31615 @item set displaced-stepping auto
31616 This is the default mode. @value{GDBN} will use displaced stepping
31617 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31618 architecture supports displaced stepping.
31621 @kindex maint check-symtabs
31622 @item maint check-symtabs
31623 Check the consistency of psymtabs and symtabs.
31625 @kindex maint cplus first_component
31626 @item maint cplus first_component @var{name}
31627 Print the first C@t{++} class/namespace component of @var{name}.
31629 @kindex maint cplus namespace
31630 @item maint cplus namespace
31631 Print the list of possible C@t{++} namespaces.
31633 @kindex maint demangle
31634 @item maint demangle @var{name}
31635 Demangle a C@t{++} or Objective-C mangled @var{name}.
31637 @kindex maint deprecate
31638 @kindex maint undeprecate
31639 @cindex deprecated commands
31640 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31641 @itemx maint undeprecate @var{command}
31642 Deprecate or undeprecate the named @var{command}. Deprecated commands
31643 cause @value{GDBN} to issue a warning when you use them. The optional
31644 argument @var{replacement} says which newer command should be used in
31645 favor of the deprecated one; if it is given, @value{GDBN} will mention
31646 the replacement as part of the warning.
31648 @kindex maint dump-me
31649 @item maint dump-me
31650 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31651 Cause a fatal signal in the debugger and force it to dump its core.
31652 This is supported only on systems which support aborting a program
31653 with the @code{SIGQUIT} signal.
31655 @kindex maint internal-error
31656 @kindex maint internal-warning
31657 @item maint internal-error @r{[}@var{message-text}@r{]}
31658 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31659 Cause @value{GDBN} to call the internal function @code{internal_error}
31660 or @code{internal_warning} and hence behave as though an internal error
31661 or internal warning has been detected. In addition to reporting the
31662 internal problem, these functions give the user the opportunity to
31663 either quit @value{GDBN} or create a core file of the current
31664 @value{GDBN} session.
31666 These commands take an optional parameter @var{message-text} that is
31667 used as the text of the error or warning message.
31669 Here's an example of using @code{internal-error}:
31672 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31673 @dots{}/maint.c:121: internal-error: testing, 1, 2
31674 A problem internal to GDB has been detected. Further
31675 debugging may prove unreliable.
31676 Quit this debugging session? (y or n) @kbd{n}
31677 Create a core file? (y or n) @kbd{n}
31681 @cindex @value{GDBN} internal error
31682 @cindex internal errors, control of @value{GDBN} behavior
31684 @kindex maint set internal-error
31685 @kindex maint show internal-error
31686 @kindex maint set internal-warning
31687 @kindex maint show internal-warning
31688 @item maint set internal-error @var{action} [ask|yes|no]
31689 @itemx maint show internal-error @var{action}
31690 @itemx maint set internal-warning @var{action} [ask|yes|no]
31691 @itemx maint show internal-warning @var{action}
31692 When @value{GDBN} reports an internal problem (error or warning) it
31693 gives the user the opportunity to both quit @value{GDBN} and create a
31694 core file of the current @value{GDBN} session. These commands let you
31695 override the default behaviour for each particular @var{action},
31696 described in the table below.
31700 You can specify that @value{GDBN} should always (yes) or never (no)
31701 quit. The default is to ask the user what to do.
31704 You can specify that @value{GDBN} should always (yes) or never (no)
31705 create a core file. The default is to ask the user what to do.
31708 @kindex maint packet
31709 @item maint packet @var{text}
31710 If @value{GDBN} is talking to an inferior via the serial protocol,
31711 then this command sends the string @var{text} to the inferior, and
31712 displays the response packet. @value{GDBN} supplies the initial
31713 @samp{$} character, the terminating @samp{#} character, and the
31716 @kindex maint print architecture
31717 @item maint print architecture @r{[}@var{file}@r{]}
31718 Print the entire architecture configuration. The optional argument
31719 @var{file} names the file where the output goes.
31721 @kindex maint print c-tdesc
31722 @item maint print c-tdesc
31723 Print the current target description (@pxref{Target Descriptions}) as
31724 a C source file. The created source file can be used in @value{GDBN}
31725 when an XML parser is not available to parse the description.
31727 @kindex maint print dummy-frames
31728 @item maint print dummy-frames
31729 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31732 (@value{GDBP}) @kbd{b add}
31734 (@value{GDBP}) @kbd{print add(2,3)}
31735 Breakpoint 2, add (a=2, b=3) at @dots{}
31737 The program being debugged stopped while in a function called from GDB.
31739 (@value{GDBP}) @kbd{maint print dummy-frames}
31740 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31741 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31742 call_lo=0x01014000 call_hi=0x01014001
31746 Takes an optional file parameter.
31748 @kindex maint print registers
31749 @kindex maint print raw-registers
31750 @kindex maint print cooked-registers
31751 @kindex maint print register-groups
31752 @kindex maint print remote-registers
31753 @item maint print registers @r{[}@var{file}@r{]}
31754 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31755 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31756 @itemx maint print register-groups @r{[}@var{file}@r{]}
31757 @itemx maint print remote-registers @r{[}@var{file}@r{]}
31758 Print @value{GDBN}'s internal register data structures.
31760 The command @code{maint print raw-registers} includes the contents of
31761 the raw register cache; the command @code{maint print
31762 cooked-registers} includes the (cooked) value of all registers,
31763 including registers which aren't available on the target nor visible
31764 to user; the command @code{maint print register-groups} includes the
31765 groups that each register is a member of; and the command @code{maint
31766 print remote-registers} includes the remote target's register numbers
31767 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
31768 @value{GDBN} Internals}.
31770 These commands take an optional parameter, a file name to which to
31771 write the information.
31773 @kindex maint print reggroups
31774 @item maint print reggroups @r{[}@var{file}@r{]}
31775 Print @value{GDBN}'s internal register group data structures. The
31776 optional argument @var{file} tells to what file to write the
31779 The register groups info looks like this:
31782 (@value{GDBP}) @kbd{maint print reggroups}
31795 This command forces @value{GDBN} to flush its internal register cache.
31797 @kindex maint print objfiles
31798 @cindex info for known object files
31799 @item maint print objfiles
31800 Print a dump of all known object files. For each object file, this
31801 command prints its name, address in memory, and all of its psymtabs
31804 @kindex maint print section-scripts
31805 @cindex info for known .debug_gdb_scripts-loaded scripts
31806 @item maint print section-scripts [@var{regexp}]
31807 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31808 If @var{regexp} is specified, only print scripts loaded by object files
31809 matching @var{regexp}.
31810 For each script, this command prints its name as specified in the objfile,
31811 and the full path if known.
31812 @xref{.debug_gdb_scripts section}.
31814 @kindex maint print statistics
31815 @cindex bcache statistics
31816 @item maint print statistics
31817 This command prints, for each object file in the program, various data
31818 about that object file followed by the byte cache (@dfn{bcache})
31819 statistics for the object file. The objfile data includes the number
31820 of minimal, partial, full, and stabs symbols, the number of types
31821 defined by the objfile, the number of as yet unexpanded psym tables,
31822 the number of line tables and string tables, and the amount of memory
31823 used by the various tables. The bcache statistics include the counts,
31824 sizes, and counts of duplicates of all and unique objects, max,
31825 average, and median entry size, total memory used and its overhead and
31826 savings, and various measures of the hash table size and chain
31829 @kindex maint print target-stack
31830 @cindex target stack description
31831 @item maint print target-stack
31832 A @dfn{target} is an interface between the debugger and a particular
31833 kind of file or process. Targets can be stacked in @dfn{strata},
31834 so that more than one target can potentially respond to a request.
31835 In particular, memory accesses will walk down the stack of targets
31836 until they find a target that is interested in handling that particular
31839 This command prints a short description of each layer that was pushed on
31840 the @dfn{target stack}, starting from the top layer down to the bottom one.
31842 @kindex maint print type
31843 @cindex type chain of a data type
31844 @item maint print type @var{expr}
31845 Print the type chain for a type specified by @var{expr}. The argument
31846 can be either a type name or a symbol. If it is a symbol, the type of
31847 that symbol is described. The type chain produced by this command is
31848 a recursive definition of the data type as stored in @value{GDBN}'s
31849 data structures, including its flags and contained types.
31851 @kindex maint set dwarf2 always-disassemble
31852 @kindex maint show dwarf2 always-disassemble
31853 @item maint set dwarf2 always-disassemble
31854 @item maint show dwarf2 always-disassemble
31855 Control the behavior of @code{info address} when using DWARF debugging
31858 The default is @code{off}, which means that @value{GDBN} should try to
31859 describe a variable's location in an easily readable format. When
31860 @code{on}, @value{GDBN} will instead display the DWARF location
31861 expression in an assembly-like format. Note that some locations are
31862 too complex for @value{GDBN} to describe simply; in this case you will
31863 always see the disassembly form.
31865 Here is an example of the resulting disassembly:
31868 (gdb) info addr argc
31869 Symbol "argc" is a complex DWARF expression:
31873 For more information on these expressions, see
31874 @uref{http://www.dwarfstd.org/, the DWARF standard}.
31876 @kindex maint set dwarf2 max-cache-age
31877 @kindex maint show dwarf2 max-cache-age
31878 @item maint set dwarf2 max-cache-age
31879 @itemx maint show dwarf2 max-cache-age
31880 Control the DWARF 2 compilation unit cache.
31882 @cindex DWARF 2 compilation units cache
31883 In object files with inter-compilation-unit references, such as those
31884 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
31885 reader needs to frequently refer to previously read compilation units.
31886 This setting controls how long a compilation unit will remain in the
31887 cache if it is not referenced. A higher limit means that cached
31888 compilation units will be stored in memory longer, and more total
31889 memory will be used. Setting it to zero disables caching, which will
31890 slow down @value{GDBN} startup, but reduce memory consumption.
31892 @kindex maint set profile
31893 @kindex maint show profile
31894 @cindex profiling GDB
31895 @item maint set profile
31896 @itemx maint show profile
31897 Control profiling of @value{GDBN}.
31899 Profiling will be disabled until you use the @samp{maint set profile}
31900 command to enable it. When you enable profiling, the system will begin
31901 collecting timing and execution count data; when you disable profiling or
31902 exit @value{GDBN}, the results will be written to a log file. Remember that
31903 if you use profiling, @value{GDBN} will overwrite the profiling log file
31904 (often called @file{gmon.out}). If you have a record of important profiling
31905 data in a @file{gmon.out} file, be sure to move it to a safe location.
31907 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31908 compiled with the @samp{-pg} compiler option.
31910 @kindex maint set show-debug-regs
31911 @kindex maint show show-debug-regs
31912 @cindex hardware debug registers
31913 @item maint set show-debug-regs
31914 @itemx maint show show-debug-regs
31915 Control whether to show variables that mirror the hardware debug
31916 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31917 enabled, the debug registers values are shown when @value{GDBN} inserts or
31918 removes a hardware breakpoint or watchpoint, and when the inferior
31919 triggers a hardware-assisted breakpoint or watchpoint.
31921 @kindex maint set show-all-tib
31922 @kindex maint show show-all-tib
31923 @item maint set show-all-tib
31924 @itemx maint show show-all-tib
31925 Control whether to show all non zero areas within a 1k block starting
31926 at thread local base, when using the @samp{info w32 thread-information-block}
31929 @kindex maint space
31930 @cindex memory used by commands
31932 Control whether to display memory usage for each command. If set to a
31933 nonzero value, @value{GDBN} will display how much memory each command
31934 took, following the command's own output. This can also be requested
31935 by invoking @value{GDBN} with the @option{--statistics} command-line
31936 switch (@pxref{Mode Options}).
31939 @cindex time of command execution
31941 Control whether to display the execution time for each command. If
31942 set to a nonzero value, @value{GDBN} will display how much time it
31943 took to execute each command, following the command's own output.
31944 The time is not printed for the commands that run the target, since
31945 there's no mechanism currently to compute how much time was spend
31946 by @value{GDBN} and how much time was spend by the program been debugged.
31947 it's not possibly currently
31948 This can also be requested by invoking @value{GDBN} with the
31949 @option{--statistics} command-line switch (@pxref{Mode Options}).
31951 @kindex maint translate-address
31952 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31953 Find the symbol stored at the location specified by the address
31954 @var{addr} and an optional section name @var{section}. If found,
31955 @value{GDBN} prints the name of the closest symbol and an offset from
31956 the symbol's location to the specified address. This is similar to
31957 the @code{info address} command (@pxref{Symbols}), except that this
31958 command also allows to find symbols in other sections.
31960 If section was not specified, the section in which the symbol was found
31961 is also printed. For dynamically linked executables, the name of
31962 executable or shared library containing the symbol is printed as well.
31966 The following command is useful for non-interactive invocations of
31967 @value{GDBN}, such as in the test suite.
31970 @item set watchdog @var{nsec}
31971 @kindex set watchdog
31972 @cindex watchdog timer
31973 @cindex timeout for commands
31974 Set the maximum number of seconds @value{GDBN} will wait for the
31975 target operation to finish. If this time expires, @value{GDBN}
31976 reports and error and the command is aborted.
31978 @item show watchdog
31979 Show the current setting of the target wait timeout.
31982 @node Remote Protocol
31983 @appendix @value{GDBN} Remote Serial Protocol
31988 * Stop Reply Packets::
31989 * General Query Packets::
31990 * Architecture-Specific Protocol Details::
31991 * Tracepoint Packets::
31992 * Host I/O Packets::
31994 * Notification Packets::
31995 * Remote Non-Stop::
31996 * Packet Acknowledgment::
31998 * File-I/O Remote Protocol Extension::
31999 * Library List Format::
32000 * Memory Map Format::
32001 * Thread List Format::
32002 * Traceframe Info Format::
32008 There may be occasions when you need to know something about the
32009 protocol---for example, if there is only one serial port to your target
32010 machine, you might want your program to do something special if it
32011 recognizes a packet meant for @value{GDBN}.
32013 In the examples below, @samp{->} and @samp{<-} are used to indicate
32014 transmitted and received data, respectively.
32016 @cindex protocol, @value{GDBN} remote serial
32017 @cindex serial protocol, @value{GDBN} remote
32018 @cindex remote serial protocol
32019 All @value{GDBN} commands and responses (other than acknowledgments
32020 and notifications, see @ref{Notification Packets}) are sent as a
32021 @var{packet}. A @var{packet} is introduced with the character
32022 @samp{$}, the actual @var{packet-data}, and the terminating character
32023 @samp{#} followed by a two-digit @var{checksum}:
32026 @code{$}@var{packet-data}@code{#}@var{checksum}
32030 @cindex checksum, for @value{GDBN} remote
32032 The two-digit @var{checksum} is computed as the modulo 256 sum of all
32033 characters between the leading @samp{$} and the trailing @samp{#} (an
32034 eight bit unsigned checksum).
32036 Implementors should note that prior to @value{GDBN} 5.0 the protocol
32037 specification also included an optional two-digit @var{sequence-id}:
32040 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
32043 @cindex sequence-id, for @value{GDBN} remote
32045 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
32046 has never output @var{sequence-id}s. Stubs that handle packets added
32047 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
32049 When either the host or the target machine receives a packet, the first
32050 response expected is an acknowledgment: either @samp{+} (to indicate
32051 the package was received correctly) or @samp{-} (to request
32055 -> @code{$}@var{packet-data}@code{#}@var{checksum}
32060 The @samp{+}/@samp{-} acknowledgments can be disabled
32061 once a connection is established.
32062 @xref{Packet Acknowledgment}, for details.
32064 The host (@value{GDBN}) sends @var{command}s, and the target (the
32065 debugging stub incorporated in your program) sends a @var{response}. In
32066 the case of step and continue @var{command}s, the response is only sent
32067 when the operation has completed, and the target has again stopped all
32068 threads in all attached processes. This is the default all-stop mode
32069 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
32070 execution mode; see @ref{Remote Non-Stop}, for details.
32072 @var{packet-data} consists of a sequence of characters with the
32073 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
32076 @cindex remote protocol, field separator
32077 Fields within the packet should be separated using @samp{,} @samp{;} or
32078 @samp{:}. Except where otherwise noted all numbers are represented in
32079 @sc{hex} with leading zeros suppressed.
32081 Implementors should note that prior to @value{GDBN} 5.0, the character
32082 @samp{:} could not appear as the third character in a packet (as it
32083 would potentially conflict with the @var{sequence-id}).
32085 @cindex remote protocol, binary data
32086 @anchor{Binary Data}
32087 Binary data in most packets is encoded either as two hexadecimal
32088 digits per byte of binary data. This allowed the traditional remote
32089 protocol to work over connections which were only seven-bit clean.
32090 Some packets designed more recently assume an eight-bit clean
32091 connection, and use a more efficient encoding to send and receive
32094 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
32095 as an escape character. Any escaped byte is transmitted as the escape
32096 character followed by the original character XORed with @code{0x20}.
32097 For example, the byte @code{0x7d} would be transmitted as the two
32098 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
32099 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
32100 @samp{@}}) must always be escaped. Responses sent by the stub
32101 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
32102 is not interpreted as the start of a run-length encoded sequence
32105 Response @var{data} can be run-length encoded to save space.
32106 Run-length encoding replaces runs of identical characters with one
32107 instance of the repeated character, followed by a @samp{*} and a
32108 repeat count. The repeat count is itself sent encoded, to avoid
32109 binary characters in @var{data}: a value of @var{n} is sent as
32110 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
32111 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
32112 code 32) for a repeat count of 3. (This is because run-length
32113 encoding starts to win for counts 3 or more.) Thus, for example,
32114 @samp{0* } is a run-length encoding of ``0000'': the space character
32115 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
32118 The printable characters @samp{#} and @samp{$} or with a numeric value
32119 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
32120 seven repeats (@samp{$}) can be expanded using a repeat count of only
32121 five (@samp{"}). For example, @samp{00000000} can be encoded as
32124 The error response returned for some packets includes a two character
32125 error number. That number is not well defined.
32127 @cindex empty response, for unsupported packets
32128 For any @var{command} not supported by the stub, an empty response
32129 (@samp{$#00}) should be returned. That way it is possible to extend the
32130 protocol. A newer @value{GDBN} can tell if a packet is supported based
32133 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
32134 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
32140 The following table provides a complete list of all currently defined
32141 @var{command}s and their corresponding response @var{data}.
32142 @xref{File-I/O Remote Protocol Extension}, for details about the File
32143 I/O extension of the remote protocol.
32145 Each packet's description has a template showing the packet's overall
32146 syntax, followed by an explanation of the packet's meaning. We
32147 include spaces in some of the templates for clarity; these are not
32148 part of the packet's syntax. No @value{GDBN} packet uses spaces to
32149 separate its components. For example, a template like @samp{foo
32150 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
32151 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
32152 @var{baz}. @value{GDBN} does not transmit a space character between the
32153 @samp{foo} and the @var{bar}, or between the @var{bar} and the
32156 @cindex @var{thread-id}, in remote protocol
32157 @anchor{thread-id syntax}
32158 Several packets and replies include a @var{thread-id} field to identify
32159 a thread. Normally these are positive numbers with a target-specific
32160 interpretation, formatted as big-endian hex strings. A @var{thread-id}
32161 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
32164 In addition, the remote protocol supports a multiprocess feature in
32165 which the @var{thread-id} syntax is extended to optionally include both
32166 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
32167 The @var{pid} (process) and @var{tid} (thread) components each have the
32168 format described above: a positive number with target-specific
32169 interpretation formatted as a big-endian hex string, literal @samp{-1}
32170 to indicate all processes or threads (respectively), or @samp{0} to
32171 indicate an arbitrary process or thread. Specifying just a process, as
32172 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
32173 error to specify all processes but a specific thread, such as
32174 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
32175 for those packets and replies explicitly documented to include a process
32176 ID, rather than a @var{thread-id}.
32178 The multiprocess @var{thread-id} syntax extensions are only used if both
32179 @value{GDBN} and the stub report support for the @samp{multiprocess}
32180 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
32183 Note that all packet forms beginning with an upper- or lower-case
32184 letter, other than those described here, are reserved for future use.
32186 Here are the packet descriptions.
32191 @cindex @samp{!} packet
32192 @anchor{extended mode}
32193 Enable extended mode. In extended mode, the remote server is made
32194 persistent. The @samp{R} packet is used to restart the program being
32200 The remote target both supports and has enabled extended mode.
32204 @cindex @samp{?} packet
32205 Indicate the reason the target halted. The reply is the same as for
32206 step and continue. This packet has a special interpretation when the
32207 target is in non-stop mode; see @ref{Remote Non-Stop}.
32210 @xref{Stop Reply Packets}, for the reply specifications.
32212 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
32213 @cindex @samp{A} packet
32214 Initialized @code{argv[]} array passed into program. @var{arglen}
32215 specifies the number of bytes in the hex encoded byte stream
32216 @var{arg}. See @code{gdbserver} for more details.
32221 The arguments were set.
32227 @cindex @samp{b} packet
32228 (Don't use this packet; its behavior is not well-defined.)
32229 Change the serial line speed to @var{baud}.
32231 JTC: @emph{When does the transport layer state change? When it's
32232 received, or after the ACK is transmitted. In either case, there are
32233 problems if the command or the acknowledgment packet is dropped.}
32235 Stan: @emph{If people really wanted to add something like this, and get
32236 it working for the first time, they ought to modify ser-unix.c to send
32237 some kind of out-of-band message to a specially-setup stub and have the
32238 switch happen "in between" packets, so that from remote protocol's point
32239 of view, nothing actually happened.}
32241 @item B @var{addr},@var{mode}
32242 @cindex @samp{B} packet
32243 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
32244 breakpoint at @var{addr}.
32246 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
32247 (@pxref{insert breakpoint or watchpoint packet}).
32249 @cindex @samp{bc} packet
32252 Backward continue. Execute the target system in reverse. No parameter.
32253 @xref{Reverse Execution}, for more information.
32256 @xref{Stop Reply Packets}, for the reply specifications.
32258 @cindex @samp{bs} packet
32261 Backward single step. Execute one instruction in reverse. No parameter.
32262 @xref{Reverse Execution}, for more information.
32265 @xref{Stop Reply Packets}, for the reply specifications.
32267 @item c @r{[}@var{addr}@r{]}
32268 @cindex @samp{c} packet
32269 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
32270 resume at current address.
32273 @xref{Stop Reply Packets}, for the reply specifications.
32275 @item C @var{sig}@r{[};@var{addr}@r{]}
32276 @cindex @samp{C} packet
32277 Continue with signal @var{sig} (hex signal number). If
32278 @samp{;@var{addr}} is omitted, resume at same address.
32281 @xref{Stop Reply Packets}, for the reply specifications.
32284 @cindex @samp{d} packet
32287 Don't use this packet; instead, define a general set packet
32288 (@pxref{General Query Packets}).
32292 @cindex @samp{D} packet
32293 The first form of the packet is used to detach @value{GDBN} from the
32294 remote system. It is sent to the remote target
32295 before @value{GDBN} disconnects via the @code{detach} command.
32297 The second form, including a process ID, is used when multiprocess
32298 protocol extensions are enabled (@pxref{multiprocess extensions}), to
32299 detach only a specific process. The @var{pid} is specified as a
32300 big-endian hex string.
32310 @item F @var{RC},@var{EE},@var{CF};@var{XX}
32311 @cindex @samp{F} packet
32312 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
32313 This is part of the File-I/O protocol extension. @xref{File-I/O
32314 Remote Protocol Extension}, for the specification.
32317 @anchor{read registers packet}
32318 @cindex @samp{g} packet
32319 Read general registers.
32323 @item @var{XX@dots{}}
32324 Each byte of register data is described by two hex digits. The bytes
32325 with the register are transmitted in target byte order. The size of
32326 each register and their position within the @samp{g} packet are
32327 determined by the @value{GDBN} internal gdbarch functions
32328 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
32329 specification of several standard @samp{g} packets is specified below.
32331 When reading registers from a trace frame (@pxref{Analyze Collected
32332 Data,,Using the Collected Data}), the stub may also return a string of
32333 literal @samp{x}'s in place of the register data digits, to indicate
32334 that the corresponding register has not been collected, thus its value
32335 is unavailable. For example, for an architecture with 4 registers of
32336 4 bytes each, the following reply indicates to @value{GDBN} that
32337 registers 0 and 2 have not been collected, while registers 1 and 3
32338 have been collected, and both have zero value:
32342 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
32349 @item G @var{XX@dots{}}
32350 @cindex @samp{G} packet
32351 Write general registers. @xref{read registers packet}, for a
32352 description of the @var{XX@dots{}} data.
32362 @item H @var{c} @var{thread-id}
32363 @cindex @samp{H} packet
32364 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
32365 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
32366 should be @samp{c} for step and continue operations, @samp{g} for other
32367 operations. The thread designator @var{thread-id} has the format and
32368 interpretation described in @ref{thread-id syntax}.
32379 @c 'H': How restrictive (or permissive) is the thread model. If a
32380 @c thread is selected and stopped, are other threads allowed
32381 @c to continue to execute? As I mentioned above, I think the
32382 @c semantics of each command when a thread is selected must be
32383 @c described. For example:
32385 @c 'g': If the stub supports threads and a specific thread is
32386 @c selected, returns the register block from that thread;
32387 @c otherwise returns current registers.
32389 @c 'G' If the stub supports threads and a specific thread is
32390 @c selected, sets the registers of the register block of
32391 @c that thread; otherwise sets current registers.
32393 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
32394 @anchor{cycle step packet}
32395 @cindex @samp{i} packet
32396 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
32397 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
32398 step starting at that address.
32401 @cindex @samp{I} packet
32402 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
32406 @cindex @samp{k} packet
32409 FIXME: @emph{There is no description of how to operate when a specific
32410 thread context has been selected (i.e.@: does 'k' kill only that
32413 @item m @var{addr},@var{length}
32414 @cindex @samp{m} packet
32415 Read @var{length} bytes of memory starting at address @var{addr}.
32416 Note that @var{addr} may not be aligned to any particular boundary.
32418 The stub need not use any particular size or alignment when gathering
32419 data from memory for the response; even if @var{addr} is word-aligned
32420 and @var{length} is a multiple of the word size, the stub is free to
32421 use byte accesses, or not. For this reason, this packet may not be
32422 suitable for accessing memory-mapped I/O devices.
32423 @cindex alignment of remote memory accesses
32424 @cindex size of remote memory accesses
32425 @cindex memory, alignment and size of remote accesses
32429 @item @var{XX@dots{}}
32430 Memory contents; each byte is transmitted as a two-digit hexadecimal
32431 number. The reply may contain fewer bytes than requested if the
32432 server was able to read only part of the region of memory.
32437 @item M @var{addr},@var{length}:@var{XX@dots{}}
32438 @cindex @samp{M} packet
32439 Write @var{length} bytes of memory starting at address @var{addr}.
32440 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
32441 hexadecimal number.
32448 for an error (this includes the case where only part of the data was
32453 @cindex @samp{p} packet
32454 Read the value of register @var{n}; @var{n} is in hex.
32455 @xref{read registers packet}, for a description of how the returned
32456 register value is encoded.
32460 @item @var{XX@dots{}}
32461 the register's value
32465 Indicating an unrecognized @var{query}.
32468 @item P @var{n@dots{}}=@var{r@dots{}}
32469 @anchor{write register packet}
32470 @cindex @samp{P} packet
32471 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
32472 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
32473 digits for each byte in the register (target byte order).
32483 @item q @var{name} @var{params}@dots{}
32484 @itemx Q @var{name} @var{params}@dots{}
32485 @cindex @samp{q} packet
32486 @cindex @samp{Q} packet
32487 General query (@samp{q}) and set (@samp{Q}). These packets are
32488 described fully in @ref{General Query Packets}.
32491 @cindex @samp{r} packet
32492 Reset the entire system.
32494 Don't use this packet; use the @samp{R} packet instead.
32497 @cindex @samp{R} packet
32498 Restart the program being debugged. @var{XX}, while needed, is ignored.
32499 This packet is only available in extended mode (@pxref{extended mode}).
32501 The @samp{R} packet has no reply.
32503 @item s @r{[}@var{addr}@r{]}
32504 @cindex @samp{s} packet
32505 Single step. @var{addr} is the address at which to resume. If
32506 @var{addr} is omitted, resume at same address.
32509 @xref{Stop Reply Packets}, for the reply specifications.
32511 @item S @var{sig}@r{[};@var{addr}@r{]}
32512 @anchor{step with signal packet}
32513 @cindex @samp{S} packet
32514 Step with signal. This is analogous to the @samp{C} packet, but
32515 requests a single-step, rather than a normal resumption of execution.
32518 @xref{Stop Reply Packets}, for the reply specifications.
32520 @item t @var{addr}:@var{PP},@var{MM}
32521 @cindex @samp{t} packet
32522 Search backwards starting at address @var{addr} for a match with pattern
32523 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
32524 @var{addr} must be at least 3 digits.
32526 @item T @var{thread-id}
32527 @cindex @samp{T} packet
32528 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
32533 thread is still alive
32539 Packets starting with @samp{v} are identified by a multi-letter name,
32540 up to the first @samp{;} or @samp{?} (or the end of the packet).
32542 @item vAttach;@var{pid}
32543 @cindex @samp{vAttach} packet
32544 Attach to a new process with the specified process ID @var{pid}.
32545 The process ID is a
32546 hexadecimal integer identifying the process. In all-stop mode, all
32547 threads in the attached process are stopped; in non-stop mode, it may be
32548 attached without being stopped if that is supported by the target.
32550 @c In non-stop mode, on a successful vAttach, the stub should set the
32551 @c current thread to a thread of the newly-attached process. After
32552 @c attaching, GDB queries for the attached process's thread ID with qC.
32553 @c Also note that, from a user perspective, whether or not the
32554 @c target is stopped on attach in non-stop mode depends on whether you
32555 @c use the foreground or background version of the attach command, not
32556 @c on what vAttach does; GDB does the right thing with respect to either
32557 @c stopping or restarting threads.
32559 This packet is only available in extended mode (@pxref{extended mode}).
32565 @item @r{Any stop packet}
32566 for success in all-stop mode (@pxref{Stop Reply Packets})
32568 for success in non-stop mode (@pxref{Remote Non-Stop})
32571 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32572 @cindex @samp{vCont} packet
32573 Resume the inferior, specifying different actions for each thread.
32574 If an action is specified with no @var{thread-id}, then it is applied to any
32575 threads that don't have a specific action specified; if no default action is
32576 specified then other threads should remain stopped in all-stop mode and
32577 in their current state in non-stop mode.
32578 Specifying multiple
32579 default actions is an error; specifying no actions is also an error.
32580 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32582 Currently supported actions are:
32588 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32592 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32597 The optional argument @var{addr} normally associated with the
32598 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32599 not supported in @samp{vCont}.
32601 The @samp{t} action is only relevant in non-stop mode
32602 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32603 A stop reply should be generated for any affected thread not already stopped.
32604 When a thread is stopped by means of a @samp{t} action,
32605 the corresponding stop reply should indicate that the thread has stopped with
32606 signal @samp{0}, regardless of whether the target uses some other signal
32607 as an implementation detail.
32610 @xref{Stop Reply Packets}, for the reply specifications.
32613 @cindex @samp{vCont?} packet
32614 Request a list of actions supported by the @samp{vCont} packet.
32618 @item vCont@r{[};@var{action}@dots{}@r{]}
32619 The @samp{vCont} packet is supported. Each @var{action} is a supported
32620 command in the @samp{vCont} packet.
32622 The @samp{vCont} packet is not supported.
32625 @item vFile:@var{operation}:@var{parameter}@dots{}
32626 @cindex @samp{vFile} packet
32627 Perform a file operation on the target system. For details,
32628 see @ref{Host I/O Packets}.
32630 @item vFlashErase:@var{addr},@var{length}
32631 @cindex @samp{vFlashErase} packet
32632 Direct the stub to erase @var{length} bytes of flash starting at
32633 @var{addr}. The region may enclose any number of flash blocks, but
32634 its start and end must fall on block boundaries, as indicated by the
32635 flash block size appearing in the memory map (@pxref{Memory Map
32636 Format}). @value{GDBN} groups flash memory programming operations
32637 together, and sends a @samp{vFlashDone} request after each group; the
32638 stub is allowed to delay erase operation until the @samp{vFlashDone}
32639 packet is received.
32641 The stub must support @samp{vCont} if it reports support for
32642 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32643 this case @samp{vCont} actions can be specified to apply to all threads
32644 in a process by using the @samp{p@var{pid}.-1} form of the
32655 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32656 @cindex @samp{vFlashWrite} packet
32657 Direct the stub to write data to flash address @var{addr}. The data
32658 is passed in binary form using the same encoding as for the @samp{X}
32659 packet (@pxref{Binary Data}). The memory ranges specified by
32660 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32661 not overlap, and must appear in order of increasing addresses
32662 (although @samp{vFlashErase} packets for higher addresses may already
32663 have been received; the ordering is guaranteed only between
32664 @samp{vFlashWrite} packets). If a packet writes to an address that was
32665 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32666 target-specific method, the results are unpredictable.
32674 for vFlashWrite addressing non-flash memory
32680 @cindex @samp{vFlashDone} packet
32681 Indicate to the stub that flash programming operation is finished.
32682 The stub is permitted to delay or batch the effects of a group of
32683 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32684 @samp{vFlashDone} packet is received. The contents of the affected
32685 regions of flash memory are unpredictable until the @samp{vFlashDone}
32686 request is completed.
32688 @item vKill;@var{pid}
32689 @cindex @samp{vKill} packet
32690 Kill the process with the specified process ID. @var{pid} is a
32691 hexadecimal integer identifying the process. This packet is used in
32692 preference to @samp{k} when multiprocess protocol extensions are
32693 supported; see @ref{multiprocess extensions}.
32703 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32704 @cindex @samp{vRun} packet
32705 Run the program @var{filename}, passing it each @var{argument} on its
32706 command line. The file and arguments are hex-encoded strings. If
32707 @var{filename} is an empty string, the stub may use a default program
32708 (e.g.@: the last program run). The program is created in the stopped
32711 @c FIXME: What about non-stop mode?
32713 This packet is only available in extended mode (@pxref{extended mode}).
32719 @item @r{Any stop packet}
32720 for success (@pxref{Stop Reply Packets})
32724 @anchor{vStopped packet}
32725 @cindex @samp{vStopped} packet
32727 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32728 reply and prompt for the stub to report another one.
32732 @item @r{Any stop packet}
32733 if there is another unreported stop event (@pxref{Stop Reply Packets})
32735 if there are no unreported stop events
32738 @item X @var{addr},@var{length}:@var{XX@dots{}}
32740 @cindex @samp{X} packet
32741 Write data to memory, where the data is transmitted in binary.
32742 @var{addr} is address, @var{length} is number of bytes,
32743 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32753 @item z @var{type},@var{addr},@var{kind}
32754 @itemx Z @var{type},@var{addr},@var{kind}
32755 @anchor{insert breakpoint or watchpoint packet}
32756 @cindex @samp{z} packet
32757 @cindex @samp{Z} packets
32758 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32759 watchpoint starting at address @var{address} of kind @var{kind}.
32761 Each breakpoint and watchpoint packet @var{type} is documented
32764 @emph{Implementation notes: A remote target shall return an empty string
32765 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32766 remote target shall support either both or neither of a given
32767 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32768 avoid potential problems with duplicate packets, the operations should
32769 be implemented in an idempotent way.}
32771 @item z0,@var{addr},@var{kind}
32772 @itemx Z0,@var{addr},@var{kind}
32773 @cindex @samp{z0} packet
32774 @cindex @samp{Z0} packet
32775 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32776 @var{addr} of type @var{kind}.
32778 A memory breakpoint is implemented by replacing the instruction at
32779 @var{addr} with a software breakpoint or trap instruction. The
32780 @var{kind} is target-specific and typically indicates the size of
32781 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32782 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32783 architectures have additional meanings for @var{kind};
32784 see @ref{Architecture-Specific Protocol Details}.
32786 @emph{Implementation note: It is possible for a target to copy or move
32787 code that contains memory breakpoints (e.g., when implementing
32788 overlays). The behavior of this packet, in the presence of such a
32789 target, is not defined.}
32801 @item z1,@var{addr},@var{kind}
32802 @itemx Z1,@var{addr},@var{kind}
32803 @cindex @samp{z1} packet
32804 @cindex @samp{Z1} packet
32805 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32806 address @var{addr}.
32808 A hardware breakpoint is implemented using a mechanism that is not
32809 dependant on being able to modify the target's memory. @var{kind}
32810 has the same meaning as in @samp{Z0} packets.
32812 @emph{Implementation note: A hardware breakpoint is not affected by code
32825 @item z2,@var{addr},@var{kind}
32826 @itemx Z2,@var{addr},@var{kind}
32827 @cindex @samp{z2} packet
32828 @cindex @samp{Z2} packet
32829 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32830 @var{kind} is interpreted as the number of bytes to watch.
32842 @item z3,@var{addr},@var{kind}
32843 @itemx Z3,@var{addr},@var{kind}
32844 @cindex @samp{z3} packet
32845 @cindex @samp{Z3} packet
32846 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
32847 @var{kind} is interpreted as the number of bytes to watch.
32859 @item z4,@var{addr},@var{kind}
32860 @itemx Z4,@var{addr},@var{kind}
32861 @cindex @samp{z4} packet
32862 @cindex @samp{Z4} packet
32863 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
32864 @var{kind} is interpreted as the number of bytes to watch.
32878 @node Stop Reply Packets
32879 @section Stop Reply Packets
32880 @cindex stop reply packets
32882 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
32883 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
32884 receive any of the below as a reply. Except for @samp{?}
32885 and @samp{vStopped}, that reply is only returned
32886 when the target halts. In the below the exact meaning of @dfn{signal
32887 number} is defined by the header @file{include/gdb/signals.h} in the
32888 @value{GDBN} source code.
32890 As in the description of request packets, we include spaces in the
32891 reply templates for clarity; these are not part of the reply packet's
32892 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
32898 The program received signal number @var{AA} (a two-digit hexadecimal
32899 number). This is equivalent to a @samp{T} response with no
32900 @var{n}:@var{r} pairs.
32902 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
32903 @cindex @samp{T} packet reply
32904 The program received signal number @var{AA} (a two-digit hexadecimal
32905 number). This is equivalent to an @samp{S} response, except that the
32906 @samp{@var{n}:@var{r}} pairs can carry values of important registers
32907 and other information directly in the stop reply packet, reducing
32908 round-trip latency. Single-step and breakpoint traps are reported
32909 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
32913 If @var{n} is a hexadecimal number, it is a register number, and the
32914 corresponding @var{r} gives that register's value. @var{r} is a
32915 series of bytes in target byte order, with each byte given by a
32916 two-digit hex number.
32919 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32920 the stopped thread, as specified in @ref{thread-id syntax}.
32923 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32924 the core on which the stop event was detected.
32927 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32928 specific event that stopped the target. The currently defined stop
32929 reasons are listed below. @var{aa} should be @samp{05}, the trap
32930 signal. At most one stop reason should be present.
32933 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32934 and go on to the next; this allows us to extend the protocol in the
32938 The currently defined stop reasons are:
32944 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32947 @cindex shared library events, remote reply
32949 The packet indicates that the loaded libraries have changed.
32950 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32951 list of loaded libraries. @var{r} is ignored.
32953 @cindex replay log events, remote reply
32955 The packet indicates that the target cannot continue replaying
32956 logged execution events, because it has reached the end (or the
32957 beginning when executing backward) of the log. The value of @var{r}
32958 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32959 for more information.
32963 @itemx W @var{AA} ; process:@var{pid}
32964 The process exited, and @var{AA} is the exit status. This is only
32965 applicable to certain targets.
32967 The second form of the response, including the process ID of the exited
32968 process, can be used only when @value{GDBN} has reported support for
32969 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32970 The @var{pid} is formatted as a big-endian hex string.
32973 @itemx X @var{AA} ; process:@var{pid}
32974 The process terminated with signal @var{AA}.
32976 The second form of the response, including the process ID of the
32977 terminated process, can be used only when @value{GDBN} has reported
32978 support for multiprocess protocol extensions; see @ref{multiprocess
32979 extensions}. The @var{pid} is formatted as a big-endian hex string.
32981 @item O @var{XX}@dots{}
32982 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
32983 written as the program's console output. This can happen at any time
32984 while the program is running and the debugger should continue to wait
32985 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
32987 @item F @var{call-id},@var{parameter}@dots{}
32988 @var{call-id} is the identifier which says which host system call should
32989 be called. This is just the name of the function. Translation into the
32990 correct system call is only applicable as it's defined in @value{GDBN}.
32991 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
32994 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
32995 this very system call.
32997 The target replies with this packet when it expects @value{GDBN} to
32998 call a host system call on behalf of the target. @value{GDBN} replies
32999 with an appropriate @samp{F} packet and keeps up waiting for the next
33000 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
33001 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
33002 Protocol Extension}, for more details.
33006 @node General Query Packets
33007 @section General Query Packets
33008 @cindex remote query requests
33010 Packets starting with @samp{q} are @dfn{general query packets};
33011 packets starting with @samp{Q} are @dfn{general set packets}. General
33012 query and set packets are a semi-unified form for retrieving and
33013 sending information to and from the stub.
33015 The initial letter of a query or set packet is followed by a name
33016 indicating what sort of thing the packet applies to. For example,
33017 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
33018 definitions with the stub. These packet names follow some
33023 The name must not contain commas, colons or semicolons.
33025 Most @value{GDBN} query and set packets have a leading upper case
33028 The names of custom vendor packets should use a company prefix, in
33029 lower case, followed by a period. For example, packets designed at
33030 the Acme Corporation might begin with @samp{qacme.foo} (for querying
33031 foos) or @samp{Qacme.bar} (for setting bars).
33034 The name of a query or set packet should be separated from any
33035 parameters by a @samp{:}; the parameters themselves should be
33036 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
33037 full packet name, and check for a separator or the end of the packet,
33038 in case two packet names share a common prefix. New packets should not begin
33039 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
33040 packets predate these conventions, and have arguments without any terminator
33041 for the packet name; we suspect they are in widespread use in places that
33042 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
33043 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
33046 Like the descriptions of the other packets, each description here
33047 has a template showing the packet's overall syntax, followed by an
33048 explanation of the packet's meaning. We include spaces in some of the
33049 templates for clarity; these are not part of the packet's syntax. No
33050 @value{GDBN} packet uses spaces to separate its components.
33052 Here are the currently defined query and set packets:
33056 @item QAllow:@var{op}:@var{val}@dots{}
33057 @cindex @samp{QAllow} packet
33058 Specify which operations @value{GDBN} expects to request of the
33059 target, as a semicolon-separated list of operation name and value
33060 pairs. Possible values for @var{op} include @samp{WriteReg},
33061 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
33062 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
33063 indicating that @value{GDBN} will not request the operation, or 1,
33064 indicating that it may. (The target can then use this to set up its
33065 own internals optimally, for instance if the debugger never expects to
33066 insert breakpoints, it may not need to install its own trap handler.)
33069 @cindex current thread, remote request
33070 @cindex @samp{qC} packet
33071 Return the current thread ID.
33075 @item QC @var{thread-id}
33076 Where @var{thread-id} is a thread ID as documented in
33077 @ref{thread-id syntax}.
33078 @item @r{(anything else)}
33079 Any other reply implies the old thread ID.
33082 @item qCRC:@var{addr},@var{length}
33083 @cindex CRC of memory block, remote request
33084 @cindex @samp{qCRC} packet
33085 Compute the CRC checksum of a block of memory using CRC-32 defined in
33086 IEEE 802.3. The CRC is computed byte at a time, taking the most
33087 significant bit of each byte first. The initial pattern code
33088 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
33090 @emph{Note:} This is the same CRC used in validating separate debug
33091 files (@pxref{Separate Debug Files, , Debugging Information in Separate
33092 Files}). However the algorithm is slightly different. When validating
33093 separate debug files, the CRC is computed taking the @emph{least}
33094 significant bit of each byte first, and the final result is inverted to
33095 detect trailing zeros.
33100 An error (such as memory fault)
33101 @item C @var{crc32}
33102 The specified memory region's checksum is @var{crc32}.
33106 @itemx qsThreadInfo
33107 @cindex list active threads, remote request
33108 @cindex @samp{qfThreadInfo} packet
33109 @cindex @samp{qsThreadInfo} packet
33110 Obtain a list of all active thread IDs from the target (OS). Since there
33111 may be too many active threads to fit into one reply packet, this query
33112 works iteratively: it may require more than one query/reply sequence to
33113 obtain the entire list of threads. The first query of the sequence will
33114 be the @samp{qfThreadInfo} query; subsequent queries in the
33115 sequence will be the @samp{qsThreadInfo} query.
33117 NOTE: This packet replaces the @samp{qL} query (see below).
33121 @item m @var{thread-id}
33123 @item m @var{thread-id},@var{thread-id}@dots{}
33124 a comma-separated list of thread IDs
33126 (lower case letter @samp{L}) denotes end of list.
33129 In response to each query, the target will reply with a list of one or
33130 more thread IDs, separated by commas.
33131 @value{GDBN} will respond to each reply with a request for more thread
33132 ids (using the @samp{qs} form of the query), until the target responds
33133 with @samp{l} (lower-case ell, for @dfn{last}).
33134 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
33137 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
33138 @cindex get thread-local storage address, remote request
33139 @cindex @samp{qGetTLSAddr} packet
33140 Fetch the address associated with thread local storage specified
33141 by @var{thread-id}, @var{offset}, and @var{lm}.
33143 @var{thread-id} is the thread ID associated with the
33144 thread for which to fetch the TLS address. @xref{thread-id syntax}.
33146 @var{offset} is the (big endian, hex encoded) offset associated with the
33147 thread local variable. (This offset is obtained from the debug
33148 information associated with the variable.)
33150 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
33151 load module associated with the thread local storage. For example,
33152 a @sc{gnu}/Linux system will pass the link map address of the shared
33153 object associated with the thread local storage under consideration.
33154 Other operating environments may choose to represent the load module
33155 differently, so the precise meaning of this parameter will vary.
33159 @item @var{XX}@dots{}
33160 Hex encoded (big endian) bytes representing the address of the thread
33161 local storage requested.
33164 An error occurred. @var{nn} are hex digits.
33167 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
33170 @item qGetTIBAddr:@var{thread-id}
33171 @cindex get thread information block address
33172 @cindex @samp{qGetTIBAddr} packet
33173 Fetch address of the Windows OS specific Thread Information Block.
33175 @var{thread-id} is the thread ID associated with the thread.
33179 @item @var{XX}@dots{}
33180 Hex encoded (big endian) bytes representing the linear address of the
33181 thread information block.
33184 An error occured. This means that either the thread was not found, or the
33185 address could not be retrieved.
33188 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
33191 @item qL @var{startflag} @var{threadcount} @var{nextthread}
33192 Obtain thread information from RTOS. Where: @var{startflag} (one hex
33193 digit) is one to indicate the first query and zero to indicate a
33194 subsequent query; @var{threadcount} (two hex digits) is the maximum
33195 number of threads the response packet can contain; and @var{nextthread}
33196 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
33197 returned in the response as @var{argthread}.
33199 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
33203 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
33204 Where: @var{count} (two hex digits) is the number of threads being
33205 returned; @var{done} (one hex digit) is zero to indicate more threads
33206 and one indicates no further threads; @var{argthreadid} (eight hex
33207 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
33208 is a sequence of thread IDs from the target. @var{threadid} (eight hex
33209 digits). See @code{remote.c:parse_threadlist_response()}.
33213 @cindex section offsets, remote request
33214 @cindex @samp{qOffsets} packet
33215 Get section offsets that the target used when relocating the downloaded
33220 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
33221 Relocate the @code{Text} section by @var{xxx} from its original address.
33222 Relocate the @code{Data} section by @var{yyy} from its original address.
33223 If the object file format provides segment information (e.g.@: @sc{elf}
33224 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
33225 segments by the supplied offsets.
33227 @emph{Note: while a @code{Bss} offset may be included in the response,
33228 @value{GDBN} ignores this and instead applies the @code{Data} offset
33229 to the @code{Bss} section.}
33231 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
33232 Relocate the first segment of the object file, which conventionally
33233 contains program code, to a starting address of @var{xxx}. If
33234 @samp{DataSeg} is specified, relocate the second segment, which
33235 conventionally contains modifiable data, to a starting address of
33236 @var{yyy}. @value{GDBN} will report an error if the object file
33237 does not contain segment information, or does not contain at least
33238 as many segments as mentioned in the reply. Extra segments are
33239 kept at fixed offsets relative to the last relocated segment.
33242 @item qP @var{mode} @var{thread-id}
33243 @cindex thread information, remote request
33244 @cindex @samp{qP} packet
33245 Returns information on @var{thread-id}. Where: @var{mode} is a hex
33246 encoded 32 bit mode; @var{thread-id} is a thread ID
33247 (@pxref{thread-id syntax}).
33249 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
33252 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
33256 @cindex non-stop mode, remote request
33257 @cindex @samp{QNonStop} packet
33259 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
33260 @xref{Remote Non-Stop}, for more information.
33265 The request succeeded.
33268 An error occurred. @var{nn} are hex digits.
33271 An empty reply indicates that @samp{QNonStop} is not supported by
33275 This packet is not probed by default; the remote stub must request it,
33276 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33277 Use of this packet is controlled by the @code{set non-stop} command;
33278 @pxref{Non-Stop Mode}.
33280 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
33281 @cindex pass signals to inferior, remote request
33282 @cindex @samp{QPassSignals} packet
33283 @anchor{QPassSignals}
33284 Each listed @var{signal} should be passed directly to the inferior process.
33285 Signals are numbered identically to continue packets and stop replies
33286 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
33287 strictly greater than the previous item. These signals do not need to stop
33288 the inferior, or be reported to @value{GDBN}. All other signals should be
33289 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
33290 combine; any earlier @samp{QPassSignals} list is completely replaced by the
33291 new list. This packet improves performance when using @samp{handle
33292 @var{signal} nostop noprint pass}.
33297 The request succeeded.
33300 An error occurred. @var{nn} are hex digits.
33303 An empty reply indicates that @samp{QPassSignals} is not supported by
33307 Use of this packet is controlled by the @code{set remote pass-signals}
33308 command (@pxref{Remote Configuration, set remote pass-signals}).
33309 This packet is not probed by default; the remote stub must request it,
33310 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33312 @item qRcmd,@var{command}
33313 @cindex execute remote command, remote request
33314 @cindex @samp{qRcmd} packet
33315 @var{command} (hex encoded) is passed to the local interpreter for
33316 execution. Invalid commands should be reported using the output
33317 string. Before the final result packet, the target may also respond
33318 with a number of intermediate @samp{O@var{output}} console output
33319 packets. @emph{Implementors should note that providing access to a
33320 stubs's interpreter may have security implications}.
33325 A command response with no output.
33327 A command response with the hex encoded output string @var{OUTPUT}.
33329 Indicate a badly formed request.
33331 An empty reply indicates that @samp{qRcmd} is not recognized.
33334 (Note that the @code{qRcmd} packet's name is separated from the
33335 command by a @samp{,}, not a @samp{:}, contrary to the naming
33336 conventions above. Please don't use this packet as a model for new
33339 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
33340 @cindex searching memory, in remote debugging
33341 @cindex @samp{qSearch:memory} packet
33342 @anchor{qSearch memory}
33343 Search @var{length} bytes at @var{address} for @var{search-pattern}.
33344 @var{address} and @var{length} are encoded in hex.
33345 @var{search-pattern} is a sequence of bytes, hex encoded.
33350 The pattern was not found.
33352 The pattern was found at @var{address}.
33354 A badly formed request or an error was encountered while searching memory.
33356 An empty reply indicates that @samp{qSearch:memory} is not recognized.
33359 @item QStartNoAckMode
33360 @cindex @samp{QStartNoAckMode} packet
33361 @anchor{QStartNoAckMode}
33362 Request that the remote stub disable the normal @samp{+}/@samp{-}
33363 protocol acknowledgments (@pxref{Packet Acknowledgment}).
33368 The stub has switched to no-acknowledgment mode.
33369 @value{GDBN} acknowledges this reponse,
33370 but neither the stub nor @value{GDBN} shall send or expect further
33371 @samp{+}/@samp{-} acknowledgments in the current connection.
33373 An empty reply indicates that the stub does not support no-acknowledgment mode.
33376 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
33377 @cindex supported packets, remote query
33378 @cindex features of the remote protocol
33379 @cindex @samp{qSupported} packet
33380 @anchor{qSupported}
33381 Tell the remote stub about features supported by @value{GDBN}, and
33382 query the stub for features it supports. This packet allows
33383 @value{GDBN} and the remote stub to take advantage of each others'
33384 features. @samp{qSupported} also consolidates multiple feature probes
33385 at startup, to improve @value{GDBN} performance---a single larger
33386 packet performs better than multiple smaller probe packets on
33387 high-latency links. Some features may enable behavior which must not
33388 be on by default, e.g.@: because it would confuse older clients or
33389 stubs. Other features may describe packets which could be
33390 automatically probed for, but are not. These features must be
33391 reported before @value{GDBN} will use them. This ``default
33392 unsupported'' behavior is not appropriate for all packets, but it
33393 helps to keep the initial connection time under control with new
33394 versions of @value{GDBN} which support increasing numbers of packets.
33398 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
33399 The stub supports or does not support each returned @var{stubfeature},
33400 depending on the form of each @var{stubfeature} (see below for the
33403 An empty reply indicates that @samp{qSupported} is not recognized,
33404 or that no features needed to be reported to @value{GDBN}.
33407 The allowed forms for each feature (either a @var{gdbfeature} in the
33408 @samp{qSupported} packet, or a @var{stubfeature} in the response)
33412 @item @var{name}=@var{value}
33413 The remote protocol feature @var{name} is supported, and associated
33414 with the specified @var{value}. The format of @var{value} depends
33415 on the feature, but it must not include a semicolon.
33417 The remote protocol feature @var{name} is supported, and does not
33418 need an associated value.
33420 The remote protocol feature @var{name} is not supported.
33422 The remote protocol feature @var{name} may be supported, and
33423 @value{GDBN} should auto-detect support in some other way when it is
33424 needed. This form will not be used for @var{gdbfeature} notifications,
33425 but may be used for @var{stubfeature} responses.
33428 Whenever the stub receives a @samp{qSupported} request, the
33429 supplied set of @value{GDBN} features should override any previous
33430 request. This allows @value{GDBN} to put the stub in a known
33431 state, even if the stub had previously been communicating with
33432 a different version of @value{GDBN}.
33434 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
33439 This feature indicates whether @value{GDBN} supports multiprocess
33440 extensions to the remote protocol. @value{GDBN} does not use such
33441 extensions unless the stub also reports that it supports them by
33442 including @samp{multiprocess+} in its @samp{qSupported} reply.
33443 @xref{multiprocess extensions}, for details.
33446 This feature indicates that @value{GDBN} supports the XML target
33447 description. If the stub sees @samp{xmlRegisters=} with target
33448 specific strings separated by a comma, it will report register
33452 This feature indicates whether @value{GDBN} supports the
33453 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
33454 instruction reply packet}).
33457 Stubs should ignore any unknown values for
33458 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
33459 packet supports receiving packets of unlimited length (earlier
33460 versions of @value{GDBN} may reject overly long responses). Additional values
33461 for @var{gdbfeature} may be defined in the future to let the stub take
33462 advantage of new features in @value{GDBN}, e.g.@: incompatible
33463 improvements in the remote protocol---the @samp{multiprocess} feature is
33464 an example of such a feature. The stub's reply should be independent
33465 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
33466 describes all the features it supports, and then the stub replies with
33467 all the features it supports.
33469 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
33470 responses, as long as each response uses one of the standard forms.
33472 Some features are flags. A stub which supports a flag feature
33473 should respond with a @samp{+} form response. Other features
33474 require values, and the stub should respond with an @samp{=}
33477 Each feature has a default value, which @value{GDBN} will use if
33478 @samp{qSupported} is not available or if the feature is not mentioned
33479 in the @samp{qSupported} response. The default values are fixed; a
33480 stub is free to omit any feature responses that match the defaults.
33482 Not all features can be probed, but for those which can, the probing
33483 mechanism is useful: in some cases, a stub's internal
33484 architecture may not allow the protocol layer to know some information
33485 about the underlying target in advance. This is especially common in
33486 stubs which may be configured for multiple targets.
33488 These are the currently defined stub features and their properties:
33490 @multitable @columnfractions 0.35 0.2 0.12 0.2
33491 @c NOTE: The first row should be @headitem, but we do not yet require
33492 @c a new enough version of Texinfo (4.7) to use @headitem.
33494 @tab Value Required
33498 @item @samp{PacketSize}
33503 @item @samp{qXfer:auxv:read}
33508 @item @samp{qXfer:features:read}
33513 @item @samp{qXfer:libraries:read}
33518 @item @samp{qXfer:memory-map:read}
33523 @item @samp{qXfer:sdata:read}
33528 @item @samp{qXfer:spu:read}
33533 @item @samp{qXfer:spu:write}
33538 @item @samp{qXfer:siginfo:read}
33543 @item @samp{qXfer:siginfo:write}
33548 @item @samp{qXfer:threads:read}
33553 @item @samp{qXfer:traceframe-info:read}
33559 @item @samp{QNonStop}
33564 @item @samp{QPassSignals}
33569 @item @samp{QStartNoAckMode}
33574 @item @samp{multiprocess}
33579 @item @samp{ConditionalTracepoints}
33584 @item @samp{ReverseContinue}
33589 @item @samp{ReverseStep}
33594 @item @samp{TracepointSource}
33599 @item @samp{QAllow}
33606 These are the currently defined stub features, in more detail:
33609 @cindex packet size, remote protocol
33610 @item PacketSize=@var{bytes}
33611 The remote stub can accept packets up to at least @var{bytes} in
33612 length. @value{GDBN} will send packets up to this size for bulk
33613 transfers, and will never send larger packets. This is a limit on the
33614 data characters in the packet, including the frame and checksum.
33615 There is no trailing NUL byte in a remote protocol packet; if the stub
33616 stores packets in a NUL-terminated format, it should allow an extra
33617 byte in its buffer for the NUL. If this stub feature is not supported,
33618 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33620 @item qXfer:auxv:read
33621 The remote stub understands the @samp{qXfer:auxv:read} packet
33622 (@pxref{qXfer auxiliary vector read}).
33624 @item qXfer:features:read
33625 The remote stub understands the @samp{qXfer:features:read} packet
33626 (@pxref{qXfer target description read}).
33628 @item qXfer:libraries:read
33629 The remote stub understands the @samp{qXfer:libraries:read} packet
33630 (@pxref{qXfer library list read}).
33632 @item qXfer:memory-map:read
33633 The remote stub understands the @samp{qXfer:memory-map:read} packet
33634 (@pxref{qXfer memory map read}).
33636 @item qXfer:sdata:read
33637 The remote stub understands the @samp{qXfer:sdata:read} packet
33638 (@pxref{qXfer sdata read}).
33640 @item qXfer:spu:read
33641 The remote stub understands the @samp{qXfer:spu:read} packet
33642 (@pxref{qXfer spu read}).
33644 @item qXfer:spu:write
33645 The remote stub understands the @samp{qXfer:spu:write} packet
33646 (@pxref{qXfer spu write}).
33648 @item qXfer:siginfo:read
33649 The remote stub understands the @samp{qXfer:siginfo:read} packet
33650 (@pxref{qXfer siginfo read}).
33652 @item qXfer:siginfo:write
33653 The remote stub understands the @samp{qXfer:siginfo:write} packet
33654 (@pxref{qXfer siginfo write}).
33656 @item qXfer:threads:read
33657 The remote stub understands the @samp{qXfer:threads:read} packet
33658 (@pxref{qXfer threads read}).
33660 @item qXfer:traceframe-info:read
33661 The remote stub understands the @samp{qXfer:traceframe-info:read}
33662 packet (@pxref{qXfer traceframe info read}).
33665 The remote stub understands the @samp{QNonStop} packet
33666 (@pxref{QNonStop}).
33669 The remote stub understands the @samp{QPassSignals} packet
33670 (@pxref{QPassSignals}).
33672 @item QStartNoAckMode
33673 The remote stub understands the @samp{QStartNoAckMode} packet and
33674 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33677 @anchor{multiprocess extensions}
33678 @cindex multiprocess extensions, in remote protocol
33679 The remote stub understands the multiprocess extensions to the remote
33680 protocol syntax. The multiprocess extensions affect the syntax of
33681 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33682 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33683 replies. Note that reporting this feature indicates support for the
33684 syntactic extensions only, not that the stub necessarily supports
33685 debugging of more than one process at a time. The stub must not use
33686 multiprocess extensions in packet replies unless @value{GDBN} has also
33687 indicated it supports them in its @samp{qSupported} request.
33689 @item qXfer:osdata:read
33690 The remote stub understands the @samp{qXfer:osdata:read} packet
33691 ((@pxref{qXfer osdata read}).
33693 @item ConditionalTracepoints
33694 The remote stub accepts and implements conditional expressions defined
33695 for tracepoints (@pxref{Tracepoint Conditions}).
33697 @item ReverseContinue
33698 The remote stub accepts and implements the reverse continue packet
33702 The remote stub accepts and implements the reverse step packet
33705 @item TracepointSource
33706 The remote stub understands the @samp{QTDPsrc} packet that supplies
33707 the source form of tracepoint definitions.
33710 The remote stub understands the @samp{QAllow} packet.
33712 @item StaticTracepoint
33713 @cindex static tracepoints, in remote protocol
33714 The remote stub supports static tracepoints.
33719 @cindex symbol lookup, remote request
33720 @cindex @samp{qSymbol} packet
33721 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33722 requests. Accept requests from the target for the values of symbols.
33727 The target does not need to look up any (more) symbols.
33728 @item qSymbol:@var{sym_name}
33729 The target requests the value of symbol @var{sym_name} (hex encoded).
33730 @value{GDBN} may provide the value by using the
33731 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33735 @item qSymbol:@var{sym_value}:@var{sym_name}
33736 Set the value of @var{sym_name} to @var{sym_value}.
33738 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33739 target has previously requested.
33741 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33742 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33748 The target does not need to look up any (more) symbols.
33749 @item qSymbol:@var{sym_name}
33750 The target requests the value of a new symbol @var{sym_name} (hex
33751 encoded). @value{GDBN} will continue to supply the values of symbols
33752 (if available), until the target ceases to request them.
33757 @item QTDisconnected
33764 @xref{Tracepoint Packets}.
33766 @item qThreadExtraInfo,@var{thread-id}
33767 @cindex thread attributes info, remote request
33768 @cindex @samp{qThreadExtraInfo} packet
33769 Obtain a printable string description of a thread's attributes from
33770 the target OS. @var{thread-id} is a thread ID;
33771 see @ref{thread-id syntax}. This
33772 string may contain anything that the target OS thinks is interesting
33773 for @value{GDBN} to tell the user about the thread. The string is
33774 displayed in @value{GDBN}'s @code{info threads} display. Some
33775 examples of possible thread extra info strings are @samp{Runnable}, or
33776 @samp{Blocked on Mutex}.
33780 @item @var{XX}@dots{}
33781 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33782 comprising the printable string containing the extra information about
33783 the thread's attributes.
33786 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33787 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33788 conventions above. Please don't use this packet as a model for new
33803 @xref{Tracepoint Packets}.
33805 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33806 @cindex read special object, remote request
33807 @cindex @samp{qXfer} packet
33808 @anchor{qXfer read}
33809 Read uninterpreted bytes from the target's special data area
33810 identified by the keyword @var{object}. Request @var{length} bytes
33811 starting at @var{offset} bytes into the data. The content and
33812 encoding of @var{annex} is specific to @var{object}; it can supply
33813 additional details about what data to access.
33815 Here are the specific requests of this form defined so far. All
33816 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33817 formats, listed below.
33820 @item qXfer:auxv:read::@var{offset},@var{length}
33821 @anchor{qXfer auxiliary vector read}
33822 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33823 auxiliary vector}. Note @var{annex} must be empty.
33825 This packet is not probed by default; the remote stub must request it,
33826 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33828 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33829 @anchor{qXfer target description read}
33830 Access the @dfn{target description}. @xref{Target Descriptions}. The
33831 annex specifies which XML document to access. The main description is
33832 always loaded from the @samp{target.xml} annex.
33834 This packet is not probed by default; the remote stub must request it,
33835 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33837 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
33838 @anchor{qXfer library list read}
33839 Access the target's list of loaded libraries. @xref{Library List Format}.
33840 The annex part of the generic @samp{qXfer} packet must be empty
33841 (@pxref{qXfer read}).
33843 Targets which maintain a list of libraries in the program's memory do
33844 not need to implement this packet; it is designed for platforms where
33845 the operating system manages the list of loaded libraries.
33847 This packet is not probed by default; the remote stub must request it,
33848 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33850 @item qXfer:memory-map:read::@var{offset},@var{length}
33851 @anchor{qXfer memory map read}
33852 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
33853 annex part of the generic @samp{qXfer} packet must be empty
33854 (@pxref{qXfer read}).
33856 This packet is not probed by default; the remote stub must request it,
33857 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33859 @item qXfer:sdata:read::@var{offset},@var{length}
33860 @anchor{qXfer sdata read}
33862 Read contents of the extra collected static tracepoint marker
33863 information. The annex part of the generic @samp{qXfer} packet must
33864 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
33867 This packet is not probed by default; the remote stub must request it,
33868 by supplying an appropriate @samp{qSupported} response
33869 (@pxref{qSupported}).
33871 @item qXfer:siginfo:read::@var{offset},@var{length}
33872 @anchor{qXfer siginfo read}
33873 Read contents of the extra signal information on the target
33874 system. The annex part of the generic @samp{qXfer} packet must be
33875 empty (@pxref{qXfer read}).
33877 This packet is not probed by default; the remote stub must request it,
33878 by supplying an appropriate @samp{qSupported} response
33879 (@pxref{qSupported}).
33881 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
33882 @anchor{qXfer spu read}
33883 Read contents of an @code{spufs} file on the target system. The
33884 annex specifies which file to read; it must be of the form
33885 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33886 in the target process, and @var{name} identifes the @code{spufs} file
33887 in that context to be accessed.
33889 This packet is not probed by default; the remote stub must request it,
33890 by supplying an appropriate @samp{qSupported} response
33891 (@pxref{qSupported}).
33893 @item qXfer:threads:read::@var{offset},@var{length}
33894 @anchor{qXfer threads read}
33895 Access the list of threads on target. @xref{Thread List Format}. The
33896 annex part of the generic @samp{qXfer} packet must be empty
33897 (@pxref{qXfer read}).
33899 This packet is not probed by default; the remote stub must request it,
33900 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33902 @item qXfer:traceframe-info:read::@var{offset},@var{length}
33903 @anchor{qXfer traceframe info read}
33905 Return a description of the current traceframe's contents.
33906 @xref{Traceframe Info Format}. The annex part of the generic
33907 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
33909 This packet is not probed by default; the remote stub must request it,
33910 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33912 @item qXfer:osdata:read::@var{offset},@var{length}
33913 @anchor{qXfer osdata read}
33914 Access the target's @dfn{operating system information}.
33915 @xref{Operating System Information}.
33922 Data @var{data} (@pxref{Binary Data}) has been read from the
33923 target. There may be more data at a higher address (although
33924 it is permitted to return @samp{m} even for the last valid
33925 block of data, as long as at least one byte of data was read).
33926 @var{data} may have fewer bytes than the @var{length} in the
33930 Data @var{data} (@pxref{Binary Data}) has been read from the target.
33931 There is no more data to be read. @var{data} may have fewer bytes
33932 than the @var{length} in the request.
33935 The @var{offset} in the request is at the end of the data.
33936 There is no more data to be read.
33939 The request was malformed, or @var{annex} was invalid.
33942 The offset was invalid, or there was an error encountered reading the data.
33943 @var{nn} is a hex-encoded @code{errno} value.
33946 An empty reply indicates the @var{object} string was not recognized by
33947 the stub, or that the object does not support reading.
33950 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33951 @cindex write data into object, remote request
33952 @anchor{qXfer write}
33953 Write uninterpreted bytes into the target's special data area
33954 identified by the keyword @var{object}, starting at @var{offset} bytes
33955 into the data. @var{data}@dots{} is the binary-encoded data
33956 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33957 is specific to @var{object}; it can supply additional details about what data
33960 Here are the specific requests of this form defined so far. All
33961 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
33962 formats, listed below.
33965 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
33966 @anchor{qXfer siginfo write}
33967 Write @var{data} to the extra signal information on the target system.
33968 The annex part of the generic @samp{qXfer} packet must be
33969 empty (@pxref{qXfer write}).
33971 This packet is not probed by default; the remote stub must request it,
33972 by supplying an appropriate @samp{qSupported} response
33973 (@pxref{qSupported}).
33975 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
33976 @anchor{qXfer spu write}
33977 Write @var{data} to an @code{spufs} file on the target system. The
33978 annex specifies which file to write; it must be of the form
33979 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33980 in the target process, and @var{name} identifes the @code{spufs} file
33981 in that context to be accessed.
33983 This packet is not probed by default; the remote stub must request it,
33984 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33990 @var{nn} (hex encoded) is the number of bytes written.
33991 This may be fewer bytes than supplied in the request.
33994 The request was malformed, or @var{annex} was invalid.
33997 The offset was invalid, or there was an error encountered writing the data.
33998 @var{nn} is a hex-encoded @code{errno} value.
34001 An empty reply indicates the @var{object} string was not
34002 recognized by the stub, or that the object does not support writing.
34005 @item qXfer:@var{object}:@var{operation}:@dots{}
34006 Requests of this form may be added in the future. When a stub does
34007 not recognize the @var{object} keyword, or its support for
34008 @var{object} does not recognize the @var{operation} keyword, the stub
34009 must respond with an empty packet.
34011 @item qAttached:@var{pid}
34012 @cindex query attached, remote request
34013 @cindex @samp{qAttached} packet
34014 Return an indication of whether the remote server attached to an
34015 existing process or created a new process. When the multiprocess
34016 protocol extensions are supported (@pxref{multiprocess extensions}),
34017 @var{pid} is an integer in hexadecimal format identifying the target
34018 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
34019 the query packet will be simplified as @samp{qAttached}.
34021 This query is used, for example, to know whether the remote process
34022 should be detached or killed when a @value{GDBN} session is ended with
34023 the @code{quit} command.
34028 The remote server attached to an existing process.
34030 The remote server created a new process.
34032 A badly formed request or an error was encountered.
34037 @node Architecture-Specific Protocol Details
34038 @section Architecture-Specific Protocol Details
34040 This section describes how the remote protocol is applied to specific
34041 target architectures. Also see @ref{Standard Target Features}, for
34042 details of XML target descriptions for each architecture.
34046 @subsubsection Breakpoint Kinds
34048 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
34053 16-bit Thumb mode breakpoint.
34056 32-bit Thumb mode (Thumb-2) breakpoint.
34059 32-bit ARM mode breakpoint.
34065 @subsubsection Register Packet Format
34067 The following @code{g}/@code{G} packets have previously been defined.
34068 In the below, some thirty-two bit registers are transferred as
34069 sixty-four bits. Those registers should be zero/sign extended (which?)
34070 to fill the space allocated. Register bytes are transferred in target
34071 byte order. The two nibbles within a register byte are transferred
34072 most-significant - least-significant.
34078 All registers are transferred as thirty-two bit quantities in the order:
34079 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
34080 registers; fsr; fir; fp.
34084 All registers are transferred as sixty-four bit quantities (including
34085 thirty-two bit registers such as @code{sr}). The ordering is the same
34090 @node Tracepoint Packets
34091 @section Tracepoint Packets
34092 @cindex tracepoint packets
34093 @cindex packets, tracepoint
34095 Here we describe the packets @value{GDBN} uses to implement
34096 tracepoints (@pxref{Tracepoints}).
34100 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
34101 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
34102 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
34103 the tracepoint is disabled. @var{step} is the tracepoint's step
34104 count, and @var{pass} is its pass count. If an @samp{F} is present,
34105 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
34106 the number of bytes that the target should copy elsewhere to make room
34107 for the tracepoint. If an @samp{X} is present, it introduces a
34108 tracepoint condition, which consists of a hexadecimal length, followed
34109 by a comma and hex-encoded bytes, in a manner similar to action
34110 encodings as described below. If the trailing @samp{-} is present,
34111 further @samp{QTDP} packets will follow to specify this tracepoint's
34117 The packet was understood and carried out.
34119 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34121 The packet was not recognized.
34124 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
34125 Define actions to be taken when a tracepoint is hit. @var{n} and
34126 @var{addr} must be the same as in the initial @samp{QTDP} packet for
34127 this tracepoint. This packet may only be sent immediately after
34128 another @samp{QTDP} packet that ended with a @samp{-}. If the
34129 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
34130 specifying more actions for this tracepoint.
34132 In the series of action packets for a given tracepoint, at most one
34133 can have an @samp{S} before its first @var{action}. If such a packet
34134 is sent, it and the following packets define ``while-stepping''
34135 actions. Any prior packets define ordinary actions --- that is, those
34136 taken when the tracepoint is first hit. If no action packet has an
34137 @samp{S}, then all the packets in the series specify ordinary
34138 tracepoint actions.
34140 The @samp{@var{action}@dots{}} portion of the packet is a series of
34141 actions, concatenated without separators. Each action has one of the
34147 Collect the registers whose bits are set in @var{mask}. @var{mask} is
34148 a hexadecimal number whose @var{i}'th bit is set if register number
34149 @var{i} should be collected. (The least significant bit is numbered
34150 zero.) Note that @var{mask} may be any number of digits long; it may
34151 not fit in a 32-bit word.
34153 @item M @var{basereg},@var{offset},@var{len}
34154 Collect @var{len} bytes of memory starting at the address in register
34155 number @var{basereg}, plus @var{offset}. If @var{basereg} is
34156 @samp{-1}, then the range has a fixed address: @var{offset} is the
34157 address of the lowest byte to collect. The @var{basereg},
34158 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
34159 values (the @samp{-1} value for @var{basereg} is a special case).
34161 @item X @var{len},@var{expr}
34162 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
34163 it directs. @var{expr} is an agent expression, as described in
34164 @ref{Agent Expressions}. Each byte of the expression is encoded as a
34165 two-digit hex number in the packet; @var{len} is the number of bytes
34166 in the expression (and thus one-half the number of hex digits in the
34171 Any number of actions may be packed together in a single @samp{QTDP}
34172 packet, as long as the packet does not exceed the maximum packet
34173 length (400 bytes, for many stubs). There may be only one @samp{R}
34174 action per tracepoint, and it must precede any @samp{M} or @samp{X}
34175 actions. Any registers referred to by @samp{M} and @samp{X} actions
34176 must be collected by a preceding @samp{R} action. (The
34177 ``while-stepping'' actions are treated as if they were attached to a
34178 separate tracepoint, as far as these restrictions are concerned.)
34183 The packet was understood and carried out.
34185 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34187 The packet was not recognized.
34190 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
34191 @cindex @samp{QTDPsrc} packet
34192 Specify a source string of tracepoint @var{n} at address @var{addr}.
34193 This is useful to get accurate reproduction of the tracepoints
34194 originally downloaded at the beginning of the trace run. @var{type}
34195 is the name of the tracepoint part, such as @samp{cond} for the
34196 tracepoint's conditional expression (see below for a list of types), while
34197 @var{bytes} is the string, encoded in hexadecimal.
34199 @var{start} is the offset of the @var{bytes} within the overall source
34200 string, while @var{slen} is the total length of the source string.
34201 This is intended for handling source strings that are longer than will
34202 fit in a single packet.
34203 @c Add detailed example when this info is moved into a dedicated
34204 @c tracepoint descriptions section.
34206 The available string types are @samp{at} for the location,
34207 @samp{cond} for the conditional, and @samp{cmd} for an action command.
34208 @value{GDBN} sends a separate packet for each command in the action
34209 list, in the same order in which the commands are stored in the list.
34211 The target does not need to do anything with source strings except
34212 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
34215 Although this packet is optional, and @value{GDBN} will only send it
34216 if the target replies with @samp{TracepointSource} @xref{General
34217 Query Packets}, it makes both disconnected tracing and trace files
34218 much easier to use. Otherwise the user must be careful that the
34219 tracepoints in effect while looking at trace frames are identical to
34220 the ones in effect during the trace run; even a small discrepancy
34221 could cause @samp{tdump} not to work, or a particular trace frame not
34224 @item QTDV:@var{n}:@var{value}
34225 @cindex define trace state variable, remote request
34226 @cindex @samp{QTDV} packet
34227 Create a new trace state variable, number @var{n}, with an initial
34228 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
34229 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
34230 the option of not using this packet for initial values of zero; the
34231 target should simply create the trace state variables as they are
34232 mentioned in expressions.
34234 @item QTFrame:@var{n}
34235 Select the @var{n}'th tracepoint frame from the buffer, and use the
34236 register and memory contents recorded there to answer subsequent
34237 request packets from @value{GDBN}.
34239 A successful reply from the stub indicates that the stub has found the
34240 requested frame. The response is a series of parts, concatenated
34241 without separators, describing the frame we selected. Each part has
34242 one of the following forms:
34246 The selected frame is number @var{n} in the trace frame buffer;
34247 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
34248 was no frame matching the criteria in the request packet.
34251 The selected trace frame records a hit of tracepoint number @var{t};
34252 @var{t} is a hexadecimal number.
34256 @item QTFrame:pc:@var{addr}
34257 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34258 currently selected frame whose PC is @var{addr};
34259 @var{addr} is a hexadecimal number.
34261 @item QTFrame:tdp:@var{t}
34262 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34263 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
34264 is a hexadecimal number.
34266 @item QTFrame:range:@var{start}:@var{end}
34267 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34268 currently selected frame whose PC is between @var{start} (inclusive)
34269 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
34272 @item QTFrame:outside:@var{start}:@var{end}
34273 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
34274 frame @emph{outside} the given range of addresses (exclusive).
34277 Begin the tracepoint experiment. Begin collecting data from
34278 tracepoint hits in the trace frame buffer. This packet supports the
34279 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
34280 instruction reply packet}).
34283 End the tracepoint experiment. Stop collecting trace frames.
34286 Clear the table of tracepoints, and empty the trace frame buffer.
34288 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
34289 Establish the given ranges of memory as ``transparent''. The stub
34290 will answer requests for these ranges from memory's current contents,
34291 if they were not collected as part of the tracepoint hit.
34293 @value{GDBN} uses this to mark read-only regions of memory, like those
34294 containing program code. Since these areas never change, they should
34295 still have the same contents they did when the tracepoint was hit, so
34296 there's no reason for the stub to refuse to provide their contents.
34298 @item QTDisconnected:@var{value}
34299 Set the choice to what to do with the tracing run when @value{GDBN}
34300 disconnects from the target. A @var{value} of 1 directs the target to
34301 continue the tracing run, while 0 tells the target to stop tracing if
34302 @value{GDBN} is no longer in the picture.
34305 Ask the stub if there is a trace experiment running right now.
34307 The reply has the form:
34311 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
34312 @var{running} is a single digit @code{1} if the trace is presently
34313 running, or @code{0} if not. It is followed by semicolon-separated
34314 optional fields that an agent may use to report additional status.
34318 If the trace is not running, the agent may report any of several
34319 explanations as one of the optional fields:
34324 No trace has been run yet.
34327 The trace was stopped by a user-originated stop command.
34330 The trace stopped because the trace buffer filled up.
34332 @item tdisconnected:0
34333 The trace stopped because @value{GDBN} disconnected from the target.
34335 @item tpasscount:@var{tpnum}
34336 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
34338 @item terror:@var{text}:@var{tpnum}
34339 The trace stopped because tracepoint @var{tpnum} had an error. The
34340 string @var{text} is available to describe the nature of the error
34341 (for instance, a divide by zero in the condition expression).
34342 @var{text} is hex encoded.
34345 The trace stopped for some other reason.
34349 Additional optional fields supply statistical and other information.
34350 Although not required, they are extremely useful for users monitoring
34351 the progress of a trace run. If a trace has stopped, and these
34352 numbers are reported, they must reflect the state of the just-stopped
34357 @item tframes:@var{n}
34358 The number of trace frames in the buffer.
34360 @item tcreated:@var{n}
34361 The total number of trace frames created during the run. This may
34362 be larger than the trace frame count, if the buffer is circular.
34364 @item tsize:@var{n}
34365 The total size of the trace buffer, in bytes.
34367 @item tfree:@var{n}
34368 The number of bytes still unused in the buffer.
34370 @item circular:@var{n}
34371 The value of the circular trace buffer flag. @code{1} means that the
34372 trace buffer is circular and old trace frames will be discarded if
34373 necessary to make room, @code{0} means that the trace buffer is linear
34376 @item disconn:@var{n}
34377 The value of the disconnected tracing flag. @code{1} means that
34378 tracing will continue after @value{GDBN} disconnects, @code{0} means
34379 that the trace run will stop.
34383 @item qTV:@var{var}
34384 @cindex trace state variable value, remote request
34385 @cindex @samp{qTV} packet
34386 Ask the stub for the value of the trace state variable number @var{var}.
34391 The value of the variable is @var{value}. This will be the current
34392 value of the variable if the user is examining a running target, or a
34393 saved value if the variable was collected in the trace frame that the
34394 user is looking at. Note that multiple requests may result in
34395 different reply values, such as when requesting values while the
34396 program is running.
34399 The value of the variable is unknown. This would occur, for example,
34400 if the user is examining a trace frame in which the requested variable
34406 These packets request data about tracepoints that are being used by
34407 the target. @value{GDBN} sends @code{qTfP} to get the first piece
34408 of data, and multiple @code{qTsP} to get additional pieces. Replies
34409 to these packets generally take the form of the @code{QTDP} packets
34410 that define tracepoints. (FIXME add detailed syntax)
34414 These packets request data about trace state variables that are on the
34415 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
34416 and multiple @code{qTsV} to get additional variables. Replies to
34417 these packets follow the syntax of the @code{QTDV} packets that define
34418 trace state variables.
34422 These packets request data about static tracepoint markers that exist
34423 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
34424 first piece of data, and multiple @code{qTsSTM} to get additional
34425 pieces. Replies to these packets take the following form:
34429 @item m @var{address}:@var{id}:@var{extra}
34431 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
34432 a comma-separated list of markers
34434 (lower case letter @samp{L}) denotes end of list.
34436 An error occurred. @var{nn} are hex digits.
34438 An empty reply indicates that the request is not supported by the
34442 @var{address} is encoded in hex.
34443 @var{id} and @var{extra} are strings encoded in hex.
34445 In response to each query, the target will reply with a list of one or
34446 more markers, separated by commas. @value{GDBN} will respond to each
34447 reply with a request for more markers (using the @samp{qs} form of the
34448 query), until the target responds with @samp{l} (lower-case ell, for
34451 @item qTSTMat:@var{address}
34452 This packets requests data about static tracepoint markers in the
34453 target program at @var{address}. Replies to this packet follow the
34454 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
34455 tracepoint markers.
34457 @item QTSave:@var{filename}
34458 This packet directs the target to save trace data to the file name
34459 @var{filename} in the target's filesystem. @var{filename} is encoded
34460 as a hex string; the interpretation of the file name (relative vs
34461 absolute, wild cards, etc) is up to the target.
34463 @item qTBuffer:@var{offset},@var{len}
34464 Return up to @var{len} bytes of the current contents of trace buffer,
34465 starting at @var{offset}. The trace buffer is treated as if it were
34466 a contiguous collection of traceframes, as per the trace file format.
34467 The reply consists as many hex-encoded bytes as the target can deliver
34468 in a packet; it is not an error to return fewer than were asked for.
34469 A reply consisting of just @code{l} indicates that no bytes are
34472 @item QTBuffer:circular:@var{value}
34473 This packet directs the target to use a circular trace buffer if
34474 @var{value} is 1, or a linear buffer if the value is 0.
34478 @subsection Relocate instruction reply packet
34479 When installing fast tracepoints in memory, the target may need to
34480 relocate the instruction currently at the tracepoint address to a
34481 different address in memory. For most instructions, a simple copy is
34482 enough, but, for example, call instructions that implicitly push the
34483 return address on the stack, and relative branches or other
34484 PC-relative instructions require offset adjustment, so that the effect
34485 of executing the instruction at a different address is the same as if
34486 it had executed in the original location.
34488 In response to several of the tracepoint packets, the target may also
34489 respond with a number of intermediate @samp{qRelocInsn} request
34490 packets before the final result packet, to have @value{GDBN} handle
34491 this relocation operation. If a packet supports this mechanism, its
34492 documentation will explicitly say so. See for example the above
34493 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
34494 format of the request is:
34497 @item qRelocInsn:@var{from};@var{to}
34499 This requests @value{GDBN} to copy instruction at address @var{from}
34500 to address @var{to}, possibly adjusted so that executing the
34501 instruction at @var{to} has the same effect as executing it at
34502 @var{from}. @value{GDBN} writes the adjusted instruction to target
34503 memory starting at @var{to}.
34508 @item qRelocInsn:@var{adjusted_size}
34509 Informs the stub the relocation is complete. @var{adjusted_size} is
34510 the length in bytes of resulting relocated instruction sequence.
34512 A badly formed request was detected, or an error was encountered while
34513 relocating the instruction.
34516 @node Host I/O Packets
34517 @section Host I/O Packets
34518 @cindex Host I/O, remote protocol
34519 @cindex file transfer, remote protocol
34521 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
34522 operations on the far side of a remote link. For example, Host I/O is
34523 used to upload and download files to a remote target with its own
34524 filesystem. Host I/O uses the same constant values and data structure
34525 layout as the target-initiated File-I/O protocol. However, the
34526 Host I/O packets are structured differently. The target-initiated
34527 protocol relies on target memory to store parameters and buffers.
34528 Host I/O requests are initiated by @value{GDBN}, and the
34529 target's memory is not involved. @xref{File-I/O Remote Protocol
34530 Extension}, for more details on the target-initiated protocol.
34532 The Host I/O request packets all encode a single operation along with
34533 its arguments. They have this format:
34537 @item vFile:@var{operation}: @var{parameter}@dots{}
34538 @var{operation} is the name of the particular request; the target
34539 should compare the entire packet name up to the second colon when checking
34540 for a supported operation. The format of @var{parameter} depends on
34541 the operation. Numbers are always passed in hexadecimal. Negative
34542 numbers have an explicit minus sign (i.e.@: two's complement is not
34543 used). Strings (e.g.@: filenames) are encoded as a series of
34544 hexadecimal bytes. The last argument to a system call may be a
34545 buffer of escaped binary data (@pxref{Binary Data}).
34549 The valid responses to Host I/O packets are:
34553 @item F @var{result} [, @var{errno}] [; @var{attachment}]
34554 @var{result} is the integer value returned by this operation, usually
34555 non-negative for success and -1 for errors. If an error has occured,
34556 @var{errno} will be included in the result. @var{errno} will have a
34557 value defined by the File-I/O protocol (@pxref{Errno Values}). For
34558 operations which return data, @var{attachment} supplies the data as a
34559 binary buffer. Binary buffers in response packets are escaped in the
34560 normal way (@pxref{Binary Data}). See the individual packet
34561 documentation for the interpretation of @var{result} and
34565 An empty response indicates that this operation is not recognized.
34569 These are the supported Host I/O operations:
34572 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
34573 Open a file at @var{pathname} and return a file descriptor for it, or
34574 return -1 if an error occurs. @var{pathname} is a string,
34575 @var{flags} is an integer indicating a mask of open flags
34576 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34577 of mode bits to use if the file is created (@pxref{mode_t Values}).
34578 @xref{open}, for details of the open flags and mode values.
34580 @item vFile:close: @var{fd}
34581 Close the open file corresponding to @var{fd} and return 0, or
34582 -1 if an error occurs.
34584 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34585 Read data from the open file corresponding to @var{fd}. Up to
34586 @var{count} bytes will be read from the file, starting at @var{offset}
34587 relative to the start of the file. The target may read fewer bytes;
34588 common reasons include packet size limits and an end-of-file
34589 condition. The number of bytes read is returned. Zero should only be
34590 returned for a successful read at the end of the file, or if
34591 @var{count} was zero.
34593 The data read should be returned as a binary attachment on success.
34594 If zero bytes were read, the response should include an empty binary
34595 attachment (i.e.@: a trailing semicolon). The return value is the
34596 number of target bytes read; the binary attachment may be longer if
34597 some characters were escaped.
34599 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34600 Write @var{data} (a binary buffer) to the open file corresponding
34601 to @var{fd}. Start the write at @var{offset} from the start of the
34602 file. Unlike many @code{write} system calls, there is no
34603 separate @var{count} argument; the length of @var{data} in the
34604 packet is used. @samp{vFile:write} returns the number of bytes written,
34605 which may be shorter than the length of @var{data}, or -1 if an
34608 @item vFile:unlink: @var{pathname}
34609 Delete the file at @var{pathname} on the target. Return 0,
34610 or -1 if an error occurs. @var{pathname} is a string.
34615 @section Interrupts
34616 @cindex interrupts (remote protocol)
34618 When a program on the remote target is running, @value{GDBN} may
34619 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34620 a @code{BREAK} followed by @code{g},
34621 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34623 The precise meaning of @code{BREAK} is defined by the transport
34624 mechanism and may, in fact, be undefined. @value{GDBN} does not
34625 currently define a @code{BREAK} mechanism for any of the network
34626 interfaces except for TCP, in which case @value{GDBN} sends the
34627 @code{telnet} BREAK sequence.
34629 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34630 transport mechanisms. It is represented by sending the single byte
34631 @code{0x03} without any of the usual packet overhead described in
34632 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34633 transmitted as part of a packet, it is considered to be packet data
34634 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34635 (@pxref{X packet}), used for binary downloads, may include an unescaped
34636 @code{0x03} as part of its packet.
34638 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
34639 When Linux kernel receives this sequence from serial port,
34640 it stops execution and connects to gdb.
34642 Stubs are not required to recognize these interrupt mechanisms and the
34643 precise meaning associated with receipt of the interrupt is
34644 implementation defined. If the target supports debugging of multiple
34645 threads and/or processes, it should attempt to interrupt all
34646 currently-executing threads and processes.
34647 If the stub is successful at interrupting the
34648 running program, it should send one of the stop
34649 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
34650 of successfully stopping the program in all-stop mode, and a stop reply
34651 for each stopped thread in non-stop mode.
34652 Interrupts received while the
34653 program is stopped are discarded.
34655 @node Notification Packets
34656 @section Notification Packets
34657 @cindex notification packets
34658 @cindex packets, notification
34660 The @value{GDBN} remote serial protocol includes @dfn{notifications},
34661 packets that require no acknowledgment. Both the GDB and the stub
34662 may send notifications (although the only notifications defined at
34663 present are sent by the stub). Notifications carry information
34664 without incurring the round-trip latency of an acknowledgment, and so
34665 are useful for low-impact communications where occasional packet loss
34668 A notification packet has the form @samp{% @var{data} #
34669 @var{checksum}}, where @var{data} is the content of the notification,
34670 and @var{checksum} is a checksum of @var{data}, computed and formatted
34671 as for ordinary @value{GDBN} packets. A notification's @var{data}
34672 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
34673 receiving a notification, the recipient sends no @samp{+} or @samp{-}
34674 to acknowledge the notification's receipt or to report its corruption.
34676 Every notification's @var{data} begins with a name, which contains no
34677 colon characters, followed by a colon character.
34679 Recipients should silently ignore corrupted notifications and
34680 notifications they do not understand. Recipients should restart
34681 timeout periods on receipt of a well-formed notification, whether or
34682 not they understand it.
34684 Senders should only send the notifications described here when this
34685 protocol description specifies that they are permitted. In the
34686 future, we may extend the protocol to permit existing notifications in
34687 new contexts; this rule helps older senders avoid confusing newer
34690 (Older versions of @value{GDBN} ignore bytes received until they see
34691 the @samp{$} byte that begins an ordinary packet, so new stubs may
34692 transmit notifications without fear of confusing older clients. There
34693 are no notifications defined for @value{GDBN} to send at the moment, but we
34694 assume that most older stubs would ignore them, as well.)
34696 The following notification packets from the stub to @value{GDBN} are
34700 @item Stop: @var{reply}
34701 Report an asynchronous stop event in non-stop mode.
34702 The @var{reply} has the form of a stop reply, as
34703 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34704 for information on how these notifications are acknowledged by
34708 @node Remote Non-Stop
34709 @section Remote Protocol Support for Non-Stop Mode
34711 @value{GDBN}'s remote protocol supports non-stop debugging of
34712 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34713 supports non-stop mode, it should report that to @value{GDBN} by including
34714 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34716 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34717 establishing a new connection with the stub. Entering non-stop mode
34718 does not alter the state of any currently-running threads, but targets
34719 must stop all threads in any already-attached processes when entering
34720 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34721 probe the target state after a mode change.
34723 In non-stop mode, when an attached process encounters an event that
34724 would otherwise be reported with a stop reply, it uses the
34725 asynchronous notification mechanism (@pxref{Notification Packets}) to
34726 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34727 in all processes are stopped when a stop reply is sent, in non-stop
34728 mode only the thread reporting the stop event is stopped. That is,
34729 when reporting a @samp{S} or @samp{T} response to indicate completion
34730 of a step operation, hitting a breakpoint, or a fault, only the
34731 affected thread is stopped; any other still-running threads continue
34732 to run. When reporting a @samp{W} or @samp{X} response, all running
34733 threads belonging to other attached processes continue to run.
34735 Only one stop reply notification at a time may be pending; if
34736 additional stop events occur before @value{GDBN} has acknowledged the
34737 previous notification, they must be queued by the stub for later
34738 synchronous transmission in response to @samp{vStopped} packets from
34739 @value{GDBN}. Because the notification mechanism is unreliable,
34740 the stub is permitted to resend a stop reply notification
34741 if it believes @value{GDBN} may not have received it. @value{GDBN}
34742 ignores additional stop reply notifications received before it has
34743 finished processing a previous notification and the stub has completed
34744 sending any queued stop events.
34746 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34747 notification at any time. Specifically, they may appear when
34748 @value{GDBN} is not otherwise reading input from the stub, or when
34749 @value{GDBN} is expecting to read a normal synchronous response or a
34750 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34751 Notification packets are distinct from any other communication from
34752 the stub so there is no ambiguity.
34754 After receiving a stop reply notification, @value{GDBN} shall
34755 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34756 as a regular, synchronous request to the stub. Such acknowledgment
34757 is not required to happen immediately, as @value{GDBN} is permitted to
34758 send other, unrelated packets to the stub first, which the stub should
34761 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34762 stop events to report to @value{GDBN}, it shall respond by sending a
34763 normal stop reply response. @value{GDBN} shall then send another
34764 @samp{vStopped} packet to solicit further responses; again, it is
34765 permitted to send other, unrelated packets as well which the stub
34766 should process normally.
34768 If the stub receives a @samp{vStopped} packet and there are no
34769 additional stop events to report, the stub shall return an @samp{OK}
34770 response. At this point, if further stop events occur, the stub shall
34771 send a new stop reply notification, @value{GDBN} shall accept the
34772 notification, and the process shall be repeated.
34774 In non-stop mode, the target shall respond to the @samp{?} packet as
34775 follows. First, any incomplete stop reply notification/@samp{vStopped}
34776 sequence in progress is abandoned. The target must begin a new
34777 sequence reporting stop events for all stopped threads, whether or not
34778 it has previously reported those events to @value{GDBN}. The first
34779 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34780 subsequent stop replies are sent as responses to @samp{vStopped} packets
34781 using the mechanism described above. The target must not send
34782 asynchronous stop reply notifications until the sequence is complete.
34783 If all threads are running when the target receives the @samp{?} packet,
34784 or if the target is not attached to any process, it shall respond
34787 @node Packet Acknowledgment
34788 @section Packet Acknowledgment
34790 @cindex acknowledgment, for @value{GDBN} remote
34791 @cindex packet acknowledgment, for @value{GDBN} remote
34792 By default, when either the host or the target machine receives a packet,
34793 the first response expected is an acknowledgment: either @samp{+} (to indicate
34794 the package was received correctly) or @samp{-} (to request retransmission).
34795 This mechanism allows the @value{GDBN} remote protocol to operate over
34796 unreliable transport mechanisms, such as a serial line.
34798 In cases where the transport mechanism is itself reliable (such as a pipe or
34799 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34800 It may be desirable to disable them in that case to reduce communication
34801 overhead, or for other reasons. This can be accomplished by means of the
34802 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34804 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34805 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34806 and response format still includes the normal checksum, as described in
34807 @ref{Overview}, but the checksum may be ignored by the receiver.
34809 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34810 no-acknowledgment mode, it should report that to @value{GDBN}
34811 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34812 @pxref{qSupported}.
34813 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34814 disabled via the @code{set remote noack-packet off} command
34815 (@pxref{Remote Configuration}),
34816 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34817 Only then may the stub actually turn off packet acknowledgments.
34818 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34819 response, which can be safely ignored by the stub.
34821 Note that @code{set remote noack-packet} command only affects negotiation
34822 between @value{GDBN} and the stub when subsequent connections are made;
34823 it does not affect the protocol acknowledgment state for any current
34825 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
34826 new connection is established,
34827 there is also no protocol request to re-enable the acknowledgments
34828 for the current connection, once disabled.
34833 Example sequence of a target being re-started. Notice how the restart
34834 does not get any direct output:
34839 @emph{target restarts}
34842 <- @code{T001:1234123412341234}
34846 Example sequence of a target being stepped by a single instruction:
34849 -> @code{G1445@dots{}}
34854 <- @code{T001:1234123412341234}
34858 <- @code{1455@dots{}}
34862 @node File-I/O Remote Protocol Extension
34863 @section File-I/O Remote Protocol Extension
34864 @cindex File-I/O remote protocol extension
34867 * File-I/O Overview::
34868 * Protocol Basics::
34869 * The F Request Packet::
34870 * The F Reply Packet::
34871 * The Ctrl-C Message::
34873 * List of Supported Calls::
34874 * Protocol-specific Representation of Datatypes::
34876 * File-I/O Examples::
34879 @node File-I/O Overview
34880 @subsection File-I/O Overview
34881 @cindex file-i/o overview
34883 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
34884 target to use the host's file system and console I/O to perform various
34885 system calls. System calls on the target system are translated into a
34886 remote protocol packet to the host system, which then performs the needed
34887 actions and returns a response packet to the target system.
34888 This simulates file system operations even on targets that lack file systems.
34890 The protocol is defined to be independent of both the host and target systems.
34891 It uses its own internal representation of datatypes and values. Both
34892 @value{GDBN} and the target's @value{GDBN} stub are responsible for
34893 translating the system-dependent value representations into the internal
34894 protocol representations when data is transmitted.
34896 The communication is synchronous. A system call is possible only when
34897 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
34898 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
34899 the target is stopped to allow deterministic access to the target's
34900 memory. Therefore File-I/O is not interruptible by target signals. On
34901 the other hand, it is possible to interrupt File-I/O by a user interrupt
34902 (@samp{Ctrl-C}) within @value{GDBN}.
34904 The target's request to perform a host system call does not finish
34905 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
34906 after finishing the system call, the target returns to continuing the
34907 previous activity (continue, step). No additional continue or step
34908 request from @value{GDBN} is required.
34911 (@value{GDBP}) continue
34912 <- target requests 'system call X'
34913 target is stopped, @value{GDBN} executes system call
34914 -> @value{GDBN} returns result
34915 ... target continues, @value{GDBN} returns to wait for the target
34916 <- target hits breakpoint and sends a Txx packet
34919 The protocol only supports I/O on the console and to regular files on
34920 the host file system. Character or block special devices, pipes,
34921 named pipes, sockets or any other communication method on the host
34922 system are not supported by this protocol.
34924 File I/O is not supported in non-stop mode.
34926 @node Protocol Basics
34927 @subsection Protocol Basics
34928 @cindex protocol basics, file-i/o
34930 The File-I/O protocol uses the @code{F} packet as the request as well
34931 as reply packet. Since a File-I/O system call can only occur when
34932 @value{GDBN} is waiting for a response from the continuing or stepping target,
34933 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34934 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34935 This @code{F} packet contains all information needed to allow @value{GDBN}
34936 to call the appropriate host system call:
34940 A unique identifier for the requested system call.
34943 All parameters to the system call. Pointers are given as addresses
34944 in the target memory address space. Pointers to strings are given as
34945 pointer/length pair. Numerical values are given as they are.
34946 Numerical control flags are given in a protocol-specific representation.
34950 At this point, @value{GDBN} has to perform the following actions.
34954 If the parameters include pointer values to data needed as input to a
34955 system call, @value{GDBN} requests this data from the target with a
34956 standard @code{m} packet request. This additional communication has to be
34957 expected by the target implementation and is handled as any other @code{m}
34961 @value{GDBN} translates all value from protocol representation to host
34962 representation as needed. Datatypes are coerced into the host types.
34965 @value{GDBN} calls the system call.
34968 It then coerces datatypes back to protocol representation.
34971 If the system call is expected to return data in buffer space specified
34972 by pointer parameters to the call, the data is transmitted to the
34973 target using a @code{M} or @code{X} packet. This packet has to be expected
34974 by the target implementation and is handled as any other @code{M} or @code{X}
34979 Eventually @value{GDBN} replies with another @code{F} packet which contains all
34980 necessary information for the target to continue. This at least contains
34987 @code{errno}, if has been changed by the system call.
34994 After having done the needed type and value coercion, the target continues
34995 the latest continue or step action.
34997 @node The F Request Packet
34998 @subsection The @code{F} Request Packet
34999 @cindex file-i/o request packet
35000 @cindex @code{F} request packet
35002 The @code{F} request packet has the following format:
35005 @item F@var{call-id},@var{parameter@dots{}}
35007 @var{call-id} is the identifier to indicate the host system call to be called.
35008 This is just the name of the function.
35010 @var{parameter@dots{}} are the parameters to the system call.
35011 Parameters are hexadecimal integer values, either the actual values in case
35012 of scalar datatypes, pointers to target buffer space in case of compound
35013 datatypes and unspecified memory areas, or pointer/length pairs in case
35014 of string parameters. These are appended to the @var{call-id} as a
35015 comma-delimited list. All values are transmitted in ASCII
35016 string representation, pointer/length pairs separated by a slash.
35022 @node The F Reply Packet
35023 @subsection The @code{F} Reply Packet
35024 @cindex file-i/o reply packet
35025 @cindex @code{F} reply packet
35027 The @code{F} reply packet has the following format:
35031 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
35033 @var{retcode} is the return code of the system call as hexadecimal value.
35035 @var{errno} is the @code{errno} set by the call, in protocol-specific
35037 This parameter can be omitted if the call was successful.
35039 @var{Ctrl-C flag} is only sent if the user requested a break. In this
35040 case, @var{errno} must be sent as well, even if the call was successful.
35041 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
35048 or, if the call was interrupted before the host call has been performed:
35055 assuming 4 is the protocol-specific representation of @code{EINTR}.
35060 @node The Ctrl-C Message
35061 @subsection The @samp{Ctrl-C} Message
35062 @cindex ctrl-c message, in file-i/o protocol
35064 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
35065 reply packet (@pxref{The F Reply Packet}),
35066 the target should behave as if it had
35067 gotten a break message. The meaning for the target is ``system call
35068 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
35069 (as with a break message) and return to @value{GDBN} with a @code{T02}
35072 It's important for the target to know in which
35073 state the system call was interrupted. There are two possible cases:
35077 The system call hasn't been performed on the host yet.
35080 The system call on the host has been finished.
35084 These two states can be distinguished by the target by the value of the
35085 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
35086 call hasn't been performed. This is equivalent to the @code{EINTR} handling
35087 on POSIX systems. In any other case, the target may presume that the
35088 system call has been finished --- successfully or not --- and should behave
35089 as if the break message arrived right after the system call.
35091 @value{GDBN} must behave reliably. If the system call has not been called
35092 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
35093 @code{errno} in the packet. If the system call on the host has been finished
35094 before the user requests a break, the full action must be finished by
35095 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
35096 The @code{F} packet may only be sent when either nothing has happened
35097 or the full action has been completed.
35100 @subsection Console I/O
35101 @cindex console i/o as part of file-i/o
35103 By default and if not explicitly closed by the target system, the file
35104 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
35105 on the @value{GDBN} console is handled as any other file output operation
35106 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
35107 by @value{GDBN} so that after the target read request from file descriptor
35108 0 all following typing is buffered until either one of the following
35113 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
35115 system call is treated as finished.
35118 The user presses @key{RET}. This is treated as end of input with a trailing
35122 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
35123 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
35127 If the user has typed more characters than fit in the buffer given to
35128 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
35129 either another @code{read(0, @dots{})} is requested by the target, or debugging
35130 is stopped at the user's request.
35133 @node List of Supported Calls
35134 @subsection List of Supported Calls
35135 @cindex list of supported file-i/o calls
35152 @unnumberedsubsubsec open
35153 @cindex open, file-i/o system call
35158 int open(const char *pathname, int flags);
35159 int open(const char *pathname, int flags, mode_t mode);
35163 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
35166 @var{flags} is the bitwise @code{OR} of the following values:
35170 If the file does not exist it will be created. The host
35171 rules apply as far as file ownership and time stamps
35175 When used with @code{O_CREAT}, if the file already exists it is
35176 an error and open() fails.
35179 If the file already exists and the open mode allows
35180 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
35181 truncated to zero length.
35184 The file is opened in append mode.
35187 The file is opened for reading only.
35190 The file is opened for writing only.
35193 The file is opened for reading and writing.
35197 Other bits are silently ignored.
35201 @var{mode} is the bitwise @code{OR} of the following values:
35205 User has read permission.
35208 User has write permission.
35211 Group has read permission.
35214 Group has write permission.
35217 Others have read permission.
35220 Others have write permission.
35224 Other bits are silently ignored.
35227 @item Return value:
35228 @code{open} returns the new file descriptor or -1 if an error
35235 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
35238 @var{pathname} refers to a directory.
35241 The requested access is not allowed.
35244 @var{pathname} was too long.
35247 A directory component in @var{pathname} does not exist.
35250 @var{pathname} refers to a device, pipe, named pipe or socket.
35253 @var{pathname} refers to a file on a read-only filesystem and
35254 write access was requested.
35257 @var{pathname} is an invalid pointer value.
35260 No space on device to create the file.
35263 The process already has the maximum number of files open.
35266 The limit on the total number of files open on the system
35270 The call was interrupted by the user.
35276 @unnumberedsubsubsec close
35277 @cindex close, file-i/o system call
35286 @samp{Fclose,@var{fd}}
35288 @item Return value:
35289 @code{close} returns zero on success, or -1 if an error occurred.
35295 @var{fd} isn't a valid open file descriptor.
35298 The call was interrupted by the user.
35304 @unnumberedsubsubsec read
35305 @cindex read, file-i/o system call
35310 int read(int fd, void *buf, unsigned int count);
35314 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
35316 @item Return value:
35317 On success, the number of bytes read is returned.
35318 Zero indicates end of file. If count is zero, read
35319 returns zero as well. On error, -1 is returned.
35325 @var{fd} is not a valid file descriptor or is not open for
35329 @var{bufptr} is an invalid pointer value.
35332 The call was interrupted by the user.
35338 @unnumberedsubsubsec write
35339 @cindex write, file-i/o system call
35344 int write(int fd, const void *buf, unsigned int count);
35348 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
35350 @item Return value:
35351 On success, the number of bytes written are returned.
35352 Zero indicates nothing was written. On error, -1
35359 @var{fd} is not a valid file descriptor or is not open for
35363 @var{bufptr} is an invalid pointer value.
35366 An attempt was made to write a file that exceeds the
35367 host-specific maximum file size allowed.
35370 No space on device to write the data.
35373 The call was interrupted by the user.
35379 @unnumberedsubsubsec lseek
35380 @cindex lseek, file-i/o system call
35385 long lseek (int fd, long offset, int flag);
35389 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
35391 @var{flag} is one of:
35395 The offset is set to @var{offset} bytes.
35398 The offset is set to its current location plus @var{offset}
35402 The offset is set to the size of the file plus @var{offset}
35406 @item Return value:
35407 On success, the resulting unsigned offset in bytes from
35408 the beginning of the file is returned. Otherwise, a
35409 value of -1 is returned.
35415 @var{fd} is not a valid open file descriptor.
35418 @var{fd} is associated with the @value{GDBN} console.
35421 @var{flag} is not a proper value.
35424 The call was interrupted by the user.
35430 @unnumberedsubsubsec rename
35431 @cindex rename, file-i/o system call
35436 int rename(const char *oldpath, const char *newpath);
35440 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
35442 @item Return value:
35443 On success, zero is returned. On error, -1 is returned.
35449 @var{newpath} is an existing directory, but @var{oldpath} is not a
35453 @var{newpath} is a non-empty directory.
35456 @var{oldpath} or @var{newpath} is a directory that is in use by some
35460 An attempt was made to make a directory a subdirectory
35464 A component used as a directory in @var{oldpath} or new
35465 path is not a directory. Or @var{oldpath} is a directory
35466 and @var{newpath} exists but is not a directory.
35469 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
35472 No access to the file or the path of the file.
35476 @var{oldpath} or @var{newpath} was too long.
35479 A directory component in @var{oldpath} or @var{newpath} does not exist.
35482 The file is on a read-only filesystem.
35485 The device containing the file has no room for the new
35489 The call was interrupted by the user.
35495 @unnumberedsubsubsec unlink
35496 @cindex unlink, file-i/o system call
35501 int unlink(const char *pathname);
35505 @samp{Funlink,@var{pathnameptr}/@var{len}}
35507 @item Return value:
35508 On success, zero is returned. On error, -1 is returned.
35514 No access to the file or the path of the file.
35517 The system does not allow unlinking of directories.
35520 The file @var{pathname} cannot be unlinked because it's
35521 being used by another process.
35524 @var{pathnameptr} is an invalid pointer value.
35527 @var{pathname} was too long.
35530 A directory component in @var{pathname} does not exist.
35533 A component of the path is not a directory.
35536 The file is on a read-only filesystem.
35539 The call was interrupted by the user.
35545 @unnumberedsubsubsec stat/fstat
35546 @cindex fstat, file-i/o system call
35547 @cindex stat, file-i/o system call
35552 int stat(const char *pathname, struct stat *buf);
35553 int fstat(int fd, struct stat *buf);
35557 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
35558 @samp{Ffstat,@var{fd},@var{bufptr}}
35560 @item Return value:
35561 On success, zero is returned. On error, -1 is returned.
35567 @var{fd} is not a valid open file.
35570 A directory component in @var{pathname} does not exist or the
35571 path is an empty string.
35574 A component of the path is not a directory.
35577 @var{pathnameptr} is an invalid pointer value.
35580 No access to the file or the path of the file.
35583 @var{pathname} was too long.
35586 The call was interrupted by the user.
35592 @unnumberedsubsubsec gettimeofday
35593 @cindex gettimeofday, file-i/o system call
35598 int gettimeofday(struct timeval *tv, void *tz);
35602 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35604 @item Return value:
35605 On success, 0 is returned, -1 otherwise.
35611 @var{tz} is a non-NULL pointer.
35614 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35620 @unnumberedsubsubsec isatty
35621 @cindex isatty, file-i/o system call
35626 int isatty(int fd);
35630 @samp{Fisatty,@var{fd}}
35632 @item Return value:
35633 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
35639 The call was interrupted by the user.
35644 Note that the @code{isatty} call is treated as a special case: it returns
35645 1 to the target if the file descriptor is attached
35646 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
35647 would require implementing @code{ioctl} and would be more complex than
35652 @unnumberedsubsubsec system
35653 @cindex system, file-i/o system call
35658 int system(const char *command);
35662 @samp{Fsystem,@var{commandptr}/@var{len}}
35664 @item Return value:
35665 If @var{len} is zero, the return value indicates whether a shell is
35666 available. A zero return value indicates a shell is not available.
35667 For non-zero @var{len}, the value returned is -1 on error and the
35668 return status of the command otherwise. Only the exit status of the
35669 command is returned, which is extracted from the host's @code{system}
35670 return value by calling @code{WEXITSTATUS(retval)}. In case
35671 @file{/bin/sh} could not be executed, 127 is returned.
35677 The call was interrupted by the user.
35682 @value{GDBN} takes over the full task of calling the necessary host calls
35683 to perform the @code{system} call. The return value of @code{system} on
35684 the host is simplified before it's returned
35685 to the target. Any termination signal information from the child process
35686 is discarded, and the return value consists
35687 entirely of the exit status of the called command.
35689 Due to security concerns, the @code{system} call is by default refused
35690 by @value{GDBN}. The user has to allow this call explicitly with the
35691 @code{set remote system-call-allowed 1} command.
35694 @item set remote system-call-allowed
35695 @kindex set remote system-call-allowed
35696 Control whether to allow the @code{system} calls in the File I/O
35697 protocol for the remote target. The default is zero (disabled).
35699 @item show remote system-call-allowed
35700 @kindex show remote system-call-allowed
35701 Show whether the @code{system} calls are allowed in the File I/O
35705 @node Protocol-specific Representation of Datatypes
35706 @subsection Protocol-specific Representation of Datatypes
35707 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35710 * Integral Datatypes::
35712 * Memory Transfer::
35717 @node Integral Datatypes
35718 @unnumberedsubsubsec Integral Datatypes
35719 @cindex integral datatypes, in file-i/o protocol
35721 The integral datatypes used in the system calls are @code{int},
35722 @code{unsigned int}, @code{long}, @code{unsigned long},
35723 @code{mode_t}, and @code{time_t}.
35725 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35726 implemented as 32 bit values in this protocol.
35728 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35730 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35731 in @file{limits.h}) to allow range checking on host and target.
35733 @code{time_t} datatypes are defined as seconds since the Epoch.
35735 All integral datatypes transferred as part of a memory read or write of a
35736 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35739 @node Pointer Values
35740 @unnumberedsubsubsec Pointer Values
35741 @cindex pointer values, in file-i/o protocol
35743 Pointers to target data are transmitted as they are. An exception
35744 is made for pointers to buffers for which the length isn't
35745 transmitted as part of the function call, namely strings. Strings
35746 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35753 which is a pointer to data of length 18 bytes at position 0x1aaf.
35754 The length is defined as the full string length in bytes, including
35755 the trailing null byte. For example, the string @code{"hello world"}
35756 at address 0x123456 is transmitted as
35762 @node Memory Transfer
35763 @unnumberedsubsubsec Memory Transfer
35764 @cindex memory transfer, in file-i/o protocol
35766 Structured data which is transferred using a memory read or write (for
35767 example, a @code{struct stat}) is expected to be in a protocol-specific format
35768 with all scalar multibyte datatypes being big endian. Translation to
35769 this representation needs to be done both by the target before the @code{F}
35770 packet is sent, and by @value{GDBN} before
35771 it transfers memory to the target. Transferred pointers to structured
35772 data should point to the already-coerced data at any time.
35776 @unnumberedsubsubsec struct stat
35777 @cindex struct stat, in file-i/o protocol
35779 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35780 is defined as follows:
35784 unsigned int st_dev; /* device */
35785 unsigned int st_ino; /* inode */
35786 mode_t st_mode; /* protection */
35787 unsigned int st_nlink; /* number of hard links */
35788 unsigned int st_uid; /* user ID of owner */
35789 unsigned int st_gid; /* group ID of owner */
35790 unsigned int st_rdev; /* device type (if inode device) */
35791 unsigned long st_size; /* total size, in bytes */
35792 unsigned long st_blksize; /* blocksize for filesystem I/O */
35793 unsigned long st_blocks; /* number of blocks allocated */
35794 time_t st_atime; /* time of last access */
35795 time_t st_mtime; /* time of last modification */
35796 time_t st_ctime; /* time of last change */
35800 The integral datatypes conform to the definitions given in the
35801 appropriate section (see @ref{Integral Datatypes}, for details) so this
35802 structure is of size 64 bytes.
35804 The values of several fields have a restricted meaning and/or
35810 A value of 0 represents a file, 1 the console.
35813 No valid meaning for the target. Transmitted unchanged.
35816 Valid mode bits are described in @ref{Constants}. Any other
35817 bits have currently no meaning for the target.
35822 No valid meaning for the target. Transmitted unchanged.
35827 These values have a host and file system dependent
35828 accuracy. Especially on Windows hosts, the file system may not
35829 support exact timing values.
35832 The target gets a @code{struct stat} of the above representation and is
35833 responsible for coercing it to the target representation before
35836 Note that due to size differences between the host, target, and protocol
35837 representations of @code{struct stat} members, these members could eventually
35838 get truncated on the target.
35840 @node struct timeval
35841 @unnumberedsubsubsec struct timeval
35842 @cindex struct timeval, in file-i/o protocol
35844 The buffer of type @code{struct timeval} used by the File-I/O protocol
35845 is defined as follows:
35849 time_t tv_sec; /* second */
35850 long tv_usec; /* microsecond */
35854 The integral datatypes conform to the definitions given in the
35855 appropriate section (see @ref{Integral Datatypes}, for details) so this
35856 structure is of size 8 bytes.
35859 @subsection Constants
35860 @cindex constants, in file-i/o protocol
35862 The following values are used for the constants inside of the
35863 protocol. @value{GDBN} and target are responsible for translating these
35864 values before and after the call as needed.
35875 @unnumberedsubsubsec Open Flags
35876 @cindex open flags, in file-i/o protocol
35878 All values are given in hexadecimal representation.
35890 @node mode_t Values
35891 @unnumberedsubsubsec mode_t Values
35892 @cindex mode_t values, in file-i/o protocol
35894 All values are given in octal representation.
35911 @unnumberedsubsubsec Errno Values
35912 @cindex errno values, in file-i/o protocol
35914 All values are given in decimal representation.
35939 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35940 any error value not in the list of supported error numbers.
35943 @unnumberedsubsubsec Lseek Flags
35944 @cindex lseek flags, in file-i/o protocol
35953 @unnumberedsubsubsec Limits
35954 @cindex limits, in file-i/o protocol
35956 All values are given in decimal representation.
35959 INT_MIN -2147483648
35961 UINT_MAX 4294967295
35962 LONG_MIN -9223372036854775808
35963 LONG_MAX 9223372036854775807
35964 ULONG_MAX 18446744073709551615
35967 @node File-I/O Examples
35968 @subsection File-I/O Examples
35969 @cindex file-i/o examples
35971 Example sequence of a write call, file descriptor 3, buffer is at target
35972 address 0x1234, 6 bytes should be written:
35975 <- @code{Fwrite,3,1234,6}
35976 @emph{request memory read from target}
35979 @emph{return "6 bytes written"}
35983 Example sequence of a read call, file descriptor 3, buffer is at target
35984 address 0x1234, 6 bytes should be read:
35987 <- @code{Fread,3,1234,6}
35988 @emph{request memory write to target}
35989 -> @code{X1234,6:XXXXXX}
35990 @emph{return "6 bytes read"}
35994 Example sequence of a read call, call fails on the host due to invalid
35995 file descriptor (@code{EBADF}):
35998 <- @code{Fread,3,1234,6}
36002 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
36006 <- @code{Fread,3,1234,6}
36011 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
36015 <- @code{Fread,3,1234,6}
36016 -> @code{X1234,6:XXXXXX}
36020 @node Library List Format
36021 @section Library List Format
36022 @cindex library list format, remote protocol
36024 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
36025 same process as your application to manage libraries. In this case,
36026 @value{GDBN} can use the loader's symbol table and normal memory
36027 operations to maintain a list of shared libraries. On other
36028 platforms, the operating system manages loaded libraries.
36029 @value{GDBN} can not retrieve the list of currently loaded libraries
36030 through memory operations, so it uses the @samp{qXfer:libraries:read}
36031 packet (@pxref{qXfer library list read}) instead. The remote stub
36032 queries the target's operating system and reports which libraries
36035 The @samp{qXfer:libraries:read} packet returns an XML document which
36036 lists loaded libraries and their offsets. Each library has an
36037 associated name and one or more segment or section base addresses,
36038 which report where the library was loaded in memory.
36040 For the common case of libraries that are fully linked binaries, the
36041 library should have a list of segments. If the target supports
36042 dynamic linking of a relocatable object file, its library XML element
36043 should instead include a list of allocated sections. The segment or
36044 section bases are start addresses, not relocation offsets; they do not
36045 depend on the library's link-time base addresses.
36047 @value{GDBN} must be linked with the Expat library to support XML
36048 library lists. @xref{Expat}.
36050 A simple memory map, with one loaded library relocated by a single
36051 offset, looks like this:
36055 <library name="/lib/libc.so.6">
36056 <segment address="0x10000000"/>
36061 Another simple memory map, with one loaded library with three
36062 allocated sections (.text, .data, .bss), looks like this:
36066 <library name="sharedlib.o">
36067 <section address="0x10000000"/>
36068 <section address="0x20000000"/>
36069 <section address="0x30000000"/>
36074 The format of a library list is described by this DTD:
36077 <!-- library-list: Root element with versioning -->
36078 <!ELEMENT library-list (library)*>
36079 <!ATTLIST library-list version CDATA #FIXED "1.0">
36080 <!ELEMENT library (segment*, section*)>
36081 <!ATTLIST library name CDATA #REQUIRED>
36082 <!ELEMENT segment EMPTY>
36083 <!ATTLIST segment address CDATA #REQUIRED>
36084 <!ELEMENT section EMPTY>
36085 <!ATTLIST section address CDATA #REQUIRED>
36088 In addition, segments and section descriptors cannot be mixed within a
36089 single library element, and you must supply at least one segment or
36090 section for each library.
36092 @node Memory Map Format
36093 @section Memory Map Format
36094 @cindex memory map format
36096 To be able to write into flash memory, @value{GDBN} needs to obtain a
36097 memory map from the target. This section describes the format of the
36100 The memory map is obtained using the @samp{qXfer:memory-map:read}
36101 (@pxref{qXfer memory map read}) packet and is an XML document that
36102 lists memory regions.
36104 @value{GDBN} must be linked with the Expat library to support XML
36105 memory maps. @xref{Expat}.
36107 The top-level structure of the document is shown below:
36110 <?xml version="1.0"?>
36111 <!DOCTYPE memory-map
36112 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36113 "http://sourceware.org/gdb/gdb-memory-map.dtd">
36119 Each region can be either:
36124 A region of RAM starting at @var{addr} and extending for @var{length}
36128 <memory type="ram" start="@var{addr}" length="@var{length}"/>
36133 A region of read-only memory:
36136 <memory type="rom" start="@var{addr}" length="@var{length}"/>
36141 A region of flash memory, with erasure blocks @var{blocksize}
36145 <memory type="flash" start="@var{addr}" length="@var{length}">
36146 <property name="blocksize">@var{blocksize}</property>
36152 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
36153 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
36154 packets to write to addresses in such ranges.
36156 The formal DTD for memory map format is given below:
36159 <!-- ................................................... -->
36160 <!-- Memory Map XML DTD ................................ -->
36161 <!-- File: memory-map.dtd .............................. -->
36162 <!-- .................................... .............. -->
36163 <!-- memory-map.dtd -->
36164 <!-- memory-map: Root element with versioning -->
36165 <!ELEMENT memory-map (memory | property)>
36166 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
36167 <!ELEMENT memory (property)>
36168 <!-- memory: Specifies a memory region,
36169 and its type, or device. -->
36170 <!ATTLIST memory type CDATA #REQUIRED
36171 start CDATA #REQUIRED
36172 length CDATA #REQUIRED
36173 device CDATA #IMPLIED>
36174 <!-- property: Generic attribute tag -->
36175 <!ELEMENT property (#PCDATA | property)*>
36176 <!ATTLIST property name CDATA #REQUIRED>
36179 @node Thread List Format
36180 @section Thread List Format
36181 @cindex thread list format
36183 To efficiently update the list of threads and their attributes,
36184 @value{GDBN} issues the @samp{qXfer:threads:read} packet
36185 (@pxref{qXfer threads read}) and obtains the XML document with
36186 the following structure:
36189 <?xml version="1.0"?>
36191 <thread id="id" core="0">
36192 ... description ...
36197 Each @samp{thread} element must have the @samp{id} attribute that
36198 identifies the thread (@pxref{thread-id syntax}). The
36199 @samp{core} attribute, if present, specifies which processor core
36200 the thread was last executing on. The content of the of @samp{thread}
36201 element is interpreted as human-readable auxilliary information.
36203 @node Traceframe Info Format
36204 @section Traceframe Info Format
36205 @cindex traceframe info format
36207 To be able to know which objects in the inferior can be examined when
36208 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
36209 memory ranges, registers and trace state variables that have been
36210 collected in a traceframe.
36212 This list is obtained using the @samp{qXfer:traceframe-info:read}
36213 (@pxref{qXfer traceframe info read}) packet and is an XML document.
36215 @value{GDBN} must be linked with the Expat library to support XML
36216 traceframe info discovery. @xref{Expat}.
36218 The top-level structure of the document is shown below:
36221 <?xml version="1.0"?>
36222 <!DOCTYPE traceframe-info
36223 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36224 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
36230 Each traceframe block can be either:
36235 A region of collected memory starting at @var{addr} and extending for
36236 @var{length} bytes from there:
36239 <memory start="@var{addr}" length="@var{length}"/>
36244 The formal DTD for the traceframe info format is given below:
36247 <!ELEMENT traceframe-info (memory)* >
36248 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
36250 <!ELEMENT memory EMPTY>
36251 <!ATTLIST memory start CDATA #REQUIRED
36252 length CDATA #REQUIRED>
36255 @include agentexpr.texi
36257 @node Target Descriptions
36258 @appendix Target Descriptions
36259 @cindex target descriptions
36261 @strong{Warning:} target descriptions are still under active development,
36262 and the contents and format may change between @value{GDBN} releases.
36263 The format is expected to stabilize in the future.
36265 One of the challenges of using @value{GDBN} to debug embedded systems
36266 is that there are so many minor variants of each processor
36267 architecture in use. It is common practice for vendors to start with
36268 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
36269 and then make changes to adapt it to a particular market niche. Some
36270 architectures have hundreds of variants, available from dozens of
36271 vendors. This leads to a number of problems:
36275 With so many different customized processors, it is difficult for
36276 the @value{GDBN} maintainers to keep up with the changes.
36278 Since individual variants may have short lifetimes or limited
36279 audiences, it may not be worthwhile to carry information about every
36280 variant in the @value{GDBN} source tree.
36282 When @value{GDBN} does support the architecture of the embedded system
36283 at hand, the task of finding the correct architecture name to give the
36284 @command{set architecture} command can be error-prone.
36287 To address these problems, the @value{GDBN} remote protocol allows a
36288 target system to not only identify itself to @value{GDBN}, but to
36289 actually describe its own features. This lets @value{GDBN} support
36290 processor variants it has never seen before --- to the extent that the
36291 descriptions are accurate, and that @value{GDBN} understands them.
36293 @value{GDBN} must be linked with the Expat library to support XML
36294 target descriptions. @xref{Expat}.
36297 * Retrieving Descriptions:: How descriptions are fetched from a target.
36298 * Target Description Format:: The contents of a target description.
36299 * Predefined Target Types:: Standard types available for target
36301 * Standard Target Features:: Features @value{GDBN} knows about.
36304 @node Retrieving Descriptions
36305 @section Retrieving Descriptions
36307 Target descriptions can be read from the target automatically, or
36308 specified by the user manually. The default behavior is to read the
36309 description from the target. @value{GDBN} retrieves it via the remote
36310 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
36311 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
36312 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
36313 XML document, of the form described in @ref{Target Description
36316 Alternatively, you can specify a file to read for the target description.
36317 If a file is set, the target will not be queried. The commands to
36318 specify a file are:
36321 @cindex set tdesc filename
36322 @item set tdesc filename @var{path}
36323 Read the target description from @var{path}.
36325 @cindex unset tdesc filename
36326 @item unset tdesc filename
36327 Do not read the XML target description from a file. @value{GDBN}
36328 will use the description supplied by the current target.
36330 @cindex show tdesc filename
36331 @item show tdesc filename
36332 Show the filename to read for a target description, if any.
36336 @node Target Description Format
36337 @section Target Description Format
36338 @cindex target descriptions, XML format
36340 A target description annex is an @uref{http://www.w3.org/XML/, XML}
36341 document which complies with the Document Type Definition provided in
36342 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
36343 means you can use generally available tools like @command{xmllint} to
36344 check that your feature descriptions are well-formed and valid.
36345 However, to help people unfamiliar with XML write descriptions for
36346 their targets, we also describe the grammar here.
36348 Target descriptions can identify the architecture of the remote target
36349 and (for some architectures) provide information about custom register
36350 sets. They can also identify the OS ABI of the remote target.
36351 @value{GDBN} can use this information to autoconfigure for your
36352 target, or to warn you if you connect to an unsupported target.
36354 Here is a simple target description:
36357 <target version="1.0">
36358 <architecture>i386:x86-64</architecture>
36363 This minimal description only says that the target uses
36364 the x86-64 architecture.
36366 A target description has the following overall form, with [ ] marking
36367 optional elements and @dots{} marking repeatable elements. The elements
36368 are explained further below.
36371 <?xml version="1.0"?>
36372 <!DOCTYPE target SYSTEM "gdb-target.dtd">
36373 <target version="1.0">
36374 @r{[}@var{architecture}@r{]}
36375 @r{[}@var{osabi}@r{]}
36376 @r{[}@var{compatible}@r{]}
36377 @r{[}@var{feature}@dots{}@r{]}
36382 The description is generally insensitive to whitespace and line
36383 breaks, under the usual common-sense rules. The XML version
36384 declaration and document type declaration can generally be omitted
36385 (@value{GDBN} does not require them), but specifying them may be
36386 useful for XML validation tools. The @samp{version} attribute for
36387 @samp{<target>} may also be omitted, but we recommend
36388 including it; if future versions of @value{GDBN} use an incompatible
36389 revision of @file{gdb-target.dtd}, they will detect and report
36390 the version mismatch.
36392 @subsection Inclusion
36393 @cindex target descriptions, inclusion
36396 @cindex <xi:include>
36399 It can sometimes be valuable to split a target description up into
36400 several different annexes, either for organizational purposes, or to
36401 share files between different possible target descriptions. You can
36402 divide a description into multiple files by replacing any element of
36403 the target description with an inclusion directive of the form:
36406 <xi:include href="@var{document}"/>
36410 When @value{GDBN} encounters an element of this form, it will retrieve
36411 the named XML @var{document}, and replace the inclusion directive with
36412 the contents of that document. If the current description was read
36413 using @samp{qXfer}, then so will be the included document;
36414 @var{document} will be interpreted as the name of an annex. If the
36415 current description was read from a file, @value{GDBN} will look for
36416 @var{document} as a file in the same directory where it found the
36417 original description.
36419 @subsection Architecture
36420 @cindex <architecture>
36422 An @samp{<architecture>} element has this form:
36425 <architecture>@var{arch}</architecture>
36428 @var{arch} is one of the architectures from the set accepted by
36429 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36432 @cindex @code{<osabi>}
36434 This optional field was introduced in @value{GDBN} version 7.0.
36435 Previous versions of @value{GDBN} ignore it.
36437 An @samp{<osabi>} element has this form:
36440 <osabi>@var{abi-name}</osabi>
36443 @var{abi-name} is an OS ABI name from the same selection accepted by
36444 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
36446 @subsection Compatible Architecture
36447 @cindex @code{<compatible>}
36449 This optional field was introduced in @value{GDBN} version 7.0.
36450 Previous versions of @value{GDBN} ignore it.
36452 A @samp{<compatible>} element has this form:
36455 <compatible>@var{arch}</compatible>
36458 @var{arch} is one of the architectures from the set accepted by
36459 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36461 A @samp{<compatible>} element is used to specify that the target
36462 is able to run binaries in some other than the main target architecture
36463 given by the @samp{<architecture>} element. For example, on the
36464 Cell Broadband Engine, the main architecture is @code{powerpc:common}
36465 or @code{powerpc:common64}, but the system is able to run binaries
36466 in the @code{spu} architecture as well. The way to describe this
36467 capability with @samp{<compatible>} is as follows:
36470 <architecture>powerpc:common</architecture>
36471 <compatible>spu</compatible>
36474 @subsection Features
36477 Each @samp{<feature>} describes some logical portion of the target
36478 system. Features are currently used to describe available CPU
36479 registers and the types of their contents. A @samp{<feature>} element
36483 <feature name="@var{name}">
36484 @r{[}@var{type}@dots{}@r{]}
36490 Each feature's name should be unique within the description. The name
36491 of a feature does not matter unless @value{GDBN} has some special
36492 knowledge of the contents of that feature; if it does, the feature
36493 should have its standard name. @xref{Standard Target Features}.
36497 Any register's value is a collection of bits which @value{GDBN} must
36498 interpret. The default interpretation is a two's complement integer,
36499 but other types can be requested by name in the register description.
36500 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
36501 Target Types}), and the description can define additional composite types.
36503 Each type element must have an @samp{id} attribute, which gives
36504 a unique (within the containing @samp{<feature>}) name to the type.
36505 Types must be defined before they are used.
36508 Some targets offer vector registers, which can be treated as arrays
36509 of scalar elements. These types are written as @samp{<vector>} elements,
36510 specifying the array element type, @var{type}, and the number of elements,
36514 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
36518 If a register's value is usefully viewed in multiple ways, define it
36519 with a union type containing the useful representations. The
36520 @samp{<union>} element contains one or more @samp{<field>} elements,
36521 each of which has a @var{name} and a @var{type}:
36524 <union id="@var{id}">
36525 <field name="@var{name}" type="@var{type}"/>
36531 If a register's value is composed from several separate values, define
36532 it with a structure type. There are two forms of the @samp{<struct>}
36533 element; a @samp{<struct>} element must either contain only bitfields
36534 or contain no bitfields. If the structure contains only bitfields,
36535 its total size in bytes must be specified, each bitfield must have an
36536 explicit start and end, and bitfields are automatically assigned an
36537 integer type. The field's @var{start} should be less than or
36538 equal to its @var{end}, and zero represents the least significant bit.
36541 <struct id="@var{id}" size="@var{size}">
36542 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36547 If the structure contains no bitfields, then each field has an
36548 explicit type, and no implicit padding is added.
36551 <struct id="@var{id}">
36552 <field name="@var{name}" type="@var{type}"/>
36558 If a register's value is a series of single-bit flags, define it with
36559 a flags type. The @samp{<flags>} element has an explicit @var{size}
36560 and contains one or more @samp{<field>} elements. Each field has a
36561 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
36565 <flags id="@var{id}" size="@var{size}">
36566 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36571 @subsection Registers
36574 Each register is represented as an element with this form:
36577 <reg name="@var{name}"
36578 bitsize="@var{size}"
36579 @r{[}regnum="@var{num}"@r{]}
36580 @r{[}save-restore="@var{save-restore}"@r{]}
36581 @r{[}type="@var{type}"@r{]}
36582 @r{[}group="@var{group}"@r{]}/>
36586 The components are as follows:
36591 The register's name; it must be unique within the target description.
36594 The register's size, in bits.
36597 The register's number. If omitted, a register's number is one greater
36598 than that of the previous register (either in the current feature or in
36599 a preceeding feature); the first register in the target description
36600 defaults to zero. This register number is used to read or write
36601 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36602 packets, and registers appear in the @code{g} and @code{G} packets
36603 in order of increasing register number.
36606 Whether the register should be preserved across inferior function
36607 calls; this must be either @code{yes} or @code{no}. The default is
36608 @code{yes}, which is appropriate for most registers except for
36609 some system control registers; this is not related to the target's
36613 The type of the register. @var{type} may be a predefined type, a type
36614 defined in the current feature, or one of the special types @code{int}
36615 and @code{float}. @code{int} is an integer type of the correct size
36616 for @var{bitsize}, and @code{float} is a floating point type (in the
36617 architecture's normal floating point format) of the correct size for
36618 @var{bitsize}. The default is @code{int}.
36621 The register group to which this register belongs. @var{group} must
36622 be either @code{general}, @code{float}, or @code{vector}. If no
36623 @var{group} is specified, @value{GDBN} will not display the register
36624 in @code{info registers}.
36628 @node Predefined Target Types
36629 @section Predefined Target Types
36630 @cindex target descriptions, predefined types
36632 Type definitions in the self-description can build up composite types
36633 from basic building blocks, but can not define fundamental types. Instead,
36634 standard identifiers are provided by @value{GDBN} for the fundamental
36635 types. The currently supported types are:
36644 Signed integer types holding the specified number of bits.
36651 Unsigned integer types holding the specified number of bits.
36655 Pointers to unspecified code and data. The program counter and
36656 any dedicated return address register may be marked as code
36657 pointers; printing a code pointer converts it into a symbolic
36658 address. The stack pointer and any dedicated address registers
36659 may be marked as data pointers.
36662 Single precision IEEE floating point.
36665 Double precision IEEE floating point.
36668 The 12-byte extended precision format used by ARM FPA registers.
36671 The 10-byte extended precision format used by x87 registers.
36674 32bit @sc{eflags} register used by x86.
36677 32bit @sc{mxcsr} register used by x86.
36681 @node Standard Target Features
36682 @section Standard Target Features
36683 @cindex target descriptions, standard features
36685 A target description must contain either no registers or all the
36686 target's registers. If the description contains no registers, then
36687 @value{GDBN} will assume a default register layout, selected based on
36688 the architecture. If the description contains any registers, the
36689 default layout will not be used; the standard registers must be
36690 described in the target description, in such a way that @value{GDBN}
36691 can recognize them.
36693 This is accomplished by giving specific names to feature elements
36694 which contain standard registers. @value{GDBN} will look for features
36695 with those names and verify that they contain the expected registers;
36696 if any known feature is missing required registers, or if any required
36697 feature is missing, @value{GDBN} will reject the target
36698 description. You can add additional registers to any of the
36699 standard features --- @value{GDBN} will display them just as if
36700 they were added to an unrecognized feature.
36702 This section lists the known features and their expected contents.
36703 Sample XML documents for these features are included in the
36704 @value{GDBN} source tree, in the directory @file{gdb/features}.
36706 Names recognized by @value{GDBN} should include the name of the
36707 company or organization which selected the name, and the overall
36708 architecture to which the feature applies; so e.g.@: the feature
36709 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36711 The names of registers are not case sensitive for the purpose
36712 of recognizing standard features, but @value{GDBN} will only display
36713 registers using the capitalization used in the description.
36720 * PowerPC Features::
36725 @subsection ARM Features
36726 @cindex target descriptions, ARM features
36728 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36730 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36731 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36733 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36734 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36735 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36738 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36739 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36741 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36742 it should contain at least registers @samp{wR0} through @samp{wR15} and
36743 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36744 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36746 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36747 should contain at least registers @samp{d0} through @samp{d15}. If
36748 they are present, @samp{d16} through @samp{d31} should also be included.
36749 @value{GDBN} will synthesize the single-precision registers from
36750 halves of the double-precision registers.
36752 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36753 need to contain registers; it instructs @value{GDBN} to display the
36754 VFP double-precision registers as vectors and to synthesize the
36755 quad-precision registers from pairs of double-precision registers.
36756 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36757 be present and include 32 double-precision registers.
36759 @node i386 Features
36760 @subsection i386 Features
36761 @cindex target descriptions, i386 features
36763 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36764 targets. It should describe the following registers:
36768 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36770 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36772 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36773 @samp{fs}, @samp{gs}
36775 @samp{st0} through @samp{st7}
36777 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36778 @samp{foseg}, @samp{fooff} and @samp{fop}
36781 The register sets may be different, depending on the target.
36783 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36784 describe registers:
36788 @samp{xmm0} through @samp{xmm7} for i386
36790 @samp{xmm0} through @samp{xmm15} for amd64
36795 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36796 @samp{org.gnu.gdb.i386.sse} feature. It should
36797 describe the upper 128 bits of @sc{ymm} registers:
36801 @samp{ymm0h} through @samp{ymm7h} for i386
36803 @samp{ymm0h} through @samp{ymm15h} for amd64
36806 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36807 describe a single register, @samp{orig_eax}.
36809 @node MIPS Features
36810 @subsection MIPS Features
36811 @cindex target descriptions, MIPS features
36813 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36814 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36815 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36818 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36819 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36820 registers. They may be 32-bit or 64-bit depending on the target.
36822 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36823 it may be optional in a future version of @value{GDBN}. It should
36824 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36825 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
36827 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
36828 contain a single register, @samp{restart}, which is used by the
36829 Linux kernel to control restartable syscalls.
36831 @node M68K Features
36832 @subsection M68K Features
36833 @cindex target descriptions, M68K features
36836 @item @samp{org.gnu.gdb.m68k.core}
36837 @itemx @samp{org.gnu.gdb.coldfire.core}
36838 @itemx @samp{org.gnu.gdb.fido.core}
36839 One of those features must be always present.
36840 The feature that is present determines which flavor of m68k is
36841 used. The feature that is present should contain registers
36842 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
36843 @samp{sp}, @samp{ps} and @samp{pc}.
36845 @item @samp{org.gnu.gdb.coldfire.fp}
36846 This feature is optional. If present, it should contain registers
36847 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
36851 @node PowerPC Features
36852 @subsection PowerPC Features
36853 @cindex target descriptions, PowerPC features
36855 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
36856 targets. It should contain registers @samp{r0} through @samp{r31},
36857 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
36858 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
36860 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
36861 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
36863 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
36864 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
36867 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
36868 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
36869 will combine these registers with the floating point registers
36870 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
36871 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
36872 through @samp{vs63}, the set of vector registers for POWER7.
36874 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
36875 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
36876 @samp{spefscr}. SPE targets should provide 32-bit registers in
36877 @samp{org.gnu.gdb.power.core} and provide the upper halves in
36878 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
36879 these to present registers @samp{ev0} through @samp{ev31} to the
36882 @node Operating System Information
36883 @appendix Operating System Information
36884 @cindex operating system information
36890 Users of @value{GDBN} often wish to obtain information about the state of
36891 the operating system running on the target---for example the list of
36892 processes, or the list of open files. This section describes the
36893 mechanism that makes it possible. This mechanism is similar to the
36894 target features mechanism (@pxref{Target Descriptions}), but focuses
36895 on a different aspect of target.
36897 Operating system information is retrived from the target via the
36898 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
36899 read}). The object name in the request should be @samp{osdata}, and
36900 the @var{annex} identifies the data to be fetched.
36903 @appendixsection Process list
36904 @cindex operating system information, process list
36906 When requesting the process list, the @var{annex} field in the
36907 @samp{qXfer} request should be @samp{processes}. The returned data is
36908 an XML document. The formal syntax of this document is defined in
36909 @file{gdb/features/osdata.dtd}.
36911 An example document is:
36914 <?xml version="1.0"?>
36915 <!DOCTYPE target SYSTEM "osdata.dtd">
36916 <osdata type="processes">
36918 <column name="pid">1</column>
36919 <column name="user">root</column>
36920 <column name="command">/sbin/init</column>
36921 <column name="cores">1,2,3</column>
36926 Each item should include a column whose name is @samp{pid}. The value
36927 of that column should identify the process on the target. The
36928 @samp{user} and @samp{command} columns are optional, and will be
36929 displayed by @value{GDBN}. The @samp{cores} column, if present,
36930 should contain a comma-separated list of cores that this process
36931 is running on. Target may provide additional columns,
36932 which @value{GDBN} currently ignores.
36934 @node Trace File Format
36935 @appendix Trace File Format
36936 @cindex trace file format
36938 The trace file comes in three parts: a header, a textual description
36939 section, and a trace frame section with binary data.
36941 The header has the form @code{\x7fTRACE0\n}. The first byte is
36942 @code{0x7f} so as to indicate that the file contains binary data,
36943 while the @code{0} is a version number that may have different values
36946 The description section consists of multiple lines of @sc{ascii} text
36947 separated by newline characters (@code{0xa}). The lines may include a
36948 variety of optional descriptive or context-setting information, such
36949 as tracepoint definitions or register set size. @value{GDBN} will
36950 ignore any line that it does not recognize. An empty line marks the end
36953 @c FIXME add some specific types of data
36955 The trace frame section consists of a number of consecutive frames.
36956 Each frame begins with a two-byte tracepoint number, followed by a
36957 four-byte size giving the amount of data in the frame. The data in
36958 the frame consists of a number of blocks, each introduced by a
36959 character indicating its type (at least register, memory, and trace
36960 state variable). The data in this section is raw binary, not a
36961 hexadecimal or other encoding; its endianness matches the target's
36964 @c FIXME bi-arch may require endianness/arch info in description section
36967 @item R @var{bytes}
36968 Register block. The number and ordering of bytes matches that of a
36969 @code{g} packet in the remote protocol. Note that these are the
36970 actual bytes, in target order and @value{GDBN} register order, not a
36971 hexadecimal encoding.
36973 @item M @var{address} @var{length} @var{bytes}...
36974 Memory block. This is a contiguous block of memory, at the 8-byte
36975 address @var{address}, with a 2-byte length @var{length}, followed by
36976 @var{length} bytes.
36978 @item V @var{number} @var{value}
36979 Trace state variable block. This records the 8-byte signed value
36980 @var{value} of trace state variable numbered @var{number}.
36984 Future enhancements of the trace file format may include additional types
36987 @node Index Section Format
36988 @appendix @code{.gdb_index} section format
36989 @cindex .gdb_index section format
36990 @cindex index section format
36992 This section documents the index section that is created by @code{save
36993 gdb-index} (@pxref{Index Files}). The index section is
36994 DWARF-specific; some knowledge of DWARF is assumed in this
36997 The mapped index file format is designed to be directly
36998 @code{mmap}able on any architecture. In most cases, a datum is
36999 represented using a little-endian 32-bit integer value, called an
37000 @code{offset_type}. Big endian machines must byte-swap the values
37001 before using them. Exceptions to this rule are noted. The data is
37002 laid out such that alignment is always respected.
37004 A mapped index consists of several areas, laid out in order.
37008 The file header. This is a sequence of values, of @code{offset_type}
37009 unless otherwise noted:
37013 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
37014 Version 4 differs by its hashing function.
37017 The offset, from the start of the file, of the CU list.
37020 The offset, from the start of the file, of the types CU list. Note
37021 that this area can be empty, in which case this offset will be equal
37022 to the next offset.
37025 The offset, from the start of the file, of the address area.
37028 The offset, from the start of the file, of the symbol table.
37031 The offset, from the start of the file, of the constant pool.
37035 The CU list. This is a sequence of pairs of 64-bit little-endian
37036 values, sorted by the CU offset. The first element in each pair is
37037 the offset of a CU in the @code{.debug_info} section. The second
37038 element in each pair is the length of that CU. References to a CU
37039 elsewhere in the map are done using a CU index, which is just the
37040 0-based index into this table. Note that if there are type CUs, then
37041 conceptually CUs and type CUs form a single list for the purposes of
37045 The types CU list. This is a sequence of triplets of 64-bit
37046 little-endian values. In a triplet, the first value is the CU offset,
37047 the second value is the type offset in the CU, and the third value is
37048 the type signature. The types CU list is not sorted.
37051 The address area. The address area consists of a sequence of address
37052 entries. Each address entry has three elements:
37056 The low address. This is a 64-bit little-endian value.
37059 The high address. This is a 64-bit little-endian value. Like
37060 @code{DW_AT_high_pc}, the value is one byte beyond the end.
37063 The CU index. This is an @code{offset_type} value.
37067 The symbol table. This is an open-addressed hash table. The size of
37068 the hash table is always a power of 2.
37070 Each slot in the hash table consists of a pair of @code{offset_type}
37071 values. The first value is the offset of the symbol's name in the
37072 constant pool. The second value is the offset of the CU vector in the
37075 If both values are 0, then this slot in the hash table is empty. This
37076 is ok because while 0 is a valid constant pool index, it cannot be a
37077 valid index for both a string and a CU vector.
37079 The hash value for a table entry is computed by applying an
37080 iterative hash function to the symbol's name. Starting with an
37081 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
37082 the string is incorporated into the hash using the formula depending on the
37087 The formula is @code{r = r * 67 + c - 113}.
37090 The formula is @code{r = r * 67 + tolower (c) - 113}.
37093 The terminating @samp{\0} is not incorporated into the hash.
37095 The step size used in the hash table is computed via
37096 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
37097 value, and @samp{size} is the size of the hash table. The step size
37098 is used to find the next candidate slot when handling a hash
37101 The names of C@t{++} symbols in the hash table are canonicalized. We
37102 don't currently have a simple description of the canonicalization
37103 algorithm; if you intend to create new index sections, you must read
37107 The constant pool. This is simply a bunch of bytes. It is organized
37108 so that alignment is correct: CU vectors are stored first, followed by
37111 A CU vector in the constant pool is a sequence of @code{offset_type}
37112 values. The first value is the number of CU indices in the vector.
37113 Each subsequent value is the index of a CU in the CU list. This
37114 element in the hash table is used to indicate which CUs define the
37117 A string in the constant pool is zero-terminated.
37122 @node GNU Free Documentation License
37123 @appendix GNU Free Documentation License
37132 % I think something like @colophon should be in texinfo. In the
37134 \long\def\colophon{\hbox to0pt{}\vfill
37135 \centerline{The body of this manual is set in}
37136 \centerline{\fontname\tenrm,}
37137 \centerline{with headings in {\bf\fontname\tenbf}}
37138 \centerline{and examples in {\tt\fontname\tentt}.}
37139 \centerline{{\it\fontname\tenit\/},}
37140 \centerline{{\bf\fontname\tenbf}, and}
37141 \centerline{{\sl\fontname\tensl\/}}
37142 \centerline{are used for emphasis.}\vfill}
37144 % Blame: doc@cygnus.com, 1991.