1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
4 @c 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 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2010 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Trace File Format:: GDB trace file format
178 * Copying:: GNU General Public License says
179 how you can copy and share GDB
180 * GNU Free Documentation License:: The license for this documentation
189 @unnumbered Summary of @value{GDBN}
191 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
192 going on ``inside'' another program while it executes---or what another
193 program was doing at the moment it crashed.
195 @value{GDBN} can do four main kinds of things (plus other things in support of
196 these) to help you catch bugs in the act:
200 Start your program, specifying anything that might affect its behavior.
203 Make your program stop on specified conditions.
206 Examine what has happened, when your program has stopped.
209 Change things in your program, so you can experiment with correcting the
210 effects of one bug and go on to learn about another.
213 You can use @value{GDBN} to debug programs written in C and C@t{++}.
214 For more information, see @ref{Supported Languages,,Supported Languages}.
215 For more information, see @ref{C,,C and C++}.
217 Support for D is partial. For information on D, see
221 Support for Modula-2 is partial. For information on Modula-2, see
222 @ref{Modula-2,,Modula-2}.
225 Debugging Pascal programs which use sets, subranges, file variables, or
226 nested functions does not currently work. @value{GDBN} does not support
227 entering expressions, printing values, or similar features using Pascal
231 @value{GDBN} can be used to debug programs written in Fortran, although
232 it may be necessary to refer to some variables with a trailing
235 @value{GDBN} can be used to debug programs written in Objective-C,
236 using either the Apple/NeXT or the GNU Objective-C runtime.
239 * Free Software:: Freely redistributable software
240 * Contributors:: Contributors to GDB
244 @unnumberedsec Free Software
246 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
247 General Public License
248 (GPL). The GPL gives you the freedom to copy or adapt a licensed
249 program---but every person getting a copy also gets with it the
250 freedom to modify that copy (which means that they must get access to
251 the source code), and the freedom to distribute further copies.
252 Typical software companies use copyrights to limit your freedoms; the
253 Free Software Foundation uses the GPL to preserve these freedoms.
255 Fundamentally, the General Public License is a license which says that
256 you have these freedoms and that you cannot take these freedoms away
259 @unnumberedsec Free Software Needs Free Documentation
261 The biggest deficiency in the free software community today is not in
262 the software---it is the lack of good free documentation that we can
263 include with the free software. Many of our most important
264 programs do not come with free reference manuals and free introductory
265 texts. Documentation is an essential part of any software package;
266 when an important free software package does not come with a free
267 manual and a free tutorial, that is a major gap. We have many such
270 Consider Perl, for instance. The tutorial manuals that people
271 normally use are non-free. How did this come about? Because the
272 authors of those manuals published them with restrictive terms---no
273 copying, no modification, source files not available---which exclude
274 them from the free software world.
276 That wasn't the first time this sort of thing happened, and it was far
277 from the last. Many times we have heard a GNU user eagerly describe a
278 manual that he is writing, his intended contribution to the community,
279 only to learn that he had ruined everything by signing a publication
280 contract to make it non-free.
282 Free documentation, like free software, is a matter of freedom, not
283 price. The problem with the non-free manual is not that publishers
284 charge a price for printed copies---that in itself is fine. (The Free
285 Software Foundation sells printed copies of manuals, too.) The
286 problem is the restrictions on the use of the manual. Free manuals
287 are available in source code form, and give you permission to copy and
288 modify. Non-free manuals do not allow this.
290 The criteria of freedom for a free manual are roughly the same as for
291 free software. Redistribution (including the normal kinds of
292 commercial redistribution) must be permitted, so that the manual can
293 accompany every copy of the program, both on-line and on paper.
295 Permission for modification of the technical content is crucial too.
296 When people modify the software, adding or changing features, if they
297 are conscientious they will change the manual too---so they can
298 provide accurate and clear documentation for the modified program. A
299 manual that leaves you no choice but to write a new manual to document
300 a changed version of the program is not really available to our
303 Some kinds of limits on the way modification is handled are
304 acceptable. For example, requirements to preserve the original
305 author's copyright notice, the distribution terms, or the list of
306 authors, are ok. It is also no problem to require modified versions
307 to include notice that they were modified. Even entire sections that
308 may not be deleted or changed are acceptable, as long as they deal
309 with nontechnical topics (like this one). These kinds of restrictions
310 are acceptable because they don't obstruct the community's normal use
313 However, it must be possible to modify all the @emph{technical}
314 content of the manual, and then distribute the result in all the usual
315 media, through all the usual channels. Otherwise, the restrictions
316 obstruct the use of the manual, it is not free, and we need another
317 manual to replace it.
319 Please spread the word about this issue. Our community continues to
320 lose manuals to proprietary publishing. If we spread the word that
321 free software needs free reference manuals and free tutorials, perhaps
322 the next person who wants to contribute by writing documentation will
323 realize, before it is too late, that only free manuals contribute to
324 the free software community.
326 If you are writing documentation, please insist on publishing it under
327 the GNU Free Documentation License or another free documentation
328 license. Remember that this decision requires your approval---you
329 don't have to let the publisher decide. Some commercial publishers
330 will use a free license if you insist, but they will not propose the
331 option; it is up to you to raise the issue and say firmly that this is
332 what you want. If the publisher you are dealing with refuses, please
333 try other publishers. If you're not sure whether a proposed license
334 is free, write to @email{licensing@@gnu.org}.
336 You can encourage commercial publishers to sell more free, copylefted
337 manuals and tutorials by buying them, and particularly by buying
338 copies from the publishers that paid for their writing or for major
339 improvements. Meanwhile, try to avoid buying non-free documentation
340 at all. Check the distribution terms of a manual before you buy it,
341 and insist that whoever seeks your business must respect your freedom.
342 Check the history of the book, and try to reward the publishers that
343 have paid or pay the authors to work on it.
345 The Free Software Foundation maintains a list of free documentation
346 published by other publishers, at
347 @url{http://www.fsf.org/doc/other-free-books.html}.
350 @unnumberedsec Contributors to @value{GDBN}
352 Richard Stallman was the original author of @value{GDBN}, and of many
353 other @sc{gnu} programs. Many others have contributed to its
354 development. This section attempts to credit major contributors. One
355 of the virtues of free software is that everyone is free to contribute
356 to it; with regret, we cannot actually acknowledge everyone here. The
357 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
358 blow-by-blow account.
360 Changes much prior to version 2.0 are lost in the mists of time.
363 @emph{Plea:} Additions to this section are particularly welcome. If you
364 or your friends (or enemies, to be evenhanded) have been unfairly
365 omitted from this list, we would like to add your names!
368 So that they may not regard their many labors as thankless, we
369 particularly thank those who shepherded @value{GDBN} through major
371 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
372 Jim Blandy (release 4.18);
373 Jason Molenda (release 4.17);
374 Stan Shebs (release 4.14);
375 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
376 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
377 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
378 Jim Kingdon (releases 3.5, 3.4, and 3.3);
379 and Randy Smith (releases 3.2, 3.1, and 3.0).
381 Richard Stallman, assisted at various times by Peter TerMaat, Chris
382 Hanson, and Richard Mlynarik, handled releases through 2.8.
384 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
385 in @value{GDBN}, with significant additional contributions from Per
386 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
387 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
388 much general update work leading to release 3.0).
390 @value{GDBN} uses the BFD subroutine library to examine multiple
391 object-file formats; BFD was a joint project of David V.
392 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
394 David Johnson wrote the original COFF support; Pace Willison did
395 the original support for encapsulated COFF.
397 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
399 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
400 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
402 Jean-Daniel Fekete contributed Sun 386i support.
403 Chris Hanson improved the HP9000 support.
404 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
405 David Johnson contributed Encore Umax support.
406 Jyrki Kuoppala contributed Altos 3068 support.
407 Jeff Law contributed HP PA and SOM support.
408 Keith Packard contributed NS32K support.
409 Doug Rabson contributed Acorn Risc Machine support.
410 Bob Rusk contributed Harris Nighthawk CX-UX support.
411 Chris Smith contributed Convex support (and Fortran debugging).
412 Jonathan Stone contributed Pyramid support.
413 Michael Tiemann contributed SPARC support.
414 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
415 Pace Willison contributed Intel 386 support.
416 Jay Vosburgh contributed Symmetry support.
417 Marko Mlinar contributed OpenRISC 1000 support.
419 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
421 Rich Schaefer and Peter Schauer helped with support of SunOS shared
424 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
425 about several machine instruction sets.
427 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
428 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
429 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
430 and RDI targets, respectively.
432 Brian Fox is the author of the readline libraries providing
433 command-line editing and command history.
435 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
436 Modula-2 support, and contributed the Languages chapter of this manual.
438 Fred Fish wrote most of the support for Unix System Vr4.
439 He also enhanced the command-completion support to cover C@t{++} overloaded
442 Hitachi America (now Renesas America), Ltd. sponsored the support for
443 H8/300, H8/500, and Super-H processors.
445 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
447 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
450 Toshiba sponsored the support for the TX39 Mips processor.
452 Matsushita sponsored the support for the MN10200 and MN10300 processors.
454 Fujitsu sponsored the support for SPARClite and FR30 processors.
456 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
459 Michael Snyder added support for tracepoints.
461 Stu Grossman wrote gdbserver.
463 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
464 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
466 The following people at the Hewlett-Packard Company contributed
467 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
468 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
469 compiler, and the Text User Interface (nee Terminal User Interface):
470 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
471 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
472 provided HP-specific information in this manual.
474 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
475 Robert Hoehne made significant contributions to the DJGPP port.
477 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
478 development since 1991. Cygnus engineers who have worked on @value{GDBN}
479 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
480 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
481 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
482 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
483 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
484 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
485 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
486 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
487 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
488 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
489 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
490 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
491 Zuhn have made contributions both large and small.
493 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
494 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
496 Jim Blandy added support for preprocessor macros, while working for Red
499 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
500 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
501 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
502 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
503 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
504 with the migration of old architectures to this new framework.
506 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
507 unwinder framework, this consisting of a fresh new design featuring
508 frame IDs, independent frame sniffers, and the sentinel frame. Mark
509 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
510 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
511 trad unwinders. The architecture-specific changes, each involving a
512 complete rewrite of the architecture's frame code, were carried out by
513 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
514 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
515 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
516 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
519 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
520 Tensilica, Inc.@: contributed support for Xtensa processors. Others
521 who have worked on the Xtensa port of @value{GDBN} in the past include
522 Steve Tjiang, John Newlin, and Scott Foehner.
524 Michael Eager and staff of Xilinx, Inc., contributed support for the
525 Xilinx MicroBlaze architecture.
528 @chapter A Sample @value{GDBN} Session
530 You can use this manual at your leisure to read all about @value{GDBN}.
531 However, a handful of commands are enough to get started using the
532 debugger. This chapter illustrates those commands.
535 In this sample session, we emphasize user input like this: @b{input},
536 to make it easier to pick out from the surrounding output.
539 @c FIXME: this example may not be appropriate for some configs, where
540 @c FIXME...primary interest is in remote use.
542 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
543 processor) exhibits the following bug: sometimes, when we change its
544 quote strings from the default, the commands used to capture one macro
545 definition within another stop working. In the following short @code{m4}
546 session, we define a macro @code{foo} which expands to @code{0000}; we
547 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
548 same thing. However, when we change the open quote string to
549 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
550 procedure fails to define a new synonym @code{baz}:
559 @b{define(bar,defn(`foo'))}
563 @b{changequote(<QUOTE>,<UNQUOTE>)}
565 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
568 m4: End of input: 0: fatal error: EOF in string
572 Let us use @value{GDBN} to try to see what is going on.
575 $ @b{@value{GDBP} m4}
576 @c FIXME: this falsifies the exact text played out, to permit smallbook
577 @c FIXME... format to come out better.
578 @value{GDBN} is free software and you are welcome to distribute copies
579 of it under certain conditions; type "show copying" to see
581 There is absolutely no warranty for @value{GDBN}; type "show warranty"
584 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
589 @value{GDBN} reads only enough symbol data to know where to find the
590 rest when needed; as a result, the first prompt comes up very quickly.
591 We now tell @value{GDBN} to use a narrower display width than usual, so
592 that examples fit in this manual.
595 (@value{GDBP}) @b{set width 70}
599 We need to see how the @code{m4} built-in @code{changequote} works.
600 Having looked at the source, we know the relevant subroutine is
601 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
602 @code{break} command.
605 (@value{GDBP}) @b{break m4_changequote}
606 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
610 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
611 control; as long as control does not reach the @code{m4_changequote}
612 subroutine, the program runs as usual:
615 (@value{GDBP}) @b{run}
616 Starting program: /work/Editorial/gdb/gnu/m4/m4
624 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
625 suspends execution of @code{m4}, displaying information about the
626 context where it stops.
629 @b{changequote(<QUOTE>,<UNQUOTE>)}
631 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
633 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
637 Now we use the command @code{n} (@code{next}) to advance execution to
638 the next line of the current function.
642 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
647 @code{set_quotes} looks like a promising subroutine. We can go into it
648 by using the command @code{s} (@code{step}) instead of @code{next}.
649 @code{step} goes to the next line to be executed in @emph{any}
650 subroutine, so it steps into @code{set_quotes}.
654 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
656 530 if (lquote != def_lquote)
660 The display that shows the subroutine where @code{m4} is now
661 suspended (and its arguments) is called a stack frame display. It
662 shows a summary of the stack. We can use the @code{backtrace}
663 command (which can also be spelled @code{bt}), to see where we are
664 in the stack as a whole: the @code{backtrace} command displays a
665 stack frame for each active subroutine.
668 (@value{GDBP}) @b{bt}
669 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
671 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
673 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
674 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
676 #4 0x79dc in expand_input () at macro.c:40
677 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
681 We step through a few more lines to see what happens. The first two
682 times, we can use @samp{s}; the next two times we use @code{n} to avoid
683 falling into the @code{xstrdup} subroutine.
687 0x3b5c 532 if (rquote != def_rquote)
689 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
690 def_lquote : xstrdup(lq);
692 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
695 538 len_lquote = strlen(rquote);
699 The last line displayed looks a little odd; we can examine the variables
700 @code{lquote} and @code{rquote} to see if they are in fact the new left
701 and right quotes we specified. We use the command @code{p}
702 (@code{print}) to see their values.
705 (@value{GDBP}) @b{p lquote}
706 $1 = 0x35d40 "<QUOTE>"
707 (@value{GDBP}) @b{p rquote}
708 $2 = 0x35d50 "<UNQUOTE>"
712 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
713 To look at some context, we can display ten lines of source
714 surrounding the current line with the @code{l} (@code{list}) command.
720 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
722 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
725 538 len_lquote = strlen(rquote);
726 539 len_rquote = strlen(lquote);
733 Let us step past the two lines that set @code{len_lquote} and
734 @code{len_rquote}, and then examine the values of those variables.
738 539 len_rquote = strlen(lquote);
741 (@value{GDBP}) @b{p len_lquote}
743 (@value{GDBP}) @b{p len_rquote}
748 That certainly looks wrong, assuming @code{len_lquote} and
749 @code{len_rquote} are meant to be the lengths of @code{lquote} and
750 @code{rquote} respectively. We can set them to better values using
751 the @code{p} command, since it can print the value of
752 any expression---and that expression can include subroutine calls and
756 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
758 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
763 Is that enough to fix the problem of using the new quotes with the
764 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
765 executing with the @code{c} (@code{continue}) command, and then try the
766 example that caused trouble initially:
772 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
779 Success! The new quotes now work just as well as the default ones. The
780 problem seems to have been just the two typos defining the wrong
781 lengths. We allow @code{m4} exit by giving it an EOF as input:
785 Program exited normally.
789 The message @samp{Program exited normally.} is from @value{GDBN}; it
790 indicates @code{m4} has finished executing. We can end our @value{GDBN}
791 session with the @value{GDBN} @code{quit} command.
794 (@value{GDBP}) @b{quit}
798 @chapter Getting In and Out of @value{GDBN}
800 This chapter discusses how to start @value{GDBN}, and how to get out of it.
804 type @samp{@value{GDBP}} to start @value{GDBN}.
806 type @kbd{quit} or @kbd{Ctrl-d} to exit.
810 * Invoking GDB:: How to start @value{GDBN}
811 * Quitting GDB:: How to quit @value{GDBN}
812 * Shell Commands:: How to use shell commands inside @value{GDBN}
813 * Logging Output:: How to log @value{GDBN}'s output to a file
817 @section Invoking @value{GDBN}
819 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
820 @value{GDBN} reads commands from the terminal until you tell it to exit.
822 You can also run @code{@value{GDBP}} with a variety of arguments and options,
823 to specify more of your debugging environment at the outset.
825 The command-line options described here are designed
826 to cover a variety of situations; in some environments, some of these
827 options may effectively be unavailable.
829 The most usual way to start @value{GDBN} is with one argument,
830 specifying an executable program:
833 @value{GDBP} @var{program}
837 You can also start with both an executable program and a core file
841 @value{GDBP} @var{program} @var{core}
844 You can, instead, specify a process ID as a second argument, if you want
845 to debug a running process:
848 @value{GDBP} @var{program} 1234
852 would attach @value{GDBN} to process @code{1234} (unless you also have a file
853 named @file{1234}; @value{GDBN} does check for a core file first).
855 Taking advantage of the second command-line argument requires a fairly
856 complete operating system; when you use @value{GDBN} as a remote
857 debugger attached to a bare board, there may not be any notion of
858 ``process'', and there is often no way to get a core dump. @value{GDBN}
859 will warn you if it is unable to attach or to read core dumps.
861 You can optionally have @code{@value{GDBP}} pass any arguments after the
862 executable file to the inferior using @code{--args}. This option stops
865 @value{GDBP} --args gcc -O2 -c foo.c
867 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
868 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
870 You can run @code{@value{GDBP}} without printing the front material, which describes
871 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
878 You can further control how @value{GDBN} starts up by using command-line
879 options. @value{GDBN} itself can remind you of the options available.
889 to display all available options and briefly describe their use
890 (@samp{@value{GDBP} -h} is a shorter equivalent).
892 All options and command line arguments you give are processed
893 in sequential order. The order makes a difference when the
894 @samp{-x} option is used.
898 * File Options:: Choosing files
899 * Mode Options:: Choosing modes
900 * Startup:: What @value{GDBN} does during startup
904 @subsection Choosing Files
906 When @value{GDBN} starts, it reads any arguments other than options as
907 specifying an executable file and core file (or process ID). This is
908 the same as if the arguments were specified by the @samp{-se} and
909 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
910 first argument that does not have an associated option flag as
911 equivalent to the @samp{-se} option followed by that argument; and the
912 second argument that does not have an associated option flag, if any, as
913 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
914 If the second argument begins with a decimal digit, @value{GDBN} will
915 first attempt to attach to it as a process, and if that fails, attempt
916 to open it as a corefile. If you have a corefile whose name begins with
917 a digit, you can prevent @value{GDBN} from treating it as a pid by
918 prefixing it with @file{./}, e.g.@: @file{./12345}.
920 If @value{GDBN} has not been configured to included core file support,
921 such as for most embedded targets, then it will complain about a second
922 argument and ignore it.
924 Many options have both long and short forms; both are shown in the
925 following list. @value{GDBN} also recognizes the long forms if you truncate
926 them, so long as enough of the option is present to be unambiguous.
927 (If you prefer, you can flag option arguments with @samp{--} rather
928 than @samp{-}, though we illustrate the more usual convention.)
930 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
931 @c way, both those who look for -foo and --foo in the index, will find
935 @item -symbols @var{file}
937 @cindex @code{--symbols}
939 Read symbol table from file @var{file}.
941 @item -exec @var{file}
943 @cindex @code{--exec}
945 Use file @var{file} as the executable file to execute when appropriate,
946 and for examining pure data in conjunction with a core dump.
950 Read symbol table from file @var{file} and use it as the executable
953 @item -core @var{file}
955 @cindex @code{--core}
957 Use file @var{file} as a core dump to examine.
959 @item -pid @var{number}
960 @itemx -p @var{number}
963 Connect to process ID @var{number}, as with the @code{attach} command.
965 @item -command @var{file}
967 @cindex @code{--command}
969 Execute commands from file @var{file}. The contents of this file is
970 evaluated exactly as the @code{source} command would.
971 @xref{Command Files,, Command files}.
973 @item -eval-command @var{command}
974 @itemx -ex @var{command}
975 @cindex @code{--eval-command}
977 Execute a single @value{GDBN} command.
979 This option may be used multiple times to call multiple commands. It may
980 also be interleaved with @samp{-command} as required.
983 @value{GDBP} -ex 'target sim' -ex 'load' \
984 -x setbreakpoints -ex 'run' a.out
987 @item -directory @var{directory}
988 @itemx -d @var{directory}
989 @cindex @code{--directory}
991 Add @var{directory} to the path to search for source and script files.
995 @cindex @code{--readnow}
997 Read each symbol file's entire symbol table immediately, rather than
998 the default, which is to read it incrementally as it is needed.
999 This makes startup slower, but makes future operations faster.
1004 @subsection Choosing Modes
1006 You can run @value{GDBN} in various alternative modes---for example, in
1007 batch mode or quiet mode.
1014 Do not execute commands found in any initialization files. Normally,
1015 @value{GDBN} executes the commands in these files after all the command
1016 options and arguments have been processed. @xref{Command Files,,Command
1022 @cindex @code{--quiet}
1023 @cindex @code{--silent}
1025 ``Quiet''. Do not print the introductory and copyright messages. These
1026 messages are also suppressed in batch mode.
1029 @cindex @code{--batch}
1030 Run in batch mode. Exit with status @code{0} after processing all the
1031 command files specified with @samp{-x} (and all commands from
1032 initialization files, if not inhibited with @samp{-n}). Exit with
1033 nonzero status if an error occurs in executing the @value{GDBN} commands
1034 in the command files. Batch mode also disables pagination, sets unlimited
1035 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1036 off} were in effect (@pxref{Messages/Warnings}).
1038 Batch mode may be useful for running @value{GDBN} as a filter, for
1039 example to download and run a program on another computer; in order to
1040 make this more useful, the message
1043 Program exited normally.
1047 (which is ordinarily issued whenever a program running under
1048 @value{GDBN} control terminates) is not issued when running in batch
1052 @cindex @code{--batch-silent}
1053 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1054 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1055 unaffected). This is much quieter than @samp{-silent} and would be useless
1056 for an interactive session.
1058 This is particularly useful when using targets that give @samp{Loading section}
1059 messages, for example.
1061 Note that targets that give their output via @value{GDBN}, as opposed to
1062 writing directly to @code{stdout}, will also be made silent.
1064 @item -return-child-result
1065 @cindex @code{--return-child-result}
1066 The return code from @value{GDBN} will be the return code from the child
1067 process (the process being debugged), with the following exceptions:
1071 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1072 internal error. In this case the exit code is the same as it would have been
1073 without @samp{-return-child-result}.
1075 The user quits with an explicit value. E.g., @samp{quit 1}.
1077 The child process never runs, or is not allowed to terminate, in which case
1078 the exit code will be -1.
1081 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1082 when @value{GDBN} is being used as a remote program loader or simulator
1087 @cindex @code{--nowindows}
1089 ``No windows''. If @value{GDBN} comes with a graphical user interface
1090 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1091 interface. If no GUI is available, this option has no effect.
1095 @cindex @code{--windows}
1097 If @value{GDBN} includes a GUI, then this option requires it to be
1100 @item -cd @var{directory}
1102 Run @value{GDBN} using @var{directory} as its working directory,
1103 instead of the current directory.
1107 @cindex @code{--fullname}
1109 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1110 subprocess. It tells @value{GDBN} to output the full file name and line
1111 number in a standard, recognizable fashion each time a stack frame is
1112 displayed (which includes each time your program stops). This
1113 recognizable format looks like two @samp{\032} characters, followed by
1114 the file name, line number and character position separated by colons,
1115 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1116 @samp{\032} characters as a signal to display the source code for the
1120 @cindex @code{--epoch}
1121 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1122 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1123 routines so as to allow Epoch to display values of expressions in a
1126 @item -annotate @var{level}
1127 @cindex @code{--annotate}
1128 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1129 effect is identical to using @samp{set annotate @var{level}}
1130 (@pxref{Annotations}). The annotation @var{level} controls how much
1131 information @value{GDBN} prints together with its prompt, values of
1132 expressions, source lines, and other types of output. Level 0 is the
1133 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1134 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1135 that control @value{GDBN}, and level 2 has been deprecated.
1137 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1141 @cindex @code{--args}
1142 Change interpretation of command line so that arguments following the
1143 executable file are passed as command line arguments to the inferior.
1144 This option stops option processing.
1146 @item -baud @var{bps}
1148 @cindex @code{--baud}
1150 Set the line speed (baud rate or bits per second) of any serial
1151 interface used by @value{GDBN} for remote debugging.
1153 @item -l @var{timeout}
1155 Set the timeout (in seconds) of any communication used by @value{GDBN}
1156 for remote debugging.
1158 @item -tty @var{device}
1159 @itemx -t @var{device}
1160 @cindex @code{--tty}
1162 Run using @var{device} for your program's standard input and output.
1163 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1165 @c resolve the situation of these eventually
1167 @cindex @code{--tui}
1168 Activate the @dfn{Text User Interface} when starting. The Text User
1169 Interface manages several text windows on the terminal, showing
1170 source, assembly, registers and @value{GDBN} command outputs
1171 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1172 Text User Interface can be enabled by invoking the program
1173 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1174 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1177 @c @cindex @code{--xdb}
1178 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1179 @c For information, see the file @file{xdb_trans.html}, which is usually
1180 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1183 @item -interpreter @var{interp}
1184 @cindex @code{--interpreter}
1185 Use the interpreter @var{interp} for interface with the controlling
1186 program or device. This option is meant to be set by programs which
1187 communicate with @value{GDBN} using it as a back end.
1188 @xref{Interpreters, , Command Interpreters}.
1190 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1191 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1192 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1193 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1194 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1195 @sc{gdb/mi} interfaces are no longer supported.
1198 @cindex @code{--write}
1199 Open the executable and core files for both reading and writing. This
1200 is equivalent to the @samp{set write on} command inside @value{GDBN}
1204 @cindex @code{--statistics}
1205 This option causes @value{GDBN} to print statistics about time and
1206 memory usage after it completes each command and returns to the prompt.
1209 @cindex @code{--version}
1210 This option causes @value{GDBN} to print its version number and
1211 no-warranty blurb, and exit.
1216 @subsection What @value{GDBN} Does During Startup
1217 @cindex @value{GDBN} startup
1219 Here's the description of what @value{GDBN} does during session startup:
1223 Sets up the command interpreter as specified by the command line
1224 (@pxref{Mode Options, interpreter}).
1228 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1229 used when building @value{GDBN}; @pxref{System-wide configuration,
1230 ,System-wide configuration and settings}) and executes all the commands in
1234 Reads the init file (if any) in your home directory@footnote{On
1235 DOS/Windows systems, the home directory is the one pointed to by the
1236 @code{HOME} environment variable.} and executes all the commands in
1240 Processes command line options and operands.
1243 Reads and executes the commands from init file (if any) in the current
1244 working directory. This is only done if the current directory is
1245 different from your home directory. Thus, you can have more than one
1246 init file, one generic in your home directory, and another, specific
1247 to the program you are debugging, in the directory where you invoke
1251 Reads command files specified by the @samp{-x} option. @xref{Command
1252 Files}, for more details about @value{GDBN} command files.
1255 Reads the command history recorded in the @dfn{history file}.
1256 @xref{Command History}, for more details about the command history and the
1257 files where @value{GDBN} records it.
1260 Init files use the same syntax as @dfn{command files} (@pxref{Command
1261 Files}) and are processed by @value{GDBN} in the same way. The init
1262 file in your home directory can set options (such as @samp{set
1263 complaints}) that affect subsequent processing of command line options
1264 and operands. Init files are not executed if you use the @samp{-nx}
1265 option (@pxref{Mode Options, ,Choosing Modes}).
1267 To display the list of init files loaded by gdb at startup, you
1268 can use @kbd{gdb --help}.
1270 @cindex init file name
1271 @cindex @file{.gdbinit}
1272 @cindex @file{gdb.ini}
1273 The @value{GDBN} init files are normally called @file{.gdbinit}.
1274 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1275 the limitations of file names imposed by DOS filesystems. The Windows
1276 ports of @value{GDBN} use the standard name, but if they find a
1277 @file{gdb.ini} file, they warn you about that and suggest to rename
1278 the file to the standard name.
1282 @section Quitting @value{GDBN}
1283 @cindex exiting @value{GDBN}
1284 @cindex leaving @value{GDBN}
1287 @kindex quit @r{[}@var{expression}@r{]}
1288 @kindex q @r{(@code{quit})}
1289 @item quit @r{[}@var{expression}@r{]}
1291 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1292 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1293 do not supply @var{expression}, @value{GDBN} will terminate normally;
1294 otherwise it will terminate using the result of @var{expression} as the
1299 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1300 terminates the action of any @value{GDBN} command that is in progress and
1301 returns to @value{GDBN} command level. It is safe to type the interrupt
1302 character at any time because @value{GDBN} does not allow it to take effect
1303 until a time when it is safe.
1305 If you have been using @value{GDBN} to control an attached process or
1306 device, you can release it with the @code{detach} command
1307 (@pxref{Attach, ,Debugging an Already-running Process}).
1309 @node Shell Commands
1310 @section Shell Commands
1312 If you need to execute occasional shell commands during your
1313 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1314 just use the @code{shell} command.
1318 @cindex shell escape
1319 @item shell @var{command string}
1320 Invoke a standard shell to execute @var{command string}.
1321 If it exists, the environment variable @code{SHELL} determines which
1322 shell to run. Otherwise @value{GDBN} uses the default shell
1323 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1326 The utility @code{make} is often needed in development environments.
1327 You do not have to use the @code{shell} command for this purpose in
1332 @cindex calling make
1333 @item make @var{make-args}
1334 Execute the @code{make} program with the specified
1335 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1338 @node Logging Output
1339 @section Logging Output
1340 @cindex logging @value{GDBN} output
1341 @cindex save @value{GDBN} output to a file
1343 You may want to save the output of @value{GDBN} commands to a file.
1344 There are several commands to control @value{GDBN}'s logging.
1348 @item set logging on
1350 @item set logging off
1352 @cindex logging file name
1353 @item set logging file @var{file}
1354 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1355 @item set logging overwrite [on|off]
1356 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1357 you want @code{set logging on} to overwrite the logfile instead.
1358 @item set logging redirect [on|off]
1359 By default, @value{GDBN} output will go to both the terminal and the logfile.
1360 Set @code{redirect} if you want output to go only to the log file.
1361 @kindex show logging
1363 Show the current values of the logging settings.
1367 @chapter @value{GDBN} Commands
1369 You can abbreviate a @value{GDBN} command to the first few letters of the command
1370 name, if that abbreviation is unambiguous; and you can repeat certain
1371 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1372 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1373 show you the alternatives available, if there is more than one possibility).
1376 * Command Syntax:: How to give commands to @value{GDBN}
1377 * Completion:: Command completion
1378 * Help:: How to ask @value{GDBN} for help
1381 @node Command Syntax
1382 @section Command Syntax
1384 A @value{GDBN} command is a single line of input. There is no limit on
1385 how long it can be. It starts with a command name, which is followed by
1386 arguments whose meaning depends on the command name. For example, the
1387 command @code{step} accepts an argument which is the number of times to
1388 step, as in @samp{step 5}. You can also use the @code{step} command
1389 with no arguments. Some commands do not allow any arguments.
1391 @cindex abbreviation
1392 @value{GDBN} command names may always be truncated if that abbreviation is
1393 unambiguous. Other possible command abbreviations are listed in the
1394 documentation for individual commands. In some cases, even ambiguous
1395 abbreviations are allowed; for example, @code{s} is specially defined as
1396 equivalent to @code{step} even though there are other commands whose
1397 names start with @code{s}. You can test abbreviations by using them as
1398 arguments to the @code{help} command.
1400 @cindex repeating commands
1401 @kindex RET @r{(repeat last command)}
1402 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1403 repeat the previous command. Certain commands (for example, @code{run})
1404 will not repeat this way; these are commands whose unintentional
1405 repetition might cause trouble and which you are unlikely to want to
1406 repeat. User-defined commands can disable this feature; see
1407 @ref{Define, dont-repeat}.
1409 The @code{list} and @code{x} commands, when you repeat them with
1410 @key{RET}, construct new arguments rather than repeating
1411 exactly as typed. This permits easy scanning of source or memory.
1413 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1414 output, in a way similar to the common utility @code{more}
1415 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1416 @key{RET} too many in this situation, @value{GDBN} disables command
1417 repetition after any command that generates this sort of display.
1419 @kindex # @r{(a comment)}
1421 Any text from a @kbd{#} to the end of the line is a comment; it does
1422 nothing. This is useful mainly in command files (@pxref{Command
1423 Files,,Command Files}).
1425 @cindex repeating command sequences
1426 @kindex Ctrl-o @r{(operate-and-get-next)}
1427 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1428 commands. This command accepts the current line, like @key{RET}, and
1429 then fetches the next line relative to the current line from the history
1433 @section Command Completion
1436 @cindex word completion
1437 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1438 only one possibility; it can also show you what the valid possibilities
1439 are for the next word in a command, at any time. This works for @value{GDBN}
1440 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1442 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1443 of a word. If there is only one possibility, @value{GDBN} fills in the
1444 word, and waits for you to finish the command (or press @key{RET} to
1445 enter it). For example, if you type
1447 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1448 @c complete accuracy in these examples; space introduced for clarity.
1449 @c If texinfo enhancements make it unnecessary, it would be nice to
1450 @c replace " @key" by "@key" in the following...
1452 (@value{GDBP}) info bre @key{TAB}
1456 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1457 the only @code{info} subcommand beginning with @samp{bre}:
1460 (@value{GDBP}) info breakpoints
1464 You can either press @key{RET} at this point, to run the @code{info
1465 breakpoints} command, or backspace and enter something else, if
1466 @samp{breakpoints} does not look like the command you expected. (If you
1467 were sure you wanted @code{info breakpoints} in the first place, you
1468 might as well just type @key{RET} immediately after @samp{info bre},
1469 to exploit command abbreviations rather than command completion).
1471 If there is more than one possibility for the next word when you press
1472 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1473 characters and try again, or just press @key{TAB} a second time;
1474 @value{GDBN} displays all the possible completions for that word. For
1475 example, you might want to set a breakpoint on a subroutine whose name
1476 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1477 just sounds the bell. Typing @key{TAB} again displays all the
1478 function names in your program that begin with those characters, for
1482 (@value{GDBP}) b make_ @key{TAB}
1483 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1484 make_a_section_from_file make_environ
1485 make_abs_section make_function_type
1486 make_blockvector make_pointer_type
1487 make_cleanup make_reference_type
1488 make_command make_symbol_completion_list
1489 (@value{GDBP}) b make_
1493 After displaying the available possibilities, @value{GDBN} copies your
1494 partial input (@samp{b make_} in the example) so you can finish the
1497 If you just want to see the list of alternatives in the first place, you
1498 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1499 means @kbd{@key{META} ?}. You can type this either by holding down a
1500 key designated as the @key{META} shift on your keyboard (if there is
1501 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1503 @cindex quotes in commands
1504 @cindex completion of quoted strings
1505 Sometimes the string you need, while logically a ``word'', may contain
1506 parentheses or other characters that @value{GDBN} normally excludes from
1507 its notion of a word. To permit word completion to work in this
1508 situation, you may enclose words in @code{'} (single quote marks) in
1509 @value{GDBN} commands.
1511 The most likely situation where you might need this is in typing the
1512 name of a C@t{++} function. This is because C@t{++} allows function
1513 overloading (multiple definitions of the same function, distinguished
1514 by argument type). For example, when you want to set a breakpoint you
1515 may need to distinguish whether you mean the version of @code{name}
1516 that takes an @code{int} parameter, @code{name(int)}, or the version
1517 that takes a @code{float} parameter, @code{name(float)}. To use the
1518 word-completion facilities in this situation, type a single quote
1519 @code{'} at the beginning of the function name. This alerts
1520 @value{GDBN} that it may need to consider more information than usual
1521 when you press @key{TAB} or @kbd{M-?} to request word completion:
1524 (@value{GDBP}) b 'bubble( @kbd{M-?}
1525 bubble(double,double) bubble(int,int)
1526 (@value{GDBP}) b 'bubble(
1529 In some cases, @value{GDBN} can tell that completing a name requires using
1530 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1531 completing as much as it can) if you do not type the quote in the first
1535 (@value{GDBP}) b bub @key{TAB}
1536 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1537 (@value{GDBP}) b 'bubble(
1541 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1542 you have not yet started typing the argument list when you ask for
1543 completion on an overloaded symbol.
1545 For more information about overloaded functions, see @ref{C Plus Plus
1546 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1547 overload-resolution off} to disable overload resolution;
1548 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1550 @cindex completion of structure field names
1551 @cindex structure field name completion
1552 @cindex completion of union field names
1553 @cindex union field name completion
1554 When completing in an expression which looks up a field in a
1555 structure, @value{GDBN} also tries@footnote{The completer can be
1556 confused by certain kinds of invalid expressions. Also, it only
1557 examines the static type of the expression, not the dynamic type.} to
1558 limit completions to the field names available in the type of the
1562 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1563 magic to_delete to_fputs to_put to_rewind
1564 to_data to_flush to_isatty to_read to_write
1568 This is because the @code{gdb_stdout} is a variable of the type
1569 @code{struct ui_file} that is defined in @value{GDBN} sources as
1576 ui_file_flush_ftype *to_flush;
1577 ui_file_write_ftype *to_write;
1578 ui_file_fputs_ftype *to_fputs;
1579 ui_file_read_ftype *to_read;
1580 ui_file_delete_ftype *to_delete;
1581 ui_file_isatty_ftype *to_isatty;
1582 ui_file_rewind_ftype *to_rewind;
1583 ui_file_put_ftype *to_put;
1590 @section Getting Help
1591 @cindex online documentation
1594 You can always ask @value{GDBN} itself for information on its commands,
1595 using the command @code{help}.
1598 @kindex h @r{(@code{help})}
1601 You can use @code{help} (abbreviated @code{h}) with no arguments to
1602 display a short list of named classes of commands:
1606 List of classes of commands:
1608 aliases -- Aliases of other commands
1609 breakpoints -- Making program stop at certain points
1610 data -- Examining data
1611 files -- Specifying and examining files
1612 internals -- Maintenance commands
1613 obscure -- Obscure features
1614 running -- Running the program
1615 stack -- Examining the stack
1616 status -- Status inquiries
1617 support -- Support facilities
1618 tracepoints -- Tracing of program execution without
1619 stopping the program
1620 user-defined -- User-defined commands
1622 Type "help" followed by a class name for a list of
1623 commands in that class.
1624 Type "help" followed by command name for full
1626 Command name abbreviations are allowed if unambiguous.
1629 @c the above line break eliminates huge line overfull...
1631 @item help @var{class}
1632 Using one of the general help classes as an argument, you can get a
1633 list of the individual commands in that class. For example, here is the
1634 help display for the class @code{status}:
1637 (@value{GDBP}) help status
1642 @c Line break in "show" line falsifies real output, but needed
1643 @c to fit in smallbook page size.
1644 info -- Generic command for showing things
1645 about the program being debugged
1646 show -- Generic command for showing things
1649 Type "help" followed by command name for full
1651 Command name abbreviations are allowed if unambiguous.
1655 @item help @var{command}
1656 With a command name as @code{help} argument, @value{GDBN} displays a
1657 short paragraph on how to use that command.
1660 @item apropos @var{args}
1661 The @code{apropos} command searches through all of the @value{GDBN}
1662 commands, and their documentation, for the regular expression specified in
1663 @var{args}. It prints out all matches found. For example:
1674 set symbol-reloading -- Set dynamic symbol table reloading
1675 multiple times in one run
1676 show symbol-reloading -- Show dynamic symbol table reloading
1677 multiple times in one run
1682 @item complete @var{args}
1683 The @code{complete @var{args}} command lists all the possible completions
1684 for the beginning of a command. Use @var{args} to specify the beginning of the
1685 command you want completed. For example:
1691 @noindent results in:
1702 @noindent This is intended for use by @sc{gnu} Emacs.
1705 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1706 and @code{show} to inquire about the state of your program, or the state
1707 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1708 manual introduces each of them in the appropriate context. The listings
1709 under @code{info} and under @code{show} in the Index point to
1710 all the sub-commands. @xref{Index}.
1715 @kindex i @r{(@code{info})}
1717 This command (abbreviated @code{i}) is for describing the state of your
1718 program. For example, you can show the arguments passed to a function
1719 with @code{info args}, list the registers currently in use with @code{info
1720 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1721 You can get a complete list of the @code{info} sub-commands with
1722 @w{@code{help info}}.
1726 You can assign the result of an expression to an environment variable with
1727 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1728 @code{set prompt $}.
1732 In contrast to @code{info}, @code{show} is for describing the state of
1733 @value{GDBN} itself.
1734 You can change most of the things you can @code{show}, by using the
1735 related command @code{set}; for example, you can control what number
1736 system is used for displays with @code{set radix}, or simply inquire
1737 which is currently in use with @code{show radix}.
1740 To display all the settable parameters and their current
1741 values, you can use @code{show} with no arguments; you may also use
1742 @code{info set}. Both commands produce the same display.
1743 @c FIXME: "info set" violates the rule that "info" is for state of
1744 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1745 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1749 Here are three miscellaneous @code{show} subcommands, all of which are
1750 exceptional in lacking corresponding @code{set} commands:
1753 @kindex show version
1754 @cindex @value{GDBN} version number
1756 Show what version of @value{GDBN} is running. You should include this
1757 information in @value{GDBN} bug-reports. If multiple versions of
1758 @value{GDBN} are in use at your site, you may need to determine which
1759 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1760 commands are introduced, and old ones may wither away. Also, many
1761 system vendors ship variant versions of @value{GDBN}, and there are
1762 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1763 The version number is the same as the one announced when you start
1766 @kindex show copying
1767 @kindex info copying
1768 @cindex display @value{GDBN} copyright
1771 Display information about permission for copying @value{GDBN}.
1773 @kindex show warranty
1774 @kindex info warranty
1776 @itemx info warranty
1777 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1778 if your version of @value{GDBN} comes with one.
1783 @chapter Running Programs Under @value{GDBN}
1785 When you run a program under @value{GDBN}, you must first generate
1786 debugging information when you compile it.
1788 You may start @value{GDBN} with its arguments, if any, in an environment
1789 of your choice. If you are doing native debugging, you may redirect
1790 your program's input and output, debug an already running process, or
1791 kill a child process.
1794 * Compilation:: Compiling for debugging
1795 * Starting:: Starting your program
1796 * Arguments:: Your program's arguments
1797 * Environment:: Your program's environment
1799 * Working Directory:: Your program's working directory
1800 * Input/Output:: Your program's input and output
1801 * Attach:: Debugging an already-running process
1802 * Kill Process:: Killing the child process
1804 * Inferiors and Programs:: Debugging multiple inferiors and programs
1805 * Threads:: Debugging programs with multiple threads
1806 * Forks:: Debugging forks
1807 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1811 @section Compiling for Debugging
1813 In order to debug a program effectively, you need to generate
1814 debugging information when you compile it. This debugging information
1815 is stored in the object file; it describes the data type of each
1816 variable or function and the correspondence between source line numbers
1817 and addresses in the executable code.
1819 To request debugging information, specify the @samp{-g} option when you run
1822 Programs that are to be shipped to your customers are compiled with
1823 optimizations, using the @samp{-O} compiler option. However, some
1824 compilers are unable to handle the @samp{-g} and @samp{-O} options
1825 together. Using those compilers, you cannot generate optimized
1826 executables containing debugging information.
1828 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1829 without @samp{-O}, making it possible to debug optimized code. We
1830 recommend that you @emph{always} use @samp{-g} whenever you compile a
1831 program. You may think your program is correct, but there is no sense
1832 in pushing your luck. For more information, see @ref{Optimized Code}.
1834 Older versions of the @sc{gnu} C compiler permitted a variant option
1835 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1836 format; if your @sc{gnu} C compiler has this option, do not use it.
1838 @value{GDBN} knows about preprocessor macros and can show you their
1839 expansion (@pxref{Macros}). Most compilers do not include information
1840 about preprocessor macros in the debugging information if you specify
1841 the @option{-g} flag alone, because this information is rather large.
1842 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1843 provides macro information if you specify the options
1844 @option{-gdwarf-2} and @option{-g3}; the former option requests
1845 debugging information in the Dwarf 2 format, and the latter requests
1846 ``extra information''. In the future, we hope to find more compact
1847 ways to represent macro information, so that it can be included with
1852 @section Starting your Program
1858 @kindex r @r{(@code{run})}
1861 Use the @code{run} command to start your program under @value{GDBN}.
1862 You must first specify the program name (except on VxWorks) with an
1863 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1864 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1865 (@pxref{Files, ,Commands to Specify Files}).
1869 If you are running your program in an execution environment that
1870 supports processes, @code{run} creates an inferior process and makes
1871 that process run your program. In some environments without processes,
1872 @code{run} jumps to the start of your program. Other targets,
1873 like @samp{remote}, are always running. If you get an error
1874 message like this one:
1877 The "remote" target does not support "run".
1878 Try "help target" or "continue".
1882 then use @code{continue} to run your program. You may need @code{load}
1883 first (@pxref{load}).
1885 The execution of a program is affected by certain information it
1886 receives from its superior. @value{GDBN} provides ways to specify this
1887 information, which you must do @emph{before} starting your program. (You
1888 can change it after starting your program, but such changes only affect
1889 your program the next time you start it.) This information may be
1890 divided into four categories:
1893 @item The @emph{arguments.}
1894 Specify the arguments to give your program as the arguments of the
1895 @code{run} command. If a shell is available on your target, the shell
1896 is used to pass the arguments, so that you may use normal conventions
1897 (such as wildcard expansion or variable substitution) in describing
1899 In Unix systems, you can control which shell is used with the
1900 @code{SHELL} environment variable.
1901 @xref{Arguments, ,Your Program's Arguments}.
1903 @item The @emph{environment.}
1904 Your program normally inherits its environment from @value{GDBN}, but you can
1905 use the @value{GDBN} commands @code{set environment} and @code{unset
1906 environment} to change parts of the environment that affect
1907 your program. @xref{Environment, ,Your Program's Environment}.
1909 @item The @emph{working directory.}
1910 Your program inherits its working directory from @value{GDBN}. You can set
1911 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1912 @xref{Working Directory, ,Your Program's Working Directory}.
1914 @item The @emph{standard input and output.}
1915 Your program normally uses the same device for standard input and
1916 standard output as @value{GDBN} is using. You can redirect input and output
1917 in the @code{run} command line, or you can use the @code{tty} command to
1918 set a different device for your program.
1919 @xref{Input/Output, ,Your Program's Input and Output}.
1922 @emph{Warning:} While input and output redirection work, you cannot use
1923 pipes to pass the output of the program you are debugging to another
1924 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1928 When you issue the @code{run} command, your program begins to execute
1929 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1930 of how to arrange for your program to stop. Once your program has
1931 stopped, you may call functions in your program, using the @code{print}
1932 or @code{call} commands. @xref{Data, ,Examining Data}.
1934 If the modification time of your symbol file has changed since the last
1935 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1936 table, and reads it again. When it does this, @value{GDBN} tries to retain
1937 your current breakpoints.
1942 @cindex run to main procedure
1943 The name of the main procedure can vary from language to language.
1944 With C or C@t{++}, the main procedure name is always @code{main}, but
1945 other languages such as Ada do not require a specific name for their
1946 main procedure. The debugger provides a convenient way to start the
1947 execution of the program and to stop at the beginning of the main
1948 procedure, depending on the language used.
1950 The @samp{start} command does the equivalent of setting a temporary
1951 breakpoint at the beginning of the main procedure and then invoking
1952 the @samp{run} command.
1954 @cindex elaboration phase
1955 Some programs contain an @dfn{elaboration} phase where some startup code is
1956 executed before the main procedure is called. This depends on the
1957 languages used to write your program. In C@t{++}, for instance,
1958 constructors for static and global objects are executed before
1959 @code{main} is called. It is therefore possible that the debugger stops
1960 before reaching the main procedure. However, the temporary breakpoint
1961 will remain to halt execution.
1963 Specify the arguments to give to your program as arguments to the
1964 @samp{start} command. These arguments will be given verbatim to the
1965 underlying @samp{run} command. Note that the same arguments will be
1966 reused if no argument is provided during subsequent calls to
1967 @samp{start} or @samp{run}.
1969 It is sometimes necessary to debug the program during elaboration. In
1970 these cases, using the @code{start} command would stop the execution of
1971 your program too late, as the program would have already completed the
1972 elaboration phase. Under these circumstances, insert breakpoints in your
1973 elaboration code before running your program.
1975 @kindex set exec-wrapper
1976 @item set exec-wrapper @var{wrapper}
1977 @itemx show exec-wrapper
1978 @itemx unset exec-wrapper
1979 When @samp{exec-wrapper} is set, the specified wrapper is used to
1980 launch programs for debugging. @value{GDBN} starts your program
1981 with a shell command of the form @kbd{exec @var{wrapper}
1982 @var{program}}. Quoting is added to @var{program} and its
1983 arguments, but not to @var{wrapper}, so you should add quotes if
1984 appropriate for your shell. The wrapper runs until it executes
1985 your program, and then @value{GDBN} takes control.
1987 You can use any program that eventually calls @code{execve} with
1988 its arguments as a wrapper. Several standard Unix utilities do
1989 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1990 with @code{exec "$@@"} will also work.
1992 For example, you can use @code{env} to pass an environment variable to
1993 the debugged program, without setting the variable in your shell's
1997 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2001 This command is available when debugging locally on most targets, excluding
2002 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2004 @kindex set disable-randomization
2005 @item set disable-randomization
2006 @itemx set disable-randomization on
2007 This option (enabled by default in @value{GDBN}) will turn off the native
2008 randomization of the virtual address space of the started program. This option
2009 is useful for multiple debugging sessions to make the execution better
2010 reproducible and memory addresses reusable across debugging sessions.
2012 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2016 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2019 @item set disable-randomization off
2020 Leave the behavior of the started executable unchanged. Some bugs rear their
2021 ugly heads only when the program is loaded at certain addresses. If your bug
2022 disappears when you run the program under @value{GDBN}, that might be because
2023 @value{GDBN} by default disables the address randomization on platforms, such
2024 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2025 disable-randomization off} to try to reproduce such elusive bugs.
2027 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2028 It protects the programs against some kinds of security attacks. In these
2029 cases the attacker needs to know the exact location of a concrete executable
2030 code. Randomizing its location makes it impossible to inject jumps misusing
2031 a code at its expected addresses.
2033 Prelinking shared libraries provides a startup performance advantage but it
2034 makes addresses in these libraries predictable for privileged processes by
2035 having just unprivileged access at the target system. Reading the shared
2036 library binary gives enough information for assembling the malicious code
2037 misusing it. Still even a prelinked shared library can get loaded at a new
2038 random address just requiring the regular relocation process during the
2039 startup. Shared libraries not already prelinked are always loaded at
2040 a randomly chosen address.
2042 Position independent executables (PIE) contain position independent code
2043 similar to the shared libraries and therefore such executables get loaded at
2044 a randomly chosen address upon startup. PIE executables always load even
2045 already prelinked shared libraries at a random address. You can build such
2046 executable using @command{gcc -fPIE -pie}.
2048 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2049 (as long as the randomization is enabled).
2051 @item show disable-randomization
2052 Show the current setting of the explicit disable of the native randomization of
2053 the virtual address space of the started program.
2058 @section Your Program's Arguments
2060 @cindex arguments (to your program)
2061 The arguments to your program can be specified by the arguments of the
2063 They are passed to a shell, which expands wildcard characters and
2064 performs redirection of I/O, and thence to your program. Your
2065 @code{SHELL} environment variable (if it exists) specifies what shell
2066 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2067 the default shell (@file{/bin/sh} on Unix).
2069 On non-Unix systems, the program is usually invoked directly by
2070 @value{GDBN}, which emulates I/O redirection via the appropriate system
2071 calls, and the wildcard characters are expanded by the startup code of
2072 the program, not by the shell.
2074 @code{run} with no arguments uses the same arguments used by the previous
2075 @code{run}, or those set by the @code{set args} command.
2080 Specify the arguments to be used the next time your program is run. If
2081 @code{set args} has no arguments, @code{run} executes your program
2082 with no arguments. Once you have run your program with arguments,
2083 using @code{set args} before the next @code{run} is the only way to run
2084 it again without arguments.
2088 Show the arguments to give your program when it is started.
2092 @section Your Program's Environment
2094 @cindex environment (of your program)
2095 The @dfn{environment} consists of a set of environment variables and
2096 their values. Environment variables conventionally record such things as
2097 your user name, your home directory, your terminal type, and your search
2098 path for programs to run. Usually you set up environment variables with
2099 the shell and they are inherited by all the other programs you run. When
2100 debugging, it can be useful to try running your program with a modified
2101 environment without having to start @value{GDBN} over again.
2105 @item path @var{directory}
2106 Add @var{directory} to the front of the @code{PATH} environment variable
2107 (the search path for executables) that will be passed to your program.
2108 The value of @code{PATH} used by @value{GDBN} does not change.
2109 You may specify several directory names, separated by whitespace or by a
2110 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2111 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2112 is moved to the front, so it is searched sooner.
2114 You can use the string @samp{$cwd} to refer to whatever is the current
2115 working directory at the time @value{GDBN} searches the path. If you
2116 use @samp{.} instead, it refers to the directory where you executed the
2117 @code{path} command. @value{GDBN} replaces @samp{.} in the
2118 @var{directory} argument (with the current path) before adding
2119 @var{directory} to the search path.
2120 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2121 @c document that, since repeating it would be a no-op.
2125 Display the list of search paths for executables (the @code{PATH}
2126 environment variable).
2128 @kindex show environment
2129 @item show environment @r{[}@var{varname}@r{]}
2130 Print the value of environment variable @var{varname} to be given to
2131 your program when it starts. If you do not supply @var{varname},
2132 print the names and values of all environment variables to be given to
2133 your program. You can abbreviate @code{environment} as @code{env}.
2135 @kindex set environment
2136 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2137 Set environment variable @var{varname} to @var{value}. The value
2138 changes for your program only, not for @value{GDBN} itself. @var{value} may
2139 be any string; the values of environment variables are just strings, and
2140 any interpretation is supplied by your program itself. The @var{value}
2141 parameter is optional; if it is eliminated, the variable is set to a
2143 @c "any string" here does not include leading, trailing
2144 @c blanks. Gnu asks: does anyone care?
2146 For example, this command:
2153 tells the debugged program, when subsequently run, that its user is named
2154 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2155 are not actually required.)
2157 @kindex unset environment
2158 @item unset environment @var{varname}
2159 Remove variable @var{varname} from the environment to be passed to your
2160 program. This is different from @samp{set env @var{varname} =};
2161 @code{unset environment} removes the variable from the environment,
2162 rather than assigning it an empty value.
2165 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2167 by your @code{SHELL} environment variable if it exists (or
2168 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2169 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2170 @file{.bashrc} for BASH---any variables you set in that file affect
2171 your program. You may wish to move setting of environment variables to
2172 files that are only run when you sign on, such as @file{.login} or
2175 @node Working Directory
2176 @section Your Program's Working Directory
2178 @cindex working directory (of your program)
2179 Each time you start your program with @code{run}, it inherits its
2180 working directory from the current working directory of @value{GDBN}.
2181 The @value{GDBN} working directory is initially whatever it inherited
2182 from its parent process (typically the shell), but you can specify a new
2183 working directory in @value{GDBN} with the @code{cd} command.
2185 The @value{GDBN} working directory also serves as a default for the commands
2186 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2191 @cindex change working directory
2192 @item cd @var{directory}
2193 Set the @value{GDBN} working directory to @var{directory}.
2197 Print the @value{GDBN} working directory.
2200 It is generally impossible to find the current working directory of
2201 the process being debugged (since a program can change its directory
2202 during its run). If you work on a system where @value{GDBN} is
2203 configured with the @file{/proc} support, you can use the @code{info
2204 proc} command (@pxref{SVR4 Process Information}) to find out the
2205 current working directory of the debuggee.
2208 @section Your Program's Input and Output
2213 By default, the program you run under @value{GDBN} does input and output to
2214 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2215 to its own terminal modes to interact with you, but it records the terminal
2216 modes your program was using and switches back to them when you continue
2217 running your program.
2220 @kindex info terminal
2222 Displays information recorded by @value{GDBN} about the terminal modes your
2226 You can redirect your program's input and/or output using shell
2227 redirection with the @code{run} command. For example,
2234 starts your program, diverting its output to the file @file{outfile}.
2237 @cindex controlling terminal
2238 Another way to specify where your program should do input and output is
2239 with the @code{tty} command. This command accepts a file name as
2240 argument, and causes this file to be the default for future @code{run}
2241 commands. It also resets the controlling terminal for the child
2242 process, for future @code{run} commands. For example,
2249 directs that processes started with subsequent @code{run} commands
2250 default to do input and output on the terminal @file{/dev/ttyb} and have
2251 that as their controlling terminal.
2253 An explicit redirection in @code{run} overrides the @code{tty} command's
2254 effect on the input/output device, but not its effect on the controlling
2257 When you use the @code{tty} command or redirect input in the @code{run}
2258 command, only the input @emph{for your program} is affected. The input
2259 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2260 for @code{set inferior-tty}.
2262 @cindex inferior tty
2263 @cindex set inferior controlling terminal
2264 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2265 display the name of the terminal that will be used for future runs of your
2269 @item set inferior-tty /dev/ttyb
2270 @kindex set inferior-tty
2271 Set the tty for the program being debugged to /dev/ttyb.
2273 @item show inferior-tty
2274 @kindex show inferior-tty
2275 Show the current tty for the program being debugged.
2279 @section Debugging an Already-running Process
2284 @item attach @var{process-id}
2285 This command attaches to a running process---one that was started
2286 outside @value{GDBN}. (@code{info files} shows your active
2287 targets.) The command takes as argument a process ID. The usual way to
2288 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2289 or with the @samp{jobs -l} shell command.
2291 @code{attach} does not repeat if you press @key{RET} a second time after
2292 executing the command.
2295 To use @code{attach}, your program must be running in an environment
2296 which supports processes; for example, @code{attach} does not work for
2297 programs on bare-board targets that lack an operating system. You must
2298 also have permission to send the process a signal.
2300 When you use @code{attach}, the debugger finds the program running in
2301 the process first by looking in the current working directory, then (if
2302 the program is not found) by using the source file search path
2303 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2304 the @code{file} command to load the program. @xref{Files, ,Commands to
2307 The first thing @value{GDBN} does after arranging to debug the specified
2308 process is to stop it. You can examine and modify an attached process
2309 with all the @value{GDBN} commands that are ordinarily available when
2310 you start processes with @code{run}. You can insert breakpoints; you
2311 can step and continue; you can modify storage. If you would rather the
2312 process continue running, you may use the @code{continue} command after
2313 attaching @value{GDBN} to the process.
2318 When you have finished debugging the attached process, you can use the
2319 @code{detach} command to release it from @value{GDBN} control. Detaching
2320 the process continues its execution. After the @code{detach} command,
2321 that process and @value{GDBN} become completely independent once more, and you
2322 are ready to @code{attach} another process or start one with @code{run}.
2323 @code{detach} does not repeat if you press @key{RET} again after
2324 executing the command.
2327 If you exit @value{GDBN} while you have an attached process, you detach
2328 that process. If you use the @code{run} command, you kill that process.
2329 By default, @value{GDBN} asks for confirmation if you try to do either of these
2330 things; you can control whether or not you need to confirm by using the
2331 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2335 @section Killing the Child Process
2340 Kill the child process in which your program is running under @value{GDBN}.
2343 This command is useful if you wish to debug a core dump instead of a
2344 running process. @value{GDBN} ignores any core dump file while your program
2347 On some operating systems, a program cannot be executed outside @value{GDBN}
2348 while you have breakpoints set on it inside @value{GDBN}. You can use the
2349 @code{kill} command in this situation to permit running your program
2350 outside the debugger.
2352 The @code{kill} command is also useful if you wish to recompile and
2353 relink your program, since on many systems it is impossible to modify an
2354 executable file while it is running in a process. In this case, when you
2355 next type @code{run}, @value{GDBN} notices that the file has changed, and
2356 reads the symbol table again (while trying to preserve your current
2357 breakpoint settings).
2359 @node Inferiors and Programs
2360 @section Debugging Multiple Inferiors and Programs
2362 @value{GDBN} lets you run and debug multiple programs in a single
2363 session. In addition, @value{GDBN} on some systems may let you run
2364 several programs simultaneously (otherwise you have to exit from one
2365 before starting another). In the most general case, you can have
2366 multiple threads of execution in each of multiple processes, launched
2367 from multiple executables.
2370 @value{GDBN} represents the state of each program execution with an
2371 object called an @dfn{inferior}. An inferior typically corresponds to
2372 a process, but is more general and applies also to targets that do not
2373 have processes. Inferiors may be created before a process runs, and
2374 may be retained after a process exits. Inferiors have unique
2375 identifiers that are different from process ids. Usually each
2376 inferior will also have its own distinct address space, although some
2377 embedded targets may have several inferiors running in different parts
2378 of a single address space. Each inferior may in turn have multiple
2379 threads running in it.
2381 To find out what inferiors exist at any moment, use @w{@code{info
2385 @kindex info inferiors
2386 @item info inferiors
2387 Print a list of all inferiors currently being managed by @value{GDBN}.
2389 @value{GDBN} displays for each inferior (in this order):
2393 the inferior number assigned by @value{GDBN}
2396 the target system's inferior identifier
2399 the name of the executable the inferior is running.
2404 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2405 indicates the current inferior.
2409 @c end table here to get a little more width for example
2412 (@value{GDBP}) info inferiors
2413 Num Description Executable
2414 2 process 2307 hello
2415 * 1 process 3401 goodbye
2418 To switch focus between inferiors, use the @code{inferior} command:
2421 @kindex inferior @var{infno}
2422 @item inferior @var{infno}
2423 Make inferior number @var{infno} the current inferior. The argument
2424 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2425 in the first field of the @samp{info inferiors} display.
2429 You can get multiple executables into a debugging session via the
2430 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2431 systems @value{GDBN} can add inferiors to the debug session
2432 automatically by following calls to @code{fork} and @code{exec}. To
2433 remove inferiors from the debugging session use the
2434 @w{@code{remove-inferior}} command.
2437 @kindex add-inferior
2438 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2439 Adds @var{n} inferiors to be run using @var{executable} as the
2440 executable. @var{n} defaults to 1. If no executable is specified,
2441 the inferiors begins empty, with no program. You can still assign or
2442 change the program assigned to the inferior at any time by using the
2443 @code{file} command with the executable name as its argument.
2445 @kindex clone-inferior
2446 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2447 Adds @var{n} inferiors ready to execute the same program as inferior
2448 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2449 number of the current inferior. This is a convenient command when you
2450 want to run another instance of the inferior you are debugging.
2453 (@value{GDBP}) info inferiors
2454 Num Description Executable
2455 * 1 process 29964 helloworld
2456 (@value{GDBP}) clone-inferior
2459 (@value{GDBP}) info inferiors
2460 Num Description Executable
2462 * 1 process 29964 helloworld
2465 You can now simply switch focus to inferior 2 and run it.
2467 @kindex remove-inferior
2468 @item remove-inferior @var{infno}
2469 Removes the inferior @var{infno}. It is not possible to remove an
2470 inferior that is running with this command. For those, use the
2471 @code{kill} or @code{detach} command first.
2475 To quit debugging one of the running inferiors that is not the current
2476 inferior, you can either detach from it by using the @w{@code{detach
2477 inferior}} command (allowing it to run independently), or kill it
2478 using the @w{@code{kill inferior}} command:
2481 @kindex detach inferior @var{infno}
2482 @item detach inferior @var{infno}
2483 Detach from the inferior identified by @value{GDBN} inferior number
2484 @var{infno}. Note that the inferior's entry still stays on the list
2485 of inferiors shown by @code{info inferiors}, but its Description will
2488 @kindex kill inferior @var{infno}
2489 @item kill inferior @var{infno}
2490 Kill the inferior identified by @value{GDBN} inferior number
2491 @var{infno}. Note that the inferior's entry still stays on the list
2492 of inferiors shown by @code{info inferiors}, but its Description will
2496 After the successful completion of a command such as @code{detach},
2497 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2498 a normal process exit, the inferior is still valid and listed with
2499 @code{info inferiors}, ready to be restarted.
2502 To be notified when inferiors are started or exit under @value{GDBN}'s
2503 control use @w{@code{set print inferior-events}}:
2506 @kindex set print inferior-events
2507 @cindex print messages on inferior start and exit
2508 @item set print inferior-events
2509 @itemx set print inferior-events on
2510 @itemx set print inferior-events off
2511 The @code{set print inferior-events} command allows you to enable or
2512 disable printing of messages when @value{GDBN} notices that new
2513 inferiors have started or that inferiors have exited or have been
2514 detached. By default, these messages will not be printed.
2516 @kindex show print inferior-events
2517 @item show print inferior-events
2518 Show whether messages will be printed when @value{GDBN} detects that
2519 inferiors have started, exited or have been detached.
2522 Many commands will work the same with multiple programs as with a
2523 single program: e.g., @code{print myglobal} will simply display the
2524 value of @code{myglobal} in the current inferior.
2527 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2528 get more info about the relationship of inferiors, programs, address
2529 spaces in a debug session. You can do that with the @w{@code{maint
2530 info program-spaces}} command.
2533 @kindex maint info program-spaces
2534 @item maint info program-spaces
2535 Print a list of all program spaces currently being managed by
2538 @value{GDBN} displays for each program space (in this order):
2542 the program space number assigned by @value{GDBN}
2545 the name of the executable loaded into the program space, with e.g.,
2546 the @code{file} command.
2551 An asterisk @samp{*} preceding the @value{GDBN} program space number
2552 indicates the current program space.
2554 In addition, below each program space line, @value{GDBN} prints extra
2555 information that isn't suitable to display in tabular form. For
2556 example, the list of inferiors bound to the program space.
2559 (@value{GDBP}) maint info program-spaces
2562 Bound inferiors: ID 1 (process 21561)
2566 Here we can see that no inferior is running the program @code{hello},
2567 while @code{process 21561} is running the program @code{goodbye}. On
2568 some targets, it is possible that multiple inferiors are bound to the
2569 same program space. The most common example is that of debugging both
2570 the parent and child processes of a @code{vfork} call. For example,
2573 (@value{GDBP}) maint info program-spaces
2576 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2579 Here, both inferior 2 and inferior 1 are running in the same program
2580 space as a result of inferior 1 having executed a @code{vfork} call.
2584 @section Debugging Programs with Multiple Threads
2586 @cindex threads of execution
2587 @cindex multiple threads
2588 @cindex switching threads
2589 In some operating systems, such as HP-UX and Solaris, a single program
2590 may have more than one @dfn{thread} of execution. The precise semantics
2591 of threads differ from one operating system to another, but in general
2592 the threads of a single program are akin to multiple processes---except
2593 that they share one address space (that is, they can all examine and
2594 modify the same variables). On the other hand, each thread has its own
2595 registers and execution stack, and perhaps private memory.
2597 @value{GDBN} provides these facilities for debugging multi-thread
2601 @item automatic notification of new threads
2602 @item @samp{thread @var{threadno}}, a command to switch among threads
2603 @item @samp{info threads}, a command to inquire about existing threads
2604 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2605 a command to apply a command to a list of threads
2606 @item thread-specific breakpoints
2607 @item @samp{set print thread-events}, which controls printing of
2608 messages on thread start and exit.
2609 @item @samp{set libthread-db-search-path @var{path}}, which lets
2610 the user specify which @code{libthread_db} to use if the default choice
2611 isn't compatible with the program.
2615 @emph{Warning:} These facilities are not yet available on every
2616 @value{GDBN} configuration where the operating system supports threads.
2617 If your @value{GDBN} does not support threads, these commands have no
2618 effect. For example, a system without thread support shows no output
2619 from @samp{info threads}, and always rejects the @code{thread} command,
2623 (@value{GDBP}) info threads
2624 (@value{GDBP}) thread 1
2625 Thread ID 1 not known. Use the "info threads" command to
2626 see the IDs of currently known threads.
2628 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2629 @c doesn't support threads"?
2632 @cindex focus of debugging
2633 @cindex current thread
2634 The @value{GDBN} thread debugging facility allows you to observe all
2635 threads while your program runs---but whenever @value{GDBN} takes
2636 control, one thread in particular is always the focus of debugging.
2637 This thread is called the @dfn{current thread}. Debugging commands show
2638 program information from the perspective of the current thread.
2640 @cindex @code{New} @var{systag} message
2641 @cindex thread identifier (system)
2642 @c FIXME-implementors!! It would be more helpful if the [New...] message
2643 @c included GDB's numeric thread handle, so you could just go to that
2644 @c thread without first checking `info threads'.
2645 Whenever @value{GDBN} detects a new thread in your program, it displays
2646 the target system's identification for the thread with a message in the
2647 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2648 whose form varies depending on the particular system. For example, on
2649 @sc{gnu}/Linux, you might see
2652 [New Thread 46912507313328 (LWP 25582)]
2656 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2657 the @var{systag} is simply something like @samp{process 368}, with no
2660 @c FIXME!! (1) Does the [New...] message appear even for the very first
2661 @c thread of a program, or does it only appear for the
2662 @c second---i.e.@: when it becomes obvious we have a multithread
2664 @c (2) *Is* there necessarily a first thread always? Or do some
2665 @c multithread systems permit starting a program with multiple
2666 @c threads ab initio?
2668 @cindex thread number
2669 @cindex thread identifier (GDB)
2670 For debugging purposes, @value{GDBN} associates its own thread
2671 number---always a single integer---with each thread in your program.
2674 @kindex info threads
2676 Display a summary of all threads currently in your
2677 program. @value{GDBN} displays for each thread (in this order):
2681 the thread number assigned by @value{GDBN}
2684 the target system's thread identifier (@var{systag})
2687 the current stack frame summary for that thread
2691 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2692 indicates the current thread.
2696 @c end table here to get a little more width for example
2699 (@value{GDBP}) info threads
2700 3 process 35 thread 27 0x34e5 in sigpause ()
2701 2 process 35 thread 23 0x34e5 in sigpause ()
2702 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2708 @cindex debugging multithreaded programs (on HP-UX)
2709 @cindex thread identifier (GDB), on HP-UX
2710 For debugging purposes, @value{GDBN} associates its own thread
2711 number---a small integer assigned in thread-creation order---with each
2712 thread in your program.
2714 @cindex @code{New} @var{systag} message, on HP-UX
2715 @cindex thread identifier (system), on HP-UX
2716 @c FIXME-implementors!! It would be more helpful if the [New...] message
2717 @c included GDB's numeric thread handle, so you could just go to that
2718 @c thread without first checking `info threads'.
2719 Whenever @value{GDBN} detects a new thread in your program, it displays
2720 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2721 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2722 whose form varies depending on the particular system. For example, on
2726 [New thread 2 (system thread 26594)]
2730 when @value{GDBN} notices a new thread.
2733 @kindex info threads (HP-UX)
2735 Display a summary of all threads currently in your
2736 program. @value{GDBN} displays for each thread (in this order):
2739 @item the thread number assigned by @value{GDBN}
2741 @item the target system's thread identifier (@var{systag})
2743 @item the current stack frame summary for that thread
2747 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2748 indicates the current thread.
2752 @c end table here to get a little more width for example
2755 (@value{GDBP}) info threads
2756 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2758 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2759 from /usr/lib/libc.2
2760 1 system thread 27905 0x7b003498 in _brk () \@*
2761 from /usr/lib/libc.2
2764 On Solaris, you can display more information about user threads with a
2765 Solaris-specific command:
2768 @item maint info sol-threads
2769 @kindex maint info sol-threads
2770 @cindex thread info (Solaris)
2771 Display info on Solaris user threads.
2775 @kindex thread @var{threadno}
2776 @item thread @var{threadno}
2777 Make thread number @var{threadno} the current thread. The command
2778 argument @var{threadno} is the internal @value{GDBN} thread number, as
2779 shown in the first field of the @samp{info threads} display.
2780 @value{GDBN} responds by displaying the system identifier of the thread
2781 you selected, and its current stack frame summary:
2784 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2785 (@value{GDBP}) thread 2
2786 [Switching to process 35 thread 23]
2787 0x34e5 in sigpause ()
2791 As with the @samp{[New @dots{}]} message, the form of the text after
2792 @samp{Switching to} depends on your system's conventions for identifying
2795 @vindex $_thread@r{, convenience variable}
2796 The debugger convenience variable @samp{$_thread} contains the number
2797 of the current thread. You may find this useful in writing breakpoint
2798 conditional expressions, command scripts, and so forth. See
2799 @xref{Convenience Vars,, Convenience Variables}, for general
2800 information on convenience variables.
2802 @kindex thread apply
2803 @cindex apply command to several threads
2804 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2805 The @code{thread apply} command allows you to apply the named
2806 @var{command} to one or more threads. Specify the numbers of the
2807 threads that you want affected with the command argument
2808 @var{threadno}. It can be a single thread number, one of the numbers
2809 shown in the first field of the @samp{info threads} display; or it
2810 could be a range of thread numbers, as in @code{2-4}. To apply a
2811 command to all threads, type @kbd{thread apply all @var{command}}.
2813 @kindex set print thread-events
2814 @cindex print messages on thread start and exit
2815 @item set print thread-events
2816 @itemx set print thread-events on
2817 @itemx set print thread-events off
2818 The @code{set print thread-events} command allows you to enable or
2819 disable printing of messages when @value{GDBN} notices that new threads have
2820 started or that threads have exited. By default, these messages will
2821 be printed if detection of these events is supported by the target.
2822 Note that these messages cannot be disabled on all targets.
2824 @kindex show print thread-events
2825 @item show print thread-events
2826 Show whether messages will be printed when @value{GDBN} detects that threads
2827 have started and exited.
2830 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2831 more information about how @value{GDBN} behaves when you stop and start
2832 programs with multiple threads.
2834 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2835 watchpoints in programs with multiple threads.
2838 @kindex set libthread-db-search-path
2839 @cindex search path for @code{libthread_db}
2840 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2841 If this variable is set, @var{path} is a colon-separated list of
2842 directories @value{GDBN} will use to search for @code{libthread_db}.
2843 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2846 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2847 @code{libthread_db} library to obtain information about threads in the
2848 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2849 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2850 with default system shared library directories, and finally the directory
2851 from which @code{libpthread} was loaded in the inferior process.
2853 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2854 @value{GDBN} attempts to initialize it with the current inferior process.
2855 If this initialization fails (which could happen because of a version
2856 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2857 will unload @code{libthread_db}, and continue with the next directory.
2858 If none of @code{libthread_db} libraries initialize successfully,
2859 @value{GDBN} will issue a warning and thread debugging will be disabled.
2861 Setting @code{libthread-db-search-path} is currently implemented
2862 only on some platforms.
2864 @kindex show libthread-db-search-path
2865 @item show libthread-db-search-path
2866 Display current libthread_db search path.
2868 @kindex set debug libthread-db
2869 @kindex show debug libthread-db
2870 @cindex debugging @code{libthread_db}
2871 @item set debug libthread-db
2872 @itemx show debug libthread-db
2873 Turns on or off display of @code{libthread_db}-related events.
2874 Use @code{1} to enable, @code{0} to disable.
2878 @section Debugging Forks
2880 @cindex fork, debugging programs which call
2881 @cindex multiple processes
2882 @cindex processes, multiple
2883 On most systems, @value{GDBN} has no special support for debugging
2884 programs which create additional processes using the @code{fork}
2885 function. When a program forks, @value{GDBN} will continue to debug the
2886 parent process and the child process will run unimpeded. If you have
2887 set a breakpoint in any code which the child then executes, the child
2888 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2889 will cause it to terminate.
2891 However, if you want to debug the child process there is a workaround
2892 which isn't too painful. Put a call to @code{sleep} in the code which
2893 the child process executes after the fork. It may be useful to sleep
2894 only if a certain environment variable is set, or a certain file exists,
2895 so that the delay need not occur when you don't want to run @value{GDBN}
2896 on the child. While the child is sleeping, use the @code{ps} program to
2897 get its process ID. Then tell @value{GDBN} (a new invocation of
2898 @value{GDBN} if you are also debugging the parent process) to attach to
2899 the child process (@pxref{Attach}). From that point on you can debug
2900 the child process just like any other process which you attached to.
2902 On some systems, @value{GDBN} provides support for debugging programs that
2903 create additional processes using the @code{fork} or @code{vfork} functions.
2904 Currently, the only platforms with this feature are HP-UX (11.x and later
2905 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2907 By default, when a program forks, @value{GDBN} will continue to debug
2908 the parent process and the child process will run unimpeded.
2910 If you want to follow the child process instead of the parent process,
2911 use the command @w{@code{set follow-fork-mode}}.
2914 @kindex set follow-fork-mode
2915 @item set follow-fork-mode @var{mode}
2916 Set the debugger response to a program call of @code{fork} or
2917 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2918 process. The @var{mode} argument can be:
2922 The original process is debugged after a fork. The child process runs
2923 unimpeded. This is the default.
2926 The new process is debugged after a fork. The parent process runs
2931 @kindex show follow-fork-mode
2932 @item show follow-fork-mode
2933 Display the current debugger response to a @code{fork} or @code{vfork} call.
2936 @cindex debugging multiple processes
2937 On Linux, if you want to debug both the parent and child processes, use the
2938 command @w{@code{set detach-on-fork}}.
2941 @kindex set detach-on-fork
2942 @item set detach-on-fork @var{mode}
2943 Tells gdb whether to detach one of the processes after a fork, or
2944 retain debugger control over them both.
2948 The child process (or parent process, depending on the value of
2949 @code{follow-fork-mode}) will be detached and allowed to run
2950 independently. This is the default.
2953 Both processes will be held under the control of @value{GDBN}.
2954 One process (child or parent, depending on the value of
2955 @code{follow-fork-mode}) is debugged as usual, while the other
2960 @kindex show detach-on-fork
2961 @item show detach-on-fork
2962 Show whether detach-on-fork mode is on/off.
2965 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2966 will retain control of all forked processes (including nested forks).
2967 You can list the forked processes under the control of @value{GDBN} by
2968 using the @w{@code{info inferiors}} command, and switch from one fork
2969 to another by using the @code{inferior} command (@pxref{Inferiors and
2970 Programs, ,Debugging Multiple Inferiors and Programs}).
2972 To quit debugging one of the forked processes, you can either detach
2973 from it by using the @w{@code{detach inferior}} command (allowing it
2974 to run independently), or kill it using the @w{@code{kill inferior}}
2975 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2978 If you ask to debug a child process and a @code{vfork} is followed by an
2979 @code{exec}, @value{GDBN} executes the new target up to the first
2980 breakpoint in the new target. If you have a breakpoint set on
2981 @code{main} in your original program, the breakpoint will also be set on
2982 the child process's @code{main}.
2984 On some systems, when a child process is spawned by @code{vfork}, you
2985 cannot debug the child or parent until an @code{exec} call completes.
2987 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2988 call executes, the new target restarts. To restart the parent
2989 process, use the @code{file} command with the parent executable name
2990 as its argument. By default, after an @code{exec} call executes,
2991 @value{GDBN} discards the symbols of the previous executable image.
2992 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2996 @kindex set follow-exec-mode
2997 @item set follow-exec-mode @var{mode}
2999 Set debugger response to a program call of @code{exec}. An
3000 @code{exec} call replaces the program image of a process.
3002 @code{follow-exec-mode} can be:
3006 @value{GDBN} creates a new inferior and rebinds the process to this
3007 new inferior. The program the process was running before the
3008 @code{exec} call can be restarted afterwards by restarting the
3014 (@value{GDBP}) info inferiors
3016 Id Description Executable
3019 process 12020 is executing new program: prog2
3020 Program exited normally.
3021 (@value{GDBP}) info inferiors
3022 Id Description Executable
3028 @value{GDBN} keeps the process bound to the same inferior. The new
3029 executable image replaces the previous executable loaded in the
3030 inferior. Restarting the inferior after the @code{exec} call, with
3031 e.g., the @code{run} command, restarts the executable the process was
3032 running after the @code{exec} call. This is the default mode.
3037 (@value{GDBP}) info inferiors
3038 Id Description Executable
3041 process 12020 is executing new program: prog2
3042 Program exited normally.
3043 (@value{GDBP}) info inferiors
3044 Id Description Executable
3051 You can use the @code{catch} command to make @value{GDBN} stop whenever
3052 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3053 Catchpoints, ,Setting Catchpoints}.
3055 @node Checkpoint/Restart
3056 @section Setting a @emph{Bookmark} to Return to Later
3061 @cindex snapshot of a process
3062 @cindex rewind program state
3064 On certain operating systems@footnote{Currently, only
3065 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3066 program's state, called a @dfn{checkpoint}, and come back to it
3069 Returning to a checkpoint effectively undoes everything that has
3070 happened in the program since the @code{checkpoint} was saved. This
3071 includes changes in memory, registers, and even (within some limits)
3072 system state. Effectively, it is like going back in time to the
3073 moment when the checkpoint was saved.
3075 Thus, if you're stepping thru a program and you think you're
3076 getting close to the point where things go wrong, you can save
3077 a checkpoint. Then, if you accidentally go too far and miss
3078 the critical statement, instead of having to restart your program
3079 from the beginning, you can just go back to the checkpoint and
3080 start again from there.
3082 This can be especially useful if it takes a lot of time or
3083 steps to reach the point where you think the bug occurs.
3085 To use the @code{checkpoint}/@code{restart} method of debugging:
3090 Save a snapshot of the debugged program's current execution state.
3091 The @code{checkpoint} command takes no arguments, but each checkpoint
3092 is assigned a small integer id, similar to a breakpoint id.
3094 @kindex info checkpoints
3095 @item info checkpoints
3096 List the checkpoints that have been saved in the current debugging
3097 session. For each checkpoint, the following information will be
3104 @item Source line, or label
3107 @kindex restart @var{checkpoint-id}
3108 @item restart @var{checkpoint-id}
3109 Restore the program state that was saved as checkpoint number
3110 @var{checkpoint-id}. All program variables, registers, stack frames
3111 etc.@: will be returned to the values that they had when the checkpoint
3112 was saved. In essence, gdb will ``wind back the clock'' to the point
3113 in time when the checkpoint was saved.
3115 Note that breakpoints, @value{GDBN} variables, command history etc.
3116 are not affected by restoring a checkpoint. In general, a checkpoint
3117 only restores things that reside in the program being debugged, not in
3120 @kindex delete checkpoint @var{checkpoint-id}
3121 @item delete checkpoint @var{checkpoint-id}
3122 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3126 Returning to a previously saved checkpoint will restore the user state
3127 of the program being debugged, plus a significant subset of the system
3128 (OS) state, including file pointers. It won't ``un-write'' data from
3129 a file, but it will rewind the file pointer to the previous location,
3130 so that the previously written data can be overwritten. For files
3131 opened in read mode, the pointer will also be restored so that the
3132 previously read data can be read again.
3134 Of course, characters that have been sent to a printer (or other
3135 external device) cannot be ``snatched back'', and characters received
3136 from eg.@: a serial device can be removed from internal program buffers,
3137 but they cannot be ``pushed back'' into the serial pipeline, ready to
3138 be received again. Similarly, the actual contents of files that have
3139 been changed cannot be restored (at this time).
3141 However, within those constraints, you actually can ``rewind'' your
3142 program to a previously saved point in time, and begin debugging it
3143 again --- and you can change the course of events so as to debug a
3144 different execution path this time.
3146 @cindex checkpoints and process id
3147 Finally, there is one bit of internal program state that will be
3148 different when you return to a checkpoint --- the program's process
3149 id. Each checkpoint will have a unique process id (or @var{pid}),
3150 and each will be different from the program's original @var{pid}.
3151 If your program has saved a local copy of its process id, this could
3152 potentially pose a problem.
3154 @subsection A Non-obvious Benefit of Using Checkpoints
3156 On some systems such as @sc{gnu}/Linux, address space randomization
3157 is performed on new processes for security reasons. This makes it
3158 difficult or impossible to set a breakpoint, or watchpoint, on an
3159 absolute address if you have to restart the program, since the
3160 absolute location of a symbol will change from one execution to the
3163 A checkpoint, however, is an @emph{identical} copy of a process.
3164 Therefore if you create a checkpoint at (eg.@:) the start of main,
3165 and simply return to that checkpoint instead of restarting the
3166 process, you can avoid the effects of address randomization and
3167 your symbols will all stay in the same place.
3170 @chapter Stopping and Continuing
3172 The principal purposes of using a debugger are so that you can stop your
3173 program before it terminates; or so that, if your program runs into
3174 trouble, you can investigate and find out why.
3176 Inside @value{GDBN}, your program may stop for any of several reasons,
3177 such as a signal, a breakpoint, or reaching a new line after a
3178 @value{GDBN} command such as @code{step}. You may then examine and
3179 change variables, set new breakpoints or remove old ones, and then
3180 continue execution. Usually, the messages shown by @value{GDBN} provide
3181 ample explanation of the status of your program---but you can also
3182 explicitly request this information at any time.
3185 @kindex info program
3187 Display information about the status of your program: whether it is
3188 running or not, what process it is, and why it stopped.
3192 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3193 * Continuing and Stepping:: Resuming execution
3195 * Thread Stops:: Stopping and starting multi-thread programs
3199 @section Breakpoints, Watchpoints, and Catchpoints
3202 A @dfn{breakpoint} makes your program stop whenever a certain point in
3203 the program is reached. For each breakpoint, you can add conditions to
3204 control in finer detail whether your program stops. You can set
3205 breakpoints with the @code{break} command and its variants (@pxref{Set
3206 Breaks, ,Setting Breakpoints}), to specify the place where your program
3207 should stop by line number, function name or exact address in the
3210 On some systems, you can set breakpoints in shared libraries before
3211 the executable is run. There is a minor limitation on HP-UX systems:
3212 you must wait until the executable is run in order to set breakpoints
3213 in shared library routines that are not called directly by the program
3214 (for example, routines that are arguments in a @code{pthread_create}
3218 @cindex data breakpoints
3219 @cindex memory tracing
3220 @cindex breakpoint on memory address
3221 @cindex breakpoint on variable modification
3222 A @dfn{watchpoint} is a special breakpoint that stops your program
3223 when the value of an expression changes. The expression may be a value
3224 of a variable, or it could involve values of one or more variables
3225 combined by operators, such as @samp{a + b}. This is sometimes called
3226 @dfn{data breakpoints}. You must use a different command to set
3227 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3228 from that, you can manage a watchpoint like any other breakpoint: you
3229 enable, disable, and delete both breakpoints and watchpoints using the
3232 You can arrange to have values from your program displayed automatically
3233 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3237 @cindex breakpoint on events
3238 A @dfn{catchpoint} is another special breakpoint that stops your program
3239 when a certain kind of event occurs, such as the throwing of a C@t{++}
3240 exception or the loading of a library. As with watchpoints, you use a
3241 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3242 Catchpoints}), but aside from that, you can manage a catchpoint like any
3243 other breakpoint. (To stop when your program receives a signal, use the
3244 @code{handle} command; see @ref{Signals, ,Signals}.)
3246 @cindex breakpoint numbers
3247 @cindex numbers for breakpoints
3248 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3249 catchpoint when you create it; these numbers are successive integers
3250 starting with one. In many of the commands for controlling various
3251 features of breakpoints you use the breakpoint number to say which
3252 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3253 @dfn{disabled}; if disabled, it has no effect on your program until you
3256 @cindex breakpoint ranges
3257 @cindex ranges of breakpoints
3258 Some @value{GDBN} commands accept a range of breakpoints on which to
3259 operate. A breakpoint range is either a single breakpoint number, like
3260 @samp{5}, or two such numbers, in increasing order, separated by a
3261 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3262 all breakpoints in that range are operated on.
3265 * Set Breaks:: Setting breakpoints
3266 * Set Watchpoints:: Setting watchpoints
3267 * Set Catchpoints:: Setting catchpoints
3268 * Delete Breaks:: Deleting breakpoints
3269 * Disabling:: Disabling breakpoints
3270 * Conditions:: Break conditions
3271 * Break Commands:: Breakpoint command lists
3272 * Save Breakpoints:: How to save breakpoints in a file
3273 * Error in Breakpoints:: ``Cannot insert breakpoints''
3274 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3278 @subsection Setting Breakpoints
3280 @c FIXME LMB what does GDB do if no code on line of breakpt?
3281 @c consider in particular declaration with/without initialization.
3283 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3286 @kindex b @r{(@code{break})}
3287 @vindex $bpnum@r{, convenience variable}
3288 @cindex latest breakpoint
3289 Breakpoints are set with the @code{break} command (abbreviated
3290 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3291 number of the breakpoint you've set most recently; see @ref{Convenience
3292 Vars,, Convenience Variables}, for a discussion of what you can do with
3293 convenience variables.
3296 @item break @var{location}
3297 Set a breakpoint at the given @var{location}, which can specify a
3298 function name, a line number, or an address of an instruction.
3299 (@xref{Specify Location}, for a list of all the possible ways to
3300 specify a @var{location}.) The breakpoint will stop your program just
3301 before it executes any of the code in the specified @var{location}.
3303 When using source languages that permit overloading of symbols, such as
3304 C@t{++}, a function name may refer to more than one possible place to break.
3305 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3308 It is also possible to insert a breakpoint that will stop the program
3309 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3310 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3313 When called without any arguments, @code{break} sets a breakpoint at
3314 the next instruction to be executed in the selected stack frame
3315 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3316 innermost, this makes your program stop as soon as control
3317 returns to that frame. This is similar to the effect of a
3318 @code{finish} command in the frame inside the selected frame---except
3319 that @code{finish} does not leave an active breakpoint. If you use
3320 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3321 the next time it reaches the current location; this may be useful
3324 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3325 least one instruction has been executed. If it did not do this, you
3326 would be unable to proceed past a breakpoint without first disabling the
3327 breakpoint. This rule applies whether or not the breakpoint already
3328 existed when your program stopped.
3330 @item break @dots{} if @var{cond}
3331 Set a breakpoint with condition @var{cond}; evaluate the expression
3332 @var{cond} each time the breakpoint is reached, and stop only if the
3333 value is nonzero---that is, if @var{cond} evaluates as true.
3334 @samp{@dots{}} stands for one of the possible arguments described
3335 above (or no argument) specifying where to break. @xref{Conditions,
3336 ,Break Conditions}, for more information on breakpoint conditions.
3339 @item tbreak @var{args}
3340 Set a breakpoint enabled only for one stop. @var{args} are the
3341 same as for the @code{break} command, and the breakpoint is set in the same
3342 way, but the breakpoint is automatically deleted after the first time your
3343 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3346 @cindex hardware breakpoints
3347 @item hbreak @var{args}
3348 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3349 @code{break} command and the breakpoint is set in the same way, but the
3350 breakpoint requires hardware support and some target hardware may not
3351 have this support. The main purpose of this is EPROM/ROM code
3352 debugging, so you can set a breakpoint at an instruction without
3353 changing the instruction. This can be used with the new trap-generation
3354 provided by SPARClite DSU and most x86-based targets. These targets
3355 will generate traps when a program accesses some data or instruction
3356 address that is assigned to the debug registers. However the hardware
3357 breakpoint registers can take a limited number of breakpoints. For
3358 example, on the DSU, only two data breakpoints can be set at a time, and
3359 @value{GDBN} will reject this command if more than two are used. Delete
3360 or disable unused hardware breakpoints before setting new ones
3361 (@pxref{Disabling, ,Disabling Breakpoints}).
3362 @xref{Conditions, ,Break Conditions}.
3363 For remote targets, you can restrict the number of hardware
3364 breakpoints @value{GDBN} will use, see @ref{set remote
3365 hardware-breakpoint-limit}.
3368 @item thbreak @var{args}
3369 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3370 are the same as for the @code{hbreak} command and the breakpoint is set in
3371 the same way. However, like the @code{tbreak} command,
3372 the breakpoint is automatically deleted after the
3373 first time your program stops there. Also, like the @code{hbreak}
3374 command, the breakpoint requires hardware support and some target hardware
3375 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3376 See also @ref{Conditions, ,Break Conditions}.
3379 @cindex regular expression
3380 @cindex breakpoints at functions matching a regexp
3381 @cindex set breakpoints in many functions
3382 @item rbreak @var{regex}
3383 Set breakpoints on all functions matching the regular expression
3384 @var{regex}. This command sets an unconditional breakpoint on all
3385 matches, printing a list of all breakpoints it set. Once these
3386 breakpoints are set, they are treated just like the breakpoints set with
3387 the @code{break} command. You can delete them, disable them, or make
3388 them conditional the same way as any other breakpoint.
3390 The syntax of the regular expression is the standard one used with tools
3391 like @file{grep}. Note that this is different from the syntax used by
3392 shells, so for instance @code{foo*} matches all functions that include
3393 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3394 @code{.*} leading and trailing the regular expression you supply, so to
3395 match only functions that begin with @code{foo}, use @code{^foo}.
3397 @cindex non-member C@t{++} functions, set breakpoint in
3398 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3399 breakpoints on overloaded functions that are not members of any special
3402 @cindex set breakpoints on all functions
3403 The @code{rbreak} command can be used to set breakpoints in
3404 @strong{all} the functions in a program, like this:
3407 (@value{GDBP}) rbreak .
3410 @item rbreak @var{file}:@var{regex}
3411 If @code{rbreak} is called with a filename qualification, it limits
3412 the search for functions matching the given regular expression to the
3413 specified @var{file}. This can be used, for example, to set breakpoints on
3414 every function in a given file:
3417 (@value{GDBP}) rbreak file.c:.
3420 The colon separating the filename qualifier from the regex may
3421 optionally be surrounded by spaces.
3423 @kindex info breakpoints
3424 @cindex @code{$_} and @code{info breakpoints}
3425 @item info breakpoints @r{[}@var{n}@r{]}
3426 @itemx info break @r{[}@var{n}@r{]}
3427 Print a table of all breakpoints, watchpoints, and catchpoints set and
3428 not deleted. Optional argument @var{n} means print information only
3429 about the specified breakpoint (or watchpoint or catchpoint). For
3430 each breakpoint, following columns are printed:
3433 @item Breakpoint Numbers
3435 Breakpoint, watchpoint, or catchpoint.
3437 Whether the breakpoint is marked to be disabled or deleted when hit.
3438 @item Enabled or Disabled
3439 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3440 that are not enabled.
3442 Where the breakpoint is in your program, as a memory address. For a
3443 pending breakpoint whose address is not yet known, this field will
3444 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3445 library that has the symbol or line referred by breakpoint is loaded.
3446 See below for details. A breakpoint with several locations will
3447 have @samp{<MULTIPLE>} in this field---see below for details.
3449 Where the breakpoint is in the source for your program, as a file and
3450 line number. For a pending breakpoint, the original string passed to
3451 the breakpoint command will be listed as it cannot be resolved until
3452 the appropriate shared library is loaded in the future.
3456 If a breakpoint is conditional, @code{info break} shows the condition on
3457 the line following the affected breakpoint; breakpoint commands, if any,
3458 are listed after that. A pending breakpoint is allowed to have a condition
3459 specified for it. The condition is not parsed for validity until a shared
3460 library is loaded that allows the pending breakpoint to resolve to a
3464 @code{info break} with a breakpoint
3465 number @var{n} as argument lists only that breakpoint. The
3466 convenience variable @code{$_} and the default examining-address for
3467 the @code{x} command are set to the address of the last breakpoint
3468 listed (@pxref{Memory, ,Examining Memory}).
3471 @code{info break} displays a count of the number of times the breakpoint
3472 has been hit. This is especially useful in conjunction with the
3473 @code{ignore} command. You can ignore a large number of breakpoint
3474 hits, look at the breakpoint info to see how many times the breakpoint
3475 was hit, and then run again, ignoring one less than that number. This
3476 will get you quickly to the last hit of that breakpoint.
3479 @value{GDBN} allows you to set any number of breakpoints at the same place in
3480 your program. There is nothing silly or meaningless about this. When
3481 the breakpoints are conditional, this is even useful
3482 (@pxref{Conditions, ,Break Conditions}).
3484 @cindex multiple locations, breakpoints
3485 @cindex breakpoints, multiple locations
3486 It is possible that a breakpoint corresponds to several locations
3487 in your program. Examples of this situation are:
3491 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3492 instances of the function body, used in different cases.
3495 For a C@t{++} template function, a given line in the function can
3496 correspond to any number of instantiations.
3499 For an inlined function, a given source line can correspond to
3500 several places where that function is inlined.
3503 In all those cases, @value{GDBN} will insert a breakpoint at all
3504 the relevant locations@footnote{
3505 As of this writing, multiple-location breakpoints work only if there's
3506 line number information for all the locations. This means that they
3507 will generally not work in system libraries, unless you have debug
3508 info with line numbers for them.}.
3510 A breakpoint with multiple locations is displayed in the breakpoint
3511 table using several rows---one header row, followed by one row for
3512 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3513 address column. The rows for individual locations contain the actual
3514 addresses for locations, and show the functions to which those
3515 locations belong. The number column for a location is of the form
3516 @var{breakpoint-number}.@var{location-number}.
3521 Num Type Disp Enb Address What
3522 1 breakpoint keep y <MULTIPLE>
3524 breakpoint already hit 1 time
3525 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3526 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3529 Each location can be individually enabled or disabled by passing
3530 @var{breakpoint-number}.@var{location-number} as argument to the
3531 @code{enable} and @code{disable} commands. Note that you cannot
3532 delete the individual locations from the list, you can only delete the
3533 entire list of locations that belong to their parent breakpoint (with
3534 the @kbd{delete @var{num}} command, where @var{num} is the number of
3535 the parent breakpoint, 1 in the above example). Disabling or enabling
3536 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3537 that belong to that breakpoint.
3539 @cindex pending breakpoints
3540 It's quite common to have a breakpoint inside a shared library.
3541 Shared libraries can be loaded and unloaded explicitly,
3542 and possibly repeatedly, as the program is executed. To support
3543 this use case, @value{GDBN} updates breakpoint locations whenever
3544 any shared library is loaded or unloaded. Typically, you would
3545 set a breakpoint in a shared library at the beginning of your
3546 debugging session, when the library is not loaded, and when the
3547 symbols from the library are not available. When you try to set
3548 breakpoint, @value{GDBN} will ask you if you want to set
3549 a so called @dfn{pending breakpoint}---breakpoint whose address
3550 is not yet resolved.
3552 After the program is run, whenever a new shared library is loaded,
3553 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3554 shared library contains the symbol or line referred to by some
3555 pending breakpoint, that breakpoint is resolved and becomes an
3556 ordinary breakpoint. When a library is unloaded, all breakpoints
3557 that refer to its symbols or source lines become pending again.
3559 This logic works for breakpoints with multiple locations, too. For
3560 example, if you have a breakpoint in a C@t{++} template function, and
3561 a newly loaded shared library has an instantiation of that template,
3562 a new location is added to the list of locations for the breakpoint.
3564 Except for having unresolved address, pending breakpoints do not
3565 differ from regular breakpoints. You can set conditions or commands,
3566 enable and disable them and perform other breakpoint operations.
3568 @value{GDBN} provides some additional commands for controlling what
3569 happens when the @samp{break} command cannot resolve breakpoint
3570 address specification to an address:
3572 @kindex set breakpoint pending
3573 @kindex show breakpoint pending
3575 @item set breakpoint pending auto
3576 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3577 location, it queries you whether a pending breakpoint should be created.
3579 @item set breakpoint pending on
3580 This indicates that an unrecognized breakpoint location should automatically
3581 result in a pending breakpoint being created.
3583 @item set breakpoint pending off
3584 This indicates that pending breakpoints are not to be created. Any
3585 unrecognized breakpoint location results in an error. This setting does
3586 not affect any pending breakpoints previously created.
3588 @item show breakpoint pending
3589 Show the current behavior setting for creating pending breakpoints.
3592 The settings above only affect the @code{break} command and its
3593 variants. Once breakpoint is set, it will be automatically updated
3594 as shared libraries are loaded and unloaded.
3596 @cindex automatic hardware breakpoints
3597 For some targets, @value{GDBN} can automatically decide if hardware or
3598 software breakpoints should be used, depending on whether the
3599 breakpoint address is read-only or read-write. This applies to
3600 breakpoints set with the @code{break} command as well as to internal
3601 breakpoints set by commands like @code{next} and @code{finish}. For
3602 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3605 You can control this automatic behaviour with the following commands::
3607 @kindex set breakpoint auto-hw
3608 @kindex show breakpoint auto-hw
3610 @item set breakpoint auto-hw on
3611 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3612 will try to use the target memory map to decide if software or hardware
3613 breakpoint must be used.
3615 @item set breakpoint auto-hw off
3616 This indicates @value{GDBN} should not automatically select breakpoint
3617 type. If the target provides a memory map, @value{GDBN} will warn when
3618 trying to set software breakpoint at a read-only address.
3621 @value{GDBN} normally implements breakpoints by replacing the program code
3622 at the breakpoint address with a special instruction, which, when
3623 executed, given control to the debugger. By default, the program
3624 code is so modified only when the program is resumed. As soon as
3625 the program stops, @value{GDBN} restores the original instructions. This
3626 behaviour guards against leaving breakpoints inserted in the
3627 target should gdb abrubptly disconnect. However, with slow remote
3628 targets, inserting and removing breakpoint can reduce the performance.
3629 This behavior can be controlled with the following commands::
3631 @kindex set breakpoint always-inserted
3632 @kindex show breakpoint always-inserted
3634 @item set breakpoint always-inserted off
3635 All breakpoints, including newly added by the user, are inserted in
3636 the target only when the target is resumed. All breakpoints are
3637 removed from the target when it stops.
3639 @item set breakpoint always-inserted on
3640 Causes all breakpoints to be inserted in the target at all times. If
3641 the user adds a new breakpoint, or changes an existing breakpoint, the
3642 breakpoints in the target are updated immediately. A breakpoint is
3643 removed from the target only when breakpoint itself is removed.
3645 @cindex non-stop mode, and @code{breakpoint always-inserted}
3646 @item set breakpoint always-inserted auto
3647 This is the default mode. If @value{GDBN} is controlling the inferior
3648 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3649 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3650 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3651 @code{breakpoint always-inserted} mode is off.
3654 @cindex negative breakpoint numbers
3655 @cindex internal @value{GDBN} breakpoints
3656 @value{GDBN} itself sometimes sets breakpoints in your program for
3657 special purposes, such as proper handling of @code{longjmp} (in C
3658 programs). These internal breakpoints are assigned negative numbers,
3659 starting with @code{-1}; @samp{info breakpoints} does not display them.
3660 You can see these breakpoints with the @value{GDBN} maintenance command
3661 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3664 @node Set Watchpoints
3665 @subsection Setting Watchpoints
3667 @cindex setting watchpoints
3668 You can use a watchpoint to stop execution whenever the value of an
3669 expression changes, without having to predict a particular place where
3670 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3671 The expression may be as simple as the value of a single variable, or
3672 as complex as many variables combined by operators. Examples include:
3676 A reference to the value of a single variable.
3679 An address cast to an appropriate data type. For example,
3680 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3681 address (assuming an @code{int} occupies 4 bytes).
3684 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3685 expression can use any operators valid in the program's native
3686 language (@pxref{Languages}).
3689 You can set a watchpoint on an expression even if the expression can
3690 not be evaluated yet. For instance, you can set a watchpoint on
3691 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3692 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3693 the expression produces a valid value. If the expression becomes
3694 valid in some other way than changing a variable (e.g.@: if the memory
3695 pointed to by @samp{*global_ptr} becomes readable as the result of a
3696 @code{malloc} call), @value{GDBN} may not stop until the next time
3697 the expression changes.
3699 @cindex software watchpoints
3700 @cindex hardware watchpoints
3701 Depending on your system, watchpoints may be implemented in software or
3702 hardware. @value{GDBN} does software watchpointing by single-stepping your
3703 program and testing the variable's value each time, which is hundreds of
3704 times slower than normal execution. (But this may still be worth it, to
3705 catch errors where you have no clue what part of your program is the
3708 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3709 x86-based targets, @value{GDBN} includes support for hardware
3710 watchpoints, which do not slow down the running of your program.
3714 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3715 Set a watchpoint for an expression. @value{GDBN} will break when the
3716 expression @var{expr} is written into by the program and its value
3717 changes. The simplest (and the most popular) use of this command is
3718 to watch the value of a single variable:
3721 (@value{GDBP}) watch foo
3724 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3725 clause, @value{GDBN} breaks only when the thread identified by
3726 @var{threadnum} changes the value of @var{expr}. If any other threads
3727 change the value of @var{expr}, @value{GDBN} will not break. Note
3728 that watchpoints restricted to a single thread in this way only work
3729 with Hardware Watchpoints.
3731 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3732 (see below). The @code{-location} argument tells @value{GDBN} to
3733 instead watch the memory referred to by @var{expr}. In this case,
3734 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3735 and watch the memory at that address. The type of the result is used
3736 to determine the size of the watched memory. If the expression's
3737 result does not have an address, then @value{GDBN} will print an
3741 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3742 Set a watchpoint that will break when the value of @var{expr} is read
3746 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3747 Set a watchpoint that will break when @var{expr} is either read from
3748 or written into by the program.
3750 @kindex info watchpoints @r{[}@var{n}@r{]}
3751 @item info watchpoints
3752 This command prints a list of watchpoints, using the same format as
3753 @code{info break} (@pxref{Set Breaks}).
3756 If you watch for a change in a numerically entered address you need to
3757 dereference it, as the address itself is just a constant number which will
3758 never change. @value{GDBN} refuses to create a watchpoint that watches
3759 a never-changing value:
3762 (@value{GDBP}) watch 0x600850
3763 Cannot watch constant value 0x600850.
3764 (@value{GDBP}) watch *(int *) 0x600850
3765 Watchpoint 1: *(int *) 6293584
3768 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3769 watchpoints execute very quickly, and the debugger reports a change in
3770 value at the exact instruction where the change occurs. If @value{GDBN}
3771 cannot set a hardware watchpoint, it sets a software watchpoint, which
3772 executes more slowly and reports the change in value at the next
3773 @emph{statement}, not the instruction, after the change occurs.
3775 @cindex use only software watchpoints
3776 You can force @value{GDBN} to use only software watchpoints with the
3777 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3778 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3779 the underlying system supports them. (Note that hardware-assisted
3780 watchpoints that were set @emph{before} setting
3781 @code{can-use-hw-watchpoints} to zero will still use the hardware
3782 mechanism of watching expression values.)
3785 @item set can-use-hw-watchpoints
3786 @kindex set can-use-hw-watchpoints
3787 Set whether or not to use hardware watchpoints.
3789 @item show can-use-hw-watchpoints
3790 @kindex show can-use-hw-watchpoints
3791 Show the current mode of using hardware watchpoints.
3794 For remote targets, you can restrict the number of hardware
3795 watchpoints @value{GDBN} will use, see @ref{set remote
3796 hardware-breakpoint-limit}.
3798 When you issue the @code{watch} command, @value{GDBN} reports
3801 Hardware watchpoint @var{num}: @var{expr}
3805 if it was able to set a hardware watchpoint.
3807 Currently, the @code{awatch} and @code{rwatch} commands can only set
3808 hardware watchpoints, because accesses to data that don't change the
3809 value of the watched expression cannot be detected without examining
3810 every instruction as it is being executed, and @value{GDBN} does not do
3811 that currently. If @value{GDBN} finds that it is unable to set a
3812 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3813 will print a message like this:
3816 Expression cannot be implemented with read/access watchpoint.
3819 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3820 data type of the watched expression is wider than what a hardware
3821 watchpoint on the target machine can handle. For example, some systems
3822 can only watch regions that are up to 4 bytes wide; on such systems you
3823 cannot set hardware watchpoints for an expression that yields a
3824 double-precision floating-point number (which is typically 8 bytes
3825 wide). As a work-around, it might be possible to break the large region
3826 into a series of smaller ones and watch them with separate watchpoints.
3828 If you set too many hardware watchpoints, @value{GDBN} might be unable
3829 to insert all of them when you resume the execution of your program.
3830 Since the precise number of active watchpoints is unknown until such
3831 time as the program is about to be resumed, @value{GDBN} might not be
3832 able to warn you about this when you set the watchpoints, and the
3833 warning will be printed only when the program is resumed:
3836 Hardware watchpoint @var{num}: Could not insert watchpoint
3840 If this happens, delete or disable some of the watchpoints.
3842 Watching complex expressions that reference many variables can also
3843 exhaust the resources available for hardware-assisted watchpoints.
3844 That's because @value{GDBN} needs to watch every variable in the
3845 expression with separately allocated resources.
3847 If you call a function interactively using @code{print} or @code{call},
3848 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3849 kind of breakpoint or the call completes.
3851 @value{GDBN} automatically deletes watchpoints that watch local
3852 (automatic) variables, or expressions that involve such variables, when
3853 they go out of scope, that is, when the execution leaves the block in
3854 which these variables were defined. In particular, when the program
3855 being debugged terminates, @emph{all} local variables go out of scope,
3856 and so only watchpoints that watch global variables remain set. If you
3857 rerun the program, you will need to set all such watchpoints again. One
3858 way of doing that would be to set a code breakpoint at the entry to the
3859 @code{main} function and when it breaks, set all the watchpoints.
3861 @cindex watchpoints and threads
3862 @cindex threads and watchpoints
3863 In multi-threaded programs, watchpoints will detect changes to the
3864 watched expression from every thread.
3867 @emph{Warning:} In multi-threaded programs, software watchpoints
3868 have only limited usefulness. If @value{GDBN} creates a software
3869 watchpoint, it can only watch the value of an expression @emph{in a
3870 single thread}. If you are confident that the expression can only
3871 change due to the current thread's activity (and if you are also
3872 confident that no other thread can become current), then you can use
3873 software watchpoints as usual. However, @value{GDBN} may not notice
3874 when a non-current thread's activity changes the expression. (Hardware
3875 watchpoints, in contrast, watch an expression in all threads.)
3878 @xref{set remote hardware-watchpoint-limit}.
3880 @node Set Catchpoints
3881 @subsection Setting Catchpoints
3882 @cindex catchpoints, setting
3883 @cindex exception handlers
3884 @cindex event handling
3886 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3887 kinds of program events, such as C@t{++} exceptions or the loading of a
3888 shared library. Use the @code{catch} command to set a catchpoint.
3892 @item catch @var{event}
3893 Stop when @var{event} occurs. @var{event} can be any of the following:
3896 @cindex stop on C@t{++} exceptions
3897 The throwing of a C@t{++} exception.
3900 The catching of a C@t{++} exception.
3903 @cindex Ada exception catching
3904 @cindex catch Ada exceptions
3905 An Ada exception being raised. If an exception name is specified
3906 at the end of the command (eg @code{catch exception Program_Error}),
3907 the debugger will stop only when this specific exception is raised.
3908 Otherwise, the debugger stops execution when any Ada exception is raised.
3910 When inserting an exception catchpoint on a user-defined exception whose
3911 name is identical to one of the exceptions defined by the language, the
3912 fully qualified name must be used as the exception name. Otherwise,
3913 @value{GDBN} will assume that it should stop on the pre-defined exception
3914 rather than the user-defined one. For instance, assuming an exception
3915 called @code{Constraint_Error} is defined in package @code{Pck}, then
3916 the command to use to catch such exceptions is @kbd{catch exception
3917 Pck.Constraint_Error}.
3919 @item exception unhandled
3920 An exception that was raised but is not handled by the program.
3923 A failed Ada assertion.
3926 @cindex break on fork/exec
3927 A call to @code{exec}. This is currently only available for HP-UX
3931 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3932 @cindex break on a system call.
3933 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3934 syscall is a mechanism for application programs to request a service
3935 from the operating system (OS) or one of the OS system services.
3936 @value{GDBN} can catch some or all of the syscalls issued by the
3937 debuggee, and show the related information for each syscall. If no
3938 argument is specified, calls to and returns from all system calls
3941 @var{name} can be any system call name that is valid for the
3942 underlying OS. Just what syscalls are valid depends on the OS. On
3943 GNU and Unix systems, you can find the full list of valid syscall
3944 names on @file{/usr/include/asm/unistd.h}.
3946 @c For MS-Windows, the syscall names and the corresponding numbers
3947 @c can be found, e.g., on this URL:
3948 @c http://www.metasploit.com/users/opcode/syscalls.html
3949 @c but we don't support Windows syscalls yet.
3951 Normally, @value{GDBN} knows in advance which syscalls are valid for
3952 each OS, so you can use the @value{GDBN} command-line completion
3953 facilities (@pxref{Completion,, command completion}) to list the
3956 You may also specify the system call numerically. A syscall's
3957 number is the value passed to the OS's syscall dispatcher to
3958 identify the requested service. When you specify the syscall by its
3959 name, @value{GDBN} uses its database of syscalls to convert the name
3960 into the corresponding numeric code, but using the number directly
3961 may be useful if @value{GDBN}'s database does not have the complete
3962 list of syscalls on your system (e.g., because @value{GDBN} lags
3963 behind the OS upgrades).
3965 The example below illustrates how this command works if you don't provide
3969 (@value{GDBP}) catch syscall
3970 Catchpoint 1 (syscall)
3972 Starting program: /tmp/catch-syscall
3974 Catchpoint 1 (call to syscall 'close'), \
3975 0xffffe424 in __kernel_vsyscall ()
3979 Catchpoint 1 (returned from syscall 'close'), \
3980 0xffffe424 in __kernel_vsyscall ()
3984 Here is an example of catching a system call by name:
3987 (@value{GDBP}) catch syscall chroot
3988 Catchpoint 1 (syscall 'chroot' [61])
3990 Starting program: /tmp/catch-syscall
3992 Catchpoint 1 (call to syscall 'chroot'), \
3993 0xffffe424 in __kernel_vsyscall ()
3997 Catchpoint 1 (returned from syscall 'chroot'), \
3998 0xffffe424 in __kernel_vsyscall ()
4002 An example of specifying a system call numerically. In the case
4003 below, the syscall number has a corresponding entry in the XML
4004 file, so @value{GDBN} finds its name and prints it:
4007 (@value{GDBP}) catch syscall 252
4008 Catchpoint 1 (syscall(s) 'exit_group')
4010 Starting program: /tmp/catch-syscall
4012 Catchpoint 1 (call to syscall 'exit_group'), \
4013 0xffffe424 in __kernel_vsyscall ()
4017 Program exited normally.
4021 However, there can be situations when there is no corresponding name
4022 in XML file for that syscall number. In this case, @value{GDBN} prints
4023 a warning message saying that it was not able to find the syscall name,
4024 but the catchpoint will be set anyway. See the example below:
4027 (@value{GDBP}) catch syscall 764
4028 warning: The number '764' does not represent a known syscall.
4029 Catchpoint 2 (syscall 764)
4033 If you configure @value{GDBN} using the @samp{--without-expat} option,
4034 it will not be able to display syscall names. Also, if your
4035 architecture does not have an XML file describing its system calls,
4036 you will not be able to see the syscall names. It is important to
4037 notice that these two features are used for accessing the syscall
4038 name database. In either case, you will see a warning like this:
4041 (@value{GDBP}) catch syscall
4042 warning: Could not open "syscalls/i386-linux.xml"
4043 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4044 GDB will not be able to display syscall names.
4045 Catchpoint 1 (syscall)
4049 Of course, the file name will change depending on your architecture and system.
4051 Still using the example above, you can also try to catch a syscall by its
4052 number. In this case, you would see something like:
4055 (@value{GDBP}) catch syscall 252
4056 Catchpoint 1 (syscall(s) 252)
4059 Again, in this case @value{GDBN} would not be able to display syscall's names.
4062 A call to @code{fork}. This is currently only available for HP-UX
4066 A call to @code{vfork}. This is currently only available for HP-UX
4071 @item tcatch @var{event}
4072 Set a catchpoint that is enabled only for one stop. The catchpoint is
4073 automatically deleted after the first time the event is caught.
4077 Use the @code{info break} command to list the current catchpoints.
4079 There are currently some limitations to C@t{++} exception handling
4080 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4084 If you call a function interactively, @value{GDBN} normally returns
4085 control to you when the function has finished executing. If the call
4086 raises an exception, however, the call may bypass the mechanism that
4087 returns control to you and cause your program either to abort or to
4088 simply continue running until it hits a breakpoint, catches a signal
4089 that @value{GDBN} is listening for, or exits. This is the case even if
4090 you set a catchpoint for the exception; catchpoints on exceptions are
4091 disabled within interactive calls.
4094 You cannot raise an exception interactively.
4097 You cannot install an exception handler interactively.
4100 @cindex raise exceptions
4101 Sometimes @code{catch} is not the best way to debug exception handling:
4102 if you need to know exactly where an exception is raised, it is better to
4103 stop @emph{before} the exception handler is called, since that way you
4104 can see the stack before any unwinding takes place. If you set a
4105 breakpoint in an exception handler instead, it may not be easy to find
4106 out where the exception was raised.
4108 To stop just before an exception handler is called, you need some
4109 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4110 raised by calling a library function named @code{__raise_exception}
4111 which has the following ANSI C interface:
4114 /* @var{addr} is where the exception identifier is stored.
4115 @var{id} is the exception identifier. */
4116 void __raise_exception (void **addr, void *id);
4120 To make the debugger catch all exceptions before any stack
4121 unwinding takes place, set a breakpoint on @code{__raise_exception}
4122 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4124 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4125 that depends on the value of @var{id}, you can stop your program when
4126 a specific exception is raised. You can use multiple conditional
4127 breakpoints to stop your program when any of a number of exceptions are
4132 @subsection Deleting Breakpoints
4134 @cindex clearing breakpoints, watchpoints, catchpoints
4135 @cindex deleting breakpoints, watchpoints, catchpoints
4136 It is often necessary to eliminate a breakpoint, watchpoint, or
4137 catchpoint once it has done its job and you no longer want your program
4138 to stop there. This is called @dfn{deleting} the breakpoint. A
4139 breakpoint that has been deleted no longer exists; it is forgotten.
4141 With the @code{clear} command you can delete breakpoints according to
4142 where they are in your program. With the @code{delete} command you can
4143 delete individual breakpoints, watchpoints, or catchpoints by specifying
4144 their breakpoint numbers.
4146 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4147 automatically ignores breakpoints on the first instruction to be executed
4148 when you continue execution without changing the execution address.
4153 Delete any breakpoints at the next instruction to be executed in the
4154 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4155 the innermost frame is selected, this is a good way to delete a
4156 breakpoint where your program just stopped.
4158 @item clear @var{location}
4159 Delete any breakpoints set at the specified @var{location}.
4160 @xref{Specify Location}, for the various forms of @var{location}; the
4161 most useful ones are listed below:
4164 @item clear @var{function}
4165 @itemx clear @var{filename}:@var{function}
4166 Delete any breakpoints set at entry to the named @var{function}.
4168 @item clear @var{linenum}
4169 @itemx clear @var{filename}:@var{linenum}
4170 Delete any breakpoints set at or within the code of the specified
4171 @var{linenum} of the specified @var{filename}.
4174 @cindex delete breakpoints
4176 @kindex d @r{(@code{delete})}
4177 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4178 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4179 ranges specified as arguments. If no argument is specified, delete all
4180 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4181 confirm off}). You can abbreviate this command as @code{d}.
4185 @subsection Disabling Breakpoints
4187 @cindex enable/disable a breakpoint
4188 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4189 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4190 it had been deleted, but remembers the information on the breakpoint so
4191 that you can @dfn{enable} it again later.
4193 You disable and enable breakpoints, watchpoints, and catchpoints with
4194 the @code{enable} and @code{disable} commands, optionally specifying
4195 one or more breakpoint numbers as arguments. Use @code{info break} to
4196 print a list of all breakpoints, watchpoints, and catchpoints if you
4197 do not know which numbers to use.
4199 Disabling and enabling a breakpoint that has multiple locations
4200 affects all of its locations.
4202 A breakpoint, watchpoint, or catchpoint can have any of four different
4203 states of enablement:
4207 Enabled. The breakpoint stops your program. A breakpoint set
4208 with the @code{break} command starts out in this state.
4210 Disabled. The breakpoint has no effect on your program.
4212 Enabled once. The breakpoint stops your program, but then becomes
4215 Enabled for deletion. The breakpoint stops your program, but
4216 immediately after it does so it is deleted permanently. A breakpoint
4217 set with the @code{tbreak} command starts out in this state.
4220 You can use the following commands to enable or disable breakpoints,
4221 watchpoints, and catchpoints:
4225 @kindex dis @r{(@code{disable})}
4226 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4227 Disable the specified breakpoints---or all breakpoints, if none are
4228 listed. A disabled breakpoint has no effect but is not forgotten. All
4229 options such as ignore-counts, conditions and commands are remembered in
4230 case the breakpoint is enabled again later. You may abbreviate
4231 @code{disable} as @code{dis}.
4234 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4235 Enable the specified breakpoints (or all defined breakpoints). They
4236 become effective once again in stopping your program.
4238 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4239 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4240 of these breakpoints immediately after stopping your program.
4242 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4243 Enable the specified breakpoints to work once, then die. @value{GDBN}
4244 deletes any of these breakpoints as soon as your program stops there.
4245 Breakpoints set by the @code{tbreak} command start out in this state.
4248 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4249 @c confusing: tbreak is also initially enabled.
4250 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4251 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4252 subsequently, they become disabled or enabled only when you use one of
4253 the commands above. (The command @code{until} can set and delete a
4254 breakpoint of its own, but it does not change the state of your other
4255 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4259 @subsection Break Conditions
4260 @cindex conditional breakpoints
4261 @cindex breakpoint conditions
4263 @c FIXME what is scope of break condition expr? Context where wanted?
4264 @c in particular for a watchpoint?
4265 The simplest sort of breakpoint breaks every time your program reaches a
4266 specified place. You can also specify a @dfn{condition} for a
4267 breakpoint. A condition is just a Boolean expression in your
4268 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4269 a condition evaluates the expression each time your program reaches it,
4270 and your program stops only if the condition is @emph{true}.
4272 This is the converse of using assertions for program validation; in that
4273 situation, you want to stop when the assertion is violated---that is,
4274 when the condition is false. In C, if you want to test an assertion expressed
4275 by the condition @var{assert}, you should set the condition
4276 @samp{! @var{assert}} on the appropriate breakpoint.
4278 Conditions are also accepted for watchpoints; you may not need them,
4279 since a watchpoint is inspecting the value of an expression anyhow---but
4280 it might be simpler, say, to just set a watchpoint on a variable name,
4281 and specify a condition that tests whether the new value is an interesting
4284 Break conditions can have side effects, and may even call functions in
4285 your program. This can be useful, for example, to activate functions
4286 that log program progress, or to use your own print functions to
4287 format special data structures. The effects are completely predictable
4288 unless there is another enabled breakpoint at the same address. (In
4289 that case, @value{GDBN} might see the other breakpoint first and stop your
4290 program without checking the condition of this one.) Note that
4291 breakpoint commands are usually more convenient and flexible than break
4293 purpose of performing side effects when a breakpoint is reached
4294 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4296 Break conditions can be specified when a breakpoint is set, by using
4297 @samp{if} in the arguments to the @code{break} command. @xref{Set
4298 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4299 with the @code{condition} command.
4301 You can also use the @code{if} keyword with the @code{watch} command.
4302 The @code{catch} command does not recognize the @code{if} keyword;
4303 @code{condition} is the only way to impose a further condition on a
4308 @item condition @var{bnum} @var{expression}
4309 Specify @var{expression} as the break condition for breakpoint,
4310 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4311 breakpoint @var{bnum} stops your program only if the value of
4312 @var{expression} is true (nonzero, in C). When you use
4313 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4314 syntactic correctness, and to determine whether symbols in it have
4315 referents in the context of your breakpoint. If @var{expression} uses
4316 symbols not referenced in the context of the breakpoint, @value{GDBN}
4317 prints an error message:
4320 No symbol "foo" in current context.
4325 not actually evaluate @var{expression} at the time the @code{condition}
4326 command (or a command that sets a breakpoint with a condition, like
4327 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4329 @item condition @var{bnum}
4330 Remove the condition from breakpoint number @var{bnum}. It becomes
4331 an ordinary unconditional breakpoint.
4334 @cindex ignore count (of breakpoint)
4335 A special case of a breakpoint condition is to stop only when the
4336 breakpoint has been reached a certain number of times. This is so
4337 useful that there is a special way to do it, using the @dfn{ignore
4338 count} of the breakpoint. Every breakpoint has an ignore count, which
4339 is an integer. Most of the time, the ignore count is zero, and
4340 therefore has no effect. But if your program reaches a breakpoint whose
4341 ignore count is positive, then instead of stopping, it just decrements
4342 the ignore count by one and continues. As a result, if the ignore count
4343 value is @var{n}, the breakpoint does not stop the next @var{n} times
4344 your program reaches it.
4348 @item ignore @var{bnum} @var{count}
4349 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4350 The next @var{count} times the breakpoint is reached, your program's
4351 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4354 To make the breakpoint stop the next time it is reached, specify
4357 When you use @code{continue} to resume execution of your program from a
4358 breakpoint, you can specify an ignore count directly as an argument to
4359 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4360 Stepping,,Continuing and Stepping}.
4362 If a breakpoint has a positive ignore count and a condition, the
4363 condition is not checked. Once the ignore count reaches zero,
4364 @value{GDBN} resumes checking the condition.
4366 You could achieve the effect of the ignore count with a condition such
4367 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4368 is decremented each time. @xref{Convenience Vars, ,Convenience
4372 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4375 @node Break Commands
4376 @subsection Breakpoint Command Lists
4378 @cindex breakpoint commands
4379 You can give any breakpoint (or watchpoint or catchpoint) a series of
4380 commands to execute when your program stops due to that breakpoint. For
4381 example, you might want to print the values of certain expressions, or
4382 enable other breakpoints.
4386 @kindex end@r{ (breakpoint commands)}
4387 @item commands @r{[}@var{range}@dots{}@r{]}
4388 @itemx @dots{} @var{command-list} @dots{}
4390 Specify a list of commands for the given breakpoints. The commands
4391 themselves appear on the following lines. Type a line containing just
4392 @code{end} to terminate the commands.
4394 To remove all commands from a breakpoint, type @code{commands} and
4395 follow it immediately with @code{end}; that is, give no commands.
4397 With no argument, @code{commands} refers to the last breakpoint,
4398 watchpoint, or catchpoint set (not to the breakpoint most recently
4399 encountered). If the most recent breakpoints were set with a single
4400 command, then the @code{commands} will apply to all the breakpoints
4401 set by that command. This applies to breakpoints set by
4402 @code{rbreak}, and also applies when a single @code{break} command
4403 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4407 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4408 disabled within a @var{command-list}.
4410 You can use breakpoint commands to start your program up again. Simply
4411 use the @code{continue} command, or @code{step}, or any other command
4412 that resumes execution.
4414 Any other commands in the command list, after a command that resumes
4415 execution, are ignored. This is because any time you resume execution
4416 (even with a simple @code{next} or @code{step}), you may encounter
4417 another breakpoint---which could have its own command list, leading to
4418 ambiguities about which list to execute.
4421 If the first command you specify in a command list is @code{silent}, the
4422 usual message about stopping at a breakpoint is not printed. This may
4423 be desirable for breakpoints that are to print a specific message and
4424 then continue. If none of the remaining commands print anything, you
4425 see no sign that the breakpoint was reached. @code{silent} is
4426 meaningful only at the beginning of a breakpoint command list.
4428 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4429 print precisely controlled output, and are often useful in silent
4430 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4432 For example, here is how you could use breakpoint commands to print the
4433 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4439 printf "x is %d\n",x
4444 One application for breakpoint commands is to compensate for one bug so
4445 you can test for another. Put a breakpoint just after the erroneous line
4446 of code, give it a condition to detect the case in which something
4447 erroneous has been done, and give it commands to assign correct values
4448 to any variables that need them. End with the @code{continue} command
4449 so that your program does not stop, and start with the @code{silent}
4450 command so that no output is produced. Here is an example:
4461 @node Save Breakpoints
4462 @subsection How to save breakpoints to a file
4464 To save breakpoint definitions to a file use the @w{@code{save
4465 breakpoints}} command.
4468 @kindex save breakpoints
4469 @cindex save breakpoints to a file for future sessions
4470 @item save breakpoints [@var{filename}]
4471 This command saves all current breakpoint definitions together with
4472 their commands and ignore counts, into a file @file{@var{filename}}
4473 suitable for use in a later debugging session. This includes all
4474 types of breakpoints (breakpoints, watchpoints, catchpoints,
4475 tracepoints). To read the saved breakpoint definitions, use the
4476 @code{source} command (@pxref{Command Files}). Note that watchpoints
4477 with expressions involving local variables may fail to be recreated
4478 because it may not be possible to access the context where the
4479 watchpoint is valid anymore. Because the saved breakpoint definitions
4480 are simply a sequence of @value{GDBN} commands that recreate the
4481 breakpoints, you can edit the file in your favorite editing program,
4482 and remove the breakpoint definitions you're not interested in, or
4483 that can no longer be recreated.
4486 @c @ifclear BARETARGET
4487 @node Error in Breakpoints
4488 @subsection ``Cannot insert breakpoints''
4490 If you request too many active hardware-assisted breakpoints and
4491 watchpoints, you will see this error message:
4493 @c FIXME: the precise wording of this message may change; the relevant
4494 @c source change is not committed yet (Sep 3, 1999).
4496 Stopped; cannot insert breakpoints.
4497 You may have requested too many hardware breakpoints and watchpoints.
4501 This message is printed when you attempt to resume the program, since
4502 only then @value{GDBN} knows exactly how many hardware breakpoints and
4503 watchpoints it needs to insert.
4505 When this message is printed, you need to disable or remove some of the
4506 hardware-assisted breakpoints and watchpoints, and then continue.
4508 @node Breakpoint-related Warnings
4509 @subsection ``Breakpoint address adjusted...''
4510 @cindex breakpoint address adjusted
4512 Some processor architectures place constraints on the addresses at
4513 which breakpoints may be placed. For architectures thus constrained,
4514 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4515 with the constraints dictated by the architecture.
4517 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4518 a VLIW architecture in which a number of RISC-like instructions may be
4519 bundled together for parallel execution. The FR-V architecture
4520 constrains the location of a breakpoint instruction within such a
4521 bundle to the instruction with the lowest address. @value{GDBN}
4522 honors this constraint by adjusting a breakpoint's address to the
4523 first in the bundle.
4525 It is not uncommon for optimized code to have bundles which contain
4526 instructions from different source statements, thus it may happen that
4527 a breakpoint's address will be adjusted from one source statement to
4528 another. Since this adjustment may significantly alter @value{GDBN}'s
4529 breakpoint related behavior from what the user expects, a warning is
4530 printed when the breakpoint is first set and also when the breakpoint
4533 A warning like the one below is printed when setting a breakpoint
4534 that's been subject to address adjustment:
4537 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4540 Such warnings are printed both for user settable and @value{GDBN}'s
4541 internal breakpoints. If you see one of these warnings, you should
4542 verify that a breakpoint set at the adjusted address will have the
4543 desired affect. If not, the breakpoint in question may be removed and
4544 other breakpoints may be set which will have the desired behavior.
4545 E.g., it may be sufficient to place the breakpoint at a later
4546 instruction. A conditional breakpoint may also be useful in some
4547 cases to prevent the breakpoint from triggering too often.
4549 @value{GDBN} will also issue a warning when stopping at one of these
4550 adjusted breakpoints:
4553 warning: Breakpoint 1 address previously adjusted from 0x00010414
4557 When this warning is encountered, it may be too late to take remedial
4558 action except in cases where the breakpoint is hit earlier or more
4559 frequently than expected.
4561 @node Continuing and Stepping
4562 @section Continuing and Stepping
4566 @cindex resuming execution
4567 @dfn{Continuing} means resuming program execution until your program
4568 completes normally. In contrast, @dfn{stepping} means executing just
4569 one more ``step'' of your program, where ``step'' may mean either one
4570 line of source code, or one machine instruction (depending on what
4571 particular command you use). Either when continuing or when stepping,
4572 your program may stop even sooner, due to a breakpoint or a signal. (If
4573 it stops due to a signal, you may want to use @code{handle}, or use
4574 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4578 @kindex c @r{(@code{continue})}
4579 @kindex fg @r{(resume foreground execution)}
4580 @item continue @r{[}@var{ignore-count}@r{]}
4581 @itemx c @r{[}@var{ignore-count}@r{]}
4582 @itemx fg @r{[}@var{ignore-count}@r{]}
4583 Resume program execution, at the address where your program last stopped;
4584 any breakpoints set at that address are bypassed. The optional argument
4585 @var{ignore-count} allows you to specify a further number of times to
4586 ignore a breakpoint at this location; its effect is like that of
4587 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4589 The argument @var{ignore-count} is meaningful only when your program
4590 stopped due to a breakpoint. At other times, the argument to
4591 @code{continue} is ignored.
4593 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4594 debugged program is deemed to be the foreground program) are provided
4595 purely for convenience, and have exactly the same behavior as
4599 To resume execution at a different place, you can use @code{return}
4600 (@pxref{Returning, ,Returning from a Function}) to go back to the
4601 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4602 Different Address}) to go to an arbitrary location in your program.
4604 A typical technique for using stepping is to set a breakpoint
4605 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4606 beginning of the function or the section of your program where a problem
4607 is believed to lie, run your program until it stops at that breakpoint,
4608 and then step through the suspect area, examining the variables that are
4609 interesting, until you see the problem happen.
4613 @kindex s @r{(@code{step})}
4615 Continue running your program until control reaches a different source
4616 line, then stop it and return control to @value{GDBN}. This command is
4617 abbreviated @code{s}.
4620 @c "without debugging information" is imprecise; actually "without line
4621 @c numbers in the debugging information". (gcc -g1 has debugging info but
4622 @c not line numbers). But it seems complex to try to make that
4623 @c distinction here.
4624 @emph{Warning:} If you use the @code{step} command while control is
4625 within a function that was compiled without debugging information,
4626 execution proceeds until control reaches a function that does have
4627 debugging information. Likewise, it will not step into a function which
4628 is compiled without debugging information. To step through functions
4629 without debugging information, use the @code{stepi} command, described
4633 The @code{step} command only stops at the first instruction of a source
4634 line. This prevents the multiple stops that could otherwise occur in
4635 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4636 to stop if a function that has debugging information is called within
4637 the line. In other words, @code{step} @emph{steps inside} any functions
4638 called within the line.
4640 Also, the @code{step} command only enters a function if there is line
4641 number information for the function. Otherwise it acts like the
4642 @code{next} command. This avoids problems when using @code{cc -gl}
4643 on MIPS machines. Previously, @code{step} entered subroutines if there
4644 was any debugging information about the routine.
4646 @item step @var{count}
4647 Continue running as in @code{step}, but do so @var{count} times. If a
4648 breakpoint is reached, or a signal not related to stepping occurs before
4649 @var{count} steps, stepping stops right away.
4652 @kindex n @r{(@code{next})}
4653 @item next @r{[}@var{count}@r{]}
4654 Continue to the next source line in the current (innermost) stack frame.
4655 This is similar to @code{step}, but function calls that appear within
4656 the line of code are executed without stopping. Execution stops when
4657 control reaches a different line of code at the original stack level
4658 that was executing when you gave the @code{next} command. This command
4659 is abbreviated @code{n}.
4661 An argument @var{count} is a repeat count, as for @code{step}.
4664 @c FIX ME!! Do we delete this, or is there a way it fits in with
4665 @c the following paragraph? --- Vctoria
4667 @c @code{next} within a function that lacks debugging information acts like
4668 @c @code{step}, but any function calls appearing within the code of the
4669 @c function are executed without stopping.
4671 The @code{next} command only stops at the first instruction of a
4672 source line. This prevents multiple stops that could otherwise occur in
4673 @code{switch} statements, @code{for} loops, etc.
4675 @kindex set step-mode
4677 @cindex functions without line info, and stepping
4678 @cindex stepping into functions with no line info
4679 @itemx set step-mode on
4680 The @code{set step-mode on} command causes the @code{step} command to
4681 stop at the first instruction of a function which contains no debug line
4682 information rather than stepping over it.
4684 This is useful in cases where you may be interested in inspecting the
4685 machine instructions of a function which has no symbolic info and do not
4686 want @value{GDBN} to automatically skip over this function.
4688 @item set step-mode off
4689 Causes the @code{step} command to step over any functions which contains no
4690 debug information. This is the default.
4692 @item show step-mode
4693 Show whether @value{GDBN} will stop in or step over functions without
4694 source line debug information.
4697 @kindex fin @r{(@code{finish})}
4699 Continue running until just after function in the selected stack frame
4700 returns. Print the returned value (if any). This command can be
4701 abbreviated as @code{fin}.
4703 Contrast this with the @code{return} command (@pxref{Returning,
4704 ,Returning from a Function}).
4707 @kindex u @r{(@code{until})}
4708 @cindex run until specified location
4711 Continue running until a source line past the current line, in the
4712 current stack frame, is reached. This command is used to avoid single
4713 stepping through a loop more than once. It is like the @code{next}
4714 command, except that when @code{until} encounters a jump, it
4715 automatically continues execution until the program counter is greater
4716 than the address of the jump.
4718 This means that when you reach the end of a loop after single stepping
4719 though it, @code{until} makes your program continue execution until it
4720 exits the loop. In contrast, a @code{next} command at the end of a loop
4721 simply steps back to the beginning of the loop, which forces you to step
4722 through the next iteration.
4724 @code{until} always stops your program if it attempts to exit the current
4727 @code{until} may produce somewhat counterintuitive results if the order
4728 of machine code does not match the order of the source lines. For
4729 example, in the following excerpt from a debugging session, the @code{f}
4730 (@code{frame}) command shows that execution is stopped at line
4731 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4735 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4737 (@value{GDBP}) until
4738 195 for ( ; argc > 0; NEXTARG) @{
4741 This happened because, for execution efficiency, the compiler had
4742 generated code for the loop closure test at the end, rather than the
4743 start, of the loop---even though the test in a C @code{for}-loop is
4744 written before the body of the loop. The @code{until} command appeared
4745 to step back to the beginning of the loop when it advanced to this
4746 expression; however, it has not really gone to an earlier
4747 statement---not in terms of the actual machine code.
4749 @code{until} with no argument works by means of single
4750 instruction stepping, and hence is slower than @code{until} with an
4753 @item until @var{location}
4754 @itemx u @var{location}
4755 Continue running your program until either the specified location is
4756 reached, or the current stack frame returns. @var{location} is any of
4757 the forms described in @ref{Specify Location}.
4758 This form of the command uses temporary breakpoints, and
4759 hence is quicker than @code{until} without an argument. The specified
4760 location is actually reached only if it is in the current frame. This
4761 implies that @code{until} can be used to skip over recursive function
4762 invocations. For instance in the code below, if the current location is
4763 line @code{96}, issuing @code{until 99} will execute the program up to
4764 line @code{99} in the same invocation of factorial, i.e., after the inner
4765 invocations have returned.
4768 94 int factorial (int value)
4770 96 if (value > 1) @{
4771 97 value *= factorial (value - 1);
4778 @kindex advance @var{location}
4779 @itemx advance @var{location}
4780 Continue running the program up to the given @var{location}. An argument is
4781 required, which should be of one of the forms described in
4782 @ref{Specify Location}.
4783 Execution will also stop upon exit from the current stack
4784 frame. This command is similar to @code{until}, but @code{advance} will
4785 not skip over recursive function calls, and the target location doesn't
4786 have to be in the same frame as the current one.
4790 @kindex si @r{(@code{stepi})}
4792 @itemx stepi @var{arg}
4794 Execute one machine instruction, then stop and return to the debugger.
4796 It is often useful to do @samp{display/i $pc} when stepping by machine
4797 instructions. This makes @value{GDBN} automatically display the next
4798 instruction to be executed, each time your program stops. @xref{Auto
4799 Display,, Automatic Display}.
4801 An argument is a repeat count, as in @code{step}.
4805 @kindex ni @r{(@code{nexti})}
4807 @itemx nexti @var{arg}
4809 Execute one machine instruction, but if it is a function call,
4810 proceed until the function returns.
4812 An argument is a repeat count, as in @code{next}.
4819 A signal is an asynchronous event that can happen in a program. The
4820 operating system defines the possible kinds of signals, and gives each
4821 kind a name and a number. For example, in Unix @code{SIGINT} is the
4822 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4823 @code{SIGSEGV} is the signal a program gets from referencing a place in
4824 memory far away from all the areas in use; @code{SIGALRM} occurs when
4825 the alarm clock timer goes off (which happens only if your program has
4826 requested an alarm).
4828 @cindex fatal signals
4829 Some signals, including @code{SIGALRM}, are a normal part of the
4830 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4831 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4832 program has not specified in advance some other way to handle the signal.
4833 @code{SIGINT} does not indicate an error in your program, but it is normally
4834 fatal so it can carry out the purpose of the interrupt: to kill the program.
4836 @value{GDBN} has the ability to detect any occurrence of a signal in your
4837 program. You can tell @value{GDBN} in advance what to do for each kind of
4840 @cindex handling signals
4841 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4842 @code{SIGALRM} be silently passed to your program
4843 (so as not to interfere with their role in the program's functioning)
4844 but to stop your program immediately whenever an error signal happens.
4845 You can change these settings with the @code{handle} command.
4848 @kindex info signals
4852 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4853 handle each one. You can use this to see the signal numbers of all
4854 the defined types of signals.
4856 @item info signals @var{sig}
4857 Similar, but print information only about the specified signal number.
4859 @code{info handle} is an alias for @code{info signals}.
4862 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4863 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4864 can be the number of a signal or its name (with or without the
4865 @samp{SIG} at the beginning); a list of signal numbers of the form
4866 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4867 known signals. Optional arguments @var{keywords}, described below,
4868 say what change to make.
4872 The keywords allowed by the @code{handle} command can be abbreviated.
4873 Their full names are:
4877 @value{GDBN} should not stop your program when this signal happens. It may
4878 still print a message telling you that the signal has come in.
4881 @value{GDBN} should stop your program when this signal happens. This implies
4882 the @code{print} keyword as well.
4885 @value{GDBN} should print a message when this signal happens.
4888 @value{GDBN} should not mention the occurrence of the signal at all. This
4889 implies the @code{nostop} keyword as well.
4893 @value{GDBN} should allow your program to see this signal; your program
4894 can handle the signal, or else it may terminate if the signal is fatal
4895 and not handled. @code{pass} and @code{noignore} are synonyms.
4899 @value{GDBN} should not allow your program to see this signal.
4900 @code{nopass} and @code{ignore} are synonyms.
4904 When a signal stops your program, the signal is not visible to the
4906 continue. Your program sees the signal then, if @code{pass} is in
4907 effect for the signal in question @emph{at that time}. In other words,
4908 after @value{GDBN} reports a signal, you can use the @code{handle}
4909 command with @code{pass} or @code{nopass} to control whether your
4910 program sees that signal when you continue.
4912 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4913 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4914 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4917 You can also use the @code{signal} command to prevent your program from
4918 seeing a signal, or cause it to see a signal it normally would not see,
4919 or to give it any signal at any time. For example, if your program stopped
4920 due to some sort of memory reference error, you might store correct
4921 values into the erroneous variables and continue, hoping to see more
4922 execution; but your program would probably terminate immediately as
4923 a result of the fatal signal once it saw the signal. To prevent this,
4924 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4927 @cindex extra signal information
4928 @anchor{extra signal information}
4930 On some targets, @value{GDBN} can inspect extra signal information
4931 associated with the intercepted signal, before it is actually
4932 delivered to the program being debugged. This information is exported
4933 by the convenience variable @code{$_siginfo}, and consists of data
4934 that is passed by the kernel to the signal handler at the time of the
4935 receipt of a signal. The data type of the information itself is
4936 target dependent. You can see the data type using the @code{ptype
4937 $_siginfo} command. On Unix systems, it typically corresponds to the
4938 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4941 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4942 referenced address that raised a segmentation fault.
4946 (@value{GDBP}) continue
4947 Program received signal SIGSEGV, Segmentation fault.
4948 0x0000000000400766 in main ()
4950 (@value{GDBP}) ptype $_siginfo
4957 struct @{...@} _kill;
4958 struct @{...@} _timer;
4960 struct @{...@} _sigchld;
4961 struct @{...@} _sigfault;
4962 struct @{...@} _sigpoll;
4965 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4969 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4970 $1 = (void *) 0x7ffff7ff7000
4974 Depending on target support, @code{$_siginfo} may also be writable.
4977 @section Stopping and Starting Multi-thread Programs
4979 @cindex stopped threads
4980 @cindex threads, stopped
4982 @cindex continuing threads
4983 @cindex threads, continuing
4985 @value{GDBN} supports debugging programs with multiple threads
4986 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4987 are two modes of controlling execution of your program within the
4988 debugger. In the default mode, referred to as @dfn{all-stop mode},
4989 when any thread in your program stops (for example, at a breakpoint
4990 or while being stepped), all other threads in the program are also stopped by
4991 @value{GDBN}. On some targets, @value{GDBN} also supports
4992 @dfn{non-stop mode}, in which other threads can continue to run freely while
4993 you examine the stopped thread in the debugger.
4996 * All-Stop Mode:: All threads stop when GDB takes control
4997 * Non-Stop Mode:: Other threads continue to execute
4998 * Background Execution:: Running your program asynchronously
4999 * Thread-Specific Breakpoints:: Controlling breakpoints
5000 * Interrupted System Calls:: GDB may interfere with system calls
5001 * Observer Mode:: GDB does not alter program behavior
5005 @subsection All-Stop Mode
5007 @cindex all-stop mode
5009 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5010 @emph{all} threads of execution stop, not just the current thread. This
5011 allows you to examine the overall state of the program, including
5012 switching between threads, without worrying that things may change
5015 Conversely, whenever you restart the program, @emph{all} threads start
5016 executing. @emph{This is true even when single-stepping} with commands
5017 like @code{step} or @code{next}.
5019 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5020 Since thread scheduling is up to your debugging target's operating
5021 system (not controlled by @value{GDBN}), other threads may
5022 execute more than one statement while the current thread completes a
5023 single step. Moreover, in general other threads stop in the middle of a
5024 statement, rather than at a clean statement boundary, when the program
5027 You might even find your program stopped in another thread after
5028 continuing or even single-stepping. This happens whenever some other
5029 thread runs into a breakpoint, a signal, or an exception before the
5030 first thread completes whatever you requested.
5032 @cindex automatic thread selection
5033 @cindex switching threads automatically
5034 @cindex threads, automatic switching
5035 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5036 signal, it automatically selects the thread where that breakpoint or
5037 signal happened. @value{GDBN} alerts you to the context switch with a
5038 message such as @samp{[Switching to Thread @var{n}]} to identify the
5041 On some OSes, you can modify @value{GDBN}'s default behavior by
5042 locking the OS scheduler to allow only a single thread to run.
5045 @item set scheduler-locking @var{mode}
5046 @cindex scheduler locking mode
5047 @cindex lock scheduler
5048 Set the scheduler locking mode. If it is @code{off}, then there is no
5049 locking and any thread may run at any time. If @code{on}, then only the
5050 current thread may run when the inferior is resumed. The @code{step}
5051 mode optimizes for single-stepping; it prevents other threads
5052 from preempting the current thread while you are stepping, so that
5053 the focus of debugging does not change unexpectedly.
5054 Other threads only rarely (or never) get a chance to run
5055 when you step. They are more likely to run when you @samp{next} over a
5056 function call, and they are completely free to run when you use commands
5057 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5058 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5059 the current thread away from the thread that you are debugging.
5061 @item show scheduler-locking
5062 Display the current scheduler locking mode.
5065 @cindex resume threads of multiple processes simultaneously
5066 By default, when you issue one of the execution commands such as
5067 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5068 threads of the current inferior to run. For example, if @value{GDBN}
5069 is attached to two inferiors, each with two threads, the
5070 @code{continue} command resumes only the two threads of the current
5071 inferior. This is useful, for example, when you debug a program that
5072 forks and you want to hold the parent stopped (so that, for instance,
5073 it doesn't run to exit), while you debug the child. In other
5074 situations, you may not be interested in inspecting the current state
5075 of any of the processes @value{GDBN} is attached to, and you may want
5076 to resume them all until some breakpoint is hit. In the latter case,
5077 you can instruct @value{GDBN} to allow all threads of all the
5078 inferiors to run with the @w{@code{set schedule-multiple}} command.
5081 @kindex set schedule-multiple
5082 @item set schedule-multiple
5083 Set the mode for allowing threads of multiple processes to be resumed
5084 when an execution command is issued. When @code{on}, all threads of
5085 all processes are allowed to run. When @code{off}, only the threads
5086 of the current process are resumed. The default is @code{off}. The
5087 @code{scheduler-locking} mode takes precedence when set to @code{on},
5088 or while you are stepping and set to @code{step}.
5090 @item show schedule-multiple
5091 Display the current mode for resuming the execution of threads of
5096 @subsection Non-Stop Mode
5098 @cindex non-stop mode
5100 @c This section is really only a place-holder, and needs to be expanded
5101 @c with more details.
5103 For some multi-threaded targets, @value{GDBN} supports an optional
5104 mode of operation in which you can examine stopped program threads in
5105 the debugger while other threads continue to execute freely. This
5106 minimizes intrusion when debugging live systems, such as programs
5107 where some threads have real-time constraints or must continue to
5108 respond to external events. This is referred to as @dfn{non-stop} mode.
5110 In non-stop mode, when a thread stops to report a debugging event,
5111 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5112 threads as well, in contrast to the all-stop mode behavior. Additionally,
5113 execution commands such as @code{continue} and @code{step} apply by default
5114 only to the current thread in non-stop mode, rather than all threads as
5115 in all-stop mode. This allows you to control threads explicitly in
5116 ways that are not possible in all-stop mode --- for example, stepping
5117 one thread while allowing others to run freely, stepping
5118 one thread while holding all others stopped, or stepping several threads
5119 independently and simultaneously.
5121 To enter non-stop mode, use this sequence of commands before you run
5122 or attach to your program:
5125 # Enable the async interface.
5128 # If using the CLI, pagination breaks non-stop.
5131 # Finally, turn it on!
5135 You can use these commands to manipulate the non-stop mode setting:
5138 @kindex set non-stop
5139 @item set non-stop on
5140 Enable selection of non-stop mode.
5141 @item set non-stop off
5142 Disable selection of non-stop mode.
5143 @kindex show non-stop
5145 Show the current non-stop enablement setting.
5148 Note these commands only reflect whether non-stop mode is enabled,
5149 not whether the currently-executing program is being run in non-stop mode.
5150 In particular, the @code{set non-stop} preference is only consulted when
5151 @value{GDBN} starts or connects to the target program, and it is generally
5152 not possible to switch modes once debugging has started. Furthermore,
5153 since not all targets support non-stop mode, even when you have enabled
5154 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5157 In non-stop mode, all execution commands apply only to the current thread
5158 by default. That is, @code{continue} only continues one thread.
5159 To continue all threads, issue @code{continue -a} or @code{c -a}.
5161 You can use @value{GDBN}'s background execution commands
5162 (@pxref{Background Execution}) to run some threads in the background
5163 while you continue to examine or step others from @value{GDBN}.
5164 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5165 always executed asynchronously in non-stop mode.
5167 Suspending execution is done with the @code{interrupt} command when
5168 running in the background, or @kbd{Ctrl-c} during foreground execution.
5169 In all-stop mode, this stops the whole process;
5170 but in non-stop mode the interrupt applies only to the current thread.
5171 To stop the whole program, use @code{interrupt -a}.
5173 Other execution commands do not currently support the @code{-a} option.
5175 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5176 that thread current, as it does in all-stop mode. This is because the
5177 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5178 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5179 changed to a different thread just as you entered a command to operate on the
5180 previously current thread.
5182 @node Background Execution
5183 @subsection Background Execution
5185 @cindex foreground execution
5186 @cindex background execution
5187 @cindex asynchronous execution
5188 @cindex execution, foreground, background and asynchronous
5190 @value{GDBN}'s execution commands have two variants: the normal
5191 foreground (synchronous) behavior, and a background
5192 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5193 the program to report that some thread has stopped before prompting for
5194 another command. In background execution, @value{GDBN} immediately gives
5195 a command prompt so that you can issue other commands while your program runs.
5197 You need to explicitly enable asynchronous mode before you can use
5198 background execution commands. You can use these commands to
5199 manipulate the asynchronous mode setting:
5202 @kindex set target-async
5203 @item set target-async on
5204 Enable asynchronous mode.
5205 @item set target-async off
5206 Disable asynchronous mode.
5207 @kindex show target-async
5208 @item show target-async
5209 Show the current target-async setting.
5212 If the target doesn't support async mode, @value{GDBN} issues an error
5213 message if you attempt to use the background execution commands.
5215 To specify background execution, add a @code{&} to the command. For example,
5216 the background form of the @code{continue} command is @code{continue&}, or
5217 just @code{c&}. The execution commands that accept background execution
5223 @xref{Starting, , Starting your Program}.
5227 @xref{Attach, , Debugging an Already-running Process}.
5231 @xref{Continuing and Stepping, step}.
5235 @xref{Continuing and Stepping, stepi}.
5239 @xref{Continuing and Stepping, next}.
5243 @xref{Continuing and Stepping, nexti}.
5247 @xref{Continuing and Stepping, continue}.
5251 @xref{Continuing and Stepping, finish}.
5255 @xref{Continuing and Stepping, until}.
5259 Background execution is especially useful in conjunction with non-stop
5260 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5261 However, you can also use these commands in the normal all-stop mode with
5262 the restriction that you cannot issue another execution command until the
5263 previous one finishes. Examples of commands that are valid in all-stop
5264 mode while the program is running include @code{help} and @code{info break}.
5266 You can interrupt your program while it is running in the background by
5267 using the @code{interrupt} command.
5274 Suspend execution of the running program. In all-stop mode,
5275 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5276 only the current thread. To stop the whole program in non-stop mode,
5277 use @code{interrupt -a}.
5280 @node Thread-Specific Breakpoints
5281 @subsection Thread-Specific Breakpoints
5283 When your program has multiple threads (@pxref{Threads,, Debugging
5284 Programs with Multiple Threads}), you can choose whether to set
5285 breakpoints on all threads, or on a particular thread.
5288 @cindex breakpoints and threads
5289 @cindex thread breakpoints
5290 @kindex break @dots{} thread @var{threadno}
5291 @item break @var{linespec} thread @var{threadno}
5292 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5293 @var{linespec} specifies source lines; there are several ways of
5294 writing them (@pxref{Specify Location}), but the effect is always to
5295 specify some source line.
5297 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5298 to specify that you only want @value{GDBN} to stop the program when a
5299 particular thread reaches this breakpoint. @var{threadno} is one of the
5300 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5301 column of the @samp{info threads} display.
5303 If you do not specify @samp{thread @var{threadno}} when you set a
5304 breakpoint, the breakpoint applies to @emph{all} threads of your
5307 You can use the @code{thread} qualifier on conditional breakpoints as
5308 well; in this case, place @samp{thread @var{threadno}} before or
5309 after the breakpoint condition, like this:
5312 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5317 @node Interrupted System Calls
5318 @subsection Interrupted System Calls
5320 @cindex thread breakpoints and system calls
5321 @cindex system calls and thread breakpoints
5322 @cindex premature return from system calls
5323 There is an unfortunate side effect when using @value{GDBN} to debug
5324 multi-threaded programs. If one thread stops for a
5325 breakpoint, or for some other reason, and another thread is blocked in a
5326 system call, then the system call may return prematurely. This is a
5327 consequence of the interaction between multiple threads and the signals
5328 that @value{GDBN} uses to implement breakpoints and other events that
5331 To handle this problem, your program should check the return value of
5332 each system call and react appropriately. This is good programming
5335 For example, do not write code like this:
5341 The call to @code{sleep} will return early if a different thread stops
5342 at a breakpoint or for some other reason.
5344 Instead, write this:
5349 unslept = sleep (unslept);
5352 A system call is allowed to return early, so the system is still
5353 conforming to its specification. But @value{GDBN} does cause your
5354 multi-threaded program to behave differently than it would without
5357 Also, @value{GDBN} uses internal breakpoints in the thread library to
5358 monitor certain events such as thread creation and thread destruction.
5359 When such an event happens, a system call in another thread may return
5360 prematurely, even though your program does not appear to stop.
5363 @subsection Observer Mode
5365 If you want to build on non-stop mode and observe program behavior
5366 without any chance of disruption by @value{GDBN}, you can set
5367 variables to disable all of the debugger's attempts to modify state,
5368 whether by writing memory, inserting breakpoints, etc. These operate
5369 at a low level, intercepting operations from all commands.
5371 When all of these are set to @code{off}, then @value{GDBN} is said to
5372 be @dfn{observer mode}. As a convenience, the variable
5373 @code{observer} can be set to disable these, plus enable non-stop
5376 Note that @value{GDBN} will not prevent you from making nonsensical
5377 combinations of these settings. For instance, if you have enabled
5378 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5379 then breakpoints that work by writing trap instructions into the code
5380 stream will still not be able to be placed.
5385 @item set observer on
5386 @itemx set observer off
5387 When set to @code{on}, this disables all the permission variables
5388 below (except for @code{insert-fast-tracepoints}), plus enables
5389 non-stop debugging. Setting this to @code{off} switches back to
5390 normal debugging, though remaining in non-stop mode.
5393 Show whether observer mode is on or off.
5395 @kindex may-write-registers
5396 @item set may-write-registers on
5397 @itemx set may-write-registers off
5398 This controls whether @value{GDBN} will attempt to alter the values of
5399 registers, such as with assignment expressions in @code{print}, or the
5400 @code{jump} command. It defaults to @code{on}.
5402 @item show may-write-registers
5403 Show the current permission to write registers.
5405 @kindex may-write-memory
5406 @item set may-write-memory on
5407 @itemx set may-write-memory off
5408 This controls whether @value{GDBN} will attempt to alter the contents
5409 of memory, such as with assignment expressions in @code{print}. It
5410 defaults to @code{on}.
5412 @item show may-write-memory
5413 Show the current permission to write memory.
5415 @kindex may-insert-breakpoints
5416 @item set may-insert-breakpoints on
5417 @itemx set may-insert-breakpoints off
5418 This controls whether @value{GDBN} will attempt to insert breakpoints.
5419 This affects all breakpoints, including internal breakpoints defined
5420 by @value{GDBN}. It defaults to @code{on}.
5422 @item show may-insert-breakpoints
5423 Show the current permission to insert breakpoints.
5425 @kindex may-insert-tracepoints
5426 @item set may-insert-tracepoints on
5427 @itemx set may-insert-tracepoints off
5428 This controls whether @value{GDBN} will attempt to insert (regular)
5429 tracepoints at the beginning of a tracing experiment. It affects only
5430 non-fast tracepoints, fast tracepoints being under the control of
5431 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5433 @item show may-insert-tracepoints
5434 Show the current permission to insert tracepoints.
5436 @kindex may-insert-fast-tracepoints
5437 @item set may-insert-fast-tracepoints on
5438 @itemx set may-insert-fast-tracepoints off
5439 This controls whether @value{GDBN} will attempt to insert fast
5440 tracepoints at the beginning of a tracing experiment. It affects only
5441 fast tracepoints, regular (non-fast) tracepoints being under the
5442 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5444 @item show may-insert-fast-tracepoints
5445 Show the current permission to insert fast tracepoints.
5447 @kindex may-interrupt
5448 @item set may-interrupt on
5449 @itemx set may-interrupt off
5450 This controls whether @value{GDBN} will attempt to interrupt or stop
5451 program execution. When this variable is @code{off}, the
5452 @code{interrupt} command will have no effect, nor will
5453 @kbd{Ctrl-c}. It defaults to @code{on}.
5455 @item show may-interrupt
5456 Show the current permission to interrupt or stop the program.
5460 @node Reverse Execution
5461 @chapter Running programs backward
5462 @cindex reverse execution
5463 @cindex running programs backward
5465 When you are debugging a program, it is not unusual to realize that
5466 you have gone too far, and some event of interest has already happened.
5467 If the target environment supports it, @value{GDBN} can allow you to
5468 ``rewind'' the program by running it backward.
5470 A target environment that supports reverse execution should be able
5471 to ``undo'' the changes in machine state that have taken place as the
5472 program was executing normally. Variables, registers etc.@: should
5473 revert to their previous values. Obviously this requires a great
5474 deal of sophistication on the part of the target environment; not
5475 all target environments can support reverse execution.
5477 When a program is executed in reverse, the instructions that
5478 have most recently been executed are ``un-executed'', in reverse
5479 order. The program counter runs backward, following the previous
5480 thread of execution in reverse. As each instruction is ``un-executed'',
5481 the values of memory and/or registers that were changed by that
5482 instruction are reverted to their previous states. After executing
5483 a piece of source code in reverse, all side effects of that code
5484 should be ``undone'', and all variables should be returned to their
5485 prior values@footnote{
5486 Note that some side effects are easier to undo than others. For instance,
5487 memory and registers are relatively easy, but device I/O is hard. Some
5488 targets may be able undo things like device I/O, and some may not.
5490 The contract between @value{GDBN} and the reverse executing target
5491 requires only that the target do something reasonable when
5492 @value{GDBN} tells it to execute backwards, and then report the
5493 results back to @value{GDBN}. Whatever the target reports back to
5494 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5495 assumes that the memory and registers that the target reports are in a
5496 consistant state, but @value{GDBN} accepts whatever it is given.
5499 If you are debugging in a target environment that supports
5500 reverse execution, @value{GDBN} provides the following commands.
5503 @kindex reverse-continue
5504 @kindex rc @r{(@code{reverse-continue})}
5505 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5506 @itemx rc @r{[}@var{ignore-count}@r{]}
5507 Beginning at the point where your program last stopped, start executing
5508 in reverse. Reverse execution will stop for breakpoints and synchronous
5509 exceptions (signals), just like normal execution. Behavior of
5510 asynchronous signals depends on the target environment.
5512 @kindex reverse-step
5513 @kindex rs @r{(@code{step})}
5514 @item reverse-step @r{[}@var{count}@r{]}
5515 Run the program backward until control reaches the start of a
5516 different source line; then stop it, and return control to @value{GDBN}.
5518 Like the @code{step} command, @code{reverse-step} will only stop
5519 at the beginning of a source line. It ``un-executes'' the previously
5520 executed source line. If the previous source line included calls to
5521 debuggable functions, @code{reverse-step} will step (backward) into
5522 the called function, stopping at the beginning of the @emph{last}
5523 statement in the called function (typically a return statement).
5525 Also, as with the @code{step} command, if non-debuggable functions are
5526 called, @code{reverse-step} will run thru them backward without stopping.
5528 @kindex reverse-stepi
5529 @kindex rsi @r{(@code{reverse-stepi})}
5530 @item reverse-stepi @r{[}@var{count}@r{]}
5531 Reverse-execute one machine instruction. Note that the instruction
5532 to be reverse-executed is @emph{not} the one pointed to by the program
5533 counter, but the instruction executed prior to that one. For instance,
5534 if the last instruction was a jump, @code{reverse-stepi} will take you
5535 back from the destination of the jump to the jump instruction itself.
5537 @kindex reverse-next
5538 @kindex rn @r{(@code{reverse-next})}
5539 @item reverse-next @r{[}@var{count}@r{]}
5540 Run backward to the beginning of the previous line executed in
5541 the current (innermost) stack frame. If the line contains function
5542 calls, they will be ``un-executed'' without stopping. Starting from
5543 the first line of a function, @code{reverse-next} will take you back
5544 to the caller of that function, @emph{before} the function was called,
5545 just as the normal @code{next} command would take you from the last
5546 line of a function back to its return to its caller
5547 @footnote{Unless the code is too heavily optimized.}.
5549 @kindex reverse-nexti
5550 @kindex rni @r{(@code{reverse-nexti})}
5551 @item reverse-nexti @r{[}@var{count}@r{]}
5552 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5553 in reverse, except that called functions are ``un-executed'' atomically.
5554 That is, if the previously executed instruction was a return from
5555 another function, @code{reverse-nexti} will continue to execute
5556 in reverse until the call to that function (from the current stack
5559 @kindex reverse-finish
5560 @item reverse-finish
5561 Just as the @code{finish} command takes you to the point where the
5562 current function returns, @code{reverse-finish} takes you to the point
5563 where it was called. Instead of ending up at the end of the current
5564 function invocation, you end up at the beginning.
5566 @kindex set exec-direction
5567 @item set exec-direction
5568 Set the direction of target execution.
5569 @itemx set exec-direction reverse
5570 @cindex execute forward or backward in time
5571 @value{GDBN} will perform all execution commands in reverse, until the
5572 exec-direction mode is changed to ``forward''. Affected commands include
5573 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5574 command cannot be used in reverse mode.
5575 @item set exec-direction forward
5576 @value{GDBN} will perform all execution commands in the normal fashion.
5577 This is the default.
5581 @node Process Record and Replay
5582 @chapter Recording Inferior's Execution and Replaying It
5583 @cindex process record and replay
5584 @cindex recording inferior's execution and replaying it
5586 On some platforms, @value{GDBN} provides a special @dfn{process record
5587 and replay} target that can record a log of the process execution, and
5588 replay it later with both forward and reverse execution commands.
5591 When this target is in use, if the execution log includes the record
5592 for the next instruction, @value{GDBN} will debug in @dfn{replay
5593 mode}. In the replay mode, the inferior does not really execute code
5594 instructions. Instead, all the events that normally happen during
5595 code execution are taken from the execution log. While code is not
5596 really executed in replay mode, the values of registers (including the
5597 program counter register) and the memory of the inferior are still
5598 changed as they normally would. Their contents are taken from the
5602 If the record for the next instruction is not in the execution log,
5603 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5604 inferior executes normally, and @value{GDBN} records the execution log
5607 The process record and replay target supports reverse execution
5608 (@pxref{Reverse Execution}), even if the platform on which the
5609 inferior runs does not. However, the reverse execution is limited in
5610 this case by the range of the instructions recorded in the execution
5611 log. In other words, reverse execution on platforms that don't
5612 support it directly can only be done in the replay mode.
5614 When debugging in the reverse direction, @value{GDBN} will work in
5615 replay mode as long as the execution log includes the record for the
5616 previous instruction; otherwise, it will work in record mode, if the
5617 platform supports reverse execution, or stop if not.
5619 For architecture environments that support process record and replay,
5620 @value{GDBN} provides the following commands:
5623 @kindex target record
5627 This command starts the process record and replay target. The process
5628 record and replay target can only debug a process that is already
5629 running. Therefore, you need first to start the process with the
5630 @kbd{run} or @kbd{start} commands, and then start the recording with
5631 the @kbd{target record} command.
5633 Both @code{record} and @code{rec} are aliases of @code{target record}.
5635 @cindex displaced stepping, and process record and replay
5636 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5637 will be automatically disabled when process record and replay target
5638 is started. That's because the process record and replay target
5639 doesn't support displaced stepping.
5641 @cindex non-stop mode, and process record and replay
5642 @cindex asynchronous execution, and process record and replay
5643 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5644 the asynchronous execution mode (@pxref{Background Execution}), the
5645 process record and replay target cannot be started because it doesn't
5646 support these two modes.
5651 Stop the process record and replay target. When process record and
5652 replay target stops, the entire execution log will be deleted and the
5653 inferior will either be terminated, or will remain in its final state.
5655 When you stop the process record and replay target in record mode (at
5656 the end of the execution log), the inferior will be stopped at the
5657 next instruction that would have been recorded. In other words, if
5658 you record for a while and then stop recording, the inferior process
5659 will be left in the same state as if the recording never happened.
5661 On the other hand, if the process record and replay target is stopped
5662 while in replay mode (that is, not at the end of the execution log,
5663 but at some earlier point), the inferior process will become ``live''
5664 at that earlier state, and it will then be possible to continue the
5665 usual ``live'' debugging of the process from that state.
5667 When the inferior process exits, or @value{GDBN} detaches from it,
5668 process record and replay target will automatically stop itself.
5671 @item record save @var{filename}
5672 Save the execution log to a file @file{@var{filename}}.
5673 Default filename is @file{gdb_record.@var{process_id}}, where
5674 @var{process_id} is the process ID of the inferior.
5676 @kindex record restore
5677 @item record restore @var{filename}
5678 Restore the execution log from a file @file{@var{filename}}.
5679 File must have been created with @code{record save}.
5681 @kindex set record insn-number-max
5682 @item set record insn-number-max @var{limit}
5683 Set the limit of instructions to be recorded. Default value is 200000.
5685 If @var{limit} is a positive number, then @value{GDBN} will start
5686 deleting instructions from the log once the number of the record
5687 instructions becomes greater than @var{limit}. For every new recorded
5688 instruction, @value{GDBN} will delete the earliest recorded
5689 instruction to keep the number of recorded instructions at the limit.
5690 (Since deleting recorded instructions loses information, @value{GDBN}
5691 lets you control what happens when the limit is reached, by means of
5692 the @code{stop-at-limit} option, described below.)
5694 If @var{limit} is zero, @value{GDBN} will never delete recorded
5695 instructions from the execution log. The number of recorded
5696 instructions is unlimited in this case.
5698 @kindex show record insn-number-max
5699 @item show record insn-number-max
5700 Show the limit of instructions to be recorded.
5702 @kindex set record stop-at-limit
5703 @item set record stop-at-limit
5704 Control the behavior when the number of recorded instructions reaches
5705 the limit. If ON (the default), @value{GDBN} will stop when the limit
5706 is reached for the first time and ask you whether you want to stop the
5707 inferior or continue running it and recording the execution log. If
5708 you decide to continue recording, each new recorded instruction will
5709 cause the oldest one to be deleted.
5711 If this option is OFF, @value{GDBN} will automatically delete the
5712 oldest record to make room for each new one, without asking.
5714 @kindex show record stop-at-limit
5715 @item show record stop-at-limit
5716 Show the current setting of @code{stop-at-limit}.
5718 @kindex set record memory-query
5719 @item set record memory-query
5720 Control the behavior when @value{GDBN} is unable to record memory
5721 changes caused by an instruction. If ON, @value{GDBN} will query
5722 whether to stop the inferior in that case.
5724 If this option is OFF (the default), @value{GDBN} will automatically
5725 ignore the effect of such instructions on memory. Later, when
5726 @value{GDBN} replays this execution log, it will mark the log of this
5727 instruction as not accessible, and it will not affect the replay
5730 @kindex show record memory-query
5731 @item show record memory-query
5732 Show the current setting of @code{memory-query}.
5736 Show various statistics about the state of process record and its
5737 in-memory execution log buffer, including:
5741 Whether in record mode or replay mode.
5743 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5745 Highest recorded instruction number.
5747 Current instruction about to be replayed (if in replay mode).
5749 Number of instructions contained in the execution log.
5751 Maximum number of instructions that may be contained in the execution log.
5754 @kindex record delete
5757 When record target runs in replay mode (``in the past''), delete the
5758 subsequent execution log and begin to record a new execution log starting
5759 from the current address. This means you will abandon the previously
5760 recorded ``future'' and begin recording a new ``future''.
5765 @chapter Examining the Stack
5767 When your program has stopped, the first thing you need to know is where it
5768 stopped and how it got there.
5771 Each time your program performs a function call, information about the call
5773 That information includes the location of the call in your program,
5774 the arguments of the call,
5775 and the local variables of the function being called.
5776 The information is saved in a block of data called a @dfn{stack frame}.
5777 The stack frames are allocated in a region of memory called the @dfn{call
5780 When your program stops, the @value{GDBN} commands for examining the
5781 stack allow you to see all of this information.
5783 @cindex selected frame
5784 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5785 @value{GDBN} commands refer implicitly to the selected frame. In
5786 particular, whenever you ask @value{GDBN} for the value of a variable in
5787 your program, the value is found in the selected frame. There are
5788 special @value{GDBN} commands to select whichever frame you are
5789 interested in. @xref{Selection, ,Selecting a Frame}.
5791 When your program stops, @value{GDBN} automatically selects the
5792 currently executing frame and describes it briefly, similar to the
5793 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5796 * Frames:: Stack frames
5797 * Backtrace:: Backtraces
5798 * Selection:: Selecting a frame
5799 * Frame Info:: Information on a frame
5804 @section Stack Frames
5806 @cindex frame, definition
5808 The call stack is divided up into contiguous pieces called @dfn{stack
5809 frames}, or @dfn{frames} for short; each frame is the data associated
5810 with one call to one function. The frame contains the arguments given
5811 to the function, the function's local variables, and the address at
5812 which the function is executing.
5814 @cindex initial frame
5815 @cindex outermost frame
5816 @cindex innermost frame
5817 When your program is started, the stack has only one frame, that of the
5818 function @code{main}. This is called the @dfn{initial} frame or the
5819 @dfn{outermost} frame. Each time a function is called, a new frame is
5820 made. Each time a function returns, the frame for that function invocation
5821 is eliminated. If a function is recursive, there can be many frames for
5822 the same function. The frame for the function in which execution is
5823 actually occurring is called the @dfn{innermost} frame. This is the most
5824 recently created of all the stack frames that still exist.
5826 @cindex frame pointer
5827 Inside your program, stack frames are identified by their addresses. A
5828 stack frame consists of many bytes, each of which has its own address; each
5829 kind of computer has a convention for choosing one byte whose
5830 address serves as the address of the frame. Usually this address is kept
5831 in a register called the @dfn{frame pointer register}
5832 (@pxref{Registers, $fp}) while execution is going on in that frame.
5834 @cindex frame number
5835 @value{GDBN} assigns numbers to all existing stack frames, starting with
5836 zero for the innermost frame, one for the frame that called it,
5837 and so on upward. These numbers do not really exist in your program;
5838 they are assigned by @value{GDBN} to give you a way of designating stack
5839 frames in @value{GDBN} commands.
5841 @c The -fomit-frame-pointer below perennially causes hbox overflow
5842 @c underflow problems.
5843 @cindex frameless execution
5844 Some compilers provide a way to compile functions so that they operate
5845 without stack frames. (For example, the @value{NGCC} option
5847 @samp{-fomit-frame-pointer}
5849 generates functions without a frame.)
5850 This is occasionally done with heavily used library functions to save
5851 the frame setup time. @value{GDBN} has limited facilities for dealing
5852 with these function invocations. If the innermost function invocation
5853 has no stack frame, @value{GDBN} nevertheless regards it as though
5854 it had a separate frame, which is numbered zero as usual, allowing
5855 correct tracing of the function call chain. However, @value{GDBN} has
5856 no provision for frameless functions elsewhere in the stack.
5859 @kindex frame@r{, command}
5860 @cindex current stack frame
5861 @item frame @var{args}
5862 The @code{frame} command allows you to move from one stack frame to another,
5863 and to print the stack frame you select. @var{args} may be either the
5864 address of the frame or the stack frame number. Without an argument,
5865 @code{frame} prints the current stack frame.
5867 @kindex select-frame
5868 @cindex selecting frame silently
5870 The @code{select-frame} command allows you to move from one stack frame
5871 to another without printing the frame. This is the silent version of
5879 @cindex call stack traces
5880 A backtrace is a summary of how your program got where it is. It shows one
5881 line per frame, for many frames, starting with the currently executing
5882 frame (frame zero), followed by its caller (frame one), and on up the
5887 @kindex bt @r{(@code{backtrace})}
5890 Print a backtrace of the entire stack: one line per frame for all
5891 frames in the stack.
5893 You can stop the backtrace at any time by typing the system interrupt
5894 character, normally @kbd{Ctrl-c}.
5896 @item backtrace @var{n}
5898 Similar, but print only the innermost @var{n} frames.
5900 @item backtrace -@var{n}
5902 Similar, but print only the outermost @var{n} frames.
5904 @item backtrace full
5906 @itemx bt full @var{n}
5907 @itemx bt full -@var{n}
5908 Print the values of the local variables also. @var{n} specifies the
5909 number of frames to print, as described above.
5914 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5915 are additional aliases for @code{backtrace}.
5917 @cindex multiple threads, backtrace
5918 In a multi-threaded program, @value{GDBN} by default shows the
5919 backtrace only for the current thread. To display the backtrace for
5920 several or all of the threads, use the command @code{thread apply}
5921 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5922 apply all backtrace}, @value{GDBN} will display the backtrace for all
5923 the threads; this is handy when you debug a core dump of a
5924 multi-threaded program.
5926 Each line in the backtrace shows the frame number and the function name.
5927 The program counter value is also shown---unless you use @code{set
5928 print address off}. The backtrace also shows the source file name and
5929 line number, as well as the arguments to the function. The program
5930 counter value is omitted if it is at the beginning of the code for that
5933 Here is an example of a backtrace. It was made with the command
5934 @samp{bt 3}, so it shows the innermost three frames.
5938 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5940 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5941 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5943 (More stack frames follow...)
5948 The display for frame zero does not begin with a program counter
5949 value, indicating that your program has stopped at the beginning of the
5950 code for line @code{993} of @code{builtin.c}.
5953 The value of parameter @code{data} in frame 1 has been replaced by
5954 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5955 only if it is a scalar (integer, pointer, enumeration, etc). See command
5956 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5957 on how to configure the way function parameter values are printed.
5959 @cindex value optimized out, in backtrace
5960 @cindex function call arguments, optimized out
5961 If your program was compiled with optimizations, some compilers will
5962 optimize away arguments passed to functions if those arguments are
5963 never used after the call. Such optimizations generate code that
5964 passes arguments through registers, but doesn't store those arguments
5965 in the stack frame. @value{GDBN} has no way of displaying such
5966 arguments in stack frames other than the innermost one. Here's what
5967 such a backtrace might look like:
5971 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5973 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5974 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5976 (More stack frames follow...)
5981 The values of arguments that were not saved in their stack frames are
5982 shown as @samp{<value optimized out>}.
5984 If you need to display the values of such optimized-out arguments,
5985 either deduce that from other variables whose values depend on the one
5986 you are interested in, or recompile without optimizations.
5988 @cindex backtrace beyond @code{main} function
5989 @cindex program entry point
5990 @cindex startup code, and backtrace
5991 Most programs have a standard user entry point---a place where system
5992 libraries and startup code transition into user code. For C this is
5993 @code{main}@footnote{
5994 Note that embedded programs (the so-called ``free-standing''
5995 environment) are not required to have a @code{main} function as the
5996 entry point. They could even have multiple entry points.}.
5997 When @value{GDBN} finds the entry function in a backtrace
5998 it will terminate the backtrace, to avoid tracing into highly
5999 system-specific (and generally uninteresting) code.
6001 If you need to examine the startup code, or limit the number of levels
6002 in a backtrace, you can change this behavior:
6005 @item set backtrace past-main
6006 @itemx set backtrace past-main on
6007 @kindex set backtrace
6008 Backtraces will continue past the user entry point.
6010 @item set backtrace past-main off
6011 Backtraces will stop when they encounter the user entry point. This is the
6014 @item show backtrace past-main
6015 @kindex show backtrace
6016 Display the current user entry point backtrace policy.
6018 @item set backtrace past-entry
6019 @itemx set backtrace past-entry on
6020 Backtraces will continue past the internal entry point of an application.
6021 This entry point is encoded by the linker when the application is built,
6022 and is likely before the user entry point @code{main} (or equivalent) is called.
6024 @item set backtrace past-entry off
6025 Backtraces will stop when they encounter the internal entry point of an
6026 application. This is the default.
6028 @item show backtrace past-entry
6029 Display the current internal entry point backtrace policy.
6031 @item set backtrace limit @var{n}
6032 @itemx set backtrace limit 0
6033 @cindex backtrace limit
6034 Limit the backtrace to @var{n} levels. A value of zero means
6037 @item show backtrace limit
6038 Display the current limit on backtrace levels.
6042 @section Selecting a Frame
6044 Most commands for examining the stack and other data in your program work on
6045 whichever stack frame is selected at the moment. Here are the commands for
6046 selecting a stack frame; all of them finish by printing a brief description
6047 of the stack frame just selected.
6050 @kindex frame@r{, selecting}
6051 @kindex f @r{(@code{frame})}
6054 Select frame number @var{n}. Recall that frame zero is the innermost
6055 (currently executing) frame, frame one is the frame that called the
6056 innermost one, and so on. The highest-numbered frame is the one for
6059 @item frame @var{addr}
6061 Select the frame at address @var{addr}. This is useful mainly if the
6062 chaining of stack frames has been damaged by a bug, making it
6063 impossible for @value{GDBN} to assign numbers properly to all frames. In
6064 addition, this can be useful when your program has multiple stacks and
6065 switches between them.
6067 On the SPARC architecture, @code{frame} needs two addresses to
6068 select an arbitrary frame: a frame pointer and a stack pointer.
6070 On the MIPS and Alpha architecture, it needs two addresses: a stack
6071 pointer and a program counter.
6073 On the 29k architecture, it needs three addresses: a register stack
6074 pointer, a program counter, and a memory stack pointer.
6078 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6079 advances toward the outermost frame, to higher frame numbers, to frames
6080 that have existed longer. @var{n} defaults to one.
6083 @kindex do @r{(@code{down})}
6085 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6086 advances toward the innermost frame, to lower frame numbers, to frames
6087 that were created more recently. @var{n} defaults to one. You may
6088 abbreviate @code{down} as @code{do}.
6091 All of these commands end by printing two lines of output describing the
6092 frame. The first line shows the frame number, the function name, the
6093 arguments, and the source file and line number of execution in that
6094 frame. The second line shows the text of that source line.
6102 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6104 10 read_input_file (argv[i]);
6108 After such a printout, the @code{list} command with no arguments
6109 prints ten lines centered on the point of execution in the frame.
6110 You can also edit the program at the point of execution with your favorite
6111 editing program by typing @code{edit}.
6112 @xref{List, ,Printing Source Lines},
6116 @kindex down-silently
6118 @item up-silently @var{n}
6119 @itemx down-silently @var{n}
6120 These two commands are variants of @code{up} and @code{down},
6121 respectively; they differ in that they do their work silently, without
6122 causing display of the new frame. They are intended primarily for use
6123 in @value{GDBN} command scripts, where the output might be unnecessary and
6128 @section Information About a Frame
6130 There are several other commands to print information about the selected
6136 When used without any argument, this command does not change which
6137 frame is selected, but prints a brief description of the currently
6138 selected stack frame. It can be abbreviated @code{f}. With an
6139 argument, this command is used to select a stack frame.
6140 @xref{Selection, ,Selecting a Frame}.
6143 @kindex info f @r{(@code{info frame})}
6146 This command prints a verbose description of the selected stack frame,
6151 the address of the frame
6153 the address of the next frame down (called by this frame)
6155 the address of the next frame up (caller of this frame)
6157 the language in which the source code corresponding to this frame is written
6159 the address of the frame's arguments
6161 the address of the frame's local variables
6163 the program counter saved in it (the address of execution in the caller frame)
6165 which registers were saved in the frame
6168 @noindent The verbose description is useful when
6169 something has gone wrong that has made the stack format fail to fit
6170 the usual conventions.
6172 @item info frame @var{addr}
6173 @itemx info f @var{addr}
6174 Print a verbose description of the frame at address @var{addr}, without
6175 selecting that frame. The selected frame remains unchanged by this
6176 command. This requires the same kind of address (more than one for some
6177 architectures) that you specify in the @code{frame} command.
6178 @xref{Selection, ,Selecting a Frame}.
6182 Print the arguments of the selected frame, each on a separate line.
6186 Print the local variables of the selected frame, each on a separate
6187 line. These are all variables (declared either static or automatic)
6188 accessible at the point of execution of the selected frame.
6191 @cindex catch exceptions, list active handlers
6192 @cindex exception handlers, how to list
6194 Print a list of all the exception handlers that are active in the
6195 current stack frame at the current point of execution. To see other
6196 exception handlers, visit the associated frame (using the @code{up},
6197 @code{down}, or @code{frame} commands); then type @code{info catch}.
6198 @xref{Set Catchpoints, , Setting Catchpoints}.
6204 @chapter Examining Source Files
6206 @value{GDBN} can print parts of your program's source, since the debugging
6207 information recorded in the program tells @value{GDBN} what source files were
6208 used to build it. When your program stops, @value{GDBN} spontaneously prints
6209 the line where it stopped. Likewise, when you select a stack frame
6210 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6211 execution in that frame has stopped. You can print other portions of
6212 source files by explicit command.
6214 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6215 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6216 @value{GDBN} under @sc{gnu} Emacs}.
6219 * List:: Printing source lines
6220 * Specify Location:: How to specify code locations
6221 * Edit:: Editing source files
6222 * Search:: Searching source files
6223 * Source Path:: Specifying source directories
6224 * Machine Code:: Source and machine code
6228 @section Printing Source Lines
6231 @kindex l @r{(@code{list})}
6232 To print lines from a source file, use the @code{list} command
6233 (abbreviated @code{l}). By default, ten lines are printed.
6234 There are several ways to specify what part of the file you want to
6235 print; see @ref{Specify Location}, for the full list.
6237 Here are the forms of the @code{list} command most commonly used:
6240 @item list @var{linenum}
6241 Print lines centered around line number @var{linenum} in the
6242 current source file.
6244 @item list @var{function}
6245 Print lines centered around the beginning of function
6249 Print more lines. If the last lines printed were printed with a
6250 @code{list} command, this prints lines following the last lines
6251 printed; however, if the last line printed was a solitary line printed
6252 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6253 Stack}), this prints lines centered around that line.
6256 Print lines just before the lines last printed.
6259 @cindex @code{list}, how many lines to display
6260 By default, @value{GDBN} prints ten source lines with any of these forms of
6261 the @code{list} command. You can change this using @code{set listsize}:
6264 @kindex set listsize
6265 @item set listsize @var{count}
6266 Make the @code{list} command display @var{count} source lines (unless
6267 the @code{list} argument explicitly specifies some other number).
6269 @kindex show listsize
6271 Display the number of lines that @code{list} prints.
6274 Repeating a @code{list} command with @key{RET} discards the argument,
6275 so it is equivalent to typing just @code{list}. This is more useful
6276 than listing the same lines again. An exception is made for an
6277 argument of @samp{-}; that argument is preserved in repetition so that
6278 each repetition moves up in the source file.
6280 In general, the @code{list} command expects you to supply zero, one or two
6281 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6282 of writing them (@pxref{Specify Location}), but the effect is always
6283 to specify some source line.
6285 Here is a complete description of the possible arguments for @code{list}:
6288 @item list @var{linespec}
6289 Print lines centered around the line specified by @var{linespec}.
6291 @item list @var{first},@var{last}
6292 Print lines from @var{first} to @var{last}. Both arguments are
6293 linespecs. When a @code{list} command has two linespecs, and the
6294 source file of the second linespec is omitted, this refers to
6295 the same source file as the first linespec.
6297 @item list ,@var{last}
6298 Print lines ending with @var{last}.
6300 @item list @var{first},
6301 Print lines starting with @var{first}.
6304 Print lines just after the lines last printed.
6307 Print lines just before the lines last printed.
6310 As described in the preceding table.
6313 @node Specify Location
6314 @section Specifying a Location
6315 @cindex specifying location
6318 Several @value{GDBN} commands accept arguments that specify a location
6319 of your program's code. Since @value{GDBN} is a source-level
6320 debugger, a location usually specifies some line in the source code;
6321 for that reason, locations are also known as @dfn{linespecs}.
6323 Here are all the different ways of specifying a code location that
6324 @value{GDBN} understands:
6328 Specifies the line number @var{linenum} of the current source file.
6331 @itemx +@var{offset}
6332 Specifies the line @var{offset} lines before or after the @dfn{current
6333 line}. For the @code{list} command, the current line is the last one
6334 printed; for the breakpoint commands, this is the line at which
6335 execution stopped in the currently selected @dfn{stack frame}
6336 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6337 used as the second of the two linespecs in a @code{list} command,
6338 this specifies the line @var{offset} lines up or down from the first
6341 @item @var{filename}:@var{linenum}
6342 Specifies the line @var{linenum} in the source file @var{filename}.
6344 @item @var{function}
6345 Specifies the line that begins the body of the function @var{function}.
6346 For example, in C, this is the line with the open brace.
6348 @item @var{filename}:@var{function}
6349 Specifies the line that begins the body of the function @var{function}
6350 in the file @var{filename}. You only need the file name with a
6351 function name to avoid ambiguity when there are identically named
6352 functions in different source files.
6355 Specifies the line at which the label named @var{label} appears.
6356 @value{GDBN} searches for the label in the function corresponding to
6357 the currently selected stack frame. If there is no current selected
6358 stack frame (for instance, if the inferior is not running), then
6359 @value{GDBN} will not search for a label.
6361 @item *@var{address}
6362 Specifies the program address @var{address}. For line-oriented
6363 commands, such as @code{list} and @code{edit}, this specifies a source
6364 line that contains @var{address}. For @code{break} and other
6365 breakpoint oriented commands, this can be used to set breakpoints in
6366 parts of your program which do not have debugging information or
6369 Here @var{address} may be any expression valid in the current working
6370 language (@pxref{Languages, working language}) that specifies a code
6371 address. In addition, as a convenience, @value{GDBN} extends the
6372 semantics of expressions used in locations to cover the situations
6373 that frequently happen during debugging. Here are the various forms
6377 @item @var{expression}
6378 Any expression valid in the current working language.
6380 @item @var{funcaddr}
6381 An address of a function or procedure derived from its name. In C,
6382 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6383 simply the function's name @var{function} (and actually a special case
6384 of a valid expression). In Pascal and Modula-2, this is
6385 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6386 (although the Pascal form also works).
6388 This form specifies the address of the function's first instruction,
6389 before the stack frame and arguments have been set up.
6391 @item '@var{filename}'::@var{funcaddr}
6392 Like @var{funcaddr} above, but also specifies the name of the source
6393 file explicitly. This is useful if the name of the function does not
6394 specify the function unambiguously, e.g., if there are several
6395 functions with identical names in different source files.
6402 @section Editing Source Files
6403 @cindex editing source files
6406 @kindex e @r{(@code{edit})}
6407 To edit the lines in a source file, use the @code{edit} command.
6408 The editing program of your choice
6409 is invoked with the current line set to
6410 the active line in the program.
6411 Alternatively, there are several ways to specify what part of the file you
6412 want to print if you want to see other parts of the program:
6415 @item edit @var{location}
6416 Edit the source file specified by @code{location}. Editing starts at
6417 that @var{location}, e.g., at the specified source line of the
6418 specified file. @xref{Specify Location}, for all the possible forms
6419 of the @var{location} argument; here are the forms of the @code{edit}
6420 command most commonly used:
6423 @item edit @var{number}
6424 Edit the current source file with @var{number} as the active line number.
6426 @item edit @var{function}
6427 Edit the file containing @var{function} at the beginning of its definition.
6432 @subsection Choosing your Editor
6433 You can customize @value{GDBN} to use any editor you want
6435 The only restriction is that your editor (say @code{ex}), recognizes the
6436 following command-line syntax:
6438 ex +@var{number} file
6440 The optional numeric value +@var{number} specifies the number of the line in
6441 the file where to start editing.}.
6442 By default, it is @file{@value{EDITOR}}, but you can change this
6443 by setting the environment variable @code{EDITOR} before using
6444 @value{GDBN}. For example, to configure @value{GDBN} to use the
6445 @code{vi} editor, you could use these commands with the @code{sh} shell:
6451 or in the @code{csh} shell,
6453 setenv EDITOR /usr/bin/vi
6458 @section Searching Source Files
6459 @cindex searching source files
6461 There are two commands for searching through the current source file for a
6466 @kindex forward-search
6467 @item forward-search @var{regexp}
6468 @itemx search @var{regexp}
6469 The command @samp{forward-search @var{regexp}} checks each line,
6470 starting with the one following the last line listed, for a match for
6471 @var{regexp}. It lists the line that is found. You can use the
6472 synonym @samp{search @var{regexp}} or abbreviate the command name as
6475 @kindex reverse-search
6476 @item reverse-search @var{regexp}
6477 The command @samp{reverse-search @var{regexp}} checks each line, starting
6478 with the one before the last line listed and going backward, for a match
6479 for @var{regexp}. It lists the line that is found. You can abbreviate
6480 this command as @code{rev}.
6484 @section Specifying Source Directories
6487 @cindex directories for source files
6488 Executable programs sometimes do not record the directories of the source
6489 files from which they were compiled, just the names. Even when they do,
6490 the directories could be moved between the compilation and your debugging
6491 session. @value{GDBN} has a list of directories to search for source files;
6492 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6493 it tries all the directories in the list, in the order they are present
6494 in the list, until it finds a file with the desired name.
6496 For example, suppose an executable references the file
6497 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6498 @file{/mnt/cross}. The file is first looked up literally; if this
6499 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6500 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6501 message is printed. @value{GDBN} does not look up the parts of the
6502 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6503 Likewise, the subdirectories of the source path are not searched: if
6504 the source path is @file{/mnt/cross}, and the binary refers to
6505 @file{foo.c}, @value{GDBN} would not find it under
6506 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6508 Plain file names, relative file names with leading directories, file
6509 names containing dots, etc.@: are all treated as described above; for
6510 instance, if the source path is @file{/mnt/cross}, and the source file
6511 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6512 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6513 that---@file{/mnt/cross/foo.c}.
6515 Note that the executable search path is @emph{not} used to locate the
6518 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6519 any information it has cached about where source files are found and where
6520 each line is in the file.
6524 When you start @value{GDBN}, its source path includes only @samp{cdir}
6525 and @samp{cwd}, in that order.
6526 To add other directories, use the @code{directory} command.
6528 The search path is used to find both program source files and @value{GDBN}
6529 script files (read using the @samp{-command} option and @samp{source} command).
6531 In addition to the source path, @value{GDBN} provides a set of commands
6532 that manage a list of source path substitution rules. A @dfn{substitution
6533 rule} specifies how to rewrite source directories stored in the program's
6534 debug information in case the sources were moved to a different
6535 directory between compilation and debugging. A rule is made of
6536 two strings, the first specifying what needs to be rewritten in
6537 the path, and the second specifying how it should be rewritten.
6538 In @ref{set substitute-path}, we name these two parts @var{from} and
6539 @var{to} respectively. @value{GDBN} does a simple string replacement
6540 of @var{from} with @var{to} at the start of the directory part of the
6541 source file name, and uses that result instead of the original file
6542 name to look up the sources.
6544 Using the previous example, suppose the @file{foo-1.0} tree has been
6545 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6546 @value{GDBN} to replace @file{/usr/src} in all source path names with
6547 @file{/mnt/cross}. The first lookup will then be
6548 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6549 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6550 substitution rule, use the @code{set substitute-path} command
6551 (@pxref{set substitute-path}).
6553 To avoid unexpected substitution results, a rule is applied only if the
6554 @var{from} part of the directory name ends at a directory separator.
6555 For instance, a rule substituting @file{/usr/source} into
6556 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6557 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6558 is applied only at the beginning of the directory name, this rule will
6559 not be applied to @file{/root/usr/source/baz.c} either.
6561 In many cases, you can achieve the same result using the @code{directory}
6562 command. However, @code{set substitute-path} can be more efficient in
6563 the case where the sources are organized in a complex tree with multiple
6564 subdirectories. With the @code{directory} command, you need to add each
6565 subdirectory of your project. If you moved the entire tree while
6566 preserving its internal organization, then @code{set substitute-path}
6567 allows you to direct the debugger to all the sources with one single
6570 @code{set substitute-path} is also more than just a shortcut command.
6571 The source path is only used if the file at the original location no
6572 longer exists. On the other hand, @code{set substitute-path} modifies
6573 the debugger behavior to look at the rewritten location instead. So, if
6574 for any reason a source file that is not relevant to your executable is
6575 located at the original location, a substitution rule is the only
6576 method available to point @value{GDBN} at the new location.
6578 @cindex @samp{--with-relocated-sources}
6579 @cindex default source path substitution
6580 You can configure a default source path substitution rule by
6581 configuring @value{GDBN} with the
6582 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6583 should be the name of a directory under @value{GDBN}'s configured
6584 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6585 directory names in debug information under @var{dir} will be adjusted
6586 automatically if the installed @value{GDBN} is moved to a new
6587 location. This is useful if @value{GDBN}, libraries or executables
6588 with debug information and corresponding source code are being moved
6592 @item directory @var{dirname} @dots{}
6593 @item dir @var{dirname} @dots{}
6594 Add directory @var{dirname} to the front of the source path. Several
6595 directory names may be given to this command, separated by @samp{:}
6596 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6597 part of absolute file names) or
6598 whitespace. You may specify a directory that is already in the source
6599 path; this moves it forward, so @value{GDBN} searches it sooner.
6603 @vindex $cdir@r{, convenience variable}
6604 @vindex $cwd@r{, convenience variable}
6605 @cindex compilation directory
6606 @cindex current directory
6607 @cindex working directory
6608 @cindex directory, current
6609 @cindex directory, compilation
6610 You can use the string @samp{$cdir} to refer to the compilation
6611 directory (if one is recorded), and @samp{$cwd} to refer to the current
6612 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6613 tracks the current working directory as it changes during your @value{GDBN}
6614 session, while the latter is immediately expanded to the current
6615 directory at the time you add an entry to the source path.
6618 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6620 @c RET-repeat for @code{directory} is explicitly disabled, but since
6621 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6623 @item show directories
6624 @kindex show directories
6625 Print the source path: show which directories it contains.
6627 @anchor{set substitute-path}
6628 @item set substitute-path @var{from} @var{to}
6629 @kindex set substitute-path
6630 Define a source path substitution rule, and add it at the end of the
6631 current list of existing substitution rules. If a rule with the same
6632 @var{from} was already defined, then the old rule is also deleted.
6634 For example, if the file @file{/foo/bar/baz.c} was moved to
6635 @file{/mnt/cross/baz.c}, then the command
6638 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6642 will tell @value{GDBN} to replace @samp{/usr/src} with
6643 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6644 @file{baz.c} even though it was moved.
6646 In the case when more than one substitution rule have been defined,
6647 the rules are evaluated one by one in the order where they have been
6648 defined. The first one matching, if any, is selected to perform
6651 For instance, if we had entered the following commands:
6654 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6655 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6659 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6660 @file{/mnt/include/defs.h} by using the first rule. However, it would
6661 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6662 @file{/mnt/src/lib/foo.c}.
6665 @item unset substitute-path [path]
6666 @kindex unset substitute-path
6667 If a path is specified, search the current list of substitution rules
6668 for a rule that would rewrite that path. Delete that rule if found.
6669 A warning is emitted by the debugger if no rule could be found.
6671 If no path is specified, then all substitution rules are deleted.
6673 @item show substitute-path [path]
6674 @kindex show substitute-path
6675 If a path is specified, then print the source path substitution rule
6676 which would rewrite that path, if any.
6678 If no path is specified, then print all existing source path substitution
6683 If your source path is cluttered with directories that are no longer of
6684 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6685 versions of source. You can correct the situation as follows:
6689 Use @code{directory} with no argument to reset the source path to its default value.
6692 Use @code{directory} with suitable arguments to reinstall the
6693 directories you want in the source path. You can add all the
6694 directories in one command.
6698 @section Source and Machine Code
6699 @cindex source line and its code address
6701 You can use the command @code{info line} to map source lines to program
6702 addresses (and vice versa), and the command @code{disassemble} to display
6703 a range of addresses as machine instructions. You can use the command
6704 @code{set disassemble-next-line} to set whether to disassemble next
6705 source line when execution stops. When run under @sc{gnu} Emacs
6706 mode, the @code{info line} command causes the arrow to point to the
6707 line specified. Also, @code{info line} prints addresses in symbolic form as
6712 @item info line @var{linespec}
6713 Print the starting and ending addresses of the compiled code for
6714 source line @var{linespec}. You can specify source lines in any of
6715 the ways documented in @ref{Specify Location}.
6718 For example, we can use @code{info line} to discover the location of
6719 the object code for the first line of function
6720 @code{m4_changequote}:
6722 @c FIXME: I think this example should also show the addresses in
6723 @c symbolic form, as they usually would be displayed.
6725 (@value{GDBP}) info line m4_changequote
6726 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6730 @cindex code address and its source line
6731 We can also inquire (using @code{*@var{addr}} as the form for
6732 @var{linespec}) what source line covers a particular address:
6734 (@value{GDBP}) info line *0x63ff
6735 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6738 @cindex @code{$_} and @code{info line}
6739 @cindex @code{x} command, default address
6740 @kindex x@r{(examine), and} info line
6741 After @code{info line}, the default address for the @code{x} command
6742 is changed to the starting address of the line, so that @samp{x/i} is
6743 sufficient to begin examining the machine code (@pxref{Memory,
6744 ,Examining Memory}). Also, this address is saved as the value of the
6745 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6750 @cindex assembly instructions
6751 @cindex instructions, assembly
6752 @cindex machine instructions
6753 @cindex listing machine instructions
6755 @itemx disassemble /m
6756 @itemx disassemble /r
6757 This specialized command dumps a range of memory as machine
6758 instructions. It can also print mixed source+disassembly by specifying
6759 the @code{/m} modifier and print the raw instructions in hex as well as
6760 in symbolic form by specifying the @code{/r}.
6761 The default memory range is the function surrounding the
6762 program counter of the selected frame. A single argument to this
6763 command is a program counter value; @value{GDBN} dumps the function
6764 surrounding this value. When two arguments are given, they should
6765 be separated by a comma, possibly surrounded by whitespace. The
6766 arguments specify a range of addresses to dump, in one of two forms:
6769 @item @var{start},@var{end}
6770 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6771 @item @var{start},+@var{length}
6772 the addresses from @var{start} (inclusive) to
6773 @code{@var{start}+@var{length}} (exclusive).
6777 When 2 arguments are specified, the name of the function is also
6778 printed (since there could be several functions in the given range).
6780 The argument(s) can be any expression yielding a numeric value, such as
6781 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6783 If the range of memory being disassembled contains current program counter,
6784 the instruction at that location is shown with a @code{=>} marker.
6787 The following example shows the disassembly of a range of addresses of
6788 HP PA-RISC 2.0 code:
6791 (@value{GDBP}) disas 0x32c4, 0x32e4
6792 Dump of assembler code from 0x32c4 to 0x32e4:
6793 0x32c4 <main+204>: addil 0,dp
6794 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6795 0x32cc <main+212>: ldil 0x3000,r31
6796 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6797 0x32d4 <main+220>: ldo 0(r31),rp
6798 0x32d8 <main+224>: addil -0x800,dp
6799 0x32dc <main+228>: ldo 0x588(r1),r26
6800 0x32e0 <main+232>: ldil 0x3000,r31
6801 End of assembler dump.
6804 Here is an example showing mixed source+assembly for Intel x86, when the
6805 program is stopped just after function prologue:
6808 (@value{GDBP}) disas /m main
6809 Dump of assembler code for function main:
6811 0x08048330 <+0>: push %ebp
6812 0x08048331 <+1>: mov %esp,%ebp
6813 0x08048333 <+3>: sub $0x8,%esp
6814 0x08048336 <+6>: and $0xfffffff0,%esp
6815 0x08048339 <+9>: sub $0x10,%esp
6817 6 printf ("Hello.\n");
6818 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6819 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6823 0x08048348 <+24>: mov $0x0,%eax
6824 0x0804834d <+29>: leave
6825 0x0804834e <+30>: ret
6827 End of assembler dump.
6830 Here is another example showing raw instructions in hex for AMD x86-64,
6833 (gdb) disas /r 0x400281,+10
6834 Dump of assembler code from 0x400281 to 0x40028b:
6835 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6836 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6837 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6838 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6839 End of assembler dump.
6842 Some architectures have more than one commonly-used set of instruction
6843 mnemonics or other syntax.
6845 For programs that were dynamically linked and use shared libraries,
6846 instructions that call functions or branch to locations in the shared
6847 libraries might show a seemingly bogus location---it's actually a
6848 location of the relocation table. On some architectures, @value{GDBN}
6849 might be able to resolve these to actual function names.
6852 @kindex set disassembly-flavor
6853 @cindex Intel disassembly flavor
6854 @cindex AT&T disassembly flavor
6855 @item set disassembly-flavor @var{instruction-set}
6856 Select the instruction set to use when disassembling the
6857 program via the @code{disassemble} or @code{x/i} commands.
6859 Currently this command is only defined for the Intel x86 family. You
6860 can set @var{instruction-set} to either @code{intel} or @code{att}.
6861 The default is @code{att}, the AT&T flavor used by default by Unix
6862 assemblers for x86-based targets.
6864 @kindex show disassembly-flavor
6865 @item show disassembly-flavor
6866 Show the current setting of the disassembly flavor.
6870 @kindex set disassemble-next-line
6871 @kindex show disassemble-next-line
6872 @item set disassemble-next-line
6873 @itemx show disassemble-next-line
6874 Control whether or not @value{GDBN} will disassemble the next source
6875 line or instruction when execution stops. If ON, @value{GDBN} will
6876 display disassembly of the next source line when execution of the
6877 program being debugged stops. This is @emph{in addition} to
6878 displaying the source line itself, which @value{GDBN} always does if
6879 possible. If the next source line cannot be displayed for some reason
6880 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6881 info in the debug info), @value{GDBN} will display disassembly of the
6882 next @emph{instruction} instead of showing the next source line. If
6883 AUTO, @value{GDBN} will display disassembly of next instruction only
6884 if the source line cannot be displayed. This setting causes
6885 @value{GDBN} to display some feedback when you step through a function
6886 with no line info or whose source file is unavailable. The default is
6887 OFF, which means never display the disassembly of the next line or
6893 @chapter Examining Data
6895 @cindex printing data
6896 @cindex examining data
6899 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6900 @c document because it is nonstandard... Under Epoch it displays in a
6901 @c different window or something like that.
6902 The usual way to examine data in your program is with the @code{print}
6903 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6904 evaluates and prints the value of an expression of the language your
6905 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6906 Different Languages}). It may also print the expression using a
6907 Python-based pretty-printer (@pxref{Pretty Printing}).
6910 @item print @var{expr}
6911 @itemx print /@var{f} @var{expr}
6912 @var{expr} is an expression (in the source language). By default the
6913 value of @var{expr} is printed in a format appropriate to its data type;
6914 you can choose a different format by specifying @samp{/@var{f}}, where
6915 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6919 @itemx print /@var{f}
6920 @cindex reprint the last value
6921 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6922 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6923 conveniently inspect the same value in an alternative format.
6926 A more low-level way of examining data is with the @code{x} command.
6927 It examines data in memory at a specified address and prints it in a
6928 specified format. @xref{Memory, ,Examining Memory}.
6930 If you are interested in information about types, or about how the
6931 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6932 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6936 * Expressions:: Expressions
6937 * Ambiguous Expressions:: Ambiguous Expressions
6938 * Variables:: Program variables
6939 * Arrays:: Artificial arrays
6940 * Output Formats:: Output formats
6941 * Memory:: Examining memory
6942 * Auto Display:: Automatic display
6943 * Print Settings:: Print settings
6944 * Pretty Printing:: Python pretty printing
6945 * Value History:: Value history
6946 * Convenience Vars:: Convenience variables
6947 * Registers:: Registers
6948 * Floating Point Hardware:: Floating point hardware
6949 * Vector Unit:: Vector Unit
6950 * OS Information:: Auxiliary data provided by operating system
6951 * Memory Region Attributes:: Memory region attributes
6952 * Dump/Restore Files:: Copy between memory and a file
6953 * Core File Generation:: Cause a program dump its core
6954 * Character Sets:: Debugging programs that use a different
6955 character set than GDB does
6956 * Caching Remote Data:: Data caching for remote targets
6957 * Searching Memory:: Searching memory for a sequence of bytes
6961 @section Expressions
6964 @code{print} and many other @value{GDBN} commands accept an expression and
6965 compute its value. Any kind of constant, variable or operator defined
6966 by the programming language you are using is valid in an expression in
6967 @value{GDBN}. This includes conditional expressions, function calls,
6968 casts, and string constants. It also includes preprocessor macros, if
6969 you compiled your program to include this information; see
6972 @cindex arrays in expressions
6973 @value{GDBN} supports array constants in expressions input by
6974 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6975 you can use the command @code{print @{1, 2, 3@}} to create an array
6976 of three integers. If you pass an array to a function or assign it
6977 to a program variable, @value{GDBN} copies the array to memory that
6978 is @code{malloc}ed in the target program.
6980 Because C is so widespread, most of the expressions shown in examples in
6981 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6982 Languages}, for information on how to use expressions in other
6985 In this section, we discuss operators that you can use in @value{GDBN}
6986 expressions regardless of your programming language.
6988 @cindex casts, in expressions
6989 Casts are supported in all languages, not just in C, because it is so
6990 useful to cast a number into a pointer in order to examine a structure
6991 at that address in memory.
6992 @c FIXME: casts supported---Mod2 true?
6994 @value{GDBN} supports these operators, in addition to those common
6995 to programming languages:
6999 @samp{@@} is a binary operator for treating parts of memory as arrays.
7000 @xref{Arrays, ,Artificial Arrays}, for more information.
7003 @samp{::} allows you to specify a variable in terms of the file or
7004 function where it is defined. @xref{Variables, ,Program Variables}.
7006 @cindex @{@var{type}@}
7007 @cindex type casting memory
7008 @cindex memory, viewing as typed object
7009 @cindex casts, to view memory
7010 @item @{@var{type}@} @var{addr}
7011 Refers to an object of type @var{type} stored at address @var{addr} in
7012 memory. @var{addr} may be any expression whose value is an integer or
7013 pointer (but parentheses are required around binary operators, just as in
7014 a cast). This construct is allowed regardless of what kind of data is
7015 normally supposed to reside at @var{addr}.
7018 @node Ambiguous Expressions
7019 @section Ambiguous Expressions
7020 @cindex ambiguous expressions
7022 Expressions can sometimes contain some ambiguous elements. For instance,
7023 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7024 a single function name to be defined several times, for application in
7025 different contexts. This is called @dfn{overloading}. Another example
7026 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7027 templates and is typically instantiated several times, resulting in
7028 the same function name being defined in different contexts.
7030 In some cases and depending on the language, it is possible to adjust
7031 the expression to remove the ambiguity. For instance in C@t{++}, you
7032 can specify the signature of the function you want to break on, as in
7033 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7034 qualified name of your function often makes the expression unambiguous
7037 When an ambiguity that needs to be resolved is detected, the debugger
7038 has the capability to display a menu of numbered choices for each
7039 possibility, and then waits for the selection with the prompt @samp{>}.
7040 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7041 aborts the current command. If the command in which the expression was
7042 used allows more than one choice to be selected, the next option in the
7043 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7046 For example, the following session excerpt shows an attempt to set a
7047 breakpoint at the overloaded symbol @code{String::after}.
7048 We choose three particular definitions of that function name:
7050 @c FIXME! This is likely to change to show arg type lists, at least
7053 (@value{GDBP}) b String::after
7056 [2] file:String.cc; line number:867
7057 [3] file:String.cc; line number:860
7058 [4] file:String.cc; line number:875
7059 [5] file:String.cc; line number:853
7060 [6] file:String.cc; line number:846
7061 [7] file:String.cc; line number:735
7063 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7064 Breakpoint 2 at 0xb344: file String.cc, line 875.
7065 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7066 Multiple breakpoints were set.
7067 Use the "delete" command to delete unwanted
7074 @kindex set multiple-symbols
7075 @item set multiple-symbols @var{mode}
7076 @cindex multiple-symbols menu
7078 This option allows you to adjust the debugger behavior when an expression
7081 By default, @var{mode} is set to @code{all}. If the command with which
7082 the expression is used allows more than one choice, then @value{GDBN}
7083 automatically selects all possible choices. For instance, inserting
7084 a breakpoint on a function using an ambiguous name results in a breakpoint
7085 inserted on each possible match. However, if a unique choice must be made,
7086 then @value{GDBN} uses the menu to help you disambiguate the expression.
7087 For instance, printing the address of an overloaded function will result
7088 in the use of the menu.
7090 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7091 when an ambiguity is detected.
7093 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7094 an error due to the ambiguity and the command is aborted.
7096 @kindex show multiple-symbols
7097 @item show multiple-symbols
7098 Show the current value of the @code{multiple-symbols} setting.
7102 @section Program Variables
7104 The most common kind of expression to use is the name of a variable
7107 Variables in expressions are understood in the selected stack frame
7108 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7112 global (or file-static)
7119 visible according to the scope rules of the
7120 programming language from the point of execution in that frame
7123 @noindent This means that in the function
7138 you can examine and use the variable @code{a} whenever your program is
7139 executing within the function @code{foo}, but you can only use or
7140 examine the variable @code{b} while your program is executing inside
7141 the block where @code{b} is declared.
7143 @cindex variable name conflict
7144 There is an exception: you can refer to a variable or function whose
7145 scope is a single source file even if the current execution point is not
7146 in this file. But it is possible to have more than one such variable or
7147 function with the same name (in different source files). If that
7148 happens, referring to that name has unpredictable effects. If you wish,
7149 you can specify a static variable in a particular function or file,
7150 using the colon-colon (@code{::}) notation:
7152 @cindex colon-colon, context for variables/functions
7154 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7155 @cindex @code{::}, context for variables/functions
7158 @var{file}::@var{variable}
7159 @var{function}::@var{variable}
7163 Here @var{file} or @var{function} is the name of the context for the
7164 static @var{variable}. In the case of file names, you can use quotes to
7165 make sure @value{GDBN} parses the file name as a single word---for example,
7166 to print a global value of @code{x} defined in @file{f2.c}:
7169 (@value{GDBP}) p 'f2.c'::x
7172 @cindex C@t{++} scope resolution
7173 This use of @samp{::} is very rarely in conflict with the very similar
7174 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7175 scope resolution operator in @value{GDBN} expressions.
7176 @c FIXME: Um, so what happens in one of those rare cases where it's in
7179 @cindex wrong values
7180 @cindex variable values, wrong
7181 @cindex function entry/exit, wrong values of variables
7182 @cindex optimized code, wrong values of variables
7184 @emph{Warning:} Occasionally, a local variable may appear to have the
7185 wrong value at certain points in a function---just after entry to a new
7186 scope, and just before exit.
7188 You may see this problem when you are stepping by machine instructions.
7189 This is because, on most machines, it takes more than one instruction to
7190 set up a stack frame (including local variable definitions); if you are
7191 stepping by machine instructions, variables may appear to have the wrong
7192 values until the stack frame is completely built. On exit, it usually
7193 also takes more than one machine instruction to destroy a stack frame;
7194 after you begin stepping through that group of instructions, local
7195 variable definitions may be gone.
7197 This may also happen when the compiler does significant optimizations.
7198 To be sure of always seeing accurate values, turn off all optimization
7201 @cindex ``No symbol "foo" in current context''
7202 Another possible effect of compiler optimizations is to optimize
7203 unused variables out of existence, or assign variables to registers (as
7204 opposed to memory addresses). Depending on the support for such cases
7205 offered by the debug info format used by the compiler, @value{GDBN}
7206 might not be able to display values for such local variables. If that
7207 happens, @value{GDBN} will print a message like this:
7210 No symbol "foo" in current context.
7213 To solve such problems, either recompile without optimizations, or use a
7214 different debug info format, if the compiler supports several such
7215 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7216 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7217 produces debug info in a format that is superior to formats such as
7218 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7219 an effective form for debug info. @xref{Debugging Options,,Options
7220 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7221 Compiler Collection (GCC)}.
7222 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7223 that are best suited to C@t{++} programs.
7225 If you ask to print an object whose contents are unknown to
7226 @value{GDBN}, e.g., because its data type is not completely specified
7227 by the debug information, @value{GDBN} will say @samp{<incomplete
7228 type>}. @xref{Symbols, incomplete type}, for more about this.
7230 Strings are identified as arrays of @code{char} values without specified
7231 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7232 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7233 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7234 defines literal string type @code{"char"} as @code{char} without a sign.
7239 signed char var1[] = "A";
7242 You get during debugging
7247 $2 = @{65 'A', 0 '\0'@}
7251 @section Artificial Arrays
7253 @cindex artificial array
7255 @kindex @@@r{, referencing memory as an array}
7256 It is often useful to print out several successive objects of the
7257 same type in memory; a section of an array, or an array of
7258 dynamically determined size for which only a pointer exists in the
7261 You can do this by referring to a contiguous span of memory as an
7262 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7263 operand of @samp{@@} should be the first element of the desired array
7264 and be an individual object. The right operand should be the desired length
7265 of the array. The result is an array value whose elements are all of
7266 the type of the left argument. The first element is actually the left
7267 argument; the second element comes from bytes of memory immediately
7268 following those that hold the first element, and so on. Here is an
7269 example. If a program says
7272 int *array = (int *) malloc (len * sizeof (int));
7276 you can print the contents of @code{array} with
7282 The left operand of @samp{@@} must reside in memory. Array values made
7283 with @samp{@@} in this way behave just like other arrays in terms of
7284 subscripting, and are coerced to pointers when used in expressions.
7285 Artificial arrays most often appear in expressions via the value history
7286 (@pxref{Value History, ,Value History}), after printing one out.
7288 Another way to create an artificial array is to use a cast.
7289 This re-interprets a value as if it were an array.
7290 The value need not be in memory:
7292 (@value{GDBP}) p/x (short[2])0x12345678
7293 $1 = @{0x1234, 0x5678@}
7296 As a convenience, if you leave the array length out (as in
7297 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7298 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7300 (@value{GDBP}) p/x (short[])0x12345678
7301 $2 = @{0x1234, 0x5678@}
7304 Sometimes the artificial array mechanism is not quite enough; in
7305 moderately complex data structures, the elements of interest may not
7306 actually be adjacent---for example, if you are interested in the values
7307 of pointers in an array. One useful work-around in this situation is
7308 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7309 Variables}) as a counter in an expression that prints the first
7310 interesting value, and then repeat that expression via @key{RET}. For
7311 instance, suppose you have an array @code{dtab} of pointers to
7312 structures, and you are interested in the values of a field @code{fv}
7313 in each structure. Here is an example of what you might type:
7323 @node Output Formats
7324 @section Output Formats
7326 @cindex formatted output
7327 @cindex output formats
7328 By default, @value{GDBN} prints a value according to its data type. Sometimes
7329 this is not what you want. For example, you might want to print a number
7330 in hex, or a pointer in decimal. Or you might want to view data in memory
7331 at a certain address as a character string or as an instruction. To do
7332 these things, specify an @dfn{output format} when you print a value.
7334 The simplest use of output formats is to say how to print a value
7335 already computed. This is done by starting the arguments of the
7336 @code{print} command with a slash and a format letter. The format
7337 letters supported are:
7341 Regard the bits of the value as an integer, and print the integer in
7345 Print as integer in signed decimal.
7348 Print as integer in unsigned decimal.
7351 Print as integer in octal.
7354 Print as integer in binary. The letter @samp{t} stands for ``two''.
7355 @footnote{@samp{b} cannot be used because these format letters are also
7356 used with the @code{x} command, where @samp{b} stands for ``byte'';
7357 see @ref{Memory,,Examining Memory}.}
7360 @cindex unknown address, locating
7361 @cindex locate address
7362 Print as an address, both absolute in hexadecimal and as an offset from
7363 the nearest preceding symbol. You can use this format used to discover
7364 where (in what function) an unknown address is located:
7367 (@value{GDBP}) p/a 0x54320
7368 $3 = 0x54320 <_initialize_vx+396>
7372 The command @code{info symbol 0x54320} yields similar results.
7373 @xref{Symbols, info symbol}.
7376 Regard as an integer and print it as a character constant. This
7377 prints both the numerical value and its character representation. The
7378 character representation is replaced with the octal escape @samp{\nnn}
7379 for characters outside the 7-bit @sc{ascii} range.
7381 Without this format, @value{GDBN} displays @code{char},
7382 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7383 constants. Single-byte members of vectors are displayed as integer
7387 Regard the bits of the value as a floating point number and print
7388 using typical floating point syntax.
7391 @cindex printing strings
7392 @cindex printing byte arrays
7393 Regard as a string, if possible. With this format, pointers to single-byte
7394 data are displayed as null-terminated strings and arrays of single-byte data
7395 are displayed as fixed-length strings. Other values are displayed in their
7398 Without this format, @value{GDBN} displays pointers to and arrays of
7399 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7400 strings. Single-byte members of a vector are displayed as an integer
7404 @cindex raw printing
7405 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7406 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7407 Printing}). This typically results in a higher-level display of the
7408 value's contents. The @samp{r} format bypasses any Python
7409 pretty-printer which might exist.
7412 For example, to print the program counter in hex (@pxref{Registers}), type
7419 Note that no space is required before the slash; this is because command
7420 names in @value{GDBN} cannot contain a slash.
7422 To reprint the last value in the value history with a different format,
7423 you can use the @code{print} command with just a format and no
7424 expression. For example, @samp{p/x} reprints the last value in hex.
7427 @section Examining Memory
7429 You can use the command @code{x} (for ``examine'') to examine memory in
7430 any of several formats, independently of your program's data types.
7432 @cindex examining memory
7434 @kindex x @r{(examine memory)}
7435 @item x/@var{nfu} @var{addr}
7438 Use the @code{x} command to examine memory.
7441 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7442 much memory to display and how to format it; @var{addr} is an
7443 expression giving the address where you want to start displaying memory.
7444 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7445 Several commands set convenient defaults for @var{addr}.
7448 @item @var{n}, the repeat count
7449 The repeat count is a decimal integer; the default is 1. It specifies
7450 how much memory (counting by units @var{u}) to display.
7451 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7454 @item @var{f}, the display format
7455 The display format is one of the formats used by @code{print}
7456 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7457 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7458 The default is @samp{x} (hexadecimal) initially. The default changes
7459 each time you use either @code{x} or @code{print}.
7461 @item @var{u}, the unit size
7462 The unit size is any of
7468 Halfwords (two bytes).
7470 Words (four bytes). This is the initial default.
7472 Giant words (eight bytes).
7475 Each time you specify a unit size with @code{x}, that size becomes the
7476 default unit the next time you use @code{x}. For the @samp{i} format,
7477 the unit size is ignored and is normally not written. For the @samp{s} format,
7478 the unit size defaults to @samp{b}, unless it is explicitly given.
7479 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7480 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7481 Note that the results depend on the programming language of the
7482 current compilation unit. If the language is C, the @samp{s}
7483 modifier will use the UTF-16 encoding while @samp{w} will use
7484 UTF-32. The encoding is set by the programming language and cannot
7487 @item @var{addr}, starting display address
7488 @var{addr} is the address where you want @value{GDBN} to begin displaying
7489 memory. The expression need not have a pointer value (though it may);
7490 it is always interpreted as an integer address of a byte of memory.
7491 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7492 @var{addr} is usually just after the last address examined---but several
7493 other commands also set the default address: @code{info breakpoints} (to
7494 the address of the last breakpoint listed), @code{info line} (to the
7495 starting address of a line), and @code{print} (if you use it to display
7496 a value from memory).
7499 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7500 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7501 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7502 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7503 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7505 Since the letters indicating unit sizes are all distinct from the
7506 letters specifying output formats, you do not have to remember whether
7507 unit size or format comes first; either order works. The output
7508 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7509 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7511 Even though the unit size @var{u} is ignored for the formats @samp{s}
7512 and @samp{i}, you might still want to use a count @var{n}; for example,
7513 @samp{3i} specifies that you want to see three machine instructions,
7514 including any operands. For convenience, especially when used with
7515 the @code{display} command, the @samp{i} format also prints branch delay
7516 slot instructions, if any, beyond the count specified, which immediately
7517 follow the last instruction that is within the count. The command
7518 @code{disassemble} gives an alternative way of inspecting machine
7519 instructions; see @ref{Machine Code,,Source and Machine Code}.
7521 All the defaults for the arguments to @code{x} are designed to make it
7522 easy to continue scanning memory with minimal specifications each time
7523 you use @code{x}. For example, after you have inspected three machine
7524 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7525 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7526 the repeat count @var{n} is used again; the other arguments default as
7527 for successive uses of @code{x}.
7529 When examining machine instructions, the instruction at current program
7530 counter is shown with a @code{=>} marker. For example:
7533 (@value{GDBP}) x/5i $pc-6
7534 0x804837f <main+11>: mov %esp,%ebp
7535 0x8048381 <main+13>: push %ecx
7536 0x8048382 <main+14>: sub $0x4,%esp
7537 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7538 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7541 @cindex @code{$_}, @code{$__}, and value history
7542 The addresses and contents printed by the @code{x} command are not saved
7543 in the value history because there is often too much of them and they
7544 would get in the way. Instead, @value{GDBN} makes these values available for
7545 subsequent use in expressions as values of the convenience variables
7546 @code{$_} and @code{$__}. After an @code{x} command, the last address
7547 examined is available for use in expressions in the convenience variable
7548 @code{$_}. The contents of that address, as examined, are available in
7549 the convenience variable @code{$__}.
7551 If the @code{x} command has a repeat count, the address and contents saved
7552 are from the last memory unit printed; this is not the same as the last
7553 address printed if several units were printed on the last line of output.
7555 @cindex remote memory comparison
7556 @cindex verify remote memory image
7557 When you are debugging a program running on a remote target machine
7558 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7559 remote machine's memory against the executable file you downloaded to
7560 the target. The @code{compare-sections} command is provided for such
7564 @kindex compare-sections
7565 @item compare-sections @r{[}@var{section-name}@r{]}
7566 Compare the data of a loadable section @var{section-name} in the
7567 executable file of the program being debugged with the same section in
7568 the remote machine's memory, and report any mismatches. With no
7569 arguments, compares all loadable sections. This command's
7570 availability depends on the target's support for the @code{"qCRC"}
7575 @section Automatic Display
7576 @cindex automatic display
7577 @cindex display of expressions
7579 If you find that you want to print the value of an expression frequently
7580 (to see how it changes), you might want to add it to the @dfn{automatic
7581 display list} so that @value{GDBN} prints its value each time your program stops.
7582 Each expression added to the list is given a number to identify it;
7583 to remove an expression from the list, you specify that number.
7584 The automatic display looks like this:
7588 3: bar[5] = (struct hack *) 0x3804
7592 This display shows item numbers, expressions and their current values. As with
7593 displays you request manually using @code{x} or @code{print}, you can
7594 specify the output format you prefer; in fact, @code{display} decides
7595 whether to use @code{print} or @code{x} depending your format
7596 specification---it uses @code{x} if you specify either the @samp{i}
7597 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7601 @item display @var{expr}
7602 Add the expression @var{expr} to the list of expressions to display
7603 each time your program stops. @xref{Expressions, ,Expressions}.
7605 @code{display} does not repeat if you press @key{RET} again after using it.
7607 @item display/@var{fmt} @var{expr}
7608 For @var{fmt} specifying only a display format and not a size or
7609 count, add the expression @var{expr} to the auto-display list but
7610 arrange to display it each time in the specified format @var{fmt}.
7611 @xref{Output Formats,,Output Formats}.
7613 @item display/@var{fmt} @var{addr}
7614 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7615 number of units, add the expression @var{addr} as a memory address to
7616 be examined each time your program stops. Examining means in effect
7617 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7620 For example, @samp{display/i $pc} can be helpful, to see the machine
7621 instruction about to be executed each time execution stops (@samp{$pc}
7622 is a common name for the program counter; @pxref{Registers, ,Registers}).
7625 @kindex delete display
7627 @item undisplay @var{dnums}@dots{}
7628 @itemx delete display @var{dnums}@dots{}
7629 Remove item numbers @var{dnums} from the list of expressions to display.
7631 @code{undisplay} does not repeat if you press @key{RET} after using it.
7632 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7634 @kindex disable display
7635 @item disable display @var{dnums}@dots{}
7636 Disable the display of item numbers @var{dnums}. A disabled display
7637 item is not printed automatically, but is not forgotten. It may be
7638 enabled again later.
7640 @kindex enable display
7641 @item enable display @var{dnums}@dots{}
7642 Enable display of item numbers @var{dnums}. It becomes effective once
7643 again in auto display of its expression, until you specify otherwise.
7646 Display the current values of the expressions on the list, just as is
7647 done when your program stops.
7649 @kindex info display
7651 Print the list of expressions previously set up to display
7652 automatically, each one with its item number, but without showing the
7653 values. This includes disabled expressions, which are marked as such.
7654 It also includes expressions which would not be displayed right now
7655 because they refer to automatic variables not currently available.
7658 @cindex display disabled out of scope
7659 If a display expression refers to local variables, then it does not make
7660 sense outside the lexical context for which it was set up. Such an
7661 expression is disabled when execution enters a context where one of its
7662 variables is not defined. For example, if you give the command
7663 @code{display last_char} while inside a function with an argument
7664 @code{last_char}, @value{GDBN} displays this argument while your program
7665 continues to stop inside that function. When it stops elsewhere---where
7666 there is no variable @code{last_char}---the display is disabled
7667 automatically. The next time your program stops where @code{last_char}
7668 is meaningful, you can enable the display expression once again.
7670 @node Print Settings
7671 @section Print Settings
7673 @cindex format options
7674 @cindex print settings
7675 @value{GDBN} provides the following ways to control how arrays, structures,
7676 and symbols are printed.
7679 These settings are useful for debugging programs in any language:
7683 @item set print address
7684 @itemx set print address on
7685 @cindex print/don't print memory addresses
7686 @value{GDBN} prints memory addresses showing the location of stack
7687 traces, structure values, pointer values, breakpoints, and so forth,
7688 even when it also displays the contents of those addresses. The default
7689 is @code{on}. For example, this is what a stack frame display looks like with
7690 @code{set print address on}:
7695 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7697 530 if (lquote != def_lquote)
7701 @item set print address off
7702 Do not print addresses when displaying their contents. For example,
7703 this is the same stack frame displayed with @code{set print address off}:
7707 (@value{GDBP}) set print addr off
7709 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7710 530 if (lquote != def_lquote)
7714 You can use @samp{set print address off} to eliminate all machine
7715 dependent displays from the @value{GDBN} interface. For example, with
7716 @code{print address off}, you should get the same text for backtraces on
7717 all machines---whether or not they involve pointer arguments.
7720 @item show print address
7721 Show whether or not addresses are to be printed.
7724 When @value{GDBN} prints a symbolic address, it normally prints the
7725 closest earlier symbol plus an offset. If that symbol does not uniquely
7726 identify the address (for example, it is a name whose scope is a single
7727 source file), you may need to clarify. One way to do this is with
7728 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7729 you can set @value{GDBN} to print the source file and line number when
7730 it prints a symbolic address:
7733 @item set print symbol-filename on
7734 @cindex source file and line of a symbol
7735 @cindex symbol, source file and line
7736 Tell @value{GDBN} to print the source file name and line number of a
7737 symbol in the symbolic form of an address.
7739 @item set print symbol-filename off
7740 Do not print source file name and line number of a symbol. This is the
7743 @item show print symbol-filename
7744 Show whether or not @value{GDBN} will print the source file name and
7745 line number of a symbol in the symbolic form of an address.
7748 Another situation where it is helpful to show symbol filenames and line
7749 numbers is when disassembling code; @value{GDBN} shows you the line
7750 number and source file that corresponds to each instruction.
7752 Also, you may wish to see the symbolic form only if the address being
7753 printed is reasonably close to the closest earlier symbol:
7756 @item set print max-symbolic-offset @var{max-offset}
7757 @cindex maximum value for offset of closest symbol
7758 Tell @value{GDBN} to only display the symbolic form of an address if the
7759 offset between the closest earlier symbol and the address is less than
7760 @var{max-offset}. The default is 0, which tells @value{GDBN}
7761 to always print the symbolic form of an address if any symbol precedes it.
7763 @item show print max-symbolic-offset
7764 Ask how large the maximum offset is that @value{GDBN} prints in a
7768 @cindex wild pointer, interpreting
7769 @cindex pointer, finding referent
7770 If you have a pointer and you are not sure where it points, try
7771 @samp{set print symbol-filename on}. Then you can determine the name
7772 and source file location of the variable where it points, using
7773 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7774 For example, here @value{GDBN} shows that a variable @code{ptt} points
7775 at another variable @code{t}, defined in @file{hi2.c}:
7778 (@value{GDBP}) set print symbol-filename on
7779 (@value{GDBP}) p/a ptt
7780 $4 = 0xe008 <t in hi2.c>
7784 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7785 does not show the symbol name and filename of the referent, even with
7786 the appropriate @code{set print} options turned on.
7789 Other settings control how different kinds of objects are printed:
7792 @item set print array
7793 @itemx set print array on
7794 @cindex pretty print arrays
7795 Pretty print arrays. This format is more convenient to read,
7796 but uses more space. The default is off.
7798 @item set print array off
7799 Return to compressed format for arrays.
7801 @item show print array
7802 Show whether compressed or pretty format is selected for displaying
7805 @cindex print array indexes
7806 @item set print array-indexes
7807 @itemx set print array-indexes on
7808 Print the index of each element when displaying arrays. May be more
7809 convenient to locate a given element in the array or quickly find the
7810 index of a given element in that printed array. The default is off.
7812 @item set print array-indexes off
7813 Stop printing element indexes when displaying arrays.
7815 @item show print array-indexes
7816 Show whether the index of each element is printed when displaying
7819 @item set print elements @var{number-of-elements}
7820 @cindex number of array elements to print
7821 @cindex limit on number of printed array elements
7822 Set a limit on how many elements of an array @value{GDBN} will print.
7823 If @value{GDBN} is printing a large array, it stops printing after it has
7824 printed the number of elements set by the @code{set print elements} command.
7825 This limit also applies to the display of strings.
7826 When @value{GDBN} starts, this limit is set to 200.
7827 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7829 @item show print elements
7830 Display the number of elements of a large array that @value{GDBN} will print.
7831 If the number is 0, then the printing is unlimited.
7833 @item set print frame-arguments @var{value}
7834 @kindex set print frame-arguments
7835 @cindex printing frame argument values
7836 @cindex print all frame argument values
7837 @cindex print frame argument values for scalars only
7838 @cindex do not print frame argument values
7839 This command allows to control how the values of arguments are printed
7840 when the debugger prints a frame (@pxref{Frames}). The possible
7845 The values of all arguments are printed.
7848 Print the value of an argument only if it is a scalar. The value of more
7849 complex arguments such as arrays, structures, unions, etc, is replaced
7850 by @code{@dots{}}. This is the default. Here is an example where
7851 only scalar arguments are shown:
7854 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7859 None of the argument values are printed. Instead, the value of each argument
7860 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7863 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7868 By default, only scalar arguments are printed. This command can be used
7869 to configure the debugger to print the value of all arguments, regardless
7870 of their type. However, it is often advantageous to not print the value
7871 of more complex parameters. For instance, it reduces the amount of
7872 information printed in each frame, making the backtrace more readable.
7873 Also, it improves performance when displaying Ada frames, because
7874 the computation of large arguments can sometimes be CPU-intensive,
7875 especially in large applications. Setting @code{print frame-arguments}
7876 to @code{scalars} (the default) or @code{none} avoids this computation,
7877 thus speeding up the display of each Ada frame.
7879 @item show print frame-arguments
7880 Show how the value of arguments should be displayed when printing a frame.
7882 @item set print repeats
7883 @cindex repeated array elements
7884 Set the threshold for suppressing display of repeated array
7885 elements. When the number of consecutive identical elements of an
7886 array exceeds the threshold, @value{GDBN} prints the string
7887 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7888 identical repetitions, instead of displaying the identical elements
7889 themselves. Setting the threshold to zero will cause all elements to
7890 be individually printed. The default threshold is 10.
7892 @item show print repeats
7893 Display the current threshold for printing repeated identical
7896 @item set print null-stop
7897 @cindex @sc{null} elements in arrays
7898 Cause @value{GDBN} to stop printing the characters of an array when the first
7899 @sc{null} is encountered. This is useful when large arrays actually
7900 contain only short strings.
7903 @item show print null-stop
7904 Show whether @value{GDBN} stops printing an array on the first
7905 @sc{null} character.
7907 @item set print pretty on
7908 @cindex print structures in indented form
7909 @cindex indentation in structure display
7910 Cause @value{GDBN} to print structures in an indented format with one member
7911 per line, like this:
7926 @item set print pretty off
7927 Cause @value{GDBN} to print structures in a compact format, like this:
7931 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7932 meat = 0x54 "Pork"@}
7937 This is the default format.
7939 @item show print pretty
7940 Show which format @value{GDBN} is using to print structures.
7942 @item set print sevenbit-strings on
7943 @cindex eight-bit characters in strings
7944 @cindex octal escapes in strings
7945 Print using only seven-bit characters; if this option is set,
7946 @value{GDBN} displays any eight-bit characters (in strings or
7947 character values) using the notation @code{\}@var{nnn}. This setting is
7948 best if you are working in English (@sc{ascii}) and you use the
7949 high-order bit of characters as a marker or ``meta'' bit.
7951 @item set print sevenbit-strings off
7952 Print full eight-bit characters. This allows the use of more
7953 international character sets, and is the default.
7955 @item show print sevenbit-strings
7956 Show whether or not @value{GDBN} is printing only seven-bit characters.
7958 @item set print union on
7959 @cindex unions in structures, printing
7960 Tell @value{GDBN} to print unions which are contained in structures
7961 and other unions. This is the default setting.
7963 @item set print union off
7964 Tell @value{GDBN} not to print unions which are contained in
7965 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7968 @item show print union
7969 Ask @value{GDBN} whether or not it will print unions which are contained in
7970 structures and other unions.
7972 For example, given the declarations
7975 typedef enum @{Tree, Bug@} Species;
7976 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7977 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7988 struct thing foo = @{Tree, @{Acorn@}@};
7992 with @code{set print union on} in effect @samp{p foo} would print
7995 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7999 and with @code{set print union off} in effect it would print
8002 $1 = @{it = Tree, form = @{...@}@}
8006 @code{set print union} affects programs written in C-like languages
8012 These settings are of interest when debugging C@t{++} programs:
8015 @cindex demangling C@t{++} names
8016 @item set print demangle
8017 @itemx set print demangle on
8018 Print C@t{++} names in their source form rather than in the encoded
8019 (``mangled'') form passed to the assembler and linker for type-safe
8020 linkage. The default is on.
8022 @item show print demangle
8023 Show whether C@t{++} names are printed in mangled or demangled form.
8025 @item set print asm-demangle
8026 @itemx set print asm-demangle on
8027 Print C@t{++} names in their source form rather than their mangled form, even
8028 in assembler code printouts such as instruction disassemblies.
8031 @item show print asm-demangle
8032 Show whether C@t{++} names in assembly listings are printed in mangled
8035 @cindex C@t{++} symbol decoding style
8036 @cindex symbol decoding style, C@t{++}
8037 @kindex set demangle-style
8038 @item set demangle-style @var{style}
8039 Choose among several encoding schemes used by different compilers to
8040 represent C@t{++} names. The choices for @var{style} are currently:
8044 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8047 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8048 This is the default.
8051 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8054 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8057 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8058 @strong{Warning:} this setting alone is not sufficient to allow
8059 debugging @code{cfront}-generated executables. @value{GDBN} would
8060 require further enhancement to permit that.
8063 If you omit @var{style}, you will see a list of possible formats.
8065 @item show demangle-style
8066 Display the encoding style currently in use for decoding C@t{++} symbols.
8068 @item set print object
8069 @itemx set print object on
8070 @cindex derived type of an object, printing
8071 @cindex display derived types
8072 When displaying a pointer to an object, identify the @emph{actual}
8073 (derived) type of the object rather than the @emph{declared} type, using
8074 the virtual function table.
8076 @item set print object off
8077 Display only the declared type of objects, without reference to the
8078 virtual function table. This is the default setting.
8080 @item show print object
8081 Show whether actual, or declared, object types are displayed.
8083 @item set print static-members
8084 @itemx set print static-members on
8085 @cindex static members of C@t{++} objects
8086 Print static members when displaying a C@t{++} object. The default is on.
8088 @item set print static-members off
8089 Do not print static members when displaying a C@t{++} object.
8091 @item show print static-members
8092 Show whether C@t{++} static members are printed or not.
8094 @item set print pascal_static-members
8095 @itemx set print pascal_static-members on
8096 @cindex static members of Pascal objects
8097 @cindex Pascal objects, static members display
8098 Print static members when displaying a Pascal object. The default is on.
8100 @item set print pascal_static-members off
8101 Do not print static members when displaying a Pascal object.
8103 @item show print pascal_static-members
8104 Show whether Pascal static members are printed or not.
8106 @c These don't work with HP ANSI C++ yet.
8107 @item set print vtbl
8108 @itemx set print vtbl on
8109 @cindex pretty print C@t{++} virtual function tables
8110 @cindex virtual functions (C@t{++}) display
8111 @cindex VTBL display
8112 Pretty print C@t{++} virtual function tables. The default is off.
8113 (The @code{vtbl} commands do not work on programs compiled with the HP
8114 ANSI C@t{++} compiler (@code{aCC}).)
8116 @item set print vtbl off
8117 Do not pretty print C@t{++} virtual function tables.
8119 @item show print vtbl
8120 Show whether C@t{++} virtual function tables are pretty printed, or not.
8123 @node Pretty Printing
8124 @section Pretty Printing
8126 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8127 Python code. It greatly simplifies the display of complex objects. This
8128 mechanism works for both MI and the CLI.
8131 * Pretty-Printer Introduction:: Introduction to pretty-printers
8132 * Pretty-Printer Example:: An example pretty-printer
8133 * Pretty-Printer Commands:: Pretty-printer commands
8136 @node Pretty-Printer Introduction
8137 @subsection Pretty-Printer Introduction
8139 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8140 registered for the value. If there is then @value{GDBN} invokes the
8141 pretty-printer to print the value. Otherwise the value is printed normally.
8143 Pretty-printers are normally named. This makes them easy to manage.
8144 The @samp{info pretty-printer} command will list all the installed
8145 pretty-printers with their names.
8146 If a pretty-printer can handle multiple data types, then its
8147 @dfn{subprinters} are the printers for the individual data types.
8148 Each such subprinter has its own name.
8149 The format of the name is @var{printer-name}:@var{subprinter-name}.
8151 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8152 Typically they are automatically loaded and registered when the corresponding
8153 debug information is loaded, thus making them available without having to
8154 do anything special.
8156 There are three places where a pretty-printer can be registered.
8160 Pretty-printers registered globally are available when debugging
8164 Pretty-printers registered with a program space are available only
8165 when debugging that program.
8166 @xref{Progspaces In Python}, for more details on program spaces in Python.
8169 Pretty-printers registered with an objfile are loaded and unloaded
8170 with the corresponding objfile (e.g., shared library).
8171 @xref{Objfiles In Python}, for more details on objfiles in Python.
8174 @xref{Selecting Pretty-Printers}, for further information on how
8175 pretty-printers are selected,
8177 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8180 @node Pretty-Printer Example
8181 @subsection Pretty-Printer Example
8183 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8186 (@value{GDBP}) print s
8188 static npos = 4294967295,
8190 <std::allocator<char>> = @{
8191 <__gnu_cxx::new_allocator<char>> = @{
8192 <No data fields>@}, <No data fields>
8194 members of std::basic_string<char, std::char_traits<char>,
8195 std::allocator<char> >::_Alloc_hider:
8196 _M_p = 0x804a014 "abcd"
8201 With a pretty-printer for @code{std::string} only the contents are printed:
8204 (@value{GDBP}) print s
8208 @node Pretty-Printer Commands
8209 @subsection Pretty-Printer Commands
8210 @cindex pretty-printer commands
8213 @kindex info pretty-printer
8214 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8215 Print the list of installed pretty-printers.
8216 This includes disabled pretty-printers, which are marked as such.
8218 @var{object-regexp} is a regular expression matching the objects
8219 whose pretty-printers to list.
8220 Objects can be @code{global}, the program space's file
8221 (@pxref{Progspaces In Python}),
8222 and the object files within that program space (@pxref{Objfiles In Python}).
8223 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8224 looks up a printer from these three objects.
8226 @var{name-regexp} is a regular expression matching the name of the printers
8229 @kindex disable pretty-printer
8230 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8231 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8232 A disabled pretty-printer is not forgotten, it may be enabled again later.
8234 @kindex enable pretty-printer
8235 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8236 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8241 Suppose we have three pretty-printers installed: one from library1.so
8242 named @code{foo} that prints objects of type @code{foo}, and
8243 another from library2.so named @code{bar} that prints two types of objects,
8244 @code{bar1} and @code{bar2}.
8247 (gdb) info pretty-printer
8254 (gdb) info pretty-printer library2
8259 (gdb) disable pretty-printer library1
8261 2 of 3 printers enabled
8262 (gdb) info pretty-printer
8269 (gdb) disable pretty-printer library2 bar:bar1
8271 1 of 3 printers enabled
8272 (gdb) info pretty-printer library2
8279 (gdb) disable pretty-printer library2 bar
8281 0 of 3 printers enabled
8282 (gdb) info pretty-printer library2
8291 Note that for @code{bar} the entire printer can be disabled,
8292 as can each individual subprinter.
8295 @section Value History
8297 @cindex value history
8298 @cindex history of values printed by @value{GDBN}
8299 Values printed by the @code{print} command are saved in the @value{GDBN}
8300 @dfn{value history}. This allows you to refer to them in other expressions.
8301 Values are kept until the symbol table is re-read or discarded
8302 (for example with the @code{file} or @code{symbol-file} commands).
8303 When the symbol table changes, the value history is discarded,
8304 since the values may contain pointers back to the types defined in the
8309 @cindex history number
8310 The values printed are given @dfn{history numbers} by which you can
8311 refer to them. These are successive integers starting with one.
8312 @code{print} shows you the history number assigned to a value by
8313 printing @samp{$@var{num} = } before the value; here @var{num} is the
8316 To refer to any previous value, use @samp{$} followed by the value's
8317 history number. The way @code{print} labels its output is designed to
8318 remind you of this. Just @code{$} refers to the most recent value in
8319 the history, and @code{$$} refers to the value before that.
8320 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8321 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8322 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8324 For example, suppose you have just printed a pointer to a structure and
8325 want to see the contents of the structure. It suffices to type
8331 If you have a chain of structures where the component @code{next} points
8332 to the next one, you can print the contents of the next one with this:
8339 You can print successive links in the chain by repeating this
8340 command---which you can do by just typing @key{RET}.
8342 Note that the history records values, not expressions. If the value of
8343 @code{x} is 4 and you type these commands:
8351 then the value recorded in the value history by the @code{print} command
8352 remains 4 even though the value of @code{x} has changed.
8357 Print the last ten values in the value history, with their item numbers.
8358 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8359 values} does not change the history.
8361 @item show values @var{n}
8362 Print ten history values centered on history item number @var{n}.
8365 Print ten history values just after the values last printed. If no more
8366 values are available, @code{show values +} produces no display.
8369 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8370 same effect as @samp{show values +}.
8372 @node Convenience Vars
8373 @section Convenience Variables
8375 @cindex convenience variables
8376 @cindex user-defined variables
8377 @value{GDBN} provides @dfn{convenience variables} that you can use within
8378 @value{GDBN} to hold on to a value and refer to it later. These variables
8379 exist entirely within @value{GDBN}; they are not part of your program, and
8380 setting a convenience variable has no direct effect on further execution
8381 of your program. That is why you can use them freely.
8383 Convenience variables are prefixed with @samp{$}. Any name preceded by
8384 @samp{$} can be used for a convenience variable, unless it is one of
8385 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8386 (Value history references, in contrast, are @emph{numbers} preceded
8387 by @samp{$}. @xref{Value History, ,Value History}.)
8389 You can save a value in a convenience variable with an assignment
8390 expression, just as you would set a variable in your program.
8394 set $foo = *object_ptr
8398 would save in @code{$foo} the value contained in the object pointed to by
8401 Using a convenience variable for the first time creates it, but its
8402 value is @code{void} until you assign a new value. You can alter the
8403 value with another assignment at any time.
8405 Convenience variables have no fixed types. You can assign a convenience
8406 variable any type of value, including structures and arrays, even if
8407 that variable already has a value of a different type. The convenience
8408 variable, when used as an expression, has the type of its current value.
8411 @kindex show convenience
8412 @cindex show all user variables
8413 @item show convenience
8414 Print a list of convenience variables used so far, and their values.
8415 Abbreviated @code{show conv}.
8417 @kindex init-if-undefined
8418 @cindex convenience variables, initializing
8419 @item init-if-undefined $@var{variable} = @var{expression}
8420 Set a convenience variable if it has not already been set. This is useful
8421 for user-defined commands that keep some state. It is similar, in concept,
8422 to using local static variables with initializers in C (except that
8423 convenience variables are global). It can also be used to allow users to
8424 override default values used in a command script.
8426 If the variable is already defined then the expression is not evaluated so
8427 any side-effects do not occur.
8430 One of the ways to use a convenience variable is as a counter to be
8431 incremented or a pointer to be advanced. For example, to print
8432 a field from successive elements of an array of structures:
8436 print bar[$i++]->contents
8440 Repeat that command by typing @key{RET}.
8442 Some convenience variables are created automatically by @value{GDBN} and given
8443 values likely to be useful.
8446 @vindex $_@r{, convenience variable}
8448 The variable @code{$_} is automatically set by the @code{x} command to
8449 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8450 commands which provide a default address for @code{x} to examine also
8451 set @code{$_} to that address; these commands include @code{info line}
8452 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8453 except when set by the @code{x} command, in which case it is a pointer
8454 to the type of @code{$__}.
8456 @vindex $__@r{, convenience variable}
8458 The variable @code{$__} is automatically set by the @code{x} command
8459 to the value found in the last address examined. Its type is chosen
8460 to match the format in which the data was printed.
8463 @vindex $_exitcode@r{, convenience variable}
8464 The variable @code{$_exitcode} is automatically set to the exit code when
8465 the program being debugged terminates.
8468 @vindex $_sdata@r{, inspect, convenience variable}
8469 The variable @code{$_sdata} contains extra collected static tracepoint
8470 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8471 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8472 if extra static tracepoint data has not been collected.
8475 @vindex $_siginfo@r{, convenience variable}
8476 The variable @code{$_siginfo} contains extra signal information
8477 (@pxref{extra signal information}). Note that @code{$_siginfo}
8478 could be empty, if the application has not yet received any signals.
8479 For example, it will be empty before you execute the @code{run} command.
8482 @vindex $_tlb@r{, convenience variable}
8483 The variable @code{$_tlb} is automatically set when debugging
8484 applications running on MS-Windows in native mode or connected to
8485 gdbserver that supports the @code{qGetTIBAddr} request.
8486 @xref{General Query Packets}.
8487 This variable contains the address of the thread information block.
8491 On HP-UX systems, if you refer to a function or variable name that
8492 begins with a dollar sign, @value{GDBN} searches for a user or system
8493 name first, before it searches for a convenience variable.
8495 @cindex convenience functions
8496 @value{GDBN} also supplies some @dfn{convenience functions}. These
8497 have a syntax similar to convenience variables. A convenience
8498 function can be used in an expression just like an ordinary function;
8499 however, a convenience function is implemented internally to
8504 @kindex help function
8505 @cindex show all convenience functions
8506 Print a list of all convenience functions.
8513 You can refer to machine register contents, in expressions, as variables
8514 with names starting with @samp{$}. The names of registers are different
8515 for each machine; use @code{info registers} to see the names used on
8519 @kindex info registers
8520 @item info registers
8521 Print the names and values of all registers except floating-point
8522 and vector registers (in the selected stack frame).
8524 @kindex info all-registers
8525 @cindex floating point registers
8526 @item info all-registers
8527 Print the names and values of all registers, including floating-point
8528 and vector registers (in the selected stack frame).
8530 @item info registers @var{regname} @dots{}
8531 Print the @dfn{relativized} value of each specified register @var{regname}.
8532 As discussed in detail below, register values are normally relative to
8533 the selected stack frame. @var{regname} may be any register name valid on
8534 the machine you are using, with or without the initial @samp{$}.
8537 @cindex stack pointer register
8538 @cindex program counter register
8539 @cindex process status register
8540 @cindex frame pointer register
8541 @cindex standard registers
8542 @value{GDBN} has four ``standard'' register names that are available (in
8543 expressions) on most machines---whenever they do not conflict with an
8544 architecture's canonical mnemonics for registers. The register names
8545 @code{$pc} and @code{$sp} are used for the program counter register and
8546 the stack pointer. @code{$fp} is used for a register that contains a
8547 pointer to the current stack frame, and @code{$ps} is used for a
8548 register that contains the processor status. For example,
8549 you could print the program counter in hex with
8556 or print the instruction to be executed next with
8563 or add four to the stack pointer@footnote{This is a way of removing
8564 one word from the stack, on machines where stacks grow downward in
8565 memory (most machines, nowadays). This assumes that the innermost
8566 stack frame is selected; setting @code{$sp} is not allowed when other
8567 stack frames are selected. To pop entire frames off the stack,
8568 regardless of machine architecture, use @code{return};
8569 see @ref{Returning, ,Returning from a Function}.} with
8575 Whenever possible, these four standard register names are available on
8576 your machine even though the machine has different canonical mnemonics,
8577 so long as there is no conflict. The @code{info registers} command
8578 shows the canonical names. For example, on the SPARC, @code{info
8579 registers} displays the processor status register as @code{$psr} but you
8580 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8581 is an alias for the @sc{eflags} register.
8583 @value{GDBN} always considers the contents of an ordinary register as an
8584 integer when the register is examined in this way. Some machines have
8585 special registers which can hold nothing but floating point; these
8586 registers are considered to have floating point values. There is no way
8587 to refer to the contents of an ordinary register as floating point value
8588 (although you can @emph{print} it as a floating point value with
8589 @samp{print/f $@var{regname}}).
8591 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8592 means that the data format in which the register contents are saved by
8593 the operating system is not the same one that your program normally
8594 sees. For example, the registers of the 68881 floating point
8595 coprocessor are always saved in ``extended'' (raw) format, but all C
8596 programs expect to work with ``double'' (virtual) format. In such
8597 cases, @value{GDBN} normally works with the virtual format only (the format
8598 that makes sense for your program), but the @code{info registers} command
8599 prints the data in both formats.
8601 @cindex SSE registers (x86)
8602 @cindex MMX registers (x86)
8603 Some machines have special registers whose contents can be interpreted
8604 in several different ways. For example, modern x86-based machines
8605 have SSE and MMX registers that can hold several values packed
8606 together in several different formats. @value{GDBN} refers to such
8607 registers in @code{struct} notation:
8610 (@value{GDBP}) print $xmm1
8612 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8613 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8614 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8615 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8616 v4_int32 = @{0, 20657912, 11, 13@},
8617 v2_int64 = @{88725056443645952, 55834574859@},
8618 uint128 = 0x0000000d0000000b013b36f800000000
8623 To set values of such registers, you need to tell @value{GDBN} which
8624 view of the register you wish to change, as if you were assigning
8625 value to a @code{struct} member:
8628 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8631 Normally, register values are relative to the selected stack frame
8632 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8633 value that the register would contain if all stack frames farther in
8634 were exited and their saved registers restored. In order to see the
8635 true contents of hardware registers, you must select the innermost
8636 frame (with @samp{frame 0}).
8638 However, @value{GDBN} must deduce where registers are saved, from the machine
8639 code generated by your compiler. If some registers are not saved, or if
8640 @value{GDBN} is unable to locate the saved registers, the selected stack
8641 frame makes no difference.
8643 @node Floating Point Hardware
8644 @section Floating Point Hardware
8645 @cindex floating point
8647 Depending on the configuration, @value{GDBN} may be able to give
8648 you more information about the status of the floating point hardware.
8653 Display hardware-dependent information about the floating
8654 point unit. The exact contents and layout vary depending on the
8655 floating point chip. Currently, @samp{info float} is supported on
8656 the ARM and x86 machines.
8660 @section Vector Unit
8663 Depending on the configuration, @value{GDBN} may be able to give you
8664 more information about the status of the vector unit.
8669 Display information about the vector unit. The exact contents and
8670 layout vary depending on the hardware.
8673 @node OS Information
8674 @section Operating System Auxiliary Information
8675 @cindex OS information
8677 @value{GDBN} provides interfaces to useful OS facilities that can help
8678 you debug your program.
8680 @cindex @code{ptrace} system call
8681 @cindex @code{struct user} contents
8682 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8683 machines), it interfaces with the inferior via the @code{ptrace}
8684 system call. The operating system creates a special sata structure,
8685 called @code{struct user}, for this interface. You can use the
8686 command @code{info udot} to display the contents of this data
8692 Display the contents of the @code{struct user} maintained by the OS
8693 kernel for the program being debugged. @value{GDBN} displays the
8694 contents of @code{struct user} as a list of hex numbers, similar to
8695 the @code{examine} command.
8698 @cindex auxiliary vector
8699 @cindex vector, auxiliary
8700 Some operating systems supply an @dfn{auxiliary vector} to programs at
8701 startup. This is akin to the arguments and environment that you
8702 specify for a program, but contains a system-dependent variety of
8703 binary values that tell system libraries important details about the
8704 hardware, operating system, and process. Each value's purpose is
8705 identified by an integer tag; the meanings are well-known but system-specific.
8706 Depending on the configuration and operating system facilities,
8707 @value{GDBN} may be able to show you this information. For remote
8708 targets, this functionality may further depend on the remote stub's
8709 support of the @samp{qXfer:auxv:read} packet, see
8710 @ref{qXfer auxiliary vector read}.
8715 Display the auxiliary vector of the inferior, which can be either a
8716 live process or a core dump file. @value{GDBN} prints each tag value
8717 numerically, and also shows names and text descriptions for recognized
8718 tags. Some values in the vector are numbers, some bit masks, and some
8719 pointers to strings or other data. @value{GDBN} displays each value in the
8720 most appropriate form for a recognized tag, and in hexadecimal for
8721 an unrecognized tag.
8724 On some targets, @value{GDBN} can access operating-system-specific information
8725 and display it to user, without interpretation. For remote targets,
8726 this functionality depends on the remote stub's support of the
8727 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8732 List the types of OS information available for the target. If the
8733 target does not return a list of possible types, this command will
8736 @kindex info os processes
8737 @item info os processes
8738 Display the list of processes on the target. For each process,
8739 @value{GDBN} prints the process identifier, the name of the user, and
8740 the command corresponding to the process.
8743 @node Memory Region Attributes
8744 @section Memory Region Attributes
8745 @cindex memory region attributes
8747 @dfn{Memory region attributes} allow you to describe special handling
8748 required by regions of your target's memory. @value{GDBN} uses
8749 attributes to determine whether to allow certain types of memory
8750 accesses; whether to use specific width accesses; and whether to cache
8751 target memory. By default the description of memory regions is
8752 fetched from the target (if the current target supports this), but the
8753 user can override the fetched regions.
8755 Defined memory regions can be individually enabled and disabled. When a
8756 memory region is disabled, @value{GDBN} uses the default attributes when
8757 accessing memory in that region. Similarly, if no memory regions have
8758 been defined, @value{GDBN} uses the default attributes when accessing
8761 When a memory region is defined, it is given a number to identify it;
8762 to enable, disable, or remove a memory region, you specify that number.
8766 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8767 Define a memory region bounded by @var{lower} and @var{upper} with
8768 attributes @var{attributes}@dots{}, and add it to the list of regions
8769 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8770 case: it is treated as the target's maximum memory address.
8771 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8774 Discard any user changes to the memory regions and use target-supplied
8775 regions, if available, or no regions if the target does not support.
8778 @item delete mem @var{nums}@dots{}
8779 Remove memory regions @var{nums}@dots{} from the list of regions
8780 monitored by @value{GDBN}.
8783 @item disable mem @var{nums}@dots{}
8784 Disable monitoring of memory regions @var{nums}@dots{}.
8785 A disabled memory region is not forgotten.
8786 It may be enabled again later.
8789 @item enable mem @var{nums}@dots{}
8790 Enable monitoring of memory regions @var{nums}@dots{}.
8794 Print a table of all defined memory regions, with the following columns
8798 @item Memory Region Number
8799 @item Enabled or Disabled.
8800 Enabled memory regions are marked with @samp{y}.
8801 Disabled memory regions are marked with @samp{n}.
8804 The address defining the inclusive lower bound of the memory region.
8807 The address defining the exclusive upper bound of the memory region.
8810 The list of attributes set for this memory region.
8815 @subsection Attributes
8817 @subsubsection Memory Access Mode
8818 The access mode attributes set whether @value{GDBN} may make read or
8819 write accesses to a memory region.
8821 While these attributes prevent @value{GDBN} from performing invalid
8822 memory accesses, they do nothing to prevent the target system, I/O DMA,
8823 etc.@: from accessing memory.
8827 Memory is read only.
8829 Memory is write only.
8831 Memory is read/write. This is the default.
8834 @subsubsection Memory Access Size
8835 The access size attribute tells @value{GDBN} to use specific sized
8836 accesses in the memory region. Often memory mapped device registers
8837 require specific sized accesses. If no access size attribute is
8838 specified, @value{GDBN} may use accesses of any size.
8842 Use 8 bit memory accesses.
8844 Use 16 bit memory accesses.
8846 Use 32 bit memory accesses.
8848 Use 64 bit memory accesses.
8851 @c @subsubsection Hardware/Software Breakpoints
8852 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8853 @c will use hardware or software breakpoints for the internal breakpoints
8854 @c used by the step, next, finish, until, etc. commands.
8858 @c Always use hardware breakpoints
8859 @c @item swbreak (default)
8862 @subsubsection Data Cache
8863 The data cache attributes set whether @value{GDBN} will cache target
8864 memory. While this generally improves performance by reducing debug
8865 protocol overhead, it can lead to incorrect results because @value{GDBN}
8866 does not know about volatile variables or memory mapped device
8871 Enable @value{GDBN} to cache target memory.
8873 Disable @value{GDBN} from caching target memory. This is the default.
8876 @subsection Memory Access Checking
8877 @value{GDBN} can be instructed to refuse accesses to memory that is
8878 not explicitly described. This can be useful if accessing such
8879 regions has undesired effects for a specific target, or to provide
8880 better error checking. The following commands control this behaviour.
8883 @kindex set mem inaccessible-by-default
8884 @item set mem inaccessible-by-default [on|off]
8885 If @code{on} is specified, make @value{GDBN} treat memory not
8886 explicitly described by the memory ranges as non-existent and refuse accesses
8887 to such memory. The checks are only performed if there's at least one
8888 memory range defined. If @code{off} is specified, make @value{GDBN}
8889 treat the memory not explicitly described by the memory ranges as RAM.
8890 The default value is @code{on}.
8891 @kindex show mem inaccessible-by-default
8892 @item show mem inaccessible-by-default
8893 Show the current handling of accesses to unknown memory.
8897 @c @subsubsection Memory Write Verification
8898 @c The memory write verification attributes set whether @value{GDBN}
8899 @c will re-reads data after each write to verify the write was successful.
8903 @c @item noverify (default)
8906 @node Dump/Restore Files
8907 @section Copy Between Memory and a File
8908 @cindex dump/restore files
8909 @cindex append data to a file
8910 @cindex dump data to a file
8911 @cindex restore data from a file
8913 You can use the commands @code{dump}, @code{append}, and
8914 @code{restore} to copy data between target memory and a file. The
8915 @code{dump} and @code{append} commands write data to a file, and the
8916 @code{restore} command reads data from a file back into the inferior's
8917 memory. Files may be in binary, Motorola S-record, Intel hex, or
8918 Tektronix Hex format; however, @value{GDBN} can only append to binary
8924 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8925 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8926 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8927 or the value of @var{expr}, to @var{filename} in the given format.
8929 The @var{format} parameter may be any one of:
8936 Motorola S-record format.
8938 Tektronix Hex format.
8941 @value{GDBN} uses the same definitions of these formats as the
8942 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8943 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8947 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8948 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8949 Append the contents of memory from @var{start_addr} to @var{end_addr},
8950 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8951 (@value{GDBN} can only append data to files in raw binary form.)
8954 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8955 Restore the contents of file @var{filename} into memory. The
8956 @code{restore} command can automatically recognize any known @sc{bfd}
8957 file format, except for raw binary. To restore a raw binary file you
8958 must specify the optional keyword @code{binary} after the filename.
8960 If @var{bias} is non-zero, its value will be added to the addresses
8961 contained in the file. Binary files always start at address zero, so
8962 they will be restored at address @var{bias}. Other bfd files have
8963 a built-in location; they will be restored at offset @var{bias}
8966 If @var{start} and/or @var{end} are non-zero, then only data between
8967 file offset @var{start} and file offset @var{end} will be restored.
8968 These offsets are relative to the addresses in the file, before
8969 the @var{bias} argument is applied.
8973 @node Core File Generation
8974 @section How to Produce a Core File from Your Program
8975 @cindex dump core from inferior
8977 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8978 image of a running process and its process status (register values
8979 etc.). Its primary use is post-mortem debugging of a program that
8980 crashed while it ran outside a debugger. A program that crashes
8981 automatically produces a core file, unless this feature is disabled by
8982 the user. @xref{Files}, for information on invoking @value{GDBN} in
8983 the post-mortem debugging mode.
8985 Occasionally, you may wish to produce a core file of the program you
8986 are debugging in order to preserve a snapshot of its state.
8987 @value{GDBN} has a special command for that.
8991 @kindex generate-core-file
8992 @item generate-core-file [@var{file}]
8993 @itemx gcore [@var{file}]
8994 Produce a core dump of the inferior process. The optional argument
8995 @var{file} specifies the file name where to put the core dump. If not
8996 specified, the file name defaults to @file{core.@var{pid}}, where
8997 @var{pid} is the inferior process ID.
8999 Note that this command is implemented only for some systems (as of
9000 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9003 @node Character Sets
9004 @section Character Sets
9005 @cindex character sets
9007 @cindex translating between character sets
9008 @cindex host character set
9009 @cindex target character set
9011 If the program you are debugging uses a different character set to
9012 represent characters and strings than the one @value{GDBN} uses itself,
9013 @value{GDBN} can automatically translate between the character sets for
9014 you. The character set @value{GDBN} uses we call the @dfn{host
9015 character set}; the one the inferior program uses we call the
9016 @dfn{target character set}.
9018 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9019 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9020 remote protocol (@pxref{Remote Debugging}) to debug a program
9021 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9022 then the host character set is Latin-1, and the target character set is
9023 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9024 target-charset EBCDIC-US}, then @value{GDBN} translates between
9025 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9026 character and string literals in expressions.
9028 @value{GDBN} has no way to automatically recognize which character set
9029 the inferior program uses; you must tell it, using the @code{set
9030 target-charset} command, described below.
9032 Here are the commands for controlling @value{GDBN}'s character set
9036 @item set target-charset @var{charset}
9037 @kindex set target-charset
9038 Set the current target character set to @var{charset}. To display the
9039 list of supported target character sets, type
9040 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9042 @item set host-charset @var{charset}
9043 @kindex set host-charset
9044 Set the current host character set to @var{charset}.
9046 By default, @value{GDBN} uses a host character set appropriate to the
9047 system it is running on; you can override that default using the
9048 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9049 automatically determine the appropriate host character set. In this
9050 case, @value{GDBN} uses @samp{UTF-8}.
9052 @value{GDBN} can only use certain character sets as its host character
9053 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9054 @value{GDBN} will list the host character sets it supports.
9056 @item set charset @var{charset}
9058 Set the current host and target character sets to @var{charset}. As
9059 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9060 @value{GDBN} will list the names of the character sets that can be used
9061 for both host and target.
9064 @kindex show charset
9065 Show the names of the current host and target character sets.
9067 @item show host-charset
9068 @kindex show host-charset
9069 Show the name of the current host character set.
9071 @item show target-charset
9072 @kindex show target-charset
9073 Show the name of the current target character set.
9075 @item set target-wide-charset @var{charset}
9076 @kindex set target-wide-charset
9077 Set the current target's wide character set to @var{charset}. This is
9078 the character set used by the target's @code{wchar_t} type. To
9079 display the list of supported wide character sets, type
9080 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9082 @item show target-wide-charset
9083 @kindex show target-wide-charset
9084 Show the name of the current target's wide character set.
9087 Here is an example of @value{GDBN}'s character set support in action.
9088 Assume that the following source code has been placed in the file
9089 @file{charset-test.c}:
9095 = @{72, 101, 108, 108, 111, 44, 32, 119,
9096 111, 114, 108, 100, 33, 10, 0@};
9097 char ibm1047_hello[]
9098 = @{200, 133, 147, 147, 150, 107, 64, 166,
9099 150, 153, 147, 132, 90, 37, 0@};
9103 printf ("Hello, world!\n");
9107 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9108 containing the string @samp{Hello, world!} followed by a newline,
9109 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9111 We compile the program, and invoke the debugger on it:
9114 $ gcc -g charset-test.c -o charset-test
9115 $ gdb -nw charset-test
9116 GNU gdb 2001-12-19-cvs
9117 Copyright 2001 Free Software Foundation, Inc.
9122 We can use the @code{show charset} command to see what character sets
9123 @value{GDBN} is currently using to interpret and display characters and
9127 (@value{GDBP}) show charset
9128 The current host and target character set is `ISO-8859-1'.
9132 For the sake of printing this manual, let's use @sc{ascii} as our
9133 initial character set:
9135 (@value{GDBP}) set charset ASCII
9136 (@value{GDBP}) show charset
9137 The current host and target character set is `ASCII'.
9141 Let's assume that @sc{ascii} is indeed the correct character set for our
9142 host system --- in other words, let's assume that if @value{GDBN} prints
9143 characters using the @sc{ascii} character set, our terminal will display
9144 them properly. Since our current target character set is also
9145 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9148 (@value{GDBP}) print ascii_hello
9149 $1 = 0x401698 "Hello, world!\n"
9150 (@value{GDBP}) print ascii_hello[0]
9155 @value{GDBN} uses the target character set for character and string
9156 literals you use in expressions:
9159 (@value{GDBP}) print '+'
9164 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9167 @value{GDBN} relies on the user to tell it which character set the
9168 target program uses. If we print @code{ibm1047_hello} while our target
9169 character set is still @sc{ascii}, we get jibberish:
9172 (@value{GDBP}) print ibm1047_hello
9173 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9174 (@value{GDBP}) print ibm1047_hello[0]
9179 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9180 @value{GDBN} tells us the character sets it supports:
9183 (@value{GDBP}) set target-charset
9184 ASCII EBCDIC-US IBM1047 ISO-8859-1
9185 (@value{GDBP}) set target-charset
9188 We can select @sc{ibm1047} as our target character set, and examine the
9189 program's strings again. Now the @sc{ascii} string is wrong, but
9190 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9191 target character set, @sc{ibm1047}, to the host character set,
9192 @sc{ascii}, and they display correctly:
9195 (@value{GDBP}) set target-charset IBM1047
9196 (@value{GDBP}) show charset
9197 The current host character set is `ASCII'.
9198 The current target character set is `IBM1047'.
9199 (@value{GDBP}) print ascii_hello
9200 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9201 (@value{GDBP}) print ascii_hello[0]
9203 (@value{GDBP}) print ibm1047_hello
9204 $8 = 0x4016a8 "Hello, world!\n"
9205 (@value{GDBP}) print ibm1047_hello[0]
9210 As above, @value{GDBN} uses the target character set for character and
9211 string literals you use in expressions:
9214 (@value{GDBP}) print '+'
9219 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9222 @node Caching Remote Data
9223 @section Caching Data of Remote Targets
9224 @cindex caching data of remote targets
9226 @value{GDBN} caches data exchanged between the debugger and a
9227 remote target (@pxref{Remote Debugging}). Such caching generally improves
9228 performance, because it reduces the overhead of the remote protocol by
9229 bundling memory reads and writes into large chunks. Unfortunately, simply
9230 caching everything would lead to incorrect results, since @value{GDBN}
9231 does not necessarily know anything about volatile values, memory-mapped I/O
9232 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9233 memory can be changed @emph{while} a gdb command is executing.
9234 Therefore, by default, @value{GDBN} only caches data
9235 known to be on the stack@footnote{In non-stop mode, it is moderately
9236 rare for a running thread to modify the stack of a stopped thread
9237 in a way that would interfere with a backtrace, and caching of
9238 stack reads provides a significant speed up of remote backtraces.}.
9239 Other regions of memory can be explicitly marked as
9240 cacheable; see @pxref{Memory Region Attributes}.
9243 @kindex set remotecache
9244 @item set remotecache on
9245 @itemx set remotecache off
9246 This option no longer does anything; it exists for compatibility
9249 @kindex show remotecache
9250 @item show remotecache
9251 Show the current state of the obsolete remotecache flag.
9253 @kindex set stack-cache
9254 @item set stack-cache on
9255 @itemx set stack-cache off
9256 Enable or disable caching of stack accesses. When @code{ON}, use
9257 caching. By default, this option is @code{ON}.
9259 @kindex show stack-cache
9260 @item show stack-cache
9261 Show the current state of data caching for memory accesses.
9264 @item info dcache @r{[}line@r{]}
9265 Print the information about the data cache performance. The
9266 information displayed includes the dcache width and depth, and for
9267 each cache line, its number, address, and how many times it was
9268 referenced. This command is useful for debugging the data cache
9271 If a line number is specified, the contents of that line will be
9275 @node Searching Memory
9276 @section Search Memory
9277 @cindex searching memory
9279 Memory can be searched for a particular sequence of bytes with the
9280 @code{find} command.
9284 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9285 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9286 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9287 etc. The search begins at address @var{start_addr} and continues for either
9288 @var{len} bytes or through to @var{end_addr} inclusive.
9291 @var{s} and @var{n} are optional parameters.
9292 They may be specified in either order, apart or together.
9295 @item @var{s}, search query size
9296 The size of each search query value.
9302 halfwords (two bytes)
9306 giant words (eight bytes)
9309 All values are interpreted in the current language.
9310 This means, for example, that if the current source language is C/C@t{++}
9311 then searching for the string ``hello'' includes the trailing '\0'.
9313 If the value size is not specified, it is taken from the
9314 value's type in the current language.
9315 This is useful when one wants to specify the search
9316 pattern as a mixture of types.
9317 Note that this means, for example, that in the case of C-like languages
9318 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9319 which is typically four bytes.
9321 @item @var{n}, maximum number of finds
9322 The maximum number of matches to print. The default is to print all finds.
9325 You can use strings as search values. Quote them with double-quotes
9327 The string value is copied into the search pattern byte by byte,
9328 regardless of the endianness of the target and the size specification.
9330 The address of each match found is printed as well as a count of the
9331 number of matches found.
9333 The address of the last value found is stored in convenience variable
9335 A count of the number of matches is stored in @samp{$numfound}.
9337 For example, if stopped at the @code{printf} in this function:
9343 static char hello[] = "hello-hello";
9344 static struct @{ char c; short s; int i; @}
9345 __attribute__ ((packed)) mixed
9346 = @{ 'c', 0x1234, 0x87654321 @};
9347 printf ("%s\n", hello);
9352 you get during debugging:
9355 (gdb) find &hello[0], +sizeof(hello), "hello"
9356 0x804956d <hello.1620+6>
9358 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9359 0x8049567 <hello.1620>
9360 0x804956d <hello.1620+6>
9362 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9363 0x8049567 <hello.1620>
9365 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9366 0x8049560 <mixed.1625>
9368 (gdb) print $numfound
9371 $2 = (void *) 0x8049560
9374 @node Optimized Code
9375 @chapter Debugging Optimized Code
9376 @cindex optimized code, debugging
9377 @cindex debugging optimized code
9379 Almost all compilers support optimization. With optimization
9380 disabled, the compiler generates assembly code that corresponds
9381 directly to your source code, in a simplistic way. As the compiler
9382 applies more powerful optimizations, the generated assembly code
9383 diverges from your original source code. With help from debugging
9384 information generated by the compiler, @value{GDBN} can map from
9385 the running program back to constructs from your original source.
9387 @value{GDBN} is more accurate with optimization disabled. If you
9388 can recompile without optimization, it is easier to follow the
9389 progress of your program during debugging. But, there are many cases
9390 where you may need to debug an optimized version.
9392 When you debug a program compiled with @samp{-g -O}, remember that the
9393 optimizer has rearranged your code; the debugger shows you what is
9394 really there. Do not be too surprised when the execution path does not
9395 exactly match your source file! An extreme example: if you define a
9396 variable, but never use it, @value{GDBN} never sees that
9397 variable---because the compiler optimizes it out of existence.
9399 Some things do not work as well with @samp{-g -O} as with just
9400 @samp{-g}, particularly on machines with instruction scheduling. If in
9401 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9402 please report it to us as a bug (including a test case!).
9403 @xref{Variables}, for more information about debugging optimized code.
9406 * Inline Functions:: How @value{GDBN} presents inlining
9409 @node Inline Functions
9410 @section Inline Functions
9411 @cindex inline functions, debugging
9413 @dfn{Inlining} is an optimization that inserts a copy of the function
9414 body directly at each call site, instead of jumping to a shared
9415 routine. @value{GDBN} displays inlined functions just like
9416 non-inlined functions. They appear in backtraces. You can view their
9417 arguments and local variables, step into them with @code{step}, skip
9418 them with @code{next}, and escape from them with @code{finish}.
9419 You can check whether a function was inlined by using the
9420 @code{info frame} command.
9422 For @value{GDBN} to support inlined functions, the compiler must
9423 record information about inlining in the debug information ---
9424 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9425 other compilers do also. @value{GDBN} only supports inlined functions
9426 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9427 do not emit two required attributes (@samp{DW_AT_call_file} and
9428 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9429 function calls with earlier versions of @value{NGCC}. It instead
9430 displays the arguments and local variables of inlined functions as
9431 local variables in the caller.
9433 The body of an inlined function is directly included at its call site;
9434 unlike a non-inlined function, there are no instructions devoted to
9435 the call. @value{GDBN} still pretends that the call site and the
9436 start of the inlined function are different instructions. Stepping to
9437 the call site shows the call site, and then stepping again shows
9438 the first line of the inlined function, even though no additional
9439 instructions are executed.
9441 This makes source-level debugging much clearer; you can see both the
9442 context of the call and then the effect of the call. Only stepping by
9443 a single instruction using @code{stepi} or @code{nexti} does not do
9444 this; single instruction steps always show the inlined body.
9446 There are some ways that @value{GDBN} does not pretend that inlined
9447 function calls are the same as normal calls:
9451 You cannot set breakpoints on inlined functions. @value{GDBN}
9452 either reports that there is no symbol with that name, or else sets the
9453 breakpoint only on non-inlined copies of the function. This limitation
9454 will be removed in a future version of @value{GDBN}; until then,
9455 set a breakpoint by line number on the first line of the inlined
9459 Setting breakpoints at the call site of an inlined function may not
9460 work, because the call site does not contain any code. @value{GDBN}
9461 may incorrectly move the breakpoint to the next line of the enclosing
9462 function, after the call. This limitation will be removed in a future
9463 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9464 or inside the inlined function instead.
9467 @value{GDBN} cannot locate the return value of inlined calls after
9468 using the @code{finish} command. This is a limitation of compiler-generated
9469 debugging information; after @code{finish}, you can step to the next line
9470 and print a variable where your program stored the return value.
9476 @chapter C Preprocessor Macros
9478 Some languages, such as C and C@t{++}, provide a way to define and invoke
9479 ``preprocessor macros'' which expand into strings of tokens.
9480 @value{GDBN} can evaluate expressions containing macro invocations, show
9481 the result of macro expansion, and show a macro's definition, including
9482 where it was defined.
9484 You may need to compile your program specially to provide @value{GDBN}
9485 with information about preprocessor macros. Most compilers do not
9486 include macros in their debugging information, even when you compile
9487 with the @option{-g} flag. @xref{Compilation}.
9489 A program may define a macro at one point, remove that definition later,
9490 and then provide a different definition after that. Thus, at different
9491 points in the program, a macro may have different definitions, or have
9492 no definition at all. If there is a current stack frame, @value{GDBN}
9493 uses the macros in scope at that frame's source code line. Otherwise,
9494 @value{GDBN} uses the macros in scope at the current listing location;
9497 Whenever @value{GDBN} evaluates an expression, it always expands any
9498 macro invocations present in the expression. @value{GDBN} also provides
9499 the following commands for working with macros explicitly.
9503 @kindex macro expand
9504 @cindex macro expansion, showing the results of preprocessor
9505 @cindex preprocessor macro expansion, showing the results of
9506 @cindex expanding preprocessor macros
9507 @item macro expand @var{expression}
9508 @itemx macro exp @var{expression}
9509 Show the results of expanding all preprocessor macro invocations in
9510 @var{expression}. Since @value{GDBN} simply expands macros, but does
9511 not parse the result, @var{expression} need not be a valid expression;
9512 it can be any string of tokens.
9515 @item macro expand-once @var{expression}
9516 @itemx macro exp1 @var{expression}
9517 @cindex expand macro once
9518 @i{(This command is not yet implemented.)} Show the results of
9519 expanding those preprocessor macro invocations that appear explicitly in
9520 @var{expression}. Macro invocations appearing in that expansion are
9521 left unchanged. This command allows you to see the effect of a
9522 particular macro more clearly, without being confused by further
9523 expansions. Since @value{GDBN} simply expands macros, but does not
9524 parse the result, @var{expression} need not be a valid expression; it
9525 can be any string of tokens.
9528 @cindex macro definition, showing
9529 @cindex definition, showing a macro's
9530 @item info macro @var{macro}
9531 Show the definition of the macro named @var{macro}, and describe the
9532 source location or compiler command-line where that definition was established.
9534 @kindex macro define
9535 @cindex user-defined macros
9536 @cindex defining macros interactively
9537 @cindex macros, user-defined
9538 @item macro define @var{macro} @var{replacement-list}
9539 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9540 Introduce a definition for a preprocessor macro named @var{macro},
9541 invocations of which are replaced by the tokens given in
9542 @var{replacement-list}. The first form of this command defines an
9543 ``object-like'' macro, which takes no arguments; the second form
9544 defines a ``function-like'' macro, which takes the arguments given in
9547 A definition introduced by this command is in scope in every
9548 expression evaluated in @value{GDBN}, until it is removed with the
9549 @code{macro undef} command, described below. The definition overrides
9550 all definitions for @var{macro} present in the program being debugged,
9551 as well as any previous user-supplied definition.
9554 @item macro undef @var{macro}
9555 Remove any user-supplied definition for the macro named @var{macro}.
9556 This command only affects definitions provided with the @code{macro
9557 define} command, described above; it cannot remove definitions present
9558 in the program being debugged.
9562 List all the macros defined using the @code{macro define} command.
9565 @cindex macros, example of debugging with
9566 Here is a transcript showing the above commands in action. First, we
9567 show our source files:
9575 #define ADD(x) (M + x)
9580 printf ("Hello, world!\n");
9582 printf ("We're so creative.\n");
9584 printf ("Goodbye, world!\n");
9591 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9592 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9593 compiler includes information about preprocessor macros in the debugging
9597 $ gcc -gdwarf-2 -g3 sample.c -o sample
9601 Now, we start @value{GDBN} on our sample program:
9605 GNU gdb 2002-05-06-cvs
9606 Copyright 2002 Free Software Foundation, Inc.
9607 GDB is free software, @dots{}
9611 We can expand macros and examine their definitions, even when the
9612 program is not running. @value{GDBN} uses the current listing position
9613 to decide which macro definitions are in scope:
9616 (@value{GDBP}) list main
9619 5 #define ADD(x) (M + x)
9624 10 printf ("Hello, world!\n");
9626 12 printf ("We're so creative.\n");
9627 (@value{GDBP}) info macro ADD
9628 Defined at /home/jimb/gdb/macros/play/sample.c:5
9629 #define ADD(x) (M + x)
9630 (@value{GDBP}) info macro Q
9631 Defined at /home/jimb/gdb/macros/play/sample.h:1
9632 included at /home/jimb/gdb/macros/play/sample.c:2
9634 (@value{GDBP}) macro expand ADD(1)
9635 expands to: (42 + 1)
9636 (@value{GDBP}) macro expand-once ADD(1)
9637 expands to: once (M + 1)
9641 In the example above, note that @code{macro expand-once} expands only
9642 the macro invocation explicit in the original text --- the invocation of
9643 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9644 which was introduced by @code{ADD}.
9646 Once the program is running, @value{GDBN} uses the macro definitions in
9647 force at the source line of the current stack frame:
9650 (@value{GDBP}) break main
9651 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9653 Starting program: /home/jimb/gdb/macros/play/sample
9655 Breakpoint 1, main () at sample.c:10
9656 10 printf ("Hello, world!\n");
9660 At line 10, the definition of the macro @code{N} at line 9 is in force:
9663 (@value{GDBP}) info macro N
9664 Defined at /home/jimb/gdb/macros/play/sample.c:9
9666 (@value{GDBP}) macro expand N Q M
9668 (@value{GDBP}) print N Q M
9673 As we step over directives that remove @code{N}'s definition, and then
9674 give it a new definition, @value{GDBN} finds the definition (or lack
9675 thereof) in force at each point:
9680 12 printf ("We're so creative.\n");
9681 (@value{GDBP}) info macro N
9682 The symbol `N' has no definition as a C/C++ preprocessor macro
9683 at /home/jimb/gdb/macros/play/sample.c:12
9686 14 printf ("Goodbye, world!\n");
9687 (@value{GDBP}) info macro N
9688 Defined at /home/jimb/gdb/macros/play/sample.c:13
9690 (@value{GDBP}) macro expand N Q M
9691 expands to: 1729 < 42
9692 (@value{GDBP}) print N Q M
9697 In addition to source files, macros can be defined on the compilation command
9698 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9699 such a way, @value{GDBN} displays the location of their definition as line zero
9700 of the source file submitted to the compiler.
9703 (@value{GDBP}) info macro __STDC__
9704 Defined at /home/jimb/gdb/macros/play/sample.c:0
9711 @chapter Tracepoints
9712 @c This chapter is based on the documentation written by Michael
9713 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9716 In some applications, it is not feasible for the debugger to interrupt
9717 the program's execution long enough for the developer to learn
9718 anything helpful about its behavior. If the program's correctness
9719 depends on its real-time behavior, delays introduced by a debugger
9720 might cause the program to change its behavior drastically, or perhaps
9721 fail, even when the code itself is correct. It is useful to be able
9722 to observe the program's behavior without interrupting it.
9724 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9725 specify locations in the program, called @dfn{tracepoints}, and
9726 arbitrary expressions to evaluate when those tracepoints are reached.
9727 Later, using the @code{tfind} command, you can examine the values
9728 those expressions had when the program hit the tracepoints. The
9729 expressions may also denote objects in memory---structures or arrays,
9730 for example---whose values @value{GDBN} should record; while visiting
9731 a particular tracepoint, you may inspect those objects as if they were
9732 in memory at that moment. However, because @value{GDBN} records these
9733 values without interacting with you, it can do so quickly and
9734 unobtrusively, hopefully not disturbing the program's behavior.
9736 The tracepoint facility is currently available only for remote
9737 targets. @xref{Targets}. In addition, your remote target must know
9738 how to collect trace data. This functionality is implemented in the
9739 remote stub; however, none of the stubs distributed with @value{GDBN}
9740 support tracepoints as of this writing. The format of the remote
9741 packets used to implement tracepoints are described in @ref{Tracepoint
9744 It is also possible to get trace data from a file, in a manner reminiscent
9745 of corefiles; you specify the filename, and use @code{tfind} to search
9746 through the file. @xref{Trace Files}, for more details.
9748 This chapter describes the tracepoint commands and features.
9752 * Analyze Collected Data::
9753 * Tracepoint Variables::
9757 @node Set Tracepoints
9758 @section Commands to Set Tracepoints
9760 Before running such a @dfn{trace experiment}, an arbitrary number of
9761 tracepoints can be set. A tracepoint is actually a special type of
9762 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9763 standard breakpoint commands. For instance, as with breakpoints,
9764 tracepoint numbers are successive integers starting from one, and many
9765 of the commands associated with tracepoints take the tracepoint number
9766 as their argument, to identify which tracepoint to work on.
9768 For each tracepoint, you can specify, in advance, some arbitrary set
9769 of data that you want the target to collect in the trace buffer when
9770 it hits that tracepoint. The collected data can include registers,
9771 local variables, or global data. Later, you can use @value{GDBN}
9772 commands to examine the values these data had at the time the
9775 Tracepoints do not support every breakpoint feature. Ignore counts on
9776 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9777 commands when they are hit. Tracepoints may not be thread-specific
9780 @cindex fast tracepoints
9781 Some targets may support @dfn{fast tracepoints}, which are inserted in
9782 a different way (such as with a jump instead of a trap), that is
9783 faster but possibly restricted in where they may be installed.
9785 @cindex static tracepoints
9786 @cindex markers, static tracepoints
9787 @cindex probing markers, static tracepoints
9788 Regular and fast tracepoints are dynamic tracing facilities, meaning
9789 that they can be used to insert tracepoints at (almost) any location
9790 in the target. Some targets may also support controlling @dfn{static
9791 tracepoints} from @value{GDBN}. With static tracing, a set of
9792 instrumentation points, also known as @dfn{markers}, are embedded in
9793 the target program, and can be activated or deactivated by name or
9794 address. These are usually placed at locations which facilitate
9795 investigating what the target is actually doing. @value{GDBN}'s
9796 support for static tracing includes being able to list instrumentation
9797 points, and attach them with @value{GDBN} defined high level
9798 tracepoints that expose the whole range of convenience of
9799 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9800 registers values and values of global or local (to the instrumentation
9801 point) variables; tracepoint conditions and trace state variables.
9802 The act of installing a @value{GDBN} static tracepoint on an
9803 instrumentation point, or marker, is referred to as @dfn{probing} a
9804 static tracepoint marker.
9806 @code{gdbserver} supports tracepoints on some target systems.
9807 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9809 This section describes commands to set tracepoints and associated
9810 conditions and actions.
9813 * Create and Delete Tracepoints::
9814 * Enable and Disable Tracepoints::
9815 * Tracepoint Passcounts::
9816 * Tracepoint Conditions::
9817 * Trace State Variables::
9818 * Tracepoint Actions::
9819 * Listing Tracepoints::
9820 * Listing Static Tracepoint Markers::
9821 * Starting and Stopping Trace Experiments::
9822 * Tracepoint Restrictions::
9825 @node Create and Delete Tracepoints
9826 @subsection Create and Delete Tracepoints
9829 @cindex set tracepoint
9831 @item trace @var{location}
9832 The @code{trace} command is very similar to the @code{break} command.
9833 Its argument @var{location} can be a source line, a function name, or
9834 an address in the target program. @xref{Specify Location}. The
9835 @code{trace} command defines a tracepoint, which is a point in the
9836 target program where the debugger will briefly stop, collect some
9837 data, and then allow the program to continue. Setting a tracepoint or
9838 changing its actions doesn't take effect until the next @code{tstart}
9839 command, and once a trace experiment is running, further changes will
9840 not have any effect until the next trace experiment starts.
9842 Here are some examples of using the @code{trace} command:
9845 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9847 (@value{GDBP}) @b{trace +2} // 2 lines forward
9849 (@value{GDBP}) @b{trace my_function} // first source line of function
9851 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9853 (@value{GDBP}) @b{trace *0x2117c4} // an address
9857 You can abbreviate @code{trace} as @code{tr}.
9859 @item trace @var{location} if @var{cond}
9860 Set a tracepoint with condition @var{cond}; evaluate the expression
9861 @var{cond} each time the tracepoint is reached, and collect data only
9862 if the value is nonzero---that is, if @var{cond} evaluates as true.
9863 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9864 information on tracepoint conditions.
9866 @item ftrace @var{location} [ if @var{cond} ]
9867 @cindex set fast tracepoint
9868 @cindex fast tracepoints, setting
9870 The @code{ftrace} command sets a fast tracepoint. For targets that
9871 support them, fast tracepoints will use a more efficient but possibly
9872 less general technique to trigger data collection, such as a jump
9873 instruction instead of a trap, or some sort of hardware support. It
9874 may not be possible to create a fast tracepoint at the desired
9875 location, in which case the command will exit with an explanatory
9878 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9881 @item strace @var{location} [ if @var{cond} ]
9882 @cindex set static tracepoint
9883 @cindex static tracepoints, setting
9884 @cindex probe static tracepoint marker
9886 The @code{strace} command sets a static tracepoint. For targets that
9887 support it, setting a static tracepoint probes a static
9888 instrumentation point, or marker, found at @var{location}. It may not
9889 be possible to set a static tracepoint at the desired location, in
9890 which case the command will exit with an explanatory message.
9892 @value{GDBN} handles arguments to @code{strace} exactly as for
9893 @code{trace}, with the addition that the user can also specify
9894 @code{-m @var{marker}} as @var{location}. This probes the marker
9895 identified by the @var{marker} string identifier. This identifier
9896 depends on the static tracepoint backend library your program is
9897 using. You can find all the marker identifiers in the @samp{ID} field
9898 of the @code{info static-tracepoint-markers} command output.
9899 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9900 Markers}. For example, in the following small program using the UST
9906 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9911 the marker id is composed of joining the first two arguments to the
9912 @code{trace_mark} call with a slash, which translates to:
9915 (@value{GDBP}) info static-tracepoint-markers
9916 Cnt Enb ID Address What
9917 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9923 so you may probe the marker above with:
9926 (@value{GDBP}) strace -m ust/bar33
9929 Static tracepoints accept an extra collect action --- @code{collect
9930 $_sdata}. This collects arbitrary user data passed in the probe point
9931 call to the tracing library. In the UST example above, you'll see
9932 that the third argument to @code{trace_mark} is a printf-like format
9933 string. The user data is then the result of running that formating
9934 string against the following arguments. Note that @code{info
9935 static-tracepoint-markers} command output lists that format string in
9936 the @samp{Data:} field.
9938 You can inspect this data when analyzing the trace buffer, by printing
9939 the $_sdata variable like any other variable available to
9940 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9943 @cindex last tracepoint number
9944 @cindex recent tracepoint number
9945 @cindex tracepoint number
9946 The convenience variable @code{$tpnum} records the tracepoint number
9947 of the most recently set tracepoint.
9949 @kindex delete tracepoint
9950 @cindex tracepoint deletion
9951 @item delete tracepoint @r{[}@var{num}@r{]}
9952 Permanently delete one or more tracepoints. With no argument, the
9953 default is to delete all tracepoints. Note that the regular
9954 @code{delete} command can remove tracepoints also.
9959 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9961 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9965 You can abbreviate this command as @code{del tr}.
9968 @node Enable and Disable Tracepoints
9969 @subsection Enable and Disable Tracepoints
9971 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9974 @kindex disable tracepoint
9975 @item disable tracepoint @r{[}@var{num}@r{]}
9976 Disable tracepoint @var{num}, or all tracepoints if no argument
9977 @var{num} is given. A disabled tracepoint will have no effect during
9978 the next trace experiment, but it is not forgotten. You can re-enable
9979 a disabled tracepoint using the @code{enable tracepoint} command.
9981 @kindex enable tracepoint
9982 @item enable tracepoint @r{[}@var{num}@r{]}
9983 Enable tracepoint @var{num}, or all tracepoints. The enabled
9984 tracepoints will become effective the next time a trace experiment is
9988 @node Tracepoint Passcounts
9989 @subsection Tracepoint Passcounts
9993 @cindex tracepoint pass count
9994 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9995 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9996 automatically stop a trace experiment. If a tracepoint's passcount is
9997 @var{n}, then the trace experiment will be automatically stopped on
9998 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9999 @var{num} is not specified, the @code{passcount} command sets the
10000 passcount of the most recently defined tracepoint. If no passcount is
10001 given, the trace experiment will run until stopped explicitly by the
10007 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10008 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10010 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10011 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10012 (@value{GDBP}) @b{trace foo}
10013 (@value{GDBP}) @b{pass 3}
10014 (@value{GDBP}) @b{trace bar}
10015 (@value{GDBP}) @b{pass 2}
10016 (@value{GDBP}) @b{trace baz}
10017 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10018 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10019 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10020 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10024 @node Tracepoint Conditions
10025 @subsection Tracepoint Conditions
10026 @cindex conditional tracepoints
10027 @cindex tracepoint conditions
10029 The simplest sort of tracepoint collects data every time your program
10030 reaches a specified place. You can also specify a @dfn{condition} for
10031 a tracepoint. A condition is just a Boolean expression in your
10032 programming language (@pxref{Expressions, ,Expressions}). A
10033 tracepoint with a condition evaluates the expression each time your
10034 program reaches it, and data collection happens only if the condition
10037 Tracepoint conditions can be specified when a tracepoint is set, by
10038 using @samp{if} in the arguments to the @code{trace} command.
10039 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10040 also be set or changed at any time with the @code{condition} command,
10041 just as with breakpoints.
10043 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10044 the conditional expression itself. Instead, @value{GDBN} encodes the
10045 expression into an agent expression (@pxref{Agent Expressions}
10046 suitable for execution on the target, independently of @value{GDBN}.
10047 Global variables become raw memory locations, locals become stack
10048 accesses, and so forth.
10050 For instance, suppose you have a function that is usually called
10051 frequently, but should not be called after an error has occurred. You
10052 could use the following tracepoint command to collect data about calls
10053 of that function that happen while the error code is propagating
10054 through the program; an unconditional tracepoint could end up
10055 collecting thousands of useless trace frames that you would have to
10059 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10062 @node Trace State Variables
10063 @subsection Trace State Variables
10064 @cindex trace state variables
10066 A @dfn{trace state variable} is a special type of variable that is
10067 created and managed by target-side code. The syntax is the same as
10068 that for GDB's convenience variables (a string prefixed with ``$''),
10069 but they are stored on the target. They must be created explicitly,
10070 using a @code{tvariable} command. They are always 64-bit signed
10073 Trace state variables are remembered by @value{GDBN}, and downloaded
10074 to the target along with tracepoint information when the trace
10075 experiment starts. There are no intrinsic limits on the number of
10076 trace state variables, beyond memory limitations of the target.
10078 @cindex convenience variables, and trace state variables
10079 Although trace state variables are managed by the target, you can use
10080 them in print commands and expressions as if they were convenience
10081 variables; @value{GDBN} will get the current value from the target
10082 while the trace experiment is running. Trace state variables share
10083 the same namespace as other ``$'' variables, which means that you
10084 cannot have trace state variables with names like @code{$23} or
10085 @code{$pc}, nor can you have a trace state variable and a convenience
10086 variable with the same name.
10090 @item tvariable $@var{name} [ = @var{expression} ]
10092 The @code{tvariable} command creates a new trace state variable named
10093 @code{$@var{name}}, and optionally gives it an initial value of
10094 @var{expression}. @var{expression} is evaluated when this command is
10095 entered; the result will be converted to an integer if possible,
10096 otherwise @value{GDBN} will report an error. A subsequent
10097 @code{tvariable} command specifying the same name does not create a
10098 variable, but instead assigns the supplied initial value to the
10099 existing variable of that name, overwriting any previous initial
10100 value. The default initial value is 0.
10102 @item info tvariables
10103 @kindex info tvariables
10104 List all the trace state variables along with their initial values.
10105 Their current values may also be displayed, if the trace experiment is
10108 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10109 @kindex delete tvariable
10110 Delete the given trace state variables, or all of them if no arguments
10115 @node Tracepoint Actions
10116 @subsection Tracepoint Action Lists
10120 @cindex tracepoint actions
10121 @item actions @r{[}@var{num}@r{]}
10122 This command will prompt for a list of actions to be taken when the
10123 tracepoint is hit. If the tracepoint number @var{num} is not
10124 specified, this command sets the actions for the one that was most
10125 recently defined (so that you can define a tracepoint and then say
10126 @code{actions} without bothering about its number). You specify the
10127 actions themselves on the following lines, one action at a time, and
10128 terminate the actions list with a line containing just @code{end}. So
10129 far, the only defined actions are @code{collect}, @code{teval}, and
10130 @code{while-stepping}.
10132 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10133 Commands, ,Breakpoint Command Lists}), except that only the defined
10134 actions are allowed; any other @value{GDBN} command is rejected.
10136 @cindex remove actions from a tracepoint
10137 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10138 and follow it immediately with @samp{end}.
10141 (@value{GDBP}) @b{collect @var{data}} // collect some data
10143 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10145 (@value{GDBP}) @b{end} // signals the end of actions.
10148 In the following example, the action list begins with @code{collect}
10149 commands indicating the things to be collected when the tracepoint is
10150 hit. Then, in order to single-step and collect additional data
10151 following the tracepoint, a @code{while-stepping} command is used,
10152 followed by the list of things to be collected after each step in a
10153 sequence of single steps. The @code{while-stepping} command is
10154 terminated by its own separate @code{end} command. Lastly, the action
10155 list is terminated by an @code{end} command.
10158 (@value{GDBP}) @b{trace foo}
10159 (@value{GDBP}) @b{actions}
10160 Enter actions for tracepoint 1, one per line:
10163 > while-stepping 12
10164 > collect $pc, arr[i]
10169 @kindex collect @r{(tracepoints)}
10170 @item collect @var{expr1}, @var{expr2}, @dots{}
10171 Collect values of the given expressions when the tracepoint is hit.
10172 This command accepts a comma-separated list of any valid expressions.
10173 In addition to global, static, or local variables, the following
10174 special arguments are supported:
10178 Collect all registers.
10181 Collect all function arguments.
10184 Collect all local variables.
10187 @vindex $_sdata@r{, collect}
10188 Collect static tracepoint marker specific data. Only available for
10189 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10190 Lists}. On the UST static tracepoints library backend, an
10191 instrumentation point resembles a @code{printf} function call. The
10192 tracing library is able to collect user specified data formatted to a
10193 character string using the format provided by the programmer that
10194 instrumented the program. Other backends have similar mechanisms.
10195 Here's an example of a UST marker call:
10198 const char master_name[] = "$your_name";
10199 trace_mark(channel1, marker1, "hello %s", master_name)
10202 In this case, collecting @code{$_sdata} collects the string
10203 @samp{hello $yourname}. When analyzing the trace buffer, you can
10204 inspect @samp{$_sdata} like any other variable available to
10208 You can give several consecutive @code{collect} commands, each one
10209 with a single argument, or one @code{collect} command with several
10210 arguments separated by commas; the effect is the same.
10212 The command @code{info scope} (@pxref{Symbols, info scope}) is
10213 particularly useful for figuring out what data to collect.
10215 @kindex teval @r{(tracepoints)}
10216 @item teval @var{expr1}, @var{expr2}, @dots{}
10217 Evaluate the given expressions when the tracepoint is hit. This
10218 command accepts a comma-separated list of expressions. The results
10219 are discarded, so this is mainly useful for assigning values to trace
10220 state variables (@pxref{Trace State Variables}) without adding those
10221 values to the trace buffer, as would be the case if the @code{collect}
10224 @kindex while-stepping @r{(tracepoints)}
10225 @item while-stepping @var{n}
10226 Perform @var{n} single-step instruction traces after the tracepoint,
10227 collecting new data after each step. The @code{while-stepping}
10228 command is followed by the list of what to collect while stepping
10229 (followed by its own @code{end} command):
10232 > while-stepping 12
10233 > collect $regs, myglobal
10239 Note that @code{$pc} is not automatically collected by
10240 @code{while-stepping}; you need to explicitly collect that register if
10241 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10244 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10245 @kindex set default-collect
10246 @cindex default collection action
10247 This variable is a list of expressions to collect at each tracepoint
10248 hit. It is effectively an additional @code{collect} action prepended
10249 to every tracepoint action list. The expressions are parsed
10250 individually for each tracepoint, so for instance a variable named
10251 @code{xyz} may be interpreted as a global for one tracepoint, and a
10252 local for another, as appropriate to the tracepoint's location.
10254 @item show default-collect
10255 @kindex show default-collect
10256 Show the list of expressions that are collected by default at each
10261 @node Listing Tracepoints
10262 @subsection Listing Tracepoints
10265 @kindex info tracepoints
10267 @cindex information about tracepoints
10268 @item info tracepoints @r{[}@var{num}@r{]}
10269 Display information about the tracepoint @var{num}. If you don't
10270 specify a tracepoint number, displays information about all the
10271 tracepoints defined so far. The format is similar to that used for
10272 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10273 command, simply restricting itself to tracepoints.
10275 A tracepoint's listing may include additional information specific to
10280 its passcount as given by the @code{passcount @var{n}} command
10284 (@value{GDBP}) @b{info trace}
10285 Num Type Disp Enb Address What
10286 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10288 collect globfoo, $regs
10297 This command can be abbreviated @code{info tp}.
10300 @node Listing Static Tracepoint Markers
10301 @subsection Listing Static Tracepoint Markers
10304 @kindex info static-tracepoint-markers
10305 @cindex information about static tracepoint markers
10306 @item info static-tracepoint-markers
10307 Display information about all static tracepoint markers defined in the
10310 For each marker, the following columns are printed:
10314 An incrementing counter, output to help readability. This is not a
10317 The marker ID, as reported by the target.
10318 @item Enabled or Disabled
10319 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10320 that are not enabled.
10322 Where the marker is in your program, as a memory address.
10324 Where the marker is in the source for your program, as a file and line
10325 number. If the debug information included in the program does not
10326 allow @value{GDBN} to locate the source of the marker, this column
10327 will be left blank.
10331 In addition, the following information may be printed for each marker:
10335 User data passed to the tracing library by the marker call. In the
10336 UST backend, this is the format string passed as argument to the
10338 @item Static tracepoints probing the marker
10339 The list of static tracepoints attached to the marker.
10343 (@value{GDBP}) info static-tracepoint-markers
10344 Cnt ID Enb Address What
10345 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10346 Data: number1 %d number2 %d
10347 Probed by static tracepoints: #2
10348 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10354 @node Starting and Stopping Trace Experiments
10355 @subsection Starting and Stopping Trace Experiments
10359 @cindex start a new trace experiment
10360 @cindex collected data discarded
10362 This command takes no arguments. It starts the trace experiment, and
10363 begins collecting data. This has the side effect of discarding all
10364 the data collected in the trace buffer during the previous trace
10368 @cindex stop a running trace experiment
10370 This command takes no arguments. It ends the trace experiment, and
10371 stops collecting data.
10373 @strong{Note}: a trace experiment and data collection may stop
10374 automatically if any tracepoint's passcount is reached
10375 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10378 @cindex status of trace data collection
10379 @cindex trace experiment, status of
10381 This command displays the status of the current trace data
10385 Here is an example of the commands we described so far:
10388 (@value{GDBP}) @b{trace gdb_c_test}
10389 (@value{GDBP}) @b{actions}
10390 Enter actions for tracepoint #1, one per line.
10391 > collect $regs,$locals,$args
10392 > while-stepping 11
10396 (@value{GDBP}) @b{tstart}
10397 [time passes @dots{}]
10398 (@value{GDBP}) @b{tstop}
10401 @cindex disconnected tracing
10402 You can choose to continue running the trace experiment even if
10403 @value{GDBN} disconnects from the target, voluntarily or
10404 involuntarily. For commands such as @code{detach}, the debugger will
10405 ask what you want to do with the trace. But for unexpected
10406 terminations (@value{GDBN} crash, network outage), it would be
10407 unfortunate to lose hard-won trace data, so the variable
10408 @code{disconnected-tracing} lets you decide whether the trace should
10409 continue running without @value{GDBN}.
10412 @item set disconnected-tracing on
10413 @itemx set disconnected-tracing off
10414 @kindex set disconnected-tracing
10415 Choose whether a tracing run should continue to run if @value{GDBN}
10416 has disconnected from the target. Note that @code{detach} or
10417 @code{quit} will ask you directly what to do about a running trace no
10418 matter what this variable's setting, so the variable is mainly useful
10419 for handling unexpected situations, such as loss of the network.
10421 @item show disconnected-tracing
10422 @kindex show disconnected-tracing
10423 Show the current choice for disconnected tracing.
10427 When you reconnect to the target, the trace experiment may or may not
10428 still be running; it might have filled the trace buffer in the
10429 meantime, or stopped for one of the other reasons. If it is running,
10430 it will continue after reconnection.
10432 Upon reconnection, the target will upload information about the
10433 tracepoints in effect. @value{GDBN} will then compare that
10434 information to the set of tracepoints currently defined, and attempt
10435 to match them up, allowing for the possibility that the numbers may
10436 have changed due to creation and deletion in the meantime. If one of
10437 the target's tracepoints does not match any in @value{GDBN}, the
10438 debugger will create a new tracepoint, so that you have a number with
10439 which to specify that tracepoint. This matching-up process is
10440 necessarily heuristic, and it may result in useless tracepoints being
10441 created; you may simply delete them if they are of no use.
10443 @cindex circular trace buffer
10444 If your target agent supports a @dfn{circular trace buffer}, then you
10445 can run a trace experiment indefinitely without filling the trace
10446 buffer; when space runs out, the agent deletes already-collected trace
10447 frames, oldest first, until there is enough room to continue
10448 collecting. This is especially useful if your tracepoints are being
10449 hit too often, and your trace gets terminated prematurely because the
10450 buffer is full. To ask for a circular trace buffer, simply set
10451 @samp{circular_trace_buffer} to on. You can set this at any time,
10452 including during tracing; if the agent can do it, it will change
10453 buffer handling on the fly, otherwise it will not take effect until
10457 @item set circular-trace-buffer on
10458 @itemx set circular-trace-buffer off
10459 @kindex set circular-trace-buffer
10460 Choose whether a tracing run should use a linear or circular buffer
10461 for trace data. A linear buffer will not lose any trace data, but may
10462 fill up prematurely, while a circular buffer will discard old trace
10463 data, but it will have always room for the latest tracepoint hits.
10465 @item show circular-trace-buffer
10466 @kindex show circular-trace-buffer
10467 Show the current choice for the trace buffer. Note that this may not
10468 match the agent's current buffer handling, nor is it guaranteed to
10469 match the setting that might have been in effect during a past run,
10470 for instance if you are looking at frames from a trace file.
10474 @node Tracepoint Restrictions
10475 @subsection Tracepoint Restrictions
10477 @cindex tracepoint restrictions
10478 There are a number of restrictions on the use of tracepoints. As
10479 described above, tracepoint data gathering occurs on the target
10480 without interaction from @value{GDBN}. Thus the full capabilities of
10481 the debugger are not available during data gathering, and then at data
10482 examination time, you will be limited by only having what was
10483 collected. The following items describe some common problems, but it
10484 is not exhaustive, and you may run into additional difficulties not
10490 Tracepoint expressions are intended to gather objects (lvalues). Thus
10491 the full flexibility of GDB's expression evaluator is not available.
10492 You cannot call functions, cast objects to aggregate types, access
10493 convenience variables or modify values (except by assignment to trace
10494 state variables). Some language features may implicitly call
10495 functions (for instance Objective-C fields with accessors), and therefore
10496 cannot be collected either.
10499 Collection of local variables, either individually or in bulk with
10500 @code{$locals} or @code{$args}, during @code{while-stepping} may
10501 behave erratically. The stepping action may enter a new scope (for
10502 instance by stepping into a function), or the location of the variable
10503 may change (for instance it is loaded into a register). The
10504 tracepoint data recorded uses the location information for the
10505 variables that is correct for the tracepoint location. When the
10506 tracepoint is created, it is not possible, in general, to determine
10507 where the steps of a @code{while-stepping} sequence will advance the
10508 program---particularly if a conditional branch is stepped.
10511 Collection of an incompletely-initialized or partially-destroyed object
10512 may result in something that @value{GDBN} cannot display, or displays
10513 in a misleading way.
10516 When @value{GDBN} displays a pointer to character it automatically
10517 dereferences the pointer to also display characters of the string
10518 being pointed to. However, collecting the pointer during tracing does
10519 not automatically collect the string. You need to explicitly
10520 dereference the pointer and provide size information if you want to
10521 collect not only the pointer, but the memory pointed to. For example,
10522 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10526 It is not possible to collect a complete stack backtrace at a
10527 tracepoint. Instead, you may collect the registers and a few hundred
10528 bytes from the stack pointer with something like @code{*$esp@@300}
10529 (adjust to use the name of the actual stack pointer register on your
10530 target architecture, and the amount of stack you wish to capture).
10531 Then the @code{backtrace} command will show a partial backtrace when
10532 using a trace frame. The number of stack frames that can be examined
10533 depends on the sizes of the frames in the collected stack. Note that
10534 if you ask for a block so large that it goes past the bottom of the
10535 stack, the target agent may report an error trying to read from an
10539 If you do not collect registers at a tracepoint, @value{GDBN} can
10540 infer that the value of @code{$pc} must be the same as the address of
10541 the tracepoint and use that when you are looking at a trace frame
10542 for that tracepoint. However, this cannot work if the tracepoint has
10543 multiple locations (for instance if it was set in a function that was
10544 inlined), or if it has a @code{while-stepping} loop. In those cases
10545 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10550 @node Analyze Collected Data
10551 @section Using the Collected Data
10553 After the tracepoint experiment ends, you use @value{GDBN} commands
10554 for examining the trace data. The basic idea is that each tracepoint
10555 collects a trace @dfn{snapshot} every time it is hit and another
10556 snapshot every time it single-steps. All these snapshots are
10557 consecutively numbered from zero and go into a buffer, and you can
10558 examine them later. The way you examine them is to @dfn{focus} on a
10559 specific trace snapshot. When the remote stub is focused on a trace
10560 snapshot, it will respond to all @value{GDBN} requests for memory and
10561 registers by reading from the buffer which belongs to that snapshot,
10562 rather than from @emph{real} memory or registers of the program being
10563 debugged. This means that @strong{all} @value{GDBN} commands
10564 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10565 behave as if we were currently debugging the program state as it was
10566 when the tracepoint occurred. Any requests for data that are not in
10567 the buffer will fail.
10570 * tfind:: How to select a trace snapshot
10571 * tdump:: How to display all data for a snapshot
10572 * save tracepoints:: How to save tracepoints for a future run
10576 @subsection @code{tfind @var{n}}
10579 @cindex select trace snapshot
10580 @cindex find trace snapshot
10581 The basic command for selecting a trace snapshot from the buffer is
10582 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10583 counting from zero. If no argument @var{n} is given, the next
10584 snapshot is selected.
10586 Here are the various forms of using the @code{tfind} command.
10590 Find the first snapshot in the buffer. This is a synonym for
10591 @code{tfind 0} (since 0 is the number of the first snapshot).
10594 Stop debugging trace snapshots, resume @emph{live} debugging.
10597 Same as @samp{tfind none}.
10600 No argument means find the next trace snapshot.
10603 Find the previous trace snapshot before the current one. This permits
10604 retracing earlier steps.
10606 @item tfind tracepoint @var{num}
10607 Find the next snapshot associated with tracepoint @var{num}. Search
10608 proceeds forward from the last examined trace snapshot. If no
10609 argument @var{num} is given, it means find the next snapshot collected
10610 for the same tracepoint as the current snapshot.
10612 @item tfind pc @var{addr}
10613 Find the next snapshot associated with the value @var{addr} of the
10614 program counter. Search proceeds forward from the last examined trace
10615 snapshot. If no argument @var{addr} is given, it means find the next
10616 snapshot with the same value of PC as the current snapshot.
10618 @item tfind outside @var{addr1}, @var{addr2}
10619 Find the next snapshot whose PC is outside the given range of
10620 addresses (exclusive).
10622 @item tfind range @var{addr1}, @var{addr2}
10623 Find the next snapshot whose PC is between @var{addr1} and
10624 @var{addr2} (inclusive).
10626 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10627 Find the next snapshot associated with the source line @var{n}. If
10628 the optional argument @var{file} is given, refer to line @var{n} in
10629 that source file. Search proceeds forward from the last examined
10630 trace snapshot. If no argument @var{n} is given, it means find the
10631 next line other than the one currently being examined; thus saying
10632 @code{tfind line} repeatedly can appear to have the same effect as
10633 stepping from line to line in a @emph{live} debugging session.
10636 The default arguments for the @code{tfind} commands are specifically
10637 designed to make it easy to scan through the trace buffer. For
10638 instance, @code{tfind} with no argument selects the next trace
10639 snapshot, and @code{tfind -} with no argument selects the previous
10640 trace snapshot. So, by giving one @code{tfind} command, and then
10641 simply hitting @key{RET} repeatedly you can examine all the trace
10642 snapshots in order. Or, by saying @code{tfind -} and then hitting
10643 @key{RET} repeatedly you can examine the snapshots in reverse order.
10644 The @code{tfind line} command with no argument selects the snapshot
10645 for the next source line executed. The @code{tfind pc} command with
10646 no argument selects the next snapshot with the same program counter
10647 (PC) as the current frame. The @code{tfind tracepoint} command with
10648 no argument selects the next trace snapshot collected by the same
10649 tracepoint as the current one.
10651 In addition to letting you scan through the trace buffer manually,
10652 these commands make it easy to construct @value{GDBN} scripts that
10653 scan through the trace buffer and print out whatever collected data
10654 you are interested in. Thus, if we want to examine the PC, FP, and SP
10655 registers from each trace frame in the buffer, we can say this:
10658 (@value{GDBP}) @b{tfind start}
10659 (@value{GDBP}) @b{while ($trace_frame != -1)}
10660 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10661 $trace_frame, $pc, $sp, $fp
10665 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10666 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10667 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10668 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10669 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10670 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10671 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10672 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10673 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10674 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10675 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10678 Or, if we want to examine the variable @code{X} at each source line in
10682 (@value{GDBP}) @b{tfind start}
10683 (@value{GDBP}) @b{while ($trace_frame != -1)}
10684 > printf "Frame %d, X == %d\n", $trace_frame, X
10694 @subsection @code{tdump}
10696 @cindex dump all data collected at tracepoint
10697 @cindex tracepoint data, display
10699 This command takes no arguments. It prints all the data collected at
10700 the current trace snapshot.
10703 (@value{GDBP}) @b{trace 444}
10704 (@value{GDBP}) @b{actions}
10705 Enter actions for tracepoint #2, one per line:
10706 > collect $regs, $locals, $args, gdb_long_test
10709 (@value{GDBP}) @b{tstart}
10711 (@value{GDBP}) @b{tfind line 444}
10712 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10714 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10716 (@value{GDBP}) @b{tdump}
10717 Data collected at tracepoint 2, trace frame 1:
10718 d0 0xc4aa0085 -995491707
10722 d4 0x71aea3d 119204413
10725 d7 0x380035 3670069
10726 a0 0x19e24a 1696330
10727 a1 0x3000668 50333288
10729 a3 0x322000 3284992
10730 a4 0x3000698 50333336
10731 a5 0x1ad3cc 1758156
10732 fp 0x30bf3c 0x30bf3c
10733 sp 0x30bf34 0x30bf34
10735 pc 0x20b2c8 0x20b2c8
10739 p = 0x20e5b4 "gdb-test"
10746 gdb_long_test = 17 '\021'
10751 @code{tdump} works by scanning the tracepoint's current collection
10752 actions and printing the value of each expression listed. So
10753 @code{tdump} can fail, if after a run, you change the tracepoint's
10754 actions to mention variables that were not collected during the run.
10756 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10757 uses the collected value of @code{$pc} to distinguish between trace
10758 frames that were collected at the tracepoint hit, and frames that were
10759 collected while stepping. This allows it to correctly choose whether
10760 to display the basic list of collections, or the collections from the
10761 body of the while-stepping loop. However, if @code{$pc} was not collected,
10762 then @code{tdump} will always attempt to dump using the basic collection
10763 list, and may fail if a while-stepping frame does not include all the
10764 same data that is collected at the tracepoint hit.
10765 @c This is getting pretty arcane, example would be good.
10767 @node save tracepoints
10768 @subsection @code{save tracepoints @var{filename}}
10769 @kindex save tracepoints
10770 @kindex save-tracepoints
10771 @cindex save tracepoints for future sessions
10773 This command saves all current tracepoint definitions together with
10774 their actions and passcounts, into a file @file{@var{filename}}
10775 suitable for use in a later debugging session. To read the saved
10776 tracepoint definitions, use the @code{source} command (@pxref{Command
10777 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10778 alias for @w{@code{save tracepoints}}
10780 @node Tracepoint Variables
10781 @section Convenience Variables for Tracepoints
10782 @cindex tracepoint variables
10783 @cindex convenience variables for tracepoints
10786 @vindex $trace_frame
10787 @item (int) $trace_frame
10788 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10789 snapshot is selected.
10791 @vindex $tracepoint
10792 @item (int) $tracepoint
10793 The tracepoint for the current trace snapshot.
10795 @vindex $trace_line
10796 @item (int) $trace_line
10797 The line number for the current trace snapshot.
10799 @vindex $trace_file
10800 @item (char []) $trace_file
10801 The source file for the current trace snapshot.
10803 @vindex $trace_func
10804 @item (char []) $trace_func
10805 The name of the function containing @code{$tracepoint}.
10808 Note: @code{$trace_file} is not suitable for use in @code{printf},
10809 use @code{output} instead.
10811 Here's a simple example of using these convenience variables for
10812 stepping through all the trace snapshots and printing some of their
10813 data. Note that these are not the same as trace state variables,
10814 which are managed by the target.
10817 (@value{GDBP}) @b{tfind start}
10819 (@value{GDBP}) @b{while $trace_frame != -1}
10820 > output $trace_file
10821 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10827 @section Using Trace Files
10828 @cindex trace files
10830 In some situations, the target running a trace experiment may no
10831 longer be available; perhaps it crashed, or the hardware was needed
10832 for a different activity. To handle these cases, you can arrange to
10833 dump the trace data into a file, and later use that file as a source
10834 of trace data, via the @code{target tfile} command.
10839 @item tsave [ -r ] @var{filename}
10840 Save the trace data to @var{filename}. By default, this command
10841 assumes that @var{filename} refers to the host filesystem, so if
10842 necessary @value{GDBN} will copy raw trace data up from the target and
10843 then save it. If the target supports it, you can also supply the
10844 optional argument @code{-r} (``remote'') to direct the target to save
10845 the data directly into @var{filename} in its own filesystem, which may be
10846 more efficient if the trace buffer is very large. (Note, however, that
10847 @code{target tfile} can only read from files accessible to the host.)
10849 @kindex target tfile
10851 @item target tfile @var{filename}
10852 Use the file named @var{filename} as a source of trace data. Commands
10853 that examine data work as they do with a live target, but it is not
10854 possible to run any new trace experiments. @code{tstatus} will report
10855 the state of the trace run at the moment the data was saved, as well
10856 as the current trace frame you are examining. @var{filename} must be
10857 on a filesystem accessible to the host.
10862 @chapter Debugging Programs That Use Overlays
10865 If your program is too large to fit completely in your target system's
10866 memory, you can sometimes use @dfn{overlays} to work around this
10867 problem. @value{GDBN} provides some support for debugging programs that
10871 * How Overlays Work:: A general explanation of overlays.
10872 * Overlay Commands:: Managing overlays in @value{GDBN}.
10873 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10874 mapped by asking the inferior.
10875 * Overlay Sample Program:: A sample program using overlays.
10878 @node How Overlays Work
10879 @section How Overlays Work
10880 @cindex mapped overlays
10881 @cindex unmapped overlays
10882 @cindex load address, overlay's
10883 @cindex mapped address
10884 @cindex overlay area
10886 Suppose you have a computer whose instruction address space is only 64
10887 kilobytes long, but which has much more memory which can be accessed by
10888 other means: special instructions, segment registers, or memory
10889 management hardware, for example. Suppose further that you want to
10890 adapt a program which is larger than 64 kilobytes to run on this system.
10892 One solution is to identify modules of your program which are relatively
10893 independent, and need not call each other directly; call these modules
10894 @dfn{overlays}. Separate the overlays from the main program, and place
10895 their machine code in the larger memory. Place your main program in
10896 instruction memory, but leave at least enough space there to hold the
10897 largest overlay as well.
10899 Now, to call a function located in an overlay, you must first copy that
10900 overlay's machine code from the large memory into the space set aside
10901 for it in the instruction memory, and then jump to its entry point
10904 @c NB: In the below the mapped area's size is greater or equal to the
10905 @c size of all overlays. This is intentional to remind the developer
10906 @c that overlays don't necessarily need to be the same size.
10910 Data Instruction Larger
10911 Address Space Address Space Address Space
10912 +-----------+ +-----------+ +-----------+
10914 +-----------+ +-----------+ +-----------+<-- overlay 1
10915 | program | | main | .----| overlay 1 | load address
10916 | variables | | program | | +-----------+
10917 | and heap | | | | | |
10918 +-----------+ | | | +-----------+<-- overlay 2
10919 | | +-----------+ | | | load address
10920 +-----------+ | | | .-| overlay 2 |
10922 mapped --->+-----------+ | | +-----------+
10923 address | | | | | |
10924 | overlay | <-' | | |
10925 | area | <---' +-----------+<-- overlay 3
10926 | | <---. | | load address
10927 +-----------+ `--| overlay 3 |
10934 @anchor{A code overlay}A code overlay
10938 The diagram (@pxref{A code overlay}) shows a system with separate data
10939 and instruction address spaces. To map an overlay, the program copies
10940 its code from the larger address space to the instruction address space.
10941 Since the overlays shown here all use the same mapped address, only one
10942 may be mapped at a time. For a system with a single address space for
10943 data and instructions, the diagram would be similar, except that the
10944 program variables and heap would share an address space with the main
10945 program and the overlay area.
10947 An overlay loaded into instruction memory and ready for use is called a
10948 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10949 instruction memory. An overlay not present (or only partially present)
10950 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10951 is its address in the larger memory. The mapped address is also called
10952 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10953 called the @dfn{load memory address}, or @dfn{LMA}.
10955 Unfortunately, overlays are not a completely transparent way to adapt a
10956 program to limited instruction memory. They introduce a new set of
10957 global constraints you must keep in mind as you design your program:
10962 Before calling or returning to a function in an overlay, your program
10963 must make sure that overlay is actually mapped. Otherwise, the call or
10964 return will transfer control to the right address, but in the wrong
10965 overlay, and your program will probably crash.
10968 If the process of mapping an overlay is expensive on your system, you
10969 will need to choose your overlays carefully to minimize their effect on
10970 your program's performance.
10973 The executable file you load onto your system must contain each
10974 overlay's instructions, appearing at the overlay's load address, not its
10975 mapped address. However, each overlay's instructions must be relocated
10976 and its symbols defined as if the overlay were at its mapped address.
10977 You can use GNU linker scripts to specify different load and relocation
10978 addresses for pieces of your program; see @ref{Overlay Description,,,
10979 ld.info, Using ld: the GNU linker}.
10982 The procedure for loading executable files onto your system must be able
10983 to load their contents into the larger address space as well as the
10984 instruction and data spaces.
10988 The overlay system described above is rather simple, and could be
10989 improved in many ways:
10994 If your system has suitable bank switch registers or memory management
10995 hardware, you could use those facilities to make an overlay's load area
10996 contents simply appear at their mapped address in instruction space.
10997 This would probably be faster than copying the overlay to its mapped
10998 area in the usual way.
11001 If your overlays are small enough, you could set aside more than one
11002 overlay area, and have more than one overlay mapped at a time.
11005 You can use overlays to manage data, as well as instructions. In
11006 general, data overlays are even less transparent to your design than
11007 code overlays: whereas code overlays only require care when you call or
11008 return to functions, data overlays require care every time you access
11009 the data. Also, if you change the contents of a data overlay, you
11010 must copy its contents back out to its load address before you can copy a
11011 different data overlay into the same mapped area.
11016 @node Overlay Commands
11017 @section Overlay Commands
11019 To use @value{GDBN}'s overlay support, each overlay in your program must
11020 correspond to a separate section of the executable file. The section's
11021 virtual memory address and load memory address must be the overlay's
11022 mapped and load addresses. Identifying overlays with sections allows
11023 @value{GDBN} to determine the appropriate address of a function or
11024 variable, depending on whether the overlay is mapped or not.
11026 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11027 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11032 Disable @value{GDBN}'s overlay support. When overlay support is
11033 disabled, @value{GDBN} assumes that all functions and variables are
11034 always present at their mapped addresses. By default, @value{GDBN}'s
11035 overlay support is disabled.
11037 @item overlay manual
11038 @cindex manual overlay debugging
11039 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11040 relies on you to tell it which overlays are mapped, and which are not,
11041 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11042 commands described below.
11044 @item overlay map-overlay @var{overlay}
11045 @itemx overlay map @var{overlay}
11046 @cindex map an overlay
11047 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11048 be the name of the object file section containing the overlay. When an
11049 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11050 functions and variables at their mapped addresses. @value{GDBN} assumes
11051 that any other overlays whose mapped ranges overlap that of
11052 @var{overlay} are now unmapped.
11054 @item overlay unmap-overlay @var{overlay}
11055 @itemx overlay unmap @var{overlay}
11056 @cindex unmap an overlay
11057 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11058 must be the name of the object file section containing the overlay.
11059 When an overlay is unmapped, @value{GDBN} assumes it can find the
11060 overlay's functions and variables at their load addresses.
11063 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11064 consults a data structure the overlay manager maintains in the inferior
11065 to see which overlays are mapped. For details, see @ref{Automatic
11066 Overlay Debugging}.
11068 @item overlay load-target
11069 @itemx overlay load
11070 @cindex reloading the overlay table
11071 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11072 re-reads the table @value{GDBN} automatically each time the inferior
11073 stops, so this command should only be necessary if you have changed the
11074 overlay mapping yourself using @value{GDBN}. This command is only
11075 useful when using automatic overlay debugging.
11077 @item overlay list-overlays
11078 @itemx overlay list
11079 @cindex listing mapped overlays
11080 Display a list of the overlays currently mapped, along with their mapped
11081 addresses, load addresses, and sizes.
11085 Normally, when @value{GDBN} prints a code address, it includes the name
11086 of the function the address falls in:
11089 (@value{GDBP}) print main
11090 $3 = @{int ()@} 0x11a0 <main>
11093 When overlay debugging is enabled, @value{GDBN} recognizes code in
11094 unmapped overlays, and prints the names of unmapped functions with
11095 asterisks around them. For example, if @code{foo} is a function in an
11096 unmapped overlay, @value{GDBN} prints it this way:
11099 (@value{GDBP}) overlay list
11100 No sections are mapped.
11101 (@value{GDBP}) print foo
11102 $5 = @{int (int)@} 0x100000 <*foo*>
11105 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11109 (@value{GDBP}) overlay list
11110 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11111 mapped at 0x1016 - 0x104a
11112 (@value{GDBP}) print foo
11113 $6 = @{int (int)@} 0x1016 <foo>
11116 When overlay debugging is enabled, @value{GDBN} can find the correct
11117 address for functions and variables in an overlay, whether or not the
11118 overlay is mapped. This allows most @value{GDBN} commands, like
11119 @code{break} and @code{disassemble}, to work normally, even on unmapped
11120 code. However, @value{GDBN}'s breakpoint support has some limitations:
11124 @cindex breakpoints in overlays
11125 @cindex overlays, setting breakpoints in
11126 You can set breakpoints in functions in unmapped overlays, as long as
11127 @value{GDBN} can write to the overlay at its load address.
11129 @value{GDBN} can not set hardware or simulator-based breakpoints in
11130 unmapped overlays. However, if you set a breakpoint at the end of your
11131 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11132 you are using manual overlay management), @value{GDBN} will re-set its
11133 breakpoints properly.
11137 @node Automatic Overlay Debugging
11138 @section Automatic Overlay Debugging
11139 @cindex automatic overlay debugging
11141 @value{GDBN} can automatically track which overlays are mapped and which
11142 are not, given some simple co-operation from the overlay manager in the
11143 inferior. If you enable automatic overlay debugging with the
11144 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11145 looks in the inferior's memory for certain variables describing the
11146 current state of the overlays.
11148 Here are the variables your overlay manager must define to support
11149 @value{GDBN}'s automatic overlay debugging:
11153 @item @code{_ovly_table}:
11154 This variable must be an array of the following structures:
11159 /* The overlay's mapped address. */
11162 /* The size of the overlay, in bytes. */
11163 unsigned long size;
11165 /* The overlay's load address. */
11168 /* Non-zero if the overlay is currently mapped;
11170 unsigned long mapped;
11174 @item @code{_novlys}:
11175 This variable must be a four-byte signed integer, holding the total
11176 number of elements in @code{_ovly_table}.
11180 To decide whether a particular overlay is mapped or not, @value{GDBN}
11181 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11182 @code{lma} members equal the VMA and LMA of the overlay's section in the
11183 executable file. When @value{GDBN} finds a matching entry, it consults
11184 the entry's @code{mapped} member to determine whether the overlay is
11187 In addition, your overlay manager may define a function called
11188 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11189 will silently set a breakpoint there. If the overlay manager then
11190 calls this function whenever it has changed the overlay table, this
11191 will enable @value{GDBN} to accurately keep track of which overlays
11192 are in program memory, and update any breakpoints that may be set
11193 in overlays. This will allow breakpoints to work even if the
11194 overlays are kept in ROM or other non-writable memory while they
11195 are not being executed.
11197 @node Overlay Sample Program
11198 @section Overlay Sample Program
11199 @cindex overlay example program
11201 When linking a program which uses overlays, you must place the overlays
11202 at their load addresses, while relocating them to run at their mapped
11203 addresses. To do this, you must write a linker script (@pxref{Overlay
11204 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11205 since linker scripts are specific to a particular host system, target
11206 architecture, and target memory layout, this manual cannot provide
11207 portable sample code demonstrating @value{GDBN}'s overlay support.
11209 However, the @value{GDBN} source distribution does contain an overlaid
11210 program, with linker scripts for a few systems, as part of its test
11211 suite. The program consists of the following files from
11212 @file{gdb/testsuite/gdb.base}:
11216 The main program file.
11218 A simple overlay manager, used by @file{overlays.c}.
11223 Overlay modules, loaded and used by @file{overlays.c}.
11226 Linker scripts for linking the test program on the @code{d10v-elf}
11227 and @code{m32r-elf} targets.
11230 You can build the test program using the @code{d10v-elf} GCC
11231 cross-compiler like this:
11234 $ d10v-elf-gcc -g -c overlays.c
11235 $ d10v-elf-gcc -g -c ovlymgr.c
11236 $ d10v-elf-gcc -g -c foo.c
11237 $ d10v-elf-gcc -g -c bar.c
11238 $ d10v-elf-gcc -g -c baz.c
11239 $ d10v-elf-gcc -g -c grbx.c
11240 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11241 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11244 The build process is identical for any other architecture, except that
11245 you must substitute the appropriate compiler and linker script for the
11246 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11250 @chapter Using @value{GDBN} with Different Languages
11253 Although programming languages generally have common aspects, they are
11254 rarely expressed in the same manner. For instance, in ANSI C,
11255 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11256 Modula-2, it is accomplished by @code{p^}. Values can also be
11257 represented (and displayed) differently. Hex numbers in C appear as
11258 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11260 @cindex working language
11261 Language-specific information is built into @value{GDBN} for some languages,
11262 allowing you to express operations like the above in your program's
11263 native language, and allowing @value{GDBN} to output values in a manner
11264 consistent with the syntax of your program's native language. The
11265 language you use to build expressions is called the @dfn{working
11269 * Setting:: Switching between source languages
11270 * Show:: Displaying the language
11271 * Checks:: Type and range checks
11272 * Supported Languages:: Supported languages
11273 * Unsupported Languages:: Unsupported languages
11277 @section Switching Between Source Languages
11279 There are two ways to control the working language---either have @value{GDBN}
11280 set it automatically, or select it manually yourself. You can use the
11281 @code{set language} command for either purpose. On startup, @value{GDBN}
11282 defaults to setting the language automatically. The working language is
11283 used to determine how expressions you type are interpreted, how values
11286 In addition to the working language, every source file that
11287 @value{GDBN} knows about has its own working language. For some object
11288 file formats, the compiler might indicate which language a particular
11289 source file is in. However, most of the time @value{GDBN} infers the
11290 language from the name of the file. The language of a source file
11291 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11292 show each frame appropriately for its own language. There is no way to
11293 set the language of a source file from within @value{GDBN}, but you can
11294 set the language associated with a filename extension. @xref{Show, ,
11295 Displaying the Language}.
11297 This is most commonly a problem when you use a program, such
11298 as @code{cfront} or @code{f2c}, that generates C but is written in
11299 another language. In that case, make the
11300 program use @code{#line} directives in its C output; that way
11301 @value{GDBN} will know the correct language of the source code of the original
11302 program, and will display that source code, not the generated C code.
11305 * Filenames:: Filename extensions and languages.
11306 * Manually:: Setting the working language manually
11307 * Automatically:: Having @value{GDBN} infer the source language
11311 @subsection List of Filename Extensions and Languages
11313 If a source file name ends in one of the following extensions, then
11314 @value{GDBN} infers that its language is the one indicated.
11332 C@t{++} source file
11338 Objective-C source file
11342 Fortran source file
11345 Modula-2 source file
11349 Assembler source file. This actually behaves almost like C, but
11350 @value{GDBN} does not skip over function prologues when stepping.
11353 In addition, you may set the language associated with a filename
11354 extension. @xref{Show, , Displaying the Language}.
11357 @subsection Setting the Working Language
11359 If you allow @value{GDBN} to set the language automatically,
11360 expressions are interpreted the same way in your debugging session and
11363 @kindex set language
11364 If you wish, you may set the language manually. To do this, issue the
11365 command @samp{set language @var{lang}}, where @var{lang} is the name of
11366 a language, such as
11367 @code{c} or @code{modula-2}.
11368 For a list of the supported languages, type @samp{set language}.
11370 Setting the language manually prevents @value{GDBN} from updating the working
11371 language automatically. This can lead to confusion if you try
11372 to debug a program when the working language is not the same as the
11373 source language, when an expression is acceptable to both
11374 languages---but means different things. For instance, if the current
11375 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11383 might not have the effect you intended. In C, this means to add
11384 @code{b} and @code{c} and place the result in @code{a}. The result
11385 printed would be the value of @code{a}. In Modula-2, this means to compare
11386 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11388 @node Automatically
11389 @subsection Having @value{GDBN} Infer the Source Language
11391 To have @value{GDBN} set the working language automatically, use
11392 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11393 then infers the working language. That is, when your program stops in a
11394 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11395 working language to the language recorded for the function in that
11396 frame. If the language for a frame is unknown (that is, if the function
11397 or block corresponding to the frame was defined in a source file that
11398 does not have a recognized extension), the current working language is
11399 not changed, and @value{GDBN} issues a warning.
11401 This may not seem necessary for most programs, which are written
11402 entirely in one source language. However, program modules and libraries
11403 written in one source language can be used by a main program written in
11404 a different source language. Using @samp{set language auto} in this
11405 case frees you from having to set the working language manually.
11408 @section Displaying the Language
11410 The following commands help you find out which language is the
11411 working language, and also what language source files were written in.
11414 @item show language
11415 @kindex show language
11416 Display the current working language. This is the
11417 language you can use with commands such as @code{print} to
11418 build and compute expressions that may involve variables in your program.
11421 @kindex info frame@r{, show the source language}
11422 Display the source language for this frame. This language becomes the
11423 working language if you use an identifier from this frame.
11424 @xref{Frame Info, ,Information about a Frame}, to identify the other
11425 information listed here.
11428 @kindex info source@r{, show the source language}
11429 Display the source language of this source file.
11430 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11431 information listed here.
11434 In unusual circumstances, you may have source files with extensions
11435 not in the standard list. You can then set the extension associated
11436 with a language explicitly:
11439 @item set extension-language @var{ext} @var{language}
11440 @kindex set extension-language
11441 Tell @value{GDBN} that source files with extension @var{ext} are to be
11442 assumed as written in the source language @var{language}.
11444 @item info extensions
11445 @kindex info extensions
11446 List all the filename extensions and the associated languages.
11450 @section Type and Range Checking
11453 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11454 checking are included, but they do not yet have any effect. This
11455 section documents the intended facilities.
11457 @c FIXME remove warning when type/range code added
11459 Some languages are designed to guard you against making seemingly common
11460 errors through a series of compile- and run-time checks. These include
11461 checking the type of arguments to functions and operators, and making
11462 sure mathematical overflows are caught at run time. Checks such as
11463 these help to ensure a program's correctness once it has been compiled
11464 by eliminating type mismatches, and providing active checks for range
11465 errors when your program is running.
11467 @value{GDBN} can check for conditions like the above if you wish.
11468 Although @value{GDBN} does not check the statements in your program,
11469 it can check expressions entered directly into @value{GDBN} for
11470 evaluation via the @code{print} command, for example. As with the
11471 working language, @value{GDBN} can also decide whether or not to check
11472 automatically based on your program's source language.
11473 @xref{Supported Languages, ,Supported Languages}, for the default
11474 settings of supported languages.
11477 * Type Checking:: An overview of type checking
11478 * Range Checking:: An overview of range checking
11481 @cindex type checking
11482 @cindex checks, type
11483 @node Type Checking
11484 @subsection An Overview of Type Checking
11486 Some languages, such as Modula-2, are strongly typed, meaning that the
11487 arguments to operators and functions have to be of the correct type,
11488 otherwise an error occurs. These checks prevent type mismatch
11489 errors from ever causing any run-time problems. For example,
11497 The second example fails because the @code{CARDINAL} 1 is not
11498 type-compatible with the @code{REAL} 2.3.
11500 For the expressions you use in @value{GDBN} commands, you can tell the
11501 @value{GDBN} type checker to skip checking;
11502 to treat any mismatches as errors and abandon the expression;
11503 or to only issue warnings when type mismatches occur,
11504 but evaluate the expression anyway. When you choose the last of
11505 these, @value{GDBN} evaluates expressions like the second example above, but
11506 also issues a warning.
11508 Even if you turn type checking off, there may be other reasons
11509 related to type that prevent @value{GDBN} from evaluating an expression.
11510 For instance, @value{GDBN} does not know how to add an @code{int} and
11511 a @code{struct foo}. These particular type errors have nothing to do
11512 with the language in use, and usually arise from expressions, such as
11513 the one described above, which make little sense to evaluate anyway.
11515 Each language defines to what degree it is strict about type. For
11516 instance, both Modula-2 and C require the arguments to arithmetical
11517 operators to be numbers. In C, enumerated types and pointers can be
11518 represented as numbers, so that they are valid arguments to mathematical
11519 operators. @xref{Supported Languages, ,Supported Languages}, for further
11520 details on specific languages.
11522 @value{GDBN} provides some additional commands for controlling the type checker:
11524 @kindex set check type
11525 @kindex show check type
11527 @item set check type auto
11528 Set type checking on or off based on the current working language.
11529 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11532 @item set check type on
11533 @itemx set check type off
11534 Set type checking on or off, overriding the default setting for the
11535 current working language. Issue a warning if the setting does not
11536 match the language default. If any type mismatches occur in
11537 evaluating an expression while type checking is on, @value{GDBN} prints a
11538 message and aborts evaluation of the expression.
11540 @item set check type warn
11541 Cause the type checker to issue warnings, but to always attempt to
11542 evaluate the expression. Evaluating the expression may still
11543 be impossible for other reasons. For example, @value{GDBN} cannot add
11544 numbers and structures.
11547 Show the current setting of the type checker, and whether or not @value{GDBN}
11548 is setting it automatically.
11551 @cindex range checking
11552 @cindex checks, range
11553 @node Range Checking
11554 @subsection An Overview of Range Checking
11556 In some languages (such as Modula-2), it is an error to exceed the
11557 bounds of a type; this is enforced with run-time checks. Such range
11558 checking is meant to ensure program correctness by making sure
11559 computations do not overflow, or indices on an array element access do
11560 not exceed the bounds of the array.
11562 For expressions you use in @value{GDBN} commands, you can tell
11563 @value{GDBN} to treat range errors in one of three ways: ignore them,
11564 always treat them as errors and abandon the expression, or issue
11565 warnings but evaluate the expression anyway.
11567 A range error can result from numerical overflow, from exceeding an
11568 array index bound, or when you type a constant that is not a member
11569 of any type. Some languages, however, do not treat overflows as an
11570 error. In many implementations of C, mathematical overflow causes the
11571 result to ``wrap around'' to lower values---for example, if @var{m} is
11572 the largest integer value, and @var{s} is the smallest, then
11575 @var{m} + 1 @result{} @var{s}
11578 This, too, is specific to individual languages, and in some cases
11579 specific to individual compilers or machines. @xref{Supported Languages, ,
11580 Supported Languages}, for further details on specific languages.
11582 @value{GDBN} provides some additional commands for controlling the range checker:
11584 @kindex set check range
11585 @kindex show check range
11587 @item set check range auto
11588 Set range checking on or off based on the current working language.
11589 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11592 @item set check range on
11593 @itemx set check range off
11594 Set range checking on or off, overriding the default setting for the
11595 current working language. A warning is issued if the setting does not
11596 match the language default. If a range error occurs and range checking is on,
11597 then a message is printed and evaluation of the expression is aborted.
11599 @item set check range warn
11600 Output messages when the @value{GDBN} range checker detects a range error,
11601 but attempt to evaluate the expression anyway. Evaluating the
11602 expression may still be impossible for other reasons, such as accessing
11603 memory that the process does not own (a typical example from many Unix
11607 Show the current setting of the range checker, and whether or not it is
11608 being set automatically by @value{GDBN}.
11611 @node Supported Languages
11612 @section Supported Languages
11614 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11615 assembly, Modula-2, and Ada.
11616 @c This is false ...
11617 Some @value{GDBN} features may be used in expressions regardless of the
11618 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11619 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11620 ,Expressions}) can be used with the constructs of any supported
11623 The following sections detail to what degree each source language is
11624 supported by @value{GDBN}. These sections are not meant to be language
11625 tutorials or references, but serve only as a reference guide to what the
11626 @value{GDBN} expression parser accepts, and what input and output
11627 formats should look like for different languages. There are many good
11628 books written on each of these languages; please look to these for a
11629 language reference or tutorial.
11632 * C:: C and C@t{++}
11634 * Objective-C:: Objective-C
11635 * Fortran:: Fortran
11637 * Modula-2:: Modula-2
11642 @subsection C and C@t{++}
11644 @cindex C and C@t{++}
11645 @cindex expressions in C or C@t{++}
11647 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11648 to both languages. Whenever this is the case, we discuss those languages
11652 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11653 @cindex @sc{gnu} C@t{++}
11654 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11655 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11656 effectively, you must compile your C@t{++} programs with a supported
11657 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11658 compiler (@code{aCC}).
11660 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11661 format; if it doesn't work on your system, try the stabs+ debugging
11662 format. You can select those formats explicitly with the @code{g++}
11663 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11664 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11665 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11668 * C Operators:: C and C@t{++} operators
11669 * C Constants:: C and C@t{++} constants
11670 * C Plus Plus Expressions:: C@t{++} expressions
11671 * C Defaults:: Default settings for C and C@t{++}
11672 * C Checks:: C and C@t{++} type and range checks
11673 * Debugging C:: @value{GDBN} and C
11674 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11675 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11679 @subsubsection C and C@t{++} Operators
11681 @cindex C and C@t{++} operators
11683 Operators must be defined on values of specific types. For instance,
11684 @code{+} is defined on numbers, but not on structures. Operators are
11685 often defined on groups of types.
11687 For the purposes of C and C@t{++}, the following definitions hold:
11692 @emph{Integral types} include @code{int} with any of its storage-class
11693 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11696 @emph{Floating-point types} include @code{float}, @code{double}, and
11697 @code{long double} (if supported by the target platform).
11700 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11703 @emph{Scalar types} include all of the above.
11708 The following operators are supported. They are listed here
11709 in order of increasing precedence:
11713 The comma or sequencing operator. Expressions in a comma-separated list
11714 are evaluated from left to right, with the result of the entire
11715 expression being the last expression evaluated.
11718 Assignment. The value of an assignment expression is the value
11719 assigned. Defined on scalar types.
11722 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11723 and translated to @w{@code{@var{a} = @var{a op b}}}.
11724 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11725 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11726 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11729 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11730 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11734 Logical @sc{or}. Defined on integral types.
11737 Logical @sc{and}. Defined on integral types.
11740 Bitwise @sc{or}. Defined on integral types.
11743 Bitwise exclusive-@sc{or}. Defined on integral types.
11746 Bitwise @sc{and}. Defined on integral types.
11749 Equality and inequality. Defined on scalar types. The value of these
11750 expressions is 0 for false and non-zero for true.
11752 @item <@r{, }>@r{, }<=@r{, }>=
11753 Less than, greater than, less than or equal, greater than or equal.
11754 Defined on scalar types. The value of these expressions is 0 for false
11755 and non-zero for true.
11758 left shift, and right shift. Defined on integral types.
11761 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11764 Addition and subtraction. Defined on integral types, floating-point types and
11767 @item *@r{, }/@r{, }%
11768 Multiplication, division, and modulus. Multiplication and division are
11769 defined on integral and floating-point types. Modulus is defined on
11773 Increment and decrement. When appearing before a variable, the
11774 operation is performed before the variable is used in an expression;
11775 when appearing after it, the variable's value is used before the
11776 operation takes place.
11779 Pointer dereferencing. Defined on pointer types. Same precedence as
11783 Address operator. Defined on variables. Same precedence as @code{++}.
11785 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11786 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11787 to examine the address
11788 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11792 Negative. Defined on integral and floating-point types. Same
11793 precedence as @code{++}.
11796 Logical negation. Defined on integral types. Same precedence as
11800 Bitwise complement operator. Defined on integral types. Same precedence as
11805 Structure member, and pointer-to-structure member. For convenience,
11806 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11807 pointer based on the stored type information.
11808 Defined on @code{struct} and @code{union} data.
11811 Dereferences of pointers to members.
11814 Array indexing. @code{@var{a}[@var{i}]} is defined as
11815 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11818 Function parameter list. Same precedence as @code{->}.
11821 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11822 and @code{class} types.
11825 Doubled colons also represent the @value{GDBN} scope operator
11826 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11830 If an operator is redefined in the user code, @value{GDBN} usually
11831 attempts to invoke the redefined version instead of using the operator's
11832 predefined meaning.
11835 @subsubsection C and C@t{++} Constants
11837 @cindex C and C@t{++} constants
11839 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11844 Integer constants are a sequence of digits. Octal constants are
11845 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11846 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11847 @samp{l}, specifying that the constant should be treated as a
11851 Floating point constants are a sequence of digits, followed by a decimal
11852 point, followed by a sequence of digits, and optionally followed by an
11853 exponent. An exponent is of the form:
11854 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11855 sequence of digits. The @samp{+} is optional for positive exponents.
11856 A floating-point constant may also end with a letter @samp{f} or
11857 @samp{F}, specifying that the constant should be treated as being of
11858 the @code{float} (as opposed to the default @code{double}) type; or with
11859 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11863 Enumerated constants consist of enumerated identifiers, or their
11864 integral equivalents.
11867 Character constants are a single character surrounded by single quotes
11868 (@code{'}), or a number---the ordinal value of the corresponding character
11869 (usually its @sc{ascii} value). Within quotes, the single character may
11870 be represented by a letter or by @dfn{escape sequences}, which are of
11871 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11872 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11873 @samp{@var{x}} is a predefined special character---for example,
11874 @samp{\n} for newline.
11877 String constants are a sequence of character constants surrounded by
11878 double quotes (@code{"}). Any valid character constant (as described
11879 above) may appear. Double quotes within the string must be preceded by
11880 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11884 Pointer constants are an integral value. You can also write pointers
11885 to constants using the C operator @samp{&}.
11888 Array constants are comma-separated lists surrounded by braces @samp{@{}
11889 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11890 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11891 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11894 @node C Plus Plus Expressions
11895 @subsubsection C@t{++} Expressions
11897 @cindex expressions in C@t{++}
11898 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11900 @cindex debugging C@t{++} programs
11901 @cindex C@t{++} compilers
11902 @cindex debug formats and C@t{++}
11903 @cindex @value{NGCC} and C@t{++}
11905 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11906 proper compiler and the proper debug format. Currently, @value{GDBN}
11907 works best when debugging C@t{++} code that is compiled with
11908 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11909 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11910 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11911 stabs+ as their default debug format, so you usually don't need to
11912 specify a debug format explicitly. Other compilers and/or debug formats
11913 are likely to work badly or not at all when using @value{GDBN} to debug
11919 @cindex member functions
11921 Member function calls are allowed; you can use expressions like
11924 count = aml->GetOriginal(x, y)
11927 @vindex this@r{, inside C@t{++} member functions}
11928 @cindex namespace in C@t{++}
11930 While a member function is active (in the selected stack frame), your
11931 expressions have the same namespace available as the member function;
11932 that is, @value{GDBN} allows implicit references to the class instance
11933 pointer @code{this} following the same rules as C@t{++}.
11935 @cindex call overloaded functions
11936 @cindex overloaded functions, calling
11937 @cindex type conversions in C@t{++}
11939 You can call overloaded functions; @value{GDBN} resolves the function
11940 call to the right definition, with some restrictions. @value{GDBN} does not
11941 perform overload resolution involving user-defined type conversions,
11942 calls to constructors, or instantiations of templates that do not exist
11943 in the program. It also cannot handle ellipsis argument lists or
11946 It does perform integral conversions and promotions, floating-point
11947 promotions, arithmetic conversions, pointer conversions, conversions of
11948 class objects to base classes, and standard conversions such as those of
11949 functions or arrays to pointers; it requires an exact match on the
11950 number of function arguments.
11952 Overload resolution is always performed, unless you have specified
11953 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11954 ,@value{GDBN} Features for C@t{++}}.
11956 You must specify @code{set overload-resolution off} in order to use an
11957 explicit function signature to call an overloaded function, as in
11959 p 'foo(char,int)'('x', 13)
11962 The @value{GDBN} command-completion facility can simplify this;
11963 see @ref{Completion, ,Command Completion}.
11965 @cindex reference declarations
11967 @value{GDBN} understands variables declared as C@t{++} references; you can use
11968 them in expressions just as you do in C@t{++} source---they are automatically
11971 In the parameter list shown when @value{GDBN} displays a frame, the values of
11972 reference variables are not displayed (unlike other variables); this
11973 avoids clutter, since references are often used for large structures.
11974 The @emph{address} of a reference variable is always shown, unless
11975 you have specified @samp{set print address off}.
11978 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11979 expressions can use it just as expressions in your program do. Since
11980 one scope may be defined in another, you can use @code{::} repeatedly if
11981 necessary, for example in an expression like
11982 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11983 resolving name scope by reference to source files, in both C and C@t{++}
11984 debugging (@pxref{Variables, ,Program Variables}).
11987 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11988 calling virtual functions correctly, printing out virtual bases of
11989 objects, calling functions in a base subobject, casting objects, and
11990 invoking user-defined operators.
11993 @subsubsection C and C@t{++} Defaults
11995 @cindex C and C@t{++} defaults
11997 If you allow @value{GDBN} to set type and range checking automatically, they
11998 both default to @code{off} whenever the working language changes to
11999 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12000 selects the working language.
12002 If you allow @value{GDBN} to set the language automatically, it
12003 recognizes source files whose names end with @file{.c}, @file{.C}, or
12004 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12005 these files, it sets the working language to C or C@t{++}.
12006 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12007 for further details.
12009 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12010 @c unimplemented. If (b) changes, it might make sense to let this node
12011 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12014 @subsubsection C and C@t{++} Type and Range Checks
12016 @cindex C and C@t{++} checks
12018 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12019 is not used. However, if you turn type checking on, @value{GDBN}
12020 considers two variables type equivalent if:
12024 The two variables are structured and have the same structure, union, or
12028 The two variables have the same type name, or types that have been
12029 declared equivalent through @code{typedef}.
12032 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12035 The two @code{struct}, @code{union}, or @code{enum} variables are
12036 declared in the same declaration. (Note: this may not be true for all C
12041 Range checking, if turned on, is done on mathematical operations. Array
12042 indices are not checked, since they are often used to index a pointer
12043 that is not itself an array.
12046 @subsubsection @value{GDBN} and C
12048 The @code{set print union} and @code{show print union} commands apply to
12049 the @code{union} type. When set to @samp{on}, any @code{union} that is
12050 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12051 appears as @samp{@{...@}}.
12053 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12054 with pointers and a memory allocation function. @xref{Expressions,
12057 @node Debugging C Plus Plus
12058 @subsubsection @value{GDBN} Features for C@t{++}
12060 @cindex commands for C@t{++}
12062 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12063 designed specifically for use with C@t{++}. Here is a summary:
12066 @cindex break in overloaded functions
12067 @item @r{breakpoint menus}
12068 When you want a breakpoint in a function whose name is overloaded,
12069 @value{GDBN} has the capability to display a menu of possible breakpoint
12070 locations to help you specify which function definition you want.
12071 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12073 @cindex overloading in C@t{++}
12074 @item rbreak @var{regex}
12075 Setting breakpoints using regular expressions is helpful for setting
12076 breakpoints on overloaded functions that are not members of any special
12078 @xref{Set Breaks, ,Setting Breakpoints}.
12080 @cindex C@t{++} exception handling
12083 Debug C@t{++} exception handling using these commands. @xref{Set
12084 Catchpoints, , Setting Catchpoints}.
12086 @cindex inheritance
12087 @item ptype @var{typename}
12088 Print inheritance relationships as well as other information for type
12090 @xref{Symbols, ,Examining the Symbol Table}.
12092 @cindex C@t{++} symbol display
12093 @item set print demangle
12094 @itemx show print demangle
12095 @itemx set print asm-demangle
12096 @itemx show print asm-demangle
12097 Control whether C@t{++} symbols display in their source form, both when
12098 displaying code as C@t{++} source and when displaying disassemblies.
12099 @xref{Print Settings, ,Print Settings}.
12101 @item set print object
12102 @itemx show print object
12103 Choose whether to print derived (actual) or declared types of objects.
12104 @xref{Print Settings, ,Print Settings}.
12106 @item set print vtbl
12107 @itemx show print vtbl
12108 Control the format for printing virtual function tables.
12109 @xref{Print Settings, ,Print Settings}.
12110 (The @code{vtbl} commands do not work on programs compiled with the HP
12111 ANSI C@t{++} compiler (@code{aCC}).)
12113 @kindex set overload-resolution
12114 @cindex overloaded functions, overload resolution
12115 @item set overload-resolution on
12116 Enable overload resolution for C@t{++} expression evaluation. The default
12117 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12118 and searches for a function whose signature matches the argument types,
12119 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12120 Expressions, ,C@t{++} Expressions}, for details).
12121 If it cannot find a match, it emits a message.
12123 @item set overload-resolution off
12124 Disable overload resolution for C@t{++} expression evaluation. For
12125 overloaded functions that are not class member functions, @value{GDBN}
12126 chooses the first function of the specified name that it finds in the
12127 symbol table, whether or not its arguments are of the correct type. For
12128 overloaded functions that are class member functions, @value{GDBN}
12129 searches for a function whose signature @emph{exactly} matches the
12132 @kindex show overload-resolution
12133 @item show overload-resolution
12134 Show the current setting of overload resolution.
12136 @item @r{Overloaded symbol names}
12137 You can specify a particular definition of an overloaded symbol, using
12138 the same notation that is used to declare such symbols in C@t{++}: type
12139 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12140 also use the @value{GDBN} command-line word completion facilities to list the
12141 available choices, or to finish the type list for you.
12142 @xref{Completion,, Command Completion}, for details on how to do this.
12145 @node Decimal Floating Point
12146 @subsubsection Decimal Floating Point format
12147 @cindex decimal floating point format
12149 @value{GDBN} can examine, set and perform computations with numbers in
12150 decimal floating point format, which in the C language correspond to the
12151 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12152 specified by the extension to support decimal floating-point arithmetic.
12154 There are two encodings in use, depending on the architecture: BID (Binary
12155 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12156 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12159 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12160 to manipulate decimal floating point numbers, it is not possible to convert
12161 (using a cast, for example) integers wider than 32-bit to decimal float.
12163 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12164 point computations, error checking in decimal float operations ignores
12165 underflow, overflow and divide by zero exceptions.
12167 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12168 to inspect @code{_Decimal128} values stored in floating point registers.
12169 See @ref{PowerPC,,PowerPC} for more details.
12175 @value{GDBN} can be used to debug programs written in D and compiled with
12176 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12177 specific feature --- dynamic arrays.
12180 @subsection Objective-C
12182 @cindex Objective-C
12183 This section provides information about some commands and command
12184 options that are useful for debugging Objective-C code. See also
12185 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12186 few more commands specific to Objective-C support.
12189 * Method Names in Commands::
12190 * The Print Command with Objective-C::
12193 @node Method Names in Commands
12194 @subsubsection Method Names in Commands
12196 The following commands have been extended to accept Objective-C method
12197 names as line specifications:
12199 @kindex clear@r{, and Objective-C}
12200 @kindex break@r{, and Objective-C}
12201 @kindex info line@r{, and Objective-C}
12202 @kindex jump@r{, and Objective-C}
12203 @kindex list@r{, and Objective-C}
12207 @item @code{info line}
12212 A fully qualified Objective-C method name is specified as
12215 -[@var{Class} @var{methodName}]
12218 where the minus sign is used to indicate an instance method and a
12219 plus sign (not shown) is used to indicate a class method. The class
12220 name @var{Class} and method name @var{methodName} are enclosed in
12221 brackets, similar to the way messages are specified in Objective-C
12222 source code. For example, to set a breakpoint at the @code{create}
12223 instance method of class @code{Fruit} in the program currently being
12227 break -[Fruit create]
12230 To list ten program lines around the @code{initialize} class method,
12234 list +[NSText initialize]
12237 In the current version of @value{GDBN}, the plus or minus sign is
12238 required. In future versions of @value{GDBN}, the plus or minus
12239 sign will be optional, but you can use it to narrow the search. It
12240 is also possible to specify just a method name:
12246 You must specify the complete method name, including any colons. If
12247 your program's source files contain more than one @code{create} method,
12248 you'll be presented with a numbered list of classes that implement that
12249 method. Indicate your choice by number, or type @samp{0} to exit if
12252 As another example, to clear a breakpoint established at the
12253 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12256 clear -[NSWindow makeKeyAndOrderFront:]
12259 @node The Print Command with Objective-C
12260 @subsubsection The Print Command With Objective-C
12261 @cindex Objective-C, print objects
12262 @kindex print-object
12263 @kindex po @r{(@code{print-object})}
12265 The print command has also been extended to accept methods. For example:
12268 print -[@var{object} hash]
12271 @cindex print an Objective-C object description
12272 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12274 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12275 and print the result. Also, an additional command has been added,
12276 @code{print-object} or @code{po} for short, which is meant to print
12277 the description of an object. However, this command may only work
12278 with certain Objective-C libraries that have a particular hook
12279 function, @code{_NSPrintForDebugger}, defined.
12282 @subsection Fortran
12283 @cindex Fortran-specific support in @value{GDBN}
12285 @value{GDBN} can be used to debug programs written in Fortran, but it
12286 currently supports only the features of Fortran 77 language.
12288 @cindex trailing underscore, in Fortran symbols
12289 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12290 among them) append an underscore to the names of variables and
12291 functions. When you debug programs compiled by those compilers, you
12292 will need to refer to variables and functions with a trailing
12296 * Fortran Operators:: Fortran operators and expressions
12297 * Fortran Defaults:: Default settings for Fortran
12298 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12301 @node Fortran Operators
12302 @subsubsection Fortran Operators and Expressions
12304 @cindex Fortran operators and expressions
12306 Operators must be defined on values of specific types. For instance,
12307 @code{+} is defined on numbers, but not on characters or other non-
12308 arithmetic types. Operators are often defined on groups of types.
12312 The exponentiation operator. It raises the first operand to the power
12316 The range operator. Normally used in the form of array(low:high) to
12317 represent a section of array.
12320 The access component operator. Normally used to access elements in derived
12321 types. Also suitable for unions. As unions aren't part of regular Fortran,
12322 this can only happen when accessing a register that uses a gdbarch-defined
12326 @node Fortran Defaults
12327 @subsubsection Fortran Defaults
12329 @cindex Fortran Defaults
12331 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12332 default uses case-insensitive matches for Fortran symbols. You can
12333 change that with the @samp{set case-insensitive} command, see
12334 @ref{Symbols}, for the details.
12336 @node Special Fortran Commands
12337 @subsubsection Special Fortran Commands
12339 @cindex Special Fortran commands
12341 @value{GDBN} has some commands to support Fortran-specific features,
12342 such as displaying common blocks.
12345 @cindex @code{COMMON} blocks, Fortran
12346 @kindex info common
12347 @item info common @r{[}@var{common-name}@r{]}
12348 This command prints the values contained in the Fortran @code{COMMON}
12349 block whose name is @var{common-name}. With no argument, the names of
12350 all @code{COMMON} blocks visible at the current program location are
12357 @cindex Pascal support in @value{GDBN}, limitations
12358 Debugging Pascal programs which use sets, subranges, file variables, or
12359 nested functions does not currently work. @value{GDBN} does not support
12360 entering expressions, printing values, or similar features using Pascal
12363 The Pascal-specific command @code{set print pascal_static-members}
12364 controls whether static members of Pascal objects are displayed.
12365 @xref{Print Settings, pascal_static-members}.
12368 @subsection Modula-2
12370 @cindex Modula-2, @value{GDBN} support
12372 The extensions made to @value{GDBN} to support Modula-2 only support
12373 output from the @sc{gnu} Modula-2 compiler (which is currently being
12374 developed). Other Modula-2 compilers are not currently supported, and
12375 attempting to debug executables produced by them is most likely
12376 to give an error as @value{GDBN} reads in the executable's symbol
12379 @cindex expressions in Modula-2
12381 * M2 Operators:: Built-in operators
12382 * Built-In Func/Proc:: Built-in functions and procedures
12383 * M2 Constants:: Modula-2 constants
12384 * M2 Types:: Modula-2 types
12385 * M2 Defaults:: Default settings for Modula-2
12386 * Deviations:: Deviations from standard Modula-2
12387 * M2 Checks:: Modula-2 type and range checks
12388 * M2 Scope:: The scope operators @code{::} and @code{.}
12389 * GDB/M2:: @value{GDBN} and Modula-2
12393 @subsubsection Operators
12394 @cindex Modula-2 operators
12396 Operators must be defined on values of specific types. For instance,
12397 @code{+} is defined on numbers, but not on structures. Operators are
12398 often defined on groups of types. For the purposes of Modula-2, the
12399 following definitions hold:
12404 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12408 @emph{Character types} consist of @code{CHAR} and its subranges.
12411 @emph{Floating-point types} consist of @code{REAL}.
12414 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12418 @emph{Scalar types} consist of all of the above.
12421 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12424 @emph{Boolean types} consist of @code{BOOLEAN}.
12428 The following operators are supported, and appear in order of
12429 increasing precedence:
12433 Function argument or array index separator.
12436 Assignment. The value of @var{var} @code{:=} @var{value} is
12440 Less than, greater than on integral, floating-point, or enumerated
12444 Less than or equal to, greater than or equal to
12445 on integral, floating-point and enumerated types, or set inclusion on
12446 set types. Same precedence as @code{<}.
12448 @item =@r{, }<>@r{, }#
12449 Equality and two ways of expressing inequality, valid on scalar types.
12450 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12451 available for inequality, since @code{#} conflicts with the script
12455 Set membership. Defined on set types and the types of their members.
12456 Same precedence as @code{<}.
12459 Boolean disjunction. Defined on boolean types.
12462 Boolean conjunction. Defined on boolean types.
12465 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12468 Addition and subtraction on integral and floating-point types, or union
12469 and difference on set types.
12472 Multiplication on integral and floating-point types, or set intersection
12476 Division on floating-point types, or symmetric set difference on set
12477 types. Same precedence as @code{*}.
12480 Integer division and remainder. Defined on integral types. Same
12481 precedence as @code{*}.
12484 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12487 Pointer dereferencing. Defined on pointer types.
12490 Boolean negation. Defined on boolean types. Same precedence as
12494 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12495 precedence as @code{^}.
12498 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12501 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12505 @value{GDBN} and Modula-2 scope operators.
12509 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12510 treats the use of the operator @code{IN}, or the use of operators
12511 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12512 @code{<=}, and @code{>=} on sets as an error.
12516 @node Built-In Func/Proc
12517 @subsubsection Built-in Functions and Procedures
12518 @cindex Modula-2 built-ins
12520 Modula-2 also makes available several built-in procedures and functions.
12521 In describing these, the following metavariables are used:
12526 represents an @code{ARRAY} variable.
12529 represents a @code{CHAR} constant or variable.
12532 represents a variable or constant of integral type.
12535 represents an identifier that belongs to a set. Generally used in the
12536 same function with the metavariable @var{s}. The type of @var{s} should
12537 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12540 represents a variable or constant of integral or floating-point type.
12543 represents a variable or constant of floating-point type.
12549 represents a variable.
12552 represents a variable or constant of one of many types. See the
12553 explanation of the function for details.
12556 All Modula-2 built-in procedures also return a result, described below.
12560 Returns the absolute value of @var{n}.
12563 If @var{c} is a lower case letter, it returns its upper case
12564 equivalent, otherwise it returns its argument.
12567 Returns the character whose ordinal value is @var{i}.
12570 Decrements the value in the variable @var{v} by one. Returns the new value.
12572 @item DEC(@var{v},@var{i})
12573 Decrements the value in the variable @var{v} by @var{i}. Returns the
12576 @item EXCL(@var{m},@var{s})
12577 Removes the element @var{m} from the set @var{s}. Returns the new
12580 @item FLOAT(@var{i})
12581 Returns the floating point equivalent of the integer @var{i}.
12583 @item HIGH(@var{a})
12584 Returns the index of the last member of @var{a}.
12587 Increments the value in the variable @var{v} by one. Returns the new value.
12589 @item INC(@var{v},@var{i})
12590 Increments the value in the variable @var{v} by @var{i}. Returns the
12593 @item INCL(@var{m},@var{s})
12594 Adds the element @var{m} to the set @var{s} if it is not already
12595 there. Returns the new set.
12598 Returns the maximum value of the type @var{t}.
12601 Returns the minimum value of the type @var{t}.
12604 Returns boolean TRUE if @var{i} is an odd number.
12607 Returns the ordinal value of its argument. For example, the ordinal
12608 value of a character is its @sc{ascii} value (on machines supporting the
12609 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12610 integral, character and enumerated types.
12612 @item SIZE(@var{x})
12613 Returns the size of its argument. @var{x} can be a variable or a type.
12615 @item TRUNC(@var{r})
12616 Returns the integral part of @var{r}.
12618 @item TSIZE(@var{x})
12619 Returns the size of its argument. @var{x} can be a variable or a type.
12621 @item VAL(@var{t},@var{i})
12622 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12626 @emph{Warning:} Sets and their operations are not yet supported, so
12627 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12631 @cindex Modula-2 constants
12633 @subsubsection Constants
12635 @value{GDBN} allows you to express the constants of Modula-2 in the following
12641 Integer constants are simply a sequence of digits. When used in an
12642 expression, a constant is interpreted to be type-compatible with the
12643 rest of the expression. Hexadecimal integers are specified by a
12644 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12647 Floating point constants appear as a sequence of digits, followed by a
12648 decimal point and another sequence of digits. An optional exponent can
12649 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12650 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12651 digits of the floating point constant must be valid decimal (base 10)
12655 Character constants consist of a single character enclosed by a pair of
12656 like quotes, either single (@code{'}) or double (@code{"}). They may
12657 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12658 followed by a @samp{C}.
12661 String constants consist of a sequence of characters enclosed by a
12662 pair of like quotes, either single (@code{'}) or double (@code{"}).
12663 Escape sequences in the style of C are also allowed. @xref{C
12664 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12668 Enumerated constants consist of an enumerated identifier.
12671 Boolean constants consist of the identifiers @code{TRUE} and
12675 Pointer constants consist of integral values only.
12678 Set constants are not yet supported.
12682 @subsubsection Modula-2 Types
12683 @cindex Modula-2 types
12685 Currently @value{GDBN} can print the following data types in Modula-2
12686 syntax: array types, record types, set types, pointer types, procedure
12687 types, enumerated types, subrange types and base types. You can also
12688 print the contents of variables declared using these type.
12689 This section gives a number of simple source code examples together with
12690 sample @value{GDBN} sessions.
12692 The first example contains the following section of code:
12701 and you can request @value{GDBN} to interrogate the type and value of
12702 @code{r} and @code{s}.
12705 (@value{GDBP}) print s
12707 (@value{GDBP}) ptype s
12709 (@value{GDBP}) print r
12711 (@value{GDBP}) ptype r
12716 Likewise if your source code declares @code{s} as:
12720 s: SET ['A'..'Z'] ;
12724 then you may query the type of @code{s} by:
12727 (@value{GDBP}) ptype s
12728 type = SET ['A'..'Z']
12732 Note that at present you cannot interactively manipulate set
12733 expressions using the debugger.
12735 The following example shows how you might declare an array in Modula-2
12736 and how you can interact with @value{GDBN} to print its type and contents:
12740 s: ARRAY [-10..10] OF CHAR ;
12744 (@value{GDBP}) ptype s
12745 ARRAY [-10..10] OF CHAR
12748 Note that the array handling is not yet complete and although the type
12749 is printed correctly, expression handling still assumes that all
12750 arrays have a lower bound of zero and not @code{-10} as in the example
12753 Here are some more type related Modula-2 examples:
12757 colour = (blue, red, yellow, green) ;
12758 t = [blue..yellow] ;
12766 The @value{GDBN} interaction shows how you can query the data type
12767 and value of a variable.
12770 (@value{GDBP}) print s
12772 (@value{GDBP}) ptype t
12773 type = [blue..yellow]
12777 In this example a Modula-2 array is declared and its contents
12778 displayed. Observe that the contents are written in the same way as
12779 their @code{C} counterparts.
12783 s: ARRAY [1..5] OF CARDINAL ;
12789 (@value{GDBP}) print s
12790 $1 = @{1, 0, 0, 0, 0@}
12791 (@value{GDBP}) ptype s
12792 type = ARRAY [1..5] OF CARDINAL
12795 The Modula-2 language interface to @value{GDBN} also understands
12796 pointer types as shown in this example:
12800 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12807 and you can request that @value{GDBN} describes the type of @code{s}.
12810 (@value{GDBP}) ptype s
12811 type = POINTER TO ARRAY [1..5] OF CARDINAL
12814 @value{GDBN} handles compound types as we can see in this example.
12815 Here we combine array types, record types, pointer types and subrange
12826 myarray = ARRAY myrange OF CARDINAL ;
12827 myrange = [-2..2] ;
12829 s: POINTER TO ARRAY myrange OF foo ;
12833 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12837 (@value{GDBP}) ptype s
12838 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12841 f3 : ARRAY [-2..2] OF CARDINAL;
12846 @subsubsection Modula-2 Defaults
12847 @cindex Modula-2 defaults
12849 If type and range checking are set automatically by @value{GDBN}, they
12850 both default to @code{on} whenever the working language changes to
12851 Modula-2. This happens regardless of whether you or @value{GDBN}
12852 selected the working language.
12854 If you allow @value{GDBN} to set the language automatically, then entering
12855 code compiled from a file whose name ends with @file{.mod} sets the
12856 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12857 Infer the Source Language}, for further details.
12860 @subsubsection Deviations from Standard Modula-2
12861 @cindex Modula-2, deviations from
12863 A few changes have been made to make Modula-2 programs easier to debug.
12864 This is done primarily via loosening its type strictness:
12868 Unlike in standard Modula-2, pointer constants can be formed by
12869 integers. This allows you to modify pointer variables during
12870 debugging. (In standard Modula-2, the actual address contained in a
12871 pointer variable is hidden from you; it can only be modified
12872 through direct assignment to another pointer variable or expression that
12873 returned a pointer.)
12876 C escape sequences can be used in strings and characters to represent
12877 non-printable characters. @value{GDBN} prints out strings with these
12878 escape sequences embedded. Single non-printable characters are
12879 printed using the @samp{CHR(@var{nnn})} format.
12882 The assignment operator (@code{:=}) returns the value of its right-hand
12886 All built-in procedures both modify @emph{and} return their argument.
12890 @subsubsection Modula-2 Type and Range Checks
12891 @cindex Modula-2 checks
12894 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12897 @c FIXME remove warning when type/range checks added
12899 @value{GDBN} considers two Modula-2 variables type equivalent if:
12903 They are of types that have been declared equivalent via a @code{TYPE
12904 @var{t1} = @var{t2}} statement
12907 They have been declared on the same line. (Note: This is true of the
12908 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12911 As long as type checking is enabled, any attempt to combine variables
12912 whose types are not equivalent is an error.
12914 Range checking is done on all mathematical operations, assignment, array
12915 index bounds, and all built-in functions and procedures.
12918 @subsubsection The Scope Operators @code{::} and @code{.}
12920 @cindex @code{.}, Modula-2 scope operator
12921 @cindex colon, doubled as scope operator
12923 @vindex colon-colon@r{, in Modula-2}
12924 @c Info cannot handle :: but TeX can.
12927 @vindex ::@r{, in Modula-2}
12930 There are a few subtle differences between the Modula-2 scope operator
12931 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12936 @var{module} . @var{id}
12937 @var{scope} :: @var{id}
12941 where @var{scope} is the name of a module or a procedure,
12942 @var{module} the name of a module, and @var{id} is any declared
12943 identifier within your program, except another module.
12945 Using the @code{::} operator makes @value{GDBN} search the scope
12946 specified by @var{scope} for the identifier @var{id}. If it is not
12947 found in the specified scope, then @value{GDBN} searches all scopes
12948 enclosing the one specified by @var{scope}.
12950 Using the @code{.} operator makes @value{GDBN} search the current scope for
12951 the identifier specified by @var{id} that was imported from the
12952 definition module specified by @var{module}. With this operator, it is
12953 an error if the identifier @var{id} was not imported from definition
12954 module @var{module}, or if @var{id} is not an identifier in
12958 @subsubsection @value{GDBN} and Modula-2
12960 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12961 Five subcommands of @code{set print} and @code{show print} apply
12962 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12963 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12964 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12965 analogue in Modula-2.
12967 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12968 with any language, is not useful with Modula-2. Its
12969 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12970 created in Modula-2 as they can in C or C@t{++}. However, because an
12971 address can be specified by an integral constant, the construct
12972 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12974 @cindex @code{#} in Modula-2
12975 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12976 interpreted as the beginning of a comment. Use @code{<>} instead.
12982 The extensions made to @value{GDBN} for Ada only support
12983 output from the @sc{gnu} Ada (GNAT) compiler.
12984 Other Ada compilers are not currently supported, and
12985 attempting to debug executables produced by them is most likely
12989 @cindex expressions in Ada
12991 * Ada Mode Intro:: General remarks on the Ada syntax
12992 and semantics supported by Ada mode
12994 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12995 * Additions to Ada:: Extensions of the Ada expression syntax.
12996 * Stopping Before Main Program:: Debugging the program during elaboration.
12997 * Ada Tasks:: Listing and setting breakpoints in tasks.
12998 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12999 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13001 * Ada Glitches:: Known peculiarities of Ada mode.
13004 @node Ada Mode Intro
13005 @subsubsection Introduction
13006 @cindex Ada mode, general
13008 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13009 syntax, with some extensions.
13010 The philosophy behind the design of this subset is
13014 That @value{GDBN} should provide basic literals and access to operations for
13015 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13016 leaving more sophisticated computations to subprograms written into the
13017 program (which therefore may be called from @value{GDBN}).
13020 That type safety and strict adherence to Ada language restrictions
13021 are not particularly important to the @value{GDBN} user.
13024 That brevity is important to the @value{GDBN} user.
13027 Thus, for brevity, the debugger acts as if all names declared in
13028 user-written packages are directly visible, even if they are not visible
13029 according to Ada rules, thus making it unnecessary to fully qualify most
13030 names with their packages, regardless of context. Where this causes
13031 ambiguity, @value{GDBN} asks the user's intent.
13033 The debugger will start in Ada mode if it detects an Ada main program.
13034 As for other languages, it will enter Ada mode when stopped in a program that
13035 was translated from an Ada source file.
13037 While in Ada mode, you may use `@t{--}' for comments. This is useful
13038 mostly for documenting command files. The standard @value{GDBN} comment
13039 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13040 middle (to allow based literals).
13042 The debugger supports limited overloading. Given a subprogram call in which
13043 the function symbol has multiple definitions, it will use the number of
13044 actual parameters and some information about their types to attempt to narrow
13045 the set of definitions. It also makes very limited use of context, preferring
13046 procedures to functions in the context of the @code{call} command, and
13047 functions to procedures elsewhere.
13049 @node Omissions from Ada
13050 @subsubsection Omissions from Ada
13051 @cindex Ada, omissions from
13053 Here are the notable omissions from the subset:
13057 Only a subset of the attributes are supported:
13061 @t{'First}, @t{'Last}, and @t{'Length}
13062 on array objects (not on types and subtypes).
13065 @t{'Min} and @t{'Max}.
13068 @t{'Pos} and @t{'Val}.
13074 @t{'Range} on array objects (not subtypes), but only as the right
13075 operand of the membership (@code{in}) operator.
13078 @t{'Access}, @t{'Unchecked_Access}, and
13079 @t{'Unrestricted_Access} (a GNAT extension).
13087 @code{Characters.Latin_1} are not available and
13088 concatenation is not implemented. Thus, escape characters in strings are
13089 not currently available.
13092 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13093 equality of representations. They will generally work correctly
13094 for strings and arrays whose elements have integer or enumeration types.
13095 They may not work correctly for arrays whose element
13096 types have user-defined equality, for arrays of real values
13097 (in particular, IEEE-conformant floating point, because of negative
13098 zeroes and NaNs), and for arrays whose elements contain unused bits with
13099 indeterminate values.
13102 The other component-by-component array operations (@code{and}, @code{or},
13103 @code{xor}, @code{not}, and relational tests other than equality)
13104 are not implemented.
13107 @cindex array aggregates (Ada)
13108 @cindex record aggregates (Ada)
13109 @cindex aggregates (Ada)
13110 There is limited support for array and record aggregates. They are
13111 permitted only on the right sides of assignments, as in these examples:
13114 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13115 (@value{GDBP}) set An_Array := (1, others => 0)
13116 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13117 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13118 (@value{GDBP}) set A_Record := (1, "Peter", True);
13119 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13123 discriminant's value by assigning an aggregate has an
13124 undefined effect if that discriminant is used within the record.
13125 However, you can first modify discriminants by directly assigning to
13126 them (which normally would not be allowed in Ada), and then performing an
13127 aggregate assignment. For example, given a variable @code{A_Rec}
13128 declared to have a type such as:
13131 type Rec (Len : Small_Integer := 0) is record
13133 Vals : IntArray (1 .. Len);
13137 you can assign a value with a different size of @code{Vals} with two
13141 (@value{GDBP}) set A_Rec.Len := 4
13142 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13145 As this example also illustrates, @value{GDBN} is very loose about the usual
13146 rules concerning aggregates. You may leave out some of the
13147 components of an array or record aggregate (such as the @code{Len}
13148 component in the assignment to @code{A_Rec} above); they will retain their
13149 original values upon assignment. You may freely use dynamic values as
13150 indices in component associations. You may even use overlapping or
13151 redundant component associations, although which component values are
13152 assigned in such cases is not defined.
13155 Calls to dispatching subprograms are not implemented.
13158 The overloading algorithm is much more limited (i.e., less selective)
13159 than that of real Ada. It makes only limited use of the context in
13160 which a subexpression appears to resolve its meaning, and it is much
13161 looser in its rules for allowing type matches. As a result, some
13162 function calls will be ambiguous, and the user will be asked to choose
13163 the proper resolution.
13166 The @code{new} operator is not implemented.
13169 Entry calls are not implemented.
13172 Aside from printing, arithmetic operations on the native VAX floating-point
13173 formats are not supported.
13176 It is not possible to slice a packed array.
13179 The names @code{True} and @code{False}, when not part of a qualified name,
13180 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13182 Should your program
13183 redefine these names in a package or procedure (at best a dubious practice),
13184 you will have to use fully qualified names to access their new definitions.
13187 @node Additions to Ada
13188 @subsubsection Additions to Ada
13189 @cindex Ada, deviations from
13191 As it does for other languages, @value{GDBN} makes certain generic
13192 extensions to Ada (@pxref{Expressions}):
13196 If the expression @var{E} is a variable residing in memory (typically
13197 a local variable or array element) and @var{N} is a positive integer,
13198 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13199 @var{N}-1 adjacent variables following it in memory as an array. In
13200 Ada, this operator is generally not necessary, since its prime use is
13201 in displaying parts of an array, and slicing will usually do this in
13202 Ada. However, there are occasional uses when debugging programs in
13203 which certain debugging information has been optimized away.
13206 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13207 appears in function or file @var{B}.'' When @var{B} is a file name,
13208 you must typically surround it in single quotes.
13211 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13212 @var{type} that appears at address @var{addr}.''
13215 A name starting with @samp{$} is a convenience variable
13216 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13219 In addition, @value{GDBN} provides a few other shortcuts and outright
13220 additions specific to Ada:
13224 The assignment statement is allowed as an expression, returning
13225 its right-hand operand as its value. Thus, you may enter
13228 (@value{GDBP}) set x := y + 3
13229 (@value{GDBP}) print A(tmp := y + 1)
13233 The semicolon is allowed as an ``operator,'' returning as its value
13234 the value of its right-hand operand.
13235 This allows, for example,
13236 complex conditional breaks:
13239 (@value{GDBP}) break f
13240 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13244 Rather than use catenation and symbolic character names to introduce special
13245 characters into strings, one may instead use a special bracket notation,
13246 which is also used to print strings. A sequence of characters of the form
13247 @samp{["@var{XX}"]} within a string or character literal denotes the
13248 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13249 sequence of characters @samp{["""]} also denotes a single quotation mark
13250 in strings. For example,
13252 "One line.["0a"]Next line.["0a"]"
13255 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13259 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13260 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13264 (@value{GDBP}) print 'max(x, y)
13268 When printing arrays, @value{GDBN} uses positional notation when the
13269 array has a lower bound of 1, and uses a modified named notation otherwise.
13270 For example, a one-dimensional array of three integers with a lower bound
13271 of 3 might print as
13278 That is, in contrast to valid Ada, only the first component has a @code{=>}
13282 You may abbreviate attributes in expressions with any unique,
13283 multi-character subsequence of
13284 their names (an exact match gets preference).
13285 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13286 in place of @t{a'length}.
13289 @cindex quoting Ada internal identifiers
13290 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13291 to lower case. The GNAT compiler uses upper-case characters for
13292 some of its internal identifiers, which are normally of no interest to users.
13293 For the rare occasions when you actually have to look at them,
13294 enclose them in angle brackets to avoid the lower-case mapping.
13297 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13301 Printing an object of class-wide type or dereferencing an
13302 access-to-class-wide value will display all the components of the object's
13303 specific type (as indicated by its run-time tag). Likewise, component
13304 selection on such a value will operate on the specific type of the
13309 @node Stopping Before Main Program
13310 @subsubsection Stopping at the Very Beginning
13312 @cindex breakpointing Ada elaboration code
13313 It is sometimes necessary to debug the program during elaboration, and
13314 before reaching the main procedure.
13315 As defined in the Ada Reference
13316 Manual, the elaboration code is invoked from a procedure called
13317 @code{adainit}. To run your program up to the beginning of
13318 elaboration, simply use the following two commands:
13319 @code{tbreak adainit} and @code{run}.
13322 @subsubsection Extensions for Ada Tasks
13323 @cindex Ada, tasking
13325 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13326 @value{GDBN} provides the following task-related commands:
13331 This command shows a list of current Ada tasks, as in the following example:
13338 (@value{GDBP}) info tasks
13339 ID TID P-ID Pri State Name
13340 1 8088000 0 15 Child Activation Wait main_task
13341 2 80a4000 1 15 Accept Statement b
13342 3 809a800 1 15 Child Activation Wait a
13343 * 4 80ae800 3 15 Runnable c
13348 In this listing, the asterisk before the last task indicates it to be the
13349 task currently being inspected.
13353 Represents @value{GDBN}'s internal task number.
13359 The parent's task ID (@value{GDBN}'s internal task number).
13362 The base priority of the task.
13365 Current state of the task.
13369 The task has been created but has not been activated. It cannot be
13373 The task is not blocked for any reason known to Ada. (It may be waiting
13374 for a mutex, though.) It is conceptually "executing" in normal mode.
13377 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13378 that were waiting on terminate alternatives have been awakened and have
13379 terminated themselves.
13381 @item Child Activation Wait
13382 The task is waiting for created tasks to complete activation.
13384 @item Accept Statement
13385 The task is waiting on an accept or selective wait statement.
13387 @item Waiting on entry call
13388 The task is waiting on an entry call.
13390 @item Async Select Wait
13391 The task is waiting to start the abortable part of an asynchronous
13395 The task is waiting on a select statement with only a delay
13398 @item Child Termination Wait
13399 The task is sleeping having completed a master within itself, and is
13400 waiting for the tasks dependent on that master to become terminated or
13401 waiting on a terminate Phase.
13403 @item Wait Child in Term Alt
13404 The task is sleeping waiting for tasks on terminate alternatives to
13405 finish terminating.
13407 @item Accepting RV with @var{taskno}
13408 The task is accepting a rendez-vous with the task @var{taskno}.
13412 Name of the task in the program.
13416 @kindex info task @var{taskno}
13417 @item info task @var{taskno}
13418 This command shows detailled informations on the specified task, as in
13419 the following example:
13424 (@value{GDBP}) info tasks
13425 ID TID P-ID Pri State Name
13426 1 8077880 0 15 Child Activation Wait main_task
13427 * 2 807c468 1 15 Runnable task_1
13428 (@value{GDBP}) info task 2
13429 Ada Task: 0x807c468
13432 Parent: 1 (main_task)
13438 @kindex task@r{ (Ada)}
13439 @cindex current Ada task ID
13440 This command prints the ID of the current task.
13446 (@value{GDBP}) info tasks
13447 ID TID P-ID Pri State Name
13448 1 8077870 0 15 Child Activation Wait main_task
13449 * 2 807c458 1 15 Runnable t
13450 (@value{GDBP}) task
13451 [Current task is 2]
13454 @item task @var{taskno}
13455 @cindex Ada task switching
13456 This command is like the @code{thread @var{threadno}}
13457 command (@pxref{Threads}). It switches the context of debugging
13458 from the current task to the given task.
13464 (@value{GDBP}) info tasks
13465 ID TID P-ID Pri State Name
13466 1 8077870 0 15 Child Activation Wait main_task
13467 * 2 807c458 1 15 Runnable t
13468 (@value{GDBP}) task 1
13469 [Switching to task 1]
13470 #0 0x8067726 in pthread_cond_wait ()
13472 #0 0x8067726 in pthread_cond_wait ()
13473 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13474 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13475 #3 0x806153e in system.tasking.stages.activate_tasks ()
13476 #4 0x804aacc in un () at un.adb:5
13479 @item break @var{linespec} task @var{taskno}
13480 @itemx break @var{linespec} task @var{taskno} if @dots{}
13481 @cindex breakpoints and tasks, in Ada
13482 @cindex task breakpoints, in Ada
13483 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13484 These commands are like the @code{break @dots{} thread @dots{}}
13485 command (@pxref{Thread Stops}).
13486 @var{linespec} specifies source lines, as described
13487 in @ref{Specify Location}.
13489 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13490 to specify that you only want @value{GDBN} to stop the program when a
13491 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13492 numeric task identifiers assigned by @value{GDBN}, shown in the first
13493 column of the @samp{info tasks} display.
13495 If you do not specify @samp{task @var{taskno}} when you set a
13496 breakpoint, the breakpoint applies to @emph{all} tasks of your
13499 You can use the @code{task} qualifier on conditional breakpoints as
13500 well; in this case, place @samp{task @var{taskno}} before the
13501 breakpoint condition (before the @code{if}).
13509 (@value{GDBP}) info tasks
13510 ID TID P-ID Pri State Name
13511 1 140022020 0 15 Child Activation Wait main_task
13512 2 140045060 1 15 Accept/Select Wait t2
13513 3 140044840 1 15 Runnable t1
13514 * 4 140056040 1 15 Runnable t3
13515 (@value{GDBP}) b 15 task 2
13516 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13517 (@value{GDBP}) cont
13522 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13524 (@value{GDBP}) info tasks
13525 ID TID P-ID Pri State Name
13526 1 140022020 0 15 Child Activation Wait main_task
13527 * 2 140045060 1 15 Runnable t2
13528 3 140044840 1 15 Runnable t1
13529 4 140056040 1 15 Delay Sleep t3
13533 @node Ada Tasks and Core Files
13534 @subsubsection Tasking Support when Debugging Core Files
13535 @cindex Ada tasking and core file debugging
13537 When inspecting a core file, as opposed to debugging a live program,
13538 tasking support may be limited or even unavailable, depending on
13539 the platform being used.
13540 For instance, on x86-linux, the list of tasks is available, but task
13541 switching is not supported. On Tru64, however, task switching will work
13544 On certain platforms, including Tru64, the debugger needs to perform some
13545 memory writes in order to provide Ada tasking support. When inspecting
13546 a core file, this means that the core file must be opened with read-write
13547 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13548 Under these circumstances, you should make a backup copy of the core
13549 file before inspecting it with @value{GDBN}.
13551 @node Ravenscar Profile
13552 @subsubsection Tasking Support when using the Ravenscar Profile
13553 @cindex Ravenscar Profile
13555 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13556 specifically designed for systems with safety-critical real-time
13560 @kindex set ravenscar task-switching on
13561 @cindex task switching with program using Ravenscar Profile
13562 @item set ravenscar task-switching on
13563 Allows task switching when debugging a program that uses the Ravenscar
13564 Profile. This is the default.
13566 @kindex set ravenscar task-switching off
13567 @item set ravenscar task-switching off
13568 Turn off task switching when debugging a program that uses the Ravenscar
13569 Profile. This is mostly intended to disable the code that adds support
13570 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13571 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13572 To be effective, this command should be run before the program is started.
13574 @kindex show ravenscar task-switching
13575 @item show ravenscar task-switching
13576 Show whether it is possible to switch from task to task in a program
13577 using the Ravenscar Profile.
13582 @subsubsection Known Peculiarities of Ada Mode
13583 @cindex Ada, problems
13585 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13586 we know of several problems with and limitations of Ada mode in
13588 some of which will be fixed with planned future releases of the debugger
13589 and the GNU Ada compiler.
13593 Currently, the debugger
13594 has insufficient information to determine whether certain pointers represent
13595 pointers to objects or the objects themselves.
13596 Thus, the user may have to tack an extra @code{.all} after an expression
13597 to get it printed properly.
13600 Static constants that the compiler chooses not to materialize as objects in
13601 storage are invisible to the debugger.
13604 Named parameter associations in function argument lists are ignored (the
13605 argument lists are treated as positional).
13608 Many useful library packages are currently invisible to the debugger.
13611 Fixed-point arithmetic, conversions, input, and output is carried out using
13612 floating-point arithmetic, and may give results that only approximate those on
13616 The GNAT compiler never generates the prefix @code{Standard} for any of
13617 the standard symbols defined by the Ada language. @value{GDBN} knows about
13618 this: it will strip the prefix from names when you use it, and will never
13619 look for a name you have so qualified among local symbols, nor match against
13620 symbols in other packages or subprograms. If you have
13621 defined entities anywhere in your program other than parameters and
13622 local variables whose simple names match names in @code{Standard},
13623 GNAT's lack of qualification here can cause confusion. When this happens,
13624 you can usually resolve the confusion
13625 by qualifying the problematic names with package
13626 @code{Standard} explicitly.
13629 Older versions of the compiler sometimes generate erroneous debugging
13630 information, resulting in the debugger incorrectly printing the value
13631 of affected entities. In some cases, the debugger is able to work
13632 around an issue automatically. In other cases, the debugger is able
13633 to work around the issue, but the work-around has to be specifically
13636 @kindex set ada trust-PAD-over-XVS
13637 @kindex show ada trust-PAD-over-XVS
13640 @item set ada trust-PAD-over-XVS on
13641 Configure GDB to strictly follow the GNAT encoding when computing the
13642 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13643 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13644 a complete description of the encoding used by the GNAT compiler).
13645 This is the default.
13647 @item set ada trust-PAD-over-XVS off
13648 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13649 sometimes prints the wrong value for certain entities, changing @code{ada
13650 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13651 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13652 @code{off}, but this incurs a slight performance penalty, so it is
13653 recommended to leave this setting to @code{on} unless necessary.
13657 @node Unsupported Languages
13658 @section Unsupported Languages
13660 @cindex unsupported languages
13661 @cindex minimal language
13662 In addition to the other fully-supported programming languages,
13663 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13664 It does not represent a real programming language, but provides a set
13665 of capabilities close to what the C or assembly languages provide.
13666 This should allow most simple operations to be performed while debugging
13667 an application that uses a language currently not supported by @value{GDBN}.
13669 If the language is set to @code{auto}, @value{GDBN} will automatically
13670 select this language if the current frame corresponds to an unsupported
13674 @chapter Examining the Symbol Table
13676 The commands described in this chapter allow you to inquire about the
13677 symbols (names of variables, functions and types) defined in your
13678 program. This information is inherent in the text of your program and
13679 does not change as your program executes. @value{GDBN} finds it in your
13680 program's symbol table, in the file indicated when you started @value{GDBN}
13681 (@pxref{File Options, ,Choosing Files}), or by one of the
13682 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13684 @cindex symbol names
13685 @cindex names of symbols
13686 @cindex quoting names
13687 Occasionally, you may need to refer to symbols that contain unusual
13688 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13689 most frequent case is in referring to static variables in other
13690 source files (@pxref{Variables,,Program Variables}). File names
13691 are recorded in object files as debugging symbols, but @value{GDBN} would
13692 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13693 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13694 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13701 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13704 @cindex case-insensitive symbol names
13705 @cindex case sensitivity in symbol names
13706 @kindex set case-sensitive
13707 @item set case-sensitive on
13708 @itemx set case-sensitive off
13709 @itemx set case-sensitive auto
13710 Normally, when @value{GDBN} looks up symbols, it matches their names
13711 with case sensitivity determined by the current source language.
13712 Occasionally, you may wish to control that. The command @code{set
13713 case-sensitive} lets you do that by specifying @code{on} for
13714 case-sensitive matches or @code{off} for case-insensitive ones. If
13715 you specify @code{auto}, case sensitivity is reset to the default
13716 suitable for the source language. The default is case-sensitive
13717 matches for all languages except for Fortran, for which the default is
13718 case-insensitive matches.
13720 @kindex show case-sensitive
13721 @item show case-sensitive
13722 This command shows the current setting of case sensitivity for symbols
13725 @kindex info address
13726 @cindex address of a symbol
13727 @item info address @var{symbol}
13728 Describe where the data for @var{symbol} is stored. For a register
13729 variable, this says which register it is kept in. For a non-register
13730 local variable, this prints the stack-frame offset at which the variable
13733 Note the contrast with @samp{print &@var{symbol}}, which does not work
13734 at all for a register variable, and for a stack local variable prints
13735 the exact address of the current instantiation of the variable.
13737 @kindex info symbol
13738 @cindex symbol from address
13739 @cindex closest symbol and offset for an address
13740 @item info symbol @var{addr}
13741 Print the name of a symbol which is stored at the address @var{addr}.
13742 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13743 nearest symbol and an offset from it:
13746 (@value{GDBP}) info symbol 0x54320
13747 _initialize_vx + 396 in section .text
13751 This is the opposite of the @code{info address} command. You can use
13752 it to find out the name of a variable or a function given its address.
13754 For dynamically linked executables, the name of executable or shared
13755 library containing the symbol is also printed:
13758 (@value{GDBP}) info symbol 0x400225
13759 _start + 5 in section .text of /tmp/a.out
13760 (@value{GDBP}) info symbol 0x2aaaac2811cf
13761 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13765 @item whatis [@var{arg}]
13766 Print the data type of @var{arg}, which can be either an expression or
13767 a data type. With no argument, print the data type of @code{$}, the
13768 last value in the value history. If @var{arg} is an expression, it is
13769 not actually evaluated, and any side-effecting operations (such as
13770 assignments or function calls) inside it do not take place. If
13771 @var{arg} is a type name, it may be the name of a type or typedef, or
13772 for C code it may have the form @samp{class @var{class-name}},
13773 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13774 @samp{enum @var{enum-tag}}.
13775 @xref{Expressions, ,Expressions}.
13778 @item ptype [@var{arg}]
13779 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13780 detailed description of the type, instead of just the name of the type.
13781 @xref{Expressions, ,Expressions}.
13783 For example, for this variable declaration:
13786 struct complex @{double real; double imag;@} v;
13790 the two commands give this output:
13794 (@value{GDBP}) whatis v
13795 type = struct complex
13796 (@value{GDBP}) ptype v
13797 type = struct complex @{
13805 As with @code{whatis}, using @code{ptype} without an argument refers to
13806 the type of @code{$}, the last value in the value history.
13808 @cindex incomplete type
13809 Sometimes, programs use opaque data types or incomplete specifications
13810 of complex data structure. If the debug information included in the
13811 program does not allow @value{GDBN} to display a full declaration of
13812 the data type, it will say @samp{<incomplete type>}. For example,
13813 given these declarations:
13817 struct foo *fooptr;
13821 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13824 (@value{GDBP}) ptype foo
13825 $1 = <incomplete type>
13829 ``Incomplete type'' is C terminology for data types that are not
13830 completely specified.
13833 @item info types @var{regexp}
13835 Print a brief description of all types whose names match the regular
13836 expression @var{regexp} (or all types in your program, if you supply
13837 no argument). Each complete typename is matched as though it were a
13838 complete line; thus, @samp{i type value} gives information on all
13839 types in your program whose names include the string @code{value}, but
13840 @samp{i type ^value$} gives information only on types whose complete
13841 name is @code{value}.
13843 This command differs from @code{ptype} in two ways: first, like
13844 @code{whatis}, it does not print a detailed description; second, it
13845 lists all source files where a type is defined.
13848 @cindex local variables
13849 @item info scope @var{location}
13850 List all the variables local to a particular scope. This command
13851 accepts a @var{location} argument---a function name, a source line, or
13852 an address preceded by a @samp{*}, and prints all the variables local
13853 to the scope defined by that location. (@xref{Specify Location}, for
13854 details about supported forms of @var{location}.) For example:
13857 (@value{GDBP}) @b{info scope command_line_handler}
13858 Scope for command_line_handler:
13859 Symbol rl is an argument at stack/frame offset 8, length 4.
13860 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13861 Symbol linelength is in static storage at address 0x150a1c, length 4.
13862 Symbol p is a local variable in register $esi, length 4.
13863 Symbol p1 is a local variable in register $ebx, length 4.
13864 Symbol nline is a local variable in register $edx, length 4.
13865 Symbol repeat is a local variable at frame offset -8, length 4.
13869 This command is especially useful for determining what data to collect
13870 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13873 @kindex info source
13875 Show information about the current source file---that is, the source file for
13876 the function containing the current point of execution:
13879 the name of the source file, and the directory containing it,
13881 the directory it was compiled in,
13883 its length, in lines,
13885 which programming language it is written in,
13887 whether the executable includes debugging information for that file, and
13888 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13890 whether the debugging information includes information about
13891 preprocessor macros.
13895 @kindex info sources
13897 Print the names of all source files in your program for which there is
13898 debugging information, organized into two lists: files whose symbols
13899 have already been read, and files whose symbols will be read when needed.
13901 @kindex info functions
13902 @item info functions
13903 Print the names and data types of all defined functions.
13905 @item info functions @var{regexp}
13906 Print the names and data types of all defined functions
13907 whose names contain a match for regular expression @var{regexp}.
13908 Thus, @samp{info fun step} finds all functions whose names
13909 include @code{step}; @samp{info fun ^step} finds those whose names
13910 start with @code{step}. If a function name contains characters
13911 that conflict with the regular expression language (e.g.@:
13912 @samp{operator*()}), they may be quoted with a backslash.
13914 @kindex info variables
13915 @item info variables
13916 Print the names and data types of all variables that are defined
13917 outside of functions (i.e.@: excluding local variables).
13919 @item info variables @var{regexp}
13920 Print the names and data types of all variables (except for local
13921 variables) whose names contain a match for regular expression
13924 @kindex info classes
13925 @cindex Objective-C, classes and selectors
13927 @itemx info classes @var{regexp}
13928 Display all Objective-C classes in your program, or
13929 (with the @var{regexp} argument) all those matching a particular regular
13932 @kindex info selectors
13933 @item info selectors
13934 @itemx info selectors @var{regexp}
13935 Display all Objective-C selectors in your program, or
13936 (with the @var{regexp} argument) all those matching a particular regular
13940 This was never implemented.
13941 @kindex info methods
13943 @itemx info methods @var{regexp}
13944 The @code{info methods} command permits the user to examine all defined
13945 methods within C@t{++} program, or (with the @var{regexp} argument) a
13946 specific set of methods found in the various C@t{++} classes. Many
13947 C@t{++} classes provide a large number of methods. Thus, the output
13948 from the @code{ptype} command can be overwhelming and hard to use. The
13949 @code{info-methods} command filters the methods, printing only those
13950 which match the regular-expression @var{regexp}.
13953 @cindex reloading symbols
13954 Some systems allow individual object files that make up your program to
13955 be replaced without stopping and restarting your program. For example,
13956 in VxWorks you can simply recompile a defective object file and keep on
13957 running. If you are running on one of these systems, you can allow
13958 @value{GDBN} to reload the symbols for automatically relinked modules:
13961 @kindex set symbol-reloading
13962 @item set symbol-reloading on
13963 Replace symbol definitions for the corresponding source file when an
13964 object file with a particular name is seen again.
13966 @item set symbol-reloading off
13967 Do not replace symbol definitions when encountering object files of the
13968 same name more than once. This is the default state; if you are not
13969 running on a system that permits automatic relinking of modules, you
13970 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13971 may discard symbols when linking large programs, that may contain
13972 several modules (from different directories or libraries) with the same
13975 @kindex show symbol-reloading
13976 @item show symbol-reloading
13977 Show the current @code{on} or @code{off} setting.
13980 @cindex opaque data types
13981 @kindex set opaque-type-resolution
13982 @item set opaque-type-resolution on
13983 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13984 declared as a pointer to a @code{struct}, @code{class}, or
13985 @code{union}---for example, @code{struct MyType *}---that is used in one
13986 source file although the full declaration of @code{struct MyType} is in
13987 another source file. The default is on.
13989 A change in the setting of this subcommand will not take effect until
13990 the next time symbols for a file are loaded.
13992 @item set opaque-type-resolution off
13993 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13994 is printed as follows:
13996 @{<no data fields>@}
13999 @kindex show opaque-type-resolution
14000 @item show opaque-type-resolution
14001 Show whether opaque types are resolved or not.
14003 @kindex maint print symbols
14004 @cindex symbol dump
14005 @kindex maint print psymbols
14006 @cindex partial symbol dump
14007 @item maint print symbols @var{filename}
14008 @itemx maint print psymbols @var{filename}
14009 @itemx maint print msymbols @var{filename}
14010 Write a dump of debugging symbol data into the file @var{filename}.
14011 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14012 symbols with debugging data are included. If you use @samp{maint print
14013 symbols}, @value{GDBN} includes all the symbols for which it has already
14014 collected full details: that is, @var{filename} reflects symbols for
14015 only those files whose symbols @value{GDBN} has read. You can use the
14016 command @code{info sources} to find out which files these are. If you
14017 use @samp{maint print psymbols} instead, the dump shows information about
14018 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14019 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14020 @samp{maint print msymbols} dumps just the minimal symbol information
14021 required for each object file from which @value{GDBN} has read some symbols.
14022 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14023 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14025 @kindex maint info symtabs
14026 @kindex maint info psymtabs
14027 @cindex listing @value{GDBN}'s internal symbol tables
14028 @cindex symbol tables, listing @value{GDBN}'s internal
14029 @cindex full symbol tables, listing @value{GDBN}'s internal
14030 @cindex partial symbol tables, listing @value{GDBN}'s internal
14031 @item maint info symtabs @r{[} @var{regexp} @r{]}
14032 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14034 List the @code{struct symtab} or @code{struct partial_symtab}
14035 structures whose names match @var{regexp}. If @var{regexp} is not
14036 given, list them all. The output includes expressions which you can
14037 copy into a @value{GDBN} debugging this one to examine a particular
14038 structure in more detail. For example:
14041 (@value{GDBP}) maint info psymtabs dwarf2read
14042 @{ objfile /home/gnu/build/gdb/gdb
14043 ((struct objfile *) 0x82e69d0)
14044 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14045 ((struct partial_symtab *) 0x8474b10)
14048 text addresses 0x814d3c8 -- 0x8158074
14049 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14050 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14051 dependencies (none)
14054 (@value{GDBP}) maint info symtabs
14058 We see that there is one partial symbol table whose filename contains
14059 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14060 and we see that @value{GDBN} has not read in any symtabs yet at all.
14061 If we set a breakpoint on a function, that will cause @value{GDBN} to
14062 read the symtab for the compilation unit containing that function:
14065 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14066 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14068 (@value{GDBP}) maint info symtabs
14069 @{ objfile /home/gnu/build/gdb/gdb
14070 ((struct objfile *) 0x82e69d0)
14071 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14072 ((struct symtab *) 0x86c1f38)
14075 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14076 linetable ((struct linetable *) 0x8370fa0)
14077 debugformat DWARF 2
14086 @chapter Altering Execution
14088 Once you think you have found an error in your program, you might want to
14089 find out for certain whether correcting the apparent error would lead to
14090 correct results in the rest of the run. You can find the answer by
14091 experiment, using the @value{GDBN} features for altering execution of the
14094 For example, you can store new values into variables or memory
14095 locations, give your program a signal, restart it at a different
14096 address, or even return prematurely from a function.
14099 * Assignment:: Assignment to variables
14100 * Jumping:: Continuing at a different address
14101 * Signaling:: Giving your program a signal
14102 * Returning:: Returning from a function
14103 * Calling:: Calling your program's functions
14104 * Patching:: Patching your program
14108 @section Assignment to Variables
14111 @cindex setting variables
14112 To alter the value of a variable, evaluate an assignment expression.
14113 @xref{Expressions, ,Expressions}. For example,
14120 stores the value 4 into the variable @code{x}, and then prints the
14121 value of the assignment expression (which is 4).
14122 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14123 information on operators in supported languages.
14125 @kindex set variable
14126 @cindex variables, setting
14127 If you are not interested in seeing the value of the assignment, use the
14128 @code{set} command instead of the @code{print} command. @code{set} is
14129 really the same as @code{print} except that the expression's value is
14130 not printed and is not put in the value history (@pxref{Value History,
14131 ,Value History}). The expression is evaluated only for its effects.
14133 If the beginning of the argument string of the @code{set} command
14134 appears identical to a @code{set} subcommand, use the @code{set
14135 variable} command instead of just @code{set}. This command is identical
14136 to @code{set} except for its lack of subcommands. For example, if your
14137 program has a variable @code{width}, you get an error if you try to set
14138 a new value with just @samp{set width=13}, because @value{GDBN} has the
14139 command @code{set width}:
14142 (@value{GDBP}) whatis width
14144 (@value{GDBP}) p width
14146 (@value{GDBP}) set width=47
14147 Invalid syntax in expression.
14151 The invalid expression, of course, is @samp{=47}. In
14152 order to actually set the program's variable @code{width}, use
14155 (@value{GDBP}) set var width=47
14158 Because the @code{set} command has many subcommands that can conflict
14159 with the names of program variables, it is a good idea to use the
14160 @code{set variable} command instead of just @code{set}. For example, if
14161 your program has a variable @code{g}, you run into problems if you try
14162 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14163 the command @code{set gnutarget}, abbreviated @code{set g}:
14167 (@value{GDBP}) whatis g
14171 (@value{GDBP}) set g=4
14175 The program being debugged has been started already.
14176 Start it from the beginning? (y or n) y
14177 Starting program: /home/smith/cc_progs/a.out
14178 "/home/smith/cc_progs/a.out": can't open to read symbols:
14179 Invalid bfd target.
14180 (@value{GDBP}) show g
14181 The current BFD target is "=4".
14186 The program variable @code{g} did not change, and you silently set the
14187 @code{gnutarget} to an invalid value. In order to set the variable
14191 (@value{GDBP}) set var g=4
14194 @value{GDBN} allows more implicit conversions in assignments than C; you can
14195 freely store an integer value into a pointer variable or vice versa,
14196 and you can convert any structure to any other structure that is the
14197 same length or shorter.
14198 @comment FIXME: how do structs align/pad in these conversions?
14199 @comment /doc@cygnus.com 18dec1990
14201 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14202 construct to generate a value of specified type at a specified address
14203 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14204 to memory location @code{0x83040} as an integer (which implies a certain size
14205 and representation in memory), and
14208 set @{int@}0x83040 = 4
14212 stores the value 4 into that memory location.
14215 @section Continuing at a Different Address
14217 Ordinarily, when you continue your program, you do so at the place where
14218 it stopped, with the @code{continue} command. You can instead continue at
14219 an address of your own choosing, with the following commands:
14223 @item jump @var{linespec}
14224 @itemx jump @var{location}
14225 Resume execution at line @var{linespec} or at address given by
14226 @var{location}. Execution stops again immediately if there is a
14227 breakpoint there. @xref{Specify Location}, for a description of the
14228 different forms of @var{linespec} and @var{location}. It is common
14229 practice to use the @code{tbreak} command in conjunction with
14230 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14232 The @code{jump} command does not change the current stack frame, or
14233 the stack pointer, or the contents of any memory location or any
14234 register other than the program counter. If line @var{linespec} is in
14235 a different function from the one currently executing, the results may
14236 be bizarre if the two functions expect different patterns of arguments or
14237 of local variables. For this reason, the @code{jump} command requests
14238 confirmation if the specified line is not in the function currently
14239 executing. However, even bizarre results are predictable if you are
14240 well acquainted with the machine-language code of your program.
14243 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14244 On many systems, you can get much the same effect as the @code{jump}
14245 command by storing a new value into the register @code{$pc}. The
14246 difference is that this does not start your program running; it only
14247 changes the address of where it @emph{will} run when you continue. For
14255 makes the next @code{continue} command or stepping command execute at
14256 address @code{0x485}, rather than at the address where your program stopped.
14257 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14259 The most common occasion to use the @code{jump} command is to back
14260 up---perhaps with more breakpoints set---over a portion of a program
14261 that has already executed, in order to examine its execution in more
14266 @section Giving your Program a Signal
14267 @cindex deliver a signal to a program
14271 @item signal @var{signal}
14272 Resume execution where your program stopped, but immediately give it the
14273 signal @var{signal}. @var{signal} can be the name or the number of a
14274 signal. For example, on many systems @code{signal 2} and @code{signal
14275 SIGINT} are both ways of sending an interrupt signal.
14277 Alternatively, if @var{signal} is zero, continue execution without
14278 giving a signal. This is useful when your program stopped on account of
14279 a signal and would ordinary see the signal when resumed with the
14280 @code{continue} command; @samp{signal 0} causes it to resume without a
14283 @code{signal} does not repeat when you press @key{RET} a second time
14284 after executing the command.
14288 Invoking the @code{signal} command is not the same as invoking the
14289 @code{kill} utility from the shell. Sending a signal with @code{kill}
14290 causes @value{GDBN} to decide what to do with the signal depending on
14291 the signal handling tables (@pxref{Signals}). The @code{signal} command
14292 passes the signal directly to your program.
14296 @section Returning from a Function
14299 @cindex returning from a function
14302 @itemx return @var{expression}
14303 You can cancel execution of a function call with the @code{return}
14304 command. If you give an
14305 @var{expression} argument, its value is used as the function's return
14309 When you use @code{return}, @value{GDBN} discards the selected stack frame
14310 (and all frames within it). You can think of this as making the
14311 discarded frame return prematurely. If you wish to specify a value to
14312 be returned, give that value as the argument to @code{return}.
14314 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14315 Frame}), and any other frames inside of it, leaving its caller as the
14316 innermost remaining frame. That frame becomes selected. The
14317 specified value is stored in the registers used for returning values
14320 The @code{return} command does not resume execution; it leaves the
14321 program stopped in the state that would exist if the function had just
14322 returned. In contrast, the @code{finish} command (@pxref{Continuing
14323 and Stepping, ,Continuing and Stepping}) resumes execution until the
14324 selected stack frame returns naturally.
14326 @value{GDBN} needs to know how the @var{expression} argument should be set for
14327 the inferior. The concrete registers assignment depends on the OS ABI and the
14328 type being returned by the selected stack frame. For example it is common for
14329 OS ABI to return floating point values in FPU registers while integer values in
14330 CPU registers. Still some ABIs return even floating point values in CPU
14331 registers. Larger integer widths (such as @code{long long int}) also have
14332 specific placement rules. @value{GDBN} already knows the OS ABI from its
14333 current target so it needs to find out also the type being returned to make the
14334 assignment into the right register(s).
14336 Normally, the selected stack frame has debug info. @value{GDBN} will always
14337 use the debug info instead of the implicit type of @var{expression} when the
14338 debug info is available. For example, if you type @kbd{return -1}, and the
14339 function in the current stack frame is declared to return a @code{long long
14340 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14341 into a @code{long long int}:
14344 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14346 (@value{GDBP}) return -1
14347 Make func return now? (y or n) y
14348 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14349 43 printf ("result=%lld\n", func ());
14353 However, if the selected stack frame does not have a debug info, e.g., if the
14354 function was compiled without debug info, @value{GDBN} has to find out the type
14355 to return from user. Specifying a different type by mistake may set the value
14356 in different inferior registers than the caller code expects. For example,
14357 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14358 of a @code{long long int} result for a debug info less function (on 32-bit
14359 architectures). Therefore the user is required to specify the return type by
14360 an appropriate cast explicitly:
14363 Breakpoint 2, 0x0040050b in func ()
14364 (@value{GDBP}) return -1
14365 Return value type not available for selected stack frame.
14366 Please use an explicit cast of the value to return.
14367 (@value{GDBP}) return (long long int) -1
14368 Make selected stack frame return now? (y or n) y
14369 #0 0x00400526 in main ()
14374 @section Calling Program Functions
14377 @cindex calling functions
14378 @cindex inferior functions, calling
14379 @item print @var{expr}
14380 Evaluate the expression @var{expr} and display the resulting value.
14381 @var{expr} may include calls to functions in the program being
14385 @item call @var{expr}
14386 Evaluate the expression @var{expr} without displaying @code{void}
14389 You can use this variant of the @code{print} command if you want to
14390 execute a function from your program that does not return anything
14391 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14392 with @code{void} returned values that @value{GDBN} will otherwise
14393 print. If the result is not void, it is printed and saved in the
14397 It is possible for the function you call via the @code{print} or
14398 @code{call} command to generate a signal (e.g., if there's a bug in
14399 the function, or if you passed it incorrect arguments). What happens
14400 in that case is controlled by the @code{set unwindonsignal} command.
14402 Similarly, with a C@t{++} program it is possible for the function you
14403 call via the @code{print} or @code{call} command to generate an
14404 exception that is not handled due to the constraints of the dummy
14405 frame. In this case, any exception that is raised in the frame, but has
14406 an out-of-frame exception handler will not be found. GDB builds a
14407 dummy-frame for the inferior function call, and the unwinder cannot
14408 seek for exception handlers outside of this dummy-frame. What happens
14409 in that case is controlled by the
14410 @code{set unwind-on-terminating-exception} command.
14413 @item set unwindonsignal
14414 @kindex set unwindonsignal
14415 @cindex unwind stack in called functions
14416 @cindex call dummy stack unwinding
14417 Set unwinding of the stack if a signal is received while in a function
14418 that @value{GDBN} called in the program being debugged. If set to on,
14419 @value{GDBN} unwinds the stack it created for the call and restores
14420 the context to what it was before the call. If set to off (the
14421 default), @value{GDBN} stops in the frame where the signal was
14424 @item show unwindonsignal
14425 @kindex show unwindonsignal
14426 Show the current setting of stack unwinding in the functions called by
14429 @item set unwind-on-terminating-exception
14430 @kindex set unwind-on-terminating-exception
14431 @cindex unwind stack in called functions with unhandled exceptions
14432 @cindex call dummy stack unwinding on unhandled exception.
14433 Set unwinding of the stack if a C@t{++} exception is raised, but left
14434 unhandled while in a function that @value{GDBN} called in the program being
14435 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14436 it created for the call and restores the context to what it was before
14437 the call. If set to off, @value{GDBN} the exception is delivered to
14438 the default C@t{++} exception handler and the inferior terminated.
14440 @item show unwind-on-terminating-exception
14441 @kindex show unwind-on-terminating-exception
14442 Show the current setting of stack unwinding in the functions called by
14447 @cindex weak alias functions
14448 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14449 for another function. In such case, @value{GDBN} might not pick up
14450 the type information, including the types of the function arguments,
14451 which causes @value{GDBN} to call the inferior function incorrectly.
14452 As a result, the called function will function erroneously and may
14453 even crash. A solution to that is to use the name of the aliased
14457 @section Patching Programs
14459 @cindex patching binaries
14460 @cindex writing into executables
14461 @cindex writing into corefiles
14463 By default, @value{GDBN} opens the file containing your program's
14464 executable code (or the corefile) read-only. This prevents accidental
14465 alterations to machine code; but it also prevents you from intentionally
14466 patching your program's binary.
14468 If you'd like to be able to patch the binary, you can specify that
14469 explicitly with the @code{set write} command. For example, you might
14470 want to turn on internal debugging flags, or even to make emergency
14476 @itemx set write off
14477 If you specify @samp{set write on}, @value{GDBN} opens executable and
14478 core files for both reading and writing; if you specify @kbd{set write
14479 off} (the default), @value{GDBN} opens them read-only.
14481 If you have already loaded a file, you must load it again (using the
14482 @code{exec-file} or @code{core-file} command) after changing @code{set
14483 write}, for your new setting to take effect.
14487 Display whether executable files and core files are opened for writing
14488 as well as reading.
14492 @chapter @value{GDBN} Files
14494 @value{GDBN} needs to know the file name of the program to be debugged,
14495 both in order to read its symbol table and in order to start your
14496 program. To debug a core dump of a previous run, you must also tell
14497 @value{GDBN} the name of the core dump file.
14500 * Files:: Commands to specify files
14501 * Separate Debug Files:: Debugging information in separate files
14502 * Index Files:: Index files speed up GDB
14503 * Symbol Errors:: Errors reading symbol files
14504 * Data Files:: GDB data files
14508 @section Commands to Specify Files
14510 @cindex symbol table
14511 @cindex core dump file
14513 You may want to specify executable and core dump file names. The usual
14514 way to do this is at start-up time, using the arguments to
14515 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14516 Out of @value{GDBN}}).
14518 Occasionally it is necessary to change to a different file during a
14519 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14520 specify a file you want to use. Or you are debugging a remote target
14521 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14522 Program}). In these situations the @value{GDBN} commands to specify
14523 new files are useful.
14526 @cindex executable file
14528 @item file @var{filename}
14529 Use @var{filename} as the program to be debugged. It is read for its
14530 symbols and for the contents of pure memory. It is also the program
14531 executed when you use the @code{run} command. If you do not specify a
14532 directory and the file is not found in the @value{GDBN} working directory,
14533 @value{GDBN} uses the environment variable @code{PATH} as a list of
14534 directories to search, just as the shell does when looking for a program
14535 to run. You can change the value of this variable, for both @value{GDBN}
14536 and your program, using the @code{path} command.
14538 @cindex unlinked object files
14539 @cindex patching object files
14540 You can load unlinked object @file{.o} files into @value{GDBN} using
14541 the @code{file} command. You will not be able to ``run'' an object
14542 file, but you can disassemble functions and inspect variables. Also,
14543 if the underlying BFD functionality supports it, you could use
14544 @kbd{gdb -write} to patch object files using this technique. Note
14545 that @value{GDBN} can neither interpret nor modify relocations in this
14546 case, so branches and some initialized variables will appear to go to
14547 the wrong place. But this feature is still handy from time to time.
14550 @code{file} with no argument makes @value{GDBN} discard any information it
14551 has on both executable file and the symbol table.
14554 @item exec-file @r{[} @var{filename} @r{]}
14555 Specify that the program to be run (but not the symbol table) is found
14556 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14557 if necessary to locate your program. Omitting @var{filename} means to
14558 discard information on the executable file.
14560 @kindex symbol-file
14561 @item symbol-file @r{[} @var{filename} @r{]}
14562 Read symbol table information from file @var{filename}. @code{PATH} is
14563 searched when necessary. Use the @code{file} command to get both symbol
14564 table and program to run from the same file.
14566 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14567 program's symbol table.
14569 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14570 some breakpoints and auto-display expressions. This is because they may
14571 contain pointers to the internal data recording symbols and data types,
14572 which are part of the old symbol table data being discarded inside
14575 @code{symbol-file} does not repeat if you press @key{RET} again after
14578 When @value{GDBN} is configured for a particular environment, it
14579 understands debugging information in whatever format is the standard
14580 generated for that environment; you may use either a @sc{gnu} compiler, or
14581 other compilers that adhere to the local conventions.
14582 Best results are usually obtained from @sc{gnu} compilers; for example,
14583 using @code{@value{NGCC}} you can generate debugging information for
14586 For most kinds of object files, with the exception of old SVR3 systems
14587 using COFF, the @code{symbol-file} command does not normally read the
14588 symbol table in full right away. Instead, it scans the symbol table
14589 quickly to find which source files and which symbols are present. The
14590 details are read later, one source file at a time, as they are needed.
14592 The purpose of this two-stage reading strategy is to make @value{GDBN}
14593 start up faster. For the most part, it is invisible except for
14594 occasional pauses while the symbol table details for a particular source
14595 file are being read. (The @code{set verbose} command can turn these
14596 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14597 Warnings and Messages}.)
14599 We have not implemented the two-stage strategy for COFF yet. When the
14600 symbol table is stored in COFF format, @code{symbol-file} reads the
14601 symbol table data in full right away. Note that ``stabs-in-COFF''
14602 still does the two-stage strategy, since the debug info is actually
14606 @cindex reading symbols immediately
14607 @cindex symbols, reading immediately
14608 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14609 @itemx file @r{[} -readnow @r{]} @var{filename}
14610 You can override the @value{GDBN} two-stage strategy for reading symbol
14611 tables by using the @samp{-readnow} option with any of the commands that
14612 load symbol table information, if you want to be sure @value{GDBN} has the
14613 entire symbol table available.
14615 @c FIXME: for now no mention of directories, since this seems to be in
14616 @c flux. 13mar1992 status is that in theory GDB would look either in
14617 @c current dir or in same dir as myprog; but issues like competing
14618 @c GDB's, or clutter in system dirs, mean that in practice right now
14619 @c only current dir is used. FFish says maybe a special GDB hierarchy
14620 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14624 @item core-file @r{[}@var{filename}@r{]}
14626 Specify the whereabouts of a core dump file to be used as the ``contents
14627 of memory''. Traditionally, core files contain only some parts of the
14628 address space of the process that generated them; @value{GDBN} can access the
14629 executable file itself for other parts.
14631 @code{core-file} with no argument specifies that no core file is
14634 Note that the core file is ignored when your program is actually running
14635 under @value{GDBN}. So, if you have been running your program and you
14636 wish to debug a core file instead, you must kill the subprocess in which
14637 the program is running. To do this, use the @code{kill} command
14638 (@pxref{Kill Process, ,Killing the Child Process}).
14640 @kindex add-symbol-file
14641 @cindex dynamic linking
14642 @item add-symbol-file @var{filename} @var{address}
14643 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14644 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14645 The @code{add-symbol-file} command reads additional symbol table
14646 information from the file @var{filename}. You would use this command
14647 when @var{filename} has been dynamically loaded (by some other means)
14648 into the program that is running. @var{address} should be the memory
14649 address at which the file has been loaded; @value{GDBN} cannot figure
14650 this out for itself. You can additionally specify an arbitrary number
14651 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14652 section name and base address for that section. You can specify any
14653 @var{address} as an expression.
14655 The symbol table of the file @var{filename} is added to the symbol table
14656 originally read with the @code{symbol-file} command. You can use the
14657 @code{add-symbol-file} command any number of times; the new symbol data
14658 thus read keeps adding to the old. To discard all old symbol data
14659 instead, use the @code{symbol-file} command without any arguments.
14661 @cindex relocatable object files, reading symbols from
14662 @cindex object files, relocatable, reading symbols from
14663 @cindex reading symbols from relocatable object files
14664 @cindex symbols, reading from relocatable object files
14665 @cindex @file{.o} files, reading symbols from
14666 Although @var{filename} is typically a shared library file, an
14667 executable file, or some other object file which has been fully
14668 relocated for loading into a process, you can also load symbolic
14669 information from relocatable @file{.o} files, as long as:
14673 the file's symbolic information refers only to linker symbols defined in
14674 that file, not to symbols defined by other object files,
14676 every section the file's symbolic information refers to has actually
14677 been loaded into the inferior, as it appears in the file, and
14679 you can determine the address at which every section was loaded, and
14680 provide these to the @code{add-symbol-file} command.
14684 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14685 relocatable files into an already running program; such systems
14686 typically make the requirements above easy to meet. However, it's
14687 important to recognize that many native systems use complex link
14688 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14689 assembly, for example) that make the requirements difficult to meet. In
14690 general, one cannot assume that using @code{add-symbol-file} to read a
14691 relocatable object file's symbolic information will have the same effect
14692 as linking the relocatable object file into the program in the normal
14695 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14697 @kindex add-symbol-file-from-memory
14698 @cindex @code{syscall DSO}
14699 @cindex load symbols from memory
14700 @item add-symbol-file-from-memory @var{address}
14701 Load symbols from the given @var{address} in a dynamically loaded
14702 object file whose image is mapped directly into the inferior's memory.
14703 For example, the Linux kernel maps a @code{syscall DSO} into each
14704 process's address space; this DSO provides kernel-specific code for
14705 some system calls. The argument can be any expression whose
14706 evaluation yields the address of the file's shared object file header.
14707 For this command to work, you must have used @code{symbol-file} or
14708 @code{exec-file} commands in advance.
14710 @kindex add-shared-symbol-files
14712 @item add-shared-symbol-files @var{library-file}
14713 @itemx assf @var{library-file}
14714 The @code{add-shared-symbol-files} command can currently be used only
14715 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14716 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14717 @value{GDBN} automatically looks for shared libraries, however if
14718 @value{GDBN} does not find yours, you can invoke
14719 @code{add-shared-symbol-files}. It takes one argument: the shared
14720 library's file name. @code{assf} is a shorthand alias for
14721 @code{add-shared-symbol-files}.
14724 @item section @var{section} @var{addr}
14725 The @code{section} command changes the base address of the named
14726 @var{section} of the exec file to @var{addr}. This can be used if the
14727 exec file does not contain section addresses, (such as in the
14728 @code{a.out} format), or when the addresses specified in the file
14729 itself are wrong. Each section must be changed separately. The
14730 @code{info files} command, described below, lists all the sections and
14734 @kindex info target
14737 @code{info files} and @code{info target} are synonymous; both print the
14738 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14739 including the names of the executable and core dump files currently in
14740 use by @value{GDBN}, and the files from which symbols were loaded. The
14741 command @code{help target} lists all possible targets rather than
14744 @kindex maint info sections
14745 @item maint info sections
14746 Another command that can give you extra information about program sections
14747 is @code{maint info sections}. In addition to the section information
14748 displayed by @code{info files}, this command displays the flags and file
14749 offset of each section in the executable and core dump files. In addition,
14750 @code{maint info sections} provides the following command options (which
14751 may be arbitrarily combined):
14755 Display sections for all loaded object files, including shared libraries.
14756 @item @var{sections}
14757 Display info only for named @var{sections}.
14758 @item @var{section-flags}
14759 Display info only for sections for which @var{section-flags} are true.
14760 The section flags that @value{GDBN} currently knows about are:
14763 Section will have space allocated in the process when loaded.
14764 Set for all sections except those containing debug information.
14766 Section will be loaded from the file into the child process memory.
14767 Set for pre-initialized code and data, clear for @code{.bss} sections.
14769 Section needs to be relocated before loading.
14771 Section cannot be modified by the child process.
14773 Section contains executable code only.
14775 Section contains data only (no executable code).
14777 Section will reside in ROM.
14779 Section contains data for constructor/destructor lists.
14781 Section is not empty.
14783 An instruction to the linker to not output the section.
14784 @item COFF_SHARED_LIBRARY
14785 A notification to the linker that the section contains
14786 COFF shared library information.
14788 Section contains common symbols.
14791 @kindex set trust-readonly-sections
14792 @cindex read-only sections
14793 @item set trust-readonly-sections on
14794 Tell @value{GDBN} that readonly sections in your object file
14795 really are read-only (i.e.@: that their contents will not change).
14796 In that case, @value{GDBN} can fetch values from these sections
14797 out of the object file, rather than from the target program.
14798 For some targets (notably embedded ones), this can be a significant
14799 enhancement to debugging performance.
14801 The default is off.
14803 @item set trust-readonly-sections off
14804 Tell @value{GDBN} not to trust readonly sections. This means that
14805 the contents of the section might change while the program is running,
14806 and must therefore be fetched from the target when needed.
14808 @item show trust-readonly-sections
14809 Show the current setting of trusting readonly sections.
14812 All file-specifying commands allow both absolute and relative file names
14813 as arguments. @value{GDBN} always converts the file name to an absolute file
14814 name and remembers it that way.
14816 @cindex shared libraries
14817 @anchor{Shared Libraries}
14818 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14819 and IBM RS/6000 AIX shared libraries.
14821 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14822 shared libraries. @xref{Expat}.
14824 @value{GDBN} automatically loads symbol definitions from shared libraries
14825 when you use the @code{run} command, or when you examine a core file.
14826 (Before you issue the @code{run} command, @value{GDBN} does not understand
14827 references to a function in a shared library, however---unless you are
14828 debugging a core file).
14830 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14831 automatically loads the symbols at the time of the @code{shl_load} call.
14833 @c FIXME: some @value{GDBN} release may permit some refs to undef
14834 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14835 @c FIXME...lib; check this from time to time when updating manual
14837 There are times, however, when you may wish to not automatically load
14838 symbol definitions from shared libraries, such as when they are
14839 particularly large or there are many of them.
14841 To control the automatic loading of shared library symbols, use the
14845 @kindex set auto-solib-add
14846 @item set auto-solib-add @var{mode}
14847 If @var{mode} is @code{on}, symbols from all shared object libraries
14848 will be loaded automatically when the inferior begins execution, you
14849 attach to an independently started inferior, or when the dynamic linker
14850 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14851 is @code{off}, symbols must be loaded manually, using the
14852 @code{sharedlibrary} command. The default value is @code{on}.
14854 @cindex memory used for symbol tables
14855 If your program uses lots of shared libraries with debug info that
14856 takes large amounts of memory, you can decrease the @value{GDBN}
14857 memory footprint by preventing it from automatically loading the
14858 symbols from shared libraries. To that end, type @kbd{set
14859 auto-solib-add off} before running the inferior, then load each
14860 library whose debug symbols you do need with @kbd{sharedlibrary
14861 @var{regexp}}, where @var{regexp} is a regular expression that matches
14862 the libraries whose symbols you want to be loaded.
14864 @kindex show auto-solib-add
14865 @item show auto-solib-add
14866 Display the current autoloading mode.
14869 @cindex load shared library
14870 To explicitly load shared library symbols, use the @code{sharedlibrary}
14874 @kindex info sharedlibrary
14876 @item info share @var{regex}
14877 @itemx info sharedlibrary @var{regex}
14878 Print the names of the shared libraries which are currently loaded
14879 that match @var{regex}. If @var{regex} is omitted then print
14880 all shared libraries that are loaded.
14882 @kindex sharedlibrary
14884 @item sharedlibrary @var{regex}
14885 @itemx share @var{regex}
14886 Load shared object library symbols for files matching a
14887 Unix regular expression.
14888 As with files loaded automatically, it only loads shared libraries
14889 required by your program for a core file or after typing @code{run}. If
14890 @var{regex} is omitted all shared libraries required by your program are
14893 @item nosharedlibrary
14894 @kindex nosharedlibrary
14895 @cindex unload symbols from shared libraries
14896 Unload all shared object library symbols. This discards all symbols
14897 that have been loaded from all shared libraries. Symbols from shared
14898 libraries that were loaded by explicit user requests are not
14902 Sometimes you may wish that @value{GDBN} stops and gives you control
14903 when any of shared library events happen. Use the @code{set
14904 stop-on-solib-events} command for this:
14907 @item set stop-on-solib-events
14908 @kindex set stop-on-solib-events
14909 This command controls whether @value{GDBN} should give you control
14910 when the dynamic linker notifies it about some shared library event.
14911 The most common event of interest is loading or unloading of a new
14914 @item show stop-on-solib-events
14915 @kindex show stop-on-solib-events
14916 Show whether @value{GDBN} stops and gives you control when shared
14917 library events happen.
14920 Shared libraries are also supported in many cross or remote debugging
14921 configurations. @value{GDBN} needs to have access to the target's libraries;
14922 this can be accomplished either by providing copies of the libraries
14923 on the host system, or by asking @value{GDBN} to automatically retrieve the
14924 libraries from the target. If copies of the target libraries are
14925 provided, they need to be the same as the target libraries, although the
14926 copies on the target can be stripped as long as the copies on the host are
14929 @cindex where to look for shared libraries
14930 For remote debugging, you need to tell @value{GDBN} where the target
14931 libraries are, so that it can load the correct copies---otherwise, it
14932 may try to load the host's libraries. @value{GDBN} has two variables
14933 to specify the search directories for target libraries.
14936 @cindex prefix for shared library file names
14937 @cindex system root, alternate
14938 @kindex set solib-absolute-prefix
14939 @kindex set sysroot
14940 @item set sysroot @var{path}
14941 Use @var{path} as the system root for the program being debugged. Any
14942 absolute shared library paths will be prefixed with @var{path}; many
14943 runtime loaders store the absolute paths to the shared library in the
14944 target program's memory. If you use @code{set sysroot} to find shared
14945 libraries, they need to be laid out in the same way that they are on
14946 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14949 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14950 retrieve the target libraries from the remote system. This is only
14951 supported when using a remote target that supports the @code{remote get}
14952 command (@pxref{File Transfer,,Sending files to a remote system}).
14953 The part of @var{path} following the initial @file{remote:}
14954 (if present) is used as system root prefix on the remote file system.
14955 @footnote{If you want to specify a local system root using a directory
14956 that happens to be named @file{remote:}, you need to use some equivalent
14957 variant of the name like @file{./remote:}.}
14959 For targets with an MS-DOS based filesystem, such as MS-Windows and
14960 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14961 absolute file name with @var{path}. But first, on Unix hosts,
14962 @value{GDBN} converts all backslash directory separators into forward
14963 slashes, because the backslash is not a directory separator on Unix:
14966 c:\foo\bar.dll @result{} c:/foo/bar.dll
14969 Then, @value{GDBN} attempts prefixing the target file name with
14970 @var{path}, and looks for the resulting file name in the host file
14974 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14977 If that does not find the shared library, @value{GDBN} tries removing
14978 the @samp{:} character from the drive spec, both for convenience, and,
14979 for the case of the host file system not supporting file names with
14983 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14986 This makes it possible to have a system root that mirrors a target
14987 with more than one drive. E.g., you may want to setup your local
14988 copies of the target system shared libraries like so (note @samp{c} vs
14992 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14993 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14994 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14998 and point the system root at @file{/path/to/sysroot}, so that
14999 @value{GDBN} can find the correct copies of both
15000 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15002 If that still does not find the shared library, @value{GDBN} tries
15003 removing the whole drive spec from the target file name:
15006 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15009 This last lookup makes it possible to not care about the drive name,
15010 if you don't want or need to.
15012 The @code{set solib-absolute-prefix} command is an alias for @code{set
15015 @cindex default system root
15016 @cindex @samp{--with-sysroot}
15017 You can set the default system root by using the configure-time
15018 @samp{--with-sysroot} option. If the system root is inside
15019 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15020 @samp{--exec-prefix}), then the default system root will be updated
15021 automatically if the installed @value{GDBN} is moved to a new
15024 @kindex show sysroot
15026 Display the current shared library prefix.
15028 @kindex set solib-search-path
15029 @item set solib-search-path @var{path}
15030 If this variable is set, @var{path} is a colon-separated list of
15031 directories to search for shared libraries. @samp{solib-search-path}
15032 is used after @samp{sysroot} fails to locate the library, or if the
15033 path to the library is relative instead of absolute. If you want to
15034 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15035 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15036 finding your host's libraries. @samp{sysroot} is preferred; setting
15037 it to a nonexistent directory may interfere with automatic loading
15038 of shared library symbols.
15040 @kindex show solib-search-path
15041 @item show solib-search-path
15042 Display the current shared library search path.
15044 @cindex DOS file-name semantics of file names.
15045 @kindex set target-file-system-kind (unix|dos-based|auto)
15046 @kindex show target-file-system-kind
15047 @item set target-file-system-kind @var{kind}
15048 Set assumed file system kind for target reported file names.
15050 Shared library file names as reported by the target system may not
15051 make sense as is on the system @value{GDBN} is running on. For
15052 example, when remote debugging a target that has MS-DOS based file
15053 system semantics, from a Unix host, the target may be reporting to
15054 @value{GDBN} a list of loaded shared libraries with file names such as
15055 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15056 drive letters, so the @samp{c:\} prefix is not normally understood as
15057 indicating an absolute file name, and neither is the backslash
15058 normally considered a directory separator character. In that case,
15059 the native file system would interpret this whole absolute file name
15060 as a relative file name with no directory components. This would make
15061 it impossible to point @value{GDBN} at a copy of the remote target's
15062 shared libraries on the host using @code{set sysroot}, and impractical
15063 with @code{set solib-search-path}. Setting
15064 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15065 to interpret such file names similarly to how the target would, and to
15066 map them to file names valid on @value{GDBN}'s native file system
15067 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15068 to one of the supported file system kinds. In that case, @value{GDBN}
15069 tries to determine the appropriate file system variant based on the
15070 current target's operating system (@pxref{ABI, ,Configuring the
15071 Current ABI}). The supported file system settings are:
15075 Instruct @value{GDBN} to assume the target file system is of Unix
15076 kind. Only file names starting the forward slash (@samp{/}) character
15077 are considered absolute, and the directory separator character is also
15081 Instruct @value{GDBN} to assume the target file system is DOS based.
15082 File names starting with either a forward slash, or a drive letter
15083 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15084 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15085 considered directory separators.
15088 Instruct @value{GDBN} to use the file system kind associated with the
15089 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15090 This is the default.
15095 @node Separate Debug Files
15096 @section Debugging Information in Separate Files
15097 @cindex separate debugging information files
15098 @cindex debugging information in separate files
15099 @cindex @file{.debug} subdirectories
15100 @cindex debugging information directory, global
15101 @cindex global debugging information directory
15102 @cindex build ID, and separate debugging files
15103 @cindex @file{.build-id} directory
15105 @value{GDBN} allows you to put a program's debugging information in a
15106 file separate from the executable itself, in a way that allows
15107 @value{GDBN} to find and load the debugging information automatically.
15108 Since debugging information can be very large---sometimes larger
15109 than the executable code itself---some systems distribute debugging
15110 information for their executables in separate files, which users can
15111 install only when they need to debug a problem.
15113 @value{GDBN} supports two ways of specifying the separate debug info
15118 The executable contains a @dfn{debug link} that specifies the name of
15119 the separate debug info file. The separate debug file's name is
15120 usually @file{@var{executable}.debug}, where @var{executable} is the
15121 name of the corresponding executable file without leading directories
15122 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15123 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15124 checksum for the debug file, which @value{GDBN} uses to validate that
15125 the executable and the debug file came from the same build.
15128 The executable contains a @dfn{build ID}, a unique bit string that is
15129 also present in the corresponding debug info file. (This is supported
15130 only on some operating systems, notably those which use the ELF format
15131 for binary files and the @sc{gnu} Binutils.) For more details about
15132 this feature, see the description of the @option{--build-id}
15133 command-line option in @ref{Options, , Command Line Options, ld.info,
15134 The GNU Linker}. The debug info file's name is not specified
15135 explicitly by the build ID, but can be computed from the build ID, see
15139 Depending on the way the debug info file is specified, @value{GDBN}
15140 uses two different methods of looking for the debug file:
15144 For the ``debug link'' method, @value{GDBN} looks up the named file in
15145 the directory of the executable file, then in a subdirectory of that
15146 directory named @file{.debug}, and finally under the global debug
15147 directory, in a subdirectory whose name is identical to the leading
15148 directories of the executable's absolute file name.
15151 For the ``build ID'' method, @value{GDBN} looks in the
15152 @file{.build-id} subdirectory of the global debug directory for a file
15153 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15154 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15155 are the rest of the bit string. (Real build ID strings are 32 or more
15156 hex characters, not 10.)
15159 So, for example, suppose you ask @value{GDBN} to debug
15160 @file{/usr/bin/ls}, which has a debug link that specifies the
15161 file @file{ls.debug}, and a build ID whose value in hex is
15162 @code{abcdef1234}. If the global debug directory is
15163 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15164 debug information files, in the indicated order:
15168 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15170 @file{/usr/bin/ls.debug}
15172 @file{/usr/bin/.debug/ls.debug}
15174 @file{/usr/lib/debug/usr/bin/ls.debug}.
15177 You can set the global debugging info directory's name, and view the
15178 name @value{GDBN} is currently using.
15182 @kindex set debug-file-directory
15183 @item set debug-file-directory @var{directories}
15184 Set the directories which @value{GDBN} searches for separate debugging
15185 information files to @var{directory}. Multiple directory components can be set
15186 concatenating them by a directory separator.
15188 @kindex show debug-file-directory
15189 @item show debug-file-directory
15190 Show the directories @value{GDBN} searches for separate debugging
15195 @cindex @code{.gnu_debuglink} sections
15196 @cindex debug link sections
15197 A debug link is a special section of the executable file named
15198 @code{.gnu_debuglink}. The section must contain:
15202 A filename, with any leading directory components removed, followed by
15205 zero to three bytes of padding, as needed to reach the next four-byte
15206 boundary within the section, and
15208 a four-byte CRC checksum, stored in the same endianness used for the
15209 executable file itself. The checksum is computed on the debugging
15210 information file's full contents by the function given below, passing
15211 zero as the @var{crc} argument.
15214 Any executable file format can carry a debug link, as long as it can
15215 contain a section named @code{.gnu_debuglink} with the contents
15218 @cindex @code{.note.gnu.build-id} sections
15219 @cindex build ID sections
15220 The build ID is a special section in the executable file (and in other
15221 ELF binary files that @value{GDBN} may consider). This section is
15222 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15223 It contains unique identification for the built files---the ID remains
15224 the same across multiple builds of the same build tree. The default
15225 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15226 content for the build ID string. The same section with an identical
15227 value is present in the original built binary with symbols, in its
15228 stripped variant, and in the separate debugging information file.
15230 The debugging information file itself should be an ordinary
15231 executable, containing a full set of linker symbols, sections, and
15232 debugging information. The sections of the debugging information file
15233 should have the same names, addresses, and sizes as the original file,
15234 but they need not contain any data---much like a @code{.bss} section
15235 in an ordinary executable.
15237 The @sc{gnu} binary utilities (Binutils) package includes the
15238 @samp{objcopy} utility that can produce
15239 the separated executable / debugging information file pairs using the
15240 following commands:
15243 @kbd{objcopy --only-keep-debug foo foo.debug}
15248 These commands remove the debugging
15249 information from the executable file @file{foo} and place it in the file
15250 @file{foo.debug}. You can use the first, second or both methods to link the
15255 The debug link method needs the following additional command to also leave
15256 behind a debug link in @file{foo}:
15259 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15262 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15263 a version of the @code{strip} command such that the command @kbd{strip foo -f
15264 foo.debug} has the same functionality as the two @code{objcopy} commands and
15265 the @code{ln -s} command above, together.
15268 Build ID gets embedded into the main executable using @code{ld --build-id} or
15269 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15270 compatibility fixes for debug files separation are present in @sc{gnu} binary
15271 utilities (Binutils) package since version 2.18.
15276 @cindex CRC algorithm definition
15277 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15278 IEEE 802.3 using the polynomial:
15280 @c TexInfo requires naked braces for multi-digit exponents for Tex
15281 @c output, but this causes HTML output to barf. HTML has to be set using
15282 @c raw commands. So we end up having to specify this equation in 2
15287 <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>
15288 + <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
15294 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15295 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15299 The function is computed byte at a time, taking the least
15300 significant bit of each byte first. The initial pattern
15301 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15302 the final result is inverted to ensure trailing zeros also affect the
15305 @emph{Note:} This is the same CRC polynomial as used in handling the
15306 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15307 , @value{GDBN} Remote Serial Protocol}). However in the
15308 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15309 significant bit first, and the result is not inverted, so trailing
15310 zeros have no effect on the CRC value.
15312 To complete the description, we show below the code of the function
15313 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15314 initially supplied @code{crc} argument means that an initial call to
15315 this function passing in zero will start computing the CRC using
15318 @kindex gnu_debuglink_crc32
15321 gnu_debuglink_crc32 (unsigned long crc,
15322 unsigned char *buf, size_t len)
15324 static const unsigned long crc32_table[256] =
15326 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15327 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15328 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15329 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15330 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15331 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15332 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15333 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15334 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15335 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15336 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15337 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15338 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15339 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15340 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15341 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15342 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15343 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15344 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15345 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15346 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15347 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15348 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15349 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15350 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15351 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15352 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15353 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15354 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15355 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15356 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15357 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15358 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15359 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15360 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15361 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15362 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15363 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15364 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15365 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15366 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15367 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15368 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15369 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15370 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15371 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15372 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15373 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15374 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15375 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15376 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15379 unsigned char *end;
15381 crc = ~crc & 0xffffffff;
15382 for (end = buf + len; buf < end; ++buf)
15383 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15384 return ~crc & 0xffffffff;
15389 This computation does not apply to the ``build ID'' method.
15393 @section Index Files Speed Up @value{GDBN}
15394 @cindex index files
15395 @cindex @samp{.gdb_index} section
15397 When @value{GDBN} finds a symbol file, it scans the symbols in the
15398 file in order to construct an internal symbol table. This lets most
15399 @value{GDBN} operations work quickly---at the cost of a delay early
15400 on. For large programs, this delay can be quite lengthy, so
15401 @value{GDBN} provides a way to build an index, which speeds up
15404 The index is stored as a section in the symbol file. @value{GDBN} can
15405 write the index to a file, then you can put it into the symbol file
15406 using @command{objcopy}.
15408 To create an index file, use the @code{save gdb-index} command:
15411 @item save gdb-index @var{directory}
15412 @kindex save gdb-index
15413 Create an index file for each symbol file currently known by
15414 @value{GDBN}. Each file is named after its corresponding symbol file,
15415 with @samp{.gdb-index} appended, and is written into the given
15419 Once you have created an index file you can merge it into your symbol
15420 file, here named @file{symfile}, using @command{objcopy}:
15423 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15424 --set-section-flags .gdb_index=readonly symfile symfile
15427 There are currently some limitation on indices. They only work when
15428 for DWARF debugging information, not stabs. And, they do not
15429 currently work for programs using Ada.
15431 @node Symbol Errors
15432 @section Errors Reading Symbol Files
15434 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15435 such as symbol types it does not recognize, or known bugs in compiler
15436 output. By default, @value{GDBN} does not notify you of such problems, since
15437 they are relatively common and primarily of interest to people
15438 debugging compilers. If you are interested in seeing information
15439 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15440 only one message about each such type of problem, no matter how many
15441 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15442 to see how many times the problems occur, with the @code{set
15443 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15446 The messages currently printed, and their meanings, include:
15449 @item inner block not inside outer block in @var{symbol}
15451 The symbol information shows where symbol scopes begin and end
15452 (such as at the start of a function or a block of statements). This
15453 error indicates that an inner scope block is not fully contained
15454 in its outer scope blocks.
15456 @value{GDBN} circumvents the problem by treating the inner block as if it had
15457 the same scope as the outer block. In the error message, @var{symbol}
15458 may be shown as ``@code{(don't know)}'' if the outer block is not a
15461 @item block at @var{address} out of order
15463 The symbol information for symbol scope blocks should occur in
15464 order of increasing addresses. This error indicates that it does not
15467 @value{GDBN} does not circumvent this problem, and has trouble
15468 locating symbols in the source file whose symbols it is reading. (You
15469 can often determine what source file is affected by specifying
15470 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15473 @item bad block start address patched
15475 The symbol information for a symbol scope block has a start address
15476 smaller than the address of the preceding source line. This is known
15477 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15479 @value{GDBN} circumvents the problem by treating the symbol scope block as
15480 starting on the previous source line.
15482 @item bad string table offset in symbol @var{n}
15485 Symbol number @var{n} contains a pointer into the string table which is
15486 larger than the size of the string table.
15488 @value{GDBN} circumvents the problem by considering the symbol to have the
15489 name @code{foo}, which may cause other problems if many symbols end up
15492 @item unknown symbol type @code{0x@var{nn}}
15494 The symbol information contains new data types that @value{GDBN} does
15495 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15496 uncomprehended information, in hexadecimal.
15498 @value{GDBN} circumvents the error by ignoring this symbol information.
15499 This usually allows you to debug your program, though certain symbols
15500 are not accessible. If you encounter such a problem and feel like
15501 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15502 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15503 and examine @code{*bufp} to see the symbol.
15505 @item stub type has NULL name
15507 @value{GDBN} could not find the full definition for a struct or class.
15509 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15510 The symbol information for a C@t{++} member function is missing some
15511 information that recent versions of the compiler should have output for
15514 @item info mismatch between compiler and debugger
15516 @value{GDBN} could not parse a type specification output by the compiler.
15521 @section GDB Data Files
15523 @cindex prefix for data files
15524 @value{GDBN} will sometimes read an auxiliary data file. These files
15525 are kept in a directory known as the @dfn{data directory}.
15527 You can set the data directory's name, and view the name @value{GDBN}
15528 is currently using.
15531 @kindex set data-directory
15532 @item set data-directory @var{directory}
15533 Set the directory which @value{GDBN} searches for auxiliary data files
15534 to @var{directory}.
15536 @kindex show data-directory
15537 @item show data-directory
15538 Show the directory @value{GDBN} searches for auxiliary data files.
15541 @cindex default data directory
15542 @cindex @samp{--with-gdb-datadir}
15543 You can set the default data directory by using the configure-time
15544 @samp{--with-gdb-datadir} option. If the data directory is inside
15545 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15546 @samp{--exec-prefix}), then the default data directory will be updated
15547 automatically if the installed @value{GDBN} is moved to a new
15551 @chapter Specifying a Debugging Target
15553 @cindex debugging target
15554 A @dfn{target} is the execution environment occupied by your program.
15556 Often, @value{GDBN} runs in the same host environment as your program;
15557 in that case, the debugging target is specified as a side effect when
15558 you use the @code{file} or @code{core} commands. When you need more
15559 flexibility---for example, running @value{GDBN} on a physically separate
15560 host, or controlling a standalone system over a serial port or a
15561 realtime system over a TCP/IP connection---you can use the @code{target}
15562 command to specify one of the target types configured for @value{GDBN}
15563 (@pxref{Target Commands, ,Commands for Managing Targets}).
15565 @cindex target architecture
15566 It is possible to build @value{GDBN} for several different @dfn{target
15567 architectures}. When @value{GDBN} is built like that, you can choose
15568 one of the available architectures with the @kbd{set architecture}
15572 @kindex set architecture
15573 @kindex show architecture
15574 @item set architecture @var{arch}
15575 This command sets the current target architecture to @var{arch}. The
15576 value of @var{arch} can be @code{"auto"}, in addition to one of the
15577 supported architectures.
15579 @item show architecture
15580 Show the current target architecture.
15582 @item set processor
15584 @kindex set processor
15585 @kindex show processor
15586 These are alias commands for, respectively, @code{set architecture}
15587 and @code{show architecture}.
15591 * Active Targets:: Active targets
15592 * Target Commands:: Commands for managing targets
15593 * Byte Order:: Choosing target byte order
15596 @node Active Targets
15597 @section Active Targets
15599 @cindex stacking targets
15600 @cindex active targets
15601 @cindex multiple targets
15603 There are multiple classes of targets such as: processes, executable files or
15604 recording sessions. Core files belong to the process class, making core file
15605 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15606 on multiple active targets, one in each class. This allows you to (for
15607 example) start a process and inspect its activity, while still having access to
15608 the executable file after the process finishes. Or if you start process
15609 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15610 presented a virtual layer of the recording target, while the process target
15611 remains stopped at the chronologically last point of the process execution.
15613 Use the @code{core-file} and @code{exec-file} commands to select a new core
15614 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15615 specify as a target a process that is already running, use the @code{attach}
15616 command (@pxref{Attach, ,Debugging an Already-running Process}).
15618 @node Target Commands
15619 @section Commands for Managing Targets
15622 @item target @var{type} @var{parameters}
15623 Connects the @value{GDBN} host environment to a target machine or
15624 process. A target is typically a protocol for talking to debugging
15625 facilities. You use the argument @var{type} to specify the type or
15626 protocol of the target machine.
15628 Further @var{parameters} are interpreted by the target protocol, but
15629 typically include things like device names or host names to connect
15630 with, process numbers, and baud rates.
15632 The @code{target} command does not repeat if you press @key{RET} again
15633 after executing the command.
15635 @kindex help target
15637 Displays the names of all targets available. To display targets
15638 currently selected, use either @code{info target} or @code{info files}
15639 (@pxref{Files, ,Commands to Specify Files}).
15641 @item help target @var{name}
15642 Describe a particular target, including any parameters necessary to
15645 @kindex set gnutarget
15646 @item set gnutarget @var{args}
15647 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15648 knows whether it is reading an @dfn{executable},
15649 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15650 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15651 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15654 @emph{Warning:} To specify a file format with @code{set gnutarget},
15655 you must know the actual BFD name.
15659 @xref{Files, , Commands to Specify Files}.
15661 @kindex show gnutarget
15662 @item show gnutarget
15663 Use the @code{show gnutarget} command to display what file format
15664 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15665 @value{GDBN} will determine the file format for each file automatically,
15666 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15669 @cindex common targets
15670 Here are some common targets (available, or not, depending on the GDB
15675 @item target exec @var{program}
15676 @cindex executable file target
15677 An executable file. @samp{target exec @var{program}} is the same as
15678 @samp{exec-file @var{program}}.
15680 @item target core @var{filename}
15681 @cindex core dump file target
15682 A core dump file. @samp{target core @var{filename}} is the same as
15683 @samp{core-file @var{filename}}.
15685 @item target remote @var{medium}
15686 @cindex remote target
15687 A remote system connected to @value{GDBN} via a serial line or network
15688 connection. This command tells @value{GDBN} to use its own remote
15689 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15691 For example, if you have a board connected to @file{/dev/ttya} on the
15692 machine running @value{GDBN}, you could say:
15695 target remote /dev/ttya
15698 @code{target remote} supports the @code{load} command. This is only
15699 useful if you have some other way of getting the stub to the target
15700 system, and you can put it somewhere in memory where it won't get
15701 clobbered by the download.
15703 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15704 @cindex built-in simulator target
15705 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15713 works; however, you cannot assume that a specific memory map, device
15714 drivers, or even basic I/O is available, although some simulators do
15715 provide these. For info about any processor-specific simulator details,
15716 see the appropriate section in @ref{Embedded Processors, ,Embedded
15721 Some configurations may include these targets as well:
15725 @item target nrom @var{dev}
15726 @cindex NetROM ROM emulator target
15727 NetROM ROM emulator. This target only supports downloading.
15731 Different targets are available on different configurations of @value{GDBN};
15732 your configuration may have more or fewer targets.
15734 Many remote targets require you to download the executable's code once
15735 you've successfully established a connection. You may wish to control
15736 various aspects of this process.
15741 @kindex set hash@r{, for remote monitors}
15742 @cindex hash mark while downloading
15743 This command controls whether a hash mark @samp{#} is displayed while
15744 downloading a file to the remote monitor. If on, a hash mark is
15745 displayed after each S-record is successfully downloaded to the
15749 @kindex show hash@r{, for remote monitors}
15750 Show the current status of displaying the hash mark.
15752 @item set debug monitor
15753 @kindex set debug monitor
15754 @cindex display remote monitor communications
15755 Enable or disable display of communications messages between
15756 @value{GDBN} and the remote monitor.
15758 @item show debug monitor
15759 @kindex show debug monitor
15760 Show the current status of displaying communications between
15761 @value{GDBN} and the remote monitor.
15766 @kindex load @var{filename}
15767 @item load @var{filename}
15769 Depending on what remote debugging facilities are configured into
15770 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15771 is meant to make @var{filename} (an executable) available for debugging
15772 on the remote system---by downloading, or dynamic linking, for example.
15773 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15774 the @code{add-symbol-file} command.
15776 If your @value{GDBN} does not have a @code{load} command, attempting to
15777 execute it gets the error message ``@code{You can't do that when your
15778 target is @dots{}}''
15780 The file is loaded at whatever address is specified in the executable.
15781 For some object file formats, you can specify the load address when you
15782 link the program; for other formats, like a.out, the object file format
15783 specifies a fixed address.
15784 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15786 Depending on the remote side capabilities, @value{GDBN} may be able to
15787 load programs into flash memory.
15789 @code{load} does not repeat if you press @key{RET} again after using it.
15793 @section Choosing Target Byte Order
15795 @cindex choosing target byte order
15796 @cindex target byte order
15798 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15799 offer the ability to run either big-endian or little-endian byte
15800 orders. Usually the executable or symbol will include a bit to
15801 designate the endian-ness, and you will not need to worry about
15802 which to use. However, you may still find it useful to adjust
15803 @value{GDBN}'s idea of processor endian-ness manually.
15807 @item set endian big
15808 Instruct @value{GDBN} to assume the target is big-endian.
15810 @item set endian little
15811 Instruct @value{GDBN} to assume the target is little-endian.
15813 @item set endian auto
15814 Instruct @value{GDBN} to use the byte order associated with the
15818 Display @value{GDBN}'s current idea of the target byte order.
15822 Note that these commands merely adjust interpretation of symbolic
15823 data on the host, and that they have absolutely no effect on the
15827 @node Remote Debugging
15828 @chapter Debugging Remote Programs
15829 @cindex remote debugging
15831 If you are trying to debug a program running on a machine that cannot run
15832 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15833 For example, you might use remote debugging on an operating system kernel,
15834 or on a small system which does not have a general purpose operating system
15835 powerful enough to run a full-featured debugger.
15837 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15838 to make this work with particular debugging targets. In addition,
15839 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15840 but not specific to any particular target system) which you can use if you
15841 write the remote stubs---the code that runs on the remote system to
15842 communicate with @value{GDBN}.
15844 Other remote targets may be available in your
15845 configuration of @value{GDBN}; use @code{help target} to list them.
15848 * Connecting:: Connecting to a remote target
15849 * File Transfer:: Sending files to a remote system
15850 * Server:: Using the gdbserver program
15851 * Remote Configuration:: Remote configuration
15852 * Remote Stub:: Implementing a remote stub
15856 @section Connecting to a Remote Target
15858 On the @value{GDBN} host machine, you will need an unstripped copy of
15859 your program, since @value{GDBN} needs symbol and debugging information.
15860 Start up @value{GDBN} as usual, using the name of the local copy of your
15861 program as the first argument.
15863 @cindex @code{target remote}
15864 @value{GDBN} can communicate with the target over a serial line, or
15865 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15866 each case, @value{GDBN} uses the same protocol for debugging your
15867 program; only the medium carrying the debugging packets varies. The
15868 @code{target remote} command establishes a connection to the target.
15869 Its arguments indicate which medium to use:
15873 @item target remote @var{serial-device}
15874 @cindex serial line, @code{target remote}
15875 Use @var{serial-device} to communicate with the target. For example,
15876 to use a serial line connected to the device named @file{/dev/ttyb}:
15879 target remote /dev/ttyb
15882 If you're using a serial line, you may want to give @value{GDBN} the
15883 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15884 (@pxref{Remote Configuration, set remotebaud}) before the
15885 @code{target} command.
15887 @item target remote @code{@var{host}:@var{port}}
15888 @itemx target remote @code{tcp:@var{host}:@var{port}}
15889 @cindex @acronym{TCP} port, @code{target remote}
15890 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15891 The @var{host} may be either a host name or a numeric @acronym{IP}
15892 address; @var{port} must be a decimal number. The @var{host} could be
15893 the target machine itself, if it is directly connected to the net, or
15894 it might be a terminal server which in turn has a serial line to the
15897 For example, to connect to port 2828 on a terminal server named
15901 target remote manyfarms:2828
15904 If your remote target is actually running on the same machine as your
15905 debugger session (e.g.@: a simulator for your target running on the
15906 same host), you can omit the hostname. For example, to connect to
15907 port 1234 on your local machine:
15910 target remote :1234
15914 Note that the colon is still required here.
15916 @item target remote @code{udp:@var{host}:@var{port}}
15917 @cindex @acronym{UDP} port, @code{target remote}
15918 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15919 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15922 target remote udp:manyfarms:2828
15925 When using a @acronym{UDP} connection for remote debugging, you should
15926 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15927 can silently drop packets on busy or unreliable networks, which will
15928 cause havoc with your debugging session.
15930 @item target remote | @var{command}
15931 @cindex pipe, @code{target remote} to
15932 Run @var{command} in the background and communicate with it using a
15933 pipe. The @var{command} is a shell command, to be parsed and expanded
15934 by the system's command shell, @code{/bin/sh}; it should expect remote
15935 protocol packets on its standard input, and send replies on its
15936 standard output. You could use this to run a stand-alone simulator
15937 that speaks the remote debugging protocol, to make net connections
15938 using programs like @code{ssh}, or for other similar tricks.
15940 If @var{command} closes its standard output (perhaps by exiting),
15941 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15942 program has already exited, this will have no effect.)
15946 Once the connection has been established, you can use all the usual
15947 commands to examine and change data. The remote program is already
15948 running; you can use @kbd{step} and @kbd{continue}, and you do not
15949 need to use @kbd{run}.
15951 @cindex interrupting remote programs
15952 @cindex remote programs, interrupting
15953 Whenever @value{GDBN} is waiting for the remote program, if you type the
15954 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15955 program. This may or may not succeed, depending in part on the hardware
15956 and the serial drivers the remote system uses. If you type the
15957 interrupt character once again, @value{GDBN} displays this prompt:
15960 Interrupted while waiting for the program.
15961 Give up (and stop debugging it)? (y or n)
15964 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15965 (If you decide you want to try again later, you can use @samp{target
15966 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15967 goes back to waiting.
15970 @kindex detach (remote)
15972 When you have finished debugging the remote program, you can use the
15973 @code{detach} command to release it from @value{GDBN} control.
15974 Detaching from the target normally resumes its execution, but the results
15975 will depend on your particular remote stub. After the @code{detach}
15976 command, @value{GDBN} is free to connect to another target.
15980 The @code{disconnect} command behaves like @code{detach}, except that
15981 the target is generally not resumed. It will wait for @value{GDBN}
15982 (this instance or another one) to connect and continue debugging. After
15983 the @code{disconnect} command, @value{GDBN} is again free to connect to
15986 @cindex send command to remote monitor
15987 @cindex extend @value{GDBN} for remote targets
15988 @cindex add new commands for external monitor
15990 @item monitor @var{cmd}
15991 This command allows you to send arbitrary commands directly to the
15992 remote monitor. Since @value{GDBN} doesn't care about the commands it
15993 sends like this, this command is the way to extend @value{GDBN}---you
15994 can add new commands that only the external monitor will understand
15998 @node File Transfer
15999 @section Sending files to a remote system
16000 @cindex remote target, file transfer
16001 @cindex file transfer
16002 @cindex sending files to remote systems
16004 Some remote targets offer the ability to transfer files over the same
16005 connection used to communicate with @value{GDBN}. This is convenient
16006 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16007 running @code{gdbserver} over a network interface. For other targets,
16008 e.g.@: embedded devices with only a single serial port, this may be
16009 the only way to upload or download files.
16011 Not all remote targets support these commands.
16015 @item remote put @var{hostfile} @var{targetfile}
16016 Copy file @var{hostfile} from the host system (the machine running
16017 @value{GDBN}) to @var{targetfile} on the target system.
16020 @item remote get @var{targetfile} @var{hostfile}
16021 Copy file @var{targetfile} from the target system to @var{hostfile}
16022 on the host system.
16024 @kindex remote delete
16025 @item remote delete @var{targetfile}
16026 Delete @var{targetfile} from the target system.
16031 @section Using the @code{gdbserver} Program
16034 @cindex remote connection without stubs
16035 @code{gdbserver} is a control program for Unix-like systems, which
16036 allows you to connect your program with a remote @value{GDBN} via
16037 @code{target remote}---but without linking in the usual debugging stub.
16039 @code{gdbserver} is not a complete replacement for the debugging stubs,
16040 because it requires essentially the same operating-system facilities
16041 that @value{GDBN} itself does. In fact, a system that can run
16042 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16043 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16044 because it is a much smaller program than @value{GDBN} itself. It is
16045 also easier to port than all of @value{GDBN}, so you may be able to get
16046 started more quickly on a new system by using @code{gdbserver}.
16047 Finally, if you develop code for real-time systems, you may find that
16048 the tradeoffs involved in real-time operation make it more convenient to
16049 do as much development work as possible on another system, for example
16050 by cross-compiling. You can use @code{gdbserver} to make a similar
16051 choice for debugging.
16053 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16054 or a TCP connection, using the standard @value{GDBN} remote serial
16058 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16059 Do not run @code{gdbserver} connected to any public network; a
16060 @value{GDBN} connection to @code{gdbserver} provides access to the
16061 target system with the same privileges as the user running
16065 @subsection Running @code{gdbserver}
16066 @cindex arguments, to @code{gdbserver}
16068 Run @code{gdbserver} on the target system. You need a copy of the
16069 program you want to debug, including any libraries it requires.
16070 @code{gdbserver} does not need your program's symbol table, so you can
16071 strip the program if necessary to save space. @value{GDBN} on the host
16072 system does all the symbol handling.
16074 To use the server, you must tell it how to communicate with @value{GDBN};
16075 the name of your program; and the arguments for your program. The usual
16079 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16082 @var{comm} is either a device name (to use a serial line) or a TCP
16083 hostname and portnumber. For example, to debug Emacs with the argument
16084 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16088 target> gdbserver /dev/com1 emacs foo.txt
16091 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16094 To use a TCP connection instead of a serial line:
16097 target> gdbserver host:2345 emacs foo.txt
16100 The only difference from the previous example is the first argument,
16101 specifying that you are communicating with the host @value{GDBN} via
16102 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16103 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16104 (Currently, the @samp{host} part is ignored.) You can choose any number
16105 you want for the port number as long as it does not conflict with any
16106 TCP ports already in use on the target system (for example, @code{23} is
16107 reserved for @code{telnet}).@footnote{If you choose a port number that
16108 conflicts with another service, @code{gdbserver} prints an error message
16109 and exits.} You must use the same port number with the host @value{GDBN}
16110 @code{target remote} command.
16112 @subsubsection Attaching to a Running Program
16114 On some targets, @code{gdbserver} can also attach to running programs.
16115 This is accomplished via the @code{--attach} argument. The syntax is:
16118 target> gdbserver --attach @var{comm} @var{pid}
16121 @var{pid} is the process ID of a currently running process. It isn't necessary
16122 to point @code{gdbserver} at a binary for the running process.
16125 @cindex attach to a program by name
16126 You can debug processes by name instead of process ID if your target has the
16127 @code{pidof} utility:
16130 target> gdbserver --attach @var{comm} `pidof @var{program}`
16133 In case more than one copy of @var{program} is running, or @var{program}
16134 has multiple threads, most versions of @code{pidof} support the
16135 @code{-s} option to only return the first process ID.
16137 @subsubsection Multi-Process Mode for @code{gdbserver}
16138 @cindex gdbserver, multiple processes
16139 @cindex multiple processes with gdbserver
16141 When you connect to @code{gdbserver} using @code{target remote},
16142 @code{gdbserver} debugs the specified program only once. When the
16143 program exits, or you detach from it, @value{GDBN} closes the connection
16144 and @code{gdbserver} exits.
16146 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16147 enters multi-process mode. When the debugged program exits, or you
16148 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16149 though no program is running. The @code{run} and @code{attach}
16150 commands instruct @code{gdbserver} to run or attach to a new program.
16151 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16152 remote exec-file}) to select the program to run. Command line
16153 arguments are supported, except for wildcard expansion and I/O
16154 redirection (@pxref{Arguments}).
16156 To start @code{gdbserver} without supplying an initial command to run
16157 or process ID to attach, use the @option{--multi} command line option.
16158 Then you can connect using @kbd{target extended-remote} and start
16159 the program you want to debug.
16161 @code{gdbserver} does not automatically exit in multi-process mode.
16162 You can terminate it by using @code{monitor exit}
16163 (@pxref{Monitor Commands for gdbserver}).
16165 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16167 The @option{--debug} option tells @code{gdbserver} to display extra
16168 status information about the debugging process. The
16169 @option{--remote-debug} option tells @code{gdbserver} to display
16170 remote protocol debug output. These options are intended for
16171 @code{gdbserver} development and for bug reports to the developers.
16173 The @option{--wrapper} option specifies a wrapper to launch programs
16174 for debugging. The option should be followed by the name of the
16175 wrapper, then any command-line arguments to pass to the wrapper, then
16176 @kbd{--} indicating the end of the wrapper arguments.
16178 @code{gdbserver} runs the specified wrapper program with a combined
16179 command line including the wrapper arguments, then the name of the
16180 program to debug, then any arguments to the program. The wrapper
16181 runs until it executes your program, and then @value{GDBN} gains control.
16183 You can use any program that eventually calls @code{execve} with
16184 its arguments as a wrapper. Several standard Unix utilities do
16185 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16186 with @code{exec "$@@"} will also work.
16188 For example, you can use @code{env} to pass an environment variable to
16189 the debugged program, without setting the variable in @code{gdbserver}'s
16193 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16196 @subsection Connecting to @code{gdbserver}
16198 Run @value{GDBN} on the host system.
16200 First make sure you have the necessary symbol files. Load symbols for
16201 your application using the @code{file} command before you connect. Use
16202 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16203 was compiled with the correct sysroot using @code{--with-sysroot}).
16205 The symbol file and target libraries must exactly match the executable
16206 and libraries on the target, with one exception: the files on the host
16207 system should not be stripped, even if the files on the target system
16208 are. Mismatched or missing files will lead to confusing results
16209 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16210 files may also prevent @code{gdbserver} from debugging multi-threaded
16213 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16214 For TCP connections, you must start up @code{gdbserver} prior to using
16215 the @code{target remote} command. Otherwise you may get an error whose
16216 text depends on the host system, but which usually looks something like
16217 @samp{Connection refused}. Don't use the @code{load}
16218 command in @value{GDBN} when using @code{gdbserver}, since the program is
16219 already on the target.
16221 @subsection Monitor Commands for @code{gdbserver}
16222 @cindex monitor commands, for @code{gdbserver}
16223 @anchor{Monitor Commands for gdbserver}
16225 During a @value{GDBN} session using @code{gdbserver}, you can use the
16226 @code{monitor} command to send special requests to @code{gdbserver}.
16227 Here are the available commands.
16231 List the available monitor commands.
16233 @item monitor set debug 0
16234 @itemx monitor set debug 1
16235 Disable or enable general debugging messages.
16237 @item monitor set remote-debug 0
16238 @itemx monitor set remote-debug 1
16239 Disable or enable specific debugging messages associated with the remote
16240 protocol (@pxref{Remote Protocol}).
16242 @item monitor set libthread-db-search-path [PATH]
16243 @cindex gdbserver, search path for @code{libthread_db}
16244 When this command is issued, @var{path} is a colon-separated list of
16245 directories to search for @code{libthread_db} (@pxref{Threads,,set
16246 libthread-db-search-path}). If you omit @var{path},
16247 @samp{libthread-db-search-path} will be reset to an empty list.
16250 Tell gdbserver to exit immediately. This command should be followed by
16251 @code{disconnect} to close the debugging session. @code{gdbserver} will
16252 detach from any attached processes and kill any processes it created.
16253 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16254 of a multi-process mode debug session.
16258 @subsection Tracepoints support in @code{gdbserver}
16259 @cindex tracepoints support in @code{gdbserver}
16261 On some targets, @code{gdbserver} supports tracepoints, fast
16262 tracepoints and static tracepoints.
16264 For fast or static tracepoints to work, a special library called the
16265 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16266 This library is built and distributed as an integral part of
16267 @code{gdbserver}. In addition, support for static tracepoints
16268 requires building the in-process agent library with static tracepoints
16269 support. At present, the UST (LTTng Userspace Tracer,
16270 @url{http://lttng.org/ust}) tracing engine is supported. This support
16271 is automatically available if UST development headers are found in the
16272 standard include path when @code{gdbserver} is built, or if
16273 @code{gdbserver} was explicitly configured using @option{--with-ust}
16274 to point at such headers. You can explicitly disable the support
16275 using @option{--with-ust=no}.
16277 There are several ways to load the in-process agent in your program:
16280 @item Specifying it as dependency at link time
16282 You can link your program dynamically with the in-process agent
16283 library. On most systems, this is accomplished by adding
16284 @code{-linproctrace} to the link command.
16286 @item Using the system's preloading mechanisms
16288 You can force loading the in-process agent at startup time by using
16289 your system's support for preloading shared libraries. Many Unixes
16290 support the concept of preloading user defined libraries. In most
16291 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16292 in the environment. See also the description of @code{gdbserver}'s
16293 @option{--wrapper} command line option.
16295 @item Using @value{GDBN} to force loading the agent at run time
16297 On some systems, you can force the inferior to load a shared library,
16298 by calling a dynamic loader function in the inferior that takes care
16299 of dynamically looking up and loading a shared library. On most Unix
16300 systems, the function is @code{dlopen}. You'll use the @code{call}
16301 command for that. For example:
16304 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16307 Note that on most Unix systems, for the @code{dlopen} function to be
16308 available, the program needs to be linked with @code{-ldl}.
16311 On systems that have a userspace dynamic loader, like most Unix
16312 systems, when you connect to @code{gdbserver} using @code{target
16313 remote}, you'll find that the program is stopped at the dynamic
16314 loader's entry point, and no shared library has been loaded in the
16315 program's address space yet, including the in-process agent. In that
16316 case, before being able to use any of the fast or static tracepoints
16317 features, you need to let the loader run and load the shared
16318 libraries. The simplest way to do that is to run the program to the
16319 main procedure. E.g., if debugging a C or C@t{++} program, start
16320 @code{gdbserver} like so:
16323 $ gdbserver :9999 myprogram
16326 Start GDB and connect to @code{gdbserver} like so, and run to main:
16330 (@value{GDBP}) target remote myhost:9999
16331 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16332 (@value{GDBP}) b main
16333 (@value{GDBP}) continue
16336 The in-process tracing agent library should now be loaded into the
16337 process; you can confirm it with the @code{info sharedlibrary}
16338 command, which will list @file{libinproctrace.so} as loaded in the
16339 process. You are now ready to install fast tracepoints, list static
16340 tracepoint markers, probe static tracepoints markers, and start
16343 @node Remote Configuration
16344 @section Remote Configuration
16347 @kindex show remote
16348 This section documents the configuration options available when
16349 debugging remote programs. For the options related to the File I/O
16350 extensions of the remote protocol, see @ref{system,
16351 system-call-allowed}.
16354 @item set remoteaddresssize @var{bits}
16355 @cindex address size for remote targets
16356 @cindex bits in remote address
16357 Set the maximum size of address in a memory packet to the specified
16358 number of bits. @value{GDBN} will mask off the address bits above
16359 that number, when it passes addresses to the remote target. The
16360 default value is the number of bits in the target's address.
16362 @item show remoteaddresssize
16363 Show the current value of remote address size in bits.
16365 @item set remotebaud @var{n}
16366 @cindex baud rate for remote targets
16367 Set the baud rate for the remote serial I/O to @var{n} baud. The
16368 value is used to set the speed of the serial port used for debugging
16371 @item show remotebaud
16372 Show the current speed of the remote connection.
16374 @item set remotebreak
16375 @cindex interrupt remote programs
16376 @cindex BREAK signal instead of Ctrl-C
16377 @anchor{set remotebreak}
16378 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16379 when you type @kbd{Ctrl-c} to interrupt the program running
16380 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16381 character instead. The default is off, since most remote systems
16382 expect to see @samp{Ctrl-C} as the interrupt signal.
16384 @item show remotebreak
16385 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16386 interrupt the remote program.
16388 @item set remoteflow on
16389 @itemx set remoteflow off
16390 @kindex set remoteflow
16391 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16392 on the serial port used to communicate to the remote target.
16394 @item show remoteflow
16395 @kindex show remoteflow
16396 Show the current setting of hardware flow control.
16398 @item set remotelogbase @var{base}
16399 Set the base (a.k.a.@: radix) of logging serial protocol
16400 communications to @var{base}. Supported values of @var{base} are:
16401 @code{ascii}, @code{octal}, and @code{hex}. The default is
16404 @item show remotelogbase
16405 Show the current setting of the radix for logging remote serial
16408 @item set remotelogfile @var{file}
16409 @cindex record serial communications on file
16410 Record remote serial communications on the named @var{file}. The
16411 default is not to record at all.
16413 @item show remotelogfile.
16414 Show the current setting of the file name on which to record the
16415 serial communications.
16417 @item set remotetimeout @var{num}
16418 @cindex timeout for serial communications
16419 @cindex remote timeout
16420 Set the timeout limit to wait for the remote target to respond to
16421 @var{num} seconds. The default is 2 seconds.
16423 @item show remotetimeout
16424 Show the current number of seconds to wait for the remote target
16427 @cindex limit hardware breakpoints and watchpoints
16428 @cindex remote target, limit break- and watchpoints
16429 @anchor{set remote hardware-watchpoint-limit}
16430 @anchor{set remote hardware-breakpoint-limit}
16431 @item set remote hardware-watchpoint-limit @var{limit}
16432 @itemx set remote hardware-breakpoint-limit @var{limit}
16433 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16434 watchpoints. A limit of -1, the default, is treated as unlimited.
16436 @item set remote exec-file @var{filename}
16437 @itemx show remote exec-file
16438 @anchor{set remote exec-file}
16439 @cindex executable file, for remote target
16440 Select the file used for @code{run} with @code{target
16441 extended-remote}. This should be set to a filename valid on the
16442 target system. If it is not set, the target will use a default
16443 filename (e.g.@: the last program run).
16445 @item set remote interrupt-sequence
16446 @cindex interrupt remote programs
16447 @cindex select Ctrl-C, BREAK or BREAK-g
16448 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16449 @samp{BREAK-g} as the
16450 sequence to the remote target in order to interrupt the execution.
16451 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16452 is high level of serial line for some certain time.
16453 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16454 It is @code{BREAK} signal followed by character @code{g}.
16456 @item show interrupt-sequence
16457 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16458 is sent by @value{GDBN} to interrupt the remote program.
16459 @code{BREAK-g} is BREAK signal followed by @code{g} and
16460 also known as Magic SysRq g.
16462 @item set remote interrupt-on-connect
16463 @cindex send interrupt-sequence on start
16464 Specify whether interrupt-sequence is sent to remote target when
16465 @value{GDBN} connects to it. This is mostly needed when you debug
16466 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16467 which is known as Magic SysRq g in order to connect @value{GDBN}.
16469 @item show interrupt-on-connect
16470 Show whether interrupt-sequence is sent
16471 to remote target when @value{GDBN} connects to it.
16475 @item set tcp auto-retry on
16476 @cindex auto-retry, for remote TCP target
16477 Enable auto-retry for remote TCP connections. This is useful if the remote
16478 debugging agent is launched in parallel with @value{GDBN}; there is a race
16479 condition because the agent may not become ready to accept the connection
16480 before @value{GDBN} attempts to connect. When auto-retry is
16481 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16482 to establish the connection using the timeout specified by
16483 @code{set tcp connect-timeout}.
16485 @item set tcp auto-retry off
16486 Do not auto-retry failed TCP connections.
16488 @item show tcp auto-retry
16489 Show the current auto-retry setting.
16491 @item set tcp connect-timeout @var{seconds}
16492 @cindex connection timeout, for remote TCP target
16493 @cindex timeout, for remote target connection
16494 Set the timeout for establishing a TCP connection to the remote target to
16495 @var{seconds}. The timeout affects both polling to retry failed connections
16496 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16497 that are merely slow to complete, and represents an approximate cumulative
16500 @item show tcp connect-timeout
16501 Show the current connection timeout setting.
16504 @cindex remote packets, enabling and disabling
16505 The @value{GDBN} remote protocol autodetects the packets supported by
16506 your debugging stub. If you need to override the autodetection, you
16507 can use these commands to enable or disable individual packets. Each
16508 packet can be set to @samp{on} (the remote target supports this
16509 packet), @samp{off} (the remote target does not support this packet),
16510 or @samp{auto} (detect remote target support for this packet). They
16511 all default to @samp{auto}. For more information about each packet,
16512 see @ref{Remote Protocol}.
16514 During normal use, you should not have to use any of these commands.
16515 If you do, that may be a bug in your remote debugging stub, or a bug
16516 in @value{GDBN}. You may want to report the problem to the
16517 @value{GDBN} developers.
16519 For each packet @var{name}, the command to enable or disable the
16520 packet is @code{set remote @var{name}-packet}. The available settings
16523 @multitable @columnfractions 0.28 0.32 0.25
16526 @tab Related Features
16528 @item @code{fetch-register}
16530 @tab @code{info registers}
16532 @item @code{set-register}
16536 @item @code{binary-download}
16538 @tab @code{load}, @code{set}
16540 @item @code{read-aux-vector}
16541 @tab @code{qXfer:auxv:read}
16542 @tab @code{info auxv}
16544 @item @code{symbol-lookup}
16545 @tab @code{qSymbol}
16546 @tab Detecting multiple threads
16548 @item @code{attach}
16549 @tab @code{vAttach}
16552 @item @code{verbose-resume}
16554 @tab Stepping or resuming multiple threads
16560 @item @code{software-breakpoint}
16564 @item @code{hardware-breakpoint}
16568 @item @code{write-watchpoint}
16572 @item @code{read-watchpoint}
16576 @item @code{access-watchpoint}
16580 @item @code{target-features}
16581 @tab @code{qXfer:features:read}
16582 @tab @code{set architecture}
16584 @item @code{library-info}
16585 @tab @code{qXfer:libraries:read}
16586 @tab @code{info sharedlibrary}
16588 @item @code{memory-map}
16589 @tab @code{qXfer:memory-map:read}
16590 @tab @code{info mem}
16592 @item @code{read-sdata-object}
16593 @tab @code{qXfer:sdata:read}
16594 @tab @code{print $_sdata}
16596 @item @code{read-spu-object}
16597 @tab @code{qXfer:spu:read}
16598 @tab @code{info spu}
16600 @item @code{write-spu-object}
16601 @tab @code{qXfer:spu:write}
16602 @tab @code{info spu}
16604 @item @code{read-siginfo-object}
16605 @tab @code{qXfer:siginfo:read}
16606 @tab @code{print $_siginfo}
16608 @item @code{write-siginfo-object}
16609 @tab @code{qXfer:siginfo:write}
16610 @tab @code{set $_siginfo}
16612 @item @code{threads}
16613 @tab @code{qXfer:threads:read}
16614 @tab @code{info threads}
16616 @item @code{get-thread-local-@*storage-address}
16617 @tab @code{qGetTLSAddr}
16618 @tab Displaying @code{__thread} variables
16620 @item @code{get-thread-information-block-address}
16621 @tab @code{qGetTIBAddr}
16622 @tab Display MS-Windows Thread Information Block.
16624 @item @code{search-memory}
16625 @tab @code{qSearch:memory}
16628 @item @code{supported-packets}
16629 @tab @code{qSupported}
16630 @tab Remote communications parameters
16632 @item @code{pass-signals}
16633 @tab @code{QPassSignals}
16634 @tab @code{handle @var{signal}}
16636 @item @code{hostio-close-packet}
16637 @tab @code{vFile:close}
16638 @tab @code{remote get}, @code{remote put}
16640 @item @code{hostio-open-packet}
16641 @tab @code{vFile:open}
16642 @tab @code{remote get}, @code{remote put}
16644 @item @code{hostio-pread-packet}
16645 @tab @code{vFile:pread}
16646 @tab @code{remote get}, @code{remote put}
16648 @item @code{hostio-pwrite-packet}
16649 @tab @code{vFile:pwrite}
16650 @tab @code{remote get}, @code{remote put}
16652 @item @code{hostio-unlink-packet}
16653 @tab @code{vFile:unlink}
16654 @tab @code{remote delete}
16656 @item @code{noack-packet}
16657 @tab @code{QStartNoAckMode}
16658 @tab Packet acknowledgment
16660 @item @code{osdata}
16661 @tab @code{qXfer:osdata:read}
16662 @tab @code{info os}
16664 @item @code{query-attached}
16665 @tab @code{qAttached}
16666 @tab Querying remote process attach state.
16670 @section Implementing a Remote Stub
16672 @cindex debugging stub, example
16673 @cindex remote stub, example
16674 @cindex stub example, remote debugging
16675 The stub files provided with @value{GDBN} implement the target side of the
16676 communication protocol, and the @value{GDBN} side is implemented in the
16677 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16678 these subroutines to communicate, and ignore the details. (If you're
16679 implementing your own stub file, you can still ignore the details: start
16680 with one of the existing stub files. @file{sparc-stub.c} is the best
16681 organized, and therefore the easiest to read.)
16683 @cindex remote serial debugging, overview
16684 To debug a program running on another machine (the debugging
16685 @dfn{target} machine), you must first arrange for all the usual
16686 prerequisites for the program to run by itself. For example, for a C
16691 A startup routine to set up the C runtime environment; these usually
16692 have a name like @file{crt0}. The startup routine may be supplied by
16693 your hardware supplier, or you may have to write your own.
16696 A C subroutine library to support your program's
16697 subroutine calls, notably managing input and output.
16700 A way of getting your program to the other machine---for example, a
16701 download program. These are often supplied by the hardware
16702 manufacturer, but you may have to write your own from hardware
16706 The next step is to arrange for your program to use a serial port to
16707 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16708 machine). In general terms, the scheme looks like this:
16712 @value{GDBN} already understands how to use this protocol; when everything
16713 else is set up, you can simply use the @samp{target remote} command
16714 (@pxref{Targets,,Specifying a Debugging Target}).
16716 @item On the target,
16717 you must link with your program a few special-purpose subroutines that
16718 implement the @value{GDBN} remote serial protocol. The file containing these
16719 subroutines is called a @dfn{debugging stub}.
16721 On certain remote targets, you can use an auxiliary program
16722 @code{gdbserver} instead of linking a stub into your program.
16723 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16726 The debugging stub is specific to the architecture of the remote
16727 machine; for example, use @file{sparc-stub.c} to debug programs on
16730 @cindex remote serial stub list
16731 These working remote stubs are distributed with @value{GDBN}:
16736 @cindex @file{i386-stub.c}
16739 For Intel 386 and compatible architectures.
16742 @cindex @file{m68k-stub.c}
16743 @cindex Motorola 680x0
16745 For Motorola 680x0 architectures.
16748 @cindex @file{sh-stub.c}
16751 For Renesas SH architectures.
16754 @cindex @file{sparc-stub.c}
16756 For @sc{sparc} architectures.
16758 @item sparcl-stub.c
16759 @cindex @file{sparcl-stub.c}
16762 For Fujitsu @sc{sparclite} architectures.
16766 The @file{README} file in the @value{GDBN} distribution may list other
16767 recently added stubs.
16770 * Stub Contents:: What the stub can do for you
16771 * Bootstrapping:: What you must do for the stub
16772 * Debug Session:: Putting it all together
16775 @node Stub Contents
16776 @subsection What the Stub Can Do for You
16778 @cindex remote serial stub
16779 The debugging stub for your architecture supplies these three
16783 @item set_debug_traps
16784 @findex set_debug_traps
16785 @cindex remote serial stub, initialization
16786 This routine arranges for @code{handle_exception} to run when your
16787 program stops. You must call this subroutine explicitly near the
16788 beginning of your program.
16790 @item handle_exception
16791 @findex handle_exception
16792 @cindex remote serial stub, main routine
16793 This is the central workhorse, but your program never calls it
16794 explicitly---the setup code arranges for @code{handle_exception} to
16795 run when a trap is triggered.
16797 @code{handle_exception} takes control when your program stops during
16798 execution (for example, on a breakpoint), and mediates communications
16799 with @value{GDBN} on the host machine. This is where the communications
16800 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16801 representative on the target machine. It begins by sending summary
16802 information on the state of your program, then continues to execute,
16803 retrieving and transmitting any information @value{GDBN} needs, until you
16804 execute a @value{GDBN} command that makes your program resume; at that point,
16805 @code{handle_exception} returns control to your own code on the target
16809 @cindex @code{breakpoint} subroutine, remote
16810 Use this auxiliary subroutine to make your program contain a
16811 breakpoint. Depending on the particular situation, this may be the only
16812 way for @value{GDBN} to get control. For instance, if your target
16813 machine has some sort of interrupt button, you won't need to call this;
16814 pressing the interrupt button transfers control to
16815 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16816 simply receiving characters on the serial port may also trigger a trap;
16817 again, in that situation, you don't need to call @code{breakpoint} from
16818 your own program---simply running @samp{target remote} from the host
16819 @value{GDBN} session gets control.
16821 Call @code{breakpoint} if none of these is true, or if you simply want
16822 to make certain your program stops at a predetermined point for the
16823 start of your debugging session.
16826 @node Bootstrapping
16827 @subsection What You Must Do for the Stub
16829 @cindex remote stub, support routines
16830 The debugging stubs that come with @value{GDBN} are set up for a particular
16831 chip architecture, but they have no information about the rest of your
16832 debugging target machine.
16834 First of all you need to tell the stub how to communicate with the
16838 @item int getDebugChar()
16839 @findex getDebugChar
16840 Write this subroutine to read a single character from the serial port.
16841 It may be identical to @code{getchar} for your target system; a
16842 different name is used to allow you to distinguish the two if you wish.
16844 @item void putDebugChar(int)
16845 @findex putDebugChar
16846 Write this subroutine to write a single character to the serial port.
16847 It may be identical to @code{putchar} for your target system; a
16848 different name is used to allow you to distinguish the two if you wish.
16851 @cindex control C, and remote debugging
16852 @cindex interrupting remote targets
16853 If you want @value{GDBN} to be able to stop your program while it is
16854 running, you need to use an interrupt-driven serial driver, and arrange
16855 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16856 character). That is the character which @value{GDBN} uses to tell the
16857 remote system to stop.
16859 Getting the debugging target to return the proper status to @value{GDBN}
16860 probably requires changes to the standard stub; one quick and dirty way
16861 is to just execute a breakpoint instruction (the ``dirty'' part is that
16862 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16864 Other routines you need to supply are:
16867 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16868 @findex exceptionHandler
16869 Write this function to install @var{exception_address} in the exception
16870 handling tables. You need to do this because the stub does not have any
16871 way of knowing what the exception handling tables on your target system
16872 are like (for example, the processor's table might be in @sc{rom},
16873 containing entries which point to a table in @sc{ram}).
16874 @var{exception_number} is the exception number which should be changed;
16875 its meaning is architecture-dependent (for example, different numbers
16876 might represent divide by zero, misaligned access, etc). When this
16877 exception occurs, control should be transferred directly to
16878 @var{exception_address}, and the processor state (stack, registers,
16879 and so on) should be just as it is when a processor exception occurs. So if
16880 you want to use a jump instruction to reach @var{exception_address}, it
16881 should be a simple jump, not a jump to subroutine.
16883 For the 386, @var{exception_address} should be installed as an interrupt
16884 gate so that interrupts are masked while the handler runs. The gate
16885 should be at privilege level 0 (the most privileged level). The
16886 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16887 help from @code{exceptionHandler}.
16889 @item void flush_i_cache()
16890 @findex flush_i_cache
16891 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16892 instruction cache, if any, on your target machine. If there is no
16893 instruction cache, this subroutine may be a no-op.
16895 On target machines that have instruction caches, @value{GDBN} requires this
16896 function to make certain that the state of your program is stable.
16900 You must also make sure this library routine is available:
16903 @item void *memset(void *, int, int)
16905 This is the standard library function @code{memset} that sets an area of
16906 memory to a known value. If you have one of the free versions of
16907 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16908 either obtain it from your hardware manufacturer, or write your own.
16911 If you do not use the GNU C compiler, you may need other standard
16912 library subroutines as well; this varies from one stub to another,
16913 but in general the stubs are likely to use any of the common library
16914 subroutines which @code{@value{NGCC}} generates as inline code.
16917 @node Debug Session
16918 @subsection Putting it All Together
16920 @cindex remote serial debugging summary
16921 In summary, when your program is ready to debug, you must follow these
16926 Make sure you have defined the supporting low-level routines
16927 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16929 @code{getDebugChar}, @code{putDebugChar},
16930 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16934 Insert these lines near the top of your program:
16942 For the 680x0 stub only, you need to provide a variable called
16943 @code{exceptionHook}. Normally you just use:
16946 void (*exceptionHook)() = 0;
16950 but if before calling @code{set_debug_traps}, you set it to point to a
16951 function in your program, that function is called when
16952 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16953 error). The function indicated by @code{exceptionHook} is called with
16954 one parameter: an @code{int} which is the exception number.
16957 Compile and link together: your program, the @value{GDBN} debugging stub for
16958 your target architecture, and the supporting subroutines.
16961 Make sure you have a serial connection between your target machine and
16962 the @value{GDBN} host, and identify the serial port on the host.
16965 @c The "remote" target now provides a `load' command, so we should
16966 @c document that. FIXME.
16967 Download your program to your target machine (or get it there by
16968 whatever means the manufacturer provides), and start it.
16971 Start @value{GDBN} on the host, and connect to the target
16972 (@pxref{Connecting,,Connecting to a Remote Target}).
16976 @node Configurations
16977 @chapter Configuration-Specific Information
16979 While nearly all @value{GDBN} commands are available for all native and
16980 cross versions of the debugger, there are some exceptions. This chapter
16981 describes things that are only available in certain configurations.
16983 There are three major categories of configurations: native
16984 configurations, where the host and target are the same, embedded
16985 operating system configurations, which are usually the same for several
16986 different processor architectures, and bare embedded processors, which
16987 are quite different from each other.
16992 * Embedded Processors::
16999 This section describes details specific to particular native
17004 * BSD libkvm Interface:: Debugging BSD kernel memory images
17005 * SVR4 Process Information:: SVR4 process information
17006 * DJGPP Native:: Features specific to the DJGPP port
17007 * Cygwin Native:: Features specific to the Cygwin port
17008 * Hurd Native:: Features specific to @sc{gnu} Hurd
17009 * Neutrino:: Features specific to QNX Neutrino
17010 * Darwin:: Features specific to Darwin
17016 On HP-UX systems, if you refer to a function or variable name that
17017 begins with a dollar sign, @value{GDBN} searches for a user or system
17018 name first, before it searches for a convenience variable.
17021 @node BSD libkvm Interface
17022 @subsection BSD libkvm Interface
17025 @cindex kernel memory image
17026 @cindex kernel crash dump
17028 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17029 interface that provides a uniform interface for accessing kernel virtual
17030 memory images, including live systems and crash dumps. @value{GDBN}
17031 uses this interface to allow you to debug live kernels and kernel crash
17032 dumps on many native BSD configurations. This is implemented as a
17033 special @code{kvm} debugging target. For debugging a live system, load
17034 the currently running kernel into @value{GDBN} and connect to the
17038 (@value{GDBP}) @b{target kvm}
17041 For debugging crash dumps, provide the file name of the crash dump as an
17045 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17048 Once connected to the @code{kvm} target, the following commands are
17054 Set current context from the @dfn{Process Control Block} (PCB) address.
17057 Set current context from proc address. This command isn't available on
17058 modern FreeBSD systems.
17061 @node SVR4 Process Information
17062 @subsection SVR4 Process Information
17064 @cindex examine process image
17065 @cindex process info via @file{/proc}
17067 Many versions of SVR4 and compatible systems provide a facility called
17068 @samp{/proc} that can be used to examine the image of a running
17069 process using file-system subroutines. If @value{GDBN} is configured
17070 for an operating system with this facility, the command @code{info
17071 proc} is available to report information about the process running
17072 your program, or about any process running on your system. @code{info
17073 proc} works only on SVR4 systems that include the @code{procfs} code.
17074 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17075 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17081 @itemx info proc @var{process-id}
17082 Summarize available information about any running process. If a
17083 process ID is specified by @var{process-id}, display information about
17084 that process; otherwise display information about the program being
17085 debugged. The summary includes the debugged process ID, the command
17086 line used to invoke it, its current working directory, and its
17087 executable file's absolute file name.
17089 On some systems, @var{process-id} can be of the form
17090 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17091 within a process. If the optional @var{pid} part is missing, it means
17092 a thread from the process being debugged (the leading @samp{/} still
17093 needs to be present, or else @value{GDBN} will interpret the number as
17094 a process ID rather than a thread ID).
17096 @item info proc mappings
17097 @cindex memory address space mappings
17098 Report the memory address space ranges accessible in the program, with
17099 information on whether the process has read, write, or execute access
17100 rights to each range. On @sc{gnu}/Linux systems, each memory range
17101 includes the object file which is mapped to that range, instead of the
17102 memory access rights to that range.
17104 @item info proc stat
17105 @itemx info proc status
17106 @cindex process detailed status information
17107 These subcommands are specific to @sc{gnu}/Linux systems. They show
17108 the process-related information, including the user ID and group ID;
17109 how many threads are there in the process; its virtual memory usage;
17110 the signals that are pending, blocked, and ignored; its TTY; its
17111 consumption of system and user time; its stack size; its @samp{nice}
17112 value; etc. For more information, see the @samp{proc} man page
17113 (type @kbd{man 5 proc} from your shell prompt).
17115 @item info proc all
17116 Show all the information about the process described under all of the
17117 above @code{info proc} subcommands.
17120 @comment These sub-options of 'info proc' were not included when
17121 @comment procfs.c was re-written. Keep their descriptions around
17122 @comment against the day when someone finds the time to put them back in.
17123 @kindex info proc times
17124 @item info proc times
17125 Starting time, user CPU time, and system CPU time for your program and
17128 @kindex info proc id
17130 Report on the process IDs related to your program: its own process ID,
17131 the ID of its parent, the process group ID, and the session ID.
17134 @item set procfs-trace
17135 @kindex set procfs-trace
17136 @cindex @code{procfs} API calls
17137 This command enables and disables tracing of @code{procfs} API calls.
17139 @item show procfs-trace
17140 @kindex show procfs-trace
17141 Show the current state of @code{procfs} API call tracing.
17143 @item set procfs-file @var{file}
17144 @kindex set procfs-file
17145 Tell @value{GDBN} to write @code{procfs} API trace to the named
17146 @var{file}. @value{GDBN} appends the trace info to the previous
17147 contents of the file. The default is to display the trace on the
17150 @item show procfs-file
17151 @kindex show procfs-file
17152 Show the file to which @code{procfs} API trace is written.
17154 @item proc-trace-entry
17155 @itemx proc-trace-exit
17156 @itemx proc-untrace-entry
17157 @itemx proc-untrace-exit
17158 @kindex proc-trace-entry
17159 @kindex proc-trace-exit
17160 @kindex proc-untrace-entry
17161 @kindex proc-untrace-exit
17162 These commands enable and disable tracing of entries into and exits
17163 from the @code{syscall} interface.
17166 @kindex info pidlist
17167 @cindex process list, QNX Neutrino
17168 For QNX Neutrino only, this command displays the list of all the
17169 processes and all the threads within each process.
17172 @kindex info meminfo
17173 @cindex mapinfo list, QNX Neutrino
17174 For QNX Neutrino only, this command displays the list of all mapinfos.
17178 @subsection Features for Debugging @sc{djgpp} Programs
17179 @cindex @sc{djgpp} debugging
17180 @cindex native @sc{djgpp} debugging
17181 @cindex MS-DOS-specific commands
17184 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17185 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17186 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17187 top of real-mode DOS systems and their emulations.
17189 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17190 defines a few commands specific to the @sc{djgpp} port. This
17191 subsection describes those commands.
17196 This is a prefix of @sc{djgpp}-specific commands which print
17197 information about the target system and important OS structures.
17200 @cindex MS-DOS system info
17201 @cindex free memory information (MS-DOS)
17202 @item info dos sysinfo
17203 This command displays assorted information about the underlying
17204 platform: the CPU type and features, the OS version and flavor, the
17205 DPMI version, and the available conventional and DPMI memory.
17210 @cindex segment descriptor tables
17211 @cindex descriptor tables display
17213 @itemx info dos ldt
17214 @itemx info dos idt
17215 These 3 commands display entries from, respectively, Global, Local,
17216 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17217 tables are data structures which store a descriptor for each segment
17218 that is currently in use. The segment's selector is an index into a
17219 descriptor table; the table entry for that index holds the
17220 descriptor's base address and limit, and its attributes and access
17223 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17224 segment (used for both data and the stack), and a DOS segment (which
17225 allows access to DOS/BIOS data structures and absolute addresses in
17226 conventional memory). However, the DPMI host will usually define
17227 additional segments in order to support the DPMI environment.
17229 @cindex garbled pointers
17230 These commands allow to display entries from the descriptor tables.
17231 Without an argument, all entries from the specified table are
17232 displayed. An argument, which should be an integer expression, means
17233 display a single entry whose index is given by the argument. For
17234 example, here's a convenient way to display information about the
17235 debugged program's data segment:
17238 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17239 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17243 This comes in handy when you want to see whether a pointer is outside
17244 the data segment's limit (i.e.@: @dfn{garbled}).
17246 @cindex page tables display (MS-DOS)
17248 @itemx info dos pte
17249 These two commands display entries from, respectively, the Page
17250 Directory and the Page Tables. Page Directories and Page Tables are
17251 data structures which control how virtual memory addresses are mapped
17252 into physical addresses. A Page Table includes an entry for every
17253 page of memory that is mapped into the program's address space; there
17254 may be several Page Tables, each one holding up to 4096 entries. A
17255 Page Directory has up to 4096 entries, one each for every Page Table
17256 that is currently in use.
17258 Without an argument, @kbd{info dos pde} displays the entire Page
17259 Directory, and @kbd{info dos pte} displays all the entries in all of
17260 the Page Tables. An argument, an integer expression, given to the
17261 @kbd{info dos pde} command means display only that entry from the Page
17262 Directory table. An argument given to the @kbd{info dos pte} command
17263 means display entries from a single Page Table, the one pointed to by
17264 the specified entry in the Page Directory.
17266 @cindex direct memory access (DMA) on MS-DOS
17267 These commands are useful when your program uses @dfn{DMA} (Direct
17268 Memory Access), which needs physical addresses to program the DMA
17271 These commands are supported only with some DPMI servers.
17273 @cindex physical address from linear address
17274 @item info dos address-pte @var{addr}
17275 This command displays the Page Table entry for a specified linear
17276 address. The argument @var{addr} is a linear address which should
17277 already have the appropriate segment's base address added to it,
17278 because this command accepts addresses which may belong to @emph{any}
17279 segment. For example, here's how to display the Page Table entry for
17280 the page where a variable @code{i} is stored:
17283 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17284 @exdent @code{Page Table entry for address 0x11a00d30:}
17285 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17289 This says that @code{i} is stored at offset @code{0xd30} from the page
17290 whose physical base address is @code{0x02698000}, and shows all the
17291 attributes of that page.
17293 Note that you must cast the addresses of variables to a @code{char *},
17294 since otherwise the value of @code{__djgpp_base_address}, the base
17295 address of all variables and functions in a @sc{djgpp} program, will
17296 be added using the rules of C pointer arithmetics: if @code{i} is
17297 declared an @code{int}, @value{GDBN} will add 4 times the value of
17298 @code{__djgpp_base_address} to the address of @code{i}.
17300 Here's another example, it displays the Page Table entry for the
17304 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17305 @exdent @code{Page Table entry for address 0x29110:}
17306 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17310 (The @code{+ 3} offset is because the transfer buffer's address is the
17311 3rd member of the @code{_go32_info_block} structure.) The output
17312 clearly shows that this DPMI server maps the addresses in conventional
17313 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17314 linear (@code{0x29110}) addresses are identical.
17316 This command is supported only with some DPMI servers.
17319 @cindex DOS serial data link, remote debugging
17320 In addition to native debugging, the DJGPP port supports remote
17321 debugging via a serial data link. The following commands are specific
17322 to remote serial debugging in the DJGPP port of @value{GDBN}.
17325 @kindex set com1base
17326 @kindex set com1irq
17327 @kindex set com2base
17328 @kindex set com2irq
17329 @kindex set com3base
17330 @kindex set com3irq
17331 @kindex set com4base
17332 @kindex set com4irq
17333 @item set com1base @var{addr}
17334 This command sets the base I/O port address of the @file{COM1} serial
17337 @item set com1irq @var{irq}
17338 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17339 for the @file{COM1} serial port.
17341 There are similar commands @samp{set com2base}, @samp{set com3irq},
17342 etc.@: for setting the port address and the @code{IRQ} lines for the
17345 @kindex show com1base
17346 @kindex show com1irq
17347 @kindex show com2base
17348 @kindex show com2irq
17349 @kindex show com3base
17350 @kindex show com3irq
17351 @kindex show com4base
17352 @kindex show com4irq
17353 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17354 display the current settings of the base address and the @code{IRQ}
17355 lines used by the COM ports.
17358 @kindex info serial
17359 @cindex DOS serial port status
17360 This command prints the status of the 4 DOS serial ports. For each
17361 port, it prints whether it's active or not, its I/O base address and
17362 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17363 counts of various errors encountered so far.
17367 @node Cygwin Native
17368 @subsection Features for Debugging MS Windows PE Executables
17369 @cindex MS Windows debugging
17370 @cindex native Cygwin debugging
17371 @cindex Cygwin-specific commands
17373 @value{GDBN} supports native debugging of MS Windows programs, including
17374 DLLs with and without symbolic debugging information.
17376 @cindex Ctrl-BREAK, MS-Windows
17377 @cindex interrupt debuggee on MS-Windows
17378 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17379 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17380 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17381 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17382 sequence, which can be used to interrupt the debuggee even if it
17385 There are various additional Cygwin-specific commands, described in
17386 this section. Working with DLLs that have no debugging symbols is
17387 described in @ref{Non-debug DLL Symbols}.
17392 This is a prefix of MS Windows-specific commands which print
17393 information about the target system and important OS structures.
17395 @item info w32 selector
17396 This command displays information returned by
17397 the Win32 API @code{GetThreadSelectorEntry} function.
17398 It takes an optional argument that is evaluated to
17399 a long value to give the information about this given selector.
17400 Without argument, this command displays information
17401 about the six segment registers.
17403 @item info w32 thread-information-block
17404 This command displays thread specific information stored in the
17405 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17406 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17410 This is a Cygwin-specific alias of @code{info shared}.
17412 @kindex dll-symbols
17414 This command loads symbols from a dll similarly to
17415 add-sym command but without the need to specify a base address.
17417 @kindex set cygwin-exceptions
17418 @cindex debugging the Cygwin DLL
17419 @cindex Cygwin DLL, debugging
17420 @item set cygwin-exceptions @var{mode}
17421 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17422 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17423 @value{GDBN} will delay recognition of exceptions, and may ignore some
17424 exceptions which seem to be caused by internal Cygwin DLL
17425 ``bookkeeping''. This option is meant primarily for debugging the
17426 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17427 @value{GDBN} users with false @code{SIGSEGV} signals.
17429 @kindex show cygwin-exceptions
17430 @item show cygwin-exceptions
17431 Displays whether @value{GDBN} will break on exceptions that happen
17432 inside the Cygwin DLL itself.
17434 @kindex set new-console
17435 @item set new-console @var{mode}
17436 If @var{mode} is @code{on} the debuggee will
17437 be started in a new console on next start.
17438 If @var{mode} is @code{off}, the debuggee will
17439 be started in the same console as the debugger.
17441 @kindex show new-console
17442 @item show new-console
17443 Displays whether a new console is used
17444 when the debuggee is started.
17446 @kindex set new-group
17447 @item set new-group @var{mode}
17448 This boolean value controls whether the debuggee should
17449 start a new group or stay in the same group as the debugger.
17450 This affects the way the Windows OS handles
17453 @kindex show new-group
17454 @item show new-group
17455 Displays current value of new-group boolean.
17457 @kindex set debugevents
17458 @item set debugevents
17459 This boolean value adds debug output concerning kernel events related
17460 to the debuggee seen by the debugger. This includes events that
17461 signal thread and process creation and exit, DLL loading and
17462 unloading, console interrupts, and debugging messages produced by the
17463 Windows @code{OutputDebugString} API call.
17465 @kindex set debugexec
17466 @item set debugexec
17467 This boolean value adds debug output concerning execute events
17468 (such as resume thread) seen by the debugger.
17470 @kindex set debugexceptions
17471 @item set debugexceptions
17472 This boolean value adds debug output concerning exceptions in the
17473 debuggee seen by the debugger.
17475 @kindex set debugmemory
17476 @item set debugmemory
17477 This boolean value adds debug output concerning debuggee memory reads
17478 and writes by the debugger.
17482 This boolean values specifies whether the debuggee is called
17483 via a shell or directly (default value is on).
17487 Displays if the debuggee will be started with a shell.
17492 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17495 @node Non-debug DLL Symbols
17496 @subsubsection Support for DLLs without Debugging Symbols
17497 @cindex DLLs with no debugging symbols
17498 @cindex Minimal symbols and DLLs
17500 Very often on windows, some of the DLLs that your program relies on do
17501 not include symbolic debugging information (for example,
17502 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17503 symbols in a DLL, it relies on the minimal amount of symbolic
17504 information contained in the DLL's export table. This section
17505 describes working with such symbols, known internally to @value{GDBN} as
17506 ``minimal symbols''.
17508 Note that before the debugged program has started execution, no DLLs
17509 will have been loaded. The easiest way around this problem is simply to
17510 start the program --- either by setting a breakpoint or letting the
17511 program run once to completion. It is also possible to force
17512 @value{GDBN} to load a particular DLL before starting the executable ---
17513 see the shared library information in @ref{Files}, or the
17514 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17515 explicitly loading symbols from a DLL with no debugging information will
17516 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17517 which may adversely affect symbol lookup performance.
17519 @subsubsection DLL Name Prefixes
17521 In keeping with the naming conventions used by the Microsoft debugging
17522 tools, DLL export symbols are made available with a prefix based on the
17523 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17524 also entered into the symbol table, so @code{CreateFileA} is often
17525 sufficient. In some cases there will be name clashes within a program
17526 (particularly if the executable itself includes full debugging symbols)
17527 necessitating the use of the fully qualified name when referring to the
17528 contents of the DLL. Use single-quotes around the name to avoid the
17529 exclamation mark (``!'') being interpreted as a language operator.
17531 Note that the internal name of the DLL may be all upper-case, even
17532 though the file name of the DLL is lower-case, or vice-versa. Since
17533 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17534 some confusion. If in doubt, try the @code{info functions} and
17535 @code{info variables} commands or even @code{maint print msymbols}
17536 (@pxref{Symbols}). Here's an example:
17539 (@value{GDBP}) info function CreateFileA
17540 All functions matching regular expression "CreateFileA":
17542 Non-debugging symbols:
17543 0x77e885f4 CreateFileA
17544 0x77e885f4 KERNEL32!CreateFileA
17548 (@value{GDBP}) info function !
17549 All functions matching regular expression "!":
17551 Non-debugging symbols:
17552 0x6100114c cygwin1!__assert
17553 0x61004034 cygwin1!_dll_crt0@@0
17554 0x61004240 cygwin1!dll_crt0(per_process *)
17558 @subsubsection Working with Minimal Symbols
17560 Symbols extracted from a DLL's export table do not contain very much
17561 type information. All that @value{GDBN} can do is guess whether a symbol
17562 refers to a function or variable depending on the linker section that
17563 contains the symbol. Also note that the actual contents of the memory
17564 contained in a DLL are not available unless the program is running. This
17565 means that you cannot examine the contents of a variable or disassemble
17566 a function within a DLL without a running program.
17568 Variables are generally treated as pointers and dereferenced
17569 automatically. For this reason, it is often necessary to prefix a
17570 variable name with the address-of operator (``&'') and provide explicit
17571 type information in the command. Here's an example of the type of
17575 (@value{GDBP}) print 'cygwin1!__argv'
17580 (@value{GDBP}) x 'cygwin1!__argv'
17581 0x10021610: "\230y\""
17584 And two possible solutions:
17587 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17588 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17592 (@value{GDBP}) x/2x &'cygwin1!__argv'
17593 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17594 (@value{GDBP}) x/x 0x10021608
17595 0x10021608: 0x0022fd98
17596 (@value{GDBP}) x/s 0x0022fd98
17597 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17600 Setting a break point within a DLL is possible even before the program
17601 starts execution. However, under these circumstances, @value{GDBN} can't
17602 examine the initial instructions of the function in order to skip the
17603 function's frame set-up code. You can work around this by using ``*&''
17604 to set the breakpoint at a raw memory address:
17607 (@value{GDBP}) break *&'python22!PyOS_Readline'
17608 Breakpoint 1 at 0x1e04eff0
17611 The author of these extensions is not entirely convinced that setting a
17612 break point within a shared DLL like @file{kernel32.dll} is completely
17616 @subsection Commands Specific to @sc{gnu} Hurd Systems
17617 @cindex @sc{gnu} Hurd debugging
17619 This subsection describes @value{GDBN} commands specific to the
17620 @sc{gnu} Hurd native debugging.
17625 @kindex set signals@r{, Hurd command}
17626 @kindex set sigs@r{, Hurd command}
17627 This command toggles the state of inferior signal interception by
17628 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17629 affected by this command. @code{sigs} is a shorthand alias for
17634 @kindex show signals@r{, Hurd command}
17635 @kindex show sigs@r{, Hurd command}
17636 Show the current state of intercepting inferior's signals.
17638 @item set signal-thread
17639 @itemx set sigthread
17640 @kindex set signal-thread
17641 @kindex set sigthread
17642 This command tells @value{GDBN} which thread is the @code{libc} signal
17643 thread. That thread is run when a signal is delivered to a running
17644 process. @code{set sigthread} is the shorthand alias of @code{set
17647 @item show signal-thread
17648 @itemx show sigthread
17649 @kindex show signal-thread
17650 @kindex show sigthread
17651 These two commands show which thread will run when the inferior is
17652 delivered a signal.
17655 @kindex set stopped@r{, Hurd command}
17656 This commands tells @value{GDBN} that the inferior process is stopped,
17657 as with the @code{SIGSTOP} signal. The stopped process can be
17658 continued by delivering a signal to it.
17661 @kindex show stopped@r{, Hurd command}
17662 This command shows whether @value{GDBN} thinks the debuggee is
17665 @item set exceptions
17666 @kindex set exceptions@r{, Hurd command}
17667 Use this command to turn off trapping of exceptions in the inferior.
17668 When exception trapping is off, neither breakpoints nor
17669 single-stepping will work. To restore the default, set exception
17672 @item show exceptions
17673 @kindex show exceptions@r{, Hurd command}
17674 Show the current state of trapping exceptions in the inferior.
17676 @item set task pause
17677 @kindex set task@r{, Hurd commands}
17678 @cindex task attributes (@sc{gnu} Hurd)
17679 @cindex pause current task (@sc{gnu} Hurd)
17680 This command toggles task suspension when @value{GDBN} has control.
17681 Setting it to on takes effect immediately, and the task is suspended
17682 whenever @value{GDBN} gets control. Setting it to off will take
17683 effect the next time the inferior is continued. If this option is set
17684 to off, you can use @code{set thread default pause on} or @code{set
17685 thread pause on} (see below) to pause individual threads.
17687 @item show task pause
17688 @kindex show task@r{, Hurd commands}
17689 Show the current state of task suspension.
17691 @item set task detach-suspend-count
17692 @cindex task suspend count
17693 @cindex detach from task, @sc{gnu} Hurd
17694 This command sets the suspend count the task will be left with when
17695 @value{GDBN} detaches from it.
17697 @item show task detach-suspend-count
17698 Show the suspend count the task will be left with when detaching.
17700 @item set task exception-port
17701 @itemx set task excp
17702 @cindex task exception port, @sc{gnu} Hurd
17703 This command sets the task exception port to which @value{GDBN} will
17704 forward exceptions. The argument should be the value of the @dfn{send
17705 rights} of the task. @code{set task excp} is a shorthand alias.
17707 @item set noninvasive
17708 @cindex noninvasive task options
17709 This command switches @value{GDBN} to a mode that is the least
17710 invasive as far as interfering with the inferior is concerned. This
17711 is the same as using @code{set task pause}, @code{set exceptions}, and
17712 @code{set signals} to values opposite to the defaults.
17714 @item info send-rights
17715 @itemx info receive-rights
17716 @itemx info port-rights
17717 @itemx info port-sets
17718 @itemx info dead-names
17721 @cindex send rights, @sc{gnu} Hurd
17722 @cindex receive rights, @sc{gnu} Hurd
17723 @cindex port rights, @sc{gnu} Hurd
17724 @cindex port sets, @sc{gnu} Hurd
17725 @cindex dead names, @sc{gnu} Hurd
17726 These commands display information about, respectively, send rights,
17727 receive rights, port rights, port sets, and dead names of a task.
17728 There are also shorthand aliases: @code{info ports} for @code{info
17729 port-rights} and @code{info psets} for @code{info port-sets}.
17731 @item set thread pause
17732 @kindex set thread@r{, Hurd command}
17733 @cindex thread properties, @sc{gnu} Hurd
17734 @cindex pause current thread (@sc{gnu} Hurd)
17735 This command toggles current thread suspension when @value{GDBN} has
17736 control. Setting it to on takes effect immediately, and the current
17737 thread is suspended whenever @value{GDBN} gets control. Setting it to
17738 off will take effect the next time the inferior is continued.
17739 Normally, this command has no effect, since when @value{GDBN} has
17740 control, the whole task is suspended. However, if you used @code{set
17741 task pause off} (see above), this command comes in handy to suspend
17742 only the current thread.
17744 @item show thread pause
17745 @kindex show thread@r{, Hurd command}
17746 This command shows the state of current thread suspension.
17748 @item set thread run
17749 This command sets whether the current thread is allowed to run.
17751 @item show thread run
17752 Show whether the current thread is allowed to run.
17754 @item set thread detach-suspend-count
17755 @cindex thread suspend count, @sc{gnu} Hurd
17756 @cindex detach from thread, @sc{gnu} Hurd
17757 This command sets the suspend count @value{GDBN} will leave on a
17758 thread when detaching. This number is relative to the suspend count
17759 found by @value{GDBN} when it notices the thread; use @code{set thread
17760 takeover-suspend-count} to force it to an absolute value.
17762 @item show thread detach-suspend-count
17763 Show the suspend count @value{GDBN} will leave on the thread when
17766 @item set thread exception-port
17767 @itemx set thread excp
17768 Set the thread exception port to which to forward exceptions. This
17769 overrides the port set by @code{set task exception-port} (see above).
17770 @code{set thread excp} is the shorthand alias.
17772 @item set thread takeover-suspend-count
17773 Normally, @value{GDBN}'s thread suspend counts are relative to the
17774 value @value{GDBN} finds when it notices each thread. This command
17775 changes the suspend counts to be absolute instead.
17777 @item set thread default
17778 @itemx show thread default
17779 @cindex thread default settings, @sc{gnu} Hurd
17780 Each of the above @code{set thread} commands has a @code{set thread
17781 default} counterpart (e.g., @code{set thread default pause}, @code{set
17782 thread default exception-port}, etc.). The @code{thread default}
17783 variety of commands sets the default thread properties for all
17784 threads; you can then change the properties of individual threads with
17785 the non-default commands.
17790 @subsection QNX Neutrino
17791 @cindex QNX Neutrino
17793 @value{GDBN} provides the following commands specific to the QNX
17797 @item set debug nto-debug
17798 @kindex set debug nto-debug
17799 When set to on, enables debugging messages specific to the QNX
17802 @item show debug nto-debug
17803 @kindex show debug nto-debug
17804 Show the current state of QNX Neutrino messages.
17811 @value{GDBN} provides the following commands specific to the Darwin target:
17814 @item set debug darwin @var{num}
17815 @kindex set debug darwin
17816 When set to a non zero value, enables debugging messages specific to
17817 the Darwin support. Higher values produce more verbose output.
17819 @item show debug darwin
17820 @kindex show debug darwin
17821 Show the current state of Darwin messages.
17823 @item set debug mach-o @var{num}
17824 @kindex set debug mach-o
17825 When set to a non zero value, enables debugging messages while
17826 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17827 file format used on Darwin for object and executable files.) Higher
17828 values produce more verbose output. This is a command to diagnose
17829 problems internal to @value{GDBN} and should not be needed in normal
17832 @item show debug mach-o
17833 @kindex show debug mach-o
17834 Show the current state of Mach-O file messages.
17836 @item set mach-exceptions on
17837 @itemx set mach-exceptions off
17838 @kindex set mach-exceptions
17839 On Darwin, faults are first reported as a Mach exception and are then
17840 mapped to a Posix signal. Use this command to turn on trapping of
17841 Mach exceptions in the inferior. This might be sometimes useful to
17842 better understand the cause of a fault. The default is off.
17844 @item show mach-exceptions
17845 @kindex show mach-exceptions
17846 Show the current state of exceptions trapping.
17851 @section Embedded Operating Systems
17853 This section describes configurations involving the debugging of
17854 embedded operating systems that are available for several different
17858 * VxWorks:: Using @value{GDBN} with VxWorks
17861 @value{GDBN} includes the ability to debug programs running on
17862 various real-time operating systems.
17865 @subsection Using @value{GDBN} with VxWorks
17871 @kindex target vxworks
17872 @item target vxworks @var{machinename}
17873 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17874 is the target system's machine name or IP address.
17878 On VxWorks, @code{load} links @var{filename} dynamically on the
17879 current target system as well as adding its symbols in @value{GDBN}.
17881 @value{GDBN} enables developers to spawn and debug tasks running on networked
17882 VxWorks targets from a Unix host. Already-running tasks spawned from
17883 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17884 both the Unix host and on the VxWorks target. The program
17885 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17886 installed with the name @code{vxgdb}, to distinguish it from a
17887 @value{GDBN} for debugging programs on the host itself.)
17890 @item VxWorks-timeout @var{args}
17891 @kindex vxworks-timeout
17892 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17893 This option is set by the user, and @var{args} represents the number of
17894 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17895 your VxWorks target is a slow software simulator or is on the far side
17896 of a thin network line.
17899 The following information on connecting to VxWorks was current when
17900 this manual was produced; newer releases of VxWorks may use revised
17903 @findex INCLUDE_RDB
17904 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17905 to include the remote debugging interface routines in the VxWorks
17906 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17907 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17908 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17909 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17910 information on configuring and remaking VxWorks, see the manufacturer's
17912 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17914 Once you have included @file{rdb.a} in your VxWorks system image and set
17915 your Unix execution search path to find @value{GDBN}, you are ready to
17916 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17917 @code{vxgdb}, depending on your installation).
17919 @value{GDBN} comes up showing the prompt:
17926 * VxWorks Connection:: Connecting to VxWorks
17927 * VxWorks Download:: VxWorks download
17928 * VxWorks Attach:: Running tasks
17931 @node VxWorks Connection
17932 @subsubsection Connecting to VxWorks
17934 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17935 network. To connect to a target whose host name is ``@code{tt}'', type:
17938 (vxgdb) target vxworks tt
17942 @value{GDBN} displays messages like these:
17945 Attaching remote machine across net...
17950 @value{GDBN} then attempts to read the symbol tables of any object modules
17951 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17952 these files by searching the directories listed in the command search
17953 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17954 to find an object file, it displays a message such as:
17957 prog.o: No such file or directory.
17960 When this happens, add the appropriate directory to the search path with
17961 the @value{GDBN} command @code{path}, and execute the @code{target}
17964 @node VxWorks Download
17965 @subsubsection VxWorks Download
17967 @cindex download to VxWorks
17968 If you have connected to the VxWorks target and you want to debug an
17969 object that has not yet been loaded, you can use the @value{GDBN}
17970 @code{load} command to download a file from Unix to VxWorks
17971 incrementally. The object file given as an argument to the @code{load}
17972 command is actually opened twice: first by the VxWorks target in order
17973 to download the code, then by @value{GDBN} in order to read the symbol
17974 table. This can lead to problems if the current working directories on
17975 the two systems differ. If both systems have NFS mounted the same
17976 filesystems, you can avoid these problems by using absolute paths.
17977 Otherwise, it is simplest to set the working directory on both systems
17978 to the directory in which the object file resides, and then to reference
17979 the file by its name, without any path. For instance, a program
17980 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17981 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17982 program, type this on VxWorks:
17985 -> cd "@var{vxpath}/vw/demo/rdb"
17989 Then, in @value{GDBN}, type:
17992 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17993 (vxgdb) load prog.o
17996 @value{GDBN} displays a response similar to this:
17999 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18002 You can also use the @code{load} command to reload an object module
18003 after editing and recompiling the corresponding source file. Note that
18004 this makes @value{GDBN} delete all currently-defined breakpoints,
18005 auto-displays, and convenience variables, and to clear the value
18006 history. (This is necessary in order to preserve the integrity of
18007 debugger's data structures that reference the target system's symbol
18010 @node VxWorks Attach
18011 @subsubsection Running Tasks
18013 @cindex running VxWorks tasks
18014 You can also attach to an existing task using the @code{attach} command as
18018 (vxgdb) attach @var{task}
18022 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18023 or suspended when you attach to it. Running tasks are suspended at
18024 the time of attachment.
18026 @node Embedded Processors
18027 @section Embedded Processors
18029 This section goes into details specific to particular embedded
18032 @cindex send command to simulator
18033 Whenever a specific embedded processor has a simulator, @value{GDBN}
18034 allows to send an arbitrary command to the simulator.
18037 @item sim @var{command}
18038 @kindex sim@r{, a command}
18039 Send an arbitrary @var{command} string to the simulator. Consult the
18040 documentation for the specific simulator in use for information about
18041 acceptable commands.
18047 * M32R/D:: Renesas M32R/D
18048 * M68K:: Motorola M68K
18049 * MicroBlaze:: Xilinx MicroBlaze
18050 * MIPS Embedded:: MIPS Embedded
18051 * OpenRISC 1000:: OpenRisc 1000
18052 * PA:: HP PA Embedded
18053 * PowerPC Embedded:: PowerPC Embedded
18054 * Sparclet:: Tsqware Sparclet
18055 * Sparclite:: Fujitsu Sparclite
18056 * Z8000:: Zilog Z8000
18059 * Super-H:: Renesas Super-H
18068 @item target rdi @var{dev}
18069 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18070 use this target to communicate with both boards running the Angel
18071 monitor, or with the EmbeddedICE JTAG debug device.
18074 @item target rdp @var{dev}
18079 @value{GDBN} provides the following ARM-specific commands:
18082 @item set arm disassembler
18084 This commands selects from a list of disassembly styles. The
18085 @code{"std"} style is the standard style.
18087 @item show arm disassembler
18089 Show the current disassembly style.
18091 @item set arm apcs32
18092 @cindex ARM 32-bit mode
18093 This command toggles ARM operation mode between 32-bit and 26-bit.
18095 @item show arm apcs32
18096 Display the current usage of the ARM 32-bit mode.
18098 @item set arm fpu @var{fputype}
18099 This command sets the ARM floating-point unit (FPU) type. The
18100 argument @var{fputype} can be one of these:
18104 Determine the FPU type by querying the OS ABI.
18106 Software FPU, with mixed-endian doubles on little-endian ARM
18109 GCC-compiled FPA co-processor.
18111 Software FPU with pure-endian doubles.
18117 Show the current type of the FPU.
18120 This command forces @value{GDBN} to use the specified ABI.
18123 Show the currently used ABI.
18125 @item set arm fallback-mode (arm|thumb|auto)
18126 @value{GDBN} uses the symbol table, when available, to determine
18127 whether instructions are ARM or Thumb. This command controls
18128 @value{GDBN}'s default behavior when the symbol table is not
18129 available. The default is @samp{auto}, which causes @value{GDBN} to
18130 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18133 @item show arm fallback-mode
18134 Show the current fallback instruction mode.
18136 @item set arm force-mode (arm|thumb|auto)
18137 This command overrides use of the symbol table to determine whether
18138 instructions are ARM or Thumb. The default is @samp{auto}, which
18139 causes @value{GDBN} to use the symbol table and then the setting
18140 of @samp{set arm fallback-mode}.
18142 @item show arm force-mode
18143 Show the current forced instruction mode.
18145 @item set debug arm
18146 Toggle whether to display ARM-specific debugging messages from the ARM
18147 target support subsystem.
18149 @item show debug arm
18150 Show whether ARM-specific debugging messages are enabled.
18153 The following commands are available when an ARM target is debugged
18154 using the RDI interface:
18157 @item rdilogfile @r{[}@var{file}@r{]}
18159 @cindex ADP (Angel Debugger Protocol) logging
18160 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18161 With an argument, sets the log file to the specified @var{file}. With
18162 no argument, show the current log file name. The default log file is
18165 @item rdilogenable @r{[}@var{arg}@r{]}
18166 @kindex rdilogenable
18167 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18168 enables logging, with an argument 0 or @code{"no"} disables it. With
18169 no arguments displays the current setting. When logging is enabled,
18170 ADP packets exchanged between @value{GDBN} and the RDI target device
18171 are logged to a file.
18173 @item set rdiromatzero
18174 @kindex set rdiromatzero
18175 @cindex ROM at zero address, RDI
18176 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18177 vector catching is disabled, so that zero address can be used. If off
18178 (the default), vector catching is enabled. For this command to take
18179 effect, it needs to be invoked prior to the @code{target rdi} command.
18181 @item show rdiromatzero
18182 @kindex show rdiromatzero
18183 Show the current setting of ROM at zero address.
18185 @item set rdiheartbeat
18186 @kindex set rdiheartbeat
18187 @cindex RDI heartbeat
18188 Enable or disable RDI heartbeat packets. It is not recommended to
18189 turn on this option, since it confuses ARM and EPI JTAG interface, as
18190 well as the Angel monitor.
18192 @item show rdiheartbeat
18193 @kindex show rdiheartbeat
18194 Show the setting of RDI heartbeat packets.
18198 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18199 The @value{GDBN} ARM simulator accepts the following optional arguments.
18202 @item --swi-support=@var{type}
18203 Tell the simulator which SWI interfaces to support.
18204 @var{type} may be a comma separated list of the following values.
18205 The default value is @code{all}.
18218 @subsection Renesas M32R/D and M32R/SDI
18221 @kindex target m32r
18222 @item target m32r @var{dev}
18223 Renesas M32R/D ROM monitor.
18225 @kindex target m32rsdi
18226 @item target m32rsdi @var{dev}
18227 Renesas M32R SDI server, connected via parallel port to the board.
18230 The following @value{GDBN} commands are specific to the M32R monitor:
18233 @item set download-path @var{path}
18234 @kindex set download-path
18235 @cindex find downloadable @sc{srec} files (M32R)
18236 Set the default path for finding downloadable @sc{srec} files.
18238 @item show download-path
18239 @kindex show download-path
18240 Show the default path for downloadable @sc{srec} files.
18242 @item set board-address @var{addr}
18243 @kindex set board-address
18244 @cindex M32-EVA target board address
18245 Set the IP address for the M32R-EVA target board.
18247 @item show board-address
18248 @kindex show board-address
18249 Show the current IP address of the target board.
18251 @item set server-address @var{addr}
18252 @kindex set server-address
18253 @cindex download server address (M32R)
18254 Set the IP address for the download server, which is the @value{GDBN}'s
18257 @item show server-address
18258 @kindex show server-address
18259 Display the IP address of the download server.
18261 @item upload @r{[}@var{file}@r{]}
18262 @kindex upload@r{, M32R}
18263 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18264 upload capability. If no @var{file} argument is given, the current
18265 executable file is uploaded.
18267 @item tload @r{[}@var{file}@r{]}
18268 @kindex tload@r{, M32R}
18269 Test the @code{upload} command.
18272 The following commands are available for M32R/SDI:
18277 @cindex reset SDI connection, M32R
18278 This command resets the SDI connection.
18282 This command shows the SDI connection status.
18285 @kindex debug_chaos
18286 @cindex M32R/Chaos debugging
18287 Instructs the remote that M32R/Chaos debugging is to be used.
18289 @item use_debug_dma
18290 @kindex use_debug_dma
18291 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18294 @kindex use_mon_code
18295 Instructs the remote to use the MON_CODE method of accessing memory.
18298 @kindex use_ib_break
18299 Instructs the remote to set breakpoints by IB break.
18301 @item use_dbt_break
18302 @kindex use_dbt_break
18303 Instructs the remote to set breakpoints by DBT.
18309 The Motorola m68k configuration includes ColdFire support, and a
18310 target command for the following ROM monitor.
18314 @kindex target dbug
18315 @item target dbug @var{dev}
18316 dBUG ROM monitor for Motorola ColdFire.
18321 @subsection MicroBlaze
18322 @cindex Xilinx MicroBlaze
18323 @cindex XMD, Xilinx Microprocessor Debugger
18325 The MicroBlaze is a soft-core processor supported on various Xilinx
18326 FPGAs, such as Spartan or Virtex series. Boards with these processors
18327 usually have JTAG ports which connect to a host system running the Xilinx
18328 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18329 This host system is used to download the configuration bitstream to
18330 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18331 communicates with the target board using the JTAG interface and
18332 presents a @code{gdbserver} interface to the board. By default
18333 @code{xmd} uses port @code{1234}. (While it is possible to change
18334 this default port, it requires the use of undocumented @code{xmd}
18335 commands. Contact Xilinx support if you need to do this.)
18337 Use these GDB commands to connect to the MicroBlaze target processor.
18340 @item target remote :1234
18341 Use this command to connect to the target if you are running @value{GDBN}
18342 on the same system as @code{xmd}.
18344 @item target remote @var{xmd-host}:1234
18345 Use this command to connect to the target if it is connected to @code{xmd}
18346 running on a different system named @var{xmd-host}.
18349 Use this command to download a program to the MicroBlaze target.
18351 @item set debug microblaze @var{n}
18352 Enable MicroBlaze-specific debugging messages if non-zero.
18354 @item show debug microblaze @var{n}
18355 Show MicroBlaze-specific debugging level.
18358 @node MIPS Embedded
18359 @subsection MIPS Embedded
18361 @cindex MIPS boards
18362 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18363 MIPS board attached to a serial line. This is available when
18364 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18367 Use these @value{GDBN} commands to specify the connection to your target board:
18370 @item target mips @var{port}
18371 @kindex target mips @var{port}
18372 To run a program on the board, start up @code{@value{GDBP}} with the
18373 name of your program as the argument. To connect to the board, use the
18374 command @samp{target mips @var{port}}, where @var{port} is the name of
18375 the serial port connected to the board. If the program has not already
18376 been downloaded to the board, you may use the @code{load} command to
18377 download it. You can then use all the usual @value{GDBN} commands.
18379 For example, this sequence connects to the target board through a serial
18380 port, and loads and runs a program called @var{prog} through the
18384 host$ @value{GDBP} @var{prog}
18385 @value{GDBN} is free software and @dots{}
18386 (@value{GDBP}) target mips /dev/ttyb
18387 (@value{GDBP}) load @var{prog}
18391 @item target mips @var{hostname}:@var{portnumber}
18392 On some @value{GDBN} host configurations, you can specify a TCP
18393 connection (for instance, to a serial line managed by a terminal
18394 concentrator) instead of a serial port, using the syntax
18395 @samp{@var{hostname}:@var{portnumber}}.
18397 @item target pmon @var{port}
18398 @kindex target pmon @var{port}
18401 @item target ddb @var{port}
18402 @kindex target ddb @var{port}
18403 NEC's DDB variant of PMON for Vr4300.
18405 @item target lsi @var{port}
18406 @kindex target lsi @var{port}
18407 LSI variant of PMON.
18409 @kindex target r3900
18410 @item target r3900 @var{dev}
18411 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18413 @kindex target array
18414 @item target array @var{dev}
18415 Array Tech LSI33K RAID controller board.
18421 @value{GDBN} also supports these special commands for MIPS targets:
18424 @item set mipsfpu double
18425 @itemx set mipsfpu single
18426 @itemx set mipsfpu none
18427 @itemx set mipsfpu auto
18428 @itemx show mipsfpu
18429 @kindex set mipsfpu
18430 @kindex show mipsfpu
18431 @cindex MIPS remote floating point
18432 @cindex floating point, MIPS remote
18433 If your target board does not support the MIPS floating point
18434 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18435 need this, you may wish to put the command in your @value{GDBN} init
18436 file). This tells @value{GDBN} how to find the return value of
18437 functions which return floating point values. It also allows
18438 @value{GDBN} to avoid saving the floating point registers when calling
18439 functions on the board. If you are using a floating point coprocessor
18440 with only single precision floating point support, as on the @sc{r4650}
18441 processor, use the command @samp{set mipsfpu single}. The default
18442 double precision floating point coprocessor may be selected using
18443 @samp{set mipsfpu double}.
18445 In previous versions the only choices were double precision or no
18446 floating point, so @samp{set mipsfpu on} will select double precision
18447 and @samp{set mipsfpu off} will select no floating point.
18449 As usual, you can inquire about the @code{mipsfpu} variable with
18450 @samp{show mipsfpu}.
18452 @item set timeout @var{seconds}
18453 @itemx set retransmit-timeout @var{seconds}
18454 @itemx show timeout
18455 @itemx show retransmit-timeout
18456 @cindex @code{timeout}, MIPS protocol
18457 @cindex @code{retransmit-timeout}, MIPS protocol
18458 @kindex set timeout
18459 @kindex show timeout
18460 @kindex set retransmit-timeout
18461 @kindex show retransmit-timeout
18462 You can control the timeout used while waiting for a packet, in the MIPS
18463 remote protocol, with the @code{set timeout @var{seconds}} command. The
18464 default is 5 seconds. Similarly, you can control the timeout used while
18465 waiting for an acknowledgment of a packet with the @code{set
18466 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18467 You can inspect both values with @code{show timeout} and @code{show
18468 retransmit-timeout}. (These commands are @emph{only} available when
18469 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18471 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18472 is waiting for your program to stop. In that case, @value{GDBN} waits
18473 forever because it has no way of knowing how long the program is going
18474 to run before stopping.
18476 @item set syn-garbage-limit @var{num}
18477 @kindex set syn-garbage-limit@r{, MIPS remote}
18478 @cindex synchronize with remote MIPS target
18479 Limit the maximum number of characters @value{GDBN} should ignore when
18480 it tries to synchronize with the remote target. The default is 10
18481 characters. Setting the limit to -1 means there's no limit.
18483 @item show syn-garbage-limit
18484 @kindex show syn-garbage-limit@r{, MIPS remote}
18485 Show the current limit on the number of characters to ignore when
18486 trying to synchronize with the remote system.
18488 @item set monitor-prompt @var{prompt}
18489 @kindex set monitor-prompt@r{, MIPS remote}
18490 @cindex remote monitor prompt
18491 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18492 remote monitor. The default depends on the target:
18502 @item show monitor-prompt
18503 @kindex show monitor-prompt@r{, MIPS remote}
18504 Show the current strings @value{GDBN} expects as the prompt from the
18507 @item set monitor-warnings
18508 @kindex set monitor-warnings@r{, MIPS remote}
18509 Enable or disable monitor warnings about hardware breakpoints. This
18510 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18511 display warning messages whose codes are returned by the @code{lsi}
18512 PMON monitor for breakpoint commands.
18514 @item show monitor-warnings
18515 @kindex show monitor-warnings@r{, MIPS remote}
18516 Show the current setting of printing monitor warnings.
18518 @item pmon @var{command}
18519 @kindex pmon@r{, MIPS remote}
18520 @cindex send PMON command
18521 This command allows sending an arbitrary @var{command} string to the
18522 monitor. The monitor must be in debug mode for this to work.
18525 @node OpenRISC 1000
18526 @subsection OpenRISC 1000
18527 @cindex OpenRISC 1000
18529 @cindex or1k boards
18530 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18531 about platform and commands.
18535 @kindex target jtag
18536 @item target jtag jtag://@var{host}:@var{port}
18538 Connects to remote JTAG server.
18539 JTAG remote server can be either an or1ksim or JTAG server,
18540 connected via parallel port to the board.
18542 Example: @code{target jtag jtag://localhost:9999}
18545 @item or1ksim @var{command}
18546 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18547 Simulator, proprietary commands can be executed.
18549 @kindex info or1k spr
18550 @item info or1k spr
18551 Displays spr groups.
18553 @item info or1k spr @var{group}
18554 @itemx info or1k spr @var{groupno}
18555 Displays register names in selected group.
18557 @item info or1k spr @var{group} @var{register}
18558 @itemx info or1k spr @var{register}
18559 @itemx info or1k spr @var{groupno} @var{registerno}
18560 @itemx info or1k spr @var{registerno}
18561 Shows information about specified spr register.
18564 @item spr @var{group} @var{register} @var{value}
18565 @itemx spr @var{register @var{value}}
18566 @itemx spr @var{groupno} @var{registerno @var{value}}
18567 @itemx spr @var{registerno @var{value}}
18568 Writes @var{value} to specified spr register.
18571 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18572 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18573 program execution and is thus much faster. Hardware breakpoints/watchpoint
18574 triggers can be set using:
18577 Load effective address/data
18579 Store effective address/data
18581 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18586 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18587 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18589 @code{htrace} commands:
18590 @cindex OpenRISC 1000 htrace
18593 @item hwatch @var{conditional}
18594 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18595 or Data. For example:
18597 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18599 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18603 Display information about current HW trace configuration.
18605 @item htrace trigger @var{conditional}
18606 Set starting criteria for HW trace.
18608 @item htrace qualifier @var{conditional}
18609 Set acquisition qualifier for HW trace.
18611 @item htrace stop @var{conditional}
18612 Set HW trace stopping criteria.
18614 @item htrace record [@var{data}]*
18615 Selects the data to be recorded, when qualifier is met and HW trace was
18618 @item htrace enable
18619 @itemx htrace disable
18620 Enables/disables the HW trace.
18622 @item htrace rewind [@var{filename}]
18623 Clears currently recorded trace data.
18625 If filename is specified, new trace file is made and any newly collected data
18626 will be written there.
18628 @item htrace print [@var{start} [@var{len}]]
18629 Prints trace buffer, using current record configuration.
18631 @item htrace mode continuous
18632 Set continuous trace mode.
18634 @item htrace mode suspend
18635 Set suspend trace mode.
18639 @node PowerPC Embedded
18640 @subsection PowerPC Embedded
18642 @cindex DVC register
18643 @value{GDBN} supports using the DVC (Data Value Compare) register to
18644 implement in hardware simple hardware watchpoint conditions of the form:
18647 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18648 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18651 The DVC register will be automatically used whenever @value{GDBN} detects
18652 such pattern in a condition expression. This feature is available in native
18653 @value{GDBN} running on a Linux kernel version 2.6.34 or newer.
18655 @value{GDBN} provides the following PowerPC-specific commands:
18658 @kindex set powerpc
18659 @item set powerpc soft-float
18660 @itemx show powerpc soft-float
18661 Force @value{GDBN} to use (or not use) a software floating point calling
18662 convention. By default, @value{GDBN} selects the calling convention based
18663 on the selected architecture and the provided executable file.
18665 @item set powerpc vector-abi
18666 @itemx show powerpc vector-abi
18667 Force @value{GDBN} to use the specified calling convention for vector
18668 arguments and return values. The valid options are @samp{auto};
18669 @samp{generic}, to avoid vector registers even if they are present;
18670 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18671 registers. By default, @value{GDBN} selects the calling convention
18672 based on the selected architecture and the provided executable file.
18674 @kindex target dink32
18675 @item target dink32 @var{dev}
18676 DINK32 ROM monitor.
18678 @kindex target ppcbug
18679 @item target ppcbug @var{dev}
18680 @kindex target ppcbug1
18681 @item target ppcbug1 @var{dev}
18682 PPCBUG ROM monitor for PowerPC.
18685 @item target sds @var{dev}
18686 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18689 @cindex SDS protocol
18690 The following commands specific to the SDS protocol are supported
18694 @item set sdstimeout @var{nsec}
18695 @kindex set sdstimeout
18696 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18697 default is 2 seconds.
18699 @item show sdstimeout
18700 @kindex show sdstimeout
18701 Show the current value of the SDS timeout.
18703 @item sds @var{command}
18704 @kindex sds@r{, a command}
18705 Send the specified @var{command} string to the SDS monitor.
18710 @subsection HP PA Embedded
18714 @kindex target op50n
18715 @item target op50n @var{dev}
18716 OP50N monitor, running on an OKI HPPA board.
18718 @kindex target w89k
18719 @item target w89k @var{dev}
18720 W89K monitor, running on a Winbond HPPA board.
18725 @subsection Tsqware Sparclet
18729 @value{GDBN} enables developers to debug tasks running on
18730 Sparclet targets from a Unix host.
18731 @value{GDBN} uses code that runs on
18732 both the Unix host and on the Sparclet target. The program
18733 @code{@value{GDBP}} is installed and executed on the Unix host.
18736 @item remotetimeout @var{args}
18737 @kindex remotetimeout
18738 @value{GDBN} supports the option @code{remotetimeout}.
18739 This option is set by the user, and @var{args} represents the number of
18740 seconds @value{GDBN} waits for responses.
18743 @cindex compiling, on Sparclet
18744 When compiling for debugging, include the options @samp{-g} to get debug
18745 information and @samp{-Ttext} to relocate the program to where you wish to
18746 load it on the target. You may also want to add the options @samp{-n} or
18747 @samp{-N} in order to reduce the size of the sections. Example:
18750 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18753 You can use @code{objdump} to verify that the addresses are what you intended:
18756 sparclet-aout-objdump --headers --syms prog
18759 @cindex running, on Sparclet
18761 your Unix execution search path to find @value{GDBN}, you are ready to
18762 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18763 (or @code{sparclet-aout-gdb}, depending on your installation).
18765 @value{GDBN} comes up showing the prompt:
18772 * Sparclet File:: Setting the file to debug
18773 * Sparclet Connection:: Connecting to Sparclet
18774 * Sparclet Download:: Sparclet download
18775 * Sparclet Execution:: Running and debugging
18778 @node Sparclet File
18779 @subsubsection Setting File to Debug
18781 The @value{GDBN} command @code{file} lets you choose with program to debug.
18784 (gdbslet) file prog
18788 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18789 @value{GDBN} locates
18790 the file by searching the directories listed in the command search
18792 If the file was compiled with debug information (option @samp{-g}), source
18793 files will be searched as well.
18794 @value{GDBN} locates
18795 the source files by searching the directories listed in the directory search
18796 path (@pxref{Environment, ,Your Program's Environment}).
18798 to find a file, it displays a message such as:
18801 prog: No such file or directory.
18804 When this happens, add the appropriate directories to the search paths with
18805 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18806 @code{target} command again.
18808 @node Sparclet Connection
18809 @subsubsection Connecting to Sparclet
18811 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18812 To connect to a target on serial port ``@code{ttya}'', type:
18815 (gdbslet) target sparclet /dev/ttya
18816 Remote target sparclet connected to /dev/ttya
18817 main () at ../prog.c:3
18821 @value{GDBN} displays messages like these:
18827 @node Sparclet Download
18828 @subsubsection Sparclet Download
18830 @cindex download to Sparclet
18831 Once connected to the Sparclet target,
18832 you can use the @value{GDBN}
18833 @code{load} command to download the file from the host to the target.
18834 The file name and load offset should be given as arguments to the @code{load}
18836 Since the file format is aout, the program must be loaded to the starting
18837 address. You can use @code{objdump} to find out what this value is. The load
18838 offset is an offset which is added to the VMA (virtual memory address)
18839 of each of the file's sections.
18840 For instance, if the program
18841 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18842 and bss at 0x12010170, in @value{GDBN}, type:
18845 (gdbslet) load prog 0x12010000
18846 Loading section .text, size 0xdb0 vma 0x12010000
18849 If the code is loaded at a different address then what the program was linked
18850 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18851 to tell @value{GDBN} where to map the symbol table.
18853 @node Sparclet Execution
18854 @subsubsection Running and Debugging
18856 @cindex running and debugging Sparclet programs
18857 You can now begin debugging the task using @value{GDBN}'s execution control
18858 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18859 manual for the list of commands.
18863 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18865 Starting program: prog
18866 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18867 3 char *symarg = 0;
18869 4 char *execarg = "hello!";
18874 @subsection Fujitsu Sparclite
18878 @kindex target sparclite
18879 @item target sparclite @var{dev}
18880 Fujitsu sparclite boards, used only for the purpose of loading.
18881 You must use an additional command to debug the program.
18882 For example: target remote @var{dev} using @value{GDBN} standard
18888 @subsection Zilog Z8000
18891 @cindex simulator, Z8000
18892 @cindex Zilog Z8000 simulator
18894 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18897 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18898 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18899 segmented variant). The simulator recognizes which architecture is
18900 appropriate by inspecting the object code.
18903 @item target sim @var{args}
18905 @kindex target sim@r{, with Z8000}
18906 Debug programs on a simulated CPU. If the simulator supports setup
18907 options, specify them via @var{args}.
18911 After specifying this target, you can debug programs for the simulated
18912 CPU in the same style as programs for your host computer; use the
18913 @code{file} command to load a new program image, the @code{run} command
18914 to run your program, and so on.
18916 As well as making available all the usual machine registers
18917 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18918 additional items of information as specially named registers:
18923 Counts clock-ticks in the simulator.
18926 Counts instructions run in the simulator.
18929 Execution time in 60ths of a second.
18933 You can refer to these values in @value{GDBN} expressions with the usual
18934 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18935 conditional breakpoint that suspends only after at least 5000
18936 simulated clock ticks.
18939 @subsection Atmel AVR
18942 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18943 following AVR-specific commands:
18946 @item info io_registers
18947 @kindex info io_registers@r{, AVR}
18948 @cindex I/O registers (Atmel AVR)
18949 This command displays information about the AVR I/O registers. For
18950 each register, @value{GDBN} prints its number and value.
18957 When configured for debugging CRIS, @value{GDBN} provides the
18958 following CRIS-specific commands:
18961 @item set cris-version @var{ver}
18962 @cindex CRIS version
18963 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18964 The CRIS version affects register names and sizes. This command is useful in
18965 case autodetection of the CRIS version fails.
18967 @item show cris-version
18968 Show the current CRIS version.
18970 @item set cris-dwarf2-cfi
18971 @cindex DWARF-2 CFI and CRIS
18972 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18973 Change to @samp{off} when using @code{gcc-cris} whose version is below
18976 @item show cris-dwarf2-cfi
18977 Show the current state of using DWARF-2 CFI.
18979 @item set cris-mode @var{mode}
18981 Set the current CRIS mode to @var{mode}. It should only be changed when
18982 debugging in guru mode, in which case it should be set to
18983 @samp{guru} (the default is @samp{normal}).
18985 @item show cris-mode
18986 Show the current CRIS mode.
18990 @subsection Renesas Super-H
18993 For the Renesas Super-H processor, @value{GDBN} provides these
18998 @kindex regs@r{, Super-H}
18999 Show the values of all Super-H registers.
19001 @item set sh calling-convention @var{convention}
19002 @kindex set sh calling-convention
19003 Set the calling-convention used when calling functions from @value{GDBN}.
19004 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19005 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19006 convention. If the DWARF-2 information of the called function specifies
19007 that the function follows the Renesas calling convention, the function
19008 is called using the Renesas calling convention. If the calling convention
19009 is set to @samp{renesas}, the Renesas calling convention is always used,
19010 regardless of the DWARF-2 information. This can be used to override the
19011 default of @samp{gcc} if debug information is missing, or the compiler
19012 does not emit the DWARF-2 calling convention entry for a function.
19014 @item show sh calling-convention
19015 @kindex show sh calling-convention
19016 Show the current calling convention setting.
19021 @node Architectures
19022 @section Architectures
19024 This section describes characteristics of architectures that affect
19025 all uses of @value{GDBN} with the architecture, both native and cross.
19032 * HPPA:: HP PA architecture
19033 * SPU:: Cell Broadband Engine SPU architecture
19038 @subsection x86 Architecture-specific Issues
19041 @item set struct-convention @var{mode}
19042 @kindex set struct-convention
19043 @cindex struct return convention
19044 @cindex struct/union returned in registers
19045 Set the convention used by the inferior to return @code{struct}s and
19046 @code{union}s from functions to @var{mode}. Possible values of
19047 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19048 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19049 are returned on the stack, while @code{"reg"} means that a
19050 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19051 be returned in a register.
19053 @item show struct-convention
19054 @kindex show struct-convention
19055 Show the current setting of the convention to return @code{struct}s
19064 @kindex set rstack_high_address
19065 @cindex AMD 29K register stack
19066 @cindex register stack, AMD29K
19067 @item set rstack_high_address @var{address}
19068 On AMD 29000 family processors, registers are saved in a separate
19069 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19070 extent of this stack. Normally, @value{GDBN} just assumes that the
19071 stack is ``large enough''. This may result in @value{GDBN} referencing
19072 memory locations that do not exist. If necessary, you can get around
19073 this problem by specifying the ending address of the register stack with
19074 the @code{set rstack_high_address} command. The argument should be an
19075 address, which you probably want to precede with @samp{0x} to specify in
19078 @kindex show rstack_high_address
19079 @item show rstack_high_address
19080 Display the current limit of the register stack, on AMD 29000 family
19088 See the following section.
19093 @cindex stack on Alpha
19094 @cindex stack on MIPS
19095 @cindex Alpha stack
19097 Alpha- and MIPS-based computers use an unusual stack frame, which
19098 sometimes requires @value{GDBN} to search backward in the object code to
19099 find the beginning of a function.
19101 @cindex response time, MIPS debugging
19102 To improve response time (especially for embedded applications, where
19103 @value{GDBN} may be restricted to a slow serial line for this search)
19104 you may want to limit the size of this search, using one of these
19108 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19109 @item set heuristic-fence-post @var{limit}
19110 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19111 search for the beginning of a function. A value of @var{0} (the
19112 default) means there is no limit. However, except for @var{0}, the
19113 larger the limit the more bytes @code{heuristic-fence-post} must search
19114 and therefore the longer it takes to run. You should only need to use
19115 this command when debugging a stripped executable.
19117 @item show heuristic-fence-post
19118 Display the current limit.
19122 These commands are available @emph{only} when @value{GDBN} is configured
19123 for debugging programs on Alpha or MIPS processors.
19125 Several MIPS-specific commands are available when debugging MIPS
19129 @item set mips abi @var{arg}
19130 @kindex set mips abi
19131 @cindex set ABI for MIPS
19132 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19133 values of @var{arg} are:
19137 The default ABI associated with the current binary (this is the
19148 @item show mips abi
19149 @kindex show mips abi
19150 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19153 @itemx show mipsfpu
19154 @xref{MIPS Embedded, set mipsfpu}.
19156 @item set mips mask-address @var{arg}
19157 @kindex set mips mask-address
19158 @cindex MIPS addresses, masking
19159 This command determines whether the most-significant 32 bits of 64-bit
19160 MIPS addresses are masked off. The argument @var{arg} can be
19161 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19162 setting, which lets @value{GDBN} determine the correct value.
19164 @item show mips mask-address
19165 @kindex show mips mask-address
19166 Show whether the upper 32 bits of MIPS addresses are masked off or
19169 @item set remote-mips64-transfers-32bit-regs
19170 @kindex set remote-mips64-transfers-32bit-regs
19171 This command controls compatibility with 64-bit MIPS targets that
19172 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19173 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19174 and 64 bits for other registers, set this option to @samp{on}.
19176 @item show remote-mips64-transfers-32bit-regs
19177 @kindex show remote-mips64-transfers-32bit-regs
19178 Show the current setting of compatibility with older MIPS 64 targets.
19180 @item set debug mips
19181 @kindex set debug mips
19182 This command turns on and off debugging messages for the MIPS-specific
19183 target code in @value{GDBN}.
19185 @item show debug mips
19186 @kindex show debug mips
19187 Show the current setting of MIPS debugging messages.
19193 @cindex HPPA support
19195 When @value{GDBN} is debugging the HP PA architecture, it provides the
19196 following special commands:
19199 @item set debug hppa
19200 @kindex set debug hppa
19201 This command determines whether HPPA architecture-specific debugging
19202 messages are to be displayed.
19204 @item show debug hppa
19205 Show whether HPPA debugging messages are displayed.
19207 @item maint print unwind @var{address}
19208 @kindex maint print unwind@r{, HPPA}
19209 This command displays the contents of the unwind table entry at the
19210 given @var{address}.
19216 @subsection Cell Broadband Engine SPU architecture
19217 @cindex Cell Broadband Engine
19220 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19221 it provides the following special commands:
19224 @item info spu event
19226 Display SPU event facility status. Shows current event mask
19227 and pending event status.
19229 @item info spu signal
19230 Display SPU signal notification facility status. Shows pending
19231 signal-control word and signal notification mode of both signal
19232 notification channels.
19234 @item info spu mailbox
19235 Display SPU mailbox facility status. Shows all pending entries,
19236 in order of processing, in each of the SPU Write Outbound,
19237 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19240 Display MFC DMA status. Shows all pending commands in the MFC
19241 DMA queue. For each entry, opcode, tag, class IDs, effective
19242 and local store addresses and transfer size are shown.
19244 @item info spu proxydma
19245 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19246 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19247 and local store addresses and transfer size are shown.
19251 When @value{GDBN} is debugging a combined PowerPC/SPU application
19252 on the Cell Broadband Engine, it provides in addition the following
19256 @item set spu stop-on-load @var{arg}
19258 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19259 will give control to the user when a new SPE thread enters its @code{main}
19260 function. The default is @code{off}.
19262 @item show spu stop-on-load
19264 Show whether to stop for new SPE threads.
19266 @item set spu auto-flush-cache @var{arg}
19267 Set whether to automatically flush the software-managed cache. When set to
19268 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19269 cache to be flushed whenever SPE execution stops. This provides a consistent
19270 view of PowerPC memory that is accessed via the cache. If an application
19271 does not use the software-managed cache, this option has no effect.
19273 @item show spu auto-flush-cache
19274 Show whether to automatically flush the software-managed cache.
19279 @subsection PowerPC
19280 @cindex PowerPC architecture
19282 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19283 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19284 numbers stored in the floating point registers. These values must be stored
19285 in two consecutive registers, always starting at an even register like
19286 @code{f0} or @code{f2}.
19288 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19289 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19290 @code{f2} and @code{f3} for @code{$dl1} and so on.
19292 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19293 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19296 @node Controlling GDB
19297 @chapter Controlling @value{GDBN}
19299 You can alter the way @value{GDBN} interacts with you by using the
19300 @code{set} command. For commands controlling how @value{GDBN} displays
19301 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19306 * Editing:: Command editing
19307 * Command History:: Command history
19308 * Screen Size:: Screen size
19309 * Numbers:: Numbers
19310 * ABI:: Configuring the current ABI
19311 * Messages/Warnings:: Optional warnings and messages
19312 * Debugging Output:: Optional messages about internal happenings
19313 * Other Misc Settings:: Other Miscellaneous Settings
19321 @value{GDBN} indicates its readiness to read a command by printing a string
19322 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19323 can change the prompt string with the @code{set prompt} command. For
19324 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19325 the prompt in one of the @value{GDBN} sessions so that you can always tell
19326 which one you are talking to.
19328 @emph{Note:} @code{set prompt} does not add a space for you after the
19329 prompt you set. This allows you to set a prompt which ends in a space
19330 or a prompt that does not.
19334 @item set prompt @var{newprompt}
19335 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19337 @kindex show prompt
19339 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19343 @section Command Editing
19345 @cindex command line editing
19347 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19348 @sc{gnu} library provides consistent behavior for programs which provide a
19349 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19350 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19351 substitution, and a storage and recall of command history across
19352 debugging sessions.
19354 You may control the behavior of command line editing in @value{GDBN} with the
19355 command @code{set}.
19358 @kindex set editing
19361 @itemx set editing on
19362 Enable command line editing (enabled by default).
19364 @item set editing off
19365 Disable command line editing.
19367 @kindex show editing
19369 Show whether command line editing is enabled.
19372 @xref{Command Line Editing}, for more details about the Readline
19373 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19374 encouraged to read that chapter.
19376 @node Command History
19377 @section Command History
19378 @cindex command history
19380 @value{GDBN} can keep track of the commands you type during your
19381 debugging sessions, so that you can be certain of precisely what
19382 happened. Use these commands to manage the @value{GDBN} command
19385 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19386 package, to provide the history facility. @xref{Using History
19387 Interactively}, for the detailed description of the History library.
19389 To issue a command to @value{GDBN} without affecting certain aspects of
19390 the state which is seen by users, prefix it with @samp{server }
19391 (@pxref{Server Prefix}). This
19392 means that this command will not affect the command history, nor will it
19393 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19394 pressed on a line by itself.
19396 @cindex @code{server}, command prefix
19397 The server prefix does not affect the recording of values into the value
19398 history; to print a value without recording it into the value history,
19399 use the @code{output} command instead of the @code{print} command.
19401 Here is the description of @value{GDBN} commands related to command
19405 @cindex history substitution
19406 @cindex history file
19407 @kindex set history filename
19408 @cindex @env{GDBHISTFILE}, environment variable
19409 @item set history filename @var{fname}
19410 Set the name of the @value{GDBN} command history file to @var{fname}.
19411 This is the file where @value{GDBN} reads an initial command history
19412 list, and where it writes the command history from this session when it
19413 exits. You can access this list through history expansion or through
19414 the history command editing characters listed below. This file defaults
19415 to the value of the environment variable @code{GDBHISTFILE}, or to
19416 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19419 @cindex save command history
19420 @kindex set history save
19421 @item set history save
19422 @itemx set history save on
19423 Record command history in a file, whose name may be specified with the
19424 @code{set history filename} command. By default, this option is disabled.
19426 @item set history save off
19427 Stop recording command history in a file.
19429 @cindex history size
19430 @kindex set history size
19431 @cindex @env{HISTSIZE}, environment variable
19432 @item set history size @var{size}
19433 Set the number of commands which @value{GDBN} keeps in its history list.
19434 This defaults to the value of the environment variable
19435 @code{HISTSIZE}, or to 256 if this variable is not set.
19438 History expansion assigns special meaning to the character @kbd{!}.
19439 @xref{Event Designators}, for more details.
19441 @cindex history expansion, turn on/off
19442 Since @kbd{!} is also the logical not operator in C, history expansion
19443 is off by default. If you decide to enable history expansion with the
19444 @code{set history expansion on} command, you may sometimes need to
19445 follow @kbd{!} (when it is used as logical not, in an expression) with
19446 a space or a tab to prevent it from being expanded. The readline
19447 history facilities do not attempt substitution on the strings
19448 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19450 The commands to control history expansion are:
19453 @item set history expansion on
19454 @itemx set history expansion
19455 @kindex set history expansion
19456 Enable history expansion. History expansion is off by default.
19458 @item set history expansion off
19459 Disable history expansion.
19462 @kindex show history
19464 @itemx show history filename
19465 @itemx show history save
19466 @itemx show history size
19467 @itemx show history expansion
19468 These commands display the state of the @value{GDBN} history parameters.
19469 @code{show history} by itself displays all four states.
19474 @kindex show commands
19475 @cindex show last commands
19476 @cindex display command history
19477 @item show commands
19478 Display the last ten commands in the command history.
19480 @item show commands @var{n}
19481 Print ten commands centered on command number @var{n}.
19483 @item show commands +
19484 Print ten commands just after the commands last printed.
19488 @section Screen Size
19489 @cindex size of screen
19490 @cindex pauses in output
19492 Certain commands to @value{GDBN} may produce large amounts of
19493 information output to the screen. To help you read all of it,
19494 @value{GDBN} pauses and asks you for input at the end of each page of
19495 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19496 to discard the remaining output. Also, the screen width setting
19497 determines when to wrap lines of output. Depending on what is being
19498 printed, @value{GDBN} tries to break the line at a readable place,
19499 rather than simply letting it overflow onto the following line.
19501 Normally @value{GDBN} knows the size of the screen from the terminal
19502 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19503 together with the value of the @code{TERM} environment variable and the
19504 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19505 you can override it with the @code{set height} and @code{set
19512 @kindex show height
19513 @item set height @var{lpp}
19515 @itemx set width @var{cpl}
19517 These @code{set} commands specify a screen height of @var{lpp} lines and
19518 a screen width of @var{cpl} characters. The associated @code{show}
19519 commands display the current settings.
19521 If you specify a height of zero lines, @value{GDBN} does not pause during
19522 output no matter how long the output is. This is useful if output is to a
19523 file or to an editor buffer.
19525 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19526 from wrapping its output.
19528 @item set pagination on
19529 @itemx set pagination off
19530 @kindex set pagination
19531 Turn the output pagination on or off; the default is on. Turning
19532 pagination off is the alternative to @code{set height 0}. Note that
19533 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19534 Options, -batch}) also automatically disables pagination.
19536 @item show pagination
19537 @kindex show pagination
19538 Show the current pagination mode.
19543 @cindex number representation
19544 @cindex entering numbers
19546 You can always enter numbers in octal, decimal, or hexadecimal in
19547 @value{GDBN} by the usual conventions: octal numbers begin with
19548 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19549 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19550 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19551 10; likewise, the default display for numbers---when no particular
19552 format is specified---is base 10. You can change the default base for
19553 both input and output with the commands described below.
19556 @kindex set input-radix
19557 @item set input-radix @var{base}
19558 Set the default base for numeric input. Supported choices
19559 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19560 specified either unambiguously or using the current input radix; for
19564 set input-radix 012
19565 set input-radix 10.
19566 set input-radix 0xa
19570 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19571 leaves the input radix unchanged, no matter what it was, since
19572 @samp{10}, being without any leading or trailing signs of its base, is
19573 interpreted in the current radix. Thus, if the current radix is 16,
19574 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19577 @kindex set output-radix
19578 @item set output-radix @var{base}
19579 Set the default base for numeric display. Supported choices
19580 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19581 specified either unambiguously or using the current input radix.
19583 @kindex show input-radix
19584 @item show input-radix
19585 Display the current default base for numeric input.
19587 @kindex show output-radix
19588 @item show output-radix
19589 Display the current default base for numeric display.
19591 @item set radix @r{[}@var{base}@r{]}
19595 These commands set and show the default base for both input and output
19596 of numbers. @code{set radix} sets the radix of input and output to
19597 the same base; without an argument, it resets the radix back to its
19598 default value of 10.
19603 @section Configuring the Current ABI
19605 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19606 application automatically. However, sometimes you need to override its
19607 conclusions. Use these commands to manage @value{GDBN}'s view of the
19614 One @value{GDBN} configuration can debug binaries for multiple operating
19615 system targets, either via remote debugging or native emulation.
19616 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19617 but you can override its conclusion using the @code{set osabi} command.
19618 One example where this is useful is in debugging of binaries which use
19619 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19620 not have the same identifying marks that the standard C library for your
19625 Show the OS ABI currently in use.
19628 With no argument, show the list of registered available OS ABI's.
19630 @item set osabi @var{abi}
19631 Set the current OS ABI to @var{abi}.
19634 @cindex float promotion
19636 Generally, the way that an argument of type @code{float} is passed to a
19637 function depends on whether the function is prototyped. For a prototyped
19638 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19639 according to the architecture's convention for @code{float}. For unprototyped
19640 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19641 @code{double} and then passed.
19643 Unfortunately, some forms of debug information do not reliably indicate whether
19644 a function is prototyped. If @value{GDBN} calls a function that is not marked
19645 as prototyped, it consults @kbd{set coerce-float-to-double}.
19648 @kindex set coerce-float-to-double
19649 @item set coerce-float-to-double
19650 @itemx set coerce-float-to-double on
19651 Arguments of type @code{float} will be promoted to @code{double} when passed
19652 to an unprototyped function. This is the default setting.
19654 @item set coerce-float-to-double off
19655 Arguments of type @code{float} will be passed directly to unprototyped
19658 @kindex show coerce-float-to-double
19659 @item show coerce-float-to-double
19660 Show the current setting of promoting @code{float} to @code{double}.
19664 @kindex show cp-abi
19665 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19666 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19667 used to build your application. @value{GDBN} only fully supports
19668 programs with a single C@t{++} ABI; if your program contains code using
19669 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19670 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19671 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19672 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19673 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19674 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19679 Show the C@t{++} ABI currently in use.
19682 With no argument, show the list of supported C@t{++} ABI's.
19684 @item set cp-abi @var{abi}
19685 @itemx set cp-abi auto
19686 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19689 @node Messages/Warnings
19690 @section Optional Warnings and Messages
19692 @cindex verbose operation
19693 @cindex optional warnings
19694 By default, @value{GDBN} is silent about its inner workings. If you are
19695 running on a slow machine, you may want to use the @code{set verbose}
19696 command. This makes @value{GDBN} tell you when it does a lengthy
19697 internal operation, so you will not think it has crashed.
19699 Currently, the messages controlled by @code{set verbose} are those
19700 which announce that the symbol table for a source file is being read;
19701 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19704 @kindex set verbose
19705 @item set verbose on
19706 Enables @value{GDBN} output of certain informational messages.
19708 @item set verbose off
19709 Disables @value{GDBN} output of certain informational messages.
19711 @kindex show verbose
19713 Displays whether @code{set verbose} is on or off.
19716 By default, if @value{GDBN} encounters bugs in the symbol table of an
19717 object file, it is silent; but if you are debugging a compiler, you may
19718 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19723 @kindex set complaints
19724 @item set complaints @var{limit}
19725 Permits @value{GDBN} to output @var{limit} complaints about each type of
19726 unusual symbols before becoming silent about the problem. Set
19727 @var{limit} to zero to suppress all complaints; set it to a large number
19728 to prevent complaints from being suppressed.
19730 @kindex show complaints
19731 @item show complaints
19732 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19736 @anchor{confirmation requests}
19737 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19738 lot of stupid questions to confirm certain commands. For example, if
19739 you try to run a program which is already running:
19743 The program being debugged has been started already.
19744 Start it from the beginning? (y or n)
19747 If you are willing to unflinchingly face the consequences of your own
19748 commands, you can disable this ``feature'':
19752 @kindex set confirm
19754 @cindex confirmation
19755 @cindex stupid questions
19756 @item set confirm off
19757 Disables confirmation requests. Note that running @value{GDBN} with
19758 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19759 automatically disables confirmation requests.
19761 @item set confirm on
19762 Enables confirmation requests (the default).
19764 @kindex show confirm
19766 Displays state of confirmation requests.
19770 @cindex command tracing
19771 If you need to debug user-defined commands or sourced files you may find it
19772 useful to enable @dfn{command tracing}. In this mode each command will be
19773 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19774 quantity denoting the call depth of each command.
19777 @kindex set trace-commands
19778 @cindex command scripts, debugging
19779 @item set trace-commands on
19780 Enable command tracing.
19781 @item set trace-commands off
19782 Disable command tracing.
19783 @item show trace-commands
19784 Display the current state of command tracing.
19787 @node Debugging Output
19788 @section Optional Messages about Internal Happenings
19789 @cindex optional debugging messages
19791 @value{GDBN} has commands that enable optional debugging messages from
19792 various @value{GDBN} subsystems; normally these commands are of
19793 interest to @value{GDBN} maintainers, or when reporting a bug. This
19794 section documents those commands.
19797 @kindex set exec-done-display
19798 @item set exec-done-display
19799 Turns on or off the notification of asynchronous commands'
19800 completion. When on, @value{GDBN} will print a message when an
19801 asynchronous command finishes its execution. The default is off.
19802 @kindex show exec-done-display
19803 @item show exec-done-display
19804 Displays the current setting of asynchronous command completion
19807 @cindex gdbarch debugging info
19808 @cindex architecture debugging info
19809 @item set debug arch
19810 Turns on or off display of gdbarch debugging info. The default is off
19812 @item show debug arch
19813 Displays the current state of displaying gdbarch debugging info.
19814 @item set debug aix-thread
19815 @cindex AIX threads
19816 Display debugging messages about inner workings of the AIX thread
19818 @item show debug aix-thread
19819 Show the current state of AIX thread debugging info display.
19820 @item set debug dwarf2-die
19821 @cindex DWARF2 DIEs
19822 Dump DWARF2 DIEs after they are read in.
19823 The value is the number of nesting levels to print.
19824 A value of zero turns off the display.
19825 @item show debug dwarf2-die
19826 Show the current state of DWARF2 DIE debugging.
19827 @item set debug displaced
19828 @cindex displaced stepping debugging info
19829 Turns on or off display of @value{GDBN} debugging info for the
19830 displaced stepping support. The default is off.
19831 @item show debug displaced
19832 Displays the current state of displaying @value{GDBN} debugging info
19833 related to displaced stepping.
19834 @item set debug event
19835 @cindex event debugging info
19836 Turns on or off display of @value{GDBN} event debugging info. The
19838 @item show debug event
19839 Displays the current state of displaying @value{GDBN} event debugging
19841 @item set debug expression
19842 @cindex expression debugging info
19843 Turns on or off display of debugging info about @value{GDBN}
19844 expression parsing. The default is off.
19845 @item show debug expression
19846 Displays the current state of displaying debugging info about
19847 @value{GDBN} expression parsing.
19848 @item set debug frame
19849 @cindex frame debugging info
19850 Turns on or off display of @value{GDBN} frame debugging info. The
19852 @item show debug frame
19853 Displays the current state of displaying @value{GDBN} frame debugging
19855 @item set debug gnu-nat
19856 @cindex @sc{gnu}/Hurd debug messages
19857 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19858 @item show debug gnu-nat
19859 Show the current state of @sc{gnu}/Hurd debugging messages.
19860 @item set debug infrun
19861 @cindex inferior debugging info
19862 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19863 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19864 for implementing operations such as single-stepping the inferior.
19865 @item show debug infrun
19866 Displays the current state of @value{GDBN} inferior debugging.
19867 @item set debug lin-lwp
19868 @cindex @sc{gnu}/Linux LWP debug messages
19869 @cindex Linux lightweight processes
19870 Turns on or off debugging messages from the Linux LWP debug support.
19871 @item show debug lin-lwp
19872 Show the current state of Linux LWP debugging messages.
19873 @item set debug lin-lwp-async
19874 @cindex @sc{gnu}/Linux LWP async debug messages
19875 @cindex Linux lightweight processes
19876 Turns on or off debugging messages from the Linux LWP async debug support.
19877 @item show debug lin-lwp-async
19878 Show the current state of Linux LWP async debugging messages.
19879 @item set debug observer
19880 @cindex observer debugging info
19881 Turns on or off display of @value{GDBN} observer debugging. This
19882 includes info such as the notification of observable events.
19883 @item show debug observer
19884 Displays the current state of observer debugging.
19885 @item set debug overload
19886 @cindex C@t{++} overload debugging info
19887 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19888 info. This includes info such as ranking of functions, etc. The default
19890 @item show debug overload
19891 Displays the current state of displaying @value{GDBN} C@t{++} overload
19893 @cindex expression parser, debugging info
19894 @cindex debug expression parser
19895 @item set debug parser
19896 Turns on or off the display of expression parser debugging output.
19897 Internally, this sets the @code{yydebug} variable in the expression
19898 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19899 details. The default is off.
19900 @item show debug parser
19901 Show the current state of expression parser debugging.
19902 @cindex packets, reporting on stdout
19903 @cindex serial connections, debugging
19904 @cindex debug remote protocol
19905 @cindex remote protocol debugging
19906 @cindex display remote packets
19907 @item set debug remote
19908 Turns on or off display of reports on all packets sent back and forth across
19909 the serial line to the remote machine. The info is printed on the
19910 @value{GDBN} standard output stream. The default is off.
19911 @item show debug remote
19912 Displays the state of display of remote packets.
19913 @item set debug serial
19914 Turns on or off display of @value{GDBN} serial debugging info. The
19916 @item show debug serial
19917 Displays the current state of displaying @value{GDBN} serial debugging
19919 @item set debug solib-frv
19920 @cindex FR-V shared-library debugging
19921 Turns on or off debugging messages for FR-V shared-library code.
19922 @item show debug solib-frv
19923 Display the current state of FR-V shared-library code debugging
19925 @item set debug target
19926 @cindex target debugging info
19927 Turns on or off display of @value{GDBN} target debugging info. This info
19928 includes what is going on at the target level of GDB, as it happens. The
19929 default is 0. Set it to 1 to track events, and to 2 to also track the
19930 value of large memory transfers. Changes to this flag do not take effect
19931 until the next time you connect to a target or use the @code{run} command.
19932 @item show debug target
19933 Displays the current state of displaying @value{GDBN} target debugging
19935 @item set debug timestamp
19936 @cindex timestampping debugging info
19937 Turns on or off display of timestamps with @value{GDBN} debugging info.
19938 When enabled, seconds and microseconds are displayed before each debugging
19940 @item show debug timestamp
19941 Displays the current state of displaying timestamps with @value{GDBN}
19943 @item set debugvarobj
19944 @cindex variable object debugging info
19945 Turns on or off display of @value{GDBN} variable object debugging
19946 info. The default is off.
19947 @item show debugvarobj
19948 Displays the current state of displaying @value{GDBN} variable object
19950 @item set debug xml
19951 @cindex XML parser debugging
19952 Turns on or off debugging messages for built-in XML parsers.
19953 @item show debug xml
19954 Displays the current state of XML debugging messages.
19957 @node Other Misc Settings
19958 @section Other Miscellaneous Settings
19959 @cindex miscellaneous settings
19962 @kindex set interactive-mode
19963 @item set interactive-mode
19964 If @code{on}, forces @value{GDBN} to operate interactively.
19965 If @code{off}, forces @value{GDBN} to operate non-interactively,
19966 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19967 based on whether the debugger was started in a terminal or not.
19969 In the vast majority of cases, the debugger should be able to guess
19970 correctly which mode should be used. But this setting can be useful
19971 in certain specific cases, such as running a MinGW @value{GDBN}
19972 inside a cygwin window.
19974 @kindex show interactive-mode
19975 @item show interactive-mode
19976 Displays whether the debugger is operating in interactive mode or not.
19979 @node Extending GDB
19980 @chapter Extending @value{GDBN}
19981 @cindex extending GDB
19983 @value{GDBN} provides two mechanisms for extension. The first is based
19984 on composition of @value{GDBN} commands, and the second is based on the
19985 Python scripting language.
19987 To facilitate the use of these extensions, @value{GDBN} is capable
19988 of evaluating the contents of a file. When doing so, @value{GDBN}
19989 can recognize which scripting language is being used by looking at
19990 the filename extension. Files with an unrecognized filename extension
19991 are always treated as a @value{GDBN} Command Files.
19992 @xref{Command Files,, Command files}.
19994 You can control how @value{GDBN} evaluates these files with the following
19998 @kindex set script-extension
19999 @kindex show script-extension
20000 @item set script-extension off
20001 All scripts are always evaluated as @value{GDBN} Command Files.
20003 @item set script-extension soft
20004 The debugger determines the scripting language based on filename
20005 extension. If this scripting language is supported, @value{GDBN}
20006 evaluates the script using that language. Otherwise, it evaluates
20007 the file as a @value{GDBN} Command File.
20009 @item set script-extension strict
20010 The debugger determines the scripting language based on filename
20011 extension, and evaluates the script using that language. If the
20012 language is not supported, then the evaluation fails.
20014 @item show script-extension
20015 Display the current value of the @code{script-extension} option.
20020 * Sequences:: Canned Sequences of Commands
20021 * Python:: Scripting @value{GDBN} using Python
20025 @section Canned Sequences of Commands
20027 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20028 Command Lists}), @value{GDBN} provides two ways to store sequences of
20029 commands for execution as a unit: user-defined commands and command
20033 * Define:: How to define your own commands
20034 * Hooks:: Hooks for user-defined commands
20035 * Command Files:: How to write scripts of commands to be stored in a file
20036 * Output:: Commands for controlled output
20040 @subsection User-defined Commands
20042 @cindex user-defined command
20043 @cindex arguments, to user-defined commands
20044 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20045 which you assign a new name as a command. This is done with the
20046 @code{define} command. User commands may accept up to 10 arguments
20047 separated by whitespace. Arguments are accessed within the user command
20048 via @code{$arg0@dots{}$arg9}. A trivial example:
20052 print $arg0 + $arg1 + $arg2
20057 To execute the command use:
20064 This defines the command @code{adder}, which prints the sum of
20065 its three arguments. Note the arguments are text substitutions, so they may
20066 reference variables, use complex expressions, or even perform inferior
20069 @cindex argument count in user-defined commands
20070 @cindex how many arguments (user-defined commands)
20071 In addition, @code{$argc} may be used to find out how many arguments have
20072 been passed. This expands to a number in the range 0@dots{}10.
20077 print $arg0 + $arg1
20080 print $arg0 + $arg1 + $arg2
20088 @item define @var{commandname}
20089 Define a command named @var{commandname}. If there is already a command
20090 by that name, you are asked to confirm that you want to redefine it.
20091 @var{commandname} may be a bare command name consisting of letters,
20092 numbers, dashes, and underscores. It may also start with any predefined
20093 prefix command. For example, @samp{define target my-target} creates
20094 a user-defined @samp{target my-target} command.
20096 The definition of the command is made up of other @value{GDBN} command lines,
20097 which are given following the @code{define} command. The end of these
20098 commands is marked by a line containing @code{end}.
20101 @kindex end@r{ (user-defined commands)}
20102 @item document @var{commandname}
20103 Document the user-defined command @var{commandname}, so that it can be
20104 accessed by @code{help}. The command @var{commandname} must already be
20105 defined. This command reads lines of documentation just as @code{define}
20106 reads the lines of the command definition, ending with @code{end}.
20107 After the @code{document} command is finished, @code{help} on command
20108 @var{commandname} displays the documentation you have written.
20110 You may use the @code{document} command again to change the
20111 documentation of a command. Redefining the command with @code{define}
20112 does not change the documentation.
20114 @kindex dont-repeat
20115 @cindex don't repeat command
20117 Used inside a user-defined command, this tells @value{GDBN} that this
20118 command should not be repeated when the user hits @key{RET}
20119 (@pxref{Command Syntax, repeat last command}).
20121 @kindex help user-defined
20122 @item help user-defined
20123 List all user-defined commands, with the first line of the documentation
20128 @itemx show user @var{commandname}
20129 Display the @value{GDBN} commands used to define @var{commandname} (but
20130 not its documentation). If no @var{commandname} is given, display the
20131 definitions for all user-defined commands.
20133 @cindex infinite recursion in user-defined commands
20134 @kindex show max-user-call-depth
20135 @kindex set max-user-call-depth
20136 @item show max-user-call-depth
20137 @itemx set max-user-call-depth
20138 The value of @code{max-user-call-depth} controls how many recursion
20139 levels are allowed in user-defined commands before @value{GDBN} suspects an
20140 infinite recursion and aborts the command.
20143 In addition to the above commands, user-defined commands frequently
20144 use control flow commands, described in @ref{Command Files}.
20146 When user-defined commands are executed, the
20147 commands of the definition are not printed. An error in any command
20148 stops execution of the user-defined command.
20150 If used interactively, commands that would ask for confirmation proceed
20151 without asking when used inside a user-defined command. Many @value{GDBN}
20152 commands that normally print messages to say what they are doing omit the
20153 messages when used in a user-defined command.
20156 @subsection User-defined Command Hooks
20157 @cindex command hooks
20158 @cindex hooks, for commands
20159 @cindex hooks, pre-command
20162 You may define @dfn{hooks}, which are a special kind of user-defined
20163 command. Whenever you run the command @samp{foo}, if the user-defined
20164 command @samp{hook-foo} exists, it is executed (with no arguments)
20165 before that command.
20167 @cindex hooks, post-command
20169 A hook may also be defined which is run after the command you executed.
20170 Whenever you run the command @samp{foo}, if the user-defined command
20171 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20172 that command. Post-execution hooks may exist simultaneously with
20173 pre-execution hooks, for the same command.
20175 It is valid for a hook to call the command which it hooks. If this
20176 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20178 @c It would be nice if hookpost could be passed a parameter indicating
20179 @c if the command it hooks executed properly or not. FIXME!
20181 @kindex stop@r{, a pseudo-command}
20182 In addition, a pseudo-command, @samp{stop} exists. Defining
20183 (@samp{hook-stop}) makes the associated commands execute every time
20184 execution stops in your program: before breakpoint commands are run,
20185 displays are printed, or the stack frame is printed.
20187 For example, to ignore @code{SIGALRM} signals while
20188 single-stepping, but treat them normally during normal execution,
20193 handle SIGALRM nopass
20197 handle SIGALRM pass
20200 define hook-continue
20201 handle SIGALRM pass
20205 As a further example, to hook at the beginning and end of the @code{echo}
20206 command, and to add extra text to the beginning and end of the message,
20214 define hookpost-echo
20218 (@value{GDBP}) echo Hello World
20219 <<<---Hello World--->>>
20224 You can define a hook for any single-word command in @value{GDBN}, but
20225 not for command aliases; you should define a hook for the basic command
20226 name, e.g.@: @code{backtrace} rather than @code{bt}.
20227 @c FIXME! So how does Joe User discover whether a command is an alias
20229 You can hook a multi-word command by adding @code{hook-} or
20230 @code{hookpost-} to the last word of the command, e.g.@:
20231 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20233 If an error occurs during the execution of your hook, execution of
20234 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20235 (before the command that you actually typed had a chance to run).
20237 If you try to define a hook which does not match any known command, you
20238 get a warning from the @code{define} command.
20240 @node Command Files
20241 @subsection Command Files
20243 @cindex command files
20244 @cindex scripting commands
20245 A command file for @value{GDBN} is a text file made of lines that are
20246 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20247 also be included. An empty line in a command file does nothing; it
20248 does not mean to repeat the last command, as it would from the
20251 You can request the execution of a command file with the @code{source}
20252 command. Note that the @code{source} command is also used to evaluate
20253 scripts that are not Command Files. The exact behavior can be configured
20254 using the @code{script-extension} setting.
20255 @xref{Extending GDB,, Extending GDB}.
20259 @cindex execute commands from a file
20260 @item source [-s] [-v] @var{filename}
20261 Execute the command file @var{filename}.
20264 The lines in a command file are generally executed sequentially,
20265 unless the order of execution is changed by one of the
20266 @emph{flow-control commands} described below. The commands are not
20267 printed as they are executed. An error in any command terminates
20268 execution of the command file and control is returned to the console.
20270 @value{GDBN} first searches for @var{filename} in the current directory.
20271 If the file is not found there, and @var{filename} does not specify a
20272 directory, then @value{GDBN} also looks for the file on the source search path
20273 (specified with the @samp{directory} command);
20274 except that @file{$cdir} is not searched because the compilation directory
20275 is not relevant to scripts.
20277 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20278 on the search path even if @var{filename} specifies a directory.
20279 The search is done by appending @var{filename} to each element of the
20280 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20281 and the search path contains @file{/home/user} then @value{GDBN} will
20282 look for the script @file{/home/user/mylib/myscript}.
20283 The search is also done if @var{filename} is an absolute path.
20284 For example, if @var{filename} is @file{/tmp/myscript} and
20285 the search path contains @file{/home/user} then @value{GDBN} will
20286 look for the script @file{/home/user/tmp/myscript}.
20287 For DOS-like systems, if @var{filename} contains a drive specification,
20288 it is stripped before concatenation. For example, if @var{filename} is
20289 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20290 will look for the script @file{c:/tmp/myscript}.
20292 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20293 each command as it is executed. The option must be given before
20294 @var{filename}, and is interpreted as part of the filename anywhere else.
20296 Commands that would ask for confirmation if used interactively proceed
20297 without asking when used in a command file. Many @value{GDBN} commands that
20298 normally print messages to say what they are doing omit the messages
20299 when called from command files.
20301 @value{GDBN} also accepts command input from standard input. In this
20302 mode, normal output goes to standard output and error output goes to
20303 standard error. Errors in a command file supplied on standard input do
20304 not terminate execution of the command file---execution continues with
20308 gdb < cmds > log 2>&1
20311 (The syntax above will vary depending on the shell used.) This example
20312 will execute commands from the file @file{cmds}. All output and errors
20313 would be directed to @file{log}.
20315 Since commands stored on command files tend to be more general than
20316 commands typed interactively, they frequently need to deal with
20317 complicated situations, such as different or unexpected values of
20318 variables and symbols, changes in how the program being debugged is
20319 built, etc. @value{GDBN} provides a set of flow-control commands to
20320 deal with these complexities. Using these commands, you can write
20321 complex scripts that loop over data structures, execute commands
20322 conditionally, etc.
20329 This command allows to include in your script conditionally executed
20330 commands. The @code{if} command takes a single argument, which is an
20331 expression to evaluate. It is followed by a series of commands that
20332 are executed only if the expression is true (its value is nonzero).
20333 There can then optionally be an @code{else} line, followed by a series
20334 of commands that are only executed if the expression was false. The
20335 end of the list is marked by a line containing @code{end}.
20339 This command allows to write loops. Its syntax is similar to
20340 @code{if}: the command takes a single argument, which is an expression
20341 to evaluate, and must be followed by the commands to execute, one per
20342 line, terminated by an @code{end}. These commands are called the
20343 @dfn{body} of the loop. The commands in the body of @code{while} are
20344 executed repeatedly as long as the expression evaluates to true.
20348 This command exits the @code{while} loop in whose body it is included.
20349 Execution of the script continues after that @code{while}s @code{end}
20352 @kindex loop_continue
20353 @item loop_continue
20354 This command skips the execution of the rest of the body of commands
20355 in the @code{while} loop in whose body it is included. Execution
20356 branches to the beginning of the @code{while} loop, where it evaluates
20357 the controlling expression.
20359 @kindex end@r{ (if/else/while commands)}
20361 Terminate the block of commands that are the body of @code{if},
20362 @code{else}, or @code{while} flow-control commands.
20367 @subsection Commands for Controlled Output
20369 During the execution of a command file or a user-defined command, normal
20370 @value{GDBN} output is suppressed; the only output that appears is what is
20371 explicitly printed by the commands in the definition. This section
20372 describes three commands useful for generating exactly the output you
20377 @item echo @var{text}
20378 @c I do not consider backslash-space a standard C escape sequence
20379 @c because it is not in ANSI.
20380 Print @var{text}. Nonprinting characters can be included in
20381 @var{text} using C escape sequences, such as @samp{\n} to print a
20382 newline. @strong{No newline is printed unless you specify one.}
20383 In addition to the standard C escape sequences, a backslash followed
20384 by a space stands for a space. This is useful for displaying a
20385 string with spaces at the beginning or the end, since leading and
20386 trailing spaces are otherwise trimmed from all arguments.
20387 To print @samp{@w{ }and foo =@w{ }}, use the command
20388 @samp{echo \@w{ }and foo = \@w{ }}.
20390 A backslash at the end of @var{text} can be used, as in C, to continue
20391 the command onto subsequent lines. For example,
20394 echo This is some text\n\
20395 which is continued\n\
20396 onto several lines.\n
20399 produces the same output as
20402 echo This is some text\n
20403 echo which is continued\n
20404 echo onto several lines.\n
20408 @item output @var{expression}
20409 Print the value of @var{expression} and nothing but that value: no
20410 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20411 value history either. @xref{Expressions, ,Expressions}, for more information
20414 @item output/@var{fmt} @var{expression}
20415 Print the value of @var{expression} in format @var{fmt}. You can use
20416 the same formats as for @code{print}. @xref{Output Formats,,Output
20417 Formats}, for more information.
20420 @item printf @var{template}, @var{expressions}@dots{}
20421 Print the values of one or more @var{expressions} under the control of
20422 the string @var{template}. To print several values, make
20423 @var{expressions} be a comma-separated list of individual expressions,
20424 which may be either numbers or pointers. Their values are printed as
20425 specified by @var{template}, exactly as a C program would do by
20426 executing the code below:
20429 printf (@var{template}, @var{expressions}@dots{});
20432 As in @code{C} @code{printf}, ordinary characters in @var{template}
20433 are printed verbatim, while @dfn{conversion specification} introduced
20434 by the @samp{%} character cause subsequent @var{expressions} to be
20435 evaluated, their values converted and formatted according to type and
20436 style information encoded in the conversion specifications, and then
20439 For example, you can print two values in hex like this:
20442 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20445 @code{printf} supports all the standard @code{C} conversion
20446 specifications, including the flags and modifiers between the @samp{%}
20447 character and the conversion letter, with the following exceptions:
20451 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20454 The modifier @samp{*} is not supported for specifying precision or
20458 The @samp{'} flag (for separation of digits into groups according to
20459 @code{LC_NUMERIC'}) is not supported.
20462 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20466 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20469 The conversion letters @samp{a} and @samp{A} are not supported.
20473 Note that the @samp{ll} type modifier is supported only if the
20474 underlying @code{C} implementation used to build @value{GDBN} supports
20475 the @code{long long int} type, and the @samp{L} type modifier is
20476 supported only if @code{long double} type is available.
20478 As in @code{C}, @code{printf} supports simple backslash-escape
20479 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20480 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20481 single character. Octal and hexadecimal escape sequences are not
20484 Additionally, @code{printf} supports conversion specifications for DFP
20485 (@dfn{Decimal Floating Point}) types using the following length modifiers
20486 together with a floating point specifier.
20491 @samp{H} for printing @code{Decimal32} types.
20494 @samp{D} for printing @code{Decimal64} types.
20497 @samp{DD} for printing @code{Decimal128} types.
20500 If the underlying @code{C} implementation used to build @value{GDBN} has
20501 support for the three length modifiers for DFP types, other modifiers
20502 such as width and precision will also be available for @value{GDBN} to use.
20504 In case there is no such @code{C} support, no additional modifiers will be
20505 available and the value will be printed in the standard way.
20507 Here's an example of printing DFP types using the above conversion letters:
20509 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20513 @item eval @var{template}, @var{expressions}@dots{}
20514 Convert the values of one or more @var{expressions} under the control of
20515 the string @var{template} to a command line, and call it.
20520 @section Scripting @value{GDBN} using Python
20521 @cindex python scripting
20522 @cindex scripting with python
20524 You can script @value{GDBN} using the @uref{http://www.python.org/,
20525 Python programming language}. This feature is available only if
20526 @value{GDBN} was configured using @option{--with-python}.
20528 @cindex python directory
20529 Python scripts used by @value{GDBN} should be installed in
20530 @file{@var{data-directory}/python}, where @var{data-directory} is
20531 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20532 This directory, known as the @dfn{python directory},
20533 is automatically added to the Python Search Path in order to allow
20534 the Python interpreter to locate all scripts installed at this location.
20537 * Python Commands:: Accessing Python from @value{GDBN}.
20538 * Python API:: Accessing @value{GDBN} from Python.
20539 * Auto-loading:: Automatically loading Python code.
20540 * Python modules:: Python modules provided by @value{GDBN}.
20543 @node Python Commands
20544 @subsection Python Commands
20545 @cindex python commands
20546 @cindex commands to access python
20548 @value{GDBN} provides one command for accessing the Python interpreter,
20549 and one related setting:
20553 @item python @r{[}@var{code}@r{]}
20554 The @code{python} command can be used to evaluate Python code.
20556 If given an argument, the @code{python} command will evaluate the
20557 argument as a Python command. For example:
20560 (@value{GDBP}) python print 23
20564 If you do not provide an argument to @code{python}, it will act as a
20565 multi-line command, like @code{define}. In this case, the Python
20566 script is made up of subsequent command lines, given after the
20567 @code{python} command. This command list is terminated using a line
20568 containing @code{end}. For example:
20571 (@value{GDBP}) python
20573 End with a line saying just "end".
20579 @kindex maint set python print-stack
20580 @item maint set python print-stack
20581 By default, @value{GDBN} will print a stack trace when an error occurs
20582 in a Python script. This can be controlled using @code{maint set
20583 python print-stack}: if @code{on}, the default, then Python stack
20584 printing is enabled; if @code{off}, then Python stack printing is
20588 It is also possible to execute a Python script from the @value{GDBN}
20592 @item source @file{script-name}
20593 The script name must end with @samp{.py} and @value{GDBN} must be configured
20594 to recognize the script language based on filename extension using
20595 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20597 @item python execfile ("script-name")
20598 This method is based on the @code{execfile} Python built-in function,
20599 and thus is always available.
20603 @subsection Python API
20605 @cindex programming in python
20607 @cindex python stdout
20608 @cindex python pagination
20609 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20610 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20611 A Python program which outputs to one of these streams may have its
20612 output interrupted by the user (@pxref{Screen Size}). In this
20613 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20616 * Basic Python:: Basic Python Functions.
20617 * Exception Handling::
20618 * Values From Inferior::
20619 * Types In Python:: Python representation of types.
20620 * Pretty Printing API:: Pretty-printing values.
20621 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20622 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20623 * Inferiors In Python:: Python representation of inferiors (processes)
20624 * Threads In Python:: Accessing inferior threads from Python.
20625 * Commands In Python:: Implementing new commands in Python.
20626 * Parameters In Python:: Adding new @value{GDBN} parameters.
20627 * Functions In Python:: Writing new convenience functions.
20628 * Progspaces In Python:: Program spaces.
20629 * Objfiles In Python:: Object files.
20630 * Frames In Python:: Accessing inferior stack frames from Python.
20631 * Blocks In Python:: Accessing frame blocks from Python.
20632 * Symbols In Python:: Python representation of symbols.
20633 * Symbol Tables In Python:: Python representation of symbol tables.
20634 * Lazy Strings In Python:: Python representation of lazy strings.
20635 * Breakpoints In Python:: Manipulating breakpoints using Python.
20639 @subsubsection Basic Python
20641 @cindex python functions
20642 @cindex python module
20644 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20645 methods and classes added by @value{GDBN} are placed in this module.
20646 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20647 use in all scripts evaluated by the @code{python} command.
20649 @findex gdb.PYTHONDIR
20651 A string containing the python directory (@pxref{Python}).
20654 @findex gdb.execute
20655 @defun execute command [from_tty] [to_string]
20656 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20657 If a GDB exception happens while @var{command} runs, it is
20658 translated as described in @ref{Exception Handling,,Exception Handling}.
20660 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20661 command as having originated from the user invoking it interactively.
20662 It must be a boolean value. If omitted, it defaults to @code{False}.
20664 By default, any output produced by @var{command} is sent to
20665 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20666 @code{True}, then output will be collected by @code{gdb.execute} and
20667 returned as a string. The default is @code{False}, in which case the
20668 return value is @code{None}. If @var{to_string} is @code{True}, the
20669 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20670 and height, and its pagination will be disabled; @pxref{Screen Size}.
20673 @findex gdb.breakpoints
20675 Return a sequence holding all of @value{GDBN}'s breakpoints.
20676 @xref{Breakpoints In Python}, for more information.
20679 @findex gdb.parameter
20680 @defun parameter parameter
20681 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20682 string naming the parameter to look up; @var{parameter} may contain
20683 spaces if the parameter has a multi-part name. For example,
20684 @samp{print object} is a valid parameter name.
20686 If the named parameter does not exist, this function throws a
20687 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20688 a Python value of the appropriate type, and returned.
20691 @findex gdb.history
20692 @defun history number
20693 Return a value from @value{GDBN}'s value history (@pxref{Value
20694 History}). @var{number} indicates which history element to return.
20695 If @var{number} is negative, then @value{GDBN} will take its absolute value
20696 and count backward from the last element (i.e., the most recent element) to
20697 find the value to return. If @var{number} is zero, then @value{GDBN} will
20698 return the most recent element. If the element specified by @var{number}
20699 doesn't exist in the value history, a @code{RuntimeError} exception will be
20702 If no exception is raised, the return value is always an instance of
20703 @code{gdb.Value} (@pxref{Values From Inferior}).
20706 @findex gdb.parse_and_eval
20707 @defun parse_and_eval expression
20708 Parse @var{expression} as an expression in the current language,
20709 evaluate it, and return the result as a @code{gdb.Value}.
20710 @var{expression} must be a string.
20712 This function can be useful when implementing a new command
20713 (@pxref{Commands In Python}), as it provides a way to parse the
20714 command's argument as an expression. It is also useful simply to
20715 compute values, for example, it is the only way to get the value of a
20716 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20719 @findex gdb.post_event
20720 @defun post_event event
20721 Put @var{event}, a callable object taking no arguments, into
20722 @value{GDBN}'s internal event queue. This callable will be invoked at
20723 some later point, during @value{GDBN}'s event processing. Events
20724 posted using @code{post_event} will be run in the order in which they
20725 were posted; however, there is no way to know when they will be
20726 processed relative to other events inside @value{GDBN}.
20728 @value{GDBN} is not thread-safe. If your Python program uses multiple
20729 threads, you must be careful to only call @value{GDBN}-specific
20730 functions in the main @value{GDBN} thread. @code{post_event} ensures
20734 (@value{GDBP}) python
20738 > def __init__(self, message):
20739 > self.message = message;
20740 > def __call__(self):
20741 > gdb.write(self.message)
20743 >class MyThread1 (threading.Thread):
20745 > gdb.post_event(Writer("Hello "))
20747 >class MyThread2 (threading.Thread):
20749 > gdb.post_event(Writer("World\n"))
20751 >MyThread1().start()
20752 >MyThread2().start()
20754 (@value{GDBP}) Hello World
20759 @defun write string
20760 Print a string to @value{GDBN}'s paginated standard output stream.
20761 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20762 call this function.
20767 Flush @value{GDBN}'s paginated standard output stream. Flushing
20768 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20772 @findex gdb.target_charset
20773 @defun target_charset
20774 Return the name of the current target character set (@pxref{Character
20775 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20776 that @samp{auto} is never returned.
20779 @findex gdb.target_wide_charset
20780 @defun target_wide_charset
20781 Return the name of the current target wide character set
20782 (@pxref{Character Sets}). This differs from
20783 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20787 @findex gdb.solib_name
20788 @defun solib_name address
20789 Return the name of the shared library holding the given @var{address}
20790 as a string, or @code{None}.
20793 @findex gdb.decode_line
20794 @defun decode_line @r{[}expression@r{]}
20795 Return locations of the line specified by @var{expression}, or of the
20796 current line if no argument was given. This function returns a Python
20797 tuple containing two elements. The first element contains a string
20798 holding any unparsed section of @var{expression} (or @code{None} if
20799 the expression has been fully parsed). The second element contains
20800 either @code{None} or another tuple that contains all the locations
20801 that match the expression represented as @code{gdb.Symtab_and_line}
20802 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
20803 provided, it is decoded the way that @value{GDBN}'s inbuilt
20804 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
20807 @node Exception Handling
20808 @subsubsection Exception Handling
20809 @cindex python exceptions
20810 @cindex exceptions, python
20812 When executing the @code{python} command, Python exceptions
20813 uncaught within the Python code are translated to calls to
20814 @value{GDBN} error-reporting mechanism. If the command that called
20815 @code{python} does not handle the error, @value{GDBN} will
20816 terminate it and print an error message containing the Python
20817 exception name, the associated value, and the Python call stack
20818 backtrace at the point where the exception was raised. Example:
20821 (@value{GDBP}) python print foo
20822 Traceback (most recent call last):
20823 File "<string>", line 1, in <module>
20824 NameError: name 'foo' is not defined
20827 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20828 code are converted to Python @code{RuntimeError} exceptions. User
20829 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20830 prompt) is translated to a Python @code{KeyboardInterrupt}
20831 exception. If you catch these exceptions in your Python code, your
20832 exception handler will see @code{RuntimeError} or
20833 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20834 message as its value, and the Python call stack backtrace at the
20835 Python statement closest to where the @value{GDBN} error occured as the
20838 @findex gdb.GdbError
20839 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20840 it is useful to be able to throw an exception that doesn't cause a
20841 traceback to be printed. For example, the user may have invoked the
20842 command incorrectly. Use the @code{gdb.GdbError} exception
20843 to handle this case. Example:
20847 >class HelloWorld (gdb.Command):
20848 > """Greet the whole world."""
20849 > def __init__ (self):
20850 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20851 > def invoke (self, args, from_tty):
20852 > argv = gdb.string_to_argv (args)
20853 > if len (argv) != 0:
20854 > raise gdb.GdbError ("hello-world takes no arguments")
20855 > print "Hello, World!"
20858 (gdb) hello-world 42
20859 hello-world takes no arguments
20862 @node Values From Inferior
20863 @subsubsection Values From Inferior
20864 @cindex values from inferior, with Python
20865 @cindex python, working with values from inferior
20867 @cindex @code{gdb.Value}
20868 @value{GDBN} provides values it obtains from the inferior program in
20869 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20870 for its internal bookkeeping of the inferior's values, and for
20871 fetching values when necessary.
20873 Inferior values that are simple scalars can be used directly in
20874 Python expressions that are valid for the value's data type. Here's
20875 an example for an integer or floating-point value @code{some_val}:
20882 As result of this, @code{bar} will also be a @code{gdb.Value} object
20883 whose values are of the same type as those of @code{some_val}.
20885 Inferior values that are structures or instances of some class can
20886 be accessed using the Python @dfn{dictionary syntax}. For example, if
20887 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20888 can access its @code{foo} element with:
20891 bar = some_val['foo']
20894 Again, @code{bar} will also be a @code{gdb.Value} object.
20896 A @code{gdb.Value} that represents a function can be executed via
20897 inferior function call. Any arguments provided to the call must match
20898 the function's prototype, and must be provided in the order specified
20901 For example, @code{some_val} is a @code{gdb.Value} instance
20902 representing a function that takes two integers as arguments. To
20903 execute this function, call it like so:
20906 result = some_val (10,20)
20909 Any values returned from a function call will be stored as a
20912 The following attributes are provided:
20915 @defivar Value address
20916 If this object is addressable, this read-only attribute holds a
20917 @code{gdb.Value} object representing the address. Otherwise,
20918 this attribute holds @code{None}.
20921 @cindex optimized out value in Python
20922 @defivar Value is_optimized_out
20923 This read-only boolean attribute is true if the compiler optimized out
20924 this value, thus it is not available for fetching from the inferior.
20927 @defivar Value type
20928 The type of this @code{gdb.Value}. The value of this attribute is a
20929 @code{gdb.Type} object (@pxref{Types In Python}).
20932 @defivar Value dynamic_type
20933 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
20934 type information (@acronym{RTTI}) to determine the dynamic type of the
20935 value. If this value is of class type, it will return the class in
20936 which the value is embedded, if any. If this value is of pointer or
20937 reference to a class type, it will compute the dynamic type of the
20938 referenced object, and return a pointer or reference to that type,
20939 respectively. In all other cases, it will return the value's static
20942 Note that this feature will only work when debugging a C@t{++} program
20943 that includes @acronym{RTTI} for the object in question. Otherwise,
20944 it will just return the static type of the value as in @kbd{ptype foo}
20945 (@pxref{Symbols, ptype}).
20949 The following methods are provided:
20952 @defmethod Value __init__ @var{val}
20953 Many Python values can be converted directly to a @code{gdb.Value} via
20954 this object initializer. Specifically:
20957 @item Python boolean
20958 A Python boolean is converted to the boolean type from the current
20961 @item Python integer
20962 A Python integer is converted to the C @code{long} type for the
20963 current architecture.
20966 A Python long is converted to the C @code{long long} type for the
20967 current architecture.
20970 A Python float is converted to the C @code{double} type for the
20971 current architecture.
20973 @item Python string
20974 A Python string is converted to a target string, using the current
20977 @item @code{gdb.Value}
20978 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
20980 @item @code{gdb.LazyString}
20981 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
20982 Python}), then the lazy string's @code{value} method is called, and
20983 its result is used.
20987 @defmethod Value cast type
20988 Return a new instance of @code{gdb.Value} that is the result of
20989 casting this instance to the type described by @var{type}, which must
20990 be a @code{gdb.Type} object. If the cast cannot be performed for some
20991 reason, this method throws an exception.
20994 @defmethod Value dereference
20995 For pointer data types, this method returns a new @code{gdb.Value} object
20996 whose contents is the object pointed to by the pointer. For example, if
20997 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21004 then you can use the corresponding @code{gdb.Value} to access what
21005 @code{foo} points to like this:
21008 bar = foo.dereference ()
21011 The result @code{bar} will be a @code{gdb.Value} object holding the
21012 value pointed to by @code{foo}.
21015 @defmethod Value dynamic_cast type
21016 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21017 operator were used. Consult a C@t{++} reference for details.
21020 @defmethod Value reinterpret_cast type
21021 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21022 operator were used. Consult a C@t{++} reference for details.
21025 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21026 If this @code{gdb.Value} represents a string, then this method
21027 converts the contents to a Python string. Otherwise, this method will
21028 throw an exception.
21030 Strings are recognized in a language-specific way; whether a given
21031 @code{gdb.Value} represents a string is determined by the current
21034 For C-like languages, a value is a string if it is a pointer to or an
21035 array of characters or ints. The string is assumed to be terminated
21036 by a zero of the appropriate width. However if the optional length
21037 argument is given, the string will be converted to that given length,
21038 ignoring any embedded zeros that the string may contain.
21040 If the optional @var{encoding} argument is given, it must be a string
21041 naming the encoding of the string in the @code{gdb.Value}, such as
21042 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21043 the same encodings as the corresponding argument to Python's
21044 @code{string.decode} method, and the Python codec machinery will be used
21045 to convert the string. If @var{encoding} is not given, or if
21046 @var{encoding} is the empty string, then either the @code{target-charset}
21047 (@pxref{Character Sets}) will be used, or a language-specific encoding
21048 will be used, if the current language is able to supply one.
21050 The optional @var{errors} argument is the same as the corresponding
21051 argument to Python's @code{string.decode} method.
21053 If the optional @var{length} argument is given, the string will be
21054 fetched and converted to the given length.
21057 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21058 If this @code{gdb.Value} represents a string, then this method
21059 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21060 In Python}). Otherwise, this method will throw an exception.
21062 If the optional @var{encoding} argument is given, it must be a string
21063 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21064 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21065 @var{encoding} argument is an encoding that @value{GDBN} does
21066 recognize, @value{GDBN} will raise an error.
21068 When a lazy string is printed, the @value{GDBN} encoding machinery is
21069 used to convert the string during printing. If the optional
21070 @var{encoding} argument is not provided, or is an empty string,
21071 @value{GDBN} will automatically select the encoding most suitable for
21072 the string type. For further information on encoding in @value{GDBN}
21073 please see @ref{Character Sets}.
21075 If the optional @var{length} argument is given, the string will be
21076 fetched and encoded to the length of characters specified. If
21077 the @var{length} argument is not provided, the string will be fetched
21078 and encoded until a null of appropriate width is found.
21082 @node Types In Python
21083 @subsubsection Types In Python
21084 @cindex types in Python
21085 @cindex Python, working with types
21088 @value{GDBN} represents types from the inferior using the class
21091 The following type-related functions are available in the @code{gdb}
21094 @findex gdb.lookup_type
21095 @defun lookup_type name [block]
21096 This function looks up a type by name. @var{name} is the name of the
21097 type to look up. It must be a string.
21099 If @var{block} is given, then @var{name} is looked up in that scope.
21100 Otherwise, it is searched for globally.
21102 Ordinarily, this function will return an instance of @code{gdb.Type}.
21103 If the named type cannot be found, it will throw an exception.
21106 An instance of @code{Type} has the following attributes:
21110 The type code for this type. The type code will be one of the
21111 @code{TYPE_CODE_} constants defined below.
21114 @defivar Type sizeof
21115 The size of this type, in target @code{char} units. Usually, a
21116 target's @code{char} type will be an 8-bit byte. However, on some
21117 unusual platforms, this type may have a different size.
21121 The tag name for this type. The tag name is the name after
21122 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21123 languages have this concept. If this type has no tag name, then
21124 @code{None} is returned.
21128 The following methods are provided:
21131 @defmethod Type fields
21132 For structure and union types, this method returns the fields. Range
21133 types have two fields, the minimum and maximum values. Enum types
21134 have one field per enum constant. Function and method types have one
21135 field per parameter. The base types of C@t{++} classes are also
21136 represented as fields. If the type has no fields, or does not fit
21137 into one of these categories, an empty sequence will be returned.
21139 Each field is an object, with some pre-defined attributes:
21142 This attribute is not available for @code{static} fields (as in
21143 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21144 position of the field.
21147 The name of the field, or @code{None} for anonymous fields.
21150 This is @code{True} if the field is artificial, usually meaning that
21151 it was provided by the compiler and not the user. This attribute is
21152 always provided, and is @code{False} if the field is not artificial.
21154 @item is_base_class
21155 This is @code{True} if the field represents a base class of a C@t{++}
21156 structure. This attribute is always provided, and is @code{False}
21157 if the field is not a base class of the type that is the argument of
21158 @code{fields}, or if that type was not a C@t{++} class.
21161 If the field is packed, or is a bitfield, then this will have a
21162 non-zero value, which is the size of the field in bits. Otherwise,
21163 this will be zero; in this case the field's size is given by its type.
21166 The type of the field. This is usually an instance of @code{Type},
21167 but it can be @code{None} in some situations.
21171 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21172 Return a new @code{gdb.Type} object which represents an array of this
21173 type. If one argument is given, it is the inclusive upper bound of
21174 the array; in this case the lower bound is zero. If two arguments are
21175 given, the first argument is the lower bound of the array, and the
21176 second argument is the upper bound of the array. An array's length
21177 must not be negative, but the bounds can be.
21180 @defmethod Type const
21181 Return a new @code{gdb.Type} object which represents a
21182 @code{const}-qualified variant of this type.
21185 @defmethod Type volatile
21186 Return a new @code{gdb.Type} object which represents a
21187 @code{volatile}-qualified variant of this type.
21190 @defmethod Type unqualified
21191 Return a new @code{gdb.Type} object which represents an unqualified
21192 variant of this type. That is, the result is neither @code{const} nor
21196 @defmethod Type range
21197 Return a Python @code{Tuple} object that contains two elements: the
21198 low bound of the argument type and the high bound of that type. If
21199 the type does not have a range, @value{GDBN} will raise a
21200 @code{RuntimeError} exception.
21203 @defmethod Type reference
21204 Return a new @code{gdb.Type} object which represents a reference to this
21208 @defmethod Type pointer
21209 Return a new @code{gdb.Type} object which represents a pointer to this
21213 @defmethod Type strip_typedefs
21214 Return a new @code{gdb.Type} that represents the real type,
21215 after removing all layers of typedefs.
21218 @defmethod Type target
21219 Return a new @code{gdb.Type} object which represents the target type
21222 For a pointer type, the target type is the type of the pointed-to
21223 object. For an array type (meaning C-like arrays), the target type is
21224 the type of the elements of the array. For a function or method type,
21225 the target type is the type of the return value. For a complex type,
21226 the target type is the type of the elements. For a typedef, the
21227 target type is the aliased type.
21229 If the type does not have a target, this method will throw an
21233 @defmethod Type template_argument n [block]
21234 If this @code{gdb.Type} is an instantiation of a template, this will
21235 return a new @code{gdb.Type} which represents the type of the
21236 @var{n}th template argument.
21238 If this @code{gdb.Type} is not a template type, this will throw an
21239 exception. Ordinarily, only C@t{++} code will have template types.
21241 If @var{block} is given, then @var{name} is looked up in that scope.
21242 Otherwise, it is searched for globally.
21247 Each type has a code, which indicates what category this type falls
21248 into. The available type categories are represented by constants
21249 defined in the @code{gdb} module:
21252 @findex TYPE_CODE_PTR
21253 @findex gdb.TYPE_CODE_PTR
21254 @item TYPE_CODE_PTR
21255 The type is a pointer.
21257 @findex TYPE_CODE_ARRAY
21258 @findex gdb.TYPE_CODE_ARRAY
21259 @item TYPE_CODE_ARRAY
21260 The type is an array.
21262 @findex TYPE_CODE_STRUCT
21263 @findex gdb.TYPE_CODE_STRUCT
21264 @item TYPE_CODE_STRUCT
21265 The type is a structure.
21267 @findex TYPE_CODE_UNION
21268 @findex gdb.TYPE_CODE_UNION
21269 @item TYPE_CODE_UNION
21270 The type is a union.
21272 @findex TYPE_CODE_ENUM
21273 @findex gdb.TYPE_CODE_ENUM
21274 @item TYPE_CODE_ENUM
21275 The type is an enum.
21277 @findex TYPE_CODE_FLAGS
21278 @findex gdb.TYPE_CODE_FLAGS
21279 @item TYPE_CODE_FLAGS
21280 A bit flags type, used for things such as status registers.
21282 @findex TYPE_CODE_FUNC
21283 @findex gdb.TYPE_CODE_FUNC
21284 @item TYPE_CODE_FUNC
21285 The type is a function.
21287 @findex TYPE_CODE_INT
21288 @findex gdb.TYPE_CODE_INT
21289 @item TYPE_CODE_INT
21290 The type is an integer type.
21292 @findex TYPE_CODE_FLT
21293 @findex gdb.TYPE_CODE_FLT
21294 @item TYPE_CODE_FLT
21295 A floating point type.
21297 @findex TYPE_CODE_VOID
21298 @findex gdb.TYPE_CODE_VOID
21299 @item TYPE_CODE_VOID
21300 The special type @code{void}.
21302 @findex TYPE_CODE_SET
21303 @findex gdb.TYPE_CODE_SET
21304 @item TYPE_CODE_SET
21307 @findex TYPE_CODE_RANGE
21308 @findex gdb.TYPE_CODE_RANGE
21309 @item TYPE_CODE_RANGE
21310 A range type, that is, an integer type with bounds.
21312 @findex TYPE_CODE_STRING
21313 @findex gdb.TYPE_CODE_STRING
21314 @item TYPE_CODE_STRING
21315 A string type. Note that this is only used for certain languages with
21316 language-defined string types; C strings are not represented this way.
21318 @findex TYPE_CODE_BITSTRING
21319 @findex gdb.TYPE_CODE_BITSTRING
21320 @item TYPE_CODE_BITSTRING
21323 @findex TYPE_CODE_ERROR
21324 @findex gdb.TYPE_CODE_ERROR
21325 @item TYPE_CODE_ERROR
21326 An unknown or erroneous type.
21328 @findex TYPE_CODE_METHOD
21329 @findex gdb.TYPE_CODE_METHOD
21330 @item TYPE_CODE_METHOD
21331 A method type, as found in C@t{++} or Java.
21333 @findex TYPE_CODE_METHODPTR
21334 @findex gdb.TYPE_CODE_METHODPTR
21335 @item TYPE_CODE_METHODPTR
21336 A pointer-to-member-function.
21338 @findex TYPE_CODE_MEMBERPTR
21339 @findex gdb.TYPE_CODE_MEMBERPTR
21340 @item TYPE_CODE_MEMBERPTR
21341 A pointer-to-member.
21343 @findex TYPE_CODE_REF
21344 @findex gdb.TYPE_CODE_REF
21345 @item TYPE_CODE_REF
21348 @findex TYPE_CODE_CHAR
21349 @findex gdb.TYPE_CODE_CHAR
21350 @item TYPE_CODE_CHAR
21353 @findex TYPE_CODE_BOOL
21354 @findex gdb.TYPE_CODE_BOOL
21355 @item TYPE_CODE_BOOL
21358 @findex TYPE_CODE_COMPLEX
21359 @findex gdb.TYPE_CODE_COMPLEX
21360 @item TYPE_CODE_COMPLEX
21361 A complex float type.
21363 @findex TYPE_CODE_TYPEDEF
21364 @findex gdb.TYPE_CODE_TYPEDEF
21365 @item TYPE_CODE_TYPEDEF
21366 A typedef to some other type.
21368 @findex TYPE_CODE_NAMESPACE
21369 @findex gdb.TYPE_CODE_NAMESPACE
21370 @item TYPE_CODE_NAMESPACE
21371 A C@t{++} namespace.
21373 @findex TYPE_CODE_DECFLOAT
21374 @findex gdb.TYPE_CODE_DECFLOAT
21375 @item TYPE_CODE_DECFLOAT
21376 A decimal floating point type.
21378 @findex TYPE_CODE_INTERNAL_FUNCTION
21379 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21380 @item TYPE_CODE_INTERNAL_FUNCTION
21381 A function internal to @value{GDBN}. This is the type used to represent
21382 convenience functions.
21385 Further support for types is provided in the @code{gdb.types}
21386 Python module (@pxref{gdb.types}).
21388 @node Pretty Printing API
21389 @subsubsection Pretty Printing API
21391 An example output is provided (@pxref{Pretty Printing}).
21393 A pretty-printer is just an object that holds a value and implements a
21394 specific interface, defined here.
21396 @defop Operation {pretty printer} children (self)
21397 @value{GDBN} will call this method on a pretty-printer to compute the
21398 children of the pretty-printer's value.
21400 This method must return an object conforming to the Python iterator
21401 protocol. Each item returned by the iterator must be a tuple holding
21402 two elements. The first element is the ``name'' of the child; the
21403 second element is the child's value. The value can be any Python
21404 object which is convertible to a @value{GDBN} value.
21406 This method is optional. If it does not exist, @value{GDBN} will act
21407 as though the value has no children.
21410 @defop Operation {pretty printer} display_hint (self)
21411 The CLI may call this method and use its result to change the
21412 formatting of a value. The result will also be supplied to an MI
21413 consumer as a @samp{displayhint} attribute of the variable being
21416 This method is optional. If it does exist, this method must return a
21419 Some display hints are predefined by @value{GDBN}:
21423 Indicate that the object being printed is ``array-like''. The CLI
21424 uses this to respect parameters such as @code{set print elements} and
21425 @code{set print array}.
21428 Indicate that the object being printed is ``map-like'', and that the
21429 children of this value can be assumed to alternate between keys and
21433 Indicate that the object being printed is ``string-like''. If the
21434 printer's @code{to_string} method returns a Python string of some
21435 kind, then @value{GDBN} will call its internal language-specific
21436 string-printing function to format the string. For the CLI this means
21437 adding quotation marks, possibly escaping some characters, respecting
21438 @code{set print elements}, and the like.
21442 @defop Operation {pretty printer} to_string (self)
21443 @value{GDBN} will call this method to display the string
21444 representation of the value passed to the object's constructor.
21446 When printing from the CLI, if the @code{to_string} method exists,
21447 then @value{GDBN} will prepend its result to the values returned by
21448 @code{children}. Exactly how this formatting is done is dependent on
21449 the display hint, and may change as more hints are added. Also,
21450 depending on the print settings (@pxref{Print Settings}), the CLI may
21451 print just the result of @code{to_string} in a stack trace, omitting
21452 the result of @code{children}.
21454 If this method returns a string, it is printed verbatim.
21456 Otherwise, if this method returns an instance of @code{gdb.Value},
21457 then @value{GDBN} prints this value. This may result in a call to
21458 another pretty-printer.
21460 If instead the method returns a Python value which is convertible to a
21461 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21462 the resulting value. Again, this may result in a call to another
21463 pretty-printer. Python scalars (integers, floats, and booleans) and
21464 strings are convertible to @code{gdb.Value}; other types are not.
21466 Finally, if this method returns @code{None} then no further operations
21467 are peformed in this method and nothing is printed.
21469 If the result is not one of these types, an exception is raised.
21472 @value{GDBN} provides a function which can be used to look up the
21473 default pretty-printer for a @code{gdb.Value}:
21475 @findex gdb.default_visualizer
21476 @defun default_visualizer value
21477 This function takes a @code{gdb.Value} object as an argument. If a
21478 pretty-printer for this value exists, then it is returned. If no such
21479 printer exists, then this returns @code{None}.
21482 @node Selecting Pretty-Printers
21483 @subsubsection Selecting Pretty-Printers
21485 The Python list @code{gdb.pretty_printers} contains an array of
21486 functions or callable objects that have been registered via addition
21487 as a pretty-printer. Printers in this list are called @code{global}
21488 printers, they're available when debugging all inferiors.
21489 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21490 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21493 Each function on these lists is passed a single @code{gdb.Value}
21494 argument and should return a pretty-printer object conforming to the
21495 interface definition above (@pxref{Pretty Printing API}). If a function
21496 cannot create a pretty-printer for the value, it should return
21499 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21500 @code{gdb.Objfile} in the current program space and iteratively calls
21501 each enabled lookup routine in the list for that @code{gdb.Objfile}
21502 until it receives a pretty-printer object.
21503 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21504 searches the pretty-printer list of the current program space,
21505 calling each enabled function until an object is returned.
21506 After these lists have been exhausted, it tries the global
21507 @code{gdb.pretty_printers} list, again calling each enabled function until an
21508 object is returned.
21510 The order in which the objfiles are searched is not specified. For a
21511 given list, functions are always invoked from the head of the list,
21512 and iterated over sequentially until the end of the list, or a printer
21513 object is returned.
21515 For various reasons a pretty-printer may not work.
21516 For example, the underlying data structure may have changed and
21517 the pretty-printer is out of date.
21519 The consequences of a broken pretty-printer are severe enough that
21520 @value{GDBN} provides support for enabling and disabling individual
21521 printers. For example, if @code{print frame-arguments} is on,
21522 a backtrace can become highly illegible if any argument is printed
21523 with a broken printer.
21525 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21526 attribute to the registered function or callable object. If this attribute
21527 is present and its value is @code{False}, the printer is disabled, otherwise
21528 the printer is enabled.
21530 @node Writing a Pretty-Printer
21531 @subsubsection Writing a Pretty-Printer
21532 @cindex writing a pretty-printer
21534 A pretty-printer consists of two parts: a lookup function to detect
21535 if the type is supported, and the printer itself.
21537 Here is an example showing how a @code{std::string} printer might be
21538 written. @xref{Pretty Printing API}, for details on the API this class
21542 class StdStringPrinter(object):
21543 "Print a std::string"
21545 def __init__(self, val):
21548 def to_string(self):
21549 return self.val['_M_dataplus']['_M_p']
21551 def display_hint(self):
21555 And here is an example showing how a lookup function for the printer
21556 example above might be written.
21559 def str_lookup_function(val):
21560 lookup_tag = val.type.tag
21561 if lookup_tag == None:
21563 regex = re.compile("^std::basic_string<char,.*>$")
21564 if regex.match(lookup_tag):
21565 return StdStringPrinter(val)
21569 The example lookup function extracts the value's type, and attempts to
21570 match it to a type that it can pretty-print. If it is a type the
21571 printer can pretty-print, it will return a printer object. If not, it
21572 returns @code{None}.
21574 We recommend that you put your core pretty-printers into a Python
21575 package. If your pretty-printers are for use with a library, we
21576 further recommend embedding a version number into the package name.
21577 This practice will enable @value{GDBN} to load multiple versions of
21578 your pretty-printers at the same time, because they will have
21581 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21582 can be evaluated multiple times without changing its meaning. An
21583 ideal auto-load file will consist solely of @code{import}s of your
21584 printer modules, followed by a call to a register pretty-printers with
21585 the current objfile.
21587 Taken as a whole, this approach will scale nicely to multiple
21588 inferiors, each potentially using a different library version.
21589 Embedding a version number in the Python package name will ensure that
21590 @value{GDBN} is able to load both sets of printers simultaneously.
21591 Then, because the search for pretty-printers is done by objfile, and
21592 because your auto-loaded code took care to register your library's
21593 printers with a specific objfile, @value{GDBN} will find the correct
21594 printers for the specific version of the library used by each
21597 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21598 this code might appear in @code{gdb.libstdcxx.v6}:
21601 def register_printers(objfile):
21602 objfile.pretty_printers.add(str_lookup_function)
21606 And then the corresponding contents of the auto-load file would be:
21609 import gdb.libstdcxx.v6
21610 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21613 The previous example illustrates a basic pretty-printer.
21614 There are a few things that can be improved on.
21615 The printer doesn't have a name, making it hard to identify in a
21616 list of installed printers. The lookup function has a name, but
21617 lookup functions can have arbitrary, even identical, names.
21619 Second, the printer only handles one type, whereas a library typically has
21620 several types. One could install a lookup function for each desired type
21621 in the library, but one could also have a single lookup function recognize
21622 several types. The latter is the conventional way this is handled.
21623 If a pretty-printer can handle multiple data types, then its
21624 @dfn{subprinters} are the printers for the individual data types.
21626 The @code{gdb.printing} module provides a formal way of solving these
21627 problems (@pxref{gdb.printing}).
21628 Here is another example that handles multiple types.
21630 These are the types we are going to pretty-print:
21633 struct foo @{ int a, b; @};
21634 struct bar @{ struct foo x, y; @};
21637 Here are the printers:
21641 """Print a foo object."""
21643 def __init__(self, val):
21646 def to_string(self):
21647 return ("a=<" + str(self.val["a"]) +
21648 "> b=<" + str(self.val["b"]) + ">")
21651 """Print a bar object."""
21653 def __init__(self, val):
21656 def to_string(self):
21657 return ("x=<" + str(self.val["x"]) +
21658 "> y=<" + str(self.val["y"]) + ">")
21661 This example doesn't need a lookup function, that is handled by the
21662 @code{gdb.printing} module. Instead a function is provided to build up
21663 the object that handles the lookup.
21666 import gdb.printing
21668 def build_pretty_printer():
21669 pp = gdb.printing.RegexpCollectionPrettyPrinter(
21671 pp.add_printer('foo', '^foo$', fooPrinter)
21672 pp.add_printer('bar', '^bar$', barPrinter)
21676 And here is the autoload support:
21679 import gdb.printing
21681 gdb.printing.register_pretty_printer(
21682 gdb.current_objfile(),
21683 my_library.build_pretty_printer())
21686 Finally, when this printer is loaded into @value{GDBN}, here is the
21687 corresponding output of @samp{info pretty-printer}:
21690 (gdb) info pretty-printer
21697 @node Inferiors In Python
21698 @subsubsection Inferiors In Python
21699 @cindex inferiors in python
21701 @findex gdb.Inferior
21702 Programs which are being run under @value{GDBN} are called inferiors
21703 (@pxref{Inferiors and Programs}). Python scripts can access
21704 information about and manipulate inferiors controlled by @value{GDBN}
21705 via objects of the @code{gdb.Inferior} class.
21707 The following inferior-related functions are available in the @code{gdb}
21711 Return a tuple containing all inferior objects.
21714 A @code{gdb.Inferior} object has the following attributes:
21717 @defivar Inferior num
21718 ID of inferior, as assigned by GDB.
21721 @defivar Inferior pid
21722 Process ID of the inferior, as assigned by the underlying operating
21726 @defivar Inferior was_attached
21727 Boolean signaling whether the inferior was created using `attach', or
21728 started by @value{GDBN} itself.
21732 A @code{gdb.Inferior} object has the following methods:
21735 @defmethod Inferior threads
21736 This method returns a tuple holding all the threads which are valid
21737 when it is called. If there are no valid threads, the method will
21738 return an empty tuple.
21741 @findex gdb.read_memory
21742 @defmethod Inferior read_memory address length
21743 Read @var{length} bytes of memory from the inferior, starting at
21744 @var{address}. Returns a buffer object, which behaves much like an array
21745 or a string. It can be modified and given to the @code{gdb.write_memory}
21749 @findex gdb.write_memory
21750 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21751 Write the contents of @var{buffer} to the inferior, starting at
21752 @var{address}. The @var{buffer} parameter must be a Python object
21753 which supports the buffer protocol, i.e., a string, an array or the
21754 object returned from @code{gdb.read_memory}. If given, @var{length}
21755 determines the number of bytes from @var{buffer} to be written.
21758 @findex gdb.search_memory
21759 @defmethod Inferior search_memory address length pattern
21760 Search a region of the inferior memory starting at @var{address} with
21761 the given @var{length} using the search pattern supplied in
21762 @var{pattern}. The @var{pattern} parameter must be a Python object
21763 which supports the buffer protocol, i.e., a string, an array or the
21764 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21765 containing the address where the pattern was found, or @code{None} if
21766 the pattern could not be found.
21770 @node Threads In Python
21771 @subsubsection Threads In Python
21772 @cindex threads in python
21774 @findex gdb.InferiorThread
21775 Python scripts can access information about, and manipulate inferior threads
21776 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21778 The following thread-related functions are available in the @code{gdb}
21781 @findex gdb.selected_thread
21782 @defun selected_thread
21783 This function returns the thread object for the selected thread. If there
21784 is no selected thread, this will return @code{None}.
21787 A @code{gdb.InferiorThread} object has the following attributes:
21790 @defivar InferiorThread num
21791 ID of the thread, as assigned by GDB.
21794 @defivar InferiorThread ptid
21795 ID of the thread, as assigned by the operating system. This attribute is a
21796 tuple containing three integers. The first is the Process ID (PID); the second
21797 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21798 Either the LWPID or TID may be 0, which indicates that the operating system
21799 does not use that identifier.
21803 A @code{gdb.InferiorThread} object has the following methods:
21806 @defmethod InferiorThread switch
21807 This changes @value{GDBN}'s currently selected thread to the one represented
21811 @defmethod InferiorThread is_stopped
21812 Return a Boolean indicating whether the thread is stopped.
21815 @defmethod InferiorThread is_running
21816 Return a Boolean indicating whether the thread is running.
21819 @defmethod InferiorThread is_exited
21820 Return a Boolean indicating whether the thread is exited.
21824 @node Commands In Python
21825 @subsubsection Commands In Python
21827 @cindex commands in python
21828 @cindex python commands
21829 You can implement new @value{GDBN} CLI commands in Python. A CLI
21830 command is implemented using an instance of the @code{gdb.Command}
21831 class, most commonly using a subclass.
21833 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21834 The object initializer for @code{Command} registers the new command
21835 with @value{GDBN}. This initializer is normally invoked from the
21836 subclass' own @code{__init__} method.
21838 @var{name} is the name of the command. If @var{name} consists of
21839 multiple words, then the initial words are looked for as prefix
21840 commands. In this case, if one of the prefix commands does not exist,
21841 an exception is raised.
21843 There is no support for multi-line commands.
21845 @var{command_class} should be one of the @samp{COMMAND_} constants
21846 defined below. This argument tells @value{GDBN} how to categorize the
21847 new command in the help system.
21849 @var{completer_class} is an optional argument. If given, it should be
21850 one of the @samp{COMPLETE_} constants defined below. This argument
21851 tells @value{GDBN} how to perform completion for this command. If not
21852 given, @value{GDBN} will attempt to complete using the object's
21853 @code{complete} method (see below); if no such method is found, an
21854 error will occur when completion is attempted.
21856 @var{prefix} is an optional argument. If @code{True}, then the new
21857 command is a prefix command; sub-commands of this command may be
21860 The help text for the new command is taken from the Python
21861 documentation string for the command's class, if there is one. If no
21862 documentation string is provided, the default value ``This command is
21863 not documented.'' is used.
21866 @cindex don't repeat Python command
21867 @defmethod Command dont_repeat
21868 By default, a @value{GDBN} command is repeated when the user enters a
21869 blank line at the command prompt. A command can suppress this
21870 behavior by invoking the @code{dont_repeat} method. This is similar
21871 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21874 @defmethod Command invoke argument from_tty
21875 This method is called by @value{GDBN} when this command is invoked.
21877 @var{argument} is a string. It is the argument to the command, after
21878 leading and trailing whitespace has been stripped.
21880 @var{from_tty} is a boolean argument. When true, this means that the
21881 command was entered by the user at the terminal; when false it means
21882 that the command came from elsewhere.
21884 If this method throws an exception, it is turned into a @value{GDBN}
21885 @code{error} call. Otherwise, the return value is ignored.
21887 @findex gdb.string_to_argv
21888 To break @var{argument} up into an argv-like string use
21889 @code{gdb.string_to_argv}. This function behaves identically to
21890 @value{GDBN}'s internal argument lexer @code{buildargv}.
21891 It is recommended to use this for consistency.
21892 Arguments are separated by spaces and may be quoted.
21896 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21897 ['1', '2 "3', '4 "5', "6 '7"]
21902 @cindex completion of Python commands
21903 @defmethod Command complete text word
21904 This method is called by @value{GDBN} when the user attempts
21905 completion on this command. All forms of completion are handled by
21906 this method, that is, the @key{TAB} and @key{M-?} key bindings
21907 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21910 The arguments @var{text} and @var{word} are both strings. @var{text}
21911 holds the complete command line up to the cursor's location.
21912 @var{word} holds the last word of the command line; this is computed
21913 using a word-breaking heuristic.
21915 The @code{complete} method can return several values:
21918 If the return value is a sequence, the contents of the sequence are
21919 used as the completions. It is up to @code{complete} to ensure that the
21920 contents actually do complete the word. A zero-length sequence is
21921 allowed, it means that there were no completions available. Only
21922 string elements of the sequence are used; other elements in the
21923 sequence are ignored.
21926 If the return value is one of the @samp{COMPLETE_} constants defined
21927 below, then the corresponding @value{GDBN}-internal completion
21928 function is invoked, and its result is used.
21931 All other results are treated as though there were no available
21936 When a new command is registered, it must be declared as a member of
21937 some general class of commands. This is used to classify top-level
21938 commands in the on-line help system; note that prefix commands are not
21939 listed under their own category but rather that of their top-level
21940 command. The available classifications are represented by constants
21941 defined in the @code{gdb} module:
21944 @findex COMMAND_NONE
21945 @findex gdb.COMMAND_NONE
21947 The command does not belong to any particular class. A command in
21948 this category will not be displayed in any of the help categories.
21950 @findex COMMAND_RUNNING
21951 @findex gdb.COMMAND_RUNNING
21952 @item COMMAND_RUNNING
21953 The command is related to running the inferior. For example,
21954 @code{start}, @code{step}, and @code{continue} are in this category.
21955 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21956 commands in this category.
21958 @findex COMMAND_DATA
21959 @findex gdb.COMMAND_DATA
21961 The command is related to data or variables. For example,
21962 @code{call}, @code{find}, and @code{print} are in this category. Type
21963 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21966 @findex COMMAND_STACK
21967 @findex gdb.COMMAND_STACK
21968 @item COMMAND_STACK
21969 The command has to do with manipulation of the stack. For example,
21970 @code{backtrace}, @code{frame}, and @code{return} are in this
21971 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21972 list of commands in this category.
21974 @findex COMMAND_FILES
21975 @findex gdb.COMMAND_FILES
21976 @item COMMAND_FILES
21977 This class is used for file-related commands. For example,
21978 @code{file}, @code{list} and @code{section} are in this category.
21979 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21980 commands in this category.
21982 @findex COMMAND_SUPPORT
21983 @findex gdb.COMMAND_SUPPORT
21984 @item COMMAND_SUPPORT
21985 This should be used for ``support facilities'', generally meaning
21986 things that are useful to the user when interacting with @value{GDBN},
21987 but not related to the state of the inferior. For example,
21988 @code{help}, @code{make}, and @code{shell} are in this category. Type
21989 @kbd{help support} at the @value{GDBN} prompt to see a list of
21990 commands in this category.
21992 @findex COMMAND_STATUS
21993 @findex gdb.COMMAND_STATUS
21994 @item COMMAND_STATUS
21995 The command is an @samp{info}-related command, that is, related to the
21996 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21997 and @code{show} are in this category. Type @kbd{help status} at the
21998 @value{GDBN} prompt to see a list of commands in this category.
22000 @findex COMMAND_BREAKPOINTS
22001 @findex gdb.COMMAND_BREAKPOINTS
22002 @item COMMAND_BREAKPOINTS
22003 The command has to do with breakpoints. For example, @code{break},
22004 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22005 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22008 @findex COMMAND_TRACEPOINTS
22009 @findex gdb.COMMAND_TRACEPOINTS
22010 @item COMMAND_TRACEPOINTS
22011 The command has to do with tracepoints. For example, @code{trace},
22012 @code{actions}, and @code{tfind} are in this category. Type
22013 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22014 commands in this category.
22016 @findex COMMAND_OBSCURE
22017 @findex gdb.COMMAND_OBSCURE
22018 @item COMMAND_OBSCURE
22019 The command is only used in unusual circumstances, or is not of
22020 general interest to users. For example, @code{checkpoint},
22021 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22022 obscure} at the @value{GDBN} prompt to see a list of commands in this
22025 @findex COMMAND_MAINTENANCE
22026 @findex gdb.COMMAND_MAINTENANCE
22027 @item COMMAND_MAINTENANCE
22028 The command is only useful to @value{GDBN} maintainers. The
22029 @code{maintenance} and @code{flushregs} commands are in this category.
22030 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22031 commands in this category.
22034 A new command can use a predefined completion function, either by
22035 specifying it via an argument at initialization, or by returning it
22036 from the @code{complete} method. These predefined completion
22037 constants are all defined in the @code{gdb} module:
22040 @findex COMPLETE_NONE
22041 @findex gdb.COMPLETE_NONE
22042 @item COMPLETE_NONE
22043 This constant means that no completion should be done.
22045 @findex COMPLETE_FILENAME
22046 @findex gdb.COMPLETE_FILENAME
22047 @item COMPLETE_FILENAME
22048 This constant means that filename completion should be performed.
22050 @findex COMPLETE_LOCATION
22051 @findex gdb.COMPLETE_LOCATION
22052 @item COMPLETE_LOCATION
22053 This constant means that location completion should be done.
22054 @xref{Specify Location}.
22056 @findex COMPLETE_COMMAND
22057 @findex gdb.COMPLETE_COMMAND
22058 @item COMPLETE_COMMAND
22059 This constant means that completion should examine @value{GDBN}
22062 @findex COMPLETE_SYMBOL
22063 @findex gdb.COMPLETE_SYMBOL
22064 @item COMPLETE_SYMBOL
22065 This constant means that completion should be done using symbol names
22069 The following code snippet shows how a trivial CLI command can be
22070 implemented in Python:
22073 class HelloWorld (gdb.Command):
22074 """Greet the whole world."""
22076 def __init__ (self):
22077 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22079 def invoke (self, arg, from_tty):
22080 print "Hello, World!"
22085 The last line instantiates the class, and is necessary to trigger the
22086 registration of the command with @value{GDBN}. Depending on how the
22087 Python code is read into @value{GDBN}, you may need to import the
22088 @code{gdb} module explicitly.
22090 @node Parameters In Python
22091 @subsubsection Parameters In Python
22093 @cindex parameters in python
22094 @cindex python parameters
22095 @tindex gdb.Parameter
22097 You can implement new @value{GDBN} parameters using Python. A new
22098 parameter is implemented as an instance of the @code{gdb.Parameter}
22101 Parameters are exposed to the user via the @code{set} and
22102 @code{show} commands. @xref{Help}.
22104 There are many parameters that already exist and can be set in
22105 @value{GDBN}. Two examples are: @code{set follow fork} and
22106 @code{set charset}. Setting these parameters influences certain
22107 behavior in @value{GDBN}. Similarly, you can define parameters that
22108 can be used to influence behavior in custom Python scripts and commands.
22110 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22111 The object initializer for @code{Parameter} registers the new
22112 parameter with @value{GDBN}. This initializer is normally invoked
22113 from the subclass' own @code{__init__} method.
22115 @var{name} is the name of the new parameter. If @var{name} consists
22116 of multiple words, then the initial words are looked for as prefix
22117 parameters. An example of this can be illustrated with the
22118 @code{set print} set of parameters. If @var{name} is
22119 @code{print foo}, then @code{print} will be searched as the prefix
22120 parameter. In this case the parameter can subsequently be accessed in
22121 @value{GDBN} as @code{set print foo}.
22123 If @var{name} consists of multiple words, and no prefix parameter group
22124 can be found, an exception is raised.
22126 @var{command-class} should be one of the @samp{COMMAND_} constants
22127 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22128 categorize the new parameter in the help system.
22130 @var{parameter-class} should be one of the @samp{PARAM_} constants
22131 defined below. This argument tells @value{GDBN} the type of the new
22132 parameter; this information is used for input validation and
22135 If @var{parameter-class} is @code{PARAM_ENUM}, then
22136 @var{enum-sequence} must be a sequence of strings. These strings
22137 represent the possible values for the parameter.
22139 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22140 of a fourth argument will cause an exception to be thrown.
22142 The help text for the new parameter is taken from the Python
22143 documentation string for the parameter's class, if there is one. If
22144 there is no documentation string, a default value is used.
22147 @defivar Parameter set_doc
22148 If this attribute exists, and is a string, then its value is used as
22149 the help text for this parameter's @code{set} command. The value is
22150 examined when @code{Parameter.__init__} is invoked; subsequent changes
22154 @defivar Parameter show_doc
22155 If this attribute exists, and is a string, then its value is used as
22156 the help text for this parameter's @code{show} command. The value is
22157 examined when @code{Parameter.__init__} is invoked; subsequent changes
22161 @defivar Parameter value
22162 The @code{value} attribute holds the underlying value of the
22163 parameter. It can be read and assigned to just as any other
22164 attribute. @value{GDBN} does validation when assignments are made.
22168 When a new parameter is defined, its type must be specified. The
22169 available types are represented by constants defined in the @code{gdb}
22173 @findex PARAM_BOOLEAN
22174 @findex gdb.PARAM_BOOLEAN
22175 @item PARAM_BOOLEAN
22176 The value is a plain boolean. The Python boolean values, @code{True}
22177 and @code{False} are the only valid values.
22179 @findex PARAM_AUTO_BOOLEAN
22180 @findex gdb.PARAM_AUTO_BOOLEAN
22181 @item PARAM_AUTO_BOOLEAN
22182 The value has three possible states: true, false, and @samp{auto}. In
22183 Python, true and false are represented using boolean constants, and
22184 @samp{auto} is represented using @code{None}.
22186 @findex PARAM_UINTEGER
22187 @findex gdb.PARAM_UINTEGER
22188 @item PARAM_UINTEGER
22189 The value is an unsigned integer. The value of 0 should be
22190 interpreted to mean ``unlimited''.
22192 @findex PARAM_INTEGER
22193 @findex gdb.PARAM_INTEGER
22194 @item PARAM_INTEGER
22195 The value is a signed integer. The value of 0 should be interpreted
22196 to mean ``unlimited''.
22198 @findex PARAM_STRING
22199 @findex gdb.PARAM_STRING
22201 The value is a string. When the user modifies the string, any escape
22202 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22203 translated into corresponding characters and encoded into the current
22206 @findex PARAM_STRING_NOESCAPE
22207 @findex gdb.PARAM_STRING_NOESCAPE
22208 @item PARAM_STRING_NOESCAPE
22209 The value is a string. When the user modifies the string, escapes are
22210 passed through untranslated.
22212 @findex PARAM_OPTIONAL_FILENAME
22213 @findex gdb.PARAM_OPTIONAL_FILENAME
22214 @item PARAM_OPTIONAL_FILENAME
22215 The value is a either a filename (a string), or @code{None}.
22217 @findex PARAM_FILENAME
22218 @findex gdb.PARAM_FILENAME
22219 @item PARAM_FILENAME
22220 The value is a filename. This is just like
22221 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22223 @findex PARAM_ZINTEGER
22224 @findex gdb.PARAM_ZINTEGER
22225 @item PARAM_ZINTEGER
22226 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22227 is interpreted as itself.
22230 @findex gdb.PARAM_ENUM
22232 The value is a string, which must be one of a collection string
22233 constants provided when the parameter is created.
22236 @node Functions In Python
22237 @subsubsection Writing new convenience functions
22239 @cindex writing convenience functions
22240 @cindex convenience functions in python
22241 @cindex python convenience functions
22242 @tindex gdb.Function
22244 You can implement new convenience functions (@pxref{Convenience Vars})
22245 in Python. A convenience function is an instance of a subclass of the
22246 class @code{gdb.Function}.
22248 @defmethod Function __init__ name
22249 The initializer for @code{Function} registers the new function with
22250 @value{GDBN}. The argument @var{name} is the name of the function,
22251 a string. The function will be visible to the user as a convenience
22252 variable of type @code{internal function}, whose name is the same as
22253 the given @var{name}.
22255 The documentation for the new function is taken from the documentation
22256 string for the new class.
22259 @defmethod Function invoke @var{*args}
22260 When a convenience function is evaluated, its arguments are converted
22261 to instances of @code{gdb.Value}, and then the function's
22262 @code{invoke} method is called. Note that @value{GDBN} does not
22263 predetermine the arity of convenience functions. Instead, all
22264 available arguments are passed to @code{invoke}, following the
22265 standard Python calling convention. In particular, a convenience
22266 function can have default values for parameters without ill effect.
22268 The return value of this method is used as its value in the enclosing
22269 expression. If an ordinary Python value is returned, it is converted
22270 to a @code{gdb.Value} following the usual rules.
22273 The following code snippet shows how a trivial convenience function can
22274 be implemented in Python:
22277 class Greet (gdb.Function):
22278 """Return string to greet someone.
22279 Takes a name as argument."""
22281 def __init__ (self):
22282 super (Greet, self).__init__ ("greet")
22284 def invoke (self, name):
22285 return "Hello, %s!" % name.string ()
22290 The last line instantiates the class, and is necessary to trigger the
22291 registration of the function with @value{GDBN}. Depending on how the
22292 Python code is read into @value{GDBN}, you may need to import the
22293 @code{gdb} module explicitly.
22295 @node Progspaces In Python
22296 @subsubsection Program Spaces In Python
22298 @cindex progspaces in python
22299 @tindex gdb.Progspace
22301 A program space, or @dfn{progspace}, represents a symbolic view
22302 of an address space.
22303 It consists of all of the objfiles of the program.
22304 @xref{Objfiles In Python}.
22305 @xref{Inferiors and Programs, program spaces}, for more details
22306 about program spaces.
22308 The following progspace-related functions are available in the
22311 @findex gdb.current_progspace
22312 @defun current_progspace
22313 This function returns the program space of the currently selected inferior.
22314 @xref{Inferiors and Programs}.
22317 @findex gdb.progspaces
22319 Return a sequence of all the progspaces currently known to @value{GDBN}.
22322 Each progspace is represented by an instance of the @code{gdb.Progspace}
22325 @defivar Progspace filename
22326 The file name of the progspace as a string.
22329 @defivar Progspace pretty_printers
22330 The @code{pretty_printers} attribute is a list of functions. It is
22331 used to look up pretty-printers. A @code{Value} is passed to each
22332 function in order; if the function returns @code{None}, then the
22333 search continues. Otherwise, the return value should be an object
22334 which is used to format the value. @xref{Pretty Printing API}, for more
22338 @node Objfiles In Python
22339 @subsubsection Objfiles In Python
22341 @cindex objfiles in python
22342 @tindex gdb.Objfile
22344 @value{GDBN} loads symbols for an inferior from various
22345 symbol-containing files (@pxref{Files}). These include the primary
22346 executable file, any shared libraries used by the inferior, and any
22347 separate debug info files (@pxref{Separate Debug Files}).
22348 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22350 The following objfile-related functions are available in the
22353 @findex gdb.current_objfile
22354 @defun current_objfile
22355 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22356 sets the ``current objfile'' to the corresponding objfile. This
22357 function returns the current objfile. If there is no current objfile,
22358 this function returns @code{None}.
22361 @findex gdb.objfiles
22363 Return a sequence of all the objfiles current known to @value{GDBN}.
22364 @xref{Objfiles In Python}.
22367 Each objfile is represented by an instance of the @code{gdb.Objfile}
22370 @defivar Objfile filename
22371 The file name of the objfile as a string.
22374 @defivar Objfile pretty_printers
22375 The @code{pretty_printers} attribute is a list of functions. It is
22376 used to look up pretty-printers. A @code{Value} is passed to each
22377 function in order; if the function returns @code{None}, then the
22378 search continues. Otherwise, the return value should be an object
22379 which is used to format the value. @xref{Pretty Printing API}, for more
22383 @node Frames In Python
22384 @subsubsection Accessing inferior stack frames from Python.
22386 @cindex frames in python
22387 When the debugged program stops, @value{GDBN} is able to analyze its call
22388 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22389 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22390 while its corresponding frame exists in the inferior's stack. If you try
22391 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
22394 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22398 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22402 The following frame-related functions are available in the @code{gdb} module:
22404 @findex gdb.selected_frame
22405 @defun selected_frame
22406 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22409 @defun frame_stop_reason_string reason
22410 Return a string explaining the reason why @value{GDBN} stopped unwinding
22411 frames, as expressed by the given @var{reason} code (an integer, see the
22412 @code{unwind_stop_reason} method further down in this section).
22415 A @code{gdb.Frame} object has the following methods:
22418 @defmethod Frame is_valid
22419 Returns true if the @code{gdb.Frame} object is valid, false if not.
22420 A frame object can become invalid if the frame it refers to doesn't
22421 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22422 an exception if it is invalid at the time the method is called.
22425 @defmethod Frame name
22426 Returns the function name of the frame, or @code{None} if it can't be
22430 @defmethod Frame type
22431 Returns the type of the frame. The value can be one of
22432 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
22433 or @code{gdb.SENTINEL_FRAME}.
22436 @defmethod Frame unwind_stop_reason
22437 Return an integer representing the reason why it's not possible to find
22438 more frames toward the outermost frame. Use
22439 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22440 function to a string.
22443 @defmethod Frame pc
22444 Returns the frame's resume address.
22447 @defmethod Frame block
22448 Return the frame's code block. @xref{Blocks In Python}.
22451 @defmethod Frame function
22452 Return the symbol for the function corresponding to this frame.
22453 @xref{Symbols In Python}.
22456 @defmethod Frame older
22457 Return the frame that called this frame.
22460 @defmethod Frame newer
22461 Return the frame called by this frame.
22464 @defmethod Frame find_sal
22465 Return the frame's symtab and line object.
22466 @xref{Symbol Tables In Python}.
22469 @defmethod Frame read_var variable @r{[}block@r{]}
22470 Return the value of @var{variable} in this frame. If the optional
22471 argument @var{block} is provided, search for the variable from that
22472 block; otherwise start at the frame's current block (which is
22473 determined by the frame's current program counter). @var{variable}
22474 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22475 @code{gdb.Block} object.
22478 @defmethod Frame select
22479 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22484 @node Blocks In Python
22485 @subsubsection Accessing frame blocks from Python.
22487 @cindex blocks in python
22490 Within each frame, @value{GDBN} maintains information on each block
22491 stored in that frame. These blocks are organized hierarchically, and
22492 are represented individually in Python as a @code{gdb.Block}.
22493 Please see @ref{Frames In Python}, for a more in-depth discussion on
22494 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22495 detailed technical information on @value{GDBN}'s book-keeping of the
22498 The following block-related functions are available in the @code{gdb}
22501 @findex gdb.block_for_pc
22502 @defun block_for_pc pc
22503 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22504 block cannot be found for the @var{pc} value specified, the function
22505 will return @code{None}.
22508 A @code{gdb.Block} object has the following attributes:
22511 @defivar Block start
22512 The start address of the block. This attribute is not writable.
22516 The end address of the block. This attribute is not writable.
22519 @defivar Block function
22520 The name of the block represented as a @code{gdb.Symbol}. If the
22521 block is not named, then this attribute holds @code{None}. This
22522 attribute is not writable.
22525 @defivar Block superblock
22526 The block containing this block. If this parent block does not exist,
22527 this attribute holds @code{None}. This attribute is not writable.
22531 @node Symbols In Python
22532 @subsubsection Python representation of Symbols.
22534 @cindex symbols in python
22537 @value{GDBN} represents every variable, function and type as an
22538 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22539 Similarly, Python represents these symbols in @value{GDBN} with the
22540 @code{gdb.Symbol} object.
22542 The following symbol-related functions are available in the @code{gdb}
22545 @findex gdb.lookup_symbol
22546 @defun lookup_symbol name [block] [domain]
22547 This function searches for a symbol by name. The search scope can be
22548 restricted to the parameters defined in the optional domain and block
22551 @var{name} is the name of the symbol. It must be a string. The
22552 optional @var{block} argument restricts the search to symbols visible
22553 in that @var{block}. The @var{block} argument must be a
22554 @code{gdb.Block} object. The optional @var{domain} argument restricts
22555 the search to the domain type. The @var{domain} argument must be a
22556 domain constant defined in the @code{gdb} module and described later
22560 A @code{gdb.Symbol} object has the following attributes:
22563 @defivar Symbol symtab
22564 The symbol table in which the symbol appears. This attribute is
22565 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22566 Python}. This attribute is not writable.
22569 @defivar Symbol name
22570 The name of the symbol as a string. This attribute is not writable.
22573 @defivar Symbol linkage_name
22574 The name of the symbol, as used by the linker (i.e., may be mangled).
22575 This attribute is not writable.
22578 @defivar Symbol print_name
22579 The name of the symbol in a form suitable for output. This is either
22580 @code{name} or @code{linkage_name}, depending on whether the user
22581 asked @value{GDBN} to display demangled or mangled names.
22584 @defivar Symbol addr_class
22585 The address class of the symbol. This classifies how to find the value
22586 of a symbol. Each address class is a constant defined in the
22587 @code{gdb} module and described later in this chapter.
22590 @defivar Symbol is_argument
22591 @code{True} if the symbol is an argument of a function.
22594 @defivar Symbol is_constant
22595 @code{True} if the symbol is a constant.
22598 @defivar Symbol is_function
22599 @code{True} if the symbol is a function or a method.
22602 @defivar Symbol is_variable
22603 @code{True} if the symbol is a variable.
22607 The available domain categories in @code{gdb.Symbol} are represented
22608 as constants in the @code{gdb} module:
22611 @findex SYMBOL_UNDEF_DOMAIN
22612 @findex gdb.SYMBOL_UNDEF_DOMAIN
22613 @item SYMBOL_UNDEF_DOMAIN
22614 This is used when a domain has not been discovered or none of the
22615 following domains apply. This usually indicates an error either
22616 in the symbol information or in @value{GDBN}'s handling of symbols.
22617 @findex SYMBOL_VAR_DOMAIN
22618 @findex gdb.SYMBOL_VAR_DOMAIN
22619 @item SYMBOL_VAR_DOMAIN
22620 This domain contains variables, function names, typedef names and enum
22622 @findex SYMBOL_STRUCT_DOMAIN
22623 @findex gdb.SYMBOL_STRUCT_DOMAIN
22624 @item SYMBOL_STRUCT_DOMAIN
22625 This domain holds struct, union and enum type names.
22626 @findex SYMBOL_LABEL_DOMAIN
22627 @findex gdb.SYMBOL_LABEL_DOMAIN
22628 @item SYMBOL_LABEL_DOMAIN
22629 This domain contains names of labels (for gotos).
22630 @findex SYMBOL_VARIABLES_DOMAIN
22631 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22632 @item SYMBOL_VARIABLES_DOMAIN
22633 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22634 contains everything minus functions and types.
22635 @findex SYMBOL_FUNCTIONS_DOMAIN
22636 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22637 @item SYMBOL_FUNCTION_DOMAIN
22638 This domain contains all functions.
22639 @findex SYMBOL_TYPES_DOMAIN
22640 @findex gdb.SYMBOL_TYPES_DOMAIN
22641 @item SYMBOL_TYPES_DOMAIN
22642 This domain contains all types.
22645 The available address class categories in @code{gdb.Symbol} are represented
22646 as constants in the @code{gdb} module:
22649 @findex SYMBOL_LOC_UNDEF
22650 @findex gdb.SYMBOL_LOC_UNDEF
22651 @item SYMBOL_LOC_UNDEF
22652 If this is returned by address class, it indicates an error either in
22653 the symbol information or in @value{GDBN}'s handling of symbols.
22654 @findex SYMBOL_LOC_CONST
22655 @findex gdb.SYMBOL_LOC_CONST
22656 @item SYMBOL_LOC_CONST
22657 Value is constant int.
22658 @findex SYMBOL_LOC_STATIC
22659 @findex gdb.SYMBOL_LOC_STATIC
22660 @item SYMBOL_LOC_STATIC
22661 Value is at a fixed address.
22662 @findex SYMBOL_LOC_REGISTER
22663 @findex gdb.SYMBOL_LOC_REGISTER
22664 @item SYMBOL_LOC_REGISTER
22665 Value is in a register.
22666 @findex SYMBOL_LOC_ARG
22667 @findex gdb.SYMBOL_LOC_ARG
22668 @item SYMBOL_LOC_ARG
22669 Value is an argument. This value is at the offset stored within the
22670 symbol inside the frame's argument list.
22671 @findex SYMBOL_LOC_REF_ARG
22672 @findex gdb.SYMBOL_LOC_REF_ARG
22673 @item SYMBOL_LOC_REF_ARG
22674 Value address is stored in the frame's argument list. Just like
22675 @code{LOC_ARG} except that the value's address is stored at the
22676 offset, not the value itself.
22677 @findex SYMBOL_LOC_REGPARM_ADDR
22678 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22679 @item SYMBOL_LOC_REGPARM_ADDR
22680 Value is a specified register. Just like @code{LOC_REGISTER} except
22681 the register holds the address of the argument instead of the argument
22683 @findex SYMBOL_LOC_LOCAL
22684 @findex gdb.SYMBOL_LOC_LOCAL
22685 @item SYMBOL_LOC_LOCAL
22686 Value is a local variable.
22687 @findex SYMBOL_LOC_TYPEDEF
22688 @findex gdb.SYMBOL_LOC_TYPEDEF
22689 @item SYMBOL_LOC_TYPEDEF
22690 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22692 @findex SYMBOL_LOC_BLOCK
22693 @findex gdb.SYMBOL_LOC_BLOCK
22694 @item SYMBOL_LOC_BLOCK
22696 @findex SYMBOL_LOC_CONST_BYTES
22697 @findex gdb.SYMBOL_LOC_CONST_BYTES
22698 @item SYMBOL_LOC_CONST_BYTES
22699 Value is a byte-sequence.
22700 @findex SYMBOL_LOC_UNRESOLVED
22701 @findex gdb.SYMBOL_LOC_UNRESOLVED
22702 @item SYMBOL_LOC_UNRESOLVED
22703 Value is at a fixed address, but the address of the variable has to be
22704 determined from the minimal symbol table whenever the variable is
22706 @findex SYMBOL_LOC_OPTIMIZED_OUT
22707 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22708 @item SYMBOL_LOC_OPTIMIZED_OUT
22709 The value does not actually exist in the program.
22710 @findex SYMBOL_LOC_COMPUTED
22711 @findex gdb.SYMBOL_LOC_COMPUTED
22712 @item SYMBOL_LOC_COMPUTED
22713 The value's address is a computed location.
22716 @node Symbol Tables In Python
22717 @subsubsection Symbol table representation in Python.
22719 @cindex symbol tables in python
22721 @tindex gdb.Symtab_and_line
22723 Access to symbol table data maintained by @value{GDBN} on the inferior
22724 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22725 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22726 from the @code{find_sal} method in @code{gdb.Frame} object.
22727 @xref{Frames In Python}.
22729 For more information on @value{GDBN}'s symbol table management, see
22730 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22732 A @code{gdb.Symtab_and_line} object has the following attributes:
22735 @defivar Symtab_and_line symtab
22736 The symbol table object (@code{gdb.Symtab}) for this frame.
22737 This attribute is not writable.
22740 @defivar Symtab_and_line pc
22741 Indicates the current program counter address. This attribute is not
22745 @defivar Symtab_and_line line
22746 Indicates the current line number for this object. This
22747 attribute is not writable.
22751 A @code{gdb.Symtab} object has the following attributes:
22754 @defivar Symtab filename
22755 The symbol table's source filename. This attribute is not writable.
22758 @defivar Symtab objfile
22759 The symbol table's backing object file. @xref{Objfiles In Python}.
22760 This attribute is not writable.
22764 The following methods are provided:
22767 @defmethod Symtab fullname
22768 Return the symbol table's source absolute file name.
22772 @node Breakpoints In Python
22773 @subsubsection Manipulating breakpoints using Python
22775 @cindex breakpoints in python
22776 @tindex gdb.Breakpoint
22778 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22781 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
22782 Create a new breakpoint. @var{spec} is a string naming the
22783 location of the breakpoint, or an expression that defines a
22784 watchpoint. The contents can be any location recognized by the
22785 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22786 command. The optional @var{type} denotes the breakpoint to create
22787 from the types defined later in this chapter. This argument can be
22788 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22789 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
22790 argument defines the class of watchpoint to create, if @var{type} is
22791 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
22792 provided, it is assumed to be a @var{WP_WRITE} class.
22795 The available watchpoint types represented by constants are defined in the
22800 @findex gdb.WP_READ
22802 Read only watchpoint.
22805 @findex gdb.WP_WRITE
22807 Write only watchpoint.
22810 @findex gdb.WP_ACCESS
22812 Read/Write watchpoint.
22815 @defmethod Breakpoint is_valid
22816 Return @code{True} if this @code{Breakpoint} object is valid,
22817 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22818 if the user deletes the breakpoint. In this case, the object still
22819 exists, but the underlying breakpoint does not. In the cases of
22820 watchpoint scope, the watchpoint remains valid even if execution of the
22821 inferior leaves the scope of that watchpoint.
22824 @defivar Breakpoint enabled
22825 This attribute is @code{True} if the breakpoint is enabled, and
22826 @code{False} otherwise. This attribute is writable.
22829 @defivar Breakpoint silent
22830 This attribute is @code{True} if the breakpoint is silent, and
22831 @code{False} otherwise. This attribute is writable.
22833 Note that a breakpoint can also be silent if it has commands and the
22834 first command is @code{silent}. This is not reported by the
22835 @code{silent} attribute.
22838 @defivar Breakpoint thread
22839 If the breakpoint is thread-specific, this attribute holds the thread
22840 id. If the breakpoint is not thread-specific, this attribute is
22841 @code{None}. This attribute is writable.
22844 @defivar Breakpoint task
22845 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22846 id. If the breakpoint is not task-specific (or the underlying
22847 language is not Ada), this attribute is @code{None}. This attribute
22851 @defivar Breakpoint ignore_count
22852 This attribute holds the ignore count for the breakpoint, an integer.
22853 This attribute is writable.
22856 @defivar Breakpoint number
22857 This attribute holds the breakpoint's number --- the identifier used by
22858 the user to manipulate the breakpoint. This attribute is not writable.
22861 @defivar Breakpoint type
22862 This attribute holds the breakpoint's type --- the identifier used to
22863 determine the actual breakpoint type or use-case. This attribute is not
22867 The available types are represented by constants defined in the @code{gdb}
22871 @findex BP_BREAKPOINT
22872 @findex gdb.BP_BREAKPOINT
22873 @item BP_BREAKPOINT
22874 Normal code breakpoint.
22876 @findex BP_WATCHPOINT
22877 @findex gdb.BP_WATCHPOINT
22878 @item BP_WATCHPOINT
22879 Watchpoint breakpoint.
22881 @findex BP_HARDWARE_WATCHPOINT
22882 @findex gdb.BP_HARDWARE_WATCHPOINT
22883 @item BP_HARDWARE_WATCHPOINT
22884 Hardware assisted watchpoint.
22886 @findex BP_READ_WATCHPOINT
22887 @findex gdb.BP_READ_WATCHPOINT
22888 @item BP_READ_WATCHPOINT
22889 Hardware assisted read watchpoint.
22891 @findex BP_ACCESS_WATCHPOINT
22892 @findex gdb.BP_ACCESS_WATCHPOINT
22893 @item BP_ACCESS_WATCHPOINT
22894 Hardware assisted access watchpoint.
22897 @defivar Breakpoint hit_count
22898 This attribute holds the hit count for the breakpoint, an integer.
22899 This attribute is writable, but currently it can only be set to zero.
22902 @defivar Breakpoint location
22903 This attribute holds the location of the breakpoint, as specified by
22904 the user. It is a string. If the breakpoint does not have a location
22905 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22906 attribute is not writable.
22909 @defivar Breakpoint expression
22910 This attribute holds a breakpoint expression, as specified by
22911 the user. It is a string. If the breakpoint does not have an
22912 expression (the breakpoint is not a watchpoint) the attribute's value
22913 is @code{None}. This attribute is not writable.
22916 @defivar Breakpoint condition
22917 This attribute holds the condition of the breakpoint, as specified by
22918 the user. It is a string. If there is no condition, this attribute's
22919 value is @code{None}. This attribute is writable.
22922 @defivar Breakpoint commands
22923 This attribute holds the commands attached to the breakpoint. If
22924 there are commands, this attribute's value is a string holding all the
22925 commands, separated by newlines. If there are no commands, this
22926 attribute is @code{None}. This attribute is not writable.
22929 @node Lazy Strings In Python
22930 @subsubsection Python representation of lazy strings.
22932 @cindex lazy strings in python
22933 @tindex gdb.LazyString
22935 A @dfn{lazy string} is a string whose contents is not retrieved or
22936 encoded until it is needed.
22938 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22939 @code{address} that points to a region of memory, an @code{encoding}
22940 that will be used to encode that region of memory, and a @code{length}
22941 to delimit the region of memory that represents the string. The
22942 difference between a @code{gdb.LazyString} and a string wrapped within
22943 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22944 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22945 retrieved and encoded during printing, while a @code{gdb.Value}
22946 wrapping a string is immediately retrieved and encoded on creation.
22948 A @code{gdb.LazyString} object has the following functions:
22950 @defmethod LazyString value
22951 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22952 will point to the string in memory, but will lose all the delayed
22953 retrieval, encoding and handling that @value{GDBN} applies to a
22954 @code{gdb.LazyString}.
22957 @defivar LazyString address
22958 This attribute holds the address of the string. This attribute is not
22962 @defivar LazyString length
22963 This attribute holds the length of the string in characters. If the
22964 length is -1, then the string will be fetched and encoded up to the
22965 first null of appropriate width. This attribute is not writable.
22968 @defivar LazyString encoding
22969 This attribute holds the encoding that will be applied to the string
22970 when the string is printed by @value{GDBN}. If the encoding is not
22971 set, or contains an empty string, then @value{GDBN} will select the
22972 most appropriate encoding when the string is printed. This attribute
22976 @defivar LazyString type
22977 This attribute holds the type that is represented by the lazy string's
22978 type. For a lazy string this will always be a pointer type. To
22979 resolve this to the lazy string's character type, use the type's
22980 @code{target} method. @xref{Types In Python}. This attribute is not
22985 @subsection Auto-loading
22986 @cindex auto-loading, Python
22988 When a new object file is read (for example, due to the @code{file}
22989 command, or because the inferior has loaded a shared library),
22990 @value{GDBN} will look for Python support scripts in several ways:
22991 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22994 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22995 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22996 * Which flavor to choose?::
22999 The auto-loading feature is useful for supplying application-specific
23000 debugging commands and scripts.
23002 Auto-loading can be enabled or disabled.
23005 @kindex maint set python auto-load
23006 @item maint set python auto-load [yes|no]
23007 Enable or disable the Python auto-loading feature.
23009 @kindex maint show python auto-load
23010 @item maint show python auto-load
23011 Show whether Python auto-loading is enabled or disabled.
23014 When reading an auto-loaded file, @value{GDBN} sets the
23015 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23016 function (@pxref{Objfiles In Python}). This can be useful for
23017 registering objfile-specific pretty-printers.
23019 @node objfile-gdb.py file
23020 @subsubsection The @file{@var{objfile}-gdb.py} file
23021 @cindex @file{@var{objfile}-gdb.py}
23023 When a new object file is read, @value{GDBN} looks for
23024 a file named @file{@var{objfile}-gdb.py},
23025 where @var{objfile} is the object file's real name, formed by ensuring
23026 that the file name is absolute, following all symlinks, and resolving
23027 @code{.} and @code{..} components. If this file exists and is
23028 readable, @value{GDBN} will evaluate it as a Python script.
23030 If this file does not exist, and if the parameter
23031 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23032 then @value{GDBN} will look for @var{real-name} in all of the
23033 directories mentioned in the value of @code{debug-file-directory}.
23035 Finally, if this file does not exist, then @value{GDBN} will look for
23036 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23037 @var{data-directory} is @value{GDBN}'s data directory (available via
23038 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23039 is the object file's real name, as described above.
23041 @value{GDBN} does not track which files it has already auto-loaded this way.
23042 @value{GDBN} will load the associated script every time the corresponding
23043 @var{objfile} is opened.
23044 So your @file{-gdb.py} file should be careful to avoid errors if it
23045 is evaluated more than once.
23047 @node .debug_gdb_scripts section
23048 @subsubsection The @code{.debug_gdb_scripts} section
23049 @cindex @code{.debug_gdb_scripts} section
23051 For systems using file formats like ELF and COFF,
23052 when @value{GDBN} loads a new object file
23053 it will look for a special section named @samp{.debug_gdb_scripts}.
23054 If this section exists, its contents is a list of names of scripts to load.
23056 @value{GDBN} will look for each specified script file first in the
23057 current directory and then along the source search path
23058 (@pxref{Source Path, ,Specifying Source Directories}),
23059 except that @file{$cdir} is not searched, since the compilation
23060 directory is not relevant to scripts.
23062 Entries can be placed in section @code{.debug_gdb_scripts} with,
23063 for example, this GCC macro:
23066 /* Note: The "MS" section flags are to remove duplicates. */
23067 #define DEFINE_GDB_SCRIPT(script_name) \
23069 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23071 .asciz \"" script_name "\"\n\
23077 Then one can reference the macro in a header or source file like this:
23080 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23083 The script name may include directories if desired.
23085 If the macro is put in a header, any application or library
23086 using this header will get a reference to the specified script.
23088 @node Which flavor to choose?
23089 @subsubsection Which flavor to choose?
23091 Given the multiple ways of auto-loading Python scripts, it might not always
23092 be clear which one to choose. This section provides some guidance.
23094 Benefits of the @file{-gdb.py} way:
23098 Can be used with file formats that don't support multiple sections.
23101 Ease of finding scripts for public libraries.
23103 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23104 in the source search path.
23105 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23106 isn't a source directory in which to find the script.
23109 Doesn't require source code additions.
23112 Benefits of the @code{.debug_gdb_scripts} way:
23116 Works with static linking.
23118 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23119 trigger their loading. When an application is statically linked the only
23120 objfile available is the executable, and it is cumbersome to attach all the
23121 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23124 Works with classes that are entirely inlined.
23126 Some classes can be entirely inlined, and thus there may not be an associated
23127 shared library to attach a @file{-gdb.py} script to.
23130 Scripts needn't be copied out of the source tree.
23132 In some circumstances, apps can be built out of large collections of internal
23133 libraries, and the build infrastructure necessary to install the
23134 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23135 cumbersome. It may be easier to specify the scripts in the
23136 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23137 top of the source tree to the source search path.
23140 @node Python modules
23141 @subsection Python modules
23142 @cindex python modules
23144 @value{GDBN} comes with a module to assist writing Python code.
23147 * gdb.printing:: Building and registering pretty-printers.
23148 * gdb.types:: Utilities for working with types.
23152 @subsubsection gdb.printing
23153 @cindex gdb.printing
23155 This module provides a collection of utilities for working with
23159 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23160 This class specifies the API that makes @samp{info pretty-printer},
23161 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23162 Pretty-printers should generally inherit from this class.
23164 @item SubPrettyPrinter (@var{name})
23165 For printers that handle multiple types, this class specifies the
23166 corresponding API for the subprinters.
23168 @item RegexpCollectionPrettyPrinter (@var{name})
23169 Utility class for handling multiple printers, all recognized via
23170 regular expressions.
23171 @xref{Writing a Pretty-Printer}, for an example.
23173 @item register_pretty_printer (@var{obj}, @var{printer})
23174 Register @var{printer} with the pretty-printer list of @var{obj}.
23178 @subsubsection gdb.types
23181 This module provides a collection of utilities for working with
23182 @code{gdb.Types} objects.
23185 @item get_basic_type (@var{type})
23186 Return @var{type} with const and volatile qualifiers stripped,
23187 and with typedefs and C@t{++} references converted to the underlying type.
23192 typedef const int const_int;
23194 const_int& foo_ref (foo);
23195 int main () @{ return 0; @}
23202 (gdb) python import gdb.types
23203 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23204 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23208 @item has_field (@var{type}, @var{field})
23209 Return @code{True} if @var{type}, assumed to be a type with fields
23210 (e.g., a structure or union), has field @var{field}.
23212 @item make_enum_dict (@var{enum_type})
23213 Return a Python @code{dictionary} type produced from @var{enum_type}.
23217 @chapter Command Interpreters
23218 @cindex command interpreters
23220 @value{GDBN} supports multiple command interpreters, and some command
23221 infrastructure to allow users or user interface writers to switch
23222 between interpreters or run commands in other interpreters.
23224 @value{GDBN} currently supports two command interpreters, the console
23225 interpreter (sometimes called the command-line interpreter or @sc{cli})
23226 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23227 describes both of these interfaces in great detail.
23229 By default, @value{GDBN} will start with the console interpreter.
23230 However, the user may choose to start @value{GDBN} with another
23231 interpreter by specifying the @option{-i} or @option{--interpreter}
23232 startup options. Defined interpreters include:
23236 @cindex console interpreter
23237 The traditional console or command-line interpreter. This is the most often
23238 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23239 @value{GDBN} will use this interpreter.
23242 @cindex mi interpreter
23243 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23244 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23245 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23249 @cindex mi2 interpreter
23250 The current @sc{gdb/mi} interface.
23253 @cindex mi1 interpreter
23254 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23258 @cindex invoke another interpreter
23259 The interpreter being used by @value{GDBN} may not be dynamically
23260 switched at runtime. Although possible, this could lead to a very
23261 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23262 enters the command "interpreter-set console" in a console view,
23263 @value{GDBN} would switch to using the console interpreter, rendering
23264 the IDE inoperable!
23266 @kindex interpreter-exec
23267 Although you may only choose a single interpreter at startup, you may execute
23268 commands in any interpreter from the current interpreter using the appropriate
23269 command. If you are running the console interpreter, simply use the
23270 @code{interpreter-exec} command:
23273 interpreter-exec mi "-data-list-register-names"
23276 @sc{gdb/mi} has a similar command, although it is only available in versions of
23277 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23280 @chapter @value{GDBN} Text User Interface
23282 @cindex Text User Interface
23285 * TUI Overview:: TUI overview
23286 * TUI Keys:: TUI key bindings
23287 * TUI Single Key Mode:: TUI single key mode
23288 * TUI Commands:: TUI-specific commands
23289 * TUI Configuration:: TUI configuration variables
23292 The @value{GDBN} Text User Interface (TUI) is a terminal
23293 interface which uses the @code{curses} library to show the source
23294 file, the assembly output, the program registers and @value{GDBN}
23295 commands in separate text windows. The TUI mode is supported only
23296 on platforms where a suitable version of the @code{curses} library
23299 @pindex @value{GDBTUI}
23300 The TUI mode is enabled by default when you invoke @value{GDBN} as
23301 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23302 You can also switch in and out of TUI mode while @value{GDBN} runs by
23303 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23304 @xref{TUI Keys, ,TUI Key Bindings}.
23307 @section TUI Overview
23309 In TUI mode, @value{GDBN} can display several text windows:
23313 This window is the @value{GDBN} command window with the @value{GDBN}
23314 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23315 managed using readline.
23318 The source window shows the source file of the program. The current
23319 line and active breakpoints are displayed in this window.
23322 The assembly window shows the disassembly output of the program.
23325 This window shows the processor registers. Registers are highlighted
23326 when their values change.
23329 The source and assembly windows show the current program position
23330 by highlighting the current line and marking it with a @samp{>} marker.
23331 Breakpoints are indicated with two markers. The first marker
23332 indicates the breakpoint type:
23336 Breakpoint which was hit at least once.
23339 Breakpoint which was never hit.
23342 Hardware breakpoint which was hit at least once.
23345 Hardware breakpoint which was never hit.
23348 The second marker indicates whether the breakpoint is enabled or not:
23352 Breakpoint is enabled.
23355 Breakpoint is disabled.
23358 The source, assembly and register windows are updated when the current
23359 thread changes, when the frame changes, or when the program counter
23362 These windows are not all visible at the same time. The command
23363 window is always visible. The others can be arranged in several
23374 source and assembly,
23377 source and registers, or
23380 assembly and registers.
23383 A status line above the command window shows the following information:
23387 Indicates the current @value{GDBN} target.
23388 (@pxref{Targets, ,Specifying a Debugging Target}).
23391 Gives the current process or thread number.
23392 When no process is being debugged, this field is set to @code{No process}.
23395 Gives the current function name for the selected frame.
23396 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23397 When there is no symbol corresponding to the current program counter,
23398 the string @code{??} is displayed.
23401 Indicates the current line number for the selected frame.
23402 When the current line number is not known, the string @code{??} is displayed.
23405 Indicates the current program counter address.
23409 @section TUI Key Bindings
23410 @cindex TUI key bindings
23412 The TUI installs several key bindings in the readline keymaps
23413 (@pxref{Command Line Editing}). The following key bindings
23414 are installed for both TUI mode and the @value{GDBN} standard mode.
23423 Enter or leave the TUI mode. When leaving the TUI mode,
23424 the curses window management stops and @value{GDBN} operates using
23425 its standard mode, writing on the terminal directly. When reentering
23426 the TUI mode, control is given back to the curses windows.
23427 The screen is then refreshed.
23431 Use a TUI layout with only one window. The layout will
23432 either be @samp{source} or @samp{assembly}. When the TUI mode
23433 is not active, it will switch to the TUI mode.
23435 Think of this key binding as the Emacs @kbd{C-x 1} binding.
23439 Use a TUI layout with at least two windows. When the current
23440 layout already has two windows, the next layout with two windows is used.
23441 When a new layout is chosen, one window will always be common to the
23442 previous layout and the new one.
23444 Think of it as the Emacs @kbd{C-x 2} binding.
23448 Change the active window. The TUI associates several key bindings
23449 (like scrolling and arrow keys) with the active window. This command
23450 gives the focus to the next TUI window.
23452 Think of it as the Emacs @kbd{C-x o} binding.
23456 Switch in and out of the TUI SingleKey mode that binds single
23457 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
23460 The following key bindings only work in the TUI mode:
23465 Scroll the active window one page up.
23469 Scroll the active window one page down.
23473 Scroll the active window one line up.
23477 Scroll the active window one line down.
23481 Scroll the active window one column left.
23485 Scroll the active window one column right.
23489 Refresh the screen.
23492 Because the arrow keys scroll the active window in the TUI mode, they
23493 are not available for their normal use by readline unless the command
23494 window has the focus. When another window is active, you must use
23495 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
23496 and @kbd{C-f} to control the command window.
23498 @node TUI Single Key Mode
23499 @section TUI Single Key Mode
23500 @cindex TUI single key mode
23502 The TUI also provides a @dfn{SingleKey} mode, which binds several
23503 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
23504 switch into this mode, where the following key bindings are used:
23507 @kindex c @r{(SingleKey TUI key)}
23511 @kindex d @r{(SingleKey TUI key)}
23515 @kindex f @r{(SingleKey TUI key)}
23519 @kindex n @r{(SingleKey TUI key)}
23523 @kindex q @r{(SingleKey TUI key)}
23525 exit the SingleKey mode.
23527 @kindex r @r{(SingleKey TUI key)}
23531 @kindex s @r{(SingleKey TUI key)}
23535 @kindex u @r{(SingleKey TUI key)}
23539 @kindex v @r{(SingleKey TUI key)}
23543 @kindex w @r{(SingleKey TUI key)}
23548 Other keys temporarily switch to the @value{GDBN} command prompt.
23549 The key that was pressed is inserted in the editing buffer so that
23550 it is possible to type most @value{GDBN} commands without interaction
23551 with the TUI SingleKey mode. Once the command is entered the TUI
23552 SingleKey mode is restored. The only way to permanently leave
23553 this mode is by typing @kbd{q} or @kbd{C-x s}.
23557 @section TUI-specific Commands
23558 @cindex TUI commands
23560 The TUI has specific commands to control the text windows.
23561 These commands are always available, even when @value{GDBN} is not in
23562 the TUI mode. When @value{GDBN} is in the standard mode, most
23563 of these commands will automatically switch to the TUI mode.
23565 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23566 terminal, or @value{GDBN} has been started with the machine interface
23567 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23568 these commands will fail with an error, because it would not be
23569 possible or desirable to enable curses window management.
23574 List and give the size of all displayed windows.
23578 Display the next layout.
23581 Display the previous layout.
23584 Display the source window only.
23587 Display the assembly window only.
23590 Display the source and assembly window.
23593 Display the register window together with the source or assembly window.
23597 Make the next window active for scrolling.
23600 Make the previous window active for scrolling.
23603 Make the source window active for scrolling.
23606 Make the assembly window active for scrolling.
23609 Make the register window active for scrolling.
23612 Make the command window active for scrolling.
23616 Refresh the screen. This is similar to typing @kbd{C-L}.
23618 @item tui reg float
23620 Show the floating point registers in the register window.
23622 @item tui reg general
23623 Show the general registers in the register window.
23626 Show the next register group. The list of register groups as well as
23627 their order is target specific. The predefined register groups are the
23628 following: @code{general}, @code{float}, @code{system}, @code{vector},
23629 @code{all}, @code{save}, @code{restore}.
23631 @item tui reg system
23632 Show the system registers in the register window.
23636 Update the source window and the current execution point.
23638 @item winheight @var{name} +@var{count}
23639 @itemx winheight @var{name} -@var{count}
23641 Change the height of the window @var{name} by @var{count}
23642 lines. Positive counts increase the height, while negative counts
23645 @item tabset @var{nchars}
23647 Set the width of tab stops to be @var{nchars} characters.
23650 @node TUI Configuration
23651 @section TUI Configuration Variables
23652 @cindex TUI configuration variables
23654 Several configuration variables control the appearance of TUI windows.
23657 @item set tui border-kind @var{kind}
23658 @kindex set tui border-kind
23659 Select the border appearance for the source, assembly and register windows.
23660 The possible values are the following:
23663 Use a space character to draw the border.
23666 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23669 Use the Alternate Character Set to draw the border. The border is
23670 drawn using character line graphics if the terminal supports them.
23673 @item set tui border-mode @var{mode}
23674 @kindex set tui border-mode
23675 @itemx set tui active-border-mode @var{mode}
23676 @kindex set tui active-border-mode
23677 Select the display attributes for the borders of the inactive windows
23678 or the active window. The @var{mode} can be one of the following:
23681 Use normal attributes to display the border.
23687 Use reverse video mode.
23690 Use half bright mode.
23692 @item half-standout
23693 Use half bright and standout mode.
23696 Use extra bright or bold mode.
23698 @item bold-standout
23699 Use extra bright or bold and standout mode.
23704 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23707 @cindex @sc{gnu} Emacs
23708 A special interface allows you to use @sc{gnu} Emacs to view (and
23709 edit) the source files for the program you are debugging with
23712 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23713 executable file you want to debug as an argument. This command starts
23714 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23715 created Emacs buffer.
23716 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23718 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23723 All ``terminal'' input and output goes through an Emacs buffer, called
23726 This applies both to @value{GDBN} commands and their output, and to the input
23727 and output done by the program you are debugging.
23729 This is useful because it means that you can copy the text of previous
23730 commands and input them again; you can even use parts of the output
23733 All the facilities of Emacs' Shell mode are available for interacting
23734 with your program. In particular, you can send signals the usual
23735 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23739 @value{GDBN} displays source code through Emacs.
23741 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23742 source file for that frame and puts an arrow (@samp{=>}) at the
23743 left margin of the current line. Emacs uses a separate buffer for
23744 source display, and splits the screen to show both your @value{GDBN} session
23747 Explicit @value{GDBN} @code{list} or search commands still produce output as
23748 usual, but you probably have no reason to use them from Emacs.
23751 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23752 a graphical mode, enabled by default, which provides further buffers
23753 that can control the execution and describe the state of your program.
23754 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23756 If you specify an absolute file name when prompted for the @kbd{M-x
23757 gdb} argument, then Emacs sets your current working directory to where
23758 your program resides. If you only specify the file name, then Emacs
23759 sets your current working directory to to the directory associated
23760 with the previous buffer. In this case, @value{GDBN} may find your
23761 program by searching your environment's @code{PATH} variable, but on
23762 some operating systems it might not find the source. So, although the
23763 @value{GDBN} input and output session proceeds normally, the auxiliary
23764 buffer does not display the current source and line of execution.
23766 The initial working directory of @value{GDBN} is printed on the top
23767 line of the GUD buffer and this serves as a default for the commands
23768 that specify files for @value{GDBN} to operate on. @xref{Files,
23769 ,Commands to Specify Files}.
23771 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23772 need to call @value{GDBN} by a different name (for example, if you
23773 keep several configurations around, with different names) you can
23774 customize the Emacs variable @code{gud-gdb-command-name} to run the
23777 In the GUD buffer, you can use these special Emacs commands in
23778 addition to the standard Shell mode commands:
23782 Describe the features of Emacs' GUD Mode.
23785 Execute to another source line, like the @value{GDBN} @code{step} command; also
23786 update the display window to show the current file and location.
23789 Execute to next source line in this function, skipping all function
23790 calls, like the @value{GDBN} @code{next} command. Then update the display window
23791 to show the current file and location.
23794 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23795 display window accordingly.
23798 Execute until exit from the selected stack frame, like the @value{GDBN}
23799 @code{finish} command.
23802 Continue execution of your program, like the @value{GDBN} @code{continue}
23806 Go up the number of frames indicated by the numeric argument
23807 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23808 like the @value{GDBN} @code{up} command.
23811 Go down the number of frames indicated by the numeric argument, like the
23812 @value{GDBN} @code{down} command.
23815 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23816 tells @value{GDBN} to set a breakpoint on the source line point is on.
23818 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23819 separate frame which shows a backtrace when the GUD buffer is current.
23820 Move point to any frame in the stack and type @key{RET} to make it
23821 become the current frame and display the associated source in the
23822 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23823 selected frame become the current one. In graphical mode, the
23824 speedbar displays watch expressions.
23826 If you accidentally delete the source-display buffer, an easy way to get
23827 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23828 request a frame display; when you run under Emacs, this recreates
23829 the source buffer if necessary to show you the context of the current
23832 The source files displayed in Emacs are in ordinary Emacs buffers
23833 which are visiting the source files in the usual way. You can edit
23834 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23835 communicates with Emacs in terms of line numbers. If you add or
23836 delete lines from the text, the line numbers that @value{GDBN} knows cease
23837 to correspond properly with the code.
23839 A more detailed description of Emacs' interaction with @value{GDBN} is
23840 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23843 @c The following dropped because Epoch is nonstandard. Reactivate
23844 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23846 @kindex Emacs Epoch environment
23850 Version 18 of @sc{gnu} Emacs has a built-in window system
23851 called the @code{epoch}
23852 environment. Users of this environment can use a new command,
23853 @code{inspect} which performs identically to @code{print} except that
23854 each value is printed in its own window.
23859 @chapter The @sc{gdb/mi} Interface
23861 @unnumberedsec Function and Purpose
23863 @cindex @sc{gdb/mi}, its purpose
23864 @sc{gdb/mi} is a line based machine oriented text interface to
23865 @value{GDBN} and is activated by specifying using the
23866 @option{--interpreter} command line option (@pxref{Mode Options}). It
23867 is specifically intended to support the development of systems which
23868 use the debugger as just one small component of a larger system.
23870 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23871 in the form of a reference manual.
23873 Note that @sc{gdb/mi} is still under construction, so some of the
23874 features described below are incomplete and subject to change
23875 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23877 @unnumberedsec Notation and Terminology
23879 @cindex notational conventions, for @sc{gdb/mi}
23880 This chapter uses the following notation:
23884 @code{|} separates two alternatives.
23887 @code{[ @var{something} ]} indicates that @var{something} is optional:
23888 it may or may not be given.
23891 @code{( @var{group} )*} means that @var{group} inside the parentheses
23892 may repeat zero or more times.
23895 @code{( @var{group} )+} means that @var{group} inside the parentheses
23896 may repeat one or more times.
23899 @code{"@var{string}"} means a literal @var{string}.
23903 @heading Dependencies
23907 * GDB/MI General Design::
23908 * GDB/MI Command Syntax::
23909 * GDB/MI Compatibility with CLI::
23910 * GDB/MI Development and Front Ends::
23911 * GDB/MI Output Records::
23912 * GDB/MI Simple Examples::
23913 * GDB/MI Command Description Format::
23914 * GDB/MI Breakpoint Commands::
23915 * GDB/MI Program Context::
23916 * GDB/MI Thread Commands::
23917 * GDB/MI Program Execution::
23918 * GDB/MI Stack Manipulation::
23919 * GDB/MI Variable Objects::
23920 * GDB/MI Data Manipulation::
23921 * GDB/MI Tracepoint Commands::
23922 * GDB/MI Symbol Query::
23923 * GDB/MI File Commands::
23925 * GDB/MI Kod Commands::
23926 * GDB/MI Memory Overlay Commands::
23927 * GDB/MI Signal Handling Commands::
23929 * GDB/MI Target Manipulation::
23930 * GDB/MI File Transfer Commands::
23931 * GDB/MI Miscellaneous Commands::
23934 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23935 @node GDB/MI General Design
23936 @section @sc{gdb/mi} General Design
23937 @cindex GDB/MI General Design
23939 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23940 parts---commands sent to @value{GDBN}, responses to those commands
23941 and notifications. Each command results in exactly one response,
23942 indicating either successful completion of the command, or an error.
23943 For the commands that do not resume the target, the response contains the
23944 requested information. For the commands that resume the target, the
23945 response only indicates whether the target was successfully resumed.
23946 Notifications is the mechanism for reporting changes in the state of the
23947 target, or in @value{GDBN} state, that cannot conveniently be associated with
23948 a command and reported as part of that command response.
23950 The important examples of notifications are:
23954 Exec notifications. These are used to report changes in
23955 target state---when a target is resumed, or stopped. It would not
23956 be feasible to include this information in response of resuming
23957 commands, because one resume commands can result in multiple events in
23958 different threads. Also, quite some time may pass before any event
23959 happens in the target, while a frontend needs to know whether the resuming
23960 command itself was successfully executed.
23963 Console output, and status notifications. Console output
23964 notifications are used to report output of CLI commands, as well as
23965 diagnostics for other commands. Status notifications are used to
23966 report the progress of a long-running operation. Naturally, including
23967 this information in command response would mean no output is produced
23968 until the command is finished, which is undesirable.
23971 General notifications. Commands may have various side effects on
23972 the @value{GDBN} or target state beyond their official purpose. For example,
23973 a command may change the selected thread. Although such changes can
23974 be included in command response, using notification allows for more
23975 orthogonal frontend design.
23979 There's no guarantee that whenever an MI command reports an error,
23980 @value{GDBN} or the target are in any specific state, and especially,
23981 the state is not reverted to the state before the MI command was
23982 processed. Therefore, whenever an MI command results in an error,
23983 we recommend that the frontend refreshes all the information shown in
23984 the user interface.
23988 * Context management::
23989 * Asynchronous and non-stop modes::
23993 @node Context management
23994 @subsection Context management
23996 In most cases when @value{GDBN} accesses the target, this access is
23997 done in context of a specific thread and frame (@pxref{Frames}).
23998 Often, even when accessing global data, the target requires that a thread
23999 be specified. The CLI interface maintains the selected thread and frame,
24000 and supplies them to target on each command. This is convenient,
24001 because a command line user would not want to specify that information
24002 explicitly on each command, and because user interacts with
24003 @value{GDBN} via a single terminal, so no confusion is possible as
24004 to what thread and frame are the current ones.
24006 In the case of MI, the concept of selected thread and frame is less
24007 useful. First, a frontend can easily remember this information
24008 itself. Second, a graphical frontend can have more than one window,
24009 each one used for debugging a different thread, and the frontend might
24010 want to access additional threads for internal purposes. This
24011 increases the risk that by relying on implicitly selected thread, the
24012 frontend may be operating on a wrong one. Therefore, each MI command
24013 should explicitly specify which thread and frame to operate on. To
24014 make it possible, each MI command accepts the @samp{--thread} and
24015 @samp{--frame} options, the value to each is @value{GDBN} identifier
24016 for thread and frame to operate on.
24018 Usually, each top-level window in a frontend allows the user to select
24019 a thread and a frame, and remembers the user selection for further
24020 operations. However, in some cases @value{GDBN} may suggest that the
24021 current thread be changed. For example, when stopping on a breakpoint
24022 it is reasonable to switch to the thread where breakpoint is hit. For
24023 another example, if the user issues the CLI @samp{thread} command via
24024 the frontend, it is desirable to change the frontend's selected thread to the
24025 one specified by user. @value{GDBN} communicates the suggestion to
24026 change current thread using the @samp{=thread-selected} notification.
24027 No such notification is available for the selected frame at the moment.
24029 Note that historically, MI shares the selected thread with CLI, so
24030 frontends used the @code{-thread-select} to execute commands in the
24031 right context. However, getting this to work right is cumbersome. The
24032 simplest way is for frontend to emit @code{-thread-select} command
24033 before every command. This doubles the number of commands that need
24034 to be sent. The alternative approach is to suppress @code{-thread-select}
24035 if the selected thread in @value{GDBN} is supposed to be identical to the
24036 thread the frontend wants to operate on. However, getting this
24037 optimization right can be tricky. In particular, if the frontend
24038 sends several commands to @value{GDBN}, and one of the commands changes the
24039 selected thread, then the behaviour of subsequent commands will
24040 change. So, a frontend should either wait for response from such
24041 problematic commands, or explicitly add @code{-thread-select} for
24042 all subsequent commands. No frontend is known to do this exactly
24043 right, so it is suggested to just always pass the @samp{--thread} and
24044 @samp{--frame} options.
24046 @node Asynchronous and non-stop modes
24047 @subsection Asynchronous command execution and non-stop mode
24049 On some targets, @value{GDBN} is capable of processing MI commands
24050 even while the target is running. This is called @dfn{asynchronous
24051 command execution} (@pxref{Background Execution}). The frontend may
24052 specify a preferrence for asynchronous execution using the
24053 @code{-gdb-set target-async 1} command, which should be emitted before
24054 either running the executable or attaching to the target. After the
24055 frontend has started the executable or attached to the target, it can
24056 find if asynchronous execution is enabled using the
24057 @code{-list-target-features} command.
24059 Even if @value{GDBN} can accept a command while target is running,
24060 many commands that access the target do not work when the target is
24061 running. Therefore, asynchronous command execution is most useful
24062 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24063 it is possible to examine the state of one thread, while other threads
24066 When a given thread is running, MI commands that try to access the
24067 target in the context of that thread may not work, or may work only on
24068 some targets. In particular, commands that try to operate on thread's
24069 stack will not work, on any target. Commands that read memory, or
24070 modify breakpoints, may work or not work, depending on the target. Note
24071 that even commands that operate on global state, such as @code{print},
24072 @code{set}, and breakpoint commands, still access the target in the
24073 context of a specific thread, so frontend should try to find a
24074 stopped thread and perform the operation on that thread (using the
24075 @samp{--thread} option).
24077 Which commands will work in the context of a running thread is
24078 highly target dependent. However, the two commands
24079 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24080 to find the state of a thread, will always work.
24082 @node Thread groups
24083 @subsection Thread groups
24084 @value{GDBN} may be used to debug several processes at the same time.
24085 On some platfroms, @value{GDBN} may support debugging of several
24086 hardware systems, each one having several cores with several different
24087 processes running on each core. This section describes the MI
24088 mechanism to support such debugging scenarios.
24090 The key observation is that regardless of the structure of the
24091 target, MI can have a global list of threads, because most commands that
24092 accept the @samp{--thread} option do not need to know what process that
24093 thread belongs to. Therefore, it is not necessary to introduce
24094 neither additional @samp{--process} option, nor an notion of the
24095 current process in the MI interface. The only strictly new feature
24096 that is required is the ability to find how the threads are grouped
24099 To allow the user to discover such grouping, and to support arbitrary
24100 hierarchy of machines/cores/processes, MI introduces the concept of a
24101 @dfn{thread group}. Thread group is a collection of threads and other
24102 thread groups. A thread group always has a string identifier, a type,
24103 and may have additional attributes specific to the type. A new
24104 command, @code{-list-thread-groups}, returns the list of top-level
24105 thread groups, which correspond to processes that @value{GDBN} is
24106 debugging at the moment. By passing an identifier of a thread group
24107 to the @code{-list-thread-groups} command, it is possible to obtain
24108 the members of specific thread group.
24110 To allow the user to easily discover processes, and other objects, he
24111 wishes to debug, a concept of @dfn{available thread group} is
24112 introduced. Available thread group is an thread group that
24113 @value{GDBN} is not debugging, but that can be attached to, using the
24114 @code{-target-attach} command. The list of available top-level thread
24115 groups can be obtained using @samp{-list-thread-groups --available}.
24116 In general, the content of a thread group may be only retrieved only
24117 after attaching to that thread group.
24119 Thread groups are related to inferiors (@pxref{Inferiors and
24120 Programs}). Each inferior corresponds to a thread group of a special
24121 type @samp{process}, and some additional operations are permitted on
24122 such thread groups.
24124 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24125 @node GDB/MI Command Syntax
24126 @section @sc{gdb/mi} Command Syntax
24129 * GDB/MI Input Syntax::
24130 * GDB/MI Output Syntax::
24133 @node GDB/MI Input Syntax
24134 @subsection @sc{gdb/mi} Input Syntax
24136 @cindex input syntax for @sc{gdb/mi}
24137 @cindex @sc{gdb/mi}, input syntax
24139 @item @var{command} @expansion{}
24140 @code{@var{cli-command} | @var{mi-command}}
24142 @item @var{cli-command} @expansion{}
24143 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24144 @var{cli-command} is any existing @value{GDBN} CLI command.
24146 @item @var{mi-command} @expansion{}
24147 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24148 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24150 @item @var{token} @expansion{}
24151 "any sequence of digits"
24153 @item @var{option} @expansion{}
24154 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24156 @item @var{parameter} @expansion{}
24157 @code{@var{non-blank-sequence} | @var{c-string}}
24159 @item @var{operation} @expansion{}
24160 @emph{any of the operations described in this chapter}
24162 @item @var{non-blank-sequence} @expansion{}
24163 @emph{anything, provided it doesn't contain special characters such as
24164 "-", @var{nl}, """ and of course " "}
24166 @item @var{c-string} @expansion{}
24167 @code{""" @var{seven-bit-iso-c-string-content} """}
24169 @item @var{nl} @expansion{}
24178 The CLI commands are still handled by the @sc{mi} interpreter; their
24179 output is described below.
24182 The @code{@var{token}}, when present, is passed back when the command
24186 Some @sc{mi} commands accept optional arguments as part of the parameter
24187 list. Each option is identified by a leading @samp{-} (dash) and may be
24188 followed by an optional argument parameter. Options occur first in the
24189 parameter list and can be delimited from normal parameters using
24190 @samp{--} (this is useful when some parameters begin with a dash).
24197 We want easy access to the existing CLI syntax (for debugging).
24200 We want it to be easy to spot a @sc{mi} operation.
24203 @node GDB/MI Output Syntax
24204 @subsection @sc{gdb/mi} Output Syntax
24206 @cindex output syntax of @sc{gdb/mi}
24207 @cindex @sc{gdb/mi}, output syntax
24208 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24209 followed, optionally, by a single result record. This result record
24210 is for the most recent command. The sequence of output records is
24211 terminated by @samp{(gdb)}.
24213 If an input command was prefixed with a @code{@var{token}} then the
24214 corresponding output for that command will also be prefixed by that same
24218 @item @var{output} @expansion{}
24219 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24221 @item @var{result-record} @expansion{}
24222 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24224 @item @var{out-of-band-record} @expansion{}
24225 @code{@var{async-record} | @var{stream-record}}
24227 @item @var{async-record} @expansion{}
24228 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24230 @item @var{exec-async-output} @expansion{}
24231 @code{[ @var{token} ] "*" @var{async-output}}
24233 @item @var{status-async-output} @expansion{}
24234 @code{[ @var{token} ] "+" @var{async-output}}
24236 @item @var{notify-async-output} @expansion{}
24237 @code{[ @var{token} ] "=" @var{async-output}}
24239 @item @var{async-output} @expansion{}
24240 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24242 @item @var{result-class} @expansion{}
24243 @code{"done" | "running" | "connected" | "error" | "exit"}
24245 @item @var{async-class} @expansion{}
24246 @code{"stopped" | @var{others}} (where @var{others} will be added
24247 depending on the needs---this is still in development).
24249 @item @var{result} @expansion{}
24250 @code{ @var{variable} "=" @var{value}}
24252 @item @var{variable} @expansion{}
24253 @code{ @var{string} }
24255 @item @var{value} @expansion{}
24256 @code{ @var{const} | @var{tuple} | @var{list} }
24258 @item @var{const} @expansion{}
24259 @code{@var{c-string}}
24261 @item @var{tuple} @expansion{}
24262 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24264 @item @var{list} @expansion{}
24265 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24266 @var{result} ( "," @var{result} )* "]" }
24268 @item @var{stream-record} @expansion{}
24269 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24271 @item @var{console-stream-output} @expansion{}
24272 @code{"~" @var{c-string}}
24274 @item @var{target-stream-output} @expansion{}
24275 @code{"@@" @var{c-string}}
24277 @item @var{log-stream-output} @expansion{}
24278 @code{"&" @var{c-string}}
24280 @item @var{nl} @expansion{}
24283 @item @var{token} @expansion{}
24284 @emph{any sequence of digits}.
24292 All output sequences end in a single line containing a period.
24295 The @code{@var{token}} is from the corresponding request. Note that
24296 for all async output, while the token is allowed by the grammar and
24297 may be output by future versions of @value{GDBN} for select async
24298 output messages, it is generally omitted. Frontends should treat
24299 all async output as reporting general changes in the state of the
24300 target and there should be no need to associate async output to any
24304 @cindex status output in @sc{gdb/mi}
24305 @var{status-async-output} contains on-going status information about the
24306 progress of a slow operation. It can be discarded. All status output is
24307 prefixed by @samp{+}.
24310 @cindex async output in @sc{gdb/mi}
24311 @var{exec-async-output} contains asynchronous state change on the target
24312 (stopped, started, disappeared). All async output is prefixed by
24316 @cindex notify output in @sc{gdb/mi}
24317 @var{notify-async-output} contains supplementary information that the
24318 client should handle (e.g., a new breakpoint information). All notify
24319 output is prefixed by @samp{=}.
24322 @cindex console output in @sc{gdb/mi}
24323 @var{console-stream-output} is output that should be displayed as is in the
24324 console. It is the textual response to a CLI command. All the console
24325 output is prefixed by @samp{~}.
24328 @cindex target output in @sc{gdb/mi}
24329 @var{target-stream-output} is the output produced by the target program.
24330 All the target output is prefixed by @samp{@@}.
24333 @cindex log output in @sc{gdb/mi}
24334 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24335 instance messages that should be displayed as part of an error log. All
24336 the log output is prefixed by @samp{&}.
24339 @cindex list output in @sc{gdb/mi}
24340 New @sc{gdb/mi} commands should only output @var{lists} containing
24346 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24347 details about the various output records.
24349 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24350 @node GDB/MI Compatibility with CLI
24351 @section @sc{gdb/mi} Compatibility with CLI
24353 @cindex compatibility, @sc{gdb/mi} and CLI
24354 @cindex @sc{gdb/mi}, compatibility with CLI
24356 For the developers convenience CLI commands can be entered directly,
24357 but there may be some unexpected behaviour. For example, commands
24358 that query the user will behave as if the user replied yes, breakpoint
24359 command lists are not executed and some CLI commands, such as
24360 @code{if}, @code{when} and @code{define}, prompt for further input with
24361 @samp{>}, which is not valid MI output.
24363 This feature may be removed at some stage in the future and it is
24364 recommended that front ends use the @code{-interpreter-exec} command
24365 (@pxref{-interpreter-exec}).
24367 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24368 @node GDB/MI Development and Front Ends
24369 @section @sc{gdb/mi} Development and Front Ends
24370 @cindex @sc{gdb/mi} development
24372 The application which takes the MI output and presents the state of the
24373 program being debugged to the user is called a @dfn{front end}.
24375 Although @sc{gdb/mi} is still incomplete, it is currently being used
24376 by a variety of front ends to @value{GDBN}. This makes it difficult
24377 to introduce new functionality without breaking existing usage. This
24378 section tries to minimize the problems by describing how the protocol
24381 Some changes in MI need not break a carefully designed front end, and
24382 for these the MI version will remain unchanged. The following is a
24383 list of changes that may occur within one level, so front ends should
24384 parse MI output in a way that can handle them:
24388 New MI commands may be added.
24391 New fields may be added to the output of any MI command.
24394 The range of values for fields with specified values, e.g.,
24395 @code{in_scope} (@pxref{-var-update}) may be extended.
24397 @c The format of field's content e.g type prefix, may change so parse it
24398 @c at your own risk. Yes, in general?
24400 @c The order of fields may change? Shouldn't really matter but it might
24401 @c resolve inconsistencies.
24404 If the changes are likely to break front ends, the MI version level
24405 will be increased by one. This will allow the front end to parse the
24406 output according to the MI version. Apart from mi0, new versions of
24407 @value{GDBN} will not support old versions of MI and it will be the
24408 responsibility of the front end to work with the new one.
24410 @c Starting with mi3, add a new command -mi-version that prints the MI
24413 The best way to avoid unexpected changes in MI that might break your front
24414 end is to make your project known to @value{GDBN} developers and
24415 follow development on @email{gdb@@sourceware.org} and
24416 @email{gdb-patches@@sourceware.org}.
24417 @cindex mailing lists
24419 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24420 @node GDB/MI Output Records
24421 @section @sc{gdb/mi} Output Records
24424 * GDB/MI Result Records::
24425 * GDB/MI Stream Records::
24426 * GDB/MI Async Records::
24427 * GDB/MI Frame Information::
24428 * GDB/MI Thread Information::
24431 @node GDB/MI Result Records
24432 @subsection @sc{gdb/mi} Result Records
24434 @cindex result records in @sc{gdb/mi}
24435 @cindex @sc{gdb/mi}, result records
24436 In addition to a number of out-of-band notifications, the response to a
24437 @sc{gdb/mi} command includes one of the following result indications:
24441 @item "^done" [ "," @var{results} ]
24442 The synchronous operation was successful, @code{@var{results}} are the return
24447 This result record is equivalent to @samp{^done}. Historically, it
24448 was output instead of @samp{^done} if the command has resumed the
24449 target. This behaviour is maintained for backward compatibility, but
24450 all frontends should treat @samp{^done} and @samp{^running}
24451 identically and rely on the @samp{*running} output record to determine
24452 which threads are resumed.
24456 @value{GDBN} has connected to a remote target.
24458 @item "^error" "," @var{c-string}
24460 The operation failed. The @code{@var{c-string}} contains the corresponding
24465 @value{GDBN} has terminated.
24469 @node GDB/MI Stream Records
24470 @subsection @sc{gdb/mi} Stream Records
24472 @cindex @sc{gdb/mi}, stream records
24473 @cindex stream records in @sc{gdb/mi}
24474 @value{GDBN} internally maintains a number of output streams: the console, the
24475 target, and the log. The output intended for each of these streams is
24476 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
24478 Each stream record begins with a unique @dfn{prefix character} which
24479 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
24480 Syntax}). In addition to the prefix, each stream record contains a
24481 @code{@var{string-output}}. This is either raw text (with an implicit new
24482 line) or a quoted C string (which does not contain an implicit newline).
24485 @item "~" @var{string-output}
24486 The console output stream contains text that should be displayed in the
24487 CLI console window. It contains the textual responses to CLI commands.
24489 @item "@@" @var{string-output}
24490 The target output stream contains any textual output from the running
24491 target. This is only present when GDB's event loop is truly
24492 asynchronous, which is currently only the case for remote targets.
24494 @item "&" @var{string-output}
24495 The log stream contains debugging messages being produced by @value{GDBN}'s
24499 @node GDB/MI Async Records
24500 @subsection @sc{gdb/mi} Async Records
24502 @cindex async records in @sc{gdb/mi}
24503 @cindex @sc{gdb/mi}, async records
24504 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
24505 additional changes that have occurred. Those changes can either be a
24506 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
24507 target activity (e.g., target stopped).
24509 The following is the list of possible async records:
24513 @item *running,thread-id="@var{thread}"
24514 The target is now running. The @var{thread} field tells which
24515 specific thread is now running, and can be @samp{all} if all threads
24516 are running. The frontend should assume that no interaction with a
24517 running thread is possible after this notification is produced.
24518 The frontend should not assume that this notification is output
24519 only once for any command. @value{GDBN} may emit this notification
24520 several times, either for different threads, because it cannot resume
24521 all threads together, or even for a single thread, if the thread must
24522 be stepped though some code before letting it run freely.
24524 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
24525 The target has stopped. The @var{reason} field can have one of the
24529 @item breakpoint-hit
24530 A breakpoint was reached.
24531 @item watchpoint-trigger
24532 A watchpoint was triggered.
24533 @item read-watchpoint-trigger
24534 A read watchpoint was triggered.
24535 @item access-watchpoint-trigger
24536 An access watchpoint was triggered.
24537 @item function-finished
24538 An -exec-finish or similar CLI command was accomplished.
24539 @item location-reached
24540 An -exec-until or similar CLI command was accomplished.
24541 @item watchpoint-scope
24542 A watchpoint has gone out of scope.
24543 @item end-stepping-range
24544 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24545 similar CLI command was accomplished.
24546 @item exited-signalled
24547 The inferior exited because of a signal.
24549 The inferior exited.
24550 @item exited-normally
24551 The inferior exited normally.
24552 @item signal-received
24553 A signal was received by the inferior.
24556 The @var{id} field identifies the thread that directly caused the stop
24557 -- for example by hitting a breakpoint. Depending on whether all-stop
24558 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24559 stop all threads, or only the thread that directly triggered the stop.
24560 If all threads are stopped, the @var{stopped} field will have the
24561 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24562 field will be a list of thread identifiers. Presently, this list will
24563 always include a single thread, but frontend should be prepared to see
24564 several threads in the list. The @var{core} field reports the
24565 processor core on which the stop event has happened. This field may be absent
24566 if such information is not available.
24568 @item =thread-group-added,id="@var{id}"
24569 @itemx =thread-group-removed,id="@var{id}"
24570 A thread group was either added or removed. The @var{id} field
24571 contains the @value{GDBN} identifier of the thread group. When a thread
24572 group is added, it generally might not be associated with a running
24573 process. When a thread group is removed, its id becomes invalid and
24574 cannot be used in any way.
24576 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24577 A thread group became associated with a running program,
24578 either because the program was just started or the thread group
24579 was attached to a program. The @var{id} field contains the
24580 @value{GDBN} identifier of the thread group. The @var{pid} field
24581 contains process identifier, specific to the operating system.
24583 @itemx =thread-group-exited,id="@var{id}"
24584 A thread group is no longer associated with a running program,
24585 either because the program has exited, or because it was detached
24586 from. The @var{id} field contains the @value{GDBN} identifier of the
24589 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24590 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24591 A thread either was created, or has exited. The @var{id} field
24592 contains the @value{GDBN} identifier of the thread. The @var{gid}
24593 field identifies the thread group this thread belongs to.
24595 @item =thread-selected,id="@var{id}"
24596 Informs that the selected thread was changed as result of the last
24597 command. This notification is not emitted as result of @code{-thread-select}
24598 command but is emitted whenever an MI command that is not documented
24599 to change the selected thread actually changes it. In particular,
24600 invoking, directly or indirectly (via user-defined command), the CLI
24601 @code{thread} command, will generate this notification.
24603 We suggest that in response to this notification, front ends
24604 highlight the selected thread and cause subsequent commands to apply to
24607 @item =library-loaded,...
24608 Reports that a new library file was loaded by the program. This
24609 notification has 4 fields---@var{id}, @var{target-name},
24610 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24611 opaque identifier of the library. For remote debugging case,
24612 @var{target-name} and @var{host-name} fields give the name of the
24613 library file on the target, and on the host respectively. For native
24614 debugging, both those fields have the same value. The
24615 @var{symbols-loaded} field reports if the debug symbols for this
24616 library are loaded. The @var{thread-group} field, if present,
24617 specifies the id of the thread group in whose context the library was loaded.
24618 If the field is absent, it means the library was loaded in the context
24619 of all present thread groups.
24621 @item =library-unloaded,...
24622 Reports that a library was unloaded by the program. This notification
24623 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24624 the same meaning as for the @code{=library-loaded} notification.
24625 The @var{thread-group} field, if present, specifies the id of the
24626 thread group in whose context the library was unloaded. If the field is
24627 absent, it means the library was unloaded in the context of all present
24632 @node GDB/MI Frame Information
24633 @subsection @sc{gdb/mi} Frame Information
24635 Response from many MI commands includes an information about stack
24636 frame. This information is a tuple that may have the following
24641 The level of the stack frame. The innermost frame has the level of
24642 zero. This field is always present.
24645 The name of the function corresponding to the frame. This field may
24646 be absent if @value{GDBN} is unable to determine the function name.
24649 The code address for the frame. This field is always present.
24652 The name of the source files that correspond to the frame's code
24653 address. This field may be absent.
24656 The source line corresponding to the frames' code address. This field
24660 The name of the binary file (either executable or shared library) the
24661 corresponds to the frame's code address. This field may be absent.
24665 @node GDB/MI Thread Information
24666 @subsection @sc{gdb/mi} Thread Information
24668 Whenever @value{GDBN} has to report an information about a thread, it
24669 uses a tuple with the following fields:
24673 The numeric id assigned to the thread by @value{GDBN}. This field is
24677 Target-specific string identifying the thread. This field is always present.
24680 Additional information about the thread provided by the target.
24681 It is supposed to be human-readable and not interpreted by the
24682 frontend. This field is optional.
24685 Either @samp{stopped} or @samp{running}, depending on whether the
24686 thread is presently running. This field is always present.
24689 The value of this field is an integer number of the processor core the
24690 thread was last seen on. This field is optional.
24694 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24695 @node GDB/MI Simple Examples
24696 @section Simple Examples of @sc{gdb/mi} Interaction
24697 @cindex @sc{gdb/mi}, simple examples
24699 This subsection presents several simple examples of interaction using
24700 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24701 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24702 the output received from @sc{gdb/mi}.
24704 Note the line breaks shown in the examples are here only for
24705 readability, they don't appear in the real output.
24707 @subheading Setting a Breakpoint
24709 Setting a breakpoint generates synchronous output which contains detailed
24710 information of the breakpoint.
24713 -> -break-insert main
24714 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24715 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24716 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24720 @subheading Program Execution
24722 Program execution generates asynchronous records and MI gives the
24723 reason that execution stopped.
24729 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24730 frame=@{addr="0x08048564",func="main",
24731 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24732 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24737 <- *stopped,reason="exited-normally"
24741 @subheading Quitting @value{GDBN}
24743 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24751 Please note that @samp{^exit} is printed immediately, but it might
24752 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24753 performs necessary cleanups, including killing programs being debugged
24754 or disconnecting from debug hardware, so the frontend should wait till
24755 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24756 fails to exit in reasonable time.
24758 @subheading A Bad Command
24760 Here's what happens if you pass a non-existent command:
24764 <- ^error,msg="Undefined MI command: rubbish"
24769 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24770 @node GDB/MI Command Description Format
24771 @section @sc{gdb/mi} Command Description Format
24773 The remaining sections describe blocks of commands. Each block of
24774 commands is laid out in a fashion similar to this section.
24776 @subheading Motivation
24778 The motivation for this collection of commands.
24780 @subheading Introduction
24782 A brief introduction to this collection of commands as a whole.
24784 @subheading Commands
24786 For each command in the block, the following is described:
24788 @subsubheading Synopsis
24791 -command @var{args}@dots{}
24794 @subsubheading Result
24796 @subsubheading @value{GDBN} Command
24798 The corresponding @value{GDBN} CLI command(s), if any.
24800 @subsubheading Example
24802 Example(s) formatted for readability. Some of the described commands have
24803 not been implemented yet and these are labeled N.A.@: (not available).
24806 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24807 @node GDB/MI Breakpoint Commands
24808 @section @sc{gdb/mi} Breakpoint Commands
24810 @cindex breakpoint commands for @sc{gdb/mi}
24811 @cindex @sc{gdb/mi}, breakpoint commands
24812 This section documents @sc{gdb/mi} commands for manipulating
24815 @subheading The @code{-break-after} Command
24816 @findex -break-after
24818 @subsubheading Synopsis
24821 -break-after @var{number} @var{count}
24824 The breakpoint number @var{number} is not in effect until it has been
24825 hit @var{count} times. To see how this is reflected in the output of
24826 the @samp{-break-list} command, see the description of the
24827 @samp{-break-list} command below.
24829 @subsubheading @value{GDBN} Command
24831 The corresponding @value{GDBN} command is @samp{ignore}.
24833 @subsubheading Example
24838 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24839 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24840 fullname="/home/foo/hello.c",line="5",times="0"@}
24847 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24848 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24849 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24850 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24851 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24852 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24853 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24854 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24855 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24856 line="5",times="0",ignore="3"@}]@}
24861 @subheading The @code{-break-catch} Command
24862 @findex -break-catch
24865 @subheading The @code{-break-commands} Command
24866 @findex -break-commands
24868 @subsubheading Synopsis
24871 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24874 Specifies the CLI commands that should be executed when breakpoint
24875 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24876 are the commands. If no command is specified, any previously-set
24877 commands are cleared. @xref{Break Commands}. Typical use of this
24878 functionality is tracing a program, that is, printing of values of
24879 some variables whenever breakpoint is hit and then continuing.
24881 @subsubheading @value{GDBN} Command
24883 The corresponding @value{GDBN} command is @samp{commands}.
24885 @subsubheading Example
24890 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24891 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24892 fullname="/home/foo/hello.c",line="5",times="0"@}
24894 -break-commands 1 "print v" "continue"
24899 @subheading The @code{-break-condition} Command
24900 @findex -break-condition
24902 @subsubheading Synopsis
24905 -break-condition @var{number} @var{expr}
24908 Breakpoint @var{number} will stop the program only if the condition in
24909 @var{expr} is true. The condition becomes part of the
24910 @samp{-break-list} output (see the description of the @samp{-break-list}
24913 @subsubheading @value{GDBN} Command
24915 The corresponding @value{GDBN} command is @samp{condition}.
24917 @subsubheading Example
24921 -break-condition 1 1
24925 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24926 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24927 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24928 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24929 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24930 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24931 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24932 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24933 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24934 line="5",cond="1",times="0",ignore="3"@}]@}
24938 @subheading The @code{-break-delete} Command
24939 @findex -break-delete
24941 @subsubheading Synopsis
24944 -break-delete ( @var{breakpoint} )+
24947 Delete the breakpoint(s) whose number(s) are specified in the argument
24948 list. This is obviously reflected in the breakpoint list.
24950 @subsubheading @value{GDBN} Command
24952 The corresponding @value{GDBN} command is @samp{delete}.
24954 @subsubheading Example
24962 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24963 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24964 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24965 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24966 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24967 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24968 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24973 @subheading The @code{-break-disable} Command
24974 @findex -break-disable
24976 @subsubheading Synopsis
24979 -break-disable ( @var{breakpoint} )+
24982 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24983 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24985 @subsubheading @value{GDBN} Command
24987 The corresponding @value{GDBN} command is @samp{disable}.
24989 @subsubheading Example
24997 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24998 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24999 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25000 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25001 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25002 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25003 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25004 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25005 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25006 line="5",times="0"@}]@}
25010 @subheading The @code{-break-enable} Command
25011 @findex -break-enable
25013 @subsubheading Synopsis
25016 -break-enable ( @var{breakpoint} )+
25019 Enable (previously disabled) @var{breakpoint}(s).
25021 @subsubheading @value{GDBN} Command
25023 The corresponding @value{GDBN} command is @samp{enable}.
25025 @subsubheading Example
25033 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25034 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25035 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25036 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25037 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25038 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25039 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25040 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25041 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25042 line="5",times="0"@}]@}
25046 @subheading The @code{-break-info} Command
25047 @findex -break-info
25049 @subsubheading Synopsis
25052 -break-info @var{breakpoint}
25056 Get information about a single breakpoint.
25058 @subsubheading @value{GDBN} Command
25060 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25062 @subsubheading Example
25065 @subheading The @code{-break-insert} Command
25066 @findex -break-insert
25068 @subsubheading Synopsis
25071 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25072 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25073 [ -p @var{thread} ] [ @var{location} ]
25077 If specified, @var{location}, can be one of:
25084 @item filename:linenum
25085 @item filename:function
25089 The possible optional parameters of this command are:
25093 Insert a temporary breakpoint.
25095 Insert a hardware breakpoint.
25096 @item -c @var{condition}
25097 Make the breakpoint conditional on @var{condition}.
25098 @item -i @var{ignore-count}
25099 Initialize the @var{ignore-count}.
25101 If @var{location} cannot be parsed (for example if it
25102 refers to unknown files or functions), create a pending
25103 breakpoint. Without this flag, @value{GDBN} will report
25104 an error, and won't create a breakpoint, if @var{location}
25107 Create a disabled breakpoint.
25109 Create a tracepoint. @xref{Tracepoints}. When this parameter
25110 is used together with @samp{-h}, a fast tracepoint is created.
25113 @subsubheading Result
25115 The result is in the form:
25118 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25119 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25120 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25121 times="@var{times}"@}
25125 where @var{number} is the @value{GDBN} number for this breakpoint,
25126 @var{funcname} is the name of the function where the breakpoint was
25127 inserted, @var{filename} is the name of the source file which contains
25128 this function, @var{lineno} is the source line number within that file
25129 and @var{times} the number of times that the breakpoint has been hit
25130 (always 0 for -break-insert but may be greater for -break-info or -break-list
25131 which use the same output).
25133 Note: this format is open to change.
25134 @c An out-of-band breakpoint instead of part of the result?
25136 @subsubheading @value{GDBN} Command
25138 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25139 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25141 @subsubheading Example
25146 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25147 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25149 -break-insert -t foo
25150 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25151 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25154 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25155 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25156 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25157 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25158 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25159 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25160 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25161 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25162 addr="0x0001072c", func="main",file="recursive2.c",
25163 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25164 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25165 addr="0x00010774",func="foo",file="recursive2.c",
25166 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25168 -break-insert -r foo.*
25169 ~int foo(int, int);
25170 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25171 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25175 @subheading The @code{-break-list} Command
25176 @findex -break-list
25178 @subsubheading Synopsis
25184 Displays the list of inserted breakpoints, showing the following fields:
25188 number of the breakpoint
25190 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25192 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25195 is the breakpoint enabled or no: @samp{y} or @samp{n}
25197 memory location at which the breakpoint is set
25199 logical location of the breakpoint, expressed by function name, file
25202 number of times the breakpoint has been hit
25205 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25206 @code{body} field is an empty list.
25208 @subsubheading @value{GDBN} Command
25210 The corresponding @value{GDBN} command is @samp{info break}.
25212 @subsubheading Example
25217 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25218 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25219 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25220 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25221 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25222 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25223 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25224 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25225 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25226 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25227 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25228 line="13",times="0"@}]@}
25232 Here's an example of the result when there are no breakpoints:
25237 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25238 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25239 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25240 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25241 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25242 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25243 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25248 @subheading The @code{-break-passcount} Command
25249 @findex -break-passcount
25251 @subsubheading Synopsis
25254 -break-passcount @var{tracepoint-number} @var{passcount}
25257 Set the passcount for tracepoint @var{tracepoint-number} to
25258 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25259 is not a tracepoint, error is emitted. This corresponds to CLI
25260 command @samp{passcount}.
25262 @subheading The @code{-break-watch} Command
25263 @findex -break-watch
25265 @subsubheading Synopsis
25268 -break-watch [ -a | -r ]
25271 Create a watchpoint. With the @samp{-a} option it will create an
25272 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25273 read from or on a write to the memory location. With the @samp{-r}
25274 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25275 trigger only when the memory location is accessed for reading. Without
25276 either of the options, the watchpoint created is a regular watchpoint,
25277 i.e., it will trigger when the memory location is accessed for writing.
25278 @xref{Set Watchpoints, , Setting Watchpoints}.
25280 Note that @samp{-break-list} will report a single list of watchpoints and
25281 breakpoints inserted.
25283 @subsubheading @value{GDBN} Command
25285 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25288 @subsubheading Example
25290 Setting a watchpoint on a variable in the @code{main} function:
25295 ^done,wpt=@{number="2",exp="x"@}
25300 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25301 value=@{old="-268439212",new="55"@},
25302 frame=@{func="main",args=[],file="recursive2.c",
25303 fullname="/home/foo/bar/recursive2.c",line="5"@}
25307 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25308 the program execution twice: first for the variable changing value, then
25309 for the watchpoint going out of scope.
25314 ^done,wpt=@{number="5",exp="C"@}
25319 *stopped,reason="watchpoint-trigger",
25320 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25321 frame=@{func="callee4",args=[],
25322 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25323 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25328 *stopped,reason="watchpoint-scope",wpnum="5",
25329 frame=@{func="callee3",args=[@{name="strarg",
25330 value="0x11940 \"A string argument.\""@}],
25331 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25332 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25336 Listing breakpoints and watchpoints, at different points in the program
25337 execution. Note that once the watchpoint goes out of scope, it is
25343 ^done,wpt=@{number="2",exp="C"@}
25346 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25347 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25348 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25349 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25350 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25351 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25352 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25353 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25354 addr="0x00010734",func="callee4",
25355 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25356 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25357 bkpt=@{number="2",type="watchpoint",disp="keep",
25358 enabled="y",addr="",what="C",times="0"@}]@}
25363 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25364 value=@{old="-276895068",new="3"@},
25365 frame=@{func="callee4",args=[],
25366 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25367 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25370 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25371 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25372 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25373 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25374 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25375 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25376 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25377 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25378 addr="0x00010734",func="callee4",
25379 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25380 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25381 bkpt=@{number="2",type="watchpoint",disp="keep",
25382 enabled="y",addr="",what="C",times="-5"@}]@}
25386 ^done,reason="watchpoint-scope",wpnum="2",
25387 frame=@{func="callee3",args=[@{name="strarg",
25388 value="0x11940 \"A string argument.\""@}],
25389 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25390 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25393 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25394 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25395 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25396 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25397 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25398 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25399 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25400 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25401 addr="0x00010734",func="callee4",
25402 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25403 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
25408 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25409 @node GDB/MI Program Context
25410 @section @sc{gdb/mi} Program Context
25412 @subheading The @code{-exec-arguments} Command
25413 @findex -exec-arguments
25416 @subsubheading Synopsis
25419 -exec-arguments @var{args}
25422 Set the inferior program arguments, to be used in the next
25425 @subsubheading @value{GDBN} Command
25427 The corresponding @value{GDBN} command is @samp{set args}.
25429 @subsubheading Example
25433 -exec-arguments -v word
25440 @subheading The @code{-exec-show-arguments} Command
25441 @findex -exec-show-arguments
25443 @subsubheading Synopsis
25446 -exec-show-arguments
25449 Print the arguments of the program.
25451 @subsubheading @value{GDBN} Command
25453 The corresponding @value{GDBN} command is @samp{show args}.
25455 @subsubheading Example
25460 @subheading The @code{-environment-cd} Command
25461 @findex -environment-cd
25463 @subsubheading Synopsis
25466 -environment-cd @var{pathdir}
25469 Set @value{GDBN}'s working directory.
25471 @subsubheading @value{GDBN} Command
25473 The corresponding @value{GDBN} command is @samp{cd}.
25475 @subsubheading Example
25479 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25485 @subheading The @code{-environment-directory} Command
25486 @findex -environment-directory
25488 @subsubheading Synopsis
25491 -environment-directory [ -r ] [ @var{pathdir} ]+
25494 Add directories @var{pathdir} to beginning of search path for source files.
25495 If the @samp{-r} option is used, the search path is reset to the default
25496 search path. If directories @var{pathdir} are supplied in addition to the
25497 @samp{-r} option, the search path is first reset and then addition
25499 Multiple directories may be specified, separated by blanks. Specifying
25500 multiple directories in a single command
25501 results in the directories added to the beginning of the
25502 search path in the same order they were presented in the command.
25503 If blanks are needed as
25504 part of a directory name, double-quotes should be used around
25505 the name. In the command output, the path will show up separated
25506 by the system directory-separator character. The directory-separator
25507 character must not be used
25508 in any directory name.
25509 If no directories are specified, the current search path is displayed.
25511 @subsubheading @value{GDBN} Command
25513 The corresponding @value{GDBN} command is @samp{dir}.
25515 @subsubheading Example
25519 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25520 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25522 -environment-directory ""
25523 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25525 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
25526 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
25528 -environment-directory -r
25529 ^done,source-path="$cdir:$cwd"
25534 @subheading The @code{-environment-path} Command
25535 @findex -environment-path
25537 @subsubheading Synopsis
25540 -environment-path [ -r ] [ @var{pathdir} ]+
25543 Add directories @var{pathdir} to beginning of search path for object files.
25544 If the @samp{-r} option is used, the search path is reset to the original
25545 search path that existed at gdb start-up. If directories @var{pathdir} are
25546 supplied in addition to the
25547 @samp{-r} option, the search path is first reset and then addition
25549 Multiple directories may be specified, separated by blanks. Specifying
25550 multiple directories in a single command
25551 results in the directories added to the beginning of the
25552 search path in the same order they were presented in the command.
25553 If blanks are needed as
25554 part of a directory name, double-quotes should be used around
25555 the name. In the command output, the path will show up separated
25556 by the system directory-separator character. The directory-separator
25557 character must not be used
25558 in any directory name.
25559 If no directories are specified, the current path is displayed.
25562 @subsubheading @value{GDBN} Command
25564 The corresponding @value{GDBN} command is @samp{path}.
25566 @subsubheading Example
25571 ^done,path="/usr/bin"
25573 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25574 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25576 -environment-path -r /usr/local/bin
25577 ^done,path="/usr/local/bin:/usr/bin"
25582 @subheading The @code{-environment-pwd} Command
25583 @findex -environment-pwd
25585 @subsubheading Synopsis
25591 Show the current working directory.
25593 @subsubheading @value{GDBN} Command
25595 The corresponding @value{GDBN} command is @samp{pwd}.
25597 @subsubheading Example
25602 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25606 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25607 @node GDB/MI Thread Commands
25608 @section @sc{gdb/mi} Thread Commands
25611 @subheading The @code{-thread-info} Command
25612 @findex -thread-info
25614 @subsubheading Synopsis
25617 -thread-info [ @var{thread-id} ]
25620 Reports information about either a specific thread, if
25621 the @var{thread-id} parameter is present, or about all
25622 threads. When printing information about all threads,
25623 also reports the current thread.
25625 @subsubheading @value{GDBN} Command
25627 The @samp{info thread} command prints the same information
25630 @subsubheading Example
25635 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25636 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25637 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25638 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25639 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25640 current-thread-id="1"
25644 The @samp{state} field may have the following values:
25648 The thread is stopped. Frame information is available for stopped
25652 The thread is running. There's no frame information for running
25657 @subheading The @code{-thread-list-ids} Command
25658 @findex -thread-list-ids
25660 @subsubheading Synopsis
25666 Produces a list of the currently known @value{GDBN} thread ids. At the
25667 end of the list it also prints the total number of such threads.
25669 This command is retained for historical reasons, the
25670 @code{-thread-info} command should be used instead.
25672 @subsubheading @value{GDBN} Command
25674 Part of @samp{info threads} supplies the same information.
25676 @subsubheading Example
25681 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25682 current-thread-id="1",number-of-threads="3"
25687 @subheading The @code{-thread-select} Command
25688 @findex -thread-select
25690 @subsubheading Synopsis
25693 -thread-select @var{threadnum}
25696 Make @var{threadnum} the current thread. It prints the number of the new
25697 current thread, and the topmost frame for that thread.
25699 This command is deprecated in favor of explicitly using the
25700 @samp{--thread} option to each command.
25702 @subsubheading @value{GDBN} Command
25704 The corresponding @value{GDBN} command is @samp{thread}.
25706 @subsubheading Example
25713 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25714 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25718 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25719 number-of-threads="3"
25722 ^done,new-thread-id="3",
25723 frame=@{level="0",func="vprintf",
25724 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25725 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25729 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25730 @node GDB/MI Program Execution
25731 @section @sc{gdb/mi} Program Execution
25733 These are the asynchronous commands which generate the out-of-band
25734 record @samp{*stopped}. Currently @value{GDBN} only really executes
25735 asynchronously with remote targets and this interaction is mimicked in
25738 @subheading The @code{-exec-continue} Command
25739 @findex -exec-continue
25741 @subsubheading Synopsis
25744 -exec-continue [--reverse] [--all|--thread-group N]
25747 Resumes the execution of the inferior program, which will continue
25748 to execute until it reaches a debugger stop event. If the
25749 @samp{--reverse} option is specified, execution resumes in reverse until
25750 it reaches a stop event. Stop events may include
25753 breakpoints or watchpoints
25755 signals or exceptions
25757 the end of the process (or its beginning under @samp{--reverse})
25759 the end or beginning of a replay log if one is being used.
25761 In all-stop mode (@pxref{All-Stop
25762 Mode}), may resume only one thread, or all threads, depending on the
25763 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25764 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25765 ignored in all-stop mode. If the @samp{--thread-group} options is
25766 specified, then all threads in that thread group are resumed.
25768 @subsubheading @value{GDBN} Command
25770 The corresponding @value{GDBN} corresponding is @samp{continue}.
25772 @subsubheading Example
25779 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25780 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25786 @subheading The @code{-exec-finish} Command
25787 @findex -exec-finish
25789 @subsubheading Synopsis
25792 -exec-finish [--reverse]
25795 Resumes the execution of the inferior program until the current
25796 function is exited. Displays the results returned by the function.
25797 If the @samp{--reverse} option is specified, resumes the reverse
25798 execution of the inferior program until the point where current
25799 function was called.
25801 @subsubheading @value{GDBN} Command
25803 The corresponding @value{GDBN} command is @samp{finish}.
25805 @subsubheading Example
25807 Function returning @code{void}.
25814 *stopped,reason="function-finished",frame=@{func="main",args=[],
25815 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25819 Function returning other than @code{void}. The name of the internal
25820 @value{GDBN} variable storing the result is printed, together with the
25827 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25828 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25829 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25830 gdb-result-var="$1",return-value="0"
25835 @subheading The @code{-exec-interrupt} Command
25836 @findex -exec-interrupt
25838 @subsubheading Synopsis
25841 -exec-interrupt [--all|--thread-group N]
25844 Interrupts the background execution of the target. Note how the token
25845 associated with the stop message is the one for the execution command
25846 that has been interrupted. The token for the interrupt itself only
25847 appears in the @samp{^done} output. If the user is trying to
25848 interrupt a non-running program, an error message will be printed.
25850 Note that when asynchronous execution is enabled, this command is
25851 asynchronous just like other execution commands. That is, first the
25852 @samp{^done} response will be printed, and the target stop will be
25853 reported after that using the @samp{*stopped} notification.
25855 In non-stop mode, only the context thread is interrupted by default.
25856 All threads (in all inferiors) will be interrupted if the
25857 @samp{--all} option is specified. If the @samp{--thread-group}
25858 option is specified, all threads in that group will be interrupted.
25860 @subsubheading @value{GDBN} Command
25862 The corresponding @value{GDBN} command is @samp{interrupt}.
25864 @subsubheading Example
25875 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25876 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25877 fullname="/home/foo/bar/try.c",line="13"@}
25882 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25886 @subheading The @code{-exec-jump} Command
25889 @subsubheading Synopsis
25892 -exec-jump @var{location}
25895 Resumes execution of the inferior program at the location specified by
25896 parameter. @xref{Specify Location}, for a description of the
25897 different forms of @var{location}.
25899 @subsubheading @value{GDBN} Command
25901 The corresponding @value{GDBN} command is @samp{jump}.
25903 @subsubheading Example
25906 -exec-jump foo.c:10
25907 *running,thread-id="all"
25912 @subheading The @code{-exec-next} Command
25915 @subsubheading Synopsis
25918 -exec-next [--reverse]
25921 Resumes execution of the inferior program, stopping when the beginning
25922 of the next source line is reached.
25924 If the @samp{--reverse} option is specified, resumes reverse execution
25925 of the inferior program, stopping at the beginning of the previous
25926 source line. If you issue this command on the first line of a
25927 function, it will take you back to the caller of that function, to the
25928 source line where the function was called.
25931 @subsubheading @value{GDBN} Command
25933 The corresponding @value{GDBN} command is @samp{next}.
25935 @subsubheading Example
25941 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25946 @subheading The @code{-exec-next-instruction} Command
25947 @findex -exec-next-instruction
25949 @subsubheading Synopsis
25952 -exec-next-instruction [--reverse]
25955 Executes one machine instruction. If the instruction is a function
25956 call, continues until the function returns. If the program stops at an
25957 instruction in the middle of a source line, the address will be
25960 If the @samp{--reverse} option is specified, resumes reverse execution
25961 of the inferior program, stopping at the previous instruction. If the
25962 previously executed instruction was a return from another function,
25963 it will continue to execute in reverse until the call to that function
25964 (from the current stack frame) is reached.
25966 @subsubheading @value{GDBN} Command
25968 The corresponding @value{GDBN} command is @samp{nexti}.
25970 @subsubheading Example
25974 -exec-next-instruction
25978 *stopped,reason="end-stepping-range",
25979 addr="0x000100d4",line="5",file="hello.c"
25984 @subheading The @code{-exec-return} Command
25985 @findex -exec-return
25987 @subsubheading Synopsis
25993 Makes current function return immediately. Doesn't execute the inferior.
25994 Displays the new current frame.
25996 @subsubheading @value{GDBN} Command
25998 The corresponding @value{GDBN} command is @samp{return}.
26000 @subsubheading Example
26004 200-break-insert callee4
26005 200^done,bkpt=@{number="1",addr="0x00010734",
26006 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26011 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26012 frame=@{func="callee4",args=[],
26013 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26014 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26020 111^done,frame=@{level="0",func="callee3",
26021 args=[@{name="strarg",
26022 value="0x11940 \"A string argument.\""@}],
26023 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26024 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26029 @subheading The @code{-exec-run} Command
26032 @subsubheading Synopsis
26035 -exec-run [--all | --thread-group N]
26038 Starts execution of the inferior from the beginning. The inferior
26039 executes until either a breakpoint is encountered or the program
26040 exits. In the latter case the output will include an exit code, if
26041 the program has exited exceptionally.
26043 When no option is specified, the current inferior is started. If the
26044 @samp{--thread-group} option is specified, it should refer to a thread
26045 group of type @samp{process}, and that thread group will be started.
26046 If the @samp{--all} option is specified, then all inferiors will be started.
26048 @subsubheading @value{GDBN} Command
26050 The corresponding @value{GDBN} command is @samp{run}.
26052 @subsubheading Examples
26057 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26062 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26063 frame=@{func="main",args=[],file="recursive2.c",
26064 fullname="/home/foo/bar/recursive2.c",line="4"@}
26069 Program exited normally:
26077 *stopped,reason="exited-normally"
26082 Program exited exceptionally:
26090 *stopped,reason="exited",exit-code="01"
26094 Another way the program can terminate is if it receives a signal such as
26095 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26099 *stopped,reason="exited-signalled",signal-name="SIGINT",
26100 signal-meaning="Interrupt"
26104 @c @subheading -exec-signal
26107 @subheading The @code{-exec-step} Command
26110 @subsubheading Synopsis
26113 -exec-step [--reverse]
26116 Resumes execution of the inferior program, stopping when the beginning
26117 of the next source line is reached, if the next source line is not a
26118 function call. If it is, stop at the first instruction of the called
26119 function. If the @samp{--reverse} option is specified, resumes reverse
26120 execution of the inferior program, stopping at the beginning of the
26121 previously executed source line.
26123 @subsubheading @value{GDBN} Command
26125 The corresponding @value{GDBN} command is @samp{step}.
26127 @subsubheading Example
26129 Stepping into a function:
26135 *stopped,reason="end-stepping-range",
26136 frame=@{func="foo",args=[@{name="a",value="10"@},
26137 @{name="b",value="0"@}],file="recursive2.c",
26138 fullname="/home/foo/bar/recursive2.c",line="11"@}
26148 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26153 @subheading The @code{-exec-step-instruction} Command
26154 @findex -exec-step-instruction
26156 @subsubheading Synopsis
26159 -exec-step-instruction [--reverse]
26162 Resumes the inferior which executes one machine instruction. If the
26163 @samp{--reverse} option is specified, resumes reverse execution of the
26164 inferior program, stopping at the previously executed instruction.
26165 The output, once @value{GDBN} has stopped, will vary depending on
26166 whether we have stopped in the middle of a source line or not. In the
26167 former case, the address at which the program stopped will be printed
26170 @subsubheading @value{GDBN} Command
26172 The corresponding @value{GDBN} command is @samp{stepi}.
26174 @subsubheading Example
26178 -exec-step-instruction
26182 *stopped,reason="end-stepping-range",
26183 frame=@{func="foo",args=[],file="try.c",
26184 fullname="/home/foo/bar/try.c",line="10"@}
26186 -exec-step-instruction
26190 *stopped,reason="end-stepping-range",
26191 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26192 fullname="/home/foo/bar/try.c",line="10"@}
26197 @subheading The @code{-exec-until} Command
26198 @findex -exec-until
26200 @subsubheading Synopsis
26203 -exec-until [ @var{location} ]
26206 Executes the inferior until the @var{location} specified in the
26207 argument is reached. If there is no argument, the inferior executes
26208 until a source line greater than the current one is reached. The
26209 reason for stopping in this case will be @samp{location-reached}.
26211 @subsubheading @value{GDBN} Command
26213 The corresponding @value{GDBN} command is @samp{until}.
26215 @subsubheading Example
26219 -exec-until recursive2.c:6
26223 *stopped,reason="location-reached",frame=@{func="main",args=[],
26224 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26229 @subheading -file-clear
26230 Is this going away????
26233 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26234 @node GDB/MI Stack Manipulation
26235 @section @sc{gdb/mi} Stack Manipulation Commands
26238 @subheading The @code{-stack-info-frame} Command
26239 @findex -stack-info-frame
26241 @subsubheading Synopsis
26247 Get info on the selected frame.
26249 @subsubheading @value{GDBN} Command
26251 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26252 (without arguments).
26254 @subsubheading Example
26259 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26260 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26261 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26265 @subheading The @code{-stack-info-depth} Command
26266 @findex -stack-info-depth
26268 @subsubheading Synopsis
26271 -stack-info-depth [ @var{max-depth} ]
26274 Return the depth of the stack. If the integer argument @var{max-depth}
26275 is specified, do not count beyond @var{max-depth} frames.
26277 @subsubheading @value{GDBN} Command
26279 There's no equivalent @value{GDBN} command.
26281 @subsubheading Example
26283 For a stack with frame levels 0 through 11:
26290 -stack-info-depth 4
26293 -stack-info-depth 12
26296 -stack-info-depth 11
26299 -stack-info-depth 13
26304 @subheading The @code{-stack-list-arguments} Command
26305 @findex -stack-list-arguments
26307 @subsubheading Synopsis
26310 -stack-list-arguments @var{print-values}
26311 [ @var{low-frame} @var{high-frame} ]
26314 Display a list of the arguments for the frames between @var{low-frame}
26315 and @var{high-frame} (inclusive). If @var{low-frame} and
26316 @var{high-frame} are not provided, list the arguments for the whole
26317 call stack. If the two arguments are equal, show the single frame
26318 at the corresponding level. It is an error if @var{low-frame} is
26319 larger than the actual number of frames. On the other hand,
26320 @var{high-frame} may be larger than the actual number of frames, in
26321 which case only existing frames will be returned.
26323 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26324 the variables; if it is 1 or @code{--all-values}, print also their
26325 values; and if it is 2 or @code{--simple-values}, print the name,
26326 type and value for simple data types, and the name and type for arrays,
26327 structures and unions.
26329 Use of this command to obtain arguments in a single frame is
26330 deprecated in favor of the @samp{-stack-list-variables} command.
26332 @subsubheading @value{GDBN} Command
26334 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26335 @samp{gdb_get_args} command which partially overlaps with the
26336 functionality of @samp{-stack-list-arguments}.
26338 @subsubheading Example
26345 frame=@{level="0",addr="0x00010734",func="callee4",
26346 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26347 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26348 frame=@{level="1",addr="0x0001076c",func="callee3",
26349 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26350 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26351 frame=@{level="2",addr="0x0001078c",func="callee2",
26352 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26353 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26354 frame=@{level="3",addr="0x000107b4",func="callee1",
26355 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26356 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
26357 frame=@{level="4",addr="0x000107e0",func="main",
26358 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26359 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
26361 -stack-list-arguments 0
26364 frame=@{level="0",args=[]@},
26365 frame=@{level="1",args=[name="strarg"]@},
26366 frame=@{level="2",args=[name="intarg",name="strarg"]@},
26367 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
26368 frame=@{level="4",args=[]@}]
26370 -stack-list-arguments 1
26373 frame=@{level="0",args=[]@},
26375 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26376 frame=@{level="2",args=[
26377 @{name="intarg",value="2"@},
26378 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26379 @{frame=@{level="3",args=[
26380 @{name="intarg",value="2"@},
26381 @{name="strarg",value="0x11940 \"A string argument.\""@},
26382 @{name="fltarg",value="3.5"@}]@},
26383 frame=@{level="4",args=[]@}]
26385 -stack-list-arguments 0 2 2
26386 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
26388 -stack-list-arguments 1 2 2
26389 ^done,stack-args=[frame=@{level="2",
26390 args=[@{name="intarg",value="2"@},
26391 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
26395 @c @subheading -stack-list-exception-handlers
26398 @subheading The @code{-stack-list-frames} Command
26399 @findex -stack-list-frames
26401 @subsubheading Synopsis
26404 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
26407 List the frames currently on the stack. For each frame it displays the
26412 The frame number, 0 being the topmost frame, i.e., the innermost function.
26414 The @code{$pc} value for that frame.
26418 File name of the source file where the function lives.
26419 @item @var{fullname}
26420 The full file name of the source file where the function lives.
26422 Line number corresponding to the @code{$pc}.
26424 The shared library where this function is defined. This is only given
26425 if the frame's function is not known.
26428 If invoked without arguments, this command prints a backtrace for the
26429 whole stack. If given two integer arguments, it shows the frames whose
26430 levels are between the two arguments (inclusive). If the two arguments
26431 are equal, it shows the single frame at the corresponding level. It is
26432 an error if @var{low-frame} is larger than the actual number of
26433 frames. On the other hand, @var{high-frame} may be larger than the
26434 actual number of frames, in which case only existing frames will be returned.
26436 @subsubheading @value{GDBN} Command
26438 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
26440 @subsubheading Example
26442 Full stack backtrace:
26448 [frame=@{level="0",addr="0x0001076c",func="foo",
26449 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
26450 frame=@{level="1",addr="0x000107a4",func="foo",
26451 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26452 frame=@{level="2",addr="0x000107a4",func="foo",
26453 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26454 frame=@{level="3",addr="0x000107a4",func="foo",
26455 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26456 frame=@{level="4",addr="0x000107a4",func="foo",
26457 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26458 frame=@{level="5",addr="0x000107a4",func="foo",
26459 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26460 frame=@{level="6",addr="0x000107a4",func="foo",
26461 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26462 frame=@{level="7",addr="0x000107a4",func="foo",
26463 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26464 frame=@{level="8",addr="0x000107a4",func="foo",
26465 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26466 frame=@{level="9",addr="0x000107a4",func="foo",
26467 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26468 frame=@{level="10",addr="0x000107a4",func="foo",
26469 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26470 frame=@{level="11",addr="0x00010738",func="main",
26471 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
26475 Show frames between @var{low_frame} and @var{high_frame}:
26479 -stack-list-frames 3 5
26481 [frame=@{level="3",addr="0x000107a4",func="foo",
26482 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26483 frame=@{level="4",addr="0x000107a4",func="foo",
26484 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26485 frame=@{level="5",addr="0x000107a4",func="foo",
26486 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26490 Show a single frame:
26494 -stack-list-frames 3 3
26496 [frame=@{level="3",addr="0x000107a4",func="foo",
26497 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26502 @subheading The @code{-stack-list-locals} Command
26503 @findex -stack-list-locals
26505 @subsubheading Synopsis
26508 -stack-list-locals @var{print-values}
26511 Display the local variable names for the selected frame. If
26512 @var{print-values} is 0 or @code{--no-values}, print only the names of
26513 the variables; if it is 1 or @code{--all-values}, print also their
26514 values; and if it is 2 or @code{--simple-values}, print the name,
26515 type and value for simple data types, and the name and type for arrays,
26516 structures and unions. In this last case, a frontend can immediately
26517 display the value of simple data types and create variable objects for
26518 other data types when the user wishes to explore their values in
26521 This command is deprecated in favor of the
26522 @samp{-stack-list-variables} command.
26524 @subsubheading @value{GDBN} Command
26526 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
26528 @subsubheading Example
26532 -stack-list-locals 0
26533 ^done,locals=[name="A",name="B",name="C"]
26535 -stack-list-locals --all-values
26536 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26537 @{name="C",value="@{1, 2, 3@}"@}]
26538 -stack-list-locals --simple-values
26539 ^done,locals=[@{name="A",type="int",value="1"@},
26540 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26544 @subheading The @code{-stack-list-variables} Command
26545 @findex -stack-list-variables
26547 @subsubheading Synopsis
26550 -stack-list-variables @var{print-values}
26553 Display the names of local variables and function arguments for the selected frame. If
26554 @var{print-values} is 0 or @code{--no-values}, print only the names of
26555 the variables; if it is 1 or @code{--all-values}, print also their
26556 values; and if it is 2 or @code{--simple-values}, print the name,
26557 type and value for simple data types, and the name and type for arrays,
26558 structures and unions.
26560 @subsubheading Example
26564 -stack-list-variables --thread 1 --frame 0 --all-values
26565 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26570 @subheading The @code{-stack-select-frame} Command
26571 @findex -stack-select-frame
26573 @subsubheading Synopsis
26576 -stack-select-frame @var{framenum}
26579 Change the selected frame. Select a different frame @var{framenum} on
26582 This command in deprecated in favor of passing the @samp{--frame}
26583 option to every command.
26585 @subsubheading @value{GDBN} Command
26587 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26588 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26590 @subsubheading Example
26594 -stack-select-frame 2
26599 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26600 @node GDB/MI Variable Objects
26601 @section @sc{gdb/mi} Variable Objects
26605 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26607 For the implementation of a variable debugger window (locals, watched
26608 expressions, etc.), we are proposing the adaptation of the existing code
26609 used by @code{Insight}.
26611 The two main reasons for that are:
26615 It has been proven in practice (it is already on its second generation).
26618 It will shorten development time (needless to say how important it is
26622 The original interface was designed to be used by Tcl code, so it was
26623 slightly changed so it could be used through @sc{gdb/mi}. This section
26624 describes the @sc{gdb/mi} operations that will be available and gives some
26625 hints about their use.
26627 @emph{Note}: In addition to the set of operations described here, we
26628 expect the @sc{gui} implementation of a variable window to require, at
26629 least, the following operations:
26632 @item @code{-gdb-show} @code{output-radix}
26633 @item @code{-stack-list-arguments}
26634 @item @code{-stack-list-locals}
26635 @item @code{-stack-select-frame}
26640 @subheading Introduction to Variable Objects
26642 @cindex variable objects in @sc{gdb/mi}
26644 Variable objects are "object-oriented" MI interface for examining and
26645 changing values of expressions. Unlike some other MI interfaces that
26646 work with expressions, variable objects are specifically designed for
26647 simple and efficient presentation in the frontend. A variable object
26648 is identified by string name. When a variable object is created, the
26649 frontend specifies the expression for that variable object. The
26650 expression can be a simple variable, or it can be an arbitrary complex
26651 expression, and can even involve CPU registers. After creating a
26652 variable object, the frontend can invoke other variable object
26653 operations---for example to obtain or change the value of a variable
26654 object, or to change display format.
26656 Variable objects have hierarchical tree structure. Any variable object
26657 that corresponds to a composite type, such as structure in C, has
26658 a number of child variable objects, for example corresponding to each
26659 element of a structure. A child variable object can itself have
26660 children, recursively. Recursion ends when we reach
26661 leaf variable objects, which always have built-in types. Child variable
26662 objects are created only by explicit request, so if a frontend
26663 is not interested in the children of a particular variable object, no
26664 child will be created.
26666 For a leaf variable object it is possible to obtain its value as a
26667 string, or set the value from a string. String value can be also
26668 obtained for a non-leaf variable object, but it's generally a string
26669 that only indicates the type of the object, and does not list its
26670 contents. Assignment to a non-leaf variable object is not allowed.
26672 A frontend does not need to read the values of all variable objects each time
26673 the program stops. Instead, MI provides an update command that lists all
26674 variable objects whose values has changed since the last update
26675 operation. This considerably reduces the amount of data that must
26676 be transferred to the frontend. As noted above, children variable
26677 objects are created on demand, and only leaf variable objects have a
26678 real value. As result, gdb will read target memory only for leaf
26679 variables that frontend has created.
26681 The automatic update is not always desirable. For example, a frontend
26682 might want to keep a value of some expression for future reference,
26683 and never update it. For another example, fetching memory is
26684 relatively slow for embedded targets, so a frontend might want
26685 to disable automatic update for the variables that are either not
26686 visible on the screen, or ``closed''. This is possible using so
26687 called ``frozen variable objects''. Such variable objects are never
26688 implicitly updated.
26690 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26691 fixed variable object, the expression is parsed when the variable
26692 object is created, including associating identifiers to specific
26693 variables. The meaning of expression never changes. For a floating
26694 variable object the values of variables whose names appear in the
26695 expressions are re-evaluated every time in the context of the current
26696 frame. Consider this example:
26701 struct work_state state;
26708 If a fixed variable object for the @code{state} variable is created in
26709 this function, and we enter the recursive call, the the variable
26710 object will report the value of @code{state} in the top-level
26711 @code{do_work} invocation. On the other hand, a floating variable
26712 object will report the value of @code{state} in the current frame.
26714 If an expression specified when creating a fixed variable object
26715 refers to a local variable, the variable object becomes bound to the
26716 thread and frame in which the variable object is created. When such
26717 variable object is updated, @value{GDBN} makes sure that the
26718 thread/frame combination the variable object is bound to still exists,
26719 and re-evaluates the variable object in context of that thread/frame.
26721 The following is the complete set of @sc{gdb/mi} operations defined to
26722 access this functionality:
26724 @multitable @columnfractions .4 .6
26725 @item @strong{Operation}
26726 @tab @strong{Description}
26728 @item @code{-enable-pretty-printing}
26729 @tab enable Python-based pretty-printing
26730 @item @code{-var-create}
26731 @tab create a variable object
26732 @item @code{-var-delete}
26733 @tab delete the variable object and/or its children
26734 @item @code{-var-set-format}
26735 @tab set the display format of this variable
26736 @item @code{-var-show-format}
26737 @tab show the display format of this variable
26738 @item @code{-var-info-num-children}
26739 @tab tells how many children this object has
26740 @item @code{-var-list-children}
26741 @tab return a list of the object's children
26742 @item @code{-var-info-type}
26743 @tab show the type of this variable object
26744 @item @code{-var-info-expression}
26745 @tab print parent-relative expression that this variable object represents
26746 @item @code{-var-info-path-expression}
26747 @tab print full expression that this variable object represents
26748 @item @code{-var-show-attributes}
26749 @tab is this variable editable? does it exist here?
26750 @item @code{-var-evaluate-expression}
26751 @tab get the value of this variable
26752 @item @code{-var-assign}
26753 @tab set the value of this variable
26754 @item @code{-var-update}
26755 @tab update the variable and its children
26756 @item @code{-var-set-frozen}
26757 @tab set frozeness attribute
26758 @item @code{-var-set-update-range}
26759 @tab set range of children to display on update
26762 In the next subsection we describe each operation in detail and suggest
26763 how it can be used.
26765 @subheading Description And Use of Operations on Variable Objects
26767 @subheading The @code{-enable-pretty-printing} Command
26768 @findex -enable-pretty-printing
26771 -enable-pretty-printing
26774 @value{GDBN} allows Python-based visualizers to affect the output of the
26775 MI variable object commands. However, because there was no way to
26776 implement this in a fully backward-compatible way, a front end must
26777 request that this functionality be enabled.
26779 Once enabled, this feature cannot be disabled.
26781 Note that if Python support has not been compiled into @value{GDBN},
26782 this command will still succeed (and do nothing).
26784 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26785 may work differently in future versions of @value{GDBN}.
26787 @subheading The @code{-var-create} Command
26788 @findex -var-create
26790 @subsubheading Synopsis
26793 -var-create @{@var{name} | "-"@}
26794 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26797 This operation creates a variable object, which allows the monitoring of
26798 a variable, the result of an expression, a memory cell or a CPU
26801 The @var{name} parameter is the string by which the object can be
26802 referenced. It must be unique. If @samp{-} is specified, the varobj
26803 system will generate a string ``varNNNNNN'' automatically. It will be
26804 unique provided that one does not specify @var{name} of that format.
26805 The command fails if a duplicate name is found.
26807 The frame under which the expression should be evaluated can be
26808 specified by @var{frame-addr}. A @samp{*} indicates that the current
26809 frame should be used. A @samp{@@} indicates that a floating variable
26810 object must be created.
26812 @var{expression} is any expression valid on the current language set (must not
26813 begin with a @samp{*}), or one of the following:
26817 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26820 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26823 @samp{$@var{regname}} --- a CPU register name
26826 @cindex dynamic varobj
26827 A varobj's contents may be provided by a Python-based pretty-printer. In this
26828 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26829 have slightly different semantics in some cases. If the
26830 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26831 will never create a dynamic varobj. This ensures backward
26832 compatibility for existing clients.
26834 @subsubheading Result
26836 This operation returns attributes of the newly-created varobj. These
26841 The name of the varobj.
26844 The number of children of the varobj. This number is not necessarily
26845 reliable for a dynamic varobj. Instead, you must examine the
26846 @samp{has_more} attribute.
26849 The varobj's scalar value. For a varobj whose type is some sort of
26850 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26851 will not be interesting.
26854 The varobj's type. This is a string representation of the type, as
26855 would be printed by the @value{GDBN} CLI.
26858 If a variable object is bound to a specific thread, then this is the
26859 thread's identifier.
26862 For a dynamic varobj, this indicates whether there appear to be any
26863 children available. For a non-dynamic varobj, this will be 0.
26866 This attribute will be present and have the value @samp{1} if the
26867 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26868 then this attribute will not be present.
26871 A dynamic varobj can supply a display hint to the front end. The
26872 value comes directly from the Python pretty-printer object's
26873 @code{display_hint} method. @xref{Pretty Printing API}.
26876 Typical output will look like this:
26879 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26880 has_more="@var{has_more}"
26884 @subheading The @code{-var-delete} Command
26885 @findex -var-delete
26887 @subsubheading Synopsis
26890 -var-delete [ -c ] @var{name}
26893 Deletes a previously created variable object and all of its children.
26894 With the @samp{-c} option, just deletes the children.
26896 Returns an error if the object @var{name} is not found.
26899 @subheading The @code{-var-set-format} Command
26900 @findex -var-set-format
26902 @subsubheading Synopsis
26905 -var-set-format @var{name} @var{format-spec}
26908 Sets the output format for the value of the object @var{name} to be
26911 @anchor{-var-set-format}
26912 The syntax for the @var{format-spec} is as follows:
26915 @var{format-spec} @expansion{}
26916 @{binary | decimal | hexadecimal | octal | natural@}
26919 The natural format is the default format choosen automatically
26920 based on the variable type (like decimal for an @code{int}, hex
26921 for pointers, etc.).
26923 For a variable with children, the format is set only on the
26924 variable itself, and the children are not affected.
26926 @subheading The @code{-var-show-format} Command
26927 @findex -var-show-format
26929 @subsubheading Synopsis
26932 -var-show-format @var{name}
26935 Returns the format used to display the value of the object @var{name}.
26938 @var{format} @expansion{}
26943 @subheading The @code{-var-info-num-children} Command
26944 @findex -var-info-num-children
26946 @subsubheading Synopsis
26949 -var-info-num-children @var{name}
26952 Returns the number of children of a variable object @var{name}:
26958 Note that this number is not completely reliable for a dynamic varobj.
26959 It will return the current number of children, but more children may
26963 @subheading The @code{-var-list-children} Command
26964 @findex -var-list-children
26966 @subsubheading Synopsis
26969 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26971 @anchor{-var-list-children}
26973 Return a list of the children of the specified variable object and
26974 create variable objects for them, if they do not already exist. With
26975 a single argument or if @var{print-values} has a value of 0 or
26976 @code{--no-values}, print only the names of the variables; if
26977 @var{print-values} is 1 or @code{--all-values}, also print their
26978 values; and if it is 2 or @code{--simple-values} print the name and
26979 value for simple data types and just the name for arrays, structures
26982 @var{from} and @var{to}, if specified, indicate the range of children
26983 to report. If @var{from} or @var{to} is less than zero, the range is
26984 reset and all children will be reported. Otherwise, children starting
26985 at @var{from} (zero-based) and up to and excluding @var{to} will be
26988 If a child range is requested, it will only affect the current call to
26989 @code{-var-list-children}, but not future calls to @code{-var-update}.
26990 For this, you must instead use @code{-var-set-update-range}. The
26991 intent of this approach is to enable a front end to implement any
26992 update approach it likes; for example, scrolling a view may cause the
26993 front end to request more children with @code{-var-list-children}, and
26994 then the front end could call @code{-var-set-update-range} with a
26995 different range to ensure that future updates are restricted to just
26998 For each child the following results are returned:
27003 Name of the variable object created for this child.
27006 The expression to be shown to the user by the front end to designate this child.
27007 For example this may be the name of a structure member.
27009 For a dynamic varobj, this value cannot be used to form an
27010 expression. There is no way to do this at all with a dynamic varobj.
27012 For C/C@t{++} structures there are several pseudo children returned to
27013 designate access qualifiers. For these pseudo children @var{exp} is
27014 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27015 type and value are not present.
27017 A dynamic varobj will not report the access qualifying
27018 pseudo-children, regardless of the language. This information is not
27019 available at all with a dynamic varobj.
27022 Number of children this child has. For a dynamic varobj, this will be
27026 The type of the child.
27029 If values were requested, this is the value.
27032 If this variable object is associated with a thread, this is the thread id.
27033 Otherwise this result is not present.
27036 If the variable object is frozen, this variable will be present with a value of 1.
27039 The result may have its own attributes:
27043 A dynamic varobj can supply a display hint to the front end. The
27044 value comes directly from the Python pretty-printer object's
27045 @code{display_hint} method. @xref{Pretty Printing API}.
27048 This is an integer attribute which is nonzero if there are children
27049 remaining after the end of the selected range.
27052 @subsubheading Example
27056 -var-list-children n
27057 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27058 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27060 -var-list-children --all-values n
27061 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27062 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27066 @subheading The @code{-var-info-type} Command
27067 @findex -var-info-type
27069 @subsubheading Synopsis
27072 -var-info-type @var{name}
27075 Returns the type of the specified variable @var{name}. The type is
27076 returned as a string in the same format as it is output by the
27080 type=@var{typename}
27084 @subheading The @code{-var-info-expression} Command
27085 @findex -var-info-expression
27087 @subsubheading Synopsis
27090 -var-info-expression @var{name}
27093 Returns a string that is suitable for presenting this
27094 variable object in user interface. The string is generally
27095 not valid expression in the current language, and cannot be evaluated.
27097 For example, if @code{a} is an array, and variable object
27098 @code{A} was created for @code{a}, then we'll get this output:
27101 (gdb) -var-info-expression A.1
27102 ^done,lang="C",exp="1"
27106 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27108 Note that the output of the @code{-var-list-children} command also
27109 includes those expressions, so the @code{-var-info-expression} command
27112 @subheading The @code{-var-info-path-expression} Command
27113 @findex -var-info-path-expression
27115 @subsubheading Synopsis
27118 -var-info-path-expression @var{name}
27121 Returns an expression that can be evaluated in the current
27122 context and will yield the same value that a variable object has.
27123 Compare this with the @code{-var-info-expression} command, which
27124 result can be used only for UI presentation. Typical use of
27125 the @code{-var-info-path-expression} command is creating a
27126 watchpoint from a variable object.
27128 This command is currently not valid for children of a dynamic varobj,
27129 and will give an error when invoked on one.
27131 For example, suppose @code{C} is a C@t{++} class, derived from class
27132 @code{Base}, and that the @code{Base} class has a member called
27133 @code{m_size}. Assume a variable @code{c} is has the type of
27134 @code{C} and a variable object @code{C} was created for variable
27135 @code{c}. Then, we'll get this output:
27137 (gdb) -var-info-path-expression C.Base.public.m_size
27138 ^done,path_expr=((Base)c).m_size)
27141 @subheading The @code{-var-show-attributes} Command
27142 @findex -var-show-attributes
27144 @subsubheading Synopsis
27147 -var-show-attributes @var{name}
27150 List attributes of the specified variable object @var{name}:
27153 status=@var{attr} [ ( ,@var{attr} )* ]
27157 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27159 @subheading The @code{-var-evaluate-expression} Command
27160 @findex -var-evaluate-expression
27162 @subsubheading Synopsis
27165 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27168 Evaluates the expression that is represented by the specified variable
27169 object and returns its value as a string. The format of the string
27170 can be specified with the @samp{-f} option. The possible values of
27171 this option are the same as for @code{-var-set-format}
27172 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27173 the current display format will be used. The current display format
27174 can be changed using the @code{-var-set-format} command.
27180 Note that one must invoke @code{-var-list-children} for a variable
27181 before the value of a child variable can be evaluated.
27183 @subheading The @code{-var-assign} Command
27184 @findex -var-assign
27186 @subsubheading Synopsis
27189 -var-assign @var{name} @var{expression}
27192 Assigns the value of @var{expression} to the variable object specified
27193 by @var{name}. The object must be @samp{editable}. If the variable's
27194 value is altered by the assign, the variable will show up in any
27195 subsequent @code{-var-update} list.
27197 @subsubheading Example
27205 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27209 @subheading The @code{-var-update} Command
27210 @findex -var-update
27212 @subsubheading Synopsis
27215 -var-update [@var{print-values}] @{@var{name} | "*"@}
27218 Reevaluate the expressions corresponding to the variable object
27219 @var{name} and all its direct and indirect children, and return the
27220 list of variable objects whose values have changed; @var{name} must
27221 be a root variable object. Here, ``changed'' means that the result of
27222 @code{-var-evaluate-expression} before and after the
27223 @code{-var-update} is different. If @samp{*} is used as the variable
27224 object names, all existing variable objects are updated, except
27225 for frozen ones (@pxref{-var-set-frozen}). The option
27226 @var{print-values} determines whether both names and values, or just
27227 names are printed. The possible values of this option are the same
27228 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27229 recommended to use the @samp{--all-values} option, to reduce the
27230 number of MI commands needed on each program stop.
27232 With the @samp{*} parameter, if a variable object is bound to a
27233 currently running thread, it will not be updated, without any
27236 If @code{-var-set-update-range} was previously used on a varobj, then
27237 only the selected range of children will be reported.
27239 @code{-var-update} reports all the changed varobjs in a tuple named
27242 Each item in the change list is itself a tuple holding:
27246 The name of the varobj.
27249 If values were requested for this update, then this field will be
27250 present and will hold the value of the varobj.
27253 @anchor{-var-update}
27254 This field is a string which may take one of three values:
27258 The variable object's current value is valid.
27261 The variable object does not currently hold a valid value but it may
27262 hold one in the future if its associated expression comes back into
27266 The variable object no longer holds a valid value.
27267 This can occur when the executable file being debugged has changed,
27268 either through recompilation or by using the @value{GDBN} @code{file}
27269 command. The front end should normally choose to delete these variable
27273 In the future new values may be added to this list so the front should
27274 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27277 This is only present if the varobj is still valid. If the type
27278 changed, then this will be the string @samp{true}; otherwise it will
27282 If the varobj's type changed, then this field will be present and will
27285 @item new_num_children
27286 For a dynamic varobj, if the number of children changed, or if the
27287 type changed, this will be the new number of children.
27289 The @samp{numchild} field in other varobj responses is generally not
27290 valid for a dynamic varobj -- it will show the number of children that
27291 @value{GDBN} knows about, but because dynamic varobjs lazily
27292 instantiate their children, this will not reflect the number of
27293 children which may be available.
27295 The @samp{new_num_children} attribute only reports changes to the
27296 number of children known by @value{GDBN}. This is the only way to
27297 detect whether an update has removed children (which necessarily can
27298 only happen at the end of the update range).
27301 The display hint, if any.
27304 This is an integer value, which will be 1 if there are more children
27305 available outside the varobj's update range.
27308 This attribute will be present and have the value @samp{1} if the
27309 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27310 then this attribute will not be present.
27313 If new children were added to a dynamic varobj within the selected
27314 update range (as set by @code{-var-set-update-range}), then they will
27315 be listed in this attribute.
27318 @subsubheading Example
27325 -var-update --all-values var1
27326 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27327 type_changed="false"@}]
27331 @subheading The @code{-var-set-frozen} Command
27332 @findex -var-set-frozen
27333 @anchor{-var-set-frozen}
27335 @subsubheading Synopsis
27338 -var-set-frozen @var{name} @var{flag}
27341 Set the frozenness flag on the variable object @var{name}. The
27342 @var{flag} parameter should be either @samp{1} to make the variable
27343 frozen or @samp{0} to make it unfrozen. If a variable object is
27344 frozen, then neither itself, nor any of its children, are
27345 implicitly updated by @code{-var-update} of
27346 a parent variable or by @code{-var-update *}. Only
27347 @code{-var-update} of the variable itself will update its value and
27348 values of its children. After a variable object is unfrozen, it is
27349 implicitly updated by all subsequent @code{-var-update} operations.
27350 Unfreezing a variable does not update it, only subsequent
27351 @code{-var-update} does.
27353 @subsubheading Example
27357 -var-set-frozen V 1
27362 @subheading The @code{-var-set-update-range} command
27363 @findex -var-set-update-range
27364 @anchor{-var-set-update-range}
27366 @subsubheading Synopsis
27369 -var-set-update-range @var{name} @var{from} @var{to}
27372 Set the range of children to be returned by future invocations of
27373 @code{-var-update}.
27375 @var{from} and @var{to} indicate the range of children to report. If
27376 @var{from} or @var{to} is less than zero, the range is reset and all
27377 children will be reported. Otherwise, children starting at @var{from}
27378 (zero-based) and up to and excluding @var{to} will be reported.
27380 @subsubheading Example
27384 -var-set-update-range V 1 2
27388 @subheading The @code{-var-set-visualizer} command
27389 @findex -var-set-visualizer
27390 @anchor{-var-set-visualizer}
27392 @subsubheading Synopsis
27395 -var-set-visualizer @var{name} @var{visualizer}
27398 Set a visualizer for the variable object @var{name}.
27400 @var{visualizer} is the visualizer to use. The special value
27401 @samp{None} means to disable any visualizer in use.
27403 If not @samp{None}, @var{visualizer} must be a Python expression.
27404 This expression must evaluate to a callable object which accepts a
27405 single argument. @value{GDBN} will call this object with the value of
27406 the varobj @var{name} as an argument (this is done so that the same
27407 Python pretty-printing code can be used for both the CLI and MI).
27408 When called, this object must return an object which conforms to the
27409 pretty-printing interface (@pxref{Pretty Printing API}).
27411 The pre-defined function @code{gdb.default_visualizer} may be used to
27412 select a visualizer by following the built-in process
27413 (@pxref{Selecting Pretty-Printers}). This is done automatically when
27414 a varobj is created, and so ordinarily is not needed.
27416 This feature is only available if Python support is enabled. The MI
27417 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
27418 can be used to check this.
27420 @subsubheading Example
27422 Resetting the visualizer:
27426 -var-set-visualizer V None
27430 Reselecting the default (type-based) visualizer:
27434 -var-set-visualizer V gdb.default_visualizer
27438 Suppose @code{SomeClass} is a visualizer class. A lambda expression
27439 can be used to instantiate this class for a varobj:
27443 -var-set-visualizer V "lambda val: SomeClass()"
27447 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27448 @node GDB/MI Data Manipulation
27449 @section @sc{gdb/mi} Data Manipulation
27451 @cindex data manipulation, in @sc{gdb/mi}
27452 @cindex @sc{gdb/mi}, data manipulation
27453 This section describes the @sc{gdb/mi} commands that manipulate data:
27454 examine memory and registers, evaluate expressions, etc.
27456 @c REMOVED FROM THE INTERFACE.
27457 @c @subheading -data-assign
27458 @c Change the value of a program variable. Plenty of side effects.
27459 @c @subsubheading GDB Command
27461 @c @subsubheading Example
27464 @subheading The @code{-data-disassemble} Command
27465 @findex -data-disassemble
27467 @subsubheading Synopsis
27471 [ -s @var{start-addr} -e @var{end-addr} ]
27472 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
27480 @item @var{start-addr}
27481 is the beginning address (or @code{$pc})
27482 @item @var{end-addr}
27484 @item @var{filename}
27485 is the name of the file to disassemble
27486 @item @var{linenum}
27487 is the line number to disassemble around
27489 is the number of disassembly lines to be produced. If it is -1,
27490 the whole function will be disassembled, in case no @var{end-addr} is
27491 specified. If @var{end-addr} is specified as a non-zero value, and
27492 @var{lines} is lower than the number of disassembly lines between
27493 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
27494 displayed; if @var{lines} is higher than the number of lines between
27495 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
27498 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
27502 @subsubheading Result
27504 The output for each instruction is composed of four fields:
27513 Note that whatever included in the instruction field, is not manipulated
27514 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
27516 @subsubheading @value{GDBN} Command
27518 There's no direct mapping from this command to the CLI.
27520 @subsubheading Example
27522 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
27526 -data-disassemble -s $pc -e "$pc + 20" -- 0
27529 @{address="0x000107c0",func-name="main",offset="4",
27530 inst="mov 2, %o0"@},
27531 @{address="0x000107c4",func-name="main",offset="8",
27532 inst="sethi %hi(0x11800), %o2"@},
27533 @{address="0x000107c8",func-name="main",offset="12",
27534 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27535 @{address="0x000107cc",func-name="main",offset="16",
27536 inst="sethi %hi(0x11800), %o2"@},
27537 @{address="0x000107d0",func-name="main",offset="20",
27538 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27542 Disassemble the whole @code{main} function. Line 32 is part of
27546 -data-disassemble -f basics.c -l 32 -- 0
27548 @{address="0x000107bc",func-name="main",offset="0",
27549 inst="save %sp, -112, %sp"@},
27550 @{address="0x000107c0",func-name="main",offset="4",
27551 inst="mov 2, %o0"@},
27552 @{address="0x000107c4",func-name="main",offset="8",
27553 inst="sethi %hi(0x11800), %o2"@},
27555 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27556 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27560 Disassemble 3 instructions from the start of @code{main}:
27564 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27566 @{address="0x000107bc",func-name="main",offset="0",
27567 inst="save %sp, -112, %sp"@},
27568 @{address="0x000107c0",func-name="main",offset="4",
27569 inst="mov 2, %o0"@},
27570 @{address="0x000107c4",func-name="main",offset="8",
27571 inst="sethi %hi(0x11800), %o2"@}]
27575 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27579 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27581 src_and_asm_line=@{line="31",
27582 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27583 testsuite/gdb.mi/basics.c",line_asm_insn=[
27584 @{address="0x000107bc",func-name="main",offset="0",
27585 inst="save %sp, -112, %sp"@}]@},
27586 src_and_asm_line=@{line="32",
27587 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27588 testsuite/gdb.mi/basics.c",line_asm_insn=[
27589 @{address="0x000107c0",func-name="main",offset="4",
27590 inst="mov 2, %o0"@},
27591 @{address="0x000107c4",func-name="main",offset="8",
27592 inst="sethi %hi(0x11800), %o2"@}]@}]
27597 @subheading The @code{-data-evaluate-expression} Command
27598 @findex -data-evaluate-expression
27600 @subsubheading Synopsis
27603 -data-evaluate-expression @var{expr}
27606 Evaluate @var{expr} as an expression. The expression could contain an
27607 inferior function call. The function call will execute synchronously.
27608 If the expression contains spaces, it must be enclosed in double quotes.
27610 @subsubheading @value{GDBN} Command
27612 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27613 @samp{call}. In @code{gdbtk} only, there's a corresponding
27614 @samp{gdb_eval} command.
27616 @subsubheading Example
27618 In the following example, the numbers that precede the commands are the
27619 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27620 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27624 211-data-evaluate-expression A
27627 311-data-evaluate-expression &A
27628 311^done,value="0xefffeb7c"
27630 411-data-evaluate-expression A+3
27633 511-data-evaluate-expression "A + 3"
27639 @subheading The @code{-data-list-changed-registers} Command
27640 @findex -data-list-changed-registers
27642 @subsubheading Synopsis
27645 -data-list-changed-registers
27648 Display a list of the registers that have changed.
27650 @subsubheading @value{GDBN} Command
27652 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27653 has the corresponding command @samp{gdb_changed_register_list}.
27655 @subsubheading Example
27657 On a PPC MBX board:
27665 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27666 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27669 -data-list-changed-registers
27670 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27671 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27672 "24","25","26","27","28","30","31","64","65","66","67","69"]
27677 @subheading The @code{-data-list-register-names} Command
27678 @findex -data-list-register-names
27680 @subsubheading Synopsis
27683 -data-list-register-names [ ( @var{regno} )+ ]
27686 Show a list of register names for the current target. If no arguments
27687 are given, it shows a list of the names of all the registers. If
27688 integer numbers are given as arguments, it will print a list of the
27689 names of the registers corresponding to the arguments. To ensure
27690 consistency between a register name and its number, the output list may
27691 include empty register names.
27693 @subsubheading @value{GDBN} Command
27695 @value{GDBN} does not have a command which corresponds to
27696 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27697 corresponding command @samp{gdb_regnames}.
27699 @subsubheading Example
27701 For the PPC MBX board:
27704 -data-list-register-names
27705 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27706 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27707 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27708 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27709 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27710 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27711 "", "pc","ps","cr","lr","ctr","xer"]
27713 -data-list-register-names 1 2 3
27714 ^done,register-names=["r1","r2","r3"]
27718 @subheading The @code{-data-list-register-values} Command
27719 @findex -data-list-register-values
27721 @subsubheading Synopsis
27724 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27727 Display the registers' contents. @var{fmt} is the format according to
27728 which the registers' contents are to be returned, followed by an optional
27729 list of numbers specifying the registers to display. A missing list of
27730 numbers indicates that the contents of all the registers must be returned.
27732 Allowed formats for @var{fmt} are:
27749 @subsubheading @value{GDBN} Command
27751 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27752 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27754 @subsubheading Example
27756 For a PPC MBX board (note: line breaks are for readability only, they
27757 don't appear in the actual output):
27761 -data-list-register-values r 64 65
27762 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27763 @{number="65",value="0x00029002"@}]
27765 -data-list-register-values x
27766 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27767 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27768 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27769 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27770 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27771 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27772 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27773 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27774 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27775 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27776 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27777 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27778 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27779 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27780 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27781 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27782 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27783 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27784 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27785 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27786 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27787 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27788 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27789 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27790 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27791 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27792 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27793 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27794 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27795 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27796 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27797 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27798 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27799 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27800 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27801 @{number="69",value="0x20002b03"@}]
27806 @subheading The @code{-data-read-memory} Command
27807 @findex -data-read-memory
27809 This command is deprecated, use @code{-data-read-memory-bytes} instead.
27811 @subsubheading Synopsis
27814 -data-read-memory [ -o @var{byte-offset} ]
27815 @var{address} @var{word-format} @var{word-size}
27816 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27823 @item @var{address}
27824 An expression specifying the address of the first memory word to be
27825 read. Complex expressions containing embedded white space should be
27826 quoted using the C convention.
27828 @item @var{word-format}
27829 The format to be used to print the memory words. The notation is the
27830 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27833 @item @var{word-size}
27834 The size of each memory word in bytes.
27836 @item @var{nr-rows}
27837 The number of rows in the output table.
27839 @item @var{nr-cols}
27840 The number of columns in the output table.
27843 If present, indicates that each row should include an @sc{ascii} dump. The
27844 value of @var{aschar} is used as a padding character when a byte is not a
27845 member of the printable @sc{ascii} character set (printable @sc{ascii}
27846 characters are those whose code is between 32 and 126, inclusively).
27848 @item @var{byte-offset}
27849 An offset to add to the @var{address} before fetching memory.
27852 This command displays memory contents as a table of @var{nr-rows} by
27853 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27854 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27855 (returned as @samp{total-bytes}). Should less than the requested number
27856 of bytes be returned by the target, the missing words are identified
27857 using @samp{N/A}. The number of bytes read from the target is returned
27858 in @samp{nr-bytes} and the starting address used to read memory in
27861 The address of the next/previous row or page is available in
27862 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27865 @subsubheading @value{GDBN} Command
27867 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27868 @samp{gdb_get_mem} memory read command.
27870 @subsubheading Example
27872 Read six bytes of memory starting at @code{bytes+6} but then offset by
27873 @code{-6} bytes. Format as three rows of two columns. One byte per
27874 word. Display each word in hex.
27878 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27879 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27880 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27881 prev-page="0x0000138a",memory=[
27882 @{addr="0x00001390",data=["0x00","0x01"]@},
27883 @{addr="0x00001392",data=["0x02","0x03"]@},
27884 @{addr="0x00001394",data=["0x04","0x05"]@}]
27888 Read two bytes of memory starting at address @code{shorts + 64} and
27889 display as a single word formatted in decimal.
27893 5-data-read-memory shorts+64 d 2 1 1
27894 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
27895 next-row="0x00001512",prev-row="0x0000150e",
27896 next-page="0x00001512",prev-page="0x0000150e",memory=[
27897 @{addr="0x00001510",data=["128"]@}]
27901 Read thirty two bytes of memory starting at @code{bytes+16} and format
27902 as eight rows of four columns. Include a string encoding with @samp{x}
27903 used as the non-printable character.
27907 4-data-read-memory bytes+16 x 1 8 4 x
27908 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
27909 next-row="0x000013c0",prev-row="0x0000139c",
27910 next-page="0x000013c0",prev-page="0x00001380",memory=[
27911 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
27912 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
27913 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
27914 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
27915 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
27916 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
27917 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
27918 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
27922 @subheading The @code{-data-read-memory-bytes} Command
27923 @findex -data-read-memory-bytes
27925 @subsubheading Synopsis
27928 -data-read-memory-bytes [ -o @var{byte-offset} ]
27929 @var{address} @var{count}
27936 @item @var{address}
27937 An expression specifying the address of the first memory word to be
27938 read. Complex expressions containing embedded white space should be
27939 quoted using the C convention.
27942 The number of bytes to read. This should be an integer literal.
27944 @item @var{byte-offset}
27945 The offsets in bytes relative to @var{address} at which to start
27946 reading. This should be an integer literal. This option is provided
27947 so that a frontend is not required to first evaluate address and then
27948 perform address arithmetics itself.
27952 This command attempts to read all accessible memory regions in the
27953 specified range. First, all regions marked as unreadable in the memory
27954 map (if one is defined) will be skipped. @xref{Memory Region
27955 Attributes}. Second, @value{GDBN} will attempt to read the remaining
27956 regions. For each one, if reading full region results in an errors,
27957 @value{GDBN} will try to read a subset of the region.
27959 In general, every single byte in the region may be readable or not,
27960 and the only way to read every readable byte is to try a read at
27961 every address, which is not practical. Therefore, @value{GDBN} will
27962 attempt to read all accessible bytes at either beginning or the end
27963 of the region, using a binary division scheme. This heuristic works
27964 well for reading accross a memory map boundary. Note that if a region
27965 has a readable range that is neither at the beginning or the end,
27966 @value{GDBN} will not read it.
27968 The result record (@pxref{GDB/MI Result Records}) that is output of
27969 the command includes a field named @samp{memory} whose content is a
27970 list of tuples. Each tuple represent a successfully read memory block
27971 and has the following fields:
27975 The start address of the memory block, as hexadecimal literal.
27978 The end address of the memory block, as hexadecimal literal.
27981 The offset of the memory block, as hexadecimal literal, relative to
27982 the start address passed to @code{-data-read-memory-bytes}.
27985 The contents of the memory block, in hex.
27991 @subsubheading @value{GDBN} Command
27993 The corresponding @value{GDBN} command is @samp{x}.
27995 @subsubheading Example
27999 -data-read-memory-bytes &a 10
28000 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28002 contents="01000000020000000300"@}]
28007 @subheading The @code{-data-write-memory-bytes} Command
28008 @findex -data-write-memory-bytes
28010 @subsubheading Synopsis
28013 -data-write-memory-bytes @var{address} @var{contents}
28020 @item @var{address}
28021 An expression specifying the address of the first memory word to be
28022 read. Complex expressions containing embedded white space should be
28023 quoted using the C convention.
28025 @item @var{contents}
28026 The hex-encoded bytes to write.
28030 @subsubheading @value{GDBN} Command
28032 There's no corresponding @value{GDBN} command.
28034 @subsubheading Example
28038 -data-write-memory-bytes &a "aabbccdd"
28044 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28045 @node GDB/MI Tracepoint Commands
28046 @section @sc{gdb/mi} Tracepoint Commands
28048 The commands defined in this section implement MI support for
28049 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28051 @subheading The @code{-trace-find} Command
28052 @findex -trace-find
28054 @subsubheading Synopsis
28057 -trace-find @var{mode} [@var{parameters}@dots{}]
28060 Find a trace frame using criteria defined by @var{mode} and
28061 @var{parameters}. The following table lists permissible
28062 modes and their parameters. For details of operation, see @ref{tfind}.
28067 No parameters are required. Stops examining trace frames.
28070 An integer is required as parameter. Selects tracepoint frame with
28073 @item tracepoint-number
28074 An integer is required as parameter. Finds next
28075 trace frame that corresponds to tracepoint with the specified number.
28078 An address is required as parameter. Finds
28079 next trace frame that corresponds to any tracepoint at the specified
28082 @item pc-inside-range
28083 Two addresses are required as parameters. Finds next trace
28084 frame that corresponds to a tracepoint at an address inside the
28085 specified range. Both bounds are considered to be inside the range.
28087 @item pc-outside-range
28088 Two addresses are required as parameters. Finds
28089 next trace frame that corresponds to a tracepoint at an address outside
28090 the specified range. Both bounds are considered to be inside the range.
28093 Line specification is required as parameter. @xref{Specify Location}.
28094 Finds next trace frame that corresponds to a tracepoint at
28095 the specified location.
28099 If @samp{none} was passed as @var{mode}, the response does not
28100 have fields. Otherwise, the response may have the following fields:
28104 This field has either @samp{0} or @samp{1} as the value, depending
28105 on whether a matching tracepoint was found.
28108 The index of the found traceframe. This field is present iff
28109 the @samp{found} field has value of @samp{1}.
28112 The index of the found tracepoint. This field is present iff
28113 the @samp{found} field has value of @samp{1}.
28116 The information about the frame corresponding to the found trace
28117 frame. This field is present only if a trace frame was found.
28118 @xref{GDB/MI Frame Information}, for description of this field.
28122 @subsubheading @value{GDBN} Command
28124 The corresponding @value{GDBN} command is @samp{tfind}.
28126 @subheading -trace-define-variable
28127 @findex -trace-define-variable
28129 @subsubheading Synopsis
28132 -trace-define-variable @var{name} [ @var{value} ]
28135 Create trace variable @var{name} if it does not exist. If
28136 @var{value} is specified, sets the initial value of the specified
28137 trace variable to that value. Note that the @var{name} should start
28138 with the @samp{$} character.
28140 @subsubheading @value{GDBN} Command
28142 The corresponding @value{GDBN} command is @samp{tvariable}.
28144 @subheading -trace-list-variables
28145 @findex -trace-list-variables
28147 @subsubheading Synopsis
28150 -trace-list-variables
28153 Return a table of all defined trace variables. Each element of the
28154 table has the following fields:
28158 The name of the trace variable. This field is always present.
28161 The initial value. This is a 64-bit signed integer. This
28162 field is always present.
28165 The value the trace variable has at the moment. This is a 64-bit
28166 signed integer. This field is absent iff current value is
28167 not defined, for example if the trace was never run, or is
28172 @subsubheading @value{GDBN} Command
28174 The corresponding @value{GDBN} command is @samp{tvariables}.
28176 @subsubheading Example
28180 -trace-list-variables
28181 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28182 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28183 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28184 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28185 body=[variable=@{name="$trace_timestamp",initial="0"@}
28186 variable=@{name="$foo",initial="10",current="15"@}]@}
28190 @subheading -trace-save
28191 @findex -trace-save
28193 @subsubheading Synopsis
28196 -trace-save [-r ] @var{filename}
28199 Saves the collected trace data to @var{filename}. Without the
28200 @samp{-r} option, the data is downloaded from the target and saved
28201 in a local file. With the @samp{-r} option the target is asked
28202 to perform the save.
28204 @subsubheading @value{GDBN} Command
28206 The corresponding @value{GDBN} command is @samp{tsave}.
28209 @subheading -trace-start
28210 @findex -trace-start
28212 @subsubheading Synopsis
28218 Starts a tracing experiments. The result of this command does not
28221 @subsubheading @value{GDBN} Command
28223 The corresponding @value{GDBN} command is @samp{tstart}.
28225 @subheading -trace-status
28226 @findex -trace-status
28228 @subsubheading Synopsis
28234 Obtains the status of a tracing experiment. The result may include
28235 the following fields:
28240 May have a value of either @samp{0}, when no tracing operations are
28241 supported, @samp{1}, when all tracing operations are supported, or
28242 @samp{file} when examining trace file. In the latter case, examining
28243 of trace frame is possible but new tracing experiement cannot be
28244 started. This field is always present.
28247 May have a value of either @samp{0} or @samp{1} depending on whether
28248 tracing experiement is in progress on target. This field is present
28249 if @samp{supported} field is not @samp{0}.
28252 Report the reason why the tracing was stopped last time. This field
28253 may be absent iff tracing was never stopped on target yet. The
28254 value of @samp{request} means the tracing was stopped as result of
28255 the @code{-trace-stop} command. The value of @samp{overflow} means
28256 the tracing buffer is full. The value of @samp{disconnection} means
28257 tracing was automatically stopped when @value{GDBN} has disconnected.
28258 The value of @samp{passcount} means tracing was stopped when a
28259 tracepoint was passed a maximal number of times for that tracepoint.
28260 This field is present if @samp{supported} field is not @samp{0}.
28262 @item stopping-tracepoint
28263 The number of tracepoint whose passcount as exceeded. This field is
28264 present iff the @samp{stop-reason} field has the value of
28268 @itemx frames-created
28269 The @samp{frames} field is a count of the total number of trace frames
28270 in the trace buffer, while @samp{frames-created} is the total created
28271 during the run, including ones that were discarded, such as when a
28272 circular trace buffer filled up. Both fields are optional.
28276 These fields tell the current size of the tracing buffer and the
28277 remaining space. These fields are optional.
28280 The value of the circular trace buffer flag. @code{1} means that the
28281 trace buffer is circular and old trace frames will be discarded if
28282 necessary to make room, @code{0} means that the trace buffer is linear
28286 The value of the disconnected tracing flag. @code{1} means that
28287 tracing will continue after @value{GDBN} disconnects, @code{0} means
28288 that the trace run will stop.
28292 @subsubheading @value{GDBN} Command
28294 The corresponding @value{GDBN} command is @samp{tstatus}.
28296 @subheading -trace-stop
28297 @findex -trace-stop
28299 @subsubheading Synopsis
28305 Stops a tracing experiment. The result of this command has the same
28306 fields as @code{-trace-status}, except that the @samp{supported} and
28307 @samp{running} fields are not output.
28309 @subsubheading @value{GDBN} Command
28311 The corresponding @value{GDBN} command is @samp{tstop}.
28314 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28315 @node GDB/MI Symbol Query
28316 @section @sc{gdb/mi} Symbol Query Commands
28320 @subheading The @code{-symbol-info-address} Command
28321 @findex -symbol-info-address
28323 @subsubheading Synopsis
28326 -symbol-info-address @var{symbol}
28329 Describe where @var{symbol} is stored.
28331 @subsubheading @value{GDBN} Command
28333 The corresponding @value{GDBN} command is @samp{info address}.
28335 @subsubheading Example
28339 @subheading The @code{-symbol-info-file} Command
28340 @findex -symbol-info-file
28342 @subsubheading Synopsis
28348 Show the file for the symbol.
28350 @subsubheading @value{GDBN} Command
28352 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28353 @samp{gdb_find_file}.
28355 @subsubheading Example
28359 @subheading The @code{-symbol-info-function} Command
28360 @findex -symbol-info-function
28362 @subsubheading Synopsis
28365 -symbol-info-function
28368 Show which function the symbol lives in.
28370 @subsubheading @value{GDBN} Command
28372 @samp{gdb_get_function} in @code{gdbtk}.
28374 @subsubheading Example
28378 @subheading The @code{-symbol-info-line} Command
28379 @findex -symbol-info-line
28381 @subsubheading Synopsis
28387 Show the core addresses of the code for a source line.
28389 @subsubheading @value{GDBN} Command
28391 The corresponding @value{GDBN} command is @samp{info line}.
28392 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
28394 @subsubheading Example
28398 @subheading The @code{-symbol-info-symbol} Command
28399 @findex -symbol-info-symbol
28401 @subsubheading Synopsis
28404 -symbol-info-symbol @var{addr}
28407 Describe what symbol is at location @var{addr}.
28409 @subsubheading @value{GDBN} Command
28411 The corresponding @value{GDBN} command is @samp{info symbol}.
28413 @subsubheading Example
28417 @subheading The @code{-symbol-list-functions} Command
28418 @findex -symbol-list-functions
28420 @subsubheading Synopsis
28423 -symbol-list-functions
28426 List the functions in the executable.
28428 @subsubheading @value{GDBN} Command
28430 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
28431 @samp{gdb_search} in @code{gdbtk}.
28433 @subsubheading Example
28438 @subheading The @code{-symbol-list-lines} Command
28439 @findex -symbol-list-lines
28441 @subsubheading Synopsis
28444 -symbol-list-lines @var{filename}
28447 Print the list of lines that contain code and their associated program
28448 addresses for the given source filename. The entries are sorted in
28449 ascending PC order.
28451 @subsubheading @value{GDBN} Command
28453 There is no corresponding @value{GDBN} command.
28455 @subsubheading Example
28458 -symbol-list-lines basics.c
28459 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
28465 @subheading The @code{-symbol-list-types} Command
28466 @findex -symbol-list-types
28468 @subsubheading Synopsis
28474 List all the type names.
28476 @subsubheading @value{GDBN} Command
28478 The corresponding commands are @samp{info types} in @value{GDBN},
28479 @samp{gdb_search} in @code{gdbtk}.
28481 @subsubheading Example
28485 @subheading The @code{-symbol-list-variables} Command
28486 @findex -symbol-list-variables
28488 @subsubheading Synopsis
28491 -symbol-list-variables
28494 List all the global and static variable names.
28496 @subsubheading @value{GDBN} Command
28498 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
28500 @subsubheading Example
28504 @subheading The @code{-symbol-locate} Command
28505 @findex -symbol-locate
28507 @subsubheading Synopsis
28513 @subsubheading @value{GDBN} Command
28515 @samp{gdb_loc} in @code{gdbtk}.
28517 @subsubheading Example
28521 @subheading The @code{-symbol-type} Command
28522 @findex -symbol-type
28524 @subsubheading Synopsis
28527 -symbol-type @var{variable}
28530 Show type of @var{variable}.
28532 @subsubheading @value{GDBN} Command
28534 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
28535 @samp{gdb_obj_variable}.
28537 @subsubheading Example
28542 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28543 @node GDB/MI File Commands
28544 @section @sc{gdb/mi} File Commands
28546 This section describes the GDB/MI commands to specify executable file names
28547 and to read in and obtain symbol table information.
28549 @subheading The @code{-file-exec-and-symbols} Command
28550 @findex -file-exec-and-symbols
28552 @subsubheading Synopsis
28555 -file-exec-and-symbols @var{file}
28558 Specify the executable file to be debugged. This file is the one from
28559 which the symbol table is also read. If no file is specified, the
28560 command clears the executable and symbol information. If breakpoints
28561 are set when using this command with no arguments, @value{GDBN} will produce
28562 error messages. Otherwise, no output is produced, except a completion
28565 @subsubheading @value{GDBN} Command
28567 The corresponding @value{GDBN} command is @samp{file}.
28569 @subsubheading Example
28573 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28579 @subheading The @code{-file-exec-file} Command
28580 @findex -file-exec-file
28582 @subsubheading Synopsis
28585 -file-exec-file @var{file}
28588 Specify the executable file to be debugged. Unlike
28589 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
28590 from this file. If used without argument, @value{GDBN} clears the information
28591 about the executable file. No output is produced, except a completion
28594 @subsubheading @value{GDBN} Command
28596 The corresponding @value{GDBN} command is @samp{exec-file}.
28598 @subsubheading Example
28602 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28609 @subheading The @code{-file-list-exec-sections} Command
28610 @findex -file-list-exec-sections
28612 @subsubheading Synopsis
28615 -file-list-exec-sections
28618 List the sections of the current executable file.
28620 @subsubheading @value{GDBN} Command
28622 The @value{GDBN} command @samp{info file} shows, among the rest, the same
28623 information as this command. @code{gdbtk} has a corresponding command
28624 @samp{gdb_load_info}.
28626 @subsubheading Example
28631 @subheading The @code{-file-list-exec-source-file} Command
28632 @findex -file-list-exec-source-file
28634 @subsubheading Synopsis
28637 -file-list-exec-source-file
28640 List the line number, the current source file, and the absolute path
28641 to the current source file for the current executable. The macro
28642 information field has a value of @samp{1} or @samp{0} depending on
28643 whether or not the file includes preprocessor macro information.
28645 @subsubheading @value{GDBN} Command
28647 The @value{GDBN} equivalent is @samp{info source}
28649 @subsubheading Example
28653 123-file-list-exec-source-file
28654 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
28659 @subheading The @code{-file-list-exec-source-files} Command
28660 @findex -file-list-exec-source-files
28662 @subsubheading Synopsis
28665 -file-list-exec-source-files
28668 List the source files for the current executable.
28670 It will always output the filename, but only when @value{GDBN} can find
28671 the absolute file name of a source file, will it output the fullname.
28673 @subsubheading @value{GDBN} Command
28675 The @value{GDBN} equivalent is @samp{info sources}.
28676 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
28678 @subsubheading Example
28681 -file-list-exec-source-files
28683 @{file=foo.c,fullname=/home/foo.c@},
28684 @{file=/home/bar.c,fullname=/home/bar.c@},
28685 @{file=gdb_could_not_find_fullpath.c@}]
28690 @subheading The @code{-file-list-shared-libraries} Command
28691 @findex -file-list-shared-libraries
28693 @subsubheading Synopsis
28696 -file-list-shared-libraries
28699 List the shared libraries in the program.
28701 @subsubheading @value{GDBN} Command
28703 The corresponding @value{GDBN} command is @samp{info shared}.
28705 @subsubheading Example
28709 @subheading The @code{-file-list-symbol-files} Command
28710 @findex -file-list-symbol-files
28712 @subsubheading Synopsis
28715 -file-list-symbol-files
28720 @subsubheading @value{GDBN} Command
28722 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28724 @subsubheading Example
28729 @subheading The @code{-file-symbol-file} Command
28730 @findex -file-symbol-file
28732 @subsubheading Synopsis
28735 -file-symbol-file @var{file}
28738 Read symbol table info from the specified @var{file} argument. When
28739 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28740 produced, except for a completion notification.
28742 @subsubheading @value{GDBN} Command
28744 The corresponding @value{GDBN} command is @samp{symbol-file}.
28746 @subsubheading Example
28750 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28757 @node GDB/MI Memory Overlay Commands
28758 @section @sc{gdb/mi} Memory Overlay Commands
28760 The memory overlay commands are not implemented.
28762 @c @subheading -overlay-auto
28764 @c @subheading -overlay-list-mapping-state
28766 @c @subheading -overlay-list-overlays
28768 @c @subheading -overlay-map
28770 @c @subheading -overlay-off
28772 @c @subheading -overlay-on
28774 @c @subheading -overlay-unmap
28776 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28777 @node GDB/MI Signal Handling Commands
28778 @section @sc{gdb/mi} Signal Handling Commands
28780 Signal handling commands are not implemented.
28782 @c @subheading -signal-handle
28784 @c @subheading -signal-list-handle-actions
28786 @c @subheading -signal-list-signal-types
28790 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28791 @node GDB/MI Target Manipulation
28792 @section @sc{gdb/mi} Target Manipulation Commands
28795 @subheading The @code{-target-attach} Command
28796 @findex -target-attach
28798 @subsubheading Synopsis
28801 -target-attach @var{pid} | @var{gid} | @var{file}
28804 Attach to a process @var{pid} or a file @var{file} outside of
28805 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28806 group, the id previously returned by
28807 @samp{-list-thread-groups --available} must be used.
28809 @subsubheading @value{GDBN} Command
28811 The corresponding @value{GDBN} command is @samp{attach}.
28813 @subsubheading Example
28817 =thread-created,id="1"
28818 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28824 @subheading The @code{-target-compare-sections} Command
28825 @findex -target-compare-sections
28827 @subsubheading Synopsis
28830 -target-compare-sections [ @var{section} ]
28833 Compare data of section @var{section} on target to the exec file.
28834 Without the argument, all sections are compared.
28836 @subsubheading @value{GDBN} Command
28838 The @value{GDBN} equivalent is @samp{compare-sections}.
28840 @subsubheading Example
28845 @subheading The @code{-target-detach} Command
28846 @findex -target-detach
28848 @subsubheading Synopsis
28851 -target-detach [ @var{pid} | @var{gid} ]
28854 Detach from the remote target which normally resumes its execution.
28855 If either @var{pid} or @var{gid} is specified, detaches from either
28856 the specified process, or specified thread group. There's no output.
28858 @subsubheading @value{GDBN} Command
28860 The corresponding @value{GDBN} command is @samp{detach}.
28862 @subsubheading Example
28872 @subheading The @code{-target-disconnect} Command
28873 @findex -target-disconnect
28875 @subsubheading Synopsis
28881 Disconnect from the remote target. There's no output and the target is
28882 generally not resumed.
28884 @subsubheading @value{GDBN} Command
28886 The corresponding @value{GDBN} command is @samp{disconnect}.
28888 @subsubheading Example
28898 @subheading The @code{-target-download} Command
28899 @findex -target-download
28901 @subsubheading Synopsis
28907 Loads the executable onto the remote target.
28908 It prints out an update message every half second, which includes the fields:
28912 The name of the section.
28914 The size of what has been sent so far for that section.
28916 The size of the section.
28918 The total size of what was sent so far (the current and the previous sections).
28920 The size of the overall executable to download.
28924 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
28925 @sc{gdb/mi} Output Syntax}).
28927 In addition, it prints the name and size of the sections, as they are
28928 downloaded. These messages include the following fields:
28932 The name of the section.
28934 The size of the section.
28936 The size of the overall executable to download.
28940 At the end, a summary is printed.
28942 @subsubheading @value{GDBN} Command
28944 The corresponding @value{GDBN} command is @samp{load}.
28946 @subsubheading Example
28948 Note: each status message appears on a single line. Here the messages
28949 have been broken down so that they can fit onto a page.
28954 +download,@{section=".text",section-size="6668",total-size="9880"@}
28955 +download,@{section=".text",section-sent="512",section-size="6668",
28956 total-sent="512",total-size="9880"@}
28957 +download,@{section=".text",section-sent="1024",section-size="6668",
28958 total-sent="1024",total-size="9880"@}
28959 +download,@{section=".text",section-sent="1536",section-size="6668",
28960 total-sent="1536",total-size="9880"@}
28961 +download,@{section=".text",section-sent="2048",section-size="6668",
28962 total-sent="2048",total-size="9880"@}
28963 +download,@{section=".text",section-sent="2560",section-size="6668",
28964 total-sent="2560",total-size="9880"@}
28965 +download,@{section=".text",section-sent="3072",section-size="6668",
28966 total-sent="3072",total-size="9880"@}
28967 +download,@{section=".text",section-sent="3584",section-size="6668",
28968 total-sent="3584",total-size="9880"@}
28969 +download,@{section=".text",section-sent="4096",section-size="6668",
28970 total-sent="4096",total-size="9880"@}
28971 +download,@{section=".text",section-sent="4608",section-size="6668",
28972 total-sent="4608",total-size="9880"@}
28973 +download,@{section=".text",section-sent="5120",section-size="6668",
28974 total-sent="5120",total-size="9880"@}
28975 +download,@{section=".text",section-sent="5632",section-size="6668",
28976 total-sent="5632",total-size="9880"@}
28977 +download,@{section=".text",section-sent="6144",section-size="6668",
28978 total-sent="6144",total-size="9880"@}
28979 +download,@{section=".text",section-sent="6656",section-size="6668",
28980 total-sent="6656",total-size="9880"@}
28981 +download,@{section=".init",section-size="28",total-size="9880"@}
28982 +download,@{section=".fini",section-size="28",total-size="9880"@}
28983 +download,@{section=".data",section-size="3156",total-size="9880"@}
28984 +download,@{section=".data",section-sent="512",section-size="3156",
28985 total-sent="7236",total-size="9880"@}
28986 +download,@{section=".data",section-sent="1024",section-size="3156",
28987 total-sent="7748",total-size="9880"@}
28988 +download,@{section=".data",section-sent="1536",section-size="3156",
28989 total-sent="8260",total-size="9880"@}
28990 +download,@{section=".data",section-sent="2048",section-size="3156",
28991 total-sent="8772",total-size="9880"@}
28992 +download,@{section=".data",section-sent="2560",section-size="3156",
28993 total-sent="9284",total-size="9880"@}
28994 +download,@{section=".data",section-sent="3072",section-size="3156",
28995 total-sent="9796",total-size="9880"@}
28996 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29003 @subheading The @code{-target-exec-status} Command
29004 @findex -target-exec-status
29006 @subsubheading Synopsis
29009 -target-exec-status
29012 Provide information on the state of the target (whether it is running or
29013 not, for instance).
29015 @subsubheading @value{GDBN} Command
29017 There's no equivalent @value{GDBN} command.
29019 @subsubheading Example
29023 @subheading The @code{-target-list-available-targets} Command
29024 @findex -target-list-available-targets
29026 @subsubheading Synopsis
29029 -target-list-available-targets
29032 List the possible targets to connect to.
29034 @subsubheading @value{GDBN} Command
29036 The corresponding @value{GDBN} command is @samp{help target}.
29038 @subsubheading Example
29042 @subheading The @code{-target-list-current-targets} Command
29043 @findex -target-list-current-targets
29045 @subsubheading Synopsis
29048 -target-list-current-targets
29051 Describe the current target.
29053 @subsubheading @value{GDBN} Command
29055 The corresponding information is printed by @samp{info file} (among
29058 @subsubheading Example
29062 @subheading The @code{-target-list-parameters} Command
29063 @findex -target-list-parameters
29065 @subsubheading Synopsis
29068 -target-list-parameters
29074 @subsubheading @value{GDBN} Command
29078 @subsubheading Example
29082 @subheading The @code{-target-select} Command
29083 @findex -target-select
29085 @subsubheading Synopsis
29088 -target-select @var{type} @var{parameters @dots{}}
29091 Connect @value{GDBN} to the remote target. This command takes two args:
29095 The type of target, for instance @samp{remote}, etc.
29096 @item @var{parameters}
29097 Device names, host names and the like. @xref{Target Commands, ,
29098 Commands for Managing Targets}, for more details.
29101 The output is a connection notification, followed by the address at
29102 which the target program is, in the following form:
29105 ^connected,addr="@var{address}",func="@var{function name}",
29106 args=[@var{arg list}]
29109 @subsubheading @value{GDBN} Command
29111 The corresponding @value{GDBN} command is @samp{target}.
29113 @subsubheading Example
29117 -target-select remote /dev/ttya
29118 ^connected,addr="0xfe00a300",func="??",args=[]
29122 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29123 @node GDB/MI File Transfer Commands
29124 @section @sc{gdb/mi} File Transfer Commands
29127 @subheading The @code{-target-file-put} Command
29128 @findex -target-file-put
29130 @subsubheading Synopsis
29133 -target-file-put @var{hostfile} @var{targetfile}
29136 Copy file @var{hostfile} from the host system (the machine running
29137 @value{GDBN}) to @var{targetfile} on the target system.
29139 @subsubheading @value{GDBN} Command
29141 The corresponding @value{GDBN} command is @samp{remote put}.
29143 @subsubheading Example
29147 -target-file-put localfile remotefile
29153 @subheading The @code{-target-file-get} Command
29154 @findex -target-file-get
29156 @subsubheading Synopsis
29159 -target-file-get @var{targetfile} @var{hostfile}
29162 Copy file @var{targetfile} from the target system to @var{hostfile}
29163 on the host system.
29165 @subsubheading @value{GDBN} Command
29167 The corresponding @value{GDBN} command is @samp{remote get}.
29169 @subsubheading Example
29173 -target-file-get remotefile localfile
29179 @subheading The @code{-target-file-delete} Command
29180 @findex -target-file-delete
29182 @subsubheading Synopsis
29185 -target-file-delete @var{targetfile}
29188 Delete @var{targetfile} from the target system.
29190 @subsubheading @value{GDBN} Command
29192 The corresponding @value{GDBN} command is @samp{remote delete}.
29194 @subsubheading Example
29198 -target-file-delete remotefile
29204 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29205 @node GDB/MI Miscellaneous Commands
29206 @section Miscellaneous @sc{gdb/mi} Commands
29208 @c @subheading -gdb-complete
29210 @subheading The @code{-gdb-exit} Command
29213 @subsubheading Synopsis
29219 Exit @value{GDBN} immediately.
29221 @subsubheading @value{GDBN} Command
29223 Approximately corresponds to @samp{quit}.
29225 @subsubheading Example
29235 @subheading The @code{-exec-abort} Command
29236 @findex -exec-abort
29238 @subsubheading Synopsis
29244 Kill the inferior running program.
29246 @subsubheading @value{GDBN} Command
29248 The corresponding @value{GDBN} command is @samp{kill}.
29250 @subsubheading Example
29255 @subheading The @code{-gdb-set} Command
29258 @subsubheading Synopsis
29264 Set an internal @value{GDBN} variable.
29265 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29267 @subsubheading @value{GDBN} Command
29269 The corresponding @value{GDBN} command is @samp{set}.
29271 @subsubheading Example
29281 @subheading The @code{-gdb-show} Command
29284 @subsubheading Synopsis
29290 Show the current value of a @value{GDBN} variable.
29292 @subsubheading @value{GDBN} Command
29294 The corresponding @value{GDBN} command is @samp{show}.
29296 @subsubheading Example
29305 @c @subheading -gdb-source
29308 @subheading The @code{-gdb-version} Command
29309 @findex -gdb-version
29311 @subsubheading Synopsis
29317 Show version information for @value{GDBN}. Used mostly in testing.
29319 @subsubheading @value{GDBN} Command
29321 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29322 default shows this information when you start an interactive session.
29324 @subsubheading Example
29326 @c This example modifies the actual output from GDB to avoid overfull
29332 ~Copyright 2000 Free Software Foundation, Inc.
29333 ~GDB is free software, covered by the GNU General Public License, and
29334 ~you are welcome to change it and/or distribute copies of it under
29335 ~ certain conditions.
29336 ~Type "show copying" to see the conditions.
29337 ~There is absolutely no warranty for GDB. Type "show warranty" for
29339 ~This GDB was configured as
29340 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29345 @subheading The @code{-list-features} Command
29346 @findex -list-features
29348 Returns a list of particular features of the MI protocol that
29349 this version of gdb implements. A feature can be a command,
29350 or a new field in an output of some command, or even an
29351 important bugfix. While a frontend can sometimes detect presence
29352 of a feature at runtime, it is easier to perform detection at debugger
29355 The command returns a list of strings, with each string naming an
29356 available feature. Each returned string is just a name, it does not
29357 have any internal structure. The list of possible feature names
29363 (gdb) -list-features
29364 ^done,result=["feature1","feature2"]
29367 The current list of features is:
29370 @item frozen-varobjs
29371 Indicates presence of the @code{-var-set-frozen} command, as well
29372 as possible presense of the @code{frozen} field in the output
29373 of @code{-varobj-create}.
29374 @item pending-breakpoints
29375 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
29377 Indicates presence of Python scripting support, Python-based
29378 pretty-printing commands, and possible presence of the
29379 @samp{display_hint} field in the output of @code{-var-list-children}
29381 Indicates presence of the @code{-thread-info} command.
29382 @item data-read-memory-bytes
29383 Indicates presense of the @code{-data-read-memory-bytes} and the
29384 @code{-data-write-memory-bytes} commands.
29388 @subheading The @code{-list-target-features} Command
29389 @findex -list-target-features
29391 Returns a list of particular features that are supported by the
29392 target. Those features affect the permitted MI commands, but
29393 unlike the features reported by the @code{-list-features} command, the
29394 features depend on which target GDB is using at the moment. Whenever
29395 a target can change, due to commands such as @code{-target-select},
29396 @code{-target-attach} or @code{-exec-run}, the list of target features
29397 may change, and the frontend should obtain it again.
29401 (gdb) -list-features
29402 ^done,result=["async"]
29405 The current list of features is:
29409 Indicates that the target is capable of asynchronous command
29410 execution, which means that @value{GDBN} will accept further commands
29411 while the target is running.
29414 Indicates that the target is capable of reverse execution.
29415 @xref{Reverse Execution}, for more information.
29419 @subheading The @code{-list-thread-groups} Command
29420 @findex -list-thread-groups
29422 @subheading Synopsis
29425 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
29428 Lists thread groups (@pxref{Thread groups}). When a single thread
29429 group is passed as the argument, lists the children of that group.
29430 When several thread group are passed, lists information about those
29431 thread groups. Without any parameters, lists information about all
29432 top-level thread groups.
29434 Normally, thread groups that are being debugged are reported.
29435 With the @samp{--available} option, @value{GDBN} reports thread groups
29436 available on the target.
29438 The output of this command may have either a @samp{threads} result or
29439 a @samp{groups} result. The @samp{thread} result has a list of tuples
29440 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
29441 Information}). The @samp{groups} result has a list of tuples as value,
29442 each tuple describing a thread group. If top-level groups are
29443 requested (that is, no parameter is passed), or when several groups
29444 are passed, the output always has a @samp{groups} result. The format
29445 of the @samp{group} result is described below.
29447 To reduce the number of roundtrips it's possible to list thread groups
29448 together with their children, by passing the @samp{--recurse} option
29449 and the recursion depth. Presently, only recursion depth of 1 is
29450 permitted. If this option is present, then every reported thread group
29451 will also include its children, either as @samp{group} or
29452 @samp{threads} field.
29454 In general, any combination of option and parameters is permitted, with
29455 the following caveats:
29459 When a single thread group is passed, the output will typically
29460 be the @samp{threads} result. Because threads may not contain
29461 anything, the @samp{recurse} option will be ignored.
29464 When the @samp{--available} option is passed, limited information may
29465 be available. In particular, the list of threads of a process might
29466 be inaccessible. Further, specifying specific thread groups might
29467 not give any performance advantage over listing all thread groups.
29468 The frontend should assume that @samp{-list-thread-groups --available}
29469 is always an expensive operation and cache the results.
29473 The @samp{groups} result is a list of tuples, where each tuple may
29474 have the following fields:
29478 Identifier of the thread group. This field is always present.
29479 The identifier is an opaque string; frontends should not try to
29480 convert it to an integer, even though it might look like one.
29483 The type of the thread group. At present, only @samp{process} is a
29487 The target-specific process identifier. This field is only present
29488 for thread groups of type @samp{process} and only if the process exists.
29491 The number of children this thread group has. This field may be
29492 absent for an available thread group.
29495 This field has a list of tuples as value, each tuple describing a
29496 thread. It may be present if the @samp{--recurse} option is
29497 specified, and it's actually possible to obtain the threads.
29500 This field is a list of integers, each identifying a core that one
29501 thread of the group is running on. This field may be absent if
29502 such information is not available.
29505 The name of the executable file that corresponds to this thread group.
29506 The field is only present for thread groups of type @samp{process},
29507 and only if there is a corresponding executable file.
29511 @subheading Example
29515 -list-thread-groups
29516 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
29517 -list-thread-groups 17
29518 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29519 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
29520 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29521 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
29522 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
29523 -list-thread-groups --available
29524 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
29525 -list-thread-groups --available --recurse 1
29526 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29527 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29528 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
29529 -list-thread-groups --available --recurse 1 17 18
29530 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29531 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29532 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
29536 @subheading The @code{-add-inferior} Command
29537 @findex -add-inferior
29539 @subheading Synopsis
29545 Creates a new inferior (@pxref{Inferiors and Programs}). The created
29546 inferior is not associated with any executable. Such association may
29547 be established with the @samp{-file-exec-and-symbols} command
29548 (@pxref{GDB/MI File Commands}). The command response has a single
29549 field, @samp{thread-group}, whose value is the identifier of the
29550 thread group corresponding to the new inferior.
29552 @subheading Example
29557 ^done,thread-group="i3"
29560 @subheading The @code{-interpreter-exec} Command
29561 @findex -interpreter-exec
29563 @subheading Synopsis
29566 -interpreter-exec @var{interpreter} @var{command}
29568 @anchor{-interpreter-exec}
29570 Execute the specified @var{command} in the given @var{interpreter}.
29572 @subheading @value{GDBN} Command
29574 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
29576 @subheading Example
29580 -interpreter-exec console "break main"
29581 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
29582 &"During symbol reading, bad structure-type format.\n"
29583 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
29588 @subheading The @code{-inferior-tty-set} Command
29589 @findex -inferior-tty-set
29591 @subheading Synopsis
29594 -inferior-tty-set /dev/pts/1
29597 Set terminal for future runs of the program being debugged.
29599 @subheading @value{GDBN} Command
29601 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
29603 @subheading Example
29607 -inferior-tty-set /dev/pts/1
29612 @subheading The @code{-inferior-tty-show} Command
29613 @findex -inferior-tty-show
29615 @subheading Synopsis
29621 Show terminal for future runs of program being debugged.
29623 @subheading @value{GDBN} Command
29625 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
29627 @subheading Example
29631 -inferior-tty-set /dev/pts/1
29635 ^done,inferior_tty_terminal="/dev/pts/1"
29639 @subheading The @code{-enable-timings} Command
29640 @findex -enable-timings
29642 @subheading Synopsis
29645 -enable-timings [yes | no]
29648 Toggle the printing of the wallclock, user and system times for an MI
29649 command as a field in its output. This command is to help frontend
29650 developers optimize the performance of their code. No argument is
29651 equivalent to @samp{yes}.
29653 @subheading @value{GDBN} Command
29657 @subheading Example
29665 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29666 addr="0x080484ed",func="main",file="myprog.c",
29667 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
29668 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
29676 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29677 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
29678 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
29679 fullname="/home/nickrob/myprog.c",line="73"@}
29684 @chapter @value{GDBN} Annotations
29686 This chapter describes annotations in @value{GDBN}. Annotations were
29687 designed to interface @value{GDBN} to graphical user interfaces or other
29688 similar programs which want to interact with @value{GDBN} at a
29689 relatively high level.
29691 The annotation mechanism has largely been superseded by @sc{gdb/mi}
29695 This is Edition @value{EDITION}, @value{DATE}.
29699 * Annotations Overview:: What annotations are; the general syntax.
29700 * Server Prefix:: Issuing a command without affecting user state.
29701 * Prompting:: Annotations marking @value{GDBN}'s need for input.
29702 * Errors:: Annotations for error messages.
29703 * Invalidation:: Some annotations describe things now invalid.
29704 * Annotations for Running::
29705 Whether the program is running, how it stopped, etc.
29706 * Source Annotations:: Annotations describing source code.
29709 @node Annotations Overview
29710 @section What is an Annotation?
29711 @cindex annotations
29713 Annotations start with a newline character, two @samp{control-z}
29714 characters, and the name of the annotation. If there is no additional
29715 information associated with this annotation, the name of the annotation
29716 is followed immediately by a newline. If there is additional
29717 information, the name of the annotation is followed by a space, the
29718 additional information, and a newline. The additional information
29719 cannot contain newline characters.
29721 Any output not beginning with a newline and two @samp{control-z}
29722 characters denotes literal output from @value{GDBN}. Currently there is
29723 no need for @value{GDBN} to output a newline followed by two
29724 @samp{control-z} characters, but if there was such a need, the
29725 annotations could be extended with an @samp{escape} annotation which
29726 means those three characters as output.
29728 The annotation @var{level}, which is specified using the
29729 @option{--annotate} command line option (@pxref{Mode Options}), controls
29730 how much information @value{GDBN} prints together with its prompt,
29731 values of expressions, source lines, and other types of output. Level 0
29732 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29733 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29734 for programs that control @value{GDBN}, and level 2 annotations have
29735 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29736 Interface, annotate, GDB's Obsolete Annotations}).
29739 @kindex set annotate
29740 @item set annotate @var{level}
29741 The @value{GDBN} command @code{set annotate} sets the level of
29742 annotations to the specified @var{level}.
29744 @item show annotate
29745 @kindex show annotate
29746 Show the current annotation level.
29749 This chapter describes level 3 annotations.
29751 A simple example of starting up @value{GDBN} with annotations is:
29754 $ @kbd{gdb --annotate=3}
29756 Copyright 2003 Free Software Foundation, Inc.
29757 GDB is free software, covered by the GNU General Public License,
29758 and you are welcome to change it and/or distribute copies of it
29759 under certain conditions.
29760 Type "show copying" to see the conditions.
29761 There is absolutely no warranty for GDB. Type "show warranty"
29763 This GDB was configured as "i386-pc-linux-gnu"
29774 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29775 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29776 denotes a @samp{control-z} character) are annotations; the rest is
29777 output from @value{GDBN}.
29779 @node Server Prefix
29780 @section The Server Prefix
29781 @cindex server prefix
29783 If you prefix a command with @samp{server } then it will not affect
29784 the command history, nor will it affect @value{GDBN}'s notion of which
29785 command to repeat if @key{RET} is pressed on a line by itself. This
29786 means that commands can be run behind a user's back by a front-end in
29787 a transparent manner.
29789 The @code{server } prefix does not affect the recording of values into
29790 the value history; to print a value without recording it into the
29791 value history, use the @code{output} command instead of the
29792 @code{print} command.
29794 Using this prefix also disables confirmation requests
29795 (@pxref{confirmation requests}).
29798 @section Annotation for @value{GDBN} Input
29800 @cindex annotations for prompts
29801 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29802 to know when to send output, when the output from a given command is
29805 Different kinds of input each have a different @dfn{input type}. Each
29806 input type has three annotations: a @code{pre-} annotation, which
29807 denotes the beginning of any prompt which is being output, a plain
29808 annotation, which denotes the end of the prompt, and then a @code{post-}
29809 annotation which denotes the end of any echo which may (or may not) be
29810 associated with the input. For example, the @code{prompt} input type
29811 features the following annotations:
29819 The input types are
29822 @findex pre-prompt annotation
29823 @findex prompt annotation
29824 @findex post-prompt annotation
29826 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29828 @findex pre-commands annotation
29829 @findex commands annotation
29830 @findex post-commands annotation
29832 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29833 command. The annotations are repeated for each command which is input.
29835 @findex pre-overload-choice annotation
29836 @findex overload-choice annotation
29837 @findex post-overload-choice annotation
29838 @item overload-choice
29839 When @value{GDBN} wants the user to select between various overloaded functions.
29841 @findex pre-query annotation
29842 @findex query annotation
29843 @findex post-query annotation
29845 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29847 @findex pre-prompt-for-continue annotation
29848 @findex prompt-for-continue annotation
29849 @findex post-prompt-for-continue annotation
29850 @item prompt-for-continue
29851 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29852 expect this to work well; instead use @code{set height 0} to disable
29853 prompting. This is because the counting of lines is buggy in the
29854 presence of annotations.
29859 @cindex annotations for errors, warnings and interrupts
29861 @findex quit annotation
29866 This annotation occurs right before @value{GDBN} responds to an interrupt.
29868 @findex error annotation
29873 This annotation occurs right before @value{GDBN} responds to an error.
29875 Quit and error annotations indicate that any annotations which @value{GDBN} was
29876 in the middle of may end abruptly. For example, if a
29877 @code{value-history-begin} annotation is followed by a @code{error}, one
29878 cannot expect to receive the matching @code{value-history-end}. One
29879 cannot expect not to receive it either, however; an error annotation
29880 does not necessarily mean that @value{GDBN} is immediately returning all the way
29883 @findex error-begin annotation
29884 A quit or error annotation may be preceded by
29890 Any output between that and the quit or error annotation is the error
29893 Warning messages are not yet annotated.
29894 @c If we want to change that, need to fix warning(), type_error(),
29895 @c range_error(), and possibly other places.
29898 @section Invalidation Notices
29900 @cindex annotations for invalidation messages
29901 The following annotations say that certain pieces of state may have
29905 @findex frames-invalid annotation
29906 @item ^Z^Zframes-invalid
29908 The frames (for example, output from the @code{backtrace} command) may
29911 @findex breakpoints-invalid annotation
29912 @item ^Z^Zbreakpoints-invalid
29914 The breakpoints may have changed. For example, the user just added or
29915 deleted a breakpoint.
29918 @node Annotations for Running
29919 @section Running the Program
29920 @cindex annotations for running programs
29922 @findex starting annotation
29923 @findex stopping annotation
29924 When the program starts executing due to a @value{GDBN} command such as
29925 @code{step} or @code{continue},
29931 is output. When the program stops,
29937 is output. Before the @code{stopped} annotation, a variety of
29938 annotations describe how the program stopped.
29941 @findex exited annotation
29942 @item ^Z^Zexited @var{exit-status}
29943 The program exited, and @var{exit-status} is the exit status (zero for
29944 successful exit, otherwise nonzero).
29946 @findex signalled annotation
29947 @findex signal-name annotation
29948 @findex signal-name-end annotation
29949 @findex signal-string annotation
29950 @findex signal-string-end annotation
29951 @item ^Z^Zsignalled
29952 The program exited with a signal. After the @code{^Z^Zsignalled}, the
29953 annotation continues:
29959 ^Z^Zsignal-name-end
29963 ^Z^Zsignal-string-end
29968 where @var{name} is the name of the signal, such as @code{SIGILL} or
29969 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
29970 as @code{Illegal Instruction} or @code{Segmentation fault}.
29971 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
29972 user's benefit and have no particular format.
29974 @findex signal annotation
29976 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
29977 just saying that the program received the signal, not that it was
29978 terminated with it.
29980 @findex breakpoint annotation
29981 @item ^Z^Zbreakpoint @var{number}
29982 The program hit breakpoint number @var{number}.
29984 @findex watchpoint annotation
29985 @item ^Z^Zwatchpoint @var{number}
29986 The program hit watchpoint number @var{number}.
29989 @node Source Annotations
29990 @section Displaying Source
29991 @cindex annotations for source display
29993 @findex source annotation
29994 The following annotation is used instead of displaying source code:
29997 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30000 where @var{filename} is an absolute file name indicating which source
30001 file, @var{line} is the line number within that file (where 1 is the
30002 first line in the file), @var{character} is the character position
30003 within the file (where 0 is the first character in the file) (for most
30004 debug formats this will necessarily point to the beginning of a line),
30005 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30006 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30007 @var{addr} is the address in the target program associated with the
30008 source which is being displayed. @var{addr} is in the form @samp{0x}
30009 followed by one or more lowercase hex digits (note that this does not
30010 depend on the language).
30012 @node JIT Interface
30013 @chapter JIT Compilation Interface
30014 @cindex just-in-time compilation
30015 @cindex JIT compilation interface
30017 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30018 interface. A JIT compiler is a program or library that generates native
30019 executable code at runtime and executes it, usually in order to achieve good
30020 performance while maintaining platform independence.
30022 Programs that use JIT compilation are normally difficult to debug because
30023 portions of their code are generated at runtime, instead of being loaded from
30024 object files, which is where @value{GDBN} normally finds the program's symbols
30025 and debug information. In order to debug programs that use JIT compilation,
30026 @value{GDBN} has an interface that allows the program to register in-memory
30027 symbol files with @value{GDBN} at runtime.
30029 If you are using @value{GDBN} to debug a program that uses this interface, then
30030 it should work transparently so long as you have not stripped the binary. If
30031 you are developing a JIT compiler, then the interface is documented in the rest
30032 of this chapter. At this time, the only known client of this interface is the
30035 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30036 JIT compiler communicates with @value{GDBN} by writing data into a global
30037 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30038 attaches, it reads a linked list of symbol files from the global variable to
30039 find existing code, and puts a breakpoint in the function so that it can find
30040 out about additional code.
30043 * Declarations:: Relevant C struct declarations
30044 * Registering Code:: Steps to register code
30045 * Unregistering Code:: Steps to unregister code
30049 @section JIT Declarations
30051 These are the relevant struct declarations that a C program should include to
30052 implement the interface:
30062 struct jit_code_entry
30064 struct jit_code_entry *next_entry;
30065 struct jit_code_entry *prev_entry;
30066 const char *symfile_addr;
30067 uint64_t symfile_size;
30070 struct jit_descriptor
30073 /* This type should be jit_actions_t, but we use uint32_t
30074 to be explicit about the bitwidth. */
30075 uint32_t action_flag;
30076 struct jit_code_entry *relevant_entry;
30077 struct jit_code_entry *first_entry;
30080 /* GDB puts a breakpoint in this function. */
30081 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30083 /* Make sure to specify the version statically, because the
30084 debugger may check the version before we can set it. */
30085 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30088 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30089 modifications to this global data properly, which can easily be done by putting
30090 a global mutex around modifications to these structures.
30092 @node Registering Code
30093 @section Registering Code
30095 To register code with @value{GDBN}, the JIT should follow this protocol:
30099 Generate an object file in memory with symbols and other desired debug
30100 information. The file must include the virtual addresses of the sections.
30103 Create a code entry for the file, which gives the start and size of the symbol
30107 Add it to the linked list in the JIT descriptor.
30110 Point the relevant_entry field of the descriptor at the entry.
30113 Set @code{action_flag} to @code{JIT_REGISTER} and call
30114 @code{__jit_debug_register_code}.
30117 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30118 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30119 new code. However, the linked list must still be maintained in order to allow
30120 @value{GDBN} to attach to a running process and still find the symbol files.
30122 @node Unregistering Code
30123 @section Unregistering Code
30125 If code is freed, then the JIT should use the following protocol:
30129 Remove the code entry corresponding to the code from the linked list.
30132 Point the @code{relevant_entry} field of the descriptor at the code entry.
30135 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30136 @code{__jit_debug_register_code}.
30139 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30140 and the JIT will leak the memory used for the associated symbol files.
30143 @chapter Reporting Bugs in @value{GDBN}
30144 @cindex bugs in @value{GDBN}
30145 @cindex reporting bugs in @value{GDBN}
30147 Your bug reports play an essential role in making @value{GDBN} reliable.
30149 Reporting a bug may help you by bringing a solution to your problem, or it
30150 may not. But in any case the principal function of a bug report is to help
30151 the entire community by making the next version of @value{GDBN} work better. Bug
30152 reports are your contribution to the maintenance of @value{GDBN}.
30154 In order for a bug report to serve its purpose, you must include the
30155 information that enables us to fix the bug.
30158 * Bug Criteria:: Have you found a bug?
30159 * Bug Reporting:: How to report bugs
30163 @section Have You Found a Bug?
30164 @cindex bug criteria
30166 If you are not sure whether you have found a bug, here are some guidelines:
30169 @cindex fatal signal
30170 @cindex debugger crash
30171 @cindex crash of debugger
30173 If the debugger gets a fatal signal, for any input whatever, that is a
30174 @value{GDBN} bug. Reliable debuggers never crash.
30176 @cindex error on valid input
30178 If @value{GDBN} produces an error message for valid input, that is a
30179 bug. (Note that if you're cross debugging, the problem may also be
30180 somewhere in the connection to the target.)
30182 @cindex invalid input
30184 If @value{GDBN} does not produce an error message for invalid input,
30185 that is a bug. However, you should note that your idea of
30186 ``invalid input'' might be our idea of ``an extension'' or ``support
30187 for traditional practice''.
30190 If you are an experienced user of debugging tools, your suggestions
30191 for improvement of @value{GDBN} are welcome in any case.
30194 @node Bug Reporting
30195 @section How to Report Bugs
30196 @cindex bug reports
30197 @cindex @value{GDBN} bugs, reporting
30199 A number of companies and individuals offer support for @sc{gnu} products.
30200 If you obtained @value{GDBN} from a support organization, we recommend you
30201 contact that organization first.
30203 You can find contact information for many support companies and
30204 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30206 @c should add a web page ref...
30209 @ifset BUGURL_DEFAULT
30210 In any event, we also recommend that you submit bug reports for
30211 @value{GDBN}. The preferred method is to submit them directly using
30212 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30213 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30216 @strong{Do not send bug reports to @samp{info-gdb}, or to
30217 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30218 not want to receive bug reports. Those that do have arranged to receive
30221 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30222 serves as a repeater. The mailing list and the newsgroup carry exactly
30223 the same messages. Often people think of posting bug reports to the
30224 newsgroup instead of mailing them. This appears to work, but it has one
30225 problem which can be crucial: a newsgroup posting often lacks a mail
30226 path back to the sender. Thus, if we need to ask for more information,
30227 we may be unable to reach you. For this reason, it is better to send
30228 bug reports to the mailing list.
30230 @ifclear BUGURL_DEFAULT
30231 In any event, we also recommend that you submit bug reports for
30232 @value{GDBN} to @value{BUGURL}.
30236 The fundamental principle of reporting bugs usefully is this:
30237 @strong{report all the facts}. If you are not sure whether to state a
30238 fact or leave it out, state it!
30240 Often people omit facts because they think they know what causes the
30241 problem and assume that some details do not matter. Thus, you might
30242 assume that the name of the variable you use in an example does not matter.
30243 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30244 stray memory reference which happens to fetch from the location where that
30245 name is stored in memory; perhaps, if the name were different, the contents
30246 of that location would fool the debugger into doing the right thing despite
30247 the bug. Play it safe and give a specific, complete example. That is the
30248 easiest thing for you to do, and the most helpful.
30250 Keep in mind that the purpose of a bug report is to enable us to fix the
30251 bug. It may be that the bug has been reported previously, but neither
30252 you nor we can know that unless your bug report is complete and
30255 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30256 bell?'' Those bug reports are useless, and we urge everyone to
30257 @emph{refuse to respond to them} except to chide the sender to report
30260 To enable us to fix the bug, you should include all these things:
30264 The version of @value{GDBN}. @value{GDBN} announces it if you start
30265 with no arguments; you can also print it at any time using @code{show
30268 Without this, we will not know whether there is any point in looking for
30269 the bug in the current version of @value{GDBN}.
30272 The type of machine you are using, and the operating system name and
30276 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30277 ``@value{GCC}--2.8.1''.
30280 What compiler (and its version) was used to compile the program you are
30281 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30282 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30283 to get this information; for other compilers, see the documentation for
30287 The command arguments you gave the compiler to compile your example and
30288 observe the bug. For example, did you use @samp{-O}? To guarantee
30289 you will not omit something important, list them all. A copy of the
30290 Makefile (or the output from make) is sufficient.
30292 If we were to try to guess the arguments, we would probably guess wrong
30293 and then we might not encounter the bug.
30296 A complete input script, and all necessary source files, that will
30300 A description of what behavior you observe that you believe is
30301 incorrect. For example, ``It gets a fatal signal.''
30303 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30304 will certainly notice it. But if the bug is incorrect output, we might
30305 not notice unless it is glaringly wrong. You might as well not give us
30306 a chance to make a mistake.
30308 Even if the problem you experience is a fatal signal, you should still
30309 say so explicitly. Suppose something strange is going on, such as, your
30310 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30311 the C library on your system. (This has happened!) Your copy might
30312 crash and ours would not. If you told us to expect a crash, then when
30313 ours fails to crash, we would know that the bug was not happening for
30314 us. If you had not told us to expect a crash, then we would not be able
30315 to draw any conclusion from our observations.
30318 @cindex recording a session script
30319 To collect all this information, you can use a session recording program
30320 such as @command{script}, which is available on many Unix systems.
30321 Just run your @value{GDBN} session inside @command{script} and then
30322 include the @file{typescript} file with your bug report.
30324 Another way to record a @value{GDBN} session is to run @value{GDBN}
30325 inside Emacs and then save the entire buffer to a file.
30328 If you wish to suggest changes to the @value{GDBN} source, send us context
30329 diffs. If you even discuss something in the @value{GDBN} source, refer to
30330 it by context, not by line number.
30332 The line numbers in our development sources will not match those in your
30333 sources. Your line numbers would convey no useful information to us.
30337 Here are some things that are not necessary:
30341 A description of the envelope of the bug.
30343 Often people who encounter a bug spend a lot of time investigating
30344 which changes to the input file will make the bug go away and which
30345 changes will not affect it.
30347 This is often time consuming and not very useful, because the way we
30348 will find the bug is by running a single example under the debugger
30349 with breakpoints, not by pure deduction from a series of examples.
30350 We recommend that you save your time for something else.
30352 Of course, if you can find a simpler example to report @emph{instead}
30353 of the original one, that is a convenience for us. Errors in the
30354 output will be easier to spot, running under the debugger will take
30355 less time, and so on.
30357 However, simplification is not vital; if you do not want to do this,
30358 report the bug anyway and send us the entire test case you used.
30361 A patch for the bug.
30363 A patch for the bug does help us if it is a good one. But do not omit
30364 the necessary information, such as the test case, on the assumption that
30365 a patch is all we need. We might see problems with your patch and decide
30366 to fix the problem another way, or we might not understand it at all.
30368 Sometimes with a program as complicated as @value{GDBN} it is very hard to
30369 construct an example that will make the program follow a certain path
30370 through the code. If you do not send us the example, we will not be able
30371 to construct one, so we will not be able to verify that the bug is fixed.
30373 And if we cannot understand what bug you are trying to fix, or why your
30374 patch should be an improvement, we will not install it. A test case will
30375 help us to understand.
30378 A guess about what the bug is or what it depends on.
30380 Such guesses are usually wrong. Even we cannot guess right about such
30381 things without first using the debugger to find the facts.
30384 @c The readline documentation is distributed with the readline code
30385 @c and consists of the two following files:
30387 @c inc-hist.texinfo
30388 @c Use -I with makeinfo to point to the appropriate directory,
30389 @c environment var TEXINPUTS with TeX.
30390 @include rluser.texi
30391 @include inc-hist.texinfo
30394 @node Formatting Documentation
30395 @appendix Formatting Documentation
30397 @cindex @value{GDBN} reference card
30398 @cindex reference card
30399 The @value{GDBN} 4 release includes an already-formatted reference card, ready
30400 for printing with PostScript or Ghostscript, in the @file{gdb}
30401 subdirectory of the main source directory@footnote{In
30402 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
30403 release.}. If you can use PostScript or Ghostscript with your printer,
30404 you can print the reference card immediately with @file{refcard.ps}.
30406 The release also includes the source for the reference card. You
30407 can format it, using @TeX{}, by typing:
30413 The @value{GDBN} reference card is designed to print in @dfn{landscape}
30414 mode on US ``letter'' size paper;
30415 that is, on a sheet 11 inches wide by 8.5 inches
30416 high. You will need to specify this form of printing as an option to
30417 your @sc{dvi} output program.
30419 @cindex documentation
30421 All the documentation for @value{GDBN} comes as part of the machine-readable
30422 distribution. The documentation is written in Texinfo format, which is
30423 a documentation system that uses a single source file to produce both
30424 on-line information and a printed manual. You can use one of the Info
30425 formatting commands to create the on-line version of the documentation
30426 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
30428 @value{GDBN} includes an already formatted copy of the on-line Info
30429 version of this manual in the @file{gdb} subdirectory. The main Info
30430 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
30431 subordinate files matching @samp{gdb.info*} in the same directory. If
30432 necessary, you can print out these files, or read them with any editor;
30433 but they are easier to read using the @code{info} subsystem in @sc{gnu}
30434 Emacs or the standalone @code{info} program, available as part of the
30435 @sc{gnu} Texinfo distribution.
30437 If you want to format these Info files yourself, you need one of the
30438 Info formatting programs, such as @code{texinfo-format-buffer} or
30441 If you have @code{makeinfo} installed, and are in the top level
30442 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
30443 version @value{GDBVN}), you can make the Info file by typing:
30450 If you want to typeset and print copies of this manual, you need @TeX{},
30451 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
30452 Texinfo definitions file.
30454 @TeX{} is a typesetting program; it does not print files directly, but
30455 produces output files called @sc{dvi} files. To print a typeset
30456 document, you need a program to print @sc{dvi} files. If your system
30457 has @TeX{} installed, chances are it has such a program. The precise
30458 command to use depends on your system; @kbd{lpr -d} is common; another
30459 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
30460 require a file name without any extension or a @samp{.dvi} extension.
30462 @TeX{} also requires a macro definitions file called
30463 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
30464 written in Texinfo format. On its own, @TeX{} cannot either read or
30465 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
30466 and is located in the @file{gdb-@var{version-number}/texinfo}
30469 If you have @TeX{} and a @sc{dvi} printer program installed, you can
30470 typeset and print this manual. First switch to the @file{gdb}
30471 subdirectory of the main source directory (for example, to
30472 @file{gdb-@value{GDBVN}/gdb}) and type:
30478 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
30480 @node Installing GDB
30481 @appendix Installing @value{GDBN}
30482 @cindex installation
30485 * Requirements:: Requirements for building @value{GDBN}
30486 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
30487 * Separate Objdir:: Compiling @value{GDBN} in another directory
30488 * Config Names:: Specifying names for hosts and targets
30489 * Configure Options:: Summary of options for configure
30490 * System-wide configuration:: Having a system-wide init file
30494 @section Requirements for Building @value{GDBN}
30495 @cindex building @value{GDBN}, requirements for
30497 Building @value{GDBN} requires various tools and packages to be available.
30498 Other packages will be used only if they are found.
30500 @heading Tools/Packages Necessary for Building @value{GDBN}
30502 @item ISO C90 compiler
30503 @value{GDBN} is written in ISO C90. It should be buildable with any
30504 working C90 compiler, e.g.@: GCC.
30508 @heading Tools/Packages Optional for Building @value{GDBN}
30512 @value{GDBN} can use the Expat XML parsing library. This library may be
30513 included with your operating system distribution; if it is not, you
30514 can get the latest version from @url{http://expat.sourceforge.net}.
30515 The @file{configure} script will search for this library in several
30516 standard locations; if it is installed in an unusual path, you can
30517 use the @option{--with-libexpat-prefix} option to specify its location.
30523 Remote protocol memory maps (@pxref{Memory Map Format})
30525 Target descriptions (@pxref{Target Descriptions})
30527 Remote shared library lists (@pxref{Library List Format})
30529 MS-Windows shared libraries (@pxref{Shared Libraries})
30533 @cindex compressed debug sections
30534 @value{GDBN} will use the @samp{zlib} library, if available, to read
30535 compressed debug sections. Some linkers, such as GNU gold, are capable
30536 of producing binaries with compressed debug sections. If @value{GDBN}
30537 is compiled with @samp{zlib}, it will be able to read the debug
30538 information in such binaries.
30540 The @samp{zlib} library is likely included with your operating system
30541 distribution; if it is not, you can get the latest version from
30542 @url{http://zlib.net}.
30545 @value{GDBN}'s features related to character sets (@pxref{Character
30546 Sets}) require a functioning @code{iconv} implementation. If you are
30547 on a GNU system, then this is provided by the GNU C Library. Some
30548 other systems also provide a working @code{iconv}.
30550 On systems with @code{iconv}, you can install GNU Libiconv. If you
30551 have previously installed Libiconv, you can use the
30552 @option{--with-libiconv-prefix} option to configure.
30554 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
30555 arrange to build Libiconv if a directory named @file{libiconv} appears
30556 in the top-most source directory. If Libiconv is built this way, and
30557 if the operating system does not provide a suitable @code{iconv}
30558 implementation, then the just-built library will automatically be used
30559 by @value{GDBN}. One easy way to set this up is to download GNU
30560 Libiconv, unpack it, and then rename the directory holding the
30561 Libiconv source code to @samp{libiconv}.
30564 @node Running Configure
30565 @section Invoking the @value{GDBN} @file{configure} Script
30566 @cindex configuring @value{GDBN}
30567 @value{GDBN} comes with a @file{configure} script that automates the process
30568 of preparing @value{GDBN} for installation; you can then use @code{make} to
30569 build the @code{gdb} program.
30571 @c irrelevant in info file; it's as current as the code it lives with.
30572 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
30573 look at the @file{README} file in the sources; we may have improved the
30574 installation procedures since publishing this manual.}
30577 The @value{GDBN} distribution includes all the source code you need for
30578 @value{GDBN} in a single directory, whose name is usually composed by
30579 appending the version number to @samp{gdb}.
30581 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
30582 @file{gdb-@value{GDBVN}} directory. That directory contains:
30585 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
30586 script for configuring @value{GDBN} and all its supporting libraries
30588 @item gdb-@value{GDBVN}/gdb
30589 the source specific to @value{GDBN} itself
30591 @item gdb-@value{GDBVN}/bfd
30592 source for the Binary File Descriptor library
30594 @item gdb-@value{GDBVN}/include
30595 @sc{gnu} include files
30597 @item gdb-@value{GDBVN}/libiberty
30598 source for the @samp{-liberty} free software library
30600 @item gdb-@value{GDBVN}/opcodes
30601 source for the library of opcode tables and disassemblers
30603 @item gdb-@value{GDBVN}/readline
30604 source for the @sc{gnu} command-line interface
30606 @item gdb-@value{GDBVN}/glob
30607 source for the @sc{gnu} filename pattern-matching subroutine
30609 @item gdb-@value{GDBVN}/mmalloc
30610 source for the @sc{gnu} memory-mapped malloc package
30613 The simplest way to configure and build @value{GDBN} is to run @file{configure}
30614 from the @file{gdb-@var{version-number}} source directory, which in
30615 this example is the @file{gdb-@value{GDBVN}} directory.
30617 First switch to the @file{gdb-@var{version-number}} source directory
30618 if you are not already in it; then run @file{configure}. Pass the
30619 identifier for the platform on which @value{GDBN} will run as an
30625 cd gdb-@value{GDBVN}
30626 ./configure @var{host}
30631 where @var{host} is an identifier such as @samp{sun4} or
30632 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
30633 (You can often leave off @var{host}; @file{configure} tries to guess the
30634 correct value by examining your system.)
30636 Running @samp{configure @var{host}} and then running @code{make} builds the
30637 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
30638 libraries, then @code{gdb} itself. The configured source files, and the
30639 binaries, are left in the corresponding source directories.
30642 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
30643 system does not recognize this automatically when you run a different
30644 shell, you may need to run @code{sh} on it explicitly:
30647 sh configure @var{host}
30650 If you run @file{configure} from a directory that contains source
30651 directories for multiple libraries or programs, such as the
30652 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
30654 creates configuration files for every directory level underneath (unless
30655 you tell it not to, with the @samp{--norecursion} option).
30657 You should run the @file{configure} script from the top directory in the
30658 source tree, the @file{gdb-@var{version-number}} directory. If you run
30659 @file{configure} from one of the subdirectories, you will configure only
30660 that subdirectory. That is usually not what you want. In particular,
30661 if you run the first @file{configure} from the @file{gdb} subdirectory
30662 of the @file{gdb-@var{version-number}} directory, you will omit the
30663 configuration of @file{bfd}, @file{readline}, and other sibling
30664 directories of the @file{gdb} subdirectory. This leads to build errors
30665 about missing include files such as @file{bfd/bfd.h}.
30667 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
30668 However, you should make sure that the shell on your path (named by
30669 the @samp{SHELL} environment variable) is publicly readable. Remember
30670 that @value{GDBN} uses the shell to start your program---some systems refuse to
30671 let @value{GDBN} debug child processes whose programs are not readable.
30673 @node Separate Objdir
30674 @section Compiling @value{GDBN} in Another Directory
30676 If you want to run @value{GDBN} versions for several host or target machines,
30677 you need a different @code{gdb} compiled for each combination of
30678 host and target. @file{configure} is designed to make this easy by
30679 allowing you to generate each configuration in a separate subdirectory,
30680 rather than in the source directory. If your @code{make} program
30681 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
30682 @code{make} in each of these directories builds the @code{gdb}
30683 program specified there.
30685 To build @code{gdb} in a separate directory, run @file{configure}
30686 with the @samp{--srcdir} option to specify where to find the source.
30687 (You also need to specify a path to find @file{configure}
30688 itself from your working directory. If the path to @file{configure}
30689 would be the same as the argument to @samp{--srcdir}, you can leave out
30690 the @samp{--srcdir} option; it is assumed.)
30692 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
30693 separate directory for a Sun 4 like this:
30697 cd gdb-@value{GDBVN}
30700 ../gdb-@value{GDBVN}/configure sun4
30705 When @file{configure} builds a configuration using a remote source
30706 directory, it creates a tree for the binaries with the same structure
30707 (and using the same names) as the tree under the source directory. In
30708 the example, you'd find the Sun 4 library @file{libiberty.a} in the
30709 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
30710 @file{gdb-sun4/gdb}.
30712 Make sure that your path to the @file{configure} script has just one
30713 instance of @file{gdb} in it. If your path to @file{configure} looks
30714 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
30715 one subdirectory of @value{GDBN}, not the whole package. This leads to
30716 build errors about missing include files such as @file{bfd/bfd.h}.
30718 One popular reason to build several @value{GDBN} configurations in separate
30719 directories is to configure @value{GDBN} for cross-compiling (where
30720 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30721 programs that run on another machine---the @dfn{target}).
30722 You specify a cross-debugging target by
30723 giving the @samp{--target=@var{target}} option to @file{configure}.
30725 When you run @code{make} to build a program or library, you must run
30726 it in a configured directory---whatever directory you were in when you
30727 called @file{configure} (or one of its subdirectories).
30729 The @code{Makefile} that @file{configure} generates in each source
30730 directory also runs recursively. If you type @code{make} in a source
30731 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30732 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30733 will build all the required libraries, and then build GDB.
30735 When you have multiple hosts or targets configured in separate
30736 directories, you can run @code{make} on them in parallel (for example,
30737 if they are NFS-mounted on each of the hosts); they will not interfere
30741 @section Specifying Names for Hosts and Targets
30743 The specifications used for hosts and targets in the @file{configure}
30744 script are based on a three-part naming scheme, but some short predefined
30745 aliases are also supported. The full naming scheme encodes three pieces
30746 of information in the following pattern:
30749 @var{architecture}-@var{vendor}-@var{os}
30752 For example, you can use the alias @code{sun4} as a @var{host} argument,
30753 or as the value for @var{target} in a @code{--target=@var{target}}
30754 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30756 The @file{configure} script accompanying @value{GDBN} does not provide
30757 any query facility to list all supported host and target names or
30758 aliases. @file{configure} calls the Bourne shell script
30759 @code{config.sub} to map abbreviations to full names; you can read the
30760 script, if you wish, or you can use it to test your guesses on
30761 abbreviations---for example:
30764 % sh config.sub i386-linux
30766 % sh config.sub alpha-linux
30767 alpha-unknown-linux-gnu
30768 % sh config.sub hp9k700
30770 % sh config.sub sun4
30771 sparc-sun-sunos4.1.1
30772 % sh config.sub sun3
30773 m68k-sun-sunos4.1.1
30774 % sh config.sub i986v
30775 Invalid configuration `i986v': machine `i986v' not recognized
30779 @code{config.sub} is also distributed in the @value{GDBN} source
30780 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30782 @node Configure Options
30783 @section @file{configure} Options
30785 Here is a summary of the @file{configure} options and arguments that
30786 are most often useful for building @value{GDBN}. @file{configure} also has
30787 several other options not listed here. @inforef{What Configure
30788 Does,,configure.info}, for a full explanation of @file{configure}.
30791 configure @r{[}--help@r{]}
30792 @r{[}--prefix=@var{dir}@r{]}
30793 @r{[}--exec-prefix=@var{dir}@r{]}
30794 @r{[}--srcdir=@var{dirname}@r{]}
30795 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30796 @r{[}--target=@var{target}@r{]}
30801 You may introduce options with a single @samp{-} rather than
30802 @samp{--} if you prefer; but you may abbreviate option names if you use
30807 Display a quick summary of how to invoke @file{configure}.
30809 @item --prefix=@var{dir}
30810 Configure the source to install programs and files under directory
30813 @item --exec-prefix=@var{dir}
30814 Configure the source to install programs under directory
30817 @c avoid splitting the warning from the explanation:
30819 @item --srcdir=@var{dirname}
30820 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30821 @code{make} that implements the @code{VPATH} feature.}@*
30822 Use this option to make configurations in directories separate from the
30823 @value{GDBN} source directories. Among other things, you can use this to
30824 build (or maintain) several configurations simultaneously, in separate
30825 directories. @file{configure} writes configuration-specific files in
30826 the current directory, but arranges for them to use the source in the
30827 directory @var{dirname}. @file{configure} creates directories under
30828 the working directory in parallel to the source directories below
30831 @item --norecursion
30832 Configure only the directory level where @file{configure} is executed; do not
30833 propagate configuration to subdirectories.
30835 @item --target=@var{target}
30836 Configure @value{GDBN} for cross-debugging programs running on the specified
30837 @var{target}. Without this option, @value{GDBN} is configured to debug
30838 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30840 There is no convenient way to generate a list of all available targets.
30842 @item @var{host} @dots{}
30843 Configure @value{GDBN} to run on the specified @var{host}.
30845 There is no convenient way to generate a list of all available hosts.
30848 There are many other options available as well, but they are generally
30849 needed for special purposes only.
30851 @node System-wide configuration
30852 @section System-wide configuration and settings
30853 @cindex system-wide init file
30855 @value{GDBN} can be configured to have a system-wide init file;
30856 this file will be read and executed at startup (@pxref{Startup, , What
30857 @value{GDBN} does during startup}).
30859 Here is the corresponding configure option:
30862 @item --with-system-gdbinit=@var{file}
30863 Specify that the default location of the system-wide init file is
30867 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
30868 it may be subject to relocation. Two possible cases:
30872 If the default location of this init file contains @file{$prefix},
30873 it will be subject to relocation. Suppose that the configure options
30874 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
30875 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
30876 init file is looked for as @file{$install/etc/gdbinit} instead of
30877 @file{$prefix/etc/gdbinit}.
30880 By contrast, if the default location does not contain the prefix,
30881 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
30882 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
30883 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
30884 wherever @value{GDBN} is installed.
30887 @node Maintenance Commands
30888 @appendix Maintenance Commands
30889 @cindex maintenance commands
30890 @cindex internal commands
30892 In addition to commands intended for @value{GDBN} users, @value{GDBN}
30893 includes a number of commands intended for @value{GDBN} developers,
30894 that are not documented elsewhere in this manual. These commands are
30895 provided here for reference. (For commands that turn on debugging
30896 messages, see @ref{Debugging Output}.)
30899 @kindex maint agent
30900 @kindex maint agent-eval
30901 @item maint agent @var{expression}
30902 @itemx maint agent-eval @var{expression}
30903 Translate the given @var{expression} into remote agent bytecodes.
30904 This command is useful for debugging the Agent Expression mechanism
30905 (@pxref{Agent Expressions}). The @samp{agent} version produces an
30906 expression useful for data collection, such as by tracepoints, while
30907 @samp{maint agent-eval} produces an expression that evaluates directly
30908 to a result. For instance, a collection expression for @code{globa +
30909 globb} will include bytecodes to record four bytes of memory at each
30910 of the addresses of @code{globa} and @code{globb}, while discarding
30911 the result of the addition, while an evaluation expression will do the
30912 addition and return the sum.
30914 @kindex maint info breakpoints
30915 @item @anchor{maint info breakpoints}maint info breakpoints
30916 Using the same format as @samp{info breakpoints}, display both the
30917 breakpoints you've set explicitly, and those @value{GDBN} is using for
30918 internal purposes. Internal breakpoints are shown with negative
30919 breakpoint numbers. The type column identifies what kind of breakpoint
30924 Normal, explicitly set breakpoint.
30927 Normal, explicitly set watchpoint.
30930 Internal breakpoint, used to handle correctly stepping through
30931 @code{longjmp} calls.
30933 @item longjmp resume
30934 Internal breakpoint at the target of a @code{longjmp}.
30937 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
30940 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
30943 Shared library events.
30947 @kindex set displaced-stepping
30948 @kindex show displaced-stepping
30949 @cindex displaced stepping support
30950 @cindex out-of-line single-stepping
30951 @item set displaced-stepping
30952 @itemx show displaced-stepping
30953 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
30954 if the target supports it. Displaced stepping is a way to single-step
30955 over breakpoints without removing them from the inferior, by executing
30956 an out-of-line copy of the instruction that was originally at the
30957 breakpoint location. It is also known as out-of-line single-stepping.
30960 @item set displaced-stepping on
30961 If the target architecture supports it, @value{GDBN} will use
30962 displaced stepping to step over breakpoints.
30964 @item set displaced-stepping off
30965 @value{GDBN} will not use displaced stepping to step over breakpoints,
30966 even if such is supported by the target architecture.
30968 @cindex non-stop mode, and @samp{set displaced-stepping}
30969 @item set displaced-stepping auto
30970 This is the default mode. @value{GDBN} will use displaced stepping
30971 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
30972 architecture supports displaced stepping.
30975 @kindex maint check-symtabs
30976 @item maint check-symtabs
30977 Check the consistency of psymtabs and symtabs.
30979 @kindex maint cplus first_component
30980 @item maint cplus first_component @var{name}
30981 Print the first C@t{++} class/namespace component of @var{name}.
30983 @kindex maint cplus namespace
30984 @item maint cplus namespace
30985 Print the list of possible C@t{++} namespaces.
30987 @kindex maint demangle
30988 @item maint demangle @var{name}
30989 Demangle a C@t{++} or Objective-C mangled @var{name}.
30991 @kindex maint deprecate
30992 @kindex maint undeprecate
30993 @cindex deprecated commands
30994 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
30995 @itemx maint undeprecate @var{command}
30996 Deprecate or undeprecate the named @var{command}. Deprecated commands
30997 cause @value{GDBN} to issue a warning when you use them. The optional
30998 argument @var{replacement} says which newer command should be used in
30999 favor of the deprecated one; if it is given, @value{GDBN} will mention
31000 the replacement as part of the warning.
31002 @kindex maint dump-me
31003 @item maint dump-me
31004 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31005 Cause a fatal signal in the debugger and force it to dump its core.
31006 This is supported only on systems which support aborting a program
31007 with the @code{SIGQUIT} signal.
31009 @kindex maint internal-error
31010 @kindex maint internal-warning
31011 @item maint internal-error @r{[}@var{message-text}@r{]}
31012 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31013 Cause @value{GDBN} to call the internal function @code{internal_error}
31014 or @code{internal_warning} and hence behave as though an internal error
31015 or internal warning has been detected. In addition to reporting the
31016 internal problem, these functions give the user the opportunity to
31017 either quit @value{GDBN} or create a core file of the current
31018 @value{GDBN} session.
31020 These commands take an optional parameter @var{message-text} that is
31021 used as the text of the error or warning message.
31023 Here's an example of using @code{internal-error}:
31026 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31027 @dots{}/maint.c:121: internal-error: testing, 1, 2
31028 A problem internal to GDB has been detected. Further
31029 debugging may prove unreliable.
31030 Quit this debugging session? (y or n) @kbd{n}
31031 Create a core file? (y or n) @kbd{n}
31035 @cindex @value{GDBN} internal error
31036 @cindex internal errors, control of @value{GDBN} behavior
31038 @kindex maint set internal-error
31039 @kindex maint show internal-error
31040 @kindex maint set internal-warning
31041 @kindex maint show internal-warning
31042 @item maint set internal-error @var{action} [ask|yes|no]
31043 @itemx maint show internal-error @var{action}
31044 @itemx maint set internal-warning @var{action} [ask|yes|no]
31045 @itemx maint show internal-warning @var{action}
31046 When @value{GDBN} reports an internal problem (error or warning) it
31047 gives the user the opportunity to both quit @value{GDBN} and create a
31048 core file of the current @value{GDBN} session. These commands let you
31049 override the default behaviour for each particular @var{action},
31050 described in the table below.
31054 You can specify that @value{GDBN} should always (yes) or never (no)
31055 quit. The default is to ask the user what to do.
31058 You can specify that @value{GDBN} should always (yes) or never (no)
31059 create a core file. The default is to ask the user what to do.
31062 @kindex maint packet
31063 @item maint packet @var{text}
31064 If @value{GDBN} is talking to an inferior via the serial protocol,
31065 then this command sends the string @var{text} to the inferior, and
31066 displays the response packet. @value{GDBN} supplies the initial
31067 @samp{$} character, the terminating @samp{#} character, and the
31070 @kindex maint print architecture
31071 @item maint print architecture @r{[}@var{file}@r{]}
31072 Print the entire architecture configuration. The optional argument
31073 @var{file} names the file where the output goes.
31075 @kindex maint print c-tdesc
31076 @item maint print c-tdesc
31077 Print the current target description (@pxref{Target Descriptions}) as
31078 a C source file. The created source file can be used in @value{GDBN}
31079 when an XML parser is not available to parse the description.
31081 @kindex maint print dummy-frames
31082 @item maint print dummy-frames
31083 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31086 (@value{GDBP}) @kbd{b add}
31088 (@value{GDBP}) @kbd{print add(2,3)}
31089 Breakpoint 2, add (a=2, b=3) at @dots{}
31091 The program being debugged stopped while in a function called from GDB.
31093 (@value{GDBP}) @kbd{maint print dummy-frames}
31094 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31095 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31096 call_lo=0x01014000 call_hi=0x01014001
31100 Takes an optional file parameter.
31102 @kindex maint print registers
31103 @kindex maint print raw-registers
31104 @kindex maint print cooked-registers
31105 @kindex maint print register-groups
31106 @item maint print registers @r{[}@var{file}@r{]}
31107 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31108 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31109 @itemx maint print register-groups @r{[}@var{file}@r{]}
31110 Print @value{GDBN}'s internal register data structures.
31112 The command @code{maint print raw-registers} includes the contents of
31113 the raw register cache; the command @code{maint print cooked-registers}
31114 includes the (cooked) value of all registers, including registers which
31115 aren't available on the target nor visible to user; and the
31116 command @code{maint print register-groups} includes the groups that each
31117 register is a member of. @xref{Registers,, Registers, gdbint,
31118 @value{GDBN} Internals}.
31120 These commands take an optional parameter, a file name to which to
31121 write the information.
31123 @kindex maint print reggroups
31124 @item maint print reggroups @r{[}@var{file}@r{]}
31125 Print @value{GDBN}'s internal register group data structures. The
31126 optional argument @var{file} tells to what file to write the
31129 The register groups info looks like this:
31132 (@value{GDBP}) @kbd{maint print reggroups}
31145 This command forces @value{GDBN} to flush its internal register cache.
31147 @kindex maint print objfiles
31148 @cindex info for known object files
31149 @item maint print objfiles
31150 Print a dump of all known object files. For each object file, this
31151 command prints its name, address in memory, and all of its psymtabs
31154 @kindex maint print section-scripts
31155 @cindex info for known .debug_gdb_scripts-loaded scripts
31156 @item maint print section-scripts [@var{regexp}]
31157 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31158 If @var{regexp} is specified, only print scripts loaded by object files
31159 matching @var{regexp}.
31160 For each script, this command prints its name as specified in the objfile,
31161 and the full path if known.
31162 @xref{.debug_gdb_scripts section}.
31164 @kindex maint print statistics
31165 @cindex bcache statistics
31166 @item maint print statistics
31167 This command prints, for each object file in the program, various data
31168 about that object file followed by the byte cache (@dfn{bcache})
31169 statistics for the object file. The objfile data includes the number
31170 of minimal, partial, full, and stabs symbols, the number of types
31171 defined by the objfile, the number of as yet unexpanded psym tables,
31172 the number of line tables and string tables, and the amount of memory
31173 used by the various tables. The bcache statistics include the counts,
31174 sizes, and counts of duplicates of all and unique objects, max,
31175 average, and median entry size, total memory used and its overhead and
31176 savings, and various measures of the hash table size and chain
31179 @kindex maint print target-stack
31180 @cindex target stack description
31181 @item maint print target-stack
31182 A @dfn{target} is an interface between the debugger and a particular
31183 kind of file or process. Targets can be stacked in @dfn{strata},
31184 so that more than one target can potentially respond to a request.
31185 In particular, memory accesses will walk down the stack of targets
31186 until they find a target that is interested in handling that particular
31189 This command prints a short description of each layer that was pushed on
31190 the @dfn{target stack}, starting from the top layer down to the bottom one.
31192 @kindex maint print type
31193 @cindex type chain of a data type
31194 @item maint print type @var{expr}
31195 Print the type chain for a type specified by @var{expr}. The argument
31196 can be either a type name or a symbol. If it is a symbol, the type of
31197 that symbol is described. The type chain produced by this command is
31198 a recursive definition of the data type as stored in @value{GDBN}'s
31199 data structures, including its flags and contained types.
31201 @kindex maint set dwarf2 always-disassemble
31202 @kindex maint show dwarf2 always-disassemble
31203 @item maint set dwarf2 always-disassemble
31204 @item maint show dwarf2 always-disassemble
31205 Control the behavior of @code{info address} when using DWARF debugging
31208 The default is @code{off}, which means that @value{GDBN} should try to
31209 describe a variable's location in an easily readable format. When
31210 @code{on}, @value{GDBN} will instead display the DWARF location
31211 expression in an assembly-like format. Note that some locations are
31212 too complex for @value{GDBN} to describe simply; in this case you will
31213 always see the disassembly form.
31215 Here is an example of the resulting disassembly:
31218 (gdb) info addr argc
31219 Symbol "argc" is a complex DWARF expression:
31223 For more information on these expressions, see
31224 @uref{http://www.dwarfstd.org/, the DWARF standard}.
31226 @kindex maint set dwarf2 max-cache-age
31227 @kindex maint show dwarf2 max-cache-age
31228 @item maint set dwarf2 max-cache-age
31229 @itemx maint show dwarf2 max-cache-age
31230 Control the DWARF 2 compilation unit cache.
31232 @cindex DWARF 2 compilation units cache
31233 In object files with inter-compilation-unit references, such as those
31234 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
31235 reader needs to frequently refer to previously read compilation units.
31236 This setting controls how long a compilation unit will remain in the
31237 cache if it is not referenced. A higher limit means that cached
31238 compilation units will be stored in memory longer, and more total
31239 memory will be used. Setting it to zero disables caching, which will
31240 slow down @value{GDBN} startup, but reduce memory consumption.
31242 @kindex maint set profile
31243 @kindex maint show profile
31244 @cindex profiling GDB
31245 @item maint set profile
31246 @itemx maint show profile
31247 Control profiling of @value{GDBN}.
31249 Profiling will be disabled until you use the @samp{maint set profile}
31250 command to enable it. When you enable profiling, the system will begin
31251 collecting timing and execution count data; when you disable profiling or
31252 exit @value{GDBN}, the results will be written to a log file. Remember that
31253 if you use profiling, @value{GDBN} will overwrite the profiling log file
31254 (often called @file{gmon.out}). If you have a record of important profiling
31255 data in a @file{gmon.out} file, be sure to move it to a safe location.
31257 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31258 compiled with the @samp{-pg} compiler option.
31260 @kindex maint set show-debug-regs
31261 @kindex maint show show-debug-regs
31262 @cindex hardware debug registers
31263 @item maint set show-debug-regs
31264 @itemx maint show show-debug-regs
31265 Control whether to show variables that mirror the hardware debug
31266 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31267 enabled, the debug registers values are shown when @value{GDBN} inserts or
31268 removes a hardware breakpoint or watchpoint, and when the inferior
31269 triggers a hardware-assisted breakpoint or watchpoint.
31271 @kindex maint set show-all-tib
31272 @kindex maint show show-all-tib
31273 @item maint set show-all-tib
31274 @itemx maint show show-all-tib
31275 Control whether to show all non zero areas within a 1k block starting
31276 at thread local base, when using the @samp{info w32 thread-information-block}
31279 @kindex maint space
31280 @cindex memory used by commands
31282 Control whether to display memory usage for each command. If set to a
31283 nonzero value, @value{GDBN} will display how much memory each command
31284 took, following the command's own output. This can also be requested
31285 by invoking @value{GDBN} with the @option{--statistics} command-line
31286 switch (@pxref{Mode Options}).
31289 @cindex time of command execution
31291 Control whether to display the execution time for each command. If
31292 set to a nonzero value, @value{GDBN} will display how much time it
31293 took to execute each command, following the command's own output.
31294 The time is not printed for the commands that run the target, since
31295 there's no mechanism currently to compute how much time was spend
31296 by @value{GDBN} and how much time was spend by the program been debugged.
31297 it's not possibly currently
31298 This can also be requested by invoking @value{GDBN} with the
31299 @option{--statistics} command-line switch (@pxref{Mode Options}).
31301 @kindex maint translate-address
31302 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31303 Find the symbol stored at the location specified by the address
31304 @var{addr} and an optional section name @var{section}. If found,
31305 @value{GDBN} prints the name of the closest symbol and an offset from
31306 the symbol's location to the specified address. This is similar to
31307 the @code{info address} command (@pxref{Symbols}), except that this
31308 command also allows to find symbols in other sections.
31310 If section was not specified, the section in which the symbol was found
31311 is also printed. For dynamically linked executables, the name of
31312 executable or shared library containing the symbol is printed as well.
31316 The following command is useful for non-interactive invocations of
31317 @value{GDBN}, such as in the test suite.
31320 @item set watchdog @var{nsec}
31321 @kindex set watchdog
31322 @cindex watchdog timer
31323 @cindex timeout for commands
31324 Set the maximum number of seconds @value{GDBN} will wait for the
31325 target operation to finish. If this time expires, @value{GDBN}
31326 reports and error and the command is aborted.
31328 @item show watchdog
31329 Show the current setting of the target wait timeout.
31332 @node Remote Protocol
31333 @appendix @value{GDBN} Remote Serial Protocol
31338 * Stop Reply Packets::
31339 * General Query Packets::
31340 * Architecture-Specific Protocol Details::
31341 * Tracepoint Packets::
31342 * Host I/O Packets::
31344 * Notification Packets::
31345 * Remote Non-Stop::
31346 * Packet Acknowledgment::
31348 * File-I/O Remote Protocol Extension::
31349 * Library List Format::
31350 * Memory Map Format::
31351 * Thread List Format::
31357 There may be occasions when you need to know something about the
31358 protocol---for example, if there is only one serial port to your target
31359 machine, you might want your program to do something special if it
31360 recognizes a packet meant for @value{GDBN}.
31362 In the examples below, @samp{->} and @samp{<-} are used to indicate
31363 transmitted and received data, respectively.
31365 @cindex protocol, @value{GDBN} remote serial
31366 @cindex serial protocol, @value{GDBN} remote
31367 @cindex remote serial protocol
31368 All @value{GDBN} commands and responses (other than acknowledgments
31369 and notifications, see @ref{Notification Packets}) are sent as a
31370 @var{packet}. A @var{packet} is introduced with the character
31371 @samp{$}, the actual @var{packet-data}, and the terminating character
31372 @samp{#} followed by a two-digit @var{checksum}:
31375 @code{$}@var{packet-data}@code{#}@var{checksum}
31379 @cindex checksum, for @value{GDBN} remote
31381 The two-digit @var{checksum} is computed as the modulo 256 sum of all
31382 characters between the leading @samp{$} and the trailing @samp{#} (an
31383 eight bit unsigned checksum).
31385 Implementors should note that prior to @value{GDBN} 5.0 the protocol
31386 specification also included an optional two-digit @var{sequence-id}:
31389 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
31392 @cindex sequence-id, for @value{GDBN} remote
31394 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
31395 has never output @var{sequence-id}s. Stubs that handle packets added
31396 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
31398 When either the host or the target machine receives a packet, the first
31399 response expected is an acknowledgment: either @samp{+} (to indicate
31400 the package was received correctly) or @samp{-} (to request
31404 -> @code{$}@var{packet-data}@code{#}@var{checksum}
31409 The @samp{+}/@samp{-} acknowledgments can be disabled
31410 once a connection is established.
31411 @xref{Packet Acknowledgment}, for details.
31413 The host (@value{GDBN}) sends @var{command}s, and the target (the
31414 debugging stub incorporated in your program) sends a @var{response}. In
31415 the case of step and continue @var{command}s, the response is only sent
31416 when the operation has completed, and the target has again stopped all
31417 threads in all attached processes. This is the default all-stop mode
31418 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
31419 execution mode; see @ref{Remote Non-Stop}, for details.
31421 @var{packet-data} consists of a sequence of characters with the
31422 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
31425 @cindex remote protocol, field separator
31426 Fields within the packet should be separated using @samp{,} @samp{;} or
31427 @samp{:}. Except where otherwise noted all numbers are represented in
31428 @sc{hex} with leading zeros suppressed.
31430 Implementors should note that prior to @value{GDBN} 5.0, the character
31431 @samp{:} could not appear as the third character in a packet (as it
31432 would potentially conflict with the @var{sequence-id}).
31434 @cindex remote protocol, binary data
31435 @anchor{Binary Data}
31436 Binary data in most packets is encoded either as two hexadecimal
31437 digits per byte of binary data. This allowed the traditional remote
31438 protocol to work over connections which were only seven-bit clean.
31439 Some packets designed more recently assume an eight-bit clean
31440 connection, and use a more efficient encoding to send and receive
31443 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
31444 as an escape character. Any escaped byte is transmitted as the escape
31445 character followed by the original character XORed with @code{0x20}.
31446 For example, the byte @code{0x7d} would be transmitted as the two
31447 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
31448 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
31449 @samp{@}}) must always be escaped. Responses sent by the stub
31450 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
31451 is not interpreted as the start of a run-length encoded sequence
31454 Response @var{data} can be run-length encoded to save space.
31455 Run-length encoding replaces runs of identical characters with one
31456 instance of the repeated character, followed by a @samp{*} and a
31457 repeat count. The repeat count is itself sent encoded, to avoid
31458 binary characters in @var{data}: a value of @var{n} is sent as
31459 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
31460 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
31461 code 32) for a repeat count of 3. (This is because run-length
31462 encoding starts to win for counts 3 or more.) Thus, for example,
31463 @samp{0* } is a run-length encoding of ``0000'': the space character
31464 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
31467 The printable characters @samp{#} and @samp{$} or with a numeric value
31468 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
31469 seven repeats (@samp{$}) can be expanded using a repeat count of only
31470 five (@samp{"}). For example, @samp{00000000} can be encoded as
31473 The error response returned for some packets includes a two character
31474 error number. That number is not well defined.
31476 @cindex empty response, for unsupported packets
31477 For any @var{command} not supported by the stub, an empty response
31478 (@samp{$#00}) should be returned. That way it is possible to extend the
31479 protocol. A newer @value{GDBN} can tell if a packet is supported based
31482 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
31483 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
31489 The following table provides a complete list of all currently defined
31490 @var{command}s and their corresponding response @var{data}.
31491 @xref{File-I/O Remote Protocol Extension}, for details about the File
31492 I/O extension of the remote protocol.
31494 Each packet's description has a template showing the packet's overall
31495 syntax, followed by an explanation of the packet's meaning. We
31496 include spaces in some of the templates for clarity; these are not
31497 part of the packet's syntax. No @value{GDBN} packet uses spaces to
31498 separate its components. For example, a template like @samp{foo
31499 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
31500 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
31501 @var{baz}. @value{GDBN} does not transmit a space character between the
31502 @samp{foo} and the @var{bar}, or between the @var{bar} and the
31505 @cindex @var{thread-id}, in remote protocol
31506 @anchor{thread-id syntax}
31507 Several packets and replies include a @var{thread-id} field to identify
31508 a thread. Normally these are positive numbers with a target-specific
31509 interpretation, formatted as big-endian hex strings. A @var{thread-id}
31510 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
31513 In addition, the remote protocol supports a multiprocess feature in
31514 which the @var{thread-id} syntax is extended to optionally include both
31515 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
31516 The @var{pid} (process) and @var{tid} (thread) components each have the
31517 format described above: a positive number with target-specific
31518 interpretation formatted as a big-endian hex string, literal @samp{-1}
31519 to indicate all processes or threads (respectively), or @samp{0} to
31520 indicate an arbitrary process or thread. Specifying just a process, as
31521 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
31522 error to specify all processes but a specific thread, such as
31523 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
31524 for those packets and replies explicitly documented to include a process
31525 ID, rather than a @var{thread-id}.
31527 The multiprocess @var{thread-id} syntax extensions are only used if both
31528 @value{GDBN} and the stub report support for the @samp{multiprocess}
31529 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
31532 Note that all packet forms beginning with an upper- or lower-case
31533 letter, other than those described here, are reserved for future use.
31535 Here are the packet descriptions.
31540 @cindex @samp{!} packet
31541 @anchor{extended mode}
31542 Enable extended mode. In extended mode, the remote server is made
31543 persistent. The @samp{R} packet is used to restart the program being
31549 The remote target both supports and has enabled extended mode.
31553 @cindex @samp{?} packet
31554 Indicate the reason the target halted. The reply is the same as for
31555 step and continue. This packet has a special interpretation when the
31556 target is in non-stop mode; see @ref{Remote Non-Stop}.
31559 @xref{Stop Reply Packets}, for the reply specifications.
31561 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
31562 @cindex @samp{A} packet
31563 Initialized @code{argv[]} array passed into program. @var{arglen}
31564 specifies the number of bytes in the hex encoded byte stream
31565 @var{arg}. See @code{gdbserver} for more details.
31570 The arguments were set.
31576 @cindex @samp{b} packet
31577 (Don't use this packet; its behavior is not well-defined.)
31578 Change the serial line speed to @var{baud}.
31580 JTC: @emph{When does the transport layer state change? When it's
31581 received, or after the ACK is transmitted. In either case, there are
31582 problems if the command or the acknowledgment packet is dropped.}
31584 Stan: @emph{If people really wanted to add something like this, and get
31585 it working for the first time, they ought to modify ser-unix.c to send
31586 some kind of out-of-band message to a specially-setup stub and have the
31587 switch happen "in between" packets, so that from remote protocol's point
31588 of view, nothing actually happened.}
31590 @item B @var{addr},@var{mode}
31591 @cindex @samp{B} packet
31592 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
31593 breakpoint at @var{addr}.
31595 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
31596 (@pxref{insert breakpoint or watchpoint packet}).
31598 @cindex @samp{bc} packet
31601 Backward continue. Execute the target system in reverse. No parameter.
31602 @xref{Reverse Execution}, for more information.
31605 @xref{Stop Reply Packets}, for the reply specifications.
31607 @cindex @samp{bs} packet
31610 Backward single step. Execute one instruction in reverse. No parameter.
31611 @xref{Reverse Execution}, for more information.
31614 @xref{Stop Reply Packets}, for the reply specifications.
31616 @item c @r{[}@var{addr}@r{]}
31617 @cindex @samp{c} packet
31618 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
31619 resume at current address.
31622 @xref{Stop Reply Packets}, for the reply specifications.
31624 @item C @var{sig}@r{[};@var{addr}@r{]}
31625 @cindex @samp{C} packet
31626 Continue with signal @var{sig} (hex signal number). If
31627 @samp{;@var{addr}} is omitted, resume at same address.
31630 @xref{Stop Reply Packets}, for the reply specifications.
31633 @cindex @samp{d} packet
31636 Don't use this packet; instead, define a general set packet
31637 (@pxref{General Query Packets}).
31641 @cindex @samp{D} packet
31642 The first form of the packet is used to detach @value{GDBN} from the
31643 remote system. It is sent to the remote target
31644 before @value{GDBN} disconnects via the @code{detach} command.
31646 The second form, including a process ID, is used when multiprocess
31647 protocol extensions are enabled (@pxref{multiprocess extensions}), to
31648 detach only a specific process. The @var{pid} is specified as a
31649 big-endian hex string.
31659 @item F @var{RC},@var{EE},@var{CF};@var{XX}
31660 @cindex @samp{F} packet
31661 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
31662 This is part of the File-I/O protocol extension. @xref{File-I/O
31663 Remote Protocol Extension}, for the specification.
31666 @anchor{read registers packet}
31667 @cindex @samp{g} packet
31668 Read general registers.
31672 @item @var{XX@dots{}}
31673 Each byte of register data is described by two hex digits. The bytes
31674 with the register are transmitted in target byte order. The size of
31675 each register and their position within the @samp{g} packet are
31676 determined by the @value{GDBN} internal gdbarch functions
31677 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
31678 specification of several standard @samp{g} packets is specified below.
31683 @item G @var{XX@dots{}}
31684 @cindex @samp{G} packet
31685 Write general registers. @xref{read registers packet}, for a
31686 description of the @var{XX@dots{}} data.
31696 @item H @var{c} @var{thread-id}
31697 @cindex @samp{H} packet
31698 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
31699 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
31700 should be @samp{c} for step and continue operations, @samp{g} for other
31701 operations. The thread designator @var{thread-id} has the format and
31702 interpretation described in @ref{thread-id syntax}.
31713 @c 'H': How restrictive (or permissive) is the thread model. If a
31714 @c thread is selected and stopped, are other threads allowed
31715 @c to continue to execute? As I mentioned above, I think the
31716 @c semantics of each command when a thread is selected must be
31717 @c described. For example:
31719 @c 'g': If the stub supports threads and a specific thread is
31720 @c selected, returns the register block from that thread;
31721 @c otherwise returns current registers.
31723 @c 'G' If the stub supports threads and a specific thread is
31724 @c selected, sets the registers of the register block of
31725 @c that thread; otherwise sets current registers.
31727 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31728 @anchor{cycle step packet}
31729 @cindex @samp{i} packet
31730 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31731 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31732 step starting at that address.
31735 @cindex @samp{I} packet
31736 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31740 @cindex @samp{k} packet
31743 FIXME: @emph{There is no description of how to operate when a specific
31744 thread context has been selected (i.e.@: does 'k' kill only that
31747 @item m @var{addr},@var{length}
31748 @cindex @samp{m} packet
31749 Read @var{length} bytes of memory starting at address @var{addr}.
31750 Note that @var{addr} may not be aligned to any particular boundary.
31752 The stub need not use any particular size or alignment when gathering
31753 data from memory for the response; even if @var{addr} is word-aligned
31754 and @var{length} is a multiple of the word size, the stub is free to
31755 use byte accesses, or not. For this reason, this packet may not be
31756 suitable for accessing memory-mapped I/O devices.
31757 @cindex alignment of remote memory accesses
31758 @cindex size of remote memory accesses
31759 @cindex memory, alignment and size of remote accesses
31763 @item @var{XX@dots{}}
31764 Memory contents; each byte is transmitted as a two-digit hexadecimal
31765 number. The reply may contain fewer bytes than requested if the
31766 server was able to read only part of the region of memory.
31771 @item M @var{addr},@var{length}:@var{XX@dots{}}
31772 @cindex @samp{M} packet
31773 Write @var{length} bytes of memory starting at address @var{addr}.
31774 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31775 hexadecimal number.
31782 for an error (this includes the case where only part of the data was
31787 @cindex @samp{p} packet
31788 Read the value of register @var{n}; @var{n} is in hex.
31789 @xref{read registers packet}, for a description of how the returned
31790 register value is encoded.
31794 @item @var{XX@dots{}}
31795 the register's value
31799 Indicating an unrecognized @var{query}.
31802 @item P @var{n@dots{}}=@var{r@dots{}}
31803 @anchor{write register packet}
31804 @cindex @samp{P} packet
31805 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31806 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31807 digits for each byte in the register (target byte order).
31817 @item q @var{name} @var{params}@dots{}
31818 @itemx Q @var{name} @var{params}@dots{}
31819 @cindex @samp{q} packet
31820 @cindex @samp{Q} packet
31821 General query (@samp{q}) and set (@samp{Q}). These packets are
31822 described fully in @ref{General Query Packets}.
31825 @cindex @samp{r} packet
31826 Reset the entire system.
31828 Don't use this packet; use the @samp{R} packet instead.
31831 @cindex @samp{R} packet
31832 Restart the program being debugged. @var{XX}, while needed, is ignored.
31833 This packet is only available in extended mode (@pxref{extended mode}).
31835 The @samp{R} packet has no reply.
31837 @item s @r{[}@var{addr}@r{]}
31838 @cindex @samp{s} packet
31839 Single step. @var{addr} is the address at which to resume. If
31840 @var{addr} is omitted, resume at same address.
31843 @xref{Stop Reply Packets}, for the reply specifications.
31845 @item S @var{sig}@r{[};@var{addr}@r{]}
31846 @anchor{step with signal packet}
31847 @cindex @samp{S} packet
31848 Step with signal. This is analogous to the @samp{C} packet, but
31849 requests a single-step, rather than a normal resumption of execution.
31852 @xref{Stop Reply Packets}, for the reply specifications.
31854 @item t @var{addr}:@var{PP},@var{MM}
31855 @cindex @samp{t} packet
31856 Search backwards starting at address @var{addr} for a match with pattern
31857 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
31858 @var{addr} must be at least 3 digits.
31860 @item T @var{thread-id}
31861 @cindex @samp{T} packet
31862 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
31867 thread is still alive
31873 Packets starting with @samp{v} are identified by a multi-letter name,
31874 up to the first @samp{;} or @samp{?} (or the end of the packet).
31876 @item vAttach;@var{pid}
31877 @cindex @samp{vAttach} packet
31878 Attach to a new process with the specified process ID @var{pid}.
31879 The process ID is a
31880 hexadecimal integer identifying the process. In all-stop mode, all
31881 threads in the attached process are stopped; in non-stop mode, it may be
31882 attached without being stopped if that is supported by the target.
31884 @c In non-stop mode, on a successful vAttach, the stub should set the
31885 @c current thread to a thread of the newly-attached process. After
31886 @c attaching, GDB queries for the attached process's thread ID with qC.
31887 @c Also note that, from a user perspective, whether or not the
31888 @c target is stopped on attach in non-stop mode depends on whether you
31889 @c use the foreground or background version of the attach command, not
31890 @c on what vAttach does; GDB does the right thing with respect to either
31891 @c stopping or restarting threads.
31893 This packet is only available in extended mode (@pxref{extended mode}).
31899 @item @r{Any stop packet}
31900 for success in all-stop mode (@pxref{Stop Reply Packets})
31902 for success in non-stop mode (@pxref{Remote Non-Stop})
31905 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
31906 @cindex @samp{vCont} packet
31907 Resume the inferior, specifying different actions for each thread.
31908 If an action is specified with no @var{thread-id}, then it is applied to any
31909 threads that don't have a specific action specified; if no default action is
31910 specified then other threads should remain stopped in all-stop mode and
31911 in their current state in non-stop mode.
31912 Specifying multiple
31913 default actions is an error; specifying no actions is also an error.
31914 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
31916 Currently supported actions are:
31922 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
31926 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
31931 The optional argument @var{addr} normally associated with the
31932 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
31933 not supported in @samp{vCont}.
31935 The @samp{t} action is only relevant in non-stop mode
31936 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
31937 A stop reply should be generated for any affected thread not already stopped.
31938 When a thread is stopped by means of a @samp{t} action,
31939 the corresponding stop reply should indicate that the thread has stopped with
31940 signal @samp{0}, regardless of whether the target uses some other signal
31941 as an implementation detail.
31944 @xref{Stop Reply Packets}, for the reply specifications.
31947 @cindex @samp{vCont?} packet
31948 Request a list of actions supported by the @samp{vCont} packet.
31952 @item vCont@r{[};@var{action}@dots{}@r{]}
31953 The @samp{vCont} packet is supported. Each @var{action} is a supported
31954 command in the @samp{vCont} packet.
31956 The @samp{vCont} packet is not supported.
31959 @item vFile:@var{operation}:@var{parameter}@dots{}
31960 @cindex @samp{vFile} packet
31961 Perform a file operation on the target system. For details,
31962 see @ref{Host I/O Packets}.
31964 @item vFlashErase:@var{addr},@var{length}
31965 @cindex @samp{vFlashErase} packet
31966 Direct the stub to erase @var{length} bytes of flash starting at
31967 @var{addr}. The region may enclose any number of flash blocks, but
31968 its start and end must fall on block boundaries, as indicated by the
31969 flash block size appearing in the memory map (@pxref{Memory Map
31970 Format}). @value{GDBN} groups flash memory programming operations
31971 together, and sends a @samp{vFlashDone} request after each group; the
31972 stub is allowed to delay erase operation until the @samp{vFlashDone}
31973 packet is received.
31975 The stub must support @samp{vCont} if it reports support for
31976 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
31977 this case @samp{vCont} actions can be specified to apply to all threads
31978 in a process by using the @samp{p@var{pid}.-1} form of the
31989 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
31990 @cindex @samp{vFlashWrite} packet
31991 Direct the stub to write data to flash address @var{addr}. The data
31992 is passed in binary form using the same encoding as for the @samp{X}
31993 packet (@pxref{Binary Data}). The memory ranges specified by
31994 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
31995 not overlap, and must appear in order of increasing addresses
31996 (although @samp{vFlashErase} packets for higher addresses may already
31997 have been received; the ordering is guaranteed only between
31998 @samp{vFlashWrite} packets). If a packet writes to an address that was
31999 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32000 target-specific method, the results are unpredictable.
32008 for vFlashWrite addressing non-flash memory
32014 @cindex @samp{vFlashDone} packet
32015 Indicate to the stub that flash programming operation is finished.
32016 The stub is permitted to delay or batch the effects of a group of
32017 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32018 @samp{vFlashDone} packet is received. The contents of the affected
32019 regions of flash memory are unpredictable until the @samp{vFlashDone}
32020 request is completed.
32022 @item vKill;@var{pid}
32023 @cindex @samp{vKill} packet
32024 Kill the process with the specified process ID. @var{pid} is a
32025 hexadecimal integer identifying the process. This packet is used in
32026 preference to @samp{k} when multiprocess protocol extensions are
32027 supported; see @ref{multiprocess extensions}.
32037 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32038 @cindex @samp{vRun} packet
32039 Run the program @var{filename}, passing it each @var{argument} on its
32040 command line. The file and arguments are hex-encoded strings. If
32041 @var{filename} is an empty string, the stub may use a default program
32042 (e.g.@: the last program run). The program is created in the stopped
32045 @c FIXME: What about non-stop mode?
32047 This packet is only available in extended mode (@pxref{extended mode}).
32053 @item @r{Any stop packet}
32054 for success (@pxref{Stop Reply Packets})
32058 @anchor{vStopped packet}
32059 @cindex @samp{vStopped} packet
32061 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32062 reply and prompt for the stub to report another one.
32066 @item @r{Any stop packet}
32067 if there is another unreported stop event (@pxref{Stop Reply Packets})
32069 if there are no unreported stop events
32072 @item X @var{addr},@var{length}:@var{XX@dots{}}
32074 @cindex @samp{X} packet
32075 Write data to memory, where the data is transmitted in binary.
32076 @var{addr} is address, @var{length} is number of bytes,
32077 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32087 @item z @var{type},@var{addr},@var{kind}
32088 @itemx Z @var{type},@var{addr},@var{kind}
32089 @anchor{insert breakpoint or watchpoint packet}
32090 @cindex @samp{z} packet
32091 @cindex @samp{Z} packets
32092 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32093 watchpoint starting at address @var{address} of kind @var{kind}.
32095 Each breakpoint and watchpoint packet @var{type} is documented
32098 @emph{Implementation notes: A remote target shall return an empty string
32099 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32100 remote target shall support either both or neither of a given
32101 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32102 avoid potential problems with duplicate packets, the operations should
32103 be implemented in an idempotent way.}
32105 @item z0,@var{addr},@var{kind}
32106 @itemx Z0,@var{addr},@var{kind}
32107 @cindex @samp{z0} packet
32108 @cindex @samp{Z0} packet
32109 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32110 @var{addr} of type @var{kind}.
32112 A memory breakpoint is implemented by replacing the instruction at
32113 @var{addr} with a software breakpoint or trap instruction. The
32114 @var{kind} is target-specific and typically indicates the size of
32115 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32116 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32117 architectures have additional meanings for @var{kind};
32118 see @ref{Architecture-Specific Protocol Details}.
32120 @emph{Implementation note: It is possible for a target to copy or move
32121 code that contains memory breakpoints (e.g., when implementing
32122 overlays). The behavior of this packet, in the presence of such a
32123 target, is not defined.}
32135 @item z1,@var{addr},@var{kind}
32136 @itemx Z1,@var{addr},@var{kind}
32137 @cindex @samp{z1} packet
32138 @cindex @samp{Z1} packet
32139 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32140 address @var{addr}.
32142 A hardware breakpoint is implemented using a mechanism that is not
32143 dependant on being able to modify the target's memory. @var{kind}
32144 has the same meaning as in @samp{Z0} packets.
32146 @emph{Implementation note: A hardware breakpoint is not affected by code
32159 @item z2,@var{addr},@var{kind}
32160 @itemx Z2,@var{addr},@var{kind}
32161 @cindex @samp{z2} packet
32162 @cindex @samp{Z2} packet
32163 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32164 @var{kind} is interpreted as the number of bytes to watch.
32176 @item z3,@var{addr},@var{kind}
32177 @itemx Z3,@var{addr},@var{kind}
32178 @cindex @samp{z3} packet
32179 @cindex @samp{Z3} packet
32180 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
32181 @var{kind} is interpreted as the number of bytes to watch.
32193 @item z4,@var{addr},@var{kind}
32194 @itemx Z4,@var{addr},@var{kind}
32195 @cindex @samp{z4} packet
32196 @cindex @samp{Z4} packet
32197 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
32198 @var{kind} is interpreted as the number of bytes to watch.
32212 @node Stop Reply Packets
32213 @section Stop Reply Packets
32214 @cindex stop reply packets
32216 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
32217 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
32218 receive any of the below as a reply. Except for @samp{?}
32219 and @samp{vStopped}, that reply is only returned
32220 when the target halts. In the below the exact meaning of @dfn{signal
32221 number} is defined by the header @file{include/gdb/signals.h} in the
32222 @value{GDBN} source code.
32224 As in the description of request packets, we include spaces in the
32225 reply templates for clarity; these are not part of the reply packet's
32226 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
32232 The program received signal number @var{AA} (a two-digit hexadecimal
32233 number). This is equivalent to a @samp{T} response with no
32234 @var{n}:@var{r} pairs.
32236 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
32237 @cindex @samp{T} packet reply
32238 The program received signal number @var{AA} (a two-digit hexadecimal
32239 number). This is equivalent to an @samp{S} response, except that the
32240 @samp{@var{n}:@var{r}} pairs can carry values of important registers
32241 and other information directly in the stop reply packet, reducing
32242 round-trip latency. Single-step and breakpoint traps are reported
32243 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
32247 If @var{n} is a hexadecimal number, it is a register number, and the
32248 corresponding @var{r} gives that register's value. @var{r} is a
32249 series of bytes in target byte order, with each byte given by a
32250 two-digit hex number.
32253 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32254 the stopped thread, as specified in @ref{thread-id syntax}.
32257 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32258 the core on which the stop event was detected.
32261 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32262 specific event that stopped the target. The currently defined stop
32263 reasons are listed below. @var{aa} should be @samp{05}, the trap
32264 signal. At most one stop reason should be present.
32267 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32268 and go on to the next; this allows us to extend the protocol in the
32272 The currently defined stop reasons are:
32278 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32281 @cindex shared library events, remote reply
32283 The packet indicates that the loaded libraries have changed.
32284 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32285 list of loaded libraries. @var{r} is ignored.
32287 @cindex replay log events, remote reply
32289 The packet indicates that the target cannot continue replaying
32290 logged execution events, because it has reached the end (or the
32291 beginning when executing backward) of the log. The value of @var{r}
32292 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32293 for more information.
32297 @itemx W @var{AA} ; process:@var{pid}
32298 The process exited, and @var{AA} is the exit status. This is only
32299 applicable to certain targets.
32301 The second form of the response, including the process ID of the exited
32302 process, can be used only when @value{GDBN} has reported support for
32303 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32304 The @var{pid} is formatted as a big-endian hex string.
32307 @itemx X @var{AA} ; process:@var{pid}
32308 The process terminated with signal @var{AA}.
32310 The second form of the response, including the process ID of the
32311 terminated process, can be used only when @value{GDBN} has reported
32312 support for multiprocess protocol extensions; see @ref{multiprocess
32313 extensions}. The @var{pid} is formatted as a big-endian hex string.
32315 @item O @var{XX}@dots{}
32316 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
32317 written as the program's console output. This can happen at any time
32318 while the program is running and the debugger should continue to wait
32319 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
32321 @item F @var{call-id},@var{parameter}@dots{}
32322 @var{call-id} is the identifier which says which host system call should
32323 be called. This is just the name of the function. Translation into the
32324 correct system call is only applicable as it's defined in @value{GDBN}.
32325 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
32328 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
32329 this very system call.
32331 The target replies with this packet when it expects @value{GDBN} to
32332 call a host system call on behalf of the target. @value{GDBN} replies
32333 with an appropriate @samp{F} packet and keeps up waiting for the next
32334 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
32335 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
32336 Protocol Extension}, for more details.
32340 @node General Query Packets
32341 @section General Query Packets
32342 @cindex remote query requests
32344 Packets starting with @samp{q} are @dfn{general query packets};
32345 packets starting with @samp{Q} are @dfn{general set packets}. General
32346 query and set packets are a semi-unified form for retrieving and
32347 sending information to and from the stub.
32349 The initial letter of a query or set packet is followed by a name
32350 indicating what sort of thing the packet applies to. For example,
32351 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
32352 definitions with the stub. These packet names follow some
32357 The name must not contain commas, colons or semicolons.
32359 Most @value{GDBN} query and set packets have a leading upper case
32362 The names of custom vendor packets should use a company prefix, in
32363 lower case, followed by a period. For example, packets designed at
32364 the Acme Corporation might begin with @samp{qacme.foo} (for querying
32365 foos) or @samp{Qacme.bar} (for setting bars).
32368 The name of a query or set packet should be separated from any
32369 parameters by a @samp{:}; the parameters themselves should be
32370 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
32371 full packet name, and check for a separator or the end of the packet,
32372 in case two packet names share a common prefix. New packets should not begin
32373 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
32374 packets predate these conventions, and have arguments without any terminator
32375 for the packet name; we suspect they are in widespread use in places that
32376 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
32377 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
32380 Like the descriptions of the other packets, each description here
32381 has a template showing the packet's overall syntax, followed by an
32382 explanation of the packet's meaning. We include spaces in some of the
32383 templates for clarity; these are not part of the packet's syntax. No
32384 @value{GDBN} packet uses spaces to separate its components.
32386 Here are the currently defined query and set packets:
32390 @item QAllow:@var{op}:@var{val}@dots{}
32391 @cindex @samp{QAllow} packet
32392 Specify which operations @value{GDBN} expects to request of the
32393 target, as a semicolon-separated list of operation name and value
32394 pairs. Possible values for @var{op} include @samp{WriteReg},
32395 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
32396 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
32397 indicating that @value{GDBN} will not request the operation, or 1,
32398 indicating that it may. (The target can then use this to set up its
32399 own internals optimally, for instance if the debugger never expects to
32400 insert breakpoints, it may not need to install its own trap handler.)
32403 @cindex current thread, remote request
32404 @cindex @samp{qC} packet
32405 Return the current thread ID.
32409 @item QC @var{thread-id}
32410 Where @var{thread-id} is a thread ID as documented in
32411 @ref{thread-id syntax}.
32412 @item @r{(anything else)}
32413 Any other reply implies the old thread ID.
32416 @item qCRC:@var{addr},@var{length}
32417 @cindex CRC of memory block, remote request
32418 @cindex @samp{qCRC} packet
32419 Compute the CRC checksum of a block of memory using CRC-32 defined in
32420 IEEE 802.3. The CRC is computed byte at a time, taking the most
32421 significant bit of each byte first. The initial pattern code
32422 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
32424 @emph{Note:} This is the same CRC used in validating separate debug
32425 files (@pxref{Separate Debug Files, , Debugging Information in Separate
32426 Files}). However the algorithm is slightly different. When validating
32427 separate debug files, the CRC is computed taking the @emph{least}
32428 significant bit of each byte first, and the final result is inverted to
32429 detect trailing zeros.
32434 An error (such as memory fault)
32435 @item C @var{crc32}
32436 The specified memory region's checksum is @var{crc32}.
32440 @itemx qsThreadInfo
32441 @cindex list active threads, remote request
32442 @cindex @samp{qfThreadInfo} packet
32443 @cindex @samp{qsThreadInfo} packet
32444 Obtain a list of all active thread IDs from the target (OS). Since there
32445 may be too many active threads to fit into one reply packet, this query
32446 works iteratively: it may require more than one query/reply sequence to
32447 obtain the entire list of threads. The first query of the sequence will
32448 be the @samp{qfThreadInfo} query; subsequent queries in the
32449 sequence will be the @samp{qsThreadInfo} query.
32451 NOTE: This packet replaces the @samp{qL} query (see below).
32455 @item m @var{thread-id}
32457 @item m @var{thread-id},@var{thread-id}@dots{}
32458 a comma-separated list of thread IDs
32460 (lower case letter @samp{L}) denotes end of list.
32463 In response to each query, the target will reply with a list of one or
32464 more thread IDs, separated by commas.
32465 @value{GDBN} will respond to each reply with a request for more thread
32466 ids (using the @samp{qs} form of the query), until the target responds
32467 with @samp{l} (lower-case ell, for @dfn{last}).
32468 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
32471 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
32472 @cindex get thread-local storage address, remote request
32473 @cindex @samp{qGetTLSAddr} packet
32474 Fetch the address associated with thread local storage specified
32475 by @var{thread-id}, @var{offset}, and @var{lm}.
32477 @var{thread-id} is the thread ID associated with the
32478 thread for which to fetch the TLS address. @xref{thread-id syntax}.
32480 @var{offset} is the (big endian, hex encoded) offset associated with the
32481 thread local variable. (This offset is obtained from the debug
32482 information associated with the variable.)
32484 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
32485 the load module associated with the thread local storage. For example,
32486 a @sc{gnu}/Linux system will pass the link map address of the shared
32487 object associated with the thread local storage under consideration.
32488 Other operating environments may choose to represent the load module
32489 differently, so the precise meaning of this parameter will vary.
32493 @item @var{XX}@dots{}
32494 Hex encoded (big endian) bytes representing the address of the thread
32495 local storage requested.
32498 An error occurred. @var{nn} are hex digits.
32501 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
32504 @item qGetTIBAddr:@var{thread-id}
32505 @cindex get thread information block address
32506 @cindex @samp{qGetTIBAddr} packet
32507 Fetch address of the Windows OS specific Thread Information Block.
32509 @var{thread-id} is the thread ID associated with the thread.
32513 @item @var{XX}@dots{}
32514 Hex encoded (big endian) bytes representing the linear address of the
32515 thread information block.
32518 An error occured. This means that either the thread was not found, or the
32519 address could not be retrieved.
32522 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
32525 @item qL @var{startflag} @var{threadcount} @var{nextthread}
32526 Obtain thread information from RTOS. Where: @var{startflag} (one hex
32527 digit) is one to indicate the first query and zero to indicate a
32528 subsequent query; @var{threadcount} (two hex digits) is the maximum
32529 number of threads the response packet can contain; and @var{nextthread}
32530 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
32531 returned in the response as @var{argthread}.
32533 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
32537 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
32538 Where: @var{count} (two hex digits) is the number of threads being
32539 returned; @var{done} (one hex digit) is zero to indicate more threads
32540 and one indicates no further threads; @var{argthreadid} (eight hex
32541 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
32542 is a sequence of thread IDs from the target. @var{threadid} (eight hex
32543 digits). See @code{remote.c:parse_threadlist_response()}.
32547 @cindex section offsets, remote request
32548 @cindex @samp{qOffsets} packet
32549 Get section offsets that the target used when relocating the downloaded
32554 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
32555 Relocate the @code{Text} section by @var{xxx} from its original address.
32556 Relocate the @code{Data} section by @var{yyy} from its original address.
32557 If the object file format provides segment information (e.g.@: @sc{elf}
32558 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
32559 segments by the supplied offsets.
32561 @emph{Note: while a @code{Bss} offset may be included in the response,
32562 @value{GDBN} ignores this and instead applies the @code{Data} offset
32563 to the @code{Bss} section.}
32565 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
32566 Relocate the first segment of the object file, which conventionally
32567 contains program code, to a starting address of @var{xxx}. If
32568 @samp{DataSeg} is specified, relocate the second segment, which
32569 conventionally contains modifiable data, to a starting address of
32570 @var{yyy}. @value{GDBN} will report an error if the object file
32571 does not contain segment information, or does not contain at least
32572 as many segments as mentioned in the reply. Extra segments are
32573 kept at fixed offsets relative to the last relocated segment.
32576 @item qP @var{mode} @var{thread-id}
32577 @cindex thread information, remote request
32578 @cindex @samp{qP} packet
32579 Returns information on @var{thread-id}. Where: @var{mode} is a hex
32580 encoded 32 bit mode; @var{thread-id} is a thread ID
32581 (@pxref{thread-id syntax}).
32583 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
32586 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
32590 @cindex non-stop mode, remote request
32591 @cindex @samp{QNonStop} packet
32593 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
32594 @xref{Remote Non-Stop}, for more information.
32599 The request succeeded.
32602 An error occurred. @var{nn} are hex digits.
32605 An empty reply indicates that @samp{QNonStop} is not supported by
32609 This packet is not probed by default; the remote stub must request it,
32610 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32611 Use of this packet is controlled by the @code{set non-stop} command;
32612 @pxref{Non-Stop Mode}.
32614 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
32615 @cindex pass signals to inferior, remote request
32616 @cindex @samp{QPassSignals} packet
32617 @anchor{QPassSignals}
32618 Each listed @var{signal} should be passed directly to the inferior process.
32619 Signals are numbered identically to continue packets and stop replies
32620 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
32621 strictly greater than the previous item. These signals do not need to stop
32622 the inferior, or be reported to @value{GDBN}. All other signals should be
32623 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
32624 combine; any earlier @samp{QPassSignals} list is completely replaced by the
32625 new list. This packet improves performance when using @samp{handle
32626 @var{signal} nostop noprint pass}.
32631 The request succeeded.
32634 An error occurred. @var{nn} are hex digits.
32637 An empty reply indicates that @samp{QPassSignals} is not supported by
32641 Use of this packet is controlled by the @code{set remote pass-signals}
32642 command (@pxref{Remote Configuration, set remote pass-signals}).
32643 This packet is not probed by default; the remote stub must request it,
32644 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32646 @item qRcmd,@var{command}
32647 @cindex execute remote command, remote request
32648 @cindex @samp{qRcmd} packet
32649 @var{command} (hex encoded) is passed to the local interpreter for
32650 execution. Invalid commands should be reported using the output
32651 string. Before the final result packet, the target may also respond
32652 with a number of intermediate @samp{O@var{output}} console output
32653 packets. @emph{Implementors should note that providing access to a
32654 stubs's interpreter may have security implications}.
32659 A command response with no output.
32661 A command response with the hex encoded output string @var{OUTPUT}.
32663 Indicate a badly formed request.
32665 An empty reply indicates that @samp{qRcmd} is not recognized.
32668 (Note that the @code{qRcmd} packet's name is separated from the
32669 command by a @samp{,}, not a @samp{:}, contrary to the naming
32670 conventions above. Please don't use this packet as a model for new
32673 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
32674 @cindex searching memory, in remote debugging
32675 @cindex @samp{qSearch:memory} packet
32676 @anchor{qSearch memory}
32677 Search @var{length} bytes at @var{address} for @var{search-pattern}.
32678 @var{address} and @var{length} are encoded in hex.
32679 @var{search-pattern} is a sequence of bytes, hex encoded.
32684 The pattern was not found.
32686 The pattern was found at @var{address}.
32688 A badly formed request or an error was encountered while searching memory.
32690 An empty reply indicates that @samp{qSearch:memory} is not recognized.
32693 @item QStartNoAckMode
32694 @cindex @samp{QStartNoAckMode} packet
32695 @anchor{QStartNoAckMode}
32696 Request that the remote stub disable the normal @samp{+}/@samp{-}
32697 protocol acknowledgments (@pxref{Packet Acknowledgment}).
32702 The stub has switched to no-acknowledgment mode.
32703 @value{GDBN} acknowledges this reponse,
32704 but neither the stub nor @value{GDBN} shall send or expect further
32705 @samp{+}/@samp{-} acknowledgments in the current connection.
32707 An empty reply indicates that the stub does not support no-acknowledgment mode.
32710 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
32711 @cindex supported packets, remote query
32712 @cindex features of the remote protocol
32713 @cindex @samp{qSupported} packet
32714 @anchor{qSupported}
32715 Tell the remote stub about features supported by @value{GDBN}, and
32716 query the stub for features it supports. This packet allows
32717 @value{GDBN} and the remote stub to take advantage of each others'
32718 features. @samp{qSupported} also consolidates multiple feature probes
32719 at startup, to improve @value{GDBN} performance---a single larger
32720 packet performs better than multiple smaller probe packets on
32721 high-latency links. Some features may enable behavior which must not
32722 be on by default, e.g.@: because it would confuse older clients or
32723 stubs. Other features may describe packets which could be
32724 automatically probed for, but are not. These features must be
32725 reported before @value{GDBN} will use them. This ``default
32726 unsupported'' behavior is not appropriate for all packets, but it
32727 helps to keep the initial connection time under control with new
32728 versions of @value{GDBN} which support increasing numbers of packets.
32732 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32733 The stub supports or does not support each returned @var{stubfeature},
32734 depending on the form of each @var{stubfeature} (see below for the
32737 An empty reply indicates that @samp{qSupported} is not recognized,
32738 or that no features needed to be reported to @value{GDBN}.
32741 The allowed forms for each feature (either a @var{gdbfeature} in the
32742 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32746 @item @var{name}=@var{value}
32747 The remote protocol feature @var{name} is supported, and associated
32748 with the specified @var{value}. The format of @var{value} depends
32749 on the feature, but it must not include a semicolon.
32751 The remote protocol feature @var{name} is supported, and does not
32752 need an associated value.
32754 The remote protocol feature @var{name} is not supported.
32756 The remote protocol feature @var{name} may be supported, and
32757 @value{GDBN} should auto-detect support in some other way when it is
32758 needed. This form will not be used for @var{gdbfeature} notifications,
32759 but may be used for @var{stubfeature} responses.
32762 Whenever the stub receives a @samp{qSupported} request, the
32763 supplied set of @value{GDBN} features should override any previous
32764 request. This allows @value{GDBN} to put the stub in a known
32765 state, even if the stub had previously been communicating with
32766 a different version of @value{GDBN}.
32768 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32773 This feature indicates whether @value{GDBN} supports multiprocess
32774 extensions to the remote protocol. @value{GDBN} does not use such
32775 extensions unless the stub also reports that it supports them by
32776 including @samp{multiprocess+} in its @samp{qSupported} reply.
32777 @xref{multiprocess extensions}, for details.
32780 This feature indicates that @value{GDBN} supports the XML target
32781 description. If the stub sees @samp{xmlRegisters=} with target
32782 specific strings separated by a comma, it will report register
32786 This feature indicates whether @value{GDBN} supports the
32787 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32788 instruction reply packet}).
32791 Stubs should ignore any unknown values for
32792 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32793 packet supports receiving packets of unlimited length (earlier
32794 versions of @value{GDBN} may reject overly long responses). Additional values
32795 for @var{gdbfeature} may be defined in the future to let the stub take
32796 advantage of new features in @value{GDBN}, e.g.@: incompatible
32797 improvements in the remote protocol---the @samp{multiprocess} feature is
32798 an example of such a feature. The stub's reply should be independent
32799 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32800 describes all the features it supports, and then the stub replies with
32801 all the features it supports.
32803 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32804 responses, as long as each response uses one of the standard forms.
32806 Some features are flags. A stub which supports a flag feature
32807 should respond with a @samp{+} form response. Other features
32808 require values, and the stub should respond with an @samp{=}
32811 Each feature has a default value, which @value{GDBN} will use if
32812 @samp{qSupported} is not available or if the feature is not mentioned
32813 in the @samp{qSupported} response. The default values are fixed; a
32814 stub is free to omit any feature responses that match the defaults.
32816 Not all features can be probed, but for those which can, the probing
32817 mechanism is useful: in some cases, a stub's internal
32818 architecture may not allow the protocol layer to know some information
32819 about the underlying target in advance. This is especially common in
32820 stubs which may be configured for multiple targets.
32822 These are the currently defined stub features and their properties:
32824 @multitable @columnfractions 0.35 0.2 0.12 0.2
32825 @c NOTE: The first row should be @headitem, but we do not yet require
32826 @c a new enough version of Texinfo (4.7) to use @headitem.
32828 @tab Value Required
32832 @item @samp{PacketSize}
32837 @item @samp{qXfer:auxv:read}
32842 @item @samp{qXfer:features:read}
32847 @item @samp{qXfer:libraries:read}
32852 @item @samp{qXfer:memory-map:read}
32857 @item @samp{qXfer:sdata:read}
32862 @item @samp{qXfer:spu:read}
32867 @item @samp{qXfer:spu:write}
32872 @item @samp{qXfer:siginfo:read}
32877 @item @samp{qXfer:siginfo:write}
32882 @item @samp{qXfer:threads:read}
32888 @item @samp{QNonStop}
32893 @item @samp{QPassSignals}
32898 @item @samp{QStartNoAckMode}
32903 @item @samp{multiprocess}
32908 @item @samp{ConditionalTracepoints}
32913 @item @samp{ReverseContinue}
32918 @item @samp{ReverseStep}
32923 @item @samp{TracepointSource}
32928 @item @samp{QAllow}
32935 These are the currently defined stub features, in more detail:
32938 @cindex packet size, remote protocol
32939 @item PacketSize=@var{bytes}
32940 The remote stub can accept packets up to at least @var{bytes} in
32941 length. @value{GDBN} will send packets up to this size for bulk
32942 transfers, and will never send larger packets. This is a limit on the
32943 data characters in the packet, including the frame and checksum.
32944 There is no trailing NUL byte in a remote protocol packet; if the stub
32945 stores packets in a NUL-terminated format, it should allow an extra
32946 byte in its buffer for the NUL. If this stub feature is not supported,
32947 @value{GDBN} guesses based on the size of the @samp{g} packet response.
32949 @item qXfer:auxv:read
32950 The remote stub understands the @samp{qXfer:auxv:read} packet
32951 (@pxref{qXfer auxiliary vector read}).
32953 @item qXfer:features:read
32954 The remote stub understands the @samp{qXfer:features:read} packet
32955 (@pxref{qXfer target description read}).
32957 @item qXfer:libraries:read
32958 The remote stub understands the @samp{qXfer:libraries:read} packet
32959 (@pxref{qXfer library list read}).
32961 @item qXfer:memory-map:read
32962 The remote stub understands the @samp{qXfer:memory-map:read} packet
32963 (@pxref{qXfer memory map read}).
32965 @item qXfer:sdata:read
32966 The remote stub understands the @samp{qXfer:sdata:read} packet
32967 (@pxref{qXfer sdata read}).
32969 @item qXfer:spu:read
32970 The remote stub understands the @samp{qXfer:spu:read} packet
32971 (@pxref{qXfer spu read}).
32973 @item qXfer:spu:write
32974 The remote stub understands the @samp{qXfer:spu:write} packet
32975 (@pxref{qXfer spu write}).
32977 @item qXfer:siginfo:read
32978 The remote stub understands the @samp{qXfer:siginfo:read} packet
32979 (@pxref{qXfer siginfo read}).
32981 @item qXfer:siginfo:write
32982 The remote stub understands the @samp{qXfer:siginfo:write} packet
32983 (@pxref{qXfer siginfo write}).
32985 @item qXfer:threads:read
32986 The remote stub understands the @samp{qXfer:threads:read} packet
32987 (@pxref{qXfer threads read}).
32990 The remote stub understands the @samp{QNonStop} packet
32991 (@pxref{QNonStop}).
32994 The remote stub understands the @samp{QPassSignals} packet
32995 (@pxref{QPassSignals}).
32997 @item QStartNoAckMode
32998 The remote stub understands the @samp{QStartNoAckMode} packet and
32999 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33002 @anchor{multiprocess extensions}
33003 @cindex multiprocess extensions, in remote protocol
33004 The remote stub understands the multiprocess extensions to the remote
33005 protocol syntax. The multiprocess extensions affect the syntax of
33006 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33007 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33008 replies. Note that reporting this feature indicates support for the
33009 syntactic extensions only, not that the stub necessarily supports
33010 debugging of more than one process at a time. The stub must not use
33011 multiprocess extensions in packet replies unless @value{GDBN} has also
33012 indicated it supports them in its @samp{qSupported} request.
33014 @item qXfer:osdata:read
33015 The remote stub understands the @samp{qXfer:osdata:read} packet
33016 ((@pxref{qXfer osdata read}).
33018 @item ConditionalTracepoints
33019 The remote stub accepts and implements conditional expressions defined
33020 for tracepoints (@pxref{Tracepoint Conditions}).
33022 @item ReverseContinue
33023 The remote stub accepts and implements the reverse continue packet
33027 The remote stub accepts and implements the reverse step packet
33030 @item TracepointSource
33031 The remote stub understands the @samp{QTDPsrc} packet that supplies
33032 the source form of tracepoint definitions.
33035 The remote stub understands the @samp{QAllow} packet.
33037 @item StaticTracepoint
33038 @cindex static tracepoints, in remote protocol
33039 The remote stub supports static tracepoints.
33044 @cindex symbol lookup, remote request
33045 @cindex @samp{qSymbol} packet
33046 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33047 requests. Accept requests from the target for the values of symbols.
33052 The target does not need to look up any (more) symbols.
33053 @item qSymbol:@var{sym_name}
33054 The target requests the value of symbol @var{sym_name} (hex encoded).
33055 @value{GDBN} may provide the value by using the
33056 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33060 @item qSymbol:@var{sym_value}:@var{sym_name}
33061 Set the value of @var{sym_name} to @var{sym_value}.
33063 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33064 target has previously requested.
33066 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33067 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33073 The target does not need to look up any (more) symbols.
33074 @item qSymbol:@var{sym_name}
33075 The target requests the value of a new symbol @var{sym_name} (hex
33076 encoded). @value{GDBN} will continue to supply the values of symbols
33077 (if available), until the target ceases to request them.
33082 @item QTDisconnected
33089 @xref{Tracepoint Packets}.
33091 @item qThreadExtraInfo,@var{thread-id}
33092 @cindex thread attributes info, remote request
33093 @cindex @samp{qThreadExtraInfo} packet
33094 Obtain a printable string description of a thread's attributes from
33095 the target OS. @var{thread-id} is a thread ID;
33096 see @ref{thread-id syntax}. This
33097 string may contain anything that the target OS thinks is interesting
33098 for @value{GDBN} to tell the user about the thread. The string is
33099 displayed in @value{GDBN}'s @code{info threads} display. Some
33100 examples of possible thread extra info strings are @samp{Runnable}, or
33101 @samp{Blocked on Mutex}.
33105 @item @var{XX}@dots{}
33106 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33107 comprising the printable string containing the extra information about
33108 the thread's attributes.
33111 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33112 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33113 conventions above. Please don't use this packet as a model for new
33128 @xref{Tracepoint Packets}.
33130 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33131 @cindex read special object, remote request
33132 @cindex @samp{qXfer} packet
33133 @anchor{qXfer read}
33134 Read uninterpreted bytes from the target's special data area
33135 identified by the keyword @var{object}. Request @var{length} bytes
33136 starting at @var{offset} bytes into the data. The content and
33137 encoding of @var{annex} is specific to @var{object}; it can supply
33138 additional details about what data to access.
33140 Here are the specific requests of this form defined so far. All
33141 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33142 formats, listed below.
33145 @item qXfer:auxv:read::@var{offset},@var{length}
33146 @anchor{qXfer auxiliary vector read}
33147 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33148 auxiliary vector}. Note @var{annex} must be empty.
33150 This packet is not probed by default; the remote stub must request it,
33151 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33153 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33154 @anchor{qXfer target description read}
33155 Access the @dfn{target description}. @xref{Target Descriptions}. The
33156 annex specifies which XML document to access. The main description is
33157 always loaded from the @samp{target.xml} annex.
33159 This packet is not probed by default; the remote stub must request it,
33160 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33162 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
33163 @anchor{qXfer library list read}
33164 Access the target's list of loaded libraries. @xref{Library List Format}.
33165 The annex part of the generic @samp{qXfer} packet must be empty
33166 (@pxref{qXfer read}).
33168 Targets which maintain a list of libraries in the program's memory do
33169 not need to implement this packet; it is designed for platforms where
33170 the operating system manages the list of loaded libraries.
33172 This packet is not probed by default; the remote stub must request it,
33173 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33175 @item qXfer:memory-map:read::@var{offset},@var{length}
33176 @anchor{qXfer memory map read}
33177 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
33178 annex part of the generic @samp{qXfer} packet must be empty
33179 (@pxref{qXfer read}).
33181 This packet is not probed by default; the remote stub must request it,
33182 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33184 @item qXfer:sdata:read::@var{offset},@var{length}
33185 @anchor{qXfer sdata read}
33187 Read contents of the extra collected static tracepoint marker
33188 information. The annex part of the generic @samp{qXfer} packet must
33189 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
33192 This packet is not probed by default; the remote stub must request it,
33193 by supplying an appropriate @samp{qSupported} response
33194 (@pxref{qSupported}).
33196 @item qXfer:siginfo:read::@var{offset},@var{length}
33197 @anchor{qXfer siginfo read}
33198 Read contents of the extra signal information on the target
33199 system. The annex part of the generic @samp{qXfer} packet must be
33200 empty (@pxref{qXfer read}).
33202 This packet is not probed by default; the remote stub must request it,
33203 by supplying an appropriate @samp{qSupported} response
33204 (@pxref{qSupported}).
33206 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
33207 @anchor{qXfer spu read}
33208 Read contents of an @code{spufs} file on the target system. The
33209 annex specifies which file to read; it must be of the form
33210 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33211 in the target process, and @var{name} identifes the @code{spufs} file
33212 in that context to be accessed.
33214 This packet is not probed by default; the remote stub must request it,
33215 by supplying an appropriate @samp{qSupported} response
33216 (@pxref{qSupported}).
33218 @item qXfer:threads:read::@var{offset},@var{length}
33219 @anchor{qXfer threads read}
33220 Access the list of threads on target. @xref{Thread List Format}. The
33221 annex part of the generic @samp{qXfer} packet must be empty
33222 (@pxref{qXfer read}).
33224 This packet is not probed by default; the remote stub must request it,
33225 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33227 @item qXfer:osdata:read::@var{offset},@var{length}
33228 @anchor{qXfer osdata read}
33229 Access the target's @dfn{operating system information}.
33230 @xref{Operating System Information}.
33237 Data @var{data} (@pxref{Binary Data}) has been read from the
33238 target. There may be more data at a higher address (although
33239 it is permitted to return @samp{m} even for the last valid
33240 block of data, as long as at least one byte of data was read).
33241 @var{data} may have fewer bytes than the @var{length} in the
33245 Data @var{data} (@pxref{Binary Data}) has been read from the target.
33246 There is no more data to be read. @var{data} may have fewer bytes
33247 than the @var{length} in the request.
33250 The @var{offset} in the request is at the end of the data.
33251 There is no more data to be read.
33254 The request was malformed, or @var{annex} was invalid.
33257 The offset was invalid, or there was an error encountered reading the data.
33258 @var{nn} is a hex-encoded @code{errno} value.
33261 An empty reply indicates the @var{object} string was not recognized by
33262 the stub, or that the object does not support reading.
33265 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33266 @cindex write data into object, remote request
33267 @anchor{qXfer write}
33268 Write uninterpreted bytes into the target's special data area
33269 identified by the keyword @var{object}, starting at @var{offset} bytes
33270 into the data. @var{data}@dots{} is the binary-encoded data
33271 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33272 is specific to @var{object}; it can supply additional details about what data
33275 Here are the specific requests of this form defined so far. All
33276 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
33277 formats, listed below.
33280 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
33281 @anchor{qXfer siginfo write}
33282 Write @var{data} to the extra signal information on the target system.
33283 The annex part of the generic @samp{qXfer} packet must be
33284 empty (@pxref{qXfer write}).
33286 This packet is not probed by default; the remote stub must request it,
33287 by supplying an appropriate @samp{qSupported} response
33288 (@pxref{qSupported}).
33290 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
33291 @anchor{qXfer spu write}
33292 Write @var{data} to an @code{spufs} file on the target system. The
33293 annex specifies which file to write; it must be of the form
33294 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33295 in the target process, and @var{name} identifes the @code{spufs} file
33296 in that context to be accessed.
33298 This packet is not probed by default; the remote stub must request it,
33299 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33305 @var{nn} (hex encoded) is the number of bytes written.
33306 This may be fewer bytes than supplied in the request.
33309 The request was malformed, or @var{annex} was invalid.
33312 The offset was invalid, or there was an error encountered writing the data.
33313 @var{nn} is a hex-encoded @code{errno} value.
33316 An empty reply indicates the @var{object} string was not
33317 recognized by the stub, or that the object does not support writing.
33320 @item qXfer:@var{object}:@var{operation}:@dots{}
33321 Requests of this form may be added in the future. When a stub does
33322 not recognize the @var{object} keyword, or its support for
33323 @var{object} does not recognize the @var{operation} keyword, the stub
33324 must respond with an empty packet.
33326 @item qAttached:@var{pid}
33327 @cindex query attached, remote request
33328 @cindex @samp{qAttached} packet
33329 Return an indication of whether the remote server attached to an
33330 existing process or created a new process. When the multiprocess
33331 protocol extensions are supported (@pxref{multiprocess extensions}),
33332 @var{pid} is an integer in hexadecimal format identifying the target
33333 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
33334 the query packet will be simplified as @samp{qAttached}.
33336 This query is used, for example, to know whether the remote process
33337 should be detached or killed when a @value{GDBN} session is ended with
33338 the @code{quit} command.
33343 The remote server attached to an existing process.
33345 The remote server created a new process.
33347 A badly formed request or an error was encountered.
33352 @node Architecture-Specific Protocol Details
33353 @section Architecture-Specific Protocol Details
33355 This section describes how the remote protocol is applied to specific
33356 target architectures. Also see @ref{Standard Target Features}, for
33357 details of XML target descriptions for each architecture.
33361 @subsubsection Breakpoint Kinds
33363 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
33368 16-bit Thumb mode breakpoint.
33371 32-bit Thumb mode (Thumb-2) breakpoint.
33374 32-bit ARM mode breakpoint.
33380 @subsubsection Register Packet Format
33382 The following @code{g}/@code{G} packets have previously been defined.
33383 In the below, some thirty-two bit registers are transferred as
33384 sixty-four bits. Those registers should be zero/sign extended (which?)
33385 to fill the space allocated. Register bytes are transferred in target
33386 byte order. The two nibbles within a register byte are transferred
33387 most-significant - least-significant.
33393 All registers are transferred as thirty-two bit quantities in the order:
33394 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
33395 registers; fsr; fir; fp.
33399 All registers are transferred as sixty-four bit quantities (including
33400 thirty-two bit registers such as @code{sr}). The ordering is the same
33405 @node Tracepoint Packets
33406 @section Tracepoint Packets
33407 @cindex tracepoint packets
33408 @cindex packets, tracepoint
33410 Here we describe the packets @value{GDBN} uses to implement
33411 tracepoints (@pxref{Tracepoints}).
33415 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
33416 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
33417 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
33418 the tracepoint is disabled. @var{step} is the tracepoint's step
33419 count, and @var{pass} is its pass count. If an @samp{F} is present,
33420 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
33421 the number of bytes that the target should copy elsewhere to make room
33422 for the tracepoint. If an @samp{X} is present, it introduces a
33423 tracepoint condition, which consists of a hexadecimal length, followed
33424 by a comma and hex-encoded bytes, in a manner similar to action
33425 encodings as described below. If the trailing @samp{-} is present,
33426 further @samp{QTDP} packets will follow to specify this tracepoint's
33432 The packet was understood and carried out.
33434 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33436 The packet was not recognized.
33439 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
33440 Define actions to be taken when a tracepoint is hit. @var{n} and
33441 @var{addr} must be the same as in the initial @samp{QTDP} packet for
33442 this tracepoint. This packet may only be sent immediately after
33443 another @samp{QTDP} packet that ended with a @samp{-}. If the
33444 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
33445 specifying more actions for this tracepoint.
33447 In the series of action packets for a given tracepoint, at most one
33448 can have an @samp{S} before its first @var{action}. If such a packet
33449 is sent, it and the following packets define ``while-stepping''
33450 actions. Any prior packets define ordinary actions --- that is, those
33451 taken when the tracepoint is first hit. If no action packet has an
33452 @samp{S}, then all the packets in the series specify ordinary
33453 tracepoint actions.
33455 The @samp{@var{action}@dots{}} portion of the packet is a series of
33456 actions, concatenated without separators. Each action has one of the
33462 Collect the registers whose bits are set in @var{mask}. @var{mask} is
33463 a hexadecimal number whose @var{i}'th bit is set if register number
33464 @var{i} should be collected. (The least significant bit is numbered
33465 zero.) Note that @var{mask} may be any number of digits long; it may
33466 not fit in a 32-bit word.
33468 @item M @var{basereg},@var{offset},@var{len}
33469 Collect @var{len} bytes of memory starting at the address in register
33470 number @var{basereg}, plus @var{offset}. If @var{basereg} is
33471 @samp{-1}, then the range has a fixed address: @var{offset} is the
33472 address of the lowest byte to collect. The @var{basereg},
33473 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
33474 values (the @samp{-1} value for @var{basereg} is a special case).
33476 @item X @var{len},@var{expr}
33477 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
33478 it directs. @var{expr} is an agent expression, as described in
33479 @ref{Agent Expressions}. Each byte of the expression is encoded as a
33480 two-digit hex number in the packet; @var{len} is the number of bytes
33481 in the expression (and thus one-half the number of hex digits in the
33486 Any number of actions may be packed together in a single @samp{QTDP}
33487 packet, as long as the packet does not exceed the maximum packet
33488 length (400 bytes, for many stubs). There may be only one @samp{R}
33489 action per tracepoint, and it must precede any @samp{M} or @samp{X}
33490 actions. Any registers referred to by @samp{M} and @samp{X} actions
33491 must be collected by a preceding @samp{R} action. (The
33492 ``while-stepping'' actions are treated as if they were attached to a
33493 separate tracepoint, as far as these restrictions are concerned.)
33498 The packet was understood and carried out.
33500 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33502 The packet was not recognized.
33505 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
33506 @cindex @samp{QTDPsrc} packet
33507 Specify a source string of tracepoint @var{n} at address @var{addr}.
33508 This is useful to get accurate reproduction of the tracepoints
33509 originally downloaded at the beginning of the trace run. @var{type}
33510 is the name of the tracepoint part, such as @samp{cond} for the
33511 tracepoint's conditional expression (see below for a list of types), while
33512 @var{bytes} is the string, encoded in hexadecimal.
33514 @var{start} is the offset of the @var{bytes} within the overall source
33515 string, while @var{slen} is the total length of the source string.
33516 This is intended for handling source strings that are longer than will
33517 fit in a single packet.
33518 @c Add detailed example when this info is moved into a dedicated
33519 @c tracepoint descriptions section.
33521 The available string types are @samp{at} for the location,
33522 @samp{cond} for the conditional, and @samp{cmd} for an action command.
33523 @value{GDBN} sends a separate packet for each command in the action
33524 list, in the same order in which the commands are stored in the list.
33526 The target does not need to do anything with source strings except
33527 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
33530 Although this packet is optional, and @value{GDBN} will only send it
33531 if the target replies with @samp{TracepointSource} @xref{General
33532 Query Packets}, it makes both disconnected tracing and trace files
33533 much easier to use. Otherwise the user must be careful that the
33534 tracepoints in effect while looking at trace frames are identical to
33535 the ones in effect during the trace run; even a small discrepancy
33536 could cause @samp{tdump} not to work, or a particular trace frame not
33539 @item QTDV:@var{n}:@var{value}
33540 @cindex define trace state variable, remote request
33541 @cindex @samp{QTDV} packet
33542 Create a new trace state variable, number @var{n}, with an initial
33543 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
33544 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
33545 the option of not using this packet for initial values of zero; the
33546 target should simply create the trace state variables as they are
33547 mentioned in expressions.
33549 @item QTFrame:@var{n}
33550 Select the @var{n}'th tracepoint frame from the buffer, and use the
33551 register and memory contents recorded there to answer subsequent
33552 request packets from @value{GDBN}.
33554 A successful reply from the stub indicates that the stub has found the
33555 requested frame. The response is a series of parts, concatenated
33556 without separators, describing the frame we selected. Each part has
33557 one of the following forms:
33561 The selected frame is number @var{n} in the trace frame buffer;
33562 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
33563 was no frame matching the criteria in the request packet.
33566 The selected trace frame records a hit of tracepoint number @var{t};
33567 @var{t} is a hexadecimal number.
33571 @item QTFrame:pc:@var{addr}
33572 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33573 currently selected frame whose PC is @var{addr};
33574 @var{addr} is a hexadecimal number.
33576 @item QTFrame:tdp:@var{t}
33577 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33578 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
33579 is a hexadecimal number.
33581 @item QTFrame:range:@var{start}:@var{end}
33582 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33583 currently selected frame whose PC is between @var{start} (inclusive)
33584 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
33587 @item QTFrame:outside:@var{start}:@var{end}
33588 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
33589 frame @emph{outside} the given range of addresses (exclusive).
33592 Begin the tracepoint experiment. Begin collecting data from
33593 tracepoint hits in the trace frame buffer. This packet supports the
33594 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
33595 instruction reply packet}).
33598 End the tracepoint experiment. Stop collecting trace frames.
33601 Clear the table of tracepoints, and empty the trace frame buffer.
33603 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
33604 Establish the given ranges of memory as ``transparent''. The stub
33605 will answer requests for these ranges from memory's current contents,
33606 if they were not collected as part of the tracepoint hit.
33608 @value{GDBN} uses this to mark read-only regions of memory, like those
33609 containing program code. Since these areas never change, they should
33610 still have the same contents they did when the tracepoint was hit, so
33611 there's no reason for the stub to refuse to provide their contents.
33613 @item QTDisconnected:@var{value}
33614 Set the choice to what to do with the tracing run when @value{GDBN}
33615 disconnects from the target. A @var{value} of 1 directs the target to
33616 continue the tracing run, while 0 tells the target to stop tracing if
33617 @value{GDBN} is no longer in the picture.
33620 Ask the stub if there is a trace experiment running right now.
33622 The reply has the form:
33626 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
33627 @var{running} is a single digit @code{1} if the trace is presently
33628 running, or @code{0} if not. It is followed by semicolon-separated
33629 optional fields that an agent may use to report additional status.
33633 If the trace is not running, the agent may report any of several
33634 explanations as one of the optional fields:
33639 No trace has been run yet.
33642 The trace was stopped by a user-originated stop command.
33645 The trace stopped because the trace buffer filled up.
33647 @item tdisconnected:0
33648 The trace stopped because @value{GDBN} disconnected from the target.
33650 @item tpasscount:@var{tpnum}
33651 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
33653 @item terror:@var{text}:@var{tpnum}
33654 The trace stopped because tracepoint @var{tpnum} had an error. The
33655 string @var{text} is available to describe the nature of the error
33656 (for instance, a divide by zero in the condition expression).
33657 @var{text} is hex encoded.
33660 The trace stopped for some other reason.
33664 Additional optional fields supply statistical and other information.
33665 Although not required, they are extremely useful for users monitoring
33666 the progress of a trace run. If a trace has stopped, and these
33667 numbers are reported, they must reflect the state of the just-stopped
33672 @item tframes:@var{n}
33673 The number of trace frames in the buffer.
33675 @item tcreated:@var{n}
33676 The total number of trace frames created during the run. This may
33677 be larger than the trace frame count, if the buffer is circular.
33679 @item tsize:@var{n}
33680 The total size of the trace buffer, in bytes.
33682 @item tfree:@var{n}
33683 The number of bytes still unused in the buffer.
33685 @item circular:@var{n}
33686 The value of the circular trace buffer flag. @code{1} means that the
33687 trace buffer is circular and old trace frames will be discarded if
33688 necessary to make room, @code{0} means that the trace buffer is linear
33691 @item disconn:@var{n}
33692 The value of the disconnected tracing flag. @code{1} means that
33693 tracing will continue after @value{GDBN} disconnects, @code{0} means
33694 that the trace run will stop.
33698 @item qTV:@var{var}
33699 @cindex trace state variable value, remote request
33700 @cindex @samp{qTV} packet
33701 Ask the stub for the value of the trace state variable number @var{var}.
33706 The value of the variable is @var{value}. This will be the current
33707 value of the variable if the user is examining a running target, or a
33708 saved value if the variable was collected in the trace frame that the
33709 user is looking at. Note that multiple requests may result in
33710 different reply values, such as when requesting values while the
33711 program is running.
33714 The value of the variable is unknown. This would occur, for example,
33715 if the user is examining a trace frame in which the requested variable
33721 These packets request data about tracepoints that are being used by
33722 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33723 of data, and multiple @code{qTsP} to get additional pieces. Replies
33724 to these packets generally take the form of the @code{QTDP} packets
33725 that define tracepoints. (FIXME add detailed syntax)
33729 These packets request data about trace state variables that are on the
33730 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33731 and multiple @code{qTsV} to get additional variables. Replies to
33732 these packets follow the syntax of the @code{QTDV} packets that define
33733 trace state variables.
33737 These packets request data about static tracepoint markers that exist
33738 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33739 first piece of data, and multiple @code{qTsSTM} to get additional
33740 pieces. Replies to these packets take the following form:
33744 @item m @var{address}:@var{id}:@var{extra}
33746 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33747 a comma-separated list of markers
33749 (lower case letter @samp{L}) denotes end of list.
33751 An error occurred. @var{nn} are hex digits.
33753 An empty reply indicates that the request is not supported by the
33757 @var{address} is encoded in hex.
33758 @var{id} and @var{extra} are strings encoded in hex.
33760 In response to each query, the target will reply with a list of one or
33761 more markers, separated by commas. @value{GDBN} will respond to each
33762 reply with a request for more markers (using the @samp{qs} form of the
33763 query), until the target responds with @samp{l} (lower-case ell, for
33766 @item qTSTMat:@var{address}
33767 This packets requests data about static tracepoint markers in the
33768 target program at @var{address}. Replies to this packet follow the
33769 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33770 tracepoint markers.
33772 @item QTSave:@var{filename}
33773 This packet directs the target to save trace data to the file name
33774 @var{filename} in the target's filesystem. @var{filename} is encoded
33775 as a hex string; the interpretation of the file name (relative vs
33776 absolute, wild cards, etc) is up to the target.
33778 @item qTBuffer:@var{offset},@var{len}
33779 Return up to @var{len} bytes of the current contents of trace buffer,
33780 starting at @var{offset}. The trace buffer is treated as if it were
33781 a contiguous collection of traceframes, as per the trace file format.
33782 The reply consists as many hex-encoded bytes as the target can deliver
33783 in a packet; it is not an error to return fewer than were asked for.
33784 A reply consisting of just @code{l} indicates that no bytes are
33787 @item QTBuffer:circular:@var{value}
33788 This packet directs the target to use a circular trace buffer if
33789 @var{value} is 1, or a linear buffer if the value is 0.
33793 @subsection Relocate instruction reply packet
33794 When installing fast tracepoints in memory, the target may need to
33795 relocate the instruction currently at the tracepoint address to a
33796 different address in memory. For most instructions, a simple copy is
33797 enough, but, for example, call instructions that implicitly push the
33798 return address on the stack, and relative branches or other
33799 PC-relative instructions require offset adjustment, so that the effect
33800 of executing the instruction at a different address is the same as if
33801 it had executed in the original location.
33803 In response to several of the tracepoint packets, the target may also
33804 respond with a number of intermediate @samp{qRelocInsn} request
33805 packets before the final result packet, to have @value{GDBN} handle
33806 this relocation operation. If a packet supports this mechanism, its
33807 documentation will explicitly say so. See for example the above
33808 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33809 format of the request is:
33812 @item qRelocInsn:@var{from};@var{to}
33814 This requests @value{GDBN} to copy instruction at address @var{from}
33815 to address @var{to}, possibly adjusted so that executing the
33816 instruction at @var{to} has the same effect as executing it at
33817 @var{from}. @value{GDBN} writes the adjusted instruction to target
33818 memory starting at @var{to}.
33823 @item qRelocInsn:@var{adjusted_size}
33824 Informs the stub the relocation is complete. @var{adjusted_size} is
33825 the length in bytes of resulting relocated instruction sequence.
33827 A badly formed request was detected, or an error was encountered while
33828 relocating the instruction.
33831 @node Host I/O Packets
33832 @section Host I/O Packets
33833 @cindex Host I/O, remote protocol
33834 @cindex file transfer, remote protocol
33836 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33837 operations on the far side of a remote link. For example, Host I/O is
33838 used to upload and download files to a remote target with its own
33839 filesystem. Host I/O uses the same constant values and data structure
33840 layout as the target-initiated File-I/O protocol. However, the
33841 Host I/O packets are structured differently. The target-initiated
33842 protocol relies on target memory to store parameters and buffers.
33843 Host I/O requests are initiated by @value{GDBN}, and the
33844 target's memory is not involved. @xref{File-I/O Remote Protocol
33845 Extension}, for more details on the target-initiated protocol.
33847 The Host I/O request packets all encode a single operation along with
33848 its arguments. They have this format:
33852 @item vFile:@var{operation}: @var{parameter}@dots{}
33853 @var{operation} is the name of the particular request; the target
33854 should compare the entire packet name up to the second colon when checking
33855 for a supported operation. The format of @var{parameter} depends on
33856 the operation. Numbers are always passed in hexadecimal. Negative
33857 numbers have an explicit minus sign (i.e.@: two's complement is not
33858 used). Strings (e.g.@: filenames) are encoded as a series of
33859 hexadecimal bytes. The last argument to a system call may be a
33860 buffer of escaped binary data (@pxref{Binary Data}).
33864 The valid responses to Host I/O packets are:
33868 @item F @var{result} [, @var{errno}] [; @var{attachment}]
33869 @var{result} is the integer value returned by this operation, usually
33870 non-negative for success and -1 for errors. If an error has occured,
33871 @var{errno} will be included in the result. @var{errno} will have a
33872 value defined by the File-I/O protocol (@pxref{Errno Values}). For
33873 operations which return data, @var{attachment} supplies the data as a
33874 binary buffer. Binary buffers in response packets are escaped in the
33875 normal way (@pxref{Binary Data}). See the individual packet
33876 documentation for the interpretation of @var{result} and
33880 An empty response indicates that this operation is not recognized.
33884 These are the supported Host I/O operations:
33887 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
33888 Open a file at @var{pathname} and return a file descriptor for it, or
33889 return -1 if an error occurs. @var{pathname} is a string,
33890 @var{flags} is an integer indicating a mask of open flags
33891 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
33892 of mode bits to use if the file is created (@pxref{mode_t Values}).
33893 @xref{open}, for details of the open flags and mode values.
33895 @item vFile:close: @var{fd}
33896 Close the open file corresponding to @var{fd} and return 0, or
33897 -1 if an error occurs.
33899 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
33900 Read data from the open file corresponding to @var{fd}. Up to
33901 @var{count} bytes will be read from the file, starting at @var{offset}
33902 relative to the start of the file. The target may read fewer bytes;
33903 common reasons include packet size limits and an end-of-file
33904 condition. The number of bytes read is returned. Zero should only be
33905 returned for a successful read at the end of the file, or if
33906 @var{count} was zero.
33908 The data read should be returned as a binary attachment on success.
33909 If zero bytes were read, the response should include an empty binary
33910 attachment (i.e.@: a trailing semicolon). The return value is the
33911 number of target bytes read; the binary attachment may be longer if
33912 some characters were escaped.
33914 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
33915 Write @var{data} (a binary buffer) to the open file corresponding
33916 to @var{fd}. Start the write at @var{offset} from the start of the
33917 file. Unlike many @code{write} system calls, there is no
33918 separate @var{count} argument; the length of @var{data} in the
33919 packet is used. @samp{vFile:write} returns the number of bytes written,
33920 which may be shorter than the length of @var{data}, or -1 if an
33923 @item vFile:unlink: @var{pathname}
33924 Delete the file at @var{pathname} on the target. Return 0,
33925 or -1 if an error occurs. @var{pathname} is a string.
33930 @section Interrupts
33931 @cindex interrupts (remote protocol)
33933 When a program on the remote target is running, @value{GDBN} may
33934 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
33935 a @code{BREAK} followed by @code{g},
33936 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
33938 The precise meaning of @code{BREAK} is defined by the transport
33939 mechanism and may, in fact, be undefined. @value{GDBN} does not
33940 currently define a @code{BREAK} mechanism for any of the network
33941 interfaces except for TCP, in which case @value{GDBN} sends the
33942 @code{telnet} BREAK sequence.
33944 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
33945 transport mechanisms. It is represented by sending the single byte
33946 @code{0x03} without any of the usual packet overhead described in
33947 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
33948 transmitted as part of a packet, it is considered to be packet data
33949 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
33950 (@pxref{X packet}), used for binary downloads, may include an unescaped
33951 @code{0x03} as part of its packet.
33953 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
33954 When Linux kernel receives this sequence from serial port,
33955 it stops execution and connects to gdb.
33957 Stubs are not required to recognize these interrupt mechanisms and the
33958 precise meaning associated with receipt of the interrupt is
33959 implementation defined. If the target supports debugging of multiple
33960 threads and/or processes, it should attempt to interrupt all
33961 currently-executing threads and processes.
33962 If the stub is successful at interrupting the
33963 running program, it should send one of the stop
33964 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
33965 of successfully stopping the program in all-stop mode, and a stop reply
33966 for each stopped thread in non-stop mode.
33967 Interrupts received while the
33968 program is stopped are discarded.
33970 @node Notification Packets
33971 @section Notification Packets
33972 @cindex notification packets
33973 @cindex packets, notification
33975 The @value{GDBN} remote serial protocol includes @dfn{notifications},
33976 packets that require no acknowledgment. Both the GDB and the stub
33977 may send notifications (although the only notifications defined at
33978 present are sent by the stub). Notifications carry information
33979 without incurring the round-trip latency of an acknowledgment, and so
33980 are useful for low-impact communications where occasional packet loss
33983 A notification packet has the form @samp{% @var{data} #
33984 @var{checksum}}, where @var{data} is the content of the notification,
33985 and @var{checksum} is a checksum of @var{data}, computed and formatted
33986 as for ordinary @value{GDBN} packets. A notification's @var{data}
33987 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
33988 receiving a notification, the recipient sends no @samp{+} or @samp{-}
33989 to acknowledge the notification's receipt or to report its corruption.
33991 Every notification's @var{data} begins with a name, which contains no
33992 colon characters, followed by a colon character.
33994 Recipients should silently ignore corrupted notifications and
33995 notifications they do not understand. Recipients should restart
33996 timeout periods on receipt of a well-formed notification, whether or
33997 not they understand it.
33999 Senders should only send the notifications described here when this
34000 protocol description specifies that they are permitted. In the
34001 future, we may extend the protocol to permit existing notifications in
34002 new contexts; this rule helps older senders avoid confusing newer
34005 (Older versions of @value{GDBN} ignore bytes received until they see
34006 the @samp{$} byte that begins an ordinary packet, so new stubs may
34007 transmit notifications without fear of confusing older clients. There
34008 are no notifications defined for @value{GDBN} to send at the moment, but we
34009 assume that most older stubs would ignore them, as well.)
34011 The following notification packets from the stub to @value{GDBN} are
34015 @item Stop: @var{reply}
34016 Report an asynchronous stop event in non-stop mode.
34017 The @var{reply} has the form of a stop reply, as
34018 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34019 for information on how these notifications are acknowledged by
34023 @node Remote Non-Stop
34024 @section Remote Protocol Support for Non-Stop Mode
34026 @value{GDBN}'s remote protocol supports non-stop debugging of
34027 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34028 supports non-stop mode, it should report that to @value{GDBN} by including
34029 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34031 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34032 establishing a new connection with the stub. Entering non-stop mode
34033 does not alter the state of any currently-running threads, but targets
34034 must stop all threads in any already-attached processes when entering
34035 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34036 probe the target state after a mode change.
34038 In non-stop mode, when an attached process encounters an event that
34039 would otherwise be reported with a stop reply, it uses the
34040 asynchronous notification mechanism (@pxref{Notification Packets}) to
34041 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34042 in all processes are stopped when a stop reply is sent, in non-stop
34043 mode only the thread reporting the stop event is stopped. That is,
34044 when reporting a @samp{S} or @samp{T} response to indicate completion
34045 of a step operation, hitting a breakpoint, or a fault, only the
34046 affected thread is stopped; any other still-running threads continue
34047 to run. When reporting a @samp{W} or @samp{X} response, all running
34048 threads belonging to other attached processes continue to run.
34050 Only one stop reply notification at a time may be pending; if
34051 additional stop events occur before @value{GDBN} has acknowledged the
34052 previous notification, they must be queued by the stub for later
34053 synchronous transmission in response to @samp{vStopped} packets from
34054 @value{GDBN}. Because the notification mechanism is unreliable,
34055 the stub is permitted to resend a stop reply notification
34056 if it believes @value{GDBN} may not have received it. @value{GDBN}
34057 ignores additional stop reply notifications received before it has
34058 finished processing a previous notification and the stub has completed
34059 sending any queued stop events.
34061 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34062 notification at any time. Specifically, they may appear when
34063 @value{GDBN} is not otherwise reading input from the stub, or when
34064 @value{GDBN} is expecting to read a normal synchronous response or a
34065 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34066 Notification packets are distinct from any other communication from
34067 the stub so there is no ambiguity.
34069 After receiving a stop reply notification, @value{GDBN} shall
34070 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34071 as a regular, synchronous request to the stub. Such acknowledgment
34072 is not required to happen immediately, as @value{GDBN} is permitted to
34073 send other, unrelated packets to the stub first, which the stub should
34076 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34077 stop events to report to @value{GDBN}, it shall respond by sending a
34078 normal stop reply response. @value{GDBN} shall then send another
34079 @samp{vStopped} packet to solicit further responses; again, it is
34080 permitted to send other, unrelated packets as well which the stub
34081 should process normally.
34083 If the stub receives a @samp{vStopped} packet and there are no
34084 additional stop events to report, the stub shall return an @samp{OK}
34085 response. At this point, if further stop events occur, the stub shall
34086 send a new stop reply notification, @value{GDBN} shall accept the
34087 notification, and the process shall be repeated.
34089 In non-stop mode, the target shall respond to the @samp{?} packet as
34090 follows. First, any incomplete stop reply notification/@samp{vStopped}
34091 sequence in progress is abandoned. The target must begin a new
34092 sequence reporting stop events for all stopped threads, whether or not
34093 it has previously reported those events to @value{GDBN}. The first
34094 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34095 subsequent stop replies are sent as responses to @samp{vStopped} packets
34096 using the mechanism described above. The target must not send
34097 asynchronous stop reply notifications until the sequence is complete.
34098 If all threads are running when the target receives the @samp{?} packet,
34099 or if the target is not attached to any process, it shall respond
34102 @node Packet Acknowledgment
34103 @section Packet Acknowledgment
34105 @cindex acknowledgment, for @value{GDBN} remote
34106 @cindex packet acknowledgment, for @value{GDBN} remote
34107 By default, when either the host or the target machine receives a packet,
34108 the first response expected is an acknowledgment: either @samp{+} (to indicate
34109 the package was received correctly) or @samp{-} (to request retransmission).
34110 This mechanism allows the @value{GDBN} remote protocol to operate over
34111 unreliable transport mechanisms, such as a serial line.
34113 In cases where the transport mechanism is itself reliable (such as a pipe or
34114 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34115 It may be desirable to disable them in that case to reduce communication
34116 overhead, or for other reasons. This can be accomplished by means of the
34117 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34119 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34120 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34121 and response format still includes the normal checksum, as described in
34122 @ref{Overview}, but the checksum may be ignored by the receiver.
34124 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34125 no-acknowledgment mode, it should report that to @value{GDBN}
34126 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34127 @pxref{qSupported}.
34128 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34129 disabled via the @code{set remote noack-packet off} command
34130 (@pxref{Remote Configuration}),
34131 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34132 Only then may the stub actually turn off packet acknowledgments.
34133 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34134 response, which can be safely ignored by the stub.
34136 Note that @code{set remote noack-packet} command only affects negotiation
34137 between @value{GDBN} and the stub when subsequent connections are made;
34138 it does not affect the protocol acknowledgment state for any current
34140 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
34141 new connection is established,
34142 there is also no protocol request to re-enable the acknowledgments
34143 for the current connection, once disabled.
34148 Example sequence of a target being re-started. Notice how the restart
34149 does not get any direct output:
34154 @emph{target restarts}
34157 <- @code{T001:1234123412341234}
34161 Example sequence of a target being stepped by a single instruction:
34164 -> @code{G1445@dots{}}
34169 <- @code{T001:1234123412341234}
34173 <- @code{1455@dots{}}
34177 @node File-I/O Remote Protocol Extension
34178 @section File-I/O Remote Protocol Extension
34179 @cindex File-I/O remote protocol extension
34182 * File-I/O Overview::
34183 * Protocol Basics::
34184 * The F Request Packet::
34185 * The F Reply Packet::
34186 * The Ctrl-C Message::
34188 * List of Supported Calls::
34189 * Protocol-specific Representation of Datatypes::
34191 * File-I/O Examples::
34194 @node File-I/O Overview
34195 @subsection File-I/O Overview
34196 @cindex file-i/o overview
34198 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
34199 target to use the host's file system and console I/O to perform various
34200 system calls. System calls on the target system are translated into a
34201 remote protocol packet to the host system, which then performs the needed
34202 actions and returns a response packet to the target system.
34203 This simulates file system operations even on targets that lack file systems.
34205 The protocol is defined to be independent of both the host and target systems.
34206 It uses its own internal representation of datatypes and values. Both
34207 @value{GDBN} and the target's @value{GDBN} stub are responsible for
34208 translating the system-dependent value representations into the internal
34209 protocol representations when data is transmitted.
34211 The communication is synchronous. A system call is possible only when
34212 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
34213 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
34214 the target is stopped to allow deterministic access to the target's
34215 memory. Therefore File-I/O is not interruptible by target signals. On
34216 the other hand, it is possible to interrupt File-I/O by a user interrupt
34217 (@samp{Ctrl-C}) within @value{GDBN}.
34219 The target's request to perform a host system call does not finish
34220 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
34221 after finishing the system call, the target returns to continuing the
34222 previous activity (continue, step). No additional continue or step
34223 request from @value{GDBN} is required.
34226 (@value{GDBP}) continue
34227 <- target requests 'system call X'
34228 target is stopped, @value{GDBN} executes system call
34229 -> @value{GDBN} returns result
34230 ... target continues, @value{GDBN} returns to wait for the target
34231 <- target hits breakpoint and sends a Txx packet
34234 The protocol only supports I/O on the console and to regular files on
34235 the host file system. Character or block special devices, pipes,
34236 named pipes, sockets or any other communication method on the host
34237 system are not supported by this protocol.
34239 File I/O is not supported in non-stop mode.
34241 @node Protocol Basics
34242 @subsection Protocol Basics
34243 @cindex protocol basics, file-i/o
34245 The File-I/O protocol uses the @code{F} packet as the request as well
34246 as reply packet. Since a File-I/O system call can only occur when
34247 @value{GDBN} is waiting for a response from the continuing or stepping target,
34248 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34249 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34250 This @code{F} packet contains all information needed to allow @value{GDBN}
34251 to call the appropriate host system call:
34255 A unique identifier for the requested system call.
34258 All parameters to the system call. Pointers are given as addresses
34259 in the target memory address space. Pointers to strings are given as
34260 pointer/length pair. Numerical values are given as they are.
34261 Numerical control flags are given in a protocol-specific representation.
34265 At this point, @value{GDBN} has to perform the following actions.
34269 If the parameters include pointer values to data needed as input to a
34270 system call, @value{GDBN} requests this data from the target with a
34271 standard @code{m} packet request. This additional communication has to be
34272 expected by the target implementation and is handled as any other @code{m}
34276 @value{GDBN} translates all value from protocol representation to host
34277 representation as needed. Datatypes are coerced into the host types.
34280 @value{GDBN} calls the system call.
34283 It then coerces datatypes back to protocol representation.
34286 If the system call is expected to return data in buffer space specified
34287 by pointer parameters to the call, the data is transmitted to the
34288 target using a @code{M} or @code{X} packet. This packet has to be expected
34289 by the target implementation and is handled as any other @code{M} or @code{X}
34294 Eventually @value{GDBN} replies with another @code{F} packet which contains all
34295 necessary information for the target to continue. This at least contains
34302 @code{errno}, if has been changed by the system call.
34309 After having done the needed type and value coercion, the target continues
34310 the latest continue or step action.
34312 @node The F Request Packet
34313 @subsection The @code{F} Request Packet
34314 @cindex file-i/o request packet
34315 @cindex @code{F} request packet
34317 The @code{F} request packet has the following format:
34320 @item F@var{call-id},@var{parameter@dots{}}
34322 @var{call-id} is the identifier to indicate the host system call to be called.
34323 This is just the name of the function.
34325 @var{parameter@dots{}} are the parameters to the system call.
34326 Parameters are hexadecimal integer values, either the actual values in case
34327 of scalar datatypes, pointers to target buffer space in case of compound
34328 datatypes and unspecified memory areas, or pointer/length pairs in case
34329 of string parameters. These are appended to the @var{call-id} as a
34330 comma-delimited list. All values are transmitted in ASCII
34331 string representation, pointer/length pairs separated by a slash.
34337 @node The F Reply Packet
34338 @subsection The @code{F} Reply Packet
34339 @cindex file-i/o reply packet
34340 @cindex @code{F} reply packet
34342 The @code{F} reply packet has the following format:
34346 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
34348 @var{retcode} is the return code of the system call as hexadecimal value.
34350 @var{errno} is the @code{errno} set by the call, in protocol-specific
34352 This parameter can be omitted if the call was successful.
34354 @var{Ctrl-C flag} is only sent if the user requested a break. In this
34355 case, @var{errno} must be sent as well, even if the call was successful.
34356 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
34363 or, if the call was interrupted before the host call has been performed:
34370 assuming 4 is the protocol-specific representation of @code{EINTR}.
34375 @node The Ctrl-C Message
34376 @subsection The @samp{Ctrl-C} Message
34377 @cindex ctrl-c message, in file-i/o protocol
34379 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
34380 reply packet (@pxref{The F Reply Packet}),
34381 the target should behave as if it had
34382 gotten a break message. The meaning for the target is ``system call
34383 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
34384 (as with a break message) and return to @value{GDBN} with a @code{T02}
34387 It's important for the target to know in which
34388 state the system call was interrupted. There are two possible cases:
34392 The system call hasn't been performed on the host yet.
34395 The system call on the host has been finished.
34399 These two states can be distinguished by the target by the value of the
34400 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
34401 call hasn't been performed. This is equivalent to the @code{EINTR} handling
34402 on POSIX systems. In any other case, the target may presume that the
34403 system call has been finished --- successfully or not --- and should behave
34404 as if the break message arrived right after the system call.
34406 @value{GDBN} must behave reliably. If the system call has not been called
34407 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
34408 @code{errno} in the packet. If the system call on the host has been finished
34409 before the user requests a break, the full action must be finished by
34410 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
34411 The @code{F} packet may only be sent when either nothing has happened
34412 or the full action has been completed.
34415 @subsection Console I/O
34416 @cindex console i/o as part of file-i/o
34418 By default and if not explicitly closed by the target system, the file
34419 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
34420 on the @value{GDBN} console is handled as any other file output operation
34421 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
34422 by @value{GDBN} so that after the target read request from file descriptor
34423 0 all following typing is buffered until either one of the following
34428 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
34430 system call is treated as finished.
34433 The user presses @key{RET}. This is treated as end of input with a trailing
34437 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
34438 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
34442 If the user has typed more characters than fit in the buffer given to
34443 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
34444 either another @code{read(0, @dots{})} is requested by the target, or debugging
34445 is stopped at the user's request.
34448 @node List of Supported Calls
34449 @subsection List of Supported Calls
34450 @cindex list of supported file-i/o calls
34467 @unnumberedsubsubsec open
34468 @cindex open, file-i/o system call
34473 int open(const char *pathname, int flags);
34474 int open(const char *pathname, int flags, mode_t mode);
34478 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
34481 @var{flags} is the bitwise @code{OR} of the following values:
34485 If the file does not exist it will be created. The host
34486 rules apply as far as file ownership and time stamps
34490 When used with @code{O_CREAT}, if the file already exists it is
34491 an error and open() fails.
34494 If the file already exists and the open mode allows
34495 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
34496 truncated to zero length.
34499 The file is opened in append mode.
34502 The file is opened for reading only.
34505 The file is opened for writing only.
34508 The file is opened for reading and writing.
34512 Other bits are silently ignored.
34516 @var{mode} is the bitwise @code{OR} of the following values:
34520 User has read permission.
34523 User has write permission.
34526 Group has read permission.
34529 Group has write permission.
34532 Others have read permission.
34535 Others have write permission.
34539 Other bits are silently ignored.
34542 @item Return value:
34543 @code{open} returns the new file descriptor or -1 if an error
34550 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
34553 @var{pathname} refers to a directory.
34556 The requested access is not allowed.
34559 @var{pathname} was too long.
34562 A directory component in @var{pathname} does not exist.
34565 @var{pathname} refers to a device, pipe, named pipe or socket.
34568 @var{pathname} refers to a file on a read-only filesystem and
34569 write access was requested.
34572 @var{pathname} is an invalid pointer value.
34575 No space on device to create the file.
34578 The process already has the maximum number of files open.
34581 The limit on the total number of files open on the system
34585 The call was interrupted by the user.
34591 @unnumberedsubsubsec close
34592 @cindex close, file-i/o system call
34601 @samp{Fclose,@var{fd}}
34603 @item Return value:
34604 @code{close} returns zero on success, or -1 if an error occurred.
34610 @var{fd} isn't a valid open file descriptor.
34613 The call was interrupted by the user.
34619 @unnumberedsubsubsec read
34620 @cindex read, file-i/o system call
34625 int read(int fd, void *buf, unsigned int count);
34629 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
34631 @item Return value:
34632 On success, the number of bytes read is returned.
34633 Zero indicates end of file. If count is zero, read
34634 returns zero as well. On error, -1 is returned.
34640 @var{fd} is not a valid file descriptor or is not open for
34644 @var{bufptr} is an invalid pointer value.
34647 The call was interrupted by the user.
34653 @unnumberedsubsubsec write
34654 @cindex write, file-i/o system call
34659 int write(int fd, const void *buf, unsigned int count);
34663 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
34665 @item Return value:
34666 On success, the number of bytes written are returned.
34667 Zero indicates nothing was written. On error, -1
34674 @var{fd} is not a valid file descriptor or is not open for
34678 @var{bufptr} is an invalid pointer value.
34681 An attempt was made to write a file that exceeds the
34682 host-specific maximum file size allowed.
34685 No space on device to write the data.
34688 The call was interrupted by the user.
34694 @unnumberedsubsubsec lseek
34695 @cindex lseek, file-i/o system call
34700 long lseek (int fd, long offset, int flag);
34704 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
34706 @var{flag} is one of:
34710 The offset is set to @var{offset} bytes.
34713 The offset is set to its current location plus @var{offset}
34717 The offset is set to the size of the file plus @var{offset}
34721 @item Return value:
34722 On success, the resulting unsigned offset in bytes from
34723 the beginning of the file is returned. Otherwise, a
34724 value of -1 is returned.
34730 @var{fd} is not a valid open file descriptor.
34733 @var{fd} is associated with the @value{GDBN} console.
34736 @var{flag} is not a proper value.
34739 The call was interrupted by the user.
34745 @unnumberedsubsubsec rename
34746 @cindex rename, file-i/o system call
34751 int rename(const char *oldpath, const char *newpath);
34755 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34757 @item Return value:
34758 On success, zero is returned. On error, -1 is returned.
34764 @var{newpath} is an existing directory, but @var{oldpath} is not a
34768 @var{newpath} is a non-empty directory.
34771 @var{oldpath} or @var{newpath} is a directory that is in use by some
34775 An attempt was made to make a directory a subdirectory
34779 A component used as a directory in @var{oldpath} or new
34780 path is not a directory. Or @var{oldpath} is a directory
34781 and @var{newpath} exists but is not a directory.
34784 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34787 No access to the file or the path of the file.
34791 @var{oldpath} or @var{newpath} was too long.
34794 A directory component in @var{oldpath} or @var{newpath} does not exist.
34797 The file is on a read-only filesystem.
34800 The device containing the file has no room for the new
34804 The call was interrupted by the user.
34810 @unnumberedsubsubsec unlink
34811 @cindex unlink, file-i/o system call
34816 int unlink(const char *pathname);
34820 @samp{Funlink,@var{pathnameptr}/@var{len}}
34822 @item Return value:
34823 On success, zero is returned. On error, -1 is returned.
34829 No access to the file or the path of the file.
34832 The system does not allow unlinking of directories.
34835 The file @var{pathname} cannot be unlinked because it's
34836 being used by another process.
34839 @var{pathnameptr} is an invalid pointer value.
34842 @var{pathname} was too long.
34845 A directory component in @var{pathname} does not exist.
34848 A component of the path is not a directory.
34851 The file is on a read-only filesystem.
34854 The call was interrupted by the user.
34860 @unnumberedsubsubsec stat/fstat
34861 @cindex fstat, file-i/o system call
34862 @cindex stat, file-i/o system call
34867 int stat(const char *pathname, struct stat *buf);
34868 int fstat(int fd, struct stat *buf);
34872 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
34873 @samp{Ffstat,@var{fd},@var{bufptr}}
34875 @item Return value:
34876 On success, zero is returned. On error, -1 is returned.
34882 @var{fd} is not a valid open file.
34885 A directory component in @var{pathname} does not exist or the
34886 path is an empty string.
34889 A component of the path is not a directory.
34892 @var{pathnameptr} is an invalid pointer value.
34895 No access to the file or the path of the file.
34898 @var{pathname} was too long.
34901 The call was interrupted by the user.
34907 @unnumberedsubsubsec gettimeofday
34908 @cindex gettimeofday, file-i/o system call
34913 int gettimeofday(struct timeval *tv, void *tz);
34917 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
34919 @item Return value:
34920 On success, 0 is returned, -1 otherwise.
34926 @var{tz} is a non-NULL pointer.
34929 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
34935 @unnumberedsubsubsec isatty
34936 @cindex isatty, file-i/o system call
34941 int isatty(int fd);
34945 @samp{Fisatty,@var{fd}}
34947 @item Return value:
34948 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
34954 The call was interrupted by the user.
34959 Note that the @code{isatty} call is treated as a special case: it returns
34960 1 to the target if the file descriptor is attached
34961 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
34962 would require implementing @code{ioctl} and would be more complex than
34967 @unnumberedsubsubsec system
34968 @cindex system, file-i/o system call
34973 int system(const char *command);
34977 @samp{Fsystem,@var{commandptr}/@var{len}}
34979 @item Return value:
34980 If @var{len} is zero, the return value indicates whether a shell is
34981 available. A zero return value indicates a shell is not available.
34982 For non-zero @var{len}, the value returned is -1 on error and the
34983 return status of the command otherwise. Only the exit status of the
34984 command is returned, which is extracted from the host's @code{system}
34985 return value by calling @code{WEXITSTATUS(retval)}. In case
34986 @file{/bin/sh} could not be executed, 127 is returned.
34992 The call was interrupted by the user.
34997 @value{GDBN} takes over the full task of calling the necessary host calls
34998 to perform the @code{system} call. The return value of @code{system} on
34999 the host is simplified before it's returned
35000 to the target. Any termination signal information from the child process
35001 is discarded, and the return value consists
35002 entirely of the exit status of the called command.
35004 Due to security concerns, the @code{system} call is by default refused
35005 by @value{GDBN}. The user has to allow this call explicitly with the
35006 @code{set remote system-call-allowed 1} command.
35009 @item set remote system-call-allowed
35010 @kindex set remote system-call-allowed
35011 Control whether to allow the @code{system} calls in the File I/O
35012 protocol for the remote target. The default is zero (disabled).
35014 @item show remote system-call-allowed
35015 @kindex show remote system-call-allowed
35016 Show whether the @code{system} calls are allowed in the File I/O
35020 @node Protocol-specific Representation of Datatypes
35021 @subsection Protocol-specific Representation of Datatypes
35022 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35025 * Integral Datatypes::
35027 * Memory Transfer::
35032 @node Integral Datatypes
35033 @unnumberedsubsubsec Integral Datatypes
35034 @cindex integral datatypes, in file-i/o protocol
35036 The integral datatypes used in the system calls are @code{int},
35037 @code{unsigned int}, @code{long}, @code{unsigned long},
35038 @code{mode_t}, and @code{time_t}.
35040 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35041 implemented as 32 bit values in this protocol.
35043 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35045 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35046 in @file{limits.h}) to allow range checking on host and target.
35048 @code{time_t} datatypes are defined as seconds since the Epoch.
35050 All integral datatypes transferred as part of a memory read or write of a
35051 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35054 @node Pointer Values
35055 @unnumberedsubsubsec Pointer Values
35056 @cindex pointer values, in file-i/o protocol
35058 Pointers to target data are transmitted as they are. An exception
35059 is made for pointers to buffers for which the length isn't
35060 transmitted as part of the function call, namely strings. Strings
35061 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35068 which is a pointer to data of length 18 bytes at position 0x1aaf.
35069 The length is defined as the full string length in bytes, including
35070 the trailing null byte. For example, the string @code{"hello world"}
35071 at address 0x123456 is transmitted as
35077 @node Memory Transfer
35078 @unnumberedsubsubsec Memory Transfer
35079 @cindex memory transfer, in file-i/o protocol
35081 Structured data which is transferred using a memory read or write (for
35082 example, a @code{struct stat}) is expected to be in a protocol-specific format
35083 with all scalar multibyte datatypes being big endian. Translation to
35084 this representation needs to be done both by the target before the @code{F}
35085 packet is sent, and by @value{GDBN} before
35086 it transfers memory to the target. Transferred pointers to structured
35087 data should point to the already-coerced data at any time.
35091 @unnumberedsubsubsec struct stat
35092 @cindex struct stat, in file-i/o protocol
35094 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35095 is defined as follows:
35099 unsigned int st_dev; /* device */
35100 unsigned int st_ino; /* inode */
35101 mode_t st_mode; /* protection */
35102 unsigned int st_nlink; /* number of hard links */
35103 unsigned int st_uid; /* user ID of owner */
35104 unsigned int st_gid; /* group ID of owner */
35105 unsigned int st_rdev; /* device type (if inode device) */
35106 unsigned long st_size; /* total size, in bytes */
35107 unsigned long st_blksize; /* blocksize for filesystem I/O */
35108 unsigned long st_blocks; /* number of blocks allocated */
35109 time_t st_atime; /* time of last access */
35110 time_t st_mtime; /* time of last modification */
35111 time_t st_ctime; /* time of last change */
35115 The integral datatypes conform to the definitions given in the
35116 appropriate section (see @ref{Integral Datatypes}, for details) so this
35117 structure is of size 64 bytes.
35119 The values of several fields have a restricted meaning and/or
35125 A value of 0 represents a file, 1 the console.
35128 No valid meaning for the target. Transmitted unchanged.
35131 Valid mode bits are described in @ref{Constants}. Any other
35132 bits have currently no meaning for the target.
35137 No valid meaning for the target. Transmitted unchanged.
35142 These values have a host and file system dependent
35143 accuracy. Especially on Windows hosts, the file system may not
35144 support exact timing values.
35147 The target gets a @code{struct stat} of the above representation and is
35148 responsible for coercing it to the target representation before
35151 Note that due to size differences between the host, target, and protocol
35152 representations of @code{struct stat} members, these members could eventually
35153 get truncated on the target.
35155 @node struct timeval
35156 @unnumberedsubsubsec struct timeval
35157 @cindex struct timeval, in file-i/o protocol
35159 The buffer of type @code{struct timeval} used by the File-I/O protocol
35160 is defined as follows:
35164 time_t tv_sec; /* second */
35165 long tv_usec; /* microsecond */
35169 The integral datatypes conform to the definitions given in the
35170 appropriate section (see @ref{Integral Datatypes}, for details) so this
35171 structure is of size 8 bytes.
35174 @subsection Constants
35175 @cindex constants, in file-i/o protocol
35177 The following values are used for the constants inside of the
35178 protocol. @value{GDBN} and target are responsible for translating these
35179 values before and after the call as needed.
35190 @unnumberedsubsubsec Open Flags
35191 @cindex open flags, in file-i/o protocol
35193 All values are given in hexadecimal representation.
35205 @node mode_t Values
35206 @unnumberedsubsubsec mode_t Values
35207 @cindex mode_t values, in file-i/o protocol
35209 All values are given in octal representation.
35226 @unnumberedsubsubsec Errno Values
35227 @cindex errno values, in file-i/o protocol
35229 All values are given in decimal representation.
35254 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35255 any error value not in the list of supported error numbers.
35258 @unnumberedsubsubsec Lseek Flags
35259 @cindex lseek flags, in file-i/o protocol
35268 @unnumberedsubsubsec Limits
35269 @cindex limits, in file-i/o protocol
35271 All values are given in decimal representation.
35274 INT_MIN -2147483648
35276 UINT_MAX 4294967295
35277 LONG_MIN -9223372036854775808
35278 LONG_MAX 9223372036854775807
35279 ULONG_MAX 18446744073709551615
35282 @node File-I/O Examples
35283 @subsection File-I/O Examples
35284 @cindex file-i/o examples
35286 Example sequence of a write call, file descriptor 3, buffer is at target
35287 address 0x1234, 6 bytes should be written:
35290 <- @code{Fwrite,3,1234,6}
35291 @emph{request memory read from target}
35294 @emph{return "6 bytes written"}
35298 Example sequence of a read call, file descriptor 3, buffer is at target
35299 address 0x1234, 6 bytes should be read:
35302 <- @code{Fread,3,1234,6}
35303 @emph{request memory write to target}
35304 -> @code{X1234,6:XXXXXX}
35305 @emph{return "6 bytes read"}
35309 Example sequence of a read call, call fails on the host due to invalid
35310 file descriptor (@code{EBADF}):
35313 <- @code{Fread,3,1234,6}
35317 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
35321 <- @code{Fread,3,1234,6}
35326 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
35330 <- @code{Fread,3,1234,6}
35331 -> @code{X1234,6:XXXXXX}
35335 @node Library List Format
35336 @section Library List Format
35337 @cindex library list format, remote protocol
35339 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
35340 same process as your application to manage libraries. In this case,
35341 @value{GDBN} can use the loader's symbol table and normal memory
35342 operations to maintain a list of shared libraries. On other
35343 platforms, the operating system manages loaded libraries.
35344 @value{GDBN} can not retrieve the list of currently loaded libraries
35345 through memory operations, so it uses the @samp{qXfer:libraries:read}
35346 packet (@pxref{qXfer library list read}) instead. The remote stub
35347 queries the target's operating system and reports which libraries
35350 The @samp{qXfer:libraries:read} packet returns an XML document which
35351 lists loaded libraries and their offsets. Each library has an
35352 associated name and one or more segment or section base addresses,
35353 which report where the library was loaded in memory.
35355 For the common case of libraries that are fully linked binaries, the
35356 library should have a list of segments. If the target supports
35357 dynamic linking of a relocatable object file, its library XML element
35358 should instead include a list of allocated sections. The segment or
35359 section bases are start addresses, not relocation offsets; they do not
35360 depend on the library's link-time base addresses.
35362 @value{GDBN} must be linked with the Expat library to support XML
35363 library lists. @xref{Expat}.
35365 A simple memory map, with one loaded library relocated by a single
35366 offset, looks like this:
35370 <library name="/lib/libc.so.6">
35371 <segment address="0x10000000"/>
35376 Another simple memory map, with one loaded library with three
35377 allocated sections (.text, .data, .bss), looks like this:
35381 <library name="sharedlib.o">
35382 <section address="0x10000000"/>
35383 <section address="0x20000000"/>
35384 <section address="0x30000000"/>
35389 The format of a library list is described by this DTD:
35392 <!-- library-list: Root element with versioning -->
35393 <!ELEMENT library-list (library)*>
35394 <!ATTLIST library-list version CDATA #FIXED "1.0">
35395 <!ELEMENT library (segment*, section*)>
35396 <!ATTLIST library name CDATA #REQUIRED>
35397 <!ELEMENT segment EMPTY>
35398 <!ATTLIST segment address CDATA #REQUIRED>
35399 <!ELEMENT section EMPTY>
35400 <!ATTLIST section address CDATA #REQUIRED>
35403 In addition, segments and section descriptors cannot be mixed within a
35404 single library element, and you must supply at least one segment or
35405 section for each library.
35407 @node Memory Map Format
35408 @section Memory Map Format
35409 @cindex memory map format
35411 To be able to write into flash memory, @value{GDBN} needs to obtain a
35412 memory map from the target. This section describes the format of the
35415 The memory map is obtained using the @samp{qXfer:memory-map:read}
35416 (@pxref{qXfer memory map read}) packet and is an XML document that
35417 lists memory regions.
35419 @value{GDBN} must be linked with the Expat library to support XML
35420 memory maps. @xref{Expat}.
35422 The top-level structure of the document is shown below:
35425 <?xml version="1.0"?>
35426 <!DOCTYPE memory-map
35427 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
35428 "http://sourceware.org/gdb/gdb-memory-map.dtd">
35434 Each region can be either:
35439 A region of RAM starting at @var{addr} and extending for @var{length}
35443 <memory type="ram" start="@var{addr}" length="@var{length}"/>
35448 A region of read-only memory:
35451 <memory type="rom" start="@var{addr}" length="@var{length}"/>
35456 A region of flash memory, with erasure blocks @var{blocksize}
35460 <memory type="flash" start="@var{addr}" length="@var{length}">
35461 <property name="blocksize">@var{blocksize}</property>
35467 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
35468 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
35469 packets to write to addresses in such ranges.
35471 The formal DTD for memory map format is given below:
35474 <!-- ................................................... -->
35475 <!-- Memory Map XML DTD ................................ -->
35476 <!-- File: memory-map.dtd .............................. -->
35477 <!-- .................................... .............. -->
35478 <!-- memory-map.dtd -->
35479 <!-- memory-map: Root element with versioning -->
35480 <!ELEMENT memory-map (memory | property)>
35481 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
35482 <!ELEMENT memory (property)>
35483 <!-- memory: Specifies a memory region,
35484 and its type, or device. -->
35485 <!ATTLIST memory type CDATA #REQUIRED
35486 start CDATA #REQUIRED
35487 length CDATA #REQUIRED
35488 device CDATA #IMPLIED>
35489 <!-- property: Generic attribute tag -->
35490 <!ELEMENT property (#PCDATA | property)*>
35491 <!ATTLIST property name CDATA #REQUIRED>
35494 @node Thread List Format
35495 @section Thread List Format
35496 @cindex thread list format
35498 To efficiently update the list of threads and their attributes,
35499 @value{GDBN} issues the @samp{qXfer:threads:read} packet
35500 (@pxref{qXfer threads read}) and obtains the XML document with
35501 the following structure:
35504 <?xml version="1.0"?>
35506 <thread id="id" core="0">
35507 ... description ...
35512 Each @samp{thread} element must have the @samp{id} attribute that
35513 identifies the thread (@pxref{thread-id syntax}). The
35514 @samp{core} attribute, if present, specifies which processor core
35515 the thread was last executing on. The content of the of @samp{thread}
35516 element is interpreted as human-readable auxilliary information.
35518 @include agentexpr.texi
35520 @node Trace File Format
35521 @appendix Trace File Format
35522 @cindex trace file format
35524 The trace file comes in three parts: a header, a textual description
35525 section, and a trace frame section with binary data.
35527 The header has the form @code{\x7fTRACE0\n}. The first byte is
35528 @code{0x7f} so as to indicate that the file contains binary data,
35529 while the @code{0} is a version number that may have different values
35532 The description section consists of multiple lines of @sc{ascii} text
35533 separated by newline characters (@code{0xa}). The lines may include a
35534 variety of optional descriptive or context-setting information, such
35535 as tracepoint definitions or register set size. @value{GDBN} will
35536 ignore any line that it does not recognize. An empty line marks the end
35539 @c FIXME add some specific types of data
35541 The trace frame section consists of a number of consecutive frames.
35542 Each frame begins with a two-byte tracepoint number, followed by a
35543 four-byte size giving the amount of data in the frame. The data in
35544 the frame consists of a number of blocks, each introduced by a
35545 character indicating its type (at least register, memory, and trace
35546 state variable). The data in this section is raw binary, not a
35547 hexadecimal or other encoding; its endianness matches the target's
35550 @c FIXME bi-arch may require endianness/arch info in description section
35553 @item R @var{bytes}
35554 Register block. The number and ordering of bytes matches that of a
35555 @code{g} packet in the remote protocol. Note that these are the
35556 actual bytes, in target order and @value{GDBN} register order, not a
35557 hexadecimal encoding.
35559 @item M @var{address} @var{length} @var{bytes}...
35560 Memory block. This is a contiguous block of memory, at the 8-byte
35561 address @var{address}, with a 2-byte length @var{length}, followed by
35562 @var{length} bytes.
35564 @item V @var{number} @var{value}
35565 Trace state variable block. This records the 8-byte signed value
35566 @var{value} of trace state variable numbered @var{number}.
35570 Future enhancements of the trace file format may include additional types
35573 @node Target Descriptions
35574 @appendix Target Descriptions
35575 @cindex target descriptions
35577 @strong{Warning:} target descriptions are still under active development,
35578 and the contents and format may change between @value{GDBN} releases.
35579 The format is expected to stabilize in the future.
35581 One of the challenges of using @value{GDBN} to debug embedded systems
35582 is that there are so many minor variants of each processor
35583 architecture in use. It is common practice for vendors to start with
35584 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
35585 and then make changes to adapt it to a particular market niche. Some
35586 architectures have hundreds of variants, available from dozens of
35587 vendors. This leads to a number of problems:
35591 With so many different customized processors, it is difficult for
35592 the @value{GDBN} maintainers to keep up with the changes.
35594 Since individual variants may have short lifetimes or limited
35595 audiences, it may not be worthwhile to carry information about every
35596 variant in the @value{GDBN} source tree.
35598 When @value{GDBN} does support the architecture of the embedded system
35599 at hand, the task of finding the correct architecture name to give the
35600 @command{set architecture} command can be error-prone.
35603 To address these problems, the @value{GDBN} remote protocol allows a
35604 target system to not only identify itself to @value{GDBN}, but to
35605 actually describe its own features. This lets @value{GDBN} support
35606 processor variants it has never seen before --- to the extent that the
35607 descriptions are accurate, and that @value{GDBN} understands them.
35609 @value{GDBN} must be linked with the Expat library to support XML
35610 target descriptions. @xref{Expat}.
35613 * Retrieving Descriptions:: How descriptions are fetched from a target.
35614 * Target Description Format:: The contents of a target description.
35615 * Predefined Target Types:: Standard types available for target
35617 * Standard Target Features:: Features @value{GDBN} knows about.
35620 @node Retrieving Descriptions
35621 @section Retrieving Descriptions
35623 Target descriptions can be read from the target automatically, or
35624 specified by the user manually. The default behavior is to read the
35625 description from the target. @value{GDBN} retrieves it via the remote
35626 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
35627 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
35628 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
35629 XML document, of the form described in @ref{Target Description
35632 Alternatively, you can specify a file to read for the target description.
35633 If a file is set, the target will not be queried. The commands to
35634 specify a file are:
35637 @cindex set tdesc filename
35638 @item set tdesc filename @var{path}
35639 Read the target description from @var{path}.
35641 @cindex unset tdesc filename
35642 @item unset tdesc filename
35643 Do not read the XML target description from a file. @value{GDBN}
35644 will use the description supplied by the current target.
35646 @cindex show tdesc filename
35647 @item show tdesc filename
35648 Show the filename to read for a target description, if any.
35652 @node Target Description Format
35653 @section Target Description Format
35654 @cindex target descriptions, XML format
35656 A target description annex is an @uref{http://www.w3.org/XML/, XML}
35657 document which complies with the Document Type Definition provided in
35658 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
35659 means you can use generally available tools like @command{xmllint} to
35660 check that your feature descriptions are well-formed and valid.
35661 However, to help people unfamiliar with XML write descriptions for
35662 their targets, we also describe the grammar here.
35664 Target descriptions can identify the architecture of the remote target
35665 and (for some architectures) provide information about custom register
35666 sets. They can also identify the OS ABI of the remote target.
35667 @value{GDBN} can use this information to autoconfigure for your
35668 target, or to warn you if you connect to an unsupported target.
35670 Here is a simple target description:
35673 <target version="1.0">
35674 <architecture>i386:x86-64</architecture>
35679 This minimal description only says that the target uses
35680 the x86-64 architecture.
35682 A target description has the following overall form, with [ ] marking
35683 optional elements and @dots{} marking repeatable elements. The elements
35684 are explained further below.
35687 <?xml version="1.0"?>
35688 <!DOCTYPE target SYSTEM "gdb-target.dtd">
35689 <target version="1.0">
35690 @r{[}@var{architecture}@r{]}
35691 @r{[}@var{osabi}@r{]}
35692 @r{[}@var{compatible}@r{]}
35693 @r{[}@var{feature}@dots{}@r{]}
35698 The description is generally insensitive to whitespace and line
35699 breaks, under the usual common-sense rules. The XML version
35700 declaration and document type declaration can generally be omitted
35701 (@value{GDBN} does not require them), but specifying them may be
35702 useful for XML validation tools. The @samp{version} attribute for
35703 @samp{<target>} may also be omitted, but we recommend
35704 including it; if future versions of @value{GDBN} use an incompatible
35705 revision of @file{gdb-target.dtd}, they will detect and report
35706 the version mismatch.
35708 @subsection Inclusion
35709 @cindex target descriptions, inclusion
35712 @cindex <xi:include>
35715 It can sometimes be valuable to split a target description up into
35716 several different annexes, either for organizational purposes, or to
35717 share files between different possible target descriptions. You can
35718 divide a description into multiple files by replacing any element of
35719 the target description with an inclusion directive of the form:
35722 <xi:include href="@var{document}"/>
35726 When @value{GDBN} encounters an element of this form, it will retrieve
35727 the named XML @var{document}, and replace the inclusion directive with
35728 the contents of that document. If the current description was read
35729 using @samp{qXfer}, then so will be the included document;
35730 @var{document} will be interpreted as the name of an annex. If the
35731 current description was read from a file, @value{GDBN} will look for
35732 @var{document} as a file in the same directory where it found the
35733 original description.
35735 @subsection Architecture
35736 @cindex <architecture>
35738 An @samp{<architecture>} element has this form:
35741 <architecture>@var{arch}</architecture>
35744 @var{arch} is one of the architectures from the set accepted by
35745 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35748 @cindex @code{<osabi>}
35750 This optional field was introduced in @value{GDBN} version 7.0.
35751 Previous versions of @value{GDBN} ignore it.
35753 An @samp{<osabi>} element has this form:
35756 <osabi>@var{abi-name}</osabi>
35759 @var{abi-name} is an OS ABI name from the same selection accepted by
35760 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35762 @subsection Compatible Architecture
35763 @cindex @code{<compatible>}
35765 This optional field was introduced in @value{GDBN} version 7.0.
35766 Previous versions of @value{GDBN} ignore it.
35768 A @samp{<compatible>} element has this form:
35771 <compatible>@var{arch}</compatible>
35774 @var{arch} is one of the architectures from the set accepted by
35775 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35777 A @samp{<compatible>} element is used to specify that the target
35778 is able to run binaries in some other than the main target architecture
35779 given by the @samp{<architecture>} element. For example, on the
35780 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35781 or @code{powerpc:common64}, but the system is able to run binaries
35782 in the @code{spu} architecture as well. The way to describe this
35783 capability with @samp{<compatible>} is as follows:
35786 <architecture>powerpc:common</architecture>
35787 <compatible>spu</compatible>
35790 @subsection Features
35793 Each @samp{<feature>} describes some logical portion of the target
35794 system. Features are currently used to describe available CPU
35795 registers and the types of their contents. A @samp{<feature>} element
35799 <feature name="@var{name}">
35800 @r{[}@var{type}@dots{}@r{]}
35806 Each feature's name should be unique within the description. The name
35807 of a feature does not matter unless @value{GDBN} has some special
35808 knowledge of the contents of that feature; if it does, the feature
35809 should have its standard name. @xref{Standard Target Features}.
35813 Any register's value is a collection of bits which @value{GDBN} must
35814 interpret. The default interpretation is a two's complement integer,
35815 but other types can be requested by name in the register description.
35816 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35817 Target Types}), and the description can define additional composite types.
35819 Each type element must have an @samp{id} attribute, which gives
35820 a unique (within the containing @samp{<feature>}) name to the type.
35821 Types must be defined before they are used.
35824 Some targets offer vector registers, which can be treated as arrays
35825 of scalar elements. These types are written as @samp{<vector>} elements,
35826 specifying the array element type, @var{type}, and the number of elements,
35830 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35834 If a register's value is usefully viewed in multiple ways, define it
35835 with a union type containing the useful representations. The
35836 @samp{<union>} element contains one or more @samp{<field>} elements,
35837 each of which has a @var{name} and a @var{type}:
35840 <union id="@var{id}">
35841 <field name="@var{name}" type="@var{type}"/>
35847 If a register's value is composed from several separate values, define
35848 it with a structure type. There are two forms of the @samp{<struct>}
35849 element; a @samp{<struct>} element must either contain only bitfields
35850 or contain no bitfields. If the structure contains only bitfields,
35851 its total size in bytes must be specified, each bitfield must have an
35852 explicit start and end, and bitfields are automatically assigned an
35853 integer type. The field's @var{start} should be less than or
35854 equal to its @var{end}, and zero represents the least significant bit.
35857 <struct id="@var{id}" size="@var{size}">
35858 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35863 If the structure contains no bitfields, then each field has an
35864 explicit type, and no implicit padding is added.
35867 <struct id="@var{id}">
35868 <field name="@var{name}" type="@var{type}"/>
35874 If a register's value is a series of single-bit flags, define it with
35875 a flags type. The @samp{<flags>} element has an explicit @var{size}
35876 and contains one or more @samp{<field>} elements. Each field has a
35877 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
35881 <flags id="@var{id}" size="@var{size}">
35882 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35887 @subsection Registers
35890 Each register is represented as an element with this form:
35893 <reg name="@var{name}"
35894 bitsize="@var{size}"
35895 @r{[}regnum="@var{num}"@r{]}
35896 @r{[}save-restore="@var{save-restore}"@r{]}
35897 @r{[}type="@var{type}"@r{]}
35898 @r{[}group="@var{group}"@r{]}/>
35902 The components are as follows:
35907 The register's name; it must be unique within the target description.
35910 The register's size, in bits.
35913 The register's number. If omitted, a register's number is one greater
35914 than that of the previous register (either in the current feature or in
35915 a preceeding feature); the first register in the target description
35916 defaults to zero. This register number is used to read or write
35917 the register; e.g.@: it is used in the remote @code{p} and @code{P}
35918 packets, and registers appear in the @code{g} and @code{G} packets
35919 in order of increasing register number.
35922 Whether the register should be preserved across inferior function
35923 calls; this must be either @code{yes} or @code{no}. The default is
35924 @code{yes}, which is appropriate for most registers except for
35925 some system control registers; this is not related to the target's
35929 The type of the register. @var{type} may be a predefined type, a type
35930 defined in the current feature, or one of the special types @code{int}
35931 and @code{float}. @code{int} is an integer type of the correct size
35932 for @var{bitsize}, and @code{float} is a floating point type (in the
35933 architecture's normal floating point format) of the correct size for
35934 @var{bitsize}. The default is @code{int}.
35937 The register group to which this register belongs. @var{group} must
35938 be either @code{general}, @code{float}, or @code{vector}. If no
35939 @var{group} is specified, @value{GDBN} will not display the register
35940 in @code{info registers}.
35944 @node Predefined Target Types
35945 @section Predefined Target Types
35946 @cindex target descriptions, predefined types
35948 Type definitions in the self-description can build up composite types
35949 from basic building blocks, but can not define fundamental types. Instead,
35950 standard identifiers are provided by @value{GDBN} for the fundamental
35951 types. The currently supported types are:
35960 Signed integer types holding the specified number of bits.
35967 Unsigned integer types holding the specified number of bits.
35971 Pointers to unspecified code and data. The program counter and
35972 any dedicated return address register may be marked as code
35973 pointers; printing a code pointer converts it into a symbolic
35974 address. The stack pointer and any dedicated address registers
35975 may be marked as data pointers.
35978 Single precision IEEE floating point.
35981 Double precision IEEE floating point.
35984 The 12-byte extended precision format used by ARM FPA registers.
35987 The 10-byte extended precision format used by x87 registers.
35990 32bit @sc{eflags} register used by x86.
35993 32bit @sc{mxcsr} register used by x86.
35997 @node Standard Target Features
35998 @section Standard Target Features
35999 @cindex target descriptions, standard features
36001 A target description must contain either no registers or all the
36002 target's registers. If the description contains no registers, then
36003 @value{GDBN} will assume a default register layout, selected based on
36004 the architecture. If the description contains any registers, the
36005 default layout will not be used; the standard registers must be
36006 described in the target description, in such a way that @value{GDBN}
36007 can recognize them.
36009 This is accomplished by giving specific names to feature elements
36010 which contain standard registers. @value{GDBN} will look for features
36011 with those names and verify that they contain the expected registers;
36012 if any known feature is missing required registers, or if any required
36013 feature is missing, @value{GDBN} will reject the target
36014 description. You can add additional registers to any of the
36015 standard features --- @value{GDBN} will display them just as if
36016 they were added to an unrecognized feature.
36018 This section lists the known features and their expected contents.
36019 Sample XML documents for these features are included in the
36020 @value{GDBN} source tree, in the directory @file{gdb/features}.
36022 Names recognized by @value{GDBN} should include the name of the
36023 company or organization which selected the name, and the overall
36024 architecture to which the feature applies; so e.g.@: the feature
36025 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36027 The names of registers are not case sensitive for the purpose
36028 of recognizing standard features, but @value{GDBN} will only display
36029 registers using the capitalization used in the description.
36036 * PowerPC Features::
36041 @subsection ARM Features
36042 @cindex target descriptions, ARM features
36044 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36046 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36047 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36049 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36050 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36051 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36054 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36055 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36057 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36058 it should contain at least registers @samp{wR0} through @samp{wR15} and
36059 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36060 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36062 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36063 should contain at least registers @samp{d0} through @samp{d15}. If
36064 they are present, @samp{d16} through @samp{d31} should also be included.
36065 @value{GDBN} will synthesize the single-precision registers from
36066 halves of the double-precision registers.
36068 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36069 need to contain registers; it instructs @value{GDBN} to display the
36070 VFP double-precision registers as vectors and to synthesize the
36071 quad-precision registers from pairs of double-precision registers.
36072 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36073 be present and include 32 double-precision registers.
36075 @node i386 Features
36076 @subsection i386 Features
36077 @cindex target descriptions, i386 features
36079 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36080 targets. It should describe the following registers:
36084 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36086 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36088 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36089 @samp{fs}, @samp{gs}
36091 @samp{st0} through @samp{st7}
36093 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36094 @samp{foseg}, @samp{fooff} and @samp{fop}
36097 The register sets may be different, depending on the target.
36099 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36100 describe registers:
36104 @samp{xmm0} through @samp{xmm7} for i386
36106 @samp{xmm0} through @samp{xmm15} for amd64
36111 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36112 @samp{org.gnu.gdb.i386.sse} feature. It should
36113 describe the upper 128 bits of @sc{ymm} registers:
36117 @samp{ymm0h} through @samp{ymm7h} for i386
36119 @samp{ymm0h} through @samp{ymm15h} for amd64
36122 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36123 describe a single register, @samp{orig_eax}.
36125 @node MIPS Features
36126 @subsection MIPS Features
36127 @cindex target descriptions, MIPS features
36129 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36130 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36131 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36134 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36135 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36136 registers. They may be 32-bit or 64-bit depending on the target.
36138 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36139 it may be optional in a future version of @value{GDBN}. It should
36140 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36141 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
36143 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
36144 contain a single register, @samp{restart}, which is used by the
36145 Linux kernel to control restartable syscalls.
36147 @node M68K Features
36148 @subsection M68K Features
36149 @cindex target descriptions, M68K features
36152 @item @samp{org.gnu.gdb.m68k.core}
36153 @itemx @samp{org.gnu.gdb.coldfire.core}
36154 @itemx @samp{org.gnu.gdb.fido.core}
36155 One of those features must be always present.
36156 The feature that is present determines which flavor of m68k is
36157 used. The feature that is present should contain registers
36158 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
36159 @samp{sp}, @samp{ps} and @samp{pc}.
36161 @item @samp{org.gnu.gdb.coldfire.fp}
36162 This feature is optional. If present, it should contain registers
36163 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
36167 @node PowerPC Features
36168 @subsection PowerPC Features
36169 @cindex target descriptions, PowerPC features
36171 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
36172 targets. It should contain registers @samp{r0} through @samp{r31},
36173 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
36174 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
36176 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
36177 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
36179 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
36180 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
36183 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
36184 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
36185 will combine these registers with the floating point registers
36186 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
36187 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
36188 through @samp{vs63}, the set of vector registers for POWER7.
36190 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
36191 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
36192 @samp{spefscr}. SPE targets should provide 32-bit registers in
36193 @samp{org.gnu.gdb.power.core} and provide the upper halves in
36194 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
36195 these to present registers @samp{ev0} through @samp{ev31} to the
36198 @node Operating System Information
36199 @appendix Operating System Information
36200 @cindex operating system information
36206 Users of @value{GDBN} often wish to obtain information about the state of
36207 the operating system running on the target---for example the list of
36208 processes, or the list of open files. This section describes the
36209 mechanism that makes it possible. This mechanism is similar to the
36210 target features mechanism (@pxref{Target Descriptions}), but focuses
36211 on a different aspect of target.
36213 Operating system information is retrived from the target via the
36214 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
36215 read}). The object name in the request should be @samp{osdata}, and
36216 the @var{annex} identifies the data to be fetched.
36219 @appendixsection Process list
36220 @cindex operating system information, process list
36222 When requesting the process list, the @var{annex} field in the
36223 @samp{qXfer} request should be @samp{processes}. The returned data is
36224 an XML document. The formal syntax of this document is defined in
36225 @file{gdb/features/osdata.dtd}.
36227 An example document is:
36230 <?xml version="1.0"?>
36231 <!DOCTYPE target SYSTEM "osdata.dtd">
36232 <osdata type="processes">
36234 <column name="pid">1</column>
36235 <column name="user">root</column>
36236 <column name="command">/sbin/init</column>
36237 <column name="cores">1,2,3</column>
36242 Each item should include a column whose name is @samp{pid}. The value
36243 of that column should identify the process on the target. The
36244 @samp{user} and @samp{command} columns are optional, and will be
36245 displayed by @value{GDBN}. The @samp{cores} column, if present,
36246 should contain a comma-separated list of cores that this process
36247 is running on. Target may provide additional columns,
36248 which @value{GDBN} currently ignores.
36252 @node GNU Free Documentation License
36253 @appendix GNU Free Documentation License
36262 % I think something like @colophon should be in texinfo. In the
36264 \long\def\colophon{\hbox to0pt{}\vfill
36265 \centerline{The body of this manual is set in}
36266 \centerline{\fontname\tenrm,}
36267 \centerline{with headings in {\bf\fontname\tenbf}}
36268 \centerline{and examples in {\tt\fontname\tentt}.}
36269 \centerline{{\it\fontname\tenit\/},}
36270 \centerline{{\bf\fontname\tenbf}, and}
36271 \centerline{{\sl\fontname\tensl\/}}
36272 \centerline{are used for emphasis.}\vfill}
36274 % Blame: doc@cygnus.com, 1991.